Abstract:
A connector installation device wherein a connector has a stationary connector element and another connector element that is movable along an engagement axis with the stationary connector element and mates therewith. An insertion cam is movable perpendicular to the engagement axis of the mating connector elements. An insertion drive mechanism is interconnected with the insertion cam and is movable along an installation axis perpendicularly to the engagement axis. A drive force applied to the insertion drive mechanism translates the insertion cam along the installation axis into contact with an insertion drive surface of the insertion cam. Pressure against the insertion drive surface translates the movable connector element along the engagement axis toward the stationary connector element. The gentle easing of the engagement of the moveable and stationary connector elements allows sufficient opportunity for guidance mechanisms on the connector housings to orient the male pins for insertion into corresponding female receptacles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 09/825,622, filed on the same date herewith, and to application Ser. No. 09/825,630, filed on the same date herewith, now pending, which applications are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to remote insertion of connector pins, particularly employing flexible drive rods. 
     BACKGROUND OF THE INVENTION 
     Many applications, including heavily packed computer cabinets and other equipment employing electrically interconnected circuit boards, are often configured for electrical connections to an interface board, such as a mother board, back plane, or another circuit board buried deep within the cabinet. Connections in such inaccessible locations generally require blind insertion of connectors on a back edge of the circuit board into mating connectors buried deep within the cabinet. Furthermore, access is generally provided only through a single opening in the cabinet opposite the connector interface. Thus, the board installer is faced with blindly aligning connectors on the circuit board with mating connectors on the back wall of the cabinet. Several methods are known for providing initial alignment of the board within the cabinet. For example, the cabinet wall is often provided with slots configured to accept an edge of the circuit board and align it within the cabinet. In another example, bayonet pins are provided on the back edge of the circuit board to mate with precision holes positioned in the back wall of the cabinet. Furthermore, the connector housings are usually formed with mating pins and slots or another lead-in mechanism to guide engagement when the connector elements are brought together. 
     SUMMARY OF THE INVENTION 
     In instances where known circuit board alignment mechanisms often provide proper mating of connectors, the alignment they provide may be too gross to safely mate connectors having large numbers of very delicate connections. Although the housings of such connectors are typically formed with corresponding guide pins or another lead in mechanism, an aggressive installation often does not provide sufficient opportunity for the slender male pins to properly align with their correspondingly narrow female receptacles. In such instances, the fragile pins generally require a gentle easing together of the mating connector elements for successful insertion of the slender male pins into the correspondingly narrow female ports to avoid bending and other damage. One or more of the male pins may fail to completely align with its female receptacle and become bent or completely crushed during installation. The connector installation device of the present invention provides the controlled force needed to gently and certainly engage connector elements, without damage. 
     The present invention provides a mechanism for gently urging counterpart male and female connector elements together. The present invention provides a connector installation device wherein a connector has a fixed or stationary connector element and another connector element that is movable along an engagement axis with the fixed connector element and mates with the fixed connector element. 
     According to one aspect of the invention, a connector installation device is provided, the installation device including a connector having a first positionally fixed connector element and a second connector element movable along a connector engagement axis and interconnecting with the positionally fixed connector element; and an insertion drive device engaged with the second connector element and moving the second connector element along the engagement axis, the insertion drive device having an externally-threaded rod engaged with a stationary internally-threaded member that is positionally fixed relative to the first positionally fixed connector element. The threaded rod is further formed as either a substantially rigid member or a substantially flexible threaded rod. 
     According to another aspect of the present invention, the flexible drive element is formed with a compressively wound helical coil springs threadedly engaged with internally threaded nuts matched thereto in diameter and pitch. The flexible drive elements are able to undergo directional changes that allow the drive torque to be input both spatially and dimensionally remotely from the respective insertion and extraction cams. Preferably, the flexible threaded rod following a curving path between a first drive input end and a second drive output end engaged with the second connector element. 
     In order to overcome helical buckling along an unsupported length of the flexible threaded rod, the invention further provides a tubular guide that directs either or both of straight and curving portions of the path of the flexible threaded rod. 
     According other aspects of the invention, the movable connector element is formed with an insertion drive surface oriented relatively to the engagement axis. An insertion cam positioned proximately to the movable connector element includes an actuation surface facing and mating with the insertion drive surface of the moveable connector. An actuator tip at the end of the actuation surface is spaced away from the insertion drive surface of the movable connector element. The insertion cam is movable perpendicular to the engagement axis of the male and female connector elements. An insertion drive mechanism is interconnected with the insertion cam and is movable along an installation axis substantially perpendicularly to the engagement axis. A drive force applied to the insertion drive mechanism translates the insertion cam tip and actuation surface along the installation axis into contact with insertion drive surface of the insertion cam. Pressure of the insertion cam&#39;s actuation surface against the insertion drive surface of the movable connector translates the movable connector element along the engagement axis toward the fixed connector element. The gentle easing of the engagement of the moveable and fixed connector elements allows sufficient opportunity for guidance mechanisms on the connector housings to orient the pins for insertion into the corresponding female receptacles. 
     According to various aspects of the invention, the actuation surface is an inclined surface formed in a wedge-shaped insertion cam and engages a matchingly inclined insertion drive surface of the moveable connector element. Preferably, the insertion cam is slidingly engaged with a guide channel that supports the insertion cam and directs it along the installation axis. 
     According to another aspect of the invention, an extraction cam is provided to disengage the moveable connector element from the stationary connector element. Accordingly, an extraction drive surface is provided on the movable connector element facing but spaced away from the insertion drive surface. An extraction cam configured similarly to but oppositely from the insertion cam is driven by an extraction drive on an extraction axis parallel to but spaced away from the insertion axis. An inclined surface on the extraction cam engages the extraction drive surface and gently eases the movable connector element along the engagement axis away from the fixed connector element. The extraction cam is slidingly engaged with an extraction cam guide that supports the extraction cam and directs it along the extraction axis. 
     According to yet other aspects of the present invention, methods are provided that utilize the insertion and extraction drivers to alternately engage and disengage the fixed and mobile connector elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates one embodiment of a flexible drive unit of the invention for connecting remote electrical contacts and an embodiment of the electrical contacts for use with the flexible drive; 
     FIG. 2A illustrates a connector having a movable connector element for mating with a stationary connector element and an actuator for engaging the connector elements according to one embodiment of the invention; 
     FIG. 2B illustrates a connector having a movable connector element for mating with a stationary connector element and an actuator for disengaging the connector elements according to one embodiment of the invention; 
     FIG. 3A illustrates an embodiment of the invention wherein a drive rod extends from within one of an insertion cam and an extraction cam toward a first stanchion in the direction of an input drive end of a respective actuator drive, wherein the drive rod is axially and rotationally fixed relative to a flexible threaded rod; 
     FIG. 3B is a section view of an actuator drive of the invention taken between a first and a second stanchion, wherein respective flexible threaded rods are terminated in a respective rotary drive input mechanism; 
     FIG. 4 illustrates an embodiment of the invention wherein a protective sheath formed around the flexible threaded rod terminates at the second stanchion; 
     FIG. 5A illustrates another embodiment of the actuator drive mechanism of the invention; 
     FIG. 5B illustrates one embodiment of the termination of both the flexible threaded rods and the flexible drive rods of the invention at respective rotary drive inputs; 
     FIG. 6A illustrates one embodiment of the mobile connector element of the invention, including first and second spaced apart inclined drive surfaces forming a truncated isosceles triangular cavity having its base facing toward the actuator; 
     FIG. 6B illustrates another embodiment of the mobile connector element of the invention, including a pair of spaced apart angular surfaces, each including a pair of intersecting surfaces, that together form a pair of cavities describing isosceles triangles intersecting and mutually truncating one another along an engagement axis between the stationary and mobile connector elements; 
     FIG. 7A illustrates one embodiment of the actuator of the invention that includes a cylindrical actuator cam slidingly engaged with a tubular insertion cam guide of the invention, wherein the cylindrical body of the actuator cam includes a conical actuation surface; 
     FIG. 7B illustrates another embodiment of the actuator of the invention that includes a cylindrical actuator cam slidingly engaged with a tubular insertion cam guide of the invention, wherein the cylindrical body of the actuator cam includes a curved actuation surface; 
     FIG. 8 illustrates the non-flexing actuator drive elements of the invention; 
     FIG. 9A illustrates one mechanism for securing the drive relative to respective actuator cams according to one embodiment of the invention; and 
     FIG. 9B illustrates another mechanism for securing the drive relative to respective actuator cams according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates one embodiment of the flexible drive for connecting remote electrical contacts and an embodiment of the electrical connectors for use with the flexible drive. The invention is described, for exemplary purposes only, using an electrical connection of the type described in U.S. Pat. No. 4,975,074, which is incorporated in its entirety herein by reference. The invention is not intended to be limited in any way by the use of the description of the electrical connection of the type described in U.S. Pat. No. 4,975,074. Rather, the invention is intended to generally encompass the remote installation of mobile connector elements into mating stationary connector elements. Electrical connector  10 A is shown in FIG. 1 having a first connector element  11 A mounted in a stationary position on an inaccessible surface of the computer or electrical cabinet. For example, stationary connector element  11 A is mounted on an electrical interface board, such as a mother board, back plane, or another circuit board of a computer system positioned oppositely from the access panel for installing circuit boards. Optionally, stationary connector element  11 A is mounted on the back plane of an electrical equipment cabinet. The present invention is applicable to either of these specific applications, or another suitable application requiring remote insertion of electrical or mechanical connectors in a difficult access area. A mating mobile connector element  11 B is mounted on the circuit board being installed in the cabinet. 
     Also illustrated in FIG. 1 is the flexible actuator unit  19  for remotely inserting electrical connectors. In a preferred embodiment, flexible actuator  19  includes two actuator drives, an insertion actuator  19 A and an extraction actuator  19 B. As will be described in greater detail below, insertion actuator  19 A and extraction actuator  19 B include respective threaded actuator drives  20 A and  20 B, which are each formed of a tightly wound helical coil tension spring. Each of flexible actuator drives  20 A,  20 B are threadedly engaged with a respective threaded member  22 ,  23 , which is mounted on the circuit board to be installed. Threaded members  23 ,  23  are, for example, a nut or an internal thread cut in a metal or plastic plate. Preferably, threaded element  22 ,  23  is positioned by a stanchion  25  fixed on the circuit board. Threaded elements  22 ,  23  are optionally threads cut in stanchion  25 . One or more internally threaded members  22 A through  22 N threadingly engage the coils of insertion actuator drive  20 A, while one or more threaded members  23 A through  23 N threadingly engage extraction actuator drive  20 B. As will be discussed below in detail, a rotational force applied to either actuator  19 A or  19 B causes the respective flexible actuator drive  20 A or  20 B to advance or retract along the longitudinal axis of respective threaded member  22 ,  23 , thereby translating the applied rotational force into a linear force directed along the longitudinal axis of respective threaded member  22  and  23 . 
     Insertion actuator unit  19 A includes an insertion cam  24 . As will be discussed below in detail, insertion cam  24  is driven by insertion actuator drive  20 A to engage the electrical contacts of mobile connector element  11 B with mating contacts of stationary connector element  11 A. Extraction actuator drive  20 B drives extraction cam  26  of extraction actuator unit  19 B to disengage mobile connector element  11 B from stationary connector element  11 A. Optionally, one or more additional connectors  10 B through  10 N are similarly engaged and disengaged by respective ones of insertion actuator unit  19 A and extraction actuator unit  19 B. 
     FIG. 2A illustrates details of connector  10  and actuator cam assembly  30 . In FIG. 2A, stationary connector element  11 A is fixed relative to a mother board, back plane or wall of a computer or other electrical equipment enclosure or cabinet (not shown). Mating connector element  11 B, however, is mounted on the circuit board to be installed in a manner that permits electrical connector element  11 B a degree of mobility along an engagement axis  32 , while restricting motion in other directions or dimensions. 
     Mobile connector element  11 B is formed with a slot  34  having an opening configured as a cavity or slot with substantially parallel internal walls  36 ,  38  oriented substantially perpendicularly relative to engagement axis  32 . Cam assembly  30  includes both insertion cam  24  and extraction cam  26  within an actuator guide  40 , which is formed as a linear cavity. According to preferred embodiments, actuator guide  40  is further at least partially subdivided by a bisecting wall  42  oriented substantially parallel with a longitudinal axis (not shown) of linear cavity  40  and centrally positioned within cavity  40 . Bisecting wall  42  defines, in combination with respective exterior walls  44 ,  46  two substantially coextensive actuator guides  40 A and  40 B, which are formed as two substantially equally sized parallel linear cavities. Insertion cam  24  and extraction cam  26  are contained within respective actuator guides  40 A and  40 B. Insertion cam  24  is formed with two substantially parallel and spaced apart support surfaces  48 A and  50 A. An actuation surface  52 A is angularly inclined between support surfaces  48 A and  50 A, whereby insertion cam  24  is formed as a wedge-shaped element. Inclined actuation surface  52 A slopes from first support surface  50 A towards a second support surface  48 A and forms a preferably blunt point with support surface  48 A; the blunt point defining an actuator tip  53 A of insertion cam  24 . Furthermore, a cavity  54 A is formed in insertion cam  24  between support surfaces  48 A,  50 A. Means are provided at an end of insertion cam  24  opposite actuator tip  53 A for rotatably attaching insertion actuator drive element  20 A. 
     Insertion cam  24  is sized to slidingly fit within linear cavity  40 A for motion along longitudinal axis  64 A of cavity  40 A without excessive lateral or side play. Insertion cam  24  is rotatably connected to insertion actuator drive  20 A in a manner substantially restricting separation between insertion actuator drive  20 A and insertion cam  24 . For example, a passage  62 A is formed between cavity  54 A and a driven end  56 A. A drive wire or rod  72 A fixed relative to insertion actuator drive  20 A extends through passage  62 A into cavity  54 A within insertion cam  24 . Drive rod  72 A is fixed therein against relative axial motion between insertion actuator drive  20 A and insertion cam  24 , while retaining rotational freedom relative to insertion cam  24 . Relative axial motion between insertion actuator drive  20 A and insertion cam  24  is restricted by, for example, expanding the diameter of drive rod  72 A within cavity  54 A. According to one embodiment of the invention, a metallic ferrule  74 A, for example, a bronze ferrule, is fixed to drive rod  72 A within cavity  54 A. For example, ferrule  74 A is mechanically bonded to drive rod  72 A by any of staking, welding, soldering, adhesive bonding, or another suitable mechanical fixing method. Preferably, rotation of drive rod  72 A relative to stanchion  25  is eased by a bushing or bearing  73 A. 
     Insertion cam  24  assembled to insertion actuator drive  20 A as described is installed in linear cavity  40 A of cam assembly  30 . Preferably, support surfaces  48 A and  50 A of insertion cam  24  are spaced apart a predetermined distance corresponding to distance D between drive surfaces  36 ,  38 , which define the interior walls of slot  34  in mobile connector element  11 B. The correspondence between the thickness of insertion cam  24  and distance D between drive surfaces  36 ,  38  is such that complete insertion of cam  24  into slot  34  ensures that mobile connector element  11 B is moved laterally from a predetermined disengaged position adjacent to but spaced-away from stationary connector elements  11 A to completely engage stationary connector element  11 A. 
     Operationally, when the circuit board is installed within the computer or electrical cabinet, stationary connector element  11 A is mounted on a plane at the back of the cabinet with its engagement surface projecting toward the seated position of the circuit board adjacent to the edge of the circuit board. Mobile connector element  11 B is disposed in a first position set slightly away from interconnection with stationary connector element  11 A when the circuit board is seated. When mobile connector element  11 B is in its first pre-engagement position, cam assembly  30  is fixed to the circuit board adjacent to mobile connector element  11 B, such that longitudinal axis  64  of linear actuator guide  40 A is substantially parallel to a linear actuation and extraction axis  80 . Axis  80  is defined as an axis perpendicular to engagement axis  32  and bisecting slot  34  of mobile connector element  11 B parallel to interior drive surfaces  36 ,  38  thereof. Linear actuator guide  40 A of actuator cam assembly  30  is disposed parallel to axis  80  and offset along engagement axis  32  toward stationary connector element  11 A. Linear cavity  40 A slightly overlaps slot  34  of mobile connector element  11 B, such that an interior wall of linear actuator guide  40 A, as defined by a wall of interior partition wall  42 , is slightly offset from interior cavity drive surface  36  of slot  34  toward interior cavity drive surface  38 . Insertion cam  24  is positioned within linear actuator guide  40 A of actuator cam assembly  30 , such that inclined actuation surface  52 A faces toward first interior drive surface  36  of slot  34  and stationary connector element  11 A, with actuator tip  53 A positioned adjacent to the opening in slot  34 . 
     Rotational force provided at insertion actuator drive  20 A is converted by engagement with threaded member  22 A into linear force directed along longitudinal axis  64 A of actuator guide  40 A by means of drive rod  72 A, which presses against a surface of insertion cam  24  opposite actuator tip  53 A. Initially, actuator tip  53 A is situated outside of slot  34  of mobile connector element  11 B adjacent to first insertion drive surface  36 . The overlap between actuator guide  40 A and slot  34  permits actuator tip  53 A of insertion cam  24  to enter slot  34  and engage first insertion drive surface  36  of slot  34  at a point adjacent to cam assembly  30 . Initial rotational force applied to insertion actuator drive  20 A is converted into linear translational force at drive rod  72 A that moves actuator tip  53 A of insertion cam  24  into slot  34  of mobile connector element  11 B and into contact with first insertion drive surface  36  thereof. Sustained rotational force applied to insertion actuator drive  20 A is converted into a relatively smooth, continuous linear translational force at drive rod  72 A, which continues to move insertion cam  24  linearly along longitudinal axis  64  of linear actuator guide  40 A. Continued linear motion of insertion cam  24  increasingly engages inclined actuation surface  52 A with first insertion drive surface  36 . The pressure of the inclined actuation surface  52 A against first insertion drive surface  36  is supported by insertion cam support surfaces  48 A,  50 A against respective interior support surfaces  82 A and  84 A within linear actuator guide  40 A. Actuator guide  40 A thus supports against insertion cam  24  pushing mobile connector element  11 B away from stationary connector element  11 A. Mobile connector element  11 B, having no translational constraints along engagement axis  32 , is thus urged by interaction with insertion cam  24  to move along engagement axis  32  toward stationary connector element  11 A. Preferably, one or more insertion guides (not shown) formed in mating connector elements  11 A and  11 B guide the final interconnection of the connector elements along engagement axis  32 , as is well-known in the art. Furthermore, male pins and female ports within respective connector halves  11 A and  11 B are formed with mating insertion guides, such as chamfers or rounds and countersinks, which are well-known in the art. The degree of incline provided on inclined actuation surface  52 A determines the rate at which mobile connector element  11 B is inserted into stationary connector element  11 A. Preferably, inclined actuation surface  52 A is inclined at a minimal slope, for example an angle less than 30 degrees, that gently urges insertion of male pins into female receptacles. However, the invention is alternately practiced with inclined actuation surface  52 A of insertion cam  24  inclined at greater angles. 
     One or more additional cam supports  86 ,  88  are stationary actuator guides mounted on the circuit board at opposing openings of slot  34  in mobile connector element  11 B. Additional actuator guides or cam supports  86 ,  88  provide continued support against twisting or lateral motion of insertion cam  24  as drive tip  53 A and insertion cam  24  leave the confines of linear cavity  40 A, thus losing the restraint of support surfaces  48 A,  50 A with respect to respective interior support surfaces  82 A,  84 A. A first cam support  86  provides continued support to insertion cam  24  at a first or entry end of slot  34 , while second insertion can support  88  engages actuator tip  53 A and lends physical support to continued linear motion of insertion cam  24  along longitudinal axis  64 A beyond first connector element  11 B. According to one or more embodiments of the present invention, additional connectors  10 B through  10 N are disposed along the edge of the circuit board in series with connector  10 A. According to such configurations, continued rotational force exerted on insertion actuator drive  20 A drives insertion cam  24  linearly along longitudinal axis  64 A into engagement with a slot  34  in a next mobile connector element  11 B positioned along the edge of the circuit board adjacent to first mobile connector clement  11 B. 
     Additional insertion cam supports  86 ,  88  positioned along a circuit board relative to each of additional connectors  10 B through  10 N provide continued directional guidance for insertion cam  24  along longitudinal axis  64 A. Additional supports  86 ,  88  also provide a reaction surface that supports insertion cam  24  when inclined actuation surface  52 A engages insertion drive surface  36  of subsequent mobile connector elements  11 B. 
     An ability to disengage previously engaged connector elements  11 A and  11 B without damaging the delicate connector pins is also desirable. Before disengaging mobile connector elements  11 B from connector elements  11 A, insertion cam  24  is retracted into cam assembly  30 . A reversing rotational force is applied to insertion actuator drive  20 A that threadedly retracts insertion actuator drive  20 A through threaded member  22 A, pulling with it drive rod  72 A. Ferrule  74 A fixed to drive  72 A and entrapped within cavity  54 A necessarily pulls insertion cam  24  back along longitudinal axis  64 A through cavities  34  of each of the one or more mobile connector elements  11 B and into cam assembly  30 . Preferably, driven end  56 A of insertion cam  24  includes a chamfer, bevel, or round to ease passage of cam supports  86 ,  88  and re-entry into slot  34  of each moveable connector element  11 B. 
     FIG. 2A also illustrates the extraction actuator drive  20 B transmitting a linear translational extraction force to an extraction cam  26  via a second drive rod  72 B. Rotation of drive rod  72 B relative to stanchion  25  is preferably eased by bushing or bearing  73 B. 
     FIG. 2B illustrates the extraction of mobile connector elements  11 B from engagement with stationary connector elements  11 A along respective engagement axes  32 . Actuator cam assembly  30  includes a second linear actuator guide  40 B defined by internal support surfaces  82 B and  84 B, which in turn define a longitudinal axis  64 B. Preferably, linear actuator guide  40 B shares interior partition wall  42  with linear actuator guide  40 A, as described above. Extraction cam  26  of actuator  19 B is configured similarly to insertion cam  24 , having an inclined actuator surface  52 B configured similarly to inclined actuator surface  52 A and facing oppositely from inclined actuator surface  52 A. Extraction cam  26  further includes an actuator tip  53 B formed oppositely from a driven end  56 B. Actuator tip  53 B, like actuator tip  53 A of insertion cam  24 , is formed as the tip of wedge-shaped extraction cam  26 . Similarly to insertion cam  24 , extraction cam  26  includes spaced apart substantially parallel surfaces  48 B and  50 B coinciding with respective internal support surfaces  82 B and  84 B that cause extraction cam  26  to move in a substantially straight line parallel with longitudinal axis  64 B of actuator guide  40 B, substantially without either lateral or rotational motion. Spaced apart surfaces  48 B and  50 B of extraction cam  26  are joined at actuator tip  53 B by an inclined actuator surface  52 B sloping from a first surface  50 B of extraction cam  26  adjacent to external wall  46  and toward a second surface  48 B of extraction cam  26  adjacent to interior partition wall  42 . Inclined actuator surface  52 B thus faces away from inclined actuator surface  52 A of insertion cam  24 . 
     Prior to activation of extraction cam  26 , while mobile connector element  11 B is engaged with stationary connector  11 A, linear actuator guide  40 B is situated adjacent to and slightly overlapping with slot  34  of mobile connector element  11 B. Actuator tip  53 B of extraction cam  26  is positioned adjacent to second drive surface  38  of mobile connector element  11 B, with inclined actuation surface  52 B within the gap defined by the overlap between actuator guide  40 B and slot  34  and facing toward second extraction drive surface  38 . The rotational drive force applied to extraction drive member  20 B and translated into a linear force by engagement with threaded member  23 B acts along drive rod  72 B in line with longitudinal axis  64 B. Drive rod  72 B pushes against an inner surface of cavity  54 B formed within extraction cam  26  to move extraction cam  26  along linear actuator guide  40 B and into slot  34  of mobile connector element  11 B adjacent to extraction drive surface  38 . As extraction cam  26  moves into slot  34 , extraction actuator tip  53 B engages extraction drive surface  38  and exerts a disengagement force thereon. The slope or inclination of inclined actuation surface  52 B increasingly engages extraction drive surface  38  as extraction cam  26  is driven deeper into slot  34  as a function of continued rotational force applied to extraction actuation drive  20 B. The slope or inclination of inclined actuation surface  52 B translates the linear drive force exerted along longitudinal axis  34 B by drive rod  72 B into a linear disengagement force acting in a direction parallel to engagement axis  32  and oppositely from stationary connector element  11 A. 
     Parallel surfaces  48 B,  50 B defining the body of extraction cam  26  are spaced apart a predetermined distance corresponding to distance D separating first and second drive surfaces  36 ,  38  of mobile connector element  11 B, such that complete insertion of extraction cam  26  within slot  34  results in complete disengagement of mobile connector element  11 B from stationary connector element  11 A. 
     Cam supports  86 ,  88  are configured with a thickness measured parallel to engagement axis  32  that is substantially identical to the thickness of interior partition wall  42  of cam assembly  30 . Therefore, each of cam supports  86 ,  88  provides support and guidance for extraction cam  26  to maintain the motion of extraction cam  26  along longitudinal axis  64 B. As extraction cam  26  exits the confines of actuator guide  40 B, cam supports  86 ,  88  prevent both lateral and rotational motion of extraction cam  26 , as discussed above in connection with insertion cam  24 . In an embodiment of the invention including multiple connectors  10 A through  10 N arranged along the edge of the circuit board, as described above, continued rotational force applied at extraction actuator drive  20 B causes continued linear motion of extraction cam  26  along longitudinal axis  64 B, whereby extraction cam  26  engages a next initially engaged mobile connector element  11 B of a next connector  10 B. The interaction of inclined actuation surface  52 B with second extraction drive surface  38  gently eases the pins of one of connector elements  11 A,  11 B out of engagement with the female receptacles of the other connector element  11 A,  11 B by pushing with a steady pressure against second extraction drive surface  38 . Mobile connector element  11 B is thereby slowly and gently eased along engagement axis  32  away from stationary connector element  11 A. 
     FIGS. 1 and 2 further illustrate the optional curving nature of insertion actuator drive  20 A and extraction actuator drive  20 B, wherein each undergoes a directional change. As described above in connection with FIGS. 1 and 2, each of insertion actuator drive  20 A and extraction actuator drive  20 B includes a respective externally threaded, elongated member or rod  98 A and  98 B threadedly engaged with a respective internally threaded member  22  and  23 . In a preferred embodiment, internally threaded members  22 ,  23  are hex nuts of a standard diameter and thread pitch that comply with one of the well-known and commercially useful machine thread standards. Optionally, threaded members  22 ,  23  are internal threads cut into the body of a block or plate, such as stanchion  25 . Insertion and extraction drive elements  20 A and  20 B include tightly coiled helical springs  98 A,  98 B, the coils of which define a diameter and pitch substantially corresponding to the threads of respective threaded member  22 ,  23 . As is generally known, a tightly coiled helical tension spring generally forms a substantially straight tubular structure that is inherently flexible or bendable as a function of such factors as: the stiffness of the wire, the wire diameter, and diameters of the individual coils. Threaded members  22  and  23  are preferably positioned downstream from a directional change in respective insertion drive element  20 A and extraction drive element  20 B. Threaded members  22  and  23  are also preferably positioned relatively near cam assembly  30  which houses both insertion cam  24  and extraction cam  26 . In other words, directional changes occur between the rotational drive input for respective drive elements  20 A and  20 B and respective threaded members  22  and  23 . In such a configuration, a rotational drive force applied to either insertion actuator drive  20 A or extraction actuator drive  20 B interacts with respective threaded member  22 ,  23  to pull respective helical coil spring  98 A,  98 B through the directional change. Alternatively, threaded member  22 ,  23  is located between the rotational drive input point and the directional change, whereby the rotational input force interacts with threaded member  22 ,  23  to pull a straight section of helical coil spring  98 A,  98 B into the curvature and push it through the curvature. As illustrated, more than one internally threaded member  22 ,  23  is optionally used with respective insertion and extraction drive elements  20 A,  20 B. Accordingly, threaded members  22 ,  23  are positioned at the entrance to and exit from the directional change, whereby helical coil spring  98 A,  98 B is both pushed into and pulled through the change in direction. 
     Preferably, helical coil spring  98 A,  98 B is wound with a diameter slightly less than the diameter of respective threaded member  22 ,  23  and having a slightly coarser thread pitch as defined by the pitch of the individual coils. Each of helical coil springs  98 A,  98 B are tightly wound tension springs with adjacent coils compressed against one another with an initial compressive force. Windings are wound in a direction relative to respective threaded member  22 ,  23  such that a rotational force applied to advance helical spring  98 A,  98 B through the threaded member tends to increasingly compress adjacent coils against one another. The increased axial compression in turn tends to cause the spring diameter to increase to fill the slightly larger diameter of the threaded member, while the slight shortening of pitch causes the thread pitch defined by the coils to more precisely match the thread pitch of respective threaded member  22 ,  23 . The increased diameter and shortened thread pitch results in more complete engagement of the threads of the coil spring with the threads of respective threaded member  22 ,  23 . More complete engagement allows a greater conversion of torque developed in the helical spring into linear force directed along the longitudinal axis of the helical spring. Thus, a greater linear translational force is developed at respective drive rod  72 A and  72 B. In contrast, an opposite or retractive rotational force applied to a respective one of insertion drive element  20 A and extraction drive element  20 B tends to stretch the respective helical coil, separating the individual coils and tilting them slightly relative to the longitudinal axis of the helical spring. This stretching of the helical spring is avoided by use of a compressively wound spring. The compressive force between adjacent coils retains the threaded configuration sufficiently to move helical spring  98 A,  98 B through respective threaded member  22 ,  23 . Thus, extraction of either insertion cam  24  or extraction cam  26  is accomplished similarly to insertion. 
     As is generally well known, a helical tension spring tends to twist or rotate out of plane when a torque is applied against a rotational resistance such that the pitch of the coils is reduced, a phenomenon also known as “helical buckling.” Such a situation is described above in connection with a rotational force applied to the helical coil spring turning it into a respective threaded member  22 ,  23 . This tendency to buckle or twist out of plane tends to be exaggerated at a directional change, i.e., a curve or bend. Therefore, a preferred embodiment of the invention provides spatially fixed stanchion  25  formed with respective channel or guide  90 A and  90 B for each of insertion drive element  20 A and extraction drive element  20 B, respectively. Respective guides  90 A,  90 B define the curvature of the directional change in respective drive elements  20 A and  20 B. Each guide  90  preferably substantially encompasses respective helical coil spring  98 A,  98 B, thereby constraining it to remain within predetermined confines. Preferably, the curvature of guides  90  is defined by the shape taken by respective helical coil spring  98 A,  98 B in its relaxed or unloaded condition, i.e., with no torque applied. 
     FIG. 1 further illustrates two relatively spatially fixed stanchions  92  and  94 . Stanchions  92  and  94  provide support for insertion actuator drive elements  20 A and  20 B and define the configuration of actuator drive  20  on the circuit board. Insertion drive element  20 A and extraction drive element  20 B include respective flexible threaded rods  98 A and  98 B, which extend from adjacent to respective drive ends  56 A and  56 B of respective insertion cam  24  and extraction cam  26  through respective channel guides  90 A and  90 B toward an accessible portion of the circuit board. As discussed in further detail below, each of flexible threaded rods  98 A and  98 B are preferably guided and supported by respective tubular guides  102 A and  102 B at least between channel guides  90  and first stanchion  92 . Tubular guides  102 A,  102 B substantially constrain flexible threaded rods  98 A,  98 B to maintain their straight tubular shape, and restrict their tendency to buckle or twist out of plane by shortening their unsupported columnar length. Accordingly, tubular guides  102  are configured to fit closely about the outer diameter of respective flexible rods  98 . Each of tubular guides  102  is in turn positionally constrained relative to the circuit board by a mechanical interconnection with each of guide  90  and first stanchion  92 . According to one embodiment of the invention, drive rods  72  are axially and/or rotationally fixed relative to flexible threaded rods  98  such that advancing or retracting flexible threaded rods  98  relative to respective threaded members  22 ,  23  similarly advances or retracts respective insertion cam  24  and extraction cam  26 . 
     FIG. 3A illustrates an embodiment of the invention wherein drive rods  72  extend from within respective cavity  54 A,  54 B of insertion cam  24  and extraction cam  26  toward the drive input end of actuator drive  20 , ending in the vicinity of first stanchion  92 . Drive rods  72  are axially and rotationally fixed relative to respective flexible threaded rods  98  by mechanical bonding. According to one embodiment, a ferrule  104 A and  104 B is swaged onto a respective one of drive rod  72 A and  72 B at or near its end. Ferrules  104  are in turn mechanically bonded to flexible threaded rods  98  by, for example, soldering, welding, adhesive bonding, swaging, or another suitable mechanical fixing or attaching technique. Between first stanchion  92  and second stanchion  94 , flexible threaded rods  98 A and  98 B are stiffened against buckling by internal support rods  106 A and  106 B, which substantially fill the tubular interior of respective flexible threaded rod  98 A and  98 B. Flexible threaded rods  98  are thereby converted into substantially rigid threaded members. Internal support rods  106  are alternatively either a substantially smooth rod fitting snugly within the internal diameter of the coils of the helical springs that form threaded rods  98 , or a rigid threaded rod having a diameter and thread pitch substantially matched to the internal thread of flexible threaded rods  98  as defined by the interior surface of the individual coils of the springs. Thus, the flexibility of threaded rods  98  is reduced substantially so that, in operation, they act substantially like rigid members. Internal support rods  106  eliminate the usefulness of a tubular guide such as tubular guide  102 . However, in a preferred embodiment, protective sheaths  108 A and  108 B provide barriers between respective threaded rods  98 A and  98 B and their environment that protect components on the circuit board. As shown in FIG. 1, sheaths  108  and  108 B extend at least between first and second stanchions  92 ,  94  and, optionally, extend beyond stanchion  94 . 
     FIG. 3B is a section view of actuator drives  20  taken between first and second stanchions  92  and  94 . In FIG. 3B, respective flexible threaded rods  98 A and  98 B are terminated in a respective rotary drive input mechanism  110 A and  110 B. Flexible threaded rods  98  are mechanically interfaced with rotary drive input mechanisms  110  such that rotation of input drive mechanisms  110 , either clockwise or counterclockwise, results in a similar rotary motion of respective flexible threaded rods  98 A and  98 B. For example, flexible threaded rods  98  are threaded into internal threads of rotary drive input mechanisms  110  and staked to prevent relative rotation therebetween. Alternatively, flexible threaded rods  98  are otherwise mechanically fixed to prevent relative rotational motion with a respective rotary drive input mechanism  110  by, for example, welding, soldering, adhesive bonding, or another suitable mechanical fixing technique. 
     Internal support rods  106 A,  106 B are preferably fixed to prevent axial motion relative to drive input  110 A and  110 B, respectively. One method of axially fixing internal support rods  106  relative to respective flexible threaded rods  98  is shown in FIG. 3B, wherein an end of respective internal support rod  106 A and  106 B extends into a respective cavity  112 A and  112 B formed in respective rotary drive input mechanism  110 A and  110 B through an appropriately sized passage. An oversized ferrule  114 A and  114 B is staked, soldered, welded, adhesively bonded, or otherwise suitably mechanically fixed to respective internal support rod  106 A,  106 B. Oversized ferrules  114  cannot pass through the passage, and therefore fix internal support rods  106  axially and translationally relative to rotary drive input mechanisms  110 . Rotary drive input mechanisms  110  further include mechanical adaptations for inputting a rotational force or torque. For example, an exposed or accessible surface of each rotary drive input mechanism  110 A and  110 B is fitted with a conventional rotational drive input structure, such as a screw driver slot  116 A and  116 B. Conventional rotational input drive structures  116 A and  116 B include a standard Phillips screwdriver slot, a straight slot for a flat bladed screwdriver, a star or hex drive, or another conventional screwdriver slot. Alternatively, rotary drive input mechanisms  110  are fitted with any of various proprietary rotational force input mechanisms. 
     In operation, a torque applied at either rotational force input slot  116  rotates a respective rotary drive input mechanism  110 , which is rotationally fixed to, and in turn rotationally drives, a respective flexible threaded rod  98 . Rotation of respective flexible threaded rods  98 A,  98 B advances respective flexible threaded rod  98 A,  98 B axially relative to respective threaded member  22 ,  23 . Drive rods  72 , which are axially fixed relative to flexible threaded rods  98 , similarly advance relative to threaded members  22 ,  23 . Advancing drive rods  72 A and  72 B imparts a linear translational motion to a respective one of insertion cam  24  and extraction cam  26  along their respective linear actuator guides  40 A and  40 B within actuator cam assembly  30 . 
     FIG. 4 illustrates an embodiment of the invention wherein protective sheaths  108  around flexible threaded rods  98  terminate at second stanchion  94 . Rotational torque input device  118  is shown as the shaft of a screwdriver adapted for mating with screwdriver slot  116 B in rotary drive input mechanism  110 B for input of a drive torque represented by arrow  120 . 
     FIG. 5A illustrates another embodiment of actuator drive mechanisms  20  of the invention. Tubular guides  102 A,  102 B again extend between respective channel guides  90 A and  90 B and first stanchion  92  to guide and support flexible threaded rod  98 A and  98 B, respectively. Protective tubular sheaths  108 A and  108 B also extend between first and second stanchions  92  and  94  as described above. According to the embodiment illustrated in FIG. 5A, drive rods  72 A and  72 B continue past first stanchion  92  and terminate at respective rotary drive input mechanisms  122 A and  122 B, shown in FIG.  5 B. 
     FIG. 5B illustrates the termination of both flexible threaded rods  98 A and  98 B and flexible drive rods  72 A and  72 B at respective rotary drive input mechanisms  122 A and  122 B. As described above, flexible threaded rods  98 A and  98 B terminate at internally threaded cavities formed in respective rotary drive input mechanisms  122 A and  122 B. Preferably, flexible threaded rods  98  are rotationally fixed relative to rotary drive input mechanisms  122  by a suitable mechanical means, such as described above. Wire drive rods  72 A and  72 B pass into respective cavities  124 A and  124 B formed in respective rotary drive input mechanisms  122 A and  122 B through appropriately sized clearance holes. Wire drive rods  72 A and  72 B are terminated in respective cavities  124 A and  124 B. Preferably, drive rods  72 A,  72 B are terminated in such manner that axial motion relative to respective flexible threaded rods  98 A,  98 B is substantially restricted. Accordingly, drive rods  72 A and  72 B are, for example, fitted with a respective ferrule  126 A and  126 B which is soldered, welded, swaged, adhesively bonded, or otherwise mechanically fixed in axial relationship thereto. An accessible surface of rotary drive input mechanisms  122 A,  122 B is adapted for inputting a rotational force such as torque  120  similarly to rotary drive input mechanisms  110 , discussed above. For example, a screwdriver slot  116  is provided for inputting a rotational force such as torque  120  via screwdriver  118 , as shown in FIG.  4 . 
     FIGS. 6A and 6B illustrate two additional embodiments of movable connector element  11 B, wherein drive surfaces  36 ,  38  are configured with an incline. According to one additional configuration shown in FIG. 6A, mobile connector element  11 C includes first and second spaced apart inclined drive surfaces  36 A and  38 A. Together, inclined insertion drive surface  36 A and inclined extraction drive surface  38 A form a truncated isosceles triangular slot  34 A having its base facing toward cam assembly  30 . 
     FIG. 6B illustrates mobile connector element  11 D formed with a pair of spaced apart angular surfaces  36 B and  38 B, each including a pair of intersecting surfaces. Angular surfaces  36 B and  38 B together form a pair of slots describing isosceles triangles intersecting and mutually truncating one another along engagement axis  32  and having respective bases formed at opposing openings in slot  34 B facing, respectively, toward and away from cam assembly  30 . Preferably, the angle of inclined actuation surface  52 A and the angles of inclined drive surfaces  36 A and  36 B are substantially identical, such that engagement of inclined actuation surface  52 A with one of inclined drive surfaces  36 A and  36 B results in a substantially planar engagement. In contrast, engagement is linear between inclined actuation surface  52 A and drive surface  36 , which is shown in FIG. 2A as formed substantially parallel to longitudinal axis  80  of slot  34 . Use of an inclined surface for drive surfaces  36 A,  36 B provides more uniform loading or pressure against drive surface  36 A,  36 B as engagement with inclined actuation surface  52 A increases. Also, such mutually inclined surfaces move the center of pressure on respective mobile connector elements  11 C and  11 D toward coincidence with engagement axis  32 . In contrast, interaction between inclined actuation surface  52 A and parallel insertion drive surface  36  limits the pressure to a line intersection at the opening to slot  34 . 
     FIGS. 7A and 7B illustrate two additional embodiments of actuator cam assembly  30 . The additional embodiments are described in relation only to insertion cam  24 . However, the embodiments are similarly applicable to extraction cam  26 . In FIG. 7A, actuator cam assembly  30 A includes a cylindrical insertion cam  24 A slidingly engaged with a tubular insertion cam guide  200 A. Cylindrical body  202 A of insertion cam  24 A defines a longitudinal axis  204 A that is coaxial with longitudinal axis  64 A of tubular insertion cam guide  200 A. A conical actuation surface  206 A is coaxial with and extends from cylinder  202 A toward movable connector element  11 B and is tipped by a conical actuator tip  208 A. Extraction cam  26 A is similarly configured as a cylinder  202 B slidingly engaged with tubular extraction cam guide  200 B and defines a longitudinal axis  204 B that is coaxial with longitudinal axis  64 B thereof. Cylindrical extraction cam  26 A similarly includes a coaxial conical actuation surface  206 B that extends toward movable connector element  11 B and is similarly tipped with a coaxial conical actuator tip  208 B. Actuator cam assembly  30 A is positioned and operates substantially the same as actuator cam assembly  30 , described above. Cylindrical insertion cam  24 A is threadedly driven into slot  34  of mobile connector element  11 B by insertion actuator drive  20 A, whereby first conical actuator tip  208 A and then conical actuation surface  206 B engage insertion actuation drive surface  36 . The inclined nature of the conical surfaces act similarly to inclined actuation surface  52 A of insertion actuator cam  24  to gently urge mobile connector element into engagement with mating stationary connector element  11 A. 
     According to one embodiment of the invention, conical actuator surfaces  206 A and  206 B of respective cylindrical actuator cams  24 A and  26 A are optionally configured with respective internal cavities  54 A and  54 B and fitted to respective drive rods  72 A and  72 B of earlier described threaded insertion actuator drive  20 A. The conical nature of actuator cam assembly  30 A, however, provides opportunities for other configurations of actuator drive  20 . All surfaces of conical drive tips  208 A,  208 B and conical actuation surfaces  206 A,  206 B are identically inclined surfaces. Therefore, cylindrical insertion and extraction cams  24 A and  26 A are optionally allowed to rotate relative to respective insertion and extraction drive surfaces  36  and  38  of mobile connector element  11 B. Rotatable insertion and extraction actuator cams  24 A and  26 A are connected directly to respective threaded rods  98 A and  98 B, without respective intermediary drive rods  72 A and  72 B. Threaded rods  98  are mechanically affixed to actuator cams  24 A,  26 A using any of the above described means or another suitable means, thus simplifying the drive mechanism. 
     Furthermore, rotatable insertion and extraction actuator cams  24 A and  26 A are optionally used in combination with either of additional embodiments  11 C and  11 D of mobile connector element  11 B. Preferably, conical actuation surface  206 A of insertion actuator cam  24 A is formed with an incline substantially matched to the incline of corresponding insertion drive surfaces  36 A and  36 B of respective mobile connector elements  11 C and  11 D. Similarly, conical actuation surface  206 B of extraction actuator cam  26 A is preferably formed with an incline substantially matched to the incline of corresponding extraction drive surfaces  38 A and  38 B of respective mobile connector elements  11 C and  11 D. 
     FIG. 7B illustrates another additionally embodiment of actuator cam assembly  30 . In FIG. 7B, actuator cam assembly  30 B includes insertion and extraction cams  24 B and  26 B configured with respective cylindrical bodies  220 A and  220 B, which are slidingly engaged with respective tubular cam guides  200 A and  200 B. Cylindrical insertion cam  24 B defines a longitudinal axis  222 A that is coincident with longitudinal axis  64 A of tubular insertion cam guide  200 A. Within tubular extraction cam guide  200 B, cylindrical extraction cam  26 B defines a longitudinal axis  222 B that is coincident with longitudinal axis  64 B. Insertion and extraction cams  24 B and  26 B are further configured with respective rounded actuator tips  224 A and  224 B, which extend from respective cylindrical bodies  220 A and  220 B toward slot  34 B of mobile connector element  11 D. 
     Actuator cam assembly  30 B is positioned and operates substantially the same as actuator cam assemblies  30  and  30 A, described above. Cylindrical insertion cam  24 B is threadedly driven into slot  34 B of mobile connector element  11 D by insertion actuator drive  20 A, whereby rounded actuation surface  224 B engages inclined insertion actuation drive surface  36 B. An inclined drive surface is preferred to interact with rounded actuation surface  224 B. The inclined drive surface of the mobile connector element acts similarly to inclined actuator surface  52 A of insertion actuator cam  24 , allowing rounded actuation surface  224 A to gently urge mobile connector element  11 B into engagement with mating stationary connector element  11 A. Such an inclined drive surface is provided by insertion drive surface  36 A in mobile connector element  11 C, and by insertion drive surface  36 B in mobile connector element  11 D, as described above. Extraction cam  26 B is similarly operated. 
     According to one embodiment of the invention, rounded actuator surfaces  224 A and  224 B of respective cylindrical actuator cams  24 B and  26 B are optionally configured with respective internal cavities  54 A and  54 B and fitted to respective drive rods  72 A and  72 B of earlier described threaded insertion actuator drive  20 A. According to the present embodiment of the invention, however, the cylindrical and rounded nature of actuator cam assembly  30 B provides that all surfaces of rounded actuation surfaces  224 A,  224 B are identically rounded surfaces. Therefore, cylindrical insertion and extraction cams  24 B and  26 B are optionally allowed to rotate relative to respective insertion and extraction drive surfaces  36 B and  38 B of mobile connector element  11 D. Rotatable insertion and extraction actuator cams  24 B and  26 B are connected directly to respective threaded rods  98 A and  98 B, without respective intermediary drive rods  72 A and  72 B. Threaded rods  98  are mechanically affixed to actuator cams  24 A,  26 A using any of the above described means or another suitable means, thus simplifying the drive mechanism. 
     FIG. 8 illustrates the use of rigid, non-flexing actuator drive elements  240 A and  240 B in place of flexible actuator drive elements  20 A and  20 B. Rigid actuator drive elements are appropriate in an application wherein access is available along longitudinal axes  64 A and  64 B of respective actuator guides  40 A and  40 B. Preferably, insertion actuator drive  240 A and extraction actuator drive  240 B are formed as respective rods  242 A and  242 B, each threaded with a standard machine thread and configured with a respective rotational drive input  116 A and  116 B, as described above. Actuator drive rods  242 A and  242 B threadedly engage respective nuts  22  and  23 , which convert torque into linear translational force along their respective longitudinal axes. 
     Actuator drive rods  242 A and  242 B are terminated in any of several suitable terminations that tie the linear translation of respective insertion and extraction cams  24  and  26  along respective actuator guide longitudinal axes  64 A and  64 B to the linear motion of a respective actuator drive rod  242 A and  242 B. For example, the diameter of each of actuator drive  242 A and  242 B is necked-down to form respective reduced diameter drive rods  244 A and  244 B that extend through appropriately sized clearance passages  62  into cavities  54  of respective insertion and extraction cams  24  and  26 . Rotation of reduced diameter drive rods  244 A and  244 B relative to stanchion  25  is preferably eased by respective bushings or bearings  73 A and  73 B. 
     Reduced diameter drive rods  244 A and  244 B are fixed against relative linear translational motion with respective actuator drive rods  242 A and  242 B while retaining rotational freedom relative to respective insertion and extraction cams  24  and  26 . Relative linear translational motion is restricted by, for example, expanding the diameter of drive rods  244 A and  244 B within cavities  54 . As described above, according to one embodiment of the invention, a metallic ferrule  74  is fixed to each drive rod  244  within cavity  54  by any of staking, welding, soldering, fixing with an adhesive, or another suitable mechanical fixing method. Alternatively, reduced diameter drive rods  244  are threaded and a corresponding threaded element, such as a standard hex or lock nut is engaged therewith within cavity  54 . Thus, insertion and extraction cams  24 ,  26  advance and retreat responsively to a positive or negative torque applied to respective drive rod  242 A and  242 B. 
     FIGS. 9A and 9B illustrate two embodiments of the invention describing mechanisms for securing drive rods  242 A and  242 B relative to respective insertion and extraction cams  24  and  26 . In FIG. 9A, for example, drive rod  242  is necked-down at reduced diameter portion  244  to clear passage  62 , but maintained at it&#39;s a larger or full diameter at its tip  246 . Necked-down portion  244  is passed through slot  248  in one of insertion and extraction cam  24 ,  26  into passage  56 , where relative rotational freedom between drive rod  242  and cam  24 ,  26  is maintained. Enlarged tip  246  is simultaneously installed into cavity  54 , thereby securing relative translation between drive rod  242  and cam  24 ,  26 . 
     FIG. 9B illustrates one of drive rods  242 A and  242 B configured with a necked-down end portion  250  that extends through clearance passage  62  into cavity  54 . Necked-down portion  250  is optionally secured within cavity  54  by any of the mechanisms utilized to secure drive rod  72 . Alternatively, necked-down portion  250  is threaded and secured with a hex or lock nut  252 . Thus, relative translational motion between drive rod  242  and cam  24 ,  26  is secured, while relative rotational independence is maintained. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.