Abstract:
The clutch includes a wear clip for a clutch which acts as a replaceable wear surface and wear indicator for the cylindrical housing drum of the clutch. The wear clip of the invention is a U-shaped clip that may be formed wear-resistant material, such as carbon steel or aluminum. The cylindrical housing drum of the clutch includes slots for engagement by one or more clutch disks, and a wear clip may be placed in each slot and checked at regular intervals of operation of the clutch and replaced as necessary in order to reduce abrasion of the cylindrical housing drum by the inner components of the clutch and extend the useful life of the clutch.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to friction clutches having a cylindrical housing drum, and more particularly relates to clutches with a plurality of slots engaged by one or more clutch disks, and in which the frictional elements engage at a predetermined speed of rotation of a power shaft.  
           [0002]    Centrifugal friction clutches which engage at a predetermined rotational speed are particularly useful in combination with internal combustion engines which tend to stall under starting load conditions, by delaying engagement until the engine is operating at a sufficiently high speed to produce enough torque to prevent stalling. One such centrifugal clutch includes a number of plates and discs which move into frictional engagement by pressure exerted by pivoting of weights arranged next to the plates and discs. Such centrifugal friction clutches are also particularly useful in connection with small displacement internal combustion engines such as are used in go-carts, a demanding application of such a clutch in which any unnecessary size and weight can be a disadvantage. Centrifugal clutches are also known in automatic multispeed transmissions, but such transmissions add a considerable amount of size and weight to a small vehicle, and go-carts or one-quarter midget racing vehicles typically are not equipped with transmissions. It is therefore necessary for the clutch to be continually engaged and disengaged.  
           [0003]    In such a centrifugal clutch, as the clutch is operated the motion of the inner components of the clutch typically abrades the inside of the cylindrical housing drum of the clutch, requiring replacement of the housing drum and rebuilding of the clutch. In order to combat the problem of wear of the clutch housing, one conventional type of clutch provides a wear shoe for placement within a slotted portion of the clutch housing. Another conventional type of clutch provides wear resistant stop blocks which prevent wear when the clutch pads are expended. It would be desirable to provide a centrifugal clutch with replaceable wear clips to serve as replaceable wear surface and wear indicators that will incur wear from the inner components of the clutch instead of the cylindrical drum during operation of the clutch, and that can be checked at regular intervals and replaced as required, in order to extend the normal useful life of the centrifugal clutch. The present invention meets these needs.  
         SUMMARY OF THE INVENTION  
         [0004]    Briefly, and in general terms, the present invention provides for a wear clip for a clutch which acts as a replaceable wear surface and wear indicator for the cylindrical housing drum of the clutch. The wear clip of the invention is a U-shaped clip that may be formed from a wear-resistant material, such as carbon steel or aluminum. The cylindrical housing drum of the clutch includes slots, and a wear clip of the invention may be placed in each slot and checked at regular intervals of operation of the clutch and replaced as necessary in order to reduce abrasion of the cylindrical housing drum by the inner components of the clutch and extend the useful life of the clutch.  
           [0005]    The present invention accordingly provides for an improvement in a clutch for transmission of torque from a rotating input connector means for supplying rotational power to an output connector means for receiving the rotational power, the clutch having frictional surfaces adapted to be engaged at a predetermined engagement speed of rotation of the input connector means, the clutch including a cylindrical housing drum having a plurality of slots, a plurality of clutch plates disposed within the cylindrical housing drum operatively engaged with the input connector means, the plurality of clutch plates including at least one clutch disk having a plurality of flanges engaging the plurality of slots of the cylindrical housing drum, respectively. The improvement in the clutch comprises a plurality of U-shaped wear clips disposed in said slots of said cylindrical housing drum, wherein each of said U-shaped wear clips comprises first and second parallel legs and a middle portion, the first and second legs extending in a perpendicular direction from the middle portion; and first and second pairs of flanges extending outwardly from said first and second legs, respectively, perpendicular to the legs, and forming an outwardly facing U-shaped channel on each of said first and second legs, each of said first and second pairs of flanges forming an interference fit with the plurality of slots of the cylindrical housing drum when the wear clips are inserted in the slots. In a preferred embodiment, the clutch is a centrifugal clutch. In one preferred aspect, the wear clips are formed from wear-resistant material, such as carbon steel or aluminum.  
           [0006]    These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is an exploded perspective view of a centrifugal clutch separated from a power takeoff shaft from an engine of a vehicle, and illustrating placement of the wear clip of the invention in the cylindrical housing drum of the centrifugal clutch.  
         [0008]    [0008]FIG. 2 is an enlarged view of a portion of FIG. 1, illustrating the wear clip of the invention and placement of the wear clip in the cylindrical housing drum of the centrifugal clutch.  
         [0009]    [0009]FIG. 3 is an enlarged view of a wear clip according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]    As is illustrated in the drawings, the invention is embodied in a clutch, such as a centrifugal clutch  10  that is contained in a generally cylindrical housing drum  12  of the clutch, allowing for transmission of torque from a power input connector such as a power takeoff shaft, for supplying rotational power to an output drive connector, such as a drive hub. The cylindrical drum is preferably coaxially aligned with and surrounds the clutch plates and the clutch disks, with the drum interlocking with the clutch disks, as will be further explained below. As is shown in FIG. 1, the centrifugal clutch includes a generally circular centrifugal force lever support plate  14 , typically formed from cast aluminum, and having a central opening  16  allowing the power takeoff shaft to pass therethrough, with a small amount of clearance. Means for applying an adjustable biasing force on the centrifugal force lever support plate towards the clutch disk and the pressure plate, described below, are provided, such as a plurality of centrifugal force levers  18 , typically arranged symmetrically about the centrifugal force lever support plate, and having pivot pins  20  mounting each of the centrifugal force levers into corresponding slots  22  of the centrifugal force lever support plate, for example. Other means for mounting the centrifugal force levers on the support plate such as apertures in the centrifugal force levers and a corresponding snap ring retained on the support plate, may also be used. The centrifugal force levers are each preferably made of a plurality of flat parallel leaves arranged perpendicular to the plane of the support plate, and include a drive portion  24  generally to one side of the pivot pins, having the major portion of mass of the force lever, and a radius  26  or cam portion generally on the other side of the aperture, so that as the force levers rotate, the centrifugal force of the drive portion of the force levers urges the radius against a generally flat, circular pressure plate  28 .  
         [0011]    The means for applying an adjustable biasing force on the support plate towards the clutch disk and the pressure plate, such as by operatively engaging the pressure plate with the centrifugal force lever support plate, in one presently preferred embodiment also comprises a plurality of compression springs  30  placed in countersunk openings  32  in the centrifugal force lever support plate, held in place by a combination of stall speed adjusting screws or spring adjusters  34  and washers  36 , screwed in corresponding internally threaded cylindrical stems  38  formed in the pressure plate. The clutch also includes frictional surfaces adapted to be engaged at a predetermined engagement speed of rotation of the power input connector, such as a first clutch disk  40  having friction liners attached to both faces of the clutch disk, and having a plurality of flanges  42  that interlock with openings or slots  44  of the cylindrical housing drum that permit air cooling of the clutch. A second clutch disk  46  may also be provided, having friction liners attached to both faces of the clutch disk, and having a plurality of flanges  48  that also interlock with the slots  44  of the cylindrical housing drum. A floating plate  50  may also be provided between the two clutch disks. The clutch disks are preferably coaxially aligned with the centrifugal force lever support plate, the floating plate and the pressure plate. The clutch disks are adapted to smoothly engage the pressure plate and the friction surfaces  52  (only one of which is shown) of the floating plate.  
         [0012]    A main drive support member or drive hub  54  conforms to and fits over a power takeoff shaft (not shown) that typically extends axially through the clutch from an engine (not shown). The drive hub is mounted to the centrifugal force lever support plate by screws or bolts  56  extending through apertures  58  in rounded flanges  60  of the drive hub. The power takeoff shaft engages the tubular shaft  64  of the drive hub, and input power is supplied to the clutch by the power takeoff shaft of an engine. A back plate or fixed plate  66  is also provided, mounted by screws or bolts  68  through apertures  70  in the fixed plate to the centrifugal force lever support plate  14 , with slots  72  of the fixed plate engaged with the rounded flanges  60  of the drive hub.  
         [0013]    In order to provide an output connector of the torque transmitted through the fixed plate and clutch plates to the cylindrical housing drum of the centrifugal clutch, a sprocket  76 , having a plurality of splines  78 , includes a raised rectangular key portion  80  that engages rectangular slot  82  of the back face of the cylindrical housing drum of the centrifugal clutch, and is mounted to the back face of the cylindrical housing drum by bolts or screws  84 . Additional plates  86  are provided for coupling the drive hub to the cylindrical housing drum.  
         [0014]    As the centrifugal force lever support plate, pressure plate, clutch disks, floating plate and fixed plate rotate during operation of the centrifugal clutch, these inner components of the centrifugal clutch typically vibrate and become somewhat distorted by heat generated by the operation of the centrifugal clutch, causing these inner components to abrade the inner surface of the cylindrical housing drum. Referring to FIGS. 1, 2 and  3 , the present invention advantageously provides for a wear clip  88  that is mounted in the slots  44  of the cylindrical housing drum. The wear clip is generally U-shaped, and includes first and second parallel planar legs  90  extending in a perpendicular direction from the ends of one side of a planar middle portion  92 . The first and second planar legs have first and second edges  94 ,  94 ′, and first and second sides  96 ,  96 ′, and the planar middle portion has first and second ends  98 ,  98 ′, and first and second sides  100 ,  100 ′. A pair of flanges  102  extends outwardly from the edges of each of the legs of the wear clip perpendicular to the legs, forming an outwardly facing U-shaped channel  104  on each of the legs of the wear clip. The distance between the flanges of each pair of flanges generally corresponds to the thickness of the cylindrical drum housing at the slots of the cylindrical drum housing so as to form an interference fit with the slots when the wear clips are inserted in the slots, so that the flanges of the wear clips will hold the wear clips in place in the slots, while allowing the wear clips to be removed for inspection and replacement when necessary. The wear clip is typically formed from wear-resistant material, such as carbon steel or aluminum, for example, with a thickness sufficient to provide wear protection to the inner surface of the cylindrical drum housing.  
         [0015]    In another aspect of the invention, as is illustrated in FIG. 2, the slots  44  of the cylindrical housing drum are generally rectilinear U-shaped slots corresponding to the shape of the wear clip, and are formed to have planar inner edges  106  and planar outer edges  108 . Since the clutch plates and floating plate are general circular and the wear clips are generally planar and rectilinear, the wear clips will form a chord across the arc segment of the cylindrical housing drum delineated by each of the slots, and the wear clips will typically first contact and show signs of wear from the inner components of the clutch in the inside facing edges of the middle portions of the wear clips, so that regular inspection and maintenance of the wear clips allows for close control of abrasion of the cylindrical housing drum by the inner components of the clutch during operation.  
         [0016]    It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.