EP1441175B1 - Process and apparatus for the generation of steam for fabric care - Google Patents

Description

The invention relates to a method and a device for generating steam for laundry care.

According to the prior art devices come to produce water vapor z. B. in espresso machines used. In this case, an evaporator is provided, whose working temperature is controlled by a thermostat. The evaporator is fed either manually or automatically water. The hot steam produced is not drip-free; it is not suitable for the treatment of laundry.

Furthermore, it is also known to regulate the amount of water supplied to the evaporator by means of a float switch. Such a mechanical control is susceptible to failure, especially in the case of water with a high lime content. It can come through limescale to jamming of the float. In addition, even with such a control no suitable for the treatment of laundry drip-free superheated steam can be generated.

From the WO96 / 32607 A1 an evaporator is known which operates according to the so-called boiler method and has a tank for liquid to be evaporated. There is provided a means for automatically supplying liquid into the tank. In order to keep the liquid to be evaporated at the lowest possible level and still have an uninterrupted flow Ensuring steam generation includes a level control which controls replenishment of liquid to be evaporated into the tank as a function of the temperature of the liquid in the tank.

The object of the invention is to eliminate the disadvantages of the prior art mentioned above, which occur in particular in steam generators, which operates on the water heater principle. In particular, a method and a device are to be specified with which reliably droplet-free superheated steam can be produced for the treatment of laundry.

This object is solved by the features of claims 1 and 12. Advantageous embodiments result from the features of claims 2 to 11 and 13 to 20.

1. a) Erzeugen eines Messsignals, welches zu einer in einem Verdampfer herrschenden Arbeitstemperatur korrespondiert,
2. b) Erzeugen einer Abfolge von Steuerimpulsen unter Verwendung des Messsignals, wobei eine Impulsbreite der Steuerimpulse zur Arbeitstemperatur korrespondiert, und
3. c) Ansteuern einer Wasserzuführvorrichtung mittels der Steuerimpulse, so dass dem Verdampfer mit zunehmender Arbeitstemperatur eine zunehmende Menge an Wasser pro Zeiteinheit zugeführt wird.

According to the invention, a method for the production of steam for laundry care is provided with the following steps:

1. a) generating a measurement signal which corresponds to a working temperature prevailing in an evaporator,
2. b) generating a sequence of control pulses using the measurement signal, wherein a pulse width of the control pulses corresponds to the working temperature, and
3. c) driving a Wasserzuführvorrichtung by means of the control pulses, so that the evaporator with increasing operating temperature, an increasing amount of water per unit time is supplied.

With the proposed method, the evaporator is cyclically fed in each case so much water that, depending on the operating temperature of the water completely evaporated and thus a drip-free superheated steam can be made available. The proposed method is not susceptible to interference. To control the amount of water supplied to the evaporator, no mechanical elements in contact with the water are needed. The proposed method is universal. It can be easily adapted to the particular performance of an evaporator.

According to one embodiment, the control pulses are generated at a constant frequency. This simplifies the technical implementation of the procedure. Furthermore, it is expedient that no control pulses are generated below a predetermined operating temperature. This always ensures the generation of a drip-free superheated steam.

Furthermore, it has proved to be expedient that the measurement signal is generated using a temperature-dependent resistor or a thermocouple. In this case, a DC voltage increasing with increasing working temperature can be generated as the measuring signal. Such a DC voltage can be implemented technically without great effort in the desired control pulses.

To supply the water to the evaporator, an electromagnetic valve can be opened or a pump can be controlled. For a particularly simple water supply is possible.

1. aa1) Erfassen des Messsignals und einer ersten vorgegebenen Impulsfolge mittels eines ersten Komparators,
2. aa2) Umwandeln der erfassten Signale in eine Wechselspannung mit einem zur Arbeitstemperatur korrespondierenden Taktverhältnis,
3. bb) Umwandeln der Wechselspannung mittels eines Integrators in eine zweite Gleichspannung, deren Größe umgekehrt proportional zur gemessenen Arbeitstemperatur ist,
4. cc1) Erfassen der zweiten Gleichspannung und einer zweiten Impulsfolge mittels eines zweiten Komparators und
5. cc2) Umwandeln der erfassten Signale in die Steuerimpulse.

To generate the control pulses, the following steps are expediently carried out:

1. aa1) detecting the measurement signal and a first predetermined pulse train by means of a first comparator,
2. aa2) converting the detected signals into an alternating voltage with a duty cycle corresponding to the operating temperature,
3. bb) converting the AC voltage by means of an integrator into a second DC voltage whose magnitude is inversely proportional to the measured operating temperature,
4. cc1) detecting the second DC voltage and a second pulse train by means of a second comparator and
5. cc2) converting the detected signals into the control pulses.

The aforementioned method steps can be realized with little effort with a conventional programmable logic controller.

It has proven to be expedient that the ratio of the frequencies of the first and the second pulse sequence is about 20: 1. The frequency of the first pulse sequence may advantageously be 10 Hz. The first and second pulse trains may be formed by sawtooth pulses. Conveniently, the sequence of control pulses is formed by rectangular pulses. This allows precise control of the water supply device.

According to another aspect of the invention, a device for generating steam for laundry care is provided with
an evaporator and an associated water supply device,
a device for generating a measuring signal which corresponds to a working temperature prevailing in the evaporator,
a device for generating a sequence of control pulses having a pulse width corresponding to the working temperature,
a device for controlling the water supply device by means of the control pulses, so that the evaporator with increasing working temperature an increasing amount of water per unit time is supplied.

The proposed device consists of few parts. It is easy to produce, relatively robust and prone to interference.

The device for generating a measurement signal may expediently have a temperature-dependent resistor or a thermocouple. This makes it possible in a simple manner to provide a DC voltage corresponding to the working temperature. The device for generating the control pulses expediently comprises a programmable logic control circuit. The programmable logic control circuit is advantageously programmed so that rectangular pulses are generated as control pulses whose pulse width corresponds to the working temperature. Furthermore, it is expedient that the control pulses are generated at a constant frequency. The control circuit may include means for adjusting the operating temperature range to be considered for the generation of control pulses. The proposed control circuit is relatively easy to implement. It can be provided cheaply.

The water supply device expediently has an electromagnetic valve or an electric water pump. Such electromechanical components are reliable and can be easily controlled by means of control pulses. According to a further embodiment feature, the evaporator, the water supply device and the stored-program control circuit are accommodated in the housing of a household laundry drier. It can be provided, preferably designed as a riser, steam supply line from the evaporator to a laundry room surrounded by a rotatable laundry drum. Such a household tumble dryer is not only suitable for drying but also for treating laundry with superheated steam. It can thus be cleaned in particular odorous laundry without having to be washed separately.

Fig. 1

ein Blockschaltbild einer Schaltung zur Dosierung von Wasser und

Fig. 2

die an den in Ziff. 1 gezeigten Messpunkten abfallenden Spannungen.

An exemplary embodiment of the invention will be explained in more detail with reference to the drawings. Show it:

Fig. 1

a block diagram of a circuit for metering water and

Fig. 2

the at the in Ziff. 1 dropping voltages shown.

Fig. 1 shows a block diagram of a device according to the invention for controlling an amount of water to be supplied to an evaporator. The amount of water supplied per unit time is regulated as a function of the operating temperature of the evaporator.

For measuring the working temperature of a conventional (not shown here) evaporator, a thermocouple 1 is provided, which is connected to a first comparator 2. An AC voltage generator 3 is followed by a level regulator 4, which is connected on the output side to the other input of the first comparator 2. On the output side, the first comparator 2 is connected to an input of a second comparator 6 with the interposition of an integrator 5.

A clock generator 7 is connected to the other input of the second comparator 6 with the interposition of a differentiating element 8. At the output of the second comparator 6 is a switching device 9, e.g. a relay, an electromagnetic valve, a water pump or the like connected.

The function of the device is as follows:

The thermal voltage generated by the thermocouple 1 (see Fig. 2 lit. d) is supplied to the first comparator 2. The AC voltage generator 3 generates an AC voltage of eg 10 Hz, which in the downstream level controller 4 in a sawtooth (see Fig. 2 lit. c) is also converted to a frequency of 10 Hz and then also the first comparator 2 is supplied. By means of the first comparator 2, the in Fig. 2 lit. e schematically indicated alternating voltage generated with a duty cycle that corresponds to the measured operating temperature.

With the integrator 5, the AC voltage is converted into a DC voltage, which is inversely proportional to the measured operating temperature (see Fig. 2 lit. f). This DC voltage is compared in the second comparator 6 with the sawtooth voltage generated by the clock generator 7 and the downstream differentiator 8 lit. b ( Fig. 2 ). As a result, the in Fig. 2 under lit. g shown control pulses output at the output of the second comparator 6. The control pulses are rectangular pulses.

LIST OF REFERENCE NUMBERS

1

thermocouple

2

first comparator

3

AC voltage generator

4

level control

5

integrator

6

second comparator

7

clock generator

8th

Differentiator

9

switchgear

Claims (20)

1. Process for generating steam for laundry care having the following steps:

   a) generating a measurement signal (d) which corresponds to an operating temperature prevailing in a vaporiser,

   b) generating a sequence of control pulses (g) using the measurement signal (d), wherein a pulse width of the control pulses (g) corresponds to the operating temperature, and

   c) activating a water-supply device (9) by means of the control pulses (g), so that an increasing quantity of water per unit of time is supplied to the vaporiser with increasing operating temperature.
2. Process according to claim 1, wherein the control pulses (g) are generated with constant frequency.
3. Process according to one of the preceding claims, wherein control pulses (g) are generated only above a preset operating temperature.
4. Process according to one of the preceding claims, wherein the measurement signal (d) is generated using a temperature-dependent resistor or a thermocouple.
5. Claim according to one of the preceding claims, wherein a direct voltage increasing with increasing operating temperature is generated as the measurement signal.
6. Process according to one of the preceding claims, wherein an electromagnetic valve (g) is opened or a pump is activated to supply the water to the vaporiser.
7. Process according to one of the preceding claims, wherein the following steps are carried out to generate the control pulses (g):

   aa1) recording the measurement signal (d) and a first preset pulse sequence (c) by means of a first comparator,

   aa2) converting the recorded signals into an alternating voltage (e) with a clock ratio corresponding to the operating temperature,

   bb) converting the alternating voltage (e) by means of an integrator (5) into a second direct voltage (f), the size of which is inversely proportional to the measured operating temperature,

   cc1) recording the second direct voltage (f) and a second pulse sequence (b) by means of a second comparator (6) and

   cc2) converting the recorded signals into the control pulses (g).
8. Process according to one of the preceding claims, wherein the ratio of the frequencies of the first (c) and of the second pulse sequence (b) is about 20:1.
9. Process according to one of the preceding claims, wherein the frequency of the first pulse sequence (c) is 10 Hz.
10. Process according to one of the preceding claims, wherein the first (c) and the second pulse sequence (b) are formed from saw-tooth pulses.
11. Process according to one of the preceding claims, wherein the sequence of control pulses (g) is formed from rectangular pulses.
12. Device for generating steam for laundry care having
    a vaporiser and a water-supply device (9) connected thereto,
    a device (1) for generating a measurment signal (d), which corresponds to an operating temperature prevailing in the vaporiser,
    a device for generating a sequence of control pulses (g) having a pulse width corresponding to the operating temperature,
    a device for activating the water-supply device (9) by means of the control pulses (g), so that an increasing quantity of water per unit of time is supplied to the vaporiser with increasing operating temperature.
13. Device according to claim 12, wherein the device for generating a measurement signal (d) has a temperature-dependent resistor or a thermocouple.
14. Device according to claim 12 or 13, wherein the device for generating the control pulses (g) comprises a stored-programmable control circuit.
15. Device according to one of claims 12 to 14, wherein the stored-program control circuit is programmed so that rectangular pulses are generated as control pulses (g), the pulse width of which corresponds to the operating temperature.
16. Device according to one of claims 12 to 15, wherein the stored-program control circuit is programmed so that control pulses (g) with constant frequency generated.
17. Device according to one of claims 12 to 16, wherein the control circuit has a device for setting an operating temperature range to be taken into account for the generation of control pulses (g).
18. Device according to one of claims 12 to 17, wherein the water-supply device (9) has an electromagnetic valve or an electric water pump.
19. Device according to one of claims 12 to 18, wherein the vaporiser, the water-supply device (9) and the stored-program control circuit are accommodated in the housing of a household laundry drier.
20. Device according to one of claims 12 to 19, wherein a steam-supply pipe preferably designed as a rising pipe, is provided from the vaporiser to a laundry treatment chamber surrounded by a rotatable laundry drum.

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