TECHNICAL FIELD
[0001] The present invention relates to an apparatus that includes a steam generator, such
as an iron for clothing, and in particular, to such an apparatus having improved control
of a steam generator, and a method of controlling such an apparatus.
BACKGROUND OF THE INVENTION
[0002] Appliances such as clothes irons, garment steamers and steam cleaners include a steam
generator system having a boiler to convert water into steam which in turn is supplied
to the soleplate of the iron and exits onto the clothing being ironed through steam
vents in the soleplate. As water is turned into steam in the boiler and vented out
of the appliance, the water level in the boiler reduces and so a water feed to boiler
is required. A pump may be used to pump water from a water reservoir within the appliance
to the boiler. The pump may be automatically controlled so as to feed sufficient water
to the boiler when required. To achieve this function, accurate and precise sensing
of water level in the boiler is required to generate a control signal for the pump.
This may be done by directly measuring the water level in the boiler or indirectly
by measuring water temperature or pressure in the boiler.
[0003] Direct boiler water level measurement is often more complicated and expensive to
manufacture due to the requirement to integrate a sensor within the boiler and also
the requirement to electrically isolate the sensor. In addition direct water level
measurement has a disadvantage that scale can form on the surface of sensor over time
which deteriorates the sensing accuracy.
[0004] Indirect boiler water level measurement is often simpler to implement but can be
less accurate since determination of the water level is often based on extrapolation
of temperature or pressure changes plotted from limited data measurement points.
EP 0843039 discloses an appliance having a steam generator that utilises indirect boiler measurement
and such extrapolation of temperature or pressure changes. In this disclosure, the
water level is determined by measuring a temperature drop of a boiler over a predetermined
time period during steam release from the boiler. However, in this disclosure, and
in other devices that utilise such a water-level determination process, the temperature
drop while the steam outlet valve is open is affected by many factors, including the
valve opening diameter, steam hose length between the boiler and steam outlet vent,
number of steam outlet vents in the appliance, the variable back pressure on steam
outlets at time of use (for example, due to steam outlet path variation due to bending
or coiling of the steam outlet hose and/or vents of an iron soleplate being covered
by a garment), the peak pressure achieved in the boiler at the point of valve opening,
and the effects of voltage amplitude applied to the heater slowing down the rate of
cooling of the boiler during steam release. Therefore, the actual line of temperature
drop against time of the boiler during the steam release is curved or significantly
varying in gradient over the period of steam release. This means that measurement
of a small number of points and extrapolation of a straight line from those few points
on such a varying and/or curved plot will render the calculation of water level within
the boiler inaccurate. This also means that the rate of temperature drop during steam
release is not constant for a given volume of water in the boiler.
SUMMARY OF THE INVENTION
[0005] It is an object of the invention to provide an apparatus including a steam generator,
and a method of controlling the same, which substantially alleviates or overcomes
the problems mentioned above.
[0006] The invention is defined by the independent claims; the dependent claims define advantageous
embodiments.
[0007] One aspect of the invention provides a steam-generating apparatus comprising a water
reservoir, a boiler for generating steam, a temperature or pressure sensor connected
to the boiler for detecting the temperature or pressure of the boiler, a pump configured
to pump water from the reservoir to the boiler, and a controller configured to receive
a signal from the sensor and to control operation of the pump in dependence on the
signal, wherein the controller is configured to determine an amount of water within
the boiler and to control the pump to supply water to the boiler when the determined
amount of water is less than a predetermined value, characterised in that the controller
is arranged to determine the amount of water by measuring at least one time interval
needed for a predetermined increase in temperature or pressure of the boiler and to
compare the measured time interval with a predetermined value.
[0008] The predetermined time value may correspond to a time interval for one or more known
amounts of water to reach the predetermined increase in temperature or pressure.
[0009] The apparatus may further comprise a control valve to allow steam to be released
from the boiler, wherein the controller may be configured to measure a time interval
for an incremental increase in boiler temperature or pressure only when the control
valve is closed and steam is prevented from being released from the boiler. This ensures
time interval(s) are measured in a condition when steam is not being expelled from
the boiler for consistent and accurate prediction and extrapolation of increasing
temperature rate. This also ensures a more stable boiler condition and more consistently
repeatable temperature of pressure measurement results, and avoids the problems of
known water-level detection methods and devices mentioned above.
[0010] The controller may be configured to start measurement of a time interval for an incremental
increase in boiler temperature or pressure following closing of the control valve
after steam has been released from the boiler, and after a predetermined time period
has elapsed after closure of the control valve. The predetermined time period may
be dependent on the time period for which the control valve has been opened. Such
a predetermined time period may comprise around 1 - 5 seconds. This advantageously
allows for the thermal inertia in the system and response time of the sensor after
the end of the previous steam expulsion event. This allows the system to settle to
a steady thermal state before commencing the process described above.
[0011] The controller may be configured to start measurement of a time interval for an incremental
increase in boiler temperature or pressure following closing of the control valve,
and once a detected temperature or pressure within the boiler reaches a threshold
value. This advantageously allows the temperature and/or pressure within the boiler
to stabilise before measurements begin to be taken, allowing for more accurate and
reliable measurements. The threshold at which measurement commences may be a threshold
temperature, and may be a threshold at or above the boiling point of water, and may
be 120°C, or may be 123°C.
[0012] The controller may be configured to operate the pump when the or each measured time
interval for an incremental increase in temperature or pressure of the boiler is less
than a predetermined time interval. This advantageously indicates when more water
is required in the boiler if the water level in the boiler is below a predetermined
minimum volume, since a smaller volume of water would heat quicker than a predetermined
threshold time interval.
[0013] The controller may be configured to operate the pump for a predetermined period of
time. The predetermined period of time may be fixed, or may be dependent upon the
determined amount of water remaining in the boiler. A fixed pump time results in a
simpler control method, although determining the volume of water to be pumped based
on the measured remaining amount allows for a more accurate control of the water level
within the boiler.
[0014] The controller may be configured to measure the or each time interval for an incremental
increase in boiler temperature or pressure during or after an operation of the pump.
The determined water level during or after an operation of the pump may be used to
determine the next operation of the pump.
[0015] The controller may be configured to stop the pump if the determined water level does
not increase in accordance to the period of time of pump operation. This advantageously
helps towards preventing continuous pumping when the water reservoir is depleted and
the potential damage to the pump.
[0016] The controller may comprise a microprocessor and one or more memory units. The predetermined
value may comprise a time interval for incremental temperature or pressure increases
of one or more known amounts of water within the boiler may be stored in one or more
look-up tables within a memory unit of the controller. These enable a quick reference
for the controller to determine the measured time intervals for incremental temperature
increases against that for known volume(s) of water in the boiler.
[0017] The controller may further be arranged to control operation of the boiler in dependence
upon a temperature or pressure signal from the sensor and may stop the boiler heating
water when the sensed temperature or pressure reaches a predetermined threshold value.
This advantageously helps towards preventing overheating of the boiler with associated
over-pressure consequences and potential damage to the apparatus.
[0018] The sensor may comprise a temperature sensor, and may comprise a thermistor, and
may comprise a negative temperature coefficient (NTC) thermistor. The thermistor may
be mounted to a metallic substrate and the metallic substrate may be mounted to the
boiler. The sensor may be mounted to a top or upper portion of the boiler. The sensor
may be mounted to an outer surface of the boiler. This advantageously avoids deterioration
of the sensor through calcification.
[0019] The apparatus may comprise more than two temperature sensors which may comprise thermistors
as described above. Each sensor may be mounted to an upper or top portion of the boiler,
or one may be mounted to an upper or top portion and another may be mounted to an
alternative portion of the boiler. This advantageously enables accurate temperature
measurement by at least one sensor being spaced apart from the heater element so as
not to detect directly the heater temperature. Placing the temperature sensors in
a spaced relationship advantageously allows determination of accurate temperature
measurement by enabling comparison of temperatures detected at different points in
the boiler. It also advantageously allows detection of a dry boiler condition, if
one sensor is placed proximate the heater, by detecting an excessive heating of the
boiler in the absence of water, or by detecting an excessive difference between temperatures
sensed by a sensor proximate the heater and a sensor remote from the heater. The sensor
proximate the heater may comprise a cut-off device such as a thermostat.
[0020] Alternatively, the or each sensor may comprise a pressure sensor. In a closed volume
boiler of known dimensions, temperature and pressure are well correlated and so may
be functionally interchangeable.
[0021] There is also disclosed herein a method of operating a steam generating apparatus
which comprises a water reservoir, a boiler for generating steam, a temperature or
pressure sensor connected to the boiler for detecting the temperature of or pressure
in the boiler, a pump configured to pump water from the reservoir to the boiler, and
a controller configured to receive a signal from the sensor and control operation
of the pump in dependence on the signal, the method comprising determining an amount
of water within the boiler and controlling the pump to supply water to the boiler
when the determined amount of water is less than a predetermined value, characerised
in that the method comprises determining the amount of water by measuring at least
one time interval for a predetermined increase in temperature of or pressure in the
boiler and comparing the measured time interval with a predetermined value.
[0022] The method may comprise measuring a time interval for an incremental increase in
boiler temperature or pressure only when a control valve to allow steam to be released
from the boiler is closed and steam is prevented from being released from the boiler.
[0023] The method may comprise starting measurement of time interval for an incremental
increase in boiler temperature or pressure following closing of the control valve
after steam has been released from the boiler, and after a predetermined time period
has elapsed after closure of the control valve. Such predetermined time period may
comprise 1 - 5 seconds, any may comprise around 3 seconds.
[0024] The method may comprise operating the pump for a predetermined period of time in
dependence upon the determined amount of water remaining in the boiler.
[0025] The step of comparing the measured time interval with a predetermined value may comprise
comparing a measured time interval with a predetermined time interval for an incremental
temperature or pressure increase of one or more known amounts of water within the
boiler stored in one or more look-up tables within a memory unit of the controller.
[0026] The method may comprise controlling operation of the boiler in dependence upon a
temperature or pressure signal from the sensor and stopping the boiler heating water
when the sensed temperature or pressure reaches a predetermined threshold value. This
prevents overheating of the boiler and/or excessive pressure build-up within the boiler.
[0027] The controller may be configured to perform measurement of one or more time intervals
for incremental increases in temperature or pressure of the boiler within a predetermined
range of temperatures or pressures of the boiler. Such range of temperatures may comprise
from 120°C to 160°C, or may comprise from 123°C to 146°C. The boiler may be configured
such that the range of temperatures over which the controller performs measurement
of the time interval(s) for one or more incremental increases in temperature of the
boiler corresponds to a predetermined range of internal pressure of the boiler. Such
predetermined range of internal pressure of the boiler may comprise between 1.5 Bar
and 6.5 Bar.
[0028] The water reservoir of the apparatus may be unpressurised. A one-way valve may be
provided between the pump and the boiler to prevent steam passing back to the pump
and/or the reservoir. This advantageously prevents inaccurate boiler control which
would result from escaping steam during a measurement process, and also avoids pump
damage by preventing exposure to steam.
[0029] The increments of increasing temperature over which time intervals are measured may
comprise constant temperature increments over the measurement range, and may comprise
increments of one degree Celsius, although the invention is not intended to be limited
to single degree Celsius increments.
[0030] The boiler may comprise one or more heating elements. The heating element(s) of the
boiler may be internal or external to the boiler. Internal elements may more efficiently
heat the water within the boiler, although external elements are advantageous in avoiding
deterioration such as calcification by the boiling of the water.
[0031] The controller may be configured to continue measuring one or more time intervals
for predetermined incremental increases in temperature or pressure of the boiler during
a heating operation of the boiler and comparing the measured time intervals with predetermined
time intervals for incremental temperature or pressure increases of one or more known
amounts of water within the boiler until an upper threshold temperature or pressure
of the boiler is reached or an actuator or trigger operating the control valve is
operated to release steam from the boiler.
[0032] The controller may be configured to perform the or each measurement of time interval(s)
for predetermined incremental increase(s) in temperature or pressure of the boiler
and compare the measured time interval(s) with known time interval(s) for incremental
temperature or pressure increase(s) of known water levels, during the period when
the sensed temperature or pressure in the boiler is below the predetermined threshold
temperature or pressure and power is being supplied to the boiler.
[0033] The apparatus may comprise an actuator button or trigger operable to actuate the
control valve. The controller may be connected to the control valve and/or the actuator
button to detect actuation of the control valve and/or the actuator button.
[0034] The apparatus may comprise a clothes steam iron appliance, and may comprise a base
portion and a hand-held portion. The hand held portion may be electrically and fluidly
connected to the base portion for the supply of power and steam from the base portion
to the hand-help portion. The reservoir, pump and boiler may be provided in the base
portion. An actuator button may be provided on the hand-held portion operable to actuate
the control valve.
[0035] These and other aspects of the invention will be apparent from and elucidated with
reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Embodiments of the invention will now be described, by way of example only, with
reference to the accompanying drawings, in which:
Fig. 1 shows a schematic diagram of an appliance according to a first embodiment of
the invention;
Fig. 2 shows a graph with a plot of boiler temperature versus time for a given volume
of water within the boiler;
Fig. 3 shows a graph with multiple plots of temperature versus time for a range of
volumes of water within the boiler
Fig. 4 shows a first exemplary look-up table of the controller of the appliance of
the invention;
Fig. 5 shows a flow chart illustrating the method of operation of the invention; and
Fig. 6 shows a second exemplary look-up table of the controller of the appliance of
the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0037] Referring now to Fig. 1, an appliance of a first embodiment of the invention is schematically
shown, which in this exemplary embodiment, comprises a steam iron 1. The steam iron
1 includes a body 2 and a soleplate 3. The steam iron 1 is configured to apply steam
to clothes being ironed through apertures 4 in the soleplate 3.
[0038] The steam iron 1 includes a water reservoir 5 and a boiler 6. A pump 7 is provided
to pump water from the reservoir 5 to the boiler 6. A first conduit 8 fluidly connects
the reservoir 5 to the pump 7, and a second conduit 9 fluidly connects the pump to
the boiler 6. The reservoir 5 is an unpressurised container. The boiler 6 comprises
a closed container or shell, with a heating element 10 to heat water within the boiler
6 to make steam. The heating element is shown disposed within the boiler 6 although
may equally be disposed on an outer surface of the boiler shell within the scope of
the invention. A third conduit 11 connects the boiler 6 to the body 2 of the steam
iron 1 for the supply of steam from the boiler 6 to the body 2 of the steam iron 1
to be expelled from the apertures 4 in the soleplate 3.
[0039] A control valve 12 is provided to control the supply of steam from the boiler 6 to
the soleplate 3. This may be provided in the third conduit as shown in Fig. 1, or
may alternatively be provided in the body 2 of the iron 1, or alternatively also on
the body 6 of the boiler. The body 2 of the iron includes an actuator 13 which operates
the control valve 12. A user can thereby control steam to be expelled through the
soleplate 3 by pressing the actuator 13.
[0040] The boiler 6 includes a sensor 14 on an upper surface of the boiler shell which,
in this first embodiment comprises a temperature sensor. However, as will be described
later, the invention is not intended to be limited to use of a temperature sensor
and alternatively, a pressure sensor may be provided within the scope of the invention.
The temperature sensor 14 is preferably a NTC thermistor which is secured to the boiler
shell, for example by being bonded thereto, and is in good thermal contact with the
boiler shell. Advantageously, the thermistor is mounted to a metallic substrate (not
shown) which is itself mounted to the boiler shell. This provides very good thermal
conductivity between the boiler shell and the thermistor and reduces the thermal inertia
and delay in response of the thermistor. The temperature sensor being mounted on an
upper surface of the boiler shell is advantageous because it means more consistent
temperature readings are obtained relating to steam temperature within the boiler.
If the temperature sensor 14 was on the bottom of the shell, for example, a significant
drop in temperature of the boiler shell would be detected whenever cool water is pumped
into the boiler 6 from the reservoir 5, distorting the indication of the amount and
temperature of steam remaining within the boiler 6.
[0041] A controller 15 is provided to control operation of the steam iron 1 and includes
a microprocessor and a memory unit. The controller 15 is connected to the heater 10
and to the pump 7 to control operation of these two components. The controller 15
is connected to the temperature sensor 14 to receive temperature signals from the
temperature sensor 14. The controller 15 is also connected to the control valve 12
to determine when the control valve 12 is on or off, as determined by a user by operation
of the actuator 13.
[0042] The steam iron 1 is connectable to an external power supply, such as domestic mains
electricity, by a power cable (not shown), to power the various components of the
iron 1, including the heating element 10 of the boiler 6, heating element(s) in the
soleplate 3 (not shown), the pump 7 and the controller 15.
[0043] The controller 15 is configured to control operation of the pump 7 to supply water
from the reservoir 5 to the boiler 6 when the water level in the boiler is low, in
dependence upon temperature signals received from the sensor 14. More specifically,
the controller determines an unknown remaining volume of water in the boiler 6 by
measuring the rate of increase in temperature of the boiler during a period when the
actuator 13 is not operated and therefore steam is not being expelled by the steam
iron 1. The controller determines time intervals taken for the sensed temperature
of the boiler to increase in pre-determined temperature increments when the heater
10 is activated. The controller 15 then compares these measured time values against
known time intervals, which are stored in the memory of the controller 15, for given
volumes of water in the boiler 6 and uses this comparison of the measured time values
against known time values to determine whether the volume of water remaining in the
boiler 6 is below a minimum threshold value at which the boiler 6 needs to be refilled.
If refilling is required, the controller 15 operates the pump 7 for an appropriate
period to refill the boiler 6 with a required volume of water.
[0044] In embodiments of the invention, the controller measures the time taken for each
degree Celsius rise in sensed temperature of the boiler 6. These measurements may
occur within a predetermined range of temperatures of the boiler 6, for example, between
120°C and 160°C, which may correspond to an internal pressure within the boiler 6
of between 1.5 Bar and 6.5 Bar. The time measurements for increasing temperature are
taken when the control valve 12 is closed and so no steam may escape or be expelled
from the boiler 6.
[0045] Since the volume of the boiler is constant, the power supplied to the boiler (e.g.
from the mains voltage) is constant, and the control valve 12 is closed during the
measurement process, the only variable factor that can affect the rate at which the
water temperature within the boiler increases is the mass of water within the boiler
6. As such, for a given boiler 6 and power input, accurate predetermined values of
time taken for incremental increases in temperature for specific volumes of water
can be calculated. Plots of such known time intervals for incremental temperature
increases are shown in Figs. 2 and 3. Fig. 2 shows a graph plot of time (y-axis) in
seconds against increasing temperature increments (x-axis) in degrees Celsius for
a given volume of water (e.g. 350ml) being heated in the boiler 6. This is shown as
the single line i in Fig. 2. Fig. 3 shows groups of plots of temperature increments
against time, each group comprising three test plots for different volumes of water
in a boiler. The graph of Fig. 3 comprises plots for 350ml (group A comprising lines
i, ii and iii), 300ml (group B comprising lines iv, v and vi), 250ml (group C comprising
lines vii, viii and ix) and 200ml (group D comprising lines x, xi and xii) of water
in a boiler. This data relating to the rising linear plot lines for known volumes
of water are stored as reference data in look-up tables in the memory of the controller
15, as shown in Fig. 4. The exemplary look up table in Fig. 4 shows data within the
temperature range mentioned above, namely a start temperature T
emp of 120°C and an end temperature T
emp of 160°C. In between these start and end temperature values are incrementally increasing
temperature values. These are not shown in Fig. 4. Instead, one pointer temperature
value T
ptr is shown in Fig. 4, which is relevant for the control process of the invention as
will be explained in more detail below. Against each temperature value are time values
in seconds for the respective volume of water in the boiler to reach each incremental
temperature value. The time values start from zero at the start temperature. In Fig.
4, the time at the end temperature value is simply shown as 'n' as this will differ
for each look-up table that relates to different volumes of water.
[0046] It can be seen from the plots in Fig. 3 that, as would be expected, the plots for
200ml of water (group D) take less time to increase in temperature (by being shallower
plot gradient) than the plot lines for 250ml (group C), which in turn are shallower
than the plot lines for 300ml (group B), which again are shallower than the plot lines
for 350ml (group A) of water.
[0047] Referring to Fig. 5, a logic process of the controller 15 of the invention is shown
as a flow chart. Since the time measurement of the control process of the invention
occurs when the control valve 12 is closed (i.e. when no steam may be expelled through
the sole plate 3), the process begins from a start point at S0 and comprises a first
step S1 at which the controller 15 determines whether the electronic control valve
12 is closed. If not, the process loops back to before step S1 until it is determined
that the control valve 12 is closed. If it is determined at step S1 that the control
valve is closed, the process proceeds to step S2.
[0048] At step S2, the temperature T
emp of the boiler 6 sensed by the sensor 14 is measured. The process then proceeds to
step S3, in which the controller determines whether the measured temperature T
emp is greater than a value of a pointer temperature minus 1 (T
ptr - 1) and less than a value of a pointer temperature plus 1 (T
ptr + 1). The control operator for this step can be represented as [(T
ptr - 1) < T
emp < (T
ptr + 1)]. Here, the pointer temperature T
ptr is the incremental increasing temperature along the x-axis against which time measurements
are to be recorded, and this value is initially set at a value at the lower end of
the range within which temperature measurements are to be taken, for example 120°C.
If the measured temperature T
emp is within the range (T
ptr - 1) and (T
ptr + 1), then the process proceeds to step S4 at which a time measurement t at that
moment, counting from the start of the measurement process, is captured. If the measured
temperature T
emp is not within the range (T
ptr - 1) and (T
ptr + 1), then process proceeds to step S5 at which the pointer temperature T
ptr is incremented by one degree. The process then loops back to step S2 to detect the
boiler 6 temperature again.
[0049] After step S4, at step S6 the controller 15 determines from the look-up tables whether
the measured time t is less than a reference time in the look-up table for the pointer
temperature value in question (t@T
ptr) at a threshold volume of water below which refilling is required. This control operator
can be represented as [t < t@T
ptr?]. If yes - namely the water in the boiler 6 has heated up quicker than a time interval
for a minimum threshold volume of water, then the volume of water within the boiler
6 is below the threshold volume and the process proceeds to step S7 at which the controller
15 activates the pump 7 for a predetermined period of time to refill the boiler 6
with water, after which the process loops back to the beginning to repeat from step
S1. The period of time the pump 7 operates to refill the boiler 6 is predetermined
based on the known boiler volume and the threshold minimum volume at which the pump
activates, and the known pump specification including the pump's fluid flow rate.
[0050] If the controller determines at step S6 that the measured time t is greater than
a reference time in the look-up table for the pointer temperature value in question
at a threshold volume of water below which refilling is required, then it is not necessary
to fill the boiler 6 with more water and so the process loops back to the beginning
to repeat from step S1. The process then continues as described above to record the
time intervals for incremental temperature increases as the water in the boiler 6
continues to heat up.
[0051] The temperature in the boiler 6 is regulated to remain below an upper threshold value.
The controller 15 receives temperature signals from the sensor 14 and if the sensed
temperature reaches the upper threshold value, the controller 15 turns off the heater
10 of the boiler 6. It will be appreciated that the above-described process occurs
whilst the heater 10 is activated and is heating water in the boiler, and the control
valve 12 is closed. Therefore, steps S2 to S7 of the above control process is repeated
until the threshold temperature is reached (and the heater 10 is then turned off by
the controller 15) or the actuator 13 is operated by the user (and the control valve
12 is thereby opened to expel steam). Thereafter, the whole process is repeated upon
every release of the actuator 13 - i.e. after each steam expulsion event.
[0052] In an embodiment of the invention, the controller 15 advantageously includes a delay
time t
d (not shown in the Figs.) after step S1 after a positive response is obtained, before
taking a temperature measurement T
emp in step S2. This delay t
d corresponds to a time delay from the moment the actuator 13 is released by a user
and the control valve 12 closes, stopping expulsion of steam from the boiler 6 through
the apertures 4 in the soleplate 3. This delay allows for the thermal inertia in the
system and response time of the sensor 14 after the end of the previous steam expulsion
event. This allows the system to settle to a steady thermal state before commencing
the process described above. Such a delay period t
d may vary within the scope of the invention but advantageously may be around 1 - 5
seconds, and may be around 3 seconds. In such an embodiment, the above-described control
process is repeated upon every release of the actuator 13 if the period after operation
of the actuator exceeds the predetermined delay time t
d.
[0053] It can be seen from Figs. 2 and 3 that the rising temperature vs. time plots are
substantially linear and so it is possible to accurately calculate the rising gradient
of the graph plot from only a few closely spaced temperature increment/time measurements
(e.g. one degree Celsius increments), and to accurately predetermine time intervals
taken for a given volume of water to heat up by given temperature increments for a
known boiler specification and power supply by extrapolation from those measurements.
The linear plots are related to, and represent, the heat capacity and specific heat
of water within the closed environment of the boiler 6 (since time measurements are
taken when the steam outlet valve is closed), and for a given (constant) volume of
water. The linearity is thereby related to these constant factors which enable the
accurate and predictable water volume prediction of the method and apparatus of the
invention. It also means that it is not critical at what boiler temperature, within
a measurement range, the time interval measurement process is commenced because the
plot line of time vs. temperature, and the rate of water heating within the boiler,
is substantially linear across the temperature range either side of the process start
point temperature. This linearity of plot lines makes the method of volume determination
of the invention significantly more accurate than other methods where, for example,
decreasing temperature or pressure measurements of a boiler of a steam generation
device are taken over a time during which steam is being expelled from the boiler.
This is because a plot of temperature decrease during steam expulsion against time
is much less linear and is more curved/parabolic, meaning extrapolation from a few
closely spaced initial measurements is inaccurate. Also, temperature decrease during
steam expulsion is affected by a number of variables, such as back pressure on the
soleplate due to garments covering the steam apertures, peak pressure and temperature
within the boiler at the point when the valve is opened to commence steam expulsion
and the degree of valve opening diameter/size. Therefore, such variables make predictions
of water volume within a boiler based on measured temperature or pressure decrease
during steam expulsion inaccurate.
[0054] The use of look-up tables in the apparatus and method of the invention compensates
for any slight non-linearity that may exist in the actual rising time vs. temperature
plot line. Also, the method and apparatus of the invention is not affected by variables
in other processes or systems such as those mentioned above. The use of look-up tables
also means that different power supply voltages, for example different mains voltages
in different countries, can easily be accounted for by including in the controller
memory further pre-programmed time interval and temperature increment data for a given
boiler specification for known volumes of water, for different power supplies. The
controller can then reference the relevant look up table data in dependence upon the
detected power supply voltage being used with the appliance.
[0055] The embodiment of the invention described above may comprise a clothes steam iron
appliance in which the water reservoir 5, pump 7 and boiler 6 are provided within
a fixed base and the body 2 of the iron and soleplate 3 are a handheld component of
the overall appliance. In such an embodiment, the base would be connected to the mains
power supply and the iron body 2 would be connected to the base by a steam supply
duct to supply steam from the boiler 6 to the soleplate 3, and an electrical power
cable for the supply of power from the base to the heating elements within the soleplate.
The actuator 13 would be provided on the body 2, although the control valve 12 may
be either within the body 2 or within the base.
[0056] In an alternative embodiment of the invention, the controller 15 may be configured
such that at step S3, if it is determined that the measured temperature T
emp is between (T
ptr - 1) and (T
ptr + 1), at step S4, the controller 15 sets the timing counter to zero (i.e. t = 0)
and then begins timing the time taken for a predetermined incremental temperature
increase (e.g. one degree Celsius) above T
ptr to occur. That is, the control system loops around taking temperature T
emp measurements until the measured temperature T
emp reaches the predetermined incremental temperature increase above T
ptr. Once that temperature increase has been achieved, the time t is captured for achieving
that increase. Then, the controller 15 may use the measured time t to reference a
relevant look-up table for the particular T
ptr value and compare if the measured time t is higher or lower than a reference time
in the look-up table, in step S6. Such a look-up table is shown, as an example only,
in Fig. 6, and may store different time period values to heat a range of volumes of
water (e.g. 50ml, 100ml, 150ml, 200ml... etc.) by an incremental temperature increase
from a given T
ptr temperature (shown as T
ptr = 135 degrees Celsius in the table of Fig. 6). If, for example, the measure t is
6.2 seconds, then the controller 15 will determine, using the exemplary look-up table
of Fig. 6, that the water level in the boiler 6 is between 150 - 200ml. Based on the
target water level to be maintained in the boiler 6 (which may be preset in the controller
or operating program instructions), the controller 15 will make a decision at step
S6 whether or not to activate the pump 7, and if yes, for how long. (For example,
if target water level is 250ml, then controller may operate the pump for 3 seconds).
In one mode of operation of the invention, the pump 7 may have only one fixed time
interval of operation. However, within the scope of the invention, the pump 7 may
have a variable mode of operation, for example, variable pumping time which may be
based on the difference between estimated water level and a target water level, and
the controller 15 may then operate the pump 7 for a required period of time depending
on how much water it is determined is required to fill the boiler 6 to the pre-determined
level.
[0057] In an alternative operation of the embodiments described above, at step S6 the controller
15 may compare the measured time t with time values of a plurality of stored look-up
table time values at the corresponding pointer temperature T
ptr (t@T
ptr) for a range of known volumes of water, instead of only determining whether the measured
time t is less than a reference time for the pointer temperature value at a threshold
minimum volume of water below which refilling is required. In this alternative embodiment,
the controller can determine the actual volume of water within the boiler 6, not just
whether volume of water within the boiler is below a minimum value for refilling.
Therefore, once the actual volume of water remaining within the boiler has been determined,
the controller 15 can determine the volume of water needed to be pumped into the boiler
6 to fill the boiler 6, and therefore can operate the pump 7 for an appropriate amount
of time to fill the boiler 6. The period of time the pump 7 operates to refill the
boiler 6 would be predetermined based on the known total boiler volume and the various
known volumes relating to each look up table, and the known pump specification including
the pump's fluid flow rate.
[0058] In an embodiment of the invention, the controller may be configured to measure the
time intervals for incremental increases in boiler temperature during or after operation
of the pump in order to provide more accurate water level control within the boiler.
In such an embodiment, the controller performs an iterative loop of time measurements
as part of the method of operation. As such, referring to Fig. 5, rather than just
performing one measurement of time for a temperature increase for each time the control
valve 12 is closed, the process loop may instead loop back from step S7 where the
pump is activated, to step S2 to repeat the temperature and time measurement process.
[0059] In such an alternative apparatus and method of the invention, the controller may
be configured to detect when the reservoir 5 is empty, by measuring a temperature
before and after a pump activation step at S7. If there is no change (or an increase)
in the sensed temperature within the boiler, it indicates that no water was fed by
the pump 7 from the reservoir 5 to the boiler because the reservoir is empty and so
the water level within the boiler has not increased. In order to prevent continuous
operation of the pump when the reservoir is empty (which could damage or cause excessive
wear to the pump), the controller 15 may be configured to stop the pump if it is determined
that the water level within the boiler does not increase after an operation of the
pump, indicated by no detected change (or an increase) in boiler temperature after
operation of the pump.
[0060] In addition to the above, in such an alternative apparatus and method of the invention,
by measurement of time intervals for incremental increases in boiler temperature during
or after operation of the pump, the controller is able to determine the water level
within the boiler and may therefore store in a memory of the controller the current
water level. This may then be used to determine the next operation of the pump, in
terms of when to next refill the boiler, or the duration of pump operation required
at the next pump operation to fill the boiler with the required amount of water.
[0061] In the embodiment described above, a single sensor 14 is provided on shell of the
boiler 6. However, in an alternative embodiment of the invention, two temperature
sensors may be provided on the boiler shell. These may both be placed on different
portions of the upper surface of the boiler shell and the controller 15 may receive
signals from both sensors and average the two values to obtain more accurate readings
of the boiler temperature. Alternatively, one sensor may be mounted on the top of
the boiler shell and another may be mounted on a side wall of the boiler shell. Again,
the controller 15 may receive signals from both sensors and average the two values
to obtain more accurate readings of the boiler temperature.
[0062] In a dry boiler condition (i.e. in the absence of water in the boiler), no steam
can be generated and therefore the sensor will not be measuring the steam temperature
and instead would be measuring the boiler shell temperature. The use of two sensors
may be used to detect a dry-boiler condition and prevent overheating. In such a case,
a first sensor is positioned away from the heater 10, preferably on the top of the
boiler shell, so as not to be affected by the heater temperature, and is used for
measuring the temperature of the steam inside the boiler. The first sensor (14, as
in Fig. 1) is therefore not sensitive to the temperature of the heater at the bottom.
A second sensor (not shown) may be provided at or near the bottom of the boiler so
that it can detect any overheating at the bottom. In such an embodiment, second sensor
may be a cut-off device such as a thermostat, which may enable the heater 10 to be
stopped if the detected temperature at the location of the second sensor exceeds a
predetermined value (indicative of the heater 10 heating to a high temperature in
the absence of water). Alternatively, the controller may be configured to compare
the sensed temperatures of the first and second sensors and, if the difference between
the two values is above a predetermined value, it indicates a dry-boiler condition.
This is because the heater would heat to a high temperature in the absence of water
and be detected by the second sensor, and the absence of steam would mean the first
sensor would not be exposed to any heated steam so would detect a lower temperature
than expected. In such a situation, the controller may be configured to stop operation
of the heater 10 to avoid damage to the apparatus.
[0063] In the embodiments described above, the sensor 14 comprises a temperature sensor.
However, it is intended with the scope of the invention that the sensor may alternatively
comprise a pressure sensor. In a closed boiler system such as that of the embodiments
described above, temperature and pressure are well correlated and so may be functionally
interchangeable. In such an alternative embodiment, operation of the apparatus would
be as described above except that where a sensor signal relating to a measured temperature
is stated, this is to be replaced with a sensor signal relating to pressure within
the boiler. The time measurements may be taken within a range of boiler pressures,
such as between 1.5 - 6.5 Bar, as mentioned above, and the look-up table, such as
that shown in Fig. 4, may store known time intervals taken to reach predetermined
boiler pressures within such a range for known volume(s) of water. Such an alternative
apparatus and method of operating such an apparatus would still provide the above-described
advantages over known systems.
[0064] Although the embodiment of the invention described above is a steam iron 1, the invention
is not intended to be limited to such an appliance and may comprise other forms of
steam generating device, for example, clothes steamers, wall-paper steamers, steam
ovens, or steam cleaning devices e.g. for cleaning floors.
[0065] It will be appreciated that the term "comprising" does not exclude other elements
or steps and that the indefinite article "a" or "an" does not exclude a plurality.
The mere fact that certain measures are recited in mutually different dependent claims
does not indicate that a combination of these measures cannot be used to an advantage.
Any reference signs in the claims should not be construed as limiting the scope of
the claims.
1. A steam-generating apparatus (1) comprising a water reservoir (5), a boiler (6) for
generating steam, a sensor (14) connected to the boiler (6) for detecting the temperature
of or pressure in the boiler (6), a pump (7) configured to pump water from the reservoir
(5) to the boiler (6), and a controller (15) configured to receive a signal from the
sensor (14) and to control operation of the pump (7) in dependence on the signal,
wherein the controller (15) is configured to determine an amount of water within the
boiler (6) and to control the pump (7) to supply water to the boiler (6) when the
determined amount of water is less than a predetermined value, characterised in that the controller (15) is arranged to determine the amount of water by measuring at
least one time interval needed for a predetermined increase in temperature of or pressure
in the boiler (6) and to compare the measured time interval with a predetermined time
value.
2. A steam-generating apparatus (1) according to claim 1 wherein the predetermined time
value corresponds to a time interval for one or more known amounts of water to reach
the predetermined increase in temperature or pressure.
3. A steam-generating apparatus (1) according to claim 1 or claim 2 further comprising
a control valve (12) to allow steam to be released from the boiler (6), wherein the
controller (15) is configured to measure a time interval for an incremental increase
in boiler (6) temperature or pressure only when the control valve (12) is closed and
steam is prevented from being released from the boiler (6).
4. A steam-generating apparatus (1) according to claim 3 wherein the controller (15)
is configured to start measurement of a time interval for an incremental increase
in boiler (6) temperature or pressure following closing of the control valve (12)
after steam has been released from the boiler (6), and after a predetermined time
period has elapsed after closure of the control valve (12).
5. A steam-generating apparatus (1) according to any preceding claim wherein the controller
(15) is configured to operate the pump (7) when the measured time interval for an
incremental increase in temperature or pressure of the boiler (6) is less than a predetermined
time interval.
6. A steam-generating apparatus (1) according to any preceding claim wherein the controller
(15) is configured to operate the pump (7) for a predetermined period of time in dependence
upon the determined amount of water remaining in the boiler (6).
7. A steam-generating apparatus (1) according to any preceding claim wherein the predetermined
time value comprises a time interval for an incremental temperature or pressure increase
of one or more known amounts of water within the boiler (6) which are stored in one
or more look-up tables within a memory unit of the controller (15).
8. A steam-generating apparatus (1) according to any preceding claim wherein the controller
(15) is arranged to further control the operation of the boiler (6) in dependence
upon a temperature or pressure signal from the sensor (14) and stops the boiler (6)
heating water when the sensed temperature or pressure reaches a predetermined threshold
value.
9. A steam-generating apparatus (1) according to any preceding claim wherein the sensor
(14) comprises a thermistor mounted to a metallic substrate and the metallic substrate
is mounted to the boiler (6).
10. A method of operating a steam generating apparatus (1) which comprises a water reservoir
(5), a boiler (6) for generating steam, a sensor (14) connected to the boiler (6)
for detecting the temperature of or pressure in the boiler (6), a pump (7) configured
to pump water from the reservoir (5) to the boiler (6), and a controller (15) configured
to receive a signal from the sensor (14) and control operation of the pump (7) in
dependence on the signal, the method comprising determining an amount of water within
the boiler (6) and controlling the pump (7) to supply water to the boiler (6) when
the determined amount of water is less than a predetermined value, characterised in that the method comprises determining the amount of water by measuring at least one time
interval needed for a predetermined increases in temperature of or pressure in the
boiler (6), and comparing the measured time interval with a predetermined time value.
11. A method according to claim 10 comprising measuring a time interval for an incremental
increase in boiler (6) temperature or pressure only when a control valve (12) to allow
steam to be released from the boiler (6) is closed and steam is prevented from being
released from the boiler (6).
12. A method according to claim 11 comprising starting measurement of a time interval
for an incremental increase in boiler (6) temperature or pressure following closing
of the control valve (12) after steam has been released from the boiler (6), and after
a predetermined time period has elapsed after closure of the control valve (12).
13. A method according to any of claims 10 to 12 comprising operating the pump (7) for
a predetermined period of time in dependence upon the determined amount of water remaining
in the boiler (6).
14. A method according to any of claims 10 to 13 wherein the step of comparing the measured
time interval with a predetermined time value comprises comparing a measured time
interval with a predetermined time interval for incremental temperature or pressure
increases of one or more known amounts of water within the boiler (6) stored in one
or more look-up tables within a memory unit of the controller (15).
15. A method according to any of claims 10 to 14 comprising controlling operation of the
boiler (6) in dependence upon a temperature or pressure signal from the sensor (14)
and stopping the boiler (6) heating water when the sensed temperature or pressure
reaches a predetermined threshold value.
1. Dampferzeugungsvorrichtung (1), umfassend einen Wasserbehälter (5), einen Heizkessel
(6) zum Erzeugen von Dampf, einen mit dem Heizkessel (6) verbundenen Sensor (14) zum
Erfassen der Temperatur des, oder des Drucks im Heizkessel (6), eine Pumpe (7), die
dazu ausgebildet ist, Wasser aus dem Behälter (5) zum Heizkessel (6) zu pumpen, und
eine Steuerung (15), die dazu ausgebildet ist, ein Signal aus dem Sensor (14) zu empfangen
und Betrieb der Pumpe (7) in Abhängigkeit von dem Signal zu steuern, wobei die Steuerung
(15) dazu ausgebildet ist, eine Wassermenge innerhalb des Heizkessels (6) zu bestimmen
und die Pumpe (7) so zu steuern, dass sie dem Heizkessel (6) Wasser zuführt, wenn
die Wassermenge, die bestimmt wurde, weniger als einen vorbestimmten Wert beträgt,
dadurch gekennzeichnet, dass die Steuerung (15) dazu eingerichtet ist, die Wassermenge durch Messen von mindestens
einem Zeitintervall zu bestimmen, das für einen vorbestimmten Anstieg der Temperatur
des, oder des Drucks im Heizkessel (6) benötigt wird, und das gemessene Zeitintervall
mit einem vorbestimmten Zeitwert zu vergleichen.
2. Dampferzeugungsvorrichtung (1) nach Anspruch 1, wobei der vorbestimmte Zeitwert einem
Zeitintervall für eine oder mehrere bekannte Wassermengen entspricht, um den vorbestimmten
Temperatur- oder Druckanstieg zu erreichen.
3. Dampferzeugungsvorrichtung (1) nach Anspruch 1 oder Anspruch 2, weiter ein Steuerventil
(12) umfassend, um zu ermöglichen, dass Dampf aus dem Heizkessel (6) abgelassen wird,
wobei die Steuerung (15) dazu ausgebildet ist, ein Zeitintervall für einen inkrementellen
Anstieg der Temperatur oder des Drucks des Heizkessels (6) nur dann zu messen, wenn
das Steuerventil (12) geschlossen ist und Dampf daran gehindert wird, aus dem Heizkessel
(6) abgelassen zu werden.
4. Dampferzeugungsvorrichtung (1) nach Anspruch 3, wobei die Steuerung (15) dazu ausgebildet
ist, die Messung eines Zeitintervalls für einen inkrementellen Anstieg der Temperatur
oder des Drucks des Heizkessels (6) im Anschluss an das Schließen des Steuerventils
(12), nachdem Dampf aus dem Heizkessel (6) abgelassen wurde und nachdem ein vorbestimmter
Zeitraum nach Schließen des Steuerventils (12) verstrichen ist, zu starten.
5. Dampferzeugungsvorrichtung (1) nach einem vorstehenden Anspruch, wobei die Steuerung
(15) dazu ausgebildet ist, die Pumpe (7) zu betreiben, wenn das gemessene Zeitintervall
für einen inkrementellen Anstieg der Temperatur oder des Drucks des Heizkessels (6)
weniger als ein vorbestimmtes Zeitintervall beträgt.
6. Dampferzeugungsvorrichtung (1) nach einem vorstehenden Anspruch, wobei die Steuerung
(15) dazu ausgebildet ist, die Pumpe (7) in Abhängigkeit von der im Heizkessel (6)
verbleibenden Wassermenge, die bestimmt wurde, für einen vorbestimmten Zeitraum zu
betreiben.
7. Dampferzeugungsvorrichtung (1) nach einem vorstehenden Anspruch, wobei der vorbestimmte
Zeitwert ein Zeitintervall für einen inkrementellen Temperatur- oder Druckanstieg
von einer oder mehreren bekannten Wassermengen innerhalb des Heizkessels (6) umfasst,
die in einer oder mehreren Nachschlagetabellen innerhalb einer Speichereinheit der
Steuerung (15) gespeichert sind.
8. Dampferzeugungsvorrichtung (1) nach einem vorstehenden Anspruch, wobei die Steuerung
(15) dazu eingerichtet ist, weiter den Betrieb des Heizkessels (6) in Abhängigkeit
von einem Temperatur- oder Drucksignal aus dem Sensor (14) zu steuern, und das Aufheizen
von Wasser durch den Heizkessel (6) stoppt, wenn die/der gefühlte Temperatur oder
Druck einen vorbestimmten Schwellenwert erreicht.
9. Dampferzeugungsvorrichtung (1) nach einem vorstehenden Anspruch, wobei der Sensor
(14) einen Thermistor umfasst, der auf einem metallischen Substrat befestigt ist,
und das metallische Substrat am Heizkessel (6) befestigt ist.
10. Verfahren zum Betreiben einer Dampferzeugungsvorrichtung (1), die einen Wasserbehälter
(5), einen Heizkessel (6) zum Erzeugen von Dampf, einen mit dem Heizkessel (6) verbundenen
Sensor (14) zum Erfassen der Temperatur des, oder des Drucks im Heizkessel (6), eine
Pumpe (7), die dazu ausgebildet ist, Wasser aus dem Behälter (5) zum Heizkessel (6)
zu pumpen, und eine Steuerung (15) umfasst, die dazu ausgebildet ist, ein Signal aus
dem Sensor (14) zu empfangen und Betrieb der Pumpe (7) in Abhängigkeit von dem Signal
zu steuern, wobei das Verfahren das Bestimmen einer Wassermenge innerhalb des Heizkessels
(6) und Steuern der Pumpe (7) so umfasst, dass sie dem Heizkessel (6) Wasser zuführt,
wenn die Wassermenge, die bestimmt wurde, weniger als einen vorbestimmten Wert beträgt,
dadurch gekennzeichnet, dass das Verfahren das Bestimmen der Wassermenge durch Messen von mindestens einem Zeitintervall,
das für einen vorbestimmten Anstieg der Temperatur des, oder des Drucks im Heizkessel
(6) benötigt wird, und Vergleichen des gemessenen Zeitintervalls mit einem vorbestimmten
Zeitwert umfasst.
11. Verfahren nach Anspruch 10, umfassend das Messen eines Zeitintervalls für einen inkrementellen
Anstieg der Temperatur oder des Drucks des Heizkessels (6) nur dann, wenn ein Steuerventil
(12), um zu ermöglichen, dass Dampf aus dem Heizkessel (6) abgelassen wird, geschlossen
ist und Dampf daran gehindert wird, aus dem Heizkessel (6) abgelassen zu werden.
12. Verfahren nach Anspruch 11, umfassend das Starten der Messung eines Zeitintervalls
für einen inkrementellen Anstieg der Temperatur oder des Drucks des Heizkessels (6)
im Anschluss an das Schließen des Steuerventils (12), nachdem Dampf aus dem Heizkessel
(6) abgelassen wurde und nachdem ein vorbestimmter Zeitraum nach Schließen des Steuerventils
(12) verstrichen ist.
13. Verfahren nach einem der Ansprüche 10 bis 12, umfassend das Betreiben der Pumpe (7)
in Abhängigkeit von der im Heizkessel (6) verbleibenden Wassermenge, die bestimmt
wurde, für einen vorbestimmten Zeitraum.
14. Verfahren nach einem der Ansprüche 10 bis 13, wobei der Schritt des Vergleichens des
gemessenen Zeitintervalls mit einem vorbestimmten Zeitwert das Vergleichen eines gemessenen
Zeitintervalls mit einem vorbestimmten Zeitintervall für inkrementelle Temperatur-
oder Druckanstiege von einer oder mehreren bekannten Wassermengen innerhalb des Heizkessels
(6) umfasst, die in einer oder mehreren Nachschlagetabellen innerhalb einer Speichereinheit
der Steuerung (15) gespeichert sind.
15. Verfahren nach einem der Ansprüche 10 bis 14, umfassend das Steuern von Betrieb des
Heizkessels (6) in Abhängigkeit von einem Temperatur- oder Drucksignal aus dem Sensor
(14) und Stoppen des Aufheizens von Wasser durch den Heizkessel (6), wenn die/der
gefühlte Temperatur oder Druck einen vorbestimmten Schwellenwert erreicht.
1. Appareil de génération de vapeur (1) comprenant un réservoir d'eau (5), une chaudière
(6) pour générer de la vapeur, un capteur (14) raccordé à la chaudière (6) pour détecter
la température ou pression dans la chaudière (6), une pompe (7) configurée pour pomper
l'eau du réservoir (5) à la chaudière (6), et un élément de commande (15) configuré
pour recevoir un signal provenant du capteur (14) et pour commander le fonctionnement
de la pompe (7) en fonction du signal, dans lequel l'élément de commande (15) est
configuré pour déterminer une quantité d'eau dans la chaudière (6) et pour commander
la pompe (7) pour alimenter en eau la chaudière (6) lorsque la quantité d'eau déterminée
est inférieure à une valeur prédéterminée, caractérisé en ce que l'élément de commande (15) est agencé pour déterminer la quantité d'eau en mesurant
au moins un intervalle de temps nécessaire pour une augmentation prédéterminée de
température ou pression dans la chaudière (6) et pour comparer l'intervalle de temps
mesuré avec une valeur de temps prédéterminée.
2. Appareil de génération de vapeur (1) selon la revendication 1, dans lequel la valeur
de temps prédéterminée correspond à un intervalle de temps pour qu'une ou plusieurs
quantités connues d'eau atteignent l'augmentation prédéterminée de température ou
pression.
3. Appareil de génération de vapeur (1) selon la revendication 1 ou 2, comprenant en
outre une valve de commande (12) pour permettre à la vapeur d'être libérée de la chaudière
(6), dans lequel l'élément de commande (15) est configuré pour mesurer un intervalle
de temps pour une augmentation progressive de température ou pression de chaudière
(6) seulement lorsque la valve de commande (12) est fermée et la vapeur est empêchée
d'être libérée de la chaudière (6).
4. Appareil de génération de vapeur (1) selon la revendication 3, dans lequel l'élément
de commande (15) est configuré pour commencer la mesure d'un intervalle de temps pour
une augmentation progressive de température ou pression de chaudière (6) suivant la
fermeture de la valve de commande (12) après que la vapeur a été libérée de la chaudière
(6), et après qu'une période de temps prédéterminée a expiré après la fermeture de
la valve de commande (12).
5. Appareil de génération de vapeur (1) selon une quelconque revendication précédente,
dans lequel l'élément de commande (15) est configuré pour faire fonctionner la pompe
(7) lorsque l'intervalle de temps mesuré pour une augmentation progressive de température
ou pression de la chaudière (6) est inférieur à un intervalle de temps prédéterminé.
6. Appareil de génération de vapeur (1) selon une quelconque revendication précédente,
dans lequel l'élément de commande (15) est configuré pour actionner la pompe (7) pour
une période de temps prédéterminée en fonction de la quantité déterminée d'eau restant
dans la chaudière (6).
7. Appareil de génération de vapeur (1) selon une quelconque revendication précédente,
dans lequel la valeur de temps prédéterminée comprend un intervalle de temps pour
une augmentation progressive de température ou pression d'une ou plusieurs quantités
connues d'eau dans la chaudière (6) qui sont enregistrées dans un ou plusieurs tableaux
de consultation dans une unité de mémoire de l'élément de commande (15).
8. Appareil de génération de vapeur (1) selon une quelconque revendication précédente,
dans lequel l'élément de commande (15) est agencé pour commander en outre le fonctionnement
de la chaudière (6) en fonction d'un signal de température ou pression provenant du
capteur (14) et arrête la chaudière (6) chauffant l'eau lorsque la température ou
pression détectée atteint une valeur seuil prédéterminée.
9. Appareil de génération de vapeur (1) selon une quelconque revendication précédente,
dans lequel le capteur (14) comprend une thermistance montée sur un substrat métallique
et le substrat métallique est monté sur la chaudière (6).
10. Procédé de fonctionnement d'un appareil de génération de vapeur (1) qui comprend un
réservoir d'eau (5), une chaudière (6) pour la génération de vapeur, un capteur (14)
raccordé à la chaudière (6) pour détecter la température ou pression dans la chaudière
(6), une pompe (7) configurée pour pomper l'eau du réservoir (5) à la chaudière (6),
et un élément de commande (15) configuré pour recevoir un signal provenant du capteur
(14) et commander le fonctionnement de la pompe (7) en fonction du signal, le procédé
comprenant la détermination d'une quantité d'eau dans la chaudière (6) et la commande
de la pompe (7) pour alimenter en eau la chaudière (6) lorsque la quantité déterminée
d'eau est inférieure à une valeur prédéterminée, caractérisé en ce que le procédé comprend la détermination de la quantité d'eau par mesure au moins d'un
intervalle de temps nécessaire pour une augmentation prédéterminée de température
ou pression dans la chaudière (6), et la comparaison de l'intervalle de temps mesuré
avec une valeur de temps prédéterminée.
11. Procédé selon la revendication 10 comprenant la mesure d'un intervalle de temps pour
une augmentation progressive de température ou pression de chaudière (6) seulement
lorsqu'une valve de commande (12), pour permettre à la valeur d'être libérée de la
chaudière (6), est fermée et la vapeur est empêchée d'être libérée de la chaudière
(6).
12. Procédé selon la revendication 11 comprenant le démarrage de la mesure d'un intervalle
de temps pour une augmentation progressive de température ou pression de chaudière
(6) suivant la fermeture de la valve de commande (12) après que la vapeur a été libérée
de la chaudière (6), et après qu'une période de temps prédéterminée a expiré après
la fermeture de la valve de commande (12).
13. Procédé selon l'une quelconque des revendications 10 à 12 comprenant le fonctionnement
de la pompe (7) pour une période de temps prédéterminée selon la quantité déterminée
d'eau restant dans la chaudière (6).
14. Procédé selon l'une quelconque des revendications 10 à 13 dans lequel l'étape de comparaison
de l'intervalle de temps mesuré avec une valeur de temps prédéterminée comprend la
comparaison d'un intervalle de temps mesuré avec un intervalle de temps prédéterminé
pour des augmentations progressives de température ou pression d'une ou plusieurs
quantités connues d'eau dans la chaudière (6) enregistrées dans un ou plusieurs tableaux
de consultation dans une unité de mémoire de l'élément de commande (15).
15. Procédé selon l'une quelconque des revendications 10 à 14 comprenant la commande du
fonctionnement de la chaudière (6) en fonction d'un signal de température ou pression
provenant du capteur (14) et l'arrêt de la chaudière (6) chauffant l'eau lorsque la
température ou pression détectée atteint une valeur seuil prédéterminée.