GB805912A - Dosimeter - Google Patents

Abstract

805,912. Electroscopes. BENDIX AVIATION CORPORATION. Dec. 7, 1956, No. 37519/56. Class 37. In a dosimeter of the pocket instrument type employing an ionization chamber with a chargeable capacitor, the chamber and capacitor are constructed as interengaging into the facilitate matching. A housing 10, of a metal such as aluminium has a cap 12 at one end which serves to hold in place a viewing lens 16 which rests against the spacer 20 and is hermetically sealed by the ring 18. The spacer 20 abuts a shoulder 22 in the housing 10 and supports a disc 28, of glass or similar material, having a scale 30 marked thereon. The ionization chamber 32, which is positioned within the housing 10 against a shoulder 34, is made from electrically conductive material such as a plastic loaded with graphite. At one end of the chamber 32 is inserted a retainer 36 which carries the objective lens 40. At the other end of the chamber 32 the electrometer assembly 46 is placed. The assembly 46 consists of a sleeve 48, of plastic moulded on to a cylindrical aluminium former 52 in which are two holes 54, Fig. 6, into which the U-frame 56 is fitted. The frame 56 may be made of an alloy containing 98 per cent magnesium, 1.2 per cent manganese, and traces of calcium, silicon, copper and nickel. The frame 56 has a pair of lugs 58 each having a notch 60, Fig. 4, in which the ends of the fibre 62 are clinched. The fibre 62 may be made of quartz on which a coating of metal, such as platinum, is sputtered. The former 52 fits into a tube 66, made of a metal such as aluminium, which is filled with a transparent material, such as polystyrene, which also occupies the space inside the former 52. At one end of the tube 66 is a metallic cross-piece 72. The capacitor 76 is wound on the tube 66 and consists of layers of aluminium foil and insulating material. One electrode of the capacitor makes contact with the tube 66 while the other electrode is connected to the housing 10. The remaining space between the tube 66 and the housing 10 may be filled with plastic. Next to this filling 82 and separated from it by a gasket 87 is a flexible diaphragm 86 in the centre of which is located a contact pin 92 which when pressed will make contact with the cross-piece 72 to allow the capacitor to be charged. The diaphragm 86 is moulded on to a ring 94 made from a material such as aluminium and has a gasket 96 between it and the inwardly turned lip 98 on the housing 10. In manufacture the deflexion sensitivity of the assembly 46 is matched to the capacity of the component 76.