Abstract: An exhaust manifold (25) of a fluid power and control system, the pressure of which is varied when the fluid motor (10) is subjected to a bidirectional positive or negative type load (W). This exhaust manifold (25) is also supplied from a source of exhaust manifold pressurizing oil (29) other than the system pump (18). This source of exhaust manifold pressurizing oil (29) may include a flow amplifying device (57) which is activated when the fluid motor (10), in the form of a cylinder, moves a load in the direction of its piston rod end (11) and when the piston rod end (11) of cylinder (10) is subjected to a negative load pressure and when the pressure in the exhaust manifold (25) drops below a certain minimum preselected level.

Abstract: In load sensing systems, pressure compensating valves are normally used to maintain a predetermined pressure differential across the orifices in the directional control valve at a predetermined level. The predetermined pressure level acting across the directional control valve can be adversely affected by flow forces acting on a valving element of the pressure compensating valve. In the subject invention, flow force compensation is provided by having a forced balancing device connected to a pressure compensated valve device so that a force that is directly proportional to the degree of flow forces acting on the pressure compensating valve device is transferred to a valving element thereof in opposition to the flow forces that are acting on the valving element. The subject arrangement is also applicable to providing flow force compensation for negative load pressure compensating valve devices.

Abstract: The flow changing response of fluid systems having variable displacements pumps are greatly effected by the inertia of the displacement changing mechanisms, such as, the swashplate and at least half of the fluid pumping piston assemblies. In the present invention, a fluid system is provided which has a first flow changing mechanism operable to maintain a relatively constant pressure differential across a variable orifice device in a valve mechanism to change the flow of the fluid being delivered from the fluid pump to the fluid system. Simultaneously therewith, a second flow changing mechanism having a fast acting bypass mechanism acts in parallel with the first flow changing mechanism to more quickly bypass fluid being delivered from the fluid pump to the fluid system thus eliminating pressure spikes in the fluid system. The second flow changing mechanism is operable to establish a second larger differential pressure across the variable orifice device.

Abstract: A hydraulic piston type motor having a rotating piston barrel abutting a fixed porting plate or head with a starting charge device including a differential area piston operating to supply a limited hydrostatic pressure between the porting plate and rotating barrel to reduce starting friction and improve starting torque.

Abstract: In the present fluid system, a variable pressure inlet system is provided and operational to control the operating pressure level of a charge pump in response to various operating parameters of the fluid system. The charge pump provides pressurized fluid to an inlet of a hydraulic pump to insure filling of the pumping chambers therein. By having the operating pressure level of a variable pressure relief valve that is connected to the charge pump controlled between a minimum pressure level and a maximum pressure level responsive to various operating perimeters of the system, the degree of horsepower needed to drive the charge pump is controlled.

Abstract: Compensated controls for a negative type load which, without degrading the quality of the control, permit direct use of the fluid power energy of the negative load for control of a resistive or positive type load, thereby greatly increasing the efficiency of the control system.

Abstract: Fluid systems having fluid motors which control aiding type loads many times have problems with cavitation in one end of the fluid type motor during lowering thereof. It is desirable to eliminate all cavitation in the fluid motor during operation. In order to eliminate cavitation during lowering of an aiding type load and to provide a positive pressure therein, the subject arrangement provides an exhaust pressurizing control for use in a fluid system. The exhaust pressurizing control includes an exhaust manifold means having selector means to provide a positive pressure in the exhaust manifold means during lowering of an aiding type load. The selector means includes pressure limiting and unloading means operative to provide a positive pressure in the exhaust manifold means during lowering of the aiding type load and to unload the pressurized fluid in the exhaust manifold means during raising of a resisting type load.

Abstract: A load responsive control system using on a selective basis the energy derived from a negative type load for operation of system controllers, which may be of various types, including electro-hydraulic multi-stage controls, for use in positioning of the main control spools and in control of other system components.

Abstract: A load responsive system having at least one direction and flow control valve, the flow control of which is accomplished in response to a control signal above a certain predetermined pressure level and a fixed displacement pump, provided with a bypass type output flow control, operable to maintain a constant pressure differential between pump discharge pressure and load pressure of the load controlled by the direction and flow control valve. The output flow control is provided with an unloading control, which maintains the discharge pressure of the pump at any preselected minimum pressure level once the control signal transmitted to the direction and flow control valve drops below a certain minimum predetermined pressure level signifying that the system is in standby condition.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals, identifying those pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator controls of the load responsive valve. The load pressure signal identifying circuit responds to the control pressure signals, which determine the desired direction of displacement of the spool of the direction control valve, while those control pressure signals are selectively isolated from the identifying circuit, in response to the direction of spool displacement from its neutral position.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals identifying those load pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator control of the load responsive valve, while also transmitting the positive load pressure signal to the pump control. The load pressure signals from individual cylinder ports, together with the signals related to the direction of displacement of the controlled load, are transmitted electrically to an electrical logic circuit, which identifies the load pressures as positive or negative and generates the required electrical signals to the electrohydraulic controls, which connect the positive or negative load pressure to throttling compensator controls of the load responsive direction and flow control valve.

Abstract: A load responsive system is provided with two synchronizing systems for positive and negative load compensation. One of the synchronizing systems varies the flow through a negative load compensator, during control of a negative load, in response to the inlet pressure of a fluid motor which is controlled by a positive load compensator. The other synchronizing system isolates the system pump from the fluid motor during control of the negative load while make-up flow to the fluid motor is supplied from the fluid exhaust system. In a more specific arrangement, the system pump is isolated from the fluid motor through the use of the positive load compensator and totally independent of any negative load compensating action. The synchronizing systems function in response to an external signal(s), which can be a function of any selected specific parameter of the system.

Abstract: A fluid fuse is quickly operable to shut off fluid flow upon rupture or other failure of fluid conducting line or other structural member downstream of the fuse. The fuse is actuated during decompression fluid flow resulting from decompression of fluid and elastic contraction of structural components downstream of the fluid fuse. During decompression fluid flow, a valve member is moved from an open position to a closed position by two forces generated by a pressure differential caused by sudden decompression of the fluid and developed across two variable, sharp edge, viscosity insensitive orifices, positioned in series and separated by a flow cut-off and sealing surface. The closing force, generated by the pressure differential of the upstream orifice is dominant and increases with the displacement of the closing member in a predetermined manner, permitting the use of a high preload and high rate opposing spring, at relatively low pressure differentials.

Abstract: A load responsive system including individual positive and negative load compensators, for control of positive or negative load and an external logic system for determination of whether the controlled load pressure is positive or negative. The deactivating valve deactivates the positive load compensator, when the negative load pressure exceeds a certain minimum predetermined level, preventing flow of fluid from the system pump to the system actuator controlling a negative load at a pressure higher than a certain predetermined level, and therefore preventing development of excessive pressure in the actuator, while also deactivating the negative load compensator below a certain minimum predetermined negative load pressure level and while the positive load is being controlled by the positive load compensator.

Abstract: A compensated control valve assembly for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load the controlled pressure level of a pressure reducing valve mechanism handling the fluid flow at negative load pressure is varied upstream of an outflow metering orifice arrangement, positioned at the outlet of the fluid motor, in response to pressure at the inlet of the fluid motor, while maintaining this controlled pressure constant at each specific level. The pressure differential across an inflow metering orifice arrangement, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by a positive load pressure compensating control device.

Abstract: A centrifugal filter separator system operable to separate from oil under pressure, contaminants and water. The centrifuged water port of the centrifugal filter separator of the system is coupled to a differential pressure responsive, sensor control, which automatically senses the presence of a layer of centrifuged water against the internal surface of the rotating drum of the centrifugal separator. The sensor control is coupled to a flow control circuit which in conjunction with the differential pressure sensor control causes automatic removal of an existing layer of centrifuged water from the rotating drum via the water exit port of the separator. When there is no adequate depth layer of centrifuged water on the inner surface of the rotating drum, the sensor control deactivates the water removal circuit, while the flow control circuit maintains a minimum generally constant flow of liquid from the water port of the separator for priming purposes.

Abstract: A compensated direction flow control valve assembly for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load, the negative load compensating control varies the level of the pressure differential across a metering orifice, positioned at the outlet of the fluid motor, in response to pressure at the inlet of the fluid motor, while maintaining this pressure differential constant at each specific level. The pressure differential across a metering orifice, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by the positive load compensator control assembly.

Abstract: A two stage relief valve, in which the pilot flow is limited by an active flow control element to a specific maximum predetermined level, to extend its maximum operating pressure range and to improve its operating characteristics. The downstream orifice may be fully open and of a fixed area type, or may be controlled by a spring or solenoid biased member. With the downstream orifice solenoid or stepper motor operated, the relief pressure level becomes responsive to an electrical input signal.

Abstract: A compensated direction flow control valve arrangement provided with a direction control spool for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load the upstream of the outflow metering orifice, positioned at the outlet of the fluid motor, is maintained at a controlled constant pressure level by a pressure reducing valve handling the fluid flow at negative load pressure. The outflow metering orifice is made independent of the direction control spool and its effective flow area is made responsive and varies with the pressure at the inlet of the fluid motor. The pressure differential across a metering orifice, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by the positive load compensator.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals, identifying those load pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator controls of the load responsive valve, while also transmitting the positive load pressure signal to the pump control. The identification and distribution of the load pressure signals to the controls of the load responsive circuit can take place with the direction control spool in its neutral position. Therefore such a load pressure sensing and transmitting circuit is capable of anticipating the command signal indicated control function.