Abstract:
A door latch for an electrical household appliance includes a closing spring arrangement which is tensioned in an open position of the door latch and relaxes upon closing of the door, and a gripping unit which grips a closing element upon closing of the door and releases it again upon opening of the door. The gripping unit in the open position of the door latch is in blocking engagement with a blocking element owing to the force of the closing spring arrangement. The closing element upon the closing of the door causes a rotary movement of the gripping unit about an axis of rotation where the gripping unit comes out of blocking engagement with the blocking element enabling a relaxation of the closing spring arrangement. The force of the relaxing closing spring arrangement causes a subsequent pull-shut movement of the gripping unit. The gripping unit has a base body bearing at least one supporting projection, projecting coaxially with respect to the axis of rotation, for supporting the gripping unit. The closing spring arrangement has a spring active axis which intersects the supporting projection.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a door latch for an electrical household appliance such as, for example, a washing machine, dishwashing machine or tumble drier. 
         [0003]    2. Description of the Prior Art 
         [0004]    In relation to the prior art regarding door latches with pull-shut function, reference is made, for example, to DE 198 37 248 C2, U.S. Pat. No. 6,290,270 B1, US 2005/0194795 A1 and U.S. Pat. No. 6,390,518 B1. A common feature of these documents is the presence of a rotary member which has a gripping section (in the form of a mouth) for gripping a closing element plunging into an entry opening of the latch upon closing of the door and is rotatably mounted on a carrier component. The carrier component is, for example, a lever or a slide; in each case, in all four documents, a plurality of closing springs responsible for the pull-shut function of the latch engage on the carrier component, without exception at a location offset from the axis of rotation of the rotary member. 
       SUMMARY OF THE INVENTION 
       [0005]    In contrast, one embodiment of a door latch of the present invention includes a closing spring arrangement which is tensioned in an open position of the door latch and relaxes upon closing of the door, and a gripping unit which grips a closing element upon closing of the door and releases it again upon opening of the door. The gripping unit in the open position of the door latch is in blocking engagement with a blocking element owing to the force of the closing spring arrangement and thus preventing the relaxation of the closing spring arrangement. The closing element upon the closing of the door causes a rotary movement of the gripping unit about an axis of rotation. Upon this rotary movement, the gripping unit comes out of blocking engagement with the blocking element and thereby enables a relaxation of the closing spring arrangement. The force of the relaxing closing spring arrangement causes a subsequent pull-shut movement of the gripping unit. The gripping unit has a base body with a gripping section for gripping engagement with the closing element. The base body bears at least one supporting projection, projecting coaxially with respect to the axis of rotation, for supporting the gripping unit. 
         [0006]    One aspect of the invention provides that the closing spring arrangement has a spring active axis which intersects the supporting projection. Preferably, in each case one supporting projection projects axially on both sides from the base body, the closing spring arrangement having a spring active axis assigned to each supporting projection and intersecting the respective supporting projection. An arrangement of the closing spring arrangement relative to the gripping unit of this type makes it possible to dispense with a rotatable mounting of the gripping unit on a separate carrier component, which for its part is movably held in a housing of the latch. The closing spring arrangement can be supported on the supporting projection or the supporting projections directly or optionally with interposition of an intermediate member, this intermediate member of course providing no radial support for the gripping unit. Instead, each supporting projection rests on such an intermediate member or directly on a section of the closing spring arrangement. Without impairing the functionality and reliability of the door latch, the construction can thus be simplified and the expenditure involved with the production can be reduced. 
         [0007]    If an intermediate member is used, it can be produced from a low-friction material or provided with a friction-reducing coating, at least in that region where a supporting projection of the gripping unit rests against it. An example of a low-friction or friction-reducing material which can be used is Teflon. 
         [0008]    According to a further aspect of the invention, which can be provided alternatively or additionally to the above-explained relative position between the supporting projection and the spring active axis of the closing spring arrangement, the door latch can comprise a guiding arrangement for guiding the supporting projection during the pull-shut movement of the gripping unit. This guiding arrangement can form a rectilinear guiding path for the supporting projection, although it is not beyond the scope of the invention to provide a path course deviating from a straight line. For example, the guiding arrangement can have a guiding channel or a guiding slot, into which the supporting projection plunges for its guidance. 
         [0009]    Further aspects of the invention, which can be realised independently of the other aspects of the invention, provide that the closing spring arrangement is supported on the supporting projection without interposition of further elements or that alternatively the closing spring arrangement is supported on the supporting projection with interposition of an intermediate member, the supporting projection being radially unsupported in relation to the intermediate member. 
         [0010]    According to a preferred configuration, the supporting projection is connected in a rotationally fixed manner to the base body of the gripping unit. The supporting projection can, for example, be of peg-like (pin-like) form. According to one variant, the supporting projection is formed by a pin body which is separate from the base body and is inserted into a pin receptacle of the base body. The base body in this case can be produced from a plastics material, while the pin body is formed by a metal pin. According to another variant, the supporting projection can be formed integrally with the base body, it being possible, if desired, for the supporting projection to be reinforced by a reinforcing pin (e.g. made of iron or steel) surrounded by the material of the supporting projection. For example, the reinforcing pin can be encapsulated by injection-moulding of the material of the supporting projection around it. Alternatively, it is conceivable to produce the supporting projection with an insertion hole, into which the reinforcing pin can subsequently be inserted. 
         [0011]    According to one embodiment, in each case one supporting projection projects axially on both sides from the base body, the closing spring arrangement comprising in each case one helical compression spring assigned to each supporting projection. 
         [0012]    According to another embodiment, the closing spring arrangement can comprise at least one helical tension spring. In this regard, for example, a configuration can be envisaged in which in each case one supporting projection projects axially on both sides from the base body, the closing spring arrangement comprising in each case one helical tension spring segment assigned to each supporting projection, the two helical tension spring segments being part of a common helical tension spring curved in the manner of a U-shape. 
         [0013]    Expediently, the door latch has a latch housing, in which the gripping unit and the closing spring arrangement are accommodated. If desired, still further components can be accommodated in the latch housing, for instance components of a locking device, by means of which the gripping unit can be locked in a closing position of the door latch, so that the door latch cannot be opened. Such a locking device in its locked state can block, for example, the gripping unit against a movement opposite the pull-shut movement. 
         [0014]    The latch housing can also have an entry opening, into which the closing element plunges upon closing of the door and through which the closing element strikes the gripping unit. 
         [0015]    Particularly in the absence of a carrier component rotatably supporting the gripping unit about an axis of rotation, it can be advantageous when the latch housing has at least one guiding shaft formed therein for receiving at least a part of a helical spring associated with the closing spring arrangement. The guiding shaft can be an integrally formed-on part of the latch housing. Guiding formations for guiding the supporting projection during the pull-shut movement of the gripping unit can also be formed on this guiding shaft, for instance in the form of a guiding slot made in the shaft wall or a guiding channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows, in perspective, components of a door latch according to a first embodiment. 
           [0017]      FIG. 2  shows, in a perspective view, the door latch according to the first embodiment with a latch housing. 
           [0018]      FIGS. 3A and 3B  show sectional views of the door latch according to the first embodiment in an open position and a closed position of the latch, respectively. 
           [0019]      FIG. 4  shows, enlarged, a detail of the door latch according to the first embodiment in the closed position of the same. 
           [0020]      FIG. 5  shows a plan view of a door latch according to a second embodiment. 
           [0021]      FIG. 6  shows a perspective view of the door latch according to the second embodiment. 
           [0022]      FIG. 7  shows, in perspective, a door latch according to a third embodiment. 
           [0023]      FIG. 8  shows, in perspective, individual components of the door latch according to the third embodiment. 
           [0024]      FIG. 9  shows a section through the door latch according to the third embodiment in an open position of the same. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Reference is first made to  FIGS. 1 to 4  and the first embodiment, shown therein, of a door latch generally denoted by  10 . The door latch  10  is provided for installation in a washing machine, a dishwashing machine or a tumble drier of the household equipment and serves to keep the door of the household appliance concerned closed. The door latch  10  has a latch housing  12  having an entry opening  14  for a closing element  16  which travels into the entry opening  14  upon closing of the door, the entry direction  14  being indicated in  FIGS. 2 and 3   a  by a direction arrow  18  in each case. Passing through the closing element  16  in the region of its leading end is a cutout  20 , leaving at the front end of the closing element  16  a cross-piece  22  which can be grasped and firmly held by a gripping unit  24  received in the latch housing  12 , in order thus to keep the door of the household appliance in the closed state. 
         [0026]    The closing element  16  can be arranged, for example, on the door of the household appliance, while the latch housing  12  with the components accommodated therein can be mounted on a main body of the household appliance, on which the door is usually pivotably fitted. It will be understood that the manner of arranging the closing element  16  and the latch housing  12  can also be reversed if desired, that is to say the closing element  16  can be fitted on the main body of the household appliance and the latch housing  12  can be fitted on the door. 
         [0027]    In addition to the gripping unit  24 , an arrangement of a plurality of (here two) closing springs  26  is accommodated in the latch housing  12 , which springs are tensioned in the open position of the latch (i.e. when the door is open) and relax upon closing of the door and thereby bring about a pull-shut movement of the gripping unit  24 , by which the gripping unit  24  is pushed approximately in the direction of the arrow  18  deeper into the latch housing  12 , i.e. away from the entry opening  14 . Simultaneously with this pull-shut movement of the gripping unit  24 , the door of the household appliance is pulled shut, which is comfortable for the user, since the forces required to compress an optionally present door seal do not have to be produced completely by the user him- or herself, but are at least partly provided by the closing springs  26 . In the exemplary case shown of the first embodiment, a total of two closing springs  26  are provided, which are both formed as helical compression springs. 
         [0028]    The gripping unit  24  forms a gripping mouth (gripping section)  28 , into which the closing element  16  plunges with its front cross-piece  22 . The gripping mouth  28  is bounded by two jaws  30 ,  32  opposite one another. In the open position of the door latch, the gripping mouth  28  is open towards the entry opening  14  (cf. illustration in  FIG. 3   a ), so that the closing element  16  can travel into the gripping mouth  28 , striking with its cross-piece  22  against the jaw  30  and thereby imparting a rotary movement about an axis of rotation  34 . In the course of this rotary movement, the other jaw  32  plunges into the cutout  20  of the closing element  16 , so that the cross-piece  22  is finally caught in the gripping mouth  28  of the gripping unit  24  (cf. the illustration in  FIG. 3   b ). 
         [0029]    The gripping mouth  28  is formed on a base body  36  of the gripping unit  24 , from which two supporting projections  38 , which are pin-shaped in the exemplary case shown, project along the axis of rotation  34  axially on both sides. As can be seen in particular in  FIG. 1 , the supporting projections  38  are arranged coaxially with respect to the axis of rotation  34 . In the case of the first embodiment, the supporting projections  38  are formed materially integrally with the base body  36  of the gripping unit  24 , preferably as a plastics injection-moulded part. The supporting projections  38  are in this case connected in a rotationally fixed manner to the base body  36 . If desired, a metal reinforcing pin can be located in the interior of the supporting projections  38 , which reinforcing pin, for example, can be placed in the injection mould upon injection-moulding of the gripping unit  24  or can be inserted into a hole formed in the supporting projections  38 . The reinforcing pin mentioned can extend from one supporting projection  38  through the base body  36  to the other supporting projection  38 ; of course, it is alternatively conceivable to provide separate reinforcing pins for each of the supporting projections  38 . 
         [0030]    According to an alternative configuration, not illustrated specifically, the supporting projections  38  can be formed by a separate supporting pin which is produced separately from the base body  36  of the gripping unit  24  and is inserted through a through-hole of the base body. A separate supporting pin of this type can be connected in a rotationally fixed manner to the base body  36 , for example, by form fit or friction fit. Of course, it is not beyond the scope of the invention to design the supporting projections  38  rotatably relative to the base body  36  (about the axis of rotation  34 ). 
         [0031]    The latch housing  12  forms for each of the closing springs  26  a guiding shaft (guiding pot)  40 , into which the respective closing spring  26  is inserted. The diameter of each guiding shaft  40  preferably corresponds substantially to the outside diameter of the respective closing spring  26 , so that the latter is seated substantially without radial play in its guiding shaft  40 . In the illustration of  FIG. 2 , only one of the guiding shafts  40  can be clearly seen; the other is largely hidden owing to the perspective chosen and is therefore not separately denoted. 
         [0032]    The closing springs  26  seated in the guiding shafts  40  are supported at one of their spring ends on the housing  12 . At their other spring end, they are supported directly on in each case one of the supporting projections  38  in the exemplary case shown. The closing springs  26  here are arranged such that their spring axes—denoted by  42  in FIG.  1 —intersect the respective supporting projection  38 . In other words, the supporting projections  38  rest so to speak centrally on the closing springs  26  (centrally with respect to the coil centre of the closing springs  26 ). 
         [0033]    Alternatively, it is conceivable to insert between the supporting projections  38  and the closing springs  26  in each case one intermediate member (not illustrated specifically), for instance in the form of an end cap placed on the respective spring end or a slide shoe placed on the respective spring end. The supporting projections  38  are supported in this case on the intermediate members, the support still being provided by merely resting on without use of a radial bearing surrounding the respective supporting projection all around. An intermediate member between the supporting projections  38  and the closing springs  26  can be advantageous particularly when the supporting projections  38  are connected in a rotationally fixed manner to the base body  36  of the gripping unit  24  and upon rotation of the gripping unit  24  therefore frictional forces may arise between the supporting projections  38  and the closing springs  26 . For this purpose, the intermediate member can be coated, for example, with Teflon or another suitable low-friction material. 
         [0034]    The active direction of the closing springs  26 , i.e. the direction of their spring axes  42 , runs substantially parallel to the entry direction  18  of the closing element  16 . In the open position of the door latch according to  FIG. 3   a  (corresponding to a release position of the gripping unit  24 ), the tensioned closing springs  16  push the gripping unit  24  into blocking engagement with a blocking element  44  formed in the case of the first embodiment by a part of the latch housing  12 . In the open position of the latch, the gripping unit  24  is supported on this blocking element  44  via a contact surface  46  formed on the base body  36 . In the exemplary case shown, the contact surface  46  is designed approximately in the form of a circular arc and allows a rotary movement of the gripping unit  24  about the axis of rotation  34  clockwise (with respect to the viewpoint of  FIG. 3   a ) without substantial translatory displacement of the gripping unit  24 . Such a rotary movement of the gripping unit  24  takes place—as mentioned—upon closing of the door, as soon as the closing element  16  strikes with its front cross-piece  22  the jaw  30  and thereby sets the gripping unit  24  in rotation. Upon this rotation, the contact surface  46  slides on the blocking element  44  until a sliding edge  48 , at which the peripheral line of the base body  36  turns abruptly radially inwards from the contact surface  46 , passes the blocking element  44 . This allows the closing springs  26  to relax. In doing so, the gripping unit  24  slides under the action of the relaxing closing springs  26  substantially along the direction of the arrow  18  further away from the entry opening  14 . Since at this stage the cross-piece  22  of the closing element  16  is caught in the gripping mouth  18  of the gripping unit  24 , the closing element  16  is drawn along upon this slipping movement of the gripping unit  24 . The door of the household appliance is thus closed tightly. The sliding movement of the gripping unit  24  can also be referred to as a pull-shut movement of the door, since it brings about a pulling-shut of the door. The closing position of the latch is shown in  FIG. 3   b ; it corresponds to a gripping position of the gripping unit  24 . In this state, the gripping unit  24  can be supported on the blocking element  44  or another part of the latch housing  12 . 
         [0035]    The pull-shut movement of the gripping unit  24  is preferably a linear movement which is guided by guiding formations formed on the latch housing  12 . In the first embodiment, these guiding formations are formed in the region of the guiding shafts  40 , in which the closing springs  26  are received. The supporting projections  38  reach transversely through the guiding shafts  40 . They are each guided at their free ends in a guiding channel  50 , relative to which the wall of the respective guiding shaft  40  is recessed. At the place where the supporting projections  38  enter the guiding shafts  40 , the wall of each guiding shaft  40  can additionally have an elongate slot  52  (shown in  FIG. 2 ), which can likewise serve to guide the supporting projections  38  and thus to guide the gripping unit  24  as a whole. 
         [0036]    To open the door latch, the user pulls on the door of the household appliance. This produces a force on the gripping unit  24  opposite the direction of the pull-shut movement of the gripping unit  24 . The gripping unit  24  thus moves, under ever-increasing tension of the closing springs  26 , in the direction towards the entry opening  14  until the contact surface  46  can snap in front of the blocking element  44 . This snapping movement can be brought about or assisted, for example, by a pretensioning spring (not illustrated specifically) which pretensions the gripping unit  24  anticlockwise from the viewpoint of  FIG. 3   b . The state according to  FIG. 3   a  then results again, an arresting lug  54  formed on the base body  36  limiting the reverse rotation of the gripping unit  24 . The angle of rotation covered by the gripping unit  24  between its release position and its gripping position is denoted by D W  in  FIG. 4 . The translatory travel of the gripping unit  24  upon its pull-shut movement is denoted by T L  in  FIG. 4 . 
         [0037]    In the further figures, identical or identically acting components to those in the first embodiment are denoted by the same reference symbols as previously, but supplemented by a small letter. Unless otherwise stated below, reference is made to the above statements for explaining such identical or identically acting components. 
         [0038]    The second embodiment shown in  FIGS. 5 and 6  differs from the first embodiment essentially by a different configuration of the latch housing  12   a , this latch housing  12   a  in the second embodiment providing additional space for accommodating components of a locking device, generally denoted by  56   a , for selectively locking and unlocking the gripping unit  24   a  in its gripping position. The locking device  56   a  is electromagnetically actuated and has a simple-acting electromagnet  58   a  which is to be pulse-actuated by a control unit (not illustrated specifically) and the armature of which is coupled to a linearly movable locking bar  60   a . A continuous-encircling slotted guide path  62   a , in which a finger  64   a  mounted on the latch housing  12   a  engages, is formed on the locking bar  60   a . The slotted guide path  62   a  defines two holding positions, into which the finger  64   a  is alternately moved upon successive actuations of the electromagnet  58   a . One of these holding positions corresponds to a locking position of the locking bar  60   a , and the other to an unlocking position of the locking bar  60   a . In the locking position, the locking bar  60   a  blocks a reverse rotation of the gripping unit  24   a  into the release position, so that the door of the household appliance cannot be opened. 
         [0039]    Reference is now made to the third embodiment illustrated in  FIGS. 7 to 9 . This embodiment differs from the two preceding embodiments by the provision of a helical tension spring as the closing spring  26   b , in the specific case there being provided a single tension closing spring  26   b  which is curved in the manner of a U-shape and the U-limbs of which each form a spring segment  26   b ′,  26   b ″ engaging on a supporting projection  38   b . The tension spring segments  26   b ′,  26   b ″ are hooked onto their respective supporting projection  38   b ; their active axes  42   b  (cf.  FIG. 7 ) intersect the supporting projections  38   b  as in the preceding embodiments. The direction of the spring force exerted by the closing spring  26   b  on the gripping unit  24   b  corresponds to the active direction of the compression closing springs employed in the first two embodiments. 
         [0040]    The closing spring  26   b  is supported in its middle part on a supporting arch  66   b  formed on the latch housing  12   b . This middle part is illustrated without coils in  FIGS. 7 and 8  for reasons of drawing simplicity; it will be understood, however, that the closing spring  26   b  is constructed from helical coils continuously from one spring end to the other. 
         [0041]    As an alternative to a single tension closing spring curved in a U-shape, it is conceivable to provide separate tension closing springs which are each hooked onto one of the supporting projections  38   b.    
         [0042]    A further difference compared with the previous two embodiments is the configuration of the blocking element  44   b  in the third embodiment. This blocking element is formed here by a rolling bearing which is arranged on an axle pin  68   b  held on the latch housing  12   b . Such a configuration of the blocking element  44   b  ensures particularly low friction which is to be overcome upon the rotation of the gripping unit  24   b . It will be understood that such a configuration of the blocking element may also be employed in the previous embodiments. Conversely, a suitably formed piece of the latch housing  12   b  may also serve as the blocking element  44   b  in the third embodiment. 
         [0043]    Otherwise, the functioning of the third embodiment corresponds to that of the first and second embodiment. 
         [0044]    Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.