A cartridge heater

Abstract

A cartridge heater (1 ) comprising an electrically insulating core (2); one or more heating elements (3a, 3b, 3c) constrained to the core (2), each one adapted to generate heat when electrically powered; wherein two respective first supply pins (4a, 4b) are connected to each heating element (3a, 3b, 3c); wherein at least a first supply pin (4a, 4b) of said two first supply pins (4a, 4b) is mechanically and electrically connected to a thermal fuse (42a) by means of a metal body (43a) into which said at least a first supply pin (4a, 4b) and the thermal fuse (42a) are inserted.

Description

[0001] A CARTRIDGE HEATER

[0002] Field of the invention

[0003] The present invention pertains to the field of electric heating devices. In particular, the invention relates to a type of electric heater referred to as a cartridge heater. Background art

[0004] Cartridge heaters are a type of electric heating device. Cartridge heaters comprise an electrically insulating core and one or more heating elements, e.g. resistive wires, adapted to generate heat when electrically powered. Each heating element is connected to two respective supply pins, which serve to electrically power the heating element.

[0005] For safety reasons, electric heaters can be provided with one or more thermal fuses. In particular, a thermal fuse can be provided connected to at least one of the two supply pins of each heating element.

[0006] The thermal fuse, for example, operates in dry operating conditions or in other abnormal operating conditions, in which undesired overheating occurs.

[0007] In known electric heaters, each thermal fuse is fastened to the respective supply pin by welding.

[0008] Disadvantageously, the fastening by welding does not allow the thermal fuse to operate rapidly for a number of reasons.

[0009] In particular, it can be difficult, or sometimes impossible, to use thermal fuses with a low intervention temperature. This because electric spot welding generates heat, which could damage, or nonetheless cause the thermal fuses to deteriorate.

[0010] Furthermore, fastening by welding involves the risk of having cold spot welds, with the consequent formation of hot spots and detachment of the thermal fuse can also occur.

[0011] Furthermore, disadvantageously, fastening by welding requires the use of specific equipment for spot welding, as well as the use of personnel who are specifically trained in the use thereof.

[0012] Disadvantageously, fastening by welding requires the use of pins made of materials compatible with the electrical spot welding process, i.e. stainless steel, nickel and carbon steel. Furthermore, fastening by welding does not ensure consistency in the positioning of thermal fuses. This can result in varying operating times of the various thermal fuses of the same electric heater and also between different electric heaters of the same product model.

[0013] It is not simple to design a cartridge heater in which the thermal fuse can operate quickly, especially when the cartridge heater is configured to generate great thermal power, in particular, a great specific thermal power.

[0014] Thus, the need is felt to overcome the limitations of the background art.

[0015] Summary of the invention

[0016] It is an object of the present invention to provide a cartridge heater equipped with one or more thermal fuses, in which such one or more thermal fuses can operate quickly in the event of abnormal operating conditions.

[0017] It is an object of the present invention to provide a cartridge heater that can be produced more quickly and more easily with respect to the prior art.

[0018] The present invention achieves at least one of such objects, and other objects, which will be apparent in light of the present description, by means of a cartridge heater, according to claim 1 , comprising an electrically insulating core, provided with a plurality of longitudinal grooves; one or more heating elements constrained to the core, each adapted to generate heat when electrically powered; wherein two respective first supply pins are connected to each heating element; wherein at least one first supply pin of said two first supply pins is mechanically and electrically connected to a respective thermal fuse by means of a metal body into which said at least one first supply pin and the thermal fuse are inserted; wherein each first supply pin is arranged, at least partially, in a respective longitudinal groove of the core; wherein each first supply pin is arranged at one same end of the core.

[0019] The invention also relates to a method according to claim 15, wherein a step is provided, in which a thermal fuse is mechanically and electrically connected to at least one first supply pin of said two first supply pins by means of said metal body into which said at least one first supply pin and the thermal fuse are inserted. Particularly advantageously, the thermal fuse and the first supply pin can be inserted into the metal body, in particular by means of a press-fit connection.

[0020] Advantageously, a cartridge heater according to the invention can be made more quickly, easily and cheaply with respect to the prior art.

[0021] Advantageously, a cartridge heater according to the invention requires no specific equipment or specialized labor in order to be produced.

[0022] Advantageously, the fastening by means of said metal body allows supply pins to be used, which are made of copper or copper alloy, in particular, without incurring any damage suffered by the supply pins during the assembly with the thermal fuse.

[0023] Advantageously, a cartridge heater according to the invention allows greater precision and consistency in the positioning of the thermal fuses and, consequently, greater stability in the intervention times thereof.

[0024] Advantageously, each thermal fuse can be fastened to the respective first supply pin after the casing has been filled with an electrically insulating material, for example, magnesium oxide.

[0025] Advantageously, by providing that each first supply pin is arranged, at least partially, in a respective longitudinal groove of the core, and by providing the connection by means of said metal body, a synergistic effect is obtained whereby the cartridge heater can be equipped with at least one thermal fuse and produced in a particularly simple manner. In particular, the supply pins can be suitably held in position during the production of the cartridge heater, and in particular, each pin, to which a respective thermal fuse is intended to be connected, can suitably be held in position during such connection.

[0026] Advantageously, since each first supply pin is arranged at the same end of the core, if the cartridge heater comprises more than one thermal fuse (each connected to a respective first supply pin), the thermal fuses are positioned close to one another. Therefore, the thermal fuses have a substantially equal operating time.

[0027] In particular, a cartridge heater according to the invention offers the following advantages: it allows increased operational reactivity of the thermal fuse because the metal body also acts as a thermal bridge; the possibility of mounting thermal fuses with operating temperatures lower than those usable with respect to a fastening with electric spot welding (and therefore with thermal input) between the thermal fuse and the supply pin; it allows constant and repetitive positioning, ensuring a uniform response of the thermal fuse operating time; simplification of the production process; it allows assembling the thermal fuse in the final operations of the production process, consequently allowing greater flexibility in product customization.

[0028] Further features and advantages of the invention will be more apparent in light of the detailed description of exemplary, but non-exclusive embodiments.

[0029] The dependent claims describe particular embodiments of the invention.

[0030] Brief description of the figures

[0031] In the description of the invention, reference is made to the accompanying drawings, provided by way of non-limiting example, in which:

[0032] Figure 1 shows a perspective view of a cartridge heater according to the invention;

[0033] Figure 2 shows a perspective view of components of the cartridge heater in Figure 1 ;

[0034] Figure 3 shows a side view of components of the heater in Figure 1 , during an assembly step (some components are not fully shown);

[0035] Figure 4 shows a side view of the cartridge heater in Figure 1 ;

[0036] Figure 5 shows section A-A in Figure 4;

[0037] Figure 6 shows an exploded side view of some components of the heater in Figure 1.

[0038] The same elements or components have the same reference numerals.

[0039] Description of exemplary embodiments of the invention

[0040] With reference to the Figures, exemplary embodiments of a cartridge heater 1 are described according to the invention.

[0041] In all embodiments, the cartridge heater 1 comprises an electrically insulating core 2, provided with a plurality of longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f; one or more heating elements 3a, 3b, 3c constrained to the core 2, each adapted to generate heat when electrically powered; two respective first supply pins 4a, 4b are connected to each heating element 3a, 3b, 3c (only two of them are numbered in the figures) at least one first supply pin 4a of said two first supply pins 4a, 4b is mechanically and electrically connected to a thermal fuse 42a, in particular to a respective thermal fuse 42a (only one of them is numbered in the figures), by means of a metal body 43a (only one of them is numbered in the figures) into which said at least one first supply pin 4a and the thermal fuse 42a are inserted; wherein each first supply pin 4a, 4b is arranged, at least partially, in a respective longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f of the core 2; wherein each first supply pin 4a, 4b is arranged at the same end 28 of the core 2.

[0042] Said metal body 43a preferably fastens the first pin 4a and the thermal fuse 42a to each other by exerting an elastic force thereon.

[0043] Said metal body 43a is preferably made of steel or copper or copper alloy or nickel or nickel alloys.

[0044] Said metal body 43a is preferably a metal cage or a metal sleeve, preferably an elastic metal cage or an elastic metal sleeve.

[0045] The metal body 43a preferably has a plurality of slots or slits 431 , in particular, to give the metal body 43a elastic properties.

[0046] The core 2 defines a longitudinal axis Y, which, in particular, is also the longitudinal axis of the cartridge heater 1. Said longitudinal axis Y is, in particular, also the central axis of the core 2, preferably also of the cartridge heater 1 .

[0047] The core 2 can be formed by one or more electrically insulating bodies. In the example shown by way of non-limiting example, the core 2 is formed by an electrically insulating body.

[0048] The core 2 is preferably made of ceramic, in particular, refractory ceramic.

[0049] The core 2 has two ends 28, 29, or axial ends.

[0050] Advantageously, the core 2 is provided with said plurality of longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f where the one or more heating elements 3a, 3b, 3c are preferably arranged, in particular, partially arranged, (in particular, see Figures. 2 and 3).

[0051] In particular, the longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f are longitudinal grooves of the side surface 27, in particular the outer side surface, of the core 2. Each longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f preferably extends over the whole length of the core 2, in particular along the longitudinal axis Y of the core 2.

[0052] The core 2 is preferably a substantially cylindrical body, the side surface 27 of which has said plurality of longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f.

[0053] Each longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f, seen in section on a plane orthogonal to the longitudinal axis Y, is preferably substantially U-shaped. Each longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f preferably has a respective plane of symmetry containing the longitudinal axis Y (in particular, the central longitudinal axis) of the core 2.

[0054] Said at least one heating element 3a, 3b, 3c preferably comprises a first stretch 31 and a second stretch 32 each arranged in a respective longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f of said plurality of longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f.

[0055] In particular, each heating element 3a, 3b, 3c extends into at least two longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f, preferably into two longitudinal grooves 20a, 20b.

[0056] In particular, each heating element 3a, 3b, 3c comprises a third stretch 33 extending outside the longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f; in particular, said third stretch 33 extends at an axial end 29 of the core 2.

[0057] In particular, the third stretch 33 of each heating element 3a, 3b, 3c is in contact with an axial end 29 of the core 2.

[0058] In particular, the third stretch 33 extends beyond the axial end 29 of the core 2, in particular, axially beyond the axial end 29 of the core 2.

[0059] In particular, the side surface 27 of the core 2 has a plurality of longitudinal protrusions 21a, 21 b, 21c, 21 d, 21 e, 21 f, in particular, protruding with respect to the longitudinal grooves. The number of longitudinal protrusions 21 a, 21 b, 21 c, 21 d, 21 e, 21f is equal to the number of longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f. There is a respective longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f between each pair of longitudinal protrusions 21 a, 21 b, 21 c, 21 d, 21 e, 21 f.

[0060] In particular, the aforesaid third stretch 33 of each heating element 3a, 3b, 3c is in contact with an axial end of the longitudinal protrusion 21 b, which is present between the two longitudinal grooves 20a, 20b, in which the first stretch 31 and the second stretch 32 are arranged, respectively. In particular, said third stretch 33 substantially passes round said axial end of said longitudinal protrusion 21 b. In particular, each heating element 3a, 3b, 3c preferably extends along a respective substantially U-shaped axis.

[0061] The longitudinal grooves 20a, 20b in which said first stretch 31 and said second stretch 32 are arranged, are consecutive to one another.

[0062] For example, each heating element 3a, 3b, 3c can have a first stretch 31 extending in a first longitudinal groove 20a, a second stretch extending in a second longitudinal groove 20b, and a third stretch 33 extending outside the longitudinal grooves 20a, 20b, 20c, 20d, 20e, 20f; in particular, said third stretch 33 extends at an axial end 29 of the core 2, and in particular, is in contact with said axial end 29. The first stretch 31 and the second stretch 32 are preferably helical or substantially helical.

[0063] Each heating element 3a, 3b, 3c, is preferably a metal wire, in particular, a resistive wire, preferably having one or more helical or substantially helical stretches 31 , 32.

[0064] Each heating element 3a, 3b, 3c preferably extends along a respective substantially U-shaped axis.

[0065] Each supply pin 4a, 4b is fastened, in particular, welded, at a respective end 38a, 38b of the respective heating element 3a, 3b, 3c.

[0066] Advantageously, each first supply pin 4a, 4b is arranged, at least partially, in a respective longitudinal groove 20a, 20b, 20c, 20d, 20e, 20f of the core 2.

[0067] Advantageously, each first supply pin 4a, 4b is arranged at the same end 28, in particular, an axial end of the core 2. The supply pins 4a, 4b preferably protrude axially with respect to said axial end 28 of the core 2.

[0068] In particular, the supply pins 4a, 4b are all arranged on the same side of the cartridge heater 1 .

[0069] The first supply pins 4a, 4b are preferably made of copper or copper alloy.

[0070] In particular, the cartridge heater 1 comprises a casing 6 (or outer body), in which said electrically insulating core 2 is arranged; and a closing element 5, or closing body that closes one end, in particular, an axial end, of said casing 6. The closing element 5 can be formed, for example, by means of a sealing material.

[0071] A respective second supply pin 41 a is fastened to each thermal fuse 42a, in particular, for the electrical connection to a source of electricity; and each second supply pin 41a crosses said closing element 5. In particular, between each first supply pin 4a, 4b and the respective second supply pin 41 a, 41 b, a respective thermal fuse 42a is present.

[0072] For each heating element 3a, 3b, 3c, each one first supply pin 4a, 4b of said two first supply pins 4a, 4b is preferably mechanically and electrically connected to a respective thermal fuse 42a by means of a respective metal body 43a into which the respective first supply pin 4a, 4b and thermal fuse 42a are inserted.

[0073] In this case, in particular, all the second supply pins 41 a, 41 b cross the same closing element 5.

[0074] If only one of the two first supply pins 4a, 4b of each heating element 3a, 3b, 3c is connected to a thermal fuse 42a, the first supply pin not connected to a thermal fuse preferably crosses the closing element 5.

[0075] Each heating element 3a, 3b, 3c is preferably incorporated in an electrically insulating material; in particular, said electrically insulating material being distinct from said core 2.

[0076] The electrically insulating material is preferably magnesium oxide or comprises magnesium oxide.

[0077] Said electrically insulating material is inside said casing 6.

[0078] Each heating element is preferably configured to generate a specific thermal power of at least 5 W / cm2, preferably from 5 to 30 W / cm2

[0079] The cartridge heater 1 preferably comprises a plurality of heating elements 3a, 3b, 3c.

[0080] In the illustrated non-limiting example, the cartridge heater 1 comprises three heating elements 3a, 3b, 3c.

[0081] The invention is also directed to a method for manufacturing a cartridge heater 1 , wherein a step is provided in which a thermal fuse 42a is mechanically and electrically connected to at least one first supply pin 4a, 4b of said two first supply pins 4a, 4b by means of said metal body 43a into which said at least one first supply pin 4a, 4b and the thermal fuse 42a are inserted.

[0082] Advantageously, each thermal fuse 42a can be fastened to the respective first supply pin 4a, 4b when the casing 6, in which the core 2, the one or more heating elements 3a, 3b, 3c and the first supply pins 4a, 4b are arranged, has been filled with said electrically insulating material (e.g. magnesium oxide).

Claims

CLAIMS1. A cartridge heater (1 ) comprising an electrically insulating core (2), provided with a plurality of longitudinal grooves (20a, 20b, 20c, 20d, 20e, 20f); one or more heating elements (3a, 3b, 3c) constrained to the core (2), each one adapted to generate heat when electrically powered; wherein two respective first supply pins (4a, 4b) are connected to each heating element (3a, 3b, 3c); wherein each first supply pin (4a, 4b) is arranged, at least partially, in a respective longitudinal groove (20a, 20b, 20c, 20d, 20e, 20f) of the core (2); wherein each first supply pin (4a, 4b) is arranged at the same end (28) of the core (2); wherein at least one first supply pin (4a) of said two first supply pins (4a, 4b) is mechanically and electrically connected to a respective thermal fuse (42a) by means of a metal body (43a) into which said at least one first supply pin (4a) and the thermal fuse (42a) are inserted.

2. A cartridge heater (1 ) according to claim 1 , wherein said metal body (43a) fastens the first pin (4a) and the thermal fuse (42a) to each other by exerting an elastic force thereon.

3. A cartridge heater (1 ) according to claim 1 or 2, wherein said metal body (43a) is a metal cage, in particular, an elastic metal cage.

4. A cartridge heater (1 ) according to any one of the preceding claims, wherein said one or more heating elements (3a, 3b, 3c) are incorporated in an electrically insulating material, in particular being distinct from said core (2), preferably wherein said electrically insulating material is magnesium oxide or comprises magnesium oxide.

5. A cartridge heater (1 ) according to any one of the preceding claims, wherein each longitudinal groove (20a, 20b, 20c, 20d, 20e, 20f) extends along the whole length of the core (2), in particular along the longitudinal axis (Y) of the core (2).

6. A cartridge heater (1 ) according to any one of the preceding claims, wherein said at least one heating element (3a, 3b, 3c) comprises a first stretch (31 ) and a secondstretch (32), each arranged in a respective longitudinal groove (20a, 20b, 20c, 20d, 20e, 20f) of said plurality of longitudinal grooves (20a, 20b, 20c, 20d, 20e, 20f).

7. A cartridge heater (1 ) according to any one of the preceding claims, wherein the pins (4a, 4b) axially protrude with respect to said end (28) of the core (2).

8. A cartridge heater (1 ) according to any one of the preceding claims, wherein the core (2) is a substantially cylindrical body, the side surface (27) of which has said plurality of longitudinal grooves (20a, 20b, 20c, 20d, 20e, 20f).

9. A cartridge heater (1 ) according to any one of the preceding claims, comprising a casing (6) in which said electrically insulating core (2) is arranged; and a closing element (5) that closes one end, in particular, an axial end, of said casing (6).

10. A cartridge heater (1 ) according to claim 9, wherein a second supply pin (41 a), in particular, for the electrical connection to a source of electricity, is fastened to each thermal fuse (42a); and wherein each second supply pin (41a) crosses said closing element (5).

11. A cartridge heater (1 ) according to any one of the preceding claims, wherein, for each heating element (3a, 3b, 3c), each first supply pin (4a, 4b) of said two first supply pins (4a, 4b) is mechanically and electrically connected to a respective thermal fuse (42a) by means of a respective metal body (43a) into which the respective first supply pin (4a, 4b) and thermal fuse (42a) are inserted.

12. A cartridge heater (1 ) according to any one of the preceding claims, wherein said at least one heating element (3a, 3b, 3c) is a metal wire, in particular, a resistive wire; and / or wherein the cartridge heater (1 ) comprises a plurality of heating elements (3a, 3b, 3c).

13. A cartridge heater (1 ) according to any one of the preceding claims, wherein each longitudinal groove (20a, 20b, 20c, 20d, 20e, 20f), seen in section on a plane orthogonal to the longitudinal axis (Y) of the core (2), is substantially U-shaped; preferably wherein each longitudinal groove (20a, 20b, 20c, 20d, 20e, 20f) has a respective plane of symmetry containing the longitudinal axis (Y) of the core (2).

14. A cartridge heater (1 ) according to any one of the preceding claims, wherein the core (2) has a side surface (27) having said plurality of longitudinal grooves (20a, 20b, 20c, 20d, 20e, 20f).

15. A method for manufacturing a cartridge heater (1 ) according to any one of the preceding claims, wherein a step is provided in which a thermal fuse (42a) is mechanically and electrically connected to at least one first supply pin (4a, 4b) of said two first supply pins (4a, 4b) by means of said metal body (43a), into which said at least one first supply pin (4a, 4b) and the thermal fuse (42a) are inserted.

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