GB2232629A

GB2232629A - Sink tops

Info

Publication number: GB2232629A
Application number: GB8912173A
Authority: GB
Inventors: Charles William Edwards
Original assignee: STOM HOLDINGS
Current assignee: STOM HOLDINGS
Priority date: 1989-05-26
Filing date: 1989-05-26
Publication date: 1990-12-19
Also published as: GB8912173D0

Abstract

A sink top is made by laying polymers into matched dies to form a gel coat, applying a shell coat of polymer concrete to the gel coat, closing the dies together and injecting a resin with foaming agent to create a cellular structure within the shell. A chip-board insert may be used as a core within the cellular filling.

Description

SINK TOPS This invention relates to kitchen sink tops and like components comprising one or more bowls and a surrounding worktop which may include for example sloping drainage areas.

Renown sink tops of the kind mentioned have been made as metal pressings with the bowl(s) and worktop integral, the worktop having a peripheral flange often with a narrow return rim (that is the flange is at 90 degrees to the worktop and the rim at 180 degrees to the worktop) so as to provide the illusion of a surface for example 20mm thick. Such a sin top requires expensive dies and a large power-press for manufacture.

The sheet metal has been vitreous enamelled, which tends to chip and is difficult to repair, or has been made of stainless steel, which tends to lose its surface finish as a result of minor scratches and abrasions. As a result, and for economic and aesthetic reasons, attention has turned to the use of other materials.

It is also known to make the bowls and adjacent drainer areas, from a single piece of synthetic resinous material. Vacuum forming or perhaps casting are available techniques for thermoplastics using relative inexpensive rnoulds, but suitable materials for such techniques have low abrasion resistance and have primarily been used to make vanitory units where the possibility of wear in use is less than in a kitchen.

For kitchen sinks, filled thermoplastics using ceramic powders as the filling (polymer concrete) have been satisfactory, made by injection moulding into matched dies. - For a kitchen sink with one or two drainer areas and possibly a multiplicity of bowls, an extremely large capacity is required by injection moulding machines, and as far as the present inventors are aware, it has not proved practical to provide a complete worktop for this reason. Instep, inset sink tops have been used where a melamine laminate covered chipboard worktop is provided with a cut-out to receive the sink top. Even in this case, the size of machine required to produce for example the popular twin-bowl double drainer sink top is such as to discourage new manufacturers from entering the market.

The object of this invention is to solve this problem and provide improved constructions of sink tops.

According to the invention, a method of making a sink top or like comprises the use of matched dies, coating the dies with a gel coat, laying at least a reinforced polyester shell in the gel coat, closing the dies together, and injecting resin and a foaming agent into one or more cavities formed in the dies so as to provide a stiffening of cellular lightweight material, and curing the complete assembly before removal from the dies.

The gel coat and/the shell are preferably mixed with a mineral or ceramic filler before laying in the mould.

Preferably chip-board is used as a further insert into the shell coat so as to be wholly enclosed and surrounded by the polymer(s).

A foaming agent may be nitrogen gas injected to achieve a predetermined pressure in the cavities, and by diffusion through the filling material this creates the required cellular structure: nitrogen is selected for its inert chemical nature and safety in handling as well as for economic reasons.

Pressure is applied externally to the dies during injection of the core making material and foaming nitrogen, but the required loading is much less than is needed for the known injection methods, making for a simpler apparatus. Because only a small volume is injected, a relatively small capacity injection machine is sufficient, and if necessary a series of separate cavities may be individually filled whilst the dies are held in a separate clamp.

In general the chipboard and possibly also the foaming, will be used only over the planar areas of work tops. fence in manufacture the gel will be applied to the whole area of each die half, the shell forming material with colouring material, structural reinforcement and abrasion resistance material will be applied overall to one or both halves, the chipboard laid in the planar area of the worktop but not of the bowl(s) and then the halves closed together. However, the foaming technique could also be used totally overall.If the total thickness of any one material is applied solely to one die half e.g. to a bowl the shell material applied to the other die half will be over the generally planar area anc will be apertured around the sink bowl and tfie rim of the aperture will contact the bowl forming material when the halves are assembled together.

The finished sink top may provide a complete worktop, that would he suitable for assembly on top of a cupboar(l like structure ("sink unit") and the thickness of the worktop portion made according to the invention may he similar to that usually employed for laminated chipboard worktops Der se for example 40mm. The worktop may he made with an integral rear upstand, and radiused front edges.

The holes required in the sink top for water taps, sink wastes and the like may he cored in during manufacture or drilled through the finished worktop.

In a typical application of the invention a gel coat is of a polyester base of suitable grade to give a high abrasion resistance applied by spraying overall to both die halves to give a thickness of 0.5my and is allowed to part cure at ambient temperature, typically say 18 degrees C for a period of 10 minutes. A suitable shell coat is the polymer called Ivitropolymer being a mineral filled polyester sold by Dutch State Mines, or similar, mixes in the ratio specified in makers instructions along with mineral filler plus any desired colouring material.

This mixture can be laid up in the gel coat also by spraying, or by hand applied extrusion from a mixing gun, or any other suitable means. Typically the thickness of the shell coat will be 2.5mm on each die half and also overall. however, where there are minor variations in external contour, for example the provision of ribs on a draining areas, the thickness may vary so that the interior is planar, especially where the material is laid up by spraying.

At this stage glass fibre reinforcing material is laid into the surface.

The core filling polymer may be nitrogen filled polyester and the apparatus used may be calibrated to give a specific gravity of 0,7 - 1,1 when injected with nitrogen at a pressure of up to 5 bar followed by curing of the whole assembly at a typical temperature of up to 100 des,C for a period of up to 12 hours.

In the accompanying drawings, Figure 1 is a plan view of a typical sink/worktop combination made by the method of the present invention as a single unit having two bowls. Figure 2 is a section on the line X-X of Figure 1.

As seen in the drawing, this typical sink top is shown with a main bowl section 10, a smaller bowl 12, and a draining area 14, all contained within a generally rectangular planar area 16.

As seen in Figure 2, the typical cross section illustrates the manufacturing steps. The plain P-P indicates the mating faces of the die halves. The gel coat 20 is laid over the areas which will form the whole of the worktop including the underside of the same and the edges, and over the interior; it may also be laid over the exterior of the bowl.

A layer of polymer concrete 22 substantially thicker than the gel coat is laid next to the gel coat over the than the gel coat is laid next to the gel coat over the bowl interior and next to the gel coat over the planar areas of the sink top, that is in both die halves. The polymer concrete is indicated by the reference numeral 22.

Next, a layer of resin with a glass fibre reinforcement is laid as the final layer over the exterior of the bowl and over the polymer concrete in both die halves over the areas which are to form the planar areas of the worktop. This resin is indicated by the reference numeral 24. Finally, a chipboard shape 26 is laid in the appropriate die half and, at this stage, is a loose fit in the laid-up layers. The die halves are closed together and nitrogen is injected into the layer 24 so as to foam that resin and cause it to expand to fill the cavity completely, the expansion being limited on the one hand by the chipboard core 26 and on the other hand by the polymer concrete layer 22. The dies are held closed until curing is complete.

Claims

1. A method of making a sink top comprising the use of matched dies, coating the dies with a gel coat, laying at least a reinforced polyester shell in the gel coat, closing the dies together, and injecting resin and a foaming agent into one or more cavities formed in the dies so as to provide a stiffening of cellular lightweight material, and curing the complete assembly before removal from the dies.

2. A method as claimed in Claim 1 wherein the gel coat is mixed with a mineral or ceramic filler before laying in the mould.

3. A method as claimed in Claim 1 or Claim 2 wherein the shell is mixed with a mineral or ceramic filler before laying in the mould.

4. A method as claimed in any of Claims 1 to 3 wherein a chip-board insert is located in the shell.

5. A method as claimed in any of Claims 1 to 4 wherein the foaming agent is nitrogen gas.

6. A method of making a sink top as claimed in Claim 4 wherein the sink top comprise a series of generally coplanar areas forming a work top and one or more bowls recessed in the work top, and said chip-board is used in the co-planar areas.

7. A method of making a sink top substantially as described.