US1336262A - Process of manufacturing plywood - Google Patents

Description

0. L'. SPONSLER M, E. DUNLA P AND s. B. HENNING. PROCESS OFWMANUFACTURING PLYWOOD. APPLICATION FILED JUNE l9, 191s.

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OLilNUS I1. SPONSLER, MATTHEW E. DUNLAP, AND SHERBURNE B. HENNING, OF MADISON, WISCONSIN, ASSIGNORS TO THE UNITED STATES OF AMERIGA.

PROCESS OF MANUFACTURING PLYWOOD.

Specification of Letters Patent.

Patented Apr. 6, 1920.

Application filed June 19, 1918. Serial No. 246,859.

To all whom it may concern:

Be it known that we, OLENUS L. SPONSLER, MATTHEW E. DUNLAP, and SHERBURNE B. HENNING, citizens of the United States,- residing at Madison, in the county of Dane.

and State of Wisconsin, have invented a new and useful Improvement in Processes of Manufacturing Plywood, of which the following is a specification.

, Our invention relates to the method of manufacturing a waterproof plywood with dry glue and has for its object the production of a plywood which is waterproof, light, strong, flexible, and tough, and which is capable of receiving a fireproof and waterproof coating. Our method of producing plywood prevents wrinkling, checking and overlapping, and results in a plywood which will not warp after it has been pressed. A. plywood prepared in accordance with our invention is adapted for use as surface coverings and especially as wing and fuselage coverings of airplanes.

Our invention avoids the difficulties attendant upon the use of wet glue such as the handling of the wood while wet. Wrinkling in the core and on the faces of plywood is usually due to swelling of the plies as a result of their absorption of moisture from Wet glues. Checking and warping are due to the same cause. Our use of #dry glue eliminates the water which is a constituent of wet glue and thus overcomes the usual defects in the production of plywood.

Wet glues normally pass through very thin plies and are apt to stick to the separating cauls if cold pressed, and to the press plates if hot pressed. This objection is overcome by the use of dry glue, which does not soften enough to pass through the face plies.

In the accompanying drawing, Figure 1 is an illustration of the general form of the plies and glue sheet.

Fig. 2, shows the plies and glue sheets between the platens of the conventional hot press, the parts only of the platens next to the sheets being shown.

In carrying out our invention, the glue to be used is prepared as follows: To twenty parts of blood albumin (black soluble) is added thirty to eighty parts of water by weight. This mixture is allowed to soak for about two hours, without stirring. It is then thoroughly stirred-and strained through a thirty to forty mesh screen. There is now added to this mixture fifteen to forty parts by weight of a sugar syrup, such for example as corn syrup, the purpose of this syrup being to retain a greater per cent. of moisture than would otherwise be retained when the mixture has dried. WVhile we have found that a sugar syrup may be advantageously used to retain the moisture to be released under the heat and pressure to be specified, we do not limit ourselves to this compound as other compounds may be used for the same purpose.

Thin plies of wood, sheets of paper, or fabric are then dipped or passed through this glue solution to become thoroughly covered and are afterward dried. These adhesive sheets may be stacked in piles or rolled for further use.

In manufacturing plywood, these sheets are placed between the plies, alternating with them. The plies and adhesive sheets are then subjected, between hot plates with or without cauls, to a pressure of about fifty to one hundred fifty pounds per square inch while the press is kept at a temperature approximately between two hundred and two hundred twenty degrees Fahrenheit. Good results are obtained by continuing said heat and pressure from two ,to four minutes.

Plywood when taken from the press after being prepared by this method contains only one to two percent. more moisture than before the pressing, while plywood manufactured in accordance with the wet glue process contains a much greater per cent. of moisture than when the plies are pressed.

In carrying out our method we may omit the sugar syrup. When sugar syrup is not used, any compound which will make the sheets flexible may be used, such for example as glycerin. If glycerin is used, one to five parts by weight is added to the mixture prepared as described above. Plywood man ufactured with glue in which glycerin instead of syrup has been used must 'be made with moist cauls. This moisture may be furnished to the oauls in any of the usual well known ways and in such quantity as experience may dictate.

While we havestated above that the glue carrying sheet may be a thin plfy of wood, a sheet of paper, or a sheet of abric, it is obvious that other materials may be used. The requisites of this carrying part are an ability to absorb and carry the glue and a lack of rigidity. This lack of rigidity is quite essential in that it insures that any irregularities of the sheet will be impotent to produce irregularities in the lywood surface. When the sheet is absor nt, we find it best to thoroughly impregnate the sheet with the glue although the surplus glue may be carried on the-surface. What is really necessary is theprovision of such a quantity of glue that on heating suificient glue will remain on the exterior of the sheet to properly unite with the ply.

The glue carrying sheets may be used where they are produced. Often, however, it may be found advisableto store themand in such cases it is convenient to roll the sheet. By using sugar syrup, glycerin, or other water carrying materlal in our glue, we insure that our glue shall not become brittle and will not crack or chip when the sheet is rolled.

Throughout the above specification we have described in detail the embodiment of our invention which we now prefer. We consider as part of our invention all changes and modifications which are within the scope of the appended claims.

, What we claim is:

1, The method of making thin, flexible plywood which consists in impregnating a glue carrier, such as a thin ply of wood, a sheet of paper, a sheet of fabric or similar material with glue composed of albumin,

water and a sugar syrup whereby said carrier is rendered flexible and capable of being rolled into cylinders for convenience in storing or transporting, drying said carrier, placing said glue carrier between two or more thin plies of wood and subjecting said plies and said glue carrier to heat and pressure.

2. The method of making thin, flexible plywood which consists in impregnatin a glue carrier, such as a thin ply of woo a sheet of paper, a sheet of fabric or similar material with glue composed of approximately twenty parts by weight of blood albumin, thirty to eighty parts by weight of water, and fifteen to forty parts by weight of a sugar syrup, whereby saidcarrier is rendered flexible and capable of being rolled into cylinders for convenience in storing or transporting, drying said carrier, placing said glue carrier between two or more thin plies of wood and subjecting said plies and said glue carrier to heat and pressure.

3. The method of making thin, flexible plywood which consists inv impregnatin a glue carrier, such as a thin ply of w a sheet of paper, a sheet of fabric or similar material with glue composed of albumin, water and a sugar syrup whereby said carrier is rendered flexible and capable of being rolled into cylinders for convenience in-storing or transporting, drying said carrier, placing said glue carrier between two or more thin plies of wood and subjecting said plies and said glue carrier to approximately one hundred pounds pressure per square inch at a temperature of approximately two hundred and ten degrees Fahrenheit.

In testimony whereof we have hereunto aflixed our signatures.

OLE-NUS L. SPON'SLER. MATTHEW E. DUNLAP. SHERBURNE B. HENNING.

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