A fluid end (15) for a multiple reciprocating pump assembly (12) includes at least three plunger bores (61) or (91) each for receiving a reciprocating plunger (35), each plunger bore having a plunger bore axis (65) or (95). The fluid end (15) includes suction valve bores (59) or (89), each suction valve bore receiving a suction valve (41) and having a suction valve bore axis (63) or (93), and the fluid end further includes discharge valve bores (57) or (87), each discharge valve bore receiving a discharge valve (43) and having a discharge valve bore axis (63) or (93). The axes of at least one of the suction and discharge valve bores is inwardly offset in the fluid end from its respective plunger bore axis.

A pumping assembly keeps a pneumatic tire from becoming underinflated. The pumping assembly includes an even number of pumps attached to the tire rim, a gravity mass for producing a pumping action, a cam fixed to the gravity mass for maintaining the cam in a fixed position relative to the gravity mass, and rollers for engaging the cam and producing the pumping action as the tire rim rotates and the gravity mass retards rotation of the cam as the tire rim rotates.

A double-headed piston type swash plate compressor includes a rotation shaft, a housing, a swash plate, two cylinder bores, a double-headed piston, and two shoes. The double-headed piston includes two shoe holders, a neck, two heads, and two coupling portions. Each of the coupling portions includes an outer portion and an inner portion. A direction orthogonal to both of an opposing direction of the inner portion and the outer portion and the axial direction of the double-headed piston is referred to as a widthwise direction. The neck is larger in the widthwise direction than in the opposing direction so that the neck is deformable in the opposing direction. Each of the two coupling portions has a width that is less than or equal to a width of the neck. The inner portion includes a narrow portion. The narrow portion is at least partially located closer to the head than the shoe holder in the inner portion. The two coupling portions are deformable in the widthwise direction when the swash plate applies load to the double-headed piston.

A double-headed piston type swash plate compressor includes a rotation shaft, a housing, a swash plate, two cylinder bores, a double-headed piston, and two shoes. The double-headed piston includes two shoe holders, a neck, two heads, and two coupling portions. Each of the coupling portions includes an outer portion and an inner portion. A direction orthogonal to both of an opposing direction of the inner portion and the outer portion and the axial direction of the double-headed piston is referred to as a widthwise direction. The inner portion includes a narrow portion and a wide portion. The wide portion projects out of the narrow portion in the widthwise direction and has a larger width than the narrow portion. An outer surface of the wide portion is slidable on a wall surface of the corresponding cylinder bore when the double-headed piston reciprocates in the cylinder bores.

A variable-pressure air pump includes a first cylinder with a first chamber and a second cylinder with a second chamber movably connected with one another. The second chamber fluidly communicable with the outside of the variable-pressure air pump selectively. A discharge device includes a connecting member and a switch movably connected with one another. The connecting member defines at least one discharge hole fluidly connecting with the second chamber. The switch has at least one flow guide portion and at least one blocking portion. The switch is movable between a first position in which the at least one flow guide portion is adjacent and opens to the at least one discharge hole and a second position in which the at least one blocking portion is adjacent to and blocks the at least one discharge hole.

A valve plate assembly for a compressor according to the principles of the present disclosure includes a valve plate and a suction valve retainer. The valve plate is configured to separate suction-pressure working fluid entering a cylinder of the compressor from discharge-pressure working fluid exiting the cylinder of the compressor, the valve plate defining a discharge valve seat. The suction valve retainer is configured to retain a suction valve within a suction valve seat disposed about a central longitudinal axis of the cylinder and to extend radially outward from the central longitudinal axis of the cylinder without extending beyond a suction passage of the compressor.

A valve plate assembly for a compressor according to the principles of the present disclosure includes a valve plate and a suction valve retainer. The valve plate is configured to separate suction-pressure working fluid entering a cylinder of the compressor from discharge-pressure working fluid exiting the cylinder of the compressor, the valve plate defining a discharge valve seat. The suction valve retainer is configured to retain a suction valve within a suction valve seat disposed about a central longitudinal axis of the cylinder and to extend radially outward from the central longitudinal axis of the cylinder without extending beyond a suction passage of the compressor.

A valve plate assembly for a compressor according to the principles of the present disclosure includes a valve plate and a suction valve retainer. The valve plate is configured to separate suction-pressure working fluid entering a cylinder of the compressor from discharge-pressure working fluid exiting the cylinder of the compressor. The valve plate defines a discharge valve seat. The suction valve retainer is configured to retain a suction valve within a suction valve seat disposed about a central longitudinal axis of the cylinder.

A valve plate assembly for a compressor according to the principles of the present disclosure includes a valve plate and a suction valve retainer. The valve plate is configured to separate suction-pressure working fluid entering a cylinder of the compressor from discharge-pressure working fluid exiting the cylinder of the compressor. The valve plate defines a discharge valve seat. The suction valve retainer is configured to retain a suction valve within a suction valve seat disposed about a central longitudinal axis of the cylinder.

An air compressor includes a compression machine configured to generate compression air, a main tank configured to store therein the compression air, an extension tank configured to store therein the compression air, a connection pipeline provided between the main tank and the extension tank to be removably inserted thereto, and a fastening unit configured to releasably connect the main tank and the extension tank with each other.