An improved free piston assembly for use in combination with a plunger lift assembly is provided. The improved free piston assembly includes a sleeve member, a flow restriction member, and retention means. In some embodiments of the invention the sleeve member has an inner surface that is contoured to provide a seat for the flow restriction member during lifting operations. The flow restriction member can be a ball held in the interior of the sleeve by retention means capable of overcoming the force of gravity but at the same time designed to release the flow restriction member when a rod of the plunger lift assembly contacts the flow restriction member. In one embodiment of the invention the retention means is a plurality of inwardly biased spring loaded held in place by a retention ring that is fittably received by a groove in the exterior surface of the sleeve. In other embodiments of the invention the retention means are in the form of a raised lip or a retention sleeve.

An improved free piston assembly for use in combination with a plunger lift assembly is provided. The improved free piston assembly includes a sleeve member, a flow restriction member, and retention means. In some embodiments of the invention the sleeve member has an inner surface that is contoured to provide a seat for the flow restriction member during lifting operations. The flow restriction member can be a ball held in the interior of the sleeve by retention means capable of overcoming the force of gravity but at the same time designed to release the flow restriction member when a rod of the plunger lift assembly contacts the flow restriction member. In one embodiment of the invention the retention means is a plurality of inwardly biased spring loaded held in place by a retention ring that is fittably received by a groove in the exterior surface of the sleeve. In other embodiments of the invention the retention means are in the form of a raised lip or a retention sleeve.

A reciprocating compressor. A hollow cylinder tube contains a piston assembly having two pistons connected by a piston rod. At each end of the cylinder tube is an outer chamber between an end plate and an outer end of the proximate piston. These two outer chambers and the outer ends of the pistons define a power cylinder at each end of the cylinder tube. In the mid-portion of the cylinder tube, a center divider is situated between the pistons and has an aperture that allows the piston rod to reciprocate through it. The two inner chambers formed thereby and the inner ends of the pistons define two compression cylinders in the mid-portion of the cylinder tube. The two compression chambers share a suction manifold and a discharge manifold, but have independently operating suction and discharge valves.

A tire air filling device according to one embodiment includes a cylinder having a first opening communicating with a tire; and a weight that has an air flow hole through which air to be supplied to the tire passes, and that moves in an axial direction of the cylinder upon a receipt of a centrifugal force, to supply the air from the first opening to the tire. The tire air filling device includes a weight airtight member interposed between the weight and an inner surface of the cylinder; and a weight spring that biases the weight to a side opposite to the tire. The cylinder has a second opening on a side opposite to the first opening, and a cap that is detachably attached to the second opening is provided.

A linear motor compressor including a compressor housing and a cylinder housing having a plurality of opposing compression chambers. A piston freely reciprocates within the cylinder housing using a linear electric motor. A piston position feedback control system provides adaptive current output as a function of position feedback and/or velocity feedback from the piston and/or the electric motor, to directly power and control the electric motor, wherein the piston reciprocates without assistance from a mechanical spring or other equivalent centering force.

A linear motor compressor including a compressor housing and a cylinder housing having a plurality of opposing compression chambers. A piston freely reciprocates within the cylinder housing using a linear electric motor. A piston position feedback control system provides adaptive current output as a function of position feedback and/or velocity feedback from the piston and/or the electric motor, to directly power and control the electric motor, wherein the piston reciprocates without assistance from a mechanical spring or other equivalent centering force.

A double-acting refrigerant compressor includes a piston freely guided on two cylinder portions arranged opposite to each other and being immobile relative to each other. The piston includes a flow channel extending internally through the piston. Each cylinder portion and the piston include, along the flow channel, respectively at least one back-check valve. The back-check valves are arranged in such a manner that their flow directions are unidirectional.

A double-acting refrigerant compressor includes a piston freely guided on two cylinder portions arranged opposite to each other and being immobile relative to each other. The piston includes a flow channel extending internally through the piston. Each cylinder portion and the piston include, along the flow channel, respectively at least one back-check valve. The back-check valves are arranged in such a manner that their flow directions are unidirectional.

A double-acting refrigerant compressor includes a piston freely guided in a fixed mounted cylinder. The cylinder includes an inlet valve plate having an inlet valve. The piston includes a flow channel extending internally through the piston. The flow channel of the piston includes at least one back-check valve being arranged with a unidirectional flow. The piston includes a second cylinder portion within which is guided over a fixed mounted inverse piston. The inverse piston includes an inverse piston flow channel with an outlet valve in fluid communication with a volume within the second cylinder portion. Alternative embodiments include a piston with interior cylinders where the piston is guided over the two inverse pistons.

A reciprocating compressor. A hollow cylinder tube contains a piston assembly having two pistons connected by a piston rod. At each end of the cylinder tube is an outer chamber between an end plate and an outer end of the proximate piston. These two outer chambers and the outer ends of the pistons define a power cylinder at each end of the cylinder tube. In the mid-portion of the cylinder tube, a center divider is situated between the pistons and has an aperture that allows the piston rod to reciprocate through it. The two inner chambers formed thereby and the inner ends of the pistons define two compression cylinders in the mid-portion of the cylinder tube. The two compression chambers share a suction manifold and a discharge manifold, but have independently operating suction and discharge valves.