液壓閥畢業設計外文翻譯(編輯修改稿)

　

【文章內容簡介】 liary devices and connections. Instead, the simplified symbol shows only the basic relief 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 pliotrelief valve if the valve is adjustable , particularly if this information is significant to circuit operation. Figure shows the plete symbol for a pound relief valve. All adjacent controls are shown, along with the main relief element . The envelope surrounding all the element may have five connections . These are pressure input , tank connection , remotecontrolstation 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 need flow to the teststation and remotecontrol connection for the respective function. The test station is generally used for a gauge connection to check fluid pressure. This does not require a flow of fluid. The remotecontrol connection passes the quantity of fluid ing through the fixed internal orifice at the rate established by the spring in the main relief element. An external drain from the pilotrelief valve, if fitted, will not pass more fluid than passes through the fixed internal orifice. Figure shows a cutaway view of pound 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 an orifice in the line . The area of the main spool is she same. In certain poppet designs。 The areas may not be exactly equal. One end may have a larger area to ensure certain function actions. In operation, if fluid cannot escape through adjustment port, a balance is provided by the equal areas at each end of the spool. The spring then maintains the spool in the position where it blocks the valve from pressure input to tank. When the pressure in the spring chamber above the spool rises to a point where it can unseat the cine at adjustment port, a portion of the fluid will be pass to the orifice into the main spring chamber, the pressure that is effective on the upper spool area may be less than that on the lower area so that balance is no longer maintained. As the pressure continue to rise at the lower end of the valve spool and the flow continues to increase through adjustment port while the degree of unbalance of the main spool bees more pronounced, the pressure will force the main spool against the spring. This creates a path from the pressure input to the tank much like that much like that created in directed springoperated relief valve. Adjustment A would provided a specific maximum relieving pressure if adjustment B were pletely relaxed. Where adjustment B is in use, providing an additive pressure to the mainspool spring, the minmum relieving providing will be fixed by adjustment A . The relieving pressure can never be less than that established by adjustment A in the valve. Pressure in the circuit could be less if there were relaxation through some other path. Resistance to pliotflow created by adjustment B may be considered as a hydraulic additive to the value of adjustment spring A. In many valves, the mainspool is not adjustable. The pocket containing the mainspool sprin