GB848102A - Improved gas mixing device - Google Patents

Abstract

848,102. Gas burners. AMAL Ltd. June 18, 1958 [June 19, 1957], No. 19281/57. Class 75(1). [Also in Group XXIX] In a gas mixing apparatus comprising an air jet 3 supplying air into a mixing chamber 2 and inducing therein combustible gas through apertures 4, the supply of combustible gas to the mixing chamber is supplemented by an additional supply controlled by pressure sensitive means operated by the pressure of the air supply. The gas apertures 4 are formed in an annular chamber 5 which is fed with a first supply of gas by a jet 6 and with a second supply of gas through a pipe 7 extending from a lower chamber 15 in a body 12 divided by a flexible diaphragm 16. The lower chamber 15 is connected by pipes 14, 14a to the gas jet 6 and an upper chamber 21 in the body 12 is connected by pipes 9, 10 to the air jet 3. The diaphragm operates a piston valve 18 controlling the flow of gas into the pipe 7 and comprising a piston 24 having an axial passage 23 and radial passages 26 and a cylinder having radial passages 27, 28. When the air pressure in the upper chamber 21 drops the piston rises to open first the lower radial cylinder passages 27 to the pipe 7 and then to open the upper radial cylinder passages 28 to the radial piston passages 26. The device maintains the gas/air ratio constant over a wide range of air pressures. The mixture passes from the mixing chamber 2 to a burner tube 1. The lower chamber 15 may be fed with gas which is different from and/or at a different pressure from the gas supplied to the jet 6. The piston valve may be replaced by a needle valve or a combination needle and piston valve. A needle may rest on the upper end of the piston valve and slide in a closed transparent tube fitted to the body 12, the arrangement serving to indicate the pressure of the air above the diaphragm. A by-pass gas supply for a pilot flame is provided by radial ports 29 located in a part of the piston clear of the cylinder and communicating with an extension 23a of the axial passage 23.