FI56216C - A screening arrangement - Google Patents

Description

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Patent- och registerstyrelMn '' Antokin inl * fd och utUkiift · »publk« rad 31.08-79 - (32) (33) (31) Pyydetty etuollwui — Begird prlorltet (71) Oy Tampella Ab, Tampere, Finland-Finland (FI) This invention relates to a screening device having a screen with a chamber with a feed opening for the mass to be screened, the chamber being adapted to be rotated about its axis. a cylindrical or slightly conical screen plate and at least one fixed screen cleaner having a detachable waste outlet pipe open towards the screen plate at a lower pressure than on the surface of the screen plate.

It is already known e.g. the so-called. Jönsson filtration, in which the coarser screen-impermeable fibers remaining on the surface of a cylindrical screen plate in a horizontal position are removed so that a water jet on the other side of the screen plate presses them out and directs them out in an open trough for removal. There are further various drum-like screen devices in which the fibers adhering to the screen and filling its holes or slits are detached by different vanes moving relative to the screen surface, which cause a pressure variation, whereby the fibers leave the screen surface. In the latter devices, the scrap mass has to migrate over the entire screen surface before it leaves the screen. This phenomenon naturally reduces the capacity of the sieve, as the same 56216 particle may enter the holes or crevices of the sieve plate several times before leaving. As the waste mass moves towards its outlet, the concentration of the waste mass also increases so that the acceptable fibers among it no longer separate, but leave with the waste mass.

Finnish patent No. 43,671 discloses a screening device which includes e.g. a screen cleaner in which nozzle tubes are arranged on the outside and inside of the rotating screen surface, which remove the fibers adhering to the screen and guide them along a trough arranged on the inside of the screen to an outlet at a distance from the nozzle tubes.

A disadvantage of this structure is not only its complex structure but also the fact that the outlet chute covers a considerable part of the screen surface, reducing the capacity of the screen.

A pressure screen device with a screen cylinder and a rotating vane around it, which wipes close to the surface of the screen cylinder on the side of the mass to be screened, is also known. This rotating vane has an end-to-end cavity which opens through a gap towards the sieve cylinder and which communicates at one end with the pulp discharge space.

The disadvantages of the above-mentioned devices can be eliminated by a simple device according to the present invention, the main features of which are apparent from the appended claim 1.

The screen cleaner according to the invention has the following advantages over known screen devices:

The coarse fibers which do not pass through the sieve are completely removed over the entire width of the sieve into the outlet pipe of the sieve cleaner, whereby the entire surface of the sieve is cleaned to receive new unscreened pulp. This device does not have vanes which cause pressure fluctuations which would force the impurities of the pulp through the sieve plate, but the vanes used in the sieve device according to the invention only remove the impurities from the sieve plate so that they can be easily removed.

3,56216 The use of a fixed screen cleaner, which also has a fixed reject outlet pipe, has the advantage of a simple structure in which the movement of the particularly difficult-to-flow reject is easily controlled due to the simple structure. When using a fixed strainer cleaner, it is technically possible to simply install a shower water pipe inside the strainer in order to improve the removal of the reject and its mobility.

Furthermore, the use of a rotating screen drum and a fixed screen cleaner which is immobile relative to the acceptor tube has the advantage that the pressure oscillation in the acceptor-w tube is small, substantially less than when using rotary screen cleaners movable relative to the acceptor tube, which cause a regular rotation. This pressure oscillation is particularly detrimental when the sorters are used in the papermaking process before the headbox of the paper machine, whereby the pressure oscillation caused by the sorters causes a harmful variation in the surface weight of the paper product.

The operation of the screening device is explained in more detail in the accompanying drawings, which show an embodiment according to the invention fitted to a pressurized wood pulp drum screen.

Figure 1 shows a vertical section of the screen device.

Figure 2 shows a horizontal section.

Figure 3 shows the different parts of the cleaning device.

In the closed state rotates in the direction shown (Figure 2) myocardial linterimäinen screen cylinder 1, from which pulp is fed aukos-to 2. The accept passes through the screen drum 1 and is removed from the top section 3. The coarser the reject adheres to the surface of the screen and moves following the drum sihdinpuhdistajaan 4, wherein there is less pressure than on the outer surface of the screen. The sieve cleaner 4 is formed by a tubular part, the length of the sieve drum, opened from the side, the so-called an outlet pipe 5 which collects the waste mass over the entire width of the sieve. In order to increase the efficiency of the cleaning of the wreckage mass, a wing-shaped release member 6 is connected to the outlet pipe, the pressure fluctuations caused by the impulses detaching the waste mass from the screen surface and its slits. The removed 4,56216 waste mass follows the inner surface of the wing into the outlet pipe 5. The cleanliness of the screen plate is enhanced by a spray pipe 8 placed inside the drum 1, which, by diluting the waste mass at its outlet, reduces the acceptable mass according to the waste. The circumferential speed of the screen drum must be high enough to cause turbulence on the surface of the drum to prevent the felting phenomenon. If sagging occurs, wings can be placed in the vicinity of the screen drum to provide pressure impulses away from the screen.

The closing piece 7 aims to ensure the flow of the mass flow in the direction of rotation of the screen drum 1. -

It is clear that the number of screen cleaners can be varied and especially in screen drums with large diameters - more screen cleaners may be required.

Claims (3)

5,56216 1. Shuttering of the chambers of the enclosure with the inerting of the chambers of the enclosure, and of the chambers of the enclosure vilket utloppsrör räder ett lägre tryck än vid siktytan, kännetecknad av, att i samband med utloppsröret anpassats ett som lösgöringsorgan för rejekt-massan fungerpl släpplist eller vinge (6) som apassats att föror-Saka en trycytäning sidan av utloppsrörets (5) öppna del finns ett avstängningsstycke (7). A screening device having a chamber with a feed opening for the mass to be screened, a cylindrical or slightly conical screen plate rotatably arranged in the chamber about its axis and at least one fixed screen cleaner with a detachable waste outlet pipe open towards the screen plate with a known lower pressure in that a discharge strip or a wing (6) is arranged in connection with the discharge pipe as a means for removing the scrap, which is adapted to cause a pressure reduction on the screen plate (1), and on the opposite side of the open part of the discharge pipe (5). 2. A signaling device according to claim 1, which can be used as a shear device (4) and a shear device (1). Device according to Claim 1, characterized in that the screen cleaner (4) is adapted to remove the waste mass over the entire width of the screen plate (1). Device according to Claim 1, characterized in that the position of the sieve cleaner (4) relative to the sieve can be adjusted arbitrarily. 3. An application as defined in claim 1, which is incorporated herein by reference in its entirety (4).