GB2065722A

GB2065722A - An automatic washing machine

Info

Publication number: GB2065722A
Application number: GB8038066A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-12-18
Filing date: 1980-11-27
Publication date: 1981-07-01
Also published as: ES8202079A1; IT8026600A0; GB2065722B; FR2472047B1; ES496910A0; DE2950928B1; IT1134698B; FR2472047A1

Abstract

In combined automatic laundering and drying machines, there is a problem in combining the measuring devices for the temperature of the washing liquid and of the laundered articles as well as for the moisture of the laundered articles into an integrated measuring system without replacing the hitherto conventional measuring organs by completely novel ones. Beyond that, it is desired completely to avoid the drying operation time control hitherto usual in such machines. In a preferred embodiment of the invention, each measurement sensor of each group of measurement sensors (11-2, 21-2, 31-1, 31-2) is associated with a first input of a respective comparator (1 to 3) which is arranged to produce output signals with a step-function characteristic and a second input of which is supplied with a respective one of fixed or adjustable reference values (10, 20, 30), the output of the comparators (1 to 3) being connected through a mixer stage (5) to a switching device (6, 61, 65) for the heating devices (62, 66). <IMAGE>

Description

SPECIFICATION An automatic washing machine The present invention relates to an automatic washing machine and, more particularly, to a circuit arrangement for the humidity-dependent and temperature-dependent control of a combined automatic washing and drying machine, equipped with electrical heating devices, with the aid of temperature and humidity sensors disposed in the washing and drying chamber and possibly in the duct carrying the discharged air from the drying device.

Various solutions for the measurement individually of temperature or humidity in washing machines or laundry driers are known (DE OS 20 37 383, DE-AS 27 51 277). These known solutions have also each for their own part been used when combined automatic washing and drying machines have had to be equipped with control systems.

Apart from the not yet generally adopted principle of temperature detection by means of temperature-dependent resistances, it is known to detect the temperature of the washing liquid by bimetallic switches, which are well proven, produced in large numbers and consequently inexpensive. Since other temperatures sometimes have to be detected also at other locations inside such a combined machine, it is usual to make use of further bimetallic switches. On occasions, temperature sensors also of other types are employed for this purpose. A control in dependence on the humidity of the laundry to be dried has not hitherto been used in combined machines because with the construction principles adopted for this, the additional expenditure for the measurement of the laundry humidity by special humidity detection and processing means has appeared to be too high.Instead, one has always contented oneself with a simple time control which has the disadvantage that it can only provide useful drying results for a specific composition and initial residual humidity of the laundry batch. In case of need, the time control has been used in conjunction with a temperature measurement in the manner that, when the temperature rises to over 650C, namely when the residual humidity decreases to values around 10%, the time control is brought into operation for the duration of a further drying phase. However, this control system also is too inaccurate for different kinds of laundry batches, yet requires too much attention on the part of the operator in respect of the association of the duration of the further drying period with the type of laundry batch and is moreover relatively expensive.

According to the present invention, there is now provided an automatic washing machine comprising first heater means to heat washing liquid contained in a chamber of the machine, second heater means to heat a current of drying air for carrying moisture from laundered articles contained in the chamber away through an exhaust duct of the machine, first sensor means to detect the temperature of the washing liquid, second sensor means to detect the temperature of the drying air current, third sensor means to detect the moisture content of the laundered articles, switch means to control the operation of the first and second heater means, comparator means to compare output signals of the sensor means with presettable target values of the output signals and to produce binary signals in dependence on the outcome of the comparison, and coupling means to apply the binary signals to the switching means.

The circuit arrangement of a preferred embodiment may comprise temperature sensors with temperature-dependent resistances that are already in occasional use and already usual sensor electrodes inside the laundering chamber for sensing the humidity of the laundry. Wiring the already present controller and programme switching devices together with the inputs and outputs of such a circuit arrangement means a simplification by comparison with the previous state. In the design of modern household appliances, it is readily possible to construct the circuit arrangement, possibly divided into groups, from individual components such as transistors, commercially listed operational amplifiers and the like, or from the internal circuit of a portion of a microprocessor.For the detecting of the physical magnitudes of temperature and degree of humidity, an individual sensor or a group of sensors appropriate for all the values of a physical magnitude can be provided for each. The output signals of the comparators can thus act in simple manner on the remaining electrical equipment of the combined machine.

In one preferred embodiment of the circuit arrangement, the first and second sensor means comprise a single common temperature sensor, the comparator means comprising a comparator device having a first input connected with the single temperature sensor and a second input connectable to selectable ones of a plurality of sources of reference signals each to represent a respective one of the presettable target values.

In further embodiment, the machine comprises a further comparator device, the further comparator device having a first input connected with the second sensor means and a second input connected with a further source of a reference signal, and a switching device responsive to outuput signals produced by the further comparator device to control means regulating the flow of coolant through a condensing device of the machine. With the aid of this additional comparator device, the circuit arrangement of this embodiment becomes suitable also for turning on a flow of coolant only when, after the drying chamber has been heated up, the temperature of the laundry has risen sufficiently for the humidity to be driven off.

In addition, this further comparator device is suitable as a substitute for an initially described time-dependently controlled further drying phase, in that the further comparator device, being conjunctively linked at its output side with the output of the comparator means connected to the humidity sensor means, is connected to a pulsecontrol device for a drum drive motor. For the duration of the further drying phase which completes the drying programme, which is terminated after the drier temperature has fallen to a specific lower temperature, for example 400C, the drum drive motor can then be switched on within short pulse-like movement phases, for example each of 5 seconds duration, in order that the laundry being cooled shall not become creased by remaining in one position. The pulse-control device is preferably a timing pulse generator.Such a timing pulse generator is usually adjustable in respect of its pulse lengths and pause lengths.

When the pulse-control device furthermore is connected to an acoustic signal transmitter, the operator can be informed of the completion of the drying programme.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a first embodiment of the control circuit of a machine embodying the present invention, and Fig. 2 shows a modification by way of simplification of the circuit of Fig. 1.

Referring now to the drawings, the circuit arrangement shown in Fig. 1 comprises four comparator devices 1 to 3. Electrical values, such as resistance-dependent current or voltage values, to be compared are applied to the two inputs of each. The comparator devices can be so arranged that they emit an output signal each time the signals at their inputs are equal. They can however also be tuned to specific differences between the input signals for each.Resistance values associated with specific laundry temperatures of the washing liquid are supplied to the upper input of the comparator device 1 through respectively appropriate switch position of the switches 10-1 to 10-4. The lower input of the comparator device 1 is connected to a voltage divider circuit 11 comprising a fixed resistor 11-1 and a temperature-dependent resistor 11-2 as temperature sensor.

The comparator device 2 is wired at its input side similarly to the comparator device 1.

However, only two different resistance values are feedable to its upper input, corresponding to drying temperature of 600C for example when the switch 20-1 is open and to a drying temperature of 1 000C for example when the switch 20-1 is closed. The lower input of the comparator device 2 is likewise connected to a voltage divider circuit 21 comprising a fixed resistor 21-1 and a temperature-dependent resistor 21-2. In order that the comparator device 2 shall be rendered inoperative during a washing operation, a switch 21-3 of a programme control device (not shown) is connected in parallel with the resistor 21-1, is closed during a washing operation and arranged to open during a drying operation thereby to render the voltage divider circuit 21 operative.

The comparator device 3 is likewise connected at its upper input to a switchable resistor combination, which when the contact 30-1 is open applies a resistance value corresponding to the drying result "dry for ironing" and when switch 30-1 is closed applies a resistance value corresponding to the drying result "cupboard dry".

The lower input of the comparator device 3 is connected to a converter 31, the inputs of which are connected to two electrodes 31-1 and 31-2, which are disposed in the drying chamber and sense the laundry humidity on the basis of a conductivity measurement. The converter 31 at its output indicates increasing resistance values as the residual humidity of the laundry to be dried decreases.

A fixed value of the resistor 40 is applied at the upper input of the comparator device 4, whereas its lower input is connected in the same manner as the comparator device 2 to the voltage divider circuit 21 of the latter. Since this voltage divider circuit provides a temperature-dependent resistance value which is also suitable for the comparator device, the comparator device 4 does not need to have its own divider circuit.

The output signals of comparator devices 1 to 4 have a step-function characteristics on the occurrence of the present input-side condition.

The outputs of the comparator devices 1 to 3 are connected to a mixer stage 5, which in the manner of an OR-gate switches on a relay 6 each time one of the comparator devices 1 to 3 emits an output signal. The output signal from the comparator device 4 also switches a relay 7 and is furthermore applied to one input of a conjunction circuit 8, which may take the form of an AND-gate. The other input of the circuit 8 is connected to the output of the comparator device 3. The conjunction circuit 8 has an ouput connected with a timing pulse generator 9 which, when an input voltage threshold is exceeded, drives a relay 12 in a pulse-like manner.

In a washing operation, only the comparator device 1 with its temperature sensor 11-2 is effective. The comparator device 3, due to the high water level in the machine chamber during washing, indicates a very humid laundry through its electrodes 31-1 and 31-2 by a very low resistance value, and the comparator device 2 is rendered ineffective by the control device by means of a switch 21-3. In addition, during a washing operation, the switch 20-1 is closed and a temperature of 1000C is therefore programmed to the comparator. An output signal at the comparator device 2 is therefore impossible.

By a suitable combination of closed and open switches 10-1 to 10-4, the desired laundry temperature is set at the comparator device 1, which on the attainment of this temperature receives a corresponding resistance value at its lower input and emits an output signal through the mixer stage 5 to the relay 6, which by means of its contacts 6-1 and through the relay 61 and its contacts 61-1 switches off a heating device 62 for the washing operation.In addition, the programme control device (not shown) executes one step through the working contact of the relay contacts 6-1. Its coupling magnet 63 receives a voltage through the switch of a water level transmitter 64, the working contact of the relay contacts 6-1 and its own change-over contacts 63-1. It thus leaves the so-called thermostop position, in which the control device, as is already known, dwells until the desired washing liquid temperature is reached.

During the following programme sections "Rinse" and "Spin", all parts of the described control device are so programmed that they cannot intervene in the programme sequence.

In the programme section "drying", the control device by its programme switch 21-3 switches the comparator device 2 to the operative state. By means of the selector switch 20-1, the comparator device 2 has been set to a temperature adapted to the type of laundry to be dried (for example 600C or 1 000C). The comparator device 1 is set by means of the switch combination 10-1 to 10-4 to a temperature which cannot be reached at the temperature sensor 11-2 during drying. It is thus ensured that this comparator device cannot emit an output signal at any time during a drying operation.Now, only the outputs of the comparator devices 2 and 3 are effective at the mixer stage 5, for which the comparator device 3 can be programmed to the desired final humidity of the laundry by the selector switch 30-1. As long as neither the selected temperature nor the selected humidity has been reached, the relay 6 remains in the illustrated, unenergised position. Its working change-over contact 6-2 conducts the voltage R through the programme switch 63-2, which is closed during drying, to the relay 65, the contacts 65-1 of which remain closed and keep the drier heater 66 in operation.During the washing operation, the drier heater is disconnected from the supply mains by the opened programme switch 63-2. The washing liquid heater 62 remains disconnected during drying, because the water level transmitter 64 cannot respond.

As soon as either the comparator device 2 detects by means of its temperature sensor 21-2 the temperature set at the switch 20-1 or the comparator device 3 detects, corresponding to the position of the switch 30-1, the desired degree of drying through its electrodes 31-1 and 31-2, one of the output signals of these two comparator devices acting through the mixer stage 5 causes the relay 6 to be energized, which switches off the drier 66 by its switch 6-2. During the drying programme, the desired drying temperature can be maintained with sufficient accuracy by on-off action of the comparator device 2 until the humidity sensor through its comparator device 3 causes final switching off of the heater 66.

The further comparator device 4, when a predetermined temperature is reached at which an appreciable humidity content is already present in the current of drying air and which can for example be 450C, acting through the relay 7 and its working contact 7-1 switches on the magnet 71 of a solenoid valve 72 connected into the water supply to a water-cooled condenser.

Simultaneously, the motor 13 may be set in operation by a further contact 7-2 of this relay in order that the laundry shall be turned over frequently and dried uniformly. The comparator device 4 has a comparatively broad hysteresis in the sense that its output signal does not decay again until the temperature has fallen below a substantially lower value than that which must exist for its output signal to be switched on. This lower temperature may for example be 400C or lower. As a result, the comparator device 4 does not switch back again until after a fairly long cooling phase with the drier heater 66 switched off, at which no notable drying effect any longer takes place. Only then are the condenser coolant and the motor switched off.

Within this fairly long cooling phase, a creaseprevention programme may be provided, which in the simultaneous presence of the output signals from the comparator devices 3 and 4 through the conjunction circuit 8 provides the operation of the timing pulse generator 9. The cyclic output signals of this generator switch on the relay 12 in a cycle of, for example, 5 seconds operation and 20 seconds pause. In this cycle, through the contacts 12-1 and 12-2 of this relay, the motor 13 (the programme switch 63-3 is during drying of course in the position opposite to that illustrated) and the signal transmitter 14 can be switched on.

The modification illustrated in Fig. 2 relates to the circuit arrangement of the comparator devices 1,2 and 4 in Fig. 1. These can here be replaced by one common comparator device 124 for all the temperatures to be detected; the output of this device 124 is connected to the mixer stage 5. The upper input of the comparator can be preprogrammed for one of eight desired washing or drying temperatures with the aid of a suitably designed reference value source assembly 240 comprising four resistors 240-1 to 240-4, which can be switched into effective position singly or in pairs by the switches 240-5 and 240-6, which may be associated with a selector switch or a programme-control device.

The lower input is connected to a fixed resistor 241-3, which together with a temperature sensor 241-1 constitutes a voltage divider 241, which can be rendered ineffective by bypassing through the switch 241-2.

In addition to this single voltage divider 241, a second, similar voltage divider for a second temperature range may be provided, which can be switched through a change-over switch into operative position in a manner not illustrated here as alternative to the first voltage divider.

Claims

1. An automatic washing machine comprising first heater means to heat washing liquid contained in a chamber of the machine, second heater means to heat a current of drying air for carrying moisture from laundered articles contained in the chamber away through an exhaust duct of the machine, first sensor means to detect the temperature of the washing liquid, second sensor means to detect the temperature of the drying air current, third sensor means to detect the moisture content of the laundered articles, switch means to control the operation of the first and second heater means, comparator means to compare output signals of the sensor means with presettable target values of the output signals and to produce binary signals in dependence on the outcome of the comparison, and coupling means to apply the binary signals to the switching means.

2. A machine as claimed in claim 1 the first sensor means comprising a respective plurality of temperature sensors disposed in the chamber.

3. A machine as claimed in either claim 1 or claim 2, the second sensor means comprising a respective plurality of temperature sensors disposed in the chamber.

4. A machine as claimed in either claim 1 or claim 2, the second sensor means comprising a respective plurality of temperature sensors disposed in the exhaust duct

5. A machine as claimed in any one of the preceding claims, the comparator means comprising three comparator devices each having a first input connected with a respective one of the sensor means and a second input connected with a respective source of at least one reference signal to represent a respective one of the presettable target values, and the coupling means comprising a mixer stage having a respective input connected with output means of each of the comparator devices.

6. A machine as claimed in claim 5, wherein the mixer stage comprises an OR-gate.

7. A machine as claimed in claim 1 , the first and second sensor means comprising a single common temperature sensor, and the comparator means comprising a comparator device having a first input connected with the single temperature sensor and a second input connectable to selectabie ones of a plurality of sources of reference signals each to represent a respective one of the presettable target values.

8. A machine as claimed in any one of claims 5 to 7, comprising a further comparator device, the further comparator device having a first input connected with the second sensor means and a second input connected with a further source of a reference signal, and a switching device responsive to output signals produced by the further comparator device to control means regulating the flow of coolant through a condensing device of the machine.

9. A machine as claimed in claim 8, wherein the further comparator device is arranged to provide output signals which are conjuctively interlinked with output signals derived from the third sensor means to operate a pulse control device arranged to control operation of a motor dirvingly coupled to a drum rotable within the chamber.

10. A machine as claimed in claim 9, wherein the pulse control device comprises a timing pulse generator.

11. A machine as claimed in either claim 9 or claim 10, wherein the pulse control device is further arranged to control operation of a source of acoustic signals.

12. An automatic washing machine substantially as hereinbefore described with reference to and as illustrated by Fig. 1 of the accompanying drawings.

13. An automatic washing machine substantially as hereinbefore described with reference to and as illustrated by Fig. 2 of the accompanying drawings.