Abstract:
A clutch system may include in certain embodiments a clutch body attached to a drive member such as a drive pulley, wherein the clutch body may be removed from the drive member without disassembling the clutch body. In various embodiments, the clutch body may include two clutch plates which enclose a spring-loaded pneumatic reciprocating assembly that in operation causes the plates to selectively separate and engage one another. In certain embodiments, the clutch body may be readily attached to a associated drive pulley in a single step by installation of a single set of fasteners.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. application Ser. No. 11/289,010 (now U.S. Pat. No. 7,438,169), filed on Nov. 29, 2005, entitled “Clutch System,” which is a continuation-in-part of U.S. application Ser. No. 10/970,356 (now U.S. Pat. No. 7,104,382) filed on Oct. 21, 2004, entitled “Clutch System,” the entire contents of which are incorporated herein by reference. 

   TECHNICAL FIELD 
   This document relates to a rotational control apparatus, and certain embodiments relate more particularly to a clutch apparatus. 
   BACKGROUND 
   Vehicle transmission systems, cooling systems, and braking systems often use clutches or like devices to selectively transmit rotational forces from a drive shaft to an output member. Conventional clutch devices include an opposing pair of engagement surfaces that can be compelled toward or away from one another using an electrical, mechanical, pneumatic, or hydraulic actuation system. In general, the actuation system causes some relative axial shifting within the clutch device. Such axial movement is used engage (or disengage) the opposing engagement surfaces, which rotationally interconnects (or rotationally disconnects) the drive shaft and the output member. 
   In clutch devices using pneumatic or hydraulic actuated systems, a piston may be acted upon by a set of springs to bias the piston toward one of the engaged or disengaged positions. Fluid pressure may act upon the piston, in a direction opposite to that of the spring force, to cause the piston portion to be axially shifted. Such axial movement is used engage (or disengage) the opposing engagement surfaces, thus selectively controlling the rotation between the drive shaft and the output member. 
   Clutch devices may require repair or replacement if the engagement surfaces have worn beyond their useful life or if a component is not properly functioning. For instance, seals and clutch engagement surfaces may wear over time and require replacement. 
   The design of the clutch device can have a significant effect on the time and cost of repair or replacement of component parts. If a clutch device has multiple pieces that must be disassembled before the clutch device can be removed from the drive shaft, the labor costs associated with the repair or replacement of the clutch device may increase. In addition, if a clutch device includes components that are spring biased, extra tooling may be required to clamp those components in place as clutch device is disassembled or removed. 
   The location and number of seals such as O-rings in the clutch device may also affect the time and cost associated with repairing or replacing clutch devices. If a seal fails and starts to leak, the time required to locate which particular seal is broken may increase if the clutch device has a larger number of seals. Furthermore, the location of the seals may affect the likelihood of contaminants entering the fluid space. If a seal is disposed between two surfaces that move both axially and rotationally relative to one another, the seal may be more susceptible to leakage. 
   The longevity of the clutch device, and thus the repair interval, may be increased by reducing wear factors such as vibration. Clutch designs built with more liberal tolerances and clutch designs that allow greater degrees of inter-part vibration may have a shorter useful life. 
   SUMMARY 
   A clutch system may include in certain embodiments a clutch body attached to a drive member such as a drive pulley, wherein the clutch body may be removed from the drive member without disassembling the clutch body. In various embodiments, the clutch body may include two clutch plates which enclose a spring-loaded pneumatic reciprocating assembly that in operation causes the plates to selectively separate and engage one another. In certain embodiments, the clutch body may be readily attached to a associated drive pulley in a single step by installation of a single set of fasteners. 
   In some embodiments, a rotation control apparatus may include a clutch member removably mounted to a drive pulley. The clutch member may have a hub portion and a piston portion. The hub portion may be selectively movable in a rotational direction relative to the drive pulley and substantially stationary in an axial direction relative to the drive pulley. The piston portion may be selectively movable in the axial direction relative to the hub portion and substantially stationary in the rotational direction relative to the hub portion. The clutch member may be removable from the drive pulley while the hub portion remains assembled with the piston portion. 
   In another embodiment, a rotational control apparatus includes a drive member rotatably mounted on a support shaft. The drive member may have a first engagement surface. A clutch member may be removably mounted to the drive member. The clutch member may comprise a piston portion assembled with a hub portion. The piston portion may be selectively movable in an axial direction relative to the hub portion and substantially stationary in a rotational direction relative. The piston portion may have a second engagement surface to selectively contact the first engagement surface. The clutch member may further include a channel in fluid communication with the piston portion, and a biasing member to urge the second engagement surface against the first engagement surface. The clutch member may be removable from the drive member while the hub portion remains assembled with the piston portion. 
   In some embodiments, a clutch member may include an engagement surface that at least partially extends in a nonradial direction. For example, the clutch member may include a frusto-conical engagement surface to selectively interface with clutch material. Particular embodiments may include a clutch device for removably mounting to a drive member. The clutch device may include a frusto-conical clutch ring, which may have an increasingly larger radius as the engagement surface extends away the driver member when the clutch device is mounted to the drive member. 
   These and other embodiments may be configured to provide one or more of the following advantages. First, the clutch member may be readily removed from the drive member upon removal of a single set of fasteners. Second, the clutch member may have a self-contained configuration that eliminates the need for additional clamps or tooling when removing the clutch member from the drive member. Third, the clutch member may have a reduced number of seals and leakage paths, thus reducing the number of seals along the periphery of the fluid-receiving chamber. Fourth, the seal member along the periphery of the fluid-receiving chamber may not rotate relative to an adjacent part, which may in turn improve seal quality and reduce the likelihood of contamination in the fluid system. Fifth, the clutch member may have a fluid-receiving chamber that is wholly within the removable clutch member, which may also reduce the likelihood of contamination in the fluid system. Sixth, a spline connection in the clutch member may reduce vibration between internal components of the clutch member. Seventh, the clutch member may use a single spring to urge the piston portion toward an engaged (or disengaged) position, which may simplify the assembly process during manufacture and repair. Some or all of these and other advantages may be provided by the clutch systems described herein. 
   The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is an exploded cross-sectional view of a rotational control apparatus in accordance with certain embodiments of the invention. 
       FIG. 2  is another exploded cross-sectional view of a rotational control apparatus of  FIG. 1 . 
       FIG. 3  is a cross-sectional side view of the rotational control apparatus  FIG. 1 . 
       FIG. 4  is another cross-sectional side view of the rotational control apparatus of  FIG. 1 . 
       FIG. 5  is an exploded cross-sectional view of a rotational control apparatus in accordance with certain embodiments of the invention. 
       FIG. 6  is a cross-sectional side view of the rotational control apparatus  FIG. 5 . 
       FIG. 7  is another cross-sectional side view of the rotational control apparatus of  FIG. 5 . 
   

   Like reference symbols in the various drawings indicate like elements. 
   DETAILED DESCRIPTION 
   A number of embodiments of the invention include a rotational control apparatus that provides simplified repair or replacement. A rotation control apparatus may include a clutch member that is removably mounted to a drive member. In some embodiments, the clutch member may be removed from the drive member without disassembly of the clutch member&#39;s component parts. 
   Referring to  FIGS. 1-2 , a drive member  100  is rotatably coupled to a support member  115  by one or more bearings  120 . A nut or collar device  116  is secured to the support member  115  and is abutted to the bearing  120  so that the bearings  120  remain substantially fixed in the axial direction relative to the support member  115 . The drive member  100  receives one or more drive inputs, such as belts, chains, gears or the like, to force the drive member  100  to rotate in a particular direction about an axis  105 . In this embodiment, the support member  115  is a substantially stationary shaft, and the drive member  100  is illustrated as a drive pulley that includes an input portion  102 . Rotational power from a motor or the like may be transmitted through one or more drive inputs (not shown in  FIGS. 1-2 ) to the input portion  102 , thus causing the drive pulley  100  to rotate about the central axis  105  of the support shaft  115 . 
   A fluid supply input  150  extends into the support member  115  for connection to a fluid supply reservoir (not shown in  FIGS. 1-2 ). A supply channel  152  extends from the fluid supply input  150  in a substantially axial direction along the central axis  105 . In this embodiment, the supply channel  152  extends through a cylindrical outlet  160 , which has a mating end  162  to mate with a face seal  260  of the clutch member  200 . The outlet  160  may also include a spacer  164  that fits into a shoulder  117  of the support member  115 , thereby aligning the outlet  160  with the central axis  105 . 
   Still referring to  FIGS. 1-2 , the outlet  160  has an insert end  161  that is fit into a biasing member  163 . The biasing member  163  of the outlet  160  is fit into an axial cavity  116  of the support member  115 . The biasing member  163  may be a spring or block of elastic material that biases the mating end  162  in a substantially axial direction toward the face seal  260 . As such, when the clutch member  200  is mounted to the drive member  100  (see, for example,  FIG. 3 ), the mating end  162  is pressed against the face seal  260  to form a mechanical seal. Accordingly, the fluid may be transmitted from the fluid supply input  150  through the outlet  160  and the face seal  260  to the fluid-receiving chamber  264  of the clutch member  200 . In some embodiments, the mating end  162 , the face seal  260 , or both may comprise metals, polymers, or composite materials that can substantially maintain the mechanical seal therebetween while the clutch member  200  is selectively rotated relative to the support member  115 . In one example, the mating end  162  and the face seal  260  comprise a hardened, polished steel material. This configuration of the mechanical seal between the mating end  162  and the face seal  260  may eliminate the need for a cap member that is fit over the mating end  162  and extends to the inner circumference of the drive pulley  100  so as to seal the radial area inside the drive pulley  100  and retain a face seal  260 . 
   The fluid transmitted to the fluid-receiving chamber  264  of the clutch member  200  may be any suitable liquid or gas, as described in more detail below. Such fluids may be received, for example, from a pneumatic air supply system or a hydraulic oil supply system. 
   Referring more closely to  FIG. 1 , the clutch member  200  is removably mounted to the drive pulley  100 . A fluid channel  262  extending axially through the face seal  260  is substantially axially aligned with the central axis  105 . In this embodiment, the clutch member  200  is removably mounted to the drive pulley  100  using bolts  110  that screw into threaded cavities  112  in the drive pulley  100 . Alternatively, clamps may be used to removably couple the clutch member  200  to the drive member  100 . 
   Such a configuration of the clutch member  200  may permit the clutch member  200  to be readily removed from the drive pulley  100 . The clutch member  200  may be removed and/or replaced in a single operation by removing a single set of bolts  110 . This configuration may obviate the need to disassemble parts of the clutch member  200  during a replacement or repair operation. Moreover, the clutch member  200  in certain configurations may lessens or eliminates the need for additional clamps or tooling when removing the clutch member  200  from the drive member  100 , as described in more detail below. Accordingly, the time and costs associated with the repair or replacement of the clutch member  200  may be significantly reduced. 
   Referring again to  FIGS. 1-2 , the clutch member  200  includes a piston portion  220  that is movably assembled with a hub portion  240 . The piston portion  220  is movable in an axial direction relative to the hub portion  240  and is substantially stationary in a rotation direction relative to the hub portion  240 . In this embodiment, the motion of the piston portion  220  relative to the hub portion  240  is accomplished by way of a spline connection. The piston portion  220  includes a first spline member  224  that is substantially mated with a second spline member  244  of the hub portion  240 . The splines  226  of the first spline member  224  are complimentary to the splines  246  of the second spline member  244  such that the spline members  224  and  244  are slidable relative to one another in an axial direction and are substantially stationary relative to one another in a rotational direction. In other embodiments, the motion of the piston portion  220  relative to the hub portion  240  may be accomplished using one or more bushings that permit relative axial movement and anti-rotation dowels that substantially prevent relative rotation between the piston portion  220  and the hub  240 . 
   In the embodiment depicted in  FIGS. 1-2 , the piston portion  220  includes an output member  222 , the first spline member  224 , and a spring-engaging member  226 . The spring-engaging member  226  has a radially extending surface  227  that abuts with a spring  280 . The spring-engaging member  226  is fixedly coupled to the output member  222 , for example, by bolts  228  screwed into threaded cavities  223  in the output member  222 . The first spline member  224  is fixedly coupled to an output member  222 , for example, by threads on an external surface  225  of the first spline member  224  that are mated into a threaded cavity  221  of the output member  222 . Alternatively, the first spline member  224  may be fixedly coupled to an output member  222 , for example, by bolts screwed into threaded cavities in the output member  222 . The output member  222  includes studs  230  that are configured to receive an output device, such as fan blades (not shown in  FIGS. 1-2 ). Accordingly, the clutch member  200  may engage the drive pulley  100  so that the output member  222  rotates with the drive pulley  200  to spin the fan blades. In such embodiments, the piston portion  220  of the clutch member  200  may have a dual function to selectively engage the drive pulley  100  and to act as the output for the rotational motion. The studs  230  may be mounted into cavities  231  in the output member  222 . In the presently preferred embodiment, the cavities  231  do not extend completely through the output member  222 , thereby obviating the need for additional seals between the studs  230  and the fluid-receiving chamber  264 . In other embodiments, the studs  230  may be threaded bolts that are inserted through threaded apertures in the output member  222  and extend forward of the output member  222 . 
   Still referring to  FIGS. 1-2 , the hub portion  240  includes a hub  242  and the second spline member  244 . The second spline member  244  is fixedly coupled to the hub  242 , for example, by threads on an external surface  245  of the second spline member  244  that are mated into a threaded cavity  243  of the hub  242 . Alternatively, the second spline member  244  may be fixedly coupled to the hub  242 , for example, by bolts screwed into threaded cavities in the hub  242 . The hub  242  includes a cavity  248  configured to receive at least a portion of the face seal  260 , and the fluid channel  262  extends axially along the central axis  105  through both the hub  242  and the second spline member  244 . The face seal  260  may include threads on an external surface  261  that mate with the cavity  248  of the hub  242 . In an alternative embodiment, the threaded cavity  243  may extend completely through the hub  242  such that the second spline member  244  mates with the face seal  260 . In such an embodiment, the face seal  260  may mate with a cavity in the second spline member  244  similar to the cavity  248  in the hub  242 . 
   At least one bearing  270  is disposed between the hub  242  and a fixed plate  275 . The fixed plate  275  is mounted to the drive pulley  100  using the bolts  110  that are positioned through apertures  276  and screwed into cavities  112 . As such, the fixed plate  275  is secured to the drive pulley  100  and rotates along with the drive pulley. The bearing  270  permits the hub portion  240  (including the hub  242 ) to rotate independently of the fixed plate  275  and the drive pulley  100 . In this embodiment, the bearing  270  is disposed along an outer circumferential surface  241  of the hub  242 . The bearing  270  may be secured to the hub  242  and the fixed plate  275  using any number of securing means, such as collar devices, locking nuts, locking rings, tongue and groove arrangements, or the like. In this embodiment, the bearing  270  is secured to the hub  242  using a locking nut  271  so that the bearing  270  remains substantially stationary relative to the hub  242  in the axial direction. The bearing  270  is secured to the fixed plate  275  using a locking ring  271  such that the bearing  270  remains substantially stationary relative to the fixed plate  275  in the axial direction. As such, the hub portion  240  may rotate independently of the fixed plate  275  and drive pulley  100 , but the hub portion  240  remains substantially stationary in the axial direction relative to the fixed plate  275  and drive pulley  100 . 
   Still referring to  FIGS. 1-2 , the hub  242  includes a spring-engaging surface  247  that abuts with the spring  280 . In this embodiment, the spring  280  is a single, coiled spring that has an inner and outer diameter to fit securely within the spring-engaging member  226  of the piston portion  220 . Using only a single spring may simplify assembly and disassembly of the clutch member  200  during manufacture or repair. Because only one spring must be placed in the spring-engaging member  226 , less time is required to properly align the spring  280  during assembly. Alternatively, other embodiments may use a more complex arrangement having a greater number of smaller springs that are positioned adjacent one another within the spring-engaging member  226  of the piston portion  220 . 
   When the clutch member  200  is assembled as shown in  FIG. 1 , the spring  280  is compressed between the spring-engaging surface  227  of the piston portion  220  and the spring engaging surface  247  of the hub portion  240 . Such an arrangement urges the piston portion  220  in an axial direction toward the drive pulley  100 . Thus, in this embodiment, the spring  280  biases the piston portion  220  such that an engagement surface  237  of the piston portion  220  is urged against a clutch material  277 , which is mounted to the drive pulley  100  using the bolts  110 . When the engagement surface  237  presses against the clutch material  277 , the clutch member  200  engages the drive pulley  100 , and the piston portion  220  and the hub portion  240  rotate with the drive pulley  100 . 
   Still referring to  FIGS. 1-2 , the clutch member  200  may disengage the drive pulley  100  when fluid is introduced into the chamber  264  under sufficient pressure to axially shift the piston portion  220  relative to the hub portion  240 . When the engagement surface  237  is shifted away from the clutch material  277  (see, for example,  FIG. 4 ), the piston portion  220  and the hub portion  240  are no longer driven by the rotation of the drive pulley  100  and are free to independently rotate (or stop rotating) via the bearing connection  270 . As previously described, fluid may enter the chamber  264  through the fluid channel  262 . In this embodiment, the fluid-receiving chamber  264  is at least partially defined by the space between the output member  222  and the hub  242 . The fluid may pass through small gaps in the spline connection between the first spline member  224  and the second spline member  244 . When a predetermined amount of fluid pressure has built up in the chamber  264 , the output member  222  is forced in an axial forward direction away from the drive pulley  100 , thus overcoming the bias of the spring  280  to urge the piston portion  220  toward the drive pulley  100 . 
   Still referring to  FIGS. 1-2 , the fluid-receiving chamber  264  is disposed internally in the clutch member  200 . In this embodiment, the fluid in the chamber  264  may have only one possible leak path, which is along the circumferential surface  249  of the hub  242 . A seal  290  is disposed along the periphery of the leak path between the circumferential surface  249  of the hub  242  and the output member  220 . The seal  290  is positioned as such to prevent fluid leakage through the leak path. Thus, a fluid leak may be quickly detected and repaired by checking the seal  290  at the circumferential surface  249  and by checking the mechanical seal at the face seal  260 . By reducing the number of seals in the clutch member design, the time and cost associated with detecting which seal is faulty may be significantly reduced. 
   In this embodiment, the seal  290  for the fluid-receiving chamber  264  is internal to the clutch member  220  and is disposed between two surfaces that do not rotate relative to one another about the central axis  105 . As previously described, the piston portion  220  may shift in the axial direction relative to the hub portion  240 , so the seal may endure a sliding motion between the circumferential surface  249  and the output member  222 . The piston portion  220  remains substantially stationary relative to the hub portion  240  in the rotational direction, so the seal  290  does not endure a rotational motion. When the seal  290  is internal to the clutch member  200  and is limited to such minimal sliding motion, the possibility of contaminants entering the chamber  264  through the seal  290  may be significantly reduced. Such a reduction is contamination may increase the longevity the clutch member  200  and may reduce the need for repair or replacement. 
   Referring to  FIGS. 1-2 , a wiper seal  291  may also be disposed between the circumferential surface  249  of the hub portion  240  and the output member  222  of the piston portion  220 . In this embodiment, the wiper  291  may slide in an axial direction when the piston portion  220  shifts relative to the hub portion  240 . The wiper  291  is positioned against the circumferential surface  249  so as to prevent or limit any contaminants that may pass into the fluid-receiving chamber. The wiper  291 , the seal  290 , or both may comprise a material that is suitable to endure the sliding motion while limiting the flow of fluid or contaminants. Such suitable materials may include polymers, rubber materials, composite materials, or the like. Depending on the manufacturing tolerances of the piston portion  220  and the hub portion  240 , a guide band (not shown in  FIGS. 1-2 ) may be disposed between the circumferential surface  249  and the output member  222  to prevent excess metal-on-metal contact between the circumferential surface  249  and the output member  222 . If such a guide band is implemented, the guide band is preferably disposed between the seal  290  and the wiper  291 . 
   Referring more specifically now to  FIG. 1 , the clutch member  200  may have a self-contained construction such that the components of clutch member  200  (e.g., the piston portion  220 , the hub portion  240 , the spring  280 , and so forth) remain in an assembled state even after the clutch member is removed from the drive pulley  100 . In the embodiment shown in  FIG. 1 , the clutch member  200  may be removed from the drive pulley  100  by removing the bolts  110  from the mounting cavities  112 . Removing these bolts  110 , however, does not permit the internal spring to move the components of the clutch member  200  apart from another and thereby cause disassembly of the clutch member  200  (e.g., the spring  280  is not be free to unexpectedly expand and separate the components when a worker attempts to remove the clutch member  200  from the drive pulley  100 ). The locking nut  272 , locking ring  271 , and other such devices may be subsequently removed to disassemble the clutch member  200  at the appropriate time. Accordingly, the clutch member  200  may be removed from the drive pulley  100  without the use of clamps or extra tooling to retain the clutch member  200  in its assembled position. 
   In operation, the clutch member  200  may selectively engage the drive member  100  so that the rotation of the output member  222  is controlled. As previously described, the depicted embodiment of the clutch member  200  may disengage the drive pulley  100  when fluid is introduced into the chamber  264  under sufficient pressure to axially shift the piston portion  220  relative to the hub portion  240 . When the engagement surface  237  is shifted away from the clutch material  277 , the piston portion  220  and the hub portion  240  are no longer driven by the rotation of the drive pulley  100  and are free to independently rotate (or stop rotating) via the bearing connection  270 . 
   Referring now to  FIG. 3 , the clutch member  200  is mounted to the drive pulley  100  and the piston portion  220  is shown in an engaged position. In this embodiment, the spring  280  is disposed between the hub portion  240  and the piston portion  220  such that the spring  280  urges the piston portion  220  in a rearward axial direction toward the drive pulley  100 . The engagement surface  237  of the piston portion  220  is pressed against the clutch material  277 , which is mounted to the drive pulley  100 . The engagement surface  237  is urged against the clutch material  277  with sufficient force so that the piston portion  220  rotates along with the clutch material  277 , which is mounted to the drive pulley  100 . As such, the output member  222  of the piston portion  220  rotates substantially synchronously with the rotation of the drive pulley  100  about the central axis  105 . When the piston portion  220  is in the engaged position, the output device (such as a fan) that is mounted to the studs  230  of the output member  222  also rotates with the drive pulley  100 . Although the hub portion  240  is not directly engaged with the drive pulley  100  or the clutch material  277 , the hub portion  240  rotates with the piston portion  220  due to the spline connection between first and second spline members  224  and  244 . Such a configuration limits the wear on the seal  290  because the seal  290  does not endure rotational motion between the hub  242  and the output member  222 . 
   Referring now to  FIG. 4 , the piston portion  220  is shifted forward in the axial direction away from the drive pulley  100  such that the piston is in a disengaged position. In this embodiment, the engagement surface  237  of the piston portion  220  is spaced from the clutch material  277  by an offset  300 . This offset  300  causes the piston portion  220  to disengage with the clutch material  277  so that the rotational motion from the drive pulley  100  is not transferred to the output member  222 . When the piston portion  220  is in the disengaged position, the piston portion  220  and hub portion  240  are free to rotate independently from the drive pulley  100  due to the bearing connection  270 . Accordingly, the piston portion  220  and the hub portion  240  may stop rotating even though the drive pulley  100  continues to rotate. 
   Referring to  FIGS. 3-4 , the offset  300  of the piston portion  220  occurs when a fluid under sufficient pressure is received in the chamber  264 . If force from the fluid pressure in the chamber  264  is sufficient to overcome the force of the spring  280 , the output member  220  (and the entire piston portion  220 ) is shifted forward in the axial direction. In some embodiments, the fluid pressure that is required to overcome the spring force may be approximately predetermined from the spring constant, the desired offset  300 , the dimensions of the chamber  264 , and other such factors. As previously described, the fluid supply input  150  receives the fluid from the reservoir (not shown in  FIGS. 3-4 ). The fluid passes through the fluid supply channel  152 , through the outlet  160  and the face seal  260 , through the fluid channel  262 , and into the chamber  264 . The mechanical seal at the face seal  260  assures that the fluid properly reaches the chamber  264 , and when the fluid is in the chamber  264 , the seal  290  prevents the fluid from passing through the potential leak path along the circumferential surface  249  ( FIG. 2 ). 
   In this embodiment of the clutch member  200  depicted in  FIGS. 3-4 , the piston portion  220  serves as both the portion that engages the drive pulley  100  (via the clutch material  277 ) and the portion that receives an output device (such as a fan). The output device mounted to the studs  230  of the piston portion  220  may also be shifted in the axial direction as the piston portion  220  is shifted, but the offset  300  in the axial direction may be relatively small such that this shifting motion has little or no impact on the output device. Similarly, the offset  300  in the axial direction may be relatively small such that the shifting motion of the output member  222  relative to the hub  242  has little or no impact on the longevity and performance of the seal  290  and the wiper  291 . It should be understood that the displacement between the clutch material  277  and the engagement surface  237  may change slightly as the clutch material  277  is worn away through normal use. 
   In another embodiment of the invention, the drive member  100  may have a configuration other than a drive pulley shown in  FIGS. 1-4 . For example, the drive member  100  may be a shaft or gear that is powered by a motor. In such embodiments, the clutch member  200  may have a mounting configuration to removably attach to the shaft or gear or may have an adapter member connected therebetween. 
   In other embodiments, the output member  222  of the clutch member  200  may be configured to receive an output device other than fan blades. For example, the output member  222  may be configured to connect with other components that are to be selectively rotated, such as output shafts, gears, brake systems, and the like. 
   In yet another embodiment, the spring  280  that biases the piston portion  220  in an axial direction is not limited to a single, coiled spring shown in  FIGS. 1-4 . Rather, the spring  280  can be any biasing member that can urge the piston portion  220  in the axial direction. A suitable biasing member may comprise one or more coil springs, leaf springs, gas springs, solid materials having appropriate elasticity properties, or the like. 
   Furthermore, some embodiments of the invention may include a clutch member configuration such that spring  280  urges the piston portion  220  to disengaged position (where the engagement surface  237  is offset from the clutch material  277 ). In such embodiments, the chamber  264  may be configured such that fluid pressure therein causes the piston portion  220  to shift toward engaged position (where the engagement surface  237  is pressed against the clutch material  277 ). 
   In other embodiments, the clutch material  277  may be integral with the fixed plate  275  or the drive member  100 . In these embodiments, the engagement surface  237  of the piston portion  220  would engage with an opposing surface on the fixed plate  275  of the drive member  100 . 
   In another embodiment, the clutch material may be mounted to the piston portion  220  such that the clutch material selectively engages with an opposing surface (e.g., the clutch material  277 , the fixed plate  275  or the drive member  100 ). In such an embodiment, an engagement surface on the clutch material would contact the opposing surface. 
   Referring to  FIGS. 5-7 , some embodiments of a clutch member  600  may include an engagement surface  637  that at least partially extends in a nonradial direction. For example, a clutch member  600  may include a frusto-conical interface between the clutch material and the engagement surface. In this embodiment, a frusto-conical clutch ring  677  may selectively engage a frusto-conical surface  637 . The frusto-conical engagement surface  637  has a first radius  639  and a second radius  641 , with the first radius  639  being axially closer to drive member  500 . In this embodiment, the first radius  639  is smaller than the second radius  641 . As such, the frusto-conical clutch ring  677  may have an increasingly larger radius as the engagement surface extends away from the drive member  500  when the clutch member  600  is mounted to the drive member  500 . 
   Similar to some previously described embodiments, the drive member  500  can be rotatably coupled to a support member  515  by one or more bearings  520 . The drive member  500  receives one or more drive inputs, such as belts, chains, gears or the like, to force the drive member  500  to rotate in a particular direction about an axis  505 . In this embodiment, the support member  515  is a substantially stationary shaft, and the drive member  500  is illustrated as a drive pulley that includes an input portion  502 . 
   A fluid supply input  550  extends into the support member  515  for connection to a fluid supply reservoir (not shown in  FIGS. 5-7 ). A supply channel  552  may extend from the fluid supply input  550  in a substantially axial direction along the central axis  505 . In this embodiment, the supply channel  552  mates with a face seal  660  of the clutch member  600 . When the clutch member  600  is mounted to the drive member  500  (see, for example,  FIG. 6 ), the supply channel  552  is pressed against the face seal  660  to form a mechanical seal. Accordingly, the fluid may be transmitted from the fluid supply input  550 , through a fluid channel  662 , and to the fluid-receiving chamber  664  of the clutch member  600 . 
   Referring to  FIG. 5 , the clutch member  600  may be removably mounted to the drive member  500 . In this embodiment, the clutch member  600  is removably mounted to the drive member  500  using bolts  510  that screw into threaded cavities  512  in the drive member  500 . In another embodiment, clamps may be used to removably couple the clutch member  600  to the drive member  500 . 
   Such a configuration of the clutch member  600  may permit the clutch member  600  to be readily removed from the drive member  500 . The clutch member  600  may be removed and/or replaced in a single operation by removing a single set of bolts  510 . Similar to some previously described embodiments, this configuration may obviate the need to disassemble parts of the clutch member  600  during a replacement or repair operation. 
   Still referring to  FIG. 5 , the clutch member  600  includes a piston portion  620  that is movably assembled with a hub portion  640 . The piston portion  620  is movable in an axial direction relative to the hub portion  640  and is substantially stationary in a rotation direction relative to the hub portion  640 . Similar to some previously described embodiments, the motion of the piston portion  620  relative to the hub portion  640  may be accomplished by way of a spline connection. The piston portion  620  includes a first spline member  624  that may be substantially mated with a second spline member  644  of the hub portion  640 . 
   The piston portion  620  includes studs  630  that are configured to receive an output device, such as fan blades (not shown in  FIGS. 5-7 ). Accordingly, the clutch member  600  may engage the drive member  500  so that the piston portion  620  rotates with the drive member  500  to spin the fan blades. In such embodiments, the piston portion  620  of the clutch member  600  may have a dual function to selectively engage the drive member  500  and to act as the output for the rotational motion. 
   In this embodiment, the hub portion  640  includes a hub  642  and the second spline member  644 . The hub  642  includes a cavity  648  configured to receive at least a portion of the face seal  660 , and the fluid channel  662  extends axially along the central axis  505  through both the hub  642  and the second spline member  644 . Similar to some previously described embodiments, a seal  690  may be disposed along the periphery of the leak path between hub  642  and the output member  620 . The seal  690  is positioned as such to prevent fluid leakage through the leak path. Thus, a fluid leak may be quickly detected and repaired by checking the seal  690  at the circumferential surface and by checking the mechanical seal at the face seal  660 . By reducing the number of seals in the clutch member design, the time and cost associated with detecting which seal is faulty may be significantly reduced. Similar to some previously described embodiments, the clutch member  600  may optionally include a wiper seal  691 . The wiper seal  691  may prevent migration of contaminants toward the seal  690  that actually borders the fluid receiving chamber  664 . 
   At least one bearing  670  may be disposed between the hub  642  and a fixed plate  675 . The fixed plate  675  may be removably mounted to the drive member  500  using the bolts  510  that are positioned through apertures  676  and screwed into cavities  512 . As such, the fixed plate  675  can be secured to the drive member  500  and rotates along with the drive member  500 . The bearing  670  permits the hub  642  to rotate independently of the fixed plate  675  and independently of the drive member  500 . In this embodiment, the bearing  670  may be secured to the hub  642  using a locking nut  672  so that the bearing  670  remains substantially stationary relative to the hub  642  in the axial direction. The bearing  670  may be secured to the fixed plate  675  using a locking ring  671  such that the bearing  670  remains substantially stationary relative to the fixed plate  675  in the axial direction. As such, the hub  642  may rotate independently of the fixed plate  675  and independently of the drive member  500 , but the hub  642  remains substantially stationary in the axial direction relative to the fixed plate  675  and drive member  500 . 
   Still referring to  FIG. 5 , the hub  642  includes a spring-engaging surface  647  that abuts with a biasing member, such as a spring  680 . In this embodiment, the spring  680  is a single, coiled spring that has an inner and outer diameter to fit securely within the spring-engaging member  626  of the piston portion  620 . 
   When the clutch member  600  is assembled as shown in  FIG. 5 , the spring  680  may be compressed between the spring-engaging surface  627  of the piston portion  620  and the spring engaging surface  647  of the hub  642 . Such an arrangement urges the piston portion  620  in an axial direction toward the drive member  500 . Thus, in this embodiment, the spring  680  biases the piston portion  620  such that the frusto-conical clutch ring  677  (mounted to the piston portion  620  in this embodiment) is urged against the frusto-conical engagement surface  637  of the fixed plate  675 , which is mounted to the drive member  500  using the bolts  510 . When the frusto-conical clutch ring  677  of the piston portion  620  presses against the frusto-conical engagement surface  637  of the fixed plate  675 , the piston portion  620  engages the fixed plate  675 , and the piston portion  620  rotates with the drive member  500 . The clutch ring  677  may comprises a metallic, ceramic or other material that is capable of providing frictional engagement and is capable of dissipating heat generated at the frictional interface. For example, some embodiments of the clutch ring  677  may comprise a material having a static coefficient or friction in the range of approximately 0.2 to approximately 0.6 and, in particular embodiments, may comprises a material having a static coefficient of friction in the range of approximately 0.4 to approximately 0.5. 
   Still referring to  FIG. 5 , the piston portion  620  may disengage the hub  642  when fluid is introduced into the chamber  664  under sufficient pressure to axially shift the piston portion  620  relative to the hub portion  640 . Such an axial shift of the piston portion  620  may cause the frusto-conical clutch ring  677  to disengage the opposing engagement surface (e.g., the engagement surface  637  of the fixed plate  675  in this embodiment). In such circumstances, the piston portion  620  may not be driven by the rotation of the drive member  500  so that the piston portion  620  is free to independently rotate (or stop rotating) due to the bearing connection  670 . 
   In this embodiment, the fluid-receiving chamber  664  is at least partially defined by the space between the output member  622  and the hub  642 . In some embodiments, the fluid may pass through small gaps in the spline connection between the first spline member  624  and the second spline member  644 . When a predetermined amount of fluid pressure has built up in the chamber  664 , the output member  622  is forced in an axial forward direction away from the hub  642 , thus overcoming the bias of the spring  680  to urge the piston portion  620  in the axial forward direction. 
   Similar to some previously described embodiments, the clutch member  600  may have a self-contained construction such that the components of clutch member  600  (e.g., the piston portion  620 , the hub portion  640 , the spring  680 , the frusto-conical clutch ring  677 , and so forth) remain in an assembled state even after the clutch member  600  is removed from the drive member  500 . In the embodiment shown in  FIG. 5 , the clutch member  600  may be removed from the drive member  500  by removing the bolts  510  from the mounting cavities  512 . 
   Referring now to  FIGS. 6-7 , the clutch member  600  may be operated to selectively engage the drive member  500  so that the rotation of the output member  622  is controlled. As previously described, the depicted embodiment of the clutch member  600  may disengage the drive member  500  when fluid is introduced into the chamber  664  under sufficient pressure to axially shift the piston portion  620  relative to the hub portion  640 . When the frusto-conical clutch ring  677  is shifted away from the frusto-conical engagement surface  637 , the piston portion  620  is no longer driven by the rotation of the drive member  500  (and the fixed plate  675 ) and is thereby free to independently rotate (or stop rotating) via the bearing connection  670 . 
   As shown in  FIG. 6 , the clutch member  600  is mounted to the drive member  500 , and the piston portion  620  is in an engaged position. In this embodiment, the spring  680  is disposed between the hub portion  640  and the piston portion  620  such that the spring  680  urges the piston portion  620  in a rearward axial direction (toward the drive member  500 ). The frusto-conical clutch ring  677  of the piston portion  620  is pressed against the frusto-conical engagement surface  637  of the fixed plate  675 , which is mounted to the drive member  500 . The frusto-conical clutch ring  677  is urged against frusto-conical engagement surface  637  with sufficient force so that the piston portion  620  rotates along with the fixed plate  675 , which is mounted to the drive member  500 . As such, the output member  622  of the piston portion  620  rotates substantially synchronously with the rotation of the drive member  500  about the central axis  505 . When the piston portion  620  is in the engaged position, the output device (such as a fan or fan blades) that is mounted to the studs  630  of the output member  622  also rotates with the drive member  500 . Although the hub  642  is not directly engaged with the drive member  500  or the frusto-conical engagement surface  637  of the fixed plate  675 , the hub  642  rotates with the piston portion  620  due to the spline connection between the first and second spline members  624  and  644 . Such a configuration may limit the wear on the seal  690  because the seal  690  does not endure rotational motion between the hub  642  and the output member  622 . 
   Referring now to  FIG. 7 , the piston portion  620  may be shifted forward in the axial direction away from the drive member  500  such that the piston portion  620  is in a disengaged position. In this embodiment, the frusto-conical clutch ring  677  may be mounted to the piston portion  620  so it is axially shifted away from the frusto-conical engagement surface  637  by an offset  700 . This offset  700  causes the piston portion  620  to disengage with the fixed plate  675  so that the rotational motion from the drive member  500  is not transferred to the output member  622 . When the piston portion  620  is in the disengaged position, the piston portion  620  and hub portion  640  are free to rotate independently from the drive member  500  due to the bearing connection  670 . Accordingly, the piston portion  620  and the hub  642  may stop rotating even though the drive member  500  and the fixed plate  675  continue to rotate. It should be understood that, in other embodiments, the clutch ring  677  may be mounted to the fixed plate  675 , in which case the clutch ring  677  may selectively engage a frusto-conical surface  628  of the piston portion  620 . In such circumstances, the piston portion  620  may be axially shifted to cause an offset between the clutch ring  677  and the frusto-conical surface  628 . 
   Referring to  FIGS. 6-7 , the offset  700  of the piston portion  620  may occur when a fluid under sufficient pressure is received in the chamber  664 . If force from the fluid pressure in the chamber  664  is sufficient to overcome the force of the spring  680 , the output member  622  (and, in this embodiment, the entire piston portion  620 ) is shifted forward in the axial direction. In some embodiments, the fluid pressure that is required to overcome the spring force may be approximately predetermined from the spring constant, the desired offset  700 , the dimensions of the chamber  664 , and other such factors. As previously described, the fluid supply input  550  may receive the fluid, such as air, from the reservoir (not shown in  FIGS. 6-7 ). The fluid passes through the fluid supply channel  552 , through the fluid channel  662 , and into the chamber  664 . The mechanical seal at the face seal  660  assures that the fluid properly reaches the chamber  664 , and when the fluid is in the chamber  664 , the seal  690  may prevent the fluid from passing through a potential leak path along the circumferential surface  649  of the hub  642 . 
   Some embodiments of a clutch member  600  having a frusto-conical engagement surface  637 , such as those embodiments described in connection with  FIGS. 5-7 , may provide substantial torque transfer capabilities between the drive member  500  and the output device. For example, some embodiments of the clutch member  600  may provide torque ratings of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs, 3000 in-lbs, or more, and particular embodiments may provide torque ratings in the range of approximately 3000 in-lbs to approximately 5000 in-lbs. As described in more detail below, the coefficient of friction of the clutch ring  677 , the conical angle of the clutch ring  677 , the force of the spring  680 , and other factors affect the torque rating of the clutch member  600 . 
   These substantial torque transfer capabilities may be caused by a number of factors. For example, the shape and orientation of the frusto-conical engagement surface  637  and the frusto-conical clutch ring  677  may provide the clutch member  600  with a conical wedging action. This conical wedging action may improve the engagement friction, thereby providing an increase in the torque transfer capabilities. 
   In another example, the shape and orientation of the frusto-conical engagement surface  637  and the frusto-conical clutch ring  677  may provide the clutch member  600  with a reduced rotational moment of inertia. Because some embodiments of the frusto-conical clutch ring  677  do not necessarily extend as far in an outward radial direction, the piston portion  620  may have less radial mass (in the form of metallic portions or other components extending generally in an outward direction away from the rotational axis). As such, the overall rotational moment of inertia of the piston portion  620  may be reduced, which may increase the torque transfer capabilities of the clutch member  600 . 
   Torque capability testing may be conducted on clutch members  600  to determine the torque ratings. For example, a torque capability test method may include mounting the clutch member  600  to a drive member  500 , as shown, for example, in  FIG. 6 . The torque capability testing method may also include securing the drive member  500  in a fixed position (e.g., in a vice or a similar device), which in turn secures the position of the engagement surface  637  (e.g., disposed on the fixed plate  675  in the depicted embodiments). In this example, a torque measuring device (e.g., a torque meter or the like) may be secured to the output member  622 . In accordance with this implementation of the torque capability test method, the clutch member may be in an engaged condition so that the frusto-conical clutch ring  677  is in frictional contact with the engagement surface  637 . The torque measuring device may be used to measure a torque applied to the output member  622  relative to the drive member  500  (e.g., applying a force in an attempt to rotate the output member  622 ) and may be monitored to determine the torque level required to cause slippage between the output member  622  and the drive member  500 . This implementation of the torque capability test method may be used to determine the torque rating of the clutch member  600  (e.g., the level of torque required to cause slippage between the output member  622  and the drive member  500  when the clutch member  600  was in an engaged condition). 
   Certain factors of the clutch member&#39;s configuration may affect the torque transfer capabilities and the torque rating of the clutch member  600 . For example, the conical angle of the clutch ring  677  (refer, for example, to angle A in  FIG. 7 ) may be selected to optimize the torque rating of the clutch member  600 . In some embodiments, the conical angle A may be approximately 10 degrees to approximately 60 degrees, approximately 15 degrees to approximately 45 degrees, or approximately 20 to approximately 40 degrees. In the embodiment depicted in  FIGS. 5-7 , the conical angle A is approximately 30 degrees. 
   In another example of a factor that can affect the torque transfer capabilities, the material of the clutch ring  677  and/or the engagement surface  637  may be selected to provide a particular coefficient of friction. In some embodiments, the clutch member  600  may include clutch ring material having a static coefficient of friction in the range of approximately 0.3 to approximately 0.6, approximately 0.35 to approximately 0.55, or approximately 0.4 to approximately 0.55. Suitable materials for the clutch ring  677  may be provided, for example, by Trimat Ltd. of Brierley Hill, England or by Scan Pac Mfg., Inc. of Menomonee Falls, Wis. 
   In a further example of a factor that can affect the torque transfer capabilities, the force of the spring  680  (or the force from the fluid pressure in the chamber  664  used to overcome the spring  680 ) may be selected to provide a particular compression force between the clutch ring  677  and the engagement surface  637 . In some embodiments, the spring  680  may provide a force (to bias the clutch ring  677  and the engagement surface  637  toward one another) of approximately 700 lbs, 800 lbs, 900 lbs, 1000 lbs, 1100 lbs, 1200 lbs, 1300 lbs, 1400 lbs, 1500 lbs, or greater. The displacement of the spring  680  may be different depending upon the wear of the clutch ring  677 , so in some embodiments, the force from the spring  680  may be in the range of approximately 800 lbs to approximately 1400 lbs. For example, the spring  680  may provide a force of approximately 1100 lbs to approximately 1400 lbs when a substantially unworn clutch ring  677  is pressed against the engagement surface  637 . In the embodiment depicted in  FIGS. 5-7 , the spring  680  may provide a force of approximately 1250 lbs when a substantially unworn clutch ring  677  is pressed against the engagement surface  637 . When the clutch ring  677  becomes substantially worn after repeated use, the displacement of the spring  680  may be different so that the compression force provide from the spring is lower. For example, the spring  680  may provide a force of approximately 800 lbs to approximately 1100 lbs when a substantially worn clutch ring  677  is pressed against the engagement surface  637 . In the embodiment depicted in  FIGS. 5-7 , the spring  680  may provide a force of approximately 1000 lbs when a substantially worn clutch ring  677  is pressed against the engagement surface  637 . 
   Accordingly, by making appropriate selections from (i) the conical angle A, (ii) the coefficient of friction at the interface between the clutch ring  677  and the engagement surface  637 , (iii) the force from the spring  680 , and (iv) other such factors, the clutch member  600  may have a torque rating of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs, 3000 in-lbs, or more, and particular embodiments may provide torque ratings in the range of approximately 3000 in-lbs to approximately 5000 in-lbs—including torque ratings in the ranges of approximately 3200 in-lbs to approximately 4000 in-lbs and approximately 4000 in-lbs to approximately 5000 in-lbs. In some embodiments of a clutch member  600  having a conical angle A of approximately 30 degrees, having a clutch ring  677  having a static coefficient of friction of approximately 0.4, and having a spring force of approximately 1250 lbs when the clutch ring  677  is substantially unworn, the clutch member  600  may have torque ratings in the range of approximately 3200 in-lbs to approximately 4000 in-lbs. For example, a clutch member  600  that had a clutch ring  677  comprising Trimat MR8728 material (supplied by Trimat Ltd.) with a static coefficient of friction of approximately 0.4, had a conical angle A of approximately 30 degrees, and had a spring force of approximately 1250 lbs (when the clutch ring  677  was substantially unworn) provided torque ratings of approximately 3540 in-lbs, 3648 in-lbs, 3780 in-lbs, 3444 in-lbs, 3576 in-lbs, and 3636 in-lbs. 
   In other embodiments, a clutch member  600  having a clutch ring material with a greater static coefficient of friction (e.g., comprising Aramid materials supplied by either Trimat Ltd. or Scan Pac Mfg., Inc., Trimat TF100 material, or the like) may provide greater torque ratings. For example, some embodiments of a clutch member  600  may have a clutch ring  677  with a static coefficient of friction of approximately 0.5 (e.g., comprising Trimat TF100 material), may have a conical angle A of approximately 30 degrees, and may have a spring force of approximately 1250 lbs when the clutch ring  677  is substantially unworn, and such a clutch member  600  may have torque ratings in the range of approximately 4000 in-lbs to approximately 5000 in-lbs. Because a greater coefficient of friction may increase the frictional interface between the clutch ring  677  and the engagement surface  637 , some embodiments of the clutch member  600  may have a torque rating greater than 5000 in-lbs. 
   Thus, some embodiments of the clutch member  600  may provide torque ratings of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs, 3000 in-lbs, or more. Particular embodiments may provide torque ratings in the range of approximately 3000 in-lbs to approximately 5000 in-lbs—including torque ratings in the ranges of approximately 3200 in-lbs to approximately 4000 in-lbs and approximately 4000 in-lbs to approximately 5000 in-lbs. 
   It should be understood that the drive member  500  may have a configuration other than a drive pulley shown in  FIGS. 5-7 . For example, the drive member  500  may be a shaft or gear that is powered by a motor. In such embodiments, the clutch member  600  may have a mounting configuration to removably attach to the shaft or gear or may have an adapter member connected therebetween. 
   In other embodiments, the output member  622  of the clutch member  600  may be configured to receive an output device other than fan blades. For example, the output member  622  may be configured to connect with other components that are to be selectively rotated, such as output shafts, gears, brake systems, and the like. 
   In yet another embodiment, the spring  680  that biases the piston portion  620  in an axial direction is not limited to a single, coiled spring shown in  FIGS. 5-7 . Rather, the spring  680  can be any biasing member that can urge the piston portion  620  in the axial direction. A suitable biasing member may comprise one or more coil springs, leaf springs, gas springs, solid materials having appropriate elasticity properties, or the like. 
   Furthermore, some embodiments may include a clutch member configuration such that the spring  680  urges the piston portion  620  into the disengaged position (where the frusto-conical engagement surface  637  is offset from the frusto-conical clutch material  677 ). In such embodiments, the chamber  664  may be configured such that fluid pressure therein causes the piston portion  620  to shift toward engaged position (where the frusto-conical engagement surface  637  is pressed against the clutch material  677 ). 
   A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.