EP1006230A1

EP1006230A1 - Household apparatus, comprising a hydraulic circuit and an opening for accessing said circuit, being normally blocked by movable closure means

Info

Publication number: EP1006230A1
Application number: EP99123717A
Authority: EP
Inventors: Costanzo Gadini
Original assignee: Eltek SpA
Current assignee: Eltek SpA
Priority date: 1998-12-01
Filing date: 1999-11-30
Publication date: 2000-06-07
Also published as: ITTO980211V0; IT245939Y1; ITTO980211U1

Abstract

A household apparatus is described, comprising a hydraulic circuit within which a fluid is present during the apparatus operation, said fluid being susceptible of reaching potentially dangerous temperatures, an aperture (2) normally closed by movable closure means (3) being provided for the access to said circuit.

According to the invention, a sensor-actuator device (6;6A;6B) is provided, being sensitive to the temperature of said fluid and operable in function of such a temperature, for preventing the opening of the closure means (3) when the temperature of the fluid is higher than a predetermined threshold, and allowing the opening of said closure means (3) when the temperature of the fluid is lower than said predetermined threshold.

Description

The present invention relates to a household apparatus comprising a hydraulic circuit in which a fluid is present during the apparatus operation, said fluid being susceptible of reaching potentially dangerous temperatures, where an opening is provided for accessing to said circuit, being normally closed by movable closure means.
As known, for instance, laundry wash machines usually provide for a filter housed along the hydraulic circuit of the machine, which is apt to intercept any foreign items eventually present in the washing liquid, such as small objects forgotten with the clothes to be washed, or fabric filaments, buttons, and so on.
Such a filter should be accessible for the user, in view of its periodical cleaning: to this purpose, washing machines are normally fitted with movable closure means on their front side, usually consisting of a threaded plug that can be unscrewed manually by the user, to have access to the seat of said filter, and then proceed to the filter removal and cleaning.
It is also known that during certain phases of an operative cycle, the washing liquid contained in the hydraulic circuit of a washing machine is capable of reaching high temperatures, at times up to 90°C; to this purpose, the machine comprises proper liquid heating means, usually consisting of electric heaters being activated during said phases.
The removal or the opening of said plug from the housing seat of the filter, if performed during any of the above cycle phases or directly after them, may entail some risks for the user, considering above all that such a removal usually causes a water loss from the machine, even if a restricted volume (usually in the order of 0.5 liters).
Let us for instance assume the event, even if remote, of a user deciding to clean the filter while some water still present in the hydraulic circuit of the machine has a potentially dangerous temperature, or the event, quite more frequent, of an accidental opening of the plug, such as caused by an undesired impact on it or by a child, with a consequent risk of burns for the child; it has to be noticed, to this regard, that the access plug to the filter is usually located on the front side of the machine cabinet, at a height easily reachable for a child.
Similar risks to the ones given by way of example with reference to a laundry washing machine may occur in a household environment also in the instance of water tanks for steam generating systems used on cooking ovens, or hot beverage automatic machines, steam irons, sterilizers, steam jet cleaners, etc., fitted with a filling and/or cleaning plug.
Solutions are known to reduce such risks, which provide for a covering door over the plug, so that access to the plug will occur only if the user performs at least an intentional actuation; however, such solutions not only entail a complex manufacture of the household appliance, but do not fully avoid some of the above risks.
According to other solutions the plug cannot be opened unless a tool is used, such as a proper wrench or screwdriver; however, also these solutions not only cause an uncomfortable plug removal, but do not completely avoid the above risks for an inattentive or incautious user removing the plug itself while high temperature liquid is still present inside the appliance.
The same applies for those solutions where double-action plugs are provided, i.e. requiring two separate actuations by the user for their removal, such as pressing the plug first and then rotating it; on the other hand, manufacture of the plug and its seat would be quite complicated with these last solutions.
From EP-A-0 374 862 a steam generator for household cooking ovens is known, whose boiler has an opening normally closed by a plug to get access to it; this solution provides a discharge outlet in the lowest section of the boiler near the opening whereon the plug is extending; the plug has sealing means cooperating with the boiler internal surface; its discharge outlet is located between the plug sealing means and the access opening; moreover, the plug is designed to delimit a conduit capable of selectively connecting the discharge outlet with the boiler internal room, following a user's control. Thus, the liquid eventually contained in the boiler can be emptied towards the discharge outlet by properly actuating the plug, before a complete removal of the plug from the access aperture is obtained.
Such a solution, which theoretically avoids an uncontrolled liquid discharge from the boiler, is however unable to fully remove the risk for the user, should the plug be quickly removed, i.e. before all the liquid available in the boiler is discharged through the proper outlet. Moreover, according to such a solution, the manufacture of the plug is rather complex and difficult; above all, the circuit should necessarily provide for an additional discharge outlet, which involves a complex manufacture of the household appliance as a whole.
From EP-A-0 337 528 a safety plug for a household pressurized steam apparatus is also known; in this case the plug consists of a closure element apt to be screwed on an orifice of the steam container and of an external housing which can be actuated by the user manually; the safety plug also comprises a membrane, which is movable under the pressure of the steam inside the container.
In a first position, when pressurized steam is in the container, the membrane is apt to stop the mechanical connection between the closure element and the external housing, so that the closure element cannot be unscrewed from the orifice, even if rotating the external housing; in a second position, i.e. when the pressure inside the container is low or there is no pressure, the mechanical connection between the closure element and the external housing is ensured by the membrane, so allowing for the complete plug removal.
Such a solution is therefore poorly versatile, since it is specifically provided as a safety means for household appliances using a pressurized fluid, and it is not suitable for use also in hydraulic circuits operating under atmospheric pressure, such as in the instance of a laundry washing machine.
Anyway, the above solution entails a manufacturing complexity for the safety plug, which must consist of several parts, being mechanically associated and movable between them, and of an elastic membrane, which may be subject in time to failures or loss of its functional features. Moreover, if on one hand said solution avoids the risk for an individual of being invested by a steam jet, on the other hand it does not fully prevent the risk - after the plug removal - of a contact with the liquid still at high temperature, i.e. potentially dangerous.
The present invention has the aim of solving the above drawbacks and provide a household apparatus comprising an hydraulic circuit and at least an opening for the access to said circuit, having simple, low-cost and reliable safety means, being capable of application in various situations, which are apt to warrant the highest safety for the user, hindering the user from removing the closure means to the access opening when the fluid in the hydraulic circuit has a temperature being higher than a determined threshold.
Such aims are reached, according to the present invention, by a household apparatus having the features of the annexed claims, which form an integral part of the present description.
Further aims, features and advantages of the present invention will become apparent from the following detailed description and the annexed drawings, which are supplied by way of non limiting example, wherein:

Fig. 1 shows schematically a household appliance, in particular a laundry washing machine, being realized according to the teachings of the present invention;
Fig. 2 shows schematically a side view of a plug being part of the household appliance according to the present invention;
Fig. 3 shows schematically a plan view of a plug being part of the household appliance according to the present invention, in a first operating condition;
Fig. 4 shows schematically a side section of the plug of Fig. 3, along the axis A - A of that figure;
Fig. 5 shows schematically a perspective view of the plug in the operating condition represented in Figs. 3 and 4;
Fig. 6 shows an enlarged section of a plug component according to the previous figures;
Fig. 7 shows schematically a plan view of a plug being part of the household appliance according to the present invention, in a second operating condition;
Fig. 8 shows schematically a side section of the plug represented in Fig. 7, along the axis A -A of that figure;
Fig. 9 shows schematically a perspective view of the plug in the operating condition represented in Figs. 7 and 8;
Figs. 10 and 11 show schematically a perspective view of a plug according to a first possible variant embodiment of the household appliance according to the present invention, in two different operating conditions;
Figs. 12 and 13 show schematically a perspective view of a plug according to a second possible variant embodiment of the household appliance according to the present invention, in two different operating conditions.

With reference to Fig. 1, number 1 indicates as a whole a household apparatus according to the present invention which, in the given example, is a laundry washing machine; the laundry washer 1 comprises inside a hydraulic circuit, along which a filter housed in a proper seat is provided, which is apt to intercept foreign items eventually contained in the washing liquid, as mentioned at the beginning of the present description; moreover, the machine comprises heating means for the washing liquid, consisting for example of one or more heaters, whose activation is controlled in a known manner, such as by means of a timer, a liquid level sensor inside the washing tub and a thermostat.
The housing seat of the filter, indicated with 2 in Fig. 1, is located on the front of the machine cabinet 1, and has a threading 2A apt to receive a plug 3, directly accessible to the user, which forms the closure means for the seat 2.
The plug 3, represented in a side view in Fig. 2, comprises a body 4 made of one piece only, preferably in a thermoplastic material resisting to high temperatures, and therefore highly cost- effective; the body 4 has a flanged portion 4A on the front, from the back of which a cylindrical threaded portion 4B is departing, apt for its screwing in the threading 2A of the seat 2.
In the front area of the flanged portion 4A a protrusion 3A is defined, being visible in Figs. 1, 4 and 8, which is apt for allowing the manual screwing and unscrewing of the plug 3 in the seat 2; moreover, sealing elements can be provided at the base of the cylindrical threaded portion 4B and/or in contact with the rear surface of the flanged portion 4A, such as a ring gasket, not represented in the figures for simplicity's sake.
As represented in Figs. 3, 4 and 5, a shaped housing 5 is defined within the cylindrical portion 4B; a thermal actuator or thermoactuator, indicated as a whole with 6, is inserted in a first portion of such a housing 5, whereas a slider 7 is inserted in a second portion of the housing 5, whose base 7A has substantially the shape of a parallelepiped, with a cylindrical pin 7B departing from its center.
In the above figures, number 8 indicates a through hole, putting the second portion of the housing 5 in which the slider 7 is inserted in communication with the outside of the cylindrical threaded portion 4B of the plug 3; as it can be seen in Figs. 2, 4 and 5, the end of the cylindrical pin 7B is inserted in such a hole 8.
Number 9 indicates an elastic element, consisting of a spiral spring inserted on the cylindrical pin 7B; as it can be seen in Figs. 3, 4 and 5, the spring 9 operates between the base 7A of the slider 7 and a surface of the second portion of the housing 5, so as to maintain the slider 7 in a backward position, i.e. with the end of the pin 7B within the overall dimensions of the cylindrical threaded portion 4B of the plug 3.
As it can be seen in Fig. 6, the thermoactuator 6 comprises a body or housing 10 made from a thermally conductive material; by way of example, the housing 10 can be made from metal and have a quadrangular section (in particular 6 x 6 mm) or round section (in particular 6 mm diameter).
The housing 10 has an aperture AA on one of its lengthwise ends and a chamber 11 delimited inside it, having for example a cylindrical section; such a chamber 11 contains a temperature expansible material C, in particular a wax.
Number 12 indicates a shaft or pusher, for example made from stainless steel, partially inserted in the housing 10 though the aperture AA: as it can be seen, a portion of the pusher 12 is directly embedded in the material C, whereas the opposite portion of the pusher 12 comes out of the housing 10.
Numbers 13 and 14 indicate two seats, delimited in an area close to the aperture AA of the housing 10 by respective cylindrical enlargements of the chamber 11; the seat 13, more inside the housing 10 with respect to the aperture AA, has a greater vertical development with respect to the seat 14.
From the aperture AA, a rigid washer 15 and an elastic gasket or cylindrical bushing 16 are inserted, in the order, in the seat 13; the washer 15 is preferably made from a metallic material, such as brass, whereas the bushing 16 is preferably made from PTFE, or Teflon®, or a similar elastic material.
In the seat 14, on the contrary, a washer 17 is inserted, preferably made from metal, such as brass, having a larger diameter with respect to the washer 15; the lower washer 15 rests on the shoulder delimited between the seat 13 and the chamber 11, whereas the upper washer 17 rests on the shoulder delimited between the seat 13 and the seat 14.
Advantageously, the shoulder delimited between the seat 13 and the seat 14 has a funnel shaped flaring, having the function of facilitating the achievement, during the assembly, by the components 15 and 16 of the relevant seat 13; advantageously, the top washer 17 has a double flaring, i.e. it is beveled along its circumference on both faces; besides facilitating its insertion within the aperture AA, such a double flaring of the washer 17 has a double function of allowing, on one hand, its exact coupling with the shoulder flaring delimited between the seats 13 and 14, and guiding, on the other hand, the end distortion of the housing 10 where the aperture AA is laying for the exact mechanical coupling with it; such end of the housing 10 is submitted in fact to a riveting operation during manufacture of the thermoactuator 6. It should also be noticed that the double flaring of the washer 17 allows for its easy assembly during an automated machining process, since no particular orientation is required for it; it is obvious that the sealing means 16 may also be more than one and have such shapes and/or materials differing from the ones previously mentioned by way of example.
Therefore, as it can be seen, the top washer 17 is housed in a first seat 14 different from the second seat 13, wherein at least a radial sealing element 16 operates on the pusher 12 and also the washer 15 is inserted, while washers 15 and 17 are delimiting an exactly well defined housing area for the sealing element 16.
In this way, the above riveting operation of the housing 10 for obtaining the closure of the thermoactuator 6, and therefore the thrust on the top washer 17, will not entail any uncontrolled compression risks on the sealing element consisting of the bushing 16; this right because the washer 17 and bushing 16 are housed in two different seats, with the seat 13 for the bushing being more inside the housing 10 and having smaller dimensions with respect to the seat 14 for the washer 17.
This will also avoid the risk of an excessive pressure being exerted on the washer 17 during the riveting stage of the housing 10, with the consequent undesired distortions or tearing of the bushing 16. It will be appreciated that the thermoactuator 6 may be deprived of the shoulder between seats 13 and 14, though warranting the required operating features described above.
Important practical effects for the manufacture of the thermoactuator 6 concerning operation of the bushing 16 are also determined by the presence of the lower washer 15. Such a lower washer 15, acting as a lower supporting means for the bushing 16, allows an exact delimitation of the seat wherein the bushing itself should operate, also warranting a wide rest surface; finally, the lower washer 15 is acting as a further guiding means for the pusher 12.
Operation of the thermoactuator 6 is quite simple.
Following a heat transmission to the housing 10, by means of a liquid in contact with it, the expansible material C contained in the chamber 11 expands, whereby such an expansion causes a linear displacement of the pusher 12 towards the outside of the housing itself; when the heat transmission to the housing 10 decreases, the expansible material C shrinks and let the pusher 12 to gradually return to its initial rest position, under the action of an elastic element.
Back to Figs. 3-5, the plug 3 shown therein is represented in its rest position, i.e. in a position where the pusher 12 of the thermoactuator 6 is fully backward; in such a situation then the pin 7A is positioned within the overall dimensions of the cylindrical threaded portion 4B of the plug 3.
Such a rest condition is typical whenever the plug 3 has already been removed from the seat 2 of Fig. 1, or though it is still inserted in such a seat, the hydraulic circuit of the machine 1 has no liquid left with a temperature higher than a determined threshold: in such a situation, then, the plug 3 can be freely loosened or screwed on in the seat 2.
Assuming now that the plug 3 is screwed in its seat 2 and the hydraulic circuit of the washing machine 1 of Fig. 1 contains some liquid having a temperature higher than a safety threshold, such as 45° C; to this regard it will be noticed that the portion of the plug 3 which is actually inserted in the aperture 2, i.e. the portion bearing means 6-9 is practically in constant contact with the liquid contained in the hydraulic circuit of the machine 1.
The temperature of such a liquid causes the housing 10 of the thermoactuator 6 to be heated, so determining a volume expansion of the material C; as a result, a movement of the pusher 12 towards the outside of the chamber 11 will ensue. The movement of the pusher 12 causes a thrust on the base 7A of the slider 7 such as to win the force of the spring 9 and cause the end of pin 7B to exit the hole 8 in the cylindrical threaded portion of the plug 3.
Under the condition represented in Figs. 6-8, the end of the pin 7B will engage a suitable cavity or groove being present along the threading of the seat 2 of Fig. 1.
It is obvious that in such a situation, the plug 3 cannot be removed from the seat 2, neither voluntarily nor accidentally, thus avoiding a possible liquid discharge and burning risks for individuals.
The locking condition of the plug 3 in the seat 2 is maintained as long as the temperature of the housing 10 containing the thermoactuator 6, i.e. the temperature of the fluid in contact with the plug 3, does not go below the predetermined threshold value of 45°C, i.e. a temperature allowing the material C to shrink and the pusher 12 to go back inside the housing 10 and the chamber 11; such a return is obtained through a backing of the slider 7 to the initial position of Figs. 3-5, as determined by the thrust produced by the spring 9.
Thus, the end of pin 7A will be released from the respective recess or groove being present in the seat 2 and then go back within the overall dimensions of the cylindrical portion 4A of the plug 3; therefore, upon reaching such a position, the plug 3 can be removed from the seat 2, since the temperature of the liquid in it will be sufficiently low to avoid any risks to individuals.
It has to be noticed that the type of expansible material used for the thermoactuator 6, in particular a wax, and/or its quantity, or the mutual position of the various components, are properly chosen according to requirements and consequently to the temperature threshold value over which it is desired to inhibit an opening of the plug 3; in other terms, it is obvious that different temperature values may be predetermined, either higher or lower than 45° C as indicated by way of example, simply changing the type or quantity of the material C, or changing either the position or working point of the thermoactuator 6.
According to possible variant embodiments of the present invention, the actuation means sensing the fluid temperature in the hydraulic circuit of the household appliance may differ from the ones previously described by way of example; to this purpose, proper sensor-actuator elements made from shape-memory alloys or bi-metallic elements may be used instead of the thermoactuator 6, which we capable of changing their own external configurations and then determine either a direct or indirect locking of the plug 3, when coming in contact with a fluid that has a higher temperature than the predetermined safety threshold.
Figs. 10 and 11 show by way of example a first possible variant embodiment of the present invention, where the plug 3 is employing a shape-memory alloy element, instead of the thermoactuator 6; in these figures the same reference numbers used in the previous figures indicate technical equivalent elements.
Since sensor-actuator elements made from shape-memory alloys are already known as such, they do not require here any further detailed description; it should only be schematically stated that the material used for their manufacture is plastically deformed during its low temperature stage (martensitic condition), being then apt to go back to its own original shape when heat is applied to it. As it can be seen, shape-memory alloys are thermal-sensitive alloys, capable of operating directly both as sensors and actuators.
As mentioned, in the instance of Figs. 10 and 11, the plug 3 of the household apparatus according to the present invention is provided with a shape-memory alloy element instead of the thermoactuator 6 shown in the previous figures; in the example, said element in shape-memory alloy is indicated with 6A and has the shape of a spiral spring.
The shape-memory alloy element 6A represented in Fig. 10 is inserted in the first portion of the shaped housing 5 and can be pressed in a cold condition by the spring 9; therefore, the situation illustrated in Fig. 10 indicates a rest position for the plug 3, i.e., when in the hydraulic circuit of the household apparatus according to the present invention there is no fluid having a temperature higher than the deforming temperature pre-set for the element 6A.
On the contrary, the shape-memory element 6A is apt to expand and overcome the force of the spring 9, getting back to its predefined shape, when heat is applied to it; as a result, should the liquid in the hydraulic circuit of the household apparatus reach a higher temperature than such a distortion temperature, then the element 6A will expand and overcome the force of the spring 9.
As highlighted in Fig. 11, the expansion of the element 6A causes the slider 7 to move, so that the end of the pin 7B comes out of the portion 4B, through the passage 8, with a consequent locking of the plug 3 in its relevant seat of the household apparatus, substantially as already described above.
It is quite obvious that when the liquid temperature decreases to a level below said distortion temperature, the shape-memory alloy element 6A will go back to the configuration of Fig. 10, due to the action of the spring 9, letting the slider 7 go backwards and unlocking the plug 3.
Figs. 12 and 13 represent a second possible variant embodiment of the present invention, where the plug 3 utilizes a bi-metallic element instead of the thermoactuator 6 or of the shape-memory alloy element 6A; also in these figures the reference numbers used in the previous figures indicate technical equivalent elements.
Also bi-metallic elements are known as such and do not require here a detailed description; it should only be remembered that they are generally obtained using a lamina consisting of two thin foils made from different metals having different expansion coefficients from each other: when heat is applied, the lamina will bend because the foil with a higher expanding capacity, i.e. the one capable of greater expansion, forms an arch with respect to the foil having a smaller expansion, such a lamina deformation being then apt to cause an actuation; therefore, as it can be seen, also bi-metallic elements are both sensing and actuating means at the same time.
Therefore, in the instance of Figs. 12 and 13, a bi-metallic lamina 6B is provided for the plug 3, instead of the actuator 6 or the element 6A illustrated in the previous figures.
In this instance, a second housing 5A is defined in the portion 4B of the plug 3, wherein said bi-metallic lamina 6B is located; as it can be appreciated, one end of such a housing 5A has a seat 5B, substantially shaped like an "L", wherein an end portion of the lamina 6B is constrained.
Moreover, Figs. 12 and 13 show how in this instance the slider 7 has a base 7A', wherein an intermediate groove 7A'' is delimited, which is apt to receive the free end portion of the bi-metallic lamina 6B.
Fig. 12 shows the rest position of the plug 3, i.e. when in the hydraulic circuit of the household apparatus according to the present invention there is no liquid having a temperature higher than a predetermined distortion threshold of the bi-metallic lamina 6B; as it can be seen with reference to Fig. 12, under such a condition the lamina 6B is flexed or bent to the right, to keep the pin 7B within the overall dimensions of the portion 4B of the plug 3.
Should the liquid coming in contact with the lamina 6B reach a higher temperature than said threshold, a change in the bending direction of the lamina itself will occur, such to cause the slider 7 to move and the end of the pin 7B to exit the portion 4B, as it can be seen in Fig. 13; thus, the plug 3 will then be locked in its relevant seat 2.
It is quite obvious that when the liquid temperature decreases to a level below said deforming temperature, the hi-metallic lamina 6B will go back to the configuration of Fig. 12, so letting the slider 7 go backwards and unlocking the plug 3.
It will be noticed how in the embodiment of Figs. 12 and 13, a contrast spring (indicated with 9 in the previous figures) is not required, since the motion of the slider 7 in both directions is obtained directly by means of the bi-metallic lamina 6B.
It should also be underlined how, according to the present invention, the safety means may be associated to the aperture 2, instead of being directly integrated inside the plug 3.
In this frame, according to the simplest embodiment, within such an aperture 2 a housing seat for the thermoactuator 6 is provided, being in hydraulic communication with the fluid to be controlled, and the pusher 12 is apt to cause a direct locking of the plug 3; to this purpose, the portion of the plug 2 inserted in the aperture 2 may be provided with a suitable groove, which is apt to receive the end of the pusher 12 when the latter is in its working position, so as to prevent the plug removal. In this instance, the pusher 12 will have a suitable striker for an elastic element, such as a spiral spring, apt to cause the backing of the pusher itself towards its respective rest position when the fluid temperature decreases below the safety threshold.
It is clear, anyway, that a locking pin may be provided also for such an embodiment, which is contrasted by a spring and actuated by the pusher for locking the plug instead of using the pusher 12 directly to that purpose.
It is also clear that in the above seat associated to the aperture 2, a shape-memory alloy element as previously indicated with 6A, or a bi-metallic element as previously indicated with 6B, may be housed, to act as a sensor-actuator means in-lieu of the thermoactuator 6 for direct or indirect locking of the plug 3, under a potential danger condition; obviously, other suitable sensor-actuator means may also be used to that purpose.
From the above description the features of the present invention are clear.
In particular a household apparatus has been described, comprising an hydraulic circuit wherein during operation of the apparatus a fluid is present, said fluid being capable of reaching potentially dangerous temperatures; an opening 2 is provided for access to said circuit, being normally closed by movable closure means, such as a manually operable plug 3.
According to the invention, a sensor- actuator device 6 or 6A or 6B is provided, which is directly sensitive to the fluid temperature and can be actuated as a function of said temperature, apt to prevent the opening of the plug 3 when the fluid has a temperature higher than a predetermined threshold, and to allow the opening of a plug 3 when the fluid has a temperature below said predetermined threshold.
The sensor-actuator device can be integrated in a portion of the body 4 of the plug 3, or housed in a seat associated to the aperture 2.
Such a sensor-actuator device may consist of an shape-memory alloy element 6A or a bi-metallic element 6B, or still a thermoactuator 6 comprising a container delimiting an internal chamber 11, apt for containing a material C whose volume increases or decreases depending on the temperature of said container, said temperature being determined by the temperature of the fluid being present in the hydraulic circuit.
From the above description also the advantages of the present invention are clear. In particular it has to be highlighted:

the high safety level warranted by the invention, which provides a mechanical system apt to prevent the opening of the plug under a potentially dangerous condition for individuals;
the low-cost of the solution, since the safety system provided by the present invention is obtained with the use of components being of simple and cost-effective manufacturing, such as standard thermoactuators, bi-metallic elements or shape-memory alloy elements, and simple mechanical parts, such as springs and sliders;
the reduced overall dimensions and the low weight of the components of the safety system, in particular of its actuation means, which can be easily housed also in small sized plugs and in correspondence of the housing seats of such plugs.

It is clear that many changes are possible for the man skilled in the art to the household apparatus described by way of example, without departing from the novelty spirit of the inventive idea.
For instance, it is clear that the closure means 3 described above may have a different coupling system with their respective seat 2, such as a bayonet joint, instead of being threaded.
It is also clear that the closure means of the seat 2 do not necessarily need to be completely removable, since they may also be hinged or constrained to a side sliding with respect to the seat 2.
As already mentioned, in the applications requiring very small dimensions of the plug, the function of the locking pin 7A may be obtained directly through the pusher 12 of the thermoactuator 6, which will be longer than that represented in the annexed figures and have a striker for a spring having similar functions as for the spring indicated with 9 in the figures.
Moreover, it is clear that the plug described above can be perfectly applied on household appliances using fluids other than liquids, such as gas or aeriform in general, without requiring any modifications to their structure; therefore, as it will be appreciated, the plug can be used on steam household apparatuses, where its portion 4B should only be capable of coming in contact with the steam and not necessarily with the water generating it.
The present invention has been described with particular reference to a laundry washing machine, even if it is also applicable on other household apparatuses, for example in combination with hydraulic circuits including water tanks or boilers for steam generating systems, which usually provide for filling and/or cleaning plugs, as normally employed on cooking apparatuses, automatic beverage machines, irons and steam ironing machines, sterilizers, steam jet cleaning machines, etc..
Other possible embodiments provide for the possibility of associating optical signaling means to the plug 3 or the seat 2, for the user to immediately recognize the plug working condition (i.e. loose or locked).
In this connection, for example, the side of the base 7A of the slider 7 oriented towards the flanged portion 4A of the plug 3 could be colored and face over a transparent zone of the front surface of such a flanged portion 4A: thus, the working condition of the plug 3 could be detectable through the positioning of the colored side of the slider with respect to said transparent zone. As an alternative, an electric switch could be provided near the seat 2 and activated by the movement of the slider 7, such as being apt to control the lighting of a special warning light, located on the control panel of the household appliance, signaling the plug working condition; such an electric switch may be utilized for sending an electric signal to the control system of the household appliance, for example used by the control system itself for verifying the correct operation of the household appliance.
Further variant embodiments may also be related to the mechanical locking system of the plug 3, which could eventually differ from the one described by way of example using a straight movable slider to that purpose; in this frame, said mechanical system may comprise for example at least a locking element actuated under an angular or rotary motion by the sensor-actuator means 6, or 6A or 6B.
According to another possible variant embodiment, the chamber 11 of the thermoactuator 6 may contain a liquid or temperature expansible fluid, instead of a wax.
Finally, it is clear that covering means can be provided over the housings of the various components 6-9, such as a lid made from a thermally conductive material in contact with the sensor-actuator element employed (6 or 6A or 6B), so that the latter may in any case detect the temperature of the fluid to be controlled.

Claims

Household apparatus, comprising a hydraulic circuit within which a fluid is present during the apparatus operation, said fluid being susceptible of reaching potentially dangerous temperatures, an aperture (2) normally closed by movable closure means (3) being provided for the access to said circuit, characterized in that a sensor-actuator device (6;6A;6B) is provided, being sensitive to the temperature of said fluid and operable in function of such a temperature, for preventing the opening of the closure means (3) when the temperature of the fluid is higher than a predetermined threshold, and allowing the opening of said closure means (3) when the temperature of the fluid is lower than said predetermined threshold.
Household apparatus, according to claim 1, characterized in that said closure means comprise a plug (3).
Household apparatus, according to claim 1 or 2, characterized in that said sensor-actuator device (6;6A;6B) is integrated in a portion (4B) of the body (4) of said closure means or plug (3), said portion (4B) being in particular apt for the insertion in said aperture (2).
Household apparatus, according to claim 1, characterized in that said sensor-actuator device (6;6A;6B) is housed in a seat associated to said aperture (2).
Household apparatus, according to claim 1 or 2, characterized in that locking means (7-9,12) are provided, which are operable by said sensor-actuator device (6;6A;6B) for producing a mechanical constraint between said closure means or plug (3) and said aperture (2), said locking means (7-9,12) being integrated in a portion (4B) of the body (4) of said closure means or plug (3) or housed in a seat associated to said aperture (2).
Household apparatus, according to claim 3 or 4, characterized in that said sensor-actuator device (6;6A;6B) comprises at least:

a container (10) defining an internal chamber (11) for containing a material (C), whose volume increases and decreases depending on the temperature of said container (C), said temperature being determined by the temperature of said fluid,

a shaft (12) being movable as a function of the increase or decrease of the volume of said material (C), said shaft (12) having at least a first end portion constantly inserted in said chamber (11) and a second end portion constantly outside said chamber (11),

closure and sealing means (13-17) for said chamber (11) and said shaft (12).
Household apparatus, according to claim 3 or 4, characterized in that said sensor-actuator device (6;6A;6B) comprises at least an element (6A) made from a shape-memory alloy, having in particular the shape of a spring.
Household apparatus, according to claim 3 or 4, characterized in that said sensor-actuator device (6;6A;6B) comprises at least a bi-metallic element (6B), in particular having the shape of a lamina.
Household apparatus, according to claim 6, characterized in that said locking means (7-9,12) comprise at least a slider element (7,12) capable of movement under a thrust produced by said sensor-actuator device (6;6A;6B).
Household apparatus, according to claims 6 and 9, characterized in that said slider element (7,12) is realized by said shaft (12).
Household apparatus, according to at least one of the previous claims, characterized in that one end of said slider element (7;12) is apt to engage in a seat or cavity defined in said aperture (2) or defined in the body of said closure means or plug (3).
Household apparatus, according to claim 9, characterized in that in the body (4) of said closure means or plug (3) a passage (8) is provided, which is apt to put an external surface of said closure means or plug (3), destined to be coupled with said aperture (2), in communication with a housing (5) defined within said body (4), wherein said slider element (7,12) is located, one end of said slider element (7) being apt for sliding in said passage (8).
Household apparatus, according to the previous claim, characterized in that following the actuation of said sensor-actuator device (6;6A;6B), said end of said slider element (7) protrudes out of said passage (8), over the overall dimensions of the external surface of said closure means or plug (3) provided for the coupling with said aperture (2).
Household apparatus, according to claim 5, characterized in that said locking means (7-9,12) comprise at least an elastic element (9), which in particular provides for favoring the return of said sensor-actuator device (6;6A;6B) to a respective rest position, following a fall of the temperature of said fluid below said predetermined threshold.
Household apparatus, according to one or more of the previous claims, characterized in that signaling means of the working condition of said sensor-actuator device (6;6 A; 6B) are provided, said signaling means comprising in particular a transparent zone of the body (4) of said closure means or plug (3) and a colored portion of at least one of said locking means (7-9,12), or an electric switch located close to said aperture (2), apt to be activated by the movement of said locking means (7-9,12).
Washing machine, comprising:

a hydraulic circuit within which, during operation, a fluid which is susceptible of reaching potentially dangerous temperatures is present,

an access aperture (2), in particular for housing a filter, located along said hydraulic circuit and normally closed by movable closure means (3),

characterized in that a sensor-actuator device (6;6A;6B) is provided, sensing the temperature of said fluid and operable in function of such a temperature, for preventing the opening of the closure means (3) when the temperature of the fluid is higher than a predetermined threshold, and allowing the opening of said closure means (3) when the temperature of the fluid is lower than said predetermined threshold.