Buckle for a safety belt

In a buckle for a safety belt a pivotable locking bar (13-17) is arranged in relation to the push-in tongue (4) in such a way that the ejector force (11) or the belt force exerting a load on the tongue urges the locking bar out of engagement. To prevent this in the closing position, there is a pivoting lever (21) which can be pivoted as a result of actuation of a slide (27) so that the locking bar (13-17) and consequently the push-in tongue (4) are released. According to the invention, this releasing pivoting movement of the locking bar is assisted because an extension piece (30) is provided on the slide (27) and a projection (32) interacting therewith is provided on the locking bar (13-17), and by means of these, when the slide (27) is pressed in, an additional torque for pivoting the locking bar into the opened position is transmitted.

DESCRIPTION 
The invention relates to a buckle for a safety belt, consisting of a 
push-in tongue with a locking recess and of a lock with a push-in path for 
the push-in tongue, the said path being limited at least on one side by 
guide devices, being open at its front end and containing an ejector 
spring, with a locking bar which is mounted pivotably in the lock and the 
pivot axis of which extends transversely to the direction of the push-in 
path and which forms a locking-bar nose which interacts with the locking 
recess in the push-in tongue and which is movable into the push-in path 
from the side remote from the guide devices and is arranged so that, in 
the locking position, the ejector spring urges the locking bar out of 
engagement, and with a pivoting lever for securing the locking bar in the 
locking position, this pivoting lever being urged into the retaining 
position as a result of spring force and being removable from this, for 
the purpose of opening the lock, as a result of actuation of a slide 
guided approximately parallel to the push-in path and located on the side 
of the latter remote from the guide devices. 
In a buckle of this type (earlier European Patent Application No. 80 10 107 
136.6 of the applicant), the lock is retained in the locked position by 
means of the pivoting lever. Although the ejector spring and also a 
tensile force acting, if appropriate, on the safety belt seek to urge the 
locking bar out of engagement, the lock cannot open because the pivoting 
lever retains the locking bar firmly in the locking position. However, 
when the slide is pressed, the pivoting lever is removed from its locking 
position, so that as a result of the force of the ejector spring the 
locking bar is pivoted and the push-in tongue is released. It can arise, 
under unfavourable conditions, that the force of the ejector spring is not 
sufficient to pivot the locking bar, for example when the lock is soiled 
or after deformation in the event of an accident. 
The object of the invention is, therefore, to provide a buckle of the type 
mentioned in the introduction, which can be opened more reliably, 
particularly as a result of forces to be exerted from outside by means of 
the slide. 
The solution according to the invention involves providing the locking bar 
on the side remote from the guide devices with a projection which, when 
the slide is actuated, interacts with the latter to pivot the locking bar 
out of the locking position. 
It is appropriate if the projection of the locking bar and the slide, which 
can be provided for this purpose with a projection, interact rigidly and 
inflexibly at least in the last phase of movement of the slide, so that 
the opening force exerted on the slide is transmitted fully to the 
projection of the locking bar. However, in addition to this or, if 
appropriate, even instead of this, an elastic member can be provided on 
the projection of the locking bar or on the slide, and this ensures that 
with a progressive displacement of the slide during the opening of the 
lock an increasing opening force is exerted on the locking bar. This 
produces a smooth opening force on the locking bar which makes operation 
of the lock convenient. 
When the slide starts to be pushed in, the locking bar is first blocked by 
the pivoting lever. The further the slide is pressed in, the greater the 
force exerted thereby on the locking bar as a result of elastic coupling 
between the slide and the locking bar. When the slide is pressed in so far 
that locking is cancelled by the pivoting lever, this force of the slide 
acting on the locking bar has meanwhile increased to such an extent that 
the opening movement of the locking bar is effectively assisted. In this 
way, the locking bar is moved out of its locking position even if, for any 
reason, automatic unlocking fails because of the internal forces or the 
tensile force of the belt. 
Elastic interaction can be achieved especially simply if the slide is 
provided with an extension piece which interacts with the projection of 
the locking bar first via an elastic part and finally, in the event of 
maximum compression of the elastic part, directly and inflexibly. The 
extension piece of the slide can consist, for example, of plastic and can 
have one or more arms as elastic members which engage transversely to 
their longitudinal direction with the projection of the locking bar and in 
so doing bend elastically. 
The projection of the locking bar can consist of plastic. In addition to 
elasticity, this material also has the advantage that it can be applied to 
the locking bar easily and economically, for example by injectionmoulding 
round the latter. 
The projection can be provided near the pivot axis of the locking bar. The 
advantage of this is that the projection executes only very slight 
movements perpendicularly to the push-in direction, and to that extent no 
substantial friction occurs between the slide or the extension piece of 
the slide, on the one hand, and the projection, on the other hand. The 
projection can be made, for example, in one piece with a plastic coating 
of the locking bar in the region of the pivot axis, this permitting simple 
production. This plastic coating can extend into the mounting of the pivot 
axis, so that there the bearing projections of the locking bar and the 
cut-outs in the bearing housing, which serve for mounting the bearing 
projections, are separated from one another at least partially, so that 
rattling noises are prevented or reduced and the life of the lock is 
prolonged.

The lock body consists of a plane bottom 1 and two side walls 2 projecting 
vertically from its parallel edges and connected rigidly to the bottom. It 
has a cross-section of U-shaped form. Its bottom 1 contains a bore 3 for 
fastening an anchoring part. 
The bottom 1 and the parts of the side walls 2 adjoining it form guide 
devices for the push-in tongue because they constitute the lower and 
lateral limitation of the push-in path of the push-in tongue 4, the front 
part 5 of which has approximately the width of the push-in path between 
the side walls 2. It has a locking recess 6 which forms a locking face at 
7. At its rear end, it is provided, in a known way, with a recess 8 for 
receiving a belt loop. Towards the top, the push-in path is limited by 
projections 9 connected rigidly to the lock body. The known casing of the 
lock body in a plastic housing is not shown for the sake of simplicity. 
All directional indications, such as "top", "right", "clockwise 
direction", etc. refer to the illustration in FIGS. 1 and 2, and "front" 
and "rear" refer to the direction of the push-in movement. 
The lock contains, in the push-in path, an ejector plate 10 which is guided 
movably therein, in a way not shown, in the direction of the push-in path 
and which is stressed counter to the push-in direction by a spring 11 
guided in bottom slits. In FIGS. 1 to 3, therefore, the push-in path can 
be recognised by means of the top side of the bottom 1, by means of the 
position of the push-in tongue 4 and the ejector plate 10 and by means of 
the projections 9. 
In the rear half (that is to say, on the right in the drawing) of the lock 
body is located, in each of the two side walls 2 at corresponding points a 
cut-out 12 for receiving lateral projections 13 of a locking-bar plate 14. 
Between the cut-outs 12 and the associated projections 13 there is so much 
play that the locking-bar plate 14 is pivotable through a small angle 
about an axis lying transversely to the push-in direction and parallel to 
the bottom 1. The two end positions occurring in practice during the 
operation of the device are shown in FIGS. 1 and 2. The locking-bar plate 
consists of a rear transverse part 15 connecting the projections 13 and of 
a plate part 16 which leads forwards in front of it and which carries at 
the front a downwardly projecting locking-bar part 17 forming a 
locking-bar nose 18 pointing to the rear. The locking-bar part 17 projects 
a little forwards in relation to the plate part 16, so that there forms on 
its top side a free face 19 limited towards the front by its front edge. 
In the locking state (FIG. 1), this face lies in the upper limiting plane 
of the push-in path or a little above it. 
The locking-bar plate 14 has at its rear end at least one projection 20 
which projects downwards near the axis of rotation of the locking-bar 
plate, determined by the front end of the cut-outs 12, and which limits 
the push-in path towards the rear. It serves, together with the ejector 
plate 10, for the positive locking of the push-in tongue. In particular, 
when pushed in, the latter moves the ejector plate 10 to the rear counter 
to the pressure of the ejector spring 11, the ejector plate 10 being made 
so long that it just butts against the projection 20, thereby causing 
rotation of the locking bar to the left in an anti-clockwise direction, 
when the locking face 7 of the push-in tongue 4 has just passed through 
under the locking-bar nose 18 of the locking-bar part 17. 
The locking-bar nose 18 of the locking-bar part 17 is, in the locking 
state, approximately perpendicular to the direction of the push-in path 
and at an obtuse angle to the connecting line with the locking-bar axis. 
When a force is exerted on the locking-bar nose 18 to the left in the 
direction of the push-in path, for example by means of a belt force acting 
on the push-in tongue or by means of the ejector spring 11, there is 
consequently exerted on the locking bar a torque which is formed by the 
force acting in the push-in path and the distance between the push-in path 
and the axis of rotation of the locking bar, as a lever arm. This torque 
seeks to rotate the locking bar in a clockwise direction, to lift the 
locking-bar part 17 out of the locking-bar recess in the push-in tongue 
and thus to release the lock. This is prevented, in the locking state, by 
the pivoting lever 21. This pivoting lever 21 is located above the 
upward-pointing face 19 of the locking part 17. It is designed as a plate 
which extends transversely in the lock body and the outline of which may 
be seen on the left in FIG. 4, whilst on the right it is partially cut 
away to give a view of the locking-bar plate. The pivoting lever is 
mounted by means of its lateral projections 22 in cut-outs 24 of the side 
walls 2, so that there arises in the region 25 (FIG. 1) an axis of 
rotation which is parallel to the axis of rotation of the locking bar 
13-17. It can therefore pivot at least between the two end positions 
illustrated in FIGS. 1 and 2. Pivoting is served, on the one hand, by a 
spring 26 which endeavours to pivot it in an anti-clockwise direction and, 
on the other hand, by the slide 27 which is guided movably in the lock 
body parallel to the push-in path in a way not shown, and during movement 
to the right butts against the upper end of the pivoting lever and thereby 
rotates the pivoting lever in a clockwise direction. The pivoting lever 21 
is held in the retaining position by the spring 26 and by means of 
self-locking. 
The spring 26 is appropriately designed so that it is supported at one end 
on the lower part of the pivoting lever and at the other end on the slide 
27. The two parts are thereby urged into their normal position with a 
double effect. It can, of course, be of a different design from that shown 
in the drawing. 
Above the region located between the projections 22, the pivoting lever is 
made narrower towards the centre. Its top part 40 (FIG. 4) forms a stop 
interacting with the slide. On the right and left of this (FIG. 4), it 
leaves room for the passage of parts 41 of the slide 27 which come 
together behind it (on the right of it in FIG. 1) to form an extension 
piece 30 of the slide. 
In the embodiment according to FIGS. 1 to 3, the extension piece 30 carries 
a pin 42 of specific length which projects to the rear (to the right in 
the illustration) and on which is guided a helical spring 43 which is 
longer than the pin. A projection 32 projects from the top side of the 
locking bar 14, near its pivot axis, up behind the pin 42 and the spring 
43, the length of which is such that, in the locking state of the lock, it 
does not reach the projection 32 and therefore does not exert any force on 
it. 
On the rear side of the locking bar there is a plastic surface 34 which 
projects into the bearing cut-outs 24 behind the bearing projections 13 of 
the locking bar and which therefore prevents direct metallic contact 
between the locking-bar projections and the cut-outs and avoids rattling 
noises. 
The arrangement described has the following mode of operation. 
When the lock is in the released state (FIG. 2), the ejector plate 10 is 
located, in the push-in path, underneath the locking-bar part 17 of the 
locking bar, so that the latter cannot block the push-in path. It is 
therefore possible to move the push-in tongue 5 to the right into the 
push-in path, the ejector plate 10 likewise being pushed to the right. 
When the ejector plate 10 reaches the projections 20, the locking recess 6 
in the push-in tongue 4 is located underneath the locking-bar part 17. 
During further movement, the locking bar is pivoted in an anti-clockwise 
direction as a result of the impact of the ejector plate 10 on the 
projection 20, so that the locking-bar part 17 must penetrate into the 
locking recess 6. 
When the lock is in the released state, the lower end of the pivoting lever 
21 rests under pre-stress against the forward-pointing nose of the 
locking-bar part 17 as a result of the spring force 26. At the moment when 
the locking-bar part is lowered into the locking recess in the push-in 
tongue, the said nose slides under the pivoting locking bar, so that the 
latter can rotate in an anti-clockwise direction under the effect of the 
spring 26, until it rests against the rear limitation 28 of the bearing 
cut-outs 24 (FIG. 1). At the same time, the downward-pointing nose 29 of 
the pivoting lever 21 is located immediately above the upward-pointing 
face 19 of the locking-bar part. In this position, in which the pivoting 
locking bar is retained by the spring 26, it secures the locking bar 13-17 
in the locking position. 
In the locking state, the locking face 7 of the push-in tongue 4 exerts on 
the locking-bar nose 18 of the locking-bar part 17 a force which is 
directed to the left in the direction of the push-in path and the line of 
influence of which runs along the push-in path and therefore at a certain 
distance below the pivot axis of the locking bar 13-17 determined by the 
cut-outs 13. If the locking bar were not secured in its position by the 
pivoting lever 21, a torque would therefore be created on the locking bar 
13-17 in a clockwise direction, and this would urge it out of the locking 
position into the opening position. The geometrical ratios are selected so 
that this torque would normally be sufficient on its own to open the 
locking bar under the effect of the ejector spring 11. 
When the slide 27 is moved to the right to open the lock (FIG. 3), the 
pivoting lever 21 is rotated in a clockwise direction, with the result 
that, when it passes the front edge of the locking-bar part 17, it loses 
its effect on the retaining face 19. The locking bar is thereby freed and 
can move upwards under the effect of the forces acting on it, and can 
release the push-in tongue as a result. 
These forces are mainly generated by the spring 43 or the pin 42. When the 
slide 27 is pressed in, the spring 43 of the slide comes up against the 
projection 32 of the locking bar and presses the latter to the right. This 
generates a torque in a clockwise direction, which pivots the locking bar 
into the open position. This torque can be increased by pressing more 
strongly on the slide, because the spring is then compressed to a greater 
extent and a correspondingly greater force is generated. Should the spring 
force be insufficient, then finally the pin 42 strikes directly against 
the projection 32, as indicated in FIG. 3, so that an opening force of any 
magnitude can be exerted on the locking bar 14. Even under unfavourable 
circumstances, the user thus acquires a high degree of certainty that the 
locking bar is actually pivoted into the open position. 
FIGS. 5 and 6 illustrate another embodiment of those parts of the lock 
described which transmit the opening force from the slide extension piece 
30 to the locking-bar projection. Located at the rear end of the slide 
extension piece 30, the rear face of which is denoted by 44, are two arms 
31 which, for example being in one piece with the slide, consist of an 
elastic plastic (for example, polyamide). They end in thickened heads 45 
which are located between the locking-bar projection 32 and the rear face 
44 of the slide extension piece. They extend transversely to the direction 
of movement of the slide. When the latter is pushed into the lock body to 
open the lock (FIG. 3), the heads 45 first come in contact with the 
locking-bar projection 32 and urge the latter, during further movement of 
the slide, to the right, the arms 31 being deformed resiliently, with the 
result that an opening force is exerted on the locking bar. When the slide 
is moved further to the right, there finally arises the state according to 
FIG. 6, in which the extension piece 30 exerts its force directly on the 
locking-bar projection via the heads 45, without the agency of the 
resilient arms 31.