FR2713432A1 - Electric heating resistance for a container intended to receive water to be heated, in particular a kettle. - Google Patents

Abstract

The electrical resistance (4) comprises a metal outer tube (7). The tube (7) is covered with a coating (9) of metal or alloy having the properties of being compatible with the feed, of resisting organic acids and of preventing the adhesion of the scale deposit resulting from the heating of the water.

Description

1 2713432

  The present invention relates to an electrical heating resistance for a container intended to receive

  water, especially a kettle.

  The invention also relates to a kettle comprising the above electric heating resistance. The electrical heating resistors fitted to water heaters, such as kettles, include an outer tube generally made of copper inside which is placed a resistive wire isolated from the outer tube by a powder in

  mineral matter such as magnesia.

  To protect the copper tube against oxidation caused by contact with hot water, this tube is generally covered by a coating of

  nickel obtained by electroplating.

  Experience shows that the above resistances

  above, gradually cover, during use, a deposit of tartar resulting from the presence in the water of mineral elements and in particular

of limestone.

  This scale deposit is strongly encrusted on the surface of the nickel coating of the element, so that after a certain period of use of the kettle, it becomes very difficult

to eliminate the deposit of tartar.

  Organic acids such as acetic acid must be used to dissolve the

deposit of tartar.

  However, these acids may damage the

resistance coating.

  The object of the present invention is to remedy

  to the disadvantages of the resistances known above.

  The invention thus relates to an electrical heating resistance for a container intended to receive water to be heated, in particular a kettle, this

2 2713432

  resistance including an external metal tube.

  According to the invention, this resistance is characterized in that said tube is covered with a metal or alloy coating having the properties of being compatible with food, of resisting organic acids and of avoiding the adhesion of the deposit. of

  scale resulting from water heating.

  According to a first version of the invention, said coating consists of a tin alloy and

  nickel, in which tin is predominant.

  According to another version of the invention, said

  coating consists of a nickel + gold bilayer.

  The Applicant has surprisingly found that when the electrical resistance of a kettle was coated with a layer of tin alloy and nickel or gold, the adhesion of the tartar was much weaker than on conventional resistors , so it was very easy to detach this tartar. This result was completely unexpected and does not follow from the properties

known from the above metals.

  Other features and advantages of

  the invention will appear from the description below

  after. In the accompanying drawings given by way of nonlimiting examples: - Figure 1 is a schematic sectional view of an electric kettle; Figure 2 is an enlarged view in

section of detail A in figure 1.

  The electric kettle shown in Figure 1 comprises a container 1 for example of

plastic with handle 2.

  Above the bottom 3 of the container 1, extends an electrical resistance 4 fixed to the side wall 5 of the

  container 4 by means of a metal flange 6.

  The electrical resistance 4 includes (see

3 2713432

  Figure 2), an outer metal tube 7 for example copper surrounding a resistive wire 8 electrically isolated from the tube 7 by a powder filling for example

made of magnesia.

  According to the invention, the tube 7 of the resistor 4 is covered with a coating 9 of metal or alloy having the properties of being compatible with food, of resisting organic acids and of avoiding encrustation, c is strong adhesion

  of the scale deposit resulting from the heating of the water.

  In a first embodiment, the coating 9 consists of an alloy of tin and

  nickel, in which tin is predominant.

  For example, this alloy comprises 80% tin and 20% nickel. The thickness of this coating is preferably between 5 and 20 μm. This coating can be applied to the outer tube 7 of the resistance by electrolysis in a solution containing

  tin and nickel ions in the above proportion.

  In a second embodiment, the

  coating 9 consists of nickel 9a and gold 9.

  The thickness of the gold layer 9 can be very small because

example between 0.1 and 2 mm.

  When the kettle is in operation,

  ie when heating the water, the metal ions in particular the calcium contained in tap water

settle on the resistor 4.

  It is noted that thanks to the coating 9 which covers the resistance, the adhesion of the limestone is weak and is easily detached during a simple descaling. Instead of becoming encrusted on the surface of the resistance to form a layer which strongly adheres to the latter, the major part of the layer of tartar comes off in the form of fine particles in the water of the container.

4 2713432

  For this purpose, it is advantageous to provide the kettle with a filter 10 placed near and upstream of the pouring spout 11, capable of retaining the limestone particles liable to form during the heating of the water. Thus, the joint use of the filter 10 with that of the coating 9 of the electrical resistance makes it possible to solve the problem due to the deposit of tartar or lime in a kettle and more generally in a heating container containing a resistance

electric in contact with water.

2713432

Claims (9)

  1. Electric heating resistor (4) for container (1) intended to receive water to be heated, in particular a kettle, this resistor (4) comprising a metal outer tube (7), characterized in that said tube ( 7) is covered with a coating (9) of metal or alloy having the properties of being compatible with food, of resisting organic acids and of avoiding the adhesion of the deposit of scale resulting from water heating.   2. Electrical resistance according to claim 1, characterized in that said coating (9) consists of an alloy of tin and nickel,   in which tin is preponderant.   3. Electrical resistance according to claim 2, characterized in that the alloy   includes 80% tin and 20% nickel.   4. Electrical resistance according to claim 1, characterized in that said coating (9) consists of gold (9) and nickel (9a) in sublayer. 5. Electrical resistance in accordance with one of the   claims 2 or 3, characterized in that the thickness   of the tin-nickel alloy coating is between 5 and 20 mm.   6. Electrical resistance according to claim 4, characterized in that the thickness of the   gold coating is between 1 and 5 mm.   7. Electrical resistance in accordance with one of the   claims 1 to 6, characterized in that the   coating (9) is obtained by electrolytic and / or chemical deposition. 8. Electric kettle including a   electrical resistance according to one of claims 1 to 7.   9. Electric kettle in accordance with 6 2713432   claim 8, characterized in that it comprises a filter (10) capable of retaining limestone particles   likely to form when heating water.