Abstract:
An actuator device which includes a fixed support structure, an actuation member movable, a biasing member tending to maintain the actuation member in a rest position, a shape-memory wire connected to the structure and to the actuation member, and an electric circuit for supplying an electric current to the shape-memory wire. The circuit includes a pair of terminals. One end of the shape-memory wire is connected to a first terminal. The circuit includes further an electric switch, including a first conducting member electrically connected with the second terminal, and a second conducting member carried by the actuation member and electrically connected with the other end of the shape-memory wire. The switch is closed when the actuation member is in the rest position, and remains closed until when the actuation member reaches a working position, and opens when the actuation member passes beyond the working position.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to electrically-controlled actuator devices, and in particular to actuator devices for use in electric household appliances. 
     Background 
     More specifically, the invention concerns an electrically-controlled actuator device of the kind comprising
         a support structure which is stationary in operation,   an actuation member displaceable relative to said structure,   biasing means tending to maintain the actuation member in a rest position,   a wire of a shape-memory material, having a first end connected to said structure and the other or second end connected to the actuation member, and   an electric circuit for supplying in a controlled manner an electric current to said shape-memory wire, said circuit comprising a pair of terminals carried by said structure, for connection to external control circuit means, one end of the shape-memory wire being connected to a first terminal of said pair.       

     An electrically-controlled actuator device comprising a shape-memory wire is disclosed for instance in the U.S. Pat. No. 7,270,135 B2, for use in a washing agents dispensing or distributing device for a dishwashing machine. 
     In said prior document, with particular reference to  FIGS. 1 and 2  thereof, there is disclosed an actuator device comprising a long shape-memory wire which extends along the whole body of the dispensing device, and wherein the displaceable actuation member is a single-arm lever, solid for rotation with a shaft and subjected to the reaction of a biasing spring arranged around said shaft. 
     Such an actuator device is not suitable for use for instance in a washing agents distributing apparatus of the kind wherein the dispensing in sequence of a first and thereafter a second and different washing agent is controlled by means of subsequent activations of a same actuator device. 
     An object of the present invention is to propose an actuator device of the above-specified kind, capable of overcoming the above-outlined inconveniences of the devices according to the prior art. 
     SUMMARY OF THE INVENTION 
     This and other objects are achieved according to the invention by an actuator device of the above-specified kind, characterized in that the above-mentioned electric circuit comprises a switch including a first conducting member, connected to the second terminal of the above-mentioned pair, and a second conducting member carried by the displaceable actuation member and electrically connected to the other end of the shape-memory wire;
         the arrangement being such that said switch is closed when the actuation member is in its rest position, and remains closed until when the actuation member reaches its working position, said switch opening when the actuation member goes beyond its working position.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention will become apparent from the following detailed description, provided merely by way of a non-limiting example, with reference to the accompanying drawings, wherein: 
         FIG. 1  is a partially exploded perspective view of an electrically-controlled actuator device according to the present invention; 
         FIG. 2  is a partial perspective view of the actuator device of  FIG. 1 ; 
         FIG. 3  is a diagrammatical representation of essential parts of the actuator according to the preceding figures; 
         FIG. 4  is a rear perspective view of a washing agents dispensing apparatus, particularly for a dishwashing machine, comprising an electrically-controlled actuator device according to the preceding figures; and 
         FIG. 5  is a view of a further apparatus including an electrically-controlled actuator device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings by  1  there is indicated as a whole an electrically-controlled actuator device according to the present invention. 
     In the illustrated exemplary embodiment the actuator device  1  comprises a support casing  2 , which is stationary in the operation, and which includes a box-like body  3  and an associated closing cover  4 . 
     In the embodiment shown, in a lateral wall of the body  3  there is provided a cut-out indicated  5  in  FIGS. 1 and 2 . 
     Through another portion of the sidewall of the box-like body  3  two electrical connection terminals  6  and  7 , shaped for instance as male plug blades, extend toward the outside. 
     Inside the box-like body  3  a two-arm lever  8  is mounted pivotable about a fulcrum or axis  9 . 
     The lever  8  has a first arm  8   a  and a second arm  8   b , which in the illustrated embodiment extend in respective directions forming an angle with one another. That angle in the exemplary embodiment is of about 90°, but could have quite different magnitudes. 
     The lever  8  is preferably made of a metal material, and the distal end of the arm  8   b  thereof is turned such as to form a transverse appendix  8   c  which extends through the cut-out  5  of the box-like body  3  (see in particular  FIG. 2 ). 
     By  10  in  FIGS. 1 to 3  there is indicated a wire made of an electrically conducting or resis-tive shape-memory material. 
     The wire  10  has one end connected to the electric terminal  6 , and the other end anchored to the distal end of the arm  8   a  of the lever  8 . 
     As it can be better seen in  FIG. 3 , in the illustrated exemplary embodiment, inside the casing  3  the electric terminal  7  extends up to beneath the distal end of the arm  8   b  of the lever  8 , and in that area forms a sort of raised shelf  7   a.    
     A helical spring  11  of an electrically conducting material rests on the shelf portion  7   a  of the electric terminal  7 , and is contained between two opposite parallel walls  12  which are integral with the box-like casing  3  (see in particular  FIGS. 2 and 3 ). 
     Conveniently, the walls  12  have upper end portions  12   a  which are turned, as it can be seen in  FIG. 3 , to limit the extension of the spring  11 . 
     An appendix  8   d  of the arm  8   b  of the lever  8  insists onto the upper end of the electro-conducting spring  11 . Said appendix  8   d  in the illustrated exemplary embodiment has an essentially L-like shape, with an essentially vertical branch which extends downward from the arm  8   d  of the lever  8 , and an essentially horizontal branch which insists onto the elec-tro-conducting spring  11 . The terms “vertical” and “horizontal” utilized above are meant for the observer of  FIGS. 2 and 3 . 
     By  13  there is indicated a biasing spring which at one end reacts against a shoulder provided in the box-like body  3 , and at the other end reacts against the arm  8   a  of the lever  8 . 
     The spring  13  tends to make the lever  8  rotate, in a counter-clockwise direction for the observer of  FIGS. 1 to 3 , such that the arm  8   b  and the relevant appendix  8   d  insist at rest onto the electro-conducting spring  11 , compressing it to a certain extent. 
     In the rest condition of the actuator device, shown in  FIGS. 2 and 3 , between the terminal  6  and  7  there is defined an electric path or circuit comprising the shape-memory wire  10 , the two-arm lever  8  and the electro-conducting spring  11 . In said rest condition the appendix  8   c  of the lever  8  is at least partially retracted inside the casing  3 ,  4 . 
     If in said rest condition an electric current is made flow in the above-described electric circuit, the shape-memory wire  10  undergoes a contraction, causing a rotation of the two-arm lever  8 , in the clockwise direction for the observer of  FIGS. 1 to 3 , against the reaction of the biasing spring  13 . As a consequence of said rotation of the lever  8 , the end appendix  8   c  thereof extends to a progressively increasing extent outside the support casing  3 ,  4  through the cut-out  5 . As the rotation of the lever  8  progresses, the electro-conducting spring  11 , which was previously compressed, is allowed to relax. 
     At a certain moment, the appendix  8   d  of the lever  8  leaves the upper end of the electro-conducting spring  11 , causing an interruption of the electric circuit between the terminals  6  and  7 . This interruption causes the end of the flow of an electric current in the shape-memory wire  10 , which starts to re-extend. The re-extension of said wire allows that, under the action of the biasing spring  13 , the lever  8  makes a though small rotation in a direction opposite the preceding one, thus in the counter-clockwise direction for whom observes for instance  FIG. 3 , such that the appendix  8   d  thereof re-engages the upper end of the elec-tro-conducting spring  11 . At that time the circuit between the terminals  6  and  7  is once again closed, and an electric current flows again through the shape-memory wire  10  which, by contracting, tends to cause a new rotation of the lever  8  in the clockwise direction for whom is looking at the Figures. 
     In summary when, starting from the rest condition of the actuator device  1 , a voltage is applied between the terminals  6  and  7 , the current which consequently flows in the above-described circuit is such as to cause a rotation by a predetermined amount of the two-arm lever  8 , which passes from its rest position to a working position. As soon as the lever passes beyond the working position, said electric circuit is interrupted, and the lever  8  tends to rotate in the opposite direction, until when the circuit is closed again, and so on. As a consequence, until when a voltage is still applied between the terminals  6  and  7 , the lever  8  substantially remains in its working position or, to be more precise, undergoes an almost non-perceptible oscillation thereabout. 
     When the application of the voltage between the terminals  6  and  7  is stopped, then also the flow of an electric current in the above-mentioned circuit, and in particular in the shape-memory wire  10 , ceases. Under the action of the biasing spring  13 , the lever  8  abandons its working position, to regain its rest position, wherein it definitely remains until a subsequent application of voltage between the terminals  6  and  7 . 
     In view of the above, in the operation the behaviour of the actuator device  1  is functionally similar to that of a conventional solenoid actuator, with respect to which it has however a much simpler structure, a lower cost and a more reliable operation. 
     The operational characteristic of an actuator according to the present invention is absolute-ly repeatable, for a very high number of activations or cycles of operation. 
     In  FIG. 4  by D is indicated as a whole a washing agents dispensing apparatus, of a per se known kind, particularly for a dishwashing machine. 
     Said dispensing device D essentially comprises two dispensing sections, indicated  20  and  30 , for dispensing a washing agent like a powder detergent, and a liquid rinsing agent, re-spectfully. 
     Dispensing devices of that kind are disclosed for instance in patent applications DE 19 756 679 and DE 19 545 773. 
     The dispensing device D is of the (per se known) kind wherein the two dispensing sections  20  and  30  can be selectively activated in sequence, through subsequent activations of a same control member  40 , activations which are conveniently caused by means of an electrically operable actuator device  1  of the kind described above, incorporated in the dispensing device D. 
     In the application illustrated in  FIG. 4  the actuator device  1  according to the invention conveniently replaces a conventional electric solenoid actuator. 
     In  FIG. 5  there is illustrated a further apparatus E which includes an actuator device  1  according to the present invention. 
     In that embodiment the end  8   c  of the two-arm lever  8  of the actuator device  1  is coupled with a pawl  21 , which cooperates with the teeth  22  of a gear wheel  23 . 
     Subsequent applications of voltage between terminals  6  and  7  of the actuator device  1  cause corresponding finite or step-like angular displacements of gear wheel  23 , as a consequence of the engagement of the pawl  21  with the teeth  22 . 
     A step-wise rotation of the gear wheel  23  can be utilized for a number of purposes. In the exemplary illustrated embodiment said gear wheel also has a crown of teeth  24  with a larg-er diameter, meshing with a toothed pinion  25  which is solid with a wall  26 . The diameters of the toothed crowns  22  and  24  and the diameter of the pinion  25  can be selected such that at each rotation step of the gear wheel  23 , caused by the actuator device  1 , a rotation of the wall  26  by 90° is caused. The wall  26  can for instance be the obturator of a conduit, which can be thus selectively switched from a condition of opening to a condition of closure, and thereafter a condition of opening, and so on. 
     The application described above with reference to  FIG. 5  is merely exemplary, the actuator device  1  according to the present invention being capable of finding a great number of useful technical applications. 
     Naturally, the principle of the invention remaining the same, the embodiments and the de-tails of construction may be widely varied with respect to what has been described and illustrated by way of non-limiting examples, without departing from the scope of the invention as defined in the annexed claims.