Patent GB-1048630-A (GB)
Title: Improvements in or relating to paper machines
IPC: D21F3/04
Filed: 1963-07-31
Abstract: 1,048,630. Rollers. BELOIT CORPORATION. July 31, 1963 [Feb. 14, 1963], No. 30431/63. Heading F2U. [Also in Divisions D2 and F4] An imperforate paper machine press roll 22 presents to a felt and paper web, or felt only, pressure nip N-3 a peripheral surface portion having a water-retaining helical groove 22a of axial width at the roll periphery narrower than the adjacent land 22b axial width at said periphery. The groove may be formed in a solid elastomer (rubber) or, for fine grooves, stainless steel cover, on an imperforate ductile iron shell. The description includes recommended groove and land proportions. The groove may, if relatively deep, have a slow taper so as to increase in width towards the roll axis. The land edges are preferably sharp. The groove bottom is rounded or square. In the arrangement shown, a web W-6 and a felt 23 are pressed between a plain roll 21 and the grooved roll 22. Water savealls 25a, 25b, 25c are provided. A resilient flat sheet wiper 29a secured to a cross-bar 29b is urged against the roll surface land so as to diverge slowly from the roll in the rotational direction thereof, thereby creating a partial vacuum so that, assisted by centrifugal and gravity forces, inrushing air sweeps water from the grooves into the saveall 25b. Water remaining on the roll surface land is removed by a conventional doctor blade 30. In Fig. 8 (not shown), the grooved roll is uppermost and a further doctor blade is provided for the plain roll. In a " divided " press, Fig. 9 (not shown), the felt is additionally de-watered by pressing between a further plain roll and a further grooved roll. In Fig. 10 (not shown), the arrangement is similar to that of Fig. 9 (not shown), except that it is a hot-press and the felt and paper web nip has a stainless steel grooved roll cover; further, there is provided a manual or automatic valvecontrolled shower for watering the felt and fluid actuation of the grooved rolls for control of the pressure at the nips. The shower and nip pressure may be controlled automatically, through a control panel responsive to a felt moisture detector signal, or manual-pneumatically by an operator reading moisture content. The two grooved rolls may be anti-deflection mounted, being supported axially inwardly of the roll ends. In Fig. 11 (not shown), a " divided " press comprises a single grooved roll co-operating with two plain rolls. In Fig. 12 (not shown), a " divided " press comprises a grooved roll co-operating at the top (web and felt) nip with a plain roll and at the bottom (felt only) nip with a further grooved roll, the top and bottom rolls being anti-deflection mounted and fluid actuated for nip-pressure control. In an overall press assembly, Fig. 13 (not shown), a web is picked up from a forming wire and then passed through 1st, 2nd and 3rd presses using successively higher nippressures. In the 1st press a pick-up felt, the web and a lower press felt are pressed between a grooved roll and a suction (or grooved) roll to transfer the web to the lower press felt, the pick-up felt passing through a felt only nip, defined by a plain roll and a suction (or grooved) roll, and round a further suction roll. The 2nd press is substantially as that shown. The 3rd press is a " divided " press comprising a web and felt nip similar to that of Fig. 8 (not shown) and a felt only nip similar to that in Fig. 9 (not shown). In this assembly there is provided anti-deflection roll mounting and, for automatic, semi-automatic or operator press control, moisture content detecting devices, control panels and showers. A chaser for cleaning the roll helical groove during operation comprises a wood block having shallow, outer, metal guide strips locating in turns of the groove and a central groove-bottoming metal cleaning strip. The block has a leading edge for retention of the chaser against the doctor blade 30 or a separate fixed guide. The chaser is started at one end of the roll, is screwed along axially of the roll, and is taken off at the other end of the roll. The chaser is preferably disposed on the approach side of the doctor blade and, to avoid its dropping off, is preferably disposed on the down-running side of the roll so that it is urged by gravity in addition to frictional drag.