Patent Publication Number: US-8109543-B2

Title: Blocking device for the door of an electric household appliance

Description:
RELATED APPLICATIONS 
     The present application is based on International Application No. PCT/IB2006/001282 filed May 16, 2006, and claims priority from Italian Application Number TO2005A000333 filed May 17, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a blocking device for the door of an electric household appliance, particularly suitable for locking a pyrolytic oven door in the closed position. 
     BACKGROUND ART 
     As is known, for safety reasons, the door of numerous types of electric household appliances, such as washing-machines, dishwashers, and pyrolytic ovens, must be locked in the closed position when the appliance is operating, to prevent the user from inadvertently opening the door. Pyrolytic ovens, in particular, in addition to normal cooking cycles, also perform a self-cleaning cycle, in which the oven temperature is much higher than normal (and therefore potentially dangerous to the user) to remove, by pyrolysis, dirt (e.g. grease) particles from the walls of the oven. At least during the self-cleaning cycle, therefore, the oven door must be locked absolutely reliably. 
     Since known door blocking devices, such as those used on washing-machines and dishwashers, are unsuitable for ovens, particularly for the extremely high temperatures of pyrolytic ovens, special pyrolytic oven door blocking devices have been devised, which are normally operated by servomotors and therefore extremely expensive and, on the whole, bulky and complex in design. 
     DISCLOSURE OF INVENTION 
     It is an object of the present invention to eliminate the aforementioned drawbacks by providing a door blocking device which is cheap, compact, highly straightforward in design and operation, and therefore highly reliable. More specifically, it is also an object of the invention to provide a door blocking device of the above type which, being straightforward and inexpensive, can be used above all on pyrolytic ovens, but also on other types of electric household appliances in which a door must be kept locked in the closed position during at least one operating cycle of the appliance. 
     According to the present invention, there is provided a blocking device for the door of a electric household appliance, in particular a pyrolytic oven, as claimed in Claim  1 . 
     More specifically, the door blocking device according to the invention comprises—all fitted to a support located, in use, close to a door opening of the door to be locked—a retaining member movable, along a given path, between a work position and a rest position, in which, in use, the retaining member respectively cooperates with and does not cooperate with a coupling member of the door when the door is in a closed position; and controlled-actuation means for controlled actuation of the retaining member, and which in turn comprise elastic means for pushing the retaining member into the rest position; means for moving the retaining member into the work position in opposition to the elastic means; a rotary member having at least one peripheral, radially projecting lobe; and an electrically controlled actuator, preferably defined by a straightforward electromagnet, for selectively moving the rotary member, preferably by means of a ratchet device, between a first angular position, in which the lobe does not interfere with the given path, thus allowing the retaining member to move between the work position and the rest position, and a second angular position, in which the lobe interferes with the given path, thus locking the retaining member in the work position in opposition to the elastic means. 
     The means for moving the retaining member into the work position comprise a push member which is movable with respect to the retaining member, cooperates with the door, and is functionally connected to the retaining member; the push member is supported to slide between a first and a second operating position, and is provided integral with a rack meshing with a ring gear integral with the retaining member, which is hinged, at an intermediate point between a first and a second of its own ends, about an axis perpendicular to the travelling direction of the push member. 
     The rotary member is defined by a wheel having a number of lobes separated by respective gaps; the wheel rotates about an axis perpendicular to both the axis of rotation of the retaining member and the travelling direction of the push member; and the wheel lies in a plane parallel to and different from that containing the axis of rotation of the retaining member, and is located, with respect to the retaining member, so that, in the second angular position, one lobe occupies the same position as the second end of the retaining member in the rest position, and rests against the second end of the retaining member in the work position. 
     The resulting door blocking device is thus highly compact, comprises very few moving parts, and can be operated by a straightforward electromagnet which is inexpensive and highly reliable even in the presence of very high temperatures. Moreover, the wheel is rotated in the same direction to both engage and release the device, which means one or both of the high-cost microswitches of known pyrolytic oven door blocking devices can be eliminated. In other words, a door blocking device in accordance with the invention is so straightforward and compact as to be usable not only on pyrolytic ovens but also other types of electric household appliances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  shows a schematic, exploded, three-quarter front view in perspective of the door blocking device according to the invention; 
         FIG. 2  shows a schematic top plan view of the  FIG. 1  device fitted to a door of an electric household appliance shown only partly; 
         FIG. 3  shows a view in perspective, turned over 180° with respect to  FIG. 1 , of a component part of the  FIG. 1  device; 
         FIGS. 4 and 5  show schematic side views, from opposite sides and with parts removed for clarity, of the  FIG. 1  device as assembled. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     With reference to  FIGS. 1 to 5 , number  1  indicates as a whole a blocking device for a door  2  ( FIG. 2 ) of an electric household appliance—in the example shown, a known pyrolytic oven, of which, for the sake of simplicity, is shown only part of a casing  3  defining a door opening  4 , against which door  2  rests substantially in fluidtight manner in the closed position (the position shown) 
     Door blocking device  1  comprises a retaining member  10  movable, along a given path indicated by arrow T in  FIG. 2 , between a work position (shown by the continuous line in  FIG. 2 ), in which retaining member  10  cooperates in use with a known coupling member  8  of door  2  when the door is in the closed position shown, and a rest position (shown partly by the dash line in  FIG. 2 ), in which retaining member  10  does not cooperate in use with coupling member  8 , by being located, for example, at a distance from coupling member  8  of door  2  in the closed position. 
     Device  1  also comprises controlled-actuation means  11  ( FIG. 1 ) for controlled actuation of retaining member  10 , and which, according to the invention, comprise elastic means  13  for pushing retaining member  10  into the rest position; means, indicated as a whole by  14 , for moving retaining member  10 , as will be seen, into the work position in opposition to elastic means  13 ; a rotary member  15  having at least one peripheral, radially projecting lobe  16 ; and an electrically controlled actuator  18  for moving rotary member  15  selectively between a first angular position, shown by the continuous line in  FIGS. 1-5 , and a second angular position, shown schematically by the dash line in  FIG. 5 . 
     According to the main aspect of the invention, rotary member  15  is designed and located so that, in the first angular position of rotary member  15 , the at least one lobe  16  of the rotary member does not interfere with given path T travelled by retaining member  10  between the work position and the rest position, thus allowing retaining member  10  to move freely between the work and rest positions; whereas, in the second angular position of rotary member  15 , the at least one lobe  16  interferes with given path T, thus locking retaining member  10  in the work position in opposition to elastic means  13 . 
     Device  1  also comprises a support  20  which is fixed in use to door opening  4  of the electric household appliance ( FIG. 2 ), and which supports retaining member  10  and controlled-actuation means  11  for controlled actuation of retaining member  10 . Support  20  is preferably in the form of a substantially prismatic casing comprising at least two members  21 ,  22  ( FIG. 1 ) molded from synthetic plastic material and joined, e.g. clicked, to each other, and at least one of which—in the example shown, both—is cup-shaped or in the form of a half-shell. 
     According to a further aspect of the invention, means  14  for moving retaining member  10  into the work position comprise a push member  25 —in the form of a straight slide, in the example shown—which is connected functionally to retaining member  10 , is fitted to support  20  to move with respect to retaining member  10 , cooperates with and is moved by door  2  into a first operating position ( FIG. 2 ) when the door is moved into the closed position, and remains resting against door  2 , locked by the door in the first operating position, when door  2  is in the closed position. 
     More specifically, push member  25  is fitted in sliding manner to support  20 , and projects from a seat  26  formed in support  20  and facing door  2  in use. And push member  25  and retaining member  10  are connected functionally so that, when push member  25  is in the first operating position, housed in a withdrawn position inside seat  26 , retaining member  10  is in the work position; and, conversely, when retaining member  10  is in the rest position, push member  25  is secured in a second operating position (not shown), in which push member  25  is extracted from seat  26 , with an end  27 , facing door  2  in use, of the push member projecting from seat  26  by a greater amount than in the withdrawn position, so that end  27  contacts door  2 , as door  2  moves into the closed position (in the direction indicated by the arrow in  FIG. 2 ), long before door  2  contacts a corresponding first end  28  of retaining member  10  projecting from seat  26  on the side facing door  2  in use. 
     In the example shown, retaining member  10  is hinged to support  20  at an intermediate point or portion  30  not necessarily equidistant from end  28  and a corresponding opposite end  29  of retaining member  10 , so that ends  28 ,  29  are free to rotate in the same direction about an axis A defined, for example, by a pin  31 , extending crosswise inside seat  26  in such a position as not to interfere with the travel of push member  25  inside seat  26 , and perpendicular to the travelling direction of push member  25  indicated by arrow S in  FIG. 2 . 
     End  28  is hook-shaped to retain coupling member  8  in use; at intermediate point  30 , retaining member  10  has an integral ring gear  35  coaxial with axis of rotation A and meshing with a rack  36  integral with push member  25 ; and elastic means  13  comprise a torsion spring—helical in the example shown—fitted coaxially to and preferably preloaded on pin  31 , and which acts directly on retaining member  10 , pushing against support  20  (against member  21  in the example shown), to produce a torque in such a direction as to rotate retaining member  10  into (and, in the absence of other forces, to keep the retaining member rotated in) the rest position. 
     As shown by the dash line in  FIG. 2 , in the rest position, end  28  is parted apart with respect to end  27  of push member  25 , which is in the extracted position. 
     At the opposite end to end  27 , push member  25  ( FIG. 1 ) has a projecting L-shaped appendix  40  which cooperates in known manner ( FIG. 4 ) with a first microswitch  41 , housed in support  20 , to activate microswitch  41 , when push member  25  is fully withdrawn (except for end  27 ) inside seat  26 , and so obtain a “door closed” signal from microswitch  41 . 
     In the example shown, rotary member  15  is defined by a wheel having a number of radially projecting lobes  16  equally spaced and separated circumferentially by respective gaps  45 ; wheel  15  is fitted to support  20  to rotate about an axis B ( FIG. 1 ) perpendicular to both axis of rotation A of retaining member  10  and the travelling direction S of push member  25 ; and second end  29  of retaining member  10  is shaped to fit selectively, as will be seen, inside gaps  45  when retaining member  10  is in the rest position; for which purpose, wheel  15  is fitted to support  20  to lie in a plane parallel to and different from that containing axis of rotation A of retaining member  10 . 
     Wheel  15  selectively assumes said first and second angular position by rotating in the same direction by a fraction of a turn equal to the number of lobes  16  (i.e. the number of gaps  45 ), and is so located in support  20  and with respect to retaining member  10  that, in the second angular position, one of lobes  16  always occupies the same position (i.e. volumetric portion of space) otherwise occupied by end  29  when retaining member  10  is in the rest position. 
     The relative position of wheel  15  in support  20  is also such that, likewise, when wheel  15  is in the second angular position, one of lobes  16  rests against end  29  when retaining member  10  is in the work position, thus preventing elastic means  13  from rotating retaining member  10 . 
     Electrically controlled actuator  18  comprises an electromagnet  50 , an armature  51  of which acts on a first end  52  of a rocker arm  53  to oscillate the rocker arm in a given direction, and in opposition to a return spring  54 , whenever electromagnet  50  is energized; a second end  55 , opposite end  52 , of rocker arm  53  is in the form of a pawl, and cooperates with a serrated ring gear  58  fitted laterally to wheel  15 ; and end  55  and ring gear  58  thus form a known ratchet device  59  ( FIG. 1 ) for rotating wheel  15  by said fraction of a turn whenever electromagnet  50  is energized and oscillates rocker arm  53 . 
     With particular reference to  FIGS. 1 and 3 , a first face of wheel  15 , on the same side as lateral ring gear  58 , has a ring gear  70  having teeth equal in number to lobes  16  and shaped to cooperate with an elastic member  71 —in the example shown, in the form of a rectangular frame having projections  72  halfway along the major, and therefore more flexible, sides—which selectively clicks inside the gaps between the teeth on ring gear  70  to ensure correct angular positioning of lobes  16  or gaps  45  exactly at end  29 , regardless of the operating precision of ratchet device  59  and electromagnet  50 , which may thus be low-cost technology types. 
     A second face of wheel  15 , opposite the first and therefore on the opposite side to lateral ring gear  58  and ring gear  70 , has a circular track  80  defined by alternating projections and/or cavities  82 , possibly separated by flat portions, and equal in number to lobes  16 ; and a second microswitch  85 , housed in support  20 , cooperates ( FIG. 4 ) with circular track  80 , so as to be selectively activated/deactivated at each fraction of a turn of wheel  15 , and so as to obtain from microswitch  85  a signal indicating the presence (or absence) of a lobe  16  in the position shown by the dash line in  FIG. 5 . 
     The blocking device, described with non-limiting reference to application to a pyrolytic oven, operates as follows. 
     When door  2  is in the open position (not shown), the inside of the oven is accessible to the user through door opening  4 , and wheel  15  is in the first angular position described above, in which a gap  45  of wheel  15  is located between the bottom wall of cup-shaped member  21  of support  20  and retaining member  10  and is aligned beneath end  29 . In which condition, spring  13  is able to keep member  10  in the rest position, in which said gap  45  is engaged by end  29 , and end  28  is parted with respect to end  27  of member  25 . 
     When door  2  is pushed shut manually by the user (or by a servomotor), member  25  is pushed by door  2  into the withdrawn position, thus rotating member  10  by means of rack  36  and ring gear  35 , and so rotating end  28  towards end  27  to reduce and eventually eliminate the distance between the two, so that, when door  2  is finally closed, member  8  is engaged by end  28 . 
     This condition being reached, microswitch  41  is activated by appendix  40  to produce a signal, which is used by the electric household appliance to energize electromagnet  50  and rotate wheel  15  by a fraction of a turn as described above, so that, beneath end  29  (with reference to the bottom wall of member  21  of support  20 ), a gap  45  is replaced by a lobe  16 . This prevents the elastic reaction of spring  13 , even if no pressure is applied on door  2 , from rotating member  10  backwards, by virtue of end  29 , in that case, interfering with and resting against lobe  16  on the circular track  80  side. Door  2  is thus locked; and rotation of wheel  15  also activates microswitch  85 , which produces a consent signal to start the self-cleaning (pyrolysis) function of the oven. 
     Once the function is completed, the central control unit of the oven energizes electromagnet  50  again to again rotate wheel  15  by a fraction of a turn, so that lobe  16  is replaced by a gap  45  beneath end  29 ; and, end  29  no longer being retained by lobe  16 , spring  13  is free to rotate member  2  into the rest position, thus parting ends  28  and  27  and releasing member  8 . 
     In this condition, door  2  is no longer locked and, in fact, is pushed automatically into a position slightly detached from door opening  4 , thus opening the oven, by virtue of rotation of member  10 , by means of ring gear  35  and rack  36 , moving member  25  into the withdrawn position, so that door  2  is pushed by end  27  into the open position.