US3336680A - Method for drying sawn wood goods in drying kilns - Google Patents

Description

United States Patent 3,336,680 METHOD FOR DRYING SAWN WOOD GOODS IN DRYING KILNS Gunnar Lennart Ahlstedt, Alfredshem, Sweden, assignor to M0 Och Domsjo Aktiebolag, Ornskaldsvig, Sweden, a corporation of Sweden No Drawing. Filed July 12, 1965, Ser. No. 471,464 Claims priority, application Sweden, July 17, 1964, 8,751/ 64 3 Claims. (CI. 34-22) This invention relates to a method for drying sawn wood goods.

In the manufacture of wood goods until some decades ago the goods were usually dried in open timber yards. For reducing the capital tied up in the timber yards and to accelerate the turnover rate, the wood goods are now to a large extent subjected to artificial drying. This drying usually is carried out in drying chambers or drying channels through which preheated air is directed. The air passing through said channels has as it object both to transport the heat required for drying the wood goods and to evacuate the water given off during the drying process. The drying capacity of artificial drying sheds is in many cases limited by the fact, that the timber assortment and the drying periods cannot always be adjusted to the volume of the drying shed available or to the calorie amount produced by the generation unit in the boiler house or which the air is capable to feed to the wood goods. It is well known that considerable differences in drying time are obtained when equal amounts with respect to volume of different wood species :are being dried, such as, for example, goods of pine and spruce. As a result thereof, an artificial drying plant employed for the drying of, for example, pine goods can be .utilized to 100 percent and in certain cases prove to be undersized in relation to the manufacturing and handling capacity in general for this material, while the drying plant is oversized for another wood species such as, for example, spruce goods which are substantially easier and quicker to dry and require smaller dried volumes.

Normally, during a certain period of the year only goods of one wood species are manufactured, for example of pine, and during another period of the year goods of another wood species, for example spruce. Thus, the capacity of the sawing lines is not fully utilized when sawing one of the said wood species, due to the too low capacity of the artificial drying shed, While during the time needed for sawing the other wood species the capacity of the drying shed is not fully utilized in spite of fully utilized sawing capacity.

The present invention eliminates the aforesaid disadvantages.

The method according to the invention adapted for drying sawn wood goods in dry-kilns is characterized in that wood species of a shorter drying time are dried in the dry-kiln at the same time as wood species of a longer drying time. The term dry-kiln in this connection is to be understood as a single so-called drying channel as well as a plurality of drying channels assembled to a drying unit.

The method is carried out such, that the two wood species are fed into the drying plant in such proportions that the capacity of the drier available is fully utilized. In cases when the drying unit comprises a plurality of drying channels, certain of the channels may be reserved for the one or the other wood species, but it is, of course, also possible to mix the diflerent wood species in the same drying channel in the proportions according to their drying time, as appears from the examples.

The application of the invention is illustrated in the examples as follows.

3,336,680 Patented Aug. 22, 1967 ice Example I The production capacity of a sawmill for sawing pine wood was at full operation of the sawing lines (frame saw lines) about 27 timber packages per 24 hours (1 timber package corresponds to about 3 standards). The

dnying unit of the sawmill comprised 8 drying channels each holding l5 packages, i.e. a total of 120 packages. At continuous operation and at a drying time of about 5 days for pine timber the drying unit could be charged with about 24 packages per day. At full operation of the frame saw lines for pine timber there Was, thus, a surplus of 3 packages a day. When sawing spruce timber in the frame saw lines, at full operation the same amount as in pine sawing could be delivered to the drying unit. Due to the shorter drying time of the spruce timber, about 3-4 days, the drying unit could be charged continuously with about 27 packages of spruce timber per day, which involved that for every cycle only 6 of the 8 drying channels had to be utilized.

When the drying unit according to the invention was charged with spruce and pine, the pine timber was supplied from two frame saw lines to 6 of the channels of the drying unit and the spruce timber from one frame saw line to the remaining two channels in the drying unit, thereby utilizing the full capacity of the drying unit, i.e. 27 packages per day. This means in practice that for a sawmill which, for example, for 8 months of the year sawed pine timber and for the remaining 4 months spruce timber, a capacity of 8 8=64 channel months of pine and 4 6=24 channel months of spruce were obtained, i.e. a total of 88 channel months by applying the conventional method. By sawing according to the invention, however, when the entire drying unit was utilized, a capacity of 8 l2=96 channel months was obtained.

Example 2 ing unit was achieved at the same time as full employment for the personnel could be provided.

With respect to sawing, the invention, in other Words, implies the idea of sawing different kinds of raw goods in one or several lines in such a manner, that the quantities of sawn goods obtained complete each other when being fed to the drying plant, so that for promoting the production the artificial timber shed is well utilized during the entire production year.

When applying the invention, the different types of raw goods may also be sawn in different Ways relative one another-this applies especially to so-called sideboards for which, for example, spruce goods are given the thickness A;" and /s" respectively and pine goods the thicknesses 1" and %1" respectively. In this Way, the said good can be measured automatically and sorted with respect to their dimension even when they are mixed and transported at relatively high velocities. Thus, an easy sorting into different types of timber is obtained which can be utilized in connection with the charging of the drying plant. The centre yield which substantially is much coarser, is found in a smaller number and can easily be divided as to wood species, because it usually is transported on separate conveyors, at least one for every sawing line.

goods may also be marked in difierent ways, which marks may be sensed, for example, by photoelectric cells controlling the sorting.

The proposed method which, of course, is adaptable also to any wood species other than spruce and pine eliminates the disadvantages mentioned above with respect to the utilization degree of the artificial drier and follows a more uniform employment of the personnel.

What I claim is:

1. A method of utilizing the full drying capacity of a kiln for drying sawed wood products by drying sawed products of different varieties and having diiferent drying times in the kiln at the same time, which comprises selecting at least two varieties of sawed products, of which at least one of the varieties has a faster drying time, and introducing such wood products into the kiln in an amount sufficient to substantially fill the kiln, and in volume proportions to one another related to the drying time of each variety, the capacity of the kiln, and the saw production capacity, continuously drying the wood products in the kiln, and removing the dried sawed wood products of each variety from the kiln when dried, so that each variety is present in the kiln for the least possible drying time, the faster drying variety being present for the shorter time, and replacing the dried wood products as they are removed with more sawed wood products, in an amount sufficient always to keep the kiln substantially filled, and at maximum capacity for the saw production of each variety.

2. A method in accordance with claim 1 wherein at least one of the varieties of wood products is identified according to drying time.

3. A method in accordance with claim 1 wherein the wood products comprise a mixture of pine and spruce.

References Cited UNITED STATES PATENTS 2,288,154 6/1942 Cobb 3426 KENNETH W. SPRAGUE, Primary Examiner.

Claims (1)

1. A METHOD OF UTILIZING THE FULL DRYING CAPACITY OF A KILN FOR DRYING SAWED WOOD PRODUCTS BY DRYING SAWED PRODUCTS OF DIFFERENT VARIETIES AND HAVING DIFFERENT DRYING TIMES IN THE KILN AT THE SAME TIME, WHICH COMPRISES SELECTING AT LEAST TWO VARIETIES OF SAWED PRODUCTS, OF WHICH AT LEAST ONE OF THE VARIETIES HAS A FASTER DRYING TIME, AND INTRODUCING SUCH WOOD PRODUCTS INTO THE KILN IN AN AMOUNT SUFFICIENT TO SUBSTANTIALLY FILL THE KILN, AND IN VOLUME PROPORTIONS TO ONE ANOTHER RELATED TO THE DRYING TIME OF EACH VARIETY, THE CAPACITY OF THE KILN, AND THE SAW PRODUCTION CAPACITY, CONTINUOUSLY DRYING THE WOOD PRODUCTS IN THE KILN, AND REMOVING THE DRIED SAWED WOOD PRODUCTS OF EACH VARIETY FROM THE KILN WHEN DRIED, SO THAT EACH VARIETY IS PRESENT IN THE KILN FOR THE LEAST POSSIBLE DRYING TIME, THE FASTER DRYING VARIETY BEING PRESENT FOR THE SHORTER TIME, AND REPLACING THE DRIED WOOD PRODUCTS AS THEY ARE REMOVED WITH MORE SAWED WOOD PRODUCTS, IN AN AMOUNT SUFFICIENT ALWAYS TO KEEP THE KILN SUBSTANTIALLY FILLED, AND AT MAXIMUM CAPACITY FOR THE SAW PRODUCTION OF EACH VARIETY.

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