US2122382A - Signaling system for railroads - Google Patents

Description

W. H. REICHARD SIGNALING sYsTEM FOR RAILROADS June 28, 1938.

3 Sheets-Sheet 1 Filed April 10, 1935 ATTORNl EY June 8- w. H. REICHARD SIGNALING SYSTEM FOR RAILROADS Filed April 10, 1935 5 Sheets-Sheet 2 INVENTOR BY 1W?!- AQ /L; ATTORN'EY o2 "Ax Il-N-CI June 28, 1938. w. H. REICHAR D v SIGNALING'SYSTEM FOR RAILROADS Filed April 10, 1935 3 Sheets-Sheet 3 ATTORNE Patented June 28, I938 PATENT OFFICE SIGNALING SYSTEM FOR RAILROADS Wade H. Reichard, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application April 10, 1935, Serial No. 15,645

11 Claims.

This invention relates to systems for signaling for railroads of the so-called coded track circuit type, in which intermittent energization of the track rails with impulses having distinctive 5." code characteristics is employed to operate track relays and suitable decoding equipment to control the indications of the wayside signals and/or cab signals for train control equipment on locomotives.

In this co-called coded track circuit type of system, the intermittent energization of a track relay is required to display a proceed, or caution, or approach restrictive wayside signal indication; and it has been proposed to employ coding and decoding devices of such design and construction that their various moving parts and contact means are adapted for continuous operation. It can be seen, however, that it is not necessary to have the coding and decoding equipment in operation to give proceed indications for the wayside signals, or provide coded rail current to control cab signal or train control apparatus on locomotives, unless a train is present to take advantage of the wayside or cab signal indications; and since railroad tracks are usually occupied by trains only a relatively small percentage of the time, it is apparent that there is a great deal of wear and deterioration of contacts and moving parts of the coding and decoding equipment which is ungo necessary if this equipment is operating continuously.

In accordance with this invention, generally speaking, it is proposed to provide a system of coded track circuit control in which the coding 35. and decoding equipment is normally inactive, but is automatically set into operation when a train approaches, thereby avoiding unnecessary wear and deterioration of the moving parts and contacts of the apparatus.

In accordance with this invention, it is also proposed to provide an organization of thermionic devices of the usual vacuum tube type in the decoding apparatus in lieu of a code following track relay intermittently opening and closing its con- 45. tacts, thereby avoiding the disadvantages and difficulties associated with contacts and devices operating at relatively high rates and with the relatively small amount of current available in the track circuit.

Other characteristic features, attributes, and advantages of the invention will be in part apparent and in part pointed out as the description progresses.

In the accompanying drawings, Fig. 1 illus- 55 trates in a simplified and diagrammatic manner one specific embodiment of the invention to provide approach control of the coding equipment; Fig. 1A is an explanatory diagram of parts of the same equipment to illustrate the condition of the various parts upon the approach of a train; and Fig. 2 shows the modified construction of the decoding apparatus involving vacuum tubes and no constantly moving parts.

Referring to Fig. 1, the trackway apparatus is illustrated for one block or track section 3, and for the ends of two adjacent blocks 2 and 4. It is contemplated that this equipment will be the same for each block; and for convenience the corresponding relay and devices for the several blocks shown are designated by the same reference letter with a distinctive suffix number. The track rails B are bonded together and divided by insulated joints 1 into track sections in the usual way, it being assumed that each track section will extend one block length. It is also contemplated that a wayside signal of any suitable type will be located at the entrance end to each block. As illustrated, it is assumed that this wayside signal will be of a typical color light signal, having lamps to be lighted to display the usual green (G), yellow (Y) and red (R) indications.

At the exit end of each block, traffic being from left to right as indicated by the arrow, the secondary of a transformer 8 is connected across the track rails; and the primary of this transformer is arranged to be energized with a steady or coded alternating current, preferably of a distinctive frequency such as 100 cycles, which may be obtained from any suitable source, in this instance assumed to be a transmission line 9 energized from a suitable generator G. At the entrance end to each block is the code following track relay T, which is assumed to be a direct current tractive type relay of the usual construction, and which is connected across the track rails through a double-wave rectifier l0 of the usual construction. This track relay T is intermittently or steadily energized in accordance with the supply of alternating current to the track rails at the exit end of the block, and is employed to control the operation of suitable decoding apparatus to close contacts selectively in accordance with the code being transmitted.

In the simplified embodiment of the invention illustrated, the code for the rail current is assumed to be of the simple rate type, in which the code character depends upon the rate or periodicity in which the rail current is supplied to the track rails. For convenience in explanation and by way of illustration, it is assumed that the -of track relay TI (see Fig. 1A).

code rate for a clear or proceed indication will be 180 impulses per minute, and for the caution indication 75 impulses per minute, a stop indication corresponding with steady rail current or absence of rail current. The type of decoding equipment shown comprises a transformer having a primary I I with a midtap connected to one terminal of a suitable source of direct current indicated conventionally by the symbol minus The opposite terminals of this primary II are connected to the other terminal of said source of current through front and back contacts of the armature or contact finger 43 of the code following track relay T. Two secondaries I2 and I2 of this transformer, the secondary I2 being connected through a suitable condenser I3, and with additional reactances if necessary, are connected to double-wave rectifiers I4 and M which in turn supply current to two direct current relays designated RI and R15.

The operation of this decoding apparatus, governed by the code following track relay T, is similar to the decoding apparatus on the locomotive shown and described, for example, in the patent to Wm. D. Hailes, No. 1,852,409, April 4, 1932. The energization and de-energization of the code following track relay T energizes the primary ii of the transformer with direct current, first in one direction and then in the other direction, thereby inducing in effect alternate voltages in the secondaries I2 and I2 of a periodicity or frequency corresponding with the code rate at which the relay T is operating; and the relative inductive and capacity reactance of the circuits of the secondaries I2 and I2 of the transformer are so selected that effective energizing current is supplied to the relay R15 when the code rate is 75 and to the relay RI80 when the code rate is 180.

The decoder relays R15 and RIBB control circuits, readily traced on the drawings, for lighting the lamps of the wayside signal, so as to light the lamp G when relay RIBU is energized, lamp Y when relay R15 is energized and RI80 de-energized, and the lamp B. when both relays are deenergized.

Associated with eachblock is a modulator or coder having contacts for intermittently opening and closing the circuit for energizing the primary of the track transformer 8. Such modulator or coder may take various forms; and for simplicity, it is assumed that such coder will comprise a suitable motor M, of a constant speed type, preferably a polyphase or synchronous motor, which operates contacts designated C15 and CIBU. The energizing circuit for the coder motor M is shown conventionally with its terminals BX and CK.

Considering now the means for providing the approach control characterizing this invention, at the exit end of each block is an approach control relay A, arranged to be energized over a line circuit if the track relay T of the corresponding block, or if either of the next two blocks in the rear thereof, is de-energized. For example, the approach control relay A3 at the end of the block 3 is energized by'a line circuit starting at a common wire, indicated by the symbol C, through the relay A3, line wire I? through back contact I8 of track relay T3, to a suitable source of direct current, designated by the symbol and thence back over the common wire, or over the line wires H and I9 through the back contact 23 of track relay T2 to or through the additional line wire 2| through the back contact 22 Each approach control relay A, when energized, supplies current to the corresponding coder M to initiate operation of the coder at the end of that block.

Considering the operation, the parts are shown in Fig. 1 in the normal condition. The approach relays A2 and A3 are de-energized; and the track rails of each block are steadily energized through the track transformer 8 by a circuit for its primary which in the case of block 3 may be traced from the lower transmission line wire 9, wire 25, primary of transformer 23, wires 26, 21, 28, through the back contact 29 of the approach control relay A3, and wire 30 back to the other transmission line wire. The code following track relays T are thus steadily energized; and the decoder relays R15 and RI 811 are de-energized, lighting the lamps R at each signal. The approach relays being deenergized, the coders are not operated. In short,

the decoding equipment is inactive and at rest, the signals indicate stop, and the track circuits are steadily energized.

Assuming now that a train approaches and enters the block I, the parts assume the condition i1- lustrated in Fig. 1A. The train X shunts the track relay TI in the usual way, closing its back contact I8 to energize approach relay AI, back contact 2% to energize relay A2, and back contact 22 to energize relay A3. The energization'of these approach control relays starts the coders at the ends of blocks I, 2, and 3. The energization of the approach control relay A3 breaks at its back contact 29 the circuit for normally supplying current to the primary of the transformer B, and closes a circuit through Wire 3i, back contact 32 of relay R15 for the block 4, wire 33, back contact 34 of relay RISK wire 35, contact C15 for coder M3 and wires 36, 2? and 26 to the primary of the transformer 8, and wire 25 back to the transmission line. Thus, impulses at the 75 coderate are supplied to the track rails at the end of the block 3, and the track relay T3 starts to operate at the 75 code rate. This picks up the decoder relay R75, establishing a circuit for supplying rail current to the block 2 through the front contact 32 of relay R15, wires 31 and 38, through the contacts Clti. Consequently, the rail current supplied to block 2 is. at the code rate, and this energizes the decoder relay RI 8!] for that block, closing its front contact 34 to connect the contacts CIfi-B into the circuit for supplying rail current to the block I.

In this manner, upon the approach of a train as X, the coders are automatically started for two blocks ahead; and assuming no trains present, the track relays and decoder relays are operated in such a manner as to display a proceed or green indication at the entrance to the next block, a caution or yellow indication at the next block in advance, with a red or stop indication at the next block still further ahead. Also, rail current at the 180 code rate is supplied to the block I in which the train X is located, so that suitable decoding equipment on this train, such as disclosed in the I-Iailes patent above mentioned, will respond and establish proceed conditions on the locomotive.

As the train advances, the approach relay for the next block 4 is energized, starting the coder for that block and changing the code rates for the blocks in the rear; and as the train progresses, the same operation is repeated.

If one of the blocks ahead'is occupied, as for example the block 4, the track relay T4 for that block is shunted and cannot respond to the coded rail current, even when the coder'for that block'is started; and a stop indication is maintained at that entrance to that occupiedblock, with a caution indication in the next block in the rear. 7

From the foregoing it can be seen that there is provided by this invention a system of coded track circuit control in which the coding and decoding equipment is normally inactive, but is automatically started into operation an appropriate distance ahead of an approaching train, so that this train receives proceed indications so long as the track is unoccupied and will receive the appropriate caution and stop indications as it approaches an occupied block. A system for three indications has been illustrated; but it is apparent that the same principles and organiza- I tionof means may be extended to provide for four or more indications.

In the arrangement shown in Fig. 1, the proper signal indication and control of rail current to the block in the rear is dependent upon the rate at which the track relay T operates its armature to open and close its front and back contacts. In other words, the armature of the track relays T will be moving at rates of 75 or 180 times per minute while the system is operating; and even if approach control means is employed as above explained, such relative rapid operation of the armature and contacts of a relay presents problems in the design and construction of the parts for reliable operation over long periods of time. For the purpose of avoiding such continuing and rapid movement of contacting parts, the arrangement shown in Fig. 2 is proposed, in which the track rail current energizes an organization of transformers and vacuum tubes in such a way that the same operation of the decoder relays R and R|80 is accomplished without rapidly operating contacts.

Referring to Fig. 2, it is assumed that high frequency alternating current is supplied to the track rails by a coder or modulator at code rates of '75 or 180 times per minute in the same manner as already described. At the entrance end of the block the input circuit of a double-wave rectifier 4D is connected across the track rails, and its output circuit is connected to the primary of a transformer 4|, so that this primary is energized with a substantially uni-direction of current while the alternating current is applied to the track rails and is deenergized when such rail current is cut off. The secondary of the transformer 4| is divided into two halves which are connected in the manner shown to the input or grid circuits of two vacuum tubes of the usual three-element type. The plate circuits of these tubes are connected to the two halves of the primary of a transformer 42, the secondary of which is connected to rectifiers and decoder relays R15 and RIBO in the same manner as previously explained. When approach control is desired, a relay, as TI is connected across the output circuit of the rectifier 4D, and utilized to control the starting of the coding apparatus as previously explained in connection with Figs. 1 and 1A.

In this form of the invention however, the function of the track relay contacts, such as contact 43 of relay T3 of Figs. 1 and 1A, is taken over by the tube hook-up, the coding relays RISU and R15 being controlled by the tubes, and in turn controlling the wayside signals and the application of coded current to the track block to the rear, exactly as explained above in connection with Figs. 1 and 1A.

Considering the operation of this modified decoding equipment shown in Fig. 2, when the track rail current is first applied, the voltage induced in the secondary of the transformer 4| raises the grid potential of one tube and lowers the grid potential of the other. This causes current to flow through the primary of the transformer 42 in one direction in much the same manner as the closing of the front contact of a code following track relay. When the rail current is cut off, a voltage of the opposite polarity is induced in the secondary of the transformer 4|, reversing the relative potential of the grid circuits and causing plate current to flow through the transformer 42 in the opposite direction. In this way, there is a pumping action through the transformer 42 in substantially the same manner as is accomplished by the closing of front and back contacts of a code following track relay.

As illustrated, the vacuum tubes are assumed to have substantially zero current at zero grid potential for the plate voltage used; but these tubes may be provided with a biasing grid potential. Also, these tubes are shown as of the simple conventional three-element type, with direct current for heating the filaments and the battery for the plate circuit; but tubes heated by alternating current, with rectified alternating current for the plate supply, and other types of thermionic devices may be employed to perform the same functions.

The specific arrangement of parts shown and described is merely typical of the nature of the invention; and various adaptations, modifications, and additions may be made without departing from the invention.

What I claim is:

1. In a system of signaling for railroads, the combination with a plurality of track circuits each having a track relay, of coding means operable to intermittently energize each of said track circuits with impulses of distinctive code characteristics, decoding means associated with each track relay and responsive to the characteristic code impulses energizing that relay for controlling the code characteristics of the current supplied to the track circuit in the rear, said coding means being normally inactive, and means for initiating operation of the coding means for a plurality of track circuits in advance of the one occupied by a train.

2. In a system of the character described, coding means for intermittently energizing each of a number of track circuits at different rates with alternating current of a. distinctive frequency, an approach control relay for initiating operation of each coding means, and means responsive to the presence of a train on a track circuit for actuating said approach control relays for a predetermined number of track circuits in advance.

3. A coded track circuit system for railroads comprising, in combination with a plurality of track circuits each having a code following track relay, a coding means associated with each circuit for supplying coded current to the exit end of its circuit, normally inactive approach control means for each track circuit operable to initiate operation of the coding means for its circuit, and means for actuating said approach control means for a plurality of track circuits in advance of one occupied by a train.

4. In a system of the character described, a plurality of track circuits having code following track relays, decoding means including relays selectively responsive to the rate of energization and deenergization of each track relay, coding means operable tointerrupt the supply of current to the track circuit in accordance with the COIL-r dition of said decoder relays associated with: the block next in advance, said coding means being normally inactive, and means for initiating operation of the coding means for a plurality of track circuitsin advance of a train.

5, In a coded track circuit system for railroads, a normally inactive coding device associated'with each track circuit section and arranged, when active, to apply coded current to its section, an approach control relay at the exit end of each section for governing the operation of the coding device for such section, and means responsive to thepresence of atrain in any track section for operating said approach control relays for predetermined number of sections in advance of the occupied section.

6. In a coded track circuit system of the character described, the combination with a plurality of track circuit sections and a normally inactive coding device for each section for supplying coded current to its section, of means responsive to the presence of a train on any given section for initiating operation of said coding devices for a predetermined number of track sections in ad- Vance of the occupied section.

'7. In a coded track circuit system of the character described, a plurality of track sections each having a track relay, a normally inactive coding device associated with each section for supplying current impulses of different code characteristics to the track rails at the exit end of that section, an approach control relay for each section acting when energized to initiate operation of the coding device for that section, and means for energizing the approach control relay for each section if any one of a plurality of track sections inthe rear of such section is occupied by a train.

8. Ina coded track circuit system of the character described, a plurality of track sections each having a track relay, a coding device for each track section for at times supplying coded cur rent to its section, an approach control relay at the exit end of each section acting when energized to cause operation of the coding device for such section, and line circuit means for energizing the approach control relay of each section and closed if the track relay of any one of a plurality'of sections in the rear of such section is deeenergized.

19. Ina coded track circuit system of the character described, a plurality of track sections each having a track relay, a coding device for each track section, an approach control relay at the exit end of each section acting when energized to cause operation of the corresponding coding device, line circuit means for energizing the'approach control relay of each section and closed if the track relay of any one of a plurality of sections in the rear thereof is de-energized, and decoding means, responsive to code from the coding device, comprising decoder relays, circuits eifective to energize said decoder relays only if the respective circuit is pulsed at a predetermined rate, and means including thermionic devices and responsive to a difference of potential between the track rails for impulsing said energizing circuits in accordance with the periodicity of energization of the track rails.

10. Decoding means for coded track circuits comprising, a transformer, decoding means including relays selectively responsive to the periodicy of the energization of said transformer, a local source of current connected to and directly energizing said transformer, and means including vacuum tube devices responsive to a difference of potential between the track rails for controlling the energization'of first one portion of said transformer in one direction and. then the other portion of said transformer in the other direction.

11. In a decoding means for coded track circuits, a decoding transformer, decoding means including relays selectively responsive to the periodicity of the energization of the decoding transformer, a local source of current, a receiving transformer having its primary connected across the coded circuit, thermionic devices connected respectively to the two terminals of the secondary of the receiving transformer so as to cause their grids to be biased by the receiving transformer,.means connecting the local source of current between an intermediate point of the primary of the coding transformer and the two filaments of the thermionic devices, whereby to energize first one part of the coding transformer primary, and then the other, in first one direction and then in the other direction.

WADE H. REICHARD.

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