Piston assembly having reduced extend force and reduced displacement volume

A piston assembly comprising:

• a shaft;
• a piston arrangement positioned on the shaft, the piston arrangement being configured to cause extension of the shaft from a retracted position to an extended position and to cause retraction of the shaft from the extended position to the retracted position;
• and
• the piston arrangement comprising a variable volume reservoir, the variable volume reservoir being at least one of:
• (a) at least one of increasing and decreasing, during at least a portion of the extension of the shaft, to conserve actuation fluid ported to and from the piston assembly;
• (b) at least one of increasing and decreasing, during at least a portion of the retraction of the shaft, to conserve actuation fluid ported to and from the piston assembly;
• (c) constant during at least a portion of the extension of the shaft to conserve actuation fluid ported to and from the piston assembly;
• and
• (d) constant during at least a portion of the retraction of the shaft, to conserve actuation fluid ported to and from the piston assembly;
• the piston arrangement has a retract-area configured for retracting the shaft and an extend-area configured for extending the shaft;
• the retract-area being greater than the extend-area so that upon application of a fluid pressure to the retract-area the piston arrangement generates and applies a retract force to the shaft and upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft;
• and
• wherein the retract force is greater than the extend force.

A piston and housing assembly comprising:

• a housing having an interior area;
• a shaft;
• a piston arrangement positioned on the shaft;
• the piston arrangement comprising a retract head slidably mounted on the shaft and configured for retracting the shaft, the piston arrangement comprising a piston head fixedly secured to the shaft and configured for extending the shaft, the retract head having a retract-area and the piston head having a extend-area;
• the retract head and the piston head being disposed entirely in the interior area of the housing;
• the retract-area having a first magnitude and the extend-area having a second magnitude, the first magnitude being greater than the second magnitude so that upon application of a fluid pressure to the retract-area the piston arrangement generates and applies a retract force to the shaft and upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft, the fluid pressure having a predetermined magnitude;
• and
• the retract force is greater than the extend force;
• the piston arrangement being configured to cause extension of the shaft from a retracted position to an extended position and to cause retraction of the shaft from the extended position to the retracted position;
• and
• a variable volume reservoir formed between the piston head and the retract head, the variable volume reservoir having a volume that is configured to change during some axial movement of the shaft and to remain constant during other axial movement of the shaft.