GB2178504A - Washing machine safety lock - Google Patents

Abstract

A safety door locking device for washing machines and the like includes a pawl (13) which is activated by a bimetallic plate (16), itself heated by a PCT pellet (15) through which power to the appliance passes. When power is supplied, the pawl (13) engages an aperture (12) in the door lock mechanism, to lock the door. To prevent the door from unlocking when power is withdrawn, the pawl (13) is latched by a locking lever (37), the movement of which is controlled by the water level within the appliance. <IMAGE>

Description

SPECIFICATION Door locking device The present invention relates to a safety locking device for the doors of, for example, washing machines, dishwashing machines and the like. The device may be integrated with the pressure switch functions of the apparatus, and being of a very simple structure, it has a very high reliability, as well as being safe and having a long working life.

The invention relates particularly, though not exclusively to the well known problem of realsing a safety locking device for doors of household electrical apparatus and appliances such as washing machines, dishwashing machines and the like. These appliances generally comprise a rotating member (the basket) and have, in some operating stages, water at a high temperature at a level higher than the opening of the door. Alternatively, the water may be at a level which is anyway easily accessible through the door opening. Therefore, for safety reasons, the door is retained in the closed position during the working of the apparatus, and the possibiiity of opening the door only occurs when, after stopping the operation of the apparatus, sufficient time has elapsed for the rotating mass to be at rest and/or for there to be no risk of hot water outflow.

The removal of the risk of careless or rash opening of the door of washing machines and the like during certain phases of the washing cycle is achieved at present by means of control devices of the delayed disengagement type already disclosed and claimed by the same Applicant in particular in Patent Applications 8448444 and 8547823. In such prior art devices, the disengagement delay of the locking device of the door is realized through a bimetallic plate heated by a PTC (positive temperature coefficient) pellet which passes an electric current and which acts on a locking pawl that locks the slider of the door lock.

Although such devices prove efficient to avoid the risk of opening the washer door while the basket is rotating, (since very few minutes are sufficient for the basket to come to rest once the supply of electric power is stopped), they prove not to be so efficient in avoiding the risk caused by a sudden interruption of the electrical power supply when the washer contains high temperature water that can damage persons (especially children) and/or things. Indeed, in that case, after the predetermind delay, which is almost always of the order of few minutes, the device unlocks and allows the washer door to be opened.

The water contained in the washer may then flow out or otherwise become accessible.

Since the water has had no time to cool, it can cause severe burns.

Thus, it is a general object of the present invention to provide a door locking device that is able to give efficient and reliable protection against the risk of opening the washer while the basket is rotating, as well as when hot water is present at a level higher than the level of the door or at a level which would be accessible through the door.

The lack of efficiency of the devices commercially available at the present time stems from the fact that they are activated by electrical power only, so that when the supply of electrical power is cut off they become completely disactivated and give no protection against the risks generated by hot water that can be present in washing machines and the like during certain stages of their operation. A more particular object of the present invention therefore is to provide a locking device of the delayed disengagement type (for example for doors of washing machines and the like), the device being operated by two quantities: the electrical power supply, and a predetermined value of the water level within the basket.

In a device realised in such a way, the presence of only one of the two quantities is sufficient to keep the door locked. The door is therefore unlocked only when the electrical power is cut off and, simultaneously, water is absent from the basket (or it is at least below a predetermined safety level for the door to be unlocked).

All washing machines and the like presently make use of one or more pressure switches which are sensitive to the water level within the basket for controlling the washing cycle.

However these act as independent devices and have no connection with the door-locking device. It is therefore an additional and more particular object of the present invention to provide a device of the integrated type which allows both the locking of the door with a higher efficiency and reliability, as described above, and also the carrying out of the operations which one or more pressure switches normally perform in an independent way during the washing cycle.

According to a first aspect of the present invention, a delayed disengagement door lock is arranged to lock a door when power is supplied to a given part of an appliance, and to release the door only when power is no longer supplied and the level of water within the appliance is below a threshold level.

According to a second aspect of the invention, there is provided a combined delayed disengagement door lock arranged to lock a door when power is supplied to a given part of an appliance, and to release the door only when power is no longer supplied and the level of water within the appliance is below threshold level; and microswitch means arranged to be operated in dependence upon the level of water with the appliance and to control operation of the appliance.

The object may also be attained in washing machines and the like, whose door locking device comprises a slider that engages with a tooth of the door and that has a locking hole, by means of a rotatable pivoted pawl which is able to penetrate the hole of the slider so as to keep the same locked in the closing position, subordinated to the action of an activation unit or assembly depending on the level of water contained in the basket, the device being integrated with the pressure microswitches and acting on the same.

According to the preferred embodiment of the present invention, the activation assembly depending on the supply of electrical power is made up of a combination of a PTC pellet and a bimetallic disk, which is inserted in the circuit that supplies electrical power to the washing machine, the bimetallic disc being of the type that reverses its bending with a rapid release and has a free end which engages with two small stakes of the locking pawl to cause the same to rotate through 90% at the moment it reverses its bending.

In a further preferred embodiment of the device the said one or more microswitches operated by the pressure switch activation assembly are of the type comrpising an overcentre central blade resting on a calibration spring which is able to close the release contact when a pressure is exerted on the spring that is higher than the calibration pressure.

According to another preferred embodiment of the invention, the pressure switch activation assembly comprises a pressure switch chamber formed by the upper edge of the device box and by the cover of said box with the interposition of a rubber membrane, the pressure switch chamber being in pneumatic or hydraulic communication with the basket containing the washing water, the assembly also comprising a pressure transfer disk of small size that is acted upon by the rubber membrane and which transmits its movement by means of a central tip or apex to a triangular plate, also of small size.The small triangular plate has a first and a second apex, both of them operating the pressure microswitches, and a third cam-type apex cooperating with a first end of a lever which has its fulcrum at the base of the device box, and whose second end is in the shape of a tooth which cooperates with a notch provided in the locking pawl in order to keep the same locked in the closing position of the door of the washing machine.

The invention may be carried into practice in a number of ways, and one specific embodiment will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a device for closing the door of a washing machine, the device incorporating a locking device of the delayed disengagement type according to the present invention; Figure 2 is an exploded view of the delayed disengagement locking device of figure 1; Figure 3 is a cross sectional view along the line Ill-Ill of Figure 2; Figure 4 is a cross-sectional view along the line IV-IV of Figure 2; and Figure 5 shows the details of three working positions of the locking pawl with which the locking lever cooperates.

With reference now to the drawings, it can be seen that the device, known per se, comprises a slider 10 that can slide on a fastening plate 11 and is provided with a locking opening 12 through which a rotatable pivoted locking pawl 13 is inserted, the pawl being of the type already known in the prior art.

The closing device comprises a base box 14 which houses a delayed disengagement locking device according to an embodiment of the present invention. The component parts are represented in Figure 2, which is a view from the side opposite to that shown in Figure 1.

Though the device is already known from the Patent Applications mentioned above, its working principle will be explained briefly. A PTC (positive temperature coefficient) material pellet 15 is included in the electrical circuit that supplies the washing machine. This pellet, on heating due to the flow of electrical current through it, heats a bent small bimetallic disk 16 which, when has reached the release temperature, reverses its bend with a rapid release motion of its free end. The free end of the said small bimetallic disc 16 is in engagement with two small stakes 17 of the pivoted locking pawl 13. Its rapid release motion therefore causes the rotation of the locking pawl 13 from its locking position, shown in Figure 2 and in Figure 5a, into the locking position shown in Figure 1 and in Figures 5b and 5c.In the latter position the pawl engages with the hole 12 of the slider 10 so as to prevent the door of the washing machine from opening.

So far, the device would be sensitive to the supply of electrical power only and could give a good protection from the risk of opening the door of the washing machine while the basket is rapidly rotating. Indeed, once the electric current supply has been cut off or has been disconnected, the cooling time of the PTC pellet and of the bimetallic plate would be sufficient to allow the rotating mass of the basket to come to rest. This, of course, is the time required for the initial bending of the plate to be re-established, with the consequent returning of the pawl 13 to its rest position.

However, a device so realised would give no protections from the risk of high temperature water outflow outside this said delay time. Indeed, the cooling time of the pelletplate assembly is of the order of some minutes, after which time the door becomes un locked and there is a risk of any water higher than the door level flowing out, when the door is opened, or at least the hot water being easily accessible to the user's hands.

In order to attempt to alleviate this drawback, on the basis of the fact that one or more pressure switches are always provided in an apparatus such as a washing machine and the like, the pressure switches also controlling other functions of the machine, the embodiment rests on the principle of making the locking of the door depend not only on the electrical power supply, as already explained above, but also on one or more levels of water contained in the basket, so as to keep the door locked if the basket has not been unloaded.

To achieve the aim mentioned above, it can be observed with particular reference to Figures 2, 3 and 4 that the inside space of the box 14 is closed at its upper edge 18 by a cup-shaped cover 19 with the interposition of a rubber membrane 20 so as to form a pressure sensor chamber 21. Said pressure sensor chamber 21 communicates with the basket of the washing machine through a thin pipe 22 for the passage of air so that changes in the water level within the basket produce as a result of a pneumatic effect, corresponding oscillations of the rubber membrane 20.

The embodiment of the present invention illustrated herein comprises two microswitches 23 and 24 of a known type ending at four terminals 25, 26, 27, and 28, by means of which the other functions of the machine are controlled. In practice, the microswitch 23 closes the contact between the end 25 and the end 26, while the microswitch 24 closes the contact between the end 27 and the end 28. The microswitches 23 and 24 are of the type comprising an over-centre central blade 29 (see Figure 3) which rests on a calibration spring 30. They also have an end contact 31 which releases so as to close the contact with the other end or terminal (28, in Figure 3) when a given pressure is exerted on the blade 29.

The oscillations of the rubber membrane 20 are transmitted through a small disc 32 which in turn transmits the pressure to a triangular plate 33.

From Figures 3 and 4 it can be seen that the small triangular plate 33 has two apexes 34, 35 bent downwards which co-opoerate with the blades 29 of the two microswitches 23 and 24. As the two microswitches 23 and 24 are provided with calibration springs 30, the operation of the two microswitches can be correlated with two pressure levels in the pressure sensor chamber 21 and therefore with two water levels in the basket. These levels can be the same or different from one another, depending on the calibration of the two adjustment springs 30.

To obtain the locking of the door of the washing machine as a function of the water level in the basket, the small triangular plate 33 is shaped so as to have a cam-shaped projection or tail 36 at its third apex, this projection cooperating with a locking lever 37.

The locking lever 37 has its fulcrum 41 at the bottom of the box 14 and has a first end 40 (Figure 2) that cooperates with the camshaped apex 36 of the small triangular plate 33, and a second, tooth-shaped end 38 that cooperates with a notch 39 (Figure 5) in the locking pawl 13.

From the functional viewpoint, it can be seen that when the small triangular plate 33 is pushed downwards by the pressure of the pressure sensor chamber 21 (by the action of the rubber membrane 20 as well as of the pressure transmission disk 32), it acts with its apexes 34, 35 on the two microswitches 23 and 24 so as to activate their functions, while, on the other side, it also drives the locking lever 37 by way of its cam-shaped projection 36. The rotation of the lever 37 clockwise around the fulcrum 41 in Figure 2 gives rise to the displacement of its toothshaped end 38 in the direction of the arrow in Figure 5c so that it engages with the notch 39 of the locking pawl 13.

Thus the position of the locking pawl 13 depends both upon the action of the assembly consisting of the PTC pellet and of the bimetallic disk, as well as upon the action of the locking lever 37 which is interlocked with the water level in the basket of the washing machine. The locking lever 37 comes back to its rest position, with the consequent unlocking of the pawl 13, through the action of a suitable return spring (not shown).

Summing up, the operation of the device occurs as follows. When, as a result of the electrical current introduced through suitable terminals, the PTC pellet 15 heats the bimetallic plate 16 upto its temperature of bending reversal, the free end of the bimetallic plate releases and causes the locking pawl 13 to rotate through 90 , to the operative position, as disclosed in the Patent Application 8547823. Once the pawl has been operated, and the door is therefore locked, the washing machine is energized and it starts its washing cycle. Water flows into the basket and the pressure within the pressure sensor chamber 21 increases, displacing the rubber membrane 20 and pressing upon the small disk 32 which transmits the pressure to the plate 33 by way of its central tip or apex 42.The cam-shaped apex 36 of the triangular plate 33 engages with the first end 40 of the locking lever 37, whose other end 38 keeps the pawl 13 locked even when the electrical power is cut off.

The two other apexes 34, 35 of the triangular plate 33 drive the over-centre blades 29 of the two microwswitches which control other functions of the washing machine. The two microswitches can be operated at two pressure levels, which levels can also be different from each other according to the values of the respective adjustment springs 30.

According to the operation disclosed above, the two functions mentioned are independent of one another and they can be activated at different water levels in the basket. In any case, the calibration is always such as to realise first the locking of the door and secondly the activation of the other functions (which are activated by means of the pressure microswitches which are separate but structurally integrated in this embodiment). Also, the operation of unlocking the door of the washing machine is always performed after the two pressure microswitches have come back to their rest positions and therefore to the washing cycle starting positions.

Claims (1)

1. A delayed disengagement door lock arranged to lock a door when power is supplied to a given part of an appliance, and to release the door only when power is no longer supplied and the level of water within the appliance is below a threshold level.

2. A lock as claimed in claim 1 including locking means acting in dependence upon the said power supplied, and latch means, arranged to hold the locking means in the locking position, acting in dependence upon the level of water within the applicance.

3. A lock as claimed in claim 2 which the locking means comprises a locking pawl which is brought into locking engagement with an aperture by a rotary action, the rotary action being caused by the bending of a bimetallic member heated by a PCT pellet through which a current, indicative of the supplied power, passes in use.

4. A lock as claimed in claim 2 or claim 3 in which the latch means is arranged to operate in dependence upon the pressure in a sensor chamber, the said pressure arranged to depend, in use, upon the water level.

5. A lock as claimed in claim 4 in which the sensor chamber comprises a flexible membrane, arranged to press upon a transfer member, the transfer member having a latch actuation portion arranged to operate with the latch means.

6. A lock as claimed in claim 5 in which the transfer member comprises a first plate having a central pointed portion arranged to press upon a second plate, the second plate including the latch actuation portion.

8. A lock as claimed in claim 6 in which the latch means comprises a pivotable latch, mounted for at least partial rotation about an axis which is substantially perpendicular to the first and second plates.

9. A lock as claimed in any one of the preceding claims including microswitch means arranged to be operated in dependence upon the level of water within the appliance.

10. A lock as claimed in claim 9 when dependent upon claim 2 in which common means are provided to actuate the microswitch means and the latch means.

11. A lock as claimed in any one of claims 5 to 8 including microswitch means arranged to be operated in dependence upon the level of water within the appliance, the microswitch means being actuated by one or more microswitch acutating portions on the transfer member.

12. A lock as claimed in claim 11 in which the microswitch means comprises two microswitches, arranged to be operated respectively by first and second microswitch actuating portions, and the latch actuation portion being the form of a cam, arranged to co-operate with a part of the latch means.

13. A combined delayed disengagement door lock arranged to lock a door when power is supplied to a given part of an appliance, and to release the door only when power is no longer supplied and the level of water within the appliance is below a threshold level; and microswitch means arranged to be operated in dependence upon the level of water within the appliance and to control operation of the appliance.

14. A combined delayed disengagement door lock and microswitch means as claimed in claim 13 including locking means acting in dependence upon the said power supplied, and latch means, arranged to hold the locking means in the locking position, acting in dependence upon the level of water within the appliance.

15. A delayed disengagement door lock substantially as specifically herein described, with reference to the drawings.

16. In washing machines and the like, which incorporate one or more functions that are activated by pressure microswitches interlocked with the level of water within the basket of the washer, and in which the device for closing the door comprises a slider which engages with a tooth of the door and has a space or hole for locking the same, a delayed disengagement locking device for said slider, which is characterised in that it comprises a rotatable, pivoted pawl which is able to penetrate said hole of the slider so as to lock the same in the closed position, said device being subordinated to the action of an activation assembly depending on the supply of electrical power and simultaneously to the action of a pressure switch activation assembly depending on the level of water contained in the basket of the washer and integrated with said pressure microswitches.

17. A locking device for doors of washing machines and the like, according to claim 16, charactersied in that said activation assembly depending on the supply of electrical power comprises a PTC pellet combined with a small bimetallic disk, the whole assembly being inserted into the circuit that supplies electrical power to the machine, in which said small bimetallic disk is of the rapid release, bending reversal type and shows a free end that engages with two small stakes of said locking pawl so as to cause its rotation through 90 at the moment of reversal in its bending.

18. A locking device for doors of washing machines and the like according to claim 16, characterised in that said microswitches are operated by said pressure switch activation assembly and they are of the type comprising an over-centre central blade resting on a calibration spring, which type is able to close the contact on release when a pressure is exterted on the spring higher than the calibration pressure.

19. A locking device for doors of washing machines and the like according to claim 16, said device being characterised in that said pressure switch activation assembly comprises a pressure sensor chamber formed by the upper edge of the device box and by the cover of said box with the interposition of a rubber membrane, a small disk for transmitting the pressure, which disk is acted upon by said rubber membrane and transmits said pressure through a central tip or apex to a small triangular plate, said small triangular plate having a first and a second apex both turned downwards for operating said microswitches and a third cam-shaped apex turned downwards for operating with a first end of a lever whose fulcurm is at the base of said box and whose second end is in the shape of a tooth and cooperates with a notch provided in the locking pawitl in order to keep the same locked in the closing position of the door of the washing machine.

20. A locking device according to claim 19, characterised in that said pressure sensor chamber communicates pneumatically with the basket of the washing machine that contains water through a thin pipe for the passage of air.

21. A locking device for doors of washing machines and the like, said device comprising a slider bearing a hole which engages with a closing tooth of the door, and a hole for locking the slider in the closing position of the door, a base box with an inside cavity limited by a peripheral edge, incorporating a pivoted pawl which is able to rotate through 900 so as to become engaged with said locking hole, an assembly for electrically driving said pawl, said assembly comprising a combination of a PTC pellet and bimetallic disk, inserted into the circuit that supplies electrical power to the washing machine, an assembly for the pressure switch operation comprising a pressure sensor chamber acting through a small transmission disk and a triangular plate on a first and a second pressure microswitch as well as on a locking lever whose fulcum is positioned at the bottom of the box, said lever having a first end and a second end which is in the shape of a tooth for the engagement with a locking notch provided in said locking pawl.

22. A locking device according to claim 21, characterised in that said pressure sensor chamber communicates penumatically with the water containing basket of the washer and is formed by the cover of said box which keeps a rubber membrane fastened along the peripheral edge of the inside cavity of said box.

23. A locking device according to claim 21, characterised in that said microswitches comprise an over-centre blade that is acted upon by a calibration spring.

24. A locking device according to claims 21 and 23, characterised in that said small triangular plate has a first and a second apex both cooperating so as to press said blades, the contact in said pressure microswitches becoming closed when the pressure exerted by said apices on the respective blades is higher than the calibration pressure of the respective spring.

25. A locking device according to claim 21, characterised in that said small triangular plate has a third, cam-shaped apex that interacts with the first end of said locking lever.

26. A locking device for doors of washing machines and the like, said device being operated by electrical power and/or by the water level, and being integrated with the pressure switch functions according to any one of the preceding claims 16 to 20 or 21 to 25 and substantially as disclosed in the disclosure above and shown in the drawings enclosed with the same.