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A clutch is a device for quickly and easily connecting or disconnecting a rotatable shaft and a rotating coaxial shaft. www.mapeng.net 马棚网机械资讯
Friction clutches www.mapeng.net 马棚网机械资讯
Friction clutches have pairs of mating conical, disk, or ring-shaped surfaces www.mapeng.net 马棚网机械资讯
means for pressing the surfaces together. The pressure may be created by a spring or by a series of levers locked in position by the wedging action of a conical spool. On a spring-loaded clutch the operator, by controlling the rate at which the spring pressure is applied to the clutch, can regulate the speed of clutch engagement and the torque applied to the driven shaft. There is always some slippage, however, and the efficiency of a friction clutch can never exceed 50 percent; i.e., during a clutching operation at least one-half of the input energy is lost by friction in the clutch and produces heat. www.mapeng.net 马棚网机械资讯
The friction surfaces on clutches should have a high coefficient of friction and be able to conduct the heat away rapidly. These properties are difficult to obtain in a single material and for this reason, one of each pair of mating surfaces is usually metallic, while the other is either leather, cork, or an asbestos-based facing riveted to a metal plate. Some friction clutches are run dry, while others operate in oil. Dry clutches have a higher coefficient of friction than wet clutches, but the oil helms to carry off the heat.www.mapeng.net 马棚网机械资讯
Figure I shows a half-section of a multiple-plate disk clutch in which input member 2 is keyed to the driving shaft 1 and output member 3 is keyed to the driven shaft 4. The friction plates b have external gear teeth or splines that mate with teeth on the inside of member 2, while friction plates c have internal teeth that mate with external teeth on member 3. Plates b can slide axially in 2, while plates c can slide axially on 3. The clutch is engaged by moving the spool to the left, which, by a wedging action, rotates the lever about the pivot p and creates a force that squeezes the plates together. www.mapeng.net 马棚网机械资讯
Magnetic clutches www.mapeng.net 马棚网机械资讯
Magnetic-particle clutches have an annular (ring-shaped) gap between the driving and driven members that is filled with powdered iron and graphite. When a magnetic field is induced across the gap by a direct-current control coil, the iron particles form chains across the gap and transmit a torque that depends on the strength of the field. Controlled by varying the current, the load can be engaged smoothly and there, is no slippage when the clutch is transmitting the torque for which it was designed. www.mapeng.net 马棚网机械资讯
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Fig I Multiple-plate disk clutch www.mapeng.net 马棚网机械资讯
Exercises www.mapeng.net 马棚网机械资讯
put the following into Chinese: www.mapeng.net 马棚网机械资讯
Automatic clutches: Automatic, smooth engagement is obtained with a centrifugal clutch. The friction shoes are segments of rings that are pivoted to or carried around by the driving member. As the driver’s speed increases the shoes gradually make tier and firmer contact with the internal cylindrical surface of the driven member. Centrifugal clutches allow the driving motor to reach operating speed before
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