EP1857740A1 - Electrode arrangement - Google Patents

Abstract

The arrangement has an electrode (3) that is formed of an electrode wire (6) and a ceramic casing (7), where the ceramic casing is enclosed in the region of an insertion opening (5). The insertion opening exhibits a larger, burner-proximity-sided diameter (D1) and a smaller, combustion chamber-sided diameter (D2), where a wall (4) of the burner exhibits a constant transition from the diameter (D1) to the diameter (D2). The ceramic casing exhibits a constant outer contour in the region between the two diameters (D1, D2), where the outer contour is form-adapted for the insertion opening.

Description

The invention relates to an electrode arrangement according to the preamble of patent claim 1.

An electrode arrangement of the type mentioned at the outset is (product name: VITODENS ^®) in a boiler of the Applicant realized (see Figure 3). This comprises at least one electrode fixed to a holding element on a burner (gas burner), wherein the burner has a wall separating a burner environment from a combustion chamber with an insertion opening for the electrode and wherein the electrode consists of an electrode wire and at least in the region of the insertion opening Ceramic sleeve is formed. Said electrode is used in a conventional manner either as a starting electrode or for ignition monitoring.

In this known solution, the insertion opening has a cylindrical shape. The ceramic sleeve, which passes through the insertion opening with clearance, is also cylindrical. On the ceramic sleeve, the already mentioned, designed as a holding plate retaining element is fastened (clamp connection), which in turn is screwed with the interposition of a sealing element on the ambient side wall of the burner.

• Der Kraftschluß zwischen Halteblech und Keramik kann zur Schädigung der Keramik führen (Haarrisse mit der Folge von Spannungsüberschlägen oder Kriechströmen);
• Durch die Schraubverbindung erfolgt indirekt auch eine Krafteinwirkung auf die Elektrode, welche insbesondere über die lange Hebelwirkung an der Spitze des Elektrodendrahtes zu unzulässigen Positionsabweichungen führen kann;
• Bei Brennwertgeräten mit Überdruck in der Brennkammer läßt sich die Verbindung Halteblech zur Keramik kaum zufriedenstellend abdichten;
• Bei Brennwertgeräten tritt permanent Kondensatanfall in der Brennkammer auf; dieser wirkt an den oftmals nur mit einem Oberflächenschutz versehenen (und durch die Elektrodenmontage teilweise zerstörten) Halteblechen stark korrosiv.

This solution has the following problems:

• The frictional connection between the holding plate and ceramic can lead to damage to the ceramic (hairline cracks resulting in flashovers or leakage currents);
• By the screw indirectly takes place a force on the electrode, which in particular can lead to inadmissible positional deviations over the long leverage at the top of the electrode wire;
• For condensing boilers with overpressure in the combustion chamber, the connection holding plate to the ceramic can hardly satisfactorily seal;
• In condensing boilers occurs permanently condensate accumulation in the combustion chamber; this has a very corrosive effect on the holding plates, which are often only provided with a surface protection (and partly destroyed by the electrode assembly).

The invention has for its object to improve an electrode assembly of the type mentioned above with respect to the disadvantages mentioned. In particular, the production cost should be reduced while improving the tightness.

This object is achieved with an electrode assembly of the type mentioned by the features listed in the characterizing part of patent claim 1.

According to the invention, it is therefore provided that the insertion opening has a first, larger, brennerumgebungsseitigen and a second, smaller, combustion chamber-side diameter that the wall has a (in the mathematical sense) continuous transition from the first to the second diameter, that the ceramic sleeve at least in the area between the two diameters has a (in the mathematical sense) continuous, conformed to the insertion opening outer contour.

In other words, the ceramic sleeve in the region of the insertion opening, for example, a conical outer contour, which fits exactly to the correspondingly shaped contour of the insertion opening. In this way, a snug fit (guide) seat of the sleeve is ensured in the opening, which also allows a waiver of other sealing elements (as previously required). According to the invention, only an insertion opening which widens steadily in the direction of the burner environment must be provided, which, together with the correspondingly formed ceramic sleeve, ensures a good fit of the electrode against the wall.

The axial fixing is carried out with the above-mentioned holding element, preferably in the form of a tension spring, which will be discussed in more detail below.

Other advantageous developments emerge from the dependent claims.

For the sake of completeness is still on the farther prior art according to the DE 195 05 218 C1 and EP 1 605 206 A1 directed.

Finally, the shows US 2,881,363 A an electrode assembly in which a part of the ceramic body is spherical; but even with this solution, a seal is arranged between the ceramic sleeve and the wall, since the wall itself does not contribute to the seal.

The electrode assembly according to the invention including its advantageous developments according to the dependent claims will be explained in more detail with reference to the drawing of a preferred embodiment.

Figur 1

im Schnitt die erfindungsgemäße Anordnung von zwei Elektroden an einer Brennerwand;

Figur 2

perspektivisch eine bevorzugte Ausführungsform des Halteelements gemäß Figur 1 zur Fixierung der erfindungsgemäßen Elektroden; und

Figur 3

im Schnitt eine nach dem Stand der Technik bekannte Elektrodenanordnung.

It shows

FIG. 1

on average, the inventive arrangement of two electrodes on a burner wall;

FIG. 2

in perspective, a preferred embodiment of the holding element according to Figure 1 for fixing the electrodes according to the invention; and

FIG. 3

in section, an electrode arrangement known from the prior art.

Reference is first made to FIG. There, the above-mentioned, known in the art electrode assembly of the applicant is shown. This includes, just like the electrode arrangement according to the invention at least one (shown in both cases two) with a holding element 8 to a burner mounted electrode 3, wherein the burner is a burner environment BU of a combustion chamber BK having separating wall 4 with an insertion opening 5 for the electrode 3 and wherein the electrode 3 is formed of an electrode wire 6 and this at least in the region of the insertion opening 5 enclosing ceramic sleeve 7.

As can be seen from FIG. 3, a seal is inserted or required between the holder 8 and the wall 4 in the known state of the art. The holder 8 has in the illustrated embodiment, two through holes 10, wherein the ceramic sleeves 7 are each arranged in a press fit in the through holes 10. As mentioned above, this can lead to damage to the ceramic sleeves 7 and accordingly to voltage flashovers or leakage currents.

In order to avoid these disadvantages, it is now provided according to the invention with reference to FIGS. 1 and 2 that the insertion opening 5 has a first, larger, combustion chamber-side diameter D1 and a second, smaller, combustion chamber-side diameter D1, D2, that the wall 4 forms a continuous transition from the first to the second diameter D1, D2 and that the ceramic sleeve 7 at least in the region between the two diameters D1 D2 has a continuous, to the insertion opening 5 shaped outer contour.

In other words, on the one hand, the outer contour of the ceramic sleeve 7 and on the other hand, the inner contour of the insertion 5 are adapted to each other so that automatically results in a fit that makes a seal dispensable (so-called "sealant-free" arrangement).

As can be seen from Figure 1, it is provided that the outer contour of the ceramic sleeve 7 is formed between the two diameters D1, D2 conical. Of course, other outer contours come into consideration; only the steady slope from the smaller to the larger diameter is essential, which on the one hand ensures the tightness and on the other hand makes it possible to mount the electrode: between the two diameters D1 and D2, at least on the wall side no diameter be smaller than the combustion chamber-side diameter D2, otherwise an undercut would occur and the electrode would then no longer be plugged through the insertion opening 5.

Furthermore, it is advantageously provided that the outer contour between the two diameters D1, D2 of the ceramic sleeve 7 is rotationally symmetrical. This requirement, for example, in comparison to a truncated pyramidal design a particularly good tightness, said in such, rather remote truncated pyramid training said diameter D1, D2, of course, not literally, but in a figurative sense to understand (similar to the so-called hydraulic diameter at a channel flow [Example from the fluid mechanics]).

Referring again to FIG. 1, it is provided that the ceramic sleeve 7 has a support collar 9 for the retaining element 8. This consists in principle of a diameter extension of substantially (will be discussed below) cylindrical ceramic sleeve, and precisely at the point at which the holding member 8 from the rear (ie brennerumgebungsseitig) acts on the electrode 3, for which purpose the holding element has a pointing in the direction of the combustion chamber, acting on the electrode 3 spring force. This spring effect can be achieved in that the holding element 8 as shown in FIG. 2 is designed as an elastic bleaching strip. The embodiment according to FIGS. 1 and 2 shows a holding element 8 for fixing two electrodes. Alternatively, of course, a single fixation or a multiple fixation of electrodes is possible in this way.

So that the holding element 8 can exert a force on the support collar 9, a press fit enabling gap is provided between the support collar 9 and the wall 4 in the axial direction.

In order to be able to support itself on the abovementioned support collar 9, a passage opening 10 per electrode 3 is provided on the holding element 8, the holding element 8 being planar in the area of this passage opening 10 in order to be able to introduce the spring force uniformly into the support collar 9.

So that the electrode 3 is not only fixed axially well on the wall 4, it is further provided that optionally at the insertion opening 5 or in the region of the passage opening 10 of the holding member 8, a rotation is arranged. As can be seen from FIG. 2, this is preferably formed from a rectilinearly extending abutment surface 11 or abutment edge, provided both at the through-opening 10 and at the ceramic sleeve 7 (insofar as mentioned above, the ceramic sleeve is not cylindrical over its entire length, but at this point has a correspondingly formed singularity).

For fastening the retaining element 8 to the wall 4, it is finally provided that this has at least one (shown are two) clip-like extension 12. This extension engages in a provided on the wall 4 recess 13, barbs 14 on the extension 12 inadvertent release of the Fortsates 12 exclude from the recess 13. As shown, the clip-like extension 12 is made by repeatedly bending the metal strip in different directions; the barbs 14 result from suitable punching or breaking certain areas on the extensions 12th

LIST OF REFERENCE NUMBERS

BU

Brenner environment

BK

combustion chamber

3

electrode

4

wall

5

Through opening

6

electrode wire

7

ceramic sleeve

8th

retaining element

9

support collar

10

Through opening

11

contact surface

12

extension

13

recess

14

barb

D1

first, larger diameter

D2

second, smaller diameter

Claims (11)

Electrode arrangement comprising at least one electrode (3) attached to a holding element (8) on a burner, the burner having a wall (4) separating a burner environment (BU) from a combustion chamber (BK) with an insertion opening (5) for the electrode (B) 3) and wherein the electrode (3) is formed from an electrode wire (6) and a ceramic sleeve (7) enclosing the same at least in the region of the insertion opening (5),
characterized,
in that the through opening (5) has a first, larger, burner environment side (D1) and a second, smaller, combustion chamber side (D2) diameter,
that the wall (4) has a continuous transition from the first to the second diameter (D1, D2),
that the ceramic sleeve (7) at least in the region between the two diameters (D1, D2) is a continuous, to the through-opening (5) adapted in shape to the outer contour. Electrode arrangement according to Claim 1,
characterized,
that the outer contour of the ceramic sleeve (7) between the two diameters (D1, D2) is conical. Electrode arrangement according to Claim 1 or 2,
characterized,
that the outer contour between the two diameters (D1, D2) of the ceramic sleeve (7) is rotationally symmetrical. Electrode arrangement according to one of Claims 1 to 3,
characterized,
that the ceramic sleeve (7) is arranged without seal in the through-opening (5). Electrode arrangement according to one of Claims 1 to 4,
characterized,
that the ceramic sleeve (7) has a support collar (9) for the holding element (8). Electrode arrangement according to one of Claims 1 to 5,
characterized,
that the holding element (8) is formed of a sheet metal strip. Electrode arrangement according to one of Claims 1 to 6,
characterized,
that the holding element (8) is formed for the fixing of more than one electrode (3). Electrode arrangement according to one of claims 1 to 7,
characterized,
that the holding element (8) acting in a forward direction the combustion chamber, to the electrode (3) spring force. Electrode arrangement according to one of Claims 1 to 8,
characterized,
in that the holding element (8) has a passage opening (10) for the electrode (3), the holding element (8) preferably being planar in the area of the passage opening (10), preferably in the area of the passage opening (10) of the holding element (8) ) an anti-rotation is arranged, wherein preferably the rotation of a both on the through hole (10) and on the ceramic sleeve (7) provided, rectilinearly extending contact surface (11) is formed. Electrode arrangement according to one of Claims 1 to 9,
characterized,
that at the insertion opening (5) an anti-rotation is arranged. Electrode arrangement according to one of Claims 1 to 10,
characterized,
in that the retaining element (8) has at least one clip-like projection (12) for connection to the wall (4), wherein a recess (13) for the clip-like extension (12) is preferably provided on the wall (4), wherein preferably the clip-like Extension (12) has at least one barb (14) for anchoring in the recess (13), wherein preferably the clip-like extension (12) is formed by multiple buckling of the metal strip in different directions.

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