US3759189A - Anti-back-up device for work carriers on power-and-free conveyor systems - Google Patents

Abstract

A work carrier for a power-and-free conveyor system has antiback-up means comprising a pair of serrated cams mounted on the carrier frame and weight-biased into one-way frictional engagement with the undersurfaces of the track channels.

Description

United States Patent [1 1 Desilets [451 Sept. 18, 1973 ANTI-BACK-UP DEVICE FOR WORK CARRIERS ON POWER-AND-FREE CONVEYOR SYSTEMS [75] Inventor: Dennis W. Desllets, Sterling Heights,

Mich.

[73] Assignee: Standard Alliance Industries, Inc.,

Chicago, 11].

[22] Filed: Sept. 14, 1971 [21] Appl. No.: 180,401

UNITED STATES PATENTS 3200;768 8/1965 Harrison 104/172 S 2,326,377 8/1943 McBride 188/67 3,415,201 12/1968 Czarnecki.... 104/172 S 2,623,614 12/1952 Herr 188/44 648,258 4/1900 Hill l88/43 Primary Examiner-Robert G. Sheridan Assistant Examiner-Lawrence J. Oresky Attorney-Harness, Dickey & Pierce [5 7] ABSTRACT A work carrier for a power-and-free conveyor system has anti-back-up means comprising a pair of serrated cams mounted on the carrier frame and weight-biased into one-way frictional engagement with the undersurfaces of the track channels.

2 Claims, 2 Drawing Figures PATENTEDSEPIBW 3.759.189

SHEET 1 BF 2 I INVENIOR. I077: 14/ Jaszfifs PATENTED SEP l-8l973 sum 2 0F 2 INVENTOR.

j 77712.? V/Jesf/az ANTI-BACK-UP DEVICEFOR WORK CARRIERS ON POWER-AND-FREE CONVEYOR SYSTEMS BACKGROUND OF THE INVENTION The invention relates to power-and-free conveyor systems of the type shown in U. S. Pat. No. 3,415,201 issued Dec. I0, 1968 to A. Czarnecki. The invention is particularly applicable to work carriers having front and rear trolleys constructed so as to permit closepacking or accumulation, and which pass through transfer points.

Among the problems existing with respect to such conveyor systems is the danger of a carrier inadvertently backing up. This could be due to the pendulum effect of the load when a carrier is being nested. In other cases, the carrier could be inadvertently released from its pusher on a slope or at a transfer point. Backing up could also occur in case of driving chain breakage.

BRIEF SUMMARY OF THE INVENTION 3 According to the invention, a pair of cams are rockably mounted on the trolley frame of a work carrier, in this case on the rear trolley of a work carrier having front and rear trolleys connected by a load bar. The cams have serrated edges engageable with the lower flanges of the track channels, and are located between the load carrying wheels of the trolley, thus acting as a trolley hold-down and preventing the cam plate from tipping up in accumulation. The provision oftwo antiback-up cams on each carrier compensates for the presence of auxiliary devices required on certain systems which extend below the channel flanges and might disengage one of the cams.

The result is an anti-,back-up device which positively prevents a work carrier from backing up in accumulation and at transfer points regardless of the speed of the conveyor of the inertia induced in the carriers. The pendulum action of the workpiece is quickly dissipated due to the stabilizing effect the anti-back-up cams have on the load bar. The anti-back-up cams also allow accumulation of carriers on slight vertical inclines without the use of any auxiliary equipment. The location of the cams under the channels increases reliability because the only tolerance which need be taken into account is that of the lower flange thickness of the channels. Additionally, the space available under the channels allows provision of an effective anti-back-up device.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is especially adapted for use with a power-and-free conveyor system of the type shown in the aforementioned US. Pat. No. 3,415,201. In such a system, a plurality of trolley-type work carriers generally indicated at 11 from which workpieces (not shown) are suspended are movable along an overhead track generally indicated at 12. A power driven chain (also not shown) or the like is located adjacent the work carriers and is provided with spaced pusher members selectably engageable with and disengageable from the work carriers in a predetermined manner to effect the desired workpiece delivery along paths defined by the track, in the direction of the arrow 13 of FIG. 1. To provide nesting or close-packing of the workpieces, each work carrier comprises interconnected front and rear trolleys, the rear trolley of one carrier 11 being indicated generally at 14. This trolley is connected to the front trolley (not shown) by a load bar indicated partially at 15 below track 12.

Track 12 comprises a pair of spaced channels 16 and 17 in facing relation, each channel having an upper flange l8 and a lower flange 19. Rear trolley 14 has a frame generally indicated at 21 extending between tracks 16 and 17. The frame has two pairs of wheels 22 and 23 in spaced relation, these wheels being disposed within channels 16 and 17 and resting on lower flanges 19. A pair of guiding rollers 24 and 25 are carried by frame 21 between flanges 19 for lateral stability of the trolley. A cam plate 26 surrnounts frame 21 and is disposed above track 12. As described further in the aforementioned patent, this cam plate is bifurcated and otherwise so shaped as to accomplish the close-packing or nesting function of adjacent work carriers.

Frame 21 has a depending portion 27 below the portion 28 thereof connected to load bar 15. A shaft 29 extends through frame portion 27 beneath track 12. A pair of bushings 30 and 31 are mounted on this shaft and rockably support a pair of anti-back-up cams indicated generally at 32 and 33 respectively.

These cams are of identical construction, each having an upwardly extending portion 34 with a slightly convex serrated upper edge 35, the teeth of which may be slightly crowned. The curvature of edge 35 is such that its leading end 36 is closer to the axis of shaft 29 than is its trailing end 37. The thickness of portion 34 is relatively small, as compared with a weighted portion 38'which extends below shaft 37. The weighted portion thus tends to hold serrated edge 35 against the undersurface 39 of flange 19. The cams are held in place by washers 41, nuts 42 and cotter pins 43.

A stop 44 projects from each side of frame 21 and is engageable by a shoulder 45 when cam 32 or 33 swings clockwise from its FIG. 1 position. This will prevent the cam from flipping over. Should the dimension between shaft 28'and surface 39 increase due to wear or some other reason, stop 44 will engage the other end of surface 45, preventing the cam from flipping counterclockwise. It should be noted that if either cam were to flip around in either direction and cause edge 35 to recontact surface 39, conveyor flow in the direction of arrow 13 would be prevented.

In order for the device to operate properly for a load of great magnitude, the rigidity of shaft 29 must be such Otherwise, the danger exists that edges 35 will not properly grip surfaces 39.

In operation, cams 32 and 33 will be inactive during I the normal powered movement of work carrier 11 in the direction of arrow 7 13. During such movement, edges 35 will be lightly dragged along undersurfaces 39 of track channel flanges 19. However, should there be any tendency for the work carrier to move in a direction opposite that of arrow 13, the teeth of serrated edges 35 will immediately bite into undersurfaces 39 and prevent such retrogression.

It should be observed that the relatively small tolerance involved in the thickness of flanges 19 will make it extremely easy to achieve proper locking action of the back-up cams, and that the generous space available beneath track 12 will permit the cams to be of an efficient shape. The location of earns 32 and 33 between the load carrying wheels 22 and 23 of trolley 14 permit the cams to act as a hold-down for the trolley and to prevent cam plate 26 from tipping upwardly during the process of nesting or accumulation.

I claim:

1. In an anti-back-up construction for use with work carriers of the type having a trolley carried by a track,

at least one cam rockably mounted on said work carrier beneath said track, said cam having an upper portion with a frictional edge engageable with the undersurface of the track, means constantly urging the frictional edge into engagement with the track, the frictional edge being so shaped as to freely permit work carrier movement in a forward direction but preventing backup movement by frictional engagement with the track, said cam having a shoulder thereon, and a stop extending from said work carrier and engageable by said shoulder to prevent said cam from flipping over in either direction.

2. The combination according to claim 1, wherein the work carrier has a pair of cams mounted on opposite sides thereof.

Claims (2)

1. In an anti-back-up construction for use with work carriers of the type having a trolley carried by a track, at least one cam rockably mounted on said work carrier beneath said track, said cam having an upper portion with a frictional edge engageable with the undersurface of the track, means constantly urging the frictional edge into engagement with the track, the frictional edge being so shaped as to freely permit work carrier movement in a forward direction but preventing back-up movement by frictional engagement with the track, said cam having a shoulder thereon, and a stop extending from said work carrier and engageable by said shoulder to prevent said cam from flipping over in either direction.

2. The combination according to claim 1, wherein the work carrier has a pair of cams mounted on opposite sides thereof.

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