The present disclosure provides an oil scavenge pump, which includes a cap member, a piston member and a resilient member. The cap member and the piston member are connected to each other and with the resilient member therebetween. The cap member includes a cap head, a valve connected to the cap head, a resilient unit disposed between the cap head and the valve, and a first sphere disposed between the resilient unit and the valve. The piston member includes a valve stopper, a main portion, a second sphere, a rod portion, a first-seal ring and a second-seal ring. The main portion has two ends respectively connected to the valve stopper and the rod portion. The second sphere is disposed between the valve stopper and the main portion. The first-seal ring and the second-seal ring respectively surround the main portion and the rod portion.

A piston rod assembly includes a piston rod having a first end configured to contact fluid, a packing retainer through which the piston rod extends, and one or more packing rings. The packing retainer includes one or more leakage ports forming passageways between an inner surface and an outer surface of the packing retainer. The one or more packing rings surround the piston rod, are adjacent the inner surface of the packing retainer, and are positioned between the one or more leakage ports and a bottom end of the packing retainer. The one or more leakage ports are positioned so that fluid that leaks past the one or more packing rings will flow through the one or more leakage ports.

A piston rod assembly includes a piston rod having a first end configured to contact fluid, a packing retainer through which the piston rod extends, and one or more packing rings. The packing retainer includes one or more leakage ports forming passageways between an inner surface and an outer surface of the packing retainer. The one or more packing rings surround the piston rod, are adjacent the inner surface of the packing retainer, and are positioned between the one or more leakage ports and a bottom end of the packing retainer. The one or more leakage ports are positioned so that fluid that leaks past the one or more packing rings will flow through the one or more leakage ports.

A rotary oscillating sub-assembly for positive displacement pumping of a fluid, said sub-assembly comprising: a hollow body defining a cavity having a wall with two ducts passing therethrough; a piston co-operating with said cavity to define a working chamber and including a channel that opens out longitudinally into said working chamber, said piston being movable angularly so as to put said working chamber into fluid-flow communication with one, then none, then the other of said ducts, and being movable in longitudinal translation to reciprocate so as to cause the volume of said working chamber to vary and successively suck in and then discharge said fluid, said piston carrying a sealing gasket that is formed of at least a sealing ring, a sealing half-ring, and at least one sealing strip that longitudinally connects said sealing ring to said sealing half-ring.

A rotary oscillating sub-assembly for positive displacement pumping of a fluid, said sub-assembly comprising: a hollow body defining a cavity having a wall with two ducts passing therethrough; a piston co-operating with said cavity to define a working chamber and including a channel that opens out longitudinally into said working chamber, said piston being movable angularly so as to put said working chamber into fluid-flow communication with one, then none, then the other of said ducts, and being movable in longitudinal translation to reciprocate so as to cause the volume of said working chamber to vary and successively suck in and then discharge said fluid, said piston carrying a sealing gasket that is formed of at least a sealing ring, a sealing half-ring, and at least one sealing strip that longitudinally connects said sealing ring to said sealing half-ring.

In order to prevent working medium from accumulating in the compressor housing (2) of a piston compressor (1) in a simple manner by means of a sealing of the piston rod (7) in the form of sealing medium barrier supplied by a hydraulic unit (12), it is provided that a ventilator (32) and a sealing medium container (37), which is partially filled with sealing medium, are provided in the hydraulic unit (12), wherein the ventilator (32) suctions air from the free space of the sealing medium container (37), and the free space (45) in the sealing medium container (37) is connected via a line (15, 17) to the compressor housing (2), and an opening (16) is provided at the compressor housing (2) for connecting the interior of the compressor housing (2) to a purge gas reservoir (18).

In order to prevent working medium from accumulating in the compressor housing (2) of a piston compressor (1) in a simple manner by means of a sealing of the piston rod (7) in the form of sealing medium barrier supplied by a hydraulic unit (12), it is provided that a ventilator (32) and a sealing medium container (37), which is partially filled with sealing medium, are provided in the hydraulic unit (12), wherein the ventilator (32) suctions air from the free space of the sealing medium container (37), and the free space (45) in the sealing medium container (37) is connected via a line (15, 17) to the compressor housing (2), and an opening (16) is provided at the compressor housing (2) for connecting the interior of the compressor housing (2) to a purge gas reservoir (18).

A positive displacement machine comprises a cylinder inside which there are a mobile piston, at least one first and one second insulation chamber containing a respective set of gaskets, at least one first and one second gland each of which is suitable for operating on one of the sets of gaskets, each gland comprising a tubular threaded portion and a ring nut fixedly attached to the tubular threaded portion. A sleeve able to slide with respect to said cylinder has a first end in contact with the first set of gaskets and a second threaded end for receiving in engagement the tubular threaded portion of the second gland, the sleeve being slidingly engaged by the first gland, and at least one of the ring nuts being a cylindrical gear wheel with straight teeth.

A positive displacement machine comprises a cylinder inside which there are a mobile piston, at least one first and one second insulation chamber containing a respective set of gaskets, at least one first and one second gland each of which is suitable for operating on one of the sets of gaskets, each gland comprising a tubular threaded portion and a ring nut fixedly attached to the tubular threaded portion. A sleeve able to slide with respect to said cylinder has a first end in contact with the first set of gaskets and a second threaded end for receiving in engagement the tubular threaded portion of the second gland, the sleeve being slidingly engaged by the first gland, and at least one of the ring nuts being a cylindrical gear wheel with straight teeth.

A pumping system utilizes a linear actuator to move a shaft attached to two pistons within cylinders to pump a working fluid. A housing is designed with coolant passageways and one-way valves such that movement of the shaft also pumps coolant past cooling fins and over a motor. The shaft is formed of several sections joined by couplers which slide within a bore of the housing. The couplers have a non-round shape and the bore has a complimentary non-round cross section such that rotation of the shaft is prevented.