US2285936A - Electrical relay - Google Patents

Description

June 9, 1942. B. MISHELEVICH 2,285,936

ELECTRICAL RELAY Filed June 21, 1941 HIS ATTORNEY Patented June 9, 1942 "UNITED STATES PAT ENT OFFICE ELECTRICAL RELAY Application June 21, 1941,Serial No.j399,145

8 Claims.

My invention relates to electrical relays, and it has particular reference to tractive armature type electrical relays of the class employed as track relays in railway track circuits.

-An electrical relay of the tractive armature type, when employed as a track relay in a railway track circuit Where it is controlled by the application of a train shunt of low resistance applied across its winding, is relativelyquick in picking up but is comparatively slow in releasing. These characteristics are in a large measure due to the fact that the energy required to pick up the armature of an ordinary relay is considerably in excess of the energy required to hold such armature in its attracted position after it has picked up. Such a relay must, of course, be designed to create its pick-up energy level, at least, in order to insure that the relay armature will be picked up properly, and as a result once this armature has reached its attracted position, the energy level in the relay then .exceeds by a considerable degree that necessary to maintain the armature in its picked-up position. In order for a train shunt to be effective to release such a relay, the shunt must be sufficiently low in resistance to shunt away from the relay winding the increment of energy above the drop-away energy level of the relay. Such shunt, however, provides a low resistance or short-circuit path across the relay winding which snubs the release of the armature by maintaining the flux in the relay for an appreciable interval of time, so that a correspondingly long time interval is required for even a low resistance train shunt to lower the energy level of the relay below its drop-away value. Various means have been proposed heretofore to obviate the slow releasing characteristics of tractive armature relays when shunted, and to provide relays having quick release, slow pick-up characteristics. My invention is directed to the provision of novel and improved means for obtaining quick release characteristics in tractive armature type relays.

Another object is to provide novel and improved forms of electrical relays particularly suitable for use as track relays in railway track circuits.

Afurther object is the provision of novel and improved means for obtaining quick release, slow pick-up characteristics in a tractive armature level only slightly. less than its pick-up energy level.

The above-mentionedand other important. objects-and characteristic features of my invention'which will become readily apparent from the following description, .are attained in accordance with my invention by providing means for at times varying'the torque arm of the flux acting on the armature. The arrangement is such that whenthe armatureis released, a resultant flux is caused to act on the armature through a relatively large torque arm, while when the armature is picked up, a resultant flux is caused to act on the armature through a relatively short torque arm. Inaddition, means are provided for delaying a change of flux acting on the armature through the long torque arm, but which means is ineffective to delay a, change of flux acting through the relatively short torque arm.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. l is a diagrammatic view illustrating a preferred form of apparatus embodyingmy invention. Figs. 2a, 2b and 2c are views showing diagrammatically the, magnetic circuits of the fluxes in the relay for various different positions of the relay armature. Figs. 3a, 3b and 3c are diagrammatic views showing the connections of the relaywindings for the different positions of the armature represented in Figs. 2a, 2b, and 20, respectively. In each of the several views similar reference characters have beenemployed to designate corresponding parts.

Referring to the drawing, the reference characters I and I a designate the track rails of a stretch of railway track divided by insulated joints 2 into an insulated track section DE. Section DE is provided with a track circuit comprising a suitable source of energy, such as a track battery 3, connected through a resistor 4 to the rails at oneend E. of the section, and the operating windings of a track relay TR connected across the rails at the other end of the section. Relay TR comprises a three-legged core structure having threemagnetizable cores or legs 5, B and 1 connected together at one end by a backstrap .8. Windings 9, l0 and H are disposed on legs 5, 6 and 1, respectively, for causing a tractivetype armature-I2 pivoted at l3 adjacent one of the outer legs; 5 of the core, to swing toward and away from the three legs simultaneously. The one core leg' I disposed mostremote from pivot I 3 of ,armature I 2 is provided with means, such as a copper ferrule M, for at times delaying achange of flux threading the leg.

Armature I2 is provided in the usual manner with one or more contact members, such as member I5, for effecting control of external circuits, and also with a bifurcated contactmember 16 comprising a common or bridging memfer type contact combination.

I threads leg 5.

When armature I2 is picked up, as represented in Fig. 1, front contact lt-l'l is closed, and windings t and it are connected in series across the rails of section DE. In this position of the armature, the fluxes due to current in the two energized windings are provided with the magnetic paths indicated in Fig. 2a, and the resultant of these fluxes operates through a rela tively short torque arm 01. That is to say, the

flux (indicated in Fig. 2a by short dash lines) due to current in winding Ill threads leg 5 and then the two outer legs 5 and I in multiple. Likewise, the flux (indicated in Fig. 2a by full lines) due to current in winding 9 threads leg 5 and then the other two legs 6 and l in multiple. In the two legs 5 and E nearest pivot E3 of the armature, the fluxes act cumulatively to attract above the drop-away value of the relay to assure i reliable operation under the various ballast conditions.

If, now, the relay is deenergized, as by the application of a low resistance train shunt across its windings due to a train entering the associated section, armature it? quickly releases since it is held attracted by a torque only slightly greater than its drop-away value. When armature [2 reaches its released position, as represented in Fig, 312, back contact HEB-l8 closes to connect windings 9 and H in series, and winding is placed on open circuit since front contact l6|1 becomes opened.

When the armature is in its released position,

and the two windings 9 and H become effectively energized, as when the train vacates the section and removes the train shunt from across the relay windings, the fluxes due to current in the windings are provided with the magnetic circuits represented in Fig. 2b. Ihe flux due to current in winding 9 is provided with a circuit comprising leg and in multiple, the other two legs 6 and l, but due to the relative reluctances of the air gaps between armature I2 and legs 6 and l, substantially all of the flux threads leg 6, as indicated in Fig. 21). Similarly, the flux (indicated in Fig. 2b by long dash lines) due to current in winding I I is provided with a circuit including leg I and, in multiple, the two legs 5 and 6, but by virtue of the smaller air gap between armature l2 and leg 5, substantially all of this flux These two fluxes oppose each other in leg 5, so that the resultant thereof may have little or no attractive effect on the armature, but the two fluxes act additively in attracting the armature at points remote from pivot l3. That is to say, the flux due to current in winding 9, threading leg 6, exerts an attractive force on the armature that acts through a moment arm d, while the flux due to current in winding ll, threading leg I, exerts an attractive force on the. armature that acts through a moment arm 6. The growth of flux due to current in winding l l is, however, delayed by the. snubbing action of copper ferrule it, so that the flux builds up slowly until it reaches a value such. that the force exerted on the armature, multiplied by its, mo-

- ment' arm e,.when added to the torque exerted by the'magnetic force of winding 9 acting through its moment arm d, is sufficient to cause armature E2 to be swung toward the cores. During the movement of the armature to its pickedup position, contact member it engages front contact member ll to form contact Iii-I1 and connect winding [0 in multiple with winding II, as represented in Fig. 30. When this happens, the flux due to current in winding lfl threads the core as represented in Fig. 2c, and this flux, act- .ing through the moment arm d, aids in the operation of the armature to its picked-up position. Further movement of the armature results in the opening 'of back contacts I6-l8, thereby placing winding H on open circuit, so that when the armature reaches its fully attracted position, the fluxes due to current in windings 9 and it again thread the cores substantially in the manner represented in Fig. 2a and the magnetic forces of such fluxes are provided with a moment arm d. It follows, therefore, that when armature I2 is released, the torque arms of the forces exerted by the relay windings on the armature are considerably longer than the torque arms of the forces exerted on the armature when it is'picked up, hence even though the magnetic forces may be of substantially equal value in both cases, the effective torque exerted on the armature by such forces is considerably more when the armature is released than when it is picked up. The increment of energy, normally available in a relay when it is picked up, above the drop-away level of the relay may thus in effect he nullified by reducing the moment arm of the magnetic force in the relay after it picks up.

In addition, it is to be noted that when the armature is released and the magnetic force, or a portion of it, is provided with a relatively long torque arm, means such as copper ferrule I4, is provided for delaying the growth of flux in the circuit having the relatively long or effective torque arm, thereby providing a delay in the pick-up of the armature. When, however, the armature is picked up, the magnetic circuits are then so arranged that substantially no resultant flux is present in the circuit provided with the ferrule so that the ferrule has substantially no effect upon the decay of the flux, hence it is ineffective to delay the release of the armature.

From the foregoing, it is readily apparent that I have provided a relay incorporating means for varying the torque arm of the magnetic force exerted on the relay armature so as to provide a relay having a drop-away energy level only slightlyv less than its pick-up level, thereby obtaining quick release characteristics in a tractive type armature relay. In addition, a relay embodying my invention embodies means for delaying the, pick-up of the armature without affecting its release.

Although I have herein shown and described only one form of an 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. In an electrical relay having an armature pivoted about an axis and contacts controlled arm:about said axis and the other having a .Shorter effective. moment arm, and means controlled by contacts of said armature for causing a resultant flux to circulate in both said circuits or in said other but not said one circuit according as said armature is released or picked up, respectively, whereby to vary the eifective moment arms of the magnetic forces exerted on said armature and reduce the torque available to hold the armature up after it has picked up.

2. In an electrical relay, in combination, an armature pivoted about an axis, a magnetizable core having two magnetic circuits through said armature, one of said circuits having a relatively long effective moment arm about said axis and the ther having a shorter effective moment arm, means for circulating flux through said other magnetic circuit, and means controlled by said armature for causing a resultant flux to circulate in or not to circulate in said one magnetic circuit according as said armature is released or picked up, respectively, whereby to vary the moment arm of the magnetic force exerted on said armature to provide the relay when shunted, with quick release characteristics.

3. An electrical relay comprising, in combination, an armature pivoted about an axis, three magnetizable cores one positioned remote from said axis and the other two positioned intermediate said one core and said axis, means controlled by said armature and efiective when it is released for energizing said remote core and one of said two other cores, and means effective when said armature is picked up for energizing both of said two other cores but not said remote core, whereby to decrease the efiective torque on .said armature when said armature is picked up.

4. An electrical relay comprising, three magnetizable cores, connected together at one end by a magnetizable backstrap, three windings one on each of said cores, an armature pivoted about an axis disposed adjacent one of said cores, means efiective when said armature is released for energizing the windings on said one core and the core most remote from said axis, to create flux having an additive action in picking up said armature, and means effective when said armature is picked up for energizing the windings on said one core and on the remaining core, to create flux having an additive action through said last-mentioned two cores but having an opposing action in said remote core, whereby to decrease the moment arm of the magnetic force on said armature when picked up, to increase the release value of the relay.

5. In an electrical relay having an armature pivoted about an axis and contacts controlled by the position of said armature, a magnetizable core having two magnetic circuits each including a portion of the armature, one of said circuits having a relatively long effective moment arm about said axis and having means for delaying a change of flux in said circuit, the other of said magnetic circuits having a shorter effective moment arm about said axis, and means controlled by contacts operated by said armature for causing a resultant flux to circulate in both said circuits or in said other but not said one circuit according as said armature is released or picked up, respectively, whereby to vary the efiective moment arms and torque of the magnetic forces exerted on said armature and provide a delay in the growth of flux in said core without delaying the decay of flux.

6. In an electrical relay having an armature pivoted about an axis for swinging movement toward and away from a magnetizable core comprising three legs one disposed remote from the said axis and the other two positioned intermediate said one leg and said axis, said legs being connected together at their ends remote from said armature, windings disposed on each of said legs, means controlled by said armature and effective when it is released for energizing the winding on said remote leg and the winding on the leg nearest said axis, by current having a polarity selected with respect to the direction of the windings to cause the fluxes due to such current to assist in swinging said armature toward said core, and means controlled by said armature when it is picked up for energizing the winding on said nearest leg and the winding on the remaining leg, by current having a polarity selected with respect to the direction of the windings to cause opposing fluxes to circulate in said remote leg, whereby to vary the effective torque arm of the fluxes acting on said armature and to reduce the torque available to hold up said armature.

7. A track relay for use in a railway track circuit where it is controlled by the application of a low resistance train shunt across the relay windings, comprising the combination of an armature pivoted about an axis for swinging movement toward and away from a magnetizable core comprising three legs one disposed remote from said axis and the other two disposed intermediate said remote leg and said axis, said legs being connected together by magnetizable material at their ends remote from said armature, three windings one disposed on each of said legs, contacts controlled by said armature, and circuit means including a back contact operated by said armature for energizing the winding on said remote leg in series the winding on one of said other two legs, the direction of the windings on the core being arranged to cause the fluxes due to currents in the two mentioned windings toassist in swinging said armature toward said core, and other circuit means including a front contact operated by said relay for energizing in series the two windings on said two other legs, the direction of the windings on said two other legs being arranged to cause fluxes to circulate in agreement through said two other legs but in opposition in said remote leg.

8. A railway track circuit comprising a source of current connected over a pair of track rails to a track relay having an armature pivoted about an axis for swinging movement toward and away from a magnetizable core, said core comprising three legs one disposed remote from said axis and two other legs disposed intermediate said remote leg and said axis, said legs having their ends remote from said armature connected by magnetizable material, contacts controlled by said armature, and means including a back contact operated by said armature for circulating flux through said three core legs through two magnetic circuits, and means including a front contact operated by said armature for circulating flux through a magnetic circuit comprising said two other core legs but not said remote core leg, whereby to vary the effective torque arm of the flux about said axis to reduce the energy available to hold said armature in its attracted position and increase the shunting sensitivity of the track circuit.

BENJAMIN MISHELEVICH.

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