59 results about "Radial piston pump" patented technology

The invention discloses a corrosion-resistant radial plunger pump with a self-cleaning function, and relates to the technical field of radial plunger pumps, the corrosion-resistant radial plunger pump comprises a shell of a hollow structure, a vertically-arranged partition plate is fixed to the center of the interior of the shell in the length direction of the partition plate, and the length direction of the partition plate is perpendicular to the length direction of the shell; the partition plate divides the interior of the shell into two cavities, and the drainage plate is rotationally connected to one end, in the length direction of the partition plate, of the partition plate; according to the device, through cooperation of the drainage mechanism, the driving mechanism, the filter screens and other components, when the filter screen on one side is blocked, the filter screens generate displacement under the action of negative pressure suction, then the drainage plate is driven to turn, switching of the flowing direction of liquid flow is achieved, the blocked filter screen can be cleaned, the conveying work cannot be stopped, manual intervention is not needed in the process, and the working efficiency is improved. And shutdown operation is not needed, so that the production interruption time caused by blockage of the filter screen is shortened, the production efficiency is improved, and the maintenance frequency is reduced.

The invention provides a hydraulic control pilot two-stage flow distribution static balance radial plunger hydraulic device and a working method, and relates to the technical field of radial plunger hydraulic devices. According to the scheme, the radial plunger hydraulic device is balanced through hydraulic control pilot two-stage flow distribution static force, flow distribution is controlled through external control pilot pressure, bidirectional rotation of a hydraulic pump motor and self-compensation after a valve plate is abraded are achieved by arranging an external control pilot oil way, and the service life is prolonged. In addition, by arranging the regular polygon driving type structure, regular polygon parts are additionally arranged between the crankshaft and the plunger, the transmission performance of the radial plunger pump is optimized, and friction force is reduced. By arranging the guide sleeve, the rubber cavity assembly and the return spring, the movement centering performance of the plunger can be effectively improved, leakage at the position of the plunger unit is reduced, and the complexity of the motor return device is simplified.

The invention discloses a variable radial plunger pump, and relates to the technical field of plunger pumps, the variable radial plunger pump comprises a first shell and a second shell which are fixed through bolts, the interiors of the first shell and the second shell are sealed to define a sealing cavity, the variable radial plunger pump further comprises an eccentric mechanism, the eccentric mechanism comprises an eccentric wheel and a clamping shaft, and the eccentric wheel is located in the sealing cavity; a sliding clamping block is in sliding connection in the radial direction, a driving assembly is fixedly connected, and the output end of the driving assembly is in threaded connection with the sliding clamping block. The eccentric distance between the eccentric wheel and the clamping shaft can be adjusted, when the eccentric wheel eccentrically rotates, the stroke of the piston column is controlled in cooperation with the spring pipe, oil pumping work of hydraulic oil of different flows is conveniently conducted, and the power of the plunger pump is rapidly adjusted; the lifting column is controlled to stretch into and draw out of the fixing pipe so as to control the size of the oil pumping working area, namely the negative pressure space, in the fixing pipe, and adjustment in a larger range can be conducted in cooperation with work of the eccentric mechanism.

The invention provides a plunger assembly lubricated by a working medium and a radial plunger pump, and belongs to the field of plunger pumps. The plunger assembly lubricated by the working medium comprises a pump body and a plunger, a plunger hole allowing the plunger to reciprocate and a pumping channel with the middle communicated with the plunger hole are formed in the pump body, the pump body is provided with a columnar structure, a guide sleeve is arranged on the columnar structure in a sleeving mode, and a liquid inlet channel allowing the working medium to flow into the guide sleeve from the outside in a one-way mode is formed in the pump body. And the end wall of the guide sleeve is provided with a lubricating through hole through which a working medium in an inner cavity of the guide sleeve flows to the outer surface of the end wall and provides lubrication during working. The radial plunger pump lubricated by the working medium comprises the plunger assembly lubricated by the working medium. According to the radial plunger pump, a new pump structure is designed in the plunger assembly, the pump structure can pump a working medium to a part needing to be lubricated, and the working medium is used for providing lubrication for the working process of the radial plunger pump.

The present invention discloses a radial piston pump, which comprises a pump body, a camshaft and a plunger assembly, wherein the pump body has an axial hole, a plunger hole, a liquid inlet and a liquid discharge port, the extension direction of the axial hole is perpendicular to the extension direction of the plunger hole; the camshaft is rotatably arranged in the axial hole; the plunger assembly comprises a cylinder sleeve and a plunger, the cylinder sleeve is arranged in the plunger hole, the plunger is arranged in the cylinder sleeve, the plunger comprises a plunger head, a plunger barrel and a working chamber, the plunger head is sealed and connected to the cylinder sleeve, the plunger barrel is movable between a liquid inlet position and a liquid discharge position, the plunger barrel is arranged spaced apart from the cylinder sleeve in the extension direction of the axial hole, the plunger has a relative blocking end and an open end, the blocking end cooperates with the camshaft, the plunger barrel at the liquid inlet position is released by the camshaft so that the liquid inlet is connected to the working chamber, and the plunger barrel at the liquid discharge position is compressed by the camshaft so that the liquid discharge port is connected to the working chamber. The radial piston pump of the embodiment of the present invention has the advantages of wide application range and high reliability.

The invention provides a pressurizing assembly for a radial plunger pump and the radial plunger pump, and belongs to the field of plunger pumps. The pressurization assembly for the radial plunger pump comprises a pressurization shell and an impeller, the pressurization shell is provided with an inner cavity, the inner cavity comprises a pressurization area used for containing the impeller and a conveying area communicating with the periphery of the pressurization area, and a suction inlet used for sucking a working medium is formed in the shell wall, corresponding to the pressurization area, of the pressurization shell. The shell wall, corresponding to the conveying area, of the pressurizing shell is provided with a discharging opening used for discharging the working medium. During use, the impeller can rotate along with the rotating shaft in the pressurizing area so that the working medium can be discharged after being pressurized in the pressurizing shell. The radial plunger pump comprises the pressurizing assembly. According to the radial plunger pump, the working medium is pressurized in advance, so that the working medium can enter the plunger assembly more easily, the phenomena of cavitation, air suction and the like are reduced, and the radial plunger pump has better working capacity and longer service life.

This invention discloses a plunger motor pump, relating to the field of hydraulic pump technology. The motor rotor has an internal mounting cavity in which a radial plunger pump core assembly is housed. The assembly includes a cylinder connected to the motor rotor, a plunger slidably disposed within a radial plunger hole in the cylinder, and a fixed eccentric shaft fixedly inserted into and eccentrically positioned within the cylinder. The outer wall of the fixed eccentric shaft has an annular groove, and the plunger head is housed within this groove. When the cylinder rotates, the plunger reciprocates along the radial plunger hole under the constraint of the annular groove. The motor housing has a self-cooling channel connecting the external working medium to the cylinder's inlet side, allowing the working medium to flow through the self-cooling channel before being pressurized upon entering the cylinder to cool the motor. A distribution plate is located at the cylinder end to achieve liquid intake / discharge switching. This design solves the problems of low integration, large size, and complex cooling systems in existing motor pumps, achieving compact integration of the motor and pump and efficient self-cooling, meeting the needs of applications such as seawater desalination.

The invention relates to the technical field of hydraulic systems, and provides a hydraulic pump station and a hydraulic system. The hydraulic pump station comprises a first radial plunger pump, a second radial plunger pump, a phase adjusting mechanism and a transmission clutch. Plungers of the first radial plunger pump communicate with plungers of the second radial plunger pump in a one-to-one correspondence mode, and the second radial plunger pump is connected with the first radial plunger pump through a transmission mechanism. The phase adjusting mechanism is connected with the second radial plunger pump and used for adjusting the plunger phase of the second radial plunger pump. And the transmission clutch is arranged between the second radial plunger pump and the transmission mechanism. When flow adjustment is needed, the second radial plunger pump is separated from the transmission mechanism through the transmission clutch, and the plunger phase of the second radial plunger pump is adjusted through the phase adjusting mechanism, so that the first radial plunger pump and the second radial plunger pump form different plunger phase differences. Therefore, the large-range real-time accurate adjustment of the flow of the hydraulic pump station is realized.

The invention relates to a radial piston pump (1) for delivering a pressure medium to a consumer (2), having a housing (3) in which cylinder bores (5) are provided, which are arranged radially with respect to a longitudinal axis (4) and in each cylinder bore a radially displaceable piston (6) is arranged. The pistons (6) form a piston row (7) in a radial plane. The radial piston pump (1) further comprises an eccentric shaft (8) arranged coaxially to the longitudinal axis (4), which eccentric shaft sets the piston (6) in a linear oscillating reciprocating motion, in which pressure medium flows from a suction chamber (10) supplied with pressure medium through a suction port (11) into the cylinder chamber (12) through a suction opening (9) formed in the piston (6) in the region of bottom dead center of the stroke motion. As a result of the movement of the piston (6) towards the top dead center, the pressure medium flows out of the cylinder chamber (12) through the pressure opening (13) to the pressure outlet (14).

The invention discloses a shaft flow distribution structure for a roller pump and a using method, and relates to the technical field of hydraulic power elements, the shaft flow distribution structure comprises an oil distribution shaft, a cylinder body and a plurality of plungers, the oil distribution shaft is internally provided with an oil inlet axial oil way and an oil return axial oil way which are independent from each other, a plurality of oil inlet distribution windows and a plurality of oil return distribution windows are formed in the outer surface of the oil distribution shaft, a plurality of radial plunger cavities are evenly distributed in the circumferential direction of the cylinder body, one end of the cylinder body is connected with power equipment, and the plungers are connected with the side walls of the radial plunger cavities in a sliding and sealing mode. When the plunger moves in the direction away from the axis of the cylinder body, oil liquid is sucked into the radial plunger cavity through the oil inlet axial oil way and the oil inlet and distribution window, and when the plunger moves in the direction close to the axis of the cylinder body, the oil liquid in the radial plunger cavity is discharged through the oil return and distribution window and the oil return axial oil way on the oil distribution shaft. The structure is simple, using is convenient, and the performance and reliability of the radial plunger pump are effectively improved.

The present invention discloses a radial piston pump array group transmission system for a wind turbine, comprising a rotor assembly, wherein the rotor assembly comprises a rotating sleeve, wherein a plurality of transmission rings distributed at equal distances are fixedly mounted coaxially on the outside of the rotating sleeve, and the outer peripheral surface of each transmission ring is a cam roller track with periodic undulations; a plurality of radial piston pumps at fixed positions are distributed in a circumferential array on the outer periphery of each transmission ring; during the rotation of the transmission ring, the periodic undulating cam roller track drives the plunger in each radial piston pump to reciprocate via a transmission member; the present invention improves the output displacement under low speed working conditions by increasing the number of times the plunger acts in a single operating cycle of the rotor, thereby increasing the number of times the plunger acts and the number of cylinders.

The application relates to a high-water-base radial plunger pump comprehensive performance test device, which comprises a T-shaped table, a test pump being detachably connected to the T-shaped table, the test pump being a double-input-shaft pump, one end of the input shaft of the test pump being detachably connected to the output shaft of a three-phase asynchronous variable-frequency motor through a first transmission part, the other end of the input shaft of the test pump being detachably connected to the output shaft of a loading system through a second transmission part, the test pump being provided with a total liquid inlet, a total liquid outlet, a plurality of lubricating oil inlets, the plurality of lubricating oil inlets being detachably connected to a lubricating system, the total liquid inlet being detachably connected to an auxiliary system, the total liquid outlet being detachably connected to a three-way pipe joint, the other end of the three-way pipe joint being detachably connected to the loading system, the third end of the three-way pipe joint and the loading system being detachably connected to the auxiliary system. The application can synchronously test the plunger pair characteristics and the whole pump performance of the plunger pump, so that the test result can more truly reflect the actual working characteristics of the hydraulic pump.

A radial piston pump (1) is disclosed. The pump (1) comprises a rotor (30) mounted for rotation on the pintle (40) of a manifold, the rotor (30) comprising a plurality of piston chambers (32), a piston (34) being mounted in each chamber (32) for reciprocal movement. The pump (1) comprises a P-port (8) for connecting the pump to a hydraulic system. The P-port (8) is a port connected to the piston chambers (32) such that, in use, fluid can flow between the P-port (8) and the piston chambers (32). The P-port 8 is connected to the piston chambers (32) by a P flow-path (6). A shut-off valve (4) is positioned along the P flow-path (6) such that when the shut-off valve (4) is in an off-position flow between the P-port (8) and the piston chambers (32) is prevented.

The utility model discloses a multi-union radial plunger pump which comprises a pump base, a transmission shaft of an eccentric structure is installed at the position of a center hole of the pump base, a multi-point connection flange plate is installed at the top of the transmission shaft, and a plurality of connection rods and a push rod are connected to the multi-point connection flange plate. The connecting rods and the push rod are distributed in the circumferential direction of the multi-point-position connecting flange plate. Pistons are installed at the other ends of the connecting rods and the push rod. A plurality of pump bodies corresponding to the pistons are installed on the pump base, the pump bodies are distributed in the circumferential direction of the pump base, and the transmission shaft drives the multi-point connection flange plate to drive the pistons to do linear reciprocating motion in the pump bodies. The utility model solves the problem that the reciprocating motion of the hydraulic plunger is influenced along with the reduction of the performance of the reset spring in the prior art.

A pump head (100) of a radial piston pump, and a radial piston pump (200). The pump head (100) of a radial piston pump comprises at least two piston cylinder mechanisms (2) and a housing (1), wherein the housing (1) comprises a transmission assembly (11), an upper cover (12), a lower cover (13), an upper housing (14) and a lower housing (15), the upper housing (14) and the lower housing (15) being snap-fitted together to form an accommodating space inside; the piston cylinder mechanisms (2) are mounted in the accommodating space in a rotationally symmetrical manner; the transmission assembly (11) is arranged in the accommodating space; the transmission assembly (11) is connected to the piston cylinder mechanisms (2); and the upper cover (12) is connected to the upper housing (14), the lower cover (13) is connected to the lower housing (15), the upper cover (12) is in communication with water inlets of all the piston cylinder mechanisms (2), and the lower cover (13) is in communication with water outlets of all the piston cylinder mechanisms (2). The radial piston pump (200) comprises the pump head (100) of a radial piston pump.

The invention discloses a polygonal radial plunger pump with special-shaped plungers and a working method of the polygonal radial plunger pump, and belongs to the technical field of hydraulic transmission. The transmission shaft, the polygonal stator and the eccentric rotor are arranged in the pump shell, the eccentric rotor is arranged outside the transmission shaft, the polygonal stator is arranged outside the eccentric rotor, the outer wall of the polygonal stator is attached to the special-shaped plunger, the special-shaped plunger is connected with the plunger spring, and the plunger spring is connected with the one-way valve shell. An oil inlet pipe is arranged at one end of the one-way valve shell, an oil outlet pipe is arranged at the other end of the one-way valve shell, and an oil suction valve core is arranged in the oil inlet pipe, is arranged at the oil inlet end of the oil inlet pipe and is elastically connected with the oil outlet end of the oil inlet pipe; and an oil outlet valve core is arranged in the oil outlet pipe, is arranged at the oil inlet end of the oil outlet pipe and is elastically connected with the oil outlet end of the oil outlet pipe. The problem of local abrasion caused by inclination of a traditional plunger is solved, and the service life is prolonged; the technical bottlenecks that a traditional radial plunger pump is poor in abrasion resistance, large in size and complex to maintain are solved.

The invention relates to the technical field of plunger pumps, and discloses an alternating flow distribution pump which comprises a first radial plunger pump and a second radial plunger pump, the first radial plunger pump and the second radial plunger pump are connected through a coupler, the first radial plunger pump comprises a plurality of first plunger assemblies arranged in the radial direction of the first radial plunger pump, and the second radial plunger pump comprises a plurality of second plunger assemblies arranged in the radial direction of the second radial plunger pump. The first radial plunger pump comprises a plurality of first plunger assemblies arranged in the radial direction of the first radial plunger pump, the second radial plunger pump comprises a plurality of second plunger assemblies arranged in the radial direction of the second radial plunger pump, the second plunger assemblies are arranged in the circumferential direction of the second radial plunger pump, and the first plunger assemblies are selectively connected with the corresponding second plunger assemblies. According to the embodiment, continuous variable control over the flow of the plunger pump can be achieved, the flow can be precisely adjusted in a large range, variable-flow precise control over the plunger pump is achieved, and the use requirements of special scenes such as an underground coal mine are met; in addition, a radial pump structure is used, and extremely high displacement density can be achieved.

The application discloses a driving motor, which comprises a motor shell, a stator assembly fixed in the motor shell, and a rotor assembly rotatably arranged in the stator assembly. The rotor assembly comprises a rotor support and a rotor core assembly. The rotor support is rotatably installed on the motor shell. A radial plunger pump is coaxially arranged in the rotor support. A camshaft of the radial plunger pump is in transmission connection with the rotor support. The radial plunger pump is fixedly connected with the motor shell at an end away from the camshaft. The radial plunger pump is provided with an oil inlet channel and an oil outlet channel. The motor shell is provided with an oil inlet port and an oil outlet port. The oil inlet port and the oil outlet port are respectively in communication with the oil inlet channel and the oil outlet channel. The application further discloses a wheel edge electric driving system integrated with an emergency steering function and using the driving motor. The application aims to provide a driving motor and a wheel edge electric driving system integrated with an emergency steering function, so that the vehicle can have the steering function when the main loop of the vehicle steering hydraulic system fails.

The invention provides a digital variable plunger pump unit and a radial plunger pump, and belongs to the technical field of plunger pumps. The digital variable plunger pump unit comprises a pump body and a plunger, a plunger hole and a pumping channel are arranged in the pump body, an inlet and an outlet of the pumping channel are provided with a suction valve and a flow control valve respectively, the flow control valve comprises a valve seat and a valve cavity arranged in the valve seat, and the valve seat is provided with a valve inlet, a valve outlet and a pressure relief opening which are communicated with the valve cavity. The flow control valve further comprises a jacking structure which elastically abuts against and seals the pressure relief opening from the outer side, and a piezoelectric ceramic piece which is used for lifting the jacking structure through extension to open the pressure relief opening at the high level is arranged between the valve seat and the jacking structure. The radial plunger pump comprises the plunger pump unit. According to the plunger pump unit, the flow control valve is arranged at the outlet of the plunger pump unit, so that accurate control over the output flow of the single plunger pump unit is achieved, and different use requirements are met.

The invention relates to a radial piston pump (1) for conveying a hydraulic fluid to a consumer (2), comprising a housing (3) in which radially arranged cylinder bores (5) are provided relative to a longitudinal axis (4), each containing a radially displaceable piston (6). The pistons (6) form a row (7) lying in a radial plane. Furthermore, the radial piston pump (1) has an eccentric shaft (8) arranged coaxially to the longitudinal axis (4), which sets the pistons (6) into a linearly oscillating stroke motion. Hydraulic fluid flows through suction openings (9) formed in the pistons (6) in the region of a bottom dead center of the stroke motion from a suction chamber (10), which is supplied with hydraulic fluid via a suction port (11), into cylinder chambers (12). As the pistons (6) move towards their top dead center, the hydraulic fluid flows through pressure openings (13) from the cylinder chambers (12) to a pressure outlet (14).At least one further piston row (15) is provided parallel to the piston row (7). The housing (3) has further cylinder bores (16) in which a piston (17) of the further piston row (15) is arranged to be radially displaceable. The eccentric shaft (8) sets the pistons (17) of the further piston row (15) into a linear oscillating stroke motion.

A radial piston pump (1) is disclosed. The pump (1) comprises a rotor (30) mounted for rotation on the pintle (40) of a manifold, the rotor (30) comprising a plurality of piston chambers (32), a piston (34) being mounted in each chamber (32) for reciprocal movement. The pump (1) comprises a P-port (8) for connecting the pump to a hydraulic system. The P-port (8) is a port connected to the piston chambers (32) such that, in use, fluid can flow between the P-port (8) and the piston chambers (32). The P-port 8 is connected to the piston chambers (32) by a P flow-path (6). A shut-off valve (4) is positioned along the P flow-path (6) such that when the shut-off valve (4) is in an off-position flow between the P-port (8) and the piston chambers (32) is prevented.

The application discloses an experimental platform and a testing method of a digital variable radial plunger pump, and relates to the technical field of digital pump experimental testing; the experimental platform comprises a plunger unit, a pressure sensor, an accumulator, a flowmeter, a controller, a host computer and an encoder; the controller comprises a control unit, an encoder interface circuit, a host computer interface circuit, a switch valve driving circuit, a power conversion circuit and an interface circuit module; the experimental platform is designed for researching a new type of digital pump; the experimental platform can obtain the pressure of the plunger cavity of the digital pump in a normal working state and an unloading state in real time, the output flow and flow pulsation of the digital pump, and verifies whether the design of the digital pump meets the expectation; after the controller obtains feedback data, the proportion of the digital code stream is changed, the displacement is corrected, and thus the closed-loop control is completed.

The present invention provides an integrated motor pump rotary joint, which fully combines the advantages of hydraulic transmission and incorporates the structural characteristics of a robot joint. It adopts the principles of integration, standardization, and modularization, facilitating integrated installation and use. It includes: an outer rotor torque motor, which includes an outer ring rotor, an inner ring stator, a stator fixed end cover, and a stator central through hole; a radial piston pump, which includes a pump body and a number of radially distributed radial pistons; a check valve; a pressurizing oil tank, which includes a pressurizing oil tank piston, a pressurizing oil tank sealing end cover, and an elastic element; a first rotating housing; a second rotating housing; a first bearing; and a flow distribution shaft, the flow distribution shaft includes a front convex flow distribution part and a rear end positioning part; the first rotating housing and the second rotating housing form an independent rotating housing mechanism through the first bearing combination; the first rotating housing and the second rotating housing form a central through cavity with a central hollow; the outer rotor torque motor is arranged in the central through cavity.

An electrohydraulic unit for a vehicle having housing 2 with two ports 8, 9, pump 3 (e.g. radial piston pump) providing to and extracting fluid from the two ports, and two valves 4, 5 controlling flui

This invention belongs to the field of hydraulic component design technology, and relates to the design, process research and manufacturing of a static pressure balance structure for high and low pressure distribution of the distribution shaft in a radial piston pump with axial flow distribution. Specifically, it is a static pressure balance distribution shaft with arc-shaped pressure equalizing grooves. This solves the technical problem of poor static pressure balance in the overall structure of the distribution shaft of current radial piston pumps with axial flow distribution, resulting in unstable pump performance under high pressure and severe wear in the high-pressure area of ​​the distribution shaft. The static pressure balance distribution shaft with arc-shaped pressure equalizing grooves has high and low pressure arc grooves and high and low pressure distribution windows on it. Internally, there are high and low pressure channels connecting the high and low pressure grooves and the corresponding distribution windows. Pressure ports and suction ports are respectively opened on the high and low pressure arc grooves. A pressure equalizing groove is opened on both the left and right sides of the high and low pressure arc grooves. The pressure equalizing grooves are circumferential arc-shaped grooves, which are arranged in a wave-like pattern around the circumference of the distribution shaft, so that the distance t between the edge of the pressure equalizing groove and the edge of the high and low pressure arc groove is controlled within a certain range.

A radial piston pump for delivering a pressure medium to a consumer may include a housing in which cylinder bores are arranged radially to a longitudinal axis and in each of which a radially displaceable piston is arranged. The pistons form a piston row lying in a radial plane. The radial piston pump furthermore has an eccentric shaft arranged coaxially to the longitudinal axis which sets the pistons in a linearly oscillating reciprocating motion, wherein pressure medium flows into cylinder chambers through suction openings formed in the piston in the region of a bottom dead centre of the stroke movement, from a suction chamber which is supplied with pressure medium through a suction port. The pressure medium flows out of the cylinder chambers to a pressure outlet through pressure openings owing to movement of the pistons towards the top dead centre. At least one further piston row is provided planar-parallel to the piston row. Further cylinder bores are provided in the housing, in each of which a piston of the further piston row is radially displaceably arranged. The eccentric shaft sets the pistons of the further piston row in a linearly oscillating reciprocating motion.

A radial piston pump for conveying fluid under high pressure has a suction port, a pressure port and a plurality of pump elements for conveying the fluid under high pressure from the suction port to the pressure port. Furthermore, the radial piston pump includes a high-pressure-resistant suction line structure connecting the suction port to at least one suction inlet of each pump element.

A radial piston pump, including a drive shaft having an eccentric and at least one piston-and-working chamber combination, wherein the piston-and-working chamber combination includes a working chamber and a piston. The radial piston pump includes at least two piston-and-working chamber combinations which extend radially from the drive shaft, wherein each working chamber is closed by a cover. The radial piston pump is equipped with at least one retaining ring for fixing all of the covers of the radial piston pump; and to a method for producing a radial piston pump.

A radial piston pump 1 is disclosed. The pump 1 comprises a rotor (30 Fig 2) mounted for rotation on the pintle (40 Fig 2) of a manifold, the rotor comprising a plurality of piston chambers (32 Fig 2), a piston (34 Fig 2) being mounted in each chamber 32 for reciprocal movement. The pump 1 comprises a P-port 8 for connecting the pump to a hydraulic system. The P-port 8 is a port connected to the piston chambers such that, in use, fluid can flow between the P-port 8 and the piston chambers. The P-port 8 is connected to the piston chambers by a P flow-path 6. A shut-off valve 4 is positioned along the P flow-path 6 such that when the shut-off valve 4 is in an off-position flow between the P-port 8 and the piston chambers is prevented.