US 3453743 A
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T. F. HALE VENEER DRYER July 8, 1969 Filed June 8, 1967 lvlllll lll'l W l'lllll i W unmwaw hnunnnnwfi F m.
INVENTOR THOMAS F. HALE BY a.
ATTORNEY T. F. HALE VENEERDRYER Jul 's, 1969 Sheet ,3 or 3 Filed June 8, 1967 INV'ENTOR THOMAS P. HALE ATTORNEY T. F. HALE VENEER DRYER Jul 8, '1969 Filed June 8, 1967 Sheet HOT AHZ 1 I In INVENTOR 2 f 38 ZJM S 40 moms FHALE.
ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE The invention consists of a veneer drying oven composed of an insulated housing containing an upper and lower conveyor system in which the lower conveyor is a series of grids supported between roller chains providing an unbroken flat surface for the veneer to rest on and an upper belt of woven wire construction adapted to rest upon the veneer and which by its weight restrains the veneer placed between the conveyors to the desired path. This conveyor structure permits the use of a series of laterally installed jet nozzles, the heated air discharge from which impinges directly on the veneer with the closest possible proximity thereto, with a controlled disbursement of this air to the recirculating fans and heating elements and then the return of said air to the nozzle structure.
Background of the invention It is conventional in the veneer drying art to provide drying ovens having conveyors passing therethrough to carry sheets of veneer or other like sheets through the oven and circulating heated gas or air through the oven for the purpose of drying the sheets of veneer. It is also conventional to impinge air at high velocities against the upper and lower surfaces of the travelling sheets of veneer by means of jet nozzles.
Attention is invited to US. patent to F. H. Milligan et al., No. 3,199,213, issued Aug. 10, 1965, which discloses a method and apparatus somewhat similar to the present construction but not having the improved features of the present apparatus, which features will be pointed out as the description of the present apparatus progresses.
In the Milligan construction, the wood pieces being treated are moved by conveyors through the drying section with the hot drying medium directed in a plurality of jets at high velocity to opposite faces of the wood pieces.
In the present system, in distinction to the Milligan system, a novel jet nozzle arrangement is provided in combination with a more economical construction of the drying chamber to obtain a more efiicient drying step with a simpler structure.
Summary of the invention The present invention involves a veneer drying oven including upper and lower plenum chambers between which veneer sheets are conveyed from one end of the oven to the other. The lower wall of the upper chamber and the upper wall of the lower chamber consist of a novel jet nozzle and recirculating system wherein the walls referred to above are formed of a series of troughlike members wherein the trough-like members are parallel to each other with the edges of adjacent members connected whereby the connecting portions between adjacent trough-like members support a plurality of jet nozzles to direct heated air or gas directly against the travelling sheets of veneer and a series of passageways are provided for the controlled recirculating of heated air or gas. A novel conveyor arrangement providing a rigid, flat surface and requiring no support rollers is used to carry the veneer between the plenums.
Brief description of the drawings FIGURE 1 is a plan view of the veneer drying machine constructed in accordance with the present invention.
FIGURE 2 is a side elevation of the machine shown in FIGURE 1.
FIGURE 3 is a transverse sectional view taken on line 33 of FIGURE 2.
FIGURE 4 is an enlarged perspective view of a section of the dryer showing the novel arrangement of the jet nozzles forming an important part of the present invention.
FIGURE 5 is an enlarged sectional view taken on line 55 of FIGURE 3; and
FIGURE 6 is a side view of the section shown in FIGURE 5.
Description of the preferred embodiment Referring to the drawings in detail wherein like numerals denote like parts throughout the several views, the present machine comprises generally a supporting base 10 supporting an elongated casing 11 having side walls 12 and 13, bottom 14, top 15, and end walls 16 and 17. The end walls 16 and 17 are suitably apertured by means of transverse slots to permit the entrance and exit of the sheets of the veneer passing through the casing during the drying operation and also to permit the passage of conveyor belts or the like, all of which is generally conventional in the veneer drying art.
The casing 11 is provided with an upper plenum chamber 18 spaced above a lower plenum chamber 19 to form a thin passage 20 therebetween. The upper plenum chamber 18 includes a solid upper wall 21 and a bottom wall 22 in the form of a jet sheet assembly. The lower plenum chamber 19 includes a solid lower wall 23 and an upper wall 24 in the form of a jet sheet assembly. At each side of the plenum chambers as viewed in FIGURE 3, side walls 25 and 26 are joined to the upper and lower walls 21 and 23 to provide a continuous passageway for the heated air directed through the upper and lower plenum chambers. Mounted at each side of the plenum chambers 18 and 19 and adjacent the bottom wall 22 and the upper wall 24 are manifolds 27 and 28. Each of the manifolds is provided with a fan 29 for supplying air under pressure to the plenum chambers. Each fan is operated by a motor 30 mounted on top of the casing 11 and rotating the fans by means of pulley belt 31.
The bottom wall 23 and the upper wall 24, in the form of jet sheet assemblies, form an important part of the present invention and will now be described in detail. Each of said walls is substantially the same but arranged opposite each other and only one need be described in detail. Referring to FIGURES 4, 5 and 6 in detail, the bottom wall 22 is formed of two sections 32, 33 as seen in FIGURE 3. The section 32 is formed of a plurality of arched members 34, each of which is connected to an adjacent arch by means of a bridging member 35 provided with a plurality of jet nozzles 36, the outer discharge end of which terminates at the thin passage 20. In the present embodiment, the arches 34 taper from one end 37 substantially midway of the dryer casing to the outer side of the casing at 38. As seen in FIGURES 4 and 5 and indicated by arrows, adjacent arches form a passageway therebetween for heated air to be fed to the nozzles 36. These passageways are indicated by numeral 39. Each arch also forms a passageway or tunnel for the return of heated air coming from the nozzles and these tunnels are indicated by numeral 40.
Mounted within the plenum chambers and extending longitudinally of the dryer casing are banks of heated pipes 41 for heating the drying air as it circulates through the plenum chambers whereby a constant supply of heated drying air is provided. A plurality of vent pipes 42 are provided on the top wall 15 of the casing, each vent pipe including a butterfly valve 43 for venting the plenum chambers to the atmosphere.
The present conveyor for the sheets of veneer being treated consists of an endless link belt 44 supported in its upper rim by angle irons 45 supported by vertical posts 46. The lower rim of the belt 44 is supported by angle irons 47 also secured to the posts 46. The link belt comprises a series of links 48, the ends of which are secured to transverse rods 49 at the ends of which are mounted rollers 50 which ride on the angle irons 45. The rods 49 are also provided with intermediate rollers 51 riding on bars 52 for providing uniform horizontal support for the link belt. As seen in FIGURE 3, inverted T-shaped bars 53 are mounted on horizontal bar 54 for providing a rolling support for the intermediate rollers 51. The sheets being treated rest on the upper rim of the link belt 44 and are thus conveyed through the dryer.
In order to aid in more positively conveying the sheets of veneer through the dryer and to prevent slippage between the sheets and the conveyor 44, there is provided a second endless belt 55 whose lower rim moves in the space between the upper rim of the lower belt and below the bottom wall 22 of the upper plenum chamber. The upper rim of the belt 55 is supported on freely rotating transverse rollers 56 secured to posts 46. The lower rim of the belt is freely suspended and is adapted to rest on the veneer sheets being conveyed and the weight of the suspended portion of the belt not only aids in advancing the veneer sheets but holds the sheets flat while being conveyed. The upper belt is made of open link construction as is the lower conveyor belt to provide relatively large openings therein to permit as much hot air or gas to pass therethrough against the upper and lower surfaces of the sheets of veneer being conveyed.
In the operation of the present invention, the sheets of veneer are inserted at the left-hand side of the oven as viewed in FIGURE 2 with the sheets first resting on lower conveyor 44 and then advanced by means of the lower rim of the upper conveyor resting on the sheets of the veneer plus the movement of the lower conveyor. As seen in FIGURE 3, air or gas is circulated through the upper and lower plenum chambers by means of the fans 29 and this air or gas is heated by passing over the heated pipes 41. This air passes between adjacent troughs and directed at high speed to the jet nozzles 36, seen in FIG- URE 5, and impinges directly on the sheets of veneer passing closely adjacent said nozzles. After leaving the surface of the sheets, the air passes through the troughs 34 to be again recirculated through the plenum chambers. The particular shape of the trough-like members enables the air to pass through more rapidly and increases the speed of recirculation. Thus, a controlled flow of treating air is obtained because of the configuration and location of the jet sheet assembly forming the bottom and top walls of the bottom and upper plenum chambers. It will be noted that both walls are similar and the same action takes place against the lower surface of each of the veneer sheets being treated.
What is claimed is:
.1. A veneer drying apparatus comprising an elongated casing, upper and lower plenum chambers mounted within the casing, the lower wall of said upper chamber lying closely adjacent to the upper wall of said lower chamber, said walls having suitable passages providing impingement of air against the upper and lower surfaces of veneer being dried, said passages being varied laterally in area to provide uniform passage of air throughout the drying area, means for conveying sheets of veneer between said two walls, and means for circulating a controlled amount of heated air through said plenum chambers and against the upper and lower surfaces of said veneer sheets, and said lower wall of the upper plenum chamber and said upper wall of the lower plenum chamber comprising a plurality of trough-like members forming tapered passageways for heated air leaving the surfaces of said veneer sheets for recirculation in said chambers and jet nozzles between said trough-like members for impinging heated air normal to said surfaces.
2. An apparatus as defined in claim 1, and said troughlike members extending across the full width of the drying apparatus.
3. A veneer drying apparatus comprising an elongated casing, upper and lower plenum chambers mounted within the casing, the lower wall of said upper chamber lying closely adjacent the upper wall of said lower chamber, means for conveying sheets of veneer between said two walls, and means for circulating a controlled amount of heated air through said plenum chambers and against the upper and lower surfaces of said veneer sheets, said lower wall of the upper plenum chamber and said upper wall of said lower chamber comprising a plurality of troughlike members forming passageways for heated air leaving the surfaces of said veneer sheets for recirculation in said chamber and jet nozzles between said trough-like members for impinging heated air normal to said surfaces, said trough-like members extending across the full width of the drying apparatus and said trough-like members being tapered outwardly from the longitudinal center of the apparatus outwardly towards the sides of said apparatus.
4. An apparatus as defined in claim 3, said conveying means comprising a lower endless conveyor having a flat, rigid upper rim upon which the sheets of veneer lie and movable between said walls, and an upper endless conveyor member having a freely suspended lower rim resting upon the upper surface of said sheets of veneer.
References Cited UNITED STATES PATENTS 3,334,421 8/1967 Morris 34-155 XR 835,843 11/1906 Baetz 34-162 2,590,850 4/1952 Dungler 34-160 XR 2,677,336 5/1954 Spooner 34-225 XR CARLTON R. CROYLE, Primary Examiner.
A. D. HERRMANN, Assistant Examiner.
US. Cl. X.R. 34-162