FIBER REINFORCED THERMOPLASTIC BATTERY TRAY AND MANUFACTURING METHOD THEREFOR

Abstract: An article such as a battery tray for a vehicle battery is made as an injection moulding in a highly chemically coupled glass fibre reinforced plastics.

Description: FIBER REINFORCED THERMOPLASTIC BATTERY TRAY AND MANUFACTURING METHOD THEREFOR This invention relates to a moulded article such as a battery tray for a vehicle battery. Currently, battery trays are usually made as sheet metal fabrications. They are protected by paintwork. A lead accumulator battery of the type currently provided in a motor vehicle is very heavy because of the weight of the lead plates. The battery tray therefore needs to be strong. Additionally, since the battery is provided within the environment of a moving car, the mounting and tray need to be capable of withstanding shocks and displacements in all directions. A battery tray also needs to resist corrosion by battery acid which may splash out of the battery at some stage. The currently used metal trays are strong but they are also heavy, not very corrosion resistant and costly to manufacture and paint. It has been proposed to make plastics trays to support vehicle batteries. However, it is clearly necessary to use a reinforced plastics.material in order to achieve the necessary strength. The currently proposed plastics trays are made using glass fibre reinforced plastics sheet which is softened by heat and is formed by pressing into a mould. Such trays are lighter than those made of metal, and have better corrosion resistance but are expensive, particularly when holes for cable attachment are required as these require additional manufacturing operations. Such plastics battery trays made from glass fibre reinforced plastics sheet are also somewhat unsatisfactory in some ways because of the nature of the manufacturing technique. The glass fibre in the plastics material tends to be damaged by the stretching of the heated plastics sheet into the die. Where complex shapes are required, the glass fibre breaks as the sheet is stretched and it will be appreciated that the breakages tend to occur mostly on the bends. Unfortunately, this is where the battery tray needs most structural strength, to withstand flexure and impact. Further, any deep wells or ribs provided in the moulding tend to be deprived of glass fibre reinforcement. This is because the glass fibre does not stretch down into these parts of the press forming die. Thus, some of the advantages of the glass fibre reinforcement are lost at the positions where it is most needed. It is therefore an object of the present invention to provide a new or improved plastics battery tray and a method of manufacturing such a tray. According to the invention there is provided an article such as a battery tray comprising an injection moulding in a glass fibre reinforced plastics material characterised by the use of a highly chemically coupled glass fibre reinforced plastics. Viewed from a further aspect, the invention provides a method of making an article such as a battery tray comprising injection moulding a plastics material comprising a highly chemically coupled.glass fibre reinforced plastics. The plastics material may be polypropylene. The glass fibre may be chemically coupled to the plastics by means of a wetting or bonding agent. The bonding agent may comprise an acid coupling system which chemically bonds the glass fibre to the polymer. An embodiment of the invention will now be described in more detail by way of example only with reference to the accompanying drawing, Figure 1, which is a perspective view of a-battery tray embodying the invention. A battery tray for a lead accumulator battery of a vehicle is generally indicated at 10. It comprises a deep tray having a base 11 and two pairs of upright walls 12, 13. The walls 13 have outwardly turned rims 14, each of which carries a boss 15 in which a threaded insert 16 is provided during the formation of the battery tray 10 as an injection moulding. The walls 12 are provided externally with elongate ribs 17 which also extend at 18 underneath the base 11. The base 11 also has a deeply projecting portion 19 having an opening 20. Further internal features 21 are provided on the walls. The battery tray 10 is made by injection moulding in a manner which is generally conventional except for the material used. The material is a homopolymer polypropylene which is reinforced with chopped glass fibre strand, of either standard or long strand type, which has been treated with a wetting or bonding agent compatible with polypropylene, to provide it with certain desirable properties. The wetting or bonding agent is used initially to treat the glass fibre and has a high affinity to the polymer. Thus, when the glass fibre is chopped and mixed in the plastics material it becomes uniformly dispersed throughout the plastics and can be injection moulded in a relatively conventional manner. The glass fibre bonded to the polymer is uniformly distributed even in reinforcing ribs 17, 18 and deep *+ wells 19 formed in the moulding. Additionally, the bonding of the glass fibre to the polymer ensures that the abrasiveness of the glass fibre is greatly reduced and this prevents or reduces damage to the mould or to the injection moulding machine which would normally take place with a conventional abrasive glass fibre. As an example, the glass fibre may be chemically bonded to the polymer .using an acid coupling system. This greatly enhances the fibre-to-matrix adhesion and imparts the necessary impact resistance to the composite for this application. It will be appreciated that current design of battery trays made of glass fibre, reinforced plastics tends to be a compromise between the most favourable design shape and the potential problems with the plastics reinforcement. By the use of a highly chemically coupled glass fibre reinforced plastics material, the plastics material can be treated as a homogeneous material and the battery tray design can therefore be made on the basis of structural considerations only. This enables sufficient strength to be obtained to support the battery weight with minimum use of materials. These considerations are likely to increase in importance since engine bonnet levels are tending to be lowered and hence the "packaging space" available for the engine is decreasing whereas battery size is tending to increase because of the requirements for increased power supply, for example over¬ running engine fans, alarm systems and the like. The battery tray 10 can be moulded by the injection moulding process in whatever manner is required. Fixing points for attachment of cables and fittings can be made by various means, conventional in the injection moulding field. It is possible to mould pegs onto parts of the tray which can be passed through openings in metal fixings and heat swaged to attach the metal fixings for example. Holes and slots can be provided where required. Inserts such as the threaded inserts 16 can be moulded into the plastics in generally known manner. A suitable plastics material for use in the manufacture of a battery tray is a homopolymer polypropylene which is highly chemically coupled to either standard or long stranded glass fillers.

Claims: CLAIMS 1. An article comprising an injection moulding in a glass fibre reinforced plastics material characterised by the use of a highly chemically coupled glass fibre reinforced plastics. 2. An article according to Claim 1 wherein the plastics material is polypropylene. 3. An article according to Claim 1 or Claim 2 wherein the glass fibre is chemically coupled to the plastics by means of a wetting or bonding agent. 4. An article according to any preceding claim wherein the wetting or bonding agent comprises an acid coupling system. 5. An article according to any preceding claim comprising a battery tray. 6. A method of making an article comprising injection moulding a plastics material comprising a highly chemically coupled glass fibre reinforced plastics. 7. A method according to Claim 6 wherein the plastics material is polypropylene. 8. A method according to Claim 6 or Claim 7 wherein the glass fibre is chemically coupled to the plastics by means of a wetting or bonding agent. 9. A method according to claim 8 wherein the wetting or bonding agent comprises an acid coupling system. 10. A method according to any one of claims 6 to 9 wherein the article is a battery tray. 11. An article comprising a battery tray substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing. 12. A method of making a battery tray according to claim 6 and substantially as hereinbefore described.

Inventors: CASEY MICHAEL JOSEPH, CASEY, MICHAEL, JOSEPH
Applicants: CLEARPLAS LTD, CLEARPLAS LTD.
Application year: 1993
Main classification: B29C45
IPC codes: B29C45, B60R16, H01M2