Cylinders in Parallel

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Cylinders in Parallel

Figure 1.10 shows a hydraulic circuit in which two cylinders are arranged in parallel. When the two cylinders are identical, the loads on the cylinders are identical, and then extension and retraction are synchronized. If the loads are not identical, the cylinder with smaller load extends first. Thus, the two cylinders are not synchronized. Practically, […]

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Locked Cylinder Using Pilot Check Valves

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Locked Cylinder Using Pilot Check Valves

A check valve (Fig. 1.9) blocks flow in one direction but allows free flow in the opposite direction. A pilot-operated check valve permits flow in the normally blocked opposite direction when pilot pressure is applied at the pilot pressure port of the valve. Pilot-operated check valves are used to lock the cylinder, so that its […]

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Automatic Cylinder Reciprocating System

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Automatic Cylinder Reciprocating System

The hydraulic circuit shown in Fig. 1.8 produces continuous reciprocation of a double-acting cylinder using two sequence valves. Each sequence valve senses the completion of stroke by the corresponding build-up pressure. Each check valve and the corresponding pilot line prevent the shifting of the four-way valve until the particular stroke of the cylinder is completed. […]

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Hydraulic Cylinder Sequencing Circuits

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Hydraulic Cylinder Sequencing Circuits

Hydraulic cylinders can be operated sequentially using a sequence valve. Figure 1.7 shows that two sequence valves are used to sequence the operation of two double-acting cylinders. When the DCV is actuated to its right-envelope mode, the bending cylinder (B) retracts fully and then the clamp cylinder (A) retracts. This sequence of cylinder operation is […]

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Counterbalance Valve Application

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Counterbalance Valve Application

A counterbalance valve (Fig. 1.6) is applied to create a back pressure or cushioning pressure on the underside of a vertically moving piston to prevent the suspended load from free falling because of gravity while it is still being lowered. Valve Operation (Lowering) The pressure setting on the counterbalance valve is set slightly higher than […]

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Double-Pump Hydraulic System

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Double-Pump Hydraulic System

Figure 1.5 shows an application for an unloading valve. It is a circuit that uses a high-pressure, low-flow pump in conjunction with a low-pressure, high-flow pump. A typical application is a sheet metal punch press in which the hydraulic cylinder must extend rapidly over a great distance with low-pressure but high-flow requirements. This occurs under […]

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Pump-Unloading Circuit

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Pump-Unloading Circuit

Figure 1.4 shows a hydraulic circuit to unload a pump using an unloading valve.When the cylinder reaches the end of its extension stroke, the pressure of oil rises because the check valve keeps the high-pressure oil. Due to high-pressure oil in the pilot line of the unloading valve, it opens and unloads the pump pressure […]

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Regenerative Cylinder Circuit

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Regenerative Cylinder Circuit

Figure 1.3 shows a regenerative circuit that is used to speed up the extending speed of a double-acting cylinder. The pipelines to both ends of the hydraulic cylinder are connected in parallel and one of the ports of the 4/3 valve is blockedby simply screwing a thread plug into the port opening. During retraction stroke, […]

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Control of a Double-Acting Hydraulic Cylinder

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Control of a Double-Acting Hydraulic Cylinder

The circuit diagram to control double-acting cylinder is shown in Fig. 1.2. The control of a double-acting hydraulic cylinder is described as follows: 1. When the 4/3 valve is in its neutral position (tandem design), the cylinder is hydraulically locked and the pump is unloaded back to the tank. 2. When the 4/3 valve is […]

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Control of a Single-Acting Hydraulic Cylinder

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Control of a Single-Acting Hydraulic Cylinder

Figure 1.1 shows that the control of a single-acting,spring return cylinder using a three-way two-position manually actuated, spring offset direction-control valve (DCV). In the spring offset mode, full pump flow goes to the tank through the pressure-relief valve (PRV). The spring in the rod end of the cylinder retracts the piston as the oil from […]

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