Belt tensioner with releasable belt load damping

  • US RE34,543 E
  • Filed: 12/21/1992
  • Issued: 02/15/1994
  • Est. Priority Date: 08/28/1987
  • Status: Expired due to Term
First Claim
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1. The combination comprisingan internal combustion engine including an engine frame subject to vibrational forces resulting from the operation of said internal combustion engine,a plurality of shafts mounted for rotational movement about parallel axes fixed with respect to said engine frame,a plurality of pulleys fixed to said plurality of shafts,one of said plurality of shafts constituting an output shaft of said internal combustion engine,an endless flexible belt of a size capable of being loosely trained about said plurality of pulleys, anda belt tensioner comprisinga fixed structure fixed with respect to said engine frame,a pivoted structure,a belt tensioning pulley mounted on said pivoted structure for rotational movement about a rotational axis,said pivoted structure being mounted on said fixed structure for pivotal movement about a fixed pivotal axis parallel with said rotational axis between a first position and a second position.spring means for resiliently biasing said pivoted structure in a direction toward said second position with a spring torque which varies as the position of said pivoted structure approaches said second position so that said belt tensioning pulley is biased into an intermediate operating static equilibrium position in tensioning engagement with said belt wherein the spring torque is equal and opposite to a belt load torque which varies with the variation in the spring torque as the intermediate operation position approaches said second position due to belt elongation by maintaining the belt load force generally constant and varying a lever arm distance to said pivotal axis through which the belt load force acts,means for damping the pivotal movements of said pivoted structure as a result of dynamic belt load forces varying from the generally constant belt load force when the belt is moving,said damping means including sliding friction surface means for establishing a damping torque resistance sufficient to restrict the pivotal movements of said pivoted structure by virtue of the pressure of interengagement of said sliding friction surface means and the position of interengagement of said sliding friction surface means from said pivotal axis to an extent such that movements in response to dynamic changes in the belt load force within a range of changes are prevented,said damping means being operable in response to the vibrational forces to which said engine frame is subject to instantaneously release the damping torque resistance to a level permitting instantaneous pivotal movements in response to dynamic changes in the belt load force which would otherwise be prevented by said sliding friction surface means as being within said range of changes.[...]. .Iadd.said range of belt load force changes varying from the generally constant belt load force to a positive extent wherein the belt load force increases and to a negative extent wherein the belt load force decreases, the range being such that the positive extent exceeds the negative extent sufficiently to provide within the excess extent positive changes in the resistance to movement which exceed the negative change in the resistance to movement heretofore considered the limit necessary to prevent hang-up. .Iaddend.

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