EP0832400A1

EP0832400A1 - Instantaneous water heater

Info

Publication number: EP0832400A1
Application number: EP96919519A
Authority: EP
Inventors: Francesco Illy; Matthias Hell
Original assignee: Creaholic SA
Current assignee: Creaholic SA
Priority date: 1995-06-13
Filing date: 1996-06-11
Publication date: 1998-04-01
Anticipated expiration: 2016-06-11
Also published as: DE59601388D1; WO1996041994A1; AU5808296A; JPH11515084A; ES2131947T3; EP0832400B1; US6192192B1

Abstract

The instantaneous water heater of the invention consists essentially of an elastic, flexible or rigid, floatingly fitted composite pipe (10) and a heat source (6). When the liquid is heated inside (1) the pipe, undesirable substances, e.g. chalk, can separate out from the liquid and be deposited on the inner walls of the pipe. If, however, the pipe (10) is moved and/or deformed by internal overpressure or external force, the separated substances fall off the inner walls. The composite pipe (10) can, for example, consist of an inner pipe (2), internal insulating layers (3-5), a heating wire (6) and outer insulating layers (7-9).

Description

CONTINUOUS HEATER

The invention relates to a water heater according to the preamble of the first claim. The instantaneous water heater according to the invention can be used in particular for heating water in coffee machines.

Devices for heating liquids in pipes or hoses are described, for example, in the patents EP-0 082 025, GB-2 181 628, US-4 156 127 or US-4 038 519. A considerable disadvantage of such instantaneous water heaters is their contamination by the precipitation of substances dissolved in the liquid. As is known, the solubility is strongly temperature-dependent. If the temperature of a solution in the tube is now increased, the solubility can be reduced; the dissolved substances are precipitated and are deposited on the inside of the pipe. This leads to pipe constrictions and, in the worst case, to pipe blockage. For example, tap drinking water that is used for the preparation of coffee contains, depending on the geographical location, more or less storable components, hereinafter also referred to as "lime". When the tap water is heated from approx. 20 ° C room temperature to approx. 95 ° C boiling temperature, the lime precipitates and settles on the inner walls of the pipe; Heavy limescale can be observed from around 60 ° C. The problem of pipe calcification complicates or in many cases prevents the use of instantaneous water heaters to heat tap water. The instantaneous water heater pipes in question would have to be decalcified or replaced regularly and relatively frequently, which would cause undesired interruptions in operation, labor and material costs. For these reasons, for example in conventional coffee machines, the water is heated with a solid electric heating block at the exit of a water supply chamber. The hot water first flows through a riser pipe into the brewing chamber, then through the coffee goods in the brewing chamber and then borrowed through a filter into the coffee jug. To save energy and to save time, heating the electric heating block for a one-off coffee preparation does not appear to make sense. The massive electric heating block of conventional coffee machines namely has a large heat capacity and a relatively small heating surface, so that it has to be supplied with a large amount of heating energy in order to heat it up at all, and the heating of the massive electric heating block and the water takes a long time, typically longer than 45 s, lasts.

The object of the invention is to heat liquids in a tube to a desired temperature, in which case precipitation of solid precipitation products on the inner walls of the tube should be avoided or reversed or made more difficult or slowed down without additional work and material expenditure. The device is said to be producible with known methods and to be usable in known applications, such as in a coffee machine, for example, without changing the basic sequence of the applications.

The object is achieved by the instantaneous water heater according to the invention, as defined in the patent claims. If there are solid breakdown products from the heated liquid on the inner wall of the instantaneous heater tube according to the invention, they are at least partially detached again after a short time and carried away by the liquid. The instantaneous water heater according to the invention therefore either does not calcify at all or does not calcify more slowly than known instantaneous water heaters and can be used, for example, in coffee machines.

The limescale detachment is brought about by movements and / or deformations of the flow heater tube; it is assumed that the pipe is floating over its entire length or over part of it. A layer of lime or other solid precipitation products is relatively stiff, brittle and brittle. If the continuous-flow heater tube is moved and / or deformed, the layer at least partially detaches from the tube inner walls and crumbles into small pieces that are carried away by the liquid.

The movements and / or deformations of the continuous-flow heater tube can in principle be ensured by three different embodiments of the tube. First, the tube can be elastic and can be expanded radially and / or axially by excess pressure in the interior of the tube. Second, the tube can be flexible and can be moved by an external force at at least one of its ends. Thirdly, the tube can be rigid and can be moved by an external force, for example excited by a vibrating pump itself, to vibrate. In addition, a distinction can be made between static and dynamic modes of action in these embodiments. The instantaneous water heater according to the invention is described in detail below with reference to figures. Show:

1 is a perspective view of the instantaneous water heater, which is laid out in layers for the purpose of clarity,

2 and 3, the deformation of a spiral flexible tube by a static pressure in the interior of the tube,

4 and 5, the deformation of a freely hanging flexible pipe by a static overpressure in the interior of the tube,

6 and 7 the deformation of an elastic tube in radial

Direction due to a static overpressure inside the pipe,

8 and 9 the dynamic deformation of a flexible pipe by a pressure front which spreads inside the pipe,

10 and 11 the deformation of a flexible pipe by a movement of a pipe end caused by an external force,

12 shows the vibration of a rigid pipe caused by a pump and

13 and 14 two versions of the instantaneous water heater with control circuit in a schematic representation. In the exemplary embodiment in FIG. 1, a liquid to be heated flows through the interior 1 of an inner tube 2 of the instantaneous water heater according to the invention. The inner tube 2 can consist, for example, of aluminum or another metal or of thermally resistant plastic. It can be surrounded by one or more, for example three, inner insulation layers 3-5. These can be required to electrically isolate the inner tube 2 from a heating wire 6 and to ensure operational safety in accordance with the standards of the household electrical industry. The insulation layers 3-5 consist of an electrically insulating, thermally resistant material, for example a high temperature resistant plastic, polyester or glass wool.

In the embodiment of the invention shown here, a heat source in the form of an electrical heating wire 6 is arranged on the outside of the inner tube 2 and the insulation layers 3-5 such that the heating wire 6 can heat the liquid in the inner tube. The heating wire 6 is, for example, wound spirally around the insulation layers and can consist, for example, of a NiCr alloy. In another embodiment, the insulation layers 3-5 can be applied around the heating wire 6 itself instead of around the inner tube 2; this variant allows a narrower winding of the heating wire and thereby a shorter heating length and better heat transfer.

The heating wire 6 shown in Fig. 1 is advantageously designed so that it has a small heat capacity. This property enables a rapid change in the temperature of the heating wire 6 and thus also facilitates rapid heating of the liquid in the water heater, so that, for example, water can be heated from 20 ° C. to approx. 95 ° C. within a few seconds using the water heater according to the invention. The However, the type of heat source does not play an important role for the present invention. The liquid in the instantaneous water heater according to the invention could also be heated by means other than an electrical heating wire, for example a gas burner.

Further, outer insulation layers 7-9, like a jacket, can comprise all of the elements 1-6 described so far. They ensure thermal insulation of the elements 1-6 against the outside and protect them from mechanical damage, moisture, dirt, electrical contact and other undesirable external influences.

The entire tube 10, consisting of the (partially optional) elements 1-9, is at least to a limited extent bendable in all directions perpendicular to the tube axis and / or at least to a limited extent parallel to the tube axis. These properties ensure that the entire pipe 10 moves and / or deforms under the influence of an internal overpressure and / or external forces, which leads to a detachment of lime from the inner pipe walls. The overall tube 10 can also be designed in other forms, not shown here; the heating wire 6 could, for example, be arranged differently or be omitted entirely, or the number of insulation layers 3-5 or 7-9 can be different. The term "tube" could also be replaced by the term "hose" throughout this document.

FIGS. 2-12 show, in schematic representations, various measures according to the invention, by means of which movements and / or deformations of the entire pipe 10 are brought about. The volume on the input side of the entire tube 10, the input chamber 11, the volume the output side of the total pipe 10 called output chamber 12; in a coffee machine, the inlet chamber 11 corresponds to the water storage chamber, the outlet chamber 12 to the brewing chamber. Of course, these volumes 11 and 12, referred to as chambers, do not have to be large storage containers, but can also be designed, for example, as tubular extensions of the continuous-flow heater overall tube 10.

In Figures 2 and 3, the entire pipe 10 is flexible and is deformed by a static overpressure in the interior of the pipe; for example, it has the shape of an expandable and compressible spiral or coil spring. FIG. 2 shows the entire pipe 10 in the idle state, in which the pressure in the pipe interior 1 is equal to the external pressure p ₀ . FIG. 3 shows the same overall pipe 10 in the operating state, in which there is a liquid with the pressure p,> p ₀ inside the pipe. Under the influence of the overpressure pj-p ₂ , the overall pipe 10 has the tendency to straighten itself or to reduce its curvature. If at least one of the two chambers 11 or 12, in this example the exit chamber 12, is movably suspended, the arrangement follows this tendency. The change in location of the exit chamber 12 is indicated in FIG. 3 by an arrow 18. As can be seen from FIG. 3, the radius of curvature of the entire pipe 10 increases; the resulting change in shape of the total pipe 10 favors the detachment of lime from the pipe inner walls.

FIGS. 4 and 5 show another arrangement according to the invention, in which a flexible overall tube 10 is deformed by a static overpressure in the interior of the tube. FIG. 4 shows a free-hanging overall pipe 10 in the idle state, in which the pressure inside the pipe 1 is equal to the outside pressure p ₀ . If the entire tube 10 itself has a negligibly small bending stiffness, its shape is largely determined in this idle state the forces acting from the outside, for example determined by the gravitational force F _g . The overall tube 10 takes approximately the shape which minimizes its total potential energy. FIG. 5 shows the same overall pipe 10 in the operating state, in which there is a liquid with the pressure p,> p ₀ inside the pipe. If the overpressure p, -p _{2 is} sufficiently large, for example a few bar, it can considerably increase the bending stiffness of the entire pipe 10. The overall tube 10 then takes on approximately the shape which minimizes the curvatures along the entire tube length. This form in the operating state can differ significantly from that in the idle state; the resulting change in shape favors the detachment of lime from the inner tube walls.

In FIGS. 6 and 7 as well, the entire pipe 10 is deformed by a static overpressure in the pipe interior 1. In this example, however, the tube is elastic and is deformed in the radial direction, so that the decalcifying effect according to the invention also applies to a straight tube, for example. FIG. 6 shows the cross section through the inner tube 2 in the rest state, the insulation layers 3-5 and 7-9 and the heater 6 being omitted for the sake of simplicity. It is assumed that a lime layer 13 had already settled on the inner walls of the pipe during the previous operation. The pressure inside the pipe 1 is equal to the outside pressure p ₀ ; the pipe diameter is d ₀ . Figure 7 shows the same tube 2 in the operating state. A pressure p,> p _{0 is} built up in the liquid inside the tube 1. The overpressure p, - p ₀ causes the inner tube diameter to increase to d,> d ₀ ; the lime layer 13 detaches from the inner walls of the pipe and crumbles into small pieces which can be transported away by the liquid. In contrast to the static pipe deformations discussed above, FIGS. 8 and 9 illustrate a dynamic pipe deformation according to the invention using an exemplary embodiment. FIG. 8 shows a flexible overall pipe 10 in the idle state. Inlet chamber 11, outlet chamber 12 and overall tube 10 can be arranged practically as desired; the only condition to be fulfilled by the arrangement is that the total pipe length 1 must be greater than the distance a between the inlet and outlet chamber. During start-up, a pump, for example in the inlet chamber 11, begins to build up a pressure p,> p ₀ in the interior of the pipe, so that a pressure front begins to run from the inlet chamber 11 to the outlet chamber 12. FIG. 9 is a snapshot shortly after commissioning. In front of the pressure front at location D, the total pipe 10 has a low bending stiffness, while the excess pressure p, - p ₀ stiffens the overall pipe behind the location D and tries to minimize its curvature. Therefore, a wave hump spreads from the input chamber 11 towards the output chamber 12. At the location of the wave hump, the pipe is strongly accelerated and deformed, which results in limescale detachment from the pipe inner walls.

A further embodiment of the invention with a flexible overall tube is shown in FIGS. 10 and 11. FIG. 10 shows the inlet chamber 11, the entire pipe 10 and the outlet chamber 12 in their normal position. Two important prerequisites are that firstly the length 1 of the entire pipe 10 is greater than the distance a ₀ between the inlet chamber 11 and outlet chamber 12 and secondly that the inlet or outlet chamber can be removed from its normal position; otherwise there are no special requirements for the arrangement. If, as shown in FIG. 11, one of the two chambers, for example the exit chamber 12, is brought out of its normal position by an external force F, the overall pipe 10 assumes a different shape than in the normal position. In the example of Fig. 11, the force increases F the distance between the inlet chamber 11 and the outlet chamber 12 from a ₀ to a,> a ₀ , so that the curvature along the total pipe length becomes smaller. Such movement and / or deformation of the entire pipe 10 also prevents pipe calcification. This embodiment is motivated by the use of the instantaneous water heater according to the invention in a coffee machine, where the coffee goods in the brewing chamber 12 have to be replaced after each coffee preparation; for this purpose the brewing chamber 12 is embedded in a movable part which can be pulled out of the coffee machine.

FIG. 12 shows a further dynamic mechanism according to the invention, which counteracts pipe calcification. In this embodiment, the entire tube 10 can also be rigid; it is moved by external forces. Movements of the entire pipe 10 are caused by a pump 14 located in the inlet chamber 11, for example. The shape of the entire tube 10 is immaterial in this embodiment. The pump 14 should be movable or suspended and vibrate during operation, as is the case, for example, with a diaphragm pump. It transmits its vibrations, the direction of which is indicated by an arrow, for example, to the entire pipe 10. The accelerations thus imposed on the entire pipe 10 prevent pipe calcification or promote the limescale detachment from the inner pipe walls.

The instantaneous water heater according to the invention can be equipped with a control circuit which ensures that the liquid at the pipe end has the desired temperature. Figures 13 and 14 show two variants with control loop. The pipe 15 is shown here without details; it is wrapped with a heating wire 6. A temperature sensor 16 measures the tube temperature T at the end of the tube 15. In another embodiment, the temperature of the liquid itself could also be measured at the end of the tube 15 or in the exit chamber 12. In the arrangement of FIG. 13, the measured temperature T is a controlled variable for the heating power P ,, generated by a heating current source 17. The pump 14 conveys a time-constant liquid flow Φ from the inlet chamber 11 into the outlet chamber 12.

In contrast, in the arrangement of FIG. 14, the heating power P _{π is} constant over time and the liquid flow Φ is variable, ie the temperature T is the controlled variable for the pump power. This variant could prove to be superior to that of FIG. 13. A time-varying liquid flow Φ can cause turbulence in the liquid and thus ensure more uniform heating of the liquid and better heat transfer. In a further embodiment, both the heating power P _M and the liquid flow Φ can be regulated simultaneously.

In summary, the instantaneous water heater according to the invention consists of an overall pipe 10 through which liquid can flow and a heat source. The entire tube 10 is supported in a floating manner such that it can be moved and / or deformed by an internal overpressure p, -p ₀ and / or by external forces F. The movements and / or deformations cause undesired precipitation products 13 to detach from the inner tube walls. The invention was stimulated by the need for a non-calcifying flow heater for water in coffee machines.

Claims

PATENT CLAIMS

1. Continuous-flow heater, consisting of an overall pipe (10) through which liquid can flow and a heat source (6), characterized in that, in order to avoid deposits (13) in the inside of the pipe, the entire pipe (10) is floating so that it is supported by a internal overpressure (p, - p ₀ ) and / or can be moved and / or deformed by external forces (F).

2. instantaneous water heater according to claim 1, characterized in that the entire tube (10) is elastic and radially and / or axially expandable by internal overpressure (p, - p ₀ ) or by external forces (F).

3. instantaneous water heater according to claim 1, characterized in that the entire tube (10) is flexible and movable by internal overpressure (p, - p ₀ ) or by external forces (F).

4. instantaneous water heater according to claim 1, characterized in that the overall tube (10) is rigid and can be moved by external forces (F).

5. water heater according to claim 4, characterized in that the entire tube (10) can be excited to vibrate by external forces (F).

6. instantaneous water heater according to claim 5, characterized in that the entire tube (10) is connected directly to a movably or overhung pump (14), the vibrations of which can be transmitted to the tube during operation.

7. instantaneous water heater according to one of claims 1-6, characterized gekennzeich¬ net that the entire tube (10) has the shape of an expandable and compressible spiral or coil spring.

8. water heater according to claim 1, characterized in that the heat source (6) is an electric heater.

9. instantaneous water heater according to claim 8, characterized in that the entire tube (10) from an inner tube (2), at least one Isolations¬ layer (3-5), at least one electrical heating wire (6) with a small heat capacity and at least one outer insulation layer ( 7-9).

10. instantaneous heater according to one of claims 1-9, characterized gekennzeich¬ net that it has a control circuit and a temperature sensor (16) at the end of the tube (15) or in the outlet chamber (12).

11. Continuous-flow heater according to claim 10, characterized in that the temperature (T) measured by the temperature sensor (16) is the controlled variable for the heating power (P _H ).

12. Continuous-flow heater according to claim 10 or 11, characterized in that the temperature (T) measured by the temperature sensor (16) is the control variable for the output of the pump (14).

13. instantaneous water heater according to claim 9, characterized in that the inner tube (2) consists of aluminum or another metal.

14. instantaneous water heater according to claim 9, characterized in that the inner tube (2) consists of thermally resistant plastic.

15. instantaneous water heater according to claim 9, characterized in that the insulation layers (3-5, 7-9) consist of at least one electrically isolating, the thermally resistant material.

16. instantaneous water heater according to claim 9, characterized in that the heating wire (6) consists of a NiCr alloy.

17. Use of the water heater according to one of claims 1-16 in a coffee machine with a water storage chamber (11) and one

Brewing chamber (12), characterized in that the overall pipe (10) connects the water storage chamber to the brewing chamber.

18. Use of the water heater according to claim 17, characterized gekenn¬ characterized in that in the coffee machine, the entire tube (10) is attached directly to the brewing chamber (12) and is moved and / or deformed when the brewing chamber is opened.