Patent GB-393411-A (GB)
Abstract: 393,411. Control of D. C. motors. LINDE AIR PRODUCTS CO., 30, East 42nd Street, New York, U.S.A.-(Assignees of Bucknam, J. H.; 19, Stratford Road, and Young, L. W. ; 2439, Delaware Avenue, both in Buffalo, New York, U.S.A.) May 27, 1932, No. 15051. Convention date, June 8, 1931. [Class 38 (iii).] In welding the longitudinal seam of a tube W fed by rolls F through a variable speed electric motor M under a blowpipe B and welding rod D or under an automatically fed arc electrode, the radiant energy, either in the form of light or red and infra red radiations, emitted by the work immediately ahead of the weld are focused on a photoelectric cell C or on a selenium cell or an electrical pyrometer, the current produced, which may pass through a thermionic amplifier A, being connected through an indicator such as the coil 16 of a milliammeter, the pointer 19 of which moves over a scale 18. Any variation of the pointer from the zero or from a pre-determined position indicates to the operator that too much or too little heat is being applied, whereupon a rheostat H in the field of the motor is automatically adjusted. For this purpose the pointer 19 forms part of a relay, being connected to a battery T, the other terminal of which is connected via solenoids 26, 27 and lamps 50, 51 of different colours to contacts 30, 31 co-operating with a contact 32 on the pointer 19. Either of the solenoids may thus be energized to close either the switches 35, 36 or 37, 38 so as to apply current in either direction to the armature of an auxiliary motor K, which adjusts the rheostat H through worm gear. The rheostat may also be manually adjusted. In a modification, the solenoids are respectively connected to switches co-operating with a pair of fixed resistances in series in the field of the feed motor, one switch normally short circuiting its resistances, and the other being normally open. In a second modification having an amplifier A receiving current from 220 volt direct current mains L, L<1>, and a relay E, the solenoids 271, 261 are connected to the mains through the major portion of a high resistance 60. The solenoids control respectively normally open contacts . 65-68, and normally open contacts 61-63 and a normally closed contact 64. A two position switch J is also used having blades 72-74 engaging either with contacts 72<1>-74<1> or 72<11>- 74<11>. When the switch is in the former position the solenoids close either of the contacts 61 or 65 so as to light up a red or a green light 511, 501 to act as a signal to the operator, whereupon the rheostat H is manually adjusted. When the switch is in its second position the contact 64 is either opened by the solenoid 261 so as to put in the resistances 54<1> or the reistance 55<1> is short circuited by closing the contact 66 by solenoid 271 so as to obtain a small amount of speed change instantly. The speed change may be continued by an auxiliary motor K<1> connected to the rheostat, the current through the armature of which may be reversed through the closing of contacts 62, 63, or 67, 68. An adjustable resistance 53<1> may be automatically inserted in the field at the tail end of the weld by mechanism which opens a normally closed switch 94 so as to speed up the motor to allow for overheating at the end of the work.