Railways – Traction – Chain
Patent
1996-07-30
1998-12-01
Le, Mark Tuan
Railways
Traction
Chain
104130, 104250, 104252, B61B 300
Patent
active
058424210
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a power and free conveying system. More particularly, the present application refers to power and free conveying systems of the type having a wide retractable power dog on the leading free trolley which permits transfer of the propulsion of the leading trolley from a wipe out power chain to a wipe in power chain. Most particularly, the present invention relates to a conveyor system which utilizes the position of a retractable wide dog in relation to the position of a power trolley to prevent jamming at transfer and switch points.
2. Description of the Prior Art
Power and free conveyor systems, both overhead and inverted, have been known in automobile plants and other plants for many years. They are particularly adapted to automotive assembly plants for movement of various components of automobile vehicles. Typically, power and free conveyors are used to convey engines, automobile bodies, and various other components to assembly areas in automotive plants.
A representative power and free conveying system includes a power track, a free track vertically spaced from a power track, a power trolley supported on the power track for movement therealong, and a free trolley to support a load on the free trolley track. The free trolley is engageable and disengageable from the power trolley. The power trolley is typically chain driven to move the free trolley along a free track from one assembly station to another.
In more complex power and free conveyor systems, the capability of providing transfer zones to which a carrier is propelled by a forwarding pusher dog or member, and from which the carrier is to be propelled by a receiving pusher dog or member, are provided. The forwarding and receiving pushers may be part of separately driven forwarding and receiving propelling means, so that carrier speed, or relative spacing, or both, may be varied as desired throughout the system.
There have always been problems in this art when the forwarding, or wipe out, pusher dog is to disengage itself from a retractable dog, and the receiving, or wipe in pusher dog, is then to pick up the retractable dog to transfer a free trolley to the work station. Originally both of these operations could not be performed on the same free trolley, and the receiving or wipe in pusher dog could only be provided on a wipe in chain spaced some distance from the wipe out or forwarding pusher. The wipe in pusher dog could only engage the lead trolley after it was pushed some distance into the transfer zone by the forwarding or wipe out pusher acting on the trailing trolley of a carrier.
While these power and free conveyors worked satisfactorily, and were manufactured by many companies such as Southern Systems, Inc. of Memphis, Tenn.; Midwest Conveyor Company of Kansas City, Kans.; the Jervis B. Webb Company of Farmington Hills, Mich.; and ACCO division of American Chain and Cable, Inc. Of Warren, Mich., the long transfer stations were uneconomical, and took up valuable space. Those skilled in the art continued to search for a way to eliminate them.
The answer to these problems in the art was the advent of the wide dog power and free conveyor system, such as that disclosed in U.S. Pat. No. 4,616,570 to Clarence A. Dehne, and assigned to the Jervis B. Webb Company of Farmington Hills, Mich. For the first time, the transfer could take place entirely on the leading free trolley, eliminating the need for the long transfer sections.
However, the ability to do this depended upon careful alignment of anti-jam cam surfaces on the forwarding pusher, the receiving pusher, and the wing portions of the driving dog of the free trolley. If these were not aligned just right, if dirt affected the positions of the cam surfaces, or a tolerance stack up misaligned the surfaces, jamming conditions could still occur. Also, because of the anti-jam cam surfaces, positive pickup of the receiving pusher dog is not assured. Thus, those skilled in the art continued to search for a
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Carlson Raymond L.
Dale Steven J.
Desilets Dennis W.
Ford Motor Company
Le Mark Tuan
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