69s
Switch
Indicators Westward home signal on the Midland Home signal on the Canadian Pacific Serve as Interlocking Control Devices
SIGNAL protection, in which switch Co-ordinated track facil of maintaining it was approaching a indicators are used as interlocking ities are ingeniously sig point where the need for a new bridge control devices, as well as for the con was clearly indicated. By ·operating ventional purpose of train-approach naled, using switch indi jointly with the Canadian Pacific over indication, has been installed by the cators, with push-button the Assinibone, it was possible to ef Midland Railway Company of Man- control, in dual role fect an appreciable saving in bridge -itoba, in a very economical and ef Desired train operation maintenance alone, apd the need for fective solution of a train-operation is attained at exception a new bridge was permanently elim problem that was encountered at inated. The bridge was sold to a Winnipeg, Man., Canada. - allv low cost. Winnipeg lumber company, by whom At the location in question, the it was removed at no cost to the rail Midland paralleled the Canadian road. Pacific for several thousand feet, and the Dominion's Board of Railway In making the two track connec crossing several streets and the Assin Commissioners, the following plan tions, the Canadian Pacific con iboine river, as shown in the sketch. was chosen. structed two 120-ft. turnouts. The Until last year each railroad operated It was decided to run the Midland Midland moved 520 ft. of track in - a separate drawbridge over the river, trains over the Canadian Pacific track order to make the Academy avenue and Portage avenue was crossed at for a distance of approximately 4,000 connection, and constructed 544 ft. of grade by both roads. In recent years ft., and to abandon the Midland draw · track with a No. 11 turnout in order the Municipality objected to these bridge and track between the points to make the connection north of grade crossings at Portage avenue, now occupied by signals 3 and 4. Portage avenue. and several plans for their elimination Thus, with only one railroad track to This preview of the events leading were proposed and discussed before contend with, the cost of grade sep up to the co-ordination of facilities the present solution was agreed upon aration at Portage avenue was discloses the nature of the signaling by all parties. brought within the realm of possi problem that was involved. As train An old contract between the Mid bility. Because of the co-operation of movements over the Midland at this land and the Municipality placed upon the two railroads in co-ordinating point are chiefly those occasioned by the Midland the obligation to partici their facilities, the Dominion and the switching, it was not considered pate in the expense ~.;f grade separa City agreed to bear the entire expense necessary to provide an elaborate in tion at Portage avenue. The expense of the Portage avenue grade sep terlocking system that would permit that would have been occasioned by aration project. non-stop moves through the junction the separation~ _ of the Midland grade ·Another factor that made this plan switches. Automatic interlocking, from the Portage avenue grade was attractive was the ·elimination of the with power-operated switches, was such as to necessitate searching for a Midland's drawbridge over the Assin not justifiable. Since traffic and oper more economical solution of the prob iboine. This was timber trestle 1,070 ating conditions were such that it was lem. With the co-operation of the ft. long, with a 246-ft. timber draw not considered objectionable to stop Canadian Pacific, the Municipality, span. The bridge was old and the cost all Midland trains upon entering and December, 1937 RAILWAY SIGNALING 699 again upon leaving the Canadian Pa pass the trolley contactor. When the current in the railroad track circmts. cific track, the Midland adopted the trolley contactor has been passed, the Some of these a-c. track circuits were, simple but effective expedient of derail closes, and the street-car can of course, in service in connection equipping the hand-throw junction then proceed, on derail indication, with the Winnipeg Electric interlock switches with switch indicators and across the Canadian Pacific track. ing. It will be noted that single-rail using these indicators as interlocking After crossing the Canadian Pacific · a-c. track circuits are used between devices for the four home signals, as track, the street-car motorman must Academy avenue and Portage avenue. well as for the commonly accepted secure another clear indication at the This was necessitated by the fact that purpose of indicating the approach of second signal shown, the latter indica the Winnipeg Electric uses one rail trains. This is believed to be the first tion being his assurance that the derail of the Canadian Pacific track to tie installation in which switch indica has returned to its normal derailing its Academy avenue and Portage tors are used in this dual capacity. position behind him. avenue street railways together. It will be seen that this signaling Canadian Pacific train movements The new interlocking uses as much arrangement is about as inexpensive over the electric line are controlled as possible of the Winnipeg Electric a system as could possibly be con through interlocking relay 1R-2R interlocking equipment, the more im ceived consistent with the particular and, therefore, the interlocking is portant connections with the old sys conditions that prevailed here. Under cleared for the electric line as soon as tem being shown in the accompanying this plan, Canadian Pacific trains the rear end of a Canadian Pacific schematic wiring plan. The Winnipeg move over the joint track under full train clears the crossing. This ar Electric interlocking utilized color signal protection, without stopping at rangement was desired here in order light signals on the Midland and either junction. Midland trains, on to expedite traffic on the electric line. semaphore signals on the Canadian the other hand, before entering the Practically no significant changes Pacific. Its control track circuits ex joint track, are required to stop at the were made in -the street-railway cross tended from A to B on the Canadian junction home signal and wait for a ing interlocking, which had been in Pacific, and approximately from C to trainman first to operate a push-but stalled many years before by the D on the old Midland line. Much of ton, then to observe the position of a Winnipeg Electric. However, the this equipment was retained in the switch indicator, and then to open the presence of the d-e. propulsion line present system, but a study of the switch. If, then, all conditions are made it imperative to use alternating layout plan will show that several proper for the movement of the Mid changes were necessitated in track cir Indicator and push-button land train over the joint track, the control station in case cuits, signal locations, etc. Midland home signal, either 3 or 4, as Because the joint track is signaled the case may be, will display a yellow as a positive block for train move aspect indicating "proceed with cau ments in either direction, the Canadian tion." When signal 3 or 4 clears, the Pacific home signals, 1 and 2, are other three home signals are auto fitted with a lunar-white marker, be matically interlocked in the stop posi low the semaphore arm, which re tion and remain in that position until quires Canadian Pacific trainmen to the Midland train has moved into the secure orders from the dispatcher be clear at the other end of the joint fore proceeding past either of these track, or until the signal system has signals when the indication is "stop." otherwise been restored to its normal In the absence of communication fa condition. Positive block protection cilities, Canadian Pacific tr.ains would is thus provided in both directions, for be required to flag through the block. both following and opposing train Midland home signals 3 and 4 are movements, as only one train at any fitted with a special stop-signal marker one time can enter this joint block on which, in effect, places Midland trains a proceed signal indication. on practically the same basis as Cana dian · Pacific trains in the event that Street-Car Crossing Interlocking proceed signals are not displayed. is Involved Color-light approach signals are lo cated 1,500 ft. in the rear of home From a design standpoint, the sig signals 3 and 4. These approach sig naling system was slightly compli- nals display a continuous yellow aspect . cated by the presence of an automatic indicating "approach next signal pre interlocking system controlled by pared to stop." The fixed semaphore trolley contactors at Academy avenue, distant signals on the Canadian Pa where the double-track Winnipeg cific were in service in the Winnipeg Electric Street Railway crosses the Electric interlocking and were re Canadian Pacific at grade, and for tained unchanged. merly crossed the Midland at grade as well. Here, as the sketch shows, Signal Operation the .Winnipeg Electric has, in each track, a derail which, together with a Normally, all signals indicate two-position, color-light signal, gov "stop." Canadian Pacific home signal erns street-car movements across the 1 or 2 automatically indicates "pro Canadian Pacific. ceed" when a train enters the ap Before a street-car motorman can proach section, starting at A for signal proceed across the Canadian Pacific, 1, and at E for signal 2. Signal 1 is he must first receive a clear signal, also controlled by the Winnipeg Elec which authorizes him, not to cross the tric interlocking at Academy avenue, Canadian Pacific track, but only to but southbound trains proceed to sig- 700 RAILWAY SIGNALING December, 1937
1320'------;;.+- Relay case af ~~Academy WE.Ry c.rossinU nal 5 before receiving an in- . dication governing move Ave. ,------J ments across the electric 1 ~AC1 line. Signal 5 is used only I l for the Winnipeg Electric Sig.1 I I crossing and is in no way ,. 1&c] HG.i • • 5 HG I to be considered as a part of To W E.Ry. I ! t 1 the joint-track interlocking derailrelays check J_. I I with which this article is ~ I +I principally concerned. I 2lRtl Midland home signals are ~-~------_j not approach cleared, as the -x+ 1M. • JHR. 15 Canadian Pacific signals ~'------.. are. Although the follow- 1 &2 HR ing description deals with the move ment of a northbound Midland train past signal 3, it is to be understood that the operation of signal 4, at junc tion B, is similar in every respect to the operation of signal 3 at junction A. A northbound Midland train stops 111d. at signal 3. A trainman then goes to the switch and opens a switch-pad locked indicator box attached to the relay case. In this box is a semaphore tends their use on main-line switches. type switch indicf!.tor which normally Heretofore, the usual function of a indicates "stop," and below it are two train is on the joint track, and the switch indicator has been only to indi push buttons, one marked N and the switch indicator at the other junction cate to the trainman, before he opens other R. The trainman presses push has not· been cleared for an opposing the switch, whether or not a train is button R, holding it closed for a few move by a Midland train. This pro approaching on the main track. Sup seconds. Thereupon, if no train is vides ample protection against all pos pos~ that a trainman, operating a con on,the joint track, or on the approach sible conflicting moves. ventional switch indicator of this type, section of Canadian Pacific home sig Either of the R push buttons can be receives an indication that the main nal 1 or 2, the switch-indicator sema operated by a tfainrpp;n ·at a.ny time, ·· track is clear and that, therefore, it is phore indicates "clear." This is the regardless of the 'presence -bf trains safe for him .to open the switch. If, trainman's authority to open the junc on any of. the tt~cks, and without in now, the trainman should wait even· tion switch. If, when the trainman any way · interf~,ri,p.g with. the-move '60 seconds while unlocking the pad has fully reversed the junction switch; ment/of ~_Canad{iln, Pacific' trains that lock before he opens the switch, it is all conditions are as they should be, may already have i.-ecei\red clear sig entirely possible that a train could signal 3 will display a yellow aspect nals. . The N push buttons, AN at have approached during this 60-sec indicating "proceed." Signal 3 is also Acad~!Q!Y avenue, BN at Portage ave ond interval, and that the trainman, controlled by the Winnipeg Electric nue, ar~~~provided for the purpose of not having looked .at the indicator. a interlocking at Academy avenue, and re..,setti11g the system in its normal second time, might open the switch in this, of course, must be taken into condition when one of the R push the face of a fast-approaching ·train. consideration by the trainman if sig buttons has been operated but the con This danger, ordinarily inherent in nal 3 does not clear after he reverses templated train movem~nt. not made. the use of switch indicators by reason the junction switch. of the time interval between the ob As the accompanying written cir Hazardous .. Condition is servation of the switch indicator and cuit plan shows, a switch indicator Eliminated " the actual opening of the switch, is cannot display a clear indication un eliminated in the Winnipeg signaling. less the trainman operates push button It will be seen that ------~~----- 1540~'----~~-- ~- 500 ' 3000'------~ 1- ~ I of-< <:IJ I ,Gr-ade sepaY01.fion. 2 :..<:IJ ...... V') I! SX'.B c. P. ~ -1----.. ~4R I NoYfh ® t...l WiJ:Jnipeq I "t Midlal"ld 6:>-----J ® To --- +< @ '-' I <>) ~~ -- ~ ~ (\) 230' )>L 1500' I I A. L -~ Push -.buHoJ:Js and -~ imiicafoy in 2-way I ;s: box a-Ha ched to cable post. Podage in the sketch. This special feeder is Ave. wired to the track through the circuit controller on switch A, as shown in the sketch, where N designates a switch-box contact that is closed only jii. the normal position, C designates contacts that are closed only when the switch is in the center position, and R designates a contact that is closed when the switch is fully reversed. With this arrangement, when a train man restores the switch to its normal position after the Midland train has cleared the fouling point, the special feeder momentarily energizes lR as the switch passes through the center position. Then, when the switch has been closed in its normal position, the Sig.2 Canadian Pacific train shunts 1R and the relay drops to its back contacts, lnol. thus enabling signal 1 to clear. It is important that the Midland trainman does not operate the junction right for it to do so, but, if it does ~'~ switch until the southbound Midland clear, it automatically locks out con train has cleared the fouling point, as flicting signals, and the trainman can the junction switch to the main· line. otherwise track relay 1R remains take as much time as required, after Track circuit 1 embodies a feature shunted by the Midland train even observing the indicator aspect, before which is of interest, despite the fact when the special feeder is connected opening the switch, without running that it is necessitated by the special to the track, and thus the purpose of the risk described above. conditions peculiar to this installation. the special feeder is defeated. There Parenthetically, it is interesting Track relays 1R and 2R are of the fore, especial care is taken to observe here to know thatthe Great Northern combination interlocking type. This the operating rule requiring trainmen has used a similar arrangement at means that when a southbound Mid to wait until the train has cleared the other locations on its railroad. How land train enters track circuit 1, track fouling point before closing the main ever, at these locations, which com relay 1R cannot drop all the way to line switch. prise branch line junctions with a its back contacts. If a northbound General -Railway Signal Company main track, a wayside signal replaces Canadian Pacific train should enter Type-K neutral relays are used, ener the switch indicator used in the Win track circuit 1 while a southbound gized by direct current taken from -nipeg installation. This has the ad- Midland train is passing through Type-BQ rectifiers floating on a 110- vantage that the engineman receives switch A, the Canadian Pacific train volt a-c. line. The switch indicators exactly the same indication that the would, in the absence of special pro are the G.R.S. Type-9A. Push-but trainman receives before opening the vision to the contrary, hold 1R "'on ton switches were furnished by the switch. The trainman first operates a the hook." Since 1R must be all the Western Railroad Supply Company. push button at or near the junction way down on its back contacts before Raco lightning arresters and Copper switch. If no trains are approaching, signal 1 can clear, this means that, weld ground rods complete the list of the wayside junction signal then dis under these circumstances, the Cana the major new equipment required. plays an aspect indicating to both the dian Pacific train would not receive a i\11 of the signal work was done by engineman and the trainman that it clear signal even after the Midland the Midland. The plant is maintained is safe for the trainman to open the train cleared the fouling point. by the Canadian Pacific signal forces. junction switch. When the trainman To circumvent this possibility, an The installation was completed in operates the push button, all conflict additional insulated joint was installed July, 1936, and, in its first year of ing signals are locked out, and no dan at F, and the special feeder was con operation, has proved to be entirely ger whatever attends the opening of nected to the track circuit, as shown satisfactory _from every standpoint.