US2999934A - Radiation detector apparatus - Google Patents

Description

Sept. 12, 1961 A. TAYLOR RADIATION DETECTOR APPARATUS Filed NOV. 29, 1939 TO AMPLIFIER) AMPLIFIER TO BALHNCIN NET WORK 2,999,934 RADIATION DETECTOR APPARATUS Laurens A. Taylor, Schenectady, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Filed Nov. 29, 1939, Ser. No. 306,755 7 Claims. (Cl. 250-833) This invention relates to thermo-responsive devices for locating distant objects by therma -radiation and it con-' stitutes a further development of the apparatus for detecting distant objects by heat radiation described and claimed in the copending application of Charles F. Green, filed November 29, 1939, Serial No. 306,753.

One object of this invention is to provide a thermoresponsive detector adapted to be used in connection with collector-thermo-couple-amplifier-indicator systems, which will materially facilitate the detection of distant objects by said systems, owing to its simplicity and rapidity in response and angle of pickup.

Another object of this invention is to provide a thermoresponsive detecting device of the character specified having a plurality of thermo-couple strips arranged and proportioned so that said device when used with a suitably dimensioned reflector will afford a wide vertical acceptance angle or spread, particularly useful in systematic searching for unseen targets.

Another object of this invention is to provide a detecting apparatus equipped with a thermo-responsive device in the nature of an evacuated tube provided with a window having a high transmission coeflicient and containing a pair of suitably disposed thermo-couple strips, in-

teroonnected within the tube to afford bucking out-' puts, the respective length of the strips being such as to provide a vertical acceptance angle, suitable for systematic searching.

Another object of this invention is to provide a detecting apparatus, including a thermo-responsive detector in the nature of an evacuated tube having a rock-salt window and containing a pair of horizontal disposed thermocouple strips folded within the tube to provide the requisite spacing for their vertically extending junction lines.

With these and other objects in view, this invention consists in certain novel details ofconstruction, combination and arrangement of parts to be more particularly hereinafter described and claimed.

Referring more particularly to the accompanying drawings in which parts are designated by similar reference characters:

FIG. 1 is a sectionized diagrammatic view of a collector-thermo-couple-amplifier-indicator system illustrating one embodiment of the instant invention; 7

FIG. 2 is a sectionized perspective'view of the thermoresponsive detecting device adapted to be used in connection with the apparatus shown in FIG. 1, and illustrating the arrangement, mounting and connections of the thermo-couple strips within the tube;

FIG. 3 is a fragmentary detailed perspective of the therrno-cou-ple strips within the detector tube; and

FIG. 4 is a perspective view of a modification of thermo-couple strips shown in FIGS. 2 and 3.

In the form of thermo-couple as described and claimed in the application of Charles F. Green, filed November 29, 1939, Serial No. 306,753, the junction strips are mounted side by side and connected in such a manner that their outputs are in bucking relation. While useful in background investigations, determination and com-- parison of ranges and characteristics of systems, this type of thermo-couple tube, owing to its limited pickup anand azimuth may be effected for the purpose of pointing gle is not suited to systematic searching for distant tar-. 7

gets. It is therefore the aim and purpose of the instant Patented Sept. 1-2, 1961 invenion to provide a line thermo-couple tube having its thermo-couple strips arranged and proportioned to provide a pickup angle which will greatly facilitate systematic searching.

In .the illustrated embodiment characterizing this invention a drum 1 is pivotally mounted at -2 betweenthe arms of a yoke 3 which is swivelly supported on base 4., This arrangement permits vertical and horizontaloscillwtion of the drum as clearly shown in FIG. 1 of the'drawings. Suitable means are provided for moving. the drum in each of the two planes whereby changes in elevation the drum. While such means maybe manualor power operated, the former is illustrated for the sake of simplicity; thus, the handwheel Soperates through the worm 6 and worm-wheel 7 .to move the drum in the vertical plane and the handwheel 8 functions through worm 9 and worm-wheel 10 to move the drum in the horizontal plane.

Within the drum is mounted the reflector 12 in the focal region of which is arranged a line thermo-couple tube 13, the tube'being suitably supported on the upper end of a standard 14 as shown in FIG. 1 of the drawings. This device comprises two thermo-couple, strips 15 and 16, which are in the present instance horizontally disposed and arranged in end to end relationwith the junction lines 20 extending vertically, as clearly shown in FIG. 2 of the drawings. V

The thermo-couple strips 15 and 16 are mounted within and near one end of an evacuated envelope 17. This envelope comprises a glass portion 18 having a metallic end portion 19, which in the present instance is a silver sleeve and a window or end plate 21 having a high trans; mission coefficient, such as rock-salt. The "sleeve has a thin tapered edge at both ends, the glass being fused over the inner end, and the outer end of the sleeveis made vacuum tight with the rock-salt window by a suitable seal such as silver chloride, which constructionis described and claimed in the copending application of August J. Kling, filed November 29, 1939, Serial No. 306,750, now Patent No. 2,593,369.

Each of the thermo-couple strips '15 and 16 is composed of two thermo-electrically dissimilar metals welded together along the junction line 20. These thermo-' couple strips have been made by welding together thin plates of the desired material at their edges and then rolling down the welded plates until they obtain the desired thinness, which is of the order of 6 to 10 millionths of an inch. Since the direction of the rolling is transversely of the strip, or in other words, in the direction of the junction line 20, the welded connection between the two metals is preserved even though the thickness of the resulting strip is reduced to a few millionths of an inch. Very successful results have been obtained by employing for one element of the thermo-couple strip an alloy composed of nickel 44%, copper 55.5% and iron 0.5%, commonly known as Copnic, and for the other element of the thermo-couple strip an alloy composed of nickel and chromium 10%, commonly known as Chromel."

Assuming that the apparatus is to be used for horizontal searching, that is, the drum and reflector are to be swung in azimuth at a given elevation, the two thermocouple strips 15 and 16 as previously stated are arranged horizontally in an end to end relation with the junction lines 20 extending vertically. The two junctions are connected in series and in a reverse manner, the two outer elements, which are of one polarity being secured to support bars 25 and 26, and the two inner or inter-' mediate elements which are of the'opposite polarity being secured to the intermediate bar 23.

With this type of thermo-couple strip the lengthof;

eachjunction line 20 is from three to seven times the length of the junction line disclosed in the thermo-couple strips described and claimed in the hereinabove mentioned application of Charles F. Green. The width of each junction is therefore many times the diameter of the image represented, for example, by the dotted circle 21a of the radiating body. The lengths of the electrically dissimilar metals forming each thermo-couple strip are substantially equal, the exact lengths being such that the rates of heat conduction to the supporting bars, considering the heat conducting properties of the materials, are equal. The intermediatebar 23 is approximately twice the size of each of the outer bars 25 and 26, whereby it has approximately twice the heat capacity thereof. The junction line 20' is substantially in the middle of each strip, but in order to bring the two junction lines closer together the inner elements 15a- 16a of the thermo-couple strips 15 and 16 are bent backward as shown in FIGS. 2, 3 and 4. By thus bringing the two junction lines 20 closer together, one junction can be made to respond to a background regionof radiation which is closer to the body whose radiation effects the other junction. By connecting the thermo-couple strips so that they oppose each other, in so far as background radiation is concerned, the one thermo-junction will exactly balance the other and no indication will be given by the indicating meter, hereinafter to be referred to.

The two thermo-couple strips are mounted with the outer elements as well as the adjacent portions of the inner elements in the focal region of the reflector and are horizontally offset so that the focal point of the reilector falls on one junction line 20 at approximately the middle thereof. As shown in FIGS. 2 and 3, the inner bar 23 is connected to and supported by the wire 24 which extends through the stem of the tube to the exterior thereof and is connected to terminal 24a of the terminal block A. The outer bars 25 and 26 are affixed to and supported by the wires 27 and 28 which extend through the stem of the tube, as clearly shown in FIG. 2, and are connected to terminals 27a and 28a of terminal block A. These terminals 27a and 28:: are connected via conductors 27b'--2S'b with the input side of an amplifier 31. The output side of amplifier 31 is connected through suitable conductors to a rnilliammeter indicator 32, as shown in FIG. 2 of the drawings.

To correct for small differences in resistance in thermojunction that may occur in manufacture, a balancing network (not shown) may be connected via conductors 24b-27c between terminals 27a--24a, whereby the two thermo-couple strips may have equal resistances when exposed to equal amounts of radiation, thus retaining the pointer of the indicator at zero.

The form of thermo-couple strip which is shown in FIGS. 2 and 3, and which is relatively wide, giving a relative long junction line 20 is equivalent to a number of narrower thermo-couple strips connected in parallel. In certain cases it may be desirable to employ a number of narrow thermo-couple strips and connect them in series relation. Such an arrangement is shown in FIG. 4, in which several narrow thermo-coupl'e strips 1512-1611 are supported by separate bars of which adjacent bars of one polarity are mounted upon the insulating supports 27d, as clearly shown in FIG. 4 of the drawings. The thermo-junction strips are suitably connected in series by the conductors 29a29b. It has been found that for thermo-couple strips constructed of the same materials and having the same area, series or parallel connections will give equal power output, provided the load resistance is matched to the thenno-junction.

In conclusion, it will be seen that this invention presents a detecting apparatus, embodying a high vacuum line thermo-couple tube having arock-salt window and containing a pair of thermo-couple junction strips, connecte'd'in bucking? relation and folded in a manner to space the vertically extending junction lines, a distance which experience has demonstrated gives the most effective results, and that when this tube is mounted in the focal region of a suitably dimensioned reflector, and connected to an amplifier-indicator system, as shown in FIG. 1, there is provided at detecting apparatus which is sensitive over a long range, rapid in response and efficient in searching for unseen targets, owing to it's relatively wide angle of pickup.

Having described my invention, what I claim as new and wish to secure by Letters Patent is:

1. In an apparatus for locating distant bodies by thermo-radiation, means for collecting: and focusing the heat radiation from a distant bodyto form a thermal image thereof, means 'within the focal region. of the collected heat radiation for translating thermal intoelectrical energy, said means including an evacuated vessel provided with a rock-salt window, ther-mo-responsive means within the vessel, said means being electrically connected in opposition to effect automatic compensation for changes in background radiation and' including a pair of vertically extending laterally spaced thermal mal image formed by said first-mentioned means and an indicating device in electrical relation with said thermo-responsive means.

2. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body to form a-thermal image thereof, means within the focal region of the collected heat radiation for translating thermal into electrical energy, said' means including an evacuated vessel provided with a rock-salt window, thermo-responsive means within the vessel, said means including a pair of ther'rno-couple strips arranged-in end to end relation and electrically connected in opposition to effect automatic compensation for changes in background radiation, each of said strips including a thermal junction line extending transversely of its length and'coextensive with-its width, the length of said coextensive line being such as to afford a relativelywide'vertical acceptance angle, one of said thermal junction lines being positioned to receive the thermal image formed by said first-mentioned means and an electro-r'esponsive indicator in electrical relation with the thermo-couple strips.

3. In an' apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing heat radiation from a distant body to form a thermal image thereof, means within the'focal region of the collected heat radiation for translating thermal into electrical energy, said means including an evacuated vessel provided tion lines being disposed to receive the thermal image formed by said first-mentioned means, and an electric responsive indicator in electrical relation with thermocouple strips.

4. 'In an apparatus for locating distant bodies'by thermoradiation, means for collecting and focusing the'heat radiation from a distant body to form a thermal image thereof, means within the focal region of the collected heat radiation for translating thermal into electrical energy, said means including an evacuated vessel provided with a rock-salt window, thermo -responsive means within the vessel, said means embodying a pair' ofthermo couple strips of a predetermined order of" thinness arranged in end to end relation andelectrically connected in. opposition to efiect automatic compensation forchanges in background radiation, each of said strips embodying a vertically disposed thermo-junction line coextensive with the width of the strip, the thermo-junction lines of the two strips being parallel and laterally spaced a predetermined distance, the length of said thermal junction lines being such as to afford a Wide vertical acceptance angle, one of said thermal junction lines being disposed to receive the thermal image formed by said first-mentioned means, and an electro-responsive indicator in electrical relation to the thermo-couple strips.

5. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body to form a thermal image thereof, means Within the focal region of the collective heat radiation for translating thermal into electrical energy, said means including an evacuated vessel provided with a rock-salt window, thermo-responsive means within the vessel, said means including a pair of thermocouple strips arranged in end to end relation, each strip being composed of electrically dissimilar alloys of a predetermined order of thinness united along a vertically disposed junction line coextensive with the width of the strip, said strips being electrically connected in opposition for effecting automatic compensation for changes in background radiation, one of said thermal junction lines being disposed to receive the thermal image formed by said first-mentioned means, the length of the re spective junction lines being such as to afiord a wide vertical acceptance angle, and an electro-responsive indicator in electrical relation with the thermo-couple strips.

6. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing heat radiation from a distant body to form a thermal image thereof, means within the focal region of the collected heat radiation for translating thermal into electrical energy, said means including an evacuated vessel provided with a rock-salt window, thermo-responsive means within the vessel, said means comprising a pair of thermocouple strips arranged in end to end relation and electrically connected in opposition to eflfect automatic compensation for changes in background radiation, each of said strips being of a predetermined order of thinness and including a vertically disposed junction line coextensive with the width of the strip, the thermal junction line of one of said strips being disposed to receive the thermal image formed by said first-mentioned means, said strips being folded rearwardly within the tube to juxtaposition the junction lines, and an electro-responsive indicator in electrical relation with said thermo-couple strips.

7. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing heat radiation from a distant body to form a thermal image thereof, means Within the focal region of the collected heat radiation for translating thermal into electrical energy, said means including an evacuated vessel having a window transparent to thermal radiation, a plurality of thermo-couple strips Within the vessel and immediately to the rear of the window, said strips being arranged in end to end relation and electrically connected in opposition to effect automatic compensation for changes in background radiation, one of said thermal junction lines being disposed to receive the thermal image formed by said first-mentioned means, said strips being of a predetermined order of thinness and including parallel laterally spaced junction lines, the length of said lines being such as to afford a Wide vertical acceptance angle, and an electro-responsive indicator in electrical relation with said thermo-couple strips.

References Cited in the file of this patent UNITED STATES PATENTS 1,343,393 Hoflman June 15, 1920 1,963,185 Wilson June 19, 1934 1,971,317 Sheldon Aug. 21, 1934 2,015,675 Hays Oct. 1, 1935 2,125,113 Kling July 26, 1938 2,144,519 Wilson Ian. 17, 1939

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