FR2520919A1 - ELECTROMAGNETIC ACTUATOR - Google Patents

Abstract

THE INVENTION RELATES TO ELECTRICAL APPARATUS. THIS ELECTROMAGNETIC ACTUATOR INCLUDES AT LEAST ONE COIL 1 INTENDED TO BE CONNECTED TO A SUPPLY SOURCE 2 THROUGH AT LEAST ONE SWITCH 4 WHICH CAN BE CONTROLLED TO ACTIVATE OR DEACTIVATE A MOBILE COMMANDER. AT LEAST ONE THERMISTOR 3A POSITIVE COEFFICIENT OF TEMPERATURE IS CONNECTED IN SERIES WITH COIL 1. APPLICATION TO APPLIANCES SUCH AS WASHING MACHINES AND DISHWASHER.

Description

The invention relates to an electromagnetic actuator

  particularly for domestic appliances of the type intended to control hydraulic

  detergent dispensers and the like.

  As is well known, these electromagnetic actuators essentially comprise a coil which, when traversed by an electric current, generates an electromagnetic field which exerts its attractive force on a mobile core which ensures the activation

  or the deactivation of a movable control member Ac-

  the coils used in electromagnetic actuators are dimensioned according to the conditions required by international safety standards, in particular by standards that require

  the adoption of coils which must be able to function

  continuously for a certain number of hours.

  without overheating or burning.

  For this purpose, the electromagnetic actuators are equipped with oversized coils in order to meet the requirements of the safety standards but, of a

  other things, they are expensive and undesirable.

  In addition, it can produce that the action-

  The electromagnetic neur remains in operation for a longer time than that provided by the acceptance tests and by the safety standards as may be

  occur, for example, for the solenoid valve of a

  washing machine which is started without having been

  lablement connected to the water pipe or for the electric detergent doser of a dishwasher in which the programmer locks in a phase of introduction of the detergent These disadvantages cause

  overheating and, in the long run, the burning of the action-

electromagnetic neur.

  It would therefore be desirable, and this constitutes a first object of the invention, to provide an electromagnetic actuator which makes it possible to use coils which are not oversized and which are therefore not very bulky and inexpensive.

  actuator must, however, also have characteristics

  extremely high reliability in all cases.

operating conditions.

  In accordance with the invention, these objects are achieved with an electromagnetic reactor comprising at least one

  coil intended to be connected to a power source

  electrical connection through at least one switch which can be controlled to actuate a control member

  mobile device, characterized in that at least one thermistor is connected

  in series with said coil In particular, the heat

  mist is of the type with positive temperature coefficient.

  The figures of the appended drawing, given by way of non-limiting example, will make it clear how the invention can be realized. In these drawings, FIG. 1 is a diagrammatic representation of an electromagnetic actuator according to the invention. FIG. schematically another

  embodiment of the actuator according to the invention.

  The electromagnetic actuator shown schematically

  Figure 1 essentially comprises a circuit arranged in series with a coil 1 and at least one

  thermiatance 3 A positive temperature coefficient The ac-

  is intended to be connected to a source of

  2 by means of an interrup-

  4 Controlled excitation of the coil 1 causes the

  formation of an electromagnetic field capable of

  In a known manner, a movable control device (not shown) As is known, the thermistor 3 with a positive temperature coefficient, also called PTC thermistor, has the characteristic of exhibiting an increase in ohmic value with the increase

  of temperature so that when the electric actuator

  tromagnetic is crossed by the current, the thermistor

  3 warms up and the ohmic value of the latter has been

in proportion.

  As a result, the gradual increase in

  the ohmic value of thermistor 3 causes a di-

  corresponding minution of the current flowing through

  the actuator and, consequently, the electromagnetic field

  generated by coil 1, until this field has reached a value that is insufficient to maintain

  of the movable control member.

  In the case where, for the reasons mentioned above, the electromagnetic actuator remains connected for a long time to the supply source 2, the increase in the resistance value of the thermistor 3 is such as to

  to reduce to a minimum the current flowing through the

  to avoid undesired overheating of the

1.

  In other words, the voltage of the source of

  Feed 2 is found substantially across the thermistor 3, determining the aforementioned deexcitation

  of coil 1 This makes it possible to undersize the bobbin

  No. 1, with consequent reduction in size and cost of the entire actuator, which in any case has greater reliability since the coil 1 is no longer subjected to excessive temperatures It is obvious that coils undersized devices can be used in electromagnetic actuators that have different operating times and, consequently, longer or shorter excitation times, for example, in the case of a washing machine or a

  dishwasher, the operating time of an electro-

  water loading valve is greater than that of the

  Thus, the maximum time of excitement of the actuator is determined by acting on the

  dimensions of the coil 1 and this maximum time obviously depends on

  the characteristics of the thermistor 3.

  In conclusion, if the coil 1 has a value

  ohmic resistance and, consequently, an absorption of

  relatively high, the temperature rise of thermistor 3 will be very fast and the voltage drop

  at the terminals of the coil 1 will also be very fast.

  Under these conditions, the electromagnet stops working in a few seconds and does not have the time to

  overheat despite the great intensity that crosses it

is.

  If, on the contrary, coil 1 has a large

  ohmic value and, therefore, a low absorp-

  current results in a decrease in current flow through the thermistor 3 and, therefore,

  an increase in the heating time of this thermistor-

  this and an increase in the operating time of the electricity

  In the case of several electronic actuators,

  magnetic devices (for example, in the case of three actuators) which form part of a single apparatus, the invention proposes the embodiment shown diagrammatically in FIG. 2, in which a single thermistorance 3 is

  connected in series with three branches arranged in

  each is constituted by a coil 1, 5, 6 respectively, in series with a switch

  ordered corresponding 4, 7, 8 respectively.

  Each coil 1, 5, 6 is intended to activate a corresponding movable member, not shown, with times

  maxima of excitation that depend on the dimensions of the

  and the actuation of its switch 4, 7, 8.

  The electromagnetic actuator according to the invention

  tion finds particular application in

  6 appliances, such as washing machines or dishwashers

  saddle, but it is obvious that it can also be used

  advantageously used in devices of another type

  and intended for other applications.

  It goes without saying that modifications can be made to the embodiment which has just been described,

  in particular by substituting equivalent technical means

  slow, without going beyond the scope of the invention.

Claims (2)

R E V E N D I C A T IO N S   Electromagnetic actuator comprising at least one coil intended to be connected to a source   electrical supply through at least one interrup-   which can be ordered to operate a   mobile controller, characterized in that at least one thermistor   tance (3) is connected in series with said coil (1).   2 Electromagnetic actuator according to the claim   1, characterized in that the thermistor (3) is   of the type & positive temperature coefficient.