Patent Description:
The damper activation allows the clutch to change states as the input changes from stationary to rotating. Features of the input engaging clutch include disengaging the clutch without movement of the input or output, while the clutch is carrying a load. These clutches can be unidirectional or bi-directional. A common application for a bi-directional clutch design is a replacement for an electromagnetic friction disc clutch. A unidirectional clutch typically utilizes cross over hub wrap spring torque transmission and a bi-directional clutch utilizes two sets of cross over hubs. However, such known clutch designs have a high part count and require precise assembly, such that they are typically not cost competitive enough in order to be used. Therefore, there is a need for a new design of an input engaging clutch that can create the bidirectional or unidirectional function in a simplified mechanism in order meet the cost expectations of these applications.

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

It is to be understood that the features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise.

<FIG> illustrates a wrap spring clutch <NUM> in accordance with one embodiment. <FIG> further illustrates an exploded view of wrap spring clutch <NUM>, illustrating further components not visible in <FIG>. <FIG> illustrates a sectional view of fully assembled wrap spring clutch <NUM>. In one embodiment, wrap spring clutch <NUM> includes an input <NUM> and an output <NUM>. In one embodiment, a shaft <NUM> and an output hub <NUM> are coupled to output <NUM>, and a slotted driver <NUM> is coupled to input <NUM>. In one embodiment, slotted driver <NUM> has a first drive surface 20a and a second drive surface 20b.

A wrap spring <NUM> is a helical-wound spring with a relaxed or equilibrium condition defining a relaxed internal diameter. Wrap spring <NUM> is helically wrapped over output hub <NUM>, and includes first spring end 22a and second spring end 22b. Output hub <NUM> has an external hub diameter that is less than the internal diameter of wrap spring <NUM> in its relaxed condition. Consequently, when wrap spring <NUM> in its relaxed condition is placed over output hub <NUM>, output hub <NUM> can rotate within wrap spring <NUM> without interference therewith. In one embodiment, each of first and second spring ends 22a and 22b are spring toes, which are bent outward away from the helically wrapped portion of spring <NUM> as is discussed further below.

In one embodiment, a control <NUM> is provided over output hub <NUM> and wrap spring <NUM>. <FIG> illustrates a further view of control <NUM>, which in one embodiment includes control slot <NUM>. In one embodiment, control slot <NUM> has a first edge 25a and a second edge 25b. In one embodiment, control <NUM> is controllably engaged with first or second spring ends 22a/22b via slot <NUM>. Depending on the relative directions of rotation, first or second spring ends 22a/22b will engage first or second edge 25a/25b via the bent spring toe.

As illustrated in <FIG>, control <NUM> is engaged with a dampening force. For example, in one embodiment, control <NUM> is engaged with a rotary damper <NUM>, for example via teeth on an outer edge of control <NUM> and on rotary damper <NUM>, which are engaged. Rotary damper <NUM> provides a relatively steady resistance to the rotating of control <NUM>. Other means of providing a dampening force or drag torque are well known, such as providing a surrounding viscous fluid that will provide a drag or controlled resistance to rotation control <NUM>. Because the dampening control forces are low, the area to which it is applied can be relatively small, such as to the bent spring toe.

In one embodiment, wrap spring clutch <NUM> allows a change of a clutch state - engaged or disengaged -- regardless of loading of wrap spring clutch <NUM>. When input <NUM> is rotated in either direction, its rotation engages wrap spring <NUM> at one of its ends 22a/22b through slotted driver <NUM>. Simultaneously, control <NUM> engages the opposite end 22a/22b, and due to the dampening force on control <NUM>, wrap spring <NUM> wraps down on output hub <NUM>, such that input <NUM> and output <NUM> rotate together. When input <NUM> is not rotated, the spring force stored in wrap spring <NUM> allows the wrap spring to unwind off the output hub <NUM>, such that input <NUM> and output <NUM> are disengaged. The relative spring force stored in wrap spring <NUM> and the relative amount of drag force on control <NUM> (such as by rotary damper <NUM>) can be adjusted so that the change of the clutch state can be readily controlled.

The drag force provided on control <NUM> by damper <NUM> is enough to overcome the spring force in wrap spring <NUM> to cause the wrap spring <NUM> to change from its equilibrium state to its flexed state when input <NUM> is rotating. The amount of spring force in wrap spring <NUM> is enough to overcome the drag force provided on control <NUM> by damper <NUM> to cause the wrap spring <NUM> to change from its flexed state to its equilibrium state when input <NUM> is no longer rotating.

In operation, wrap spring clutch <NUM> can alternatively engage and disengage input <NUM> to output <NUM>. For example, input <NUM> has two modes: it will either be rotating in one direction or it will not be rotating and held stationary. In one embodiment, input <NUM> may be coupled to a motor that can be turned on and off to alternatively provide a rotating force in either or both directions, or no rotating force to input <NUM>. Output <NUM> may then be coupled to a device, such as a gear that will move a door or other movable device. When the motor coupled to input <NUM> is off, wrap spring clutch <NUM> is disengaged, such that input <NUM> and output <NUM> are not coupled together. Input <NUM> is in a stationary mode when the motor is off. When the motor is turned on, however, input <NUM> changes to a rotating mode. With the motor on, input <NUM> is forced to rotate causing input engaging clutch <NUM> to be engaged, that is, input <NUM> and output <NUM> are coupled, such that output <NUM> rotates with input <NUM>.

In one embodiment, when input <NUM> is rotated in the clockwise direction indicated in the arrow on <FIG> and <FIG>, first drive surface 20a of slotted driver <NUM> engages first end 22a of wrap spring <NUM> and drives it in the indicated clockwise direction. In one embodiment, first end 22a of wrap spring <NUM> is a spring toe that is bent outward from the helical turns of wrap spring <NUM> such that it is readily engaged by first drive surface 20a of slotted driver <NUM>. As input <NUM> and spring <NUM> rotate, the second end 22b, which in one embodiment is a spring toe bent outward, comes into engagement with second edge 25b of slot <NUM> within control <NUM>. The spring still in its relaxed state begins to rotate control <NUM> along with the input. When the amount of drag force on control <NUM> is sufficient to overcome the energy stored in wrap spring <NUM>, second edge 25b of slot <NUM> will push second spring end 22bin the counterclockwise direction, opposite the arrow in <FIG> and <FIG>, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub <NUM>. As such, input <NUM> and output <NUM> rotate together.

When input <NUM> is no longer being rotated, the energy stored in wrap spring <NUM> is sufficient to overcome the amount of drag force on control <NUM> causing wrap spring <NUM> to transition from its flexed state to its equilibrium state and wrap open off output hub <NUM>. In such case, input <NUM> and output <NUM> are disconnected and output <NUM> will rotate independent of input <NUM>.

In one embodiment, when input <NUM> is rotated in the counterclockwise direction, opposite that indicated in the arrow on <FIG> and <FIG>, second drive surface 20b of slotted driver engages second end 22b of wrap spring <NUM> and drives it in the counterclockwise direction. As input <NUM> and spring <NUM> rotate, the first end 22a, which in one embodiment is a spring toe bent outward, comes into engagement with first edge 25a of slot <NUM> within control <NUM>. The spring still in its relaxed state begins to rotate control <NUM> along with the input. When the amount of drag force on control <NUM> is sufficient to overcome the energy stored in wrap spring <NUM>, first edge 25a of slot <NUM> will push first spring end 22a in the clockwise direction indicated by the arrow in <FIG> and <FIG>, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub <NUM>. As such, input <NUM> and output <NUM> rotate together.

Prior input engaging clutches, such as that described in <CIT>, required two hubs over which the wrap spring crosses. This type of cross-over clutch transfers torque from one hub to another via a spring. This type of design requires multiple hubs and minimal axial clearance to prevent the spring from wedging into gaps and causing failure over life of the clutch. Present embodiments eliminate the use of two hubs required in prior embodiments, and also does away with the precise assembly required for a cross over spring clutch of prior embodiments, which require the load precisely cross over from an input hub to an output hub. In one embodiment, wrap spring clutch <NUM> has the input engaging feature is combined with a toe drive spring, such that clutching loads are transmitted through the end of wrap spring <NUM>. This results in both reduced part count and reduced complications in assembly.

<FIG> illustrates a wrap spring clutch <NUM> in accordance with one embodiment. <FIG> further illustrates an exploded view of wrap spring clutch <NUM>, illustrating further components not visible in <FIG>. <FIG> illustrates a sectional view of fully assembled wrap spring clutch <NUM>. Wrap spring clutch <NUM> of <FIG> is analogous to that in <FIG>. In one embodiment, wrap spring clutch <NUM> includes an input <NUM> and an output <NUM>. In one embodiment, output <NUM> and an output hub <NUM> are coupled to shaft <NUM>, and a slotted driver <NUM>, with first and second drive surfaces 20a/20b, is coupled to input <NUM>. A wrap spring <NUM>, with first and second spring ends 22a/22b is helically wrapped over output hub <NUM>.

In one embodiment, a control <NUM>, a control hub <NUM> and a drag spring <NUM> are provided over output hub <NUM> and wrap spring <NUM>. In one embodiment of wrap spring clutch <NUM>, control <NUM> and control hub <NUM> are selectively coupled together via drag spring <NUM>. In one embodiment, control <NUM> has a projection 24a, which is configured to be located within slot 28a of drag spring <NUM> when wrap spring clutch <NUM> is fully assembled. The addition of drag spring <NUM> allows further control to assist a drag force from a damper, such as rotary damper <NUM> illustrated in <FIG>, to translate that damping force locking control <NUM> to control hub <NUM>, thereby engaging one of the first and second spring ends 22a/22b with slot <NUM>. Control slot <NUM>, with its first and second edges 25a/25b, is illustrated in <FIG>.

In operation, wrap spring clutch <NUM> of <FIG> functions analogously to that in <FIG> with a slight variation of the operation of control <NUM>, control hub <NUM> and drag spring <NUM>, which is allowed to slip under some conditions. When input <NUM> is rotated in the clockwise direction indicated in the arrow on <FIG> and <FIG>, first drive surface 20a of slotted driver <NUM> engages first end 22a of wrap spring <NUM> and drives it in the indicated clockwise direction. With this rotation, second end 22b, engages second edge 25b of slot <NUM> within control <NUM>. When the amount of drag force on control <NUM> (such as from a rotary damper <NUM> in <FIG>) is sufficient to overcome the energy stored in wrap spring <NUM>, the drag force translates to control <NUM> via its external teeth, to drag spring <NUM> via projection 24a within slot 28a, to control hub <NUM>, such that second edge 25b of slot <NUM> will push second spring end 22b in the counterclockwise direction, opposite the arrow in <FIG> and <FIG>, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub <NUM>. As such, input <NUM> and output <NUM> rotate together.

Drag spring <NUM> limits the amount of force and energy that is transmitted to the damper <NUM> from input <NUM>. When drag spring <NUM> slips, it still passes enough energy to keep spring <NUM> wrapped down, but it reduces some revolutions of the rotary damper.

<FIG>, which is an opposite perspective view relative to <FIG>, illustrates arrows indicating the torque path of an engaged clutch <NUM>, when input <NUM> is driven in the clockwise direction as just described. The rotation of input <NUM> drives first end 22a of wrap spring <NUM> via slotted driver <NUM>. Because wrap spring <NUM> is wrapped down on output hub <NUM> which is coupled to shaft <NUM>, shaft <NUM> is accordingly driven. Also, because output <NUM> is fixed to shaft <NUM>, output <NUM> is also driven.

<FIG>, which is an opposite perspective view relative to <FIG>, illustrates arrows indicating the torque path for the control <NUM> of an engaged clutch <NUM>, when the input is driven in the clockwise direction as just described. As illustrated, torque transfers from second spring end 22b, to second edge 25b of slot <NUM> in control hub <NUM>, to drag spring <NUM>, to control <NUM>.

When input <NUM> is no longer being rotated, the energy stored in wrap spring <NUM> is sufficient to overcome the amount of drag force on control <NUM> causing wrap spring <NUM> to transition from its flexed state to its equilibrium state and wrap open off output hub <NUM>. In such case, input <NUM> and output <NUM> are disconnected and output <NUM> will rotate independent of input <NUM>. With rotary damper <NUM> engaged with control <NUM>, the drag force acting on control <NUM> is proportional to the speed of rotation. When there are higher speeds on damper <NUM>, there is a higher force output. The drag force from damper <NUM> decreases at lower rotational speeds.

When input <NUM> rotates in the opposite counterclockwise direction, opposite that indicated in the arrow on <FIG> and <FIG>, second drive surface 20b of slotted driver <NUM> engages second end 22b of wrap spring <NUM> and drives it in the counterclockwise direction. With this rotation, first end 22a, engages first edge 25a of slot <NUM> within control <NUM>. When the amount of drag force on control <NUM> is sufficient to overcome the energy stored in wrap spring <NUM>, the drag force translates to control <NUM> via its external teeth, to drag spring <NUM> via projection 24a within slot 28a, to control hub <NUM>, such that second edge 25b of slot <NUM> will push second spring end 22b in the counterclockwise direction, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub <NUM>. As such, input <NUM> and output <NUM> rotate together.

<FIG>, which is an opposite perspective view relative to <FIG>, illustrates arrows indicating the torque path of an engaged clutch <NUM>, when input <NUM> is driven in the counterclockwise direction. The rotation of input <NUM> drives second end 22b of wrap spring <NUM> via slotted driver <NUM>. Because wrap spring <NUM> is wrapped down on output hub <NUM> which is coupled to shaft <NUM>, shaft <NUM> is accordingly driven. Also, because output <NUM> is fixed to shaft <NUM>, output <NUM> is also driven.

<FIG>, which is an opposite perspective view relative to <FIG>, illustrates arrows indicating the torque path for the control <NUM> of an engaged clutch <NUM>, when the input is driven in the counterclockwise direction. As illustrated, torque transfers from first spring end 22a, to first edge 25b of slot <NUM> in control hub <NUM>, to drag spring <NUM>, to control <NUM>.

<FIG> illustrates a wrap spring clutch <NUM> in accordance with one embodiment. <FIG> further illustrates an exploded view of wrap spring clutch <NUM>, illustrating further components not visible in <FIG>. <FIG> illustrates a sectional view of fully assembled wrap spring clutch <NUM>. Wrap spring clutch <NUM> of <FIG> is analogous to wrap spring clutch <NUM> in <FIG>, except wrap spring clutch <NUM> uses spline input and outputs rather than the gear input and output, such that it can be used in a spindle application, for example.

In one embodiment, wrap spring clutch <NUM> includes an input <NUM> and an output <NUM>. In one embodiment, output <NUM> includes an output hub surface 64a, and input <NUM> includes a slotted driver opening 62a defining drive surfaces on either side of the slot opening. A wrap spring <NUM>, with first and second spring ends 72a/72b is helically wrapped over output hub surface 64a.

In one embodiment, a control <NUM>, a control hub <NUM> and a drag spring <NUM> are provided over output <NUM> and wrap spring <NUM>. In one embodiment of wrap spring clutch <NUM>, control <NUM> and control hub <NUM> are selectively coupled together via drag spring <NUM>. In one embodiment, control <NUM> has a projection 74a, which is configured to be located within slot 78a of drag spring <NUM> when wrap spring clutch <NUM> is fully assembled. Drag spring <NUM> allows further control to assist a drag force from a damper, such as rotary damper <NUM> illustrated in <FIG>, to translate that damping force from damper <NUM> to control <NUM>, to drag spring <NUM>, to control hub <NUM>, and thereby engaging one of the first and second spring ends 72a/72b with a slot in control <NUM> (analogous to previously described slots <NUM> illustrated in <FIG> and <FIG>).

In operation, wrap spring clutch <NUM> of <FIG> functions analogously to that in <FIG>. When input <NUM> is rotated in the clockwise direction indicated in the arrow on <FIG> and <FIG>, a drive surface of slotted driver opening 62a engages first end 72a of wrap spring <NUM> and drives it in the indicated clockwise direction. When the amount of drag force on control <NUM> (such as from a rotary damper <NUM> in <FIG>) is sufficient to overcome the energy stored in wrap spring <NUM>, the drag force is translated from damper <NUM>, to control <NUM>, to drag spring <NUM>, to control hub <NUM>, such that an edge of the slot in control <NUM> will push second spring end 72b in the counterclockwise direction, opposite the arrow in <FIG> and <FIG>, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub surface 64a. As such, input <NUM> and output <NUM> rotate together.

When input <NUM> is no longer being rotated, the energy stored in wrap spring <NUM> is sufficient to overcome the amount of drag force on control <NUM> causing wrap spring <NUM> to transition from its flexed state to its equilibrium state and wrap open off output hub surface 64a. In such case, input <NUM> and output <NUM> are disconnected and output <NUM> will rotate independent of input <NUM>.

When input <NUM> rotates in the counterclockwise direction, opposite that indicated in the arrow on <FIG> and <FIG>, a drive surface of slotted driver opening 62a engages second end 72b of wrap spring <NUM> and drives it in the counterclockwise direction. When the amount of drag force on control <NUM> is sufficient to overcome the energy stored in wrap spring <NUM>, the drag force is translated from damper <NUM>, to drag spring <NUM>, to control hub <NUM>, such that an edge of the slot in control <NUM> will push first spring end 72a in the counterclockwise direction, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap down onto output hub surface 64a. As such, input <NUM> and output <NUM> rotate together.

<FIG> illustrates a wrap spring clutch <NUM> in accordance with one embodiment. <FIG> further illustrates an exploded view of wrap spring clutch <NUM>, illustrating further components not visible in <FIG>. <FIG> illustrates a sectional view of fully assembled wrap spring clutch <NUM>. Whereas previous-described wrap spring clutches <NUM> and <NUM> are bidirectional, wrap spring clutch <NUM> is configured as a unidirectional input clutch such that it operates in a single direction of rotation, either clockwise or counterclockwise. In the illustrated embodiment of <FIG>, wrap spring clutch <NUM> is configured so that the input engages in the clockwise direction, indicated by the arrow.

In one embodiment, wrap spring clutch <NUM> includes an input <NUM> and an output <NUM>. In one embodiment, output <NUM> includes an output hub surface 84a, and input <NUM> includes a spring end slot <NUM>. A wrap spring <NUM>, with first and second spring ends 92a/92b is helically wrapped over output hub surface 84a. In one embodiment, first spring end 92a is spring toe bent outward and assembled within spring end slot <NUM>, such that wrap spring <NUM> will rotate with rotation of input <NUM>. A control <NUM> is provided over output hub <NUM> and wrap spring <NUM>. In one embodiment, control <NUM> is engaged with a drag force from a damper, such as rotary damper <NUM> illustrated in <FIG>, to translate that damping force to control <NUM>, for example, via teeth on the outer perimeter of control <NUM> and damper <NUM>.

In operation, wrap spring clutch <NUM> of <FIG> functions somewhat analogously to that in prior Figures, except that it operates only with input <NUM> rotating in a single direction. When input <NUM> is rotated in the clockwise direction indicated in the arrow on <FIG> and <FIG>, wrap spring <NUM> also rotates in the clockwise direction by virtue of first spring end 92a being coupled within spring end slot <NUM>. When the amount of drag force on control <NUM> (such as from a rotary damper <NUM> in <FIG>) is sufficient to overcome the energy stored in wrap spring <NUM>, second spring end 92b will cause wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrapping down onto output hub surface 84a. As such, input <NUM> and output <NUM> rotate together.

In one embodiment, the helical wraps of wrap spring <NUM> will have a larger diameter at second spring end 92b than the rest of wrap spring <NUM>. This is illustrated, for example, in <FIG> where the last few turns of wrap spring <NUM> have a larger diameter at second spring end 92b. While second spring 92b is always engaged with control <NUM>, this method of connection allows for relative motion at a specific torque. Once the torque is exceeded, spring end 92b will slip inside of the bore, while still transmitting enough force to engage the clutch spring wraps. This larger diameter at spring end 92b assists in the engagement of wrap spring <NUM> with control <NUM> so that wrap spring <NUM> wraps down onto output hub surface 84a, and provides damper protection.

When input <NUM> is no longer being rotated, the energy stored in wrap spring <NUM> is sufficient to overcome the amount of drag force on control <NUM> causing wrap spring <NUM> to transition from its flexed state to its equilibrium state and wrap open off output hub surface 84a. In such case, input <NUM> and output <NUM> are disconnected and output <NUM> will rotate independent of input <NUM>.

<FIG> illustrates further detail of input <NUM>. Spring end slot <NUM> is illustrated and is where first spring end 92a is coupled within. First and second drive surfaces 83a/83b are further illustrated. When wrap spring clutch <NUM> is configured to engage with input rotation in the clockwise direction (as in <FIG>), first drive surface 83a will drive the spring toe of first spring end 92a thereby engaging the clutch. As is evident, wrap spring clutch <NUM> can also be configured to engage with input rotation in the counterclockwise direction by reversing the helical orientation of wrap spring <NUM>, in which case second drive surface 83b will drive the spring toe of first spring end 92a thereby engaging the clutch.

<FIG> illustrates a wrap spring clutch <NUM> in accordance with one embodiment. <FIG> further illustrates an exploded view of wrap spring clutch <NUM>, illustrating further components not visible in <FIG>. <FIG> illustrates a sectional view of fully assembled wrap spring clutch <NUM>. Whereas previous-described wrap spring clutches <NUM>, <NUM> and <NUM> are wrap down configurations, wrap spring clutch <NUM> is configured as a wrap open input clutch and it operates with a bidirectional input rotation, both clockwise and counterclockwise.

In one embodiment, wrap spring clutch <NUM> includes an input <NUM> and an output <NUM>. In one embodiment, a shaft <NUM> and an output hub <NUM> are coupled to output <NUM>. A drive spline <NUM> extends from a center of input <NUM> and is fixed thereto, and shaft <NUM> extends through drive spline <NUM>. Drive spline <NUM> includes first and second spline slots 111a/111b. In one embodiment, first and second drive hubs <NUM>/<NUM> are assembled over drive spline <NUM>. <FIG> illustrates a further view of first drive hub <NUM>. First drive hub <NUM> includes first drive surface 120a, second drive surface 120b, control slot 120c, first spline ridge 120d and second spline ridge 120e. Second drive hub <NUM> is similarly configured with a first drive surface 121a, second drive surface 121b, control slot 121c, first spline ridge 121d and second spline ridge 121e.

When wrap spring clutch <NUM> is assembled and first and second drive hubs <NUM>/<NUM> are assembled over drive spline <NUM>, first spline ridge 120d and first spline ridge 121d are fit into first spline slot 111a and second spline ridge 120e and second spline ridge 121e are fit into second spline slot 111b. Accordingly, rotation of input <NUM> and drive spline <NUM> will also initially drive first and second drive hubs <NUM>/<NUM> in the same direction of rotation.

A wrap spring <NUM> is a helical-wound spring with a relaxed or equilibrium condition defining a relaxed external diameter. Wrap spring <NUM> is helically wrapped over first and second drive hubs <NUM>/<NUM>, and includes first spring end 122a and second spring end 122b.

Output hub <NUM> is assembled over wrap spring <NUM> and has an internal hub diameter that is more than the external diameter of wrap spring <NUM> in its relaxed condition. Consequently, when wrap spring <NUM> in its relaxed condition is placed within output hub <NUM>, output hub <NUM> can rotate over wrap spring <NUM> without interference therewith.

In one embodiment, a control <NUM> is provided over output hub <NUM> and wrap spring <NUM>. <FIG> illustrates a further view of control <NUM>, which in one embodiment has a first control finger 124a, a second control finger 124b and includes teeth on its outer perimeter. In one embodiment, when wrap spring clutch <NUM> is assembled, first control finger 124a is configured to slide into control slot 120c of first drive hub <NUM> and second control finger is configured to slide into control slot 121c of second drive hub <NUM>. A drag force from a damper, such as rotary damper <NUM> illustrated in <FIG>, translates a damping force to control <NUM> via the teeth on the periphery.

In operation, wrap spring clutch <NUM> of <FIG> functions somewhat analogously to previous described bi-directional embodiments in <FIG>, except that wrap spring <NUM> wraps open rather than wrapping down when transitioning from a relaxed to a flexed state. When input <NUM> is rotated in the clockwise direction indicated in the arrow on <FIG> and <FIG>, drive spline <NUM> drives second drive hub <NUM> clockwise. This rotation of second drive hub <NUM> forces second drive surface 121b against second spring end 122b also rotating wrap spring <NUM> clockwise. When the amount of drag force on control <NUM> (such as from a rotary damper <NUM> in <FIG>) is sufficient to overcome the energy stored in wrap spring <NUM>, control <NUM> will push counterclockwise, and by virtue of first control finger 124a extending through control slot 120c of first drive hub <NUM>, first drive hub <NUM> will push in a counterclockwise direction forcing second drive surface 120b against first spring end 122a, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap open against the inner diameter of output <NUM>. Since output <NUM> is fixed to output <NUM> via shaft <NUM>, input <NUM> and output <NUM> rotate together.

When input <NUM> is no longer being rotated, the energy stored in wrap spring <NUM> is sufficient to overcome the amount of drag force on control <NUM> causing wrap spring <NUM> to transition from its flexed state to its equilibrium state and wrap down off the inner surface of output <NUM>. In such case, input <NUM> and output <NUM> are disconnected and output <NUM> will rotate independent of input <NUM>.

When input <NUM> rotates in the counterclockwise direction, opposite that indicated in the arrow on <FIG> and <FIG>, drive spline <NUM> drives first drive hub <NUM> counterclockwise. This rotation of first drive hub <NUM> forces first drive surface 120a against first spring end 122a also rotating wrap spring <NUM> counterclockwise. When the amount of drag force on control <NUM> (such as from a rotary damper <NUM> in <FIG>) is sufficient to overcome the energy stored in wrap spring <NUM>, control <NUM> will push clockwise, and by virtue of second control finger 124b extending through control slot 121c of second drive hub <NUM>, second drive hub <NUM> will push in a clockwise direction forcing second drive surface 121b against second spring end 122b, causing wrap spring <NUM> to transition from its equilibrium state to its flexed state and wrap open against the inner diameter of output <NUM>. Since output <NUM> is fixed to output <NUM> via shaft <NUM>, input <NUM> and output <NUM> rotate together.

In each of the disclosed embodiments, there is only a single hub upon which the wrap spring wraps down or wraps open. None of the embodiments include an input hub onto which the input torque is applied. Accordingly, there is no transfer of the input torque through the main body of the wrap spring such as where a portion is wrapped on an input hub and a portion on an output hub. Rather, the input drives torque exclusively through the spring end. Such embodiments do away with the precise assembly required for a cross over spring clutch of prior embodiments. Previous embodiments also required the load precisely cross over from an input hub to an output hub, which of course is not an issue with present embodiments. The present embodiments result in both reduced part count and reduced complications in assembly.

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 and to ground, 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.

The clutch embodiments described are constructed as input engaging clutches, which are disengaged without input rotation and which engage the clutch upon rotation of the input. One skilled in the art understands that the embodiments are readily constructible as input disengaging clutches, which are engaged without input rotation and which disengage the clutch upon rotation of the input. This can be adjusted based on the size of the equilibrium state of the spring compared to the output. For the input disengaging embodiment, the spring is still engaged on one end with the input and on the damper with the other.

In addition to clutching, when an embodiment includes a slip clutch, another embodiment can be realized as a brake.

Claim 1:
A wrap spring clutch (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a rotatable input (<NUM>, <NUM>, <NUM>, <NUM>);
a spring (<NUM>, <NUM>, <NUM>, <NUM>) comprising a first and a second end and having an equilibrium state and a flexed state, the spring (<NUM>, <NUM>, <NUM>, <NUM>) engaged with the input (<NUM>, <NUM>, <NUM>, <NUM>) through one of the first and second ends such that the spring rotates with the input and with an input torque transmitted exclusively through one of the first and second ends when the input (<NUM>, <NUM>, <NUM>, <NUM>) rotates;
a damper mechanism (<NUM>) engaged with one of the first and second ends such that the damper mechanism (<NUM>) causes the spring (<NUM>, <NUM>, <NUM>, <NUM>) to change from its equilibrium to its flexed state when the input (<NUM>, <NUM>, <NUM>, <NUM>) transitions from stationary to rotational, and such that the damper mechanism (<NUM>) allows the spring (<NUM>, <NUM>, <NUM>, <NUM>) to change from its flexed to its equilibrium state when the input (<NUM>, <NUM>, <NUM>, <NUM>) transitions from rotational to stationary;
characterized in that it further comprises
a rotatable output (<NUM>, <NUM>, <NUM>, <NUM>) positioned relative to the spring (<NUM>, <NUM>, <NUM>, <NUM>) such that the output (<NUM>, <NUM>, <NUM>, <NUM>) alternately rotates independently and synchronously with the input (<NUM>, <NUM>, <NUM>, <NUM>) when the spring (<NUM>, <NUM>, <NUM>, <NUM>) changes between its flexed and equilibrium states.