GB557121A - Improvements in or relating to radiography - Google Patents

Abstract

557,121. R÷ntgen-ray apparatus. WATSON, W., and ILFORD, Ltd. Aug. 5, 1942, No. 10919. [Class 98 (i)] The Potter-Bucky or like grid used in radiography is connected with one or more spring members so that it may be oscillated in the plane of the grid bars and in a direction inclined to them by flexing and releasing the members, the oscillations thus produced dying away and so avoiding the formation of shadow patterns of the grid at the ends of its movement which occurs when the oscillations are of constant amplitude. In the form shown a rectangular grid 14 is carried by a frame 13 supported by leaf springs 11 from a base 10 which carries the film cassette. The springs are flexed and released mechanically or manually, for example by a cord secured to one of them, and oscillate the frame 13 in a diagonal direction. The grid may be inserted in the frame in two angularly related, as shown mutually perpendicular, positions. In another form, the grid is carried by a turntable mounted in the frame, and in order that the direction of oscillation may be maintained transverse to that of the grid bars, however the grid is oriented, the leaf springs 11 are connected to the frame by ball joints and are secured at their lower ends to spindles mounted on the base 10. The spindles are simultaneously rotatably adjusted by sprockets engaged by a common sprocket chain, thus maintaining the flat surfaces of the springs in parallel planes. Fig. 4 shows electrical means for giving intermittent impulses to the springs during a long exposure, comprising a solenoid 34 the energizing circuit of which is controlled by contacts of which one is mounted on the spring 11 which it operates, and by a valve 39 which becomes intermittently conductive at periods determined by the build-up of potential in a condenser resistance circuit 43, 40. The grid may comprise two superposed and mutually inclined sets of grid bars. Two superposed grids having their sets of grid bars mutually inclined may be independently oscillated in opposite directions ; they may be arranged in a vertical plane and oscillated in a substantially horizontal direction in this plane.