US2830382A - Apparatus for drying lumber - Google Patents

Description

April 15, 1958 u. K. PETERSEN 2,830,382

APPARATUS FOR DRYING LUMBER original Filed Aug. 27. 1951 2 sheets-sheet 1 1 1r r n HHM ` ATTORNEYS INVENTOR l April l5, 1958 A U, K, PETERSEN. r 2,830,382

APPARATUS FoR DRYING LUMBER Original Filed Aug. 27, 1951 2 Sheets-Sheet 2 La-WL ATTonnEYs UnitedStates Patent O APPARATUS FOR DRYING LUMBER Ulric K. Petersen, Sonora, Calif.

Continuation of application Serial No. 243,797, August 27, 1951. This application March 18, 1955, Serial No. 495,239

3 Claims. (Cl. 'S4-45) As to all common subject matter, this application is a continuation of application Serial No. 243,797, filed August 27, 1951, now abandoned.

This invention relates to the material drying art and is particularly directed toward the introduction into the art of a new method and apparatus for removing moisture from lumber.

Heretofore the general practice in the drying of lumber has been to subject it to the action of currents of air, usually heated, and to continuously flow these air currents over the lumber until the desired amount of moisture has been abstracted therefrom. Lumber thus dried usually becomes porous and capable of again rapidly absorbing moisture. Furthermore, this previous method tends to reduce the tensile strength of the lumber by baking out all sap and moisture, allowing the knots to fall out and reducing the grade of the lumber. Also, the lumber boards have to be carefully stacked and sticked apart so as to allow complete air circulation about each individual board. This involves a considerable expense for labor and material and requires a quite large enclosure to receive the lumber to be dried; and many times the boards on the outside of the pile and at the sticking points are over-treated with the heat and burn, which again reduces the grade of the nished lumber. The old method also involves the use of large, heavy, and costly operating equipment and extensive operating costs.

The primary object of the present invention is to provide a compact drying chamber unit (which may be readily portable if so desired) and in which the lumber may be compactly stacked board upon board and side by side without sticking or providing for any spacing between the boards; the unit including simple operating means whereby the chamber in which the lumber, as so stacked, may be held at a low temperature of about 35 degrees Fahrenheit but never below freezing; and further including means to maintain a constant flow of air induced by suction on the chamber held at such temperature and moving over the lumber to gradually suck or extract moisture therefrom.

A further object of the invention is to control the stated temperature in the chamber through the medium of a conventional refrigeration unit including pipe coils within the chamber through which the refrigerant material passes and on which a substantial part of the moisture extracted from the lumber will accumulate in congealed and/ or frozen form.

A still further object of the invention is to provide means to periodically discontinue refrigerating action of the material flowing through the pipe coils to allow the accumulated ice to melt and llow from the chamber in liquid form; and at the same time to provide means to discontinue the suction on the chamber to allow the condensed liquid to flow therefrom by gravity.

A still further object of the invention is to provide means to admit warm air to the chamber to prevent the Mice lumber from freezing during the defrosting of the pipe coils or when the atmospheric air entering the chamber from outside thereof is of a temperature below freezing.

These primary objects and others of co-incidental nature with respect to the accomplishment thereof are attained through the provision of the novel apparatus and the method of operation thereof as disclosed in this specification, the apparatus being shown in the accompanying drawings in which Fig. l is a longitudinal sectional view of the drying chamber showing the mechanical operating elements connected therewith but minus the electrical control circuits for effecting the operation of said elements.

Fig. 2 is a diagrammatic outline of the electrical control circuits for the mechanical operating elements shown in Fig. l.

Fig. 3 is a fragmentary sectional view taken on a line 3-3 of Fig. 1.

Referring now more particularly to the characters of reference on the drawings, the numeral 1 designates the drying chamber which may optionally be either stationary or portable. The walls of said chamber will be substantially impervious to the passage of air and heat and will be of a strength to withstand a predetermined vacuum pressure from within and will be properly insulated to permit of a temperature substantially 35 degrees, Fahrenheit, being maintained within the chamber regardless of the temperature of the atmosphere outside the chamber.

One end of the chamber 1 is provided with doors, as at 2, to permit the ingress and egress of lumber into and from the chamber.

A suction fan 3, or pump, or blower is mounted at some convenient point on the chamber 1, the intake side of the fan or blower being in communication with the chamber adjacent the top thereof.

An air inlet and liquid outlet opening 4 is provided in the bottom of the chamber 1 on each side thereof and valves of selected type control the open and closed position of these openings 4. In the present instance, each of these valves comprises a disc 5 framing the outer end of the opening 4 and mounted on an arm 6 pivoted at 7 whereby the valve 5 may be normally held closed against the opening 4 by vacuum pressure induced within the chamber 1. The mode of operating the valve unit will be later described.

A conventional refrigeration unit R, having a conventional defrosting means, is preferably mounted outside the chamber 1 with the pipe coils 8 of the unit extending into the chamber 1 and being banked along the side walls thereof, one bank being on each side of the chamber.

Within the chamber 1, and extending longitudinally beneath each bank of pipe coils 8, is an inclined trough 9 leading to a point of discharge immediately above one of the openings 4.

At some convenient point at the botom and within the chamber 1, preferably below each trough 9, is a small longitudinally disposed tunnel 10. One end of this tunnel 10 preferably terminates adjacent one of the openings 4. A heating element 11 is disposed within the tunnel at that end and a blower 12 is disposed adjacent the opposite end of the tunnel with its discharge end in communication with the tunnel.

The elements 3, 5, 11, 12 and R are all automatically operated and the operation thereof controlled through the medium of electrical circuits diagrammatically set out in Fig. 2 and which will now be described in detail.

Clock circuit Predetermined periodical defrosting of the pipe coil 8 is accomplished through the medium of a clock circuit. The numeral 13 designates one of the main line electric supply wires and the numeral 14 designates the other main line wire. A control clock C is provided and includes two separated wiper plates 15 and 16 over which rotates a wiper blade or linger 17 driven by a motor 18. The motor is driven by energy supplied from a wire 19 leading from line wire 13 to the motor and other wire 20 leading from the motor to the other line wire 14. Primary energization of this circuit, as well as the other circuits to be described, is controlled by a master switch 21.

Refrigerator circuit A wire 22 leads from the Wire 19 to the wiper blade 17. A wire 23 leads from the line wire 13 and to the compressor motor 24 of the refrigerating unit R via the usual temperature control relay 25 and coil pressure control valve 26. From the motor 24, a wire 27 leads to the othermain line wire 14. As already stated, the refrigeration unit R is conventional and as long as the switch 21 is closed, the chamber 1 is held at approximately its predetermined temperature which is above freezing and preferably at about 35 degrees Fahrenheit, subject to certain other controls as will be later described.

Suction fan circuit The suction fan circuit is etlective to operate the suction fan 3 to establish vacuum pressure within the chamber 1.

This circuit includes a wire 28 leading from the main line wire 14 to the motor 29 of the suction fan 3.

From the motor 29 a wire 30 leads to a switch 31 which is normally closed in contact with wire 30 as by a spring 31a during the refrigeration cycle of the apparatus. From the switch 31 another wire 32 leads to another solenoid switch 33 which is normally held closed as by a spring 33a in contact with the wire 32 during the refrigeration cycle. From this switch 33 a wire 34 leads to the main line wire 13.

Air inlet valve circuit This circuit controls the operation of the air inlet valve 5, and comprises a iirst valve operating means and a second valve operating means or a primary circuit and a secondary circuit. The irst circuit for controlling said rst valve operating means comprises a wire 35 leading from the main line wire 14 to a motor 36 which drives a shaft 37 on which is an eccentric cam 38. The cam alternately engages and releases the swing arm 6. As the cam engages the arm, the valve opens admitting air to chamber 1 under the influence of the vacuum in the chamber developed by the fan 3. Upon the cam 38 releasing the arm 6, suction against the valve 5 from within the chamber closes the valve. Valve closure is conveniently commenced and assisted by any appropriate mechanism such as a spring 5a.

From the motor 36 a wire 39 leads to a solenoid switch 40 normally held closed in contact with wire 39 as by a spring 40a during the refrigeration cycle. A wire 41 leads from switch 40 to the main line wire 13.

A second valve operating means is eiective to hold the valve 5 open during the defrosting cycle or in the event of excessive vacuum in chamber 1. This second circuit for controlling said second valve operating means consists of a wire 42 leading from main line wire 14 to a solenoidcontrolled plunger 43. When the solenoid is excited it driveslthe plunger into contact with arm 6 holding the valve 5 open as long as thesolenod is energized. A wire 44 leads from the solenoid of the plunger 43 and has two branches 45 and 46. The branch 45 leads to switch 40 and the branch 46 leads to the switch 31. The switch 40 is normally held open outof contact with the wire 45 as long as the vacuum pressure in chamber 1 holds at its predetermined maximum, preferably about two pounds. The switch 3l is normally held open out of contact with the wire 46 as long as the suction fan circuit is closed.

Defrosting circuit This circuit opens the valves which permit circulation of warm gas through the pipe coils during the defrosting period as determined by the setting of the clock C. It consists of a wire 47 leading from the main line wire 14 and having two branches 48 and 49 leading to valve operating solenoids 50 and 51 operating the valves 52 and 53, respectively, in pipes leading from the gas reservoir of the refrigerating unit R to the pipe coils 8 in the usual manner. A wire 54 connects the solenoids 50-51 and a wire 55 leads from this wire 54 to the switch 33 which is normally held out of contact with such wire 55 during the refrigeration cycle.

Switch holding circuits The switches 33 and 40 are held in their normal closed positions in contact with the wires 32 and 39, respectively, by this holding circuit. This circuit consists of a wire 56 leading from the wiper plate 15 to the holding solenoid 57 of the switch 33 and a wire 58 leads from this solenoid to the main line wire 14. A branch wire 59 leads from wire 56 to the holding solenoid 60 of switch 40 and a wire 61 leads from this solenoid to the main line wire 14. Interposed in the wire 56 is a conventional hair humidostat 62 and interposed in the wire 61 is a vacuum control relay 63. The purpose and operation of these members 62 and 63 will be described later.

Heat control circuit The purpose of this circuit is to furnish Warm air to chamber 1 when the temperature in the chamber falls below 35 degrees Fahrenheit so as to prevent the moisture in the lumber from freezing. The circuit consists of a wire 64 leading from the main line wire 13 to a thermostat switch 65 and the wire 66 leads from switch 65 to the motor 12 with branches 67 leading to the heating coil 11.

Operation When the apparatus is to be used, the lumber may be stacked in a solid pile within the chamber 1, and the doors 2 are closed.

The switch 21 is closed and with the wiper arm 17 running in contact with the wiper blade 15, the refrigerator circuit, the suction fan circuit, and the air inlet valve circuit are all closed to operate the corresponding apparatus controlled thereby in the manner described above.

Thus, the temperature within the chamber 1 is reduced to and held at a point above freezing and preferably not above 35 degrees Fahrenheit. Concurrently, the blower 3 reduces the pressure within the chamber and continues to operate so long as the switches 31 and 33 are held in the closed circuit positions shown in Figure 2 and which are the normal positions obtaining during the refrigeration cycle. At predetermined intervals governed by the rotation of the motor 36 and the cam 37 the valve 5 is opened, permitting air to enter the chamber and increase .the pressure within the chamber, and thus to relieve the vacuum During the periods of low vacuum the low pressure of the gases surrounding the lumber permits fluids within the lumber, for example water, oilsand other extractives, to evaporate into the chamber. As the valve 5 is opened and air enters the chamber through the valve a gas ow pattern is created, the blower 29 still being operative. Some of the evaporated lumber uid passes outwardly through the blower, but the majority migrates toward the refrigerating coils 8 and conge'als thereon.

Removal of the congealed extractives is eiected by intermittent defrostng of the coils.

At predetermined periods the wiper blade 17 leaves the wiper plate 15 and moves onto the wiper plate 16. This opens the suction fan circuit and the primary air inlet circuit and closes the secondary air inlet circuit and defrosting circuit and opens the switch holding circuits.

Consequently, the defrosting valves 52 and S3 are held open as are also the valves 5.

Thus, the warm gas is circulated through the coils 8 melting the accumulated material thereon to liquid form which liquid falls into the troughs 9 from whence it ows out of the chamber 1 through openings 4.

The defrosting and liquid removing cycle continues until the wiper blade 17 leaves the wiper plate 16 and returns to the wiper plate whereby the moisture removing cycle is resumed.

In order to prevent the lumber from freezing in the event of an extremely low atmospheric temperature outside the chamber, warm air is furnished by the blower heater 11-12, controlled by the thermostat 65.

If, for any reason, a continuous flow of air through the chamber 1 is desired under any given vacuum pressure, spring-pressed louvers 68 may be provided in the sides of the chamber 1 adjacent the ends thereof. The spring constants for the louvers 68 are chosen so that the louvers will open in the event the vacuum falls to a dangerously low amount, occasioned, for example, by jamming of the vacuum control relay 63.

Excessive vacuum in the chamber 1 above a predetermined amount is controlled by the pressure operated switch 63 which may be hand set at a determined operating point. Opening of this relay switch opens circuit to motor 36 and closes circuit to solenoid plunger 43, thus holding valve 5 open until the excessive vacuum is overcome.

When the moisture content of the air in the chamber is reduced to a predetermined amount, the humidostat relay 62 opens and functions to open the fan circuit and establish a defrosting cycle through the action of the valves S2 and 53 and the functioning of the plunger 43 to open valve 5, All excess material on the coils is then condensed and the liquid ows out of valve 5. When the said predetermined state of humidity is again established the humidostat closes and the normal cycle of operation in the removal of extractives from the material is reestablished.

It has been determined from experiment that when the temperature of the wood is lowered and the wood is subjected to the alternate establishment and relief of the vacuum in the chamber, the oils and other extractives in the wood (other than the water) tend to be sucked from the wood before the water. It has, therefore, been found practicable to subject the wood to the described process only until it appears that the extractives, other than Water, have been substantially removed from the Wood. Then the wood is removed from the chamber and the water content is air-dried out of the wood. The oils and other extractives are found to be useful and valuable in many ways, and are, therefore, flowed into containers and retained for further processing.

It has also been found that when the extractives, other than water, have been removed from the wood, then the water content which remains will evaporate therefrom in the open air much more rapidly than would otherwise be the case.

From the foregoing description of the operation of the apparatus it will be apparent as to how the objects of the invention are accomplished, the operation continuing until the lumber is relieved of the desired amount of moisture as determined by conventional tests.

While the foregoing specification defines the presently preferred form of apparatus, useful for carrying out the improved method of drying lumber, it is not intended that the application be limited thereto since certain variations in the detail thereof may be resorted to without departing from the substance of the invention as dened by the appended claims.

What is claimed is:

1. A lumber treating apparatus including a substantially air-tight enclosure for lengths of lumber to be dried, a vacuum pump connected to the enclosure to draw extractives from the lumber, longitudinal refrigeration coils set vertically on edge within the enclosure at the sides thereof and directly exposed to the lumber and on which extractives drawn from the lumber deposit in congealed form, means in the enclosure forming tunnels extending lengthwise thereof below the coils and open at their ends to the interior of the enclosure, blowers to pass air through the tunnels from one end to the other, and heating elements in the tunnels disposed in the path of the flow of air therethrough.

2. An apparatus, as in claim 1, with a circuit in which the heaters and blowers are interposed, and a normally open thermostatic switch actuated by predetermined 10W temperature conditions within the enclosures to close the switch.

3. A lumber treating apparatus comprising a substantially air tight enclosure to receive the lumber to be treated, means for creating a vacuum within said enclosure, an outlet at the bottom of said enclosure, a valve in said outlet, means for cyclically opening and closing said valve whereby atmospheric air is admitted to said enclosure at predetermined intervals, means in said enclosure for congealing extractives evaporated from the lumber during the intervals of low pressure in said enclosure, means for cyclically defrosting said congealing means, means for holding open said valve during the defrosting period, said valve and said outlet also serving to conduct the melted extractives to a location exterior of said enclosure during the defrosting period.

References Cited in the le of this patent UNITED STATES PATENTS 688,711 Amthor Dec. 10, 1901 763,482 Gray June 28, 1904 1,421,685 Glessner July 4, 1922 1,672,326 Kobiolke June 5, 1928 2,132,897 Gentele Oct. l1, 1938 2,389,452 Patterson Nov. 20, 1945 2,436,693 Hickman Feb. 24, 1948 2,441,730 Strumia May 18, 1948 2,585,086 Brunsing Feb. 12, 1952

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