An axial piston machine may include a housing, a guide, a shaft, at least two cylinders each delimited by an associated cylinder wall, at least two pistons, a feed configured to supply a working fluid, an exhaust configured to discharge the working fluid, and at least one actuator configured to open and close a plurality of secondary outlets. Each associated cylinder wall may include a primary outlet and a secondary outlet of the plurality of secondary outlets. Each primary outlet and each secondary outlet may be fluidically connected to an outlet chamber that is fluidically connected to the exhaust. Each primary outlet may open into an associated primary outlet channel that opens into the outlet chamber. Each secondary outlet may be fluidically connected to an associated secondary outlet channel that opens into the outlet chamber and is separate from the plurality of primary outlet channels.

A fluid end having as fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having as fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

An axial piston motor having a cylinder housing, in which a plurality of cylinders are formed, and having pistons which are movably guided in the cylinders, wherein the pistons are attached to a swash plate and wherein a flow of a fluid that has entered via an inlet into the axial piston motor is controlled into and out of the cylinders by means of inlet and outlet valves, wherein the inlet and/or outlet valves comprise fluid change openings which are formed in a cylinder head plate and which can be temporarily released and covered by means of a rotary slide, for which purpose the rotary slide forms at least one passage opening.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A variable displacement pump-motor includes a pump-motor having a plurality of cylinders and pistons, and further including a main shaft rotatable relative to the system body. A hydro mechanical control system includes a plurality of main stage valves in communication with the plurality of cylinders. Each of the main stage valves is configured to open and close a cylinder of the plurality of cylinders to one or more of high or low pressure fluid sources. A pilot spool valve is in selective communication with each of the main stage valves. The pilot spool rotates with the main shaft. The pilot spool includes coding configured to operate each of the main stage valves to open and close the respective cylinders to the one or more high and low pressure fluid sources according to a translational position of the pilot spool and rotation of the pilot spool by the main shaft.

A variable displacement pump-motor includes a pump-motor having a plurality of cylinders and pistons, and further including a main shaft rotatable relative to the system body. A hydro mechanical control system includes a plurality of main stage valves in communication with the plurality of cylinders. Each of the main stage valves is configured to open and close a cylinder of the plurality of cylinders to one or more of high or low pressure fluid sources. A pilot spool valve is in selective communication with each of the main stage valves. The pilot spool rotates with the main shaft. The pilot spool includes coding configured to operate each of the main stage valves to open and close the respective cylinders to the one or more high and low pressure fluid sources according to a translational position of the pilot spool and rotation of the pilot spool by the main shaft.

A plunger pump fluid end in which the suction valve and seat is aligned with the plunger and the fluid end housing is constructed with multiple modules. Modules are held in a rigid assembly by staybolts that connect to the power end of the plunger pump. Said staybolts pass though bores in the central fluid module and the suction seat module and bound by a conventional threaded nut. Packing box modules are bound to the central fluid module by bolts that also pass through separate bores in the same central module. A suction valve spring retainer/plunger spacer within the plunger bore of the assembly shields the intersection of the plunger bore and the discharge bore from destructive erosion damage.

A plunger pump fluid end in which the suction valve and seat is aligned with the plunger and the fluid end housing is constructed with multiple modules. Modules are held in a rigid assembly by staybolts that connect to the power end of the plunger pump. Said staybolts pass though bores in the central fluid module and the suction seat module and bound by a conventional threaded nut. Packing box modules are bound to the central fluid module by bolts that also pass through separate bores in the same central module. A suction valve spring retainer/plunger spacer within the plunger bore of the assembly shields the intersection of the plunger bore and the discharge bore from destructive erosion damage.