Buckle device

In a buckle device in which a tongue plate is inserted into a buckle body secured to a vehicle body and is latched to a lock lever disposed in the buckle body, an opening portion of the tongue plate and a pawl of the lock lever are caused to contact with each other at two points spaced in a predetermined distance and a clearance is formed between the opening portion and the pawl in respect of the two points. In an ordinary situation of the vehicle the clearance is kept smooth, and, when a large load acts upon the tongue plate in an emergency situation of the vehicle, the contact portions of the opening portion and the pawl at the two points are deformed, whereby portions of the opening portions and the pawl existing between both the points are caused to contact with each other. Accordingly, the lock lever is capable of being operated with a small force and the tongue plate can be pulled out of the buckle device smoothly.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a buckle device adapted for use in 
seatbelt system for protecting an occupant in an emergency situation of 
such a vehicle as an automobile or an airplane and more particularly to a 
buckle device improved in locking portion between a lock lever and a 
tongue plate. 
2. Description of the Prior Art 
As is well known, the buckle device is such constructed that a tongue plate 
secured to one end of an occupant-restraining webbing is inserted into a 
buckle body and a lock lever disposed in the buckle body is latched to an 
opening portion of the tongue plate to prevent the tongue plate from being 
pulled out, whereby an occupant is placed in his webbing-fastening 
situation. 
Also, in case that the occupant releases the webbing-fastening situation, 
he pushes down a release button mounted on the buckle body to cause the 
lock lever to separate from the opening portion of the tongue plate, 
thereby to pull the tongue plate out of the buckle body. 
FIGS. 1 and 2 are a plan view and a sectional view showing a locking 
portion of a conventional buckle device. 
A buckle body 10 is provided therein with a lock lever 12, and a pawl 14 
formed on the lock lever 12 is caught in an opening portion 18 of a tongue 
plate 16 inserted in the buckle body 10. In this case, the pawl 14 usually 
contacts with the opening portion 18 approximately at their center 
portions 19, as shown in FIG. 1, but the contact portions of the pawl 14 
and the opening portion 18 are moved in accordance with variations of load 
acting upon the webbing. That is to say, in such a condition that the 
tongue plate 16 is locked into the buckle body 10 a clearance exists 
between the inside of the buckle body 10 and each of both side edges of 
the tongue plate 16, and in such a condition the tongue plate 16 is 
slightly rotatable centering around the center portions 19 in directions 
of the width of the buckle body 10. Therefore, the contact portions of the 
pawl 14 and the opening portion 18 are moved rotatably centering around 
the center portions 19 due to changes of attitude of the occupant fastened 
by the webbing or the like. 
Accordingly, the pawl 14 and the opening portion 18 of the tongue plate 16 
are caused to contact with, or rub against, each other approximately all 
over their locking faces in accordance with increase in number of use of 
the buckle device, and the locking faces are made rough approximately in 
their whole surfaces, whereby most of the respective locking faces is 
decreased in smoothness and the friction between both the locking faces is 
increased approximately all over the locking faces. As a result, when a 
large load acts upon the webbing, for example, when the centre portions 19 
are deformed or crushed in such an emergency situation of the vehicle as a 
collision and the contact portions of the opening portion 18 and the pawl 
14 are enlarged, portions of the opening portion 18 and the pawl 14 newly 
caused to contact with each other in the emergency situation have already 
been made rough, i.e., they have already been increased in frictional 
force therebetween, as set forth above, and, therefore, in order to 
release the tongue plate 16 from the pawl 14 it is required that a release 
button (not shown) mounted on the buckle body 10 is operated with a large 
force, or power. 
SUMMARY OF THE INVENTION 
In view of the above facts, the present invention has as its object the 
provision of a buckle device in which a lock lever provided in a buckle 
body and a tongue plate fixed to an occupant-restraining webbing are 
capable of being released from their locking situation by a small 
releasing force even in such a condition that a large load acts upon the 
webbing. 
In the buckle device according to the present invention, a locking face of 
a pawl of the lock lever and a locking face of an opening portion of the 
tongue plate are caused to contact with each other only at two points 
under a locking situation of the buckle device, and under such a situation 
a clearance is formed between both the locking faces in their intermediate 
portions. Therefore, the intermediate portions of both the locking faces 
are protected from being made rough in an ordinary use of the buckle 
device. Also, in an emergency situation of a vehicle, such as a collision, 
when a large load acts upon the webbing, both the contact portions of both 
the locking faces are deformed and the intermediate portions are caused to 
contact with each other, whereby the locking situation between the lock 
lever and the tongue plate can securely be maintained in the buckle 
device. In addition, the intermediate portions are kept smooth owing to 
that they do not contact with each other in the ordinary use of the buckle 
device, so that a contact friction between the intermediate portions is 
not increased, which does not obstruct a release of the lock lever from 
the tongue plate. 
In another aspect of the buckle device according to the present invention, 
the pawl of the lock lever and an inner surface of an inlet portion of the 
buckle body are subjected to a polytetrafluorethylene coating, whereby the 
release of the lock lever from the pawl, and insertion and pulling-out of 
the tongue plate can be conducted more smoothly. 
Description will hereinunder be given of embodiments of the present 
invention with reference to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 3 is a magnified plan view showing a locking situation of a buckle 
device of the present invention and FIG. 4 is a disassembled view of the 
buckle device. 
In a buckle body 20 (shown with a double-dotted chain line in FIG. 3), a 
pawl 24 of a lock lever 22 is latched to an opening portion 28 of a tongue 
plate 26. As is well known, secured to the tongue plate 26 is one end of 
an occupant-restraining webbing (not shown), and mounted on a rear end 
portion (a right side in FIG. 3) of the buckle body 20 are a connecting 
plate and an anchor (not shown). 
Formed at a forward end portion of the lock lever 22 is a hole 30 in which 
a spring (not shown) is received. The spring always biases the pawl 24 of 
the lock lever 22 in such a direction as to cause the pawl 24 of the lock 
lever 22 to abut against the opening portion 28 of the tongue plate 26. 
The lock lever 22 is provided on its upper face with a release button (not 
shown), and when the button is pushed down, the lock lever 22 is pushed 
down against a biasing force of the spring, so that the locking situation 
between the lock lever 22 and the tongue plate 26 is released. 
In the embodiment the pawl 24 of the lock lever 22 has a locking face 24a 
of a substantially flat shape abutting against the opening portion 28 of 
the tongue plate 26, and the locking face 24a is formed at its both sides 
with notches 31, as shown in FIGS. 3 and 4. On the other hand, the opening 
portion 28 of the tongue plate 26 also has a locking face 28a of a 
substantially curved shape formed at its both sides with recess portions 
32. Accordingly, when the pawl 24 of the lock lever 22 is latched to the 
opening portion 28 of the tongue plate 26, both the locking faces 24a and 
28a contact with each other only at two points and a predetermined 
clearance is formed between both the locking faces 24a and 28a in their 
intermediate portions. 
Thus, in an ordinary use of the buckle device the respective locking faces 
24a and 28a of the pawl 24 and the opening portion 28 are little worn 
away, i.e. they are made little rough, and the smoothness in each of the 
locking faces 24a and 28a is protected from being decreased. In addition, 
when a large load acts upon the webbing and the tongue plate 26 in an 
emergency situation of a vehicle, such as a collision, the contact 
portions of both the locking faces 24a and 28a are crushed or deformed, so 
that the contact areas thereof are enlarged, but, as most of the locking 
faces 24a and 28a are kept smooth, a friction occurring at a time of the 
release of the tongue plate 26 from the lock lever 22 is kept small. 
Therefore, when an occupant fastened by the webbing escapes from the 
vehicle, he can release the pawl 24 from the opening portion 28 of the 
tongue plate 26 with a small releasing force required therefor. 
There are several means for forming the clearance between the locking face 
24a and the locking face 28a besides this embodiment. For example, formed 
at both the end portions of the locking face 24a of the pawl 24 can be two 
projections contacting with the locking face 28a of the opening portion 
28. 
FIG. 5 shows another embodiment in which the releasing property between the 
lock plate and the tongue plate is much enhanced. As noted from FIG. 5, 
the pawl 24 of the lock lever 22 is subjected to a polytetrafluorethylene 
coating. All surfaces of the pawl 24 is not required to be coated with the 
polytetrafluorethylene film 34 but it meets the enhancement of the 
releasing property that only the locking face 24A and a part of an upper 
surface of the pawl contacting with the tongue plate 26 at the time of the 
release thereof are coated with the film 34. The formation of the film 34 
enhances a wear resistance and a corrosion resistance of the pawl 24 and 
it decreases a frictional force occurring between the locking face 24a of 
the pawl 24 and the locking face 28a of the opening portion 28, to thereby 
improve the releasing property between the lock lever 22 and the tongue 
plate 26. 
Furthermore, in case that an inlet portion of the buckle body 20 shown in 
FIG. 4, especially portions 36, 38 and 40 contacting with the tongue plate 
26 in times of its insertion and pulling-out, is also subjected to the 
polytetrafluorethylene coating, the insertion and pulling-out of the 
tongue plate 26 can be performed still more smoothly. 
In this second embodiment the polytetrafluorethylene commercially available 
as Teflon S (Trade Mark) is used. The Teflon S is a relatively novel 
coating material, and it reveals a relatively strong adhesion property by 
its one coating, a film thereof being hard and being excellent in a wear 
resistance. Of course, other polytetrafluorethylene materials can also be 
applied to the present invention.