Abstract:
A novel adjustable slave cylinder is disclosed. The improved slave cylinder is particularly well suited for use with a clutch incorporating an expanding friction disk. The adjustable slave cylinder provides a means for adjusting a clutch pressure plate&#39;s position via an adjustment mechanism external to the inside of an engine.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a clutch system of the friction type placed in a power transmission system. Typical clutch systems include a clutch input such as a clutch basket, a clutch output such as a center clutch, and one or more plates making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled. The clutch pack is typically compressed by a pressure plate; the pressure plate typically providing a compressive force via a spring mechanism or through a centrifugally actuated mechanism. 
         [0002]    Typically, such clutch systems include a clutch disengagement system consisting of a lever mechanically coupled to the pressure plate such that when the lever is actuated, the pressure plate&#39;s compressive force on the clutch pack is removed, disconnecting the rotational coupling between the clutch input and clutch output. Clutch disengagement systems typically couple the lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system. 
         [0003]    Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch is engaged/disengaged by the driver via a lever mounted on the handlebar. Although the lever operated clutch allows the driver to control the clutch engagement/disengagement, often times motorcycle drivers find the clutch lever difficult to operate smoothly. New riders have difficulty adjusting to smoothly engaging the clutch while operating the throttle to move the vehicle from a standing start. Experienced riders may need to partially disengage the clutch when traveling slowly to allow the engine to continue running without stalling. Motorcycle racers often have a difficult time controlling the engagement of the clutch and the application of the throttle to maximize acceleration. Off-road motorcycle racers often need to stop the rear wheel suddenly with the rear brake, causing the engine to stall if the clutch is not first disengaged. An automatic clutch can help overcome many of the problems associated with a manual clutch. 
         [0004]    U.S. patent application Ser. No. 12/412,245 discloses an automatic clutch system incorporating an expanding friction disk and is incorporated herein by reference. One of the benefits of the improved automatic clutch system is the ability for the operator to override the automatic engagement of the clutch via a clutch lever without a significant change in how the clutch lever responds due to the centrifugal mechanism in the automatic clutch. Such a clutch system requires the pressure plate to be lifted away from the clutch pack to function properly. In application Ser. No. 12/412,245, lifting the pressure plate away from the clutch pack is accomplished with an adjuster within the engine cases. 
         [0005]    However, for some motorcycle operators, the ability to adjust the position of the pressure plate without opening the engine cover to gain access to the clutch is important. Being able to adjust the position of the pressure plate externally allows the operator to make adjustments to the clutch system to compensate for clutch pack wear for example. By adjusting the position of the pressure plate so that it comes in contact with the clutch pack, allows the operator to quickly and easily configure the clutch so that when the engine is not spinning, the clutch is engaged. In this configuration, the clutch operation is similar to a manual clutch and allows the operator to “bump start” the engine. When the engine is off, with a gear selected and the clutch lever engaged, rolling the motorcycle at sufficient speed and then suddenly releasing the clutch lever to engage the clutch, can start the engine. 
         [0006]    For typical hydraulic clutch disengagement systems, no such provision exists for positioning the pressure plate relative to the clutch pack through an external adjuster. 
         [0007]    Hydraulic clutch disengagement systems are well known in the art and are typified by systems made by Magura and Brembo and included on motorcycles such as those provided by KTM such as the KTM model year 2010 KTM 250 XCW. 
         [0008]    A typical hydraulic clutch disengagement system includes a master cylinder incorporating a reservoir for hydraulic fluid and a lever acting on a piston. A slave cylinder incorporates a bore and a piston; the piston typically acts upon the clutch throwout to lift the pressure plate for disengagement. A hydraulic line typically couples the master and slave cylinders and provides a conduit for the hydraulic fluid. 
         [0009]    Therefore a need exists for an adjustment mechanism with adjustment access external to the inside of the engine that can lift the clutch pressure plate to create a gap between the pressure plate and clutch pack. For typical hydraulically actuated clutch disengagement systems, the adjustment mechanism should maintain the use of the clutch lever maintaining the clutch levers capability to manually lift the pressure plate. 
         [0010]    It is therefore an object of the present invention to provide an adjuster mechanism with adjustment access external to the inside of the engine, for a typical hydraulic clutch disengagement system that allows a gap between the pressure plate and clutch pack to be created and adjusted while retaining the capability to manually lift the pressure plate to force disengagement of the clutch. 
         [0011]    The present invention for typical hydraulically actuated clutch disengagement systems is disclosed in  FIGS. 1 through 6 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an exploded view of the present invention; 
           [0013]      FIG. 2  is a section view of the present invention configured for use in a hydraulically actuated clutch disengagement system, wherein the clutch disengagement system is not actuated and the novel adjuster mechanism is adjusted to lift the pressure plate to create an installed gap; 
           [0014]      FIG. 3  is a section view of the present invention configured for use in a hydraulically actuated clutch disengagement system, containing an automatic clutch system incorporating an expanding friction disk, wherein the clutch disengagement system is not actuated and the novel adjuster mechanism is adjusted to lift the pressure plate to create an installed gap. 
           [0015]      FIG. 4  is a section view of the present invention configured for use in a hydraulically actuated clutch disengagement system, containing an automatic clutch system incorporating an expanding friction disk, wherein the clutch disengagement system is not actuated and the novel adjuster mechanism is adjusted allowing the pressure plate to contact the clutch pack. 
           [0016]      FIG. 5  is a section view of the present invention configured for use in a hydraulically actuated clutch disengagement system, containing an automatic clutch system incorporating an expanding friction disk, wherein the clutch disengagement system is actuated and the novel adjuster mechanism is no longer acting on the pressure plate. 
           [0017]      FIG. 6  is a section view of another embodiment of the present invention designed for minimal thickness. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Reference throughout this specification to “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
         [0019]    Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0020]    Hydraulic clutch disengagement systems are well known in the art and are typified by systems made by Magura and Brembo and included on motorcycles such as those provided by KTM such as the KTM model year 2010 KTM 250 XCW. 
         [0021]    A typical hydraulic clutch disengagement system includes a master cylinder and slave cylinder with a hydraulic line coupling the master cylinder and slave cylinder together with a conduit of hydraulic fluid. The master cylinder incorporates a reservoir for hydraulic fluid and a lever acting on a piston. The slave cylinder incorporates a bore and a piston. When the lever of the master cylinder acts on the piston within the master cylinder hydraulic fluid is displaced displacing the piston within the slave cylinder. The piston within the slave cylinder typically acts upon a clutch throwout to lift a clutch pressure plate and provide clutch disengagement. 
         [0022]    When the lever of the master cylinder is in the disengaged position and not acting on the master cylinder piston, typically, an open port exists between the slave cylinder piston and the reservoir of the master cylinder. The slave cylinder typically incorporates a spring that pushes the piston in the slave cylinder towards the pressure plate. Because an open port exists to the master cylinder reservoir, the slave cylinder is free to move inward or outward towards the pressure plate to allow for self-adjustment of the slave cylinder piston position relative to the pressure plate position. 
         [0023]    When the lever of the master cylinder is in the engaged position and acting on the master cylinder piston, the open port between the reservoir and the slave cylinder is closed, and the master cylinder piston acts on the slave cylinder piston through the fluid conduit displacing the slave cylinder piston and moving the position of the pressure plate. When the clutch lever is in the engaged position, the open port between the reservoir and the slave cylinder is closed, and no self-adjustment can take place. 
         [0024]    The present invention provides for a novel, external adjustment mechanism suitable for use in a clutch system that requires a gap to be formed between the pressure plate and clutch pack; such as disclosed in application Ser. No. 12/412,245. Two embodiments are disclosed for a typical hydraulic clutch disengagement system. 
         [0025]      FIGS. 1 through 5  disclose a preferred embodiment of a novel adjustable slave cylinder  100  configured to be used in a typical hydraulically actuated clutch disengagement system connected to a typical master cylinder. 
         [0026]      FIG. 6  discloses another embodiment of a novel adjustable slave cylinder  600  where the slave piston and threaded adjuster are designed to allow for minimum thickness. 
         [0027]    As can best be seen in  FIG. 1 , the novel adjustable slave cylinder  100  consists of a body  110 , having an input port  111  that connects the adjustable slave cylinder  100  to an input hydraulic line  112  using a banjo bolt  113  with sealing crush washers  119 . The adjustable slave cylinder  100  has a slave piston  114  with slave piston sealing o-rings  115 . The adjustable slave cylinder  100  has a threaded adjuster  116  with adjuster o-ring seal  117  and an optional lock nut  118 . 
         [0028]      FIG. 2  discloses a cross-section view of the novel adjustable slave cylinder  100  having a slave piston  114  which is configured to push against a throw-out rod  201 . The adjustable slave cylinder  100  has a body  110  having a threaded hole  202  for the threaded adjuster  116  to thread into. The adjustable slave cylinder  100  has a body  110  having an o-ring groove  203  which contains the adjuster o-ring seal  117  to seal between the body  110  and the threaded adjuster  116  preventing hydraulic fluid from escaping the system and contaminants from entering the system. The adjustable slave cylinder  100  has a body  110  containing a bore  204  which contains the slave piston  114  with slave piston sealing o-rings  115 . The slave piston sealing o-rings  115  provide a seal between the slave piston  114  and bore  204  allowing the system to maintain pressure and prevent hydraulic fluid from escaping between the slave piston  114  and bore  204 . The threaded adjuster  116  is configured to push against the slave piston  114  through the piston locating surface  205  for the purpose of positioning the slave piston  114  within the body  110 . 
         [0029]    The threaded adjuster  116  threads into the threaded hole  202  of the body  110 . The threads of the threaded hole  202  and the threads of the threaded adjuster  116  are configured such that when the threaded adjuster  116  is turned clockwise relative to the body  110 , the threaded adjuster  116  moves in an outward direction  210 . Consequently, when the threaded adjuster  116  is turned counter-clockwise relative to the body  110 , the threaded adjuster  116  moves in an inward direction  211 . 
         [0030]    A lock nut  118  allows the position of the threaded adjuster  116  to be fixed into a position. In another embodiment, the adjuster o-ring seal  117  provides adequate friction to maintain the position of the threaded adjuster  116  and the lock nut  118  is not needed. 
         [0031]    A ball bearing  206  is disposed between the slave piston  114  and throw-out rod  201  for the purpose of providing support when the slave piston  114  acts on the throw-out rod  201 . In another embodiment the throw-out rod  201  has a dome profile formed into its end eliminating the need for the ball. In another embodiment the slave piston  114  contacts the throw-out rod  201  directly. 
         [0032]      FIG. 3  depicts the novel adjustable slave cylinder  100  attached to an engine case  300  and master cylinder  301  through an input hydraulic line  112  using a banjo bolt  113 . Contained within the engine case  300  is a clutch assembly  320  similar to what is disclosed in U.S. patent application Ser. No. 12/412,245. The clutch assembly  320  includes a pressure plate  302  with springs  303  which bias the pressure plate  302  in the inward direction  211 . The clutch assembly  320  includes a throwout assembly  321  disposed between the pressure plate  302  and throwout rod  201 . 
         [0033]      FIG. 3  depicts the system in a state where the master cylinder  301  is not engaged and the threaded adjuster  116  of the novel adjustable slave cylinder  100  is adjusted in the outward direction  210  to lift the pressure plate  302  creating the installed gap  304  between the pressure plate  302  and clutch pack  305 . 
         [0034]      FIG. 4  depicts the system in a state where the master cylinder  301  is not engaged and threaded adjuster  116  of the novel adjustable slave cylinder  100  is adjusted in the inward direction  211  to eliminate the installed gap  304  allowing the pressure plate  302  to contact the clutch pack  305 . An adjusted off gap  401  exists between the threaded adjuster  116  and slave piston  114  allowing the pressure plate  302  to position the slave piston  114  in the inward direction  211  via the springs  303  limited by the clutch pack  305 . With the pressure plate  302  touching the clutch pack  305  the clutch assembly  320  is in a state where it can be bump started. 
         [0035]      FIG. 5  depicts the system in a state where the threaded adjuster  116  of the novel adjustable slave cylinder  100  is adjusted in to lift the pressure plate  302  and the master cylinder is engaged to further displace the pressure plate in the outward direction  210 . The position of the threaded adjuster  116  is the same as shown in  FIG. 3 . However, in  FIG. 5  the operator has engaged master cylinder  301  causing hydraulic fluid to be pushed into the input chamber  501  and displace the slave piston  114  in the outward direction  210  away from the master cylinder  301  further lifting the pressure plate  302  from the position in  FIG. 3  consequently increasing the installed gap  304  to accommodate clutch disengagement via the engagement of the master cylinder  301 . A disengaged gap  502  is formed between the threaded adjuster  116  and slave piston  114  via the displacement of the slave piston  114  from the master cylinder  301  being engaged. 
         [0036]      FIG. 6  discloses a cross-section view of another embodiment of the novel adjustable slave cylinder  600  optimized for minimum width. This embodiment of the novel adjustable slave cylinder  600  consists of a body  610 , having an input port  111  that connects the adjustable slave cylinder  600  to an input hydraulic line  112  using a banjo bolt  113 . The adjustable slave cylinder  600  has a slave piston  614  with slave piston sealing o-rings  615 . The adjustable slave cylinder  600  has a threaded adjuster  616  with adjuster o-ring seals  617 . 
         [0037]      FIG. 6  depicts a slave piston  614  which is configured to push against a throw-out rod  201 . The adjustable slave cylinder  600  has a body  610  having a threaded hole  618  for the threaded adjuster  616  to thread into. The threaded adjuster has a groove  620  containing the adjuster o-ring seals  617 . The adjustable slave cylinder  600  has a body  610  having an adjuster bore  619  which provides a sealing surface for the adjuster o-ring seals  617  to seal between the body  610  and the threaded adjuster  616  preventing hydraulic fluid from escaping the system and contaminants from entering the system. The adjustable slave cylinder  600  has a body  610  containing a bore  204  which contains the slave piston  614  with slave piston sealing x-rings  615 . The slave piston sealing x-rings  615  provide a seal between the slave piston  614  and bore  204  in an outward direction  210  and inward direction  211  allowing the system to maintain pressure and prevent hydraulic fluid from escaping between the slave piston  614  and bore  204 . The threaded adjuster  616  is configured to push against the slave piston  614  through the piston locating surface  205  for the purpose of positioning the slave piston  614  within the body  610 . 
         [0038]    The threaded adjuster  616  threads into the threaded hole  618  of the body  610 . The threads of the threaded hole  618  and the threads of the threaded adjuster  616  are configured such that when the threaded adjuster  616  is turned clockwise relative to the body  610 , the threaded adjuster  616  moves in an outward direction  210 . Consequently, when the threaded adjuster  616  is turned counter-clockwise relative to the body  610 , the threaded adjuster  616  moves in an inward direction  211 . 
         [0039]    The adjuster o-ring seals  617  are configured to provide adequate friction to maintain the position of the threaded adjuster  616 . 
         [0040]    A ball bearing  206  is disposed between the slave piston  614  and throw-out rod  201  for the purpose of providing support when the slave piston  614  acts on the throw-out rod  201 . 
         [0041]    The primary novel characteristic of the embodiment disclosed in  FIG. 6  is a narrower slave piston  614  that allows the adjustable slave cylinder  600  to have a slimmer profile. To prevent the slave piston  614  from rocking in the bore and possibly becoming stuck, the slave piston  614  is configured with a centering boss  630  and groove  631 . The centering boss  630  locates into the center pocket  632  of the body  610  which allows for proper slave piston  614  alignment when moved in an outward direction  210  or inward direction  211  within the bore  204  of the body  610 . The centering boss  630 , clearance groove  631  and center pocket  632  configured as shown minimize the width of the slave piston  614  allowing the novel adjustable slave cylinder  600  to have a slimmer profile while maintaining optimal axial alignment of the slave piston  614  with respect to the bore  204  of the body  610 . 
         [0042]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, for one skilled in the art, the present invention could be adapted for use in other types of vehicles that use clutch disengagement systems. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.