Steam generator for domestic and industrial use

Abstract: A steam generator for domestic and industrial use, of the type comprising a boiler (5) provided with a resistance heater element (17) and a steam and energy take-off (10), characterised in that at least a first solenoid valve (7) and a second solenoid valve (8) or equivalent are connected between said boiler (5) and said take-off (10), said generator (1) comprising an electronic card (13) for controlling the generator operation.

Description: This industrial invention patent relates to a steam generator for domestic and industrial use. More particularly, the present invention provides a steam generator which enables the user to obtain maximum steam efficiency and minimum wastage of electrical energy. EP-A-0069858 discloses an electrical household appliance for producing and feeding steam to an electric iron. It comprises a boiler of stainless steel, heated by electric resistances and arranged at the center of an outer housing or body of insulating and shock resistant plastic material. The boiler is provided with a pressure switch to adjust the steam pressure. A thermostat checking lack of water in the boiler and a safety valve to avoid overpressure and accidents due to untimely opening of the boiler plug, are also provided. Italian patent application No. 2927 A/87 describes a steam generator which can be used for distributing steam to a plurality of appliances, non-limiting examples of which are a smoothing iron, general cleaning appliances, saunas, humidifiers, etc. This steam generator has given excellent industrial results but requires the availability of an electrical system able to sustain sudden absorbed current increases to an extent not always possible in the case of normal users. These absorbed current increases are due to the fact that when the generator is used for feeding steam to appliances which themselves absorb electrical energy, such as a smoothing iron, switching on the appliance results in a current increase and, as stated, implies the need of a large installed power availability. A further limitation on the generator of the said patent application is that in order to ensure that the electromechanical pressure switch retains its reliability with time, it is not possible for constructional reasons to reduce the operating pressure hysteresis to a minimum. An object of the present Invention is to provide a steam generator which does not suffer from the aforesaid drawbacks. In order to achieve the above-mentioned aim the steam generator comprises: a boiler provided with a resistance heater element for heating water in said boiler; a steam and electrical energy take-off unit; an electronic controller card for controlling the generator operation; characterised in that said controller card is connected to said take-off unit and includes means to automatically reduce the electrical energy to said resistance element proportionally, the proportion by which it is reduced depending on the amount of electrical energy withdrawn from said take-off unit by an external user item, so that the electrical energy consumption of the generator remains constant, and in that at least a first solenoid valve and a second solenoid valve are connected between the boiler and the take-off unit. Specifically, in the steam generator according to the invention: a) the maximum operating pressure is regulated by a hysteresisfree pressure switch, ie free from on-off hysteresis, with consequent constant operating pressure without surges due to hysteresis; b) the power of the resistance heater element of the generator is reduced when the heater element of another appliance connected to the generator is switched on, such as a smoothing iron or the like, thus resulting in constant mains energy consumption without sudden increases due to the switching on of the appliance; c) an indication is given by visual and/or acoustic or other means when the pressure is sufficient for use; d) a device can be provided for reducing the heating power of the generator (energy saving); e) means are provided for interrupting the electrical energy feed.to the generator after a predetermined time of operation without water. These and further objects of the invention will be apparent to the expert of the art on reading the following description. The steam generator according to the invention is illustrated by way of non-limiting example in the figures of the accompanying drawings, in which: Figure 1 is an overall perspective view of the generator; Figure 2 is a partial view of the generator with its cover open; and Figure 3 is a block diagram of the generator. With reference to said figures, the generator, indicated overall by 1, consists essentially of a base 2 provided with castors 3, and a cover 4. In the base 2 there is mounted a boiler 5, of the type described in said patent application No. 2927 A/87, suitably covered with insulating material and provided with a filling cap 6 with a double-acting safety valve. To the boiler 5 there are connected a first solenoid valve 7 and a second solenoid valve 8, the two outlets of which, 7' and 8' respectively, are connected to a single pipe 9 with which there is associated a steam and energy take-off 10, to which the appliances and relative controls, such as a smoothing iron, are connected as required. There is also connected to the boiler 5 a hysteresis-free pressure switch or equivalent, 11, the output 12 of which is connected to an electronic control card 13, the functions of which are displayed by a plurality of LEDs 14 1 , 14 2 .......14 9 , and which is powered by the mains 15. The output 16 of the card 13 controls the resistance element 17, the output 18 controls the solenoid valve 7, the output 19 controls the solenoid valve 8 and the output 20 is associated with the take-off 10. The input 21 to the card 13 is associated with the thermostat 22 provided on the boiler 5, the inputs 23, 24, of low voltage and isolated from the mains, are associated with the take-off 10, and the inputs 25, 26 and 27 are associated with a steam selector switch 28. In operation, having filled the boiler 5 with the scheduled quantity of water, the user operates a main switch 29 and then selects the type of operation by setting the switch 28 (steam OFF, steam ON with 100% of energy, steam ON with 50% of energy, economizer operation and/or humidification). In the described example of operation it will be assumed that 100% ON operation has been selected. In this case on operating the switch 28 the LED 14 9 lights to indicate this selection, and the resistance element 17 is fed with 100% of its power, to consequently commence steam production. During this initial stage the LED 14 8 also lights to indicate a steam pressure which is too low for use. When the pressure in the boiler 5 reaches the working value the LED 14 8 is extinguished and the LED 14 7 lights to indicate that the working pressure has been reached. As heating continues, the maximum allowable working pressure is reached, as measured by the pressure switch 11, and the LED 14 6 lights jointly with the LED 14 7 . The lighting of the LED 14 6 causes the resistance element 17 to be switched off. The pressure in the boiler 5 is regulated by the hysteresis-free pressure switch 11, which measures it with maximum precision due to the lack of system hysteresis. From the time the LED 14 7 lights, the generator is ready for use, and the user by operating the switches associated with the inputs 23 and 24 can select three different steam loads via the take-off 10, as follows: by operating the switch associated with the input 23 he activates the solenoid valve 7 and lights the LED 14 3 to indicate minimum steam withdrawal, by operating the switch associated with the input 24 he activates the solenoid valve and lights the LEDs and 14 4 and 14 5 to indicate medium steam withdrawal, and by operating the switches associated with the inputs 23 and 24 simultaneously he activates both the solenoid valves 7 and 8 and lights the LEDs 14 3 , 14 4 and 14 5 to indicate maximum steam withdrawal. With continued steam withdrawal, the water in the boiler 5 will ultimately be completely consumed, with consequent temperature rise as measured by the thermostat 22, which lights the flashing LED 14 2 and disconnects the resistance element 17. If this situation persists beyond a certain predetermined time, power is switched off to the system. Reactivation can only be done by switching off and switching on the switch 29. If electrical energy is also withdrawn from the take-off via the output 20, for example for the smoothing iron, the card 13 automatically reduces the energy to the resistance element 17 proportionally, to maintain the electrical energy consumption of the generator constant. This means that the installed electrical system can be as for normal use. If the 50% ON function is selected, for example for operating the system as a humidifier, the LED 14 9 lights with 50% brightness to indicate this selection, while the other functions remain unaltered. If the generator 1 is to be used without steam, the switch 28 is put in the steam OFF position. The LED 14 9 will therefore not light, so indicating this selection, and only electrical energy will be available at the take-off 10 via the output 20 of the card 13, for example to allow a smoothing iron to be used dry. The LED 14 1 associated with the switch 29 lights to indicate that the generator 1 is powered.

Claims: A steam generator for domestic and industrial use, comprising: a boiler (5) provided with a resistance heater element (17) for heating water in the boiler (5); a steam and electrical energy take-off unit (10); and an electronic controlling card (13) for controlling the generator operation; characterised in that the controlling card (13) is connected to the take-off unit (10) and includes means to automatically reduce the electrical energy to the resistance element (17) proportionally, the proportion by which it is reduced depending on the amount of electrical energy withdrawn from the take-off unit (10) by an external user item, so that the electrical energy consumption of the generator remains constant, and in that at least a first solenoid valve (7) and a second solenoid valve (8) are connected between the boiler (5) and the take-off unit (10). A steam generator as claimed in Claim 1, wherein through the first solenoid valve (7), when activated, passes steam at a first rate, and through the second solenoid valve (8), when activated, passes steam at a second rate greater than the first rate. A steam generator as claimed in Claim 1 or 2, wherein a substantially hysteresis-free pressure switch (11) for measuring the pressure in said boiler is provided. A generator as claimed in anyone of the preceding claims, wherein said card (13) is connected to at least two function user selection switches (28), the selected function being displayed by one or more LEDs (14 1 - 14 9 ). A generator as claimed in anyone of the Claims 1-3, wherein optical means (14 1 - 14 9 ) are associated with said card (13) in order to indicate the function and/or the state of operation of said generator. A generator as claimed in anyone of the preceding claims, wherein a thermostat (22) for detecting when the water in said boiler (5) has been totally consumed is connected to said controller card (13) to cause said resistance element (17) to be disconnected and, after a certain predetermined time, said generator (1) to be switched off. A generator as claimed in any of the claims 2-6, wherein the control command for said solenoid valves (7,8) is initiated at said take-off unit (10) by low voltage switches isolated from the power mains supplying power to the remainder of said generator (1). A generator as claimed in Claim 7, wherein said low voltage switches are located remotely from said generator (1). A generator as claimed in claim 7 or 8, wherein said switch means on said take-off unit (10) is operative to deactivate both said solenoid valves (7,8), thereby blocking any steam from reaching said take-off unit.

Inventors: CARRETTO EMANUEL, CARRETTO, EMANUEL
Applicants: STEM SRL, S.T.E.M. S.R.L.
Application year: 1990
Main classification: F22B1
IPC codes: D06F75, F22B1