US2092824A - Track shunting apparatus - Google Patents

Description

p 1937. G. w. BAUGHMAN 2,092,824

TRACK SHUNTING APPARATUS Filed Dec. 23, 1932 INVENTOR George WfBaug/mzazz HIS ATTORNEY Patented Sept. 14, 1937 TRACK SHUNTING APPARATUS George W. Baughman, Pitt'sburgh,'Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application December 23, 1932, Serial No, 648,609

11 Claims." (01. 24634) 7 Q My invention relates to track shunting apparatus, and more specifically to apparatus'for,

shunting track circuits by light weight rail vehicles having steel wheels or pneumatic tired wheels.

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

The track shunting apparatus set forth in my present application is somewhat similar to that set forth in the copending application of Howard A. Thompson, Serial No. 629,030, filed on August 16, 1932, for Apparatus for decreasing rail contactresistance, and also the copending applicafiled on November .25, 1932, for Track shunting apparatus, which copending applications contain claims covering broadly certain features of the invention described in my present application.

no The accompanying drawing is a diagrammatic View showing one form, of apparatus embodying my invention, as applied to an alternating current track circuit.

It has been found that by impressing a voltage to cause an appreciable current to flow between a rail contact and the rail surface, the resistance film which is ordinarily present on the rail surface can be effectively broken down, and the volt.-

age-impressing circuit, or portions thereof, may

be so arranged as to become available as shunt paths from rail to rail, for the fiow of track circuit current, to cause shunting of the track relay, thereby providing the necessary protection to following traffic. In practice, however, the impedance of the voltage-impressing circuit is usually appreciable, thereby reducing the effectiveness of the shunt paths from rail to rail, particularly in the case of alternating current track circuits.

One object of my invention is to providea low impedance track shunting path, at the same time providing an effective rail film breakdown circuit, Other objects and advantages will be apparent from the description which follows.

Referring to the drawing, the track section D-E is providedlwith the usual type of alternate ing current track circuit comprising a track relay TR, and a track transformer T energized from a wayside source BXCX and supplying alternating track circuit current to the. rails of the track through a limiting reactor X. The re-. maining apparatus illustrated is intended to be carried on the rail vehicle,

The alternating current generator G is driven by a motor M, energized from the car battery CB,

and supplies the rail film breakdown energy tion of Bernard E. OHagen, Serial No. 644,180,

through the medium of two transformersshown within the'dotted rectangles'T andfI' which, if desired, may have a common core, the energy of transformer T being applied to rail 5 by con-,-. tact shoes l2, and the energy of transformer 'I being applied to rail fi'by contact'shoe st3 4. Transformer T has a primary winding 1 shown in two sections for purposes of illustration, and a secondary made up of two windings 8 and 9 having substantially the same number of turns. 10: The plus terminal of winding 8 is connected to the rail shoe 1, and the minusv terminal of winding 9 is connected to the rail shoe 2 through the primary winding E5 of a current transformer T the pur-. pose of which will be explained hereinafter. 7 The 15 two remaining terminals of windings} and 9 are connected together througha reactor X 7 Transformers T and T and reactors X and X are preferably similar in design, and the 0011-, nections of windings l0 and H of transformer 20 T are made in an analogous manner to that de-. scribed for transformer T 'Ihemid-points of reactors X and X are joined together by a'low resistance conductor ll'which is firmly fastened to therespective reactors to minimize the danger 5 of breakage, ,asthe shunting effectiveness of the apparatus isin a-large measure dependent upon the integrity of conductor l2. 1 7

It will be apparent from the drawing that the voltage which causes the-film breakdown current 30 to flow between rail shoes I and .2 and the rail, is the sum of the voltages induced in windings 8 and 9. Similarly, the film breakdown current through rail shoes 3 and 4 is caused by the added voltages of windings H! and H. When the wind- 35 ings oftransformers T and T are independent I magnetically, the breakdown current in rail 5 is practically independent of the breakdown current in rail 6, making itpossible for any one rail shoe of the group to make imperfect contact with the 9,0 rail without materially affecting the value of the breakdown current in the other rail or the magnitude of the'breakdown voltag'e'effective at the rail with which imperfect contact is being made. However, based on other considerations to be ex- 5L5 plained hereinafter, it may be desirable to'use a common core for transformers T andT?,-hav,-' ing asingle primary winding and. four secondary windings mounted thereon. v

When 'the film breakdown currents in rails 5 59 and 6 are ,of sufficient magnitude, indicating that the rail contact resistance at shoes l.2 and 34 has. been reduced to a satisfactorily low value, sufficient voltage will be induced in the secondary windings l3 and I4 of current transformers T. 5?

and T to pick up relays K and K through their respective rectifiers R and R thereby closing the energizing circuit for indicator L over front contacts I! and I8, to provide a visual indication to the car operator that the apparatus is functioning properly. Primary windings I5 and I6 of transformers T and T can also be connected in series with the primary windings I and I1 respectively of transformers T and T to eliminate the impedance of windings I5 and I6 from the film breakdown current path, and also from the track shunting path which includes rail shoes 2 and 4. However, by connecting windings I5 and I6 as illustrated, a check is provided on short circuits occurring in windings 8-9, and IDI I, which might otherwise remain undetected. The impedance of windings I5 and I6 is sufiiciently low to cause no serious interference with the proper operation of the apparatus.

When the rail film has been broken down at the rail shoes I2 and 34, there will exist two shunt paths from rail 5 to rail 6, one of which includes rail shoe I, winding 8, one-half of reactor X conductor I2, one-half of reactor X winding I0, and rail shoe 3, and the other of which includes rail shoe 2, windings I5 and 9, the other half of reactor X conductor I2, the other half of reactor X windings II and I6, and rail shoe 4. Assuming that substantially equal track shunting currents from the track circuit source BX-CX flow over each of the two shunt paths, the directions which these currents take through windings III and I I, and the two halves of reactor X will be opposing, thereby substantially neutralizing the reactance of windings I0 and II and of reactor X with respect to the track circuit current. In a similar manner, the reactance of windings 8 and 9, and of reactor X will be substantially neutralized, so that the shunt path between rail shoes I and 3 will consist chiefly of the resistance of the windings and connections in this path. Similarly, the shunt path between rail shoes 2 and 4 will be mainly a resistance path, plus the comparatively small impedance of windings I5 and I6. If the impedance of a winding such as I5 is objectionable, a second winding on transformer T similar to winding I5, can be used, this winding being connected between winding 8 and rail shoe I in such direction that the currents in the two shunt paths will oppose each other in these windings, to neutralize the reactance.

By using heavy copper in the secondary windings of transformers T and T in reactors X and X as Well as in windings I5 and I6 of transformers T and T the shunt resistance can be made sufliciently low to provide reliable and safe shunting of the track relay TR. Should one or more rail shoes fail to make satisfactory contact with the rail, one or both relays K and K will release, deenergizing indicator L to warn the operator immediately of the unsafe shunting condition. Reactors X and X serve to limit the magnitude of the film breakdown current, to conserve the output of generator G. If desired, a set of the shunting apparatus can be installed at both ends of the car, to provide shunting protection when the car is bridging insulated rail joints.

It will be apparent that the shunting apparatus disclosed may also be used on direct current track circuits. In the case of alternating current track circuits, the frequency of the current supplied by generator G should be sufiiciently different from the track circuit frequency to avoid the possibility of false operation of the track relay.

To decrease the impedance of the two shunt paths from rail to rail, particularly if the currents in the two paths are not equally divided, reactors X and X may be eliminated from the shunt paths and connected in series with primary windings I and II respectively, if two separate cores are used for transformers T and T or, if a common core is used, a single reactor in series with the common primarywinding may be used for limiting the maximum film breakdown current. In the latter case, however, the breakdown voltage in one rail path will not be completely independent of the breakdown voltage in the other rail path. With the reactors X and X eliminated from the secondary circuits of transformers T and T windings 8 and 9, and II and I I, may be replaced by single secondary windings having their mid-points joined together by conductor I2.

If it is desired to prevent the feed-over of track circuit current around insulated rail joints which will, at times,'be located between the shoes I2 and 34, the common core transformer in which the windings 8, I I], 9 and II are linked magnetically, can be used advantageously. By choosing the relative direction of windings 8-Iil and 9--II in such manner that the fluxes set up by track circuit current from rail to rail tend to neutralize each other, substantially zero potential with respect to the track circuit source will exist between the rails beyond the insulated joints, thereby preventing possible false energization of a track relay in an adjoining track circuit.

Although I have herein shown and described only one form of track circuit shunting apparatus 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 combination with a rail vehicle and a stretch of railway track, a source of varying current on said vehicle; two transformers on said vehicle, one for each rail of the track, each having a primary winding energized from said source, and a secondary winding, the voltage of each secondary winding being applied across a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; and a connection from the mid-point of one secondary winding to the mid-point of the other secondary winding for completing a shunt path from one to the other rail for shunting said track.

2. In combination with a rail vehicle and a stretch of railway track, a source of varying current on said vehicle; a transformer on, said vehicle having a primary winding energized from said source and having two secondary windings, one for each rail, the Voltage of each secondary winding being applied across a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; and a connection from the mid-point of one secondary winding to the midpoint of the other secondary winding for completing a shunt path from one tothe other rail for shunting said track. 7

3. In combination with a rail vehicle and a stretch of railway track, a source of varying current on said vehicle; a transformer having a primary winding energized from said source and having two secondary windings, one for each rail, each secondary winding comprising two substantially equal sections joined together through a reactor which connects terminals of opposite polarity of the two sections, the voltage of each of said two secondary windings being applied across a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; and a connection from the mid-point of one reactor to the mid-point of the other reactor for completing a shunt path from one to the other rail for shunting said track.

4. In combination with a rail vehicle and a stretch of railway track, a source of varying current on said vehicle; a transformer on said vehicle having a primary winding energized from said source and having two secondary windings, one for each rail, the voltage of each secondary winding being applied across a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; an indicator for each rail controlled by the film breakdown current flowing between a rail and its associated rail contacts for indicating that the rail film has been broken down, and a connection from the midpoint of one secondary winding to the mid-point of the other secondary winding for completing a shunt path from one to the other rail for shunting said track.

5. In combination with an alternating current track circuit, a source of varying current of such character as to be incapable of operating said track circuit; two transformers, one for each rail of the track, each having a. primary winding energized from said source and each having a secondary winding the terminals of which are connected across a portion of the rail associated therewith by means of rail contacts for breaking down the rail film between said rail contacts and the rail; and a connection from the mid-point of one secondary winding to the mid-point of the other secondary winding for completing a shunt path from one to the other rail for shunting said track circuit.

6. In combination with an alternating current track circuit, a source of varying current of such character as to be incapable of operating said track circuit; a transformer having aprimary winding energized from said source and having two secondary windings, one for each rail, the voltage of each secondary winding being applied across a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; and a connection from one to the other secondary winding for completing a shunt path from one to the other rail for shunting said track circuit, said connection being made at such point of each of said two secondary windings that track circuit currents fiowing from rail to rail over said shunt path will result in substantially equal and opposite flux linkages in each of the two' secondary windings thereby decreasing the impedance of said shunt path to improve shunting of said track circuit.

'7. In combination with an alternating current track circuit and a rail vehicle, a source of varying current on said vehicle of such character as to be incapable of operating said track circuit; a transformer on said vehicle having a primary winding energized from said source and having two secondary windings, one for each rail, of

substantially equal flux linkages, the voltage of each of said two secondary windings being applied across a lengthwise portion of the rail associated therewith by means of a forward and a rear rail contact to break down the rail film between said contacts and the rail, the relative directions of said two secondary windings being such that the fluxes caused by the rail to rail track circuit current are substantially neutralized therein; and a connection from the midpoint of one secondary winding to the mid-point of the other secondary Winding for completing a shunt path from rail to rail to shunt said track circuit, said path being also eifective atsuch times as said forward and rear rail contacts bridge insulated rail joints for preventing feedo-ver of track circuit current beyond the rail joints due to said neutralizing action of the secondary windings.

8. In combination with .a railway vehicle operable along metallic rails, a plurality of shunt shoes on the vehicle in contact with each of the rails, a source of alternating current energy on the vehicle, a transformer having a first secondary winding inducing said alternating current in a circuit including two of the shunt shoes contacting with one rail, a second secondary winding of the transformer inducing said alternating current in a. circuit including two of the shunt shoes contacting with the other cuit including the other of said secondary windings and two of the shunt shoes contacting with the other rail.

10. In combination with a railway vehicle operable along metallic rails, a plurality of shunt shoes on the vehicle in contact with each of the r rails, a source of alternating current on the vehicle, a transformer having a primary winding rail, a first relay energized in accordance with" the amount of current flowing in the first secenergized from said source and having two secondary windings, a first circuit including one of said secondary windings and two of the shunt shoes contacting with one rail, a second circuit including the other of said secondary windings and two of the shunt shoes contacting with the other rail, and'a shunting connection from said first to said second circuit.

11. In combination with a track circuit, a source of current of such character as to be incapable of operating said track circuit; a transformer having a primary winding energized from said source and having two secondary windings, one for each rail, the voltage of each secondary :winding being appliedacross a portion of the rail associated therewith by means of rail contacts to break down the rail film between said rail contacts and the rail; and a connection from one to the other secondary winding for completing a shunt path from one to the other rail for shunting said track circuit.

GEORGE W. BAUGHMAN.

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