US2611059A - Electric switch with permanentmagnet blowout field - Google Patents

Description

Sept. 16, 1952 R. B. IMMEL ETAL 2,611,059

ELECTRIC SWITCH WITH PERMANENT-MAGNET BLOWOUT FIELD Filed July 7, 1950 Fig.1. Fig.2.

I 8 I 3 B I 3 l '0"? o l8 L 25 |8 "W 6 25 L a? "11, 5 7 4 5 '9 v 7 k u i 9 I I2 22 H 4 l4 u I 6 l4 L- :22- a I- 2. l5 g l5 vi/masses: INVENTORS Ralph B. Immel and I Lawrence Pierce. 77%;? flu! '--/*-1 ATTORNEY Patented Sept. 16, 1952 ELECTRIC SWITCH WITH PERMANENT- MAGNET BLOWOUT FIELD Ralph E. Immel, Wiliiamsviile, and Lawrence Pierce, Buffalo, N. Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 7, 1950, Serial No. 172,522

3 Claims. 1

Our invention relates to manually or automatically operated electric switches and more particularly to switch contact devices with 1plermanent magnets to provide an arc blowout eld.

Known devices of this kind have, for each interrupting gap, a single permanent magnet mounted staticnarily in the vicinity of the stationary switch contacts. Unless the magnet is very large and thus occupies considerable space in excess of that needed by the contact device proper, the blowout eflect and, accordingly, the interrupting rating of these known devices are rather limited.

It is an object of our invention to materially increase the interrupting rating of switching devices of the above-mentioned kind by providing a blowout field of higher intensity or eiiectiveness with the aid of permanent magnets of simple design and little or no space requirements in excess of the space needed for the switching devices proper. Another, related ob- .iect of the invention is to provide a permanentmagnet blowout unit that is generally suitable for direct-current contact devices and can readily be substituted for devices without blowout by mounting it in the same place and space.

To achieve these objects, and in accordance with the invention, we mount a permanent magnet behind the stationary contact member of the switching device and mount another permanent magnet on and behind the appertaining movable contact member in sufiiciently close magnetic relation to the stationary magnet to jointly produce a blowout field not only of higher intensity but also of a more favorable orientation than otherwise obtainable, these and other features of the invention being apparent from the embodiment exemplified on the drawing and described in the following:

In the drawing, Fig. 1 is a part-sectional side view of a switching device according to the invention in closed condition; Fig. 2 is a similar view but shows the device in open condition; Fig. 3 is a perspective view of the same device during opening performance; and Fig. 4 is an explanatory illustration showing a section through the contact members and permanent magnets in a relative position corresponding to Fig. 3 and schematically representing the blowout field by lines of force.

The drawing demonstrates the invention in its application to a manually operated cam-type master or control switch although it should be understood that the invention is applicable to all types of switching devices involving a mom ing contact and a stationary contact in which the are drawn between the contacts, during separation of the movable contact from the stationary contact, is to be extinguished by means of a permanent magnetfield.

The illustrated switching device has an insulating panel or base I. A stationary contact memher 2 is mounted on the base I by a threaded stud 3 which serves also as an electrical terminal. Another stationary contact member 4 is positioned beneath assembly 2 and secured to base I by a stud 5 which serves also as an electrical terminal.

The contact members 2 and 4 carry respective contact buttons 6 and l which areengageable with respective contact buttons 8 and S of a movable contact bridge iii. The contact buttons consist preferably of good electrical conducting material, for example, silver. The bridge i8 is resiliently secured to an arm [I which is pivoted at 2 in a support i3. Support :3 is firmly attached to base I by a screw it and is indexed by means of a dowel pin 15 engaging a hole in the base I. The resilient mounting for bridge I0 includesa pin I! which is fitted through a hole in arm H and passes through a clearance hole ofv bridge It. Bridge It! can slide along pin 1'! and is biased toward a supporting surface of arm II by a compression spring I8. Spring i8 is seated on pin l1, between the bridge to and a washer 19 at the extremity of pin H.

The movable arm II is biased in a clockwise direction, as viewed in Fig. 1, by a compression spring 20, which isdisposed between a shoulder 2| on the movable arm I! and seats against the bottom of a hole 22 in the supporting member l3. Spring 29 tends to force the movable contact assembly against the stationary contact assemblies under compression of the weaker spring 53.

In this application, the movable arm H is cam actuated and to this end is provided with a roller 23 which is pivotally mounted at a point displaced from the pivot I2. Roller 23 is engageable by a control cam 25. Rotation of the cam from the position shown in Fig. 1 to a position in which it engages the roller 23 results in counterclockwise rotation of the movable member to the switch-opening position shown in Fig. 2.

The stationary contact member 2 is U-shaped. A permanent magnet 25 is secured between the U-legs of the member. Magnet 25 is also U-shaped and has its north and south pole ends, marked N and S in Fig. 4, abut against the one leg of member 2 that carries the contact button 6. The movable bridge member II] has a U-shaped end portion near contact button it. Another permanent magnet 26 is secured between the legs of this end portion. Magnet 26 is also U-shaped and has its pole ends, marked N and S in Fig. 4, in abutment with the one leg of bridge that carries the adjacent contact button 8.

The two magnets and 26 consist of a material of high coercive force and high remanence, for instance, of a sintered .aluminumeni'ckel cobalt alloy, although other permanentmagn'ets of highly magnetic material are also suitable. The material of the stationary contact member 2 and the bridge I 0 is nonmagnetic, andallother parts of the stationary and movable contact assemblies are preferably also nonmagnetic.

Magnet 26 is held in place by a set screw shown at 21 in Figs. 1 and 3. The set screw engages a small dowel hole of the magnet. Magnet 25 is similarly fastened to'member 2 by a chamfer of screw 3 which entersinto a small dowel recess'of' the magnet. Other ways of fastening the magnets, of course, may be used, but the one just mentioned is simple and prevents damaging the magnets mechanically or magnetically especially if magnets as brittle as aluminum nickelcobalt type magnets are used.

The arrangement or poling of the two permanent magnets is'such that respective poles' of like polarity lie at thesame side 'of the switching device as is apparent from'Fig'. 4. .Polin'g the magnets in this manner concentrates thefield at the place where the contacts separate and results in lines of force approximately parallel' to the contact surfaces and perpendicular to'the arc. The. relationship of current flow in the'arc, magnetic field direction, and are movement then obtaining is elucidated byarrowsin Fig. Sand Fig. 4. In Fig. 3 the'arrows Cindicate the.direction of current flow undergivenconditions, and the'arrow marked Currentfin the top portion and below the illustration of structure .in Fig. 3 denotes the'corr'esponding direction of .current flow in thearc. Arrows Fs in Figs- 3 and 4 denote the prevailing force line directions .of the stationary magneticfield component while arrows Fm in both figures denote the corresponding prevailing directions for'the movable magnet field. The resultant field direction is denoted by the arrow marked Field at the bottom of Fig. 3 for the indicated north (N) and south (S polarity arrangement of the magnets. The direction of the arc movement is denoted in Fig. 3 by the arrows marked Arc.

As thus made apparent in Figs. 3 and'4, the resultant magnetic flux is concentrated in one desirable path perpendicularto the arc. It may be mentioned that this condition and theresulting improvement in arc extinction and interrupting capacity. is obtained .only .if opposite poles of the respective magnetsareof like polarity. If .these polesare. of the opposite polarity, the flux is concentrated not inone desirablepath, but. in. two. less desirable paths parallel to .the arc, and the .result, .as tests have shown, is no betterthan when onemagnet only is mounted on the stationary. contact assembly.

Devices accordingto theinventionare especially advantageous for switches thatmayinvolve a slow-operating contact separation. .For instance aside from. manual switches. theinvention is particularly well suitedas a. limit switch for motor operatedrheostats. .Insuch'applications, the rheostat mechanism may open the contact very slowly so that the contact surfaces of the customary switches may become damaged by burning before the arc is extinguished, while such defects are greatly minimized or prevented by the invention. However, fast-operating switching devices as well as switching apparatus other than. hereinspeciflcally mentioned al'so-benefitfrom-the invention in permitting a higher interrupting rating; and it will also be obvious to those skilled in the art that changes and modifications in design, arrangement and structuralldetails, can readily be made without d'eparturelfrom the objects and essential features .of the invention.

We claim as our. invention:

1. I'm anelectric. switching device, the combinationincluding, a base of insulating material, a contact member stationarily mounted on the base, "a stationary permanent magnet mounted substantially behind the stationary contact member and having respective north and south poles directed away from the base, a movable contact member having a U-shaped portion with two parallel legs. andibeing, engageable at the outside of. one of said legs with said stationary contact member, a movable permanent magnet mounted onthe. U-shaped. portion between. the. two legs of the .U and. having respective. north and south poles directed. toward the stationary permanent magnet, said twomagnetshaving respective poles otlike polarities. substantially facing each other.

2-. .In an-electric switching device, the combination including, abase. of insulating material, a stationary U-shaped member mounted on the base with one leg against the base and theother leg disposed away from the base, a stationary contact fixed to the .outer surface of the said other leg, a one piece permanent magnet mounted inthe'bight' of the U and having its poles disposed substantially at the respective sides of the stationary contact, amovable U-shaped member disposed substantially opposite the stationary U-shaped member, a movable contact fixed to the outer surface of the legof the movable U-shaped memberin relation for engagement with the stationarycontact, a one piece permanent magnet mounted inthebight of the U of the movable U-shaped member and having its poles disposed substantially at the respective sides of the movable: contact, said two magnets having respective poles of like; polarities substantially facing each other.

:3.:In-an-electricswitching device, the combinationincluding, a base of insulating material, a Ueshaped member mounted on the base with one leg of the U against the base and the other facing outwardly, or away, from the base, an upper stationary contact mounted on the outer surface'ef the outer leg of the U, a lower stationary contact mounted'on the base substantially in the plane of the upper stationary contact,-an arm pivoted below the lower stationary ccntact abontact bridging member, having an upper contact and a lower-contact, for bridging the'stationary'contacts, said contact bridging member.being-mountedon the-arm whereby the upper contacts'are disposed a greater distance from'each'otherwhen" the arm moves the contact bridging member, away from the stationary contacts,..a one piece U-shaped permanent mag- .net mounted in the U-shaped member so that the poles thereof are substantially at the sides of the up er. stationary contact, a one piece U-shaped permanent ma net similarly mounted with respect tofthe upper movable contacts, said two magnetshaying respective poles of like polarities disposed to substantially face each other.

The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Name Date E Q IMMEL- E 2,180,147 Hopp Nov. 14, 1939 WRENCE PIERC 5 2,237,278 Willing Apr. 1, 1941 2,340,682 Powell Feb. 1, 1944 REFERENCES CITED 2,356,039 Ellis et a1 Aug. 15, 1944

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