GB802647A - Beam therapy diaphragm - Google Patents

Abstract

802,647. Apparatus for radiation therapy. ATOMIC ENERGY OF CANADA, Ltd. Nov. 1, 1956 [July 18, 1956], No. 33411/56. Class 98(1) In a beam - limiting diaphragm, two pairs of blocks are movable towards and away from each other in directions perpendicular to the beam of radiation, each block being in sliding contact with two other blocks, and one block at least is divided along an oblique line terminating at the intersection of the inner faces of the block mentioned and of a block in contact therewith, the parts of the block being in sliding contact. As shown in Fig. 1, the diaphragm assembly 10 is rotatably mounted on an indicating- light housing 11, which in turn is mounted on a shielding container 12 for a source of radiation. A knob 15 locks the assembly. Guide plates 21, 22, Fig. 3, are mounted by tongue-and-groove connections to slide between the parallel straight edges of segmental guide plates 17, 18 mounted on the upper part of a housing 16. Plates 21, 22 have grooves 23, 24 to receive pairs of spaced rollers 25, 27 mounted on blocks 26, 28 (see also Fig. 6). Blocks 26, 28 have dovetail groove connections with a second pair of blocks 33, 34 so that each block is maintained in slidable contact with each of the other pair of blocks. The blocks rest on an upper cam plate 42 which carries rollers 43, 44 engaging grooves 45, 46 in blocks 26, 28, which cause the blocks to move towards each other or apart when the cam plate is turned by means of a knob 49 fast with a pinion 48 meshing with an arcuate rack 47 on cam plate 42. A lower cam plate 50 carries rollers 51, 52 engaging grooves 53, 54 in blocks 34, 33, which are thereby moved towards each other or apart when cam plate 50 is turned by a knob 57 fast with a pinion 56 meshing with an arcuate rack 55 on cam plate 50. The rollers 43, 44, 51, 52 are mounted on ears projecting into central circular apertures in the cam plates. Each of the blocks is divided into two parts, e.g. block 34 is divided into relatively slidable parts 66, 67, Fig. 8, with a dovetail groove connection. A screw 73, connected to a knob 71 by a shaft 72, is mounted in the part 66 and engages a nut 76 on part 67, so that the parts slide on one another when knob 71 is rotated. By rotating also three similar knobs controlling the relatively slidable parts of the other blocks, the aperture between the blocks may be made eightsided instead of four-sided, or to have an intermediate number of sides, and may be otherwise varied in shape. Manipulation of knobs 49, 47 affect both the shape and the size of the aperture. Canadian Specification 514,793 is referred to.