Assembly for monitoring helmet thermal conditions

• US 5,200,736 A
• Filed: 09/20/1991
• Issued: 04/06/1993
• Est. Priority Date: 11/13/1989
• Status: Expired due to Term

• Current Assignee: Mine Safety Appliances Company (MSA Safety, Inc.)
• Original Assignee: Cairns & Brother, Inc.
• Inventors: Keohane, Gene, Coombs, Christopher E., Gray, Robert E., Armstrong, Robert M.
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US07/763,190
• Time in Patent Office: 564 Days
• Field of Search: 340/586, 340/573, 340/590, 340/691, 2/5, 2/7, 2/8
• US Class Current: 340/586
• CPC Class Codes: A42B 3/046 Means for detecting hazards or accidents
• CPC Class Codes: G01K 3/005 Circuits arrangements for indicating a predetermined temperature fire detection G08B17/00

Abstract

An assembly is disposed on a helmet for monitoring predetermined thresholds of ambient thermal condition of the helmet. Such assembly includes at least one thermistor for sensing the status of an ambient thermal condition and a signal comparator for detecting each predetermined threshold. Individual LED'"'"'s visually indicate when each predetermined threshold is reached, while an audible alarm indicates when a hazardous predetermined threshold is reached. The audible alarm is further utilized to indicate if the battery voltage is under a predetermined threshold which is predicated on the breakdown voltage of a reference diode when a test switch is closed. A temperature responsive switch is also included to conserve the life of the battery by activating and deactivating the assembly about a predetermined temperature level.

Claims

1. A battery operated assembly for monitoring at least one predetermined threshold of a thermal condition within a helmet of a user, comprising:

means disposed in said helmet for sensing said thermal condition;

means disposed in said helmet for detecting when said thermal condition reaches said predetermined threshold; and

means disposed in said helmet in the field of view of said user for visually indicating to said user when said predetermined threshold is reached.

2. The assembly as defined in claim 1 wherein said sensing means includes at least one thermistor from which signals relating to the status of the thermal condition are derived.

3. The assembly as defined in claim 2 wherein the helmet includes an impact protection shell and said thermistors are securable in contact therewith.

4. The assembly as defined in claim 1 wherein said detecting means includes an individual signal comparator for deriving each predetermined threshold, each said comparator generating a high level signal at an output terminal thereof when the voltage level at an input terminal thereof equals or exceeds the voltage level at a threshold set terminal thereof.

5. The assembly as defined in claim 4 wherein said detecting means further includes a voltage divider having the individual nodes thereof respectively connected to the threshold set terminals of said comparators.

6. The assembly as defined in claim 1 wherein said indicating means includes an individual LED for each predetermined threshold, each said LED being securable on the helmet in the field of view therefrom and being illuminated when the threshold to which it relates is reached.

7. The assembly as defined in claim 6 wherein the illumination from each said LED is of a different color.

8. The assembly as defined in claim 1 wherein an audible alarm is actuated within said indicating means when the thermal condition reaches a critical predetermined threshold.

9. The assembly as defined in claim 8 wherein said audible alarm is actuated intermittently through a relaxation oscillator when an alarm trigger signal is applied to the output of an operational amplifier therein, said operational amplifier having separate feedback resistors connected from its output to its inverting and non-inverting inputs, with its inverting input being grounded through a capacitor, while the battery voltage is applied to its output through a resistor and to its non-inverting input through a voltage divider.

10. The assembly as defined in claim 9 wherein said detecting means includes a comparator for generating said alarm trigger signal at its output terminal, said comparator having a voltage level representation of the thermal condition applied to its input terminal from said sensing means and a voltage level representation of the critical predetermined threshold applied to its threshold set terminal.

11. The assembly as defined in claim 1 wherein an audible alarm indicates when the battery voltage is under a predetermined threshold.

12. The assembly as defined in claim 11 wherein said audible alarm is actuated intermittently through a relaxation oscillator when a battery alarm signal is applied to the output of an operational amplifier therein, said operational amplifier having separate feedback resistors connected from its output to its inverting and non-inverting inputs, with its inverting input being grounded through a capacitor, while the battery voltage is applied to its output through a resistor and to its non-inverting input through a voltage divider.

13. The assembly as defined in claim 12 wherein said detecting means includes a first comparator for generating said battery alarm signal at its output terminal, said first comparator having the battery voltage applied directly to its input terminal and the output terminal of a second comparator connected to its threshold set terminal, the battery voltage threshold being predetermined by said second comparator in accordance with the breakdown voltage of a reference diode.

14. The assembly as defined in claim 13 wherein the battery voltage is applied through a double pole, double throw test switch which closes to generally apply such voltage to said assembly through one pole thereof and also to apply said voltage directly to the input terminal of said first comparator through the other pole thereof.

15. The assembly as defined in claim 13 wherein the battery voltage is further applied to backbias said reference diode through a current limiting resistor and also across a voltage divider having a node at which the voltage level is maintained in direct proportion to the battery voltage, said reference diode having its breakdown voltage applied to the threshold set terminal of said second comparator and said node being connected to the input terminal of said second comparator.

16. The assembly as defined in claim 1 wherein the battery is connected through a single pole, single throw, temperature responsive switch which activates said assembly when the temperature thereof rises above a predetermined level and deactivates said assembly when the temperature thereof falls below that predetermined level.

29. The assembly as defined in claim 1 wherein said assembly is for monitoring a plurality of predetermined thresholds each of a respective thermal condition within said helmet of said user, wherein said sensing means is for sensing each of said respective thermal conditions, wherein said detecting means is for detecting when each of said thermal conditions reaches one of said predetermined thresholds, and wherein said indicating means is for visually indicating to said user when each of said predetermined thresholds is reached.

17. In a helmet of the type for use in activity during which a hazardous thermal condition may be encountered therein, the improvement comprising:

at least one thermistor for sensing the status of the thermal condition;

at least one signal comparator for detecting when the status of the thermal condition reaches a predetermined threshold, each said comparator generating a high level voltage at an output terminal thereof when the voltage level at an input terminal thereof exceeds the voltage level at a threshold set terminal thereof;

a voltage divider having the individual nodes thereof respectively connected to the threshold set terminals of said comparators; and

an individual LED for each predetermined threshold, each said LED being disposed on said helmet in the field of view therefrom and being illuminated when the threshold to which it relates is reached.

18. The helmet as defined in claim 17 having an impact protection shell included therein and said thermistors secured in contact with said shell.

19. The helmet as defined in claim 17 wherein the illumination from each said LED is of a different color.

20. The helmet as defined in claim 17 wherein an audible alarm is actuated when the thermal condition reaches a critical predetermined threshold.

21. The helmet as defined in claim 20 wherein said audible alarm is actuated intermittently through a relaxation oscillator when an alarm trigger signal is applied to the output of an operational amplifier therein, said operational amplifier having separate feedback resistors connected from its output to its inverting and non-inverting inputs, with its inverting input being grounded through a capacitor, while a battery voltage is applied to its output through a resistor and to its non-inverting input through a voltage divider.

22. The helmet as defined in claim 21 wherein one of said signal comparators generates said alarm trigger signal at its output terminal, said one comparator having a voltage level representation of the thermal condition applied to its input terminal from said thermistors and a voltage level representation of the critical predetermined threshold applied to its threshold set terminal from one node of said divider.

23. The helmet as defined in claim 17 wherein said helmet further comprises a battery and an audible alarm which indicates when the voltage of said battery is under a predetermined threshold.

24. The helmet as defined in claim 23 wherein said audible alarm is actuated intermittently through a relaxation oscillator when a battery alarm signal is applied to the output of an operational amplifier therein, said operational amplifier having separate feedback resistors connected from its output to its inverting and non-inverting inputs, with its inverting input being grounded through a capacitor, while the battery voltage is applied to its output through a resistor and to its non-inverting input through a voltage divider.

25. The helmet as defined in claim 24 wherein a first of said signal comparators generates said battery alarm signal at its output terminal, said first comparator having the battery voltage applied directly to its input terminal and the output terminal of a second of said comparators connected to its threshold set terminal, the battery voltage threshold being predetermined by said second comparator in accordance with the breakdown voltage of a reference diode.

26. The helmet as defined in claim 25 wherein the battery voltage is applied through a double pole, double throw test switch which closes generally to apply such voltage to the circuitry through one pole thereof and also to apply such voltage directly to the input of said first comparator through the other pole thereof.

27. The helmet as defined in claim 25 wherein the battery voltage is further applied to backbias said reference diode through a current limiting resistor and also across a voltage divider having a node at which the voltage level is maintained in direct proportion to the battery voltage, said reference diode having its breakdown voltage applied to the threshold set terminal of said second comparator and said node being connected to the input terminal of said second comparator.

28. The helmet as defined in claim 17 wherein said helmet further comprises a battery and wherein said battery is connected through a single pole, single throw, temperature responsive switch which activates the circuitry when the temperature thereof rises to a predetermined level and deactivates the circuitry when the temperature thereof falls below that predetermined level.

30. A battery operated assembly for monitoring a plurality of predetermined thresholds each related to a different thermal condition within a helmet of a user, comprising:

sensing means disposed in said helmet for sensing the presence of each of said thermal conditions;

detecting means disposed in said helmet for detecting when each of said thermal conditions reaches one of said predetermined thresholds; and

indicating means disposed on said helmet for indicating to said user when each of said predetermined thresholds is reached.

31. A battery operated assembly for monitoring at least one predetermined threshold of an ambient thermal condition of a helmet of a user, comprising:

sensing means disposed immediately adjacent said helmet for sensing said thermal condition;

detecting means disposed on said helmet for detecting when said thermal condition reaches said predetermined threshold; and

indicating means disposed on said helmet in the field of view of said user for visually indicating to said user when said predetermined threshold is reached.

32. The assembly as defined in claim 31 wherein said helmet has an interior and wherein said sensing means are disposed in said interior of said helmet.

33. The assembly as defined in claim 31 wherein said helmet has an exterior surface and wherein said sensing means are disposed immediately adjacent said exterior surface of said helmet.

34. The assembly as defined in claim 31 wherein said helmet includes a top front portion, wherein a face shield having a top portion is mounted pivotally to said top front portion of said helmet, and wherein said sensing means are disposed on said top portion of said face shield.

35. The assembly as defined in claim 31 wherein said sensing means comprise a thermal sensor which in its normal condition for sensing said thermal condition provides a continuous electrical circuit condition therethrough and which thermal sensor upon being in an abnormal condition is unable to sense said thermal condition and provides an open electrical circuit condition therethrough, and wherein said assembly further includes thermal sensor monitoring means for monitoring the electrical circuit condition of said thermal sensor and for providing an indication to said user upon the presence of said open electrical circuit condition through said thermal sensor.