外文翻译---液压与气压系统

外文翻译---液压与气压系统内容摘要：

neral， fluid power systems use fewer moving parts than parable mechanical or electrical systems． Thus， they ale simpler to maintain and operate． This， in turn， maximizes safety， pactness， and reliability． For example， a new power steering contr01 designed has made all other kinds of power systems obsolete on many off— highway vehicles． The Steering unit consists of a manually operated directional control valve and meter in a single body． 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． Because the steering unit is fully fluid 1inked， mechanical linkages，universal joints。 bearings， reduction gears， etc． are eliminated． This provides a simple， pact system． In addition， very little input torque is required to produce the control needed for the toughest applications． This is important where 1imitations of control space require a small steering wheel and it bees necessary to reduce operator fatigue． 设计巴巴工作室 There are several types of shaft couplings。 their characteristics depend on the prupose for which they are used. If an exceptionally long shaft is required for a line shaft in the manufacturing plant or a propeller shaft on ship, it is made in sections that are coupled together with rigid couplings. Additional benefits of fluid power systems include instantly reversible motion。 automatic． protection against overloads， and infinitely variable speed contr01． Fluid power systems also have the highest horsepower per weight rati0 of any known power source． In spite of al 1 these highly desirable features of fluid power， it is not a panacea for all power transmission problems． work revolves as the table moves along the ways, a helical or spiral cut is produced。 as shown in millingcutters, helical gears, twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one plete revolution. Before the helix can be machined the lead and angle of helix are twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one plete revolution. Hydraulic oil s are messy． and leakage is impossible to pletely eliminate． Also， most hydraulic oil s Carl cause fires if an oil 1eak occur in an area of hot equipment． Pneumatic System Pneumatic systems use pressurized gases to transmit and control power． As the name implies， pneumatic systems typically use air(rather than some other gas)as the fluid medium because air is a safe， low cost， and readily available fluid． It is particularly safe in environment s where an e1 electrical spark could ignite leaks from system ponent s． Worm wheel are similar to bevel gears and are generally used to connect skew shafts transmitting high velocity rations. The worm wheel give line contact between mating teeth unlike a point contact in the case of bevel gears. This improves the load carrying capacity of the gear train. In pneumatic systems pressors are used to press and supply the necessary quantities of air． Compressors are typically of the piston， vane or Screw type． Basically a pressor． Increase the pressure of a gas by reducing its v01ume as described by the perfect gas 1aws． 设计巴巴工作室 In connecting shafts belonging to separate devices(such as an electrical motor and gearbox) precise aligning of the shafts is diffcult and a flexible coupling is used. This coupling connects the shafts is such a way as to minimize the harmful effects of shaft misalignment. Flexible couplings also permit the shafts to defect under their separate systems of loads and to move freely in the axial direction without interfering with one another. Flexible couplings can also serve to reduce the intensity of shock load and vibrations transmitted from one shaft to another. Pneumatic systems normally use a large centralized air pressor which is considered t。