GB2377483A

GB2377483A - Steam generator for a cooking device

Info

Publication number: GB2377483A
Application number: GB0204512A
Authority: GB
Inventors: Peter Kohlstrung; Peter Wiedemann
Original assignee: Rational AG
Current assignee: Rational AG
Priority date: 2001-02-26
Filing date: 2002-02-26
Publication date: 2003-01-15
Anticipated expiration: 2022-02-26
Also published as: GB2377483B; FR2821658A1; DE10109251C1; GB0204512D0; FR2821658B1; ITMI20020377A1; ITMI20020377A0

Abstract

The generator 1 has a boiler chamber 2 with a frusto-conical wall 3 that diverges toward a base 15. A heating device, such as an electrical coil 7, is used to heat the water 4 externally from the chamber. The heating may alternatively be provided by hot combustion gases or by induction. A water inlet 5 supplies water to the bottom of the chamber which also forms a pump sump. The evaporated water, together with entrained water, exits via a steam outlet 8. The entrained water may be removed by a water separator 9 before it is returned to the boiler chamber via a pump 11 and pipe 12. The internal surface of the boiler chamber wall 3 may have a glass, ceramic, or metal surface. A soil-resistant pump 17 may be provided to allow removal of boiler scale 13 and 14.

Description

The invention relates to a steam generator, particularly for a cooking

device, comprising a boiler inner chamber to receive water, said boiler inner chamber being defined by boiler walls and a boiler base, a water inlet to the boiler inner chamber, a water outlet from the boiler inner chamber, a heating device for evaporating water from the boiler inner chamber and a steam outlet for the evaporated water.

Numerous steam generators of this kind are known from the prior art wherein the water is heated and

evaporated by heating elements inside the boiler housing. For example, DE 199 12 444 discloses a steam generator for a cooking device such as a table or upright unit operating with hot air and/or hot steam. The known steam generator comprises a boiler inner chamber for water for evaporation and contains heating elements inter alla. Changes in the boiler inner chamber filling volume due to limescale deposits are monitored to show when descaling is necessary and/or for descaling to be carried out automatically as soon as necessary.

The disadvantage of the generic steam generator is that it occupies a large volume within the cooking device. If this volume is reduced by reducing the boiler inner chamber base area then, given a constant quantity of steam generated, this results in the disadvantage that the speed of the steam

through the surface of the water increases and thus water droplets are increasingly entrained together with the ascending steam. Also, a base area reduction of this kind results in accelerated scale formation since the heating elements must be closer together to-ensure adequate heat transfer to the water. The object of the present invention, therefore, is so to develop the generic steam generator as to overcome the disadvantages of the prior art,

particularly by reducing the volume of the steam generator and hence the space required in the cooking device without water increasingly reaching the cooking chamber, while in addition the rate and extent of limescale formation are reduced and easy removal of lime residues in the form of boiler scale on the boiler walls is rendered possible.

According to the invention, to this end, the boiler walls are treatable from outside, the boiler walls are constructed to diverge from one another towards the boiler base and the boiler base forras a pump sump.

According to one feature of the invention the boiler walls may be of conical or frusto-pyramidal construction. According to another proposal of the invention the boiler walls facing the boiler inner chamber have a

c i -3 smooth surface, preferably comprising glass' ceramic or metal.

According to another feature of the invention the boiler walls may be treatable by way of hot combustion gases, inductively or electrically.

According to another proposal of the invention the boiler walls are electrically treatable by way of heating resistances, the latter preferably comprising heating filaments wound around the boiler walls or printed circuits applied by th ck-film technology. Preferably, according to the invention, a water separator is disposed between the steam outlet and a return to the boiler inner chamber.

According to another feature of the invention the water separator may comprise a cyclone, a baffle plate or a swirl nozzle.

According to another feature of the invention a first pump may be disposed between the water separator and the boiler inner chamber. This is necessary is the geodetic height difference between the water separator and the entry point of the return to the boiler inner chamber is such that separated water cannot flow into the boiler inner chamber by gravity.

According to the invention, a second soiling-

resistant pump is disposed between the boiler base and the outlet.

According to another proposal of the invention the second pump comprises a comminuting device, more particularly for boiler scale.

Further features and advantages of the invention will be apparent from the following description in

which one exemplified embodiment of the invention is explained in detail with reference to a diagrammatic drawing. The drawing, which comprises a single Figure, is a longitudinal section of a steam generator according to the invention.

As shown in the drawing, a steam generator 1 according to the invention comprises a boiler inner chamber 2 having a frusto-conical boiler wall to receive water 4 which can be supplied via a water inlet 5 up to a water level 6. The water 4 is treatable and ultimately evaporatable by means of heating elements 7 which are wound around the boiler wall 3. The steam thus generated, together with entrained water, leaves the boiler inner chamber 3 through a steam outlet 8, the entrained water being separated in a water separator 9, for example in the form of a cyclone, before the steam can reach a cooking chamber (not shown) via a connection 10.

The water separated in the water separator 9 is returned to the boiler inner chamber 2 by means of a pump 11 and via a return 12..

Since water, as already stated is partially entrained with generated steam it at least temporarily adheres to the boiler walls 3 and evaporates from there, and this may lead to the formation of boiler scale 13. The boiler walls 3 are preferably made from ceramic in order to have a very smooth surface, to effect a continuous detachment of boiler scale 13 due to mechanical stresses caused by different thermal expansion between the boiler walls 3 and the boiler scale 13.

Also, because of the frusto-conical shape of the Doiler walls 3 the boiler scale 13 can unobstructedly drop by gravity into the water 4.

The boiler scale 14 thus removed collects on the boiler base 15, which is preferably constructed in the form of a pump sump.

When a relatively large quantity of boiler scale 14 has accumulated on the boiler base 15, the water 4 together with the boiler scale 14 can be disposed of via an outlet 16 and via a soiling-resistant draining pump 17, which comminutes the accumulating boiler scale 14 and thus forms a slurry, and then to an outlet lD for disposal.

Thus a steam generator is provided in simple manner according to the invention and occupies a small volume in a cooking device, guarantees reduced lime scaling and prevents water from directly entering the cooking chamber.

"I

The features of the invention as disclosed in the foregoing description, in the drawing, and in the

claims may be significant both individually and in any desired combination to embody the invention in its various forms.

List of references 1. Steam generator 2. Boiler inner chamber 3. Boiler wall 4. Water 5. Water inlet 6. Water level 7. Heating filament 8. Steam outlet 9. Water separator 10. Connection to cooking chamber 1 1. Pump 12. Return 13. Boiler scale 14. Detached boiler scale 15. Boiler base 16. Outlet 17. Soil resistant draining pump 16. Outlet

Claims

- Claims

1. steam generator (1), particularly for a cooking device, comprising a boiler inner chamber (2) to receive water (4), said boiler inner chamber being defined by boiler walls (at and a boiler base (15), a water inlet (5) to the boiler inner chamber (2), a water outlet (16 18) from the boiler inner chamber (2}, a heating device (7) for evaporating water (4) from the boiler inner chamber (2) and a steam outlet (8) for the evaporated water (4), characterized in that the boiler walls (3) are treatable from outside, the boiler walls (3) are constructed to diverge from one another towards the boiler base (15) and the boiler base (15) forms a pump sump.

2. A steam generator according to claim 1, characterized in that the boiler walls 13) are of conical or frusto-pyramidal construction.

3 A steam generator according to claim 1 or 2, characterized in that the boiler walls (3) facing the boiler inner chamber (2) have a smooth surface, preferably comprising glass, ceramic or metal.

4. A steam generator according to any one of the preceding claims, characterized in that the boiler walls (3) are treatable by way of hot combustion gases, inductively or electrically.

5. A steam generator according to claim 4, characterized in that the boiler walls (3) are electrically treatable by way of heating resistances, the latter preferably comprising heating filaments (7) wound around the boiler walls (3) or printed circuits applied by thick-film technology.

6. A steam generator according to any one of the preceding claims, characterized by a water separator (9) disposed between the steam outlet (8) and a return (12) to the boiler inner chamber (21.

7. A Steen generator according to claim 6, characterized in that the water separator (9) comprises a cyclone, a baffle plate or a swirl nozzle.

8. A steam generator according to claim 6 or 7, charactertsed by a first pump (11) between the water separator (9) and the boiler inner chamber (2) .

9. A steam generator according to any one of the preceding claims, characterized by a second soiling-

resistant pump (17) between the boiler base and the outlet (18).

10. A steam generator according to claim 9, characterized in that the second pump (17) comprises a comminuting device, more particularly for boiler scale (13, 14).