Liquid heaters and vaporizers – Miscellaneous
Reexamination Certificate
2003-04-01
2004-09-07
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Miscellaneous
C122S506000, C392S451000, C392S453000
Reexamination Certificate
active
06786182
ABSTRACT:
DESCRIPTION
The present invention relates to a household appliance for steam generation, comprising a boiler-in turn comprising a heating source for water vaporisation-steam delivery means, and means for adjusting the pressure value of the steam in the boiler, suitable for switching the heating source on/off so as to maintain the steam pressure at a desired value.
The present invention also relates to a method for adjusting the pressure value of the steam in a boiler of a household appliance for steam generation.
Household appliances for steam generation are known.
Typically, such household appliances comprise a heating source for vaporising the boiler water, and means for maintaining a desired pressure value and a desired water level in the boiler.
Document DE 37 20 583 describes an appliance for steam generation comprising a water vaporisation boiler, a pump for feeding water to the boiler, a heating source wound as a spiral around the boiler, two temperature sensors, also wound as a spiral around the boiler, a manometer and a pressure regulator. One of the two sensors is used to detect the heating source temperature and draw water into the boiler when the detected temperature exceeds a first threshold temperature. The second sensor is used to detect the heating source temperature and turn it off when the detected temperature exceeds a second threshold temperature that is higher than the first threshold temperature. The manometer and the pressure regulator are, on the other hand, used for maintaining a desired value of steam pressure in the boiler.
Patent application PCT/ITOO/00112 filed by the Applicant, describes an apparatus for steam generation comprising a water vaporisation boiler, a pump for feeding water to the boiler, a heating source having an elevated portion, a temperature sensor in contact with such elevated portion, and a manometer with associated respective control means. The sensor is used to detect the heating source temperature and draw water into the boiler when the detected temperature exceeds a threshold temperature. In turn, the manometer is used to detect the steam pressure in the boiler, and the control means is used to switch the heating source on/off in function of the pressure value detected by the manometer, so as to maintain a desired steam pressure value in the boiler.
However, the use of the manometer for adjusting the water pressure value in the boiler of the appliances described by the above documents has the disadvantage of implying high costs. Moreover, the manometer exhibits the disadvantage of being relatively cumbersome.
The Applicant has thus faced the technical problem of realising a household appliance for steam generation at reduced costs and cumber.
Thus, in a first aspect thereof, the present invention relates to a household appliance for steam generation, comprising
a boiler comprising, in turn, a heating source for water vaporisation, intended to be at least partly immersed in water,
control means comprising, in turn, means for adjusting the pressure value of the steam in the boiler, said means being operatively associated with the heating source to switch it on/off so as to maintain the steam pressure at a desired value,
steam delivering means,
characterised in that the means for adjusting the pressure value in the boiler is operatively associated with the steam delivery means so as to switch the heating source on/off in function of the open/closed status of the steam delivery means.
The pressure adjusting means of the appliance of the invention regulate the pressure value in the boiler through a simple control of the status (open/closed) of the steam delivery means.
Such function can be performed by simple circuit diagrams which, with respect to the use of a manometer, allow the costs and cumber of the appliance to be reduced.
In the present description and claims, the expression “standby condition” is used to indicate the situation in which the heating source is immersed in water, the steam pressure in the boiler substantially has the desired value, the boiler is ready to deliver steam and the steam delivery means is closed. In turn, the expression “steam delivery condition” is used to indicate the situation in which the boiler delivers steam, for example, to a user equipment, and the steam delivery means is open or in its opening or closing transient.
Typically, the boiler also comprises a temperature sensor suitable for detecting the heating source temperature.
Preferably, the sensor is in contact with the heating source.
Advantageously, the means for adjusting the pressure value in the boiler is operatively connected to the temperature sensor so as to switch the heating source on/off in function of the temperature value detected by the sensor (
12
) when the steam delivery means status is closed.
To this purpose, the Applicant notes that when the boiler is in standby condition, the water present into the boiler is in saturation conditions, so that pressure and temperature are connected to one another by a bi-univocal correspondence. Moreover, the temperature detected by the temperature sensor is substantially equivalent to the water temperature. It is thus possible to maintain the desired pressure value in function of the temperature value detected by the sensor.
On the other hand, during the initial heating of the appliance, when the temperature of the water present in the boiler is less than that detected by the temperature sensor, the sensor detects a higher temperature than the actual water temperature. As a consequence, the heating source is switched on/off a certain number of times before reaching the standby desired pressure value. However, this is not a problem since if a user requires steam delivery when the pressure in the boiler has not reached the desired value yet, the means for adjusting the pressure value would keep the heating source on during the opening time of the steam delivery means (see below), thus bringing the pressure to the desired value.
Advantageously, the means for adjusting the pressure value in the boiler is suitable for switching the heating source off when the sensor detects a higher temperature than a first temperature threshold S
1
and switching the heating source on when the sensor detects a lower temperature than said first temperature threshold S
1
.
Preferably, the value of the first threshold S
1
corresponds to the value detected by the temperature sensor in standby condition when the steam in the boiler reaches the desired pressure value (for example, 2 bar).
Advantageously, when the status of the steam delivery means switches from closed to open, the means for adjusting the pressure value in the boiler is suitable for switching the heating source on.
This allows the pressure loss in the boiler caused by steam delivery to be remedied immediately.
In fact, the Applicant notes that when the steam delivery means open, the boiler undergoes an immediate pressure loss. Such pressure loss causes a corresponding cooling of the water and of the heating source, and thus, a decrease in the temperature detected by the temperature sensor, with respect to the value of the first threshold S
1
. However, the temperature detected by the probe decreases at a much slower rate than that at which the pressure decreases. Thus, without the switching of the heating source on upon the opening of the steam delivery means, the heating source would be switched on behind time with respect to the pressure loss, thus delaying the restoration of the desired pressure value.
Preferably, at the switching of the steam delivery means status from closed to open, the heating source is switched on with a predetermined delay with respect to the opening of the steam delivery means. This allows preventing useless switching on of the heating source in case of steam delivery lasting a non significant time.
Preferably, when the status of the steam delivery means is open, the means for adjusting the pressure value in the boiler is suitable for keeping the heating source on.
This allows remedying the pressure loss in the boiler
Morgandi Arturo
Pietra Diego
Haldiman Robert C.
Husch & Eppenberger LLC
Imetec S.p.A.
Wilson Gregory
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