The invention relates to a snap lock, in particular for closing a window, a door or the like, comprising a base member, a latch having a projecting part for engagement with a striking plate and adapted to be displaced from a closing position against a spring power and an actuator device for taking the latch into a retracted opening position, wherein the latch is also pivotal in relation to the base member about an axis transverse to the direction of said displacement, the opening position is a position turned out about said axis, and a resilient member is arranged to retain the latch in a non-turned-out position parallel to the closing position, and wherein the base member, the latch and the actuator device consitute elements in a four-linked mechanism the components of which are hinged to each other substantially with mu¬ tually parallel hinge axes.

Such a snap lock is known from DE-B-1,021,750 dealing with a lock for a refrigerator door in which the latch and the base member are neighbouring com¬ ponents in the four-link mechanism.

DE-GM-71 28 377.7 relates to a snap lock by the use of which it is possible to close for instance a window by slamming, thereby locking the window, i.e. the snap lock must be released actively before reopening the window.

It is sometimes desirable to close for instance a window actively against a sealing pressure by means of the lock and in other cases it is desirable that the snap lock may be inactivated so that the window will net be locked by being banged.

The object of the invention is to provide a snap lock which fulfills the above requirements.

This is fulfilled by means of a snap lock of the above mentioned type which is characterized in that the

latch and the base member constitute opposite members in the four-link mechanism, the latch being hinged by means of a first hinge at the end comprising the pro¬ jecting part to a link which again by means of a second hinge is hinged to the base member, the latch being hinged at its other end by means of a third hinge to the actuator device which again by means of a fourth hinge is hinged to the base member. It is thereby obtained that the snap lock besides operating as an ordinary snap lock may, on one hand, close a window actively against a sealing pressure by pivoting the latch from the outwards pivoted opening position to the closing position, in that the resilient member prevents the snap lock from being disengaged unintentionally and, on the other hand, be inactivated so that the win¬ dow or the door may be closed without being locked.

In an embodiment the third hinge includes a hinge pin which is journalled in a slot provided either in the latch or in the actuator device, said slot extending in the direction of said displacement when the latch is in the closing position. The slot ensures the possibility of displacing the latch.

In a further embodiment the four-link mechanism is dimensioned so that the first, the second and the fourth hinge in a plane perpendicular to the hinge axes form an obtuse angle when the latch is in the closing position and an acute angle when the latch is in the opening position. This provides for obtaining that the latch by said displacement is substantially displaced as to parallel.

In a further embodiment the snap lock has a stop adapted so that the third, the first and the second hinge in a plane perpendicular to the hinge axes form an obtuse angle less than 180° when the latch is in the opening position. This provides for obtaining that the snap lock is not self-locking in the opening position.

The latch is, moreover, in an embodiment substantially designed as an L, in which the first hinge is arranged at the bend of the L, and the third hinge is disposed at the end of the long leg of the L, the short leg of the L extends away from the base member and has at its remote end an abutment face for engagement with the striking plate when the latch is in the closing position, and the intended point of attack of the abutment face, the first and the second hinge in a plane perpendicular to the hinge axes form an obtuse angle that is concave in comparison with the remainder of the four-link mechanism, and the intended direction of attack in the point of attack corresponds substan¬ tially to the direction from the point of attack towards the first hinge when the latch is in the closing position. This provides for obtaining that the snap lock is self-locking in the closing position.

In a further embodiment the base member has an abutment face for mounting and an external delimitation close to the second hinge, the link has in relation to the four-link mechanism an external surface which when the latch is in the closing position extends from said external delimitation of the base member substantially perpendicular to its abutment face and through a bend¬ ing away from the remainder of the four-link mechanism to a point in the vicinity of the first hinge. Said external surface thereby constitutes an abutment face for the striking plate when a window with the snap lock according to the invention has been banged, whereby the link operates as a lever and forces the latch backwards against the spring power, said bending ensuring that the lever of the link from the second hinge to the point of attack of the striking plate attains a suf¬ ficient size to ensure a reliable effect.

The resilient member actuates preferably the actuator device in the direction away from the opening

position in order to be capable of keeping the latch in the non-turned-out position.

In a further embodiment the snap lock includes a second resilient member to retain the latch in the opening position, whereby the link may comprise a cam which when the latch is in the opening position cooper¬ ates with the second resilient member to retain the latch in the opening position. This provides for obtaining that the snap lock may be inactivated so that the window is not locked by being banged.

The invention will now be exlained in detail by means of an example with reference to the schematical drawings, in which

Fig. 1 shows a section through a snap lock according to the invention, mounted for instance on a window frame,

Fig. 2 is a view in the direction of the arrow II in Fig. 1, and

Fig. 3 is a view corresponding to Fig. 1 but with the snap lock in the opening position.

In Fig. 2 the snap lock is shown alone whereas in Fig. 1 it is shown mounted in a window frame 1 which by means of a seal 2 is sealed against a sill 3. A Striking plate 4 for engagement with the snap lock is mounted on the sill 3.

The snap lock proper accommodates a latch 5 with a roll 6 pivotally mounted about an axis per¬ pendicular to the plane of the drawing. The latch 5 is by means of a first hinge pin 7 hinged to a link 8 which again by means of a second hinge pin 9 is hinged to a base member 10.

The latch 5 is further by means of a third hinge pin 11 hinged to an actuator device 12 that is again hinged by means of a fourth hinge pin 13 to the base member 10. Towards the window frame 1 said base member has an abutment face 14 from which a pair

of hollow legs 15 extends into which screws may be screwed when mounting the snap lock on the window frame 1.

The actuator device 12 is provided with a handle in the form of a sectional bar extending in a direction perpendicular to the plane of the drawing. The actuator device 12 is further provided with a slot 17 in which a third hinge pin is journalled. The hinge pin 11 is by a pressure spring 18 kept in engagement with the left side of the slot 17, shown in Fig. 1. Moreover, the actuator device 12 is biassed counterclockwise by means of a helical spring 19, shown in Figs 1 and 3.

When the snap lock according to the invention is used as an ordinary snap lock, i.e. when the window frame l is banged, the window frame passes across the striking plate 4 and so does part of the link 8. This link has a face 20 which after bending inclines in relation to a plane perpendicular to the plane of the window frame 1, in the direction towards the striking plate 4 which has a corresponding inclined face 21. The inclined part of the face 20 hits the inclined face 21 and is pressed away from the striking plate 4, whereby the link 8 operates as a lever and through the first hinge pin 7 presses the latch 5 away from the striking plate 4. This is possible because the third hinge pin 11 moves in the slot 17 against the power from the pressure spring 18. When the link 8 as well as the roll 6 have passed the inclined face 21 the latch 5 will reoc- cupy the closing position illustrated in Fig. 1, thereby causing the roll 6 to engage a locking face 22 of the striking plate 4 and lock the window frame 1.

When opening the window the latch 5 is set in an opening position by pivoting the actuator device 12

clockwise by means of the handle 16 about the fourth hinge pin 13, illustrated in Figs 1 and 3.

The snap lock then occupies the opening posi¬ tion, shown in Fig. 3, which is delimited by the fact that the link 8 strikes a stop 23. By influencing the actuator device 12 counterclockwise the helical spring attempts to guide the snap lock back to the position shown in Fig. 1, but the helical spring 19 is not strong enough to overcome the engagement between a resilient tongue 24 on the base member 10 and a cam 25 of the link 8 and, therefore, the snap lock may remain in the opening position shown in Fig. 3. By means of the handle 15 a person can, however, bring the snap lock back into the closing position shown in Fig. 1. The centre of roll 6 will then substantially follow the path 26 shown in dashed lines and it will be seen that the snap lock is in a position to close the window actively, thereby creating a sealing pressure against the seal 2.

In respect of the good effect of the snap lock a series of geometrical and mechanical requirements is fulfilled. Thus, the axis of the first hinge pin 7 is in Fig. 1 located to the left of the connecting line between the axis of the roll 6 and the. axis of the second hinge pin 9. This ensures that the snap lock is self-locking in the closing position. It appears, moreover, that the axes of the first, the third and the fourth hinge pin in the closing position shown in Fig. 1 are substantially aligned. When the snap lock oper¬ ates as an ordinary snap lock by banging the window frame 1, the axis of the third hinge pin will be posi¬ tioned above the connecting line between the first and the fourth hinge pin and a moment therefore occurs attempting to pivot the actuator device 12 clockwise, thereby opening the snap lock. However, the helical spring 19 prevents this pivotal movement the strength

of said spring being appropriately adapted to the strength of the pressure spring 18. Finally, the stop 23 is designed so as to ensure that the axis of the first hinge pin 7, as illustrated in Fig. 3, is always located above the connecting line between the second hinge pin 9 and the third hinge pin 11. It is thus ensured that the snap lock does not lock itself in the opening position whereas it may always be manually brought back to the closing position.