Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3086094 A
Publication typeGrant
Publication dateApr 16, 1963
Filing dateFeb 24, 1958
Priority dateFeb 24, 1958
Publication numberUS 3086094 A, US 3086094A, US-A-3086094, US3086094 A, US3086094A
InventorsOvshinsky Herbert C
Original AssigneeTann Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Magnetic switching device
US 3086094 A
Abstract  available in
Images(4)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

April 16, 1963 H. C. OVSHINSKY MAGNETIC SWITCHING DEVICE q H 4 m 5 N E mm M 2 G n w 0 g m l 2 3 l 5 W m 4 Q 3 II :1 a 1 W l fi 2 M w; v III. III e m 3% III I M, Q m f w. IIMI III 2 m T I m L F A. 0/

April 16, 1963 H. c. OVSHINSKY MAGNETIC SWITCHING DEVICE 4 Sheets-Sheet 2 Filed Feb. 24, 1958 April 16, 1963 H. c. OVSHINSKY 3,036,094

MAGNETIC SWITCHING DEVICE Filed Feb. 24, 1958 4 Shasta-Sheet 3 W Yf ca -7 7TdF/YEY5,

4 Sheets-Sheet 4 firm/Mfrs,

April 16, 1963 Filed Feb. 24, 1958 nited States Patent 3,086,694- MAGNE'IIC SWITCHING DEVIIIE Herbert C. Qvshinslty, Oak Park, Mich, ascignor to Tana Corporation, Detroit, Mich, a corporation of Michigan Filed Feb. 24, 1958, No. 717M7 2? 7 Qlaims. Cl. 200-87) This invention relates to an improved magnetic switching device, and more particularly to such a device in which a free-floating contact member is employed to positively break and make a current with a pair of electrical contact members.

In an electrical switch according to the present invention, a conductive ball confined for limited travel within a chamber is magnetically drivable into bridging engagement with a pair of spaced electrical contacts disposed within or adjacent to one end of the chamber. A pair of washerlike members confines the ball to limited movement on the end of an armature by which the ball is positively moved. The limited movement of the ball permits it to index and presents a new, randomly selected portion of its surface to the contacts each time the switch is actuated, thereby distributing wear evenly over the entire surface of the ball. In its various forms, the switch may be energized by a solenoid coil or by an externally mounted magnet, and it may be of either the normally open or normally closed type.

The principal objects of the present invention are: to provide an improved magnetically actuatable electrical switch; to provide an improved magnetically operatable electrical switch having either a rapid action or a time delay characteristic; to provide an improved magnetically operatable electrical switch in which a freely floating but captured ball is positively moved to and from engagement with a pair of electrical contacts; to provide an improved electrical switch of the type in which a movable conductive member changes its point of engagement with a pair of fixed electrodes when completing a circuit thereacross; to provide a movable ball on the end of a magnet so as to move therewith while being movable relative thereto so that difierent surface areas thereof engage the electrodes on successive actuations of the switch; to provide an improved proximity-type limit switch of either the normally open or of the normally closed type which is positively actuated by a magnet carried by a movable member of a machine or the like; and, in general, to provide an improved magnetically operatable electrical switch which is of simple and rugged construction, positive in operation, and economical of manufacture.

Other objects and features of novelty of the invention will be specifically pointed out, or will become apparent when referring, for a better understanding of the invention, to the following description, taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is an elevational view of a magnetically operatable electrical switch according to one embodiment of the invention;

FIG. 2 is a plan view of the switch illustrated in FIG. 1;

FIG. 3 is a sectional view of the switch illustrated in FIG. 1, taken along the line 3-3 thereof;

FIG. 4 is a broken sectional view of structure, similar to that illustrated in FIG. 3, showing another form thereof;

FIG. 5 is a broken sectional view of structure similar to that illustrated in FIG. 1, showing another form which the invention may assume;

FIG. 6 is a sectional view of the structure illustrated in FIG. 5, taken along the line 6-6 thereof;

FIG. 7 is a sectional view of structure similar to that illustrated in FIG. 1, showing still another form of the invention;

$386,994 Patented Apr. 16, 1963 FIG. 8 is a sectional view of structure, similar to that illustrated in FIG. 1, showing a further form which the invention may assume;

FIG. 9 is a side elevational view of the structure illustrated in FIG. 8;

FIG. 10 is a sectional view of the structure illustrated in FIG. 8, taken along the line 9--9 thereof;

FIG. 11 is a view of structure similar to that illustrated in FIG. 8, showing another form of the invention; and

FIG. 12 is a side view of the structure illustrated in FIG. 11.

A switch 20 manufactured in accordance with an embodiment of the invention is of the relay type, being solenoid energized to close the circuit and magnetically retained in open position. The operative parts of the switch are mounted upon a base 22; which may be secured upon any convenient support 24, such as a wall or a control panel. A pair of switch contacts 26 are mounted at one end of conductive spring fingers 28, the opposite ends of which are fixed to the base 22, the opposite ends having screws or other means for securing a pair of conductors 30, of an external circuit to be controlled. The faces of the contacts 26 are positioned at an angle to each other and are centered about the upper end of the axis of a solenoid coil 32.

The solenoid coil 32 is preferably encased within a top and bottom shield 34 and 35 forming a flux path. The bottom shield 35 has a cylinder element 39 secured thereon to enclose a spring 37. Spring clips 36 are fixed to the base 22. and are shaped and positioned to engage the shield 34, and cylinder element 39 and retain the coil 32 in alignment with the contacts 26. The coil 32 is wound upon an insulating spool 38, having an upwardly extending conical portion 40 which separates the contacts 26 and provides an abutment rest therefor.

A magnetic, magnetizable or a nonmagnetizable electrically conductive ball 42 is movable within the bore 44 of the spool 38 by the solenoid plunger '46 to which it is secured by the washerlike elements 47 attached to the end of the plunger. The ball is loosely confined by the elements 47 so that it is free to change its position when it engages the inner surface of a spool 38 during the reciprocation of the plunger 46 to change the points at which the ball engages the contacts 26. The plunger 46 is held in its lower position when the coil 32 is deener-gized by a magnet 48 which is mounted upon the base 22 to project outwardly beneath the plunger. The plunger 46 has a magnetizable plate 50 secured to the lower end which engages the bottom of the flux shield 35, when the plunger is raised, and which is engaged by the magnet 48 when the plunger is in lowered position. The ball 42, being free to rotate, presents a new, randomly selected area to the contacts 26 each time the plunger is moved upwardly, which assures even distribution of wear on the ball, especially with regard to the effects of contact friction and arcing.

In operation, when the coil 32 is energized, the plunger 46 is drawn upwardly, moving the ball '42 into pressure engagement with the contacts 26, springing the contacts slightly outwardly and rubbing the ball across the surfaces of the contacts with a wiping and cleaning action. When thereafter the coil 32 is deenergized, the plunger 46' moves down and positively moves the ball therewith, the movement being aided by the magnet 48 which produces a quick separation of the ball from the contacts.

The ball 42 may be made entirely of a good electrical contact material such as silver, copper and the like, or, alternatively, in the interest of greater economy it may have only a surface layer of such contact material and a hollow or solid core of less expensive material of metal, plastic or the like including a material resisting the pas- 3 sage of current, to control the flow thereof through the device.

As shown in FIG. 3, the insulating spool 38 and the coil 32 wound thereon are enclosed by the flux path shields 34. This arrangement may be modified, if desired, as illustrated in FIG. 4, by fitting an insulating tube 54 between the solenoid coil 32 and the flux path shields 34 to provide further protection for the coil.

It is apparent that the magnet 48 provides a force in addition to that of the spring 37 to retard the upward movement of the armature 46 in response to the energizetion of the coil 32. This provides a time delay action so that the switch does not respond immediately to energization of the coil. This time delay action may also be provided by other devices, such as suction cups, as illustrated in FIGS. and 6, by way of example and not limitation. A shaft 56 is secured to the plunger 46' and extends downwardly therefrom in a position to support a disc 58 on its lower end for universal movement. The disc 58 is loosely fitted within a cup 60 which is mounted beneath the coil 32 for rotational adjustment through a thread engagement with a supporting sleeve 61. The bottom of the cup 60 and the bottom of the disc 58 are complementarily shaped, each being provided with a pair of oppositely raised quadrant sectors 6'4 and 66, respectively, so that changes in their relative angular positions effect changes in the area of surface contact between them. The cup 6t) contains oil to a depth to be above the level of the contacting surfaces of the sectors *64 and 66 which are machined to be perfectly fiat. The oil wets the contacting surfaces and creates an adhesive force between them to delay the response of the plunger 46 when the solenoid coil is energized and to provide a snap action closing at the end of the delay period.

The time delay may be varied by rotating the cup 60 to adjust the contact area of the sectors and the total adhesive force produced thereby. The disc 58 is universally tiltable on the rod 5 6 which is fixed to the plunger 46', the plunger containing a slot 68 in which a projection '69 of the shield 34 extends to retain the plunger against rotation. A spring detent finger '71 is mounted on the sleeve 61 for engaging the annular row of corruga tions on the cup 60 to hold it in the selected position after adjustment. 'It will be appreciated, of course, that the time delay device employing the surface tension principle is illustrated only by way of example, and that many other time delay mechanisms including the suction and magnetic devices, may be used to delay the bridging of the contacts 26 for any predetermined time after energization of the coil 32.

A proximity switch 72 according to another embodiment of the invention is illustrated in FIG. 7. The switch includes a solenoid coil 32 which when energized actuates a plunger 73 of magnetizable material to move a nonmagnetic conductive ball 42 into engagement with a pair of contacts 74. The contacts are mounted upon relatively stiff movable conductors 75 of magnetic material which are connected to conductors 30 of a circuit which is to be controlled. The contacts 74 are positioned within the bore of the spool 76 and are biased in a downward direction toward the ball 42 by individual springs 77. The springs are illustrated as being of the compression coil type mounted about the conductors between an insulating cover plate '78 through which the conductors extend and washers 79 or the conductors 75 medially of the lengths thereof.

The exterior portions of the conductors 75 are of substantial width to present a relatively large area to the field of an actuating magnet 81 which is mounted for travel toward and away from the top of the switch. Normally, the conductors 75 rest against the cover plate 78 and support the contacts 74 in a position to be engaged by the ball '42 when it is moved upwardly by the plunger 73 in response to energization of the coil 32. When the magnet 81 approaches the conductors 75, the latter are attracted and are moved away from the cover plate 73, moving the contacts 74 upwardly out of reach of the ball 42, and thereby opens the circuit through the conductors 36. When the magnet 81 moves away from the device, the biasing springs 77 return the contacts 74 into engagement with the ball 42 if it is in raised position, thus completing the circuit. The circuit is completed across the contacts 74 when the coil 32 is energized and the magnet 31 has not attracted the conductors 75 against the bias of the springs 77. Thus, a circuit can be completed when the coil 32 is energized and the magnet 81 is remote from the switch and can be broken when the magnet 81 overcomes the bias of the springs 77 or when the coil 32 is de-energized.

The plunger 73 has the washerlike elements 47 confining the ball 42; and is provided with an enlarged head 82. at its lower end. An angle bracket 83 engages the bottom of the head 82 and limits the downward movement of the plunger 73 and the separation of the ball 42 from the contacts 74.

Referring to FIGS. 8, 9 and 10, a further form of the device is illustrated, that wherein housings 84 are made in two similar halves containing coils 85, connected to terminals 86 which extend from opposite faces of the housings. The upper and lower half of the housing contains a U-shaped magnet 37 in its end and a plunger 83 which extends through the center of the coil. The plungers are joined together by a pair of rectangular plates 89 having a pair of apertures t} therein which loosely confine a pair of balls 91, as clearly illustrated in FIG. 9. The plates 89 are made of insulating material and are provided with aligned studs 92 which are screwed into apertures in the plungers 88. The plungers 88 have enlarged heads 93 which complete the flux path through the adjacent magnet 37 and produce the rapid separation of the balls from the contacts 94 or 95 as the case may be. The contacts are mounted on spring fingers $6 in each half of the housing, the projecting ends 98 forming terminals to which the conductors of a circuit are connected. The housing is split on the center line to permit the assembly of the balls 91, the plungers 83 and the coils therein. The halves of the housing are sccured together by screws 80, the housing being secured to a base by bolts in apertures 97. Two single-pole, doublethrow switches are contained within the device herein illustrated and such device has been operated for millions of times on five amperes of current without any deleterious effects on the ball surface or the contact faces. The device is not limited to five amperes current and may carry more directly and when the contacts and balls are connected in parallel. When connected in series relation, a plurality of breaks occurs in the circuit, specifically should a separation occur between two points on the ball and the engaged faces of the contacts. In the position illustrated in FIG. 8, in which the upper contacts 94 break a circuit and the lower contacts make a circuit, the energization of the lower coil 85 overcomes the force of the lower magnet 87 to move the plungers 88 upwardly Where they are retained by the upper magnet 87 when the coil is deenergized. This movement positively moves the balls 91 from engagement with the contacts 95 and moves them into engagement with the contacts 94. This breaks a circuit across the lower terminals 98 and completes a circuit through the conductors connected to the upper terminals. The energization of the lower coil 85 moves the plungers S8 downwardly and moves the balls from the two sets of contacts 94 to break the circuits therethrough and move the balls into engagement with the sets of contacts 95 to complete circuits thereacross. In this arrangement, the balls are positively moved into and out of engagement with a pair of contacts and are retained in bridging relation to pairs of contacts by the completion of a flux path through one of the magnets 87 and the adjacent plate 93. It is to be understood that a device having a single ball may be employed as a unit and two such devices are employed to make the device illustrated in FIG. 9, having the two balls. Any number of the units could be stacked to provide a control for a large number of circuits, some of 'which may be normally closed while others are normally open. It is also to be understood that a single device may be provided having any number of balls therein to form a single unit having a plurality of open and closed contacts.

Referring to FIGS. 11 and 12, a still further form of the invention is illustrated, that wherein a coil 97 has a plunger 98 extending through its center retained therein by the head 99 on one end and a washer 101 threaded or otherwise secured to the other end. The plunger 98 and head 99 are secured to oppositely disposed walls 102 of an inverted U-shaped housing 103. The housing has a back plate 104 secured thereto and provided with a forwardly extending flange 105 at the bottom. A U-shaped element 106 of magnetizable material extends about the coil 97, plunger 98 and head 99, urged downwardly into engagement with the flange 105 by a spring i107. The spring is confined at its ends in aligned apertures in the plunger 98 and the base of the U-shaped element 106.

A plurality of balls 108 are loosely supported in apertures 109 in a pair of insulating plates 111 and 112, the plates being secured by screws 113 to the ends of the U-shaped element 106, as clearly illustrated in FIG. l1. The balls are confined between contacts 94 and 95 which are mounted on spring fingers 96 that extend through the walls 102 with the terminal portions 86 on the outside of the device. When the coil 97 is energized, the U- shaped element 106 is moved upwardly, moving the balls 108 upwardly therewith to break the bridging relation with the contacts 95 and make the bridging relation with the contacts 94. When the coil is de-energized, the element 106 is urged downwardly by the spring 107, moving the ball from engagement with the contacts 94 into engagement with the contacts 95. The balls are rotatively held by the plates 1 11 and 112 and are positively moved from engagement with one set of contacts into engagement with the other while being capable of rotation relative to the plunger. All four of the circuits through the four balls may be connected in parallel so that the device will have a high current carrying rating, or the circuits may be connected singly, or in pairs for lower current ratings. The balls 108 are freely rotatable within the apertures 109 in the plates 111 and 112 and random indexing will automatically take place so that all points of the balls may engage the contacts to complete the circuits. This prevents repeated arcing at the same point on the ball and protects the surface of the balls and the contacts so that the life of the switch is substantially indefinite. Apertures 114 may be employed to support the bracket in position on a wall or a mounting panel.

The use of a contact ball which is randomly oriented, or indexed during or after every actuation of the switch provides a substantial advantage over fixed contacts as to contact wear and maintenance. The life of the ball is relatively long as compared to the life of a non-indexing type of contact, since in this latter type the make and break points are always the same, and once arcing occurs the contacts deteriorate rapidly. The rotatable ball of the present invention has the make and break points constantly changing in a random manner sothat the entire surface of the ball is subjected to relatively even wear. Moreover, the free-floating ball may be readily removed for servicing or replacement since it is not permanently secured in the switch. The switching devices of the present invention may be of the solenoid actuated relay type, or of the proximity type, or of both types, and may be either normally open or normally closed. The conducting coating on the ball permits heavy currents to pass through the device and the positive movement of the ball produces quick separation without arcing or with only a very slight occasional are.

What is claimed:

1. A magnetically actuatable electrical switch comprising a pair of contacts for connection to an electrical circuit to be controlled, a conductive member for bridging said contacts, means for confining said member for freefloating travel toward and away from said contacts, magnetically actuated means supporting said confining means for moving said member therewith into bridging engagement with said contacts, and means for indexing said member relative to said confining means each time it is moved to present different portions of its surface to said contacts on successive actuations of said switch.

2. A magnetically actuatable electrical switch comprising a pair of contacts made of an electrically conductive low coercivity magnetic material, an electrically conductive member for bridging engagement with the contacts, magnetically actuated means loosely securing said conducting member and positively moving it into and from engagement with said contacts, and means for indexing said member relative to said confining means each time it is moved to present different portions of its surface to said contacts on successive actuations of said switch.

3. In a magnetically actuatable electrical switch, a coil, a pair of contacts resiliently mounted adjacent to one end of said coil, a plunger within said coil movable toward said contacts in response to energization of said coil, a ball of conductive material between said contacts and said plunger, means loosely securing said ball to said plunger so as to be positively moved thereby to and from the contacts, and means for indexing said ball relative to said first mentioned means each time it is moved to present different portions of its surface to said contact on successive actuations of said switch.

4. In a magnetically actuatable electrical switch, a coil, a pair of contacts resiliently mounted adjacent to one end of said coil, a plunger within said coil movable toward said contacts in response to energization of said coil, 21 ball of conductive material between said contacts and said plunger, means loosely securing said ball to said plunger so as to move therewith into bridging engagement with said contacts, and means for indexing said ball relative to said first mentioned means each time it is moved to present different portions of its surface to said contacts on successive actuations of said switch, said contacts being arranged at an angle to each other to have the ball have a rolling and wiping action with the contacts to assure a full conducting engagement therebetween.

5. In a magnetically actuatable time delay switch, a pair of electrical contacts for connection to an electrical circuit to be controlled, a conductive member, means for confining said member for free-floating movement relative thereto and for movement therewith toward and away from said contacts, magnetic flux producing means for moving said member into bridging engagement with said contacts, means for indexing said member relative to said confining means each time it is moved to present different portions of its surface to said contacts on successive actuations of said switch, and means delaying the response of said member to said magnetic flux producing means.

6. In a magnetically actuatable electrical switch, a coil having an aperture, a pair of contacts mounted adjacent to one end of said coil, a plunger movably fitted within said aperture and movable toward said contacts in response to energization of said coil, a ball of conductive material loosely fitted to said plunger for positive movement therewith into engaged and disengaged relation with said contacts, means for indexing said ball relative to said plunger each time it is moved to present different portions of its surface to said contacts on successive actuations of said switch, and time delay means retarding the movement of said plunger upon the energization of said coil.

7. In a magnetically actuatable switch, a coil having an aperture, a pair of electrically conductive contacts adjacent to said coil, a plunger in said aperture, a ball loosely secured to said plunger and carried therewith, spring means biasing said plunger away from said contacts, and a permanent magnet acting as a stop against which said spring urges the plunger to add a further holding force which resists the movement of the plunger toward the contacts.

References Cited in the file of this patent UNITED STATES PATENTS Wurts Oct. 29, 1901 Sedgwick et a1 Aug. 16, 1904 Ridderhof et a1. Oct. 18, 1904 Saunders Mar. 12, 1907 Finnigan Jan. 25, 1916 Spangler Feb. 13, 1917 Briggs Apr. 17, 1917 Cheney June 22, 1920 Hodgkins Aug. 30, 1921 8 Batcheller Oct. 30, 1928 Austin Dec. 24, 1929 Van Nostrand Jan. 21, 1930 Hammerly Nov. 29, 1932 Allen Oct. 3, 1933 Hammerly Apr. 24, 1934 Lodge June 17, 1941 Allen Apr. 7, 1942 Irwin et al. Feb. 13, 1945 Rowe Sept. 28, 1948 Packard Nov. 22, 1949 Mossrnan et a1. Jan. 30, 1951 Buckingham Jan. 24, 1956 Reynolds May 28 1957 Fisher et al Sept. 24, 1957 Drescher Dec. 29, 1959 FOREIGN PATENTS Italy "4 Mar. 13, 1956

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US685549 *Apr 17, 1901Oct 29, 1901George WestinghouseElectric cut-out.
US767599 *Sep 17, 1903Aug 16, 1904Charles E SedgwickElectrically-operated apparatus.
US772908 *Dec 9, 1903Oct 18, 1904Wilmarth & Morman CompanyFlashing device for incandescent electric lamps.
US846624 *Jun 27, 1905Mar 12, 1907Daniel K HickeyDevice to disclose opening of the shunt-circuits of electric meters.
US1169475 *Mar 26, 1914Jan 25, 1916George P FinniganMagnetic apparatus.
US1215423 *Aug 16, 1915Feb 13, 1917Clarence Long CCurrent-limiter.
US1223143 *Oct 12, 1914Apr 17, 1917Briggs & Stratton CompanyVibrator-contact.
US1344199 *Aug 5, 1918Jun 22, 1920Allis Chalmers Mfg CoRetarded switch
US1389140 *Nov 18, 1916Aug 30, 1921WestingElectromagnet device
US1689852 *Oct 9, 1926Oct 30, 1928Bojac Mfg Co IncElectrical switch
US1740640 *May 25, 1925Dec 24, 1929Ohio Brass CoElectric switch
US1744346 *May 26, 1925Jan 21, 1930Telautograph CorpElectromagnet device
US1889515 *Jun 11, 1932Nov 29, 1932Trumbull Electric Mfg CoElectric switch
US1928846 *Oct 30, 1931Oct 3, 1933Eclipse Aviat CorpSwitch mechanism
US1956422 *May 29, 1933Apr 24, 1934Trumbull Electric Mfg CoElectric switch
US2246373 *Jan 30, 1939Jun 17, 1941Stackopole Carbon CompanyElectric switch
US2278967 *Jan 22, 1941Apr 7, 1942Bendix Aviat CorpElectromagnetic mechanism
US2369296 *Sep 24, 1943Feb 13, 1945Cooperative Dev CoElectrical switch
US2450256 *Jul 31, 1945Sep 28, 1948Trumbull Electric Mfg CoElectric switch
US2488928 *Feb 4, 1946Nov 22, 1949Struthers DunnElectromagnetically operated switch
US2539547 *Jun 13, 1945Jan 30, 1951Clare & Co C PRelay
US2732458 *Aug 27, 1952Jan 24, 1956The Western Union Telegraph Companybuckingham
US2794178 *Apr 5, 1954May 28, 1957Boeing CoMagnetically actuated and held ball armature switching devices
US2807688 *Nov 26, 1954Sep 24, 1957Bulova Res And Dev Lab IncElectromagnetic relay
US2919323 *Jul 1, 1957Dec 29, 1959Drescher John FElectric relay
IT540762B * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3764945 *Feb 2, 1972Oct 9, 1973Sam Marcel BraunElectrical switch devices
US7663457May 31, 2007Feb 16, 2010Cooper Technologies CompanyMagnetic latch for a voice coil actuator
US9053882 *Jun 4, 2012Jun 9, 2015Abb Technology AgMagnetic actuator unit for a circuit-breaker arrangement
US20080297986 *May 31, 2007Dec 4, 2008Cooper Technologies CompanyMagnetic latch for a voice coil actuator
US20120268223 *Jun 4, 2012Oct 25, 2012Abb Technology AgMagnetic actuator unit for a circuit-breaker arrangement
WO2008150287A1 *May 31, 2007Dec 11, 2008Cooper Technologies CompanyMagnetic latch for a voice coil actuator
Classifications
U.S. Classification335/63, 335/196, 335/187, 335/179, 335/180, 200/277, 335/255, 335/126
International ClassificationH01H50/20, H01H50/00, H01H1/12, H01H51/28, H01H50/88, H01H50/16, H01H1/16, H01H51/00
Cooperative ClassificationH01H50/20, H01H51/288, H01H50/88, H01H1/16
European ClassificationH01H50/20, H01H1/16, H01H51/28H, H01H50/88