Heating group for diathermic fluid radiant elements

Abstract

 A heating group (1) for diathermic fluid radiant elements (A, B) comprising: a heater (2) put in contact with the diathermic fluid and consisting of a tubular body (4) containing an electric insulator (4a) in which at least an electric resistance (5) is immersed; a tubular sleeve (6) disposed at one end of the tubular body (4) and provided with fastening means (6a) to the radiant element (A, B); a feeding group (7) of the heater (2), comprising at least a solid-state switch (8) able to connect the electric resistance (5) to a distribution power grid (9); electronic control means (10) for switching off and switching on the switch (8). The solid-state switch (8) is disposed inside the sleeve (6), where it is incorporated in a thermo-conductive core (11; 19; 20) adherent to the inner wall (6a) of the sleeve (6).

Description

[0001] The present invention is about a heating group for diathermic fluid radiant elements, in particular radiators and towel heaters especially for domestic use.

[0002] It is known that, in the electric radiators used to heat rooms or napkins and towels, the heat is supplied by proper heating groups which comprise a heater inserted in the radiant element and fed by electric current through a feeding group.

[0003] In particular, a radiator or a towel heater of known type comprises a heating group consisting of a tubular body inserted in the radiant element and put in contact with the diathermic fluid, which contains an insulating material in which one or more electric resistances are inserted.

[0004] The tubular body is provided at one end with a tubular sleeve for the fastening to the radiant element, and through it they pass conductive elements for the connection of the electric resistance to a feeding group, which is housed in a box fixed to the radiant element.

[0005] In particular, the feeding group, according to the prior art, comprises a solid-state switch, generally a bidirectional thyristor commonly called TRIAC or SCR, connected to electronic control means which set its switching on and switching off.

[0006] In all known embodiments, the thyristor cooling is particularly difficult, since the box in which it is contained is closed to avoid the entrance of humidity or water. The considerable heat produced by the thyristor makes the temperature inside the box to increase, and this can compromise the correct operation of the electronic components.

[0007] In particular, if the temperature exceeds 100°C, the operation of the thyristor itself is compromised.

[0008] The use of heat sinks applied to the box in which the thyristor is contained does not solve the problem in a satisfactory way and makes also more complex the manufacturing of the whole heating group.

[0009] Another inconvenience found in known embodiments is due to the fact that the electric resistance undergoes damages, sometimes irreparable, when a good contact between the diathermic fluid and the heater is not carried out, since the resistance operates partially in contact with air and this increases the specific load which causes its burnout.

[0010] The present invention intends to overcome the aforementioned inconveniences.

[0011] In particular, it is a first object of the invention to provide for a heating group for diathermic fluid radiant elements in which, during operation, the temperature of the solid-state switch, which fits out the resistance feeding group, is constantly below the highest allowed temperature.

[0012] It is another object that said temperature value is maintained without requiring heat sinks.

[0013] It is a further object to reduce the possibility that the resistance is burned out in case of failed contact between the heating element and the diathermic fluid.

[0014] Not the least object is that the heating group of the invention maintains at least the same electric safety standards found in the prior art heating groups.

[0015] Said objects are obtained by a heating group for diathermic fluid radiant elements which, according to the main claim, comprises:

• a heater inserted in a housing present in said radiant element and put in contact with said diathermic fluid, said heater consisting of a tubular body containing an electric insulator in which at least an electric resistance is inserted;
• a tubular sleeve disposed at one end of said tubular body and provided with fastening means to said radiant element;
• a feeding group of said heater, comprising at least a solid-state switch able to connect said electric resistance to a distribution power grid;
• electronic control means for switching off and switching on said switch, and it is characterized in that said solid-state switch is disposed in said sleeve where it is incorporated in a thermo-conductive core adherent to the inner wall of said sleeve.

[0016] According to a preferred executive embodiment, the solid-state switch is a bidirectional thyristor coupled with a support base incorporated in the thermo-conductive core.

[0017] First terminals for the connection to the electric resistance, second terminals for the connection to the distribution power grid and third terminals for the connection to the electronic control means of the thyristor are present in the support base.

[0018] The support base comprises a printed circuit consisting of conductive stripes to connect the solid-state switch to the connection terminals.

[0019] According to an executive embodiment, the solid-state switch is incorporated in the thermo-conductive core, being connected in the air to the electric resistance, to the distribution power grid and to the electronic control means.

[0020] Preferably, the heating group also comprises a resistive protection element with positive temperature coefficient, commonly called PTC (Positive Temperature Control), which is connected in series between the solid-state switch and the electronic control means which control its switching on and switching off.

[0021] Advantageously, the heating group of the invention is more reliable with respect to the known heating groups, since the thermal dispersion that the thyristor carries out inside the sleeve that houses it is greater than that achievable in known embodiments, in which the thermal exchange takes place directly in the air or by means of heat sinks.

[0022] Consequently, and in a still advantageous way, the heating group of the invention is also more reliable in its operation with respect to the equivalent heating groups of known type.

[0023] Furthermore advantageously, the presence of the resistive element with positive temperature coefficient warrants an effective protection against the electric resistance burnout, especially in case of the specific load on the resistance is raised beyond unacceptable values for a lack of contact with the diathermic fluid.

[0024] The aforesaid objects and advantages will be better highlighted in the description of preferred executive embodiments of the invention, given in an explanatory but not limiting way hereinafter, with reference to the figures of the annexed drawings, wherein:

• Figures 1 and 2 show two different views of a radiator to which the heating group of the invention is applied;
• Figures 3 and 4 show two different views of a towel heater to which the heating group of the invention is applied;
• Figure 5 shows a detail of the heating group of the invention shown in Figures 1 to 4;
• Figure 6 is an axonometric exploded view of a detail of Figure 5;
• Figure 6a is a front view of the detail of figure 6 in assembled configuration;
• Figure 7 is a different executive embodiment of the detail of Figure 6;
• Figure 7a is a front view of the detail of figure 7 in assembled configuration;
• Figure 8 is another executive embodiment of the detail of Figure 6;
• Figure 8a is a front view of the detail of figure 8 in assembled configuration;
• Figure 9 is a further executive embodiment of the detail of Figure 6;
• Figure 10 shows the electric diagram of the heating group of the invention for any of the executive embodiments of Figures 6 to 8; and
• Figure 11 shows an executive embodiment of the electric diagram of Figure 10.

[0025] The heating group of the invention is shown in Figures 1 to 4, where it is generally indicated with numeral 1.

[0026] In particular, in Figures 1 and 2 said group is applied to a diathermic fluid radiator, generally indicated with A, while in Figures 3 and 4 it is applied to a towel heater, with diathermic fluid too, generally indicated with B.

[0027] It is evident that the heating group of the invention could be also applied to fixed or mobile radiant element of other kind.

[0028] One can see that the heating group 1 comprises a heater 2 of known type, which is inserted in a housing 3 present in the radiant element A, B and which, as one can see in greater detail in Figure 5, is composed by a tubular body 4 put in contact with the diathermic fluid, said body containing an electric insulator 4a in which an electric resistance, schematically shown in Figure 5 and indicated with numeral 5, is inserted.

[0029] It is pointed out that also several electric resistances could be housed inside the tubular body 4.

[0030] According to the prior art, a thermo-fuse 5a and a protective electro mechanic thermostat 5b, disposed inside the tubular body 4, are coupled with the resistance 5.

[0031] A tubular sleeve, generally indicated with numeral 6, is disposed at the end of the tubular body 4 and it is provided with fastening means consisting, for example, of a threaded collar 6a which is screwed to the radiant element.

[0032] In other executive embodiments, the fastening means could also be of other kind, like for instance screws.

[0033] The heating group 1 also comprises a feeding group, generally indicated with numeral 7 and shown in axonometric view in Figure 6, provided with a solid-state switch 8 for the connection of the electric resistance 5 to a distribution power grid 9 according to the electric diagram of Figure 10.

[0034] Electronic control means, generally indicated with numeral 10 and shown in the electric diagram of Figure 10, are present too for switching off and switching on the switch 8.

[0035] According to the invention, the solid-state switch 8 is disposed inside the sleeve 6, where it is contained in a thermo-conductive core 11 adherent to the inner wall 6a of the sleeve 6.

[0036] According to the executive embodiment shown in Figures 6 and 6a, and with reference to the electric diagram of Figure 10, the solid-state switch 8 is coupled with a support base 12, which is incorporated in the thermo-conductive core 11 and on which are present:

• first terminals 13 and respective conductors 13a for the connection to the electric resistance 5;
• second terminals 14 and respective conductors 14a for the connection to the distribution power grid 9;
• third terminals 15 and respective conductors 15a for the connection to the electronic control means 10 for switching on and switching off the switch 8.

[0037] The support base 12 comprises conductive stripes 16 to connect the solid-state switch 8 to the connection terminals 13, 14 and 15 which are completely immersed in the thermo-conductive core 11 after the support base 12 has been inserted in the tubular sleeve 6.

[0038] In particular, one can see in Figures 6 and 6a that the thermo-conductive core 11 comprises a first thermo-conductive body 17 with a circular sector cross section, made of metallic material, and a second thermo-conductive body 18, made of thermo-conductive resin, between which the support base 12 is present, as one can see in detail in Figure 6.

[0039] Operatively, the manufacturing process provides for the assembly of the solid state switch 8 on the support base 12 and the connection of the terminals to the respective wires, and thus the fastening of the base 12 to the first thermo-conductive body 17 through fastening means.

[0040] Once the fastening is performed, the support base 12, together with the thermo-conductor 17, is inserted in the tubular sleeve 6.

[0041] Then, the space inside the sleeve 6 comprised between the support base 12 and the inner surface 6a of the sleeve 6 is filled with thermo-conductive resin, obtaining the second thermo-conductive body 18 shown in Figure 6a.

[0042] In this way, the so obtained thermo-conductive core 11 perfectly adheres with interference to the inner surface 6a of the sleeve 6, providing for the connection stability of the support base 12 and all the components associated therewith inside the tubular sleeve 6.

[0043] The perfect adhesion of the thermo-conductive core 11 to the inner surface 6a of the sleeve 6 enhances the thermal exchange and assures the operation of the solid-state switch 8 at an optimal constant temperature, comprised between 70°C and 80°C, thus considerably below the dangerous threshold of 100°C.

[0044] A different executive embodiment of the invention is shown in Figures 7 and 7a, which is different from that previously described in that the support base 12 of the solid-state switch 8 and the terminals 13, 14 and 15 is incorporated in a single thermo-conductive body, generally indicated with numeral 19, which is obtained injecting thermo-conductive resin inside the sleeve 6 after the insertion of the support base 12, centred on the sleeve 6.

[0045] Another executive embodiment is shown in Figures 8 and 8a, and it differs from those previously described in that the solid-state switch 8 is assembled in the air directly to the conductors 13a for the connection to the electric resistance 5, to the conductors 14a for the connection to the distribution power grid 9 and to the conductor 15a for the connection to the electronic control means 10.

[0046] Said switch is incorporated in a thermo-conductive core, generally indicated with numeral 20, which is obtained injecting thermo-conductive resin inside the sleeve 6 after the interposition of an insulating ring 21 circumferentially close to the inner surface 6a of said sleeve 6.

[0047] All the described embodiments could be made according to a different circuit diagram shown in Figures 9 and 11, which provides for the insertion of a resistive protection element with positive temperature coefficient (PTC), indicated with numeral 22, instead of the electro mechanic thermostat 5b.

[0048] As one can see in the electric diagram of Figure 11, the resistive element 22 is connected in series between the solid-state switch 8 and the electronic control means 10 which control its switching on and switching off.

[0049] On the basis of the aforesaid description, it should be understood that the heating group of the invention achieves all the intended objects.

[0050] In particular, incorporating the solid-state switch inside the sleeve for fastening the heater to the radiant element, a greater heat dispersion is obtained, since in the area in which the sleeve is connected to the radiant element the operative temperature is constantly around values comprised between 70°C and 80°C, and thus far from the temperature threshold of 100°C which is dangerous for the switch 8.

[0051] As previously mentioned, the heating group of the invention could be applied to radiant elements of any kind, both of fixed installation and of mobile installation.

[0052] The thermo-conductive materials used could be of any kind, as long as thermo-conductive and thus able to provide for an optimal dispersion of the heat produced by the solid-state switch during operation.

[0053] It is important to point out that said switch could be a thyristor of TRIAC or SCR type.

[0054] It is intended that further executive embodiments of the invention, neither described nor shown in the drawings, if they fall within the scope of protection of the following claims, should be intended as protected by the present patent.

Claims

1. A heating group (1) for diathermic fluid radiant elements (A, B) comprising:

- a heater (2) inserted in a housing (3) present in said radiant element (A, B) and put in contact with said diathermic fluid, said heater (2) consisting of a tubular body (4) containing an electric insulator (4a) in which at least an electric resistance (5) is inserted;

- a tubular sleeve (6) disposed at one end of said tubular body (4) and provided with fastening means (6a) to said radiant element (A, B);

- a feeding group (7) of said heater (2), comprising at least a solid-state switch (8) able to connect said electric resistance (5) to a distribution power grid (9);

- electronic control means (10) for switching off and switching on said switch (8),

characterized in that said solid-state switch (8) is disposed in said sleeve (6) where it is incorporated in a thermo-conductive core (11; 19; 20) adherent to the inner wall (6a) of said sleeve (6).

2. The heating group (1) according to claim 1), characterized in that said solid-state switch (8) is coupled with a support base (12) incorporated in said thermo-conductive core (11), in which base (12) first terminals (13) for the connection to said electric resistance (5), second terminals (14) for the connection to said distribution power grid (9) and third terminals (15) for the connection to said electronic control means (10) are present.

3. The heating group (1) according to claim 2), characterized in that said support base (12) comprises conductive stripes (16) to connect said solid-state switch (8) to said connection terminals (13; 14; 15).

4. The heating group (1) according to claim 1), characterized in that said solid-state switch (8) is disposed in the air and it is connected to said electric resistance (5), to said distribution power grid (9) and to said electronic control means (10), being incorporated in said thermo-conductive core (20).

5. The heating group (1) according to claim 2), characterized in that said thermo-conductive core (11) comprises a first thermo-conductive body (17), made of metallic material, and a second thermo-conductive body (18), with semicircular cross section and made of thermo-conductive resin, said first body (17) and said second body (18) being of circular sector cross section and having mutually facing contact surfaces between which said support base (12) of said solid-state switch (8) is comprised.

6. The heating group (1) according to claim 5), characterized in that said first body (17) and said second body (18) are coupled with interference with the inner surface (6a) in said tubular sleeve (6).

7. The heating group (1) according to claims 2) or 4), characterized in that said thermo-conductive core comprises a single thermo-conductive body (19) made of thermo-conductive resin, having circular cross section and being coupled with interference with said tubular sleeve (6).

8. The heating group (1) according to claim 7), characterized in that an annular jacket (21), made of thermo-conductive and electrically insulated material, is interposed between said single thermo-conductive body (20) and the inner surface (6a) of said tubular sleeve (6).

9. The heating group (1) according to any of the preceding claims, characterized by comprising a protective thermo-fuse (5a) disposed in said tubular body (4) and electrically connected to said electric resistance (5).

10. The heating group (1) according to any of the claims 1) to 8), characterized by comprising a resistive protection element (22) with positive temperature coefficient connected in series between said solid-state switch (8) and said switching on and switching off electric control means.

11. The heating group (1) according to any of the preceding claims, characterized in that said solid-state switch (8) is a thyristor.

12. The heating group (1) according to any of the preceding claims, characterized in that said solid-state switch (8) is a SCR.

13. The heating group (1) according to what claimed and described.

Drawing