|December 1924, Vol. 17, No. 2||Railway Signaling (Chicago IL)||Page 463, col. 1|
Canadian National low-voltage plant
Operating crossover and junction switches from gate tower, expedites traffic and effects economies
C. H. Tillet, Signal Engineer, Central Region, Canadian National
At Brantford, Ontario, on the Canadian National Railways, two single track branch lines form a junction with the double track main line in such a manner that trains from Buffalo, N. Y., and Tilsonburg, Ont., are required to run for a short distance against the normal direction of traffic on the double track, before getting on to the westbound main track, or into the yard. The switches were handled by a switch tender who also furnished the protection for the westbound movement, and eastbound trains observed a permanent slow order. The crossovers are located near two street crossings, at which crossing gates are operated from an elevated gate tower. It was thought that better protection could be afforded to both railway and highway and that considerable economy could be effected, if the duties of the two sets of men were combined, by operating the switches from the same point that the gates were operated from.
Room was not available on the right-of-way for the erection of a standard interlocking tower, nor was additional right-of-way available on account of a street on one side and a cemetery on the other. Therefore, the existing gate tower, which was 6 ft. by 12 ft., was enlarged by making an 18 in. extension on the field side for the accommodation of a relay and battery case and a stove. A bay window was added on the track side to form a shelf 2 ft. by 6 ft. upon which to mount eight units of the General Railway Signal Company's interlocked desk circuit controllers, which serve as the interlocking machine.
Operating features and special circuits
A chase for the wire was built from the underside of this shelf, underneath the floor to the relay case, joining with the vertical chase so that wires can be run in all directions. The circuit controllers themselves, contain sufficient indicators to furnish all the information required to operate the plant. The manipulation chart, time releases and push buttons for clearing the call-on signals, are mounted above the machine and a space on the shelf at the ends is sufficient to provide for switches for operating the crossing gates electrically at some future time.
One lever is used for each of the two crossovers, and one each for the two junction switches; the levers control normal and reverse relays at the switches. Switch circuits are so carried through the relay and lever contacts that the normal control wire acts as the reverse indication wire and vice versa. The locking sectors of the switch levers allow free movement between indicating positions, but the levers cannot be placed in the extreme positions to release the mechanical locking until the switches operated from them are locked in a position corresponding to the position of the lever. For indicating purposes, a battery at the switches is used, while the switch control relays are energized from a central control battery located in the tower. To simplify the selection of signal circuits over the crossovers, SS relays in the tower in multiple with the indication lock, provide the necessary contacts. Selection of the signal circuits over the junction switches was done in the switch machines direct.
Signal levers are normal in the center position, the extreme right or left position putting current from the tower battery on the signal control wire to clear the signals, and can only be moved to the indicating position, when being restored to normal, when all the signals controlled by that position of the lever, have assumed the stop indication. This indication current comes from the battery at the signals through all the signals in series. Typical circuits for switch levers and signal levers are shown in the illustrations.
The switches are operated by G.R.S. Model 5 switch machines from two 24-volt batteries, one at each group of switches. A hand crank is placed in a box at each battery location and locked with a switch lock. The removal of a crank from the box cuts off the current from the operating battery to the group of switches, so that when the switches are being operated from the ground for emergency or test, the possibility of movement from the tower is removed.
The signals are Hall Searchlight type and the lamps on the home signals and dwarf signals burn continuously at 10 volts a. c. Reserve lighting source is provided by the 10-volt indication batteries, which automatically take the load if the a. c. line fails. The top signals of the three high home signals on the double track are semi-automatic, and form part of the automatic signal system of the double track line. Movement into an occupied block is made by the bottom signal, which can be cleared by a push button after the signal lever is in the proper position. Bottom signals also govern on diverging routes and when the route is so set, the reversal of the signal lever will clear the bottom signal without the use of the push button.
All relays, rectifiers and battery for each group of switches and signals are housed in a concrete house loccated conveniently to the group operated. These houses are moulded in place at each location and are of a size sufficient to permit all the battery required to be set on the floor with wall type relays and rectifiers placed conveniently on the walls. These houses are provided with double doors. The top outside door swings upward to form a canopy, while the other doors are hinged on the side, so that the workman and the apparatus are quite well protected with the doors open in bad weather.
As a source of energy, Exide KXH-7 storage batteries, made by the Exide Batteries of Canada, Limited, were used throughout this installation; the charging being done by General Electric Company 60-cycle Magnar chargers. Wire made according to A. R. A. specifications was furnished by the Northern Electric Company. Plans were made in the office of the signal engineer of the Central region of the railway and the construction was done by the forces of the South-Western Ontario district, under the direction of W. H. Patton, superintendent of signals and J. J. Killingsworth, supervisor of signals of the Stratford division.
The operation of the plant is found to be fast enough to meet the traffic conditions at this point, as the full movement of the switch levers is obtained in about 12 seconds average time. The same type of plant has been constructed at Lynden Junction, Ontario, about eight miles east of Brantford, where a new wye has been constructed. At this point a 7-unit circuit controller operates 5 switches and 15 signals. In this plant the operation is effected from the tower of the existing mechanical interlocking plant, which operates the old junction that forms the third end of the wye. The nearest switch of the new wye is 3,300 ft. and the farthest 3,900 ft. from the machine.