US1791938A - Safety device for railroad operation - Google Patents

Description

Feb. 10, 1931. F. SCHROETER ET AL 1,791,938

SAFETY DEVICE FOR RAILROAD OPERATION Filed Nov. 16. 1929 FRlTZ SCHROETER AND BY FRIT MICHELE NY ATTORNEY Patented Feb. 10, 1931 UNITED STATES PATENT OFFICE FRITZ SCHROETER AND FRITZ MIGHELSSEN, OF BERLIN, GERMANY, ASSIGNORS TO TELEFUNKEN GESELLSCHAFT FOR DRAHTLOSE TELEGRAPHIE M. B. IL, BER- LIN, GERMANY, A CORPORATION OF GERMANY SAFETY DEVICE FOR RAILROAD OPERATION Application filed November 18, 1929, Serial No. 407,649, and in Germany November 27, 1928.

This invention relates generally to improvements in railway signalling systems and more particularly to a railway signalling system which utilizes infra-red rays.

It is known in the prior art that the presence of infra-red rays may be detected by certain sensitive devices which react to the modulated frequencies of transmitted infra-red rays. The modulation of infra-red rays may be effected either in a mechanical way (e. g. by periodic shutting) or by electrical means. In order to modulate properly the infra-red radiation of incandescent lamps by way of rhythmic variations of the feed current it is necessary, as demonstrated by tests, to use a filament wire which is very thin and is able to burn in an atmosphere of hydrogen. The filament may be of a loop or zig-zag structure. It is known that infra-red rays may be directed exactly and furthermore that they can be completely separated from the visible part of the radiance of the transmitter by suitable filters. In addition infra-red rays possess the faculty of penetrating fog which fre- 2 quently prevents the recognition of optical signals. The devices for the establishment of infra-red rays are based on the influence which they exert on certain electrical properties of the indicators; thus it becomes possible to apply the modern amplifying technique.

The present invention makes use of this and other qualities of the infra-red waves for a new safety device on railroads which is obviously applicable also for subways and for street traflic regulation. The railroads use for the regulation of train sequence and for the purpose of preventing accidents, collisions, derailments etc., optical signal lamps of various colors which consist of advance signals and main signals and signify, according to their color, either go ahead or stop.

In daylight these signals are transmitted in the form of different semaphore positions.

This method of signalling is, however, ineffective in a fog. It is furthermore a fact that even with good visibility there is a danger of the signals not being seen on account of failure or inattention of the engine crew. The main purpose of this invention is to supplement or replace the various existing visible signals by invisible signals of directed infrared transmitters with various modulating frequencies. For instance, a modulating frequency of 50 cycles may signify go ahead and a frequency of 25 cycles may denote step. A separate infra-red transmitter may, of course. be provided for every signal but it is equally possible to modulate one single transmitter in accordance with the various signals. As compared to o tical signals these infra-red signals have tile advantage of a long range of action with a small expenditure of energy. The advance signals heretofore necessary may therefore eventually be dispensed with. Besides being invisible, these infra-red signals do not confuse the engine crew, as there is no possibility of mistaking them for other optical signals which may exist. Furthermore, the infrared signals remain operative in a fog which would render the optical signals ineffective.

The receiving arrangement in the locomotive consists of infra-red indicators which permit the recording of the various modulating frequencies. The latter may, if necessary, be amplified by electrical means and filtered out by suitable electrical or mechanical resonance systems.

The single figure of the drawing shows by way of example one embodiment of the invention.

In said figure, 1 illustrates a parabolic reflector with a source of infra-red rays 2 at its focus. The infra-red rays may be modulated in any well known manner by a frequency of 50 cycles and 25 cycles to correspond to the conditions of the track by the presence or absence of a train on the particular block in question. On each train will be located a parabolic reflector 3 arranged in such a position that light from the track signal reflector 1 willbe foeussed toward paraboli reflector 3. At the focus of reflector 3 any suitable detecting device may be employed such as a platinum wire 4 whose resistance changes in accordance with infra-red rays. The change of resistance of 4 will in turn vary the current flowing around circuit 10 made up of resistance 4, battery 5 and primary winding 6 of transformer 11. The secondary 7 of transformer 11 is connected to the input of an amplifier 8 which may be comprised of a triode, the output of which may be connected to certain tuned relays not shown for the purpose of indicating the signal transmitted by source 2.

It is evident that the resistance of circuit 10 changes in accordance to the modulations produced at 2 so that the grid of tube 8 being directly dependent thereon will in turn transn'iit the modulation frequency to the output circuit 9 with the result that the properly tuned relay will respond.

The advantage of receiving modulated infra-red waves consists in the elimination of interference from other sources of infra-red rays such as the sun, blast furnaces etc. These sources are capable of causing only a steady current to flow in the receiver which can be eliminated by electrical circuit elements. The reading or detection of these signals may be effected in various ways. The signals may be communicated to the crew by means of their variations in pitch. It is also feasible to connect the receiver to a device which contains glow-discharge or incandescent lamps in the usual colors of the railroad signals, the circuit being arranged in such a manner that every time a lamp flashes up, of the color which corresponds to the modulation frequency of the infra-red assigned to the color in question. Inasmuch as the infra-red rays possess a long range of action the signal becomes perceptible to the engine crew earlier than with the present devices. To eliminate the danger of the crew not heeding the signal this invention may be arranged so as to automatically operate the controlling levers of the locomotive in any well known manner. It is, for instance, feasible to actuate by means of electrical or mechanical resonators different relays for the different signals, the relays being made to control the locomotive by magnetic forces. It is of course possible to radiate the various modulation frequencies with light serving as a carrier frequency. In this case sensitized cells are employed on the locomotive. By the application of suitable filters the radiators, that is, the transmitters may be made to radiate the colored lights as well as the infra-red waves. The radiators may thus serve the double purpose of being optical signals as well as transmitters of the various modulated frequencies of the infra-red waves.

Claims:

1. In a railway signalling system having a signal emitter adapted to emit desired signals by means of infra-red rays, a receiver on a train comprising in combination an infra-red ray responsive device and an amplifier coupled thereto.

2. In a railway signalling system having a signal emitter adapted to emit desired signals by means of infra-red rays, a receiver on a train comprising in combination an inframamas red ray responsive device, an amplifying circuit comprising a space discharge device having an input and an output circuit, said input circuit bein connected to said infra-red ray responsive evice and a tuned relay system connected to said output circuit.

3. In a railway signalling system having a signal emitter adapted to emit desired signals by means of modulated infra-red. rays, each difl'erent signal to be transmitted being distinguished by modulating the infra-red ray with a particular frequency, a receiver on a train comprising in combination an infrared ray responsive device, an amplifier coupled thereto and a tuned relay system adapted to distinguish and segregate the received signals.

FRITZ SCHROETER. FRITZ MICHELSSEN.

Images