Patent Publication Number: US-6210232-B1

Title: Electrical connector with polyswitch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector, and particularly to an electrical connector with a polyswitch retained therein for preventing excessive current from damaging the connector. 
     2. Description of Prior Art 
     A resettable device is commonly used to protect against a current exceeding a rated operational value anticipated by an electronic device such as a monitor, a keyboard and a stand-alone hub. The resettable device may take various forms such as a fuse, a bimetal, a ceramic PTC device or a polymeric PTC device which can be a polyswitch. To prevent excessive current from damaging or destroying an electronic system such as a computer, the resettable device is conventionally mounted on a mother board and occupies a significant amount of space thereon. Since the efficient use of space on the mother board is extremely important due to the trend of miniaturization, removing the resettable device from the mother board to reduce the occupied space thereon is requisite. 
     Therefore, a long and unfilled need exists in the prior art for removing the resettable device from the mother board in promotion of miniaturization. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide an electrical connector with a polyswitch retained therein for reducing occupied space on a mother board and for preventing excessive current from damaging an electronic system thereby ensuring reliable signal transmission. 
     Another object of the present invention is to provide a method for simply and securely retaining a polyswitch in an electrical connector by means of a pair of contact members. 
     In order to achieve the objects set forth, an electrical connector in accordance with a preferred embodiment of the present invention comprises an insulative body defining a plurality of contact-receiving passageways therein, a shield enclosing the insulative body, a plurality of contacts received in the corresponding passageways of the insulative body, and a polyswitch retained in the insulative body. The plurality of contacts comprises a contact consisting of first and second contact members. The first contact member is adapted for mating with a corresponding mating contact of a complementary connector, and the second contact member is adapted for being soldered to a circuit board. 
     The polyswitch sandwiched between the first and second contact members is made from a polymer composition containing polymer materials of high molecular weight. Under normal temperature conditions, the polyswitch acts as a conductor, whereas under high temperature conditions, the polyswitch acts as an insulator. Accordingly, when a current passing through the first contact member due to connection with the mating contact is within the rated operational current of an electronic system, the polyswitch acts as a conductor to allow the current to pass through the second contact member to form a closed circuit. When the current passing through the first contact member exceeds the rated operational current, the polyswitch acts as an insulator and creates an open circuit thereby preventing damage to the electronic system. 
     A transverse T-shaped cavity is formed in the insulative body for retaining the first and second contact members and the polyswitch. The polyswitch is sandwiched between the first and second contact members thereby being securely retained in the insulative body instead of being mounted on a mother board and occupying a significant amount of space thereon. 
     Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of an electrical connector and a polyswitch in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is an assembled view of FIG. 1; and 
     FIGS. 3 and 4 are schematic views illustrating how the polyswitch is assembled to the connector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to a preferred embodiment of the present invention in conjunction with the drawings. Referring first to FIG. 1, an electrical connector  1  comprises an insulative body  2 , a shield  3 , a plurality of contacts  4 ,  5 , and a polyswitch  6 . The insulative body  2  comprises a main body  20  defining a mating surface  200  and an opposite assembly surface  201 . A mating portion  21  projects from the mating surface  200  for mating with a complementary electrical connector (not shown). A plurality of recesses (not shown) corresponding to the number of the contacts  4 ,  5  is formed in a bottom surface  210  of the mating portion  21 . The recesses are in communication with corresponding openings  211 ,  211   a  defined through the main body  20  and corresponding through holes  213  formed in a top surface  212  of the mating portion  21 . The openings  211 ,  211   a , the recesses and the through holes  213  together define a plurality of contact-receiving passageways (not labeled) for receiving the contacts  4 ,  5 . A plurality of protrusions  22  is formed on the assembly surface  201  adjacent to a bottom edge of the main body  20 . A groove  220  is defined between each pair of adjacent protrusions  22 . A transverse T-shaped receiving cavity  23  is defined in the main body  20  in communication with the opening  211   a  with the adjacent protrusion  22  partially cut away. An L-shaped slot  24  is disposed in the partially cut protrusion  22  in communication with the adjacent groove  220  and the receiving cavity  23 . Extending from opposite side surfaces  202  of the main body  20  is a pair of bosses  25 . 
     The shield  3  is adapted for enclosing the insulative body  2  and shielding the contacts  4 ,  5  received in the body  2  from EMI (electromagnetic interference). The shield  3  comprises an upper shielding plate  30 , a lower shielding plate  31  and a pair of opposite side shielding plates  32 . Resilient tangs  33  are stamped from the shieldingplates  30 ,  31 ,  32  forengagingwiththecomplementaryconnector. A hole  34  is disposed in each side shielding plate  32  adjacent to the corresponding tang  33  for engaging with the corresponding boss  25  of the insulative body  2  thereby securely enclosing the insulative body  2 . A pair of legs  35  downwardly extends from bottom edges of the side shielding plates  32  below the corresponding holes  34  for insertion into corresponding holes in a printed circuit board (not shown) thereby mounting the connector  1  thereon. 
     Each contact  4  includes a curved contact section  40  for mating with a corresponding mating contact of the complementary connector, a retention section  41  for interferentially engaging with the corresponding openings  211  of the insulative body  2 , a supporting section  42  approximately perpendicularly extending from the retention section  41 , and a horizontal solder section  43  for being soldered to solder pads on the printed circuit board. 
     The contact  5  consists of a first contact member  50  and a second contact member  55 . The first contact member  50  comprises a first retention section  51  for interferentially engaging with the opening  211   a  of the insulative body  2 , a curved first contact section  52  forwardly extending from the first retention section  51  for mating with the corresponding mating contact of the complementary connector, a first abutment section  53  perpendicularly extending from the retention section  51 , and a tongue section  54  perpendicularly extending from the abutment section  53 . The second contact member  55  comprises a second retention section  56 , a second abutment section  57  upwardly extending from the second retention section  56  with a projection  570  formed thereon, a second supporting section  58  downwardly extending from the retention section  56 , and a horizontal second solder section  59  for being soldered to the circuit board. 
     The polyswitch  6  having a rectangular shape is received in the cavity  23  of the insulative body  2  and is sandwiched between the first and second contact members  50 ,  55 . The polyswitch  6  is provided for preventing excessive current from passing through the connector  1  which may damage or destroy an electronic system due to overheating. To complement such a function, the polyswitch  6  is made from a conductive polymer composition containing polymer materials of high molecular weight. Under normal temperature conditions, the polyswitch  6  acts as a conductor, while under high temperature conditions the polyswitch  6  acts as an insulator. The critical temperature of the polyswitch  6  is adjustable by changing the composition thereof. 
     Also referring to FIG. 2, in assembly, each contact  4  is first received in the insulative body  2  with the contact section  40  thereof extending through the corresponding opening  211  of the main body  20  into the through hole  213  of the mating portion  21 . The retention section  41  of each contact  4  interferentially engages with the corresponding opening  211  of the main body  20 . The supporting section  42  of each contact  4  is retained in the corresponding groove  220 . Thus, the contacts  4  are securely retained in the insulative body  2 . The shield  3  is then assembled to the insulative body  2  in a direction facing the mating portion  21  by engagement between the bosses  25  of the insulative body  2  and the corresponding holes  34  of the shield  3 . 
     Referring to FIGS. 3 and 4 in conjunction with FIG. 1, when assembling the polyswitch  6  to the insulative body  2 , the first contact member  50  is received in the opening  211   a  of the insulative body  2  with the first contact section  52  thereof entering into the corresponding through hole  213  for mating with the corresponding mating contact of the complementary connector. The first retention section  51  interferentially engages with the opening  211   a  whereby the first abutment section  53  abuts against an inner side surface  230  of the cavity  23  and the tongue section  54  abuts against an inner upper surface  231  of the cavity  23 . Thus, the first contact member  50  is securely retained in the insulative body  2 . The second contact member  55  is then assembled to the insulative body  2  by inserting the second retention section  56  thereof into the slot  24  whereby the second abutment section  57  abuts against an inner side surface (not labeled) of the cavity  23  and the second supporting section  58  is retained in the corresponding groove  220 . The second solder section  59  is soldered to the corresponding solder pad on the printed circuit board. The polyswitch  6  is fully inserted into the cavity  23  whereby the tongue section  54  of the first contact member  50  abuts against a side surface thereof and the second abutment section  57  of the second contact member  55  abuts against an opposite side surface thereof. A rearward movement of the polyswitch  6  is prevented by the projection  570  of the second contact member  55 . Thus, the polyswitch  6  is securely sandwiched between the first and second contact members  50 ,  55 . 
     When a current passing through the first contact member  50  of the contact  5  due to connection with the complementary connector is within the rated operational current of the electronic system, temperature associated with the current is lower than the critical temperature of the polyswitch  6 . In such a case, the polyswitch  6  acts as a conductor and allows the current to pass through the second contact member  55  soldered to the circuit board thereby forming a closed circuit. When the current passing through the first contact member  50  exceeds the rated operational current of the electronic system, the temperature associated with the current is higher than the critical temperature of the polyswitch  6 . In such a case, the polyswitch  6  acts as an insulator whereby the current is switched off to obviate damage to the electronic system caused by overheating. 
     In addition, the polyswitch  6  is securely retained in the connector  1  by being sandwiched between the first and second contact members  50 ,  55  with only a slight modification to the original design of the connector  1 . In other words, the polyswitch  6  utilizes an unused portion of the original connector  1  to implement the additional specific function, i.e., excessive current protection with only slight modification to the original design thereof, thereby significantly reducing the occupied space on the mother board. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.