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THE AMERICAN CROSSING SIGNAL.
Railway Engineering and Mechanics—June, 1894

As long as grade crossings exist a perfectly reliable and automatic crossing signal is essential to safety. The American Signal Co. of Baltimore, Md., are furnishing a signal which has stood the test of five years of service, and is to be commended for its simplicity and reliability. In the accompanying cuts we show its essential features, Fig. 1 being the track instrument for single track roads, and Fig. 2 the alarm box and bell.

As will be seen in Fig. 1, the single track instrument has two concussion bars, 1 and 1a, shaped so that when a train is approaching a crossing bar la is depressed thereby de pressing lever 20 which releases latch 18 and causes it to pass under the end of a mercury tube 0. The second bar 1 is next depressed which acts upon lever 6, tilting the mercury tube 0 and making an electric contact. After the train has passed the crossing it arrives at the second instrument (placed for traffic in the opposite direction) and then the bar 1 is first depressed, which causes latch 18 to pass over, instead of under, mercury tube 0, and prevents the closing of circuit and giving of alarm.

The double track instrument has but one concussion bar, which is depressed and acts upon lever 6 which tilts mercury tube 7 allowing mercury to pass to end of tube and make the contact.

When the circuit is thus closed at the track instrument, the armature 32 (Fig. 2) is attached to the magnet 30. As the armature 32 moves, the detent hook 26 is raised out of the notch in the drum 17 and held suspended by the spring 24 until it is released by the trip pin 27, when it again falls on the drum 17. When the armature 32 is attracted to the magnet 30, the hinged contact plate 6 which rests on it, falls to the contact point 28, causing the current from the battery to go to the magnet 31, operating the bell and ratchet pawl 1. As long as the, detent hook 26 rests on the drum 17 the armature 32 cannot fall back far enough to break the contact between 6 and 28, consequently the bell must ring until the detent wheel 16 has made an entire revolution, when the hook will fall into a notch and the circuit be broken and the bell will stop. Should it happen that a train teaches the circuit-closer on one track when another train has nearly reached the crossing on another track, the detent wheel 16 will make a second revolution, causing the bell to ring just twice as long as it would had there been but one train.

The simplicity of the construction is thus apparent, there being few working parts and these are all well made of the best material. There is practically nothing to get out of order, so that the bell can be relied upon for effective service for a long term of years. This freedom from frequent repairs, which seems to be necessary in many devices of this character, is one of its strongest claims for economy. It is not affected by the speed of trains, and is adapted to roads having frequent and high speed train service, and can be placed at such distance from the crossing as to give warning to from one-half to three minutes before the arrival of train. The track instrument can be placed on bridges or in the centre of streets, for its dimensions being 15 inches long, 8 inches wide and 3 inches deep, it offers no obstruction to vehicles in the latter position. Its motive power is eight one-gallon jars of the Edison-Lelande battery. This battery will withstand a temperature of 50 degrees below zero, which places it beyond the reach of probable climatic changes.

The following are some of the special features of this signal: It will withstand a temperature of 50 degrees below zero; it is not affected by the speed of trains: the crossing is protected whether the train is a fast or slow one, as the detent wheel makes a second revolution when the train is a slow one, taking fifteen seconds or more to pass over the track instrument, thus protecting it twice as long for a slow as for a fast train; the track instrument can be placed on bridges, trestles or in the centre of streets, without fear of obstruction or breakage, and it is not continually out of repair; there are no "cut outs" necessary on the track as the cutting out is done automatically in the alarm apparatus; there are no timbers necessary, the track instrument being placed on the end of a sound cross-tie; the track instrument is not affected by snow nor is the apparatus "burned out" by lightning.


The company furnishes the signal complete, including wire, insulators and brackets, and sends a man to erect them. The works are at Thurmont, Md., (formerly Mechanicstown) where the company is equipped to turn them out in large numbers. During the five years in which the signal has been used the company has received many strong testimonials of its value.


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