WO2016097980A1

WO2016097980A1 - Boiler with electric heating

Info

Publication number: WO2016097980A1
Application number: PCT/IB2015/059597
Authority: WO
Inventors: Federico ZOPPAS; Roberto FRARE; Roberto VEDOVATO; Paolo De Noni; Giuseppe Dominici; Carlo Sonego
Original assignee: I.R.C.A. S.P.A. Industria Resistenze Corazzate E Affini
Priority date: 2014-12-15
Filing date: 2015-12-14
Publication date: 2016-06-23

Abstract

A boiler for heating water of the type having a water container, inside which there is a heating electric resistor, wherein the end parts of said resistor protruding from the container are laser welded onto the edges of two through holes made in a wall of said container by using weld material.

Description

BOILER WITH ELECTRIC HEATING

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Field of the invention

The present invention relates to a boiler for generating hot water of the type which contains an internal electric resistor as heating element.

Background art

Boilers for generating hot water or steam which are electrically heated by means of resistive elements consist, in general, of a container for the liquid to be heated in which the resistive element is located either external to the container in contact with the walls or internal to said container immersed in the liquid to be heated.

In the case of electric resistor external to the container, it is important to consider the thermal inertia caused by the thickness of the walls which inevitably causes longer heating times and losses of heat.

An improvement from this point of view is the use of boilers in which the heating resistor is located inside the container, this solution being particularly interesting in machines for preparing hot beverages, in particular in espresso coffee machines. The resistor can be introduced inside the container which is formed by two parts subsequently welded to each other, one part of which could be a lid with specific holes through which the terminals of the resistor may exit for connecting to the power supply circuit.

In the case of internal resistor, it is important to guarantee the hydraulic sealing and the positioning of the resistor by welding it into the container at the passage holes. For sealing reasons, the passage holes must have a narrow tolerance with respect to the dimensions of the cross section of the resistor, which is generally circular. Furthermore, the walls of the container are typically thin for production saving reasons, thus implying both a limited availability of the material to be melted and possible deformations of the container. The use of specific flanges or collars, as described in WO 2006/002965, is therefore needed. Such flanges, which protrude beyond the outer wall of the container, surround the openings in which the end parts of the resistor are directly welded to the latter. Disadvantageously, such flanges or collars complicate the pattern of such boilers, thus reducing the production speed and increasing the costs thereof. The need is thus felt to make an internal resistor boiler and a method for producing internal resistor boilers which allows to overcome the aforesaid drawbacks.

Summary of the invention

It is an object of the present invention to make a boiler with internal electric heater in which the heating electric resistor is fixed to a wall of the container of said boiler by means of a laser welding and without the use of particular flanges and thus equally ensuring a good hydraulic seal.

Laser welding can offer the opportunity to optimize the production cycles in addition to limiting thermal distortions of the components.

The present invention thus reaches at least the object discussed above by making a boiler for heating water or generating steam according to claim 1 , comprising:

- a container provided with an inlet for the cold water and an outlet for the hot water,

- a tubular-shaped sheathed resistor contained in said container, wherein said resistor is provided with two end parts for connections to a power supply system, wherein said end parts cross a wall of said container, through two holes obtained in said wall having geometric shape conforming to the cross section of said sheathed resistor, without protrusions beyond the contour of the wall,

wherein said end parts are fixed to said wall along the edges of said holes by laser welding using weld material not obtained from the material of said wall.

It is another object of the present invention to make a method, according to claim 6, for producing a boiler for heating water or generating steam, comprising the following steps:

- providing a container for the water formed by two or more parts formed by means of a molding process,

- providing two holes in a wall of one of said parts without protrusions beyond the contour of the wall,

- providing a sheathed resistor having two end parts and a central portion, said central portion being positioned inside said container,

- inserting the end parts of said sheathed resistor in the two holes,

- laser welding said end parts to the edges of said holes using weld material,

- joining two or more parts which compose the container.

The laser welding contemplates the use of weld material and is performed by melting all three concerned materials, i.e. the weld material, the material of the boiler, in particular the material of the wall near the holes, and the material of the sheathed resistor, in particular the wall of the resistor in a welding zone. Alternatively, the laser welding occurs by melting only the weld material, i.e. by means of a brazing process. Hereinafter, it is understood that, when reference is made to a welding process, it can also be a brazing process.

Advantageously, a uniform welding bath is obtained by using the weld material. Advantageously, the weld material will be the most adapted to weld the material of the sheath of the resistor to the material of the boiler.

Preferably, the weld material is raw material, meaning it does not have a specific shape, so as to minimize production costs.

Preferably, the container comprises two parts welded to each other which are identical to each other. Preferably, in this case, the only difference between the two parts is that one of the two is provided with two holes.

Advantageously, in all embodiments of the invention, the holes do not have any particular feature such as raising, deep-drawings, deformations or protrusions of the edges beyond the outer profile of the wall in order to facilitate the welding, i.e. to provide material for welding because such weld material is provided only externally and not obtained to the detriment of the thickness of the wall or of the possible sheath of the resistor. In particular, the edges of the holes do not have deformations or protrusions in direction of the axis of the end parts of the resistor.

The dependent claims describe preferred embodiments of the invention.

Brief description of the figures

Further features and advantages of the invention will be more apparent in light of the detailed description of a preferred, but not exclusive embodiment of a boiler for heating water illustrated by way of non-limitative example, with reference to the accompanying drawings, in which:

Fig. 1 is a boiler according to the invention;

Fig. 2 is an enlarged detail showing where the laser welding is applied.

The same reference numbers in the figures identify the same members or components.

Detailed description of a preferred embodiment of the invention Fig. 1 and 2 show a water heating boiler according to an embodiment in a preferred embodiment of the present invention. The boiler 100 comprises the water container 1 formed by two parts 10 and 11 , which are symmetrical with respect to a plane perpendicular to the longitudinal central axis X, said parts being cup-shaped.

The two bases of the two cups are provided with a hole for inserting the cold water supply pipe 4 and the hot water outlet pipe 5, respectively.

The sheathed resistor 6 shaped as a serpentine is located inside the assembled boiler.

The sheathed resistor 6 ends with two end parts 7, 8 which protrude from the container through two holes obtained in one of the two walls of the container, in the example in figure on the wall 11 which is a base of one of the two cups.

It is worth noting that the holes do not have any particular feature such as raising, deep-drawings, deformations or protrusions of the edges beyond the outer profile of the wall 11 in order to facilitate the welding, i.e. to provide material for welding because such weld material 3 is provided only externally and not obtained to the detriment of the thickness of the wall or of the possible sheath of the resistor. In particular, at least the thickness of the inner wall which delimits each hole is substantially constant. Preferably, at least the thickness of such an inner wall is very thin and is comprised between 0.5 and 2 mm, even more preferably between 0.8 and 1 .5 mm. Preferably, the thickness of the entire wall 11 is comprised between 0.5 and 2 mm, even more preferably between 0.8 and 1 .5 mm. It is further preferable that the thickness of all the walls of the container is comprised between 0.5 and 2 mm, even more preferably between 0.8 and 1 .5 mm.

Fig. 2 shows a detail of such a welding around the edges of one of said holes. The fixing by means of laser welding using weld material 3 offers the advantage that the laser can be focused, by means of a specific optics, mainly only on the weld material 3 so that the parts to be welded, the sheath of the resistor and the base of the container do not undergo any deformation due to the low thermal contribution ensured by the use of a laser.

By virtue of the limited thermal contribution of the laser welding and the use of the weld material 3, the assembly of the complete resistor of the boiler can occur without damaging the components of the resistor itself, such as for example thermal protections, sealing, plastic elements, thermal fuses etc.

Another advantage of laser welding using weld material 3 is, as noted above, that the passage hole does not require particular finishing or special shapes to be exploited as weld material because the contribution of such a material 3 is completely external and is not taken to the detriment of the material of the wall of the tank, the thickness of which, for example, is not reduced.

Furthermore, another advantage is that the most suitable weld material 3 can be chosen for welding the material of the resistor sheath to the material of the boiler. For example, if the container is made of stainless steel, the weld material 3 is preferably made of stainless steel or nickel alloy.

Once the sheathed resistor is fixed onto one of the walls of the two cups which form the boiler, the latter can be assembled by joining, e.g. by welding, said two cups so as to close the container.

Another advantage of not needing to form a lid provided with possible flanges for welding is that the container can be formed by means of the same mold used for the two parts which compose the container, which two parts may indeed be identical. Furthermore, besides the formation of the holes, such a container does not require another type of processing, and so the production processes can be accelerated. Such holes can, by way of example only, be produced by means of a simple piercing process. Furthermore, the inner diameter of the holes is only slightly greater than the outer diameter of the wall of the resistor. For example, but not exclusively, the inner diameter of the wall of each hole is greater than the outer diameter of the wall of each end portion of the resistor by 0.8 mm at most, preferably 0.5 mm at most. The invention has been described with reference to a preferred embodiment of the boiler but it is apparent that other types of construction are possible without departing from the spirit of the invention which consists in its essence in fixing a sheathed resistor onto a wall of the container of a boiler for heating water or for generating steam, by means of laser welding with the use of weld material.

Claims

1 . A boiler (100) for heating water or for generating steam, comprising:

- a container (1 ) formed by two or more parts (10, 11 ) and provided with an inlet (4) for cold water and an outlet (5) for hot water,

- a tubular-shaped sheathed resistor (6) contained in said container (1 ) wherein said resistor is provided with two end parts (7, 8) for connections to a power supply system,

wherein said end parts (7, 8) cross a wall (11 ) of said container, through two holes made in said wall (11 ) having geometric shape conforming to the cross section of said sheathed resistor, without protrusions beyond the contour of the wall, wherein said end parts (7, 8) are fixed to said wall along the edges of said holes by laser welding using weld material (3) not obtained from the material of said wall (11 ).

2. A boiler according to claim 1 , wherein said sheathed resistor (6) defines a contiguous central section to said end parts (7, 8) shaped as a serpentine contained within said container (1 ).

3. A boiler according to claim 1 or 2, wherein the thickness of the wall (11 ) is comprised between 0.5 and 2 mm.

4. A boiler according to claim 3, wherein the thickness of the wall (11 ) is comprised between 0.8 and 1 .5 mm.

5. A coffee machine or machine for making hot beverages comprising a boiler (100) according to one of the preceding claims.

6. A method for producing a boiler (100) for heating water or for generating steam according to the preceding claims, comprising the following steps:

- providing a container (1 ) for the water formed by two or more parts (10, 11 ) formed by means of a molding process,

- providing two holes in a wall of one of said parts,

- providing a sheathed resistor (6) having two end parts (7, 8) and a central portion, said central portion being positioned inside said container (1 ),

- inserting the end parts (7, 8) of said sheathed resistor (6) in the two holes, - laser welding said end parts (7, 8) to the edges of said holes using weld material (3) not obtained from the material of said wall,

- joining two or more parts (10, 11 ) which compose the container (1 ).

7. A method according to claim 6, wherein said welding is performed by melting the weld material (3), the wall (11 ) near the holes and a portion of the outer wall portion of the sheathed resistor (6).