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(11) | EP 1 479 970 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Boiler to generate steam in domestic appliances and professional machines, such as ironing or cleaning apparatuses or suchlike |
| (57) Boiler to generate steam in domestic appliances and professional machines, such as
ironing or cleaning apparatuses or suchlike, comprising a container (12) able to contain
water and connected to feed means (38) able to introduce water inside the container
(12), and at least a heat generator (14) to heat the water inside the container (12)
and transform it into steam. A water circuit (16), arranged outside the container
(12), communicates therewith, so that the same water level (L) present in the container
(12) is established in the water circuit (16). Sensor means (18) are associated with
the water circuit (16) in correspondence with a pre-determined level (S) and are connected
to at least the feed means (38). The sensor means (18) are of the capacitive type
and are able to detect at least the presence of the water, in correspondence with
the pre-determined level (S), in order to command the feed means (38). |
FIELD OF THE INVENTION
[0001] The present invention concerns a boiler to generate steam in domestic appliances and professional machines, such as for example ironing or cleaning apparatuses or suchlike, comprising a container inside which water is able to be introduced by means of a feed pump. An outer water circuit communicates with the container, so that, according to the principle of communicating vessels, the same water level is established therein as in the container. A level sensor of the capacitive type is connected to the water circuit in order to detect the presence of the water in correspondence with a pre-determined threshold level. The sensor is connected to the feed pump so as to regulate, according to the level, the flow of water inside the container.
BACKGROUND OF THE INVENTION
[0002] A boiler is known that generates steam in domestic appliances, comprising a metal container into which water is automatically fed by means of a pump that pumps water from an outer tank, not under pressure.
[0003] The level in the boiler is managed by means of a metal sensor arranged vertically inside the boiler and electrically insulated both from the boiler and from the earth circuit connected thereto.
[0004] When the water level inside the boiler touches the metal sensor, the electric circuit is closed with respect to the earth circuit. The electronic module that manages the level thus stops the feed pump of the boiler.
[0005] On the contrary, when continuity in the electric circuit is interrupted, following a reduction in the water level, the pump is activated.
[0006] A first disadvantage of the known boiler is that, when it is not immersed in the water, the metal sensor is affected by the conductivity of the steam which is in the metal container, so much so that the detection of the water level can be quite imprecise and the electric circuit can close even when the water has not reached the pre-determined level.
[0007] Another disadvantage of the known boiler is that the metal sensor is also subject to possible calcium deposits, which can distort the measurement of the level.
[0008] Another disadvantage of the known boiler is that the metal sensor is housed in a through hole made in the wall of the metal container. Sealing washers and insulating elements must therefore necessarily be interposed between the metal sensor and the wall of the container in order to prevent dispersions of electricity and losses of water. The known boiler therefore requires a plurality of working steps, both to make the hole where the metal sensor is housed, and also for the relative positioning, insulation and attachment. For example, it is necessary to make at least a hollow pipe, surrounding the metal sensor, in which the water of the boiler is conveyed to prevent a false measurement of the level being made, in the case of possible oscillations of the water inside the tank.
[0009] Applicant has devised and embodied the present invention in order to overcome these shortcomings of the state of the art and to obtain other advantages.
SUMMARY OF THE INVENTION
[0010] The present invention is set forth and characterized essentially in the main claim, while the dependent claims describe other innovative features of the invention.
[0011] One purpose of the invention is to achieve a boiler to generate steam by means of which it is possible to detect, sensitively, accurately, simply and immediately, the water level in correspondence with a determinate threshold.
[0012] Another purpose of the present invention is to achieve a boiler provided with a level sensor that can easily be installed in the boiler and removed from the boiler itself.
[0013] In accordance with these purposes, a boiler to generate steam in domestic appliances and professional machines according to the present invention comprises a container able to contain water and connected to feed means able to introduce water inside the container, and at least a heat generator to heat the water inside the container and transform it into steam. A water circuit is arranged outside the container and communicates therewith, so that the same water level as is present in the container is established in the outer water circuit. Sensor means are associated with the water circuit in correspondence with a pre-determined threshold level and are connected at least to the feed means. According to the main characteristic of the present invention, the sensor means are of the capacitive type and are able to detect at least the presence of the water, in correspondence with said pre-determined level, in order to command the afore-said feed means.
[0014] The capacitive-type sensor means comprise a condenser consisting of an element conducting electric current, such as a ring, a bar or otherwise, which forms the first plate, and is directly associated with an outer wall of the water circuit. Advantageously, the water itself constitutes the second plate of the condenser.
[0015] The water circuit comprises, for example, a tubular pipe which starts from the container and is made of insulating material, such as a fluorinated or Teflon resin or similar. The insulating pipe constitutes the dielectric means, interposed between the plates of the condenser.
[0016] When the water level inside the container rises until it reaches the pre-determined threshold level, the electric capacity of the condenser increases, because the distance between the two plates decreases.
[0017] In a preferential form of embodiment, the water circuit comprises a tubular pipe that starts from the container, while the element conducting electric current consists of a metal ring which surrounds, with contact, the tubular pipe. The electrically conductive ring is able to be associated, advantageously from the outside, with the water circuit, without needing to make holes or apertures in the tubular pipe.
[0018] The conductor ring is electrically connected to an electronic control unit associated with a measuring unit to measure the electric capacity. The electronic control unit is connected to other functional elements of the boiler, such as the valve to regulate the outlet of steam and the valve to regulate the introduction of cold water inside the container. When the water level has reached the pre-determined reference level, the electronic control unit blocks the introduction of cold water inside the container.
[0019] According to a variant, the electronic control unit is programmed so as to calculate the water level automatically according to the value of the capacity measured by the measuring unit.
BRIEF DESCRIPTION OF THE DRAWING
[0020] These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawing wherein fig. 1 is a section view of the boiler according to the present invention.
DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT OF THE INVENTION
[0021] With reference to fig. 1, a boiler 10 according to the present invention comprises a hermetically sealed steel container 12, and an electric resistance 14 to heat the water, arranged inside the container 12 and connected to a feeder 15 by means of an electronic control unit 22. A water circuit 16 is arranged outside the container 12 and communicates therewith.
[0022] To be more exact, the water circuit 16 comprises a tubular pipe 19, made of insulating material, such as for example a fluorinated resin, and arranged vertical and parallel to a lateral wall 17 of the container 12. Inside the water circuit 16, due to the principle of communicating vessels, the same water level as is present inside the container 12 is established.
[0023] To prevent signal losses or unwanted capacitive effects, due to connection cables, directly on the outer side of the tubular pipe 19 a capacitive sensor 18 is arranged, which comprises a conductor ring 20, which constitutes the first plate of the condenser and is electrically connected to the electronic control unit 22.
[0024] The water contained inside the tubular pipe 19 constitutes the second plate of the condenser, while the tubular pipe 19 constitutes the dielectric means interposed between the two plates of the capacitive sensor 18.
[0025] The electronic control unit 22 comprises at least a measuring unit 24, of a known type, to measure the capacity, and is electrically connected to the bottom wall 25 of the container 12, and then to an earth circuit, of a known type and not shown in the drawing.
[0026] The electric capacity of the capacitive sensor 18 varies according to the water level, since it is inversely proportionate to the distance between the plates. When the real water level L is in correspondence with a pre-determined theoretical level, or threshold, S, where the conductor ring 20 is arranged, the capacity measured by the measuring unit 24 considerably increases, because the distance between the conductor ring 20 and the water level L considerably decreases.
[0027] The boiler 10 also comprises other components of a known type, such as a pressure switch 28 to control the pressure inside the container 12, a valve 30 by means of which the flow of steam is controlled through a first pipe 32 towards the outside of the boiler 10, and a second pipe 34 connected in a lower zone of the tubular pipe 19.
[0028] According to another variant, not shown in the drawing, the second pipe 34 is connected directly to the container 12.
[0029] Through the second pipe 34, the container 12 is connected to a tank 36, not under pressure, where cold water is contained. By means of a pump 38, the cold water is taken from the tank 36, in a flow regulated by means of a one-way valve 40.
[0030] The electronic control unit 22 is electrically connected to the steam outlet valve 30, the pressure switch 28, the electric resistance 14 and the pump 38.
[0031] When the water level reaches the threshold S, the electronic control unit 22 causes the pump 38 to stop and the one-way valve 40 to close.
[0032] Moreover, when the pressure inside the container 12 has reached an appropriate value, as detected by the pressure switch 28, the electric resistance 14 is switched off.
[0033] One advantage of the capacitive sensor 18 according to the present invention is that, in the water circuit 16, the capacitive-type measurement is not influenced by the steam present in the water circuit 16 and hence the detection of the water level L, in proximity with the threshold S, is highly reliable and precise, since it is not influenced by any non-measurable variable such as for example the conductivity of the steam.
[0034] Another advantage of the boiler 10 according to the invention is that, in the zone where the capacitive sensor 18 is arranged, no calcium deposits are formed due to the heating of the water, because the cold water is introduced directly into the water circuit 16 by means of the pipe 34. Moreover, the cold water, as it rises and descends continuously inside the circuit 16, continuously washes and cleans the inner walls of the tubular pipe 19, thus preventing the formation of calcium or other unwanted deposits.
1. Boiler to generate steam in domestic appliances and professional machines, such as
ironing or cleaning apparatuses or suchlike, comprising a container (12) able to contain
water and connected to feed means (38) able to introduce water inside said container
(12), at least a heat generator (14) to heat said water inside said container (12)
and transform it into steam, a water circuit (16) arranged outside said container
(12) and communicating therewith, so that the same water level (L) present in said
container (12) is established in said water circuit (16), and sensor means (18) associated
with said water circuit (16) in correspondence with a pre-determined level (S) and
connected to at least said feed means (38), characterized in that said sensor means (18) are of the capacitive type and are able to detect at least
the presence of said water, in correspondence with said pre-determined level (S),
in order to command said feed means (38).
2. Boiler as in claim 1, characterized in that said water circuit (16) comprises a pipe (19).
3. Boiler as in claim 1, characterized in that said pipe (19) is of the tubular type.
4. Boiler as in claim 2 or 3, characterized in that said pipe (19) is made of electrically insulating material.
5. Boiler as in claim 2, 3 or 4, characterized in that said pipe (19) is arranged vertical and parallel to a lateral wall (17) of said container
(12).
6. Boiler as in any claim from 2 to 5 inclusive, characterized in that said sensor means (18) comprise an electrically conductive annular element (20).
7. Boiler as in claim 6, characterized in that said annular element (20) is arranged directly in contact with the outside of said
pipe (19), in correspondence with said pre-determined level (S).
8. Boiler as in any claim hereinbefore, characterized in that said sensor means (18) are electrically connected to an electronic control unit (22)
which comprises at least a measuring unit (24) to measure the electric capacity.
9. Boiler as in any claim hereinbefore, characterized in that a cold water introduction pipe (34), connected to said feed means (38), is directly
connected to said water circuit (16) or to said container (12).