Showing papers on "Hydraulic machinery published in 1991"

Hydraulic Control Systems

Abstract: Hydraulic Fluids. Fluid Flow Fundamentals. Hydraulic Pumps and Motors. Hydraulic Control Valves. Hydraulic Power Elements. Electrohydraulic Servovalves. Electrohydraulic Servomechanisms. Hydromechanical Servomechanisms. Nonlinearities in Control Systems. Pressure and Flow Control Valves. Hydraulic Power Supplies. Index.

Hydraulic power supplies

Abstract: Hydraulic power supplies for aircraft which have such hydraulically operated systems as flaps, ailerons, spoilers, rudders, elevators, brakes, and retractable and steerable landing gear. Typically, the aircraft will be of the multiengine type; and there will also be a multiplicity of hydraulic power supplies and engines. This scheme can be utilized to provide operating redundancy for the hydraulically operated devices of the aircraft. Each hydraulic power supply has a solid state controller which has a number of inputs as well as control and information providing functions. Control over the functioning of each hydraulic power supply can also be exercised by flight deck crew-operated switches which are connected to inputs of the solid state controllers.

Rechargeable hydraulic power source for actuating downhole tool

Abstract: A downhole tool includes a hydraulic power supply containing a volume of compressed gas. The hydraulic power supply can be recharged while the tool is located downhole in the well by recompressing the gas in the power supply chamber.

Control apparatus and method for automatically controlling a hydraulic system for heavy construction equipment

Abstract: A control system for automatically controlling the operation of a hydraulic system for heavy construction equipment. The system of this invention provides a controller optimally connected to sensors and to control devices on the hydraulic system so that it automatically and optimally preheats the engine coolant and the hydraulic fluid of the heavy construction equipment before a normal starting operation in order to reach to an optimal operating temperature in a relatively short time. The control system automatically checks the operating temperature of the engine coolant and the hydraulic fluid by temperature sensors, and alarms the operator to any overheat condition by an alarm device. The control system also automatically controls the operational mode in order to remove the overheat condition thus preventing the temperature of the engine coolant and the hydraulic fluid from rising above a predetermined temperature. The system also always optimally starts the engine of the heavy construction, and includes a retry sequence for same.

Feedforward control for automatic transmission torque converter bypass clutch slip

Abstract: A powertrain including an engine controlled by the position of a throttle valve, a hydrodynamic torque converter having a bypass clutch, multiple ratio automatic transmission connected to the drive wheels of the vehicle, a solenoid-operated hydraulic valve that supplies pressurized fluid to engage and release the bypass clutch, is controlled by operation of a feedforward control system. An engine math model produces a signal representing the net torque output by the engine, which signal is applied as input to an inverse mathematical model of the solenoid-operated valve that supplies hydraulic fluid to the bypass clutch. The unique relationship of phase to gain, the frequency response of the solenoid valve, is inverted to remove the effects of delay and transient rise time. Torque converter slip error determined as the difference between torque converter impeller speed and turbine speed, is applied as input to a PID compensated feedback control whose output is summed with the inverse of the solenoid valve frequency response to produce a duty cycle supplied to the solenoid of the bypass pressure hydraulic valve.

Hydraulic system for a wheel loader

Abstract: A hydraulic system for a wheel loader having an implement arranged for elevational and tilting movements relative to a frame of the loader. The hydraulic system includes selectively operable lifting and tilting circuitry for adjusting the position of the implement and a shock absorbing mechanism arranged in combination with the lift circuitry for allowing relative movement between the implement and the frame to provide a cushioning effect which reduces pitching of the loader. To inhibit inadvertent vertical displacement of the implement, the shock absorbing mechanism is responsive to an initial lifting action of the implement. In a preferred form of the invention, the shock absorbing mechanism is responsive to hydraulic conditions indicative of imminent tilting movement of the implement thereby eliminating inadvertent vertical displacement of the implement when the implement reaches a limit of its tilting travel.

Vibration and oscillation of hydraulic machinery

Abstract: Note: International editorial committee (IECBSHM), Duan C.G., chairman, Boldy P.A., secretary Reference Record created on 2004-09-07, modified on 2016-08-08

The impedance characteristics of fluid power components: relief valves and accumulators

Abstract: This paper describes an experimental and theoretical investigation of the impedance characteristics of various relief valves and an accumulator. The test programme involved the measurement of pressure ripples at three locations in a specially designed test circuit. From these measurements, the impedance of a component was evaluated as a function of frequency.The experimental results are compared with mathematical models. For a single-stage relief valve, a simple orifice model has been found to be adequate. For two-stage valves, a much more complex model was considered. This was found to predict the basic trends but was not accurate.Tests on an accumulator yielded results which correlated well with a relatively simple mathematical model. However, it is difficult to quantify the model parameters. It is concluded that for the more complex components used in hydraulic systems it is necessary to measure the impedance characteristics rather than predict them. There is a need to adopt a standard test procedure f...

Seawater hydraulic actuator system for underwater manipulator

Abstract: A seawater hydraulic actuator system for a subsea robot has been developed. The system consists of a high pressure axial piston pump, flow control servovalves and actuators which transform controlled flow into motion, and it is very effective in miniaturizing a subsea robot. In order to confirm overall characteristic of this power systems, a prototype telemanipulator for underwater work has been also developed. A manipulator control system is based on a master-slave method with some telepresence technique to provide easy operation of a manipulator. Through running experiments in underwater manipulation, overall characteristic of the seawater hydraulic system and working performance of the prototype subsea manipulator have been confirmed to be good enough for practical use. >

Valve timing control device

Abstract: PURPOSE:To avoid lowering of hydraulic pressure of a hydraulic power source and increase of oil residual pressure in an oil pressure chamber by closing an oil passage communicated with the hydraulic power source when a control valve is switched to release the oil in the oil pressure chamber to a drain. CONSTITUTION:In a valve timing control device 10, at the time of returning the valve timing to the initial state, an electric current applied to a control valve 100 is switched off to release the oil in an oil pressure chamber 24 to a drain through an outlet port 113 and a drain port 115. Simultaneously the communication between an inlet port 111 and the outlet port 113 is interrupted to close an oil passage connected to an oil pump. Thus, the oil of engine hydraulic pressure generated in the oil pump can be prevented from being released to the drain port 115, so that it is possible to avoid such a problem that the engine hydraulic pressure on oil pump side is lowered. The release amount of oil in the oil pressure chamber 24 to the drain can be increased so that it is also possible to avoid such a problem that the residual pressure of oil remains in the oil pressure chamber 24.

Large bore hydraulic drilling jar

Abstract: A double acting hydraulic drilling jar 1 includes a mandrel 2 arranged in a housing 3 for sliding longitudinal movement. A hammer 69 is positioned on the mandrel 2 and interacts with anvil surfaces 64, 66 in the housing 3 to deliver both upward and downward jarring forces to a drill string. A hydraulic valve arrangement permits the storage of large amounts of static force before releasing the hammer 69 to strike the anvil surfaces with great force. The hydraulic valve arrangement includes a tripping valve 95 positioned to be actuated by a first pair of engaging surfaces in response to downward movement of the mandrel 2 in the housing 3 and a second pair of engaging surfaces in response to upward movement of the mandrel 2 in the housing 3. Thus, independent control over the upward and downward jarring action is achieved.

Lubrication system for V-type overhead camshaft engine

Abstract: A lubrication system for a double overhead camshaft engine has a lubrication oil passage for applying regulated pressurized oil to each of intake and exhaust overhead camshafts for lubrication; oil passages branching off from the lubrication oil passage for applying pressurized oil to hydraulic valve lash adjusters and a variable valve timing mechanism, respectively, for hydraulic operation. The oil passage for the variable valve timing mechanism is formed in one of the intake and exhaust overhead camshafts to which the variable valve timing mechanism is installed and is provided with a control valve for opening the oil passage so as to actuate the hydraulic variable valve timing mechanism with pressurized oil when the engine operates at lower engine speeds.

Pressurized fluid supply system for automatic power transmission for automotive vehicle

Abstract: A novel hydraulic system for an automotive automatic power transmission improves efficiency of working fluid supply for controlling transmission operation and for lubricating transmission components. The hydraulic system employs independently fabricated lubrication circuit for lubricating transmission components and a hydraulic control circuit for controlling operation of transmission components. The hydraulic system employs a first fluid pump connected to the hydraulic control circuit for supplying working fluid thereto, and a second fluid pump connected to the lubrication circuit for supplying working fluid thereto, and operative independently of the first fluid pump.

An Experimental Study on the Position Control of a Hydraulic Cylinder using a Fuzzy Logic Controller.

Abstract: In this paper, a fuzzy-PID controller implemented in the personal computer PC/XT is proposed and applied to control the position of a servo-hydraulic cylinder. The experimental results show that the performance of the control system with variable load is excellent. This indicates that the proposed controller is one of the possible approaches to control a nonlinear and time-varying hydraulic system.

Hydraulic circuit for shaking a bucket on a vehicle

Abstract: A hydraulic system for a vehicle that includes an implement such as a bucket that is operated by a hydraulic actuator and a directional valve which controls flow from a load sensing variable displacement pump. A hydraulic bucket shake circuit is provided which is selectively operable to force the pump to a maximum displacement condition thereby providing standby pressure and flow to the directional valve so that the directional valve can be operated rapidly in order to shake the bucket and dislodge mud, clay and debris from the bucket or to allow penetration into frozen ground.

Hydraulic servo steering system - has double action piston and with throttle valves in return direction

Abstract: The rack and pinion steering is reinforced by a double action hydraulice piston (1) linked to the hydraulic system by two end connections (4,5) fitted with return flow throttle valves. The valves provide a flow restriction in the return direction to dampen any oscillations in the steering action. The flow restriction valves can be simply provided by parallel action valves, with a flow restriction in one branch and a non return valve in the other branch. This allow an unimpeded flow in the operating direction and a simple control flow. ADVANTAGE - Simple control valves, damped steering action.

Safety valve for discharge chutes on cement mixer

Abstract: A safety valve which prevents the discharge chute from rapidly falling due to a sudden loss of hydraulic fluid pressure. The valve is located between the chute lift cylinder port and hydraulic system hose. The valve is actuated when the flow leaving the chute lift cylinder exceeds a predetermined flow. The valve immediately stops the hydraulic fluid from leaving the chute lift cylinder maintaining the position of the discharge chute.

Fork lift truck energy-saving hydraulic control system

Abstract: The utility model relates to an energy conservation hydraulic system regarding the static pressure driving battery forklift The system works through that a DC electric machine drives a variable capacity pump, whose intake side is allocated with a one-way valve and two bi-bit two-way valves so as to control a low pressure energy accumulator and a high pressure accumulator respectively through electricity or liquid, make a recovery of the fork lift truck lifting mechanism potential energy and the running mechanism braking kinetic energy, and to make full use of all the energy so that the DC electric machine fork lift truck won't produce heavy current when it starts up and the happening of storage battery heavy current discharging is decreased with the result that the application capacity and life length of the storage battery is prolonged The system can also be applied to other handling trucks of various kinds

Unified approach for the optimization on nonlinear hydraulic systems

Abstract: A theory for the optimization of nonlinear hydraulic systems is presented. The problem has been solved in spite of the nonlinear system model and the mixed-integer nature of the decision variables. The optimization problem is formulated in terms of the time-distribution-function concept. This leads to a numerically efficient two-level algorithm. No specific control model is needed: the algorithm employs a system simulator. The general approach is also applicable to other nonlinear systems. The paper concludes with a practical application, together with numerical results.

Variable speed hydraulic pump system for liquid trailer

Abstract: The present invention relates to a hydraulic pump system comprising: (a) a variable displacement pump; (b) an engine used to drive the variable displacement pump; (c) a power takeoff unit for engaging or disengaging the engine from the variable displacement pump; (d) a hydraulic motor driven by the variable displacement pump via hydraulic fluid pressure; (e) a liquid pump driven by the hydraulic motor; (f) a hydraulic fluid cooler in communication with the hydraulic motor; (g) a hydraulic fluid reservoir in communication with the cooling means and the inlet the variable displacement pump; (h) hydraulic piping and/or hose for connecting the hydraulic motor, cooler, reservoir and variable displacement pump; and (i) filters located within the hydraulic piping and/or hose.

Portable soil sampling device and method

Abstract: A portable soil sampling device is provided that is easily positoned in confined and hard-to-reach locations. The device includes a mast assembly comprising a pair of upright masts mounted on a frame having a pair of wheels. By tilting the frame and mast assembly back using a provided handle, the device may be transported to a sampling location. Where low overhead locations are encountered, such as within buildings, the mast assembly may be lowered with the use of a hinged connection intermediate its ends. The device is powered by hydraulic power from a remote source through flexible hydraulic hose, so as to help reduce the size and weight of the device. A hydraulic motor on the device is used to position a hydraulic hammer over a tube for driving. A hydraulic cylinder on the device is used to pull the sample tube from the ground after it has been driven to the desired depth. The invention also involves the method steps in accomplishing the above operation.

Device for improvement of running condition in hydraulic system

Abstract: 2073000 9107596 PCTABS00005 The present patent application refers to a device for the improvement of the running conditions in a hydraulic installation or in so-called hydraulic system. The device contains a central circulating circuit separated from the influence of the atmosphere. To the circulating circuit are connected an outlet and an inlet for the connection of the hydraulic fluid to the other parts of the hydraulic system. The mentioned circulating circuit is divided into at least two chambers separated by pressure generating respectively pressure reducing units (3, 4, 5). The first chamber (1) is to a certain extent an expansion room for the hydraulic fluid in the system which is separated from the atmosphere and it forms a low-pressure part in the circuit. The second chamber (2) forms a high-pressure part which directly or indirectly is connected to the said outlet. The circulating circuit holds medium (4, 13) for the cooling and filtering of the hydraulic fluid.

Hydraulic power unit for hydraulic elevator

Abstract: PURPOSE:To allow lifting operations to be performed with no interference with an oil tank by fixing guide members which restrain a hydraulic drive equipment from being moved back and forth and side to side, on each inner wall of the oil tank, and thereby attaching engaging pieces which can be vertically moved along the guide members, onto the aforesaid drive equipment. CONSTITUTION:Guide members 17 are fixed on each inner wall of an oil tank 1. Engaging pieces 15 are mounted on each frame 3a of an electric motor 3, are engaged with the guide members 17 in such a way as to be freely moved vertically, but are concurrently restrained from being moved back and forth and side to side. When assembled, the engaging pieces 18 of a hydraulic drive equipment composed of the electric motor 3 and a pump 7 are engaged with each guide member 17 from top, and are successively lowered down along the guide members 17. This thereby allows the hydraulic drive equipment to be lowered down within the oil tank 1 so as to be housed in while movement being restrained back and forth and side to side so that a suspension fixture 6 is fixed onto a mount fitting 5 thereafter. This thereby eliminates a need for assisting a lifting operation with hands not to interfere with the oil tank 1, assembly works can thereby be made safely.

Power steering assembly

Abstract: A hydraulic power rack and pinion steering assembly includes a modular control valve assembly. The modular control valve assembly can be assembled and tested at a location remote from a separate rack housing. The modular control valve assembly comprises a tubular steel member supporting a hydraulic fluid control valve that controls a hydraulic cylinder for moving the rack.

Convertible with automatic window operation

Abstract: A convertible vehicle has a body with a passenger compartment, a pair of passenger access doors each having a window and a pair of rear quarter windows, all mounted on the body for movement between raised and lowered positions. A folding top is mounted on the body for movement between a raised position covering the passenger compartment and a lowered position opening the passenger compartment. A hydraulic system includes a hydraulic pump, two hydraulic top actuators for raising and lowering the top, and a pair of hydraulic window actuators operatively connected to the quarter windows for raising and lowering the windows with less pressure than required to raise and lower the top. A hydraulic circuit connects all of the cylinders in parallel which enables sequential operation of the windows and then the top. A three-position control switch enables the windows to be lowered and raised when the top is in raised or lowered position by moving the control to respective "down" and "up" positions. The windows are hydraulically locked in any selected position by actuation of a solenoid valve when the control is moved to "off" position. In another embodiment the hydraulic system includes actuators for the door windows. This embodiment features many possible sequences of operation of the windows.

Hydraulic drive system and valve apparatus

Abstract: A valve apparatus (30) of a hydraulic valve system has a plurality of directional control valves (78, 79) that control the flow of the hydraulic fluid to a plurality of actuators (34, 35). Check valves (59, 60) are provided for taking out, as a first control pressure, a maximum load pressure among load pressures of the plurality of actuators, first pressure generating devices (89, 91) for generating second control pressures different from the first control pressure, and second pressure generating devices (90, 92) for generating third control pressures different from said first and second control pressures. Flow control valves (36, 39) control flow rates of the hydraulic fluid passing between supply passages (42, 43) and first passages (44, 45) dependent upon openings of variable restrictors (52, 53; 54, 55) disposed therebetween, and also for selectively communicating between second passages (50, 51) and load passages (46, 47; 48, 49), and pressure control valves (70, 71) disposed between the first passages and the second passages for controlling pressures inside the first passages.

Load sensing hydraulic control system

Abstract: The use of a pair of small variable displacement hydraulic pumps in a hydraulic system offers some advantages. The output of the two pumps of the known systems is normally not combined, but is selectively combined under a majority of the operating conditions. The subject load sensing hydraulic control system has first and second hydraulic circuits with each circuit having a plurality of pilot operated control valves operatively connected to a variable displacement pump. The output flow of both pumps is normally made available to both hydraulic circuits through a combiner valve so that the output capability of both pumps can be used to satisfy the demand for fluid by a single control valve or by one or more of the control valves from each circuit. A valve arrangement connects the highest load pressure of the control system to both pumps when the output flow thereof is being combined. Under certain operating conditions of some of the control valves, the combiner valve and the valve arrangement are selectively moved to a position to isolate the first and second hydraulic circuits from each other and to direct the highest load pressure of each circuit only to the displacement controller of the pump connected to that circuit.

Load sensing control system for hydraulic machine

Abstract: A load sensing control system for a hydraulic machine sets a variable target differential pressure between a delivery pump pressure and a load pressure of an actuator. A control factor is determined that becomes larger as the deviation between the target differential pressure and the actual differential pressure is increased, and that becomes smaller as the differential pressure deviation is decreased. The control factor also becomes larger as the target differential pressure becomes smaller. The target displacement volume for the hydraulic pump is based on the differential pressure deviation, which is calculated from the target differential pressure and the control factor.