Chain hoist governor

Claim 1

THE COMBINATION, WITH A ROLLING DOOR HAVING A DRUM AND DOOR CONNECTED WITH THE DRUM TO BE ROLLED UP THEREON, THE SAID DRUM BEING PROVIDED WITH COUNTERBALANCING MEANS, A MANUALLY OPERATED SPROCKET, REDUCTION GEARING CONNECTING THE SPROCKET WITH THE DRUM SO THAT ROTATION OF THE SPROCKET IN ONE DIRECTION WILL TURN THE DRUM TO RAISE THE DOOR WHILE ROTATION OF THE SPROCKET IN THE OTHER DIRECTION WILL TURN THE DRUM TO LOWER THE DOOR; OF A SUPPORT PLATE ADJACENT THE SPROCKET, AND CAM MEANS ON THE PLATE RESILIENTLY URGED TOWARD THE SPROCKET SO AS TO ENGAGE THE TEETH OF THE SPROCKET, SAID CAM BEING OPERABLE TO RESIST ROTATION OF THE SPROCKET AT LEAST IN SAID OTHER DIRECTION THEREBY TO TEND TO LIMIT THE SPEED OF DESCENT OF THE DOOR UPON PARTIAL FAILURE OF THE SAID COUNTERBALANCE MEANS, SAID CAM MEANS HAVING INCLINED FACES THAT ARE ENGAGED BY THE TEETH OF THE SPROCKET WITH THE INCLINE ON THE SIDE OF THE CAM MEANS ENGAGED BY THE SPROCKET TEETH WHEN THE SPROCKET IS TURNING IN ITS SAID OTHER DIRECTION BEING AT SUBSTANTIALLY A STEEPER ANGLE THAN THE INCLINE ON THE OTHER SIDE, SAID SUPPORT PLATE BEING DETACHABLY MOUNTED ON THE DOOR STRUCTURE.