Hydraulic motor with orbiting drive member

Claim 1

An orbital drive fluid motor comprising a casing defining a cavity bonded by an inwardly facing annular surface, a rotatable drive shaft extending through said cavity and having a pinion thereon, an annular drive member having an inner periphery larger than and surrounding said pinion with teeth thereon which are more in number than the teeth on said pinion, an outer periphery surrounded by and smaller in diameter than the annular surface bonding said chamber, and opposite end surfaces, a pair of port plates having inner surfaces respectively disposed against the end surfaces of said drive member and having limited freedom of movement towards and away from the same, a plurality of divider means extending between the outer periphery of the drive member and the surrounding annular surface and providing therebetween a plurality of fluid coupling chambers, a plurality of eccentric bearing members extending through bores through said drive member from end-to-end thereof and having opposite ends thereof supported in said port plates, said bearing members restraining said drive members against other than orbital movement wherein the teeth on the inner periphery thereof engage the teeth a few at a time of the pinion and wherein fluid coupling chambers on one side of the drive member undergo expansive phases while those on the opposite side undergo contractile phrases, said drive member having on opposite ends thereof slots which terminate at said fluid coupling chambers, said casing having trepan chambers on each outer side of said port plates, one of which is for connection with a high pressure fluid supply line while the other is for connection with a low pressure fluid return line, said port plates having therethrough ports, those on one of which plates register with slots terminating in fluid coupling chambers on one end of said drive members and connect the same with one of said trepan chambers while those on the other plate connect said fluid coupling chambers on the other side of said drive member with the other trepan chamber, means for hydraulically balancing the opposite sides of said port plates, and means for charging the bearing bores with fluid from said fluid coupling chambers.