GB544860A - Improved method and apparatus for desurfacing, severing and like operations on ferrous metal bodies involving the combustion of metal - Google Patents

Abstract

544,860. Control of D.C. motors. LINDE AIR PRODUCTS CO. Jan. 25, 1941, No. 1001. Convention date, Jan. 27, 1940. [Class 38 (iii)] [Also in Group XXII] In de-surfacing or cutting a ferrous metal body W, as in Specification 494,990, [Group XXII], starting is facilitated by depositing molten metal on a long starting area, directing oxidizing gas on to said area, and displacing the gas nozzles 8 relative to the body W in a forward direction parallel to said surface and at right angles' to the length of said area. The work may be positioned by a roll conveyer 6 driven by a reversing motor 7 constructed and connected to have quick starting, a pre-set forward feed and a more rapid reverse all controlled by a hand-operated master switch MS. A press button PB initiates the de-surfacing, operating by eriergising a time-delay relay TD and relays X, Y which energize solenoids RF, PH to release iron or iron alloy rods N to fall into contact with the body W and open a valve V to admit heating gases to the nozzles 8, which may be ignited by a byepass flame. After a predetermined time the relay TD opens a switch TD2 and closes TD1, TD3 to stop the rod feed and energize solenoids CO, F to turn on the. cutting oxygen valve V1 and start the motor 7 in the forward direction. The operation may be stopped by press button S-PB. When shunt wound the motor 7 is started thus or by moving the switch MS from its normal position MSO to MSF the operation is effected by relay F closing a switch FC, in a circuit including the armature A, a portion R<SP>2</SP> of a dynamic brake resistance, a field fluttering relay coil FA, a starting resistance 47 and a relay coil 1A. As the motor accelerates the voltage across its armature will increase and close switch 1AS, thus short-circuiting 47, open 1AC, thus iritroducing a resistance 51 in circuit of F to prevent damage thereto. The field 52 is normally fully excited by a circuit passing through switch 1A2 but when coil 1A operates it opens this and the field is energized through a circuit .including contacts CR1 and rheostat 53. This causes a rise in armature current and speed and the switch FAC to close, thus short-circuiting the rheostat 53. The consequent increase of speed and decrease of armature current will cause the switch FAC to open and the process will be repeated until the motor reaches the pre-set speed. When the armature A is not energized this and the resistance 46 are in a closed circuit to apply a dynamic brake. When the switch MS is in the reverse position MSR relay R closes switch RC1 so that current passes through the armature in the reverse direction, the circuit including resistance R3, the coil FA and the resistance 47. The field fluttering relay acts as before but if no de-surfacing is done during reverse a relay CR in parallel with R operates switches CR1, CR2 to introduce resistance 71 - in the field circuit in place of 53 and give a higher final speed. The circuit of the coil CR has a current limiting resistance 62 and of the coil RF, a resistance introduced by the mechanically operated switch RFC. The gas and oxygen pipes may be cleared before commencing operations by moving a hand switch PS into positions PH and CUT-OX to close contacts PS-1 and PS-2. The rods N may be 3/16th inch in diameter or be replaced by ribbons, which may be fed positively with their edges or flat sides to the flames and may be greater, equal, or less in number than the nozzles 8. For desurfacing areas to a pre-determined pattern, nozzles may be turned off and on as required. The relay TD may be replaced by a switch operated by a synchronous motor or fluid escape device.