HOT BOX ALARM SYSTEM

• US 3,731,087 A
• Filed: 11/16/1970
• Issued: 05/01/1973
• Est. Priority Date: 11/16/1970
• Status: Expired due to Term

• Current Assignee: Joseph W. King
• Original Assignee: Joseph W. King
• Inventors: King, Joseph W.
• Primary Examiner(s): Forlenza, Gerald M.
• Assistant Examiner(s): Libman, George H.
• Application Number:
  US05/089,910
• Time in Patent Office: 897 Days
• Field of Search: 246/169D 340/248 328/147,148 179/1.1VC
• US Class Current: 246/169.00D
• CPC Class Codes: B61K 9/04 Detectors for indicating the overheating of axle bearings and the like, e.g. associated with the brake system for applying the brakes in case of a fault

Abstract

Method and apparatus for evaluating temperature indicating signals from a railway hot box detector and producing an alarm signal therefrom. The signals are differentially evaluated and are compared to appropriate reference signals to detect overheated solid or roller bearings. False alarm signals produced from the differential evaluation because of the difficulty in distinguishing the temperatures of normally operating roller bearings from those of overheated solid bearings are detected and cancelled. False alarm signals caused by noise and by time displacement between temperature indicating signals are cancelled by checking the duration of all alarm signals and passing only those that have long enough durations not to have been produced by noise or by differential evaluation of time displaced temperature indicating signals. The alarm system is advantageously connected in circuit with a chart recorder to produce a permanent record of hot boxes.

Claims

1. A system for evaluating a pair of input signals having amplitudes indicative of the temperatures of journals on opposite ends of a railroad car axle and producing an overheated journal alarm therefrom comprising, means for obtaining a signal representing the difference in amplitude between said input signals, a comparator for comparing said difference signal to a reference signal representing a predetermined difference in temperature between said journals and for providing an output alarm signal when said difference signal is greater than said predetermined difference signal, and an output alarm signal cancellation circuit including means for comparing the amplitude of each of said input signals to a first reference signal representing a first predetermined temperature of said journals and for preventing the giving of said output alarm signal from said comparator when the amplitudes of both of said signals exceed said first reference signal.

2. The system as claimed in claim 1 wherein said first reference signal represents a temperature above the range of temperatures in which solid bearings normally operate whereby said output alarm signal is cancelled when both said temperature indicating signals are determined to represent temperatures above those at which solid bearings normally operate.

3. The system as claimed in claim 1 further comprising means for comparing each of said input signals to a second reference signal representing a second predetermined temperature of said journals higher than said first temperature and for providing an output alarm signal when the amplitude of either of said input signals exceeds said second reference signal.

4. The system as claimed in claim 3 wherein said second reference signal represents a temperature above which both roller bearings and solid bearings are considered to be overheated.

5. The system as claimed in claim 1 wherein said output alarm signal cancellation circuit comprises first and second comparators for comparing said input signals to said first reference signal, gate means connected to the outputs of said first and second comparators for producing a cancellation signal when both said input signals exceed said first reference signal, and means for utilizing said cancellation signal to cancel said output alarm signal.

6. The system as claimed in claim 5 wherein said means for utilizing said cancellation signal to cancel said output alarm signal includes means for combining said cancellation signal with said predetermined difference signal to render said predetermined difference signal larger than said difference signal, whereby said output alarm signal is cancelled.

7. The system as claimed in claim 1 further comprising a graphic recorder that receives and records said input signals, and means for conveying said output alarm signal to said recorder to provide an event mark thereon indicating input signals that represent an overheated journal.

8. The system as claimed in claim 1 including audio alarm means activated by said output alarm signal.

9. The system As claimed in claim 1 further comprising circuit means responsive to the time duration of said difference signal for cancelling said output alarm signal when it was produced by a noise pulse or by time displacement between said input signals.

10. The system as claimed in claim 9 wherein said circuit means includes a circuit for comparing the duration of said difference signal to a time interval representing the maximum time displacement that is likely to occur between said input signals and for preventing the giving of said output alarm signal unless the duration of said difference signal is greater than said time interval.

11. An alarm system for receiving input signals from a hot box detector system and producing temporary and permanent indications of overheated journals therefrom, said signals including a pair having amplitudes indicative of the temperatures of journals on opposite ends of a railroad car axle and a signal indicating the presence of journals to be monitored comprising, means for obtaining a signal representing the difference in amplitude between said pair of input signals, a comparator for comparing said difference signal to a reference signal representing a predetermined difference in temperature between said journals and for providing an output alarm signal when said difference signal is greater than said predetermined difference signal, an output alarm signal cancellation circuit including means for comparing the amplitude of each of said pair of input signals to a first reference signal representing a first predetermined temperature of said journals and for cancelling said output alarm signal from said comparator when the amplitude of each of said pair of input signals exceeds said first reference signal, means for comparing each of said pair of input signals to a second reference signal greater than said first reference signal and for producing an output alarm signal when the amplitude of either of said pair of input signals exceeds said second reference signal, a graphic recorder for receiving and recording said pair of input signals, and means for conveying said output alarm signal to said recorder to provide an event mark thereon indicating a pair of signals that represent an overheated journal.

12. The system as claimed in claim 11 wherein said recorder is a chart recorder and drive for said chart is initiated by said signal indicating the presence of journals to be monitored, and further comprising switch means responsive to the initiation of chart drive of said recorder for providing a signal to enable said output alarm signal to be conveyed to said chart recorder to provide an event mark thereon.

13. The system as claimed in claim 12 further comprising delay circuit means for delaying said enabling signal to prevent noise signals generated by the start of chart movement from producing a false output alarm signal.

14. A method for detecting and indicating overheated journals on the axles of railroad cars without giving false indications thereof comprising the steps of, obtaining the temperatures of the journals on the two ends of an axle, obtaining a quantity indicative of the difference between the temperatures, comparing the difference with a predetermined difference to provide an output alarm indication when the magnitude of said difference exceeds said predetermined difference, and comparing each of said temperatures to a first predetermined reference to prevent the giving of said output alarm indication when both said temperatures exceed the first predetermined reference.

15. The method as claimed in claim 14 including the step of comparing each of said temperatures to a second predetermined reference larger than said first predetermined reference to provide an output alarm indication when either of said temperatures exceeds the second predetermined reference, regardless of whether said temperatures exceed said first predetermined reference.

16. The method as claimed in claim 14 wherein said temperatures are obtained in the foRm of electrical temperature indicating signals and further comprising the steps of checking the duration of the difference indicating signal and preventing the giving of an output alarm indication unless the duration of the difference indicating signal is greater than a predetermined duration representing the maximum time displacement that is likely to occur between the temperature indicating signals.

17. A system for evaluating a pair of input signals having amplitudes indicative of the temperatures of journals on opposite sides of a railroad car axle and producing an overheated journal alarm therefrom comprising means for obtaining a signal representing the difference in amplitude between said input signals, a comparator for comparing said difference signal to a signal representing a predetermined difference in temperature between said journals and for producing an output alarm signal when said difference signal is greater than said predetermined difference signal, an output alarm signal cancellation circuit for comparing the amplitude of each of said input signals to a first reference signal representing a first predetermined temperature of said journals and for preventing the giving of an output alarm signal from said comparator when the amplitudes of both of said input signals exceeds said first reference signal, means for comparing the amplitude of each of said input signals to a second reference signal representing a second predetermined temperature greater than said first predetermined temperature and for providing an output alarm signal when either of said input signals exceeds said second reference signal, and means for comparing the duration of said output alarm signal to a predetermined time interval at least as great as the maximum time displacement that is likely to occur between said input signals and for preventing the giving of said output alarm signal unless the duration of said output alarm signal exceeds said time interval.

18. The system as claimed in claim 17 further comprising a graphic recorder that receives and records said input signals, and means for conveying said output alarm signal to said recorder to provide an event mark thereon indicating input signals that represent an overheated journal.

19. A method for detecting and indicating overheated journal on the axles of a railroad car without giving false indications thereof comprising the steps of obtaining electrical pulses having amplitudes indicative of the temperatures of the journals on the two ends of an axle, comparing the temperature pulses to obtain a pulse indicating the difference between said temperatures, comparing the difference pulse with a predetermined difference signal to provide an output alarm indication when said difference pulse exceeds said predetermined difference signal, comparing each of said temperature indicating pulses to a first predetermined reference signal to produce an indicating signal when both said temperature indicating pulses exceed said first predetermined reference signal, utilizing said indicating signal to prevent the giving of an output alarm indication, comparing each of said temperature indicating pulses to a second predetermined reference signal larger than said first predetermined reference signal to provide an output alarm indication regardless of the production of said indicating signal when either of said temperature indicating pulses exceeds the second predetermined reference signal, checking the duration of said difference indicating pulse, and preventing the giving of an output alarm indication unless the duration of said difference indication pulse is greater than a predetermined duration representing the maximum time displacement that is likely to occur between said temperature indicating pulses.

20. The method as claimed in claim 19 including the steps of recording said temperature indicating pulses and utilizing said output alarm indication to record an event mark indicating that said temperature indicAting pulses represent an overheated journal.

21. A system for evaluating a pair of input signals having amplitudes indicative of the temperatures of a journal of a railroad car axle and of a reference object and producing an overheated journal alarm therefrom comprising means for obtaining a signal representing the difference in amplitude between said input signals, a comparator for comparing said difference signal to a reference signal representing a predetermined difference in temperature between said journal and said reference object and for providing an output alarm signal when said difference signal is greater than said predetermined difference signal, and a pulse width discriminator for checking the duration of said difference signal and for preventing the giving of an alarm signal unless the duration of said difference signal is greater than the maximum time displacement that is likely to occur between said input signals, said pulse width discriminator including a relaxation oscillator having a period between pulses at least as great as the maximum time displacement that is likely to occur between said input signals, and switch means maintaining said oscillator normally inoperative, said switch means allowing said oscillator to operate for the duration of said difference signal whereby an output alarm signal is produced or not by said oscillator according to whether the duration of said difference signal is greater or less than the period between pulses of said oscillator.

22. A system for evaluating a pair of input signals having amplitudes indicative of the temperatures of the journal of the railroad car axle and of a reference object and producing an overheated journal alarm therefrom comprising means for obtaining a signal representing the difference in amplitude between said input signals, a comparator for comparing said difference signal to a reference signal representing a predetermined difference in temperature between said journal and said reference object and for providing an output alarm signal when said difference signal is greater than said predetermined difference signal, RC circuit means for providing a delay interval at least as great as the maximum time displacement that is likely to occur between said input signals, and means for comparing said delay interval to the duration of said difference signal and for preventing the giving of an alarm signal unless the duration of said difference signal is greater than said delay interval.