Patent GB-191127281-A (GB)
Title: Improvements in and relating to Detectors of Combustible Gases.
Inventor: PHILIP ARNOLD
IPC: G01N27/16
Filed: 1911-12-05
Granted: 1913-03-05
Abstract: 27,281. Philip, A., and Steele, L. J. Dec. 5. [Cognate Applications, 1469/12 and 15,677/12.] Explosive and combustible gases, detecting.-In a draught-proof catalytic detector comprising a wire adapted to be heated by the catalytic combustion of the gas to be tested, and means for indicating the resulting change in the electrical resistance of the wire, the casing 43, Fig. 7, in which the wire is mounted is itself mounted in a relatively large chamber 41, which may be filled by a pump 47 with the gas to be tested. Layers of gauze 45 and asbestos fibre 46 are provided between the inlet from the pump and the chamber proper, so that the wire is supplied with gas, by the natural draught created by itself, from the sample atmosphere in the chamber, unaffected by draught in the mine or fluctuations in the supply to the chamber. The indicating-apparatus in the form of a galvanometer 50 is mounted on the casing 41, together with adjusting devices contained in a casing 51 and operated by buttons 52, 53. In a modified form of the apparatus, the active and inactive wires, which are preferably arranged in the form of a wheatstone bridge, are mounted in a tube 1, Fig. 1, closed at the ends with gauze 12. The active wires may be mounted in the upper half of the tube 1 and the inactive wires in the lower half, the two sets of wires being separated by a gauze layer 12. The inlet and outlet 9, 9 for the gases both face in the same direction and are protected by gauze, an inner passage 10 being provided in both inlet and outlet pipes to prevent moisture from entering the tube 1. For further protection against draught, a separate member 13 may be attached to the inlet and outlet pipes 9, this member having itself a protected inlet and outlet at different levels from the pipes 9. The lower part of the casing forms a handle containing a switch 15 for opening or closing the circuit through the wires, and the upper part carries a pith ball 18 for indicating the direction of the draught and when the apparatus is in use, the inlet and outlet are turned away from the draught. In another modification, the active and inactive wires are mounted in parallel casings 33, Fig. 5, with protected openings 37, these openings being symmetrically arranged with regard to the inlet and outlet 39 of the apparatus, which, as before, both face in the same direction so that they may be turned away from the draught. The complete detecting apparatus is in three parts which are connected by flexible conductors, namely (1) an ordinary miner's lamp and battery, (2) a galvanometer, and (3) the detector proper. The lamp may be carried in the hand, and the other two parts suspended from the shoulders by means of the flexible conductors. A valve may be provided for controlling the admission of gas to the tube 1, and the valve may be controlled with the switch 15 so that when one is open the other is closed. Specifications 22,129/06, 5142/10, and 3002/13 are referred to. Provisional Specification 1469/12 states also that the inlet and outlet pipe may be V-shaped at their outer ends. and each provided with two hinged flaps, one of which covers the upper half, while the other falls back so as to leave the lower half open. Falling water is thus prevented from entering the apparatus.