US2259183A - Electrical relay - Google Patents

Description

Oct.A 14, l1941. c, s. sNAvELY ELECTRICAL RELAY Filed Dec. 23, 1939 2 Sheets-Sheet l fig 4.

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INVENTOR HIS ATTORNEY Oct 14, 1941- c. s. sNAvELY ELECTRICAL RELAY Filed Dec. 23, 1939 2 Sheets-Sheet 2 INVENTOR Claence L Snape@ IS ATTORN EY Patented Oct. 14, 1941 UNITED STATES, PATENT OFFICE ELECTRICAL RELAY Glalfence S. Snavely, PittsburghPa., assignor to The Union Switch & Signal Company, Swissvale; Pa., acorporation of PennsylvaniaL Application December 23, 1939, Serial No. 310,713

(Cl. ZOO- 104) 5 Claims.

My invention relates to electrical relays,y and particularly to electrical relays suitable for use in centralized traffic controlling systems for railroads.. such, for example, as that. disclosed in an application for Letters Patent of the United States, Serial No. 222,860, led by myself and another on August 3',A 1938, for Remote control systems.

One object of my invention isl to provide an improved'A relay of' the type' described of simple, ruggedandk compact construction, which will operate without appreciable wear or change in operating characteristics over along period of timel Other objects and characteristic features of my invention will appear as the description proceeds. The relay forming the subject matter of my present'application is an improvement upon that disclosed and claimed in my prior Patent No.

2,178,289, granted on October 31, 1939, for electrical relays.

I shall describe one form of relay embodying my invention, and one method for securing` certain parts of said relay together, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a front elevational view showing one form of relay embodying myl invention, the front plate of the relay being removed to better illustrate the con 'struction of the operating parts of the relay.

Fig. 2 is a vertical sectional view of the relay shown in Fig. 1 taken substantially on the line II-II of Fig. 1. Fig. 3 is a top plan View of the relay shown in Fig. 1. Fig. 4 is a sectional view of the relay shown in Fig. l taken substantially pieces are formed on cores which are moulded into the top and bottom walls of an insulating frame,and the one pair of pole pieces is constantly magnetized by a permanent magnet while the other pair is at times energized by an electromagnet of which the associated cores form a part. The two armatures are secured to the opposite ends of a moulded contact operating member which is mounted for sliding movement in a manner to permit the two armatures to move -g toward` and away from the associated pole pieces.

' he contact operating member is provided between thevtwo armatures with a plurality of projections which form vertically spaced slots. Each of these slots receives the intermediate portion of a cooperating flexible contact nger which is moulded at one end into one of the side walls of the frame and which cooperates at its free end with a xed contact finger also moulded into a side wall oi the frame. The relay is calibrated to provide the desired operating characteristics by charging the permanent magnet and then discharging it to a value which will give the desired piek-up current, and also by varying the air gaps between the cores and the backstrap of the elec- 1 on the line IV-IV of Fig. 1. Figs. 5, 6 and 7 are back, side and top views, respectively, of the contact operating member 21 forming part of the relay shown in Fig. 1. Fig. 8 is a detail view of the member 32 forming part of the relay shown in Figs. 1 and 2. Figs. 9, 10 and 11 are diagrammatic views illustrating certain features of the relay embodying my invention. Figs. 12 and 13 are enlargedv views showing the means employed for securing the backstrap I3 to the cores Il and Ila of the electromaget A of the relay shown in Fig. 1 together with a mould for applying this means.

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

Referring rst to Figs. 1, 2 and 3, the relay in the form here shown comprises a suitable case consisting of a front cover plate I and a back cover plate 2 clamped by suitable means not shown against the opposite sides of a rectangular frame 'I of suitable insulating material, such for example as a phenol condensation product. This case encloses all of the operating parts of the relay, and in order to permit ready inspection of the operating parts without the necessity for removing the cover plates, the front cover plate is formed with a window 8 which is closed by a window glass 9.

Mounted on the top wall 1a of the frame 'I is an electromagnet A comprising a pair of coils I0 and Illa disposed on spaced parallel cores I I and I Ia, the lower ends of which extend downwardly through the top wall 'Ia and terminate on the underside thereof in enlarged pole pieces I2 and The cores II and IIa may be secured to the top wall 1a in any convenient manner, but-as here shown they are moulded into the top wall.

The relay also comprises an auxiliary pair of spaced parallel cores I6 and Ita which are moulded into the bottom wall 1d of the frame 1 in axial alignment with the cores I0 and Illa of the electromagnet A, and which terminate at their upper ends in enlarged auxiliary pole pieces I1 and I'Ia. The lower ends of the cores I6 and Ia are also enlarged and are engaged by the opposite ends of a permanent magnet I8. The permanent magnet I8 is held against the enlarged ends of the cores I6 and I'a by means of a curved flexible strip 2li and a bottom plate 2|, and in order to provide an efficient magnetic connection between the auxiliary cores and the permanent magnet, the engaging faces of the auxiliary cores and the permanent magnet are ground to lie in the same plane. The bottom plate 2| fits at its ends in transverse grooves 23 provided in depending legs 1e and 1f which form extensions of the side walls 1b and 1c of the vframe 1, and at its sides in grooves 24 and 24a formed respectively in the front and back cover plates I and 2.

'I'he pole pieces I2 and I2a cooperate with a main armature 25, While the auxiliary pole pieces I1 and I1a cooperate with an auxiliary armature 26. vThe two armatures 25 and 26 are moulded onto, or otherwise secured to, the opposite ends of a Contact operating member 21 of suitable insulating material in such manner that the upper face of the armature 25 and the lower face -of the. armature 26 lie in parallel planes, and these armatures act to move the contact operating member vertically between a lower position in which the armature 26 engages a stop 28 moulded onto the bottom wall 1d of the frame 1 and an upper position in which the armature 25 engages the lower faces of the pole pieces I2 and I2a, according as the electromagnet A is deenergized or energized. The parallel faces of the two armaturesare chromium plated to present smooth wearing surfaces to their respective engaging surfaces. .Furthermore the pole pieces with which the armatures cooperate are also chromium plated and polished, the chromium plating on the pole pieces I2 and I2a. serving in conjunction with the chromium plating on the armature 25 to take the place of the usual core pins to prevent the armature 25 from sticking in its attracted position due to any residual magnetism which may be present in the cores of the electromagnet A when it is deenergized. Y The contact operating member 21 is guided to move vertically by means of a vertical guide rod 3D which extends with some clearance through aligned opening 21a formed in vertically spaced lugs 21h provided on the rear side of the operating member 21. This guide rod is mounted at its upper end in an opening 3l provided in a transversely extending bar 32,*and at its lower end in an opening 33 provided in the bottom wall 1d of the frame 1. The bar 32 fits at its ends in recesses 33 formed in the side walls 1b and 1c of the frame 1 above the coil connectors I #la and I-tb and is held in place in the recesses by means of the back cover plate 2. The lower end of the guide rod is held in place in the opening 33 by means of a mass 33a of material which can be applied in a liquid or molten state and which will subsequently harden. A preferred material for this purpose is 'l per cent antimony lead. To reduce friction and wear to a minimum lthe guide rod 33 is provided with a smootlr polished surface, such for example as that obtainable by chromium plating.

'I'he bar 32, in addition to serving as a positioning means for the upper end of the guideI rod 21, is provided on the side adjacent to the: armature 25 with laterally projecting pads 32a and 32h which cooperate with the side of the armature 25 to hold it and the contact operating: member 21 in the desired angular position relative to the pole pieces and other parts of the relay. These pads are preferably chromium plated and polished to reduce friction to a minimum.

Formed on the rear side of the contact operating member 21 are a plurality of projections 35 which form slots 36. The slots 36 receive a plurality of vertically spaced superposed contact fingers 31 intermediate the ends of the fingers. The contact ngers 31 are moulded into the opposite side walls 1b and 1c of the `frame 1 in such manner that alternate fingers are located in different legs and extend in opposite directions, and, as here shown, each of the upper fingers cooperates with an associated fixed front contact finger 38 which is moulded into the side wall of the frame 1 opposite the side wall in which the finger is located, while the remaining fingers each cooperate with a fixed back contact finger 39 which is likewise moulded in the side wall of the frame 1 opposite the side wall in which Ythe associated flexible nger is moulded. To decrease contact resistance, the flexible contact fingers are each provided with Contact buttons 49 of low resistance conducting material such as silver, which contact buttons cooperate with contact button ill, also of low resistance conducting material such as silver, provided on the associated xed contact fingers. 'Ihe contact fingers each extend through the associated side Walls of the frame 1 and are provided with rounded outer ends which constitute plug portions to enable the relay to be readily plugged into suitable connectors such for example as those described in my copending application for Letters Patent of the United States, Serial No. 291,721, filed on August 24, 1939, for a Mounting means for relays. The outer ends of the two coil connectors Mc and I 4b similarly extend outwardly through the associated side walls and are provided with rounded outer ends.

The operation of the relay as a whole is as follows: The parts are so proportioned that when contact operating member 21 is in its mid-stroke position, the flexible contact fingers 31 will be substantially unexed and the contact buttons 40 on those flexible ngers which cooperate with the fixed front contact fingers 38 will be spaced the same distance from the buttons 4I on the front contact fingers as the contact buttons 40 on the flexible fingers which cooperate with the fixed back contact fingers 39 are spaced from the contact buttons 4I) on these latter contact fingers. The parts are further so proportioned that when ythe electromagnetA is deenergi-zed'the-flux from the .permanent .magnet I;8 traversing the auxiliary pole pieces v|| and v|6a, together 'with the weight -of the two armatures A'.25 and 26 andthe weight of the contact operating .member 21, will .exert a suflicient biasing .force on the contact operating member to move it downwardly .to its 'lower position in which the armature 26 engages the stop 2.8, and that before thecontact operating vmember reaches -its lower position, the contact buttons .40 on each of the three lower fiexible fin- :gers will move into engagement with the contact fbuttons on the associated fixed contact fingers 39. It will .be seen, therefore, that v.the movement of the contact operating member 21 toits lowerlmost .position will cause the centers of those flexible fingers which cooperate with fixed 'back .con tact fingers to become forced downwardly at .the .point where they are engaged Iby the projections 3.5, thereby providing a, limited .amount of wiping `action .between the engaging contact 'buttons on the flexible contact fingers and the buttons on :the fixed .back Acontact fingers as the contact operating member moves to its lowermost position, and hence insuring that when the operating member .occupies this lowermost position, vthe contact buttons on the flexible fingers willengage the contact buttons on the associated fixed back contact fingers with sufficient force to provide an .effective low resistance contact. The downward movement of the contact operating member 21 will cause each of the fiexible contact fingers which does not engage with a fixed back contact finger to continue to move downwardly at its free .end until the armature 26 reaches its lower extreme position in which it engages the stop 28. 4It will be seen, therefore, that when `the permanent magnet |8 is in place and the parts are properly adjusted, if the electromagnet A is then deenergized, the front contacts 31-38 of the relay will be open and the back contacts 31-33 will be closed.

When the electromagnet A becomes energized, .the resultant fiux which is set up by the current traversing the coils l and |0a will cause the armature 25 to move upwardly, in opposition to the bias of the permanent magnet and the weight of the two armatures and the associated Contact operating member', and will thus move the contact operating member 21 to its 4upper extreme vposition in which it engages the pole pieces |2 and |2a. This upward movement will cause the .conn tact buttons 46 on the flexible contact finger to move out of engagement with the button 4| on the back contact fingers 39, and into engagement with the buttons 4| on the front Contact members, thereby opening the back contacts 31-39 and closing the front contacts 31-38. rI'he parts are further so proportioned that the contact buttons M on the flexible contact fingers will move into engagement with the buttons 4| on the front contact fingers 38 before the armature 25 reaches its upper extreme position, and it will be seen, therefore, that the movement of the armature 25 to its upper extreme position will cause the fiexible contact fingers 31 to become bowed upwardly intermediate their ends and will thus cause a limited amount of wiping action between the engaging contact buttons 43 and 4| as the armature 25 completes its upward movement, as well as insuring a good contact pressure to provide an efiicient low resistance contact.

It will be noted from an inspection of Fig. that alternate ones of the projections 35 on the contact operating member 21 are disposed on Aoppositeisides =of the center line. This arrangement affords Vanumber of advantages which can Abest be l.explained by reference to the views shown in Figs. 9, and 11.

Referring to these views, Fig. 10'shows one of lthe front contacts 31-38 so adjusted that when the :associated linger 31 is unstressed, the button 4.0 .carried thereby will just touch the button 4| von theassociated iixedfront contact finger. With l:the finger adjusted in Vthis manner, vwhen the contact is opened vby `driving the operating member 21 downwardly to the yposition shown in Fig. l-l, ithe finger 31 will free itself from the lower pro- :jection 3.5 as 'shown bythe spa-ce 35a between the projection and the finger. Thus there is no `tendency for the projection to bind the finger when 'the contact is open. When the operating member 2.1 'is driven upwardly from the position shown in Fig. 10, as is the case when the armature'25 is attracted, the contact member 31 vthen becomes compressed .as shown in Fig. '9, and :under :these conditions the finger 31 frees itself from the upper projection V35. Thus there is no tendency to bind when the contact is compressed. .Since there is no tendency for the contact finger .to bind between .the projections 35, it is unnecessary to accurately control the thickness of the projections or the distance between them. Furthermore,.maladjustment of the contacts W'ill not .so adversely affect the operating characteristics of the relay as would otherwise be the case. Con- Sider again Fig. 9. The bend in the contact finger 31 is exaggerated t0 show the non-binding advantage. Actually the spacing between the upper projection 35 and the finger is relatively small. Assume that the fixed front contact finger 38 is not adjusted as intended, but is bent upwardly from the position shown. When the contact button on the finger 31 is driven upwardly by the lower projection 35, it will not strike the .button on the fixed front contact finger 38 at the point shown, since this latter nger is bent out of position. The finger 31 will, however, be bent as may be seen since the upper projection 35 pre- 'vents free counterclockwse rotation of the finger 31. The force necessary from the armature '25 vof the relay to push the drive element 21 from one position to the other is only slightly less than if the fixed front contact finger has been correctly adjusted. A fixed front contact finger is shown in the diagram, but the same reasoning applies to a fixed back contact finger. The relay therefore has more stable characteristics when maladjustments occur than other relays of its type.

Refer again to Fig. l0. Assume that the contact button on the movable Contact finger 31 sticks to the contact button d! on the fixed contact finger 38 due to frost or some other reason. When the contact operating member 21 is pulled downwardly by means of the permanent magnet, the upper projection 35 will force the contact finger 31 downwardly and will actually force the contact buttons 40 and 4| apart.

In assembling a relay constructed in accordance with my invention the cont-act alignment of the Contact fingers with respect to the frame 1 is first checked in a suitable tool provided especially for that purpose. The contact operating member 21 is then placed inside the frame 1 with the slots 36 facing toward the rear, and receiving the flexible contact fingers 31. The bar 32 is next placed with its ends in the notches 34 in the frame 1 and with the pads 32a and 32o facing the armature 25. The guide rod 30 is then inserted from the bottom of the relay through lquire no adjustment.

the opening 33 in the bottom wall 1d and through the twoholes 21a in the lugs 2lb of the contact operating member 2l into the hole SI in the bar 32. The relay is then turned upside down land a magnetic force is applied to the cores II and IIa to hold the armature 25 against the pole pieces i2 and i217.. The securing means 33a. is next applied, thereby insuring that the contact `operating member 3'! will be secured in place in the properposition with respect to the pole pieces. While the magnetic force is still applied .to the cores, spacers of a definite thickness are linserted between the armature 25 and the pole pieces I 2 and I'Za, and the contact buttons on the front contact fingers 33 are then adjusted to just touch the contact buttons on the iiexible Acontact iingers Si. The coils are then placed on' the cores of the relay, and the backstrap I3 is placed on top oi the cores il and Ila. The permanent magnet i8 is next adjusted as to strength by charging it fully and then discharging it to a value which will give the relay the correct pick-up value. Finally, the release time is adjusted in a manner which I shall ,describe presently, after which the relay is recalibrated, the front, back and bottom covers are assembled, and the relay is sealed.

As was pointed out hereinbefore, a relay embodying my invention is intended for use in centralized traic controlling systems for railroads wherein large numbers of quickly replaceable relays are employed, and in systems of this type when the relays are used for timing purposes it isl essential that relays performing like functions should have like release times to eliminate the necessity for providing excess operating margin. If the parts from which the relays are constructed are very accurately controlled, both with regard to dimensions and quality of material, the relays can be made near enough alike to re- However, when relays are built in large quantities on a production basis, variables are liable to creep into both the dimensions and the quality of the material and the presence of these variables makes it desirable to provide some convenient means for compensating for the variations between relays. There are a variety of methods to obtain the necessary compensation, but due to the necessary qualities the method must have, particularly when applied to a centralized traffic control system, for example, there are very few methods which are entirely satisfactory. For example, temperature, vibration, humidity, time or use must not alter the adjustment once it has been made. The adjustment must not be too sensitive, so that it can be easily made. The parts must not be too complicated, particularly when silicon steel is used for the magnetic circuit, since silicon steel is difficult to work into shape. Above all, the adjustment must be tamper proof. That is, it must not be altered except by an authorized person.

In my improved relay I prefer to accomplish the necessary adjustment by varying the position of the backstrap I3 relative to the cores II and I Ia of the electromagnet A, thereby varying the length of the air gaps between these members. The resulting variation in the reluctance of the magnetic circuit supplied with flux by the coils I and Ia provides a means whereby the release time or the shunt point of the relay may be varied minutely to accurately obtain a specic value. As shown in the drawings, the backstrap is fastened to the upper ends of the cores II and IIav in a preadjusted position to provide the proper release time or shunt point of the relay by means of tWo masses and d6 of a material which can be applied in a liquid, molten or plastic condition and which will subsequently harden. A number of different materialsmay be used for the securing means, but I prefer to use 7 per cent antimony lead because it pours very nicely when suiciently hot, and retains its dimensions while cooling. In applying this securing material, I use a mould fil or any other device capable of holding the material in place long enough to permit it to set. This mould is placed over the cores Il and Ila on top of the coils IIB and lila, and is secured in place by means of spring clips 48. The backstrap I3 is placed above the cores and held there temporarily by any suitable means such for example as a jig. lIhe relay is then checked for `release current or release time, depending upon which of these characteristics it is desired to accurately control. If the air gaps between the backstrap I3 and the cores are not such as to give the desired characteristics, these gaps are altered to provide the desired characteristics. There are Several ways whereby the desired air gaps may be obtained. One way to accomplish this result is to leave the ends of the cores and the surfaces of the backstrap I3 opposite the cores unplated and insert non-magnetic spacers between the backstrap and the cores. Another way to accomplish this result is to plate the cores or the backstrap or both and gradually remove a part of the plating as by a fine abrasive until the desired air gaps are obtained. A third way of accomplishing this result is to hold the backstrap away from the cores by spring means and to gradually compress this spring means to force the backstrap toward the cores, by means of screws provided in the jig which holds the backstrap in place, until the proper air gaps are 0btained. After the desired air gaps have been obtained, the securing means i5 and 4% are inserted into the moulds and allowed to harden. Themould is then removed by pulling on the two clips i8 and pulling the two halves apart.

In case it is desired to subsequently alter the adjustment once it has been made, it is only necessary to pry the backstrap oit and remove the securing means 45 and M from the cores and the backstrap and then repeat the process just described.

To facilitate holding the backstrap I3 in place by means of the material 45 and 45, annular grooves lil may be provided in the upper ends of the cores II and IIa and pins 50 may be inserted in the backstrap in positions to be engaged by the fastening means.

One advantage of securing the backstrap I3 to the cores in the manner just described is that the necessary adjustment may be made as accurately as measuring instruments will measure it.

Another advantage of securing the backstrap to the cores in the manner just described is that the adjustment is simple enough to be made by anyone capable of reading an ordinary measuring instrument.

A third advantage of securing the backstrap to the cores in the manner just described is that the adjustment is sensitive enough to be obtained easily, but is not so sensitive as to be unstable. Furthermore, after the adjustment has once been made, it is permanently fixed until changes in operating conditions require that the adjustment be altered when it can readily be changed.

Afurther :advantage of, securing the backstrap to the cores in the, manner described is that this means is economicaly since the parts are simple and the adjustment is easily made. Y

Anal. advantage ofA securingv the backstrap to the cores in the manner describedris that the adjustment is fooll proof since it is necessary to have the propery tools to remake it.

One advantage of therelay as a whole when constructed in the manner described is that since thel permanentmagnet circuit is separated from the electromagnet circuit, itis easy to design the magnetic circuit to produce the desired results. Furthermore, the results obtained from the relay are the A same regardless of which direction the current flowsl through the-operating coils l and Illa. This decreases the cost of manufacture as Well as ofl maintenance.

The fact that the coresY and permanent magnet pole pieces are all moulded into the same piece as the contacts permits the elimination of two moulded parts and therefore greatly decreases cost. This fact also makes the contact frame sturdier and therefore less liable to warp or break. The fact that the contact frame is sturdier permits the Bakelite walls to be much thinner, which in turn eliminates a serious manufacturing objection. For example, the flexible contact fingers 31 are inserted into slots in the steel mould during the moulding process, the portions of the springs shown inside the Bakelite being in the cavity formed by the mould, while the portions of the springs outside of the Bakelite being xed by the walls of the mould. While the Bakelite is semifluid and the plunger of the mould is being closed, the plastic flows into the cavity of the mould in either direction past the Contact fingers depending on the shape of the piece and how evenly the loading is done. This flow of semi-fluid Bakelite past a Contact finger sets up a condition on the nger similar to the conditions on a uniformly loaded beam xed at both ends. From the theory of beams the deflection of a beam at the center, in this case the deection of the finger at the center of the Bakelite wall, varies directly as the fourth power of the length and inversely as the cube of the thickness. For operating reasons it is not desirable to increase the thickness of the ngers. addition of reinforcement is not desirable due complexity. If, however, the thickwall can be decreased from say to 1A; of an inch the deflection of the finger at the center is less by the ratio of 40 to 140. This fact alone decreases the amount of labor necessary to assemble and adjust the relay as well as making it a more reliable instrument.

Although I have herein shown and described only one form of electrical relay 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. An electrical relay comprising a plurality of flexible contact ngers rigidly supported at one end and cooperating at their free ends with fixed contact fingers, a contact operating member mounted for straight line movement between two extreme positions and provided with a plurality of projections forming slots through which the entire width ofI said flexible ngers extend intermediate their ends, the two projections which form each slot being disposed on opposite sides ness of the of the center line of said member and being so spaced that whenv saidmember isin its midstroke position they will just touchV the opposite sides of the associated fingenwhereby said fingers are positively moved between two positions in response tomovement of said member between its two positions but that bindingr of said fingers in said slots is prevented, and electromagnetic means for actuating said'contact operating mem.- ber between its two extreme positions.

2. An electrical relay comprising a rectangular frame of moulded insulating material provided in its opposite side walls adjacent. one end thereof with slots, a plurality of flexible contactngers moulded into the side walls of said frame in parallel spaced relation, fixed contact fingers moulded into` the side walls of said frame and cooperating with said flexible fingers. at their free ends, a bar mounted at its ends in. said slots and providedwith a hole, a guide rod having one end disposed in said hole and the other end secured in a hole in the opposite end wall of said frame, a contact operating member provided with spaced lugs provided with aligned holes which receive said guide rod with clearance for limiting the movement of said contact operating members to longitudinal sliding movement, means on said contact operating member for engaging said flexible fingers intermediate their ends, and electromagnetic means for moving said contact operating members between two extreme positions to operate said flexible contact fingers.

3. An electrical relay comprising a rectangular frame of moulded insulating material provided in its opposite side walls adjacent one end thereof with slots, a plurality of flexible contact ngers moulded into the side walls of said frame in parallel spaced relation, fixed contact ngers moulded into the side walls of said frame and cooperating with said flexible fingers at their free ends, a bar mounted at its ends in said slots and provided with a hole, a guide rod having one end disposed in said hole and the other end secured in a hole in the opposite end wall of said frame, a contact operating member provided with spaced lugs provided with aligned holes which receive said guide rod with clearance for limiting the movement of said contact operating member to longitudinal sliding movement, means on said contact operating member for engaging said fingers intermediate their ends, an armature provided on said bar to prevent said contact operating member from turning, and electromagnet means including said armature for moving said contact operating member between two extreme positions to operate said contacts.

4. An electrical relay comprising a rectangular frame provided in its opposite side walls adjacent one end thereof with slots and having a rst pair of cores moulded into one end wall and a second pair of cores moulded into the other end wall, said two pairs of cores being provided at their inner ends with pole faces which lie in parallel planes, windings on one pair of cores for at times magnetizing them, a permanent magnet engaging the other pair of cores for constantly magnetizing them, exible contact ngers moulded into the side walls of said frame in parallel spaced relation and cooperating with fixed Contact fingers moulded into the side walls of said frame, a bar mounted at its ends in said with a hole, a guide rod having one end disposed in said hole and the other end secured ing member for cooperation with the pole faces of said two pairs of cores respectively, said bar being provided with pads which cooperate with the one side of one of said armatures to prevent v said Contact operating member from turning. Y 5. An electrical relay comprising a rectangular frame of moulded insulating material, a plurality of flexible contact ngers moulded into the side walls of said frame in parallel spaced relation and cooperating with fixed Contact fingers moulded into the side walls of said frame, each iixedl contact nger being moulded into the side wall opposite to that nwhch the eiible finger with which it cooperates is moulded, a contact operating member mounted in said frame for straight line movement between two extreme positions and provided with a plurality of projections forming slots through which the entire widths of said flexible fingers extendintermediate ther'ends, alternate ones of said projections being disposed on opposite sides of the center line of said member and being spaced apart such a distance that when said member is in its mid stroke position the two projections on Opposite sides of each flexible nger will just touch the finger, whereby the exible fingers are positively moved in both directions by said member to operate the relay contacts but that binding of the fingers within the slots formed by said proj ections is prevented, and electromagnetic means Vfor actuating said contact operating member between its two extreme positions.

CLARENCE S. SNAVELY.

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