Hydraulic planetary piston engine having free wheeling valve

摘要

The invention relates to a hydraulic planetary piston motor of the type having an externally serrated pinion gear which meshes with an internally serrated ring gear and has rotatable and orbital movement relative thereto. The unit has plate type distributor valving with fixed and moveable members and a piston, subject to control pressures on both sides thereof, for biasing the moveable valve member into sealing engagement with the fixed valve member. A change-over valve which may be pressure controllable functions to either cause biasing of the piston to effect the sealing mode or to relieve the biasing to cause a separation of the valve members to effect a short circuiting unloading thereof.