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Chain tension-imparting device

  • US 7,063,634 B2
  • Filed: 11/18/2003
  • Issued: 06/20/2006
  • Est. Priority Date: 12/27/2002
  • Status: Expired due to Fees
First Claim
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1. A tension-imparting device comprising:

  • a housing having a plunger-receiving hole with an enlarged end portion;

    a plunger slidable in said hole, extending through said enlarged end portion, and protruding therefrom in a protruding direction, for exerting a tensioning force against a traveling flexible transmission medium;

    toothed racks formed on opposite sides of the plunger;

    a protrusion biasing spring biasing the plunger in the protruding direction;

    a cam-receiving ring fitted on the outside of plunger and disposed in said enlarged end portion of the plunger-receiving hole, said cam-receiving ring having a pair of grooves with oblique cam-engaging surfaces;

    a spring, also disposed in said enlarged end portion, biasing the cam-receiving ring in said protruding direction;

    a pair of wedge-shaped cam chips, also disposed in said enlarged end portion of the plunger-receiving hole, the cam chips being situated respectively in said grooves and engaged with, and slidable on, said oblique, cam-engaging surfaces of the cam-receiving ring, said cam chips having teeth engaged respectively with said toothed racks on opposite sides of the plunger;

    a cam guide ring, fitted on the plunger, and also disposed within the enlarged end portion of the plunger-receiving hole, for guiding and controlling disengagement of the pair of wedge-shaped cam chips from said racks;

    a seal plate having a central opening slidably fitting the plunger, and sealing the biasing spring, the cam-receiving ring, the cam chips, and the cam guide ring, all of which are disposed in the enlarged end portion of the plunger-receiving hole; and

    a plunger releasing mechanism, for temporarily holding the plunger in a retracted condition, and responsive to an external pressing force urging the plunger in a retracting direction opposite to the protruding direction, for releasing the plunger for protruding movement,in which said plunger releasing mechanism comprises a pin protruding laterally from the plunger, a loop-shaped retainer engageable with said pin, and a roll-shaped tube on the seal plate, said loop-shaped retainer being engaged with, and pivoted in, said roll-shaped tube, and movable from a first position, in which it engages said laterally protruding pin and thereby holds the plunger in its retracted condition, to a second position, in which it releases the plunger for protruding movement.

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