Instantaneous water heater

Details Instantaneous water heater Instantaneous water heater

1998-01-29

2001-02-20

Walberg, Teresa (Department: 3742)

Electric resistance heating devices

Heating devices

Continuous flow type fluid heater

C392S481000, C392S466000, C165S085000

Reexamination Certificate

active

06192192

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a continuous flow heater which is particularly useful for heating water in coffee machines, the heater including a pipe which is moved or deformed to prevent or remove scale formed on the inner walls of the pipe.
BACKGROUND OF THE INVENTION
Devices for heating liquids in pipes or tubes are, e.g., described in the following patents: EP 82 025, GB-2 181 628, U.S. Pat. No. 4,156,127 and U.S. Pat. No. 4,038,519. An important disadvantage of such continuous flow heaters is their contamination by the precipitation of substances dissolved in the liquid. As is known, solubility is highly temperature-dependent. If the temperature of a solution in a pipe is increased, the solubility can be reduced. The dissolved substances are precipitated and are deposited on the pipe inner walls. This leads to pipe narrowing and, in the worst case, to pipe blockage. Thus, e.g., tap water used for coffee preparation contains more or less depositable fractions as a function of the geographical location and these fractions are hereinafter referred to as “scale”. When tap water is heated from approximately 20° C. or ambient temperature to approximately 95° C. or boiling temperature, scale is precipitated from the liquid and deposited on the pipe inner walls. Pronounced scaling can be observed from about 60° C.
The pipe scaling problem makes more difficult, or prevents in many cases, the use of continuous flow heaters for heating tap water. Pipes for such continuous flow heaters must be regularly and relatively frequently descaled or replaced, which would give rise to undesired interruptions to operation, as well as labor and material costs. Therefore, e.g., in conventional coffee machines, the water is heated with a solid electrical heating unit at the outlet from a water storage chamber. The hot water first flows through a riser into a boiling chamber, then through the coffee in the boiling chamber and finally through a filter into the coffee jug. For energy saving and time reasons, it is inappropriate to heat the electrical heating unit for preparing a single coffee serving. The solid electrical heating unit of conventional coffee machines has a high heat capacity and a relatively small heating surface, so that high thermal energy must be supplied to it in order to heat it and the heating of the solid unit and the water takes a long time, typically longer than 45 sec.
SUMMARY OF THE INVENTION
An object of the invention is to provide a continuous flow heater device to heat liquids in a pipe to a desired temperature, while avoiding, cancelling out without additional labor and material costs, rendering difficult or slowing down deposit of solid precipitation products on the pipe inner walls. The device can be manufactured using known methods and can be used in known applications, e.g., a coffee machine, without modifying the fundamental sequences of the applications.
Using a continuous flow heater, if solid precipitation products from the heated liquid are deposited on the inner wall of the inventive continuous flow heater, after a short time they are at least partly detached again and carried away by the liquid. Thus, the continuous flow heater according to the invention is either not subject, or is more slowly subject, to scale than known continuous flow heaters and can, e.g., be used in coffee machines.
The detachment of scale such as lime is brought about by movements and/or deformations of the continuous flow heater pipe. It is assumed that over all or part of its length the pipe is mounted in a floating manner. A layer of scale or other solid precipitation products is relatively rigid, brittle and friable. If the continuous flow heater pipe is adequately moved and/or deformed, the layer is at least partly detached from the pipe inner walls and crumbles into small fragments, which are carried away by the liquid.
The movements and/or deformations of the continuous flow heater can fundamentally be ensured by three different embodiments of the pipe. First, the pipe can be elastic and can be radially and/or axially expanded by an overpressure in the pipe interior. Second, the pipe can be flexible and moved by an external force, at at least one of its ends. Third, the pipe can be rigid and moved by an external force, e.g., it can be made to vibrate by a vibrating pump. In these embodiments, distinctions can also be made between static and dynamic operations.


REFERENCES:
patent: 3921708 (1975-11-01), Brenner
patent: 4032748 (1977-06-01), Vischer et al.
patent: 4184064 (1980-01-01), Williams
patent: 4667084 (1987-05-01), Regge
patent: 4778105 (1988-10-01), Cholkeri et al.
patent: 5022557 (1991-06-01), Turner
patent: 5381511 (1995-01-01), Bahar et al.
patent: 5575262 (1996-11-01), Rohde
patent: 176 206 (1906-10-01), None
patent: 606 028 (1934-11-01), None
patent: 44 31 980 (1995-03-01), None
patent: 518 787 (1992-12-01), None
patent: 2 184 928 (1987-07-01), None

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