JPS6118080Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a headbox for a paper machine.

A paper machine headbox is the most important component of a paper machine in determining paper quality. The paper stock ejected from the head box is dehydrated in the wire part and forms a wet paper.The jet of paper stock ejected at this time has fibers uniformly dispersed therein, and the surface of the jet is stable and smooth. It must be. In this way, in Headbox,
The purpose is to promote the dispersion of paper fibers and create a smooth jet. However,
With conventional headboxes, it is difficult to create the turbulence necessary for fiber dispersion when the fiber concentration in the stock is high or when the papermaking speed is slow.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to propose a headbox for a paper machine that can produce paper of excellent quality even at high density or low speed.

By the way, the fluidity of the pulp liquid varies depending on its fiber concentration and flow rate, as shown in FIG. 1. That is, the higher the concentration or the slower the flow rate, the more difficult it is to maintain a laminar flow state and obtain the shear force due to flow turbulence necessary for fiber dispersion. Therefore, when papermaking is performed with a high headbox concentration, it is necessary to devise ways to maintain a turbulent flow of the pulp liquid. For this purpose, it is necessary to increase the flow velocity within the headbox as much as possible.

A conventional configuration is shown in FIG. Here, the headbox 1 has a perforated plate 3 of an approach flow (tapered header) 2 positioned at right angles to the plane of the headbox, that is, facing the outlet 4. 5 indicates a wire, and 6 indicates a prestrol. According to the head box 1 having such a structure, since the upper and lower surfaces 7 and 8 have an inclined shape that becomes narrower toward the downstream, the flow velocity Vo decreases, resulting in a laminar flow, which causes turbulence in the flow necessary for fiber dispersion. It is not possible to obtain shear force due to

In contrast, the present invention, as shown in FIG. 3 which is an embodiment thereof, has a head box 10 in which a perforated plate 12 having a plurality of holes arranged in rows of an approach flow 11 is arranged in parallel to the head box. The perforated plate 12 is arranged so as to correspond to and parallel to the inner upper surface 14 of the upper and lower surfaces 14 and 15, that is, the perforated plate 12
3, the upper surface 14 of the upper and lower surfaces 14 and 15
It is formed to face. 16 is wire, 1
7 indicates prestrol. According to this, the height of the flow path of the head box 10 is kept very low.

FIG. 4 shows a modification, in which the perforated plate 12 is made into a diffuser or the like to increase the fiber dispersion effect in this portion.

According to the present invention described above, the following effects can be expected.

Γ By locating the perforated plate of the approach flow of the headbox so that it corresponds to and parallel to the inner upper surface of the parallel upper and lower surfaces of the headbox, it is possible to reduce the height of the rectifying section, which disturbs the fiber velocity in this section. The flow can be kept constant and above the flow limit. Furthermore, since there are multiple rows of holes along the flow direction of the paper stock in the head box, the flow of paper stock that is jetted from the holes on the upstream side and exhibits a non-uniform flow velocity distribution in the width direction is instead jetted from the holes on the downstream side. Since the flow of paper stocks can be supplemented, the degree of dispersion of fibers is stabilized, and even if the flow velocity increases, a uniform flow in the width direction can be obtained, making it possible to improve production efficiency.

Γ The head box becomes more compact.

Γ Easy to manufacture and process.

Γ Can handle high density paper making.

[Brief explanation of the drawing]

Fig. 1 is a graph showing pulp liquid flow properties, Fig. 2 is a longitudinal sectional view of a conventional example, Fig. 3 is a longitudinal sectional view showing an embodiment of the present invention, and Fig. 3 is a main part showing a modified example. FIG. 10... Head box, 11... Approach flow, 12... Perforated plate, 13... Exit, 14,
15... Surface, 16... Wire, 17... Prestrol.

Claims (1)

[Scope of utility model registration request] 1. A headbox for a paper machine, characterized in that a perforated plate having a plurality of holes arranged in rows of approach flow is positioned parallel to and corresponding to the inner upper surface of the parallel upper and lower surfaces of the headbox.