METHOD OF PATCHING PLYWOOD PANELS AND THE PANEL PRODUCED THEREBY
United States Patent 3616117
Defects in the surfaces of plywood panels are routed and wood patches, with glue applied to their undersides, are seated in the routed-out sections of the panels. The patches are held in place in uniform contact with the routed-out panel sections by plastic tacks so that a cold-setting glue can be employed to bond the patches to the panels regardless of patch size.
Anderson, Carol Dwight (Salem, OR)
Wilson, Gerald Mack (Lyons, OR)
Molloy, Robert Kenneth (Bayside, CA)
Durant, Kenneth Floyd (Arcata, CA)
Simpson Timber Company (Seattle, WA)
144/346, 144/371, 156/92, 156/94, 156/98, 156/153, 156/293, 428/86, 428/91, 428/133
B27G1/00; (IPC1-7): B32B7/08; B32B35/00
Field of Search:
Goolkasian, John T.
Gil, Joseph C.
The embodiments of the invention in which an
exclusive property or privilege is claimed are defined as follows
1. A method of repairing a plywood panel face which comprises the steps of routing out defective sections on the surface region, said routing extending only through the panel face, applying a cold setting adhesive to one surface of a wood patch which has been precut to the same dimensions and configuration as the routed-out section, firmly seating the patch in the routed-out section forming a glue line between the patch and the bottom of the routed-out section; driving at least one plastic tack through the patch and into the panel, curing the cold setting adhesive to permanently secure the patch to the panel, the plastic tack being retained in the panel face during subsequent finishing and ultimate use, whereby plywood panel patches of any size may be applied with cold setting adhesive to avoid the step of heat and pressure setting a thermosetting adhesive to an otherwise cured plywood panel.
2. The method of claim 1 wherein the patch is seated in the routed-out section of the panel with a portion thereof protruding from the panel face; and including the step of sanding the patches and the plastic tack flush with the panel face.
3. A repaired laminated panel comprising multiple wood plys, wood patches adhesively bonded in routed-out sections in a face ply, nonmetallic plastic tacks extending through the patches and into the panel body, said patches and the plastic tacks being flush with the remaining portion of the face ply.
BACKGROUND OF INVENTION
Finished plywood panels, i.e., panels that have been trimmed and sanded, often have surface defects resulting from rough handling, imperfections in the outer plys, or the like that downgrade the quality of the panels. In order to raise the quality grade of these panels, their surface defects often can be repaired by routing them out and applying wood patches in the routed-out panel sections. These patches are glued in place, smaller patches being glued with a cold-setting glue, (called "cold patching") and larger patches being glued with a glue which can be set only by application of heat and pressure (called "hot patching").
It has been found that patches greater than about 1×3 inches and 1 1/4 ×4 inches cannot be "cold patched." Larger patches will not maintain uniform contact with the panel for a sufficiently long period to create the required bond between the patch and the panel. Therefore, these larger patches must be bonded with a heat-setting glue under the application of heat and pressure.
Each panel with a surface defect is diverted for repair to a defect routing station where defects are routed out and where "cold" patches are applied. If only cold patches need be applied the patched panels are conveyed to a sanding station to sand off any excess patch material, and are then conveyed to a storage area. If "hot" patches must be applied, the panels are routed and then diverted again to a hot-patching station where glue-bearing patches are applied and cured by the application of heat and pressure. Such panels are conveyed to a sanding station to sand off any excess patch material and are then conveyed to a storage area. "Hot patched" panels are thus relatively costly to repair because of the extra conveying and repair equipment required in the second diversion.
A primary object of this invention is to provide a method for patching plywood panels which does not require the use of a thermosetting glue to bond larger patches to the panel. Another object is to provide such a method wherein "cold" patches are applied to plywood panels and held in position with plastic tacks so that the required bond between patches and panel can be accomplished. The material used for the tack can be of any plastic material having sufficient rigidity, the choice being well within the scope of one skilled in the art. A further object is to provide a patched plywood panel wherein patches contain plastic tacks applied in the above-described method.
These and other objects and advantages of this invention will become apparent from the following description and the accompanying drawings, of which:
DESCRIPTION OF DRAWING
FIG. 1 is a perspective view of a plywood panel segment showing two routed-out sections;
FIG. 2 is a perspective view of the FIG. 1 plywood panel segment showing two patches applied and tacked into the routed-out sections; and
FIG. 3 is a perspective view of the FIGS. 1-2 plywood panel segment with the two patches sanded flush with the panel face.
SUMMARY OF INVENTION
In brief, this invention comprises the steps of routing-out a plywood panel surface defect, applying a glue-coated patch to the routed-out panel section, and tacking the patch to the panel with plastic tacks to hold the patch uniformly in contact with the panel while the glue cures to effect the required bond between the panel and the patch.
DESCRIPTION OF INVENTION
With reference to FIG. 1, surface defects in a plywood panel 10 are routed to leave routed-out sections 12-14. These sections would usually be formed by routing tools preset to yield routed-out sections of predetermined depth and length. In routing surface defects, an operator would usually have several preset routing tools of different sizes at hand so as to be able to route defects of various preset sizes without unnecessarily cutting away sound surface material.
The "cold-setting" glue (i.e., a glue that cures at room temperature) applied may be a polyvinyl acetate base glue, such as manufactured by National Starch under the brand name "Durolock;" an acid-curing glue, such as manufactured by Sinco; a resorcinal resin adhesive, such as manufactured by the Borden Company; a phenolic rubber base glue, as manufactured by Pittsburgh Plate Glass; or the like. The "Duralock" glue has a relatively short curing time on the order of about three hours and the resulting glue line meets American Plywood Assoc. standards for exterior grade plywood. Other glues may also be employed where a longer curing time is permissible or where only interior grade plywood standards need be met.
Next, wood patches 16-18, precut to fit the routed-out sections 12-14, are coated with a cold-setting glue on their undersides and set in place in the respective routed-out sections, the resulting glue line being indicated by the dark line 20 at the lower edge of patch 16. These patches may be glued and set by machine or by hand, the latter being the usual manner at the present time. When set by hand, the patches are firmly seated by tapping them into place with a mallet.
Following the seating of the patch in the respective routed-out section, a plurality of plastic tacks 22 are hammered through the patch into the panel. The number of plastic tacks required per patch will vary depending upon the width and length of the patch. In general, as few plastic tacks as possible are used simply for the sake of the appearance of the panel. The plastic tacks are most conveniently provided in the form of a tack strip and applied by a pneumatic tack gun, although other application means or techniques may be employed if desired.
Any of a number of thermosetting plastics can be molded into suitable tack strips. Generally speaking, such plastics must be sufficiently resilient to enable individual tacks to be sheared from a strip and sufficiently strong to be driven into a plywood panel without shattering. If desired, normal plastic-coloring procedures may be employed to color the plastic material before it is molded so that the resulting tacks will have the same general coloration of the wood panel into which the tacks are driven.
In the usual case, the patches have greater thickness than the depth of the respective routed-out sections so that the patches as applied will protrude from the panel surface as shown in FIG. 2. This is to permit the patched panel to be resanded so that the patch can be sanded flush with the panel face as shown in FIG. 3 without having to remove a significant amount of the panel outer ply to achieve a smooth panel face. In sanding the patch, the heads of the plastic tacks will be removed, leaving the ends of the plastic tack shanks exposed flush with the panel face.
It has been observed that the plastic tacks apparently are heated when driven into the patch and panel and, upon cooling down, swell sufficiently to produce a very tight friction fit between the plastic tack shanks and the patch and panel. Consequently, the patches are maintained in good, uniform contact with the routed-out sections of the panel when tacking in place with plastic tacks.
It is believed that the invention will have been clearly understood from the foregoing detailed description of our now-preferred illustrated embodiment. Changes in the details of construction may be resorted to without departing from the spirit of the invention.