US1328660A - Process of drying lumber - Google Patents

Description

F. K. FISH, In.

PROCESS OF-DRYING LUMBER.

APPLICATION FILED MAR-8, 1917. RENEWED DEC. 13,1919.

Patented Jan. 20, 19 20.

' of New York and State of UNITED STATES PATENT ornicn.

FREDERICK KJFISH, JR., OF NEW YORK, N. Y., 'ASSIGNOR TO LUMBER 'IIE AND TIMBER VULCANIZING COMPANY, OF NEW YORK, N. Y.

Specification of Letters Patent.

Patented J an. 20, 1920.

Application filed March 8, 1917, Serial No.'153,489. Renewed December-13, 1919. Serial No. 344,751.

To allwhom it may concern:

Be it known that I, FREDERICK K. FIsH, J12, a citizen'of .the United States, residing at 2 Stone street, New York city, in the county New York, have invented-certain new and useful Improvements in Processes of Dryin Lumber, of which the following is a specification.

The present invention is based upon a proper recognition of the physical characteristics of wood and analogous substances, the chemical constituency of their fluid content, andthe possibility of convertin into an agency for preservation, certain o their contained elements, which, under natural conditions, would form the basis of their deterioration or destruction but refers more particularly to wood.

structurally, wood consists of a skeleton of cellulose intermingledwith other organic substances, collectively designated as lignin, together with a minor proportion of mineral matter or ash. Lignin, while not fully understood chemically, is closel allied to the cellulose element of the woo and since it forms a part of the permanent structure of the wood, it may, for purposes of the present invention, be regarded identical with the cellulose.

To utilize the natural bases of resin, acetic and tannic acid, existing in wood, as preservatives of the wood, it is necessary that they be dislodged from their cellular confinement, separated from their aqueous solvent or vehicle, converted by oxidation and properly distributed through or deposited upon the cellular and fibrous structure of the wood.

I am aware that certain patents have been obtained for drying wood with free steam, and heat under vacuum. By these methods wood may be dried but they require such a length of time to accomplish an ideal and uniform product as to make them uncommercial, from a lumbermans viewpoint and cost such a large amount of money that such a process would not have any commercial value. If the time required to treat wood under such a process were reduced to a point where the methods would produce an amount of wood which would make it of interest to the lumber manufacturer, the heat in the sterilizer under the vacuum step would be of a degree that would cause the a furt er object is of time that only the surface moisture is removed and the resin and gums are distributed upon the fiber of the wood.

One of the objects of the herein set forth process is the reduction of time required for dr 'ing wood and analogous substances;

the drying of certain destructible substances ate may be obtained. A still further object is the treatment of wood in such manner as to fix therein such natural properties of the wood as may be desirable.

The release and conversion of the properties especially the most important of them, namely, the volatile oils which, when oxidized, form resin, is accomplished, according to my invention, by first placing the-wood in a sterilizer which is metically closed; then introducing live steam into the sterilizer under pressure; the temperature and pressure within the sterilizer varying according to the requirements Ofthe substance operated upon in such manner as to prevent injury to the material being treated, simultaneously introducing steam in the heating coils within the sterilizer until the desired temperature and pressure is obtained-and maintaining the temperature for such period of time as may 'be found to be suitable to the material to be operated upon.

At the desired moment a vacuum is created within the sterilizer by the operation of the vacuum pump. If it is advisable to obtain the distillate, a surface condenser is preferable. Simultaneously, all means used to bring the interior of the sterilizer under pressure are operated in such manner and to such extent as is found desirable. The heat in the coils may also be varied to such degree as may be found suitable. The connection with the condenser ermits the steam to flow away from the steri izer, which tends to create a vacuum and reducesthe temperafrom whichthe distill-- capable of being herture therein. This induces a rapid giving able that the transition from .ed, especially,

off of the vapor contained inthe substance",

depending upon the material being treated and the condition of the moisture contained therein. The heating fluids or gases are drawn out of the radiating pipes at this stage of the process and the material placed in a cooling shed, (not shown),-and subjected to a moderately heated, moist atmosphere until the temperature of the interior of the wood and the surrounding atmosphere are harmonized.

Under certain conditions it may be desirpressure to vacuum be extremely gradual in order to maintain the desired conditions of the medium surrounding the material being treat with regard to the degree of saturation thereof.

By way of teaching the invention more in detail, one approved method of practising the same will be described with reference to the accompanying drawing, in which Figure I is a vertical longitudinal section of a sterilizer, suitable for carrying out the steps of the process.

Fig. II is an end view, of the sterilizer.

Fig. III is a schematic view of the apparatus associated with the sterilizer for controlling it.

1 represents a sterilizer of construction suitable for containing water at a temperature and under pressure considerably above the boiling point. It is preferably provided with a presser plate 2 with adjusting screws 3, through means of which the char e of wood may be keptunder pressure whi e being treated. It is also provided with heating' coils 4, by which the temperature of the atmosphere or steam within the sterilizer may be heated to the desired degree; and with pipes 5.-which may be perforated for the purpose of supplying free st'eam within the sterilizer when desired. To equip the sterilizer 1 for conveniently developing the several conditions incident to the difl'erent steps of the process, it is provided with an exhaust pipe 6 leading to a vacuum pump 7 with partly in section interposed condenser 8; 9 represents tracks to receive the car or truck upon which the wood is loaded for introduction in the sterilizer; 10 represents an escape valve.

In order that my process may be more fully and better understood, I will recite in detail the several steps thereof in the drying of 1" x 2" requires from six to seven days, to dry in the ordinary kiln to shipping weight, which is about three-fifths of the weight of green wood. The wood is firstplaced on a truck,

with stickers placed between the layers there-' of and run into the sterilizer 1. The sterirounded the cell walls or fibers now cypress lumber, which ordinarily lizer is then closed and steam is turned into the heating coils at, say, one hundred pounds pressure. The drain or exhaust valve 10 leading from the sterilizer being opened,

steam is then gradually introduced into 7 sterilizer 1,'through perforated pipes 5 until the wood is heated and the steam begins to pass out through valve 10, valve 10 is then closed and the pressure in the sterilizer" raised t0,f say, thirty pou' as above atmosphere, this pressure being maintained for approximately one hour by admitting steam at thirty pounds pressure through perforated pipe 5. Then valve 10 is opened and the pressure in the sterilizer allowed to drop slowly and gradually, say, at the rate of three pounds per hour at the beginning of the said reduction of pressure, steam being crease of'pressure continues the rate thereof is reduced, say, when ten pounds above at- 0 mosphere is reached, the rate of decreased pressure is maintained at two pounds per hour. This reduction is continued until the pressure is reduced to say, ten pounds, be-. low atmosphere, or five pounds absolute. At the state of this final reduction of pressurea sliglft heating takes place as a temperature I of say, 200 F. is maintained; the boiling point is about 126 F. The heat is then cut off from, the heating coils, also the steam from perforated pipes 5,, the vacuum is maintalned until the heat drops below the saturation temperature, when the vacuum isv broken and the wood placed in a cooling compartment, (not shown), ment being preferably provided with insulated walls and a moderately heated, moist atmosphere created therein in which the wood is allowed to remain until the interior temperature thereof and the surrounding atmosphere are harmonized.

The wood will now be thoroughly dried without removing the values of its sap; the latter will be converted especially as to its volatile oils, into resin; this resin having permeated the entire cellular structure of the wood, while the 'moisture was still present. and the pores opened up and temperature high, will have precipitated upon or surthat themoisture has departed. Thus, the wood has been rendered homogeneous throughout, indurated, sterilized and rendered less hygro scopic and correspondingly immune from spores or. fermentation or the like. And all these conditions are attained-without checking, warping, case hardening or'other deterioration of the physical characteristics of the wood.

From the foregoing, it will be seen that said compart- 105 the first essential condition to be produced is the thorough softening and opening up of the wood structure and the.dissolving of its gummy sap matters and freeing them from their confinement; so that they can be distributed through the wood structure.

I claim 1. The process of drying wood, which consists in, surrounding the wood by a body of live steam under pressure; then gradually reducing the pressure while supplying heat; finally drying in a slightly heated moist atmosphere.

2. The process of drying wood, which consists in subjecting the wood to live steam under pressure; then reducing the pressure to below atmospheric pressure at the same time maintaininiglthe steam at a super-heated temperature; ally drying the woodat atmospheric pressure and in the presence of a moderatel heated, moist atmosphere.

3; he process of drylng wood, which con-- the wood to a body ofsteam at substantially the dew point thereof sists in subjectm under pressure; then gradually reducing the pressure; finally drying in a, moderately heated atmosphere at atmospheric pressure.

4. The process of drying wood, which consists in subjecting the wood to a body of live steam under pressure; then withdrawing moisture therefrom while decreasing the pressure; finally drying in a body of moderately heated, moist atmosphere at atmospheric pressure jandharmonizing the temperature of the interior of the wood with the surrounding atmosphere,

In testimony whereof I'aflix my signature.

FREDERICK K. FISH, JR.

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