US2227675A - Track circuit apparatus - Google Patents

Description

Jan. 7, w STQU'F ETAL 2,227,675

TRACK CIRCUIT AiPARATUS Filed Nov. 18, 1939 14 1 ,P l 5 10 3 B c 3/9 INVENTOR5 lUaZzerL Siam and THEIR ATTORNEY Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE TRACK CIRCUIT APPARATUS Walter L. Stout, Penn Township,

Allegheny County, and Arba G. Williamson, Carnegie, Pa., assignors to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsyl- Vania Application November 18, 1939, Serial No. 305,158

5 Claims.

Our invention relates to track circuit apparatus and more particularly to apparatus of this type having improved operating characteristics.

One object of apparatus embodying our invention is to provide a track circuit in which the track relay combination operates with increased shunting sensitivity and a quicker and more positive release. Other objects and advantages will become clear from the description which follows.

We shall describe two forms of apparatus embodying our invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of track circuit apparatus embodying our invention. Fig. 2 is a diagrammatic view showing a modified form of the track relay combination shown in Fig. 1, also embodying our invention.

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

In railway signaling track circuits, it is desirable to maintain the upward pull on a track relay armature at a suitably low value when the track section is unoccupied so that when a train enters the section, sensitive release of the track relay will be obtained. One way in which this result can be accomplished is by means of the wellknown primary-secondary relay combination 30 wherein a separate secondary relay is used to decrease the energization of the primary relay following pick-up, so as to render the combination sensitive to the presence of a train shunt. Our invention combines the functions of a pri- 3 mary-secondary relay in one structure which is capable of providing certain additional advantages such as quicker and more positive release of the track relay armature when a train enters the section, and a more positive pick-up when 40 the section becomes unoccupied.

Referring to Fig. 1 of the drawing, the reference characters I and la designate the two rails of a section of track which is insulated from adjoining sections by means of the usual insulated rail joints 2. Located at one end of the section is a suitable source of current, here shown as a battery 3, which is connected across the rails through an adjustable current limiting resistor 4. Connected across the rails at the other end of the section is a track relay. combination designated generally by the reference character A. This relay combination comprises a pair of magnet structures B and C with which the armature 5 cooperates to provide the improved operation to which our invention is directed. The armature 5 is pivoted at 6 and operates the usual signal controlling contacts (not shown) and also the back contact 'I--8. Suitable non-magnetizable core pins limit the movement of the armature when energized. The contact 'l-8 is so adjusted that it will not open until the armature has almost reached its fully picked-up position.

The main magnet B of the relay A is provided witha pair of operating coils 9 and I normally connected in series with the magnetizing coils H and I2 of the auxiliary magnet C. The coils I l and |2should be connected in a direction such as to aid the flux which is established in the armature by coils 9 and I0. Magnet C may also be provided with a short-circuited winding ii), if desired, for a purpose which will be described hereinafter. The windings, air gaps, and core structures of the magnets Band C are so designed and proportioned as to provide just sufiicient holding energy to maintain armature picked up under the wet ballast condition but to insure pickup of the armature following the exit of a train under this same ballast condition.

If desired, the magnet B may be provided with a restrictedcore portion such as that indicated at IS. The sectional area of this restricted portion should be such as to cause this portion of the core to become substantially saturated at a flux density slightly above that normally required to pick up the relay armature. In this manner, when the ballast dries out and the voltage at the relay terminals increases, the downward pull of the magnet C will increase in greater proportion than the upward pull of magnet B. Accordingly, the track relay combination will provide a certainamount of compensation for track ballast resistance changes by virtue of the change in the flux division between the magnets B and C which is broughtabout by the restricted core portion J6. An additional advantage in providing magnet B with a restricted section is that under dry ballast conditions the flux in magnet B will tend to die away more quickly than would be the case if the flux were permitted to build up to a high value. Therefore, a train shunt effective at such a time will produce a slightly quicker release of the armature.

The operation of the apparatus will be best understood from a consideration of what happens when a train enters and leaves the track section.

Normally, when the section is unoccupied, the armature will be in the picked-up position in which it is shown, Under this condition, the

back contact '!8 will be open so that the resistance of coils l l and [2 will be effective to cut down the current in the operating windings 9 and ID to its holding value. Also, there will be a downward pull exercised on the armature by the auxiliary magnet due to the current flowing in windings H and I2. This pull will, of course, be insufficient to overcome the attraction established by the operating magnet B, so that the armature will normally remain in its picked-up position.

When a train entersthe section, the shunt provided by the train will decrease the current in coils 9 and I sufficiently to cause the armature to release. After the armature has moved part way, it will close back contact 'I8, thus short-.circuiting the windings II and [2. The snubbing effect of these windings closed on themselves (aided by the snubbing effect of ferrule winding l3, if used) will prevent a too rapid change of flux in the core of magnet C so that this magnet will continue to exert its downward pull to aid full release of the armature. The resistance of windings H and I2 will thus be eliminated from the circuit of coils 9 and lil so that an increased current will flow in these coils, but since the armature air gap is now relatively large, this current will not be sufficient to pick up the armature until the train vacates the section. In practice, the shunt for windings H and I2 will preferably pass through a suitable contact finger on the armature, rather than the armature itself, but is shown as passing through the armature in order to simplify the disclosure. Subsequent pick-up of the armature is aided not only because the current in windings 9 and I0 is increased, but also because the downward or opposing pull of magnet C becomes negligible a short time after the back contact 'l-B becomes closed.

As soon as the train leaves the section, the train axle shunt will be removed from across the operating coils 9 and so that the full pick-up energization will be effective in magnet B. Accordingly, the armature will quickly pick up and in so doing will open contact 1--8 near the end of its stroke, thus restoring the apparatus to its normal condition in which it is illustrated.

The short-circuited or ferrule winding l3 may or may not be used, as preferred, but when used, this winding performs a useful function in that it accentuates the beneficial effect of the .auxiliary magnet C. When a train enters the section, the flux in magnet B will collapse more quickly than in magnet C because the flux in the latter magnet will be maintained for .a short interval of time through the action of the ferrule l 3, even before contact '!-8 becomes closed. Accordingly, the downward pull of magnet C will decrease more slowly than the upward pull of magnet B and will persist for a longer time, thus providing a quicker and more positive release of the armature. Conversely, when the train leaves the section, the ferrule 13 will prevent the flux in magnet C from building up as rapidly as in magnet B, so that the latter magnet will have ample opportunity to pick up the armature before the opposing pull of magnet C becomes fully effective. During the time that contact 1-8 is closed, the windings II and I2 act somewhat in the nature of winding 13, and for this reason the resistance of these windings should not be too high. This resistance must, of course, be sulficient as compared with that of windings 9 and H] to provide the necessary spread between the pick-up and holding torque of the relay.

The ferrule l3 has an additional advantage in that it provides during the initial shunting interval a certain amount of compensation for track ballast resistance changes, (in addition to the compensation which results from the use of the restricted core portion l6) by preventing too great a decrease in shunting sensitivity when the ballast dries out. Under dry ballast conditions with the track unoccupied, the energization of both magnets B and C will be relatively high due to the increased track voltage then effective. When a train shunt is applied at such a time, the high initial energization in magnet C is actually helpful because, in view of the unequal rate of decay of the fluxes in magnets B and C caused by the ferrule 13, (as well as the restricted section IS) the increased downward pull due to high. energization of magnet 0 tends to offset to some degree the higher initial energization of magnet B. Accordingly, more uniform shunting sensitivity tends to be maintained over a wider range of ballast resistance variation, due to the presence of the ferrule winding l3.

Referring now to Fig. 2, the track relay combination of this figure is quite similar to that of Fig. 1, with the exception that the back contact 1-8 as well as the short-circuit for windings H and [2 are both eliminated and the ferrule winding I3 is replaced by .a pair of ferrule windings l4 and I5 for increased effect. The operation of the apparatus shown in Fig. 2 will be clear from the description of the apparatus of Fig. 1, and particularly those portions which deal with the effect of the restricted core portion 16 and the effect of the ferrule winding I3. Since the current in the operating magnet B is not decreased after pick-up of the armature in Fig. 2, the improvement in shunting sensitivity is due mainly to the slower rate of decay of the flux in magnet C, whereby a quicker and greater downward pull is effective for releasing the armature when a train enters the section. Similarly, a quicker and more effective upward pull for picking up the armature by means of magnet B is present when a train leaves the section, since the flux in magnet C will lag appreciably behind the flux in magnet B. Two ferrules I l and [5 are pref erably used and are placed in close proximity to the coils H and I2, respectively, in order that retardation of the flux change in magnet C may be as great as possible. Obviously, .a single ferrule, as in Fig. 1, may be used in the apparatus of Fig. 2. Also, in Fig. 1, if it is desired to in crease the ferrule effect, two ferrules placed as in Fig. 2 may be employed.

Although we have shown the two magnets B and C located one over the other with the armature in between, this has been done mainly for convenience in illustration. Obviously, the two magnets may be placed side by side, with the armature pivoted between them so that opposing armature torques are produced thereby. It will be understood, therefore, that magnet C may be positioned in many other obvious ways with respect to the magnet B, provided that it produces an opposing torque on the armature, without altering the inventive concept underlying our invention.

Although we have herein shown and described only two forms of track circuit apparatus 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 combination with a section of railway track and a source of current connected across the rails of said section, a track relay having two magnetic circuits so arranged with respect to the armature that one aids pick-up of the armature and the other opposes pick-up thereof, an operating winding for said aiding magnetic circuit connected across the rails of said section and effective for causing said armature to pick up when said section is unoccupied, an energizing winding for said opposing magnetic circuit connected in series with said operating winding and efiective to aid the release of said armature when the section becomes occupied, and means for v causing said aiding magnetic circuit to become magnetic circuits so arranged with respect to the armature that one aids pick-up of the armature and the other opposes pick-up thereof, an operating winding for said aiding magnetic circuit connected across the rails of said section and effective for causing said armature to pick up when said section is unoccupied, an energizing winding for said opposing magnetic circuit connected in series with said operating winding and eifectve to aid therelease of said armature when the section becomes occupied, and a core portion of restricted sectional area in said aiding magnetic circuit for causing substantial saturation thereof when the track ballast of said section dries out whereby the relative pull of said opposing magnetic circuit will be increased to thereby provide partial compensation for ballast resistance variations.

3. In combination with a section of railway track and a source of current connected across the rails of said section, a track relay having two magnetic circuits so arranged with respect to the armature that one aids pick-up of the armature and the other opposes pick-up thereof, an operating winding for said aiding magnetic circuit connected across the rails of said section and effective for causing said armature to pick up when said section is unoccupied, an energizing winding for said opposing magnetic circuit connected in series with said operating winding and effective to aid the release of said armature when the section becomes occupied, means associated with said opposing magnetic circuit for retarding a rapid flux change therein to aid quick release of said armature when the section becomes occupied and to aid quick pick-up of said armature when said section becomes unoccupied, and means for causing said aiding magnetic circuit to become substantially saturated when the track ballast of said section dries out to thereby increase the relative pull of said opposing magnetic circuit and partly compensate for ballast resistance variations.

4. In combination with a section of railway track and a source of current connected across the rails of said section, a track relay having two magnetic circuits so arranged with respect to the armature that one aids pick-up of the armature and the other opposes pick-up thereof, an operating winding for said aiding magnetic circuit energized from said source over the rails of said section, an energizing winding for said opposing magnetic circuit also receiving current from said source over said rails and efiective to aid the release of said armature when the section becomes occupied, and means for causing said aiding magnetic circuit to become substantially saturated when the track ballast of said section dries out to thereby increase the relative pull of said opposing magnetic circuit and partly compensate for ballast resistance variations.

5. A track relay for improving the shunting sensitivity of a track circuit comprising, in combination, two magnetic circuits each including the armature of said track relay as the common portion thereof, an energizing winding for each of said magnetic circuits, one of said magnetic circuits being efiective to pick up said armature when its associated winding is energized and the other of said magnetic circuits being effective to establish an opposing torque on said armature when its associated winding is energized for at times aiding the release of said armature, means for passing the same energizing current through both of said windings, and means for causing said one magnetic circuit to become substantially saturated above the pick-up value of said armature to thereby increase the relative pull of said other magnetic circuit and partly compensate for the effect of excess current in the windings of said track relay.

WALTER L. STOUT. ARBA G. WILLIAMSON.

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