Abstract:
Clutch actuating lever arrangements for friction clutches are disclosed. The actuating levers are circumferentially spaced and are pivotally mounted on a clutch cover and a pressure ring. The pivotable actuating levers extend inwardly at angles offset from the radial direction of the clutch. As the rate of rotation of the clutch accelerates, the angled levers pivot due to centrifugal force to increase actuating pressure through the pressure clutch. The clutch may be disengaged by applying pressure to release tips of the levers. The angled lever arrangement provides a higher lever ratio for engagement and disengagement of the pressure ring, and provides even plate loads at optimal locations on the pressure ring.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. ______ entitled “Method of Clutch Lever Design for Friction Clutch Units” naming Robin Christopher Boninfante and Nicholas John Boninfante, Sr. as inventors, which was mailed by First Class mail to the U.S. Patent and Trademark Office on Jan. 4, 2005 and has a filing date of January ______ , 2005, and which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to vehicle clutches, and more particularly relates to clutch actuating lever arrangements for friction clutches.  
       BACKGROUND INFORMATION  
       [0003]     Clutches for vehicles are used to couple and decouple an engine to a drive shaft. Examples of prior art friction clutches are disclosed in U.S. Pat. Nos. 4,989,711 and 5,785,163, which are incorporated herein by reference. In such designs, clutch actuating levers are pivotally mounted on a pressure ring by devises and pins that allow each lever to centrifugally apply pressure to the pressure ring through its respective clutch clevis. A clutch clevis is a part of a friction clutch unit that provides support for the clutch lever and bolts to the clutch pressure ring. The pressure ring applies pressure to friction discs and steel plates. These components are attached to a clutch cover, which in turn is attached to a flywheel. The flywheel and clutch cover may be provided as a unit that is bolted directly to the back of a vehicle crankshaft. The clutch unit allows the vehicle to gradually move from a standing start by allowing the clutch to slip, thereby preventing the engine of the vehicle from stalling or straining, or preventing the drive tires from losing traction by applying too much power to the driveline.  
         [0004]     Currently, actuating levers used in friction clutch units extend radially inward from the pressure ring toward the axial center of the clutch unit. Although effective, such radially aligned lever designs have shortcomings including limited gain in lever ratio, which prevents the clutch units from performing to their potential. Furthermore, the current radial lever design severely limits the diameter of clutch units that can be built. Because it is important that the lever and clevis apply an even plate load to the pressure ring, current designs prevent the manufacture of smaller, lighter and more efficient clutch designs.  
         [0005]     Also, on smaller diameter clutch designs, the current radial levers cause uneven pressure applied from the lever through the clevis to the pressure ring because pressure is applied on the outer diameter of the pressure ring. This off-center pressure may cause permanent damage to the flatness of the pressure ring, which degrades operation of the clutch assembly. Because it is important for the pressure ring to remain flat throughout its life for maximum performance, a deformed or bent pressure ring causes a decrease in performance.  
         [0006]     From the foregoing, it can be appreciated that there exists a need for a friction clutch actuating lever design that allows a gain in lever ratio while still providing the desired direct pressure from the lever to the clevis to the pressure ring without damage to the flat surface of the pressure ring, which in turn allows the design of smaller, lighter and more efficient clutch units.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides an angled clutch actuating lever arrangement which allows friction clutches to gain greater amounts of lever ratio to the clutch pressure ring. The angled levers and their respective devises apply direct pressure at optimal locations on the pressure ring to achieve direct and even plate load through the levers to the pressure ring. Benefits of the present invention include increased lever ratios, the application of even plate loads to the clutch pressure ring, the reduction or elimination of flexing and permanent damage to the flatness of the pressure ring, the ability to produce smaller and lighter clutch units, and reduced effort in lifting of the pressure ring for disengagement of the clutch.  
         [0008]     The present invention provides an efficient and effective friction clutch design. In one embodiment of the invention, each lever is pivotally attached to the clutch cover and to the pressure ring, and extends inwardly at an angle offset from the radial direction of the clutch unit, e.g., at an angle greater than 0° and less than 90° with respect to the radial direction. Because the levers are attached at such angles, additional lever ratio is obtained, and smaller, lighter and more efficient clutch units can be designed without compromising cross-directional load and proper direct pressure to the pressure ring. The present design reduces or eliminates the flexing that distorts or bends the pressure ring, while reducing the clutch peddle pressure required for clutch disengagement.  
         [0009]     An aspect of the present invention is to provide a clutch cover and pressure ring assembly comprising a generally annular clutch cover having a central axis, a generally annular pressure ring having a central axis substantially aligned with the central axis of the clutch cover, wherein the clutch cover and pressure ring are rotatable with each other around their central axes and axially movable with respect to each other, and at least one actuating lever pivotally mounted on the clutch cover and/or pressure ring and extending radially inward at an angle offset from a radial direction of the clutch cover and pressure ring.  
         [0010]     Another aspect of the present invention is to provide an annular clutch cover having a central axis and comprising a plurality of slots structured and arranged for receiving actuating levers, wherein each slot extends radially inward at an angle offset from a radial direction of the clutch cover.  
         [0011]     A further aspect of the present invention is to provide an annular clutch pressure ring having a central axis and comprising a plurality of recesses structured and arranged to receive actuating levers, wherein each recess is oriented at an angle offset from a radial direction of the pressure ring.  
         [0012]     These and other aspects of the present invention will be more apparent from the following description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an isometric sectional view of a friction clutch cover and pressure ring assembly with angled actuating levers in accordance with an embodiment of the present invention. The levers are pivotally connected to the clutch cover and pressure ring at angles offset from the radial direction which allows the levers to achieve a greater lever ratio.  
         [0014]      FIG. 2  is a top view of the friction clutch cover and pressure ring assembly of  FIG. 1 .  
         [0015]      FIG. 3  is a bottom view of the friction clutch cover and pressure ring assembly of  FIG. 1 .  
         [0016]      FIG. 4  is an exploded isometric view of the friction clutch cover and pressure ring assembly of  FIG. 1 .  
         [0017]      FIG. 5  is a top view of a clutch cover in accordance with an embodiment of the present invention.  
         [0018]      FIG. 6  is a bottom view of the clutch cover of  FIG. 5 .  
         [0019]      FIG. 7  is a bottom view of a clutch pressure ring in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 1  is an isometric sectional view,  FIG. 2  is a top view,  FIG. 3  is a bottom view and  FIG. 4  is an exploded isometric view of a friction clutch cover and pressure ring assembly  10  in accordance with an embodiment of the present invention. The assembly  10  includes a clutch cover  20 , clutch pressure ring  30 , and multiple actuating levers  40  pivotally connected to the clutch cover  20  and pressure ring  30 .  
         [0021]     Details of the clutch cover  20  are most clearly shown in  FIGS. 2 and 4 - 6 .  FIG. 5  is a top view of the clutch cover  20 , while  FIG. 6  is a bottom view. The clutch cover  20  includes bolt holes  21  which receive conventional clutch bolts (not shown) which connect the clutch cover  20  to a conventional clutch flywheel (not shown), for example, as shown in U.S. Pat. Nos. 4,989,711 and 5,785,163. The clutch assembly may include conventional friction plates, e.g., as described in U.S. Pat. Nos. 4,989,711 and 5,785,163. The clutch cover  20  includes six spring holes  22  which receive spring cups  23 . As most clearly shown in  FIG. 1 , the spring cups  23  extend upwardly through the clutch cover  20 . As shown in the exploded view of  FIG. 4 , a spring bolt  24  is threaded through a hole in the top of each spring cup  23 , and a spring washer  25  and nut  26  are secured to each spring bolt  24 . As more fully described below, each spring bolt  24  is threaded into a spring cap  35  which is received in the end of a spring  33 .  
         [0022]     As shown most clearly in  FIGS. 1, 2 ,  5  and  6 , the clutch cover  20  includes six slots  27  extending through the thickness of the cover. Each slot  27  includes a circular portion which receives a clevis  36  connected to the pressure ring  30 , as more fully described below. Each slot  27  also includes an elongated portion which extends at an angle A offset from a radial direction of the clutch, as shown in  FIGS. 5 and 6 .  
         [0023]     As shown in the bottom view of the clutch cover  20  in  FIG. 6 , a recess  28  is provided in the bottom surface of the clutch cover  20  extending perpendicularly from the elongated portion of each slot  27 . As more fully described below, the generally cylindrical recesses  28  in the bottom surface of the clutch cover  20  receive pins which extend from the actuating levers  40  in order to provide a pivotal connection between the levers  40  and the clutch cover  20 . As shown most clearly in  FIG. 4 , bolts  29  are used to secure the lever  40  with respect to the clutch cover  20 , as more clearly described below.  
         [0024]     Details of the clutch pressure ring  30  are provided in  FIGS. 1, 3 ,  4  and  7 . A heat shield  31  is provided on the lower surface of the pressure ring  30 . Radial extensions  32  having semicircular recesses extend radially outward from the generally annular pressure ring  30 . In accordance with conventional clutch designs, the recesses of the radial extensions  32  receive conventional clutch bolts (not shown) which extend through the bolt holes  21  of the clutch cover  20  and connect to a conventional clutch flywheel (not shown). The radial extensions  32  thereby prevent relative rotation between the pressure ring  30  and clutch cover  20 , while allowing axial movement therebetween.  
         [0025]     As shown most clearly in  FIGS. 1, 4  and  7 , the pressure ring  30  includes cylindrical recesses  34  in which ends of the springs  33  are seated. Spring caps  35  are inserted in the opposite ends of the springs  33 . The spring bolts  24  are threaded through holes in the spring caps  35  to help secure the springs  33  within the spring cups  23 .  
         [0026]     As most clearly shown in  FIGS. 1, 4  and  7 , six devises  36  are mounted in generally rectangular recesses  37  in the pressure ring  30  and secured by bolts  38 . Each clevis  36  includes a generally cylindrical post with a longitudinal slot dividing opposing portions of the post. A pin  39  extends perpendicularly through the slot between the opposing portions of each clevis  36 . The post of each clevis  36  is received within the circular portion of a respective slot  27  in the clutch cover  20 .  
         [0027]     The actuating levers  40  include an arm  41  extending radially inward toward a release tip  42 . A hole  43  extends through an upper portion of each actuating lever  40  in order to allow the optional installation of bolts (not shown) or other centrifugal weights which may be used to adjust the amount of centrifugal force applied through the levers  40  during rotation of the clutch assembly. Each actuating lever  40  includes an elongated hole  44  which receives the pin  39  of a respective clevis  36  mounted on the pressure ring  30 . Each actuating lever  40  also includes a pin  45  extending from opposite faces of the lever  40  which is received in a respective recess  28  of the clutch cover  20 . The pin  45  may be fixedly mounted or rotatably mounted on the lever  40 . Each lever  40  is thus pivotally mounted with respect to the pressure ring  30  by means of the hole  44  and clevis pin  39 , and is also pivotally mounted with respect to the clutch cover  20  by means of the pins  45  received within the recesses  28 . When the lever release tips  42  are forced downward (e.g., by a conventional throw out bearing - not shown), the pressure ring  30  is forced upward toward the clutch cover  20  against the bias of springs  33  to disengage the clutch. When the lever release tips  42  move upward due to centrifugal force generated by the rotating clutch unit, the pressure ring  30  is forced downward away from the clutch cover  20  to increase the clutch engagement force.  
         [0028]     As an alternative embodiment, the lever  40  may be pivotally mounted on the clutch cover as shown in the figures, but the pivotal pressure ring mounting  44 ,  39  may be replaced with direct contact between the lever  40  and the upper surface of the pressure ring, in which case the bottom edge of the lever  40  may act as a cam surface against the pressure ring  30 .  
         [0029]     In accordance with the present invention, the actuating levers  40  are oriented at offset angles A from the radial direction of the assembly  10 . The offset angle A enables the length of the lever arms  41  to be extended beyond the length possible with conventional radial lever designs. As shown in  FIG. 2 , the length L of each lever  40  measured from its clevis pin mounting hole  44  to its release tip  42  is longer than that possible with conventional radial lever designs. Although the levers  40  shown in  FIG. 2  are substantially straight, curved or angled levers may be used.  
         [0030]     The lever offset angle A may range from greater than 0° to less than 90°, for example, from about 5° to about 80°. Typically, the lever offset angle may range from about 10° to about 60°, for example, from about 20° to about 40°. For larger diameter clutches, smaller offset angles may be desirable.  
         [0031]     The angled lever arrangement of the present invention also provides increased distance between the clevis pin hole  44  and the pin  45  of each actuating lever  40 . This increased distance provides an increased lever ratio and an increased axial throw distance between the clutch cover  20  and pressure ring  30 . In addition, the angled levers  40  and their respective clevises  36  apply pressure at optimal radial locations around the circumference of the pressure ring in order to achieve an evenly distributed plate load. This is accomplished by allowing the devises  36  to be centrally located C between the inner ID and outer OD diameters of the pressure ring  30 , as shown in  FIG. 1 . This avoids the uneven application of pressure near the outer diameter OD of the pressure ring  30  which can cause uneven wear and decreased performance in conventional clutch designs. Furthermore, the present angled lever arrangement allows the design of smaller diameter, lighter and more efficient clutch units.  
         [0032]     Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.