actuator is close to full retraction in operation when the compensator 6 senses that the circuit requires a greater supply of fluid fluid is permitted to flow from the line 34 through line 27 to drain this starts emptying chamber 19 under the influence of the spring 22 the fluid flows out through the bore 18 thence through the bore 35 line 34 compensator 6 line 27 passage 14 chamber 24 chamber 29 and out through the drain port 28 until the needs of the circuit are met when the actuator 20 reaches a point close to full retraction the movable part 10 slides over and closes off the drain port 28 and the remaining fluid is locked in the chamber 19 thereby stopping any further movement of actuator 20 this prevents the movable part 10 from striking the back plate 8 or the outer end of the fixed part 12 whichever is closer the passage 16 conducts a supply of pressurized fluid from the charging port 26 to the chamber 24 where it replenishes fluid lost through normal leakage and thus keeps sufficient fluid in the chamber 19 while drain port 28 is closed to keep the movable part 10 from striking the back plate 8 or other fixed parts if closer referring now to fig3 a second embodiment of the hydraulic stop is shown with a different valving means for closing off the drainage of an actuator 20 39 and a different routing of the pressurized fluid to replenish the actuator 20 39 while the valving is closed the relevant parts of the conventional variable displacement axial piston pump are again shown in fig3 a back plate 8 39 serves as a support for the cam plate positioning actuator 20 39 and usually contains the.