JPS5858480B2 - head box - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a headbox for discharging a fiber suspension onto the wire of a paper-making machine, and its purpose is to disperse fibers in the fiber suspension discharging from a slicing opening. The objective is to obtain a complete and uniform flow state in the width direction of the flow.

Most papers currently manufactured are made by draining a fiber suspension in which pulp fibers are dispersed onto the wire of a paper-making machine through the slicing opening in the head box, and dehydrating the water contained in the fibers on the wire. Although pulp fibers are manufactured by paper-cutting, when they are fluidized as a fiber suspension, they have the property of gathering together in a very short period of time to form fiber aggregates called flocs. If the fiber suspension in which such flocs have been formed is directly flowed from the head box onto the wire of a paper making machine, the paper produced will have uneven formation (local fluctuations in basis weight), resulting in poor aesthetic appearance and strength. This will have an adverse effect on the finish of sheath printing, suitability for processing, etc., and the commercial value of the paper will be significantly impaired.

Therefore, it is an essential requirement in the paper making process to prevent paper formation unevenness from occurring, and the most effective method for preventing such formation unevenness is to reduce the pulp fiber concentration in the fiber suspension. Was that.

However, even with methods that reduce pulp fiber concentration,
Since the basis weight of the paper to be manufactured must be the same as the desired basis weight, the amount of fiber suspension to be reduced will increase, resulting in an increase in water usage and power consumption, which is in line with the current energy consumption trend. It is not recognized as an ideal method because it goes backwards.

Another method is to violently agitate the fiber suspension near the slice opening of the headbox, but if such a method is implemented, the flow of the fiber suspension flowing out from the slice opening becomes uneven. Therefore, only paper with low commercial value and with large fluctuations in basis weight distribution can be obtained.

The present invention eliminates the drawbacks of the conventional paper that prevents the production of paper with high commercial value due to uneven formation, and provides a head box that has a simple structure and is capable of producing high-quality paper without uneven formation. This is what we provide.

That is, the present invention has straight tubular sections that are connected to the header and are parallel to each other, and is connected to the straight tubular sections, and the flow channels are expanded and contracted repeatedly to expand the flow channels to the same width as the paper making width. A paper stock supply section consisting of an expanding/contracting channel section that allows the suspension to flow out in an almost uniform state; A parallel flow path portion comprising two or more flow path forming portions and the flow velocity increasing as it goes downstream, and a slice opening connected to the parallel flow path portion and having the same width as the paper making width and located at the most downstream side. The present invention relates to a head box characterized by comprising a slicing chamber in which the distance between the upper plate and the lower plate can be adjusted while the upper plate and the lower plate are parallel to each other.

Hereinafter, one embodiment of the head box according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view of one embodiment of a head box according to the present invention, FIG. 2 is a sectional view taken along line A--A in FIG. 1, and FIG. 3 is an enlarged view of section B in FIG. 2.

In the drawing, 1 is a header to which a fiber suspension for paper making is supplied, and this header 1 has a truncated pyramidal shape with a wide cross-sectional area on the inlet side of the fiber suspension and a narrow cross-sectional area on the downstream side. One side 1a of this pyramid-shaped part is parallel to the flow direction of the fiber suspension at the inlet end, and the downstream side of the pyramid-shaped part is a part of the fiber suspension that has not flowed into the paper-making machine. It is connected to an outflow pipe that drains the turbid liquid.

The reason why this header 1 has a truncated pyramidal shape is that the fibers are suspended in the same condition in a large number of parallel straight pipe-shaped portions 2, each of which has an inlet for the fiber suspension on one side 1a. This is to make the fluid pressure the same at all inlets of the straight tubular portion 2 so that the liquid flows.

3 communicates with the header 1 and is connected to mutually parallel straight tubular portions 2, and allows the fiber suspension flowing out from the straight tubular portions 2 in the form of a jet to flow out in a substantially uniform state. This is an expansion/contraction flow path section that repeatedly expands and contracts the flow path to expand the flow path to the same radius as the paper making width W and allows the flow to flow out.

The header 1, the straight tubular portion 2, and the expansion/contraction channel portion 3 constitute a stock supply section I.

Reference numeral 4 denotes a parallel flow path forming portion which is connected to the expansion/contraction flow path portion 3 of the paper stock supply section I and has the same width as the papermaking width W and has an upper plate 4a and a lower plate 4b parallel to each other. 4 is provided in two or more stages, and the interval between the upper plate 4a and the lower plate 4b of the parallel flow path forming section 4 on the downstream side is set so that the flow velocity increases as it goes downstream. Upper plate 4a and lower plate 4
It is narrower than the distance with b.

Further, the cross-sectional area of the flow path is reduced relatively rapidly so that a uniform acceleration field is not generated between the downstream side of the upstream parallel flow path forming section 4 and the upstream side of the downstream parallel flow path formation section 4. They are connected by a flow path reduction section 5.

In this way, the parallel flow path forming section 4 equipped with the flow path reduction section 5 constitutes the parallel flow path section (■), and this parallel flow path forming section (■) flows out from the stock supply section I. This is a part where the fiber suspension increases the flow rate to the flow path where the next floc is destroyed without causing the floc to grow, that is, to the flow velocity just before reaching the critical flow velocity at which the floc is destroyed.
The condensed flow path portion needs to have a taper angle θ of 60° or less, preferably in the range of 45° to 30°, and a short flow path length.

In order to satisfy such requirements, the ratio of the distance between the upper plate 4a and the lower plate 4b of the parallel flow path forming portion 4 adjacent to both sides of the flow path reduction portion 5 should be 4 or less, preferably 1.5.2. 5, and it is more preferable if the flow path reduction part 5 has a smooth curved slope instead of a straight slope as in the illustrated embodiment. .

7 is connected to the parallel flow path forming section 4 on the most downstream side of the parallel flow path section (■) via a flow path reduction section 6 similar to the flow path reduction section 5 of the parallel flow path section (■), and is sliced on the most downstream side. A slice opening 9 is formed by the opening plate 8, and the upper plate 7a and the lower plate 7
b is parallel to the upper plate 7a and the lower plate 7b, the interval between the upper plate 7a and the lower plate 7b is formed in a freely adjustable manner, and the flow passage width is the same width as the papermaking width W. 6, the floc-destroying channel section 7, and the slicing aperture plate 8 constitute a slicing chamber (2).

This slicing chamber ■ is designed to uniformly flow the fiber suspension flowing out from the parallel flow path section ■ at a flow rate that destroys the flocs and flow out from the slicing opening 9. The flow velocity of the fiber suspension is critical because it is necessary to maintain the flow velocity above the critical flow velocity for destroying flocs and not to disturb the flow of the fiber suspension in order to produce good paper with even texture. It is preferable that the flow velocity be close to that of the flow rate, so that the dispersion state of fibers in the fiber suspension flowing in the floc-breaking channel T in the vicinity of the slicing opening 9 can be detected. It is preferable to provide a detection means 10 of.

The detection means 10 includes a light source that emits light onto the fiber suspension flowing in the floc-breaking channel T, and light that is emitted from the light source and passes through the fiber suspension, or is reflected from the fiber suspension. Preferably, it consists of a light receiving part that receives light,
The illustrated embodiment is made up of a plurality of glass fibers, some of which form an outgoing path for supplying light from a light source, and the remainder forming a return path that guides light reflected from a fiber suspension to a light receiving element. It's intimidating.

Note that reference numeral 11 denotes a moving means for moving one or more of the upper plate 7a and the lower plate 7b of the floc-destroying channel section 7 in the slicing chamber (3) to adjust the distance between the upper plate 7a and the lower plate 7b.

In such a slicing chamber (2), in order to form the slicing opening 9, in the case of a normal paper making machine with a set of signal wires as in the illustrated embodiment, the slicing aperture plate 8 and the lower plate 7b, which are made of a slicing lip plate, are required. However, in the case of a double wire set paper making machine that has come into use in recent years, the slice aperture plate 8, which is better than the slice nozzle plate, is sufficient, and in the case of this slice nozzle plate, the floc breaking flow A partition plate may be provided between the upper plate 7a and the lower plate 7b of the passage I to partition the upper flow path and the lower flow path.

Next, the operation of the head box according to the present invention having such a structure will be explained.

The fiber suspension is flowed into the tapered header 1 by means such as a fan pump, with the majority flowing onto one side 1 of the header 1.
The water flows into the straight tubular part 2 through the inlet port of the straight tubular part 2 opened at a, and the remaining part flows out from the outflow pipe connected to the side opposite to the inflow side of the header 1.

It is preferable that the fiber suspension be supplied to the header 1 in a state in which pulsations have been previously removed by means such as an attenuator.

In this way, the fiber suspension that has flowed into the straight tubular section 2 flows in a substantially uniform state within each of the many parallel straight tubular sections 2, and forms a jet from the outlet of the straight tubular section 2, completely removing the flocs. The broken state flows into the expansion/contraction flow path section 3, and due to the pressure loss caused by the expansion and contraction of the flow path, a uniform flow becomes almost uniform and flows to the outlet of the expansion/contraction flow path section 3. At this point, the flow is expanded into a flow having a cross section equal to the paper making width W and the same cross section as the inlet of the parallel flow path section (2), and then flows into the parallel flow path section (2).

In the stock supply section (3), the fiber suspension flows from the header 1 into the straight tube section 2, and when it flows out from the straight tube section 2, the flocs are completely destroyed because the flow is a jet flow. , the jet flow is calmed down and the flow has the same flow cross section as the parallel flow path section ■.The many large vortices generated in the expanding and contracting flow path section 3 gradually transform into smaller vortices, and finally the vortices disappear. During the flow within the expansion/contraction channel section 3 until the state is reached, a small amount of flocs will be formed again.

The reason for providing such an expanding/contracting channel section 3 is that if the fiber suspension were allowed to flow out as a jet directly from the straight tubular section 2, the disturbance of the fiber suspension would be magnified by the jet, making it extremely difficult to obtain a uniform flow. It is.

In this way, the fiber suspension flowing from the stock supply section I to the parallel flow path section (2) is completely quenched by reducing its flow velocity in the first parallel flow path forming section 4, and then is prevented from forming a flock. The flow passes through a short channel reducing section 5 that reduces the cross-sectional area of the channel, and then flows into the next parallel channel forming section 4, and the flow velocity is higher than that flowing into the stock supply section I, but is made uniform. In this state, it flows out from the outlet of the parallel flow path section (2) and flows into the slicing chamber (2).

In this slicing chamber (2), the flow velocity is increased to a level above the critical flow velocity for destroying flocs by a channel reduction section 6 similar to the channel reduction section 5 of the parallel channel section (2). The fiber suspension flows through the floc-breaking channel section 7, where the flow is uniform, the fibers are completely dispersed, and there are no flocs, and the fiber suspension flows through the slice opening 9 on the most downstream side of the paper making machine. It leaks onto the wire.

Of course, the flow rate of the fiber suspension in the slicing chamber (2) must be higher than the critical flow rate in order to completely destroy the flocs, but if the flow rate is increased unnecessarily,
Since the pressure increases in proportion to the square of the flow velocity, each part of the machine is likely to go awry, and the strength of the members forming the slicing chamber (2) must be increased unnecessarily, which is uneconomical. If the gap with 7b becomes too narrow, clogging is likely to occur and the flow of the fiber suspension tends to become uneven, so it is preferable that the flow velocity be as close to the critical flow velocity as possible. In order to bring the flow velocity close to the critical flow velocity, a detection means 10 is provided in the floc destruction channel 7 close to the slice opening 9, and the fluctuations in the amount of light received by the detection means 10 are frequency-analyzed, and the frequency analysis results are analyzed. The distance between the upper plate 7a and the lower plate 7b of the floc-destroying channel section 7 can be adjusted by the moving means 11 so that the flow velocity is such that no peak occurs in the spectrum curve.

In this way, the fiber suspension flowing out from the slicing opening 9 of the slicing chamber 1 is in a uniform state with no flocs, so that it is possible to make high-quality paper with uniform texture and no irregularities.

The head box according to the present invention as described in detail above is easy to maintain because the stock supply section I and the parallel flow path section (■) have a simple structure with no moving parts and there are no obstacles that could cause dirt if they become clogged. Both the slicing chamber and the slicing chamber have excellent advantages in that they can very easily produce a uniform flow state without flocs without the need to modify the fiber suspension. It is possible to produce paper stably at all times, and even if the liquid composition of the fiber suspension, the type of pulp fiber, the fiber length, etc. change, it is possible to immediately make paper without any unevenness. Its industrial value is enormous.

[Brief explanation of drawings]

FIG. 1 is a plan view of one embodiment of a head box according to the present invention, FIG. 2 is a sectional view taken along line A--A in FIG. 1, and FIG. 3 is an enlarged view of section B in FIG. 2. ■・・・Paper stock supply section, 1・・・・・・Header,
1a... One side, 2... Straight tubular part, 3
...... Expansion/contraction channel section, ■... Parallel channel section,
4... Parallel flow path forming part, 4a... Upper plate, 4b... Lower plate, 5... Channel reduction part,
■... Slice chamber, 6... Channel reduction section, 7... Flock destruction channel section, 7a...
- Upper plate, 7b... Lower plate, 8... Slice opening plate, 9... Slice opening, 10...
...detection means, 11...movement means, W...
... Paper width, θ ... Taper angle of the flow path reduction section.

Claims (1)

[Scope of Claims] 1. Straight tubular portions 2 that are connected to the header 1 and parallel to each other, and are connected to the straight tubular portions 2, and the flow path is repeatedly enlarged and contracted so that the flow has the same width as the paper making width W. Expansion/contraction channel section 3 that expands the channel and allows the fiber suspension to flow out in a substantially uniform state.
A paper stock supply section I consisting of a stock supply section I, and two or more stages of parallel flow path forming sections 4 connected to this stock supply section I and having the same width as the paper making width W and having an upper plate 4a and a lower plate 4b parallel to each other. It has a parallel flow path section (2) in which the flow velocity increases as it goes downstream, and is connected to this parallel flow path section (2) and has a slice opening 9 at the most downstream side with the same width as the paper making width W. A head box characterized by comprising a slicing chamber (2) in which the interval between the upper plate 7a and the lower plate 7b can be freely adjusted while the plate 7a and the lower plate 7b are parallel to each other. 2. According to claim 1, the ratio of the distance between the upper plate 4a and the lower plate 4b of the adjacent parallel flow path portions 4 of the parallel flow path portion (2) is between 1.5 and 2.5.・＼Radbox. 3 The slicing opening 9 of the slicing chamber (■) is connected to the slicing opening plate 8 made of a slicing lip plate and the floc destruction channel section 7.
The headbox according to claim 1 or 2, which is a slicing opening for a single-wire set paper making machine, which is formed by a lower plate 7b of a single wire. 4. The slicing opening 9 of the slicing chamber (1) is a slicing opening for a double-wire set paper making machine, which is formed of a slicing aperture plate made of a slicing nozzle plate. head box. 5. The slicing chamber (2) is equipped with a detection means 10 in the floc-breaking channel section 7 close to the slicing opening 9 for detecting the dispersion state of fibers in the fiber suspension flowing in the floc-breaking channel section 7. Claim 1, which is a slicing chamber in which
The head box according to any one of paragraphs to paragraphs 4 to 4.