Patent Publication Number: US-9885141-B2

Title: Apparatus for controlling the closing of a door of a household appliance, in particular for a washing machine, such as a dishwasher

Description:
This application claims benefit of Serial No. TO2013A000691, filed 13 Aug. 2013 in Italy and which application is incorporated herein by reference. To the extent appropriate, a claim of priority is made to the above disclosed application. 
     TECHNICAL FIELD 
     The present invention relates to an apparatus for controlling the closing of a door of a household appliance, in particular for a washing machine, such as a dishwasher. 
     BACKGROUND 
     In the field of household appliances, solutions have to be found, in order to allow an inner chamber obtained in a casing of said appliances, typically a washing chamber of a washing machine, such as a dishwasher, to be closed. To this regard, a door is used, which is mobile relative to the casing so as to open and close an access opening, through which the inner chamber is able to communicate with the outside of the household appliance. 
     Generally, these apparatus comprise an engagement element, which is intended to be fitted on one between said casing and said door, and a retaining element, which is intended to be fitted on the other one between the door and the casing. The retaining element is suited to hold the engagement element in a releasable manner, so as to constrain the door to the casing, when the household appliance is being used. 
     Typically, the coupling between the engagement element and the retaining element takes place by means of the action of a user, who brings them closer by manually pushing the door against the casing, so as to obtain a complete closing. The uncoupling between the engagement element and the retaining element takes place by means of the action of the user, who acts upon suitable control interfaces (for example, provided on the front wall of the door or on the front or upper face of the casing), which activate inner mechanisms of the retaining element, which release the engagement element from the retaining element. 
     In this field, some apparatuses have turn out to be technically advantageous, namely those apparatuses that are designed to permit a so-called “pre-opening” of the door, in particular of washing machine, especially of dishwashers. In detail, the door is brought to an ajar state, in which it is only slightly angularly spaced apart from the casing of the household appliance, thus creating, together with the latter, a slit that is able to establish a fluid communication between the washing chamber and the outside. This solution is particularly advantageous in washing machines, for example dishwashers, since it allows the steam generated during the washing cycle to be let out, thus contributing to the at least partial drying of the articles contained in the washing chamber. 
     To obtain the above-mentioned pre-opening of the door, some variants of these apparatuses provide a striker, which is mounted so as to be mobile relative to a support body between a retracted position and an extracted position. When the striker is coupled to the retaining element and assumes the retracted position, the door is in a complete closing condition, in which it closes the access opening of the casing in a fluid-tight manner. On the other hand, when the striker is coupled to the retaining element and assumes the extracted position, the door is in a pre-opening condition, in which it is spaced apart from the access opening of the casing. The liberation of the striker, so that it can move from the extracted position to the retracted position, is further subordinate to a stop mechanism, which tends to move from a release position to a locking position and, in doing so, is electrically controlled by driving means, such as a motor or an actuator, which are suited to control the movement of the stop mechanism from the locking position to a release position. In the release condition the stop mechanism is adapted to free the striker, thus allowing it to move from the retracted position to the extracted position, when the striker is coupled to the retaining element. On the other hand, in the locking position condition the stop mechanism is adapted to hold the striker, when the latter is in the retracted position. 
     Though, these apparatus suffer from some drawbacks. 
     One drawback lies in the fact that, in these systems, when the washing machine is deactivated, the stop mechanism normally tends to move to the locking condition and to remain there. This situation can be potentially dangerous in case of an incorrect or accidental use of the machine on which the apparatus is installed, in particular by a baby. Consider, for example, what could happen if a baby were to enter the inner chamber of the washing machine through the access opening and close the door behind his/her back. In this case, the striker would be pushed backwards in the retracted position and the mechanism—which is in the locking position—would hold the striker in this position, thus leaving the door in a complete closed condition, with the risk for the baby of being trapped in the washing chamber. 
     SUMMARY 
     The object of the present invention is to provide and apparatus for the closing of a door of a household appliance, in particular a washing machine, such as a dishwasher, wherein the apparatus has an improved safety, even in case of an incorrect or accidental use, in particular by babies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention will be best understood upon perusal of the following detailed description, which is provided by way of example and is not limiting, with reference to the accompanying drawings, which specifically show what follows: 
         FIG. 1  is a perspective view of a dishwasher comprising an apparatus for controlling the closing of a door of a household appliance according to a first explanatory embodiment of the present invention; 
         FIG. 2  is a partial schematic view, in particular a plan view from the top, of the dishwasher of  FIG. 1 , but without the lid and with the door in a complete closed position; 
         FIG. 3  is a partial perspective view of the apparatus shown in the previous figures, with some inner components visible; 
         FIG. 4  is an exploded perspective view of the apparatus shown in the previous figures; 
         FIG. 5  is a perspective view of a component of a stop mechanism of the apparatus shown in the previous figures; 
         FIGS. 6 and 7  are perspective views of the apparatus shown in the previous figures, which, here, is shown in two different operating conditions; and 
         FIG. 8  is a front perspective view of manufacturing details concerning the stop mechanism of the apparatus shown in the previous figures. 
     
    
    
     DETAILED DESCRIPTION 
     With reference, in particular, to  FIG. 1 , W indicates, as a whole, an example of a washing machine, on which an explanatory embodiment of an apparatus  10  according to the present invention is intended to be installed. The washing machine is a dishwasher, though, as confirmed by the following description, apparatus  10  can also be applied to different washing machines (for example a laundry washing machine) or to other household appliances. 
     With reference, in particular, to  FIG. 1 , dishwasher W has a casing C, in which a washing tank or chamber WT is defined, which is suited to receive the dishes to be washed. Washing tank WT has an access opening O, through which washing tank WT communicates with the outside and which, therefore, is able to house the dishes. Furthermore, dishwasher W has a door D, which is intended to open and close access opening O. 
     Access opening O is arranged on a front face of casing C and, preferably, the door is pivotable relative to casing C, for example it is hinged around a horizontal axis that is arranged in the lower part of the latter. In the embodiment shown, access opening O is peripherally provided with a sealing gasket (without reference number), so as to allow washing tank WT to be closed in a fluid-tight manner, when door D is in a completely closed condition. 
     In the embodiment shown, casing C has a lid L, which is advantageously arranged on the top of said casing C. 
     In  FIG. 2 , washing machine W is shown in a partial view and without lid L, which is typically arranged on the top of casing C. Machine W preferably has a cross bar CB, which is arranged above a wall of washing tank WT. 
     Furthermore,  FIG. 2  shows a pair of partitions or transverse walls P 1 , P 2 , which are arranged in the upper part of casing C and are provided so that lid L can be arranged above them. The function of these walls P 1  and P 2  will be described more in detail in the description below. 
     Apparatus  10  is suited to allow door D of dishwasher W to be closed and comprises an engagement element  11 , which is suited to be fitted in correspondence to casing C, for example on cross bar CB arranged between casing C and lid L. Engagement element  11  is adapted to be held in a releasable manner by a retaining element  16 , which is suited to be fitted on door D, for example on its rear face facing access opening O. 
     Retaining element  16  is suited to hold engagement element  11  in a releasable manner, so as to constrain door D to casing C, when washing machine W is being used. In the first embodiment shown, engagement element  11  is fitted on casing C and retaining element  16  is fitted on door D. 
     Engagement element  11  comprises a support body  12 , which, in the embodiment shown, is fitted to casing C, and a striker  14 , which is associated with support body  12  and is suited to be coupled in a releasable manner to retaining element  16 , which is fitted on door D, so as to constrain door D to casing C, when dishwasher W is being used. In the embodiment shown, support body  12  is manufactured as an internally hollow case, for example comprising a pair of half-shells or cups  12   a ,  12   b , which are coupled to one another, in particular in a snap manner, in correspondence to their periphery. 
     In the embodiment shown, half-shells  12   a ,  12   b  of support body  12  are manufactured with a plastic material, for example by means of injection molding. Preferably, support body  12  is screwed to casing C of household appliance W, for example in correspondence to cross bar CB. 
     As explained in the description below, striker  14  is mounted so as to move relative to support body  12  between a retracted position ( FIGS. 2, 3, 6 and 7 ) and an extracted position. Advantageously, striker  14  is mobile in such a way that it is guided by support body  12 , in particular by inner walls thereof. Preferably, striker  14  can slide relative to support body  12 . In particular, striker  14  is manufactured with a plastic material, for example by means of injection molding. 
     In both the embodiments shown, in the retracted position, striker  14  partially projects from support body  12  with a segment of its, whereas, in the extracted position, striker  14  further projects with an additional segment. Preferably, striker  14  projects through a slit (without reference number), which is obtained on the front face of wall P 1  of casing C of dishwasher W, on which engagement element  11 , as a whole, is mounted. 
     In particular, when striker  14  is coupled to retaining element  16  and moves to the extracted position, retaining element  16  is moved away relative to support body  12 , which consequently causes door D to be moved away, remaining at the same time constrained to casing C, though without being closed in a fluid-tight manner in correspondence to access opening O. 
     Restraining element  16  is substantially of a known type and has, for example, a containing body, which is provided with a slit and houses a coupling mechanism, which can be accessed by striker  14  through said slid, so as to allow the striker  14  itself to be coupled in a releasable manner to said coupling mechanism. Generally, said coupling mechanism is pivotable between an operating position and a rest position and comprises a rotary member, whose movement is opposed by an elastic member and which is suited be engaged in a releasable manner by striker  14 . In the operating position, the rotary member of the coupling mechanism holds striker  14  when door D is closed. On the other hand, in the rest position, the rotary member of the coupling mechanism liberates striker  14  when the user operates a suitable release mechanism (not shown), for example including a push-button, a lever or a knob, which is arranged on door D. 
     Examples of a retaining element  16  of the type described above are widely known in the technical field and are described in detail in many prior art documents. In order to provide complete information, the Italian patent applications no. TO97A1120, TO2000A000383 and TO2001A01003 are mentioned, whose content is to be considered as included herein by means of reference and by mere way of example. Therefore, for sake of brevity, retaining element  16  will not be further described in the description below. 
     When striker  14  is coupled to retaining element  16  and is arranged in its retracted position, engagement element  11  is in the arrangement shown in  FIG. 2 , in which door D is in a complete closing condition, thus closing access opening O of washing chamber WT in a fluid-tight manner. On the other hand, when striker  14  is coupled to retaining element  16 , but is arranged in its extracted position, door D assumes a pre-opening condition, thus being slightly spaced apart from access opening O of casing C, so as to establish a fluid communication between washing chamber WT and the outside of casing C. In particular, in the pre-opening condition, the steam contained in washing tank WT (which, for example, is generated during a washing cycle of dishwasher W) is allowed to flow out of dishwasher W, so as to allow the dishes contained therein to be at least partially dried. 
     In other words, when striker  14  is coupled to retaining element  16  and moves to the extracted position, it allows retaining element  16  to be moved away from support body  12 , which consequently causes door D to be moved away from casing C. Though, due to the coupling between striker  14  and retaining element  16 , door D remains in any case constrained to casing C, though without closing access opening O in a fluid-tight manner. 
     With reference, in particular, to  FIGS. 6 and 7 , engagement element  11  comprises, furthermore, a stop mechanism, which is indicated, as a whole, with number  18 . In both the embodiments shown, stop mechanism  18  is fitted on support body  12 ; in particular, it is contained in the cavity defined by support body  12  itself. 
     Stop mechanism  18  tends to move 
     from a release position (not shown), in which it is adapted to liberate striker  14 , thus allowing the latter to move from the retracted position to the extracted position, when said striker  14  is coupled to retaining element  16 , 
     to a locking position ( FIGS. 6, 7 ), in which it is adapted to hold striker  14 , when striker  14  is in the retracted position. 
     Furthermore, engagement element  11  comprises driving means, in the embodiment shown an electrically-operated actuator  20 , which is suited to control the movement of stop mechanism  18  from the locking condition to the release condition. By way of example, this movement is performed when actuator  20  is excited by the passage of an electric current. In other embodiments, an electric motor can be used instead of actuator  20 . 
     In the embodiment shown, actuator  20  is connected to an outer control unit associated with household appliance W and is able to supply power to actuator  20  in predetermined operating conditions. Preferably, actuator  20  is mounted on support body  12 , for example it is housed in the cavity defined therein. 
     According to the present invention, stop mechanism  18  comprises a safety element  18   a , which can be manually controlled by a user and can be moved between a liberation arrangement and an inhibition arrangement. In the liberation arrangement (shown in  FIG. 6 ), safety element  18   a  allows stop mechanism  18  to move between the locking condition and the release condition, in particular in such a way that it is controlled by the driving means, for example by actuator  20 . On the other hand, in the inhibition arrangement, safety element  18   a  forcedly constrains stop mechanism  18  in the release condition, thus preventing it from assuming the locking condition. 
     In this way, the safety of apparatus  10  is improved, especially in case of an incorrect use of dishwasher W, in particular by babies. As a matter of fact, if the safety element is manually moved by a user to the inhibition arrangement, should a baby enter the inner chamber of washing machine W through access opening O and close door D behind his/her back, striker  14  would be pushed backwards to the retracted position, but mechanism  18  would not be able to reach the locking condition. Therefore, even if striker  14  were to be coupled to engagement element  11 , stop mechanism  18  would not be able to hold striker  14  in the retracted position and, hence, door D would move back outwards in the pre-opening position, thus preventing the baby from getting trapped in the washing tank with the risk of suffocating. 
     Further advantageous features and preferred details of safety element  18   a  will be described more in particular in the description below. 
     Furthermore, engagement element  11  preferably comprises return means  15 , which are suited to optionally cause striker  14  to go back to the retracted position when the striker is uncoupled from retaining element  16 . In particular, return means  15  are fitted on support body  12 . In this way, striker  14  is prevented from excessively projecting—in a way that can possibly be dangerous for the safety of the users—from casing C of dishwasher W, when a user uncouples striker  14  from retaining element  16 , by acting upon the proper release mechanisms provided on dishwasher W, and moves door D from the pre-opening condition to the complete closing condition. 
     Preferably, the return means comprise elastic return means, for example including a return spring  15 . In particular, the elastic return means are adapted to operate in a pulling manner. 
     Preferably, apparatus  10  comprises, furthermore, a pushing member  19 , which is able to deliver a thrust in the moving direction of striker  14  from the retracted position to the extracted position, which is intended to be exerted on door D, thus helping it move to the pre-opening condition, when striker  14  is coupled to retaining element  16  and stop mechanism  18  is in the release condition. In this way, the movement of door D from the complete closing condition to the pre-opening condition becomes easier and more reliable. 
     In simpler alternative variants, pushing member  19  can be omitted from the apparatus, since the own weight of door D, combined with the elastic force exerted by the sealing gasket fitted around opening O, can be able to allow door D to open. In this variant, elastic return means  15  can be left out, as well, so as to facilitate the pre-opening of door D, provided that the projection of striker  14  with the door completely open is substantially negligible and does not constitute a problem or a danger for the users. 
     In the embodiment shown, pushing member  19 , for example with a substantially oblong shape, is mounted so as to be mobile relative to support body  12  and exert the aforesaid thrust, thus moving from a retracted condition to an extracted condition. In this way, manufacturers can obtain a compact configuration of apparatus  10  by using a pushing member  19  that is built-in in the structure of engagement element  11 . 
     In particular, in the retracted condition, pushing member  19  slightly projects from support body  12  with a segment (or, if necessary, it can also be completely contained therein), whereas, in the extracted condition, pushing member  19  further projects with an additional segment. 
     Advantageously, pushing member  19  is housed inside support body  12  so as to slide relative to the latter, for example so as to be guided by inner walls of said support body  12 . 
     In the embodiment shown, engagement element  11  comprises, furthermore, elastic stressing means  21 , which act upon pushing means  19  and tend to move it to the extracted condition. 
     In particular, elastic stressing means  21  act upon pushing member  19  in such a way that they tend to move it to the extracted condition. In the embodiment shown, elastic stressing means  21  are mounted between support body  12  and pushing member  19  and, for example, are adapted to operate in a pulling manner, thus attracting pushing member  19  towards the outside of the support body. Advantageously, elastic stressing means  21  comprise at least one pulling spring  21  and, in particular, a pair of pulling springs  21  are provided. 
     In the embodiment shown, striker  14  and pushing member  19  are mobile in directions that are parallel to one another. 
     Preferably, striker  14  and pushing member  19  are fitted to one another in a mutually guided manner, in particular by means of sliding. 
     More preferably, striker  14  and pushing member  19  are mutually integral during their movement from the respective retracted position or condition to the relative extracted position or condition, when striker  14  is coupled to said retaining element  16  and stop mechanism  18  liberates striker  14 , thus moving from the locking condition to the release condition. This solution is particularly useful to avoid that—during the movement from the retracted position to the extracted position of striker  14 —pushing member  19  and door D (whose position depends on the position of striker  14  due to the coupling between engagement element  11  and retaining element  16 ) end up in mutual position that are not ideal to perform a pushing action during the preopening. In the embodiment shown, pushing member  19  is caused to be integral with striker  14  in a sliding manner by causing striker  14  to lie on pushing member  19 . 
     Conveniently, striker  14  is able to slide relative to pushing member  19  along at least a segment of the movement from the extracted position to the retracted position and, in doing so, is controlled by said return means  15  when striker  14  and retaining element  16  are uncoupled. In this embodiment, striker  14  can slide from the extracted position to the retracted position regardless of the movement of pushing member  19 . 
     In the embodiment shown, striker  14  and pushing member  19  have mutual proximal sliders  14   a  and  19   a , which cooperate with one another so as to perform the guided sliding described above. In this first embodiment shown, proximal slider  14   a  has a transverse extension  14   b  where proximal slider  19   a  is mounted so as to slide, advantageously in a “drawer-like” manner, in an axial direction between the retracted condition and the extracted condition of pushing member  19 . With reference, in particular, to  FIG. 4 a   , transverse extension  14   b  has suitable slots  14   c , which are axially oriented and within which complementary projections, for example pins  19   c , carried by proximal slider  19   a  can slide. 
     In the embodiment shown, striker  14  and pushing member  19  have mutual distal appendages  14   d  and  19   d , which are mounted on proximal sliders  14   a  and  19   a  and are adapted to project outwards from support body  12  (through front slits or openings made on the latter), so as to cooperate with retaining element  16  and door D. In particular, each distal appendage  14   d  and  19   d  has a pair of connection stems (without reference numbers), which can be elastically spread apart and can be coupled, by means of interference, in suitable slits (without reference numbers) that are frontally obtained in proximal sliders  14   a  and  19   a.    
     In the embodiment shown, unlike the distal appendages  14   d  and  19   d , proximal portions  14   a  and  14   b  are advantageously always contained inside the case defined by support body  12 , without projecting outwards from the latter during the movements of striker  14  and of pushing member  19 . 
     In this embodiment, return spring  15 , advantageously operating in a pulling manner, is mounted between a pin  14   e  carried by striker  14 , in particular by proximal slider  14   a , and a respective pin  12   e  carried by support body  12 . 
     In the embodiment shown, each stressing spring  21 , advantageously operating in a pulling manner, is mounted between a respective pin  19   f  carried by proximal slider  19   a  and a respective pin  12   f  carried by support body  12 . 
     In particular, when return spring  15  is provided, the force exerted by it upon striker  14  is advantageously smaller than the force exerted by stressing spring  21  upon pushing member  19 . 
     In the embodiment shown, respective proximal portions  14   a  and  19   a  have respective abutments  14   g  and  19   g , adapted to mutually lean against one another during the movement from the respective retracted position or condition to the respective extracted position or condition. In particular, abutment  14   g  is adapted to lean against abutment  19   g  so as to cause pushing member  19 , in use, to be kept lying against door D, in order to exert an ideal thrust during the preopening. 
     By way of example, the abutment of striker  14  is defined by an upper edge  14   g , which is brought to an axially forward position by the transverse extension  14   b , whereas the abutment of pushing member  19  is defined by a tooth  19   g , which projects from the upper part of the proximal portion  19   a  in an axially forward position thereof. 
     Clearly, during the return of striker  14  towards the retracted position, the contact between abutments  14   g  and  19   g  stops, thus causing the position of striker  14  along pushing member  19  to become independent. 
     Preferably, stop mechanism  18  is intended to constrain striker  14 , thus preventing it from moving to the extracted position, when striker  14  is in the respective retracted position and stop mechanism  18  is in the locking condition. 
     In this way, stop mechanism  18  is designed to directly act upon striker  14 , thus preventing door D from moving away from casing C against the action of pushing member  19 . 
     Preferably, stop mechanism  18  is suited to act in a transverse direction relative to the direction of the movement of striker  14 . 
     In this embodiment, stop mechanism  18  is suited to act so as to liberate or hold a transverse projection  14   h  carried by striker  14 , for example by transverse extension  14   b.    
     Preferably, apparatus  10  comprises detector means  23 , which are suited to detect the extracted condition or position of at least one between striker  14  and pushing member  19 . In this way, one can obtain an indirect indication on the state of door D during the use. In this embodiment, the detector means are intended to monitor the position of striker  14  and, therefore, are adapted to provide an indication concerning the fact that striker  14  is in the extracted position—and, hence, that door D is in the preopening condition. 
     Advantageously, detector means  23  comprise a mobile element  23   a , which can be moved relative to the support body  12  and, in doing so, is controlled by at least one between striker  14  and pushing member  19 , as well as a sensitive member  23   b , which is intended to provide an indication of the position assumed by mobile element  23   a.    
     For example, mobile element  23   a  can be moved from support body  12  in a guided manner, in particular in a transverse direction relative to the direction in which striker  14  or pushing member  19  is adapted to be moved. Advantageously, mobile element  23   a  is housed inside the case created by support body  12 . Preferably, the mobile element is a sliding cursor  23   a , which, on one side, cooperates with striker  14  or pushing member  19  and, on the other side, cooperates with sensitive member  23   b.    
     For example, the sensitive member is a switch  23   b , in particular a micro-switch, suited to be activated by mobile element  23   a , for example by an appendage (without reference number), which is carried by mobile element  23   a  and is able to activate switch  23   b  according to predetermined criteria. 
     Preferably, mobile element  23   a  is suited to be pushed, while lying against striker  14 , due to counteracting elastic means (without reference numbers). More in detail, the action of the counteracting elastic means takes place so as to bring mobile element  23   a    
     from a normally inactive condition, in which it does not activate sensitive member  23   a  when striker  14  is in the retracted position, 
     to an active condition, in which it activates sensitive member  23   a  when striker  14  is in the extracted position or condition. 
     In this embodiment, mobile element  23   a  is associated with and pushed by striker  14 , for example by transverse projection  14   h , which tends to push it towards the normally inactive condition. When transverse projection  14   h , during the movement of the striker towards the extracted position, moves past mobile element  23   a , the latter is able to move to the active condition. 
     Preferably, actuator  20  is suited to move from a normally extended condition ( FIGS. 6 and 7 ) to a contracted condition. In the extended condition, actuator  20  allows stop mechanism  18  to assume the locking position, whereas, in the contracted position, actuator  20  brings stop mechanism  18  to the release position. 
     More preferably, actuator  20  comprises a shape-memory conductor element  22 , which is mechanically connected to and cooperates with stop mechanism  18 . In particular, conductor element  22  is made of a shape memory alloy (SMA), which is able to assume a predetermined shape (in this case, corresponding to the one assumed in the contracted condition) subsequent to a variation of the due temperature, in the embodiment shown, due to the Joule heating caused by the passage of current through it. 
     In alternative embodiments, which are not shown, conductor element  22  can be replaced by different types of electric actuators; in these embodiments, the actuator can comprise an electromagnetic actuator (e.g. of the solenoid type) or an electrothermal actuator (e.g. of the wax type). The above-mentioned types of actuators are known in the technical field and, therefore, for the sake of brevity, they will not be described hereinafter. 
     As described more in detail below, in the embodiment shown, conductor element  22  has the shape of a wire, which is mechanically connected to—and acts upon—stop mechanism  18 , so as to move the latter from the normal locking condition to the release condition. 
     In the embodiment shown, conductor element  22  is advantageously connected in series to a positive temperature coefficient (PTC) thermistor. 
     Preferably, stop mechanism  18  comprises a slider  24 , which is mounted so as to move—in particular to slide—relative to support body  12  from a locking position ( FIG. 6 ) to a release position ( FIG. 7 ). In the locking position, slider  24  is adapted to hold striker  14  when it is arranged in the retracted position, thus preventing it from moving to the extracted position and to the extracted condition, respectively. On the other hand, in the release position, slider  24  allows striker  14  to move (from the retracted position to the extracted position) due to an electric excitation of actuator  20 . Furthermore, stop mechanism  18  comprises an elastic member  26 , which is prone to hold slider  24  in the locking position. In the embodiment shown, elastic member  26  is interposed between support body  12  and slider  24 . Preferably, elastic member  26  is a spring, for example a compression-preloaded spring, advantageously of the helical type. 
     Preferably, slider  24  is positioned against a projection, which is transversely obtained in striker  14 , when slider  24  is in the locking position and striker  14  is in the retracted position. In the embodiment shown, the aforesaid projection advantageously coincides with transverse projection  14   h  of striker  14 . 
     Therefore, in the embodiment shown, stop mechanism  18  substantially has the properties of a ratchet device, in which slider  24  acts as a ratchet, which is adapted to prevent striker  14  from moving. In particular, when engagement element  11  and retaining element  16  are coupled to one another, striker  14 , on the one hand, is subject to “extraction” forces, which are due to the pushing force of pushing member  19  and also to the weight of door D, if necessary with the help of the elastic compression of sealing gasket SG. On the other hand, when engagement element  11  and retaining element  16  are coupled to one another, striker  14  is subject to “retraction” forces, which are due to the action of possible return means  15  and are generally smaller then the stressing forces exerted during the opening. Hence, when stop mechanism  18  is in the locking condition, the slider  24  that constrains the striker  14  prevents the “extraction” forces from being able to activate apparatus  10  so as to move door D to the pre-opening condition. 
     In this embodiment and with reference, in particular, to  FIG. 7 , striker  14  and slider  24  preferably have complementary profiles  28  and  30 , which cooperate one with the another. Profiles  28  and  30  are adapted to permit, by means of interference, the forced movement of striker  14  from the extracted position to the retracted position, if necessary performed with the contribution of return means  15  opposing the action of elastic member  26 . To this regard, if return means  15  are provided, they are preferably dimensioned so as to exert a return force, for example an elastic pulling force, with an intensity that is such as to overcome the opposing elastic force of elastic member  26 . 
     In this embodiment shown, profiles  28  and  29  are respective inclined sections of projecting noses (without reference numbers), which are supported by striker  14  and slider  24 , respectively, in particular by the transverse projection. The cooperation between profiles  28  and  30  will be described in detail below, together with the overall operation of apparatus  10 . 
     In the embodiment shown, stop mechanism  18  comprises, furthermore, a cursor  36 , which can be moved by means of actuator  20  and is mounted so as to move—in particular can slide—relative to support body  12  from an inactive position ( FIGS. 3, 5, 6 and 7 ) to an active position. In the inactive position, cursor  36  allows slider  24  to move from the release position to the locking position due to the action of elastic member  26 . On the other hand, in the active position, cursor  36  drags slider  24  from the locking position to the release position against the action of elastic member  26 , when actuator  20  is electrically excited. Furthermore, stop mechanism  18  comprises an elastic element  38 , which is intended to hold cursor  36  in the locking position. In the embodiment shown, elastic element  38  is mounted between support body  12  and cursor  36 . Preferably, the aforesaid elastic element  38  is a spring, for example a compression-preloaded spring, advantageously of the helical type. 
     Preferably, cursor  36  is mechanically connected to shape-memory element  22  and, therefore, is adapted to be dragged by the latter between the inactive position and the active condition. In the embodiment shown, shape-memory element  22  is configured as a conductor wire  22 , which is connected to cursor  36  and, for example, is arranged in a U-shape so as to surround a part of cursor  36  with its loop. 
     In the embodiment shown, slider  24  and cursor  36  are coupled with a sliding clearance. Preferably, the coupling between slider  24  and the cursor substantially is of the so-called “coulisse” type. More preferably, cursor  36  has a mushroom-shaped end  40  and slider  24  has a shaped cavity  42 , which houses mushroom-shaped end  40  with an axial clearance. Even more preferably, mushroom-shaped end  40  has a transversely wide head and a narrow neck transversely tapering from the head; cavity  42 , in turn, has a transversely wide proximal portion, which houses the head with an axial clearance, and a transversely narrow distal portion, which starts from the proximal portion and allows the neck to axially slide through it (details without reference numbers). Advantageously, shaped cavity  42  is defined by a pair of lateral arms  44 , which are arranged at the end of slider  24  and transversely converge inwards in correspondence to their free ends. Advantageously a closing crosspiece  44   a  is fitted above lateral arms  44 , after the coupling with head  42 —for example by means of interference; in this way, one can reduce the risk of an undesired displacement of head  42  beyond the lateral arms  44 . 
     In the embodiment shown, elastic element  38  exerts a return elastic force upon cursor  36 , which is greater than the return elastic force exerted by elastic member  26  upon slider  24 . In this way, elastic element  38  is able to effectively cause cursor  36  to return to its active position, in particular by causing conductor wire  22  to return in a reliable manner and with a high intensity force. Furthermore, in this way, elastic organ  36  is able to bring slider  24  back to the locking position, without for this reason causing the action of possible return means  15  to become uncomfortable by applying an excessive resistance, return means  15  being used to forcedly cause the uncoupling of striker  14  of engagement element  11  from retaining element  16  by acting upon a proper release mechanism arranged on door D or on casing C. 
     In the embodiment shown, slider  24  and/or cursor  36  can be moved in a direction that is substantially transverse, and preferably orthogonal, to the movement direction of striker  14 . By way of example, slider  24  and cursor  36  can be moved in the same direction. 
     Preferably, stop mechanism  18  is suited to interrupt the electric excitation of actuator  20  after stop mechanism  18  has assumed the release condition. More preferably, actuator  20  comprises a safety switch  45 , for example a micro-switch, which is controlled by stop mechanism  18  and is suited to electrically disconnect actuator  20  from the outer control unit, when stop mechanism  18  reaches the release condition. In the embodiment shown, switch  45  is electrically connected downstream of one of the supply contacts (without reference numbers) that allow actuator  20  to be connected to the outer control unit. By way of example, the supply contacts are electrically connected to the ends of conductor wire  22 . 
     Preferably, switch  45  comprises a stationary contact (without reference number) and a mobile contact (without reference number), which cooperates with stop mechanism  18 , so as to be moved away from the stationary contact when stop mechanism  18  reaches the release condition. In the embodiment shown, the mobile contact has a shaped projection, adapted to come into contact with a corresponding projection  52  supported by stop mechanism  18 , for example by cursor  36 , so that the mobile contact moves away, for example by bending, from the stationary contact, when stop mechanism  18  reaches the release condition, for example when cursor  36  reaches the active position. Preferably, the shaped projection of the mobile contact has a spire-shaped profile. Preferably, projection  52  has the shape of an inclined segment, which substantially matches the segment of the spire-shaped profile provided by the mobile contact. 
     Preferably, elastic member  26  is axially interposed between a projecting overhang  58  of slider  24  and a stationary bracket  59  projecting from support body  12 , for example from the lower half-shell  12   b . Preferably, bracket  59  is housed in correspondence to a guide opening  60 , which is obtained through slider  24 . In this way, elastic member  26  is able to push overhang  58 , which is integral to slider  24 , until an end edge of the aforesaid guide opening  60  comes into contact with stationary bracket  59 , which corresponds to the locking position of slider  24 . Therefore, stationary bracket  59  also acts as a limit stop for slider  24 . 
     Preferably, cursor  36  can slide in support body  12  and, in doing so, is preferably guided by the inner walls of support body  12 , for example by walls of the lower half-shell  12   b  and by the bottom walls of both half-shells  12   a  and  12   b.    
     Preferably, elastic element  38  is axially interposed between a further overhang (without reference number) projecting from cursor  36  and a further stationary bracket  61  projecting from support body  12 , for example from the lower half-shell  12   b  Preferably, the further bracket  61  is housed in correspondence to a further guide opening  62 , which is obtained through cursor  36 , for example close to the further overhang. In this way, elastic element  38  is able to push the further overhang, which is integral to cursor  36 , until an end edge of the further guide opening  62  comes into contact with the further stationary bracket  61 , which corresponds to the inactive position of cursor  36 . Therefore, the further stationary bracket  61  also acts as a limit stop for the cursor. 
     In the embodiment shown, switches  23   b  and  45 , together with the PTC thermistor are carried by a support or plate PCB, in which a printed circuit is obtained, which connects the switches and the thermistor. Advantageously, support PCB has two pairs of connection terminals  70  and  72 , which are suited to supply electric power to the actuator means and to detector means  23 , respectively, for example through the PTC thermistor and through switch  23   b , respectively. 
     Below you can find a more detailed description of the structure and the function of safety element  18   a.    
     In the embodiment shown, safety element  18   a  prevents slider  24  from moving to the locking position, when safety element  18   a  itself is in its inhibition arrangement ( FIG. 7 ). In particular, safety element  18   a  holds slide  24  in the release position, when it is in its inhibition arrangement, which corresponds to the fact that stop mechanism  18  is not able to assume the locking condition. 
     Preferably, slider  24  carries safety element  18   a.    
     In the embodiment shown, safety element  18   a  is integral to, preferably manufactured as one single piece together with, slider  24 , so that, in the inhibition arrangement, by generating a mechanical constraint associated with safety element  18   a , slider  24  is accordingly prevented from moving. 
     Preferably, safety element  18   a  is a lever or appendage  76 , for example with an oblong shape, capable of projecting from said slider  24  in a position in which it is accessible to a user and is fit to be grabbed by the latter. In this way, the user can easily and comfortably interact with safety element  18   a  so as to manually move it between the liberation arrangement and the inhibition arrangement. In the embodiment shown, lever or appendage  27  projects from slider  24  in a substantially transverse direction relative to the movement axis of slider  24 . 
     Preferably, lever or appendage  76  projects outwards from support body  12 , in the embodiment shown through a groove  78 , which is obtained on support body  12 , for example on half-shell  12   b . In particular, lever or appendage  76  is guided by groove  78  so as to also guide the movement of slider  24  between the locking position and the release position. 
     In the embodiment shown, lever or appendage  76  is provided with a portion, for example its distal end  79 , adapted to cooperate with a shaped profile  80 , in which, in the inhibition arrangement, distal end  79  is constrained to shaped profile  80 , thus preventing slider  24  from moving towards the release position. In particular, in the inhibition arrangement, shaped profile  80  mechanically locks the movement of distal end  79 , thus preventing slider  24  from moving from the release position, until a user manually intervenes by moving again lever or appendage  76  to the liberation arrangement. In alternative embodiments, the aforesaid portion—cooperating with shaped profile  80 —can be different from distal end  79 , for example it can also be an intermediate segment of the above-mentioned lever or appendage  76 . 
     Preferably, distal end  79  of the lever or appendage is substantially shaped as a pin, which, for example, can be inserted into and removed from (in particular, laterally) a part of shaped profile  80 , so as to create and release, respectively, the forced mechanical constraint of stop mechanism  18 . 
     In the embodiment shown, shaped profile  80  is provided by a slot  82 , which is obtained in the washing machine and in which distal end  79  is adapted to be engaged in the inhibition arrangement 
     In particular, slot  82  has a narrow segment  82   a , in which distal end  79  can be inserted in an engagement condition, by slightly bending (in this embodiment, upwards) lever or appendage  76 , so that narrow portion  82   a  can steadily receive, for example by means of mechanical interference, distal end  79 . In other words, lever or appendage  76  is moved until slider  24  reaches the release position and, then, it is slightly bent towards narrow portion  82   a  of slot  82 , so as to avoid a subsequent return translation movement towards the locking position. 
     In particular, slot  82  also comprises a wide segment  82   b , which ends in narrow segment  82   a  and in which distal end  79  of lever or appendage  76  can normally slide. In this way, when distal end  79  is coupled in a sliding manner in the aforesaid narrow segment  82   a , slider  24  is freely mobile between its locking position and its release position, pretending that a user decides to act by moving lever or appendage  76 , thus coupling distal end  79  (or another portion of lever or appendage  76  cooperating with profile  80 ) to narrow segment  82   a.    
     In the embodiment show, shaped profile  80 , and in particular slot  82 , is obtained in washing machine W, for example in a part that is operatively stationary and associated with casing C. In particular, shaped profile  80  is obtained in wall or partition P 1  delimiting the upper edge of access opening O. 
     The operating mode of apparatus  10  according to the embodiment shown of the present invention will be described below. 
     First of all, one should consider the configuration of dishwasher W with door D partially open ( FIG. 1 ). 
     In this configuration, engagement element  11  has striker  14  kept in the retracted position by return means  15 , stop mechanism  18  arranged in the locking position, pushing member  19  held in the extracted condition by stressing means  21 , actuator  20  electrically unexcited, and detector means  23  detecting the retracted position of striker  14 . More in detail, slider  24  is held in the locking position by elastic member  26 , whereas cursor  36  is held in the inactive position by elastic element  38 . Furthermore, conductor wire  22  is in the extended condition and is subject to a pull force. Furthermore, projection  14   h  leans against slider  24 . 
     Now, safety element  18   a  is moved to the inhibition arrangement, thus moving stop mechanism  18  to the release condition and, hence, in this embodiment, slider  24  to its release position. In this way, if door D were accidentally pushed backwards, thus coupling retaining element  16  to engagement element  11 , door D could not anyway be moved to the complete closing position, because stop mechanism  18  would not be able to hold, in particular by means of the action of slider  24 , striker  14  in the retracted position. Therefore, as discussed above, manufacturers can improve the safety against an improper use of washing machine W, in particular by a baby. 
     Now, safety element  18   a  can be moved again to the liberation arrangement by an operator, who decides to perform a washing cycle. 
     In this situation, door D, with engagement element  11  uncoupled from retaining element  16 , can be completely opened by a user and, therefore, the dishes to be washed can be introduced into washing chamber WT. Subsequently, the user can choose the washing cycle to be performed by dishwasher W by acting upon proper control interfaces that are typically available on door D. 
     Afterwards, the user closes door D towards casing C. During this operation, retaining element  16  and striker  14  of engagement element  11  are moved closer to one another so as to be coupled and, at the same time, door D pushes pushing member  19  from the extracted condition to the retracted condition and, in doing so, is guided by striker  14 , in particular by lateral extension  14   b.    
     After the above-mentioned closing operation has been performed by the user, dishwasher W has door D completely closed and engagement element  11  is arranged in the configuration shown in  FIG. 2  and is coupled to retaining element  16 . It has to be noted how pushing member  19 —which is in contact with door D—exerts its action against door D, but is not able to cause it to open, since striker  14  acts as a “lock bolt”, which holds door D in the closing position. As a matter of fact, even though striker  14  is able to move from the retracted position to the extracted position, it remains locked and steadily held in the retracted position due to the action of stop mechanism  18 , in particular due to the fact that slider  24  leans against striker  14  (for example, against transverse projection  14   h ). 
     Therefore, in this door complete closing configuration, engagement element  11  has striker  14  in the retracted position, stop mechanism  18  in the locking condition, pushing member  19  in the retracted position, actuator means  20  electrically unexcited, and detector means  23  detecting the retracted position of striker  14 . Hence, more in detail, slider  24  is held in the locking position by elastic member  26 , whereas cursor  36  is held in the inactive position by elastic element  38 . Furthermore, conductor wire  22  is in the extended and stretched condition. 
     Therefore, the washing cycle chosen by the user can be automatically started by the outer control unit of dishwasher W. 
     At the end of the above-mentioned washing cycle performed by washing machine W, the outer control unit provides actuator  20  with a current impulse, so as to electrically excite actuator  20  itself and, therefore, move stop mechanism  18  to the release condition. 
     The passage of electric current causes conductor wire  22  to heat up and to rapidly shift from the extended condition to the contracted condition, thus becoming shorter and dragging cursor  36  backwards from the inactive position to the active position against the action of elastic element  38 . Therefore, after a short loadless travel (for example, approximately a half millimeter long), cursor  36  drags slider  24  from the locking position to the release position. More in detail, mushroom-shaped end  40  comes into contact with the converging ends of lateral arms  44  and, in this way, causes slider  24  to be dragged backwards. 
     In the embodiment shown, conductor wire  22  is designed to reduce its length by approximately 3.5% during the passage from the extended and stretched condition to the contracted and shortened condition. 
     In this way, striker  14  is free to move to the extracted position due to the connection with retaining element  16 , which is carried by door D, with the help of pushing member  19 . Indeed, pushing member  19  helps push door D away from casing C against the retaining action of return means  15 , which act upon striker  14 , thus keeping it in the retracted position. When striker  14  and pushing member  19  are in the extracted position or condition, the respective proximal sliders  14   a  and  19   a  lean against the walls of support body  12 , for example on the periphery of the lower half-shell  12   a , thus preventing them from being subject to a possible undesired overtravel. 
     Advantageously, during this step, abutment  14   g  of striker  14  leans against abutment  19   g  of pushing member  19 , so that striker  14  and pushing member  19  are integral in the movement towards the respective extracted condition or position. 
     Preferably, striker  14  and pushing member  19  are designed, when they are arranged in the extracted position, to further project from support body  12  with a length measuring centimeters (preferably ranging from 1 cm to 3 cm, but, in some use conditions, even measuring more than 5 cm relative to the normal projection that striker  14  and pushing member  19  assume when they are arranged in the retracted position or condition); in this way, the distance between door D and access opening O corresponds to the length mentioned above, which is sufficient to permit a fluid communication between washing chamber WT and the outside of casing C. In the embodiment shown, the aforesaid length is equal to approximately 5.5 cm. 
     Furthermore, when striker  14  moves past mobile element  23   a , detector means  23  detect the movement of striker  14  to the extracted position, which, in this case, indicates that the pre-opening position of door D has been reached. 
     At the end of the electric current impulse provided by outer control unit, actuator  20  goes back to the electrically unexcited condition and stop mechanism  18  goes back to the locking condition. 
     During this step, when the electric current impulse has ended, conductor wire  22  starts cooling down and gradually goes back to the extended condition, thus becoming longer, and elastic element  38  accordingly and progressively pushes cursor  36  forward towards the inactive position following the loop of conductor wire  22 , which is extending; in particular, mushroom-shaped end  40  of elastic element  38  gradually moves forward towards the inactive position following the stretching out of conductor wire  22 . Consequently, lateral arms  44  of slider  24 , which had been previously dragged backwards by cursor  36 , tend to follow the forward movement of mushroom-shaped head  40  due to elastic member  26  and cause slider  24  to gradually move back to the locking position. 
     In the embodiment shown, elastic element  38  has an elastic compression preload of approximately 0.5 kg and conductor wire  22  has a diameter of approximately 0.38 mm. The preload of elastic element  38  is adjusted as a function of the diameter of conductor wire  22 , so that cursor  36  can actually be brought back to the inactive position. 
     In the embodiment shown, elastic member  26  has an elastic compression preload of approximately 200 g, which is smaller than the one of the elastic element. As a matter of fact, elastic member  26  fulfills the main function of preventing slider  24  from correctly repositioning itself in the locking position, in particular in case the returning action of elastic element  38 , which is suited to cause the return of conductor wire  22 , is affected by accidental jamming or seizing. 
     In the embodiment shown, conductor wire  22  is designed to cool down and go back from the contracted and shortened condition to the extended and stretched condition over a time of approximately 13 s. 
     Optionally, when stop mechanism  18  reaches the release condition, it interrupts the electric connection between the outer control unit and actuator  20 . This measure is adopted in order to prevent conductor wire  22  from being damaged due to an excessive overheating caused by a possible accidentally and anomalously prolonged duration of the excitation current impulse provided by the outer control unit (provoked, for example, by a failed interruption of the nominal operating times). This measure can be implemented in different ways. 
     A first way involves safety switch  45 . More in detail, when cursor  36  reaches the active position, it interferes with safety switch  45 , thus opening it and interrupting the passage of current through conductor wire  22 . In particular, projection  52  of cursor  36  leans against the shaped projection of the mobile contact of safety switch  45 , thus moving it away from the stationary contact associated therewith. 
     A second way involves the use of sensor means  23 . More in detail, when mobile element  23   a  is brought by striker  14  (in particular, cooperating with its transverse projection  14   h ) from the normally inactive condition to the active condition, sensitive element  23   b  detects its movement and is suited to signal it to the outer control unit of the dishwasher, for example through contacts  72 . In this way, the outer control unit receives the signal coming from sensitive element  23   b  and interrupts the current flowing through actuator means  20 , in particular conductor wire  22 . In the embodiment shown, when mobile element  23   a  moves to the active condition, the appendage of the latter interacts with the mobile contact of switch  23   b , so that switch  23   b  generates the above-mentioned signal, which is intended to be received by the outer control unit. 
     If necessary, the two switches  23   b  and  45  can cooperate with one another, thus providing the outer control unit with the signal, only if they are both properly activated by mobile element  23   a , in particular with its terminal appendage, and, respectively, by stop mechanism  18 , in particular by cursor  36  (for example, with its projection  52 ). In both the embodiments shown, switches  23   b  and  45  are designed to signal the movement of striker  14  from the retracted condition to the extracted condition (in this case indicating the movement of door D to the pre-opening condition), when they are both open. 
     When stop mechanism  18  goes back to the locking position and striker  14  has moved to the extracted condition, door D is in the pre-opening condition, in which it is sufficiently spaced apart from access opening O to allow a fluid communication between washing chamber WT and the outside to be established. The distance between door D and access opening O allows the steam generated during a washing cycle of dishwasher W to flow out and, therefore, allows the dishes contained in washing chamber WT to be dried. 
     With reference, in particular, to  FIG. 7 , at the end of the overall operating cycle of the dishwasher, the user can uncouple door D from casing C by acting upon mechanisms arranged on door D and by moving retaining element  16  to the rest position. This is how retaining element  16  is uncoupled from striker  14  of engagement element  11 . 
     In this way, return means  15  are not subject any longer the opposition to the return of striker  14  to the retracted position, since striker  14  is not constrained to door D. The return force exerted by return spring  15  causes profile  30  carried by striker  14  (in particular, by transverse projection  14   h ) to rest against profile  28  carried by slider  24 , so as to generate a transverse thrust relative to striker  14 . As already mentioned above, return spring  15  is dimensioned so as to generate a transverse thrust that is able to move slider  24  backwards, thus overcoming the opposition force developed by elastic member  26 . When profile  30  of striker  14  moves past profile  28  of slider  24 , striker  14  cannot exert the aforesaid transverse thrust any longer and, therefore, elastic member  26  brings slider  24  back to the locking position, in particular by positioning itself under striker  14 . 
     During the cooperation between profiles  28  and  30 , the backward movement of slider  24  does not interfere with the position of cursor  36  and elastic element  38 , as a consequence, is not stressed, in particular thanks to the sliding coupling with clearance between the two of them. More in detail, the proximal portion of cavity  42  moves relative to the head of mushroom-shaped end  40 , without them hitting against one another. 
     Therefore, in both the embodiments shown, the cooperation between slider  24  and cursor  36  leads to an advantage that consists in preventing conductor wire  22 , during the movement of striker  14  from the extracted position to the retracted position, from temporarily releasing stop mechanism  18 , thus causing a failure or a damage of apparatus  10 . Indeed, when striker  14  is moved from the extracted position to the retracted position by return means  15 , slider  24  can freely move from the locking position to the release position against the action of elastic member  26  without interfering with cursor  36 , in particular thanks to the sliding clearance that is advantageously created between mushroom-shaped head  40  and lateral arms  44 . In this way, cursor  36  is not moved backwards and does not release the pull of conductor wire  22 , which, instead, always remains subject to a pull force. 
     Simultaneously, pushing member  19  is kept in the extracted condition by elastic stressing means  21 , which are not subject to any opposition by stop mechanism  18  or by striker  14 . Therefore, in this embodiment, stop mechanism  18  is neither directly cooperating with nor directly constrained to pushing member  19 , but through striker  14 . 
     Hence, door D can be further opened relative to the pre-opening configuration and the dishes that have been washed—and at least partially dried—can be removed by the user, so that operations can be started again to perform a further washing cycle, thus repeating the operation steps described above. 
     Please, note that, once the user has finished using the machine, door D can be finally closed by the user, by leaning against pushing member  19 , by pushing it backwards in the retracted condition and by coupling striker  14  to retaining element  16 . In the embodiment shown, the movement from the extracted condition to the retracted condition of pushing member  19  is controlled by the backward thrust exerted by means of door D, which is pushed by the user so as to get closed. The fact that pushing member  19  is kept in the retracted condition is ensured by the coupling of striker  14  to retaining element  16 . Indeed, this coupling holds door D in contact with pushing member  19  by means of stop mechanism  18 , which prevents striker  14  from moving relative to the support body. This situation corresponds to the operating configuration shown in  FIG. 5 . 
     Naturally, the principle of the present invention being set forth, the embodiments and the implementation details can be widely changed relative to what described above and shown in the drawings as a mere way of non-limiting example, without in this way going beyond the scope of protection provided by the accompanying claims. 
     For example, the places in which engagement element  11  and retaining element  16  are fitted can be switched compared to what described above and shown in the drawings (in particular, engagement element  11  can be mounted on door D, whereas retaining element  16  can be mounted on casing C).