TEMPERATURE INDICATOR FOR AIRCRAFT BRAKES AND THE LIKE

• US 3,582,926 A
• Filed: 04/08/1968
• Issued: 06/01/1971
• Est. Priority Date: 04/08/1968
• Status: Expired due to Term

• Current Assignee: Mohammed A. Hassan
• Original Assignee: Mohammed A. Hassan
• Inventors: Hassan, Mohammed A.
• Application Number:
  US04/719,491
• Time in Patent Office: 1,149 Days
• US Class Current: 340/449
• CPC Class Codes: F16D 2066/001 Temperature
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/021 Particular circuit arrangements G01K7/026, G01K7/12, G01K7/14 take precedence

Abstract

A temperature indicating and warning system utilizing thermocouple heat sensors connected through cabling to individual amplifying and readout facilities at a remote location and equipped with means for compensating for changes in the ambient temperature at the cold junction reference for the several heat sensors. In a typical application the heat sensors are used to sense temperature conditions at each braked wheel of aircraft landing gear and connected to readout facilities in the pilot'"'"''"'"'s compartment. These facilities include means providing distinctive signals when the temperature at any braked wheel exceeds different selected levels and includes simple manually operated means enabling a crew member to determine which one or ones of the wheels are affected. The system also includes means for checking it for operativeness prior to use.

Claims

1. A temperature indicating system adapted to indicate increase in temperature above first and second temperature levels sensed at a plurality of spaced apart temperatures sensor locations, said system comprising:

power supply means;

a plurality of temperature sensor means including junction thermocouple means arranged to sense temperature at a respective one of said spaced apart locations and each having a sensing junction and a reference junction which reference junctions are located at a common station remote from the respective sensing junctions and subject to the same temperature conditions;

operational amplifier means connected to said power supply means and to each of said thermocouple means and having respective feedback circuit means including temperature-sensitive resistive means effective to compensate for changes in ambient temperature at said common station for said reference junctions of said thermocouple means; and

first and second potential-sensitive circuit means connected to the output of said amplifier means and to said power supply means and each comprising a respective indicator means and each rendered active incident to sensing of a respective one of said first and second temperatures at said thermocouple means thereby to provide respective indications of attainment of said first and second temperature levels at said thermocouple means.

2. A temperature indicating system as defined in claIm 1 characterized in that said operational amplifier means has a pair of signal input terminals bridged by said thermocouple means and operable to amplify potential changes generated by said thermocouple means.

3. A temperature indicating system as defined in claim 2 characterized in the provision of test circuit means for checking said temperature indicating system for operability prior to use including means connecting the test circuit means to said power supply means and to said temperature indicating system, said test circuit means being effective to provide positive indication of a nonfunctioning condition in said temperature indicating system.

4. A temperature indicating system as defined in claim 1 characterized in the provision of a plurality of sets of thermocouple means and associated operational amplifier means connected in parallel between said power supply means and said temperature indicator means, and said temperature indicator means being operable to indicate the attainment of said first and second temperatures by any one of said thermocouple means.

5. A temperature indicating system as defined in claim 4 characterized in the provision of multiple position selector switch means for operably connecting the outputs of each of said operational amplifiers individually to said indicator means and alternatively collectively connecting all of the outputs of said amplifier means to said indicator means via respective diode means.

6. A temperature indicating system as defined in claim 5 characterized in the provision of test circuit means for said temperature indicating system, said test circuit means comprising an amplifier connected to receive constant operating potential bias from said power supply means, said bias being of value less than the normal output potential of either of said operational amplifier means, and means for connecting said amplifier to any of said operational amplifier means to receive the output thereof whereby such output overcomes said constant operating potential bias and biases said amplifier to nonconductive state, and a signal device in said test circuit connected to said amplifier to operate in response to conduction by said amplifier, whereby said signal device is inoperative when connected to any of said operational amplifier means having a normal output potential value and whereby said signal device is operative to furnish a signal when connected to any of said operational amplifier means having an output potential value less than normal.

7. A temperature indicating system as defined in claim 4 characterized in that the operational amplifier means and the feedback circuit means therefor are grouped together at a location remote from all of said thermocouple means, and means at said grouped amplifier means for compensating for changes in ambient temperature.

8. A temperature indicating system adapted for use with the braking components of the individually braked wheels of an aircraft and operable to provide a crew member with notice if the temperature of any braked wheel rises above a selected temperature, said indicating system comprising, in combination with the respective aircraft wheel brake means, thermocouple heat-sensing means located at each braked wheel, means operatively connecting the cold junctions of each thermocouple means with respective operational amplifier means for each heat-sensing means located together at a common point remote from the individual heat-sensing means and including means for compensating for changes in ambient temperature at the cold junction terminals of said thermocouple means, and indicator means responsive to the output signal of any amplifier means in excess of different selected magnitudes each representative of a known temperature level condition at the hot junction of one or more of said heat-sensing means.

9. A temperature indicating system as defined in claim 8 characterized in the provision of selector means operable to connect the output of any individual one Of said amplifier means to said indicator means whereby the temperature condition of any braked wheel can be checked at the operator'"'"''"'"'s option.

10. A temperature indicating system as defined in claim 8 characterized in that said thermocouple heat-sensing means is encapsulated in a protective housing with the hot junction thereof in good heat transfer with the brake component the temperature of which is to be monitored.

11. A temperature indicating system as defined in claim 10 characterized in the provision of means interconnecting said amplifier means and said selector means and selectively operable in one position of said selector means to pass an output signal from any amplifier means to said indicator means and operable in other positions thereof to pass the output signal from only a selected one of said amplifier means to said indicator means.

12. A temperature indicating system as defined in claim 11 characterized in that said indicating means includes respective indicator means operable to indicate the attainment of each of a plurality of selected temperature levels.

13. A temperature indicating system as defined in claim 12 characterized in that as many of said indicator means are simultaneously activated as are included within the temperature range up to the highest temperature then being displayed on said indicator means.

14. A temperature indicating system as defined in claim 8 characterized in the provision of separate indicator means responsive to attainment of a different temperature level by said thermocouple heat sensor means.

15. A temperature indicating system as defined in claim 14 characterized in the provision of a respective indicator means for each temperature level to be monitored, and selector means operable in one position to connect all of said amplifier means to each of said indicator means and selectively operable to connect any selected one only of said amplifier means to all of said indicator means. 16, A temperature sensing system adapted to indicate a change in temperature from a particular temperature level of any of a plurality of aircraft wheel brake means, said device comprising:

a plurality of sensor means each including thermocouple means having a respective sensing junction arranged to sense a change in temperature and a respective reference junction, all of said reference junctions being at a common location remote from any of said sensing junctions; and

a plurality of operational amplifiers each connected to a respective one of said reference junctions and each of said amplifiers having operatively connected thereto a respective temperature-sensitive means effective to compensate for changes in ambient temperature at the respective reference junction of the respective one of said thermocouple means, whereby each of said amplifier means provides an output signal having a value proportional to the potential change produced at the respective sensor means irrespective of ambient temperature change at said common location.

17. A temperature-sensing and alarm system for a vehicle having a number N of independently braked wheels each having a respective brake device, said system being adapted to sense the temperature at each of the brake devices independently and continuously and to provide a first alarm signal incident to sensing a temperature of a first predetermined value at any of said devices and to provide a second alarm signal incident to sensing a temperature of a second predetermined value at any of said devices, said system comprising:

first means, including N electrical temperature-sensing means, each disposed at a respective brake device to sense the temperature thereat, and electric signal lead means each leading from a respective temperature-sensing means and extending to a common location;

second means, including at said common location a set of signal amplifier units N in number, each connected to a respective one of said signal lead means to receive signals therefrom, and each having a signal output line;

third means, including unidirectional electric signal transmitting means, each connected in a respective one of said output signal lines and to a common junction; and

fourth means, including first and second electrical alarm signal means, each connected to said common junction and each responsive only to a respective output signal level equal to or in excess of a level representative of a respective one of said first and second predetermined temperature values.

18. A temperature-sensing and alarm system according to claim 17, including, switch means having N+1 switching contacts, N contacts of which are directly connected to respective ones of said output signal lines, and connections between said switch means and said first and second alarm signal means to permit selection of the output signal on any one of said output signal lines for transmission to said alarm signal means, thereby to permit determination of the individual location of any of said temperature-sensing means which initiates a signal to which said fourth means is responsive.

19. A temperature-sensing and alarm system according to claim 17, in which said amplifier units each comprise operational amplifier means and means compensating said operational amplifier means for changes in the ambient temperature thereat.

20. A temperature-sensing and alarm system according to claim 17, in which each of said temperature-sensing means is a thermocouple means, and in which each of said signal lead means is of electrical resistance greatly in excess of the resistance of the respective thermocouple means, thereby to minimize effects of change of the difference in the ambient temperature at said common location and the ambient temperature at the thermocouple means.

21. A temperature-sensing and alarm system according to claim 17, including means for detecting failure of a signal on either of said output signal lines to attain a value indicative of effective functional operation of the respective amplifier means.