.FIELDOFINVENTION

THIS INVENTION relates to vacuum form encapsulated articles. The invention has particular application to surfcraft, but is not limited to this field of use.

BACKGROUNDART

The technique of vacuum forming elements has been practised in the art for at least fifty years, and vacuum forming a covering onto a former hias been practised in the art for nearly as long to form vacuum form covered articles. In order to provide a completely covered, or encapsulated, article, two or more sheet are used to cover separate, sometimes overlapping, portions of the exterior surface in two or more vacuum forming steps.

Subsequent to the use of wooden boards, the construction of surfcraft, such as s~urfboards, sailboards and the like, has involved coating a shape former of lightweight material, such as expanded polystyrene (EPS) with a composite resin, such as fibreglass. Such a technique is relatively labour intensive and can expose shapers to potentially harmful chemicals. However, the traditional technique remains popular because the finished board has a seamless coating with a smooth outer surface. Attempts to provide a mechanical process for the production of surfcraft have sometimes resulted in roughness on the surface, weaknesses in the coating, particularly around the inevitable seam, permitting ingress of water whereby the board can lose buoyancy and/or becomes sluggish to manoeuvre in the water.

The present invention aims to provide a vacuum form encapsulated article which alleviates one or more of the disadvantages of the prior art. Other aims and advantages of the invention may become apparent from the following description. DISCLOSUREOFTHEINVENTION

With the foregoing in view, this invention in one aspect resides broadly in a method of forming an encapsulated article including:

supporting a core component between two sheets of thermaLly deformable material in a vacuum forming mould having a cavity conforming to a shape larger than the core component when t he mould is closed;

heating the sheeting to a temperature sufficient to deform the sheets;

applying a first pressure differential across the sheets to deform at least one of the sheets into the cavity of tlhe mould;

closing the mould such that the two sheets are brouglit together;

applying a second pressure differential to the coxe component to deform the sheets against the outer surface of ttie core component;

cooling the encapsulated article; and

opening the mould.

The mould is suitably a twin sheet or twin coating mould. Cooling of the article takes place prior to the opening of ttαe mould, but the encapsulated article may be allowed to cool further upon opening of the mould before being removed mechanically or by hand. Preferably, the cooling is effected by providing for the passage of temperature controlled water through aluminium tooling operatively associated with the moulcL Preferably, the first and second pressure differentials arre applied by providing a source of vacuum to firstly deform one or both sheets into the cavity of the mould, and secondly^ the same vacuum is applied to the core component to deform the sheeting against the core component. Then, once the sheeting has been vacuumed onto the core, one or both sheets may, if necessary, be then vacuumed back to the tool shape.

The core component may be formed from one or more shape defining elements. For example, for a surfcraft, the core component preferably includes an expanded polystyrene core which may have a stringer along the central elongate axis according to established surfcraft manufacturing practice.

In another aspect, the present invention resid&s broadly in a vacuum form encapsulated article including:

one or more shape defining elements arranged to form a core component; and

an encapsulating covering vacuum formed onto the external surface or surfaces of the core component;

wherein the encapsulating covering is formed from two sheets of thermally deformable material vacuum formed to the core component substantially simultaneously with the weldiaag of the sheets together.

In another aspect, the present invention resides broadly in a method of forming a vacuum form encapsulated! article including:

providing one or more shape defining elements ariranged to form a core component;

providing an encapsulating covering formed from two sheets of thermally deformable material; aligning the encapsulating covering in relative disposition with respect to the core component for encapsulation thereby;

heating the encapsulating covering to a temperature sufficient to permit deformation thereof;

applying a pressure differential across the encapsulating covering sufficient to deform the encapsulating covering onto the core component and bonding the sheets of thermal.Iy deformable material together to form a substantially integral encapsulating covering on the external surface or surfaces of the core component.

In another aspect, the present invention resides broadly in a method of forming a surfcraft body including :

supporting a surfcraft core component shaped substantially to a surfcraft form between two sheets of thermal_ly deformable material in twin sheet vacuum forming mould having a cavity conforming to a shape larger than the core component when the mould is closed;

heating the sheeting to a temperature suffici_ent to deform the sheets;

applying a first pressure differential across the sheets to deform at least one of the sheets into the cavity of the mould;

closing the mould such that the two sheets are brought together;

applying a second pressure differential to the core component to deform the sheets against the outer surface of the core component;

cooling the encapsulated article; and opening the mould.

Upon opening of the mould, the surfcraft body is allowed to cool before being removed mechanically or by hand. Preferably^, the first and second pressure differentials are applied by a source of vacuum to firstly deform one or both sheets into the cavity of the mould, and secondly, the same vacuum is applied to the surfcraft core component to deform the sheeting against the core component . Then, once the sheeting has been vacuumed onto the core, one or both sheets may, if necessary, be then vacuumed back to the tool shape. The surfcraft core component may includes a stringer, but it is believed that the structure of the surfcraft body being akin to a monocoque construction may obviate the necessity for a stringer. Of course, other surfcraft components may be moulded in to the surfcraft body, such as fin boxes, mast connector boxes, leg-rope connectors and such like-

The core component is preferably formed from expandecϋ polystyrene (EPS) , but may be any suitable material. The covering is preferably formed from a compatible material. In the case ofΞ an EPS core component, it is preferred that ASA or high impact polystyrene (HIPS) sheeting be used. The materials off constructions would be selected from those which afford thermal, deformability, thermal weldability and/or thermal sinterability-

BRIEFDESCRIPTIONOFTHEDRAWINGS

In order that the invention may be more readily understood!! and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein: -

Fig. 1 is a diagrammatic sectional view illustrating the formation of vacuum form encapsulated article according to the invention. -S-

DETAILEDDESCRIPTIONOFTHEDRAWINGS

The method illustrated in Fig 1 shows a core component 11 disposed between two sheets of thermally deformable material, an upper sheet 12 and a lower sheet 13 mounted in between upper and lower temperature controlled tools 14 and 15 respectively. The upper and lower temperature controlled tools are mounted to respective upper and lower mould assemblies 16 and 17, each having a vacuum port 18 and heat transfer fluid inlet and outlet ports 19 and 20 respectively whereby temperature control is effected by passing heat transfer fluid (in the present example, water) through passages (not shown) in the tools.

Vacuum pins as shown at 21 are inserted into the core component to allow a vacuum to be applied thereto. 10 removing inserts 22 are also included in operative relation with the core component .

The temperature controlled tools have shaped edge portions arranged to mate with one another and nip the upper and lower sheets together for welding together to one another. The heated moving inserts weld off the openings in the weld line where the pins were inserted.

For example, an EPS core is suspended mechanically between two sheets of plastic. The sheets of plastic are heated to their moulding temperature by normal means such as irradiation. These two sheets are then formed in the twin sheet tools by the vacuum and then the tools are forced together using pressure and thus creating a weld around the core and fusing the product together. Vacuum is also applied during the weld or joining process to remove air from the EPS core. The heated moving inserts are urged against one another, welding off the pin openings once the pins are removed. Cooling is effected by way of the tool being cooled by passing cooler heat transfer fluid through the tools. The tools are then separated where cooling can take place. The product is then removed manually or mechanically from the tools .

Although the invention has been described with reference to one or more specific examples, it will be appreciated by persons skilled in the art that the invention may be embodied in other forms which are encompassed within the broad scope and ambit of the invention as claimed by the followLng claims.