diskshaped bottom wall 34 which has extending therefrom within the circular periphery thereof a general cylindrical side wall 36 the latter is provided with flat portions 38 and 38 39 in which are provided slots for permitting securing of cup 32 to a cylindrical portion of housing 26 as by conventional screw fasteners so as to enclose the normally open motor end of housing 26 suitable seals not shown can permit the chamber within housing 26 to be filled with a lubricating oil and the like not shown to facilitate movement of the various elements within housing 26 bottom wall 34 is provided with an opening disposed centrally thereof with a hollow stepped hub 40 being disposed within the opening for receiving the adjacent end of the abutment 28 resilient assembly 30 also includes a stem 42 which extends longitudinally substantially coaxial with shaft 14 and is slidably mounted in housing 26 and a spiral torsion spring 44 disposed within the hollow chamber of cup 32 and having an inner end 46 and an outer end 48 the latter end is affixed to side wall 36 of cup 32 in a conventional manner such as by the illustrated screw fastener with inner end 46 being connected to stem 42 for winding tight the spring upon rotation of cup 32 together with the housing 26 and pulley 24 disposed within housing 26 at the juncture of the chamber portion thereof in which cup 32 is arranged and a smaller diameter portion connecting the chamber portion to pulley 24 is a nut 50 having internal screw threads 52 which selectively threadingly.