EP0696706A1

EP0696706A1 - Safety device for vapour generator

Info

Publication number: EP0696706A1
Application number: EP94830397A
Authority: EP
Inventors: Giuseppe Giannelli
Original assignee: VELTRO Srl
Current assignee: VELTRO S.R.L.
Priority date: 1994-08-08
Filing date: 1994-08-08
Publication date: 1996-02-14

Abstract

In vapour-generating apparatus having a boiler (10) into which fluid is introduced for evaporation, in which the fluid is evaporated by a heat source (13) and from which the vapour generated is drawn for use, the boiler (10) is constituted by a vessel (11) closed by a lid (12), the vessel (11) and the lid (12) being securely fixed together by a resilient closure (16-18) which exerts a predetermined resilient closure pressure on the lid (12) so that, in the event of excessive steam pressure, the lid (12) is raised from the vessel (11) so as to discharge steam.

Description

The present invention relates to apparatus for generating vapour.
Household appliances which use steam-generating apparatus are known, such as, for example, ironing appliances or machines for washing floors, windows and the like.
Normally, appliances for generating steam for domestic use mainly consist of a boiler constituted by a sealed vessel housing an electrical resistance. The boiler has an opening, closed by a cap, for filling the vessel with water. The electrical resistance causes the water in the vessel to evaporate until a predetermined pressure builds up in the boiler. The steam which forms in the vessel is drawn off by means of a solenoid valve activated by an external control and flows through a tube to the appliance requiring it. This appliance may be an iron with a soleplate provided with outlet holes for the steam or a nozzle for the outlet of steam for cleaning floors, windows and the like.
Obviously such a steam generator is highly dangerous as it contains pressurised steam which could burst out of the vessel for various reasons and injure the user, possibly seriously.
Mechanical or electrical safety devices, such as safety caps, maximum-pressure valves, pressure switches or thermostats are used to reduce this danger.
However, mechanical safety devices may be rendered inoperative by lime blocking the tiny ducts through which the steam is discharged.
Electrical safety devices on the other hand may be rendered inoperative by a fall or a knock, which could happen to the appliance either while being carried or during use.
It is therefore clear that while the need for a high degree of safety remains strong, current safety devices are not entirely reliable.
The object of the present invention is to provide vapour-generating apparatus that satisfies this safety requirement.
This object is achieved by providing vapour-generating apparatus which includes a boiler into which fluid is introduced for evaporation and in which the fluid is evaporated by a heat source and from which the vapour generated is drawn for use, characterised in that the boiler comprises a vessel closed by a lid and in that the vessel and the lid are securely fixed together by resilient closure means which exert a predetermined resilient closure pressure on the lid which allows the lid to be raised in the event of excessive pressure to discharge the vapour to the exterior.
In order better to understand the invention, one embodiment thereof is described hereafter purely by way of non-limitative example and illustrated in the appended drawings, in which:

Figure 1 is an exploded perspective view of the boiler of steam-generating apparatus according to the invention;
Figure 2 is a partially cut-away elevation of the boiler of Figure 1;
Figure 3 shows the boiler illustrated in Figure 2 in a safe operating condition;
Figure 4 is a circuit diagram of steam-generating apparatus according to the invention including the said boiler;
Figure 5 is a partially cut-away perspective view of a component of the circuit of Figure 4;
Figure 6 is a sectioned view of a household appliance incorporating the said steam-generating apparatus; and
Figure 7 is a sectioned view of another household appliance incorporating a simplified version of the said steam-generating apparatus.

The boiler of the apparatus according to the invention, illustrated in Figure 1 and generally indicated 10, includes a vessel 11, a lid 12 for closing the vessel and an electrical resistance 13 housed in the vessel.
The vessel 11 and the lid 12 are securely fixed together by a series of bolts which exert a clamping action through springs. In particular, a series of holes 14 is formed around a rim 11A of the vessel 11 and a corresponding series of holes 15 is formed around a corresponding rim of the lid 12 so that, when the lid 12 is fitted on the vessel 11, each hole 15 is aligned with a respective hole 14; a screw 16 is fitted through each pair of holes 14, 15 until its head, which is uppermost, bears against the lid and a spring 17 is then fitted onto its shank, of which only the end portion is threaded, the remaining part being smooth and then a nut 18 is screwed in. The nut 18 is tightened so as to compress the spring 17 and thus clamp the lid 12 resiliently against the rim 11A of the vessel 11 since, because the spring acts on the nut and reacts against the inner surface of the rim 11A it transmits a resilient force, directed towards the vessel, to the head of the screw 16 through its shank. A seal 19 is provided between the vessel 11 and the lid 12.
The electrical resistance 13 is sealingly fixed to the lid 12. A short connector tube 20 is also sealingly fixed to the lid 12 puts the inside of the vessel 11 into communication with the outside; a closure cap 21 is screwed onto this tube 20.
The vessel 11 also houses a thermometric probe 22, also sealingly fixed to the lid 12, for measuring the temperature inside the vessel.
As shown in Figure 4, the resistance 13 and the thermometric probe 22 are electrically connected to an electronic supply and control unit 23. The electronic unit 23 is controlled by an external push-button 24 by which steam can be released. An external indicator 44 is also connected to the unit 23 for warning of abnormal conditions, this indicator being either acoustic and/or light-emitting.
Finally, the vessel 11 houses a dip tube 25, also sealingly fixed to the lid 12. Outside the lid 12, the dip tube 25 is connected, by means of an additional tube 26, to the suction side of a pump 27 which may, for example, be of an electromagnetic type operated by a series of electrical pulses. The delivery of the pump 27 is connected to the inlet of a vaporiser 29 by means of a tube 28. The outlet of the vaporiser 29 is connected to a utiliser appliance through a first tube 30 and a second tube 31. The tubes 30 and 31 are connected to each other by a "T" connector 32 with the tubes 31 and 32 fitted to the branches of the head of the T and the stem fixed to the lid 12 of the vessel 11. A non-return ball valve is mounted inside the connector 32.
Figure 5 illustrates in detail the vaporiser 29. This is formed by a body 34 containing two electrical resistances 35 and having a face 36 rebated into it with dividing ridges 37. A lid 38 is sealingly fixed to the body 34 over the rebated face 36. The face 36, the ridges 37 and the lid 38 define a sort of tortuous, substantially laminar duct communicating at one end with the inlet and at the other with the outlet of the vaporiser 29. The body 34 also contains a thermometric probe 39.
The pump 27 is electrically powered by an electronic supply and control unit 40. The electronic unit 40 is controlled in turn by an external push-button 41 for activating the pump 27 and by a knob 42 for regulating the delivery of the pump.
The resistances 35 and the probe 39 associated with the vaporiser 29 are connected, on the other hand, to an electronic thermostat 43.
The steam-generating apparatus illustrated in Figure 4 operates as follows.
Firstly the boiler 10 must be filled with fluid to be evaporated, which in the present example is water. This is done by unscrewing the cap 21, pouring water into the vessel 11 through the tube 20 and screwing the cap 21 back on.
Power is then supplied to the apparatus by means of an external control which is not shown.
Switching on the apparatus activates the electronic unit 23 which supplies the electrical resistance 13 until the water reaches a temperature just below its boiling point, for example a temperature of between 95°C and 98°C, and cuts off power when the thermometric probe 22 indicates that the water has reached this temperature. Once this temperature has been reached, the electronic unit 23 maintains it by switching the electrical resistance 13 on or off according to the readings of the thermometric probe 22.
The switching on of the apparatus also activates the electrical resistances 35 of the vaporiser 29. In this case, the electronic thermostat 43, by measuring the temperature by means of the thermometric probe 39, causes the body 34 of the vaporiser 29 to reach and maintain a temperature far higher than the boiling point of the water, a temperature, for example, of between 150°C and 160°C.
When steam is needed, the operator presses the push-button 24 and, by means of the electrical resistance 13 and the thermometric probe 22, the electronic unit 23 brings the water in the boiler 10 to a temperature slightly higher than the boiling point of the water, that is to a temperature just over 100°C, and maintains it there. In this way steam is produced in the boiler 10; this steam enters the tube 31 through the non-return valve 33 and flows through this tube 31 to the utiliser appliance.
The apparatus described can give more steam, at a greater pressure, than that generated in the boiler 10. To achieve this, the push-button 41 is pressed instead of the push-button 24. This causes the electronic unit 40 to activate the pump 27 with its delivery controlled by the regulator knob 42. The pump 27 draws water from the boiler 10, at a temperature just below its boiling point, through the tubes 25 and 26 and delivers it through the tube 28 to the evaporator 29. In the evaporator, by virtue of the high temperature and the tortuous, laminar duct, the water temperature rises sharply and more steam, under greater pressure, is generated than that generated in the boiler 10. This steam is forced by the pressure through the tubes 30 and 31 to the utiliser appliance. The non-return valve 33 prevents the steam from entering the boiler 10.
The steam-generating apparatus described and illustrated above offers several advantages.
Firstly, the boiler meets with the most stringent safety requirements. In fact, when the pressure in the boiler is excessive, the lid 12 is raised slightly from the vessel 11 by the pressure itself overcoming the action of the springs 17, thus releasing steam and returning the pressure in the boiler to normal, as shown in sequence in Figures 2 and 3. The resilient load put on the springs 17 by the nuts 18 is calibrated so that the lid 12 is raised at a predetermined level of excess pressure.
It should be noted that lime does not affect the operation of this efficient safety system as the steam-release aperture formed by raising the lid 12 is of considerable size and cannot be blocked by lime deposits as occurs in prior art appliances.
In addition, as this safety system is purely mechanical and fairly robust, it is not affected by any knocks as are prior art electrical safety systems.
It should be emphasized, however, that when steam is not required, the electronic unit 23 ensures that no steam forms in the boiler by maintaining the water below its boiling point, thus offering an additional safety feature. In addition, should the pressure in the boiler 10 be excessive or should there not be enough water, the electronic unit 23 would detect an abnormal increase in temperature by means of the thermometric probe 22, and would switch off the electrical resistance 13 and switch on the warning indicator 44.
The fact that the boiler does not normally contain pressurised steam means that it may be opened for refilling it with water without any delay as there is no danger of a violent discharge of steam. In addition, the fact that the water in the boiler is normally at a temperature close to its boiling point means that, when required, steam is available very quickly as the temperature need only be raised very slightly.
The availability of more steam at a greater pressure is a definite advantage to satisfy different requirements. By means of the regulator knob 42 it is also possible to adjust the quantity and the pressure of the steam as, by means of the electronic unit 40, this regulator knob 42 varies the delivery of the pump 27 and thus the quantity of hot water reaching the vaporiser 29 and being vaporised.
Figure 6 shows the steam-generating apparatus of Figure 4 used in a household appliance for washing floors and the like, generally indicated 50. This appliance 50 includes a trolley 51 with a box-shaped body housing the aforesaid apparatus. The tube 31 of the apparatus is connected to a nozzle 53 which discharges the steam onto the surface to be treated and which constitutes the utiliser device. Apertures 52 are provided in the underside of the body of the trolley 51 for the steam released from the boiler 10 to be discharged should the lid 12 be raised owing to excess pressure in the boiler.
Figure 7 shows a simplified version of the aforesaid apparatus being used in a household ironing appliance, generally indicated 60. This simplified version has no vaporiser 90 or associated hydraulic and electrical circuits (pump 27, tubes 25, 26, 28, 30, electronic unit 40, push-button 41, knob 42, electronic thermostat 43). The simplified apparatus is housed in a base 61 of the appliance 60 on which an iron 62 rests. In this case, the tube 20 for filling the boiler with water has a nozzle 45 to which is connected a tube 46 which connects externally to the iron 62; the steam generated in the boiler 10 thus reaches the iron through the nozzle 45 and the tube 46 and is discharged through holes in the soleplate of the iron. Apertures 63 are formed in the underside of the base 61 for discharging steam released from the boiler 10 when excessive pressure raises the lid 12. In this ironing application, the electronic unit 23 and associated external controls enable the quantity of steam to be adjusted according to the type of material being ironed, with the electrical resistance 13 switched off if there is too much steam.
Naturally, the simplified apparatus without vaporiser could be used in the floor-washing appliance 50 while the apparatus with vaporiser could be used in the ironing appliance 60.
It is of course possible to make variants and/or additions to the apparatus described and illustrated here.
In particular, the boiler may have any shape whatever.
More electrical resistances may be provided.
Any other heat source may be used instead of the electrical resistance.
The vaporiser may also be shaped differently and have a different number of electrical resistances or a different type of heat source.
The lid may be resiliently clamped to the boiler vessel in any way which provides for resilient closure as described above. For example, an equivalent bolt system or a system of resilient clips or the like may be used.
A single electronic supply and control unit may be provided to control the boiler, the pump and the vaporiser.
The pump for delivering hot fluid to the vaporiser may be of any type.
Switches may be used instead of push-buttons to control the steam.
The apparatus described and illustrated may be used in any household appliance requiring steam, either in its simplified version without the vaporiser or in the version with vaporiser.
In general, the apparatus of the invention may also be used outside the domain of household appliances and may be adapted, making obvious modifications, to suit any professional or industrial appliance requiring steam. In addition, any type of fluid may be used.

Claims

Vapour-generating apparatus which includes a boiler (10) into which fluid is introduced for evaporation and in which the fluid is evaporated by a heat source (13) and from which the vapour generated is drawn for use, characterised in that the boiler (10) comprises a vessel (11) closed by a lid (12), the vessel (11) and the lid (12) being securely fixed together by resilient closure means (16-18) which exert a predetermined resilient closure pressure on the lid (12) so as to allow the lid (12) to be raised from the vessel (11) in the event of excessive pressure to discharge vapour to the exterior.
Apparatus according to Claim 1, in which the lid (12) is fixed to the vessel (11) by a series of bolts (16,18) which exert a clamping action through springs (17).
Apparatus according to Claim 2, in which each bolt is constituted by a screw-threaded member (16) which passes through a hole (15) in the lid (12) and an aligned hole (14) in the vessel (11) and has fitted onto it a spring (17) and a nut (18) screwed onto the threading so as to load the spring (17) resiliently, the head of the screw-threaded member (16) and the spring (17) being arranged on opposite sides of the junction between the lid (12) and the vessel (11).
Apparatus according to Claim 1 in which the heat source is constituted by an electrical resistance (13), in which a thermometric probe (22) is housed in the vessel (11) and in which an electronic unit (23) is provided to power the electrical resistance (13) and control the temperature in the vessel (11) by means of the thermometric probe (22).
Apparatus according to Claim 4, in which the electronic unit (23) maintains the fluid in the vessel (11) at a temperature slightly below its boiling point and, when vapour is requested by an external command (44), heats the fluid to a temperature just above its boiling point whereby vapour is made available to the utiliser appliance.
Apparatus according to Claim 5, in which, when the fluid is water, the said temperature is between 95°C and 98°C.
Apparatus according to Claim 5, in which a light-emitting and/or acoustic warning indicator (44) is connected to the electronic unit (23) for warning of excessive temperatures in the boiler (10) measured by the thermometric probe (22).
Apparatus according to Claim 1 or Claim 5, in which an additional evaporation circuit is provided which includes a pump (27) which draws hot fluid from the boiler (10) and a vaporiser (29) which receives hot fluid from the pump (27), vaporises it at a high temperature and sends it to the utiliser appliance.
Apparatus according to Claim 8, in which electrical resistances (35) are provided for heating the vaporiser (29) and a thermometric probe (39) is provided for monitoring the temperature.
Apparatus according to Claim 9, in which the electrical resistances (35) and the thermometric probe (39) are connected to a thermostat (43) which maintains the vaporiser (29) at a temperature far higher than the boiling point of the fluid.
Apparatus according to Claim 10, in which, when the fluid is water, this temperature is between 150°C and 160°C.
Apparatus according to Claim 10, in which the vaporiser comprises a body (34) containing the electrical resistances (35) and the thermometric probe (39) and in which there is formed a tortuous, substantially laminar duct communicating at one end with the inlet and at the other with the outlet of the vaporiser (29).
Apparatus according to Claim 8, in which the pump (27) is supplied by an electronic supply and control unit (40) connected to an external control (41) for activating the pump (27) and to a regulator (42) for adjusting the delivery of the pump (27).
Apparatus according to Claim 8, in which the outlet of the boiler (10) and the outlet of the vaporiser (29) are connected to a common tube (31) through which the steam is conveyed to the utiliser, a non-return valve (33) being provided to prevent vapour from the vaporiser (29) from entering the boiler (10).
Apparatus according to Claim 8, in which a single supply and control unit is provided to operate the boiler (10), the pump (27) and the vaporiser (29).
Apparatus according to any one of the preceding Claims, used in a vapour-utilising household appliance such as a floor-washing appliance (50) or an ironing appliance (60).