Shock absorbing feed wheel assembly

Abstract

A strapping machine of the type that feeds, retracts, tensions and seals strap to itself to form a loop of strap around a load, has a shock absorbing feed wheel assembly. The machine includes a frame, a feed head having a motor, a tension head, a sealing head and a strap chute mounted to the frame. The feed wheel assembly has a friction engaging surface and at least one pocket formed therein. A spring hub is engaged with the feed wheel and has at least one pocket formed therein corresponding to the feed wheel pocket. The spring hub is operably connected to the feed head motor. At least one spring is positioned in the feed wheel pocket and the spring hub pocket and is sandwiched between the feed wheel and the spring hub. The feed wheel is driven by rotation of the spring hub and engagement of the spring with the feed wheel pocket and spring hub pocket. The shock absorbing feed wheel assembly dampens the forces on the feed head motor and drive when the feed wheel comes to an abrupt stop and prevents strap slippage.

Claims

1. A strapping machine comprising: a frame; a tension head mounted to the frame; a sealing head mounted to the frame; a strap chute mounted to the frame, and a feed head mounted to the frame and comprising: an output shaft; a motor drivingly engaged to the output shaft; a feed wheel having a friction engaging surface and defining a feed wheel pocket; a spring hub defining a spring hub pocket and engaged with the feed wheel such that the spring hub pocket is aligned with the feed wheel pocket, wherein the output shaft is operably connected to the spring hub to rotate the spring hub; a biasing element positioned in the feed wheel pocket and the spring hub pocket such that the biasing element is sandwiched between the feed wheel and the spring hub and operably connects the feed wheel and the spring hub such that rotation of the spring hub by the output shaft causes the spring hub to drive the feed wheel by engagement of the biasing element with the feed wheel and the spring hub; and a disc spring positioned on an opposite side of the spring hub from the feed wheel, the disc spring forcing the spring hub into engagement with the feed wheel.

2. The strapping machine of claim 1, wherein the biasing element comprises a spring.

3. The strapping machine of claim 1, wherein the feed wheel further comprises a radially inwardly extending flange, and wherein the feed wheel pocket is defined in the flange.

4. The strapping machine of claim 1, wherein the feed wheel pocket and the spring hub pocket form a pocket pair in which the biasing element is positioned.

5. The strapping machine of claim 1, wherein the feed wheel comprises a projection that at least in part defines the feed wheel pocket.

6. The strapping machine of claim 5, wherein the biasing element engages the projection.

7. The strapping machine of claim 1, wherein the feed wheel defines four feed wheel pockets and the spring hub defines four spring hub pockets, and wherein the spring hub engages the feed wheel such that each of the feed wheel pockets is aligned with a different one of the spring hub pockets to form a pocket pair, the feed head further comprising four biasing elements, each biasing element positioned in a different one of the pocket pairs.

8. The strapping machine of claim 7, wherein the pocket pairs are equally circumferentially spaced from one another.

9. The strapping machine of claim 1, wherein the feed head further comprises a shaft adapter operably connecting the output shaft and the spring hub.

10. The strapping machine of claim 9, wherein the output shaft and the shaft adapter are mounted to one another to rotate together, and wherein the shaft adapter and the spring hub are mounted to one another to rotate together.

11. The strapping machine of claim 10, wherein the spring hub and the shaft adapter are mounted to one another by a key-in-slot configuration, and wherein the shaft adapter and the output shaft are mounted to one another by another key-in-slot configuration.

12. The strapping machine of claim 1, wherein the biasing element is configured to dampen forces on the output shaft responsive to rotation of the feed wheel stopping.

13. The strapping machine of claim 1, wherein the feed head further comprises a gear box comprising the output shaft.

14. A strapping machine comprising: a frame; a tension head mounted to the frame; a sealing head mounted to the frame; a strap chute mounted to the frame, and a feed head mounted to the frame and comprising: an output shaft; a motor drivingly engaged to the output shaft; a feed wheel having a friction engaging surface and defining a feed wheel pocket, wherein the output shaft is operably connected to the feed wheel to rotate the feed wheel in a feed direction to feed a strap through the strap chute and in a retraction direction to retract the strap from the strap chute onto a load; a shock absorber operably engaged to the output shaft to dampen forces on the output shaft responsive to rotation of the feed wheel in the retraction direction stopping when the strap is retracted onto the load; and a disc spring positioned to force the shock absorber to engage the feed wheel.

15. The strapping machine of claim 14, wherein the shock absorber comprises: a spring hub defining a spring hub pocket; and a biasing element.

16. The strapping machine of claim 15, wherein the output shaft is operably connected to the spring hub to rotate the spring hub, wherein the spring hub is engaged with the feed wheel such that the spring hub pocket is aligned with the feed wheel pocket and the biasing element is positioned in the feed wheel pocket such that the biasing element is sandwiched between the feed wheel and the spring hub and operably connects the feed wheel and the spring hub so that rotation of the spring hub by the output shaft causes the spring hub to drive the feed wheel by engagement of the biasing element with the feed wheel and the spring hub.

17. The strapping machine of claim 15, wherein the feed wheel comprises a projection that at least in part defines the feed wheel pocket.

18. The strapping machine of claim 17, wherein the biasing element engages the projection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustration of a strapping machine having a feed head with an embodiment of a shock absorbing feed wheel assembly;

(2) FIG. 2 is a partially exploded view of a prior art feed head;

(3) FIG. 3 is a partially exploded view of an embodiment of a feed head with a shock absorbing feed wheel assembly, illustrating one example of the feed wheel, shaft adapter and springs;

(4) FIG. 4 is a partially exploded view of an embodiment of the feed wheel assembly illustrating one example of the spring hub, seal, disk spring and support plate; and

(5) FIG. 5 is a an exploded view of the feed wheel assembly.

DETAILED DESCRIPTION

(6) While the present disclosure is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described one or more embodiments with the understanding that the present disclosure is to be considered illustrative only and is not intended to limit the disclosure to any specific embodiment described or illustrated.

(7) Referring now to the FIG. 1, an example of a strapping machine 10 is shown. The strapping machine 10 is configured for use with steel strap S that can be tensioned and sealed to itself to form a loop of strap around a load L. The strapping machine 10 includes, generally, a frame 12, a feed head 14, a tension head 16, a sealing head 18 and a strap chute 20 through which the strap S is conveyed around the load L. Strap S is fed from a strap supply such as a strap dispenser (not shown). In an embodiment, the strapping machine 10 is controlled by a controller 22.

(8) Briefly, in a typical operation, strap S is pulled from the dispenser and fed into the machine 10 by the feed head 14. The feed head 14 conveys the strap S through the tension head 16, through the sealing head 18, into and around the strap chute 20 and back to the sealing head 18 in a forward direction. Once the lead end of the strap S is secured in the sealing head 18, the feed head 14 operates in reverse to withdraw or retract the strap S from the strap chute 20 onto the load L. The tension head 16 then draws tension in the strap S as it is positioned around the load L and holds tension in the strap S at the commencement of the sealing cycle.

(9) The timing of the strap feed and retraction portions of the cycle can be quite quick and are carried out automatically and sequentially. As such, when the strap S is retracted it can come to an abrupt stop once it is drawn tightly around the load L. This is especially so when the load L is hard or solid materials, such as metal coils, ingots and the like, because these materials have no resilience. That is, there is no “give” in these materials. In addition, the retracted strap can slip along the feed wheel surface resulting in premature wear of the feed wheel surface.

(10) In order to lessen the stresses or dampen the forces on the feed head 14, and to prevent strap slippage, an embodiment of the shock absorbing feed wheel assembly 26 includes a biased connection between the drive elements of the feed head 14, e.g., a feed motor 28 and a feed wheel 30. Referring to FIGS. 3-5, an embodiment of the shock absorbing feed wheel assembly 26 includes a shaft adapter 32 that is mounted to a gearbox 24 at the gearbox output shaft 34 using a keyed configuration. The shaft adapter 32 has a back plate 36 and a sleeve 38 extending from the back plate 36. The sleeve 38 fits over the gearbox output shaft 34. In an embodiment, a slot 40 in the interior of the sleeve 38 and a slot in 39 on the exterior of the output shaft 34 cooperate to receive a key 42 to secure the output shaft 34 and the sleeve 38. In this manner, the gearbox output shaft 34 rotationally drives the shaft adapter 32. The sleeve 38 also includes a slot 44 in an outer surface as discussed in more detail below.

(11) In an embodiment, the feed wheel 30 has an outer rim 48 with a frictional gripping surface 50 and a radially extending, inwardly oriented, circumferential flange 52. The flange 52 has a central opening 54 to fit over the shaft adapter sleeve 38. The feed wheel 30 includes at least one pocket or recess 46 formed in the flange 52. In an embodiment, the feed wheel flange 52 includes four pockets 46 that extend circumferentially around the flange 52 in an interior 35 of the feed wheel 30. The pockets 46 can be formed equally circumferentially spaced from one another which, as shown, when the feed wheel 30 includes four pockets 46, are at 90 degrees from one another.

(12) Biasing elements 58 are positioned and seated in the feed wheel pockets 46. In an embodiment the biasing elements 58 are coil springs, such as die springs that fit into the pockets 46. Projections or walls 37 on the sides of the pockets 46 maintain the springs 58 in place in the pockets 46.

(13) A spring hub 60 has a stub 61 having a central opening 62 and is positioned on the adapter sleeve 38 outboard of the feed wheel 30. In an embodiment the spring hub 60 includes one or more pockets 64 that correspond to or align with the feed wheel flange pockets 46. The illustrated embodiment of the assembly 26 includes four such pocket pairs, each pocket pair being a feed wheel pocket 46 and its corresponding spring hub pocket 64. Although four feed wheel pockets 46, biasing elements 58 and spring hub pockets 64 are shown, the shock absorbing feed wheel assembly 26 can include any number, for example, between one and five or six pockets 46, 64 (e.g., pocket pairs) and biasing elements 58. Those skilled in the art will appreciate that more or less of these can be used as desired. In an embodiment, the spring hub has an peripheral channel or recess 63 formed therein, discussed in more detail below.

(14) When assembled, the feed wheel 30 abuts the back plate 36 and the spring hub 60 engages and abuts the feed wheel 30 to sandwich the springs 58 between the feed wheel 30 and the spring hub 60. The spring hub 60 has a slot 66 in the central opening 62. A key 68 is positioned in the spring hub slot 66 and the adapter sleeve outer slot 44. The key 68 affixes and locks rotation of the shaft adapter 32 and the spring hub 60, again, with the feed wheel 30 and springs 58 sandwiched between the adapter 32 and hub 60.

(15) In an embodiment, one or more springs, such as the illustrated disk spring 70 and a taper bearing 72 are positioned over the end of the shaft adapter sleeve 38. The spring 70 and taper bearing 72 are positioned at the spring hub stub 61, so as to minimize exposure of the bearing to debris. In an embodiment, a seal 75 is positioned in spring hub channel 63 to prevent debris (for example, debris generated by the feed wheel 30 engaging the strap S) from entering the bearing 72.

(16) A shaft support plate 74 is positioned outboard of the taper bearing 72, shaft adapter sleeve 38 and spring hub stub 61 to retain the shock absorbing feed wheel assembly 26 as assembled and in place in the feed head 14, and in engagement with the gearbox output shaft 34. In an embodiment the shaft support plate 74 includes a recess 77 in which the bearing 72 is seated. The shaft support plate 74 is secured to the feed head 14 by fasteners 76. The force of the disk spring 70 against the taper bearing 72 (which bears against the shaft support plate 74) and against the spring hub 60 ensures that the components of the feed wheel assembly 26 all fully engage one another and that the assembly 26 remains in place (longitudinally relative to the gearbox 24) with the die springs 58 in place in the feed wheel pockets 46 and spring hub pockets 64. That is, the disk spring 70 being positioned outboard of the spring hub 60 maintains the hub 60, feed wheel 30 and springs 58 in a sandwiched state.

(17) In an embodiment, the die springs 58 are configured with a sufficiently high spring rate (stiffness) so that the springs 58 do not compress during normal feed and take-up (retraction) portions of the cycle. Rather, the springs 58 are configured so that they compress between the hub pocket 64 walls and the feed wheel walls or projections 37 when the wheel 30 abruptly stops, or when there is significant tension in the strap S to prevent the strap S from slipping along the feed wheel surface 50. Once the forces due to the abruptly stopping strap S cease or once the tension in the strap is relieved, the springs 58 return the feed wheel 30 to an original position (non-compressed spring 58 condition) relative to the gearbox 24 and output shaft 34, ready for the next strapping cycle.

(18) The shock absorbing feed wheel assembly 26 in accordance with the examples of the present disclosure provides a number of advantages over fixed feed wheel assemblies. For example, when the feed head 14 reverses to draw the strap S onto hard or solid loads L, such as metal coils and the like, and the strap S comes to an abrupt stop, the springs 58 in the feed wheel assembly 26 absorb the force of the abruptly stopping strap S, and the stresses that would otherwise be induced in the adapter, keys, gearbox and output shaft of a fixed system, thus potentially preventing premature failure of these components.

(19) Moreover, because feed wheels 30 typically have a serrated or toothed friction surface 50, high frictional forces are created between the wheel surface 50 and the strap S. Thus, when there is a fixed connection between the wheel and the strap, as the strap comes to a stop, the strap may pull or slip between the wheel surface and an anvil against which the strap is held, or if the friction is sufficiently high, the forces can be induced back into the gearbox. Again, the present shock absorbing feed wheel assembly 26 has a biased or floating connection between the feed wheel 30 and the gearbox 24 which prevents such strap S slippage, and prevents premature wear or failure of the feed wheel frictional surface 50, thus prolonging the life of the feed wheel frictional surface 50.

(20) In addition, the use of one or more outboard springs 70, such as the disk spring in the illustrated embodiment, provides positive engagement of the feed wheel assembly 26 with the gear box 24 and output shaft 34 in the axial direction, thus eliminating the need for pins or other securing elements to maintain the feed wheel assembly engaged with the gear box output shaft.

(21) It will be appreciated by those skilled in the art that the relative directional terms such as sides, upper, lower, rearward, forward and the like are for explanatory purposes only and are not intended to limit the scope of the disclosure.

(22) All patents or patent applications referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure.

(23) In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular.

(24) It should be understood that various changes and modifications to the presently preferred embodiments disclosed herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present disclosure and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.