US3575791A - Inclined continuous digester with mechanical conveying screws of decreasing pitch - Google Patents

Abstract

A CONTINUOUS DIGESTER UNIT COMPRISING PARALLEL SPACED INCLINED TUBES POSITIONED ONE ABOVE THE OTHER WITH THE LOWER END PORTIONS CONNECTED, AND THE TUBES ENCLOSING CORRESPONDING CONVEYER SCREWS CONSTRUCTED TO REDUCE THE VOLUME OF THE MATERIAL AS IT MOVES WITHIN THE TUBES AND ABSORBS LIQUOR FOR OBTAINING MAXIMUM CAPACITY AND SMOOTH FLOW WITHIN A MINIMUM AREA OF FLOOR SPACE. THE CONVEYOR SCREWS INCLUDE SPIRAL FLIGHTS HAVING A CONSTANT UNIFORM OUTER DIAMETER AND A DECREASING PITCH IN THE DIRECTION OF TRAVEL OF MATERIAL. THE TUBES ARE PIVOTALLY SUPPORTED IN THEIR INCLINED POSITION TO PERMIT POSITIONING OF THE TUBES IN A HORIZONTAL DIRECTION WHEN DESIRED.

Description

P 29, 1971 H. s. MESSING 3,575,791

INCLINED CONTINUOUS DIGESTER WITH MECHANICAL CONVEYING SCREWS OF DECREASING PITCH Filed May 1. 1967 5 Sheets-Sheet 1 I 2a 17 "A C n 88 17 L. D w

INVENTOR GA HJALMAR s. MESSING ATTORNEYS i 2Q, 3971 H. s. MESSING INCLINED CONTINUOUS DIGESTER WITH MECHANICAL CONVEYING SCREWS OF DECREASING' PITCH 5 Sheets-Sheet 2 Filed may 1, 196'? April! 26, "1%71 s, gssmc, 3,575,791

INCLINED CONTINUOUS DIGESTER WITH MECHANICAL CONVEYING SCREWS OF DECREASING PITCH Filed gay 1, 1957 s S hee:ts-Sheet s United States Patent O 3,575,791 INCLINED CONTINUOUS DIGESTER WITH MECHANICAL CONVEYING SCREWS F DECREASING PIT CH Hjalmar S. Messing, New York, N.Y., assignor to Mary Agnes Messing, Fort Fairfield, Maine Filed May 1, 1967, Ser. No. 635,012 Int. Cl. D21c 7/00 U.S. Cl. 162236 11 Claims ABSTRACT OF THE DISCLOSURE A continuous digester unit comprising parallel spaced inclined tubes positioned one above the other with the lower end portions connected, and the tubes enclosing corresponding conveyor screws constructed to reduce the volume of the material as it moves within the tubes and absorbs liquor for obtaining maximum capacity and smooth flow within a minimum area of floor space. The conveyor screws include spiral flights having a constant uniform outer diameter and a decreasing pitch in the direction of travel of material. The tubes are pivotally supported in their inclined position to permit positioning of the tubes in a horizontal direction when desired.

SUMMARY OF THE INVENTION This invention relates to cookers or digesters for treating solid material in fragmentary form, such as fibrous wood chips and the like. According to a preferred form of the invention, the digester incorporates one or more units each including a pair of parallel spaced tubes disposed in inclined position, one above the other. The upper tube encloses a conveyor screw including a continuous flight having a pitch which gradually decreases from the top of the tube, where the material is fed into the tube, to the bottom of the upper tube where the material is transferred by a downwardly extending cross channel to the bottom of the lower tube. The lower tube encloses a similar conveyor screw whose flight pitch gradually decreases from the bottom of the lower tube to the top of the lower tube where the material is discharged downwardly through an outlet.

In order to transfer the material downwardly through the cross channel, the lower end of the upper screw is preferably provided with a set of vanes pitched oppositely to the helix angle of the screw flight. The lower screw, at its lower end, has one or two flights having a larger pitch than the remaining helical flights thereon for receiving the material from the cross channel. The upper end portion of the lower screw also has a set of vanes pitched oppositely to the helix angle of the conveyor screw flight for directing the material downwardly through the discharge opening.

The shafts for the conveyor screws are preferably hollow to provide buoyancy to avoid sagging of the screws, and fluid pressure cylinders are provided for counteracting the weight of the screws and the material carried thereby. The unit is provided with means for handling expansion due to temperature change, as for example, the upper end of the lower tube is anchored to a fixed support while the lower end of the lower tube is slidably mounted on a fixed support. The upper portion of the upper tube is pivotally supported by a series of links extending from the lower tube while the lower portion of the upper tube is rigidly connected by the cross channel to the lower tube. Each conveyor screw may be independently driven by a hydro-mechanical drive such as a hydraulic motor operating through a gear reducer or the conveyors may be driven in fixed timed relationship by a single drive motor.

When multiple units are used, the second unit may be constructed similarly to the first unit and disposed under the first unit. A cross channel connects the upper end of the lower tube of the first unit with the upper end of the upper tube of the second unit. Means are provided for handling expansion of both units, and with units of substantial size, the cross channel of a single unit may be constructed in sections to permit the tubes to be shipped separately and assembled in the field.

A digester constructed in accordance with the invention not only provides an economic construction but is eflicient and reliable in operation. The digester also provides maximum capacity and uniform treatment of fibrous material within a minimum area of floor space, a significant reduction in the wear and the maximum stresses on the components, and smooth flow or transfer of material downwardly through the tubes.

Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a single digester unit constructed in accordance with the invention;

FIG. 2 is an enlarged view of the unit shown in FIG. 1 with a portion broken away to show internal construction;

FIG. 3 is a lower end view of the digester unit as taken along the line 33 of FIG. 2;

FIG. 4 is a section through the unit as taken generally along the line 44 of FIG. 2;

FIG. 5 is a section through the unit as taken generally along the line 5-5 of FIG. 2;

FIG. 6 is an upper end view of the unit as taken generally along the line 66 of FIG. 2;

FIG. 7 is an enlarged fragmentary, longitudinal section taken through the upper tube and with the middle portion broken away;

FIG. 8 is a side elevation of a two unit form of digester constructed in accordance with the invention;

FIG. 9 is a section view taken along the line 9-9 of FIG. 8;

FIG. 10 is a bottom end view of a modified form of single unit with upper and lower tubes removably connected;

FIG. 11 is a longitudinal section taken generally along the line 1111 of FIG. 10 and with the middle portion broken away; and

FIG. 12 is a section through the cross channel as taken generally along the line 1212 of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a single digester unit is shown in FIGS. 1-7. Generally this unit comprises an upper cylindrical tube or tank 10, a lower cylindrical tube or tank 11, connected by a lower cross channel 12. A rotary feeder valve 13 feeds pulp into the top of the upper tube 10 through a supply conduit .14 and a rotary discharger 15 removes the cooked pulp from the upper end of the lower tube 11 through a discharge conduit 16. The longitudinal parallel axes of both tubes are inclined at an angle of approximately 45 degrees to the horizontal.

The lines A and B indicate the level of the liquor, and lines C and D indicate the level of the pulp in the tubes. In lets 17 are formed within the upper tube 10 for the purpose of introducing liquor or steam and inlet 18 are formed in the lower tube 11 for the same purpose. Drain outlets 19, 20 and 21 are formed in the lower tube 11 for the purpose of draining liquor at these points. Each drain outlet is equipped with a strainer 22 (FIG. 2) to prevent discharge of pulp through the outlets.

The tubes and .11 are mounted on expansion supports (FIG. 2) to permit relative movement for expansion and contraction of the tubes due to changes in temperature of the tubes. The lower tube 11 is pivotally supported by a pin 23 extending through aligned holes formed within a bracket 24 mounted on the tube, and interfitting support member 25 resting on a column extending from the floor of the building. The lower end of the tube 11 has a foot 26 which is slidably mounted on a support 27 also resting on the floor of the building. The upper tube 10 is rigidly connected to the lower tube 11 by the cross channel 12 and is supported by the lower tube 11 through a series of links 28 (FIGS. 1 and 2).

Referring to FIGS. 1 and 5, the lower and intermediate sets of links 28 are pivotally connected to corresponding blocks 32 welded to the tubes 10 and 11. These connections are relatively loose so that the upper block can slide with respect to the lower block with expansion and contraction between the tubes. The upper links 28 are similarly connected to blocks 32 which are welded to the rings 33 as illustrated in FIG. 6. The supply and discharge conduits 14 and 16 connected to the rotary feeder 13 and rotary discharger 15 respectively, have sufficient flexibility to allow for the small expansion and contraction of the tubes 10 and 11. A flange 34 (FIGS. 1 and 2) extends from the bottom of the upper tube 10 and is adapted to be connected to a line from a hoist for tilting the unit on the axis of the pin 23 after the supply and discharge conduits are disconnected, until the axes of the tubes 10 and 11 extend horizontally.

Referring to FIG. 2, a conveyor screw 35 is positioned within the upper tube 10, and a conveyor screw 26 is positioned within the lower tube 11. These screws have continuous flights 37 and 38 each having a uniform outer diameter which is somewhat less than the inner diameter of its respective tube to provide ample clearance therebetween. The pitch between the flights 37 of the upper screw 35 gradually decreases from maximum at the feed conduit 14 to the lower end of the upper tube 10. The lower screw 36 has one or two flights 39 at its bottom which have an enlarged pitch, but the pitch of the remaining flights 38 of the lower screw 36 gradually decreases from the bottom of lower tube 11 to the upper discharge conduit 16. Except for the enlarged pitch of the flights 39, the pitch of the conveyor flights, considering both tubes as one, gradually decreases from the feed conduit 14 to the discharge conduit 16.

As shown in FIG. 2, each of the cylindrical tubes 11 and 10 are connected by an upper head 44 through a ring 46. The lower end portions of the tubes are connected by an end wall 47, an inner wall 48 and side walls 49 (FIGS. 3 and 4) which cooperate to form the channel 12 defining a passageway for transfering material from the upper tube to the lower tube. Ribs 51 (FIG. 4) reinforce the side walls 49 and a rib 52 (FIG. 2) reinforces the outer or bottom wall 47.

Referring to FIG. 7, the upper conveyor screw 35 includes a tubular or hollow shaft 53 around which extend the helical flights 37. Mounted on the lower end of shaft 53 are four radially projecting vanes 55 which have a pitch opposite the helix angle of the flights 37 and oppose the downward flow of pulp within the tube 11 for directing the pulp downwardly through the channel 12 into the flights 39 of lower conveyor screw 36.

At the uper end of the tubular shaft 53 is a stub shaft 56 which is secured to the shaft 53 by spaced disks 57. The stub shaft 56 passes through a seal 58 mounted in the head wall 44, and is journaled in outboard bearing 59 mounted on a bracket 60 secured to the head wall. A hydraulic motor 61 is mounted on a support plate 62 and drives the conveyor stub shaft 56 through a pinion and gear set indicated by 63.

A lower bearing 64 (FIG. 7) for the upper conveyor 4 screw 35 comprises an outer support sleeve 66 which is secured to the bottom wall 47 and is covered by an end plate 67. A tubular stub shaft 68 is secured within the outer shaft 53 and is enclosed by plug disks 69 and 70. The stub shaft 68 is journaled in the sleeve 66 by bearing sleeves 71.

A pressure pipe 72 is connected to the end plate 67 for applying steam pressure to the disk 69 connected to the lower end of the stub shaft 68. The steam pressure exerts an axial force upwardly on the screw shaft 35 to oppose the cooker pressure on the disk 7 at the upper end of the shaft 53. The submergence of the conveyor screw 35 in the liquor results in the sealed hollow shaft 53 producing buoyancy and lift which, together with the steam pressure on the closed end of the shaft 68, aids in offsetting the conveyor screws own weight and the weight of the conveyed pulp confined between the flights. The lower conveyor screw 36 is constructed, supported and driven in the same manner as the upper conveyor screw 35.

As an example of an upward force which can be produced by the lower bearing 64, the lower stub shaft 68 may have a 12-inch outside diameter providing an area of approximately 112 square inches. Thus a 150 p.s.i. steam pressure in the pipe 72 would produce a lifting force of approximately 16,800 pounds.

In a ty ical embodiment, the tubes 10 and 11 may each have a diameter of 48 inches and each tube may be forty feet in length. The screw speed may the in the neighborhood of one or two rpm. and the travel time of pulp passing through one complete unit, from inlet conduit 14 to discharge outlet 16, may be of the order of one hour. This would subject the pulp to approximately five minutes in the dry area at the upper end of the upper tube between lines A and C, about twenty five minutes to pass down through the liquor to the bottom of the upper tube, approximately another twenty-five minutes to pass up the lower tube through liquor to the line B, and thence about five minutes to pass through the dry area between lines B and D into the discharge conduit 16.

As mentioned above, the conveyor screws have a progressively diminishing pitch from the top of the top tube 10 to the top of the bottom tube 11 (except for the pitch enlargement of the flights 39), and this feature compensates for compaction of the material and its absorption of liquor during cooking of the material. Thus the invention utilizes the greater part of the inside volume of the cooker tubes for almost complete filling from end to end and crosswise through the channel 12, providing a capacity of approximately 85% of the total available volume.

The tubes will be filled with liquor and pressure ad justed as indicated by the liquor level lines A and B. Fresh liquor or steam is introduced into inlets 17 and 18 (FIG. 1), and spent liquor is removed through outlets 19, 20 and 21. The various feed and drain rates are so regulated as to provide the hydraulic gradient illustrated by the liquor level B in the lower tube 11 being lower than the liquor level A in the upper tube 10.

The transfer of material from one tube to the other is through the short, large area cross channel 12, and the flow of material and liquor through the channel is assured, either by maintaining suflicient hydraulic gradient as, for example, two feet, or by steam or liquor injec tion and extraction, assisted by gravity. That is, triple inlets 17 (FIG. 4) are provided at the cross channel 12 and assist transfer by directing jets of liquor through the channel which help to carry the material through the channel. As indicated diagrammatically in FIG. 1, a pump 75 may be connected to the lower inlets 17 and to outlet 19 to provide circulation of liquor at the lower ends of the tubes in the direction of the arrow.

FIGS. 89 show a two-unit embodiment of the invention wherein the upper unit comprises an upper tube and lower tube 81 and is supported by a column 82 resting on the floor and engaging a bracket 83 mounted on lower tube 81. The lower end of lower tube 81 has a foot 84 slidably mounted on a lower support 85. Tubes 80 and 81 of the upper unit are connected by a cross channel 86, and the upper tube 80 is fed by a rotary feed valve 87. The lower tube 81 is connected by a separable cross channel 88 to an upper tube 89 of the lower unit comprising parallel spaced tubes 89 and 90.

Upper tube 80 of the upper unit is supported by the lower tube 81 through links 91 in a manner similar to the links 28 of FIGS. 1, 2, and 6. The upper tube 89 of the lower unit has a bracket 92 secured to the column 82 and the lower end of lower tube 90 has a lower foot 93 slidably mounted on a support 94. The lower ends of tubes 89 and 90 are connected by a cross channel 95, and the upper end of the lower tube 90 is suspended from upper tube 89 by a series of links 101 pivoted to corresponding strips 105 welded to tubes 89 and 90 as illustrated in FIG. 9. A rotary discharge valve 106 connects with the upper end of the lower tube 90 of the lower unit.

The tubes 80, 81, 89 and 90 contain conveyor screws (not shown) which are constructed and driven in the same manner as the screws shown in FIGS. 1 to 7. Also the pitch of the four screws diminishes uniformly, starting with maximum pitch at the entrance from the rotary feed valve 87 and ending with the minimum pitch at the exit to rotary discharge valve 106. This decrease in pitch from feed valve 8 7 to discharge valve 106 is preferably uniform, considering the four tubes as a single unit. The several conveyor screws also support inclined thrust vanes (not shown) at the entrance to each of the cross channels 86, 88 and 95, and the conveyor screws have flights of enlarged pitch at the exit from these cross channels, all in a manner similar to the thrust vanes 55 and flights 39 in the unit shown in FIGS. 1 to 7.

In operation, the material is fed through the feed valve 87 down tube 80, up tube 81, down tube 89, and up tube 90 to the discharge valve 106. The upper sides of each tube have steam or liquor inlets 107 similar to the inlets 17 and 18 of FIG. 1, and the lower sides of the tubes have drain outlets 108 similar to outlets 19, 20 and 21 of FIG. 1. These inlets and outlets may be used to provide differential local treatments, as for example, the first treatment may be liquor impregnation, the second treatment may be cooking, the third treatment may be high heat washing, and the last treatment may be a cold wash before discharge. By proper control of pressure applied to the inlets and outlets, the local liquor circulations could be concurrent, or countercurrent with respect to the flow of material being treated, and the liquor levels may be maintained at the positions indicated by lines E, F, G and H.

FIGS. 12 show a unit in which the upper and lower tubes are separable for convenience in shipping. Except for the differences which are described below and illustrated in the drawing, however, the construction and operation is substantially the same as the embodiment shown in FIGS. 1 to 7. The separable unit comprises an upper tank or tube 115 and a lower tank or tube 116 connected by a cross channel 117 located generally tangentially near the lower ends of the tubes. The upper tube 115 has a lower end wall 118 supporting bearing 119, and lower tube 116 has lower end wall 120 supporting a bearing 121.

The cross channel 117 is formed in separable sections 122 and 123. Tubular wall of upper section 122 has an opening intersecting a wall opening 124 in the tubular wall of upper tank 115, the edges of these openings being suitably welded together. The lower section 123 is connected to the lower tank 116 in a similar manner. Cross channel 117 has an inlet 125 (FIG. 12) for steam or liquor and a guide plate 126 assists the flow of material from the upper tank 115 to the lower tank 116.

The lower section 123 has a screen 127 through which liquor may be discharged into outlet 128.

The sections 122 and 123 are connected by a flange coupling 129 which extends laterally to a point between bearings 119 and 121. Braces 130 and 132 connect the bearings 119 and 121 to the flange coupling 129 and braces 133 connect the bearing 121 to a support foot 134. The oifsetting of the axis of the cross channel 117 from the axes of tubes 115 and 116 has the advantage of providing more room to insert the bolts passing through the flanges of coupling 129 and also enables the tubes to be placed closer together in addition to providing for smooth generally tangential flow of material from the upper tube to the lower tube.

The separable form shown in FIGS. 10 to 12 may be supported for expansion and in an inclined position in a manner similar to the form shown in FIGS. 1 to 7. The lower foot 134 may be slidably mounted upon a support (not shown) similar to support 27. The upper end of lower tank 116 may be pivotally supported by a column (not shown) similar to column 25. The upper end of upper tank 115 may be supported by a series of blocks and link assemblies on the upper end of the lower tank 116 in a manner similar to the support afforded by the links 28-30 in FIGS. 17.

Referring to FIG. 11, the upper tank 115 encloses a conveyor screw journaled in upper outboard bearing 143 and the lower tank 116 encloses a conveyor screw 142 journaled in another outboard bearing 143. The upper conveyor screw 140 carries a gear 144 and the lower conveyor 142 carries a gear 145. These gears are driven in an opposite direction by an intermediate pinion gear 146 which, in turn, is driven counterclockwise by a hydraulic motor 147 looking in a direction from the drive end of the inclined tanks. Material is fed into inlet 150, passes down through tube 115, through the cross channel 117, up through tank 116, and is discharged through outlet 151.

From the drawings and the above description, it can be seen that a digester unit constructed in accordance with the invention provides desirable features and advantages. For example, the digester unit provides for submerged cooking of solids in fragmentary form and receives and conveys the material in such a manner to provide maximum capacity. That is, the reducing pitch of the helical conveyor screws slows down the movement of the solids as liquor is absorbed by the solids and thus produces a fill which efliciently utilizes almost 100% of the volume of the tubes. Furthermore, the location of one tube under the other and in an inclined position minimizes floor space and utilizes gravity feed to help in transferring the material from the upper tube to the lower tube. In addition, the distributed steam and liquor inlets and outlets permit flexibility in introducing liquor or steam and for draining liquor at desired points for maintaining the desired pressure differentials and liquid levels.

The hollow shafts of the conveyor screws adds buoyancy which is not only desirable during operation to make the screws weightless and thereby prevent the screws from sagging and rubbing the inner surfaces of the tubes, but is also desirable during assembly and dissassembly of screws into and out of their tubes. That is, during assembly and disassembly, the tubes may be filled with water to use buoyancy to facilitate introduction and removeal of the screws. The screws within the embodiment shown in FIGS. 17 can also be conveniently disassembled and reassembled by tilting the entire unit on the axis of the pin 23 until the tubes are in a horizontal position, thus enabling the screws to be withdrawn horizontally instead of having to be lifted out of the tubes.

The auxiliary vanes 55 with reverse pitch and located at the cross channels as well as the forced circulation of liquor at the lower ends of the tubes also assist in directing the material into the cross channels. In addition, the flights 39 with enlarged pitch at the exit of the cross channels help in receiving the material from the cross channels. Furthermore, the expansion supports provide for relative movement between the tubes due to differential thermal expansion and contraction and thereby minimizes stresses within the tubes. The digester of the invention also lends itself to use in the form of a single unit or as a plurality of units, and for larger sizes, the tubes of each unit may be shipped separately and the sections of the cross channel bolted or welded together in the field when the digester is erected.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A continuous digester unit for treating fibrous material, comprising a set of elongated cylindrical tubes each having end portions, means supporting said tubes in an inclined position with one tube generally above the other, channel means connecting the lower said end portions of said tubes and defining a passageway therebetween, a feed screw rotatably supported within each said tube and including spiral flight means having a constant uniform outer diameter, means defining a material inlet within the upper said end portion of the upper said tube, means defining a material outlet within the upper said end portion of the lower said tube, means for introducing treating liquor into said tubes and for maintaining a predetermined liquor level within the upper said end portion of each said tube, drive means for rotating each said screw for feeding the material received within said inlet downwardly within said upper tube, through said passageway and upwardly within said lower tube to said outlet for uniformly subjecting the material to the liquor within said tubes, means pivotally supporting said tubes to provide for positioning said tubes with their axes extending generally horizontally, and said flight means of each of said screws having a pitch decreasing in the direction of travel of material for obtaining a maximum capacity of material within said digester as the material absorbs liquor.

2. A digester as defined in claim 1 wherein said flight means of said screws decreases substantially uniformly from said inlet towards said outlet.

3. A digester unit as defined in claim 1 including vane means connected to said screw within said upper tube for rotation therewith and positioned adjacent said channel means, and said vane means having a pitch opposite to the pitch of said flight means of said screw for aiding in directing the material from the upper said tube downwardly through said passageway.

4. A digester unit as defined in claim 1 including means for directing a positive flow of fluid through said passageway to aid in transferring material from said upper tube to said lower tube.

5. A digester unit as defined in claim 1 wherein said drive means include a separate hydraulic drive unit for each said screw to provide for independent controlled rotation of each said screw at a predetermined speed.

6. A digester unit as defined in claim 1 including fluid cylinder means connected to the lower said end portion of at least one of said tubes, and means connecting said cylinder means to the corresponding said screw for opposing the weight of said screw and the internal pressure acting thereon.

7. A digester unit as defined in claim 1 wherein said screw within the lower said tube includes flight means adjacent said passageway and having an enlarged pitch to provide for receiving material transferred through said passageway.

8. A digester unit as defined in claim 1 wherein at least one of said screws includes a hollow sealed shaft for providing buoyancy to aid in offsetting the weight of said screw and prevent sagging of said screw within the corresponding said tube.

9. A digester unit as defined in claim 1 wherein said channel means include a laterally extending duct member generally tangential to each said tube.

10. A digester as defined in claim 9 wherein said duct member includes a section connected to each said tube, and flange means connected to each said section for connecting said sections together.

11. Digester apparatus comprising two of said digester units as defined in claim 1 and disposed in vertically spaced relationship, channel means defining a passageway connecting said outlet of the upper said unit to said inlet of the lower said unit, and said flight means decreasing in pitch in a direction from said inlet of said upper unit towards said outlet of said lower unit.

References Cited UNITED STATES PATENTS 2,355,091 8/1944 McDonald 16260 1,915,812 6/1933 Wollenberg 162-237X 1,938,802 12/1933 Braun et al 162237X 3,181,454 5/1965 Ginaven et a1 162237X 3,258,390 6/ 1966 Tomlinson 162237X 3,332,836 7/1967 Lowgren et al. l62237 FOREIGN PATENTS 30,484 12/1959 Finland 162237 17,752 1/1959 Japan 162-233 S. LEON BASHORE, Primary Examiner ALFRED DANDREA, 1a., Assistant Examiner US. Cl. X.R. 162l7, 237, 243

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