Abstract:
An anti-static sole is provided with a pad body between a midsole and an insole. In the pad body is provided a chip resistor. The chip resistor includes a connecting pin at each of two opposite ends thereof. The two connecting pins of the chip resistor are electrically connected to the insole and the midsole, respectively. Since the chip resistor has no exposed wires, damage to the wires is avoided. Further, the anti-static effect can be improved since the resistance of the chip resistor is stable.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a shoe attached with a grounding device, and more particularly to an anti-static sole. 
     2. Description of the Prior Art 
     Generally speaking, the phenomenon that charge transfer occurs when an insulator accumulated with charges is brought into contact with a conductor, or charge transfer occurs and potential difference is produced when two objects rub each other is called static electricity. The static electricity generally has no effect on the human body, but it will cause damage to precision equipments such as electronic elements or magnetic memory card. Therefore, the person who processes the electronic elements or the magnetic memory cards must clear the static charges from his body before work. Conductive shoe is one of the existing equipments for eliminating the static charges on the person. 
     Conventionally, the existing conductive shoe is provided with a ceramic resistor between a midsole and an insole of a sole, and the ceramic resistor is connected to the midsole and the insole, respectively to allow the static charges on the user to be conducted to the midsole through the ceramic resistor and then conducted to the ground from the midsole. By such arrangements, the static charges on the user can be partially eliminated such that the remaining static charges cannot cause any damage to the electronic elements or magnetic memory cards. 
     However, the ceramic resistor is made up of a middle ceramic portion and two metallic wires at both ends of the middle ceramic portion, and the connecting structures for connecting the ceramic portion and the two metallic wires are quite fragile, so that after being bent for many times or pressed for a long time, the metallic wires will be damaged or even broken, and the ceramic portion is likely to rupture due to overlarge pressure applied by the user. If the user finds the above defects, he must replace his shoes, but if the user fails to find the above defects, the static charges on the user cannot be eliminated properly, inevitably causing damage to the electronic elements or magnetic memory cards. 
     Hence, U.S. Pat. No. 6,421,222, entitled “PRECISION FAIL-SAFE ELECTROSTATIC DISSIPATING DEVICE”, disclosed an apparatus for dissipating static charges which is constructed of several conductive layers and a set of parallel resistors, if either resistor of the parallel resistor fails, the static charges can also be dissipated through the remained resistors, ensuring fail-safe dissipation of static electricity, but it can be found that the production cost is greatly increased due to the increase of the number of the resistors. 
     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide an anti-static sole which is provided with a chip resistor between a midsole and an insole to solve the problems of the ceramic resistor and reduce the cost. 
     In order to achieve the above objective, an anti-static sole in accordance with the present invention comprises a midsole, a pad body and an insole. The midsole is conductive and provided with a first conductive element which can be made of conductive fabric. The pad body has a bottom surface thereof disposed on the midsole. The pad body interiorly includes a chip resistor. The chip resistor includes a connecting pin at each of two opposite ends thereof. The two connecting pins are located at the top surface and the bottom surface of the pad body, respectively, and one of the two connecting pins is electrically connected to the first conductive element of the midsole. The insole is disposed on and cooperates with the midsole to clamp the pad body. The insole is provided with a second conductive element which can be made of conductive fabric. The second conductive element has a first portion located at the top surface of the insole and a second portion located at the bottom surface of the insole, and the second portion of the second conductive element located at the bottom surface of the insole is covered by the pad body and electrically connected to the other of the connecting pins of the chip resistor. 
     When the user steps on the insole, the foot of the user will contact the first portion of the second conductive element located at the top surface of the insole, so that the static charges on the user will be conducted to the chip resistor through the second conductive element and then conducted to the first conductive element from the chip resistor and finally conducted to the ground from the midsole, thus reducing the static charges on the user. 
     Since the ceramic resistor is replaced by the chip resistor of the present invention which utilizes two connecting pins at two ends thereof to realize electrical connection and conduction, no metallic wires are exposed, thus avoiding the damage of the resistor, and since the chip resistor is packaged, the outside frame is unneeded, thus saving cost. 
     The secondary objective of the present invention is to provide an anti-static shoe which is provided with a shoe upper on the anti-static sole to utilize the chip resistor on the shoe to conduct the static charges on the user who wears the anti-static shoe to the ground, and further the chip resistor is difficult to be damaged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exposed view of an anti-static sole in accordance with the present invention; 
         FIG. 2  is another exploded view of the anti-static sole in accordance with the present invention; 
         FIG. 3   a  is an exploded view of a pad body of the anti-static sole in accordance with the present invention; 
         FIG. 3   b  is a perspective view showing another chip resistor for the anti-static sole in accordance with the present invention; 
         FIG. 4  is a perspective view of the anti-static sole in accordance with the present invention; 
         FIG. 5  is a schematic view showing another form of the second conductive element for the anti-static sole in accordance with the present invention; 
         FIG. 6  is an exposed view showing that the anti-static sole in accordance with the present invention is additionally provided with a shoe upper; 
         FIG. 7  is a perspective view showing that the anti-static sole in accordance with the present invention is additionally provided with a shoe upper; and 
         FIG. 8  is an exposed view showing that the second conductive element of the present invention includes two segments. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be clearer from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 
     Referring to  FIGS. 1-4 , an anti-static sole in accordance with the present invention comprises a midsole  10 , a pad body  20 , and an insole  30 . 
     The midsole  10  is made of conductive material and provided with a first conductive element  11 . The first conductive element  11  is made of conductive fabric formed by mixed weaving of fiber and wires, so the wires can be used to conduct electricity. The first conductive element  11  is exposed from a top surface of the midsole  10 . 
     The pad body  20  has a bottom surface disposed at the top surface of the midsole  10 . The pad body  20 , as shown in  FIG. 3   a,  includes a main pad  21 , an assistant pad  22 , a chip resistor  23 , an upper conductive fabric  24  and a lower conductive fabric  25 . The main pad  21  includes a through hole  211 . The assistant pad  22  is disposed at the bottom surface of the main pad  21  and includes a receiving hole  221  in alignment with the through hole  211 . The chip resistor  23  is received in both the through hole  211  and the receiving hole  221 . The chip resistor  23  (commonly called SMD (surface-mount device) resistor) includes a packaging layer  231  and two connecting pins  232 . The packaging layer  231  includes an inner resistive circuit, and the two connecting pins  232  are disposed at and abutted against two opposite ends of the packaging layer  231 . The two connecting pins  232  are electrically connected to the resistive circuit, respectively. One of the two connecting pins  232  is exposed from the top surface of the main pad  21 , and the other of the two connecting pins  232  is exposed from the bottom surface of the assistant pad  22 . The upper conductive fabric  24  is disposed at the top surface of the main pad  21  and covers a corresponding connecting pin  232  of the chip resistor  23  in such a manner that the upper conductive fabric  24  is in electrical contact with this connecting pin  232 . The lower conductive fabric  25  is disposed at the bottom surface of the assistant pad  22  and covers a corresponding connecting pin  232  of the chip resistor in such a manner that the lower conductive fabric  25  is in electrical contact with this connecting pin  232 . The lower conductive fabric  25  is further in electrical contact with the first conductive element  11  of the midsole  10 . In the present embodiment, the chip resistor  23  is a thick film chip resistor as shown in  FIG. 3   a.  In addition, the chip resistor  23  of the present invention can also be a power metal film chip resistor as shown in  FIG. 3   b  in another embodiment. It is to be noted that the above two resistors are described by way of example only and not limitation. 
     The insole  30  is disposed at a top surface of the midsole  10  and cooperates with the midsole  10  to clamp the pad body  20 . The insole  30  is provided with a second conductive element  31 . The second conductive element  31  is made of conductive fabric and includes a first segment  311  and a second segment  312  at the top surface of the insole  30 , and a third segment  313  at the bottom surface of the insole  30 . The third segment  313  of the second conductive element  31  is covered by the pad body  20 , so that the third segment  313  can be prevented from electrically connecting the midsole  10  or the first conductive element  11  of the midsole  10 . The upper conductive fabric  24  of the pad body  20  is in electrical contact with the third segment  313  of the second conductive element  31 . In the present embodiment,  FIG. 2  shows that the second conductive element  31  is disposed on the insole  30  in such a manner that two ends of the second conductive element  31  penetrate to the top surface of the insole  30  from the bottom surface thereof to form the first segment  311  and the second segment  312 , and the middle portion of the second conductive element  31  forms the third segment  313 . Alternatively, as shown in  FIG. 5 , two ends of the second conductive element  31  can be wound from the bottom surface of the insole  30  to the top surface of the insole  30  in such a manner that the two ends of the second conductive element  31  can also form the first segment  311  and the second segment  312 , and the middle portion of the second conductive element  31  can also form the third segment  313 . 
     When the anti-static sole of the present invention is in use, the bottom of the foot of the user is in contact with the first segment  311  and the second segment  312  of the second conductive element  31  of the insole  30 , respectively, so that the static charges on the user can be conducted to the third segment  313  through the first segment  311  and the second segment  312 , and next conducted to the chip resistor  23  from the third segment  313  through the upper conductive fabric  24  and one of the connecting pins  232  of the chip resistor  23 , and then conducted to the first conductive element  11  of the midsole  10  through the other of the connecting pins  232  of the chip resistor  23  and the lower conductive fabric  25 , and finally conducted to the ground through the midsole  10 , thus reducing the static charges on the user. 
     Since the ceramic resistor is replaced by the chip resistor  23 , and the connecting pins  232  abutted against both ends of the chip resistor  23  are used to realize electrical connection, it can solve the problems of the ceramic resistor, such as the damage of the metallic wires and the ceramic portion, and the broken circuit. Further, the chip resistor  23  will be packaged during the production process to include the packaging layer  231  which can resist an external force and further prevent the two abutted connecting pins  232  from deformation, thus saving cost without the use of the outside frame. 
     Additionally, as shown in  FIGS. 6 and 7 , on the anti-static sole of the present invention is provided a shoe upper  40  which is connected to the top surfaces of the midsole  10  and the insole  30 , respectively. The shoe upper  40  covers the insole  30  to form a shoe, so that when the user wears it, the static charges on the user can be conducted to the ground. 
     According to the skill of the present invention, as long as the second conductive element  31  of the present invention have two portions located at both the top surface and the bottom surface of the insole  30 , and the portion of the second conductive element  31  at the bottom surface of the insole  30  is covered by the pad body  20 , the second conductive can exert the same function as described above, such as shown in  FIG. 8 , the second conductive element  31  includes a second segment  312  located at the top surface of the insole  30  and a third segment  313  located at the bottom surface of the insole  30 , and the third segment  313  of the second conductive element  31  is covered by the pad body  20 , so that the static charges on the user can also be conducted to the third segment  313  through the second segment  312  and then to the first conductive element  11  from the third segment  313  through the chip resistor  23 , thus finally conducting the static charges on the user to the ground. 
     While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.