Apparatus for Producing a Thermoplastic Article Having an Undercut Cross-Section

The present invention relates to equipment for producing an article made of thermoplastic material and having an undercut cross-section, particularly for internal linings for motor vehicles, such as an internal door-lining panel or a vehicle door-handle integral with the lining panel or fixable thereto.

Although the invention has been developed with particular reference to components for the internal fittings of motor vehicles, it is not intended to be limited to this field and can be used whenever it is desired to produce a component having an undercut cross section and composed of a sheet of thermoplastic material which may be covered and which is shaped by thermal compression-moulding.

In the specific field of the moulding of sheets of thermoplastic material, considerable difficulties are encountered in the production of the dies when a component with an undercut cross-section is to be produced. In fact, the conventional technique for the thermal compression-moulding of sheets of thermoplastic material consists of compressing the sheet to be moulded between the shaping surfaces of two moulding elements, which involves the need to form the moulding elements with movable portions in order to produce projections which are disposed at angles of less than 90.degree. to the direction of the relative movement of the moulding elements.

In older to overcome the aforementioned problems, the subject of the present invention is equipment for producing a component of a thermoplastic material and having an undercut cross-section, particularly a handle for motor-vehicle doors, comprising a first moulding element having a working surface the shape of which corresponds to a portion of an outer surface of the component when completed; a second moulding element having a shaping surface which, in a moulding operation, is spaced from the working surface of the first moulding element by a distance substantially corresponding to a thickness of the thermoplastic material; a pair of sliders, at least one of the sliders being disposed in slidable engagement with the first moulding element and defining a cavity having a working shaping surface, the slider being movable from an inoperative position wherein the cavity is spaced from the working surface of the first moulding element, to an operative position wherein the surface of the cavity is a continuation of the working surface of the first moulding element; and a compressed-air supply means carried by the second moulding element, for directing jets of compressed air against the edges of the thermoplastic material to deform the edges thereof and force them into the cavity to provide an undercut cross-section to the component upon completion of the moulding operation.

The present invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which:

FIG. 1 is a schematic, perspective view of a motor-vehicle door having an article produced by equipment according to the present invention,

FIG. 2 is a section taken on the line II--II of FIG. 1,

FIGS. 3 and 4 are schematic views showing the operation of a first embodiment of equipment according to the invention, and

FIGS. 5 and 6 are schematic views showing the operation of a second embodiment of the equipment according to the invention.

With reference to FIG. 1, a motor-vehicle door is indicated 1 and a lining panel 2 with a handle 4, which also forms an armrest 6, is fitted on the inner side thereof. The handle may be constituted by a separate component fixed to the lining panel 2 or may form an integral part thereof.

As can be seen in FIG. 2, the handle 4 has an undercut cross-section having a generally channel-shaped configuration with an arcuate portion 8 and two ends 10 which face one another.

With reference now to FIGS. 3 and 4, the handle is produced by a thermal compression-moulding process, starting with a previously-heated sheet 12 of thermoplastic material to the outer surface of which an aesthetic covering 14 is applied. A first moulding element, indicated 76, has a working surface 18 of a shape corresponding to that of the arcuate-profiled portion 8 of the handle 4. Two sliders, indicated 20, are movable between the inoperative positions of FIG. 3 and the operative positions of FIG. 4 and have respective working surfaces 22 which, in the operative positions of FIG. 4, are connected to the working surface 18 of the first moulding element 16.

The equipment also comprises 0 second moulding element 24 which is movable relative to the first moulding element 16 between the two operative positions shown in FIGS. 3 and 4. The second moulding element 24 has a shaping surface 26 which is intended to be urged against a portion of the inner surface of the sheet 12. The shaping surface 26 of the moulding element 24 has one or more seats for housing respective fixing members 28 each constituted by a metal plate having fixing appendages 30 to which a screw 32 is fixed.

A duct 34 in the second moulding element 24 is connected to a compressed-air source (not shown). The duct 34 communicates with a series of holes 36 in the outer surface of the element 24, near its upper end.

The sheet 12 of thermoplastic material is supported in a semi-plastic state on top of the second moulding element 24, after the fixing members 28 have been positioned in the respective seats. The sheet 14 of covering material is kept extended above the sheet 12. The second moulding element 24 is then brought alongside the first element 16 so as to bring the sheet 12 towards the surface 18 of the first moulding clement 16. The covering sheet 14 thus remains interposed between the working surface 18 and the outer surface of the sheet.

The two sliders 20 are then brought to their operative configurations shown in FIG. 4. In this configuration, the sliders 20 define two cavities 38 with undercut cross-sections, each of which encloses a portion 12a of the sheet 12, a corresponding portion of the covering 34, as well as a hole 36 for the supply of compressed air. As the sliders 20 move from the positions of FIG. 3 to those of FIG. 4, they bond the ends of the sheet 12 towards one another. The handle 4 is formed by the supply of a powerful jet of compressed air into the region 38, by means of the duct 34 and the holes 36, so as to press the heated thermoplastic sheet 12 against the shaping surfaces 18 and 22 of the first moulding element and of the sliders 20. The second moulding element 24 simultaneously exerts pressure on the inner surface of the sheet 12 so as to insert the anchoring appendages 30 of the fixing member 28 in the body of the sheet 12.

The jet of compressed air enables the desired undercut cross-section of the handle 4 to be produced without the need to exert the necessary shaping pressure on the inner surface of the sheet with mechanical members, thus avoiding excessive complexity of the moulding equipment. The finished component is removed simply by returning the sliders 20 to their positions of FIG. 3 and by moving the second moulding element 24 away from the first moulding element 16. When the sheet has cooled, the covering 14 is fixed firmly to the outer surface of the sheet and the fixing member or members 28 remain anchored to the inner surface of the sheet 12. The fixing members 28 will serve to fix the handle to the lining panel 2 but the fixing members are not intended to be applied if the handle is formed integrally with the lining panel.

The technology described above is also particularly advantageous for forming an upset edge along the perimeter of the lining panel 2. As shown in FIGS. 5 and 6, in which elements corresponding to those described above are indicated by the same reference numerals, the slider 20 is movable between the operative position of FIG. 5 and the operative position of FIG. 6 in a direction perpendicular to that in which the two moulding elements 16 and 24 are closed.

In the position of FIG. 5, the slider 20 defines a cavity 38 which encloses a perimetral portion 12a of the sheet and the hole 36 for supplying the jet of compressed air which presses the portion of the sheet 12 against the shaping surfaces 22 and 18 of the slider 20 and of the moulding element 16.

By providing several sliders along the sides of the equipment it is possible to produce an upset edge along the entire perimeter of the panel 2 with simple and cheap moulding equipment.