Trolley retention abutment for overhead conveying system

Abstract

Overhead conveying system trolleys supported by canted driven rollers engage on and form spiral loci of engagement with a rotated drive shaft in a powered section, and each has a top wheel used to lift the driven rollers off of the drive shaft as the trolley enters a gravity rail section where the wheel is supported on a rail and where a step feeder releases trolleys one at a time from or along the gravity rail section. A pivoted step feeder arm in a receiving and holding position receives the wheel of the lead trolley, which actuates a release limit switch, to cause the arm to rotate and release the trolley. In this release position, the retention abutment mounted on the accumulation side of the arm, prevents any following trolley from actuating the release limit switch. The arm remains in the release position until a second limit switch is actuated by the released trolley moving away, to cause the arm to rotate to the receiving and holding position to receive the next lead trolley. The retention abutment has a cam that will engage and force back the following trolley while the arm rotates into the release position and thereby keep the following trolley from swinging and actuating the release limit switch while the gravity line is exposed to significant back pressure from accumulated trolleys.