| 摘要 |
1,168,813. Automatic control of coating. UNITED STATES STEEL CORP. Nov.1, 1966 [Nov.10, 1965], No.48945/66. Heading G3R. In a system for coating a moving strip of material in a vacuum, the intensity of an electron beam heating metal in a crucible adjacent to the path of the strip is automatically controlled in dependence on the speed of the strip to keep the coating thickness constant. In Fig.1, strip 14 passing through an evacuated chamber 10 is coated on both sides with metal deposited from vapour generated by crucibles 17, 18. The crucibles are heated by beams from electron guns 19 which are suitably deflected by electromagnets 20. Each crucible has five electron beams arranged transversely relative to the direction of strip travel, those further from the centre of the strip being of greater power so as to produce a uniform coating. This distribution of power is produced by suitably biasing magnetic amplifiers controlling the supply to the gun filaments. Deviations of coating thickness are detected by gauges 23 which control, through systems including servos 60, three potentiometers, Fig. 1a (not shown), adjusting the HT and filament supplies and the rate of feed of wire 21 associated with the appropriate crucible. The automatically controlled quantities are suitably modified to suit the speed of the strip by applying the output of a tachometer generator 24 to the system controlling the three potentiometers. Manually adjusted potentiometers 63, 64 further modify the automatically controlled quantities in accordance with the width of strip and thickness of coating desired. Selector switches (not shown) are provided for modifying the automatically controlled quantities to suit the number of crucibles in use. One of the three servo-controlled potentiometers adjusts, through a saturable reactor, the datum of a closed loop system controlling the total HT power supplied to all five guns. A second potentiometer adjusts the datum of closed loop systems controlling the current supplies to the gun filaments. A Zener diode is arranged so that HT variations outside a predetermined range modify the filament currents. The third potentiometer adjusts the datum of a closed loop speed control system associated with a motor 56 so that wire 21 is fed to the crucible at a suitable rate. A current regulator 67 associated with electromagnets 20 is automatically varied in dependence on the HT power supplied to the guns. Tachometer generator 24 also modifies the "off" time of a photocell-operated timer 65 so that servo 60 is interrupted for periods sufficient to permit corrections at the crucible to be detected by gauge 23. The strip is pre-heated to a desired temperature by electron guns 15 the different powers of which are automatically controlled by a temperature detector 22 arranged in a control system similar to those provided for controlling the crucibles. |
