FI61535B - ANORDNING FOER UTSLAETANDE AV EN PAPPERSMASKINS TRANSPORTBAND - Google Patents

Description

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Patent and ocean registration '' Aniektn utiagd och uti.ikrifun pubUcumd du.ua.o ^ (32) (33) (31) Pyydtty «Tuoikws - B« Girt priorityvt 13.12.72

England-England (GB) 57617/72 27.09.73 Canada (CA) 182110 (71) JWI Ltd., 1 Westmount Square, Montreal, Quebec, Canada (CA) (72) Robert Andrew Truesdale, Decatur, Georgia, United States )

The present invention relates to an apparatus for applying an endless conveyor belt (wire) to a paper machine, the apparatus comprising a tube, an apparatus for applying an endless conveyor belt (wire) to a paper machine, the apparatus comprising a tube, an apparatus for applying a paper machine conveyor belt (wire). mounted transversely over the strip and in the vicinity of its surface and at least two groups of nozzles for spraying the pressurized medium conducted by the tube.

For example, in the Fourdrinier wire portion of a paper machine, a as-fire is discharged onto the upper surface of a moving endless screen cloth called a Fourdrinier or forming wire. The wire passes over the dewatering devices and is subjected to considerable traction as it is pulled by the traction roll. The wire must therefore transfer considerable force to the dewatering members and this develops a strong tensile stress on the top of the wire immediately in front of the felting or drawing roll. The high tensile stress before the felt roll causes the wire to stretch slightly in the machine direction (longitudinally), and because this is the case for most flexible materials, it tends to contract in the cross-machine direction, i.e. it narrows just as it enters the draw roll.

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The wire remains under strong traction for most of its travel around the traction roll, but shortly before the outgoing tangent of the roll is reached, the traction gradually loosens, after which the wire tends to retract in the machine direction and expand in the cross-machine direction. Some longitudinal constriction occurs with the wire still in contact with the roll surface on the exit side and local slip of the wire on the surface occurs at this point, causing relative movement between the wire and the roll in the longitudinal direction. Possibly just before the wire separates from the roll at this starting tangent, there is also a small increase in width, which creates a relative movement between the wire and the roll in the transverse direction. Thereafter, since the minimum value is reached in the return portion (downstream) of the wire, there is a slight increase in width while the wire is still under cross-narrowing due to contact with the roll, resulting in the formation of ridges and corrugations.

Small temporary ridges or corrugations are not harmful as long as they do not damage the flatness of the wire as it passes over the dewatering section of the machine. However, it often happens, especially in high speed machines where the transmitted force is large and the wire is wide, that the ridges or waves are particularly clear and may remain permanent, thus adversely affecting the smoothness of the wire in the dewatering section and thus causing deformation in the paper to be produced. Eventually, one or more of the permanent folds may become so large that they form wrinkles that may extend around the entire wire, so that further use is no longer possible and the wire must be removed from the paper machine.

To reduce this creasing effect, a curved spreader roll (not shown) can be mounted close to where the wire leaves the felt roll. The spreading roll is curved mainly in the direction away from the felt roll so as to apply an spreading effect to the wire, which causes a transverse tension extending outwards from the center of the wire, thus reducing or removing the ridges. However, these curved rollers cause maintenance difficulties and are expensive to build and install, especially for a wide paper machine.

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Although the problem of corrugation occurs to some extent when the wires are metallic, made of e.g. bronze or stainless steel, the corrugations are most pronounced when the wire is a plastic wire with less width in width than the metal wire, so that the tendency to crimp is greater when the wire is made.

The device according to the invention is characterized in that the nozzles in the first group are turned outwards towards the first edge of the strip and the nozzles of the second group are directed towards the second edge of the strip or wire. In a preferred embodiment, the invention may comprise a jet tube spreader for use in a forming section of a Fourdrinier paper machine comprising a forming fabric in the form of an endless wide strip, a wire having a high tensile upstream section and a low tensile downstream section as described above. , wherein the tube is arranged between the upper and lower parts of the endless wire to run across the wire substantially parallel to its lower part, the nozzles being directed towards the lower part of the wire.

The invention can also be applied to forming parts using endless wires other than the Fourdrinier type, e.g. Vertiforma, Bel-Baie Former, Papriformer, etc.

The invention is not limited to the forming part of a paper machine, but can also be applied to a press part in which oscillating needle-jet spray tubes are used for cleaning paper-carrying felts. In this application, the spray tube spreader can be used instead of one or more screw spreading rollers.

The spray tube spreader can also be used in the drying section of a paper machine in places where the felt tends to wrinkle.

The nozzles of the spray tube spreader are preferably directed outwards at an angle of 10 to 60 °, with angles of 20 ° to 30 ° being most preferred, with the nozzles mainly on the left side of the manifold facing the left edge of the Fourdrinier wire and the nozzles on the substantially right side facing the Fourdrinier wire (flat wire). towards the right edge.

4,61535

The oscillating high pressure jet tube on the low tensile stressed portion of the wire, which is commonly used to open the holes in the wire from fibers, resin agglomerates, fillers, etc., can be modified as described above to perform the application function as well as its normal function. This is the most preferred arrangement.

The invention will be explained in more detail below with reference to the accompanying drawings, in which Fig. 1 shows a Fourd-rinier or flat wire section of a felt-rolled paper machine, Fig. 2 shows a flat wire drive section with a separate draw roll, Fig. 3 is a perspective view of the paper machine. of parts to illustrate the problems to be overcome by the invention, Fig. 4 shows one embodiment of a needle-shaped jet tube according to the invention, Fig. 5 shows another embodiment of a needle-shaped spray tube according to the invention and Fig. 6 shows the use of fan-shaped jet tube nozzles.

In the flat wire section of the paper machine shown in Figs. 1 and 3, a wire in the form of an endless fabric loop 1 containing a top 1a and a bottom 1b is conveyed over dewatering devices comprising foils 4, register rolls 5 and suction boxes 7 by means of a felt draw roll 9. To overcome the problem of wire clogging caused by paper fibers, fillers, resin particles, etc., many mills install a needle-type, low-flowing high-pressure jet tube 11 on the lower part 1b of the wire 1. When using needle-type nozzles, the manifold must swing back and forth over the wire to ensure that the entire wire is cleaned. These jet tubes use high pressure water jets to expel foreign matter from the wire without adding an uneconomically large volume of water to the circulating water entering the pulp. The spray tube is generally installed immediately after the immersion pull roller 9 in the embodiment of Figure 1. In a machine with e-roll felting and drawing rollers 9 and 13 (see Fig. 2), the shower tube 11 is placed after the drawing roller 13. In either case, the spray tube 11 is placed between the top and bottom of the wire and the nozzles are placed at a short distance from the bottom of the wire and directed towards it. In practice, it has been found that when the wire is plastic instead of metal, the mesh has a greater tendency to clog and the use of a high pressure jet pipe is very important.

The corrugations, i.e. the ridges, formed when the wire moves from the high tensile stress region at its top to the low tensile stress region at the beginning of the lower part and leaves the roll 9 are shown at 15 in Figure 3.

The nozzles arranged according to the invention are shown in Figures 4 and 5. The nozzle 11 shown in Figure 4 comprises a plurality of nozzles 12, each throwing a flowing medium, usually a needle-like jet 14 formed by water. 0 at an angle to the wire. The nozzles to the left of the central nozzle 12c are directed to the left edge of the wire, while the nozzles to the right of the nozzle 12c are directed to the right edge of the wire. In this embodiment, the nozzles are spaced evenly and each nozzle is oriented at the same angle so that the horizontal component provided by each nozzle is equal. If it is desired to change the force in the transverse direction of the wire, the angle of inclination can be changed as shown in Fig. 5. Here, the angle of inclination 0 gradually increases from each edge toward the center, so that the angle of impact increases from 0 to 0 ^ on the side edge, and so on up to 0g in the center. The nozzles are preferably arranged identically obliquely on each side of the center.

The force acting in the transverse direction of the wire can also be changed by resizing the nozzles from the center to each edge. Again, the nozzle size could change identically on either side of the center.

It is also within the scope of the invention to provide a variable distance between the nozzles if this is advantageous in special cases.

Although needle-type jets have been commonly used in cleaning jet tubes, it has been found that other types of jets can be advantageously used in accordance with the invention. Thus, fishtail jets have been found to be satisfactory. \ 'y ► 6 61535 and, in fact, they can, as will be shown below, be even better than needle-type showers. In addition, although the purge nozzles use only water, it has been found that other flowable materials, such as air and possibly steam, could be used in accordance with the invention.

In the above description, the angle 0 is the angle between the center plane of the jet and the wire, measured in the transverse direction of the machine. Local deviations from this level due to corrugation or bending due to the jet are not taken into account. In this description, the angle 0, which represents the angle of inclination of the spray tube, is also the angle of impact of the spray with the wire. Considering the question of preferred parameters, it is known that the largest horizontal component of the force produced by each nozzle is obtained from the formula: F = ^ cosini 0 where p = pressure d = inside diameter of the nozzle 0 = angle of impact in degrees

It appears from the formula that the application can be achieved with high pressure and small nozzle diameter (small liquid volume) or with low pressure and large nozzle diameter (large liquid volume). When the liquid (flowable substance) is water, the pressure to volume ratio could normally only be selected after taking into account the additional volume of water that the paper machine could efficiently absorb. It is generally preferred to minimize the amount of water added to the system and this can be achieved by reducing the nozzle size and using high pressure. In experiments to determine the preferred parameters, it was found to achieve satisfactory operation in the slope angle range of 10 ° to 60 °. The best results were obtained at angles of 20 ° ... 30 °. The above results were obtained when the fluid used was either water or air.

When considering the issue of low pressure, i. the pressure at which the water is supplied was assumed to depend on the amount of water that could be received, which in turn would depend on the nozzle size. In any case, at a given nozzle size, the pressure should be high enough to provide sufficient lateral force to spread the wire.

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Although the full range of pressures was not determined, satisfactory results were obtained with both air and water at pressures of 7, 14, 28 and 42 kp / cm. The tested nozzle sizes were 0.91 ... 1.70 mm in diameter.

Another parameter is the height of the nozzle above the wire, the height being measured from the tip of the nozzle perpendicular to the wire, i. the vertical height of the nozzle tips above the wire.

It was found that when the fluid was water and the test heights were about 5 to 15 cm, the results were in fact independent of height. With the fluid in the air, on the other hand, it was found that if the nozzles were more than 12 mm above the wire, the transverse component of the jet force was greatly reduced, so that the air jet pipe should preferably be kept no more than 12 mm above the wire.

As stated above, according to the invention, it is possible to use fishtail nozzles rather than needle-shaped nozzles. In this regard, it should be said that a large portion of the tailbone jet could run in the longitudinal direction of the wire. However, it has been found that it would be advantageous to place a wide portion of the nozzle in the transverse direction of the wire as shown in Figure 6. In this case, it would be advantageous for the shower of each nozzle to overlap the shower of the adjacent nozzle. Thus, it is possible to cover the entire width of the wire without causing the spray tube 11 to oscillate, which is required when using needle-type nozzles.

It is also possible to rotate the fishtail nozzles so that cleaning takes place both in the longitudinal and transverse directions of the wire.

Although in the preferred embodiment the cleaning nozzle is modified to perform both cleaning and application tasks, it is apparent that separate nozzles could be used for both purposes. Thus, as shown in Figure 2, it would be possible to use the nozzle 11 to apply the wire and the nozzle 25 to clean it. When using the same nozzle for both purposes, the parameters must be adjusted to ensure that both tasks are performed. Thus, although a smaller angle of inclination of the nozzles from the tube may provide better application performance, it is possible that the cleaning effect will be impaired. This S1 · '· · 3 61535 must be taken into account when manufacturing and setting up the device according to the invention.

In cases where the insertion of the resin into the wire mesh is a particular problem and the resin cannot be eliminated by any force other than the needle jet tube placed perpendicular to the surface of the wire, it may be necessary to use a special cleaning nozzle in addition to the applicator nozzle. Or, if space is limited, use a single manifold with vertical nozzles for cleaning and obliquely oriented nozzles to eliminate creases.

Although only one jet perpendicular to the longitudinal direction of the wire is contemplated (14 in Figure 1), it is also possible to place the nozzle at an oblique position so as to be at some other angle to the longitudinal direction of the wire, e.g. 14a and 14b in Figure 1. against the direction of movement, i.e. in the direction of 14c. But if the nozzles is tilted like this, then there will be used for the cover 20 to ensure that the water does not splash back into the couch roll 9, from which it may be most unpleasant consequences have to be formed in the paper through the underside of the fabric of the couch roll by.

Although several embodiments have been described above, this has been done for illustrative purposes only without wishing to limit the invention. Various modifications that will be readily apparent to those skilled in the art are within the scope of the invention.

Claims (4)

9 61535 An apparatus for applying an endless conveyor belt (1) (wire) of a paper machine, the apparatus comprising a tube (11) mounted transversely over the belt (1) and in the vicinity of its surface and at least two groups of nozzles (12) for pressurized medium by the tube (11) for spraying, characterized in that the nozzles (12) in the first group are turned outwards towards the first edge of the strip (1) and the nozzles (12) of the second group are directed towards the second edge of the strip or wire (1) so that the nozzles (12) convey to the strip ( 1) a force directed from its center to its edges. Device according to claim 1, characterized in that each nozzle (12) forms an angle of 20 ° to 30 ° with the longitudinal axis of the tube (22). Device according to claim 1 or 2, characterized in that the nozzle (12) provides a jet resembling a fish tail which is wide at its lower part and whose length extends beyond the width of the strip (1) and that the lower parts of adjacent nozzles overlap at least when touching the strip. (1) surface. Device according to one of Claims 1 to 3, characterized in that the nozzles are needle nozzles, the tube (11) being caused to oscillate in a direction perpendicular to the direction of movement of the strip (1). % V