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4 IJ7 Patented July 2, 1946 2,403,316 ` ­ July 2,11946. ' c. w. wALLH-AUsEN > 2,403,316 v RADIoAcTIvE APPARATUS Filed July 14, 1945 #4 IJ7 Patented July 2, 1946 2,403,316 ` ­ UNITED <s'rßrrla'. S PATENT OFFICE I RADIoAcTIvE APPARATUS Clarence W.` Wal-lhausen, Morristown, N. J., as signor to United States Radium Corporation, New York, N. Y., a corporation of Delaware Application July 14,1943, sena1No.494,616 . ' 5 Claims. (Cl. Z50-72) 1 ' 2 . , Í. ,s This invention is concerned with self-luminous the zinc sulphide, but bombardment can beJ inter indicators such as clock dials, electrical instru" rupted in accordance with my inventionby inten. ment dials, and the like, and provides an improved posing between the activator member and the apparatus having a much longer life than those face member, i. e. the glass plate bearing the ~ available heretofore. ' ` markers, a sheet of material, for example, a metal It has been customary to produce self-luminous slide which is impervious to alpha radiations.A instrument dials by painting thedials with a paint By interposing the metal slide between the glassy comprising a phosphor, i. e. a phosphorescent ma slide and the radioactive film, except whenîthe terial such as zinc sulphide, and a radioactive ma indicator is in use, the life of the face member terialV such asa radium salt which gives off rays 10 can be increased many times. ' . 'y ­ that bombard the phosphor and cause it to glow. In another form of. the apparatus of my in Dials so constructed are used in a variety of in vention, which is herein claimed, the face mem struments and haverecently found Wider applica ber, constructed like an lordinaryclock dial, is vof tion in airplane instrument dials, especially in translucent material, with one ormore numbers,_ Y air-craft adapted for night flying. 15 or other markers painted on the face thereof _with >It has been found that selffluminous indicator a' Vnon-luminous Y but ray-responsive phosphor,­ dials fashioned as described above have rela suchqas zinc sulphidepaint, n, >_The activator. mem-'1 tively short useful life, even though the» propor ber >in this case is a pointer which rotates aroundk tion of ` radioactive material employed is high.y in front of the markers, which conveniently are4 This is believed to be due to the ‘fact that the 20 arranged in a circle with the axle of the pointer as I. bombardment of the' phosphor' (e. g. >zinc {sul a` centers-The pointer carries'a Vradioactive foil phide) by radium results in deterioration of the or film on its underside 0in theneighborhood. of phosphor (e. g. sulphide crystal) and the eventual the markers. As the pointer rotates, each marker y loss of luminosity.v Whatever be the explanation, on the dial is caused to glow consecutively ,v'vhilet I have found that the useful life of self-luminous 25 theothers remain dark., This type of [structure indicator dials, and the like,­ can be increased affords two distinct advantages; The life ofthe many fold if means are provided for interrupting phosphorescent material, i. e. the zincsulphide the bombardment of the phosphor by rays, etc., paint is increased because most of the time each marker is beyond the range of >rays given _offby from vthe radioactive material, except rduring 30 times when observations are being made.` By the radioactive foil or film on >the pointer mein',-V employing a­ face member, 'such as an indicator ber, and, so does not deteriorate under bombard-~ dial, having thereon a marker comprising a phos~ ment. Moreover, the eyes of an ' observer’are` ’ ‘phorescent coating material that is non­radio~ caused to concentrate on only the pertinent ob­. active but is capable of being activated by alpha servation, i. e. the marker that is‘illuminated. rays, an activator member coated with a non~ 35 This reduces fatigue, an‘important consideration luminous radio active materialcapable of emit in night flying and the like. ’ ting alpha rays and spaced from but loperatively These and other features of my inventîonwill ' associated With the face member, and means for be understood more thoroughly in the light of ' interrupting the passage of alpha rays from the the following detailed description, taken incon activating member to the marker, I4 am able to 40 junction with the `accompanying `drawing,'x'inl increase the useful life of the phosphorescent which: coating matería1 many times. A simple form of Figs. 1 and 2 illustrate one type Yof indicator­ apparatus of my` invention comprises a trans mechanism constructed in accordance with myY parent slide, for example a plate of glass which invention; ' ' carries markers, for example numbers painted 45 Figs. 3, 4, 5f and 6` illustrate modified andpre-Y " thereon with non-radioactive but responsive zinc ferred forms of indicators of my invention;v and sulphide paint.` Back of the glass dial and spaced Fig. 7 illustratesa further form _of apparatus therefrom a short distance is the activator mem-l of Amy invention in which :the bombardment ‘of’ ber, which may be a radioactive foil or a ñlm of the >responsive phosphor is interrupted by'intere coating composition containing a radioactive ma~ 60 posing a screen such as a metal slidebetween the terial. In either case, the activator member is phosphor and the activatorA member where >the non-luminous, *butv gives _off alpha rays which rays originate. v ` ' j v ` strike the markers on the glass side or dial .and Referring to Figs. ­1 and 2, it will be observed cause thezinc sulphide therein to glow.> , The glow that the apparatus comprises a face or dial mem will continue as long „as the alpha rays bombard ber l0', provided with a plurality ofrmarkersfl lj, 2,403,316 3 4 lz, la, n.15, ls, l1, ls on the face of the marker spot 50 will appear on the marker arc between ’ - and arranged lin a circle around it's periphery. the numerals 5 and I 0. ¿The markers are ñlms of a non-radioactive phos Naturally enough, the markers on the dial mayV Íphor, for example zinc sulphide paint. which con take a great variety of forms and may be placed îtains no radioactive substance but which will glow in a variety of ways. ' `under bombardment by alpha particles. The ap In the apparatus of Fig. 7, thevactivator mem paratus is also provided with a pointer I9» in the ber is not movable. In this apparatus, the vface `form of an _ordinary `clock hand rotatable comprises a glass slide 1’0'von thev underside of `abo-ut an axis 2| at the center of the dial. On which a 4plurality of markers 1|, 12 are provided. the underside of the pointer near its outer end io y'I‘hese markers are made of non-radioactive but Y1 and immediately over the circle of markers >is responsive phosphor such as Zinc sulphide paint. lplaced a radioactive member_22jsuch as apiece The glass slide is mounted in a .case 'I3 of con `of Vradioactive foil or a radium ñlm. The radio ventional design. The bottom of the case 14 is `active foil or ñlm is spacedfrom the markers, but coated. with a ñlm of radioactive substance, forV ‘ passes over them when the pointer' is rotated, 1s example, a sheet of radioactive copper foil 15. iso thatïeach marker successively is Ibombarded Alpha rays from the foil cause the 'markers ony lby alpha rays. The pointer is rotated by means, the underside ofïthe glass slide to glow when the ‘such as a clock-work (not shown). However, as. apparatus is in use. When the apparatus is taken f i »it rotates, only that portion of the marker or out of service a removable metal slide 16 is slid îmarkers which is beingusefully employed for 2o into the case between the foil and the phosphor, îobservation'purposes is activated at the moment. thereby blocking off alpha radiations and permit ‘The other markers are outside lthe range of the ting lthe markers to “rest.” v ïalpha particles and so are at rest and unborn Iclaim: Y `barded'. , . ` ‘ 1. In a self-luminous indicator, the combina-` j Thev dial constructed inaccordancewith Figs. 25 tion which comprises ar translucent face mem- l 1 and 2 will last many times longer thandials ber, Ya marker mounted on the back of the face `formed by painting the severalî markers with a member and formed of a non-radioactive but re fself-luminous paint, for example,.a paint formed sponsive phosphor capable A,of being activated by> :of` zinc sulphide containing a radium active sub alpha rays, a pointer spaced from> but movable stance, such asradium chloride. y 3c over the rear surface of the face member. in prox l Figs. 3, 4, 5` andô illustrate three preferred Vimity to theY marker, and a radioactive member 3modiñcations Yof an indicator. constructedV in ac of non-luminescent radio-active material which cordance with my invention. In allfcases, the ap emits alpha rays, said radioactive member‘being lparatus comprisesa dial or face member,v 30 of .e mounted on the pointer in such a position that transparent or- translucent ­material, for example ¿s alpha rays therefrom strikethe marker when- the Iglass or plastic. The front face of the dial is pointer passes over it. ' ’ ` p » masked .witha materialwhich-cuts. off light.> 2. Ina self-luminousV indicatoni the combina ‘_Thus, the face ofthe/material, except at.¿the­ tion which comprises a translucent face member, Y lmarkersßl, 32, 33, „34, 35, 367/31, 38,1may be a marker mounted on the back ofthe face meme Vjcoated’with blackpaint Yor thelike. The markerv ¿o ber and >formed of a non-radioactive 'but respon ’fareas.
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