in the figures piston 56 comprises a partial sleeve downward movement i e to the right in the figures of piston 56 is restricted by piston stop 60 shown as a restriction of the inner diameter of piston chamber 54 similarly upward movement i e to the left in the figures of piston 56 is restricted by piston stop 61 shown as a separate component disposed on the wall of piston chamber 54 piston mandrel 64 facilitates connection between piston 56 and upper coupling 66 disposed between outer wall surface 32 of inner mandrel 30 and inner wall surface 42 of outer mandrel 40 is annulus 68 disposed in annulus 68 is piston mandrel 64 secured to upper coupling 66 which is operatively associated with a return member shown in the embodiments of the figures as including spring 70 spring 70 is disposed within sleeve 72 spring stop or detent 74 provides a surface for compression of spring 70 detent 74 is maintained against outer wall surface 32 of inner mandrel 30 but is not secured to sleeve 72 or outer mandrel 40 in one embodiment detent 74 is maintained against outer wall surface 32 by the force generated by spring 70 pushing detent 74 into shoulder 75 attachment member 67 shown as a c ring is also operatively associated with upper coupling 66 to secure upper coupling 66 to sleeve 72 in addition to spring 70 return member can also comprise atmospheric chamber 73 as a result as.