Hydraulic Motors

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Hydraulic motors can be used to convert the controlled fluid power from a valve or pump into rota.ting mechanical power for driving a load. The Buid Bow is changed to rotational velocity or speed, and the pressure is converted into torque to move the load. Physically, hydraulic motors are similar in construction to hydraulic pumps. …

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Variable Displacement Pump Flow and Pressure Characteristics

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Variable Displacement Pump Flow and Pressure Characteristics

Generally, the flow and pressure characteristics of variable-displacement pumps are given as constants assuming linear characteristics. As stated before, for high-pressure operation with low-viscosity fluids, the pump characteristics may become more nonlinear. In this case, the nonlinearities should be considered in the system servo analysis work. Complete pump characteristics of flow and pressure can also …

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Variable Displacement Pump Leakage Characteristics

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If the pump is driven at constant speed, the flow from the pump is directly proportional to the pump stroke. The output pressure or discharge pressure from the pump is determined by the load or the restriction to the pump discharge flow. As the pressure is increased, the discharge flow will decrease because of leakage …

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VARIABLE-DISPLACEMENT PUMPS

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VARIABLE-DISPLACEMENT PUMPS

In servo control systems, the variable-displacement or servo pump performs the same basic function as the control valve. However, the servo pump generates the controlled fluid power as demanded in response to an input control signal. In most applications, the pump is driven at nearly constant speed by an electric motor or some other mechanical …

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Jet Control Valves

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Jet Control Valves

The principle of converting pressure into kinetic energy and then reconverting this energy into a controlled pressure can be utilized as a control means. The various types of jet control valves use this mode of operation. Proportional control is obtained beither deflecting or directing the high-velocity stream of fluid in relationship t.o a fixed receiving …

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Four-way Flapper-nozzle Control Valve

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Four-way Flapper-nozzle Control Valve

The four-way flapper-nozzle valve has two identical hydraulic circuits, one supplies flow and pressure to one side of an actuator, the other circuit supplies the hydraulic fluid to the other side of the actuator. In other words l the valve provides proportional push-pull control to the actuator. The common point of the two circuits is …

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Three-way Flapper-nozzle Control Valve

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Three-way Flapper-nozzle Control Valve

The flapper-nozzle valve has certain mechanical design advantages mainly the simpler construction and the feature of no close-clearance sliding parts as compared to the spool-type valves. However, flapper nozzle valves must be very .accurately designed to provide characteristics which exactly suit the requirements of a particular application. Figure 1.24 shows a three-way flapper-nozzle control valve. …

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Two-way Valve Constant-flow Source Characteristic

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Two-way Valve Constant-flow Source Characteristic

The two-way valve is merely a throttling valve having one variable-area orifice. When used in conjunction with a constant-flow source, the two-way valve can be used to position a piston actuator &s shown by Fig. 1.22. As indicated, a return spring or an external force is required to return the piston in the one direction. …

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Four-way Open-center Hydraulic Valve

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Four-way Open-center Hydraulic Valve

When a valve is designed to use a constant-flow source of fluid, the valve does not have its cont.rolling edges covering their corresponding port edges. Instead, each port edge is uncovered in the centered valve position. This type of valve is then said to be underlapped or open-centered as shown by Fig. 1.15. When the …

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