GB812053A - Improvements in or relating to oxygen cutting machine burner control - Google Patents

Abstract

812,053. Cutting by fusion. HANCOCK & CO. (ENGINEERS) Ltd. Aug. 4, 1955 [Aug. 4, 1954], No. 22576/54. Class 83 (4). [Also in Group XXXV] In a system for maintaining constant height of the nozzle of a flame cutting machine above a workplate, the burner is automatically raised. when sparking occurs between the workplate and an electrode associated with the burner, and is automatically lowered when sparking ceases. The nozzle 7, Fig. 2, of a flame cutting machine is movable in perpendicular horizontal directions over a workplate (not shown) and is supplied with oxygen through a pipe 24 and with pre-heating oxygen and acetylene through pipes 25a and 25b respectively. Nozzle 7 may also be rotated about the horizontal axis of a bearing 1 and may be moved vertically by a member 17 attached to a spring- loaded trolley (not shown) moving along vertical guides inside a casing 18. To maintain a constant height of the nozzle above the workplate, electrodes 34 attached to the nozzle and supplied at a high potential are automatically maintained in such a position that sparking to the workplate is just possible. A bellows 28 operated by the supply of pre-heating oxygen ensures that, when there is pre-heating, electrodes 34 are raised relative to nozzle 7 so that nozzle position is unaffected by the ionisation of the gas in the neighbourhood of electrodes 34. The effect of this ionisation is reduced by enclosing electrodes 34 in insulating sheaths 35 forming air pockets at the lower ends of the electrodes. The high potential applied between electrodes 34 and workplate 15, Fig. 5, is supplied by an induction coil 52. When sparking occurs the resulting current through a resistor biases a thermionic valve V to deenergize a relay R1 so that an electromagnetic clutch 43 is energized to couple a continuously running motor 45 (see also Fig. 4) to drive a winder drum 47 in such a direction that a flexible remote control cable 41 attached to the trolley within casing 18 raises nozzle 7. When sparking ceases the bias of valve V disappears and relay R1 changes over so that clutch 44 is energized to cause lowering of nozzle 7. The threshold sparking condition is thus maintained automatically and the sparks serve also to ignite the burner. Nozzle 7 may be raised and lowered under manual electrical control by operation of push-buttons 57 and 58 associated with a latching relay R2, R3. Contacts 60 operate to raise the nozzle if the supply of oxygen fails. In a modification a reversible electric motor replaces the continuously operating motor and the electromagnetic clutches. The Specification also refers to (a) use of a transformer instead of an induction coil to supply the high potential; (b) automatically reducing the high potential applied to the electrodes by transformer tap-changing or insertion of impedance instead of raising the electrodes relative to the nozzle when preheating oxygen is supplied; (c) addition of an auxiliary electrode to cause the nozzle to be raised automatically if the edge of the workplate is reached.