FR2680129A1 - PROCESS AND DEVICE FOR MANUFACTURING A CONTINUOUS TABLE OF DRY VENEERS FROM VERY SMALL ELEMENTS OF GREEN VENEERS OBTAINED BY ROLLING UP AND PRODUCTS THUS OBTAINED. - Google Patents

Abstract

The subject of the invention is a method for manufacturing veneer sheets from elements of unrolled wood of length, in the direction of the grain, less than the length or the width of said sheet, in which the unrolled wood is previously cut into strips of uniform dimensions, said elements being assembled by weaving using an added thread.

Description

The invention relates to the formation of veneers in the form of a sheet.

continues large dimensions to

  from elements of reduced dimensions of green veneers.

  In the conventional process of peeling and drying of veneer for, for example, manufacturing plywood panels, it is first sought a length of

  log equal to the length or width of the veneer to be

  hold on. In this way, the veneer unrolled from the log is likely to cover the full width of the panel. The defects of the wood proper mean that there is waste in this operation and that we find, in I -

  general, 30% plating capable in smaller dimensions

  less than the desired length or width and 70% of

large format plating.

  Generally, the veneers obtained in large format are dried in hot air dryers and then

  stored as is Other products below

  mensions are either joined to restore the width,

  either scarfed to reconstitute the length or successive-

  the two operations for the smallest of them.

  These reconstitution operations are all characteristic

  laughed at by the fact that they are carried out on

  dry cages and that the connection is made by an adhesive or

  by threads themselves impregnated with glue.

  The need to operate on a dry veneer is linked to the fact that the constituent elements are only held in position relative to one another by the adhesive which gives its cohesion to the final product. This adhesive cannot be effective on products. green Fitness

  of the ply ply from elements of low di-

  mensions can only be obtained in traditional techniques

  than using previously dried wood.

  In addition, in traditional manufacturing, the priority search for large elements makes it compulsory to use long logs with a diameter greater than 20 cm to obtain correct support during the peeling operation Too small a diameter or a wood of high density would cause defects due to the importance of the cutting force involved For these reasons, not only the diameter of the logs must be important but also, the choice is oriented

  towards species of low density.

  The invention proposes to provide a veneer production technique which allows the use of logs of very short length and less than the length or width of the desired veneer and, consequently, the unrolling of small diameter logs maintaining being much more

  easy to make over a short length.

  Another object of the invention is the use of species known to be hard, such as oak, hornbeam, beech, without a prior heating or baking operation, due to the short unwinding length limiting the effort. total cutting.

  Having a process using small lengths

  The unrolling feeders also give access to coppice stands made of generally less straight wood, but which can be "straightened" by cutting them in

  short lengths (for example 50 cm).

  The invention consists of starting from unrolled wood

  i 3 ble thickness and reduced dimensions, to cut this wood unrolled into strips whose length extends in the direction of the wire, this length being less than the length and

  the width of the veneer to form and assemble a multi-

  plicity of these straps to each other in the form of a weaving whose straps constitute the chain, a thread

-appoxlté forming the frame.

  The strips cut from the unrolled wood are of uniform dimensions. They are obtained after unrolling by cutting in the direction of the grain of the wood.

  length of the strips is that of the logs or logs

  rolled, the length being fixed by the cutting pitch.

  If the technique according to the invention can be implemented with strips of variable length, practical reasons mean that these dimensions rarely exceed 1 m

  and, most often, will be between 25 and 80 cm.

  The width of the strips is preferably chosen between a few tens of millimeters and a few tens

  of centimeters For very small widths, the regulation

  weaving may be difficult to maintain indoors

  pour, for very wide strips, the structural modifications during the later stages of production,

  especially during drying, can lead to cracks

  undesirable surations Given these two limits,

  the strips preferably have a width that is

taken between 20 mm and 150 mm.

  The weft thread can be in various materials: natural fiber, vegetable, animal, mineral, fiber

  polymer Its main role is to maintain the

  plating nières in the form of a continuous strip -4 - until the strips are glued together If necessary, the adhesive used for gluing consists, at least in part, of the wire itself This may be the case in particular when the wire is made of a thermoplastic material A hot compression ensures the fusion of the wire and the bonding

straps between them.

  The weaving of the veneer is advantageously done by passing the thread alternately above and below each strap over the entire width of the width and returning

  in reverse to reach the other edge of the width.

  Other modes of weaving are, of course, possible.

  We will see in the following the modes of formation of

  this weaving by detailing the attached drawings.

  To give the product its cohesion in the lengthwise direction, the strips are distributed in such a way that the junctions between two successive strips in the lengthwise direction are offset between laterally contiguous strips. A simple mode of implementation consists, by example, to shift half a length each strap relative to its neighbors, but provisions

  different are also suitable.

  Once the weaving has been carried out, the veneer ply can undergo a certain number of operations. It is first of all a question of leveling it. some thread

  absorbing the modifications of the woven set The opera-

  drying of the strips in the press heated to the

  fear completes the operation During this operation, when the wire is hot-melt, the strips are glued via the weft When the wire used does not melt at the time of drying, the high pressure imposed makes it possible to insert the thread in the wood texture, this

  sufficient to keep it cohesive until used

  subsequent plating After drying the sheet is,

  possibly, cut into elements of appropriate dimensions

quates for plating and stored.

  The technique according to the invention is described in more detail with reference to the drawings illustrating: in FIG. 1 is a schematic mode of - representation of a ply sheet according to the invention,

  * Figure 2 shows, schematically, the success

  transfer of operations: cutting, weaving, planing, * Figure 3 illustrates the respective position of two contiguous strips and weft threads, * Figure 4 illustrates, in perspective, a train of

  rollers leading three contiguous strips in the opera-

weaving,

  * Figure 5 is similar to Figure 4 and does not

  door that the lower roller train with the weft thread positioning system, a Figures 6 a to d show, schematically in

  seen from above, the succession of the different stages

  weaving technique according to the invention.

  The ply sheet shown diagrammatically in FIG. 1 is formed, in length, by three series of strips A, B,

  C In practice, the veneers according to the invention are

  with a greater number of sets of straps.

  For usual dimensions, for example 120 cm and strips initially 4 cm, the tablecloth consists of

slats across the width.

  The same principles set out below with the model to

  three straps are reproduced in the making of

  cages comprising a large number of series of lamellae.

  The representation of FIG. 1 alternates the slats so that, in a series, the junction between two consecutive strips (A, A ^) "end to end" is offset by half a length with respect to the contiguous series ( B) This provision or any other equivalent

  ensures the longitudinal continuity of the sheet.

  Weft thread 1 is shown slightly

  inclined with respect to the transverse direction In pra-

  tick, for effective widths, the "pitch" of the weft thread is relatively small compared to this width and the position of the weft thread is in position

  practically perpendicular to the straps.

  The number of weft threads passing over each strap can vary widely. It goes without saying that the higher this number, the more resistant the assembly. To properly maintain a strap in position, its length must be taken into account. strips are long, the more it is desirable to increase the number of threads In all cases, this number is not less than three and is, most often, between 4 and 10 depending on the length In FIG. 1, this number is 4, or 2 on each side of a strap. The process leading to plating is illustrated in Figure 2 Its main phases are from unrolled elements of reduced dimensions, for example of the order of x 50 cm: * unstacking and introduction of the 2 green elements into a system cutting into strips,

  * cutting into strips using, for example,

  seams of cutting wheels 3 spaced the width of a strip, * the constitution of the weaving itself from the strips in 4 as will be detailed below: the planing of the woven assembly in 5 to bring the strips in the same plane, the thread, by its elasticity, this time describing a non-rectilinear curve made of succession of straight line segments, the dynamic storage in 6 of the woven veneer between the

  weaving system and a drying press so as to com-

  hoeing two successions of operations operating step by step but with sequences of different amplitudes,

  drying in press in 7, for example, by

  tact heating plate, the cutting of the ribbon into discontinuous elements at 8. The cutting, in particular by knurls, is carried out in a known manner This cutting, when the raw material is a green plating of thin thickness 0.8 mm to 2 mm,

  allows perfectly straight straps to be obtained.

  During leveling, the pressure exerted on the

  nières et les fils can lead to a certain rearrangement of the assembly To obtain better flatness, the

  pressure exerted is preferably applied progressively

  starting from the center of the width For this, we 7 -

uses a train of rollers.

  Leveling is carried out, for example, using rou-

  The pressers arranged in a triangular arrangement.

  The triangular arrangement is such that the length of the first rolls is short and that it grows up to the

  width of the width for the last rolls.

  Drying is carried out in a manner known for this type of technique. It is advantageous to use drying under fluted press plates. It is contact drying which gives good transmission of calories and which does not destroy the assembly woven beforehand with veneers. green Performed for example at 180 W, 0.5 kg / cm 2 in addition to the fact that the drying cycle can be very short (about seconds for a thickness of 1 mm) there is no risk of surface removal of the wood Experience shows

  that if microcracks can appear in the

  However, the initial width remains unchanged and therefore does not constitute a risk factor for breaking the

thread already in slight tension.

  Weaving, in general, consists of passing with the aid of rollers (or rollers) strips of veneer alternately above and below a previously arranged weft. Figures 4, 5 and 6 illustrate a mode of implementation

  2 S weaving work produced according to the invention.

  Figure 4 shows a set of rollers limited to what corresponds to the treatment of three strips for the

simplicity of representation.

  The rollers are associated two by two in the direction of progression Each weaving roller 9, 10 comprises elements of different diameters Each element 9 a, b,

  etc corresponds substantially to the width of a strap.

  The elements of a roller are complementary to those of the roller matched to a small diameter element 9 a, 9 c

  corresponds to a large diameter element 10 a, 10 b and invert-

  sement. The rollers are rotated simultaneously by means such as chains, themselves driven by

  an engine These means are not shown.

-8 -

  The elements of the rollers of the same pair are main-

  tenius at a short distance corresponding to the thickness of a

  lanyard They ensure the mobility of lanyards

  nement and guiding the straps is done by friction but with a certain clearance allowing the strap to slide on the rollers. This is necessary, on the one hand,

  the fact that the roller elements having diameters

  very different, the speed of progression in contact with the two elements facing each other is not the same and, on the other hand, to allow the bonding of the straps on the set of straps which precedes them, the placing end to end being done in

  bringing the new game into abutment on the previous one.

  The distance between the elements indicated above

  is also adjusted so as to prevent overlapping.

  Checking two consecutive strips The adjustment of the progression of the sets of successive strips is such that the junction is preferably made at the level of a pair.

  rollers thus ensuring regular placement.

  The sliding of the strips on the edges is facilitated by the straightness of the cut in the direction of the wood grain and

  a coefficient of friction between green wood and green wood

tively weak.

  The length of the train of rollers is chosen in my-

  so as to be able to introduce the weaving of a set of strips while the previous play is still maintained in the rollers When the offset between the contiguous strips is half the length of the strip, this implies that the train of rollers extends on at least one and a half times

the length of a thong.

  In the train of rollers, the straps describe a

  sinusoidal trajectory passing over suc-

  stops whose dimensions are reversed (9 to 1 Oa;

lla 12 a;).

  In Figure 5, the position of the

  ners on the lower roller train and the passage of

  these strips on and under the weft threads which are main-

  kept fixed during this operation.

  In FIG. 6, only the straps of the A and B series are represented. The operation corresponds to the end of the cycle 9 - of weaving formation The end of the straps An, and B. being in contact with the preceding straps A _ 1 and B = -1 which are still engaged in the roller train, the

  junction taking place at the level of the rollers.

  Each strap is held in place by 4 weft threads. During the previous operation of

  pass the straps over the weft threads stretched and immo-

  biles, a new frame length is put in place on the carrying mechanism consisting of two endless chains 13 and 14 (or two belts) carrying pins regularly

  spaced on which the wire is stretched passing alternative-

  ment from chain 13 to chain 14 and vice versa The pitch

  between the successive pins corresponds to the distance se-

countering pairs of rollers.

  In the next step, all of the woven straps and the mechanism carrying the weft threads moves a length 1 corresponding to the length of a strap. This translation leads the weft threads, previously stretched, into position immediately in downstream of a pair of rollers at equal distance and parallel to their axes. The ends of the straps are repositioned at the

roller level.

  A new set of strips, previously cut out,

  is carried by the moving rollers while the dis-

  positive carrying the weft threads remains stationary The

  nières are inserted into these threads stretched as pre-

  previously indicated until it hits the end of the straps

  previous At this stage, the cycle is completed.

  At the end of the train of weaving rollers, the change in orientation of the chains 13 and 14 carrying the weft releases the pins, the weft thread remaining caught in the strips Released from the pins, the thread relaxes Under

  the effect of its elasticity, it can nevertheless come

  quer more or less tense on the songs of the

  nières located on the edges of the width.

  Beyond the weaving rollers, the strips can be carried on rollers of uniform diameter over their entire length up to the leveling means of which it has -

already been question.

  FIG. 6 illustrates the different steps indicated above. In 6 a, the weaving assembly is stopped after advancing a set of strips. The weft has been put in place to receive a new set of strips. n + 1 In 6 b, the straps n + 1 are in motion Driven by the

  rollers, they meander between the weft threads before-

  completely installed In FIG. 6, the central strap is already in abutment on the end of the preceding strap

  while the two side straps are still moving

  In 6 c, the movement of the straps n + 1 is completed In 6 the movement of the woven assembly and of the means for supporting the weft of a length of strap takes place. At the end of the movement indicated in 6 d the n + 1 strips are

  in the initial position of the strips N of FIG. 6 a.

  The cycle is ready to renew.

  As a first nonlimiting example, the process

  described makes it possible to produce a width of 250 cm on a long

  infinite cheeur constituted by a weft in solid polypropylene thread and by a chain in thick charm plating

  equal to 1.5 mm The ribbon thus formed comprises la-

  50 cm long and 4 cm wide and the distance between two threads taken on the same strap is cm. As a second nonlimiting example, the method makes it possible to produce a width in which the strips in

  charm are replaced by oak strips.

  The method according to the invention makes it possible to manufacture woven veneers in different applications such as: * a single layer serving as a separator between two solids or two powdery materials, * component of a multilayer panel with crossed or parallel thread, * product of decor by the aspect which recalls that of

parquet.

  il - R Ov Njj ICATIONS 1 Process for manufacturing veneer sheets from elements of unrolled wood of length, in the direction of the thread, less than the length or the width of said sheet, in which the unrolled wood is previously cut into strips of uniform dimensions, said elements

  being assembled by weaving using an added thread.

  2 The method of claim 1, wherein

operates on green peeled wood.

  3 Process according to claim 1 or the claim

  tion 2, in which the fabric is made with a

  frame of a thermoplastic polymer material.

  4 Method according to one of the preceding claims,

  in which the laterally contiguous strips have their ends offset so as to ensure the continuity of the fabric. The method of claim 2, wherein the

  formed fabric is "planed" and dried.

  6 Device for producing the plating fabric comprising means providing plating strips of constant dimensions, weaving means comprising a set of rollers making the strips describe that they transport sinusoidal type trajectories, the

  trajectories of two contiguous strips being in opposite

  tion, and means positioning the weft son downstream

  rollers, the straps thus moving

  natively above and below the stretched weft threads.

  7 Device according to claim 6 comprising, in

  in addition, leveling means smoothing the weaving obtained.

  8 Device according to claim 6 or the claim

  cation 7 further comprising a drying assembly for

  the treatment of green peeled wood.

  9 High density wood veneer obtained by

  method according to one of claims 1 to 5.