US2057605A - Electrical relay - Google Patents

Description

Oct. 13, 1936. H. G. BLOSSER ELECTRICAL RELAY Filed Jan -16, 1936 2 Sheets-Sheet l 1/ 1/ l l l/l l llll ll/ l/////// Herman 0.3[03591 INVENTOR QRVLLLAL .um ATTORNEY Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE ELECTRICAL RELAY Application January 16, 1936, Serial No. 59,441

13 Claims.

My invention relates to electrical relays, and particularly to electrical relays which are suitable for use as track or line relays in railway signaling systems employing for the control of the signaling devices direct current which is periodically interrupted or coded at different frequencies in accordance with different traific conditions.

More particularly, my present invention relates to improvenents in relays of the type described in Letters Patent of the United States No. l,975,652, granted to me on October 2, 1934.

One object of my invention is to increase the life of relays of the type described.

Another object of my invention is to improve the electrical characteristics of relays of the type described.

Other objects of my invention will appear as the description proceeds.

20 I will describe two forms of electrical relays embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, F'g. 1 is a front elevational View showing one form of relay embodying my invention, certain of the parts being broken away or 'sectioned to better illustrate the Construction. Fig. 2 is a side View of the relay shown in Fig. 1. Fig. 3 is a sectional view taken on the line III- III of Fig. 2. Fig. 4 30 is a detail View showing on an enlarged scale a portion of the relay illustrated in Fig. 1. Fig. 5 is a view showing a modification of the relay illustrated in Fig. l, and also embodying my invention. Fig. 6 is a detail View of a portion of the relay illustrated in Fig. 5.

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

Referring first to Figs. 1 and 2, the relay comprises a suitable case consisting o-f a top plate l of insulating material Secured to the upper end of a substantially U-shaped non-magnetizable bracket 2, a metallic base plate 3 Secured to the lower end of the bracket 2, and a transparent glass cylinder 4 clamped between the top plate i and the base plate 3. A gasket 5 of cork or other suitable material is interposed between the top plate l and the upper end of the cylinder and a similar gasket 6 is interposed between the bottom plate and the lower end of the cylinder, thereby scaling the case against the entry of dust and other ;foreign Lubstances.

The Operating mechanism of the relay is mounted on the U-shaped bracket 2 and, as 55 here shown, comprises a core structure consisting of two vertically disposed magnetizable bars 'I and 'l secured, respectively, to the legs Z and Z of the bracket 2 by means of studs 8, which studs pass through clearance holes in the bars and are screwed into tapped holes provided in lugs which are ormed integral with the legs 2 and 2 The bars 'i and l are provided at their upper ends with adjustable pole pieces 9 and 9 having confronting pole faces !U and l and at their lower ends with adjustable pole pieces ll and H provided with confronting pole faces !2 and !2 Associated With the core structure is a permanent magnet !3 which, as here shown, com\- prises a rectangular bar bent into a U-shape. This magnet is disposed With its two legs engaging the bars 'I and l at points approximately midway between the two sets of pole pieces, and is Secured to the bracket 2 by means of a clamping strap !4 and studs !5. The permanent magnet !3 is preferably made of cobalt steel because of its well known property of retaining a high degree of magnetic saturation over long periods of time.

A resilient strip l'l of suitable material, such as phosphor bronze, is clamped at its lower end between two clamping plates !8 which are secured to the bracket 2 by means of studs IS, and the upper end of this spring is astened, as by riveting, to the lower end of a magnetizable armature 20. The armature extends upwardly between the confronting pole faces l2 and !Z of the pole pieces ll and H and the confronting pole faces m and l of the pole pieces s and 9 and is provided adjacent its upper end with core pins 2| of brass or other nonmagnetic material, which core pins cooperate with the pole pieces 9 and 9 to prevent the armature from coming into direct contact with these pole pieces. When the relay is in operation, the armature 20 oscillates between the pole pieces 9 and 9 and the pole pieces ll and ll at a rapid rate, and to prevent breakage of the resilient strip l'l due to the resultant fiexing of this strip, the upper ends of the clamping plates !8 are rounded, as shown` in Fig. 1, in such manner that any flexing of the strip which occurs adjacent the upper ends of these plates will be in the form of a gradual curve. Furthermore, the lower end of the armature 20 is likewise rounded, and a clamping plate 22 having a rounded lower edge is disposed on the opposite side of the strip I'I from the armature to prevent sharp bends in the fiexible strip adjacent the lower end of the armature.

The armature 20 and the magnetizable parts of the magnetic circuit are preferably made of 50% nickel steel because of the high coercivity of this material.

surrounding the armature 20 between the two sets of pole pieces is an Operating winding 23 which is wound on a hollow spool 24. The leads 23 and 23 of the winding 23 extend upwardly and are Secured at their upper ends to terminal posts 25 and 25 mounted on the top plate l. Painted or otherwise ormed on the top plate l adjacent the terminal posts 25 and 25 respectively, are the symbols plus and minus (not shown) indicating the correct polarity of the current on which the relay is intended to be operated.

With the above described Construction, the polarizing flux due to the permanent magnet !3 traverses several diiferent paths. One of these paths passes downwardly from the righthand end of the permanent magnet !3, as viewed in Fig. 1, through the lower end of the bar T the pole piece H the air gap between the pole piece ll and the lower end of the armature 20, the lower end of the armature 20, the air gap between the lower end of the armature 20 and the pole piece ll the pole piece ll and then upwardly through the lower end of the bar l to the other end of the permanent magnet. Another path passes upwardly from the righthand end of the permanent magnet !3, as viewed in Fig. l, through the upper end of the bar T the pole piece 9 the air gap between the pole piece 9 and the upper end of the armature 20, the upper end of the armature 20, the air gap between the upper end of the armature 20 and the pole piece S the pole piece 9, and then downwardly through the bar 'l to the lefthand end of the permanent magnet l3. Another path for the polarizing fiux extends upwardly through bar T as viewed in Fig. 1, pole piece 9 the air gap between the pole piece s and the armature 20, downwardly through the length of the armature 20, the air gap between the lower end of the armature and the pole piece ll the pole piece ll and then upwardly through the bar 'l to the lefthand end of the permanent magnet. When the armature occupies the opposite extreme position from that in which it is shown in Fig. 1, some of the flux which leaves the righthand end of the permanent magnet will pass downwardly through bar I through pole piece ll the air gap between the pole piece ll and the lower end of the armature 20, then upwardly through the armature, across the air gap between the upper end of the armature and the pole piece 9 the pole piece 9, and then downwardly through bar 'l to the lefthand end of the permanent magnet.

It will be apparent, therefore, that both the amount and the direction of the polarizing fiux which passes lengthwise through the armature 20 depends upon the position of the armature with respect to the pole pieces 9 and a When the armature is midway between these pole pieces, there is no polarizing fiux through the armature in the direction of its length because both ends of the armature are then at the same magnetic potential, but as the armature moves toward one or the other of the pole pieces !l and 9 fiux flows through the armature in one direction or the other depending upon which one of these pole pieces is approached.

The path of the fiux, due to the current flowing in the Operating winding 23 of the relay,

may be traced from the upper end of the armature 20 where it divides between the air gaps, to pole pieces 9 and S then through the bars 7" and l the pole pieces ll and H and the air gaps between the pole pieces Il and H to the lower end of the armature. The direction of the flux in these paths depends, of course, upon the polarity of the current supplied to the Operating winding 23, and it will be apparent that when this flux is in one direction, the armature 20 will be repelled from the pole piece 9 and attracted to the pole piece S but with the current reversecl and this flux in the opposite direction, the armature will then be repelled from the pole piece 9 and attracted to the pole piece s There is also a third path for the Operating fiux passing through the permanent magnet, but due to the fact that the magnetomotive force of the electromagnetic flux is at about the same potential as that of the permanent magnet at the connecting points, and also due to the high reluctance of the permanent magnet, as compared to that of the core structure, practically no part of the ux returns by this path.

The armature 20 is constantly biased to the position in which the core pins 2| engage the pole piece 9* by means of contact mechanism which I will now describe. Referring now also to Fig. 3, this contact mechanism in the form here shown comprises two inverted U-shaped supporting brackets 30 and 311 which are fastened to the underside of`the top plate l adjacent the opposite sides of the top plate by means of terminal posts ai and 3I respectively. A flexible strap 33 is Secured at one end to the depending leg 34 of the bracket 30 and the other end of this strap is Secured to a contact nger 32 intermediate the ends of the finger. The strap 33 at the end which is attached to the leg 34 of the bracket 30% is spaced from the bracket by a spacing member 36 having a rounded edge 3l and the finger 32 extends parallel to the strap 3:1 on the side of the strap opposite to the spacing member to a point opposite the rounded edge 31 in such manner that if the end of the finger is moved in a manner to defiect the strap, the fiexing of the strap will occur adjacent the rounded edge of the spacing member and the flexed portion will be in the form of a gradual curve. The finger 32 extends horizontally toward the armature 20 in a plane substantially parallel to the plane oi the armature and is provided at its free end with a rounded button 26 which cooperates with a chromium-plated insert 21 mounted in an insulating member 35 which is Secured to the upper end of the armature, as best seen in Fig. 4. The insulating member 35 is provided with a 'ecess 35 which receives the upper end of the armature in such manner that the insulating member cannot turn relative to the armature. A compressed coil spring 38 is interposed between the depending leg 39 of the bracket 30 and the contact finger 32 and this spring engages the finger 32 at a point between the rounded edge 31 of the spacing member 36 and the pointwhere the strap 33 is Secured to the finger in such manner that the armature 20 is biased by the spring through the medium of the finger in the position shown The spring 38 is held in place between the leg 319 of the bracket 30 and the nger 32 by means of suitable spring supports 40 and dl riveted, respectively, to the leg 39 ^and to the finger 32 Contact buttons 42 and 43 are attached to the finger 32 on opposite sides of the finger and these contact buttons cooperate, respectively, with similar contact buttons M and :5 Secured to front and back contact springs Mi and 41 to close a back contact Iz M or a front contact m -at according as the armature 20 occupies the position in which the core pins 2! engage the pole piece 9 or the position in which the core pins 2! engage the pole piece 9. The ront and back contact springs Mi and 11 are Secured to the top plate l by means of terminal posts 48 and 49 and are provided with suitable stops 50 and 51 to accurately position these springs when the springs are not being engaged by the contact buttons 42 and 43 attached to the finger 32% A contact finger 112 is attached to the bracket 30 in the same manner that the finger 32 is attached to the bracket 30 and this finger is biased to a position in which a rounded button 26 Secured to the end of the finger engages a chromium-plated insert 21 mounted in the insulating member 35, and this :nger cooperates with front and back Contacts, in the same nanner that the finger 32 is biased into engagement with the other button 21 mounted in the member 35 and cooperates with front and back contacts.

The o-peration of the relay as a whole is as follows: When the winding 23 is deenergized the armature 26 is held in the position shown by the contact mechanism of the relay, and also by a small force due to the pull which is* exerted on the armature by the permanent magnet flux, and

35 under these conditions, the back Contacts 42 l l and 42 -44 are both closed, while the front Contacts te te and 43 15 are both open. When, however, the winding 23 is supplied with current in accordance With the polarity markings on the top plate the armature 20 is repelled from the pole piece s and attracted toward the pole piece s thus causing the armature to move from the position shown to the position in which the core pins 2! engage the pole piece gb and, under these conditions, the back contacts 42 -4 1 and u -M become opened and the front contacts is -45 and IS l5 become closed. It will be obvious, of course, that when the armature is once moved from the position shown to its other position as just described, it will remain in its other position until the winding 23 again' becomes deenergized, at which time the armature will return to the position shown due to the bias of the contact mechanism. If current having a polarity opposite to that indicated by the markings on the top plate of the relay should be supplied to the relay for any reason, the armature will remain in the position shown because the armature will then be attracted to the pole piece s and repelled from thepole piece 9 Referring now to the modified form of relay illustrated in Figs. 5 and 6, as here shown, the armature 20 instead of being supported at its lower end by means of a fiexible strap, in the manner shown in Figs. l and 2, is supported by means of a knife-edge bearing comprising a knife-edge member which fits into an inverted v-shaped groove 20 provided in the lower end of' the armature. The knife-edge member 50 is Secured to the bottom of the bracket 2 in a vertical position by means of laterally spaced studs i, and interposed between the knife-edge member and the bracket 2 is a spacer 52 and an armature retaining bracket 53. The bracket 53 is provided at its upper end with laterally spaced horizontally extending fingers 53 and 53 (see Fig. 6-) which project loosely through notches' 2-0 and Zli formed in the opposite sides of the armature 20 a short distance above the lower end of the armature to prevent Vertical displacement of the armature. The bracket 53 is also provided at its opposite sides with two other laterally spaced fingers 53 and 53 which extend parallel to the fingers li?, and 53 and Secured to the fingers 53 and 53 adjacent their free ends are round- headed members 54 and 55 which cooperate with the sides of the armature to prevent lateral displacement of the armature relative to the knife-edge member 50. It will be seen, thererfore, that with the armature supported in the manner just described it is free to oscillate between its two extreme positions with substantially no iriction, and that wear of the parts is reduced to a minimum.

It will be readily understocd that when the armature 20 is supported by means of a bearing of the type just described it is desirable that the core pins 2! should strike the pole faces IE) and m exactly square to avoid any twisting motion of the armature which would cause undue wear of the armature hearing. In order to insure that the core pins Zi will strike the pole faces in the desired manner, and at the same time allow for slight mechanical variations which may occur' in shop manufacture, the pole pieces 9 and 9 are preferably constructed in such manner that the pole faces lil and lil of these pole pieces are inclned at a slight angle to the axis of the pole pieces, thus making it possible for the mechanic who assembles the relay to adjust the pole faces by rotating the pole pieces until the pole faces' are exactly parallel at the point where the core pins 2| strike these pole faces. To facilitate rotating the pole pieces, a saw cut 56 is provided in the outer ends of the pole pieces. In addtion to preventing wear on the armature hearing due to the prevention of a twisting motion as above described, the proper alignment of the pole faces with respect to the armature core pins also prevents wear by tending to keep the armature centrally located r with respect to the magnetic circuit.

It will be noted from an inspection of Fig. 4 that the insulating member 35 which operates the contact fingers 32* and 32 is provided with spaced laterally projecting arms 35 and 35 which arms extend between the ends of the contact fingers. One function of these arms is to prevent lateral displacement of the upper end of the armature 20 when a hearing structure of the type just described is used.

One advantage of a relay embodying my present invention is that the armature supporting structure is located wholly outside of the magnetic circuit formed by the magnetizable members E 1 the pole pieces 9 a li and ll and the armature 20, thus making it possible to use any desired type of bearing regardless'of its size or the type of metals employed without danger of affecting the electrical characteristics of the magnetic circuit. The locating of the armature supporting structure outside of the magnetic circuit also permits the use of an armature having a uniform cross section throughout all that portion which is included in the magnetic circuit, thus insuring a low reluctance path through the armature and, hence, providing a relay of high effciency. Furthermore, the locating of the armature supporting structure outside of the magnetic circuit greatly facilitates inspection of the bearing structure and insures that any metal particles which may become loosened from the bearing structure due to wear will not interfere with the proper operation of the relay.

Another advantage of a relay embodying my invention is that, since the lower pole pieces H and II are adjustable, variations which occur in the magnetic circuit due to variations in manufacture can be compensated for in such manner that it is possible to obtain not only the desired pickup and release values of the relay, but also the exact electrical operation of the relay for all positions of the armature from its full released position to its full stroke position and back to its full released position. This feature is very deslrable because it permits the relay to be so adjusted that when sufficient energy is supplied to move the armature from its full released position the armature will move all the way to its full stroke position with a snap action and that, when the energy in the relay winding is reduced to the point where the armature leaves its full stroke position, it will move all the way back to its full released position. This feature is also important because it permits the use of commercial tolerances on all mechanical parts of the relay, and eliminates the necessity for a permanent magnet shunt to obtain the desired plckup and release values.

Although I have herein shown and described only two forms of electrical relays embodying my invention, it is to be understood that various changes and modiflcations may be made 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 relay comprising a pair of magnetizable bars provided with two sets of confronting pole pieces, a magnetizable armature disposed between the pole pieces of both sets and movably supported at one end by means located outside the magnetic circuit formed by said bars, said armature, and said pole pieces in such manner that said armature is free to oscillate between the pole pieces, a winding surrounding said armature between said two sets of pole pieces, a permanent magnet connected with said two bars between said two sets of pole pieces for polarizing said relay, and contact mechanism controlled by said armature.

2. A relay comprising a pair of magnetizable bars provided with two sets of confronting pole pieces, a magnetizable armature disposed between the pole pieces of both sets and movably supported at one end by means located outside the magnetic circuit formed by said bars, said armature, and said pole pieces in such manner that said armature is free to oscillate between the pole pieces, a winding surrounding said armature between said two sets of pole pieces, a permanent magnet connected with said two bars between said two sets of pole pieces for polarizing said relay, and contact mechanism controlled by said armature and acting to bias the armature to the position in which it engages one pole piece of the one set, whereby said relay will respond to current of one polarity only in said winding.

3. A relay comprsing a pair of magnetizable bars, two sets of confronting pole pieces adjustably secured to said bars in such manner that the pole pieces of each set are movable toward and away from each other, a magnetizable armature disposed between the pole pieces of both sets and movably supported at one end by means located outside the magnetic circuit formed by said bars, said armature, and said pole pieces in such manner that said armature is free to oscillate between the pole pieces, a winding surrounding said armature between said two sets of pole pieces, a permanent magnet connected with said two bars between said two sets of pole pieces for polarizing said relay, and contact mechanism controlled by said armature.

4. A relay comprising a pair of magnetizable bars, two sets of confronting pole pieces adjustably secured to said bars in such manner that the pole pieces of each set are movable toward and away from each other, a magnetizable armature disposed between the pole pieces of both sets and movably supported at one end by means located outside the magnetic circuit for-med by said bars, said armature, and said pole pieces in such manner that said armature is free to oscillate between the pole pieces, a winding surrounding said armature between said two sets of pole pieces, a permanent magnet connected with said two bars between said two sets of pole pieces for polarizing said relay, and contact mechanism controlled by said armature and acting to bias the armature to the position in which it engages c ne pole piece of said one set, whereby said relay will respond to current of only one polarity in said winding.

5. A relay comprising a pair of magnetizable bars provided with two sets of confronting pole pieces, a magnetizable armature disposed between the pole pieces of both sets and movably supported at one end by means located outside the magnetc circuit formed by said bars, said armature, and said pole pieces in such manner that said armature is free to oscillate between the pole pieces, the pole pieces which are disposed farthest away from the armature supporting means being rotatable about their aXes and having their pole faces inclined at an angle to their axes in such manner that by rotating said pole pieces the plane of the pole faces may be made parallel to each other irrespective of slight variation in manufacture of the magnetizable bars and the pole pieces, a winding surrounding said armature between said two sets of pole pieces, a permanent magnet connected with said two bars between said two sets of pole pieces for polarizing said relay, and contact mechanism controlled by said armature.

6. A relay comprising a pair of magnetizable bars provided with two sets of confronting pole pieces, a flexible strip clamped at one end between two clamping blocks, the ends oi said blocks which are disposed nearest the free end of said strip being rounded in such manner that if said strip is flexed it will bend in a gradual curve adjacent the rounded ends of said blocks, an armature disposed between the pole pieces of both sets and secured at one end to the free ,end of said fiexible strip in such manner that said armature is free to oscillate between said pole pieces, said armature at the end which is secured to said strip being rounded and a clamping block having a rounded end being secured to said armature on the side of said strip which is away from said armature, whereby any flexing of said strip which occurs adjacent the end of said armature due to oscillation of said armature will be in the form of a gradual curve, a permanent magnet connecting said bars between said pole pieces for polarizing said armature, a winding surrounding said armature between said two sets of pole pieces, and contact mechanism controlled by said armature.

'7. A relay comprising a pair of magnetizable bars, two sets of pole pieces Secured to said bars in such manner that the pole pieces of each set are movable toward and away from each other, a fiexible strip having one end held in a fixed position, an armature disposed between the pole pieces of both sets and Secured at one end to the free end of said strip, whereby said armature is free to oscillate between the pole pieces of both sets; said strip being located wholly outside the magnetic circuit formed by said' bars, said pole pieces, and the portion of said armature which is disposed between said po1e pieces; a permanent magnet connected with said bars between said two sets of pole pieces for polarizing said relay, a winding surrounding said armature between said two sets of po1e pieces, and contact mechanism controlled by said armature.

8. A relay comprising a pair of vertically disposed magnetizable bars, a first pair of confronting pole pieces Secured to said bars adjacent the upper ends of said bars, a second pair of confronting po1e pieces secured to said bars adjacent the lower ends of said bars, a knie edge member disposed directly below the air gap between the lower pair of pole pieces, an armature disposed in the air gaps between pole pieces of both pairs and provided at its lower end with an inverted V-shaped groove which receives the knife-edge of said kniie edge member, whereby said armature is free to oscillate between the po1e pieces, said armature being provided in its opposite sides adjacent its lower end with a pair of notches, a fixed armature retaining bracket provided with a first pair of fingers which extend loosely into said notches in a manner to prevent vertical displacemert of said armature and with a second pair of fingers which cooperate with the sides of said armature to prevent lateral displacement of said armature, a permanent magnet connected with said bars between said two sets of po1e pieces for polarizing said relay, a winding surrounding said armature between said two' sets of pole pieces, and contact mechanism controlled by said. armature.

9. A relay comprising a pair of vertically disposed spaced parallel magnetizable bars, a first pair of axally aligned pole pieces secured to said bars adjacent their upper ends in such manner that the pole pieces may be moved toward and away from each other and may be rotated about their axes, the po1e faces of said first pair of pole pieces being disposed at an angle to the axis of these pole pieces in such manner that by rotating said pole pieces about their axes the planes of the po1e faces may be made parallel to each other irrespectve of slight Variations in manufacture of the bars and pole pieces, a second pair of pole pieces secured to said bars adjacent their lower ends in such manner that the pole pieces of said second pair may be moved toward and away from each other, an armature disposed between the po1e pieces of both pairs and loosely supported at its lower end by means located below the lower po1e pieces in such manner that said armature is free to oscillate between the po1e pieces, a pair of non-magnetizable core pins Secured to said armature between the pole pieces of said first pair to prevent the armature from coming into contact with the pole pieces of said first pair, the pole pieces of said first pair being rotated to such position that when the core pins move into engagement with either of these pole pieces they will simultaneously engage the pole face of such pole` piece, a permanent magnet connected with said bars between said two sets of pole pieces for polarizing said relay, a winding surrounding said armature between said two sets: of pole pieces, and contact mechanism controlled by said armature.

10. A relay comprising a pair of vertically disposed spaced parallel magnetizable bars, a first pair of axially aligned pole pieces secured to said bars adjacent their upper ends in such manner that the pole pieces may be moved toward and away from each other and may be rotated about their axes, the pole faces of said first pair of po1e pieces being disposed at an angle to. the axis of these po1e pieces in such manner that by rotating said po1e pieces the planes of the po1e faces may be made parallel to each other irrespective of slight variations in manufacture of the bars and po1e pieces, a second pair of pole pieces secured to said bars adjacent their lower ends in such manner that the pole pieces of said second pair' may be moved toward and away from each other, a knife edge member disposed directly below the air gap between the lower pair of pole pieces, an armature disposed in the air gaps between both pairs of pole pieces and provided at its lower end with an inverted V-shaped groove which receves the knife edge of said knife member', whereby said armature is free to oscillate between the pole pieces, said armature being provided in its opposite sides adjacent its lower end with a pair of notches, a fixed armature retaining bracketi provided with a first pair of fingers which extend loosely into said notches in` a manner to prevent vertical displacement of said armature and with a second pair of fingers which cooperate with the sdes of said armature to prevent, lateral displacement of said armature, a pair of nonmagnetizable core pins Secured to said armature between the pole pieces of said. first pair to: prevent the armature from coming into contact' with the pole pieces of said first pair, the po1e pieces of said first pair being rotated to such positions that when the core pins move into engagement with either of these po1e pieces they will simultaneously engage the pole face of such pole piece, a permanent magnet connected with said bars between said two sets of pole pieces for polarizing said relay, a winding surrounding said armature between said two sets of pole pieces, and contact mechanism controlled by said armature.

11. A relay comprising a pair of vertically disposed spaced magnetizable bars, a first pair of axially aligned pole pieces secured to said bars adjacent their upper ends in such manner that the pole pieces may be moved toward and away from each other and may be rotated about their axes, a second pair of po1e pieces Secured to said bars adjacent their lower ends in such manner that the po1e pieces of said second pair may be moved toward and away from each other, an armature disposed between the po1e pieces of both pairs and loosely supported at its lower end by a knife edge hearing located wholly outside the magnetic circuit formed by said bars, said po1e pieces, and the armature, a pair of core ins secured to said armature between the po1e pieces of said first pair and cooperating with the pole pieces of said first pair to prevent said armature from coming into contact with the pole pieces of said first pair, the pole faces of said first pair, being disposed at an angle to their axes in such manner that by rotating said pole pieces the pole faces may be made parallel irrespective of variations in the dimensions of the parts due to manufacturing tolerances and that said core pins will simultaneously strike the pole face of each pole piece toward which the armature is moved, a permanent magnet connected with said bars between said two sets of pole pieces for polarizing said relay, a winding surrounding said armature between said two sets of pole pieces, and contact mechanism controlled by said armature.

12. A relay comprising a pair of magnetizable bars provided with two pairs of confronting pole pieces, a magnetizable armature disposed between the pole pieces of both pairs and loosely supported at one end for oscillation between the pole pieces, a permanent magnet connected with said two bars between said two pairs of pole pieces for polarizing said relay, a winding surrounding said armature between said two pairs of pole pieces, an insulating member Secured to said armature at the end opposite to said bear ing, two chromium-plated inserts mounted in said insulating member, two contact fingers each engaging said inserts and serving to bias said armature to one position in which it engages one pole piece of the pair of pole pieces which is nearest said insulating member, whereby said relay will respond to current of one polarity only, and Contacts controlled by said contact finger.

13. A relay comprising a pair of magnetizable bars provided with two pairs of confronting pole pieces, a magnetizable armature disposed between the pole pieces of both pairs and loosely supported at one end for oscillation between the pole pieces, a permanent magnet connected with said two bars between said two pairs of pole pieces for polarizing said relay, a winding surrounding said armature between said two pairs of pole pieces, an insulating member Secured to said armature at the end opposite to said bearing, two chromium-plated inserts mounted in opposite sides of said insulating member, two contact ngers extending laterally toward said armature on opposite sides of said armature and provided at their free ends with rounded buttons which engage said chromium-plated inserts, said fingers being biased to one position and serving to bias said armature to the position in which it engages one pole piece of the pair of pole pieces which is nearest said insulating member, where by said relay will respond to current of one polarity only, Contacts controlled by said contact fingers, and Iaterally projecting arms formed on said insulating member and cooperating with the ends of said fingers to prevent lateral displacement of said armature.

HERMAN G. BLOSSER.

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