US1502907A - X-ray device - Google Patents

Description

Jul 29, 1924.

, W. D. COOLIDGE X-RAY DEVICE Filed June so. 1919 Inventor William DCOOIidQe,

7 MW v:

His Attorney.

Patented July 29, 1924.

UNITED STATES PATENT OFFICE.

W D. OOOLIDGE, O]? SCHENEOTADY, NEW YORK, ASSIGNOB '10 GENERAJHELIO- TRIO COMPANY, A CORPORATION OF NEW YORK.

x-RAY DEVICE.

Application filed June 80, 1919. Serial No. 807,814.

To all whom it may concern.

Be it known that I, WILLIAM D. Coomnon, a citizen of the United States, residin at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in X-Ray Devices, of which the following is a specification.

The present invention comprises an X-ray tube capable of substantially silent operation, that-is without the hissin and crackling noises which acoompanie the operation of X-ray tubes as formerly constructed. I have discovered that when the thickness of the glass wall of an X-ray tube is materially increased that the crackling noises formerly attendant on the operation of an X-ray tube are substantially eliminated, and that the operation of the tube accordingly is free from the current fluctuations accoman no-is operation.

p l h a beenzustomary to make X-ray tubes about 0.02 inch in thickness, that is, as thin as permissible without collapse of the bulb under the influence of the external atmospheric pressure. In accordance with my invention the walls of the entire tube or at least the part of the tube directly surrounding the cathode and the anode head are made of glass having a thickness greater than about inch and preferably a thickness of about inch. Preferably the tube consists in part of lead glass and is provided with a thin window consisting of material transparent to X-rays such as lime glass.

The accompanying drawing illustrates an X-ray tube embodying my invention, shown partly in section.

Referring to the drawin the X-ray tube illustrated comprises a big y evacuated envelope 1 comprising a somewhat bulbous electrode chamber 2, and outwardly extending arms 3, 4, into which are sealed the conductors for the cathode 5, and the anode 6. The cathode and the anode are of usual wellknown construction, the cathode comprising an incandescent filament of tungsten, or other refractory metal (shown by a dotted line) and the anode of a block of copper containing a button of tungsten (also shown in dotted outline). The anode stem 7 projects outside the tube envelope and external to the tube carries a radiator 8. The structural details are similar to the radiator type of tube shown and described by me on page igltf the General Electric Review, January,

The wall of the electrode chamber 2 which closely surrounds the electrodes consists of lead glass about 1 inch in thickness, the wall tapering in the tube illustrated to a lesser thickness for the cathode and anode arms. In some cases the thickness of the glass may be uniform throughout the tube except for a window 9 opposite the face of the anode consisting of material permeable to X-rays such, for example, as lime glass. The lime glass window is slightly concave and is sealed to the lead glass bulb on a slightly progecting lip, as indicated in the drawing and preferably is thinner walled than the electrode bulb so as to reduce the absorption of X-rays thereby. As shown in the drawing, the envelo e has a substantially tubular shape and so 0 osely surrounds the electrodes that the electrode chamber 2 constitutes but a slight enlargement. The window 9 although slightly concave to secure mechanical strength in general conforms to the general contour of the envelope. This construction rendersthe device especially suitable when compactness and light weight is desired, and simplifies its manufacture.

In my opinion the quietness and stability of operation of a thick-walled bulb is to be ascribed to the smaller-electrostatic capacity of the thick-walled tube. In an X-ray tube the inside surface of the tube wall becomes electrostatically charged by the electrons emitted from the cathode and this electrostatic charge is bound by an equal charge of opposite polarity on the outer conducting surface of the tube. When high frequency surges are set up for any reason the variation in electrostatic charge produces the crackling noise observed in the operation of the ordinary thin-walled X-ray tube. With a thick-walled tube the electrostatic condenser action is very much decreased. It is likely that there is also some leakage of electricity through the glass which is responsible in some measure for the crackling noise. It is evident, however, that the benefits of my invention are secured irrespective of what may be the theory of the cause of the crackling noise as formerly observed.

It is not essential that an X-ray tube embodying my invention shall consist in part of lead glass in order to possess the property of silent operation. I have found thickwallcd tubes consisting entirely of lead-free glass may also be operated noiselcssly. Of course, the heavy lead glass possesses the cided advantage of giving better protection to the operator.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. An X-ray tube adapted for substantially inaudible operation comprising a cathode adapted' to operate at incandesccnce, an anode and an enclosing evacuated envelope of glass closely surrounding said electrodes having a thickness of the order of about one-fourth inch.

2. An X-ray device comprising cooperating electrodes, an enclosing evacuated envelope of substantially tubular shape consisting of lead lass being materially greater than oneeight inch thickness at regions closely adj acent said electrodes so as to be capable of silent operation, and having opposite said anode a thinner window of substantially lead-free glass sealed into said envelope and conforming substantially to the general contour of said envelope.

3. An X-ray device comprising cooperating electrodes, an envelope closely surrounding said electrodes and having, at the region adjacent said electrodes, a wall of suflicient thickness to prevent substantially the electric disturbances in the operation of the device which cause crackling noises, and a window consisting of material permeable to X- rays scaled into said envelope in the path of X-rays generated by said device.

4. An X-ray tube comprising cooperating electrodes, and an envelope therefor having a wall of sufficient thickness to substantially prevent the occurrence of high frequency surges during the operation of said tube, said envelope being provided adjacent the anode with a window consisting of material permeable to X-rays, the portions of said envelope adjoining the window being spaced as closely to the electrodes as said window.

5. An X-ray device comprising a filamentary cathode capal'le of operating at incande'scencc, an anode of materially greater mass and an envelope closely surrounding said electrodes consisting of lead glass having a thickness approximating about onefourth inch and having a thinner window of curved surface and consisting of lime glass sealed therein, the space within said envelope being evacuated to a. pressure so low that gas ionization is inappreciable during operation.

In Witness whereof, I my hand this 27th day of have hereunto set June, 1919.

WILLIAM D. COOLIDGE.

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