Patent Publication Number: US-6334637-B1

Title: Locking and unlocking device for the door of a domestic electrical appliance

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a locking and unlocking device for the door of a domestic electrical appliance, such as a washing machine or a washing and drying machine. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a locking and unlocking device whose construction is simplified, that can be produced economically with a limited number of parts and components and that is nevertheless able to ensure highly reliable operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and characteristics of the invention will become clear from the following detailed description, provided purely by way of non-limiting example and given with reference to the appended drawings in which: 
     FIG. 1 is a front view of a locking and unlocking device of the invention; 
     FIG. 2 is a side view of the device of FIG. 1; 
     FIG. 3 is a cross-section, on an enlarged scale, along the line III—III of FIG. 2; 
     FIG. 4 is a sectional view, along the line IV—IV of FIG. 3; 
     FIG. 5 is a view partly in section along the line V—V of FIG. 3; 
     FIGS. 6 and 7 are views similar to that of FIG. 4, and show the device in other operating conditions; 
     FIG. 8 is a view similar to that of FIG. 5, and shows part of the device in the operating condition to which FIG. 7 refers; 
     FIG. 9 is an electrical diagram of the device shown in the preceding drawings; 
     FIG. 10 is a view similar to that of FIG.  3  and shows a variant; 
     FIG. 11 is a sectional view along the line XI—XI of FIG. 10; and 
     FIG. 12 is an electrical diagram of the device of FIGS.  10  and  11 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIGS. 1 and 2, a locking and unlocking device of the invention is shown overall by  1 . 
     This device comprises a support housing  2 , of electrically insulating material, adapted to be secured to the body of a domestic electrical appliance, in the vicinity of a loading or access opening associated with a door P (FIG. 2) provided in a manner known per se with a hook member A. In the embodiment shown, the support housing  2  is formed by two half-shells  3  and  4  which are coupled together (FIGS.  2  and  4 ). 
     As shown in FIG. 1, the housing  2  of the device  1  has an opening  5  for the introduction of the hook member A borne by the door. 
     A retaining member or slide  6  provided with a window opening  7  adapted to be traversed by the hook member A is mounted to slide in the support housing  2  of the device  1 . 
     When the door P is open (FIG.  2 ), the retaining member  6  is held (by an associated spring which is not shown) in a rest position (FIG. 1) in which its window  7  faces the opening  5  of the housing  2 . In this position, the hook member A of the door may be introduced into the opening  5  and the window  7  when the door is closed and, vice versa, may be disengaged from this window and from this opening when the door is opened. 
     As shown in FIGS. 1 and 4, when the retaining member or slide  6  is in the rest position, it covers an opening  8  provided in the upper half-shell  3  of the support housing  2 , into which a locking member  9  may be extended in translation. 
     In a manner known per se, the device is such that when the door is closed, the hook member A engages with the opening or window  7  of the retaining member or slide  6  and causes the latter to move in translation (to the right with respect to the FIGS. 1 or  4 ) in order to release the opening  8 , as shown in FIG.  6 . 
     With reference to FIG. 3, a switch, shown overall by  10 , is disposed within the lower half-shell  4  of the housing  2 . This switch comprises a fixed contact  11  borne by a shaped metal member  12 , one end  12   a  of which is shaped as a flat pin that extends, as a connection terminal, into a hollow seat  18  of the support housing (FIG.  3 ). 
     The switch  10  further comprises a moving contact  13  (FIGS. 4,  6  and  7 ) borne by one end of a metal plate  14 , the other end of which is disposed above a shaped metal member  15  (FIG. 3) and is permanently connected with the latter to the support housing, for instance by means of a rivet  16 . 
     The end of the plate  14  that bears the moving contact  13  extends below the fixed contact  11 . 
     A helical spring  17  (FIGS. 3 and 4) is interposed between the base wall of the support housing  2  and the intermediate portion of the plate  14 . This spring tends to urge the plate  14  upwards, and therefore the moving contact  13  towards the fixed contact  11 . 
     The end of the plate  14  that bears the moving contact  13  is engaged in a lateral seat or heel  9   b  of the locking member  9 , as can be seen for instance in FIGS. 4 and 6. Consequently, the spring  17  also tends to urge the locking member  9  from the lowered or disengaged position of FIGS. 4 and 6 towards a raised or engaged position shown in FIG. 7, in which this locking member protrudes partially from the opening  8  and is disposed in the path of the retaining member or slide  6 , preventing it from returning to the rest position in which it enables the door P to be opened. 
     The metal connection member  15  forms a projection or end  15   a  (FIG. 3) shaped as a flat pin, which extends into the seat  18  of the support housing and acts as a connection terminal. 
     As can be seen for instance from FIG. 4, the locking member  9  has a lower radial projection  9   a  on the side opposite the plate  14 . This projection cooperates, as will be explained below, with a cam or toothed profile of a toothed wheel  20  mounted to rotate in the support housing about a pin  21 , adjacent to the locking member  9 . The toothed wheel  20  is conveniently made from plastic material. It may be monolithic or—for simplicity of moulding—may be made in two parts glued or otherwise fixed together. The upper portion of the wheel  20  comprises saw teeth  22 , while the lower portion of this wheel comprises a plurality of cams or front teeth  23  equally angularly spaced and separated by intervals  24  (FIG.  5 ). 
     In a preferred embodiment, the teeth  23  have a trapezoidal/rectangular shape, with one side or flank inclined and the other side or flank straight. 
     In the embodiment shown by way of illustration, the wheel  20  has twelve saw teeth  22  and four lower teeth  23 . The amplitude of the intervals  24  between consecutive teeth  23  is slightly smaller than the angular field corresponding to two adjacent saw teeth  22 . The arrangement is such that when the radial projection  9   a  of the locking member  9  extends below a cam or tooth  23  of the wheel  20 , the locking member  9  is held in the lowered or disengaged position, against the action of the spring  17 , as shown in FIGS. 4 to  6 . 
     When, however, following an angular displacement, the wheel  20  presents the radial projection  9   a  of the locking member  9  with an interval  24  between two consecutive teeth or cams  23 , the locking member  9  is able to move into the forward engaged or locking position under the action of the spring  17 , as shown in FIGS. 7 and 8. 
     An electrically controlled actuator is shown overall by  25  in FIG.  3 . In the embodiment shown by way of illustration, this actuator comprises a coil or solenoid  26  within which a core  27 , one of whose ends is connected to a rod  28 , is mounted such that it can move in axial translation. The end of the rod  28  opposite the core  27  is disposed in a hollow seat of a shaped member shown overall by  29 . The median portion of this member has an eyelet opening  30  into which a fixed pin or peg  31 , rigid with the support housing of the device, extends. 
     The end  29   a  of the member  29  opposite the actuator  25  is hook-shaped and engages between a pair of consecutive saw teeth  22  of the wheel  20 . 
     A pawl  32  is mounted to oscillate about a fixed pin  33  and is also engaged between a pair of consecutive saw teeth of the toothed wheel  20 , under the action of a helical spring  34  interposed between this pawl and the end of the shaped member  29  adjacent to the actuator  25 . 
     The arrangement described above is such that each time the actuator  25  is excited, the core  27  moves in translation (upwards with respect to FIG. 3) and via the rod  28  causes a displacement of the shaped member  29 , which in turn causes the toothed wheel  20  to rotate by one step, i.e. by a distance corresponding to one saw tooth  22 . Once this angular displacement has taken place, the pawl  32  again stabilizes the angular position of the toothed wheel  20 . 
     In the embodiment of FIG. 3, the winding or solenoid  26  of the electromagnetic actuator has its terminals connected to a shaped electrically conducting member  35  and respectively to the connection member  12 ,  12   a  via a conducting bridge  36 . 
     Conveniently, although not necessarily, the shaped connection member  35  may be connected to a conducting member  37 , having an end that extends into the hollow seat  18  of the housing of the device and is shaped as a flat pin in order to act as a connection terminal. A positive temperature coefficient (PTC) resistor, shown by  38  in FIGS. 3 and 9, is preferably interposed between the connection members  35  and  37 . This resistor advantageously makes it possible automatically to limit the intensity of the current supplied to the coil of the electromagnetic actuator  25  when the duration of supply of this current exceeds a predetermined time. The use of the PTC resistor  38  therefore makes it possible to use an electromagnetic actuator  25  provided with a small-dimension and relatively economic coil  26 . 
     The operation of the locking and unlocking device described above is as follows. 
     When the door P is opened, the locking and unlocking device  1  is in the condition shown in FIGS.  4  and  5 : the locking member  9  is “covered” by the retaining member or slide  6  and is held in the retracted disengaged position under the action of a trapezoidal tooth or cam  23  of the toothed wheel  20  which is disposed on the radial projection  9   a  of this member (FIG.  5 ). 
     When the door P is closed, as mentioned above, the slide  6  moves in translation and “uncovers” the locking member  9 . At this stage, the locking member  9  is nevertheless held in the retracted disengaged position by the toothed wheel  20  which is still in the same position as in the previous stage. 
     When the user of the domestic electrical appliance sets this appliance to operate, a control unit of the domestic electrical appliance causes the excitation of the actuator  25  in a manner known per se. As a result of this excitation, the member  29  causes the toothed wheel  20  to rotate by an amount equivalent to the angular extension of a tooth  22  of this wheel. The latter is then disposed in the position shown in FIGS. 7 and 8, in which the lower portion of this wheel presents the radial projection  9   a  of the locking member  9  with an interval  24  between two consecutive trapezoidal teeth or cams  23 . Consequently, the locking member  9  is brought into the forward engaged position (FIG. 7) as a result of the thrust exerted by the spring  17  on the plate  14 . At the same time, the contact  13  is brought against the fixed contact  11 , i.e. the switch  10  is closed. When the locking member  9  is in the forward position, the retaining member or slide  6  is prevented from returning to the rest position in which it enables the door P to be opened. 
     At the end of the operating cycle of the domestic electrical appliance, in order to enable the door to be opened, the control unit of the appliance causes two successive excitation pulses to be supplied to the coil  26  of the electromagnetic actuator  25 . As a result of this, the toothed wheel  20  is caused to rotate by a distance corresponding to the extension of two of its saw teeth. This rotation causes the radial projection  9   a  of the locking member  9  to be engaged by a new trapezoidal tooth or cam  23  of this wheel. The locking member  9  is thus brought back into the retracted or disengaged position shown in FIGS. 5 and 6, in which it again allows the retaining member or slide  6  to return to the position in which the door can be opened. 
     When the locking member  9  is returned, as described above, into the retracted disengaged position, it simultaneously causes the opening of the switch  10 . 
     As a result of the two excitation pulses needed to enable unlocking, the operation of the device described above is particularly reliable and makes it possible to prevent unlocking from being enabled following an accidental excitation of the actuator  25  due, for instance, to any electromagnetic disturbance that is picked up. The device may, moreover, be configured such that a single excitation pulse needs to be supplied to the electromagnetic actuator  25  for unlocking. In this case, the lower portion of the toothed wheel  20  will obviously have a different number of trapezoidal teeth or cams for the control of the position of the moving member  9 . 
     In any case, in order to enable the door to be unlocked and therefore opened in the event of a discontinuation of the mains current supply, for instance during a power cut, a cable member, such as the member  40  shown in dashed lines in FIG. 3, can be connected to the member  29  such that traction on this cable member causes, via the member  29 , the rotation of the toothed wheel  20 . 
     As an alternative, a flexible traction member may be coupled directly to the moving locking member  9  so as to enable this member to be returned to the retracted position in which it enables the door to be opened. 
     FIGS. 10 to  12  show a variant of the device described above. In these drawings, parts and components already described bear the same reference numerals. 
     In the embodiment of FIGS. 10 to  12 , the plate  14  is not a simple metal plate, but a bimetallic plate. Rather than a helical spring, a positive temperature coefficient resistor shown by  50  is disposed below this plate. This resistor  50  bears on a shaped electrically conducting member  51 , one end  51   a  of which is shaped as a flat pin and extends into the seat  18  for connection to the control unit of the domestic electrical appliance. 
     A helical spring  52  (FIG. 11) is disposed between the upper half-shell  3  of the support housing of the device and the bimetallic plate  14 , at the location of the PTC resistor  50 . This spring ensures that the bimetallic plate  14  remains permanently in contact with the resistor  50 . 
     In the embodiment of FIGS. 10 to  12 , the solenoid  26  of the electromagnetic actuator  25  is connected on one side to the shaped conducting member  51  and on the other side to a further connection member  52 , ending in a flat pin  52   a  which extends into the seat  18 . 
     The operation of the device of FIGS. 10 to  12  is similar to that of the device described with reference to the preceding drawings, with respect to which it differs in the following respects. 
     When the domestic electrical appliance is set to operate and the control unit of this appliance supplies an excitation pulse to the actuator  25 , the toothed wheel  20  frees the radial projection  9   a  of the locking member  9 , as shown in FIG.  8 . However, the locking member  9  initially continues to be held in the retracted disengaged position until the PTC resistor  50  reaches a temperature sufficient to cause the switching of the bimetallic plate  14  so as to close the line switch  10  and thus urge the locking member  9  into the forward engaged position. 
     At the end of the operating cycle of the domestic electrical appliance, following one or more excitation pulses supplied to the actuator  25 , the toothed wheel  20  causes the locking member  9  to be lowered and the door P can then be immediately opened, in contrast to conventional PTC and bimetallic plate devices with which the door can be opened only after the PTC resistor has cooled down. 
     If the current supply is discontinued during an operating cycle of the domestic electrical appliance, the device of FIGS. 10 to  12  enables the door P to be opened without the need for flexible traction members. When the current supply fails and as soon as the PTC resistor  50  has cooled down, the bimetallic plate  14  returns to its rest position, lowering the locking member  9  and opening the line switch  10 . 
     Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, which have been given purely by way of non-limiting example, without thereby departing from the scope of the invention as set out in the accompanying claims.