Patent Publication Number: US-6210199-B1

Title: Locking mechanism for a cam lever used in a pin grid array socket

Description:
BACKGROUND OF THE INVENTION 
     1. Field of The Invention 
     The present invention relates to a locking mechanism for a cam lever used in a pin grid array socket, especially a locking mechanism for retaining the cam lever in a tightened status and preventing the latter from leaving the status due to tension existed in the contacts of the pin grid array socket. 
     2. The Prior Art 
     Conventional pin grid array sockets normally comprise a cover defining a plurality of upper passageways therein and slidably engaging with a base which defines a corresponding number of lower passageways retaining contact therein. The upper passageways and the lower passageways are in constant communication with each other. A cam is received in a space defined between the cover and the base and operative to move the cover along the base thereby positioning the socket at either a loosened status ready for insertion of pins of the CPU or a tightened status forcing the pins of the CPU to abut against the corresponding contacts. When the socket is in the loosened status, the pins of the CPU are inserted into the upper passageways and the lower passageways with a substantially zero insertion force (ZIF), but are not in electrical contact with the contacts retained in the lower passageways. The cam is then operated to drive the cover to move laterally along the base thereby urging the pins of the CPU module to electrically connect with the contact of the base. The CPU module is moved by the cover of the socket when the socket is changed from the loosened status to the tightened status. 
     The CPU module is commonly engaged with a heat sink for heat dissipation. However, due to the high density of modularization, the CPU module is heavy and has a large dimension. Thus, the addition of the heat sink causes the assembly of the CPU module and the heat sink to be larger and heavier which in turn causes difficulty for the cam to drive the cover on which the CPU module and the heat sink are seated. 
     To solve the problem, U.S. Pat. No. 6,017,234, which is enclosed herein for reference and which are invented by the same inventors of the present application, discloses a two-layer ZIF PGA socket comprising a mother housing having a first recess and a hole defined in an edge of the first recess, a beam exposing to the hole and the first recess and a pivot extending from the beam. Two daughter housings are slidably received in the first recess of the mother housing and each daughter housing comprises a C-shaped head portion extending out the mother housing and defining a second recess for loosely receiving the beam of the mother housing. The C-shaped head portions of the daughter housings are matingly configured to define a first reception space therebetween and together are movable along a same direction. A cam lever comprises a cam and a handle bar connected to the cam. The cam is rotatably received in the first reception space between the daughter housings and defines a hole for rotatably receiving the pivot of the mother housing. A first block and a second block extend from the cam and both are spaced away by the hole of the cam and the beam of the mother housing for respectively driving the configured daughter housings to move in opposite directions when the handle bar is manually operated in different directions. 
     Although U.S. Pat. No. 6,017,234 can solve the problems encountered in the prior art, it has a minor problem to be solved, that is the retention of the cam lever in the tightened status may not strong enough to retain its status because the tension of the contacts may force the daughter housings to move backward and leave its tightened status. 
     It is requisite to provide a locking mechanism configured with the cam lever for retaining the cam lever in the tightened status and preventing the latter from leaving this status due to tension existed in the contacts of the pin grid array socket. 
     SUMMARY OF THE INVENTION 
     The primary purpose of the present invention is to provide a locking mechanism configured with a cam lever which is used to drive a ZIF pin grid array socket between a loosened status and a tightened status. 
     Another purpose of the present invention is to provide a socket having a locking mechanism for locking the socket in a specific status. 
     In accordance with one aspect of the present invention, a locking mechanism is provided in a socket which comprises a movably housing and a stationary housing. The locking mechanism comprises a cam lever having a handle bar connected to a cam which is pivotally connected to the stationary housing and operative to drive the movable housing to move in opposite directions. An elongated channel is defined along the handle bar. A first reception member is formed in the movable housing. A latch is movably and rotatably received in the elongated channel. A head of the latch is movably engaged with the first reception member for locking the cam lever and preventing the movable housing from movement. 
     In accordance with another aspect of the present invention, a socket comprises a daughter housing unit movably received in a mother housing, a cam lever having a handle bar connected to a cam which is pivotally connected to the mother housing and operative to drive the daughter housing unit to move in opposite directions. An elongated channel is defined along the handle bar. A first reception member is formed in the daughter housing unit. A latch is movably and rotatably received in the elongated channel. The latch is movably engaged with the first reception member for locking the cam lever and preventing the daughter housing unit from movement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a ZIF pin grid array socket in accordance with the present invention; 
     FIG. 2 is a perspective view of a daughter housing of FIG. 1 for particularly illustrating a reception groove thereof; 
     FIG. 3 is an assembly view of the cam lever and the locking member of FIG. 1; 
     FIG. 4 is an assembly view of FIG. 1; 
     FIG. 5 is a perspective view showing that the pin grid array socket is locked in a loosened status; and 
     FIG. 6 is a perspective view showing that the pin grid array socket is locked in a tightened status. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a ZIF PGA socket in accordance with the present invention comprises a mother housing  1  defining a plurality of first passageways  100  for receiving pins of a CPU module (not shown), a first and a second daughter housings  21 ,  22  slidably received in the mother housing  1  and each defining a plurality of second passageways  200  each of which aligns with the corresponding first passageway  100  and receives a contact  7  therein. The mother housing  1  has a pivot  15  formed near one edge thereof and a semicircular slot  12  defined near the edge proximate to the pivot  15 . The first and second housings  21 ,  22  each have two engagement tabs  211 ,  221  extending from two parallel sides thereof, a head  212 ,  222  extending from a corner thereof. 
     The assembling between the mother housing  1  and the daughter housings  21 ,  22  and the function thereof have been detailed in U.S. Pat. No. 6,017,234 which is enclosed herein. Differently, a flange  216  extends from the head  212  of the first daughter housing  21  and defines a first reception groove  2160  at a bottom surface thereof. Also referring to FIG. 2, a second reception groove  2220  is defined at a bottom surface of the head  222  of the second daughter housing  22  and spaced away from the first reception groove  2160  with a predetermined distance. Both the first reception groove  2160  and the second reception groove  2220  are converged from an outer portion thereof to an inner portion thereof. 
     A cam lever  3  similar to that disclosed in U.S. Pat. No. 6,017,234 comprises a handle bar  31  connected to a cam  32  which defines a hole  320  adapted to rotatably receive the pivot  15  of the mother housing  1  and comprises a first block  321  and a second block  322  spaced by the hole  320  for respectively driving the daughter housings  21 ,  22  to move in opposite directions when the cam lever  3  is pivotally rotated in opposite directions with respect to the pivot  15 . Two protrusions  33  extend from one end of the handle bar  31  for facilitating manual operation. Different to that disclosed in U.S. patent application Ser. No. 09/256,639, a positioning cutout  330  is defined in one of the protrusions  33 . An elongated channel  310  is defined along the handle bar  31  and a portion of the elongated channel  310  is located between the two protrusions  33 . Two covers  311  are formed on the handle bar  31  and passed by the elongated channel  310 . An L-shaped latch  35  includes an elongated section  351  having a head  353  and a lateral section  352  bent from the elongated section  351 . The elongated section  351  of the L-shaped latch  35  is movably and rotatably received in the elongated channel  310  as shown in FIG.  3 . 
     A stud  4  identical to that disclosed in U.S. Pat. No. 6,017,234 has a circular cap portion  41  having a diameter greater than the diameter of the hole  320  of the cam  32  and a threaded rod portion  42  extending from a center of the circular cap portion  41  and threaded into the pivot  15  of the mother housing  1  for pivotably fixing the cam  32  to the pivot  15 . 
     The ZIF PGA socket may be assembled as shown in FIG. 4, where the L-shaped latch  35  is movably retained in the elongated channel  310  and the lateral section  352  thereof extends beyond the protrusions  33  of the cam lever  3  for at least a distance to ensure that the head  353  of the L-shaped latch  35  not be blocked by the flange  216  when the cam lever  3  is pivotally moved with respect to the pivot  15 . The covers  311  may be used to further limit the elongated section  351  of the L-shaped latch  35  in the elongated channel  310 . 
     Normally, the socket is operative to be in a loosened status ready for receiving CPU pins with zero insertion force. In the loosened status, the head  353  of the L-shaped latch  35  is retained in the first reception groove  2160  of the flange  216 , the lateral section  352  is located adjacent to the protrusions  33  of the cam lever  3 , and the cam lever  3  is locked in a first orientation with respect to the pivot  15  of the mother housing  1 , as shown in FIG.  5 . After CPU pins are inserted into the socket, the socket may be further operated to change from the loosened status to a tightened status by pulling the L-shaped latch  35  to release it from the retention of the first reception groove  2160 , pivotally moving the cam lever  3  to a rightmost position, pushing the head  353  of the L-shaped latch  35  into the second reception groove  2220 , and rotate the lateral section  352  of the L-shaped latch  35  to retain it in the positioning cutout  330  as shown in FIG.  6 . The cam lever  3  is locked in a second orientation with respect to the pivot  15  of the mother housing  1  during the tightened status. The lateral section  352  of the L-shaped latch  35  facilitates a user to rotate and move the L-shaped latch  35  in the elongated channel  310  for locking/releasing the latch  35  on/from the daughter housings  21 ,  22 . 
     In conclusion, the L-shaped latch  35 , the cam lever  3 , and the reception grooves  2160 ,  2220  constitute a locking mechanism preventing the socket from leaving its loosened or tightened status. 
     While the present invention has been described with reference to a specific embodiment, the description is illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications to the present invention can be made to the preferred embodiment by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.