液压专业英语教程1VIP免费

Unit 1 Introduction to Basic Devices and systems Many different machines and processes use a fluid for developing a force to move or hold an object or for controlling an action. In automobiles, for example, hydraulic brakes are used to stop the car. In road construction and repair, another example, compressed air is used to operate chipping hammers. Machines and processed are becoming more and more automated in order to meet competition and more automated in order to meet competition and to reduce human error. HYDRAULIC AND PNEUMATIC SYSTEMS Generally speaking, a number of fluids can be used in devices and systems. The term hydraulic refers to a liquid. For example, the term hydraulic turbine can be used to designate a turbine involving water flow. In a hydraulic system, oil, water, or other liquid can be used. Besides a liquid, either a gas or a compressible fluid can be used. In actual practice, two fluids are most commonly is used in this book, oil is called a ―hydraulic ― system. A fluid system that uses compressed air is called a ―pneumatic ― system. Both types of fluid systems are treated in this book. Hydraulic Systems Fig.1 illustrates a typical hydraulic system . Oil from a tank or reservoir flows through a tube or pipe into a pump. The pump can be driven by an electric motor , air motor , gas turbine , or internal combustion engine , The pump increases the pressure of the oil; the oil pressure at the pump outlet may be 5 to 5000 or more pounds per square inch .High-pressure oil flows in a tube or piping through a control valve ; this valve can be used to change the oil flow. A relief valve is used to protect the system ; the valve can be set at a desi...