DESCRIPTION OF PREFERRED EMBODIMENTS

[0072] General Remarks

[0073] The description of preferred embodiments is divided in sections being referenced with Roman numerals wherein the figures associated to the different sections are provided with the respective Roman numerals followed by a consecutive numbering in Arabic numerals. Further, the reference numerals given in the single sections have been given independent in respect to each other.

[0074] Embodiments—Part I

[0075] In the units defined as door latches at the beginning, memory metal actuators are used wherein a memory metal actuator is meant as a unit which generates forces by means of a memory metal, in particular by means of its temperature dependent shape variation. Accordingly, here, memory metal actuators comprise several or bundled memory metal wires, units comprising the same, unit comprising components made from memory metal, memory metal components in the shape of bending beams, bodies and the like.

[0076] Further, in the following, activation of a memory metal actuator is meant such that the memory metal actuator is heated such that, in case of an one-way memory metal actuator, its threshold temperature and, in case of a two-way memory metal actuator, its upper threshold temperature is exceeded wherein occurring shape changes and forces associated therewith, respectively, are employed.

[0077] In order to heat at least the memory metal itself for activation of memory metal actuators, the memory metal actuator can be directly connected to a current or voltage source. Here, for activation, a control is used for the current or voltage source in order to generate a desired heating of the memory metal without damaging the same. This arrangement is schematically illustrated in FIG. I 2 a.

[0078] As can be seen in FIG. I 2 b , an activation of memory metal actuator can also be obtained by means of a thermal element (PTC element) which is thermically coupled to the memory metal actuator and which is controlled in dependence of the type of forces to be generated by the memory metal actuator. In a non-illustrated embodiment, a thermal element for activation of a memory metal actuator is used which provides its heating as soon as the household appliance is started. For example, this can be accomplished in that the thermal element is coupled to and supplied from, respectively, the energy supply of the household appliance.

[0079] Further, it is possible, to employ heat for activation of memory metal actuators which is produced in operation of a household appliance anyhow. Examples hereof are the heat radiation generated by heating elements of a washing machine or a dishwasher, heat occurring during the operation of a kitchen stove, heat generated during operation of a household appliance from moveable parts thereof and the like. In case of a household appliance utilizing microwaves, it is further possible to couple a memory metal actuator with a material which can be heated by the used microwave radiation in a manner to effect, during operation, i.e. during generation of microwaves, an activation of the memory metal actuator.

[0080] A particularly preferred embodiment for activation of a memory metal actuator is an arrangement shown in FIG. I 3 a wherein the memory metal actuator being connected with a PTC element in series is supplied with energy. Here, the fact is used that PTC elements, if being connected with a current supply for activating/heating, have a very low ohmic resistance for a short period of time upon turning on the current supply and, subsequently, undergo a transition into a condition having a very high ohmic resistance in a virtually step-like manner. Accordingly, a current course is obtained which initially comprises a short pulse-like high current followed by an essentially constant low current. For a connection of a PTC element and the memory metal actuator in series, this results that the memory metal actuator is activted by the pulse-like current for a short period of time and, thus, that pulse-like forces are generated.

[0081] By means of a suitable selection of a PTC element and its voltage supply, it is possible to accomplish that, subsequent to the initial current pulse, the flowing current is low such that it is not sufficient for an activation of the memory metal actuator any more. Accordingly, subsequent to the activation by the current pulse, the memory metal actuator can cool, i.e. the memory metal actuator is deactivated. In that approach, the PTC element being connected in series with the memory metal actuator acts comparable to a switch whereby a complex control conventionally required for generating pulse-like currents is avoided.

[0082] Further, it is possible to arrange the PTC element being connected in series with the memory metal actuator such that the PTC element is also thermically coupled to the memory metal actuator. This procedure being illustrated in FIG. I 3 b makes it possible to maintain, subsequent to an activation of the memory metal actuator effected by the initial current pulse, the memory metal actuator activated, i.e. to maintain it warm enough, such that it maintains the shape given for its activation (i.e. access of the threshold temperature) and maintains the forces associated thereto, respectively. As set forth above, subsequent to a pulse-like activation by means of a direct driving with a suitably controlled current, the heating of the memory metal actuator can be maintained.

[0083] Further, it is possible, as set forth at the beginning, to maintain an operation condition taken subsequent to a pulse-like activation of the memory metal actuator by, for example, a PTC element or a connecting link guide cooperating with the memory metal actuator.

[0084] As an alternative thereto, a thermal coupling of the PTC element with the memory metal actuator can be adapted such that the period of time up to a deactivation of the memory metal actuator is set to a desired or given, respectively, value. For that purpose, the heat applied from the PTC element to the memory metal actuator is selected such that its cooling process is retarded such that the deactivation (resetting, back-shaping) of the memory metal actuator just occurs after a desired and given, respectively, period of time.

[0085] In both cases, the thermal coupling of the PTC element to the memory metal actuator also provides for enhanced security. In case, for a unnormal operation condition, for example for a power failure, the PTC element is not supplied with energy any more, i.e. is not heated any more, the heat emitted in the cooling down process of the PTC element to the memory metal actuator provides that its deactivation is retarded. In this manner it is possible, for example, to release in case of a failure of a household appliance its door latch only after a certain period of time for unlatching has elapsed which can be adjusted by means of the cooling processes of the PTC element and the memory metal actuator.

[0086] For deactivation of a memory metal actuator, in case of a one-way memory metal actuator, it is operated such that its temperature falls below the corresponding threshold temperature after which a one-way memory metal actuator can be deformed in any desired manner by external forces ( e.g. spring forces). For a two-way memory metal actuator, a deactivation is meant as an operation of the actuator wherein the-two-way memory metal actuator is brought to a temperature below the corresponding lower threshold temperature.

[0087] In any cases, the memory metal actuator is to be cooled for a deactivation. In dependence, for example, of thermal properties of used memory metals and of a period of time given and/or desired for deactivation, as easiest case, a deactivation can occur by cooling the memory metal actuator by itself. In order to accelerate a deactivation, active elements, such as blowers or other cooling components, can be used. In case cooling means are already existing or cooling operation conditions are provided in the concerned household appliance, it is advantageous to use the same also for cooling the memory metal actuators. An example are dryers which, in general, employ air to cool laundry subsequent to completion of a drying program in order to avoid creasing of the laundry. This cooling air can also be used, if desired, to deactivate memory metal actuators.

[0088] Embodiments—Part II

[0089] In FIGS. II 1 a and II 1 b , a door latch for household appliance is illustrated which comprises a housing 10 , a latching slider 12 and a closing hook 16 being arranged rotatably about an axle 14 . On one end, the closing hook 16 includes a nose 18 and the closing hook 16 is biased to the left in the position shown in the figures by means of a not illustrated spring. The latching slider 12 cooperates with a compression spring 20 . After closing a not illustrated appliance door which comprises the closing hook 16 , the door latch takes the condition shown in FIG. II 1 a . Closing the appliance door, the closing hook 16 is moved through an opening 22 in the housing 10 wherein a surface 24 of the nose 18 slides along a surface 26 of the housing 10 inwards and is guided through an opening 28 formed in the latching slider 12 . When the nose 18 has passed the opening 22 , the closing hook 16 moves into the biased position illustrated in the figures. Here, the latching slider 12 is moved in opposite direction to the right by means of the forces generated by the compression spring 20 .

[0090] Further, the door latch comprises a locking slider 30 having an opening 32 formed therein through which a one-way memory actuator 34 is guided. The memory metal actuator 34 is mounted with one end 36 to the housing 10 and cooperates, with an end 38 , with a tension spring 40 . In the activated condition of the memory metal actuator 34 , which is not illustrated in FIG. II 2 a , the tension spring 40 maintains the memory metal actuator 34 and, as a result, the locking slider 30 in the positions shown there.

[0091] In order to latch the door latch, i.e. to ensure that the closing hook 16 cannot be moved from the position shown in FIG. II 1 a , the locking slider 30 is, as illustrated in FIG. II 1 b , guided, at least partially, through an opening 42 in the latching slider 12 . Thereby, movements of the latching slider 12 are prevented.

[0092] For moving the locking slider 30 in the position shown in FIG. II 1 b , the memory metal actuator 34 is activated wherein it takes the shape illustrated there. The memory metal actuator 34 can be activated in pulse-like manner and can be maintained in heated condition, in which the memory metal actuator 34 maintains the shape shown in FIG. II 1 b , for example, as describe above, by means of a PTC element 44 .

[0093] In order to unlatch the door latch, the memory metal actuator 34 is deactivated and the tension spring 40 provides for a transition of the locking slider 30 in the position shown in FIG. II 1 a . Then, the closing hook 16 can be removed through the opening 22 from the housing 10 if, during opening the not illustrated household appliance door, the closing hook 16 is rotated in clockwise direction and the latching slider 12 is moved at the same time so far to the left that the nose 18 can be moved out of the opening 28 and through the opening 22 .

[0094] The variation of the door latch illustrated in FIGS. II 2 a and II 2 b comprises, in place of the one-way memory metal actuator 34 , a two-way memory metal actuator 46 which takes in cooled condition, i.e. below its lower threshold temperature, the position shown in FIG. II 2 a . Accordingly, the tension spring 40 is not necessary here.

[0095] In order to achieve the latched condition of the door latch illustrated in FIG. II 2 b , the two-way memory metal actuator 46 is (maintained) heated above its upper threshold temperature by means of the PTC element 44 . The engagement of the locking slider 30 with the latching slider 12 is maintained by a respectively continued activation of the two-way memory metal actuator 46 . For unlatching the door latch, the two-way memory metal actuator 46 is cooled below its lower threshold temperature, for example, by turning off the PTC element 44 . After falling below its lower threshold temperature, the two-way memory metal actuator 46 takes the shape illustrated in FIG. II 2 a wherein the locking slider 30 is moved upwards and the latching slider 12 is released.

[0096] Embodiments—Part III

[0097] The door latch illustrated in FIG. III 1 comprises a housing 10 , a latching slider 12 and a closing hook 14 having a nose 16 formed for cooperation with the latching slider 12 . The latching slider 12 is engaged by a compression spring 18 and is moved, upon closing a not illustrated household appliance door comprising the closing hook 14 , against the compression spring 18 to the right. For that purpose, the nose 16 comprises a guiding surface 20 which moves the latching slider 12 to the right upon closing. In case, the closing hook 14 is moved far enough into the housing 10 such that the nose 16 has completely passed the latching slider 12 according to FIG. III 1 , the compression spring 18 moves the latching slider 12 to the left. Thereby, the closing hook 16 cannot be removed from the housing 10 any more and the door latch is latched. In this embodiment, the latching of the door latch automatically occurs upon closing the household appliance door by a user.

[0098] For unlatching the door latch, a one-way memory metal actuator 22 is activated in order to move the latching slider 12 to the right and to release the closing hook 14 . An advantage of that door latch is that, comparable to the combined closing and latching process, the unlatching and opening occurs cooperatively. For that purpose, a compression spring 24 is provided which engages the closing hook 14 and moves the same, upon an activation of the memory metal actuator 22 , downwards at least such that the latching slider 12 cannot cooperate with the nose 16 for latching any more. Accordingly, it is only necessary to activate the memory metal actuator 22 until the compression spring 24 has moved the closing hook 14 downwards far enough. Then, the latching slider 12 can be moved via the guiding surface 20 of the nose 16 due to the force effect of the compression spring 18 whereby the closing hook 14 is further moved downwards. In this manner it is possible not only to unlatch the door latch but also to effect an actual, at least partial, opening of the household appliance door.

[0099] FIGS. III 2 a and III 2 b show arrangements for the door latch according to FIG. III 1 wherein the memory metal actuator 22 cooperates with the latching slider 12 by means of an intermediate lever 26 . In the arrangement illustrated in FIG. III 2 a , a force translation is realized via the intermediate lever 26 whereas in the arrangement shown in FIG. III 2 b a path translation is obtained.

[0100] The door latch illustrated in FIG. III 3 comprises a housing 10 , a latching slider 12 , a bolt nab 14 being connected to a not illustrated household appliance door and a rotation latch 16 . The rotation latch 16 is supported rotatably around an axle 18 and is biased in opening direction (here in clockwise direction) by means of a not illustrated spring. The latching lever 12 is engaged by a compression spring 20 which abuts on a stop 22 formed on the housing 10 .

[0101] Upon closing the household appliance door, the bolt nab 14 is inserted into a recess 24 of the rotation latch 16 and is moved upwards whereby the rotation latch 16 is moved, in anti-clockwise direction, in the position shown in FIG. III 3 . During the rotation of the rotation latch 16 , a guiding surface 26 of the rotation latch 16 moves the latching lever 12 against the compression spring 20 to the right. In case, the rotation latch 16 is in the position shown in FIG. III 3 , the compression spring 20 moves the latching lever 12 again to the right and prevents due to an engagement of a stop surface 28 of the latching lever 12 with a surface 30 of the rotation latch 16 that the latter one can be rotated in opening direction, i.e. in clockwise direction. Thus, the household appliance door is closed and the door latch is latched. Comparable to the embodiment according to FIG. III 1 , here again a combined closing and latching action occurs.

[0102] For unlatching the door latch and for at least partially opening of the household appliance door, a memory metal actuator 32 is actuated in pulse-like manner in order to move the latching lever 12 to the right. Thereby, the rotation latch 16 is released and moved in opening direction, i.e. in clockwise direction, due to the not illustrated biasing spring. Thereby, the bolt nab block 14 is moved downwards and the household appliance door it at least partially opened.

[0103] Embodiments—Part IV

[0104] The door latch illustrated in FIGS. IV 1 a to IV 1 c comprises a housing 10 , a rotation latch 14 being supported rotatably about on an axle 12 and a bolt nab 16 being attached to a not illustrated household appliance door. Between the rotation latch 14 and a lever 20 being arranged rotatably about an axle 18 , a compression spring 22 is arranged. The compression spring 22 is connected to the rotation latch 14 such that the compression spring 22 maintains the rotation latch 14 in the position shown in FIG. IV 1 a and is caused upon a rotation of the rotation latch 14 in clockwise direction, in the position shown in FIG. IX 1 b . During such a rotation of the rotation latch 14 , a snap point for the compression spring 22 is overcome such that the compression spring 22 snaps in the position shown in FIG. IV 1 b and maintains the rotation latch 14 in the position shown in FIG. IV 1 b . The same respectively applies for a rotation of the rotation latch 14 in anti-clockwise direction. Advantageously, the forces generated by the compression spring 22 in the two positions and the forces required to overcome the snap point are dimensioned such that the rotation latch 14 can be easily moved during closing and opening of the household appliance door.

[0105] For closing the household appliance door, the bolt nab 16 is moved into engagement with a recess 24 formed in the rotation latch 14 and the rotation latch 14 is rotated in clockwise direction. Having overcome the snap point, the forces provided by the compression spring 22 support the closing process at least partially. After completion of the closing process, the forces, which are generated by the compression spring 22 in the position shown in FIG. IV 1 b , effect that the household appliance door is maintained closed by a given force. Advantageously, as set for the above, this force also referred to a contact force is dimensioned such that the household appliance door can be opened without a high force effort for the user.

[0106] In order to maintain, during operation of the household appliance, its door securely closed, the contact force generated by the compression spring 22 is increased by moving the lever 20 in the position shown in FIG. IV 1 c . For that purpose, a one-way memory metal actuator 26 is activated which engages an end 30 of the lever 20 and moves the same to the left after activation. Thereby, the compression spring 22 is compressed and the contact force generated by the same increased. This condition is maintained by means of a driving mode for the memory metal actuator 28 explained at the beginning. Here, it is contemplated that the thusly increased contact force is large to an extent that, during an operation condition of the household appliance wherein the household appliance door is not be opened, an opening of the household appliance door is prevented or only possible with a (significantly remarkably) increased force effort.

[0107] For operation conditions of the household appliance wherein the household appliance door is allowed to be opened, the memory metal actuator 28 is deactivated and the compression spring 22 moves the lever 20 back in the position illustrated in FIG. IV 1 b . The thusly reduced contact force allows an easy opening of the appliance door.

[0108] In the variation illustrated in FIGS. IV 2 a to IV 2 c it is not necessary to activate the memory metal actuator 28 in a continuous manner in order to maintain the lever 20 in the inclined position necessary for increasing the contact force. For that purpose, a connecting link guide 32 cooperating with the lever 20 is used which includes a guiding groove 34 formed therein in which a not illustrated guiding pin arranged on lever 20 can be moved. In case, a contact force is to be increased for an operation condition of the household appliance, i.e. the lever 20 is to be inclined to the left and to be maintained in that position, the memory metal actuator 28 is activated in pulse-like manner. Upon the thusly effected inclination movement of the lever 20 , its guiding pin moves to the left in the guiding groove 34 until a groove portion 36 or a groove portion 38 is reached. After the pulse-like activation of the memory metal actuator 28 , the compression spring 22 pushes the lever 20 a bit to the right wherein the guiding pin reaches a groove portion 44 due to the force generated by a spring 40 and rotating the connecting link guide 32 about an axle 42 . Depending of the spring 40 being a compression spring or being a tension spring, here, the connecting link guide is rotated in clockwise direction or in anti-clockwise direction. As the guiding pin of the lever 20 is in the groove portion 44 , the lever 20 is maintained in is the position shown in FIG. IV 2 c.

[0109] In order to cause the lever 20 out of its inclined position and to thusly reduce the contact force, the memory metal actuator 28 is further activated in pulse-like manner. Initially, this effects a stronger inclination of the lever 20 to the left such that its guiding pin gets to the groove portion 38 or to the groove portion 36 . After completion of the activation of the memory metal actuator 28 , the compression spring 22 pushes the lever 20 back to the right in its starting position wherein the guiding pin of the lever 20 moves back in the guiding groove 34 into a groove portion 46 .

[0110] Embodiments—Part V

[0111] In particular, in washing machines, dishwashers and dryers, it is necessary to securely close appliance doors during operation, i.e. to generate forces (see part II) which maintain the appliance doors in closed position. As set forth above, this can be accomplished by appliances doors being moved into their closing positions or being maintained there by means of one or several memory metal actuators. In door latches in which securing of appliances doors in the closed condition is accomplished, for example, by means of spring elements, it can be necessary that significant forces must be applied by a user for closing the appliances doors which limit the comfort. In order to support a user in those cases in closing appliances doors, it is known to employ electric motors which generate forces supporting the user in closing the appliances doors. Here, powerful and large electric motors as well as mechanical means connected thereto (e.g. transmissions, gears and the like) are necessary whereby this approach is cost intensive and complex as regards construction.

[0112] Memory metal actuators which are able to generate high forces at small dimensions solve these problems. In order to support a closing process, memory metal actuators can be arranged in a door latch such that, if a bolt nab of an appliance door comes into engagement with respective components of the door latch (e.g. a gripping latch), the memory metal actuator is activated such that it at least supports the movements of components of the door latch occurring during the closing process, preferably accomplishing the same virtually without forces to be applied by the user. Here, the bolt nab and the door latch are caused into a closed condition whereby the appliance door is pulled closed. A thread to users for example in the form of clamping of fingers, can be avoided here by activating of the memory metal actuator supporting the closing process when the bolt nab comes into engagement with the door latch, i.e. the appliance door is at least “leant on”, thus, no gaps are present between the appliance door and the housing of the household appliance.

[0113] The support of closing processes of doors of household appliances can also be accomplished by means of memory metal actuators being arranged in portions in which household appliances doors are rotatably and pivotably, respectively, connected to the housing of the respective household appliances.

[0114] In FIGS. V 1 a and V 1 b , an embodiment of a door latch is illustrated which supports the closing process of a household appliance door. In a housing 10 , a rotation latch 14 , which is biased in anti-clockwise direction by means of not illustrated spring, is arranged supported rotatably about an axle 12 . The rotation latch 14 cooperates with a lever 16 which can be operated by means of a memory metal actuator 18 in order to effect rotations of the rotation latch 14 . During closing a household appliance door comprising bolt nab 20 , an end 22 of the bolt nab is moved into engagement with a recess 22 formed in the rotation latch 14 . Closing the household appliance door, the rotation latch 14 is rotated in clockwise direction wherein the rotation of the rotation latch 14 and, thus, the closing process are actively supported by means of a respectively controlled activation of the memory metal actuator 18 . In this manner, the household appliance door is pulled closed by the forces generated by the memory metal actuator 18 and can be maintained in the closed condition with increased force if the memory metal actuator 18 remains activated in a continuous manner according to one of the above described ways.

[0115] For opening the household appliance door, the memory metal actuator 18 is deactivated whereby the closing forces acting on the household appliance door are released and the household appliance door can easily be opened. In case, only the closing process and the closing condition, respectively, of the household appliance door should be supported in that door latch, a one-way memory metal actuator is used as the memory metal actuator 18 . Support of the opening process can, for example, be effected by a spring which provides a rotation of the rotation latch 14 in anti-clockwise direction when the memory metal actuator 18 is deactivated.

[0116] Further, it is possible to support the opening of the household appliance door by means of a one-way memory metal actuator (no illustrated) which is activated upon an deactivation of the memory metal actuator 18 and at least supports rotations of the rotation latch 14 in anti-clockwise direction. As an alternative, it is possible to use a two-way memory metal actuator as the memory metal actuator 18 which is heated above its upper threshold temperature when closing (pulling closed) the household appliance door and which is, advantageously, maintained above its upper threshold temperature for securing the household appliance door. Cooling of the two-way memory metal actuator below its lower threshold temperature effects or at least supports rotations of the rotation latch 14 in anti-clockwise direction whereby the opening of the appliance door it at least supported. The cooling of the two-way memory actuator required for that purpose can, as described at the beginning, accelerated by active measures.

[0117] In the variation of the above described embodiment illustrated in FIG. V 2 a and FIG. V 2 b , a connecting link guide 26 cooperating with a lever 16 is used. The function of the connecting link guide 26 is comparable to the connecting link guide described with reference to FIGS. IV 2 a to IV 2 c . Thus, a one-way memory metal actuator can be uses as the memory metal actuator 18 which is activated in pulse-like manner for pulling the household appliance door, i.e. for rotating the rotation latch 14 in clockwise direction. Here, the lever 16 cooperates, for example, with a not illustrated guiding pin and a guiding groove 28 formed in the connecting link guide 26 such that, subsequent to the pulse-like activation of the memory metal actuator 18 , the position illustrated in FIG. V 2 b is taken and maintained. In order to release the rotation latch 14 for opening the household appliance door, the one-way memory metal actuator 18 is activated once more in pulse-like manner whereby the position shown in FIG. V 2 a is taken. The transition into this position can be effected by means of the not illustrated biasing spring for the rotation latch 14 , by means of a compression spring (not illustrated) cooperating with the lever 16 and the like.

[0118] Embodiments—Part VI

[0119] In FIGS. VI 1 a and VI 1 b , a door latch for household appliance is illustrated which comprises a housing 10 , a latching slider 12 and a closing hook 16 being arranged rotatably about an axle 14 . On one end, the closing hook 16 includes a nose 18 and the closing hook 16 is biased to the left in the position shown in the figures by means of a not illustrated spring. The latching slider 12 cooperates with a compression spring 20 . After closing a not illustrated appliance door which comprises the closing hook 16 , the door latch takes the condition shown in FIG. VI 1 a . Closing the appliance door, the closing hook 16 is moved through an opening 22 in the housing 10 wherein a surface 24 of the nose 18 slides along a surface 26 of the housing 10 inwards and is guided through an opening 28 formed in the latching slider 12 . When the nose 18 has passed the opening 22 , the closing hook 16 moves into the biased position illustrated in the figures. Here, the latching slider 12 is moved in opposite direction to the right by means of the forces generated by the compression spring 20 .

[0120] Further, the door latch comprises a locking slider 30 having an opening 32 formed therein through which a one-way memory actuator 34 is guided. The memory metal actuator 34 is mounted with one end 36 to the housing 10 and cooperates, with an end 38 , with a tension spring 40 . In the activated condition of the memory metal actuator 34 , which is not illustrated in FIG. VI 2 a , the tension spring 40 maintains the memory metal actuator 34 and, as a result, the locking slider 30 in the positions shown there.

[0121] In order to latch the door latch, i.e. to ensure that the closing hook 16 cannot be moved from the position shown in FIG. VI 1 a , the locking slider 30 is, as illustrated in FIG. VI 1 b , guided, at least partially, through an opening 42 in the latching slider 12 . Thereby, movements of the latching slider 12 are prevented.

[0122] For moving the locking slider 30 in the position shown in FIG. VI 1 b , the memory metal actuator 34 is activated wherein it takes the shape illustrated there. The memory metal actuator 34 can be activated in pulse-like manner and can be maintained in heated condition, in which the memory metal actuator 34 maintains the shape shown in FIG. VI 1 b , for example, as describe above, by means of a PTC element 44 .

[0123] In order to unlatch the door latch, the memory metal actuator 34 is deactivated and the tension spring 40 provides for a transition of the locking sliver 30 in the position shown in FIG. II 1 a . Then, the closing hook 16 can be removed through the opening 22 from the housing 10 if, during opening the not illustrated household appliance door, the closing hook 16 is rotated in clockwise direction and the latching sliver 12 is moved at the same time so far to the left that the nose 18 can be moved out of the opening 28 and through the opening 22 .

[0124] As an alternative, the tension spring 42 and the memory metal actuator 44 in this embodiment can be arranged such that the tension spring generates a force acting to the left which maintains the lever 36 in the position shown in FIG. VI 1 b , whereas the memory metal actuator 44 , upon an activation, generates forces which rotate the lever 36 in clockwise direction. In this variation, the end 46 of the locking slider 30 rests on the upper surface 48 of the latching slider 12 when the closing hook 16 and in particular its nose 18 are outside the housing 10 . If, in the above-described closing process, the latching slider 12 is moved to the right by the closing hook 16 and its nose 18 , respectively, against the compression spring 20 , the end 26 of the locking slider 30 engages the opening 46 of the latching slider 12 due to the force action of the tension spring 42 in an automatic manner and, thus, latches the door latch.

[0125] For unlatching, the memory metal actuator 44 is activated in order to rotate the lever 36 in clockwise direction and, thus, to move the locking slider 30 upwards and to release the latching slider 12 . This embodiment provides for an automatic latching of the household appliance door without the need for an actuation of the memory metal actuator.

[0126] In the embodiments illustrated in FIG. VI 2 a and FIG. VI 2 b , a L-shaped locking lever 50 is used which is arranged rotatably around an axle 52 . A tension spring 54 , engaging on a leg of the locking lever 50 , maintains the locking lever 50 in the position shown in FIG. VI 2 a wherein an end 56 of the locking lever 50 does not engage an opening 58 in the latching slider 12 . Accordingly, these door latch is not in a latched condition.

[0127] For latching this door latch, a memory metal actuator 60 is activated which moves the locking lever 50 in the position shown in FIG. VI 2 b wherein its end 56 engages the opening 58 and, thus, locks the latching slider 12 . For unlatching, the memory metal actuator 60 is deactivated and the tension spring 54 moves the locking lever 50 in the position shown in FIG. VI 2 a . Thereby, the end 56 of the locking lever 50 is moved out of the opening 58 in the latching slider 12 and the same is released.

[0128] In the variation illustrated in FIGS. VI 3 a and VI 3 b , it is not necessary to activate the memory metal actuator 44 in a continuous manner in order to maintain the lever 36 and, thus, the locking slider 30 in the position illustrated in FIG. VI 3 b and FIG. VI 1 b , respectively. Here, a connecting link guide 62 cooperating with the lever 36 is used which, as described above, provides upon activation of the memory metal actuator 44 that the lever 36 and, thus, the locking slider 30 are maintained in the position necessary for latching the door latch without an activation of the memory metal actuator 44 (see FIG. VI 3 b ). For unlatching, the memory metal actuator 44 is activated in pulse-like manner whereby, in cooperation with the connecting link guide 62 , the lever 36 is slightly rotated in clockwise direction and, then, moved into the position shown in FIG. VI 3 a by the tension spring 42 .

[0129] Embodiments—Part VII

[0130] The door lock 1 shown in FIG. VII 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 one way memory metal actuator 16 , being not activated here, is arranged between the end of the closing lever 14 opposite the axle 12 and the securing device 10 . Due to its deactivated condition, the memory metal actuator 16 can be deformed by external forces. As described in the following, the allows operating the closing lever 14 and components associated thereto.

[0131] 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 memory metal actuator 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. VII 1 , as will be described below, or to exert rotary forces upon the gripping device 18 in a clockwise direction. This has the benefit that the gripping device 18 is maintained in the position shown in FIG. VII 1 a and cannot be moved from this position “by its own” by external forces, such as vibrations. In a comparable manner, a torsion spring not shown can be arranged on the axle 12 and can cooperate with the closing lever 14 such that this is also maintained in the position shown in FIG. VII 1 a.

[0132] The gripping device 18 comprises a gripping latch 22 . The gripping latch 22 is an eccentric indentation in the circumferential line of the gripping device 18 . In the open position (FIG. VII 1 a ), the opening of the gripping latch 22 points in a direction in which it can receive a bolt nab or closing hook 24 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 bolt nab 24 is guided (for example by an opening, not indicated, appropriately arranged in the securing device 10 ) into the receiving region of the gripping latch 27 , where it presses against a contact surface 26 and rotates the gripping device 18 in an anti-clockwise direction according to FIG. VII 1 a . As a result of this rotation, an abutment position 28 of the gripping device 18 contacts a stop 30 formed on the free hand of the closing lever 14 . Thereby, the closing lever 14 , also in an anti-clockwise direction, is cooperatively moved until the closing lever 14 contacts a not shown stop being formed on the housing 10 which limits movements of the closing lever 14 . A termination of the rotation of the closing lever 14 in an anti-clockwise direction can also accomplished by the appliance door comprising the bolt nab 24 abutting on respective surfaces of the housing. The condition of the door lock 1 referred to as closed position is shown in FIG. VII 1 b.

[0133] In order to maintain the door lock 1 in the closed position shown in FIG. VII 1 b , the memory metal actuator 16 is actuated in order to apply forces which maintain the closing lever 14 and the gripping device 18 in its positions shown in FIG. VII 1 b . In particular, it is contemplated that the memory metal actuator 16 applies forces being large enough to securely maintain the bolt nab 24 in the gripping latch 22 for operation of the household appliance.

[0134] After operation of the household appliance, the activation of the memory metal actuator 16 is terminated. When its temperature falls below a corresponding threshold temperature, above which the shape variation occurs being required for generation of the said forces, the memory metal actuator can be deformed in any way by external forces. This allows to bring the gripping device 18 and the closing lever 14 in the positions shown in FIG. XII 1 a , for example, by opening the appliance door comprising the closing lever 14 . As described above, if required, the cooling of the memory metal actuator 16 necessary for that purpose can be supported by further measures.

[0135] In a not shown embodiment, in addition to the memory metal actuator 16 used for securing the closed position (FIG. VII 1 b ), a further one-way memory metal actuator is used which supports at least the transition from the closed position (FIG. VII 1 b ) into the open position (FIG. II 1 a ). For that purpose, this further memory metal actuator is activated in order to generate forces which cause the gripping device 18 and the closing lever 14 in the positions shown in FIG. VII 1 a . In dependence of the design of this memory metal actuator, in this manner, an actual opening of the appliance door comprising the closing lever 14 can be effected.

[0136] Embodiments—Part VIII

[0137] FIGS. VIII 1 to VIII 4 schematically illustrate a sectional view through a latching device for the door of, for example, a washing machine. The shown latching device serves to latch a door hook in a closing position of the door. In FIGS. VIII 1 to VIII 4 , the door and the door hook are not shown. These are shown in FIG. VIII 5 and VIII 6 and cooperate according to FIGS. VIII 1 to VIII 4 with the latching device in a manner described below by reference to FIG. VIII 5 and VIII 6 .

[0138] In the illustrated embodiment, the latching device according to FIGS. VIII 1 to VII 4 is arranged in a housing 10 of the washing machine.

[0139] The latching device comprises a latching body 12 which is linearly displaceable to the left and to the right, respectively, in FIGS. VIII 1 to VIII 4 (see arrow 30 ).

[0140] A locking bolt 14 serves to latch the latching body 12 in a closing position for specific operation positions wherein the latching body, due to its arrest, also maintains the door closed which is described below by reference to FIGS. VIII 5 and VIII 6 .

[0141] In the embodiment according to FIGS. VIII 1 to VIII 4 , a bi-stable element 16 is formed as swivable lever and serves to move the locking bolt 14 in different operation positions.

[0142] In the latching body 12 , a window 18 is formed which comprises bars 20 and 22 , respectively, on, referring to FIG. VIII 1 to VIII 4 , left and right sides which can also be seen in FIGS. VIII and VIII 6 .

[0143] A spring 24 effects a bi-stable support of the latching body 12 . For that purpose, the spiral spring 24 is securely connected with both ends with the latching body 12 and is concentrically guided by two jaws 26 , 28 which are rigidly connected with the housing.

[0144] The possibility to linearly displace the latching body 12 is obtained by guiding the same between two guides 36 , 38 such that it is displaceable in direction of the double arrow 30 to the left and to the right, respectively.

[0145] On the right end of the latching body 12 , there is provided a coupling part 34 in form of a loop bent out of the drawing plane being integrally connected to the latching body 12 . The coupling part 34 effects a force coupling between the latching body 12 and a first electrical switch 40 . The electrical switch 40 comprises two arms 42 , 44 which comprise on their ends contact pieces which can be brought in contact with each other. The arm 44 of the switch 40 illustrated on the right side in FIG. VIII 1 is prevented from a movement to the left by a pin 45 . The arms 42 , 44 are resiliently biased such that they move towards each other without external force exposure and close the contact (see FIGS. VIII 2 and VIII 3 ). Also, the arm 44 can be formed rigidly such that only the arm 42 is resiliently biased and moveable.

[0146] The bi-stable element 16 being formed as lever is rotatably about a rotation axle 46 . Two one-way memory metal actuators 50 and 52 , which can be activated independently with respect to each, other engage a level arm end of the bi-stable element 16 such that, by means of an activation of the memory metal actuator 50 or 52 , a movement of the bi-stable element can be initiated in a desired direction. Depending in which direction the bi-stable element 16 is to be moved, either memory metal actuator 50 or memory metal actuator 52 is actuated, i.e. heated such that the respective threshold temperature is exceeded above which the memory metal components of the actuators 50 and 52 , respectively, take the respective predefined shape and, thus, generate the forces required for operation of the bi-stable element 16 . For energy supply, the memory metal actuators 50 and 52 are provided with flexible supplies 50 a and 50 b.

[0147] In a not illustrated embodiment, in place of the one-way memory metal actuators 50 and 52 , a single two-way memory metal actuator is used. Here, the operation of the bi-stable element 16 is obtained by heating the memory metal components above their upper threshold temperature or by cooling below the lower threshold temperature. For cooling the two-way memory metal actuator, the measures mentioned at the beginning can be taken in case the time up to the operation of the bi-stable element 16 associated with the cooling below a threshold temperature is to be reduced, thus, in case, one does not intend to wait until the two-way memory metal actuator cools below the lower threshold temperature without additional cooling. In order to avoid an undesired cooling, one or both memory metal actuators 50 and 52 can be maintained heated in the above described ways.

[0148] In a further not illustrated embodiment, in contrast to the arrangement illustrated in FIG. VIII 1 , the one-way memory metal actuators are arranged such that they engage on opposite sides of the lever arm end of the bi-stable element 16 .

[0149] The bi-stable element 16 is supported by means of a spring 54 such that it is biased in its two swivel end positions. For that purpose, the spiral spring 54 , which is securely connected with its both ends (as illustrated) with the bi-stable element 16 , is guided between two jaws 56 , 58 which are securely connected with the housing 10 . FIGS. VIII 1 and VIII 2 show two stable end positions of the bi-stable element 16 . In the below further described open position of the latching device shown in FIG. VIII 1 , the spring 54 pushes the bi-stable element 16 in clockwise direction. In the closing position of the latching device according to FIG. VIII 2 , the spring 54 pushes the lever shaped bi-stable element 16 in anti-clockwise direction. In a transition of the operation position of the bi-stable element 16 according to FIG. VIII 1 in the position according to FIG. VIII 2 (and vice versa), the spring 54 is squeezed together against its spread force such that it reaches, at a specific transition location between the two positions, a snap point with a maximum of potential energy which is partially transformed in kinetic energy upon further swiveling of the bi-stable element 16 about its rotation axle 46 and which causes the bi-stable element 16 in the illustrated end positions to which it is referred in detail further below.

[0150] The bi-stable element 16 includes an integ