FR2845309A1 - Thermoforming mould e.g. for motor vehicle interior carpet has blank holder in form of upper and lower pressure elements - Google Patents

Abstract

The thermoforming mould (1) for a blank (2), comprising a matrix (3) and a die (4) that move relative to one another between open and closed positions, has a holder for the edge of the blank on one side of the mould. The blank holder consists of upper (5) and lower (6) pressure elements that can move to grip the edge of the blank. The thermoforming mould (1) for a blank (2), comprising a matrix (3) and a die (4) that move relative to one another between open and closed positions, has a holder for the edge of the blank on one side of the mould. The blank holder consists of upper (5) and lower (6) pressure elements that can move to grip the edge of the blank, with a clamp (7) in a cavity (8) between their surfaces to lock the blank between a matching rib and groove.

Description

The invention relates to a mold for thermoforming a blank, as well

  than a thermoforming process for a blank using this mold, and a cabin carpet

  motor vehicle comprising such a blank.

  In order to obtain a carpet intended for the passenger compartment of a motor vehicle, a blank is generally used, comprising a thermoplastic polymer material, which is capable of being hot formed. This blank is shaped by thermoforming, then is associated with a layer acting as a spring, such

  than a layer of foam or felt, to form the final piece.

  To implement the thermoforming process optimally, it is necessary to firmly hold the blank around the thermoforming mold, in order to avoid any undesired deformation of the material. To this end, it is known to place the blank on a peripheral holding device such as a frame 15 with pins, possibly associated with holding clips.

  Such pins penetrate into the blank at the periphery thereof, over an area of sufficiently large width to allow effective maintenance. During thermoforming, this peripheral zone comprising the pins must necessarily be left outside the mold.

  In addition, during a possible subsequent foaming step, in order to obtain a spring layer, the peripheral zone of the thermoformed blank must also be maintained outside the mold, since it then comprises orifices through which foam is likely to pass through

not desired.

  Such holding devices therefore have the drawback of damaging the periphery of the blank, which makes this zone unusable for the desired application. It is therefore essential to cut and discard this area of the carpet, this

  which leads to significant material losses.

  To remedy this drawback, and consequently reduce the costs associated with the use of such holding devices, the invention provides a mold for thermoforming a blank, comprising a device for holding the periphery of the blank, arranged to limit maximum material losses, without deteriorating said periphery, which allows it to be left as is on the mat.

  This device also has the advantage of ensuring optimal maintenance of the blank before closing the mold *, so that, during closing, the peripheral zone cannot slide inside the molding cavity. This would in fact lead to deformations of the blank which are troublesome for its shaping.

  To this end, and according to a first aspect, the invention provides a mold for thermoforming a blank, of the type comprising a matrix and a punch movable relative to each other between an open position, allowing the 15 arrangement of the blank inside the mold, and a closed position in which a molding cavity is formed between the die and the punch, said mold comprising a blank holding device which is provided at the periphery of the mold so as to maintain the blank on at least two of its opposite sides, said holding device comprising two pressing members 20 respectively lower and upper which are mutually movable by actuating means between a first position, in which they are distant from one 'other, and a second position, in which they are sufficiently close to each other to clamp the periphery of the blank, and at least one clamp intended to come and grip the blank at level of its periphery, said clamp being arranged to be housed in a housing provided in the pressing members, so that the contact zones between the blank and the

  holding device form parting line during thermoforming.

  According to a second aspect, the invention provides a method for thermoforming a blank using such a mold, comprising the following successive steps: - provision of a blank in the open mold; - grasping the periphery of the blank using pliers; - reciprocal movement of the lower and upper pressing members from their first to their second position, the clamps being housed in the housings provided for this purpose; - closing the mold so as to thermoform the blank; release of the thermoformed blank.

  According to a third aspect, the invention provides a carpet for a motor vehicle cabin, comprising a blank thermoformed by such a method, said blank comprising a layer of thermoformable material and a layer of textile covering.

  Other objects and advantages of the invention will become apparent during the course of the

  description which follows, made with reference to the appended drawings in which:

  - Figure 1 is a schematic perspective view of part of a mold according to the invention, showing according to a first embodiment the pressing members and a clamp holding a blank, the mold being in the open position; FIGS. 2a and 2b are schematic sectional views of part of the mold according to the invention, showing according to a second embodiment the pressing members holding a blank, the mold being respectively in the open position and in the closed position, - Figure 3 is a schematic perspective view of a clamp forming part of the holding device, according to one embodiment; - Figure 4 is a schematic perspective view of a portion of an upper pressing member showing a housing for the clamp of Figure 3, as well as hooking means of the periphery of the blank; - Figure 5 is a schematic perspective view of part of a lower pressing member showing the complementary housing of the housing

  Figure 4, as well as hooking means of the periphery of the blank.

  The mold 1 according to the invention, shown in FIGS. 1 and 2, is intended for thermoforming a blank 2, this blank 2 being for example used for making

  motor vehicle interior carpet.

  This mold 1 comprises a die 3 and a punch 4 movable relative to each other. In the open position, the die 3 and the punch 4 are sufficiently

  distant from each other to allow the introduction and arrangement of a blank 2 inside the mold 1. And, in the closed position, that is to say when the die 3 and the punch 4 are brought together one from the other, a mold cavity is formed between these two elements 3, 4, so as to allow the blank 2 to be shaped by thermoforming.

  It will be recalled that the thermoforming process typically consists in heating the blank 2 to its transformation temperature, in placing the blank 2 inside the mold 1, in shaping the blank 2 by relative approximation of the punch 4 and the matrix 3, to cool the thermoformed blank 2 and then to unmold it. The mold 1 according to the invention comprises a device for holding the blank 2, for firmly holding the latter during thermoforming. This device is provided at the periphery of the mold 1, so as to maintain the blank 2 on at least

two of its opposite sides.

  In the embodiments shown, the device maintains the blank 2 on two of its opposite sides. Figures 1 and 2 show a first part of the device, holding one side of the blank, the second part of the device being

  symmetrical to the first with respect to the center of the mold 1.

  The holding device shown in FIGS. 1 and 2 comprises two respectively upper 5 and lower 6 pressing members. These members 5, 6 are mutually displaceable by actuation means between two positions: a first position in which they are spaced apart. 'from each other, 5 and a second position in which they are close enough to each other to tighten the periphery of the blank 2. In the embodiments shown, these pressing members 5, 6 are formed of metal plates operable under sufficient pressure to be able to exercise effectively

their maintenance function.

  The holding device also comprises at least one clamp 7 arranged to be housed in housings 8 provided in the pressing members, 6, and intended to come to grip the periphery of the blank 2. According to the embodiment shown in FIG. 3 , this clamp 7 comprises two jaws 9, 10 respectively upper and lower, the ends 11 of which intended to grip the blank are oriented towards the inside of the mold 1. Each end 11 is formed of a flat part associated with the jaw 9, 10, so as to be actuated by it. The flat parts are wider, and protrude downward respectively for the jaw

  upper 9, and upwards for the lower jaw 10.

  According to this embodiment, the lower jaw 10 is movable in rotation relative to the upper jaw 9 by means of a cam 12 inserted into a slot 13 in the wall of said lower jaw 10, this slot 13 forming

cam path.

  The housings 8 of the pressing members 5, 6 intended to receive the clamp (s) 7, once closed (s), is formed by two recesses 14 provided in the thickness of the walls of said members 5, 6.

  The recess 14 of the upper pressing member 5 comprises, according to the embodiment shown in FIG. 4, two zones: a first zone 15, the depth of which is provided for receiving the upper jaw 9 of the clamp 7, and a second zone 16 of lesser depth, into which comes

  lodge the end 11 of the upper jaw 9.

  The recess 14 of the lower pressing member 6 comprises, according to the embodiment shown in FIG. 5, a first zone 23, the depth of which is provided for housing the lower jaw 10, and a second zone 24, of lesser depth , intended to accommodate the end 11 of the lower jaw 10. Each clamp 7 is therefore intended to be housed in a housing 8, respectively in a recess 14 in the upper member 5 for the upper jaw 9, and in the recess 14 complementary to the lower member 6

for the lower jaw 10.

  The number of pliers 7 used depends on the size of the blank 2 to be thermoformed.

  For example, for the thermoforming of a blank intended for a passenger compartment carpet of a motor vehicle, four clamps 7 can be provided equally spaced over the entire length of the pressing members 5, 6, and therefore 4 housings 8 intended respectively for receive them.

  The mold 1 according to the invention is arranged so that the contact zones 17 between the blank 2 and the holding device form a joint plane during thermoforming.

  In fact, these zones 17 are provided to be in continuity with the joint plane 25 18 of the mold 1 when the latter is in the closed position. Thus, during thermoforming, the holding device forms with the rest of the mold 1 a compact assembly, and maintains the blank 2 over a peripheral zone of width

  minimal, which limits material loss.

  According to one embodiment, shown in FIG. 1, the lower pressing member 6 is integrated into the die 3 of the mold 1, so that only the upper pressing member 5 is movable and moves in order to approach said said

lower organ 6.

  According to another embodiment, shown in Figures 2a and 2b, the two members 5, 6 are both movable, and are therefore movable

independently of each other.

  According to a variant not shown, it is possible to provide, in the walls of the mold 1, housings adapted to these members 5, 6, these housings comprising orifices allowing the means to pass through.

  actuation of their movement.

  The means for actuating the movement of the member or members are for example formed by jacks 19, as shown diagrammatically on the

Figures 1 and 2.

  To improve the holding of the blank 2, the surfaces 20 of the pressing members, 6 and of the clamp (s) 7 which are intended to be in contact with the

  periphery of the blank 2 comprise hooking means.

  According to one embodiment, the means for hooking the upper pressing member 5 and the upper jaw 9 of the clamp (s) 7

  are formed by a groove 21 extending over the entire length of said member 5 and the end 11 of said jaw 9, and the means for hooking the lower pressing member 6 and the lower jaw 10 of the (or) clamp (s) 7 are formed by a projection 22 extending over the entire length of said member 6 and 25 from the end 11 of said jaw 10.

  In particular, the groove 21 is of frustoconical shape (see FIG. 4) the projection 22

  corresponding being of complementary form.

  Thus, during thermoforming, when the mold 1 is closed, the hooking means of the clamp 7 disposed in the corresponding housing 8, come in continuity with the hooking means of the upper 5 and lower 6 members. The continuous projection 22 is therefore disposed in the continuous groove 21, the periphery of the blank 2 being held firmly between said groove 21 and

said projection 22.

  We will now describe, according to one embodiment, the steps of a process for thermoforming a blank 2 using such a mold 1. The blank 2 is first transported to a heating zone using of a first set of pliers which make it possible to maintain the periphery of the blank 2 during the transport thereof. The blank is then brought to its transformation temperature. It is then transported to the thermoforming mold 1,

  always using the first set of pliers.

  The clips 7 of the holding device then replace the first set of clips to hold the blank 2, the periphery of the latter being optimally stretched.

  Then the actuating means of the pressing members 5, 6 are put into operation, so as to allow the reciprocal movement of said

  organs 5, 6 from their first to their second position.

  In the embodiment shown in Figures 2a and 2b, the upper member 5, placed on the side of the punch 4, is moved down, that is to say towards the die 3 of the mold 1, and the lower member 6, placed on the side of the matrix

  3, is moved upwards, that is to say towards the punch 4.

  During this movement, the clamps 7 are housed in the housings

  8 of the members 5, 6 provided for this purpose.

  When the pressing members 5, 6 are in their second position, that is to say when they tighten the blank 2 optimally, the entire device constituted by the pressing members 5, 6 and the clamps 7 descends up to the level of the joint plane 18 of the mold 1. Thus, before the mold 1 is closed, the blank 2 is moved by means of the device for holding against the cavity of

  molding, its periphery being optimally maintained by said device.

  In the embodiment shown in FIG. 1, in which only the upper member 5 is movable, the periphery of the blank 2 is clamped by lowering the upper member 5 against the lower member 6, said organ

  lower 6 being integrated into the matrix 3.

  In a particular example, in which a blank 2 intended for a passenger compartment carpet 10 of a motor vehicle is formed, each pressing member 5, 6 of length

  substantially equal to 1.5 meters exerts on the blank 2 a pressure of the order of 300 kg, and the means for hooking the members 5, 6 and the clamps 7 respectively have a width of 50 mm. This arrangement makes it possible to firmly hold the periphery of the blank 2 without slipping of the latter inside the mold 1.

  In addition, provision may be made, in certain zones of the periphery of the blank 2, for the presence of additional clamps arranged to contribute to the maintenance of the blank 2 during thermoforming. These clamps are for example provided on the 20 flat zones of the periphery of the blank 2 which are not in contact with the holding device, in the case in particular where said device is present only on two opposite sides of the mold 1. They can also be provided on the curved zones of said periphery, in the case where the joint plane 18

  has a complex geometry surface.

  Then the mold 1 is closed so as to thermoform the blank 2, the pressing members 5, 6 then being arranged against the transverse external walls of the mold 1, in the case where these two members 5, 6 are movable (FIG. 2b ). And, once thermoformed, the blank 2 is demolded to obtain the final part 30.

  After demoulding, the blank 2 then comprises, by the presence of the attachment means of the holding device, a groove on at least part of its periphery, this groove not being a nuisance during any subsequent foaming steps of the final piece. And, during the subsequent use of the blank, its periphery does not require trimming since it is not

  deteriorated as is the case with spikes.

  As stated previously, this part can be a passenger compartment carpet of

motor vehicle.

  In this case, the blank 2 comprises a layer of thermoformable material, such as a layer of thermoplastic polymeric material, associated with a layer

textile coating.

  The thermoplastic polymer can be of the EPDM (ethylenepropylene monomer) or PVC type, and the textile layer is for example a nonwoven layer, of polyester type or polyester / polypropylene mixture.

  The mat may further comprise, associated with the blank 2, a support, in particular made of foam or felt. For this purpose, the blank 2, once thermoformed, is associated with the support layer, so as to obtain a passenger compartment carpet having both an aesthetic function and an acoustic insulation function.

Claims (9)

  1. Mold (1) for thermoforming a blank (2), of the type comprising a matrix (3) and a punch (4) movable relative to each other between an open position, allowing the arrangement blank (2) inside the mold (1), and a closed position in which a molding cavity is formed between the die (3) and the punch (4), said mold (1) comprising a holding device of the blank (2) which is provided at the periphery of the mold (1) so as to hold the blank (2) on at least two of its opposite sides, characterized in that the holding device comprises two pressing members respectively upper (5) and lower (6) which are mutually movable by actuating means between a first position, in which they are distant from each other, and a second position, in which they are sufficiently close together on the other to tighten the periphery of the blank (2), and at least one clamp (7) intended to grip the blank (2) at its periphery, said clamp (7) being arranged to be housed in a housing (8) provided in the pressing members (5, 6), so that the contact zones ( 17) between the blank (2) and the   holding device form parting line during thermoforming.   2. Mold according to claim 1, characterized in that the surfaces (20) of the pressing members (5, 6) and of the clamp (7) which are intended to be in contact with the periphery of the blank (2) comprise hanging means. 3. Mold according to claim 2, characterized in that the attachment means of the upper member (5) and the upper jaw (9) of the (or) clamp (s) (7) are formed of a groove (21), the means for hooking the lower member (6) and the lower jaw (10) of the clamp (s) (7) being formed by a projection (22) , so that, during thermoforming, the projection (22) is arranged in the groove (21) so substantially continuous.   4. Mold according to one of claims 1 to 3, characterized in that the member   lower (6) is integrated into the matrix (3) of the mold (1).   5. Mold according to one of claims 1 to 3, characterized in that the two members (5, 6) are movable independently of one another and are   arranged, during thermoforming, against the external transverse walls of the mold (1).   6. Method for thermoforming a blank (2) using a mold according to one of   Claims 1 to 5, comprising the following successive steps:   - provision of a blank (2) in the open mold (1); - gripping the periphery of the blank (2) using the pliers (7); - reciprocal movement of the upper (5) and lower (6) pressing members from their first to their second position, the clamps (7) being housed in the housings (8) provided for this purpose; - closing the mold (1) so as to thermoform the blank (2);   - release of the thermoformed blank (2).   7. Method according to claim 6 when it does not depend on claim 4, characterized in that, before the mold is closed (1), the blank (2) is moved by means of the holding device against the cavity of molding.   8. Motor vehicle interior carpet, characterized in that it comprises a blank (2) thermoformed by a method according to one of claims 6 or   7, said blank (2) comprising a layer of thermoformable material and a textile coating layer.   9. Carpet according to claim 8, characterized in that it further comprises, associated with the blank (2), a support in particular made of foam or felt.