Patent GB-619057-A (GB)
Title: Improvements in devices for the diaphragm-control of x-rays
IPC: G21K1/04
Filed: 1946-06-04
Abstract: 619,057. R÷ntgen-ray apparatus. PHILIPS LAMPS, Ltd. June 4, 1946, No. 16938. Convention date, March 21, 1942. [Class 98 (i)] A device for limiting a beam of X-rays comprises a housing having a window, a diaphragm stop of X-ray impervious material movably mounted in the housing and defining an aperture in the window for the passage of X-rays, and control means for adjustably positioning the diaphragm with respect to the housing so as to move the centre of the aperture relative to the centre of the window. The stop may have an invariable aperture, or may consist of an iris stop or of two plates each having a V-shaped indentation forming a square aperture, or, as preferred, of four movable plates defining a rectangular aperture. The control means may be a pair of knobs, each controlling two of the four plates of a stop and capable of rotation and translation, the plates being moved at equal speeds towards one another, by one kind of motion, or away from one another, by the other kind of motion. The knobs may be connected to the plates by rods and levers, or by Bowden cables. As shown in Fig. 3, one control knob operates a lever 33 pivoted at its mid-point 35. The ends of the lever 33 are connected by Bowden cables 27, 28 to plates 23, 24 of X-ray opaque material mounted for horizontal movement in an X-ray opaque housing 21 having a window 22, and urged together by springs 29, 30. When the lever 33 is rotated about its pivot 35, both plates move equally in the same direction, but when the lever is moved in the direction of the arrow without altering its inclination, the plates move equally in opposite directions. The housing also contains similar plates 25, 26 mounted for vertical movement and controlled similarly by a second control knob operating a lever 34 pivoted at 37 connected to the plates by cables 31, 32. The two controls may form a single assembly. A shaft 49, Fig. 4, mounted on a base-plate 48, carries a cardan suspension supporting a part 44, to which is attached a plate 45 and cup 46 together forming a hemisphere. A step bearing 43 in the part 44 supports one end of a spindle 41 over which fits for rotation a tube 42 turning in a bearing in the cup 46. The spindle 41 and tube 42 are rotated by concentric knobs 51, 54 and respectively carry on threaded portions nuts 50, 53. The nuts carry rods 55, 56 sliding between two partitions 57 secured to the cup 46, and are thereby constrained to move axially when the knobs are turned. A pair of Bowden cables 58, 59, whose sleeves 63 are fixed to the plate 48, are connected at one pair of ends to diametrically opposite points of the nut 50, and at the other pair of ends to a pair of plates of a square-leaf diaphragm. Rotation of the knob 51 thus moves the plates to open or close the slit between them, while turning the spindles about the axis 66 (perpendicular to the plane of Fig. 4) shifts the slit without change of width. The nut 53 is similarly connected by a second pair of cables, lying in a plane perpendicular to that of cables 58, 59, to the other pair of diaphragm plates. The width of the slit between these plates is controlled by the knob 54, and its position is controlled by turning the spindles about an axis 67 perpendicular to the axis 66. The cup 46 slides in a dust cover 68, and a conical cover 64, merging into a flexible tube 65, encloses the Bowden cables. The nuts have left-hand threads so that clockwise movements of the knobs correspond to the closing movement of the plates. Alternatively, the movement of the plates may be reversed by a system of gears or levers. Displacement of the knobs corresponds in direction with the movement of the aperture.