Abstract:
A setting mechanism for a triggering device employs a knob fixed to a rotating part of the triggering device. The knob carries a selector lever that is pivotable to radially project from the knob in angularly spaced directions. Arcuate walls surround the knob to define gaps corresponding to alternative rotational periods for the knob. The selector is pivoted to travel in one or the other gap. The selected rotational period may correspond to a predetermined time.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to a device for selectively holding and releasing reefing lines on parachute canopies or the like, and more particularly to a timer setting mechanism for such dereefing devices.  
           [0003]    2. Description of the Related Art  
           [0004]    The use of parachutes, either for air dropping heavy payloads or decelerating high-speed aircraft, requires the incorporation of suitable means to regulate the opening of the various parachute canopies. If not regulated, deceleration of the payload caused by rapid parachute canopy opening may be excessive, imposing potentially destructive forces on the attached payload. Additionally, for payloads delivered using multiple parachutes, the opening of each parachute must be controlled so that no single parachute interferes with, or “starves”, the opening of the remaining parachutes.  
           [0005]    To control the opening rate of each parachute canopy, so-called reefing lines are employed, typically encircling the rim of the parachute canopy. The reefing lines are held by a dereefing device and the reefing line is sized so that the parachute canopy cannot fully open as long as the reefing line ends are held by the dereefing device. The dereefing devices are associated with timers or barometrically controlled devices, which after a given time or at a given altitude release the reefing line ends, enabling full opening of the associated parachute canopy. Multiple, differently sized reefing lines may be used for each parachute canopy, with each reefing line released sequentially so that the canopy can be opened in controlled stages, allowing further control over payload deceleration.  
           [0006]    Dereefing devices can generally be classified into either destructive or nondestructive types. The destructive types include those using explosive charges or mechanically actuated blades to sever the reefing line. Destructive dereefing devices do not allow reuse of the reefing line and/or the dereefing devices themselves. Nondestructive reefing devices typically capture a reefing line end loop around a pin. The pin is releasably held within a yoke. The pin is withdrawn from the yoke to release the dereefing line end loops.  
           [0007]    Some nondestructive dereefing devices utilize mechanical timers to determine the release point for the mechanical dereefer. There is a need in the art for a timer-setting mechanism which ensures accurate and repeatable timer setting and actuation.  
         SUMMARY OF THE INVENTION  
         [0008]    A preferred embodiment of a timer-setting mechanism comprises a knob mounted to the shaft of a mechanical timer. The knob carries a pivotable selector lever in a slot that permits the lever to pivot over an arc of 180° between first and second timing selection positions where the lever radially projects from opposite sides of the knob. Two arcuate walls, which in a preferred embodiment project from a dereefer housing, partially surround the assembled knob/lever/timer shaft. Each arcuate wall extends around the knob between a start face and a timeout face. The arcuate walls are arranged such that the timeout faces are associated with the same rotational position of the knob and attached timer shaft as will be further explained below. Arcuate gaps are defined between the start face of a first arcuate wall and the timeout face of the second arcuate wall. The arcuate gaps have first and second arcuate lengths, with a first gap having an arcuate length, for example, associated with a timer setting of four seconds and a second smaller gap having an arcuate length associated with a timer setting of, for example, two seconds.  
           [0009]    To select the representative two- or four-second timer settings discussed above, the selector lever is pivoted to radially project from the knob into the shorter or longer arcuate gap, respectively. The selector lever and knob are equipped with means for releasably retaining the selector lever in a position projecting into the selected gap as will be further explained below. When at rest (e.g., before the timer is wound or set), the selector lever will be adjacent the timeout face of one or the other arcuate gap. When the desired release time is selected by pivoting the lever, the radially projecting selector lever may then be used to rotate the knob and thus the timer shaft to wind or set the mechanical timer.  
           [0010]    The arcuate walls and knob define release pin holes and receiving apertures, respectively. A pair of holes and apertures align when the knob is rotated such that the selector lever is against the selected start face, e.g., when the timer is set. One pair of release pin hole and receiving aperture are associated with each timer set position. When the timer is set, a release pin is inserted through the release pin hole defined by an arcuate wall and into the receiving aperture defined by the knob to maintain the knob (and hence the timer) at the desired setting until released by removal of the release pin. Once released, the timer counts down the selected time and actuates the mechanical dereefer when the selector lever reaches the timeout face defining the end of the of the selected release time. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a plan view with a cover removed and partly in phantom of a prior art mechanical dereefer with the latch maintained in the capture position;  
         [0012]    [0012]FIG. 2 is a perspective view, partly broken away and shown in phantom, of a mechanical dereefer housing equipped with a timer setting mechanism in accordance with the present invention;  
         [0013]    [0013]FIG. 3 is an alternative perspective view of the dereefer housing and timer-setting mechanism of FIG. 2;  
         [0014]    [0014]FIG. 4 is a perspective view, partly broken away, of a dereefer housing equipped with arcuate walls in accordance with the present invention;  
         [0015]    [0015]FIG. 5 is a perspective view partly broken away of the dereefer housing of FIG. 4 in reverse view;  
         [0016]    [0016]FIG. 6 is a side view, partly broken away and partly shown in phantom, of the dereefer housing illustrated in FIG. 4;  
         [0017]    [0017]FIG. 7 is a top view, broken away and partly shown in phantom of the dereefer housing of FIG. 6;  
         [0018]    [0018]FIGS. 8 and 9 are front and rear side perspective views of a mechanical timer suitable for use in association with the timer-setting mechanism of the present invention;  
         [0019]    FIGS.  10 - 12  are top and side views of a timer knob appropriate for use in a timer-setting mechanism in accordance with the present invention with internal features shown in phantom; and  
         [0020]    FIGS.  13 - 15  are exterior plan views of a selector lever suitable for use in conjunction with the timer knob illustrated in FIGS.  9 - 12  as part of a timer-setting mechanism in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    Reference is made to FIG. 1 for the purpose of introducing one preferred use environment for a setting mechanism in accordance with the present invention. FIG. 1 illustrates a prior art mechanical dereefer  10  comprising a frame  22  with a bifurcated portion  24  and an opposing housing portion  26 . The housing portion  26  includes walls that define a frame cavity  30 . Within the frame cavity  30  are arranged mechanical linkages  122 ,  102 ,  90  and spring  96 . The bifurcated portion  24  of the housing pivotably retains a latch  18 , which in FIG. 1 is shown in the capture position with reefing line end loops  12 ,  14  held between the latch  18  and the bifurcated portion  24  of the dereefer housing. A latch lock  90  projects through an aperture in the housing  22  to maintain the latch  18  in the capture position as illustrated in FIG. 1. A triggering device (shown separately) is arranged in the housing cavity  30  to engage an aperture  130  in the trigger link. The triggering device may be a barometrically controlled device or a mechanical timer.  
         [0022]    At the selected altitude or, in the case of a timer, after the selected time has elapsed, the triggering device will act on the triggering link which in turn releases the latch lock  90  which is retrieved by the spring  96  to release the latch  18  and free the reefing line ends  12 ,  14 .  
         [0023]    It should be understood that the prior art mechanical dereefer illustrated in FIG. 1, its configuration and release mechanism, do not form part of the present invention and are shown for the purposes of illustrating one possible use environment for a setting mechanism in accordance with the present invention.  
         [0024]    [0024]FIGS. 8 and 9 illustrate a mechanical timer  16  suitable for use in conjunction with the present invention. The mechanical timer  16  has a shaft  15  projecting from one side of the timer body  40 . A triggering projection  13  fixed to a lever arm projects from a face of the timer body  40  opposite the timer setting shaft  15 . Fasteners  42  engage fastener receptacles  44  to fix the timer body  40  to, for example a dereefer such as that illustrated in FIG. 1. It will be understood that many suitable triggering devices are available and the form and features of the illustrated mechanical timer  16  do not form any part of the present invention and are introduced for the purpose of discussing the invention.  
         [0025]    [0025]FIGS. 2 and 3 illustrate one preferred embodiment of a setting mechanism  100  in accordance with the present invention. The setting mechanism  100  comprises a knob  120  engagable with a triggering device such that the rotational period of a rotating part of the triggering device may be selected by limiting rotary movement of the knob. The knob  120  is diametrically bisected by a slot  122 . A selector lever  130  pivots in the slot  122  to alternatively project from opposite sides of the knob  120 . The illustrated lever/knob assembly  120 ,  130  is partially surrounded by two arcuate walls  142 ,  144  projecting from a representative housing  140 . Together, the arcuate walls  142 ,  144  define two gaps  146 ,  148  of different angular extent. Each gap  142 ,  144  extends from a start face  145  to a timeout or triggering face  147 .  
         [0026]    In the illustrated embodiment, the arcuate walls  142 ,  144  and knob/lever assembly  120 ,  130  and are arranged such that the radially projecting selector lever  130  comes to rest against one or the other timeout face  147  at the end of the selected rotational period. This position of the selector lever  130  against a timeout face  147  coincides with the triggering of the triggering device (not shown here). FIGS. 2 and 3 illustrate the selector lever  130  pivoted to radially project into the longer gap  148  and at rest against the timeout face  147  of the longer arcuate wall  142 .  
         [0027]    The difference between the length of the gaps  142 ,  144  is permits the setting device to provide two alternative rotational periods for the knob  120  and, ultimately a rotating part of a triggering device. This rotating part may be the shaft  15  of a mechanical timer  16  such as that illustrated in FIGS. 8 and 9. For example, if the illustrated setting device were connected to the shaft  15  of the mechanical timer  16 , the shorter gap  146  might be associated with a time of two seconds and the longer gap  148  might be associated with a time of four seconds. With the selector lever in the position illustrated in FIGS. 2 and 3, clockwise rotation of the knob to bring the selector lever to bear against the start face  145  of the longer gap  148  would set the mechanical timer  16  for a four-second trigger time.  
         [0028]    Each of the arcuate walls  142 ,  144  defines a hole  141 ,  143  which is complementary to and aligned with a particular associated aperture  123 ,  125  in the knob  120  when the selector lever  130  is adjacent one of the start faces or abutments  145 . For example, one complementary pair of release pin hole  143  and aperture  123  align for a knob position corresponding to the selector lever  130  bearing against the start face  145  of the longer arucate gap  148 . With the selector lever  130  positioned against a selected start face  145 , a release pin is inserted through the aligned hole  143  to engage the complementary aligned aperture  123  in the knob  120 . The pin (not illustrated) maintains the setting mechanism in the selected set position until activated by removal of the release pin. It will be understood by those of skill in the art that the pin may be released by a static line, a reefing line, the opening of another parachute canopy or the like. Once activated, the rotating part of a triggering device is free to move toward its trigger position.  
         [0029]    It will be understood by those of skill in the art that other means for maintaining the setting mechanism in its selected set position are readily applicable to the present invention.  
         [0030]    FIGS.  4 - 7  illustrate a representative housing  140  incorporating one preferred configuration for the arcuate walls  142 ,  144 . The dereefer housing  140  defines fastener openings  151  through which fasteners may be inserted to secure a triggering device. The housing  140  also defines a shaft opening  153  through which, e.g, a shaft may pass to engage the knob  120 . The illustrated embodiment shows reinforcing webs  149  extending from the representative housing  140  to support the arcuate walls  142 ,  144 . Mechanical dereefers, for example, are frequently subjected to severe abuse and such reinforcement may be necessary to improve reliability of a setting mechanism in such a use environment. FIG. 5 is a reverse view of the representative housing illustrated in FIG. 4. The housing defines a cavity  150  for a triggering mechanism and associated release linkages (not illustrated). FIG. 7 clearly illustrates the angular spacing of the start faces  145  and timeout faces  147  of the gaps  146 ,  148 .  
         [0031]    FIGS.  10 - 12  illustrate the knob  120  and its various features. An axial opening  121  is configured to receive a shaft projecting from a triggering device. The knob  120  is fixable to the shaft for rotation therewith. Those of skill in the art will understand that the knob may include a projection or projections for engagement with a rotating part of a triggering device other than a shaft as an alternative to the illustrated configuration. A slot  122  diametrically bisects the knob  120 . The knob  120  defines a pivot pin opening  124  configured to receive a pivot pin (not illustrated) on which the selector lever  130  will pivot. Two bores  126  are configured to receive spring and ball check arrangements (not illustrated) to project into the slot  122  to engage a groove  132  or other depression in the selector lever  130 .  
         [0032]    FIGS.  13 - 15  are several views of the selector lever  130 . A pivot pin aperture  134  receives a pivot pin (not illustrated) passing through the pivot pin opening  124  defined in the knob  120  so that the selector lever  130  is pivotally retained to the knob  120 . The selector lever  130  is pivotable over an arc of 180° to radially project from opposed sides of the knob  120 . The selector lever groove  132  and spring-actuated balls (not illustrated) in bores  126  are arranged such that one or the other ball engages the groove  132  when the selector lever  130  is in either of its opposed positions. This spring-actuated ball/groove engagement releasably retains the selector lever in the selected position.  
         [0033]    With reference to FIGS.  10 - 12 , two pin-receiving apertures  123 ,  125  pass through the knob at alternative angular orientations relative to the slot  122 . This permits one or the other of the pin-receiving apertures  123 ,  125  in the knob  120  to align with a release pin hole  141 ,  143  defined by one or the other of the arcuate walls  142 ,  144 , depending upon the selected position of the selector lever  130 .  
         [0034]    [0034]FIGS. 2 and 3 illustrate the selector lever  130  positioned in the longer gap  148 . To select the shorter of the two available gaps  146 , the lever would be pivoted 180° to come to rest against the angularly opposite timeout face  147 . The setting mechanism is then set and pinned as described above. When the release pin is removed, the knob will move the selector lever  130  over a rotational period corresponding to the shorter gap  146  with the radially projecting selector lever  130  coming to rest against the timeout face  147  associated with the shorter arcuate wall  144 .  
         [0035]    The illustrated embodiment shows a setting device that defines two alternative rotational periods for a knob. It should be understood that three, four or more alternative rotational periods for a knob may be defined using the principals and structures illustrated in this application. The invention claimed herein is intended to encompass such further embodiments.  
         [0036]    While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.