Classifying – separating – and assorting solids – Sifting – Drum sifters
Patent
1987-05-18
1988-11-15
Reeves, Robert B.
Classifying, separating, and assorting solids
Sifting
Drum sifters
209385, 209664, 366228, B07B 122
Patent
active
047847611
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a drum screen comprising a rotatable screen drum with screening slits extending in circumferential direction and formed between a plurality of parallel rings arranged one after the other and joined together at a predetermined distance from each other by means of cross pieces extending axially on the inside of the rings.
In most chip screens the chips are sorted according to size. In this method screens are generally used having holes or apertures of suitable sizes to allow chips of a predetermined size to pass therethrough. The chips obtained are then treated in various ways. The largest chips are reduced to smaller pieces, medium-sized chips are utilized directly for pulp processes and the finest fraction, splinter-chips and undersize chips, is returned to the process or rescreened, the undersize chips then being utilized for combustion.
Another type of chip screens screen the chips according to thickness. This method results in superior chip quality and considerably higher yield from the economic point of view than screening according to size. The principal screens for thickness screening are known as disc screens and are either flat or V-shaped. In the flat disc screen the chips are fed forward by the rotary. movement of the discs. In the V-shaped disc creen the discs rotate perpendicular to the direction of movement of the chips. The difficulty with both these types, and also with other screens for thickness screening, has been to obtain and maintain a predetermined gap width between the movable machine elements so that no chips thicker than the gap can accompany the prime chips, i.e. those chips wich are thinner than the gap. Furthermore, prime chips often accompany the oversize chips which are returned for re-chipping. In both cases the economic value of thickness screening diminishes. AT 300 441 and AT 373 510 describe drums for sorting corn and squash seeds, respectively. The drums are constructed of a plurality of rings defining therebetween slits through which material can pass. However, the drums described would not be able to be utilized for thickness screening of chip material because of the fact that a great portion of prime chips would accompany the oversize chips which are returned for further chipping.
The object of the invention is to provide a drum screen having a screen drum of the type defined in the introduction which advantageously can be used for thickness screening of chip material. Thereby the invention will obtain said advantages associated with thickness screening such as superior chip quality and considerably higher yield from the economic point of view than screening according to size.
This object is obtained by the invention in that at least a plurality of the rings of the drum screen is provided with a plurality of guide plates arranged along their inner circumference surfaces, substantially parallel to the screening slits between the rings in order to turn long splinters and chip pieces, enabling them to pass through the screening slits intended for that particular chip thickness, that the rings, as is known per se, consist of tubes or rods having radius cross section and bent to substantially circular shape, and that the cross pieces are formed as chip lifters extending in the direction towards the centre-line of the rings.
The invention will be described further in the following with reference to the drawing.
FIG. 1 is an elevational view of a drum screen according to an embodiment of the invention.
FIG. 2 is an end view of the drum screen according to FIG. 1 seen from the outlet end.
FIG. 3 shows parts of a clearing device of the drum screen according to FIGS. 1 and 2.
FIG. 4 shows an elevation of a drum screen according to an alternative embodiment of the invention.
FIG. 5 shows a fragmentary perspective view of the drum screen according to one embodiment of the invention.
FIG. 6 shows a fragmentary perspective view similar to FIG. 5 but according to an alternative embodiment of the invention.
With reference to FIGS. 1 and 2 it is shown
REFERENCES:
patent: 2687212 (1954-08-01), Kerr
patent: 2915182 (1959-12-01), Burnet et al.
patent: 4018675 (1977-04-01), Petrucci
patent: 4178238 (1979-12-01), Harris
patent: 4535895 (1985-08-01), Takiguchi et al.
patent: 4635860 (1987-01-01), Kruyer
Hajec Donald T.
Kone-KMW AB
Reeves Robert B.
LandOfFree
Drum screen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drum screen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drum screen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1102287