EP3714094B1

EP3714094B1 - Steam generation system for use in household appliance

Info

Publication number: EP3714094B1
Application number: EP18825781.0A
Authority: EP
Inventors: Federico ZOPPAS; Maurizio Biasi; Giuliano ZANETTE; Otello TAFFAREL; Giacomo DURIGON
Original assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Current assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Priority date: 2017-11-23
Filing date: 2018-11-23
Publication date: 2023-01-11
Anticipated expiration: 2038-11-23
Also published as: WO2019102407A1; EP3714094A1; PL3714094T3

Description

Field of the invention

The present invention relates to a steam generation system with possibility of dosing the amount of steam. The steam generation system is particularly adapted to be used in a household appliance, e.g. a tumble dryer or a domestic oven with steam cycle.

Background art

Steam generation systems, e.g. for tumble dryers, often use a pump for feeding, dosing a flow of water, an electric heater. The electric heater converts the water into steam, which is then introduced into the basket of the tumble dryer according to the intended cycle. In particular in household appliances, such as tumble dryers, dosing the steam is an important requirement in order to ensure a successful steam cycle with a result appreciated by users.
Using a pump in a steam generation system offers advantages because it allows accurate dosing of the water flow introduced into the heater. However, the pump is an expensive and delicate device.
Therefore, the need is felt to find a steam generation system solution which also allows dosing water, and thus steam, which is cost-effective to manufacture. US2013091647A1 discloses a steam mop equipped with a check valve installed on the water feeding tube.

Summary of the invention

It is an object of the present invention to provide a steam generation system which overcomes the drawbacks mentioned above and which offers an accurate dosing capacity at a low cost.
It is another object of the present invention to provide a steam generation system which is constructionally simple.
Therefore, the present invention aims to achieve at least one of such objects by providing a steam generation system according to claim 1.
In particular, the steam generator comprises means for generating such a counterpressure, which either comprise or are said choke and/or said pipe made with said ratio, for example.
In a non-limiting example, a choke of the steam outlet pipe may be provided, having for example a section area, in particular a minimum section area, from 0.78 mm² to 78 mm², so as to have a concentrated loss of load.
In another non-limiting example, a pipe for the passage of fluid is provided, comprising said outlet pipe of the steam generator which has a length-to-inner diameter ratio from 50 to 500 and/or an inner diameter from 3 mm to 15 mm. Preferably, such a pipe is a pipe of a thermal block, preferably a serpentine pipe.
In general, it is preferred that the steam generator has a maximum power from 350 W to 3500 W, preferably from 700 W to 1750 W.
The invention also comprises a method of operating such a steam generation system according to claim 8.
Advantageously, during the steam generating step, in particular during said step c), the amount of water in the steam generator is self-adjusted.
The invention also comprises an electric household appliance, in particular a tumble dryer or an oven, provided with a steam generation system as defined above.
It is worth noting that the ranges indicated in the present description also preferably comprise the extreme values.
Further features and advantages of the present invention will become more apparent in light of the detailed description of preferred, but not exclusive embodiments.
The dependent claims describe particular embodiments of the invention.

Brief description of the drawings

The description of the invention refers to the accompanying drawings, which are provided by way of non-limiting example, in which:

Fig. 1 shows a diagram of the hydraulic circuit of an embodiment of a steam generation system according to the present invention in a first operating position;
Fig. 2 shows the diagram in Fig. 1 in a second operating position;
Fig. 3 shows an example of a component which can be inserted into the hydraulic circuit in Fig. 1 and Fig. 2;
Figs. 4A, 4B, 4C show an example of a component of the system according to the invention, under three respective conditions.

Equal reference numerals in the various figures correspond to the same elements or components.

Detailed description of exemplary embodiments of the invention

An embodiment of the steam generation system or evaporation system of the invention is shown in figures 1 and 2.
The steam generation system comprises a tank 1 for a liquid, e.g. water, to be converted into steam by heating; a valve, preferably an intercept valve 5, preferably a two-way and two-position valve; a check valve 15; and a steam generator 3. A pipe can convey the water from the tank 1 to the steam generator 3. The valve 5 is provided along such a pipe. In particular, the valve 5 is arranged between a pipe segment 10, connected to the tank 1, and a pipe segment 12 connected to the steam generator 3.
In the steam generator 3, or evaporator, the water is evaporated by taking it to its evaporation temperature by means of one or more heating elements inserted into the evaporator 3 or otherwise arranged so as to transfer the heat energy to the water. A pipe 13 makes the steam exit from the evaporator 3 towards the space where the steam must be used, e.g. a basket of a tumble dryer or the cooking space of a food cooking oven.
The valve 5 can either interrupt or put into communication the two pipe segments 10 and 12 as a function of its position. In particular, the pipe segment 10 and the pipe segment 12 are alternately put into communication and interrupted by the valve 5 as a function of the position taken by the latter. The check valve 15, also referred to as a non-return valve or one-way valve, is provided along the pipe segment 12, before the engagement of the pipe segment 12 in the evaporator 3.
Preferably, the check valve 15 is configured so that under static conditions, in particular in the absence of the pressure applied by the liquid coming from the tank 1, the check valve 15 is always closed, in particular irrespective of the force of gravity. Preferably, for this purpose, there are provided closing means, preferably elastic means, which are adapted to keep the valve closed under static conditions. Preferably, the check valve 15 can only open because of the opening pressure applied by the liquid coming from the tank 1, which, in particular, is greater than the force applied by said closing means.
Preferably, a second choke 14 is also provided upstream of the one-way valve 15 along the pipe segment 12.
The operating cycle of the steam generation system is as follows. When the valve 5 is in the closing position (Fig. 1, step F1), the steam generator 3 is heated until the operating temperature is reached by the heating means, which are known per se in this technical field. In the next step F2, shown in figure 2, the valve 5 is arranged in opening position thus putting into communication the pipe segment 10 with the pipe segment 12, whereby the water flows from the tank 1 to the steam generator 3, preferably by gravity, preferably only by gravity. The valve 5 remains in this opening position for the entire duration of the steam generating step. The valve 5 is then arranged back in the closing position, whereby the communication between the pipe segments 10 and 12 is interrupted. The heating of the steam generator 3 is then interrupted preferably with a delay with respect to the closing of the valve 5. The delay in the interruption of the heating can be a fixed time or based on reaching a temperature higher than the operating temperature, e.g. by using a thermostat, not shown in the figures. This delay has the purpose of ensuring that the steam generator 3 does not contain water in the liquid state at the end of cycle.
In this embodiment of the invention, the operating dynamic during the steam generating step provides for the water to flow from the tank 1 to the steam generator 3, which is already at operating temperature because it is preheated by passing through the choke 14 (when provided), which acts as a water flow rate limiter, and through the one-way valve 15. The one-way valve 15 is opened by the pressure applied by the water, also referred to as an opening pressure.
When a given amount of water which has reached the steam generator 3 is evaporated, the steam inside the steam generator 3 creates a counterpressure which closes the one-way valve 15, which will block the flow of the water toward the steam generator 3. The water flow will remain blocked until the counterpressure is reduced upon the exit of the steam present in the steam generator 3 through the pipe 13. As the counterpressure reduces, the one-way valve 15 reopens, thus making the water flow again from the tank 1 to the steam generator 3. The process is repeated as above until the intercept valve 5 remains open.
By way of non-limiting example, Fig. 4A, 4B, 4C show an example of one-way valve 15 (or check valve), under three respective conditions of the steam generation system.
The one-way valve 15 comprises a movable element 151, e.g. a piston, having a head 152 and a stem 153.
The one-way valve 15 also comprises an abutment wall 154 and a guide body 155. The abutment wall 154 is preferably annular, and defines an opening.
The movable element 151, in particular the stem 153 thereof, is at least partially inserted into the guide body 155.
Closing means 156, e.g. elastic closing means such as a spring, are preferably provided between the movable element 151 and the guide body 155.
The movable element 151, e.g. the stem 153 thereof, is preferably constrained to the guide body 155 by said closing means 156.
Under static conditions (Fig. 4A), in particular in the absence of opening pressure applied by the liquid coming from the tank 1, the movable element 151, in particular the head 152 thereof, abuts against the abutment wall 154, thus closing the opening delimited by the abutment wall 154. Therefore, the one-way valve 15 is closed, in particular sealingly closed. The closing means 156, when provided, apply a closing force to keep the one-way valve 15 closed.
With reference to Fig. 4B, when the liquid coming from the tank 1 applies an opening pressure (diagrammatically shown by arrow "P") which is greater than said closing force, the movable element 151 slides along an axis, whereby it separates from the abutment wall 154 and the one-way valve 15 opens, thus allowing a flow of liquid therethrough.
With reference to Fig. 4C, when the aforesaid counterpressure (diagrammatically shown by arrow "CP") being greater than the opening pressure (P) is generated, the one-way valve 15 closes again.
In a variant included in the invention, the choke 14 is optional and in further variants the choke 14 and/or the one-way valve 15, or both elements, can be integrated in the intercept valve 5. In other words, in this variant, a single component performs the functions of intercept valve (e.g. a two-way and two-position valve), choke and/or one-way valve.
Those skilled in the art can appreciate that the use of a steam generator 3 which produces a counterpressure in the pipe segment 12 is provided.
For example, a steam generator 3 capable of generating a counterpressure comprises a choke 16 on the steam outlet pipe 13 so as to obtain a loss of load. Preferably, but not exclusively, in order to generate a counterpressure, the choke 16 has a minimum passage section having a value selected in the range from about 0.78 mm² to about 78 mm², the extreme values being preferably included. For example, when the choke section 16 is of circular shape, the choke has an inner diameter having a value from about 1 mm to about 10 mm.
Another example of steam generator 3 capable of generating a counterpressure provides for the outlet pipe 13 to be sized so as to generate a distributed loss of load and hence an adequate counterpressure. For example, in this case, an outlet pipe 13 may be provided, having a length-to-inner diameter ratio having a value selected in the range from 50 to 500 or from 50 to 300, the extreme values being preferably included.
Another example of steam generator 3 capable of generating a counterpressure either comprises or consists of a thermal block (also referred to as a heat block or block).
Indeed, a thermal block comprises a pipe, preferably a serpentine pipe, in which the water flows, thus causing a distributed loss of load.
Preferably, the steam generator 3 either comprises or consists of a thermal block 103 (Fig. 3) which, according to a non-limiting example, comprises:

a block 120, or outer body, preferably a solid block made of a mass of heat conducting material, e.g. aluminum;
a pipe 122, preferably made of metal, e.g. steel, for the passage of the liquid to be heated;
at least one resistive element, e.g. a sheathed resistance 124.

The pipe 122 and the sheathed resistance 124 are arranged in the block 120. The ends of the pipe 122, which define an inlet opening and an outlet opening for the fluid, respectively, protrude from the block 120. The ends of the sheathed resistance 124 also protrude from the block 120, so as to be connected to an electric power source. When the sheathed resistance 124 is heated by Joule effect, the heat is transferred by conduction to the block 120 and pipe 122, so that the fluid therein is heated.
The pipe 122 preferably comprises at least one bent portion, e.g. bent so as to form a serpentine. Preferably, but not exclusively, the pipe 122 has at least one corrugated, i.e. non-smooth, segment. In particular, the corrugated segment has inner protrusions or surface irregularities.
Preferably, but not exclusively, the pipe 122 has a length-to-inner diameter ratio having a value selected in the range from 50 to 500, or from 50 to 300 (the extreme values being preferably included), and/or an inner diameter having a value selected in the range from 3 mm to 15 mm, e.g. from 5.1 to 10 mm (the extreme values being preferably included).
The outlet pipe 13 preferably forms part of said pipe 122, i.e. the pipe 122 comprises said outlet pipe 13.
Preferably but not exclusively, in all variants, the steam generator has a maximum power from 350 W to 3500 W, preferably from 700 W to 1750 W.
In general, the choke 14 and the choke 16 may be a restriction or choking element, of the corresponding pipe or a component arranged along the corresponding pipe.
The steam generation system is controlled by a control device (not shown) which actuates the valve 5 as a function of the amount of water which must be transformed into steam and other factors known to those skilled in the art in the field of household appliances.
Advantageously, a steam generation system according to the invention, preferably by using only two valves, adequately doses an amount of water in a simple and cost-effective manner, and according to adequate modes and amounts for use in major household appliances, for example but not exclusively ovens, tumble dryers, washing machines and dishwashers.
According to an aspect, the invention further comprises an electric household appliance comprising a steam generation system according to the invention.
In particular, according to an aspect, the invention further comprises a household tumble dryer (not shown) comprising a space for the laundry to be dried, e.g. a basket, and a steam generation system, in which the steam generator 3 is connected to the laundry space by means of the pipe 13, whereby the steam generated by the steam generator 3 can be introduced into the laundry space.
According to another aspect, the invention further comprises a household oven (not shown) comprising a space for cooking food, wherein the steam generator 3 is connected to said space by means of the pipe 13, whereby the steam generated by the steam generator 3 is adapted to be introduced into said space.

Claims

A steam generation system for a household appliance, comprising:
- a tank (1) adapted to contain a liquid to be heated to generate steam:

- a steam generator (3) arranged downstream of the tank (1);

- a pipe (10, 12) which connects the tank (1) to the steam generator (3);

- a valve (5) arranged along the pipe (10, 12) and having an opening position, in which it allows the passage of liquid from the tank (1) to the steam generator (3), and a closing position, in which it closes the passage of liquid from the tank (1) to the steam generator (3);

- a check valve (15) arranged along the pipe (10, 12) and adapted to allow the passage of liquid only towards the steam generator (3);

wherein the steam generator (3) is configured to generate a counterpressure adapted to close the check valve (15) and

wherein a steam outlet pipe (13) is provided

characterized in that, in order to generate said counterpressure, a choke (16) is provided along the steam outlet pipe (13) and/or the steam outlet pipe (13) has a length-to-inner diameter ratio from 50 to 500.
A steam generation system according to claim 1, wherein the valve (5) is an intercept valve, preferably a two-position valve, preferably with two ways and two positions.
A steam generation system according to any one of the preceding claims, wherein the check valve (15) is either arranged downstream of the valve (5) or is integrated in the valve (5).
A steam generation system according to any one of the preceding claims, wherein a second choke (14) is provided either along the pipe (10, 12), preferably downstream of the valve (5) and upstream of the check valve (15) or integrated in the valve (5).
A steam generation system according to any one of the preceding claims, wherein said steam outlet pipe (13) is at least partially arranged inside the steam generator (3).
A steam generation system according to claim 5, wherein the steam generator (3) comprises a thermal block (103) having a pipe (122), preferably a serpentine pipe, and at least one resistor (124); wherein said steam outlet pipe (13) is part of said pipe (122).
A steam generation system according to claim 6, wherein said pipe (122) and said at least one resistor (124) are at least partially arranged inside a block (120) of the thermal block (103).
A method of operating a steam generation system for a household appliance according to any one of the preceding claims, wherein the following steps are included:
a) providing a liquid in the tank (1), the valve (5) in the closing position and a heating of the steam generator (3) to a temperature adapted to generate steam;

b) arranging the valve (5) in the opening position to allow the liquid to exit from the tank (1) and apply an opening pressure which opens the check valve (15) so that said liquid enters into the steam generator (3);

c) generating steam by means of said steam generator (3), whereby the check valve (15) remains open until the opening pressure is higher than a counterpressure gradually generated by the steam inside the steam generator (3), while the check valve (15) closes when said counterpressure is higher than said opening pressure.
A method according to claim 8, wherein after step c) the valve (5) is arranged in said closing position and, after a predetermined time, the heating of the steam generator (3) is interrupted.
A household appliance comprising a steam generation system according to any one of the claims from 1 to 7.
A household appliance according to claim 10, wherein the household appliance is a tumble dryer comprising a space for the laundry to be dried, and wherein the steam generator (3) is connected to said space by means of an outlet pipe (13), so that the steam generated by the steam generator (3) is adapted to be introduced into said space;
or wherein the household appliance is an oven comprising a space for cooking food, wherein the steam generator (3) is connected to said space by means of an outlet pipe (13), whereby the steam generated by the steam generator (3) is adapted to be introduced into said space.