A device for an overhead conveyor system of the type where a plurality of carriages (7) by contracting a rotating drive shaft (5) are propellable along a rail (2). The device comprises an operating arm (28) arranged in connection with a first carriage (7b) and adapted to actuate, by turning about an axis of rotation (26), a power transmission element (24) to disconnect the carriage from contact with the drive shaft, and an angled supporting surface (20) arranged in connection with a second carriage (7a). One end of the operating arm (28) is further adapted, when said carriages (7a, 7b) are moved towards each other, to contact said angled supporting surface (20) and be moved along the same, so that the operating arm (28) thus performs a turning motion and disconnects said first carriage (7b). According to the invention, the drive of the carriage will thus be interrupted as soon as its operating arm is contacted with the supporting surface of an anteriorly situated carriage. In this manner, carriages can be buffered.

A cam bar assembly for transferring a trolley from driving engagement with a first chain to driving engagement with a second chain wherein the cam bar assembly includes a cam bar having a first longitudinal axis, a cam surface centered about the first longitudinal axis, a second longitudinal axis, and a cam face centered about the second longitudinal axis. The second longitudinal axis is offset from the first longitudinal axis. The present invention is also directed to a power and free conveyor having the cam bar assembly as well as a drive trolley disposed within a free track for movement in a driven direction and having a retractable surface movable between an engaging position and a retracted position. The power and free conveyor also includes a first drive chain, a second drive chain, and a transfer zone having an entrance and an exit. The first drive chain is positioned to drivably engage the drive trolley at the entrance and the second drive chain is positioned to drivably engage the drive trolley at the exit. The cam bar is positioned in the transfer zone to engage the drive trolley and move the retractable surface from its engaging position to its retracted position.

The invention relates to a power & free conveyor which comprises a free rail (3) and a power chain (1) that follows said free rail (3), to a large extent, in a parallel manner. A transport carriage (4) provided with a front runner (5) and a rear runner (6) are arranged on the free rail (3). The front runner (5) and the rear runner (6) each comprise a carrier (11, 14) that can pivot between two positions. In an area of the movement path of the transport carriage (4), the course of the power chain (1) deviates from that of the free rail (3) so that the transport carriages (4) can no longer be moved via the front runner carrier (1) thereof. Instead, the transport carriage is pushed by the interaction between a chain carrier (2) and the rear runner carrier (14) that is swung out into a carrying position. The rear runner carrier (14) comprises two stabile positions which can be changed by overcoming a resistance. To this end switch-over devices (24, 22) are provided which are arranged at the necessary locations along the movement path of the transport carriages (4).