WO1997021057A1

WO1997021057A1 - Boiler with fast steam generation

Info

Publication number: WO1997021057A1
Application number: PCT/EP1996/005340
Authority: WO
Inventors: Giuliano Franchini
Original assignee: Giuliano Franchini
Priority date: 1995-12-07
Filing date: 1996-12-02
Publication date: 1997-06-12
Also published as: IT1278873B1; ITVR950097A1; ITVR950097A0; AU1096397A

Abstract

A boiler unit with fast steam generation, comprising a boiler body (2) which accommodates at least one source of heat based on an electric resistor (7), a water reservoir (3), and a pump (4) for feeding water from the reservoir (3) to the boiler. The pump (4) is a metering pump for loading preset and constant quantities of water and has a check valve on its delivery. A device (13) is provided for detecting a preset minimum level of the water contained in the boiler which is adapted to make the pump (4) start when the water in the boiler (2) reaches the preset level.

Description

BOILER WITH FAST STEAM GENERATION Technical Field

The present invention relates to a boiler unit with fast • steam generation, usable for both industrial and household applications. Background Art

In household and industrial appliances requiring the use of steam, such as irons and ironing devices for home and industrial use and steam-using cleaning devices for floors, glass panes, and the like, there is a rising demand for steam sources which instantly deliver significant amounts of steam, so as to minimize waiting times while the steam-using appliances assume their operating condition.

Electric boilers for generating steam with an electric discharge valve and a flow control valve have already been proposed which have a separate reservoir for feeding consumable water, which is fed to the boiler by a pump and an electric valve driven by a control unit.

The amount of water fed each time into the boiler is very small and sufficient to keep the electric evaporation resistors only just submerged, so that the heat energy developed by the resistors is not wasted in heating a large mass of water but is entirely used to cause the very rapid evaporation of a relatively very small amount of water, which is loaded continuously or discontinuously, taking it from the supply reservoir.

The level of the water in the boiler must be measured with highly sensitive devices to perform the necessary replenishment of the water by means of an electric valve, in order to avoid waste of electric power in the absence of water .

Although these boilers have proved themselves satisfactory in some regards, they entail high manufacturing and maintenance costs and therefore have failed to prove themselves truly competitive on the market.

Disclosure of the Invention

A principal aim of the present invention is ro provide a boiler unit with fast steam generation, which is novel in its concept and allows a modest consumption of electric power. Another object of the present invention is to provide a boiler which is very simple in its structure and operation and is capable of favorably competing with conventional boilers providing the same performance.

This aim, these objects, and others which will become apparent hereinafter are achieved by a boiler unit with fast steam generation, comprising a boiler body which accommodates at least one heat source based on an electric resistor, a water reservoir, and a pump for feeding water from the reservoir to the boiler, and is characterized in that said pump is a metering pump for loading preset and constant quantities of water and has a check valve on its delivery, and in that it has a device for detecting a preset minimum level of the water contained in the boiler which is adapted to make the pump start when the water in the boiler reaches said preset minimum level.

Advantageously, the device for detecting the level of the water in the boiler floats on the water in the boiler and shifts as the water level decreases or increases. Brief Description of the Drawings

Further characteristics and advantages of the present invention will become apparent from the following detailed description of some currently preferred embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic view of a first embodiment of the boiler according to the invention; figure 2 is a schematic view of a second embodiment of the boiler according to the invention; figure 3 is a schematic view of a third embodiment of the boiler according to the invention; figure 4 is a schematic view of a fourth embodiment of the boiler according to the invention; and figure 5 is a schematic perspective view of a boiler according to a fifth embodiment of figure 4. Ways of carrying out the Invention

In the above figures, identical or similar parts and components have been designated by the same reference numerals.

Initially with reference to figure 1, it is clearly shown that a boiler unit with fast steam generation 1 , according to the invention, is formed by a boiler body 2, formed for example by three stainless steel shells with a thickness of 1-1.5 mm, by a separate reservoir for storing the reserve of cold water to be fed into the boiler 2, and by a pump 4 for feeding water from the reservoir 3 to the boiler, which is driven by an electric motor, not shown, and has an electronic control board and a check valve on the delivery (also not shown in the drawings). The boiler body 2 is structured so as to internally delimit a preheating chamber 5, which is meant to receive the water supplied by the pump 4, and an evaporation chamber 6, the lower part whereof accommodates one or more electrical resistors 7, preferably of the type provided with a thermostat 8. The chambers 5 and 6 are separated by a fixed heat-conducting (stainless steel) partition 9, which has an opening 10 for the passage of water that is shaped for example like a spillway, in order to always keep a metered amount of water above or adjacent to the steam generation chamber 6 to ensure its preheating before reaching the evaporation chamber 6.

Typically, the preheating chamber 5 can have a volume which is approximately equal to one fifth of the total volume and the chamber 6 can have a volume of approximately 750 cc.

The chamber 5 is connected, at the top, to an end of a supply duct 11, the other end whereof is connected to the delivery of the pump 4, whilst the evaporation chamber 6 can deliver steam through an upper duct 12 which passes through the partition 9 and the preheating chamber 5.

A device 13 for detecting the level of the water contained in the chamber draws from the evaporation chamber 6 and is capable of emitting control signals for the electronic board of the pump 4 so as to activate the pump 4 whenever the level in the evaporation chamber 6 drops below the level at which the resistor or resistors 7 is/are provided.

The evaporation chamber 6 is also provided with a vent valve 14 to prevent the accidental generation of unwanted excess pressures inside it.

The pump 4 is a pump for loading a preset and constant amount of water and is preferably a piston pump actuated by an electromagnetic vibrator driven by an electronic control board, also not shown in the drawings. The delivery of the pump, or the duct 11, has a check valve, not shown in the drawings, to prevent leakage of steam towards the pump, with a consequent pressure drop in the boiler 2.

The water reservoir 3 is advantageously provided with a device 15 for checking the level of the water inside it, which is capable of emitting a control signal to inhibit the startup of the pump 4 if there is no water in the reservoir and to switch on a visual indicator or other signalling device for the operator. The operation of the above-described boiler unit 1 is extremely simple and efficient.

Once the pump 4 has fed into the preheating chamber 5 a metered amount of water, for example 25 cc (which advantageously is the amount that said chamber can contain), and a subsequent load, which by rising above the spillway 10 spills into the evaporation chamber 6 , the device 13 reports the presence of sufficient water in the chamber 6 and therefore current is supplied to the resistor or resistors 7, which in the initial stage cause the evaporation of the water in the evaporation chamber 6 and heat the water in the overlying preheating chamber 5.

The steam generated in the evaporation chamber 6 is delivered through the discharge duct 12. When the level of the water in the evaporation chamber drops below a preset threshold value, the water level detection device 13 emits a control signal for feeding a new dose of water from the reservoir 3.

In this manner, a small amount of water, previously preheated in the chamber 5, is always fed into the chamber 6. The cold water supplied by the pump 4 in fact settles in the lowermost part of the chamber 5, causing the overflow, through the opening 10, of the warmer water already present in said chamber.

A lower liquid phase and a pressurized vapor phase above the water, ready to be delivered to the user, are therefore present in the evaporation chamber 6.

In a second embodiment of the invention shown in figure 2 the pump is driven by means of a thermoelectric system instead of by means of a level detector. This example provides for one or more electric resistors 7a, meant to be at a lower level in order to be immersed in the liquid phase, and one or more upper electric resistors 7b, which have a thermostat and are meant to be immersed in the vapor phase to perform thermal control of the water level in the evaporation chamber 6, based on the difference in temperature between the upper resistors and the lower resistors. Whenever the level of the water in the evaporation chamber 6 drops below the level of the lower resistors, so that they remain exposed, the resistors in fact increase their temperature, so that a tempera^ture level comparator 16 sends a control signal to the electric board for driving the pump 4, which feeds a fresh dose of water drawn from the reservoir 3.

Figure 3 illustrates a third embodiment according to which the preheating chamber 5 is arranged so as to fully surround the evaporation chamber 6 and has a direct heat exchange therewith, so that the duct 11 feeds metered amounts of cold water at the bottom of the chamber 5; this, as mentioned, causes the overflow of a corresponding amount of water into the chamber 6 through the spillway opening 10.

In the fourth embodiment shown in figure 4 there is provided a heating element 17 meant to float on the water contained in the evaporation chamber 6. The floating element 17 is capable of producing steam almost instantaneously, since it causes the evaporation only of the surface water and at the same time preheats the remaining underlying mass of water contained in the chamber 6. According to this embodiment, the height of the boiler may also be considerable, in which case water can be supplied from the reservoir at much longer intervals than in the previous embodiments and by relatively large amounts. Advantageously, the heating element 17 is guided in its vertical movement by guiding means, constituted for example by an axial central sliding guide 18 or by guides provided along the inner wall of the chamber 6. The heating element 17 can have one or more floating contact sensors 19 which protrude downwards and upwards with respect to the heating element 17 and are meant to give good flotation characteristics to the heating element 17 and to emit a control signal for the pump 4, so as to start the pump when they touch the bottom of the chamber 6 and interrupt its operation when they touch the top of said chamber. The chamber 5 is delimited by a wraparound jacket 20 for the evaporation chamber 6 and is fed from the downward region by the duct 11.

.The heating element 17 can preferably have a plate- like configuration and holes 21 for the upward passage of the steam and can be constituted, for example, by a light alloy plate which includes a system of electric resistors.

The fifth embodiment shown in figure 5 illustrates a boiler with an evaporation chamber 6 having a plurality of interconnected compartments. The various compartments are delimited by fixed plate-like heating elements 22 arranged at different levels in the evaporation chamber and having a smaller peripheral dimension than the inner space of the chamber, so as to interconnect the various compartments delimited thereby.

The various heating elements 22 can be supplied with electric power either all together or sequentially, starting from the uppermost one, which instantaneously produces steam, followed by the one lying directly below it, which is activated whilst the uppermost element is switched off, and so forth, until the lowest element is exposed. By detecting the minimum level with a thermoelectric system or with a level measurement system, as explained above, the pump is activated, replenishing the water in the evaporation chamber.

Advantageously, in the lower part of the evaporation chamber 6 there is provided a removable plug for optional maintenance operations and particularly for discharging the scale which forms in the chamber after a preset work period of the boiler, for example after 300-400 hours of work. The above-described boiler unit is susceptible of numerous modifications and variations, all of which are within the protective scope defined by the spirit of the appended claims.

Claims

1. A boiler unit with fast steam generation, comprising a boiler body which accommodates at least one source of heat based on an electric resistor, a water reservoir, and a pump for feeding water from the reservoir to the boiler, characterized in that said pump is a metering pump for loading preset and constant quantities of water and has a check valve on its delivery, and in that it has a device for detecting a preset minimum level of the water contained in the boiler which is adapted to make the pump start when the water in the boiler reaches said preset minimum level.

2. A boiler unit according to claim 1, characterized in that said level detection device comprises a thermoelectric system formed by at least two electric resistors arranged at different levels and by an electronic board for comparing the temperature levels of said resistors, said electronic board being meant to emit a control signal for starting the pump when said preset level is reached.

3. A boiler unit according to claim 1, characterized in that said boiler body has at least one evaporation chamber which is divided into a plurality of interconnected compartments delimited by a plurality of fixed plate-like heating elements which are arranged at different levels in the evaporation chamber to cause the evaporation of the water that is present in the chamber from the top to the bottom.

4. A boiler unit according to claim 3, characterized in that said heating elements have a smaller peripheral bulk than the internal space cf the chamber. S. A boiler unit according to claim 1, characterized in that said boiler body is structured so as to delimit, inside it, a preheating chamber, which is meant to receive the water supplied by the pump, and an evaporation chamber, which accommodates the or each heat source. 6. A boiler unit according to claim 5, characterized in that said preheating chamber is arranged so as to fully surround the evaporation chamber and exchanges heat therewith. 7. A boiler unit according to claim 5, characterized in that said preheating chamber and said evaporation chamber are separated by a fixed heat-conducting partition having at least one water passage opening. 8. A boiler unit according to claim 7, characterized in that said at least one water passage opening is shaped like a spillway, in order to always keep a metered amount of water to be preheated above or adjacent to the evaporation chamber. 9. A boiler unit according to claim 3 , characterized in that said evaporation chamber has a vent valve to prevent the acc idental f ormation o f unwanted exc ess pressures inside it . 10. A boiler unit according to claim 1, characterized in that said water reservoir has a device for controlling the level of the water inside it which is capable of emitting a control signal to inhibit the startup of the pump if there is a lack of water in the reservoir. 11. A boiler unit according to claim 5, characterized in that said preheating chamber is separated from said evaporation chamber by means of a movable element which is adapted to float on the water contained in the evaporation chamher. 12. A boiler unit according to claim 11, characterized in that said movable element is a heating element which can cause the evaporation of the surface water and simultaneously preheat the remaining water contained in the evaporation chamber. 13. A boiler unit according to claim 12, characterized in that said heating element is vertically movable, guided by guiding means. 14. A boiler unit according to claim 12, characterized in that the heating element is provided with at least one floating contact sensor which emits a control signal for the pump when it touches the bottom or the top of the evaporation chamber. 15. A boiler unit according to claim 12, characterized in that the heating element has a plate-like configuration and is provided with openings for the rise of the steam. 16. A boiler unit according to claim 15, characterized in that the heating element is constituted by a ight alloy plate which includes a system of electric resistors.