Railways – Traction – Chain
Reexamination Certificate
2000-10-13
2001-10-30
Le, Mark T. (Department: 3617)
Railways
Traction
Chain
Reexamination Certificate
active
06308637
ABSTRACT:
BACKGROUND
The present invention relates to a flexible pusher dog for a power chain driven overhead conveyor system.
Cost-efficient automated production facilities depend heavily on the versatility, dependability and performance of their conveyor systems. To minimize the use of valuable floor space, overhead conveyor systems are commonly used. These overhead systems can be configured to include changes in elevation, cornering and diagonal banking, without requiring major modifications to the floor plan of the production facility. Spur lines can be added for additional flexibility. Examples of a couple common overhead conveyor systems are described in U.S. Pat. Nos. 3,744,432, 3,948,186 and 4,223,610, which are incorporated herein by reference.
Two types of overhead conveyors are commonly used. Both types of conveyors use two-track systems, each having an upper power track and a lower free track, and are designed to support and move load-bearing trolleys along the overhead systems. Normally, at least two load-bearing trolleys—a leading trolley and a trailing trolley—are used to support each load. In both types of conveyors, the trolleys are carried by a lower channel-shaped free track, i.e. the wheels of the trolleys ride within the free track. Because the free track does not include any type of drive system, without some external force, trolleys supported by the free track remain stationary.
The drive force for the trolleys is found in the upper power tracks. In one type of conveyor system, a drive chain—such as a universal link drive chain which features alternating vertical load wheels and horizontal guide wheels—is threaded through a channel-shaped upper power track. Because the drive chain is enclosed in the power track, the chain is protected from dirt and debris thereby reducing maintenance costs and prolonging chain life. A second type of conveyor uses an I-beam shaped upper power track. A strong but flexible drive chain, such as an X-348 chain, is suspended from the upper power track by chain support trolleys. Although the drive chain in this type of system is exposed to the environment, the use of the I-beam to support the chain allows the conveyor to carry heavier loads than can be accommodated with the channel-shaped track systems.
In both types of conveyors, projections—referred to as pusher dogs—are suspended from the respective drive chain. With the universal link drive chain, typically a drop-forged pusher dog, such as shown in
FIG. 1
, is suspended from a universal link. The drop-forged pusher dog (
510
) includes a pivoted connector (
512
), having a hook (
514
) and a recessed stop (
516
), attached to the universal link (
511
) by a pivot pin (
518
). The leading trolley (
520
) includes a non-retractable flange (
522
), or power dog, which can be engaged by the pusher dog (
510
) to move the leading load-bearing trolley (
520
), and hence to move the load. When the load is being pulled forward the hook (
514
) of the pusher dog (
510
) engages the flange (
522
) of the lead trolley (
520
) causing the trolley (
520
) to move. However, when the load is on a slight downward slope, such that the load can move without being pulled by the pusher dog (
510
), the recessed stop (
516
) engages the flange (
522
) to keep the load from moving along the conveyor at an uncontrollable rate. When the leading trolley (
520
) reaches a predetermined position along the track, the connector (
512
) can be forced to pivot away from the power dog (
522
) thereby preventing further movement of the load. For example, as the leading trolley (
520
) approaches a stopped trailing trolley (
524
), a beaver tail (
526
) on the trailing trolley (
524
) causes the connector (
512
) to pivot away from the power dog (
522
). Without a driving force to move the leading trolley (
520
), the load stops its forward movement.
The heavy-duty link chain used in the I-beam conveyor system has not been previously used to support a drop-forged type pusher dog. Rather, as shown in
FIG. 2
, the pusher dogs for these systems have been limited to simple side-link pusher dogs (
550
), or simple pivotal pusher dogs such as shown in U.S. Pat. Nos. 4,243,325 and 4,424,749, incorporated herein by reference. These pusher dogs require a leading trolley (
560
) to have a relatively complicated engagement system that includes a pivotal power dog (
562
) at the front end of the leading trolley (
560
) and a pivotal hold back dog (
564
) at the rear end of the leading trolley (
560
). When the load is being pulled forward, the sidelink pusher dog (
550
) engages the power dog (
562
) to drive the trolley (
560
). However, when the load is on a downward slope, the contact between the pusher dog (
550
) and the power dog (
562
) is broken, and the pusher dog (
550
) instead engages with the hold back dog (
564
), thereby preventing the trolley from moving forward too rapidly. When the trolley (
560
) approaches a stopped object, a stop blade (
566
), attached for example to a trailing trolley (
568
), breaks the connection between the pusher dog (
550
) and the power dog (
562
), thereby preventing any further movement of the load.
Because the I-beam type of conveyor can carry heavier loads than the channel type conveyor but the channel type conveyor allows the use of the simpler non-retractable power dog on its trolleys, it would be beneficial to have an overhead conveyor system that uses an I-beam power track, with a pusher dog that can pivot away from the load-bearing trolley, thereby allowing the conveyor to use a leading trolley with a fixed power dog. Such a design could provide cost savings to the user from both an initial cost and equipment maintenance basis.
SUMMARY OF THE PREFERRED EMBODIMENT
The present invention describes a pusher dog that has a pivotal connector and that is incorporated within a heavy-duty chain drive for use with for an I-beam-shaped power track. By providing the pusher dog with the pivotal connector the pusher dog can be used with a load-bearing trolley, that rides within a channel-shaped free track, that has a fixed power dog at the front end of the leading trolley and that does not require a hold back dog.
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patent: 4483252 (1984-11-01), Pierson
patent: 4614158 (1986-09-01), Helde
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Burke James
Sheets Kenneth E.
Sheets Steve
Le Mark T.
Miller, Jr. Maurice L.
Rapid Industries, Inc.
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