GB972012A - Improvements in or relating to electronic valves and grid structures therefor - Google Patents

Abstract

972,012. Making grids for thermionic valves. POSTMASTER GENERAL. Jan. 10, 1961 [Jan. 14, 1960], No. 1439/60. Heading B3A. [Also in Division H1] Control grid and screen grid helices 4, 7, Fig. 1, are wound under tension on a frame comprising two inner control grid support rods 1 and two outer screen grid supports rods 5 rigidly supported in planar, parallel alignment by common spacing means 2, 3 secured to at least rods 1, grid helix 4 being wound before rods 5 are assembled in position. As shown in Fig. 1, the frame comprises two pairs of molybdenum cross-members 2, 3 brazed to molybdenum rods 1 with an alloy of 75% gold and 25% nickel. Rods 5 of synthetic sapphire are formed with flats 6 to co-operate with the cross-members. The control and screen grid helices both wound under tension are cemented to the rods and may be of equal pitch with their corresponding wires in alignment, or one of the rods 5 may be longitudinally displaced so that the wires of the two grids are inclined to one another. Connection to the screen grid is made through a platinum tape 8 inserted adjacent one of the rods 5. Alternatively, both pairs of rods 1, 5, Fig. 7, may be of synthetic sapphire or polycrystallized alumina, the cross members 40 comprising transverse molybdenum plates each formed with a central rectangular aperture for insertion of the cathode and three D-shaped holes 42-44 and a circular hole 45 for the reception of the rods 1, 5. The circular holes 45 allow insertion of rods 5, one from above and one from below, after winding of the control grid helix. Platinum tapes for connection to helices 4, 7 pass through slots 46, 47 in plate 40. In a further arrangement, Fig. 9 (not shown), both pairs of rods are of metal and pass through bushes of synthetic ruby set in the transverse molybdenum plates 40.