Clutches

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Clutches. Section IX. Talking Points. Clutch? Types of Clutches Plate or Disk Clutches Cone Clutches Engaging Cone Clutches. Clutch?. Clutch is a friction device which permits the connection and disconnection of shafts. Cone Clutch.
Transcript
Clutches Section IXTalking Points
  • Clutch?
  • Types of Clutches
  • Plate or Disk Clutches
  • Cone Clutches
  • Engaging Cone Clutches
  • Clutch?
  • Clutch is a friction device which permits the connection and disconnection of shafts.
  • Cone Clutch
  • The design of clutches and brakes are comparable in many respects.
  • Cone BrakeTypes of ClutchesPlate or Disk ClutchesCone Clutches
  • 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.
  • 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):Alternate form:Where:Rm= mean radius = 0.5 (Ro + Ri)b = face width, ma = pitch cone angleOR:PowerThe capacity:The axial force (F):The power capacity:Where:T = torque capacity, NmF = axial force, Nf = coefficient of frictionRf = friction radiusn = number of pairs if surfaces in contact Where:p = the average pressureB) The torque capacity (based on uniform wear):Where:T = shaft torque, NmN = speed of rotation, rpmPressure variationMaximum pressureAt smallest radiusMinimum pressureAt largest radiusIf the contact pressure is assumed uniformAverage pressureOR: Cone ClutchIf wear is assumed uniformPowerWhere:Ro= outside radius of contact of surfaces, mRi= inside radius of contact of surfaces, mMultiple Disk ClutchEngaging 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 Fe necessary to engage the cup and cone is:
  • This force is the maximum required to obtain the desired normal force Fn 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:andThe 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.cosa > sina, an axial force Fd may be necessary to disengage the parts:
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