US2888213A - Comminuting machine - Google Patents

Description

y 1959 G. HUBNER EI'AL 2,888,213

COMMINUTINC MACHINE Filed Nov. 30; 1955 4 Sheets-Sheet 1 I M TW' ATTORNE May 26, 1959 G. HUBNER Er AL 2,888,213

COMMINUTING MACHINE Filed Nov. 50, 1955 Y sheets-sneet 2 INVENTORS GUSTAV HUEBNER BY FRANZ ALBERT KM.WM,WJ-T% ATTORNEYS y 6, 1959 G; HUBNER ETAL 2,888,213

' COMMINUTING MACHINE Filed Nov. 30, 1955 {Sheets-Sheet 3 INVENTORS GUSTAV HUEBNER BY FRANZ ALBERT flw me ngw ATTORNEYS such as a rotor and stator.

' able. more than one grinding or comminuting stages, each having an array of rotor teeth and an array of stator teeth which are moved past each other with a small "clearance by the relative motion of the members on United States Patent Ofiice j CONIMINUTIN G MACHINE Application November 30, 1955, Serial No. 550,181

' 3 Claims. (01. 241-46 This invention relates to a method and apparatus for grinding, comminuting, and dispersing materials.

According to the invention the material to be dispersed or subdivided is prepared as a liquid suspension of coarsely subdivided particles and is passed through one, and preferably more than one, grinding or comminuting stages in each of which a number of parallel connected channels are provided in the form of slots between adjacent teeth of relatively rotating members, The flow of the material is lengthwise of the channels, with an added circumferential component due to relative motion of the rotor and stator members. channels are periodically consolidated (as rotor and stator slots come into coincidence) and subdivided (as they In each stage, upon such motion the have their outlets largely or completely closed off.

The machine of the invention for the practice of this process is of the rotating type, usually with rotor and stator members, although both members may be rotat- The machine includes at least one and preferably which they are arranged. When plural grinding stages are provided, they are connected in series by annular chambers of small volume provided by appropriate formations in the relatively rotating members.

The teeth of each stage and in particular the rotor teeth are so shaped that they, and hence the slots or spaces between them, have along their length a comin passing through these slots by the motion of the rotor to the influence of centrifugal force which urges the material through the channels from an input flow terminal on or adjacent the axis of the machine to an output flow terminal radially farther from the axis than the input flow terminal. l i

According to a feature of the machlne of the invention,

the rotor and stator teeth of one stage are so constructed that the flow passages for the suspension which are formed by the slots between adjacent teeth of the rotor in that stage are periodically closed off by the teeth of the stator to form, upon such closure between each pair of adjacent rotor teeth, a chamber which is closed on all sides except that which is upstream in the direction of flow. When two or more comminuting stages are provided, the stage in which the periodically closed chamhers are formed is preceded by one or more stages up- Patented May 26, 1959 stream in the sense of the flow of material through the machine. Without prejudice to the scope of applicants invention, which is set forth in the appended claims, applicants believe that the chambers so formed result in the development and propagation upstream of the direction of flow of acoustic waves which add to the dispersing effect not only in the stage where the chambers are successively formed and dissolved, but in all previous commlnuting stages.

The invention will now be further described in conjunction with the accompanying drawingsfin which there is shown a preferred form of machine accordingtothe invention and in which:

Fig. l is a perspective exterior view of such a machine, shown coupled with its driving motor;

Fig. 2 is a view partly in axial section through the machine of Fig. 1; P Fig. 3 is a plan view of the rotor of the machine of Fig. 4 is a plan view of the stator of the machine of Fig. j I

Fig. 5 is an enlarged fragmentary axial-section of the machine of Fig. 2; I

Figs. 6 to 8 are fragmentary sectional views at a still larger scale taken on the section lines of 6- 6, 77, and 88, respectively, in Fig. 5; and 1 Fig. 9 is an additional fragmentary sectional View similar to that of Fig. 7, but illustrating the closed position of the chambers periodically formed in the machine of Fig. 2 on relative motion of the rotor and stator.

The embodiment of the machine of the invention generally illustrated in Figs. 1 and 2 comprises an exterior housing generally indicated at 2, supported on a suitable base 4. The base may also support a suitable driving element such as the motor 6 shown in Fig. 1 which, however, need not form part of the dispersing machine. The housing 2 has afixed thereto the structural elements which make up the operative stator of the machine within which, in the embodiment illustrated, moves the rotor generally indicated at 8 in Fig. 2. An inlet conduit 10 connects the machine with a supply of material to be treated, and an outlet conduit 12 carries the treated material away.

Referring to Fig. 2, the rotor is supported'on a shaft 14 borne in suitable bearings 16 to run true within close tolerances. For admission of the suspension of 'material to be treated, the housing is extended beyond the rotor in the direction opposite that of the shaft 14 and terminates at a flange 18 to which the inlet conduit 10 connects. The material to be dispersed or subdivided in the machine arrives via the conduit 10 in a suspension formed by suitable auxiliary apparatus, which may be of known type, and which may include means for eifecting a preliminary subdivision if the material as received is too coarse to pass into the first grinding stage of the machine.

As illustrated in Fig. 2, the rotor 8 may for manufacturing reasons he made up of a plurality of parts, the most important of which for purposes of explaining the operation of the machine are identified as a cap 20 and rings 22 and; 24. Elements 20, 22, and 24 are assembled with suitable supporting structure into a rigid body which is affixed coaxially to shaft 14. The stator may similarly be made up of rings 26, 28, 30, and 32 all directly employed in the comminuting process and assembled with 2 suitable auxiliary elements into a structure rigid with J) move under centrifugal force radially outwards towards the housing to enter the first grinding stage.

Referring to Figs. and 6, the first grinding stage is composed of an array of teeth 36 on the rotor and 38 on the stator, the slots between adjacent rotor teeth 36 being identified at 37 and similarly the slots between stator teeth 38 being identified at 39.

The teeth 36 and 38, and hence the slots 37 and 39 between them, possess both axial and radial extension, and may but need not lie in planes which contain the axis of rotation X-X of the machine, i.e., they may but need not lie in meridian planes of the machine. The teeth 36 and 38 may be formed by the provision of the slots 37 and 39 in the rotor elements 20 and 22 and in the corresponding stator elements 26 and 28, after which the lands between these slots or channels on both rotor and stator are accurately finished into matching conical surfaces, as by grinding operations performed on the separately assembled rotor and stator, to provide within close tolerances a uniform small clearance between rotor and stator teeth as the rotor moves.

The number of teeth or more particularly the number of slots and the shape and dimensions thereof are so selected that the peripheral dimension of the lands between adjacent slots on both rotor and stator is substantially larger than the peripheral dimension of the slots themselves. These relationships are illustrated in Fig. 6. It is also clear from Fig. 6 that upon motion of the rotor and stator, rotor and stator channels 37 and 39 are periodically consolidated into channels of substantially circular cylindrical shape and subdivided into channels of semicylindrical shape, lengthwise of which the material moves in its progress through the machine.

In one design of a machine according to the invention which has been successfully built and operated for the production of a variety of dispersions, this first grinding stage comprised 32 rotor and 32 stator teeth, and hence equal numbers of rotor and stator slots. These were formed on surfaces conforming to conical frusta having a half angle of 15, with small and large diameters of approximately 13 and 18 cm., respectively the slant height of the teeth being approximately cm. The slots 01 channels between adjacent rotor and stator teeth were of semicircular section. Clearance between rotor and stator lands was approximately 0.2 mm.

The second grinding stage of the machine illustrated in the drawings comprises rotor teeth 40 and stator teeth 42, the. slots or channels between adjacent rotor teeth being identified at 41 and the channels between adjacent stator teeth 42 being identified at 43. The teeth of the second stage are preferably much finer and more numerous than those of the first stage, numbering 176 in the particular machines having 32 teeth in the first stage to which reference has been made.

The material emerging from the channels of the first stage passes into those of the second stage via an annular space 46 which connects the two stages together. In the machine illustrated in the drawings, the rotor and stator teeth 40 and 42, and hence the channels 41 and 43 between them, lie or have their length in planes perpendicular to the machine axis. They may alternatively conform to conical arrays. Preferably, however, they are inclined along their length to the teeth of the first stage so that the material under treatment undergoes a deviation in passing from the first stage to the second.

The channels of the second stage may be formed by milling slots into rotor and stator members 24 and 30 at uniform and equal spacings. The shape of the channels in the second grinding stage is illustrated in Fig. 7, where it may be observed that the width of both rotor and stator teeth is larger than the width of the slots or channels which separate them. The channels are of uniform width,;i.e., taken circumferentially of the machine axis, along their length so that the width of the teeth varies along the length thereof, but the slots are so propor- 4 tioned and spaced that even at the radially inner end thereof, they are narrower than the teeth that separate them.

As indicated in Fig. 5, rotor member 24 terminates at its radially outer end in a generally conical surface 48 with which there mates, at least across the radially outer ends of the teeth 40, a similar conical surface 50 on the stator member 32. Member 32 is provided with the same number of teeth 44 separated by slots 45 as is stator member 30. As illustrated in Fig. 4, the teeth 42 register with teeth 44 so that the channels 43 between adjacent teeth 42 open into and are continuous with the channels 45 beween adjacent teeth 44. The channels 45 open at their radially outward ends into an annular discharge channel indicated at 52 in Fig. 2, and within which a number of impeller blades affixed to the rotor may move. If desired, the rotor member 24 may be relieved below the base of the slots 41 as indicated at 54 in Fig. 5 to facilitate discharge of the material upon its emergence from the second grinding stage.

In the particular machines according to the invention, some of whose dimensions have been hereinabove given, the channels 41 and 43 of the second stage had a depth axially of the machine of 4 mm., a width circumferentially of the machine of 1.6 mm., and a length radially of the machine of approximately 1.5 cm., whereas the clearance between the lands which separate adjacent channels was 0.3 mm. The clearance between the radially outward ends of the rotor teeth 40 and stator teeth 44 was approximately 0.2 mm. and the depth of channels 45 between stator teeth 44 was 4.25 mm. The circumferential width of the teeth 40 and 42 was approximately 2.4 mm. midway along the length thereof.

In operation of the machine, motion of the teeth 40 past the teeth 42 subjects the material under treatment to a second stage of comminution by the alternate exposure of rotor and stator channels 41 and 43 to each other and to the teeth 42 and 44 respectively. In addition, when the relative position of rotor and stator is such that a stator tooth 42 is opposite the axial end of a rotor channel 41, a stator tooth 44 is opposite to and effectively closes off the radially outward end of such channel 41, as indicated in Fig. 9. Consequently, except for clearances, which are small compared to the dimensions of the chan nel 41 under consideration, that channel forms a chamber closed on all sides except its radially inner end presented to the annular space 46. Conversely, as illustrated in Fig. 7, when the rotor teeth 40 match stator teeth 42, the rotor channels 41 are open not only to stator channels 43, but also to the channels 45 between stator teeth 44, and the content of rotor channels 41 can flow freely out through gtzator channels 45 into the annular discharge channel A machine according to the invention of the particular type described herein has been successfully employed in the reduction of old paper stock to its individual fibers. Accepting as raw material paper stock reduced in a prior pulping operation to pieces of maximum dimension of approximately 1 cm. and supported in a suspension of 5% dry paper stock by Weight to by weight of Water, this machine turning at 3,000 r.p.m. and consuming about 50 H.P. had a throughput of about 70 cubic meters of suspension per hour, containing from 1,500 to 2,000 kilograms of dry cellulose. This machine thus reduced hourly between 1,500 and 2,000 kilograms of paper stock to individual fibers of the order of 5 mm. long, the fibers having a diameter of the order of 2 to 3 microns. The suspension was supplied to the machine with substantially no head applied, the centrifugal pumping action of the machine itself being relied upon to force the suspension through it.

In a particular application, two machines according to the invention as described in the preceding paragraph replaced three conical refiners consuming 64 kilowatts each.

It has been found that the machines of the invention sesame operate, at least primarily and as regards the fine degree of subdivision available therewith, by a shearing process.

v Applicants believe on the contrary that the machines of thejn'vention operate'by intense shock or acoustic waves generated in the fluid vehicle'orsusp'ension medium upon the periodic consolidation and subdivision of the'parallel channels of their stages as rotor and stator slots are successively brought into and out of coincidence and especially upon the cyclic formation in the outlet stage of these machines of channels which are closed off at their downstream or outlet ends and which are open only at their upstream ends.

Theinvention has been described in terms of a particular embodiment shown in the drawings. Various modifications in the shape and structure of the machine illustrated may however be made without departing from the invention, which includes also a method defined in the appended claims which is independent of any particular apparatus.

The successive stages may be joined together by conduits other than the annular chambers of the embodiment illustrated, it being sufficient, when plural stages are pro- Wided to cooperate together, to provide in effect a header between each pair of successive stages, so that waves generated at the downstream end of the machine canbe propagated back into channels of preceding stages, where interference effects may take place. Usually, though not necessarily, the channels of the later stages are finer and more numerous than those of the earlier stages, having reference to the direction of flow of the material through the machine.

It is considered presently preferable to build apparatus in accordance with the invention, as is that which has been described herein, in such form that a centrifugal pumping action inheres in its operation to assist in driving through the machine the suspension of material undergoing comminution. This is not necessary however and separate pumping means may be relied upon for this purpose.

Moreover, while it is desirable that the length of the teeth (and of the channels between them) in adjoining stages be angularly inclined to each other, considering in particular the component of length of the teeth and channels lying in common meridian planes of the machine, it is not necessary that the teeth of the first stage lie on conical surfaces and that those of the second stage lie on plane surfaces, as in the machine illustrated in the drawings. The teeth of the first stage, in a two-stage machine such as that illustrated in the drawings, may be formed on cylindrical surfaces and those of the second stage on conical surfaces, or both stages may be conical, the plane surfaces to which conform the teeth of the second stage in the machine illustrated in the drawings hereof being in fact only the limiting case of conical surfaces ihaving a'half angle of 90 instead of some smaller angle. In each stage the channels are preferably formed on sur- :faces of revolution which are similar and which may differ only as required to provide the desired clearances Ibetween relatively rotating members. The clearances may even be slightly tapered, particularly in the earlier stages of the machine, in which case the two surfaces of revolution in such stages will be of slightly dissimilar shape as well as of different sizes.

We claim:

1. A comminuting machine comprising two rotation- :ally symmetric relatively rotatable members, said members including each a first portion conforming substantially to a frustum of a common cone, a second portion conforming substantially to a common surface of revolution generated by a straight line inclined to the axis of :s mmetry of the machine by an angle larger than the angle of said cone and a third portion conforming substantially to a common conical surface of smaller ihalf 'angle, than said angle of inclination, the radially inner limits of said second and third portions being respectively adjacent the radially outer limits of said first and second portions, teeth on each of said first portions extending from the top to the base of said frustum, teeth in equal numbers on each of said second portions of greater width throughout their length than the width of the slots between them extending substantially between the radially inner and outer limits of said second portions, the slots between adjacent teeth on each of said first portions communicating with the slots between adjacent teeth on each of said second portions via a single annular space between said members at the base of said frustum, and teeth on the third portion of one of said members in the same number as and registering with the teeth on the second portion of said one member, the third portion of the other of said members being without teeth, whereby the slots between adjacent teeth on the second portion of said other member open at their ends remote from said annular space only to the slots between adjacent teeth on the third portion of said one member.

2. A comminuting machine comprising rotationally symmetric rotor and stator members, said members including each a first portion conforming to a first frustum of a first common cone, a second portion conforming to a second frustum of a second common cone of larger half angle than that of said first cone, and a third por tion conforming to a third frustum of a third common cone of smaller half angle than that of said second cone, rotor and stator teeth on said first portions extending the slant height of said first frustum, rotor and stator teeth in equal number on said second portions extending the slant height of said second frustum, and stator teeth on said third stator portion in the same number as and registering with the teeth on said second stator portion, the teeth on said second portions communicating at their radially inner ends with the teeth on said first portions via an annular space between rotor and stator members at the intersection of said first and second frusta, the rotor teeth of said second portion opening at their radially outer ends onto said third rotor portion, said third rotor portion being without teeth, each tooth having throughout its length a greater width circumferentially of the common axis of symmetry than the space between such tooth and the adjacent tooth on the same member, the clearance between rotor and stator members on each of said portions being small compared to the depth of the slots between adjacent teeth on any of said portions.

3. A comminuting machine comprising rotationally symmetric rotor and stator members, and means to support said rotor member for rotation within said stator member with small clearances between the surfaces of said members which conform to common geometrical surfaces, said members including each first, second and third portions, said first portions conforming substantially to ,a first common surface of revolution, said second portions conforming substantially to a second common surface of revolution generated by a straight line inclined to the axis of said first surface of revolution by a larger angle than the generators of said first surface of revolution, said third portions conforming substantially to a third surface of revolution generated by a straight line inclined to the said axis by a smaller angle than the angle of inclination of the generators of said second surface of revolution, the radially inner limits of said second and ,third portions being respectively adjacent the radially outer limits of said first and second portions each of said first and second portions having an equal plurality of slots therein of circumferential dimension smaller throughout their length than the width of the lands separating adjacent slots on said first and second portions respectively, the slots in said first and second portions communicating with each other via an annular channel between said members adjacent the intersection of said first and second surfaces of revolution, the slots in said second rotor portion opening onto said third rotor portion, said third stator portion having formed therein slots in the same number as and registering with those of said second stator portion, whereby upon relative rotation of said members the slots of said second rotor portion are periodically closed except at the ends thereof presented to said annular channel by the lands between adjacent slots in said second and third stator portions.

References Cited in the file of this patent UNITED STATES PATENTS

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