Showing papers on "Hydraulic machinery published in 1988"

Dual hydraulic hospital bed with emergency bypass circuit

Abstract: A hydraulically operated hospital bed with dual hydraulic power systems for operation with or without electrical service. The bed has its head and thigh/leg elevation functions performed by hydraulic cylinders. A control circuit meters the introduction and removal of hydraulic fluid from these cylinders so an occupant of the bed is not subjected to any sudden movement. In case of an emergency requiring the bed occupant to be in a supine position (the need to perform CPR), the normal control circuit is bypassed by an emergency circuit that allows much faster than normal lowering of the head and thigh/leg portions of the bed.

Low speed spool emergency power extraction system

Abstract: An emergency on board power source (28) for jet aircraft having high (22) and low speed (14) spools is disclosed for operation above altitudes where auxiliary power units (14) are operational. A power takeoff (56) is provided from the low speed spool of the jet engine to drive an emergency power unit (28) for supplying electrical and/or hydraulic on board power to the aircraft to maintain control during emergency conditions during which the auxiliary power unit is not operational or is not operational to supply sufficient power to maintain hydraulic or elecrical on board power to uninterruptible electrical and hydraulic power loads.

Hydraulic system for a work vehicle

Abstract: The present invention is directed to a hybrid hydraulic system for a work vehicle having both an open center hydraulic circuit and a close center hydraulic circuit. An internal combustion engine drives a fixed displacement pump and a variable displacement pump. The fixed displacement pump provides hydraulic fluid to the open center circuit which directs hydraulic fluid to a steering circuit and the working circuit through a priority valve. The variable displacement pump provides hydraulic fluid to the close center circuit which directs hydraulic fluid to a braking circuit and a pressure reduction circuit. The pressure reduction circuit directs hydraulic fluid to a pilot control system, a clutch cutoff and a differential lock out. Both pumps receive hydraulic fluid from a common sump and a common suction line. The braking circuit comprises two independent braking circuits. Each of the braking circuits include a manually shiftable regulating valve which is hydraulically balanced between its output and the output of the other regulating valve. In this way, the regulating valves are hydraulically interconnected for piloting each other. The pressure reduction system is provided with a first two position solenoid valve which is fluidically positioned between the variable displacement pump and a pressure reducing valve which directs hydraulic fluid to the pilot control system. A working actuator provides an alternate source of hydraulic fluid which is fluidically coupled to the pilot control system when the first solenoid valve is energized. The pressure reduction system houses the first solenoid valve, the pressure reduction valve, and second and third solenoid valves for directing hydraulic fluid to the differential lock out and clutch cutoff, respectively.

Hydraulic system for use with snow-ice removal vehicles

Abstract: A hydraulic system is provided including a hydraulic pump which is continuously coupled with the engine of a utility such as a dump truck utilized for snow-ice removal. When hydraulic implements employed on the truck are not actuated, the pump operates in a cavitation mode. During this cavitation mode of operation, there is no ingress of air through seals or the like to a venting of the gear pump chamber essentially to tank or atmosphere. A poppet valve is actuated in conjunction with periodic use of hydraulic elements on the truck to actuate the pump to an operational or pressurized mode. A key actuated calibrating system is employed to calibrate snow-ice removal components in a secure manner. Calibration is provided in conjunction with EEPROM memory.

Hydraulic system in formation test tools having a hydraulic pad pressure priority system and high speed extension of the setting pistons

Abstract: A formation tester is set forth. The device utilizes a snorkel extending from the formation tester to obtain a pressure test and collect samples from a formation of interest. The apparatus includes multiple sample storage containers, thereby cooperating with an equalizing valve to selectively isolate the snorkel from fluid and fluid pressures in the well. A control valve system in a hydraulic circuit operate backup shoes and a snorkel seal until testing is over to assure sealing against well fluid invasion in unconsolidated formation. A speed up sequence for both the backup piston and cylinder arrangement as well as the pad setting piston and snorkel arrangement is illustrated.

Motorized dumping vehicle

Abstract: A motorized dump-type vehicle is provided having a chassis frame, a gasoline engine mounted on said frame, a dump container pivotally mounted on the front of said frame and a hydraulic system enabling said container to be raised and lowered by a hydraulic cylinder and said vehicle to be driven in either forward or reverse directions and braked by hydraulic drive motors. The hydraulic fluid is cooled by an oil reservoir tank forming a structural part of the frame and positioned such that heat from the hydraulic fluid can dissipate itself in the container and its contents.

Adaptive model following control of electrohydraulic velocity control systems subjected to unknown disturbances

Abstract: This paper considers the velocity control problem of nonlinear hydraulic servo systems subjected to unknown and time-varying external load disturbances. Hydraulically operated processes are usually represented by a hydraulic actuator-load system whose dynamic characteristics are complex and highly nonlinear, owing either to the flow-pressure relationships of the hydraulic system or to a load system motion itself. Furthermore, these characteristics are sometimes unknown owing to the uncertainty in external load disturbances to the processes. Therefore, the conventional approach to the controller design of these systems may not assure satisfactory control performance. To obtain better performance an adaptive model following control scheme was derived based upon Lyapunov's direct method [8]. In order to deal with the uncertainties that are associated with the plant dynamics and the unknown disturbances, this method uses a small ultimate bound of the state error as an adaptation criterion. A series of simulation studies were performed to demonstrate the effectiveness of this controller. The results show that the proposed AMFC is fairly robust to unknown and timevarying external load disturbances, yielding improved performance characteristics when compared with a suboptimal PID controller with constant feedback gain.

Drive control system for hydraulic machine

Abstract: A drive control system, which is suitable for use in a hydraulic machine, is equipped with an electric lever device (3A-3F;77;77A,77B;100A,100B) having a manipulation lever (4A-4F;78;78A,78B) and a potentiometer (5A-5F;79;79A-79B) for generating an electrical manipulation signal corresponding to the degree of each manipulation of the lever, a control valve (2A-2F;74;74A,74B;102A,102B) connected to a hydraulic circuit adapted to actuate a hydraulic actuator (1A-1B;73;73A;73B), and a controller unit (6;80) equipped with a main controller (10) for receiving the manipulation signal and computing a control signal for the control valve on the basis of the manipulation signal and an output device (12A-12F) for generating an electrical actuation signal corres­ponding to the control signal. The system also includes a neutral position sensing means (30A-30F;90;­90A,90B;101A,101B) provided with the electric lever device and adapted to sense a neutral position of the manipulation lever and an inhibition device (31-34;40;­41;43;45-47;92;97A,97B;109) which receives an output signal from the neutral position sensing means and when the manipulation lever is at the neutral position, inhibits the transmission of a signal between the main controller of the control means and the control valve.

Noise Control for Hydraulic Machinery

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Hydraulic spring vehicle barricade and hydraulic circuit therefor

Abstract: A vehicle barricade comprises a frame to which a barrier plate is pivotally mounted for being moved between a passage and a blocking position. First and second hydraulic motors operably interconnect the plate and the frame. An hydraulic power supply is operably connected with the hydraulic motors and includes an uninterrupted line for assuring constant power supply to the first hydraulic motor for thereby biasing the first hydraulic motor into extension and control valve means for selectively supplying power to the second motor for thereby causing selective pivoting of the plate.

Method and apparatus for regulating mold clamping force in an injection molding machine

Abstract: A method and apparatus for controlling the hydraulic pressure in an hydraulic clamping cylinder to correspond with a desired clamping force and to compensate for overshoot of the hydraulic pressure caused by time delays in operating the components in the hydraulic circuit. The control arrangement involves the sensing of the actual hydraulic pressure during the clamp force maintenance portion of a clamping cycle and comparing the actual pressure with a desired pressure to provide a correction signal to be utilized to control the operation of the hydraulic system during the next succeeding cycle so that the actual hydraulic pressure during the clamp maintenance portion of the clamping cycle during the next succeeding cycle results in a clamping force that is closer to the desired clamping force.

Automated mechanical transmission system for use in commercial vehicles

Abstract: An automated mechanical transmission system for use in commercial vehicles comprises an oil spray type oil hydraulic clutch, a mechanical transmission having a shift cylinder, a shift valve, a select cylinder, and a select valve, a hydraulic system control circuit, a clutch oil spray circuit, and a clutch/transmission select valve. The oil hydraulic clutch includes an oil hydraulic clutch servo cylinder for sandwiching a clutch disk between a pressure plate and a clutch cover, the system control circuit includes a high pressure side and a low pressure side hydraulic clutch control lines connected with the clutch servo cylinder, and a hydraulic transmission control line connected with the shift cylinder and select cylinder through the shift valve and select valve. A pressure control valve actuated by a pressure control pilot valve is disposed at the low pressure side hydraulic clutch control line. The pressure control valve adjusts oil pressure of the oil hydraulic circuit to connect or disconnect the clutch, thereby to gear shift the transmission. An oil spray control valve is disposed in the clutch oil spray circuit and controls the flow rate of oil displayed to the clutch disk spray according to each state of the clutch.

Hydraulic control for earth working machines

Abstract: The hydraulic control is constructed for time-sharing of the pump which normally controls the turning mechanism, to operate other hydraulic equipment in conjunction with other pumps.

Stability analysis of a load-sensing hydraulic system

Abstract: The load-sensing hydraulic system is an energy saving hydraulic system which improves the efficiency of transmitting power from the pump to the load However, its stability characteristics deteriorate critically due to the addition of the load-sensing mechanism, compared with those of the conventional system In this paper, a non-linear mathematical model of the load-sensing hydraulic system is formulated, taking into consideration the dynamics of the load-sensing pump Based upon linearization of this model for various operating conditions, the stability analysis has been made using the Routh-Hurwitz stability criterion The results of the theoretical stability analysis were assured through experiments Both results show that stability is critical to the choice of system parameters such as the setting pressure of the pump compensator and the load inertia

Optimal Control Theory Applied to a Pump With Single-Stage Electrohydraulic Servovalve

Abstract: Application de la theorie de la commande optimale a une pompe commandee par une servovalve electrohydraulique a un etage

Stability analysis of a load-sensing hydraulic system

Abstract: The load-sensing hydraulic system is an energy saving hydraulic system which improves the efficiency of transmitting power from the pump to the load. However, its stability characteristics deteriorate critically due to the addition of the load-sensing mechanism, compared with those of the conventional system. In this paper, a non-linear mathematical model of the load-sensing hydraulic system is formulated, taking into consideration the dynamics of the load-sensing pump. Based upon linearization of this model for various operating conditions, the stability analysis has been made using the Routh-Hurwitz stability criterion. The results of the theoretical stability analysis were assured through experiments. Both results show that stability is critical to the choice of system parameters such as the setting pressure of the pump compensator and the load inertia.

Auxiliary coupler pressure relief hydraulic system with pump drive ignition switch relief

Abstract: An auxiliary coupler pressure relief hydraulic system for off-road vehicles including a battery, an engine, an engine ignition system, a reservoir of hydraulic fluid, and a pump for providing hydraulic fluid under pressure. Quick couplers couple hydraulic fluid to an attachment mounted to the vehicle. An electro-hydraulic spool valve is connected to a source of pilot pressure and controls the flow of hydraulic fluid to the quick couplers in response to valve actuating signals. Forward and reverse auxiliary control switches are coupled to the spool valve and provide valve actuating signals resulting in fluid flow to the quick couplers in forward and reverse directions. Also included is an ignition switch having RUN, OFF and RELIEF positions. When switched from its RUN position to its RELIEF position, the ignition switch provides pressure relief valve actuating signals which stroke the spool valve and bleed pressure trapped between the valve and the quick couplers while the engine RPM is decreasing and pilot pressure is still available.

Automatic engine control for an excavator

Abstract: An excavator has a number of different hydraulically powered functions that are controlled by a closed center hydraulic system that features a pair of variable displacement, engine driven hydraulic pumps, the displacement of which is responsive to the demands of the system. The flow to the various hydraulic motors is controlled by pilot operated load sensing control valves that direct fluid pressure to a load sensing line when one of the hydraulic motors in the system is being operated. The load sensing line is connected to the control system of the pumps to place the pumps in stroke when a flow of pressurized fluid is required. The flow of the load sensing pressure to the controls for one of the pumps can be optionally disconnected to place said pump in a standby condition and thereby reduce the flow capacity of the hydraulic system at the option of the operator. The load sensing line is also connected to a pressure actuated switch that closes when pressure in the line falls below a predetermined point, which occurs when none of the hydraulic motors are being actuated. The closed switch provides electric power to a solenoid through a time delay circuit so that the solenoid shifts the throttle control level on the excavator engine to its idle condition at a delay after the hydraulic pressure demand falls below the predetermined level.

Brushing and washing machine

Abstract: A mobile washing machine for washing vertical surfaces includes a brush rotatable about a vertical axis mounted on a framework adapted to be carried on the forks of a fork lift truck. The framework carries a tank for the washing fluid and a pump to pump the fluid to a series of spray nozzles. The brush is driven by a hydraulic motor supplied with hydraulic fluid from the hydraulic system on the fork lift truck.

Machine tool auxiliary function hydraulic system

Abstract: An auxiliary-function hydraulic system is provided for a computerized numerical control (CNC) machine tooling unit. Hydraulic power is provided for locking collet or chuck to an open or closed position and providing an affirmative collet-open and/or collet-closed signal to communicate the collet position to the host computer. The tailstock can be brought gently forward to contact a workpiece and can be returned rapidly to the home position, with a break-away pressure feature being employed to overcome initial static friction. A pressure switch indicates that the tailstock is in position against the workpiece. A spindle brake applies braking to the spindle to stop the same from high speed either on command or in the event of system failure. In the latter case, braking occurs prior to loss of pressure to the collet closer cylinder. Also, a turret clamp locks and unlocks a tool changer turret.

Backhoe scraper apparatus

Abstract: A scraper roller mounted in a backhoe bucket is provided for attachment to a backhoe tractor or similar boom device with hydraulic pressure line couplings The roller is attached to supporting bearings at each end and is covered with a plurality of radially extending replaceable cutting blades around its circumference Attached to one end of the roller is a drive mechanism which extends the length of the bucket and is coupled to a hydraulic motor mounted near the bucket to boom pivot attachment point The hydraulic motor utilizes fluid coupling attachments for connecting into a hydraulic power system on the tractor The drive mechanism is covered by a detachable protective shield Rotation of the roller, assisted when necessary with the downward pressure provided by the backhoe hydraulic piston assembly and the partial weight of the tractor, results in the scraping of a uniform width trench

Fundamentals of hydraulic power transmission

Abstract: 1. Hydraulic calculations (basic formulae). Mechanical properties of the hydraulic fluid. 2. Hydraulic power transmission. 3. Basic types and main characteristics of hydraulic transmissions. Hydraulic control elements. 4. Alternating current hydraulic power transmissions. 5. Some examples of the practical application of hydraulic power transmission. Bibliography. Subject index.

Hydraulic system for an industrial machine

Abstract: An excavator has a number of different hydraulically powered functions that are controlled by a closed center hydraulic system that features a pair of variable displacement, engine driving hydraulic pumps, the displacement of which is responsive to the demands of the system. The flow to the various hydraulic motors is controlled by pilot operated load sensing control valves that direct fluid pressure to a load sensing line when one of the hydraulic motors in the system is being operated. The load sensing line is connected to the control system of the pumps to place the pumps in stroke when a flow of pressurized fluid is required. The flow of the load sensing pressure to the controls for one of the pumps can be optionally disconnected to place said pump in a standby condition and thereby reduce the flow capacity of the hydraulic system at the option of the operator.

Device for controlling and synchronizing the guide vanes of a distributor of hydraulic machines, particularly of turbines

Abstract: This invention relates to a device for controlling and synchronizing the guide vanes of a distributor of hydraulic machines, particulalry of turbines, which comprises ramps borne by spaced apart radial tabs secured with the synchronization ring. Each lever fitted angularly on the journal of each guide vane presents a free end which cooperates with the corresponding ramp by a roller. The profile of the guide vanes is such that the hydrodynamic force tend to close them.

Hydraulic actuator system having non-cavitating flow equalizer

Abstract: A hydraulic system having multiple actuators is provided with positive pressure flow equalization for both advancing and retracting movements of the system by means of first and second flow divider elements for each actuator The flow divider elements are cross-coupled between the actuators, a controllable source of pressurized fluid and a reservoir The flow divider elements are positive-displacement gear or vane pump units that are connected by a common shaft for coordinating fluid flow to the various actuators Two or more of the actuators can be connected for lifting a load such as an automobile, the system being provided with safety latches at each actuator, the flow dividers not only coordinating the actuator movements during normal raising and lowering operation, but also preventing loss of synchronization of the actuators in case of engagement of a subset only of the latches Synchronism is maintained even under negative loading because positive pressure is maintained between the dividers and each of the actuators, preventing cavitation

Dual acting hydraulic actuator for active suspension system

Abstract: Active suspension for vehicles with a dual acting hydraulic actuator providing foreshortened overall length for a given amount of stroke. A conventional suspension unit when designed to give appropriate wheel travel protruded through the hood. The cylinder tube of the actuator of this invention makes use of concentric tubes proportioned to provide the same pressure-force relationship in both directions and to be no larger than the conventional unit. This actuator also incorporates a trapped air volume that is separate from the oil volumes. This air volume can be appropriately sized so that an air-spring is created by the moving piston. The air spring is of approximately the correct load an rate for the vehicle. This removes the requirement for carrying static vehicle load from the hydraulic portion of the device, which reduces power consumption. This eliminates the requirement for a coil spring around the actuator to carry these static loads and provides a "limp-home" capability in the event that the hydraulic system becomes damaged.

PWM-digital control of hydraulic actuator utilizing 2-way solenoid valves

Abstract: The objet of this study was to propose a mathematical model for the PWM-actuator system, to control digitally each types of hydraulic systems. This PWM hydraulic actuator system was made up of two 2-way solenoid valves operated in the PWM (pulse width modulation)-digital mode by a personal computer, a hydraulic actuator and pipes. The static and dynamic characteristics of the system were verified in comparison with experimental results, simulating numerically based on the proposed model. Main results were as follows: Representing the relationship between the valve displacement and the input voltage to the solenoid as a linear function with time lage existing between the input and output signals of the valves, the behavior of the on/off action of the solenoid valves were rationally described; hydraulic transient in the pipes connected with the solenoid valve could not be ignored while the valve were operated with high speed on/off action. It is necessary to attach importance to the natural frequency decreasing caused by existing of the element of pipes in the system on the view point of the resonance oscillation at PWM-digital control system. 8 references, 8 figures, 2 tables.

Hydraulic system and manifold assembly

Abstract: The invention provides an improved manifold assembly and hydraulic system for use in connecting hydraulic lines according to a predetermined circuit design. The invention is especially useful in a pilot control circuit for operating heavy equipment that is multifunctional or has the ability to operate multiple attachments. The manifold assembly comprises a baseplate having a plurality of inlet and outlet ports that are connected to various components in the hydraulic circuit. Connecting elements are then used to connect the designated inlet and outlet ports. In a preferred embodiment, the connecting elements include one or more channel plates attached to the baseplate that have segregated flow channels or passageways and interconnect the designated inlet and outlet ports. In order to convert the system from operation of one type of attachment to another, it is only necessary to exchange one set of designated channel plates for another. This provides ease and simplicity in the conversion from the use of one attachement to another.

Hydraulic braking system for a vehicle

Abstract: A hydraulic braking system for a vehicle includes a hydraulic power pressure source which produces a hydraulic power pressure and a hydraulic braking pressure generator which generates a hydraulic pressure in response to the operation of a brake pedal. A regulator valve is provided for regulating, in dependence upon the operation of the pressure generator, the pressure which is supplied from the pressure source and for supplying a regulated hydraulic pressure to an output hydraulic pressure passage. A control valve controls the communication between the generator and a plurality of brake cylinders as well as between the regulator valve and the brake cylinders and between a reservoir and the brake cylinders. Also, a changeover valve is provided which, in a first position, blocks communication between the hydraulic pressure source and the output pressure passage of the regulator valve, and which, in a second position, introduces pressure supplied from the pressure source to the output pressure passage.