Abstract:
A high voltage plug-in and unplugged type gas immersed cable termination comprising a recess inside the blind end of the electrode to allow the extension of the locking pin to lock the connector with the electrode and thereby anchor the power cable. The locking pin is designed to anchor the power cable to safeguard against sliding down of the power cable during the operation period. The high voltage plug-in and unplugged type gas immersed cable termination can be unplugged manually. The locking pin can be replaced before re-plugging-in of the termination.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of U.S. provisional Application No. 61/834,433 filed Jun. 13, 2013, the whole of which is hereby incorporated by reference herein 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention is related to a system for positioning a power cable and in particular to a system which carries a locking device to position the power cable and safeguard it from sliding down. 
       BACKGROUND OF INVENTION 
       [0003]    In the operation of high voltage equipment, the control of the electric field according to the physical positioning of the power cable is very essential. Movement of the power cable inside a termination may affect the electric field distribution, which will in turn affect the life of the cable termination and may even lead to the failure of the power supply system. 
         [0004]    The mainstream technique at the current stage of suspending the power cable inside a high voltage plug-in and unplugged type gas immersed cable termination is to depend on the friction of the power cable with the outer layers. However, with large conductors, the heavy weight of the core increases the risk of its falling down. 
         [0005]    For power cable with corrugated aluminium sheath, the friction between the core and the metallic sheath is rather low. There are cases of loosening due to poor manufacturing of cable cores for the corrugated aluminium sheath cable. In this respect, the suspension of the power cable by friction becomes ineffective. Such corrugated aluminum sheath cable is commonly used inside substations where vibration of the transformer under load exists. 
       SUMMARY OF INVENTION 
       [0006]    In the light of the foregoing background, it is an object of the present invention to develop a system which carries a locking device to position the power cable and safeguard it from sliding down with high reliability during operating condition. Particularly, the advantage of the system of the present invention includes preventing the power cable from slide down during all circumstances of operating conditions and/or due to heavy weight of conductor and insulation loadings. 
         [0007]    Accordingly, the present invention, in one aspect, provides a system for positioning a power cable comprising a connector, wherein the connector comprising a housing comprising a cable end and an opposing engagement end defining an insertion axis there between; a cable cavity disposed on the cable end and configured to receive the power cable; an actuator placed at the housing at the engagement end and movable along the insertion axis towards the cable end; the actuator movable between a pre-engagement position and an engagement position; at least one locking pin provided within the housing and movable along an engagement axis axial to the insertion axis; the locking pin engaged to the actuator and movable from an unlocked to a locked position. When the actuator in the pre-engagement position provides a space for the locking pin to stay in the unlocked position. When the actuator in the engagement position pushes the locking pin into the locked position and is anchored by the locking pin such that the power cable is electrically connected to the electrode. 
         [0008]    In an exemplary embodiment of the present invention, wherein the connector further comprises a locking pin cavity positioned along the engagement axis, wherein the locking pin cavity further comprises a locking pin stopper and a locking pin spring disposed around the locking pin, and wherein the locking pin is movably disposed within the locking pin cavity, and when the locking pin is at the second locked position at least a portion of the locking pin is extended out of the locking pin cavity. 
         [0009]    In an exemplary embodiment of the present invention, wherein the locking pin stopper further comprises a hollow threaded screw unit. 
         [0010]    In an exemplary embodiment of the present invention, wherein the locking pin stopper is configured to fix the locking pin on the insertion axis. 
         [0011]    In an exemplary embodiment of the present invention, wherein the actuator is a mandril. 
         [0012]    In an exemplary embodiment of the present invention, wherein the mandril has a head and a narrower tail. 
         [0013]    In an exemplary embodiment of the present invention, wherein the connector further comprises a mandril cavity positioned along the insertion axis, wherein the mandril is movably disposed within the mandril cavity and is configured to push the locking pin at one end thereof. 
         [0014]    In an exemplary embodiment of the present invention, wherein the mandril cavity further comprises a mandril spring disposed at one end of the mandril cavity and a plurality of mandril stoppers at the other end of the mandril cavity, wherein the mandril is deposited between the mandril spring and the plurality of mandril stopper while at least a portion of mandril is extended outside the mandril cavity. 
         [0015]    In an exemplary embodiment of the present invention, wherein the mandril further comprises an intermediate portion disposed between the head and the narrower tail of the mandril; and a fringe extended outwardly from the head of the mandril and disposed between the head and the intermediate portion, wherein the intermediate portion comprises an inclined surface connecting between the narrower tail and the fringe, when at the engagement position, the inclined surface is configured to push the locking pin into the locked position and the fringe is anchored by the one end of the locking pin such that the mandril is held at the engagement position and the locking pin is held at the locked position. 
         [0016]    In an exemplary embodiment of the present invention, wherein the mandril further comprises a fringe extended outwardly configured to be captured by the plurality of mandril stoppers when the mandril is at the pre-engagement position. 
         [0017]    In an exemplary embodiment of the present invention, wherein the connector has recesses on its cylindrical exterior. 
         [0018]    In an exemplary embodiment of the present invention, wherein the system further comprises an electrode, which comprises a recess positioned near the blind end of the electrode, wherein at least a portion of the electrode is covered by an epoxy resin insulating cone. 
         [0019]    In an exemplary embodiment of the present invention, wherein the locking pin is made of aluminum alloy. 
         [0020]    In a further aspect of the present invention, wherein a method of locking a power cable to an electrode is provided, comprising the step of providing a connector comprising a housing, an actuator and a locking pin; plugging the connector into the electrode till the actuator is at a engagement position thereby actuates the locking pin to fix the connector such that the power cable is electrically connected to the electrode. 
         [0021]    In an exemplary embodiment of the present invention, wherein the actuator further comprises a mandril, and the locking pin is actuated by being pushed away from an unlocked position to a locked position by the mandril, which is pushed against the electrode. 
         [0022]    In an exemplary embodiment of the present invention, wherein the method further comprises a step of attaching the locking pin to an interior wall of the electrode. 
         [0023]    In one embodiment, the system is a high voltage plug-in and unplugged type gas immersed cable termination. 
         [0024]    Accordingly, the present invention provides a high voltage plug-in and unplugged type gas immersed cable termination comprising of a locking system which is independent of the friction between layers of power cables. 
         [0025]    Accordingly, the present invention provides a high voltage plug-in and unplugged type gas immersed cable termination that can be unplugged without the necessity of disturbing any major components of the cable termination. To facilitate the plug-in and unplugged function, it is possible to remove the power cable manually without disturbing of the rest of the major components of the cable termination. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0026]    For a complete understanding of the present invention, reference is made to the following detailed description and accompanying drawings, in which: 
           [0027]      FIG. 1  is a schematic view of the high voltage plug-in and unplugged type gas immersed cable termination with the connector according to the first embodiment of the present invention; 
           [0028]      FIG. 2  is a cross-sectional view of the high voltage plug-in and unplugged type gas immersed cable termination with the connector according to the first embodiment of the present invention; 
           [0029]      FIG. 3  is a schematic view of the connector with the locking pin according to the first embodiment of the present invention; 
           [0030]      FIG. 4  is a cross-sectional view of the connector with the locking pin according to the first embodiment of the present invention; 
           [0031]      FIG. 5  is a cross-sectional view of the connector installed inside the epoxy cone with the locking pin according to the first embodiment of the present invention; 
           [0032]      FIG. 6  is a cross-sectional view of the high voltage plug-in and unplugged type gas immersed cable termination with the connector at plugged in position according to the second embodiment of the present invention; 
           [0033]      FIG. 7  is a cross-sectional view of the connector with the locking pin at unplugged position according to the second embodiment of the present invention; and 
           [0034]      FIG. 8  is a cross-sectional view of the connector with the locking pin at plugged in position according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    As used herein and in the claims, “comprising” means including the following elements but not excluding others. As used herein and in the claims, “comprising” means including the following elements but not excluding others. 
         [0036]    As used herein and in the claims, “couple” or “connect” refers to electrical coupling or connection either directly or indirectly via one or more electrical means unless otherwise stated. 
         [0037]    For a more complete understanding of the present invention, reference is made to the following detailed description: 
         [0038]    Referring to  FIG. 1 , the high voltage plug-in and unplugged type gas immersed cable termination  20  includes an epoxy resin insulating cone  22 , a power cable  24 , a connector  26 , and a high voltage (HV) electrode  28 . The HV electrode  28  is partially covered by the epoxy resin insulating cone  22 . Particularly, the upper end of the HV electrode  28  is not covered by the epoxy resin insulating cone  22  (uncovered portion  34 ), only the lower end of the HV electrode  28  is covered (covered portion). The HV electrode  28  is in substantially cylindrical shape and includes a hollow portion  30 . The hollow portion  30  of the HV electrode  28  is configured to receive the connector  26 . The inner wall  32  of the HV electrode  28  is substantially flat/smooth and does not contain any groove. Under the epoxy resin insulating cone  22 , the power cable  24  is connected to the connector  26 . Thereby, the HV electrode  28  is in electrical connectivity with the power cable  24  through the connector  26 . The connector  26  includes a housing for holding all the elements of the connector  26 . The housing includes a cable end and an opposing engagement end defining an insertion axis there between. The connector  26  includes a cable cavity  58  at the cable end  60  for receiving and connecting the power cable  24 . 
         [0039]    As shown in  FIG. 2 , the cable termination  20  further comprises a stress cone  38 , a compression unit  40 , a compression housing  42  and a cable gland  44 . The stress cone  38  is tightly compressed against the epoxy resin insulating cone  22  by the compression unit  40  enclosed in the compression housing  42 . There is an interface surface between the stress cone  38  and the epoxy resin insulating cone  22 . To prevent the creepage of electricity along the interface surface, it is necessary to compress the stress cone  38  tightly against the epoxy resin insulating cone  22 . The power cable  24  finally comes out of the high voltage plug-in and unplugged type gas immersed cable termination  20  through the cable gland  44 . The stress cone  38  is made of polymeric materials, which is a component made of insulating and electrical semi-conducting material. The HV electrode  28  further includes a recess  36  located between the hollow portion  30  of the HV electrode  28  and the uncovered portion  34  of the HV electrode  28  to receive the head portion  46  of the connector  26 . 
         [0040]      FIG. 3  and  FIG. 4  show a schematic view and a cross section view of the connector  26  with a locking pin  48  selectively projected from it. As shown in  FIG. 3 , the connector  26  includes a locking pin  48  disposed at the head portion  46 . The locking pin  48  is selectively movable from an unlocked position and a locked position. At least a portion of the locking pin  48  is projected from the connector  26  when it is at the locked position. The locking pin  48  is made of aluminum. The connector  26  is substantially in cylindrical shape. The surface of the connector  26  has a plurality of recesses  50 . The connector  26  further comprises a plurality of multi contact rings placed around the surface of the connector  26  and configured to facilitate the transfer of electricity at high power. Each of the multi contact rings comprises a pair of legs at its side edges, which is inserted into the recesses  50  and a flexible cushion disposed on its surface between the side edges. A clamping ring is further disposed at each of the recesses  50  and on each of the legs of the multi contact ring for fixing the multi contact ring on the surface of the connector  26 . The radius of the multi contact ring at the flexible cushion portion is slightly larger than the radius of the connector  26 . When the connector  26  is inserted into the HV electrode  28 , the flexible cushion is compressed by the wall of the HV electrode  28  and the surface wall of the connector  26 , thereby an electric connection between the connector  26  and the HV electrode  28  is secured through the multi contact rings. With the plurality of multi contact rings used over the recesses  50 , the cable termination  20  can transfer electricity at 3700 A or more from the power cable  24  to the HV electrode  28  through the connector  26 . The multi contact rings also ensure a good conductivity or to allow a smooth current flow. As shown in  FIG. 4 , the connector  26  includes a cavity  58  at the tail end  60  for receiving and connecting the power cable  24 . At the head portion  46  of the connector  26 , a locking pin cavity  54  is formed. The locking pin cavity  54  is positioned along an engagement axis that is perpendicularly to the insertion axis of the connector  26 . Inside the locking pin cavity  54  includes the locking pin  48 , a locking pin stopper  56  and a locking pin spring  52 . The locking pin stopper  56  is a hollow threaded screw unit. The locking pin cavity  54  has two portions. The first portion  62  of the locking pin cavity  54  has a diameter to fitly accommodate the locking pin spring  52 , the locking pin  48  and the locking pin stopper  56 , while the second portion  64  has a diameter smaller than the first portion  62 . The locking pin stopper  56  is installed in the opening end  66  at the connector&#39;s surface while the locking pin spring  52  is installed at the other end of the first portion that is next to the second portion  64 . The locking pin  48  includes a pin with an enlarged head  68  at one end. The diameter of the enlarged head  68  is substantially larger than the diameter of the locking pin stopper  56  such that when the locking pin  48  is installed between the locking pin stopper  56  and the locking pin spring  52  with the enlarged head  68  facing the locking pin spring  52 , only a portion of the pin is extended out of the connector  26  as the enlarged head  68  of the locking pin  48  is blocked by the locking pin stopper  56  when the locking pin spring  52  pushes the locking pin  48  away from the locking pin cavity  54 . The first portion  62  has a length to hold the whole length of the locking pin  48  when it is retracted into the locking pin cavity  54  by external force. The diameter of the projected end of the locking pin  48  is 3.8±0.05 mm while the diameter of the enlarged head  68  of the locking pin  48  is 5.6±0.05 mm. 
         [0041]    In  FIG. 5 , the recess  36  is configured to receive the head portion  46  of the connector  26  with the locking pin  48 . In operation, the connector  26  is inserted into the hollow portion  30  of the HV electrode  28 . The connector  26  is optionally connected to the power cable  24  at the tail end  60  during the insertion. As the head portion  46  of the connector  26  with the locking pin  48  reaches the recess  36 , the locking pin  48  will be moved from the connector  26  towards the recess  36  thereby attaches to a wall  70  of the recess  36 , which is adjacent to the extended portion of the locking pin  48 . Thus, the position of the power cable  24  is fixed. It can be seen that the end of the locking pin  48  is enlarged to ensure that it holds the power cable  24  tightly. 
         [0042]      FIG. 6  shows the high voltage plug-in and unplugged type gas immersed cable termination  20  includes the epoxy resin insulating cone  22  as the housing, a connector  26  according to the second embodiment of the present invention, and the HV electrode  28 . The connector  26  according to the second embodiment includes a mandril  72  in order to act as sensing device/actuator and a locking pin  48 . The mandril  72  is placed at the engagement end of the housing of the connector  26  and movable along the insertion axis towards the cable end between a pre-engagement position and an engagement position. The mandril  72  has a head and a narrower tail with an intermediate portion of inclined surface therebetween. The epoxy resin insulating cone  22  and the HV electrode  28  are the same as disclosed in above. The inner wall  32  of the HV electrode  28  is substantially flat/smooth and does not contain any groove. The connector  26  also includes a housing for holding all the elements of the connector  26 . The housing includes a cable end and an opposing engagement end defining an insertion axis therebetween. 
         [0043]      FIG. 7  shows a connector  26  of the second embodiment at its unplugged position (i.e. before the mandril  72  engages an interior roof of the recess  36 ). The connector  26  has a housing that is substantially in cylindrical shape. The connector  26  includes the locking pin  48  disposed radially at the head portion  46  of the housing. The locking pin  48  is selectively movable from an unlocked position and a locked position. At least a portion of the locking pin  48  is projected from the connector  26  when it is at the locked position. The locking pin  48  is made of aluminum. The surface of the connector  26  has a plurality of recesses  50 . The connector  26  further comprises a plurality of multi contact rings  114  placed around the surface of the connector  26  and configured to facilitate the transfer of electricity at high power. Each of the multi contact rings  114  comprises a pair of legs at its side edges, which is inserted into the recesses  50  and a flexible cushion  112  disposed on its surface between the side edges. A clamping ring  110  is further disposed at each of the recesses  50  and on each of the legs of the multi contact ring  114  for fixing the multi contact ring  114  on the surface of the connector  26 . The radius of the multi contact ring  114  at the flexible cushion  112  portion is slightly larger than the radius of the connector  26 . When the connector  26  is inserted into the HV electrode  28 , the flexible cushion  112  is compressed by the wall of the HV electrode  28  and the surface wall of the connector  26 , thereby an electric connection between the connector  26  and the HV electrode  28  is secured through the multi contact rings  114 . With the plurality of multi contact rings  114  used over the recesses  50 , the cable termination  20  can transfer electricity at 3700 A or more from the power cable  24  to the HV electrode  28  through the connector  26 . The multi contact rings  114  also ensure a good conductivity or to allow a smooth current flow. The connector  26  includes a cable cavity  58  at the cable end  60  for receiving and connecting the power cable  24 . At the head portion  46  of the connector  26 , a locking pin cavity  54  is formed. The locking pin cavity  54  is positioned along an engagement axis that is perpendicularly to the insertion axis of the connector  26 . Inside the locking pin cavity  54  includes the locking pin  48 , a locking pin stopper  56  and a locking pin spring  52 . The locking pin stopper  56  is a hollow threaded screw unit. The head portion  46  of the connector  26  further includes a mandril cavity  80  positioned along the insertion axis of the connector  26 . 
         [0044]    The locking pin cavity  54  has a diameter to fitly accommodate the locking pin spring  52 , the locking pin  48  and the locking pin stopper  56 . The locking pin stopper  56  and the locking pin spring  52  are disposed around the locking pin  48 . The locking pin stopper  56  is installed in the opening end  66  of the locking pin cavity  54 , where the opening end  66  is located at the connector&#39;s outer surface. The locking pin  48  includes a pin with an enlarged box-like head  82  at one end. The enlarged box-like head  82  of the locking pin  48  is substantially in box-like shape with one inclined portion  84 . At least one side of the enlarged box-like head  82  is larger than the diameter of the pin which is in cylindrical shape. The locking pin spring  52  is installed between the locking pin stopper  56  and the enlarged box-like head  82 . Also at least one side of the enlarged box-like head  82  is substantially larger than the diameter of the locking pin stopper  56  such that when the locking pin  48  is pushed out by the mandril  72 , only a portion of the pin is extended out of the connector  26  as the enlarged box-like head  82  is blocked by the locking pin stopper  56  when the locking pin spring  52  pushes the locking pin  48  away from the locking pin cavity  54 . The locking pin cavity  54  has a length to hold the whole length of the locking pin  48  when it is retracted into the locking pin cavity  54 . The diameter of the projected end of the locking pin  48  is 3.8±0.05 mm while the dimension of one side of the enlarged box-like head  82  of the locking pin  48  is 5.6±0.05 mm. 
         [0045]    The mandril cavity  80  includes the mandril  72 , a mandril spring  78  disposed at the close end  88  of the mandril cavity  80  and a first mandril stopper  74  and a second mandril stopper  76  at the open end  86  of the mandril cavity  80 . The mandril  72  is deposited among the mandril spring  78 , the first mandril stopper  74  and the second mandril stopper  76 . The mandril  72  has a cylindrical head  90  and a cylindrical tail  92 . The diameter of the cylindrical head  90  is larger than the diameter of the cylindrical tail  92 . The mandril  72  further includes a fringe  94  extended from the surface of the cylindrical head  90 . An inclined surface  96  (as an intermediate portion) is formed/connected between the fringe  94  and the cylindrical tail  92  of the mandril  72 . The cylindrical head  90  of the mandril  72  is extended away from the mandril cavity  80  at the open end  86  of the mandril cavity  80 . The fringe  94  and the cylindrical tail  92  are disposed within the mandril cavity  80 . The mandril  72  is supported by the mandril spring  78  at the cylindrical tail  92 . At the unplugged position, the first mandril stopper  74  and the second mandril stopper  76  capture the fringe  94  of the mandril  72  as the mandril  72  is pushed by the mandril spring  78  at the cylindrical tail  92  of the mandril  72 . As a result, the mandril  72  is held in the mandril cavity  80 . Further, the mandril cavity  80  includes an interactive portion  98  located at one side of the mandril cavity  80  and the second end of the locking pin cavity  54 , which is opposite to the opening end  66 . The interactive portion  98  provides a space for the mandril  72  to interact/actuate the locking pin  48 . At the pre-enegement position also provides a space for the locking pin  48  to stay in the unlocked position. The inclined surface  96  of the mandril  72  is fitly in contact with the inclined portion  84  of the locking pin  48  at the unplugged position. The mandril  72  is movably positioned along the insertion axis of the connector  26  and configured to exert a force along the engagement axis that is perpendicular to the insertion axis of the connector  26  to the locking pin  48  at the inclined portion  84  of the enlarged box-like head  82  thereof at the interactive portion  98 . The first mandril stopper  74  is substantially in disk shape and the second mandril stopper  76  is substantially in circular shape. At least a portion of the first mandril stopper  74  and the second mandril stopper  76  cover the open end  86  of the mandril cavity  80 . At least a portion of the second mandril stopper  76  is on a boss hole  100 , which is next to the mandril cavity  80 . 
         [0046]      FIG. 8  shows the connector  26  at plugged in position. At the plugged in position, the cylindrical head  90  of the mandril  72  engages an interior roof of the recess  36  of the HV electrode  28  as the connector  26  is inserted into the HV electrode  28 . The recess  36  is configured to receive the head portion  46  of the connector  26  with the locking pin  48  as the connector  26  is inserted into the hollow portion  30  of the HV electrode  28 . The connector  26  is optionally connected to the power cable  24  at the tail end  60  during the insertion. As the head portion  46  of the connector  26  approaches the recess  36 , the wall of the recess  36  presses against the mandril  72 , which pushes the mandril  72  into the mandril cavity  80 . The mandril spring  78  is compressed by the cylindrical tail  92  of the mandril  72  in this process. As the mandril  72  retracts into the mandril cavity  80 , the fringe  94  and the inclined surface  96  of the mandril  72  pushes the locking pin  48  away from the locking pin cavity  54  at the inclined portion  84 . As a result, the locking pin  48  is push radially away from the center of the connector  26  such that it protrudes outside the exterior surface of the connector and towards the recess  36  thereby becomes inserted therein. As a result, the pin attaches to a wall  70  of the recess  36 , which is adjacent to the projected portion of the locking pin  48 . When at the engagement position, the inclined surface is configured to push the locking pin  48  into the locked position and the fringe is anchored by the enlarged box-like head of the locking pin  48  such that the mandril  92  is held at the engagement position and said locking pin  48  is held at said locked position. Thus, the position of the power cable  24  is fixed. It can be seen that the end of the locking pin  48  is enlarged to ensure that it holds the power cable tightly. 
         [0047]    Accordingly, the present invention provides a high voltage plug-in and unplugged type gas immersed cable termination with a locking system holding the power cable tightly enough without loosening during fault conditions or vibrations over the years on load or due to the heavy conductor and insulation loading. 
         [0048]    When unlocking the connector  26  from the electrode  28 , the power cable  24  and the connector  26  are pulled away from the HV electrode  28  with sufficient force in order to wreck the projected portion of the locking pin  48 . There is no dis-engagement position for the mandril  72  is introduced. Thus, it is possible for the power cable  24  to be removed manually directly from the engagement position without disturbing the major components of the cable termination  20 . 
         [0049]    The locking pin  48  can be broken by screwing the termination at the bottom of the compression unit during the unplugging operation. Then the power cable can be removed whenever necessary. 
         [0050]    The locking pin  48  can be replaced when plug-in operation is necessary again after un-plugging. 
         [0051]    In one exemplary embodiment, the length of the locking pin  48  is 18.9±0.1 mm while the length of the enlarged head  68  of the locking pin  48  in the axis direction is 7.0±0.1 mm. One side of the enlarge head  68  of the locking pin  48  according to the second embodiment is 5.9±0.05 mm while the diameter of the projected end of the locking pin  48  is 3.0±0.05 mm. 
         [0052]    Accordingly, the diameter of the locking pin cavity  54  is 6.0±0.1 mm. 
         [0053]    In one exemplary embodiment, the diameter of the cylindrical head  90  of the mandril  72  is 10.8±0.1 mm. The external diameter of the fringe  94  of the mandril  72  is 12.8±0.1 mm the diameter of the cylindrical tail  92  of the mandril  72  is 4.9±0.05 mm. The length of the mandril  72  is 36.0±0.1 mm while the length of the cylindrical tail  92  is 14.4±0.1 mm. The length of the inclined surface  96  is 6.8±0.1 mm while the length of the fringe  94  in the axis direction is 0.5±0.1 mm. The inclined surface  96  is 30° from the insertion axis of the mandril  72 . The mandril  72  is made of stainless steel. 
         [0054]    Accordingly, the diameter of the open end  86  of the mandril cavity  80  is 13±0.1 mm while the diameter of the close end  88  of the mandril cavity  80  is 5.0±0.1 mm. The length of the mandril cavity  80  is 36.5±0 5 mm while the length of the cylindrical portion with enlarged diameter is 11.7±0.1 mm. The inclined surface  96  thereof is 30° from the insertion axis of the mandril cavity  80 . 
         [0055]    In one embodiment, the length of the locking pin cavity  54  is as same as the diameter of the connector  26 . Each of the two open ends at the connector&#39;s surface comprises the locking pin stopper  56 . In another embodiment, first mandril stopper and the second mandrial stopper are substantially in circular shape. At least a portion of the first mandril stopper and the second mandril stopper cover the open end  86  of the mandril cavity  80 . At least a portion of the first and second mandril stopper is on a boss hole, which is next to the mandril cavity  80 . 
         [0056]    In one embodiment, there are more than one locking pin. In another embodiment, the locking pin cavity  54  is positioned along an engagement axis that is perpendicularly to the insertion axis of the connector  26 . In yet another embodiment, the locking pin the mandril  72  is movably positioned along the insertion axis of the connector  26  and configured to exert a force that is perpendicular to the insertion axis of the connector  26  to the locking pin  48  at the inclined portion  84  of the enlarged box-like head  82  thereof at the interactive portion  98 . 
         [0057]    The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein.