| 摘要 |
<p>712,733. Photo-electric pin-hole detectors. UNITED STATES STEEL CORPORATION. Nov. 24, 1952 [March 18, 1952], No. 29612/52. Class 40 (3) Apparatus for testing a roll of steel strip for pinholes with a photocell before being tinned and cut into sheets comprises means for marking the strip at the pinhole, and actuating a deflecting gate subsequently by means of a mark detector in combination with photocells sensitive to the leading and trailing edges of the sheet to deflect the reject sheet on to a reject pile. As shown, a strip of metal S is examined by a light source 20 and photo-cell 22, the presence of a pinhole producing a pulse which is amplified at 24 to actuate a magnetic marker 26 at approximately the same place on the strip as the pinhole. After treatment and shearing into individual sheets S', the magnetic mark on the faulty sheet S<SP>1</SP> is sensed by a detector 34 to produce via amplifier 42 a positive bias on a thyratron 44 to cause it to conduct, whereupon a negative pulse is sent to the grid of a further thyratron 50. When the leading edge of the faulty, marked sheet S' passes between a light 28 and photocell 30 a negative pulse is sent to the anode of valve 44 to extinguish this valve, thereby sending a positive pulse to valve 50 and causing it to fire, energizing a relay coil 56 in its anode circuit, followed by solenoid 60 to actuate a deflector gate 14. The trailing edge of the marked sheet produces a pulse in a further photocell 32 which is amplified at 64 to extinguish valve 50, thereby restoring the gate 14 to its normal position. The strip marking may be other than magnetic.</p> |
