Hydraulic motor

Claim 1

A hydraulic motor for intermittently rotating a crank shaft through a certain angle only which comprises a crank shaft; a plurality of hydraulic cylinders having respective pistons which are disposed in radial directions from said crank shaft at regular angular intervals, said pistons being engaged with an eccentric member means formed integrally with said crank shaft; a pressure source of oil with separate oil line means connected to each of said hydraulic cylinders; combined check and choke valve means in each of said separate oil line means wherein each combined valve means comprises a check valve operable to allow said oil from said pressure source of oil to flow in said each separate oil line means towards said each cylinder, said each combined valve means further comprising a choke valve in parallel flow relation to said check valve so as to control the flow of discharged oil in each separate oil line means from said each hydraulic cylinder; wherein said each separate oil line means further comprises an externally operated changeover valve means between said each combined check and choke valve means and said pressure source of oil, means for selectively energizing said externally operated changeover valve means to selectively connect, independently of synchronism with said crank shaft, only one of said hydraulic cylinders to said pressure source of oil while venting the oil lines from said other cylinders to an oil tank; and being characterized in that said selective connection of oil pressure to said one cylinder causes said crank shaft together with said eccentric member to selectively rotate for said certain angle only.