Patent ID: 7066074

Claim:
A liner fluid motor having a piston within a close-ended cylinder, wherein the piston, the cylinder sidewall and the cylinder ends divide the cylinder into two variable volumes, the piston and the cylinder being relatively movable between first and second rest positions by selectively introducing a fluid through a first port into one of the variable volumes and simultaneously evacuating fluid through a second port from the other variable volume, comprising: means carried by and movable with the piston (i) for restricting the introduction of the fluid into the one variable volume while the piston-cylinder is in the first rest position and until there has occurred a selected amount of relative movement out of the first rest position, (ii) for restricting the exhaustion of the fluid from the other variable volume until there can occur a selected amount of relative movement into the second rest position and while the piston-cylinder is in the second rest position, and (iii) for otherwise permitting unrestricted flow of the fluid into or out of the variable volumes to limit the velocity of the relative movement near the end positions, the restricting means including, seals located on the piston that define between the cylinder and the piston first and second fixed-volume chambers movable with the piston; and first and second restrictive orifices, the first orifice interconnecting the first chamber with the first variable volume, the second orifice interconnecting the second chamber with the second variable volume, the ports and the orifices being so related that, when the end positions are achieved and when the selected amount of relative movement has occurred or can occur, the fluid that is introduced or evacuated into or from the variable volume enters or leaves the associated chamber and thereafter enters or leaves the associated variable volume via the associated restrictive orifice; and wherein the first and second ports are respectively shaped so that as the fixed-volume chambers move into and out of communication therewith the rate of fluid movement into or out of the chambers changes gradually.