EP2203027B1 - Heating cartridge - Google Patents

Description

The invention relates to a heating cartridge with at least one heating wire coil having at least two preferably coreless spiral strands which extend along the two sides of a matched in its width to the inner diameter of a metal shell support wall of insulating material and embedded in the metal shell in a granulated insulating material, wherein the Heizdrahtenden are each provided with protruding from the same end of the metal shell terminals, and wherein the Heizdrahtwendeln in the region of the connection remote, closed end of the metal shell facing end edge of the support wall are electrically connected together, and where necessary along the length of the Heizdrahtwendel at the longitudinal edges of the support wall distributed spacers are arranged of insulating material, which keep the coil strands insulating from the metal shell.

Here, the connection remote ends of the two Heizdrahtwendeln, as shown DE 20 2005 011 686 U1 known, be interconnected by a helical portion which is guided around a lower deflection edge of the insulating material. In this known immersion heater, the Isolierstoffwand only serves to keep the two helical strands mutually at a distance and thus to isolate electrically against each other. In order to keep the helical strands also from the metal shell, special, bow-shaped spacers are provided, which are arranged on both sides of the insulating material in more or less large distances and attached to the edges of the insulating wall self-holding. The filling of the metal shell with, for example, MgO granules, into which the insulating wall with the two spiral strands is already inserted, takes place in a substantially vertical position of the metal shell with the open upper end. The lying in the region of this open end of the metal sheath Heizdrahtenden, or the verbundnenen with these Heizdrahtenden connection connector must be held by means of auxiliary equipment so that they do not disturb the filling and not get into the metal shell on the one hand. Only after the filling of the granules, the metal shell can be closed by means of a plug, which also has to take the connection connector. This working method is very time consuming and therefore costly.

A compacted heating element of the generic type is also made DE 70 31 974 U known. In this Heizpatrone two or more Heizleiterwendeln (in the publication called "Heizleiterspiralen" called) with different wire thicknesses and different coil diameters concentrically exposed to each other housed in a cylindrical cartridge housing having at one end a solid frontal bottom and the other end by a metal disc with wart-shaped Drilling is closed. Instead of the usual connection bolts provided with Isoliermänteln strands are connected within the cartridge housing to the Heizdrahtenden. These strands are guided with their Isoliermänteln through the metal plate inside, so that there is an insulation between the metal plate and the conductor wires of the strands. Means which isolate the coaxial helical strands against each other and against the metal cartridge housing are not provided. Even with this heating cartridge filling the Isoliergranulats is cumbersome and expensive.

Out DE 197 16 010 C1 is an electric jacket tube heater with integrated temperature sensor is known in which the Heizdrahtwendel hairpin is applied in the metal sheath tube and the connection of the heating element at one end of the metal sheath tube and the terminals of the connection temperature sensor are led out at the other end of the jacket tube. The two parallel strands of Heizdrahtwendel are embedded without partition in compacted insulating material. It is necessary to fill the originally granulated insulating material in the two legs of the U-shaped bent metal casing tube before the ends are closed with sealing plugs.

In these known heating cartridges no support elements are provided for the heating wire coil within the metal tube, which ensure that the Heizwendelwindungen not come into contact with the pipe wall when filling the insulating granules. Rather, when filling the granules, make sure that the Heizdrahtwendel get no bends and are kept physically away from the pipe jacket. This complicates the filling of the granules and causes high production costs.

From the DE 20 2005 011 686 U1 is a heating cartridge with a Heizdrahtwendel having two coreless helical strands, known which along the two sides of a matched in width to the inner diameter of a metal shell carrier wall made of insulating material and embedded in the metal shell in a granulated insulating material, wherein the Heizdrahtenden each with wherein the Heizdrahtwendeln are electrically connected to each other in the region of a terminal remote from the closed end of the metal shell end edge of the support wall, and arranged over the length of the Heizdrahtwendel at the longitudinal edges of the support wall spacers made of insulating material are, which keep the spiral strands insulating from the metal shell.

From the US 3,512,114 A It is known to provide the connection-side end of a heating cartridge with a dimensionally stable support wall with a mounted coil holder to which the Heizdrahtenden are secured under a turn of the Heizdrahtwendel holding at a distance holding tension, and which is provided with a filling opening for the granulated insulating material, or whose contour with the metal shell forms such a filling opening.

From the FR 2 734 686 A is a heating cartridge with an integrated temperature sensor known.

The invention has for its object to provide a heating cartridge of the type mentioned, which is inexpensive to produce with minimal labor and material costs and offers the opportunity to accommodate in the region of the closed end portion of the metal shell safety switching elements against thermal overload.

This object is achieved according to the invention in that at least the terminal end of a dimensionally stable support wall is provided with a mounted coil holder to which the Heizdrahtenden are mounted under a holding the turns of Heizdrahtwendel at a distance holding tension and which is provided with at least one filling opening for the granulated insulating material or its contour with the metal shell such Filling opening forms and that also at the lower, ie connection remote end of the support wall, a coil holder is arranged, which holds tensile strength connected to the ends of the coil strands connecting connector to tension, through which they are connected to an overload protection.

The inventive arrangement and the provision of a dimensionally stable support wall made of insulating material with at least one coil holder, which keeps the Heizdrahtwendeln along the support wall both when inserted into the metal shell and during subsequent filling of the insulating granules, the production of such heating cartridges is much easier and cheaper. For short and not minimally thin metal shells (under 3 mm ∅) can even on spacers, which keep the Heizdrahtwendeln away from the metal shell, be waived. With very long cartridge heaters of 1.5 m in length and more to get compared to conventional cartridges of the generic type with significantly fewer spacers. In addition, the ends of the Heizdrahtwendeln can be provided with the connecting elements before their introduction into the metal shell and fixed in a very simple manner to the one or more Wendelhaltern in final, functionally correct position, the tension also significantly facilitates this operation.

Whether or not a coil holder is arranged at the remote from the filling opening of the metal shell, that is at the remote terminal end of the support wall depends essentially on the wire thickness of the heating wire, its tension and incidentally also on whether in this area connecting elements for additional Switching elements are needed. If no coil holder is needed at this terminal-distal end of the support wall, the connecting coil portion may consist of a short wire section or comprise one or more turns.

For example, can be used as a deflection edge, a peripheral edge of a recess in the support wall, which from the ground the metal sheath has a certain distance, so that the guided around this deflecting helix section with the ground can not come into contact.

Another simple way to isolate the guided around this lower end edge coil portion against the bottom of the metal shell or to keep away from this, is to provide an insulating or spacer ring.

Usually, the fillings consisting of MgO granulate or quartz sand are compacted by radial compression of the metal shell.

Due to the embodiment of the invention according to claims 2 and 3, it is particularly easy to attach the Heizdrahtenden to the coil holder.

The embodiment according to claim 4 also shows a very advantageous possibility of accommodating safety switching elements against thermal overloading in the region of the closed end section of the metal jacket.

For heating cartridges, which have a greater length, it is advantageous to provide spacers according to claim 7. Through them, even with larger lengths of the danger avoid that the Heizdrahtwendeln come into contact with the metal shell.

With the further embodiments according to claims 6 and 7, the insulation and breakdown safety of Heizdrahtwendeln relative to the metal shell can be significantly enhanced.

In order to have the possibility of arranging two Heizdrahtwendel on each flat side of the support wall, the embodiments are provided according to claim 10, wherein each pairwise interconnected Heizdrahtwendel may be assigned to different heating circuits on the two flat sides of the support wall.

Fig. 1:

in Schnittdarstellung eine noch unverdichtete Heizpatrone mit zwei Wendelsträngen und mit thermischen Sicherheitsschaltelementen ;

Fig. 2:

in 3D- Darstellung einer Heizpatrone aus dem Stand der Technik zur Veranschaulichung des Aufbaus der Heizpatrone aus Fig. 1 mit Abstandhaltern;

Fig. 3:

in isometrischer Darstellung die Trägerwand aus Fig. 2 als Einzelteil;

Fig. 4:

einen Abstandhalter aus Fig. 2 als Einzelteil in 3D-Darstellung;

Fig. 5:

einen Wendelhalter aus Fig 1 in vergrößerter Draufsicht;

Fig. 6:

einen Schnitt VI -VI aus Fig. 5;

Fig. 7:

in Seitenansicht die Trägerwand mit einer Distanzplatte und zwei Wendelhaltern aus Fig. 1;

Fig. 8:

einen Wendelhalter aus Fig. 7 in Draufsicht;

Fig. 9:

in vergrößerter Schnittdarstellung den oberen, anschlussseitigen Wendelhalter aus Fig. 1;

Fig. 9a:

die gleichen Teile wie Fig. 9, jedoch mit abweichend gestalteten Durchlassöffnungen;

Fig. 10:

einen anderen Wendelhalter in Draufsicht;

Fig. 11:

einen Schnitt XI - XI aus Fig. 10;

Fig. 12:

einen Schnitt XII - XII aus Fig 10;

Fig. 13;

in vereinfachter 3D-Darstellung mit aufgeschnittenem Metallmantel den Aufbau einer Heizpatrone gemäß Stand der Technik mit vier Wendelsträngen;

Fig. 14:

die Heizpatrone gemäß Stand der Technik der Fig. 13 im Schnitt;

Fig. 15:

einen Schnitt XV - XV aus Fig. 14;

Fig. 15a:

die gleiche Schnittdarstellung Fig. 15, jedoch mit einem anderen Wendelhalter;

Fig. 16:

in auseinander gezogener Seitenansicht eine Trägerwand mit dazugehörigen Wendelhaltern im Schnitt;

Fig. 17:

eine Distanzplatte aus Fig. 14 als Einzelteil in Seitenansicht;

Fig. 18:

in Draufsicht einen Wendelhalter aus Fig. 14 und 15;

Fig. 19:

einen Abstandhalter aus Fig. 14 als Einzelteil;

Fig. 20:

in vergrößerter Seitenansicht einen Anschlussverbinder aus Fig. 2;

Fig. 20a:

einen Schnitt XVIIIa - XVIIIa aus Fig. 18;

Fig. 21:

ein anderes Anschlusselement für ein Heizdrahtende in vergrößerter Seitenansicht;

Fig. 21a:

einen Schnitt XX'- XX aus Fig. 19;

With reference to the drawings, the invention will be explained in more detail below. It shows:

Fig. 1:

in section a still uncompressed heating cartridge with two spiral strands and with thermal safety switching elements;

Fig. 2:

in a 3D representation of a heating cartridge of the prior art to illustrate the structure of the heating cartridge Fig. 1 with spacers;

3:

in an isometric view of the support wall Fig. 2 as a single item;

4:

a spacer Fig. 2 as an item in 3D representation;

Fig. 5:

a spiral holder Fig. 1 in enlarged plan view;

Fig. 6:

a cut VI -VI off Fig. 5 ;

Fig. 7:

in side view, the support wall with a spacer plate and two Wendelhaltern Fig. 1 ;

Fig. 8:

a spiral holder Fig. 7 in plan view;

Fig. 9:

in enlarged sectional view of the upper, connection-side spiral holder Fig. 1 ;

Fig. 9a:

the same parts as Fig. 9 , but with differently shaped passage openings;

Fig. 10:

another coil holder in plan view;

Fig. 11:

a cut XI - XI Fig. 10 ;

Fig. 12:

a section XII - XII off FIG. 10 ;

Fig. 13;

in a simplified 3D representation with cut metal shell the structure of a heating cartridge according to the prior art with four spiral strands;

Fig. 14:

the heating cartridge according to the prior art of Fig. 13 on average;

Fig. 15:

a section XV - XV off Fig. 14 ;

Fig. 15a:

the same sectional view Fig. 15 but with a different spiral holder;

Fig. 16:

in exploded side view of a support wall with associated Wendelhaltern in section;

Fig. 17:

a spacer plate Fig. 14 as an item in side view;

Fig. 18:

in plan view a spiral holder Fig. 14 and 15 ;

Fig. 19:

a spacer Fig. 14 as a single item;

Fig. 20:

in enlarged side view of a connection connector Fig. 2 ;

Fig. 20a:

a section XVIIIa - XVIIIa Fig. 18 ;

Fig. 21:

another connection element for a Heizdrahtende in enlarged side view;

Fig. 21a:

a section XX'-XX off Fig. 19 ;

The in the Fig. 1 illustrated heating cartridge according to the invention and in Figures 2 or 13 and 14 for better understanding of their construction not shown heating cartridges 1 or, 1/1 each have a cylindrical metal shell 2, which is provided with a solid bottom 3 and the upper open end, as in Fig. 1 , can be closed by a shutter disk 4. The metal shell 2 is preferably made of copper or stainless steel.

The closure disk 4 consists of an insulating material and is provided with through-holes for two connecting wires 5 and 6. At this provided with Isoliermänteln connection strands 5, 6, the Heizdrahtenden 9 and 10 of a two spiral strands 11 and 12 existing Heizdrahtwendel 13 are connected electrically contacting and mechanically zugfest each with the help of terminal connectors 7 and 8.

The two spiral strands 11 and 12 extend along the two flat sides of a centrally arranged in the metal shell 2 support wall 14, which serves as a support for the two spiral strands 11, 12 of the heating wire coil 13. The width d of the support wall 14 is matched to the inner diameter dl of the metal shell 2, that the support wall is easily inserted into the metal shell, but is so stably guided in the metal shell 2, that it occupies a central position therein. The support wall 14 consists of a dimensionally stable insulating material, for. As micanite, so that it can be produced in long lengths of up to 200 cm or more and with small widths d of only a few mm. Their required dimensional stability, in particular their flexural strength, must be so great as to withstand at least the tension of two helical strands running along their two flat sides. To at least one Heizdrahtwendel 13 with two each along a flat side of the support wall 14 extending helical strands 11, 12 in the in Fig. 1 and 2 shown to be able to arrange under tension, at least the connection-side end of the support wall 14 provided with a frontally mounted coil holder 15. The tensile stress is caused by the pulling apart of the Heizdrahtwicklungen when the originally wound with closely spaced turns Heizdrahtwendel is drawn to the greater length of the support wall. Before this clamping operation, the Heizdrahtenden 9, 10 are connected to the terminal connectors 7 and 8 and through this with the connecting leads 5, 6. It is important that the connection connectors 7, 8 are able to absorb the tensile stress of the helical strands 11, 12. This tensile connection can be made in different ways, for example by soldering, welding, clamping, crimping or bending.

In order to be able to fasten the connection connectors 7, 8 connected in this way to the heating wire ends in a simple manner to generate or maintain the tensile stress, this is provided with axial passage openings 16, 17 for the heating wire ends 9, 10 and with support surfaces 18, 19. These support surfaces 18, 19 are in the in the Fig. 5, 6 and 8 and 10 illustrated helical holders 15 are each formed by the edge surfaces of the passage openings 16, 17, in that the connection connectors 7, 8 each have a larger diameter than the passage openings 16, 17.

In order to facilitate the threading of the Heizdrahtenden in the passage openings 16, 17, the passage openings 16, 17 each provided with edge-open slots 20, 21 or, as Fig. 10 shows, designed as such. In order to form support surfaces for the connection connectors 7, 8, the slots 20, 21 each have a width b (FIG. Fig. 10 ), which is smaller than the diameter of the terminal connector. Again Fig. 8 can be seen, there is also the possibility in principle, the passage openings 16, 17 form as axially extending bores.

Likewise, it may be appropriate to provide passage openings 16 ', 17', which are formed stepwise with different diameters, so that, as in Fig. 9a is shown, as a support surface, an annular shoulder 18 'is formed, on which a connection connector 7, 8 is seated and at the same time guided centered by the surrounding him bore wall 19' in its functional position.

In order for the helical holder 15 to receive a reliably firm seat at the end of the support wall 14, the helix holder 15 is provided with a preferably continuous receiving slot 22 for an axially projecting centering tongue 23 of the support wall 14. Since the receiving slot 22 and the centering tongue 23 are narrower than the support wall 14, the coil holder 15 sits on the two lateral shoulders 24, 25 of the support wall 14.

For heating cartridges with a large length, it may be necessary or at least appropriate to support the two spiral strands 11 and 12 against deflection. These are, as is well known and in Fig. 2 shown, bow-shaped spacers 45 of insulating material, for example of ceramic bodies, provided which are distributed over the length of the support wall 14 at appropriate intervals from each other. These spacers 45 each have a U-shaped recess 46, through which a spiral strand 11 or 12 is guided in order not to come into contact with the metal shell 2.

These spacers are each provided with lateral clamping fingers 47 and 48 which engage positively in notches 49 of the support wall 14.

Depending on the design of the heating cartridge, the end of the support wall 14 remote from the connection can either also be provided with a centering tongue 23 or only with a deflection edge 26 about which a connecting section 27 of the two spiral strands 11 and 12 is guided. This deflection edge can be at a distance from the bottom 3, for example from the edge of a bore 28 (FIG. Fig. 2 ) or formed by a boundary edge 29 of a U-shaped or rectangular cutout 30.

At the in Fig. 1 The illustrated design is also at the bottom, ie remote terminal end of the support wall 14, a coil holder 15 is arranged, which holds the tensile strength connected to the ends 31, 32 of the two spiral strands 11 and 12 connected terminal connector 33, 34. About these two terminal connectors 33 and 34, the two helical strands 11 and 12 are connected to electrically connected in series, thermal safety switches 35, 36, which may be formed as a fuse, bimetallic switch or the like.

In order to create sufficient space in the metal casing between the lower coil holder 15 and the bottom 3 for the safety switches 35, 36, a spacer wall 37 aligned with the support wall 14 is arranged in this region. This spacer wall 37 is supported on the one hand on the bottom 3 and on the other hand with two shoulders 38, 39 on the coil holder 15, wherein a centering tongue 23 'in the slot 22 of the coil holder 15 protrudes. For passing a connecting line 40, the lower end of the spacer wall 37 is provided with a recess 41.

Depending on the design of the safety switch 35, 36 can be dispensed with the spacer wall.

The preassembled module, consisting of the support wall 14, the coil holders 15, the attached coil strands 11, 12, the terminal connectors 7.8 and 33, 34, the connecting wires 5, 6 and the spacer wall 37 with the safety switches 35, 36 is in pushed the unilaterally open metal shell 2 until the spacer wall 37 rests on the bottom 3.

After that, the existing below the upper coil holder 15 cavities in the metal shell 2 in a simple manner with MgO granules 20, quartz sand or other free-flowing insulating material To be able to fill, the coil holder 15 are provided on the circumference with a plurality of filling openings 42, which expediently consist of open-edged recesses, like the Fig. 5 . 8 and 10 reveal. The cross-sectional shape of these recesses can be selected largely arbitrary, provided that the stability and tensile strength of the coil holder 15 to be maintained is taken into account.

In contrast to the embodiment of Fig. 2 is at the heating cartridge of Fig. 1 the metal shell 2 extends beyond the upper, connection-side coil holder 15 addition. The thus formed cavity 43 is also filled with the used Isolierstoffgranulat and closed by means of the shutter disk 4.

In this state, the compression takes place by radial compression of the metal shell. 2

It should be noted at this point that the drawings reproduce the immersion heater 1 in the uncompressed state.

In the FIGS. 13 and 14 a heating cartridge 1/1 known from the prior art is shown in different views, in which two spiral strands 11/1, 11/2 and 12/1 and 12/2 are arranged on both flat sides of a support wall 14/1, the each form a contiguous Heizdrahtwendel 13/1 and 13/2.

Like the representation of the FIGS. 13 and 14 shows, the support wall 14/1 is provided both at its upper, connection-side end and at the other end in each case with an attached coil holder 15/1, to which the helical strands 11/1 to 12/2 are fastened with exploded turns under tension.

The coil holders 15/1 used here, preferably consisting of a ceramic body, are provided with four axial bores arranged in pairs symmetrically with respect to the support wall 14/1 16 'is provided, whose end-side edge surfaces form the bearing surfaces 18' for the connection connectors 7, 7 ', 8 and 8'. About the terminal connector 7, 7 ', 8, 8', the individual coil strands 11/1 to 12/2 tensile strength with the connecting leads 5, 5 'and 6, 6' are connected. The lower, remote connection ends of each of a pair of heating wire coil 13/1 and 13/2 forming coil strands 11/1 and 12/1 or 11/2 and 12/2 are each connected by Heizdrahtabschnitte 26, 26 'to each other, each between two holes 16 'are guided around the lower end face of the lower coil holder 15.

In contrast to the spiral holder 15 of Fig. 5 is the coil holder 15/1 with two diametrically aligned opposite receiving slots 22 'provided to accommodate the two separated by a frontal recess 51 guide tongues 23' of the support wall and the coil holder 15/1 when placing a stable fit. Thus, the previously on the terminal connectors 7, 7 ', 8, 8' tensile strength fixed ends 9 ', 10' of the individual coil strands 11/1 to 12/2 can be easily inserted into the bores 16 ', these holes 16' are each with provided at the edge open slots 20 '.

In order to establish a safe or defined distance between the Heizdrahtabschnitten 26, 26 'and the bottom 3, provided with two engaging in the slots 22' of the lower coil holder 15/1 tongues 23 'spacer plate provided, but also by other means can be replaced.

Again, with correspondingly long construction spacers 45/1 may be provided with two cutouts 46/1, which keep the 11/1 to 12/2 stretched along the support wall 14/1 coil strands insulating away from the metal shell.

In this preassembled state, this assembly can just as easily and quickly in the designated metal shell 2 are inserted. So that then the granulated insulating material 50, in which the Heizdrahtwendeln 13/1 and 13/2 are embedded, can be filled easily and as quickly as possible in the metal shell 2, and the coil holder 15/1 are provided with edge-open recesses 42 '.

In Fig. 15a a coil holder 15/2 is shown, which has a smaller outer diameter with the same large inner diameter of the metal shell 2 as the coil holder 15/1. As a result, an annular gap 42/1 is formed with concentric arrangement between the circumference of the coil holder 15/2 and the metal shell 2 on both sides of the support wall 14/1, which can also be used instead of the recesses 42 'for filling the Isolierstoffgranulats 50.

As already mentioned, it is customary to subject the metal shells 2 thus filled with insulating material 50 to a radial compression in order to obtain better performance results.

Only exemplary are in the Fig. 20 to 21a possible embodiments of a connector shown. The connection connector 8 of FIGS. 20 and 20a consists of a preferably slotted sleeve, which encloses the one of the insulating jacket freed end of the pigtail 6 together with the Heizdrahtende 10 'with generated by pressing radial stress.

In the embodiment of the Figs. 21 and 21a the connection connector 8/1 consists of the thicker end portion 8/1 of a cylindrical connecting bolt 6/1, which is provided for receiving a Heizdrahtendes 10 'with a blind bore 52 in which the Heizdrahtende 10' can be fastened by compression or otherwise tensile strength ,

In order to increase the dielectric strength, it is expedient to apply to the inner surface of the metal shell 2 a single-layer or multi-layered insulating film, within which the heating wire coil (s) (13, 13/1) is embedded in the granulated insulating material, for example of polyimide.

Claims (6)

1. Heating cartridge having at least one heating wire coil (13) which has at least two preferably coreless coil strands (11, 12) that run along the two sides of a carrier wall (14), which is made of insulating material and which is tailored in terms of its width to the internal diameter of a metal jacket (2), and in the metal jacket (2) are embedded in a granulated insulating material (50), wherein the heating wire ends (9, 10) are each provided with terminals projecting from the same end of the metal jacket (2), and wherein the heating wire coils (11, 12) are electrically connected to one another in the region of an end edge of the carrier wall (14) facing towards a closed end of the metal jacket (2) remote from said terminals, and wherein, if necessary, spacers (45) made of insulating material are arranged along the length of the heating wire coil in a manner distributed on the longitudinal edges of the carrier wall (14), which spacers keep the coil strands (11, 12) away from the metal jacket (2) in an insulating manner, characterized in that at least the terminal-side end of a shape-stable carrier wall (14) is provided with a coil holder (15, 15/1) which is placed thereon and to which the heating wire ends (9, 10) are fastened under a tensile stress that maintains a distance between the windings of the heating wire coil (13), and which is provided with at least one filling opening (42) for the granulated insulating material (50) or the contour of which forms with the metal jacket (2) such a filling opening (42/1), and in that the terminal-remote ends (31, 32) of two coil strands (11, 12) running on opposite sides of a carrier wall (14) are fastened to a second coil holder (15), which is placed onto the terminal-remote end section of the carrier wall (14), by means of terminal connectors (33, 34) by which they are connected to an overload protection means (35, 36), in particular a fuse and/or a bimetal switch.
2. Heating cartridge according to claim 1, characterized in that the coil holder (15, 15/1) is provided with through-openings (16, 17, 16') for the heating wire ends (9, 10) fastened to terminal connectors (7, 8), and with support faces (18, 19) for the terminal connectors (7, 8).
3. Heating cartridge according to claim 1 or 2, characterized in that the through-openings (16, 17, 16') of the coil holder (15, 15/1) are provided with slots (20, 21, 20') which are open at the edge or consist only of such slots.
4. Heating cartridge according to claim 1, characterized in that the spacers (45, 45/1) consist of ceramic bodies which engage in a clip-like manner around the longitudinal edges of the carrier wall (14) and in doing so enclose in each case one coil strand (11, 12).
5. Heating cartridge according to any one of claims 1 to 4, characterized in that there is placed on the inner face of the metal jacket (2) a single-layer or multilayer insulating film, within which the heating wire coil(s) (13, 13/1) is or are embedded in the granulated insulating material (50).
6. Heating cartridge according to claim 5, characterized in that the insulating film is made of polyamide.

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