A piston assembly is provided for an unloader valve of an air compressor. The assembly comprises an unloader piston having a first bore of a first diameter, and a second bore of a second diameter which is smaller than the diameter of the first bore. The assembly also comprises a coil spring having a central opening, one end portion disposed in the second bore, and an opposite end portion extending into the first bore. The assembly further comprises a balance piston including a head portion sized to be disposed in the first bore, a first stem portion extending from the head portion and having a diameter smaller than the first and second bores, and a second stem portion extending from the first stem portion and extending into the central opening of the coil spring and having a diameter smaller than the first stem portion.

A piston assembly is provided for an unloader valve of an air compressor. The assembly comprises an unloader piston having a first bore of a first diameter, and a second bore of a second diameter which is smaller than the diameter of the first bore. The assembly also comprises a coil spring having a central opening, one end portion disposed in the second bore, and an opposite end portion extending into the first bore. The assembly further comprises a balance piston including a head portion sized to be disposed in the first bore, a first stem portion extending from the head portion and having a diameter smaller than the first and second bores, and a second stem portion extending from the first stem portion and extending into the central opening of the coil spring and having a diameter smaller than the first stem portion.

A hybrid opposed piston engine is described that can include a cylindrical chamber and first and second pistons slidably disposed in the cylindrical chamber, surfaces of the first and second pistons and walls of the cylindrical chamber defining an internal combustion volume. The hybrid opposed piston engine can also include at least one port in the cylindrical chamber to allow air and fuel into and exhaust gas out of the internal combustion volume. In some embodiments, the hybrid opposed piston engine includes a drive shaft including a first mechanical linkage between the first piston and a crankshaft that is configured to move the first piston within the cylindrical chamber. In some embodiments, the hybrid opposed piston engine includes an electrical component adjacent to the second piston, the electrical component configured to move the second piston within the cylindrical chamber.

A hybrid opposed piston engine is described that can include a cylindrical chamber and first and second pistons slidably disposed in the cylindrical chamber, surfaces of the first and second pistons and walls of the cylindrical chamber defining an internal combustion volume. The hybrid opposed piston engine can also include at least one port in the cylindrical chamber to allow air and fuel into and exhaust gas out of the internal combustion volume. In some embodiments, the hybrid opposed piston engine includes a drive shaft including a first mechanical linkage between the first piston and a crankshaft that is configured to move the first piston within the cylindrical chamber. In some embodiments, the hybrid opposed piston engine includes an electrical component adjacent to the second piston, the electrical component configured to move the second piston within the cylindrical chamber.

A plunger and cylinder assembly for the fluid end of a reciprocating pump. The assembly comprises a traveling cylinder, a stationary plunger, and an optional sleeve secured to the traveling cylinder in a detachable manner. The traveling cylinder is displaced along its axis by a thrust component and acts cooperatively with the stationary plunger to create a pressure change in the reciprocating pump.

A plunger and cylinder assembly for the fluid end of a reciprocating pump. The assembly comprises a traveling cylinder, a stationary plunger, and an optional sleeve secured to the traveling cylinder in a detachable manner. The traveling cylinder is displaced along its axis by a thrust component and acts cooperatively with the stationary plunger to create a pressure change in the reciprocating pump.

A cylinder unit includes a piston disposed in the cylinder bore that is connected to a piston connecting frame member. The piston connecting frame member replaces a conventional connecting rod, and reciprocates exclusively along the bore axis. A crank connecting member has a linear rail at its top that is captured in a transverse gap along the bottom of the piston connecting frame member, and converts the circular movement of a crank throw to linear motion of the piston connecting frame member.

A reciprocating piston and cylinder apparatus with adjustable stroke volume. The apparatus comprises an axially displaceable traveling cylinder, a stationary piston, and an optional sleeve secured to the traveling cylinder in a detachable manner. The traveling cylinder is displaced along its axis by a thrust component and acts cooperatively with the stationary piston to create a pressure change within the housing.

A reciprocating piston and cylinder apparatus with adjustable stroke volume. The apparatus comprises an axially displaceable traveling cylinder, a stationary piston, and an optional sleeve secured to the traveling cylinder in a detachable manner. The traveling cylinder is displaced along its axis by a thrust component and acts cooperatively with the stationary piston to create a pressure change within the housing.

A piston pin assembly is provided including a cylindrical pin body having a hollow interior. A mass is disposed in the hollow interior of the cylindrical pin body and a viscoelastic, plastic, or elastomeric material is disposed in the hollow interior between the mass and the cylindrical pin body. The mass and viscoelastic, plastic, and elastomeric material provides a damper for the piston and piston pin to delay the acceleration of piston lateral motion and stabilize the piston rotation and reduce the noise and friction.