GB2079791A - Washing machine - Google Patents

Abstract

A washing machine comprises a washing unit, which is capable of oscillating freely in a housing 1 and which comprises a container 3 supported by spring legs 2. Disposed on the container 3 is an abutment 4 which co-operates with a feeler 5 detecting the oscillatory travel of the container. Associated with the feeler 5, e.g. a bellows, is a switch 7, e.g. a pressure switch, which is mounted on the housing 1 and which above a certain oscillatory deflection of the container delivers a signal. The container 3 contains a rotatable drum driven by a drive motor, the rotational speed of which is controlled by a thyristor or a triac. To avoid damage of the machine, in the event of failure of the thyristor or triac, the switch 7 is arranged in the motor supply current circuit and is so actuated by the feeler 5 in response to sensing of an impermissible amount of container oscillation as to interrupt the motor current circuit. The switch 7 is not automatically resettable into its closed position, but can be re-set by a mechanical pull element 8. In another embodiment, Fig. 4 (not shown), the feeler is provided by a rocker (11) of a toggle switch (10) and is actuable by a resilient member (9) on the container (3). <IMAGE>

Description

SPECIFICATION Washing machine The present invention relates to a drum washing machine.

In DE-OS 26 56 555 there is disclosed a washing machine comprising a container oscillatingly mounted in a housing and receiving a rotating drum, a drive motor, and a switching device which interrupts the current supply circuit of the drive motor when the tub executes impermissible oscillations.

Compared with a known washing machine with a pendulating switch arranged on the oscillating container (DE-PS 17 60 740), a simple key switch, a proximity switch controllable by an electrical or magnetic field or an adjustable resistance can, for example, be mounted as a feeler on the housing of the washing machine according to DE-OS 26 56 555 so that the electrical connecting lines do not have to be arranged to oscillate. The actuating element of the key switch can project into the oscillatory travel of an abutment arranged on the container in such a manner that the key switch is actuated after a predetermined amount of deflection or that a switching operation, through which the drive motor is temporarily stopped, can be triggered at a certain change of a magnetic or electrical field or of a resistance value dependent on the oscillatory travel.On stopping of the drum, the laundry therein redistributes itself and a renewed speeding-up of the drum or a restarting of the drive motor automatically follows.

It has been found that in an electronic rotational speed control for the drive motor of the drum of the washing machine, which operates on the principle of the firing angle control either with a thyristor in half-wave control or with a triac in full-wave control, the thyristor or the triac can fail. This leads to speeding-up of the motor so that the resulting imbalance can effect large unbalancing oscillations of the drum and thereby lead to damage of the machine.

There is accordingly a need for a drum washing machine in which machine damage due to failure of a speed control device such as a thyristor or triac can be avoided.

According to the present invention there is provided a washing machine comprising a housing, a container mounted in the housing to be capable of oscillation relative thereto, a laundry drum rotatably mounted in the container, an electric motor for rotationally driving the drum, circuit means for supplying operating current to the motor, the circuit means including a semiconductor switching device for controlling the speed of the motor, and drive interrupter means comprising detecting means arranged on the housing to detect oscillatory travel of the container in excess of a predetermined amount and to provide a signal in response to such detection and nonautomatically resettable switching means arranged in the circuit means and adapted to be triggered by such signal to interrupt the circuit means.

In a washing machine embodying the present invention, it is secured that in the event of failure of the semiconductor switching device, for example thyristor or triac, the motor for the drum is switched off as soon as the container executes such large oscillations due to imbalance caused by the rising rotational speed of the motor that the feeler is acted on, for example by an abutment of the container, and the feeler through the switching means effects interruption of the motor supply circuit. In that case, the switching means interrupting the circuit is not automatically resettable. Service personnel can reset the switching means for closing of the circuit, for example by way of a mechanical pull switch, only after removal of the damage. The switching-on again can also be effected by way of a relay and a key.

Embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram of a motor current supply circuit with a thyristor, according to one embodiment of the invention, Figure 2 is a circuit diagram similar to that of Fig. 1 but with a triac, according to another embodiment of the invention, and Figures 3 and 4 are schematic elevations of drum washing machines embodying the invention, the washing machine incorporating the circuit of Fig. 1 or Fig. 2.

Referring now to the drawings, there is shown in Fig. 1 an alternating current supply circuit for a drive motor M of a washing machine drum, the speed of motor being controlled by firing angle control. The motor M is connected in series in the circuit with a thyristor Th and a motor current circuit interrupter switch S (shown in opened position).

Connected parallel to the thyristor Th is an RC-device comprising a potentiometer R and a capacitor C and operating as a phase shifter to deliver a variable control voltage to the control connection of the thyristor. The resistor R limits the charging current of the capacitor C.

It requires a certain time for the capacitor to be charged to the value of the ignition voltage of the thyristor. As soon as the thyristor ignites, an ignition current flows, which rapidly discharges the capacitor so that a rapid recharging can take place. The current flow angle of the current flowing through the thyristor and thereby the load of the consuming device can be controlled by the potentiometer.

In Fig. 2 there is shown a circuit in which a triac Tr is provided beside the RC-device for firing angle control, wherein a diac (not shown) before the gate connection of the triac to the RC-device ensures a secure ignition of the triac. The triac receives its breakthrough voltage from the RC-device, which operates as phase shifter and thereby delivers a variable control voltage to the diac. This switches into the conductive state when its ignition voltage is reached at the capacitor. With the diac opened, positive as well as negative half-wave components, the size of which depends on the setting of the potentiometer, flow through the triac.

In Fig. 3 there is shown a drum washing machine comprising a washing unit, which is capable of oscillating freely in a housing 1 and which comprises a container 3 containing a rotatable drum (not shown) and supported by spring legs 2. The drum is rotationally driven by the drive motor M of Fig. 1 or Fig.

2. A possibly resilient abutment 4 is disposed on the container 3. Provided opposite the abutment 4 is a feeler 5, which is firmly connected with the housing 1 and detects the oscillatory travel of the container 3. The feeler comprises, for example, a bellows or a diaphragm switch.

If due to failure of the thyristor Th or the triac Tr, the rotational speed of the drive motor M increases to an undesired level and thereby, due to imbalances acting on the washing unit, leads to deflection of the container 3 in excess of a certain permissible deflection, then the abutment 4 acts on the feeler 5. The feeler, which in the embodiment of Fig. 3 is constructed as bellows, is deformed by the abutment and thereby generates a pressure pulse which is supplied through a duct 6 to a pressure switch 7.

Through the compression of a diaphragm closing off a pressure transducer, contacts of the pressure switch are actuated, the contacts constituting the interrupter switch S in the current circuit of the drive motor M. The switch S is not automatically resettable from the opened to the closed position, so that the motor cannot restart and speed up again in the case of a damaged rotational speed control. After rectification of the damage to the rotational speed control, the switch S can be reset into its closed setting by, for example, a mechanical pull switch or a key 8 acting on the pressure switch 7.

In Fig. 4 there is shown a drum washing machine which is similar to that of Fig. 3 but in which the container 3 has a spring lobe, for example projecting radially from the container wall, a metal bracket or a spring bow 9 so that the feeler, which is constructed as rocker 11, of a toggle switch 10 can detect horizontal as well as vertical oscillations. The electrical contact elements, forming the switch S, of the toggle switch are arranged in the motor current circuit 12. The resetting of the opened toggle switch into the closed position can be effected by a mechanical pull or pressure switch after rectification of the damage to the triac or thyristor. An automatic closing of the current circuit after a previous interruption is possible by means of a relay with self-maintaining contact.

Claims (8)

1. A washing machine comprising a housing, a container mounted in the housing to be capable of oscillation relative thereto, a laundry drum rotatably mounted in the container, an electric motor for rotationally driving the drum, circuit means for supplying operating current to the motor, the circuit means including a semiconductor switching device for controlling the speed of the motor, and drive interrupter means comprising detecting means, arranged on the housing to detect oscillatory travel of the container in excess of a predetermined amount and to provide a signal in response to such detection and non-automatically resettable switching means arranged in the circuit means and adapted to be triggered by such signal to interrupt the circuit means.

2. A washing machine as claimed in claim 1, wherein the semiconductor switching device comprises a triac or a thyristor.

3. A washing machine as claimed in either claim 1 or claim 2, comprising a manually operable pull element for resetting the switching means to close the circuit means.

4. A washing machine as claimed in either claim 1 or claim 2, comprising relay means operable by a key for resetting the switching means to close the circuit means.

5. A washing machine as claimed in any one of the preceding claims, the detecting means comprising a feeler element.

6. A washing machine as claimed in claim 5, the feeler element comprising a bellows and the switching means comprising a pressure switch operable by a pressure pulse generated by the bellows and supplied through a duct.

7. A washing machine as claimed in claim 5, the switching means comprising a toggle switch and the feeler element being provided by a rocker of the toggle switch, the rocker being actuable by a radially projecting resilient' member attached to the container.

8. A washing machine substantially as hereinbefore described with reference to any one of the accompanying drawings.