Dual cam surface clutch

Abstract

The invention relates to a belt-driven clutch system having a driven clutch with a particular arrangement of cam followers and cam slots. One embodiment of the invention is a clutch having a fixed sheave, a movable sheave and a housing mounted to the movable sheave. The housing has a cam slot with first and second cam surfaces. The clutch also includes a pair of cam followers that is secured to the fixed sheave for acting upon the cam surfaces of the cam slot. A first cam follower of the pair of cam followers acts upon a first cam surface of the cam slot and a second cam follower of the pair of cam followers acts upon the second cam surface of the cam slot to reduce backlash and provide more responsive operation. The invention also provides adjustment of spring tension and belt width without requiring removal or disassembly of the clutch.

We claim:  
     
         1 . A clutch comprising: 
 a fixed sheave;    a movable sheave;    a housing mounted to the movable sheave, the housing having a cam slot with first and second opposing surfaces;    a pair of cam followers secured to the fixed sheave;    wherein a first cam follower of the pair of cam followers acts upon the first cam surface and a second cam follower of the pair of cam followers acts upon the second cam surface.    
     
     
         2 . The clutch of  claim 1  wherein the clutch comprises at least two pair of cam followers and the housing comprises at least two cam slots, each of the cam slots being provided with a pair of cam followers.  
     
     
         3 . The clutch of  claim 2  wherein the cam slots are equally spaced around a circumference of the housing.  
     
     
         4 . The clutch of  claim 1  wherein the clutch comprises three pairs of cam followers and the housing comprises three cam slots, and wherein a first pair of cam followers acts upon a first cam slot, a second pair of cam followers different from the first pair of cam followers acts upon a second cam slot, and a third pair of cam followers different from the first and second pair of cam followers acts upon a third cam slot.  
     
     
         5 . The clutch of  claim 1  further comprising a compression spring acting within the housing between the housing and the fixed sheave.  
     
     
         6 . The clutch of  claim 1  wherein the cam slot is substantially helical shaped.  
     
     
         7 . The clutch of  claim 1  wherein the cam slot is linear and angled with respect to an axis that extends axially through the clutch.  
     
     
         8 . The clutch of  claim 1  wherein the cam slot is nonlinear having multiple angles along a length of the slot, with respect to an axis that extends axially through the clutch.  
     
     
         9 . The clutch of  claim 1  wherein the housing has a first end and a second end, the second housing end being secured to the movable sheave, and a spring tension adjustment mechanism being secured to the first housing end, the spring tension adjustment mechanism adjusting the tension of a spring positioned within the housing.  
     
     
         10 . The clutch of  claim 9  wherein tension of the spring mounted in the housing is adjusted by the spring tension adjustment mechanism without disassembling the clutch.  
     
     
         11 . The clutch of  claim 1  further comprising a shaft attachment secured to the fixed sheave, the shaft attachment having internal attachment features that mate with external attachment features of a shaft, the shaft attachment removably securing the fixed sheave to the shaft.  
     
     
         12 . The clutch of  claim 11  further comprising a belt width adjustment mechanism comprising threads formed on an exterior surface of the mechanism, the threads rotatably engaging threads formed on an inner surface of the shaft attachment, whereby rotation of the belt width adjustment mechanism in the shaft attachment adjusts a position of the fixed sheave relative to the shaft.  
     
     
         13 . The clutch of  claim 12  wherein a distance between the movable sheave and the fixed sheave is adjusted by adjusting the belt width adjustment mechanism, and the distance between the movable sheave and the fixed sheave is adjusted without disassembling the clutch.  
     
     
         14 . The clutch of  claim 1  wherein the movable sheave comprises lugs for mounting the cam followers, wherein the lugs extend axially away from the movable sheave.  
     
     
         15 . The clutch of  claim 1  wherein the movable sheave and the fixed sheave have a belt surface and an opposing vane surface, and vanes extend from the vane surface.  
     
     
         16 . The clutch of  claim 1  wherein the housing is generally cylindrically shaped with an first end and a second end, wherein the first end is secured to the movable sheave and the second end is configured to receive a spring tension adjustment mechanism.  
     
     
         17 . The clutch of  claim 1  wherein the housing comprises first and second ends, the housing first end engaging the movable sheave, the clutch further comprising an end cap secured to the housing second end, the end cap having first and second apertures, the first aperture providing access to a spring tension adjustment mechanism, and the second aperture receiving a belt width adjustment mechanism.  
     
     
         18 . A snowmobile comprising an engine and a continuously variable transmission including the clutch of  claim 1 .  
     
     
         19 . An ATV comprising an engine and a continuously variable transmission including the clutch of  claim 1 .  
     
     
         20 . A go kart comprising an engine and a continuously variable transmission including the clutch of  claim 1.