A device for locking the porthole door of a washing machine

Abstract

 A device for locking the porthole door of a washing machine and similar appliances is provided with an opening (5) for the passage of a hook mounted on the porthole door. The device comprises a slider (7) cooperating with the end of the door hook and an electromechanical delaying device (20) electrically connected to the operating controls of the washing machine and adapted to block said slider (7) through a slider stopper. The contact terminal for applying a voltage to a thermistor of the delaying device (20) is formed by two metal strips (28, 29) the ends of which project from the housing of said delaying device (20), with the blades positioned one in front of the other in correspondence of a conductive member (11) fastened to said slider (7) and adapted to close the circuit when the porthole door is closed.

Description

[0001] The present invention relates to electronic components of domestic appliances and particularly to a safety latch device for locking the porthole door of a washing machine and similar appliances.

[0002] Front load washing machines are provided with a porthole door laterally hinged to the front panel of the washing machine and provided with a closure hook in a diametrically opposite position with respect to the hinged one, such hook being engaged by a locking device also mounted on the front panel.

[0003] In addition to allowing the door opening and its snap closure, the locking device incorporates a device, generally known as "door lock device" for immediately locking the porthole door and for its release.

[0004] The function of a door lock device is that of blocking the closed porthole door when the machine is being started and of delaying the opening of the porthole door once the operating cycle has been terminated until the inertial rotation of the tub has stopped. Moreover the door lock device prevents the starting of the machine when the porthole door is open.

[0005] There are known devices both electromechanical and electronic that accomplish the above functions.

[0006] More particularly there are known devices in which the arrangement for locking the porthole hook comprises a sliding bolt adapted to engage the hook for closing the porthole door, which interacts with a locking plug or peg that is actuated upon the occurrence of predetermined conditions for the blade of the movable contact in a microswitch that is connected in series on a phase line carrying the current of the machine. The movable contact of the microswitch is in turn operated by a deformation (bending) of one or more bimetallic strips that are properly heated by a thermistor, also this latter being electrically connected to the machine controls.

[0007] The operation of the device provides that upon supplying power to the machine after closing the porthole door, the plug snaps into such a position to block the sliding bolt that engages the porthole hook, thus preventing the opening of the porthole door until the plug has been driven back. The return motion of the blocking plug will take occur after a given delay with respect to the current interruption, this delay being a function of the cooling time and the characteristics of the thermistor-bimetallic strip assembly.

[0008] If power is supplied to the machine when the porthole door is open, the displacement of the blocking plug, and therefore the closing of the machine actuating circuit, is inhibited by the position of the sliding bolt.

[0009] Such devices therefore mechanically prevent the starting of the machine when the porthole door is open, but have the drawback that the thermistor is being fed until the porthole door has been closed.

[0010] Moreover a possible open condition of the porthole door is not detected without using an additional microswitch for signalling the open/closed condition of the door.

[0011] It is an object of the present invention to provide a device for locking the porthole door of washing machines and the like that overcome the limitations and the drawbacks of the prior art, and more particularly that not only mechanically prevents the starting of the machine when the porthole door is open, but also inhibits the closing of the electric circuit of the device.

[0012] Moreover the invention allows for detecting whether the porthole door is open or closed and for using such information, for instance, to activate a visual signalling without requiring the addition of further connections.

[0013] According to the invention these objects are achieved through a device for locking the porthole door of a washing machine as claimed in claim 1. Further advantageous characteristics are recited in the dependent claims.

[0014] The invention will now be disclosed with reference to the attached drawings that illustrate a preferred, but non limiting embodiment of the invention, in which:

Fig. 1 is an axonometric exploded view that illustrates a locking device according to the invention;

Fig. 2 is a front view showing the locking device of Fig. 1 in an open position of the porthole;

Fig. 3 is a cross-section view along line I-I of Fig. 2;

Fig. 4 is a front view showing the device of Fig. 1 in a closed position of the porthole;

Fig. 5 is a cross-section view along line II-II of Fig. 4;

Fig. 6 shows two different axonometric views of the locking device of Figure 1.

[0015] With reference to Figures 1 to 5, the device according to the invention comprises an elongated body or case 1, preferably of a thermoplastic material, that comprises a portion 2 to be fastened to the front panel of a washing machine, such portion being provided with a closing lid 4 and a portion 3 adapted to house an electromechanical time delaying device 20.

[0016] In the fastening portion 2 there is formed an opening 5 for receiving the hook 6 of the porthole.

[0017] A sliding member or slider 7 is housed inside the body 1 and is movable against spring (resilient) means 8. The slider provides for an opening or hole 9 adapted for engaging the end of the porthole hook 6 and a window 13 formed in correspondence of the area housing the electromechanical delaying device 20. A seat 10 is provided for receiving a locking plug or peg 21 actuated by the electromechanical delaying device 20.

[0018] A contact spring 11 is fitted to a transverse member 12 that is fastened to the slider 7.

[0019] Device 20 is an electromechanical delaying device of a substantially known type, comprising a snapping contact blade 22 driving the locking plug 21, a thermistor or a P.C.T. resistor 23 and a bimetallic arrangement with two strips 24 and 25, located one over the other.

[0020] Referring to Figure 6, the device 20 is provided with three electrical terminals protruding outside into a seat, and forming a set of quick connection terminals, namely a terminal 26 connected to the snapping contact blade 22, an NA contact terminal 27 and a contact terminal for applying a voltage to the P.T.C. 23.

[0021] The conductive member applying a voltage to the P.T.C. 23 is made up by two metal blades 28 , 29 the ends of which project from the housing of the door locking device 20, with the blades positioned one in front of the other and contained in the space formed by the window 13 formed in the slider 7. The blade 29 protrudes in the form of a quick-connection contact in a seat provided therefor (see Figure 6), while the other end of the blade 28 is connected to an adjustment grub screw 30 onto which rests the strip 25 (this connection not being shown in the figure).

[0022] The operation of the device according to the invention is as follows.

[0023] When the porthole door is open, the reciprocal positions of the parts forming the device are shown in Figures 2 and 3. More particularly the opening 9 of the slider 7 subjected to the action of the spring 8 is axially aligned with the opening 5. Accordingly the resilient contact 11 is in an opening position in respect of the ends of terminals (blades) 28 and 29, i.e. no power is applied to the P.T.C. 23 even if the machine is powered.

[0024] As shown in Figures 4 and 5, upon closing the porthole door the hook 6 is inserted in the hole 9 and pushes forward the slider 7. Consequently the contact spring 11 is driven to a closing position over the contacts 28 and 29.

[0025] The closing of the circuit allows therefore the feeding of the P.T.C. 23 and consequently activates the mechanism for locking the slider 7.

[0026] More precisely a current circulates through the contact 28, the grub screw 30, the bimetal strips 25 and 24 and feeds the P.T.C. resistor which in turn is almost immediately heated and transmits heat to the strip 24 thus causing its bending and the consequent snapping downwards of the strip 22. This way the circuit of terminal 26 and terminal 27 is closed and a voltage is applied to the machine movers. At the same time the locking plug 21 penetrates the housing (seat) 10 of the slider 7 thus blocking this latter in a position retaining the porthole hook 6 as long as the above condition is maintained.

[0027] By reading the ohmic value of the circuit formed by the terminal blade - terminal contact P.T.C. (bimetal) it is possible to detect the open/closed condition of the machine porthole door.

[0028] The device fulfils therefore the function of a microswitch for signalling the open/closed condition of the porthole door without increasing the number of terminals.

[0029] Additionally the arrangement of the device is such as to allow a creeping of the spring 11 over the fixed contacts 28, 29 during the closing and the opening of the circuit. Such action has a self-cleaning effect since it can break oxides that might have formed over the contacts and ensures a long term proper operation of the device.

[0030] The invention has been illustrated with reference to preferred embodiments, but more generally the same is susceptible of other applications and changes that fall within the scope of the invention, as it will be evident to the skilled of the art.

Claims

1. A device for locking the porthole door of a washing machine and similar appliances, comprising a case (1) housing a slider (7) cooperating with the end of a hook (6) secured to the machine porthole door, and an electromechanical delaying device (20) capable of blocking said slider (7) upon the occurrence of predetermined conditions by means of a locking plug (21), said electromechanical delaying device (20) being provided with a thermistor (23) electrically connected to the operating controls of the washing machine, characterised in that
one of the conductive members for applying a voltage to said thermistor (23) comprises two metal blades (28, 29) the ends of which project from the case of the delaying device (20) and are located one in front of the other in correspondence of a conductive member (11) fastened to said slider (7) and adapted to close the electric circuit when the porthole door is closed.

2. A locking device as claimed in claim 1 characterised in that said conductive member (11) is formed as a resilient contact positioned on a transverse member (12) fastened to said slider (7).

3. A locking device as claimed in claims 1 or 2, characterised in that said contact terminal or blade (29) projects outside of the electromechanical delaying device (20) into a seat formed as a quick connection contact.

4. A locking device as claimed in the preceding claims, characterised in that said electromechanical delaying device (20) comprises a snap contact blade (22) that actuates the locking plug (21) and is in turn operated by a bimetallic arrangement comprising two strips (24 and 25) heated by said thermistor (23).

5. A locking device as claimed in claim 4, characterised in that that said strip (28) is connected to an adjustment grub screw (30) connected to said bimetallic strip (25).

Drawing