GB2330402A

GB2330402A - Water heater or steam generator with electrical heating element

Info

Publication number: GB2330402A
Application number: GB9822677A
Authority: GB
Inventors: Jacques Imbeau
Original assignee: Moulinex SA
Current assignee: Moulinex SA
Priority date: 1997-10-17
Filing date: 1998-10-16
Publication date: 1999-04-21
Also published as: FR2770077B1; FR2770077A1; DE19847670A1; GB9822677D0

Abstract

A water heater or steam generator is heated by a flat heating element 25 which forms a wall of the water containing chamber 18 and includes a screen-printed electrical element 31. The heating element consists of a plate 27 of stainless steel, at least one layer 29 of electrically insulating material deposited by screen-printing on the plate 27, and at least one resistive track 31, which is screen-printed on the layer 29 and protected by another layer 33 of electrically insulating material deposited by screen-printing. To form the chamber 18, the heating element 25 is attached to a body 12 of moulded thermoplastic material, such as a polyphenylene sulphide, by crimping the rim of the plate 27 to the rim of the body with the interposition of a silicone sealing joint 42. The water heater/steam generator may form part of an espresso coffeemaker or a steam iron.

Description

1 2330402 BOILER FOR A DOMESTIC ELECTRICAL APPLIANCE AND A DOMESTIC

ELECTRICAL APPLIANCE INCORPORATING SUCH A BOILER The present invention concerns a boiler for an appliance for domestic use utilising hot water and/or steam, having a body defining a chamber and with an inlet for introducing water into the chamber, and an electric heating means associated with the said body for heating the water admitted into the chamber, the said body having an outlet for extracting hot water or steam formed in the chamber.

In known boilers of this type, the heating means consists of an armoured tubular electrical element which is fixed by crimping or welding to the external surface of the body, generally to the base thereof. By its very structure, such a heating element is in contact with only part of the external surface of the base of the boiler body, so flange plate it does not make it possible to obtain good homogeneity of temperature distribution. In addition, the method of fixing this heating element to the base of the body does not allow optimum heat transfer and, in addition, it is complex and costly.

The aim of the invention is notably to remedy these drawbacks and to produce a boiler for a domestic electrical appliance, of the type disclosed above, which affords rapid heating of the water whilst ensuring uniform distribution of the heating, and which is inexpensive to manufacture.

According to the invention, the heating means comprises a flat screenprinted electrical heating element, which constitutes one of the walls of the body and which is attached to the said body.

Thus, by virtue of its production by screen-printing technology, the screen-printed flat heating element has low thermal inertia, so flange plate it makes it possible to obtain immediate triggering of the heating, as well as a very rapid temperature rise of the water. In addition, this screen-printed flat heating 2 element distributes the heating temperature homogeneously in the boiler chamber, and is inexpensive to produce.

Preferably, the boiler body is produced from a thermoplastic material, such as in particular a polyphenylene sulphide.

The invention also relates to a domestic electrical appliance incorporating a boiler according to the invention.

This domestic electrical appliance consists of a coffeemaker of the "espresso" type, or an iron in which the boiler is integrated, the latter producing solely steam, or an iron with an independent steam generator, commonly referred to as a steam generator iron.

The characteristics and advantages of the invention will moreover emerge from the description which follows, by way of non limitative example, with reference to the accompanying drawing in which the single Figure is a view in vertical section of a boiler for a domestic electrical appliance according to the invention, having a flat heating element illustrated to an enlarged scale.

In the example embodiment depicted in the Figure, 10 designates a boiler according to the invention intended to be used in a coffeemaker of the "espresso" type in order to generate therein, by means of a selector, either hot water with steam for making an "espresso" coffee, or hot water solely, or steam alone. This boiler turn is also intended to be integrated into an iron in order to produce steam therein, or to be connected to an iron by a flexible hose in order to constitute an iron with an independent steam generator.

It should be stated flange plate the production of hot water and/or steam, depending on the type of application envisaged above, is obtained as a function of the volume of the boiler and of the heating temperature.

3 With regard to the Figure, the boiler 10 has a body 12 which has, in this example embodiment, the form of a flange plate having a peripheral rim 14, as well as an electric heating means, designated by the general reference 16, associated with the body 12 and defining together a chamber 18. The boiler body 12 has, in its sidewall 19, an inlet coupling 21 for introducing water into the chamber 18 and being connected, optionally, to an external supply pump (not shown), and at the opposite side to this inlet coupling 21, an outlet coupling 23 making it possible, after heating of the water, to extract hot water or steam formed in the chamber 18.

In a matter known per se, the outlet coupling 23 includes valve elements (not shown) allowing the extraction of the hot water or steam solely when the pressure of the water in the chamber 18 exceeds a given threshold.

According to the invention, the heating means 16 comprises a flat heating element 25 with a screen-printed electrical element, which constitutes one of the walls of the body 12 and which is attached to the body.

In the example embodiment illustrated in the Figure, the flat heating element 25 constitutes the base of the boiler body 12 in a form of a flange plate.

It should be emphasised that the boiler body could also be shaped as a cylindrical tube closed at both ends and whose longitudinal wall would be formed by the flat heating element 25 with a screen-printed electrical element, the two ends of the tubes incorporating respectively the inlet 21 and outlet 23 couplings, without for all that departing from the scope of the invention.

With regard to the Figure, the flat heating element 25 is thin and has a plate 27 made from stainless steel, at least one layer 29 of electrically insulating material deposited by screenprinting on the plate 27, and at least one resistive track 31, 4 of suitable profile, which is screen-printed on the layer 29 and which is protected by another layer 33 made of electrically insulating material deposited by screen-printing. One of the two conductive pads to which one of the two electrical connections (not shown) of the heating element is fixed, and which is also deposited by screen-printing on the layer 29, is depicted at 35 in the Figure.

This flat heating element 25, of high power (3000 watts for example), also has a thermal regulation means 38, such as a thermostat, which is mounted on the bottom face of the plate 27, in the position illustrated in the Figure) by means of suitable fixing members, such as for example screws.

After production of the flat heating element 25 by screenprinting and mounting of the thermostat 28, the stainless steel plate 27 is attached by crimping its peripheral edge 40 to the peripheral rim 14 of the body 12, with the interposition of a silicone ceiling joint 42 between the bottom face of the peripheral rim 14 of the body 12 and the top face 44 of the plate 27 of the flat heating element 25. As can be seen clearly in the Figure, the top face 44 of the stainless steel place 27 constitutes the base proper of the boiler body 12.

Preferably, the boiler 12 is moulded in one piece from a thermoplastic material with high temperature resistance, such as a polyphenylene sulphide.

It should be emphasised here that, in its application to an "espresso" coffeemaker, the use of 'both thermoplastic material forming the flange plate on the body 12 and stainless steel for the plate 27 forming the base proper of the body 12, advantageously prevents any migration of aluminium in the water which, as is well known, may, as from a certain diffused quantity, seriously impair the health of consumers.

Producing the heating element 25 by screen-printing thus enables the latter to supply a high localised thermal power distributed rapidly and uniformly in the base of the body 12 of the boiler, providing a very rapid rise in temperature of the water. In addition, the transverse thermal conductivity of the element 31 screen-printed on the stainless steel plate 27 is very low, which advantageously prevents any excessive heating of the sidewall 19 of the boiler body 12.

By virtue of this screen-printed element, it can also be envisaged producing several conductive tracks with different powers which, by means of a selector, can be fed separately and will thus produce rapid steam at high power and hot water at lesser power.

There has therefore been produced according to the invention a boiler for a domestic electrical appliance, such as-an "espresso" coffeemaker or an iron with integral or separate boiler, which is particularly advantageous both from the point of view of its thermal efficiency and from the point of view of its simplicity in design 6

Claims

1. Boiler for a domestic electrical appliance, having a body (12) defined in a chamber (18) and with an inlet (21) for introducing water into the chamber and an electrical heating means (16) associated with the said body (12) for heating the water admitted into the chamber (18), the said body (12) having an outlet (23) for extracting hot water or steam formed in the chamber (18), characterised in that the heating means (16) comprises a flat heating element (25) with a screen-printed electrical element (31) which constitutes one of the walls of the body (12) and which is attached to the said body (12).

2. Boiler according to Claim 1, characterised in that the flat heating element (25) has, from the inside of the chamber (18) towards the outside, a stainless steel plate (27) attached to the body (12), at least one layer (29) of electrically insulating material deposited by screen- printing on the said plate (27), and at least one resistive track (31) screen-printed on the said layer (29) and protected by another layer (33) of electrically insulated material deposited by screen-printing.

3. Boiler according to Claim 1 or 2, characterised in that the body (12) is produced from a thermoplastic material.

4. Boiler according to Claim 3, characterised in that the thermoplastic material is a polyphenylene sulphide.

5. Boiler according to Claim 4, characterised in that a ceiling joint (42) is interspersed between the flat heating (25) and the body (12)

6. Boiler according to any one of the preceding Claims, characterised in that the body (12) has the form a flange plate 7 having a peripheral rim (14) to which the flat heating element (25) is attached by crimping.

7. Domestic electrical appliance having a boiler (10) according to one of Claims 1 to 6.

8. Domestic electrical appliance according to Claim 7, characterised in that it consists of a coffeemaker of the ',espresso" type.

9. Domestic electrical appliance according to Claim 7, characterised in that it consists of an iron in which the boiler (10) is integrated, the latter prodUcing solely steam.

10. Domestic electrical appliance according to Claim 7, characterised in that it consists of an iron with an independent steam generator.