GB924307A - Improvements in centrifugal clutches - Google Patents

Abstract

924,307. Friction clutches; clutch combinations; ratchet clutches. ZAVODY 9. KVETNA NARODNI PODNIK. May 8, 1961 [May 11, 1960], No. 16708/61. Addition to 919,296. Class 80 (2). In a centrifugal friction clutch of the parent Specification, wherein lined clutch shoes 1 having conical friction surfaces and pivoted on a driving carrier 9 are centrifugally moved to an extent limited by stops 5, against return springs 8, to engage corresponding friction surfaces of one or two driven clutch plates (not shown), means providing a centrifugal disengaging speed, e.g. 1200 r.p.m., substantially below the centrifugal engaging speed, e.g. 1800 r.p.m., comprises masses 12 pivoted at 14 on the carrier 9 between the clutch axis 11 and the shoes and having return springs 18, shoeengaging arms r<SP>1</SP>, the length of which is equal to but not less than the radial distance between the pivots 14 and the inner surfaces of the shoes when the latter are fully expanded, and centres of gravity arranged to one side of the arm, and limit stops 16 on the shoes providing that in their outermost mass position the arms r<SP>1</SP> are, in the extreme case, radial to the clutch axis 11, such that the speed at which the moment of centrifugal force acting on each mass equals the moment exerted by its return spring 18 is less than the speed at which the moment of centrifugal force acting on each shoe equals the moment exerted by its return spring 8. The carrier and driven clutch plates are axially spring-loaded and disengagement at any speed may be effected by axial plate separation. As carrier 9 accelerates, the masses 12 swing out faster than the shoes 1 until their arms r<SP>1</SP> contact the shoe inner surfaces. The masses are relatively small and do not substantially affect shoe expansion so that the engaged position of the parts shown is not reached until the engaging speed (e.g. 1800 r.p.m.). When the speed falls below the engaging speed the centrifugal moment on the masses exceeds their return spring moment so that the masses prevent shoe retraction until the speed at which the moment exerted by the return springs 18 exceeds the combination of the moment of centrifugal force of the masses and the moment of the frictional force due to the load of the shoe return springs on the masses. As the masses begin to return, the friction between the shoes and the masses changes from static to dynamic and an additional moment due to the load of the shoe return springs on the masses assists the mass return spring moment with increasing effect to allow abrupt shoe retraction. The stops 16 may be arranged to arrest the masses in positions short of, but not beyond, the radial position of the arm r<SP>1</SP> shown, in order that the masses will be subject to a shoe return spring moment at all speeds below the engaging speed.