GB578794A - Improvements in or relating to electrical devices for sensing holes in insulating sheet material - Google Patents

Abstract

578,794. Detecting, indicating, and locating faults. BRITISH TABULATING MACHINE CO., Ltd. Oct. 6, 1944, No. 19241. Convention date, Oct. 9, 1943. [Class 37] [Also in Group XIX] A device for sensing holes in insulating sheet material comprises a pair of contact members, one on each side of the sheet material, one contact member having a surface of an electrically conducting fluid adapted to be extruded through a hole in the sheet material to establish an electrical connection with the other contact member, the latter member having a surface not wetted by the fluid. The invention as applied to the sensing of perforated record cards comprises two rollers between which a record card C passes. The lower roller picks up a film of mercury from a bath 106 and, where a perforation occurs in the card, the mercury is extruded through the hole to contact the metal surface 35 of the upper roller and thereby complete a circuit through a wire 133, brush 113 (bearing upon one of a series of insulated rings corresponding with the columns of the record card), the mercury (or mercury amalgam) film, the mercury bath 106, and wire 132. The lower roller may be formed by a conducting sleeve 101, made from a metal wetted by mercury, disposed between an insulating sleeve 100 and a rubber sleeve 102 formed with cells 103 partly filled with substantially solid mercury amalgam 104 which picks up the mercury 108. Alternatively the rubber sleeve may be thinner and the mercury amalgam dispensed with, or the rubber sleeve also could be dispensed with in which case the mercury would be picked up by the metal sleeve 101. A surface of roughened rubber is also proposed or a metal powder may be incorporated in the rubber. A scraper 107 removes surplus mercury from the roller and a further scraper 116 removes mercury from the card.