Projection tube with X-ray shielding means on target

#1. Field of the Invention

#The present invention relates to projection tubes of the type including a target having a fluorescent screen adapted to be irradiated with an electron beam and means for projecting in front the image produced on the fluorescent screen, and more particularly the invention relates to an improved projection tube including an X-ray shield disposed to cover the surfaces of the target excluding the fluorescent screen.

#2. Description of the Prior Art

#FIG. 1 is a sectional view of a prior art projection tube.

#FIG. 2 shows the details of the prior art projection tube, with FIG. 2A showing a side view of the target and its supporting members and FIG. 2B showing a front view of the target and its supporting members.

#FIG. 3 is a side view of the target of the prior art projection tube,

#The present invention comprises a projection tube featuring an X-ray shield which provides shielding against leakage to the front of the tube of the X-rays emitted by the bombardment of the electron beam against the fluorescent screen of the target, and it has the advantages of an improved shielding against X-ray penetration, improved dissipation of the heat from the target and improved assembling accuracy in the manufacture of the target.

#Referring now to FIG. 6, a projection tube has a neck 1 housing an electron gun 2 for producing an electron beam, and a funnel section 18 houses an assembly comprising a target 4 formed with a fluorescent screen 3 disposed opposite to the electron gun 2, a concave mirror 5 for projecting forward the light emitted from the fluorescent screen 3 and a supporting ring 6 in which the target 4 and the concave mirror 5 are mounted to oppose each other. The registration of the supporting ring 6 and the funnel section 18 is accomplished by means of fitting members 15. The front end of the funnel section 18 is sealed with a faceplate 7, and a correction lens 8 is mounted by screws 16 in a position which is in front and at a predetermined distance from the faceplate 7. The target 4 is provided with an X-ray shield 19 of a structure which does not disturb the light path of the reflected light from the concave mirror 5, and the X-ray shield 19 is fixed to one end of supporting arms 10 whose remaining ends are welded to the inner surface of the supporting ring 6 thus holding the target 4 in a predetermined position.

#FIG. 7 shows the target 4, the X-ray shield 19 and their supporting structure. The X-ray shield 19 covers all the surfaces of the target 4 except the fluorescent screen 3, and the X-ray shield 19 is formed into a shape large enough to closely fit over the sides and back surface of the target 4, thus allowing the target 4 to be fixed in place fully firmly by pressing it into the shield 19 by suitable fitting means. The four supporting arms 10 each has its one end welded to the X-ray shield 19 and its other end welded to the inner surface of the supporting ring 6.