1 Clutches Section IX

2 Clutch? Types of Clutches Plate or Disk Clutches Cone Clutches Engaging Cone Clutches Talking Points

3 Clutch is a friction device which permits the connection and disconnection of shafts. Clutch? The design of clutches and brakes are comparable in many respects. Cone Clutch Cone Brake

4 The plates shown in figure below shown as A are usually steel and are set on splines on shaft C to permit axial motion (except for the last disk). The plates shown as B are usually bronze and are set on splines on shaft D. The number of pairs of surfaces transmitting power is one less than the sum of the steel and bronze disks. Types of Clutches Plate or Disk ClutchesCone Clutches Multiple Disk Clutch Cone Clutch The capacity: Where: T = torque capacity, Nm F = axial force, N f = coefficient of friction R f = friction radius n = number of pairs if surfaces in contact OR: If the contact pressure is assumed uniform If wear is assumed uniform Where: R o = outside radius of contact of surfaces, m R i = inside radius of contact of surfaces, m The axial force ( F ):The power capacity: Where: p = the average pressure Where: T = shaft torque, Nm N = speed of rotation, rpm A cone clutch achieves its effectiveness by the wedging action of the cone part in the cup part. A) The torque capacity (based on uniform pressure): OR: Alternate form: Where: R m = mean radius = 0.5 ( R o + R i ) b = face width, m  = pitch cone angle B) The torque capacity (based on uniform wear): Pressure variation Maximum pressureAt smallest radius Minimum pressureAt largest radius Average pressure Power

5 Engaging Cone Clutches A problem encountered with cone clutches not encountered with multi-disk clutches is the possibility of a large force to engage a clutch than that required during operation when the cup and cone are rotating at the same speed. A conservative procedure is to assume that no relative rotary motion occurs during engagement, for which the maximum axial force F e necessary to engage the cup and cone is: This force is the maximum required to obtain the desired normal force F n which in turn develops the frictional force to give the desired frictional torque. The axial force required to hold cup and cone in engagement (with friction taken into account) will vary between: and The axial force required to disengage the cup and cone: Ordinarily, with the cone angles commonly used, no force is necessary to disengage the parts, although it is possible that is f.cos  > sin , an axial force F d may be necessary to disengage the parts: