液压阀外文翻译

1、毕业设计（论文）外文翻译（）外文题目： Valve 译文题目： 阀 学生姓名： 学 号： 专业班级： 机械设计制造及其自动化0806班 指导教师： 所在学院： 机械工程学院 Valves Pressure-Control Valves Pressure-control valves are used in hydraulic circuits to maintain desired pressure levels in various parts of the circuits. A pressure-control valve maintains the desired pressure levels by diverting higher-pressure fluid to a lower-pressure area. Thereby limiting the pressure in the higher-pressure area by restricting flow into another area. Valves that divert fluid can be safe

2、ty, relief, counterbalance, sequence, and unloading types. Valves that restrict flow into another area can be of the reducing type. A pressure-control valve may also be defined as either a normally closed or normally open two-way valve. Relief, sequence, unloading and counterbalance valves are normally closed, two-way valves that are partially or fully open valve that restricts and finally blocks fluid flow a secondary. With either type of operation, the valve can be said to create automatically

3、 an orifice to provide the desired pressure control. An orifice is nit always created unloading valve. It is piloted from an external source. One valve of this type is the unloading valve. Relief, reducing, counterbalance, and sequence valves can be fully automatic in operation. With the operating signal taken from within the envelop. In this chapter, we shall study the different types of pressure-control valves and learn how they are used in various hydraulic circuits. Types of Pressure-Control

4、 Valves Eight popular devices for pressure-control are: Safety valve .Usually a poppet-type two-way valve intended to release fluid to a secondary area .when the fluid pressure approaches the set opening pressure of the valve. This type of valve protects piping and equipment from excessive pressure. Relief value which limits the maximum pressure that can be applied in that portion of the circuit to which it is connected. Counterbalance value which maintains resistance against flow to one directi

5、on but permits free flow in the other direction. Sequence value which directs flow to more than one portion of a fluid circuit in sequence. Unloading valve Value which allows pressure to build up to an adjustable setting, then bypasses the flow as long as a remote source maintains the preset pressure on the pilot port. Pressure-reducing valve which maintains a reduced pressure at its outlet regardless of the higher inlet pressure. Hydraulic fuse . Device equipped with a frangible disk which esta

6、blishes the maximum pressure in a hydraulic circuit by rupturing at a preset pressure valve. Pressure switch operated by fluid pressure and responsive to raise or fall in fluid pressure.Compound Relief Valves In the study of ISO hydraulic symbol, it was stated that simplified symbol are widely used. Because f this, pressure-relief valves used in common hydraulic circuits are rarely shown complete with all auxiliary devices and connections. Instead, the simplified symbol shows only the basic reli

7、ef valve, pressure input tank connection, valve spring, and the offset arrow indicating that the valve is normally closed. A slash arrow as shows on the bias spring of the pilot-relief valve if the valve is adjustable, particularly if this information is significant to circuit operation. Figure shows the complete symbol for a compound relief valve. All adjacent controls are shown, along with the main relief element. The envelope surrounding the entire element may have five connections. These are

8、 pressure input , tank connection , remote-control-station connections, test station , and external drain for the pilot relief that is provided only on special order. The input pressure and tank connection provide the major flow through the valve. Only enough fluid needs flow to the test-station and remote-control connection for the respective function. The test stations generally used for a gauge connection to check fluid pressure. This does not require a flow of fluid. The remote-control conne

9、ction passes the quantity of fluid coming through the fixed internal orifice at the rate established by the spring in the main relief element. An external drain from the pilot-relief valve, if fitted, will not pass more fluid than passes through the fixed internal orifice. Figure shows a cutaway view of compound relief valve. Note that the main spool is held by the spring in a position that blocks the passage from the pressure input port to the tank port, just as the symbol in Figure shows. Input pressure is directed to the bottom of the spool below the spring cavity without restriction. The supply line to the spring cavity is restricted by

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