Patent ID: 7874377

Claim:
In a motor grader including a drawbar, a circle defining an annular gear and being mounted to said drawbar for rotation about an upright axis, a blade fixed for moving with said circle, a circle drive arrangement including said annular gear, a hydraulic motor having an output shaft and a gear arrangement being coupled between said output shaft and said annular gear for driving said circle to thereby adjust said blade angularly about said axis, the improvement comprising: said hydraulic motor being a variable displacement motor including a displacement adjuster movable between maximum and minimum displacement positions; a pressure responsive control device being coupled to said displacement adjuster for selectively moving said displacement adjuster between said maximum and minimum displacement positions; a selector valve being coupled to said pressure responsive control device and to a source of fluid pressure and a sump and selectively movable between a normal first position connecting said source of fluid pressure to said control device so as to effect said maximum displacement position of said displacement adjuster and a second position connecting said source of fluid pressure to said control device so as to effect said minimum displacement position of said displacement adjuster.