US1275844A - Electromagnetic switch. - Google Patents

Description

E. R. cAmcHoFyf. ELECTROMAGNEUC SWH'GH. APPLlCAUON FIL-ED SEPZFJ, 1916.

Patente Aug. 13, 15H8,

HHH

Inventor: Eugene R. Carcbof?, by MM His Tttorneg. A'

' a citizen of the United States, residin vUruTniD STATES PATENT OFFICE.

EUGENE B. CABICHOFF, QF SCHENECTADY,`N EW YORK, ASSIGNOR ELECTRIC COMPANY, A CQRPORATICN 0F -NEW YORK.

ELECTBOMAGNETIC SWITCH.

Specication of Letters Patent.

applicati@ and september' as, 191e. semi no. 121,967.`

To all whom it may concern: i.

Be it known that I, EUGENE R. CARIcHorF, at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in Electromagnetic Switches, of which the following is a specification. f My invention relatesV to electromagnetic switches for controlling electric circuits and more particularly to switches of this character which hold open'when the current in a circuit is relatively high and/close when the current drops to a predetermined value.

In the starting of-electric motors, ithasv been thepractice, to employ A aplurality of electromagnetic switches `which close successlvely to cut out sections of reslstance from the motor circuit and bring the motor up to speed. Various means have been devised for controlling theoperation of the switches so that they will only close when the current is at a proper value, that is, after a switch has operated to cut out a sec# tionof resistance the next switch will'not operate until the current has dropped to a safe value due tothe speedin up of the motor.

A form of switch W 'ch has frequently been proposed for this purpose is one in which a shunt'coil'closesthe switch and a series coil', instead ofcontrolling the circuit of the shunt coil, positively prevents the switch from closing by actually holding it open, that is, the shunt coil pullsagainst the series or holding out coil.: a A switch of this general character is disclosed in patent to Fraser #$655,335. vThe diiculty with the device shown in this patent is that the value of current in the holding out winding at which the switch will close depends upon the pull of the shunt4 coihwhich of course will vary with `the voltage and also with the tem erature of the coil. In other words, the setting of the switch, i. e., ythe motor current value at which .it'closes, changes with change of voltage. It alsoy closes .at

one value of current inthe series coil when the shunt coil is cold and another when itis at its operating temperature which is ordinarily about degrees C.` j y Attempts have beenmade to overcome Vthis difficulty byyhavig an auxiliary member, which is o erated -by the shunt coil, place a spring un er tension which `tends to move ythe-switch member to closed positirnnrv 4This To emanan,

PatentedAug. 1351918.; i

tendency is opposed by'thef series coiliwlen f the current 1s high and when the current drops to a ,predetermined value, the spring overcomes the pull of the series coil and closes the switch.` Such an arrangement is unsatisfactory for the reason that the switch is closed by a spring insteadof by electromagnetic pull, and it is impossible to obtain the required pressure between the contacts'.` Thesp'nng weakens as theswitch .memberf moves toward closed position, and the ressing together of the contacts is accompished when the 'spring is weakest. As thepa'rtsfl wear, the pressure between the contacts lde-v creases. One of the obJects of my invention is to improve the electromagnetic switch of the type above described by providing vmeans ated so as to 4be positively closed and wiped home by the magnetic pull ofthe shunt coil.,4 when the current in the series coil drops to a predetermined value, vthis being accom-l plished by the rovision of means whereby;

the switch mem er-is held openby the shunt 4whereby the switch member will beV o r4 of my invention I employ a. halnmer-blow device which is. moved to operative position by the shunt coll but is held inoperative position by the series coil. When the `current in the series coil drops to' a predetermined 'f value the hammer-blow devlce operates and" releases. the switch armfrom the open positionin which'it is held by the pull ofthe shunt coil thereby permitting it to. beclpsedj by the shunt coil. The result'jo'f tliisfarv rangement' is that the value of current in the series coil at which the switch closes willbe independent of the variations inpullof the shunt coil due to variations ofvoltage and magnetically. y v p Infr the accompanying drawingfillustratf ,other causes 'and the switch will in one formof my inventionFlgure 1'is a.

si e elevation. of a'vv complete electromagnetic switch embodying my improvements;'Fig. 2 isa vfront elevation ofthe same, and Figs'.

3,4 and5 show in outlinethe` yarious positions which thevswitch assumes in'lpractice. y

.Referring to Figs. 1 and 2, 10 represents an energizing win ing whichris shown as a fine wire windingsuitable for use as "a shunt winding non; an electromagnetic switch 'for .controlling motor circuits. This winding is arranged to energize themagnetic structurel composed of core 11 mounted in .and projecting through bloc-k 12 of brass or other non magnetic material, and a pole piece 13 connected with the core at its lower end.

Thispole piece has a projectingportion 14- bent upward at right angles, this projection being surrounded by a copper band 15 for the purposes hereinafter set forth. ,A switch member 16'is pivoted at 17 to 4ears on the block 12 and is provided with a contact 18 which'coperates with a stationary contact -19 mounted upon the insulating base 20.

The contact 18 isfpivoted at 21 to the main portion of the switch arm and V.is pressed in the direction of the fixed contacty 19 .by a

j25 of non-magnetic' material.

adjusts the gap between the tail piece 24 and the bent portion 140i the pole piece 13` spring 22 so as to provideI a yielding en, gagement between the two contacts which wipe or roll upon 4each otherv in a well .understood manner. The main lportion of the switch arm consists or' the armature portion 23 which cooperates with the core 11- and atail portion 24 at an angle thereto.

This switch member is so pivoted and weighted that it normally assumes the position shown in thedrawing, so that the tail piece 24 rests against the adjusting screw rlhis screw and is moved in and out by turningf the knurled head 25. This gap 26 determines the holding. out pull exerted upon the switch arm. Pivoted on the pivot 17 -is a frame vof non-magnetic material composed of side pieces 27 and a cross connecting 'bar '28 v which is oit-set out of the plane of themembers 27. The off-set isy suiiicient to bring the cross, bar 28 into close proximity tothe tail piece 24 but not touching it, when the latter is in its normal position shown vin the drawing.l One of the members 27 has a projection 29 'extending downward and the pivot 17, between the side pieces 27 is` terminating in an armature `30 of magnetic material coperating with the core 31 of a magnet having a winding 32. This windingI it will be observed is a heavy or coarse winding of a type suitable for carrying the armature current wherelthe switch is used for controlling an electric motor. -Pivoted on an armature 33 the free end of whichcooperates with the projecting portionL 14 of the pole piece 13 so .as to be attractedthereby. Betweenthis armature 3 3 and the oil'- set cross piece 28 is a spring 34 which is compressed when the armature 33 isv at tracted by the projecting pole piece 14, thereby exerting a pressure upon the frame 27 which is resisted by the core 31. .VVhen,\`

however, the pull dit the core v31` decreases sufficiently dueto the drop of current in the winding 32, `the spring willprepondrate,

whereupon the frame will respond to the harass@ spring pressure and deliver la slight hammer blow to the tail pieceA 24, thereby releasing the latter from the projection 14 of 4will be held open and the parts will assume the position shown in Fig. 4. It will be noted by reference vto Figs. 3 and 4 thatthe only part that has moved is the armature 337 which is moved into engagement with the.

projecting pole piece 14. The copper band 1 5 retards the rise of flux in the projection 14and softens the blow of the armature 33 against the projection. The frame composed of the side bars 27 is held in place by the pole pie'ce31 and the spring 34 is-therefore compressed bu't the switch arm is held in its normal position by the pull across the gap 26. Then the current in the winding,y

32 drops to the proper value, the armature 30 will be released, whereupon ycross member 28 will strike the tail piece 24 a slight blow which will release it from the influence of the pole piece 14, whereupon the pole piece 11 will attract the switch warm and `move it to closed position as shown in Fig. 5.

What I claim as new and desire to secure by Letters Patent of the United States, 1s: 1. Anelectromagnetic switch comprising an energizing winding and a magnetic structure therefor, a switch arm normally in open position and held in said position by magnetism set up by said winding, a member movedupon the energization of said winding to set up a force tending to release the switch arm and move it in a closing direction, a holding out winding and means lfor restraining the said releasing force until.

the current in the holding out winding drops to a predetermined value.

2. An electromagnetic switch comprising a switch arm, an energizing winding and a magnetic structure therefor` which holds it in open position andmoves it to closed position, a' member moved by the magnetic force set upby the said winding to set up a force tending torelease the switch arm from the open position in whichfit is held so that it will be closed by said winding,7 a holding out winding and means for restraining the releasing force until, the current 'in the holding out winding d-'ops to a predetermined 3. An electromagnetic fswitch' comprising a switch arm, an energizing windingand a magnetic structure therefor which holds it in open position and moves it to closed position, a member moved by the magnetic force set up by said winding to store energy for releasing the switch arm from the open position in which it is held by the winding, a holding out winding and means whereby the stored energy causes a hammer blow to be delivered to the switch arm to permit the latter to be closed by the operating winding when the current in the holding out winding drops to a predetermined value.

4. An electromagnetic switch comprising an energizing winding and a magnetic structure therefor, a switch arm normally in open position and held in said position by the magnetic force set up by said winding,l

a hammer blow device moved to operative position by said windingand arranged to release the switch arm from the open position in which it is held by the said winding so that it will be closed by the winding, a holding out winding and means controlled thereby for restraining the hammer blow device until the current in the holding out winding drops to a predetermined value.

5. VAn electromagnetic switch comprising an energizing winding and a magnetic structure therefor, a switch arm normally in open position and held in said position as well as in the closed position by the magnetism set up by said winding, a hammerblow device moved to operative position by said winding and arranged to release the switch arm from the open position in which it is held by the said Winding so that it is closed by the winding, a holding out Winding and means controlled thereby for restraining the hammer blow device until the current in the holding out winding drops to a predetermined value.

G. An electromagnetic switch comprising an energizing winding and a magnetic structure therefor, a switch arm normally inopenposition and held in such position as well as in closed position by the magnetism set up by said winding, a member moved by the said winding to set up a force tending to release the arm from the winding and move it in the closing direction.l a holding out winding and means for rest-raining the said releasing force until the current in the holding out winding drops to a predeter-f mined value.

In witness whereof, I have hereunto set my hand this :23rd day of September, 1916.

EUGENE R. CARICHOFF.

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