US3666592A - Method for automatically laying up plywood panels - Google Patents

Abstract

A METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS, PARTICULARLY THREE PLY, IS DESCRIBED IN WHICH THE FRONT AND BACK VENEER SHEETS ARE FED CROSSWISE TO RESPECTIVE PARALLEL VACUUM DRUM ASSEMBLIES THAT ARE ROTATED IN OPPOSITE DIRECTIONS. THE DRUMS BEND THE SHEETS ABOUT THE PERIPHERIES THEREOF AND MOVE THE SHEETS IN A 180* PATH TO CONVERGE BETWEEN THE DRUM ASSEMBLIES. A CORE SHEET IS FED BETWEEN THE DRUM ASSEMBLIES TO INTERPOSE BETWEEN THE FRONT AND

BACK SHEETS. THE FRONT, CORE AND BACK SHEETS ARE FED IN A TIMED RELATION TO ALIGN THE LEADING EDGES OF THE SHEETS AS THEY CONVERGE.

Description

May 30, 1972 H. A. KELLER EI'AL METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS 4 Sheets-Sheet 1 Filed April 9, 1969 IN VIENTORS. HHPOLD fl- KELLER Pl? TRICK J: YOUNG y 30, 1972 H. A. KELLER ErAL 3,666,592

METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS Filed April 9, 1969 4 Sheets-Sheet 2 HRROLD I). KELLER PflTR/CKJI YOUNG BY ww-P flrrys.

I NVE NTOR.

y 30, 1972 .H. A. KELLER ET AL METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS -?iled April 9, 1969 4 Sheets-Sheet 3 INVENTORS. HHROLD H. KELLER PfiTR/CK .71 YOUNG wdh lbw flTTys.

y 30, 1972 H. A. KELLER ETAL 3,666,592

METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS Filed April 9, 1969 4 Sheets-Sheet 4 43 4 INVENTORS.

HHROLD R. KELLER um k-W- flrrys.

United States Patent O 3,666,592 METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS Harold A. Keller and Patrick J. Young, Lewiston, Idaho, assignors to Potlatch Forests, Inc., Lewiston, Idaho Filed Apr. 9, 1969, Ser. No. 814,581 Int. Cl. B27d 1/04 US. Cl. 156-285 4 Claims ABSTRACT OF THE DISCLOSURE A method for automatically laying up plywood panels, particularly three ply, is described in which the front and back veneer sheets are fed crosswise to respective parallel vacuum drum assemblies that are rotated in opposite directions. The drums bend the sheets about the peripheries thereof and move the sheets in a 180 path to converge between the drum assemblies. A core sheet is fed between the drum assemblies to interpose between the front and back sheets. The front, core and back sheets are fed in a timed relation to align the leading edges of the sheets as they converge.

BACKGROUND OF THE INVENTION This invention relates to methods for manufacturing plywood panels and more particularly to methods for automatically laying up plywood panels from face veneer and core sheets.

Plywood is generally defined as wood panels made up of an odd number of veneer sheets glued together in which the grain of each sheet is perpendicular to the adjacent sheets. The most common size of plywood panels is 4 x 8 feet. Most frequently the grain of the outside veneer sheets generally referred to as the face veneers (front and back), runs lengthwise with the grain of the interior sheets, collectively referred to as the core, running alternating grain directions. The sheets of the core that run am'dthwise are generally referred to as the cross band sheets. The cross band sheets are frequently made up of a plurality of small pieces four feet in length that are positioned in side by side relation until a full sheet is constructed. If the cross band sheets are to be handled, the small pieces are frequently held together by string, tape or edge gluing.

Even with the availability of the most modern technology and machineries known to the plywood industry, most of the plywood panels, are still being assembled or layed up manually. The cost of the manual layup step represents a substantial portion of the final cost of the product. It is diflicult to maintain uniform results with the manuallayup process. Wood material and glue losses from rejection are not insignificant.

Although many attempts have been made in the plywood industry to develop efiicient and reliable methods and equipment for automatically laying up plywood panels, noneseem to have been commercially successful.

One reason for the difiiculty lies in the nature of plywood veneers. Plywood veneers are quite thin and delicate requiring equipment that is capable of efficiently and rapidly handling veneers without subjecting the veneers to damage. In one .direction the veneer sheets are flexible and in theother direction the sheets are quite stiff. It is difiicult to rapidly and consistently align the edges of the wood veneers during the layup process because of the thinness and size of the plywood veneers. Misalignment results in an inferior product with material losses.

One of the principal objects of this invention is to provide a method for automatically laying up plywood panels which is reliable, efficient and inexpensive.

An additional object of this invention is to provide 3,666,592 Patented May 30, 1972 automatic layup method requiring apparatus that requires a minimum of manufacturing floor space and which is inexpensive to manufacture, simple to operate, and reliable and efficient in performance.

A further object of this invention is to utilize the directional strength properties of the veneer sheets to minimize the space requirements of the automatic layup equipment.

An additional object of this invention is to provide a method that can be performed by compact automatic layup equipment that is capable of accurately laying up the plywood veneer with a minimum of waste material.

An additional object of this invention is to provide automatic layup method carried out by moving the face sheets crosswise in one direction and the core sheet crosswise in an opposite direction between the face sheets and then bending the face sheets into curved converging paths to place the face sheets on the core sheet with the leading I BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings, in which:

'FIG. 1 is a side elevational view of an apparatus for sequentially laying up plywood panels embodying the principle features of this invention;

FIG. 2 is a plan view of the automatic layup equipment;

FIG. 3 is a fragmentary enlarged side view of a portion of the layup equipment emphasizing the drive system;

FIG. 4 is a vertical cross sectional view taken along line 44 in FIG. 2 showing the initial portion of the layup sequence with the face veneer sheets moving in an opposite direction to the core sheet; and

FIG. 5 is a vertical cross sectional view similar to FIG. 4 except showing the convergence of the face and core sheets to form a plywood panel.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now in detail to the drawings, there is shown in FIG. 1 an automatic layup apparatus generally designated by the arrow 10. The apparatus 10 forms plywood panels from face sheets and core sheets. The face sheets are placed on both sides of the core sheet with glue therebetween to adhere the sheets together. For purpose of this description one face sheet will be referred to as the front veneer sheet FS and the other will be referred to as the back veneer sheet BS. The grain of the face sheets runs parallel with the length. The core sheet CS may be a single cross band veneer sheet or may be an uneven number of sheets with the outer sheets having their grains running crosswise.

The automatic layup apparatus includes a core feeding section 11, a face sheet feeding section 12 and a layup section 13 all mounted on a general framework 9. The front and back veneer sheets are fed in a substantially horizontal direction indicated by the arrow 14 in vertically spaced substantially horizontal planes 15 and '16 respectively. The horizontal planes 15 and 16 are sufficiently spaced to permit the face sheets to be flexed and moved in tangential curved paths of approximately to an intermediate horizontal plane .18 that is equidistant between horizontal planes 15 and 16. The core sheets are fed along the intermediate substantially horizontal plane in a horizontal direction 17 that is opposite to the direction 14.

At the layup section 13, the face sheets are moved in a curved path designated by the arrows 19 and 20 to converge in the horizontal plane 18. The layup section 13 includes horizontal upper drum assembly 22 having a plurality of transversely spaced vacuum wheels 23 (FIGS. 2, 4 and '5) mounted on a common axle cylinder 23a that rotates about a horizontal axis 24 which is perpendicular to the horizontal directions .14 and 17. The peripheries of the wheels 23 are approximately tangent to the horizontal planes 15 and 18.

The vacuum section further includes a lower drum assembly 25 having a plurality of spaced vacuum wheels 26 that are mounted on a common axle cylinder 26a that rotates about a horizontal axis 2 7. The axis 27 is vertically aligned and parallel with the axis 24. The peripheries of the wheels 26 are substantially tangent to the planes 16 and .18.

Each of the vacuum wheels 23 and 26 have apertures 28 therein for communicating vacuum pressure from the axle cylinders 23a and 26a to the Wheel peripheries. A common vacuum duct 31 (FIG. 2) is mounted on the framework 9 in communication with the axle cylinders 23a and 26a to provide a source of vacuum pressure for the vacuum wheels.

The veneer sheet feeding section 12 includes a front veneer sheet feeding means 32 that is elevated vertically above a back veneer sheet feeding means 33 (FIGS. 1, 4 and The sheet feeding means 32 feeds front veneer sheets FS crosswise to the drum assembly 22 with the grain of the sheets parallel with the drum axis 24. The sheets are fed tangentially to the wheels in such a manner that positive control is maintained on the sheets to assure precise alignment.

The front veneer sheet feeding means 32 includes a horizontal crowder conveyor 34 comprising a plurality of transversely spaced elongated continuous friction belts 35. The front ends of the belts extend into the spaces between the vacuum wheels 23 to frictionally bias the sheets forward until the sheets are on the vacuum Wheels 23. The upper flight of the crowder belts support the sheets in the horizontal plane 15. The front veneer sheet feeding means 32 further includes an alignment conveyor 37 parallel with an in between the crowder belts 35. The alignment conveyor 37 has two endless chains 38 that are driven through a common drive shaft 40 (FIGS. 4 and 5). The chains 38 have lugs 41 mounted thereon at evenly spaced intervals with the lugs of each chain transversely aligned with lugs of the other chain to align the leading edge of the sheets on the crowder conveyor parallel with the axes 24 and 26 of the vacuum drum assemblies.

The crowder conveyor 34 moves at a faster rate than the lugs 41 to push the individual sheets crosswise up against the lugs 41 to align the leading edge so that the sheets are moved onto the vacuum wheels 23 with the grain of the sheets parallel with the axes of the drum assemblies.

The back veneer sheet feeding means 33 has a similar conveyor arrangement having a crowder conveyor 42 with an alignment conveyor 43 in between the individual belts of the crowder conveyor for aligning the leading back veneer sheets parallel with the axis of the Wheels 26. The lower alignment conveyor 43 has endless chains 44 mounted between the alignment conveyor elements with a plurality of lugs 45 mounted thereon at evenly spaced intervals with each lug transversely aligned with a lug of the other chain for aligning the leading edge of the veneer sheets. The endless chains 44 are driven by a common drive shaft 46.

Longitudinal bar guides 50 are mounted on the framework in a substantially horizontal relationship spaced immediately above the horizontal planes 15 and 16 for preventing the veneer sheets from rippling or buckling while the sheets are being conveyed to the layup section.

A transverse alignment device (FIG. 2) is mounted alongside each of the crowder conveyors 34 and 42 for transversely centering the sheets on the belts. Each of the transverse alignment means includes an upright continuous belt 53 that is mounted at an angle to center the sheets on the conveyors.

The core feeding section :11 includes a vacuum pickup apparatus 54 that is mounted over a core stack roll case 55. A stack of core sheets is moved into position on the roll case so that the major dimension of the core sheets is perpendicular to the direction 17 and the grain of the core sheets is paralled with the direction 17. The core vacuum pickup apparatus includes elongated vacuum head 56 that includes a vacuum source for holding the veneer sheets to the bottom of the vacuum hood. An actuator 57 is mounted on the framework 9 for moving one end of the vacuum head down to grasp the top sheet of a stack and then up to remove the sheet from the stack. The vacuum hood 56 has a vacuum duct 58 that interconnects the hood with the vacuum source. A plurality of elongated horizontal rollers 59 (FIGS. 4 and 5] driven by synchronous motor 59a, are mounted along the bottom of the vacuum hood perpendicular to the horizontal direction .17 for moving the core sheets crosswise along the bottom of the vacuum hood 56. The rollers 59 move the core sheet parallel with direction 17 and into an elongated horizontal stop 60 (FIGS. 4 and 5). The stop 60 is mounted perpendicular to the horizontal direction 17 for aligning the leading edge of the core sheets. The elongated stop 60 includes an elongated flange that extends outwardly from a roll 61. To release the stop the roll 61 is rotated to move the stop out of the path of the sheets and to permit the sheet to move to a drive roller 62 (FIGS. 4 and 5). A nip roller 63 is used in conjunction with the drive roller to bias the sheet against the drive roller to transmit the rotation of the drive roller to the sheets. The drive roller 62 is driven by aksynchronous motor 64 that is mounted on the framewor From the drive roller 62 core sheets are fed forward through an adhesive applicator or glue spreader 66. The glue spreader 66 includes upper glue rolls 67 and lower glue rolls 68 for applying adhesive or glue to both sides of the core sheet prior to applying the front and back face veneers to the core sheet at a layup section 13. The rolls 67 and 68 are driven by a synchronous motor 69 (FIG. 2) The glue spreader 66 is mounted on a movable frame 70 (FIG. 1) that moves transversely on tracks 71 for enabling the glue applicator to be readily and conveniently cleaned. The movable frame 70 has a motor 72 for moving the frame transversely back and forth from the operating position to a cleaning position.

A series of discs on an elongated shaft 74 (FIGS. 4 and 5) are mounted between the glue spreader and drum assemblies with the shaft axis parallel to the drum assembly shaft and the top peripheries of the discs approximately tangent to the plane 18. This arrangement supports the core between the spreader rolls and drum assemblies without unduly disturbing the coating of glue. The discs are driven at the same peripheral speed as the drum assemblies.

Th e drive means for operating the front veneer sheet feeding means 32, the back veneer sheet feeding means 33 and the core stop 60 is synchronized together through a common drive 75 (FIGS. 1, 2 and 3) so that the sheets converge between the vacuum wheels in the intermediate plane 18 with the leading edge of each of the sheets vertically aligned to provide the resultant plywood panel with a flush side edge. The common drive 75 is driven from a motor 76 (FIG. 3) that is mounted on the framework. The motor drives a belt 77 that is connected to a pulley 78 mounted on a horizontal main drive shaft 80. The belt 77 also drives a pulley 81 that is connected to a reduction box 82 for driving the disc roller 74. A universal coupling 83 interconnects the main drive shaft with a shaft 84 which extends to an intermittent drive box 85v for sequentially operating the core stop 60 at precise intervals and in coordination with the position and movement of the lugs 41 and 45.

A universal coupling 87 interconnects the other end of the main drive shaft 80 with a T gear box 88. A drive shaft 90 extends upward from one side of the gear box 88 and a drive shaft 81 extends downward from the other side. The drive shaft 90 extends to a reduction gear box 92 that in turn drives a sprocket 93. A chain 94 extends from the sprocket 93 to a sprocket 95 for rotating the upper drum assembly '22. The drive shaft 90 also operates a reduction gear 96 that is connected to the drive shaft 40 of the upper alignment conveyor 37.

The drive shaft 91 extends to a reduction gear box 101 having an output sprocket 102 for driving a chain -3. The chain 103 drives a sprocket 104 operatively connected to the axle 2612 of the lower drum assembly. The drive shaft 91 also operates a reduction gear box 106 that is operatively connected to the common drive shaft 46 for moving the alignment conveyor 43.

The relative position of the veneers may be adjusted by adjusting the drive shafts to the gear boxes.

The automatic layup apparatus also includes an outfeed means 111 for receiving the formed plywood panels from the layup section and conveying the panels in the horizontal plane 18 from the automatic layup apparatus. The outfeed means includes a plurality of continuous belts 112 that are positioned between the vacuum wheels 26 with the upper flights of the belts extending along the plane 18 tangentially from the peripheries of vacuum wheels 26. The outfeed means include belt tracks 1114 for supporting the upper fiight of the belt conveyors 112. The belts 112 also serve the purpose of stripping the back veneer sheets from the vacuum wheels 26 in the horizontal plane 18.

Stripping members 116 are mounted on the framework in the spaces 28 between the vacuum wheels 23 of the upper drum assembly and adjacent the intermediate horizontal plane 18 for stripping the front veneer sheets from the vacuum drum as the sheets converge in the intermediate horizontal plane 18.

The upper drum assembly 22 is supported on a pivotal frame 118 (FIGS. 1 and 2) mounted on the framework 9. Actuators 120 (FIGS. 1 and 2) are mounted on the frame 110 with connecting arms extending downward to the pivotal frame 118 for partially supporting the upper drum assembly 22 to reduce the pressure on the resultant plywood sheet between the drum assemblies. The position of the actuator 120 may be adjusted by adjustment bolts 121 to increase or decrease the space between the vacuum wheels 23 and 26. Motion equalizing device 123 is operatively connected to the connecting arms 122 to equalize the vertical movement at both ends of the drum assembly. The motion equalizing device include a tongue bar 124 rotatably mounted on the frame parallel with the drum axes. Radius arms 125 extend from the ends of the tongue bar 124 to the connecting arms 122.

It should be particularly noted that the automatic layup apparatus requires a minimum of floor space with the veneer face sheets and the core sheets under positive control during the entire feeding and layup process. The front veneer sheet feeding means and the back veneer sheet feeding means extend between the vacuum wheels so that the positive control of the veneer sheets is maintained while the sheets are being transferred to the vacuum drum assemblies. The synchronous drive system through the common drive 75 assures that the leading edge of each of the sheets will be aligned as the sheets converge between the drum assemblies.

What is claimed is:

1. In a method for laying up plywood panels having first and second face veneer sheets, and an interposed core sheet, the steps comprising:

engaging the leading edge of each first face veneer sheet in a successive row of sheets While moving the first face veneer sheets in a direction perpendicular to their wood grain along a first path containing the sheets, the spacing of the engaged leading edges of the successive first face veneer sheets being greater than their sheet dimension perpendicular to the grain;

engaging the leading edge of each second face veneer sheet in a successive row of sheets while moving the second face veneer sheets in a direction perpendicular to their wood grain along a second path spaced from and underlying the first path, the direction of movement and spacing of the leading edges of the second face veneer sheets being common to that of the first face veneer sheets; releasably engaging the leading edges of individual core sheets along a path containing the core sheets and equally spaced between the first and second paths;

subsequently moving the individual core sheets along the third path in a direction opposite to the direction of movement of the first and second face veneer sheets along the first and second paths following release of the leading edges of the core veneer sheets;

grasping the individual first and second face veneer sheets while their leading edges are engaged along the first and second paths and subsequently releasing each sheet from such engagement and imparting movement to the grasped sheets along converging curved paths respectively tangential to the first and third paths and to the second and third paths while reversing the direction of movement of the sheets;

and synchronously controlling the movement of the grasped leading edges of the first and second face veneer sheets, the movement of the grasped sheets along the curved paths and the release and movement of the core sheets along the third path to bring individual first and second face veneer sheets into converging abutting engagement with a core sheet along the third path with the leading edges of the abutting sheets in a common plane perpendicular to the third path; and

applying adhesive material to the sheets along one or more of the respective surfaces thereof brought into abutting engagement with one another.

2. A method as defined in claim 1 wherein the adhesive material is applied to both sides of the core sheets prior to interposing the core sheets between the front and back veneer sheets.

3. The method as defined in claim 1 wherein the front and back venoor sheets are moved from the first and second horizontal planes to the mid-horizontal planes by synchronized vacuum wheels that are positioned tangentially between the first and second horizontal planes and the mid-horizontal plane.

4. The method as defined in claim 3 wherein the front and back veneer sheets are stripped from the vacuum wheels at the mid-horizontal plane.

References Cited UNITED STATES PATENTS 1,714,858 5/1929 Elmendorf 156-313- 2,318,215 5/1943 Gans 156303 3,384,137 5/1968 Ash 156-313 3,438,830 4/ 1969 Harmsworth 156578 3,455,770 7/1969 Dahl, Jr 156-303 3,508,993 4/1970 Belcher et al. 156--285 3,133,850 5/1964 Alenius 156-458 3,415,707 12/1968 Barnes 156-559 CARL D. QUARFORTH, Primary Examiner E. E. IJEHMANN, Assistant Examiner US. Cl. X.R.

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