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Trolley with tractor drive for use in curved enclosed tracks and system including the same

Trolley with tractor drive for use in curved enclosed tracks and system including the same description/claims

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Not Applicable

Not Applicable

1. Field of Invention

This invention relates generally to overhead conveyor systems and more particularly to systems making use of an enclosed track in which a trolley is arranged to roll to support something from the trolley.

2. Description of Related Art

Enclosed track conveyor systems are commonly used to support and carry items from a wheeled trolley located within the interior of an enclosed track. As is known enclosed tracks are hollow members having a top-wall, a pair of sidewalls projecting downward from the top wall and a pair of marginal flanges extending horizontally from respective ones of the sidewalls. The flanges are spaced from each other to form a slot therebetween. The trolley is located within the interior of the track, with its wheels or rollers disposed on the interior (upper) surface of the flanges.

Examples of enclosed track systems including internally located trolleys for rolling down the interior of the track are found in U.S. Pat. No. 3,589,503 (Leach), U.S. Pat. No. 3 627,595 (Leach) and U.S. Pat. No. 6,450,326 (Hoffinan et al.). The trolleys of the foregoing patents are arranged so that they can negotiate curves in the track.

In some prior art systems, the movement or rolling of a trolley down the interior of an enclosed track is accomplished by using a tractor drive that is mounted on the trolley, but located outside of the track. Such tractor drives make use of a drive wheel, which extends through the slot in the track to frictionally engage the inner surface of the top wall of the track. The drive wheel is rotated by a motor mounted on the externally located tractor. This arrangement requires that the drive wheel be of a relatively large diameter. As a result such tractors are not suitable for use in systems wherein the enclosed track includes a relatively small radius curve, since the drive wheel would engage or bind in the slot. While some enclosed track systems make use of tractors having drive wheels that engage and ride on the bottom of the track, i.e., the inner surface of one or more of the flanges, such systems are not practical due to splices used on the track, which results in an uneven drive surface, and make it difficult to keep a constant pressure on the drive wheel.

In U.S. Pat. No. 6,718,885, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed an enclosed track system that makes use of a drive system facilitating the driving of a trolley through a curve in an enclosed track. To that end, the system of that patent includes an enclosed track system comprising an enclosed track having at least one curved portion and a trolley. The track includes a slot extending along its length. The trolley includes a rolling section having first and second roller portions and an externally located drive section. The first and second roller portions are located within the track and spaced from each other. The second roller portion includes a pair of guide rollers disposed within the slot in the track and a passive or floating driven wheel located within the track. The driven wheel is arranged to be driven by frictional engagement of a driving wheel and is arranged to roll on an inner surface of the track to propel the trolley along the track. To the end the drive section includes a motor to cause the drive wheel to rotate, whereupon it causes the driven wheel to rotate so that the trolley rolls along the track. The drive section has an articulated joint coupling the first and second roller portions to each other, with the articulated joint enabling the first and second roller portions to pivot longitudinally with respect to each other so that the trolley can negotiate curves in the track. The articulated joint is in the form of a dual-hinged, articulated tow-arm assembly. That assembly basically comprises an elongated tow-arm member having a pair of brackets at its opposite ends. One bracket is secured via a hinged connection to a portion of the frame supporting the motor at the second roller portion, while the other bracket is secured via a hinged connection and an associated clevis to a portion of the first roller portion. The pivot point at the second roller portion is located forward of the longitudinal position of the guide rollers.

While the drive system of the '885 patent is suitable for its intended purposes, it leaves something to be desired from two standpoints. In particular, one is potential slippage of the driven wheel, since it is a floating member driven by frictional engagement from the driving wheel. The other is possible side loading torque resulting from the construction of the articulated joint coupling, and in particular the fact that the pivot axis for the second roller portion is located forwardly of the guide rollers and the point at which the driven roller engages the inner surface of the track. Such a side load torque could result in accelerated wear of the guide rollers.

This invention relates to a trolley for use with an enclosed track having at least one curved portion, the enclosed track being an elongated hollow member having a top wall portion, a pair of side wall portions and a pair of flanged portions, the flanged portions being spaced from each other to define a slot therebetween extending longitudinally along the track. The trolley comprises a rolling section and a drive section, with the rolling section having first and second roller portions. The first roller portion is located within the track and comprises at least one support roller arranged to roll on at least one of the flange portions of the track. The second roller portion comprises a driven wheel, a pair of support rollers and a pair of guide rollers mounted on respective vertically extending rods. Each of the guide rollers is located within the slot of the track, with the guide rollers being positioned immediately fore and aft of the position of the driven wheel. The pair of support rollers comprises an upstream support roller and a downstream support roller. The upstream support roller is located adjacent one side of the drive wheel and is mounted on the drive section for pivoting action about an upstream vertical axis. The downstream support roller is located adjacent a diametrically opposed side of the driven wheel and mounted on the drive section for pivoting action about a downstream vertical axis, whereupon the upstream and downstream support rollers are enabled to roll along at least one of the flange portions of the track while said driven wheel rolls along the top wall portion of the track in the center thereof. The drive section is located outside of the track.

In one preferred aspect of this invention the drive section includes a driving sprocket and an associated driving loop, e.g., a chain. The driving sprocket is arranged for positively engaging the driving loop. The driving loop is arranged for positively engaging the driven wheel to cause the driven wheel to rotate about a horizontal axis so that it rolls on the inner surface of the track to propel the trolley along the track.

In another preferred aspect of this invention the first roller portion of the trolley is coupled to the second roller portion by an articulated joint. The articulated joint comprises an elongated member having a first end portion and a second end portion. The first end portion is pivotably coupled to the first roller portion at a first vertically extending axis. The second end portion is pivotably coupled to the second roller portion at a second vertically extending axis. The second vertically extending axis is located approximately midway between the vertically extending rods for the guide rollers.

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