FR3121380A1 - Mold for thermoforming by pressure difference of honeycomb trays for handling or packaging and associated thermoforming process - Google Patents

Abstract

The invention relates to a mold (100) for thermoforming by pressure difference of honeycomb trays for handling or packaging, comprising at least one honeycomb plate (1) forming, during thermoforming, a honeycomb bottom of the trays, and a outer frame (3) forming, during thermoforming, a stiffening outer rim and vertical spacer for the trays, characterized in that the honeycombed plate (1) and the outer frame (3) are separate, and fit together two by two so as to be interchangeable with dimpled plates (1) and external frames (3) of different dimensions to allow adaptation of the dimensions and shapes of the cells and of the external edge of the vacuum thermoformed trays Figure for the abstract: Fig.1

Description

Mold for thermoforming by pressure difference of honeycomb trays for handling or packaging and associated thermoforming process

The present invention relates to the thermoforming of plastic packaging, in particular to vacuum or overpressure thermoforming of honeycomb trays for handling and/or packaging for potentially sensitive parts and products.

The packaging and handling honeycomb trays are trays having a generally flat shape, with a plurality of cells sized so as to receive and maintain individual products such as small consumer products or intermediate industrial products.

Such honeycomb trays are used, for example, to package and separate chocolates, biscuits or confectionery in a cardboard box forming an overwrap, with one portion per honeycomb. In handling, these honeycomb trays are used in particular to hold and separate parts which, by knocking together, could be damaged, for example machined metal parts that have been turned or have undergone surface treatment, printed circuits, sub-assemblies of provisionally assembled machine, etc.

These trays can also be trays for presenting products to the consumer, or trays intended for use in the context of automated assembly processes.

In particular for handling, the trays have an outer rim, in the form of a shoulder surrounding the cells. This edge has in particular a role of stiffening and vertical spacing during the stacking of the trays filled with their contents, in particular in boxes or bins for the dispatch of the parts contained in the trays. These external edges must then have standardized external dimensions corresponding to the dimensions of the cartons or bins.

These trays therefore have forms as varied as their uses.

The thermoforming of these trays is done almost exclusively by thermoforming by pressure difference, either vacuum or overpressure, from a mold machined to measure from a block in aluminum by three-dimensional computer-assisted machining.

These molds are inserted into an airtight chamber comprising a bottom, where the mold is placed, and a lid closing the chamber above. A thermoformable plastic film is then pinched between the bottom and the lid and then heated. The mold has through holes, through which the air contained in the vacuum chamber between the mold and the film is sucked in by the bottom (vacuum thermoforming) or is expelled by an overpressure between the cover and the film (thermoforming by overpressure), so that said film deforms and presses against the mould. The whole is then cooled, and the plate thus formed is extracted from the chamber and separated from the mould.

The molds must therefore each time be machined for the specific needs of the user of the tray: number and shape of the cells, height and rigidity of the rim, etc. thus vary according to the subsequent use of the trays.

The machining of such a mold represents an investment which is usually amortized by the production of a large number of plates, made possible by the simplicity of vacuum thermoforming. Manufacturers of honeycomb trays therefore generally present a number of tray models with standardized shapes and dimensions in their catalogs, with each reference corresponding to a mould.

However, if a user requires a relatively small number of non-standard trays, the cost of producing the corresponding mold will be passed on to the cost price of the unit tray, which can then be high.

Thus, there is a need for a method of producing varied vacuum thermoforming molds at reduced prices, in order to allow the production of varied ranges of honeycomb trays at an optimized cost price.

In order to meet this need, the invention proposes a mold for thermoforming by pressure difference of honeycomb trays for handling or packaging, comprising at least one honeycomb plate forming, during thermoforming, a honeycomb bottom of the trays, and a frame exterior forming, during thermoforming, an outer rim stiffening and vertical spacer of the trays, characterized in that the honeycomb plate and the outer frame are separate, and fit together in pairs so as to be interchangeable with honeycomb plates and external frames of different dimensions to allow adaptation of the dimensions and shapes of the cells and of the outer edge of the thermoformed trays by pressure difference.

The thermoforming mold by pressure difference thus obtained can be adjusted according to the needs in terms of shapes and dimensions of the required trays. In addition, to extend the range of trays that can be obtained using said mould, only part of the tray (frame or dimpled plate) can be machined to measure, instead of having to completely machine a new complete mold in one piece.

The thermoforming mold by pressure difference according to the invention may also have one or more of the following characteristics.

The dimpled plate may have cells with a polygonal or circular bottom, separated by columns and raised shoulders, machined in the dimpled plate.

The honeycombed plate may comprise longitudinal trenches whose section corresponds to the longitudinal section of the cells of the thermoformed trays, transverse grooves passing through the at least one honeycombed plate and a plurality of shaped strips corresponding to the transverse grooves, machined so as to either flush with a bottom and vertical walls of the longitudinal trenches, or to form, during thermoforming, a transverse wall separating two cells longitudinally adjacent to a plate.

The strips may comprise straight strips, of rectangular or trapezoidal shape, and machined strips having recesses corresponding to the longitudinal section of the longitudinal trenches so as to be flush with the bottom of the longitudinal trenches.

The trenches can have a polygonal longitudinal section or a portion of an ellipse.

At least one of the strips may have a cutout in its upper part, at the level of at least one of the longitudinal trenches when inserted into a groove, forming a wall partially closing off said longitudinal trench.

At least one of the strips may have a cutout in its upper part, at the level of at least one of the longitudinal trenches when inserted into a slot, adjusted to the cross-section of a given product, so that the said product bears against the wall formed by the bar when placed in the cavity of the plate formed by thermoforming by differential pressure by means of the thermoforming plate by differential pressure.

The cutting of the upper part of the bar can have a recess for the passage of a finger.

The cutting of the upper part of the bar can be adjusted to the longitudinal profile of a product.

The dimpled plate, the outer frame and/or the strips may comprise grooves on their outer faces at the level of their edges in contact, connecting, when assembled to form the thermoforming mold by pressure difference, the upper and lower faces of the differential pressure thermoforming mold so as to form air suction ducts for differential pressure thermoforming.

The honeycombed plate may include holes forming air intake ducts distributed over its outer periphery, at the corner of a peripheral shoulder forming an insertion guide for the outer frame and a horizontal rim against which the outer frame comes to rest. vertical when assembling the thermoforming mold by pressure difference, and the outer frame has recesses at the locations vis-à-vis said holes.

The invention also relates to the method of thermoforming by pressure difference of cellular trays for handling or packaging by means of a thermoforming mold by pressure difference as described above, characterized in that it comprises the steps :
selection of a honeycomb plate and an outer frame corresponding to the shapes and dimensions desired for the honeycomb tray,
assembly of the thermoforming mold by pressure difference from the selected dimpled plate and outer frame,
thermoforming by pressure difference of the honeycomb tray using the assembled mould.

If the dimpled plate comprises longitudinal trenches whose section corresponds to the longitudinal section of the dimples of the thermoformed trays, transverse grooves crossing the at least one dimpled plate and a plurality of bars of shape corresponding to the transverse grooves, machined so as to either flush with a bottom and vertical walls of the longitudinal trenches, or to form, during thermoforming, a transverse wall separating two longitudinally adjacent cells from a plate,
the step of selecting a dimpled plate and an outer frame can include an additional sub-step of selecting the strips,
and the step of assembling the thermoforming mold by pressure difference may include a sub-step of inserting the strips into the transverse grooves to longitudinally delimit the cells of the honeycombed tray.

Other advantages and characteristics will appear on reading the following description of the figures, among which:

is an exploded perspective view of one embodiment of the invention,

is a cross-sectional view of the embodiment of the ,

is a perspective view of the section of the embodiment of Figures 1 and 2,

is a partial and schematic sectional view of trays obtained by means of a mold according to the invention illustrating their vertical stacking,

is an exploded perspective view of one embodiment of the invention,

is a cross-sectional view of the embodiment of the ,

is a perspective view of the section of the embodiment of Figures 5 and 6,

illustrates several embodiments of transverse bars for the mold of Figures 5 to 7,

is an exploded perspective view of an alternative embodiment of mold analogous to the mold of the ,

illustrates several embodiments of transverse bars for the mold of the ,

,

,

and

illustrate the thermoforming by pressure difference of a plate by means of a mold according to the invention.

The embodiments presented in the figures and described below are given by way of descriptive and non-limiting example. Other embodiments can be obtained by slightly modifying the characteristics of the described embodiments or by combining characteristics of different embodiments when possible.

The is an exploded perspective view of a differential pressure thermoforming mold 100 according to one embodiment of the invention, for differential pressure thermoforming of blister trays 200 (see ). An xyz mark indicates a reference orientation. The longitudinal axis x and the transverse axis y delimit a defined horizontal plane, and the z axis is defined vertical. This orientation is for reference only, and in use, the actual orientation of mold 100 may be different.

The term "thermoforming by pressure difference" is understood here to mean either vacuum thermoforming or thermoforming by overpressure.

These two processes are based on the insertion of a film of thermoplastic polymer between a bottom, in which the mold 100 is placed, and a lid, the bottom and the lid forming an airtight enclosure. The thermoplastic polymer film is then heated and pressed against the mold 100 either by creating an overpressure between the cover and the thermoplastic polymer film (thermoforming by overpressure) or by sucking the air between the thermoplastic polymer film and the bottom (thermoforming empty).

Certain elements of the mold 100, such as the cells 10, are present in large numbers. Consequently, in the figures, only some of these elements are indicated by an arrow and/or a number. Identical elements even not indicated are of course included in the designation of the set as part of the description.

The mold 100 comprises a honeycomb plate 1 and an outer frame 3, both substantially horizontal, and generally rectangular in shape, as does the mold 100 obtained by their assembly.

The dimpled plate 1 comprises an upper surface having concave dimples 10, separated by vertical walls, here in the form of columns 11, from which extend longitudinal (x axis) and transverse (y axis) shoulders, raised which delimit the cells 10 by forming walls during molding by pressure difference of the plate 200. The columns 11 are arranged at the level of the intersection of the edges of the cells 10 which pave the cell plate 1 according to a square paving, and the shoulders s extend between the neighboring columns 11 along the sides of the squares of the paving, and a raised peripheral shoulder 11a surrounds the cells 10 and delimits the edge of the cell plate. The peripheral shoulder 11a and the columns 11 are in particular of substantially equal height.

The cells 10 have a bottom of circular shape, but this bottom can be, as an alternative, polygonal, for example square, hexagonal or octagonal, depending on the shape of the product intended to be placed in the cells 10, or even the wish of the user. for aesthetic reasons, or else the paving and the spacing of the cells can be varied, for example by means of a hexagonal paving, however less indicated compared to the rectangular shape of the dimpled plate.

The cells 10, the columns 11 and the shoulders are machined directly in the cell plate 1, in particular by computer-assisted machining in the mass.

In particular, it is then possible to produce varied profiles and distributions of cells 10 on the cell plate 1.

The frame 3 is rectangular, and fits over the rectangular outer edge of the dimpled plate 1 which it surrounds. To allow this interlocking, the honeycomb plate 1 has a horizontal rim 13 of lower height than the peripheral shoulder 11a, and the frame 3 is in vertical support, when the mold 100 is assembled, on the horizontal rim 13.

The horizontal rim 13 also has several positioning recesses 13a, which cooperate with positioning protrusions (not shown), of corresponding arrangement and dimensions of the frame 3, in order to allow the positioning and the maintenance in position of the frame 3 at the assembly.

The peripheral shoulder 11a is in particular inclined inwards starting from the bottom, in order to form a guide for the insertion of the frame 3.

At the corner of the horizontal rim 13 and of the peripheral shoulder 11a open holes 13b, which pass through the honeycomb plate 1 right through, and thus form air suction ducts during vacuum thermoforming, or evacuation of air during overpressure thermoforming.

In particular, by means of the dimensional tolerances between the honeycomb plate 1 and the frame 3, the suction exerted at the level of the holes 13b is transmitted at the level of the gap between the honeycomb plate 1 and the frame 3 by forming a continuity of the air suction pipe, and thus contributes to flattening, during thermoforming, the thermoformed plastic against the corner between the peripheral shoulder 11a and the inner edge of the frame 3 (see ).

Thus, by changing the cellular plate 1 of the mold 100, it is possible to change the shape, size and distribution of the cells 10. By changing the frame 3 of the mold, it is possible to change the shape of the outer rim of the plate 200 This outer rim has a stiffening and spacer role when the trays 200 are stacked or when they are overwrapped, for example by means of a sealing plastic film.

The frame 3 is here configured for the vacuum thermoforming of a handling tray 200, and therefore has recesses 31 and 33 on its outer periphery. Two of the recesses 31 are arranged on opposite sides of the frame 3 and are under trapezoidal recessed shape over the entire height of the frame 3, which extends into the horizontal rim 13. They form, during the thermoforming of the plate 200, recessed handles, allowing for example the extraction of the plate 200 from a cardboard box or easily, the outer dimensions of said tray 200 being adjusted to the inner dimensions of the box to wedge the tray 200 in the box or tray for transport.

The other recesses 33 are in the form of recesses in an arc of a circle, over a portion of the height of the frame 3. They form a support during the stacking of the trays 200 (see ). These recesses 33 forming a support are distributed in a non-symmetrical and non-invariant manner by rotation on the edges of the sides of the frame 3.

For example, on the long sides of the frame 3, one of said long sides has three recesses 33 forming a support evenly distributed over its length, and the other long side has four recesses 33 forming a support evenly distributed over its length. On the short sides of the frame 3, the two short sides have two recesses 33 forming a support, but they are spaced apart on one of the two short sides, and close together on the other short side.

Thus, the trays 200 obtained by means of the mold 100 using the frame 3 previously described can be nested in a compact manner when they are oriented in the same way for increased compactness when empty, and can be stacked with a spacing by simple rotation of 180° of a plate 200 out of two, in order to avoid the crushing of the products contained in a plate 200 by those of the plate 200 above.

Figures 2 and 3 are sectional views respectively from the front and in perspective of the mold 100 in exploded view of the .

The section plane is in particular the vertical transverse yz plane, and intersects the dimpled plate 1 at the level of a row of columns 11.

In particular, the section reveals the presence, under the columns 11, of air suction nozzles 15 located under the columns 11 and at the border between the peripheral shoulder 11a and the adjacent cells 10, hollowed out in the cell plate 1 .

These air suction nozzles 15 have a substantially circular or polygonal circular lower mouth, which, during vacuum thermoforming, is inserted into an air suction pipe. Each air suction nozzle 15 opens into three air suction holes, one of which in turn opens into the center of a hollow which forms the upper surface of the column 11 located above the nozzle. 15, and for the other two at the bottom of the cell 10. These air suction pipes allow the thermoformed plastic to be pressed against the mold 100 during vacuum thermoforming.

The frame 3 has recesses 35 located, when the frame 3 is placed on the honeycomb plate 1, above the holes 13b of the horizontal rim 13, and open onto the inner rim of the frame 3. These recesses improve the suction of air through the holes 13b at the level of the slot between the frame 3 and the peripheral shoulder 11a, and an air suction nozzle 37 opening into the substantially horizontal surface of the recess 33. Such a suction nozzle d air 37 can in particular be provided for each of the recesses 33 forming a support for the stacking of the trays 200.

Instead of the holes 13b, the dimpled plate 1 may comprise, according to an alternative embodiment, grooves located at the level of the horizontal rim 13 on the surfaces in contact with the frame 3, and extending to the lower outer corner of said rim landscape 13.

According to yet another embodiment, the grooves can be dug entirely in the frame 3, at its surfaces in contact with the horizontal rim 13.

More generally, the holes forming the air suction pipes can be replaced by grooves on the surfaces in contact with different elements of the mold 100, or said air suction pipes can be replaced by section or emerge in such grooves.

The is a schematic sectional representation of two trays 200 being stacked (arrow), partially shown.

The trays 200 include a peripheral rim 201, on the left in , and a plurality of cells 203, separated by raised walls 205. The part on the right trays 200 is not shown, but also includes a rim 201, which goes around the tray 200.

The rim 201 is in particular itself raised relative to the walls 205, and is formed, during thermoforming, by the frame 3. The dimensions and the shape of the rim 201 are thus a function of those of the frame 3.

The cells 203 of the plate 200 as well as the walls 205 form the central part of the plate 200 and are formed, during vacuum thermoforming, by the cell plate 1. Their shapes and dimensions are therefore a function of those of the cell plate 1. The rim 201 shown of the upper plate 200 has a recess forming a support 207, corresponding to the recesses 33 of the frame 3.

This recess forming a support 207 has a substantially horizontal surface, which comes, when the trays 200 are stacked, to bear against the outer corner of the tray 200 located below, which does not have a recess forming a support 207 below that of the plate 200 above, because the lower plate 200 is, as previously discussed, turned by 180° with respect to that above, and the locations of the recesses forming support 207, corresponding to those of the recesses 33 of the frame 3, are variants by rotation.

Products 300 are placed in the cells 203. These products can be either consumer goods (food, in particular confectionery and chocolates, small items, for example cosmetics, etc.) or intermediate products (machined parts, printed circuits , electronic components, temporarily assembled parts, etc.) which must be transported to complete their production cycle or be incorporated into another product.

The shape of the cells 203 is in particular adjusted to that of the products 300, in order to keep them at the bottom of said cells 203 during transport. The stacking with the supports formed by the recesses 207 makes it possible in particular to space the products 300 vertically in the stacked trays 200, which prevents the products 300 from a tray 200 from being subjected to the weight of the products 300 from the tray 200 at the above, thus avoiding the risk of damaging or crushing them.

The is an exploded perspective view of a mold 100 according to an alternative embodiment of the invention, comprising a frame 3 and a dimpled plate 1.

In this mold 100, the frame 3 is substantially identical to that of the . The peripheral shoulder 11a and the horizontal rim 13 of the honeycomb plate 1 are likewise substantially identical to those of the .

The honeycombed plate 1 comprises longitudinal trenches 17 (axis x), here four in number and of rectangular section, separated by vertical walls extending over the entire length of the honeycombed plate 1 delimited by the peripheral shoulder 11a (plan xz). The trenches 17 can in particular vary in depth, shape of section (polygonal, arc of ellipse, see ), or in number, with more or less thick vertical walls in the transverse direction y, according to the desired longitudinal section for the cells 203 of the plate 200.

Transversal grooves 19 are dug in the honeycomb plate 1, orthogonally to the trenches 17. These grooves 19 open onto the lower surface of said honeycomb plate 1 in the trenches 17, and have a height lower than that of the peripheral shoulder 11a, and here in particular also less than the height of the vertical walls separating the longitudinal trenches 17, which are of identical height to that of said peripheral shoulder 11a. This prevents the blister plate 1 from being cut into several separate pieces by the grooves 19, and said blister plate 1 thus remains easier to handle.

The grooves 19 do not entirely cross the peripheral shoulder 11a in width either (y-axis), which also contributes to keeping the blister plate 1 in a single piece that is solid and easy to handle.

The trenches 17 can in particular be machined in the mass of the honeycomb plate 1 from the top of the latter by rapid milling followed by more precise passes, and the grooves 19 can in particular be obtained by milling from the underside of the honeycomb plate 1.

Bars 5 are inserted into the grooves 19 from below the honeycomb plate 1. These bars 5 have a shape complementary to that of the grooves 19, and are machined so as to be flush with the wall of the trench 17 to close the groove. 19 in the continuity of the trench 17, or to form a transverse vertical wall (plane yz) separating two cells 10 of the mold 100 longitudinally adjacent.

A strictly equivalent embodiment can be obtained with transverse trenches 17 and longitudinal grooves 19, simply corresponding to a change of reference.

A cross-sectional view along the vertical transverse plane yz at the level of a bar 5 inserted in a groove 19 is represented in front view in and in exploded perspective .

Bar 5 is double hatched in and hatched in .

The illustrates different possible shapes of bars 5. The bar 5 of the section of FIGS. 6 and 7 corresponds to the first of the shapes illustrated in .

The bar 5 at the level of the section of said figures 6 and 7 is a bar 5 which closes the groove 19 in which it is inserted, and is flush with the wall of the trenches 17.

This strip 5 has the general shape of a comb, with a horizontal bar 51 from which teeth 53 extend at the level, when inserted into the corresponding groove 19, of the vertical walls separating the trenches 17. The section of the teeth 53 corresponds to the section of the vertical wall in which the bar 5 is inserted. Between the teeth 53 is a trapezoidal hollow 55, the shape of which corresponds to the section S (see bar 5 following in ) of the trench 17 at which this hollow 55 is located when the bar 5 is inserted into a slot 19.

The bar 5 further comprises vertical grooves 57, dug in the transverse walls thereof. These grooves 57 open out onto the upper horizontal surface at the bottom of the hollows 55, at the level of the longitudinal corners of said hollow 55 and onto the lower horizontal surface of the strip 5.

These grooves 57 thus form an air suction pipe during vacuum thermoforming making it possible to ensure that the thermoplastic is placed against the walls of the trenches 17 extended by the strips 5. In particular, a groove is more easily and quickly machined than a small-diameter hole that requires a long, thin, and therefore potentially brittle, drill bit.

According to an alternative embodiment, it is possible to provide a clearance between the bar 5 and the groove 19 which makes it possible to create a passage for the air suction without resorting to dedicated grooves 57.

Bars 5 of alternative embodiment are shown in under the previously discussed embodiment ("comb").

The second embodiment of strip 5 of the is a so-called “full” strip. This bar 5 is trapezoidal in shape with a straight upper edge, which thus closes the section S (shown in dotted lines) of the trenches 17 over the entire height of the grooves 19.

The grooves 57 which are then machined on the transverse faces of the bar 5 extend only a few millimeters or even tenths of a millimeter further than the limit of the section S of the trenches, so as to cause the air suction pipe to emerge that they always generate at the corner of said section S.

The grooves 19 are regularly distributed over the length of the trenches 17 and the "solid" strips 5 thus form during thermoforming each a solid wall longitudinally delimiting (axis x) two cells 10.

In particular, the mold 100 of FIGS. 5 to 7 comprises, in the grooves 19 which are regularly distributed along the trenches 17, an alternation of "comb" strips 5 and "solid" strips 5 . More particularly, said mold 100 comprises each time three “comb” strips 5 in succession, then a “full” strip 5 . Bars 5 located on the right in are represented out of their bleeding 19.

The cells 10 thus formed have a length (along the x axis) corresponding to four times the pitch separating two grooves 19 longitudinally adjacent. By changing the number of "comb" strips 5 between two "full" strips 5, it is possible to vary the length of the cells 10, either uniformly over the entire mold 100, or to generate cells 10 of different lengths on a same tray 200.

The third bar 5 of the is “full” per section. This bar comprises an alternation of hollow 55 and solid portions at the level of the section S of a trench 17 between two teeth 53.

More particularly, this embodiment of bar 5 comprises two portions with a hollow 55 on either side of a central portion corresponding to two solid sections S of trench 17.

By means of such a strip 5, it is possible to extend longitudinally only part of the cells 10 formed by the parallel trenches 17 of the mold 100.

The fourth bar 5 of the comprises more complex cutouts at the level of the sections of trenches S, forming, during vacuum thermoforming, walls partially closing the cells 10.

Starting from the left, the first cutout is straight, approximately halfway up the section S. The wall thermoformed by this portion of the strip 5 will thus be straight, but lower than the wall formed by a “full” section.

The second cut has a trapezoidal recess, which will form, during vacuum thermoforming, a wall forming a bottleneck with a trapezoidal opening corresponding to the recess.

The third cutout is circular, and will therefore form a shoulder during thermoforming.

The fourth cutout has a semi-circle indent and approximates the second cutout. This cutout will form a bottleneck with a semicircular opening.

The semicircular or trapezoidal withdrawals can in particular be used to allow the passage of a user's finger to better access the product 300 and extract it from the cell 203 obtained.

More generally, complex cutouts can thus be machined starting from a “full” bar 5.

By three-dimensionally adjusting these cutouts to the longitudinal section of a product 300 which will be placed in the honeycomb tray 200, it is possible to generate a tray 200 with transverse walls in its cells 203 which form at regular intervals a support for the product 300 in adjusting the bars 5 to the transverse section of said product 300 at the level of the grooves 19. These supports make it possible to place in the cells 201 of the tray 200 thus obtained potentially fragile products 300 and/or to maintain these products in place thanks to the support walls adjusted to the section of the product 300 at regular intervals.

Thus the mold 100 according to this embodiment makes it possible to produce a wide variety of different trays 200, with cells 203 of variable length and of parallelepiped shape here, simply by inverting a "full" bar 5 with a "comb" bar 5 in the alternation of the bars 5 inserted in the grooves 19 of the honeycomb plate 1.

In particular, by having only strips 5 "comb" in the grooves 19, cells 203 in number corresponding to that of the trenches 17 and covering the entire length of said plate 200, matching the shape of said trenches 17, will be generated.

By placing only "full" strips 5 in the grooves 19, a plate 200 with the maximum number of cells 203 is obtained, each cell 203 then having a length corresponding to the pitch separating two grooves 19 longitudinally.

All the intermediate configurations are also accessible, by implementing an alternation of “comb” and “solid” strips 5, and therefore without having to machine any element of the mold 100 in a specific way.

In addition, by machining only the strips 5 to measure, therefore with a potentially greatly reduced cost compared to the cost of machining a complete honeycomb plate 1 or even a complete mold 100, the cells 10 of the mold 100 and cells 203 of the tray 200 of variable shape and specifically adapted to a particular product 300 can be generated.

The is an exploded perspective view of a mold 100 according to an alternative embodiment similar to that of Figures 6 and 7.

In particular, in this embodiment, the trenches 17 have a section in a semicircle, and not trapezoidal as in FIGS. 6 and 7. The frame 3, the peripheral shoulder 11a and the horizontal rim 13 of the honeycomb plate 1 remain however unchanged.

The shows two examples of strips 5 associated with this mold 100.
The first strip 5 shown is a “comb” strip 5. In this bar 5, the recesses 55 located between the teeth 53, to be flush with the wall of the trench 17 and extend it, are half-disc, corresponding in shape and dimensions with the section S of said trenches 17.

The second strip 5 shown in includes, starting from the left:
- an open section, with a hollow half-disc corresponding to the S section,
- a section comprising a wall partially closing the section S and a recess in the shape of a semicircle,
- a closed section, where the strip 5 has a continuous upper wall with the teeth 53 and thus covers the section S,
- A second section comprising a wall partially closing the section S and a recess in the shape of a semicircle.

It is thus possible to produce with the strips 5 walls similar to those generated in the case of trenches 17 with a trapezoidal section, in order to obtain walls at the level of the grooves 19 which can be closed, open, partially closed, or even adjusted to the cross section of the product 300 placed in the cells 203 of the plate 200 thermoformed by means of the mold 100.

Figures 11 to 14 illustrate the main steps of the thermoforming process associated with the molds previously described.

The first step illustrated in is the assembly of the mold 100 according to the required specifications. To do this, a honeycombed plate 1, a frame 3 and, if the mold 100 includes them, strips 5, of the required shapes and dimensions, are selected.

The mold 100 is then assembled from these elements.

The second step is the placement of the assembled mold 100 in a thermoforming chamber by pressure difference 400, comprising a bottom 401 and a lid 403, with a film of thermoplastic polymer 405 placed above the mold 100. The thermoforming chamber by pressure difference 400 is then closed by the cover 403 which grips the film of thermoplastic polymer against the bottom 401 in a sealed manner.

The differential pressure thermoforming chamber 400 closed with the thermoplastic polymer film 405 and the mold 100 in place is shown in .

Next, the vacuum thermoforming chamber 400 and in particular the thermoplastic polymer film 405 are heated until the thermoplastic polymer of the thermoplastic polymer film 405 softens.

The air between the thermoplastic polymer film 405 and the mold 100 is then sucked in by the air suction pipes in the case of vacuum thermoforming or else, in the case of overpressure thermoforming, air air or another gas is injected between the thermoplastic polymer film 405 and the cover 403, which stretches and presses the thermoplastic polymer film 405 against the upper surface of the mold 100, thereby shaping it.

The thermoplastic polymer film 405 thus deformed and the thermoforming chamber by pressure difference 400 with the mold 100 are shown in .

The thermoforming chamber by pressure difference 400 with the mold 100 and the thermoplastic polymer film 405 are, after that, cooled with a maintenance of the pressure difference, until the hardening of the formed thermoplastic polymer film 405 against the mold 100.

The portion of the thermoplastic polymer film 405 corresponding to the plate 200 is then cut (dotted lines ).

The mold 100 and the thermoplastic polymer film 405 are then extracted from the thermoforming chamber by pressure difference 400, and the thermoplastic polymer film 405 is separated from the mold 100.

The plate 200 thus obtained is shown in .

The molds 100 according to the invention thus make it possible to produce a very wide range of trays 200 without resorting to tailor-made machining, or by machining tailor-made only part of the mold 100 (dimpled plate 1 and/or strips 5).

The unit cost price of each tray 200 is consequently reduced so that users who, with the molds of the prior art, would have favored different packaging and handling solutions (individual overwrapping, cardboard, etc.), can thus having recourse to trays 200 thermoformed by vacuum or by overpressure.

Claims (12)

Mold (100) for thermoforming by pressure difference of honeycomb trays (200) for handling or packaging, comprising at least one honeycomb plate (1) forming, during thermoforming, a honeycomb bottom of the trays (200), and a frame (3) forming, during thermoforming, an outer rim (201) stiffening and vertical spacer of the plates (200), characterized in that the honeycombed plate (1) and the outer frame (3) are separated, and fit together two-by-two so as to be interchangeable with dimpled plates (1) and external frames (3) of different dimensions to allow adaptation of the dimensions and shapes of the cells (203) and of the external rim (201) of the trays ( 200) thermoformed by pressure difference. Mold (100) thermoforming by pressure difference according to claim 1, characterized in that the cellular plate (1) has cells (10) with a polygonal or circular bottom, separated by columns (11) and raised shoulders, machined in the honeycomb plate (1). Mold (100) thermoforming by pressure difference according to claim 1, characterized in that the at least one alveolate plate (1) comprises longitudinal trenches (17) whose section corresponds to the longitudinal section (S) of the alveoli (203) thermoformed trays (200), transverse grooves (19) passing through the at least one honeycomb plate (1) and a plurality of strips (5) of shape corresponding to the transverse grooves (19), machined so as to be flush with a bottom and vertical walls of the longitudinal trenches (17), or to form, during thermoforming, a transverse wall separating two cells (203) longitudinally adjacent to a plate (200). Mold (100) for thermoforming by pressure difference according to Claim 3, characterized in that the strips (5) comprise straight strips, of rectangular or trapezoidal shape, and machined strips (5) having recesses (55) corresponding to the longitudinal section (S) of the longitudinal trenches (17) so as to be flush with the bottom of the longitudinal trenches (17). Mold (100) for thermoforming by pressure difference according to Claim 3 or 4, characterized in that the trenches (17) have a longitudinal section (S) that is polygonal or in the portion of an ellipse. Mold (100) for thermoforming by pressure difference according to Claim 3, 4 or 5, characterized in that at least one of the strips (5) has a cutout in its upper part, at the level of at least one of the trenches ( 17) longitudinal when inserted into a groove (19), forming a wall partially closing said trench (17) longitudinal. Mold (100) for thermoforming by pressure difference according to Claim 3, 4 or 5, characterized in that at least one of the strips (5) has a cutout in its upper part, at the level of at least one of the trenches ( 17) longitudinal when inserted into a groove (19), adjusted to the section of a determined product (300), so that said product (300) bears against the wall (205) formed by the bar (5) when placed in the cavity (203) of the tray (200) formed by differential pressure thermoforming using the differential pressure thermoforming mold (100). Mold (100) for thermoforming by pressure difference according to Claim 7, characterized in that the cut-out of the upper part of the bar (5) has a recess for the passage of a finger. Mold (100) for thermoforming by pressure difference according to one of Claims 3 to 8, characterized in that the honeycombed plate (1), the outer frame (3) and/or the strips (5) comprise grooves (57 ) on their outer faces at their contacting edges, connecting, when assembled to form the differential pressure thermoforming mold (100), the upper and lower faces of the differential pressure thermoforming mold (100), so as to form air suction lines for thermoforming by pressure difference. Mold (100) for thermoforming by pressure difference according to the preceding claim, characterized in that the honeycombed plate (1) comprises bores (13a) forming air suction ducts distributed over its outer periphery, at the corner of a shoulder peripheral (11a) forming a guide for inserting the outer frame (3) and a horizontal rim (13) against which the outer frame (3) comes into vertical support during assembly of the mold (100) for thermoforming by difference pressure, and the outer frame (3) has recesses (35) at the locations vis-à-vis said holes (13a). Method of thermoforming by pressure difference of cellular trays (200) for handling or packaging by means of a mold (100) for thermoforming by pressure difference according to one of the preceding claims, characterized in that it comprises the steps :
selection of a honeycomb plate (1) and an outer frame (3) corresponding to the shapes and dimensions desired for the honeycomb tray (200),
assembly of the mold (100) for thermoforming by pressure difference from the selected honeycomb plate (1) and outer frame (3),
thermoforming by pressure difference of the honeycomb tray (200) by means of the assembled mold (100). Process according to the preceding claim, characterized in that:
the dimpled plate (1) comprises longitudinal trenches (17) whose cross section corresponds to the longitudinal cross section (S) of the dimples (203) of the thermoformed trays (200), transverse grooves (19) passing through the at least one dimpled plate (1) and a plurality of strips (5) of shape corresponding to the transverse grooves (19), machined so as to either be flush with a bottom and the vertical walls of the longitudinal trenches (17), or to form, during thermoforming, a transverse wall separating two longitudinally adjacent cells (203) from a plate (200),
the step of selecting a dimpled plate (1) and an outer frame (3) includes an additional sub-step of selecting the strips (5),
and in that the step of assembling the mold (100) for thermoforming by pressure difference comprises a sub-step of inserting the strips (5) into the transverse grooves (19) to longitudinally delimit the cells (203) of the honeycomb tray (200).