BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The present invention generally relates to connectors and, more particularly, to zero-insertion-force connectors for mounting computer chips on circuit boards. 
   2. Description of the Prior Art 
   Zero-Insertion-Force (ZIF) connectors are commonly used in installing a central processing unit (CPU) on a circuit board. As the computing power of the CPUs is continuously enhanced, the pins of the CPUs are also significantly increased in numbers. The increased number of CPU pins requires the exertion of additional force so as to mount the CPU in a ZIP connector. Additionally, as customers continuously demand the electronic device to be even smaller, the ZIP connector has to be reduced in size as well. Together these present the following challenges to the conventional ZIP connectors. 
   As shown in  FIG. 14 , a ZIP connector for use in a notebook computer has a cam  70  configured at a side of the ZIF connector. When the cam  70  is rotated by a screw driver, the cover plate  71 , with the CPU  60  on top of the cover plate  71 , would horizontally slide relative to the body  72  of the ZIP connector, so that the pins of the CPU  60  could establish electrical contacts to the pin holes of the body  72 . A user has to exert additional force to overcome the larger resistance resulted from the increased number of CPU pins. If too much force is exerted, a phenomenon shown in  FIG. 13  would occur. As illustrated, if the cam  70  is not reliably positioned, the excessive force would cause a biased torque to the cam  70 , displacing the axis of the cam  70  and resulting gaps S 1  and S 2  between the cam  70  and the body  72 , and between the cam  70  and the cover plate  71 , respectively. In the mean time, the body  72  and the cover plate  71  would suffer deformation, and the electrical contacts between the CPU pins and the pin holes would also be affected, or even disrupted. 
   In other words, if the cover plate  71  and the body  72  are made of plastic while the cam  70  is made of a metallic material, excessive force applied to the cam  70  when the cover plate  71  has already reached its terminal location would easily deform the cover plate  71  and/or the body  72 . At least, the axial hole for the cam  70  would be widened or damaged. 
   SUMMARY OF THE INVENTION 
   The primary purpose of the present invention is to obviate the foregoing problems; a ZIF connector structure is disclosed herein. One of the major characteristics of the present invention is having a reinforcing plate configured inside the body of the ZIF connector. The reinforcing plate has a through hole allowing the cam of the ZIF connector to pass through. The through hole has a ring flange to confine the cam so that the cam wouldn&#39;t deviate under excessive force. The reinforcing plate is also configured with bended legs for embedding into the body of the ZIF connector so as to avoid the deformation of the cover plate of the ZIF connector. 
   Another characteristic of the present invention is having a positioning plate configured with a through hole for the insertion of the cam. The positioning plate has a number of wedges configured so that, when the cam is rotated in either direction, the cam would be stopped by one of the wedges. As such, the cam has a very clear range of rotation to avoid the exertion of excessive force. 
   The foregoing object and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts. 
   Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the various parts of the ZIF connector according to the present invention. 
       FIG. 2  is a perspective view showing the body according to the present invention. 
       FIG. 3  is a perspective view showing the reinforcing plate according to the present invention. 
       FIG. 4  is a section view showing the inner structure of the present invention along the b—b line of  FIG. 2 . 
       FIG. 5  is a section view showing the inner structure of the present invention along the c—c line of  FIG. 2 . 
       FIG. 6  is a perspective view showing the cover plate and the body according to the present invention. 
       FIG. 7  is a section view showing the inner structure of the present invention along the x—x line of  FIG. 2 . 
       FIG. 8  is a section view showing the inner structure of the present invention along the a—a line of  FIG. 2 . 
       FIG. 9  is a top view showing the cam according to the present invention is rotated in one direction. 
       FIG. 10  is a top view showing the cam according to the present invention is rotated in the other direction. 
       FIG. 11  shows another embodiment of the positioning plate according to the present invention. 
       FIG. 12  shows yet another embodiment of the positioning plate according to the present invention. 
       FIG. 13  is a sectional view showing the deformation of a conventional ZIF connector when the cam is rotated with excessive force. 
       FIG. 14  is a sectional view showing a conventional ZIF connector before the cam is rotated. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following descriptions are of exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims. 
   Please refer to  FIGS. 1 and 6 . The present invention has a rectangular body  10  with a large number of pin holes  11  for the insertion of a chip&#39;s pins. Along two opposing sides of the body  10 , there are a number of hooks  15  and, along one of the other two sides, there is a platform  13  extended outward to have a sunken tray  14  with a through hole  12  in the center. The platform  13  has at least a ladder-like through passage  141  penetrating through the body  10  along the side of the sunken tray  14  closer to the body  10 . The platform  13  has two elongated notches  16  along two opposing sides of the tray  14  respectively, parallel to the two sides of the body  10  having the hooks  15 . 
   A cover plate  20  corresponding to the body  10  has pin holes  21 , a platform  22 , and clasps  26  at matching locations to the pin holes  11 , platform  13 , and hooks  15  of the body  10 , respectively. The claps  26  and the hooks  15  join the cover plate  20  and the body  10  tightly together. The platform  22  also has a rectangular through hole  24  in the center and two protruding blocks  25  corresponding to the notches  16 . The length of the protruding blocks  25  is smaller than that of the notches  16  so that the blocks  25 , as shown in  FIGS. 7 and 8 , could be fit inside the notches  16  and, when the cover plate  20  slides relatively to the body  10 , the cover plate  20  could move reliably along the direction P 1  as shown  FIG. 2  without deviation. Please refer to  FIG. 1  again. The platform  22  has protruding cylindrical positioning columns  23  with stoppers  231  along a portion of their circumferences so that a positioning plate  40  could be fixed on the platform  22  with correct orientation. 
   The positioning plate  40  is made of a material stronger than plastic such as a metallic material. Besides a center through hole  41 , as shown in  FIGS. 1 and 2 , the positioning plate  40  has two concaves  43  for the accommodation of the positioning columns  23  so that the center through hole  41  is aligned with the through hole  24 . The positioning plate  40  also has two wedges  42  configured along two opposing sides of the through hole  41  adjacent to the concaves  43 . 
     FIG. 11  shows another embodiment of the positioning plate. As illustrated, the positioning plate  80  has through holes  83  for the penetration of the protruding columns  23 .  FIG. 12  shows yet another embodiment of the positioning plate in which bolts  70 , instead of protruding columns  23 , are used to fasten the positioning plate  80  to the top cover  20  through the through holes  83 . 
   Please refer to  FIGS. 1 ,  3 , and  4 . The reinforcing plate  50  is best made of a metallic material. The reinforcing plate  50  has a through hole  51  at an appropriate location with a ring flange  52  protruding from at least one of the reinforcing plate  50 &#39;s two flat surfaces. As such, the depth of the through hole  51  is the sum of the thickness of the reinforcing plate  50  and the height of the ring flange  52 . At a side of the reinforcing plate  50 , there are legs  53  and  54 , both with ladder-like bended sections  55  and  56  at the ends respectively. There are also extended sections  57  and  58  on the other sides of the reinforcing plate  50  so that the reinforcing plate  50  could be fitted reliably into the sunken try  14  of the body  10 . 
   Please see  FIGS. 1 and 4 . When the reinforcing plate  50  is fitted inside the sunken tray  14 , the bended section  55  and  56  of the two legs  53  and  54  are inserted into the ladder-like through passages  141 . 
   Please see  FIGS. 1 ,  2 , and  5 . A cam  30  contains a circular upper section  31 , an eccentric middle section  32 , and an axial bottom section  33 . On top of the upper section  31 , there is a diametric groove  34  containing a linear segment  341  and a hexagonal center  342 . In an alternative embodiment, two linear segments are configured to form an X shape with a hexagonal center. The circumference of the upper section  31  has an extended section  35  and thereby forms a stopper  36 . 
   Please see  FIGS. 1 ,  2 , and  7 . The cam  31  has its middle and bottom sections  32  and  33  inserted into the through holes  41 ,  24 ,  51 , and  12 , and fixed by rivet, C-shaped ring, or E-shaped ring. The upper section  31  rests upon the positioning plate  40 . As shown in  FIGS. 1 and 9 , when the cam  31  is rotated in one direction, one of the wedges  42  would collide with the stopper  36  of the extended section  35  and the cam  31  could not be rotated further. When this happens, the eccentric middle section  32  would have forced the cover plate  20  to slide to one of its terminal locations. On the other hand, as shown in  FIG. 10 , when the cam  31  is rotated in the other direction, the stopper  36  of the extended section  35  would be stopped by the other wedges  42  and the eccentric middle section  32  would have forced the cover plate  20  to slide to the other terminal location. As such, the cam  31  has a clear range of rotation to avoid the application of excessive force. 
   Please refer to  FIGS. 1 ,  4 , and  5 . As the cam  31  is inserted through the through hole  51  of the reinforcing plate  50 , the bottom section  33  of the cam  31  is confined by the ring flange  52  so that the cam  31  couldn&#39;t be displaced easily, enhancing the cam  31  to be more resilient to the external torque. In addition, by fitting the bended sections  55  and  56  inside the ladder-like passages  141 , the reinforcing plate  50  more reliably clings to the body  10  which has a better rigidity. The cam  31  is therefore provided with a better support, which in turn prevents the cover plate  20  from deformation and tilting. 
   The advantages of the present invention could be summarized as follows. First of all, the ring flange of the reinforcing plate equivalently extends the thickness of the reinforcing plate so that the cam is reliable confined in its position. This not only prevents the cam from deviation, but also indirectly prevents the cover plate from deformation and tilting. 
   Secondly, by embedding the bended legs of the reinforcing plate into the body, the stability of the reinforcing plate is significantly enhanced, which in turn provides a reliable support to the cam. As such, when the cam is rotated, the deformation and tilting of the cover plate is prevented. 
   Thirdly, the positioning plate is directly configured on top of the body, which could be easily accessed and maintained. The protruding wedges provide effective confinement to the cam&#39;s rotational range. 
   Additionally, the protruding blocks of the cover plate and the notches of the body allow the cover plate to slide more reliably and accurately. 
   It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
   While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.
A zero-insertion-force connector structure is provided herein. The major characteristic of the invention is to have a reinforcing plate configured inside the body of the connector so as to, along with the related cam, positioning plate, etc., avoid the deformation of the connector under excessive force and provide more sensible operation.