Patent GB-571537-A (GB)
Title: Improvements in or relating to apparatus for applying elongated particles such as abrasives to webs
IPC: B24D11/00
Filed: 1943-05-10
Abstract: 571,537. Coated fabrics. CARBORUNDUM CO. May 10, 1943, No. 7415. Convention date, May 9, 1942. [Class 140] [Also in Group XXIII] Apparatus for applying elongated particles such as granular or fibrous materials or bristles to a web as of paper, cloth, or vulcanised fibre, of the kind wherein an electrostatic field is used in conjunction with mechanical vibratory means to orientate the particles with their longer dimensions normal to the web, comprises a feed table which is vibrated so as to cause the particles to move along it progressively, means for feeding an adhesive-coated web in the direction of progression of the particles so that its coated face is downwardly directed towards the table, and means to create a high-tension electrostatic field between the surface of the table and the web so as to project the particles upon the web. The apparatus described includes also means for feeding the particles from a hopper to the table, means for regulating this feed and also the amplitude of vibration of the table, and means for drying the product. In the form shown, the web is drawn from a roll 2 over guide rollers delivering it between coacting rollers 6, 7 of which 6 dips into a pan of adhesive 9. The coated web 1a is fed via guide rollers beneath an electrode 12 of good electrical conductivity, e.g. metal, the coated surface of the web facing a table 15 on the underside of which are disposed one or more electrodes 16' of good electrical conductivity, e.g. metal sheets or sprayed-on metal, connected to bus bars 17' by flexible conductors 19 any one of which may be disconnected to vary the extent of the electrostatic field. The electrodes 12, 16' are connected to mains L<1>, L<2> supplying a highundirectional, intermittent, or alternating e.m.f. which may be 20,000 volts or higher. The table 15 is of non-conducting material such as wood, or the materials known under the registered Trade Marks Bakelite and Micarta, or fibrous material bonded with such materials; it is supported by tilted steel springs 22 secured to a base 23 mounted on rubber blocks 24; and it is vibrated in a direction which, owing to the inclination of the supports 22, makes an acute angle with the direction of feed of the web 1b by an electromagnetic vibrator 25, the stator of which is fed by an alternating current from supply mains L3, L4 through a regulator 34 which permits variation of the amplitude of vibration. The particles are fed to the table from a hopper 27 having a feed-gate 28 which is similarly vibrated in a regulable manner by a vibrator 29; and because of the vibration of the table on its tilted supports 22, the particles are fed along it in a series of saw-toothed hops. On reaching the electrostatic field between the electrodes 12, 16<1>, the particles are projected upward on to the adhesive face of the web 1b; upstanding edges 17 on the table prevent lateral escape of particles, and the surplus is delivered finally into a bin 37. The web proceeds over further guide rollers including a suction drum 38 to a conveyer 41 which loops it on sticks delivered successively to a travelling rack 40 in a drying chamber. An alternative apparatus is described in which the table 15 is itself inclined to the horizontal and is supported by leafspring assembles whtch are horizontally vibrated by electromagnetic means described in detail; the electrodes are similarly inclined, the upper electrode being carried by a frame supported at its corners so that these individually, or all four together may be adjusted to or from the table; and the particleintake end of the table carries an upwardlycurved baffle plate which co-operates with the table top and its upstanding edges 17 to form an enclosed particle duct terminating inwardly at or near the edge of the electrostatic field. Specifications 396,385, 433,128, 455,639, and 457,462, [all in Group XXIII], and U.S.A. Specification 2,161,342 are referred to.