US2633487A - Self-interlocking electromagnetic reversing switch - Google Patents

Description

March 31, 1953 J, D w 2,633,487

SELF-INTERLOCKING ELECTROMAGNETIC REVERSING SWITCH Filed Feb. 25, 1950 2 SHEETS-SHEET vl I A. J. DAWE SELF-INTERLOCKING ELECTROMAGNETIC REVERSING SWITCH March 31, 1953 2 SI-IEETS-SHEET 2 Filed Feb. 25, 1950 22362 or -M f 7 Patented Mar. 31, 1953 UNITED STATES PATENT 2,633,487

- SELF-INTEREOCKI'N G ELEGTROMAGNETIC REVERSING SWITCH Albert. J. Dawe, Milwaukee, Wis ass ignor to. Ailenefiradley Company, Milwaukee, Wis..,.a

corporation of Wisconsin Application February. 25, 1950,'Seria1No..146,341

.1. Claim- 1 magnet being connected to. b en reiaedsimub taneous y wit the opp singo the other magnet with th resu at. the armature (ifn y one ma n t a t m may b mov d t or maintained in attracted position.

Electro-magnets intended to be operated alternatively in pairs are commonly employed. for the operation of so-called reversing switches. Reversing switches are interposed in the-power connections of electric loads such as motors in such manner that closure of both switches simultaneously will cause a short circuit. For the purpose of avoiding such short circuits it has been common to provide interlock controlcom tacts for magnetically operated reversing switches so arranged that when one switchis closed, the energizing circuit iorthe magnet of the opposite switch is opened-and vice versa. This. method of interlocking is obiectionabien or the reason that, it is possible by closing both the, iorward and reverse position pushbuttons-sie. multaneously to cause a momentary closure of both switches.

With the object in mind of precluding such abuse f t e a paratus some, revers switche are provided with mechanical interlocking means in addition to the electrical interlocking contacts above referred to. Such mechanical ins terlocking means are usually made up of a. system of pivots, levers and linkage so arranged as to interpose a positive mechanical hindrance to the closure of one switch whenever the other switch is in closed position and to positively hinder both switches if a condition arises under which the magnets are energized simultaneously The reliability of mechanical interlocking are. rangements is dependent upon their remaining in good mechanical condition, but, wear ultimately introduces the possibility oi failure! Also it is difiicult to arrange mechanical interlocking systems so that the magnets forming the pair may be separated by any substantial distance,

I ac ordance w the presen invention a Pair of interlocked electr c-magnets:incapablezof simultaneous operation and. which may be as idely separat as may be desired is provided without d pendence up n mechanical linkaseand with ut resort to i te ckin contacts. Thisis accomplished by p ov din each ma et oi the pair ith. an operating coil c nahle of exert-ins a t e f rce adequa e to mo e the armature and y pr ng each ma et ofthe pair wi an o p si soi wh ch when ener ized. iseiiec t e t pr ve t th opera in co lirom moving h armature but whi h in and of..itse1..f when. energized one is i capable voi exerting .sufir eienta t a e o ce to more the armature- The twomagnets provided with windin s; asthns describ d are p o ded. w th circuit. c nnections such th e operat n l of one ma net and. the. p si co f the other be omeenergized. si multaneously. By rea on of this. arrangement if bot p r in coi s are s multaneously .ener z dh e a n t wi l close and; if one. masn t is i clo ed pos ion t the t me. such simulus h reiaa ion. s establis ed, the closed m gnet will drop to op position The i v ntion is h e n described b -ifeierence to the accomp n d n s .iorm ns a part her of. in wh the eis set i rth byway of i1- lust a ion and n t o imitation one form in whi h the apparatus of. this invention may be emb died.

I he drawin s:

Fig. 1 is a ront p an v w with parts-broken a y a d n se ti n of arevers ns switch emp oyins a pai of magn ts constructedinac- Cordance with this. invention, and

Fig- 2 is a c rc it am showin thecircuit f the mag ets sh wn i a. l

Th form of the. appar t s of his. invention whi h is set. forth in the drawi -s is shown. ap plied to a. so-called reversing switch. of well known construction. As there shcwn the a s paratus of this invention ismade lip'ofv apair of magnets designated genera-11y land). The ma nets l and- 2 are of iden cal o struotionand includ rou hly rectangular -rnas-notic field frames 3, and}! having gaps ii andfi intheiniower sides as ap ea s m e rly in; ist 2'. Arra ed for sl di g movement thr u h the: sanst and-.6, are ma a matures 1 rtist heiTeshaned heads of which when in closed position ,eng age, pol fa es-S an I0 w ich are formedas a part of their res e ve field fra s and flanks ins posi i n-adja nt. he spec ve aps Sandi.

Attach d to. hep nds of the tongues of the armatures 7 and 8 are actuator bars. Hand 12 which pass through slots not shown in the tops of the respective field frames 3 andA. The actuator bars ll and I2 are attached, respectivelwto insulating movable contact carriers l3 and I4 carrying a plurality of movable contacts one of which is shown at I5. Th movable contacts l5 are arranged to bridge electrically in well known manner pairs of terminals as, for example, terminals I6 and Il. The terminals [3 and H are mounted upon the stationary con tact mounting and housing I8 and similar terminals and stationary contacts are mounted upon housing I9. Since the parts of the switch proper form no part of this invention the detail of the same is shown only sufiiciently to permit understanding of the parts of the apparatus with which the invention is concerned. 7

Surrounding the path of travel of the tongue of the armature l and within the rectangular opening in the field frame 3 is a closing coil 29) having terminals 2| and 22. Located immediately above the closing coil 23 and positioned substantially opposite the air gap which exists when armature l is in open position is an opposing coil 23 having terminals 24 and 25.- The coils 2G and 23 are held in place by a guiding sleeve 26 through which the tongue of the armature may slide and by a spring clip 21.

-The magnet 2 is provided with a closing coil 28 corresponding to the closing coil 22 of magnet I similarly located and held in place by guiding sleeve 23. Coil 28 is provided with terminals 38 and 3i. Above the closing coil 28 is disposed an opposing coil 32 corresponding to the opposing coil 23 of magnet I. The opposing coil 32 is guided also by the sleeve 23 and is held in place by a clamping spring 33. The opposing coil 32 is provided with terminals 34 and 35.

The magnets l and 2 are intended to be mounted in vertical position so that gravity acting upon the armature and switch parts secured thereto causes these parts to be continuously urged to open position with a substantial force. To overcome the opening force coils and 28 are wound to create a magnetic attractive force somewhat in excess of that necessary to cause the armature to move to closed position. The opposing coils 23 and 32 are wound in magnetic opposition to their respective closing coils 28 and 28 and are provided with that number of ampere turns which is Sufficient to offset something more than the excess attractive force which closing coils 22 and 28 are capable of exerting.

The relationship of the characteristics of the opening and closing coils above described is availed of as indicated more clearly in Fig. 2 by connecting closing coil through its terminal 22 and the lead 36 with terminal 34 of the opposing coil 32 of magnet 2. Terminal 2! of coil 20 is joined by a lead 31 to a normally open push button 38 which is connected in turn through leads 38 and 48'with line L-2 of the source of actuating current. Terminal of coil 32 is joined by lead 4I and ballast resistor 42 with line L-l of the source of actuating current. By reason of the connections above described when the push button 38 is closed coils 23 and 32 become connected in series with one another through the ballast resistor 42 to a source of actuating current.

In similar fashion coil 28 is joined with line L 2 of the actuating current source by leads and 43, a normally open push button 44, lead 45 and the coil terminal 33. The opposite terminal 3i of the coil 28 is joined by a lead 43 with terminal 25 of coil 23 which is connected in turn through its terminal 24, lead 47 and ballast resistor 42 with line L-i of the actuating current source. Upon-closure of push button 14 coils 28 4 and 23 become connected in series with one another through the ballast resistor 42 with the source of actuating current.

The energization of coils 20 and 32 by closure of push button 38 causes a sufficient attractive force to be applied to the armature I to cause the same to move to closed position. Some attractive force is applied by the coil 32 to the armature 3 of magnet 2, but this attractive force by reason of the characteristics of winding 32 is lnsuficient to move the armature 8. An exactly similar action occurs with respect to coils 28 and 23 upon closure of push button 44. This action results in movement of the armature 8 without any movement of armature I taking place. There is thus obtained the normal, simple action of a pair of magnets capable of being alternatively operated.

The interlocking properties of the apparatus of this invention are brought into play when the push buttons 38 and 44 are for any reason operated simultaneously rather than alternatively. For example, if While push button 38 is held in closed position and magnet I is in closed position one attempts to simultaneously close the push button 44, magnet 2 will refuse to close by reason of theopposing eifect produced by current flowing in coil 32. By reason of the symmetrical arrangement of the circuit it is obvious also that if push button 44 is held in closed position causing magnet 2 to be closed, closure of push button 38 will be without eifect to cause closure of magnet I. It is thus apparent that with the apparatus of this invention, simultaneous operation of the two magnets is precluded without dependence upon any mechanical interlocking device or any magnet operated contacts. The two magnets forming the pair may be spaced any convenient distance apart calling only for simple wire connections between them.

Not only are the magnets of this invention positively interlocked against simultaneous functioning but by reason of the relationship of the coils simultaneous closure of push buttons 38 and 44 calls for a condition under which both magnets are in open position. If, for example, magnet I is previously closed by closure of push button 38 closure of push button 44 Wil not only fail to cause movement of armature 8 but armature I will be caused to drop to open position. The converse is true if push button 44 is first closed followed by closure of push button 38. Where a pair of magnets is employed for the operation of reversing switch mechanism as shown in Fig. 1 the user of the apparatus is thus discouraged from ever attempting to close both push buttons 38 and 44 simultaneously.

The coils 23 and 32 are preferably placed as shown opposite the air gap formed when the armatures 7 and 8 are in open position. By reason of this arrangement under normal operation the impedance of the opposing coils 23 and 32 is low with the result that the closing coils 20 and 28 receive adequate current to cause them to perform the closing function. The closing of either magnet, however, substantially increases the impedance of the opposing coil associated therewith with the result that a subsequent attempt to simultaneously close the opposite mags net is inhibited not only by the effect of the opposing coil of that magnet but by a substantially reduced current supply to its closing coil. If for any reason both magnets should be simultaneously energized for any appreciable period, the impedances of the circuits of both will-be ab normally low by reason of the open condition of the same, and for this purpose the ballast resistor 42 is provided to limit the current which may be drawn.

The selection of the proper number of turns in any given pair of magnets for the closing and opposing coils may be made on the basis of well known properties of magnetic circuits and will depend upon the dimensions and configuration of the magnet parts and th amount of closing effort required. In one instance in a pair of magnets employed for the actuation of a pair of reversing switches of 50 ampere capacity of well known construction the closing coils Were provided with 550 turns while the opposing coils were provided with 275 turns. In this case the magnets were arranged to be operated by alternating current at 115 v. and 60 cycles. A ballast resistor having a resistance of 20 ohms was sufficient to limit maximum current to a moderate value.

In selecting the number of turns to be employed in the Opposing coil for any given magnet the same should be of sufficient strength to oliset something more than the excess closin force which may be exerted by the closing coil. Since it is important that th opposing coil not exert in and of itself sufficient closin force to move the armature, it is obvious that the closing coil should not be of sufficient strength as to exert a large excess closing force either in the open position or in the closed position of the magnet. For example, in a magnet requiring 4 pounds of closing force when in open position to overcome friction and gravity or other biasing force tending to hold the magnet in open position a closing coil capable of exerting about 5 pounds of closing force would preferably be employed. Under these conditions an opposing coil capable of exertin an opposing efiect equivalent to 2 pounds would, if simultaneously energized with the closin coil, reduce the net closing force to 3 pounds which would be inadequate to move th armature. If for any reason the opposing coil were energized alone the closing effort produced thereby would be approximately 2 pounds and this also would be inadequate to cause closure of the magnet. With these relationships in mind the proportioning of windings in any given magnet in accordance with this invention may be arrived at by well known methods. Since each magnet is provided with an independent closing circuit which also acts to preclude closure of the opposite magnet without exerting suflicient attractive force to close the opposite magnet the need for simultaneous weak excitation of the opposite magnets closing circuit is avoided. In this way the circuit is simplified and an apparatus is provided which fails safe in case of derangement of the closing circuits.

I claim:

In a pair of interlocked alternatively operative electro-magnets the combination comprising a 6 first field piece, a first movable armature normally biased in open position spaced from said first field piece with an air gap therebetween, a first operating windin for said first movable armature positioned to apply an attractive force thereto when energized sufiicient to move said armature through said air gap to closed position with respect to said first field piece, a first opposing winding for said first movable armature encircling said air gap to create when energized an opposing flux sufficient to render the attractive force of said first operating winding ineffective to move said armature, said opposing flux being insufficient in and of itself to create an attractive force sufficient to move said first armature, a second field piece, a second movable armature normally biased in open position spaced from said second field piece with an air gap therebetween, a second operatin windin for said second movable armature positioned to apply an attractive force thereto when energized sufficient to move said second armature through said second air gap to closed position with respect to said second field piece, a second opposing winding for said second movable armature disposed about said second air gap to create when energized an opposing flux sufiicient to render the attractive force of said second operating winding ineffective to move said second armature, said opposing flux of said second opp s n winding being insumcient in and of itself to create an attractive force suificient to move said second armature, a normally open actuating current supply circuit including means for closing the same joining said first operating winding and said second opposing winding in series adapted to excite said windings when closed and to exclude therefrom when open any substantially effective excitation current, and a normally open actuating current supply circuit including means for closing the same joining said second operating winding and said first opposing winding in series, said circuit being effective to excite said windings when closed and to exclude any substantally effective excitation current therefrom when open.

ALBERT J. DAVIE.

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

UNITED STATES PATENTS Number Name Date 306,187 Smith Oct, 7, 1884 1,169,251 Gaffney Jan. 25, 1916 1,732,711 Boddie M Oct. 22, 1929 1,758,540 Shaw May 13, 1930 1,792,859 Mitchell Feb. 16, 1931 1,964,355 Hovey June 26, 1934 2,186,498 Riggs Jan. 9, 1940 2,343,423 Reagan Mar. 7, 1944 2,436,102 Douglas Feb. 17, 1948

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