Showing papers on "Hydraulic machinery published in 1994"

Hydraulic brake system with slip control

Abstract: A hydraulic brake system with slip control for automotive vehicles comprising a master cylinder (2) pressurizable by a hydraulic power booster (1), in which system valve(s) (31,27,32,28,33,23) are inserted between the master cylinder (2) and the wheel brakes (29,30,24,25) connected to the master cylinder (2) which allow pressure fluid removal from the wheel brakes (29,30,24,25) that can be replenished out of the pressure chamber (19) of the hydraulic power booster (1) by way of a change-over valve (36). A stroke limitation of the brake pedal (8) is effected during slip control. The end surface of the master cylinder piston (5) close to the working chamber (16) being larger than the is effective surface of the booster piston (4), and wherein a stepped piston is employed as master cylinder piston (5) with an annular surface (18) thereof being adapted to be acted upon in the actuating direction by the pressure prevailing in the working chamber (16). A non-return valve (37, 38) is connected to the change-over valve (36) normally assuming its closed position through which the wheel brakes (29,30,24,25) can reacted upon directly by the pressure prevailing in the pressure chamber (10) of the hydraulic power booster (1).

The Variation of Oil Effective Bulk Modulus With Pressure in Hydraulic Systems

Abstract: The paper presents theoretical modeling and an experimental investigation of the variation of oil effective bulk modulus (β e ) with pressure in hydraulic systems. A pressure sensitive model of the and its several simplified forms have been derived. In addition, a method for parameter identification has been formulated. In an actual hydraulic system, values for β e at different load pressures were obtained, model parameters identified and modelling errors evaluated

Fast Pipeline Models for Simulation of Hydraulic Systems

Abstract: In most cases it is justified to regard pipelines as lumped capacitances when hydraulic systems are simulated. In some cases, however, when the system is widely distributed the wave propagation effects in lines may become important and there exists very good models today to simulate these effects. The price to be paid is that of a much larger computational effort. In this paper, a numerically highly efficient model is presented which is just slightly more demanding than a model to represent a pure capacitance, yet it captures all the essential characteristics of a line, the finite wave propagation speed and the distributed frequency dependent friction. The model only calculates state variables at the ends of a line and not in any internal nodes as most models do. Despite this, the model gives good results both in the time and frequency domain which compared to more elaborate models. If for some reason internal state variables are wanted they can be obtained by representing a line with several line elements. The model is integrated in the library of the HOPSAN simulation package and has been used successfully for simulation of oil hydraulic systems as well as the human cardiovascular system.

Hydraulic machines : turbines and pumps

Abstract: This second edition of "Hydraulic Machines" is devoted to the operating principles, design and performance characteristics of hydraulic machines used in electric power plants, municiple facilities, construction works, hydraulic engineering industry and agriculture. The book emphasizes the types and construction of the machinery, especially the mechanical aspects of their operation, including head, discharge, power, efficiency, cavitation factors, reliability and maintenance.

A six degree-of-freedom, hydraulic, one person motion simulator

Abstract: This paper describes the design of a one-person hydraulic motion simulator with six degrees of freedom. An inverted, ceiling-mounted Stewart platform design enables the use of narrower hydraulic cylinders than required with floor-mounted designs, and significantly reduces hydraulic flow requirements and hence the cost. The paper details the platform geometry, shows the effectiveness of Newton's method in solving the direct kinematics, and describes a tested hydraulic system design. Issues of control and safety are also addressed. It is expected that this motion simulator will provide 9.8 m/s/sup 2/, 400/spl deg//s/sup 2/ accelerations and 1 m/s, 30/spl deg//s speeds to a 250 kg payload with 1 m, 45/spl deg/ displacements from a nominal center. Preliminary experiments at low-pressure have been encouraging. >

Adaptiv hydropneumatic pulsation damper

Abstract: The invention relates to an adaptive hydropneumatic pulsation damper which is especially suitable for hydraulic systems prone to pulsations and having a greatly varying operating pressure and makes possible during an effective damping action a hydraulically rigid coupling between the elements, e.g. pressure source and consumer, of a hydraulic system.

Resolved-Mode Teleoperated Control of Heavy-Duty Hydraulic Machines

Abstract: This paper addresses the control problem for a class of heavy-duty hydraulic machines in order to achieve coordinated motion control of the implement. A model and sensor-based control algorithm is proposed which is applied in conjunction with closed-loop components. The algorithm is basically a feedforward load compensating scheme which uses the measured hydraulic line pressures along with the appropriate portion of the hydraulic model to control the joint velocities

Fast start hydraulic system for electrohydraulic valvetrain

Abstract: A hydraulic system for controlling an engine valvetrain wherein each of the reciprocating intake and/or exhaust valves is hydraulically controlled and selectively connected to a source of high pressure fluid and a source of low pressure fluid. The hydraulic system maintains fluid pressure both when the engine is running, by employing a pump and an auxiliary pump, and when engine is off, by employing an accumulator and by selectively employing an auxiliary pump controlled by an engine control system. By maintaining pressure in the hydraulic system, the engine valves begin operating immediately upon start-up of the engine even after it has been left idle for an extended period of time.

Hydraulic pressure control valve

Abstract: A hydraulic pressure control valve, such as a pilot-operated relief valve and such as a direct-acting differential piston relief valve, having a spring chamber pressurized with fluid from a passage though a movable relief piston. The fluid within the spring chamber may be at the same pressure as that at the inlet valve closing pressure to assist a coil spring acting against the inner face of the relief piston. Inlet pressure in the valve working on an area difference between the faces of the relief piston produces the hydraulic force which is opposed by the spring to open the valve. At its other end, the spring transmits force against a movable biasing piston immediately adjacent a closed end of the spring chamber. The biasing piston provides automatic linearly increasing adjustment of the set pressure in response to inlet pressure acting over a greater net area than that of the relief piston. Inlet pressure fluid flowing into the valve moves the biasing piston toward a stop within the spring chamber to compress the spring and, in doing so, serves to buffer otherwise abrupt pressure spikes as the system is activated. Various types of pressure relief and pressure control valves in hydraulic systems are provided.

Electrohydraulic fan control

Abstract: An electrohydraulic fan control system includes an engine, a hydraulic pump, hydraulic lines, a hydraulic cooling fan, and a solenoid controlled hydraulic valve. The engine includes an electronic control circuit which generates a control signal based on various temperature sensors which is used by the hydraulic valve to control the speed of the cooling fan.

Hydraulic gas compressor and method for use

Abstract: A gas compressor with at least three hydraulic cylinders is connected to a source of natural gas by a gas line. The gas line can also be removably attached to a storage tank. A hydraulic system is also connected to the cylinders. The compressor additionally includes pressure controls which allow the pistons in the hydraulic cylinders to complete the compression stroke in a staged manner. The cylinders are thereby sequentially emptied of gas. Gas at a sufficient initial pressure, entering the cylinders at the completion of the compression cycle, drives the return stroke of the pistons. A pressure switch controls the pressure level of the compressed gas, and aborts the compression cycle when a predetermined pressure in the storage tank has been reached. If the initial pressure of the natural gas from the gas source is insufficient, a low compression one stage compressor is connected to the gas line upstream of the gas compressor to pressurize the natural gas to sufficient initial pressure prior to introducing the gas into the gas compressor. A pressure distribution assembly having a pressure relief cylinder can also be attached to one or more of the hydraulic cylinders.

Power electronics transforms aircraft systems

Abstract: This paper describes the secondary power sources available on a large transport aircraft and discusses expectation that power electronics will enable the transforming of present aircraft systems into new highly integrated systems. The benefits expected from integrating all of the engine-based hydraulic and pneumatic power sources into a single electrical system are identified in qualitative terms. The estimated capacity of an all-electric secondary power system for a tri-jet and a new large transport are compared. A power system architecture that eliminates the need for a pneumatic and hydraulic power distribution system is illustrated. Particular emphasis is given to the flight control system and the electrical power system needs to ensure integrity of power and data for critical flight control functions. The data bus and power source redundancy for flight control actuation is discussed using an integrated power and cable concept in conjunction with an intelligent power controller. >

Packing machine for wrapping objects in stretch foil - has hydraulic system connected to wrapping device to compensate tension of stretch foil.

Abstract: The packing machine operates with a wrapping device (3) which rotates around the article being packed. A self-sufficient hydraulic system is connected to the wrapping device and draws its energy from a hydraulic pump drive (18) which is mechanically tapped as the wrapping device rotates. The foil is guided over a pair of stretching rollers (6,7) which rotate at different speeds and are driven by a hydraulic motor (8) which can be controlled according to the tractive force. The hydraulic pump can receive its energy through a driving friction or gearwheel (18) meshing with a fixed rim (19) supporting the wrapping device. USE/ADVANTAGE- The compensating device works with the wrapping device rotating round the package.

Hydraulic system for backhoe

Abstract: Disclosed is a hydraulic system for a machine having a pump, a steering circuit and first and second hydraulic implements, e.g., a hydraulic loader and a backhoe, powered by first and second valve sections, respectively. In the improvement, the system includes a priority valve receiving fluid from the pump and configured for movement between a first position and a second position. In the first position, the priority valve flows fluid to the steering circuit and to the second valve section and in the second position, the priority valve flows fluid to the both valve sections which are connected in series.

Vehicle with hydraulically adjustable tie rod

Abstract: A tie rod assembly for a steering wheel structure for an agricultural vehicle such as a row crop applicator uses hydraulic cylinders to set the track width of the vehicle The track width may be modulated between a minimum and a maximum track setting and modified until a desired track width is achieved while the vehicle is in motion and negotiating a turn without affecting toe-in settings Toe-in settings are maintained by a closed loop series hydraulic system which further has the capability to reinitialize any toe-in setting to a preset condition in the event any hydraulic cylinder experiences cylinder drift

Undersea hydraulic coupling member

Abstract: An undersea hydraulic coupling member is disclosed having angled flow ports to prevent ingress of debris into the hydraulic lines, and having a bleed passage to allow trapped hydraulic fluid to bleed off when the coupling members are disconnected. The poppet valve in combination with the angled flow ports helps keep the hydraulic system clear of debris when the members are disconnected.

Method and apparatus for controlling hydraulic systems of construction equipment

Abstract: A controller regulates a hydraulic pump for hydraulic equipment to allow long-term use of environmentally safe hydraulic fluids. This is accomplished by limiting the hydraulic pump power output to a level established to prevent the operating temperature from exceeding a specified level. A manual mode for switching between power curves permits alternative use of hydraulic fluids having different maximum operating temperatures. An automatic mode detects the type of hydraulic fluid and automatically selects and applies a suitable power mode curve to limit the maximum operating temperature to a value suitable for the detected type of fluid.

Hydraulic system for hydraulically actuating an ambulance lifting table

Abstract: A hydraulic system for hydraulically actuating a vertically adjustable ambulance lifting table used for receiving thereon a stretcher and adapted to be selectively switched to a cushioned mode of operation comprises a cylinder for actuating the lifting table, a hydraulic accumulator for cushioning the lifting table, a pump, a three-way valve, and a discharge valve connected to a reservoir of the hydraulic system on the outlet side thereof. In order to prevent the patient and/or the medical personnel from being exposed to danger by the lifting table when the above-mentioned hydraulic system is used, and even if the hydraulic system is actuated incorrectly, the three-way valve is in fluid connection with the pump and the hydraulic accumulator on the inlet side thereof and with the cylinder on the outlet side thereof, a valves is provided between the cylinder on the one hand and the hydraulic accumulator on the other, the valves is controlled such that it assumes an open position only if the pressure in the hydraulic accumulator exceeds the pressure within the cylinder by not more than a predetermined pressure difference, and the input side of the discharge valve is in fluid connection either with the hydraulic accumulator or with the cylinder depending on the pressure prevailing in the hydraulic accumulator relative to the pressure prevailing in the cylinder.

Hydraulic lift device for battery operated industrial trucks or the like

Abstract: A hydraulic lift device for battery operated industrial trucks comprising a hydraulic ram, a hydraulic machine operating as a pump in a load raising cycle and as a motor in a load lowering cycle, a separately excited DC machine operating as a motor in the load raising cycle and as a generator in the load lowering cycle, and energy recovering circuitry which is fed by the DC machine in the load lowering cycle. A load holding valve is disposed in the fluid path between the hydraulic ram and the hydraulic machine. Speed of the DC machine is set by a speed control. A separate field current control includes a desired value setting circuit for determining a desired value for the field current (IFSoll) from a predetermined relationship between the speed (nIst) and the armature current (IASoll). Power switches are associated with the field winding and the armature, and are actuated by the current control. The power switches are arranged and controlled such than the intensity and the direction of the current through the armature and field winding are defined. The current control comprises a directional setting control for the lowering and raising cycle generating signals to control the load holding valve.

Damping device, particularly for hydraulic brake system

Abstract: A damping device for pressure pulsations having a first hollow chamber for receiving hydraulic pressure fluid and a second hollow chamber. An elastic metal diaphragm that divides the second hollow chamber hermetically from the first hollow chamber. The second hollow chamber is evacuated, so that in the event that the metal diaphragm should possibly leak, no air can get into the hydraulic pressure fluid. The damping device can be used in hydraulic brake systems having a master cylinder and in other hydraulic systems.

Modeling Requirements for the Parallel Simulation of Hydraulic Systems

Abstract: Parallel simulation of systems offers the benefit of increased speed of execution, but requires the system model to be partitioned to enable numerical tasks to be performed concurrently. Hydraulic systems are characterised by a transport delay in the pipelines connecting physical components, which is due to the propagation of waves at the speed of sound through the fluid medium. The transmission delay allows component models to be decoupled for the current time step, enabling a parallel solution; the inputs to each component model are delayed outputs from connected models. This paper describes a simulation environment suitable for the simulation of hydraulic system performance, using the transmission line modelling approach for the pipelines, decoupling the component models in a hydraulic circuit simulation. Computationally efficient models for cavitation and friction are developed and evaluated. In addition, partitioning strategies for parallel operation are outlined, although these have yet to be implemented

Method and apparatus for supplying driving energy to vehicle subassemblies

Abstract: A method of supplying driving energy to subassemblies of a vehicle having an engine, a braking system including a brake pedal, a hydraulic machine, a hydraulic accumulator and a clutch having an engaged state for connecting the engine to the hydraulic machine for driving the hydraulic machine from the engine and a disengaged state for disconnecting the engine from the hydraulic machine. The method includes the following steps: supplying the subassemblies with the required driving energy at least indirectly from the hydraulic accumulator in a disengaged state of the clutch as long as a predetermined sufficient hydraulic pressure prevails in the hydraulic accumulator; driving the hydraulic machine by the engine in an engaged state of the clutch as long as a pressure prevailing in the hydraulic accumulator is less than the predetermined sufficient hydraulic pressure for supplying the subassemblies with the required driving energy at least indirectly from the engine and for simultaneously charging the hydraulic accumulator by the hydraulic machine with hydraulic fluid until the predetermined sufficient hydraulic pressure in the hydraulic accumulator is reached; and for performing the supplying and driving steps, controlling the clutch for selectively placing the clutch into the engaged and disengaged state as a function of the prevailing hydraulic pressure in the hydraulic accumulator and/or the energy requirement of the subassemblies and/or a braking force represented by the position of the brake pedal.

Method for controlling the drive for a hydraulic press having a plurality of operating phases

Abstract: A method for controlling the drive of a hydraulic press and an associated device for carrying out the method are proposed, the piston/cylinder unit belonging to a press ram being driven via several hydraulic devices connected in series. Depending on the operating phase of the press, the hydraulic devices are here used as required either as hydraulic motors or hydraulic pumps, which effect a delivery of pressure medium into the respective cylinder chamber.

A nonlinear fault detection method for a hydraulic system

Abstract: A fault detection method is proposed for generating robust residuals for a bilinear system with unknown inputs. Necessary and sufficient conditions for the existence of a fault detection observer are given. The method is applied to a hydraulic system and simulation results are given.< >

Valve drive device

Abstract: A hydraulic valve drive device for intake/exhaust valves of an internal combustion engine using an oil pump similar to a distributor type injection pump. A plunger rotates and engages in reciprocating motion to pressurize hydraulic fluid taken into a pressure chamber and opens to discharge the same into a hydraulic cylinder of a specific intake/exhaust valve in register with the passage. The intake/exhaust valve maintains its valve lift to continue remaining open when the supply of the hydraulic fluid is stopped, but closes when the plunger rotates so that the passage is communicated with a relief channel and the relief valve opens.

Method and apparatus for extruding and casting aluminium alloy vehicle wheel

Abstract: The present invention refers to a method and apparatus for extruding and casting aluminium alloy vehicle wheel. It uses a general hydraulic machine, a traisectional mould with inclined pull rod and a lift-out mechanism to realize automation of opening-closing of the middle mould and knockout of the casting product, resulting in greatly simplified hydraulic mechanism and reduced equipment cost. The pressure is maintained for a certain period after the mould cavity is filled with molten aluminium during dasting, making the casting solidified at high pressure witgh some plastic deformation. The aluminium wheel thus made has high quality and can be strengthened through heat treatment.

Hydraulic actuator analysis for industrial robot multivariable control

Abstract: This paper aims to obtain a general mathematical function for hydraulic actuators which can be used for the design of multivariable controllers. The paper shows that the current/torque relationships of linear actuators may be represented as first order resulting overall in a third order input/output function for robots with large supply pressure. The model caters for the greatest source of instability in hydraulic systems, namely the compressibility feedback can be used to solve the problem of supply pressure variations resulting from multi-joint movements of robot arms. A large hydraulic robot, the Workmaster, formerly manufactured by Thorn EMI Robotics, is modeled without loss of generality.

Integrated hydraulic system for automotive vehicle

Abstract: An integrated hydraulic system for an automotive vehicle includes a hydraulic pump (16) coupled with and driven by an internal combustion engine (12) and internal and external hydraulic circuits for operating hydraulically powered engine accessories and hydraulically powered chassis components. An electronic controller (18)) sensing a variety of operating parameters controls the output of the hydraulic pump (16) so as to assure that adequate hydraulic fluid is provided to the various components and accessories.

Apparatus and method for attenuation of fluid-borne noise

Abstract: In many hydraulic systems, fluid-borne noise is generated during operation due to the effects of the hydraulic pump. This fluid-borne noise is then transmitted to the hydraulic valves, hydraulic lines, and other structure that valves and lines are mounted on. These structures then emit vibrations that create the largest portion of the system air-borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid-borne noise in a hydraulic system. The apparatus includes a mechanism for effectively sensing the flow ripple produced by the pump and a mechanism for transmitting a signal (C) representative of the flow ripple to a negative ripple generator which provides a corrective flow to the hydraulic system to cancel the flow ripple. By eliminating the flow ripple in the hydraulic system, the associated air-borne noise that is created by various components that are associated with the hydraulic system is attenuated.