US3726747A

US3726747A - Continuous-feed high-frequency gluing press

Info

Publication number: US3726747A
Application number: US00040163A
Authority: US
Inventors: P Zottu
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-05-25
Filing date: 1970-05-25
Publication date: 1973-04-10
Anticipated expiration: 1990-04-10

Abstract

A press continuously bonds strips edge-coated with glue in edge-to-edge relation with one other or with a structural panel to form a composite sheet of indefinite length. The press feeds the sheet, under compression applied in a feeding direction transverse to the strips, between planar electrode platens through which a high-frequency alternating current is applied to the sheet to thermo-set the glue. Pressure is also applied against the major surfaces of the sheet to prevent buckling of the strips as the glue is set.

Description

pll 10, 1,973 P. D. zo'rTu 3,726,747

CONTINUOUS-FEED HIGH FREQUENCY CLUING PRESS April l0, 1973 P, D. zoT-ru CONTINUOUSFEED HIGH FREQUENCY CLUING PRESS Filed May 25, 1970 7 Sheets-Sheet 2 Ami rwm-T-r- I P. D. zoTTU 3,726,747

CONTINUOUS-FEED HIGH FREQUENCY CLUING PRESS 7 Sheets-Sheet 5 April 1o, 1973 Filed may 25, 1970 April 10, 1973 E. D. zoTTu 3,726,747

CONT1NUOUS"FEED HIGH FREQUENCY C'LIUING PRESS Filed May 25, 1970 7 Sheets-Shea?I 4 April 10, 1973 P. D. zoTTu 3,726,747

CONTINUOUS-FEED HIGH FREQUENCY CLUING PRESS Filed May 25, 1970 '7 Sheets-Sheet 5 P. D. ZOTTU Aprn 1o, 1973 CONTINUOUS-FEED HIGH FREQUENCY CLUING PRESS '7 Sheets-Sheet 6 Filed May 25, 1970 'Vivir' Izwezz'ozd.- Pazzi L. Zoff/zb,

Hwa-megs April 10, 1973 P. D. zoTTu 3,726,747

CONTINUOUS-FEED HIGH FREQUENCY CLUING PRESS Filed lMany 25, 1970 7 Sheets-Sheet 7 @Lm/Q35 Klaag# +657@ Rf @R5 607% Q ILE- aaa l/ 330 E -asa-a aso 23a /J gta-ggg...

2&8 Iwezow:

.Paul L. Zoi'lb, y M mw dbneys United States Patent 3,726,747 CONTINUOUS-FEED HIGH-FREQUENCY GLUING PRESS Paul D. Zottu, Needham, Mass. Industron Corporation, 1 Hillside Park, Needham Heights, Mass. 02194) Filed May Z5, 1970, Ser. No. 40,163 Int. Cl. B32b 31/12, 31/20 U.S. Cl. 156-580 23 Claims ABSTRACT F THE DISCLOSURE BACKGROUND OF THE INVENTION It is a conventional practice to glue narrow strips of wood in edge-to-edge relation to form composite sheets of indefinite length and of large surface area. The composite sheet is cut to any desired lengths after the glue has been cured. These sheets can be veneered or otherwise surfaced to form solid-core panels, doors, furniture tops, and the like. Another practice is to glue strips of wood along the edges of a sheet of particle-board or chip-board, which can then be veneered or otherwise surfaced. Either method of bonding produces a panel which has the appearance and other characteristics of a single, solid piece of the surfacing material, but results in substantial cost savings because inexpensive particle-board or Wood strips of low grade can be used to form the composite core sheet. The strips must have a uniformly similar quadrilateral cross-section to fit together properly; but they can be tapered from end to end of the top and botom surfaces, and laid with the wider ends of alternating strips at opposite edges of the sheet, to form a rectangular sheet with parallel edges. Strips of this nature can be cut from low-grade inexpensive lumber. Furthermore, panels made of such strips stay flatter and do not warp as much with use as wide natural boards.

The conventional press used for curing the glue between the strips employs steam-heated platens, which must be of great length to provide any assurance of heating the glue hot enough, at a satisfactory feed rate, to set the glue securely, Platens about 20 feet long, and heated to about 350 F., serve to cure the glue to a depth of only about Ms inch from the opposite major surfaces of the sheet. It is frequently necessary t0 pre-heat the sheet to secure even this partial degree of curing. The results are not uniformly satisfactory, since the partially-cured seams sometimes pop apart when cooled. Furthermore, the high temperature required tends to dry and shrink the wood strips. This is especially troublesome when the feeding is stopped, as it must be from time to time when the manual layingup of the strips is interrupted. Because of shrinkage, the strips must be subjected to high pressure to hold the glued edges in rm contact over the length of the press, and thus insure a good bond. Another short-coming of a steam-heated press is that the time required for curing necessitates a rather slow rate of feed through the heated platens, even though they are very long; production rates are therefore rather slow. A further disadvantage is the extremely slow feed rate needed for processing thick strips of hard-textured wood.

ICC

It has been proposed to use high-frequency electric current to set the glue. However, efforts to bring this method into commercial application have not met with substantial success, so far as l am aware. A press offered for the purpose was designed to operate with wood strips laid parallel to the length dimension of the composite sheet. This necessitated the application of pressure across the width of the sheet to hold the glued edges firmly together as the glue was cured. Consequently, it was necessary to control the width of the sheet very closely. This does not permit rapid laying-up and lamination of strips which not only vary in width from one another, but which are also commonly tapered from end to end, being cut from low-grade lumber. Furthermore, the method does not permit continuous manufacture of a sheet which can be cut to desired panel sizes without waste.

BRIEF DESCRIPTION OF THE INVENTION It is the primary object of this invention to provide means to increase the rate of production and to improve the quality of inexpensive composite sheets made of narrow strips. It is a specific object to provide an improved gluing press for the continuous production of composite sheets comprising edge-glued strips. It is another object to attain uniform curing of the glue in such sheets, while providing an increased rate of production. It is a further object to provide an improved press for these purposes which is more compact than those hitherto available, requiring a smaller amount of factory floor space. It is still another object to provide an improved gluing press which requires less care and precision in laying up the strips, and is therefore less subject to production-rate limitations irnposed by manual capabilities. Further objects and advantages of the invention will appear as the following description proceeds.

Briefly stated, according to a preferred embodiment of the invention, I provide a press for curing glued strips laid in side edge-contacting relation to one another or to a structural panel, to form a composite sheet. The press includes means for feeding the sheet under pressure in a direction transverse to the side edges of the strips, that is, lengthwise of the sheet, to hold the glued side edges firmly together as the glue is cured. Curing is achieved by passing the composite sheet between planar electrode platens,

which pass a high-freqeuncy alternating electrical current through the sheet and the glue to heat and thus set the glue.

lIn a preferred embodiment, the sheet is fed by driven rolls through the platens, and thence through drag shoes which yieldably resist the feeding motion and therefore apply pressure between the glued side edges of the strips. At least one set of the opposed driven rolls are movable normal to the major surfaces of the composite sheet, and are resiliently biased against it, to obtain an effective grip for feeding it forwardly in a positive manner. The resulting application of pressure against the sheet also prevents the strips from buckling out of the planes of the sheet. To the same end, at least one of the electrode platens is mounted for movement normal to the sheet, and is resiliently biased against it. The drag shoes have planar surfaces which apply frictional resistance to the feeding of the sheet, being pressed by resilient means against its major surfaces.

According to a feature of the invention, the movable driven rolls, the movable platen, and the drag shoes are biased against the composite sheet by air bags or other expansible-chamber devices, which allow strips of varying thickness to pass, but maintain desired adjustable pressure against the sheet at all times. The air bags are opposed by return springs so that a release of air pressure immediately withdraws the selected rolls, platen and/or drag shoes from the composite sheet. This allows prompt c0r 3 rection of any jamming, strip-splitting, or other operating diiculty.

According to another feature, a plurality of driven feed rolls are arranged in a row across the press, and are independently movable normal to the sheet, each by its own air bag and air supply pressure regulator. By appropriate adjustment of the relative pressures acting on the several rolls, any tendency of the composite sheet to deviate from a correct path through the press can be corrected; that is, the sheet can be steered through the press. For a similar reason, a plurality of drag shoes may be arranged across the sheet, each independently movable by its own air bag and pressure regulator. These arrangements also facilitate operation of the press to form simultaneously a group of relatively narrow composite sheets, arranged side-by-side across the press.

I have found that the electrode platens may have a relatively short length in the direction of sheet movement, even though relatively high feed rates are obtained, because the use of high-frequency current cures the glue very rapidly. The initially-wet glue is highly conductive, and this allows rapid initial heating and curing. Typically, I have found it satisfactory to use platens four feet in length, with a 20 kw. high-frequency generator to obtain complete glue line curing, as compared with a length of 2O feet of steam-heated platens operating at 300 to 350 F. and curing only to depth of 1/s inch from the surfaces. The feed rate is effectively limited only by the manual capacity of workers who lay up the strips to form the composite sheet; and rates ranging from 6 to 18 feet per minute are attained in practice.

DESCRIPTION OF PREFERRED EMBODIMENTS SHOWN IN THE DRAWINGS While the specification concludes with claims particularly pointing out the subject matter which I regard as my invention, it is believed that a clearer understanding may be gained from the following detailed description of preferred embodiments thereof, referring to the accompanying drawings, in which:

FIG. 1 is a sectional view in side elevation of a preferred form of the improved press;

FIG. 2 is a schematic plan View showing the general arrangement of the press and related equipment;

FIG. 3 is a fragmentary plan view of the press, partially in section;

FIG. 4 is a fragmentary view in side elevation of a drive train for feed rolls;

FIG. 5 is a sectional view of feed roll arrangements, taken along line 5-5 in FIG. 1, looking in the direction of the arrows;

FIG. 6 is a fragmentary view in end elevation, showing the exit end of the press;

FIG. 7 is a diagrammatic view of pressure control arrangements for biasing feed rolls and drag shoe elements of the press;

FIG. 8 is a plan view illustrating one form of composite sheet which can be glued by the press, after one stage of lamination; and

FIG. 9 is a plan view of the sheet of FIG. 8, after the second stage of lamination.

Referring to FIGS. 1 6, a preferred construction of the improved continuous-feed high-frequency gluing press is organized about a framework comprising

base members

10, 20,

transverse beams

12, 14, 15, 18, 22, 24, 26, and 30 longitudinal beams 16 and frames 28 and 120 and upright leftand right-

side plates

13 and 17.

Associated with the press, as shown in FIGS. l and 2, is an in-feed conveyor 9, having conveyor chains 32 trained about

drive shafts

31, 33, to feed strips 34 of wood or other material into the press. These strips are brought to an operators station at the conveyor 9 by means of a transverse conveyor generally indicated at 36, which applies a layer of liquid thermosettable glue to one of the side edges 35 of each strip 34. The conveyors 9 and 36 are of a conventional nature forming no part of the present invention, and no further detailed description thereof is believed necessary.

The operator manually removes the strips 34 from the conveyor 9, and places them in side edge-to-side edge contacting relation on the plane surface provided by the infeed conveyor 9. As shown, the strips ordinarily used have rectangular cross-sections, but some may be tapered from end to end, so that their upper and lower surfaces 38 and 40, respectively, are non-rectangular quadrilateral surfaces. Strips of this shape are often cut for maximum utilization of the lumber. By laying up these strips with their wider ends alternating at the left and right, the operator can form a composite sheet 42 which has essentially straight edges. The upper and lower surfaces 38 and 40 of the strips form planar major surfaces of the composite sheet. Subsequent to curing of the glue in the press conproper, the sheet issues on to a delivery conveyor 184 (FIG. 2), and desired lengths are cut off by a flying saw 180, which traverses the sheet on a beam 182. The arrangements of the saw and delivery conveyor are conventional, and as they form no part of the present invention, no further detailed description thereof is believed necesary.

A series of weighted idler rolls 44 are supported by a transverse rod 48 in axially-spaced relation across the width of the press, each roll being mounted for independent pivotal motion by a pair of arms 46. These rolls apply pressure to the sheet 42 normal to its major surfaces, and thus help to provide a continuous ribbon of strips to the main feed rollers 2 and 4.

Passing from the conveyor 9, the sheet is supported by a flat upper surface of the transverse beam 15, as it passes toward opposed driven feed rolls 72 and 74. These rolls have grooved surfaces to secure a firm engagement with the sheet 42. In the construction shown, four upper rolls 72 are spaced across the width of the press, in opposition to two coaxial lower rolls 74, each of the latter being approximately twice the length of the former. The axles 114 of the lower rolls 74 are rotationally supported on fixed axes by bearings and 192 (FIG. 5), respectively mounted in the frames 17 and 13- and in a pedestal 194 at the centerline of the press:

The axles 106 of the upper rolls 72 are normally coaxial, but are independently movable with a component of direction normal to the sheet 42, each being rotatably supported yby bearings 73 in one of a group of swinging frames 50. 'Ihese frames comprise transverse channels 54, 60, and 70, joining end plates 51 which carry the bearings 73. Each frame 50 is mounted for independent pivotal motion about a transverse shaft 52 by a pair of self-aligning bearing journals 53. Each of the frames is biased upwardly by a pair of compression springs 64, received on rods 62 which are secured to the transverse channels 60, and compressed between the stationary beam 12 and nuts 66 secured to the upper ends of the rods. Each of the rolls 72 can be pressed downwardly against the sheet 42 by means of one of a series of associated air bags 68 interposed between the beam 12 and the channel 70` attached to the corresponding swinging frame 50. Means for supplying and controlling air pressure to the air bags will be described hereinafter. The pressure supplied should be sufficient to securely grip the sheet 42 against the lower rolls 74 by friction or groove indentation so that positive forward feeding is obtained. A release of pressure from the air bags 68 allows the compressed springs to raise the frames 50 and rolls 72 immediately from the sheet 42, so that access to the sheet is readily available if any operational dini culty occurs.

The pressure between the

rolls

72 and 74 serves not only to insure a positive forward feed, but also helps to prevent any tendency of the strips 34 to buckle upwardly from the sheet under the compression which is applied between the strips in the plane of the sheet. .As afurther means of preventing any buckling, guide plates 56 and 58 extend extend transversely of each swinging frame 50 to the end plates 51, and provide planar guide surfaces that extend substantially tangentially the surfaces of the rolls 72 at the lines of contact of these rolls with the sheet 42.

To drive the

rolls

72 and 74, a drive train best shown in FIGS. 3 and 4 connects these rolls with a motor 76. A belt l82 connects a motor-driven sheave 81 with the sheave 84 and input shaft 83 of a conventional shaft mounted speed-reducer 86, whose drive speed may be varied by means of a hand-crank 78 mounted on the motor base 80. The shaft-mounted speed-reducer 86, which is located near the center-line of the press, has its output shaft 88 extending through the

frame members

13 and 17, each being connected by identical chain drives to drive two of the four rolls 72 and one of the two rolls 74; only one of the chain drives is illustrated.

A pair of identical sprockets 90 is mounted on each end of the shaft 88, one of each pair to drive a chain 94 and a sprocket 98 which is mounted on one of the pivot shafts v52, the other of each pair to drive a chain 92 and a sprocket 112 mounted on the shaft 114 of one of the lower rolls 74. Since the

rolls

72 and 74 must be driven in opposite rotational directions, as shown by the arrows in FIG. 4, in order to drive the sheet 42 in a common linear direction, the chain 92 is not wrapped around the sprocket 112, but is trained over idler sprockets 108 and `110 to reverse the rotation of the sprocket 112, being arranged to engage a sufficiently large arc of the sprocket 112 to ensure that an ample number of teeth engage the chain.

Each pivot shaft 52 carries a pair of sprockets 100, to drive the shafts 106 of the two associated upper rolls 72 by means of chains 102 and sprockets 104. Thus the several rolls 72 and frames 50 are free to rock independently about the pivot shaft 52 without interfering with the roll drive trains.

As best shown in FIG. 5, the upper rolls 72 are fabricated as hollow cylindrical shells, having supporting discs 198 welded to the interior surfaces of these shells and to the shafts 106. Similarly, the lower rolls 74 are formed as cylindrical shells, connected to their shafts -114 by welded discs 205.

It is preferred to heat the lower rolls with steam, in order to keep them free of glue accumulation, and those discs 205 which fall in the central parts of these rolls are provided with ports 207 to allow for a circulating flow of steam and condensed water. Steam is introduced through a stationary pipe 200 extending coaxially into the hollow shaft 114 of each roll 74, and through a sealing collar 202. A plug 196 closes the inboard end of the shaft. The steam is admitted to the interior of the roll 74 through a radial tube 204 threaded into the shaft. Condensed water is drained from the outboard end of the roll by a pair of radial tubes 209 threaded into the shaft at 18.0 intervals, and each having a gravity-actuated check valve comprising a ball 208 received in an open cage 206. When either of the tubes 209 is in an upright position, its ball 208 closes the valve to prevent the escape of steam; but as the tube turns to an inverted position, water accumulated in the bottom of the roll is forced out by steam pressure through the hollow axle 114. A conventional rotating water seal (not shown) can be mounted on the outboard end of the rotating shaft to permit draining the water Without leakage.

As the composite sheet 42 leaves the feed rolls 72 and 74, it passes between upper and lower planar electrode platens 124 and 122. These platens extend substantially the full width of the press, and have sufficient length to bring about effectively complete curing of the glue joining the strips 34 by dielectric heating. I have found that a length of about 44 to 48 inches is normally ample, as compared with a length of about feet for conventional steam-heated platens.

The platens are respectively connected to the leads 7 and 8 of a conventional high-frequency alternating current generator 6, shown schematically in FIG. 2. In

practice a coaxial output is used with the inner conductor connected to the top insulated electrode or platen 124 and the outer conductor to ground, or the platen 122. The generator is shown at one side of the press, although it may be preferable to mount it on top of the frame to allow free access to both sides of the press so that any jams or other difficulties can be corrected more promptly. I have found that a power output rating of 20 kw. is ample for curing sheets up to two inches in thickness, at a feed rate up to 1r8 feet per minute. The current flows readily through the initially-wet and highly conductive glue, quickly heating it to a curing temperature of about 20G-250 F. The efficiency of the curing process is substantially greater than that of conventional batch press high frequency curing in terms of square inches of glue line cured per kw./hr., and the loss through conductivity of the wood strips detracts little from the overall improvement. Further, the glue is fully cured throughout the thickness of the sheet 42, whereas this is practically never obtained by steam curing even though temperatures as high as 300 to 350 F. are commonly employed and the platens are far longer.

The lower platen I122 is supported rigidly on a heavy frame 120, which is mounted on the longitudinal beams 1=6, It extends forwardly of the upper platen 124 to support the sheet 42 as it departs from the feed rolls 72 and 74.

It is preferred to provide steam heating means (not shown) to elevate the temperature of the lower platen to about 15G-200 F.; this is not intended, and cannot serve to cure the glue in the seams between the strips 34, but only to dry any glue that becomes smeared over the lower platen 122, so that it can be fiaked off. For the same reason, it is preferable to heat the upper platen to about 15G-200 F., although it may be more convenient to use electric strip heaters (not shown) for this purpose.

The upper platen 124 is attached to a rigidly-constructed frame 126 of insulating material such as wood, to the top of which is secured a braced steel frame 128. This assembly is resiliently supported from the longitudinal frame member 28 by means of two groups of laterally-spaced compression springs 1-42 arranged at the front and rear of the platen. The springs 142 are received on rods I secured at their lower ends in the frame 126, and are compressed between the member 28 and nuts 144 attached to the upper ends of the rods.

The platen 124 may be pressed downwardly against the sheet 42 and the platen 122 by means of a pair of symmetrically-spaced air bags 130, which extend substantially across the full width of the press, and act upon the lower surface of the member 28 to force the frames 126 and 1'28 and platen 124- downwardly. Conduit means (not shown) are provided for supplying air under regulated pressure to the bags 130, and these means have shutoff valves so that the pressure can be quickly reduced in the event of an operating diculty. When the pressure is removed, the spring 142 immediately raise the platen 124, and the frames 126 and 128, from the sheet 42, so that correction of any difficulty can be effected promptly. The pressure applied by the platens to the sheet 42 resists any tendency of the strips 34 to buckle before the glue is fully cured.

In the preferred construction, the downward motion of platen 124. is adjustably limited by two groups of laterally-spaced limit-screws I146, arranged symmetrically at the front and rear ends of the platen. As illustrated, only two screws 146 are used in each lateral group, but more may be spaced at intervals across the press if the frames 126 and 128 are flexible and heavy enough to deflect materially in the center. These screws are rotatably supported by bearing collars 156 on the member 28, and have sprockets 150 fixed on their upper ends and interconnected by a chain 152. All of the screws are simultaneously rotatable by a hand-crank 154 to raise or lower stop nuts 14S, which are threaded on the lower ends of the screws and held against rotation by portions of the frame 12S. Downward motion of the platen 124 is halted when the stop nuts 148 engage the plate 128. The platen 124 can be prevented, by proper adjustment of the hand crank 154, from making direct contact with the platen 122 when there is no sheet 42 present to separate them, and this averts the risk of a short-circuit.

As the sheet 42 leaves the platens now fully cured, it is supported by a plate 159 resting on the beam 18.

To apply longitudinal compression to the composite strip 42 during the curing process, that is, compression between the glued side edges 35 of the strips 34, I provide a series of planar drag shoes 166 (see FIGS. 1 and 6) arranged in laterallyspaced relation across the press. Each of these shoes is guided for vertical movement by a pair of parallel plates 164 attached to its front and rear edges, and slidably engaging parallel vertical sides of the beam 22. Pairs of vertical guide strips 168` are attached to the beam 22 to prevent the drag shoes 166 from tilting out of the horizontal plane.

Each of the drag shoes is resiliently biased away from the sheet 42 by a pair of compression springs 160, received on a pair of rods 158 which are welded to the plates 164. The springs are compressed between the stationary channel member 26 and nuts 1'62 threaded on the upper ends of the rods. A series of air bags 170 are spaced across the press, one interposed between each shoe 166 and the lower surface of the transverse beam 22, to force the shoes into frictional engagement With the upper surface of the sheet 42. Means for supplying air to the bags 170 under a regulated pressure will be described below. The shoes 166 serve to apply a frictional drag against the forward feeding of the sheet 42 by the driven rolls 72 and 74, thereby subjecting the sheet to longitudinal compression as it is cured between the platens 122 and 124. The amount of compression can be controlled by adjusting the pressure supplied to the bags and thus the amount of the frictional drag force.

Referring to FIG. 7, adjustable pressure-supply means are illustrated for the air bags 68 associated with the feed rolls 72, and for the air bags 170 associated with the drag shoes 166. A branched conduit 220 is connected to any suitable air pressure supply, and through a series of manually-adjustable pressure regulators 222 to each of the bags 68. Similarly, a branched conduit 224 is connected to the pressure supply, and through a series of manually-adjustable pressure regulators 22'6 to each of the bags 170. The air bags 130 associated with the platen 124 are connected with the pressure source through a similar regulator (not shown), but will not ordinarily require individual pressure adjustment. The purpose of the individual adjustability of the pressure supplied to each bag 68 or 17) is to enable the operator steer the sheet by pressing more heavily at one side or the other, if it tends to Wander from a straight path. This facility also makes it feasible to form a series of relatively narrow sheets simultaneously by feeding them side-by-side through the press, even though these sheets may have dierent thicknesses.

The adjustable regulating valves also enable the operator to shut o the pressure supply quickly in case the strips split or jam in the press; the springs 64, 142, and 161i` then open the press immediately, interrupting the feeding of the sheet and allowing correction to be made without delay.

It should be observed that resilient biasing means, such as the combination of air bags and springs in the preferred construction, are desirable because they allow normal variations in the thickness of the strips to pass through the press without hindrance. Other types of expansible-chamber devices may replace the air bags, and other resilient means may be used instead of the compression springs shown.

Referring now to FIGS. 8 and 9', a composite sheet of a different nature is shown, which is also suited for bonding by the improved press. The central part 228 of this sheet comprises a pre-cut panel of particle-board, chipboard or the like, which forms the core of the finished panel. This panel is first layed up as shown in FIG. 8 with two edge strips 2301 of wood, whose edges abutting the panel are first coated with glue. This assembly is cured by feeding it through the press transverse to the strips 230 with the glue lines at right angles to the direction of feed. The ends are then trimmed square. Pre-glued end strips 232 are then laid against the ends of the panel as shown in FIG. 9, and the panel is run through the press a second time in a direction transverse to the end strips 232. After this two-step laminating process, the panel may be surfaced in a conventional manner with wood veneer or any other desired surfacing material.

What I claim is:

1. A press for gluing strips of material having an approximately uniform dimension between upper and lower surfaces thereof, and having layers of thermosetting glue applied therebetween, to form a composite sheet of indefinite length in which side edges of the strips are glued together or to a structural panel of substantially the same thickness, upper and lower surfaces of the strips form planar major surfaces of the composite sheet, and the side edges of the strips extend transversely to the longitudinal dimension of the composite sheet; said press comprising, in combination:

feeding means constructed and arranged for continuously pushing said strips, laid in side edge-contacting relation, in a direction transverse to the side edges of the strips, thereby continuously to apply pressure between said side edges;

a pair of opposed planar electrode platens extending parallel to said major surfaces and arranged to receive said composite sheet from said feeding means in slidable relation therebetween, said platens eX- tending across the entire lateral dimension of said sheet, and means for applying a high-frequency alternating electrical potential across said platens to establish a uniform high-frequency field through the composite sheet to heat and thermoset the glue;

means for yieldably biasing said platens against the opposite surfaces of said sheet to prevent buckling of said sheet;

and means for yieldably resisting the feeding of said composite sheet and arranged to receive the composite sheet delivering from said platens, to maintain pressure between said side edges of the strips as the glue thereon is set.

2. A press as recited in claim 1, together with means for applying pressure against the composite sheet normal to said major surfaces thereof as the composite sheet is pushed through the press, to prevent buckling of the strips out of the planes of the major surfaces of the composite sheet.

3. A press as recited in claim 2, in which said pressure means comprises eXpansible-chamber means and means for supplying pressure liuid thereto.

4. A press as recited in claim 2, together with means for resiliently opposing said pressure means.

5. A press as recited in claim 2, in which said pressure means comprises at least one weighted roll movably supported for resting against a major surface of said composite sheet.

6. A press as recited in claim 1, in which said feeding means comprises opposed rolls having their peripheral surfaces tangentially engageable with the opposite major surfaces of said composite sheet, and having rotational axes substantially parallel both to the lateral dimension and to the major surfaces of said composite sheet, and means for rotationally driving at least one of said rolls to push the composite sheet.

7. A press as recited in claim 6, said driving means being connected to drive both of said opposed rolls at the same linear surface velocity but in opposite rotational directions so that their peripheral surface portions in contact with the major surfaces of the composite sheet travel in the same linear direction of feed of the composite sheet.

8. A press as recited in claim 6, at least one of said rolls being movable in a direction normal to the major surfaces of said composite sheet, together with means resiliently biasing said movable roll toward the opposed roll to apply pressure against the composite sheet.

9. A press as recited in claim 8, said biasing means comprising expansible-chamber means for urging at least one of said rolls against said composite sheet, means for supplying pressure fluid to said expansible-chamber means and resilient means opposing said expansible-chamber means.

10. A press as recited in claim 6, together with a frame rotationally supporting at least one of said rolls, said frame being pivotally supported about an axis parallel to the rotational axis of said roll supported therein whereby said roll is movable in a direction normal to the major surfaces of the composite sheet; and means resiliently biasing said frame and the roll supported therein toward the composite sheet.

11. A press as recited in claim 6, together with guide plates extending substantially tangentially toward the surface of at least one of said rolls at a line of contact between said one roll and the composite sheet, to prevent buckling of the strips out of the planes of the major surfaces of portions of the composite sheet passing between said opposed rolls.

12. A press as recited in claim 6, there being a plurality of said rolls arranged in two opposed groups, the rolls of each group normally being coaxially aligned in spaced relation, means mounting the rolls of at least one of the groups for independent movement in a direction normal to the major surfaces of the composite sheet, together with means resiliently biasing the group of movable rolls independently of one another against the cornposite sheet.

13. A press as recited in claim 12, said biasing means comprising a group of expansible-chamber means one arranged to bias each of said movable rolls against the composite sheet, together with a group of pressure uid supply means one connected with each of said expansiblechamber means, and pressure regulating means constructed and arranged to provide for independent adjustment of the pressure of fluid delivered to each of said expansible-chamber means.

14. A press as recited in claim 1, at least one of said platens being mounted for movement in a direction normal to the major surfaces of said composite sheet, together with means for resiliently biasing said movable platen toward the opposed platen to apply pressure against the composite sheet.

15. A press as recited in claim 14, said biasing means comprising expansible-chamber means for urging said movable platen toward the opposed said platen, means for supplying pressure uid to said expansible-chamber means, and resilient means opposing said expansiblechamber means.

16. A press as recited in claim 15, said resilient means comprising a group of rods secured symmetrically about said movable platen and extending generally normal to the major surfaces thereof, together with spring means urging said rods and said movable platen in a direction away from the opposed said platen.

17. A press as recited in claim 14, together with ad- 10 justable stop means constructed and arranged to limit the movement of said movable platen toward the said opposed platen under the urging of said biasing means.

18. A press as recited in claim 17, said adjustable stop means comprising a group of threaded rod and nut means symmetrically disposed about said movable platen, extending generally normal to the major surfaces thereof, and connected therewith, whereby the limit of motion of said movable platen may be adjusted by relative rotation of said rod and nut means; together with adjusting means operatively connected with all of said rod and nut means for simultaneous equal adjustment thereof.

19. A press as recited in claim 1, said resisting means comprising: at least one planar drag shoe supported for movement normal to the major surfaces of the composite sheet delivering from said platens, and sheet-supporting means forming a planar surface; said planar drag shoe and said sheet-supporting means being opposed and arranged in parallel relation to the opposed major surfaces of the composite sheet for slidable engagement therewith; together with means for resiliently biasing said drag shoe toward said sheet-supporting means to apply pressure against the composite sheet, thereby to resist feeding of the composite sheet and maintain pressure between the side edges of said strips as the glue is set.

20. A press as recited in claim 19, said biasing means comprising expansible chamber means for urging said drag shoe toward said sheet-supporting means, means for supplying pressure fluid to said expansible-chamber means, and resilient means.

21. A press as recited in claim 20, said resilient means comprising a pair of rods secured to said planar drag shoe and extending generally normal to the surface of said planar drag shoe, together with spring means urging said rods and said drag shoe in a direction away from said sheet-supporting means.

22. A press as recited in claim 19, there being a plurality of said planar drag shoes arranged transversely to the longitudinal dimension of the composite sheet and supported for independent movement normal to said sheet-supporting means, said biasing means being arranged to bias all of said drag shoes independently toward said sheet-supporting means.

23. A press as recited in claim 22, said biasing means comprising a group of expansible-chamber means one arranged to bias each of said drag shoes toward said sheetsupporting means, together with a group of pressure uid supply means one connected with each of said expansiblechamber means, and pressure-regulating means constructed and arranged to provide for independent adjustment of the pressure of fluid delivered to each of said expansible-chamber means.

References Cited UNITED STATES PATENTS 2,453,185 11/1948 Bilhuber 156-559 X 3,021,248 2/19621 Mann et al. 156-558 X 2,409,777 10/ 1946 Maurer 156-558 2,407,070 19/1946 Frame 156-558 2,488,759 11/ 1949 Bolling 156-558 1,702,175 2/ 1929 Weber 156-558 BENJAMIN A. BORCHELT, Primary Examiner J. M. HANLEY, Assistant Examiner U.S. Cl. X.R. 156-559