GB1175216A - Diaphragm for Limitation of Ionizing Radiation Beam. - Google Patents

Abstract

1,175,216. Diaphragm. A. E. ATOVMIAN, I. E. DAVYDOVA, A. B. LITVAN, S. V. NESTERENKO, N. P. PUKOV and V. K. YAGOLKOVSKY. 22 March, 1967, No. 13513/67. Heading H5R. A diaphragm for defining a beam of ionizing radiation comprises wedge-like elements, e.g. 4, 5, 6, 7, 8, 9, 10, 11, made of shielding material (e.g. tungsten) and accommodated in a housing 1, said elements being slidably interconnected (e.g. by tie plates 12) at their edges to be free to move in a plane perpendicular to the beam axis (the plane of Fig. 2) so as to form a polygonal aperture through which the beam can emerge, the elements being movable by at least two ring gears (e.g. 13, 14, 15) mounted inside the housing, each of said ring gears being operatively associated with at least one of the wedge-like elements, the ring gears having a common drive, e.g. toothed ring 16, by which drive the ring gears and hence the elements may be moved simultaneously or selectively. Preferably the drive is taken to each ring gear through independently operable clutch means (Fig. 6, not shown) and the toothed ring 16 may be driven by an electric motor 61 via gear 63. Stop blocks, of which 68, 69 and 70 may be seen on Fig. 2, (64 to 67 being on Fig. 7, not shown) are fitted to limit the relative displacement of the ring gears and hence the relative positions of the wedge-like elements. Preferably the diaphragm comprises two carriages 18, 19 seen most clearly in Fig. 1, adapted to be driven by ring gear 13 and gears 26, 27 in opposite but parallel directions in the plane of Fig. 2 and aligned vertically with respect to this Figure, each carriage supporting a corresponding but complementary set of wedge-like elements which project towards each other to define a central aperture between the carriages, a corresponding one of each set of wedge-like elements, e.g. 4 and 8 being fitted so as to be movable towards and away from each other transverse to the direction of movement of carriages 18, 19, this transverse movement being actuated from ring gear 14 via gear 38 for element 4, bevel gears 40 (Fig. 3) pinion 36, which is elongated to accommodate the sliding of carriage 18, and rack 34, gear 39 being similarly equipped to move element 8. Thus the movements of carriages 18, 19 and racks 34, 35 govern the effective overall dimensions of the aperture. To change the shape of the aperture, one of the wedge-like elements supported by each of the carriages 18, 19 comprises two portions viz 6, 7 and 10, 11 which are adapted to slide transversely of the aperture relative to each other, such motion being initiated by ring gear 15 which activates gears, 48, 49, gear 48 as shown in Fig. 4, operating through bevel gears 47, extensible shaft 46 (necessary to accommodate sliding of carriage 18) and bevel gears 45 a pinion 44, which drives racks 42, 43 attached to wedge elements 10, 11 to achieve the desired relative transverse motion, gear 49 similarly driving elements 6, 7. Thus by the present arrangement, the length, breadth and shape of the aperture may be changed separately or simultaneously by activating the appropriate clutch of which only the driving sprocket 52 may be seen on Fig. 2. As is illustrated in Fig. 6 (not shown), the clutch may be spring loaded and electromagnetically actuated. A hexagonal, rectangular or octagonal aperture may be produced according to the relative positions of joint elements 6, 7 and 10, 11.