DE2415138A1 - ELECTRICAL HOUSEHOLD APPLIANCE WITH UNIVERSAL MOTOR DRIVE - Google Patents

Description

PATENT ADVOCATE

DR. ΗΛΝ-S ULRICH MAY ^Δ * '° ^iO ° D 8 MÖNCHEN 2, OTTOSTRASSE 1a TELEGRAMS: MAYPATENT MUNICH TELEPHONE CO81-O 5936 82

M-2-P-44/1268 Munich, March 28, 1974

DB / 2ÖÖ Dr.M./cs

Moulinex S.A. in F-93 Bagnolet / France

Electric household appliance with universal motor drive

The invention relates to household electrical appliances with a universal motor as a drive.

The invention relates particularly to electric coffee grinders, and more particularly to those with a so-called grind selector. Such a coffee grinder is described in French patent application 72 03638 and has a fly knife that is driven about a vertical axis in a working chamber, the side wall of which consists of a tubular sieve that is inside a collecting container for the ground material is arranged.

As is known, there is a tendency in such a device; that the motor speed increases when the working chamber runs out of coffee beans. This can cause the engine to stall and thus lead to considerable damage.

The invention is particularly intended for a household electrical appliance a coffee grinder, this disadvantage can be eliminated.

This object is achieved according to the invention in that the household electrical appliance an electronic device to limit the

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Has engine speed.

According to the invention it is provided that the electronic device has an electronic interrupter which is connected in series with the motor and a control connection for its conductive state and a control circuit for applying a signal dependent on the motor speed to the terminal.

The invention is explained with further properties and advantages - tert by the following description of an embodiment, which refers to the accompanying drawings. Show here:

Fig. 1 - a schematic representation of the main components of the electronic Facility;

Fig. 2 is an electrical circuit diagram showing details of an embodiment the electronic device.

Fig. 1 shows the invention applied to a universal motor, whose exciter winding 10 and rotor 12 are shown schematically. The motor is powered by an alternating voltage network with connections 14 and 16 fed.

The engine is equipped with an electronic speed limit device equipped, which has an electronic switch 18 which is arranged in series with the motor and a control connection 20 has for its conductive state. Terminal 20 is on an output of a control circuit 22 connected to this Connection applies a signal curve representing the engine speed. The control circuit 22 has an amplifier, its Input parallel to part of the excitation winding 10 between the both points 24 and 26 is switched on

The electronic device also includes a trigger circuit

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28 for applying a trigger pulse to terminal 20 when it is conductive Switch 18 after manual operation by the user. This trigger circuit 28 is parallel to the switch 18 between the two Points 30 and 32 switched.

This facility works as follows. Assume first that the electronic switch 18 is open. To close it and thus to cause the motor to start, a trigger pulse with a larger one must be applied to the terminal 20 with the aid of the trigger circuit 28 Amplitude can be applied as a predetermined value. After starting, a current runs through the excitation winding 10 and it occurs between the points 24 and 26 a voltage which is applied to the input of the amplifier 22 is applied as long as the motor is in its normal operating mode, i.e. as long as the current in the winding 10 has a sufficiently high strength, the output signal of the Amplifier 22 to a value which is sufficient to switch the switch 18 in Control state, i.e. to be kept in the connected state. If the Motor runs away, i.e. if its speed increases to a value above a predetermined value, the Current intensity in the winding 10 up to a value below a threshold value for which the output signal of the amplifier 22 is no longer sufficient to switch the switch 18 to its conducting state keep. The supply to the motor is therefore interrupted and the motor stops.

In the circuit diagram according to FIG. 2, those elements that correspond to the in Fig. 1 correspond to the components shown, with the same reference numerals Mistake. The electronic switch 18 comprises a semiconductor 33 of the type of a bidirectional thyristor, i.e. a TRIAC, the control electrode 34 of which is connected to the terminal 20.

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The trigger circuit 28 has a voltage divider which is formed from two resistors 36 and 38 lying in series with one another, whose common point is connected to the terminal 20, as well as a pressure switch 40, the ζγ / ischen the point 30 and the resistor 36 lies. A short press on the switch 40 is enough to apply a trigger pulse to the terminal 20.

The amplifier 22 contains an input circuit 41 for taking off and Rectification of the voltage between the terminals 24 and 26, which has a diode 42. The diode 42 is one of them Side on connection 24 and with the other side on external connection 44 a voltage divider, the other side of which is connected to the terminal 26, and two fixed resistors 46 and 48 on the one hand and a potentiometer 50 on the other hand. The input circuit 41 further includes a smoothing capacitor 52, a Zener diode 54 and a resistor 56. That from the input circuit 41 generated signal is applied to an output circuit 57 which has a transistor 58, the base of which is connected to the sliding contact 59 of the potentiometer, the emitter of which is connected to the Zener diode 54 and its collector via an intermediate resistor 60 the terminal 20 are connected.

According to FIG. 2, in addition to the TRIAC 33, the electronic switch 18 can also have a non-linear resistor 62 with a positive temperature coefficient, which is connected in series between the terminal 20 of the switch 18 and the electrode 34 of the TRIAC 33. This resistance represents an additional protective device that takes effect thermally. It can be arranged directly next to the excitation winding 10 in the motor and, in the event of an abnormal temperature increase, causes the signal applied to the electrode to drop or sink, which results in an opening of the switch " ^c · ^{0 ·,}

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Claims (1)

Claims 1 ή household electrical appliance, especially coffee grinder, with a universal motor drive , characterized in that an electronic device is provided for limiting the motor speed. 2. Household electrical appliance according to claim 1, characterized in that that in a working chamber a rotating blade is provided about a vertical axis and the side wall of the working chamber consists of a tubular sieve which is arranged inside a collecting container for the ground material. 3. Household electrical appliance according to claim 1 or 2, characterized in that that the electronic device for speed limiting an electronic switch (18) in series with the motor is switched, and a connection (20) for controlling its conductive state and a control circuit (22) for applying a signal curve representing the motor speed to the connection (20). 4. Sheet metal household appliance according to claim 3, characterized in that that the electronic device for speed limitation has a trigger circuit (28) for applying a trigger pulse for has the conductive state or for switching through to the control terminal (20). 5. Household electrical appliance according to claim 3 or 4, characterized in that the control circuit (22) contains an amplifier, the input of which is connected in parallel to part of an excitation winding (10) of the motor, and from the output of which a signal for maintaining the conductive state to the Control connection (20) of the switching 409846/0702 ters (18) can be applied as long as the excitation current of the motor is above a swell value * 5. Household electrical appliance according to one or more of claims 3 to 5j, characterized in that the electronic switch (18) has a two- ^{directional thyristor or f} £ RIAC (33) as a semiconductor element. 7. Household electrical appliance according to claim 6, characterized in that that the electronic switch (18) has a non-linear resistance (62) with a positive temperature coefficient, which is in series between the control connection (20) of the switch (18) and the Control electrode (34) for the conductive state of the TRIAC (33) is connected. 409846/0702