Field of the Invention

The present invention relates to a shower tray and method of manufacturing such a tray.

Background of the Invention

Currently, the most popular shower tray is the acrylic tray. This is made using a sheet of acrylic material that is heated until soft and then clamped onto a mould in the shape of a tray. A vacuum is applied through the tray mould and the sheet is sucked onto the mould and sets in the desired shape. The manufacturer then adds a layer of fibreglass or wood on the inside to give some minimal strength and then makes a wooden or steel frame for the tray to sit on. This is the cheapest and fastest way to make a shower tray. Another type is the ABS capped resin tray. This is made using the same initial process as the acrylic tray but rather than adding a layer of fibreglass or wood on the inside, the void at the back of the acrylic sheet is filled with a mixture of resin and filler, usually an inorganic bulking material, which sets hard to give strength and durability. Another example is the gel coated resin tray. To make this, a mould is manufactured from aluminium or steel and a resin and filler mix is poured in and allowed to set. Once this is done, the set material removed from the mould, the material being set in a tray shape. The external surface of the material is then painted with epoxy type gel paint and allowed to set. Resin trays of this type are by far the most common available. However, they suffer from a number of problems. For example, once installed if a tray is not bedded in and supported properly its base can crack. Also, the colour of the tray is applied as a thin layer of paint, which, if scratched, is extremely difficult to repair.

Acrylic capped resin trays are becoming popular. These combine the rigidity of the stone resin tray, but have the added advantage of being capped in a material that produces a surface more resistant to impact and can be polished if scratched. To make this type of tray, a sheet of ABS / Acrylic plastic approx. 4mm to 6mm thick and slightly bigger than the area of the tray required is heated in a flat oven until it is pliable and soft and it is then placed on a vacuum mould in the shape of the tray desired. The edges of the sheet are then clamped to the edges of the mould or the structure of the moulding machine and a vacuum is created by sucking air through small holes in the tray mould. This forces the soft acrylic sheet onto the mould and cooling it down.

When the sheet is cooled enough it sets hard and the clamps are removed and the vacuum turned off. The moulded tray shape is then placed in a metal support mould - exactly opposite to the shape of the tray to provide full support to all parts of the acrylic moulded sheet - on a flat conveyor belt system. At this point a glue or adhesive is sprayed onto the underside of the tray to help the resin adhere to the plastic and the resin / ash mixture is poured into the void on the underside of the tray. This filled tray is then allowed to sit until the resin / ash mixture has hardened and the tray is then put through the final process step. This is the most time consuming and costly step in terms of time and manpower as the excess acrylic sheet from the clamping and the excess resin from the fill are ground off the tray using angle grinders and power tools. The tray is then polished and packed into boxes ready for shipment.

Summary of the Invention

According to one aspect of the present invention, there is provided a shower tray comprising an injection or rotation moulded top back filled with a strengthening material. An advantage of using injection or rotation moulding is that there is no waste or excess material.

The strengthening material may comprise one or more of: resin; plastic; rubber.

A void may be formed in the injection or rotation moulded top.

A generator may be provided for powering one or more electrical devices. The electrical devices comprise one or more lights.

The moulded top may have a thickness of more than 5 mm for example more than 8mm.

The moulded top may have two layers, these being a top layer that presents an external surface and a base. The top layer may be made of one or more of Styrene Acrylonitrile (SAN) / Polycarbonate (PC) / Acrylonitrile butadiene styrene (ABS), and preferably a combination of all of these, and / or the base is made of one or more of: a polymer; plastic; rubber, where one or more of these is recycled.

According to another aspect of the invention, there is provided a method comprising forming an upper tray portion that defines an external surface of the tray and a rear cavity; and at least partially or wholly in-filling the rear cavity. The method may involve forming the upper tray portion of two layers, a top layer and a base.

The top layer may be made of one or more of Styrene Acrylonitrile (SAN) / Polycarbonate (PC) / Acrylonitrile butadiene styrene (ABS), and preferably a combination of all of these, and / or the base is made of one or more of: a polymer; plastic; rubber, where one or more of these may be recycled.

The upper tray may be injection moulded. This may be done using at least one mould part; retaining the upper tray in the mould part and back-filling the tray whilst it is retained within the mould.

Brief Description of the Drawings

Various aspects of the invention will now be described by way of example only with reference to the following drawings, of which:

Figure 1 shows the steps taken in a first method for making a shower tray that is back filled with a strengthening material;

Figure 2 shows the steps taken in a second method for making a shower tray that is back filled with a strengthening material;

Figure 3 is a schematic view of a system for making a tray that has an internal void;

Figure 4(a) is a plan view of a base part of a tray shell;

Figure 4(b) is a cross section through a two layer tray prior to in-filling;

Figure 5 shows a method for making another dual layer tray, and

Figure 6 is a schematic view of a shower that has an integral lighting system associated with the shower tray. Detailed Description of the Invention

In accordance with the invention, a shower tray is made by preparing an initial injection moulded top shell without a sub structure or with a limited sub structure and then filling the void underneath with a resin mixture. Pure resin is chosen as it sets hard in a short space of time and is strong and durable when solid but this resin is expensive and is normally bulked out with inert materials such as power station ash and volcanic ash and stone debris etc. This also serves to give the tray additional weight which is perceived as a benefit in the marketplace.

Figure 1 shows a first method for making a shower tray in accordance with the invention. In this case, the initial shape of the tray and the skin or shell for pouring in the back fill mixture is produced by injection or rotation moulding using a standard injection moulding barrel 10, which is horizontally positioned, and two mould parts. The upper surface 1 1 of the tray 12 is shaped to present a suitable external surface to the user. The underside has a cavity 13 formed in it for receiving a strengthening/filler material. The material of the moulded tray could be any polymer suitable for injection moulding, for example any one of more of ABS / SIN / SUN / PC / UPVC etc. Once set the tray is removed from the mould. Resin is poured directly into the back of the mould from a filling station 14. To avoid the need for a support frame, the thickness and structure of the tray are designed to withstand the pressure and weight of the resin mixture without warping and bending. In practice, this means that the walls of the tray have to be 8 to 10 mm or more. Having a self supporting skin/shell 12 saves the time and the cost of the frames and the time to locate these and provide the space needed.

The tray 12 is filled whist being vibrated from underneath on a vibrating pad / table or is then placed on a vibrating pad once filled. This can either be part of a long conveyor system straight from the filling station or a separate unit. The vibrations cause any air pockets to be removed and ensure that the resin reaches every point and has good contact with the inside surface of the tray and provides a perfectly flat surface finish at the exposed base of the tray so that no grinding is required as a secondary step when the resin is set. The trays are then placed or continue on the conveyor to a drying tunnel 16 that heats and sets the resin more quickly under the action of a resin setting chemical promoter and the dried and finished tray would appear from the end of the tunnel. The tray is polished and placed in a box ready for shipment.

The whole process can be automated by using robotic arms to remove the tray from the injection mould machine and place this on a moving conveyor which then moves to the resin filling point. The resin would be located in a tank or vessel above or beside the conveyor and be released or pumped into the mould. Sensors detect the resin reaching the top of the mould by light refraction / back pressure or by pre set weight (having weight sensors under the conveyor) - this can also be done by a volumetric calculation and the resin delivered by pre set syringe / vessel type arrangement. The conveyor then moves on and enters the heat tunnel which can be speed controlled or length / temperature controlled to a set speed to give the most efficient and fastest curing of the resin mix and then automatically packed and stacked at the end when cooled.

Figure 2 shows another method for making shower trays. In this case, rather than using a standard injection moulding barrel, which is horizontally positioned, the injection barrel 20 is located vertically above the mould. Plastic is inserted into the barrel 20 as normal. Friction and pressure increases as the plastic progresses along the barrel and with some additional heat from outside the barrel with jacket heaters the plastic melts and is under great pressure when it reaches the thin gated end of the screw. At the end of the barrel is a gate valve which leads to the mould. When the gate between the barrel and the mould is opened this allows the plastic to flow into the mould and take up the shape of the void within the mould. The tray still in the lower mould part 22 is then moved along a conveyor belt to a filling location 24 where it is filled with resin or a resin / filler mixture. Because the moulded plastic is not removed from the mould 22, sufficient support is provided to allow the thickness to be relatively low, for example 3 to 4mm. Once filled, the tray is moved onto a vibrating table or is on a vibrating table whist filled. As before, this can either be part of a long conveyor system straight from the filling station or a separate unit. The vibrations cause any air pockets to be removed and ensure that the resin reaches every point of the inside of the tray and provides a perfectly flat surface at the base of the tray so that no grinding is required as a secondary step when the resin is set. The trays are then placed or continue on the conveyor to a drying tunnel 26 that heats and sets the resin more quickly under the action of a resin setting chemical promoter. The dried and finished tray emerges from the end of the tunnel. The tray is polished and placed in a box ready for shipment. This production process is very fast as the bottom half of the mould that holds the tray can be made over and over again with only one top half needing to be attached to the injection barrel. The bottom parts of the mould that holds the shape of the tray are placed in a line before the barrel and are conveyed to the barrel one after another so when the front mould is filled with the tray skin and moves to the filling point, the next mould is placed under the barrel and the process is repeated manually or automatically and controlled sensorially. When the tray is finished and the mould no longer needed it is returned for re-use manually or automatically by conveyor.

Using the injection moulded and in-filled tray of the present invention, a strong but very thin tray can be made, for example a shower tray that is only 25mm high (or less) on the outer edge. This allows the tray to be sold as a certified disabled / easy access tray for wheelchair users and also for the elderly / infirm. It is not possible to make this height of tray easily or commercially using current vacuum moulding methods. In the methods described above, pure resin can be used to fill the void in the tray. However, typically another lower cost material is used to bulk out and reduce the cost of the volume needed. Many different materials can be used and examples would be paper, all plastics (except polystyrene), material such as cloth, fibreglass and glass, carbon fibre, stones, aggregate, concrete, wood, sawdust and sand. The most useful materials that can be used as the filler, for example, are resin and ash mixture or a rubber and resin mixture. This latter option has the advantage of providing some elasticity and cushioning properties, which may prevent the surface cracking or wearing under the action of wheelchairs also. Another option for making the tray is to co-inject plastic and nitrogen gas into a mould at the same time. This is illustrated in Figure 3. In this case, the plastic is fed into the mould 30 using two injection barrels 32 as part of a co-injection process to make the moulded tray part. After the mould has made the part a section within the mould is retracted whilst the main outer parts of the mould stay in place and the seal from the outside atmosphere is maintained. This creates a small void space in the enclosed mould. An injector lance 34 is fed into the void space by a motor and when positioned within the plastic of the base section of the part - nitrogen gas or another gas is forced into the mould. This has the effect of "blowing up" the plastic section like a balloon and creating a gas space the same shape as the void created by the retraction of the mould part. When the plastic reaches the new void limits, it stops expanding. This void space volume can be calculated in advance and the exact amount of gas equal to this new volume injected or an excess of gas can be added to create a space with higher pressure and therefore more resistance to shock or heavy weight bearing. This can have the effect of producing a stronger tray and also one with more cushioning effect for the user. If a further step of filling the underside voids with resin is to be done then it also benefits the cost of producing the tray and the manufacturing time by reducing the amount resin needed and also the setting time of this resin / resin mixture.

In all of the methods described above, the top shell may comprise two or more parts: a base section and a top layer. A structural plastic / polymer can be used to make the base part. This is designed for strength and durability and also stiffness to retain the flat shape and give more stability when a person is standing on the tray. The top layer is formed over the base part to provide the external surface of the tray. The top layer may be a plastic / polymer designed for surface properties such as brightness or scratch resistance or colourfastness etc but which might be quite pliable and "soft". It is also possible to use a semi-permeable top layer plastic such as HDPE if the base layer is completely water proof or vice versa. Using a double layered top shell, additives can be used in either the top or base layer to make the tray more forgiving of temperature and weight changes meaning a stronger overall tray and longer lasting structure. By working with multiple plastics and varied additives a better tray can be produced using better suited polymers.

Various materials can be used for the structural base part of the top shell. In a preferred embodiment, recycled plastic or rubber is used. This is possible, because the base is not seen by the purchaser / user, and so the lower grade finish that results from using such material is not visible. This provides significant cost and environmental benefits. Coloured or off white recycled (post consumer) / virgin (not post consumer) plastic can be used allowing the use of plastics that have superior structural properties but may be naturally coloured after manufacture. Lighter trays can be made by selecting a stronger base plastic that has no surface properties. As less of it is needed to provide the required strength, this would reduce cost, increase production speed, reduce warpage and benefit the environment by reducing the oil needed for production and also the weight of the product in transport and the fuel needed. Various materials can be used for the top layer of the top shell. In a preferred embodiment, the material used for the top layer is any one or more of Styrene Acrylonitrile (SAN) / Polycarbonate (PC) / Acrylonitrile butadiene styrene (ABS). Additives can be included in the top layer to provide, for example, a non-slip upper surface or temperature sensitive indicators indicative of water temperature. Additives can also be added to help the final shape and improve the colour / light fastness. These are important for the shower tray because the surface must be perfectly smooth and flat on the outside rim to give a correct seal against the wall tiles and also the inside walls and slope must be perfect with no sagging so that the water runs away to the drain and does not pool inside the tray. Colourfastness is important because the tray must colour and shade match the tiles and the other ceramics in the bathroom and so must not fade over time. The additives must also give the surface strength and scratch / impact resistance to maintain the life of the tray and allow scrubbing and abrasive cleaning to treat mould and hard to remove deposits like scale and calcium. Fill and measurement of the resin / filler application may be by volumetric or sensor control - volumetric by pre set vessel or syringe type and then poured or pumped into the mould at set points within the structure or by weight or light sensor. The pump / valve is shut off when a pre set weight or increase in weight from the fill is reached or a light sensor at the side of the tray is set at a pre determined angle to the tray and when the tray is filled the light reflection angle changes - when the desired level is reached the reflection will hit a receptor that is light sensitive triggering the pump or valve to close. All or a selected few of the spaces can be filled to provide additional strength at points on the tray where there is extra weight or wear. In this way, a tray could be made with less plastic knowing that it was too weak in certain areas such as the middle where people stand, but then reinforced with resin underneath to prevent flexing and failure and give additional strength and weight.

There are a number of possible techniques for making a top shell or skin that has two or more parts. In a first method, two separate machines are used side by side with a single screw feed. Alternatively, one machine may be used with a single screw feed and a change of mould after enough bases have been made. In either case, two moulds are used and the base is made using the first mould and the top layer is formed using a second mould. Where two machines are used, the second mould may be provided on the second machine and the base moved to fit onto it or where a single machine is used, the first mould is removed and replaced with the second mould. In any case, the base is fitted into the second mould and the top layer of plastic injected to fill the void between the inside of the second mould and the top surface of the base tray. To avoid leaving a nipple or injection mark on the surface of the tray, the top layer is injected from the back side of the second mould. To do this, injection holes have to be provided on the base. To this end, the first mould has removable / screw in cylindrical sections at various points. When the first moulding is made, these cylinders are screwed in and sit proud of the rest of the mould half and touch the front half of the mould. This means that when the plastic is injected into the mould through the front or the back halves of the mould it leaves circular holes 40 in the surface of the base 42 where the cylinders were, as shown in Figure 4(a). These can then be used to inject the material for the top layer 44 through, thereby to form the two layer top shell, as shown in Figure 4(b).

In another technique, a single metal mould fixed on one machine is used. After the base is made, the whole mould moves or rotates on the machine to then present the second injection holes to a second injection screw fitted to the same machine. The top injection is then made through the holes to create the top surface. The back of the mould is motorised to create the second injection void after the first injection stage. With this process, production is faster and more efficient, and because only one machine is powered up and heated rather than two, energy is reduced and wear and tear / maintenance is halved. In the methods described above, if the materials for the base and top layers used are very similar then it is preferable to inject the top layer onto the still warm or semi set base and cool them together, as doing so reduces the shrinkage and mould time and the part comes out with less internal stress. If the parts are very different materials or have a large difference in melting / setting temperature or shrinkage rate then the first plastic needs to have set before the second can be injected. Yet another technique uses a single screw feed chamber that positions a first molton material inside a second material. In the present case, the base material, which is provided for strength would be the internal material, and the top later material, which determines the look and feel of the tray would be the second external material. The molten blob is injected into a single mould 50 and makes the tray in single step. This process is illustrated in Figure 5. In this case, the base material 51 , for example recycled plastic, is forced along the outer section of the screw 52 between its outer and inner walls, as shown in Figure 5 (a). Then the plastic for the top layer 53 begins its journey along the inner tube or screw 52 to reach the gate at the front of the barrel, see Figure 5 (b). Both plastics reach the gate at the head of the screw, Figure 5 (c). The middle barrel and outer barrel points retract to create the "shot" that goes into the mould, as shown in Figure 5 (d). The gate on the barrel opens and forces the plastic into the mould together - with the virgin plastic entering first. Recycled plastic 51 follows the virgin plastic 53 into the mould and sits in the middle of the "shot". In this case, even though the base material may be made of recycled material the end product looks as if it is made entirely from virgin plastic whilst having a centre of recycled plastic. There are numerous benefits of this process. For example, there is less chance of warpage and the cost and complexity of multiple moulds, machines, screw feeds or moulds can be avoided.

In all of the methods described above, the material used for the base is selected for its strength. Since its external surface is completely covered by the top layer, its appearance does not matter. Because of this, the base may be made from materials such as plastic and rubber. In contrast the top layer has to be made from material with good quality external properties. As a specific example, the base may be made of recycled material and the top layer may be made from virgin plastic. This could give a tray that has recycled plastic in the base of approx. 5 kg and virgin plastic on the surface that is approx. 3.4 kg for a 900mm x 900mm quadrant shaped tray. The weights of the top shell can be varied, as can the materials. For the base, one option is a blend of PP (polypropylene) + PC (polycarbonate) + ABS (Acrylonitrile butadiene styrene) + PVC (polyvinylchloride) and PS (polysulphones). For the top surface, a blend of SAN + PC + ABS and a plasticiser / rubberiser may be used to improve its flexibility, so that when this is applied and it contracts over the base it does not contract so strongly that it warps the tray. When it contracts it stretches to cover the surface. A benefit of using a rubber mix is that the hardness is reduced of the top surface making it more comfortable to stand on. Also, the material provides increased grip with reduced slippiness making it safer. The types of chemicals used for this surface plastic are commonly described as - TPO(thermoplastic olefin), TPV(thermoplastic vulcanizate), SBC(styrenic block copolymer blend), TPE or TPU(thermoplastic urethane elastomer), COPE(co-polyester elastomer), SEBS(styrene-ethylene/butylene-styrene block copolymer), POE(polyolefin elastomer), SBC(styrenic block copolymer), SBS(styrene-butadiene-styrene), SIS(styrene- isoprene-styrene), COPA( co-polyamide elastomer).

A lighting system may be added to the tray. The lights - an example being LED (light emitting diode) lights of any colour or size may be moulded into the base and powered by a small turbine fitted in line to the cold or hot water feed pipe leading to the shower valve. When the shower is turned on rotation of the turbine blades causes generation of a small amount of electricity, sufficient to turn the lights on. The lights can be used for illumination or can be arranged for use as a temperature gauge. In the latter case, a temperature sensor would be provided for sensing the temperature of the water. The sensor is linked to a controller that controls the lights depending on the sensed temperature. This would also have the safety benefit of warning the user of the shower of any sudden changes in the temperature of the water travelling to the shower head and enable the user to remove themselves from the shower stream before the varied temperature water reached them.

Figure 6 shows a shower tray 60 that is fitted with a generator 61 that is connected in- line with the water supply for the shower 62. Connected to the generator 61 is a controller 62 that is connected to a temperature sensor 64 and a plurality of lights 65. The lights may be of any colour but in a preferred embodiment, are presented in a column with the lower third being blue to indicate that the water is cold; the middle third being green to indicate that the water is at a comfortable temperature and the top third being red to indicate that the water is hot. When the water is turned on the generator generates power, which powers up the controller, which in turn activates the temperature sensor. The sensor 64 sends information on the temperature to the controller which causes the appropriate light to be illuminated. In this way a visible indication of the water temperature is automatically provided. Excess power from the turbine may be stored in a battery next to the generator. When the shower is turned off the lights will stay lit using the retained power in the battery until this is expended and then extinguish. The lights can be in any colour, shape or pattern and can also be controlled to flash in sequence or when a sudden change in temperature is detected. The temperature lights can also be placed within the tray, on the tray surface or on the wall or shower column next to the tray.

Whilst the lights of Figure 6 are provided separately from the tray, they could be moulded directly into the surface or between two injections of the plastic. In this case, the first (top part) of the tray can be made from clear or semi transparent polycarbonate / ABS / impact modified S.A.N. (STYRENE- ACRYLONITRILE ) or other polymer. This would be at the bottom of the mould and the lights in a string formation would be placed in the desired pattern on this Polycarbonate / plastic etc. layer. The mould would then close and a second injection of plastic would then seal the lights inside the tray between the two layers. The second layer can be the recycled layer of plastic or any type of plastic. This can also be another thin layer of plastic with and without a sub structure so that resin can then be filled into the void behind or left with a substructure and sold without any filler.

A skilled person will appreciate that variations of the disclosed arrangements are possible without departing from the invention. For example, the double layer injection techniques described above could be used to make a bath. In this case back-filling would be unnecessary. Accordingly, the above description of specific embodiments is made by way of example only and not for the purposes of limitations. It will be clear to the skilled person that minor modifications may be made without significant changes to the operation described.