US2038658A - Method and apparatus for removing bark from timber by means of fluid jets - Google Patents

Description

April 28, 1936. K. J. KARLSTROM 2,038,658

METHOD AND APPARATUS FOR REMOVING BARK I FROM TIMBER BY MEANS OF FLUID JETS Filed June 26, 1933 211' /.s+r a m /5 INVCNTOK Patented Apr. 28, 1936 PATENT QFFICE METH OD AND APPARATUS FOR REMOVING BARK FROM TIIVIBER BY MEANS OF FLUID JETS Karl Johan Karlstriim. Thurbo, Hedemora, Sweden, assignor to Wikmanshytte Bruks Aktiebolag, Wikmanshyttan, Sweden, a corporation of Sweden Application June 26, 1933, Serial No. 677,758 In Sweden July 30, 1932 6 Claims. (Cl. 144208) Various methods of removing bark from timber or pulp wood have been suggested, the means generally used for this object being machines with rotating knives or cutters, or barking drums within which the logs are placed, the removal of the bark being effected by the tumbling and abrading ac-v tion of the logs upon each other, or the action of barking irons in the drum upon the logs, when rotating the drum. entails a considerable loss of wood, say 10l'2% of the solid wood of the timber. It is true that the use of a barking drum does not entail anyconsiderable loss of wood, but thenthere arises another drawback, the rubbing action of the blocks upon each other or against the barking irons, causing bark or other impurities to be forced into superficial cracks in the logs. This is a great disadvantage, when the timber is to be used in the manufacture of wood pulp. The bark removing machines and the barking drums have ohe disadvantage in common, i. e. great costs, both considering procuring and running expenses. e

It has also been suggested and attempted. to use fluid jets for the removal of the bark, but the attempts hitherto made have not proved successful, inasmuch as it has proved hard or even impossible to remove the bark, especially when handling fresh cut timber or timber cut during any other season than the sap-time. In those cases the bark is tightly cemented to the wood and the loosening effect of the fluid jet will be merely partial or even none at all.

My present invention relates to a method for barking timber by means of fluid jets, said method in practical operation having proved highly successful, the results being excellent even from economical points of view.

The invention is characterized by the following features. At first, the non-barked timber by means of hot water or steam is heated to a suitable temperature below 100 C. whereupon the timber is immediately subjected to a quick cooling action by means of water or any'other suitable fluid. The timber thus prepared is subjected to the'action of one or more powerful'fluid jets, directed crossways against the timber and caused to move'along the length of the same. Preferably, during the action of the jets thetimbers are fed slowly along and at the same time imparted an intermittent turning movement, turning a certain angle for each step, with the object Barking 'by means of knives the wood in order to loosen the bark. These attempts were carried out in closed containers and to high temperatures, more than 100 C., and after the heating the timber was allowed to cool slowly. In this procedure it appeared that the bark loosened by the heat, fastened anew during the cooling, the cause probably being that the resinous matters or other adhesives, which cement the bark to the wood, and which had softened during the strong heating, regain their former state during the slow cooling period, thus causing the bark to stick anew. In this case it is impossible to remove the bark by means of water jets.

Thus, it is evidently a matter of great importance that the wood is floated or soaked in water or any other cooling medium of comparatively,

low temperature immediately after the heating procedure. 4

Bythis proceeding the following advantages are attained:

(1) The timber is cooled quickly, which prevents the heat latent in the superficial wood and in the bark from drying the resinous matters or other adhesives, and consequently also prevents said resinous matters or adhesives from cementing the bark to the wood anew.

(2) The bark, having been brought into a mellow or loosened condition by means of the heat, will readily absorb fluid, which also contributes to the easy removal of the bark.

(3) The treatment with cooling fluid causes strains in the layer of bark and the superficial wood-layer, which strains also have a profitable Fig. 2, Fig. 2 is a plan view of the apparatus.

Figs. Sand 4 illustrate alongitudinal section and an end view respectively, of a preferredform or an apparatus for treating the timbers withhot water previous to the 'removaljof the barkfland.

Figures 5 and 6 'are respectively side and plan views showinga log transported by conveyors.

The apparatus in question comprises a number of containers, l, 2,. 3, 4, 5, 6, within which the logs to betreated are placed, the containers being provided with covers. In case the preparatory treatment involves the use of steam these covers only need to be placed loosely on the containers,

no pressure being introduced. The covers being brought into place, steam is introduced into the containers through pipes at the bottom, and the temperature is allowed to rise to about IO-90 0. According to the hardness of the bark, i. e.'if the timbers have previously. been floated or not,

.the temperature is maintained during 3-6 hours.

the upper level of the container (Fig.1; showing; this moment of the treatment) from where. they are-transmitted to carriers 1 and'8, feeding the timbers to the obliquely placed diverting members 9 and Ill respectively, each of which. leads the timber to a feeding arrangement. By this feeding arrangement the timbers at. a constant velocity are fed vertically down. to the bark removing apparatus proper. The. feeding arrange,- ment consists of a container l I', from the walls of which alternately stretch a number of inwardly sloping shelves l2 placed on different levels andv sloping alternately from two opposite sides towards the middle of the container, as shown in Fig. 1. This figure. shows the logs i3 at the'mo ment, when they are about to leave the respective shelves to bev brought over to other shelves, where they are caused to move in a direction opposite to their former movement. The lowest shelf of the apparatus carries the logs to the barka certain distance from each other. Between the planks of each group extend endless chains l1, running over chain wheels and designed to move continuously. The chains are provided with catches l8, placed at a certain distance from each other and designed to catch the logs, when leaving the feed arrangement, and carry them along. According to Fig; 2, in a container 26 are arranged two barking or washing tables l4, one of which is designed to take logs from carrier 1 and the other from can'ier 8.

The logs, as they are fed along over the tables M, are subjected to the action of powerful jets of water, from nozzles l9 and 20, directed transversely against the logs and moved sideways in the length direction of the log. Thus the jetsefl'ectively remove the bark, and as the logs ,are periodically turned through an'angIe during the feeding movement, their entire-surface will be '55 acted upon by the jets and the bark will be uniformly removed.

The catches is are placed so far apart, that there is ample time for finishing the barking of a one iog before the next log is brought into barking position. As shown in the drawing the wash.

ing table I4 is placed at an angle, rising from the point where the log enters upon the table, the

' rising angle being adapted to prevent the log from constantly rolling on the table when brought along by the catches. However, as mentioned, above, it is to be noted, that the log must periodically turn through an angle, the intervals of time allowing the barking jets to be brought to work upon the whole surface of the log when the log is moving along the washing table. For this object the table is provided with upwardly extending pins or other obstacles 28 placed at equal distances'apart and each causing the log to turn through an angle during the movement along the table. Having passed the washing table, the log is entirelystripped. Then it is brought over to the carrier 2 I, by which. thelogs are conveyed toa washing drum 22. In this drum possibly remain-r" ing rudiments of bark: or other impurities. removed. However,,the use of the washing'd'rum: is not always necessary. By way of example,the washing drum may be dispensed with in case the Wood is to be used inthe manufacture of sulphate pulp or bleached sulphite pulp.

When leaving the washing drum, the. logs. by

means of a carrier 23 are brought'to thevcontrolling-or check-table 2Q. From-v thezchecki tabl'ez a carrier 25 transports. the logs to the. chipping,

machine.

Evidently, themethod and; apparatus described, above may be varied as to the details, without departing from the range'of the invention.

The present method offers many profitabl'efea-- tures compared to bark removing methodshithento in use. As one of the most importantfeatures. the method in practical use, will turn out much cheaper than former methods. and, at the same. time, it affords extraordinarily good results, as with a careful handling of the apparatus, no wood will be wasted.

These profits to a great extent depend on th preparatory treatment mentioned above, 1. e. the

heating of the timber immediately followed by a-- quick cooling action, a procedure which loosens the bark from the wood and prevents any recementing of the bark to the wood. The heating being carried out at comparatively low temperatures the expenditure of heat and consequently the. fuel consumption will turn out relatively low. As another consequence of the low temperature, the design of the heat treatment containers may be of the simplest and plainest kind.

Using temperatures above 0., would mean work under pressure, and in this case the containers regarding strength, tightness etc. must be designed and manufactured with utmost care. Moreover, the expenditure of heat and the fuel consumption then would be high enough to render the method unpracticable from economical points .of view. Besides the risk is always at hand, that the wood easily shows a-brown colour. In case the wood is to be used in the manufacture of pulp, this means a brown colouring, i. e. a deterioration of the .pulp.

Figs. 3 and 4 show another modification of an apparatus for preparatorily treating the logs with hot water. The log container is denoted with the figure 30. A pump 3| by means of a conduit 32 is connected with the inside of the container, another conduit 33 leading the water rapidly cooling said logs immediately after said heat-treatment by means of any suitable fluid, and subjecting said logs soon after the cooling step to the action of powerful fluid-jets so as to remove the bark, previously softened and loosened by the preceding treatment with heat and cooling fluid.

2. A method for removing bark from timber,

consisting in preliminarily heating the logs by means of steam to a temperature of at most 0., immediately after said treatment drenching and quickly cooling the logs by means or water or other fluid, feeding the logs thus treated slowly along and exposing them along their whole length to the action of powerful fluid jets, directed crossways towards said logs, and causing-said logs during such treatment to intermittently turn through an angle in order to expose all parts of the log surface to the action of the jets.

consisting of a number of containers with means for supplying heating and cooling agents to said logs with the bark attached, one or more washing tables, means for conveying said logs onto said tables, endless carriers combined with the washing tables and provided with catches for moving the logs along said tables, said washing tables being provided with upstanding projections in the way of said logs, so as to cause the logs to intermittently turn through an angle while being fed forward, nozzles'arranged in front of said washing tables, said nozzles being adapted to be 3 moved to and fro in the lengthwise direction of the logs.

4. An apparatus as claimed in claim 3, characterized in this that each washing table consists of a number of longitudinal supports arranged in groups, the supports of each group being arranged at a certain distance from each other, the space between the supports of each group containing said endless carriers provided with the catches and said catches being spaced at such a distance from each other that there will be ample time for conipleting the removal of the bark from one log before the feeding of the next log begins.

5. An apparatus as claimed in claim 3, characterized in this that the washing tables are arranged with a slope, rising in the direction towards the nozzles.-

6. Apparatus as claimed in claim 3, characterized in this that the two washing tables-are arranged within each container, said log convey

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