GB867240A - Improvements relating to beam defining apparatus - Google Patents

Abstract

867,240. X-ray apparatus. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 8, 1959 [April 23, 1958], No. 12907/58. Class 98(1) Apparatus for defining and varying the crosssection of a beam of penetrating radiation comprises a first pair of blocks, between which the beam passes, movable transversely across the beam, and a second and third pair of blocks located respectively before and after the first pair with respect to the direction of travel of the beam, the second and third pairs being movable transversely across the beam in a, direction different to that of the first pair; the thickness of the first pair of blocks measured along the length of the beam is substantially equal to the combined thickness of the other two pairs. The beam of radiation 23 passes as shown between the pair of blocks 5 and 6, 71 and 81, 7<SP>11</SP> and 8<SP>11</SP> of radiation-absorbing material (Fig. 1). The blocks 5, 6 are transversely adjustable towards or away from the beam, and the other two pairs are similarly adjustable but in a direction at right angles to that of blocks 5, 6. (Blocks 71, 711 and 81, 811 are joined by rods 9, 10 so that the outer pairs of blocks move together). The blocks thus define between them a beam of rectangular section which can be varied in size. The source 1 of X or y radiation is enclosed in a mass of radiation-absorbent material 2 having a conical aperture 4. Blocks 5 and 6 are constrained to move in circular arcs centred at 1 by means of attached rollers 11 and 12 engaging in arcuate grooves 13, 14 in members 15, 16 forming part of a supporting framework 24. The other pairs of blocks 71, 711 and 81, 811 are similarly constrained by rollers 17, 18 engaging in arcuate grooves 19, 20. Movement of blocks 5, 6 towards or away from each other, to alter the beam width, is controlled by roller-driven belts 31, 32. Arms 37, 38 are rigidly attached to the upper parts of the belts, and engage in the slots of slotted members 39, 40 attached to block 5. Similarly arms 41, 42 are rigidly attached to the lower parts of the belts, and engage in the slots of members 43, 44 attached to block 6. Thus movement of the belts, caused by turning handwheel 36, moves members 39, 43 and 40, 44 towards or away from each other, according to the direction of turning, with corresponding movement of blocks 5, 6. Handwheel 45 operates a similar arrangement for controlling the movement of the other pairs of blocks. In the modification of Fig. 5 (not shown), movement of the blocks is controlled by an arrangement of screwed rods instead of belts.