EP2105527B1

EP2105527B1 - Electrical appliance with door provided with an electrically operated locking device

Info

Publication number: EP2105527B1
Application number: EP09155880.9A
Authority: EP
Inventors: Fabrizio Promutico; Claudio Belli; Antonino Sidari
Original assignee: Bitron SpA
Current assignee: Bitron SpA
Priority date: 2008-03-25
Filing date: 2009-03-23
Publication date: 2013-05-29
Anticipated expiration: 2029-03-23
Also published as: EP2105527A1; ITTO20080224A1

Description

The present invention relates to an electrical appliance, such as a domestic electrical appliance, particularly a washing machine or a washer-dryer.
More specifically, the invention relates to an electrical appliance comprising:

a chamber closed by a door,
a locking device associated with the door, including an operating solenoid connected with a PTC resistor between a first and a second electrical terminals, which, as the result of a first energizing and at least one subsequent additional energizing of the solenoid, is capable of assuming, respectively, a locked condition in which it retains the door in the position which closes the chamber, and an unlocked condition in which it allows said door to be opened; and
control means connected to said electrical terminals and capable of causing subsequent energizing of said solenoid by means of subsequent applications of voltage across said terminals;
the control means being designed to apply a voltage to the PTC resistor after the first energizing or after each first energizing of said solenoid for a predetermined time in such a way that the resistance of the PTC resistor reaches and is kept approximately at a value such as to prevent said solenoid being energized.

An electrical appliance provided with a door locking device of the type defined above is described for example in European patent application EP 1 808 558 A belonging to this Applicant.
In the appliance described and illustrated in that earlier application, the PTC resistor and the operating solenoid are connected together in series, and after a first energizing of the solenoid they are both kept live, so that the current flowing causes an increase in the resistance of the PTC resistor which in turn causes a reduction in the strength of that current. In this way the PTC resistor prevents undesired energizing of the operating solenoid due to external electromagnetic interference.
One object of the present invention is to provide an improved electrical appliance of the type specified above.
This and other objects are achieved according to the invention with an electrical appliance of the type defined above, characterized by the aspects defined in the attached Claim 1.
In particular, the invention eliminates the vibrations (buzzing) generated by the operating solenoid.
Other features and advantages of the invention will become clear in the course of the following detailed description, which is offered purely by way of non-restrictive example with reference to the appended drawings, in which:

Figure 1 is a front view of a locking and unlocking device for an electrical appliance according to the invention;
Figure 2 is a side view of the device seen in Figure 1;
Figure 3 is an enlarged view at the plane marked III-III in Figure 2;
Figure 4 is a perspective view of the device shown in Figure 3;
Figure 5 is a circuit diagram, partially in block form, of part of an electrical appliance according to the present invention; and
Figure 6 is a series of diagrams showing qualitatively, as a function of the time t on the x-axis, illustrative graphs of various electrical parameters during operation of an appliance according to the present invention.

In Figures 1 and 2, reference number 1 is a general reference for a device for locking and unlocking a door P for closing a chamber of an electrical appliance such as a washing machine or a washer-dryer or other domestic electrical appliance.
The locking device 1 comprises a supporting casing 2, of electrically insulating material, designed to be fixed to the structure of the electrical appliance, near the access opening to its abovementioned chamber, fitted to which opening is a door P (Figure 2) which in a manner known per se is provided with a catch member H. In the embodiment presented by way of example, the supporting casing 2 is composed of two half shells 3 and 4 joined together.
As can be seen in Figure 1, the casing 2 of the device 1 has an opening 5 for the insertion of the catch member H attached to the door P.
Mounted inside the supporting casing 2 of the device 1 is a sliding retention member or slider 6 provided with a window opening 7 through which the catch member H can pass.
When the door P is open (Figure 2), the retention member 6 is held (by an associated spring, not shown) in a rest position (Figure 1) in which its window 7 coincides with the opening 5 of the casing 2. In this condition the door catch member H can be inserted into the opening 5 and into the window 7 when the door is closed, and conversely can be disengaged from this window and from said opening when the door is opened.
As is shown in Figure 1, when the retention member or slider 6 is in the rest position, it covers an opening 8 in the top half shell 3 of the supporting casing 2, in which opening there extends a locking member 9 capable of translational movement.
As in the prior art, the arrangement is such that, when the door P is closed, the catch member H engages in the opening or window 7 in the retention member or slider 6 and causes a translational movement of the latter (towards the right when observing Figure 1) such that the opening 8 is uncovered.
Referring to Figure 3, the bottom half shell 4 of the casing 2 contains a switch bearing the general reference 10. This switch comprises a fixed contact 11 on a shaped metal element 12, one end 12a of which, in the shape of a thin blade, extends, as a connecting terminal, into a concave seat 18 in the supporting casing.
The switch 10 also comprises a moving contact 13 (not visible in Figure 3 but shown in Figure 4) on one end of a metal blade 14, facing the fixed contact 11. The other end of the blade 14 is fixed over a shaped metal member 15 and is firmly mounted with the latter on the supporting casing, for example by means of a rivet 16.
The end of the blade 14 that carries the moving contact 13 used with the fixed contact 11 extends underneath the latter.
A helical spring 17, visible in Figure 4, is interposed between the bottom wall of the half shell 4 of the supporting casing 2 and the blade 14. This spring attempts to push a blade 14 upwards so that it closes against the fixed contact 11.
The end of the blade 14 that carries the moving contact 13 is connected to the locking member 9 in such a way that the spring 17 also attempts to push the locking member 9 from a lowered or disengaged position, in which it does not project from the supporting casing 2, to a raised or engaged position in which this locking member partially protrudes from the opening 8, into the path of the retention member or slider 6, thereby preventing the latter from returning to the rest position in which it allows the door P to be opened. For more details on the construction of the locking device the reader may also refer to US patent No. 6,334,637 belonging to the present Applicant.
The metal connecting member 15 forms a projection or end 15a (Figures 3 and 4) shaped like a thin blade, which extends into the seat 18 and functions as a connecting terminal.
The locking member 9 is also provided with an electromechanical control device, such as that illustrated by way of example in Figures 3 and 4. This device is of a type known per se and is described in detail in the aforementioned US patent.
Referring to Figures 3 and 4, said electromechanical control device essentially comprises a toothed wheel 20 mounted rotatably in the half shell 4 about a pin 21, adjacent to the locking member 9. This toothed wheel has an upper portion provided with sawtooth-shaped teeth 22 (Figure 4).
An electrically operated actuator shown with the general reference 25 comprises a coil or solenoid 26 inside which is a core 27 able to move translationally axially, with a rod 28 attached to one end (Figure 3). The end of the rod 28 directed away from the core 27 presses against a shaped member bearing the general reference 29. In the middle of this member is an opening 30 in the shape of a slot into which extends a fixed peg or pin 31 mounted on the supporting casing of the device.
That end 29a (Figure 3) of the member 29 which is furthest from the actuator 25 is pawl-shaped and engages between two consecutive sawteeth 22 of the toothed wheel 20.
A detent 32 pivots about a fixed pin 33 and it too is engaged between a pair of consecutive sawteeth of the toothed wheel 20, being pushed by a helical spring 34 fitted between said detent and the end of the shaped member 29 adjacent to the actuator 25.
The arrangement described above is such that whenever the actuator 25 - specifically the solenoid 26 - is energized, the core 27 moves translationally (upwards when observing Figure 3) and, via the rod 28, displaces the shaped member 29, which in turn causes the toothed wheel 20 to rotate one step, i.e. an amount corresponding to one sawtooth 22. Following this angular displacement, the detent 32 again stabilizes the angular position of the wheel 20.
In the illustrated embodiment, the winding or solenoid 26 of the electromagnetic actuator is connected at one end to an electrically conducting shaped member 35 and at the other to the connecting member 15-15a.
A resistor with a positive temperature coefficient (PTC) 38 is connected between the connecting member 35 and a conducting member 37, one end 37a of which latter extends into the concave seat 18 of the device casing and is shaped in the form of a thin blade to function as a connecting terminal.
In Figures 3 to 5, 60 denotes another electrically conducting element connected to the conducting member 35 and having an end 60a in the form of a thin blade which extends into the concave seat 18 to function as a connecting terminal.
In the circuit diagram, Figure 5, parts and elements already described are again given the same reference numbers as earlier. In Figure 4, 40 is a control unit or circuit for the electrical appliance. This unit or circuit has four terminals A, B, C and D connected in order to the connecting terminals 12a, 15a, 37a and 60a of the door lock device 1.
The appliance described above operates in the following manner.
When the door P is open the locking device 1 is in the condition illustrated in Figures 1 and 2: the locking member 9 is "covered" by the retention member or slider 6, and is also held in the retracted position of disengagement from the toothed wheel 20 (see the earlier US patent mentioned above for a more detailed description and illustration).
When the door P is closed, the slider 6 moves translationally to "uncover" the locking member 9. During this step the locking member however remains held in the retracted position of disengagement from the toothed wheel 20, which is still in the same position it had in the previous step.
When the user of the electrical appliance turns the appliance on, at an instant t₁ (Figure 6) the control unit 40 of this appliance causes a first energizing of the actuator 25 by applying a voltage V_BC across the terminals 15a and 37a of the locking device 1, causing current to flow from the terminal B towards the solenoid 26 and towards the PTC resistor 38. Owing to this energizing, the member 29 of the locking device 1 causes the toothed wheel 20 to rotate by an amount equal to the angular amplitude of one tooth 22 of this wheel. As a result, the locking member 9 can move into the extended position engagement as the spring 17 pushes against the blade 14. At the same time the moving contact 13 on the blade 14 meets the fixed contact 11, meaning that the switch 10 is closed. With the locking member 9 in the extended position, the retention member or slider 6 is prevented from returning to the rest position in which the door P could be opened.
At an instant t'₁ subsequent to t₁, the unit 40 then discontinues the application of the voltage V_BC to the terminals 15a and 37a.
In the appliance according to the invention, the control unit 40 is furthermore designed to apply to the PTC resistor 38 a voltage V_DC (Figure 6) across the terminals 60a and 37a, from the instant t₁ or t'₁, or from an instant between t₁ and t'₁, at the same time as the first energizing, or each first energizing, of the locking device 1, ending at a predetermined subsequent instant t₂ (Figure 6). The voltage V_DC is such that the resistance R of the PTC resistor 38 rapidly reaches and remains at a value such as to reduce to a very low level the current I (Figure 6) flowing through this resistor and thereby prevent the solenoid 26 from being energized for substantially the entire duration of the time interval t₂-t'₁.
Near the end of the operating cycle of the electrical appliance, and in order to allow the door P to be opened, the control unit 40 discontinues the application of the voltage V_DC to the terminals 60a, 37a at the instant t₂ (Figure 6). The resistance R of the PTC resistor 38 now drops, at a rate which can be advantageously increased by the judicious location of this resistor 38 near a portion of the outer wall of the supporting casing of the door lock device, which may optionally be provided with multiple integral fins to promote heat dissipation.
When the operating cycle of the domestic electrical appliance is finished, and in order to allow the door P to be opened, the control unit 40 causes one or two successive energizing pulses to be sent to the solenoid 26 of the electromagnetic actuator 25. These pulses are denoted V1 and V2 in the top graph of Figure 6. As a result of this, the toothed wheel 20 is caused to rotate by an amount such that it is able to return the locking member 9 to the retracted or disengaged position, in which it allows the retention member or slider 6 to move back to the position in which the door is allowed to be opened.
The continuing application of the energizing voltage V_DC across the terminals 60a and 37a of the door lock device 1 after the first energizing, or after each first energizing, for the time interval ending at t₂, allows the operation of the solenoid 26 to be inhibited for the entire duration of this time interval, making the device correspondingly immune to undesirable energizing caused by external electromagnetic interference. Obviously, the instant t₂ at which the application of the voltage V across the aforementioned terminals is interrupted is determined by the control unit 40 to take place a suitable length of time before the instant at which it is intended that the door should become unlockable, in order to give the PTC resistor 38 the time to cool down sufficiently.
It should be observed that while in the time interval t'₁ to t₂ the PTC resistor prevents the possible energizing of the solenoid 26, there is no voltage being applied to the latter.
Naturally, without altering the principle of the invention, the embodiments and details of construction may vary considerably from those described and illustrated purely by way of non-restrictive example, without thereby departing from the scope of the invention as defined in the appended claims.

Claims

Electrical appliance comprising:
a chamber closed by a door (P),

a locking device (1) associated with the door (P), including an operating solenoid (26) connected with a PTC resistor (38) between a first and a second electrical connecting terminals (15a, 37a), which, as the result of a first energizing and at least one subsequent additional energizing of the solenoid (26), is capable of assuming, respectively, a locked condition in which it retains the door (P) in the position which closes the chamber, and an unlocked condition in which it allows the door (P) to be opened; and

control means (40) connected to said electrical terminals (15a, 37a) and capable of causing subsequent energizing of said solenoid (26) by means of subsequent applications of voltage across said terminals (15a, 37a);

said control means (40) being designed to apply a voltage (V_DC) to the PTC resistor (38) after the first energizing or after each first energizing of the solenoid (26) for a predetermined time interval (t₂-t'₁) in such a way that the resistance (R) of the PTC resistor (38) reaches and is kept approximately at a value such as to prevent said solenoid (26) being energized in said time interval (t₂-t'₁);

the appliance being characterized in that said control means (40) are connected to the PTC resistor (38) in such a way that they are capable of applying said voltage (V_DC) to it without causing current to flow through said solenoid (26).
Appliance according to Claim 1, in which the PTC resistor (38) is connected to one (37a) of said two electrical terminals (15a, 37a) and the control means (40) have an output (D) connected to another electrical terminal (60a) of the locking device (1) which in turn is connected to an intermediate point between the solenoid (26) and the PTC resistor (38).