Hydraulic System
There are only three basic methods of transmitting power：Electrical，mechanical．and fluid power．Most applications actually u a combination of the three methods to obtain the most efficient overall system．To properly determine which principle method to u。it is important to know the salient features of each type．For example，fluid systems call transmit power more economically Over greater distances than Can mechanical types．However。fluid systems are restricted to shorter distances than are electrical systems．
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蒸笼Hydraulic power transmission system ale concerned with the generation, modulation, and control of pressure and flow and ,and in general such systems include:
上海市劳动合同条例丁豆1．Pumps which convert available power from the prime mover to hydraulic power at the actuator．
2．Valves which control the direction of pump--flow，the level of power produced，and the amount of fluid一一flow to the actuators．The power level is determined by controlling both the flow and pressure level．
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3．Actuators which convert hydraulic power to usable mechanical power Output at the point required．
4．The medium，which is a liquid，provides rigid transmission and control as well as 1ubrication of component s，aling in valves．and cooling of the system．
5．Connectors which link the various system components，provide power conductors for the fluid under pressure，and fluid flow return to tank(rervoir)． ．
溶洞的形成>奶奶生日祝福6、Fluid storage and conditioning equipment which ensure sufficient quality and quantity as well as cooling of the fluid．
7、pneumatics systems required a lubricator to inject。a very fine mist of oil into the air discharging from the pressure regulator．This prevents wear of the cloly fitting moving parts of pneumatic
Hydraulic systems ale ud in industrial applications such as stamping press，steel mills，and general manufacturing，agricultural machines，mining industry，aviation，sp
穷奇ace technology，deep—a exploration, transportation，marine technology，and offshore gas and petroleum exploration．In short，very few people get through a day of their 1ives without somehow benefiting from the technology of hydraulics2．
The principle of electrical-discharge machining also called electro is or spark-erosion machining, is bad on the erosion of metals by spark discharges. We know that when two current-conduct in wires are allowed to touch each other, an arc is produced. If we look cloly at the point of contact between the two wires, we note that a small portion of the metal has been eroded away, leaving a small crater.
The basic EDM system consists of a shape tool and the workpiece, connected to a dc power supply and placed in a dielectric fluid this is one of the most widely ud machining process, particularly for die-sinking operations when the potential difference between the tool and the work piece is sufficiently high, a transient spark discharges through the fluid, removing a very small amount of metal from the workpiece surface.
The capacitor discharge is repeated at rates of between 50,with voltages usually ranging
between 50vand 380v and currents from 0.1A to 500A.
Mechanical control includes cams and governors. Although they have been ud for the control of very complex machines, to be cost effectively, today they are ud for simple and fixed-cycle task control. Some automated machines, such as screw machines, still u cam-bad control. Mechanical control is difficult to manufacture and is subject to wear.
Pneumatic control is still very popular for certain applications. It us compresd air, valves, and switchs to construct simple control logic, but is easily slow. Becau standard compaonents are ud to construct the logic, it is easier to build than a mechanical control . Pneumatic control parts are subject to wear.
As does a mechanical control, an electromechanical control us switches, relays, times counters, and so on, to construct logic, it is faster and more flexible. The controllers using electromechanical control are called relay devices.
The values in the express the relative tool distance from the home position. This distance is shown in the relative or incremental coordinates, U and W.when reading the values in the not possible to know directly how far the tool is from the part origin. Just how far it is from the home position. mounted on exhaust ports of air valves and actuators to reduce noi and prevent operating personnel from possible injury resulting not only from exposure to noi but also from high—speed airborne particles.The sign of the coordinates is zero or negative becau the tool cannot move farther than the machine origin . thus at prent , the values are zero so the tool is at the home position. The values in the are normally ud when tting up the tools in order to find the real tool distances from the part origin.
