Torque-limiting clutches

Claim 1

In a torque-limiting clutch which includes an outer member having a bore which receives an inner member having a radial passage therein, roller means contained in said radial passage, an axial bore in the outer member containing a spring-loaded spindle which has a head provided with a generally conical surface which engages the roller means to effect radially outward biasing thereof into engagement with the seating formation formed in the wall of the bore of the outer member for the transmission of torque between the inner anD outer members, the arrangement being such that, under torque overload conditions, said roller means is displaced radially inwardly out of said seating formation and moves the spindle axially against the action of its spring loading, the improvement wherein the generally conical surface of the head of the spindle includes a first portion having a first apical angle and a second portion having a second apical angle greater than said first apical angle, the roller means engaging said first portion during transmission of torque between the inner and outer members and the spindle moving relative to the inner member into a position in which the roller means engages said second portion when the roller means moves radially inwardly to disengage from the seating formation of the outer member under torque overload conditions and said spindle has a shoulder arranged to engage the stop provided in the bore in the inner member to limit the extent of movement of the spindle under the action of its spring loading such engagement of the shoulder and the stop being arranged to take place prior to the roller means having completed its radially outward movement so as to avoid the transmission of impacts between the roller means and the spindle.