Abstract:
A clutch has a rotatable input, a rotatable output, a spring and a damper mechanism. The rotatable input is capable of being rotated and of being held stationary. The spring is coupled to the input such that each time the input changes modes the spring changes states. The damper mechanism allows the spring to change states without rotating the input. The rotatable output is positioned relative to the spring such that the output synchronously rotates with the input when the spring is in the first state and rotates independently of the input when the spring is in the second state.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority from provisional U.S. Application No. 60/316,493, filed on Aug. 31, 2001 for INPUT ENGAGING CLUTCH for Joseph E. Arnold and Ted J. Perron, which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is an input engaging clutch wherein the clutch engages by turning the input to the clutch. When the input to the clutch stops turning, the clutch disengages the output from the input. 
     A typical electric wrap spring clutch includes an input, an output and a wrap spring, which transfers torque from the input to the output. Typically, a control piece is attached to the spring to controllably wrap the spring down onto a hub when a signal voltage is provided and the input is rotated, thereby engaging the hub. When the control signal is removed the control piece is freed allowing the spring to unwrap and disengage the hub. In some applications it is desirable to energize and de-energize the clutch each time the input to the clutch is energized and de-energized. In this configuration, however, the clutch must receive a control signal that will actuate the control piece to engage and disengage the clutch each time that the input is energized and de-energized. A clutch that allows engagement and disengagement of the input and output without requiring a control signal would be desirable in certain applications. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to an input engaging clutch. The input engaging clutch has a rotatable input that is capable of being rotated and capable of being held stationary. The clutch has a wrap spring that is coupled to the input. The wrap spring has an equilibrium state and rotates with the input when the input is rotating. The clutch also has a damper mechanism that is coupled to the spring such that the damper mechanism allows the spring to change from its equilibrium state to a flexed state—either wrapping open or wrapping down—when the input is rotated. In one embodiment, the clutch has a rotatable output that is positioned relative to the spring in such a way that the output rotates synchronously with the input when the spring is in its flexed state and rotates independently of the input when the spring is in its equilibrium state. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an input engaging clutch in accordance with the present invention. 
     FIG. 2 is an exploded view of the input engaging clutch of FIG.  1 . 
     FIG. 3A is a cross-sectional view of the input engaging clutch of FIG.  1 . 
     FIG. 3B is an end view indicating the cross-section of FIG.  3 A. 
     FIG. 4 is a perspective view of an alternative embodiment of an input engaging clutch in accordance with the present invention. 
     FIG. 5 is an exploded view of the input engaging clutch of FIG.  4 . 
     FIG. 6A is a cross-sectional view of the input engaging clutch of FIG.  4 . 
     FIG. 6B is an end view indicating the cross-section of FIG.  6 A. 
     FIG. 7 is a perspective view of an alternative input engaging clutch in accordance with the present invention. 
     FIG. 8 is a cross-sectional view of the input engaging clutch of FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows input engaging clutch  10  in accordance with the present invention. Input engaging clutch  10  includes input  12 , case  14 , and output  16 . In operation, input engaging clutch  10  can alternatively engage and disengage input  12  to output  16 . For example, input  12  has two modes: it will either be rotating in one direction or it will not be rotating and held stationary. Input  12  may be coupled to a motor that can be turned on and off to alternatively provide a rotating force and no rotating force to input  12 . Output  16  may then be coupled to a device, such as a gear that will move a door. When the motor coupled to input  12  is off, input engaging clutch  10  is disengaged such that input  12  and output  16  are not coupled together. Input  12  is in a stationary mode when the motor is off. When the motor is turned on, however, input  12  changes to a rotating mode. With the motor on, input  12  is forced to rotate causing input engaging clutch  10  to be engaged, that is, input  12  and output  16  are coupled such that output  16  rotates with input  12 . 
     FIG. 2 shows and exploded view of input engaging clutch  10  in accordance with the present invention. Input engaging clutch  10  includes input  12 , case  14 , retaining ring  15 , output  16 , output shaft  17 , wrap spring  18 , spring sleeve  20 , output hub  22 , and end cap  24 . Output hub  22  and end cap  24  are press fit onto, and thus integral with, output shaft  17 . When clutch  10  is fully assembled, retaining ring  15  helps to hold the assembly together. 
     Wrap spring  18  is a helical-wound spring having a relaxed condition defining a relaxed internal diameter. Input  12  includes input hub  13 , which has an external hub diameter. The internal diameter of wrap spring  18  in its relaxed condition is less than the external diameter of input hub  13 . Consequently, when wrap spring  18  is placed over input hub  13  it is in interference fit therewith. Thus, wrap spring  18  rotates with input  12  when input  12  is rotated. Wrap spring  18  may also include a first spring toe  19 A, which can be engaged with input  12  in order to further ensure that when input hub  12  is rotating, wrap spring  18  is also rotating because of their engagement. 
     When input engaging clutch  10  is fully assembled and input  12  is not rotating, wrap spring  18  is in an equilibrium state. Wrap spring  18  has a second spring toe  19 B, which is configured to fit into slot  21  in spring sleeve  20 . Spring sleeve  20  is configured to rotate with input  12  when input  12  is rotating, because of the interconnection of input  12 , wrap spring  18 , second spring toe  19 B, and spring sleeve  20 . Output shaft  17 , however, is disengaged from input  12  when wrap spring  18  is in its equilibrium state. In its equilibrium state, the inside diameter of wrap spring  18  is larger than the outer diameter of output hub  22 . Consequently, when wrap spring  18  is in its equilibrium state, output shaft  17  may freely rotate within wrap spring  18  without interference therewith. 
     Wrap spring  18  may be wrapped open or wrapped down out of its equilibrium state into a flexed state. When spring  18  is wrapped down, its internal diameter will be smaller than its equilibrium internal diameter. When spring  18  is wrapped open, its internal diameter will be larger than its equilibrium internal diameter. Input clutch  10  may take advantage of wrap spring  18  changing from its equilibrium state to its flexed state to engage input  12  with output  16 . For example, wrap spring  18  can be caused to wrap down onto output hub  22  such that rotation of input  12  will cause rotation of output shaft  17 . 
     FIG. 3 shows a cross-section of input engaging clutch  10  fully assembled. Input engaging clutch  10  includes input  12 , input hub  13 , case  14 , output  16 , output shaft  17 , wrap spring  18 , output hub  22 , end cap  24 , and viscous fluid  26 . In operation, input engaging clutch  10  maybe used to alternatively engage and disengage input  12  and output  16  in response to input  12  alternating between rotating mode and stationary mode. 
     When input engaging clutch  10  is fully assembled, viscous fluid  26  is contained in the area between case  14  and spring sleeve  20 , thereby surrounding spring sleeve  20 . When input  12  is in a rotating mode, input  12  rotates wrap spring  18  and spring sleeve  20 , because of their interconnection. Viscous fluid  26  in the area between spring sleeve  20  and case  14  supplies drag torque to the outside diameter of spring sleeve  20  opposing its rotation. The drag torque on spring sleeve  20  supplied by viscous fluid  26  varies with the speed at which input  12  is rotating and with the viscosity of viscous fluid  26 . In some cases, for example at very low rotating speeds for input  12  and low viscosity of viscous fluid  26 , the drag torque on the outside diameter of spring sleeve  20  may not be enough to cause wrap spring  18  to wrap down on output hub  22 . With sufficient rotating speed and viscosity, however, this drag torque caused by viscous fluid  26  acting on the outside diameter of spring sleeve  20  is sufficient to cause wrap spring  18  to transition from its equilibrium state to its flexed state. Specifically, the drag torque on the outside diameter of spring sleeve  20  will cause wrap spring  18  to wrap down across input hub  13  and output hub  22  thereby engaging clutch  10 . 
     When input  12  transitions from rotating mode to stationary mode and thus stops rotating, the drag torque from viscous fluid  26  dissipates. Wrap spring  18  meanwhile, has stored energy in its flexed state having wrapped down on input hub  13  and output hub  22  with the rotating of input  12 . When input  12  stops rotating, this stored energy in wrap spring  18  tends to cause wrap spring  18  to unwind. This stored energy in wrap spring  18  is dissipated through the rotation of spring sleeve  20  within fluid  26 . Thus, wrap spring  18  transitions from its flexed state back to its equilibrium state when input  12  transitions from its rotating mode to its stationary mode. This small amount of rotation of wrap spring  18  and spring sleeve  20  releases output hub  22  from engagement with wrap spring  18 , thereby disengaging clutch  10 . 
     In this way, when an input turning force is applied to input  12  at a speed above the threshold speed, clutch  10  is engaged, that is, input  12  and output shaft  17  rotate together. When input  12  stops turning, input engaging clutch  10  is disengaged, that is, output hub  22  and output shaft  17  can rotate independently of input  12 . In this disengaged state, output shaft  17  rotates freely within wrap spring  18 . The disengagement of clutch  10  does not rely on counter-rotation of input  12 . 
     Input engaging clutch  10  can be used in applications where it is desirable to have a clutch engaged whenever a rotating force is applied to the input and disengaged when that rotating stops. For example, in some applications a turning force can be applied to input  12  of input engaging clutch  10  through some type of turning gear. When that gear rotates, input  12  will also rotate causing wrap spring  18  to wrap down across input hub  13  and output hub  22  causing output shaft  17  to rotate with input  12 . In some configurations, when this gear-type force supplied to input  12  stops rotating, input  12  is prevented from rotating in a direction opposite to the direction in which it was originally driven. In this way, the stored energy in wrap spring  18  cannot be dissipated by allowing input  12  to counter-rotate and unwind wrap spring  18 . Instead, input engaging clutch  10  allows wrap spring  18  to unwind by rotating spring sleeve  20 . When wrap spring  18  is allowed to unwind by moving spring sleeve  20 , output shaft  17  is released and input engaging clutch  10  is disengaged. As long as the stored energy in wrap spring  18  is sufficient to overcome the drag torque provided by viscous fluid  26  on the fin outside diameter of spring sleeve  20 , wrap spring  18  can wrap open and release output shaft  17 . 
     Clutch  10  can be used to alternatively automatically and manually move a vehicle door. A drive motor connected to input  12  can be activated to drive a gear connected to output  16  that drives the door to automatically move. When the drive motor is deactivated, clutch  12  disengages thereby allowing the door to be moved manually without interference from the drive motor connected to input  12 . 
     Clutch  10  can also be used as an amplified damper. For example, clutch  10  can be configured for use as a lid damper to provide a constant speed of closing for the lid relative to a base or ground. In this way, input  12  is connected to the lid to be closed, and case  14  and output  16  are connected to ground. As the lid tends to close relative to ground due to gravity acting on its mass, input  12  will be rotated. Because spring  18  will wrap down on output  16  for higher speeds of input  12  rotation, clutch  10  provides a limit on the closing speed of the lid. Spring sleeve  20  rotating within viscous fluid  26  provides a resistance to the lid closing providing desirable closing characteristics for the lid. 
     FIGS. 4-6 show alternative input engaging clutch  40  in accordance with the present invention. Clutch  40  includes input  42 , input hub  43 , retaining ring  44 , press ring  45 , output  46 , output shaft  47 , wrap spring  48 , drag spring  50 , output hub  52 , gear  54 , gear hub  56 , damper gear  58 , rotary damper  59 , and housing  62 . In operation, input engaging clutch  40  may be used to alternatively engage and disengage input  42  with output  46  in response to alternatively rotating and holding stationary input  42 . 
     Input engaging clutch  40  may be used in the same way as input engaging clutch  10 . For example, input  42  may be coupled to a motor that can be turned on and off to alternatively provide a rotating force and no rotating force to input  42 . Output  46  may then be coupled to a device, such as a gear that will move a door. When the motor coupled to input  42  is off, input  42  is in a stationary mode and will not rotate. In this mode, input engaging clutch  40  is disengaged such that input  42  and output  46  are not coupled together. When the motor is turned on, however, input  42  transitions to a rotating mode. Input  42  is forced to rotate causing input engaging clutch  40  to be engaged, that is, input  42  and output  46  are coupled such that output shaft  47  rotates with rotation of input  42 . 
     Wrap spring  48  is coupled to input  42  via input hub  43  similarly to wrap spring  18  and input engaging clutch  10  described above. Wrap spring  48  has a relaxed internal diameter when in a relaxed condition. The internal diameter of wrap spring  48  in its relaxed condition is smaller than the diameter of input hub  43 . In this way, when clutch  40  is fully assembled wrap spring  48  is frictionally engaged with input  42 , and specifically engaged with input hub  43 . Alternatively, or in addition, wrap spring  48  may have a first spring toe  49 A that engages input  42  thereby further connecting wrap spring  48  and input  42 . In this way, wrap spring  48  rotates with rotation of input  42 . 
     Wrap spring  48  includes second spring toe  49 B, which is configured to engage drag spring  50  when clutch  40  is fully assembled. Drag spring  50  also has a relaxed internal diameter when in a relaxed condition. The internal diameter of drag spring  50  in its relaxed condition is smaller than the external diameter of gear hub  56 . In this way, when drag spring  50  is assembled over gear hub  56 , it is frictionally engaged therewith. Gear hub  56  is integral with gear  54 . Drag spring  50  includes drag spring toes  51  and  53 . Gear  54  includes a plurality of teeth. Damper gear  58  also includes a plurality of teeth that are configured to engage the teeth of gear  54 . Damper gear  58  is mounted to rotary damper  59 , which provides a relatively steady resistance to the rotating of damper gear  58 . When clutch  40  is fully assembled, press ring  45  and retaining ring  44  help to hold the assembly together. 
     In operation, clutch  40  alternately engages and disengages input  42  to output  46 . When clutch  40  is fully assembled and input  42  is not rotating, wrap spring  48  is in an equilibrium state. When input  42  is in rotating mode, it rotates and wrap spring  48  also rotates with input  42  because of their interconnection. When input  42  is rotating clockwise in the direction  60  (shown in FIG.  4 ), wrap spring  48  also rotates in that same direction  60 . When input  42  is rotating in direction  60 , second spring toe  49 B engages drag spring toe  53  of drag spring  50 . This tends to rotate drag spring  50  in the same direction  60  as input  42  and wrap spring  48 . Gear  54  tends to rotate in the same direction  60  as input  42  because of the interference fit between drag spring  50  and gear hub  56 . Because of the interconnection of the teeth on gear  54  and the teeth on damper gear  58 , damper gear  58  tends to rotate in a counter-clockwise direction opposite direction  60 . Damper gear  58  is coupled to rotary damper  59 , which is configured to supply a drag torque such that damper gear  58  provides a resistance to rotation of gear  54 . 
     For very slow speeds of rotation of input  42  and sufficiently low levels of drag torque supplied by damper gear  58  and rotary damper  59 , second spring toe  49 B of wrap spring  48  may rotate drag spring  50  via drag spring toe  53  sufficiently to prevent wrap spring  48  from wrapping down on output hub  52 . However, with significant speeds of rotation of input  42  and with damper gear  58  and rotary damper  59  configured to provide significant drag torque, second spring toe  49 B of wrap spring  48  will not be able to rotate drag spring  50  and gear  54  at a high enough rate of rotation to prevent wrap spring  48  from wrapping down across input hub  43  and output hub  52 . Thus, wrap spring  48  will transition from its equilibrium state to its flexed state. When wrap spring  48  wraps down across input hub  43  and output hub  52 , clutch  40  is engaged and output shaft  47  will rotate with rotation of input  42 . When input  42  transitions from its rotating mode to its stationary mode, the energy stored in wrap spring  48  from having wrapped down across output hub  52  tends to dissipate. This stored energy will dissipate by wrap spring  48  wrapping open from its flexed state back to its equilibrium state. Since input  42 , in many cases, is prevented from rotating in a direction opposite the original direction of rotation  60 , when wrap spring  48  wraps open second spring toe  49 B will rotate against drag spring toe  53  and thereby rotate drag spring  50 , gear  54 , and gear hub  56  in direction  60 , the same direction that input  42  was originally rotated. Damper gear  58  is then rotated in a direction opposite direction  60  because of the interaction of the teeth on gear  54  and on damper gear  58 . When wrap spring  48  wraps open from its flexed state to its equilibrium state, clutch  40  is disengaged. That is, when wrap spring  48  is in its equilibrium state output shaft  47  may freely rotate within wrap spring  48  and independent of input  42 . 
     Input clutch  40  has an additional feature not provided in clutch  10 . The inclusion of drag spring  50  between wrap spring  48  and gear  54  for input clutch  40  allows for slippage between wrap spring  48  and gear  54  in clutch  40  that does occur between wrap spring  18  and spring sleeve  20  in clutch  10 . In this way, for clutch  10 , the speed at which input  12  rotates is controlling over the speed at which spring sleeve  20  rotates within viscous fluid  26 . For clutch  40 , however, the slippage between wrap spring  48  and gear  54  provides that the speed at which gear  54  rotates is a function of both the speed at which input  42  is rotated and by the interference fit between drag spring  50  and gear hub  56 . For very slow rotational speeds of input  42 , gear  54  will rotate with input  42  when there is no slippage between drag spring  50  and gear hub  56 . Once sufficient speed of rotation is established for input  42 , however, drag spring  50  will start slipping with respect to gear hub  56 . Once drag spring  50  is slipping with respect to gear hub  56 , the rotational speed of gear  54  will remain constant even though the rotation of  42  is continually increased. 
     Although not necessary to the invention, this slippage of drag spring  50  within clutch  40  may have advantages in some applications. For example, rotary damper  59  will likely only function properly for a range of rotational speeds of rotary gear  58 , including some maximum acceptable rotational speed. In some cases, input  42  may rotate at significantly higher rotational speeds than is acceptable for rotary gear  58 . In those cases where it is also not practicable to adjust the gear ratio to accommodate the speed differential, this slippage of drag spring  50  within clutch  40  can provide a good solution. 
     The amount that wrap spring  48  must rotate before it will wrap down onto output hub  46  is known as the wrap down angle. The larger this wrap down angle, the more energy will be stored in spring  48 . The energy stored in spring  48  in its flexed state is sufficient to overcome the drag torque from damper gear  58  and rotary damper  59  such that the transition of spring  48  from its flexed state to its equilibrium state will rotate gear  54  and damper gear  58  thereby disengaging clutch  40 . Any number of rotary dampers are acceptable for damper gear  58  and rotary damper  59 . Examples of off-the-shelf rotary dampers that are acceptable for the present invention are models FRT-C2, FRN-C2, FRT-D2 and FRN-D2 from Ace Controls International. These types of dampers contain a viscous fluid that causes the damper to have speed-dependent resistance to rotation. One skilled in the art will understand that any number of configurations that will provide resistance to rotation are acceptable for use as a damper in the present invention. 
     Input engaging clutch  40  can also be modified in accordance with the present invention such that it operates as an input engaging clutch that is engaged when input  42  is in its stationary mode and is disengaged when input  42  transitions to its rotating mode. This opposite result from clutch  40  described above is essentially achieved by having wrap spring  48  wrapped down onto input hub  43  and output hub  52  in its equilibrium state, and by moving gear  54  and rotary damper  58  relative to the input  43 . When input  43  transitions from its stationary mode to its rotating mode, wrap spring  48  wraps open off of output hub  52  into its flexed state. In this flexed state, output hub  52  may freely rotate within wrap spring  48  and modified clutch  40  is disengaged. When input  43  transitions from its rotating mode to its stationary mode, wrap spring  48  wraps back down onto output hub  52  to its equilibrium state. In this equilibrium state, output hub  52  is coupled to wrap spring  48  and modified clutch  40  is engaged. 
     Such a modified input engaging clutch  40  may be used in a variety of applications. For example, it can be used in conjunction with a braking system for a wheeled cart. Input  42  may be coupled to a wheel that will alternatively rotate and be held stationary as the cart is moved and held stationary. Output shaft  47  may then be fixed to the cart or ground such that it cannot rotate. When the wheel coupled to input  42  is not rotating, input  42  is in a stationary mode and will not rotate. In this mode, modified input engaging clutch  40  is engaged such that input  42  and output  46  are coupled together. Since output shaft  47  is fixed and cannot rotate, modified clutch  40  acts as a brake when input  42  is in the stationary mode. When the wheel is rotated, however, input  42  transitions to a rotating mode. Input  42  is forced to rotate with the wheel causing modified input engaging clutch  40  to be disengaged, that is input  42  and output shaft  47  are no longer coupled such that output shaft  47  is no longer coupled to input  42 . This release of input  42  from output shaft  47  in the rotating mode of input  42  causes the release of the brake effect that existed when input  42  was in the stationary mode. 
     Such a modified input engaging clutch  40  could also be employed to be used in an overload condition. For example, a traditional electric spring clutch may be used in normal operating conditions and a modified clutch  40  could be coupled in to be engaged when an overload condition is reached such that rotation of the input  42  of modified clutch  40  would disengage the output  46  and release modified clutch  42  from ground in this overloaded condition. 
     FIGS. 7 and 8 shows alternative bi-directional input engaging clutch  200  in accordance with the present invention. Clutch  200  includes input  242 , input hub  243 , retaining ring  244 , press ring  245 , output  246 , wrap spring  248 , drag spring  250 , outer gear  254 , inner gear  255 , pinion gear  257 , damper gear  258 , rotary damper  259 , input housing  260 , and case  261 . Output  246  includes output shaft  247 , inner drum hub  252  and outer drum hub  253 , all of which are integral, and thus, rotate together. 
     Input engaging clutch  200  operates similarly to input engaging clutch  40 , except that input engaging clutch  200  maybe operated in a bi-directional manner. Specifically, input  242  can be coupled to a drive force that alternatively rotates input  242  in a clockwise and a counter-clockwise direction. Output  246  may be coupled to a device, such as a gear that will open and close a door. When the drive force coupled to input  242  is off, input  242  is in a stationary mode and will not rotate. In this mode, input engaging clutch  200  is disengaged such that input  242  and output  246  are not coupled together. When the drive force is supplied, however, input  242  transitions to a rotational mode. When input  242  is forced to rotate, in either a clockwise or a counter-clockwise direction, input engaging clutch  242  will be engaged, that is, input  242  and output  246  are coupled such that output shaft  247  rotates with input  242 . 
     Wrap spring  248  is coupled to input  242  such that rotation of input  242  also rotates wrap spring  248 . Input  242  has a circular groove cut into input hub  243  such that wrap spring  248  may be press fit into the groove on input hub  243 . Press fitting wrap spring  248  to input  242  ensures that wrap spring  248  will continue to rotate with input  242 , regardless of the direction of rotation of input  242 . Wrap spring  248  can be connected to input  242  in any of a variety of ways, one of which is described in detail in U.S. Pat. No. 4,638,899 (Kossett) entitled Simplified Method of Securing the Clutch Spring to the Torque Input Drum of a Spring Clutch, and Resulting Mechanism, which is incorporated by reference herein. 
     Similar to that described with respect to input engaging clutch  40 , wrap spring  248  of input engaging clutch  200  includes a spring toe (not shown in FIG. 8) which is configured to engage drag spring  250 . The internal diameter of drag spring  250  in its relaxed condition is smaller than the external diameter of inner gear  255 . In this way, drag spring  250  is frictionally engaged with inner gear  255  when clutch  200  is filly assembled. Inner gear  255  is configured to engage pinion gear  257  upon rotation of inner gear  255 . In a preferred embodiment, both inner gear  255  and pinion  257  have teeth that will engage upon rotation. Pinion gear  257  is configured to engage outer gear  254 . Outer gear  254  similarly has teeth that are configured to engage teeth on pinion gear  257 . Finally, damper gear  258  also has teeth that are configured to engage outer gear  254 . When clutch  200  is fully assembled, retaining ring  244  and press ring  245  help to hold the assembly together. Housing  260  surrounds and protects a portion of clutch  200  and is coupled to outer drum hub  253  such that it rotates with output  246 . Case  261  surrounds and protects outer gear  254  and rotary damper  259 . 
     In operation, clutch  200  alternatively engages and disengages input  242  to output  246 . When input  242  is rotating, in either a clockwise or counter-clockwise direction, it is in a rotating mode. In this rotating mode wrap spring  248  also rotates with input  242  because of their interconnection. Rotating wrap spring  48  also rotates drag spring  250  because of the engagement of the respective spring toes (not shown in FIG. 8) of drag spring  250  and wrap spring  248 . This engagement of spring toes is not shown in FIG. 8, but is essentially the same as that shown by spring toes  49 B,  51 , and  53  in FIG. 4, and as explained in conjunction with clutch  40  above. Thus, rotating wrap spring  248  also rotates, drag spring  250 , which in turn rotates inner gear  255 , which in turn rotates pinion gear  257 , which in turn rotates outer gear  254 , which in turn rotates damper gear  258 , all because of the interconnection of the respective teeth on these gears. Damper gear  258  is coupled to rotary damper  259 , which is configured to supply a relatively steady drag torque such that damper gear  258  provides a relatively steady resistance to rotation. When input  242  is rotated in a clockwise direction at a sufficient speed of rotation, rotary damper  259  through damper gear  258 , outer gear  254 , pinion gear  257 , inner gear  255 , and drag spring  250 , will cause wrap spring  248  to wrap down onto inner drum hub  252 . When wrap spring  248  wraps down onto inner drum hub  252 , clutch  200  is engaged, that is, output  256  and output shaft  257  rotate with input  242 . Similarly, when input  242  is rotated counter-clockwise at a sufficient speed of rotation, rotary damper  259  provides sufficient drag torque, through damper gear  258 , outer gear  254 , pinion gear  257 , inner gear  255 , and drag spring  250 , to cause wrap spring  248  to wrap open against outer drum hub  253 . In this way, counterclockwise rotation of input  242  engages clutch  200 , that is, output  246  and output shaft  247  rotate with input  242 . 
     When input  242  transitions from its rotating mode (in either clockwise or counter-clockwise rotation) to its stationary mode, the energy stored in wrap spring  248  from having flexed, either by wrapping down onto inner drum hub  252 , or by having wrapped open against outer drum hub  253 , will tend to dissipate. This stored energy will dissipate through wrap spring  242  wrapping open or wrapping down from its flexed state to its equilibrium state. Since input  242 , in many cases, is prevented from rotating in a direction opposite the original direction of rotation, when wrap spring  242  wraps open or wraps down, the spring toe on wrap spring  248  will engage the spring toe on drag spring  250  thereby rotating drag spring  250 , inner gear  255 , pinion gear  257 , outer gear  254 , and damper gear  258 . This rotation allows wrap spring  248  to return to its equilibrium state such that clutch  200  is disengaged, that is, output  246  may rotate independently of input  242 . 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.