US2978582A - Smoke detector - Google Patents

Description

April 4, 1961 A. SCHOEPE ET AL SMOKE DETECTOR 2 Sheets-Sheet 1 Filed Aug. 16, 1957 E v s T R Y mm m z. a G N O E P F W 0 LM 1 2 mm" M AA April 4, 1961 A. SCHOEPE ET AL SMOKE DETECTOR 2 Sheets-Sheet 2 Filed Aug. 16, 1957 ADOLF SCHOEPE ADAM OGI NT INVENTORS BY I'm M QJ 1:

ArTaPA/H Unite States Patent SMOKE DETECTOR Filed Aug. 16, 1957, Ser. No. 678,627

7 Claims. (Cl. 250-435) This invention relates to a smoke detector and, more particularly, to a smoke detector adapted to be utilized in various types of buildings in detecting smoke prior to the commencement of a full-scale confiagration.

There are, at present, on the market various types of devices which are sensitive to the increase in temperature incidental to a full-scale conflagration in the vicinity and there are also devices which will function when a relatively large amount of smoke is present. The latter devices for detecting smoke are generally photo-electric in character and require a relatively large quantity of dense smoke to cause the energization of the same.

It is, therefore, an object of our invention to provide a smoke detector which is extremely sensitive and which is capable of response to relatively small quantities of smoke, thus permitting the energization of the smoke detector and the detection of smoldering fires prior to the initiation of a full-scale conflagration.

A further object of our invention is the provision of a smoke detector which includes first and second detecting means, one of which is more sensitive to ultraviolet radiation than its associated detecting means, said smoke detecting means being juxtaposed to a source of ultraviolet ray radiation and being incorporated inan electrical circuit having a signal emitting means therein whereby when the smoke detecting means are subjected to the passage of smoke through the field thereof, the circuit and the signal constituting a part thereof are energized to give a warning of smoke conditions in the vicinity of the smoke detector of our invention.

A further object of our invention is the provision of a smoke detecting device of the aforementioned character wherein the more sensitive of the smoke detecting means is constituted by a metal such as selenium, cesiumoxide, tantalum, zinc, or the like which, when exposed to ultraviolet radiation becomes electronegative and which normally retains said electronegative charge as long as its exposure to a source of ultraviolet radiation with which it is associated 'in the smoke detector of our invention is not interfered with.

However, we have discovered that when a smoke detecting means of the electronegative character described immediately hereinabove is associated with a nonsensitive detecting means or one of less sensitivity, the exposure of the more sensitive detecting means to smoke particles will lessen the electronegative character of the sensitive electronegative detecting means and cause the energization of a circuit associated therewith to create a signal or to actuate a warning device associated with the smoke detector of our invention.

Other objects and advantages of our invention will be apparent from the following specification and the accompanying drawings which are for the purpose of illustration only and in which:

Fig. 1 is a partially sectional view of a smoke detector fabricated in accordance with the teachings of our invention;

Patented Apr. 4, 1961 Fig. 2 is a transverse, sectional view taken on the broken line 22 of Fig. 1;

Fig. 3 is a vertical, sectional view taken on the broken line 3-3 of Fig. 2;

Fig. .4 is a schematic electrical circuit showing the various components thereof incorporated in the smoke detector of our invention; and

Fig. 5 is an enlarged schematic view showing the electrical relationship between the first and second detectors of our invention.

Referring to the drawings and particularly to Figs. l-3 thereof, we show a smoke detector 10 constructed in accordance with the teachings of our invention and including a housing 12 which includes oppositely disposed, spaced end plates 14 of substantially cylindrical coufiguration.

The end plates 14, as best shown in Fig. 3 of the drawings, include axially extending cylindrical mounting flanges 16 formed from insulating material and provided with a plurality of mounting slots 18, for a purpose which will be described in greater detail below. The end plates 14 are retained in operative and spaced relationship with each other by tie bolts 20 having nuts 22 secured to the outer extremities thereof, as best shown in Fig. 3 of the drawings. Electrical receptors or sockets 24 are mounted centrally of the end plates 14 and are adapted to receive argon glow lamps 26 which are connected by leads 28 to a suitable source of electrical energy.

Mounted between the end plates 14 and supported in the slots 18 provided in the cylindrical flanges 16 thereof are individual smoke detectors constituted, respectively, by internested, substantially V- shaped plates 30 and 32 and individual rectangular plates 34 mounted between opposed legs of the V.-shaped plates 30. The oppositely disposed legs of the V-shaped plates 30 provide first detector elements 36 while the second detector elements 38 are constituted by the rectangular plates 34. The oppositely disposed legsof the V-shaped' plates 32 constitute third detector elements 40.

In the present embodiment of our invention the first detector plates are formed from zinc, selenium, cesium oxide, tantalum, or other metal or metal oxide which, When exposed to'ultraviolet radiation, acquires an electronegative charge. Since the flanges 16 on the end plates 14 are formed from insulating material, the first detector elements constituted by oppositely disposed legs of the V-shaped plates 30 are insulated to isolate said first detector elements 36 from ground.

The rectangular plates 34 constituting the second detector elements are preferably formed from a material which is completely insensitive to ultraviolet radiation or which is less sensitive to such ultraviolet radiation than the first detector elements 36 so that when the first and second detector elements 36 and 38 are associated in an electronic circuit, to be described hereinbelow, an ionization effect can be created by the passage of smoke into the field thereof to cause the energization of said circuit and the operation of an alarm signal or other device.

The second detector element 38 constituted by the rectangular plate 34 can be fabricated from copper, carbon, or similar materials which are quite insensitive to the operation of the ultraviolet ray radiation emanating from the argon lamps 26 and which are electropositive in contradistinction to the electronegative first detector elements 36 constituted by the oppositely disposedlegs of the V-shaped plates 30.

The V-shaped plates 32 are also formed from the same material as the V-shaped plates 30 and thus, when the plates 30 are formed from copper, the plates 32 will be formed from the same material.

While we have disclosed the various mechanical and electro-mechanical elements of the smoke detector of our invention as formed in predetermined shapes and arranged in predetermined operative and mechanical com binations, as illustrated in Figs. 1-3 of the drawings, it is, of course, conceivable that variations in the operative relationship between the component parts such as the argon lamps 26 and the first, second, and third detector elements may be made. However, by the provision of a mechanical construction of the character previously disclosed, the infiltration of smoke between the first, second, and third detector elements 36, 38, and 40, respectively, is facilitated so that the operation of the smoke detector 10 of our invention is both extremely precise and sensitive.

There is shown in Fig. 4 of the drawings an electrical circuit 50, the input leads 52 and 54 of which are connected to a simple source of 60 cycle, 115 volt, alternating current. A lead 56 is connected between the input lead 54 and a rectifier 58 whose output of pulsating D.C. voltage is applied to the anode 60 of a thyratron tube 62. Connected across the anode 60 of the thyratron tube 62 i a capacitor 64 which is connected to the output of the rectifier 58. A limiting capacitor 66 is disposed in parallel relationship with the capacitor 64.

The first detector element 36 is connected through a resistance 70 to the grid 72 of the thyratron tube 62 and is exposed to the ultraviolet ray radiation from the argon gas glow lamp 26. Incidentally, the glow lamp 26 utilized is an AR3 glow lamp manufactured by General Electric and operating in the approximate range of 2800 to 2900 Angstrom units.

Since the first detector element is fabricated from a metal which is rendered electronegative by the action of the ultraviolet ray radiation, the grid 72 of the thyratron tube 62 and the first detector element 36 are floating from a potential standpoint.

The second detector element 38 is connected through a resistance 74 to the pulsating DC. voltage from the rectifier 58 and is thus maintained at the same potential as the anode 60 of the thyratron tube 62. The third detector element 40 is connected through a resistance 76 to the lead 54 and is thus supplied with AC. potential.

A relay 80 is connected to the output of the thyratron tube 62 and when energized by the thyratron tube 62 causes simultaneous energization of a holding relay 82 whose output 84 is connected to a suitable alarm or other device intended to give notice of the existence of smoke conditions and the possible existence of a confiagration constituting the source of the same.

The maintenance of the grid 72 of the thyratron tube at floating potential to maintain the thyratron tube 62 at cut-off depends on several factors, among them being the distance between the ultraviolet radiation source 26 and the total energy of its saturation constant; the distance between the first and second detector elements 36 and 38; the resistance in ohms of the resistor 70; the capacitance on the capacitor 64 and the condition of the air between the detector elements 36, 38, and 40.

When the proper relationship between these elements is accomplished by the methods well-known to those skilled in the art, the grid 72 will be maintained in floating bias and the thyratron tube 62 maintained at cutoff to prevent energization of the relays 80 and 82 and the alarm 84 associated therewith.

However, should smoke infiltrate into the field of the detector elements 36, 38, and 40, the smoke particles will be acted upon by the electrons and positive ions between the detector elements to accomplish ionization of the same. The positive ions are attracted to the previously electronegative first detector element 36 and the electrons are attracted to the second detector element 38. The positive ions attracted to the first detector element 36 alter the electronegative characteristic of said first detector element and raise the potential of the grid 72 of the thyratron tube 62 sufiiciently to cause the thyratron tube 62 to fire so that the relays and 82 are simultaneously energized to introduce a signal to the output 84 of the relay 82.

The thyratron 62, when energized, discharges the capacitor 64 and the thyratron 62 is thus returned to cutolf and will remain at the cut-off until smoke once again enters the field of the first, second, and third detector elements 36, 38, and 40. The capacitor 66 acts as a limiting capacitor to prevent recurrent energization of the thyratron 62 once the relay 84 has been energized in the above described manner.

The manner in which the electronegative plate 36 functions when exposed to ultraviolet radiation is graphically illustrated in Fig. 5 of the drawings. When exposed to ultraviolet radiation, the plate 36 becomes electronegative and the positive ions are attracted to the plate 38. When smoke enters the field between the plates 36 and 38, the plate 36 becomes less electronegative and the grid 72 of the thyratron 62 discharges said thyratron to discharge the capacitor 64.

We thus provide by our invention a smoke detector which is characterized by its extreme sensitivity attributable, in large part, to the utilization of detecting elements having different levels of sensitivity to an ultraviolet radiation source rendering at least one of the elements more electronegative than an associated element, the electronegative element being associated with the grid of a thyratron tube to control the energization of the same and the energization of a warning signal circuit.

We claim:

1. In a smoke detecting device, the combination of: a source of ultraviolet rays; a first detector element exposed to said source and sensitive thereto; a second detector element exposed to said source and insensitive thereto; a normally inoperative circuit connecting said first and second detector elements in operative relationship with each other; and signal emitting means operable by said circuit upon the exposure of said detector elements to smoke.

2. In a smoke detecting device, the combination of: a source of ultraviolet rays; a first detector element exposed to said source and sensitive thereto, said first detector element incorporating selenium as the ultraviolet ray sensitive medium; a second detector element exposed to said source and insensitive thereto, said second detector element incorporating carbon as the ultraviolet ray insensitive medium; a normally inoperative circuit connecting said first and second detector elements in operative relationship with each other; and signal emitting means operable by said circuit upon the exposure of said detector elements to smoke.

3. In a smoke detecting device, the combination of: a source of ultraviolet rays; a first detector element exposed to said source and sensitive thereto, said first de tector element incorporating zinc as the ultraviolet ray sensitive medium; a second detector element exposed to said source and insensitive thereto, said second detector element incorporating copper as the ultraviolet ray insensitive medium; a normally inoperative circuit connecting said first and second detector elements in operative relationship with each other; and signal emitting means operable by said circuit upon the exposure of said detector elements to smoke.

4. In a smoke detecting device, the combination of: a source of ultraviolet radiation; a first ultraviolet ray sensitive detector exposed to said radiation; 21 second ultraviolet ray insensitive detector juxtaposed to said first detector; a normally inoperative circuit operatively connecting said first and second detectors; and signal emitting means connected in said circuit and energizable thereby when smoke in the field between said detectors causes the energization of said circuit.

5. In a smoke detecting device, the combination of: a source of ultraviolet radiation; first and second detectors having different levels of sensitivity to said radiation; a normally inoperative circuit connecting said first and second detectors in operative relationship with each other; and signal emitting means operatively connected in said circuit and energizable thereby when smoke in the field between said detectors causes the energization of said circuit.

6. In a smoke detector, the combination of: a source of ultraviolet radiation; first and second detectors juxtaposed to said source, one of said detectors being normally rendered electronegative by said radiation; a circuit incorporating said detectors and being maintained inoperative by said electronegative detector; and a signal operatively connected in said circuit and energizable thereby when said electronegative detector is rendered less negative by the passage of smoke into the field of said detectors to cause the energization of said circuit.

7. In a smoke detector, the combination of: a source of ultraviolet radiation; first and second detectors juxtaposed to said source, one of said detectors being normally rendered electronegative by said radiation and said detectors being constituted by spaced plates contiguous to said source; a circuit incorporating said detectors and being maintained inoperative by said electronegative detector; and a signal operatively connected in said circuit and energizable thereby when said electronegative deinto the field of said detectors to cause the energization of said circuit. I

References Cited in the file of this patent UNITED STATES .PATENTS 799,555 Gati Sept. 12, 1,070,556 Strong Aug. 19, 1913 1,071,532 Strong .2 Aug. 26, 1913 1,168,227 Schmidt Jan. 11, 1916 1,421,720 Roberts July 4, 1922, 2,627,543 Obermaier Feb. 3, 1953 2,665,129 Durbin et a1. Jan. 5, 1954 2,682,613 Uhl June 29, 1954 2,702,898 Meili Feb. 22, 1955 2,737,592 Ohmart Mar. 6, 1956 2,766,386 Ralls Oct. 9, 1956 2,783,390 Mendenhall Feb. 26, 1957 2,818,508 Johanson et al. Dec. 31, 1957 2,901,625 Friedman et a1 Aug. 25, 1959 FOREIGN PATENTS 387,474 Germany May 21, 1922 398,722 Great Britain Feb. 7, 1933 OTHER REFERENCES Photo-Electricity, by Zworykin et al., published by John Wiley & Sons Inc., N.Y., N.Y., in 1949, pages 3-9 and 429-435. a r

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