CA1203060A - Masking apparatus for selectively charging honeycomb structures - Google Patents

Abstract

ABSTRACT

Improved masking apparatus and methods for bulk charging a flowable material into selected cell ends exposed at an end face of a honeycomb structure. The masking apparatus utilize protrusions which assist in properly aligning the apparatus to the end face and reduce the possibility of improperly charging cells. In one apparatus embodiment, a planar body is provided having a plurality of hollow protrusions which extend into selected cell ends when the planar body is fitted against an end face of the structure. A flowable material charged against the planar body passes through the hollow protrusions into the selected cell ends. In another embodiment, a plurality of preformed protrusions or plugs are mounted along thin, flexible members at predetermined locations. The plugs are inserted into and block or cover the ends of an equal plurality of cells. A flowable material charged against the end face passes into the remaining, uncovered cells.
The invention is of particular use in fabricating solid particulate filter bodies from ceramic-based honeycomb structures.
Preferably the mask is made of a flexible material, for instance a polymer, preferably an elastomer. Also described are apparatus and dies for making the die.
Furthermore, a method of aligning the flexible mask with a honeycomb body by vibration is described.

Description

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BACKGROUND OF TE~E INVENTION
This invention relates ko charging flowable materials into selected cells of a honeycomb structure and, more particularly, to methods and related apparatus for selectively manifolding (i.e. plugging) cells of a honey-comb structure for the fabrication of filter bodies and other selectively sealed honeycomb structures.
Honeycomb structures having transverse, cross-sectional cellular densities of one-ten~h to o~ehundred or more cells per square centimeter, especially when formed from ceramic materials, have several uses, such as solid particulate filter ~odies and stationary heat e~Angers, which may require selected cells of the structure to be closed or blocked by manifolding or other means at one or both of their ends.
A solid particulate filter body may be fabricated utilizing a honeycomb structure having a matrix of intersecting, thin, porous walls which extend across and between two of its opposing open end ~aces and form a large number of adjoining hollow passages or cells which also extend between and are open at the end faces. To form a filter, one end of each o~ th~ cells is closed, a first subset of cells being closed at one end face and the remaining cells at the re~;n;ng end ace, so that either may be used as the inlet or outlet end of the filter. A
con~;n~ted fluid is broughtunder pressure to one face (i.e. the "inlet" face) and enters the filter bodies via the cells which are open at the inlet face (i~e. the "inlet" cells). Because the inlet cells are sealed at the remaining (i.e. "outlet") end face of the body, the cont~m;n~ted fluid is forced through the thin, porous walls into adjoining cells which are sealed at the inlet face and open at the opposing 'loutlet" end face o the filter body (i.e. "outlet" cells~. The solid particulate contamina~t in the fluid which is too large to pas9 through ~1 3~60 the porous openings in the walls is left behind and cleansed fluid exits the outlet face of the fil~er body through the outlet cells for use.
Parallel work by applicant, as disclosed in the European application issued under No. 8130298S.5, has resulted in a most efficient solid particulate filter body formed ~rom a honeycomb structure in which the cells are provided in transverse, cross-sectional densities between approximately one and one hundr~d cells per square centi-meter with transverse, cross sectional geometries havingno internal angles less than thirty degre~s, such as squares, rectangles, equilateral and certain other triangles, circles, certain elipses, etc. The cells are also arranged in mutually parallel rows and/or columns.
Alternate cells at one end ace are filled in a checkered or checkerboard pattern and the remaining alternate cells are filled at the remaining end face of the structure in a reversed pattern. Thus formed, either end face of the filter body may be used as its inlet or outlet face and each inlet cell shares common walls with only adjoining outlet cells, and vice versa. Other cellular cross-sectional geometries and other patterns of sealed cells may be employed to fabricate effective, although perhaps less efficient filter bodies than those disclosed by the aforesaid application.
For the mass production of such filters, it is highly desirable to be able to block selected cell ends as rapidly and as inexpensively as possibleO The previously referred to European application No. 81302986.5 describes fabricating filter bodies by plugging the end of each cell individually with a hand-held, single nozzle, air actuated sealing gun. The hand plugging of individual cells by this process is long and tedious and is not suited for the commercial production of such filters which may have 6~

thousands of cells to be selectively sealed. European application No. 81302986.5 also postulates the use of a sealing gun mounting an array o~ sealant nozzles so that the plugging mixture may be simultaneously injected into a plurality or all of the alternate cells at each end face of the honeycomb structure. ~owever, a working model of this device is not known to exist for plugging honeycomb structures having the higher cell densities referred ~o.
An alternative approach to manifolding selected cells at an end face of a honeycomb structure has been developed by the applicant, in which an open surface of a honeycomb structure is covered by a mask having a numher of openings extending through it. Plugging material is charged against the outer surface of the mask and through its openings into the proximal open ends of cells opposite the openings. A rigid plate having a plurali~y of bores extending through it which are spaced and sized to coincide with the open ends of the selected cells a~ the end face of a honeycomb structure when the plate is positioned against the end face in alignment with its bores opposite the selected cells is used. Successful use of such an apparatus is dependent upon the ability to provide honey-comb structures having end faces conforming to the face ~of the masking apparatus so as to prevent gaps therebetween which would allow the sealing material to charge into adjoining cells and to provide predetermined, undistorted positioning of the cells at the end face of the honeycomb structure for accurate registration of the selected cells with the openings in the mask, again, to prevent possible charging of sealing material into ad~oining cells.
In a related area, U.S~ Patent 4,410,591 describes alternate methods of fabricating a multiple flow path body such as a stationary heat exchanger in which a honeycomb structure is provided having its cells arranged in columns across its open end faces, an open end face of a honeycomb structure is dipped into a flowable resist material and ~LZa~3~

the resist material L~lVV~d from selected columns by cutting it away together with the a~n~n walls of the adjoining cells in the selected column or, alternatively,the wal~ between the adjoining cells of the selected columns are cut away at the open end face of the structure before dipping the end face into the flowable resist material, then the resist material is blown from the selected columns using compressed air directed down the selected columns where the adjoining cell walls have been removed. The end face was thereafter dipped into a slurry of cement to form a sealed channel across each of the selected columns. The remaining flowable resist material was subsequently removed by heating.
Although these methods do not involve charging a permanent plugging material into cells as the purpose is to create channels across the ends of cells, sufficient plugging material could be provided to block the cell ends exposed by the cutting step. As the cross-sectional density of cells in the honeycomb structure is increased, for example to improve the efficiency of a filter body, the tolerances needed for the removal of adjoining cell walls required by these methods tighten. The problem is particularly heightened when the filter bodies are fabricated from extruded ceramic or ceramic-based honey-comb structures as the present state of the ceramic extrusion art cannot provide perfectly parallel rows and/
or columns of cells. Also, these methods requir~ the partial destruction of adjoining cell walls and are entirely unsuited for the fabrication of filter bodies or other selectively sealed honeycomb structurPs where the cells are plugged in a checkered or other possible alternating cell patterns at the end faces.

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SVMMARY OF THE INVENTION
The invention relates to a mask for use in bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of opposing end faces and a matrix of thin walls defining a multiplicity of hollow, open ended cells extending through said structure between said pair of end faces, said mask apparatus comprising:
at least one base member adopted to be positioned across one end face, a plurality of protruding members extending from each base member in the same direction and in special and shaped arrangement that permits each protruding member to register with, be inserted in an open end of one of said cells, and means at said one end face for providing open access to open ends of cells in said selected subset by said flowable material.
The invention further relates to a method of bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of opposing end faces and a matrix of thin walls defining a multiplicity of hollow open ended cells extending through said structure between said pair of end faces, comprising the steps of providing a mask apparatus, applying said mask apparatus to an end face and charging said flowable material against and through said mask apparatus and into said selected subset of cells, the improvement comprising the steps of:
providing the mask described above and during said applying step, inserting said each protruding member into an open end of one of said cells.

12~3~60 It is an object of the in~ention to provide a method for selectively bulk charging cells of a honeycomb structure with a flowable material which is compatible with any desired pattern of cells selected to be charged.
It is yet another object of the invention to minimize the overspill of sealing material when bulk charging selected cells of a honeycomb structure.
It is yet another object of the invention to provide a method of selectively manifolding large numbers of cells of honeycomb structures that is more rapid and less expensive than hand filling individual cell en.ds.
The invention further related to a die for foEming a flexible mask, said mask for use in bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of opposing end faces and a matrix of thin walls defining a multiplicity of hollow, open ended cells extending through said structure between said pair of end faces, wherein said mask apparatus is comprised of:
~0 at least one base member adopted to be positioned across one end face, a plurality of flexible protrusions extendiny from each base member in the same direction and in special and shaped arrangement that permits each protruding member to register with, be inserted in an open end of one of said cells, and a plurality of openings at said one end face for providing open acess to open ends of cells in said selected subset by said-flowable material; said die comprising a die piece having a mask formin~ outer surface, a first plurality of bores extending through said mask forming outer surface and said die piece, and means extending from said mask forming outer surface for forming a cavity therewith within which said mask is formed.

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6a In a further embodiment, the in~ention relates to a die for forming a flexible mask, said mask for use in bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of Dpposing end faces and a matrix of thin walls d~fining a multiplicity of hollow, open ended cells extending through said structure between said pair of end faces, wherein said mask apparatus is comprised of:
at least one base member adopted to be positioned across one end face, a plurality of flexible protrusions extending from each base.~ember in the same direction and in special and shaped arrangement that permits each protruding member to register with, be inserted in an open end of one of said cells, and a plurality of openings at said one end face for providing open access to open ends of cells in said selected subset by said flowable material; said die comprising first clie means for forming a plurality of openings to constitute said means for providing open access;
second die means positioned against said first means for forming said plurality o protruding members, said first and second means also forming a cavity therebetween;
and stripping means positioned within said cavity for removing said flexible mask after being formed.
Further objects and advantages of the invention will become apparent as the description thereof proceeds.
A summary of the invention and its various aspects will ~e found in the appended claims.
DESCRIPTION OF THE DR:AWINGS
The various aspects of the invention are better understood with reference to the accompanying drawings, in which:
Figs. 1 and la depict a solid particulate filter body fabricated using the inventive methods and apparatus;

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6b Fig. 2 depicts a honeycomb structure and first mask embodiment;
Fig. 3 depicts in a sectioned, profile view, the mask embodiment of Fig. 2 fitted to the honeycomb structure;
Fig. 4 depicts a flowable material being charged through one o the hollow protrusions of the mask embodiment of Figs. 2 and 3 into a cell of the honeycomb structure;
Fig. 5 depicts a press apparatus for using the several mask embodiments of Figs. 2 through 4 and 6 through 7b;
Fig. 6 depicts a second mask embodiment of- the invention being fi~ted to an end face of the honeycomb;
Fig. 6a depicts a thin flexible member and performed plugs of Fig. 6 in an expanded view;

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Fig. 6b is an expanded, sectioned, view of area 6b of Fig. 6 depicting the covering of the open ends of some of the cells by individual plug members and their protrusion into the cell ends;
Fig. 6c is an expanded end view of the area 6c of Fig. 6 showing the arrangement of plug elements in alternate cells of the honeycomb structure exposing the remaining cells in a checkered pattern for filling;
Fig. 7 depicts a preferred embodiment of the invention, an elastic mask, and a honeycomb structure with which it is used;
Fig. 7a is a view of the downstream face of the mask embodiment of FigO 7 along the lines 7a-7a depicting the relative positioning of some of its protrusions and openings;
Fig. 7b is a cross-sectional profile ~iew along lines 7b-7b of Figure 7;
Fig. 8 is a perspective, schematic view of the subject flexible mask and a honeycomb structure with which it is used;
Fig. 9 is an end face schematic view of the subject flexible mask of Fig. 1 showing the relative positioning of some of its adjoining openings and protrusions;
Fig. 10 is a sectioned view of the subject flexible mask being fitted to an end face of the honeycomb structure;
Fig. 11 is a greatly expanded and sectioned schematic view of the mask fitted to the end face of the honeycomb structure;
Fig. 12 is a schematic ~iew of a solid particulate filter body formed using the mask and honeycomb structure of Figs. 1 through 4;
Fig. 12a is a sectioned view of the ilter body of Fig. 12 along lines 12a-12a;

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Fig. 13a is a sectioned schematic view of a simple die for casting a flexible mask having protrusions but no openings;
Fig. 13b is a sectioned schematic view of the mask formed on the simple die depicted in Fig. 13a having openings being formed through it;
Fig. 14a is a sectioned schematic view of a second simple die for forming a flexible mask having both protrusions and openings, showing a polymer being loaded into the die;
Fig. 14b depicts the upper surface of the polymer cast into the second simple die of Fig. 14a being smoothed to form an outer surface of a flexible mask;
Fig. 14c depicts schematically the curing of the mask in the second simple die in an oven;
Fig. 14d depicts schematically the flashing being removed from the lower outer surface of the second simple die after the mask has been cured;
Fig. 14e depicts a sectioned, schematic, profile view of the mask produced in the second simple die by the steps depicted in Figs. 14a through 14d;
Fig. 14f depicts schematically the undersizing of the mask with respect to the cells of th~ honeycomb structure;
Fig. 15a is an exploded schematic view of a compound mask forming die appartus;
Fig. 15b is a sectioned profile view of the compound die apparatus of Fig. 15a in an assembled form;
Fig. 16 is a sectioned, schematic ~iew of a press apparatus for charging a plastically formable material such as a plugging cement into a honeycomb structure using the subject flexible mask; and Fig. 17 is a schematic sectioned view of a envisioned press apparatus having a subject flexible mask incorporated into its exit orifice.

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Fig. 18 is a schematic view of apparatus for aligning a mask having protrusions to an end face of a honeycomb structure;
Fig 19 is a cross-sectional view of the mask fitted to the end face of the honeycomb structure of Fig. 18;
Fig. 20 is a schematic view of a preferred filter body abricated with the mask and honeycomb structure of Figs. 18 and 19;
Fig. 21 is a cross-sectional view of the filter body of ~ig. 20 along the lines 21-21 showing the pa~tern of cells being plugged at alternate ends;
Fig. 22 depicts patterns of openings and protrusion l~cations for the central portions of reverse mask.s centered over a cell on the end faces of a honeycomb structure;
Fig. 23 depicts a view of the central portion of an end face and the two subsets of cells which are exposed using identical masks centered on the end face at one of two locations over a thin wall forming the cells;
Fig. 24 is an exploded view of the central portion of identical masks showing the two corresponding locations of their axial centers used with each o~ the two axial center locations of the end face represented in Fig. 23;
Figs.~S through 27 depict various embodiments using rigid members extending between a mask and end face to restrict their relative lateral or lateral and angular movement during the step of vibrating the mask into alignment.
DETAILED DESCRIPTION OF THE lNV~N'l'lON
A preferred use of each of the embodiments of the present invention is the fabrication of solid parti-culate filter bodies as described in the aforesaid European application No~ 81302986.5. An exemplary preferred filter body of that invention is depicted in Fig. 1 and 3~6@~

in a cross-sectioned view along the line la-la in Fig. la.
The filter body comprises a honeycomb structure 10 having a multiplicity of hollow, open ended passages or cells 11 which typically extend in an essentially mutually parallel fashion through the structure 10 so as to reduce back pressure in the filter body being fabricated. The ends of the cells 11 are open at and form a pair of substantially identical open outer surfaces at end faces 12 and 13 of the structure. The cells 11 are themselves formed by a matrix of intersecting walls 14 which extend between each of the end faces 12 and 130 For filter body applications, the walls 14 are perous and continuous across the end faces 12 and 13 and prefera~l~ uniformly thin, although walls of non-uniform thickness may be used with less efficiency. A thicker, outer "skin" 15 may be provided around the cells 11 and thin walls 14 between the end faces 12 and 13.
Honeycomb structures for solid particulate filtering and other applications may be formed from a variety of porous materials including ceramics, glass-ceramics, glasses, metals, cermets, resins or organic polymers, papers, or textile fabrics (with or without fillers, etc.), and various combinations thereof and by a variety of methods depending upon the material(s) selected. Honeycomb structures having the necessary uniformly thin, porous and interconnected walls for solid particulate filtering applications are preferably abricated from plastically formable and sinterable, finely divided particles and/or short length fibers of substances that yield a porous~ sintered material after being fired to afect their sintering, especially metallic powders, ceramics, glass-ceramics, cermets, and other ceramic-based mixtures. An extruded ceramic honeycomb structure having cordierite as its primary crystal phase, which i.s preferred for moderately high temperature solid 6~

particulate filtering applications (1,000 Centigrade or more) due to its low thermal expansion characteristics, may be provided in the manner described in the afore-mentioned European application No. 81302986.5. Several exemplary raw material mixtures are described therein which yield honeycomb structures with thin walls having various open porosities. The filter body is formed by plugging, covering or otherwise blocki~g the ends of a subset of alternative cells at one end face o~ the structure and the rema~ining cells at th remaining end face of the structureO In Figs. 1 and la, alternate cells 11 of the honeycomb structure 10 have been blocked wi~h plugs 16 at either end face in a checked or checkerboard pattern described and claimed in the aforesaid European application No. 81~02986.5. The plugging pattern on the end face 13 thidden in Fig. 1) is the reverse of that depicted on the end face 12. Further information regarding the use and operation of the described filter bodies is provided in the aforesaid European application No. 81302986.5.
The plugs 16 are selected from a material compatible with the composition of the honeycomb structure and its ultimate use as a filter body. Where the aforesaid cordierite structures are used for filtering applications, cordierite cement plugs 16 are preferably provided for compatibility. Suitable foaming cordierite cements are described and claimed in a copending Canadian application Serial No. 380,875 filed June 30, 1981 and entitled PATICULATE FILTER AND MATERIAL FOR PRODUCING THE SAME, which is assigned to the assignee of this application.
A particular composition of the cement preferred for high sodium ion exhaust gas filtering applications is provided in the aforesaid European application No. 81302986.5.
Nonfoaming cordierite cement compositions may be used with the porous walled cordierite substrates identified in the aforesaid ~uropean Patent No. 81302986.5. Alter~
natively, other ceramic cements and other plugging 3~6~

materials may be used with cordierite or other honeycomb structures to fabricate filter bodies and other selectively plugged honeycomb structures using the subject invention which is hereinafter described in three embodiments, including a preferred embodiment, in the context of fabricating the described solid particulate filter bodies.
Fig. 2 depicts a honeycomb structure 10 again having cells 11 formed by thin walls 14 extending between end faces 12 and 13 with a first embodLment mask 20 of the subject invention. The mask 20 comprises a rigid, essentially plate-like body 21 having opposing upstream and downstream faces 22 and 23. The body 21 has a plurality of bores 21a extending axially between its surfaces 22 and 23 each of which i5 fitted with a hollow tube 24 which protrudes like a nipple from the downstream surface 23 of the mask body 21. The mask 20 is used by positioning its downstream face 23 against an end face 12 (or 13) of the structure 10 as indicated by the arrows 25, preferably until the down-stream surface 23 is substantially flush with the end face 12 (or 13) as is depicted in Fig. 3. The tubes 24 are positioned with respect to one another across the mask body 21 and sized so as to coincide with and extend into the ends of selected cells when the mask 20 is ~itted to the end face 12 (or 13) of the structure 10. A suitably flowable material (indicated by shading in Fig. 4), such as one of the aforesaid ceramic plugging cements, which is charged against the upstream face 22 of the mask 20 under pressure passes through the tubes 24, as is indicated by the arrows 26 in Fig. 4, into the ends of the selected cells into which each tube 24 extends. Desirably, the outer surface of protruding nipples of tubes 24 taper inwardly as they ex~end from the plate-like body 21 so as to present a smaller transverse cross-sectional area at their tip for easier registration with the open cell ends.

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The base o~ the nipples may be su~ficiently wide so as to rest on or ~i~ snugly into the ends of th~ selected cells 11 to prevent the flowable plugging matexial from spilling or oozing over into adjacent cells which are to remain open or unplugged. The mask 20 may be made from metal components by assembly, in the manner described, or monolithically by such methods as casting, or alternakively, from other formable or machinable rigid materials. It is also envisioned that the mask may be formed monolithically from a flexible or elastic polymer material in a manner similar to the preferred embodiment subsequently described herein.
Fig. 5 depicts an exemplary press apparatus 30 which may be used with the first embodiment mask 20 to charge a plastically formable cement or other viscous material into selected cell ends of a honeycomb structure.
The apparatus 30 comprises a press head 31 housing a piston 32 traveling in a bore 33 which is open at an outer surface 31a of the head 31 and additional frame members 34 supporting a hand-operated screw 35 or other suitable means for moving the piston 32 in the bore 33. A honeycomb structure 10 is charged using the mask embodiment 20 and the subject press apparatus 30 by withdrawing the piston 32 into the chamber 33 ~orming a cavity between its head 32a and the outer surface 31a of the press head 31. The ceramic cement or other material to be charged into the structure 10 is loaded into the cavity. The honeycomb structure lO with fitted mask 20 is applied over the bore 33 and against the surface 31a of the press head. The structure 10 and mask 20 are held in position by suitable means such as a bar 36 pos~itioned over the opposing end face 13 of the structure, which bar is held in position by suitable means such a threaded bolts 37 extending into suitably threaded bores 38 in the press head 31. The piston ~2 is then advanced towards khe mask 20 by means of the ~3~

screw 35 and presses the material in the cavity through the tubes 24 into ~he proximal en~s of ~he cells 11 forming plugs 16. Plugs 16a have been formed in the remaining alternate calls of the structure 10 at the opposite end face 13 in a similar, previou~ filling operation. The structure 10 is then removed from the press head and the plugs 16 and 16a fixed in position by sintering in the case of the aforesaid cordierite cements or by drying, curing or other appropriate steps for other plugging materials.
Figs. 6 through 6c depict a second embodimen-t of the invention, a multiplicity of preformed plug elements each of which is inserted into and blocks or covers the open end of a cell 11 at an end face 12 (or 13) o a honeycomb structure 10. For convenience, the plugging elements 40 are preferably prepositioned along elongated members 41 such as flexible wires, which are sufficiently thin (i.e. of width perpendicular to members 40 smaller than width of cells) so as to not overlap or substantially block cells adjoining those temporarily plugged with the members 40. The flexible members 41 assist considerably the use of the plug elements 40. The flexibility of the members 41 allows some latitude in aligning the plug elements 40 with distorted arrangements of cells at an end face. ~he members 41 also locate the plug elements 40 in the vicinity o the appropriate cell ends during inser-tion and provide a means for quickly removing the plugs after the selected cells of the structure have been charged. Each element 40 has a central body portion 4Oa which is sufficiently small in diameter so as to be 3Q inserted into an open end of a cell 11. ~dditionally, each plug element 40 is pro~ided with a larger head portion 40b having a diameter greater than the minimum diameter or width of the open, transverse, cross-sectional areas of the cells. Head portion 40b both covers the cell ~5 ends preventing their charging and prevents the plugs 40 from being pushed completely past the end fa~e into a cell 3~6~

end during the charging process. To plug alternate cells 11 arranged in rows and columns at an end face 12 of a honeycomb structure in the aforementioned checkered or checkerboard pattern, flexible elements 41 each carrying oneor more plug elements 40 are arranged along alternate, parallel diagonals of cells at an end face, as indicated in Fig. 6c. The plug elements 40 may be inserted into the cells along the remaining alternate diagonals at the opposing end face of the structure 10 to achieve the desired, reversed, checkered or checkerboard plugging pattern. The flexible members 41 may be provided sufficiently long so as to overlap the sidewalls 14 of the structure 10 where they may be held in place by suitable means 42 for the charging methods selected. For example, the press apparatu~ 30 of Fig. 5 may be used by stretch-fitting an oversized collar, such as an annular, hollow neoprene ring having an inner circumference slightly less than the outer circumference of the end face 12, over the end face 12 and onto the structure sidewalls 15 and ends of the flexible members 41. Alternatively, an adjustable clamp, tape or other means may be used to secure the ends of the flexible members 41 to the sides 15 of the structure 10. A working model of the masking apparatus depicted was fabricated by soldering small, copper rivets at predetermined locations along thin, copper wires.
~lthough the depicted arrangement of the flexible members 41 along diagonals of cells arranged in rows and columns is preferred for the fabrication of solid particulate filter bodies having the preferred checked plugging pattern depicted in Fig. 1, it is envisioned that other plugging patterns can be achieved by other spacings of the plugging elements 40 along the flexible members 41 and other orientations of the members 41 across an open end face of a honeycomb structure 10.
An embodiment of the invention which is preferred ~or fabricating solid particulate filter bodies or for otherwise charging flowable materials into selected cells of honeycomb structures in which the open ends of he cells or the arrangement of the cells across the end face may be somewhat distorted is an elastic mask described and claimed in U.SO application Serial No. 283,734, filed July 15, 1981, and issu d as U.S. Patent No. 4,411,856 entitled MET~IOD AND APPAR~TUS FOR HIGH SPEED ~!IANIFOLDING
OF HONEYCOMB STRUCTURES, which is assigned to the assignee of this application. An exemplary elastic mask 50 is depicted in Figs. 7 through 7b toge-ther with an exemplary honeycomb structure 10 with which it is used. The mask 50 consists of a substantially plate-like body section 51 having a plura]ity of openings 52 extending substantially axially therethrough between an upstream face 53 and downstream face 54. A second plurality of protrusions 55 is also provided extending in a substantially axial direction from the downstream face 54. The openings 52 and protrusions 55 are spaced with respec. to one another and sized so as to coincide with selected cells 11 when the mask i5 fitted to an end face 12 (or 13) of the structuxe 10. A portion of the openings 52 and protrusions 55 are depicted in Fig. 8a in a view of the downstream face 54 of the mask 50. The openings 52 and protrusions 55 are alternated with one another along rows and columns parallel and perpendicular, respectively, to the line 56 o~ Fig. ~a so as to coincide with alternate cells arranged in xows and columns, respectively, at the end face 12 (or 13) of the structure 10. The mask 50 is fitted to the end face 12 (or 13) of the structure 10, as indicated by the arrows 57 in Fig. 7, with the downstream face 54 flush against the ends of the cells 11, as depicted in Fig. 7b.
Preferably, ~he protrusions 55 are also elastic and taper as they extend away from the downstream face 54 from a cross-sectionaldiameter equal to or greater than a cross-sectional diameter less than the minimum diameter of the open, cross-sectional area of the cell ends into which 33~

they protrude. The pr3~rusions 55 assist in aligning the mask to the end face with its openings opposite the proper cell ends and temporarily block the cell ends into which they are inserted preventing the plugging or other flowable material being charged through the mask 50 from entering those cells. A more detailed description of the ~abrication and use of the mask 50 is provided in the aforesaid U.S.
Patent Number 4,411,856. A preferred embodiment for fitting the mask 50 to an end face of a honeycomb structuré
is provided in European Patent No. 8230366.1. A preferred embodiment for fitting the mask 52 and end face of a honeycomb structure involves sintering the mask with one end face of the honeycomb structure and then vibrating the mask into alignment against that end face. With its openings exposing the first subset of cells and its plurality of protrusions engaging in equal plurality of the remaining cells~ If a pair of masks is provlded, first one mask is sintered with one end phase of the honeycomb structure, and then vibrated as mentioned before, and there-after the remainin~ mask is approximately sintered with the remaining end face and then is vibrated into alignment against that remaining end face, with its openings exposing substantially all of the remaining cells and its protrusions engaging on equal plurality of the first subset of cells.
It will be appreciated that the described embodiments are exemplary and that variations and modifications may be made with respect to each. For example, although the first embodiment of Figs. 2 through 4 was depicted in Fig. 5 with a press apparatus for chargin~ a plastically formable or other highly viscousmaterial into selected cell ends, it is envisioned that the apparatus 20 may be used to charge less viscous materials such as a plugging cement slurry into selected cell ends. One way to accomplish this would be to position the honeycomb structure on its side with its end faces 12 and 13 in a vertical orientation. The apparatus ~3~6~

20 is fitted to an end face in the manner described with its hollow tubes extending into the selected cell endsO
A cement slurry is charged against the upstream face 22 of the mask and injected through ~he hollow tubes 24 into the cell ends 11 while the mask 20 is slowly withdrawn from the end face 12 of ~he structure 10. The mask 20 would be withdrawn at the rate at about which the slurry is being deposited into the cell ends. The f1QW o slurry would be halted just before the hollow tubès 24 clear the end face of the structure 10. The structure 10 may be rolled or vibrated to assure distribution of the slurry across the cell end. Also, in accordance with Montierth's teaching in the aforesaid U.S. Patent Number 4,411,856, the plugs 40 of the second embodiment depicted in Figs. 6 through 6c may be made of a flexible or elastic material and in a tapered configuration similar to the protrusions 55 of the mask embodiment of Figs. 7 through 7b so as to conform to or temporarily seal the c~ll ends into which they are inserted.
We shall now describe the embodiments of the invention shown by Figures 8~17.
Fig. 8 depicts an exemplary mask apparatus 120 and a honeycomb structure 121 with which it i5 used for forming a solid particulate filter body in which the cells 2S 127 are sealed in a checkered pattern as indicated in Fig. 12. The mask 120 consists of a body 122, having a pair of opposing, ~ypically planar, outer surfaces 123 and 124 (see Figs. 9-11). A number of openings 125 extend through the body 122 between and through the opposing outer surfaces 123 and 124. A number of protrusions 126 extend from the downstream face 124 of the mask 120. The central longitudinal axes of the openings 125 and protrusions 126 are typically normal to those surfacesl24 although it is possible and in certain situations may be desirable to have the openings 125 ~3~6~

incline in a uniform direction with respect to the surface 124. When the mask 120 is applied to an end face 128 or 129 of a honeycomb structure 121, the openings 125 allow a sealant or other flowahle material to pass through the mask 120 into those cells 127 of the honeycomb structure 121 opposite each opening 125. Again, the protrusions are typically normal to the surface 124 but may be inclined, if desired or required, with respect to that outer surface 1240 The honeycomh structure 121 has a large number of adjoining hollow passages or cells 127 which extend in a substantially mutually parallel fashion through the structure between its end faces 128 and 129 (hidden). The end faces 128 and 129 typically are substantially square or perpendicular to the central longitudinal axes of the cells 127 but may be inclined thereto if desired Qr required.
In such case the protrusions must be comparably angled so as to fittably engage the cells and allow the mask to sit flush to the end face. The cell axes desirably align substantially with those of the protrusions 126 and openings 125, making fitting of the mask 120 to the end faces 128 and/or 129 easier, and direct the flowable material passed through the openings 125 directly into the cells for uniform filling across the cross-sections.
The cells 127 are formed by a matrix o thin, intersecting walls 130 which extend across and between the end faces 128 and 129. For solid particulate filter bodies, the walls 130 are also porous and continuous across and between the end faces 128 and 129. The structure 121 may also be provided with an outer skin 131 between the end faces 128 and 129 surrounding the cells 127.
A honeycomb structure 121 may be provided from any of a variety of suitabl~ materials including metal, ceramics, slasses, paper, cloth and natural or man~-made f~D3~

organic compounds, as well as combinations thereof, by any method suitable for the materials selected. For the production o solid particulate filter bodies~ porous walled honeycomb structures may be conventionally formed by extrusion from sinterable mixtures in the manner described in U.S. Patents 3,919,384 and 4,008,003.
Cordier.ite compositions preferred for foxming substantially thermostable ceramic honeycomb structures wi.th various degrees of open porosity, are described in the aforesaid 10 European Patent No~ 81302986.5 and in the copending Canadian application serial No. 380,875. An impervious, unglazed, sintered manganese-containing ceramic material has as its major and primary crystal phase a cordierite crystal structure, has an analytical molar composition of ~5 about 1.7-2.4 RO 1.9-2.4 A12O3 . 4.5-5.2 SiO2 and is made of mineral batch composition selected from (a) wholly raw ceramic material wherein RO comprises, as mole %
of RO, about 55-95~ MnO and 5-45~ MgO, and (b) at least about 50 wt.~ prereacted cordierite material and the 20 balance thereof is raw ceramic material, and wherein RO
comprises, as mole % of RO, about 5-40% MnO and 60-95%
MgO. It will be appreciated that a subject mask however, may be used with honeycomb structures 21 ormed from other materials and/or by other methods.
The open, transverse cross-sectional areas of the cells 127 are square and are arran-ged at the end faces 128 and 129 in mutually parallel rows and mutually parallel columns which are mutually perpendicular to one another It will be appreciated that the rows and columns may not 30 be exactly parallel and perpendicular due to manufacturing limitations in fabricating the honeycomb structure 121.
The square, cross-sectional geometry and the row and column arrangement of cells at the end faces depicted in this application are exemplary. A mask 120 may be fabricated to fit a variety of cellular arrangements and cellular cross-sectional geometries and to pro~ide a variety of selected cell charging pa~terns.
The positioning of the openings 125 in and protxusions 126 on the mask 120 are made with respect to the cells 127 of the honeycomb structure 121 with which the mask is used. Each opening 125 is positioned on the mask to coincide with the open end of a cell to be charged 10 with a filling material through the mask when the mask is properly positioned over the end face (see Fig. 11).
The openings 125 are suitably sized to expose the open ends of the selected cell or cells sufficiently for charging but not so large as to expose part or all 15 of any other cell not to be charged. Larger openings can be provided to expose several adjacent cells if desired.
Each protrusion 126 is similarly positioned on the mask to suitably engage and is pre~erably sized to seal a single cell at the end face 128 or 129 over which 20 the mask 120 is fitted. The protrusions 126 are preferably elastic and taper from a diameter at their base which is equal or larger than, to a diameter at their tip which is smaller ~han the minimum cross-sectional diameter of the open end of cell with which they engage. Cone~topped 25 cylindrical protrusions depicted in Figs. 8-11 are easy to orm as are other shapes having a surface of rotation (i.e. cones, domes, domed cylinders, bullet shapes etc).
The protrusions need not taper along their entire length although it is desirable that ~he protrusion tip distal to 30 the mask body 122 be tapered to provide some tolerance duxing initial registration of the protrusions with the cell ends. The included angle of taper T between the protrusion side walls 133 (see Fig, 11~ near the distal tip of the protrusion 126 should be less than 90 degrees 35 and desirably between approximately 10 and 50 degxees~

~3~

The mask 120 is formed from a flexible material impermeable to and non-reactive with the sealing material or other flowable material to be charged through the mask 120. Flexibility allows the mask 120 to conform to unevenness and some distortions and deformities in the cellular arrangements at the structure's end faces 128 and 129. This characteristic is significant because in many cases, notably the ceramic arts, undistorted and undeformed honeycomb structures cannot be provided with regularity 10 by conventional manufacturing techniques. This problem increases with increasing cell densities, increasing end face dimensions and decreasing structural stiffness during formation of the structure, and is relatively significant with respect to a mass fabrication of ceramic-based filter 15 bodies such as the diesel particulate filter embodiment described in the aforesaid European Patent No. 81302986.5.
Preferably the mask and its protrusions are also elastic.
Such masks are most conveniently formed monolithically from any of several possible elastomers (i.e., elastic 20 polymers) by casting or injection molding in a manner to be later described. Elastic masks have been success~ully ormed from various silicones and urethane although it is envisioned that other flexible materials including other elastic polymers may be used. Elasticity also allows 25 the mask 120 and protrusions 126 to ~ te cellular spacing distortions at the end faces 128 and 129 and the tapered protrusions to sealably fit the open ends of cells 127 withou~ damaging them when the mask 120 is applied.
It is envisioned that the flexible masks will be fabricated 30 from any of several moldable, polymerizable resins including silicones and urethanes or other materials also having a Durometer Shore A value ranging between approximately 10 and 70 (See ASTM Standard D-1706) and a Young's (E) Modulus of approximately 30,000 psi (about 2110 kg./cm. ) or less, 35 although a Young's Modulus in the range of approximately 500 to 3000 psi (about 35 to 211 kg./cm~ ) is preferred for ~¢33~

elastic masks used in fabricating solid par~iculate filter bodies from the aforesaid ceramic-based honeycomb structures.
The mask 1?0 depicted is sized to cover the open end faces 128 and 129 of the structure 121. Protrusions 1~6 are provided on the mask 120 to fitably engage each cell which is not to be charged with a sealing material through the mask. It should be appreciated that a protrusion need not be provided for each cell which is not to be charged at the covered end face and that many of the protrusions 126 on the exemplary mask 120 of Figs. 8 through 11 could have been eliminated without detrimental effects. Inde~d, because cells at the periphery of an end face may have partial or reduced cross-sectional areas which will make fitting a full-sized protrusion difficult or impossible, it may also be desirable in some applications to reduce the surface area of the mask to less than that of the end faces allowing the cells at the periphery of the end face to be charged, or, if that is unacceptable, to eliminate the protrusions at the outer edge of the mask. Similarly, in certain applications it may also be desirable to omit openings through certain areas of the mask so as to leave two or more adjoining cells unplugged.
Care should be taken to account for any shrinkage which occurs in the fabrication of the mask. If a polymer-~5 izable resin is used, it will typically experience shrinkageat a rate which will differ as the proportions of i~s components and the conditions under which it is cured are varied. Exact sizing of a mask to i~s honeycomb structure is prefexred as dimensional mismatch will mak~ the fitting of the mask to an end face more difficult. It was observed that if mask opening/protrusion spacing were excessively undersi~ed or oversi~ed with respect to the corresponding cell spacing the elastic protrusions would "knuckle under"
while an elastic mask was being pressed against the end face making fitting impossible. Some tolerance to elastic 3~6~

mask undersizing has been observed in applying masks approximately .125 inches (3 mm.) thick and having protrusions about .125 inches (3 mm.) long and about .07 inches (about 1.8 mm.) thick, openings about ~086 inches (about 2mm.) in diameter and a Young's Modulus of approxi-mately 3000 p5i (abou~ 211 kg/cm2) or less to honeycomb structures having cell densities o~ approximately 100 cells/
sq.in. (about 15.5 cells/sq.cm.) that for very small areas, approximately one-half inch (1.27 cm) in diameter, about 8 10 to 10% undersizing of the mask could be accommodated; at diameters of about 4 inches (10.16 cm) about 4~ undersizing of the mask could be accommodated; at a diameter of approximately 6 inches (15.24 cm) approximately 1% under-sizing of the mask could be ~ ted. No tolerance for elastic mask oversi~ing was observed although very minor oversizing (less than 1~) might be ~cc(~,.,.~dted. It is believed that approximately 1% undersizing over a 6 inch diameter area could be A~c~r~ted for other elastic masks (having a Young's Modulus of up to approximately 10,000 psi 20 (about 703 kg./sq. cm.)). Undersizing o the mask to the stxucture is depicted in Fig. 14f with reference to the centerlines 163 of adjoining protrusions 126 and the centerlines 164 of the cells 127 with which they engage.
Fig. 9 is a view of the outer surface 124 o the 25 mask 120 shown in Fig. 8 and depicts a portion of its openings 125 and protrusions 126. The openings 125 and protrusions 126 are alternated with one another along rows and columns parallel or perpendicular to the line 10-10 so as to coincide with the rows and columns of cells 127 30 at the end faces 128 and 129. Each opening 125 and protrusion 126 of the mask 120 in Fig. 9 will be positioned juxtapose one cell 127 when the mask 120 is applied to either end ace 128 or 129. As the mask 120 has been ~abricated to it and expose in a checkered pattern the 35 squaxe cells o the honeycomb structure 121, the ~3~Q

openings 125 and protruslons 126 are formed in rows mutually parallel to the line 10a 10a. The line 10a-lOa bisects a row of evenly spaced protrusions 126. Rows of evenly spaced openings 125 and evenly spaced protrusions 126 are alternated with one another across the mask surface 124 to either side of the row of protrusions bisected by line 10a-lOa. These rows of protrusions 126 and openings 125 will align with the diagonals of the cells 127 when the mask 120 is fitted to the end face 128 or 1290 If a 10 plugging material is charged through the openings 125 in the mask 120, the open ends of the cells 127 in an adjoining end face 128 or 129 will be filled in a checkered or checkerboard pattern as is indicated in Figs. 12 and 12a.
The mask 120 may be hand fitted to an end face lS 128 or 129 of a honeycomb structure in the manner depicted in Fig. 10~ It is suggested that the protrusions 126 at or near one outer edge of the mask 120 be fitted into corresponding cells 127 near an edge of the end face. The mask may be moved laterally for very short distances in a 20 variety of directions across the end face and rotated in opposing directions to start the engagement of one or more of the protrusions with appropriate cells in the end face.
Other protrusions 126 are fi~ted into appropriate corres-ponding cells in directions radiating from the initially 25 aligned protrusions as indicated by the arrows extending across the outer surface 123 o~ the mask 120 in Fig. 10.
It is helpful to stretch an undersized mask and vibrate i~
slightly back and forth across the end face 128 or 129 during this process to align the protrusions 126 with the 30 appropriate cell ends. Once it is sensed that the protrusions have aligned with underlying cells, the outer surface 123 of the mask is pressed down to insert the aligned protrusions into the cell ends. This process is continued until the mask 120 is fitted flush across the 35 entire end face 128 or 129 of the structure 121.

3~

A solid particulate filter body is formed by charging a flowable sealing material through the openings 125 in the mask 120 into a subset of alternate cells at one end face 128 or 129, remo~ring the mask 120, applying it or a comparable mask to the remaining end Eace of the structure 121 with the openings 125 aligned over the remaining alternate cells and charging the sealing material into those cells. The structure and sealing material may be cured or fired, if appropriate. Foam-type cordierite ceramic cements, which are compatible with the aforementioned cordierite structures and chargeable with the subject mask, are described in the aforesaid co-pending Canadian application Serial No. 380,875 entitled PARTICULATE FILTER AND MATERIAL FOR PRODUCING THE SAME, filed June 30, 1981, and a preferred composition of this cement is described in the aforesaid European application No. 81302986.5. A foamable particulate ceramic cement capable of forming a sintered cordierite foamed ceramic mass may consist essentially, by weight, of: 1-40%
cordierite grog, 99-60~ ceramic base material and an effective amount of a foaming agent to effect foaming of the cement upon firing to produce the foamed ceramic mass.
he base material is a raw ceramic material that has an analytical molar composition consisting essentially of about 1.7-2.4 MO 1.2-2.4 A12O3 Ds.5-5.4 SiO2 wherein MO comprises, as mole % o MO, about 0-55% MgO and at least 45% MnO. ~rhe grog is a ceramic material that has been previously fired and conaninuted, and that has an analytical molar composition consisting essentially of about:
1.7-2.4 RO 1.9-2.4 A12O3 ~ 4.5-5.2 SiO2 wherein RO
comprises, as mole % of RO, MnO in an amount of 0% up to a mole % that is about 20 mole 9~ lower than the mole of MO that is MnO and the balance is substantially MgO.
It is envisioned that the subject masks may also be used 35 to charge non-foaming ceramic cements as well as other 3C~

flowable materials of various viscosities into selected cells of honeycomb structures for ~arious applications.
A filter body formed from the structure 121 of Figs. 8 through 11 is depicted in Figs. 12 and 12a with alternate cells 127 sealed in a checkered pattern on end face 128. This pattern is reversed on the end face 129 as can be seen in part in Fig. 12a, a cross-sectioned view along a row of the cells in the filter body of Fig. 12 depicting the plugs 132 formed by the sealing material 10 charged through the mask openings 125. Flow of a contam-inated fluid through the filter is indicated in Fig~ 12a by arrows 134. The contaminated fluid enters through the "inlet" cells 127 open at the left ("inlet") end face 128, passes through the thin, porous walls 130, into 15 adjoining ~'outlet" cells open at the right ("outlet") end face 129, and in the process leaves the cont~m;nAnts too large to pass through the walls 130 in the inlet cells open at end face 128. Additionally the plugs 132 may be formed with open porosity equal to or less than that of the thin 20 walls 130 and allow some fluid flow therethrough which will not impair the operation of the filter body. Operation of the filter is described in more detail.in the aforesaid European application No. 81302986.5.
A second aspect of the invention is die apparatus 25 and methods for using the same to fabricate a flexible or elastic mask similar to that depicted in Figs. 8 through 11.
A first mask ~orming apparatus is depicted in cross section in Fig. 13a and consists of a mold 140 having a mask forming outer surface 141~ typically planar, and a multiplicity of 30 bores 142 extending through the mask forming surface 141 and mold 140 in directions essentially normal to the mask forming surface 141. A cavity 144 in which the mask body i.s formed is defined by a ridge 143 which extends outwardly from the mask forming surface 1410 The bores 142 form the 35 protrusions 126 of the mask and are desirably tapered inwardly as they extend away from the mask forming 3~

2~

surface 141, preferably at an included angle between approximately 10 and 50 degrees. A~ter being cast in a manner to be subsequently described, the mask is removed from the mold 140 and openings 125 made through the body of the mask 120 at selected locations among the protruslons 126 as indicated in Fig. 13b. The openings 125 may be made by any suitable means such as but not limited to boring, cutting, drilling (depicted), burning and melting. If formed from anelastic polymer, the mask may be chilled to make the operation easier to perform. In the pre~erred embodiment, the openings 125 are also essentially normal to the outer downstream surface 124 of the mask 120 from which the protrusions 126 extend.
Fig. 14a depicts a cross-sectioned profile ~iew a second mask forming apparatus. Like the first apparatus of Fig. 13a, the second apparatus of Fig. 14a consists of a mold 150 having a plurality of tapered bores 152, a mask forming surface 151, and a ridge 153 which forms with the mask forming surface 151 a cavity 154 within which the body of the mask is formed. The second apparatus further includes a plurality of means 155, such as pins, for forming an equal plurality of openings through the mask. It is preferred that the tops of the means 155 form a common plane with the top of the ridge 153 to assist in forming a flat outer surface on the mask, as will be subsequently described~
A mask 120 formed within the apparatus of Fig. 14a is depicted in cross-section in FigO 14e and has a pair of opposing outer surfaces 123 and 124, a first plurality of openings 125 extending through and between the outer surfaces 123 and 124, and a second multiplicity of protrusions 126 extending from the outer surface 124. Again, the protrusions 126 are preferably tapered downward at an included angle of between about 10 and 50 degrees and the protrusions 126 and the openings 125 extend essentially normally from the outer surface 124.

33 13~

Simple working models of die apparatus corres-ponding to those depicted in ~igs. 13a and 14a through 14d can be formed from transverse cross-sections of the honey-comb structures with which the masks are to be used. To form the die of Fig. 13a, the cells of a honeycomb section are filled with an easily removed solid material such as wax and affixed to a supporting plate using wax or a suit-able adhesive. The wax or other solid material is removed from selected cells in which protrusions of the mask will 10 be formed. The outer perimeter of the sectioned structure is then surrounded with a collar to form ridge 143 and a selected polymer is cast in the mold thus formed~ A die apparatus similar to that depicted in Figs. 14a through 14d may be formed by the additional insertion of pins into 15 selected cells of the sec-tioned structure. A Conap, Inc. No.
TU-65 urethane was mixed according to directions and cast in such an apparatus to establish the ~easibility of the casting processes. ~fter a room temperature cure for about 18 hours, the solidified mask was remo~ed from the die and 20 oven heated at about 200 Fahrenheit (93 Centigrade) for about 16 hours to complete curing. Preferably, however, the die apparatus is fabricated from a rigid, machinable mat~rial such as metal for precise dimensioning o the ~ormed mask. It will urther be appreciated that the die 25 apparatus of Figs. 13a and 14a through 14d can be constructed in two pieces consisting o~ a flat plate having a mask forming surface~ 141 or 151 with, in the latter case, openings forming means 155 protruding therefrom and bores 142 or 152 extending therefrom and therethrough and a second plate 30 having a center cutout which is attached to the first plate 140 cr 150 to provide the ridge 143 or 153 forming the cavity 144 or 154.
A mask is formed in the mold 150 in the manner depicted in Figs. 14a through 14d. The mold 150 is cleaned 35 with a suitable agent such as acetone or xylene prior to ~3~

forming each mask. After cleaning the inner surfaces of the mask forming cavity 154 and bores 152 are coated with a suitable releasing agerlt, such as a 20:1 ratio by weight solution of methylene chloride and JohnsonTM Paste Wax.
A suitable polymerizable resin ("polymer'!) is mixed and de-aired by an appropriate device such as a vacuum chamber.
A mass o~ mixed and de-aired polymer 156 is applied to top of the mold 150 and is worked into the cavity 154 and bores 152 with a suitable tool 157 such as a spatula or putty 10 knife. The mold 150 may be mounted on a vibrator platform 158 and/or a vacuum source 159 may be applied to the ends of the bores 152 opposite the mask forming surface 151 in order to work the polymer into the bores 152 and recesses of the cavity 154. Other devices such as ultrasound sources 15 (not depicted) may be employed in working the polymer into the cavity 154 and bores 152. The surface of the polymer is leveled with the upper surfaces of the ridge 153 and opening forming means 155 with the tool 157. The extrusion of the polymer material through all of the openings of the 20 bores 152 at the bottom surace 161 of the mold 150 i.ndicates that the cavity 154 and bores 152 are filled.
The tops of the means 155 then are scraped clean with a sharp edge 160 such as a razor as depicted in Fig. 14b, leaving a smooth outer face on the molded po]ymer. The 25 polymer is then cured in a manner appropriate for the materials selected. The curing of many polymers may be accelerated by baking as is depicted in Fig~ 14c. After baking, the mold 150 and cured polymer are removed from the oven and are allowed to cool. Once the mold 150 is 30 sufficiently cooled to be handled, the polymer extruded through the bottom of the bores 154 and beyond the bottom surface 161 of the mold 150 are removed by suitable means 162 such as a razor blade or scraper as indicated in Fig.
14d~ The cured polymer is then pulled from the mold and 35 trimmed to an appropriate size, if required. Except for ~3~

the cleaning of the pin tops (Fig. 14b), the same steps are followed in casting a mask in the mold 140 (Fig. 13a).
Again, openings must be formed through ~he mask af~er its removal from the mold 140 (~ig. 13b).
Yet another apparatus, an envisioned compound die for ~orming a mask, is depicted in an exploded view in Fig. 15a and in a sectioned profile view in Fig. 15b, and consists of a first die piece 165 having means 166 to form the plurality of openings in the subject mask, a second 10 die piece 167 for forming the flexible protrusions extending from one face of the mask and a third die piece 168 positioned between the die pieces 165 and 167 for stripping the subject mask from the die after being formed. This compound die apparatus allows faster and easier mask 15 fabrication than either of the die appara us depicted in Figs. 13a and 14a through 14d. The first die piece 165 has an essentially planar bottom outer surface 169 (hidden) from which extends a plurality of means 166 such as pins or tubes for forming the openings 125 in the mask 120 20 (see Figs. 8 through 11). The second die piece 167 has an upper outer surface 170 designed to contactably mate wîth the ends of the means lh6. For ease of use it is suggested that the ends of the means 166 be flat and form a common plane and that the outer surface 170 of the 25 second di~ piece 167 also be planar. The second die piece 167 is further provided with a plurality of bores 171 extending therethrough from the outer surface 170. The walls of the bores 171, which form the protrusions 126 of the mask 120 (Figs. 8 through 11~, extend normally away 30 from the outer surface 170 for a short distance and then taper inwardly, suggestedly at an included angle of between approximately 10 and 50 degrees as they extend away from the outer surface 170. The third die piece 168 is essen~ially planar and is positioned within a cavity 172 35 foxmed between the first and second die pieces 165 and 167, ~;~03~

respestively, when the opening forming means 166 are positioned against the second piece outer surface 170 (see Fig. 15b). The third die piece 168 is pro~ided with a second plurality of bores 173 equal to the number of means 166 which are positioned and sized so as to allow the third die piece 168 to be slid along the means 166 and positioned against the surface 169 of the first die piece 165 with the means 166 extending completely through ~nd protruding from lower surface 174 of the third die piece 168. The 10 tolerances between the plurality of bores 173 and means 166 should also be sufficiently tigh~ to prevent the intrusion of polymer and the formation of flash during the fabrication of the mask. However, if flash is formed it may be removed by suitable means such as water jetting or burnishing. The 15 mask is formed between the lower surface 174 of the third die piece 168 and upper surface 170 of the second die piece 167.
A mask may be cast in the third die apparatus in a manner similar to that used with the first two die 20 embodiments. The die pieces 165, 167 and 168 are cleaned and a removal agent applied to the mask ~orming surfaces.
~ ~uitabl~ polymer is mixed, de-aired and applied to the upper ~ace 170 of the second die piece 167 and is worked into the bores 171. The second piece 167 may be formed 25 with a ridge 175 to contain the polymer during this process.
The mated first and third die pieces 165 and 168 are pressed against the second die upper surface 170 and held in place by suitable means 176 such as clamps (depicted) or screws or nuts and bolts during the curing of the polymer.
30 If the peripheral ridge 175 is provided, it should be low enough so that one or more narrow gaps 177 are formed around the cavity 172 through which excess polymer material may be squeezed (see Fig. 15b~. The third die piece 168 is held against the first die piece 165 by the polymer 35 between the piece 168 and the second die piece 167. After curing, polymer extruded through ~he tapered bores 171 is ~3~0 again removed by a suitable tool such as a razor knife (see Fig. 14d). The means 176 used to hold the three die pieces together are removed and the second die piece 167 removed from the first and third die pieces 165 and 168.
Frictional forces will hold the mask 120 to the opening forming means 166 extending through the mask forming lower surface 174 of the third die piece 168. This mask forming lowersurface 174 eliminates the separate upper mask surface forming step required in the first two die embodiments (see particularly Figs. 14a and 14b). The mask 120 thus formed within the cavity 172 and tapered bores 171 may be stripped from the opening forming means 166 by sliding the third die piece 168 along the means 166 away from the first die piece 165. If desired or necessary, the formed mask may be trimmed to a suitable shape for use.
Comparable die pieces may also be used for injection molding of the mask. In an injection molding apparatus, means are provided for injecting the polymer or other flowable material into the cavity, such as through the qap(s) 177-Sintered honeycomb structures with which the described mask have been used, typically experience shrinkage during their drying and sintering cycles which vary with compositional and drying/curing schedule ~5 variati~ns. By varying polymer mixturss and/or curing schedules, the shrinkage and thus the relative dimensions of the flexible mask fabricated may also be controllably varied. In this way, a single die apparatus may be used to fabricate different masks accommodating honeycomb 3Q structures experiencing slightly different shrinkages.
Again, exact sizing of the mask to the structure is desired but to the extent that that goal cannot be achieved slight undersizing is preferred to oversizing. Several silicone formulations have been successfully cast using a 35 die apparatus similar to that depicted in Figs. 14a

3~

through 14d ~ormed from machined brass plates incorporating steel, opening forming pins. In each case, the polymer components were mixed,de-aired with an approximately 28 inch (:71.l cm.) mercury vacuum for abou~ 20 minutes, applied to the die apparatus and heated for about 8 to lO minutes at about240 to 260 Centigrade to accelerate curing. After cooling and removing from the die apparatus, some masks were subjected to an additional post-curing cycle in which each was again heated at approximately 230 to 250 Centi-grade for about 16 hours~ In each such case, post-curing yielded additional shrinkage. Silicone mixtures which have been successfully cast and their observed linear shrinkage from original die ~i~en~ions under the aforesaid oven curingand where indicated, post-curing schedules are as follows (.all % are by volume except where otherwise indicated~.

ADDITIONAL TOTAL
CURE POST-CURE SHRINK-SHRINKAGE SHRINKAGE AGE %
POLYMER % (APPROX.~ %(APPROX.) (APPROX.) l. Dow Corning Q3-9595*
silicone resin (.50%
A component mixed w.ith 50% B component~ 3.0-3.3 0. 5-0. 8 3.8-4.0 25 2. Dow Corning Q3-9590*
silicone resin (.50% A
component mixed with 50~ B component~ 2. 3-2.6 l.4-l.7 about 4.0 3. Dow Corning Q3-9595*
(.50% component A mixed with 50~ component B~
mixed with additional 10% (by weight~ Dow Corning X3-6596A* sili-cone resin (A compo-nent only). 2~8-3.0 0.8-l.0 3.8-4.0

4. Dow Corning X3-9592*
(50% A component mixed with 50% B component1 2.5-2. 8 0.7-l.0 3.2-3.5 *Trad~ar.k 3Q~

ADDI:TION~,L TOTAL
CURE POST-~U~E 5HRINK-SH~ INKAGE SHRINKAGE AGE 96 POLYMER - % (:APP~:OX. ~ % (APPRO~. ~ (APP:ROX. )

5. 50% (by weight) Dow Cornin~ Q3-9595* B com-ponent silicone resin mixed with 50~ (hy weight) Dow Corning X3-6596*A component silicone resin 2.8-3.0 about 1.0 3.8-4.0

6. Dow Corning X3-6596*
silicone resin (50% A
component mixed 50% B
component) 1.9-2.1 0.7-0.9 2.7~3.0

7. 25% (bv weight)Dow Corning Q3-9590*sili-cone resin (50% A
component mixed with 50% B componentl mix-ed with 75% (by weightl Dow Corning X3~6596* silicone resin (50~ A component mixed with 50~ B component~ 2.2-2.4 1.0-1.2 3.5-3.7 3. 25% Dow Corning Q3-9590*silicone resin (50% A component mixed with 50% B com-ponent) mixed with .
75~ Dow Corning X3-6596*
silicone resin (50~ A
component mixed with 50~ B component) 2.5-3.0 9. 90% Dow Corning Q3--9595*
silicone resin (50% A
component mixed with 50% B component~ mixed with.10% Dow Corning 3X-659Ç*A component silicone resin 2.5-3.0 10. Dow Corning No. 732*
silicone resin (.50%
A component mixed with 50~ B component~ 1.3 *Trademark ~3~

ADDITIONAL TOTAL
CURE POST--CURE SHRINK-~IRINKAGE SHRINKA~E A~:E %
POLYMER % (APPROX. ) % (APP~OX. ) (APPROX.
11. Dow-Corning No. 734*
silicone resin (50%
A component mixed with 50% B component) 1.8 Silicone oils have also been added to silicone resins to obtain even greater shrinkages. In each case, the oil was mixed into a mixed silïcone resin, de-aired, cast and heated in a mold throu~h the a~oresaid curing schedule (230 to 260 Centigrade for 8 to 10 minutesl but was subjected to a post-cure baking at about 230 Centigrade ~or only about 4 hours.
mhe mixtures examined and their cuxe, additional post-cure and total shrinkages are as ~ollows (all ~ are ayain by volume unless otherwise indicated).
ADDITIONAL TOTAL
CURE POST-~URE SHRINK-SHRINKAGE SHRINKA~E AGE %
POLYMER %(APPROX.) ~(APPROX.) (APPROX.) 12. 82.5% (by weight)Dow Co~ning X3-6596* sil-icone resin (50~ A
component mixed with 50% B component) mixed with 17.5~ Dow 200 Sil-icone Oil 20CS* 2.6 2.8 1.8-2.0 4.4-4.6 13. 90~ (by weight) Dow Corning X3-6596* sil-icone resin (50~ A
component mixed with`
50% B component) mixed with 10~ Dow 200 Silicone Oil 500CS* 2.4-2.7 0.6-0.8 3.1-3.5 Other ratios and curing schedules should yield a range of shrinkages. At least one silicone resin, Dow Corning 184*, could not be cast on the aforesaid mold apparently due to in-teraction with the brass. Adverse reactions ma~ be encountered with other die material and polymer mixes.

*Trademark 3~

Yet ano~her aspect of the in~ention are methods and apparatus for maniolding selected cells of a honeycomb structure as w~uld be done during the ~abrication of solid particulate filter bodies, using the flexible, elastic masks heretofore described. An exemplary press apparatus 180 is depicted in cross-section in ~ig. 16. A flexible mask 120 and honeyco~b structure 121 are provided in the manner previously described. The mask 120 has been applied to an end face 128 of the honeycomb structure 121 with i~s protrusions 126 and openings 125 aligned with the ends o~
alternate cells 127 at the end face 128~ Slight under-sizing of the mask 120 will provide mechanical self-locking of it to the structure 121. Moreo~er, it is suggested that a flexible tubular collar 181 of a suitable material such as neoprene be stretch ~itted o~er the peripheral edges of the mask 120 an~ outer sidewall 131 of the structure 121 adjoining the end face 128 to assist in holding the mask 120 to the structure 121 and in sealing -the structure 121 over an orifice 183 on the upper face 194 of a press head 186. An adjustable, flexible clamp 182 is provided around the collar 181 so as to better secure it to the mask 170 and structure 121. The press apparatus 180 comprises the press head 186 supported by a frame 188. The head 186 is e~uipped with a piston 184 slidably mounted in a bore 185 for char~ing a cement mixture through the orifice 183 over which a honeycomb structure 121 is secured. Prior to charging, the piston 184 is backed away sufficiently from face 194 to form a chamber above the piston head which is loaded throu~h the orifice 183 with a suitable amount of a ceramic cement such as the foam~type cements previously referred to. The mask 12Q
and structure 121 ~ounting the collar 181 and clamp 182 are then placed over the orifice 183 and held in place by suitable means such as a bar 189 placed across the remaining end face 129 of the structure 121 and held into place by suitable means such as bolts 190 extenaing through the bar and into suitably threaded bores 191 o~
the press head 186. The piston 184 is ~hen ad~anced 3~

towards the exit orifice 183 b~ ~eans of a hand-operated screw 187 or other suitable means and, in the process, presses the ce~ent mass a~ove the piston 184, agains~ the mask 120, and through its openings 125 into the proximal open ends o~ the cells 127 juxtaposed to the openings 125 forming cement plugs 192. During this step, the flexible collar 181 also seals the circumferential edge of the orifice 183 preventing the cement from being forced out past the end face 128. Similar plugs 193 have already been formed in the ends of the remaining alternate cells 127 proximal the end ~ace 129 in a previous filling. The structure 121 may then be removed from the press apparatus 180 and the flexible collar 181 and mask 120 removed from the structure 121, which is ready for ~iring to sinter plugs 192 and 193 and structure 121, if appropriate.
Parallel work by the applicant has resulted in a double headed cement press for simultaneously filling both ends of a honeycomb structure using a pair of the subject masks. Where a pair of masks are used, they may be held in place during handling of the honeycomb structure before its insertion into the press by providing under-sized masks or by temporarily securing the masks to the end faces of the honeycomb structure with a mild adhesive which will allow their easy removal a~ter charging.
It is Purther envisioned that the subject mask 120 may be fitted across the feed orifice 201 of a filling device such as a cement press having a press head 200 as depicted schematically in Fig. 17 so as to feed a flo~-able material, in this embodi~ent a plastically formable cement, into a honeycomb struc~ure fitted to the filling device's fle~ible mask 120. The mask 120 is secured to the press head 200 in a suitable collar 202 by an annular plate 203 or other suitable means. The collar 202 is secured across the ~eed orifice 201 again by suitable ~eans such as threading 204 or fasteners (not depictedl.
The structure 121 is brought to the mask and fitted ~Z533¢0 ~

against its exposed protrusions 126. Cement (shading~
is ied into a ca~ity 206 ~ormed in the press head 200 bet~een a piston 205 and the upstrea~ face 123 of the mask 120 through appropriate ~eans such as feed kubes 207. The piston 205 is advanced as indicated by arrow 208 and forces the cement against the mask 120 and through its openings 125 into the open ends of the opposing subset of cells 127. It is further envisioned ~or ~abrication of solid particulate filter bodies and other honeycomb structures mani~olded at both tneir end faces that a second press head similar to the head 200 depicted be provided with an appropriate mask 120 for simultaneous charging of both end faces of the structure.
A pre~erred embodiment of a method ~or automatically fitting a subject flexible ~ask to a honeycomb structure will be described with xeference to ~igures 18-27.
According to the invention, a~ter being placed on the end face 312, as indicated by the arrows 322, the mask 311 is rapidly vibrated about and around the center o~ the end face 312 until it moves into lateral and angular alignmen-t with its protrusions 315 enga~ing the cells 316.
In Fig. 18, the honeyco~b structure 310 has been positioned on the surEace 323 o~ a mechanical vibration source.
Preferably the surface 323 imparts a rotational vibrating motion. A suitable device has been constructed by mounting to the base of a commercially available rotary vibratory parts feeder in place of its feeder bowl, a flat plate.
The surface of the plate rotates back and forth through a short arc about its center, the motion being sharp in one direction and relatively slower in the return direction.
The surface experiences no net lateral or rotational movement but a su~icient]y light object (such as a structure and mask~ placed upon its sur~ace will rotatel and, if placed o~f-center fxom the rotational axis, orbit in short hops about the rotational axis. Desirably, means are also provided to control the amplitude of ~he v;bra-tory motion generated and thereby control the rotationalspeed of the mask and/or structure. Yibration amplitude o~ the previously re~erred to parts ~eeder ~as controlled by means of a rheostat. A Yibrational frequency o~ about 60 hertz has been used to seat the described masks but it is envisione~ that a ~ide range of ~requencies, approxi-mately 30 to 200 hertz or more, may be employed success~ully in seating the described flexible masks.
Other ~requency ranges may be found desirable for other applications of the invention. Rotational vibration is transmitted ~rom the surface 323 to ~he mask 311 resting on the end face 312 through the structure 310 which is preferably centered over the axis o~ rotation o~ the surface to minimize lateral movement of structure 310 and mask 311. Alternatively, it is envisioned that the mask 311 mav be directly contacted by a vibration source and vibrated into aligNment. Also it is envisioned that the positions of the mask 311 and structure 310 may be reversed with the mask 311 on the surace 319, its protrusions extending upwards. Although random, linear or orbital (planar, orbitting movement without rotation of the vibrating plane) vibration may be used, rotational vibration in the plane between the end face 312 and mask 311 is preferred as it causes the mask 311 to rotate steadily around the end face 312 ~acilitating angular as well as lateral alignment. Rotation of the mask with respect to the end face may have to be otherwise accomplished if randon, linear or orbital vibration is used. PreferablY, the structure 310 is temporarily held in position on the sur~ace 319 to better transmit the vibrational motion ~rom the sur~ace 319 ~o the mask 3110 The structure may be held by any of several suitable methods including the use o~ a removable temporary adhesive, clamps, or a pair of pins ox the like extending through the plat~orm surface and into a pair of the structure's cell ends sitting on the sur~ace 319.

~2~3~6C~

A collar 324 has heen attached to the side walls 318 o~
the structure 310 and e~tends a~o~e the end face 312 50 as to con~ine the ~ask 311 within the collar~ In this ~anner, the lateral movement o~ the axial center of the mask 311 across the end face 312 is limited to a small predet~rm;ned area about the axial center of the end face 312. The ~aces 320 and 321 o~ the mask 311 can be appropriately sized to define the size of the area about the axial center o~ the end face 312 in which axial center of the mask 311 is confined. It is envisioned that in some configurations, proper alignment of a mask 311 and end face 312 or 313 may be achieved simply through orbital vibration without the use of a constrain~ such as the collar 324. Other means of lLmiting the lateral movement between the mask and honeycomb structure will be described subsequently.
To fabricate the solid particulate filt2r body 325 the mask 311 is aligned over the end ~ace 312 with i-ts openings exposing a first subset of cells. A similar mask (not depicted) is aligned over the end face 313 of the honeycomb structure 310 with its openings exposing a subs~antially different subset of cells. The exposed cells 316 are plugged with a suitable material passed through the openings 314 of both masks. It will be appreciated, of course, that each end ~ace may be covered with a mask and filled in sequence or ~.hat both end aces may first be covered and then filled sLmultaneously or in sequence. The filter body 325 of Figs. 20 and 21 has been formed ~rom the structure 310 of FigsO 18 and 19 by plugging the cells 316 in a desired checkered pattern at the end ~aces 312 and 313. The pattern of plugged cells on end ~ace 312, depicted in ~ig. 2C, is reversed on the hidden end ~ace 313 as can be ascertained in Fig. 21 where the filter body 325 has been sectioned along a line Crow or column~ o~ cells 316 revealing the plugs 326 formed in alternating cell ends along the line.

~3~36~

To achieve the checkered plugying pattern e~h;hjted by the filter body 325 in Fiys. 20 and 21, the openings 314 of the mask 311 used with the structure 310 ~ere arranged in mutually parallel rows and colu~ns across the mask sur~ace with pro~rusions 315 located there~
between to engage all or sub~tantially all of the remaining alternate cells at the end ace. It will be appxeciated that for various applications other than filtering, it may be desirable to plug some cells at both their ends, to leave some cells unplugged or both.
Also, plugging patterns other than the depicted checkered arrangement may be employed. In each case, however, the plugging pattern on each end ~ace of the ilter body will be substantially, if not, identically, the reverse of that at the remaining end face. Typical fluid flow throu~h the îlter body 325 is indicated by the arrows 328.
The aligning of bodies, such as flexible masks to honeycomb sur~aces such as the described end faces, may be automated. For the fabrication o solid particulate filter bodies, automation is simpliied by using particu-lar honeycomb structures and masks to assure proper cell exposure through the masks at the two end faces.
A first embodiment comprises in part a honeycomb structure such as the structure 310 of Figs. 18 and 19 with the axial centers of its end faces located at or approxi~ately at the center of the transverse cross-sectional area of one of its square cells. A pair of so-called "reverse" masks is also provided. The openings 314 of each of the reverse ~asks will expose completely or substantially different subsets of cells when each o~ the masks is identically located on an end face of this honeycomb structure. Fig. ~2 depicts the area of an end ace 312 or 313; about its central cell 329 and adjoinin~ cells 316 o~ the s-tructure 310 arranged as they are arranged across ~he end ~aces 312 and 313 in rows and columns~ The cells 316 are divided into alternate ~3~

subsets ~hich are identi~ied by "X's" and "O's" and yield the desired checkered patte~n o~ plugged cells illustrated in Figs. 20 and 210 The "X's" and "o's" also ~epresent the locations of openings and possible protrusions, respectively in one o~ the reverse masks and the con~erse on the other reverse mask of the pair. Again, a protrusion typically but not necessarily islocated opposite each cell end not to be filled. Each reverse mask is fitted to an end face by approximately centering the mask against the end ~ace (i.e. positioning the mask with its axial center within the confines of the central cell 329 or sufficiently near to the central cell so that the axial center o~ the mask is prevented from aligning over any cell other than the central cell 32g due to the thic~ness o the protrusions) and vibrating the mask into alignment. Again, means such as the collar 324 (see ~ig3 18~ are preferably provided to assure that the axial center o~ the ~ask aligns over the center cell 329. This area within which the axial center of the mask is initially positioned and later confined during alignment is centered at the center of the central cell 329, and, in the case o~ the uniformly sized cells 316 depicted, can have a maximum diameter at least as great as a cell pitch (i.e. the distance between the centers of adjoining cells in a row or column~, and may have a some-what greater diameter, dependin~ upon the diameters of the protrusions at their tips, but in no event will the maxim~ diameter be as great as twice the magnitude of a cell pitch as this would allow the mask to center over a cell other than the central cell 329. Each of the reverse masks will align opposite the center cell 329 in one of four possible angular orientations separated by 90. On the mask having its protrusion locations represented by "X's", apart ~ro~ the protrusion which may be provided to engage the central cell 329, the four protrusion locations closest ko the axial center o~ the ~ask will always align in those four cells lying along the 3~

diagonal lines a, b, c, and d and the ~ask will always expose the same subset of cells indicated by the "o's".
Similarly, the four protrusion locations closest to ~he axial center of the remaining reverse mask (:represented in Fig. 22 by the "O's" about the central cell 329~ will always align only in the cells lying along the ~ertical and horizontal lines e, fl g and h.and expose only the cells identified by "X's". It will be noted that in this embodiment, the positions o~ the plugged cells at the end faces of the filter ~ody are not congruently spaced when measured from the center of the central cell at each o~
the end faces. Similarlv, the openings 314 in each of the revexse ~asks will not be congruently spaced be-tween the masks when measured with respect to their axial centers.
Two other embodiments are depicted with respect to Figs. 23 and 24 and utilize a pair of identical masks with a honeycomb structure having the axial centers of its end faces in a thin wall between cells. The honey-comb structure 310 may again be provided circular end faces 312 and 313, the axial centers of which are located in the center o~ or near the center of a thin wall 317:
in one embodiment at or near the mid point o~ a length of wall between adjoining cells 316, as indicated by the point 330 in Fig. 23 ! and in another embodiment at or nea.r the intersection of a pair of thin walls, as indicated by the point 331 at the intersection of the thin walls numbered 317 and 332 in the same figure~ A pair of identical circular masks are used, again having openings 314 and protrusion locations 31$ alternated in rows and columns as indicated in Fig~ 24 corresponding to the rows and columns o~ cells of FigO 23. Their axial centers lie, in the first embodiment, between an opening location and an adjoining protrusion location as represent~d by the point333 (when used with end faces centered at ~he point 3301, and, in the second embod~lent, between four ad-joining opening and protrusion locations as represented ~3~

by the point 334 (when used wi~h end ~aces centered at point 331), as depicted in Fig. 24. A mask ha~ing its axial center at the point333 ~hen aligned on the end faces 312 and 313 with that point over the point 330 will lie in one of two orientations 180 apart. Each orientation will expose a diferent subset of cells indicated by the "X's" and "O's", respecti~ely, in Fig.
23. A mask ha~ing its axial center at the poin-t 334 when aligned on an end face 312 or 313 with that point over the point 331 will lie in one o~ four orientations 90 apart. Each orientation will again expose one of the two subsets of cells indicated by the "X's" and "O's"
in Fig. 23, the subsets of cells exposed by adjoining orientations (i.e. those separated by 90) being different while those exposed by opposite orientations (i.e. separate by 180) being the same. In either case, alignment of the mask and end face axial centers can again be achieved by approximately centering the mask agains-t the end face (i.e. positioning it with its axial center within an area centered about the axial center of the end face and sufficiently small so that the mask will only align with its axial center opposing that of the end face) and vibratlng it into alignment while its axial center remains in that area. Again, this area will have a diameter somewhat less than twice the magnitude of the cell pitch, dependin~ upon the tip diameters oE the protrusions, but may always be as great as one cell pitch in magnitude regardless of the protxusion tip dia~eter.
It is envisioned that in some applications, it will be found that the masks may be appxoximately centered in selected initial angular orientations on the end face and ~ibrated into alignment in a preselected relative angular relationship. Alternatively, the proper relative angular orientation of the identical ~asks would be veri~ied in some automatic fashion to assuxe that when desired, di~ferent subsets of cells are exposed at each of the ~3~

end faces in the honeyco~b structure for plugging. One way would be to mark each m~sk in sQ~e way, say at a point on its periphery, so that the relati~e angular orientation of the two masks can be compared by suitable sensing equipment and circuitry to signal that desired relatiYe angular alignment is achie~ed. Another way would be to optically view either end ~ace of a structure having a pair of masks fitted or a structure having cells plugged at one end face and a mask fitted to its remaining end face to ascertain if light is passing through the structure between the end ~aces. Appropriately aligned masks should allow no light to pass through the structure in the area where cells are to be alternately plugged. An appropriate signal can be generated to indicate proper alignment is achieved and that the structure is ready for plugging or that alignment was not achieved.
It is further envisioned that where elastic masks are being automatically fitted to honeycomb structures, it may be necessary to provide means to press the mask against the end face to assure complete insertion of the elastic protrusions.
Although the invention has been described with respect to aligning circular ~asks to circular end ~aces and square cell cross-sections, it is en~isioned that tha invention may be successfully employed with other end face and cellular geometries. Other desirable end ~ace geometries may include oval and race-track con~igurations.
Cellular geometries can be circular, oval or any suitable polygon shape, including triangle, hexagon, and any quadralateral. A corral, if provided in such cases, may be circular allowing 360 rotation of the body about the surface. In such cases, the axial center of the mask and end face will lie at the center of the smallest circular area in which the body or end ~ace ~ay be axially rotated 360, typically the midpoint of the longest transverse axis across the mask or end face Ce.g. the diagonal o~

~23~3~6~

a s~uare or rectangular ~nd face~. Alternatively, a non-circular corral ~y he used ~o limi~ the range o~
angular motion o a non~ircular mask so as to assure alignment in a particular or one of a limited number of angular orientations.
It is also en~isioned that a corral, i provided, need not be affixed to the honeyco~b structure as previously described, but may alternatively be affixed to some other stationary object or e~en affi~ed to the vibration source.
Moreover, it is envisioned that in some applications lateral and/or angular alignment may be assisted by the use o~ unusually siæed and/or shaped cells and protrusions provided at discrete locations on the body and surface to more particularly limit the lateral and/or angular orientation in which the body may align on the surface.
It is also envisioned that means other than a corral around the periphery of the ~ask (or honeycomb structure~ may be used to limit the relative lateral and, if desired, rotation~l motion between the body carrying the protrusions in the honeycomb surface. For example, a rigi.d member such as a pin or similar means may be passed through and between a mask and an end ace of a honeycomb structure as fixing their relati~e lateral positions during the vibrating step. In one embodiment depicted in Fig. 25, a member 340 has been inserted through an opening 341 at the axial center of a first reverse mask 311. The mask 311 with member 340 is positioned against an end face 312 o~ -the structure 310 as indicated by the arrows 342 ~ith the m~mber 340 extending into the central cell 329 of the end face 312.
The mask 311 is then vibrated into alignment. In this configuration, the mask 311 is free to rotate but is constrained in the lateral ~o~ement of its axial center~
The member 340 may then ~e removed through the mask 311 ~3~

and cement pressed through the opening 341 into the proxLmal end of the central cell 329 during the plugging step. In a second em~odiment, a solid rod 343 or the like may be passed through the length o~ a central cell 32~ o~ a honeycomb structure, as indicated in Figs. 26 and 26a. In Fig. 26, the rod 343 extends rom the central cell 329 at a ~irst end face 312 of the structure 310. A first reverse mask 311 similar to ~hat in ~ig.
25 and having a similar opening 341 at its axial center is positioned with the rod 343 through the opening 341 and vibrated into alignment. The structure 310 is then inverted, as indicated in Fig. 26a, with the rod 343 protruding from the remaining end ~ace 313 of the structure 310. The remaining mask 311a o~ the pair of reversed masks, which is also proYided with an opening 341a at its axial center, is placed over the rod 343 and against the end face 313 and vibra~ed into alignment.
The rod 343 is then removed Erom the structure for plugging of the alternate cells at its two end faces 312 and 313 through the masks 311 and 311a. The opening 341 or 341a at the axial center of the one reverse mask 311 or 311a that corresponds to a protrusion location in the plugging pattern o~ that mask is te~porarily capped to prevent the plugging o that end of the central cell 329. It is urther envisioned that two or more rigid members 344, as depicted in Fig. 27, may be provided between an end face 312 oE a honeycomb structure 310 and mask 311 to curtail relative rotational as well as relative lateral movement between the mask 311 and the end face 312. The membexs 344 may be inserted into any two of the openings 345 of the mask and the members 344 inserted into the proper corresponding cells at the end face 312. The protrusion 315 of the mask 311 may then be vibrated into engagement.
Lastly, relative movement between a first body member and a second honeyco~b sur~ace member need not ~l~g33~

be restricted by a means extending between the two members but rather ~ay be restr;cted by means, again such as a pin, extending between one of the two members and a ~ixed object. For example, a pin may be pro~ided protruding from the upstream face of the mask and the lateral motion o~ the mask restricted by fixed means such as a tube fixed in a ~rame which accepts and restricts the movement of the pin protruding from the mask to the inner diameter of the tube.
While fundamental novel features of the invention have been shown and described with respect to a preferred and other embodiments, it will be understood that various omissions, substitutions and changes in the form and details of the methods and apparatus heretofore described may be made by those skilled in the art ~ithout departing from the scope of the invention which is set forth in the following claims.

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A die for forming a flexible mask, said mask for use in bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of opposing end faces and a matrix of thin walls defining a multiplicity of hollow, open ended cells extending through said structure between said pair of end faces, wherein said mask apparatus is comprised of:
at least one base member adopted to be positioned across one end face, a plurality of flexible protrusions extending from each base member in the same direction and in special and shaped arrangement that permits each protruding member to register with, be inserted in an open end of one of said cells, and a plurality of openings at said one end face for providing open access to open ends of cells in said selected subset by said flowable material; said die comprising a die piece having a mask forming outer surface, a first plurality of bores extending through said mask forming outer surface and said die piece, and means extending from said mask forming outer surface for forming a cavity therewith within which said mask is formed.

2. The die of claim 1 wherein said bores taper inwardly as they extend from said mask forming outer surface.

3. The die of claim 1 further comprising means extending from said mask forming outer surface for form-ing a plurality of openings through said mask to constitute said means for providing open access.

4. The die of claim 3 wherein said means for forming a plurality of openings comprises a second die piece having an equal plurality of protruding members extending therefrom, said second die piece being positioned with said protruding members in contact with said mask forming outer surface.

5. A die for forming a flexible mask, said mask for use in bulk charging a flowable material into a selected subset of cells of a honeycomb structure having a pair of opposing end faces and a matrix of thin walls defining a multiplicity of hollow, open ended cells extending through said structure between said pair of end faces, wherein said mask apparatus is comprised of:
at least one base member adopted to be positioned across one end face, a plurality of flexible protrusions extending from each base member in the same direction and in special and shaped arrangement that permits each protruding member to register with, be inserted in an open end of one of said cells, and a plurality of openings at said one end face for providing open access to open ends of cells in said selected subset by said flowable material; said die comprising first die means for forming a plurality of openings to constitute said means for providing open access;
second die means positioned against said first means for forming said plurality of protruding members, said first and second means also forming a cavity therebetween; and stripping means positioned within said cavity for removing said flexible mask after being formed.

6. The die of claim 5 wherein said first die means comprises a first plate having an outer surface and a plurality of opening forming elements equal to said plurality of openings extending therefrom.

7. The die of claim 6 wherein said stripping means comprises a second plate having a plurality of bores equal to said plurality of opening forming elements extending therethrough and positioned with said opening forming elements extending through said bores.

8. The die of claim 7 wherein said second means for forming comprises a third plate having an outer surface against which said opening forming elements of said first plate are positioned and a third plurality of bores equal to said plurality of protruding members extending through said outer surface and said third plate.