EP0184478B1 - Method and apparatus for manufacturing laminated wooden articles - Google Patents

Description

The present invention relates to a method and a machine for manufacturing pieces of glued laminated wood, from elongated elementary strips of rectangular section; the composite pieces of wood comprise several continuous and juxtaposed layers formed by the lamellae, the lamellae being butted by finger joints in at least two layers.

Obtaining very long pieces of wood having good mechanical strength requires that the elementary lamellae of the different layers be glued to each other, in the same layer, by finger joints. In the absence of such bonding of the splices, the mechanical resistance of the formed parts is reduced.

There is already known a method and a machine intended for the production of such pieces of wood having several continuous layers formed of lamellae which are butted by finger joints. More specifically, the document DE-A-1528135 describes a method and a machine according to which lamellas of the different layers are juxtaposed, the grooves of the lamellas of the adjacent layers being offset in the direction of the length of the layers, and the adjacent layers are glued by pressing in the stacking direction of the layers. All of the layers are braked but not stopped when they pass through a continuous manufacturing machine, the pressing force being applied by two track elements which progressively advance during the manufacture of the bonded part. Good bonding of the cuts of the lamellae of the different layers is obtained by applying, to each successive lamella of each layer, a feed force acting along the length. In this way, the bonding made at each cut can be of good quality.

This document therefore describes the production of pieces of glued laminated wood having good mechanical strength. However, the method and the machine described have certain drawbacks. First, the pieces of wood obtained must undergo planing, at least on the faces where the slices of the strips end. This planing is of the order of fifteen millimeters, in the case of pieces of wood of medium size, so that the losses of wood are significant. Then, the devices which exert feed forces on the elementary lamellae are offset along the length of the lamellae, in the different layers, so that the lamellae of the adjacent layers exhibit a certain buckling which risks displacing the lamellae at the level of the grooves. . Finally, the machine produced only allows the production of pieces of wood whose different blades or layers have the same thickness.

U.S. Patent No. 2,675,037 describes a hydraulic press for applying pressure to stacked pieces of wood in their stacking direction. In addition, this press comprises grills which locally apply pressures in the transverse direction to this stacking direction.

The invention relates to a method and a machine for eliminating planing after manufacturing the piece of wood. Consequently, it allows a very significant reduction in wood losses. Thus, the elementary strips are planed before the formation of the piece of wood, this planing bearing only on a small thickness, for example 3 mm, and the planing of the finished piece of wood is eliminated and is replaced by a simple sanding intended to remove the marks left by the mechanical advance devices and the glue burrs.

The method and apparatus according to the invention also suppress any relative buckling of the lamellae by applying forces to the individual lamellae in the same plane transverse to the direction of advance of the piece of wood produced. This characteristic is obtained by using thin drive members.

Finally, the method and apparatus according to the invention allow the manufacture of pieces of wood having layers of different thicknesses. In fact, it was realized that it was important that two marginal parts of the pieces of wood be formed of relatively thin layers, but that the central part could be made of relatively thick layers, without reduction of the final mechanical properties obtained. The invention allows the production of such pieces of wood having layers of different thickness.

• - la juxtaposition des lamelles des différentes couches de manière que les entures des lamelles des couches adjacentes soient décalées dans la direction de la longueur des couches, et
• - le collage des couches adjacentes.

More specifically, the invention relates to a method of manufacturing pieces of glued laminated wood, from elongated elementary strips of rectangular section, each finished piece of wood comprising several continuous and juxtaposed layers formed by the strips, at least part lamellae, in at least two layers, being finger-jointed, the method being of the type which comprises:

• - the juxtaposition of the lamellae of the different layers so that the grooves of the lamellae of the adjacent layers are offset in the direction of the length of the layers, and
• - bonding of adjacent layers.

• - l'application, à l'ensemble des cou r-mant la pièce de bois, d'une force de freinage agissant dans la direction de la longueur des couches et suffisant pour qu'elle arrête pratiquement l'avance de la pièce de bois, - dans deux couches au moins, et en amont de l'endroit du freinage, l'application séparée d'une force individuelle d'avance à une lamelle de la couche, chaque force d'avance agissant dans la direction de la longueur de la couche mais en sens inverse de celui de la force de freinage,
• - en amont de l'endroit du freinage, l'application de forces principales de pressage dans la direction d'empilement des couches,
• - en amont de l'endroit du freinage, l'application de forces complémentaires de pressage, en direction transversale à la fois à la longueur des couches et à la direction des forces principales de pressage, dans un même plan transversal, ou à proximité de ce même plan, que ces forces principales, et, finalement,
• - le déserrage du freinage et l'avance de la pièce de bois.

The process is cyclical, each cycle including:

• - the application, to all the lines of the piece of wood, of a braking force acting in the direction of the length of the layers and sufficient for it to practically stop the advance of the piece of wood , - in at least two layers, and upstream of the braking location, the separate application of an individual advance force to a layer of the layer, each advance force acting in the direction of the length of the layer but in the opposite direction to that of the braking force,
• - upstream of the braking location, the application of main pressing forces in the layer stacking direction,
• - upstream of the braking location, the application of additional pressing forces, in transverse direction both to the length of the layers and to the direction of the main pressing forces, in the same transverse plane, or near this same plan, as these main forces, and ultimately
• - brake release and advance of the piece of wood.

It is advantageous that the advance forces applied individually to the lamellae of the different layers are all applied substantially in a plane transverse to the length of the layers.

In addition, the areas of application of the feed forces to the lamellae of the different layers are preferably adjustable in the plane transverse to the length of the layers.

The invention also relates to a machine for manufacturing glued-laminated pieces of wood from elongated strips of rectangular section, each finished piece of wood comprising several continuous and juxtaposed layers formed by the strips, part of the strips of '' at least two layers being finger-jointed, the machine being of the type which comprises a frame which delimits a direction of advance of the pieces of wood at least two individual advance devices each intended to apply an individual force of advance to the minus one layer of a layer, and

• - un dispositif de freinage à action temporaire, placé en aval du dispositif principal de pressage, destiné à appliquer une force de freinage dans la direction d'avance, mais en sens opposé au sens d'avance, et à assurer pratiquement un arrêt temporaire de la pièce de bois,
• - un dispositif complémentaire de pressage destiné à appliquer une force complémentaire de pressage en direction transversale à la direction d'avance et transversale à la direction des forces principales de pressage, dans un même plan transversal, ou à proximité de ce même plan, que ces forces principales,
• - les dispositifs de freinage et de pressage ayant un fonctionnement cyclique.

a main pressing device for applying main pressing forces in a direction transverse to the direction of advance. According to the invention, the machine comprises:

• - a temporary action braking device, placed downstream of the main pressing device, intended to apply a braking force in the direction of advance, but in the opposite direction to the direction of advance, and to practically ensure a temporary stopping of the piece of wood,
• - a complementary pressing device intended to apply a complementary pressing force in a direction transverse to the direction of advance and transverse to the direction of the main pressing forces, in the same transverse plane, or near this same plane, as these main forces,
• - braking and pressing devices having a cyclic operation.

It is advantageous that the individual advance devices are arranged so that the areas of force application to the lamellae of the different layers are all substantially in the same plane transverse to the direction of advance. It is preferable that the spacing of the advance devices is adjustable in this plane, in the direction of the main pressing forces.

It is advantageous for the individual advance devices to be driven by a common power source to which they are connected by individual transmissions. These transmissions can for example be torque limiters, friction clutches, etc., preferably allowing the force applied to the blades to be adjusted. For example, in the case of a machine with continuous operation, the feed devices advantageously include friction clutches.

• - la figure 1 est un perspective schématique d'une machine de fabrication de pièces de bois en lamellé-collé selon l'invention ;
• - les figures 2 et 3 représentent des assemblages à entures, réalisés dans deux directions perpendiculaires, et qui peuvent tous deux être utilisés lors de la fabrication de pièces de bois par mise en oeuvre du procédé de l'invention ;
• - la figure 4 représente schématiquement des dispositifs d'avance individuelle des lamelles des différentes couches, tels que représentés sur la figure 1 ;
• - la figure 5 est une coupe d'une pièce de bois réalisée selon l'invention avec des couches d'épaisseurs différentes ; et
• - les figures 6 et 7 sont respectivement des coupes suivant les lignes 6-6 et 7-7 des figures 7 et 6 représentant une partie des dispositifs d'avance représentés sur la figure 4.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings in which:

• - Figure 1 is a schematic perspective of a machine for manufacturing glued laminated wood pieces according to the invention;
• - Figures 2 and 3 show finger joints, made in two perpendicular directions, which can both be used during the manufacture of pieces of wood by implementing the method of the invention;
• - Figure 4 schematically shows individual advance devices of the lamellae of the different layers, as shown in Figure 1;
• - Figure 5 is a section of a piece of wood made according to the invention with layers of different thicknesses; and
• FIGS. 6 and 7 are respectively sections along lines 6-6 and 7-7 of FIGS. 7 and 6 showing a part of the advance devices shown in FIG. 4.

Figure 1 is a general schematic perspective showing the essential elements of a machine according to the invention. The machine frame is not shown, but it carries the various elements essential to the operation of the machine.

It should first be noted that the piece of glued laminated timber which is manufactured moves in the direction A, in the direction of the arrow, and that the different layers are stacked in a direction B which is perpendicular to the direction d 'advance, this direction being horizontal in the particular embodiment of Figure 1. The arrow C corresponds to the direction of the width of the slats. In this specification, we call lengths the measurements parallel to direction A, thicknesses the measurements in direction B and widths the measurements in direction C. For example, the piece of wood shown in FIG. 1 has a thickness greater than its width.

It is noted in FIG. 1 that the manufactured piece of wood 14 leaving the pressing device, is formed by several layers 12 each consisting of elongated strips 10. These strips appear more clearly in FIG. 4 which indicates that the successive strips of a same layer are butted by finger joints 16. FIGS. 2 and 3 moreover show in more detail two types of finger joints which can be used according to the invention, the type represented in FIG. 2 being more suitable for a machine of the discontinuous type, that is to say with sequential advance, whereas the type of FIG. 3 is better suited to a machine with continuous advance.

The machine of FIG. 1 comprises a main pressing device 32 which comprises a plate fixed 34 and a movable plate 36, capable of providing heating; the movable plate can be moved by jacks 38 forming with the plates the main pressing device in the thickness direction, that is to say in the direction of stacking of the lamellae.

A braking device 26 is placed downstream of the press 32 and, in the schematic form shown, it comprises two clamping bars 28 which can be moved apart or brought closer by a jack 30. When they are brought closer, they stop the advance of the piece of wood in the machine.

In addition to the main pressing device 32, the machine comprises an additional pressing device 20 which includes fixed and mobile heating plates 22, the mobile plate being able to be moved by jacks 24. It is noted in the figure that the width of the plates 34 , 36 of the main press must be less than the width of the slats, for example a few millimeters.

A device for advancing the lamellae of the different layers individually bears the reference 40 and is shown more clearly in FIGS. 4, 6 and 7. It comprises several splined wheels 44 driven by a common shaft 42. This device is described in more detail in the remainder of this specification, but it can be noted in FIG. 4 that each of the fluted wheels 44 which advances a strip 10 is in contact with this strip in a zone 18, a suitable device such as a mad roller being placed under the strips, opposite the device 40.

During the operation of the press, the slats, previously positioned, arrive one next to the other under the device 40 for individual advance. When the braking device 26 is applied and prevents any advance, the device 40 assembles the strips and the two presses 32 and 20 are then controlled. It should be noted that the plates 34 and 36 may be outside the plates of the press 20, wooden spacers of suitable size being placed between the plates and the outer strips.

When the two presses have operated for the necessary time, in a conventional manner, they are open and the braking device 26 is released so that the piece of wood can advance. When it has advanced by a length substantially corresponding to the length of the plates 22, the braking device 26 is again tightened and the cycle begins again.

Figure 1 shows two important features of the invention. First, the complementary press 20 puts the edges of all the strips 10 in two same planes so that the finished piece of wood 14 does not require planing thanks to the correction of the linearity defect of the strips. Then, all the wheels 44 of the feed device 40 have their zones 18 of cooperation with the juxtaposed lamellae which are all aligned in a direction transverse to the feed direction. In this way, the lamellae cannot exhibit buckling.

Figures 5 to 7 show another characteristic of the invention. More specifically, we realized that, in a piece of glued laminated wood, it was not necessary for all the layers to have the same thickness. Wood pieces having excellent strength can be obtained by bonding relatively thin layers on the sides and relatively thick layers in the center. Figure 5 is a schematic section of such a piece of wood having, on each of two opposite faces, two relatively thin layers formed by lamellae 10a and 5 relatively thick layers formed by lamellae 10b. For example, the thicknesses of the strips 10a and 10b can be 17 and 44 mm respectively. The mechanical strength of such a beam is practically the same as that of a beam in which the strips 10b are replaced by thinner strips having an identical total thickness.

It is therefore advantageous to be able to adjust the spacing and the force of the advance devices, as a function of the dimensions of the lamellae of the juxtaposed layers.

Figures 6 and 7 show an example of a feed device allowing such adjustment.

More specifically, a main motor, not shown, drives a shaft 42 which has grooves or two longitudinal grooves 43 as shown in Figure 7. Friction clutch plates 52 are mounted on the shaft and have parts which penetrate in the grooves 43 so that these plates can move along the tree but are forced to rotate with it. These plates 52 carry brake linings which delimit an external surface 50 of cooperation with an adjacent surface 48 of a drive wheel 44. The surface of the latter is grooved as indicated by reference 46, so that it does not slip in contact with an adjacent strip.

The shaft 42 normally carries a stack of plates 52 and wheels 44 which alternate. The wheels 44 can rotate freely around the shaft 42 when they are not in contact with a lining of a plate 52. A part of the shaft 42 carries a clutch plate 56 which is integral with the tree and cannot move in translation along it. In this way, when a support collar 58 is pushed back by an actuating part 60 against the adjacent wheel 44, all the wheels 44 and the clutch plates 52 come into contact so that each wheel 44 is driven, as long as that the resistance force exerted on its external surface does not exceed the friction forces between the two surfaces 48 and 50. In this way, when the members 58 and 60 compress the stack of wheels 44 and plates 52, all the wheels 44 are trained.

When the machine is to be used for the manufacture of beams having layers of different thicknesses as indicated in FIG. 5, several wheels 44 can be used for the same layer such as 10b. When the thickness of a layer such that 10b is not exactly equal to an integer multiple of the thickness of a single wheel 44, a spacer is mounted in a suitable position on the shaft, between a wheel and an adjacent clutch plate . Such a spacer is represented by the reference 54 in FIG. 6. As the thickness of the layers can be arbitrary, the shaft 42 usually comprises a number of spacers less than one unit than the number of layers and, between two neighboring spacers , one, two or three wheels 44 for example. In this way, the spacing of the feed devices can be adjusted. Furthermore, the force exerted by the advancing devices can be adjusted by adjusting the force of application of the wheels against the clutch plates 52.

Although a clutch system has been described, any other device allowing the separate application of an adjustable torque, at the suitable location, that is to say in front of each layer, can be used within the framework of the invention. Hydraulic torque converters, mechanical torque limiters, for example ball bearings, etc. are devices which can be used advantageously.

Thus, FIGS. 6 and 7 represent a third important characteristic of the invention which is the adjustment of the position of the advancing devices so that they allow the production of lamellar parts having layers of different thicknesses.

Thanks to the additional pressing device acting along the width of the blades (C in Figure 1), it is also possible to make pieces of wood in which certain layers are formed by strips juxtaposed in the width direction, that is i.e. in direction C.

Although the use of heating plates has been described for pressing, any device usually used for bonding is suitable according to the invention. For example, high frequency or microwave devices are ideal.

Claims (8)

1. Process for manufacturing laminated wood pieces, from elongated elementary laminae (10) having a rectangular cross-section, each completed wood piece (14) including several continuous and juxtaposed layers (12) formed by laminae, at least some of laminae of at least two layers forming scarf joints, said process being of the type which includes :

- juxtaposing laminae (10) of different layers (12) so that joints of laminae of adjacent layers are shifted in the longitudinal direction of layers, and

- bonding adjacent layers (12),

- said process being cyclical, each cycle including :

- applying to the whole layers constituting said wood piece (14) a braking load acting in the longitudinal direction of layers and sufficient for substantially stopping feeding of said wood piece (14),

- in at least two layers and upstream of braking position, separately applying an individual feeding load to a lamina (10) of the layer, each feeding load acting in the longitudinal direction of said layer (12) but with a direction opposite to that of braking load,

- upstream of braking position, applying main pressing loads in the stacking direction (B) of layers (12),

- upstream of the braking position, applying complementary pressing loads in a direction (C) transverse both to layer length (12) and to main pressing load direction in or near a same transverse plane as said main loads and, finally,

- loosening said braking action and feeding said wood piece (14).

2. Process according to claim 1, characterized in that feeding loads individually applied to laminae (10) of different layers (12) are all applied substantially in a plane transverse to layer length.

3. Process according to claim 2, characterized in that areas (18) for applying feeding loads to laminae (10) of different layers (12) are controllable in a plane transverse to layer length.

4. Machine for manufacturing laminated wood pieces (14) from elongated laminae (10) having a rectangular cross-section, each completed wood piece including several continuous and juxtaposed layers (12) formed by said laminae (10), a portion of laminae of at least two layers being scarf jointed, said machine being of the type which includes a frame defining a feeding direction for wood pieces (14), at least two individual feeding means (44) each for applying an individual feeding force to at least a layer lamina (10), and main pressing means (32) for applying main pressing loads in a direction transverse to feeding direction, and being characterized in that it includes :

- braking means (26) with temporary action, positioned after said main pressing means and for applying a braking force in a direction opposite to said feeding direction, and for providing substantially a temporary stop of said wood piece (14), and

- complementary pressing means (20) for applying a complementary pressing load in a direction transverse to said feeding direction and transverse to main pressing load direction in or near a same transverse plane as said main loads,

- braking and pressing means having a cyclical action.

5. Machine according to claim 4, characterized in that said individual feeding means (44) are positioned in such a manner as load application areas (18) to laminae (10) of different layers (12) are all substantially in a same plane transverse to said feeding direction.

6. Machine according to claim 5, characterized in that feeding means (44) spacing is controllable in a plane transverse to said feeding direction, in main pressing load direction.

7. Machine according to any one of claims 4 to 6, characterized in that individual feeding means (44) are driven by a common driving source (42) to which they are connected by individual transmissions.

8. Machine according to claim 7, characterized in that said transmissions. are selected in the group including overload clutches and friction clutches.

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