Archive for December, 2009

Hydraulic Radial Piston Pump

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Hydraulic Radial Piston Pump

The principle of operation of the radial piston pump is shown in Fig. 4.16. In this case, the cylinders are positioned radially around the axis of rotation. As the shaft rotates, the connecting rods push the pistons back and forth in the cylinders to develop the pumping action. The design is used to pump both …

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Hydraulic Axial Piston Pump

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Hydraulic Axial Piston Pump

The axial piston pump has a series of cylinders (typically 7 or 9) mounted parallel to the axis of rotation. (The arrangement is similar to shell chambers in a revolver.) Pistons are installed in the cylinders. Each piston has a spherical end that mounts in a shoe (Fig. 4.12). The shoe is held against a …

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Hydraulic Vane Pump

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Hydraulic Vane Pump

A vane pump (Fig. 4.7) has a series of vanes that slide back and forth in slots. There are springs in these slots that push the vanes out until the tip contacts the cam ring. (Some designs port pressurized fluid into the slots to force the vanes out.) A chamber is formed between adjacent vanes …

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Hydraulic Variable Displacement Pump Circuits

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Hydraulic Variable Displacement Pump Circuits

Variable displacement pump circuits are called demand flow circuits. A simple example is shown in Fig. 4.6. (The astute reader will quickly observe that this circuit is the first circuit we have studied with no relief valve. Although no relief valve is shown, it is recommended that a relief valve always be used to ensure …

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Hydraulic Fixed Displacement Pump Circuits

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Hydraulic Fixed Displacement Pump Circuits

A simple circuit with fixed displacement pump is shown in Fig. 4.3. Circuits with fixed displacement pumps are called constant-flow circuits. The key concept is stated below. Each revolution of a fixed displacement pump delivers a certain volume of fluid to the circuit. This fluid ultimately returns to the reservoir, either as a return flow, …

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Hydraulic Fixed Displacement Pumps

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Hydraulic Fixed Displacement Pumps

Vane and piston pumps are available as fixed or variable displacement pumps. If the cam ring is fixed in position (vane pump), or the swashplate is fixed in position (piston pump), the displacement is fixed. Gear pumps, however, are available only with a fixed displacement. These pumps are less expensive, so they are widely used. …

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Basic Concept of Hydraulic Cylinder

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Basic Concept of Hydraulic Cylinder

Suppose a flow of fluid is delivered to a hydraulic cylinder, causing it to extend. The cylinder has a cross-sectional area A and delivers a force F while moving a distance x (Fig. 1.2). The distance moved is related to the fluid volume delivered to the cylinder. x = V/A                    (1.5) where x = distance …

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Hydraulic Positive Displacement Pump, Gear Pump

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Hydraulic Positive Displacement Pump, Gear Pump

The simplest and most robust positive displacement pump, having just two moving parts, is the gear pump. Its parts are non-reciprocating, move at constant speed and experience a uniform force. Internal construction, shown in Figure 2.7, consists of just two close meshing gear wheels which rotate as shown. The direction of rotation of the gears …

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Hydraulics Pump, Power Equation

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Hydraulics Pump, Power Equation

The motor power required to drive a pump is determined by the pump capacity and working pressure. From expression 1.6: In Figure 2.3, a pump forces fluid along a pipe of area A against a pressure P, moving fluid a distance d in time T. The force is PA, which, when substituted into expression 2.1, …

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