GB2506490A

GB2506490A - Vacuum fluid extraction apparatus for a dandy roll

Info

Publication number: GB2506490A
Application number: GB201313346A
Authority: GB
Inventors: Stuart Robertson; Fred Bowden
Original assignee: Woollard & Henry Ltd
Current assignee: Woollard & Henry Ltd
Priority date: 2012-07-26
Filing date: 2013-07-26
Publication date: 2014-04-02
Also published as: GB201313346D0; DE102013214650A1; GB201213350D0

Abstract

A dandy roll (1) for use in the paper forming process used to consolidate the paper substrate and impart a watermark, comprises a hollow cylinder, comprising an internal perforated body (2) and an outer cover (3). The roll further comprises an internal chamber (8) within the perforated body and a vacuum device connected to the internal chamber for drawing water or other manufacturing fluids out of a paper substrate and through the roll as the paper substrate comes in contact with the outer surface of the dandy roll. The dandy roll is incorporated within a frame (4) which comprises a plurality of rollers (7) that contact the outer surface of the dandy roll as an aid to maintain a constant speed of rotation.

Description

IMPROVEMENTS IN OR RELATING TO PAPER FORMING APPARATUS

This invention relates to improvements in apparatus for forming paper or paper substrates and more specifically relates to an improved roller and more specifically still to an improved dandy roll and more importantly to an improved dandy roll which is particularly useful in the paper manufacturing industry.

The manufacture of paper or paper substrates typically begins with a pulp or slurry of material which is fed or pumped onto a moving conveyor bell where it is passed through several processing stations. A know type of machine is a Fourdrinier machine. Pulp is fed into the Fourdrinier machine on a moving bell of fine mesh screening. The pulp passes over drainage devices below the belt to drain off water. If the paper is to receive a water-mark, a light cylinder or roller covered by a material similar to a screen that is embossed with a pattern or electrotype known as a dandy roll moves across the sheet of pulp and presses a design into it.

The paper then moves onto the press section of the machine, where it is pressed between rollers of felts. The paper then passes over a series of steam-heated cylinders to remove the remaining water.

Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars. Finally) the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use.

Paper mills are continuously looking to improve their efficiency and to extend the weight range of the products they manufacture. One known way to achieve this is to fit a wire former onto a roller under which the paper substrate passes which improves the top surface of the paper substrate and also helps with water removal by applying a vacuum to the top of the sheet of the substrate whilst it is still in a wet state.

As noted above, watermarks can be formed during the manufacturing process by impressing a metal stamp known such as a dandy roll or cylinder mould onto the paper during manufacture.

Consolidating the surface and removing excess water allows the paper machine to run faster, improves the efficiency of the process and allows for heavier weight products to be produced.

Dandy rolls currently have two main purposes) they consolidate the paper substrate and/or impart a watermark to the substrate for branding or security purposes.

According to one aspect of the present invention there is provided a dandy roll for use in a paper forming process, the apparatus comprising a hollow cylinder, said cyllnder comprising an internal perforated body and an outer cover said roll comprising an internal chamber within the perforated body and a vacuum device connected to the internal chamber for drawing water or other manufacturing fluids out a paper substrate and through the roller as the substrate in contact with the outer surface of the dandy roll.

Advantageously the outer cover is perforated to allow fluid to pass through the cover from the outer surface to the inner surface and into the chamber.

Advantageously the outer cover of the dandy roll can be adapted to provide a watermark in the surface of a paper substrate as the roll rotates over the substrate.

Conveniently the outer cover comprises a wire or plastics mesh.

Advantageously the chamber has an inlet adjacent to the inner surface of the cover.

Preferably means are provided to establish a seal between the inner surface of the cover and the chamber.

Preferably the seal means comprises a longitudinal strip of material extending the length of the roll.

Advantageously the strip of material comprises plastics. Conveniently the plastics strip is resilient. Alternatively the strip of material may comprise a resilient material such as rubber.

Conveniently the internal chamber is mounted in a fixed position within the roll.

Preferably the internal chamber comprises a dam to prevent fluids from flowing out of the chamber.

Advantageously the vacuum device comprises a vacuum pump. Alternatively the vacuum device comprises a fan. In either case, the vacuum device is operated to establish a vacuum within the internal chamber.

Advantageously a frame is provided within which the roil is mounted for rotation relative to the frame.

Conveniently the internal chamber is connected to the frame such that the internal chamber is held in a fixed position. The arrangement is such that as the dandy roll rotates relative to the frame, the internal chamber is held in a fixed position by the frame. As the vacuum device is actuated) a vacuum is established within the chamber and fluids are drawn out of a paper substrate in contact with the outer surface of the roll, through the cover of the roll and into the internal chamber.

Preferably, a plurality of follower rollers are mounted on the frame surrounding the outer surface of the dandy roll to aid in maintaining a constant speed of rotation of the dandy roll. Conveniently three or more follower rollers may be provided equi-spaced around the circumference of the dandy roll.

Conveniently pipe work is provided between the internal chamber and the vacuum device to establish a vacuum within the internal chamber thus drawing fluids out of the surface of the paper substrate and into the internal chamber.

According to a second aspect of the present invention there is provided a paper forming apparatus comprising a dandy roll according to the first aspect of the invention.

Features of the first aspect of the present invention may be incorporated into an apparatus according to the second aspect of the invention.

According to a third aspect of the present invention there is provided a method of forming paper or a paper substrate comprising the step of passing a dandy roll according to the first aspect of the present invention over the paper substrate and operating the vacuum device to draw water out of the surface of the paper substrate, through the outer cover of the roll and into the internal chamber.

An embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic part cross-sectional view through a dandy roll according to one embodiment of the present invention; Figure 2 is a further schematic cross sectional view of the dandy roll of figure 1 showing a further internal chamber; Figure 3 is a schematic end view of the frame for mounting the dandy roll of Figure 1 in position; Figure 4 is a schematic view of the other end of the frame of Figure 1. from that shown in Figure 3, and Figure 5 is a schematic front view of the dandy roll of Figure 3.

Turning now to the figures there is shown in Figures 1 and 2 a dandy roll 1 according to one embodiment of the present invention. The dandy roll comprises a hollow cylinder. A hollow clylindrical perforated shell 2 is provided within the

S

dandy roll. The shell may be formed of a metal or plastics material. Preferably the shell is formed of a metal such as for example stainless steel or phosphor bronze.

The dandy roll further comprises an outer cover 3. The outer cover is preferably a wire mesh and may be formed of a plurality of layers of such mesh. The outer cover may be embossed with a pattern or electrotype for imparting a water mark to a substrate as the roll apparatus passes over it. Different covers may be provided for the roll such that different embossings or watermarks may be imparted to the finished product.

The shell may have a spiral wire [not shown] wound around the outer surface. The spiral is open such as to leave spaces between successive windings of the wire.

When included, the wire increases the space between the outer surface of the shell of the roll and the inner surface of the cover and acts to prevent marking of the paper substrate during the forming process.

The roll of the present invention is a dandy roll to consolidate the paper substrate and/or impart a watermark to the substrate for branding or securing purposes. The outer cover of the dandy roll is fixed to the shell such that the cover and shell can rotate together and is perforated as will be described further below.

The dandy roll is mounted within a frame 4 which is more clearly shown in Figure 3.

Drive means are provided at one end of the dandy roll for rotating the shell and outer cover of the roll about its longitudinal axis. A drive shaft S passes longitudinally through the roll and is mounted at either end on the frame through a bearing (not shown). The drive shaft is coupled to the shell at one end, for example through a series of spokes 6. Typically the drive means comprises a motor (not shown) which is connected to the drive shaft such that rotation of the drive shaft causes rotation of the shell and the outer cover of the dandy roll.

One or more rollers 7 are mounted on the frame 4 preferably at the other end of the roll, remote from the driving means to assist with smooth rotation of the shell and outer cover of the roll on the drive shaft In the preferred embodiment 3 such rollers 7 are provided substantially equispaced about the circumference of the dandy roll although the precise number of such rollers and their positioning can be altered by the skilled person. For example in some embodiments it may be preferable to alter the spacing of the rollers.

The walls of the outer cover of the dandy roll are formed of a mesh of metal or plastic wires (not shown] such that small spaces or voids (not shown) are provided between the wires.

A vacuum chamber S is mounted internally within the hollow shell. The vacuum chamber may be formed of any suitable material such as metal, plastic or fibre-glass.

In the preferred embodiment, two vacuum chambers 8, 8' are provided in a side by side relationship although other constructions of the vacuum chamber are envisaged. This arrangement is shown in Figures 1 and 2.

Each vacuum chamber comprises a substantially rectangular box 9 with top, bottom and side walls 10, 11, 12. Each box extends for substantially the length of the shell 2. One side wall 12 of each box comprises inner and outer portion, the inner portion being closer to the centre of the vacuum chamber. The side wall 12 has an opening 13 therein between the inner and outer side wall portions and the outer portion of the side wall extends downwardly past the bottom wall towards the inner surface of the cover 3 of the shell.

The inner portion of the side wall 16 of the box also extends downwardly past the bottom wall of the vacuum chamber towards the inner surface 15 of the cover. The upper part of the inner portion of the side wall under the opening 13 is extended inwardly and downwardly within the box to provide a dam to prevent fluid collected in the box from entering the opening in the side wall.

The downwardly extended side walls of the box form side walls of a substantially rectangular conduit 14 extending longitudinally along the shell under the vacuum chamber.

Additionally in the preferred embodiment, a viewing window (not shown) is provided into the vacuum chamber S to assist in monitoring the level of fluid within the chamber. A gradation or calibration may be provided on the window or the wall of the vacuum chamber adjacent the window to assist further.

Pipe work 17 is connected between the vacuum chamber and a vacuum pump (not shown). Preferably the vacuum pump is mounted externally of the shell. The opening of the pipe work 17 into the vacuum chambers is shown in Figure 2.

In the preferred embodiment the vacuum chamber and pipe work is coupled to the frame and supported in a fixed position within the shell on one side of the frame 4 as shown in Figure 3.

A pair of substantially vertical posts 18 are mounted on the frame, preferably at a position slightly in front of the dandy roll. A post is mounted at each end of the frame with the roll extending between the posts. A rod 19 extends substantially horizontally between the posts and a spray head 20 is mounted on the rod. The height of the rod above the roll, and the position of the rod adjacent to the roll can be adjusted by adjusting the position of the posts along the frame of the apparatus.

A piston 21 is mounted on the rod for advancing the spray head along the rod such that the spray head oscillates across the outer surface of the dandy roll at a position slightly above the outer surface of the dandy roll moving between the posts on either side of the frame.

In the preferred embodiment a suction unit 22 is mounted internally within the roll in a position which corresponds to the external position of the spray head 20. The suction unit comprises a further vacuum chamber 23 which is connected through pipe work 24 to a further vacuum pump (not shown). Alternatively the same vacuum pump may be connected to the suction unit 21 as is connected to the vacuum chambers 8 of the roll. The further vacuum chamber 23 is mounted adjacent to the inner surface of the outer cover 3 of the roll and comprises a box with top, bottom and side wails 25, 26, 27. The further vacuum chamber is preferably mounted in an upper part of the roll and in the embodiment shown is mounted at around 45 degrees from the top centre position of the roll. The chamber extends along the length of the roll and has an opening in the top wall 25 which extends along the length of the chamber. The operation of the suction unit will be described further below.

The or each conduit 14 of the or each vacuum chamber has an inlet 28 at the lower end of the conduit which is adjacent to the inner surface of the outer cover 3 of the dandy roil. In the illustrated embodiment where two vacuum chambers 8, 8' are provided, two inlets 28, 28' are provided, one for each conduit into a vacuum chamber Each inlet has side walls 29. In this embodiment the walls of the inlets are provided by longitudinal members which extend along the length of the underside of the vacuum chamber(s) 8, 8'. Seal means 30 are provided between the underside of the walls of the inlets 28 and the inner surface of the outer cover 3 of the dandy roll. The seal means may be a strip of resilient plastics material which seats in a groove (not shown) in the underside of the channel members.

The inner surface of the outer cover of the cylinder is smooth in order to allow a a good seal to be formed between the inner surface of the cover of the and the inlets 28 of the conduits into the vacuum chambers.

The operation of the dandy roll will now be described. The dandy roll 1 is mounted in position in a paper manufacturing apparatus above a conveyor belt upon which a paper substrate is deposited at an earlier stage of the forming process. The driving means is actuated to rotate the drive shaft S which in turn rotates the outer cover 3 and shell of the roll 2. The follower rollers 7 ensure that the outer cover rotates smoothly at the required speed.

As the outer cover and shell rotates, the internal vacuum chamber 8 remains stationary in a fixed position held by the frame as discussed above. A paper substrate passes along the conveyor bell under the roll and is pressed between the roil and the belt upon which the paper substrate is supported.

A device such as for example one or more springs (not shown) mounted below the belt assist in pushing the belt up towards the roil and in turn aid in pressing the paper substrate against the dandy roll to create a positive pressure between the paper substrate and the roll.

When the vacuum pump is operated, a vacuum is established within the conduits 14 of the vacuum chambers 8. Water is drawn upwards out of the paper substrate and into the in'ets 28 of the conduits between the inlet wails 27. As the inlets extend across the length of the roll, water is drawn out of the paper substrate across its entire width as it passes below the roll.

The seal means 30 act to ensure that the water drawn out of the substrate remains within the inlets where the vacuum pump can then draw the water upwards through the conduits 14 and into the vacuum chambers and also assist in maintaining the vacuum within the conduits.

The water is drawn upwardly through the conduits 14 and enters the vacuum chambers 8, 8' through the openings 13 in the side walls. The water then falls under gravity into the vacuum chamber where the portion 16 of the chamber prevents the water from re-entering the opening 13 in the side wall.

As the eve of water in the vacuum chamber rises the operator will be abk to monitor the levels by checking the kvel indicators through the windows in the chambers.

During rotation of the dandy roll, water and fibres from the surface of the substrate may collect in the voids in the outer surface of the dandy roll cover 3. During operation, conditioning fluid which may be water or may include additional cleaning chemicals is sprayed under high pressure from the spray head 20 onto the outer surface of the cover. Preferably the spray head functions continuously although in some embodiments the operation of the spray head may follow a set pattern or may be dispensed with. As water is sprayed onto the roll it is drawn through the surface of the cover by the vacuum pump of the suction unit 22 and into the further vacuum chamber 23 mounted in the roll.

This also assists in drawing excess water which is picked up by the voids out of the surface of the cover before it returns to a point of contact with the paper substrate and ensures that the outer surface of the cover is as clean as possible when it comes into contact with the paper substrate to avoid depositing a layer of fibres on the surface of the substrate from the voids in the cover thus improving the finished qualily of the paper substrate.

When the eve1 of water in the vacuum chambers reaches a point determined by the operator to indicate that the vacuum chambers are full, the process can be halted and the vacuum chambers withdrawn from the shell of the roll where they can be emptied quickly and returned to an operational position to allow the process to be restarted.

Water withdrawn from the surface of the substrate may be recycled for use in an earlier processing stage of the manufacture of the substrate. Similarly, the water and or water and chemical solution applied by the spray head to the outer surface of the dandy roll cover may be recycled from the further vacuum chamber within the roll through pipe work which could lead back to the spray head.

It will be understood by the skilled person that the dandy roB 1 as described above may be incorporated into an existing paper manufacturing process by simply removing the existing dandy roll system and replacing it with the dandy roll system of the present invention. This allows existing processes to be modified simply and quickly and increases the utility of the present invention and provides a significant advantage over existing machinery in that the amount of water than can be drawn out of the paper substrate can be increased through the process which results in improved consolidation of the surface of the paper substrate and further allows the paper machine to run faster. This in turn improves the efficiency of the process and allows for heavier weight products to be produced. Furthermore, by incorporating the vacuum into a dandy roll, the step of producing a watermark or embossed pattern on the paper substrate can be combined with drawing water from the substrate, thereby shortening the production process and improving watermark clarity.

Furthermore, it is anticipated that the higher efficiency of the present invention is drawing water out of the surface of the substrate will lead to further savings in the amount of chemicals required for conditioning the paper substrate. This also improves the surface of the paper substrate and gives it a more even texture.

It is envisaged that modifications may be made to the dandy roll of the present invention as described above such as for example only a single vacuum chamber may be mounted within the inner shell. Alternatively the number of vacuum chambers within the shell may be increased as required each with a separate inlet leading from the conduit(s) 14.

A range of covers may be provided for the dandy roll such that the outer characteristics of the roll can be changed easily and quickly by changing one cover for another whilst still retaining the advantage of the internal vacuum chambers to draw excess water out of the surface of the paper substrate.

Furthermore, the seal means may be formed of a resilient material such as a material comprising rubber and may be compressed between the inner surface of the cover and the underside of the conduits 14 in order to further enhance the seal between the inlet of the conduits and the inner surface of the cover of the roll thus ensuring the integrity of the vacuum within the conduits.

It is envisaged that the vacuum pump will be operated at a constant suction but it may be that in some embodiments the level of suction may be altered during rotation of the dandy roll. The speed of the pump can be akered to control the suction of water from the paper substrate.

In an alternative embodiment the vacuum pump as described above is replaced by a fan or impeller which is rotated within or adjacent to the chamber or pipe work to create suction through the chamber to draw fluids into the chamber from the surface of the paper substrate. The speed of rotation of the fan or impeller can be akered as above to control the suction of water from the paper substrate.

Claims

CLAIMS1. A dandy roll for use in a paper forming process) the apparatus comprising a hollow cylinder, said cylinder comprising an internal perforated body and an outer cover said roll comprising an internal chamber within the perforated body and a vacuum device connected to the internal chamber for drawing water or other manufacturing fluids out a paper substrate and through the roller as the substrate in contact with the outer surface of the dandy roll.
2. A dandy roll according to claim 1, wherein the outer cover is perforated to allow fluid to pass through the cover from the outer surface to the inner surface and into the chamber.
3. A dandy roll according to claim 1 or 2, wherein the outer cover of the dandy roll is adapted to provide a watermark in the surface of a paper substrate as the roll rotates over the substrate.
4. A dandy roll according to any of the preceding claims, wherein the outer cover comprises a wire or plastics mesh.
5. A dandy roll according to any of the preceding claims, wherein the chamber has an inlet adjacent to the inner surface of the cover.
6. A dandy roll according to any of the preceding claims, wherein means are provided to establish a seal between the inner surface of the cover and the chamber.
7. A dandy roll according to claim 6, wherein the seal means comprises a longitudinal strip of material extending the length of the roll.
B. A dandy roll according to claim 7, wherein the strip of material comprises plastics.
9. A dandy roll according to claim 8, wherein the plastics strip is resilient
10. A dandy roll according to any of claims 1-7, wherein the strip of material is resilient
11. A dandy roll according to claim 10, wherein the material is rubber.
12. A dandy roll according to any of the preceding claims) wherein the internal chamber is mounted in a fixed position within the rolL
13. A dandy roll according to any of the preceding claims, wherein the internal chamber comprises a dam to prevent fluids from flowing out of the chamber.
14. A dandy roll according to any of the preceding claims, wherein the vacuum device comprises a vacuum pump.
15. A dandy roll according to any of claims 1-13, wherein the vacuum device comprises a fan.
16. A dandy roll according to either claim 14 or 15, wherein the vacuum device is operated to establish a vacuum within the internal chamber.
17. A dandy roll according to any of the preceding claims) wherein a frame is provided within which the roll is mounted for rotation relative to the frame.
18. A dandy roll according to any of claims 12 or 13-17 when dependent upon claim 12, wherein the internal chamber is connected to the frame such that the internal chamber is held in a fixed position.
19. A dandy roll according to claim 17 or 18 when dependent upon claim 17) wherein a plurality of follower rollers are mounted on the frame surrounding the outer surface of the dandy roll to aid in maintaining a constant speed of rotation of the dandy roll.
20. A dandy roll according to any of the preceding daims, wherein pipe work is provided between the internal chamber and the vacuum device to establish a vacuum within the internal chamber thus drawing fluids out of the surface of the paper substrate and into the interna' chamber.
21. A dandy roll substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
22. A paper forming apparatus comprising a dandy roll according to the first aspect of the invention.
23. A paper forming apparatus substantially as hereinbefore described.
24. A method of forming paper or a paper substrate comprising the step of passing a dandy roll according to any of claims 1-21 over the paper substrate and operating the vacuum device to draw water out of the surface of the paper or paper substrate, through the outer cover of the roll and into the internal chamber.
25. A method of forming paper or a paper substrate substantially as hereinbefore described.