US1609475A - X-ray screen - Google Patents

Description

Dec. 1926.

F. JANUS x-RAY SCREEN Filed April 11. 1924 Patented Dec. 7, 1926.

FRIEDRICH Janus, ormumcgenlnvranx, as srenfon'ro srnnnnsanansxnn rrnnensnmscnerr, or srnnnnssainn'r. nnnn'isnnrrn, .eniaivnanr,,n,:connota-a,`

TION OF GERMANY..

x-nAY sonnen.

Application filed April 1,-1, 1924, serial No. 705,807. ana in Germany 'apra 19, 192s.

My invention relates to improvements vin X-ray screens for intercepting the secondary rays produced in the 'body penetrated by the X-rays and render-ing -in X-,ray photography the pictures indistinct.

In known screens of this kind flat bars'or' strips of a material which .is almost impervious to X-rays are used, these bars or strips being arranged edgewise upon a disc-shaped 1G base plate mounted rotatably around its centre. The strips are so disposed that they either point to the centre of rotation or lie spirally around it. In order towprevent the portions of the X-ray plate situated near the l5 circumference from being exposed to Vthe X-rays for longer periods than .those situated nearer the centre, the number of radial bars has been increased towards the circumference or the bars have been made wedgeshaped. Both constructions'have certain disadvantages, particularly as far as their manufacture is concerned. v

It has also been proposed to construct screens of strips of material impervious to X-rays and strips of permeable material, which are combined in layers to form a cylindrical shell. This body is then during the exposure rotated around its cylinder axis. Such screens require a considerable amount of space between the part of the body exposedV to the rays and the photographic plate. In the drawing athxed to my specification and forming part thereof two embodiments of my invention are illustrated by way of example.

In the drawings is: Fig. 1 a plan of my improved screen, Fig. 2 a vertical section along line I I of Fig. l and Y Fig. 3 a plan of a slightly modified construction of the screen.

Similar parts are indicated by the same numerals of reference in all the figures.

Referring to Figs. l and 2, it will be seen that the screen has the shape of a circular disc l of comparatively small thickness. This disc is supported in three grooved rollers 2 disposed around the circumference.

3. The circumference of the disc is provided with a groove into which a cord 4 is placed by means of which and a driving pulley 5 provided with a crank 6 and handle also fixed upon the frame 3 the disc is adapted to These rollers are iixed upon a suitable frame be rotated.y The `ratio of transmission of. the cord drive 'is 'suchtfhat the screen disc can be rotated withy a comparatively high speed.

The screendisc is composed of `a comparatively large number of sector-like parts or iieldsi. Each ofthese parts consists in itselfof' a .comparatively large number of strips ofmaterial pervious to X-rays and other strips lof a material impervious to X-J rays. These strips consist, for instance, afl- `ternately of lead'foilv and of celluloid, hard paper,bakelite which is aproduct of conden-4 sation of phenol and formaldehyde, or a similar solid' material Vperviousf'to X-rays. These strips are packed very closely together and are either directly combinedvinto a. soli-d' disc by cementing or pasting'the strips to# such as'the disc 8in F i-g. which also conh sists-of a material pervious to- X-rays and which around its raised edgef) lis provided with the groove fort'he driving cord 4.' In

gether or they are fixed; upon a base-plate,

the strip composing the individual sectoreach of theviields, the layers or strips of f material pervious to Xfrays alternate with lay-ers of material substantially impervious to such rays, and all layers of the same field are parallel to each other, but form an angle with vthe directions of the layers in the neighboring fields.

Although .purely theoretically only one l single strip of the material impervious to the X-rays is in both cases situated accurately in the direction of the radiation emanatingy from the,` X-ray tube, the focus of the tube being assumed to be situated vertically above Vthe centre of the disc, theV variations Vof the l shadows caused by the inaccurate position of the other strips in relation to the X-ray tube, are so small that they are no longer perceivable on the X-ray photograph, provided that the strips and the sectors are made sufficiently narrow. The n individual sectorother strips ot' the same sector being like parts 7 are preferably also made of .different Width, as illustrated in Fig. l.

It Will be understood that I do not limit myself to the ldetails of construction described and illustrated by Way of example, but that these may be varied in many Ways, which Will easily` suggest themselves to those skilled in the art Without departing from the spirit of my invention.

What'I claim as my invention and desire to secure by Letters Patent is:v

l. An X-ray screen consisting of a circular disc built up of a plurality of sectors composed oilr alternate strips ot a material pervious to X-rays and of a material substantially impervious to X-rays, the central strip of each sector disposed radially to said disc and the other strips parallel to Vsaid central strip, and means for rotating said disc.

2. An X-ray screen consisting of a disc mounted to turn and built up of a plurality of sectors each comprising a series of spaced strips made of a. material substantially impervious to X-rays, one strip of each sector being radial With respect to the aXis about" which the disc is mounted to turn, and the parallel to such radial strip.

3. An AX-ray screen consisting of a disc mounted to turn and built u p of a plurality of sectors each comprising a series of spaced strips made of a material substantially impervious to X-rays, .the central strip of each sector being radial'with respect to the axis about which the disc is mounted to turn, and the other strips of the same sector being parallel to such central strip.

' an angle to the directions of the layers in the neighboring iields'. Y

5. An X-ray screen consisting of a disc mounted to turn and composed of a plurality of sectors forming individual iields, each ofsaid sectors comprising parallel layers oi a material substantially impervious to X- rays alternating With parallel layers of-a material substantially pervious to k-rays,y

all of said layers being disposed at right angles to the plane of the screen, andthe Ylayers of each individual sector extending ina direction at an angle to the directions oi"- the layers 1n the neighboring sectors.'

6. An X-ray screen consisting of a. body mounted to turn and composed of aV plurality of individual fields, each of such lields comprising spaced parallel strips of a material substantially imperviousto X-rays, said strips being arranged' edgewise withv respect to a plane of rotation, and the strips ot each individual field extending ina'direction at an angleY to the directions of the strips in the neighboring fields. i Y

ln testimony whereof lA affix my signature. 1

FRIEDRICH JANUS.

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