FI12320U1 - Screen of a fibre web machine - Google Patents

Description

Fiber screen machine screen

The invention relates to a screen in a fiber web machine, such as a paper or board machine. More particularly, the invention relates to a fiber web machine screen and more particularly to a fiber web machine screen according to the preamble of claim 1.

As is known in the art, fiber web machines include devices for screening and / or sorting unwanted ingredients from a mixture of liquid and other material, which are removed from the fiber web as a reject and the remaining desired portion continues to be accepted for fiber web production. Such devices are used in fiber web machines, inter alia, for coating and surface sizing, as well as for machine cycle and pulping and chemical processing. The purpose of screening / sorting is thus to remove contaminant particles, such as dry matter aggregates, dirt particles, fibers and other foreign matter, as appropriate. A pressure sieve is one such fiber web machine device which, as is known in the art, typically comprises a chamber for flowing a screenable / screenable mixture which is formed as a space on a screen drum having a screen drum surface structure comprising screening slots or apertures therethrough. Within the screen drum, the chamber typically has a rotor element, i.e., a rotatable shaft, for providing the flow of the mixture. Mechanical scrapers mounted on a rotatable shaft have been used to keep the inner surface of the screen drum and especially the screening slots or apertures clean. The scraper typically comprises a blade holder and a scraper blade.

One problem with molding strainers, especially pressure strainers, is the poor molding result, especially when molding fibrous impurities fractions from the surface of a screen drum. The disadvantage of prior art scrapers has been that they often merely flatten / press impurity particles against the screen drum and cause them to press and seal more tightly into the screen drum slots, although the purpose of the pattern is to remove the dirt particles from the screen drum surface and thereby prevent the screen drum.

The object of the invention is to provide a sieve for a fiber web machine in which the problems related to the patterning of the prior art screens are eliminated or at least minimized.

In particular, it is an object of the invention to provide a screen for a fiber web machine where the result of the molding is good and the impurity particles are detached from the surface of the screen drum, thereby preventing blocking of the screen drum.

In order to achieve the foregoing and further objects, the screen of the fiber web machine according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

According to the invention, the screen of a fiber web machine comprises a rotatable shaft and a screen drum spaced about a distance thereof, and an inner surface of a doctor blade disposed on the rotatable blade, is in contact with the inside surface of the screen drum.

According to a further advantageous feature of the invention, the doctor blade is mounted on a rotatable shaft for spring loading via a spring. Preferably, the spring is secured at one end to a clamping projection mounted on a rotatable shaft and at one end to a doctor blade holder. Preferably, at least two spaced apart springs are disposed in the longitudinal direction of the rotatable shaft and the doctor blade between the doctor blade and the shaft.

According to a further advantageous feature of the invention, the material of the screen scraper blade is reinforced, preferably glass fiber, carbon fiber or aramid fiber reinforced, thermoset, preferably epoxy, or acid-proof stainless steel.

According to a further advantageous feature of the invention, the scrubbing edge of the doctor blade has an acute angle of 25 to 40 °.

According to a further advantageous feature of the invention, the screen comprises two doctor blades disposed on opposite sides of the shaft with an angle of 180 °.

According to a preferred feature of the invention, the screen of a fiber web machine is a screen of a coating or surface sizing part of a fiber web machine or a screen of a machine rotation.

According to a preferred feature of the invention, the screen of the fiber web machine is a pressure screen.

According to the invention, the doctor blade for molding the inner surface of the screen screen drum is sharp-pointed so as to provide shear forces between the screen drum and the blade, whereby impurity particles are cleaved off the drum and impurity particles are removed from the screen drum surface.

According to a preferred embodiment of the invention, the material of the doctor blade is a hard and abrasion resistant material, whereby the cutting properties of the doctor blade are maintained throughout the life of the doctor blade.

The screening according to the invention and its advantageous further features provides a better fiber web quality through a more efficient screening / sorting process and a more efficient screening / sorting process, since impurity particles can be effectively removed and at the same time blocking of screen gaps / openings. Furthermore, changing the doctor blade according to the invention is quick and efficient.

In the following, the invention will be described in more detail with reference to the figures in the accompanying drawings, the details of which, however, are not intended to be limited in any way.

Fig. 1 schematically shows a top view of a preferred embodiment of the invention.

Fig. 2 is a schematic side elevational view of a preferred example of the invention.

In the figures, like parts refer to like parts, unless otherwise indicated.

In the example shown in Figures 1-2, the screen 10 comprises a rotatable shaft 12 and a screening drum 15 spaced about it. The direction of rotation of the shaft 12 is indicated by the arrow S in the figure. The shaft 12 is provided with a securing bracket 21 having a spring a blade holder 23 with a doctor blade 24 attached thereto, the cleaning edge 25 of which is in contact with the inner surface of the screen drum 15 and thereby cleans the inner surface of the screen drum 15 from impurities. Preferably, the screen 10 comprises two doctor blades 24 disposed on opposite sides of the shaft 12, having an angle of 180 ° between them. The doctor blade 23 is thus secured to the shaft 12 for spring loading via a spring 22 between the clamp projection 21 and the blade holder 23. Preferably, the stencil blade 24 is loaded with a constant load through the spring loading provided by the spring 22 against the inner surface of the screen drum 15. The spring 22 is thus secured at one end to the mounting projection 21 fixed to the shaft 12 and at the other end to the blade holder 23 of the doctor blade 24. Preferably at least two spaced apart springs 22 between the longitudinal fastening projections 21.

The doctor blade 24 is knife-shaped so that the cleaning edge 25 of the doctor blade 24 is sharp and therefore sharp, with an angle of preferably 25 to 40 ° C. The sharp angle of the cleaning edge 25 is in contact with the inner surface of the screen drum 15. The material of the doctor blade 24 is reinforced, preferably glass fiber, carbon fiber or aramid fiber reinforced, thermoset plastic, preferably epoxy, or acid-proof stainless steel.

The invention has been described above with reference only to a preferred example thereof, the details of which are not to be construed in any way as being narrowly limited. Many modifications and variations are possible within the scope of the inventive idea.

Claims (6)

protection Requirements A screen (10) for a fiber web machine, comprising a rotatable shaft (12) and a screening drum (15) spaced about a distance thereof and a doctor blade (24) disposed in the space between the shaft (12) and the screening drum (15). For keeping the inner surface of the screen drum (15) clean, the doctor blade (24) is mounted on a rotatable shaft (12) for spring loading via a spring (22) and the doctor blade (24) comprises an acute angle cleaning edge (25) Screen (10) according to Claim 1, characterized in that the spring (22) is attached at one end to a clamping projection (21) fixed to a rotatable shaft (12) and to the blade holder (23) of the doctor blade (24). Screen according to one of the preceding claims, characterized in that the cleaning edge (25) of the doctor blade (24) has an acute angle of 25 to 40 -. Screen according to one of the preceding claims, characterized in that the material of the doctor blade (24) is reinforced, preferably glass fiber, carbon fiber or aramid fiber reinforced, thermosetting, preferably epoxy, or acid-proof stainless steel. Screen according to one of the preceding claims, characterized in that the screen (10) of the fibrous web machine is a screen or a machine screen screen of a coating or surface sizing part. Screen according to one of the preceding claims, characterized in that the screen (10) of the fiber web machine is a pressure screen.