US3341137A - Tamping arrangement for supplying a material to crushing rollers - Google Patents

Description

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. RETTENMAIER TO CRUSHING ROLLERS Filed July 28, 1964 TAMPING ARRANGEMENT FOR SUPPLYING A MATERIAL Sept. 12". 1967 United States Patent 3,341,137 TAMPING ARRANGEMENT FOR SUPPLYING A MATERIAL TO CRUSHING ROLLERS Josef Rettenmaier, Holzmuhle Gemeinde, Rosenberg,

Germany, assignor to J. Rettenmaier & Siihne, Holzmuhle, Rosenberg uber Ellwangen, Jagst, Germany Filed July 28, 1964, Ser. No. 385,674 Claims priority, application Germany, July 31, 1963, R 35,803 13 Claims. (Cl. 241-222) The present invention relates to an apparatus for supplying relatively small particles to the gap between a pair of rotary crushing rollers, and more particularly to apparatus for further reducing the size of the small particles.

It is known to reduce the size of the small particles by moving a mass of such particles through the gap between cooperating crushing rollers. Under practical conditions, considerable difiiculties develop. In the event that the gap is relatively small, a comparatively large mass of particle accumulates in the bight of the rollers above the gap, and the rollers are incapable of gripping the compressed and lumpy mass. On the other hand, if the gap is relatively wide, the desired reduction of size of the particle is not achieved.

It is the object of the present invention to overcome the disadvantages of methods and apparatus for reducing the size of small particles, and to supply relatively small particles to the gap between a pair of crushing rollers in such a manner that the size of the particles is further reduced by the action of the crushing rollers.

Another object of the invention is to subject a mass of particles fed to the gap between a pair of crushing rollers at a periodically varying pressure.

Another object of the invention is to prevent the formation of a compressed and lumpy mass of small particles in the bight between crushing rollers by subjecting the mass to a periodically varying pressure acting in the direction of the gap.

Another object of the invention is to transport precompressed small particles periodically into the gap between a pair of crushing rollers.

With these objects in view, the present invention is advantageously applied to small particles, such as wood shavings, small pieces of plant peels or nut shells, or mixtures of different kinds of small particles. The mass of small particles is supplied to the bight on top of at least one pair of cooperating crushing rollers, so that it accumulates and tends to pass into the gap due to gravity. In accordance with the present invention, a pressure exceeding the gravity is applied to the mass of small particles accumulated and confined in a space before the gap, for example, mechanical pressure may be applied. In this manner, the mass of small particles is pressed into the gap, and in accordance with the preferred embodiment of the invention, the pressure is applied in the direction of the gap and periodically varied, for example by reciprocation of a stamping or tamping means in a closed passage into which the mass is fed.

By the periodically and rhythmical variation of the pressure, lump formation and sticking together of the small particles of the fed mass is avoided.

The desired reduction of size of the particles is favorably influenced if the crushing rollers are resiliently mounted for movement toward and away from each other so that the width of the gap varies when the pressure is periodically increased and decreased, permitting the transport of the mass of particles through a relatively small gap while being subjected through the action of the crushing rollers.

An improvement of the desired result is achieved at 3,341,137 Patented Sept. 12, 1967 any frequency or rhythm of the pressure increases, but it is preferred to select the frequency of the pressure variation and the peripheral speed of the crushing rollers in such a manner that the crushed par-ticles flow away from the crushing roller in a substantially uniform stream with relatively small fluctuations.

To achieve this result, it is advantageous to use crushing rollers having a diameter between 200 mm. and 300 mm., and to rotate the crushing rollers at a low speed, for example at 40 revolutions per minute.

The results of the present invention are particularly favorable if the mass is accumulated in a confined space adjacent the bight between the rollers in a pre-compressed condition, since in this event the pressure variations act on a precompressed material so that the same enters the gap between the rollers in compressed condition.

An apparatus according to the invention comprises a tamping means which is reciprocable in the direction of the gap between a pair of crushing rollers, and feeding means for feeding a mass of small particles to the bight on one side of a gap between the crushing rollers. A tamping means reciprocates preferably in a closed passage into which the feeding means supply the small particles, so that the reciprocation of the tamping means periodically varies the pressure acting on the mass of accumulated particles in the region of the gap, the pressure changing between a maximum achieved when the tamping means moves toward the gap, and a minimum, that is substantially zero, when the tamping means moves away from the gap. Due to the reciprocation of the tamping means, not only the pressure is varied, but at the same time, a feeding of the mass of particles in the region directly before the gap is accomplished, since every time the tamping means moves away from the gap and forms an empty space, another amount of the mass of particles is fed by the feeding means to fill the empty space, and such newly fed amount is then fed into the gap between the crushing rollers by the forward reciprocating stroke of the tamping means. Consequently, a mixing of the mass of particles takes place at the same time, sothat formation of lumps and sticking together of the particles is prevented.

The reciprocating motion of the tamping means is designed so that the leading operative end of the tamping means moves into the close proximity of the'gap, without touching the surface of the crushing rollers. Consequently, a thin layer of the mass of particles remains under all operational conditions between the crushing rollers and the tamping means.

The effect of the tamping means is substantially improved if its leading operative face is disposed perpendicularly to the direction of movement of the tamping means, and has a shape corresponding to the shape of the gap, for example an elongated rectangular shape. In this event, the tamping means is a plate and the operative end face has a length corresponding to the axial length of the crushing rollers, and a width or thickness corresponding to the width of the gap.

In this manner, a substantially uniform effect of the tamping plate on the accumulated mass is achieved, and the pressure along the entire gap varies uniformly between a maximum and a minimum within the part of the mass located in the region for the gap. A plateshaped tamping means has the advantage that no parts of the accumulated mass of particles is pulled back during the return stroke of the tamping plate, particularly if the tamping plate is guided between guide walls. This may be eifected with the aid of leaf springs mounted on one hand on a stationary housing part and on the other 'hand on the tamping plate, the resiliency of springs betamping plate remains possible. A straight motion is best etfected by guiding the tamping plate not only between the straight walls of the passage leading to the gap, but also by pairs of guiding rollers abutting the lateral faces of the tamping plate.

The mass of particles is fed in the direction transverse to the direction of reciprocating movement of the tamping plate, preferably through a duct having a discharge end in the region of the tamping plate so that the mass of particles is pressed against a lateral face of the tamping plate when the same is in the advanced position. Sealing means are provided between the discharge end of the sealing duct and the tamping plate to maintain a high pressure in the accumulated mass.

Transporting screws are disposed in the feeding duct, preferably in parallel positions, and dead spaces between the transporting screws advantageously taken up by ribs secured to the upper and inner walls of the duct. The transporting screws compress the mass of small particles, particularly in the passage in which the tamping plate reciprocates, so that the mass is in compressed condition when engaged and transported by the advancing tamping plate. In order to obtain the best transporting and feeding condition, it is advantageous to provide bearings only for the ends of the transporting screws remote from the discharge end of the duct, and to drive only these rear ends of the transporting screws.

In order to prevent leaking of the compressed mass, it is preferred to arrange the reciprocating motion of the tamping means in such a manner that the tamping means in its uppermost position farthest spaced from the gap is still located at the upper end of the passage in which the tamping plate moves, and preferably only at the middle of the passage. The discharge end of the feeding duct opens into the passage, and is uncovered in the retracted position of the tamping plate.

The passage is bounded on the side of the tamping means remote from the feeding duct by a wall slidingly engaged by the tamping plate so that the entire passage before the gap is closed and sealed whereby the mass of particles located in the passage under the tamping plate is maintained in compressed condition.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary sectional view illustrating one embodiment of the invention;

FIG. 2 is a fragmentary sectional view taken on line 22 in FIG. 1; and

FIG. 3 is a fragmentary perspective view illustrating the leading operative end of a tamping plate on an enlarged scale.

Referring now to the drawings, a support or housing supports in its lower portion a pair of crushing rollers 11 and 12 which are mounted on shafts 13 and 14 carried by bearings 15 and 16, each of which is subjected to the pressure of resilient means 19 and 20 to urge the crushing rollers toward each other so that gap between crushing rollers 11 and 12 is of variable width.

Receiving container means 26 are provided below crushing rollers 11 and 12 to receive material crushed and reduced in particle size by rollers 11 and 12.

Housing 10 supports a hopper 30 in which a mass of small particles which are to be reduced in size is placed. The lower conical end 33 of hopper 30 is connected by vertical conduit 35 to a duct 37 in housing 10. The length of duct 37 corresponds to the axial length of rollers 11 and 12, and consequently to the length of gap 25. The height of duct 37 is selected so that a plurality of transporting screws 40 can be disposed in duct 37 adjacent and parallel to each other to feed particles supplied through conduit 35 toward the region of the gap between the crushing rollers, but located above the same. Shafts 44 of the transporting screws are mounted in bearings 42 only at one end, and a motor 43 is mounted in a lower cavity of housing 10 and drives through gears 45 and 46, a gear 48 on one of the shafts 44. Each shaft 44 carries a gear 48, and idle pinions are located between each pair of gears 48 meshing with the same so that all gears 48 and shafts 44 rotate in the same direction.

A tamping plate 50 is disposed in a plane perpendicular to the plane which is defined by the axes of shafts 13 and 14 about which the crushing rollers rotate. Tamping plate 50 is connected to pin means 56 on eccentric crank means 55 driven by motor means 54 so that tamping plate 56 is reciprocated between the advanced position shown in FIG. 1 and a raised retracted position.

The upper end of tamping plate 50 is guided between a plurality of guide means, each of which includes a pair of guide rollers 61 engaging opposite lateral faces of tamping plate 50, and being mounted on brackets 60 secured to housing 10. The lower end of tamping plate 50 is guided in a passage which includes on one side of the tamping plate a wall 64 and a sealing means 63 between wall 64 and the lateral face of the tamping plate, and on the other side a wall 66 and a sealing means 67. Walls 66 and 64, and end walls at the ends thereof form a passage for tamping plate 50 into which the discharge end of feed duct 37 opens. A space 70 in the passage is formed in the raised retracted position of tamping plate 50 which is still located between walls 66 and 64, but uncovers the discharge end of duct 37. Since the surfaces at the bottom of housing 10 are closely spaced and parallel to the surfaces of crushing rollers 11 and 12, the lower end of the passage can be considered closed so that a closed space 70 is located between the gap and the leading lower operative end of the tamping plate, which has a rectangular planar face 51, best seen in FIG. 3, and extending parallel to a plane passing through the axes of the crushing rollers. In the lower position of tamping plate 50, the discharge end of feed duct 37 is closed, and face 51 is in the region of the gap, slightly spaced from the surfaces of the crushing rollers.

The apparatus operates as follows: An amount of small particles 31, which may be the result of a previous crushing operation, are filled into hopper 30 and drop due to gravity through conduit 35, which extends along the length of the crushing rollers, into duct 37 which has a corresponding length. The particles fall between the threads of the transporting screws 40 at the rear ends of the same, and are transported through duct 37 toward the space 70. In the illustrated advanced position of tamping plate 50 the material is pressed against a lateral face of the tamping plate and compressed. When due to the operation of motor means 54 the tamping plate 50 is raised and uncovers the discharge end of duct 57, the material enters space 70 and is pressed against the sealing means 37 and wall 66 and into the space of the passage which was previously taken up by the lowered tamping plate. Since transporting screws continue to rotate, the pressure of the fed mass is maintained, and when tamping plate 50 moves down toward the advanced position, the pressed material is pushed out of the passage and into gap 25 where it is crushed by the crushing rollers 11 and 12. The tamping plate 50 is again retracted to a raised position uncovering the discharge end of duct 37 so that another amount of particles 31 is pressed into space 70. The increased pressure of the downwardly moving tamping plate 50 may cause rollers 11 and 12 to slightly move apart to increase the width of the gap which is possible due to the provision of the resiliently mounted bearings 15 and 16.

In accordance with the present invention, the particles are not pressed into the gap by the pressure of feeding means 40, but by the pressure of the independent tamping means 50 which causes a periodically varying pressure acting on the mass of small particles accumulated in the region of the gap to move into the gap so that the pressure in the gap varies.

The arrangement of the present invention permits a relatively slow rotary speed of the crushing rollers, and the speed may lie between 20 and 50 revolutions per minute with 35 to 40 being a preferable speed for the rollers 11 and 12. The diameter of the rollers depends on the circumferential speed, and in connection with the aforementioned rotary speeds, the diameters of the rollers may be between 150 and 300 mm. and a preferred diameter is 220 mm. The width of the gap 25 between the rollers 11 and 12 may range between .4 and 2 mm. and is preferably about 1 mm. This gap depends on the production rate, i.e. the amount of particles passing the rollers, and furthermore on the surface texture of the rollers. The frequency of reciprocation of the tamping plate 50 is, as a rule, chosen rather high and is approximately between 800 and 1200 and preferably about 1000 reeiprocations per minute.

The size of the particles to be processed may range between .1 and 5 mm., while the hardness depends on the organic material used for the particles. Wood, and other organic material like cellulose, straw, and Waste material of agricultural products can be used.

It will be understood that each of the elements described above or two or more together may also find a useful application in other types of crushing methods and apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in apparatus for supplying small particles at a periodically varying pressure into the gap between a pair of rotating crushing rollers, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. An apparatus for reducing the size of particles, comprising, in combination, a pair of cooperating rotary rollers having parallel axes and defining a gap between each other; feeding means for feeding the particles to said rollers and including a feed duct extending in a direction substantially parallel to a plane extending through said axes and having a discharge end located in the region of said gap so that a mass of particles accumulates on one side of said rollers in the region of said gap; a tamping means disposed at said discharge end on said side reciprocable perpendicularly to said plane toward and away from said gap so that the mass is periodically urged into said gap; passage means for said tamping means having an opening forming said discharge end of said feed duct, said tamping means being movable between an advanced position closing said discharge end of said duct, and a retracted position in which the operative end of said tamping means is spaced from said gap uncovering said discharge end and still located in said passage and means for reciprocating said tamping means.

2. An apparatus as set forth in claim 1 wherein said tamping means is *a plate located in a plane passing through said gap perpendicularly to a plane extending through said axes; and wherein said discharge end of said feeding duct is located in the close proximity of said plate; and including sealing means between said discharge end and said plate.

3. An apparatus as set forth in claim 1 wherein said operative end of said tamping means in said retracted position is located substantially in the middle of said passage.

4. An apparatus for reducing the size of particles, comprising, in combination, a pair of cooperating rotary rollers having parallel axes and defining a gap between each other; feeding means for feeding the particles to said rollers and including a feed duct extending in a direction substantially parallel to a plane extending through said axes and having a discharge and located in the region of said gap so that a mass of particles accumulates on one side of said rollers in the region of said gap; a tamping means disposed at said discharge end on said side reciprocable perpendicularly to said plane toward and away from said gap so that the mass is periodically urged into said gap; a wall located on the side of said tamping means remote from said discharge end of said feed duct for holding in the region of said gap particles fed through said discharge end; and means for reciprocating said tamping means.

5. An apparatus as set forth in claim 4 wherein said wall engages said tamping means in both end positions of the reciprocating movement of the same; and sealing means between said wall and said tam-ping means.

6. An apparatus of the type described comprising, in combination, a pair of cooperating rotary rollers having parallel axes and defining a gap between each other; housing means formed with a passage extending toward said gap transversely to a plane passing through said axes and also formed with a feed duct having a discharge opening connected with said passage; a tamping means mounted in said passage for reciprocating movement between a retracted position, and an advanced position in which the leading end of said tamping mean confronts said gap and is located in close proximity to the surfaces of said rollers, said tamping means in said retracted position uncovering said discharge opening, and covering the same in said advanced position; feeding means in said duct for transporting a material through said discharge opening into said passage so that the material accumulates under pressure in said passage and in the bight between said rollers in the region of said gap while said tamping means is in said retracted position; and drive means for reciprocating said tamping means so that said accumulated mass is periodically urged into said gap by said leading end of said tamping means.

7. An apparatus of the type described comprising, in combination, a pair of cooperating rotary rollers having parallel axes and defining a gap between each other; housing means formed with a passage bounded by wall surfaces extending toward said gap transversely to a plane passing through said axes and also formed with a feed duct and having a discharge opening connected with said passage; resilient means for supporting said roller for movement toward and away from each other so that said gap is of variable width; a tamping plate means mounteed in said passage slidably engaging said wall surfaces and for reciprocating movement between a retracted position, and an advanced position in which the leading end of said tamping plate means confronts said gap and is located in close proximity to the surfaces of said rollers, said tamping plate means in said retracteed position uncovering said discharge opening, and covering the same in said advanced position; feeding means in said duct for transporting a material through said discharge opening into said passage so that the material accumulates under pressure in said passage and in the bight between said rollers in the region of said gap while said tamping plate means is in said retracted position; and drive means for reciprocating said tamping plate means so that said accumulated mass is periodically urged into said gap by said leading end of said tamping plate means.

8. A tamping arrangement comprising a pair of rotary rollers having parallel axes and defining a gap between each other; a tamping device forming with said rollers 21 confined space communicating with said gap, and including wall means extending to said rollers and having an opening, and a tamping mean guided by said wall means for reciprocation toward and away from said gap and between an advanced position in which said tamping means is-located in the proximity of said gap and closes said opening, and a retracted position in which said tamping means at least partly uncovers said opening; and feeding means for feeding a material through said opening into said confined space whereby a mas of particles accumulates in the region of said gap while said tamping means is in said retracted position so that the material is pressed into said gap when said tamping means moves to said advanced position.

9. A tamping arrangement a claimed in claim 8 wherein said wall means include a wall located adjacent said gap on the side of said tamping means remote from said opening and said feeeding means for holding material fed through said opening in the region of said gap.

10. A tamping arrangement as claimed in claim 8 wherein said tamping means has an operative end located in the proximity of said gap in said advanced position and having a length and width matching the length and width of said gap; and wherein said wall means form a passage for guiding said tamping means in a plane passing through said gap perpendicular to the axes of said rollers.

11. A tamping arrangement as claimed in claim 10 wherein said wall means include a wall formed with said opening and bounding said passage on one side, wherein said opening has a length matching the length of said gap and of said operative end of said tamping means; and wherein said feeding means is disposed along the length of said opening to feed material into said confined space along the length of said gap.

12. A tamping arrangement as claimed in claim 8 wherein said feeding means includes a plurality of parallel transporting screws having axes transverse to the axes of said rollers.

13. A tamping arrangement as claimed in claim 8 comprising resilient means for mounting said rollers for movement toward and away from each other so that the width of said gap varies with the pressure produced in the material by said tamping means.

References Cited UNITED STATES PATENTS 2,144,911 1/1939 Cohn.

2,612,832 10/1952 Wiemer 241- -222 X 2,734,688 2/1956 Sloane 241-222 2,828,924 4/1958 Ellsworth 241222 ANDREW R. JUHASZ, Primary Examiner.

Claims (1)

1. AN APPARATUS FOR REDUCING THE SIZE OF PARTICLES, COMPRISING, IN COMBINATION, A PAIR OF COOPERATING ROTARY ROLLERS HAVING PARALLEL AXES AND DEFINING A GAP BETWEEN EACH OTHER; FEEDING MEANS FOR FEEDING THE PARTICLES TO SAID ROLLERS AND INCLUDING A FEED DUCT EXTENDING IN A DIRECTION SUBSTANTIALLY PARALLEL TO A PLANE EXTENDING THROUGH SAID AXES AND HAVING A DISCHARGE END LOCATED IN THE REGION OF SAID GAP SO THAT A MASS OF PARTICLES ACCUMULATES ON ONE SIDE OF SAID ROLLERS IN THE REGION OF SAID GAP; A TAMPING MEANS DISPOSED AT SAID DISCHARGE END ON SAID SIDE RECIPROCABLE PERPENDICULARLY TO SAID PLANE TOWARD AND AWAY FROM SAID GAP SO THAT THE MASS IS PERIODICALLY URGED INTO SAID GAP; PASSAGE MEANS FOR SAID TAMPING MEANS HAVING AN OPENING FORMING SAID DISCHARGE END OF SAID FEED DUCT, SAID TAMPING MEANS BEING MOVABLE BETWEEN AN ADVANCED POSITION CLOSING SAID DISCHARGE END OF SAID DUCT, AND A RETRACTED POSITION IN WHICH THE OPERATIVE END OF SAID TAMPING MEANS IS SPACED FROM SAID GAP UNCOVERING SAID DISCHARGE END AND STILL LOCATED IN SAID PASSAGE AND MEANS FOR RECIPROCATING SAID TAMPING MEANS.

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