MOTION SENSOR SYSTEM

• US 3,777,139 A
• Filed: 12/03/1970
• Issued: 12/04/1973
• Est. Priority Date: 12/03/1970
• Status: Expired due to Term

• Current Assignee: Richard V. Peel
• Original Assignee: Richard V. Peel
• Inventors: Peel, Richard V.
• Primary Examiner(s): Forlenza, Gerald M.
• Assistant Examiner(s): Libman, George H.
• Application Number:
  US05/094,955
• Time in Patent Office: 1,097 Days
• Field of Search: 246/125-130
• US Class Current: 246/125
• CPC Class Codes: B61L 29/286 using conductor circuits controlled by the vehicle

Abstract

A system for providing grade crossing protection by sensing the presence of trains exceeding a preselected velocity in an approach track section defined by shunts across the rails. Detector circuits provide fail-safe protection from defects in the associated track section such as a broken rail or low ballast impedance between rails. A time-sharing self-test subsystem simulates an approaching high speed train by applying a fraction of a second test signal to the system every few seconds to monitor the operation of the overall system; and a low gain detector checks the gain of the system to assure that the train'"'"''"'"'s speed is accurately measured.

Claims

1. An apparatus for detecting an approaching train within a track section between a feed point and at least one low impedance connection across the rails, said apparatus comprising:

transmitter means coupled to the rails at the feed point for applying a current to the track section;

receiver means coupled to the track section for producing a first signal representative of the impedance of said track section;

differentiator means, coupled to said receiver means, for producing a second signal representative of the rate of change of said first signal;

motion detector means, coupled to said differentiator means, for producing a warning signal when said second signal is of a selected polarity and exceeds a preselected magnitude, whereby the presence of a train in the section, approaching the feed point at a speed greater than a preselected speed produces a warning signal;

low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value, whereby a defect in said track section which causes an abnormally low impedance therein produces a warning signal; and

track-occupied means, coupled to said low signal detector means and to said motion detector means, for inhibiting said low signal deTector means from producing a warning signal during the time period that a warning signal is produced by said motion detector means and for a preselected time period thereafter.

2. An apparatus for detecting an approaching train within a track section between a feed point and at least one low impedance connection across the rails, said apparatus comprising:

transmitter means coupled to the rails at the feed point for applying a current to the track section;

receiver means coupled to the track section for producing a first signal representative of the impedance of said track section;

differentiator means, coupled to said receiver means, for producing a second signal representative of the rate of change of said first signal;

motion detector means, coupled to said differentiator means, for producing a warning signal when said second signal is of a selected polarity and exceeds a preselected magnitude, whereby the presence of a train in the section, approaching the feed point at a speed greater than a preselected speed produces a warning signal; and

low gain detector means, coupled to said receiver means, for providing a warning signal when said first signal is less than a preselected value;

said low gain detector means including an impedance device coupled between said transmitter means and one of the rails, and between said one rail and said receiver means.

3. The apparatus of claim 2 further comprising high signal detector means coupled to said receiver means for providing a warning signal when said first signal exceeds a preselected value.

4. The apparatus of claim 2 wherein said transmitter means provides an alternating current and said impedance device is an adjustable inductor.

5. The apparatus of claim 2 further comprising self-check means for providing a warning signal upon the occurrence of a malfunction in said apparatus;

said self-check means including means coupled to said transmitter means, for periodically modulating said current, means coupled to said differentiator means, for sensing the periodic increase in the value of said second signal resulting from said modulation, and means for providing a warning signal if said periodic increase in said second signal is not sensed for a preselected time.

6. The apparatus of claim 2 further comprising low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value, whereby a defect in said track section which causes an abnormally low impedance therein produces a warning signal.

7. The apparatus of claim 2 further comprising low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value, whereby a defect in said track section which causes an abnormally low impedance therein produces a warning signal;

and high signal detector means coupled to said receiver means for providing a warning signal when said first signal exceeds a second preselected value.

8. The apparatus of claim 2 further comprising low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value, whereby a defect in said track section which causes an abnormally low impedance therein produces a warning signal;

and self-check means for providing a warning signal upon the occurrence of a malfunction in said apparatus;

said self-check means including means coupled to said transmitter means, for periodically modulating said current, means coupled to said differentiator means, for sensing the periodic increase in the value of said second signal resulting from said modulation, and means for providing a warning signal if said periodic increase in said second signal is not sensed for a preselected time.

9. An apparatus for detecting an approaching train within a track section between a feed point and at least one low impedance connection across the rails, said apparatus compRising:

transmitter means coupled to the rails at the feed point for applying a current to the track section;

receiver means coupled to the track section for producing a first signal representative of the impedance of said track section;

differentiator means, coupled to said receiver means, for producing a second signal representative of the rate of change of said first signal;

motion detector means, coupled to said differentiator means, for producing a warning signal when said second signal is of a selected polarity and exceeds a preselected magnitude, whereby the presence of a train in the section, approaching the feed point at a speed greater than a preselected speed produces a warning signal;

high signal detector means coupled to said receiver means for providing a warning signal when said first signal exceeds a preselected value;

low gain detector means, coupled to said receiver means, for providing a warning signal when said first signal is less than a second preselected value;

said low gain detector means including an impedance device coupled between said transmitter means and one of the rails, and between said one rail and said receiver means; and

self-check means for providing a warning signal upon the occurrence of a malfunction in said apparatus;

said self-check means including means coupled to said transmitter means, for periodically modulating said current, means coupled to said differentiator means, for sensing the periodic increase in the value of said second signal resulting from said modulation, and means for providing a warning signal if said periodic increase in said second signal is not sensed for a preselected time.

10. An apparatus for detecting an approaching train within a track section between a feed point and at least one low impedance connection across the rails, said apparatus comprising:

transmitter means coupled to the rails at the feed point for applying a current to the track section;

receiver means coupled to the track section for producing a first signal representative of the impedance of said track section;

differentiator means, coupled to said receiver means, for producing a second signal representative of the rate of change of said first signal;

motion detector means, coupled to said differentiator means, for producing a warning signal when said second signal is of a selected polarity and exceeds a preselected magnitude, whereby the presence of a train in the section, approaching the feed point at a speed greater than a preselected speed produces a warning signal;

low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value;

high signal detector means coupled to said receiver means for providing a warning signal when said first signal exceeds a second preselected value;

low gain detector means, coupled to said receiver means, for providing a warning signal when said first signal is less than a third preselected value;

said low gain detector means including an impedance device coupled between said transmitter means and one of the rails, and between said one rail and said receiver means; and

self-check means for providing a warning signal upon the occurrence of a malfunction in said apparatus;

said self-check means including means coupled to said transmitter means, for periodically modulating said current, means coupled to said differentiator means, for sensing the periodic increase in the value of said second signal resulting from said modulation, and means for providing a warning signal if said periodic increase in said second signal is not sensed for a preselected time.

11. The apparatus of claim 10 further comprising track-occupied means, coupled to said low signal detector means and to said motion detector means, for inhibiting said low signal detector means from producing a warning signal during the time period that a warning signal is produced by said motion detector means and for a preSelected time period thereafter.

12. The apparatus of claim 10 wherein said self-check means further includes means for adjusting the scale factor of said sensing means during the modulation periods to compensate for the component of the second signal due to the motion of a train within said track section.

13. The apparatus of claim 12 further comprising means for inhibiting said self-check means during the time a warning signal is produced by said motion detector means.

14. The apparatus of claim 13 wherein said differentiator means includes a capacitor coupled to an amplifier, and said means for adjusting the scale factor includes an energy storage network normally coupled to the output of said amplifier, and means for switching said storage network from the output to the input of said amplifier shortly before and during said modulation periods.