US 2990013 A
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Description (OCR text may contain errors)
June 27, 1961 H. F. RANCE ETAL 2,990,013
PAPER MAKING MACHINES Filed June 22, 1955 3 Sheets-She 1 June 27, 1961 H. F. RANGE ETAL 2,990,013
PAPER MAKING MACHINES Filed June 22, 1955 3 Sheets-Sheet 2 June 27, 1961 H. F; RANGE EI'AL 2,990,013
PAPER MAKING MACHINES Filed June 22, 1955 3 Sheets-Sheet 8 United Sta e P w 2,990,013 PAPER MAKING MACHINES Herbert Frederick Rance, Merrik Burrell Baggallay, and
William Frederick Edward Robinson, London, England, assignors to Bertrams Limited, Edinburgh, Scotland, a British company Filed June 22, 1955, Ser. No. 517,221 Claims priority, application Great Britain July 8, 1954 Claims. (Cl. 162-307) The invention relates to paper making machines of the kind in which the paper, formed fi'om pulp as a continuous web on a travelling endless wire mesh band or on a wire mesh drum and, after removal of some of the water,'is transferred from the wire to a travelling receiving surface, usually a felt.
It is an object of the invention to improve the separation of the paper web from the wire. a
The invention is based on the appreciation of the facts that if the web is subjected to suction through the wire, water is sucked from the web and forms a film between the web and the wire, that this water facilitates clean removal of the web after release from the suction, provided that such removal is effected before re-absorption of the water is allowed to occur, and that if the web is transferred to the felt across a gap so that there is no pressure applied between the felt and the wire, there will be less tendency for the web to adhere to the wire or to be marked thereby and, further, unwanted trim from the edges of the web will not be transferred to the felt.
It is known in a machine of the above kind to remove the web fi'om the wire immediately after passing a'perforated suction-couch but it is found that the perforations tend to produce shadow markings on the paper and separation may be more diflicult from the land areas between the perforations.
According to the present invention a machine of the above kind is characterised by the features that the receiving surface is spaced from the wire by a small distance at the transfer position and there is at, or immediately preceding, the transfer position a continuous transverse suction slot which draws water from the web into the wire over substantially the whole width of the web and so facilitates separation of the web and wire.
In a preferred form of the machine according-to the invention there is included a transverse slot closely or immediately following the suction slot for emission of compressed air to assist in separation of the web from the wire and transfer of the web to the felt. It is further preferred that the air slot extends across the full width of the web and the arrangement may be that the air is emitted continuously during the operation of the machine.
In one construction of the machine according to the invention the web-carrying wire passes over a perforated suction couch before reaching'the suction. slot aforesaid and there is a sufficient distance between the couch and the slot for local inequalities in the water content of the web caused by the couch and which might result in shadow markings in the final product, to become sufliciently 2,990,013 Patented June 27, 1961 2 said suction slot at or immediately before the transfer position... If desired both a suction box or boxes and a suction couch roll may be used.
By way of example of how the invention may be carried into effect there will now be described with reference' to ;the accompanying drawings, a box embodying suction and compressed slots and some specific applications of this box to paper making machines.
In the drawings IFIGURE l is a side elevation of the box,
., FIGURE 2 is a plan view showing a part of the box, FIGURE 3 is a section on the line 33 in FIGURE FIGURE 4 is a view of one of the end cover plates for the box,
' FIGURE 5 is a diagram showing the application of the box to a paper making machine,
FIGURE 6 is a diagram showing the application of the boxto a modified'form of machine, and FIGURE 7 is a diagram showing another application of the box.
i and at each end are provided with flange plates 21, 22.
Acover plate 23 is attached to the flange 22 to form a closure for the ends of the channels and a plate 24 is bolted to the flange 21. The plate 24 has pipe connections 26, 27 for suction and air respectively which lead equalised to avoid production of such markings. ,The
distance required for this purpose varies considerably with the speed of operation of the machine and other factors such as the kind and weight of paper being made. It may for example be between three inches and two feet. A distance of twenty to twenty-four inches is comslots over which the web passes before reaching the aforethrough ports 28, 29 to the ends of the channels 16, 17.
Cover plates 30 close the mouths of the channels at each end of the box and plates 31 screwed to the edges of the plates replace the distance pieces 13, 14 for a short distance at each end.
Secured to the upper edges of the plates 10, 11 and 12 there are metal channels 33, 34, 35 which hold laminated plastic strips 36, 37, 38 defining slots 39, and 40 for the suction and air, the air slot 40 being narrower than the suction slot 39. The ends of the slots are defined by short cross strips 42 of plastic.
Brackets 43, 44 are secured to the side plates 10 and 11 and provide means by which the box may be secured to the frame members of the machine. The brackets have slots 45 for securing bolts and the brackets 44 have adjusting screws 46 by which the box may be adjusted in position lengthwise of the machine before the bolts are tightened.
In one machine embodying the invention, see FIGURE 5, the web-carrying wire 50 is taken around a perforated suction'couch roll 51 and then along a downward sloping path to a lower, driving roll 52. At a position intermediate between the couch roll 5-1 and the driving roll 52 there is located a suction and compressed air box 54 as above described with the suction slot 39 preceding the compressed air slot 40. The slots extend cross-wise and below the wire. Immediately opposite to the box there is a vacuum transfer roll 56 around which there passes an upper felt 57. The felt is a short distance (i.e. /2 inch or less) from the'web carried on the wire 50.
In use some of the water is extracted from the web into the couch roll 51. The web then passes to the suction and air box, there being sufiicient distance (e.g. one to two feet depending on the speed of travel of the web) between the couch roll and the box for sufficient equalization of the Water content of the web to avoid the production of shadow marking. As the web passes over the suction slot 39, water is extracted substantially evenly tween the web and the wire. The web then passes immediately to the compressed air slot 40 and is readily separated from the wire by the air and blown on to the felt 57 as the latter passes over the vacuum transfer roll 56. The web then passes to a press embodying" a lower felt 58 and a suction roll 59 by which further water is ex-. tracted. The trim which lies outside the ends of the suction and compressed air slots remains on the Wire and may be removed from the wire when it passes over the driving roll and run to a hog pit 60 from which it may. be pumped back forimmediate re-use. I
In the modified form of-the machine as just described, shown in FIGURE 6, the upper felt5 7 is replaced by a lower felt 62 which passes around a roll 63 opposite to the box, the roll not necessarily being ofthe vacuum type. The web is blown onto the top of the felt and runs with the felt through a plain press 64, 65. a
In another example of the machine according to the invention, shown in FIGURE 7, the web-carrying wire 70' passes in a horizontal run firstly over two suction boxes 71,72 and then to the above described combined suction and compressed air box .73. The air blowsthe web 74 upwardly on to a lower 'felt 75 which passes over a roll 76- spaced a short distance above the wire. The wire then continues to a driving roll 7 7. No suction roll couch is employed in this example. The felt carries the web to a plain press 78, 79. The invention is particularly suitable for the use in the manufacture of very light weight or very wet beaten papers and has the advantages that the formation of shadowmarkings may be avoided or reduced, damage to the under side of the paper at the point of release-from the wire is reduced, wire marks resulting from the pressure of a transfer roll on the web are avoided, damage to the felt or wire due to lumps passing beneath the transfer roll is reduced, difficulties due tothe transfer of trim to the pick-up felt are avoided and the trim may be removed from thewire in a form convenient for re-use (i.e. without requiring to be separated from water employed to wash the-trim off the wire). a
The invention is not restricted to the construction details of the above examples. For instance the suction and compressed air'box may be built up from round suction tube divided into suction and aircompartment'sby a diametrical partition and the slots defined by one or more longitudinal-strips covering longitudinal openings-in the walls of the tubes. In the case of the first described machine the drive roll may be replaced by an idling roll andthe wire driven by othermeans. We claim: r
1. In a papermaking machine of the kind comprising a travelling endless'wire mesh onwhich' pulp is-carried and'partly dried to forma continuous paper web, and at a transfer position where the mesh follows a substantially straight path, a travelling receiving surface to which the web'is transferred from the wire, thecombination of a suction box having continuous transverse suctionslot located immediately beneath the wire'and immediately before the transfer position to draw water from the web into the wire over substantially the whole width of the web .with the feature that the receiving surface is spaced a small distance, greater than the thickness of the web, from the wire. 1
2. A paper makingmachine as claimed in claim -1 and includinga compressed air box having a slot immediately following the slot ofthe suction box for emission of compressed air to assist inseparation of the-web from the wire.
3. A paper makingmachine as-claimed in claim 2 in which theslotof the compressed" air box extends across substantially the full width of the "Web;
4-. A paper making machine as claimed in claim- 1 and including at least one'additional suction devicehawinga slot-over which the web-carrying wire passes before reachingthe transfer position, to-effect' a-preliminar'y're ductioncfthe'water content of the web.
5. A machine as claimed in claim 1 in which there is, at the transfer position, a combined suction and compressed air box providing a transverse suction slot immediately followed by a transverse air slot, the box comprising three parallel transverse. plates, distance pieces which space the plates apart to provide two channels, means for connecting one channel to a source of suctionand; the other to a source of compressed air' and means confining the mouths of the channels to narrow slots extending transversely beneath the wire. i
6. A machine as claimed in claim 1 including a perforated suction couch roll around which the web-carrying wire passes on its way to the transfer position, a wire driving roll around which. the wire. passes after'leavi'ng the transfer position, a box having a slot for emission of compressed air located? immediately after the'slot in the suction box at the transfer position, a vacuum transfer a roll at the'transfer position and spaced from. the; wire and an upper felt which passes around the transfer roll spaced a short distance from the .wire and to which the web is transferred.
7. A machine as claimed in claim 1 including a perforated suction couch roll around which the. web. carrying wirepasseson its way to the transfer position, a web driving roll: around which the wire passes after. leaving the transfer position, a box having aslot for emission of compressed air located immediately after the suction slot at thetransfer position, a transfer roll at the transfer. position and spaced from the wire and a lower felt which passes around the. transfer roll spaced a short distance from the wire and toiwhich the web is transferred.
8. A machine as claimed in claim 1 including at least one preliminary suctionbox having a slot over which the web-carrying wire passes in a run to the transfer position, a compressed air box having a slot following the suctionslot' at theitransfer position, -a roll spaced a short distance from the wire at the. transfer position and a lower felt which passes around the roll spaced a short distance from the wire and to which the web is transferred.
9. A paper making machine as claimed in claim 1 and including a perforated suction couch over which the web-carrying wire passes before it reaches the slot of the suction box, the length of the path of the wire between the couch and the slot being between three and twentyfour inches.
10. In a paper making machine of the kind comprising a travelling endless wire mesh on which pulp is deposited-,toform a continuous paper web, a perforated suction couch roll over which the web-carrying wire passes and a travelling receiving surface to which the web is transferred from the wire, the combination of the feature that the receiving surface is located at a position spaced apart along thewire from the couch roll with a suction box having -a continuous transverse suction slot immediately beneath the wireat the transfer position to draw water from the web into the wire over substantially the whole width of the web.