Backlash correcting device for swivel arm of robot

Claim 1

A swivel shaft backlash correcting device for a robot, comprising: a gear shaft, a spur gear mounted at one end of said shaft and having first and second axial surfaces and a plurality of threaded axial holes, said spur gear further having an axially-extending first pin having a predetermined length fixed to said first axial surface of said spur gear, said shaft being coupled through a speed reducer to an electric motor; a correcting gear having first and second axial surfaces and disposed with its second axial surface facing said first axial surface of said spur gear, said correcting gear having an axial through-hole through which said first pin extends, a plurality of additional through-holes in alignment with said threaded axial holes in said spur gear and an axially-extending second pin having a predetermined length, said correcting gear having the same diameter and number of teeth as said spur gear; a retaining ring disposed adjacent said first axial surface of said correcting gear and engaged with said first and second pins in a contracted or compressed state of said retaining ring to apply a force of expansion to said gear shaft and said correcting gear; a center gear fixedly secured to a stationary stand and engaged with said correcting gear and said spur gear; and a plurality of bolts for extending through said additional through-holes in said correcting gear and threadedly engaging respective ones of said threaded holes in said spur gear.