Abstract:
A high stability ball-in-cone type latch mechanism is taught that is particularly useful for large deployable optical systems. It provides a nearly perfect kinematic mount between structural or optical elements and can easily be remotely controlled. The latching device comprises a latch core; at least one coupler link having a pawl at a first end thereof and a cam follower at a second end thereof, the at least one coupler link pivotally connected to follower link, the follower link being pivotally connected to the latch core; a bearing housing affixed to the latch core; a spherical bearing residing in the bearing housing, the spherical bearing having a ball stem extending therefrom through the bearing housing; a lead screw connected to the ball stem; a drive cam threadably engaged on the lead screw, the cam follower engaging the drive cam; and a motor to drive rotation of the lead screw to control travel of the cam on the lead screw thereby causing the at least one coupler link to move from an open position to a clamping position.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to actuated mechanical interlock mechanisms and, more particularly, to high stability latching of deployable optical metering structures.  
         BACKGROUND OF THE INVENTION  
         [0002]    To extend the range of astronomical telescopes, it is necessary to increase the effective aperture. This implies that larger diameter primary mirrors must be employed. Unfortunately, the current state of the art is at the practical size limit of monolithic mirrors. As a result, segmented primary mirrors comprising a plurality of petals surrounding a monolithic center segment must be devised. A space born telescope of this configuration will require deployment after being placed in orbit. Linear, stable, high stiffness precision latches must be used to interlock the metering structure once the mirror is deployed to maintain mirror performance. Current latching technology does not address the need for high stiffness, linearity, and precision. Latch technology as used in satellite antennae does not meet optical tolerance requirements. Their repeatability and stability are typically two orders of magnitude below optical system requirements.  
           [0003]    Latching mechanisms commonly found can be categorized either as a retaining type or a mating type. Retaining types are preset in the latched position and release in their operating state. Examples of this type are illustrated in U.S. Pat. No. 4,682,804 to Palmer, et al. and U.S. Pat. No. 4,508,296 to Clark. These devices are used to retain payloads during transport, preventing damage due to shock and vibration. Remote release of the latch allows the payload to be removed from the support structure. High reliability and preload are their key performance requirements.  
           [0004]    Mating type latching mechanisms are illustrated in U.S. Pat. No. 4,431,333 to Chandler and U.S. Pat. No. 4,905,938 to Braccio et al., 1990. These devices have male couplings that mate with female sockets. Latching occurs after the halves are mated and serve to connect two bodies after contact. These are used to grapple satellites for repair or connection of trusses where only low tolerance alignment is necessary. Again no consideration is given to dynamic performance of the connection.  
         SUMMARY OF THE INVENTION  
         [0005]    It is therefore an object of the present invention to provide a linear, stable, high stiffness precision latch mechanism.  
           [0006]    It is a further object of the present invention to provide a precision latch mechanism with high repeatability and stability.  
           [0007]    Yet another object of the present invention is to provide a latch mechanism for use in the deployment of a segmented primary mirror comprising a plurality of petals surrounding a monolithic center segment.  
           [0008]    Still another object of the present invention is to provide a precision latch mechanism that can be used to interlock the metering structure of a segmented mirror once the mirror is deployed to thereby maintain mirror performance.  
           [0009]    Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon review of the detailed description, claims and drawings set forth herein. These features, objects and advantages are accomplished by providing a high stability ball-in-cone type latch mechanism designed specifically for large deployable optical systems. It provides a nearly perfect kinematic mount between structural or optical elements and can easily be remotely controlled. Clamping force and drive position feedback can be incorporated to allow controlled closure and continuous force monitoring during and after clamping. When in the closed position, the interface consists of a ball captured between two conical surfaces. A flexured ball and floating clamp plate is typically attached to the structure being deployed. The latch base is equipped with a conical seat to accept the ball, and three clamp fingers to grip the floating clamp plate once the ball is seated in the socket. A lead screw driven axial cam serves to drive the clamping mechanism into both a clamped and a retracted position. A four bar linkage is formed by the latch cam, coupler link, follower link, and seat. Once the follower link is grounded on the seat, the coupler link acts as a simple lever applying force to the clamp plate. Advantage is taken of the relatively large motion available from a four bar mechanism, as well as the mechanical advantage of a simple lever once latching is initiated. Large clamping forces generated at the interface by the coupler are reacted at the seat thereby providing high interface stiffness and linearity. No latching forces are transferred to the optical support structure. High interface clamping forces on the order of 1000 lbs. can be achieved with low input torque at the lead screw by choosing appropriate cam angles. Employing a flat cam area at the end of travel eliminates the need for accurate final cam position. Choosing appropriate materials can eliminate thermally induced force variation. End mounting the lead screw in the latch seat with a spherical bearing compensates for part tolerances, equalizing clamp finger force during latching. Limit sensors at extremes of cam travel and strain gauges on clamp arms can be provided to monitor operation during the latching procedure. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIGS. 1, 2 and  3  are perspective illustrations of the latching sequence of the latch mechanism of the present invention in conjunction with an exemplary deployed member and an exemplary reference structure.  
         [0011]    [0011]FIG. 4 is a perspective view of the latch and flexured ball assembly removed from the exemplary deployed member and the exemplary reference structure shown in FIGS. 1 through 3.  
         [0012]    [0012]FIG. 5 is a cross-sectional view of the latch mechanism and flexured ball assembly taken along line  5 - 5  of FIG. 4.  
         [0013]    [0013]FIG. 6 is an exploded perspective view of the spherical bearing assembly.  
         [0014]    [0014]FIG. 7 is an exploded perspective view of the lead screw/cam assembly.  
         [0015]    [0015]FIG. 8 is an exploded perspective view of the flexured ball assembly.  
         [0016]    [0016]FIG. 9 is an exploded perspective view of the linkage assembly.  
         [0017]    [0017]FIG. 10 is an exploded perspective view of the latch and flexured ball assembly of FIG. 4.  
         [0018]    [0018]FIGS. 11 a ,  11   b  and  11   c  are simplified elevational views of the latch and flexured ball asssembly (showing only a single linkage assembly) illustrating the three basic kinematic stages of the latch operation.  
         [0019]    [0019]FIGS. 12 a ,  12   b ,  12   c ,  12   d , and  12   e  are simplified side elevational views of the lead screw/cam assembly in combination with a single coupler link illustrating cam/follower relationship for the five phases of the latching operation. 
     
    
       [0020]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring to FIGS. 1 through 3 there are three distinct stages which occur during the deployment operation in a large optical system. A single comer of a typical deployed optical system is illustrated in FIGS. 1 through 3. During the first stage as illustrated in FIG. 1, the deployed member  10  has attached to it a flexured ball assembly  12 . The flexured ball assembly  12  (shown in greater detail in FIGS. 4 and 8) is in alignment with the latch mechanism  14  (shown in greater detail in FIGS. 4, 5 and  10 ) which is mounted in the reference structure  16 . Any number of common methods can be used to maintain axial alignment. Latching pawls  18  are driven to their open position, providing clearance for the approaching flexured ball assembly  12 . As deployment proceeds, the flexured ball assembly  12 , makes contact with the latch mechanism  14  as shown in FIG. 2. Position sensing of the deployed member  10  is generally provided by an external system (not shown), and indicates when the flexured ball assembly  12 , is in its mated position with latch mechanism  14 . At this point the latch mechanism  14  is actuated, which causes the latching pawls  18  to engage the flexured ball assembly  12 , as illustrated in FIG. 3. Applying a large force, typically about 1000 pounds, to seat the ball assembly  12  completes the latching operation.  
         [0022]    Turning to FIG. 4 there is shown more detailed views of the latch  14  and flexured ball assembly  12  removed from their respective structures  10 ,  16 . Mounting plate  20  serves as the interface between the latch  14  and the reference structure  16  to which it is mounted. Drive motor  22  moves the latching pawls  18  in or out and supplies clamping force when the latching pawls  18  are in the latched state. The latch mechanism  14  is capable of locking the pawls  18  tightly in an open position as well as applying a large clamping force when the latching pawls  18  are in the fully latched position. The latching pawls  18  are supported within a main housing  24  to which mounting plate  20  is mounted.  
         [0023]    Referring next to FIG. 5 there is shown a cross-sectional view of the latch mechanism  14  and flexured ball assembly  12  taken along line  5 - 5  of FIG. 4. Residing within and attached to main housing  24  is latch core  26  which provides the clamping force reaction structure. The joint stiffness relative to the structure is controlled by the interface stiffness of mount plate  20 . The actual latch stiffness is controlled by the interface characteristics of the ball seat  28 , clamp plate  30 , and ball  32 . Consequently, the latch mechanism  14  and flexured ball assembly  12  are generally made of a hard material. Although FIG. 5 shows the mount plate  20 , latch core  26 , and ball seat  28  as separate elements, those skilled in the art will recognize that it is possible to combine them into a single component to reduce part count and increase stiffness.  
         [0024]    Still referring to FIG. 5, there is a spherical bearing assembly  34  (shown in an exploded view in FIG. 6) attached to the latch core  26 . The spherical bearing assembly  34  is comprised of a spherical bearing  36 , bearing cups  38 , and bearing housing  40 . The geometry of bearing cups  38  is such that when bearing housing  40  is mounted on the base of the latch core  26  (see FIG. 5), bearing cups  38  provide a running fit with the spherical bearing  36 . Ball stem  42  extends through an axial bore  44  in the lower bearing cup  38  and through an opening in the bearing housing  40 . The axial bore  44  is sized (larger than diameter of ball stem  42 ) to allow up to 15° of tilt on the ball stem  42 . A radial bore  46  is provided through ball stem  42  to allow for connection to the lead screw/cam assembly  48  (shown in exploded detail in FIG. 7). Material selection for the bearing cups  38  (typically hardened 440c stainless steel) must be different from spherical bearing  36  material (typically hardened M6 tool steel) to prevent micro welding at the contact area which can occur if lubricant migrates. Solid lubricants or low friction coatings may also be used on the contacting surfaces.  
         [0025]    The lead screw/cam assembly  48  is comprised of drive cam  50 , lead screw  52 , cam insert  54 , lower cam stop  56 , upper cam stop  58 , cam stop pin  60 , and anti-rotation pins  62 . The cam insert  54  is preferably a hardened steel material threaded to mate with the lead screw  52  that is preferably made of hardened stainless steel. A fine pitch thread, typically ¼-80, is employed to provide great mechanical advantage and axial load bearing capabilities. The fine pitch thread provides a “low ramp” adjustment of the mechanism. The resultant large number of threads also provides for increased mechanical engagement with the nut (cam insert) and therefore, a higher load capability. Other threads may be used based on available motor torque, link geometry, and required clamping force. Optimization methods for these mechanisms are well known in the art. Cam insert  54  is press fit into drive cam  50  and may be pinned if required for higher latch loads. Cam material can be of any dissimilar metal from the coupler links  64  from which pawls  18  extend. For lubricated interfaces, red brass or titanium is used. Similar materials for the drive cam  50  and coupler links  64  may be employed if low friction coatings are applied to mating surfaces. Lower cam stop  56  is internally threaded to match the thread of lead screw  52 . Lower cam stop  56  is positioned on the lower end of lead screw  52  to serve as a limit or travel stop for drive cam  50  when the latch is in the full open state. Once properly located, lower cam stop  56  is pinned in place to prevent axial movement when contacted. Upper cam stop  58  also has internal screw threads to match lead screw  52  and is positioned on the upper end to serve an upper limit or travel stop for drive cam  50 . Cam stop pin  60  serves to lock upper cam stop  58  in place and lock ball stem  42  of the spherical bearing assembly  34  into the end bore  66  on the lead screw  52 . The drive cam  50  is kept from rotating as the lead screw  52  turns via three anti-rotation pins  62  that engage the main housing  24 . Since the anti-rotation pins  62  encounter low forces, they may be made from a material dissimilar to the main housing  24 , or a low friction surface treatment may be employed.  
         [0026]    Lead screw  52  extends through drive cam  50 . The bottom of the lead screw  52  interfaces with or is otherwise coupled to the drive shaft  68  of drive motor  70 . Drive motor  70  is supported from motor mount  72  which is attached to the main housing  24 . An inward radial force is applied to the coupler links  64  by a spring element  74 , which is seated in a circumferential groove machined into the main housing  24 . The main housing  24  also serves as an anti-rotation surface for the drive cam  50  and as a mounting surface for the motor mount  72 . Lead screw/cam assembly  48  resides inside of main housing  24  and attaches to the spherical bearing assembly  34 . Drive cam  50  engages the actuating arms  76  of coupler links  64  to operate the latch.  
         [0027]    An exploded view of the flexured ball assembly  12  is shown in FIG. 8. The flexured ball assembly  12  comprises a flexured stem  80  including a cylindrical mounting shaft  82 , a clamp plate retaining flange  84 , a clamp plate centering shoulder  86 , and a threaded shank  88 . The cylindrical mounting shaft  82  is typically mounted in an interface block attached to a bipod flexure pair (not shown). Three such bipod flexure pairs constitute an arrangement well known in the art as a kinematic mount. O-ring  90  is placed on threaded shank  88  and moved down until it meets the clamp plate retaining flange  84 . Clamp plate  30  is placed on the threaded shank  88  and also moved down to meet O-ring  90 . Ball  32  is then threaded onto threaded shank  88  and is tightened against clamp plate centering shoulder  86 . A diametrically located hole  92  is provided in ball  32  to allow the ball  32  to be pinned by drilling a hole through the threaded shank  88  after assembly. The geometry of the plate centering shoulder  86 , clamp plate inner bore  94 , clamp plate conical surface  96 , and ball  32 , is such that O-ring  90  is only slightly compressed, keeping the clamp plate  30  perpendicular to the axis of flexure stem  80 , and clamp plate conical surface  96  in contact with the ball  32 . Clamp plate inner bore  94  is slightly larger than centering shoulder  86  allowing the clamp plate  30  to tip about the axis with only a slight force on the edge of the clamp plate  30 . This “floating clamp” feature prevents locking in strains due to deployment mechanism misalignment or part variations in the latch. Ball  32  and clamp plate  30  are preferably made from hardened 440c stainless steel since they define the clamped interface stiffness. Flexure stem  80  can be of any metal although a 400 series stainless steel is preferred.  
         [0028]    Each link  64  is part of a linkage assembly  100  shown in an exploded view in FIG. 9. Each linkage assembly  100  is comprised of a coupler link  64 , follower links  102 , spacers  104 , and upper pivot pin  106 . Upper pivot pin  106  inserts through bores  108  in follower links  102  and bore  110  in coupler link  64  as well as through spacers  104 . Bores  108  in follower links  102  are sized to allow a press fit of upper pivot pin  106 . Bore  110  in the coupler link  64  is sized as a running fit with upper pivot pin  106 . Spacers  104  are made of 0.010 inch thick brass and serve to prevent binding of follower links  102  with coupler link  64  after assembly. High stresses in follower links  104  and coupler link  64  in the regions of the bores  108 ,  110  require these to be made of a high tensile strength material such as hardened 440c stainless steel. Similarly the pivot pin  106  is precision ground hardened tool steel. Lower pivot bores  112  must be aligned during assembly to allow kinematic stops  114  to properly interface with the latch core  26 . Each coupler link  64  has a pawl  18  that applies force to the clamp plate  30 . Each coupler link  64  forms a simple lever, where the lever arms are the distance from the center of the pivot bore  110  to the end of the respective pawl  18 , and from the center of the pivot bore  110  to the cam follower  116  at the ends of actuating arms  76 . Tab  118  is provided to allow the coupler links  64  to be drawn into the open position. A relief  120  in each coupler link  64  provides a pocket for residence of spring element  74 , and allows the bending stiffness of the coupler link  64  to be controlled. The bending stiffness of coupler link  64  and the amount of deflection produced by cam  50  controls the force applied to the clamp plate  30 .  
         [0029]    An exploded view of the complete latch of the present invention is shown in FIG. 10 to illustrate the final assembly procedure. Internal subassemblies including the linkage assemblies  100 , lead screw/cam assembly  48 , and ball seat  28  are assembled onto the latch core  26 . Main pivot pins  122  are inserted through lower pivot holes  112  on the follower links  102  and main pivot holes  124  in the latch core  26 . Lower pivot holes  112  on the follower links  102  are a running fit with the hardened base pins  122 . Main pivot holes  124  in the latch core  26  provide a press fit for main pivot pins  122 . Ball seat  28  is also press fit into the axial bore  126  of latch core  26 . Clearance holes in the bearing housing  40  allow the lead screw/cam assembly  48  to be mounted to the bottom of the latch core  26  with screws. The assembled mechanism comprising the latch core  26  and ball seat  28 , linkage assemblies  100 , and lead screw/cam assembly  48 , is then inserted into main housing  24 . Mounting plate  20  is placed over the core assembly such that counter sunk screw holes  128  on the mounting plate  20  align with the clearance holes  130  on the latch core  26 , which in turn align with tapped holes  132  in the main housing  24 . Clearance slots  134  in the mounting plate  20  allow free movement of the linkage assemblies  100 . Coupler links  102  are then pushed into lower clearance slots  136  in the main housing  24  until they contact the surface of drive cam  50 . Spring element  74  (typically an O-ring) is then place around the main housing  24  to reside in a groove  138  therein to apply a radially inwardly directed force to the backs of coupler links  64 . Lower clearance slots  136  allow for radial and tangential motion (actually rotational motion about spherical bearing  36 ) of each coupler link  64  within the main housing  24  due to tilting of the latch control mechanism, while the sides of lower clearance slots  136  provide a reaction surface for the anti-rotation pins  62 . Motor mount  72  spaces the drive shaft  68  from the end of lead screw  52 . Preferably, a drive pin  137  extending from drive shaft  68  fits loosely into a drive slot  139  in the lead screw  52  to allow angular motion at the spherical bearing  36 . The entire clamping mechanism is allowed to float with in the main housing  26 , allowing clamping to occur even if debris enters the system.  
         [0030]    To better understand the functions of the individual latch parts, it is necessary to understand the basic kinematic stages of the latching operation. These are illustrated schematically in FIGS. 11 a, b  and  c,  by showing only one linkage assembly  100  on the latch core  26 . It is assumed the flexured ball assembly  12  is seated in the latch core  26  when the latching operation begins. The first stage illustrated in FIG. 11 a  shows the pawl  18  in its widest position, allowing clamp plate  30  of the flexured ball assembly  12  to easily move into the latch. Drive cam  50  on the lead screw  52  pulls the coupler link  64  into its lowest position. Contact between the drive cam  50  and coupler link  64  is maintained by the inward force from spring  74 . A four bar linkage is formed by the drive cam  50 , lead screw  52 , coupler link  64 , and follower link  102  in this stage. In the second stage illustrated in FIG. 11 b,  drive cam  50  has moved up on lead screw  52  toward the latch core  26  allowing stops  114  of the follower link  102  to contact the latch core  26 . At this point the clamp plate  30  is considered captured. Although no force is being applied, the flexured ball assembly  12  cannot move out of the capture range of the latch. Grounding stop  114  of the follower link  102  on the latch core  26  degenerates the four bar linkage into a simple lever that is activated by the drive cam  50 . The end of the third stage of the latching process is illustrated in FIG. 11 c.  Here the drive cam  50  has moved up to its final position on the lead screw  52 . Movement of the coupler link  64  along the drive cam  50  initiates contact of pawl  18  with the clamp ring  30  and applies the full clamping force.  
         [0031]    Drive cam  50  is designed to have five distinct operating regions as illustrated in FIGS. 12 a, b, c, d, e.  The first state is shown schematically in FIG. 12 a  where coupler link  64  is fully retracted, putting the latch in its open position. The top of drive cam  50  is equipped with a flange  140  having a lip  142  that prevents tab  118  from leaving upper cam surface  144  as it is pulled down by lead screw  52 . Spherical bearing  36  reacts an upward force from the lead screw  52  while spring  74  applies a radially directed force on coupler link  64 . Cam follower  116  is not in contact with the drive cam  50  surface.  
         [0032]    The second state is shown schematically in FIG. 12 b  where drive cam  50  has moved up on the lead screw  52  to a point where tab  118  is still in contact with upper cam surface  144  but has moved in radially from lip  142 . Cam follower  116  is now in contact with the cylindrical surface  146  of the drive cam  50 . Contact between coupler link  64  and cylindrical surface  146  is maintained by spring  74  only. A slight downward force is applied to the spherical bearing  36  by lead screw  52 . The four bar linkage degenerates into a simple lever at this stage since the follower link  102  (not shown) is grounded to the latch core  26  (not shown).  
         [0033]    The third state is shown schematically in FIG. 12 c  where drive cam  50  moved up further along lead screw  52 . Cam follower  116  has moved from the cylindrical surface  146  to the steep tapered surface  148  on drive cam  50 , while tab  118  is no longer in contact with any surface. Spherical bearing  36  reacts only a light upward force and spring  74  maintains a radially directed force on coupler link  64 . Pawls  18  (not shown) are closing on the clamp plate  30  (not shown) during this stage. When cam follower  116  reaches the end of the steep tapered surface  148 , the pawls  18  (not shown) are in contact with the clamp plate  30  (not shown).  
         [0034]    The fourth state is shown schematically in FIG. 12 d  where drive cam  50  has moved up further along lead screw  52  almost to its final position. Cam follower  116  has moved from the steep tapered surface  148  to a shallow tapered surface  150  on drive cam  50 . Displacement due to the cam motion bends the coupler link  64  applying a high load on the clamp ring  30  (not shown). Spherical bearing  36  reacts a high downward force substantially greater than spring  74 . When cam follower  116  reaches the end of the shallow tapered surface  150 , the pawls  18  (not shown) generate the maximum force on clamp plate  30  (not shown). Use of a shallow taper gives a large mechanical advantage while clamping, thereby reducing the required motor torque for a desired clamping force. At this point, the stop projecting from the coupler link engages the latch core when the latch plate is fully captured and final clamping begins.  
         [0035]    The final state is shown schematically in FIG. 12 e  where drive cam  50  has reached its final position on lead screw  52 . Cam follower  116  has moved from the shallow tapered surface  150  to a lower cylindrical surface  152  on drive cam  50 . No changes in reaction forces are seen since the coupler link  64  has experienced no further deflection on the lower cylindrical surface  152  than that seen at the end of the shallow tapered surface  150 . This eliminates the need to have a precise stopping point for the motor and allows motor slip to occur with out changing the clamping force.  
         [0036]    From the foregoing, it will be seen that this invention is one well adapted to obtain all of the ends and objects hereinabove set forth together with other advantages which are apparent and which are inherent to the apparatus.  
         [0037]    It will be understood that certain features and sub-combinations are of utility and may be employed with reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.  
         [0038]    As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth and shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.  
       Parts List  
       [0039]    [0039] 10  deployed member  
         [0040]    [0040] 12  flexured ball assembly  
         [0041]    [0041] 14  latch mechanism  
         [0042]    [0042] 16  reference structure  
         [0043]    [0043] 18  pawls  
         [0044]    [0044] 20  mounting plate  
         [0045]    [0045] 22  drive motor  
         [0046]    [0046] 24  main housing  
         [0047]    [0047] 26  latch core  
         [0048]    [0048] 28  ball seat  
         [0049]    [0049] 30  clamp plate  
         [0050]    [0050] 32  ball  
         [0051]    [0051] 34  spherical bearing assembly  
         [0052]    [0052] 36  spherical bearing  
         [0053]    [0053] 38  bearing clips  
         [0054]    [0054] 40  bearing housing  
         [0055]    [0055] 42  ball stem  
         [0056]    [0056] 44  axial bore  
         [0057]    [0057] 46  radial bore  
         [0058]    [0058] 48  lead screw/cam assembly  
         [0059]    [0059] 50  drive cam  
         [0060]    [0060] 52  lead screw  
         [0061]    [0061] 54  cam insert  
         [0062]    [0062] 56  lower cam stop  
         [0063]    [0063] 58  upper cam stop  
         [0064]    [0064] 60  cam stop pin  
         [0065]    [0065] 62  anti-rotation pins  
         [0066]    [0066] 64  couple links  
         [0067]    [0067] 66  end bore  
         [0068]    [0068] 68  drive shaft  
         [0069]    [0069] 70  drive motor  
         [0070]    [0070] 72  motor mount  
         [0071]    [0071] 74  spring element  
         [0072]    [0072] 76  acuating arms  
         [0073]    [0073] 80  flexured stem  
         [0074]    [0074] 82  cylindrical mounting shaft  
         [0075]    [0075] 84  clamp plate retaining flange  
         [0076]    [0076] 86  clamp plate centering shoulder  
         [0077]    [0077] 88  threaded shank  
         [0078]    [0078] 90  O-ring  
         [0079]    [0079] 92  diametrically located hole  
         [0080]    [0080] 94  clamp plate inner bore  
         [0081]    [0081] 96  clamp plate conical surface  
         [0082]    [0082] 100  linkage assembly  
         [0083]    [0083] 102  follower links  
         [0084]    [0084] 104  spaces  
         [0085]    [0085] 106  upper pivot pin  
         [0086]    [0086] 108  bores  
         [0087]    [0087] 112  lower pivot bore  
         [0088]    [0088] 114  kinematic stops  
         [0089]    [0089] 116  cam follower  
         [0090]    [0090] 118  tab  
         [0091]    [0091] 120  relief  
         [0092]    [0092] 122  main pivot pins  
         [0093]    [0093] 124  main pivot holes  
         [0094]    [0094] 126  axial bore  
         [0095]    [0095] 128  counter sunk screw holes  
         [0096]    [0096] 130  clearance  
         [0097]    [0097] 132  tapered holes  
         [0098]    [0098] 134  clearance slots  
         [0099]    [0099] 136  lower clearance slots  
         [0100]    [0100] 137  drive pin  
         [0101]    [0101] 138  groove  
         [0102]    [0102] 139  drive slot  
         [0103]    [0103] 140  flange  
         [0104]    [0104] 142  lip  
         [0105]    [0105] 144  upper cam surface