Railway switches and signals – Train-position indication – Train annunciators or indicators
Patent
1991-09-09
1993-11-30
Huppert, Michael S.
Railway switches and signals
Train-position indication
Train annunciators or indicators
246169S, 246270R, 73636, B61L 106, B61L 2502
Patent
active
052658317
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an arrangement for detecting an object containing an impact sound-receiver for detection of impact sound produced by the object and transmitted in a sound-conducting medium to the receiver, and containing an evaluation circuit which receives an output signal from the receiver and delivers a warning signal when this output signal fulfills predetermined criteria, as well as to the use of this arrangement, especially for determining an approaching train.
2. Description of the Related Art
Such an arrangement is known, for example, from Swiss Patent No. 643,078. It serves for detecting an intruder during an attempt to break through a wall or a safe door in that there are detected impact sound-vibrations transmitted through the brickwork, wall or door serving as sound-conducting medium to the impact sound-receiver and processed by the evaluation circuit. With this arrangement, the signal evaluation is accomplished such that there are reliably distinguished the vibrations arising during an intrusion attempt from spurious vibrations emanating from the surroundings and there is avoided giving of a false alarm signal. In this regard it is attempted to suppress the delivery of a signal for such length of time until it is ensured that the received impact sound really has been caused by an intrusion attempt.
For other uses where, for example, an object which generates an impact sound with continuously increasing or decreasing intensity, must be indicated in all events, and a short-time faulty signal output caused by possible spurious vibrations can be absolutely tolerated, the aforementioned known arrangements are only suitable to a limited extent. In those situations, there was previously preferred purely human monitoring which is frequently unreliable and oftentimes resulted in serious accidents.
SUMMARY OF THE INVENTION
The invention is concerned with the object of further developing the aforementioned arrangements for detecting an object by means of impact sound produced by the object in such a manner that there can be positively signalled in any event also an object with continuously increasing or decreasing intensity of the generated impact sound and also in the presence of other spurious vibrations.
According to the invention this object is achieved in that the evaluation circuit is constructed to deliver a signal to a warning device when the output signal of the impact sound-receiver within a predetermined time exhibits a predetermined change in intensity, for example, when the intensity exceeds a predetermined threshold value between two points in time.
It is advantageous when the evaluation circuit periodically checks the intensity at uniform time intervals by means of a comparator and triggers a warning signal in the event that between at least two successive points in time the intensity has exceeded a threshold value, and if the warning signal is maintained for such length of time until the intensity between two later measuring time points has again fallen beneath a predetermined threshold value.
It is particularly advantageous if there are provided a plurality of threshold values, and a warning signal is then triggered when the intensity of the impact sound has passed through both of the threshold values within a specific frequency range during predetermined time intervals, something which is an unmistakable sign of an object having continuously increasing intensity of the generated impact sound.
Such an arrangement can be used to advantage, for instance, for the detection of an approaching vehicle. It is particularly suitable for the detection of a track-bound vehicle, for instance a railroad train or a locomotive upon a track, in order, for example, to warn track maintenance workers of an approaching train or to close and again open at the proper time a barrier at a railroad crossing. The impact sound-receivers are mounted at the rails and record the impact sound generated by the train and transmitted through the rails to
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Copy of International Search Report and Annex.
Huppert Michael S.
Lowe Scott L.
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