GB1598923A

GB1598923A - Clothes washing and spin drying machines

Info

Publication number: GB1598923A
Application number: GB31559/77A
Authority: GB
Original assignee: Hotpoint Ltd
Current assignee: Hotpoint Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-09-23

Description

(54) IMPROVEMENTS IN OR RELATING TO CLOTHES WASHING AND SPIN DRYING MACHINES (71) We, HOTPOINT LIMITED, of Peterborough, England, PE2 9JB., a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to clothes washing and spin drying machines or spin drying machines, of the kind incorporating a clothes drum rotatable about a non-vertical axis, and is an improvement in or modification of the invention which forms the subject of Patent No. 1,266,691.

In accordance with Claim 1 of said patent such a machine has a d.c. electric motor for rotating the drum both at a relatively slow speed and also at a much higher speed for spin drying, a controlled semi-conductor device connected in series with the electric motor with respect to input terminals which are arranged to be connected to a source of alternating current, and a motor speed control circuit capable of controlling the operation of the semiconductor device in such manner that for carrying out a spin drying operation the motor can be caused to accelerate relatively slowly through a critical speed at which the centrifugal force on the clothes within the drum equals the force due to gravity and subsequently to accelerate more rapidly until said higher speed is attained.

In accordance with the present invention the motor for rotating the drum is of a type which is operable on alternating current, and in use the motor speed control circuit controls the operation of one or more controlled semi-conductor devices connected in series with the motor with respect to the source of alternating current the connection and the device or devices being such as to control the power supplied to the motor in each half cycle of the alternating current supply.

It will be understood that the statement that the motor is of a type which is operable on alternating current means that the motor can be operated on connection of its terminals to an appropriate alternating current electrical supply, and although it may be specifically designed for such use it may alternatively be a universal type motor, that is to say one which can be operated on both alternating and direct current, operation of the motor of a machine in accordance with the present invention, however being, in effect, operation on alternating current.

The motor speed control circuit conveniently incorporates solid state elements and is arranged to generate a series of electric pulses which control the periods of conduction of the controlled semi-conductor device or devices, for governing the power supply to the electric motor in order to produce the different accelerations, as well as steady controlled speeds.

The motor speed control circuit preferably includes feed-back means which normally tends to maintain the motor rotating with a selected constant slow speed, and time-dependent means arranged to modify the operating mode of the feed-back means when a spin drying operation is initiated, as in the case of the motor speed control circuit described by way of example in the Specification of Patent No. 1,266,691.

The invention includes within its scope a control unit as defined in claim 12 of Specification No. 1,266,691 for controlling the drum speed of a clothes washing and spin drying machine, having an electric motor of a type which is operable on alternating current; wherein the unit has input terminals for connection to a source of alternating current output terminals for connection to the motor, and the solid state control elements are so connected and arranged that in use of the unit with the motor connected between the output terminals, and the input terminals connected to said source of alternating current, the elements control the power supplied to the motor in each half cycle of the alternating current supply.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing which rep resents one form of control arrangement for a combined clothes washing and spin drying machine in accordance with the invention.

The machine itself is not illustrated in the drawing but typically it can comprise a drum mounted on a shaft in bearings so as to be rotatable on a horizontal axis within a liquid container which is suspended by means of cooperating springs and dampers within an outer chamber. A commutator motor within the outer container is drivingly coupled by means of a 'V' or a multi-V belt drive system to a pulley wheel secured to the drum shaft outside the liquid container. The system is such that the drum rotates in use at a speed well below the motor speed.

The various functions of the washing machine are controlled by a programme controller which can be of any convenient form, the functions either being initiated by a mechanical or electro-mechanical timer, or by a solid state control programmer.

For carrying out a "wash" function the drum is arranged to be rotated for short periods, say 15 seconds, alternately in opposite directions at a relatively low speed, for example approximately 50 revjminute, and during a "spin" function the drum is arranged to be accelerated in one direction up to a much higher speed, initially with a relatively slow acceleration up to a critical speed at which the centrifugal force on the clothes in the drum equals the force due to gravity, and during which time clothes are distributed around the drum walls, and subsequently with an increased acceleration up to spin speed.

Control of the motor speed, and hence the speed of rotation of the drum, is effected by the circuit arrangement illustrated. The washing machine drum is driven by a DC electric series motor M which is supplied through a triac T from an AC supply applied to terminals T1, T2. A circuit protecting the triac T from voltages of excessive amplitude and/or rate of change consists of resistors R32, R30, R33, and a capacitor C7. The resistor R32 is a voltage dependent resistor and limits voltage amplitudes, while the capacitor C7 and the resistor R33 form a "commutation filter". The resistor R30 maintains a current path for the capacitor C7 when the motor M is disconnected during operation of a changeover switch SWS reversing the motor.

The uiac T is fired by a pulse producing circuit A whose output to the triac is controlled by a feed-back circuit B which is sensitive both to changing motor speed and reference voltage derived from a speed selector circuit C A rectification and smoothing arrangement provided by the diodes D19 and D20, and the capacitor C6 and resistor R28 provide a reduced DC voltage for the operation of these circuits.

The pulse producing circuit A is basically a transistor latch comprising complementary transistors TR7 and TR8, with some negative feedback due to a capacitor CS. The transistors TR7 and TR8 are normally OFF until an output voltage from the feed-back circuit B at the cathode of a diode D16 which is connected to the emitter of the transistor TR7 becomes lower than voltage at the base of the transistor set by potential divider resistors R22, R23; the base emitter junction of the transistor TR7 then becomes forward biased, and the transistor starts to conduct.

This will then supply base current to the transistor TR8, turning it on and, through a resistor R24 and capacitor CS, producing further conduction of the transistor TR7. This action is cummulative and both transistors rapidly saturate. This causes the capacitor C4 to be discharged through the transistors TR7, TR8, and the gate of the triac T, thus trigger ing the latter. The triggering latch then turns OFF again allowing the feed-back circuit B to recharge the capacitor C4 at a controlled rate, until the voltage is again sufficient to start the transistors TR7 and TR8 conducting, thereby causing the process to be repeated.

The circuit D is a zero voltage detector comrpising transistors TR5 and TR6, with diodes D17, and D18 and resistors R20 R21 and R29 and is operative to discharge the capacitor C4 every time the mains AC voltage is approximately zero, so that charging of the capacitor C4 by the control circuit B com mences from a known condition at the beginning of every half period of the mains voltage sine wave.

The speed selector circuit C provides a constant and time varying reference voltage output at the junction of the resistor R15 and the diode D14 appropriate to the speed and speed sequence selected by one of a number of switches SW1-SW4.

The control circuit B compares this output with a motor speed dependent signal from a tacho generator TG driven by the motor M.

The resultant error voltage is supplied, via a filter provided by resistors R16 and R35 a diode D15 and capacitor C3, to the base of an emitter follower amplifier, provided by a transistor TR4 and a resistor R19, which in turn charges the capacitor C4 through the resistor R18 at a rate proportional to the error voltage. A thermistor TH within the motor serves to protect it against overheating by prevenung or at least reducing the rate of charge of the capacitor C4 should this occur by reducing the voltage at the base af the transistor TR4 by rendering the transistor TR3 conductive.

When "wash" speed is selected by closure of the switch SW2 the reference voltage is derived by a potential divider provided by diodes D12, and D13 and resistors R10, R11 and R12, connected as shown. A lower wash speed can be selected by the closure of the switch SW1 causing the potential divider to be modified by the addition of a resistor R14 at the top of the chain. A "Distribution" speed can be selected by closure of the switch SW3 this resulting in a reference voltage being initially derived by the same potential divider as in "wash" mode except that the diode D12 is replaced by a different diode D9. Also the capacitor C1 is slowly charged through the diode D2 and resistor R3 until the diode DS clamps it to the voltage of the Zener diode D1.

The diode D7 and the resistor R6 cause a steadily increasing current to be supplied to the output of the circuit C, as the capacitor C1 charges, thus increasing the output reference voltage. This corresponds to a gradual rise of Distribution speed. During the gradual acceleration of the motor, and hence the washing machine drum, to "Distribution" speed, centrifugal force on the clothes within the drum gradually increases, this having the effect of moving the clothes outward to distribute them around the wall of the drum in a balanced manner.

"Spin" speed is selected by closure of the switch SW4, and again the first "wash" speed reference voltage is derived through the diode D4 and the "wash" mode potential divider.

Also the capacitor C1 is charged through diodes D3 and D2 and the resistor R3 so that the output reference voltage and in turn the motor speed gradually increase to Distribution speed causing the clothes to be distributed around the wall of the drum in a balanced manner as above described.

Only when the voltage on the capacitor C1 is the same as that of the diode D1 do the transistors TR1 and TR2 start turning OFF.

This increases the output reference voltage at a greater rate, producing a more rapid acceleration of the motor, and hence of the washing machine drum until the voltage is sufficient to allow almost continuous conduction of triac T, and thus causing the motor to turn at high spin speed.

However the turningsff of the transistors TR1 and TR2 is slowed down by the capacitor C2 to allow soft start of spin acceleration from Distribution speed up to spin speed.

The switches SWl to SW4 are conveniently arranged to be operated automatically at appropriate instants in a washing programme, although means may also be provided for enabling the switches to be operated manually if desired.

The selection of "Distribution" speed, by closure of switch SW3 usually takes place between rinses, to provide a set period in which excess water can be drained by actuating the pump whilst the clothes rotate at relatively low speed. After a predetermined time interval the switch SW4 is closed to cause the drum to accelerate rapidly to spin speed, with pump operation maintained. The normal or "long" spin is brought about by closure of the switch SW4 directly, the length of time during which clothes are distributed and excess water is pumped out before spin commences being determined only by the "electronic" distribution ramp in the manner described.

The invention has the advantage that the speed control circuit can readily be modified to provide different spin speeds controllable by the user, for example a normal spin speed for the majority of fabrics, and a lower spin speed for more delicate fabrics. In addition means may be provided to enable the user to select any one of a number of different spin speeds between two limiting values or to provide a continuous adjustment which would enable the user to select any required speed within that range.

WHAT WE CLAIM IS:- 1. A clothes washing and spin drying machine or a spin drying machine as claimed in Claim 1 of Patent No. 1,266,691 wherein the motor for rotating the drum is of a type which is operable on alternating current, and in use the motor speed control circuit controls the operation of one or more controlled semiconductor devices connected in series with the motor with respect to the source of alternating current, the connection and the device or devices being such as to control the power supplied to the motor in each half cycle of the alternating current supply.

2. A machine according to Claim 1 in which the electric motor is a universal type motor, and the controlled semi-conductor device controwed by the motor speed control circuit is a triac.

3. A machine according to Claim 1 or 2 wherein the motor speed control circuit incorporates solid state elements and is arranged to generate a series of electric pulses which control the periods of conduction of the controlled semi-conductor device or devices, for governing the power supply to the electric motor in order to produce the different accelerations.

4. A machine according to Claim 3 wherein the motor speed control circuit includes feedback means which normally tends to maintain the motor rotating with a selected constant slow speed, and time-dependent means arranged to modify the operating mode of the feed-back means when a spin drying operation is initiated.

5. A machine according to Claim 4 wherein the motor speed control circuit incorporates a capacitor, means for charging the capacitor during each half cycle of the supply at a rate dependent upon feed-back signals, and means responsive to the charge on the capacitor for generating a said electric pulse when the charge on the capacitor reaches a predetermined value.

6. A machine according to Claim 5 including a pair of transistors normally non-conduct

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. be modified by the addition of a resistor R14 at the top of the chain. A "Distribution" speed can be selected by closure of the switch SW3 this resulting in a reference voltage being initially derived by the same potential divider as in "wash" mode except that the diode D12 is replaced by a different diode D9. Also the capacitor C1 is slowly charged through the diode D2 and resistor R3 until the diode DS clamps it to the voltage of the Zener diode D1. The diode D7 and the resistor R6 cause a steadily increasing current to be supplied to the output of the circuit C, as the capacitor C1 charges, thus increasing the output reference voltage. This corresponds to a gradual rise of Distribution speed. During the gradual acceleration of the motor, and hence the washing machine drum, to "Distribution" speed, centrifugal force on the clothes within the drum gradually increases, this having the effect of moving the clothes outward to distribute them around the wall of the drum in a balanced manner. "Spin" speed is selected by closure of the switch SW4, and again the first "wash" speed reference voltage is derived through the diode D4 and the "wash" mode potential divider. Also the capacitor C1 is charged through diodes D3 and D2 and the resistor R3 so that the output reference voltage and in turn the motor speed gradually increase to Distribution speed causing the clothes to be distributed around the wall of the drum in a balanced manner as above described. Only when the voltage on the capacitor C1 is the same as that of the diode D1 do the transistors TR1 and TR2 start turning OFF. This increases the output reference voltage at a greater rate, producing a more rapid acceleration of the motor, and hence of the washing machine drum until the voltage is sufficient to allow almost continuous conduction of triac T, and thus causing the motor to turn at high spin speed. However the turningsff of the transistors TR1 and TR2 is slowed down by the capacitor C2 to allow soft start of spin acceleration from Distribution speed up to spin speed. The switches SWl to SW4 are conveniently arranged to be operated automatically at appropriate instants in a washing programme, although means may also be provided for enabling the switches to be operated manually if desired. The selection of "Distribution" speed, by closure of switch SW3 usually takes place between rinses, to provide a set period in which excess water can be drained by actuating the pump whilst the clothes rotate at relatively low speed. After a predetermined time interval the switch SW4 is closed to cause the drum to accelerate rapidly to spin speed, with pump operation maintained. The normal or "long" spin is brought about by closure of the switch SW4 directly, the length of time during which clothes are distributed and excess water is pumped out before spin commences being determined only by the "electronic" distribution ramp in the manner described. The invention has the advantage that the speed control circuit can readily be modified to provide different spin speeds controllable by the user, for example a normal spin speed for the majority of fabrics, and a lower spin speed for more delicate fabrics. In addition means may be provided to enable the user to select any one of a number of different spin speeds between two limiting values or to provide a continuous adjustment which would enable the user to select any required speed within that range. WHAT WE CLAIM IS:-

1. A clothes washing and spin drying machine or a spin drying machine as claimed in Claim 1 of Patent No. 1,266,691 wherein the motor for rotating the drum is of a type which is operable on alternating current, and in use the motor speed control circuit controls the operation of one or more controlled semiconductor devices connected in series with the motor with respect to the source of alternating current, the connection and the device or devices being such as to control the power supplied to the motor in each half cycle of the alternating current supply.

ing, one of which transistors is connected so as to become conducting when the charge on the capacitor reaches said predetermined value, and being so connected to the other by regenerative feed-back connections that rapid saturation of both transistors takes place, resulting in the generation of a said electric pulse.

7. A machine according to any preceding claim incorporating a solid state control programmer for initiating the various functions of the machine in a selected sequence.

8. A washing and spin drying machine including a control circuit for controlling the speed of an electric motor driving the clothes drum of the machine substantially as shown in and as hereinbefore described with reference to the accompanying drawing.

9. A control unit as claimed in Claim 12 of Patent No. 1,266,691 for controlling the drum speed of a said clothes washing and spin drying machine in which said electric motor is of a type which is operable on alternating current, wherein the unit has input terminals for connection to a source of alternating current, output terminals for connection to the motor, and the solid state control elements are so connected and arranged that in use of the unit with the motor connected between the output terminals, and the input terminals connected to said source of alternating current, the elements control the power supplied to the motor in each half cycle of the alternating current supply.

10. A control circuit substantially as shown in and as hereinbefore described with reference to the accompanying drawing.