EP1523224B2 - Electrical heating cartridge - Google Patents

Abstract

An electric heating cartridge (1), especially for heating liquids and/or gaseous media, comprises at least one positive temperature coefficient element (10), two electrodes (9), and an insulating element (8) that electrically insulates a housing (2). The insulating element consists of a polyimide film. The cartridge has at least two heat conducting members.

Description

The invention relates to an electric heating cartridge according to the preamble of claim 1.

Cartridges of this type are characterized by their small construction and the fact that they are both heating and temperature control simultaneously. This dual function is achieved through the use of PTC elements (Positive Temperature Coefficient), so-called PTC thermistors. A PTC element has the property of heating only up to a predetermined limit temperature. From this limit temperature, the electrical resistance increases suddenly, so that the PTC element stops heating. As a result, PTC elements are self-regulating and require no additional temperature control. It is possible to produce PTC elements for different electrical voltages and different limit temperatures. By a structurally simple construction, which essentially comprises the actual PTC element and two electrode body, and a simple power supply via a two-wire cable is to realize the relatively small construction of the heating cartridges.

Due to the described properties, heating cartridges of the type mentioned have a variety of applications, such as e.g. in industry, medical technology or in the household. They are used, for example, in laminators, inhalers and in the automotive industry.

A heating cartridge of the prior art is for example in the DE 202 12 580 U1 described. When the heating cartridge of DE 202 12 580 U1 the power is supplied via the housing body of the heating cartridge. For this reason, the heating cartridge is not suitable for use in electrically conductive or electrically dissociating media.

Another heating cartridge is in the DE 197 37 241 C2 described. Here are two PTC elements with two electrode bodies, which are embedded together in a plurality of insulating elements, received in a metal housing body biased. The insulating elements are in this case made of an elastic metal oxide, which are pre-pressed and bias the components within the housing body.

A disadvantage of the heating cartridge of DE 197 37 241 C2 is that the metal oxide expands depending on temperature, so that different biasing forces are generated depending on the temperature. As a result, the heat energy released by the immersion heater to the medium to be heated varies at different temperatures.

Other heating elements are in the DE 201 21 116 U1 and the US 4,822,980 described. In the device of DE 201 21 116 U1 are several PTC elements with electrode bodies in a housing, which dips in operation in a liquid to be heated, arranged. The US 4,822,980 describes a heating element in which a surrounded by an insulating PTC element is disposed in an aluminum housing. The aluminum housing is designed with radially acting spring elements and pressed in a pot.

In the DE 92 00 944 U1 , An electric immersion heater is described, are arranged in the lying between two electrode bodies PTC elements in an elastic insulating tube. The Isotierschlauch is in turn surrounded by a longitudinally slotted, radially resilient metal shell. To nearest prior art, the GB 2 079 570 A , An electric immersion heater is described in which a PTC element is arranged between two electrode bodies. A Kuntstofffolie isolated the electrode body relative to the substantially cup-shaped housing body. Two heat-conducting pressure bodies are arranged between the electrically insulating plastic film and the housing body in order to hold the PTC element centered in the housing body.

The invention has for its object to provide an improved heating cartridge, which is used in liquid or gaseous media and protected from contamination.

This object is achieved according to the invention for the heater cartridge mentioned by the features of claim 1.

This solution is structurally simple and such a running heating cartridge can be produced inexpensively.

The bias applied by the housing body compresses the components within the housing body. This ensures that the heat conduction surfaces of the housing body and the inner components abut each other and thereby a previously calculated heat energy to be delivered is transferable to the medium to be heated. Because, in contrast to the prior art, the housing body now serves as a spring element, a uniform preload force can be generated over wide temperature ranges. Surprisingly, the temperature dependence of the biasing force generated by the housing body seems to be less pronounced than in the embodiment of the insulating body as spring elements. One reason for this could be the small wall thickness of the housing body. This ensures a secure concern the Wärmeleitflächen of the components together.

Characterized in that the insulating element is made inelastic with respect to the housing body, the bias voltage is well passed to the electrode body and the PTC element.

The thus improved heating device can be further developed by various independent and each advantageous developments, as they are explained below.

Thus, in an advantageous embodiment of the housing body made of an elastic material be designed. This has the advantage that the housing body is elastically deformable and thereby the bias can be generated in the interior of the housing body.

In order to give the housing body a particularly advantageous shape, the housing body can be made substantially pot-shaped. As a result, the heating cartridge according to the invention must be closed only on one side, thereby reducing the cost of mounting the heating element and the number of items. The substantially cup-shaped housing body may also be made of a thin-walled material, e.g. by deep drawing. As a result, on the one hand, the housing body is elastic and on the other hand, he can thereby better direct the generated heat energy to the outside. The shape of the pot-shaped housing body is not limited and may e.g. be cylindrical, but also four, six or octagonal executed.

In order to increase the service life of the heating cartridge according to the invention and to increase its possible field of application, the housing body can, in an advantageous development, be made of a corrosion-resistant material, e.g. a metal, be made. In addition, in order to use the heating cartridge for aggressive liquid media, the housing body may also be made of an acid-resistant material.

Furthermore, the at least one insulating element is made of a plastic film. The plastic film may be a polyimide film. This material is particularly suitable because it provides good electrical insulation and on the other is particularly thermally conductive. The polyimide film may be, for example, a Kapton film. The design as a thin-walled film in this case enhances the inelasticity of the insulating element, so that the spring force is generated almost exclusively by the housing body.

In a further advantageous embodiment, the electrode body can each have a contact element, by which the electrode body can be connected to a voltage source. The contact elements may be designed as a welding contact or as a plug to provide a good connection option. The electrode bodies are also usually made of a thermally conductive material, in particular a metal.

In an advantageous development, the heating cartridge according to the invention may comprise at least two heat-conducting pressure bodies, which are formed by a spring force transferring from the housing body in the direction of at least one PTC element. This has the advantage that the pressure bodies are made of a low cost, easy to produce thermally conductive material, e.g. made of extruded aluminum, can be made and so fill the housing body, transfer heat and conduct the spring force inward. The cost-effective components, such as PTC element, electrode body and insulating element can thereby be made smaller and thus save material, which leads to the reduction of material costs. The pressure bodies can in particular be arranged between the housing body and the PTC element. You can also sandwich the PTC element. Furthermore, the pressure bodies can be designed as electrode body. You may also be surrounded by the insulating in a development.

Furthermore, the width of a stack of the pressure bodies, the at least one insulating element, the electrode bodies and the at least one PTC element in an advantageous development can be greater than the inside diameter of the housing body. As a result, during the assembly of the heating cartridge, the housing body is elastically expanded when the stack is inserted into the housing body. This elastic expansion creates the desired preload inside the heating cartridge. By the size of the excess of the width of the stack and the clear width of the case body, the magnitude of the bias voltage can be predetermined. To ensure that the biasing force is generated substantially or almost exclusively by the housing body, taking into account the respective thicknesses, the elasticity of the pressure body is dimensioned smaller than that of the housing body. Due to the higher elasticity, the pressure bodies remain under the action of the biasing force therefore substantially undeformed.

In a further advantageous embodiment, the heating cartridge may have at least one closure element, by which the housing body is substantially closed fluid-tight. This makes it possible to use the heating cartridge according to the invention in liquid or gaseous media. The interior of the housing body of the heating cartridge according to the invention is thus also protected against contamination, whereby a use in very dirty environments is possible.

In addition, the closure element may be made in a further advantageous embodiment of a permanently elastic material, in particular an elastomer. This is advantageous because permanently elastic material is resistant to aging and does not break or become porous even with temperature fluctuations. For use in corrosive, alkaline and / or acidic fluids, the closure element can be designed to be resistant to corrosion and / or acid.

In a further advantageous embodiment, the housing body may be configured with a latching means into which the closure element engages positively with a corresponding mating catch. As a result, the closure element is fixed in a simple manner in the housing body. Furthermore, by the outside use of the locking means of the housing body, for example, in a tubular receiving device be attached. By the latching means of the housing body and thus the heating cartridge is held by frictional engagement or positive engagement in the receiving device.

In order to secure the components in the interior of the housing body against displacement, the closure element can be configured in an advantageous development with a holding means which is formed axially securing the pressure body.

In a further advantageous embodiment, the heating cartridge may comprise at least one connection element, by which the electrode body can be connected to a voltage source. As a result, a simple way is provided to supply the heating element according to the invention with electricity. Furthermore, the at least one connecting element can also be designed as a fastening element and hold the heating cartridge in the medium to be heated. As a result, the heating cartridge, e.g. when heating a liquid medium directly and without receiving means are mounted in this, held by the connecting element.

In a further advantageous embodiment, the closure element may have at least one sealed opening through which a respective connection element extends. This has the advantage that the PTC element can be supplied with power without the inventive heating cartridge is leaking. Alternatively, the closure element may be formed as a part of a plug-in connection into which, for example, a plug element for supplying power to the heating cartridge can be inserted. Advantageously, the plug connection for the use of the immersion heater in liquids is designed to be fluid-tight.

The invention will now be described by way of example with reference to the accompanying drawings. The different features can be combined independently of each other, as has already been explained above in the individual advantageous embodiments.

Fig. 1

eine Ausführungsform der erfindungsgemäßen elektrischen Heizpatrone in einer schematischen Perspektivansicht;

Fig. 2

die Ausführungsform der elektrischen Heizpatrone aus Fig. 1 im Vollschnitt;

Fig.3

die Ausführungsform der elektrischen Heizvorrichtung aus Fig. 1 in einer Explosionsdarstellung.

Show it:

Fig. 1

an embodiment of the electric heating element according to the invention in a schematic perspective view;

Fig. 2

the embodiment of the electric heating cartridge Fig. 1 in full section;

Figure 3

the embodiment of the electric heater Fig. 1 in an exploded view.

Fig. 1 shows an embodiment of the electric heating cartridge 1 according to the invention with a housing body 2 and two connection elements 3. The housing body 2 is in Fig. 1 by way of example cup-shaped, whereby the heating element 1 is automatically closed at the bottom 4 of the housing body 2. The housing body 2 is cylindrical and thus z. B. in a tubular receiving device in a plug E E inserted. The heating cartridge 1 can be inserted up to a flange-shaped stopper 5 in the receiving device. Below the stop 5 is located on the housing body 2, a locking means 6 in the form of a hollow bead. By the latching means 6, the heating cartridge 1 is fixed in the receiving device. The fixation can be achieved in that the outer diameter of the locking means 6 is greater than the inner diameter of the receiving device, whereby the heating element 1 is frictionally fixed in the receiving device. But it is also conceivable that the receiving device has a recess into which the locking means 6 engages positively and thus fixes the heating cartridge 1. The locking means 6 is in Fig. 1 exemplified circumferentially on the entire circumference of the housing body 2. However, it is also possible that the latching means 6 is designed, for example, only in sections on the circumference of the housing body 2.

The two connection elements 3, e.g. in the form of a plug-in connection, emerge at the top from the housing body 2 for connection of the heating cartridge 1 to a voltage source (not shown). By the connection elements 3, there is also a further possibility of mounting the heating cartridge 1 according to the invention. For this purpose, the connection elements 3 are made of a flexibly bendable material. The connecting elements 3 serve in this embodiment as fastening elements and the heating cartridge 1 is, hanging on the connecting elements 3, placed directly in the medium to be heated. By manually bending the connection elements 3, the position of the heating cartridge 1 can be varied.

In order for the heating cartridge 1 also to be used for heating aggressive media, the housing body 2 is made of a corrosion and acid resistant material, e.g. a metal, made.

Fig. 2 shows by way of example the embodiment of the heating cartridge 1 according to the invention Fig. 1 in full section 1, whereby the components in the interior of the housing body 2 are visible in the installed state. In this case, the heating cartridge 1 according to the invention comprises a stack of two pressure bodies 7, an insulating element 8, two electrode bodies 9 and a PTC element 10 in the interior of the housing body 2. The PTC element 10 is formed as a thin, preferably rectangular plate with the largest possible Plate surface designed to form a maximum heat conduction surface. The PTC element 10 is in a position within the housing body 2, in which it can take the greatest possible length. This position is, for example, a diameter for a housing body with a circular cross section and a diagonal for a body with a polygonal cross section.

At the two plate surfaces of the PTGE element 10 are two electrode bodies 9 at. The two Electrode bodies 9 are substantially formed as thin, preferably rectangular plates and have at least the same plate surface as the PTC element 10 so that they can supply the PTG element 10 on the entire plate surface with power and can dissipate the generated heat well. The electrode bodies 9 are each connected via a connection element 3 to a voltage source (not shown). In Fig. 2 only one of two connection elements 3 is shown, since the other connection element 3, which connects the second electrode body to the voltage source, is located in the non-illustrated part of the heating cartridge 1. The connecting elements 3 and the electrode body 9 may be configured in one piece.

To the electrode body 9 together with the PTC element 10 around is inelastic compared to the housing body 2, foil-shaped insulating 8. The insulating 8 isolates the electrode body 9 and the PTC element 10 electrically against the pressure bodies 7 and the housing body 2. But one To ensure good heat conduction from the PTC element 10 and the electrode bodies 9 to the pressure bodies 7, the insulating member 8 is made of a thermally conductive material. In the exemplary embodiment in FIG Fig. 2 the insulating element 8 is made of a polyimide film, in particular of a Kapton film.

The PTC element 10, the electrode body 9 and the insulating body 8 are sandwiched between the two semicircular pressure bodies 7. The pressure bodies 7 are made of a thermally conductive material, e.g. made of aluminum, and are completely on the electrode bodies 9 and on the insulating element 8 at. The stack 7, 8, 9, 10 is located in the interior of the housing body 2 and is under a bias, since the width of the stack is greater than the inside diameter of the housing body 2, whereby the wall of the housing body 2 is elastically deflected outwardly and thereby the bias in the interior of the housing body 2 is formed. The bias compresses the two pressure body 7 in a direction of action F together. The pressure bodies 7 in turn press the insulating element 8, the electrode body 9 and the PTC element 10 together centrally. By compressing by the bias in the interior of the housing body 2 ensures that, for example, air gaps, which may be caused by manufacturing tolerances of the individual components or by different thermal expansions are reliably pushed away, whereby a good heat conduction is ensured within the heating cartridge 1 according to the invention.

As in Fig. 2 is shown, the housing body 2 is closed at the upper end of a closure element 11. The closure element 11 seals the housing body 2 in a fluid-tight manner, so that, for example, a fluid to be heated can not get into the interior of the heating cartridge 1. The closure element 11 has a widening which, in the installed state, positively engages in the latching means 6 of the housing body 2 and fixes the closure element 11. Furthermore, the closure element 11 has a stop flange 12, which rests in the installed state on the stop 5 of the housing body 2. In order to further improve the sealing effect, the closure element 11 is made of a permanently elastic plastic, namely an elastomer. The elastomer also offers the advantage that the closure element is dimensionally stable with respect to temperature fluctuations, does not age and thus does not leak. The elastomer can also be cast directly into the housing body 2 and harden therein, whereby an optimal positive connection with the inner surface of the housing body 2 is achieved. The closure element 11 has two sealed openings through which the connection elements 3 lead. Alternatively, the closure element 11 may form a part of a fluid-tight plug connection in which a counterpart of the plug connection for supplying power to the heating cartridge can be inserted. The connection elements 3 are likewise sealed by the closure element 11. The closure element 11 may be made of a corrosion-resistant material for use in corrosive media.

In order to prevent slippage of the pressure body 7 in the interior of the housing body 2, a holding means 13 is executed on the closure element 11. When installed, the holding means 13 limits the pressure bodies 7. The pressure bodies 7 are thus fixed in their axial position on one side by a shoulder at the end of the housing body 2 and on the other side by the holding means 13 of the closure element 11.

At the bottom 4 of the housing body 2 is located between the housing body 2 and the pressure bodies 7, an air-filled space, which forms an insulating layer and a heat loss down, for example when heating a solid, reduced.

Fig. 3 shows the electric heating cartridge 1 according to the invention Fig. 1 and 2 in an exploded view. The electric heating cartridge 1 comprises the housing body 2 in which the two semicircular pressure bodies 7 are accommodated. Between the two pressure bodies 7 is the PTC element 10, which is surrounded on each side by an electrode body 9, and both are enclosed by the insulating element 8. In Fig. 3 It can be seen that the insulating member 8 in this exemplary illustration is pocket-shaped around the PTC element 10 and the electrode body 9 around. This ensures electrical insulation of the electrode body 9 and the PTC element 10 on five sides. PTC element 10 and the electrode body 9 are inserted in the insertion direction E in the pocket-shaped insulating body 8. The electrode bodies 9 each comprise a contact element 14 to which the connection element 3 is attached. The connection is usually carried out by soldering or welding, but also a pluggable connection is conceivable.

As in Fig. 3 illustrated, the heating cartridge 1 is completed by the closure member 11 upwards. The individual components are introduced during assembly of the heating element 1 in the insertion direction E in the housing body 2.

Claims (10)

1. An electrical heating cartridge (1) for heating liquid and/or gaseous media, having at least one PTC element (10), two electrode bodies (9) assigned to the at least one PTC element (10) which are accommodated in an essentially cup-shaped housing body (2) electrically insulated from the electrode bodies (9) by means of at least one insulating element (8) and compressed under pretensioning, the housing body (2) being in the form of a spring element producing the pretensioning and the at least one insulating element (8), which is produced from a synthetic film, being designed to be inelastic with respect to the housing body (2), and having at least two heat-conducting pressure bodies (7) which are shaped to transfer the pretensioning from the housing body (2) towards the at least one PTC element (10), characterised in that there is an air-filled free space located on a base (4) of the housing body (2) between the housing body (2) and the pressure bodies (7) forming an insulating layer, that the heating cartridge (1) has at least one closure element (11) made of a permanently elastic material by means of which the housing body (2) is sealed off in a substantially liquid tight manner and which is designed with a holding means (13) shaped to secure the pressure bodies (7) axially and has at least one sealed opening through which a respective connection element (3) extends, that the housing body (2) is designed with a securing means (6) in which the closure element (11) engages, with form locking, with a counter-detent, and that the pressure bodies (7) are fixed in their axial position on the one side by means of a shoulder on the end of the housing body (2) and on the other side by the holding means (13).
2. The electrical heating cartridge (1) according to Claim 1, characterised in that the housing body (2) is produced from an elastic material.
3. The electrical heating cartridge (1) according to Claim 1 or 2, characterised in that the housing body (2) is produced substantially in a cup-shape.
4. The electrical heating cartridge (1) according to any of the claims specified above, characterised in that the housing body (2) is produced from a corrosion-resistant material.
5. The electrical heating cartridge (1) according to Claim 4, characterised in that the synthetic film is a polyimide film.
6. The electrical heating cartridge (1) according to any of the claims specified above, characterised in that the electrode bodies (9) respectively have a contact element (14) by means of which the electrode bodies (9) can be connected to a voltage source.
7. The electrical heating cartridge (1) according to Claim 1, characterised in that the width of a stack comprising the pressure bodies (7), the at least one insulating element (8), the electrode bodies (9) and the at least one PTC element (10) is larger than the inner width of the housing body (2).
8. The electrical heating cartridge (1) according to Claim 1 or 7, characterised in that the at least two pressure bodies (7) are produced from aluminium.
9. The electrical heating cartridge (1) according to any of the claims specified above, characterised in that the heating cartridge (1) comprises at least one connection element (3) which is designed as a fixing element by means of which the heating cartridge (1) can be attached within the medium to be heated.
10. The electrical heating cartridge (1) according to any of the claims specified above, characterised in that as regards the pretensioning force, the pressure bodies (7) are designed to be less flexible than the housing body (2).

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