US1541444A - Reversible-circulation internal fan kiln - Google Patents

Description

June 9, 1925.

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Ori gina1FiledNov. 7,l925

3 Sheets-Sheet 1 oomooooooooo E oooom oooooo S! 83 E g E 4 OOOOOOOQOOOG L y I 1 INVENTOIL Fjjrl @LF HELE? Y MW ATTORNEY- June 9, 1925. 1,541,444

- R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Originl Filed Nov. '7, 1923 3 Sheets-Sheet 2 -m-mm INVENTOR. ROLF IHELEN BY ATTORNEYS.

June 9, 1925. 1,541,444

R.- THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Original Filed Nov. v, 1923 3 SheetsSheet s Fig. -5

-INVEN50R. RoLFIHsLEN BYWWW- ATTORNEYS.

Patented June '9, 1925.

UNITED STATES ROLF THELEN, OF MADISON, WISCONSIN,

DEDICATED, ,BY MESNE ASSIGNMENTS, TO

PATE

THE CITIZENS OF THE UNITED STATES OF AMERICA.

REVERSIBLE-CIRCULATION INTERNAL FAN KI'LN.

Original application filed November 7, 1923, Serial No. 673,340. Divided and this application filed 1 March 7, 1925. -Ser1a1 No. 14 ,425.

(GRANTED UNDER THE ACT OF MARCH 3, 1883; 22 STAT. I1. 625.)

I To all whom it mayconcern: i

' Be it known that I, RoLr THELEN, a citizen of the United States of America, and an employee of the Department of Agriculture, 5 residing in Madison, Wisconsin (whose postoflice address is Madison, Wisconsin), have invented a new and Improved Reversible- Circulation Internal Fan Kiln.

I This application is a division of an application filed November 7, 1923, which bears Serial Number 673,340. a

This application is made under the act of March 3, 1883, chapter 143 (22 Stat. 625), and the invention herein desgribed and claimed may be used by the Government of the United States, its oflicers and employees, and by any person in the United States without the payment'to me of any royalty there on. I hereby dedicate the same to the'free use of the Government and the people of the United States. I

My invention consists in an improvement inthe design of forced circulation kilns or chambers for drying and conditioning lum- 25 her or similar material. However, its use is not limited to wood or wood products. It consists in the adaptation of fans of the disk type, or similar types, to the production of a unique internal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 3. Figure 1 represents a cross-sectional elevation. Figure 2 represents a horizontal cross-section taken at varying levels near the base. Figure 3 is a vertical longitudinal section showing some of the fan details.

The principal feature which I claim as novel and an improvement over existing kilns is the use and arrangement of the fans and the air distributing system. This arrangement is such that avery fast and uniform circulation of air and vapor through the piles of lumber may be secured and it permits the tion of the air movement by simply reyersing'the direction of rotation of the fans.

The air distributing system provides a very uniform flow of air throughout the length.

and breadth of the kiln and eliminates the non-uniformity of drying, which is one of eriodic reversal of the directhe commonest troubles experienced in the ordinary kiln. I The arrangement of the fans upon two parallel shafts extending throughout the length of the kiln provides a simple means'of producing a brisk circulation; and the elimination of comparatively small ducts such as those used in external blower kilns reduces very materially the work required to produce a given circulation. The differences in air pressure'required in the operation of this kiln are much smaller than those ordinarily required in kilns employing cen trifugal blowers, and the disk fans 0 crate very efliciently at these low pressures. easurements recently made indicate that the static pressures necessary for the successful operation of this system are materially less than one-eighth of an inch of water 'pressure. It is possible, therefore, by the use of this invention to produce a very great and uniform circulation of 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 difl'erent types, this invention -is limited to single track, kilns in which the lumber is edge stacked. In edge stacked lumber the width of each board is in a vertical direction, the

thickness and length being in horizontal directions.

-An y well-known means of heating the air and the vapor in the kiln may be used in conjunction with this invention. When steam pipes are used they may be arranged beneath the lumber piles at the sides of the kiln or in any other convenient manner. Any convenient. form and arrangement of heaters may be used. I

The drawings show and the specification describes steam jet pipes for increasing the humidityfand air inlet flues and air outlet fiues with suitable dampers for decreasing the humidity. I

While the drawings show and the specification describes specific means for heat the air and the vapor in the kiln and for regulating the humidity of the air in the kiln, ,this invention is not limited specifically to the arrangements described, but may make use of any other well-known and suitable means for accomplishing the same purposes. I While the drawings illustrate and the speci- 'fication describes certain specific forms of piling, the invention is not limited to these particular forms since it is equally applicable to other forms; neither is the invention limited to the specific form of rails, trucks, and track supports illustrated in the drawin s and described in the specification.

eferring to Figures 1, 2," and 3, which are correspondingly lettered: AA represent the side deflecting partitions. These partitions serve to form a passageway for the air from the spaces at the sides of the kiln to the fans and vice versa, the air moving in a more or less horizontal direction either inward towards the fans or outward from them, depending upon the direction of the rotation of the fans. BB are the fans producing the circulation. Straightbladed disk fans are preferable. Any type of fan, however, in which the reversal of 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. CC are the shafts upon which the fans are mounted. Provision is made to take care ofthe expansion and contraction of these shafts with changes in the temperature in the kiln, and to take care of the thrust of the fans. This provision con-- sists in equipping one of the bearings, II, with suitable thrust rings or collars and equipping all of the other bearings, II, on each shaft with any well known means tor armature. While the drawings show and the. specification describes an electric motor, any other suitable driving means ()0 are fitted. W W are the side air passages between the piles of lumber and the side walls of the kiln. X is the main air distributor. YY are the upper diffusers. ZZ are the lower diffusers. The plenum chambers between the upper diffusers and the lower diffusers are the secondary plenum chambers. bb are the fan housings and partitions. .ee are the return diffusers.

The operation of the kiln is briefly as follows: The lumber is placed in the kiln, the doors and all of the dampers are closed, and the kiln is started. Steam' is turned into the coils and the steam jets are turned on. vided to control and regulate the supply of steam to the heating coils and the.supply of steam to the steam jets. If it is found impossible to reduce the humidity to the desired point with the steam 'ets all turned off, the dampers DD and O are opened to allow fresh air to enter and moist air to escape. These dampers should be adjusted so that a humidity below that desired will be secured. The steam jets may then supply a sufiicient amount of steam to brin the humidity up to the desired point. if the direction of rotation of the for longitudinal motion. ,Plain bearings? fans is such that the air and vapor pass and roller bearings require no special provision of this kind. Certain types of ballbearings require housings which permit the entirebearing to slide longitudinally within them. DD are air inlet dampers used to regulate and control the amount of air entering the kiln from the outside. EF. are the heating coils These may be of the return bend type or other. convenient type. FF are the steam jet pipes used to increase the humidity of the air in the kiln. Suitable openings are provided to permit the escape of the steam throughout the length of the kiln. Various other common and well-known arrangements may be used. GGrv are the lumber-supporting trucks. I-II-I are the shaft hangers. II are bearings-for the shafts CC. JJ are the tracks upon which the lumber-supporting trucks run. KK are the side walls of the kiln. LL is the lumber to be dried. MM are the track supports. NN are the shaft pulleys. are air outlet dampers for controlling the amount of air being exhausted. from the kiln. PP are the belts passing over the pulleys NN and Q. Q is the motor pulley. R is the motor which furnishes the power to drive the fans. S is a switch for controlling the speed and rotation of the moupward through the piles of lumber, the movementis as follows: From the fans BB it passes laterall to the right and the left past the side de ecting partitions AA, over the heating coils EE, which are located in the main air distributor X, which will be un der slight pressure and will act asa plenum chamber. The air and vapor pass upward from this plenum chamber through the lower diffusers ZZ which may be in a single row or in two rows as illustrated, into the sec- W ondary plenum chambers, and finally through the upper diffusers YY vertically through the lumber piles, horizontally outward between the tops of the lumber piles and the ceiling. of the kiln downward through. the side air passages WW, past the return diflusers ee, thence to the fans BB, repeating the cycle continuously. When the direction of rotation of the fans is reversed, the direction of travel of the air and vapor is likewise reversed. The use of the two sets of difi'users in the manner indicated produces a very uniform flow of airthrough the length of the kiln. The unbalancing effect of the'horiz'ontal air flow produced by the fans is practically eliminated by allowing a sli ht pressure to build up in the main air distributor. This is still further eliminated by the slight plenum in the space between the upper and lower dis tributors. It is obvious that the kiln would work reasonably well with single sets of diffusers for each main air distributor and that still further uniformity in air distribution might be secured by adding a thirzl or evenra fourth set of diffusers. The principle, of course, remains the same and practical expediency will determine the balance between increased uniformity of air distribution secured by the addition of more sets of distributors and the loss in efi'iciencywhich they cause. It is also obvious that any well-known form of distributor may be used. The invention is not restricted to the form illustrated in which the openings consist simply of spaces between the slats running the 'full length of the kiln.

When the direction of air circulation is downward through the lumber piles, the air distributing system, which consists of the main air distributor, the side deflecting partitions, the plenum chamber, and the upper and lower diffusers, does not materially assist in producing a uniform air circulation. The comparatively great length of air travel from the fans to the point at which the air enters the lumber and the return diffusers ee have been found suflicient to produce the desired uniformity. It has been found through experience with a great many different types of forced circulation in dry kilns that it is not possible to secure uniformity of air distribution. if the air be handledat high velocities. In order produce uniform satisfactory circulation 1t is essential that the air be moved at low Velocities and that special means be provided for the uniform distribution of the air throughout the kiln. Theuse ofinternal fans and large lenum chambers produces this result since the velocity of the air through the fans themselves. is comparatively low and the velocity within the plenum chambers is so small that the velocity head cannot be measured with manometers and similar instruments usually used for the purpose.

It is well understood that when the circulation of the air and the vapor in the kiln is continuously in one direction, that portion of the pile at which'the air enters will dry more rapidly than the opposite side since the air in its passage through the lum- -ber 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,

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 exacl. period being determined by the condioriginal a 1. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mountedfor rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; and an air distributing system comprising side deflecting partitions, a main air distributor, and two sets of diffusers.

2. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of thecirculation of the air and, vapor in said kiln; dampered air inlet flues and dampered air outlet flues; and an air distributing system comprising side deflecting partitions, a main air distributor, and two sets of diffusers.

3. In a single track dry kiln arranged for edge stackin two series of fans, two shafts on whlchthe fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; and an air distributing system comprising side deflecting partitions, a main air distributor, and'two sets. of diffusers.

4. In a single track dry kiln arranged for I edge stacking: twoseries of fans; two shafts on which the, fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dam ered air outlet flues; means for heatin the 'ln and its contents; means for humi ifying the atmosphere in the kiln; and an air distributing system comprising side deflecting partitions, a main air distributor, and two sets of diffusers.

5. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted forrotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and va. or in said kiln; a lenum chamber for ear: pair of fans; and a 'fi'user Ill] ' with restricted discharge passages for each plenum chamber.

6. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered. air outlet flues; a plenum chamber for each pair of fans; and a difl'user with restricted discharge passages for each plenum chamber.

7 In a single track dry kiln arranged for edgestacking: two series of fans; two shafts on which the fans are mounted for rotation;

means for rotating said shafts in either d'i- Qrection to cause reversal of the circulation air inlet flues and dampered air" outlet fiues;

means for heating the kiln and its contents; means for humidifying the'atmosphere in the kiln; a plenum chamber for each pair of fans; and adilfuser with restricted discharge passages for each plenum chamber.

9. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for, rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and 'va or in said kiln; a series of plenum cham ers for each air of fans; and a diffuser with restricted scharge pa ssages for each plenum chamber.

7 10. In a single track dry kiln arranged for of fans; and a diffuser with restricted discharge passages for each plenum chamber.

11. In a single track'dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; a series of plenum chambers for each pair of fans; and aidifi'user with restricted discharge passages for each plenum chamber.

12. In a single track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation;

means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet fines; means for heatin the kiln and its contents; means for humi ifying the atmos here in the-kiln; a series of plenum cham' ers for each pair of fans; and a diffuser with restricted discharge passages for each plenum chamber. a

13. In a single track dry kiln arranged for edge stacking: two series of internal fans; a plenum chamber for each air of fans; and a diffuser with restricted discharge passages for each plenum chamber.

14. In a single track dry kiln arranged for edge stacking: two series of internal fans; a series of lenum chambers for each pair of fans; an charge passages for each plenum chamber.

February 12 1925.. I

ROLF THELEN.

a difi'user with restricted dis-

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