US 3508523 A
Abstract available in
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Description (OCR text may contain errors)
A. H. DE MEERLEER I 3,508,523
A ril 28, 1970 APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK 5 Sheets-Sheet 1 INVENTOR.
Albert H. DeMeer/eer April 28, 1970 A. H. DE MEERLEER 3,508,523
APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK 5 Sheets-Sheet 2 Filed May 15, 1967 1' N VEN TOR.
A/berf H. DeMeer/fi'r BY MK ATTORNEY April 1970 A. H. DE MEERLEER 3,508,523
APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK Filed May 15, 1967 5 Sheets-Sheet 3 INVENTOR. A/berf H. De Meek/ear ATTORNEY April 1970 A. H. DE MEERLEER 3,508,523
APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK Filed May 15, 1967 5 Sheets-Sheet 4 INVENTOR' A/berf H. Dee/486F168? April 28, 1970 A. H. DE MEERLEER 3,508,523
APPARATUS FOR APPLYING ADHESIVE TO woon STOCK Filed May 1.5, 196? 5 SheetsSheet 5 INVENTOR. A/berf H. De Meek/66;
ATTORNEY United States Patent 3,508,523 APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK Albert H. De Meerleer, Tacoma, Wash., assignor to Plywood Research Foundation, Tacoma, Wash., a
corporation of Washington Filed May 15, 1967, Ser. No. 638,461 Int. Cl. B44d 1/48 U.S. Cl. 118-63 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process and apparatus for applying an adhesive layer of substantially uniform thickness to a wood stock surface, as plywood veneer, regardless of thickness variations of the wood stock and surface deviations from a planar surface. In general, the invention contemplates the applying of an adhesive to the surface of the wood to provide a substantially uniform composite thickness of wood stock and adhesive and then the removing of excess applied adhesive over a predetermined substantially uniform adhesive thickness and this regardless of the wood stock thickness and the deviations of a wood stock surface from a planar surface. The excess applied adhesive is removed by means of an air knife comprising a tubular member with a plurality of spaced openings. The tubular member is kept clean by means of a reciprocating scraper mounted thereon.
The prior art of laying up plywood, or providing a sandwich comprising a wood core with a wood veneer front or back face (or both) on the wood core, contemplated the use of an adhesive between contacting wood surfaces and the adhesive used was generally in a liquid form. The said wood cores comprise: a wood veneer sheet, plywood formed of Wood veneer sheets, chipboard, hardboard, flakeboard, and lumber stock. The conventional means in the prior art for applying such liquid adhesive provided travel to wood core by feeding it between rotatably driven glue spreader rolls, either metallic or rubber coated metallic rolls, and attempted to apply a uniform coat of liquid adhesive to the glue spreader rolls by the use of doctor rolls. However, the prior art failed to provide a uniform coating of the adhesive on the wood surface regardless of how uniform the adhesive was spread on the rolls.
One of the reasons for such failure to provide for uniform spread of adhesive on the wood surfaces resides in the fact that the wood core is not uniform in thickness and rotatably driven glue rolls, even when operating under optimum conditions, only attempt to determine a uniform composite thickness of wood core and adhesive, and thus any variations in thickness of the wood core result in a complementary variation in the thickness of the adhesive applied to the wood core. Thus, the thickness of the adhesive layer increases at the areas of lesser thickness of wood core and decreases at the areas of greater thickness of wood core.
Another reason for such failure to provide even spread of adhesive on the wood stock lies in the fact that the surfaces of the wood stock to which the adhesive is applied are nonplanar and have deviations therefrom generally characterized by ridges and valleys.
Another reason for such failure to provide a uniform spread of liquid adhesive is that the glue spreader rolls are subject to excessive wear by the frictional contact which the rolls (acting by frictional contact to function as a conveyor for the wood stock) have with the rough wood surfaces on which they are applying adhesive. Generally, workmen normally feed more wood stock in certain laterally disposed areas than others and thus there is not only generally surface wear of the glue spreader rolls but there are areas of greater wear disposed laterally on the glue spreader rolls. This wear adversely affects the uniformity of glue spread of said glue rolls even to provide a uniformity of composite thickness of wood stock and adhesive.
In the hot pressing of plywood, wood veneer sandwiches are commercially loaded into the openings of multiple opening hot presses. A large number of panels are pressed at one time, such as between 20 and 40. Each sandwich is given the same treatment as to temperature, pressure, and time, and thus each uncured sandwich must be as near as possible to the others to obtain uniformity in the finished plywood panel.
Due to the fact that the installed cost of plywood hot presses in an investment in the order of some hundreds of thousands of dollars, the maximum production possible is a necessity. Such maximum production requires that the sandwiches must conform to the requirements of the hot presses rather than having the hot presses conform to the various requirements of individual sandwiches. Thus, a predetermined pressing cycle and conditions are determined, such as: pressurep.s.i.; platen temperatures-285 F. to 300 F.; press close or pressing timea definite time selected, generally in the range of 3 /2 to 6 minutes; and a press opening selected time, depending upon the time requirements of automatic loaders and unloaders employed and in the order of 1 minute.
In order to make the requirements of the individual sandwiches as uniform as possible, very substantial improvements have been made in the art to improve the adhesives employed, the veneer dryers employed, and moisture meters to ensure that the veneer moisture content of the various veneer employed is within a given range. However, the feature of providing a uniform thickness layer of adhesive on the wood veneer surfaces to be adhered together has heretofore eluded the practical commercial arts.
With prior art conventional glue spreader rolls, the optimum possible result will be a uniform composite thickness of adhesive and wood stock. Thus, in general, there is excess adhesive at thin areas of the Wood stock and too little adhesive at the thick areas thereof. However, the wood stock must contact the adhesive on the glue rolls to remove glue therefrom and deposit the same on the wood stock. Thus, if the wood stock is too thin to make such contact (even though the wood stock is usable) no adhesive will be deposited on the wood stock at such areas. When workmen see areas of wood stock on which there has been no deposit of adhesives, they promptly discard such wood stock and the same is thrown away. The loss involved is not only the loss of wood stock but is the loss of the adhesive on portions of the said thrownaway wood stock. It is a primary object of this invention to minimize the loss of such materials.
On extra thick areas of wood stock and where the glue spread is too thin or a starved glue line exists, a condition exists which is diflicult to be determined by eyesight and hence the error generally is not discovered until after the sandwiches have been pressed and cured and then the loss is in plywood panels. Such loss in plywood panels is obviously a greater loss and the amount of the loss increases as the time required for discovery increases. Obviously, if the same is not discovered until the panels are used in connection with structures, then the potential loss will include the structures as well as the panels.
In areas where the adhesive thickness is excessive, there are often pools of adhesive and such pools cannot readily be seen by the workmen. Thus, they generally continue to exist until the sandwiches are pressed and the adhesive cured. With areas or pools of excessive glue, there is the adverse result of uncured glue and improper bonding, because the wood surfaces to be adhered together are spaced apart and do not have proper contact. It must be remembered that liquid adhesives are noncompressible and will thus provide means to maintain wood surfaces spaced. While at times the pressure utilized in the presses will cause migration of the glue tending to break down pools of excessive glue, yet at many times the glue cannot migrate laterally and the pools remain and the problems incident in blows and blisters are still a major problem in the plywood art. While the blows and blisters are common in the hot pressing of plywood, yet excessive glue areas still provide improper bonding in cold pressing of plywood panels. In any event, excessive glue areas and starved glue lines are to be avoided whether the panels are hot pressed or cold pressed. The prior art failed to provide uniform spread of adhesive on wood surfaces and this primarily because of the naturally occurring differences in thickness of the wood stock and the naturally occurring surface defects and variations of the wood surface from a planar surface. It is a primary object of this invention to provide a uniform spread of adhesive on wood surfaces in the plywood art.
As wood stock passes through the conventional glue spreader rolls, the areas where no adhesive has been shpread are often visible. Thus, the practice in the art has been to increase the thickness of adhesive spread by the conventional glue spreader rolls to limit the amount of readily seen areas on which there is no adhesive. This practice has not only increased the problems resulting from overspread as blows, blisters, and improper bonded areas but has resulted in the usage of excess amounts of glue, all resulting in a very substantial loss to industry. Thus, this invention, in providing a process and apparatus for providing a substantially uniform spread of adhesive on wood stock surfaces, has a primary object in the saving of the total amount of adhesive used.
Another object of this invention is the providing of a uniform coating of adhesive on a surface of rotary cut wood veneer.
Another object of this invention includes the spreading of excess adhesive on a surface of a piece of wood stock and then the removal of all excess adhesive over a predetermined uniform thickness of adhesive regardless of the thickness of the piece of wood stock or the surface contour thereof.
Another object of this invention is to remove such excess of adhesive by use of a tubular member, air supply means for said tubular member, and spaced apart longitudinally alined openings in said tubular member, and spaced apart longitudinally alined openings in said tubular member providing jets of air impinging upon said excess adhesive and moving the same away from the jets of air.
Another object of this invention is to direct such jets of air so the same impinge upon the adhesive coating on said surface and at acute angles thereto.
Another object of this invention is to maintain a relatively horizontal position of the adhesively coated wood surface at the time of impinging said jets of air thereagainst.
Another object of this invention is to maintain said tubular members free and clear of foreign matter, such as adhesive or adhesive containing residues.
Other objects of this invention will now become apparent from the detailed description of the invention and the following description of the drawings, throughout which like reference numerals relate to like parts.
FIGURE 1 is a fragmentary and somewhat schematic view of a device embodying this invention and with the veneer guides only generally and fragmentarily shown in view of the scale to which FIG. 1 is drawn;
FIG. 2 is a front elevational view of the device of FIG. 1 applied to a conventional glue spreader used in the plywood art and with parts broken away;
FIG. 3 is a somewhat schematic view, on a much smaller scale than FIGS. 1 and 2, and showing primarily mounting means for this invention;
FIG. 4 is a view, partly in section and partly in elevation, taken substantially on broken line 44 of FIG. 2 and on a larger scale than the showing in FIG. 2;
FIG. 5 is a fragmentary sectional view, with parts shown in elevation, and on a larger scale than FIG. 4 and taken substantially on broken line 55 of FIG. 2;
FIG. 6 is a fragmentary view of structure shown in FIG. 5 on a larger scale than FIG. 5;
FIG. 7 is a fragmentary perspective view of parts of the structure shown in FIG. 1 of the drawings particularly indicating, more completely, the veneer guides shown only fragmentarily in FIG. 1 of the drawings;
FIG. 8 is a fragmentary view showing an alternate form of veneer guides and particularly applicable for use in connection with veneer fed in a direction at right angles to the wood grain thereof;
FIG. 9 is an end elevational view of the structure of FIG. 8;
FIG. 10 is an enlarged fragmentary view, taken substantially on broken line 10'10 of FIG. 6, and illustrates one type of air knife cleaner means which may be employed with this invention;
FIG. 11 is a fragmentary sectional view on a larger scale, taken substantially on broken line 1111 of FIG. 10 and also illustrating a sheet of material to which adhesive has been applied;
FIG. 12 is an enlarged fragmentary view of the showing of FIG. 11 as to air knife adhesive spreader;
FIG. 13 is a fragmentary enlarged sectional view of parts shown in FIG. 10 of the drawings;
FIG. 14 is a fragmentary perspective view of parts shown in FIG. 6 of the drawings;
FIG. 15 is a fragmentary view of one form of air knife cleaner means which may be used with this invention;
FIG. 16 is an enlarged fragmentary view showing additional details of the air knife cleaning system depicted in FIG. 15 of the drawings; and
FIG. 17 is a fragmentary and somewhat schematic view of an alternate form of cleaning means for the air knife.
Referring more particularly to FIG. 1 of the drawings, the device of this invention may be connected with and operate in conjunction with the glue spreader rolls of a conventional glue spreader commonly used in connection with the manufacture of plywood. Such a conventional glue spreader will comprise an upper adhesive applicator roll 20, an upper adhesive doctor roll 22, and end plates 24 so that an adhesive well is formed between the rolls 20 and 22 and the end plates 24. This adhesive well contains adhesive of suitable characteristics and to a desired level. The rolls turn in the direction of the arrows and thus the doctor roll 22, which is adjustable toward and away from the adhesive applicator roll 20 (by conventional meansnot shown), will determine an adjusted layer thickness of adhesive present on adhesive applicator roll 20 at the time a piece of veneer 26 is passing under and contacts the adhesive applicator roll 20.
The lower surface of the veneer 26 is contacted by the lower adhesive applicator roll 28 as the veneer 26 passes over the same. The layer thickness of adhesive present on the said roll 28 at this time is determined by a lower doctor roll 30 which is adjustable toward and away from the lower adhesive roll 28 (by conventional meansnot shown). In the form of conventional adhesive spreader shown in FIG. 1 where the doctor roll 30 precedes the lower adhesive roll 28 in the direction of travel of the veneer 26, an adhesive trough 32 is employed and the lower adhesive applicator roll 28 extends into the trough 32 and below the surface level of adhesive in said glue trough 32. Other types of lower glue applicator-doctor roll combinations are commonly employed and thus the type illustrated is to be considered illustrative and not restrictive.
It is common to adjust doctor rolls 22 and in the plywood art to spread glue at predetermined rates, such as a rate of about 60 pounds of wet glue per thousand square feet of double glue line for exterior type glue.
This invention contemplates the employment of the adhesive spreader air knives, and associated parts exemplified in FIG. 1 by upper tubular member 34 and lower tubular member 36. These tubular members 34 and 36 cause air to be directed out through openings therein, all of which is considered and explained in detail in connection with later figures. However, these said tubular members 34 and 36 require periodic cleaning of the exterior surface thereof to remove residue, including adhesive, and as an illustration of cleaner-scraper means, there is indicated in connection with FIG. 1 of the drawings the scrapers 38 and 40 which are mounted for traveling movement respectively on said tubular members 34 and 36 and for travel from one side of the machine to the other and from said other side of the machine back to the first mentioned side. The said tubular members 34 and 36 are connected with the devices of this invention by means later described.
One way of causing said travel of the tubular scraper and cleaner members 38 and 40 is to connect the same with an endless cable means 42. Endless cable means 42 is reeved about suitable main pulleys 44, 46, 48, and and alinement of said endless cable means 42 is obtained by said pulleys and also by guide pulleys 52, 54, and 56. As it is desired to make devices of this invention either as a part of a combination adhesive spreader or as accessories usable in connection with existing adhesive spreader rolls, preferably the pulleys mentioned are employed so that there will be a flight of the cable 42 in a suitable direction, shown as vertical, so as to minimize space requirements or to ensure that there will be sufficient room to attach the device as an accessory to existing glue Spreaders. Also, in view of the fact that the vertical flight, as shown in FIG. 1, must have suitable length, a break line is shown to indicate any desired length of the vertical flight.
One means of causing said endless cable means 42 to travel crosswise of the machine and sequentially in either direction is to connect the same by connector 64 to a driven endless cable 62. Endless cable 62 is reeved about driven sprocket 58 and idler sprocket 60 and thus is driven. Driven sprocket 58 is connected to any suitable source of rotary power (not shown) and is selectively driven a desired amount in either direction (by means not shown) to determine the direction and amount of turning movement of driven sprocket 58, and in turn the amount and direction of travel of endless cable means 62 and endless cable means 42.
FIGS. 1 and 2 show mounting means for the tubular members 34 and 36 and associated parts. Some of the parts are broken away in FIG. 2 of the drawings in view of the scale to which said figure is drawn. FIG. 3 is drawn to a smaller scale and shows somewhat more completely the mounting means. The adhesive applicator rolls 20 and 28 are shown in FIG. 3 (on a larger scale in FIG. 2) and are carried by suitable bearings. Two of such bearings 63 and 65 are shown to the right in FIG. 2 of the drawings. Such bearings are supported by the main frame of a conventional adhesive spreader used in the plywood art and to which the device of this invention may be applied either as an accessory or the same may be fabricated together as a combination. The tubular members 34 and 36, and associated parts operating in conjunction therewith (many of which have been previously described), are mounted separately of the main machine frame of the conventional adhesive spreader so that all of said associated parts are movable into operative position relative to the applicator rolls 20 and 28 or they are movable out of operative position relative thereto to permit usual maintenance and repair of the conventional glue spreader and movement of the tubular members 34 and 36 and associated parts as a safety precaution in case of a jarnb of veneer or other possible faulty operation.
The support for such tubular members 34 and 36 and associated parts may comprise a vertical standard 68 (see FIG. 3) rotatably mounted on a fixed base 70. The base 70 and main machine frame (not shown) may be sup orted at a common floor level.
The upper frame 74 for directly supporting the upper tubular member 34 and associated parts and indirectly supporting lower tubular member 36 and associated parts (as will be later explained) is secured at one erd portion thereof to vertical standard 68 by hearing 76. The other end portion of the upper frame 74 is suspendedly supported by rigid means 78 (shown in FIG. 3 and with a fragment thereof shown in FIG. 2). The rigid means 78 is connected at one end portion thereof to the upper frame 74 and at the other end portion thereof to standard 68 by connecting means 80 (see FIG. 3). The tubular members 34 and 36 are supported at their end portions by cross frames or strong backs 79. The tubular scraper members 38 and 40 are supported on groove tracks (see also FIG. 14) carried by the cross frames 79, as will be more specifically later described. Also, cross frames 79 support upper veneer guides 82 and lower veneer guides 84 as a strong back therefor. Thus, all of the said parts will swing together as a unit with rotation of vertical standard 68.
The said upper frame 74 is releasably connected with a main frame structure part 81 (see FIG. 2-upper right) by releasable means 83 carried by upper frame 74. At all times during normal operation, the swinging structure of this invention will be relatively fixed to the main frame of the machine supporting the adhesive applicator rolls 20 and 28 and parts associated therewith.
The adhesive applicator rolls 20 and 28 wear with use and thus lose their precise cylindrical configuration and it becomes necessary to place them on a lathe, from time to time, and to turn them down to a diameter so they are true cylinders. As a practical expedient in conventional adhesive Spreaders, the operative axis of only one of said applicator rolls 20, 28 is fixed and the axis of the other thereof (as lower adhesive applicator roll 28) is adjustable toward and away from the fixed axis of the other (upper adhesive applicator roll 20).
Also, to adjust for different thicknesses of veneer, the spacing between adhesive applicator rails 20 and 28 must be adjusted. As the center line between applicator rolls 20 and 28 changes in elevation and they change in diameter, the center line between the tubular members 34 and 36 and between veneer guides 82 and 84 and their spaced distance to said adhesive applicator rolls 20, 28 must be adjusted to match such changes in the adhesive applicator rolls 20 and 28. This is accomplished by adjusting the relative position of vertical standard 68 by any suitable means (not shown).
Referring generally to FIGS. 4, 5, and 6 of the drawings, only the end portions of the upper tubular member 34 and the end portions of the lower tubular member 36 at both ends of the device are carried by end portions of the upper and lower cross frames 79 (in order to scrape tubular members 34 and 36 throughout their entire lengths they must be supported only at their end portions). The veneer guides 82 and 84 are carried by the upper and lower cross frames 79 and each guide must be supported for strength requirements. The upper and lower cross frames 79 are separately adjustable toward and away from each other to provide a desired extent of opening therebetween, as will be hereinafter explained.
As the structure of the ends of the machine are identical, FIGS. 4, 5, and 6 illustrate only one end portion of the machine. The lower cross frame or strong back 79 terminates in end portions 100, each of which is carried by and moves with a slidable end frame 75 (the details thereof will be explained later). Each end frame 75 is connected with and slides with a slidable end frame portion 77. End thrust bearings and guides 71 and end brackets 88 are supported by the upper frame 74. Vertical shafts 90 threadedly engage slidable supports 73. By reason of such threaded engagement between shafts 90 and the slidable supports 73 and the fact that vertical movement of shafts 90 is prevented by end thrust bearing 71, turning movement of the shafts 90 imparts vertical travel to the supports 73 relative to upper frame 74, thrust bearings 71, and end brackets 88. Such vertical travel of supports 73 is imparted to frames 77 and 75 and to the end portions 100 of the lower cross frame 79, as well as parts connected with said lower cross frame 79. Such associated parts connected with lower cross frame 79 will include such structure as tubular members 36 and lower veneer guides 84.
The vertical shafts 90 (see also FIG. 2) are interconnected by worm and gear means 92, and cross shaft 94. Rotary movement to the cross shaft 94 (in either direction) may be imparted by hand wheel 96 connected to cross shaft 94. Thus, upon turning of the hand wheel 96, the lower tubular member 36 and lower veneer guides 84 may be adjusted relative to the upper tubular member 34 and upper veneer guides 82 to accommodate the passage of wood stock therebetween, such as veneer, of different thicknesses. Of course, at the same time, the adhesive applicator rolls 20 and 28 are similarly adjusted.
Individual end elevational adjustment of the veneer guides 82 and 84 and parts connected therewith (see particularly FIG. 4) is provided by terminating the upper cross frames 79 in diagonal upper slide guides 98 and lower cross frames 79 in lower slide guides 100. The said guides 100 are mounted for sliding movement in slots in the slidable end frames 75. Bolts 102 may be employed to interconnect lower slide guides 100 with the slidable end frames 75 and thus upon loosening and adjustments, the relative position of the slide guides 100 to end frames 75 may be determined. This provides for individual vertical adjustments of the ends of lower cross frame 79 and parts carried thereby to adjust the lower cross frame 79 into a desired horizontal plane.
Preferably, the slide guides 98 (terminal end portions of upper cross frame 79) are held in place by safety releasable means and with each having adjustable length linkage (not shown) to provide for individual end elevation adjustment of upper slide guides 98 and to thus adjust the upper cross frame 79 into a desired horizontal plane. Such safety release means may comprise pre-loaded safety release air cylinders 104 (FIG. 2), which are pre-loaded so that any pressure exerted above said pre-loading and which pressure may be exerted by veneer jambing between veneer guides 82 and '84 (also see FIGS. 5, 6, 7, and 14) will cause diagonal guide 98 (FIG. 4) to release and slide in slide guides 98 in fixed brackets 88 and thus increase the relative size of the opening between veneer guides 82 and 84 and parts carried therewith. Thus, the spacing between veneer guides 82 and 84 may be selected as one suitable for particular thickness of veneer passing between said veneer guides but at the same time in case of a jamb up, there will be a safety feature so that the said opening may be increased rapidly and automatically in response to extra pressure exerted between the veneer guides 82 and 84 caused by malfunction through extra size of veneer passing therebetween.
The tubular scraper members 38 and 40 are best shown in details in FIGS. 5, 6, l0, 11, 13, and 14. As the upper and lower scraper members are identical, the parts of each thereof are given the same numbers. The housing of each scraper comprises two housing parts 106 and 108 (see FIGS. 6 and 14) held together by set screws 110 and sliding clearance between housing 106, 108 and a tubular member 34 or 36 may be obtained by appropriate use of selected shims 112. Preferably there are two circular scrapers (see FIGS. 10 and 13) 114 and 116 for each scraper 38 or 40 previously generally described. The circular scrapers 114 and 116 have splits 117 (FIG. 11) and are spring loaded so that the said rings 114 and 116 resiliently engage and scrape tubular members 34 and 36. A groove 119 is provided in each ring 114 and 116 and with such groove in registration with the longitudinally alined openings 118 (in tubular members 34 and 36). If the rings 114 and 116 are to be operated when the said openings 118 are not being used to spread adhesive, then such grooves 119 may be eliminated. However, if said rings 114 and 116 are used for scraping during normal operation of openings 118, then such grooves 119 provide for lateral air adjacent an opening 118 which tends to prevent build-up of adhesive adjacent the opening 118 over which a ring 114, 116 is registering. Preferably the rings 114 and 116 have a width, as respects the spacing of openings 118, so that only one opening 118 is covered. By such lateral air and the width of rings 114 and 116, no substantial interference of the free flow of air from openings 118 results. Any substantial interference with air leaving said tubular members 34 and 36 through openings 118 would cause malfunctions in uniform adhesive spread and thus must be prevented. In order to provide precision in the alinement of the grooves 119 in the circular scrapers 114, 116 and the alined openings 118 in tubular members 34 and 36, pins 120 are provided which fit into openings jointly provided in housing parts 108 and scrapers 114, 116 of scraper members 38 and 40. The relative angular position of the scraper housing parts 106, 108 is determined by plates 122 locking the relative angular position between the housing parts 106, 108 and the cross frames 79.
The individual veneer guides 82 are secured to the cross frames 79 by set screws 124. In order to positively determine that each of the veneer guides 82 and 84 will project identical distances away from cross frame 79, selected shims 126 may be suitably employed.
Scraper members 38 and 40 may be secured to the endless cable means 42 by any suitable means, such as clevises 128, best shown in FIGS. 2, 7, 10, 14, and 15.
The internal structure of each scraper 38, 40 is illustrated in a somewhat enlarged view in FIG. 13. The scraper housing parts 106, 108 are provided with similar inclined tracks. In FIG. 13, the housing part 108 has two inclined spaced apart track portions 130 and each scraper 114, 116 has mating, inclined surfaces with said track portions 130. Thus, as the housing part 108 is moved toward the right (as respects the showing in FIG. 13), the scraper blade 116 is urged downwardly and into close scraping contact with a tubular member 36. Also, it will be apparent upon movement in the other direction, that the circular scraper 114 will be moved into close scraping contact with a tubular member 36. Thus, as the scrapers 38 and 40 are caused to travel first in one direction relative to the tubular members 34, 36 and then in the other direction, that the said tubular scraper members 38 and 40 will cleanly scrape foreign materials which may accumulate on the external periphery of the tubular members 34 and 36. Preferably the rings of the scrapers 38, 40 will not scrape over the alined openings 118 in the said tubular members 34 and 38. Also, the scrapers 38, 40 may be operated periodically or continuously, as desired.
In addition to providing close contact between scrapers 38, 40 and the tubular members 34, 36, it is preferable to provide at the time of scraping contact, a diluentor solvent-cleaning liquid for the residue, including the adhesive used, to aid in cleaning the said scrapers and the said tubular members. One construction for such purpose is best shown in FIGS. 15 and 16 of the drawings. The
scraper 38 for the tubular member 34 is provided with passageway 132 so that liquids entering the same communicate with the circular scraper 114, 116. A container 134 for said cleaning liquid 136 is provided with inlet valve means 138 so there is a supply of cleaning liquid 136 under pressure. Spring loaded, outlet liquid valve means 140 is positioned in the path of travel of tubular scraper member 38 so that at the end of the travel of the tubular scraper member 38 in one direction and toward the container 134, the movement of the scraper member 38 upon contact with said valve means 140 will actuate the said valve means 140 and a predetermined amount of cleaning liquid 136 will be injected upon the circular scrapers 114, 116 of the upper tubular scraper member 38. The lower tubular scraper member 40 is similarly equipped and during its tavel when it contacts the valve means 142 (similar in function to the valve means 140), a predetermined amount of cleaning liquid 136 Will be. injected upon the circular scrapers 114, 116 of the lower tubular scraper member 40. In this form of the invention, cleaning fluid 136 is injected periodically upon the circular scrapers 11.4, 116 of the scraper members 38, 40 when said scraper members consecutively contact the outlet.- valve means 140 and 142.
The modified form of structure to provide cleaning fluid to the said circular scrapers 114, 116 of tubular scrapers 38, 40 is shown in FIG. 17 of the drawings. As an illustration, the tubular scraper 38 is provided with passageways 144 communicating between circular scrapers 114, 116 and inlet passageway 146, which in turn connects to a flexible conduit 148 connected to a suitable source (not shown) of cleaning fluid under pressure which will be similar, in that respect, to container 134 and cleaning fluid 136 therein. In this form of the invention, cleaning fluid will be discharged (whenever pressure is applied to the liquid in conduit 148) on the circular scrapers 114, 11.6 of each of the tubular scrapers 38, 40 and at intervals regulated by any suitable valves means (not shown). A similar construction to that shown in connection with tubular scraper 38 of FIG. 17 will be used in connection with the tubular scraper 40 and thus both constructions are now obvious.
The structure employing veneer guides 82, 84 will be operated in conjunction with the veneer 26, which veneer travels in a direction lengthwise of the wood grain thereof. Thus, the axes of the usual ridges and valleys present in dried veneer to which adhesive is to be applied to one or both surfaces, will be parallel to the direction of travel of the wood veneer 26. If said veneer 26 is utilized as cross banding stock of plywood, it will have adhesive spread on its upper and lower surfaces. If such veneer is used elsewhere in the manufacture of plywood, only one surface, as the upper surface, will have adhesive spread thereon. In such instances, only an upper adhesive applicator roll 20 will be employed and a lower adhesive applicator roll 28 will not be employed. Because of the surfaces to be coated with adhesive, the fact that the veneer 26 is traveling in the direction of its Wood grain, the veneer guides 82 and 84 will be adequate to keep the veneer sufficiently flat and properly located at the time the veneer 26 passes between tubular members 34 and 36 or merely below tubular member 34.
However, if the veneer sheet is traveling in a direction crosswise of its wood grain (as depicted by veneer sheets 150 in FIGS. 8 and 9) then modified veneer guides are used for veneer guides 82 and 84 and the modified adhesive applicator rolls are used for the upper and lower adhesive applicator rolls 20 and 28. In order to simplify the drawings, FIGS. 8 and 9 show generally only the modification and the remaining parts generally not shown and 154 are elongated in length to iron out ridges and valleys in the dried veneer which ridges and valleys are traveling crosswise of the machine due to the direction of travel of the veneer crosswise of its wood grain. The upper and lower adhesive applicator rolls 156, 158 replace the upper and lower adhesive applicator rolls 20, 28 of the other figures. Also, the upper and lower adhesive applicator rolls are provided with grooves 160, 162 to permit vertical movement of the elongated veneer guides 152, 154. The structures of FIGS. 8 and 9 is of particular utility in applying adhesive to one or both surfaces (upper and lower) of veneer which is substantiall a continuous sheet. When cross-banding stock has comprised a plurality of pieces of veneer edge joined together to form a continuous sheet, the problem of applying a uniform spread of adhesive has proved to be insurmountable in prior art devicesthe adverse results in spreading adhesive crosswise of the grain has been much more than in the other direction. However, such continuous sheet of cross-banding stock can be readily caused to travel crosswise of the direction of its grain through devices of this invention and at the same time with a uniform spread of adhesive.
The forward end portions of the veneer guides 152, 154 and the tubular members 34 and 36 are supported in the same fashion as that indicated in the previous figures through cross frames 79 and thus the same adjustments obtain for the veneer guides 152, 154 as obtained for the veneer guides 82, 84.
In the foregoing, references have been made to the applying of an adhesive coat to wood pieces of veneer 26 or veneer sheet (formed of a plurality of edge joined wood veneer pieces). These are to be considered as examples of a core to be faced with other pieces of wood veneer on either the top or bottom thereof, or both. Other cores will include products commonly termed in the art as chipboard, hardboard, flakeboard, and lumber stock. To such cores, a wood veneer front or back face (or both) is to be consolidated by a glue line. The adhesive to be applied to provide such glue line may be applied to the core with a double glue line or it may be applied to the inner surface of the wood veneer facing by a single glue line.
The adhesive employed may be either a hot press type or a cold press type. With either type, pressing is necessary to provide the necessary intimate contact between the surfaces to be adhered together. If the glue line is not uniform in thickness, then inadequate glue line results. With hot pressing, nonuniform thickness of glue line often results in blows, blisters, areas of noncured adhesives, and sparse (thin or starved) glue line areas. With cold pressing, nonuniform thickness of glue line often results in too thick or too thin glue lines and inherent adverse results. The conventional glue spreader rolls 20 and 28 provide a common thickness but of two items, (1) of core, as veneer 26, and (2) of adhesive, as the top and bottom layers of adhesive. Wood veneer stock to be veneered to a core is commonly rotary cut or sliced. With sliced wood veneer stock, we have a surface which is characterized by having a nonplanar surface with ridge and valley deviations from a planar surface. Such deviations are multiplied and exaggerated with the rotary cut veneer because of inherent conditions present during rotary cutting. Regardless of the type of wood veneer used or the type of wood core stock employed, the said conventional glue spreader rolls 20 and 28 tend to provide thicker glue lines in the valley deviations and thin or sparse or starved glue lines in the ridge deviations. Also, as the liquid adhesive is noncompressible, the adhesive in said valley deviations tends to maintain separation of the wood surfaces during pressing resulting in the adverse results previously mentioned either in cold or hot pressing.
With this invention, the doctor rolls 22 and 30 are adjusted relative to the upper and lower adhesive rolls 20 and 28 to provide for an over spread or excess spread of adhesive over that determined as the ultimate for the type of pressing used and the particular grade of wood employed. Thus, by way of example, if it is determined that the final glue spread shall be at the rate of about 60 pounds of wet glue line per thousand square feet of double glue line, then said doctor rolls 22 and 30 will be adjusted to spread at the rate of about 70 pounds of wet glue line per one thousand square feet of double glue line.
Air under pressure is provided in the tubular members 34 and 36 and in the range of to 50 p.s.i. The openings 118 in said tubular members have a diameter preferably in the range of 0.024 to 0.062 inch and they are preferably spaced apart different distances in the range of 0.10 to 0.25 inch. Referring to FIGS. 11 and 12, the walls providing the openings 118 are maintained so that the downwardly directed jet of air from the upper tubular member 34 and the upwardly directed jet of air from the lower tubular member 36 impinge at an acute angle to the traveling wood stock, as veneer 26. Such acute angle is preferably in the range of 6080.
Such jets of air distribute adhesive to a controlled adhesive thickness on a wood surface even though the said wood surface has the usual nonplanar surface with ridge and valley deviations from a planar surface and even though the wood stock is of nonuniform thickness. Where we have valley deviations, obviously, there will be greater deposits of adhesives in said valleys. Also, where we have variations in thickness of the wood stock, the thicker the wood stock, the thinner the adhesive coating and the thinner the Wood stock, the thicker the adhesive coating to a point. Obviously, if the thickness of the adhesive on one of the adhesive rolls or 28 is not sufficient to contact the surface of the wood stock, then there will be no deposit of adhesive in view of the extra thinness of the wood stock.
In the prior art, it was the tendency to increase the rate of adhesive spread whenever pieces of Wood stock had observable area on which no adhesive was present. While such practice of increasing adhesive spread to cure the problem of barren areas on which no adhesive appeared, such practice created more difficult ones and particularly those involved in excessive adhesive spread. In view of the fact that the present invention contemplates the applying initially of excessive adhesive, then the prior art problems resulting from initial overspread of adhesive are no longer present as the tubular members 34 and 36 will remove all excess of adhesive over a final predetermined adhesive thickness spread. All excess adhesive will be moved by the air stream emitting from the openings 118 toward adhesive rolls 20 and 28 and such excess will be picked up by such adhesive rolls.
Previously, curtain coating, spraying, and dipping have been attempted to apply adhesive to the surfaces of wood stock to be adhered together. Such practices of the prior art have had the shortcoming of nonuniform adhesive spread, including areas of excessive adhesive spread, and their use in the practical arts has been rather insignificant as compared to the use of adhesive applicator rolls, such as 20 and 28. However, such curtain coatings, spraying, and dipping to provide an initial coat or layer of adhesive on wood stock can well be used in combination with the tubular members 34 and 36 as it is desired to initially provide an excess coating or layer of adhesive.
The tubular members 34 and 36 are provided with a plurality of spaced and longitudinally alined openings 118 and thus the surface of the adhesive finally remaining is characterized by laterally spaced apart slight valleys and ridges extending in the direction of travel of the Wood stock. Such valleys and ridges of adhesive are not of sufficient magnitude to cause any substantial variation in the uniform thickness of the final adhesive spread. Rather than harming, such valleys and ridges aid in the final adhesion of the wood surfaces to be contacted and adhered together by an adhesive. With slight variation and the presence of slight excess of adhesive in the ridges in the final adhesive thickness and where the adhesive is provided to a substantially uniform thickness, then migration of adhesive brought about during the pressing cycle causes more intimate contact between the wood surfaces and the adhesive resulting in better glue lines. One theory as to why such slight variations from absolute uniformity of adhesive thickness is highly desirable and useful, resides in the fact that the adhesive is applied directly to only one of the wood surfaces to be adhered together and if slight migration occurs during pressing, this relative movement crosswise between the wood surface and the adhesive enhances the spreading of the adhesive on the wood surface on which no adhesive was originally deposited. Such limited migration is to be distinguished from the relatively large migration which occurred in the prior art practices. If pools or wells of adhesive are left, they will not move to the desired extent by migration and will remain pools of adhesive which become incompressible separators between the wood surfaces, preventing wood contact and proper bonding.
Regardless of the theory, this invention provides for uniform and practical results by utilizing the spaced apart longitudinally alined openings 118 rather than a continuous slot. Attempts have been made to utilize a continuous slot but without success. The thickness of the adhesive coating required on wood varies with the grade quality of the wood, the specie of the wood stock, and characteristics of the adhesive. Thus, the adhesive spread required may vary from 50 pounds to pounds per double wet glue line per 1000 square feet of wood surface. By the use of longitudinally alined spaced apart openings 118, then variations in the air pressure to tubular members 34 and 36 result in variation in the thickness of adhesive spread and the results from varying said air pressure on the thickness of the final glue spread are readily predictable and controllable. On the other hand, with a continuous slot, such predictable and controllable results are absent.
In the event that the initial coating of adhesive is provided by adhesive applicator rolls, such as 20 or 28, and the amount of excess adhesive is determined by the adjustment of doctor rolls 22 and 30, then all excess of adhesive over a predetermined uniform thickness of adhesive applicator rolls 20 and 28.
Veneer 26 may be formed from one or more than one piece of wood veneer. When formed from more than one piece, the said pieces are preferably edge joined together so that they are handled as one piece. However, the veneer depicted as veneer 26 will be traveling in a direction parallel to the wood grain. Such a piece of veneer 26 will have a surface portion having many deviations from a planar surface and such deviations result from the mechanical means slicing or in rotary cutting the veneer, difference in the wood stock or trees providing the veneer, and differences resulting from uneven drying of the veneer after the same has been cut. These deviations of the surface of veneer 26 from a planar surface include not only ridge and valley deviations but also in thickness variations. The thickness variations are found in a single piece of veneer and between pieces of veneer which may form the veneer piece 26. Also, the adhesive applicator and veneer conveyor rolls 20 and 28 wear and change in diameter as well as in surface contour and therefore do not accurately spread the adhesive on a veneer sheet to even a composite uniform thickness of veneer sheet and adhesive. Thus, the present invention in providing a common thickness of adhesive on veneer stock 26, traveling in the direction of the wood grain, has provided a very substantial contribution to the prior art and has solved a long felt need.
The problem of providing an even thickness coating of adhesive on the surfaces of the edge-joined-together pieces of veneer stock, traveling in a direction crosswise of the wood grain, is an even more complex problem. Referring to FIGS. 8 and 9 of the drawings, the veneer sheet 150 is formed of a plurality of pieces of veneer which have been edge joined together to form a continuous sheet of veneer. The surface of the said sheet 150 has deviations from a planar surface by difference in thickness in different areas of a single piece of veneer, different thicknesses of pieces of veneer forming the sheet 150, deviations by ridges and valleys from a planar surface, and has rather long undulating ridges and valleys extending crosswise of the direction of travel of the veneer due to the fact that the sheet in drying tends to form such contour because of differences of shrinkage in various areas obtaining during the drying process of the veneer. Different densities of the wood in different areas forming a sheet, both rotary cut and sliced veneer sheets, tend to enhance the formation of long undulating ridges and valleys and the veneer sheet .150 does not tend to lie flat and does not tend to assume a definite position.
Thus, in FIGS. 8 and 9 of the drawing, the upper and lower veneer guides 152 and 154 are somewhat elongated to iron out the long undulating ridges and valleys which are caused during the drying process of the veneer. It is desirable that wood stock or veneer be held flat and in a predetermined position at the time of impingement of the air through openings 118 so that the angle at which the said air is impinged on the sheets of veneer 26 or 150 and the relative position of tubular members 34 and 36 to the wood stock can be controlled within the limits of this invention.
The prior art has suggested continuous processes of laying up plywood and all of such processes, which have been given serious consideration in the art, have contemplated the use of a continuous sheet of core laid up by edge joining pieces of veneer to form a continuous sheet, such as veneer sheet 150. The most serious difficulties encountered in attempting to apply said proposed continuous lay up of veneer has been the providing of an even spread of glue on both faces of traveling veneer stock traveling in a direction crosswise of the wood grain of the stock. However, with the present invention, the problem of providing a uniform thickness of adhesive to the surface of the traveling wood stock has been demonstrated to be successful even though the surfaces of said traveling wood stock have deviations from a planar surface as indicated. Thus, the present invention makes many of the prior art contemplated processes of continuously laying up plywood now practically feasible.
In order to positively control the amount of glue remaining on a wood surface, such as veneer 26, the openings 118 are disposed in close proximity to the adhesive on the surfaces of said veneer 26. Thus, some of the adhesive will become air borne and will be carried onto the tubular members 34 and 3-6 and such tubular members 34 and 36 must be periodically cleaned. This is accomplished by the scraper members 38 and 40. If operations would permit the cleaning of the tubular members 34 and 36 While air is not being delivered out openings 120, then the circular scrapers 114 and 116 of the scraper members 38 and 40 may be continuous circular scrapers. However, it is generally desirable to provide for a continuous availability of the spreading of adhesive and hence, normally, the circular scrapers 114 and 116 must function to clean the tubular members 34 and 36 While air is being ejected through openings 118. Thus, preferably, there is provided the grooves 119 in the rings 114 and 116 and the rings 114 and 116 are of a crosswise dimension of less than a spacing between openings 118. Thus, a circular ring scraper 114 or 116 will be in registration with only one opening 118 at any particular time period and at that time, air from that particular opening 118 is permitted to exhaust in a lateral direction and which air traveling laterally tends to clean the space in tubular members 34 and 36 adjacent the particular opening 118 involved.
In cleaning the outer surfaces of the tubular members 34 and 36, we encounter deposits of adhesive and also deposits of adhesive mixed with foreign matter. Thus, the material to be scraped and to be moved tends to adhere to the said tubular members. Thus, preferably, a cleaning liquid, of the adhesive solvent or adhesive diluent type, is preferably employed. Thus, there is illustrated the cleaning liquid 136 of FIG. 16, or a similar liquid which is delivered to the flexible conduit 148 of FIG. 17, which is delivered to the circular scrapers 114 and 116. The said circular scrapers 114 and 116 are spring loaded to resiliently urge themselves around and adjacent the tubular members 34 and 36 and thus augment their clening-scraping action. The said scrapers 114 and 116 are split rings with splits 117 and thus may be provided with the resiliency and tendency to follow the surfaces of the said tubular members 34 and 36. If desired, additional pressure is obtained urging said circular scrapers 114 and 116 against the tubular members 34 and 36 by reason of the inclined surfaces or inclined tracks 130 shown in FIG. 13 of the drawings cooperating with said scrapers 114 and 116.
1. Apparatus for providing controlled adhesive spread on traveling wood sheet stock, said stock being characterized by having a nonplanar surface with ridge and valley deviations from a planar surface and by having a nonuniform thickness, comprising wood sheet stock conveyor means; adhesive applying means providing an adhesive coating on said stock; an adhesive moving air knife comprising a tubular member, the air outlet of which comprises a plurality of spaced longitudinally alined openings, said air knife providing an air stream disposed at an acute angle to the surface of said adhesive on said stock, directed counter to the travel of said stock, removing adhesive from adhesive over a pre- 0 determined thickness present by reason of ridge and valley deviations from a planar surface of stock and by 'thinness of said stock, and adding adhesive to adhesive under a predetermined thickness present by reason of ridge and valley deviations from a planar surface of stock and by thickness of said stock; and tubular scraper members mounted for reciprocating travel on said tubular member and in scraping-cleaning position relative to the external surface thereof.
2. The combination of claim 1, wherein said scraper means are provided with a groove disposing in noncontacting relation with said tubular member and which groove registers with the spaced apart longitudinally alined openings in the tubular member avoiding scraping the area in which said openings are located and which groove functions to deflect air in said longitudinal direction.
3. The combination of claim 1, wherein a solventdiluent cleaning liquid dispenser delivers cleaning liquid to said tubular scraper means.
4. The combination of claim 3, wherein said cleaning liquid dispenser intermittently delivers cleaning fluid to said tubular scraping means.
References Cited UNITED STATES PATENTS ALFRED L. LEAVI'IT, Primary Examiner C. R. WILSON, Assistant Examiner US. Cl. X.R.