Material handling apparatus

Abstract

A material handling apparatus includes an improved force transmitting assembly which is utilized to rotate a base boom section relative to a cradle and to retain the base boom section against axial movement relative to the cradle. The force transmitting assemby is advantageously disposed between an inner end portion of the base boom section and an upstanding end portion of the cradle and includes a gear drive arrangement which is operated by a relatively high speed motor to rotate the base boom section about its central axis at a relatively low speed. The gear drive arrangement includes a stator or internally toothed ring gear which is fixedly connected with the cradle. A rotor gear or wheel has an external diameter which is less than the internal diameter of the ring gear and has external teeth which are disposed in meshing engagement with the internal teeth of the ring gear. The central axis of the rotor gear is offset from the central axis of the ring gear. An eccentric is rotatable by the relatively high speed motor to effect orbital movement of the rotor gear about the central axis of the ring gear. During this orbital movement of the rotor gear, the teeth of the ring and rotor gears cooperate to effect rotational movement of the rotor gear about its own central axis at a relatively low speed. This low speed rotational movement of the rotor gear is utilized to effect low speed rotation of the base boom section about its central axis. A thrust bearing assembly is advantageously mounted in a coaxial relationship with the eccentric to hold the base boom section against axial movement relative to the cradle.