1. Field of the Invention
The present invention relates generally to a door latch for an electrical household appliance. Particularly, the present invention relates to a door latch for a laundry treatment appliance, for example a washing machine.
2. Description of the Prior Art
The door latch considered here is one of the so-called types with an indirect locking mechanism. Such a latch type has a gripping unit which serves to grip and retain a striker (or other closing body) as a door of the household appliance is closed and thereby hold the door closed. The gripping unit can be locked in a closed position by a plurality of mechanically series-connected arresting elements so that it cannot be opened. Each of the arresting elements can be displaced between two positions. A first arresting element can be moved into a position in which it effects a blocking of the gripping unit. After the first arresting element has moved into its position blocking the gripping unit, a second arresting element is in turn moved into a locking position in which it effects a blocking of the first arresting element so that this cannot move out if its blocking position. This corresponds to a closed and locked state of the door.
If the second arresting element is guided back out of its locking position into an unlocking position, the first arresting element is free again. This corresponds to a closed, but unlocked, state of the door. In this state, the gripping unit can drive the first blocking element out of its blocking position into a release position (typically in opposition to spring force) if the door is pulled in order to open it.
Typically, in the type of door latches considered here, an actuator is associated with the last arresting element in the chain of arresting elements and this can be used to move it between its locking position and its unlocking position.
For the prior art of such door latches with an indirect locking mechanism, please refer to WO 2011/132213 A1 and WO 2013/109585 A2.
According to WO 2011/132213 A1, a rotational body serving as a gripping unit is constructed with a so-called cavity into which a first arresting element dips as the door is closed. Inclined surfaces on the walls of the cavity and on the first arresting element ensure that a division of force takes place if an attempt is made to rip open the door when the door is closed and locked. Part of the force transmitted here from the gripping unit to the first arresting element is diverted directly into a housing of the latch by way of the first arresting element. Only a residual part of the force is transmitted from the first arresting element to a second arresting element which serves to selectively block the first arresting element.
According to WO 2013/109585 A2, a division of force does not take place between a gripping unit and a first arresting element, but between the first arresting element and an intermediate element which is seated in the force-transmission path between the gripping unit and the first arresting element. The intermediate element and the first arresting element are guided at a right-angle to one another, with a wedge-type engagement between both elements ensuring the desired division of force. If the door is pulled when it is closed and locked, the force acting on the gripping unit is transmitted via the intermediate element and from there into the first arresting element. The wedge-type engagement between the intermediate element and the first arresting element causes part of the force from the first arresting element to be diverted directly into a housing of the latch so that only a residual part of the force is transmitted further to a second arresting element serving to selectively block the first arresting element.
The solution according to WO 2011/132213 A1 is problematic in that the required cavity on the gripping unit is associated with a weakening of the material, which can have a disadvantageous effect on the load bearing capacity of the gripping unit.
The present invention moreover takes as its starting point a door latch for an electrical household appliance that includes a latch housing, a gripping unit which is received in the latch housing and is movable in a rotational plane between an open rotational position and a closed rotational position and which, in the closed rotational position, grips a striker for holding a door of the household appliance closed and, in the open rotational position, releases the striker for opening the door, a first arresting element which is received in the latch housing such that it is movable between a release position and an arresting position and which, in the arresting position, effects a blocking of the gripping unit to prevent rotation into the open rotational position and, in the release position, permits a rotation of the gripping unit into the open rotational position, where the first arresting element has an engagement surface which, in the arresting position, is opposite an engagement counter-surface of the gripping unit, where an engagement between the engagement surface of the first arresting element and the engagement counter-surface of the gripping unit generates a force component which acts parallel to the rotational plane of the gripping unit on the first arresting element, and a second arresting element which is received in the latch housing such that it is movable between an unlocking position and a locking position and which, in the locking position, effects a blocking of the first arresting element to prevent movement into the release position and, in the unlocking position, permits a movement of the first arresting element from the arresting position into the release position.
A door latch of this type is characterized according to the present invention by a guide arrangement which guides the first arresting element such that it is movable relative to the latch housing in a guide direction extending at an incline to the rotational plane of the gripping unit. This design enables a division of force between the first arresting element and the guide arrangement so that the second arresting element is protected from a load exerted by the full force which can occur in the closed and locked state of the door when the door is pulled. Part of this force can be diverted from the first arresting element via the guide arrangement; only a residual part is conducted further from the first arresting element to the second arresting element. The design according to the invention requires neither a cavity in the gripping unit nor an additional slide element to effect a division of force in conjunction with the first arresting element.
In one embodiment, the guide arrangement is constructed on the latch housing. For example, the latch housing can form a system of one or more guide walls on which the first arresting element is movably guided in the guide direction.
In one embodiment, the guide direction is linear. Instead of a linearly movable slide, the first arresting element can alternatively be constructed as a rotary slide. In this case, the guide direction extends along a curved path (e.g. a circular path).
With a linear course of the guide direction, this can extend at an angle between 20 and 50 degrees or an angle between 25 and 45 degrees or an angle between 30 and 40 degrees relative to a normal direction to the rotational plane of the gripping unit. The residual force which is transmitted to the second element when the closed and locked door is pulled can decrease as the angle increases. However, a larger angle can increase the force which a user wanting to open the closed but unlocked door has to apply to drive the first arresting element out of its blocking position. The concretely selected angle between the guide direction and the normal direction to the rotational plane of the gripping unit can therefore be the result of a compromise which, on the one hand, ensures that a user can open the door relatively easily—if it is unlocked—and, on the other hand, ensures that the second arresting element is not subjected to an excessive load if the closed and locked door is pulled.
In embodiments of the invention, upon an engagement between the engagement surface and the engagement counter-surface, a resultant force acting on the first arresting element is generated, which has a parallel direction of action to the rotational plane of the gripping unit. A division of force between the gripping unit and the first arresting element is thereby prevented. For example, the engagement surface and the engagement counter-surface can be constructed as planar surfaces with a surface plane which is in each case orthogonal to the rotational plane of the gripping unit.
The gripping unit can form a gripping jaw which is delimited by two cheeks and in which the striker is captured as the door is closed, with the striker impacting against a first cheek of the gripping jaw as the door is closed and thereby setting the gripping unit in rotation, and with the second cheek of the gripping jaw reaching behind the striker in the closed rotational position of the gripping unit. To prevent the gripping unit from breaking if the door is pulled with excessive force, without having to increase the material thickness of the gripping unit unnecessarily, the gripping unit can be metal-reinforced at least in a region of the second cheek. To this end, the gripping unit can have a base body made from a plastic material, which has a cutout equipped with a metal pin in the region of the second cheek. It is alternatively conceivable for the gripping unit to have a reinforcing plate body which is sheathed with a plastic material and extends from the second cheek into the region of the first cheek. The reinforcing plate body can be for exampled a punched sheet-metal part.
The object of the invention is furthermore a laundry treatment appliance which has a main appliance housing and a door which is mounted on the main appliance housing for the purpose of closing an access opening to a laundry treatment space of the appliance. According to the invention, such a laundry treatment appliance is equipped with a door latch of the type mentioned above. A possible laundry treatment appliance is, for example, a washing machine. An embodiment as a washer dryer is likewise feasible.
The invention is explained in more detail below with reference to the accompanying drawings.
Reference is first of all made to the comparative examples according to
It is possible to lock the closed door in that a locking element 20, which is for example linearly displaceably guided between an unlocking position and a locking position (indicated by a double-headed arrow 22), is moved in front of the blocking slide 14 in the closed state of the door in such a way that this blocking slide cannot draw back when the door is pulled. This situation is shown in
In
In the comparative example according to
In the inventive embodiment according to
Contrary to the two comparative examples according to
If an attempt is made to open the door when the door is closed but not locked, the gripping unit 10b can drive the blocking slide 14b aside owing to its inclined guidance on the housing 24b and the door can therefore be opened. However, this cannot happen if the blocking slide 14b is blocked by the locking element 20b. The force introduced from the gripping unit 10b into the blocking slide 14b is then divided into two force components as a result of the inclined guidance on the housing 24b. One of these force components is diverted from the blocking slide 14b directly into the housing 24b, the other force component is transmitted to the locking element 20b. The amount of force introduced into the locking element 20b can be influenced by the size of the angle α.
The blocking slide 14b forms a first arresting element according to the invention, the locking element 20b forms a second arresting element according to the invention.
Reference is now made to the concrete embodiment according to
The gripping unit 104 forms a gripping jaw 110, which is delimited by two cheeks 112, 114. As the door of the household appliance is closed, a striker 116 dips into the closing jaw 110 with a leading end region 116a and abuts against the closing or first cheek 114. This sets the gripping unit 104 in rotation (shown counter-clockwise in
In the closed rotational position, the gripping unit 104 can be blocked by a blocking slide 124. The blocking slide 124 corresponds for example to the blocking slide 14b according to
In its arresting position, the blocking slide 124 can be blocked by a locking element 138 (indicated by a dashed line in
When the door is open, the blocking slide 124 abuts under pre-tension against a side cheek 140 of the gripping unit 104. If the gripping unit 104 is rotated out of its open rotational position into the closed rotational position, the blocking slide 124 slips along the side cheek 140 until an anti-slip edge formed at the transition between the side cheek 140 and the engagement counter-surface 132 moves past the blocking slide 124. At this moment, the blocking slide 124 snaps into its arresting position, upon which the engagement surface 130 arrives in front of the engagement counter-surface 132. This corresponds to the closed state of the door.
In order to open the door, a user has to pull on it forcefully enough to enable the gripping unit 104 to drive the blocking slide 124 out of the arresting position into the release position in opposition to the force of the pre-tensioning spring of the blocking slide 124. As is clearly shown in
Further accommodated in the latch housing 102 is an auxiliary slide 154 which is linearly displaceable along a displacement direction indicated by a double-headed arrow 156. The auxiliary slide 154 serves to actuate an electrical door switch (not illustrated in more detail) whereof the switch status (open or closed) can be detected by an electrical control unit (likewise not illustrated in more detail) to determine whether the door of the household appliance is open or closed.
In the situation according to
Reference is now made to
In the variant according to
In the variant according to
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.
Number | Date | Country | Kind |
---|---|---|---|
10 2015 002 538.4 | Feb 2015 | DE | national |