Piston assembly

An apparatus for varying the output volume of a piston assembly, comprising:

• a piston rod configured and arranged for linear motion, a transition arm coupled to, the piston rod, the transition arm including a nose pin,
• a support to which the transition arm is mounted for movement relative to the support, and
• a rotatable member coupled to the transition arm nose pin, a radial position of the nose pin relative to an axis of rotation of the rotatable member being adjustable while the rotatable member and the support remain axially stationary, a center of movement about which the transition arm moves to adjust the radial position of the nose pin being on the axis of rotation of the rotatable member.

20-27. (Canceled).

A method of varying the output volume of a piston assembly, comprising:

• providing a piston assembly including a piston rod configured and arranged for linear motion and a transition arm coupled to the piston rod, the transition arm including a nose pin, a support to which the transition arm is mounted for movement relative to the support, and a rotatable member coupled to the transition arm nose pin,
• moving the nose pin relative to the rotatable member to adjust a position of the nose pin relative to an axis of rotation of the rotatable member while the rotatable member and the support remain axially stationary, a center of movement about which the transition arm moves to adjust the radial position of the nose pin being on the axis of rotation of the rotatable member.

An assembly, comprising:

• a transition arm coupled to a stationary support, the transition arm including at least two piston arms,
• at least two double-ended members, each double-ended member coupled to one of the at least two piston arms, and
• a rotatable member coupled to the transition arm, a position of the transition arm relative to an axis of rotation of the rotatable member being adjustable to vary the output volume of the double-ended members to zero, the rotatable member defining an arc-shaped guide for guiding movement of the transition arm when the position of the transition arm relative to the axis of rotation of the rotatable member is adjusted.

A method, comprising:

• providing a piston assembly including at least two double-ended members, a transition arm having at least two piston arms, each double-ended member coupled to one of the at least two piston arms, and a stationary support to which the transition arm is mounted, and
• moving the transition arm along an arc-shaped guide to vary the output volume of the piston assembly during operation of the piston assembly.