US2001001A - Reversible circulation internal fan kiln - Google Patents

Description

May 14, 1935. R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 23, 1932 s sheets sheet 1 FIG. 1

INVENTOR ROLF THELE/V ATTORNEY May 14, 1935. v R. THELEN 2,001,001

v REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 25, 1932 3 Sheets-Sheet 2 FIG. 2

INVENTOR ROLF THELE/V- ATTORNEY May 14, 1935. R. THELEN 2,001,

7 REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 25, 1952 s Sheets-Sheet s INVENTOR ROLF THELE/V ATTORNEY Patented May 14, 1935 nEvEnsiBLE CIRCULATION INTERNAL FAN KILN Rolf Thelen, Madison, Wis; dedicated to the free i use of the Public Application November 23, 1932, Serial No. 644,010

1 Claim. (Cl. 3446) (Granted under the act of March 3, 1883, as

, amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described may be manufactured and used by or for the Government, for governmental purposes, without payment to me of anyroyalty thereon.

I hereby dedicate the invention herein 'described to the free use of the public,,to take effect upon the granting of a-patent to me.

My invention consists in an improvement in the design of forced circulation. kilns for drying and conditioning lumber and other materials. It consists in the adaptation offans of the disk type, or similar types, to the production of a unique internal circulation of the air and vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln. I H

. This invention is illustrated in Figures 1, 2, and 3. Figure 1 represents a cross-sectional elevation of the kilntaken on line 5-! of Figure 2 and looking in the direction of the arrows. Figure 2 represents a longitudinal sectional elevation of. the kiln taken on line 2-2 of Figure 1 and looking in the direction of the arrows. Figure 3 represents a horizontal crossesection of the kiln taken'on line 33 of Figure l and looking in the direction of the arrows.

The principal feature which I claim as novel and an improvement over existing kilns isthe use and arrangement of the fans and the air distributer. This arrangement is such that a very fast and uniform circulation of-the air and vapor through the lumber piles may be secured and it permits the periodic reversal of the direction of the air and vapor movement by reversing the direction of rotation of the fans. The air distributer provides a very uniform flow of air throughoutthe length and breadth of the kiln and eliminates the non-uniformity of drywhich is one of the commonest troubles exfeature is of special advantage in installing fans in existing structures. The elimination of comparatively. small ducts such as those used in externalblowerkilns reduces very materially the power required to produce a-given circulation. Thedifierences in air pressure required in the operation of this kiln are much smaller than those ordinarily required in kilns employing centrifugal blowers, and the disk fans operate very efficiently at these low pressures. Measurements recently made vindicate that the static pressures necessary for the successful operation of this system are materially less than-loneeighth of an inch of water pressure. It is possible, therefore, by the use of thisinvention to produce a very large and uniform circulation of the air and vapor within the kiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the use of internal fans can be adapted to dry kilns of different types, this invention is limited to kilns in which the lumber is flat piled and in which the circulation of the air and vapor throughout the lumber piles is in a substantially horizontal direction from edge to edge of the piles.

Any well-known means of heating the air and vapor in the kiln may be used in conjunction with this invention. When steam pipes are used they may be most conveniently arranged above the lumber piles at the sides of the kiln. Any convenient form and arrangement of heaters maybe used. The temperature may be con:- trolled by hand or by any suitable automatic means. i

While the drawings show and-the specification describes specific means for heating the air and vapor in the kiln and for regulating the humidity of the kiln atmosphere, this invention is not limited specifically to the arrangements -described, but may make use of any other wellknown and suitable means for accomplishing the same purposes. The humidity may be controlled by hand or by any suitable automatic means.

Referring to Figures 1, 2, and 3, which are correspondingly lettered: AA are the motors which furnish the power to drive the fans. BB are the fans producing the circulation. Straight-bladed disk fans are preferable. Any

type of fan, however, in which the reversalof the direction of rotation of the fan produces a reversal in the direction of the flow of the air current passing through the fan can be used. C0 are the shafts upon which the fans are mounted. Provision is made to take careof the expansion and contraction of these shafts with changes in the temperature in the kiln by means of a suitable flexible coupling" be: tween each motor and the fan. DD are inlet dampers used to regulate and control the amount of air entering the kiln from the outside. EE are the heating coils. These may be of any convenient type and arrangement. F is the steam jet pipe used to increase the humidity of the atmosphere in the kiln. Suitable openings areprovided in this pipe to permit the escape of steam throughout the length of the kiln. The precise location of this steam jet pipe is not of prime importance. Various other common and well-known arrangements may be used. G is the support for the lumber piles. HH are the lumber piles. II are bearings for the shafts CC. J is a hinged joint in the lower part L of the air distributor. KK are the side walls of the kiln. L is the lower part of the air distributor. M is the upper part of the air distributor. N is the central part of the air distributor. N is a support on the upper part of the air distributor and supports and maintains the bearing I and air distributor assembly. These three parts compose the air distributor. 00 are air outlet dampers for controlling the amount of air being exhausted from the kiln. P is a kiln door. Q is the kiln roof. RR are flexible couplings between the motors and the fans. SS are switches for controlling the speed and direction of the rotation of the motor armatures and fans. While the drawings show and the specification describes single speed electric motors, variable speed or multi-speed motors, or any other suitable driving means may be used. TT are air inlet flues in which the dampers DD are fitted. UU are air outlet flues in which the dampers 00 are fitted. V is the floor of the kiln. WW are the side air passages between the lumber piles and the side walls of the kiln. XX are the end walls of the kiln. YY are members supporting the air distributor assembly. ZZ are the stickers between the layers of lumber.

While the air distributor and the substantially horizontal arrangement of the fans are essential parts of my invention, considerable latitude, particularly in the design of the air distributor, is permitted. The air distributor illustrated and described has been for the sake of convenience and accessibility divided into three parts, each of said parts running continuously from end to end of the kiln. The upper part M of the air distributor is a solid sheet of suitable material curved in such manner as to facilitate the fiow of the air and vapor. The central part N of the air distributor is a substantially horizontal sheet of suitable material provided with circular openings into which the fan casings are fitted. The lower part L of the air distributor is composed, for the sake of convenience, of two suitable curved continuous sheets of suitable material connected together with a continuous hinged joint J. This joint permits the substantially horizontal portion of the lower part L of the air distributor to be dropped down for convenience in inspecting the fans. The air distributor is in the nature of a septum dividing the left half of the kiln from the right half-Figure l--and guides the flow of the air and vapor in the desired direction.

The operation of the kiln is briefly as follows:

The lumber is piled in the kiln, care being taken to provide side air passages WW of suitable width between the lumber piles and the side walls of the kiln. The door and all of the dampers are closed. Steam is turned into the heating coils and into the steam jet pipe. Suitable regulating devices are provided to control and regulate the supply of steam to the heating coils and the supply of steam to the steam jet pipe. If it be found impossible to reduce the humidity within the kiln to the desired point with the steam jet pipe closed, the dampers DD and 00 are opened to allow fresh air to enter and moist air to escape. These dampers should be adjusted so that a humidity somewhat below that desired will be secured. The steam jet pipe may then supply a sufficient amount of steam to bring the humidity up to the desired point. Referring to Figure 1; if the direction of rotation of the fans BB is such that the air and vapor pass downward through said fans the lower part L of the air distributor will deflect said air and vapor to the right and upward. Thence the path of the movement of said air and vapor is downward through the right-hand heating coils E into the right-hand side air passage W, thence horizontally through the lumber piles l-II-I into the left-hand side air passage W, upward through the left-hand heating coils E, past the steam jet pipe F, and thence back to the fans BB, repeating the cycle continuously. When the direction or" the rotation of the fans BB is reversed the direction of the circulation of the air and vapor is likewise reversed. The location and arrangement of the various parts eliminate the necessity for air diifusers and especially constructed plenum chambers. The heating coils EE act effectively as air difiusers and the comparatively large spaces above said heating coils act in the capacity of plenum and vacuum chambers, materially assisting in the uniform distribution of the air and vapor lengthwise of the kiln.

It is well understood that when the circulation of the air and vapor in a kiln is continuously in one direction, that portion of the lumber piles at which the air and vapor enter will dry more rapidly than the opposite side since the air in its passage through the lumber piles picks up moisture and thus reduces its drying capacity. The reversal of the direction of the air circulation overcomes this defect since that edge of each lumber pile which was the entering air edge before reversal becomes the leaving air edge after reversal. These portions of the lumber piles which dried fastest before reversal dry most slowly after reversal. The reversal of the circulation will in practice be done periodically every two or three days or oftener, the exact period being determined by the condition of the lumber in the kiln.

Having fully described the principles of this invention and a manner in which they can be embodied in a dry kiln, I claim as original:

In a dry kiln adapted to receive a single row of fiat piled stacks of lumber, comprising a plurality of horizontal fans centrally located above the lumber; heating coils located at the side walls above the lumber; an air distributor centrally located above the lumber, extending the full length of the dry kiln and consisting of a substantially horizontal central part, provided with means for supporting said fans, and extending from a point in proximity to said heating coils on one side to a point in proximity to said heating coils on the other side of the kiln; a curved upper part extending from one edge of said central part to the dry kiln ceiling, and a curved, hinged, lower part, extending from the other edge of the central part substantially transversely across the dry kiln to a point in proximity to said coils opposite said other edge of said central part, and reversible driving means for said fans.

ROLF THELEN.

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