Abstract:
A rotatable latch is provided for securing an object to a holder and for preventing unintended removal of the object. In a preferred embodiment, the rotatable latch has at least two actuators flexibly mounted to a body. Each actuator has a hooked portion which engages a portion of the holder. A lever portion may be provided for releasing the hooked portion. The hooked portion is rotated about a pivot point to release the object from the holder. Rotation occurs when actuators are released through use of at least two lever portions. To prevent accidental removal of the object, the second actuator cannot be released until the first actuator has been released. The latch requires at least two actions, pressing the levers in succession, to release the object. The invention is applicable, for example, to circuit packs for electronic circuit boards.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an apparatus for securing a rigid plate and, in particular, to a multiple actuator latch used to secure a circuit board. 
     2. Description of the Related Art 
     System flexibility is a highly desirable trait which allows a system to respond to the changing needs and/or requirements of a user or group of users. One solution to the need for flexibility is the incorporation of interchangeable parts within such systems. This is especially true in electronics applications, where interchangability of parts increases the lifespan and functionality of a system. Interchangeable parts may be switched, upgraded, or removed without having to replace the entire system. One such interchangeable part often used in computer-based applications is the printed circuit board (PCB). Computer systems may be fabricated to use a plurality of PCBs, each containing a portion of the electronics required to allow the computer system to operate. 
     To address the need for interchangeability in complex electronics applications, e.g. computer systems, “card racks” (or “card cages”) have been developed. A card rack is a relatively large enclosure containing racks or shelves capable of holding a number of PCBs in a parallel configuration. A typical card rack  500  holding a number of PCBs  501  is shown in FIG.  8 . Card rack  500  consists of side plates  502  and  503  connected by supports  504 . A backplane  505  is connected to side plates  502  and  503  and includes electrical connectors  506 , at least one connector  506  being provided for each of the PCBs  501 . Connectors  506  releasably engage connectors  507  on the PCBs  501  to allow communication between the PCB  501  and the system of which card rack  500  is a portion. Plug  508  is inserted through aperture  509  into engagement with pin connectors to complete the physical installation of the PCBs  501 . 
     Card racks and PCB&#39;s are found in numerous telecommunications applications, e.g. line units and trunk units. PCBs  501  for telecommunications applications may be in the form of circuit packs  516 , as shown in FIG.  9 . Each circuit pack  516  includes a plurality of signal processing components  518  mounted on a planar surface  520  of a rigid plate  522 . The rigid plate  522  includes conductive paths  524  for interconnecting the components  518  to one another and to connector  507 . Connector  507  is mounted on the rigid plate  522 , generally on an end face of the rigid plate  522 . The connector  507  contains pins and/or sockets for mating with matching connectors fixedly mounted on a rear wall of a card rack. Circuit pack  516 , a specific type of PCB  501 , may be removably mounted in a side-by-side, parallel relationship within a card rack  500  relative to other PCBs  501  and side plates  502 ,  503 , as shown in FIG.  8 . 
     The circuit pack  516  has a front face plate  528  which is mounted to the rigid plate  522 . Mounting and dismounting of the circuit pack  516  occurs by sliding the edges of the rigid plate  522  along grooves within support walls of the card rack  500 . Latches  530  are provided on the face plate  528  or rigid plate  522  to allow the circuit pack  516  to be secured to the card rack  500 . 
     A known latch  530  is shown in FIG.  10 . The latch  530  consists of a body portion  532 ; a handle portion  534  comprising both an actuating member  536  and a stop portion  538 ; a locking portion  540 ; a hooked portion  542 ; and a pivot point  544  which is used to pivotally mount latch  530  to rigid plate  522 . The portion  545  of latch  530  nearest the rigid plate  522  is split into two sections to a depth defined by dotted line  547  which allows latch  530  to straddle the edge  549  of rigid plate  522 . In operation, the latch  530  is pivoted about a pin  546  and pivot point  544  until locking portion  540  contacts an inside surface of card rack  500 . The latch  530  is secured by applying downward pressure, e.g. through an operator&#39;s finger, in direction  550  to actuator  536  which allows hooked portion  542  to be raised above pin  548 . While retaining downward pressure in direction  550 , additional pressure is placed on the actuator  536  in direction  552  until hooked portion  542  passes over pin  548 . The pressure on actuator  536  is then released, e.g. by the operator removing the finger, allowing hooked portion  542  to be lowered and engage pin  548 . To release the latch  530 , downward pressure is again applied to actuator  536  which raises hooked portion  542  and allows the latch  530  to become disengaged from pin  548  and rotate freely in the reverse of direction  552 . 
     Latches  530  of the type shown in FIG. 10 are susceptible to inadvertent or accidental removal of the rigid plate  522 . A single motion on the actuator  536  may cause the latch  530  to become disengaged and allow the circuit pack  516  to be removed. In addition, if an actuator  530  becomes weakened or loose (e.g. from use, environmental conditions, etc.) the latch  530  may become disengaged. Such a result is not only undesirable, but may result in large-scale system failure if an essential circuit pack  516  is inadvertently removed. 
     Thus, there exists a need for a securing mechanism for a circuit board which prevents accidental or inadvertent removal of the board once it is inserted and connected into a card rack. 
     SUMMARY OF THE INVENTION 
     The present invention provides a latch that is able to secure a printed circuit board or circuit pack to a card rack while preventing its accidental or undesired removal. In a preferred embodiment, the latch includes at least two actuators flexibly mounted to a body. Each actuator has a hooked portion for securing the actuator from movement and a lever portion to release the hooked portion. The body is pivotably mounted to a circuit board or circuit pack. When fully latched, the object is secured to a card rack by the hooked portion. The hooked portion is capable of being moved when the body is rotated about the pivot point. Rotation occurs when the actuators are released through use of the lever portions. To prevent unintended removal of a circuit board or circuit pack secured by the latch, the second actuator may not be released until the first actuator has been released. The latch thus requires at least two actions, pressing the lever portions in succession, to release the circuit board or circuit pack from a card rack. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other advantages and features of the invention will become more apparent from the detailed description of preferred embodiments of the invention given below with reference to the accompanying drawings in which: 
     FIG. 1 is a side view of a circuit pack employing a latch of the present invention; 
     FIG. 2 is a perspective view of a latch of the present invention; 
     FIG. 3 is a side view of the latch of FIG. 2; 
     FIGS. 4-6 are diagrams of the latch of FIG. 2 in use; 
     FIG. 7 is a partially broken away end view of the faceplate of the circuit pack of FIG. 1; 
     FIG. 8 is a perspective view of a known card rack and printed circuit board; 
     FIG. 9 is a side view of the circuit pack of FIG. 8; and 
     FIG. 10 is a side view of a known latch. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, where like reference numerals designate like elements, there is shown in FIG. 1 a circuit card or pack  50  having latches constructed according to the invention. Circuit pack  50  may have electronic circuitry  56  mounted thereon. The pack  50  may be plugged into a connector on a card rack  68 . The circuit pack  50  includes a thin rigid plate  52  which has a flat surface  54  with electronic circuitry  56  mounted thereon. Conductor lines  58  connect the circuitry  56  to an electrical connector  60  disposed on at least one of the end surfaces  62 ,  64  of the rigid plate  52 . Mounted on the end surface  64  of the circuit pack  50  is a faceplate  66 . Near the top and bottom corners of the faceplate  66  and rigid plate  52  are latching levers  100  which are used to aid in the insertion and removal of the circuit pack  50 . In addition, latches  100  engage card rack  68  to secure the circuit pack  50  from movement. 
     Referring now to FIGS. 2 and 3, each latch  100  has a body portion  106  and an actuator assembly  101 . Latch  100  is preferably formed of molded polypropylene or nylon, but may be constructed of other suitable materials or combinations of materials. The body portion  106  includes a solid body having side surfaces  128 , a bottom surface  131 , a top surface  132 , a concave finger rest  133 , and a hooked portion  130 . Hooked portion  130  is a portion of the body portion  106  which forms an indentation between top surface  132  and bottom surface  131 . When the latch  100  is in a latched position, the hooked portion  130  engages card rack  68  to prevent removal of the circuit pack  50 . The body portion  106  also includes a cylindrical aperture  134  for receiving a cylindrical pin or rod (not shown). The latch  100  may be rotatably mounted on the pin or rod. The pin or rod may be integrally connected to the main portion of the circuit pack  50 . 
     The actuator assembly  101  extends from the body portion  106  in a direction  103  which is generally perpendicular to top surface  132  and parallel to side surfaces  128 . The actuator assembly  101  may have at least two actuators  102 ,  104  connected to a support portion  108 . The support portion  108  is connected to the body portion  106 . The support portion  108  may be generally perpendicular to top surface  132 . In addition, to further prevent movement, the support portion  108  and body portion  106  are, preferably, further attached to one another through a brace portion  110 . Actuators  102 ,  104  each include respective activation portions  112 ,  114 , retainers  116 ,  118 , connector portions  120 ,  122 , and flex portions  124 ,  126 . Flex portion  124  extends approximately perpendicularly from support portion  108  in direction  105 . 
     Connector portions  120 ,  122  extend from respective flex portions  124 ,  126  in a direction opposite direction  102 . The direction  102  is generally perpendicular to the flex portions  124 ,  126  and toward body portion  106 . Activation portions  112 ,  114  extend generally in direction  105  from the ends of respective connector portions  120 ,  122  which are opposite the flex portions  124 ,  126 . Activation portion  112  is preferably longer than activation portion  114  in direction  105 . The ends of the activation portions  112 ,  114  opposite connector portions  120 ,  122  are located in a common plane parallel to direction  103 . The illustrated arrangement allows a user unobscured access to either activation portion  112 ,  114 . 
     The retainers  116 ,  118  extend in direction  105  from respective connector portions  120 ,  122  and are thus generally parallel to flex portions  124 ,  126 . The retainers  116 ,  118  are located between the flex portions  124 ,  126  and activation portions  112 ,  114 . Connector portion  120  preferably has a width greater than that of connector portion  122 . Retainer  116  preferably has a width less than that of connector portion  120 . Retainer  118  preferably has a width approximately equal to connector portion  122 . The combined width of the retainers  116 ,  118  equals the width of the connector portion  120 . Connector portion  122  is displaced in direction  107  such that retainer  116  is not obscured by connector portion  122  when viewed in the direction  105 . 
     Each retainer  116 ,  118  includes respective sloping surfaces  135 ,  137 , horizontal upper surfaces  136 ,  138  and locking surfaces  140 ,  142 . Upper surfaces  136 ,  138  are substantially parallel to connector portions  120 ,  122 . The sloping surfaces  135 ,  137  are opposite locking surfaces  140 ,  142  and face the activation portions  112 ,  114 . Retainer  118  is preferably laterally displaced from retainer  116  in direction  103 . Locking surface  142 , while having a similar width, is also preferably longer in direction  105  than locking surface  140 . This prevents inadvertent release of locking surface  142  when activation portion  112  is pushed toward support  108 . 
     FIGS. 4 to  6  illustrate the latch  100  in operation. Card rack  68  is capable of holding at least one circuit pack  50  in a secured fashion by the engagement of latch hooked portion  130  with a portion of card rack  68 . FIG. 4 shows a circuit pack  50  prior to its being locked in place within a card rack  68 . Latch  100  is secured to circuit pack  50  prior to insertion into card rack  68  through cylindrical aperture  134  which engages pin  144 . While shown with one latch  100 , it may be preferable to have two latches  100  mounted on a selected or critical circuit pack  50  to further ensure that unintended removal of the circuit pack  50  will not occur. Latch  100  is free to rotate about cylindrical aperture  134  along path  149 . 
     To insert the circuit pack  50  into the card rack  68 , a force is applied against finger rest  133  (or on the faceplate  66 ) in direction  103 . The circuit pack  50  is pushed in as far as possible to engage connectors  60  with connectors in card rack  68  as shown in FIG.  1 . Returning to FIG. 4, as the circuit pack  50  is inserted into the card rack  68 , the hooked portion  130  engages the end portion  152  causing the latch  100  to rotate clockwise about the pin  144  toward a closed position. 
     In the locked position, end portion  152  of card rack  68  is within the space defined by hooked portion  130 , effectively securing the circuit pack  50  from being withdrawn in direction  151 . This is effective, however, only so long as the latch  100  is restricted from pivoting about cylindrical aperture  134 . To prevent the latch  100  from rotating, the latch  100  is secured to the faceplate  66 . Retainers  116 ,  118  are secured within faceplate  66  by contact with edges  146 ,  148 , respectively. The faceplate  66  may be constructed such that edges  146 ,  148  are perpendicular to direction  105 , as shown in FIG.  7 . Edges  146 ,  148  are sized to accommodate retainers  116 ,  118  and are separated by a distance  147  which is approximately equal to the distance between locking surfaces  140 ,  142  along direction  103 , as shown in FIGS. 4 and 7. 
     As pressure is applied to finger rest  133  in direction  103 , the base of sloping surface  137  engages edge  148  on faceplate  66 , as shown in FIG.  4 . The resultant camming action causes the actuator  104  to flex toward support piece  108  until edge  148  passes over upper surface  138  and engages locking surface  142  as shown in FIG.  5 . Actuator  104  reflexively returns to its initial position through the resilience of flex portion  126 . Thus, latch  100  is prevented from further rotation about cylindrical aperture  134 . The engagement of locking surface  142  with cutout portion  148  prevents clockwise motion along path  149 . The engagement of hooked portion  130  with card rack  68  prevents counterclockwise motion along path  149 . 
     While engagement of locking surface  142  prevents the latch  100  from rotation about cylindrical aperture  134 , further engagement of actuator  102  with edge  146  will effectively prevent inadvertent or accidental removal of circuit pack  50 . Actuator  102  is engaged in a similar manner to that described above with reference to actuator  104 . Pressure continues to be applied to finger rest  133  in direction  103  which causes the base of sloped surface  135  to engage edge  146 . Further pressure forces the actuator  102  to flex toward support piece  108  until edge  146  passes over upper surface  136  and engages locking surface  140 . Actuator  102  then reflexively returns to its initial position through the resilience of flex portion  124 . Now both actuators  102 ,  104  independently secure the latch  100  to faceplate  66 , as shown in FIG.  6 . 
     To disengage latch  100  and allow release of the circuit pack  50  from card rack  68 , both actuators  102 ,  104  must be released. A user places pressure on activation portion  112  in direction  150  such that actuator  102  flexes toward support member  108 . Pressure on activation portion  112  in direction  150  allows latch  100  to rotate counterclockwise along path  149 . This action causes edge  146  to pass over upper portion  136  and release retainer  116  from engagement with face plate  66 . However, latch  100  will still be prevented from releasing the circuit pack  50  due to the engagement of locking surface  142  with edge  148 . 
     To fully release the latch  100 , the user next places pressure on activation portion  114  in direction  150 , as shown in FIG. 5, such that actuator  104  flexes toward support member  108  until edge  148  is released from engagement with locking portion  142 . The user then continues to rotate the latch  100  counterclockwise along path  149  such that cutout portion  148  passes over upper portion  138 . This releases retainer  118  and allows latch  100  to fully pivot about pin  144  until end portion  152  is no longer secured by hooked portion  130 . By requiring two separate actuators  102 ,  104  to be individually and sequentially actuated to release circuit pack  50 , a secure, cost efficient, and effective mechanism for reliably holding the circuit pack  50  in the card rack  68  is achieved. In addition, by having two actuators  102 ,  104  which are integral to the latch  100 , no additional or extra part is necessary to provide the security of the double actuator latch of the invention. 
     Although the invention has been described with reference to circuit packs, it is to be understood that the invention also may be used on trunk cards, interface cards, or other devices. 
     The above description and drawings illustrate preferred embodiments which achieve the objects, features and advantages of the present invention. It is not intended that the present invention be limited to the illustrated embodiments, however. Any modification of the present invention which comes within the spirit and scope of the following claims should be considered part of the present invention.