Clock-controlled electronic switch for motor piloting

Abstract

 A clock-controlled electronic switch for piloting motors, with outputs for the reversal of the motor revolution direction, comprising a main timer (3) of mechanical or electro-mechanical type, and asn electronic inverter (5) equipped with solid-state switches (6₁, 6₂ 6_n), integrated with one another.

Description

[0001] The present invention relates to a clock-controlled electronic switch for piloting motors.

[0002] More particularly, the present invention relates to an electronic switch suitable for programming the operating time of apparatuses which, during their use, require frequent reversals of the revolution direction of a motor.

[0003] The clock-controlled electronic switch according to the present invention makes it possible a sequence of states of commutation of a set of contacts capable of accomplishing reversals in the direction of revolution of motors, such as, e.g., the motors of household electrical apparatuses and appliances, or of other devices, to be programmed for a variable time, comprised within the range of from a few minutes up to some hours.

[0004] A preferred application of the clock-controlled electronic switch according to the present invention is in laundry dryers in which, as known, a continuous reversal of the direction of revolution of the dryer basket is required during the drying process.

[0005] Several devices which make it possible the above reported functions to be performed are known from the prior art and are available from the market. In general, such devices comprise a mechanical or electromechanical clock which pilotes a set of cams and gearwheels which perform the required switchings of the electrical contacts.

[0006] Unfortunately, the devices known from the prior art are affected by several drawbacks which limit their use. One of such drawbacks is given by the fact that, inasmuch as such devices are driven by a mechanical means, such as a small electrical motor, they require a rather long time in order to carry out the reversal of the direction of revolution of the main motor. Furthermore, such devices are rather complex, in particular when the simultaneous presence is required of electrical contacts with relatively long switching cycles, and of electrical contacts with rather short switching cycles.

[0007] In that case, in fact, a large number of gearwheels are required in order to accomplish time cycles which are very different from one another.

[0008] Furthermore, in the devices known from the prior art, once that the ratios between the various switchgears are fixed, said ratios cannot be changed at a later time, unless the same gearwheels are completely substituted.

[0009] Another drawbacks displayed by the devices known from the prior art is that a rapid switching of the contacts, such as to eliminate arc discharges or opening or closing extra currents -- which, as known, cause a wear of the contacts, with the consequent decrease of their useful life (number of possible switching operations) -- is difficult to be obtained.

[0010] The purpose of the present invention is of providing a clock-controlled electronic switch which does not show the above reminded drawbacks.

[0011] More particularly, the purpose of the present invention is of providing a clock-controlled electronic switch for motor piloting which is reliable, simple to be manufactured, which has small overall dimensions, and which makes it possible the time of switching of the electrical contacts to be varied as desired, and the wear of said electrical contacts to be reduced.

[0012] According to the present invention, these and still further purposes which will be clear from the following disclosure, are achieved by means of a clock-controlled electronic switch which comprises two main modules integrated with each other, wherein:

a) one of said modules is a main timer of mechanical or electromechanical type, and

b) the other module is an electronic inverter equipped with solid-state switches.

[0013] The mechanical or electromechanical timer makes it possible the total time to be programmed, and the electronic inverter makes it possible the sequence of motor operating steps to be programmed.

[0014] The main timer of mechanical or electromechanical type renders the electronic switch according to the present invention particularly reliable, so that said electronic switch can be given a rating which assigns it to the highest reliability classes; and the presence of an electronic inverter makes it possible both fast and reliable switchings to be carried out, and the contacts of possibly present relays to be actuated in the absence of electrical current, so as to secure a very reduced wear of such contacts.

[0015] Finally, the presence of solid-state switches makes it possible a high reliability to be obtained, in particular in case of fast and short switchings, and of long-lasting switchings.

[0016] The structural and functional characteristics of the clock-controlled electronic switch according to the present invention can be better understood from the following disclosure, in which reference is made to the figures of the hereto attached drawing tables, which show a preferred, exemplifying, non-limitative form of practical embodiment of the present invention, in which:

- Figure 1 shows the schematic block view of the clock-­controlled electronic switch according to the present invention;

- Figure 2 shows the schematic block view of the main timer of electromechanical type;

- Figure 3 shows the schematic block view of the electronic inverter; and

- Figure 4 shows the schematic view of the clock-controlled electronic switch according to the present invention, applied to a laudry dryer.

[0017] Referring to Figure 1 , the clock-controlled electronic timer according to the present invention comprises a main mechanical switchgear (2) installed between the electrical power input (1) and a mechanical timer (3). A set of primary contacts (A₁, A₂, A_n) can be inserted between the main switchgear (1) and the timer (3), through intermediate switches (4′, 4˝, and so forth).

[0018] The output from the timer (3) is connected with the primary contacts (A₁, A₂, A_n) and with an electronic inverter (5) equipped with solid-state switches (6₁, 6₂, 6_n) in their turn connected with secondary contacts (B₁, B₂, B_n).

[0019] Figure 2 shows a schematic view of the electromechanical timer (3) of Figure 1. Said timer comprises a gear reduction unit (7) actuated by a synchronous motor (8). The reducer (7) actuates a cam (9). The necessary time for the cam to make a complete revolution depends on the revolution speed (rpm) of the motor (8) and on the transmission ratio of the gear reduction unit (7).

[0020] The cam (9) directly actuates the electrical contacts (10) constituted by elastic metal blades accurately following the contour of the cam (9). The electrical contacts (10) transmit the electrical power from the inlet (1 ) to the primary contacts (A₁, A₂, A_n, and so forth), to the electronic inverter (5) and to the motor (8). On the gear reduction unit (7) a control knob (11) is installed.

[0021] The electronic timer operates as follows.

[0022] The control knob (11) is rotated up to the desire delay time. By means of its own shaft, said control knob causes the cam (9), which closes the contacts (10), to rotate. The electrical power incoming from the input (1) is thus fed to the motor (8), to the electronic inverter (5) and to the various primary contacts (A₁, A₂, A_n), used in order to feed auxiliary electrical elements, such as electrical heating resistors, pilot lamps, and so forth.

[0023] The motor (8) actuates the gear reduction unit (7) and consequently the cam (9), in the direction opposite to the revolution direction supplied by the control knob (11). When the time entered by the control knob (11) has elapsed, the cam (9) opens the contacts (10) and the various outputs are isolated from the input (1).

[0024] Figure 3 shows a schematic view of the electronic inverted (5) connected with the electromechanical timer (3) of Figure 2.

[0025] The electrical power coming from the contacts (10) of the electromechanical timer (3) is reduced in voltage, is rectified, and is stabilized by the circuits (12) and (13) of type known from the prior art.

[0026] The output of the circuit (13) is connected with the electronic circuits (14) and (15), one of which (14) generates a frequency which acts as the time reference basis, and the other one (15) is formed by a plurality of dividers and of logic circuits for generating the required time sequence. Such electronic circuits (14) and (15) are of a type known from the prior art, and therefore they need not to be disclosed in detail. The electronic circuit (15) is connected with an inverter (16) through a logic level of the time sequence. Said inverter (16), piloted by the sequence of commands at the logic level, transmits to the outputs (17, 18) the electrical power present at its input (19). The outputs are connected with the electrical motor (20) of a laundry dryer or of another household appliance, or of other apparatuses.

[0027] A diagram of application of the clock-controlled electronic switch according to the present invention to a laundry dryer is shown in Figure 4, in which the primary contact A₂ is connected with the heating resistor R and both outputs (17) and (18) of the electronic inverter (5) are connected with the dryer basket motor (20) through triacs (21) and (22).

[0028] According to a preferred form of practical embodiment, the timer of electromechanical type can be a synchrotimer JV100 of the type with two open contacts.

[0029] With the electronic switch according to the present invention, within a total time of 135 minutes, 27 cycles can be performed, with each cycle being of 300 seconds. The time schedule of each cycle is:
- 150 seconds or basket revolution in clockwise direction;
- 2,5 seconds of pause;
- 150 seconds or basket revolution in counterclockwise direction;
- 2,5 seconds of pause

Claims

1. Clock-controlled electronic switch for piloting apparatuses requiring frequent reversals of direction of revolution of a motor, which comprises two main modules integrated with each other, wherein:

a) one of said modules is a main timer of mechanical or electromechanical type, and

b) the other module is an electronic inverter which programs the sequence of motor operating steps, and is equipped with solid-state switches.

2. Electronic switch according to claim 1, wherein the main timer is connected with primary contacts used in order to feed auxiliary electrical devices with electrical power.

3. Electronic switch according to claim 1 or claim 2, wherein the main timer comprises:
- a gear reduction unit;
- a cam driven by said gear reduction unit;
- a motor driving said gear reduction unit;
- electrical contacts which transmit electrical power from timer input to the primary contacts, to the electronic inverter and to the motor, directly actuated by said cam; and
- a control knob installed on the gear reduction unit.

4. Electronic switch according to any of the preceding claims, wherein the electronic inverter comprises circuits for reducing, rectifying and stabilizing the voltage, an electronic circuit generating the frequency acting as the time reference basis, logic circuits for producing the required time sequence and an inverter transmitting the electrical power to an electrical motor, piloted by the sequence of commands at logic level.

Drawing