Patent Publication Number: US-2007107929-A1

Title: Insulator integrated with clamp

Description:
TECHNICAL FIELD  
      The present invention relates, in general, to an insulator for supporting a power cable and, more particularly, to an insulator integrated with a clamp, which has an easily manufactured structure, and in which the insulator is integrated with the clamp for connection to a power cable.  
     BACKGROUND ART  
      Generally, a power cable is installed in various forms, either above ground or underground, to deliver power from a power plant to an individual consumer. A method of utilizing electric poles has been generally used as a method of installing a power cable above ground.  
      According to the method of supporting a power cable using electric poles, the electric poles are installed at regular intervals, and the power cable is supported by the electric poles, thus stably maintaining the power cable in the correctly installed position.  
      The electric poles and the power cable are connected to each other through an insulation structure to prevent a current flowing from the power cable to the electric poles. This insulation structure is formed in such a way that an insulator is positioned between a power cable and a supporting member. The supporting member is mounted on each electric pole and supports the power cable.  
      That is, the supporting member and the power cable are connected to each other through the insulator, thus preventing the current flowing from the power cable to the electric poles.  
      In this case, insulators are classified into a ceramic insulator made of a ceramic material and a composite insulator made of a polymer material, such as glass, silicon or Ethylene Propylene Diene Monomer (EPDM). The ceramic insulator is advantageous in that it has better insulating properties, but disadvantageous in that there is a high risk of damage during transportation and installation; the ceramic insulator has a heavy weight, and; it is inconvenient to connect the ceramic insulator to a fitting.  
      The composite insulator is designed to overcome the disadvantages of the ceramic insulator, and is comprised of a center rod  10 , and metal connecting caps  20  and  20 ′ situated at both ends of the center rod  10  to connect the center rod  10  to a power cable and a fitting, respectively, as shown in  FIG. 1 .  
      In this case, the center rod  10  includes an insulating rod  12  made of a glass material, and an insulating coating  14  made of a polymer material constituting a plurality of disc-type fins  141  covering the insulating rod  12 , as shown in  FIG. 1 . The composite insulator is characterized in that, since it has a light weight according to the properties of materials of the insulating rod  12  and the insulating coating  14  that constitute the center rod  10 , it can be easily carried and installed.  
      For one of the connection structures between the composite insulator and the power cable, a so-called clamp scheme is used in which the connecting cap  20  at one end of the center rod  10  is attached to a fitting  110  (refer to  FIG. 2 ) and the connecting cap  20 ′ at the other end of the center rod  10  is attached to a power cable  100  through a clamp  30 .  
      The clamp  30  (refer to  FIG. 1 ) is comprised of various components, such as a body  32 , a pair of jaw elements  34  mounted on the body  32 , and springs (not shown) used for the mechanical operation of the jaw elements  34 . The body  32  includes a trapezoid-shaped casing unit  321  having an opening formed therein to narrow toward the end thereof and a bar-shaped connecting unit  322  formed on one end of the casing unit  321  and connected to the center rod  10 , through connection cap  20 ′.  
      In this case, the casing unit  321  has a shape with an opened top to allow a control lever  341  formed on one jaw element  34  to be projected upward from the casing unit  321 , and the casing unit  321  is constructed so that the tops of both sidewalls thereof are oppositely bent inward to form cover units  323  so as to prevent the jaw elements  34  provided in the casing unit  321  from deviating from the casing unit  321 .  
      Such a clamp  30  is operated in such a way that the jaw elements  34  are pushed inward by the springs after the jaw elements  34  are positioned in the inner space of the casing unit  321 , so that the gap between the jaw elements  34  becomes small enough to perform a clamping operation. In this case, the connecting unit  322  is connected to one connecting cap  20 ′ by a cotter  40  and a pin  42 , so that the clamp  30  is connected to the insulator.  
      Therefore, in the conventional composite insulator, the connecting cap  20  at one end of the center rod is connected to the fitting  110 , and the connecting cap  20 ′ at the other end thereof is connected to the clamp  30 , as shown in  FIG. 2 . Furthermore, the composite insulator supports the power cable  100  is supported in such a way by being clamped by the jaw elements  34  of the clamp  30 .  
      In the meantime, with this conventional composite insulator setup, several problems may occur due to the connection structure between the clamp  30  and the center rod  10 , and the structure of the clamp  3 ) 0  which are described in detail.  
      First, in the connection structure between the clamp  30  and the center rod  10 , a problem of low productivity and efficiency during installation is caused due to the reason that the structure between the connecting cap  20 ′ and the clamp  30  must be designed in a complicated form in which the cotter  40  penetrates through the connecting cap  20 ′ so as to accommodate a cotter-pin scheme. Additional parts, such as the cotter  40  and the pin  42 , are required, and the operation of connecting the connecting cap  20 ′ and the clamp  30  to each other is required prior to the installation.  
      Furthermore, according to the cotter-pin scheme, a strong shear force is applied to both the cotter  40  and the connecting cap  20 ′, so that the cotter  40  or the connecting cap  20 ′ may be damaged or the pin  42  fastening the cotter  40  may fall out and then the clamp  30  may be separated from the center rod  10 . When the clamp  30  is separated from the center rod  10 , the power cable  100  may be separated from the electric pole  120 , thus badly affecting the stability of the supply of power.  
      Furthermore, the problem of the structure of the clamp  30  itself is based on the manufacturing method thereof. That is, since the clamp  30  is formed and manufactured as a single structure by molding a core must be used to obtain a space within the casing unit  321  according to the characteristics of the molding in order to form the cover unit  323  having an inwards bending shape on the top of the casing unit  321 .  
      The core is used to form an opening in a formed product by making molding sand in a specific shape and arranging this molding sand in a metal mold. Therefore, there occurs a problem in that the core formed using a chemical adhesive, so that environmental pollution is caused and disposal costs are incurred when the core is disposed of and the costs required to manufacture products related to the core are increased.  
      Furthermore, when the core is used the inner surface of the casing unit  321  is roughly formed according to the properties of a core made of molding sand so that several operational problems may occur, including a condition in which the motions of both jaw elements  34  coming into contact with the inner surface of the casing unit  321  are not smooth.  
     DISCLOSURE OF INVENTION  
      Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an insulator integrated with a clamp and a connecting cap, so that the stability of supporting a power cable and operational efficiencies during installation is improved and which employs a structure of manufacturing the clamp without using a core, so that manufacturing productivity is improved.  
      In order to accomplish the above objective, the present invention provides an insulator integrated with a clamp, comprising a center rod comprised of an insulating rod made of a glass material, and an insulating coating made of a polymer material to cover the insulating rod; a connecting cap connected to one end of the center rod; and the clamp comprised of a body provided with a wedge-shaped casing unit having an inner space formed to narrow toward an end of the casing unit and a connecting unit formed on the other end of the casing unit, and a pair of jaw elements positioned in the inner space of the casing unit and pushed inward by springs, so that an interval between the jaw elements is reduced to perform a clamping operation, and the connecting unit having a permanent connection to the other end of the center rod.  
      Preferably, the connecting unit of the clamp may be formed in a pipe shape with a diameter slightly greater than a diameter of the insulating rod so that the appropriate end of the insulating rod is tightly fitted into the connecting unit, thus enabling the clamp and the center rod to be fixedly connected to each other.  
      Preferably, the casing unit of the clamp may be formed to have a fully opened top; and the clamp may further comprise separate cover panels attached to tops of both sidewalls of the casing unit so that the cover panels partially  
      cover the opened top and thus prevent the jaw elements included in the casing unit from deviating upwards from the casing unit. 
    
    
     DESCRIPTION OF DRAWINGS  
      The above mentioned, as well as other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a perspective view showing the structure of a conventional composite insulator/clamp combination;  
       FIG. 2  is a view showing an example of the supporting of a power cable using the conventional composite insulator/clamp combination;  
       FIG. 3  is an exploded perspective view showing the structure of an insulator integrated with a clamp according to an embodiment of the present invention;  
       FIG. 4  is a perspective view showing the structure of the assembled insulator integrated with a clamp according to the embodiment of the present invention;  
       FIG. 5  is a perspective view showing the structure of the clamp according to the embodiment of the present invention;  
       FIG. 6  is a perspective view showing the operation of the clamp according to the embodiment of the present invention; and  
       FIG. 7  is a view showing an example of the supporting of a power cable using the insulator integrated with a clamp according to the embodiment of the present invention. 
    
    
     BEST MODE  
      Hereinafter, embodiments of the present invention will be described in detail with reference to  FIGS. 3 through 7 .  
      Reference should now be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.  
      An insulator integrated with a clamp according to the embodiment of the present invention includes a clamp  50  attached to one end of the center rod  10 , and a connecting cap  20  attached to the other end of the center rod  10 , as shown in  FIGS. 3 and 4 . The center rod  10  is comprised of an insulating rod  12  (refer to  FIG. 1 ) made of a glass material and an insulating coating  14  made of a polymer material to cover the insulating rod  12 , similar to the conventional composite insulator.  
      The clamp  50  includes various components, such as a body  52 , a pair of jaw elements  54  mounted on the body  52 , springs (not shown) required for the mechanical operation of the jaw elements  54 . The body  52  includes a trapezoid-shaped casing unit  521  having an opening formed therein to narrow toward the end thereof and a bar-shaped connecting unit  522  formed on one end of the casing unit  521  and tightly connected to the center rod  10 .  
      Furthermore, as shown in  FIGS. 5 and 6 , the two guide channels  60  are formed in the bottom of casing unit  521  to provide a sliding route for the jaw elements  54 . The important aspect of the guide channels  60  is that a limitation stub  61  is formed in one or both of the guide channels to limit the jaw elements&#39; movement. As a counterpart of the limitation stub  61 , a detach prevention stub (not shown) is formed in the bottom of the one or both of the jaw elements.  
      Specifically, when the jaw elements are moved in direction A (refer to  FIG. 6 ), after moving for predetermined distance B, the jaw elements are stopped by the limitation stub  61 . Without the limitation stub  61 , there is very high possibility for jaw elements  54  to be detached from casing unit  521 , when jaw elements are moved in direction A to widen the space between each jaw elements.  
      The connecting unit  522  is formed in a pipe shape having a diameter slightly greater than that of the insulating rod. One end of the insulating rod  12  is tightly fitted into the connecting unit  522 , so that the clamp  50  and the center rod  10  can be permanently connected to each other.  
      Furthermore, according to the embodiment of the present invention, the casing unit  521  of the clamp  50  is formed to have a fully opened top, and separate cover panels  53  are attached to the tops of both sidewalls of the casing unit  521 , instead of conventional cover units  323  integrated with the casing unit  321  (refer to  FIG. 1 ).  
      The cover panels  53  are formed to have a width exceeding the thickness of each sidewall of the casing unit  521 , and fastened to the tops of the casing unit  521  through fastening bolts, after the jaw elements  54  are inserted in the casing unit  521 , thus preventing the jaw elements  54  from deviating from the casing unit  521 .  
      In the above-described insulator integrated with a clamp according to the embodiment of the present invention, the clamp  50  and the center rod  10  are fixedly connected to each other, so that there is no need to execute a separate process of engaging the clamp  30  (refer to  FIG. 1 ) with the center rod  10  in a cotter-pin manner prior to the connection to the power cable  100 , as in the case of a conventional insulator.  
      Furthermore, with regard to the shape of the clamp  50 , since the clamp  50  is constructed without a conventional complicated structure for the cotter-pin connection, but rather with a simple pipe-shaped connecting unit  522  into which the insulating rod  12  is tightly fitted, thus improving structural strength at the connection points.  
      In the insulator integrated with a clamp according to the embodiment of the present invention having the above construction, the connecting cap  20  at one end of the center rod  10  is attached to the fitting  110  and then mounted on the electric pole  120 , as shown in  FIG. 5 . The power cable  100  is supported in such a way that it is clamped by the jaw elements  54  of the clamp  50 ( FIG. 7 ).  
      According to the embodiment of the present invention, the body of the clamp can be formed without using a core to form an opening in the casing unit  521 , as the structure of the casing unit  521  has a fully opened top.  
      Therefore, since the inner surface of the casing unit  521  is formed smoothly, the operation of the jaw elements  54  is improved thus solving various problems occurring due to the use of the core.  
     INDUSTRIAL APPLICABILITY  
      As described above, the present invention provides an insulator integrated with a clamp, which is implemented with a simple structure in which a center rod and a clamp are permanently connected to each other, so that the low productivity and efficiency during installation is improved and in which the connection part between the clamp and the center rod is strongly constructed so that the stability of supporting a power cable is improved thus stably supplying power.  
      Furthermore, the present invention is advantageous in that, since it does not require a core in a process of manufacturing the body of a clamp, problems related to the increased costs and environmental pollution attributable to the use of the core do not occur.  
      Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.