Abstract:
The present invention relates to an emergency door locking device for household appliances, in particular for tumble dryers, 
     More specifically, the device according to the present invention allows the door of a household appliance to be locked, thus preventing the opening thereof by the user, when a predetermined temperature, deemed anomalous and/or dangerous, is reached inside the compartment of the household appliance. 
     The emergency device according to the present invention therefore constitutes a mechanical safety, which is therefore also able to operate when the anomalous event that caused the increase in temperature compromises the correct operation of the control electronics of the household appliance.

Description:
[0001]    This application claims the benefit of Italian Patent Application No. MI2011A002081 filed Nov. 16, 2011, which is hereby incorporated by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to an emergency door locking device for household appliances, in particular for tumble dryers. 
         [0003]    More specifically, the device according to the present invention relates to a device suitable for locking the door of the household appliance, thus preventing the opening thereof by the user, when a predetermined temperature is reached inside the household appliance compartment. 
       BACKGROUND OF THE INVENTION 
       [0004]    Door locking devices suitable for preventing the accidental or voluntary opening of the door of the household appliance by the user under certain conditions are currently available on the market and commonly used in the sector of household appliances such as washing machines, tumble dryers, ovens and so forth. 
         [0005]    For example, the use of said door locking devices in household ovens is known in the prior art, in particular in self-cleaning ovens with pyrolysis function, but also in washing machines, in which the door locking device is controlled by the control electronics of the household appliance and keeps the door tightly closed during the entire operating cycle of the household appliance. 
         [0006]    In certain types of household appliances however, a further safety function may be required that is not linked to the normal operating cycle of the household appliance itself but is linked to the occurrence of specific emergency situations. 
         [0007]    One example of such a situation may be the case in which a fire starts, or in any case, a higher than normal temperature is recorded inside the drum of a washing machine. In this situation, which could also compromise the correct operation of the control electronics of the household appliance itself, there is currently a need which is not met, for an additional mechanical safety device to prevent the door from being opened. 
         [0008]    Indeed, as is known by those with planning experience, purely mechanical safety devices capable of guaranteeing operation, even when the device&#39;s control electronics have been compromised, are generally envisaged alongside electronic devices. 
       SUMMARY OF THE INVENTION 
       [0009]    The main aim of the present invention is therefore that of providing an emergency door locking device, suitable for firmly locking the opening of the door only on the occurrence of certain, predetermined conditions, which constitutes a mechanical safety lock, thus allowing a need identified in the sector to be met. 
         [0010]    In particular, the aim of the present invention is that of providing a thermostatic emergency door locking device that is suitable for entering into operation only on the reaching of a predetermined temperature. Even more in particular, said device, once placed in the compartment of the household appliance at the level of the door&#39;s hook closure, detects the temperature present inside the internal compartment of the household appliance and releases, thus locking the door once said temperature reaches a threshold value. 
         [0011]    Within the scope of these aims, the object of the present invention is to provide a mechanically activated, emergency door locking device suitable for being released thus locking the door within a predetermined time interval from when the temperature inside the household appliance has reached a predetermined threshold value. 
         [0012]    Yet another object of the present invention is that of providing a door locking device suitable for use with doors having hook closures of different dimensions. 
         [0013]    Not last, object of the present invention is that of providing a door locking device capable of eliminating the dimensional tolerances that are to be found on the hook closures of the doors of domestic appliances. 
         [0014]    This aim and these and other objects that will become clearer below following a detailed description of the present invention given here by way of a non-limiting example, are achieved by a safety door locking device comprising a main body to which sliding locking means of the door hook of the household appliance are associated, said locking means being mobile between a first inactive position in which said means do not interact with said door hood and a second, locking position of the door in which said means interact with said door hook, said locking means being associated to an elastic element adapted to move said locking means from said first position that is retracted towards the external of said main body in said second locking position, characterised in that the said locking means comprise, at the end intended to come into contact with said hook of said door, a serrated profile, said profile further presenting at least one abutment adapted to be held by a portion of a thermostatic element, so as to keep said locking means in a retracted position when the temperature detected by said thermostatic element is lower that a predetermined value T 1 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Further characteristics and advantages of the present invention shall become clearer from the following detailed description, provided by way of a non-limiting example and is illustrated in the annexed drawings, wherein: 
           [0016]      FIG. 1  shows a perspective top view of the door locking device according to the present invention in accordance with a first embodiment thereof; 
           [0017]      FIG. 2  again shows a perspective top view of the device of  FIG. 1  in a condition wherein the locking means do not interact with the door hook; 
           [0018]      FIG. 3  shows a sectional side view of the door locking device in accordance with the embodiment of drawings  1  and  2 , in a condition in which the said locking means interact with the door hook; 
           [0019]      FIG. 4  shows a detail of the thermostatic element according to the first embodiment of the device of the present invention; 
           [0020]      FIG. 5  shows a perspective top view of the door locking device according to the present invention in accordance with a second embodiment thereof; 
           [0021]      FIG. 6  again shows a perspective top view of the device of  FIG. 5  in a condition in which the locking means do not interact with the door hook; 
           [0022]      FIG. 7  shows a sectional side view of the door locking device in accordance with the embodiment of drawings  5  and  6 , in a condition in which the said locking means interact with the door hook; 
           [0023]      FIG. 8  shows a detail of the thermostatic element according to the second embodiment of the device of the present invention; 
           [0024]      FIG. 9  shows the device according to the present invention, coupled with the door hook of a household appliance. The figure shows how the device is able to eliminate any misalignment of the hook and the device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    With particular reference to  FIG. 1 , the device  1  according to the present invention comprises a main body  10  preferably having a box shape. 
         [0026]    The main body  10  can be advantageously made of a single, suitably bent sheet element, or can be obtained the unison of multiple sheet metal parts, but could also be obtained from other materials having physical and mechanical properties suitable for the purpose. 
         [0027]    The main body  10  is intended to be firmly connected to the household appliance or to a part thereof  200  inside the compartment of the household appliance itself and in proximity of the door, in particular of the door&#39;s hook closure  100 . 
         [0028]    The device according to the present invention comprises locking means  20  of said door that are movable between a first position in which said means do not interact with said door hook  100  and a second locking position of the door in which said means interact with said door hook  100 . 
         [0029]    Said locking means comprise, in the example shown in the accompanying drawings, a rod  20  having a substantially longitudinal development, which presents at least one portion  21  shaped like a blade adapted to interact with said hook  100  of said door of the household appliance when said locking means are in the second locking position. 
         [0030]    In particular, at the level of said first position in which said means do not interact with said hook  100 , said rod  20  is refracted within the main body  10  of the device, while at the level of the second door locking position, said road protrudes from the main body  10  of the device towards the outside from the part of said main body which, when the device is assembled onto the household appliance as shown in  FIG. 1 , faces towards said hook  100 , the end portion  21  of said road going on to interact with said hook  100  thus maintaining the door in a closed position. 
         [0031]    According to the preferred embodiment shown in the accompanying drawings, the rod  20  has a substantially longitudinal development, and is shaped like a foil, the thickness of which is contained. 
         [0032]    Other forms may naturally be envisaged by persons skilled in the art according to their specific experience and without deviating from the scope of protection of the present invention defined by the accompanying claims. 
         [0033]    As mentioned, the rod  20  presents one end  21  adapted to interact with the hook  100  of said door. In particular, the end  21  of said rod presents, on a longitudinal plane, an inclined profile, that is for example triangular or wedge-shaped. 
         [0034]    With particular reference to the view of  FIG. 3 , which shows a section of the present device with an axial longitudinal plane, it is noted how the rod  20  presents at the level of the end  21  a tapered section in the advancement direction of the rod  20  from the first inactive position to the second door locking position. Said tapered section further presents a serrated profile  23 . 
         [0035]    Defining the terms “above”, “below”, “lower” and “upper”, in compliance with the identified direction of the axis Z of the reference system shown in  FIGS. 1 and 3 , and the terms “front” and “rear”, “advancement” e “backward motion” with reference to the identified direction of the axis X, said end  21  of the rod  20  is wedge-tapered and presents, at least at the level of its upper edge, a serrated profile comprising a plurality of serrations  23 , each of said serrations being suitable to abut the internal profile of said hook  100 , which is normally ring-shaped. 
         [0036]    Thanks to the particular wedge-shape of the end  21  of the rod  20 , and thanks in particular to the serrated profile comprising a plurality of  23  at least on the upper edge of said end  21 , the rod  20  is able to insert itself inside the ring of the hook  100 , thus eliminating any slack or tolerances that may exist between the positioning of the hook  100  and that of the device  1 . Said advantage obtainable by the device according to the present invention is well illustrated by  FIG. 9 , in which it is noted how the plurality of serrations  23  of the serrated profile and the wedge-shape of the end  21  of the rod  20  are able to eliminated misalignments of the door hook  100  in respect of both the axis X and the axis Z. 
         [0037]    Indeed, in particular, it is intuitive how the end  21  of the rod  20  will always be able to find the desired interference with the internal profile of the hook  100 , even when the positioning of the ring of the hook along the axis Z should not be perfectly aligned in respect of the rod  20 . 
         [0038]    The function carried out by the presence of the serrated profile of the end  21  will become clearer once the methods by which the rod  20  moves along the direction X have been illustrated. 
         [0039]    The movement of said rod  20  along the longitudinal direction X takes place thank to the presence of actuating means  30 . 
         [0040]    In particular, in the example shown in the drawings, said actuating means  30  comprise elastic means, in particular a helical spring  30 , interposed between said main body  10  and said rod  20 . 
         [0041]    In particular, said helical spring  30  is compressed when said rod  20  is in said first position, refracted inside said main body  10 , in which it does not interfere with said hook  100  of said door. In this condition therefore the action of the spring exercises a force on said rod  20 , onto which the spring itself abuts, which tends to push the rod  20  into said second locking position of the door hook, in which the end  21  of said rod  20  protrudes from the main body  10 . 
         [0042]    The device according to the present invention thus further comprises at least one thermostatic element  40  comprising at least one abutment adapted to interact with said locking means  20  thus contracting the thrust exercised on said locking means  20  by the spring  30  when said locking means are in the first position of non interference with said hook  100  of said door. 
         [0043]    In the examples shown in the accompanying drawings said thermostatic element  40  is made of a bimetal. 
         [0044]    As is known in the prior art, the term “bimetal” here indicates a sheet consisting of two thin metal bands, each having different chemical and physical properties, that are joined together by means of any procedure whatsoever, for example by means of lamination or compression. 
         [0045]    In the present patent description, the term “bimetal” indicates a thermal bimetal or bimetallic foil, with which the springs, discs, foils for sensitive elements of thermostats, switches and similar are made, according to what is known in prior art. It is thus formed by two metals having very different linear expansion coefficients from each other (for example iron and brass, nickel and iron, platinum and iridium). The bimetal flexes by effect of the temperature variation. 
         [0046]    Bimetal deformation can be controlled by suitably selecting the materials, the thicknesses and so forth, so as to “programme” the bimetal to deform at a given temperature T 1 . 
         [0047]    According to the first embodiment of the device according to the present invention, shown in  FIGS. 1 to 4 , the thermostatic element  40  is made of a bimetal with non-linear deformation, preferably of the “on-off” type also indicated in the sector by the English term “snap”, adapted to firmly maintain said locking means  20  in their first position when the temperature detected by said thermostatic device is inferior to a predetermined value T 1 . Since, as mentioned, the device according to the present invention is advantageously positioned inside the compartment of the household appliance, it detects the temperature T present inside the compartment. 
         [0048]    When the temperature T inside the compartment exceeds the predetermined threshold value T 1 , the bimetal  40  instantly deforms, the portion  41  of said bimetal  40  no longer abuts the portion  24  of said locking means  20 , and the rod  20  is therefore free to move forward towards the locking position of the door pushed by the spring  30 . 
         [0049]    According to the first preferred embodiment of the present invention shown in  FIGS. 1 to 4 , the thermostatic element  40  is made of a bimetal with non-linear deformation. 
         [0050]    When the device  1  according to the present invention is equipped, as in the second embodiment of  FIGS. 5 to 8 , with a bimetal with linear deformation, when the temperature detected by the device reaches the value T 1  the linear deformation of the bimetal element  40 ′ begins to deform and the safety device  1  does not therefore immediately snap into closing the door, but there will be a transitional period from the moment in which the device detects the temperature T 1  and the moment in which the serration  41 ′ frees the rod  20 , triggering the device. 
         [0051]    By suitably dimensioning the thicknesses of the bimetal and suitably selecting the type of materials that comprise it, it is possible to determine the duration of the deformation transition of the bimetal  40 ′. 
         [0052]    It has thus been shown that the method and the apparatus according to the present invention achieve the proposed aim and objectives. 
         [0053]    In particular, it has been illustrated how the door locking device according to the present invention allows a single, extremely simple mechanical safety device to be used that is suitable for producing the locking of the door of a household appliance on a predetermined temperature being reached. 
         [0054]    It has also been shown how the emergency door locking device according to the present invention allows any alignment problems between the locking device itself and the door hook, thus simplifying the assembly operations of the device, particularly as regards the dimensional control of the positioning. 
         [0055]    A number of changes can be made by the sector profession without straying from the scope of protection pursuant to this invention. 
         [0056]    The scope of protection of the claims should not therefore be restricted to the illustrations or to the preferred embodiments provided by way of example in the description; the claims should instead include all the characteristics of patentable novelty arsing from the present invention, including all the characteristics that are deemed to be equivalent by a person skilled in the art.