H-Key adjustable pulley

In an adjustable pulley construction comprising a first disc having at least one belt-engaging surface and having an axially extending centrally located internally threaded annular hub, said hub having an exterior flat face and an interior recess, a second disc defining at least one belt-engaging surface and having a centrally located externally threaded axle, said hub being coaxially and threadedly connected to said axle and being axially movable relative thereto, said belt-engaging surface being positioned in facing relationship, whereby a pulley belt can be located therebetween, the improvement comprising means securing said hub to said axle thereby to maintain a desired spaced relationship between said belt-engaging surfaces, said securing means including a threaded bore provided in said hub, said bore being transverse to said axle, a set screw received in said bore, a longitudinal, axially-extending, keyway recess in said hub communicating with said threaded bore, a keyway land provided on said axle adapted to be located in line with said set screw, and a generally H-shaped key having a rectangular body and a pair of arms positioned between said bore in said hub and said keyway land of said axle, the thickness of said key relative to the depth of said keyway recess being so related that said key may be positioned completely within said keyway recess, thereby allowing said hub to be rotated relative to said axle, said key being urgeable out of said keyway recess and into contact with said keyway land, thereby preventing said hub from being rotated relative to said axle, said key having a clamping base defined by said rectangular body for engagement with said set screw, turning of said set screw operating to move the end of said set screw relative to said key to provide a frictional clamping action of said key onto said keyway land, a first arm of said H-shaped key projecting outwardly beyond the exterior flat face of said hub, a second arm of said H-shaped key projecting inwardly into said interior recess and the length of said arms being greater than the width of said keyway recess, thereby to retain said key within said recess upon removal of said screw.