DEVICE CONSISTING OP MODULAR ELEMENTS FOR THE ELECTRICAL INSULATION OF PIPES

D E S CRIP TION

The object of the present invention is a safety device of the type suitable for preventing dangerous electric discharges from being transmitted from a first portion of metal piping to a second consecutive portion; in particular, such electrical discharges from being transmitted from an electrical storage or instant water heater, 5 to user-accessible parts.

It is known that in electrical storage water heaters, heating occurs through electrical resistance immersed in water, substantially consisting of an outer metal sheath, an inner resistive filament and a layer of dielectric material interposed between sheath and resistive filament.

10 Breakage of the outer sheath allows the water contained in the tank to contact the resistive filament, so that the water is under power and therewith, all the electrically conductive parts connected thereto.

If the safety rules are observed both in the construction of the product and in the making of the electrical plant, such breakage of the sheath does not cause dangerous

15 situations, hi fact all the metal parts of the water heater, as well as the electrical plant, have a ground connection, besides the fact that a cut-out box is provided. Actually, it can often happen that the electrical plant is inattentively not provided with ground or even worse, in some Countries it can happen that the three phase, neutral and ground wires are connected in a totally casual manner to the terminals of

20 the electrical socket. In that case, right through the grounding connections of the

water heater, the user or the installer could be immediately electrocuted as soon as the water heater, even if undamaged, is connected to the mains. The remedy to such situation of course seems very easy: the installer should not connect the water heater if the electrical plant is not regular; in some areas or Countries, however, it is not safe to rely upon the sense of responsibility of the installer.

Such very serious risk is therefore prevented with two types of protections that are conceptually very different; the first one is active and the second one is passive. The active protection type uses electronic and electromechanical means and consists in a device interposed between the electrical plant of the water heater and the current socket, which detects any anomalies in the electrical plant; if found, the device prevents the electrical connection of the water heater to the mains. Devices of this type are not cumbersome and substantially do not alter the architecture of the water heater, but exhibit the drawback that a fault thereof could allow dangerous situations.

The passive protection type, on the other hand, ensures full electrical insulation of the water heater from any part that could come into contact with the user and this occurs through two different devices: insulation of the accessible metal parts of the water heater: all the normally accessible metal parts of the water heater (enclosure and wall brackets, for example) are electrically insulated from the inside metal parts and from water; insulation of the water heater from all the user accessible pipes by a pair of devices hereinafter called water insulators; water insulators are static devices interposed between the hydraulic connections of a water heater and the corresponding delivery and collecting pipes, so that the incoming and outgoing water from the water heater flows therethrough, in a duct made of electrically insulating material and sufficiently long to prevent currents with dangerous or in any case undesired value from passing through the water contained therein, despite being electrically conductive. The use of water insulators has been known for years in many electrical instant water

heaters, wherein heating takes place by resistive electrical filaments directly in contact with water, but there is no current transmission outside the water heater through the pipes because water paths are provided upstream and downstream of the electrical filaments traced as coils in sufficiently long ducts of plastic material. Hereinafter, "water path" shall be used to mean the length of the path the electrical current must flow through from a first conductive element of the water heater, subject to a predetermined electrical potential, along pipes or ducts of insulating material, up to a second conductive element separate from the water heater, and directly or indirectly accessible by a user subject to a different potential (in particular to the ground potential).

The minimum length of the water path that prevents dangerous or undesired electrical discharges is proportional to the electrical conductivity of water that could greatly vary according to the zone or to the Country, depending on the quantity of substances dissolved in water. By way of an example, the electrical conductivity measured in some places follows. Place Conductivity (μS/cm)

Centre of Italy 790

Calcutta 3500

Shangai 700 Quang Nam (Vietnam) 65

Hai Phong (Vietnam) 4890

Water insulators have been used for a few years in emerging Countries as safety device for the above reasons. Several technical solutions thereof exist, but they all substantially consist in pipe portions of plastic material interposed between water heater and water network.

Some solutions, reference shall be made for example to the figures supplied with document CN 1.358.971, provide for such pipes to be inside the water heater tank. Other solutions envisage the pipes external to the tank, in the form of spirals of flexible pipes or winding paths with stiff pipes and elbows, optionally protected by fairing.

A drawback of the arrangement inside the tank is that the length of the water path is predetermined upon production and therefore must take into account the worst cases or give up taking them into account because the space occupied by the pipes would be too much. Another serious drawback is that any damages to the plastic pipes, for example due to accidental overheating of the tank, cannot be detected.

As regards the arrangement outside the tank, a drawback of known solutions certainly is the space occupied, besides the appearance.

The general object of the present invention is to reduce, at least partly, the drawbacks mentioned hereinabove.

A specific object of the present invention is to indicate water insulators with a compact shape so that the overall volume thereof is reduced as much as possible relative to the length of the water path obtained.

A further specific object of the present invention, is to indicate water insulators wherein the length of the water path is easily changeable according to the electrical conductivity of water.

A further object of the present invention is to indicate water insulators whose appearance should be pleasant.

Said objects and further advantages are achieved with a water insulator as described below, in some preferred embodiments thereof, with the aid of the accompanying figures and in the annexed claims, which are an integral part of the description itself.

Fig. 1 shows a schematic view, in section, of a water insulator according to a possible variation of the invention, with elements first separate from each other and then combined. Fig. 2 shows a schematic view, in section, of a water insulator according to other possible embodiments of the invention.

Fig. 3 shows a schematic view of the bottom and top faces of some of the end and modular elements, provided in the water insulator according to possible embodiments of the invention. Fig. 4 shows a schematic view of the bottom and top faces of some of the end and

modular elements, provided in the water insulator according to other possible embodiments of the invention.

Fig. 5 shows a schematic front view of the bottom and top faces of some of the end and modular elements, provided in the water insulator according to further possible embodiment of the invention.

Fig. 6 shows a view of the end and modular elements, first separate from each other and then combined, provided in the water insulator according to a possible embodiment of the invention.

Fig. 7 shows a front view of the bottom face of a first modular element provided in the water insulator of fig. 6.

Fig. 8 shows a front view of the top face of said first modular element provided in the water insulator of fig. 6.

Fig. 9 shows a front view of the bottom face of a second modular element provided in the water insulator of fig. 6. Fig. 10 shows a front view of the top face of said second modular element provided in the water insulator of fig. 6.

Fig. 11 shows a perspective view, in section, of the water insulator of fig. 6.

Fig. 12 shows a view, in section, of a detail of a possible connection of the elements provided in the water insulator according to the invention to each other, first separate from each other and then combined.

Fig. 13 shows a view, in section, of a water heater with two water insulators according to the invention mounted at the water inlet and outlet.

As already clear from a brief examination of the figures, the water insulator according to the invention envisages: a pile of elements of an insulating material between whose opposite faces winding ducts for water flow are obtained; the fact that some of said elements of insulating material are modular and can be added at will in a repetitive manner, so as to adjust the length of the water path according to the electrical resistance required. Figs. 1 and 2 show, according to two embodiments, a water insulator 1 consisting of

a pile of multiple elements 2, 3, 4, 5.

More in detail, a first connector 2, provided with means 201 for the hydraulic connection to the water heater or to the pipes, is shown. The top face Sup of said connector 2 contacts the bottom face Inf of a first distributor 3, whose top face Sup in turn contacts the bottom face Inf of a first type modular element 4, which accordingly, has the top face Sup contacting the bottom one Inf of a second type modular element 5 which in turn, at the top may be provided, even if not shown in the figure, with a first type modular element 4 again, which may be followed by a further second type modular element 5, and so on, up to end the hydraulic pipe connection with a second distributor 3 and a second connector 2.

It is noted that the terms "bottom" and "top", as well as the identifications "Inf' and "Sup", only refer to the position with which the faces of elements 2, 3, 4, 5 are represented in some of the annexed figures and have no reference to the actual arrangement of the elements described. Each element 2, 3, 4, 5 of said pile is provided with a channel 801 dug on at least one of the faces thereof and a passage 802; the latter crosses the entire thickness of each element 2, 3, 4, 5 and is arranged in such position as to put in communication the second end of a first channel 801, arranged at a face of said element 2, 3, 4, 5, with the first end of a second channel 801, arranged at the other face of element 2, 3, 4, 5 itself.

By channels 801 arranged at a face of a generic element 2, 3, 4, 5 it is not meant that the channels themselves are necessarily dug on the face itself. In fact, said channels 801 may be arranged on a single face (reference shall be made to fig. 2) or on both (reference shall be made to fig. 1) of said elements 2, 3, 4, 5 but if they are arranged on both faces, those arranged on two faces intended for being contacted to each other match in their pattern.

Actually, elements 2, 3, 4, 5 provided with channels 801 may be alternating with diaphragms D (not shown) without channels 801, provided that said diaphragms D are provided with at least one passage 802 intended for establishing the connections described above.

A diaphragm D may usefully consist, for example, of a flat seal of elastic material, intended for separating the two channels 801 of the two elements 2, 3, 4, 5, between which diaphragm D itself is tightened, putting in communication said channels 801 only by passage 802 it is provided with. The result of such combination of elements 2, 3, 4, 5, and optionally of diaphragms D, is that said water insulator 1 is crossed by a winding and continuous duct 8, which begins at passage 802 of the first connector 2 to end at passage 802 of the second connector 2. Such duct 8 develops in a compact manner within elements 2, 3, 4, 5 and in addition, the length of the water path is variable at will, providing the necessary number of first and second type modular elements 4 and 5.

The embodiments, that envisage channels 801 dug on both faces of elements 2, 3, 4, 5 and facing each other in twos, are preferred as they allow obtaining ducts 8 with circular section that offer less load losses, passage section being equal. Figs. 3, 4 and 5 show, in a schematic manner, in a sequence from the left rightwards and separated by a dash and dot line, the bottom face Inf and the top one Sup of possible elements 2, 3, 4, and 5 which, for graphical simplicity, are shown in a square plan shape. In the figures, each top face Sup is shown in the view obtained by upturning each element 2, 3, 4, 5 according to said vertical dash and dot lines.

Each side face of elements 2, 3, 4, and 5 is marked by letters A, B, C and D; the pile assembly takes place by placing the faces identified by the same letter A, B, C and D on the same side of the pile itself. Of course, the bottom face Inf of each element 2, 3, 4, and 5, with reference to any side A, B, C and D, has a channel 801 that is the mirror image of that provided on the top face Sup of element 2, 3, 4 or 5 that precedes it in the pile.

As is clear in figs. 3 and 4, said first and second type modular elements 4 and 5 may be identical or different from each other. In fig. 4, said first and second type modular elements 4 and 5 have spiral channels 801 with passages 802 alternately at the periphery and at the centre of the modular

elements themselves and, at least for this reason, they are different from each other, whereas in fig. 3, which shows first and second type modular elements 4 and 5 with coil channels 801 and passages 802 always placed in the same position, it can be noted that the second type modular element 5 may consist in the first type modular element 4 rotated by 180°.

However, since the spiral shape of ducts 8 offers less load losses with equal length as compared to the zigzag one, the spiral solution is a preferred solution, even if it requires two modular elements 4 and 5 differing from each other. Fig. 5 shows another possible group of embodiments of the invention, wherein a single connector-distributor element 23 carries out the functions separately carried out by connectors 2 and distributors 3 of the previous examples. Connectors 2 and distributors 3, or connectors-distributors 23, arranged at an end of the water insulator 1, may be identical or different from those arranged at the other end, according to the shape of the first and second type modular elements 4 and 5 facing thereto.

Of course, said means 201 for the hydraulic connection to the water heater or to the metal pipes connectors 2 and connectors-distributors 23 are provided with may consist without distinction of male or female threaded inlets. Figs. 6 to 11 show a possible practical embodiment of the water insulator 1 with spiral ducts 8. The identification numbers used are the same already used in the previous figures.

It is clear that the best shape of elements 2, 3, 4 and 5 (23 if ducts 8 are spiral shaped), is that with circular plan. An essential aspect of the water insulator 1 is that the single sections of ducts 8 are perfectly sealed both to the exterior and also towards the other sections of duct 8 that run adjacent, otherwise a path shortening also occurs with water leakage, with the danger of hazardous electrical discharges.

Such sealing of channels 801 that make the sections of duct 8 may also be provided in several manners, also according to the material used for said elements 2, 3, 4, 5, 23 which, in any case, preferably, is a thermoplastic material with sufficient mechanical

and thermal features; for example, polyamide charged with fibreglass according to percentages of 30 - 40%.

A first sealing means may consist in suitably shaped rubber seals, for example the already mentioned diaphragms D, interposed between each bottom face Inf and corresponding top one Sup.

A second means may consist in the application of sealing mastics.

Of course such means require the single elements 2, 3, 4, 5, 23 to be kept tightened to each other by tie rods, not shown in the figures.

In any case, the preferred means consists in ultrasound welding of each element 2, 3, 4, 5, 23 to the next one, which is very reliable as regards completeness of the sealing and tensile strength.

Fig. 12 shows a detail of the connection between two generic consecutive elements 2, 3, 4, 5, 23, before and after the ultrasound welding process; a first element 2, 3, 4, 5 or 23, on the top face Sup exhibits a groove 9 which runs adjacent all the edges of channels 801, whereas the other element 2, 3, 4, 5 or 23, on the bottom face Inf exhibits a rib 10 intended for inserting in said groove 9.

Rib 10 ends with a sharp edge 1001 which, during the ultrasound welding, in known manner, e is made to press against bottom 901 of groove 9, acting as trigger for the local fusion made by the welding, and once fused, filling and closing groove 9. Fig. 13 finally shows an electrical storage water heater 11 heated by an electrical resistance 1101, wherein the cold water enters through pipe 1102 and exits through pipe 1103. Both outer ends of said pipes 1102 and 1103 are connected to the water network 1104 by two water insulators 1. The water insulator 1 has been described so far as a safety device against electrical discharges to be applied to electrical storage water heaters 11, but it can also be used in electrical instant water heaters 11 and in general, wherever the risk of transmission, through water and/or metal pipes, of electrical currents with dangerous or in any case harmful intensity (for example causing corrosion phenomena) should be avoided, interposing it between two sections of said metal piping.