GB896869A - Improvements relating to apparatus for testing the caliper of a paper web - Google Patents

Abstract

896,869. Feeding webs; delivering sheets. WARREN CO., S. D. April 27, 1960 [May 13, 1959], No. 14804/60. Class 100(1) [Also in Group XIX] Apparatus for detecting abrupt changes in caliper of a moving web of paper as it passes over a roll comprises a pivotally mounted skid capable of bearing lightly against the web and at least the part thereof which engages the web being flexible, and a transducer mounted on the skid and responsive to flexing of the skid caused by an abrupt change in caliper of the web to produce an electrical signal indicative of the abrupt change. As shown the web 6 passes over a roller 4 above and parallel to which is mounted a beam 2. A series of brackets 10 is secured to the beam and on these brackets skids 14 are pivotally mounted. Each skid comprises two thick plates 16, 18 between which is sandwiched-one end of a rectangular metallic plate 22. The other end of the plate 22 is formed with a lip 40 to prevent longitudinal flexing of the plate and rests lightly on the web 6. A crystal-type gramophone pickup cartridge 46 is mounted by means of a bracket 56 on the plate 16. An L-shaped wire rod 68 is secured at one end in the hole in the cartridge normally occupied by the gramophone needle and at the other end carries a hexagon nut 76 in which is threaded a screw 78. The screw 78 is turned down into contact with the plate 22 at a point about half-way between its side edges. When a bump occurs in the web 6 it causes the plate 22 to flex momentarily about a line parallel to the front edges 42 of the plates 16, 18 which in turn causes distortion of the crystal in the cartridge 46. This distortion is translated into an electrical signal which is transmitted through a band pass filter and amplifying devices to a magnetic recorder. Instead of being recorded the signal may be applied to work an alarm system or a warning light. The band pass filter passes only signals between 200 and 2000 cycles since signals generated by bumps in a web concentrated in that band.