A conveyor system having pusher assemblies on a driven chain supported above a carrier track along which carriers are propelled with each carrier having a front trolley having a push lug and a rear trolley having a release camming lug. The pusher assemblies include a pivotedly supported front pusher dog assembly and a pivotally supported rear pusher dog assembly with the front pusher dog assembly including a forwardly projecting release blade for releasing the pusher dog from driving engagement with the push lug on the carrier. Provision is also made for accumulation of carriers, batch re-entry of carriers, carrier switchout and control of the carriers when traversing inclines.

The mechanism is incorporated in a conveyor system of the type which propels vehicles, or pallets, by frictional contact between a rotating drive shaft and a drive wheel carried by the vehicle. The disclosed conveyor system includes two such rotating drive shafts and associated parallel tracks. The mechanism transfers the vehicles from one set of parallel tracks to the other via concentric tracks. An upright drive shaft drives a radially-extending pivoted arm on which is mounted an elongaged, arcuate member. The member has a downwardly inclined ramp at its front to ride over any preceding vehicle, and a depending dog at its rear to engage the vehicle and advance it. A ramp raises the arm at the outlet of the concentric tracks to disengage the vehicle, and lowers the arm to operative position at the inlet thereof.

An overhead conveyor having an accumulation dock and crabs which are movable in a track, which crabs can be temporarily arrested in the accumulation dock. For their movement the crabs can be coupled to a transporting chain circulating in the accumulation dock and provided with pivotable pawls which can be locked to a coupling element of the crabs. For arresting the crabs the pawls are unlocked by means of stationary pivotable uncoupler assemblies which are controlled by the crabs. The transport is started again by the successive automatic coupling of the crabs to the transporting chain.

In a power-and-free conveyor system wherein carriers running in a carrier track system are propelled along the carrier track system by pushers depending from endless chains supported by a chain track system, a vertically displaceable platform is installed at a transfer region where the carriers are transferable from a main carrier track to a branch carrier track. The platform serves to lift a vertically displaceable rearward driving dog of a carrier into a position in which the dog is engageable by pushers on the chain of the main carrier track to advance the carrier along the branch carrier track.

In a power-and-free conveyor including a first free rail, a second free rail branching off from the first free rail, a first and a second power rail provided above the free rails respectively, a transfer system for transferring the carriers movably supported by the first free rail to the second free rail. An auxiliary rail attached to the first of the free rails slightly projects above the first free rail and has a cutaway section of requred length to the rear of the branching point of the second free rail. The carrier has at its front portion a pair of tilting drive and back-up dogs engageable with the propelling member driven along the power rail and at its rear portion a propelling member raising cam member. When a carrier advances into the cutaway section, a raising plate disposed near the front end of the rail cut-away portion, disengages the propelling member from the tilting drive dog on the carrier. A following propelling member advancing behind the disengaged propelling member engages under the cam member on the carrier in the cutaway section to push the carrier from behind and to advance the carrier to the second free rail. When the rear portion of the carrier approaches the branching point, the pushing propelling member ascends an upwardly slanting disengaging edge of the auxiliary rail at the front end of the cutaway section and is thereby disengaged from the carrier.