EP1239702A2 - Electrical heating coil which heats a flowing gaseous medium and its electrical resistive heating element - Google Patents

Abstract

The heater is deflected in the peripheral surface of the coil (1) from the inclined gradient line alternately in opposite directions. The deflections may be zigzag-shaped or wave-shape. The heater consists of a wire (2) with a circular cross-section, preferably a thermistor passive thermal control (PCT) wire.

Description

The invention relates to a heating conductor coil for heating a flowing gaseous medium, primarily air, and an electrical Resistance heating element with a heating conductor coil, which is interposed is fastened by holding elements on a carrier plate.

Helical, but also zigzag or meandering heating conductors find especially as heating elements in electrical devices for heating Air, such as hair dryers, fan heaters, convectors or tumble dryers same application; but they can also be used in the same way Use heating other gaseous media. With such devices, a Airflow generated by a fan through one of at least one Such heating element led existing radiator. During the Flow occurs between the heating conductor and the air flow Heat exchange instead of the most evenly and possibly without Heat loss should take place.

In most known heating elements, the heating conductor consists of one helical or meandering shaped resistance wire, which directly with a carrier plate made of electrically insulating and heat-resistant material, such as for example Micanit, is connected (DE 25 30 075 A1, DE 25 35 478 A1, DE-PS 29 44 132). These known heating elements have in common that the heating wire requires direct contact with the carrier plate to fix it, also, that the way of attaching the heating wire to the support plate from depends on the shape of the heating element. Because the heating wire with electrical energy is applied, the carrier plate does not only have to be electrical insulating, but also made of a heat-resistant material, such as Micanite. By lying parallel to the direction of flow The flow cross-section is divided into individual chambers that support plates affect an even heat exchange.

However, a heating element is also already known in which the helical one Heating conductor no longer directly on the carrier plate, but indirectly with the help is fastened by holding elements which are fixed on the one hand to the carrier plate and on the other hand, the heating conductor coil is attached (DE 44 43 725 A1). As a result, there are direct contact points between the heating conductor and Carrier plates avoided, which increases the durability of the carrier plates extended. There is also the further advantage that the flow cross-section is no longer divided by carrier plates, which means better heat dissipation and thus results in better efficiency.

The holding elements for fixing the heating conductor coil exist in this known heating element from a shaft, at one end a holding part to fix the helix and a foot part at the other end Attachment are arranged on the support plate. The holding part forms a flat, approximately U-shaped undercut receptacle for a turn tip of a helix with a flat oval to flat rectangular cross section. The foot section consists of two parallel legs protruding from the shaft at right angles on the underside Protruding tabs that are inserted through slots in the carrier plate and then be bent.

This design of a heating element not only has the advantage that Avoid direct contact points between the heating conductor and carrier plate be, but also the further advantage that as a result of the holding elements that in Direction of flow can be very narrow, the heating conductor coil freely in the Airflow is that a relatively cheap heat emission is achieved.

Against this background, the invention is based on the object Possibility to show in such electrical Resistance heating elements to enable even better heat utilization.

According to the invention, this object is achieved with a heating conductor coil Features of claim 1, the use of such a heating conductor coil in an electrical resistance heating element according to claim 8 and a Heating element with the features of claim 9 solved.

Advantageous further developments result from the subclaims.

The basic idea of the invention is that by combining a Heating conductor coil, in particular a coil with a flat rectangular cross section and with short-wave undulations in relation to the dimensions of the helix the circumferential surface of the helix formed by the slope line of the helix the flow cross section of the heat conductor generating the heat very much is enforced closely. This results in a diverse swirling of the air flowing through a heating element equipped with such a coil with the consequence of a much cheaper transfer of heat from the heating conductor on the air flowing through. This does not result in the same heat yield inconsiderable reduction in energy consumption by 20 to 25%.

In this context, there are also particular advantages if the heating conductor consists of a thermistor wire, d. H. from a material in which the electrical resistance changes with temperature, in particular from one with a positive temperature coefficient (PTC).

A heating conductor coil designed according to the invention can in principle be used for arbitrarily designed heating elements are used in which the filament is arranged transversely to the flow direction. There are special advantages but when used in an electrical resistance heating element in which at least one coil with the interposition of holding elements on one Carrier plate is attached.

The functional and manufacturing advantages also offer here inventive design of the holding elements for the heating conductor coil, so the intermediate links between the heating conductor coil and the carrier plate, which effect the largely free suspension of the helix. Because of the special Design of the holding part of these elements, each one turn of the spiral captured on two opposite sections, one succeeds Functional holding of the helix without deflection of individual turns and a secure fixation of the helix. In contrast, the foot section of the Holding elements according to the respective structure of the heating element be trained. It is possible to make the heating conductor coil approximately circular around a central circular support plate, the Holding elements lie in the plane of the support plate and the spiral, as well as the Arrange holding elements at right angles to a support plate to also the To be able to provide helix in the corresponding direction.

A particularly advantageous embodiment of a heating element solves this Problem that known holding elements due to their respective shape tend to retain dust particles and lint in the gas flow. in the Over time, this creates accumulations of dust and lint initially lead to a reduction in the flow cross-section and thus the flow resistance increases so that to operate a heating element more energy needs to be supplied.

However, the danger that the dust and Ignite lint accumulations on the hot heating conductor and thereby a fire is triggered. To counter this danger, it is therefore necessary to use known heating elements equipped devices at regular time intervals wait and clean. This problem is increasing for example in tumble dryers; where a disproportionate amount of fluff in the Gas stream are carried.

This problem is solved according to the invention with a holding element with the features of independent claim 16, which in the Advantageously further developed sub-claims. It should be emphasized that a such holding element not according to heating elements with a heating conductor Claim 1 is limited. Rather come for the invention Holding elements all heating conductors known from the prior art, which are attached indirectly to a carrier element.

Fig. 1

einen Ausschnitt aus einer Draufsicht auf eine erfindungsgemäß ausgebildete Heizleiterwendel für ein elektrisches Widerstandsheizelement,

Fig. 2

einen Querschnitt durch die Heizleiterwendel gemäß Fig. 1 und

Fig. 3

einen Ausschnitt aus Fig. 1 in größerem Maßstab;

Fig. 4

zeigt einen Teil einer Draufsicht auf ein kreisförmiges Heizelement,

Fig. 5

einen Querschnitt entlang der Linie V-V in Fig. 1,

Fig. 6

eine schrägbildliche Darstellung eines Halteelementes,

Fig. 7

einen Ausschnitt aus einem Querschnitt durch eine Trägerplatte mit der Befestigung eines Halteelementes gemäß Fig. 6, die

Fig. 8 und 9

weitere Ausführungsformen für im Rahmen der Erfindung anwendbare Halteelemente,

Fig. 10

eine Vorderansicht einer besonders vorteilhaften Ausführungsform eines Halteelements,

Fig. 11

eine Seitenansicht des in Fig. 10 dargestellten Halteelements,

Fig. 12

eine Draufsicht des in den Fig. 10 und 11 dargestellten Halteelements und

Fig. 13

eine Schrägansicht des in den Fig. 10 bis 12 dargestellten Halteelements.

The invention is explained below with reference to the drawing. It shows

Fig. 1

1 shows a detail from a top view of a heating conductor coil designed according to the invention for an electrical resistance heating element,

Fig. 2

a cross section through the heating conductor coil according to FIG. 1 and

Fig. 3

a section of Figure 1 on a larger scale.

Fig. 4

shows part of a plan view of a circular heating element,

Fig. 5

2 shows a cross section along the line VV in FIG. 1,

Fig. 6

an oblique representation of a holding element,

Fig. 7

a section of a cross section through a carrier plate with the attachment of a holding element according to FIG. 6, the

8 and 9

further embodiments for holding elements that can be used within the scope of the invention,

Fig. 10

2 shows a front view of a particularly advantageous embodiment of a holding element,

Fig. 11

10 shows a side view of the holding element shown in FIG. 10,

Fig. 12

a plan view of the holding element shown in FIGS. 10 and 11

Fig. 13

an oblique view of the holding element shown in FIGS. 10 to 12.

1 shows a heating conductor coil 1 in accordance with the invention Side view shown, i.e. in a view from the direction in which it is from flows through a gaseous medium to be heated. A cross section through the helix 1 according to FIG. 1 shows FIG. 2. It shows how the Heating wire 2 to flat rectangular turns 3 of two essentially straight longitudinal sides 3a and 3b with approximately semicircular Inversion points 3c and 3d is deformed. This helix shape is known per se compared to a circular cross-section, the main advantage is a smaller one Width expansion, i.e. a smaller space requirement in the direction of flow.

As in FIG. 1, but in particular the representation on a larger scale in 3, the heating conductor 2 forming the coil 1 is in the course of Windings, namely in that formed by the slope line SL of the helix Alternate circumferential surface from the slope line SL opposite directions deflected. The spiral wire has in this Circumferential surface has an approximately wavy or zigzag shape. In particular 1, as seen in the flow direction D, the front and rear sections of the individual turns 3 of the helix 1 themselves superimpose, so that the flow cross-section, in particular in the central Area is tight and, above all, evenly penetrated by the heating wire. hereby very fine air turbulence is achieved, which is not only a reduction of energy consumption, but also due to lower heat load long service life of the helix.

A heating conductor coil 1 designed in this way according to the invention can basically in any electrical resistance heater as a heating element can be used, provided that there is a possibility of freely rotating the helix Fix the air flow without vibrations. However, that appears to be particularly advantageous Use in connection with a heating element in which one or several coils of this type with the interposition of holding elements a support structure, in particular a support plate are attached. A Possibility for fastening heating conductor coils with a flat oval cross-section by means of holding elements is known from DE 44 43 725 A1, both in the Form in which the direction of extension of the helix parallel to the plane of the Carrier plate lies at right angles to it.

An example of the use of a helix in accordance with the invention in a heating element is indicated in FIGS. 4 and 5. 4 shows one Quarter circle section from a circular heating element 4, in which a circularly curved heating conductor coil 1 by means of individual holding elements 5 a circular support plate 6, here in the form of a disc, is attached. there it goes without saying that the heating conductor coil 1 in the illustration in FIG. 4 has the shape shown in Fig. 1; it just became the simpler representation half shown with a straight course of the individual turns.

FIG. 5 shows a cross section along the line V-V in FIG. 4, which shows that radially outside of the carrier disk 6 each above and below one Washer 7 two heating conductor coils 1 parallel to each other and at a distance are fastened from one another by means of holding elements 5. The holding elements 5 each comprise a turn 3 of a helix 1 and are with one at the other end of the cranked shaft 9 - not here recognizable - base 10 fastened in a base 11. This base 11 is in this embodiment in one piece from the material of the carrier disk 6, preferably plastic. A heating element of FIGS. 4 and 5 shown type, that is with a circularly curved heating conductor coil 1 preferably used for circular flow cross-sections.

The invention relates not only to the design of the Heizleiterwendel, as described above, but also on the design of the Holding parts 8, which serve to heat a filament 1 almost at a point hold and attach to the support plate 6. One particularly advantageous design of the holding elements, which is suitable on the one hand, the Fix the heating conductor coil 1, but also to the coil either in the plane of the carrier disk 6 (cf. FIG. 5), but also at right angles to it (cf. 8 and 9) can be explained with reference to FIGS. 6 and 7. Fig. 6 shows a holding element 5 on a larger scale in an oblique representation and 7 its attachment to the carrier disk 6.

As already mentioned, the holding element 5 consists of a shaft 9 on its a holding part 8 at one end and a foot part 10 at the other end are arranged. The holding element 5 expediently consists of a stamped part made of sheet metal, which can then be deformed in a corresponding manner. Advantageous is a sheet made of stainless steel, which has a lower thermal conductivity brings a lower temperature load on the carrier disk 6.

The holding part 8 serving to fix the helix consists of two arms 12, 13, each spread slightly after a crank 14 by the by the Project from shaft 9 formed level. The spread corresponds to the slope S of the Wendel. At the end of each of the two arms 12, 13 there is a side protruding approach 15, 16. The approaches 15, 16 are in the assembled state initially flat, but then become flat after the holding element has been brought together 5 with a heating conductor coil 1 each around a section of a turn 3 of the Spiral 1 bent around. Each approach 15, 16 thus forms a closed one Recording to enclose a section of a turn of the helix 1. Die Bend 14 forms a stop for the lower end of a turn of the helix 1.

While the shaft 9 still a bead-like extending in the longitudinal direction Stiffening rib 17 may have, the foot part 10 in turn has one on one side laterally protruding from the shaft 9 approach 18 which is approximately U-shaped in cross section is bent with a sloping leg 19 to a kind of spring.

FIG. 7 shows a section on a larger scale through the one already in FIG. 5 indicated base parts 11, which are arranged on the carrier plate 6, mainly are monolithically connected to it. Each of these base parts 11 forms one approximately rectangular receptacle 20 for a foot part 10 of a holding element 5. When Inserting the holding element 5 from above (arrow 21) gives way to the protruding free one Leg 17 resiliently back and forms an abutment on one in the end position undercut edge 22 of a lateral recess 23. The stiffening rib 17 rests on the opposite wall of the receptacle 20. So that's one extraordinarily simple, but at the same time safe, especially machine-friendly Assembly of these parts guaranteed.

8 and 9, as already indicated, a possibility is shown how by means of appropriately trained holding elements according to the invention designed heating conductor coil also attached to a flat carrier plate can be that the direction of extension of the helix is perpendicular to the plane the carrier plate runs. 8 shows a side view of the helix and Fig. 9 shows a cross section.

It can be seen from FIG. 8 how a turn 3 of a helix through a holding part 25 is fixed, which in turn is attached to a support plate 26. It is clear recognizable as the shaft 27 of the holding element 25, which in turn in cross section Is bent in a Z-shape, continues upwards into two arms 28, 29, which in the shown in Fig. 6 each section of a turn 3 of the coil 1 include. The spread of the arms also corresponds to the slope the coil 1 can be seen. At the foot part 30 of the shaft 25, two tabs 31; 32 formed, which are inserted through slots 33 in the support plate 26 and then be bent.

In this way it is possible to use a heating conductor coil designed according to the invention 1 to a certain extent freely cantilevered on one support element attach to the flowing medium largely undisturbed suspend.

The holding element 34 shown in FIGS. 10 to 13 essentially settles composed of a holding part 35 and a foot part 36. The foot part 36 has three tabs 37, which are not stretched through openings in one Carrier plate shown inserted and then for anchoring be bent at right angles.

The holding part 35 essentially consists of a tubular section 38, which is adapted in its cross-sectional dimensions to the geometry of the helix 39 is. In the present example, the tubular section 38 encloses one narrow, roughly rectangular cavity in which the pointed end of a Winding a coil 39 is inserted. The longitudinal extent of the cavity therefore corresponds to the width of the turn of the helix 39. The transverse extent of the Cavity corresponds at least to the thickness of the heating conductor. To consider the pitch of the helix 39 and, where appropriate, deflections of the Heat conductor in the longitudinal direction of the coil 39 can the transverse extent of the Cavity advantageously be chosen larger, for example twice the Heating conductor thickness.

The tubular section 38 has two diagonally opposite one another Recesses 40 and 41 in the free edge area a closed outer surface. The recesses 40 and 41 extend to the upper free end of the tubular section 38 and serve to carry out the helix 39th forming heating conductor.

The end face of the holding part 35 in the region of the foot part 36 can be open, since the Cavity after mounting on a carrier plate from the carrier plate is closed. The opposite upper end of the holding part 35 can also remain open, but a closed one is preferred Embodiment as shown in Figs. 10 to 13.

The cover 42 according to the invention is composed of the folding elements 43 and 44 together. Both folding elements 43 and 44 form part of the outer surface, which are offset in their longitudinal direction at the opposite edges of the tubular portion 38 are attached. After inserting a turn of the Helix 39 in the tubular section 38 become the folding elements 43 and 44 around its folding axis, which coincides with the edge. As a result of Longitudinal offset complement the two folding elements 43 and 44 such that the entire front opening of the holding element 34 is closed. The outer corner of the folding elements 43 and 44 is cut off, so that together with the recesses 40 and 41, the passage of the heating conductor 39 is facilitated.

In this way, a one-sided winding for one turn is created a heating conductor coil 39, which the dust and Fluff particles offers hardly any surface to attack. With this, collections of Dust and fluff largely prevented and thus the risk of Burns inside a heating element.

Claims (23)

Heating conductor coil for heating a flowing gaseous medium, primarily air, for attachment to a support structure, in particular for use in an electrical resistance heating element,
characterized in that the heating conductor forming the coil is deflected alternately in opposite directions in the circumferential surface of the coil formed by the pitch line of the coil. Heating conductor coil according to claim 1, characterized in that the deflections are zigzag. Heating conductor coil according to claim 1, characterized in that the deflections are wave-shaped. Heating element according to one of claims 1 to 3, characterized in that the heating conductor consists of a wire with a circular cross section. Heating element according to one of claims 1 to 4, characterized in that the heating conductor consists of a thermistor (PTC) wire. Heating element according to one of claims 1 to 5, characterized in that the heating conductor coil has an elongated cross-section deviating from the circular shape. Heating element according to claim 6, characterized in that the coil is approximately rectangular in cross section with two substantially straight longitudinal sides and U-shaped reversal points. Use of a heating conductor coil according to one of claims 1 to 7 in an electrical resistance heating element for heating a flowing gaseous medium, primarily air, with at least one helix attached to a support plate with the interposition of holding elements is. Electrical resistance heating element according to claim 8, in which the holding elements for fastening the heating conductor coil to the carrier plate each have a holding part for holding a turn of the heating conductor coil and a foot part for fastening to the carrier plate, characterized in that the holding part comprises two arms each of which is formed a receptacle for fastening a section of a turn of the heating conductor coil. Heating element according to claim 9, characterized in that the arms are spread according to the pitch of the coil. Heating element according to claim 8 or 9, characterized in that the receptacles are formed from shoulders projecting laterally from the arms, which can be folded around a section of a turn of the coil. Heating element according to one of claims 8 to 11, characterized in that the foot part comprises a shoulder which projects laterally from the shaft and which is bent to form a spring which is approximately U-shaped in cross section. Heating element according to one of claims 8 to 12, characterized in that bases are provided for fastening the holding elements to the carrier plate, each forming a snap-in connection for the spring of a holding element. Heating element according to one of claims 8 to 13, characterized in that the shaft has at least one bead-like stiffening rib running in its longitudinal direction. Holding element according to one of claims 8 to 14, characterized in that the holding element consists of a stamped part. Holding element (34) suitable for fastening a heating conductor coil according to claim 1 to a heating element with a holding part (35) for holding a turn of a heating conductor coil (39) and a foot part (36) for fastening to a support element, characterized in that the holding part (35 ) consists of a tubular section (38) with a substantially closed lateral surface, one turn of the heating conductor coil (39) being insertable into the tubular section (38). Holding element according to claim 16, characterized in that the tubular section (38) is adapted in cross section to the pitch height and geometry of the heating conductor coil (39). Holding element according to claim 16 or 17, characterized in that at least one end of the tubular section (38) is closable by means of a cover (42). Holding element according to claim 18, characterized in that the cover (42) is part of the tubular section (38) which is designed to be bendable for the purpose of closing around the upper edge of the tubular section (38). Holding element according to claim 19, characterized in that the cover (42) is divided into two, the two folding elements (43 and 44) each being attached to the opposite edges of the tubular section (38). Holding element according to one of claims 18 to 20, characterized in that the cover (42) is recessed in the area of the passage of the heating conductor coil (39). Holding element according to one of claims 16 to 21, characterized in that the tubular section (38) in the edge region of the free end has recesses (40, 41) for the passage of the heating conductor coil (39). Holding element according to one of claims 16 to 22, characterized in that longitudinal edges are rounded in the outer surface of the tubular section (38).

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