CA1096678A - Chip dryer - Google Patents

Abstract

Abstract of the disclosure A chip washer comprising a tank holding washing fluid, a conveyor for supplying chips into the tank, a means for setting the fluid and therewith the chips into motion in the tank, a conduit provided with valve for removal from the tank of the foreign substances sepa-rated from the chips and a washed chips removing conveyor, this latter consisting of a screw conveyor ascending obliquely upwardly from the tank with its lower end extending into the washing fluid and the mantle of which is constituted by a strainer tube. The strainer tube of the screw conveyor is encircled by a collecting tube or trough, which returns the washing fluid running off the chips, back to the tank.

Description

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I,~nprovement in a chip dryer The present invention concerns a chip dryer comprising a tank holdins ~,Jashin~ fluid, a conveyor for feeding the chips into the tank, a means for agitatin~ the liquid and therewith the chips in the tank, a conduit with valve for removing from the tank the foreign matter separated from the ch1ps and a conveyor removing the washed chips, this conveyor consisting of an obliquely ascending screw conveyor of which the lower end extends into the washing fluid and the mantle of which consists of a strainer tube.
The chip washer is used to remove from among the wood constituents those foreign substances which could damage the machines employed in cellulose and paper manufacturin~ and which would impair the quality of the pulp and paper~ Suc~ foreign matter is represented by bark, stones, sand, glass shards, scrap iron, etc. The washing fluid used in chip washers is commonly w~ater or white liquor, but other washing liquids may also ~e considered.
In prio~ art a chip washer is known through the UOS. Patent No~
4,022,231. This chip washer of prlor art has the drawback that large quantities of washing fluid escape alon~ with the chips and separate equipment is needed for its separation from the chips.
The object of the present invention is to provide a new type of chip washer wherein the separation of the washin~ fluid from the washed chips takes place in the chip removing conveyor. The invent~on is characterized in that the strainer tube of the screw conveyor is encircled by a collectin~ tube or trough, which returns to the tank the washin~ fluid runnincy off the chips. As the washed chips proceed at a comparatively low speed upwardly, lifted by the screw conveyor, the washin~ fluid will~run off the chips throu~h the strainer tube and along the collecting tube or trough.
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It is necessary, owin~ to mechan~c~l reasons, that there is a cle~r-ance of about 20 t~ 30 m~ between the conveyor screw and the strainer tube, a~d this causes a chip layer to acc~lmulate on the surface of the strainer tube which the screw will not scrape off. This layer impedes the passa~e of water through the tube. In order to eliminate this drawback~ the screw of the screw conveyor of the lnvention is flexible enough to cause it to drag alon~ the mantle of the screw conveyor, or the strainer tube. ~he strainer tube is kept clean by this means.
Flexibility of the screw conveyor is achieved, for instance, in that the screw has no shaft in its portion opposite the Mantle.It is ad-vantageous, on the other hand, to carry the screw of the screw convey-or in ~earings at its top end only, whereby it is caused to drag without restraint a~ainst the inner surface of the strainer tube.
The invention is described in the follo~ing with reference ~eing made to the attached drawing, wherein:-Fig. 1 presents the chip washer of an em~odiment of the invention~sectioned. For the sake of clarity the chip removing conveyor has been omitted in the figure.
Fig. 2 shows the same chip washer, sectioned as well, but turned through 90 degrees compared wi~h Fig. 1.
Fig. 3 shows the same chip washer in top vlew.
In the drawin~, the reference numeral 1 indicatqs the tank of the chip washer, having an upper cylindrical part 2 and a lower, co~ical part 3. From the lower end of the coniaal part 3 departs downwardly the conduit 4, in which stop: valves~ and 6 have been mounted.
The wood chips to be washed are supplied in the dlrection of arrow 7 by t~e screw conveyor 8. Subsequently, the screw conveyor 9 pushes the chips to be washed in under the surface lO of the washing fluid in the tank 1. The shaft of the screw conveyor 9 carries at its low-er end a vane 11, which puts into rotation the washlng fluid and chips in the tank 1, whereby the impurities separate from the chips and settle downwardly. The valve 5 is open and the valve 6 closed, whereby the impùrities accumulate ln the conduit 4. Through the pipe 12, water or washing fluid enters the co~ical part 3~of the tank and lifts the soaked chlps upwardly, whereby only impurities go into the conduit 4.
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The ~hips rising to the surface 10 of the washing fluld are removed in an oblique upward direction with the aid of the ascending screw conveyor 13. The chips fall from the upper end of the screw conveyor 13 into the tube 14, whence they are carried forward in the process.
The screw 15 of the screw conveyox 13 is surrounded by a strainer tube 16, through which the washing fluid runs into th~ collecting tube 17 and thence back into the tank 1. The strainer tube keeps clean and open thanks to the circumstance that at this point the screw 15 lacks a shaft and the screw is flexible enough to drag lghtly against the inner surface of the strainer tu~e 16. For the same rea-son the lower end of the screw ha~s been left without bearing. In con-trast there is a bearing 20 for the shaft 19 at the top end of the screw.
The impurities are removed from the conduit 4 by opening the valve 6 and introducing water through the pipe 18 under pressure, When the conduit 4 has been emptied, the valve 6 is closed and valve 5 opened.
-~ It is obvious to a person skilled in the art that different embodi-ments of the invention may vary within the scope of the claims pre-sented below, This concerns, for instance, the inclination of the chip removing conveyor and the length of the conveyor. The steeper the ascent of the conveyor 13 and the greater its lèngth, the ~igher -is~the~efficiency with which the washing fluid is-separated-from the chips.

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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Improvement in a chip washer comprising a tank holding washing fluid, a conveyor for supplying chips into the tank, a means for set-ting the fluid and therewith the chips into motion in the tank, a conduit provided with valve for removal from the tank of the foreign substances separated from the chips and a washed chips removing conveyor, this latter consisting of a screw conveyor ascending obli-quely upwardly from the tank with its lower end extending into the washing fluid and the mantle of which is constituted by a strainer tube, wherein the improvement comprises that the strainer tube of the screw conveyor is encircled by a collecting tube or trough, which returns the washing fluid running off the chips, back to the tank.

2. A chip washer according to claim 1, characterized in that the screw of the screw conveyor is flexible enough to cause it to drag against the mantle of the screw conveyor.

3. A chip washer according to claim 1, characterosed in that the screw of the screw conveyor lacks a shaft opposite the mantle.

4. A chip washer according to claim 1, characterized in that the screw of the screw conveyor is provided with bearing at its top end only.