Drive assemblies for shell stock feeder assemblies and methods of feeding material into shell presses

Abstract

A drive assembly for a feeding assembly for a shell press system includes a drive shaft. The drive shaft is integrally disposed in or attached to the feed roll. A gearbox is operatively connected to the drive shaft. A main motor is operatively connected to the gearbox. As such, the main motor is designed to rotate the drive shaft and the feed roll through the gearbox. An auxiliary motor is operatively connected to the drive shaft. The auxiliary motor is a servomotor.

Description

FIELD OF THE INVENTION

[0001] The disclosed concept relates generally to feeding assemblies for shell presses and, more particularly, to shell stock feed assemblies and associated methods for feeding material into shell presses.BACKGROUND OF THE INVENTION

[0002] The formation of can ends or shells for can bodies, namely aluminum or steel cans, is generally well known in the art.

[0003] FIG. 1 shows an example shell press 2 including a shell press 4 designed to form shells 6 (shown in simplified form) from a material 50 (e.g., without limitation, aluminum) as it is fed between a die set 10 (indicated generally and not shown in detail in FIG. 1). More specifically, in the exemplary embodiment, the material 50 is supplied as coil stock 52 (shown in simplified form). A feeding assembly 20 having a plurality of rolls 22, 24 forms a stock loop 26 to facilitate delivery of the material 50 to and between the die set 10 of the shell press 4. The feeding assembly 20 is spaced apart from the shell press 4 a distance, d. This distance, d, measured between the centerline 14 of the shell press 4 and the centerline 28 of the feeding assembly 20, corresponds to the indexing stock of material 50. Supporting elements 30 are included to support the indexing stock of material 50 between the feeding assembly 20 and the shell press, and conveyance equipment 40 is provided for conveying the shells 6 from the shell press 4 after being formed by the die set 10.

[0004] There is an ongoing desire in the can making industry to manufacture high volumes of shells as rapidly and efficiently as possible. Among other ways companies have attempted to achieve these objectives are: (1) to increase the number of pockets in the die set, within which shells may be formed; and (2) to increase the speed (e.g., strokes per minute (spm)) at which the shell press operates. In general, with each stroke of the shell press ram, one shell is formed in each tooling pocket of the die assembly. Thus, a 24-out die assembly, for example, which has 24 tooling pockets, is capable of forming 24 shells, per stroke.

[0005] Feeding such material at relatively high speeds creates a number of unique design challenges. For example, inefficient positioning of the material 50 during indexing can create an excessive amount of scrap material that is discarded. Although the amount of scrap material is relatively small compared to the amount of material retained as shells, the waste is significant at a large scale. Furthermore, indexing is challenging even when using precision machines like a servomotor to control the mechanism for feeding the material 50.

[0006] A significant reason for the challenges in accurately indexing the material at high speeds is the presence of backlash in gear-driven drive assemblies. In a gear assembly, the teeth of each gear have gaps between them. The gaps are larger than the corresponding teeth of an opposing gear. These gaps are necessary to allow rotation of the gears and also allow space for lubricant between the teeth. However, when a gear assembly rotates, backlash occurs. Backlash is a loss of motion created by these spaces. As shown in FIG. 2, this backlash B is represented by the distance between a first tooth 61 of a first gear 60 and a first tooth 71 of a second gear 70 when the first tooth 71 of the second gear 70 is in contact with a second tooth 62 of the first gear 60, such as when the first gear 60 is rotating in a clockwise direction and the second gear 70 is rotating in a counterclockwise direction.

[0007] There are several methods of addressing backlash. For example, precision gears utilize complex geometries in their teeth to minimize backlash. However, precision gears are more expensive, require more complex maintenance and cleaning to preserve, and are generally more difficult to install and drive. Furthermore, certain gear assemblies have been spring-loaded to apply tension to the assembly and hold gear teeth in contact with each other. However, these systems lack variable force controls and are not operable for gear assemblies requiring relatively large amounts of power.

[0008] There is, therefore, room for improvement in feeding assemblies for shell presses, and in feeding assemblies for shell presses that address backlash in high torque systems while reducing wear and tear on feeding assembly components.SUMMARY OF THE INVENTION

[0009] The above-described needs, and others, are met by the presently disclosed technology, which provides a system and / or technique for eliminating or substantially reducing backlash, including in drive assemblies for feeder assemblies for shell presses.

[0010] In one exemplary embodiment of the presently disclosed technology, a drive assembly may be used for a feed assembly including a feed roll coupled to a support element. The feed assembly may be configured to feed a material into a shell press. The drive assembly may include a drive shaft. The drive shaft may be integrally disposed in or attached to the feed roll. A gearbox may be operatively connected to the drive shaft. A main motor may be operatively connected to the gearbox. As such, the main motor may be configured to rotate the drive shaft and the feed roll through the gearbox. An auxiliary motor may be operatively connected to the drive shaft. The auxiliary motor may be a servomotor.

[0011] In another exemplary embodiment of the presently disclosed technology, a shell press system may be configured to press a material into a plurality of can shells. The shell press system may comprise a shell press. The shell press may include a base and a die set. The shell press system may further comprise a feeding assembly. The feeding assembly may be configured to feed material into the shell press, between the die set, to form a plurality of can shells. The feeding assembly may comprise a drive shaft. The drive shaft may be integrally disposed in the feed roll or attached to the feed roll. A gearbox may be operatively connected to the drive shaft. A main motor may be operatively connected to the gearbox. As such, the main motor may be configured to rotate the drive shaft and the feed roll through the gearbox. An auxiliary motor may be operatively connected to the drive shaft. The auxiliary motor may be a servomotor.

[0012] In a further exemplary embodiment of the presently disclosed technology, a method of indexing material in a shell press system may include placing a material onto a feed roll. The feed roll may be rotated by rotating a drive shaft with a main motor. The drive shaft may be integrally disposed in the feed roll or attached to the feed roll. The material may be moved into a die set of a shell press. The material may be indexed by the main motor and the auxiliary motor. The auxiliary motor may be a servomotor.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

[0014] FIG. 1 is an elevation view of a prior art shell press;

[0015] FIG. 2 is a close-up view of a representative gear assembly of one embodiment of the presently disclosed technology;

[0016] FIG. 3 is a perspective view of a drive assembly for a feeding assembly for a shell press of one embodiment of the presently disclosed technology;

[0017] FIG. 4 is a front elevation view of the drive assembly of FIG. 3;

[0018] FIG. 5 is a perspective view of a feeding assembly for a shell press of one embodiment of the presently disclosed technology;

[0019] FIG. 6 is a graph plotting the position of material and percentage of continuous current applied by a main motor and an auxiliary motor over time according one embodiment of the presently disclosed technology;

[0020] FIG. 7 is a graph plotting the position of the material and percentage of continuous current applied by the main motor and the auxiliary motor over time according one embodiment of the presently disclosed technology; and

[0021] FIG. 8 is a graph plotting the bounce of backlash in an exemplary gearbox of one embodiment of the presently disclosed technology.DETAILED DESCRIPTION OF THE INVENTION

[0022] For purposes of illustration, embodiments of the disclosed concept will be described as applied to a wide out shell press, although it will become apparent that they could also be applied to a variety of alternative shell presses having any known or suitable size and / or configuration of metal forming tooling and related components.

[0023] Directional phrases used herein such as, for example, clockwise, counterclockwise, upper, lower, top, bottom, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

[0024] As employed herein, the term “can” refers to any known or suitable container, which is structured to contain a substance (e.g., without limitation, liquid; food; any other suitable substance), and expressly includes, but is not limited to, beverage cans, such as aluminum beer and soda cans, as well as food cans.

[0025] As employed herein, the term “can end” refers to the closure that is structured to be coupled to the can, in order to seal the can.

[0026] As employed herein, the term “material” refers to any material that is capable of being fed into a shell press and formed into can shells. The material can be a formable metal material, such as aluminum. Furthermore, it is contemplated that the material can be provided in any form which may be continuously fed into the shell press, such as a coil stock.

[0027] As employed herein, the terms “shell” and “can end shell” refer to the member that is formed in the disclosed shell press and is subsequently acted upon and converted by suitable tooling, typically within a conversion press, in order to provide the desired can end.

[0028] As employed herein, the term “servomotor” refers to a motor that includes an integrated feedback system. The integrated feedback system may include one or more sensors to gather and relay data into the feedback system. However, as used herein, the term “servomotor” is not limited to any specific feedback mechanisms.

[0029] A shell press 4 is configured to press a material into a plurality of can end shells to be used to form a can. The shell press 4 includes a die set 10. The die set 10 is pressed into the material by a shell press ram 12. The shell press ram 12, in an exemplary embodiment, may stroke 675 times a minute. The shell press 4 requires an input of the material to press into can end shell. The material is generally fed into the shell press using a feed assembly 101. To accommodate the high stroke speed of the shell press 4, the feed assembly 101 utilizes an index and dwell feeding cycle. The dwell occurs where the material is stationary for the shell to be formed. The index occurs where the material is positioned (or indexed) for the next series of shells to be formed.

[0030] The feed assembly 101, generally, includes a drive assembly 201 configured to move the material into the shell press 4, and more specifically to index the material in a manner to efficiently press the material into as many can shells as possible while minimizing the amount of material lost as scrap after being pressed. The feed assembly 101 includes a feed roll 102. The feed roll 102 is coupled to a support element 103. The feed assembly 101 is configured to feed a material into a shell press 4.

[0031] In the exemplary embodiments, the drive assembly 201 includes a drive shaft 202. The drive shaft 202 is configured to drive and / or rotate the feed roll 102. As such, the drive shaft 202 may be disposed in the feed roll 102 and fixedly attached to and / or integrally formed therewith. In the illustrated exemplary embodiment, the drive shaft 202 extends outward from the feed roll 102. As such, the drive shaft 202 may be structurally connected to one or more driving mechanisms to drive rotation of the drive shaft 202.

[0032] A gearbox 203 is operatively connected to the drive shaft 202. The gearbox 203 includes at least a pair of gears. The pair of gears are meshed, such that rotation of a first gear in a first direction will drive rotation of a second gear in a second direction. Ultimately, the gearbox 203 is configured to receive energy from a first or main motor 204 and to convert that energy into rotational energy of the drive shaft 202.

[0033] The main motor 204 is operatively connected to the gearbox 203. As such the main motor 204 is configured to rotate the drive shaft 202 and the feed roll 102 through the gearbox 203. In an exemplary embodiment, the main motor 204 is a servomotor. In a further exemplary embodiment, the main motor 204 is a servomotor programmed to index the material in the shell press 4. The use of a servomotor allows for index length adjustments to be made quickly, such as within 50 milliseconds, and accurately. The main motor 204 is primarily responsible for generating sufficient torque to move the material along the feed roll 102 and between the die set 10 of the shell press 4. In an exemplary embodiment, the main motor 204 may be programmed to position the material 50 in the shell press within 0.001 inch of a targeted location at the end of the index.

[0034] The drive assembly 201 further includes a second or auxiliary motor 205. In the illustrated exemplary embodiment, the auxiliary motor 205 is located on an opposite side of the drive shaft 201 from the main motor 204. In such an embodiment the feed roll 102 is disposed between the main motor 204 and the auxiliary motor 205 such that the feed roll 102 is controllable by coordinated action of the main motor 204 and the auxiliary motor 205. In an exemplary embodiment, the auxiliary motor is a servomotor. The auxiliary motor 205 is configured to assist or supplement the main motor 204 in moving the material between the die set 10 of the shell press 4. The auxiliary motor 205 may further be programmed to assist the main motor 204 in indexing the material in the shell press 4. In an exemplary embodiment, the auxiliary motor 205 may be programmed to offset backlash in the drive assembly 201 when positioning the material 50 between the die set of the shell press during indexing. For example, the auxiliary motor 205 may be configured to accelerate and decelerate the feed roll 102 to further improve position accuracy of the material.

[0035] Conventionally, the use of a main motor 204 and an auxiliary motor 205 would be ill-advised because the simultaneous use of the main motor 204 with the auxiliary motor 205 would decrease stability of the drive assembly 201. As such, the main motor 204 may be a larger and / or more powerful servomotor than the auxiliary motor 205. For example, the main motor 204 may be a servomotor with a rated torque of 110.4 Newton-meters (Nm) while the auxiliary motor 205 may be a servomotor with a rated torque of 14.1 Nm. As such the auxiliary motor 205 will have a strong enough effect on the drive assembly 201 to index the material with only a negligible opposing force applied to the main motor 204.

[0036] Backlash in the gearbox 203 may result in a diminishment of position accuracy. In conjunction, the main motor 204 and the auxiliary motor 205 prevent or at least reduce backlash when the drive assembly 201 is stopped. Specifically, the auxiliary motor 205 applies torque to the drive assembly 201 against the torque of the main motor 204 to remove backlash from the entire drive assembly 201. When the gears of the gearbox 203 are stopped, the position of the drive shaft 202 is maintained (e.g., clearance is removed) between the gears in the gearbox 203. By preloading the drive assembly 201 to one side of the backlash, the degree of displacement from backlash may be substantially or entirely eliminated. Furthermore, use of both the main motor 204 and the auxiliary motor 205 reduces backlash at the end of the indexing and does not add any additional load or resistance to the drive assembly 201. Furthermore, reduced “bounce” at the end of the indexing phase will extend the operational lifespan of the gears and the gearbox 203.

[0037] In an exemplary embodiment, a gearbox including gears with a greater degree of backlash may be utilized in the drive assembly 201. Specifically, a gearbox 203 having a backlash of greater than 2 arc minutes may be utilized. In a further embodiment, the gearbox 203 may have a backlash greater than 4 arc minutes. In yet another embodiment, the gearbox 203 may have a backlash between 2 and 5 arc minutes. Gearboxes 203 having a greater degree of backlash may be preferable as they are less expensive than precision gears.

[0038] As demonstrated in FIG. 6, in one embodiment, the main motor 204 and the auxiliary motor 205 preload the drive shaft 202 between the main motor 204 and the auxiliary motor 205, thereby holding the drive shaft 202 to one side of the backlash. Without preloading the drive shaft 202, the final position of the feed roll 102 could be anywhere within the backlash of the drive shaft 202. Preloading the drive shaft 202 allows for a tangible increase in positional accuracy of the material indexed by the feed assembly 101. As shown specifically, the material position has a lower variance when an auxiliary motor 205 is used and when the auxiliary motor 205 applies a preload to the drive shaft 102.

[0039] Furthermore, as demonstrated in FIG. 7, in an exemplary embodiment, the main motor 204 and the auxiliary motor 205 selectively load the drive shaft 202 only during indexing. Generally, systems for preloading drive assemblies apply a constant load. For example, a spring-loaded drive assembly applies constant force on the main motor due to the tensioned nature of the spring. In contrast, the auxiliary motor 205 is selectively actuatable, meaning that the drive shaft 202 may be preloaded only during the index phase of the shell press process. By alleviating the constant load applied by conventional preloading systems, there is less wear on the main motor 204. Selectively loading the drive shaft 202 exclusively during indexing reduces the load and heat on the drive assembly 201 components and extends their operational lifespan. As shown specifically, the auxiliary motor 205 significantly reduces the load on the main motor 204. Once indexed, the preload can be removed from the drive shaft 202 by unwinding the drive shaft 202 away from the backlash in the gearbox 203. As such, the drive assembly 201 will be reset for the next stroke of the shell press.

[0040] Additionally, as demonstrated in FIG. 8, the “bounce” associated with an abrupt stop resulting from backlash in a drive system is substantially reduced or eliminated by preloading the drive shaft 202. By eliminating or substantially reducing bounce associated with backlash, the drive assembly 201 will have greater position accuracy when indexing the material in the shell press 4. Furthermore, eliminating or substantially reducing the “bounce” associated with backlash will prolong the operational lifespan of the drive assembly 201 and its components. As shown specifically, adding additional preload to the auxiliary motor 205 reduces bounce and / or rattling in the backlash. In turn, this improves position accuracy during indexing.

[0041] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Claims

1. A drive assembly for a feed assembly, the feed assembly including a feed roll coupled to a support element, and the feed assembly being configured to feed a material into a shell press, the drive assembly comprising:a drive shaft integrally disposed in or attached to the feed roll;a gearbox operatively connected to the drive shaft;a main motor operatively connected to the gearbox, such that the main motor is configured to rotate the drive shaft and the feed roll through the gearbox; andan auxiliary motor operatively connected to the drive shaft, wherein the auxiliary motor is a servomotor.

2. The drive assembly of claim 1, wherein the main motor is a servomotor.

3. The drive assembly of claim 2, wherein the auxiliary motor and the main motor eliminate backlash when the drive assembly is stopped.

4. The drive assembly of claim 2, wherein the auxiliary motor is located on an opposite side of the drive shaft from the main motor.

5. The drive assembly of claim 1, wherein the gearbox comprises at least a pair of gears, wherein the gears define a backlash greater than 2 arc minutes.

6. The drive assembly of claim 1, wherein the main motor is programmed to position the material in the shell press within 0.001 inch of a targeted location at the end of an index.

7. The drive assembly of claim 6, wherein the auxiliary motor is programmed to offset backlash in the drive assembly when positioning the material in the shell press during indexing.

8. The drive assembly of claim 7, wherein the main motor is configured to generate torque sufficient to move the material and the auxiliary motor is configured to accelerate and decelerate the drive shaft and to preload the gearbox against a backlash therein.

9. The drive assembly of claim 1, wherein the main motor is configured to generate more torque than the auxiliary motor.

10. A shell press system configured to press a material into a plurality of can shells, comprising:a shell press including a base and a die set;a feeding assembly for feeding material to the shell press and between the die set to form a plurality of shells, the feeding assembly comprising:a drive shaft integrally disposed in the feed roll;a main motor in operable connection with a gearbox;the gearbox in operable connection with the drive shaft, such that the main motor is configured to rotate the drive shaft and the feed roll; andan auxiliary motor in operable connection with the drive shaft, wherein the auxiliary motor is a servomotor.

11. The shell press of claim 10, wherein the main motor is a servomotor.

12. The shell press of claim 11, wherein the gearbox comprises at least a pair of gears meshed therein, wherein the gears define a backlash greater than 2 arc minutes.

13. The shell press of claim 10, wherein the main motor is programmed to position the material between the die set within 0.001 inch of a targeted location at the end of an index.

14. The shell press of claim 13, wherein the auxiliary motor is programmed to offset backlash in the drive assembly when positioning the material between the die set during indexing.

15. The shell press of claim 13, wherein the main motor is configured to generate torque sufficient to move the material and the auxiliary motor is configured to accelerate and decelerate the drive shaft and to preload the gearbox against a backlash therein.

16. The shell press of claim 10, wherein the main motor is configured to generate more torque than the auxiliary motor.

17. A method of indexing material in a shell press system, comprising:placing a material onto a feed roll;rotating the feed roll by rotating a drive shaft with a main motor, wherein the drive shaft is integrally disposed in the feed roll; andindexing the material between a die set with both the main motor and an auxiliary motor, wherein the auxiliary motor is a servomotor.

18. The method of claim 15, further comprising preloading the drive shaft with the auxiliary motor, thus holding the drive shaft to one side of a backlash.

19. The method of claim 15, further comprising pressing the die set onto the material to form a plurality of shells.

20. The method of claim 16, further comprising unwinding the preload applied by the auxiliary motor from the drive shaft applied by the auxiliary motor.

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