CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.

61/733,701, filed December 5, 2012, which is incorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

This invention relates generally to pelletizing machinery and, more particularly, a pelleting roller assembly.

BACKGROUND OF THE INVENTION

Pellet mills are used to form a variety of pellet products, such as pelletized animal feed, from mash product composed of various grains or other particulate material. See, for example, pelleting mills described in U.S. Patent Nos. 3,280,426 and 5,486,102 and in U.S. Patent Application Publication No. 2009/0110766, which are hereby incorporated herein. Referring to FIGS. 1 and 2, particulate material is feed into the cavity of a ring- shaped die 10. Rollers 12 within the die force particulate material 14 through extrusion holes formed through the die. Knives outside of the die shear off the extruded material to form pellets 16. Each roller 12 can be adjusted so that a small gap is formed between the die inner face and the roller. The narrow gap creates a nip point that forces particulate material 14 through the extrusion holes. The gap can be adjusted by rotating an eccentric shaft on which the rollers are mounted. Adjusting the gap alters pelleting performance and compensates for wear of the rollers.

Each roller 12 includes an outer surface where the pelleting work forces are concentrated. FIG. 3 shows roller assembly 18 having a single-piece roller 20 mounted on bearings 22 on roller shaft 24. FIG. 4 shows how a two-piece roller may be constructed from hub 24 and shell 26. Hub 24 is mounted to roller shaft 24, and then cap screws 28 are used to engage shell 26 to hub 24. Also see, for example, the rollers describe U.S. Patent Application Publication No. 2010/0183759, which is hereby incorporated herein.

Rollers are consumable and eventually need to be replaced. Rollers are typically heat treated to provide wear resistance. However, a heat treat problem can occur on thick rollers which are used in large pellet mills. Heat treatment of thick rollers can cause a softer material condition which results in premature wear. Reducing the thickness of the roller by decreasing its outer diameter is unacceptable as pelleting efficiency is reduced due to poor pelleting nip angle. The most efficient rollers are generally ones with the largest outer diameter that the die will accommodate, which will create the best nip angle.

Accordingly, there a need for a roller that addresses the heat treat problems that cause soft material condition. There is also need for an effective and convenient way to assemble and disassemble a roller assembly to allow for replacement of a roller.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed to a pelleting roller assembly and pelleting apparatus.

In aspects of the present invention, a pelleting roller assembly comprises a shell including a frustoconical inner surface, and a hub including a frustoconical outer surface configured to fit within and engage the frustoconical inner surface of the shell. The frustoconical outer surface and the frustoconical inner surface form a tapered joint when the frustoconical outer surface is engaged to the frustoconical inner surface. A plurality of threaded connector holes are formed at the tapered joint. At least one threaded jacking hole is formed at the tapered joint.

In aspects of the present invention, a pelleting apparatus comprises a die including a tubular wall and a plurality of perforations formed through the tubular wall, and one or more of pelleting roller assembly disposed within the die. The pelleting roller assembly comprises a shell including a frustoconical inner surface, and a hub including a frustoconical outer surface configured to fit within and engage the frustoconical inner surface of the shell. The frustoconical outer surface and the frustoconical inner surface form a tapered joint when the frustoconical outer surface is engaged to the frustoconical inner surface. A plurality of threaded connector holes are formed at the tapered joint. At least one threaded jacking hole is formed at the tapered joint.

The features and advantages of the invention will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a die containing three rollers.

FIG. 2 is a front end view showing three rollers extruding material through a die. FIG. 3 is a cross-section view of a roller assembly having a single piece roller. FIG. 4 is a cross-section view of two-piece roller for use in a roller assembly. FIG. 5 is an internal view of a pelleting apparatus, the view showing a die rotatable within a housing.

FIG. 6 is a cross-section view of a roller shaft and bearings on which a roller can be mounted. FIG. 7 is a perspective, exploded view of a roller, the view showing a tapered shell disassembled from a tapered hub.

FIG. 8 is a cross-section view of the roller of FIG. 7 when the tapered shell and the tapered hub are assembled, the view showing cap screws within connector holes at a tapered joint between the tapered shell and the tapered hub.

FIG. 9 is a detailed cross-section view of another location of the tapered joint, the view showing one of many jacking holes formed at the tapered joint.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in the present specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. To the extent there are any inconsistent usages of words and/or phrases between an incorporated publication or patent and the present specification, these words and/or phrases will have a meaning that is consistent with the manner in which they are used in the present specification.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in more detail to the exemplary drawings for purposes of illustrating embodiments of the invention, wherein like reference numerals designate corresponding or like elements among the several views, there is shown in FIG. 5 exemplary pelleting apparatus 30 used to form pellet products, such as pelletized animal feed and biomass fuel, from flowable material composed of various grains or other particulate material. The flowable material enters top opening 32 of housing 34 and is guided to front opening 36 of ring-shaped die 40. Die 40 has the shape of a hollow cylinder with inner and outer surfaces on tubular wall 42. Tubular wall 42 includes a plurality of extrusion holes or perforations 44 that extend through the inner and outer surfaces. The flowable material is extruded through perforations 44 by rollers described below. Mainshaft 46 is connected to an armature within the cavity of die 40, which in turn caries a plurality of rollers described below.

There can be any number of roller assemblies within the cavity of die 40. For example, there can be three roller assemblies, such as in FIGS. 1 and 2, which are arranged 120 degrees apart from each other. Alternatively, there can be two roller assemblies arranged 180 degrees apart from each other.

FIG. 6 shows exemplary pelleting roller assembly 50 with its roller (shown in FIGS. 7 and 8) having been removed. Pelleting roller assembly 50 includes the roller, roller shaft 52, seals 54, and a pair of cylindrical bearings 57. Roller shaft 52 to configured to be connected to an armature attached to mainshaft 46 (FIG. 5). Cylindrical bearings 57 are configured to allow the roller described below to rotate relative to roller shaft 52. Each cylindrical bearing 57 includes inner ring 59 and outer ring 61. Inner ring 59 is fixedly attached to roller shaft 52. Outer ring 61 is configured to rotate relative to inner ring 59 and roller shaft 52. Seals 54 are configured to prevent liquid lubricant in cylindrical bearings 57 from leaking out of pelleting roller assembly 50. Protrusions 56 adjacent to cylindrical bearings 57 are configured to engage the roller described below. Protrusions 56 extend radially outward and may be in the form of a ring.

Central axis 53 of roller shaft 52 is offset from rotation axis 55 of the roller described below. The offset distance between roller shaft central axis 53 and roller rotation axis 55 allows the position of the roller to be adjusted in relation to the internal face of die 40. Adjustment is accomplished by slightly rotating roller shaft 52 about its central axis 53. As shown in FIGS. 7 and 8, roller 60 is a two-piece design. Roller 60 includes hub 62 and shell 64. Hub 62 and shell 64 are hollow cylinders having complementary frustoconical surfaces that mate with other. Hub 62 includes a pair of annular grooves 66 formed into inner surface 68. One of the grooves 66 is located adjacent to front end 70 of hub 62, and the other groove 66 adjacent to rear end 72 of hub 62. In pellet apparatus 30 (FIG. 5), hub front end 70 is closer than hub rear end 72 to front opening 36, and hub rear end 72 is closer hub than front end 70 to mainshaft 46. Each annular groove 66 is configured to receive and engage protrusion 56 (FIG. 6) attached to roller shaft 52 in a manner that prevents hub 62 from sliding axially relative to roller shaft 52 in the direction of arrows 74 and 75.

In operation, rollers 60 and die 40 rotate simultaneously. Die 40 rotates about its central axis 41 (FIG. 5) while rollers 60 rotate about their individual axes 53 (FIGS. 6 and 8). Roller rotation axes 53 remain stationary during normal operation. As mentioned above, the position of roller rotation axes 53 relative to die 40 can be adjusted when needed by rotating roller shaft 52.

Outer surface 76 of hub 62 is smooth and has a tapered outer diameter that forms a frustoconical shape having an included angle A (FIG. 8) within a range from 7 degrees to 15 degrees. Hub outer diameter 78 at front end 70 is smaller than hub outer diameter 80 at rear end 72, which allows shell 64 to be pushed onto and around hub frustoconical outer surface 76.

Inner surface 82 of shell 64 is smooth and has a tapered inner diameter that forms a frustoconical shape having an included angle A (FIG. 8) within a range from 7 degrees to 15 degrees. Shell inner diameter 84 at front end 86 is smaller than shell inner diameter 88 (FIG. 8) at rear end 90. At the front end, shell inner diameter 84 can be the same as hub outer diameter 78. At the rear end, shell inner diameter 88 can be the same as hub outer diameter 80.

The shape of hub frustoconical outer surface 76 matches the shape of shell frustoconical inner surface 82. Hub frustoconical outer surface 76 is configured to fit within and engage shell frustoconical inner surface 82. Hub frustoconical outer surface

76 and shell frustoconical inner surface 82 form tapered joint 97 (FIG. 8) when hub frustoconical outer surface 76 is engaged with shell frustoconical inner surface 82.

Tapered joint 97 is where hub frustoconical outer surface 76 makes contact with shell frustoconical inner surface 82.

As shown in FIGS. 7 and 8, pelleting roller assembly 50 includes cap screws 92 and hardened washers 94 used to assemble hub 62 and shell 64 together. When pelleting roller assembly 50 is fully assembled, cap screws 92 are disposed within threaded connector holes 96 (FIG. 8) formed at tapered joint 97. Connector holes 96 are spaced equally apart from each other around the circumference of roller 60. Six connector holes 96 and an equal number of cap screws 92 are illustrated, although a greater or lesser number may be implemented depending on the size of the roller. Each connector hole 96 has a counter bore.

Each connector hole 96 is split axially in two opposing grooves separated by tapered joint 97. Each connector hole 96 is formed by hub connector groove 98 formed into hub frustoconical outer surface 76 and by opposing shell connector groove 100 formed into shell frustoconical inner surface 82. When hub 62 and shell 64 are assembled together, hub connector grooves 98 align with shell connector grooves 100 to form connector holes 96.

In order to assemble hub 62 and shell 64, shell 64 is positioned onto hub 62. Cap screws 92 are inserted into connector holes 96 so that each cap screw 92 engages screw threads on hub connector groove 98. A person may use a tool to rotate cap screws 92 so that each cap screw 92 moves axially further into hub connector groove 98 until the head of the cap screw rests on shell ledge 102 in the counterbore of connector holes 96. With continued rotation, the head of cap screw pushes shell 64 in the direction of arrow 74. Movement of shell 64 in the direction of arrow 74 relative to hub 62 causes shell frustoconical inner surface 82 to compresses tightly around hub frustoconical outer surface 76. Shell connector groove 100 may be smooth and be without screw threads in order to facilitate free rotation of cap screws 92 when installing shell 64 onto hub 62.

To remove shell 64 from hub 62, cap screws 92 can be rotated in the reverse direction. Due to friction, shell 64 may remain tightly engaged onto hub 62 even after cap screws 92 are loosened or removed. Disassembly cap screw 110 is used to pull shell 64 off of hub 62 in the direction of arrow 75. Disassembly cap screw 110 is inserted into threaded jacking hole. Multiple jacking holes are spaced equally apart from each other around the circumference of roller 60. Jacking holes may alternate with connector holes 96 around the circumference of roller 60.

One of the jacking holes 112 is shown in FIG. 9. Each jacking hole 112 is formed at tapered joint 97. As shown in FIGS. 7 and 9, each jacking hole 112 is split axially in two opposing grooves separated by tapered joint 97. Each jacking hole 112 is formed by hub jacking groove 114 formed into hub frustoconical outer surface 76 and by opposing shell jacking groove 116 formed into shell frustoconical inner surface 82. As shown in FIG. 9, axial depth 118 of hub jacking groove 114 is less than axial depth 120 of shell jacking groove 116 and is also less than axial length 122 of disassembly cap screw 110. When disassembly cap screw 110 is inserted into jacking hole 1 12, disassembly cap screw 110 engages screw threads on shell jacking groove 116. A person may user a tool to rotate disassembly cap screw 110 so that it moves deeper into jacking hole 112. When disassembly cap screw 110 comes into contact with the bottom of hub jacking groove 1 14, continued rotation of disassembly cap screw 1 10 pulls shell 64 in the direction of arrow 75 off of hub 62. Hub jacking groove 114 may be smooth and be without screw threads in order to facilitate free rotation of disassembly cap screw 110 relative to hub 62.

Although only one disassembly cap screw 110 is shown in FIG. 7, multiple disassembly cap screws 110 can be used simultaneously, with one disassembly cap screw 110 in each jacking hole 112, in order to apply a uniform removal force and avoid damage to roller 60. In some embodiments, cap screws 92 can have the same size and screw thread as disassembly cap screw 110. During disassembly, cap screws 92 can be removed from connector holes 96 and then threaded into jacking holes 112 to force shell 64 off of hub 62.

Tapered-bore joint 97 described above between hub 62 and shell 64 is capable of holding the two parts tight, and allows the two parts to run true with no wobble.

Tapered-bore joint 97 described above also allows for easy installation and removal, which reduces the time and costs associated with rebuilding the roller when replacing the shell and during periodic maintenance.

It will be appreciated from the foregoing description that the two-piece design of roller 60 reduces the thickness of material to be heat treated. That is, the radial thickness of shell 64 is substantially less than what the overall radial thickness of a single piece roller (hub 62 combined with shell 64) would be. With reduced material thickness, problems with heat treatment that occur with thicker materials can be avoided. The radial thickness of shell 64 can be selected to allow for through hardening, i.e., hardening throughout shell 64. In some embodiments, shell 64 is heat treated to have a greater material hardness than hub 62 since pelleting forces are concentrated on outer surface 124 of shell 64. Hub 62 can be made of a suitable material that provides strength and hardness that allows for its reuse.

As shown in FIGS. 7-9, a plurality of grooves 124 are formed into outer surface

126 of shell 64. Grooves 124 are parallel to each other and are axially aligned. Grooves 124 provide a corrugated texture to outer surface 126 which can improve traction of roller 60 on a feed pad which drives rotation of rollers 60 within die 40. Other textures for outer surface 126 can be implemented, such as dimpled and hardfaced. As shown in FIG. 8, shell outer surface 126 has outer diameter 128 at shell front end 86 and outer diameter 130 at shell rear end 64. Outer surface 128 is the same as outer diameter 130.

The pelleting roller assembly and roller described herein can be used in a variety of different pelleting apparatuses in addition to pelleting apparatus 30 of FIG. 5.

While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications can be made without departing from the scope of the invention. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.