US2355959A - Electrical relay - Google Patents

Description

Aug. 15, 1944. Doom ELECTRICAL RELAY 2 SheefiS-Sheet 1 Filed March 19, 1943 INVENTOR flmbzzr E. fioda Hjf ATTORN EY -Aug. 15, 1944. o D

ELECTRICAL RELAY Filed March 19, 1943 2 Sheets-Sheet 2 INVENTOR flPf/R P Z. Dada Q1 1f Hff ATTORNEY Patented Aug. 15, 1944 UNITED STATES PATENT OFFICE ELECTRICAL RELAY Arthur E. Dodd, Edgewood, Pa., assignor to The Union Switch 8a Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application March 19, 1943, Serial No. 479,759

2 Claims.

My invention relates in general to electrical relays, and in particular to electrical relays suitable for use in railway signaling systems.

One object or my invention is to provide improved magnetic blowout means which can be applied to the contacts of relays of the type described, and which will greatly increase the current which safely can be interrupted by the contacts without danger of pitting and arc over.

Another object of my invention is to provide a magnetic blowout utilizing a minimum amount high retentivity permanently magnetizable material such as Alnico.

A further object of my invention is to so arrange the magnet that it will divide the are into at least two parts, thus cooling the arc and introducing two are drops in series, and hence causing more rapid extinction of the arc.

Another object of my invention is to so arrange the magnet that the arc will be blown toward the tront of the relay and will be confined to its own contact space without the use of baiiles.

A further object of my invention is to so mount the permanent magnet that it can readily be applied to existing relays, and that it will be insulated from both the fixed and movable contact members of the associated contact and also from the other parts of the relay.

A still further object of my invention is to provide means on the movable contact fingers of the relay forming a path for the arc to follow which causes the arc to remain in a part of the magnetic field sufiiciently strong to keep the arc moving, thus preventing the are from developing sufficient heat at any particular point to cause burning.

According to my invention, I support a small Alnico magnet adjacent to the cooperating contact members by means which insulates the magnet from the contact members and from all other parts of the relay. The magnet is so disposed that it sets up a field which is at right angles to the direction of current flow in the arc which forms when the contact is opened, and is so poled with respect to the direction of current flow through the contacts that the arc will move toward the magnet. Furthermore, the magnet is disposed sufilciently close to the cooperating contact members that as the arc moves toward the magnet it will divide into two paths. The one contact member is provided with an extension which forms a path for the are as it increases in length to maintain it within the strong part of the field of the magnet.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe several forms of relays embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a vertical sectional view showing a relay having one of its contacts provided with magnetic blowout means embodying my invention. Fig, 2 is an enlarged detail sectional view taken substantially on the line IL-II of Fig. l and explaining the action of the blowout means embodying my invention. Fig. 3 is a fragmentary view similar to Fig. 1 showing the progressive positions assumed by the are when the blowout means is in operation. Figs. 4, 6 and 8 are fragmentary views showing modified forms of blowout means embodying my invention. Fig. 5 is a side view of the blowout means shown in Fig. 4. Fig. 'l is a sectional view taken on the line VII-VII of Fig. 6. Fig, 9 is an isometric view of one of the parts of the blowout means shown in Fig. 6.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the relay here shown is of a well known type, and comprises an electromagnet M mounted on a top plate I of suitable insulating material such as a phenol condensation product. The electromagnet M comprises a core 2 of magnetizable material which passes through the top plate and terminates on the underside of the top plate in an enlarged pole piece 3. Only one core and one pole piece are shown in the drawings, but in accordance with usual practice the relay is provided with two such cores and pole pieces, one of which is directly behind the other in the drawings. The upper ends of the two cores are connected by a backstrap 4, and the cores are surrounded by the usual energizing windings 5.

Electromagnet M controls a magnetizable armature '6 which is pivotally mounted in a bracket 8 attached to the pole pieces 3. The movement of the armature toward the pole pieces is limited by the usual core pins 9, while the movement of the armature away from the pole pieces is limited by the usual stop screw 10.

A movable contact finger H is secured to the underside of the armature 6 by means of an insulating support l2, and cooperates with a fixed front contact member l3 to form a front contact ll-I3 which is closed or open according as the armature is moved toward the pole pieces to its picked-up or attracted position or away from the pole pieces to its released position. The front contact member II is mounted in a bracket l4 securedtoaterminalpost ilcarriedbythetop plate I.

The magnetic blowout means my present invention is particularly suitable for, although in no way limited to, application to the contacts of relays of the type described. and in the form illustrated comprises a small U-shaped tact members il-ll with its poles in close proximitytheretoinsuchmannerthatitsetsupa field which is at right angles to the direction in which current will fiow in any are which will form between the contact members when they become separated .due to deenergimtion of the relay. The magnet is so poled with respect to the direction of current fiow through the contact members that the arc will move toward the magnet for a purpose which will appear presently. The supporting bracket fl is substantially Z-shaped and has one vertical leg lla secured to the magnet between the legs of the magnet as by rivets 23. The width of the leg Ila is such that it will Just fit between the legs of the magnet, whereby the magnet is prevented from turning with respect to the bracket. The other vertical leg 2lb of the bracket is clamped against the head no of the supporting post 22 by means of a stud 24, and is held in non-turning relation with respect to the post by means of a U-shaped positioning member 25 the web of which is interposed between the outer side of the leg flb and the head of the stud 24, and the legs of which straddle with only slight clearance the leg lib and the head no. It will be obvious, of course, that the magnet is effectively insulated from the cooperating contact members and from all other conducting part of the relay except the associatcd supporting members. A depending extension Ila is formed on the end of the movable contact finger ll adjacent to the magnet for a purpose which will be made clear presently.

The operation of the magnetic blowout means embodying my invention will best be understood by reference to Figs. 2 and 3. Referring first to Fig. 2, the shaded area It represents the area of contact between the low resistance contact tip of the contact finger ii and the front contact member ll, while the lines 21 represent the lines of force set up by the magnet on the side facing the contact. It is apparent that when the contact members separate, an arc may form at any point within the shaded area of contact. Assuming that the contact finger ii is positive with respect to the fixed front contact member I! so that the direction of current flow is upwardly, as viewed in Fig. 2, the arc will set up a field which surrounds the arc in a counterclockwise direction, and this field will react with the lines of force set up by the magnet to cause the arc to move at right angles to the magnetic field. It is desirable that the arc should move toward the magnet for a purpose which will be made clear presently, and to this end the magnet is in a direction so disposed that its right-hand pole will be a north pole and its left-hand pole will be a south pole, as indicated by the letters N and S in the drawings. With the magnet poled in this manner, the direction of the field 21 will be counterclockwise, and if the separation occurs at point A, the reaction between the magnet field and the field resulting from the arc, and indicated by the dash lines 2|, will cause the arc to move to ward the center of the magnet as indicated by thearrowll. Inasimilarmanneniffinalcontact separation occurs at points B or C, the reaction between the magnet field and the field resulting from the arcs and indicated by the dash lines II and 32 will likewise cause the arc to move toward the center of the magnet as indicatcd by the arrows II and II. It follows, therefore, that with the parts arranged in the manner Just described a separation of the contact formed by the cooperating contact members at any point within the contact area will cause the arc to move to center itself with respect to the magnet. This centering action confines the arc to a limited space adjacent to the associated contacts and prevents it from attaching itself to adjacent contact members or other adjacent parts with which the relay may be provided Referring now to Fig. 3, as here illustrated, the successive positions of an are as it moves away from the contact member is indicated by the irregular lines a, b, c, d and s, respectively. At position a, the arc is short and has its center drawn toward the magnet. At position b, the upper end of the arc has moved upwardly along the contact member I3, and the lower end of the arc has moved downwardly along the extension liaofthefinger ii,while thecentralpartofthe arc becomes extended toward the magnet to where it almost touches the magnet. At position c, the arc has attached itself to the magnet which causes it to separate into an upper and a lower are. In positions d and e the upper and lower arcs have continued to lengthen out. The distance that the arc travels and the amount that it lengthens out before it is extinguished depends upon the strength of the current which is interrupted. For small arcs the arc becomes extinguished at about position a or b, whereas for larger arcs position c, d or e will be reached before extinction occurs depending upon the magnitude of the current.

The magnet being a large mass of cool metal, causes cooling of the arc. The extension lid on the contact finger i I provides a path for the lower end of the arc to follow whereby the arc is maintained in a strong part of the magnetic field until extinction occurs. For best results, it is important that both ends of the arc be kept moving during the time that it is lengthening out, for the reason that if the end of the arc remains stationary at any one point for any appreciable length of time, a large amount of heat will develq: at that point increasing electron emission and resulting in pitting and burning of the contact members. Omission of the projection lid on the contact finger would result in the lower end of the arc running down under the contact spring and away from the magnet since the direction of current flow in the lower end of the arc will then be downward. If this were permitted to happen. the lower end of the arc would be in a diverging field. so that control over the direction of travel of the lower end of the arc would be lost, and a poorer centering action would result.

The polarities of the magnet and contact finshorter distance of arc travel and less are flare by splitting the are into more parts, and in Fig. 4 I have shown a modified form of blowout means which accomplishes this result. Referring to Fig. 4, as here illustrated, the magnet which is here designated 35 is soldered or brazed to a supporting bracket 36 secured to the lower end of the terminal post 22. The magnet 35 is of the bar type, and is disposed in an inclined plane in the manner shown to permit a somewhat larger magnet to be mounted in the limited space available. The magnet is magnetized in the same manner as the magnet 20 illustrated in the preceding views and has its pole face inclined at such an angle that when the magnet is in place this pole face will lie in a vertical plane contiguous to the cooperating contact members H and I3. Secured to the upper side of the magnet by means of a bolt 31 are a pair of superposed-arcing plates 38a and 38b spaced apart by insulating spacers 39, and secured to the underside of the magnet by means of the same bolt 31 is a third arcing plate 40 which is spaced from the head of the bolt and from the magnet by other insulating spacers 42. i'he bolt 31 is surrounded by an insulating tube 4! which passes through the plates and spacers and which insulates the magnet and plates from the bolt.

With the blowout means arranged as shown in Fig. 4 when an arc is formed by the separation of the cooperating contact members it moves toward the magnet in the same manner as in Fig. 1, but due to the arcing plates when the arc reaches the magnet it is caused to split into five smaller arcs, a first one of which extends from the contact member i3 to the upper plate 381:, a second one of which extends from the plate 38!: to the plate 380, the third one of which extends from the plate 38a to the magnet, the fourth one of which extends from the magnet to the plate 40, and the fifth one of which extends from the plate 40 to the extension Ila of the finger II. The splitting up of the are into these five smaller parts increases the current that can safely be broken by the contacts.

Referring now to Figs. 6 and 'l, I have here illustrated another form of blowout means embodying my invention which latter means also serves to split the are up into a number of parts as it moves toward the magnet. As here illustrated, a pair of insulating end plates 45 and 46 are disposed on opposite ends of the magnet 4 and are secured to supporting plates 41 and 45 disposed above and below the magnet, respectively, The end plates are secured to the supporting plates by means of ears 49 on the supporting plates which extend through slots in the end plates and have their outer ends bent at right angles to the plane of the supporting plates, and the supporting plates are secured to the magnet by the spring action of two return bends 48a and 48b formed in the opposite sides of the plate 48 and by a finger 48c which is formed in the return bend 48a and which extends into one end of a vertical hole 50 formed in the magnet (see Figs. '7 and 9) The end plates support two arcing plates 5| and 52 disposed above and below the supporting plates 41 and 48 respectively in parallel spaced relation. The arcing plates are secured to the end plates in the same manner as the supporting plates.

The operation of the blowout means shown in Figs. 6 and 7 is similar to that shown in Fig. 4, and will be apparent from the foregoing without further detailed description. One advantage of the blowout means shown in Figs. 6 and 7 over that shown in Figs. 4 and 5 is that the insulation which insulates the plates from each other and from the magnet is removed from the arc path.

Referring next to Fig. 8, as here illustrated two very small bar type magnets 55 and 56 are secured respectively to the contact finger ii and to the fixed contact member l3. The bar magnet 55 is disposed underneath the low resistance contact tip of the finger II, and is fastened thereto as by soldering. The other magnet 56 is surrounded -by a very thin supporting member 51 which is clamped between the contact supporting bracket l4 and the front contact member l3. Both magnets are magnetized to blow the arc toward the front of the relay.

While the arrangement shown in Fig. 8 does not have as high a current interrupting capacity as the other arrangements described above it will permit the contacts to satisfactorily interrupt an inductive load of 15 amperes at volts direct current. The interrupting capacity of the same contact without any blowout means is about 1 ampere at 110 volts.

One advantage of blowout means embodying my invention is that it permits the same type of relay contacts to be used for interrupting relatively large currents that heretofore have only been satisfactorily used for interrupting relatively small currents at low voltages.

Another advantage of blowout means embodying my invention is that it can be applied to existing relays without disturbing the contact structure of the relay.

although I have herein shown and described only several forms of relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. A magnetic blowout means for extinguishing arcs formed by the separation of the cooperating contact members of an electrical relay, said blowout means comprising two relatively small bar type permanent magnets secured to said cooperating contact members, respectively, and poled to blow the arc toward the front of the relay.

2. In a relay blowout means, in combination, cooperating fixed and movable contact members, a permanent magnet supported in front of said contact members in close proximity thereto by means which insulates the magnet from the contact members, said magnet being so disposed that it sets up a field which is at right angles to the direction of current flow in any arc which might form when the contact members are separated and being so poled with respect to the direction of current flow through said contact members that the arc will move toward the magnet, insulating end plates supported on opposite sides of the magnet by supporting plates disposed above and below the magnet, said end plates being secured to the supporting plates by means of ear: provided on the supporting pletee and extendinlthrough slotl provided in the end plltea and having their outer ends bent at right melee to the plane 01' the supporting plates, aid supporting plates bein: secured to the magnet by the spring action ottwo return bends formed on the one plate and by e finger formed on one return bend and extending into a hole provided in the magnet, and two orcing pletu supported it their ends above end below the meanet in apeeed relation thereto, eeid ercin: plates being lecured to "1d end plates in the some mmner thetuideupportingphteeuelecuredtouid end plates ARTHUR H. DODD.

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