Title: Device for making a part made of a reinforced material by overmolding
Abstract: The invention relates to a picking-up device and assembly for making a part made of a reinforced plastics material in a mold. The picking-up device includes at least one presser having a shaped front face and first needles mounted to have end portions that project beyond the front face in one position and retract so as to be set back from the front face in a second position. The picking-up device may have a base mounted to move relative to the picking-up device. A production line may be formed from use of two picking-up devices.
Patent Number: 6,893,247 Issued on 05/17/2005 to Uytterhaeghe, et al.
| Inventors:
|
Uytterhaeghe; Luc (Arbent, FR);
Blanchon; Charles-Guillaume (Oyonnax, FR);
Chene; Anthony (Oyonnax, FR);
Charpy; Robert (Bellignat, FR)
|
| Assignee:
|
Compagnie Plastic Omnium (Lyons, FR)
|
| Appl. No.:
|
283271 |
| Filed:
|
October 30, 2002 |
Foreign Application Priority Data
| Current U.S. Class: |
425/397; 294/61; 414/19; 425/400; 425/403 |
| Intern'l Class: |
B29C 070/42 |
| Field of Search: |
425/397,400,394,403,405.1
294/61
414/19,802
|
References Cited [Referenced By]
U.S. Patent Documents
| 4124242 | Nov., 1978 | Canner.
| |
| 4571320 | Feb., 1986 | Walker.
| |
| 4946551 | Aug., 1990 | Ishige et al.
| |
| 4961700 | Oct., 1990 | Dunbar.
| |
| 5388978 | Feb., 1995 | Bellettato.
| |
| Foreign Patent Documents |
| 0 480 652 | Apr., 1992 | EP.
| |
| 0 588 363 | Mar., 1994 | EP.
| |
Primary Examiner: Nguyen; Thu Khanh T.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Parent Case Text
This is a Division of Application No. 09/548,342 filed Apr.
12,
2000
now U.S. Pat. No. 6,495,086.
Claims
1. A picking-up device, comprising:
at least one presser that has a front face;
first needles passing through the presser, each having an end portion; and
second needles that slope relative to the first needles;
wherein the first needles are mounted to move relative to the presser so that
in a first configuration, the end portions of the first needles project beyond
the front face of the presser, and, in a second configuration, the end portions
are set back from the front face of the presser.
2. The picking-up device according to claim 1, wherein the second needles are
mounted to move relative to the presser.
3. The picking-up device according to claim 1, wherein the second needles have
a fixed angle relative to the first needles.
4. The assembly according to claim 3, further comprising abutments movably mounted
on the base and configured to engage over the picking-up device for entraining
the picking-up device when the base is displaced to pull on the picking-up device.
5. The assembly according to claim 4, wherein the base has arms and the abutments
are movably mounted at ends thereof.
6. The assembly according to claim 4, wherein the picking-up device comprises
at least one beam on which the pressers are disposed, and wherein when the abutments
are engaged over the picking-up device, the abutments abut against the at least
one beam.
7. The assembly according to claim 6, wherein the pressers are fixed to the at
least one beam through springs.
8. The picking-up device according to claim 1, wherein the at least one presser
includes through bores in which the first needles and the second needles are received.
9. The picking-up device according to claim 1, wherein the at least one presser
includes a front presser and side pressers.
10. The picking-up device according to claim 1, wherein the picking-up device
includes an inflatable insert that moves apart two elongate blocks of the at least
one presser.
11. An assembly for applying a sheet against a first mold portion, comprising:
the first mold portion, and
a picking-up device including:
at least one presser that has a front face shaped like a region of the first
mold portion and capable of pressing a portion of a sheet against the first mold
portion, and
first needles passing through the presser, the first needles being movable relative
to the presser and capable of spearing the sheet.
12. The assembly according to claim 11, wherein the first mold portion has an
outer side wall, and the base comprises a frame that is slidable in contact with
the outer side wall.
13. The assembly according to claim 11, further comprising a manipulator arm
carrying the picking-up device.
14. A production line for manufacturing parts made of a plastics material reinforced
by overmolding sheets, the production line comprising:
a mold having a first mold portion and a second mold portion movable relative
to each other in order to close the mold;
a place of storage;
a heating oven;
a pre-forming station;
a first picking-up device comprising at least one presser that has a front face
shaped like a region of the first mold portion and capable of pressing a portion
of a sheet against the first mold portion, and first needles passing through the
presser, the first needles being movable relative to the presser and capable of
spearing a sheet, wherein the first picking-up device is configured to transfer
a sheet from the pre-forming station to the mold; and
a second picking-up device configured to handle cold sheets so as to bring them
firstly from the place of storage to the heating oven in which they are heated,
then from the heating oven to the pre-forming station where they are shaped substantially
to match the relief of the first mold portion.
15. The production line according to claim 14, wherein the second picking-up
device is equipped with a suction system which is suitable for picking-up cold
sheets so as to transfer them to the heating oven.
16. The assembly according to claim 11, further comprising a base mounted to
move relative to the first mold portion and configured to pull the picking-up device
towards the first mold portion and to press the sheet thereagainst.
17. The assembly according to claim 11, wherein the at least one presser includes
through bores in which the first needles are received.
18. The assembly according to claim 11, wherein the at least one presser includes
a front presser and side pressers.
19. The assembly according to claim 11, wherein the picking-up device includes
an inflatable insert that moves apart two elongate blocks of the at least one presser.
20. The production line according to claim 14, wherein the second picking-up
device comprises a needle system capable of picking-up heated sheets.
21. The production line according to claim 14, wherein the at least one presser
comprises through bores in which the first needles are received.
22. The production line according to claim 14, wherein the at least one presser
includes a front presser and side pressers.
23. The production line according to claim 10, wherein the first picking-up device
includes an inflatable insert to move apart two elongate blocks of the at least
one presser.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method of making a part made of a reinforced
plastics material by overmolding a sheet, to a device for implementing the method,
and to an assembly and to a production line including said device.
It is already known that single-layer sheets can be used to make parts made of
plastics materials and having a certain stiffness, in particular for making structural
parts of motor vehicles.
For example, with the material known as stampable reinforced thermoplastic (SRT),
which is polypropylene reinforced with glass fibers, the method consists in heating
sheets of SRT, then in depositing them in an open mold, and then in closing the
mold to cause the plastics material to flow and to fill the cavity of the mold.
It is also known that multi-layer materials can be used that are obtained by
superposing
sheets of SRT and sheets of Twintex (a trademark of Verotex), Twintex being a woven
sheet of commingled glass fibers and polypropylene fibers.
The Twintex sheets become soft during the heating prior to placing the lay-up
of superposed sheets in the mold, but the SRT sheets are stiff enough to enable
the heated material to be handled.
In contrast, when one or more sheets of Twintex only are to be overmolded, it
is difficult to place them in the mold because the heated Twintex sheets are too
soft and therefore difficult to handle.
As a result, the only known methods of overmolding sheets of Twintex consist
in
conveying the sheets horizontally from a heating station to the mold, which mold
is mounted on a vertical press so that the portion of it that is to receive the
sheet(s) of Twintex is horizontal.
This difficulty of handling heated sheets of Twintex therefore imposes, as a
first limit to their being overmolded, the obligation of using molds that are mounted
on vertical presses.
In addition, conveying the sheet of Twintex does not enable it to be positioned
accurately enough in the mold. As a result, it is preferred to leave a safety margin
by cutting the sheet of Twintex larger than necessary so as to make sure that it
extends over the entire desired area of the part to be made, even if the edges
of the sheet of Twintex that project beyond the periphery of the part then need
to be cut off after the part has been molded.
A second limit to overmolding sheets of Twintex lies in the fact that the resulting
parts must be trimmed after they have been molded.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method that solves all or
some
of the above-mentioned problems.
The present invention provides, in particular, a method of making a part made
of a reinforced plastics material in a mold comprising at least two portions and
from a reinforced sheet or from a lay-up of reinforced sheets comprising at least
one reinforced sheet, in which method the reinforced sheet is pre-heated, said
method being characterized by the fact that it comprises the following steps:
the reinforced sheet or said lay-up of reinforced sheets is presented to a first
portion of the open mold by means of a picking-up device including pressers;
at least a region of the reinforced sheet or of said lay-up is applied against
a corresponding region of the first mold portion by means of pressers on the picking-up device;
the remainder of its surface is applied against said first mold portion while
holding stationary said region of the reinforced sheet or of said lay-up;
the mold is closed; and
the resulting part is removed from the mold.
In the description below, the term "application portion" is used to designate
that portion of the mold against which the reinforced sheet is applied.
The picking-up device may optionally be used to apply the remainder of the surface
of the sheet or of said lay-up against the first portion of the mold.
It is possible to superpose a plurality of sheets in the mold, optionally with
local reinforcements sandwiched between the sheets.
The above-mentioned region may correspond to at least one edge, and preferably
both edges of the reinforced sheet or of said lay-up, or, in a variant, to a central zone.
The method of the invention offers the essential advantage of making it possible
to automate positioning of the sheet or of said lay-up.
It can also make it possible to omit the trimming step consisting in cutting
off
the edges of the sheet or of said lay-up that project beyond the part obtained
after overmolding. This is achieved because the edges of the sheet or of said lay-up
can be positioned accurately relative to the mold. Once this positioning has been
performed, the remainder of the sheet or of said lay-up is applied against the
remainder of the first portion of the mold.
Use is thus made of the absence of stiffness of the sheet or of said lay-up to
press it against the first portion of the mold, without it projecting from the
periphery of the mold.
In a particular implementation, pressers are used that comprise rigid chocks
mounted
on actuators.
In a variant, a rigid chock comprises a plurality of elements separated by inflatable
inserts that space them apart so that the chock hugs the shape of the first mold
portion as well as possible.
The pressers may also be constituted by inflatable cases which, in the inflated
state, exactly match the shape of the first mold portion.
In order to position it accurately on the first mold portion, the sheet or said
lay-up is advantageously retained by needles disposed on the picking-up device.
When sheets and/or local reinforcements are superposed, such needles advantageously
serve to hold the various superposed layers in position relative to one another,
by being inserted into the lay-up.
Preferably, the needles are mounted on the same support as the pressers.
In a particular implementation, the needles are substantially parallel to the
direction in which the mold closes.
Preferably, certain needles may be suitable for moving sideways to accommodate
the deformations of the sheet or of said lay-up, when said sheet or said lay-up
adapts its surface to fit the real surface of the application portion of the mold.
This adaptation may also be referred to as "draping", the initial surface of
the sheet or of said lay-up being plane and corresponding to the developed surface
area of the application portion of the mold, while the final surface of the sheet
or of said lay-up has all of the relief of the application portion of the mold.
The needles mounted to move sideways are particularly useful when the sheet or
said lay-up is not pre-shaped to the relief of the first portion of the mold.
In order to preform the sheet or said lay-up, it is possible, in a particular
implementation, to deposit it on a rack of suitable shape and to heat it, e.g.
by inserting it in an oven.
Pre-forming the sheet or said lay-up may further be supplemented prior
to being put in place in the mold, by acting on the sheet or said lay-up at an
intermediate station lying between the place at which the sheets are picked up
and the mold.
In a particular implementation, the mold has a join plane that is substantially vertical.
The picking-up device may be carried by a manipulator arm which exerts the mechanical
forces necessary to apply the sheet or said lay-up against the first portion of
the mold.
In a variant, the picking-up device may be pulled towards the first mold portion
to press the sheet or said lay-up thereagainst by means of a base mounted to move
relative to the first mold portion.
This makes it possible to relieve the manipulator arm and to use a manipulator
arm that is less powerful and therefore less costly.
Advantageously, abutments mounted to move relative to the base are
used to entrain the picking-up device, these abutments being disposed to come into
engagement over the picking-up device when the base is in the "out" position, and
then remaining in place when the base is displaced to pull on the picking-up device.
In a particular implementation, the sheet or said lay-up is overmolded as applied
against the first mold portion, i.e. a complementary quantity of plastics material
is inserted into the mold in order to fill the entire cavity of the mold, it being
possible for the filling to take place by depositing material in the open mold
or by injecting material into the closed mold.
The present invention also provides a picking-up device for taking hold of one
or more sheets.
This device comprises at least one presser that has a front face shaped like
a region of a first mold portion, e.g. a portion of its periphery or a central
zone, and first needles passing through said presser, which needles are mounted
to move relative to the presser so that, in a first relative configuration of the
presser and of the needles, the needles include end portions projecting beyond
the front face of the presser, and, in a second relative configuration of the presser
and of the needles, the same end portions of the needles are situated set back
from the front face of the presser.
This device is used as follows.
With the presser(s) lying in the first configuration relative to the needles,
the sheet is speared, e.g. at its periphery, with the end portions of the needles
that project from the presser(s).
The sheet as held by the needles is then brought facing the first portion of
the mold, and the device is move towards the mold so that the ends of the needles
come flush with a predetermined region of the first portion of the mold, e.g. its periphery.
The presser(s) is/are then moved towards the first portion of the mold, while
holding the needles in position relative thereto.
As a result, the needles are bared, and once the pressers have reached the second
configuration relative to the needles, the sheet is then held only by compression
between said pressers and the first portion of the mold.
A retaining system which may, for example, be constituted by needles or by any
other mechanism integrated in the mold, then takes over from the pressers by holding
the sheet in position in the mold, thereby making it possible to withdraw the picking-up
device and to close the mold.
It can be understood that the device of the invention is particularly well suited
to handling a sheet or a lay-up of sheets that is to be positioned vertically in
a mold mounted on a horizontal press.
In a particular embodiment of the device, other needles that slope relative to
the first needles serve to retain the sheet when the pressers lie in the first
configuration relative to the needles.
The crossing over of the two sets of needles holds the sheet stationary on the
device, thereby making it possible, in particular, to pick up a sheet from a horizontal plane.
The present invention also provides an assembly for applying a sheet against
a first mold portion, said assembly being characterized by the fact that it includes
the above-described picking-up device and a base mounted to move relative to the
first mold portion so as to pull the picking-up device towards the first mold portion
and to press the sheet or said lay-up thereagainst.
By means of this assembly, it is possible to avoid the need to use heavy-duty
mechanical means to manipulate the picking-up device.
The base can deliver most of the forces necessary to applying the sheet against
the first mold portion.
The assembly may include abutments mounted to move relative to the base, and
suitable for engaging over the picking-up device when the base is in an "out" position,
then for entraining the picking-up device when the base is displaced to pull on
the picking-up device.
Preferably, the abutments are disposed at the ends of arms secured to
the base.
In a particular embodiment, when the abutments are engaged over the picking-up
device, they abut against at least one beam that is secured to the picking-up device
and on which pressers are disposed.
Pressers may be fixed to the beam(s) in question with springs being interposed.
Advantageously, the mold has an outer side wall, and the base includes
a frame that can slide in contact with said side wall.
The base being disposed on the first mold portion is particularly simple to implement,
and also guarantees that the base is moved accurately relative to the first mold portion.
Preferably, the picking-up device is secured to a manipulator arm.
The manipulator arm may be released when the picking-up device is pulled by the
base towards the first mold portion.
The present invention also provides a production line for manufacturing parts
made of a plastics material reinforced by overmolding sheets, said production line
being characterized by the fact that it includes a first picking-up device as described
above, and a second picking up device serving to handle cold sheets so as to bring
them firstly from a place of storage to an oven in which they are heated, then
from the heating oven to a pre-forming station where they are shaped substantially
to match the relief of the mold, the first picking-up device transferring the heated
and pre-formed sheets to a mold.
In an advantageous variant, the second picking-up device is equipped both with
a suction system which is suitable for picking-up cold sheets so as to transfer
them to the heating oven, and also with a needle system which is suitable for picking
up the heated sheets so as to transfer them to the pre-forming station, and then
from the pre-forming station to the mold.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to make the invention better understood, embodiments are described below
by way of examples that do not limit the scope of the invention, and with reference
to the accompanying drawings, in which:
FIG. 1 is a section view showing a punching die of a mold serving to make a
part of complex shape, and a plane reinforcement sheet that is to be put in place
on said die;
FIG. 2 is a section view of a picking-up device provided with needles, the device
being shown as it is about to pick up the reinforcement sheet;
FIG. 3 is a view analogous to FIG. 2, showing the device and the sheet during
pre-forming, immediately before the reinforcement sheet is deposited on the die;
FIG. 4 is a view analogous to the preceding figures, showing the reinforcement
sheet in its ultimate draped state;
FIG. 5 is a perspective view of a presser provided with needles of the device
of FIGS. 2 to 4;
FIG. 6 is a perspective view of a presser provided with an inflatable insert;
FIG. 7 is an overall perspective view of a production line for manufacturing
reinforced parts;
FIG. 8 is an elevation view of a bumper beam;
FIG. 9 is a view from above of FIG. 8; and
FIG. 10 is a diagrammatic perspective view of an assembly including the picking-up
device and a base mounted to move relative to a first portion of the mold.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In section, the punching die shown in FIG. 1 has relief
2 in its central
portion, this relief itself being provided with a groove
3.
The die
1 serves to make a bumper beam for a motor vehicle.
The beam is made of polypropylene mixed with glass fibers and reinforced with
a sheet
4 of a fiber-reinforced plastics material of the Twintex type.
The sheet of Twintex is rectangular, its width corresponding to the developed
width of the die, which width is constant.
As described below, firstly the reinforcement sheet
4 is heated.
Once it has been heated, it is put in place over the die by means of a picking-up
device
5 comprising two positioning side pressers
6a and
6b
and a draping central presser
7, which pressers are mounted on a slide
rail
8 via actuators
9.
Each of the pressers is shown in detail in FIG. 5 from which the actuators have
been omitted for reasons of clarity.
Each presser is made up of an elongate block
10 provided with two sets
of through bores
11, the first set of bores being perpendicular to the join
plane of the mold, i.e. to the front face
12 of the presser, and the second
set slants relative to the first set.
Each set of bores
11 receives a respective set of needles
13 moved
by actuators
13a. The two sets of needles
13 cross in the
vicinity of the front face
12 of the presser, each set of needles being
mounted to slide axially relative to the presser.
As shown in FIG. 2, the two positioning side pressers
6a and
6b
and the draping central presser
7 are secured to the sheet of Twintex
by the crossing over of their respective sets of needles
13.
One of the side pressers (
6b, i.e. the side presser on the right
of the figures) is then moved in translation towards the center of the device,
while the central presser
7 is placed above the initial plane of the sheet
of Twintex, thereby pre-forming the sheet to the general relief of the die, as
shown in FIG.
3.
The sheet, as thus roughly pre-formed, is then conveyed to the die, against which
it is applied, firstly via its edges that coincide with the periphery of the die,
by means of the side pressers
6a and
6b, then by means
of the draping central presser
7 which presses the central zone of the sheet
of Twintex against the bottom of the groove
3.
It is then necessary merely to withdraw the picking-up device and to close the
mold in order to overmold a reinforced beam, from which beam no edge of the sheet
of Twintex projects.
FIG. 6 shows a variant of the draping central presser
7′ which
is made up of two elongate blocks
7′
a and
7′
b,
one of which (
7′
a) is secured to the actuators
9′
that connect it to the slide rail, and the other of which (
7′
b)
is connected to the first block
7′
a via a transverse slide
mechanism (not shown).
As shown by the arrows
15 and
16 in FIG. 6, the insert
14
being inflated moves the two elongate blocks apart and applies the reinforcement
sheet firmly against the walls of the groove
3 in the die.
As a result, the reinforcement sheet is draped optimally over the die, the edges
of the reinforcement sheet also being suitably positioned and held by the side
pressers of the device.
As shown in the overall view given in FIG. 7, a mold
17 is mounted on a
vertical press, and a picking-up device
18 of the above-described type is
mounted in the vicinity of said mold.
The device is mounted on a rail which makes it sufficiently mobile to move towards
and away from the mold
17.
The reinforced sheets picked up by the picking-up device for the purposes of
pre-forming them and putting them in place in the mold have been heated and optionally
preformed on stations further up the production line.
From upstream to downstream, the production line is made up of a loading station
19 on which an operator places cold reinforcement sheets, of an infrared
oven
20 which heats individually each reinforcement sheet that is placed
on the loading station and delivers it at the end of the oven that is further from
the loading station, and of a second picking-up device
21 which picks up
the heated sheets and can place them in two different places depending on the type
of part to be made.
For a part using a plurality of reinforcement sheets, the second picking-up device
21 stacks up the reinforcement sheets exiting from the oven and then, when
there are enough of them, places them on a pre-forming rack. The sheets as stacked
up for pre-forming purposes are inserted into a hot-air oven
22 so as to
bring them to the temperature at which they were on exiting from the infrared oven
20.
For a part using a single reinforcement sheet, the second picking-up device
21
makes the reinforcement sheets available directly to the first picking-up device
18 so that they can be placed immediately in the mold
17.
It should be noted that the picking-up device
18 made up by pressers each
having two sets of needles is particularly well suited to handling heated reinforcement
sheets of the Twintex type, and to handling them in a vertical position, as applies
in the production line shown in FIG.
7.
Firstly, the heated sheets are easy to spear, and secondly the heated sheets
are easy for the needles to hold because said needles are perpendicular to the
plane of the sheet.
In addition, the vertical position of the sheet makes it possible to remove firstly
the slanting set of needles on putting the draped sheet in place in the mold, without
said sheet being released from the picking-up device.
Once the slanting needles have been removed, the presser(s) can be moved towards
the mold by baring the needles which then serve as guides for holding the reinforcement
sheet in position in the mold.
Thus, the needles serve not only to pick up the sheet, but also to position
it accurately in the mold.
In the example shown in FIGS. 8 and 9, the beam
23 is of symmetrical shape
over a portion
24 of its length and of asymmetrical shape over the remainder
25 of its length. FIG. 9 shows dot-dash lines
26 joining up the middles
of the widths of the beam before and after draping, and it can be observed that
these lines are separate in the portion
25 of the beam.
This non-coincidence of the middles of the widths might pose a problem for draping
the reinforcement sheet if said draping were performed in this embodiment by starting
from the center of the part to be made.
However, in this embodiment of the invention, the reinforcement sheet is
positioned via its edges which are applied firstly against the periphery of the
mold, so draping the reinforcement sheet over a non-symmetrical die raises no difficulty.
That is why applying the pressers against the zones
27 shown in bold
lines in FIG. 8 makes it possible to obtain the non-symmetrical beam shown in FIGS.
8 and 9.
Naturally, the above-described embodiments are in no way limiting, and
any desirable modifications may be made to them without going beyond the ambit
of the invention.
For example, as shown in FIG. 10, it is possible to make an assembly serving
to make it possible to use a manipulator arm that is less powerful.
In addition to a picking-up device
30, the assembly comprises a base
43
that is mounted to move relative to a first mold portion
40 and that is
suitable for pulling the device
30 onto said mold portion to press a sheet
4 against it.
The picking-up device
30 is secured to a manipulator arm
31 and
it includes three central pressers
32 and four peripheral pressers
35
that are shorter than the central pressers
32 and that are disposed substantially
at the four corners of the picking-up device.
Each presser
32 or
35 has a front face
38 for applying
the sheet
4 against the first mold portion
40, and a rear face
39.
The pressers
32 and
35 are supported by a set of parallel beams
comprising a central beam
36, and two side beams
33 that extend over
substantially the entire width of the sheet
4.
The central pressers
32 are fixed to the beams
33 and
36
with springs
34 being interposed that come into abutment at one end against
the beams
33 and
36, and at the other end against their rear faces
39.
The peripheral pressers
35 may optionally be moved relative to the beams
33 while the sheet
4 is being draped over the mold portion
40
and they are provided with sets of straight needles
50 and with sets of
slanting needles, as in the above-described embodiments.
The springs
34 make it possible for the pressers
32 to adapt to
fit the shape of the first mold portion
40 on clamping the picking-up device
30 thereagainst.
In a variant, it is possible to replace the springs
34 by actuators.
However, the use of springs offers the advantage of being simpler and lower
in cost than the use of actuators.
The first mold portion
40 is suitable for cooperating with a second mold
portion (not shown) on closing the mold, the two mold portions being mounted on
a horizontal press.
The mold portion
40 has a die
41 provided with a central groove
and serving to shape the sheet
4 so as to form a beam for a motor vehicle.
It also has a plane peripheral surface
42 around the die
41 and
serving as an abutment surface for the peripheral pressers
35.
The mold portion
40 has an outer side surface
45 on which the base
43 slides, which base is mounted to move in a direction a.
The base
43 includes a rectangular frame on which four arms
44
are disposed, which arms extend towards the second mold portion.
Each of the arms
44 is provided with an abutment
47 that is mounted
to move in a direction b that is perpendicular to the direction a, each abutment
47 being suitable for coming into abutment against one of the rear faces
of the beams
33 when the base
43 is in an "out" position.
A description follows of the steps of an operation of draping the sheet
4
over the first mold portion
40 by means of said assembly, the base
43
being initially in an "out" position in which the abutments
47 have been
moved to the maximum extent towards the second mold portion.
The picking-up device
30 starts by picking up a hot sheet
4 and
presenting it to the first mold portion
40.
The picking-up device
30 then applies the sheet
4 against the first
mold portion
40 by exerting a small pressure on the sheet
4 so as
to hold it against said mold portion.
The central pressers
32 engage over the die
41 and they hold the
sheet
4 stationary relative to the first mold portion at the level of said die.
The sheet
4 is thus brought into register relative to the first mold portion.
The abutments
47 are then actuated so as to come into abutment against
the rear faces of the beams
33.
The manipulator arm
31 is declutched, and the base
43 is displaced
by means of an actuator drive mechanism (not shown) over a predetermined distance
away from the second mold portion so as to pull on the picking-up device
30.
The central pressers
32 hold the sheet
4 applied against the die
41 and stationary relative thereto.
Then the abutments
47 are displaced towards the outside of the first
mold portion
40, and the picking-up device is removed, the sheet
4
being held pressed against the first mold portion
40 by retaining means
(not shown) until the mold is closed.
The use of the base
43 makes it possible to prevent the manipulator arm
31 from having to exert large forces in order to press the sheet
4
against the first mold portion
40, the forces necessary to clamp the picking-up
device
30 against the first mold portion
40 being delivered substantially
by the displacement of the base
43.
*
