US2843025A

US2843025A - Paper-making machines

Info

Publication number: US2843025A
Application number: US420132A
Authority: US
Inventors: Holden Herbert
Original assignee: Beloit Iron Works Inc
Current assignee: Beloit Iron Works Inc
Priority date: 1953-04-02
Filing date: 1954-03-31
Publication date: 1958-07-15
Anticipated expiration: 1975-07-15

Description

July 15, 1958 H. HOLDEN PAPER-MAKING MACHINES 2 Sheets-Sheet 1 Filed March 51. 1954 Inventor A tlorneys July 15, 1958 r H. HOLDEN PAPER-MAKING MACHINES 2 Sheets-Sheet 2 Filed March 31, 1954 Inventor 155588627 [fa/.05

By k Attorneys United States Patent PAPER-MAKING MACHINES Herbert Holden, Sheflield, England, assignor to B eloit Iron Works, Beloit, Wis., a corporation of Wisconsin Application March 31, 1954, Serial No. 420,132 Claims priority, application Great Britain April 2, 1953 2 Claims. (Cl. 92-49) This invention relates to paper-making machines of the type in which the paper web is removed from the forming wire by means of a vacuum pick-up roll and a transfer felt.

The usual arrangement has the vacuum pick-up roll so disposed as to bring the transfer felt into contact with the web on the wire either atthe periphery of the couch roll or in a run of the Wire from the couch roll to a forward drive (or return) roll, and the first contact of the transfer felt with the web is at the nip formed by the pick-up roll and the wire. There is thus at the nip simultaneous contactbetween the four elements: pick-up roll, transfer felt, paper web, and wire. In the case of pickup at the couch roll, there is simultaneous contact with a fifth element: the couch roll itself. In some cases, the pick-up roll is the bottom roll of a stacked press, into which the web is directly carried.

Pick-up at the couch roll has the advantage that the couch roll itself provides a firm backing for pressure to be applied to the web during transfer, the pick-up roll and the couch serving as a preliminary press section, with the vacuum applied primarily for the pick-up also serving to extract from the transfer feltwater expressed into it from the web. However, the newly-formed web may have some variations in thickness or small lumps of fibres, and damage to the web in such early stage of its formation may result from the localised pressure arising from the passage of these through a positive nip between the pick-up roll and the couch roll.

The object of the invention is to provide a vacuum pickup arrangement that gives a press action at the couch roll, and yet permits the passage of inaccuracies of the kind mentioned without damage to the web or wire.

According to the present invention, a vacuum pickup mechanism for a paper-making machine comprises a couch roll over which the forming wire passes, a transfer felt, a vacuum pick-up roll, and a guide roll for the transfer felt in advance of the vacuum pick-up roll, the guide roll and the pick-up roll in operative position lying clear of the forming wire by an amount greater than the thickness of the felt, which amount provides 'that a straight line tangential to the outer felted surfaces of both the guide roll and the pick-up roll would, for a portion of its length, form a chord of the circle provided by the lap of the wire round the couch roll.

This means that the couch roll must deflect the felt to something approximating to its own curvature in the span of the felt between the guide roll and the pickup roll. It also means that the web makes its first contact with the felt at a point between the guide roll and the pick-up roll and leaves the wire before the felt reaches the pick-up roll. Between these points, the web is sub jected to pressure exerted solely by an arc of felt conforming to the curvature of the couch roll (the web and the wire constituting intermediate arcs of similar length), and the felt thus forms a flexible bite, capable of passing lumps and variations in thickness without the same like- 2,843,025 Patented July 15, 1958 lihood of damage to the web or wire that arises in passage through a positive nip.

The invention will now be described in greater detail with reference to the accompanying drawings, in which Figure 1 is a vertical section through the pick-up mechanism of a paper-making machine before pick-up of the web commences;

Figure 2 is an elevation of one of the two end mountings of the pick-up roll and felt guide roll;

Figure 3 is a section corresponding to Figure 1 at the point when pick-up of the web commences;

Figure 4 is a further section corresponding to Figure l with continuous pick-up of the web; and

Figure 5 is an enlarged fragment of Figure 4.

In Figures 1, 3, and 4, a forming wire 10 carrying a paper web 11 passes over a couch roll 12 having a suction box 13 divided into two compartments 14, 15. A felt 16 is directed round a guide roll 17 to pass between the couch roll 12 and a vacuum pick-up roll 18 having a suction box 19. The pick-up roll 18 lies clear of the forming wire 10 at a distance greater than the combined thickness of the felt 16 and the paper web 11 by an amount 20 (Figure 1), so that the paper in passing between the pick-up roll 18 and the couch roll 12 is not subjected to any positive nip by the two

rolls

12, 18.

In Figure 2, the vacuum pick-up roll18 is mounted at each end in a housing 21 attached to a slide 22 adapted to be moved vertically on an upright 23 of the machine frame for setting of the pick-up roll position. The guide roll 17 is mounted at each end in a bracket 24 adapted to swing about a pivot 25 attached to a projection 26 of the housing 21. The roll is moved from one extreme position A of its axis to an opposite extreme position B by means of pneumatic cylinder 27 attached by a pivot 28 and a projection 29 to the housing 21, and an adjustable piston rod 30 attached to the bracket 24 by a pivot 31. Equivalent mechanical, hydraulic, or other means may also be used to effect the movement of the roll 17.

In Figure l, the guide roll 17 is in the position A, and the felt 16 is clear of the web 11 on the wire 10. Until pick-up takes place, the web 11 is repeatedly severed prior to reaching the couch roll 12 and the broke 11A is later doctored from the return run of the wire into a hog-pit (not shown).

Movement of the guide roll 17 to the axial position B,

' when it makes its nearest approach to the couch roll,

brings the felt 16 into contact with the web 11 over a small arc (Figure 3). The compartment 14 of the suction box 13 is under normal vacuum to remove water from the web 11, whilst the other compartment 15 is supplied with high velocity air to assist the suction pickup first of a starting tail (cut from the full width of the web by the usual jet cutter over the wire) by blowing it on to the underside of the felt 16, and later of the full width Web itself, by bringing the tail and then the web into reach of the suction applied by the box 19 in the pick-up roll 18.

When the starting tail, followed by the full width of the web 11, has been fed successfully through the machine, the compartment 15 is changed over from high velocity air blown outwards to low vacuum producing a high velocity flow inwards to remove any water in the meshes of the wire and in the holes of the couch roll, to prevent this water from being flung centrifugally back on to the Web 11 after the latter has passed the vacuum compartment 14.

In the normal running position (Figure 4) of the pickup mechanism, the felt 16 remains deflected approximately to the curvature of the couch roll 12 over a small are 32 in the span of the felt between the guide roll 17 and the pick-up roll 18. This means that the web 11 makes its first contact with the felt 16 at a point between the 3 guide roll 17 and the pick-up roll 18 and leaves the wire 10 before the felt 16 reaches the pick-up roll 18. Therefore, between these points, the web 11 is subjected to pressure exerted solely by the are 32 (seen more clearly in Figure 5) of felt conforming to the curvature of the couch roll 12, and the felt 16 thus forms a flexible bite. The thickness of the'web is normally less than the clearance 20 (Figure l), and the clearance allows for any variation in thickness, and also for the passage of small fibre lumps, which are therefore not crushed into the web at this early stage of its formation, there being flexibility in the contact between the felt 16 and the web 11 over the length 33 (Figure 5) of mutual contact directly following the are 32-.

The clearance of the pick-up roll with respect to the couch roll may be adjusted by raising or lowering the slides 22 according to the expected variation in web thickness or the size of small lumps or fibre. The position of the guide roll may also be adjusted in its nearest approach to the couch roll by the adjusting means 34 in the links 30 for varying the amount and extent of the deflection of the felt by the couch roll. The spacing of the centres of the

rolls

17, 18 is such as to produce the required amount and extent of the deflection of the felt 16 by the couch roll 12.

The flexible bite provided over the are 32 assists in expressing water from the web 11, and the compartment 14 of the suction box 13 extracts this water, including any pool forming between the web 11 and the felt 16 just in front of the arc 32. The compartment 15 discharges high velocity air through the perforations of the couch roll 12 and the wire 10 just beyond the contact length 33 and the air readily lifts the web (or its starting tail) into contact with the felt 16 when transfer is started.

The suction box 19 of the pick-up roll 18 covers an arc commencing opposite the centre of the length 33 and extending sufficiently to maintain contact of the web 11 with the felt 16 after the web has been lifted clear of the wire 10. Although the drawings show the felt 16 leaving the pick-up roll 18 on its way to a separate press section, the pick-up roll could be the bottom roll of a stacked press, in which case the felt 16 would continue in contact with the roll until it passed through the bite of that roll with the superimposed roll of the stacked press.

The arrangement is applicable both to machines in which the wire is returned by the couch roll and to machines in which the wire proceeds from the couch roll to a forward driving (or return) roll, the wire only leaving the couch roll after the felt and the web have left the wire.

What I claim is:

1. In a vacuum pick-up mechanism in a paper making machine including a suction couch roll, a forming wire for forming and carrying a paper web, said forming wire being looped around said couch roll to be held in contact therewith and to overlie the suction area thereof, and a transfer felt, the combination therewith of a vacuum pickup roll spaced from said couch roll in operating position by a distance slightly greater than the combined thicknesses of said wire, web and transfer felt to provide an open nip, said couch and pick-up rolls having closely adjacent overlying suction areas continuous respectively from immediately in advance of to beyond said nip, an

4 adjustable guide roll immediately in advance of said nip and having said transfer felt trained therearound to guide said felt into said nip and into its first contact with said pick-up roll, said guide roll in non-operating position holding said felt clear of said web carried by said wire and being so positioned in operating position that said transfer felt after leaving said guide roll first contacts the web on said wire backed by said suction couch roll while said wire is subjected to the suction effect of said couch roll in advance of said nip and the felt then passes into and through said nip and is subjected to the vacuum effect of said pick-up roll to be held thereagainst with the web transferred to said pick-up roll, said web at and beyond said nip being carried by said transfer felt free of said wire and said wire continuing in contact with said couch roll before, at and beyond said nip, whereby the web is not subjected to positive roll pressure at said nip.

2. A vacuum pick'up mechanism in a paper making machine having a forming wire on which the web is formed and conveyed, a suction couch roll around which said forming Wire is trained to lie in contact therewith and with the suction area thereof, a vacuum pick-up roll arranged in close proximity to said couch roll to form an open nip therebetween, a guide roll immediately in advance of said pick-up roll, means for moving said guide roll about said pick-up roll toward and away from said couch roll into operating and non-operating positions, respectively, and a transfer felt trained over said guide roll to be guided thereby into said open nip, said guide roll in non-operating position holding said felt clear of said web carried by said wire and in operating position guiding said felt first into contact with said web on said wire at the suction area of said couch roll and then into contact with said pick-up roll at the suction area of the latter, the operating positions of said guide roll, couch roll and pick-up rolls being such that a tangential line between said guide and pick-up rolls on the outer surface of said felt intersects an arc of said wire on said couch roll before said wire and felt reach a line joining the centers of said couch and pick-up rolls, the suction areas of said couch and pick-up rolls being so closely positioned in overlapping relationship in the area of the nip as to exert a substantially continuous suction effect on the web as the same is carried through said nip, said web at and beyond said nip being carried by said transfer felt free of said wire and said wire continuing in contact with said couch roll before, at and beyond said nip, whereby said wire, web and felt are not subjected to positive roll pressure at said nip.

References Cited in the file of this patent UNITED STATES PATENTS 1,991,346 Ellis Feb. 12, 1935 2,204,426 Millspaugh June 11, 1940 2,209,757 Berry July 30, 1940 2,415,350 Hornbostel et a1. Feb. 4, 1947 2,415,351 Hornbostel et a1. Feb. 4, 1947 FOREIGN PATENTS 232,059 Germany Feb. 23, 1910 499,657 Great Britain Jan. 26, 1939