Steam generator

Abstract

 The steam generator according to the present invention, comprises a pressure boiler to produce and to maintain in equilibrium a two-phase liquid-steam system and means (8) for withdrawing and delivering water in the liquid state present in the boiler. Such means for withdrawing and delivering water comprise at least one collection intake set (8) above the surface of the water in the liquid state present in the boiler.

Description

[0001] The present invention relates to a steam generator of the type comprising a pressure boiler capable of producing and maintaining a two-phase liquid-steam system in equilibrium, as well as means for withdrawing water in liquid phase from the boiler and delivering it into the external environment, and which is particularly suitable for domestic applications.

[0002] Steam generators are being increasingly used in domestic environments, above all for cleaning walls or large objects, because of their practicality, efficiency and ever greater safety in use.

[0003] In particular, steam generators for domestic use comprise a boiler filled with water at ambient temperature, which allows the generation of steam under pre-set thermodynamic conditions. Inside the boiler, in contact with the steam, there is generally a collection intake which is connected via a conduit to an external delivery nozzle. Between the collection intake and the nozzle there is at least one user-operated valve to control the opening and closing of the conduit and, accordingly, delivery of the steam.

[0004] Recently, the traditional steam generator, in which the boiler also served as reservoir, is being replaced by apparatus that provides for the separation of reservoir and boiler and that maintains constant the quantity of steam and water in the liquid state present in the same boiler. The domestic use of the steam generators, however, has made more and more obvious the requirement not only for steam, but also for hot water in the liquid state, for instance, to carry out particular washing operations. Some steam generators provide a choice of delivering hot water either as steam or in the liquid state.

[0005] In these latest embodiments, the boiler is usually equipped with means for generating and maintaining a two-phase liquid-steam system in equilibrium under pressure, as well as keeping constant the level of the water in the liquid state in those generators with separate boiler and reservoir. A collection intake, connected to a pump which is activated from the outside, is located well under the surface of the water and allows hot water to be withdrawn from the boiler.

[0006] The water, driven by the pump, passes from the collection intake into a linking conduit and subsequently arrives at a delivery nozzle external to the generator.

[0007] However, in addition to the increased complexity of the embodiment, the use of such means for collecting water in the liquid phase also involves a reduction of the general reliability of the steam generator, due above all to the presence of the water pump.

[0008] Furthermore, the use of the pump to withdraw and deliver water in the liquid state increases the consumption of electric power and therefore the running costs.

[0009] It is an aim of the present invention to produce a steam generator, of the type equipped with means for delivering water in the liquid state, that is not highly complex to construct and is reliable.

[0010] Another purpose of the present invention is to supply a steam generator endowed with means for delivering water in the liquid state that has low running costs.

[0011] The steam generator according to the present invention, as vindicated in Claim 1 achieves these purposes.

[0012] Further particular characteristics of the steam generator according to the invention are contained in the following dependent claims.

[0013] The steam generator according to the present invention, comprises a pressure boiler to produce and to maintain in equilibrium a two-phase liquid-steam system and means for withdrawing and delivering water in the liquid state present in the boiler. Such means for withdrawing and delivering water comprise at least one collection intake located above the surface of the water in the liquid state present in the boiler.

[0014] According to a particular aspect of the present invention, the means of withdrawing and delivering the water in the liquid state comprise, in addition to the collection intake, a nozzle for delivery of the water to the external environment. Between the collection intake and the delivery nozzle there is a linking conduit and at least one externally controlled valve.

[0015] According to a further particular aspect of the present invention, the steam generator comprises a reservoir for water at ambient temperature and means for maintaining constant the surface level of the water in liquid phase present in the boiler.

[0016] A form of embodiment of the present invention will now be described by way of example but not of limitation, making reference to the attached figures in which:

Figure 1 is a schematic diagram of a particular embodiment of the steam generator according to the present invention,

Figure 2 is a partial schematic view, in section, of a domestic apparatus for cleaning comprising the steam generator shown in figure 1; and

Figure 3 is a prospective view, partially in section, of an apparatus for cleaning equipped with a steam generator according to the present invention.

[0017] With reference to the scheme of figure 1, the steam generator comprises a reservoir 1 fitted with an intake duct 2 and connected via conduit to a boiler 6. The conduit 2 allows the user to fill the reservoir 1, for instance with water at ambient temperature, even during operation of the generator.

[0018] There is a pump 3 between the boiler 6 and the reservoir 2 which, governed by control unit 10, ensures the filling of the boiler 6.

[0019] The boiler 6 comprises means, not shown in figure 1, for generating and maintaining in equilibrium a two-phase liquid-steam system and means for checking and maintaining constant the surface level of the liquid 4 inside the same boiler 6. The latter comprise a sensor 9 that checks the level of the liquid 4 continuously and sends out a corresponding electric signal, together with a control unit 10 which, on the basis of the signal received from the sensor 9, controls the supply of water from the reservoir 1 to the boiler 6, for the purpose of maintaining constant the level of the liquid 4 in the same boiler 6.

[0020] Also present in the boiler 6 are the collecting intakes 7 and 8, for steam and liquid respectively, both located in contact with the steam phase 5 in the boiler 6.

[0021] In particular, intake 8 is located a little above the surface of the liquid 4, while intake 7 is situated above intake 8, in proximity to the top of the dome of the boiler 6.

[0022] The intake 7 is connected via conduit 11 to branch 16 in a "Y"-pipe fitting 18. Along the conduit 11, between the intake 7 and the pipe fitting 18 there are two user-operated electro-valves 12 and 13 in parallel, to regulate the flow of steam 5.

[0023] The intake 8 is connected to conduit 14 containing an electro-valve 15 to regulate the flow of water in the liquid state 4. Conduit 14 finally connects to branch 17 of the "Y"-pipe fitting 18.

[0024] When the scheduled thermodynamic conditions which provide for the maintenance of the steam 5 above atmospheric pressure are reached in the boiler 6, the operation of one or both the electro-vales 12 and 13 causes the delivery of steam 5 from the pipe fitting 18 to the external environment.

[0025] The opening of the valve 15 causes delivery of hot water in the liquid state instead, from the same "Y" pipe fitting. In fact, the short distance of the intake 8 from the surface of the liquid 4 and the pressure drop created in proximity of the same intake 8 by the opening of valve 15, cause suction of water in the liquid state 4 present in the boiler 6.

[0026] Preferably, the pressure reached inside the boiler is somewhere between 4 and 6 bar and the distance of the intake 8 from the surface of the liquid 4 is maintained between 8 and 16mm, for the purpose of enabling delivery of water in the liquid state.

[0027] The withdrawing of liquid 4 and/or steam 5 from the boiler 6 causes a lowering of the level of the liquid 4 and, accordingly, an increase in the distance between intake 8 and surface of liquid 4. The sensor 9 detects this lowering of level and sends a corresponding signal direct to the control unit 10. The control unit 10, in turn, on the basis of the signal from the sensor 9, operates the pump 3 that introduces water from the reservoir 1 into the boiler 6, bringing the distance of the intake 8 from the liquid 4 within the pre-set conditions once again.

[0028] Figure 2 shows schematically part of a domestic apparatus for cleaning surfaces or objects. The apparatus comprises a bodyshell 22, fitted with small wheels 23a and 23b, containing the steam generator described above. Within the bodyshell is a reservoir 1' having a water filler duct 2' which has an entry section, closed by a watertight cover 21, accessible from the outside.

[0029] The reservoir 1' is connected via conduit to a boiler 6' in which a two-phase liquid-steam system is generated and maintained in equilibrium. Between the reservoir 1' and the boiler 6' there is a pump (not shown).

[0030] There is a heating element 20 in the boiler 6', for instance constituted by electrical resistance, governed by a control unit connected to a pressure sensor (not shown) and to a thermostat 19, for the purpose of maintaining the conditions of pressure and temperature inside the same boiler 6' constant.

[0031] Also present In the boiler 6' are the collecting conduits 7' and 8' for the steam 5' and for the liquid 4' respectively and the surface level sensor 9' of the liquid 4.'

[0032] Finally, water in the liquid state and/or steam is supplied downstream of a "Y"-pipe fitting 18' by means of the delivery pipe 24.

[0033] According to a particular aspect of the invention, the intake 8 can assume different positions inside the boiler 6 leading to different distances from the surface from the liquid 4. In this case, the collecting intake 7 of the steam 5 would be redundant, since, when the intake 8 is a short distance from the liquid 4, the opening of valve 15 causes water to be delivered in the liquid state, while, when the intake 8 is more distant from the surface of the liquid 4, opening the same valve 15 causes steam alone to be supplied.

[0034] Furthermore, limited separation of the intake 8 from the surface of the liquid 4 causes delivery of liquid 4 mixed with steam 5, in varying proportions.

[0035] Figure 3 illustrates a further apparatus for cleaning, equipped with a steam generator according to the present invention. The apparatus for cleaning comprises a brush 26'' which delivers a flow of steam and/or liquid 27'' toward the outside, a bodyshell 22'' containing the steam generator, and means, comprising a delivery pipe 24'', for connecting the steam generator to the same brush 26.''

[0036] The steam generator, in turn, comprises a reservoir 1'' that is closed by a watertight cover 21'' for the restoring water 28''.

[0037] The reservoir 1'' is connected via conduit to a boiler 6'' to maintain a two-phase liquid-steam system in equilibrium under pressure. Between the reservoir 1'' and the boiler 6'' there is a pump 3'' that allows the filling of the same boiler 6.''

[0038] Conduits leave from the boiler 6'', connecting to the "T"- pipe fitting 18'' to deliver steam and water in the liquid state. Such connection conduits are equipped with electro-vales 12,'' 13'' and 15,'' operated by the switch 25,'' that allows the user to control the outflow of liquid and/or steam to the brush 26.''

[0039] In an advantageous form of embodiment of the present invention, the steam generator, equipped with separate reservoir and boiler, comprises means for preheating the filling water from the reservoir, before its entry into the boiler.

[0040] In particular, the connection conduit between reservoir and boiler could be in the form of a serpentine between the external wall and the heat insulation of the same boiler, allowing effective and low-cost preheating of the water.

[0041] The steam generator according to the present invention allows the delivery of hot water in the liquid state, without there being any mechanical or electro-mechanical actuators, such as a pump downstream of the boiler, to pump the liquid from the same boiler. That makes for simpler construction and, accordingly, more reliable steam generation according to the present invention.

[0042] Besides, the absence of any actuators to pump liquid from the boiler, results in low electrical energy consumption and therefore small running expenses.

Claims

1. Steam generator of the type comprising a pressure boiler equipped with means to generate and maintain a two-phase liquid-steam system in equilibrium, as well as means for withdrawing and delivering water in the liquid state from said boiler to an external delivery nozzle, characterized in that said means for withdrawing and delivering water in the liquid state comprise a collecting intake set above the surface of the water in the liquid state contained in said boiler.

2. Generator according to Claim 1, characterized by there being a connecting conduit and an externally controllable valve between said collection intake and said delivery nozzle.

3. Generator according to Claim 1 or 2, characterized by comprising means for withdrawing and delivering steam from said boiler to an external nozzle.

4. Generator according to Claim 3, characterized by said means for withdrawing and delivering water and said means for withdrawing and delivering steam being one and the same.

5. Generator according to Claim 3, characterized by said means for withdrawing and delivering water and said means for withdrawing and delivering steam being separate.

6. Generator according to Claim 5, characterized by the internal pressure in the boiler being between 4 and 6 bar inclusive and by the distance between water collection intake and the surface of the water being between 8 and 16mm inclusive.

7. Generator according to Claim 6, characterized by said distance between water collection intake and the surface of water being equal to 10mm.

8. Generator according to any of the preceding Claims, characterized by said means for withdrawing and delivering water being mobile with respect to said surface of the wafer in the liquid state contained in said boiler.

9. Generator according to any of the preceding claims, characterized by comprising a reservoir for the water, means for the hydraulic connection of said reservoir to said boiler, as well as means for maintaining substantially constant the surface level of the water in the liquid state within said boiler.

10. Generator according to Claim 9, characterized by said means for the hydraulic connection comprising at least one pump for delivery of water from said reservoir to said boiler and by said means for maintaining substantially constant the surface level of the water comprising means for the detection of the level of the water in the liquid state within said boiler and means of regulation and control of said pump, said means of regulation and control of said pump being connected to said means for the detection of the level of the water.

11. Generator according to Claim 9 or 10, characterized by comprising means for preheating the water introduced from said reservoir into said boiler.

12. Generator according to Claim 11, characterized by said means for preheating comprising a serpentine in heat-exchange contact with the fluid on the inside of said boiler, said serpentine being a part of said means for the hydraulic connection of said reservoir to said boiler.

13. Method for delivering liquid from a boiler under pressure equipped with means for generating and maintaining in equilibrium a two-phase liquid-steam system and comprising means for withdrawing and delivering the liquid contained in said boiler, said means being provided with at least one collection intake of the liquid inside said boiler and at least one delivery valve of, characterized by comprising the following phases:

-- positioning said collection intake at a controlled distance above the surface of the liquid phase;

-- opening said valve to allow the outflow of the liquid;

-- maintaining surface of the liquid phase within said boiler at constant level.

14. Method for the alternative delivery of liquid and steam from a pressure boiler equipped with means to generate and maintain a two-phase liquid-steam system in equilibrium and comprising means for withdrawing and delivering the fluids contained in said boiler, said means being provided with at least one collection intake of fluid from inside said boiler and of at least one delivery valve, characterized by comprising the following phases:

-- positioning said collection intake above the surface of the liquid phase, at a controllable distance;

-- opening said valve to allow the outflow of fluid;

-- maintaining constant surface level of the liquid phase within said boiler;

-- varying the distance of said collection intake from the surface of the liquid phase.

15. Apparatus for washing, especially for domestic use, of the type comprising means for the delivery of steam and/or hot water, characterized by comprising a steam generator according to any of the Claims from 1 to 12.

Drawing