A WATER HEATER MADE OF PRESSURE-RESISTANT PLASTIC MATERIAL

The present invention relates to the field of water heaters. The invention can be applied to electric water heaters, in particular those made of plastic materials.

Plastic materials are generally used for building water heaters of the type mentioned above, in order to avoid the drawbacks of traditional apparatus comprised of metal tanks which need to be specially arranged to withstand corrosion.

Document EP-A-0 674 139 shows a water heater made by joining two shells of a single plastic material, in particular polypropylene.

Document FR-A-2 620 803 shows a water heater with a shell of thermoinsulating expanded material, coated with a polyurethane foam jacket.

All water heaters of a known type mentioned above have a small capacity and cannot stand high pressures, for example operating pressures of 8 bar, at temperatures of up to 90°-100° C. They can stand, however, peak pressures of at least 16 bars as required by the field regulations in force. In addition, water heaters of a known type need to be made with rather thick layers of insulating expanded material in order to avoid a rapid loss of heat towards the outside.

The document DE-A-3 013 757 shows a water heater realised in plastic material, comprising a main body constituted by two semi-shells, which has a opening in the said main body in order to insert a heating element; each of the said semi-shell including radial reinforcing elements extending from each peripheral border to converge into a central area of each semi-shell.

The aim of the present invention is to overcome the drawbacks of the prior art technique, providing a water heater wherein the structural characteristics of the two semi-shells and the relevant joining method, contribute to obtain characteristics of high mechanical resistance and reliability in time also whenever high pressures are present.

Another aim of the present invention is to build a water heater that does not need a supplementary insulating layer besides the shells.

A still further aim of the present invention is to produce a water heater which is easy and cheap to build.

These aims are attaigned by a water heater comprising the features of claim 1.

The water heater of plastic material according to the invention, comprises a main body which has an opening suitable for insertion of an heating element and includes two semi-shells having a plurality of reinforcing elements extending from each peripheral border to converge into a central area of each of the said semi-shells, is characterised in that the peripheral border of each said semi-shell is supply with coupling means reciprocally coupable to form a more resistant bend.

Further characteristics and advantages of the present invention will better emerge from the detailed description of a preferred embodiment that follows with particular reference to the figures of the accompanying drawings, in which:

• figure 1 is a schematic cross section of a water heater built according to the present invention;
• figure 2 is a lateral view, partially in section, of one of the two semi-shells belonging to the water heater of figure 1, and
• figure 3 is a section, in a larger scale, of the borders of the two semi-shells positioned one next to the other before they are joined together.

With reference to figure 1, a water heater 1 made of plastic material resistant to relatively high pressures is comprised of a main body 2 consisting of two semi-shells 2a, 2b, wherein an electrical heating 3 is to be found which is fixed to a flange 4 mounted so as to cover an opening 5 on one of the two semi-shells 2a. Ducts 6 flow into the main body for feeding water in and out the water heater 1. An external box 7, which has mainly an aesthetic function, encloses the main body 2.

As may be observed in figure 2, each semi-shells 2a, 2b has a flattened cap shape and is entirely reinforced by a plurality of radial ribs 8. Along the periphery 9 of each semi-shells complementary joining belts 10a, 10b have been made for grafting into one another, as it is better shown in figure 3. In a preferred embodiment of the present invention, a joining belt 10b comprises a groove 11 within which it is possible to house a ring 12 of connecting material for constraining the two semi-shells 2a, 2b so as to form the main body 2. In particular, the joining belts 10a, 10b co-operate to form a cord of plastic material the thickness of which is bigger than the average thickness of each semi-shells.

The two semi-shells 2a, 2b are made of thermoplastic material, selected in order to ensure a high mechanical resistance and a low transmission of heat of the main body 2.

The special shaping of the joining belts 10a, 10b makes it possible, once these have been soldered together with techniques of a generally known type in the field of plastic materials, to perform a soldering between the two semi-shells 2a, 2b which is particularly resistant to deformations caused by the pressure inside the water heater.