JPS5932593B2 - Anti-pulsation screen device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a screen device that filters and selects paper stock in the final process of feeding the paper stock into a paper machine, and particularly relates to a pulsation-preventing screen device that is used as an online screen to prevent pulsation from occurring on the line discharge side. This invention relates to a screen device.

Generally, the flow in piping tends to cause pulsations on the secondary side due to the rotation of the pump and various effects on the primary side.

Theoretically, this pulsation could be avoided by adjusting the flow rate by operating the control pipe, but it is extremely difficult to predict the occurrence of pulsation and perform feedforward control under all conditions.

Especially the forming section of the paper machine (Formig 5ection)
In the screen device installed just before the hydraulic head box that discharges paper stock in the form of a solution, the discharge port is directly connected to the hydraulic head box that serves as the discharge terminal, and the piping length is short, so the pulsation that occurs can be avoided. This is a pulsating phenomenon of the amount of discharge from the hydraulic head box.

If there is any variation in the discharge rate, this variation will cause non-uniformity in the basis weight produced by the paper machine.

In order to prevent this phenomenon, in conventional paper making equipment,
Measures have been taken such as installing a separate air cushion tank as a surge tank in the stock supply piping of the hydrolink head box, or installing a head box with an air cushion box.

However, a separate air cushion tank requires installation space, and the installation of a head box with an air cushion box is subject to major restrictions on posture, which poses many difficulties in paper machine design.

Based on the above-mentioned viewpoints, the present invention provides a pulsation-preventing screen that is used as a screen device for supplying selected stock to a hydraulic head box, and is capable of completely eliminating pulsation in the line, particularly on the discharge side of the screen device. An air chamber with adjustable pressure is installed at the top of the filter body with a screen cylinder, and a pressure detector is installed to detect the pressure at the bottom of the screen cylinder, and the pressure in the air chamber is determined based on the detection result. The feature is that the pressure on the discharge side is kept constant regardless of pressure fluctuations on the supply side.

Furthermore, the second invention according to the combined application provides a pressure-adjustable air chamber at the top of the filter body having a screen cylinder, and automatically adjusts the pressure in the air chamber based on the detected pressure at the bottom of the screen cylinder. By installing a liquid level control device that keeps the liquid level in the air chamber constant, it is possible to effectively deaerate the paper stock, and the pressure on the discharge side is more reliably maintained. has.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The anti-pulsation screen device of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system diagram of an example of a paper making apparatus in which a screen device of the present invention is installed in a pipeline.

FIG. 2 shows a longitudinal sectional view of an embodiment of the screen device of the present invention.

Further, FIG. 3 shows an enlarged view of the portion seen along line 2--2 in FIG.

As shown in FIG. 1, a screen device 1 of the present invention
is a device that supplies selected stock to a hydraulic head box 4 that injects selected stock (a good valve aqueous solution filtered to a state suitable for paper making) onto an endless net 3 of a continuous paper machine 2, and includes a fan pump 5. The raw material from the seed box (raw material aqueous solution tank) 6 sent by the paper machine 2 and the circulating white water that drips from the endless net 3 of the continuous paper machine 2 and enters the tank 7 are received from the inlet 8. There is.

The screen device 1 of the present invention has an internal structure as shown in FIG.

The inflow port 8 is provided approximately midway between the top and bottom of the cylindrical tank 9, and is provided to enable raw material to be supplied into a screen cylinder 10 that is concentrically installed in the lower half of the cylindrical tank 9.

That is, an annular chamber 11 formed between the screen cylinder 10 and the cylindrical tank 9 has its upper end closed off by an inward flange 12 that projects horizontally from the inner peripheral surface of the cylindrical tank 9.

This inward flange 12 is provided to prevent the raw material aqueous solution (mixed circulating white water) supplied from the inlet 8 from directly entering the chamber 11 .

On the other hand, an airfoil-shaped scraper blade 13 faces inside the screen cylinder 10.

Three to four airfoil scraper blades 13 are provided at equal intervals.

Each airfoil scraper blade 13 has a screen cylinder 1
They are attached to upper and lower arms 15A and 15B on a rotating shaft 14 that is erected at the center so that the axes coincide with 0 and 0.

The arms 15A and 15B form an upper and lower pair, and the upper arm 15A is located at the front and the lower arm is located slightly at the rear in the rotational direction of the rotating shaft 14 (in this embodiment, the rotational direction of the clock hands when viewed from above). The airfoil-shaped scraper blades 13 fixed to the tips of these two arms are inclined so that the upper part is forward in the direction of rotation and the lower part is slightly backward.

Each airfoil-shaped scraper blade 13 has an airfoil-shaped cross section that is thicker at the leading edge in the direction of rotation and becomes thinner toward the rear edge, and is provided with a clearance of about 2 nm from the inner peripheral surface of the screen cylinder 10.

Inside the cylindrical tank 9 slightly above the inlet 8,
A partition wall 16 shaped like an inverted hopper bottom is provided so as to become higher toward the center.

The center of the partition wall 16 is formed with a hole 17 that passes through the partition wall 16 vertically, so that air in the raw material aqueous solution generated by the operation of the airfoil scraper blade 13 can float upward from the center.

Above the partition wall 16 is a diaphragm 1 that covers the liquid level in the cylindrical tank 9.
8 is included.

This diaphragm can be slid up and down with its outer periphery in close contact with the inner periphery of the cylindrical tank 9. It is a flexible membrane with an air vent hole 19 in the center, and the wall surface of the gas-liquid interface is free from dirt. It helps in prevention.

An air chamber 20 is formed above the diaphragm 16 .

Pressure air is supplied to this air chamber 20 from a nutsch type compressor 21, so that a constant pressure is always applied to the liquid level a.

The pressure inside the air chamber 20 is always kept constant by exhausting excess pressure by opening and closing the pressure control valve 22.

The pressure control valve 22 is operated by a signal from a pressure detector (D/P cell) 23 attached to the bottom of the circumferential tank 9.

On the other hand, a liquid level control device 24 is provided outside the upper half of the cylindrical tank 9.

This liquid level control device has an upper part connected to the air chamber 20 via a ventilation pipe 25, and a lower part connected to the partition wall 16 via a liquid passage pipe 26.
It communicates with the liquid chamber 9A on the upper side, and has an outlet 28 in the middle that is opened and closed by a valve 27.

The cylindrical tank also has an annular chamber 1 formed in the lower half.
A discharge port 29 for taking out the selected stock from the lower end of the screen cylinder 1 is provided in the bottom plate 30, and the screen cylinder 1 is provided without being filtered.
A discharge port 31 is provided for discharging inferior components remaining inside the container.

This discharge port 31 is opened and closed by a bleed valve 32.

Although the rotating shaft 14 uses a motor 33 and a belt 34, it may be driven as a gear hook.

Since the present invention is configured as described above, the raw material aqueous solution supplied from the inlet 8 to the cylindrical tank 9 by the fan pump 5 is transferred to the airfoil scraper blade 13 which is rotated along the inner peripheral surface of the screen cylinder 10. The stock is filtered into the chamber 11 as a selected stock, and is then pressure-fed to the hydraulic head box 4 through the discharge port 29.

At this time, due to disturbances such as the rotation of the fan pump 5 and fluctuations in the liquid level on the downstream side of the pump, a condition is created in which the discharge pressure and amount change slightly, but the liquid level a in the cylindrical tank 9 Since the constant pressure in the air chamber 20 acts and pressurizes the liquid, no pulsation occurs in the selected stock exiting the discharge port 29.

The pressure in the air chamber 20, that is, the pressure applied to the liquid in the cylindrical tank 9, is adjusted by detecting the pressure of this liquid with the pressure detector 23, and is at a value that can avoid pulsation. A constant amount of carefully selected stock is always injected onto the endless net 3 from the hydraulic head box 4.

Therefore, there is no need to provide an inconvenient air cushion chamber to the hydraulic Radbox 4.

In addition, since the liquid level a in the cylindrical tank can be maintained very easily and accurately by the liquid level control device 24, the pressure detector 23 can accurately detect fluctuations in air pressure with respect to a constant liquid head and adjust the pressure. control valve 22
It becomes possible to give an operating signal to the

Therefore, the device of the present invention not only makes it possible to stably discharge selected stock from the hydraulic head box of a paper machine and even out the amount of paper, but also makes it possible to discharge air cushion from the hydraulic head box. Since it is possible to eliminate the chamber, it has excellent effects such as greatly easing restrictions on paper machine installation.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a paper machine using the device of this invention, Fig. 2 is a vertical cross-sectional side view showing an embodiment of the device of this invention, and Fig. 3 is a system diagram of a paper machine using the device of this invention.
The figure is an enlarged □ plan view of the section viewed from the line ■-■ in Figure 2. 1...Screen device, 9...Cylindrical tank, 10...Screen cylinder, 20...
...Air chamber, 22...Pressure control valve, 23...Pressure detector.

Claims (1)

[Claims] 1. A pressure control valve in which the upper part of a cylindrical tank with a built-in screen cylinder and which is capable of freely filtering selected stock from raw material aqueous liquid is formed into an air chamber, and the pressure in this air chamber can be freely adjusted. An anti-pulsation type screen device characterized in that a pressure detector capable of receiving an operating signal is provided at a position at the bottom of a screen cylinder where pressure can be freely detected, thereby absorbing pressure fluctuations in a pipeline. 2 A cylindrical tank with a built-in screen cylinder that can freely filter selected stock from raw material aqueous solution has an air chamber formed in the upper part, and a pressure sensor that gives an operating signal to a pressure control valve that can freely adjust the pressure in this air chamber. The screen cylinder is located at a position where pressure can be detected freely at the bottom, and a liquid level control device is installed to maintain a constant liquid level in the cylindrical tank, making it possible to absorb pressure fluctuations in the pipeline. Anti-pulsation type screen device.