H2-O2 Gas Safety Control
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
A need has arisen in dry process etching to enable H2 and O2 gases to be used in the same tool but not at the same time since mixing H2 and O2 gases can cause an explosion. This article describes a valving mechanism that allows both H2 and O2 gases to be connected to the same tool at the same time but does not allow the two gases to mix regardless of any failure mode, i.e., loss of electrical power, loss of compressed air or a tool malfunction. The significant component of the design of the valving mechanism is the "delay-coupling". The mechanism (Fig. 1) consists of two manually operated bellows-type sealed valves 11, 12, with a fifteen-pound spring return (contained within the valve), a double acting-double ended air cylinder 13 and two "delay-couplings" 14, 15. Fig. 2 shows an expanded view of "delay coupling" 14. Fig.