JPS6238832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a support plate made of an insulating material, and a heat-generating conductor made of a resistance wire wound around the support plate, and the heat-generating conductor is formed in a spiral shape, and It relates to an electrical heating element for a fluid, for example a gas, supported on the support edge of a plate.

Heating bodies of this construction are known in many different embodiments and are used, for example, in devices of different sizes for heating air. Although the invention basically relates to heating bodies of any size, it is advantageously used in relatively small electrical hot air generators, such as dryers, hot air blowers, etc. Although this is not absolutely necessary, it is customary in this case for the medium to be heated to be passed through the heating element by means of a blower or the like.

The resistance wire can be wound smoothly or in a threaded or meandering pattern, depending on the power, operating temperature and cross-sectional shape (circular or rectangular); in both cases it can be wound around the support plate in the form of a spiral. Can be attached. In this case, the electrically conductive curvature is supported on the support edge of the support plate, or, to be more precise, on the narrow side of the support plate. The support plate can be formed as a flat plate with two opposite support edge surfaces, or the support plate can also have a plurality of support edge surfaces, for example with a cross-shaped cross section. , it can also be formed from two plates that are fitted into each other using corresponding slots.

In known heating elements of the type described (see German Patent No. 1 615 246), the heat-generating conductor bends sag as a result of thermal expansion and shift at the supporting edge surface due to the temperature change requirements determined by the operation. occurs,
As a result, during operation, it is no longer guaranteed that the conductor bends are maintained at a predetermined spacing, and this may lead to undesired contact between the conductor bends, which could even lead to damage to the heating element. This also applies to heating elements of the type mentioned at the outset, in which the heat-generating conductor itself is wound in a meandering manner (cf. German Patent Application No. 2830532.0, German Patent Application No. 2830533.1). . Such a risk arises even when the curved part of the heat-generating conductor is fixed in the edge recess of the support plate. In this case, the curved portion of the heating conductor may protrude from the edge notch due to expansion due to heat and come into contact with an adjacent curved portion. Realizing the edge notch with such a depth that this type of deviation of the curvature is reliably excluded requires extremely difficult manufacturing techniques and is therefore not a problem in practice in this direction.

The object of the invention is to provide an electrical heating element of the type mentioned at the outset, which can be produced in a simple and problem-free manner and which ensures a reliable fixation of the curved part of the heating conductor under all circumstances. It's about giving your body.

According to the invention, this problem is solved by providing the support plate with a curved part of the heat-generating conductor in the region of the support edge surface.
This problem is solved by attaching a covering made of heat-resistant adhesive. In this case, the present invention
The adhesive is adhesively bonded to the support plate, which can be made of synthetic mica, for example, and the advantage is that this bond retains a corresponding strength even at the operating temperature of the heating element. Adhesives of this type are known to those skilled in the art. This adhesive coating according to the invention, which advantageously extends over the entire length of the support edge, at the same time forms a track with which the curved part of the heat-generating conductor can be securely fixed on the support edge.

The curved part of the heat-generating conductor can be embedded in the adhesive covering in any case in the region of the supporting edge surface. In this case, the heat conduction into the support plate is disadvantageously increased, but at the same time the adhesive coating reduces the heat radiation from the heat-generating conductor in the region of the support edge surface.
From this point of view, the width of the adhesive coating (as seen perpendicular to the plane of the support plate) is such that the adhesive coating is almost limited to the narrow side of the support plate, and in some cases directly to the wide side of the support plate. Advantageously, it is limited to the abutting area, but does not extend substantially to the wide side of the support plate. From a thermal point of view, an optimum embodiment is obtained if the width of the adhesive coating approximately corresponds to the thickness of the support plate. If this is technically difficult during manufacture or fixing, an embodiment in which the width of the adhesive covering approximately corresponds to the width of the curved part of the heat-generating conductor spanning the supporting edge surface, for example a meandering conductor, is preferred. is desirable. In both cases, the heating conductor is coated with adhesive only in the region of the supporting edge surface, so that the heat radiation takes place unhindered over as large a portion of the length of the heating conductor as possible.

A further embodiment of the invention provides for the fixing of the curved part of the heat-generating conductor by fixing the heat-generating conductor in a manner known per se in the edge recess of the support plate and, in the best case, by cutting the adhesive covering into the edge cut. Further improvement can be achieved by extending it to the base of . As a result, the heat transfer is only slightly disturbed and the bends of the heat-generating conductors are fixed even more securely, with the particular advantage that it is sufficient to form the edge recesses to a significantly shallower depth. At the point. This is advantageous in view of the production and winding of the supporting plate, and it also reduces the risk of breaking the webs that occur between the edge notches. Since the winding of the heat-generating conductor on the support plate is unproblematic, it is advantageous to form the edge recess as a recess with a triangular cross section with a relatively wide angle. In this case, it is necessary to realize a correspondingly high web between the edge recesses and a correspondingly large spacing between the curves, so that the curves do not protrude out of the edge recesses, which is particularly important in small structures and This is disadvantageous in view of high power density. By using the adhesive sheath according to the invention, an advantageous embodiment of the invention is thus obtained, which requires only a small depth of the edge notch and which nevertheless guarantees a reliable fixation of the curved part of the heat-generating conductor. can get. By extending the adhesive sheath to the base of the edge recess, the coverage of the heat-generating conductor by the adhesive sheath is limited to the area directly in contact with the supporting edge surface.

However, it is advantageous that the adhesive covering can be realized less strongly, in which case it only has to extend to a depth that is significantly shallower than the base of the edge recess. In the customary embodiment in which the web between the edge notches protrudes beyond the outer surface of the heat-generating conductor, the adhesive sheath does not extend deeper than the outer surface of the heat-generating conductor in view of optimum heat dissipation. It is desirable to do so. Particularly advantageous in this respect are embodiments in which the adhesive covering extends very little beyond the contour of the support plate into the edge recess. The adhesive covering therefore simultaneously forms a bridge part in the area of the edge cutout, from which it has no or in any case only negligible contact with the heat-generating conductor, so that the heat dissipation is minimized as much as possible. This will require minimal interference. This measure is made more reliable by using an adhesive that does not wet the material of the heating conductor.

The adhesive coating according to the invention can be applied manually in a simple manner and with little working time. In mass production, spraying can also be carried out using slotted nozzles whose length corresponds in each case to the length of the support edge and whose width can be adjusted to the working width of the adhesive coating.

Next, the present invention will be explained in detail using the drawings.

The electric heating body shown in FIGS. 1 and 2 has a predominantly cross-shaped cross section. It consists of a support plate 1 made of an insulating material and a heating conductor 2 made of a resistance wire. The heating conductor itself, which is wound helically around the support plate 1, is also wound in a meandering manner (see FIG. Supported on the width. In the embodiment shown, the support plate 1 has a support edge 3 with
It is provided with an edge cutout 4 in the area of which a meandering curved part 5 of the heating conductor 2 spans the supporting edge surface.

As can clearly be seen from the figure, the support plates 1 are each provided with a coating 6 in the form of a relatively narrow strip of adhesive. This covering covers the curved part of the heating conductor 2 in the region of the supporting edge surface 3.
The adhesive consists of a known suitable material of sufficient heat resistance and is adhesively bonded to the material of the support plate 1 and fixes the curved part of the heating conductor 2 to the support edge 3.
The adhesive covering 6 extends over the entire length of the supporting edge surface 3.

Further details can be seen from FIGS. 3 to 6. Fourth
It can be seen from the figures and the cross-sectional view in FIG. 6 that the adhesive coating 6 is essentially confined to the area of the support edge 3 and extends only slightly on the wide side of the support plate 1. As a result, the heating conductor 2 is covered with adhesive only in the area of the supporting edge surface 3, and the heat dissipation is not hindered elsewhere.

In the embodiment shown in FIGS. 3 and 4, as can be seen especially from the partial cross-sectional view in FIG. It is fixed within 4. The depth of the edge recess 4 is relatively small and corresponds essentially to the height of the cross section of the heating conductor 2. In order to securely fix the heating conductor 2 under any circumstances, an adhesive covering 6 is used. The width b of this adhesive covering corresponds approximately to the length of the curved part 5 spanning the support plate 1 (see FIG. 4). In the depth direction, ie in the direction of the plane of the support plate, the adhesive covering 6 does not extend completely to the base of the edge recess 4.

In the embodiment shown in FIGS. 5 and 6, the heat-generating conductor 2 has a circular cross section, and the support plate 1 has three
An edge cutout 4 with a square cross section is provided. The width b of the adhesive sheath 6 corresponds approximately to the thickness of the support plate 1 in this case, and the adhesive sheath extends approximately in the direction of the depth of the support plate 1 on the outside of the curved part of the heating conductor 2. It only extends to the surface (see Figure 6).

Although not shown in the drawings, an embodiment in which the adhesive covering part 6 extends in the width direction is also possible, in which case the adhesive covering part extends beyond the contour of the support plate 1 into an edge notch. It hardly extends within 4. In an embodiment of this kind, which still allows for a sufficiently secure fixing of the heating element 2, the connection area between the support plate 1 and the adhesive covering 6 is actually limited only to the narrow side of the support plate 1. Therefore, as a result, the adhesive covering part 6
at the same time forms a bridge for the edge notch 4.

[Brief explanation of the drawing]

FIG. 1 is a side view of the electric heating element of the present invention;
Fig. 2 is a front view of the heating element shown in Fig. 1, Fig. 3 is an enlarged partial sectional view of the heating element shown in Fig. 1, Fig. 4 is a cross-sectional view of the heating element shown in Fig. 3, and Fig. 5 is a cross-sectional view of the heating element shown in Fig. 3. An enlarged partial sectional view of another embodiment of the heating element, FIG. 6 is a cross-sectional view of FIG. 5. DESCRIPTION OF SYMBOLS 1...Support plate, 2...Heating conductor, 3...Support edge surface, 4...Edge notch, 5...Conductor curved part, 6...
Adhesive coating.

Claims (1)

[Scope of Claims] 1. It has a support plate made of an insulating material, and a heating conductor made of a resistance wire wound around the support plate, the heating conductor is formed as a spiral winding, and the heating conductor is formed as a spiral winding, and In an electrical heating element for fluid supported on a supporting edge surface, a covering part 6 made of a heat-resistant adhesive is attached to the supporting plate 1 to cover the curved part of the heating conductor in the area of the supporting edge surface 3. An electric heating element characterized by: 2. The heating element according to claim 1, wherein the width b of the adhesive coating portion 6 corresponds approximately to the thickness of the support plate 1. 3. The heating element according to claim 1, wherein the width b of the adhesive covering portion 6 corresponds approximately to the length of the heating conductor portion 5 spanning the supporting edge surface 3. 4. The heat-generating conductor 2 is fixed in the edge cutout 4 of the support plate 1, and the adhesive coating 6 extends at most to the base of the edge cutout 4. heating body. 5. Heating element according to claim 3, in which the adhesive covering 6 does not extend too far beyond the contour of the support plate 1 into the edge recess 4. 6. The heating element according to claim 1, wherein the adhesive covering portion 6 does not wet the material of the heating conductor 2.