Water-bearing household appliance with at least one heating element

Abstract

Water-bearing household appliance (1) with at least one liquid-exposed body (12) on which a heating device (11) is arranged, which has current-carrying conductor tracks (13), characterized by that the conductor tracks (13) run in such a way that individual sections (14, 15) of the conductor tracks (13) are essentially parallel to the wall (17) of the liquid-exposed body (12) and have a minimum distance (d1, d2) from each other, which approximately three times the thickness (D) of the body wall (17) of the liquid-exposed body (12) to which the heating device (11) is assigned, wherein the body (12) in the area to which the heating device (11) is assigned forms at least substantially a round cross-section and wherein the conductor tracks (13) meander around a large part of the body circumference of the liquid-exposed body (12).

Description

[0001] The invention relates to a water-conducting household appliance, in particular a dishwasher, having at least one body, in particular a circulation pump, through which liquid is applied, in particular through which liquid flows, on which, in particular on the outside, a heating device is arranged, which has conductor tracks through which current can flow, according to the preamble of claim 1.

[0002] Such water-conducting household appliances are known to have external heaters that generate heat via meandering conductors through which current flows during operation. These conductors conduct heat through the wall of a body on which they rest externally, for example, a circulation pump, into the interior of the body and the fluid moving there. These conductors are therefore also referred to as heating conductors.

[0003] The problem here is that the fluid often contains substances, in particular limescale, that deposit on the inside of the body wall of the body exposed to the liquid, or in particular through which liquid flows. These deposits settle inhomogeneously on the inside of the body wall of the body exposed to the liquid, or in particular through which liquid flows. The layer thickness of the deposits is greatest directly beneath the heating elements. It initially decreases with increasing distance from the respective heating element, measured parallel to the body wall, before then increasing again as the system approaches the next heating element located on the outside. In order to avoid a significant deterioration in heat transfer from the outside to the fluid flowing inside the body, the formation of continuous limescale layers in particular should be prevented.

[0004] DE 10 2007 017 271 A1 shows a fluid-flowing body, in particular a circulation pump, which is externally equipped with a heating device with current-carrying conductors. These conductors are not described in terms of their dimensions or spacing, and are shown in the drawing completely out of scale and exaggerated relative to the housing wall. Therefore, this document does not provide any reference to dimensional information regarding the conductors of the heating conductors and their spacing.

[0005] US 2002 / 0 159 767 A1 discloses a heating device with a body through which fluid flows, with a heating device arranged on the outside of the body. This heating device comprises conductor tracks through which current can flow, with individual sections of the conductor tracks lying meandering on the surface.

[0006] There, in the cited drawing figures 9 and 10, a pair of two wires 146 is shown as a meander, through which current flows in different directions. The two wires are so close to each other that their distance is smaller than their respective diameters, as in Fig. 10 becomes clear. Apparently, the two wires 146 of the forward and return lines are as close to each other as was structurally possible.

[0007] In the heating device according to the Fig. 1 or the Fig. 4 of EP 0 485 211 B1, an approximately rectangular plate with an electric heating element having a conductive track made of a printed thick-film circuit in rectangular waveform forms a wall area of ​​a container for liquid to be heated.

[0008] US Pat. No. 6,736,598 B2 relates to a pump, particularly for washing machines, dishwashers, or the like, comprising a housing and a heating device for continuously heating a liquid. The heating device is designed as a peripheral wall of the housing. The heating device can comprise a tubular heater or a thick-film heater.

[0009] The invention is based on the problem of achieving an improvement here.

[0010] The invention solves this problem by a water-conducting household appliance, in particular a dishwasher, having the features of claim 1. Further advantages and features as well as developments of the invention are specified in claims 2 to 14, the features of which can each be implemented individually or in combination with one another.

[0011] The invention provides a water-conducting household appliance, such as a dishwasher, in which, by maintaining a minimum distance between individual conductor track sections of the heating device, which, measured essentially parallel to the body wall of its body exposed to liquid, in particular through which liquid flows, corresponds approximately to three times the body wall thickness of the body exposed to liquid, in particular through which liquid flows, the warmest areas in the fluid-flowed area, in particular the fluid-flowed interior of the body, are so far apart from each other that no or at least significantly fewer areas of accumulating deposits, in particular limescale layers, build up.

[0012] In this way, during operation of the household appliance, a wet area carrying liquid, in particular a processing chamber for cleaning items to be washed or washed, can be supplied with a liquid which - preferably at least the circulating part of which - can be heated by acting on, in particular flowing through, at least one body, in particular a circulating pump, on which, in particular on the outside, a heating device is arranged which has conductor tracks through which current can flow according to the design principle according to the invention. In the case of a household dishwasher, the circulating part of the liquid preferably passes through a liquid circulation system which comprises, among other things, a circulating pump, a heating device, one or more connecting lines leading from the circulating pump on the pressure side to one or more spray devices, a water diverter, and a pump sump in the base of the washing container. The heating device can, if necessary,be housed in the circulation pump or alternatively provided at another location in the liquid circulation system.

[0013] The heating device designed according to the invention can also be provided for heating a liquid in another liquid reservoir or a liquid line of a household appliance.

[0014] For example, with a body wall thickness of 0.8 millimeters, it is advantageous to keep the distance between individual sections of the conductor tracks at about 2.3 or more millimeters parallel to the body wall.

[0015] For effective heat transfer, it is also advantageous if the conductor tracks meander around a large part of the circumference of the body exposed to fluid, especially through which fluid flows. The heat can then be introduced fairly evenly into the fluid-exposed area, especially the interior of the body through which fluid flows, over a large part of the circumference and a certain length of the body, typically several centimeters. Alternatively, the heating device can also be arranged on a more or less flat plate, for example, the end plate of a pump body.

[0016] Ideally, the individual meander sections are positioned predominantly at least nearly in the longitudinal direction of the body, ensuring good heating performance across a large portion of the heating device's width. In particular, this arrangement also ensures that the meander sections are positioned transversely to the flow direction of the fluid moving or flowing within the body, at least over a large portion of their length. This helps prevent deposit formation.

[0017] In particular, with such an arrangement of the meander sections, the body can form at least substantially a round cross-section in the region to which the heating device is assigned, wherein the liquid in the body continues to circulate or flow with a component in the circumferential direction along the body wall, i.e. transversely to the said meander sections, and optionally can additionally be conveyed with a component radially to the body wall.

[0018] If the individual meander sections maintain the minimum distance both to the adjacent section of the same meander and to the nearest section of the adjacent meander according to an advantageous development of the invention, the coalescence of deposits, in particular lime deposits, over the entire surface of the body exposed to, and in particular through which, fluid flows is effectively prevented.

[0019] Advantageously, the meander sections are aligned largely straight and parallel to each other over a large part of their length in order to cover a large area with heating conductors and yet still be able to choose sufficiently large minimum distances between them.

[0020] If the heating device forms a so-called thick-film heater, in which the current-carrying conductor tracks are printed on a glass-like paste on the outside of the body wall, good heat transfer to the body and the fluid flowing past it or transported within it is ensured.

[0021] With the invention, the improved heat transfer into the interior of the body also allows for a significant increase in the surface load of the heating device, allowing the heating device to be made smaller overall. In particular, the conductor tracks can be made narrower, for example, from a typical width of 5 to 8 millimeters to a width of 1 to 2 millimeters parallel to the body wall. This results in a significant reduction in the electrical conductor material, which usually contains silver, in these conductor tracks.

[0022] Further advantages and features emerge from embodiments of the subject matter of the invention shown in the drawing and described below.

[0023] It shows in schematic representation: Fig. 1 an exemplary water-conducting household appliance, here designed as a dishwasher, in a schematic and partially broken-away side view, wherein a washing container is provided which has a so-called pump pot in its lower area, from which washing liquor can be conveyed via a circulation pump which can be heated here and is to be fed back into the washing container, Fig. 2 a detailed illustration of a heatable circulation pump, Fig. 3 a perspective detail view of a body wall of the pump body with a heating device arranged on the outside, and Fig. 4 the body wall of Fig. 3 in an imaginary, developed representation. Elements with the same function and mode of operation are provided with the same reference numerals in the figures.

[0024] The Fig. The dishwasher 1 schematically illustrated in FIG. 1 is a water-conducting household appliance, exemplified here as a domestic dishwasher. It has at least one washing container 2 for holding items to be washed, such as dishes, pots, cutlery, glasses, cooking utensils, and the like.

[0025] The washing container 2 can be tightly closed, particularly at its front, by a door 3. This door 3 is in Fig. 1 is shown in the closed position and can be pivoted forward and downward, for example, around a lower horizontal axis. An opening movement other than pivoting is also possible.

[0026] The wash tank 2 can be supplied with fresh water FW via a fresh water inlet. The fresh water FW is provided, in particular, with cleaning, drying and / or shine agents in its circulation and can flow into a pump sump 5 as wash liquor liquid in the area of ​​the floor 4. From there, the wash liquor liquid is recirculated as wash liquor liquid S via a circulation pump 6 and a pipe system LS connected to it and can be used again, for example, via spray devices 7, 8, here rotatable spray arms, to spray the washware held in the wash baskets 9, 10. If necessary, it can be partially or completely pumped out of the device 1 as waste water AW at the end of each liquid-carrying partial wash cycle via another pump (waste water pump, which has been omitted here for the sake of simplicity of the drawing).

[0027] At least a part S of the liquid FW, S, which circulates in the circulation circuit formed by the circulation pump 6, the pipe system LS, the spray devices 7, 8 and the pump sump 5, can be heated in certain phases of the cleaning.

[0028] In the exemplary embodiment shown here, a heating device 11 is arranged for this purpose at least on a body 12 exposed to liquid, in particular through which liquid flows, in particular the circulation pump 6. An arrangement on another body 12 exposed to liquid, in particular through which liquid flows, for example, a pipe section, is also possible additionally or alternatively.

[0029] The heating device 11 has electrical conductors 13 through which electrical current flows, thereby enabling heat transfer to the body 12. The current flow can be switched via the dishwasher's control unit, depending on the program phase. Thermostatic control is also possible.

[0030] The conductor tracks 13 run in a meandering manner, for example, in order to be able to arrange many conductor tracks 13 on a small surface. The arrangement is such that individual sections 14, 15 of the conductor tracks 13 parallel to the wall 17 of the body 12 have a minimum distance d1 within the respective meander 18 and a minimum distance d2 to the nearest section 15 or 14 of the adjacent meander 18, wherein both the minimum distance d1 and the minimum distance d2 correspond approximately to three times the thickness D of the body wall 17 to which the heating device 11 is assigned.

[0031] According to the drawing - in particular Fig. 4 - not just some, but all sections 14, 15 of the conductor tracks 13 transverse to the longitudinal direction 16, 16' of the liquid-exposed, in particular liquid-flowing, body 12 have a minimum distance d1, d2 from one another, which corresponds to three times the thickness D of the body wall 17. This results here from the fact that the heating device 11 is formed regularly over its length and the individual sections 14, 15 extend in uniform meanders 18.

[0032] In this meandering arrangement, the conductor tracks 13 each encircle a large portion of the circularly symmetrical circumference of the body 12 of the circulation pump 6. In this exemplary embodiment, the body 12 is thus circularly cylindrical. In particular, the circumference of this body 12 is encircled almost completely in order to achieve a uniform and effective introduction of heat into the wash liquor S.

[0033] The meanders 18 are arranged such that the individual meander sections 14, 15 each run predominantly at least almost in the longitudinal direction of the body 12 – and thus transversely to the flow circulating in the circumferential direction 23 of the body, which is preferably approximately circular-cylindrical in shape, within its interior. Any growth of deposits, particularly lime, that may form beneath the respective meander sections 14, 15 can thus be removed mechanically much more easily than if they were formed in the direction of flow. This is a further significant advantage of the invention, since this not only eliminates the formation of deposits, but also significantly promotes deposit removal.

[0034] The individual meander sections 14 maintain the minimum distance d1, d2 measured in the circumferential direction 23, i.e. in the main flow direction of the liquid, both from the adjacent section 15 of the same meander 18 and from the nearest section 15 of the circumferentially adjacent meander 18, which is set into a circulating movement in the tubular body 12 by the rotating impeller 19.

[0035] According to the drawing, all meander sections 14, 15 are aligned largely straight and parallel to one another over a large part of their extent, this alignment being in the longitudinal direction 16, 16', in particular the axial longitudinal direction, of the body 12.

[0036] Since, as mentioned, the rinsing liquor liquid S flowing in through the inlet-side, in particular centrally arranged, intake channel AK of the pump 6 in the longitudinal or axial inflow direction 16 is conveyed by an impeller 19 in the downstream pump chamber PK of the pump 6, initially radially outwards in the radial direction 25 and then circulating essentially parallel to the circumference, i.e. in the circumferential direction 23 of the body 12 with an additional movement component in a longitudinal, in particular axial, outflow direction 16' opposite to the inflow direction 16 through a downstream pressure chamber DK in the section of the body 12 on which the heating device 11 is arranged on the outside, to the outlet 21, in particular the outlet nozzle, the meandering sections 14, 15 are therefore automatically also transverse to the circulation direction 23 of the flow 20 of the liquid moving in the circumferential direction in the body 12, at least over a large part of their longitudinal extension.This cross-flow can at least prevent adjacent deposit areas of particles (such as lime particles present in the rinsing liquid), which may form in stripes on the inner wall of the body 12 through which the liquid flows, below the meandering sections 14, 15 adjacent in the circumferential direction 23 along their longitudinal extent, from growing together to form a common deposit area. In the most favorable case, the cross-flow even ensures that deposit areas of particles, which form in stripes on the inner wall of the body 12 through which the liquid flows, below the meandering sections 14, 15 adjacent in the circumferential direction along their longitudinal extent, are partially or completely removed by the liquid flow 20 circulating in the circumferential direction 23, so that the inner wall surface of the tubular body 12 remains largely free of deposits.In this way, an unacceptable overheating of the electrical conductors, which is caused by deposit areas becoming too large and thus by insufficient or non-existent heat removal by the rinsing solution, is avoided.

[0037] E.g. in Fig. 3 shows that the body 12, in the region to which the heating device 11 is assigned, has at least a substantially round cross-section, so that a round cylinder is formed there. The body wall 17 is made of chromium steel with a thickness D of typically 0.7 to 0.9 millimeters. With such a wall, tests show that the deposit formation grows up to 1.25 millimeters laterally beyond the respective electrical heating conductor. Due to the large distance d1, d2 between the sections 14, 15 according to the invention, which is at least three times the thickness of the body wall, the coalescence of deposit layers that can form below the heating conductors 13 on the inside of the body wall 17 is avoided.

[0038] In the embodiment of the body 12 shown here by the circulation pump 6, the liquid S in the body 12 can be conveyed with a component radially to the body wall 17 and then runs further inside along the wall 17 in the circumferential direction 23 circulating, ie with a flow component in the circumferential direction 23, along the body wall 17 in the longitudinal direction 16' (here in particular parallel to the central axis of the impeller 19) to the outlet 21, as in Fig. 2 is clearly visible.

[0039] The heating device 11 preferably forms a so-called thick-film heater on the outer circumference of the wall 17, wherein the current-carrying electrical conductor tracks 13 are printed onto a glass-like paste 22 on the outer side of the body wall 17. The invention allows for considerable savings in paste material due to the higher surface load.

[0040] The distance d3 (measured in the longitudinal direction 16') between heating conductor sections 24' lying parallel to the longitudinal movement component of the flow 20 can also advantageously be at least three times as large as the thickness D of the wall 17.

[0041] Since the invention solves the problem of deposit formation and deposit removal, the surface load of such a heating device 11 can be significantly higher than the currently usual 36 W / cm 2 A surface load of over 75 W / cm 2 on at least 75% of the heating element surface.

[0042] The risk of air bubbles forming due to the flaking of once-formed layer accumulations, which could virtually prevent heat conduction at certain points and result in localized peak heating with the risk of burnout (hotspots) for the heating elements 13, is also significantly reduced and completely eliminated, especially in water with normal hardness. The heater 11 is thus significantly more robust and has a longer service life.

[0043] Generally speaking, the body can also have a geometry other than a circular cylinder, allowing the inventive attachment of the heating conductors and their application, in particular the flow of fluid to be heated. For example, the body can be formed by a concentric Doppler tube arrangement, through whose annular gap fluid flows. In this case, the heating elements can expediently be provided on the outer casing of the inner tube and / or on the inner casing of the outer tube. List of reference symbols 1 dishwasher, 2 rinsing containers, 3 doors, 3a swivel axis, 4 Bottom of the rinsing container, 5 swamp, 6 circulation pump, 7 spray arm, 8 spray arm, 9 Dishwasher basket, 10 dishwashing basket, 11 heating device, 12 body exposed to liquid, in particular through which liquid flows, 13 conductor tracks, 14 sections of the conductor tracks, 15 sections of the conductor tracks, 16 Longitudinal direction or axial inflow direction, 16' axial outflow direction 17 body wall, 18 meanders, 19 impeller, 20 fluid flow, 21 Pump outlet, 22 Paste on the wall 23 Circumferential direction of the body exposed to liquid, in particular through which liquid flows, or circulation direction of the liquid flow 20, 24' heating conductor sections running parallel to the circulation direction of the liquid flow 20, 25 radial direction, AK intake duct, AW Wastewater, D thickness of the body wall, DK pressure chamber, d1, d2 minimum distance, FW fresh water, LS piping system, PK pump chamber, S rinsing liquor,

Claims

[1] Water-conducting household appliance (1) with at least one liquid-loaded body (12) on which a heating device (11) is arranged, which has conductor tracks (13) through which current can flow, characterized by , that the conductor tracks (13) run in such a way that individual sections (14, 15) of the conductor tracks (13) are substantially parallel to the wall (17) of the liquid-loaded body (12) and have a minimum distance (d1, d2) from one another, which approximately three times the thickness (D) of the body wall (17) of the liquid-charged body (12) to which the heating device (11) is assigned, wherein the body (12) forms at least substantially a round cross-section in the region to which the heating device (11) is assigned, and wherein the conductor tracks (13) each meander around a large part of the body circumference of the liquid-charged body (12). [2] Water-conducting household appliance (1) according to claim 1, characterized by , that all sections (14, 15) of the conductor tracks (13) have a minimum distance (d1, d2) to each other, which corresponds approximately to three times the thickness (D) of the body wall (17) to which the heating device (11) is assigned. [3] Household appliance (1) according to one of claims 1 or 2, characterized by that the individual meander sections (14, 15) each run predominantly at least almost in the longitudinal direction (16, 16') of the body (12). [4] Household appliance (1) according to one of claims 1 to 3, characterized by that the individual meander sections (14, 15) maintain the minimum distance (d1) from both the adjacent section (15, 14) of the same meander and the minimum distance (d2) from the nearest section (15, 14) of the adjacent meander. [5] Household appliance (1) according to one of the preceding claims, characterized bythat the meander sections (14, 15) are largely straight and parallel to each other over a large part of their extent. [6] Household appliance (1) according to one of the preceding claims, characterized by that the meander sections (14, 15) lie at least over a large part of their extent transverse to the flow direction (23) of the liquid (S) flowing in the body (12). [7] Household appliance (1) according to one of the preceding claims, characterized by that the liquid (S) in the body (12) can be conveyed with a component radial to the body wall (17). [8] Household appliance (1) according to one of the preceding claims, characterized by that the liquid (S) in the body (12) can be conveyed with a component in the circumferential direction along the body wall (17). [9] Household appliance (1) according to one of the preceding claims, characterized by that the heating device (11) forms a so-called thick-film heating. [10] Household appliance (1) according to one of the preceding claims, characterized by that the current-carrying conductor tracks (13) are printed on a glass-like paste on the outside of the body wall (17). [11] Household appliance (1) according to one of the preceding claims, characterized by that the body wall (17) is made of a chromium steel with a thickness of 0.7 to 0.9 millimeters. [12] Household appliance (1) according to one of the preceding claims, characterized by that the water-conducting household appliance (1) is a dishwasher. [13] Household appliance (1) according to one of the preceding claims, characterized by that the liquid-loaded body (12) is the liquid-flowing body of a circulation pump (6). [14] Household appliance (1) according to one of the preceding claims, characterized by that the heating device (11) is arranged on the outside of the liquid-loaded body (12).

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