US2900476A - Electrical switching apparatus - Google Patents

Electrical switching apparatus Download PDF

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Publication number
US2900476A
US2900476A US651280A US65128057A US2900476A US 2900476 A US2900476 A US 2900476A US 651280 A US651280 A US 651280A US 65128057 A US65128057 A US 65128057A US 2900476 A US2900476 A US 2900476A
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United States
Prior art keywords
switch
contacts
copper
contact
active material
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US651280A
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English (en)
Inventor
Reece Michael Peter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ERA Patents Ltd
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ERA Patents Ltd
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Publication date
Application filed by ERA Patents Ltd filed Critical ERA Patents Ltd
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Publication of US2900476A publication Critical patent/US2900476A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/0203—Contacts characterised by the material thereof specially adapted for vacuum switches

Definitions

  • This invention relates to vacuum switches for alternating current operation and is particularly concerned with such switches suitable for use as contactors in which the contacts have to open and close very frequently.
  • the contacts for example of copper (tungsten and steel are also employed), are formed initially with operating faces which although theoretically flat or domed are actually in contact with one another at a few very small points.
  • the contacts are separated, with the production between them of arcs in the copper vapor emitted from the cathode spots, molten bridges of copper are drawn out between the contacts at these points.
  • each contact comprises a mechanically strong conducting body having in its operating face one or more recesses containing a nonfluid material (i.e; a material which is not fluid when the switch is inoperative) which has a lower arcing voltage than that of the body and which is capable of constituting an adherent conducting film on the operating faces during operations of the switch.
  • a nonfluid material i.e; a material which is not fluid when the switch is inoperative
  • the operating faces would be exposed when the contacts are new, so that these faces come into direct engagement with one another as the contacts are brought together, but during operations of the switch these faces become covered with a film of the material (referred to as the active material) 2 in the recesses. This covering process takes place as follows, assuming that the contacts are new.
  • the cathode spot of the arc drawn between their operating faces splits up into many spots (each with the arcing voltage of the body) and these spots very quickly move about the surfaces of the contacts until one or more of these spots reach the active material in the recesses.
  • the arcing voltage of these particular spots falls to the arcing voltage of the active material, while the remaining spots die out.
  • all the current is transferred to the spots of lower arcing voltage (i.e. those on the active material), and these spots split up and quickly spread over the surface of this active material.
  • the material in the immediate neighborhood of the spots liquifies and evaporates and most is transferred from the recess or recesses containing the cathode spots into a recess in the other contact.
  • the switch is employed to control alternating current, during its many operations as much active material is transferred in one direction from one contact to the other as in the opposite direction, so that little active material is lost from the recesses.
  • Some of the active material moves away from the recesses and is deposited on to the operating faces of the body of the contacts to form the film, while a very small amount is lost completely by passing out of the region between the contacts and collecting on the walls of the envelope in which the switch operates.
  • the film of active material increases in thickness until it reaches a stable value (of the order of 0.01 mm.) at which as much active material is lost from the operating faces (being deposited on the envelope walls or returning to the recesses) as is gained from the material in the recesses. If the film becomes thinner than this stable value for any reason, the cathode spots of the are are found to move very quickly into the region of the recesses and then remain there so that more active material is evaporated from these recesses: this material is then deposited on the operating faces and increases the thickness of the film.
  • the cathode spots are found to move more slowly over the contacts so that more of the active material is evaporated from the operating faces and less from the recesses.
  • the attainment of a stable thickness, with no erosion of the body of either contact ensures, of course, that the same relative movement of the contacts will bring about opening and closing of the switch for very many millions of operations: for example, one contactor has been constructed according to the invention capable of performing 10 operations, which is many times as many as in other known contactors.
  • the bodies must, of course, be mechanically strong enough to withstand such a large number of operations.
  • the active material is chosen partly for its electrical and partly for its mechanical properties. Thus this material must not give rise to over-voltages (by chopping small inductive currents) greater than are allowable in relation to the voltage for which the switch is to be used, and the material must also have a suflicient voltage interrupting ability for the particular switch required: both these properties are related to the arclng voltage of the material (which in turn is related in general to the thermal conductivity of the material and its volatility or boiling point. Since the thermal con- :ductivities of a large number of active materials are of the same order, the differences between different active materials depend to a large extent on their different volatilities).
  • the material must not form an inadherent film (such as would be found if carbon were employed), for the film would be disintegrated and removed by the operation of the switch.
  • Mercury too is not suitable, partly because of its natural fluid state which makes it difficult to retain in the recesses of both contacts, and partly because its great volatility would quickly lead to its being lost from the recesses by evaporation.
  • the active material may be arsenic, bismuth or an amalgam of mercury (the bodies ,of the contacts being made of copper, steel, molybdenum, tungsten or a sintered mixture of copper and tungsten); to interrupt voltages of the order of 3,300 volts, lead, cadmium, sodium or zinc may constitute the active ma terial (the bodies then being of copper, steel, molybdenum, tungsten, aluminium or a sintered mixture of copper and tungsten); for voltages of the order 6,600 volts, the active material may be magnesium or tin (the bodies then being of copper, steel, molybdenum, tungsten or a sintered mixture of copper and tungsten); for voltages of the order of 11,000 volts the active material may be aluminium or silver (the bodies then being of steel, molybdenum or tungsten); and for voltages of the order of 22,000 volts, the active material may be copper (
  • the vacuum in which the switch operates should not have a pressure higher than 10- millimeters of mercury and for voltages above 11,000 volts, this pressure should be less than 10- millimeters of mercury. Rigorous degassing of the'switch is, of course, essential: in particular active materials having high vapor pressures should be vacuum distilled.
  • Figure l is a side elevation, partly in section of the switch
  • Figure 2 is a plan View of the lower contact of the switch
  • Figure 3 is a cross-section of this contact, taken along the line IIIIII of Figure 2;
  • Figure 4 is a corresponding cross-section of the modified form of contact.
  • the envelope in which the switch is housed includes a glass tube 1, two nickeliron alloy tubes 2 and 3 fixed to opposite ends of the tube 1 and a pair of metal end fittings 4 and 5 which are brazed on to the tubes 2 and 3 respectively.
  • the upper fitting 4 is formed with an opening through which a copper stem 6, threaded at both ends, passes into the envelope. This stem 6 is brazed onto the fitting 4, as indicated at 7.
  • a conductor 8 for the alternating current is secured to the stem 6 by nuts 9.
  • the lower fitting 5 is secured by screws 10 to a mounting bracket 11 which is formed with an opening in which is brazed a tube 13 for guiding a reciprocatory copper stem 14.
  • This stem 14 is threaded at both its ends and is reciprocated by conventional mechanism (not shown) through an insulating sleeve 12.
  • the other conductor for 4 alternating current, shown at 15, is secured to the stem 14 by nuts 16.
  • a metal bellows 18 is brazed at one end to the fitting 5 and at its other end to the stem 14.
  • the operating voltage of the contactor depends, of course, on the sizes and the materials of the contacts, which are identical and shown at 25a and 25b.
  • the particular contactor being described is to be employed for frequent interruption of currents up to 300 amperes and for occasional interruption of up to 3000 amperes, and for this purpose the contacts 25 are of cylindrical shape having a diameter of one and one eighth inches.
  • the contactor is to be employed at 3,300 volts, and thus each contact is made up of a mechanically strong steel body 26 (see Figure 3) having in its operating face 28 a number of recesses 29 each containing cadmium, indicated at 30.
  • Each contact 25 is formed with a threaded recess 27 in its rear for screwing onto the stem 6 or 14, and each is retained in position by a split pin 27a.
  • the major part of the cadmium moves back and borth between opposite recesses as the switch is operated, but a little is deposited on the operating face 28 at 28a to form a film which finally attains a stable thickness.
  • An extremely small proportion of the cadmium passes out of the region of the operating faces and collects on the inner surface of a metal ring 31 (see Figure l) which is held in place at the level of the contacts by dimples 32 formed in the glass tube 1.
  • the amount of cadmium lost in this way is exceedingly small partly because the contacts 25 are, never separated by more than a millimeter or so.
  • the recesses may of course be in the form of grooves.
  • a vacuum switch comprising an evacuated envelope, and two contacts mounted in said envelope for movement into and out of engagement with one another to close and open said switch, each of said contacts comprising a mechanically strong body having at least one recess formed within its contact area, and non-fluid conducting material disposed in said recess, the contact bodies being arranged to engage each other in a contact area completely surrounding said recess and exerting pressure on one another through their operating faces on closing of the switch, said contact bodies being formed of a material substantially more refractory than said nonfluid material, and said non-fiuid material having a lower arcing voltage than that of the said bodies and being capable of forming an adherent film on the operating faces of the contact bodies during operations of the switch.
  • each of the contact bodies having at least two recesses, each recess on a contact being arranged directly opposite a recess in the other contact.
  • a switch according to claim 1 for use at 400 volts said non-fluid material being chosen from the group of relatively low arcing voltage materials consisting of arsenic, bismuth and amalgams of mercury, and the contact body being made of a material chosen from the group of relatively high arcing voltage materials consisting of copper, steel, molybdenum, tungsten and a sintered mixture of copper and tungsten.
  • the contact body being made of a material chosen from the group of relatively high arcing voltage materials consisting of copper, steel, molybdenum, aluminium, tungsten and a sintered mixture of copper and tungsten.
  • a switch according to claim 1 for use at 6,600 volts said non-fluid material being chosen from the group of relatively low arcing voltage materials consisting of magnesium and tin, and the contact body being made of a material chosen from the group of relatively high arcing voltage materials consisting of copper, steel, molybdenum, tungsten and a sintered mixture of copper and tungsten.
  • a switch according to claim 1 for use at 11,000 volts said non-fluid material being chosen from the group of relatively low arcing voltage materials consisting of aluminium and silver, and the contact body being made of a material chosen from the group of relatively high arcing voltage materials consisting of steel, molybdenum and tungsten.

Landscapes

  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
US651280A 1956-04-17 1957-04-08 Electrical switching apparatus Expired - Lifetime US2900476A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB345930X 1956-04-17

Publications (1)

Publication Number Publication Date
US2900476A true US2900476A (en) 1959-08-18

Family

ID=10367562

Family Applications (1)

Application Number Title Priority Date Filing Date
US651280A Expired - Lifetime US2900476A (en) 1956-04-17 1957-04-08 Electrical switching apparatus

Country Status (8)

Country Link
US (1) US2900476A (de)
BE (1) BE556719A (de)
CH (1) CH345930A (de)
DE (1) DE1048625B (de)
FR (1) FR1175455A (de)
GB (1) GB835253A (de)
IT (1) IT570073A (de)
NL (1) NL216321A (de)

Cited By (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975254A (en) * 1958-06-25 1961-03-14 Allis Chalmers Mfg Co Spring bearing for vacuumized electric devices
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US2979588A (en) * 1958-12-09 1961-04-11 Jennings Radio Mfg Corp Vacuum switch
US2979587A (en) * 1958-10-28 1961-04-11 Jennings Radio Mfg Corp Vacuum electric switch
US3014107A (en) * 1959-01-02 1961-12-19 Gen Electric Vacuum switch
US3021407A (en) * 1958-09-16 1962-02-13 Jennings Radio Mfg Corp Vacuumized electric switch
US3026394A (en) * 1959-11-10 1962-03-20 Jennings Radio Mfg Corp Vacuumized electric switch
US3038980A (en) * 1959-12-17 1962-06-12 Gen Electric Vacuum-type circuit interrupter
US3089936A (en) * 1960-02-23 1963-05-14 Gen Electric Contact structure for an electric circuit interrupter
US3140374A (en) * 1962-09-20 1964-07-07 Fred H Cole Circuit breaker interrupter
US3151225A (en) * 1960-03-07 1964-09-29 Gerhard W Senlen Shielding means for an electromagnetic electrical contactor
US3163736A (en) * 1961-05-23 1964-12-29 S & C Electric Co High voltage gas type circuit interrupter
US3163734A (en) * 1962-01-26 1964-12-29 Gen Electric Vacuum-type circuit interrupter with improved vapor-condensing shielding
US3182156A (en) * 1961-09-19 1965-05-04 Gen Electric Vacuum-type circuit interrupter
US3194932A (en) * 1963-05-07 1965-07-13 Bell Telephone Labor Inc Contacts for mercury switches including mercury recovery cowls
DE1207989B (de) * 1962-07-17 1965-12-30 Gen Electric Vakuumschalter fuer Wechselstrom
US3234351A (en) * 1961-10-19 1966-02-08 Gen Electric Vacuum devices having arc electrodes free of adsorbed gas and gas-forming constituents
US3270172A (en) * 1961-06-30 1966-08-30 English Electric Co Ltd Switch having an arc stabilizing electrode
DE1226693B (de) * 1962-04-03 1966-10-13 Gen Electric Elektrischer Schalter
US3281563A (en) * 1963-04-23 1966-10-25 Ass Elect Ind Vacuum switch having an improved electrode tip
US3348012A (en) * 1965-02-16 1967-10-17 Ass Elect Ind Contact structure for an electric vacuum switch
US3454811A (en) * 1967-04-18 1969-07-08 Bell Telephone Labor Inc Gas tube surge (overload) protection device
US3485978A (en) * 1965-11-17 1969-12-23 Ass Elect Ind Vacuum switch
US3612795A (en) * 1969-01-09 1971-10-12 Westinghouse Electric Corp Shielding arrangements for vacuum-type circuit interrupters of the two-contact type
US3670129A (en) * 1970-08-17 1972-06-13 Westinghouse Electric Corp Electrical contact members
US3674969A (en) * 1971-08-04 1972-07-04 Honeywell Inc Stainless steel snap acting mechanism with low resistance electrical path
US3783213A (en) * 1972-04-27 1974-01-01 Gen Electric Vacuum type electric circuit interrupter
US3980850A (en) * 1974-12-19 1976-09-14 Westinghouse Electric Corporation Vacuum interrupter with cup-shaped contact having an inner arc controlling electrode
US4061894A (en) * 1976-04-28 1977-12-06 General Electric Company Vacuum-type circuit interrupter with improved protection for bellows
US4147909A (en) * 1976-05-03 1979-04-03 Siemens Aktiengesellschaft Sintered composite material as contact material for medium-voltage vacuum power circuit breakers
US4376235A (en) * 1981-02-12 1983-03-08 Westinghouse Electric Corp. Electrical junction of high conductivity for a circuit breaker or other electrical apparatus
US4384179A (en) * 1981-02-12 1983-05-17 Westinghouse Electric Corp. Stiff flexible connector for a circuit breaker or other electrical apparatus
US4665287A (en) * 1985-11-08 1987-05-12 General Electric Company Shield assembly of a vacuum interrupter
US4695688A (en) * 1986-03-24 1987-09-22 General Electric Company Electrical contact construction
US5903203A (en) * 1997-08-06 1999-05-11 Elenbaas; George H. Electromechanical switch
WO2000058981A1 (de) * 1999-03-29 2000-10-05 Siemens Aktiengesellschaft Schaltkontakt für elektrische schaltgeräte

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1385794A (fr) * 1963-01-30 1965-01-15 Thomson Houston Comp Francaise Perfectionnements apportés à un interrupteur de circuit électrique du type interrupteur à vide
GB1087074A (en) * 1963-07-18 1967-10-11 Ass Elect Ind Improvements relating to vacuum switch contacts
GB1065886A (en) * 1963-10-11 1967-04-19 Ass Elect Ind Improvements relating to vacuum-switch contacts
US3225167A (en) * 1964-03-16 1965-12-21 Gen Electric Vacuum circuit breaker with arc rotation contact means
GB1194674A (en) * 1966-05-27 1970-06-10 English Electric Co Ltd Vacuum Type Electric Circuit Interrupting Devices
DE3215020A1 (de) * 1982-04-22 1983-10-27 Calor-Emag Elektrizitäts-Aktiengesellschaft, 4030 Ratingen Vakuumschalter
DE3528890A1 (de) * 1985-08-12 1987-02-19 Siemens Ag Kontaktstueck

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US550360A (en) * 1895-11-26 Alexander jay wurts
US1556573A (en) * 1921-09-01 1925-10-13 Westinghouse Electric & Mfg Co Thermal relay and cut-out
US1648100A (en) * 1925-04-17 1927-11-08 Aichele Ernest Composition of matter
GB289021A (en) * 1927-04-20 1929-06-26 Ass Telephone & Telegraph Co Improvements in electric contacts
US1875765A (en) * 1927-07-01 1932-09-06 Scherbius Arthur Vacuum switch
US1906602A (en) * 1930-08-06 1933-05-02 Gen Electric Lightning arrester
US2064998A (en) * 1935-08-27 1936-12-22 Otis Elevator Co Switch contact
US2234834A (en) * 1937-10-09 1941-03-11 Westinghouse Electric & Mfg Co Electrical contact
US2253401A (en) * 1937-10-09 1941-08-19 Westinghouse Electric & Mfg Co Circuit interrupter contact
US2294783A (en) * 1940-04-13 1942-09-01 Westinghouse Electric & Mfg Co Contact member
US2370400A (en) * 1941-09-25 1945-02-27 Ite Circuit Breaker Ltd Contact materials
GB591183A (en) * 1944-01-08 1947-08-11 Rene Pointout Improvements in electric contacts
US2641670A (en) * 1950-08-22 1953-06-09 Gibson Electric Company Serrated contact
US2794885A (en) * 1954-12-13 1957-06-04 Jennings Radio Mfg Corp Vacuum switch

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US550360A (en) * 1895-11-26 Alexander jay wurts
US1556573A (en) * 1921-09-01 1925-10-13 Westinghouse Electric & Mfg Co Thermal relay and cut-out
US1648100A (en) * 1925-04-17 1927-11-08 Aichele Ernest Composition of matter
GB289021A (en) * 1927-04-20 1929-06-26 Ass Telephone & Telegraph Co Improvements in electric contacts
US1875765A (en) * 1927-07-01 1932-09-06 Scherbius Arthur Vacuum switch
US1906602A (en) * 1930-08-06 1933-05-02 Gen Electric Lightning arrester
US2064998A (en) * 1935-08-27 1936-12-22 Otis Elevator Co Switch contact
US2234834A (en) * 1937-10-09 1941-03-11 Westinghouse Electric & Mfg Co Electrical contact
US2253401A (en) * 1937-10-09 1941-08-19 Westinghouse Electric & Mfg Co Circuit interrupter contact
US2294783A (en) * 1940-04-13 1942-09-01 Westinghouse Electric & Mfg Co Contact member
US2370400A (en) * 1941-09-25 1945-02-27 Ite Circuit Breaker Ltd Contact materials
GB591183A (en) * 1944-01-08 1947-08-11 Rene Pointout Improvements in electric contacts
US2641670A (en) * 1950-08-22 1953-06-09 Gibson Electric Company Serrated contact
US2794885A (en) * 1954-12-13 1957-06-04 Jennings Radio Mfg Corp Vacuum switch

Cited By (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975254A (en) * 1958-06-25 1961-03-14 Allis Chalmers Mfg Co Spring bearing for vacuumized electric devices
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US3016436A (en) * 1958-07-24 1962-01-09 Gen Electric Vacuum circuit interrupters
US3021407A (en) * 1958-09-16 1962-02-13 Jennings Radio Mfg Corp Vacuumized electric switch
US2979587A (en) * 1958-10-28 1961-04-11 Jennings Radio Mfg Corp Vacuum electric switch
US2979588A (en) * 1958-12-09 1961-04-11 Jennings Radio Mfg Corp Vacuum switch
US3014107A (en) * 1959-01-02 1961-12-19 Gen Electric Vacuum switch
US3026394A (en) * 1959-11-10 1962-03-20 Jennings Radio Mfg Corp Vacuumized electric switch
US3038980A (en) * 1959-12-17 1962-06-12 Gen Electric Vacuum-type circuit interrupter
US3089936A (en) * 1960-02-23 1963-05-14 Gen Electric Contact structure for an electric circuit interrupter
US3151225A (en) * 1960-03-07 1964-09-29 Gerhard W Senlen Shielding means for an electromagnetic electrical contactor
US3163736A (en) * 1961-05-23 1964-12-29 S & C Electric Co High voltage gas type circuit interrupter
US3270172A (en) * 1961-06-30 1966-08-30 English Electric Co Ltd Switch having an arc stabilizing electrode
US3182156A (en) * 1961-09-19 1965-05-04 Gen Electric Vacuum-type circuit interrupter
US3234351A (en) * 1961-10-19 1966-02-08 Gen Electric Vacuum devices having arc electrodes free of adsorbed gas and gas-forming constituents
US3163734A (en) * 1962-01-26 1964-12-29 Gen Electric Vacuum-type circuit interrupter with improved vapor-condensing shielding
DE1226693B (de) * 1962-04-03 1966-10-13 Gen Electric Elektrischer Schalter
DE1207989B (de) * 1962-07-17 1965-12-30 Gen Electric Vakuumschalter fuer Wechselstrom
US3140374A (en) * 1962-09-20 1964-07-07 Fred H Cole Circuit breaker interrupter
US3281563A (en) * 1963-04-23 1966-10-25 Ass Elect Ind Vacuum switch having an improved electrode tip
US3194932A (en) * 1963-05-07 1965-07-13 Bell Telephone Labor Inc Contacts for mercury switches including mercury recovery cowls
US3348012A (en) * 1965-02-16 1967-10-17 Ass Elect Ind Contact structure for an electric vacuum switch
US3485978A (en) * 1965-11-17 1969-12-23 Ass Elect Ind Vacuum switch
US3454811A (en) * 1967-04-18 1969-07-08 Bell Telephone Labor Inc Gas tube surge (overload) protection device
US3612795A (en) * 1969-01-09 1971-10-12 Westinghouse Electric Corp Shielding arrangements for vacuum-type circuit interrupters of the two-contact type
US3670129A (en) * 1970-08-17 1972-06-13 Westinghouse Electric Corp Electrical contact members
US3674969A (en) * 1971-08-04 1972-07-04 Honeywell Inc Stainless steel snap acting mechanism with low resistance electrical path
US3783213A (en) * 1972-04-27 1974-01-01 Gen Electric Vacuum type electric circuit interrupter
US3980850A (en) * 1974-12-19 1976-09-14 Westinghouse Electric Corporation Vacuum interrupter with cup-shaped contact having an inner arc controlling electrode
US4061894A (en) * 1976-04-28 1977-12-06 General Electric Company Vacuum-type circuit interrupter with improved protection for bellows
US4147909A (en) * 1976-05-03 1979-04-03 Siemens Aktiengesellschaft Sintered composite material as contact material for medium-voltage vacuum power circuit breakers
US4376235A (en) * 1981-02-12 1983-03-08 Westinghouse Electric Corp. Electrical junction of high conductivity for a circuit breaker or other electrical apparatus
US4384179A (en) * 1981-02-12 1983-05-17 Westinghouse Electric Corp. Stiff flexible connector for a circuit breaker or other electrical apparatus
US4665287A (en) * 1985-11-08 1987-05-12 General Electric Company Shield assembly of a vacuum interrupter
US4695688A (en) * 1986-03-24 1987-09-22 General Electric Company Electrical contact construction
US5903203A (en) * 1997-08-06 1999-05-11 Elenbaas; George H. Electromechanical switch
WO2000058981A1 (de) * 1999-03-29 2000-10-05 Siemens Aktiengesellschaft Schaltkontakt für elektrische schaltgeräte

Also Published As

Publication number Publication date
NL216321A (de)
CH345930A (fr) 1960-04-30
FR1175455A (fr) 1959-03-26
BE556719A (de)
GB835253A (en) 1960-05-18
DE1048625B (de)
IT570073A (de)

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