GB2139258A - A fibre distribution method and device for a dry paper machine - Google Patents

Abstract

A dry paper machine fibre distribution method and device for the even distribution of fibres to achieve the formation of a web in the transverse direction. For the attainement of smooth fibre distribution the air/fibre mixture is led to one end of a long pipe-like distribution element (1) and the air/fibre mixture is blown out from the distribution element (1) with the aid of the air nozzles (2) in the essentially open side (5) of the element. The air nozzles (2) are spaced at 50-250 mm intervals. The air pressure coming to each nozzle (2) can be regulated with the aid of valve 3 and pressure can be read from meter 4. <IMAGE>

Description

SPECIFICATION A fibre distribution method and device for a dry paper machine The subject of this invention is a method and device for dry paper machine fibre distribution of the web in the transverse direction.

In the paper industry dry paper machine it is important to achieve he desired transverse fibre profile in the dry paper web to be made.

In order that a certain profile may be achieved the formation of the web must be under control and regulation over the full web width.

In the formation part of the stuff track of a conventional dry paper machine and fibre distribution equipment for the control of the transverse fibre distribution (the profile) are based on the use of either suction air control in the machine transverse direction e.g. by means of valves, or by use of a sheet or similar device in the machine transverse direction to control the secondary air used in forming the web.

The control of fibre distribution in the transverse direction is not usually very successful with these designs because mechanical control elements are not fundamentally very precise, since they are subject to malfunction and require servicing. In additiont their passive control mode makes them insensitive to local disturbance in the fibre air mixture, as in fibre bunching and other concentration malfunctions.

For the abovementioned reasons the distribution of fibres in the transverse direction using conventional equipment is not very successful, as the variations in the transverse direction of the web are typically 5-10%.

The purpose of this invention is to eradicate the aforementioned drawbacks and achieve a fibre distribution method and relevant equipment that distributes the fibre in the direction transverse to the formation wire evenly into the desired stuff track In order to achieve this effect it is characteristic to the method according to this invention that the air/fibre mixture is led into a long pipelike distribution element at one end, the air/fibre mixture being blown out of its essentially open side with the aid of the nozzles in the element.

It is characteristic to one advantageous mode of application according to the invention that the distribution of the air/fibre mixture while it is blown out of the distribution element is adjusted by separately regulating the air pressure of each nozzle.

It is characteristic to the method according to this invention applied to the distribution equipment of a dry paper machine, that the fibre distribution equipment consists of a long pipelike distribution element, to one end of which the air/fibre mixture can be led and from the essentially open side of which the air/fibre can be blown out and that the distribution element is furnished with air nozzles at 50-250 mm intervals. By regulation the blowing pressure of the air nozzles so that the air/fibre mixture blown into the distribution element is evenly distributed along its length, a control system free of mechanical operations is achieved, which in addition efficiently mixes the air/fibre mixture to disperse possible local fibre concentrations.

It is characteristic to several advantageous modes of application of fibre distribution equipment in accordance with the invention that the distribution element is formed of pipe cut along its longitudinal section. This is a simple and cheap means of achieving an operationally serviceable distribution element, in which the longitudinal cut form the gap through which the fibres directed to the wire are blown.

It is characteristic to several modes of application of fibre distribution equipment that the pressure of each air nozzle is regulated as desired by separately operated devices and measured by separate measuring elements.

The invention is described more precisely in the following example with the aid of reference to the accompanying drawings.

Figure 1 represents a cross-section of a distribution element in accordance with the invention in which the distribution element essentially consists of pipe cut along the longitudinal section and pressed to size somewhat from the sides.

Figure 2 represents the pipe illustrated in Fig. 1 as seen from one side.

The air and fibre mixture is led in from one end of the distribution pipe 1 (in Fig. 2 for example from the right). The pipe is cut through along its entire length and pressed somewhat from the side to size soXthat a longitudinal opening 5 is formed in it. Blowing nozzles 2 are installed in pipe 1, typically at about 100 mm separation distances. The air pressure coming to each nozzle can be regulated with the aid of valve 3 and pressure can be read from meter 4. The feed lines to the nozzles are led outside pipe 4 in a separate casing 6.

The distribution speed of the air/fibre mixture led into pipe 1 is regulated by valves 3 which control the blow pressure of nozzles 2 to such a value that an equal quantity of fibres per unit time evenly leaves the opening 5 along the length of pipe 1. When the desired transverse fibre distribution has been achieved, the readings of meters 4 are recorded in order that the same result can be easily repeated at a later date.

To expert persons in this field it is clear that the various modes of application of the invention are not only limited to the example put forward above but may be varied within the framework of the patent claims hereinafter put forward.

Claims (7)

1. A fibre distribution method for a dry paper machine, in which method fibres are made to spread evenly in the web to be formed in a transverse direction, characterised in that the air/fibre mixture is led into a long pipe-shaped distribution element (1) from one end and that the fibre/air mixture is blow out from the distribution element (1) from its essentially open side (5) by means of the air nozzles (2) in the element.

2. A method in accordance with Patent Claim 1 characterised in that the distribution of the air/fibre mixture in its leaving the distribution element (1) is regulated by adjusting the said blowing pressure of all the air nozzles (2) separately.

3. A dry paper machine fibre distribution element intended to be realised in accordance with either Patent Claim 1 or 2 characterised in that the fibre distribution unit consists of a long pipe-shaped distribution element (1) to one end of which is led the air/fibre mixture to be distributed and from the essentially open side (5) which the air/fibre is exited, and that the distribution element (1) is furnished with air nozzles (2) at 50-250 mm separation distances.

4. A fibre distribution element in accordance with Patent Claim 3, characterised in that the distribution element is composed of longitudinally cut pipe.

5. A fibre distribution element according to Patent Claim 3-4, characterised in that the pressure of each air nozzle (2) is adjustable as desired by separate operating devices (3) and measured by separate measuring element (4).

6. A fibre distribution method substantially as hereinbefore described with reference to the accompanying drawing.

7. A dry paper machine fibre distribution element substantiall as hereinbefore described with reference to and as illustrated in the accompanying drawing.