Patent Publication Number: US-6664494-B2

Title: Current collector and gas circuit breaker

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a current collector and a gas circuit breaker, and more particularly, to a current collector, in which moving and fixed contacts constituting a breaker for making an electric circuit ON and OFF come toward and away from each other to thereby carry and shut off current, and a gas circuit breaker. 
     2. Description of the Related Art 
     Typical of this type of gas circuit breaker is a puffer type gas circuit breaker. With this type of gas circuit breaker, an interrupting section is arranged in a metallic container filled with an arc-extinguishing gas such as SF 6  gas to be insulated electrically from the container, the arc-extinguishing gas is compressed in a compression device in relation to coming toward and away actions of contacts (current collector), which constitute the interrupting section, and the compressed gas is blown against an arc to extinguish. 
     An explanation will be given to conventional contacts (current collector) constituting an interrupting section of such puffer type gas circuit breaker. 
     FIGS. 5A,  5 B and  6  show each a conventional current collector. In these figures, an outside fixed contact  14  formed from an electrically conductive member and an inside moving contact  13  are constructed to be concentrically cylindrical structure in a fitting contact relationship (the outside fixed contact  14  is cylindrically structured to be hollow and torus-shaped, and the inside moving contact  13  is cylindrically structured to be hollow or solid). Current flows, for example, to the inside moving contact  13  through a contact portion  15   a  from the outside fixed contact  14 . The inside moving contact  13  is constituted so as to move on the outside fixed contact  14  with a circuit opening and closing operation of a circuit breaker so that a current-carrying contact portion slides. Formed on the fixed contact  14  are n slits, which extend therethrough radially, run a predetermined length in an axial direction, and partial fixed contacts  14   1 ,  14   2 , - - -  14   n  constitute the fixed contact  14 . Before the moving contact  13  and the fixed contact  14  fit together, the fixed contact  14  has an inside diameter φD 1  and an outside diameter φD 3  while the moving contact  13  has an outside diameter φD 2 . Here, by virtue of φD 1 &gt;φD 2 , when the moving contact  13  and the fixed contact  14  fit together, an outside diameter of the fixed contact  14  becomes φD 3 ,&gt;φD 3  so that the fixed contact  14  is flexed outward to give contact forces to the contact portion  15   a.    
     However, with the above structure of a conventional current collector, as seen in FIG. 7 showing the detail of the contact portion  15   a  between the moving contact  13  and the fixed contact  14 , inside and outside diameters of the moving contact  13  and the fixed contact  14  have the relationship of φD 1 &lt;φD 2  and a processing problem is involved, so that the actual contact portion  15   a  forms the only part of circumferential end portions of the moving contact  13  and the fixed contact  14 . 
     When the moving contact  13  and the fixed contact  14  slide in such contact (current-carrying) state, there is caused a problem that temperature rise is caused locally due to the high current density in the contact portion  15   a , so that the members are decreased in hardness whereby the contact portion  15   a  undergoes excessive dissolved loss as compared with the case where the moving contact  13  and the fixed contact  14  do not slide relative to each other to decrease the durability of the current collector extremely. 
     SUMMARY OF THE INVENTION 
     The invention has been made in view of the above point, and has its object to provide a current collector or a gas circuit breaker, which is enhanced in durability as well as current-carrying performance without causing dissolved loss in a contact portion even when both moving and fixed contacts come into sliding contact with each other. 
     In order to attain the above object, the invention provides a current collector comprising a container, with an insulating arc-extinguishing medium being sealed therein, has a cylindrical-shaped fixed contact and an torus-shaped moving contact disposed concentrically with the fixed contact and adapted to come into fitting contact with the fixed contact to carry current stored therein, and a torus-shaped current collecting member formed from a conductive material is provided on a contact portion of either of the fixed contact and moving contact. 
     In order to attain the above object, the invention also provides a gas circuit breaker comprising a container with an insulating gas sealed therein, a fixed contact arranged in the container, a moving contact disposed facing the fixed contact in an opposed manner to be able to come toward and away from the fixed contact, a central shaft having a hollow portion and for making the moving contact movable by an operating force transmitted via an insulating rod from an operating device, a compression device provided outside of the central shaft for compressing a gas blown against an arc generated between the fixed contact and the moving contact, and an insulating nozzle for conducting to the arc the gas compressed by the compression device, wherein the fixed contact and the moving contact are connected together via a torus-shaped current collecting member to permit current to be carried. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B show an embodiment of a current collector, FIG. 1A being a cross sectional view, and FIG. 1B being a transverse cross sectional view. 
     FIG. 2 is a view showing the dimensional relationship between a moving contact and a fixed contact before and after insertion. 
     FIGS. 3A and 3B show an example of a current collecting member adopted in the invention, FIG. 3A being a side view and FIG. 3B being a front view. 
     FIGS. 4A and 4B show a not her example of a current collecting member adopted in the invention, FIG. 4A being a side view and FIG. 4B being a front view. 
     FIGS. 5A and 5B show an example of a conventional current collector, FIG. 5A being a cross sectional view, and FIG. 5B being a transverse cross sectional view. 
     FIG. 6 is a view showing the dimensional relationship between a moving contact and a fixed contact before and after insertion in FIG.  5 A. 
     FIG. 7 is a view showing a state, in which a moving contact and a fixed contact in the prior art contact with each other. 
     FIG. 8 is a view showing a state, in which a moving contact and a fixed contact in an embodiment of the invention contact with each other. 
     FIG. 9 is a cross sectional view showing another embodiment of a current collector according to the invention. 
     FIG. 10 is a view showing a state, in which the moving contact and the fixed contact in the embodiment of the invention shown in FIG. 9 contact with each other. 
     FIG. 11 is a view showing another embodiment of a current collector according to the invention corresponding to FIG.  1 A. 
     FIG. 12 is a cross sectional view showing an embodiment of a gas circuit breaker according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An explanation will be given below to a current collector of the invention on the basis of the embodiments shown in the drawings. FIG. 12 is an example of a puffer type gas circuit breaker, in which the current collector of the invention is adopted. 
     In this figure, an opening/shutting mechanism section arranged in a metallic container  1  is composed of a fixed opening/shutting mechanism section provided on one side (right-side facing the figure) of the metallic container  1  with an insulating support  2  therebetween, and a moving opening/shutting mechanism section provided on the other side (left-side facing the figure) of the metallic container  1  with an insulating support  35  therebetween, the both opening/shutting mechanism sections being arranged facing each other in a direction along a central axis of the metallic container  1 . 
     The insulating support  2  is fixed and supported by a support portion  3 . A current-carrying member  4  connected to a central conductor  7  is fixed and supported on an opposite side of the support portion  3  of the insulating support  2 . 
     The current-carrying member  4  is a cylindrical-shaped member having conductivity, which is provided at an upper portion thereof with a cylindrical-shaped conductor connecting portion  4   a , projecting upward. A central conductor  7  is inserted into the conductor connecting portion  4   a  and also an end of the insulating support  2  on a side opposed to the support portion  3  is fixed on the conductor connecting portion  4   a.    
     A fixed main-contact  27  is provided on a tip end of the current-carrying member  4  on a side opposed to the insulating support  2 . The fixed main-contact  27  is a cylindrical-shaped contact electrode with a tip end thereof on the moving opening/shutting mechanism section side projecting radially inward. A support portion  4   b  projects radially inward from an inner peripheral surface of a lower portion of the current-carrying member  4 , and a fixed arc contact  36  is fixed and supported on the support portion  4   b . The fixed arc contact  36  is a rod-shaped contact electrode provided on a central axis of the metallic container  1  (or on a central axis of the fixed main-contact  27 ) to extend to a tip end of the fixed main-contact  27  from the support portion  4   b.    
     An insulating support member  35  is cylindrical-shaped to be fixed and supported on the metallic container  1 . An end cover  18  is provided on the other end of the metallic container  1 . Arranged in the end cover  18  is a rotating shaft lever  17 , which is connected to an operating rod (not shown) extending from an operating device (not shown) and to which an insulating rod  16  is connected. The insulating rod  16  is disposed on the central axis of the metallic container  1  to extend toward the fixed opening/shutting mechanism section through an interior of the insulating support member  35 , and can be moved in a direction (horizontal direction) of the central axis of the metallic container  1  with an operating force of the operating device transmitted through the operating rod and the rotating shaft lever  17 . A moving shaft  19  is provided on a tip end of the insulating rod  16  toward the fixed opening/shutting mechanism section. The moving shaft  19  is formed with a hollow portion  19   a , which extends continuously in the direction along the central axis of the metallic container  1 . 
     Provided on a tip end of the moving shaft  19  toward the fixed opening/shutting mechanism section is a moving arc contact  20  movable along the central axis of the metallic container  1  together with moving shaft  19 . The moving arc contact  20  is a contact electrode structured to be able to come toward and away from the fixed arc contact  36  disposed facing each other in the direction along the central axis of the metallic container  1 . That is, the moving shaft  19  moves toward the fixed opening/shutting mechanism section whereby an inner periphery of the moving arc contact  20  and an outer periphery of the fixed arc contact  36  come into sliding contact with each other, and the moving shaft  19  moves away from the fixed opening/shutting mechanism section toward the opposite side whereby the inner periphery of the moving arc contact  20  and the outer periphery of the fixed arc contact  36  come away from each other. 
     Provided on an outer periphery of the moving shaft  19  is a puffer cylinder  21 , which is formed integrally with the moving shaft  19  and can move along the central axis of the metallic container  1  together with the moving shaft  19 . The puffer cylinder  21  is a current-carrying member formed from a conductive member and structured to be double-cylindrical shape to be composed of an outer peripheral wall (called also an outer cylinder) and an inner peripheral wall (called also an inner cylinder). A moving main-contact  6  is provided on an outer peripheral surface of an end of the outer peripheral wall of the puffer cylinder  21  toward the fixed opening/shutting mechanism section. The moving main-contact  6  is a contact electrode structured to come toward and away from the fixed main-contact  27  arranged facing each other in the direction along the central axis of the metallic container  1 . That is, the puffer cylinder  21  moves toward the fixed opening/shutting mechanism section together with the moving shaft  19  whereby an outer periphery of the moving main-contact  6  and an inner periphery of the fixed main-contact  27  come into sliding contact with each other, and the puffer cylinder  21  moves away from the fixed opening/shutting mechanism section together with the moving shaft  19  whereby the outer periphery of the moving main-contact  6  and the inner periphery of the fixed main-contact  27  are separated from each other. 
     An insulating nozzle  22  is provided on a tip end of the puffer cylinder  21  toward the fixed opening/shutting mechanism section in a manner to cover an outer periphery of the moving arc contact  20 . The insulating nozzle  22  is a cylindrical-shaped member to cooperate with the outer periphery of the moving arc contact  20  to form a flow passage  22   a , through which an insulating gas discharged from an interior of the puffer cylinder  21  is conducted toward a tip end of the moving arc contact  20 . 
     A current-carrying member  23  connected to the central conductor  7  is fixed and supported on a tip end of the insulating support member  35  toward the fixed opening/shutting mechanism section. The current-carrying member  23  is a cylindrical-shaped conductive member provided on an upper portion thereof with an upward projecting conductor connection  23   a , into which the central conductor  7  is inserted. A fixed contact  12  is provided on a tip end of the current-carrying member  23  toward the fixed opening/shutting mechanism section to come into contact with the moving main-contact  6 . 
     A top of a tip end of a puffer piston  25  toward the insulating support member  35  is fixed and supported on a support  23   c  projecting radially inward from an inner periphery of the current-carrying member  23 . The puffer piston  25  is a cylindrical-shaped member, which is disposed in the puffer cylinder  21  and is larger in radial thickness than the remaining portion thereof so that a tip end thereof toward the fixed opening/shutting mechanism section projects radially outward. The puffer piston  25  is formed to be larger in inner diameter on a side toward the insulating support member  35  than the remaining portion thereof. 
     The puffer cylinder  21  and the puffer piston  25  form a puffer chamber  26  on an outer periphery of the moving shaft  19 . The puffer cylinder  21  is moved relative to the fixed puffer piston  25  to thereby cause the SF 6  gas as an insulating gas to be compressed in the puffer chamber  26 . The insulating gas compressed in the puffer chamber  26  is discharged into the flow passage  22   a  via an exhaust hole (not shown), which is provided on a side of the puffer chamber  26  toward the insulating nozzle  22  to communicate the flow passage  22   a  to an interior of the puffer chamber  26 , and blown against an arc generated between the fixed arc contact  36  and the moving arc contact  20  through the flow passage  22   a.    
     An exhaust hood  28  defined by the current-carrying member  23  and the fixed contact  12  is provided rearwardly of the puffer chamber  26 , that is, on a side of the insulating support member  35 , so that a hot gas branching toward the moving side is discharged into the exhaust hood  28  via the hollow portion  19   a  of the moving shaft  19 . Exhaust holes  19   b  for permitting a hot gas flowing through the hollow portion  19   a  to be discharged are provided on a side of the moving shaft  19  toward the insulating rod  16  and formed at two circumferential locations facing each other vertically relative to a horizontal plane to permit the hot gas to be discharged toward the moving opening/shutting mechanism section from the fixed opening/shutting mechanism section. 
     The current collector according to the embodiment comprises, as shown in FIGS. 1A and 1B, a torus-shaped current collecting member  30 , which is provided on the fixed contact  12  at a contact portion of the outside fixed contact  12  and the inside moving main-contact  6  and formed from a conductive material (for example, chromium-copper and brass having a spring quality, lightweight aluminum, cylindrical-shaped copper, copper and chromium-copper having a good conductivity). Formed on the torus-shaped fixed contact  12  are n slits, which extend therethrough radially as shown in FIG.  1 B and run a predetermined length in an axial direction, and a plurality of partial fixed contacts  12   1 ,  12   2 , - - -  12   n  constitute the fixed contact. A torus-shaped groove (recess) is provided partially on contact surfaces of the partial fixed contacts  12   1 ,  12   2 , - - -  12   n  and the above current collecting member  30  is fitted into the groove (recess). Current, for example, flows from the fixed contact  12  to the moving main-contact  6  via the current collecting member  30 . 
     In this manner, with the current collector according to the embodiment, the outside fixed contact  12  and the inside moving main-contact  6 , which are concentric and cylindrical-shaped, are constructed in a fitting manner and electrically connected to each other via the current collecting member  30  to carry current. 
     The schematic, dimensional relationship among the moving main-contact  6 , fixed contact  12  and the current collecting member  30  is shown in FIG.  2 . 
     As described above, the current collecting member  30  is fitted into the groove (recess) formed inside the fixed contact  12 . Before the moving main-contact  6  having an outside diameter φD 2  is inserted into the fixed contact  12 , to which the current collecting member  30  has been mounted, an inside diameter of the current collecting member  30  is φD 1 , and inside and outside diameters of the fixed contact  12  are φD 4  and φD 3 , respectively. Here, by virtue of φD 1  &lt;φD 2 , when the moving main-contact  6  is inserted into the fixed contact  12  and the moving main-contact  6  and the current collecting member  30  fit together, the relationship between the outside diameter φD 3  before fitting and the outside diameter φD 3 , after fitting, of the fixed contact  12  becomes φD 3 ,&gt;φD 3 , and thus flexing of the current collecting member  30  gives a contact force to the contact portion  15   a.    
     FIGS. 3A,  3 B and FIGS. 4A,  4 B show the current collecting member  30  in detail. As described above, the current collecting member  30  is composed of a torus-shaped conductive material and partially formed with a notch  41  as shown in FIGS. 3A,  3 B or a notch  42  as shown in FIGS. 4A,  4 B, and has an outside diameter φD 5  and an inside diameter φD 1 . In the example shown in FIGS. 3A,  3 B, the notch  41  having a width S 1 , is provided in the current collecting member  30  to be in parallel to a central axis of the torus, and a difference in diameter between φD 1  and φD 2  is accommodated by inserting and withdrawing the moving main-contact  6  within or from the fixed contact  12 , to which the current collecting member  30  has been mounted. In the example shown in FIGS. 4A,  4 B, the notch  42  having a width S 2  is provided obliquely, and a difference in diameter can be accommodated in the same manner as in FIGS. 3A,  3 B. In addition, although not shown, it goes without saying that a similar effect to the above can be obtained in the case where a plurality of notches are provided in the current collecting member  30 . 
     FIG. 8 shows in detail the contact portion  15  of the current collector shown in FIG.  1 . In the related art, contact on actual sliding surfaces occurs partially on a circumference of the contacts due to a difference between outside and inside diameters of the moving contact  13  and the fixed contact  14 . 
     In contrast, with the embodiment, the fixed contact  12  and the moving main-contact  6  interpose therebetween the current collecting member  30  to hold the same, so that an inner periphery of the current collecting member  30  follows and contacts the outer periphery of the moving main-contact  6 . As a result, the non-sliding contact between the current collecting member  30  and the fixed contact  12  occupies a part of a circumference but the sliding contact between the current collecting member  30  and the moving main-contact  6  occupies an entire circumference. 
     It is commonly known that in the case of sliding as compared with the case of non-sliding, a current-carrying performance is extremely degraded to undergo dissolved loss in the contact portion. In order to solve this problem, it is effective to decrease a current density of a current-carrying portion to suppress local temperature rise in a contact portion. In the embodiment, a contact area of the sliding contact portion is greatly enlarged to enable to decrease current density as seen from the comparison between FIG.  7  and FIG. 8, so that even when both current-carrying and sliding are performed simultaneously in a current collector, dissolved loss can be prevented from generating in the sliding portion. As a result, it becomes possible to improve the current-carrying performance and durability of a current collector to extend the service life thereof and enhance reliability thereof, and further to increase the current-carrying capacity for achievement of a large capacity in a current collector. 
     FIGS. 9 and 10 show another embodiment of the invention. 
     With the embodiment shown, the contact portion of a current collecting member  30  and the fixed contact  12 , is formed to have a circular-shaped cross section having a curvature R. FIG. 10 shows a state, in which the moving main-contact  6  is stored in the case where the current collecting member  30  shown in FIG. 9 is used. 
     According to this embodiment, the fixed contact  12  is pressed by the moving main-contact  6 , with a moving main-contact  6  stored in the fixed contact  12 , and the fixed contact  12  is in some cases distorted at an angle θ relative to a horizontal direction, so that the current collecting member  30  formed to be rectangular parallelopiped in cross section is decreased in an area where it contacts with the moving main-contact  6 . However, since that portion of a current collecting member  30 , which contacts with the fixed contact  12 , is formed to have a circular-shaped cross section having a curvature R, the circular shape accommodates distortion of the fixed contact  12  to materialize enlargement of an area where the current collecting member  30  contacts with the moving main-contact  6 , and further there comes out a state, in which the fixed contact  12  and the current collecting member  30  contact stably with each other even when the fixed contact  12  is distorted. 
     FIG. 11 shows a further embodiment of the invention. The construction in the embodiment shown is such that a fixed contact  12   a  is fitted into a moving main-contact  6   a , a current collecting member  30   a  is provided on an outer periphery of the fixed contact  12   a , and the outer periphery of the fixed contact  12   a , on which the current collecting member  30   a  is present, and an inner periphery of the moving main-contact  6   a  slidingly contact with each other to enable carrying current between the both. Such construction is the same in effect as that in the above-mentioned embodiments. 
     In addition, while an explanation has been given to the case where a current collecting member is provided on an inner periphery or outer periphery of a fixed contact, it goes without saying that the current collecting member may be provided on an inner periphery or outer periphery of a moving contact. Also, while a current collecting member is provided on a moving contact or a fixed contact, the same effect is obtained in the case where it is provided on the current collecting member, which is not accompanied by the opening and closing action of the moving contact but only slides. 
     According to the invention described above, contact portions are free from dissolved loss even in an arrangement, in which both fixed and moving contacts slidingly contact with each other, and so there is obtained an effect that durability as well as the current-carrying performance is improved.