EP0816777B1 - Method for making a combustion chamber, esp. for gas fired water heaters, and combustion chamber obtained by such method - Google Patents

Description

State of the art

The invention is based on a method of manufacture a combustion chamber according to the preamble of claim 1 and one Combustion chamber for gas-fired Water heater according to the preamble of claim 13.

In a known method of the type mentioned the two made of stainless steel to form a combustion chamber existing wall plates first each with the Provide ducting corresponding formations that according to welding the wall panels together form the channels accordingly. After that, the Wall plates bent into U-shaped parts and two each Parts to a closed combustion chamber welded together. In this version, gaps can be between the wall panels in the adjacent to the channels Zones not or only with a lot of effort in Avoid welding the sheets. Exists in these zones hence the risk of crevice corrosion, so that too Sheet quality must meet high requirements.

In addition, it is known in the manufacture of planes Heat exchangers two stainless steel wall plates initially to be connected locally with weld seams and then with a fluid working fluid under high pressure to expand to form channels.

WO 92/20976 A1 describes a method for producing a Combustion chamber known, the walls of which are two together welded wall plates exist, the channels after welding the wall panels along the later channel edges by shaping the between the welds themselves located sheet metal areas by means of a pressure between the wall sheets introduced fluid working fluid formed become.

In the utility model DE 92 00 780 U1 there is a combustion chamber with double jacket manufactured by two s-blow dryer curved wall panels with two opposite wall sections spaced apart and the right-angled Legs are welded together.

Another combustion chamber with a double jacket made of sheet metal for the flow of liquid is from the DE 42 24 212 A1 is known, the outer and Inner walls are arranged distributed beads, which increase the rigidity of the wall surface of the double jacket should.

Advantages of the invention

In the method according to the invention with the characteristic Features of claim 1 is also in the bending zones of the Corner areas of the combustion chamber an even expansion the channels for flow guidance are reached and it will prevents the inner wall panel from folding and the canal cross-sections narrow there.

The fact that the distances of an external tool in Corner area larger than in the extended support areas are dimensioned, the flow channels in the Corner areas with the same cross-sectional width as in the stretched channel areas are produced.

The recesses of the inner tool open out immediately in front of the corners in excess to accommodate Recessed pockets for materials. This will make one Stiffening achieves greater stability contributes when a heat exchanger for water to be heated is mounted on the combustion chamber. In addition, one Counteracted wrinkling of the inner wall plate.

The weld seams connecting the wall panels are used in the Manufacture of channels for the water-cooled combustion chamber in advantageously not directly between the inner and supported outer tool. The welds as well as the adjacent sheet metal areas are thus at Making the channels stretched, reducing tensile strength increased, and the wall thickness of the sheet metal areas reduced becomes.

To supply the fluid widening the channels Working equipment can simply be one of the two wall plates welding to the other wall panel with an opening be provided, which can also be used to connect a Line for a fluid resource, in particular Heating water.

This opening is expedient in a dome-like Spreading of the wall plate is provided to reduce pressure losses in the flow of work equipment and operating supplies increases slightly hold.

The welding of the wall plates is facilitated and the Available wall surfaces of the combustion chamber are used for optimal heat exchange with the fluid equipment used when the welds are arranged and formed in this way be that parallel channels and their Entrance and exit areas result in common chambers, and further if the openings for the connecting lines in Area of the external chambers can be provided.

With this arrangement of the weld seams and channels, the Wrinkles in the corners of the wall panels can also be counteracted if the weld seams like this be arranged that common chambers over the Extend corner areas of the wall panels. The same purpose serves the proposal to offset the start of the individual channels to arrange each other.

The present invention further proposes that the Ends of the weld seams tapering in a circular line be carried out. This ensures that the Transition of the individual channels into the common chambers result in uniform, "pillow-shaped" widenings and therefore an impermissibly high stress on the material is avoided.

The production of a cooled combustion chamber for gas-fired Water heater and maintenance in the combustion chamber contained functional elements, such as burner and Heat exchanger, will be easier if the one with the other welded wall panels to one the back wall and the Side walls of the combustion chamber forming a U-shaped body be bent, and the front wall of the combustion chamber as separate part made and detachable with the side walls is designed to be connectable.

drawing

An embodiment of the invention is in the drawing shown and in the following description explained. 1 shows a perspective view a combustion chamber for gas-fired water heaters with a lifted upwards as a slat block with passed through water pipes trained heat exchanger and one detachable with the side walls of the combustion chamber connectable front wall, Figure 2 on an enlarged scale a vertical section through the side wall of the Combustion chamber and a partial section through the attached Heat exchanger according to Figure 1, Figure 3 is a plan view one of two welded wall plates existing circuit board, which after welding to a die Rear wall and the two side walls of the combustion chamber forming the U-shaped part, Figure 4 is a enlarged section along the line IV in Figure 3, Figure 5 a cross section through a corner region of the combustion chamber, in the entrance area in front of the heat exchanger, 6 shows a cross section corresponding to FIG. 5 an alternative corner area of the combustion chamber, Figure 7 is a plan view of a corner area of the Combustion chamber, Figure 8 is a partial section through a alternative design of the front wall, FIG. 9 and FIG. 10 Partial cuts through an inner and outer Tool existing device for receiving the U-shaped curved combustion chamber and Figure 11 is a stress-strain diagram.

Description of the embodiment

The water heater has a combustion chamber (10) with a Rear wall (12) and two integrally connected to this Side walls (14, 16) on which a front wall (18) can be detached is attached. The combustion chamber (10) is from above Heat exchanger (20) can be placed on it as a lamella block performed water pipes is formed. The sidewalls (14, 16) of the combustion chamber (10) are with the upper front edge provided open recesses (22) to the fit Inclusion of protruding from the outer slats (24) Tube ends (26) (Figure 2) of the heat exchanger (20) are used. The crenellated between the recesses (22) Sections (28) of the side walls (14, 16) are with bead-shaped depressions (30) provided on the outer slats (24) fit without gaps and the Set the heat exchanger (20) without play. The pipe ends (26) are connected to one another by caps (32a, b, c) also the connections (34, 36) of the heat exchanger (20) are provided.

The combustion chamber walls each consist of two together adjacent and welded wall plates (38.40) made of stainless steel, the molded sheet metal areas (42.44) have, between which a further below described channel system (46) for the combustion chamber (10) cooling heating water flow is formed. The Channel system (46) is produced in that the Wall plates (38.40) initially still in their essence flat initial shape due to straight weld seams (48) be connected to each other and only then the duct system (46) by shaping the between the weld seams (48) located sheet metal areas (42, 44) by means of a Pressing pressure inserted between the wall plates (38.40) fluid working fluid is formed.

The channel system (46) in the rear wall (12) and Sidewalls (14, 16) is in accordance with the settlement of these Wall parts according to Figure 3 formed by one closed all-round weld seam (48a) and four straight weld seams (48b, c, d, e). As a result, there are two individual channels (46a) in the side wall (14) connected to one another via a chamber (46b) are and opens into a chamber (46c). Three of these lead parallel individual channels (46d) in the rear wall (12) further in a chamber (46e) which has two individual channels (46f) in the Sidewall (16) connected to an outer chamber (46g) is. The two are analogous to this training Wall plates of the front wall (18) by a circumferential Weld seam (48f) and by individual weld seams (48g, h) interconnected, formed between the channels (46h) are, which open on both sides in chambers (46i, j).

Before welding, dome-like features (50) with openings (52) for inserting connecting pieces (54) are molded into the outer wall plate at the connection points of the duct system (46). In the same way, the front wall (18) is provided with connection elements (56). After welding, the circuit board shown in FIG. 3 is bent into the U-shape according to FIG. 1 with a bending radius r ₂ using a bending device (not shown ₎ . The lines (58) drawn with dashed lines in FIG. 3 show the position and the limits of the corner regions which form, hereinafter referred to as bending zones (60).

After the combustion chamber 10 has been bent into a U shape, it is clamped into a device (FIG. 9) consisting of an inner (80) and an outer tool (82), the two bending zones (60) of the inner wall plate 40 being on the inner one Place the tool (80) on. The bending radius of the inner tool (80) coincides with the bending radius r _{2 of} the inner wall plate (40). In the remaining zones, recesses are formed between the inner wall plate (40) and the inner tool (80) and between the outer wall plate (38) and the outer tool (82) there are clearances for the duct system (46) to be produced.

The fluid working fluid for expanding the between the Weld seams (48) lying sheet metal areas (42,44) pressed between the wall plates (38.40), the to be formed sheet metal areas (42,44) in the recesses and the distances are pushed in. In the field of Bending zones (60) are only the outer wall plate (38) deformed outside, while the inner wall plate (40) in this Area remains undeformed. The outer tool (82) is in the bending zones (60) with a greater distance from the outside Provide wall plate (38). This can make it stronger Dimensions than in the stretched channel areas to the outside expand. In the embodiment of the The device is in the outer tool (82) in the Bending zones (60) on a counterpart for limiting the outer wall plate (38) dispensed with because of a defined pressure supply the desired channel width a can be manufactured.

As FIG. 10 shows, the weld seams (48) connecting the inner and outer wall plates (38, 40) to form the channel system (46) are deliberately not supported when the plate regions (42, 44) are expanded. As a result, a tensile force is applied to the weld seams (48) and to the adjacent sheet metal areas and the material is stretched. This stretching takes place as shown in the stress-strain diagram in FIG. 11, up to the plastic region with a permanent strain ε _r . The line a shown in broken lines shows the stress-strain curve for the stretching method used, while line b represents a comparable curve curve without stretching. By stretching into the plastic area accompanied by a reduction in wall thickness, the tensile strength in the weld area is increased and the stretch is reduced. The stainless steel used to manufacture the water-cooled combustion chamber is particularly suitable for this stretching process due to its high elongation at break.

The duct system (46) to be produced is based on a minimum flow cross section a _min , which ensures adequate cooling of the combustion chamber (10). Therefore, the arrangement is such that the largest possible cooling of the combustion chamber (10), the channel width is selected both in the stretched channel area (sum of depth b and width c) and in the corner area (width a) so that the minimum flow cross section a _{min is} observed.

Furthermore, the width a of the flow cross section in the Bending zones (60) equal to the sum of the depth b and the Width c selected in the stretched channel area. Thereby and by the fact that in the bending zones (60) Chambers (46c, e) are located, the water flow in the Corner areas or bending zones (60) not or only insignificantly affected. For the training of symmetrical sheet metal areas (42,44) the depth b of the Cross section of the recess equal to the width c of the Cross-section of the distance selected.

In the alternative embodiment according to FIG. 6, the inside is Tool (80) next to the bending zones (60) locally provided recesses so that there are excess material (62) of the inner wall plate (40) can mold into it. In the connection piece (54) opposite support surfaces is the inner tool (80) each with a trough-shaped depression to form a dome-shaped bulge of the inner wall plate (40) provided, whereby the flow resistance at the entrance and further reduced at the exit of the channel system (46).

The weld seams running between the individual channels (48) have circular ends (66), so the sheet metal material there when the individual channels are widened Bulge without pillows without the risk of cracking can. The circle diameter of the ends (66) should not be smaller than 5 mm, but also not larger than 15 mm the consequent loss of more effective Keep heat transfer surface within reasonable limits. at a preferred embodiment was the circle diameter 12 mm selected. Wrinkling is also caused by the counteracted further measure that the ends (66) of the parallel channels (48c, d or 48g, h) offset to be arranged to each other.

From Figure 3 it can be seen that the channel system (46) in the rear wall (12) extends up to the area overlapping the heat exchanger (20) and that there the wall plates (38, 40) in the bending zones (60) directly against one another issue. The combustion chamber (10) has a corner radius r ₁ of, for example, 5 mm in this upper region, which closely surrounds the heat exchanger (20), whereas in the corner regions of the combustion chamber (10) below, over which the chambers (46c, e) of the Extend channel system (46), the corner radius r _{2 is} dimensioned much larger and is, for example, 20 mm. The transition from one corner radius to the other is made without gaps in that the entire board, after it has been bent with the larger corner radius r ₂ and is supported between the inner and outer tool, is stretched with the smaller corner radius r ₁ by stretching the wall plates (38.40) is molded from the inside out.

The individual channels of the channel system (46) are through the Weld seams (48) immediately limited, so that at their Longitudinal edges (78) (Figure 2) do not form any gaps in which corrosion products could deposit. The welds (48) are in the practically still flat condition of the wall sheets (38.40), which makes manufacturing easier. Through the detachable connections of the heat exchanger (20) and Front wall (18) of the other wall parts (12, 14, 16) of the Combustion chamber (10) will maintain and assemble the Heat exchanger (20), and the manufacture of the combustion chamber (10) relieved. The connections (54, 56) of the duct system (46) are advantageously placed so that the channel system of is flowed through from the bottom up. This makes it possible Bleed the system more easily. The heating efficiency can be improved when the heat transfer from heating gas to the combustion chamber wall by increasing the radiation number y increased due to oxidation or blackening of the inner surface becomes.

The front wall (68) shown in FIG. 8 consists of an outer wall plate (70) and one in parallel spacing arranged inner wall plate (72), which consists of a particularly temperature-resistant material. On the Inside of the wall plate (70) is preferably one shiny metallic radiation protection layer (74), optionally in the form of an additional sheet metal part, intended. The between the two wall plates (70.72) formed space (76) goes through one Air flow, the heat absorbed there to the heat exchanger (20) transported.

Claims (15)

1. Method for producing a combustion chamber, in particular for gas-fired water heaters, the walls of which combustion chamber are formed from inner and outer wall panels (42, 44) which are welded to one another and which are provided with local shaped-out portions for the formation of ducts (46) for a fluid, in particular for heating water serving as coolant, the ducts (46), after welding along the subsequent duct edges, being formed by the shaping-out of the panel regions (42, 44) located between the weld seams (48), by means of a fluid working medium introduced with pressure between the wall panels (38, 40), and the walls with the welded wall panels having bending zones (60), in which the walls are bent in relation to the combustion chamber, characterized in that the inner wall panel (40) is supported in the bending zone (60) on an inner die (80) before the supply of the fluid working medium and the outer wall panel (38) forms, in relation to an outer die (82), a clearance which forms the limits for shaping out the ducts (46) after the supply of the fluid working medium, the clearance of the outer die (82) in relation to the outer wall panel (38) being dimensioned larger in the bending zone (60) than in the extended supporting regions.
2. Method according to Claim 1, characterized in that the inner die (80) has, in front of the bending zone (60), at least one recess which forms, on the inner wall panel (40), recessed pockets serving for receiving excess material (62).
3. Method according to Claim 1, characterized in that, during the production of the ducts (46), the weld seams (48) and the panel regions (42, 44) contiguous to them are stretched, in that the weld seams are arranged, free of support, between the inner die (80) and the outer die (82).
4. Method according to Claim 3, characterized in that stretching takes place into the plastic range with a permanent elongation ε_r.
5. Method according to one of the preceding claims, characterized in that the weld seams (48) are arranged in such a way that common chambers (46c, e) extend over the corner regions of the wall panels (38, 40).
6. Method according to one of the preceding claims, characterized in that, before being welded to the inner wall panel (40), the outer wall panel (38) is provided with an orifice (52) for the supply of the fluid working medium and for the subsequent connection of a line for a fluid service medium, in particular heating water.
7. Method according to Claim 6, characterized in that the orifice (52) is provided in a dome-like stamped-out portion (50) of the wall panel (38).
8. Method according to Claim 6 or 7, characterized in that the weld seams (48) are arranged and produced in such a way that individual ducts (46 a, d, f, h) running parallel, and in their inlet and outlet regions, common chambers (46 b, c, e, g, i, j), result and, furthermore, in that the orifices (52) for the connecting lines are provided in the region of the outer chambers (46 b, g, i, j).
9. Method according to Claim 8, characterized in that the weld seams (48) are arranged in such a way that common chambers (46c, e) extend over the corner regions of the wall panels (38, 40).
10. Method according to Claim 8 or 9, characterized in that the start of the individual ducts (46 d, h) are arranged so as to be offset relative to one another.
11. Method according to one of Claims 7 to 10, characterized in that the ends (66) of the weld seams (48) are produced so as to terminate in the form of a circular line.
12. Method according to Claim 1, characterized in that the wall panels (38, 40) welded to one another are bent into a U-shaped body forming the rear wall (12) and the side walls (14, 16) of the combustion chamber (10), and the front wall (18) of the combustion chamber (10) is produced as a separate part and is designed to be capable of being connected releasably to the side walls (14, 16).
13. Combustion chamber for gas-fired water heaters, which is produced according to one of Claims 1 to 12 and the walls of which consist of two wall panels (42, 44) which are welded to one another and between which ducts (46) for a water run-through cooling the combustion chamber (10) are formed in local shaped-out portions, characterized in that the minimum flow cross section a_min corresponds to the throughflow quantity for the fluid, in particular heating water, necessary for cooling the combustion chamber (10), and in that, in the case of a predetermined cooling surface for the combustion chamber (10), the duct width is larger than or equal to the minimum flow cross section a_min both in the extended duct region and in the corner region of the bending zone (60).
14. Combustion chamber according to Claim 13, characterized in that, in the extended duct region, the depth (b) of the recess is equal to the width (c) of the clearance.
15. Combustion chamber according to Claim 13 or 14, characterized in that the width (a) of the flow cross section in the bending zones (60) is equal to the sum of the depth (b) of the recess and the width (c) of the clearance in the extended duct region.

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