Patent GB-1173752-A (GB)
Title: Improvements in or relating to the Formation of Webs
IPC: D04H1/72
Filed: 1966-11-09
Abstract: 1173752 Web forming apparatus; calender rollers CANADIAN INTERNATIONAL PAPER CO 9 Nov 1966 [10 Nov 1965] 50121/66 Headings D1R R1F2 R1C3Y and R1C3B A web of fibrous material e.g. for incorporating in a diaper is formed by conveying loose fibrous material in an air-stream to a moving air pervious carrier and depositing said material on a first area of the carrier in a greater thickness than in an adjacent area, the areas being adjacent transverse of the direction of movement of said carrier. As shown fibres in an air-stream are passed along a duct (32) of increasing height see Fig. 1 (not shown), to a duct (60) transversely of the end of which an air permeable carrier (44) moves see also Fig. 9 (not shown). Behind carrier (44) is an arrangement of suction tubes 206, the suction effect of which can be varied individually by valves 208 which allow limited communication with a suction duct (190). In opposite walls of duct (60) are adjustable baffles (46) which disturb the air-flow in duct (60) so that there is a high speed central current and slower speed edge currents. To prevent movement of fibres along the face of carrier (44) the central column of tubes (206) is arranged to provide a greater suction than the flanking tubes; thus a greater volume of air is drawn through the central region and a central portion of greater depth formed. The width of the central portion may be adjusted by movement of the baffles (46). Adjustment of the width of the web may be obtained by movement of pivoted wall sections (158). Adjustable plates (234) lie beneath each edge section of carrier (44) so that the pressure in balancing chambers (152) can be adjusted, preferably so that there is a slight flow of gas past the ends of wall sections (158) into duct (60). The vertical bars on a grid plate (148) covering suction tubes (206) are beveled at alternating angles Fig. 12 (not shown), to make more gradual pressure differentials between the areas of high and lowpressure. In a second embodiment, Figs. 18-22 (not shown), the carrier is partially shielded from the fibre carrying air-stream by wedge-shaped shields. Compressing rolls Upon bearing grid 148 the web passes beneath three pressing rolls (252, 250, 252) Figs. 15, 16, 17 (not shown), the three rolls have the same diameter but the centre roll having its axis further from the web to accommodate the raised central portion of the web. A mounting and driving arrangement is described whereby the three rolls are driven at the same speed. Spring blades are provided to clean the rolls. Producing the fibre stream One or two sheets of sheet pulp (86) Fig. 4 (not shown), are moistened in a device (80), shredded by a device (82) which is also provided with an air intake which permits mixing of air with the stock and the shredded pieces ground in a mill (84). The fibres are then dropped into a Venturi-shaped section (72), Fig. 1 (not shown), to be taken up in an air-stream recirculating through the apparatus. A perforated disc (74) is placed in the duct prior to the point where the fibres are introduced. The air having passed through the carrier (44) passes to a duct (190), to a blower which circulates the air, to an air processing device and then returns to duct (32) in which the fibre is introduced.