Patent Publication Number: US-9834956-B2

Title: Safety mechanism for door handle

Description:
BACKGROUND 
     The present invention relates to coupling and uncoupling mechanism or “safety mechanism” for a door handle assembly or other assembly that includes a rotatable spindle. 
     SUMMARY 
     The invention provides a door latching apparatus comprising: a latching mechanism configured to be mounted on a door, the latching mechanism including a latching member having extended and retracted positions relative to the door for releasably securing the door relative to an adjacent structure, and the latching mechanism including a pivoting member operably connected to the latching member such that pivotal movement of the pivoting member about an axis moves the latching member between the extended and retracted positions, the pivoting member having therein an aperture defined by a wall, a handle manually pivotable about the axis, the handle including a hub surrounding a portion of the pivoting member, the hub having therein an opening, and a safety mechanism including a manually movable cam member having a detent surface and a driving surface, the cam member movable relative to the hub between an inner position, an outer position and an intermediate position between the inner and outer positions, and the mechanism also including a first spring exerting on the cam member a force biasing the cam member in the direction from the intermediate position to the inner position, and a second spring exerting on the cam member a force biasing the cam member in the direction from the inner position to the intermediate position, the first and second springs having spring forces such that the cam member is in the intermediate position absent external forces, wherein, when the cam member is in the intermediate position, the cam member extends partially into the aperture such that if the handle is pivoted relative to the pivoting member, engagement between the detent surface and the wall causes the cam member to move against the force of the spring to the outer position, wherein, when the cam member is in the outer position, the cam member is withdrawn from the aperture such that pivotal movement of the handle does not cause pivotal movement of the pivoting member, and wherein, when the cam member is in the inner position, the cam member extends fully into the aperture such that if the handle is pivoted relative to the pivoting member, the driving surface of the cam member engages the wall and pivotal movement of the handle causes pivotal movement of the pivoting member. 
     The invention also provides an apparatus comprising: a pivoting member pivotable about an axis and configured to be operably connected to a device to be operated, the pivoting member having therein an aperture defined by a wall, an actuating member manually pivotable about the axis, the actuating member including a hub surrounding a portion of the pivoting member, the hub having therein an opening, and a safety mechanism including a manually movable cam member having a detent surface and a driving surface, the cam member movable relative to the hub between an inner position, an outer position and an intermediate position between the inner and outer positions, and the mechanism also including a first spring exerting on the cam member a force biasing the cam member in the direction from the intermediate position to the inner position, and a second spring exerting on the cam member a force biasing the cam member in the direction from the inner position to the intermediate position, the first and second springs having spring forces such that the cam member is in the intermediate position absent external forces, wherein, when the cam member is in the intermediate position, the cam member extends partially into the aperture such that if the actuating member is pivoted relative to the pivoting member, engagement between the detent surface and the wall causes the cam member to move against the force of the spring to the outer position, wherein, when the cam member is in the outer position, the cam member is withdrawn from the aperture such that pivotal movement of the actuating member does not cause pivotal movement of the pivoting member, and wherein, when the cam member is in the inner position, the cam member extends fully into the aperture such that if the actuating member is pivoted relative to the pivoting member, the driving surface of the cam member engages the wall and pivotal movement of the actuating member causes pivotal movement of the pivoting member. 
     The invention also provides a mechanism for selectively coupling a first moving part with a second moving part such that the first and second moving parts move together, the second moving part having an aperture, the mechanism comprising: an engaging member carried by the first part, the engaging member having a detent surface and a load transferring surface, the engaging member being movable between a detent position in which the detent surface is within the aperture of the second moving part, a uncoupled position in which the engaging member is fully retracted from the aperture, and a coupled position in which the load transferring surface is within the aperture; a biasing member acting with a biasing force on the engaging member to bias the engaging member into the detent position or into the coupled position; and an actuating member for manually actuating the engaging member to overcome the biasing force of the biasing member and move the engaging member into the coupled position or detent position; wherein relative movement of the first moving part and second moving part with the engaging member in the detent position results in a component of force acting against the biasing force, such that the biasing force is overcome and the engaging member rides out of the aperture in the second moving member, into the uncoupled position. 
     In some embodiments, the first moving part comprises a handle and the second moving part comprises a spindle on which the handle is supported, the handle and spindle rotating about a concentric axis of rotation. In some embodiments, the handle includes a lever; wherein the lever is in a horizontal condition when the engaging member is in the detent position; and wherein the biasing force is sufficient to maintain the engaging member in the detent position under at-rest torque applied to the lever under the influence of gravity. In some embodiments, the engaging member includes a cam member that defines the detent surface and load transferring surface, and a stem having a first free end extending through a portion of the first moving part and an opposite second end that is attached to the cam member; wherein the stem defines a stem axis; and wherein movement of the engaging member between the detent, coupled, and uncoupled positions is in a direction parallel to the stem axis. In some embodiments, movement of the engaging member from the detent position to the uncoupled position is in an opposite direction from movement of the engaging member from the detent position to the coupled position. In some embodiments, the first moving part and second moving part are rotatable about a common pivot axis; wherein the stem axis is perpendicular to the pivot axis; wherein movement of the engaging member from the detent position to the uncoupled position is radially away from the pivot axis; and wherein movement of the engaging member from the detent position to the coupled position is radially toward the pivot axis. In some embodiments, the engaging member includes a button mounted to the first end of the stem. In some embodiments, the engaging member moves in a first direction from the detent position to the uncoupled position and in a second direction, opposite the first direction, from the detent position to the coupled position; and wherein the biasing member includes first and second springs applying respective opposing first and second biasing forces on the engaging member, a combination of the first and second opposing biasing forces resulting in the biasing force that biases the engaging member toward the detent position; wherein movement of the engaging member toward the coupled position deflects the first spring to increase the first biasing force and relaxes the second spring to decrease the second biasing force; and wherein movement of the engaging member toward the uncoupled position deflects the second spring to increase the second biasing force and relaxes the first spring to decrease the first biasing force. In some embodiments, the invention further comprises a locking mechanism with which the engaging member can be manually moved and locked into the detent position or the coupled position against the biasing force. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a door having a handle that incorporates a safety mechanism according to the present invention. 
         FIG. 2 . is a cross-sectional view of the handle and safety mechanism in an intermediate position. 
         FIG. 3  is a cross-sectional view of a portion of the handle in which the safety mechanism received. 
         FIG. 4  is a cross-sectional view of the safety mechanism. 
         FIG. 5  is a cross-sectional view of the safety mechanism in an outer position and the handle rotated. 
         FIG. 6  is a cross-sectional view of the safety mechanism in an inner position. 
         FIG. 7  is an exploded, cross-sectional view of an alternative assembly for the safety mechanism. 
         FIG. 8  is an exploded, perspective view of another alternative assembly for the safety mechanism. 
         FIG. 9  is a cross-sectional view of the safety mechanism of  FIG. 8  installed on the door handle. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a door  10  including a child safety handle according to the present invention. As will be noted below, the invention can be applied to virtually any mechanism that selectively couples and uncouples a handle with a concentric spindle on which the handle is supported, but for the sake of example, the invention is illustrated in a door handle application. The door  10  includes a hinge edge  30  and a free edge  40 . The door  10  pivots within a door jamb between open and closed positions. Mounted to the door  10  are a latching mechanism  50  and a door handle assembly  60 . 
     The latching mechanism  50  is configured to be mounted on the door  10 , and includes a latching member  70  and a spindle or pivoting member  80  ( FIG. 2 ). The terms “latch,” “latching,” and variations thereon are intended to cover a mechanism that can temporarily latch the door closed or that can lock the door closed. In this regard, “latch” and its variations should be interpreted as “latch or lock” in this written description and the appended claims. The latching member  70  is movable between an extended position and a retracted position relative to the door  10 . In the extended position, a free end of the latching member  70  extends out of the free edge  40  of the door  10 . The latching member  70  is biased into the extended position. In the retracted position, the latching member  70  is moved axially against a biasing force into the door  10 . In the retracted position, the end of the latching member  70  does not extend significantly, if at all, beyond the free edge  40  of the door  10 . When the door  10  is moved into the closed position, the latching member  70  deflects axially into the retracted position in response to the free end impacting the door jamb. The biasing force moves the latching member  70  axially into the extended position when the latching member  70  aligns with a receptacle in the door jamb. When in the extended position and engaged in the receptacle, the latching member  70  retains the door  10  in the closed position, and releasably secures the door  10  relative to an adjacent structure, such as a wall to which the jamb is mounted. 
     Referring to  FIG. 2 , the pivoting member  80  of the latching mechanism  50  includes a wall that defines an aperture  90 . In the illustrated embodiment, and in known door handle assemblies and mechanisms, the aperture  90  is a keyway. As used in this specification, the term “aperture” is intended to include any slot, hole, recess, bore, blind bore, groove, or the like. Rotation of the pivoting member  80  about an axis  100  moves the latching member  70  between the extended and retracted positions. With the pivoting member  80  pivoted and the latching member  70  in the retracted position, the door  10  can be pushed or pulled into the open position because the latching member  70  is retracted from the receptacle in the doorjamb. 
     The door handle assembly  60  includes a handle  110 , a hub  120 , and a safety mechanism  130 . The hub  120  surrounds and is supported by the pivoting member  80 . The handle  110  and hub  120  are manually pivotable about the pivot axis  100 . The safety mechanism  130  is mounted to the hub  120 . The handle  110  is illustrated as having a lever shape for illustrative purposes only, and can in other embodiments be provided as a round door knob or a handle of any other shape that is turned to actuate the latching mechanism  50 . In this regard, the term “handle” is intended to broadly encompass any manually rotatable element, without regard to its shape. 
     In known door handle assemblies  60 , there is no safety mechanism  130  and the hub  120  includes an inwardly-projecting key that mates with the keyway  90  of the pivoting member  80 , such that the hub  120  is always coupled for rotation with the pivoting member  80 . Known safety apparatus for door knobs often surround the knob, such that a person grasps the safety apparatus. Such known safety apparatus rotate with respect to the door knob (i.e., transmit no torque to the door knob) unless the person actuates an element that couples the safety apparatus and door knob (e.g., by friction). Such known safety apparatus have at least a few disadvantages compared to the safety mechanism of the present invention: the known safety apparatus are only useful on round door knobs; the known safety apparatus cover the door knob, which creates a different (often undesirable) visual impression of the door knob compared to other door knobs in the building; and such safety apparatus are often not lockable into a coupled condition with the door knob (i.e., the safety apparatus has to be actuated every time to door knob is turned, even when it is desired to leave the safety apparatus and door knob coupled for a period). 
     Referring now to  FIG. 3 , the hub  120  includes a boss  140  that has side walls  150  and an end wall  160 . In a circular boss  140 , such as that illustrated, the side walls  150  are actually a single, continuous side wall  150 . The side walls  150  and end wall  160  define therebetween a cavity  170 . The end wall  160  includes an inner surface  180  facing into the cavity  170  and an outer surface  190  facing away from the cavity  170 . The end wall  160  also defines a clearance opening  200  that communicates with the cavity  170 . The clearance opening  200  aligns with a hole  205  in the hub  120 , and with the aperture  90  in the pivoting member  80  when the door handle assembly  60  is in an at-rest position (illustrated in  FIG. 2 ). 
     The safety mechanism  130  is manually movable relative to the hub  120  between the inner position ( FIG. 6 ), an outer position ( FIG. 5 ), and an intermediate position ( FIG. 2 ) between the inner and outer positions. 
     With reference to  FIG. 4 , the safety mechanism  130  includes a button  210 , a stem  220 , a cam member  230 , a first spring  240 , and a second spring  250 . The button  210  includes a flat engagement surface  260  on one side, a connection point  270  on an opposite side, and a spring seat  280  surrounding the connection point  270 . The stem  220  defines a stem axis  290  and includes a first end  300  that connects to the button connection point  270  and a second end  310  that connects to the cam member  230 . The stem axis  290  is perpendicular to the pivot axis  100  of the pivoting member  80 . In the illustrated embodiment, the stem axis  290  intersects the pivot axis  100 . 
     The cam member  230  defines at one end a shoulder  320  that surrounds the second end  310  of the stem  220 , and a blunt tip  330  at the end opposite the shoulder  320 . The cam member  230  defines a detent surface  340  adjacent the tip  330 , and a driving surface  350  between the detent surface  340  and the shoulder  320 . The detent surface  340  (which may alternatively be termed a “detent surface”) is angled greater than 0° and less than 90° with respect to the stem axis  290 . A lateral force (i.e., perpendicular to the stem axis  290 ) applied to the detent surface  340  will result in a component of force acting on the safety mechanism  130  parallel to the stem axis  290 . The driving surface  350  is parallel to the stem axis  290 , so a lateral force applied to the driving surface  350  will include no component that is parallel to the stem axis  290 . 
     The first spring  240  and the second spring  250  are compression springs having approximately equal lengths and spring coefficients in the illustrated embodiment, although springs of mixed sizes, types, and stiffness can be employed in other embodiments. The first spring  240  exerts a first biasing force on the cam member  230  toward the inner position, and the second spring  250  exerts a second biasing force on the button  210  toward the outer position. The first biasing force may be said to be directed “radially inward” because it is directed parallel to the stem axis  290  toward the pivot axis  100 , and the second biasing force may be said to be directed “radially outward” because it is directed parallel to the stem axis  290  away from the pivot axis  100 . In the absence of other external forces, the first and second biasing forces equal each other when the cam member  230  is in the intermediate position, such that the first and second springs  240 ,  250  can be said to cooperate to bias the cam member  230  into the intermediate position. 
     The safety mechanism  130  is mounted to the boss  140 . More specifically, the first spring  240  is placed around the stem  220 , and the first end  300  of the stem  220  is extended through the clearance hole  200 , such that the first spring  240  and the cam member  230  are positioned within the cavity  170 . The second spring  250  is positioned around the first end  300  of the stem  220  outside of the cavity  170 . The first end  300  of the stem  220  is secured to the button  210  at the connection point  270  with a suitable connection arrangement, such as glue, friction welding, swaging, press fitting, or a threaded engagement, or the button  210 , stem  220 , and cam  230  (or any two of those components) can be die cast as a single component. As can be seen in the drawings, the ends of the second spring  250  engage the spring seat  280  of the button  210  and the outer surface  190  of the end wall  160  of the boss  140 , and the ends of the first spring  240  engage the inner surface  180  of the end wall  160  of the boss  140  and the shoulder  320  of the cam member  230 . 
     In the intermediate position, the detent surface  340  of the cam member  230  is within the aperture  90  in the pivoting member  80 . In the outer position, the tip  330  of the cam member  230  abuts the outer surface of the pivoting member  80 . The outer position may also be termed the “disengaged position” or “uncoupled position.” In the inner position, the driving surface  350  of the cam member  230  abuts the pivoting member  80  within the aperture  90 . The inner position may also be termed the “engaged position” or “coupled position.” 
     With reference to  FIG. 2 , the engagement of the detent surface  340  within the aperture  90  resists rotation of the handle  110  and hub  120  with respect to the pivoting member  80 . In the illustrated embodiment, the handle  110  is a lever, which is supported in cantilever fashion by the pivoting member. It is often desirable, for aesthetic and functional reasons, to hold the lever  110  in a horizontally-extending position (as in  FIGS. 1 and 2 ) when in the intermediate position. Gravity acting on the lever  110  creates a clockwise (as viewed in  FIG. 2 , although it could be counterclockwise in other configurations) torque on the handle  110  (which will be referred to herein as “at-rest torque”) about the pivot axis  100 . 
     The arrangement of the detent surface  340  and the first spring  240  preferably provides sufficient detent holding force such that the at-rest torque, acting alone, does not deflect the first spring  240  to an extent sufficient to remove the cam member  230  from the aperture  90 . The safety mechanism  130  can therefore be referred to as a detent mechanism for holding the handle  110  in the intermediate position until a person applies additional torque (i.e., in addition to the at-rest torque) to the handle  110 . 
     With reference to  FIG. 5 , in the event the handle  110  and hub  120  are turned while the safety mechanism  130  is in the intermediate position, a lateral force is applied by the edge of the aperture  90  against the detent surface  340  of the cam member  230 . As noted above, the lateral force gives rise to a radially outward force component applied to the safety mechanism  130 . If the radially outward component of force is sufficient to overcome the first biasing force, it causes the cam member  230  to ride out of the aperture  90  in the pivoting member  80 , into the outer position. 
     As the cam member  230  moves radially outward, the first spring  240  is compressed between the inner surface  180  of the end wall  160  and the shoulder  320  of the cam member  230 , and the second spring  250  is relaxed as the button  210  moves radially outward away from the end wall  160 . The first biasing force increases as the first spring  240  is compressed, and the second biasing force decreases as the second spring  250  relaxes. With the cam member  230  removed from the aperture  90 , the hub  120  is uncoupled from the pivoting member  80  and the handle  110  and hub  120  are free to rotate with respect to the pivoting member  80 . Consequently, no torque is transmitted from the handle  110  and hub  120  to the pivoting member  80  and the pivoting member  80  is not rotated. The safety mechanism  130  returns to the intermediate position under the influence of the first biasing force when the handle  110  and hub  120  are rotated back to the neutral position and the cam member  230  is aligned with the aperture  90 . 
     With reference to  FIG. 6 , when the safety mechanism  130  is actuated into the inner position, the cam member  230  is moved axially into the aperture  90  in the pivoting member  80  such that the driving surface  350  of the cam member  230  is within the aperture  90 . The safety mechanism  130  may be actuated from the intermediate position into the inner position by a person applying a radially inward deflecting force on the button  210  (e.g., with the person&#39;s thumb or finger). 
     As the safety mechanism  130  moves toward the inner position, the second spring  250  is compressed between the button  210  and the outer surface  190  of the end wall  160 , and the first spring  240  is relaxed as the cam member  230  moves axially inward away from the end wall  160 . The second biasing force increases as the second spring  250  is compressed, and the first biasing force decreases as the first spring  240  relaxes. With the driving surface  350  moved into the aperture  90 , the hub  120  is coupled for rotation with the pivoting member  80  and the handle  110 , and torque is transmitted from the handle  110  and hub  120  to the pivoting member  80 . Pivoting of the pivoting member  80  causes the latching member  70  to be retracted from the receptacle in the door jamb to permit the door  10  to be opened. The safety mechanism  130  returns to the intermediate position under the influence of the second biasing force when the deflecting force is removed from the button  210 . 
       FIG. 7  illustrates a variation on the safety mechanism  130 , in which the second end  310  of the stem  220  is threaded, and the cam member  230  includes a threaded hole  410  for receiving the second end  310  by a threaded connection. The pivoting member  80  in this embodiment includes retaining walls  420 , or a single retaining wall  420  if it is circular or tubular. The retaining walls  420  are angled to match the shape of the driving surface  350  and the detent surface  340  of the cam member  230 . The retaining walls  420  define a gap into which the blunt tip  330  of the cam member  230  fits. The retaining walls  420  are deep enough to receive substantially the entire cam member  230 , such that the shoulder surface  320  of the cam member  230  does not contact the hub  120  during assembly. 
     The door handle assembly  60  is installed onto the pivoting member  80  by first inserting the cam member  230  through the aperture  90 , into the space within the retaining walls  420 . The first spring  240  is placed in the cavity  170 . Then the hub  120  is slid over the pivoting member  80  so that the cam member  230  is aligned with the cavity  170 . The stem  220  and button  210  are provided as a single, integral component or a pre-assembled component. The second spring  250  is positioned around the stem  220  and in the spring seat  280 . The second end  310  of the stem  220  is inserted into the cavity  170  via the clearance hole  200 . With the stem  220  pushing the cam member  230  against the retaining walls  420 , the second end  310  is threaded into the threaded hole  410  in the cam member  230 . The retaining walls  420  provide a bearing surface against which the cam member  230  is pressed, and the shape of the retaining walls  420  maximizes surface area contact and frictional engagement with the cam member  230  to facilitate a tight threaded engagement. As the cam member  230  is pressed against the retaining walls  420 , the tip  330  is within the gap and therefore not exposed to forces or impact that would mar it as the stem  220  is threaded into the cam member  230 . The tip  330  should be maintained reasonably smooth so that the tip  330  can slide over the outer surface of the pivoting member  80  without imparting significant torque to the pivoting member  80  when the hub  120  is uncoupled from the pivoting member  80 . 
       FIGS. 8 and 9 , illustrate another arrangement of the present invention, which features a twist-lock mechanism for holding the safety mechanism  130  in the inner position. In this arrangement, the stem  220  includes a stub  510  extending perpendicular to the stem axis  290  and the boss  140  includes a slot or channel  520 . The slot  520  extends parallel to the stem axis  290  along a side of the clearance hole  200 . 
     As illustrated in  FIG. 9 , the stem  220  is inserted in the clearance opening  200 , with the stub  510  received in the slot  520 . A deflecting force  530  moves the safety mechanism  130  axially, and the stub  510  moves axially as illustrated with arrow  540 . When the stub  510  has cleared the end wall  160  (i.e., is within the cavity  170 ), the button  210  can be twisted, as illustrated with arrow  550 , to move the stub  510  out of alignment with the slot  520 , as illustrated with arrow  560 . When the button  210  is released, the second spring  250  biases the button  210  and stem  220  axially outward, but the stub  510  abuts against the inner surface  180  of the end wall  160  to prevent the axial movement. As a result, the cam member  230  is locked in the engaged position, with the driving surface  350  in the aperture  90 . As a result, the pivoting member  80  and hub  120  are coupled until the button  210  is rotated to align the stub  510  with the slot  520 , at which time the second biasing force will move the safety mechanism  130  axially outward into the disengaged position. 
     The invention is not limited to the illustrated embodiment, and can be applied to other apparatus in which it is desirable to disengage a handle from performing its function unless a safety mechanism is actuated. A non-exclusive list of examples of such apparatus includes: knobs, hot water faucets, and oven or stove dials. In such alternative apparatus, the handle and hub described above may be more generically referred to as an actuating member that is manually pivotable about the axis of the pivoting member. 
     For example, the invention could be more broadly described as a mechanism for selectively coupling a first moving part with a second moving part. The moving parts do not necessarily need to be pivoting members. When coupled, the first and second moving parts move together, and when uncoupled, the first moving part moves with respect to the second moving part. The second moving part includes an aperture (e.g., including an aperture similar to aperture  90 ). The mechanism includes an engaging member (e.g., including members such as the cam member  230 ), a biasing member (e.g., including arrangements such as the first and second springs  240 ,  250 ), and an actuating member (e.g., including a members similar to the button  210 ). 
     The engaging member is carried by the first part, and has a detent surface and a load transferring surface (e.g., which may be similar to the detent surface  340  and driving surface  350  or another arrangement). The engaging member is movable between a detent position in which the detent surface is within the aperture of the second moving part, a uncoupled position in which the engaging member is fully retracted from the aperture, and a coupled position in which the load transferring surface is within the aperture. 
     The biasing member acts with a biasing force on the engaging member to bias the engaging member into the detent position. Alternatively, the biasing force may bias the engagement member into the coupled position. 
     The actuating member may be manually manipulated to actuate the engaging member to overcome the biasing force of the biasing member and move the engaging member into the coupled position (or detent position, as the case may be) such that the first and second moving parts are coupled for movement together (or held with a detent force, as the case may be). With the engaging member in the detent position, relative movement of the first moving part and second moving part results in a component of force acting against the biasing force, such that the biasing force is overcome and the engaging member rides out of the aperture in the second moving member, into the uncoupled position. 
     As noted in the illustrated embodiment, the first moving part may comprise a handle and the second moving part may comprises a spindle on which the handle is supported, with the handle and spindle rotating about a concentric axis of rotation. The handle may take the form of a lever, as illustrated and described above. The lever may be maintained in a horizontal condition when the engaging member is in the detent position. The biasing force should be sufficient to maintain the engaging member in the detent position under at-rest torque applied to the lever under the influence of gravity. 
     The engaging member may include a cam member that defines the detent surface and load transferring surface, and a stem having a first free end extending through a portion of the first moving part and an opposite second end that is attached to the cam member. The stem may define a stem axis, and movement of the engaging member between the detent, coupled, and uncoupled positions is in a direction parallel to the stem axis. Movement of the engaging member from the detent position to the uncoupled position may be in an opposite direction from movement of the engaging member from the detent position to the coupled position. 
     If the first moving part and second moving part are rotatable about a common pivot axis, the stem axis may be perpendicular to the pivot axis. In such an arrangement, movement of the engaging member from the detent position to the uncoupled position could be radially away from the pivot axis, and movement of the engaging member from the detent position to the coupled position could be radially toward the pivot axis. In other embodiments, the movement could be reversed (moving radially toward the pivot axis into the uncoupled position and radially away from the pivot axis into the coupled position). 
     The biasing member might include first and second springs applying respective opposing first and second biasing forces on the engaging member, as described and illustrated above. The biasing member could have other arrangements, in which the first and second opposing biasing forces result in the biasing force that biases the engaging member toward the detent position. Movement of the engaging member toward the coupled position may deflect the first spring to increase the first biasing force and relaxes the second spring to decrease the second biasing force, and movement of the engaging member toward the uncoupled position may deflect the second spring to increase the second biasing force and relaxes the first spring to decrease the first biasing force. 
     In embodiments in which the engaging member is biased into the detent position, there may be provided a locking mechanism (e.g., similar to the twist-lock mechanism) that can be employed to keep the engaging member in the coupled position and resist movement of the engaging member back to the detent position. In embodiments in which the engaging member is biased into the coupled position, the locking mechanism may be used to hold the engaging member in the detent position (such that it will ride out into the uncoupled position upon relative movement between the first and second moving parts) and resist movement of the engaging member back into the coupled position. 
     Thus, the invention provides, among other things, a safety mechanism for coupling an actuator to a pivoting member when the safety mechanism is manually actuated, and for uncoupling the actuator and pivoting member when the safety mechanism is not manually actuated. Various features and advantages of the invention are set forth in the following claims.