the idling spring 92 39 is carried within a preforated pot 93 through which extends an actuator rod 67 39 the upper free end of which is provided with an annular groove that is provided with a ring which supports a retainer for a spring assembly as will now be explained the pot includes an annular flange that is received in a recess in lever 41 39 and an idling spring 92 39 which encircles rod 67 39 is interposed between the base of the pot 93 and a flange 94 of a perforated hub 95 the axial elongation of which hub serves as the excursion limit of the idling spring 92 39 in a mirror image disposition to this first spring support 94 there is a further spring support 97 which also has a hub shaped interior against which the adapter spring 85 39 thrusts the axial elongation 97 serves to limit the excursion of this hub by cooperating with the retainer 98 against which the adapter spring 85 39 abuts the second spring support 98 thrusts against a guard ring 99 lying in an annular groove 100 adjacent to the end of the connecting rod 67 39 the perforated.