Slotted Or Grooved Patents (Class 218/128)
  • Patent number: 11721503
    Abstract: A vacuum interrupter includes: an insulation cylinder; a fixed-side flange; a movable-side flange; a fixed-side electrode rod fixed to the fixed-side flange at one end and having a fixed-side electrode fitting shaft on a fixed-side end surface at another end; a movable-side electrode rod connected to the movable-side flange via a bellows at one end and having a movable-side electrode fitting shaft on a movable-side end surface at another end; a fixed-side windmill-shaped electrode fixed to the fixed-side electrode fitting shaft; and a movable-side windmill-shaped electrode fixed to the movable-side electrode fitting shaft. A fixed-side support member having a fixed-side spacer portion and a fixed-side planar portion is provided between the fixed-side end surface and the fixed-side windmill-shaped electrode, and a movable-side support member having a movable-side spacer portion and a movable-side planar portion is provided between the movable-side end surface and the movable-side windmill-shaped electrode.
    Type: Grant
    Filed: April 16, 2020
    Date of Patent: August 8, 2023
    Assignee: MITSUBISHI ELECTRIC CORPORATION
    Inventor: Masashi Kawada
  • Patent number: 9552941
    Abstract: An electrical contact is for a vacuum switching apparatus. The vacuum switching apparatus includes a second electrical contact. The electrical contact includes a body having a center point and a periphery, the body including a plurality of arcing surfaces structured to face in a first direction toward the second electrical contact and structured to move into and out of engagement with the second electrical contact, and a plurality of arc spinning portions each defining a slot extending inwardly from the periphery generally toward the center point, the plurality of arc spinning portions generally separating the plurality of arcing surfaces from one another. At least one arc spinning portion narrows from a corresponding pair of adjacent arcing surfaces of the body to an interior thereof in a second direction opposite the first direction.
    Type: Grant
    Filed: August 24, 2015
    Date of Patent: January 24, 2017
    Assignee: EATON CORPORATION
    Inventors: Wangpei Li, Martin B. J. Leusenkamp, Franklin Willis Freeborn
  • Patent number: 9208960
    Abstract: An electrode for a vacuum circuit breaker comprises a cylindrical conducting body, a contact electrode as a combination electrode, and a plurality of slits provided on a surface area of the cylindrical conducting body, the slits being inclined with respect to an axial direction of the cylindrical conducting body, wherein an angle between the slits and the axial direction of the cylindrical conducting body is smaller as the slit becomes farther away from the contact electrode.
    Type: Grant
    Filed: April 21, 2014
    Date of Patent: December 8, 2015
    Assignee: HITACHI, LTD.
    Inventors: Kunihiko Tomiyasu, Hiroyuki Shirai, Takashi Sato, Masato Kobayashi
  • Publication number: 20140367362
    Abstract: An electrode for a vacuum circuit breaker comprises a cylindrical conducting body, a contact electrode as a combination electrode, and a plurality of slits provided on a surface area of the cylindrical conducting body, the slits being inclined with respect to an axial direction of the cylindrical conducting body, wherein an angle between the slits and the axial direction of the cylindrical conducting body is smaller as the slit becomes farther away from the contact electrode.
    Type: Application
    Filed: April 21, 2014
    Publication date: December 18, 2014
    Applicant: Hitachi, Ltd.
    Inventors: Kunihiko TOMIYASU, Hiroyuki SHIRAI, Takashi SATO, Masato KOBAYASHI
  • Patent number: 8288674
    Abstract: A copper-based winding implementing a copper-based winding of diameter that is typically greater than 90 mm, designed to generate a magnetic field in an electrical contact for a medium-voltage vacuum circuit-breaker. The winding is constituted by a hollow cylinder including helical slots about its longitudinal axis and opening out both into the hollow and to the exterior of the cylinder, winding in which the space between two consecutive slots that form a turn is empty of material and the width of each initial slot is less than 1 mm.
    Type: Grant
    Filed: June 2, 2010
    Date of Patent: October 16, 2012
    Assignee: Areva T&D SAS
    Inventors: Saïd Kantas, Bruno Berthon, Cédric Triaire
  • Patent number: 8269127
    Abstract: Disclosed is a tulip contacting device for a vacuum circuit breaker employed to quickly break off an electric power system, in which contact fingers are bidirectionally rotatable in a state of being restricted at an outer diameter portion of a mover holder, such that the flexibility of the contact fingers can be increased, whereby it is possible, upon connecting the vacuum circuit breaker to a case, to flexibly deal with the variation of axial angles of terminals inserted in both sides of the tulip contacting device, and also springs may be coupled to the contact fingers, respectively, so as to effectively prevent separation and overall destroy of the contact fingers from the mover holder during installation.
    Type: Grant
    Filed: November 19, 2009
    Date of Patent: September 18, 2012
    Assignee: LS Industrial Systems Co., Ltd.
    Inventor: Jae-Kwan Seo
  • Publication number: 20120091102
    Abstract: According to the present invention, there is disclosed a contact of the vacuum interrupter, comprises a plurality of slot portions formed in an extended manner toward an outer circumferential surface from a plurality of positions, respectively, spaced apart from the center of a contact surface, and a petal portion formed between a pair of the adjacent slot portions, and to minimize a mechanical fragile part having a narrow width in the petal portion while inducing the rotational movement of an arc, each of the slot portion comprises a first end portion closed and adjacent to the center, a second end portion open and adjacent to the outer circumferential surface, a first slot portion linearly extended from the first end portion, and a second slot portion linearly extended to the second end portion by bending the first slot portion at a predetermined angle.
    Type: Application
    Filed: October 18, 2011
    Publication date: April 19, 2012
    Inventors: Sung Tae Kim, Byung Chul Kim
  • Patent number: 7721428
    Abstract: An electrode assembly for use in a vacuum interrupter is made by joining a first side of a substantially disk-shaped structure to an end of a substantially cylindrical coil segment, and joining an electrical contact to a second side of the disk-shaped structure. The disk-shaped structure has a higher resistivity than a resistivity of the coil segment.
    Type: Grant
    Filed: September 26, 2005
    Date of Patent: May 25, 2010
    Assignee: Cooper Technologies Company
    Inventors: Paul N. Stoving, E. Fred Bestel
  • Patent number: 7662208
    Abstract: An electrical contact used herein comprises chromium; one of copper and silver; and a carbide, in which the electrical contact comprises a matrix and chromium, the matrix phase mainly comprising one of copper and silver, and the chromium being surrounded by the carbide and dispersed in the matrix. The electrical contact contains 1 to 30 percent by weight of a carbide, with the balance being copper. Another electrical contact contains chromium, copper, and a carbide and has a weight ratio of chromium to the carbide within the range of 1:1.5 to 1:50.
    Type: Grant
    Filed: July 6, 2006
    Date of Patent: February 16, 2010
    Assignee: Hitachi, Ltd.
    Inventors: Shigeru Kikuchi, Ayumu Morita, Masato Kobayashi, Satoru Kajiwara, Noboru Baba
  • Publication number: 20080197114
    Abstract: A contact configuration for a vacuum switch includes cup-shaped contacts, which are movable one after another in a longitudinal direction and provided with slots for producing a radial magnetic field. A contact carrier whose side wall is provided with a front surface faces the opposite contact and a bottom section. Each contact has at least partially erosion-resistant contact elements, which cover at least the front surface and the internal bottom surface of the bottom section of the contact carrier facing the opposite contact.
    Type: Application
    Filed: May 31, 2006
    Publication date: August 21, 2008
    Applicant: SIEMENS AKTIENGESELLSCHAFT
    Inventors: Nils Anger, Roman Renz, Andreas Stelzer
  • Patent number: 7250584
    Abstract: The aim of the invention is to prevent local spikes from being created in a contact element of a contact arrangement used for interrupting a current in a distribution network, said contact element comprising a contact support (8) that encompasses a hollow cylindrical wall section (9) and a bottom wall (10), and a contact disk (11) which is located opposite the bottom wall (10) in a longitudinal direction while slots (2) are provided for generating a magnetic field. Said aim is achieved by providing the slots (2) with rounded edges (3) having a defined radius.
    Type: Grant
    Filed: October 13, 2003
    Date of Patent: July 31, 2007
    Assignee: Siemens Aktiengesellschaft
    Inventors: Caspar Asmus, Klaus Oberndörfer, Roman Renz
  • Patent number: 7041929
    Abstract: The invention relates to a contact arrangement for a vacuum switch tube for low-voltage power switches. The aim of the invention is to reduce the contact force required to control short circuit currents. To this end, a twin-contact contact arrangement is used wherein every contact comprises a plurality of separate individual contacts having a defined spring rate. At least one of the contact bodies (4) is configured as a two-layer spiral contact with a lower layer consisting of a highly elastic material and an upper layer (7) consisting of a highly electroconductive material. A contact coat (9) consisting of a contact material is provided on the upper layer in the outer zone of every contact arm (10).
    Type: Grant
    Filed: November 27, 2001
    Date of Patent: May 9, 2006
    Assignee: Siemens Aktiengesellschaft
    Inventors: Johannes-Gerhard Banghard, Klemens Fieberg, Michael Hahn, Werner Hartmann, Roman Renz
  • Patent number: 6870118
    Abstract: A contact for a vacuum interrupter, includes: 1) a contact plate; and 2) a contact carrier. The contact carrier includes: a first end face which is fitted with the contact plate, and a peripheral face which is formed with a slit portion in such a manner as to form a coil part. The coil part flows a current such that a longitudinal magnetic field is formed in an axial direction of the contact carrier. The first end face fitted with the contact plate is formed with a circumferential slit portion which connects to the slit portion.
    Type: Grant
    Filed: December 17, 2003
    Date of Patent: March 22, 2005
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Akira Nishijima, Hidemitsu Takebuchi, Yoshihiko Matsui, Takaaki Furuhata
  • Patent number: 6765168
    Abstract: An electrode of a vacuum circuit breaker has a cup member and a contact. The cup member has an opening and a periphery which is formed with a slit so as to form a coil section. An electric current flows in the coil section so as to generate a longitudinal magnetic field in a direction along an axis of the cup member. The slit is bent and continuously extends on the periphery from a first end of the cup member to a second end of the cup member opposite to the first end of the cup member. The contact is shaped into a plate, and seals the opening of the cup member.
    Type: Grant
    Filed: February 27, 2002
    Date of Patent: July 20, 2004
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Hidemitsu Takebuchi, Yoshihiko Matsui, Akira Nishijima, Yoshihiro Fukatsu
  • Patent number: 6740838
    Abstract: A contact and a vacuum interrupter using the contact. The contact includes a hollow cylindrical contact carrier and a contact plate disposed on one of the axial end faces of the contact carrier. First slits and second slits extend from the one of the axial end faces of the contact carrier and the other thereof, respectively. The first slits and the second slits are inclined with respect to the center axis of the contact carrier and have a first height x and a second height y extending in the axial direction of the contact carrier, respectively. Assuming that the axial length of the contact carrier is 1, the first height x and the second height y satisfies a relationship given by the following expressions (1)-(3): (1) 0.9≧x, (2) x≧y≧0.2x, (3) 1.4≧x+y≧0.8.
    Type: Grant
    Filed: August 15, 2003
    Date of Patent: May 25, 2004
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Yoshihiko Matsui, Hidemitsu Takebuchi, Akira Nishijima
  • Patent number: 6686552
    Abstract: A contact for a vacuum interrupter, includes: 1) a contact plate; and 2) a contact carrier. The contact carrier includes: a first end face which is fitted with the contact plate, and a peripheral face which is formed with a slit portion in such a manner as to form a coil part. The coil part flows a current such that a longitudinal magnetic field is formed in an axial direction of the contact carrier. The first end face fitted with the contact plate is formed with a circumferential slit portion which connects to the slit portion.
    Type: Grant
    Filed: September 11, 2002
    Date of Patent: February 3, 2004
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Akira Nishijima, Hidemitsu Takebuchi, Yoshihiko Matsui, Takaaki Furuhata
  • Patent number: 6649855
    Abstract: In a contact arrangement and a vacuum interrupter using the contact arrangement, the contact arrangement includes: a hollow cylindrical contact carrier on one end surface of which a contact plate is attached; a plurality of first slits formed on the contact carrier from the one end surface of the contact carrier; and a plurality of second slits formed on the contact carrier from each predetermined point of midway through an axial direction of the contact carrier, each of the first and second slits being tilted with respect to the axial direction of the contact carrier, a coil portion being formed on a portion of the hollow cylindrical contact carrier between each of the first and second slits and an adjacent one of the first and second slits and a longitudinal magnetic field being formed along the axial direction of the contact carrier by a current flowing on the coil portion.
    Type: Grant
    Filed: September 11, 2002
    Date of Patent: November 18, 2003
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Akira Nishijima, Hidemitsu Takebuchi, Yoshihiko Matsui
  • Patent number: 6639169
    Abstract: A contact and a vacuum interrupter using the contact. The contact includes a hollow cylindrical contact carrier and a contact plate disposed on one of the axial end faces of the contact carrier. First slits and second slits extend from the one of the axial end faces of the contact carrier and the other thereof, respectively. The first slits and the second slits are inclined with respect to the center axis of the contact carrier and have a first height x and a second height y extending in the axial direction of the contact carrier, respectively. Assuming that the axial length of the contact carrier is 1, the first height x and the second height y satisfies a relationship given by the following expressions (1)-(3): (1) 0.9≧x, (2) x≧y≧0.2x, (3) 1.4≧x+y≧0.
    Type: Grant
    Filed: September 11, 2002
    Date of Patent: October 28, 2003
    Assignee: Kabushiki Kaisha Meidensha
    Inventors: Yoshihiko Matsui, Hidemitsu Takebuchi, Akira Nishijima
  • Patent number: 6541726
    Abstract: A vacuum cartridge, in particular for an electrical protection apparatus such as a switch or circuit breaker, comprising an enclosure of appreciably cylindrical shape closed by two end-plates, two contacts extending axially inside the enclosure, at least one of which contacts called the movable contact is connected to an operating mechanism and is slidingly mounted between a closed position of the contacts corresponding to a rest position of the apparatus and a position in which the arcing contacts are separated and form an electric arc between them, separation of the contacts resulting in breaking of the electrical circuit, and a means for producing an axial magnetic field for diffusion of the arc in the arc formation area. The cartridge comprises means for speeding up cooling of the contact material in liquid form flowing on the contact surface of said arcing contacts during breaking.
    Type: Grant
    Filed: April 10, 2001
    Date of Patent: April 1, 2003
    Assignee: Schneider Electric Industries SA
    Inventors: Hans Schellekens, Denis Giraud, Serge Olive, Christophe Arnaud
  • Patent number: 6506992
    Abstract: A vacuum interrupter for a vacuum breaker, by which melting on contact surface caused by are concentration when a large current is broken and the arc can be rapidly extinguished by forming a strong magnetic field in vertical direction same as the arc when electrodes are separated, comprises: a vacuum container; a stationary cylinder electrode fixed on upper part of the vacuum container so as to be sealed; a movable cylinder electrode disposed on lower part of the vacuum container so as to be moved in vertical direction; and a stationary contact assembly and a movable contact assembly respectively connected to the stationary cylinder electrode and to the movable cylinder electrode for inducing electric current to be rotated to one direction and forming a compounded vertical magnetic field.
    Type: Grant
    Filed: October 15, 2001
    Date of Patent: January 14, 2003
    Assignee: LG Industrial Systems Co., Ltd.
    Inventor: Sung IL Kim
  • Patent number: 6479779
    Abstract: A vacuum switching device comprising an evacuated envelope including an insulating cylinder, a stationary contact electrode and a movable contact electrode housed within the envelope. The electrodes are adapted to be engaged or disengaged to close or open a circuit in which the device is connected. At least one of the electrodes comprises a coil which, in use, is adapted to generate magnetic fields to control the formation of arcs when the electrodes are disengaged, each electrode having an end face adapted to contact the other electrode when in the engaged condition. At least one of the electrodes has a low resistance electrical path transverse to the axis of the electrode in a region of the end face.
    Type: Grant
    Filed: October 5, 2001
    Date of Patent: November 12, 2002
    Assignee: Alstom UK Limited
    Inventors: Leslie Falkingham, Rama Parashar
  • Patent number: 6426475
    Abstract: The flux density Bct is applied at the center area of the electrode. The flux density Bct is adjusted within the range A of 0.75 to 0.9 times greater than the axial flux density Bcr which gives the lowest arc voltage between the electrodes against each breaking current. The axial flux density monotonously increases from the center to the circumferential area of the electrode. Here, the radial position where the axial flux density Bcr which gives the lowest arc voltage Vmin is adjusted within the region B of 20% to 40% of the radius of the electrode. The axial flux density is made monotonously increase in an outer area from the region B and give the maximum value Bp in a circumferential area equal to or beyond 70% of the radius of the electrode. The maximum value Bp is adjusted within the range C of 1.4 to 2.4 times greater than the flux density Bct given at the electrode center.
    Type: Grant
    Filed: June 14, 2001
    Date of Patent: July 30, 2002
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Kenji Watanabe, Kumi Uchiyama, Kiyoshi Kagenaga, Junichi Sato, Eiji Kaneko, Mitsutaka Honma, Hiromichi Somei
  • Patent number: 6163002
    Abstract: The present invention relates to an interrupter for a circuit breaker for a transmission or distribution line which can distribute and weaken an arc resulting from separation of contacts, can reduce loss of the contacts by the arc, and can improve interruption performance, when an abnormal current such as overcurrent is generated. A plurality of horizontal loops of conductive path are formed on a fixed electrode and a movable electrode, thereby forming a plurality of vertical magnetic fields in parallel with a generation direction of the arc. When the arc is generated between a fixed contactor and a movable contactor respectively connected to the fixed electrode and the movable electrode, the arc can be evenly distributed on the fixed and movable contactors. At the same time, a movement of the arc can be interrupted.
    Type: Grant
    Filed: July 16, 1999
    Date of Patent: December 19, 2000
    Assignee: LG Industrial Systems Co., Ltd.
    Inventors: Hee Il Ahn, Hong Tae Park
  • Patent number: 6140599
    Abstract: A contact configuration for vacuum switches includes two mutually opposite switch parts having a predetermined radius R.sub.K. Each switch part has slots which proceed from a center and which extend outward to form a spiral contact. The contours of the slots have a variable radius with a foot which coincides with the center of the switch part. Preferably, the slots end at a recess which has a predetermined radius R.sub.I and lies at the center of the switch part or they slightly overlap the recess, where R.sub.I .apprxeq.0.25-0.33 .multidot.R.sub.K. Specific mathematical functions can be specified for the slot contours.
    Type: Grant
    Filed: December 21, 1998
    Date of Patent: October 31, 2000
    Assignee: Siemens Aktiengesellschaft
    Inventor: Wilfried Haas
  • Patent number: 6072141
    Abstract: A vacuum circuit-breaker contact arrangement includes a pair of contacts each being relatively axially movable from a position of engagement to a position of disengagement to establish a circuit interrupting arc therebetween, at least one of said contacts being provided with a generally cup shaped member having a base portion and a wall portion, a plurality of slots which produce winding sections being arranged in said cup shaped member, the inside of the cup shaped member being at least partly covered by a contact- and electrode-member mounted at a front side of the cup shaped member and facing the other contact, the other contact having a contact- and arc-carrying-member generally aligned with the contact- and electrode-member of the at least one contact, wherein the plurality of slots includes at least one first slot and a second slot, the base portion of at least one contact being provided with at least one first slot which essentially extends along a part of a circle and penetrates at least partly the ba
    Type: Grant
    Filed: June 23, 1997
    Date of Patent: June 6, 2000
    Inventor: Ernst Slamecka
  • Patent number: 5952636
    Abstract: In a vacuum type switch gear device an L shaped stationary and movable conductors arrangement, a transitive portion from one spiral arc groove to a neighboring another spiral arc groove on the surface of a movable electrode defined by the terminating end portion of the one spiral groove, the starting end of the adjacent neighboring other spiral groove and the outer circumferential edge portion of the movable electrode is arranged in a substantially overlapping relationship in a vertical direction with the movable conductor. Thus an adverse effect of a current loop flowing through the movable conductor against an arc generated between movable and stationary electrodes is limited to thereby improve the circuit breaking performance.
    Type: Grant
    Filed: June 25, 1998
    Date of Patent: September 14, 1999
    Assignees: Hitachi, Ltd., The Tokyo Electric Power Co., Ltd.
    Inventors: Ayumu Morita, Takashi Sato, Youichi Ohshita, Tooru Tanimizu, Masayoshi Hayakawa, Toshio Horikoshi, Ryutaro Yamamoto
  • Patent number: 5852266
    Abstract: According to the present invention there are provided a highly reliable electrode of high strength which undergoes little change even with the lapse of time, and a method for making the same, as well as a vacuum valve using such electrode and a vacuum circuit breaker using such vacuum valve. The vacuum circuit breaker has a fixed electrode and a movable electrode, each comprising an arc electrode, an arc electrode support member for supporting the arc electrode, and a coil electrode contiguous to the arc electrode support member, the arc electrode, the arc electrode support member and the coil electrode being formed as an integral structure by melting, not by bonding, particularly the arc electrode support member and the coil electrode being constituted by a Cu alloy containing 0.05-2.5% by weight of at least one of Cr, Ag, W, V and Zr.
    Type: Grant
    Filed: May 5, 1997
    Date of Patent: December 22, 1998
    Assignee: Hitachi, Ltd.
    Inventors: Katsuhiro Komuro, Yoshitaka Kojima, Yukio Kurosawa, Yoshio Koguchi, Toru Tanimizu, Yoshimi Hakamata, Shunkichi Endo
  • Patent number: 5804788
    Abstract: A vacuum interrupter includes a pair of separable electrode assemblies within a vacuum envelope, each electrode assembly including a contact confronting the contact of the other electrode assembly and an electrode coil assembly located behind the contact for generating a magnetic field in a region between the contacts. The electrode coil assembly, which is energized by an a.c. current in the interrupter, includes a generally annular-shaped member having a plurality of slots extending radially between a peripheral surface and an interior surface, the slots defining a substantially circumferential current path. The slots include an axially extending slot and a circumferentially extending slot that define a coil. The electrode coil member is connected in series between a terminal post and the contact of the electrode assembly. The electrode coil assembly also can include a tubular support for the contact.
    Type: Grant
    Filed: February 18, 1997
    Date of Patent: September 8, 1998
    Assignee: Eaton Corporation
    Inventor: Robert Kirkland Smith
  • Patent number: 5763848
    Abstract: An electrode for a vacuum circuit breaker provided with a connecting portion made of a material having the same resistivity as the arc running face portions across the corresponding arc guiding channel at the outer circumferential end thereof, wherein when the outer diameter of the connecting portion is D.sub.1 and the inner diameter of the connecting portion is D.sub.2, the width of the connecting portion is designed so that the ratio D.sub.2 /D.sub.1 is in a range of more than 0.9 and less than 1.0. An arc generated between the electrodes is magnetically driven over the arc running face portions via the connecting portion so that the current interrupting capacity of the electrode is increased and the size and weight of the electrode are reduced.
    Type: Grant
    Filed: April 23, 1996
    Date of Patent: June 9, 1998
    Assignee: Hitachi, Ltd.
    Inventors: Yoshimi Hakamata, Toru Tanimizu, Masato Kobayashi, Hitoshi Okabe, Katsuhiro Komuro, Akira Wada
  • Patent number: 5691522
    Abstract: An axial magnetic field vacuum interrupter includes a field producing structure associated with only one of two opposing electrode assemblies. The field producing structure is characterized in that when the instantaneous peak arc current is I.sub.m, measured in kiloamperes, and the electrode assemblies are in the open circuit position, the instantaneous component of the axial magnetic filed (AMF) B in the axial direction B.sub.a, measured in milliteslas, imposed on the majority of each electrode contact surface is given by the analytical expression.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: November 25, 1997
    Assignee: Eaton Corporation
    Inventors: Michael Bruce Schulman, Paul G. Slade
  • Patent number: 5612523
    Abstract: A portion of a highly conductive metal member is infiltrated in voids of a porous high melting point metal member, and both the metal members are integrally joined to each other. An arc electrode portion 13 is formed of a high melting point area 11 in which the highly conductive metal is infiltrated in voids of the high melting point metal member. A coil electrode portion 14 is formed by hollowing out the interior of a highly conductive metal area 12 composed only of highly conductive metal and by forming slits 15 to 17 thereon. A rod 18 is hard-brazed on the rear surface of the coil electrode portion 14. With this electrode, it is possible to reduce the number of parts, and to omit the brazing portion between the arc electrode portion 13 and the coil electrode portion 14 for lowering the electric resistance and thereby the calorific value.
    Type: Grant
    Filed: March 7, 1994
    Date of Patent: March 18, 1997
    Assignee: Hitachi, Ltd.
    Inventors: Yoshimi Hakamata, Toru Tanimizu, Akira Osaka, Katsuhiro Komuro