US2344722A - Method of making plywood panels - Google Patents

Description

March 21, 1944. PASQUlER METHOD OF MAKING PLYWOOD PANELS Filed July 1, 1940 5 HWHHHIII" WW Patented Mar. 21, 1944 METHOD OF MAKING PLYWOOD PANELS Michel Pasquier, Portland, reg., assignor to M and M Wood Working Company, Portland, 0reg., a corporation of Oregon Application July 1, 1940, Serial No. 343,433

Claims.

This invention relates to an improved method of making plywood panels, and has particular reference to a method of uniting preformed panels of standard lengths, or shorter, to make panels of any desired length.

Plywood is manufactured by one of two methods. In cold press operations the newly laid up panels are stacked one upon another until 9. press load of panels has been made, and this press load of panels is placed in a hydraulic press and subjected to a pressure of approximately 150 pounds per square inch to insure intimate contact of the respective plies along the glue line between the plies forming each panel. Thereupon suitable clamps are applied and the pressure applied by the hydraulic press is maintained by these clamps until the bond has set. While cold press glues may be water resistant, so that plywood bonded therewith may be soaked in water for as long as 72 hours without serious detriment thereto, it generally is conceded that plywood made by this process is not suitable for use where it will be subjected to weathering conditions, or for other purposes where moisture is a factor. t

On the other hand, plywood made by the hot press process is suitable for any. use, including uses which will subject the plywood to intimate contact with water or other weathering conditions. This plywood is fabricated in hot plate presses with the use of a theme-setting resinous glue, which is first liquified by the application of the heat of the press, and thereupon is forced into the pores or cells of the wood, where the further action of theheat converts it into an inert substance permanently bonding the veneer plies together to form a plywood panel. The bond produced by this process is not affected by water, acids or organic solvents, and is impervious to fungi, termites or bacteria. For this reason, hot press plywood has found a large market for use for every purpose where moisture is a factor, as in the construction of boats, concrete forms, sign boards, and the like, and very recently has come into vogue as exterior surfacing for all types of buildings.

The use of hot pressed plywood has been more or less limited, however, to constructions which may utilize standard length, or shorter, panels,

since cracks or crevices formed by joints between abutting panels are not desirable in certain of the uses to which such plywood may be adapted. It will be appreciated that hot press plywood panels can, of course, be made as large as availmethod, however, the capacity of the press is reduced as much as 90%, and the cost of the completed panel is accordingly increased out of proportion to the benefits enjoyed by the consumer.

The present invention refers to the manufacture of plywood panels of special lengths by splicing together preformed, completed, hot press panels by means of long scarf joints, the scarfed ends of the panels being first coated with a resin glue. The glue thus applied to the scarfed ends of the panels is allowed to dry, whereupon the ends of the panels are placed in overlapping relation and the scarf Joint thus formed is introduced between platens of a hot platepress. Heat is transmitted to the glue line from the heated platens of the press through the wood forming the separate panels to be spliced. The application of heat acts initially to liquify the glue. and the simultaneous application of pressure forces the liquifled glue into the pores and cells of the respective panels. The continued application of heat sets the resin glue into a substance which is not again affected by the application of heat. However, in this process, if heat is transmitted to the glue so as to cause it to liquify and then set without at the same time being forced into the pores and cells of the respective panels, no bond whatever is created, and no amount of pressure subsequently applied to the joint would serve to form a bond. Likewise, the application of pressure alone, without heat, would not serve to create the bond. The application of heat to the glue, and the application of pressure to the joint must be simultaneous.

It will be appreciated that a slight difference in thickness between two panels scarfed together will prevent a satisfactory application of heat and pressure upon the joint, since the thicker panel at one end of the joint tends to support the platens of the press away from the thinner panel at the other end of the joint. In such event the transmission of heat through the thicker panel will cause the glue to set before able hot plate presses, and panels of dimensions the application of pressure upon the thinner application liquified glue into thepores or cells of the wood In the manufacture of plywood panels embodying applicant's invention, preformed, completed,

hot pressed panels |-l are scarfed at their ends to providea bevel 2 having an upstanding coak or tenon 3 on the beveled surface, said coak or tenon 3 being-slightly closer to the inner end 4 ness being computed as follows: 2 (sin angle of scarf) (distance of coak from center of scarf).

After the panels to be spliced are formed as above described, a resin base glue is applied to the scarfed surface of each panel and the scarf joint by which the separate panels are spliced is there- I after introduced between the heated platens of a hot plate press and subjected to temperatures 'ranging from 220 to 350 F. during the pressing operation, the amount of heat applied being determined by the type of resin glue employed, and the period of time varying with the thickness of the panel being pressed. The application of heat liquifies the resinous glue, and the simultaneous of pressure to the joint forces the where it sets and permanently bonds the abutting panels to form a completed plywood panel of the desired length. The pressure applied by the press in a direction normal to the faces of the panel is transformed by the presence of the coak or tenon 3 into a resultant force which is exerted in a direction normal to the glue line. The coak or tenon resists the vertical force of the press, and

so prevents displacement of the abutting panels, and causes the pressure to be applied in a direction normal to the lineof cleavage between the panels. The action of the hot plate press serves to compress the wood at the scarf joint to the thickness of the remainder of the panel, thus insuring a satisfactory application of pressure to the joint simultaneously with the transmission of heat from the platens to the resinous glue.

While I have described quite specifically a particular embodiment of the invention, it is to be understood that the foregoing is to be interpreted as illustrative, and not in a limiting sense, except as required by the prior art, and by the spirit of the appended claims.

Having now described my invention and in what manner the same may,be used, what I claim as new and desire to protect by Letters Patent is: 1. The method of splicing completed preformed plywood panels, comprising the steps of forming like scarfs on the abutting ends of said panels, providing each said scarfed surface with a transverse upstanding coak or tenon adapted to interlock with a like coak or tenon on the 'scarfed surface of the abutting panel for preventing longitudinal separation of said panels upon application of pressure to the joint, positioning each said coak or tenon closer to the inner end of said scarfed surface than to the outer end thereof whereby the thickness of the joint prior to the application of pressure thereto will be greater than the thickness of the panel beyond the joint to insure a satisfactory application of pressure to the joint simultaneously with the application of heat to the glue, applying a thermo-setting resinous glue to said scarfed surfaces, overlapping the scarfed ends of abutting panels to make a scarf joint, and applying heat and pressure to said joint simultaneously, sufllcient to liquify said glue and force it into the cells andpores of the abutting panels and then cause said glue to set.

panels, which comprises providing preformed hot pressed plywood panels with like scarred end faces, providing the scarfed end face of each panel with a transverse coal: or tenon slightly 5 closer to the inner end of said scarfed face than tenon on the scarred surface of the abutting panel to the outer end thereof whereby the thickness of the joint prior to the application of pressure thereto is greater than the thickness of the panel beyond the joint to insure satisfactory application of pressure to the joint simultaneously with g the application of heat to the glue, said coak or Y tenon adapted to interlock with a like coak or for preventing longitudinal separation of said Panels upon application of pressure to the joint, applying a resin base glue to the scarred end face of each of two panels, overlapping, the scarfed faces of abutting panels with said coaks or tenons' ,in interlocking 'relation to form an interlocked scarf joint, and applying heat and pressure to said joint simultaneous y, sufficient to llquify said glue and force it into the'cells and pores of th: abutting panels and then cause said glue to se l 3. The method of making a plywod panel which comprises providing a relatively long scarf flatwise on the end of each of a pair of preformed panel sections, forming a shoulder intermediate the ends of the scarf and facing toward the body 40 of each section, positioning said shoulder slightly nearer the inner end of each scarf than the outer end, applying a thermo-setting adhesive to the faces of each of said'scarfs, placing said scarfed ends in an overlapping face to face relation to 5 form a joint wherein said shoulders engage with each other to cause the combined thickness of said overlapping scarfed ends to be greater than the thickness of either of said panel sections, applying heat and pressure simultaneously to the overlapping portions of said sections to reduce the thickness of the joint to substantially the thickness of said sections and to form a bond, said cooperatively engaging shoulders preventing endwise separation of said panel sections upon the 55' application of said pressure and insuring satisfactory application of pressure to the joint simultaneously with the application of heat to the glue.

4. The method of splicing plywood panels, com- 00 prising the steps of providing preformed panels with scarfed end faces, applying glue to said scarfed faces, placing the scarfed ends of panels to be joined in an overlapping relation to form a scarf oint, so forming said joint that the thickness of the joint is greater than the thickness of either of said panels beyond the joint, providing said overlapping faces with interlocking means coextensive withthe width of said joint for preventing relative longitudinal separation of said panels during the application of pressure thereto,

and applying pressure to said joint and allowing said glue to set.

5. The method of splicing plywood panels, comprising the steps ofproviding preformed panels 2. The method of splicing preformed'plywood with searfed end feces, applying a thermo-setting resinous glue to said scarfecl faces, placing the seatrfed ends of said panels in an overlapping relation to form a. scarfed joint, so forming said joint that the thickness of the joint is greater than the thickness of either of said panels beyond the joint, providing said overlapping faces with interlocking means coextensive with the 45,1 sees-me width of said joint for preventing relative longitudinal separation of said panels during the spplicntion of pressure thereto, and applying heat and pressure to said joint simultaneously, sufi= cient to liquefy said glue and force it into the cells and pores of the scaried end faces of said panels and causethe glue to set.

MCHEL PASQUIER.

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