Archive for May, 2010

Types of Hydraulic Cylinders

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Types of Hydraulic Cylinders

The types of cylinders are: Double-acting (Fig. 7.14a) Single-acting, spring return (Fig. 7.14b) Double-rod (Fig. 7.14c) Tandem (Fig. 7.14d) Telescoping (Fig. 7.14e) The double-rod cylinder has the same annular area on both sides, so it develops the same maximum force in both directions for a given relief valve pressure. It also extends and retracts at […]

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Rephasing of Hydraulic Cylinders

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Rephasing of Hydraulic Cylinders

When cylinders are connected in series, it is necessary to provide a feature for rephasing these cylinders when they are fully retracted. Otherwise, leakage will cause the downstream cylinder to not fully extend. An example of the need for rephasing is an agricultural implement (planter, cultivator, disk harrow, grain drill, etc.) that must be folded […]

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Hydraulic Cylinder Cushioning

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Hydraulic Cylinder Cushioning

When cylinders reach the end of their stroke, the pressure rises quickly, creating a shock wave in the hydraulic circuit. Cushioning is done to reduce this stock. The concept, shown in Fig. 7.6, is quite simple. First, we consider the case in which the cylinder is retracting. The spear closes off the large opening where […]

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Manually Operated Servo Pump

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Manually Operated Servo Pump

Before beginning our discussion of closed-loop hydrostatic transmissions, it is necessary to first learn how a servo-controlled pump operates. A variable displacement axial piston pump will be used as an illustration. When configured for servo control, this pump will have a control piston mounted in the pump housing. When the control piston extends, it moves […]

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Vehicle with Two Hydrostatic Transmissions

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Vehicle with Two Hydrostatic Transmissions

The vehicle shown in Fig. 6.14 has a separate in-line hydrostatic transmission for each drive wheel. The engine delivers power via a universal joint driveline to a right-angle drive gearbox. Each side of this gearbox powers an inline hydrostatic transmission. The wheel is connected to the hydraulic motor. A final drive may or may not […]

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