US3064245A - Heat detection device - Google Patents

Description

Nov. 13, 1962 y J. E. LINDBERG, JR 3,064,245

HEAT DETECTION DEVICE original Filed May 25, 1959 vv lll] F162 E I MGE 1:16.!

' ./aH/v E LINDBERG, JR. BY Z Z ATIY "ilnited tates Patent 3,004,245 Patented Nov. 13, 1952 hee 3,064,245 HEAT DETECN DEX/TCE John E. Lindberg, Latini/ette, Calif. (102.4 Addrienne Drive, Alamo, Caii.) l @riginal application May 25, 1959, Ser. No. 815,406. Divided and this applicaties; Jan. 18, 1961, Ser. No. 83,399

Claims. (Cl. 340-227) This invention relates to heat detection devices. This application is a division of application Serial No. 815,406 tiled May @25, 1959.

An important object of the invention is to measure a plurality of dilerent temperatures with a single detecting instrument.

Another object is to provide a flashing-lamp type of temperature indicator.

Another object is to provide a single device that can indicate two diierent average temperatures.

Another object is to provide a single circuit for a plurality of such detecting devices.

Other objects and advantages of the invention will appear from the following description of some embodiments thereof.

In the drawings:

FIG. 1 is a view in elevation and in section of a device embodying one form of the invention and connected to a circuit, shown diagrammatically. The sensor is broken in the middle to conserve space.

FIG. 2 is a similar View of a modified form of the invention.

FIG. 3 is a similar view of a plurality of the devices of FIG. 2 joined in a single circuit.

(l) Indication of Two Different Average Temperatures by a Single-Blister Type of Responder, and a Single Gas-Filled Sensor (FIG. 1)

Indication of two different temperatures can be obtained from a single-blister responder 400 (a type of gas pressure-actuated switch fully described in the parent application) and an associated alarm circuit. A sensor tube 401 is sealed gas-tight at the end 401e away from the responder 400 with a gas 402 inside. Preferably a gas 402 which does not react chemically with the tube 401 is used; e.g., one or more of the noble gases such as argon or neon.

The responder 400 has two metal housing plates 403 and 404 land a metal diaphragm 405 sealed to the plates 403 and 404 except for a single blister 406, an integral metal portion formed to a generally spherical segment. The -blister 406 divides a sensor chamber 407 from an anti-sensor chamber 408. A ceramic or other electrically nsulating non-porous tube 410 connected to the anti-sensor chamber 40S is lled with a solid which liberates gas when heated and takes it back up when cooled. This material 411, for example, may be fully ingassed calcium hydride or other hydride of an alkaline or alkaline earth metal or of any other metal of the type that liberates hydrogen when heated, as mentioned in the parent application. In the material 411 (preferably pretreated as described in a co-pending application Serial No. 65,891 filed October 31, 1960) is embedded a iilament 412, at one end of which is an electrode 413 extending into the chamber 40S below the tube 410. A lead 414 from the ilament 412 goes through the top of a sealing cap 415 and goes directly to an alarm circuit comprising a lamp 416 and a current source 417. The electrode 413 may be annular and may be specially designed to retain the hydride 411 within the ceramic tube 410 while yet 4allowing gas released from the hydride 411 to pass into the anti-sensor chamber 40S.

Thus, the sensor chamber 407 and the inside of the sensor tube 401 enjoy a common gas-lled atmosphere to the exclusion of any other, while the anti-sensor chamber 40S and the inside of the tube 410 enjoy a separate atmosphere to the exclusion of any other. The gas 402 in the tube 401 expands when the tube 401 is subjected to heat, the pressure within the sensor chamber 407 and the tube 401 corresponding to the average temperature to which the sensor tube 401 is exposed. When the sensor tube 401 is exposed to heat at a sufcient level to deflect the blister 406 against the electrode 413, lthe electrical circuit is closed, and current passes from the current source 417 to the lamp 416 and thence to the filament 412, the electrode 413, and the diaphragm 405, returning to the current source 417 via a ground 418.

The passage of current through the lament 412 heats the hydride 411, and as a consequence hydrogen is liberated. This gas is confined to the region on the antisensor side of the blister 406 and exerts pressure on the blister 406 which soon redelects the blister 406 away from the electrode 413, thereby breaking the electrical circuit and causing the lamp 416 to go out. Then the hydride 411 cools and reabsorbs some or all of the previously released gas, thereby lowering pressure in the anti-sensor chamber 408. If the sensor tube 401 is still exposed to the original source of heat, the pressure in the sensor chamber 407 will then deflect the blister 406 against the electrode 413, completing the circuit again.

Under these conditions, the blister 406 performs cyclically to make and break contact with the electrode 413. This results in the lamp 416 ashing on and oit. This alternating illumination of the lamp 416 indicates that the sensor tube 401 is exposed to an average temperature at or above a certain level.

As the temperature to which the sensor tube 401 is exposed is elevated, the pressure on the sensor chamber 407v becomes increasingly greater, and the eiect on the cycle can be calibrated to indicate temperature. Finally a point is reached at which the pressure in the chamber 407 holds the blister 406 in contact with electrode 413 regardless of the gas-liberating effect of the hydride 411 on the blister 406. Contact between the blister 406 and the electrode 413 will then be maintained until the pressure within the sensor tube 401 is reduced below a certain critical value, due to a drop of the average temperature below a certain critical value. One can select design parameters of the system, i.e., the deilecting force of the blister 406, the amount and type of hydride 411 (or other gas-releasing material of similar characteristics) contained within the tube 410, so as to differentiate between any two temperatures.

'When the pressure in the sensor chamber 407 holds the blister 406 constantly against the electrode 413, the lamp 416 stays lighted. Thus the two types of temperature conditions applied to the sensor 401 are readily distinguished by the alarm circuit C. For -a fire temperature, the lamp 416 is steadily illuminated, while yfor the lower temperature which may represent overheating below lire, lthe lamp 416 flashes on and ot. As a particular example of design, flashing may be obtained at 600 F. and a steady illumination at 1500l F.

(2) Indication of Two Different Average Temperatures by a Single Blister Type of Responder and a Single Sensor Containing a Gas-Lberating Solid (FIG. 2)

FIG. 2 shows a responder 420 like the responder 400 except that a testing device is included, along with an alarm circuit and a sensor that' contains a gas-liberating solid. Thus, a sensor tube 421 contains a solid transducing agent 422 such as a compound like zirconium hydride. This compound retains its gas until heated to or above a certain threshold temperature, at which ternperature release of hydrogen begins. The amount of gas released increases as the temperature is increased above the threshold temperature. The elaborated gas obeys the gas laws, and the pressure etiects are augmented as temperatures are increased by a further release of gas. The quantity of such evolved gas, once the threshold point has been reached, and the resulting pressure, are proportional yto the responsible temperature. phenomenon is useful for discriminatory temperature sensing.

The responder 420 has plates 423, 424, a diaphragm 425 with a blister 426 and a hole 427, a sensor chamber 428, and an anti-sensor chamber 429. An insulating tube 430 is filled with material 431 such as calcium or zirconium hydride. A lilament 432, an electrode 433, and a cap 434 are like the corresponding elements in FIG. l, A circuit lead 435 extends from the filament 432 to a parallel arrangement of a lamp 436 and Variable resistor 437 and from there proceeds to 4a relay 438 and up to a current source 440. A supplementary circuit 441, operated by the relay 433, includes a bell circuit 442 in series' with a battery 443 to ring a bell 444. The responder 420 is grounded at 445.

When the sensor 421 of FIG. 2 is heated to a particular temperature level, for example 600 F., where its outgassing threshold is reached and somewhat exceeded, gas is evolved to exert pressure against the diaphragm blister 426. Suiiicient pressure causes the blister 426 to deiiect and make contact with the electrode 433, closing the electrical circuit C. This lights the lamp 436, energizes the relay 438, and heats the filament 432. Heat pro- This duced by the filament 432 causes the hydride 431 in the tube 430 to liberate gas rapidly, until suicient force is developed to re-defiect the blister 426 back away from the electrode 433, thus opening the power circuit, pultting out the lamp 436, opening the relay 438, and cooling the Ifilament 432. The cooling hydride 431 reingasses, lowering the pressure in the anti-sensor chamber 429. The pressure in the sensor chamber 428 then forces the blister 426 back into contact with the alarm electrode 433. 'Ihe lamp 436 again lights, the filament 432 again heats, and the hydride 431 in the tube 430 again liberates gas, This make-break operation recycles at a rapid rate as long as pressure from the sensor 421 is available and so long as enough pressure can be developed by the hydride 431 to periodically overcome the sensor pressure.

Since the pressures from both the sensor 421 and the tube 430 are a function of their respective temperatures, the cyclic operation of the blister 426 may be made to provide a ashing alarm light 436 when pressures in the sensor chamber 428 are of the order of magnitude produced by non-extreme heating of the sensor 421, or as it is commonly termed in the art, an overheat condition as contrasted with a fire condition. Relative values of heating levels and resultant gas pressure may be selected so that when the sensor 421 is heated to temperatures in excess of the overheat level, for example 1500" F., then gas is evolved at a more rapid rate from the sensor 421 and attains such a high pressure that the pressure derived from the tube 430 as a result of the alarm circuit closure is insuicient to separate the diaphragm blister 426 from the electrode 433. The cyclic operation of the alarm system no longer occurs, and the signal is steady. The user can thus differentiate between an overheat condition and 'a fire in the areas sensed by the sensor.

The circuit of FIG. 2 also provides aural indication of the sensor condition. When current passes through the filament 432, it also passes through the relay 438, and rings the bell. Cyclic operation provides intermittent ringing ofthe bell 444, while re conditions cause a steady ringing of the bell 444.

The variable vresistor 437 in parallel with the lamp 436 regulates the magnitude of current ow to the filament 432 and thereby regulates the pressure that can be achieved'in the anti-sensor chamber 429. This resistor 4 437 makes it possible to vary as one pleases the temperature points causing intermittent operation and steady' operation.

The testing system includes a tube 450 containing a.

quantity of metallic hydride 451 such as titanium hydride, and a filament 452. The filament 452 is connected to ground at the point 445 -and is connected to the power supply 440 via a resistor 453 and a test switch 454, An annular cap 455 at the base of the tube 450 serves to contain the hydride 451 while allowing gas to pass between the tube 450 and the sensor chamber 428 at all times. Closure of the test switch 454 energizes the heater 452, causing elaboration of gas from the hydride 451. Gas pressure from this source then results in actuation of the alarm circuit if everything is satisfactory. It thus simultaneously tests the transducer system for leaks and the alarm system for proper operation.

As an example of magnitude of the circuit components and selected values used in a device in my laboratory, the following data is furnished. The resistance of the iilament 432 was 12 ohms and that of iilament 452 was 7 ohms. Both Ifilaments were constructed of .002" diameter tungsten wire. Both tubes 430 and 45t! contained about 0.2 gram of zirconium hydride. The transducing agent consisted of about 24 feet of 0.010 to 0 .015" diameter zirconium wire provided with a molybdenumribbon wrap constructed as shown in the parent application. The lamp 436 had a D.C. resistance of 13 ohms and was rated at 2%: volts. The resistor 437 was generally set to give a resistance or" approximately l0 ohms with variation above and below that value. The relay 43S had an impedance of about 0.073 ohm, and the current source 440 was direct current at 28 volts.

(3) Use of a Plltralty of the Devices of FIG. 2 (FIG. 3)

A source 460 of alternating current (or a pulsating direct current D.C. source) provides pulsating direct current to the transducers (after passing through a rectifier 461 if A.C. current is used). rlhe warning circuits 462 are in parallel with each other, as are the test filaments 452. A single resistor 463 and a single switch 464 are used lfor the test filaments 452. Since the voltage supplied by the rectifier 461 is fixed, a series of variable resistors 465 are preferably employed to limit the current flow through the filaments 432 to a given maximum value. Continuous indication in the case of re is obtained by proper setting of the variable resistors 465.

FIG. 3 shows a neon warning light 466 in each warning circuit, while ya single bell-circuit 467 is used to indicate fire, or overheat, at any or al1 the sensors 421. A gasfilled lamp, such as each lamp 466, presents a very high impedance until the potential across it is sufiicient to cause a glow discharge to take place in the lamp, at which time its impedance is low. During the time that the blister 426 is in contact withl the electrode 433, a capacitor 475 ldraws a small charging current through a variable resistor 468. When the voltage across the capacitor 475 reaches the ring potential of the lamp 466, the lamp tires and discharges the capacitor 475 with the help of a resistor 469, which has a high resistance. The capacitor 475 is then ready for another cycle of operation. The time constant of the lamp 466 and capacitor 475 circuit is fixed primarily by the values of voltage supplied by the rectifier 461 and the resistance of the resistors 468 and 465 and the capacitance of the capacitor 475. Thus, the resistor 468 varies the interval over which the capacitor 475 reaches sufficient potential to discharge through 4the lamp 466. 'I-f, while a blister 426 iscycling at a given rate, the resistor 468 is adjusted so that the capacitor 475 can reach the proper potential, the lamp will Hash; but if the bleed of this charge by the resistor 469 is too great for the charging forces to overcome, the lamp 466 will not fire. Thus it may be seen that the minimum diaphragm cycling frequency at which the lamp will give indication of an overheat condition is set by ,the variable resistor 46S. Since the cycling frequency is proportional to the transducer temperature, the resistor 468 may be said to adjust the lowest temperature at the sensor A, at which overheat warning will occur.

This gas present freely in the sensor A sets up an ambient pressure. As the sensor environment becomes colder, this pressure would drop below its ambient, and it will become higher if the sensor tube temperature rises. Thus, when used in this manner, the device becomes a gas thermometer, the back pressure used in the diaphragm being proportional to the sensor temperature. Since this back pressure is produced by the current in the larnent 432 resulting in outgassing the surrounding hydride 431, the average current passing through the lament 432 is proportional to the temperature of the sensor A. Therefore, by inserting an ammeter 470 in series with the iilament 432, another visual indication of the average temperature may be obtained, and the ammeter 470 may be calibrated to read this temperature directly.

To those skilled in the art to which this invention relates, many changes in construction and widely diiering embodiments and applications of the invention will suggest themselves Without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. A critical-temperature detection system comprising a sensor tube containing and conlining gas which, when heated, raises the internal pressure of the tube; a diaphragm; a housing divided by said diaphragm into two chambers, namely, a sensor chamber in communication with said tube and its gas and an anti-sensor chamber; a solid material in said anti-sensor chamber of the type that liberates gas when heated and takes up gas when cooled, resulting in pressure changes in said anti-sensor chamber; and an electrical circuit including, in series, an indicator actuated by closure of said circuit, and a switch actuated by said diaphragm, being closed when the sensor chamber pressure exceeds the anti-sensor pressure by a certain amount, thereby closing the circuit, actuating the indicator, and heating said material, which then releases gas in said anti-sensor 4chamber to open said circuit, whereupon said material cools and reduces the pressure in said anti-sensor chamber, said device thus being able to cycle.

2. The system of claim 1 in which said sensor tube also contains solid material of the type that liberates gas when heated and takes up gas when cooled.

3. The system of claim 2 wherein there are: a second tube opening into said sensor chamber and otherwise closed; a gas-releasing transducing agent in said second tube; and electrical heating means for heating siad agent in said second tube and thereby releasing gas therefrom so as to test the action of said system.

4. The system comprising a plurality of units of claim 1 with a single electrical circuit incorporating all said circuits in parallel with each other.

5. The system of claim 4 having a single audible warning device in said last-named circuit, actuated when any of said switches closes.

6. The system of claim l wherein said indicator is a lamp that flashes on and ofi as the circuit cycles.

7. The system of claim 6 wherein said lamp is a gasiilled discharge tube.

8. The system of claim l wherein said indicator is an ammeter calibrated to read in terms of temperature.

9. A critical-temperature detection system comprising a sensor tube containing and conning noble gas which, when heated, raises the internal pressure of the tube; a diaphragm; a housing divided by said diaphragm into two chambers, namely, a sensor chamber in communication with said tube and its gas and an anti-sensor chamber; a solid material in said anti-sensor chamber of the type that gives on? gas when heated and takes up gas when cooled, resulting in pressure changes in said anti-sensor chamber; and an electrical circuit including, in series, an indicator actuated by closure of said circuit; a heater filament embedded in said material, and a switch actuated by said diaphragm, being closed when the sensor chamber pressure exceeds the anti-sensor pressure by a certain amount, thereby closing the circuit, actuating the indicator, and heating said material, which then releases gas in said antisensor chamber to open said circuit, whereupon said material cools and reduces the pressure in said anti-sensor chamber, said device thus being able to cycle.

l0. A critical-temperature detection system comprising a sensor tube containing a solid transducing agent that releases large quantities of gas when heated to critical temperatures and takes it up when cooled; a diaphragm; a housing divided by said diaphragm into two chambers, namely, a sensor chamber in communication with said transducing agent and the gas released therefrom and an anti-sensor chamber; a solid transducing agent in said anti-sensor chamber that releases large quantities of gas when heated; and an electrical circuit including in series indicator means actuated by closure of said circuit, electrical heating means for said agent in said anti-sensor chamber, and a switch closed by said diaphragm when the pressure in said sensor chamber overbalances the pressure in said anti-sensor chamber by a certain amount, closing of said circuit causing said heating means to heat the agent in said anti-sensor chamber and increase the pressure therein so as to tend to open said circuit so that said agent in said anti-sensor chamber acts to decrease the pressure in said anti-sensor chamber, resulting in cycling. f

11. The system of claim 10 wherein there are: a second tube opening into said sensor chamber and otherwise closed; a solid transducing agent of the type in said antisensor chamber in said second tube; and electrical heating means for heating said agent in said second tube and thereby releasing gas therefrom so as to test the action of said system.

12. The system comprising a plurality of units of claim 11 with a single electrical circuit incorporating all said circuits in parallel with each other.

13. The system of claim 11 having a single audible warning device in said last-named circuit, actuated when any of said switches closes.

14. The system of claim l0 wherein said indicator means comprises an ammeter.

l5. The system of claim 10 wherein said indicator `means comprises a dashing lamp.

No references cited. t

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 3,064,245 November 13E 1962 John Ea Lindberg, Jiu1 1t is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belo` .i

Column 3, line 35, for "pultting" read puttingf--g l'ine :for: '"Ehe" read Then column 5, line 38, after clrcnlt," insert electric heating means for heatingi said material,

Signed and sealed this 3rd day of September l93 (SEAL) Attest:

DAVID L. LADD Commissioner of Patents `EIQES'I' W. SWIDER Attesting Officer

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