US2845036A - Pellet mill - Google Patents

Description

y 29, 1958 -c. FISHER 2,845,036

PELLET MILL 2 Sheets-Sheet 1 Filed March .5, 1954 FIG-1 42, az 83 80 88 87 3142a INVENTOR.

- CHESTER DONALD FISHER W, M M4 ATTORNEYS s so 69 United State I PELLET MILL Application March 5, 1954, Serial No. 414,274

6 Claims. (Cl. 107-14) This invention relates to pellet mills of the type employing a perforated annular die and a plurality of rolls mounted within the die for forcing the material to be formed into pellets through the perforations in the die.

The invention is particularly adapted to pellet mills in which the rolls are stationarily supported within the die and the die is mounted for rotation with respect to the rolls. In operation, a damp or soggy mass of grain or feed or other material to be formed into pellets is introduced into the interior of the die.. As the die rotates, the material is carried through the nips formed by the inner surface of the rotating die and the stationary rolls bearing thereagainst, thus forcing the material outwardly through perforations or extrusion openings in the die. Cutoff knives are mounted adjacent the outer surface of the die to cut off the'extruded material in the form of pellets as the material emerges outwardly from perforations in the die.

Dies with different diameter perforations or extrusion openings may be interchanged on the machine depending upon the type of material being pelleted, the diameter of pellet desired, etc. When the die perforations are of relatively small diameter (e. g., inch) sufiicient materi'al may be extruded through the, die during but one revolution of the mill so that a pellet of the desired length may be cut off from each perforation upon each revolution of the mill by the cutoff knife bearing against the outer surface of the die. With dies with larger openings (e. g., inch), however, the situation may be such that insuflicient material will be forced through the larger diameter holes during but one revolution of the mill to form a pellet of desired length. If the cutoff knives are spaced outwardly from the surface of the die in order to lengthen the pellet, the knives will serve merely as bumping bars which break the pellet off unevenly at the dies, rather than cutting it cleanly as when the knife bears directly against the surface of the die.

lt-is accordingly an object of this invention to provide a. pellet mill construction such that pellets of various lengths may be produced and cut off cleanly with the cutoff knives adjusted to bear against the outer surface of the die notwithstanding the fact that it may require more than one revolution of the die to force through the perforations. thereof sufficient material to form the length of pellet desired- In accordance with the invention, the cutoff knife is mounted for rotation about the axis of the die, and variable speed means are provided whereby the knife may be rotated at a speed different from that of the die so that, by adjusting the relative speed of rotation of the knife and the die, more than one revolution of the die may occur between sequential contacts of the cutoff knife with a given perforation in the die.

One of the objects of this invention, accordingly, is to provide a pellet mill of the character described having a cutoff knife mounted for rotation circumferentially around and bearing against the outer annular surface of the die.

atent O Another object of this invention is to provide in such a pellet mill variable speed drive means for rotating the cutoff knife at a variable speed differential with respect to the rotation of the die.

A further object of this invention is to provide such a pellet mill construction in which the rotating cutoff knife and the rotating die are both driven from the same motor or other source of power through a transmission providing a controllably variable speed differential therebetween.

Still another object of this invention is to provide such a pellet mill construction in which a cutoff knife is mounted in the main mill housing and for rotation with respect to the die in such manner as not to interfere with the normal operation of feeding material into the die and so as to seal off the interior working parts of the mill from the penetration thereinto of pelleting material.

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

In the drawings Fig. 1 is a view of the front of a pellet mill embodying the invention with parts of the feed hopper and front covers broken away; i

Fig. 2 is a view in vertical section through the pellet mill along the line 22 of Fig. '1; g V

Fig. 3 is a top view of a portion of a pellet mill embodying this invention with the top of the housing removed;

Fig. 4 is a fragmentary view on a somewhat larger scale of the cutoff knife and a portion of the die of such a pellet millrand Fig. 5 is a view in section along the line 5-5 of Fig; 4.

Referring to the drawings, which illustrate a preferred embodiment of the invention, the base 10 includes a stand 11 in which a shaft 12 is mounted at its rearward end by bushings 13. At the forward end of shaft 12 is a fork 14 which forms a support for two rollers 15. The shaft 12 is normally held stationary in such position that the fork 14 extends horizontally to support the rollers 15 in side-by-side relation in a substantially horizontal plane. A tie bar 16 extends between the forward ends of the rollers to maintain them in proper parallel alignment.

An annular die 20 having multiple perforations 21 therein is bolted to a carrier or housing 22 which is mounted for free rotation on shaft 12, as by means of bearings 23. The drive motor for rotating die 20 is shown at 25, and its shaft carries a drive pulley 28 connected through belts 26 with a large driven pulley 27 pinned or otherwise secured to the housing 22 which carries die 20. The motor 25 is shown as carried by blade 30 hinged at 31 on base 10 and provided with a threaded rod 33 attached to the stand 11 at 34 for adjusting the tension of the drive belts 26. The shaft 12 is normally held stationary in stand 11 by means of a shear pin 35 carried by boss portions of stand 11 and a shear pin collar 36 keyed or otherwise secured to shaft 12.

A cylindrical cover 50 for the die 20 includes a flange portion 51 by which it is bolted to the frontrface of die 20 for notation with the die. The cover 50 has a circular opening 52 through the outer end thereof which receives the material to be formed into pellets from a feed spout or hopper 55 mounted on the outer mill housing 56. Housing 56 is mounted on the circular belt guard housing 42 carried by the base 10. The feed spout 55 is fitted for attachment to any suitable supply means for the material to be pelleted, and housing 56 has a discharge space 58 at its lower end for the formed pellets to be discharged into any suitable collecting means.

A carrying ring member 60 is mounted for rotation about the outer periphery of housing 22 and includes a race 61, overriding a flange member 62 on housing 22, and felt seal 63. One side of the ring member 60 has an outwardly extending flange 65 to which is aflixed, as by bolts 66, the cutoff knife assembly comprising plate 67, arm 68 and knife blade 69. A driven pulley 75 is pinned or otherwise secured to ring 60 and mounted for rotation about housing 22 with felt seal 76. Pulley 75 is driven by belt 77 from a variable pitch sheave 80 mounted on shaft 81 of the flange mounted adaptor to sheave 28.

Variable pitch sheave 80 is of known construction and comprises two plates 82 urged toward each other by spring 83 and forming a V-notch therebetween such that varying the tension on belt 77 will vary the proximity of belt 77 to shaft 31 and hence the speed ratio between variable pitch sheave 80 and driven pulley 75. The tension on belt 77 is varied by idler pulley 85, which rides on the top of belt 77. Idler 85 is mounted on arm 86, which is pivoted to housing 42 at 87. The position of idler pulley 85 may be adjusted from outside the pellet mill as by moving arm 86 about pivot 87 with handle 88, and locking the device in the desired position by tightening bolt 89 in an annular slot in quadrant 90. Thus the speed of rotation of the annular ring member 60, and consequently the cutoff knife attachment and knife blade 69 carried thereby, is variable with respect to the main drive motor 25 by adjusting the positioning of idling pulley 85 and, consequently, the tension on belt 77, to alter the effective diameter of variable pitch drive sheave 80. In order to prevent the accumulation in the bearing surface between ring member 60, pulley 75, and flange member 52, of crumbs or other debris from the pelleting operations, felt seals 63 and 76 are held by clamp rings 40, and seal 41 is provided.

In normal operation, rotation of the die 20 causes material supplied to the interior thereof through spout 55 to be carried into the nips formed by the inner annular surface of the die and the rollers 15, and this material is thus forced through the perforations 21 to the outside of the die, where it is cut off in the form of pellets as the knife blade 69 engages successive perforations 21. If, in the illustrated construction, some jamming should occur, shear pin 35 breaks and the shaft 12 begins to rotate instead of remaining stationary. In such case, the shear pin collar 36 rotates with the shaft and operates a microswitch 44 mounted on stand 11 and effective to shut off the motor 25 when the operating arm 45 of the microswitch is engaged by the boss portion of the collar 36.

With both the die 20 and the cutoff knife 69 rotating in the same direction but at different speeds, material will be extruded from a given perforation 21 just having passed knife 69 until such time as knife 69 again contacts the same perforation, at which time the extruded material will be cut off cleanly at the outer surface of the die 20 by the leading edge of cutoff knife 69. If cutoff knife 69 were stationary, pellets would. be cut off from a given perforation in die 20 after each complete revolution thereof. Accordingly, for a given speed of rotation, there would be but a constant time during which material could be extruded from a given perforation in die 20 to form a pelletregardless of the length of pellet desired or of the diameter of the perforation or the ease of extruding material therethrough;

Since, however, the cutoff knife 69 is not stationary but is rotating with respect to die 20, the length of. time during which material may be extruded from a given perforation in die 20 before being. cut off by knife 69 may be more or less than one revolution of die 20 by virtue of the almost infinitely variable speed differential between cutoff knife 69'and die 20. Thus, pellets of the desired length may be secured by adjusting the speed of rotation of knife 69 with respect to die 20 so that only the proper time intervenes between successive contactings of a given perforation 21 by cutoff knife 69, with, of course, due regard for the length of pellet desired, the diameter of the perforations 21, the amount of material which must be extruded to form the proper length of pellet, the consistency or ease with which the material can be extruded, etc. It will also be seen that knife 69 nee-d not be backed off or spaced from the outer surface of die 20 in order to achieve a longer pellet, but may always be set to cut the pellets cleanly right at the surface of the die. Variation in pellet length, according to the invention, is achieved by varying the speed differential between rotating cut-off knife 69 and rotating die 20 by means of the variable speed transmission providedby variable pitch sheave 8t) and the tension adjusting mechanism 90.

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. In a pellet mill of the character described and having a generally circular pellet forming die with substantially radial extrusion perforations therein, a rotatable carrier for said die adapted to rotate said die about the axis thereof at a predetermined peripheral speed, and means for extruding material to be pelleted outwardly through said perforations upon rotation of said die, the combination which comprises a circular bearing surface around the circumference of said rotatable carrier, a ring member surrounding said carrier and carried by said bearing surface, means for rotating said ring member around said carrier with respect thereto, a cut-off knife for cutting material extruded from said die into pellets, means for mounting said cut-off knife on said ring member and disposed to contact material extruded from said die immediately adjacent the outer surface of said die, and means for varying the speed of said ring member and said cut-off knife with respect to said die for controlling the amount of material extruded through said die between successive cuttings by said knife.

2. In a pellet mill of the character described and having a generally circular pellet forming die with substantially radial extrusion perforations therein, a rotatable carrier for said die adapted to rotate said die about the axis thereof at a predetermined peripheral speed, and means for extruding material to be pelleted outwardly through said perforations upon rotation of said die, the combination which comprises a circular bearing surface around the circumference of said rotatable carrier, a ring member surrounding said carrier and carried by said bearing surface, means for rotating said ring member around said carrier with respect thereto, a cut-off knife for cutting material extruded from said die into pellets, means for mounting said cut-off knife on said ring member and disposed to contact material extruded from said die immediately adjacent the outer surface of said die, a driven pulley mounted on said ring member, a variable pitch drive pulley, a drive belt connecting said pulleys for driving said ring member and said cut-off knife, and means for selectively varying the tension on said belt to vary the effective diameter of said variable pitch drive pulley for controlling the speed of said ring member with respect to said die to vary the amount of material extruded through said die between successive cuttings by said knife.

3. In a pellet mill of the character described and having a generally circular pellet forming die with substantially radial extrusion perforations therein, a rotatable carrier for said die adapted to rotate said die about the axis thereof at a predetermined peripheral speed, and means for extruding material to be pelleted outwardly through said perforations upon rotation of said die, the

' combination which comprises a circular bearing surface around the circumference of said rotatable carrier, a ring member surrounding said carrier and carried by said bearing surface, means for rotating said ring member around said carrier with respect thereto, a cut-off knife for cutting material extruded from said die into pellets, means for mounting said cut-off knife on said ring member and disposed to contact material extruded from said die immediately adjacent the outer surface of said die, sealing meanson said ring member for excluding material to be pelleted from said bearing surface on said carrier, and means for varying the speed of said ring member and said cut-ofi knife with respect to said die for controlling the amount of material extruded through said die between successive cuttings by said knife.

4. In a pellet mill of the character described and having a generally circular pellet forming die with substantially radial extrusion perforations therein, a rotatable carrier for said die adapted to rotate said die about the axis thereof at a predetermined peripheral speed, and means for extruding material to be pelleted outwardly through said perforations upon rotation of said die, the combination which comprises a circular bearing surface around the circumference of said rotatable carrier, a ring member surrounding said carrier and carried by said bearing surface, a circumferential race in the inner surface of said ring member, a circumferential flange on said bearing surface for maintaining axial alignment of said ring member with respect to said carrier, means for rotating said ring member around said carrier with respect thereto, a cut-off knife for cutting material extruded from said die into pellets, means for mounting said cutoff knife on said ring member and disposed to contact material extruded from said die immediately adjacent the outer surface of said die, and means for varying the speed of said ring member and said cut-ofi knife with respect to said die for controlling the amount of material extruded through said die between successive cuttings by said knife.

5. A pellet mill comprising an annular carrier flared at one end and having a plurality of annular bearings within the other end, a fixed shaft extending through said carrier in contact with said bearings to support said carrier, a driven pulley fastened around the outside of said carrier at said other end to rotate said carrier, a flange extending outwardly from said flared end, an annular die having a series of radial extrusion openings therethrough, means for mounting said die on said flared end of said carrier, a plurality of rollers within said die, means for supporting said rollers on the end of said fixed shaft for cooperating engagement with the inner surface of said die to force material through said extrusion openings upon rotation of said die, an annular ring having a race formed in its inner surface to embrace said flange, a groove in the outer surface of said ring to receive a belt for driving said ring, a cutoff knife for cutting into pellets material extruded through said die, means for supporting said knife on said ring and extending across the outer surface of said die, a drive shaft extending parallel to said fixed shaft, a drive pulley on said drive shaft for driving said driven pulley on said carrier at a substantially constant speed, a variable pitch pulley on said drive shaft, a belt connecting said groove on said ring and said variable pitch pulley, and means for selectively varying the tension on said belt for varying the effective diameter of saidvariable pitch pulley to control the movement of said knife relative to the outer surface of said die.

6. A pellet mill comprising an annular carrier flared at one end and having a plurality of annular bearings within the other end, a fixed shaft extending through said carrier in contact with said hearings to support said carrier, a driven pulley fastened around the outside of said carrier at said other end to rotate said carrier, a flange extending outwardly from said flared end, an annular die having a series of radial extrusion openings therethrough, means for mounting said die on said flared end of said carrier, a plurality of rollers within said die, means for supporting said rollers on the end of said fixed shaft for cooperating engagement with the inner surface of said die to force material through said extrusion openings upon rotation of said die, an annular ring having a race formed in its inner surface to embrace said flange, a plurality of bearings on said inner surface of said ring for rotation of said ring about said carrier, a groove in the outer surface of said ring to receive a belt for driving said ring, a cutoff knife for cutting into pellets material extruded through said die, means for supporting said knife on said ring and extending across the outer surface of said die, a drive shaft extending parallel to said fixed shaft, a drive pulley on said drive shaft for driving said driven pulley on said carrier at a substantially constant speed, a variable pitch pulley on said drive shaft, a belt connecting said groove on said ring and said variable pitch pulley, and means for selectively varying the tension on said belt for varying the effective diameter of said variable pitch pulley to control the movement of said knife relative to the outer surface of said die.

References Cited in the file of this patent UNITED STATES PATENTS 1,848,332 Estes Mar. 8, 1932 2,162,647 Sizer June 13, 1939 2,174,141 Sizer Sept. 26, 1939 2,241,546 Evenstad et al May 13, 1941 2,336,114 Meakin Dec. 7, 1943 2,648,296 Oliver Aug. 11, 1953 2,700,941 Johnson Feb. 1, 1955

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