Abstract: A pump unit which has at least one high-pressure port and at least one low-pressure port, having a motor and a hydraulic pump which has at least one high-pressure outlet and at least one low-pressure outlet, wherein the high-pressure outlet is connected to the high-pressure port via at least one pressure-regulating valve.

Abstract: A double-piston compressor of a compressed air supply device includes a first pressure stage and a second pressure stage, each having a cylinder with a piston guided therein in an axially movable manner. The piston of the cylinder of the first pressure stage and the cylinder of the second pressure stage are rigidly connected to one another via a piston rod and are in driving connection with the drive shaft via a slotted guide. The slotted guide comprises a recess which is formed in the piston rod, provided with a slotted guide track and oriented perpendicularly to an axis of rotation of the drive shaft with its cross-sectional plane. The slotted guide comprises a drive roller which is engaged with the recess and fastened to the drive shaft in an axially parallel, eccentric, and also rotatable manner with respect to the axis of rotation of the drive shaft.

Abstract: An air compressor unit for vehicle (2) includes an air compressor (13) for compressing sucked air, an electric motor (14) for driving the air compressor (13), an after-cooler (17) for cooling compressed air generated in the air compressor (13) and an after-cooler cooling fan (18) for generating cooling air for the after-cooler (17) by being driven by a drive force of the electric motor (14). The air compressor (13) and the electric motor (14) are arranged one above the other.

Abstract: A first check valve of a hydraulic control system allows oil to flow in only a direction from a first oil pump toward an oil receiving portion. A second check valve allows oil to flow in only a direction from a second oil pump toward the oil receiving portion. A third oil passage is configured to provide communication between a merging point of a first oil passage and a second oil passage, and the second oil pump by bypassing the second check valve. The third oil passage includes a throttle mechanism. The third oil passage is configured to restrict a flow rate of oil that is discharged from the second oil pump.

Abstract: A fuel system includes a pump unit having at least a fixed displacement pump supplying pressurized flow. A fuel control assembly receives flow from the pump unit and includes at least one metering valve and at least one throttling valve. A control (bypass valve control) for the fixed displacement pump receives first and second pressure signals indicative of a pressure differential across the throttling valve, or across the metering valve/throttling valve combination, for altering output from the fixed displacement pump in response to the pressure differential. In other embodiments, the pump unit includes a centrifugal pump and a fixed displacement pump that can be fully or partially redundant depending on sizing of the pumps, and the system requirements.

Abstract: A reciprocating compressor for the oil and gas industry, the reciprocating compressor has a chamber, a timing valve, an actuator and a controller. A fluid entering the chamber via a suction valve is compressed inside the chamber, and evacuated from the chamber via a discharge valve. The timing valve is located between the chamber and a fluid volume at a relief pressure that is lower than a pressure in the chamber when the timing valve is opened. The actuator is configured to actuate the timing valve. The controller is configured to control the actuator such that to open the timing valve during an expansion phase of the compression cycle, and to close the timing valve when the relief pressure becomes equal to the pressure in the chamber or when the suction valve is opened.

Abstract: A flow sensing dual pump switching system and method are provided that control the supply of fuel from a dual pump fuel system to a fuel metering unit. The system senses bypass pressure from the fuel metering unit to control the differential pressurization of the second pump. As the bypass is reduced, the pressure of the second pump is increased so that it may be added to that of the first pump to supply the increased fuel consumption needs of an engine. As the fuel consumption needs decrease, the flow from the second pump added to the first pump is reduced and the differential pressure of the second pump is similarly reduced. If the bypass pressure remains high, the switching system disconnects the output of the second pump from that of the first in favor of bypassing the flow to its input to reduce its differential pressure and conserve energy.

Abstract: A hydraulic pump system for an automatic transmission has the advantages of preventing excessive power loss and durability deterioration. The hydraulic pump system may include a first hydraulic pump that generates a first hydraulic pressure to supply a low pressure portion with the first hydraulic pump, a second hydraulic pump that receives the first hydraulic pressure to generate a second hydraulic pressure higher than the first hydraulic pressure and supplies a high pressure portion with the second hydraulic pressure, and a drive portion that rotates a drive shaft that integrally connects the first hydraulic pump with the second hydraulic pump.

Abstract: A hydraulic system, including fluid flow generated by a primary pump and a secondary pump, utilizes a regulator control assembly to control fluid flow from each of the primary and secondary pumps such that a desired fluid flow and pressure is maintained at the outlet for varying actuator demands. The regulator control assembly controls the transition from using only the primary pump, to using both the primary and secondary pumps to provide a desired fluid flow and pressure through the outlet to the actuator.

Abstract: A dual-supply fluid distribution system includes a first pump having an inlet and an outlet. The first pump is configured to supply a first fluid flow. A second pump has an inlet and an outlet, and is configured to supply a second fluid flow. A check valve is coupled between the first and second pump outlets. The check valve is configured to combine the second fluid flow with the first fluid. A bypass valve is coupled to the outlet of the first pump. The bypass valve has an integral pilot valve and is configured to permit fluid flow from the pump outlets in excess of the fluid demand to recirculate back to the first and second pump inlets. The bypass valve and integral pilot valve are configured to cause the check valve to open when the flow of fluid through the bypass valve is below a threshold amount.

Abstract: A fuel flow system for a gas turbine engine includes a first pump, a second pump, a bypass loop, an integrating bypass valve and a pilot valve. The first pump connects to an actuator and a metering valve. The second pump connects to the metering valve and is arranged in parallel with the first pump. The bypass loop recycles fuel flow from the first pump and the second pump to inlets of the first pump and second pump integrating bypass valve includes first and second windows. The first window regulates fuel from the first pump through the bypass loop and the second window that regulates fuel from the second pump through the bypass loop. The pilot valve controls the size of the first and second windows.

Abstract: A power transmission device includes a clutch that transmits power from a motor to an axle; a first pump that is driven by power from the motor to generate and output fluid pressure; a second pump that receives and is driven by a supply of electric power to generate and output fluid pressure; a pressure regulating valve that functions as a linear solenoid valve and is formed with an input port, an output port that is connected to the clutch, and a drain port; and a switching valve that switches between a first connection state.

Abstract: A flow sensing dual pump switching system and method are provided that control the supply of fuel from a dual pump fuel system to a fuel metering unit. The system senses bypass pressure from the fuel metering unit to control the differential pressurization of the second pump. As the bypass is reduced, the pressure of the second pump is increased so that it may be added to that of the first pump to supply the increased fuel consumption needs of an engine. As the fuel consumption needs decrease, the flow from the second pump added to the first pump is reduced and the differential pressure of the second pump is similarly reduced. If the bypass pressure remains high, the switching system disconnects the output of the second pump from that of the first in favor of bypassing the flow to its input to reduce its differential pressure and conserve energy.

Abstract: An apparatus for changing capacity of a multi-stage compressor comprises: a first cylinder provided with a first suction and a first discharge port, and divided into a first suction chamber and a first compression chamber by a first rolling piston which orbits and a first vane which makes a linear movement in contact with the first rolling piston; a second cylinder provided with a second suction port and a second discharge port, and divided into a second suction chamber and a second compression chamber by a second rolling piston which orbits and a second vane which makes a linear movement in contact with the second rolling piston; a middle bearing inserted between the first cylinder and the second cylinder, having a bypass hole to allow communication between the compression chambers of the first cylinder and the second cylinder, and having a valve hole for communication in the middle of the bypass hole; a sliding valve slidingly coupled to the valve hole of the middle bearing, and selectively opening or closi

Abstract: A power pack unit includes a first hydraulic pump including a first pump enclosure accommodating a first pump cartridge. A second hydraulic pump includes a second pump enclosure accommodating a second pump cartridge. A hydraulic fluid reservoir is positioned between the first and second hydraulic pumps. A first end of the reservoir is secured to the first pump enclosure and a second end of the reservoir is secured to the second pump enclosure. The first and second hydraulic pumps and the reservoir can extend along a common axis. First and second motors can be connected to the first and second pumps. The entire structure can extend along a common axis.

Abstract: A multiple stage pump having valves downstream from each respective pump in a same line thereof. The respective lines then merge into a common line. The multiple stage pump prevents pressure variations and shot to shot fuel variations.

Abstract: A multiple stage pump having valves downstream from each respective pump in a same line thereof. The respective lines then merge into a common line. The multiple stage pump prevents pressure variations. The multiple stage pump includes a first pump in a first stage and a second pump in a second stage. At least one valve is downstream from one of the first pump and the second pump in at least one of the first stage and the second stage. A common branch line connects the first stage and the second stage to a common hydraulic system.

Abstract: A multiple stage pump having valves upstream from each respective pump in a same line thereof. The respective lines then merge into a common line. The multiple stage pump prevents pressure variations. The multiple stage pump includes a first pump in a first stage and a second pump in a second stage. At least one valve is upstream from one of the first pump and the second pump in at least one of the first stage and the second stage. A common branch line connects the first stage and the second stage to a common hydraulic system.

Abstract: A tandem fixed displacement pump circuit with torque control includes first and second pumps that draw fluid from a reservoir to supply respective load circuits, pressure relief valves for each of the load circuits, and a pilot operated sequence valve that monitors the pressure for each of the circuits and reduces the pressure of one of the circuits as the pressure in the other circuit rises. The sequence valve modulates to control the pressure in the secondary priority circuit so that a predetermined input torque value is not exceeded.

Abstract: A valve spool (70) for an oil pump assembly (10) that includes a pilot pressure relief valve (80) to provide pilot pressure relief that increases the stability of the pump assembly (10) and eliminates the delay between the change in the discharge pressure and the associated response to the pilot pressure. The valve spool (70) operates in response to the pilot pressure to increase or decrease the pump discharge pressure during vehicle operation. A chamber (72) within the valve spool (70) is in fluid communication with the discharge flow and pressure at one end and the pilot pressure at the other end. When the pilot pressure exceeds the discharge pressure, the relief valve (80) opens, allowing the discharge pressure and the pilot pressure to equalize.

Abstract: A sewage lifting station having at least two solid waste collection chambers for receiving pumped solid waste-contaminated sewage. The station has a collection tank for receiving pre-treated waste water flowing from the solid waste collection chambers via connection pipes. Each solid waste collection chamber is connected to a pump to empty the collection tank via one of the connection pipes and solid waste collection chambers to pump the current of sewage into a pressure pipeline. There is a closing device connected to each connection pipe to selectively close an exit orifice in the connection pipe and open a connection to an operating pump to drain the collection tank. A control device alternately closes and opens the exit orifices with the closing devices so that an exit orifice allocated to an operating pump is closed and an exit orifice allocated to a non-operating pump is simultaneously and automatically opened.

Abstract: A gerotor pump is described for use with non-compressible fluids such as automotive coolant or hydraulic oil. The pump includes three separate pump outlet ports, a bypass return passage, find an integral four position spool valve. Increasing back pressure from a downstream load is sensed be the spool valve which moves accordingly to restrict the fluid supplied. In the first position a full flow fluid is supplied to the load from all three ports. In the second position one port is vented to the bypass and the flow from the other two ports is directed to the load. In the third position two ports vent to bypass, and one ports drives the load. In the fourth position all ports vent to bypass. In each case flow vented to bypass is not first compressed, permitting a smaller motor to be used.

Abstract: A gear pump having three gears, including; a pump case consisting of a pump body and a cover for covering most of the body; three gears which are supported by a rotating shaft on the pump case and engaged with each other in series; first and second gear pumps each composed of one central drive gear and one of the driven gears on both sides of the drive gear; a non-return valve and a flow regulation valve which are opened at a predetermined pressure; an inlet port which is opened at one end of the pump case and connected through a feed path to the suction side of the two gear pumps; an outlet port formed on the discharge side of the first gear pump in the pump case; a regulation path passing from the discharge side of the second gear pump through the non-return valve to the outlet port; and a flow regulation path passing from the regulation path through the flow regulation valve to an oil pan.

Abstract: A pump system is disclosed which operates at high efficency in either a high volume, low pressure mode or a low volume, high pressure mode. First and second internal gear pumps are driven by a common drive shaft. The first pump has a smaller displacment than the second pump and both pumps deliver pressurized fluid to a common discharge passage. An unloading valve is operative to dump the output of the second pump in response to fluid pressure in the discharge passage so that it delivers fluid to the load device only when the pressure is below a predetermined value. The unloading valve also performs the function of a low capacity accumulator. A check valve is provided to prevent back flow in the outlet of the second pump.

Abstract: A constructionally simplified hydraulic pump has two pump elements which discharge from a common suction chamber. The flows can be alternatively fed in common to a pressure outlet or separately to two outlets, one of which outlets leads back into the suction chamber. The pressure-side chambers for the separated flows can be connected, via a unidirectional valve, through which, in the open state, the flow of one pump element can be united with that of the second pump element. The different flow guide modes are switched via control valves whose position depends only on the pressure prevailing at the pressure outlet of the hydraulic pump. The control valves to be switched are a common component of a single control slide valve.

Abstract: An unloading arrangement for a rotary screw compressor includes discrete and different unloading apparatus associated with the male and female rotors respectively. The unloading apparatus associated with the male rotor is an axial piston continuous unloader movably disposed in a bore which is remote from but in flow communication, through a series of ports, with the compressor's working chamber. The unloading apparatus associated with the female rotor is a step unloader which, when opened, unloads the compressor in a single, relatively large capacity step. The compressor is therefore capable of being unloaded both over a continuous operating range and in a discontinuous, stepwise fashion. By duplexing compressors of this type, continuous capacity modulation of a multiple compressor system is made available over a large operating range without the employment of compressors unloaded by slide valve mechanisms.

Abstract: The first of two serially arranged electromagnetically operated spool type drain control valves is conditioned to select the drain passage of smaller the pump before the second valve is moved from its closed or communication cut-off position, to its open position wherein hydraulic fluid can be drained therethrough, whereby the spool of the second valve is exposed to a relatively small flow generated force which acts thereon and which tends to move the valve spool toward to its closed position. In another embodiment the hydraulic fluid temperature is monitored and used to modify the control schedule via which the switching of the drain control valves is determined. A further embodiment monitors a parameter which is indicative of the prime mover rotational speed and inhibits the closure of the second of the two valves when the rotational speed is above a predetermined limit.

Abstract: A dual capacity pump having at least two gear pump stages with a common fluid inlet passage, each pump stage having a discharge port, the discharge port for one stage communicating with a fluid pressure load through a flow delivery passage and the discharge port for the other stage communicating with the flow delivery passage through a one-way flow valve, and flow control valve means responsive to an operating variable for connecting the discharge side of the other stage to the common fluid inlet passage during operation in a first operating range of low driving speeds for the pump and to said flow delivery passage through the one-way flow valve during operation in a calibrated range of values for the operating variable.

Abstract: In a compressor having a plurality of banks of cylinders, smaller steps of unloading are achieved by unloading a single cylinder in a bank. When only one cylinder is to be unloaded, gas bypass is used in order to maintain a closer balance of forces in the bank. When the entire bank is unloaded, it is preferably done via the suction cutoff method.

Abstract: A pump and regulator valve assembly having multiple pump and multiple regulator valve means that establish pressures of two or more operating pressure levels in a control system wherein the valve means has multiple valves that selectively respond to varying flow demands of the different regions of the control system to connect one or more pumps to reduced pressure regions when the flow demands of higher pressure regions are satisfied.

Abstract: A pump system is disclosed which operates at high efficency in either a high volume, low pressure mode or a low volume, high pressure mode. First and second internal gear pumps are driven by a common drive shaft. The first pump has a smaller displacement than the second pump and both pumps deliver pressurized fluid to a common discharge passage. An unloading valve is operative to dump the output of the second pump in response to fluid pressure in the discharge passage so that it delivers fluid to the load device only when the pressure is below a predetermined value. The unloading valve also performs the function of a pressure relief valve. A check valve is provided to prevent back flow in the outlet of the second pump.

Abstract: A plurality of unloading steps for a compressor are achieved by providing the compressor with at least two cylinders having different displacements. By unloading different cylinders, the compressor output is better able to match system demand.

Abstract: An improved unloading and sequencing control valve for a two pump hydraulic system is adapted to be mounted directly onto the bearing carrier of a two section gear pump or at a remote location and connected to the pumps by plumbing and is capable of operating in a flow sensing mode only, a pressure sensing mode only, or a combination flow sensing and pressure sensing mode. The control valve includes a removable adjustable flow sensing orifice and is adapted for remote pressure sensing and remote pressure adjustment as well as multiple selective preset flow sensing pressure to provide any desired unloading or sequencing pressure within limits of pump capacity.

Abstract: Controls for a dual element pump having first and second pumps with separate outputs wherein a modulating valve is positionable to control the amount of fuel delivered by a first pump to a fuel control and additionally to selectively control the utilization of flow delivered by the second pump. The flow from the second pump is bypassed when not needed through a pressure regulating valve having a minimal setting and with the setting of the pressure regulating valve being increased by operation of the modulating valve prior to the flow from the second pump being added to the flow from the first pump. The control of the modulating valve is by means of a flow control valve operating through dynamic compensator structure. The flow control valve is positioned by a head sensor including a jet pipe shiftable from a null position by a pressure differential signal delivered by two pressure sensing lines sensing a pressure differential across a variable area opening in a valve forming part of the fuel control.

Abstract: An oil pump assembly comprises a pump body assembly composed of a pair of front and rear pump bodies, the rear pump body housing in a pump housing space a pair of pumps each including a pump cartridge having a rotor supported on a common drive shaft rotatably supported on the front pump body, and a cam ring accommodating the rotor. A single side plate is axially slidably interposed between the pump cartridges. A pressure plate is disposed between one of the pump cartridges remote from the front pump body and a pump discharge pressure chamber defined at the bottom of the pump housing space and communicating with a main passage through which one of the pumps communicates with a discharge port. The other pump is selectively connected by a directional control valve to the main passage. The pump and valve parts can easily be assembled into the pump bodies, and hence the oil pump assembly can be mass-produced efficiently, less costly, and is small in size and lightweight.

Abstract: The control valving for a dual pump hydraulic system has two regulator valves which control the distribution of pressurized fluid, on a priority basis, to a high pressure system, a low pressure system and a lube system. One regulator valve controls flow from both pumps to the high and low pressure systems. The other regulator valve controls flow from one pump to the lube system and bypasses excess flow from the other pump to the system reservoir. The first regulator valve satisfies the high pressure system requirements before any fluid is directed to the low pressure system. The other regulator valve receives fluid downstream of the first regulator valve and satisfies the low pressure system before any fluid is directed to the lube system or to the fluid return passage to the reservoir.

Abstract: There is disclosed a multistage gear pump and control valve arrangement comprising two hydraulic gear pump sets each having a suction port connected to a common sump and a discharge port for delivering hydraulic fluid to a circuit line. Only one of the discharge ports is continuously open to the circuit line while a check valve operates to connect the other of the discharge ports to the circuit line and prevent reverse flow. A regulator valve regulates the pump discharge to the circuit line by diverting fluid therefrom in response to circuit line pressure below a predetermined setting while both the discharge ports are delivering fluid thereto and by being responsive to circuit line pressures thereabove to connect the other discharge port to the sump to thereby relieve the associated gear pump set of hydraulic work while again regulating the pump discharge to the circuit line by diverting fluid therefrom but with only the one discharge port delivering fluid thereto.

Abstract: A flow path switching valve is provided, operating to merge hydraulic fluid from a plurality of pumps in accordance with a magnitude of a loading applied to a hydraulic unit, and a variable orifice is defined adjacent to the valve. A flow control valve is also provided for returning part of the hydraulic fluid to a tank, and operates in accordance with the throttle opening of the variable orifice which changes in accordance with the operation of the flow path switching valve.

Abstract: To supply hydraulic fluid to a hydraulic apparatus, a plurality of pumps are used. One of the pumps is used as a main pump while the remaining pump or pumps are used as sub-pumps. A flow path switching mechanism selectively disconnects the sub-pumps from a supply passage to the hydraulic apparatus. In this manner, a required minimum supply of hydraulic fluid is assured with a simple arrangement while eliminating wasteful energy loss and reducing the dissipation of the horsepower. A reliable operation is maintained without any adverse influence upon the hydraulic apparatus. In one embodiment, a pair of pumps, and a control including a pair of switching valves operating as a pressure sensor and a flow controller are assembled into a pump body. The switching valves assure a reasonable supply of hydraulic fluid to the hydraulic apparatus while minimizing the dissipation of the horsepower.

Abstract: A hydraulic power pack for supplying hydraulic fluid under pressure for operating apparatus such as hydraulic workover units used in servicing oil and gas wells. The power pack provides substantially constant hydraulic power input to the driven apparatus over a wide range of pressures and flow rates. The power pack includes a constant speed engine, a gear box driven by the engine, a bank of positive fixed displacement pumps of varying sizes driven by the gear box and having discharge ports connected with a common discharge manifold, a hydraulic fluid reservoir, an intake manifold between the reservoir and the pumps, a return line to the reservoir, a recirculating line connected between the discharge from each of the pumps and the return line, and an unloading valve in each of the recirculating lines operable responsive to the pressure in the discharge manifold for recirculating each of the pumps to the reservoir at a predetermined pressure value.

Abstract: A process to control the delivery of a single screw compressor comprising a screw meshing with two pinion wheels and rotatable inside a casing. A channel with obturating means is provided to connect the high pressure orifice pertaining to a one pinion-wheel and the low pressure orifice. Auxiliary orifices are arranged to connect the various zones of the casing exposed to pressure with the low pressure orifice, said auxiliary orifices being provided with obturating devices. Said orifices are sequentially opened to diminish the delivery, starting from the orifice located near the low pressure orifice. First, the orifices pertaining to the first pinion wheel are sequentially opened. Then, the channel connecting the high pressure orifice of the first pinion and the low pressure orifice is opened. Then, the auxiliary orifices pertaining to the second pinion are sequentially opened.

Abstract: In a fluid pumping system in which a fluid is pumped from a fluid supply to a load, two continuously driven fixed displacement pumps are operated in parallel to provide the pumping action. The two pumps are arranged with a common inlet, and with a common outlet, the flow delivered to the load from one of the two pumps passing through a check valve upstream of the common outlet. The fluid flow is regulated to provide a constant pressure by sequentially bypassing fluid around each pump through separate pump bypass ducts. This sequential fluid bypassing or pump unloading is effected by a single control responsive to the flow requirements of the load necessary to maintain that constant pressure. The pump whose delivered flow outlet contains the check valve is the pump whose flow is bypassed initially when less than full pumping capacity is desired. During maximum flow demand operation, both pumps are delivering against full delivery pressure.

Abstract: A fluid pumping system comprises a fluid pump having multiple fluid outlet flows coupled to relatively low and high pressure loads. A control valve system controls the pressure levels of the low and high pressure flows, and relieves excess fluid from the high pressure flow to the low pressure flow to augment the low pressure flow.

Abstract: A fluid transmission circuit in which three or more pumps, adapted to be driven in unison by a prime mover operating at constant power output, draw fluid from a reservoir and deliver it to a reversible fluid motor via a control valve incorporating forward, neutral and reverse positions, the motor being driven, when the circuit is in use, against a fluctuating resistive force. The fluid outputs of two or more of said pumps are controlled by the output of a diverting valve whose input is connected by a separate pressure-sensing line to the fluid flow through the motor and which is initially biassed into a position in which each of said fluid outputs from said pumps is delivered to the motor.

Abstract: A vane-type double lobe hydraulic pump having a casing with a rotor having a plurality of slots with each slot mounting a vane for tracking of a surrounding cam ring and porting for pumping from both undervane and intervane pumping chambers. The cam ring has two generally elliptical sections of different contour whereby the volumes of fluid pumped by the vanes in coacting with one of said sections differ from the pumped volumes of the vanes when coacting with the other section. In one embodiment, there are four independent volume outputs while, in other embodiments, valve elements control the output of the pump whereby it may be the total of the pumped fluid or lesser amounts including only the volume pumped by the vanes in coacting with one of said cam ring sections or only part thereof.

Abstract: A method and plural embodiments of apparatus for delivering a pressure-compensated supply of fluid to a hydraulic steering circuit, wherein first and second pumps are respectively operated by a vehicle engine and by a ground wheel when the vehicle is in motion, output fluid from the two pumps being simultaneously directed to the steering circuit by a control valve with inlet relief valve means modulating output pressure of the sources in response to operation of the control valve. One embodiment contemplates dual inlet relief valves for separately modulating output from the two pumps while another embodiment contemplates one of the pumps having a variable output.

Abstract: This hydraulic engine utilizes two sets of hydraulic cylinders connected to a shaft so as to be alternately pressurized as the shaft is reciprocally driven by a pair of conventional internal combustion chambers. The outlets of all hydraulic cylinders are connected to a common output line via valves. During each power stroke certain of the hydraulic cylinders being pressurized are selectively disconnected (depressurized) from the output line. This effectively decreases the load on the driving chamber, and insures a relatively constant, high pressure hydraulic fluid output level despite changes in supplied force during each power stroke. The selective cylinder disconnection may be implemented programmatically in response to changes in engine parameters such as combustion pressure. The engine also includes a pump for supplying input hydraulic fluid to each set of cylinders while that set is not being compressed. The input fluid force is additive to the power supplied by the operative combustion chamber.

Abstract: This hydraulic engine utilizes two sets of hydraulic cylinders connected to a shaft so as to be alternately pressurized as the shaft is reciprocally driven by a pair of conventional internal combustion chambers. The outlets of all hydraulic cylinders are connected to a common output line via valves. During each power stroke certain of the hydraulic cylinders being pressurized are selectively disconnected (depressurized) from the output line. This effectively decreases the load on the driving chamber, and insures a relatively constant, high pressure hydraulic fluid output level despite changes in supplied force during each power stroke. The selective cylinder disconnection may be implemented programmatically in response to changes in engine parameters such as combustion chamber pressure. The engine also includes a pump for supplying input hydraulic fluid to each set of cylinders while that set is not being pressurized. The input fluid force is additive to the power supplied by the operative combustion chamber.

Abstract: A pumping system for a plurality of recirculating toilets sharing a common tank is described. A variable volume pump has a by-pass valve which is controlled by a pressure sensor in the flush line, to prevent excessive fluid pressure at the toilets. For applications in which the total number of toilets in the system requires a flow exceeding the output of a single pump, additional, substantially identical pumps are provided. A time delay circuit is connected to a pressure switch for energizing a second pump, if the fluid pressure at the toilets does not exceed a predetermined pressure within a set time interval.