1. Field of the Invention
The present invention relates to a door-closing device for a domestic electrical appliance. Particularly, the present invention relates to a door-closing device comprising a frame with an aperture for the introduction of a keeper or the like, a closing unit which is arranged on the frame so as to be movable, relative to the latter, and which, in a closing position, holds the keeper fast for the purpose of keeping the door closed and, in an open position, releases the keeper for the purpose of opening the door, the closing unit, in the course of its transfer from the open position into the closing position, drawing the keeper along with it along part of the keeper's path of movement, relative to the frame, a closing spring arrangement which acts upon the closing unit and which supplies the force necessary for drawing the keeper along with the unit, and a blocking system by which the closing unit can be blocked from moving out of the open position and into the closing position, it being possible to set aside the blocking of the closing unit by relative movement of said blocking system and closing unit.
2. Description of the Prior Art
A door-closing device of this kind with a pulling-shut function, that is to say spring-assisted pulling-shut of the door, is known, for example, from US 2005/0194795 A1. In this known solution, a blocking pin is provided which is arranged so as to be integral with the frame. The closing unit comprises a linearly movable carriage on which a rotary member is held so as to be movable about an axis of rotation. An arrangement of a number of helical compression springs is inserted between the carriage and a framework belonging to the door-closing device. The force of the helical compression springs pretensions the rotary member towards the blocking pin. The rotary member possesses a slot which is open in the radially outward direction and into which, when the closing unit is in the open position, the keeper moves on closure of the door. In the process, the keeper strikes against one of the flanks of the slot. This action of the keeper upon the rotary member leads to rotation of the latter about the axis of rotation, the outer peripheral face of said rotary member sliding along the blocking pin. Under these circumstances, considerable frictional forces can operate between the blocking pin and the rotary member, depending upon the firmness of the helical compression springs. While the keeper which has been introduced is rotating the rotary member, that part of said rotary member which adjoins the other flank of the slot engages in a clearance in the keeper. As soon as an edge at which the outer peripheral face of the rotary member bends away in the radially inward direction slips past the blocking pin, the helical compression springs are able to expand and thrust the carriage away. In the course of this displacement of the carriage, the keeper is drawn along with the rotary member by the latter, which now presses, with the other flank of its slot, against said keeper.
Another door fastener with a pulling-shut function, which door fastener is not a generic one however, is known from EP 1 344 486 A2. In this door fastener, a rotary member, to which a helical compression spring which supplies the pulling-shut force is attached by one of its ends, serves as the closing unit. When the fastener is in an open state, the straight line of force extending between the points at which the helical compression spring is attached lies on one side of the axis of rotation of the rotary member and pretensions the latter in the direction of an open position. When the fastener is closed, the straight line of force of the helical compression spring moves away over the axis of rotation of the rotary member and comes to rest on the other side of said axis of rotation. The pretensioning action of the helical compression spring is then in the direction of the closing position of the rotary member. In order to close the door, it is therefore first necessary to operate against the force of the helical compression spring. This comes about through the fact that a keeper which has been introduced strikes against one of the flanks of a slot constructed in the rotary member and thereby moves the latter away over the dead centre at which the straight line of force of the helical compression spring passes precisely through the axis of rotation. As soon as the dead centre has been crossed, the spring expands and drives the rotary member into its closing position. In the process, the keeper which is now trapped in the slot in the rotary member is drawn along with it. What is problematic about the fastener according to EP 1 344 486 A2 is that, for a low initial force of resistance when the door is being closed, the straight line of force of the helical compression spring is supposed to be removed only a little way from the dead-centre position, but this at the same time entails an increased susceptibility to unwanted automatic closing of the catch if vibration or jolting occurs.
German Laying-Open Specification DE 10 2006 037 494 A1, which was published subsequently, indicates a door-closing device with a pulling-shut function in which, on closure of the door, a closing body with a projecting nose plunges into a closing trough formed on the door and then snaps back under the action of an expanding closing spring, as a result of which the door is pulled shut. Said door first of all strikes against a control lever which is separated from the closing body and which is set in motion as a result. The rotating control lever in turn presses the closing body down against a blocking face formed by a base frame of the closing device. As soon as the closing body passes the blocking face, the closing spring is able to expand.
German Laying-Open Specification DE 10 2007 025 295 A1, which was likewise published subsequently, indicates a door fastener having a closing member which is guided, via two spindles, so as to be movable within a guide groove in a fastener housing and which, on closure of the door, grasps a closing catch arranged on the door and then moves, under the action of an expanding closing spring, in such a way that the door catch is pulled into the fastener. The course of the guide groove exhibits an inflexion which has to be overcome by one of the spindles of the closing member so that the closing spring is able to expand for the purpose of deploying its pulling-shut action.