GB716869A - Improvements in or relating to glow discharge chambers - Google Patents

Abstract

716,869. Nitriding. BERGHAUS, B., [trading as BLEKTROPHYSIKALISCHE ANSTALT B. BERGHAUS]. May 7, 1951 [May 8, 1950], No. 10701/51. Class 72 [Also in Group XL(a)] A glow discharge chamber 12 for the treatment of work-pieces such as nitriding or for effecting chemical reactions by means of high intensity gaseous discharges has a current leadin assembly comprising two electrodes, a cathode 4 and an anode 1 (which also forms the wall of the chamber), spaced by an insulator 20, which together define a gap 19 at their end adjacent the chamber, the length of the gap being normally great compared with its width, characterized in that the gap has at least one discontinuity, for example 30, along its length the width of the gap at the discontinuity being great compared with the length along the gap of the discontinuity. The discontinuities may be located in the insulator as at 28, 30, in the anode as at 29, 33 or in the cathode. A discontinuity such as 29 may be bounded on one side by the anode 1 and anode cap 13 and on the other side by the insulator 20. A further discontinuity 21, 22, 24 can be provided between the insulator 20 and the cathode ring 18 and annular part 23 of the cathode. The parts defining the discontinuities are so formed and are made of such materials that changes due to heat . do not materially affect the width of the gap. The anode 1 can be cooled by cooling medium in the space 3 and the cathode 4 can be cooled by cooling medium through pipes 7, 8. Pressures in the discharge chamber of below 5 mm. of mercury, from 5-40 mm. and up to atmospheric and beyond are referred to. The cathode 4 has a threaded extension 5 for attachment of workpieces to be treated, for example by nitriding in an atmosphere of nitrogen.