Electric heater for machine for preparing hot beverages

Abstract

An electric heater (1), in particular a flow-through heater, for a machine for preparing hot beverages, comprising: a metal body (2); at least one electrical heating element (3, 4) arranged in the metal body (2), the electrical heating element (3, 4) being particularly adapted to generate heat when an electrical current flows through; a metal tube (5) arranged in the metal body (2) for the passage of the liquid to be heated; wherein the metal tube (5) is formed by a wall (50) extending around an axis (X); wherein the metal tube (5) has two end extensions (51, 52) and a central extension (53); wherein the roughness (Ra3) of the outer surface of the central extension (53) is greater than the roughness (Ra1, Ra2) of the outer surface of each of the two end extensions (51, 52).

Description

Technical Field

[0001] The present invention relates to an electric heater, in particular an electric heater of the flow through heater (FTH) type, for use in a machine for preparing hot beverages, such as coffee. Background Art

[0002] Electric heaters are commonly used to heat a liquid, such as water, flowing in a tube. One particularly advantageous type of electric heater is known as a "flow-through heater" or FTH.

[0003] FTHs are often used in machines for preparing hot beverages, such as coffee.

[0004] The FTH comprises a metal body in which a tube and one or more electrical heating elements, such as one or more resistors, are arranged. The liquid to be heated can flow in the tube, and the one or more resistors are adapted to heat the tube and, thus, the liquid flowing in the tube. In particular, the one or more resistors transfer the heat generated thereby to the metal body, which in turn transfers the heat to the tube.

[0005] Typically, the tube is brazed to the metal body. For brazing, a brazing paste or a paste for brazing is usually used.

[0006] It is important to get the best braze possible.

[0007] In fact, the quality of the brazing affects the conduction of heat from the metal body to the tube.

[0008] However, the brazing quality has not been optimal so far.

[0009] In particular, it is disadvantageous that the distribution of the brazing paste between the tube and the metal body may not be uniform.

[0010] Another disadvantage that may occur during the brazing process is the outflow of brazing paste from the metal body, which may undesirably cover the end extension of the tube located outside the metal body.

[0011] Furthermore, brazing has hitherto been carried out in a rather complicated manner.

[0012] Therefore, there is a need for improved FTH heaters, particularly to overcome the above-mentioned limitations of the background art.

[0013] Patent US 2009 / 310951 A1 describes a heater according to the prior art. Summary of the invention

[0014] The object of the present invention is to produce an electric heater, in particular of the FTH type, for a machine for preparing hot beverages, which allows a more effective, rapid and efficient heating of liquids, in particular water.

[0015] In particular, the object of the invention is to produce an electric heater in which the metal body and the tube are better fixed to each other.

[0016] In particular, it is an object of the invention to improve the brazing between a metal body and a tube.

[0017] Another object of the invention is to produce an electric heater which can be produced more easily relative to the background art.

[0018] The present invention achieves at least one of these objects, as well as other objects that will become apparent from the present description, by an electric heater according to claim 1, in particular a flow-through heater for a machine for preparing hot beverages, such as a household appliance, comprising:

[0019] -Metal body;

[0020] at least one electrical heating element arranged in the metal body, the electrical heating element being particularly adapted to generate heat when an electric current is passed through it;

[0021] a metal pipe arranged in the metal body for the passage of the liquid to be heated;

[0022] wherein the metal tube is formed by a wall extending around an axis;

[0023] Wherein, the metal tube has two end extension sections and a central extension section;

[0024] The roughness of the outer surface of the central extension section is greater than the roughness of the outer surface of each of the two end extension sections.

[0025] In particular, the metal tube and the metal body are brazed to each other, in particular by means of a brazing material. The brazing material is preferably a brazing paste or a paste for brazing.

[0026] Advantageously, the roughness of the central extension allows an improved distribution of the brazing material, in particular brazing paste. In fact, the brazing material penetrates into the grooves or channels of the outer surface of the central extension.

[0027] Since the roughness of the end extensions is less than that of the central extension, the brazing material can also be better confined to the central extension to prevent it from covering the end extensions.

[0028] By means of a channel or groove extending at least partially substantially around the axis of the tube, improved results are obtained, in particular with reference to the aforementioned limitations. Such a channel or groove extending in this way can be obtained, for example, by a satin finish, wherein the satin finish direction extends substantially around the axis of the tube.

[0029] One of the advantageous technical effects of the invention is improved brazing quality.Thus, advantageously, the electric heater according to the invention allows fast and efficient heating of liquids, in particular water.

[0030] Furthermore, greater constructional convenience is achieved, since it is easier to distribute the brazing paste over the central extension and it is also easier to confine the brazing paste to the central extension of the tube.

[0031] The invention also relates to a machine, such as a household appliance, for preparing hot beverages according to claim 10 .

[0032] According to claim 11, the invention also relates to a method for obtaining an electric heater, wherein the following steps are provided:

[0033] a) Mechanically finishing, preferably satin-finishing, the surface of a central extension of a metal tube, the roughness of which is greater than the roughness of the outer surface of each of the two end extensions, in order to obtain said metal tube.

[0034] Besides forming the above-mentioned channels or grooves, which allow an improved distribution of the brazing paste, the machining, and in particular the satin machining, allows the removal of impurities which are undesirable for obtaining a good brazing.

[0035] Further features and advantages of the present invention will become more apparent from the detailed description of exemplary but non-exclusive embodiments.

[0036] The dependent claims describe particular embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the description of the invention, reference is made to the accompanying drawings, which are provided by way of non-limiting examples, in which:

[0038] Figure 1 A top plan view showing an example of an electric heater according to the present invention;

[0039] Figure 2 Shows Figure 1 Section AA;

[0040] Figure 3 A tube of an electric heater according to the invention is schematically shown.

[0041] The same elements or components have the same reference numerals. DETAILED DESCRIPTION

[0042] With reference to the accompanying drawings, an exemplary embodiment of an electric heater 1 according to the present invention is described.

[0043] The electric heater 1 is particularly designed for use in a machine, such as a household appliance, for preparing hot beverages, such as coffee.

[0044] The electric heater 1 comprises:

[0045] Metal body 2;

[0046] at least one (ie one or more) electric heating element 3, 4 arranged in the metal body 2, in particular suitable for generating heat when an electric current flows through it;

[0047] A metal pipe 5 is arranged in the metal body 2 for the passage of the liquid to be heated.

[0048] In particular, the metal tube 5 is formed by a wall 50 extending around an axis X.

[0049] The metal tube 5 has two end extensions 51 , 52 and a central extension 53 .

[0050] The roughness Ra3 of the outer surface of the central extension 53 (particularly the outer surface of the wall 50 of the central extension 53) is greater than the roughness Ra1, Ra2 of the outer surface of each of the two end extensions 51, 52. Therefore, Ra3 is greater than Ra1, and Ra3 is greater than Ra2.

[0051] The axis X, also referred to as the axis of the tube 5, may be straight (as in the example shown) or curved, or it may comprise one or more straight extensions and one or more curved extensions. For example, the axis X may comprise a curved extension extending between two straight extensions.

[0052] Thus, in other words, the tube 5 may be straight, or may be curved, or may comprise one or more straight stretches and one or more curved stretches.

[0053] In particular, axis X is a longitudinal axis.

[0054] “Roughness” refers to the surface roughness, in particular the arithmetic mean roughness value, in particular according to ISO 4287, more particularly ISO 4287:1997.

[0055] In particular, an “extension” of the tube refers to a tube portion extending around the axis X, in particular a tube portion extending completely around the axis X and having a length along the axis X.

[0056] The central extension section 53 is located between the two end extension sections 51, 52. In particular, the central extension section 53 is adjacent to the two end extension sections 51, 52.

[0057] In particular, the metal tube 5 and the metal body 2 are brazed to each other, in particular by a brazing material. The brazing material is preferably a brazing paste or a paste for brazing.

[0058] In particular, the outer surface of the central extension section 53 is provided with a plurality of channels or grooves.

[0059] Preferably, and advantageously, the outer surface of the central extension 53 is provided with a plurality of channels or grooves extending substantially at least partially (eg partially or completely) around said axis X. Preferably, the channels or grooves extend around the axis X.

[0060] Preferably, the outer surface of the central extension 53 has a satin finish.

[0061] In particular, the outer surface of the central extension 53 preferably has a satin finish, the direction of which extends substantially around said axis X. Thus, the channels or grooves produced on the surface of the central extension 53 extend at least partially around the axis X.

[0062] Advantageously, the brazing material, such as brazing paste or a paste for brazing, penetrates the channel or groove. In particular, the brazing material, in particular the solidified brazing paste, is present between the metal tube 5 and the metal body 2, in particular between the central extension 53 and the metal body 2; in particular, the brazing material is located in the channel or groove of the outer surface of the central extension 53.

[0063] Thus, an improved brazing is obtained between the central extension 53 and the metal body 2. In fact, the brazing paste penetrating the grooves or channels is optimally distributed.

[0064] Furthermore, in embodiments in which the aforementioned satin finishing direction is selected, or despite this, when the channel or groove extends at least partially around the axis X, outflow of the brazing paste from the metal body 2 is prevented or reduced, thereby preventing the brazing paste from covering a portion of the end extensions 51, 52 of the tube 2 outside the metal body 2.

[0065] Preferably, the roughness Ra3 of the outer surface of the central extension 53 is 1.5 to 20 times greater than the roughness Ra1 , Ra2 of the outer surface of each of the two end extensions 51 , 52 , for example 2 to 20 times or 3 to 20 times or 1.5 to 10 times greater.

[0066] Preferably, the roughness Ra3 of the outer surface of the central extension section 53 is 1 to 5 μm. Specifically, the surface roughness value Ra3 is an arithmetic mean roughness value, specifically, according to ISO 4287 standard, more specifically, according to ISO 4287:1997 standard.

[0067] The above values ​​were selected on the basis of laboratory tests and it was observed that the best results were obtained with the above values, especially with regard to the brazing quality and the limitations of the brazing paste.

[0068] The central extension section 53 is located inside the metal body 2. Preferably, the central extension section 53 is completely inside the metal body 2.

[0069] The central extension 53 is arranged in the metal body 2 such that the metal body can transfer heat generated by the at least one electric heating element 3 , 4 to the central extension 53 , in particular by conduction.

[0070] In particular, the central extension 53 is embedded in the metal body 2 .

[0071] The end extensions 51, 52 are at least partially located outside the metal body 2. Preferably, the end extensions 51, 52 are completely outside the metal body 2.

[0072] Each end extension 51, 52 of the tube 5 defines a respective opening in the tube 5. Preferably, the tube 5 is provided with only these two openings.

[0073] Preferably, the length of the central extension 53 is greater than the length of the two end extensions 51, 52. The lengths of the extensions 51, 52, 53 are measured along the axis X.

[0074] Preferably, the length of each end extension 51 , 52 of the tube 5 is 10 to 50 mm, preferably 8 to 30 mm.

[0075] Preferably, the length of the central extension section 53 is 80 to 300 mm, preferably 100 to 250 mm.

[0076] The tube 5 is a different element relative to the metal body 2 .

[0077] The tube 5 is preferably made of steel, preferably stainless steel.

[0078] The cross-sectional area of ​​the tube 5 may be, for example, from 15 to 5000 mm 2 ; The cross section is perpendicular to the axis X.

[0079] The tube 5 may have, for example, a circular or substantially circular or oval cross section, or it may also have another shape.

[0080] In all embodiments, the electric heater 1 is configured, in particular, such that the one or more electric heating elements 3 , 4 can transfer heat to the tube 5 through the metal body 2 .

[0081] In particular, one or more electric heating elements 3 , 4 are embedded in the metal body 2 , preferably they are partially embedded in the metal body 2 .

[0082] The one or more electric heating elements 3, 4 are adapted to be connected to a power supply and they are adapted to generate heat when electric current flows through them, ie they may generate heat by the Joule effect.

[0083] As a non-limiting example, each electric heating element 3 , 4 may comprise a wire or another resistive element (or resistor) embedded in an electrically insulating material (eg magnesium oxide). Each electric heating element 3 , 4 is arranged in a respective hole of the metal body 2 .

[0084] The electrically insulating material may be in direct contact with the metal body 2. Alternatively, a metal shell may be provided between the electrically insulating material and the metal body 2.

[0085] Preferably, both ends of each electric heating body 3 , 4 extend out from the metal body 2 .

[0086] The metal body 2 is preferably made of aluminum or an aluminum alloy. The metal body 2 is preferably made by die casting.

[0087] Preferably, the one or more electric heating elements 3, 4 extend parallel to the tube 5. In particular, the longitudinal axis of each electric heating element 3, 4 preferably extends parallel to the axis X of the tube 5.

[0088] exist Figure 1 In the non-limiting example shown, the electric heater 1 comprises two electric heating elements 3, 4. The electric heating elements 3, 4 are located on the sides of the tube 5. In particular, the tube 5 is preferably arranged between the two electric heating elements 3, 4.

[0089] The invention also relates to a machine (not shown), such as a household appliance, for preparing a hot beverage, in particular coffee, comprising an electric heater 1 .

[0090] The electric heater 1 can be obtained, for example, by a method comprising the following steps:

[0091] a) Mechanically machining, preferably satin-finishing, the surface of the central extension of the metal tube in order to obtain said metal tube 5 having a central extension 53 whose roughness Ra3 is greater than the roughness Ra1, Ra2 of the outer surface of each of the two end extensions 51, 52.

[0092] Machining is performed by a machine. In particular, satin finishing is performed by a satin finishing device, especially for metal pipes.

[0093] Besides creating the above-mentioned channels or grooves which allow an improved distribution of the brazing paste, machining also allows the removal of impurities which are undesirable for obtaining a good brazing.

[0094] The outer surface of the end extension of the tube is preferably not machined.

[0095] Preferably, the machining, in particular the satin finishing, is performed such that the outer surface of the central extension 53 has the aforementioned plurality of channels or grooves extending substantially at least partially around the axis X.

[0096] After step a), the tube 5 is arranged in the metal body 2, in particular in a hole of the metal body 2, in particular in a hole different from each hole dedicated to a respective electric heating element 3, 4. Next, the central extension 53 is brazed to the metal body 2 using a brazing material, in particular a brazing paste.

Claims

1. An electric heater (1) for a machine for preparing hot beverages, in particular a flow-through heater, comprising: - a metal body (2); - at least one electric heating element (3, 4) arranged in the metal body (2), the at least one electric heating element (3, 4) being particularly suitable for generating heat when an electric current flows through it; - a metal tube (5) arranged in the metal body (2) for the passage of the liquid to be heated; - wherein the metal tube (5) is formed by a wall (50) extending around an axis (X); - wherein the metal tube (5) has two end extensions (51, 52) and a central extension (53); It is characterized in that the roughness (Ra3) of the outer surface of the central extension section (53) is greater than the roughness (Ra1, Ra2) of the outer surface of each of the two end extension sections (51, 52).

2. The electric heater (1) according to claim 1, wherein: The outer surface of the central extension section (53) is provided with a plurality of channels or grooves.

3. The electric heater (1) according to claim 2, wherein: Said channel or groove extends substantially at least partially around said axis (X).

4. An electric heater (1) according to any one of the preceding claims, wherein: The outer surface of the central extension section (53) is satin-finished.

5. The electric heater according to claim 4, wherein: The outer surface of the central extension section (53) is satin-finished, and the direction of the satin-finishing extends substantially around the axis (X).

6. An electric heater (1) according to any one of the preceding claims, wherein: The roughness (Ra3) of the outer surface of the central extension (53) is 1.5 to 20 times greater than the roughness (Ra1, Ra2) of the outer surface of each of the two end extensions (51, 52).

7. An electric heater (1) according to any one of the preceding claims, wherein: The roughness (Ra3) of the outer surface of the central extension section (53) is 1 to 5 μm.

8. An electric heater (1) according to any one of the preceding claims, wherein: The central extension (53) is located inside the metal body (2); and wherein the end extensions (51, 52) are at least partially located outside the metal body (2).

9. An electric heater (1) according to any one of the preceding claims, wherein: Brazing material exists between the metal tube (5) and the metal body (2), in particular between the central extension (53) and the metal body (2); the brazing material is particularly located in a channel or groove on the outer surface of the central extension (53).

10. A machine for preparing hot beverages comprising an electric heater (1) according to any one of the preceding claims.

11. A method for obtaining an electric heater (1) according to any one of the preceding claims, wherein: Provide the following steps: a) Mechanically processing the surface of the central extension of the metal tube, preferably satin-finishing it, so as to obtain the metal tube (5) having a central extension (53) whose roughness (Ra3) is greater than the roughness (Ra1, Ra2) of the outer surface of each of the two end extensions (51, 52).

12. The method according to claim 11, wherein: The machining, in particular the satin finishing, is performed so that the outer surface of the central extension (53) has a plurality of channels or grooves extending substantially at least partially around the axis (X).

13. The method according to claim 11 or 12, wherein: After step a), the tube (5) is inserted into the metal body (2), and then the central extension (53) is brazed to the metal body (2) using a brazing material.

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