Separating apparatus

The invention relates to an apparatus for the separation of edge trimmings, in connection with a pulper. The upper portion of the jacket of the pulper (1) serves as a jacket of a first cyclone (5), a second cyclone (8) opposite in direction being provided within said cyclone (5). When the air flow enters the second cyclone and the direction thereof is reversed, it is essentially retarded, whereby also light paper particles fall into the stock contained in the pulper. The object is to provide an efficient device for the separation of edge trimmings, which device does not spread dust in the surroundings.

In paper production, relatively large amounts of surplus paper are formed, 
especially so called edge trimmings. Such surplus paper is fed back into 
the process, i.e. into a so called pulper. 
Previously the most common practice has been to first cut the edge 
trimmings and the like paper into relatively small pieces in a fan 
provided with blades, whereafter the paper pieces have been fed through an 
overpressure pipe into a pulper having an open upper end. Disadvantages of 
this practice are the noise in connection with the cutting of the paper 
and an abundant dust formation above the pulper. 
The object is to provide a new apparatus for the separation of edge 
trimmings and the like, in connection with a pulper, which apparatus 
eliminates the above disadvantages. 
The apparatus according to the invention is characterized in that it 
comprises at least one cyclone provided in connection with the upper 
portion of the pulper. The upper portion of the jacket of the pulper 
preferably serves as the cyclone jacket as well. 
One cyclone may suffice, if the paper in question is relatively coarse i.e. 
heavy. In order to increase the efficiency of the separating properties, 
especially in view of finer paper, there is, according to a preferred 
embodiment of the invention, arranged a second cyclone within the first 
one, the second cyclone being reversed, i.e. opposite in direction with 
respect to the first cyclone. When the direction of the air flow is 
reversed on entering the second cyclone, it is essentially retarded, 
whereby also light paper particles fall into the stock contained in the 
pulper. 
The cover of the pulper can be provided with water nozzles, whereby the 
paper which has possibly remained on the surface of the stock is pressed 
down into the stock by intermittent water sprays through said nozzles.

In the drawing, the pulper is generally indicated by the reference numeral 
1, the stock contained in the pulper being indicated by the reference 
numeral 2. The reference numeral 3 indicates a stock agitator propeller 
which is driven by an electrical motor 4. The stock discharge pipe is not 
shown in the drawing. 
The upper portion of the jacket of the pulper forms the jacket of a first 
cyclone 5. A cover of the cyclone 5, which cover closes the pulper, is 
indicated by the reference 5a and cyclone inlets by 6 and 7, the reference 
numeral 6a indicating separate conduits of the inlet 6. A second cyclone 8 
is positioned within the first cyclone 5, preferably in the middle 
thereof. Said cyclone 8 is opposite in direction with respect to the first 
cyclone 5 and replaces the central pipe of the cyclone 5. Inlets of the 
second cyclone 8 are indicated by 9 and 10, and the jacket 11 of the 
cyclone 8 extends to a certain extent down into the stock 2, whereby the 
stock surface 2a rises slightly within the jacket 11 under the influence 
of underpressure. A fan 15 sucks the air flow out of the cyclone 8 through 
a central pipe 12 thereof. 
The reference numeral 13 indicates water nozzles positioned in the cover(s) 
of the cyclones 5 and 8, whereby the paper which has remained on the 
surface of the stock is pressed down into the stock by intermittent water 
sprays through said nozzles. The reference numeral 14 indicates a 
circulation pipe for the spray water, including a pump. However, the stock 
2 may be too thick for the system of FIG. 2 to be operative in this 
respect, whereby the water required is obtained from somewhere else. 
By virtue of the apparatus according to the invention, edge trimmings and 
the like can be passed into the pulper as such without any cutting 
thereof, thus avoiding the formation of dust. The number of the conduits 
6a can be chosen to meet the requirements of each particular case. A 
plurality of edge trimmings can be passed through each conduits 6a. Said 
conveyor pipes from different locations are not more closely shown in the 
drawing nor means for adjusting the flow rate and the pressure. The 
required vacuum in the pulper is dependent on the material to be conveyed, 
the conveying distance and, more or less, the speed of the blades. The 
vacuum required for the conveyance can be adjusted by means of a vane 
adjuster provided in the sucking opening of the fan or by varying the 
speed of rotation of the drive motor of the fan.