US2249037A - Highway crossing protection - Google Patents

Description

July 15, 1941- G. R. PFLAsTERER 2,249,037y

HIGHWAY RossINGv PROTECTION Filed July 25, 1939 52?@52 /55 54 my l 6 5 21%; a 25 Patented July 15, 1941 UNITED STATES PATENToFFIcE HIGHWAY CROSSING ritorlicrlohr George R.. Pflasterer, Greenville, assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application July 25, 1939, SerialNo. 286,328 s claims. (c1. 24e-13o.)

My invention relates to highway crossing protection, that is, to apparatus for protecting the intersections of railways and highways.

I shall describe three forms of apparatus embodying my invention, and shall then point out these signals has been temporarily discontinued by the manipulation of a stop button or other suitable device at the crossing. Prompt restoration of automatic operation is desirable at crossings in the vicinity of which switching movements take place which do not necessarily require passage of a train over the crossing. Another object of my invention is the provision of highway crossing track circuits which enable extended shunt protection to be obtained without requiring additional contacts on the interlocking relay. Other objects, features and advantages will become apparent from the description which follows.

Referring to Fig. 1 of the drawing, the reference characters I and Ia designate the rails of a stretch of railway track which is divided-by insulated rail joints 2 to form the block A-B. This block is subdivided by means of rail ljoints 2a and 2b to provide two track circuits A-D and C-B for controlling a suitable highway crossing signal XS at the highway intersection. Connected across the rails at the highway intersection are the two magnets 3 and 4 of a direct current interlocking relay XR. The construction of this relay is well known and it will be suiiicient t for the purpose of my invention to state that the armatures of the magnets 3 and 4 are so interlocked mechanically that if magnet 3 is first to release, then magnet 4 will be prevented from closing its back contacts, though this magnet is deenergized at the time. Conversely, if magnet l is 'rst to release, then magnet 3 will have its armature locked out and will be incapable of closing its back contacts until such time as magnet 4 becomes picked up. It will be apparent that the interlocking feature is not an essential element of V-myinvention so that the interlocking relay XR may be replaced by two independent track relays which correspond with the magnets `3 and 4.- The purpose of the interlocking feature vis -to insure that the warning will be discontinued after the train passes beyond the intersection but my invention is not specifically concerned with this feature and other arrangements can be'V provided vfor accomplishing this result, if desired, when independent-track relays are used'. Y

Magnet 3 has an energizing circuit which extends from the upper terminal of the secondary winding 5 of track transformer TI, through wire I2, rail Ia, rectier-Rl, rail I, wires II, II) and 9, winding Vof magnet 3, and wires 8 andl, to

theother terminal of the secondary winding 5. Similarly, the energizing circuit for magnet 4 extends from the lower terminal of winding 6 of transformer T2, through wires I3 and I4, winding of magnet 4, wires I5, i6 and I'I, rail I a, rectifier R2, rail I, and wire I8, to the other terminal of winding 6. The input windings I9 .and 20 of transformers TI and T2 are constantly energized from a suitable source of alternating current (not shown) having the terminals BX and CX. Thedirect current magnets 3 and 4 are energized from the alternating current source because of the presence of rectiers RI and R2 across the rails and in serieswith the respective magnets so that pulsating `unidirectional current is normally supplied to these magnets when v the section is unoccupied.

When a train enters the track section A-D from the left, magnet 3 will release because the train-shunt will short-circuit the rectifier RI, thus depriving this magnet of its unidirectional energizing current. The release of magnet 3 will close a shunt around rail joint 2a over an obvious circuit which includes the back contact 2| of magnet 3. Shunting the rail joint 2a due to the entry of a train causes the track circuit to be extended up to the rail joint 2b beyond the crossing, thereby insuring that a warning will vbe provided by the signal XS until the train has fully cleared the crossing.

' Release of the magnet 3 will also close the back contact 22 which is included in the energizing circuit for the lamps LI and L2 of signal XS, thus-providing the necessary warning to highway trafc approaching the crossing. The circuit for these lamps extends from one terminal-BX of a suitable' sourceof current, through wires 23 and 24, back contact 22 of magnet 3,

wires 25 and 26, back contact 21 of a normally deenergized auxiliary relay AR, Wire 28, and lamps L! and L2, to the other terminal CX of the source. As long as any part of the track circuit A--D is occupied, the magnet 3 will remain released and a warning will continue to be given by the signal XS.

When the forward end of the train passes beyond the rail joint 2b, rectifier R2 will become shunted and magnet 4 will be deprived of operating energy. However, back contacts 29 and 30 of this magnet will not close because, since magnet 3 was iirst to release, the interlocking feature of the relay XR will come into play and will prevent full release of the armature of magnet 4 such as is necessary for closing the back contacts.

When the train completely vacates the track circuit A-D, the shunt will be removed from across rectier Rl so that magnet 3 will again receive unidirectional current impulses and will pick up, opening the shunt around rail joint 2a and discontinuing the waning indication lof signal XS by opening the back Contact 22.

As long as any part of the train occupies the track circuit D-B, magnet 4 will remain deenergized, although contact 38 will be prevented from closing due to the interlocking feature previously mentioned. Once the train vacates the section, magnet 4 will Pick up and all of the apparatus will then be restored to the condition in which it is shown in the drawing.

The sequence of operations which take place when a train traveling from rightto left passes through the track circuit D-B is identical with that described above, that is, the release of magnet 4 will extend the track circuit beyond the crossing by closing a shunt around rail joint 2b over back contact 29, and will cause lamps LI and L2 of signal XS to become lighted over the same circuit as previously traced, except now including contact 30 and wire 3| instead of contact 22 and wire 24,

The operations so far described assume that the train passes through the entering track circuit and over the crossing without stopping. Instances may occur, however, where a car or train after entering the track circuit and starting the operation of the highway crossing apparatus, will make a stop for a switching move without coming close enough to the crossing to endanger highway traflic passing thereover. In such cases it is highly desirable to discontinue the warning given by the signal for the time being, restoring the apparatus to its fully automatic operation once progress of the car or train toward the crossing is resumed. The apparatus embodying my invention enables these additional operations to be performed in a simple and reliable manner.

It will be noted that With a train occupying either track circuit, the lighting circuit for lamps LI and L2 includes back contact 21 of the normally deenergized auxiliary relay AR. If now it is desired to discontinue the warning given by the signal, this can be done bydepressing the "stop button SI which closes a pick-up circuit for the relay AR. This pick-up circuit may be traced from the terminal BX, through wire 23, contact 33 0r 22 (depending upon which track circuit is occupied at the time), wires 25, 26 and 32, push button SI depressed, wires 33 and 34, winding of relay AR, wire 35, rectifier R3, and resistor 3G, to the other terminal CX of the source. The resistor 36 is merely a current limiting device and may or may not be used, depending upon the resistance of the relay and voltage of the Source. 75

Once relay AR picks up, the push button SI may thereafter be released because the relay will close an obvious stick circuit for itself over front contact 31 and wire 38.

Following the manipulation of the "stop button, if it is then desired to restore automatic operation of the apparatus, this can be done by depressing the starting button S2. Push button S2 connects a suitably poled rectifier across each of the magnets 3 and 4, thus permitting one or the other or both magnets to pick up, depending upon the condition of occupancy of the track section. The polarity of rectiers R4 and R5 should be so chosen with respect to the polarity of rectiers-RI and R2 that the direction of current flow in the magnets 3 and 4 will be the same whether these magnets are energized over the track rectiers or are energized by means of the rectiers associated with the push button S2.

The presence of a train in the track circuit A-D, for example, will not interfere with the pick up of magnet 3 by means of the push button S2 because a path will be established for the now of current through this magnet as follows: Starting at the upper terminal of winding 5, through wire I2, rail I a, the train shunt, rail l, wires II, lil and 9, winding of magnet 3, and wires 8 and l, to the lower terminal of winding 5. The shunt path provided by rectiiier R4, with push button S2 depressed, will by-pass current of the undesired polarity away from the magnet 3, thus enabling this magnet to pick up. A similar circuit may be traced for magnet 4 when the track circuit D-B is occupied. If this latter track circuit is not occupied, the magnet 4 will, of course, be energized over its track circuit in the usual manner, the rectier R5 being so poled'as not to interfere with the normal energization of magnet 4 when the push button is depressed.

Pick-up of magnet 3 (or magnet 4) will interruptthe previously established stick circuit for relay AR, restoring this relay toits normally deenergized condition. When push button S2 is` thereafter released, magnet 3 or magnet 4 will release, depending on the location of the train in the section, and the lamps Ll and L2 will become lighted, as in the normal operation which takes place when a train rst enters the track circuit. Accordingly, automatic operation will now have been fully restored.

The polarity of rectier RI should be so chosen with respect to the polarity of rectifier R2, that in the event of a simultaneous release of both magnets 3 and 4 (and the closing of contacts 2| and 29 whereby the two track circuits would be superimposed upon each other) a net unidirectional potential will remain across the track, thus enabling the magnets 3 and 4 to pick up when the section becomes unoccupied. Should one of the rectiiers be connected in the reverse direction from that shown in the drawings, the interrail potential might be short-circuited whereupon pick up of the magnets would be impossible without the aid of the starting button S2.

The purpose served by resistors 58 and 53 which are connected across the magnets 3 and 4 respectively, is to provide a certain amount of snubbing action so as to prevent chatter of the armatures caused by energization of the magnets 0n half-Wave rectified current. Without the snubbing resistors, a higher voltage would be required at the relay terminals for quiet operation. Consequently, these resistors make possible the use of a lower track voltage and provide more sensitive track circuit operation.

It will be apparent from the foregoing'description of Fig, 1 Ythat I have provided means for obtaining extended shunt protection in a simple and direct manner, as well as means for at times discontinuing the warning at the crossing and thereafter restoring the apparatus to its fully automatic condition with a minimum of apparatus required for reliable operation.`

Referring now to. Fig. 2, I have shown in this iigure a modification of the track circuit portion of the apparatus of Fig. 1. from the drawings, this modification requires but one transformer for both track circuits, and no back contacts on magnets 3A and 4A of the' interlocking relay XRA are required for the purpose of providing the equivalent of extended shunt protection. In Fig. 2, I have not shown the details of the highway crossing signal control apparatus as this apparatus is shown in Fig. 1, the presentV figure being concerned primarily with the track circuit portion of the apparatus.

The energizing circuit for magnet 3A extends from the lower terminal of winding A, through wires 43 and 44, winding of magnet 3A, wire 45, rail Ia, rectifier RIA, rail I, and wires 4B and 41, to the upper terminal of winding 5A, Similarly, the energizing circuit for magnet 4A maybe traced from the lower terminal of winding 5A, wire 59, rail Ia, rectifier RZA, rail I, wire 49, winding of magnet 4A, and wires 48 and 41, to the upper terminal of winding 5A. It will be apparent that due to the presence of rectiers RIA and RZA, the direct current magnets 3A and 4A will be energized over the respective track circuits from the alternating current source having the terminals BX-CX which terminals are connected to the input winding oi the track transformer TA.

When a train enters the track circuit A-C, the train shunt will render the rectifier RIA ineffective so that magnet 3A'will no longer receive unidirectional current and so will release, thereby initiating the highway crossing indication over plicity. The presence of the train will also close a shunt around the rail joint 2a, thus extending the track circuit to the' location D beyond the highway intersection. The shunt path around the rail joint 2a may be traced as follows: Starting at Vthe left-hand side of the joint, through rail la, the train shunt, `rail 1, Wires 46 and 41, winding 5A, and wires 43 and 5I), to the other side of the rail joint. During the time that any part of As will be observed ,a suitable contact which is not shown,`for simu the train occupies the portion C-D of the track i section, winding 5A will be partly short-'cirouited by the train shunt, so that neither magnet 3A or 4A will receive suiiicient energy for pick-up under this condition, Accordingly, magnet 3A will remain deenergized and the crossing signal will continue its warning until the train completely passes beyond the'ral joint 2b at locationD.

In order to prevent the flow of an excessive current from winding 5A during the time that any part of the train occupies portion C-D of wires 50 and 43, winding 5A, and wires 41 and 46,

to the other side of the rail joint.

The resistors 4I and 42 perform a similar snubbing function to that referred to in connection with Fig. 1, and in addition, provide an independent adjustment for the operating current in each of the two magnets 3A and 4A to take care of possible differences in the two track circuits with respect to length of track circuit, ballast resistance, or other governing factors. The resistors 58 and 59 of Fig.' 1 may, of course, also be made adjustable, as in Fig'. 2. If desired, wires 43 and`41 over which the track circuit current is supplied to the rails may be connected directly to the respective rails, independently of the relay leads, rather than to the relay leads 50 and 46 as shown in the drawing. One advantage resulting from such a connection is that in the event of a broken track rail connection, the source of track circuit current will be completely cut off, thus removing any danger of false pick-up of the interlocking relay.

Referring nowto Fig; 3, the apparatus of this figure is identical with that of Fig. 2'with the exception that the terminals 5I and 52 of winding 5B are connected to the outside terminals of the respective rail joints'a and2b, rather than to the inside terminals, as in Fig, 2. With this connection, the left-hand magnet 3B is energized through the rectifier R4A at the right-hand end of the section, `and thev magnet 4B receives its energy through the rectier R3A at the'lefti-'hand end of the section.

The energizing circuit for magnet 3B is as follows: From the upper'terminal of winding 5B, through' wires 5I and 55, winding of magnet 3B, wire 54, railIa, rectiilerRAA, rail I, and wires 53 and 52 to the lower terminal of winding 5B. Sim-y ilarly, the circuit for magnet 4B extends from the upper terminal of winding 5B,`wires 5I and 56, rail Ia, rectier RSA, rail I, wire 51, winding of magnet 4B, and wires 53 and 52, to the lower terminal of winding 5B.

Entry of a train into either track circuit A-C or D-B will deenergize the respective magnet 4B or 3B ofthe interlocking vrelay XRB by shunting the respective rectiiier RSA or R4A, thus initiating the warning indication at the crossing. n In Fig. 3 the length of track section C-D should preferably be less than the length of the shortest train traversing the track. If this is' not so, there may be an interval of timeduring which one or the other or both magnetsv 3B and 4B will receive pick-up energy while the train is wholly within the limits of section C-D, The transit time of a train over the crossing is usually short enoughV so that this occurrence will not interfere withsatisfactory performance. In Fig. 2 the occurrence described above can not happen, because in Fig. 2 a train wholly within section C-D places an eifective shunt across the winding 5a.

From the foregoing description, it will be apparent that I vhave provided a relatively simple form of track circuit apparatus for highway crossing protection and have incorporated into this apparatus extendedshunt protection features which may or may not require contacts of the interlocking relay.V I have also provided 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:

l. In combination with a section of railway track, a first insulated rail joint in one rail of said section, a second insulated rail joint in the other rail of said section, said two rail joints dividing said section into two adjoining track circuits, a first and a secondrectifier connected across the rails at one and the other end respectively of said section, a iirst direct current track relay connected with said one rail at opposite sides of .said rst insulated joint, a second direct current track relay connected with said other rail at opposite sides of said second insulated joint, `and a source of alternating current connected from one to the other rail of said section so as to energize said two track relays in multiple over said first and said second. rectiers respectively when said section is unoccupied.

2. In combination with a section of railway track, a first insulated rail joint in one rail of said section, a second insulated rail joint in the other rail cf said section, said two rail joints dividing said section into two adjoining track circuits. 'a first and a second rectiiier connected across the rails at one andthe other end respectively of said section, a first direct current track relay connected with said one rail at opposite sides of said first insulated joint, a second direct current track relay connected with said other rail at opposite sides oi said second insulated joint, a source of alternating current connected from one to the other rail of said section so as to energize said two track relays in multiple over said iirst and said second rectiers respectiveiy when said section is unoccupied, and an adjustable resistor connected across each of said track relays for providing a separate adjustment of the current received from the respective track circuit by the associated track relay.

3. In combination with a section of railway track intersected by a highway, a first insulated rail joint in one rail at on-e side of the highway, a second insulated rail join-t in the other rail at the other side of the highway, said two rail joints dividing said section into two adjoining track circuits, a rst and a second rectifier connected across the rails at one and the other end respectively of said section, a first direct current track relay connected with said one rail at opposite sides of said first insulated joint, a second direct current track relay connected with said other rail at opposite sides of said second insulated joint, and `a source of alternating current for energizing said two track relays over said iirst and said second rectiers respectively when said section is unoccupied, one terminal of said source being connected with said one rail between said irst insulated joint and the highway and the other terminal of said source being connested with said other rail between said second rail joint and said highway.

4. In combination with a section of railway track intersected by a highway, a first insulated rail joint in one rail at one side of the highway, a second insulated rail joint in the other rail vat the other side of the highway, said two rail joints dividing said section into two adjoining track circuits, a rst and a second rectifier connected across the rails at one and the other end respectively of said section, a rst direct current track relay connected with said one rail at opposite s'ides of said rst insulated joint, a second direct current track relay connected with said other rail.at opposite sides of said second insulated joint, and a source of 'alternating current for energizing said two track relays over said irst and said second rectiers respectively when said section is unoccupied, one terminal of said source being connected with said one rail between said first insulated joint and that end of the first track circuit which is away from the highway and the other terminal of said source being connected with said other rail between said second rail joint and that end of the second track circuit which is away from said highway. Y

5. In combination with a section of railway track intersected by a highway, a first insulated rail joint in one rail at one side of the highway, a second insulated rail joint in the other rail at the other side of the highway, said two rail joints dividing said section into two adjoining track circuits, a irst and a second rectifier connected across the rails at one and the other end respectively of said section, a direct current interlocking relay havingr one magnet connected with said one rail at opposite sides of said first insulated joint and having the other magnet connected with said other rail at opposite sides of said second insulated joint, and a source of alternating current connecting the two rail terminals of said magnets which are nearest said highway for energizing said magnets over said rst and said second rectifiers respectively when said section is unoccupied.

6. In combination with a section of railway track intersected by a highway, a rst insulated rail joint in one rail at one side of the highway, a second insulated rail joint in the other rail at the other side of the highway, said two rail joints dividing said section into two adjoining track circuits, a rst and a second rectier connected across the rails at one and the other end respectively of said section, a direct current interlocking relay having one magnet connected with said one rail at opposite sides of said rst insulated joint and having the other magnet connected with said other rail at opposite sides of said second insulated joint, and a source of alternating current connecting the two rail terminals of said magnets whichfare farthest from said highway for energizing said magnets over said rst and said second rectiers respectively when said section is unoccupied.

7. In combination with a section of railway track intersected by a highway, a rst insulated rail `joint in one rail at one side of the highway, a second insulated rail joint in the other rail at the other side of the highway, a direct current interlocking relay having one magnet connected around said rst rail joint and having another magnet connected around said second rail joint, a first and a second rectifier connected across the rails at one and the other end respectively of said section, a first track circuit for said section terminated by said two rail joints and including said rst rectifier and said one magnet, a second adjoining track circuit for said section also terminated by said two rail joints and including said second rectier and said other magnet, both of said rectiers being poled in the same direction from said one rail to said other rail whereby simultaneous shunting of said two rail joints due to the passage of a train will cause the voltages of said two track circuits to aid one another rather than to neutralize, a source of alternating current for energizing both said track circuits with an inter-rail potential of the same instantaneous polarity in the respective rails thereof and connected across the track at said highway location from a rail of one track circuit to the opposite rail of the other track circuit, and signaling apparatus controlled by said interlocking relay.

8. In combination with a section of railway track intersected by a highway, a rst insulated rail joint in one rail at one side of the highway, a second insulated rail joint in the other rail at the other side of the highway, said two rail joints dividing said section into a first and second adjoining track circuit, a rst and a second rectiiier connected across the rails at one and the other end respectively of said section, both of said rectiers being poled in the same direction from said one rail to said other rail whereby simultaneous shunting of said two rail joints due to the passage of a train will cause the voltages of said two track circuits to aid one another rather than to neutralize, a direct current interlocking relay having one magnet included in said iirst track circuit and having another magnet included in said second track circuit, said one magnet being connected around said rst rail joint and said other magnet being connected around said second rail joint, and a source of alternating current for energizing both said track circuits with an interrail potential of the same instantaneous polarity in the respective rails thereof and connected across the track at Said highway location from a rail of one track circuit to the opposite rail of the other track circuit to thereby energize said two magnets of the interlocking relay when said section is unoccupied.

GEORGE R. PFLASTERER.

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