GB1238757A - - Google Patents

Abstract

1,238,757. Drying apparatus. J. M. VOITH G.m.b.H. 19 Nov., 1969 [20 Nov., 1968; 27 June, 1969 (2)], No. 56669/69. Heading F4G. [Also in Division F2] Web material is dried by being passed over a cylinder having a plurality of elements of higher thermal conductivity than the cylinder material arranged therein. A roller for a paper-making machine, Fig. 1, comprises a grey cast iron cylinder 1 and end plates 2. A hollow axle 4 running in bearings 6 supplies superheated steam to the inside of the cylinder through perforations '3. The steam and condensate is removed by a siphon tube 5. The heat flow to the surface of the cylinder 1 is improved by a plurality of copper pins 7 embedded in the internal surface and projecting into the steam flow. At the ends of the cylinder 1 where the wall is thicker, the pins extend further into the wall to provide an even heat flow right across the cylinder 1 (Fig. 2, not shown). The pins may be fixed into the cylinder by knocking a frustoconical pin (7) into a conically reamed sleeve (10) inserted into a bore (11) in the cylinder (Fig. 3, not shown). Alternatively the free end of the pins (7) may be formed with slightly oversize portions (16) or ribs (13) which deform when the pin is knocked into the bore (11) (Figs. 4-5, not shown). The other end of the pin may have a frusto-conical bore into which a conical pin (15) is forced to widen the pin and make a tight fit. The pin-may have an enlarged head (19) and a resilient seal between the head (19) and cylinder (1). In a further embodiment, Fig. 6, the bore into which the pin is knocked has a narrower inner portion 9. A sleeve of soft solder 7 is slipped over the pin before it is inserted. The pin is held in place by oversize ribs 6. When the casing is heated and rotated, the solder melts and is forced into the narrow portion 9 by centrifugal force. On cooling to normal operating temperature the solder solidifies forming a good thermal bridge. The heads of the pins may support heating coils (Figs. 8- 9, not shown). Ring segments may be used instead of pins, these being embedded in grooves in the outer surface of the cylinder. In this case a sintered metal layer is placed over the outer surface to prevent localized overdrying of the web (Figs. 10-11, not shown). The principle of improved thermal flow using these elements may be used to even out differences in thermal conductivity over the surface of a cast cylinder casing.