FI73764C - Paper machine inlet box. - Google Patents

Description

73764

Headbox for paper machine

The invention relates to paper machines and in particular to a paper machine headbox. The invention is most preferably used in the paper industry to form a web of high density pulp. The invention can also be used for the production of various paperboards as well as sheet-like cellulose, hemicellulose and wood pulp and other fibrous semi-finished products. More specifically, the invention relates to a headbox for a paper machine 10 comprising a chamber having a pulp feed manifold and a pulp flow divider, an oscillating defloculator placed inside the chamber and provided with plates attached to rods connected to the vibratory drive, and an outflow tube-15. ken, which is located in connection with the outlet of the chamber and at the inlet of which a pulse damper is placed.

Existing headbox structures for paper machines do not meet some of the requirements for high consistency pulp in the web preparation process. This creates a need to modify existing paper machine headboxes.

A paper machine headbox is known from the prior art (see U.S. Patent No. 458,138 Cl. D 21 F 106, published 1973), which has a chamber arranged to mix and disperse the pulp and provided with a plurality of cylindrical channels which become a narrow channel. , which communicates with a mixing chamber which in turn communicates with a narrow lip gap which becomes an outflow channel.

In the headbox shown above, a pulp having a consistency of 1-6% by weight (preferably 4-5%) is pumped through said channels, a mixing chamber, a narrow lip gap and an outflow channel, whereby the pulp receives a turbulent flow with a gradual decrease in turbulence. while its intensity gradually increases.

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A certain amount of mass passing through the narrow lip gap is, of course, first compressed into an expansion as the mass reaches the outflow channel, whereby the consistency of the mass in this particular amount gradually decreases towards its center-5 from this circumference. This can result in unevenness in the pulp structure, which ultimately degrades the quality of the paper. In addition, a pulp having a consistency of 4-5% by weight can be made to flow in large quantities only at a flow rate of about 250-300 m / min at the outlet of the headbox outflow channel 10. If the flow rate at this point is below said critical value, clogging will occur in the channels and lip gap, reducing the working capacity of the headbox.

This is also the reason for the difficulties encountered when starting or stopping the headbox, as it is necessary to either cause the pulp to flow from zero to 250-300 m / min in a virtually instantaneous manner and to reduce the pulp flow from 250- 300 m / min 20 to zero or else considerably reduces the consistency of the pulp by diluting it with water. For these reasons, this headbox is not used to form cellulosic fibrous webs and other fiber-based semi-finished products with a production speed of well below 250 m / min. In addition, the paper or paperboard obtained may be uneven, which also results in some difficulties in the operation of the headbox.

Also known in the art is a paper machine headbox (see U.S. Patent No. 3,562,108, Cl. 162-141, published 1971), comprising a chamber having a pulp-supplying manifold and a pulp flow distributor with an oscillating device disposed within said chamber. deflocculator, i.e. a fiber fluff diffuser with torn plates attached to rods connected to a vibratory drive and an outlet tube on the outlet side of the chamber. The plates 35 are divided by baffles and mounted on rods by means of a spring and oscillate transversely to the mass flow, pumping it back and forth through its holes.

3 73764 However, near the surface of the vibrating plates there is a so-called an active zone in which strong decomposition of the fiber piles takes place, whereas such a process is not observed further away from the surface of the sheets due to a considerable decrease in the pulsation strength of the pulp suspension, which is due to the special characteristics of the headbox, such as insufficiently efficient dispersion of the entire amount of mass fed to the headbox. This is particularly relevant in high density pulps (above 110% by weight), where the active zone above the plates is very small due to the high viscosity of the pulp due to the damping of the dispersion suspension (water) pulses very close to the fibers.

In addition, the perforations made in the vibratory plates create large turbulent vortices which - although they exert a dispersing effect on a certain part of the low-density (less than 1% by weight) mass fed to the headbox, have the exact opposite effect on the higher-density mass, i.e. cause the pulp to flocculate so strongly, i.e. flocculate in the outflow pipe, that this also results in clogging.

The main object of the present invention is to provide a paper machine headbox in which the channel through which the paper pulp passes into the outflow tube is so constructed and equipped as to effectively disperse the entire high density pulp and thus the headbox to operate efficiently regardless of pulp flow rate. 30 I get the periodic heartbeats I give birth to.

This main object is achieved by the headbox of a paper machine, characterized in that it further comprises solid plates fixed to the chamber walls and that the plates of the oscillating deflocculator are also made solid and together with the plates fixed to the chamber walls form a meandering channel through which the pulp can reach. the outflow pipe.

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A headbox of such construction, in which the solid plates fixed to the walls of the chamber and the solid plates of the oscillating deflocculator are arranged so as to form a tortuous channel through which the pulp is passed, provides a dispersing effect on the entire pulp through the pulp. In addition, the entire amount of mass passing through the narrow portions of the meandering channel is subjected to further dispersion.

10 This headbox structure eliminates large turbulent vortices that can intensify the flocculation of a high-density mass.

A headbox equipped with a pulse damper placed at the inlet of the outflow tube provides a uniform structure to the formed paper, cargon or cellulosic fibrous sheet by creating optimal conditions for the formation of a flat mesh structure in the outflow tube.

It is recommended to make the pacemaker current-20 in the form of a mass flow distributor, e.g., a cylindrical roller. In such a design, such a pulp damper attenuates the pulses by conducting the pulses in opposite phases on top of each other due to the different distance that the pulp divided into two streams has to travel. It is suitable to use a pulsation damper of this design at low and medium mass flow rates.

In certain cases, it is recommended to make the pulse damper in the form of, for example, a membrane-type vibration damping member. A pacemaker of this design dampens 30 pulses due to the resilience of the damping member as it absorbs the pulse energy of the mass. It is suitable to use a pacemaker of this design when the pulse of the mass has a rather large amplitude.

It is sometimes recommended that the pulse damper be formed of a streamlined mass flow distributor and a vibration damper member positioned above it. By design, such a pulse damper effectively dampens the high-amplitude pulses of the mass flowing at all operating speeds.

The present invention will be explained in more detail below with reference to its embodiments with reference to the accompanying drawings, in which Figure 1 is a partial sectional overview of a headbox of a paper machine according to the invention; Fig. 2 is a sectional view, partly in section, of Fig. 10 taken along line II-II; Fig. 3 is an enlarged sectional view of the top of the headbox with the pulse damper in the form of a mass flow distributor; Fig. 4 is an enlarged sectional view of the upper part 15 of the headbox with the pulse damper in the form of a vibration damping member; and Fig. 5 is an enlarged sectional view of the top of the headbox with the pulse damper formed by the pulse damper and the vibration damping member.

Referring first to the drawings and first to Figure 1, the headbox of a paper machine shown here comprises a chamber 1 with a pulp feed or so-called manifold tube 2 and mass flow distributor 3, a vibration-type deflocculator 4 placed inside the chamber 1 and having fixed blades 5 on rods 6 connected to a vibrating drive 7 comprising an electric motor (not shown), non-Kesko 8, a power transmission lever mechanism 9 with a ball joint 10. The chamber 1 and the vibrating drive 7 are mounted on the body 11. Between the body 11 and the flanges 12 of the rods 6, 30 strong resisting springs 13 are mounted, which give the vibrating drive 7 a stable operation over a wide pulp ejection area. At the top of the chamber there is an outflow pipe 14. Rigid plates 15 are rigidly attached to the walls of the chamber 1, which together with the solid plates 5 form a bending channel 16 through which the pulp can enter the outflow pipe 14. At the inlet ____ .. - TT "___ 6 set pulp damper 17. The rods 6 (Figs. 1 and 2) are connected to the vibrating drive 7 in pairs and their number depends on the width of the paper web obtained.The plates 5 attached to the rods 6 are support structures.The distances between adjacent plates 5 and 15 are selected from 5-20 mm, so that the entire pulp stock flowing through the headbox is subjected to deflocculation treatment in its active zone near the surface of the vibratory plates 5. The distance between the inner wall of the chamber 1 and the reciprocating solid plates 10 5 is selected from 2 to 6 mm depending on the mass type. taking into account the type of pulp, the consistency of the pulp and its velocity p erälaa are filled with.

Fig. 3 best shows the top of the headbox, if the pulse damper 17 is a streamlined, in this special case e.g. a cylindrical mass flow distributor 18 rigidly attached to the side walls of the headbox chamber 1. The mass flow distributor 18 is located at the axis of the outflow pipe 14. The height of the manifold 18 should be 2-6 times the height of the lip gap of the outflow pipe 14.

Fig. 4 shows the upper part of the headbox, in which the pulse damper 17 is in the form of a vibration damping member 19, which in this particular case is a membrane. Elastic spacers 20 are arranged between the damping member 25 and the upper wall of the chamber 1 to adjust the elasticity of the damping member 19.

Fig. 5 again shows the upper part of the headbox, in which the pulse damper 17 comprises both a mass flow 30 distribution member 18, in this particular case in the form of a cylindrical roller, and a damping member 19, in this particular case in the form of a film. Close to the outlet of the outflow pipe 14 (Fig. 1) is a web dosing point 21.

35 The headbox works as follows. The pulp is fed from the manifold 2 (Fig. 1) through the pulp distributor 3 to the lower part of the chamber 1. From this, the pulp passes through a winding channel 16 between the movable mass plates 7 73764 and the solid mass plates 15 to an outflow pipe 14, through which it flows to the web-forming site 21, whereby the pulp passes through a pulse damper 17. When a headbox is used in which the pulse damper 17 (Fig. 3) is in the form of a mass flow divider 18, the mass flows around this divider 18, resulting in the overlap of two pulsating mass flows and the attenuation of the pulses of the flowing mass due to interference. When a pulsation damper 17 (Fig. 4) in the form of a membrane damping member 19 is used in the headbox, the membrane of the member 19 begins to vibrate under the influence of the pulsating movement of the mass and thus dampens the vibration energy of the mass. When a pulse damper 17 (Fig. 5) is used in the headbox, which consists of a mass flow distributor-15 18 and a damping member 19, the pulse of the mass is damped by their combined effect.

The operating principle of the proposed headbox is based on the defocculation and homogenization effect of the pulsating vibrations of the pulp stock liquid component when flocs, i.e. pulsating liquid suspension (water) around 20 flocs

25 The value of the rate of pulsating motion above which flocs are intensively decomposed must exceed a certain critical value, which depends on the type and consistency of the pulp.

Figure 1 shows the flow of the pulp by means of arrows.

30 The pulp fed to the headbox is subjected to multiple treatment in an active flake disintegration zone. By the time the pulp passes through the meandering channel 16, new layers of fiber suspension are associated with the active deflocculation zone. The pulp is exposed to the additional scattering effect of the flakes 35 as it passes through a narrow channel formed by the outer edge of the moving solid plates 5 and the inner wall of the chamber 1. This process is followed by a considerable .. TT -------- 8 73764 energy dissipation, which is proportional to the pressure drop and is followed by mass deflocculation. The vibrations generated during the vibration deflection are damped either by the occurrence of interference conditions or by the vibration of the membrane damping member 5 19. The same goal can be achieved under the influence of both the interference and the resilient vibrations of the damping member 19.

It will be readily apparent to those skilled in the art that the above object, as well as others apparent from the detailed description of the present invention, will be achieved within the scope of the invention. The above embodiments of the invention do not limit its scope and are intended to illustrate the invention by way of example only. It will be appreciated that some modifications may be made to the construction described above without departing from the scope of the invention. For example, the pulse damper may be in the form of any streamlined mass flow divider, and when the vibration damping member is used, the membrane may be replaced by an air cushion. It is obvious that any other insignificant changes can be made in the headbox structure. However, all such modifications are to be considered within the scope and spirit of the invention as defined in the following claims.

Claims (1)

A paper machine headbox comprising a chamber (1) with a pulp feed pipe (2) and a pulp flow distributor (3), an oscillating defloculator (4) housed inside the chamber (1) and provided with plates (5). ) attached to rods (6) connected to the vibrating drive (7) and to an outflow tube (14) located in connection with the outlet opening of the chamber (1), at the inlet position of which a pulse damper (17) is arranged, that it further comprises solid plates (15) fixed to the walls of the chamber (1), and that the plates (5) of the oscillating defloculator (4) are also made solid and together form the plates (15) fixed to the walls of the chamber (1). ) with a meandering channel (16) through which the pulp can enter the outflow tube (14).