Patent Publication Number: US-7210711-B2

Title: Door lock

Description:
DESCRIPTION 
   1. Field of the Invention 
   The present invention relates to a door lock for electrical household appliances, such as washing machines, dishwashers and tumble driers, for example. In particular, the present invention relates to a door lock for electrical household appliances in which the acting forces required for opening and closing the door lock for full opening and closing procedures of an appliance door essentially correspond to one another. 
   2. State of the Art 
   A disadvantage in known door locks for household appliances, as are described, for example, in DE 195 40 843 C2 and DE 198 37 248 C2, is that the forces required for a full opening procedure of an appliance door (i.e. a transition of the door lock from the closed position to the open position) are greater than the forces required for a closure (i.e. a transition from the open position to the closed position). 
   The different forces for opening and closing the door lock result, amongst other things, from the fact that appliance doors of electrical household appliances are usually prestressed in an open state, i.e. in the open position of the door lock, in such a manner that the appliance door and therefore the door lock close automatically. If the angle of opening falls short of a predetermined angle of opening for the appliance door, so that a snap point for the door lock is reached, closing forces are generated by the door lock, which suffice to fully close the appliance door without any forces having to be applied by a user. Furthermore, in the closed position of the door lock, i.e. in the closed state of the appliance door, a large force is usually present in order to reliably lock the appliance door. These holding-shut forces existing in the closed position are typically so great that a door seal for the appliance door is compressed, in order to prevent, for example, the undesirable escape of water in the case of washing machines and dishwashers or heated air in the case of tumble driers. 
   When opening the appliance door, a user is required to apply forces in order to overcome the holding-shut and closing forces of the door lock, until the snap point is reached. 
   A disadvantage here is that a force-path function results for the forces acting upon the door lock, which comprises a hysteresis at least for the closing and holding-shut forces, which are generated by the door lock during the closing procedure after overcoming the snap point, and for the forces which need to be applied by the user during the opening procedure until the snap point is reached. Since the closing and holding-shut forces generated by the door lock are great, as described above, an opening of the appliance door is uncomfortable for a user. 
   A further disadvantage consists in that the force-path function generally comprises a hysteresis over the entire opening and closing paths, which are normally of equal length. This means that forces need to be applied by a user even after overcoming the snap point of the door lock in order to achieve a full opening procedure. 
   In order to remedy this problem, it is known to use a servomotor, which is activated prior to opening the door lock and which, as a result of the forces which it supplies, allows for a reduction in the opening forces which need to be applied by a user. This structurally complex and expensive solution is susceptible to faults, since the servomotor and components required for its operation need to be arranged in an appliance door together with the door lock. Consequently, incorrect closing procedures of the appliance door (“slamming” of the appliance door) can result in damage. Furthermore, this arrangement increases the weight of the appliance door and as a consequence of the additional space requirement can result in increased dimensions of the appliance door. Accordingly, this solution is not suitable for appliance doors in which the weight and/or the dimensions are to be minimised. 
   OBJECT OF THE INVENTION 
   It is the object of the present invention to provide a door lock whose force-path function for forces acting on the door lock does not exhibit a hysteresis or at least exhibits a minimised hysteresis for at least those sections in which forces need to be applied by a user during an opening procedure. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The solution according to the invention is based upon the knowledge that in door locks, as are known for example from DE 195 40 843 C2 and DE 198 37 248 C2, the above-described undesirable hysteresis of the force-path function can be avoided or at least minimised if the (frictional) forces acting during transitions from open positions to closed positions and vice versa are minimised and/or avoided. In this respect, it is the object of the present invention to at least reduce (frictional) forces acting in bearings for rotatable components of door locks and/or between surfaces displaceable relative to one another. In this manner, it is attained that forces required for a transition from a closed position to an open position essentially correspond to forces required for a transition from the open position to the closed position. 
   Proceeding from the door lock according to DE 198 37 248 C2, the present invention provides a door lock with a contact region and a gripping device, which comprises an active region. The active region is shaped in such a manner that, in combination with the contact region, the active region holds the gripping device and therefore the door lock in an open position and a locked position. Furthermore, the gripping device and in particular the active region are shaped in such a manner that the gripping device, which in the open position contacts the contact region, loses contact with the contact region during a transition from the open position to the closed position, and during a transition from the closed position to the open position the contact is produced (again). 
   According to the invention, the contact region and/or the active region are constructed in such a manner that the forces required in order to effect a transition from the closed position to the open position essentially correspond to forces required for a transition from the open position to the closed position. 
   As will be explained in the following, this is attained in that the friction occurring between the contact region and the active region and the forces resulting therefrom are minimised at least during a transition from the closed position to the open position. Preferably, a comparable reduction in friction occurring during transitions from the open position to the closed position and forces resulting therefrom is also provided. Thus, frictional forces occurring during a transition from the closed position to the open position are attained, which essentially correspond to frictional forces occurring during a transition from the open position to the closed position. 
   The contact region can be provided on a circumferential line of a rotatably mounted axle or on a circumferential line of a bearing fitted so as to be rotatable relative to an axle. The minimisation of the friction obtained as a result of the rotatable characteristic of the axle or the bearing can be improved by a suitable selection of the surface composition of the contact region and/or of the active region. 
   The desired minimisation of friction can also be attained by means of a device in the active region which is rotatable by contact with the contact region. To this end, one or more bearings (e.g. roller bearings, anti-friction bearings) can be fitted in the active region, which are rotated upon contact with the contact region and thereby minimise the friction between the corresponding regions of the active region and contact region. 
   In addition, a desirable force-path function for the door lock is obtained if the contact region and/or the gripping device are displaced relative to one another during a transition from the closed position to the open position in such a manner that the function provided by the contact region and the active region in order to maintain the closed position is lifted and resulting frictional forces between the contact region and the active region are minimised or prevented. 
   An example of the above is a door lock in which the gripping device is rotatable and comprises a recess and in which the contact region is provided on a circumferential line of a rotatably mounted axle. In the closed position, the axle is arranged in the recess and preferably contacts said recess in order to securely hold the door lock in the closed position. 
   In order to open the door lock, i.e. for a transition from the closed position to the open position, the gripping device and/or the axle are displaced relative to one another in such a manner that the axle moves away from the gripping device at least in the region of the recess and is preferably removed from the region of the recess. In this manner, at least the friction and (contact) forces acting between the axle and the gripping device for transitions from the closed position are avoided. 
   In this respect, it is also possible to move the axle and/or the gripping device in such a manner that, during the transition from the closed position to the open position, forces acting between the contact region (axle) and the active region are (substantially) reduced. In this case, contact between the contact region (axle) and the active region is provided. 
   Furthermore, it is provided that the contact region and/or the gripping device are displaced relative to one another for a transition from the open position to the closed position in such a manner that the contact of the active region and the contact region for the open position is lifted. 
   If the gripping device is a gripping device rotatable about an axle, it is possible, as an alternative or supplement to the solutions stated above, to use a bearing arranged between the axle for the gripping device and the said gripping device in order to obtain the desired force ratios. 
   The use of a bearing between an axle of a pivotable closing lever, which is used for pivoting the gripping devices, also represents a solution according to the invention. 
   Proceeding from DE 195 40 843 C2, the invention provides a door lock in which a closing lever is mounted on a frame, which closing lever is pivotable back and forth between a closed position and an open position for the door lock. According to the invention, the mounting of the closing lever in the frame is designed in such a manner that the forces required during a transition from the closed position to the open position essentially correspond to forces required for a transition from the open position to the closed position. 
   Preferably, bearings (e.g. roller bearings, anti-friction bearings, ball bearings) are used to this end, which are arranged between the closing lever and the frame and are fitted, for example, on axle journals of the closing lever and/or bearing bores of the frame. 
   Alternatively or in addition to the above, the desired force ratios can be obtained for transitions from the stated positions for the door lock if a tensioning lever pivotably mounted on the frame is accordingly mounted. To this end, roller, ball and anti-friction bearings and other types of bearing can be arranged between the frame and the tensioning lever, which are fitted, for example, on axle journals of the tensioning lever and/or in bearing bores of the frame. 
   In a door lock of this type, a steering rod, which is hingedly connected to the closing lever at one end and at the other end is guided on the tensioning lever, is preferably connected to the closing lever in such a manner that frictional forces occurring during transitions from the closed position to the open position and during reverse transitions are minimised. A reduction in frictional forces of this type can be obtained by arranging anti-friction bearings, ball bearings or the like on axle journals of the steering rod and/or in bearing bores of the closing lever. 
   A further improvement can be obtained if the forces occurring during the guidance of the steering rod on the tensioning lever during actuation of the door lock are reduced. In this respect, in cases where the guidance of the steering rod on the tensioning lever is effected by means of crankpins of the steering rod in a guide groove of the tensioning lever, it is possible to arrange a ball bearing, anti-friction bearing or the like on the crankpins of the steering rod. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following description of preferred embodiments of the invention, reference is made to the attached drawings, in which: 
       FIG. 1   a  is a schematic illustration of an embodiment of a door lock according to the invention in the open position, 
       FIG. 1   b  is a schematic illustration of the embodiment of  FIG. 1   a  in the closed position, 
       FIG. 2   a  is a graph showing a force-path function of a door lock according to the state of the art, 
       FIG. 2   b  is a graph showing a force-path function of the door lock according to the invention from  FIGS. 1   a  and  1   b,    
       FIG. 3   a  is a schematic illustration of the embodiment of the gripping device according to the invention of  FIG. 1   a  in the open position, 
       FIG. 3   b  is a schematic illustration of the embodiment of the gripping device according to the invention of  FIG. 1   b  in the closed position, 
       FIGS. 4   a,    4   b  to 
       FIGS. 8   a,    8   b  are schematic illustrations of further embodiments of gripping devices according to the invention in the open position (a) and in the closed position (b), 
       FIGS. 9   a  to  9   e  are schematic illustrations of states of an embodiment of a displaceable gripping device according to the invention, 
       FIG. 10   a  is a schematic illustration of a further embodiment of a door lock according to the invention in the open position, 
       FIG. 10   b  is a schematic illustration of the embodiment of  FIG. 10   a  in the closed position, and 
       FIGS. 11 and 12  are perspective views of the embodiment of  FIG. 10   b.    
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   The door lock  1  shown in  FIG. 1   a  in an open position comprises a securing device  10  for receiving the components of the door lock  1  described in the following. The securing device  10  may be a stand, a frame or a housing, for example. Arranged in the securing device  10  so as to be pivotable about an axle  12  is a closing lever  14 . In the illustrated open position, a closing spring  16  is tensioned between the end of the closing lever  14  opposite the axle  12  and the securing device  10  in such a manner that the closing lever  14  is forced in an anti-clockwise direction in  FIG. 1   a.    
   A gripping device  18  described in detail in the following is accommodated so as to rotate about an axle  20 . The axle  20  is arranged between the end of the closing lever  14  contacting the closing spring  16  and the end of the closing lever  14  connected to the axle  12 . A torsion spring, not shown here, is connected to the gripping device  18  and exerts forces upon the gripping device  18  in order to at least support rotations of the gripping device  18  in a clockwise direction according to  FIG. 1 , as will be described below, or to exert rotary forces upon the gripping device  18  in a clockwise direction. 
   In an active region  22 , the gripping device  18  comprises two recesses  24  and  26 . The active region  22 , or more precisely the recesses  24  and  26 , are used to hold the gripping device  18  and therefore the door lock  1  in the open position shown in  FIG. 1   a  and in a closed position shown in  FIG. 1   b.    
   In order to provide this function of the gripping device  18 , an axle  28  is arranged on the securing device  10 . The axle  28  is rotatable about its longitudinal axis by means of suitable bearings (not shown) fitted to the securing device  10 . 
   The recess  24  is an eccentric indentation in the circumferential line of the gripping device  18 . The recess  24  is dimensioned and shaped as a function of the outer circumference of the axle  28  in the region of the gripping device  18  in such a manner that it contacts regions of the outer circumferential surface of the axle  28  in the region of the gripping device  18  in the open position shown in  FIG. 1   a  as a result of the force action of the closing spring  16 . The outer circumferential region of the axle  28  at least partially contacting the recess  24  is referred to in the following as the contact region  30 . Furthermore, the recess  24  comprises a sliding edge  32 , which extends radially inwards away from the circumferential line of the gripping device  18  and describes an arc here around the axle  20 . As will be described in the following, the sliding edge  32  is used to support the transition of the door lock  1  from the open position to the closed position and vice versa. The sliding edge  32  extends into an abutment edge  33 , which here in the open position can act as an abutment for the axle  28 . An abutment of this type can also be provided by an external abutment, which is not constructed on the gripping device  18 , but separately therefrom and is arranged, for example, on the securing device  10 . 
   In order to bring the door lock  1  from the open position shown in  FIG. 1   a  to the closed position shown in  FIG. 1   b,  the gripping device  18  is rotated in an anti-clockwise direction according to these drawings. In so doing, the gripping device  18  slides with the sliding edge  32  along the axle  28 , until the axle  28  reaches the radially outer end of the sliding edge  32 . A further rotation of the gripping device  18  results in the axle  28  reaching a transition region  34  between the recesses  24  and  26 , constructed here as a corner. This transition region, i.e. the corner  34 , acts as a snap point, which means that the closing spring  16  can relax, so that the closing lever  14  rotates about the axle  12 . In this respect, the gripping device  18  slides with a sliding edge  36  of the recess  26  along the outer circumference of the axle  28  disposed in the region of the gripping device  18 , until the axle  28  reaches an abutment edge  38  of the recess  26 . The sliding edge  36  extends radially inwards at an angle away from a tangent of the circumferential line of the gripping device  18  and extends into the abutment edge  38 , which extends as far as the circumferential line of the gripping device  18 . In order to press the sliding edge  36  and/or the abutment edge  38  against the axle  28 , the above-mentioned torsion spring, not shown here, for the gripping device  18  can be used. The door lock  1  is now in the locked position shown in  FIG. 1   b.    
   In order to effect the above-described transition from the open position to the closed position, the gripping device  18  comprises a gripping latch  40 . The gripping latch  40  is constructed as an eccentric indentation in the circumference of the gripping device  18 . In the open position ( FIG. 1   a ), the opening of the gripping latch  40  points in a direction in which it can receive a closing dog or closing hook  42  of an appliance door, not shown, which is to be closed by means of the door lock  1 . In order to close the appliance door and therefore the door lock  1 , the closing dog  42  is guided (for example by an opening, not indicated, appropriately arranged in the securing device  10 ) into the receiving region of the gripping latch  40 , where it presses against a contact surface  44  and rotates the gripping device  18  in an anti-clockwise direction according to  FIG. 1   a.  As a result of the rotation of the gripping device  18  caused by the closing dog  42  (and possibly as a result of the optional torsion spring), the above-described operation of the gripping device  18  is produced. 
   During the opening of the door lock  1 , i.e. during a transition from the closed position ( FIG. 1   b ) to the open position ( FIG. 1   a ), the closing lever  14  is rotated in a clockwise direction about the axle  12 , for example by using an opening lever, not shown, so that the closing spring  16  is compressed. The gripping device  18  thereby slides with the sliding edge  36  along the circumferential surface of the axle  28  disposed in the region of the gripping device  18  as far as the corner  34  acting as a snap point. Subsequently, the gripping device  18  is rotated in a clockwise direction, so that the gripping device  18  slides behind the corner  34  with the sliding edge  32  along the axle  28 , until the latter is positioned in the recess  24  according to the open position. The rotation of the gripping device  18  can be obtained here by the removal of the closing dog  42  from the gripping latch  40 , possibly together with a seal (not shown) forcing the housing door away, and/or by the above-mentioned torsion spring for the gripping device  18 . 
   As mentioned at the beginning, the force-path function, which reproduces the forces acting upon the door lock  1 , for a closure (i.e. a transition from the open position to the closed position) and a subsequent opening (i.e. a transition from the closed position to the open position) comprises a hysteresis. Consequently, the forces required during the transition from the open position to the closed position are less than the forces required during the transition from the closed position to the open position. A force-path function of this type is outlined by way of example in  FIG. 2   a,  which illustrates a complete closing procedure in function sections I and II and a complete opening procedure in function sections III and IV. 
   In order to close the door lock  1 , a user applies the forces reproduced by section I of the illustration function by means of the closing dog  42 , until the snap point provided by the corner  34  and indicated here by SP s  is reached. The closing spring  16  then relaxes, so that the door lock  1  is closed and held in the closed position. The forces generated in this respect are reproduced by the function curve II. 
   In order to open the door lock  1 , the user needs to apply the forces reproduced by function section III in order to move the gripping device  18  and the closing lever  14 , it being necessary to overcome the forces generated by the closing spring  16 . As is clearly visible in  FIG. 2   a,  the forces which need to be applied by a user and which are required for section III of the opening procedure are clearly greater than the forces which are applied by the door lock during the closing procedure in section II and which act as closing and holding-shut forces. 
   Amongst other things, this hysteresis results from the fact that a large closing force is provided in the closed position of the door lock  1  in order to securely lock the appliance door. This closing force is also usually dimensioned in such a manner that a seal for the appliance door is compressed in the closed position. Furthermore, the hysteresis of the force-path function also results from the fact that the appliance door is normally prestressed in such a manner that it closes automatically after a predetermined angle of opening, i.e. without the introduction of force by a user. 
   Once the snap point provided by the corner  34  and indicated in  FIG. 2   a  by SP o  is reached during the opening of the door lock  1 , the user needs to apply further forces by means of the closing dog  42  in order to bring the gripping device  18  into its position required for the open position. The above-mentioned torsion spring for the gripping device  18  does not suffice to this end, since the forces acting upon the gripping device  18  as a result of contact with the axle  28  are too great. The forces which need to be applied by the user during this part of the opening procedure are reproduced by the function section IV. Consequently, a hysteresis also results for sections I and IV. 
   The hystereses of the force-path function for sections II and III as well as I and IV are now prevented by reducing the friction acting between the gripping device  18  and the axle  28  in such a manner that the forces which need to be applied during the transitions to the closed position and open position essentially correspond to one another. 
   As described above, the axle  28  is rotatably mounted. Consequently, during the transition from the open position to the closed position and during the transition from the closed position to the open position, the axle  28  rotates as a result of contact with the sliding edge  32 , the corner  34  and the sliding edge  36 . 
   As a result of the rotatability of the axle  28 , the friction generated during movements of the gripping device  18  is not sliding friction, in contrast to the state of the art. Rather, the axle  28  rolls during movements of the gripping device  18  over the contacted surfaces of the recess  24 , the corner  34  and the recess  26 . Experimental tests have shown that the hysteresis of the force-path function described above is substantially prevented in this manner. A force-path function for a door lock according to the door lock illustrated in  FIG. 1   a  and  FIG. 1   b  is shown in  FIG. 2   b.    
   The sections of the function illustrated in  FIG. 2   b  and designated by the references I, II, III and IV, reproduce the resulting forces for the sections of the closing and opening procedures described with reference to  FIG. 2   a.  In this respect, it can be clearly seen that, as a result of the described friction reduction between the gripping device  18  and the axle  28 , a hysteresis for the force-path function in sections II and III is substantially avoided. 
   Furthermore, as a result of the above-mentioned friction reduction, it is substantially unnecessary, upon reaching the snap point when opening the door lock  1 , which is indicated in  FIG. 2   b  by the reference SP o , for the user to apply any force in order to bring the gripping device  18  into its position required for the open position of the door lock  1 . The reduction in the forces acting between the gripping device  18  and the axle  28  also means that the torsion spring for the gripping device  18  is sufficient in order to bring the gripping device into its position for the open position of the door lock  1 . In this manner, a hysteresis is also substantially avoided for sections I and IV. 
   The same result can be obtained if, instead of the rotatable axle  28 , a non-rotatable axle is used, which in the region of the gripping device  18  comprises a bearing (e.g. anti-friction bearing) arranged on its outer circumference. In this embodiment, which is not illustrated, the gripping device  18  does not roll upon the axle  28 , as described above, but upon the bearing. 
   A further optimisation of the door lock  1  is obtained if bearings, e.g. ball or anti-friction bearings, not shown in the drawings, are used between the axle  20  and the gripping device  18  and/or between the axle  12  and the closing lever  14 . 
   As explained, force-path functions without or with minimised hysteresis are obtained if the frictional forces acting upon the gripping device  18  are reduced during transitions from the open position to the closed position and vice versa. Further exemplary embodiments, which result in a frictional force reduction of this type, will be explained in the following with reference to  FIG. 3   a/b  to  FIG. 8   a/b.  For the sake of clarity in these drawings, only the gripping device  18  in different embodiments is illustrated as well as the axle  28  or the devices fulfilling the function of the axle  28 . As in  FIGS. 1   a  and  1   b,  the drawings labelled with the addition “a” show the gripping device  18  in the open position, whilst the drawings labelled with the addition “b” show the gripping device  18  in the closed position. 
   For better understanding of the explanation of further embodiments, the gripping device  18  and the axle  28  according to the embodiment of  FIG. 1  are schematically illustrated in  FIG. 3 . 
   As shown in  FIG. 4 , the recess  24  can be omitted, so that the active region  22  is substantially formed by the recess  26 , the corner  34  and the circumferential line of the gripping device  18  adjacent the corner  34 . 
   Instead of the axle  28 , it is possible, as shown in  FIGS. 5 and 6 , to use an abutment element  44  connected to the securing device  10 . The abutment element  44  comprises a first abutment surface  46  and a second abutment surface  48 , which encompass the contact region  30 . As described above, the first abutment surface  46  cooperates in the open position and during a transition from the open position to the closed position with the recess  24  and the corner  34 . In corresponding fashion, the second abutment surface  48  cooperates with the corner  34  and the recess  26  in the closed position and during a transition from the closed position to the open position. As with the use of the axle  28 , it is also possible in this case to dispense with the recess  24  (cf.  FIG. 6 ). 
   The above-described reduction in the friction is obtained in these cases in that the first abutment surface  46  and/or the second abutment surface  48  and/or the recess  24  and/or the corner  34  and/or the recess  26  each comprise a surface composition which, considered alone or in cooperation with a corresponding other surface, ensures a suitable reduction in friction. A surface composition of this type of individual, several or all of the above surfaces can be attained, for example, by a suitable coating with materials which reduce the occurring frictional forces during movements of the gripping device  18 . An additional improvement is obtained if the transition between the first abutment surface  46  and the second abutment surface  48  and/or the corner  34  has a rounded construction. 
   In the embodiments illustrated in  FIGS. 7 and 8 , the abutment element  44  or an axle, not indicated, are used, the gripping device  18  comprising a rotatable axle, an (anti-friction) bearing or the like in the region of the corner  34 . A device of this type, indicated by the reference numeral  50 , is to be arranged in the region of the corner  34  in such a manner that it is contacted and rotated by the abutment element  44  (or the axle) during transitions from the open position to the closed position and vice versa, so that a force-path function without or with minimised hysteresis is obtained as a result of the reduction in the occurring frictional forces. 
   In particular in the embodiment illustrated in  FIG. 8 , an additional reduction in friction is obtained if the device  50  of the gripping device  18  is used in combination with the rotatably mounted axle  28  according to  FIG. 1 , or, as described above, if bearings arranged on a non-rotatable axle are used. 
   As described above, the forces which usually need to be applied during opening of a door lock are greater than the forces which need to be applied during closure. A further solution for minimising the forces required during an opening procedure, i.e. a transition from the closed position to the open position, of a door lock, consists in preventing contact of the gripping device with a corresponding contact region during opening of the door lock. 
   The solution described in the following, in which the gripping device  18  is moved in a direction radial to its circumferential line during a transition from the closed position to the open position, is more complex than the solutions described above. This additional outlay can be advantageous if the embodiments described above do not reduce the frictional forces to a degree sufficient for the respective application and/or if the additional outlay is justified for the application in question (e.g. for reasons relating to safety, comfort, etc.). 
   In  FIGS. 9   a  to  9   e,  the operating states (positions) of the gripping device  18  are schematically illustrated for a transition from the open position to the closed position and back to the open position. For the sake of simplicity, the abutment element  44  and the gripping device  18  are shown without the recess  24 . 
   Proceeding from  FIG. 9   a,  which shows the open position, the gripping device  18  is brought into the closed position illustrated in  FIG. 9   b,  as described above. In this position, the abutment element  44  is located in the recess  26  and locks the door lock, not shown in  FIG. 9 , as a result of contact with the abutment edge  38  and/or with the sliding edge  36 . 
   In order to open the door lock, i.e. to bring the door lock from the closed position to the open position, the closing lever  14  is rotated about the axle  12 , as described above. In so doing, the gripping device  18  is moved in a direction radial to its circumferential line (i.e. in a direction perpendicular to the longitudinal axis of the axle  20 ). This direction of movement of the gripping device  18  is indicated in  FIG. 9   c  by the arrow P. As an alternative to the vertically downwardly directed movement according to  FIG. 9   c,  it is provided that the gripping device  18  is also moved in other directions in order to open the door lock  1 , so long as the effect described in the following is obtained. Thus, the gripping device  18  can be moved linearly, for example, and/or non-linearly in directions with vertical and/or horizontal components of movement. 
   As is visible in  FIG. 9   c,  as a result of the movement of the gripping device  18 , its spatial position relative to the abutment element  44  is changed in such a manner that the reciprocal action between the abutment element  44  and the recess  26  desired in the closed position is not maintained. Rather, the change in spatial position of the gripping device  18 , as described above, allows for a clockwise rotation for the open position. This is illustrated schematically in  FIG. 9   d.    
   During the rotation of the gripping device  18  or at the end of the rotary movement, when the gripping latch  40  allows for a removal of the closing dog  42 , the gripping device  18  is moved back again into its starting position, which it adopts in the open position. The state of the door lock  1  shown in  FIG. 9   e  corresponds to the open position illustrated in  FIG. 9   a.    
   These movements of the gripping device  18  during the opening of the locking device  1  mean that the gripping device  18  does not contact the abutment element  44  (or comparable devices) during a transition from the closed position to the open position, so that the forces which need to be applied in order to open the door lock  1  are reduced as a result of the lack of friction. This reduction prevents force-path functions with hysteresis. Depending on the respective application of this embodiment, more particularly the appliance door used in connection with this embodiment, the forces which need to be applied for opening can be thus reduced in such a manner that they are less than the forces which need to be applied for closure. 
   In order to move the gripping device  18  in the manner described above, a type of sliding block switch, for example, can be used, which is used to guide the axle  20  relative to the closing lever  14 . Furthermore, it is provided that the axle  20  is guided in a slot arranged in the longitudinal direction of the closing lever  14  and that the movements of the gripping device  18  are generated by spring elements, which as a function of the respective position of the door lock  1  exert forces upon the gripping device  18  and/or the axle  20 . 
   The door lock illustrated in  FIGS. 10 to 12  comprises a frame  100 , in which two parallel side walls  102  are provided for mounting various axle journals. 
   A closing lever  104  is constructed as a two-arm lever and comprises a steering arm  106  and a latch arm  108  pointing approximately in the opposite direction to the steering arm  106 . One end of the latch arm  108  is forked in the shape of a latch with a locking nose  110  and a closing nose  112 . 
   The steering arm  106  of the closing lever  104  is formed by two parallel partial arms constructed in mirror-image fashion, which are connected to one another by the latch arm  108 , so that an open, U-shaped frame is formed. 
   Two axle journals  114  of the closing lever  104  engage in each case in bearing bores, not shown in the drawings, of the side walls  102  and allow for a pivotable mounting of the closing lever  104  about an (imaginary) pivot axis  116 . 
   A steering rod  118  is constructed as a U-shaped crank. It comprises two lateral axle journals  120 , two cylindrical rolling surfaces  122 , a crankpin  124  and two lateral cheeks  126 , which each connect one end of the crankpin  124  to an axle journal  120 . The ends of the crankpin which are each connected to the axle journals  120  are rounded and form the rolling surfaces  122 . The axle journals  120  engage in each case in a bearing bore, in each case in the vicinity of one end of the partial arms of the steering arm  106 , where they are pivotably mounted. A pivot axis  128  (which is imaginary and is displaced with a pivoting movement of the closing lever  104 ) of the steering rod  118  extends through both axle journals  120 . 
   A tensioning lever  130  comprises a hollow, tubular guide arm  132  with a cross section in the form of a square with rounded corners. Constructed along the guide arm  132  on both sides is a projection, which in each case forms a sliding surface  134  for the rolling surfaces  122 . An end  138  of the guide arm  132  remote from a pivot axis  136  comprises a groove guide  140 , which is formed by two recesses arranged in each case in a lateral surface of the guide arm  132  and extending approximately perpendicular to the pivot axis  136 . The crankpin  124  of the steering rod  118  engages in the groove guide  140  and can execute both a rotary and a longitudinal movement therein. 
   A spring  142  constructed as a helical compression spring is tensioned in the tubular interior of the guide arm  132  between one end  144  and the crankpin  124  of the steering rod  118 . 
   The end  142  of the guide arm  132  extends into an operating arm  146  of the tensioning lever  130 , at whose lateral ends an axle journal  148  is arranged in each case. The axle journals  148  engage in each case in a bearing bore, not shown here, in the side walls  12  of the frame  10  where they are rotatably mounted. 
   The operating arm  146  of the tensioning lever  130  engages with sliding surfaces  150  in each case in a recess  152  of an operating device  154 , which engages by means of two axle journals  156  in each case in a bearing bore in the side walls  12  of the frame  10 . 
   A closing fitting  158  of an electrical household appliance comprises a closing journal  160 , which can engage in the latch formed by the locking nose  110  and the closing nose  112 , so that the door is locked. 
   In the perspective views of  FIG. 11  and  FIG. 12 , the closing lever  104 , the steering rod  118  and the tensioning lever  130  are each illustrated in the closed position of the lock according to  FIG. 10   b.  In this respect,  FIG. 12  is a view approximately in the direction of the arrow A in  FIG. 10   b,  whilst  FIG. 13  is a view approximately in the direction of the arrow B. 
   In order to explain the method of operation of this door lock, reference is made here to DE 195 40 843 C2. 
   In order to obtain force ratios comparable to the door lock described above, in which the forces required for a transition from the closed position to the open position and the forces required for a transition from the open position to the closed position essentially correspond, roller bearings, anti-friction bearings or the like are arranged between the axle journals  114  of the closing lever  104  and the corresponding bearing bores of the side walls  102 . Alternatively or in addition, bearings of this type are used between the axle journals  148  of the tensioning lever  130  and the corresponding bearing bores of the side walls  12 . Additional optimisation is obtained if the lateral axle journals  120  of the steering rod  118  are pivotably arranged in the bearing bores of the partial arms of the steering arm  106  by means of bearings. 
   Since the crankpins  124  of the steering rod  118  also execute rotary movements in the groove guide  140  of the tensioning lever  130 , frictional forces occurring at this location are reduced if bearings of a suitable type are fitted to the crankpins  124 . The use of bearings between the axle journals  156  of the operating device  154  and corresponding bearing bores of the frame  100  also represents an optimisation.