US2166910A - Electrical relay - Google Patents

Description

July 18, 1939. B. LAZICH ET AL 2,166,910

ELECTRICAL RELAY Filed Aug. 14, 1935 2 Sheets-Sheet l l Ia;

INVENTORS Branlco LQjiCb and BY Paul K. Z'clclzardl.

, 4C. THEIR ATTORNEY July 18, 1939. B LAZICH ET AL 2,166,910

ELECTRICAL RELAY Filed Aug. 14, 1935 2 Sheets-Sheet 2 INVENTORS .BnznlcoLagicb and I PauZKFckbardt. fig 5a. fig. 52;. m

TJYEIR ATTORNEY Patented July 18, 1939 UNITED STATES PATENT OFFICE ELECTRICAL RELAY tion of Pennsylvania Application August 14,

15 Claims.

Our invention relates to electrical relays, and has for an object the provision of electrical relays characterized by a high sensitivity in the release of the contact carrying armature and which sensitivity is unaffected over a relatively wide range of values of energizing current.

Relays embodying our invention are particularly suitable for, although not limited to, use in railway track circuits. In track circuits for railway signaling it is very important that the track relay should be highly sensitive to the shunting of the track rails by a train, and the release of the contact carrying armature should be unaffected over the range of energizing current values caused by variations in ballast resistance and other operating conditions.

We will describe three forms of electrical relays embodying our invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a View, partly in front elevation and partly diagrammatic, showing one form of electrical relay embodying our invention and which relay is illustrated.

in connection with a track circuit. Fig. 2 is a view partly in side elevation and partly diagrammatic of the relay of Fig. 1. Fig. 3 is a view partly in side elevation and partly diagrammatic showing an alternate form of the relay of Figs. 1 and 2, and which form also embodies our invention. Fig. 4 is a View, partly isometric and partly diagrammatic of another form of relay embodying our invention, and Figs. 4a, 4b, and 4c are views illustrating various positions of the movable magnetizable member of the relay of Fig. 4. Figs. 5a and 5b are detail views. of the brake mechanism of the relay of Fig. 4.

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

Referring first to Fig. 1, the reference characters l and la designate the track rails of a stretch of railway and which rails are formed into a track section EF by the usual insulated rail joints. track section E--F is provided with a track circuit comprising a source of current such as, for example, a battery 2 and a resistor 3 connected across the rails at one end of the section, and a winding 4 of a relay designated as a whole by the reference character R connected across the rails at the opposite end of the section.

This relay R which is constructed in accordance with our invention, comprises as its essential parts a magnetic core structure, an operating winding, a contact carrying armature and a magnetic shunt path co-acting with the core struc- 1935, Serial No. 36,153

ture. As here shown, the magnetic core structure is of the type having two parallel cores 5a and 5?: connected together at their upper ends by a back strap 6 and provided at their lower ends with enlarged pole pieces C and D, respectively, the entire core structure being preferably supported for convenience in a. top plate T of suitable non-magnetic and insulating material. The cores 5a and 5b each carry a portion of the operating winding 4 which portions are connected for adding their effects in the usual manner, the operating winding 4 being included in the track circuit for the section E-F as pointed out above.

The contact carrying armature ID of relay R is mounted for swinging toward and away from the pole pieces C and D by being pivoted on two pivot screws I la and Ilb, which are secured in two non-magnetic brackets 8a and 8b, respective ly, and which brackets are attached to the outside surfaces of the pole pieces C and D by screws 9. Attached to the underside of the armature l but insulated therefrom are circuit controlling contact fingers one such contact finger [2 being shown in Fig. 2. This contact finger I2 is adaptable to make engagement with either a fixed front contact block 83 or a fixed back contact block M to close contacts I2--|3 or l2l4, the contact blocks I3 and M as well as a heel connection for the contact finger l2 being attached to terminals secured in the top plate 1 in the usual manner but which terminals are not shown in the drawings for the sake of simplicity. It is clear the armature ii) is free to swing downward under its own weight about the pivot screws Ila and Ilb until the contact finger l2 engages the back contact H, but that magnetic attraction between the armature I0 and the pole pieces C and D of sufficient force causes the armature to swing upward against a non-magnetic core pin l and in which position of the armature the contact finger l2 engages the front contact block l3. Also, attached to the underside of the armature i0 is a brake member ll the function of which we will point out hereinafter. The parts consisting of the armature I0, contact finger l2 and brake member I! are so proportioned as to be relative- 1y light in weight with the result that they possess relatively small inertia. Furthermore, the armature I0 is provided at its central portion with a recess it which gives the armature a restricted cross sectional area at the point between the pole pieces C and D as will be understood by an in.- spection of Fig. l. The parts are so proportioned that due to this restricted area of armature I0, magnetic saturation is reached at a value of energizing current just sufficient to attract the armature it and close the front contact l2l3. That is, with energization of the relay just sufficient to pick up the armature i9, magnetic saturation of the armature is effected when the armature is up against the core pin l5 and the air gap between the armature and the pole pieces is reduced. It follows that for any larger energizcurrent the reluctance of the armature is increased.

The magnetic shunt for relay R includes a movable magnetizable member I8, a brake wheel 59 and a helical biasing spring 20. The brackets to; and 8b are provided with downward extending legs Zia and Zlb, respectively, and the brake wheel is is supported between these two legs by pins 22- and 23. The brake wheel I9 is constructed relatively large in size and hence possesses relatively large inertia. An arm 25 is rigidly pinned at 29 to one face of the brake wheel 99 and a second arm 24 is likewise pinned to the opposite face of the wheel H9. The magnetizable member i8 is rigidly fixed to the upper ends of the two arms 24 and 25 in a position to extend along the rear surfaces of the pole pieces C and D for magnetic relationship therewith. The biasing spring 28 has one end hooked to the arm 25 and its other end hooked to an adjusting screw 25 secured in a bracket 21. A stop pin 28 is also secured in the bracket 2! and engages at its inner end the arm 25 for adjusting the position of the member l8 with respect to the pole pieces C and D when that member is pulled back by the force of the spring 20.

The operation of the relay R when connected in the track circuit illustrated in Fig. 1 is as follows: The parts are so proportioned and adjusted that the Voltage created by the current source 2 across the track rails at the relay end of the section E-F under the Worst ballast con dition, produces a current flow in the winding a which creates a magnetic flux in the air gap between the armature l0 and the pole pieces just sufficient to attract the armature from its full down position to the position against the core pin 55. The magnetic shunt member 18 is, under such operating conditions, held back against the stop 23 under the influence of the biasing spring 26, and the air gap between the member l3 and the pole pieces is of such length that the pick up of armature i0 is not appreciably affected.

As set forth hereinbefore, magnetic saturation of armature it! occurs at the flux density created by the pick up value of current. Assuming the ballast conditions of section EF to be more favorable and its resistance higher, the voltage existing across the track rails at the relay end of the section is higher and the current flowing in the winding 4 of relay R is increased with the result that the magnetic flux created thereby is increased. Since saturation of armature ill is eifected at the pick-up value of current, the major portion of the increase in magnetic flux caused by the increase in energizing current is shunted through the member l8 and the attraction thereof is increased and it is pulled toward the pole ieces C and D until a balance between 1e force of the spring 20 and the magnetic attraction is obtained. When the member it is thus attracted toward the pole pieces, the brake wheel it is rotated counter-clockwise as viewed in Fig. 2 a corresponding amount. It is to be seen, therefore, that the magnetic flux, which operates the armature i0 is substantially no greater under the higher energizing current than under the current just sufficient to pick up the armature, since the magnetic shunt path including the member it automatically compensates for the increase in energization. Hence, approximately the same reduction of energizing current is effective to release the armature l0 under the operating conditions that result in a relatively high value of energizing current as obtains when the energization is only just sufficient to pick up the armature.

Assuming now that under operating conditions of section E-F that effects a relatively high energizing current, a train enters the track section, shunts current away from the winding 4 and the armature ill is released. When the armature lll is released, the brake member l! engages the brake wheel 19 and the brake wheel along with the shunt member l8 are held at the position to which they had automatically advanced under the influence of the flux shunted through the member l8. That is, if the ballast resistance is high and the energizing current for relay R is high and the member I8 is attracted toward the pole pieces, the member I 8 is held at that position subsequent to a train entering the section and shunting the relay to release the armature l0, since the brake wheel [9 is relatively large in size and of relatively large inertia and does not move an appreciable distance prior to the release of the armature it which possesses small inertia. The magnetic shunt thus retained at the position effected by the higher energizing current subsequent to the deenergizing of the relay, acts to shunt a portion of the flux away from the armature Ill and the picking up of the armature as a result of a poor train shunt resistance while the train is passing through the section and the relay R is partially reenergized, is avoided. When the train vacates the track section and such higher energizing current is again supplied to the winding 4, the magnetic flux available to pick up the armature l0, notwithstanding the shunt member I8 is now in a position to shunt a portion of the flux away from the armature, is sufficient. A gradual change in the ballast resistance automatically changes the setting of the shunt member l8, but a sudden decrease in the energizing current due to a train entering the section is operative to release the contact carrying armature and that armature in falling is effective to retain the shunt member at its former setting due to the higher inertia of the parts associated with the shunt member. It follows that with the relay constructed in the manner described, the armature i0 is released at practically a constant value of current reductionregardless of the ballast condition due to the fact that the magnetic shunt path automatically compensates for the over energization. Furthermore, since the magnetic shunt is retained effective after the contact carrying armature is released, partial reenergization of the relay due to a poor train shunt is ineffective to operate the armature. Consequently, the relay R is characterized by a high release sensitivity over a relatively wide range of values of energizing current.

An alternate form of the relay R of Figs. 1 and 2 is shown in Fig. 3. In this form, the magnetic core structure is of the type similar to that provided in Fig. 1 and includes two parallel core members 5a and 5b which terminate in two pole pieces C and D, respectively, the core 512 and pole piece D only being visible in Fig. 3. Likewise, the operating winding is mounted on the cores 5a and 5b the same as in Fig. ,1. The contact carrying armature |0a is mounted on two pivot screws which are secured in two nonmagnetic brackets attached on the opposite outside surfaces of the pole pieces C and D. In Fig. 3, only the one pivot screw 42 and its associated bracket 43 attached to the pole piece D are visible. A ratchet pawl 44 is attached to the underside of armature |0a and this pawl engages the teeth of a ratchet wheel segment 3| to be described later. The parts are so constructed that when the armature Ida is attracted up against a core pin 46, the front contact |2| 3 of the relay is closed and the ratchet pawl 44 is free from the teeth of the segment 3|, but that when. the armature Hm is released and the back contact |2|4 is closed, the ratchet pawl 44 engages the teeth of the segment 3|. The armature Illa and its associated parts are constructed relatively light in weight to possess small inertia, and the armature la is preferably constructed with a restricted cross-sectional area the same as armature ID of Fig. 1.

In the modified form of relay disclosed in Fig. 3, the magnetic shunt consists of a movable magnetizable member 30, the ratchet wheel segment 3| and a biasing spring 32. The magnetizable member 30 is mounted rigid on two arms 33 pinned at 34 to the segment 3|, there being an arm on each side of the segment. The member 30 is positioned to extend along the rear surfaces of the pole pieces C and D for magnetic relationship therewith. The ratchet wheel segment 3| is mounted for rotation on a pivot pin 35 which pin is journaled in any convenient manner not shown, and the segment is provided with counterweights 36 and 31 to give a relatively high inertia for the segment 3| and its associated parts. The biasing spring 32 has one end hooked to the arm 33 and its other end hooked to an adjusting screw 38 which is secured in a bracket 33. Normally the spring 32 is adjusted to re tract the member 30 from the pole pieces and to rotate the segment 3| clockwise as viewed in Fig. 3 to a position where a stop member 40 engages a stop screw 4| which is also secured in the bracket 39. In such position of the magnetic shunt, the member 30 is adjusted for a relatively large air gap between it and the pole pieces.

The parts are so proportioned and adjusted that when a voltage is impressed across the operating winding of the relay just sufiicient to effect a pick up of the armature Ma, the shunt member 30 and the ratchet Wheel segment 3| are held back in the position against stop 4| and the shunt member 30 does not efiect the operation of the relay appreciably. With a somewhat higher voltage impressed across the terminals of the operating winding and the magnetic fiux increased accordingly, the increase in flux is largely shunted through the member 33 due to the magnetic saturation of the armature Ina, and the member 30 is attracted toward the pole pieces until a balance between the attraction and the force of the biasing spring is obtained. Under this latter condition of energization if the relay is shunted to release the armature Illa, the ratchet pawl 34 Will engage with the teeth of the ratchet wheel segment 3| and it, as well as the member 33, are held at the position to which they had been advanced. This position of member 33 is retained. subsequent to deenergizing of the relay since the armature Illa and its parts have small inertia whereas the segment 3| and its parts are of relatively high inertia. It is clear that the modified form of the relay disclosed in Fig. 3 when connected in the track circuit of Fig. 1 will operate in the manner described for relay R of Figs. 1 and 2.

In the form of the invention disclosed in Fig. 4, the relay comprises a magnetic core structure, an. operating winding mounted thereon, a contact carrying armature, and a magnetic shunt path, similar to the previous forms of relays. In this last form of relay the magnetic core structure consists of two parallel core members 49a and 431) which are joined together at their top ends by a back strap 50 and the lower ends of which terminate in enlarged pole pieces G and H, respectively. The operating winding 5| consists of two portions one carried on each of the cores 49a. and 49b and which are preferably connected to add their effects.

Attached to the rear side of the pole pieces G and H are two non-magnetic brackets, only one bracket 52 attached to the pole piece G being visible in the drawings. The contact carrying armature 53 is mounted on these brackets by two pivot screws, the pivot screw 54 only being visible in the drawings. A contact finger 55 is secured to but insulated from the underside of armature 53, and is adapted to engage a fixed front contact 56 or a fixed back contact 51. It follows that armature 53 is free to swing away from the pole pieces when no current or insufficient current flows in the operating winding 5|, and is attracted toward the pole pieces when sufficient current is supplied to the winding 5|.

The magnetic shunt for the relay of Fig. 4, consists of two magnetizable L-shaped arms 58 and 59 which extend from the pole pieces G and H, respectively, a movable magnetizable member 60 which is adapted to fit the space between the pole faces of the arms 58 and 59 as will readily be understood from an inspection of Fig. 4, a biasing spring 5?, and a brake mechanism 12. The magnetizable member 63 is carried on a non-magnetic lever arm 5| which is pivoted on a non-magnetic pin 32 secured to the two inner surfaces of the pole pieces G and H. An adjustable stop screw 63 is secured in a non-magnetic bracket 13 carried on arms 58 and 59 for limiting the downward movement or" member 66, the parts being so proportioned and adjusted that with the member 60 in its full down position in engagement with the stop screw 63 the lever arm 6| clears the armature 53 even with the armature up against its core pins. This full down position of member 60 is illustrated in Fig. 4a. In this position of member 60, the magnetic shunt path including arms 58 and 59 and the member 53 is of relatively high reluctance clue to the wide air gaps between member 60 and pole faces of arms 53 and 59. When the winding is energized, the member 3!! is attracted and brought up into the space between the pole faces of arms 58 and 59, the pole faces and the sides-of the member 53 being preferably tapered to insure alignment and to improve the magnetic attraction. As here shown, the parts are so proportioned that after a slight movement of member 30 off the stop 33, the member 63 engages a biasing spring '5'! which is confined between a stationary plate 68 and the head of a bolt 59. From this pcint on, the attraction of member 50 opposes the force of the biasing spring 51 until a balance is obtained. Such a position of member 63 is illustra'ted in Fig. 4c. The parts are further so proportioned and adjusted that when the energizing current is of a value just sufficient to pick up they armature the flux shunted through the shuntv path is just sufficient to raise the member 69 tothe position to engage the biasing spring 61 but not sufficient to compress the spring, that is, it is drawn to the position illustrated in Fig. 411.

Two short-circuited windings i and "H are mounted on the arms 58 and 59, respectively, toprovide the magnetic shunt with slow acting characteristics. When the operating winding is. deenergized and the magnetic flux dies away, the decay of the flux threading the shunt path isdelayed due to the snubbing action of windings 7i] and H with the result that the member 66 is. retained in the position to which it had advanced a short period subsequent to the release of the contact carrying armature 53. Again, the'windings it and ll tend to delay the building up of flux; in the shunt path when the operating winding 5| is first supplied with energizing current with the result the shunt path is not effective to shunt the flux away from the armature 53 until after the armature is raised into position against its corepins.

The brake mechanism 72 is preferably con-- structed as follows: A non-magnetic brake member 14 is hinged on a pin 75 secured in the polepiece H, and the armature 53 carries a roller l6 adapted to ride on a wedge surface H. (see Fig. 5a) of member "54 when the armature 53 is released,.

and which roller is lifted clear of the wedge surface 'i'l when the armature 53 is picked up againstits core pins. Thebrake member 14 is provided with ratchet teeth 18 (see Fig. 5a) adapted to engage the lever arm 6| when the member M isactuated by the roller 16 in response to release of the armature 53. A light biasing spring it has one end hooked to a stationary member 86 and its. other end hooked to the lower end of the brake member 54. It follows that when the armature 53 is picked up and the roller 18 clears the member- 14 the spring 80 is eifective to pull the member 74 to a position where the ratchet teeth 78 clear the arm Bl, but that release of armature 53 causes the roller iii to engage the surface Ti and forces the member i against the action of the spring E9 to a position where the ratchet teeth 78 engage the arm 3 l. Consequently, the arm iii and the member 58 carried thereon are held in the position to which they had been advanced in response to energizing of the winding 5| subsequent to deenergizing of the winding and release of the contact carrying armature 53. In place of the ratchet teeth "t8, the brake member l4 may be provided with a brake strip ill, as shown in Fig. 5b. With this latter construction the arm 6! is held in position by the frictional engagement between the brake strip at and the arm. In practicing my invention, two such brake mechanisms would preferably be provided one on each side of the lever arm 6 l, but only one mechanism is shown in the drawings for the sake of clearness.

In this form of relay, the magnetic core structure is preferably provided with a restricted crosssectional area which is proportioned for magnetic saturation at the higher values of energization of the operating winding. As shown in Fig. l, the back strap 56 is constructed with a recess 65 to provide the restricted cross-sectional area of the core structure.

In describing the operation of the relay of 4, we shall assume the relay is included in the track circuit for the track section E-F, and that the relay has been shunted as a result of the section being occupied by a train. Furthermore, We

shall first consider wet ballast conditions under which the voltage across the rails at the relay end of thesecti'on is just suflicient to pick up the relay with the section unoccupied. When the train leaves the section and current is supplied to the operating winding 5|, substantially the entire fiux created by such energizing of the winding 5| threads the armature 53 for picking up the armature, since the shunt path is snubbed by windings it and H and since the member 69 is, under such roperating conditions, down against the stop 63. When the armature 53 is picked up, the magneto- :motive force drop at the restricted cross-sectional :area 55 is increased somewhat due to increase in imagnetic flux. The snubbing action of windings "it, and ll soon loses its effectiveness and the :member (it is attracted to the position where it engages the biasing spring 61 (Fig. 422) by the :flux threading the shunt path. The flux threading the shunt path further increases the magneto- :motive force drop at the restricted cross-sectional area 65 with the result that the attractive force on the armature 53 is reduced. Hence the relay of Fig. 4 is provided with a high release sensitivity. When the next train enters the section and shunts the operating winding 5! the snubbing action of windings l5 and it retains the magnetic shunt in effect for a short interval and release of the armature 53 is expedited, since the shunt path and the restricted cross-sectional area provide the relay with a high release sensitivity as explained above.

"Under dry ballast conditions, the voltage across the rails at the relay end of the track section is materially increased and the current flowing in the operating winding 5| is correspondingly increased. The magnetic flux created by this increase of current is effective to pick up the armature although the magnetomotive force drop :at the restricted cross-sectional area 66 is increased, the magnetic shunt path being ineffective due to the snubbing action of the windings ll! and it until the armature 53 is picked up. The increase in the flux threading the shunt path now causes the member 60 to be drawn upward into the space between the pole faces of arms 58 and 59 against the force of the biasing spring 67! until a balance is obtained. In such position of the member 60 the air gaps between it and the pole faces of arms 58 and 59 are relatively short and the reluctance of the magnetic shunt path is correspondingly reduced. Thus the shunt path is now operative to further reduce the magnetic flux threading the armature 53 with the result that the release sensitivity of the armature is not materially increased by the increase in energizing current. When the armature 53 is released in response to shunting of the winding 5|, the roller l6 engages the wedge surface it and forces the member M. to the position for engaging the arm 6!. Thus the arm 6| and the member 6 carried thereon are retained in the position to which'they had been advanced by the high energizing current subsequent to the release of armature 53 with the result that picking up of the armature 53 due to a poor train shunt resistance while a train is passing through the section and the relay is partially reenergized is avoided. It is clear that the relay of Fig. 4 when included in the track circuit for the section EF operates in a manner similar to that described for the relay of Figs. 1, 2 and 3, since the relay of Fig. 4 is characterized by a relatively high release sensitivity and since such sensitivity is unaffected over a relatively large range of energizing current.

As set forth hereinbefore, relays embodying our invention are particularly adaptable for use in track circuits for railway signaling, but it will be understood their use is not limited to this one application and many places where relays embodying our invention will be useful will suggest themselves to those skilled in the art.

Although we have herein shown and described only three forms of electrical relays embodying our 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 our invention.

Having thus described our invention, what we claim is:

1. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on the core, an armature biased to a position away from the pole pieces and movable toward said pole pieces in response to magnetic flux created by current supplied to the winding, a magnetic shunt path including a magnetizable member movable to diiierent positions relative to said pole pieces for magnetically shunting away from said armature variable amounts of the flux which would otherwise pass through the armature in response to variations in the magnitude of the current supplied to the winding, and means controlled in part by said armature for governing the position of said member.

2. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic. flux created by current supplied to said winding, an auxiliary magnetizabie member mounted for movement relative to said pole pieces in response to such magnetic flux for magnetically shunting away from said armature a portion of the flux which would otherwise pass through the armature in response to variations in the current strength supplied to the winding, a biasing device for governing the position of said member when influenced by the flux, and means controlled by said armature operative when the armature is released in response to decnergizing the winding to retain said auxiliary member at the position to which it was moved by the magnetic flux.

3. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, an auxiliary magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for compensating for the increase in the flux through the armature caused by current above a predetermined value supplied to the winding, an inertia member connected rigidly to said auxiliary member for movement therewith, a biasing device for governing the position of the auxiliary member, and means controlled by said armature operative to engage said inertia member when said armature is released to retain the auxiliary member at the position to which it was moved by the magnetic flux.

4. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, an auxiliary magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for compensating for the increase in the flux through the armature caused by current above a predetermined value supplied to the winding, a brake wheel constructed for relatively high inertia and connected with said auxiliary member for rotation in response to movement of the member, a biasing device for governing the position of the auxiliary member when influenced by the flux, and a brake shoe connected with the armature for engaging the brake wheel when said armature is released to retain the auxiliary member at the position to which it was moved by the magnetic flux.

5. In combination, a section of railway track, a source of current connected across the rails of said section, an electromagnet receiving current from said rails and having an armature adjusted for predetermined pick-up value of current, a movable magnetizable member co-acting with the core structure of the electromagnet for shunting magnetic flux away from said armature to establish a relatively high release value of current for the armature, biasing means operatively connected to said member for governing its position relative to the core structure to compensate for changes in energizing current supplied by said source, and means to retain said member at its relative position with respect to the core structure when the source of current is shunted.

6. In combination, a section of railway track, a source of current connected across the rails of said section, an electromagnet receiving current from said rails and having an armature adjusted for predetermined pick-up value of current, a movable magnetizable member co-acting with the core structure of the electromagnet for shunting magnetic flux away from said armature to establish a relatively high release value of current for the armature, and means controlled in part by said armature for governing the position of said member relative to the core structure to compensate for changes in the energizing current supplied by said source.

7. In combination, a section of railway track, a source of current connected across the rails of said section, an electromagnet receiving current from said rails and having an armature adjusted for operation when the magnetic flux acting thereon is that created by a predetermined value of current, a movable magnetizable member operable to different positions relative to the core structure or" the electromagnet for shunting magnetic flux away from said armature to reduce in the armature the flux created by currents greater than said predetermined value, and means controlled in part by the position of said armature for governing the position of said member.

8. In combination, a section of railway track, a source of current connected across the rails of said section, a track relay receiving current from said rails, a contact carrying armature for said relay characterized by possessing relatively small inertia, a magnetic shunt means including a magnetizable member mounted for movement relative to the pole pieces of said relay for regulating the flux through said armature and said means characterized by possessing relatively large inertia, and means controlled by said armature when released to retain said member at the position to which it was moved under the influence of the magnetic flux created when the relay was energized, whereby movement of the armature When the relay is partially reenergized due to a poor train shunt is avoided.

9. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by a predetermined value of current supplied to said winding, said armature characterized by possessing relatively small inertia, a magnetic shunt means including a magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for compensating for the flux through the armature caused by increased values of current supplied to the. winding, said magnetic shunt means characterized by possessing relatively large inertia, a biasing device for governing the position of said magnetizable member, and means controlled by said armature operative to retain said magnetizable member at the position to which it was moved by the magnetic flux when said armature is released.

10. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, a magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for regulating the flux through the armature, means to normally bias said member away from said pole pieces, and said armature provided with a restricted cross-sectional area operative to efiect magnetic saturation at the pick-up value of current to shunt the flux created by higher values of current through said member.

11. In a relay, a magnetic core structure terminating in two pole pieces, a. winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, a magnetic shunt including two magnetizable arms extending from said pole pieces and a movable magnetizable member adapted for movement between the pole faces of said arms, biasing means operative to control the final position of said member relative to said arms for regulating the flux through the armature, and a short-circuited winding mounted on at least one of said arms to provide slow acting characteristics for said magnetic shunt.

12. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, an auxiliary magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for regulating the flux through the armature when current above a predetermined value is supplied to the winding, a

ratchet wheel segment constructed for relatively high inertia and connected with said auxiliary member for movement in response to movement of the member, a biasing device for governing the position of the auxiliary member when influenced by the flux, and a ratchet pawl attached to the armature for engaging said segment when said armature is released to retain the auxiliary member at the position to which it was moved by the magnetic flux.

13. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, a magnetic shunt path including a magnetizable member mounted for magnetic relationship with said pole pieces for magnetically shunting away from said armature substantially all of the magnetic flux above a predetermined value when current above a predetermined value is supplied 7 to the winding, and a short-circuited winding mounted on the shunt path for delaying the dying away and the building up of flux through said shunt path.

14. In a relay, a magnetic core structure terminating in two pole pieces and provided with a restricted cross-sectional area, a winding mounted on said core, an armature biased to a position away from the pole pieces and movable toward said pieces in response to magnetic flux created by current supplied to said winding, said parts being so proportioned that varying degrees of magnetic saturation at the restricted cross-sectional area is efiected at the higher values of energization of said winding and a magnetic shunt path including a movable magnetizable member mounted for movement relative to the pole pieces for shunting magnetic flux away from said armature whereby said relay is characterized by a high release sensitivity of its armature over a relatively wide range of values of energizing current.

15. In combination, a section of railway track, a source or current connected across the rails of said section, a track relay receiving current from said rails and adjusted for release of its armature at a predetermined value of current, a movable magnetizable member mounted for movement relative to the pole pieces of the relay for shunting magnetic flux away from said armature, and means to associate movement of the member with movement of the armature whereby a gradual change in the ballast resistance of the section automatically changes the setting of the member but a sudden decrease in the energizing current to release the armature causes the member to be retained in its former setting.

BRANKo LAZICH. PAUL K. ECKI-IARDT.

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