GB2248420A

GB2248420A - Injecting plastics foam within an outer cover having an interior structural frame

Info

Publication number: GB2248420A
Application number: GB9021601A
Authority: GB
Inventors: Barry Passingham
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1990-10-04
Filing date: 1990-10-04
Publication date: 1992-04-08
Also published as: GB9021601D0

Abstract

The process moulds an article e.g. a vehicle headrest frame having a foam core from which the embedded rigid structural frame (18) projects exteriorly. The cover (10) and frame (18) are located in a mould cavity (25), with the frame being located by clamping its exteriorly projecting pant, (18); an injection nozzle (30) is inserted into the cover (10) aligned with a section (33) of the frame (18) and a foamable composition stream from the nozzle (30) is injected into the cover (10), by directing it on to a section (33) of the frame (18), thereby dissipating the energy of the injected stream of foamable composition to prevent it impinging directly upon. and penetrating the cover (10). After withdrawal of the injecting nozzle (30), the composition foams & rises to fill the cover (10). The foam may be polyurethane, and the cover of textile fabric laminated to polyester foam, & having stitched seams covered by impervious polyurethane film. <IMAGE>

Description

METHOD OF MOULDING ARTICLES OF FOAMED PLASTICS MATERIAL The present invention provides a method of moulding articles from foamed plastics material and in particular to the moulding of articles, such as headrests, having a cover layer, a foam core a rigid supporting structure partially embedded in the foam core.

Hitherto headrests having a textile outer cover with foam plastics core have been produced by forming the core in a mould then applying the textile cover to the core. It has been proposed that the foamed core should be formed insitu within the textile outer cover. i{owever, the high velocity of the foamable composition issuing from the foam injecting machine will result in penetration of the compositio through the fabric layer. This problem has been mitigated by the use of an interlayer of low porosity. However, even so, hitherto it has been found necessary to inject the foamable composition into the cover via a funnel in order to dissipate its energy.This method presents problems with regard to cleaning of the funnel prior to withdrawing it from the cover, so that the foamable composition is not transferred to the outside of the cover.

The present invention provides a method of forming moulded plastics articles in which a foamable composition may be injected directly into the cover of the article.

According to one aspect of the present invention a method of moulding an article having a foam core with an outer cover and a rigid structural frame partially embedded in the foam core and emerging therefrom through the outer cover, comprises; assembling the cover on the structural frame and locating the cover in a mould cavity defining the shape of the core; clamping the structural frame so that the portion embedded in the core is located in the cover within the mould cavity; inserting an injecting nozzle into the cover so that it is aligned with a section of the structural frame within the cover; and injecting a foamable composition directly into the cover, directing the foa.able composition onto the section of the structural frame.

Once sufficient foamable composition has been injected into the cover, the injecting nozzle may be removed and the foamable composition allowed to rise, so that it fills the cover and conforms to the mould cavity. Directing the injected foamable composition onto the structural frame will dissipate the energy thereof so that the composition may be injected at high pressures/velocities without the mixture penetrating the cover material. This will allow good mixing of the foamable composition so that a high quality foam will be produced.

Where the cover is made of a porous material, it may be lined with an interlayer of low porosity. Even with cover materials of low porosity, if the seams are stitched, an interlayer of impervious or low porosity material may be applied to the seams. The interlayer may be an impervious film material such as polyurethane film or a layer of low porosity, for example a polyether slabstock foam of the order of 5mm thick or a low porosity polyester slabstock foam of the order of 2mm thick.

The injection nozzle is preferably introduced through a gap in a seam of the cover, flaps being provided on either side of the gap, these flaps being arranged so that as the foam rises within the cover, they will be forced together to seal the gap and contain the foam within the cover.

Holes are provided through the cover to allow the structural frame to emerge from the cover. These holes should be a tight fit about the structural frame in order to provide a seal therewith and prevent the foam, as it rises, from escaping from the cover.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a cross-section through a mould used to mould vehicle headrests by a method in accordance with the present invention; and Figure 2 is a sectional view along the line Il-Il of Figure 1 after the foam has risen.

The vehicle headrest moulded by the process illustrated in Figures 1 and 2 comprises a cover 10 made of textile material. An interlayer 11 of low porosity polyester slabstock foam 3mm thick is laminated onto the material, in known manner. The cover 10 is formed from a pair of end pieces 12 of generally circular shape and a central piece 13, the two end pieces 12 being attached to the central piece 13 by stitched seams. The ends of the central piece 13 are again stitched together adjacent each end piece 13 to form a longitudinal seam, said seam being left unstitched in the centre to form a gap 14 which will provide access to the cover 10. Excess material is provided adjacent the gap 14 to provide a pair of flaps 15 which extend inwardly of the cover.

A structural frame 18 has a pair of parallel stem portions 19 which extend from the headrest to provide means of securing the headrest to the back of a seat. A transverse serpentine portion 20 interconnects the stem portions 19 and serves the stiffen the headrest. The stem portions 19 of the structural frame 18 extend through apertures in the cover 10, the apertures being a tight fit about the stem portions 19.

The structural frame 18 and cover 10 are assembled, the structural frame 18 being threaded through apertures 21 until the serpentine portion 20 is in its appropriate place within the cover 10.

The cover 10 is then located within a mould cavity 25 of a mould 26. The stem portions 19 emerge from the cavity 25 through apertures in the mould 26 and are secured by clamps 27, so that the serpentine portion 20 of the structural frame 18 is located in the correct position within the mould cavity 25.

A nozzle 30 of a high pressure mixing head 31 of a foam injection machine is introduced through an aperture 32 in the mould 26 and through the gap 14 in the longitudinal seam of the cover 10. The nozzle 30, movement of which may be controlled by, for example, a robot arm, is aligned so that its end is in close proximity to and is directed at a central section 33 of the serpentine portion 20 of structural frame 18.

A foamable polyurethane composition comprising a polyol and an isocyanate in the ratio by weight of 100:53 is formed in the mixing head 31, the polyol being dispensed at a pressure of 195 bar and the isocyanate at a pressure of 180 bar. This foamable polyurethane composition is then injected from nozzle 30 at a rate of 214 grammes per second into the cover 10. The injected polyurethane composition impinges on the central section 33 of support frame 18 which absorbs the energy thereof so that the velocity of the incoming mixture is reduced. The stream of incoming polyurethane composition is also deflected towards the longitudinal sides of the cover 10. After 0.8 seconds, when a metered amount of the polyurethane composition has been injected into the cover 10, the nozzle 30 is rapidly removed vertically from the mould 26.In order to ensure that the full metered amount is injected into the cover 10 before the nozzle 30 is removed, the nozzle 30 may be cleared by means of a ram or blast of air. The polyurethane composition within the mould is then allowed to rise, taking from 20 to 25 seconds to fill the cover 10 and conform to the surface of the mould cavity 25. The deflection of the polyurethane composition towards the longitudinal side walls of the cover 10 will result in a predominance of the composition being deposited in these areas, so that as the foam rises, it will do so from the sides of the cover, causing the flaps 15 to be moved together closing the gap 14 so that the foam will be retained in the cover 10.

Once the polyurethane foam has risen, the mould 26 may be split and the headrest removed therefrom. A typical headrest formed in accordance with the present invention will have a foam density of 40 to 50 Kg.m3.

Various modifications may be made without departing from the invention. For example, while the method described in the above embodiment utilises a high pressure mixing head, the invention is equally applicable to the use of low pressure mixing heads.

Claims

1. A method of moulding an article having a foam core with outer cover and a rigid structural frame partially embedded in the foam core and emerging therefrom through the outer cover, comprising; assembling the cover on the structural frame and locating the cover in a mould cavity defining the shape of the core; clamping the structural frame so that the portion embedded in the core is located in the cover within the mould cavity; inserting an injecting nozzle into the cover so that it is aligned with a section of the structural frame within the cover; and injecting a foamable composition directly into the cover, directing the foamable composition onto the section of the structural frame.

2. A method according to Claim 1 in which once a metered amount of foamable composition is injected into the cover, the nozzle is removable and the foamable composition permitted to rise.

3. A method according to Claim 1 or 2 in which the cover is lined with an interlayer of low porosity.

4. A method according to Claim 1 or 2 in which the seams of the cover are stitched, the stitched seams being lined with an interlayer of low porosity.

5. A method according to Claim 3 or 4 in which the interlayer is an impervious film material.

6. A method according to Claim 3 or 4 in which the interlayer is a low porosity foamed material.

7. A method according to Claim 6 in which the interlayer is a polyether slabstock foam at least 5mm thick or a low porosity polyester slabstock foam at least 2mm thick.

8. A method according to any one of the preceding claims in which the injection nozzle is introduced through a gap in a seam of the cover.

9. A method according to Claim 8 in which flaps are provided on either side of the gap, these flaps being arranged so that as the foam rises within the cover, the flaps will be forced together to seal the gap.

10. A method according to any one of the preceding claims in which the article is a vehicle headrest comprising a foam core with an outer cover and a rigid structural frame comprising a pair of parallel stem portions which extend from the core and cover to provide means of securing the headrest to a seat back and a transverse serpentine portion interconnecting the stem portions and being embedded in the foam core.

11. A method of moulding an article having a foam core with an outer cover and a rigid structural frame partially embedded in the foam core and emerging therefrom through the outer cover, substantially as described herein, with reference to and as shown in Figures 1 and 2 of the accompanying drawings.