Abstract:
An adjusting mechanism to compensate for clutch disc wear is located in the lever linkage of the clutch, fixed to the cover. Rotational movement axially moves an adjusting ring, thus performing the adjustment. In a first embodiment, the locking member is pushed down to release the bolt head for the adjusting mechanism to allow it to be rotated. In a second embodiment, the locking member is pushed down to release the locking member, which also engages the bolt head for the adjusting mechanism, to permit rotation of the locking member and, consequently, adjustment of the clutch. In a third embodiment, the locking member is attached by means of a fastener to the bolt head and is removed to permit adjustment.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a mechanism for adjusting spring-loaded friction clutches of large automotive vehicles. In particular, this invention relates to a clutch adjuster that secures or locks-in the adjustment and prevents rotational movement between the adjusting ring and the gear of the clutch adjuster.  
         [0002]     Most clutches used in heavy trucks contain some type of clutch adjuster in which a manually-operated rotary gear meshes with the internal teeth of the adjusting ring to accomplish the adjustment. The rotating gear typically includes a central bolt terminating in a hex-head that is engaged by a socket wrench for rotating the gear. The clutch adjuster is locked in position by a strap that prevents rotation of the head associated with the gear. The locking and unlocking of the clutch adjuster is done by moving or removing the lock strap, which requires of manipulation of the hold-down screws that secure the strap to the clutch housing. The hold-down screws are often difficult to access, thus complicating adjustment of the clutch with this type of clutch adjuster.  
         [0003]     This drawback was addressed by the clutch adjusters shown in Flowtow et al. U.S. Pat. No. 4,953,680. The Flowtow et al. clutch adjusters are designed to unlock by pressing the center bolt down at a reasonable force (e.g., 15 lbs.). Specifically, axial movement of the center bolt is necessary to perform the locking and unlocking of the clutch adjuster. Due to the dirty environment and the size of the ring to be rotated, the teeth of the adjusting ring and clutch adjuster can become frozen or locked. This increases substantially the force needed to axially move the center bolt to unlock the adjuster, and may make it practically impossible. Further, in the commercial version (shown in  FIG. 5 ), the locking is “blind,” i.e., the locking surfaces are obscured from view. This leads to uncertainty as to whether locking has, in fact, occurred. If the Flowtow et al. clutch adjuster is not, in fact, locked into position, upon the first engagement of the clutch, the central bolt will rotate, and damage the locking strap. This results in gross mis-adjustment of the clutch, and the requires that the clutch adjuster be replaced.  
         [0004]     Therefore, it is an object of the present invention to provide a clutch adjuster in which manipulation of a lock strap and mounting screws is not required.  
         [0005]     It is a further object to provide such a clutch adjuster that provides a visual indication that the adjuster is locked into position, thus offering safety and certainty in operation.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention a clutch adjuster is provided that does not include a removable strap for locking and adjustment operation. The clutch adjuster includes a bracket having a central depressed area between two arms. In a first embodiment, a locking member is provided that is placed under the head of the adjusting bolt in the central area of the bracket. The locking member is biased upwardly into engagement with the head of the adjusting bolt by, e.g., a waved or spring washer. While a spring washer is shown in the illustrated embodiment, other biasing or resilient means may be used interchangeably, such as a spring, a compressible rubber washer, etc. The locking member is pushed down with a socket wrench, releasing the head of the bolt, and allowing the bolt to be freely rotated by the socket wrench. Upon removal of the socket wrench, the lock is returned to its initial position by the force of the spring, which thus engages and locks the head of the bolt. The relative position between the head of the bolt and the locking member is visible, thus allowing corrective rotation of the bolt, if necessary, to assure the locking. Rotation of the locking member, and thus the central bolt when engaged by the locking member, is prevented by the arms of the bracket.  
         [0007]     In a second embodiment, a locking and adjusting member is provided that is in axial alignment with the bolt and is moveable between adjusting and locking positions. The locking and adjusting member includes a socket shaped to engage the head of the bolt, a head adapted to be engaged by a tool, and opposed shoulders beneath the head. The arms of the bracket further comprise locking arms that extend at least partially over the central area and are adapted to engage the opposed shoulders on the locking and adjusting member when in the locking position. The locking and adjusting member is biased toward the locking position by a resilient member, such as a spring.  
         [0008]     In a third embodiment of the invention, the locking member overlies the head of the bolt and is removeably attached to the center bolt by a screw to permit adjustment. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a plan view, with portions broken away to show detail, of a clutch which incorporates clutch adjuster according to the present invention.  
         [0010]      FIG. 2  is an enlarged plan view of the clutch adjuster according to a first embodiment of the present invention.  
         [0011]      FIG. 3  is a cross-sectional view taken along line A-A of  FIG. 2 .  
         [0012]      FIG. 4  is an enlarged, plan view of a second embodiment of the clutch adjuster according to the present invention.  
         [0013]      FIG. 5  is a cross-sectional view taken along line B-B of  FIG. 4 .  
         [0014]      FIG. 6  is an enlarged plan view of a third embodiment of the clutch adjuster of the according to the present invention.  
         [0015]      FIG. 7  is a cross-sectional view taken along line C-C of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring to  FIG. 1 , there is schematically illustrated a conventional friction clutch  10  which incorporates a first preferred embodiment of a clutch adjuster  20 . Turning to  FIGS. 2 and 3 , the adjuster  20  includes a strap or bracket  24  with two generally L-shaped arms  24   a  that flank a central depressed area  24   b . The central area  24   b  includes an aperture that captures the central bolt  30  which carries a rotary gear or sprocket  25 . The teeth of the sprocket  25  are configured to engage the teeth of a clutch adjusting ring  15 . The adjuster  20  is secured to the clutch cover  12  by two bolts  14 .  
         [0017]     With reference to  FIGS. 2 and 3 , the adjuster  20  includes a central bolt  30  which has a head  32  (preferably hex- or square-shaped) adapted to be engaged by a torque-applying tool, such as a socket wrench. The shaft of the bolt  30  is captured for rotation in an aperture in the central area  24   b  of the bracket  24 . As illustrated, the shaft of the bolt  30  has different diameters for proper assembly with the remainder of the components. Specifically, the portion of the shaft immediately beneath the head  32  is enlarged with respect to the remainder of the shaft so as to not be capable of passing through the aperture in the bracket  24 . The rotary gear  25  is secured to the lower portion of the shaft  30  so as to substantially prevent axial movement of the bolt  30  with respect to the bracket  24 .  
         [0018]     A locking member  22  is mounted to the enlarged portion of the shaft of the bolt  30  immediately under the head  32  of the central bolt  30 . The locking member  22  is configured with a recessed portion  22   a  between two opposed raised portions  22   b  (best seen in  FIG. 3 ), which are adapted to engage two sides of the head  32  of the bolt  30  when in the locking position. The locking member  22  seats in the central portion  24   b  of the bracket  24  between the two L-shaped arms  24   a  so that rotation of the locking member  22  with respect to the bracket  24  is prevented. As illustrated, a spring washer  26  is positioned between the locking member  22  and the bracket  24  to bias the lock in a upward direction, thus engaging the shaped head of the bolt, which would otherwise rotate freely. As noted above, other resilient means may be substituted for the spring washer. The spring  26  should have a resiliency such that the force required to move the locking member  22  out of engagement with the head  32  of the bolt  30  is approximately 8 pounds. This force remains constant regardless of the condition of the clutch components. Consequently, by using a socket wrench, locking member  22  can be pushed down against the force of the spring washer  26 , and the shaped head  32  will be free to rotate along with sprocket  25  upon rotation of the wrench, thus making the clutch adjustment possible. By removing the socket wrench, the spring washer  26  biases the locking member  22  upwardly to capture and lock the head. Since whether locking engagement has occurred can be easily visually confirmed, damage to the clutch or accidents due to the clutch adjuster not being properly locked can be avoided. For better visibility, the locking member  22  and the bracket  24  can be of contrasting colors.  
         [0019]     Turning to  FIGS. 4 and 5 , a second embodiment of a clutch adjuster according to the present invention is shown. Like the clutch adjuster of  FIGS. 2 and 3 , the clutch adjuster  20  includes a bracket  24  with two L-shaped arms  24   a  bounding a central depressed region  24   b . Two bolts  14  secure the bracket  24  to the cover  12 . The central area  24   b  includes an aperture that captures the central bolt  92  that carries the rotary gear  25 , the teeth of the gear  25  being configured to engage the clutch adjusting ring  15 . As can be seen from  FIG. 5 , the spacing between the head  93  of the bolt  92  and the rotary gear  25  is such that substantially no axial movement of the bolt  92  is permitted with respect to the bracket  24 .  
         [0020]     In keeping with this embodiment of the invention, a locking and adjusting member  90  is provided that overlies the head  93  of the bolt  92  and is moveable axially with respect to the bolt between a locking position (shown in  FIG. 5 ) and an adjusting position. The locking and adjusting member  90  includes a socket  95  shaped to engage the head  93  of the bolt  92  and a head  98 , preferably hex-shaped, adapted to be engaged by a wrench for rotating the member  90  and, consequently, the bolt  92 . The socket  95  is preferably in engagement with the head  93  of the bolt  92  throughout its range of axial movement. The locking and adjusting member  90  includes a shoulder  99  between its head  98  and socket  95  that is shaped to be engaged by opposed locking arms  94   a  that are attached (by e.g., welding) to bracket arms  24   a  and extend partially across the central depressed area  24   b  of the bracket. As illustrated, the shoulder  99  has a square shape (when viewed from above as in  FIG. 4 ) thus presenting four facets, but may be of other polygonal shapes (e.g. hexagonal or octagonal) as long as the facets of the shoulder present a sufficient contact area with respect to the edges of the locking arms  94   a  to prevent the shoulder from being stripped when a torque is applied to the locking and adjusting member  90  in the locking position. A spring  96  is provided to bias the locking and adjusting member  90  toward the locked position. As illustrated, the spring  96  is positioned between the head of the bolt  92  and the top wall of the socket  95 , with the spring  96  seated in a recess in the head  93  of the bolt  90 . Alternatively, the spring  94  can be seated around the head  93  of the bolt  92  between the central area  24   b  of the bracket  24  and the bottom side of the locking and adjusting member  90 .  
         [0021]     Consequently, if a clutch to which the clutch adjuster of  FIGS. 4 and 5  is attached requires adjustment, a socket wrench is used to engage the head  98  of the locking and adjusting member  90 . The wrench is pushed down against the force of the spring  96  to move the locking and adjusting member  90  toward the head  93  of the bolt  92  until the shoulder  99  is located below the lower edges of the locking arms  94   a . In this position, a member  90  will be free to rotate upon rotation of the wrench, thus making clutch adjustment possible. When proper adjustment is achieved, and the adjusting member  90  is oriented so that the opposed edges of the shoulders  99  are aligned with the edges of the locking arms  94   a . Thus, when the locking member  90  is biased upwardly by the force of the spring  96 , the shoulders  99  are aligned with and engaged by the locking arms  94   a  to prevent rotation of the locking member, which, in turn, prevents rotation of the bolt  92 .  
         [0022]     Turning to  FIGS. 6 and 7 , a third embodiment of the clutch adjuster  20  is shown which incorporates a removable locking member  40 . Like locking member  22 , locking member  40  has a central recessed portion  40   b  between two opposed raised portions  40   a  which are configured to engage two sides of the shaped head  52  of the center bolt  50  when in its locking position. However, instead of being placed under the head  52 , the locking member  40  is placed over the shaped head  52  of the center bolt  50 , and is secured in the locking position to the head of the bolt  50  by a threaded fastener, such as screw  53 . A retaining washer  54  is secured to the shaft of the screw  53  between the lock  40  and the head  52 . Thus, the retaining washer  54  maintains the locking member  40  on the screw  53 , while permitting the locking member  40  to rotate with respect to the screw  53 . The center bolt  50  is secured to the sprocket  25 . When in the locking position, the center bolt shaped head  52  and the locking member  40  resides substantially in the central portion of strap  24  between the two L-shaped arms  24   a , thus preventing both the lock and the center bolt from rotating. By removing the lock assembly (locking member  40 , screw  53 , retaining washer  54 ), access to the center bolt is gained and adjustment of the clutch can be achieved. The clutch adjustment can be performed with a socket wrench, as set forth above. When the lock assembly is reattached, a visual check can be made to insure that locking has been accomplished.  
         [0023]     As can be appreciated, in none of the embodiments is there any axial movement of the sprocket  25  or center bolt  30 . This insures more reliable operation of the clutch adjuster.  
         [0024]     Those skilled in the art will appreciate that there are slight variations which will work equally as well as the one presented. Although the invention has been described in terms of certain preferred embodiments, the invention is not to be limited to the same. Instead the invention is to be defined by the scope of the following claims.