Abstract:
A clutch actuation method and apparatus is provided. In one embodiment, a slave cylinder is mounted about a transmission input shaft, with a release bearing coupled to a first end of the slave cylinder, the release bearing having a release face structured to contact the release spring in the clutch pressure plate. A thrust bearing is coupled to a second end of the slave cylinder, the thrust bearing having a thrust face, and a thrust plate is coupled to the clutch housing, and sized to receive the thrust face on the thrust bearing. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the subject matter of the disclosure contained herein. This Abstract is submitted with the explicit understanding that it will not be used to interpret or to limit the scope or the meaning of the claims.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to clutches. More particularly, the invention concerns a method and apparatus to actuate a vehicle clutch.  
       BACKGROUND OF THE INVENTION  
       [0002]     With regard to vehicles, a clutch is a device within a vehicles&#39;drive train system that also includes the engine, transmission, and differential. The drive train components provide the vehicles&#39; motive force, enabling the vehicle to transition from a stationary state to one of motion. One function performed by the drive train is to allow intermittent disengagement of the engine during the transmission&#39;s gear changes.  
         [0003]     Engagement and subsequent disengagement of the engine from the transmission is made possible by the clutch. The most basic function of the clutch is to connect, and disconnect the engine from the remaining drive train. The term “clutch” refers to the friction disc, flywheel, throwout bearing, diaphragm spring and the pressure plate. The clutch enables the vehicle operator to start, stop, idle in neutral and shift gears. When a clutch is engaged it enables the remaining drive train components to operate at maximum efficiency. However, when the clutch “slips” engine power that should be transmitted to the driving wheels is lost in the form of heat caused by the slippage between the friction disk and the flywheel.  
         [0004]     Generally, the amount of engine torque a clutch can transmit to the transmission is directly related to the load generated by the pressure plate that pushes the clutch&#39;s friction disk against the engine&#39;s flywheel. Engines that generate large amounts of torque require high-load pressure plates.  
         [0005]     However, to disengage the clutch, the same load generated by the pressure plate must be overcome. A release mechanism, usually a concentric hydraulic slave cylinder, or a clutch fork contacting the throwout bearing push against the tips of the diaphragm spring located in the pressure plate. Pressure on the spring releases the pressure against the friction disk, disengaging the clutch. To exert the force against the spring, the concentric slave cylinder, or the clutch fork, are attached to the transmission case or a bell housing, which provides the support against which the slave, or clutch fork can push.  
         [0006]     The force exerted by the concentric slave, or the clutch fork against the spring in the pressure plate is also transmitted to the engine&#39;s crankshaft, because the pressure plate is bolted to the flywheel, which is bolted to the crankshaft. High pressure-plate loads can place excessive force on the crankshaft thrust main bearings, wearing both the crankshaft and the bearing surfaces.  
         [0007]     When the spring in the pressure plate is forced toward the engine, the clutch is known as a “push-type” and when the spring is pulled away from the engine, the clutch is known as a “pull-type.” That is, the throwout bearing on a push-type clutch pushes the diaphragm spring toward the engine, and with a pull-type, the throwout bearing pulls on the diaphragm spring. However, both systems exert the same total force on the crankshaft main bearings, either pushing against the crankshaft (push-type), or pulling on the crankshaft (pull-type).  
         [0008]     For this reason, all crankshafts must employ a means to limit fore and aft movement within the block. This is accomplished with a crankshaft thrust main bearing. The crankshaft thrust main bearing is different from the other crankshaft main bearings because it employs lips that give the crankshaft thrust surfaces something against which to ride.  
         [0009]     To address the thrust loads imparted by engagement and disengagement of the clutch, main bearing manufacturers design special crankshaft thrust main bearings. Some feature various grooves machined into the flange surface. The groove designs provide added lubrication for engines subject to high crankshaft main bearing thrust loads.  
         [0010]     However, the flanged crankshaft thrust main bearings, and other crankshaft main bearing designs increase friction, thereby robbing horsepower from the engine. Also, engines constructed with these special crankshaft main bearing thrust designs are still prone to premature bearing failure due to the high thrust loads imparted by high thrust force pressure plates.  
         [0011]     Therefore, there remains a need to overcome one or more of the limitations in the above-described, existing art. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic view of clutch actuator constructed according to one embodiment of the present invention for use with a pull-type clutch;  
         [0013]      FIG. 2  is a partial sectional view of the embodiment of  FIG. 1 , showing a sectional view of the pull-type clutch and an elevation view of the clutch actuator;  
         [0014]      FIG. 3  is a sectional view of the clutch actuator shown in  FIG. 2 ;  
         [0015]      FIG. 4  is a partial sectional view of a pull-type clutch and an elevation view of a pull-type clutch actuator constructed according to another embodiment of the present invention;  
         [0016]      FIG. 5  is a partial sectional view of a pull-type clutch and an elevation view of a pull-type clutch actuator constructed according to yet another embodiment of the present invention; and  
         [0017]      FIG. 6  is a partial sectional view of a pull-type clutch and an elevation view of a pull-type clutch actuator constructed according to a final embodiment of the present invention.  
         [0018]     It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. The Figures are provided for the purpose of illustrating one or more embodiments of the invention with the explicit understanding that they will not be used to limit the scope or the meaning of the claims. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     In the following paragraphs, the present invention will be described in detail by way of example with reference to the attached drawings. While this invention is capable of embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. That is, throughout this description, the embodiments and examples shown should be considered as exemplars, rather than as limitations on the present invention. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s).  
         [0020]     Generally, the present invention eliminates any pressure, or thrust loads on the engine crankshaft during actuation of the clutch. Conventional “push-type” clutch actuation systems employ a concentric slave cylinder, or actuation fork that compresses the spring in the pressure plate. The concentric slave cylinder, or the support for the actuation fork is mounted to the transmission case or bell housing. The slave cylinder, or support for the actuation fork pushes against the transmission case or bell housing, enabling it to generate a compression force against the spring. The compression force is transmitted through the pressure plate and the flywheel to the crankshaft. Similarly, conventional “pull-type” clutch actuation systems also employ an actuation fork that pulls the spring away from the engine. The support for the actuation fork is similarly mounted to the transmission case or bell housing, resulting in the crankshaft experiencing a “pull” force.  
         [0021]     One embodiment of the present invention tailored for use in a “push-type” clutch system eliminates the force acting upon the crankshaft by mounting a concentric hydraulic slave cylinder in a cage that is mounted directly to the pressure plate. Because the pressure plate itself provides the support for the slave cylinder, no thrust force is exerted on the crankshaft.  
         [0022]     Another embodiment of the present invention tailored for use in a “pull-type” clutch system also eliminates the force acting upon the crankshaft. One embodiment employs a concentric slave cylinder having a bearing assembly mounted at each end of the slave cylinder. The slave cylinder expands, and pushes against the pressure plate and against a pull tube assembly, or splined tube (which are components used in “pull-type” clutches, discussed below) and thereby eliminates the generation of any external forces because, again, the pressure plate itself provides the support for the slave cylinder, thus eliminating any thrust forces on the crankshaft. Another embodiment of the present invention tailored for use in a “pull-type” clutch system employs a concentric slave cylinder having a bearing assembly mounted between the pull tube assembly and the diaphragm spring and a second bearing assembly mounted between the concentric slave cylinder and the pressure plate. This arrangement again uses the pressure plate to provide the support for the slave cylinder, thus eliminating any thrust forces on the crankshaft.  
         [0023]     Put simply, for every action there is an equal and opposite reaction. In conventional clutch actuation systems, the clutch fork or concentric slave cylinder are mounted to the transmission case or bell housing, and push against these components when they push against the spring in the pressure plate. The present invention eliminates the transmission or bell housing mount, thereby also eliminating the generation of any external force that must be resisted by the crankshaft.  
         [0024]     In the case of a “push-type” clutch system, the support is a cage that is mounted to the pressure plate. In the case of the “pull-type” clutch system, one end of a concentric slave cylinder “expands” away from the pressure plate, creating the pull force required to actuate the clutch, yet without generating a “pull” force on the crankshaft. In this embodiment, not only are pull forces on the crankshaft eliminated, but the clutch fork, and related components are also eliminated, as a concentric slave cylinder using two roller bearing assemblies is employed. This reduction in parts decreases manufacturing costs and maintenance costs, as well as system complexity.  
         [0025]     Another advantage of any of the embodiments described herein is that smaller diameter friction disks, and their associated components (pressure plate and flywheel) can be employed. This is because one aspect of clutch design is a tradeoff between friction disk diameter and the clamp pressure, or load generated by the pressure plate. As the friction disk diameter decreases, the torque that it can transfer to the transmission input shaft also decreases. Conventional clutch manufacturers increase the pressure plate clamp pressure to compensate for the smaller diameter friction disks. However, high pressure plate clamp loads place excessive load on the crankshaft. Because the present invention eliminates crankshaft loads during clutch actuation, smaller diameter friction disks can be employed, decreasing manufacturing costs and increasing packaging options during drive train design.  
         [0026]     Referring now to  FIG. 1 , a schematic illustration of a push-type clutch actuation system constructed according to one embodiment of the present invention is shown. The clutch  25  is mounted to the engine flywheel  20 , which is mounted to the end of the engine crankshaft  18  that is rotatably driven by the engine  15 . The crankshaft  18 , flywheel  20 , and clutch  25  all rotate and transfer the rotation force (i.e., torque) to the transmission  35  via the transmission input shaft  40 . Some vehicles employ a bell housing  12  that joins the engine  15  to the transmission  35 . Other vehicles do not employ a bell housing  12 , instead mounting the engine  15  directly to the transmission  35 , which is sized to fit the illustrated components within it. It will be appreciated that the present invention may be employed within a bell housing  12 , or within a transmission  35 .  
         [0027]     As shown in  FIGS. 1 and 2 , the clutch actuation system  10  comprises a clutch actuator  30  that includes a concentric slave assembly  45  with a throwout bearing  65  and a thrust bearing  70  located at opposite ends. A thrust plate  34  is fastened to a mount plate  32  by fasteners  36 . Fasteners  36  may be rods, bolts, or any suitable component for attaching the thrust plate  34  to the mount plate  32 , such as a cylindrical tube that connects the thrust plate to the mount plate  32 . The mount plate  32  is fastened to the pressure plate  50  by suitable fasteners such as rivets, bolts, or other fastening means. As defined herein, pressure plate  50  also includes the housing that covers the pressure plate elements  50 , such as the floater plates  52  (shown in  FIGS. 2 and 4 ), and other associated pressure plate elements that are known in the art. It will be appreciated that alternative embodiments may not employ a mount plate  32 , but instead fasten the thrust plate  34  directly to the pressure plate  50 .  
         [0028]     The clutch  25 , shown in  FIG. 2 , includes the pressure plate  50  with a diaphragm spring, or spring fingers  55  attached thereto. The diaphragm spring  55  may be a Belville spring or individual spring finger elements, or their equivalents, as known in the art. The pressure plate  50  also includes one or more floater plates  52  that clamp one or more friction disks, or driven plates  60 .  FIGS. 2 and 4  illustrate two friction disks  60 , but one or more that two friction disks  60  may be employed. The friction disks  60  have a splined center section that is sized to receive the corresponding splines on the transmission input shaft  40  (not shown). The construction of the pressure plate  50 , diaphragm spring  55 , friction disk(s)  60 , and transmission input shaft and related components is well known in the art, and the present invention may be employed by any type of clutch construction.  
         [0029]     Referring now to  FIG. 3 , the components included in the concentric slave assembly  45 , throwout bearing  65  and thrust bearing  70  are illustrated. The concentric slave assembly  45  has an annular transmission input shaft housing  72  that allows the transmission input shaft  40  to rotate freely within. Surrounding the annular transmission input shaft housing  72  are the annular walls  74   a  and  74   b , with the annular wall  74   a  having a piston bore  75  that slideably receives the annular wall  74   b . A bump stop  79  is positioned at the tip of annular wall  74   b , and in conjunction with preload spring  77 , keeps the annular wall  74   b  from “bottoming” within the piston bore  75 . Hydraulic fluid (not shown) is pumped into, and out of, the piston bore  75  through fluid ports  80  (shown in  FIG. 2 ) that may extend from the end (as shown) of the concentric slave assembly  45 , or they may extend from the side (not shown) of the concentric slave assembly  45 . As is known in the art, the fluid ports  80  are in fluid communication with a clutch master cylinder (not shown) that is actuated by the vehicle operator depressing a clutch pedal (not shown). Alternatively, the concentric slave may be operated by a hydraulic pump that is electronically controlled. Similar to the pressure plate  50 , concentric slave assemblies, their operation and their internal construction are well known in the art, and the present invention may employ any type of concentric slave assembly, including types that may vary in construction from the one described and illustrated herein. However, in one embodiment, the present invention employs a concentric slave that includes a thrust bearing  70 . This is in contrast to conventional concentric slave assemblies that only have a throwout bearing  65 .  
         [0030]     This is because a conventional clutch system that employs a conventional concentric slave mounts the concentric slave about the transmission input shaft, with one end of the slave attached to the front of the transmission, or to the bell housing, and the other end having a throwout bearing  65  in contact with the spring fingers  55 . In operation, the pressure plate  50   5  rotates, along with the spring fingers  55  and the transmission input shaft  40 . However, the slave assembly  45  does not rotate, as it is attached to the transmission or the bell housing. As shown in detail in  FIG. 3 , the throwout bearing  65  enables relative rotation between the slave assembly  45  and the spring fingers  55 . The throwout bearing  65  comprises a release face, or thrust face  67  and a slave face  69  that are joined by a ball bearing cage having a plurality of ball bearings. When the release face  67  contacts the spring fingers  55  during clutch actuation, the release face  67  rotates with the spring fingers  55 . However, the ball bearing cage allows the slave face  65  to remain substantially motionless, enabling the attachment of the slave assembly  45  to the transmission  35  or bell housing  12 . The construction and operation of throwout bearings is well known in the art, and for example, in one embodiment of the present invention the throwout bearing  65  may be a high quality steel caged radius contact ball bearing. The throwout bearing  65  may have steel cages and hardened steel shells for durability and may be filled with grease that can withstand high temperatures. But, it will be appreciated that the present invention is not limited to a specific bearing construction, but instead may employ a throwout bearing  65  of virtually any construction.  
         [0031]     Referring again to  FIG. 3 , one feature of the present invention not found on conventional concentric slave assemblies is the thrust bearing  70 , mounted opposite the throwout bearing  65 . As discussed above, conventional slave assemblies have the end opposite of the throwout bearing  65  attached directly to the transmission or the bell housing. As these components do not rotate, a bearing assembly is not required. But, as discussed above, the conventional slave assembly thrusts against the transmission or bell housing when actuating the spring fingers, thereby transmitting that thrust force ultimately to the crankshaft.  
         [0032]     The present invention eliminates the generation of thrust forces against the crankshaft by eliminating the connection between the slave assembly and the transmission or bell housing. As shown in  FIG. 2 , the end of the slave assembly  45  opposite the throwout bearing  65  is mounted to thrust plate  34 , which is attached to the pressure plate  50  by fasteners  36 . Because the pressure plate  50  rotates, the mount plate  32 , fasteners  36 , and thrust plate  34  also rotate. To keep the main body of the slave assembly  45  relatively stationary, a thrust bearing  70  is positioned between the thrust plate  34  and the end of the slave assembly  45  proximate to the thrust plate  34 . One embodiment of the present invention contemplates a slave assembly  45  with the throwout bearing  65  and thrust bearing  70  constructed integral to the slave assembly  45 . However, it will also be appreciated that a non-integral thrust bearing  70  may also be employed.  
         [0033]     As shown in detail in  FIG. 3 , in one embodiment of the present invention, the thrust bearing  70  is constructed substantially identically to the throwout bearing  65 . Specifically, the release face, or thrust face  67  is in contact with the thrust plate  34 , and the slave face  69  is attached to the annular wall  74   a  of the slave assembly  45 . Between the release face  67  and the slave face  69  is a ball bearing cage having a plurality of ball bearings. As discussed above in connection with the throwout bearing  65 , the thrust bearing  70  may be a high quality steel caged radius contact ball bearing. The thrust bearing  70  may have steel cages and hardened steel shells for durability and may be filled with grease that can withstand high temperatures. But, it will be appreciated that the present invention is not limited to a specific bearing construction, but instead may employ a thrust bearing  70  of virtually any construction.  
         [0034]     Referring again to  FIG. 2 , the main body of the slave assembly  45 , comprising the annular walls  74   a  and  74   b , can now remain substantially motionless, while the thrust plate  34 , fasteners  36 , and mount plate  32  all rotate with the pressure plate  50 . The fluid ports  80  also remain substantially motionless as they communicate with one of the annular walls  74   a  or  74   b , depending on the specific construction of the slave assembly  45 . For example, in one embodiment, the fluid ports  80  exit as shown in  FIG. 2 , adjacent to the transmission input shaft  40 . In another embodiment, the fluid ports  80  may exit out the side of one of the annular walls  74   a  or  74   b . The present invention contemplates different arrangements for the fluid ports  80 , as required for each type of transmission or bell housing.  
         [0035]     Referring now to  FIGS. 2 and 3 , the operation of the clutch actuator system  10  will now be described. When the transmission input shaft  40  is engaged with the crankshaft  18 , the flywheel  20 , pressure plate  50 , mount plate  32 , fasteners  36  and thrust plate  34  are all rotating at the same rate, or revolutional speed. When the vehicle operator wishes to disengage the transmission  35  from the engine  15 , hydraulic fluid is pumped into one fluid port  80 , and the annular walls  74   a  and  74   b  are forced apart by the hydraulic fluid. Annular wall  74   a  pushes thrust bearing  70  against thrust plate  34 , while annular wall  74   b  pushes throwout bearing  65  against spring fingers  55 . However, the slave faces  69  of the throwout bearing  65  and thrust bearing  70 , which are connected to the annular walls  74   b , and  74   a , respectively, do not rotate, enabling the annular walls  74   a  and  74   b  to remain substantially rotation-free. As the piston bore  75  fills with hydraulic fluid and pushes the annular walls  74   a  and  74   b  away from each other, the spring fingers are pushed toward the flywheel  20  (shown by arrows in  FIG. 2 ) causing the floater plates  52  to release the friction disk, or disks  60 . The friction disks  60 , which are connected via a splined center section to the splines (not shown) on the transmission input shaft  40 , are now allowed to cease rotation, or rotate at a revolution different than the engine&#39;s crankshaft  18 . In this manner, a different gear may be selected in the transmission  35 , or the vehicle may become stationary, while the crankshaft  18  continues to rotate.  
         [0036]     However, because the slave assembly  45  pushes against the thrust plate  34  to generate the force used to depress the spring fingers  55 , and the thrust plate  34  is attached to the pressure plate  50 , the crankshaft  18  does not experience any thrust forces. Put differently, by eliminating the transmission mount or bell housing mount for the slave assembly, the external thrust force is also eliminated. Thus, the extreme clutch pressure-plate loads on manual-transmission vehicles that place excessive pressure on the crankshaft thrust bearing, wearing both the crankshaft and the bearing surfaces, is eliminated. It will be appreciated that the above discussion is related to “manual” transmission vehicles, where the vehicle operator actuates the clutch by depressing a clutch pedal. However, the present invention may also be employed by electronically controlled drive trains, where for example, the vehicle operator selects a specific gear in the transmission by pushing a button or moving a gear shift lever, or “paddle.” The electronically controlled transmission then actuates the concentric slave assembly by using an electronically controlled hydraulic pump, thus eliminating the need for use of the clutch pedal (which may be retained for activation of the drive train in a “manual mode,” where electronic control is reduced).  
         [0037]     The above discussion in connection with  FIGS. 1-3  relates to “push-type” clutches, as the spring fingers  55  are “pushed” toward the engine  15 . Other embodiments of the present invention, designed for use with “pull-type” clutches are illustrated in  FIGS. 4-6 . As shown in  FIGS. 4-6 , a “pull-type” clutch pulls the spring fingers  55  away from the engine&#39;s crankshaft  18 . Specifically, the diaphragm spring, or spring fingers  55 , which may be a Belville spring, or individual spring fingers, or any equivalents, are generally positioned so that the tips of the spring fingers  55  are pointed toward the flywheel  20 . In contrast, the tips of the spring fingers  55  on a “pull-type” clutch, shown in  FIG. 2 , generally point away from the flywheel  20 . In the embodiment illustrated in  FIG. 4 , a pull-tube assembly  85 , including pull-tube hardware  90  is positioned between the spring fingers  55  and the friction disk, or disks  60 . In the embodiment illustrated in  FIG. 5 , a pull-tube assembly  85 , including pull-tube hardware  90  is positioned behind the throwout bearing  65 , which contacts the spring fingers  55 . In the embodiment illustrated in  FIG. 6 , a pull-tube assembly  85 , including pull-tube hardware  90  is positioned adjacent to the tips of the spring fingers  55 .  
         [0038]     Referring to  FIG. 4 , one embodiment of the present invention for use with a “pull-type” clutch is illustrated. A mount plate  32  is attached to the pressure plate  50 , or to a “hat” located over the pressure plate  50 . This is because some pull-type clutches found on semi-tractors may include a “hat” or cover that fits over the pressure plate  50 . The present invention may also be employed by these types of pull-type clutches, as well as pull-type clutches that may be found on other types of trucks, vans, passenger automobiles, off-road vehicles (such as farm machinery, and earth-moving equipment) and any other vehicle that may employ a pull-type clutch. In a preferred embodiment, the pressure plate  50 , or “hat” may be constructed to receive the slave assembly  45 , thereby eliminating the mount plate  32 . As described above in connection with a “pull-type” clutch, throwout bearing  65  is positioned adjacent to the mount plate, with a thrust bearing  70  located opposite the throwout bearing  65 . In this embodiment, the release face  67  of the throwout bearing  65  contacts the mount plate  32 , with the slave face  69  attached to the annular wall  74   b , as shown in  FIG. 3 . Similarly, the slave face  69  on the thrust bearing  70  is attached to the annular wall  74   a , as also shown in  FIG. 3 , but the release face  67  now engages the pull tube hardware  90  that is attached to the pull-tube  85 . In this embodiment, the thrust plate  34 , and fasteners  36  are eliminated.  
         [0039]     In operation, the slave assembly  45  expands, pulling the pull tube  85  and the pull-tube hardware  90  away from the flywheel  20 , thereby also pulling the spring fingers  55  away from the flywheel  20 . Specifically, and similar to the embodiment illustrated in  FIGS. 2 and 3 , when the vehicle operator wishes to disengage the transmission  35  from the engine  15 , hydraulic fluid is pumped into one fluid port  80  (not shown in  FIG. 4 ), and the annular walls  74   a  and  74   b  are forced apart by the hydraulic fluid. Annular wall  74   a  pushes the release face  67  of the thrust bearing  70  against the pull tube hardware  90  (which at this location may be a flange, or ring), while the annular wall  74   b  pushes the release face  67  of the throwout bearing  65  against the mount plate  32 . However, the slave faces  69  of the throwout bearing  65  and thrust bearing  70 , which are connected to the annular walls  74   b , and  74   a , respectively, do not rotate, enabling the annular walls  74   a  and  74   b  to remain substantially rotation-free. As the piston bore  75  fills with hydraulic fluid and pushes the annular walls  74   a  and  74   b  away from each other, the pull tube  85 , which is connected to the pull-tube hardware  90  (which in this embodiment may be a flange, ring, disk or other component) pulls the spring fingers  55  away from the flywheel  20  (shown by arrows in  FIG. 4 ). This causes the floater plates  52  to release the friction disk, or disks  60 . The friction disks  60 , which are connected via a splined center section to the splines (not shown) on the transmission input shaft  40 , are now allowed to cease rotation, or rotate at a revolution  5  different than the engine&#39;s crankshaft  18 . In this manner, a different gear may be selected in the transmission  35 , or the vehicle may become stationary, while the crankshaft  18  continues to rotate.  
         [0040]     Referring now to  FIG. 5 , the pull-tube hardware  90 , as well as the pull-tube  85  do not rotate, as they are insulated from the rotating spring fingers  55  by the throwout bearing  65 . In this embodiment, the throwout bearing  65  is positioned between the diaphragm spring, or spring fingers  55  and the pull-tube hardware  90 . Now, the release face  67  (not shown) of the throwout bearing  65  contacts the pull-tube hardware  90 , and the slave face  69  (not shown) of the throwout bearing  65  contacts the spring fingers  55 . The thrust bearing  70  is now positioned between the slave assembly  45  and the mount plate  32 . The mount plate  32  rotates, but the release face  67  (not shown) of the thrust bearing  70  contacts the mount plate  32 , and the slave face  69  (not shown) of the thrust bearing  70  is attached to the annular wall  74   b  of the slave assembly  45 . The pull-tube hardware  90  (in this embodiment, a flange, ring, disk or other component) rests against the top of the slave assembly  45 , and neither the slave assembly  45  or the pull-tube  85  or pull-tube hardware  90  rotate. As the piston bore  75  (shown in  FIG. 3 ) in the slave assembly  45  fills with hydraulic fluid and pushes the annular walls  74   a  and  74   b  away from each other, the pull-tube hardware  90  at the top, or adjacent to the top of the slave assembly  45  expands away from the clutch  25 , thereby pulling the pull-tube hardware  90  located adjacent to the throwout bearing  65  against the spring fingers  55 , which move away from the flywheel  20  (shown by arrows in  FIG. 5 ). This causes the floater plates  52  to release the friction disk, or disks  60 , which are connected via a splined center section to the splines (not shown) on the transmission input shaft  40 . The transmission input shaft  40  is now allowed to cease rotation, or rotate at a revolution different than the engine&#39;s crankshaft  18 . In this manner, a different gear may be selected in the transmission  35 , or the vehicle may become stationary, while the crankshaft  18  continues to rotate.  
         [0041]     The embodiment illustrated in  FIG. 6  functions similarly to that illustrated in  FIG. 5 , in that the pull-tube hardware  60  and pull-tube assembly  85  do not rotate, but in this embodiment, a spring finger bearing assembly  95  is employed. In this embodiment, the spring finger bearing assembly  95  is positioned between the diaphragm spring tips, or spring finger  55  tips and the pull-tube hardware  90 . That is, the spring finger bearing assembly  95  is oriented so that an outer bearing surface contacts the ends of the spring fingers  55 , and an inner bearing surface contacts the pull-tube  85  allowing relative rotation between the two (thus the rotational axis of this bearing is rotated 90 degrees from the rotational axis of the thrust bearing  70 ). Because the diameter defined by the spring fingers  55  changes as they move, the outer bearing surface contacting the spring fingers  55  is allowed to “float.” This may be accomplished a number of different ways, such as having a bearing surface with two lips or flanges that slideably capture the spring fingers  55  between them.  
         [0042]     Now, the bearing face contacting the spring fingers  55  rotates, but the bearing face contacting the pull-tube  85  does not rotate. Similar to  FIG. 5 , the thrust bearing  70  is now positioned between the slave assembly  45  and the mount plate  32 . The mount plate  32  rotates, but the release face  67  (not shown) of the thrust bearing  70  contacts the mount plate  32 , and the slave face  69  (not shown) of the thrust bearing  70  is attached to the annular wall  74   b  of the slave assembly  45 . The pull-tube hardware  90  (in this embodiment, a flange, ring, disk or other component) rests against the top, or adjacent to the top of the slave assembly  45 , and neither the slave assembly  45  or the pull-tube  85  or pull-tube hardware  90  rotate. As the piston bore  75  (shown in  FIG. 3 ) in the slave assembly  45  fills with hydraulic fluid and pushes the annular walls  74   a  and  74   b  away from each other, the pull-tube hardware  90  at the top of the slave assembly  45  expands away from the clutch  25 , thereby pulling the pull-tube hardware  90  and the spring finger bearing assembly  95  against the spring fingers  55 , which move away from the flywheel  20  (shown by arrows in  FIG. 6 ). This causes the floater plates  52  to release the friction disk, or disks  60 , which are connected via a splined center section to the splines (not shown) on the transmission input shaft  40 . The transmission input shaft  40  is now allowed to cease rotation, or rotate at a revolution different than the engine&#39;s crankshaft  18 . In this manner, a different gear may be selected in the transmission  35 , or the vehicle may become stationary, while the crankshaft  18  continues to rotate.  
         [0043]     The embodiments discussed above, and illustrated in  FIGS. 4-6 , of the present invention eliminates the clutch fork, clutch fork mount, and related components used to actuate the clutch fork found on semi-tractors and other trucks, and passenger automobiles. A substantial cost, and weight savings is realized, along with a decrease in maintenance costs.  
         [0044]     In the embodiments illustrated in  FIGS. 4-6 , the pull-tube hardware  90  may be flanges, rings, clips, disks and other components that are well known in the art. For example, the pull-tube  85  may comprise a splined, or un-splined tube that may be integrally constructed with the pull tube hardware  90 . Alternatively, the pull-tube hardware  90  may be separate from the pull-tube  85 , and during construction, the pull-tube hardware  90  may be attached to the pull-tube  85 . For example, as is well known in the art, the pull-tube  85  may be a splined tube, or other arrangement, which is attached to the pull-tube hardware  90  by use of a snap-ring seated in a slot (not shown), within the pull tube  85 . The embodiments illustrated in  FIGS. 4-6  may use any type of pull-tube hardware  90 , and pull-tube  85 , regardless of its specific configuration, as pull-tube hardware  90 , and pull-tubes  85  are well known in the art.  
         [0045]     Similarly, many different pull-type pressure plate  50  and clutch  25  arrangements exist. For example, a pull-type pressure plate  50  and clutch  25  arrangement for a semi-tractor may vary significantly from one used for passenger vehicles. The present invention is not limited to the pull-type pressure plate  50  and clutch  25  arrangement illustrated in the Figures, but may be employed by any type of pull-type pressure plate  50  and clutch  25  arrangement.  
         [0046]     For the purposes of interpreting words used in the claims, it is to be noticed that the term “comprising”, should not be interpreted as being limitative to the claim elements listed thereafter. Thus, the scope of the expression “a device comprising elements A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.  
         [0047]     Similarly, it is to be noticed that the term “coupled”, also used in the claims, should not be interpreted as meaning attached or joined together, but not limitative to direct connections only. Thus, the scope of the expression “an element A coupled to an element B” should not be limited to devices or systems wherein element A is directly connected to element B. It means that there exists a path between A and B which may be a path including other elements or means. In addition, when element A is “coupled” to element B, relative motion may be allowed between element A and element B.  
         [0048]     Thus, it is seen that a clutch actuation method and apparatus is provided. One skilled in the art will appreciate that the present invention can be practiced by other than the above-described embodiments, which are presented in this description for purposes of illustration and not of limitation. The specification and drawings are not intended to limit the exclusionary scope of this patent document. It is noted that various equivalents for the particular embodiments discussed in this description may practice the invention as well. That is, while the present invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims. The fact that a product, process or method exhibits differences from one or more of the above-described exemplary embodiments does not mean that the product or process is outside the scope (literal scope and/or other legally-recognized scope) of the following claims.