Multimode clutch arrangements

A clutch for selectively preventing rotation of a rotating component may include a first and second pawls pivotable between engagement and disengagement with the rotating component to selectively prevent or allow rotation of the rotating component in one or both directions. An armature moveable between a first and second armature positions may have a common member pivotally connected thereto and engaging the first and second pawls, with a torque spring biasing the common member to rotate toward the first pawl and away from the second pawl. In an intermediate armature position, the common member may disengage the first pawl from the rotating component while engaging the second pawl to allow rotation in one direction while preventing rotation in the opposite direction. In embodiments, a clutch may include a cam actuator rotating to selectively control engagement of the pawls with the rotating component and locking in one or both directions.

TECHNICAL FIELD

This disclosure relates generally to clutches, and in particular to clutches having multiple modes of engagement with a rotating element for selectively locking the element against rotation and allowing the element to rotate freely in one or both directions.

BACKGROUND

An automotive vehicle typically includes an internal combustion engine containing a rotary crankshaft configured to transfer motive power from the engine through a driveshaft to turn the wheels. A transmission is interposed between engine and driveshaft components to selectively control torque and speed ratios between the crankshaft and driveshaft. In a manually operated transmission, a corresponding manually operated clutch may be interposed between the engine and transmission to selectively engage and disengage the crankshaft from the driveshaft to facilitate manual shifting among available transmission gear ratios.

On the other hand, if the transmission is automatic, the transmission will normally include an internal plurality of automatically actuated clutch units adapted to dynamically shift among variously available gear ratios without requiring driver intervention. Pluralities of such clutch units, also called clutch modules, are incorporated within such transmissions to facilitate the automatic gear ratio changes.

In an automatic transmission for an automobile, anywhere from three to ten forward gear ratios may be available, not including a reverse gear. The various gears may be structurally comprised of inner gears, intermediate gears such as planet or pinion gears supported by carriers, and outer ring gears. Specific transmission clutches may be associated with specific sets of the selectable gears within the transmission to facilitate the desired ratio changes.

Because automatic transmissions include pluralities of gear sets to accommodate multiple gear ratios, the reliability of actuators used for automatically switching clutch modules between and/or among various available operating modes is a consistent design concern. It is also desirable to provide smooth transitions between the operating modes when the clutch modules engage and disengage from the gears. These considerations are also important in other operating environments where multimode clutch modules may be implemented to selectively allow and restrict the rotation of rotating components such as gears, shafts, torque converter components and the like. Therefore, much effort has been directed to finding ways to assure actuator reliability and seamless performance at competitive costs.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a clutch for selectively preventing rotation of a rotating component is disclosed. The clutch may include a first pawl that is pivotable about a first pawl pivot between engagement with the rotating component to prevent rotation of the rotating component in a first direction and disengagement with the rotating component to allow rotation of the rotating component in the first direction, a second pawl that is pivotable about a second pawl pivot between engagement with the rotating component to prevent rotation of the rotating component in a second direction and disengagement from the rotating component to allow rotation of the rotating component in the second direction, and an armature that is moveable between a first armature position and a second armature position. The clutch may further include a common member pivotally connected to the armature and engaging the first pawl and the second pawl to move the first pawl and the second pawl between engagement with and disengagement from the rotating component, and a torque spring biasing the common member to rotate toward the first pawl and away from the second pawl. When the armature is in the first armature position, the common member engages the first pawl and the second pawl to disengage the first pawl and the second pawl from the rotating component and allow rotation of the rotating component in the first direction and the second direction, when the armature is in the second armature position, the common member engages the first pawl and the second pawl to cause the first pawl and the second pawl to engage the rotating component and prevent rotation of the rotating component in the first direction and the second direction, and when the armature is in an intermediate armature position between the first armature position and the second armature position, the common member engages the first pawl to disengage the first pawl from the rotating component and allow the rotating component to rotate in the first direction, and engages the second pawl to cause me second pawl to engage the rotating component and prevent rotation of the rotating component in the second direction.

In various embodiments, the clutch may include an armature return spring biasing the armature toward the first armature position, an actuator coupled to the armature and actuatable to move the armature from the first armature position to the second armature position and the actuator may be actuatable to maintain the armature at the intermediate armature position. In other embodiments, the clutch may include a pawl spring connected to the armature or a clutch housing and biasing the first pawl and the second pawl toward engagement with the rotating component. The common member may include a bottom surface having a first distal end engaging the first pawl and a second distal end engaging the second pawl, the armature may include a pivot arm extending outwardly from the armature and the common member may be pivotally mounted on the pivot arm for rotation of the common member relative to the armature, and the torque spring may be mounted to the armature and the common member and may include a coil portion wrapped around the pivot arm, a first spring arm engaging the armature, and a second spring arm engaging the common member. In other configurations, the armature may include an upper pivot arm extending outwardly from the armature, a lower pivot arm extending outwardly from the armature and axially spaced apart from the upper pivot arm along the armature, with the common member being pivotally mounted on the armature between the upper pivot arm and the lower pivot arm.

In another aspect of the present disclosure, a clutch for preventing rotational movement of a gear is disclosed. The clutch may include a first pawl that includes a first toe and pivots about a first pawl pivot, a second pawl that includes a second toe and pivots about a second pawl pivot, and a cam actuator that rotates to selectively control engagement of the first toe and the second toe with the gear.

In various embodiments, the cam actuator may engage a first heel of the first pawl and a second heel of the second pawl, and the clutch may include a spring biased against the first heel of the first pawl and the second heel of the second pawl. In other embodiments, the clutch may include a first mechanical link connecting the cam actuator and the first toe and a second mechanical link connecting the cam actuator and the second toe. When the cam actuator is positioned in a first mode, the first toe and the second toe do not engage the gear, when the cam actuator is positioned in a second mode, the first toe engages the gear to prevent rotation of the gear in a first direction and the second toe does not engage the gear, and when the cam actuator is positioned in a third mode, the second toe engages the gear to prevent rotation of the gear in a second direction and the first does not engage the gear. When the cam actuator is positioned in a fourth mode, the first toe and the second toe engage the gear to prevent rotation of the gear in the first direction and the second direction. In one embodiment, the cam actuator may include an outer cam surface having a first protuberance, and second protuberance and a primary detent, wherein when the cam actuator is positioned in a first mode, the primary detent engages the first pawl and the second protuberance engages the second pawl to cause the first toe and the second toe to engage the gear to prevent rotation of the gear in a first direction and a second direction, when the cam actuator is positioned in a second mode, the first protuberance engages the first pawl to cause the first toe to engage the gear to prevent rotation of the gear in the first direction and the second protuberance engages the second pawl so that the second toe does not engage the gear, when the cam actuator is positioned in a third mode, the first protuberance engages the first pawl and the second protuberance engages the second pawl so that the first toe and the second toe do not engage the gear, and when the cam actuator is positioned in a fourth mode, the first protuberance engages the first pawl so that the first toe does not engage the gear and the primary detent engages the second pawl to cause the second toe to engage the gear to prevent rotation of the gear in the second direction.

Additional aspects are defined by the claims of this patent.

DETAILED DESCRIPTION

A first embodiment of a clutch described below can control the rotational movement of a rotating component, such as a gear having a plurality of teeth, cogs, detents or similar components. The clutch can include a first pawl and a second pawl that pivot about separate axes to selectively engage and disengage the gear and permit or prevent rotational motion of the gear. The first and second pawls can be controlled by a cam actuator that moves the first pawl, the second pawl, or both pawls into contact with the gear as well as disengaging the first pawl, the second pawl, or both from the gear. The embodiments of the clutch shown and described can be used in a wide variety of applications that benefit from controlling gears. The clutch can be used to control movement of gears within vehicle transmissions but other applications involving selectively allowing rotational motion are possible as well.

Turning toFIGS. 1-3, an embodiment of a clutch10is shown as it engages a gear12. In this embodiment, the clutch10includes a primary or first pawl14, a secondary or second pawl16, a spring18, a cam actuator20, and a drive sprocket22that are carried by a clutch housing24. The clutch10can be positioned adjacent to the gear12such that portions of the first pawl14and the second pawl16selectively engage gear teeth26positioned on an outer surface28of the gear12. While gear teeth26in this embodiment are shown on the outer surface28, other configurations are possible. For example, the clutch10can be used with different gear designs, such as internal spur gears or splines that are known to those skilled in the art. Rotation of the gear12can include four states: unimpeded rotation, fully-prevented rotation, rotation only in a clockwise direction, and rotation only in a counterclockwise rotation. The cam actuator20can control the clutch10to permit the gear12to move in accordance with one of these four states by selectively engaging and disengaging the first pawl14, the second pawl16, or both with respect to the gear12.

The first pawl14can include a primary or first toe30and a primary or first heel32while the second pawl16can include a secondary or second toe34and a secondary or second heel36. A primary or first pawl pivot38can be located between or at the first toe30and the first heel32while a secondary or second pawl pivot40can be located between the second toe34and the second heel36. The spring18can be carried by the clutch housing24and bias both the first heel32and second heel36into contact with the cam actuator20. The force of the spring18can also pivot the first pawl14and the second pawl16about their respective pivots38,40such that the first toe30and second toe34engage the gear teeth26.

The embodiment of the clutch10shown inFIG. 3includes a drive sprocket22having a plurality of teeth42. A recessed portion of the cam actuator20can receive the teeth42and transmit rotational force from the drive sprocket22to the cam actuator20. As the drive sprocket22is rotated in one direction, it rotates the cam actuator20in the opposite direction and in the process controls the first pawl14and the second pawl16. The drive sprocket22can be powered by a wide variety of electrical or mechanical devices used to create rotational motion. For example, the drive sprocket22can be rotated using an electric motor, a solenoid, a hydraulic drive or other similar device. In alternative embodiments, a linear actuator may be used in place of the drive sprocket22to drive the cam actuator20via an appropriate mechanical connection such as a rack and pinion arrangement. WhileFIG. 3depicts the cam actuator20controlled by the drive sprocket22, it is also possible to implement the clutch10without the drive sprocket22such that the electrical/mechanical devices rotate the cam actuator20directly. The cam actuator20can include an outer cam surface44that is shaped so that the first pawl14and the second pawl16can be sequentially actuated in response to rotation of the cam actuator20in one direction. The outer cam surface44can also include a primary or first protuberance46, a primary detent48, and a secondary or second protuberance50. The operation of the cam actuator20and the various portions of the outer cam surface44will be described in more detail with respect toFIGS. 4-7.

The gear12can be prevented from rotating about an axis A in both a clockwise and counterclockwise direction when the first toe30and the second toe34are biased into contact with the gear teeth26about the first pawl pivot38and the second pawl pivot40, respectively, by the spring18. In this position of the cam actuator20, the first protuberance46and the second protuberance50of the outer cam surface44allow the first pawl14and the second pawl16, respectively, to rotate toward the outer surface28of the gear12. This can be referred to as a first mode, a two-way lock mode or a default mode and is shown inFIG. 4. Though “clockwise” and “counterclockwise” are used herein for clarity between the illustrations of the embodiments and the directions of rotation of the elements, the rotation of the elements could also be considered to be in “a first direction of rotation” and “a second direction of rotation” that is opposite the first direction of rotation.

In a second mode or a one-way lock mode, the clutch10can permit the gear12to rotate in a clockwise direction as shown in the drawing figures, but prevent rotational motion in a counterclockwise direction. The configuration of the components of the clutch10for the second mode is shown inFIG. 5. To configure the clutch10for the second mode, the cam actuator20can be rotated in a clockwise direction so that the second protuberance50displaces the second heel36toward the gear teeth26. The second pawl16can pivot in the clockwise direction and disengage the second toe34from the gear teeth26permitting the gear12to freely rotate in the clockwise direction. As the gear12rotates in the clockwise direction, the gear teeth26rotate the first pawl14in the counterclockwise direction and move the first toe30in an outward direction toward the clutch10against the spring18acting on the first heel32and biasing the first toe30in the clockwise direction back toward the gear teeth26. The amount of angular rotation used by the second protuberance50to release the second toe34can be equal to or less than the arc of the primary detent48. The primary detent48can be shaped such that when the cam actuator20rotates and moves the second pawl16with the second protuberance50, the primary detent48permits the first toe30to remain engaged with the gear teeth26despite the cam actuator rotation.

A third mode or a two-way unlock mode is shown inFIG. 6in which the cam actuator20continues rotating in the clockwise direction past its location in the second mode to disengage both the first toe30as well as the second toe34from the gear teeth26. During the third mode, the second protuberance50can include a profile that maintains the second toe34in a disengaged relationship with the gear teeth26while the first heel32is engaged by the first protuberance46and pivoted toward the gear teeth26. As the first heel32is moved toward the gear teeth26against the force of the spring18, the first toe30can disengage from the gear teeth26. When the first toe30and the second toe34are disengaged from the gear teeth26, the gear12is free to rotate in either the clockwise or the counterclockwise direction.

The cam actuator20can continue to rotate in a clockwise direction from the third mode to a fourth mode or an additional one-way lock mode (FIG. 7) that permits rotation of the gear12only in the counterclockwise direction. As the cam actuator20rotates from its position in the third mode to the fourth mode, the second protuberance50of the outer cam surface44may rotate past the second heel36and align the second heel36with the primary detent48. As the second heel36transitions between the second protuberance50and the primary detent48, the force of the spring18rotates the second pawl16in the counterclockwise direction so the second heel36moves toward the primary detent48of the outer cam surface44thereby pivoting the second toe34into contact with the outer surface28and the gear teeth26. While the second toe34engages the gear teeth26, the first protuberance46can maintain the first toe30in a disengaged position with respect to the gear teeth26. The relative positions of the first toe30and the second toe34can prevent rotational motion of the gear12in the clockwise direction while allowing rotational motion in the counterclockwise direction.

Other implementations of the clutch are possible besides those shown inFIGS. 1-7. For example,FIG. 8depicts an embodiment of the clutch10that includes the first pawl14, the second pawl16, and the cam actuator20. Here, the cam actuator20can be connected to the first toe30via a primary or first mechanical link52and a secondary or second toe34via a secondary or second mechanical link54. A primary or first spring56and a secondary or second spring58can be included in the first mechanical link52and the second mechanical link54, respectively.FIG. 8depicts a single cam actuator20controlling both the first mechanical link52and the second mechanical link54. As shown, both the first toe30and the second toe34are disengaged from the gear teeth26to allow free rotation of the gear12in either direction in a similar manner as the third mode as shown inFIG. 6. In this implementation, the cam actuator20can be rotated in the counterclockwise direction to pull the first toe30further away from the gear teeth26, while at the same time the cam actuator20can also apply force on the second toe34via the second mechanical link54to rotate the second toe34of the second pawl16into engagement with the gear teeth26. Similar to the fourth mode ofFIG. 7, the gear12is permitted to rotate in the counterclockwise direction while rotation in the clockwise direction is prevented. The gear12can overcome the force applied by the second spring58as it rotates in the counterclockwise direction and the gear teeth26will move the second toe34toward the cam actuator20, but the second toe34will engage the gear teeth26to prevent rotation in the clockwise direction. Conversely, the cam actuator20can be rotated in a clockwise direction to pull the second toe34away from the gear teeth26. At the same time, the cam actuator20can also apply force on the first toe30via the first mechanical link52to engage the gear teeth26. This can permit the gear12to rotate in a clockwise direction while preventing rotation in a counterclockwise direction in a similar manner as the second mode shown inFIG. 5. The gear12can rotate in a clockwise direction and the gear teeth26can move the first toe30toward the cam actuator20and overcome the force applied by the first spring56.

The implementation of the clutch10shown inFIG. 8may prevent rotation in only one direction at a time, or allow free rotation in both directions. However, it should be appreciated that other implementations of the clutches10described herein are possible. For instance, the cam actuator20shown inFIGS. 1-7could be substituted with a clutch10that used a first cam actuator and a second cam actuator. That is, rather than using a single cam that sequentially enters the four modes described above, the clutch10could use two cam actuators to directly move from any one of those modes to any other mode without entering an intermediate mode. The two cam actuators can engage the first pawl14and second pawl16at the same time, disengage the first pawl14and the second pawl16at the same time, or separately engage or disengage the first pawl14and the second pawl16. That is, the cams can be actuated at the same time or deactivated at the same time. In another implementation, the clutch10could be configured to eliminate either the first pawl14or the second pawl16. Eliminating one of the pawls14,16can render a one-way or two-mode clutch10that allows free movement of the gear12or limits rotational motion in one direction. In another example, the clutch10shown inFIG. 8could use a first cam actuator and a second cam actuator. In such an arrangement, the four modes of operation discussed above could be realized in a toe-actuated system.

A further alternative embodiment of a clutch100is shown inFIGS. 9-14. Referring toFIG. 9, the clutch100as shown is implemented with a gear102to control the rotation of the gear102by selectively engaging and disengaging from gear teeth104disposed on an outer surface106of the gear102. While the gear teeth104in this embodiment are shown on the outer surface106, other configurations are possible, such as the use of the clutch100with different gear designs such as internal spur gears or splines as discussed with the embodiments described above. In this embodiment, the clutch100includes a primary or first pawl108and a secondary or second pawl110that are carried on a clutch bracket or clutch housing112, and an actuator114that will control the positioning of the pawls108,110to lock and unlock the clutch100. The clutch housing112is shown in cross-section to facilitate illustration and description of the components of the clutch100residing therein. In a similar manner as described above for the pawls14,16, the first pawl108can include a first tooth engaging end or first toe116and a first releasing end or first heel118while the second pawl110can include a second tooth engaging end or second toe120and a second releasing end or second heel122. A first pawl pivot124having first pivot ends can be located between the first toe116and the first heel118, and a second pawl pivot126having second pivot ends can be located between the second toe120and the second heel122, and can be mounted in corresponding apertures of the clutch housing112as discussed below to allow the pawls108,110to pivot between locked and unlocked positions.

The clutch housing112is shown in greater detail inFIG. 10. The clutch housing112includes a substantially U-shaped cross section and a plurality of apertures through which elements of the clutch100can pass. The clutch housing112includes primary or first pawl apertures128for receiving corresponding ends of the first pawl pivot124of the first pawl108as well as secondary or second pawl apertures130for receiving corresponding ends of the second pawl pivot126of the second pawl110. The first pawl apertures128and the second pawl apertures130can be axially spaced from each other on opposite sides132,134of the clutch housing112. The axial spacing of the apertures128,130can permit the first pawl108and the second pawl110to each pivot about different axes136,138located between and passing through the sides132,134, respectively. The clutch housing112may have additional openings, including vertical slots140through the sides132,134and an armature aperture142through a top wall144of the clutch housing112, for other components of the clutch100as will be discussed further hereinafter. The clutch housing112can be formed from a variety of materials as will be apparent to those skilled in the art. In one implementation, the clutch housing112can be formed from a metal alloy using extrusion techniques. However, it should be appreciated that the shape and design of the clutch housing112can deviate from what is shown herein.

Returning toFIG. 9, the actuator114as shown may be a solenoid, hydraulic or other appropriate type of linear actuator capable of creating linear motion as described herein. In alternative embodiments, the actuator may be a rotary actuator such as a stepper motor operatively connected to the elements of the clutch100by a linkage or other appropriate mechanism known in the art for converting rotation generated by the rotary actuator into the linear motion described herein. The illustrated actuator114may include a piston or armature146extending therefrom through the armature aperture142of the clutch housing112and into the interior of the clutch housing112to a first armature position or an extended armature position. The armature146may include pivot arm148extending outwardly on both sides of the armature146and being received by the vertical slots140through the sides132,134of the clutch housing112to allow the armature146to move linearly upwardly and downwardly within the limits allowed by the vertical slots140. The pivot arm148may pass through the armature146and extend outwardly. In alternative embodiments, the pivot arm148may be integrally formed with the armature146.

The clutch100further includes a common member150pivotally mounted on the pivot arm148of the armature146and disposed above the first pawl108and the second pawl110with a primary or first distal end152of a bottom surface of the common member150engaging the first heel118and a secondary or second distal end154engaging the second heel122. The pivot arm148are received in corresponding common member pivot apertures156on either side of the common member150so that the common member150can pivot about an axis that is approximately parallel to the axes136,138of the pawls108,110, respectively. The interconnection between the armature146and the common member150is shown in greater detail inFIG. 11in which the common member150is shown in partial cross-section. A vertical opening158through the common member150through which the armature146passes provides sufficient space for the common member150to pivot about the pivot arms148without engaging the armature146during operation of the clutch100as discussed more fully below. Where the pivot arm148is a separate component, the common member150may be positioned relative to the armature146, and then the pivot arm148may be inserted through the pivot apertures156and the corresponding hole through the armature146. If the armature146and pivot arm148are integrally formed, the common member150may be formed in two halves that can be installed on the pivot arm148on each side of the armature146and then secured together. In further alternative embodiments, the armature146and the common member150may be formed concurrently through three-dimensional printing, injection molding or other appropriate integrated manufacturing technique.

FIG. 11also shows various biasing mechanisms that may be used to control the movement of the armature146, the common member150and the pawls108,110during operation of the clutch100. A compressive spring or armature return spring160may be provided to bias the armature146and the common member150toward a normal or two-way unlocked position shown inFIGS. 9 and 11when the actuator114is not actuated. In the present embodiment, the armature return spring160is a coil spring disposed around the armature146and positioned between an inner surface162of the top wall144of the clutch housing112and a top surface164of the common member150to bias the common member150away from the actuator114. With this configuration, the armature return spring160may allow the common member150to pivot about the pivot arms148while applying the biasing force. The coil spring arrangement of the armature return spring160is exemplary only, and other configurations of biasing mechanisms for biasing the armature146and the common member150toward the illustrated position while allowing the common member150to pivot will be apparent to those skilled in the art.

A torsional spring or torque spring166may be provided to bias the common member150to rotate in a counterclockwise direction about the pivot arms148as shown inFIGS. 9 and 11. As shown, the torque spring166includes a coil portion168wrapped around the pivot arms148of the armature146, a first spring arm170engaging the armature146, and a second spring arm172engaging the common member150. The tension in the coil portion168of the torque spring166tends to pull or rotate the spring arms170,172toward each other. With the first spring arm170fixed to the armature146, the second spring arm172will rotate counterclockwise toward the armature146as shown inFIGS. 9 and 11and cause a corresponding rotation of the common member150. The illustrated arrangement of the torque spring166is exemplary only, and other configurations of biasing mechanisms for causing the common member150to rotate relative to the armature146are contemplated by the inventors.

In addition to the armature return spring160and the torque spring166, the clutch100may include an additional biasing mechanism in the form of a pawl spring174engaging the heels118,122of the pawls108,110opposite the distal ends152,154of the common member150. The pawl spring174may be a cantilever or leaf spring connected to the armature146at a distal end176that is opposite the actuator114and beneath or outward of the common member150. The pawl spring174may have a first spring portion178extending outwardly toward and engaging the first heel118of the first pawl108to provide a biasing force tending to rotate the first pawl108in the counterclockwise direction as shown. In a similar way, a second spring portion180extends outwardly toward and engages the second heel122of the second pawl110to provide a biasing force tending to rotate the second pawl110in the clockwise direction as shown. Configured in this way, the pawl spring174tends to rotate the toes116,120of the pawls108,110toward the outer surface106of the gear102and into their locking positions. The illustrated arrangement of the pawl spring174is exemplary only, and other configurations of biasing mechanisms for causing the pawls108,110to rotate toward their locked positions are contemplated by the inventors. For example, the pawl spring174could be mounted to inner surface162of the clutch housing112instead of the armature146while still providing the necessary biasing force to rotate the pawls108,110in the desired direction. Moreover, separate springs may be provided for each of the pawls108,110and may have any appropriate configuration for biasing the pawls108,110independently to provide the range of motion required of the pawls108,110during operation of the clutch100as discussed hereinafter.

Returning toFIG. 9, the clutch100is illustrated in a first or normal position or a first mode of operation wherein the pawls108,110are rotated so that the toes116,120are out of engagement with the teeth104of the gear102and the gear102is free to rotate in either direction. This may be considered to be a two-way unlock position or mode of the clutch100. The armature146and the common member150may have moved to this position due to the biasing force of the armature return spring160when the actuator114is not actuated, such as when pressure is relieved from a hydraulic actuator or electricity is cut off to a solenoid actuator.

When it is desired to engage the clutch100to lock the gear102from rotation in one or both directions, the actuator114may be actuated to cause the armature146to move upwardly as shown in the drawing figures against the biasing force of the armature return spring160.FIG. 12illustrates the armature146and the common member150in an intermediate armature position or mode that will lock the gear102to prevent rotation in the counterclockwise direction while allowing free rotation in the gear102in the clockwise direction. As the armature146, the common member150and the pawl spring174are drawn upward by the actuator114, the combined torque of the torque spring166biasing the common member150in the counterclockwise direction and the second spring portion180biasing the second pawl110in the clockwise direction and urging the second distal end154of the common member150in the counterclockwise direction is greater than the torque of the first spring portion178biasing the first pawl108in the counterclockwise direction which in turn applies a force to the first distal end152of the common member150in the clockwise direction. If necessary, the clutch100may include a corresponding stop (not shown) for one or both of the pawls108to limit their rotation toward the unlocked positions shown inFIG. 9. The presence of a stop for the first pawl108may allow the torque spring166to be sized to create sufficient torque to exceed the torque created by the first spring portion178of the pawl spring174for a desired amount of deflection of the first spring portion178but without causing the first pawl108to rotate too far in the clockwise direction such that the first heel118may engage the teeth104of the gear102.

As the common member150rotates in the counterclockwise direction to the position shown inFIG. 12while being drawn upward by the armature146, the second distal end154correspondingly rotates away from the second heel122of the second pawl110, thereby allowing the second spring portion180to rotate the second pawl110in the clockwise direction toward the locked position. Eventually, at the intermediate position shown inFIG. 12, the second pawl110rotates to the locked position where the second toe120will engage the teeth104of the gear102to prevent rotation of the gear102in the counterclockwise direction. At the same time, the torque applied by the first distal end152of the common member150to the first heel118of the first pawl108causes the first pawl108to remain in the unlocked position so that the gear102is still free to rotate in the clockwise direction. Depending on the configuration of the actuator114and a control unit (not shown) for the clutch100, the intermediate position or mode ofFIG. 12may be a discrete position of the armature146and the common member150that can be sustained by the actuator114to maintain the one-way locked for an extended duration. In other implementations of the clutch100, the intermediate position or mode may be a transient position through which the armature146and the common member150pass before a second or two-way locked position or mode as discussed hereinafter.

As the armature146, the common member150and the pawl spring174continue to move upward due to the force from the actuator114acting against the armature return spring160, the deflection and the stress in the first spring portion178of the pawl spring174will become sufficient to overcome the torque generated by the torque spring166and, if the second heel122is still engaging the second distal end154of the common member150, the second spring portion180of the pawl spring174. At that point, the first spring portion178will cause the first pawl108to begin to rotate in the counterclockwise direction toward its locked position. At the same time, the engagement of the first distal end152of the common member150by the first heel118will cause the common member150to rotate back in the clockwise direction against the forces of the torque spring166and the second spring portion180of the pawl spring174. Eventually, at a second armature position or a two-way locked position or mode of the clutch100shown inFIG. 13, the first pawl108rotates to a position where the first toe116will engage the teeth104of the gear102to prevent rotation of the gear102in the clockwise direction. The second pawl110remains in its locked position so the gear102cannot rotate in either direction.

When the clutch100is to be unlocked, the actuator114is deactivated so that the armature146and the common member150can be moved downward from the second position ofFIG. 13to the first position ofFIG. 9under the urging of the compressed armature return spring160. As the armature146begins to move downward, the common member150will rotate in the counterclockwise under the urging of the torque spring166. The rotation of the common member150will cause the first pawl108to rotate in the clockwise direction and out of engagement with the teeth104of the gear102to first unlock the gear102in the clockwise direction. The second pawl110will initially remain in its locked position as shown inFIG. 12. After the first pawl108reaches its full unlocked position, further downward movement of the armature146and engagement of the first distal end152of the common member150by the first heel118will cause the common member150to rotate in the clockwise direction against the force of the torque spring166. The clockwise rotation causes engagement of the second heel122by the second distal end154of the common member150and corresponding counterclockwise rotation of the second pawl110out of the locked position ofFIGS. 12 and 13and into the unlocked position illustrated inFIG. 9.

FIGS. 14-16illustrate a further alternative embodiment of a clutch200that is generally similar to the clutch100but having a modified armature and common member arrangement. The same components of the clutches100,200are identified with the same reference numerals for purposes of clarity and brevity. Referring toFIG. 14, the clutch200includes a modified clutch housing202formed from a pair of housing plates204(near plate removed to reveal internal components of the clutch200) separated by a spacer plate206. The housing plates204and spacer plate206may be provided with an opening208configured to receive and retain an actuator210that operates to move the clutch200between unlocked and locked positions or modes as will be discussed further below. The housing plates204may further include pawl apertures (not shown) that receive the pawl pivots124,126and allow the pawls108,110to pivot about the pawl pivots124,126, and vertical slots212similar to those illustrated and described above. Also in this embodiment, the pawl spring174is mounted between the housing plates204with the spring portions178,180engaging the heels118,122of the pawls108,110to bias the pawls108,110toward their locked positions.

The actuator210includes an armature214extending downwardly therefrom between the housing plates204. In this embodiment, the actuator may include an internal armature return spring (not shown) that biases the armature toward the downward extended position shown inFIG. 14when the actuator210is not actuated. The armature214includes outwardly extending upper pivot arm or arms216and lower pivot arm or arms218are axially spaced apart along the armature214. The pivot arms216,218may extend through the corresponding vertical slots212of the housing plates204to guide the pivot arms216,218as the armature214is extended by the armature return spring and retracted when the actuator210is actuated.

A modified common member220is mounted on the armature214between the upper pivot arms216and the lower pivot arms218and disposed above the first pawl108and the second pawl110with a first distal end222of a bottom surface of the common member220engaging the first heel118and a second distal end224engaging the second heel122. The pivot arms216,218receive the common member220so that the common member220can pivot about an axis that is approximately parallel to the axes136,138of the pawls108,110, respectively. A torque spring226may be provided to bias the common member220to rotate in a counterclockwise between the pivot arms216,218as shown inFIGS. 14-16. As shown, the torque spring226includes a coil portion228between the pivot arms216,218of the armature214, a first spring arm230engaging the armature214, and a second spring arm232engaging a top surface234of the common member220. The tension in the coil portion228of the torque spring226tends to push or rotate the spring arms230,232away from each other. With the first spring arm230fixed to the armature214, the second spring arm232will rotate counterclockwise away from the armature214as shown inFIGS. 14-16and cause a corresponding rotation of the common member220. The illustrated arrangement of the torque spring226is exemplary only, and other configurations of biasing mechanisms for causing the common member220to rotate relative to the armature214are contemplated by the inventors.

The clutch200operates in a generally similar manner as the clutch100as illustrated and described above. Referring toFIG. 14, the two-way unlock position or mode of the clutch200is shown with the pawls108,110rotated so that the toes116,120are out of engagement with the teeth104of the gear102. The armature214and the common member220may have moved to this position due to the biasing force of the armature return spring when the actuator210is not actuated. When the actuator210is actuated, the armature214moves upwardly against the biasing force of the internal armature return spring.FIG. 15illustrates the armature214and the common member220in the intermediate position or mode that prevents rotation of the gear102in the counterclockwise direction while allowing free rotation in the gear102in the clockwise direction. The common member220rotates in the counterclockwise direction and biases the first pawl108in the clockwise direction to maintain the first pawl108in the unlocked position. At the same time, the second distal end224rotates away from the second heel122of the second pawl110to allow the second spring portion180to rotate the second pawl110in the clockwise direction toward the locked position and eventually to the locked position where the second toe120engages the teeth104to prevent rotation of the gear102in the counterclockwise direction. As discussed above, the intermediate position or mode ofFIG. 15may be a discrete position of the armature214and the common member220that can be sustained by the actuator210or a transient position through which the armature214and the common member220pass before the second or two-way locked position or mode.

As the armature214and the common member220continue to move upward, the first spring portion178of the pawl spring174overcomes the torque generated by the torque spring226. At that point, the first pawl108begins to rotate toward its locked position, and the first heel118will cause the common member220to rotate back in the clockwise direction. At the second or two-way locked position or mode of the clutch200shown inFIG. 16, the first toe116will engage the teeth104to prevent rotation of the gear102in the clockwise direction while the second pawl110remains in its locked position so the gear102cannot rotate in either direction.

The actuator210is deactivated so that the armature146and the common member150can be moved downward from the second position ofFIG. 16to the first position ofFIG. 14to unlock the clutch200. As the armature214begins to move downward, the common member220rotates in the counterclockwise under the urging of the torque spring226to cause the first pawl108to rotate in the clockwise direction and out of engagement with the teeth104to initially unlock the gear102for rotation in the clockwise direction while the second pawl110remains in its locked position as shown onFIG. 15. After the first pawl108reaches its full unlocked position, further downward movement of the armature214will cause the common member220to rotate in the clockwise direction against the force of the torque spring226. The clockwise rotation of the common member220causes counterclockwise rotation of the second pawl110out of the locked position ofFIGS. 14 and 15and into the unlocked position illustrated inFIG. 13.

INDUSTRIAL APPLICABILITY

The clutches described above can selectively control the engagement of a first pawl and a second pawl that each prevents rotation in one direction of a rotational part that may have teeth, cogs, or detents. The clutches can selectively engage and disengage the first and second pawls by converting movement created by an actuator into rotation of the first and second pawls via an intervening mechanism such as a cam actuator or a common member as described above. In locking positions, toes of the first and second pawls engage teeth or other elements of a rotating part to prevent rotation of the part. When desired, the clutches can selectively be placed in one-way or two-way unlocking positions to partially or completely disengage the clutch to allow rotation of the rotating part. In some embodiments, the clutches can include a torque spring that biases a common member to rotate in one direction to sequentially disengage one pawl and then the other pawl to transition between a two-way locked position or mode to a one-way locked position or mode and then to a two-way unlocked position or mode. With these configurations, clutches in accordance with the present disclosure can provide a smooth transition from being unlocked or disengaged to being locked or engaged and vice versa, which can improve the experience of the operator of the apparatus in which the clutches are implemented and reduce wear and tear on the components of the apparatus.