Patent Publication Number: US-7585006-B2

Title: Household appliance, namely a machine for washing and/or drying laundry, with a door block/release device that can be actuated electrically

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a household appliance, namely a machine for washing and/or drying laundry, comprising a cabinet, a door and a door block/release device that can be actuated electrically. 
   Various types of household appliances have the characteristics indicated above. For example, machines for washing and/or drying laundry, be they of the front loading or top loading type, are provided with a door, through which the user has access to a drum, for the normal operations of loading and unloading the laundry. Machines of the aforementioned type are also provided with a device for locking/releasing the door; for regulatory reasons, the aforesaid device incorporates safety means, operative to prevent the door from opening during the operating cycle of the machine, and vice versa the operation of the machine with the door open. 
   In some types of machines, the locking/releasing device can be operated by means of a handle associated with the door. In the case of front loading laundry washing or drying machines, given the generally lowered position of the door, the actuation of the aforesaid handle forces the user to bend down in tiring fashion. 
   For this purposes, therefore, machines have been proposed with mechanical transmission systems, to allow to transfer control over the locking/releasing device to a more favourable position, in particular by means of a push-button positioned on the control panel of the machine. Such devices with remote mechanical actuation are oftentimes not fully satisfactory, both due to the high force of control required, and to their structural complexity. 
   Therefore, locking/releasing mechanisms have also been proposed whose mechanical part is actuated locally by actuator means which are electrically powered as a result of the actuation of a push-button positioned on the control panel of the machine, or as a result of a signal generated by the control system of the household appliance,. 
   In such electrically actuated devices, in some situation, it is necessary to unlock the door manually. Think for instance of the case of a malfunction of the actuator that actuates the mechanical part of the locking/releasing device, or of a malfunction of the control system that operates said device, or else of an interruption in the mains voltage powering the household appliance. 
   The document EP-A-0 977 104 discloses a bi-stable actuation system, operated through a wax electro-thermal actuator and usable in combination with a mechanical device for locking/releasing the door of a household appliance. The described system can be unlocked manually, through an appropriate mechanical arrangement, if the need arises, e.g. if main power supply fails or the control system of the household appliance malfunctions. Said arrangement comprises a slot formed in the casing of the device, accessible from the exterior of the household appliance, in which the end of an appropriate tool can be inserted to “reset” the system, towards a respective door release position. The system according to the aforementioned prior document, in addition to requiring the use of an appropriate tool, is complex from the mechanical viewpoint and hence potentially not very reliable over time. 
   SUMMARY OF THE INVENTION 
   In light of the prior art described above, the object of the present invention is to provide a household appliance equipped with a device for locking/releasing the respective door, able to be actuated both electrically and manually, which is of new conception, simple to manufacture and has minimal bulk. 
   This object is achieved, according to the present invention, by a household appliance having the characteristics specified in the appended claim  1 . Particularly advantageous characteristics of the household appliance according to the invention are set out in the dependent claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects, characteristics and advantages of the invention shall become readily apparent from the description that follows with reference to the accompanying drawings, provided purely by way of non limiting example, in which: 
       FIG. 1  is a front schematic view of a machine for washing and/or drying laundry according to the invention, with the front loading door closed; 
       FIG. 2  is a schematic lateral view of the machine of  FIG. 1 , with the front loading door half opened; 
       FIGS. 3 and 4  are schematic sections of two mechanical components of a door block/release device of the machine shown in  FIGS. 1 and 2 , in two different operative conditions; 
       FIG. 5  is a schematic, partially sectioned view of a system for actuating one of the components shown in  FIGS. 3 and 4 , 
       FIG. 6 and 7  are schematic views similar to  FIG. 5 , showing the actuating system following an electrical and a manual actuation, respectively, and 
     FIG  8  is an exploded perspective view of a detail of an actuator device used in the system of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  show a household appliance according to the invention which, in the case exemplified herein, is a front loading laundry washing machine, globally designated by the reference  1 ; however, the invention can be applied to other types of household appliances, such as laundry washer-dryer machines, laundry dryer machines, dishwashers, cooking ovens, etcetera. 
   The machine  1  comprises a metal plate cabinet  2 , in the upper part whereof is mounted a control panel  3 ; in the front part of the cabinet  2  is present an opening, designated by the reference  4  in  FIG. 2 , for access to an internal drum of the machine, for the purposes of the normal laundry loading/unloading operations. The reference number  5  globally designates the loading door of the machine  1 , which is provided, for closing the aforesaid opening  4 . 
   The machine  1  is provided with a system for locking/releasing the door  5 , shown only schematically in  FIG. 1 , and globally designated by the reference  6 ; the reference  7  designates a small door present on the front wall of the cabinet  2 , aimed at allowing to access internal components of the machine, such as the filter of a washing pump, for the purposes of its periodic cleaning. 
   In the case shown merely by way of example in  FIG. 2 , the block/release system  6  comprises an engagement tooth  8 , associated with the door  5 , and an opening  9 , defined on the front wall of the cabinet  2 , into which opening the tooth  8  is able to be inserted; inside the cabinet  2 , substantially at the opening  9 , is mounted a mechanical device for blocking/releasing the tooth  8 , which in normal conditions is actuated by electrical actuating means, but in conditions of necessity can be actuated manually. For this purpose, as will become readily apparent below, the system  6  comprises a manual command part, accessible at the area to the rear of the door  7 . 
   The aforesaid mechanical device can be of any known type, since its construction has no bearing on the aims of the present invention; the device could, for instance, be of the type comprising a plate provided with a slot, in which the tooth  8  is able to engage, the plate being able to slide as a result of the operation of the aforesaid electrical actuator means to produce the disengagement of the slot from the tooth  8 ; alternatively, the aforesaid mechanical device could comprise a lever able to move angularly, between a first position of engagement and a second position of disengagement with respect to the tooth  8 , the passage between the first and the second position being produced by the operation of the aforesaid electrical actuator means. 
   In yet a different possible embodiment, the block/release device  6  could have an inverse arrangement with respect to the one exemplified, i.e. it could have an angularly moveable tooth, mounted on the cabinet  2  of the machine, and an engagement seat for said tooth, defined on the door  5 , the angular movement of the tooth, in the sense of freeing itself from the engagement seat, being produced by the action of the aforesaid electrical actuator means. 
   In the case exemplified in  FIG. 2 , and as shown also in  FIG. 3 , substantially at the opening  9  and inside the cabinet  2 , is mounted a plate  10 , capable of sliding vertically, provided with a slot  11  into which the tooth  8  is capable of engaging. The operating principle of the mechanical system constituted by the tooth  8  and by the plate  10  is schematically shown in  FIGS. 3 and 4 . 
   In  FIG. 3 , the plate  10  is in a first operative position in which, closing the door  5 , the tooth  8  penetrates into the opening  9  and then enters the slot  11 ; the tooth  8  is so shaped that its frontal part, coming in contact with the lower edge of the slot  11 , determines a slight lowering of the plate  10 , with the subsequent engagement of the tooth on the aforesaid edge, and the simultaneous return of the plate  10  to the initial position, by virtue of the action of elastic return means (schematically represented in  FIG. 5  by two helical springs  15 ); in combination or alternatively, the tooth  8  could be mounted elastically on the door  5 , with the possibility of slight angular movement upwards, to “overcome” the lower edge of the slot  11 . 
   In the condition of  FIG. 3 , therefore, the door  5  is locked shut. 
   To allow the opening of the door  5 , the plate  10  must be moved downwards, so that the lower edge of its slot  11  frees the tooth  8 , as shown in  FIG. 4 . The vertical downwards translation of the plate  10  is produced in normal conditions by electrical actuator means, comprised in the system  6  illustrated in detail in  FIG. 5 . 
   The block/release system  6  can further comprise an electrical safety device, for instance bimetallic, mounted inside the cabinet  1 , which mechanically blocks the tooth  8  throughout the duration of an operating cycle of the machine, thereby preventing an accidental opening of the door  5 . The same safety device is conceived to prevent the machine  1  from starting to operate if the door  5  is open. The aforesaid safety device is not shown, as it can be of any known kind, its construction being outside the scope of the objects of the present description. 
   In  FIG. 5 , the plate  10  is shown in view; the plate  10  is associated to guiding means  13 , in such a way as to be able to slide only in the vertical direction; the guiding means  13  are integral with a support S of the system, fastened to the structure of the machine  2 ; to the support S are also associated stands  14  for respective springs  15 , tending to maintain the plate  10  in the raised position, i.e. the position of  FIG. 3 . 
   In the lower part of  FIG. 5  is shown the actuation system of the plate  10 , which comprises an electrically powered actuator. 
   Said actuator comprises an element constructed, at least for a portion thereof, of a shape memory metal alloy. The shape memory actuator elements have long been known and used in various fields in which it is necessary to have simple and low cost actuator means available. They use shape memory metal alloys able to be deformed as a result of exceeding a predetermined transition temperature. In general, heating can be obtained by feeding an electrical current through the actuator element, in order to heat it by Joule effect. In this case, the electrical power supply means can be associated with electronic control means able to control the current supply as needed. 
   In the embodiment shown herein, the aforesaid actuator made of shape memory allow is configured as a flexible cable  22 , formed by a wire made at least in part of a shape memory alloy, designated by the reference number  23 , embedded within a respective coating  24 . The wire  23  has a U configuration inside the coating  24 , with a first run and a return run and its two ends mutually adjacent; this allows an easy electrical connection of the wire  23  to electrical power supply means. 
   In the example the upper end of the cable  22 , constituted by the actual U-shaped portion of the wire  23  which projects from the coating  24 , is secured to an element  25  made integral with the plate  10 . At the lower end of the cable  22 , from the coating  24  project the two ends of the wire  23 ; the lower end of the cable  22 , or otherwise the two projecting ends of the wire  23  are mechanically anchored to the support S, by fastening means  26 , known in themselves; said ends of the wire  23  are connected to a power supply circuit  27 , comprising a source of electrical power supply  28  and a switch  29 . In a preferred embodiment, the power supply circuit  27  comprises, protection means  28   a  of the element made of shape memory material, constituted for example by a PTC element (i.e., a resistor with positive temperature coefficient), connected in series between the source  28  and the wire  23 . When a PTC element is powered electrically, in voltage or in current, it initially has a relatively low ohmic resistance value for a short time, and subsequently passes to a condition distinguished by a high value of ohmic resistance. This property allows to use the PTC element  28   a  as a sort of switch, to obtain a rapid power supply and hence a rapid actuation of the wire  23 , in the initial low-resistance phase; once a certain period of time, predetermined during the design stage, expires, the PTC element  28   a  passes to the final phase of high resistance, in fact automatically interrupting the electrical power supply to the wire  23 . 
   The cable  22  extends inside a flexible sheath  30 , with the possibility for relative sliding, the sheath  30  being able to be obtained from any known material typically adopted for said purpose. Between the cable  22  and the sheath  30  can be provided a spacer layer  31 . 
   At the upper end of the sheath  30  is anchored a first bushing  32 , able to slide within an inner cavity  33  of a body  34 , in turn able to slide within respective guiding means  34   a , and with which the element  25  is integral. The bushing  32  abuts against an end surface  33 ′ of the aforesaid cavity  33  of the body  34 . 
   To the lower end of the sheath  30  is anchored a second bushing  35 , whereto is connected a cable  36  fastened to a ring  37 , shown in dashed lines in  FIG. 5 ; the cable  36  has such length that the ring  37  is positioned substantially at a compartment behind the small door  7  present on the front wall of the cabinet  2  of the machine  1 ; as can be intuited, the cable  36  allows to transfer to the sheath  30  a manual traction exerted by means of the ring  37 . 
   On the sheath  30  is further secured an intermediate bushing  38 , designed to abut against a fixed stop  39  fastened to the support S. The co-operating action of the bushing  38  integral with the sheath  30  and of the stop  39  prevents a displacement of the sheath in the direction indicated by the arrow A. 
   The operation of the system  6  illustrated in  FIG. 5  is as follows. 
   In conditions of normal operation of the machine  1 , the displacement of the plate  10  between the position of  FIG. 3  to that of  FIG. 4  is obtained by means of the electrical actuator constituted by the cable  22 . 
   For this purpose, the cable  22  is powered through the circuit  27  which, as a result of the closure of the switch  29 , applies a difference in potential between the two ends of the wire  23  made of active shape memory material. The shutting of the switch  29  is preferably automatically commanded by the control system of the machine, designated by the reference SC, at the end of a wash cycle; alternatively, the operation of the switch  29  could be produced, in known fashion, as a result of the pressing of a push-button, located on the control panel  3 , which can be operated by the user of the machine  1 . 
   As a result of being powered, the wire  23  of the cable  22  heats up by Joule effect; upon exceeding a transition temperature, typical of the shape memory material or alloy in use, the wire  23  shortens, also determining a compression of the respective coating  24 , and hence, essentially, a shortening of the cable  22  as a whole, as indicated by C in  FIG. 6 . 
   Given that the ends of the cable  22  and/or the ends of the wire  23  are secured in a fixed position, through the means  26 , their shortening causes a corresponding downward sliding C of the body  34  over the sheath  30 , with the abutting surface  33 ′ of the respective cavity  33  which distances itself from the bushing  32  integral with the sheath  30 . Said sheath  30  remains motionless, not being able to move upwards as a result of the engagement of the intermediate bushing  38  against the fixed stop  39 . The downwards motion of the body  34  and of the element  25  associated therewith thereby determines a displacement of the plate  10  in the direction of actuation indicated by the arrow B, with its passage from the position of  FIG. 3  to the position of  FIG. 4 . The device  6  is then in the respective position of release, and the door  5  can be opened. 
   In a possible embodiment, between the cabinet  2  of the machine  1  and the door  5  can be provided an elastic system, for example with springs, able to produce an automatic opening motion of the door itself, after the tooth  8  is released by the plate  10 . In this case, some instants after the actuation, and the consequent automatic opening of the door, the control system SC reopens the circuit  27 , interrupting power supply to the cable  22 . 
   Alternatively, the opening of the door  5 , and hence the exit of the tooth  8  from the slot  11  of the plate  10  can be detected by known sensor means (e.g., a micro-switch); the signal produced by said sensor means is used by the control system SC to command the opening of the switch  29 . 
   If, for any reason (e.g., a malfunction of the control system SC, a mains black-out, etcetera) the electrical actuator is not capable of being operated in the normal manner described above, the user of the machine can actuate the system  6  manually, opening the small door  7  and acting on the ring  37 . 
   The mechanical traction imparted manually on the ring  37 , and hence on the cable  36 , is transmitted to the sheath  30 , which then moves downwards in the direction of actuation B, causing the intermediate bushing  38  to move away from the fixed stop  39 , as indicated by C′ in  FIG. 7 . The displacement of the sheath  30  causes a corresponding downwards displacement C′ of the body  34 , since to the upper end of the sheath  30  is anchored the bushing  32 , which abuts against the end surface  33 ′ of the cavity  33  of the body  34 . The displacement thereof consequently causes a similar displacement of the element  25 , and hence of the commanded member constituted by the plate  10 , which reaches the position of  FIG. 4 . The maximum limit of downwards displacement of the body  5  can be determined by the stands  14 , or by additional stops integral with the support S, not shown. 
   The support S, and hence all the components of the block/release system  6  shown in  FIG. 5 , is mounted internally to the cabinet  2 ; the tooth  8  is, as stated, associated with the door  5  and the ring  37  is accessible through the small door  7 . 
   In the preferred embodiment of the invention, the actuation device constituted by the cable  22  and by the sheath  26  has a structure of the type shown in  FIG. 6 . As shown, the flexible cable, with the flexible sheath  30 , and the spacer layer  31 , which in the illustrated case is constituted by a metal braiding, are provided. 
   The flexible cable  22  capable of sliding within the sheath  30  comprises the shape memory wire  23 , U-shaped, over which is moulded the coating layer  24 , which adheres to the wire itself; the coating layer  24  is made of an elastomeric/silicone or synthetic material, such as to favour both the cooling of the wire  23  after the cessation of the passage of electrical current, and the return of the wire  23 , and hence of the entire cable  22 , in its extended resting configuration, by effect of the elastic return of the coating. 
   The coating  24 , which is adherent to the wire  23 , therefore serves the function of a longitudinally distributed spring, which is subjected to compression when the wire  23  shortens as a result of its actuation, and consequently favours the return of the cable to the resting position through its elastic return. 
   Naturally, without altering the principle of the invention, the construction details and the embodiments may vary widely from what is described and illustrated purely by way of example herein, without thereby departing from the scope of the present invention. 
   For example, one can mention the possibility of using, for the purpose of embodying the invention, a cable  22  comprising a plurality of shape memory wires  23  within a same moulded coating  24 . 
   The ring  37  could naturally be made accessible in any other area of the cabinet of the household appliance deemed convenient, e.g. in its rear part. 
   Instead of the ring  37 , the traction on the sheath  30  aimed at determining the manual release of the system  6  could be obtained through any other known mechanical system, for instance based on a lever, a mechanical push-button, a rotary knob, a sliding cursor etcetera.