GB2080387A - Locking buckle for safety belts in motor vehicles - Google Patents

Abstract

A safety belt buckle formed of two plates (3, 4) fastened together and having two pawls (18) laterally movable to engage catch areas (6b) of a tongue (6). A spring (19) which urges pawls (18) towards each other has a steep characteristic. Pawls (18) slide within lateral slots (16, 17) formed in plates (3, 4). These slots which are so short that the front end (6a) of tongue (6) can only just be moved past the pawls (18). These refinements are to prevent single-pawl latching. There is an ejector (13, 15). <IMAGE>

Description

SPECIFICATION Locking buckle for safety belts in motor vehicles The invention relates to a locking buckle for safety belts in vehicles, the buckle having a housing connected to the vehicle at an anchor point by means of an attachment system and comprising a receiving opening for a buckle tongue and a cavity formed by means of opposite plates, in which cavity two pawls which can be brought into engagement with the buckle tongue are disposed to slide crosswise to the direction of insertion of the tongue and are tensioned toward each other by a spring, an ejector tensioned by a spring being provided movable in lengthwise direction of the locking buckle.

Such a locking buckle is known from U.S. Pat.

4,181,832, wherein the two opposite plates forming the cavity are stamped from one piece and bent. This results in a lower plate which iS provided via lateral webs with two upper plate portions bent in C form and directed toward each other. Between the upper plate portions, a slot extends in lengthwise direction of the locking buckle, in which the ejector can slide, which moreover is arranged slidable in an additional lower slot in the lower plate.

A similar locking buckle is known from U.S. Pat.

4,171,557, wherein the two pawls disposed symmetrical to the longitudinal axis of the locking buckle are tensioned toward each other by extension springs, but upon opening slide in slots extending obliquely to the direction of insertion.

The above buckles includes two locking pawls for engagement with a tongue having a shoulder or catch are symmetrically on both sides of its longitudinal median line. It is quite possible that only one of the two pawls snaps in behind only one of the two catch areas, while the ejector is mbved backward in the direction of insertion of the tongue far enough for the release button to be released and to indicate the locked state, so that only one side of the buckle is locked.

Also with the first-named locking buckle the disadvantage occurs that only one of the two pawls slides behind a catch area as the tongue is being inserted into the buckle, while the other pawl remains in the retracted state lying laterally farther outward. The locking force reached in this position is, however, not sufficient with certainty to secure the buckled passenger in the desired and prescribed manner.

As locking buckles are known to be massproduced, there is always danger that due to tolerances or slight dimensional deviations, which apply also to the buckle tongues, buckles may be formed so that disadvantageously in use only one instead of both pawls snaps in behind only one catch area of the front end of the tongue.

With some locking buckles one can indeed hear the clicking noise as the pawls snap in behind the catch areas, but the user's ear is unable to establish with certainty and at all times whether both pawls are actually in locking position.

It is, therefore, an object of this invention to provide a locking buckle of the above-mentioned kind wherein the snapping in of only one of two pawls and hence the half-locking or locking of the belt buckle on one side only is avoided.

This problem is solved according to the invention in that the spring which tensions the two pawls toward each other has a steep characteristic and the slots in the plates are made so short that the front end of the buckle tongue can just be moved past the pawls. By these features, it is ensured in a simple manner and yet with unexpectedly good certairity that the user automatically provides for a complete locking, i.e.

a snapping in of both pawls. Should the case arise in a locking buckle, due to deviations in production, machining or installation, that actually upon insertion of the front end of the buckle tongue at first only one pawl snaps in behind one catch area with a relatively large time lead, then, by the high directional force or respectively by the sharp gradient of the spring characteristic, the compressive force of the spring which tensions the pawls toward each other is immediately reduced so much so that the user feels a diminished insertion resistance and unconsciously can and must push the tongue with his hand deeper into the locking buckle. It is thereby ensured that the mushroom-type or arrow-shaped front end of the buckle tongue is with certainty also guided past the second pawl far enough for it to snap in behind the other catch area also in the desired manner.In this way, complete locking on both sides of the median axis of the tongue and buckle is always ensured.

This result with the effect of the steep characteristic of the spring is further supported by the additional feature that the slots in the upper and lower plates are made short. In contrast to the known long slots extending at an angle to the lengthwise direction of the buckle, and also in contrast to known crosswise slots which are unlimited toward the outside, provision is made by the short slots of this invention that the pawls can move apart only just so far that the front end of the tongue can be moved past widthwise. In this way the steeply rising spring constant attains its full effect, i.e. there then results in reliable manner the desired abrupt reduction of the insertion resistance after a pawl has snapped in behind the catch area of the tongue.

By the measures according to the invention, therefore, a locking buckle is obtained with a breakthrough effect which ensures the locking of both pawls without additional, not only complicated, but also costly, measures. Although other buckles are already known in which care is indeed taken that both pawls engage, this is effected by ensuring that the wide part of the front end of the tongue is moved past the pawls far enough before the pawls engage behind the catch areas. However, a release device must disadvantageously be provided in such designs which only after deeper insertion of the tongue in the buckle releases the pawls for snapping in. This is the so-called mousetrap principle, which requires a special release system with the disadvantage connected therewith of increased complication and higher price.By the measures according to the invention, the same safety is provided, but with simpler and more economical means.

It is further advantageous according to the invention if the part of the ejector which can be brought into engagement with the buckle tongue - is almost as wide as the front end of the tongue and is arranged, in the unlocked state, between the pawls. In known locking buckles it has been found that by the pressing apart of the two springtensioned pawls by the front end of the tongue the latter is subject to considerable wear by attrition, after which metal splinters or small chips can fall into the buckle. Thereby the danger is again increased that only one instead of both pawls locks. But if both pawls are held apart by the front end of the ejector in the unlocked state, much less attrition will result at the front end of the tongue, and locking of only one pawl on only one side is further avoided with increased safety of operation of the locking buckle.

These problems play a considerable role with respect to the general tendency to make not only the motor vehicles but also the safety devices, hence also the buckle tongues and locking buckles, lighter. This results in thinner plates, whose function, however, should not be diminished by attrition.

Advantageously the invention is further developed in that guide members protruding crosswise from the plane of the plate are disposed symmetrically to the lengthwise direction of the locking buckle at the end of one plate turned toward the buckle tongue. Thereby the tongue is brought into the correct position, so that the direction of insertion coincides with the longitudinal median axis of the tongue. The smaller the angle of the longitudinal median axes between tongue and buckle is during insertion, the less danger there will be that only one pawl engages behind the catch area. The guide members reduce this angle to almost zero, so that by this alone the bilateral locking is enhanced.

By the guide members, which in a further preferred realization of the invention consist of bent parallel sheet metal clips extending in lengthwise direction of the locking buckle or of correspondingly arranged beads or ribs, the possibility that the tongue is moved into the buckle under a wring angle (not equal to zero), or respectively the tongue is rotated during insertion about an axis perpendicular to the plane area of the tongue, is prevented in like manner and additionally as by the short slots in the upper and lower plates for limitation of the sliding path of the pawls. By such undesired turning of the tongue, in fact, one could even pull back a pawl and bring it out of engagement with the catch area of the belt buckle.In other words, by the measures of the invention straightening of the tongue is achieved by the guide members, i.e. clips, beads or ribs, even after oblique insertion of the tongue.

Further advantages, features and possibiiities of application of the present invention will become evident from the foliowing description of preferred embodiments in conjunction with the drawings, in which: Fig. 1 shows in perspective an exploded view of the essential parts of the locking buckle, parts immaterial for the invention, such as the outer housing, having been omitted, for better comprehension; Fig. 2, half in top view and half in section, an assembled locking buckle without buckle tongue; Fig. 3, a sectional view along line A-A in Figure 2; Fig. 4, in top view, schematically and broken off, the essential parts of the locking buckle which become operative as the buckle tongue is inserted, before insertion; Fig. 5, a similar view as Figure 4, but with the front end of the tongue inserted a little further into the buckle;; Fig. 6, a similar view as Figures 4 and 5, but with one pawl already introduced behind a catch area, while the other pawl still remains in the unlocked state; Fig. 7, a similar view as Figure 4 to 6, but showing the locked state of the buckle; Fig. 8, a similar view as in Figure 4 to 7, but showing the schematic truncated representation of the underneath of the release button when detaching the tongue from the buckle; and Fig. 9, the same view as in Figure 8, but with the release button shown in the extended state before detaching or unbuckling.

The locking buckle shown in Figures 1-3 and marked 1 in general comprises inside housing 2 a lower plate 3 and spaced therefrom an upper plate 4 which, at its front end (to the left in the drawings), form a cavity 5 for inserting a buckle tongue 6 shown in Figures 4 to 7. The release button 7 is biased in the usual manner through a compression spring 8 into the position shown in Figures 2 and 3, i.e. the extended position, the compression spring 8 taking support at its rear end against a bridge 9 supported on upper plate 4.

At the rear end of the buckle 1 a cable 10 is provided as fastening means for attachment at an anchor point (not shown) in the vehicle. Cable 10 has a flattened eye 11 through which a bolt or screw 12 joins together plates 3 and 4.

An ejector 13 is movable between the platesin = the direction of the longitudinal axis 14 of the locking buckle 1 and is tensioned by a compression spring 1 5 forwardly, i.e. towards the left in Figures 2 and 3. Ejector 13 includes a forward portion 1 3a which can be brought into engagement with buckle tongue 6 and whose width is, as shown in Figures 4 to 7, almost as great as the width of the arrow-shaped or mushroom-shaped part 6a of tongue 6.

As viewed from above, the front end of tongue 6 is formed with the mushroom-shaped part 6a, on the rear of which are formed two catch areas 6b extending crosswise to the lengthwise axis 14 on tongue 6 up to neck 6c thereof. The slants of tongue portion 6a, which are connected together by a forward rounded portion, are at the front end of tongue 6 substantially flush against part 1 3a of ejector 13 when tongue 6 is inserted into the buckle for fastening as shown in Figures 4 to 7.

In the lower plate 3, crosswise to the longitudinal axis 14, two short slots 1 6 are formed in spaced relation and in alignment, above which corresponding slots 1 7 are disposed in the upper plate 4. Slots 1 6 and 17 end outwardly toward the side before the outer edges of plates 3 and 4 and thereby have a certain limitation.

Two plate-type pawls 1 8 are movable by a certain amount in slots 16 and 17 crosswise to the longitudinal axis 14 against the tensioning force of a substantially U-shaped spring 1 9. At the rear end of buckle 1, spring 1 9 is placed around two posts 20 which extend downwardly from bridge 9 into corresponding holes in the plates.

On the plane of the upper plate 4, two guide clips 21 are bent downwardly crosswise at the front end about bending lines 22; they as well as the ribs 23 which are pressed downwardly from plate 4 serve as guide members for the parallel edges 24 of tongue 6.

Lastly there are arranged on the bottom portion of release button 7 oblique expansion cam surfaces 71, whose function is evident from Figures 8 and 9.

From the drawings it is seen in conjunction with the above description that the slots 1 6 and 1 7 in plates 3 and 4 are made just only so short or respectively are arranged at their outer ends at such a distance from the lateral edges of plates 3 and 4 that the mushroom-shaped part 6a of tongue 6 can, as the latter is being inserted into the locking buckle 1 according to Figures 4 to 7, just be pushed past the two spread-apart pawls 18. For example, the pawls 18 can move a distance of about 1 mm in the slots.

The operation and function of the locking buckle can be seen most clearly from Figures 4 to 7 on the one hand, and Figures 8 and 9 on the other.

According to Figure 4, the buckle tongue 6 is at first inserted exactly straight into the cavity 5 of buckle 1. In other words, the longitudinal median line lies exactly along axis 14. The angle enclosed between such line and axis 14 is zero. The slant areas in the front of the mushroom-shaped part 6a of tongue 6 are placed (according to Figure 4) flush against the corresponding engagement part 1 3a of ejector 13, which in the unlocked position is held between the two pawls 1 8 by spring 15, so that the U-shaped spring 1 9 is spread relatively far apart.

Now if the user pushes tongue 6 further into the locking buckle 1, the state of Figure 5 is reached. The slants at the mushroom-shaped part 6a have pressed the pawls 1 8 outwardly only little beyond the state of Figure 4 under tension of spring 19, while the sheet metal clips 21 guide the parallel edges 24 of tongue 6.

Should it happen nevertheless that due to a slight manufacturing defect one pawl, namely according to Figure 6 the right pawl 18, engages behind its respective catch area 6b first, while the left pawl 1 8 still remains unlocked, then, due to the steep characteristic of the U-shaped spring 1 9 (e.g., about 0.6 to 1 Newton/mm), the resistance to insertion of tongue 6 into buckle 1 diminishes abruptly in such a way that the user automatically presses the tongue 6 further into the buckle 1, to attain the state of Figure 7, i.e. the locked position.

That is, in such situation the insertion resistance is substantially reduced and only a slight additional insertion effort is required to lock the tongue.

As an example, the normal pretension force of ejector spring 1 5 may be about 6.5 N. When tongue 6 is inserted and moves ejector 1 5 rearward, this force may be increased to about 10 N. Upon further insertion of tongue 6, the resistance of spring 1 9 against pawls 1 8 increases the total resistance to insertion to about 1 7 N.

When, however, one of the pawls is engaged in a catch, the resistance to insertion immediately decreases to about 5 N, thereby ensuring that the tongue becomes fully locked.

For releasing the tongue, release button 7 is moved rearwardly from the position of Figure 9 to that of Figure 8, with cam surfaces 71 forcing the pawls 1 8 outward out of engagement with the catch areas 6b. When the pawls 1 8 have been moved outward overcoming the force of spring 19, ejector 13 pushes the tongue 6 out of the buckle due to the force of spring 1 5.

Claims (7)

1. Locking buckle for safety belts in vehicles having a housing connected to the vehicle at an anchor point by an attachment system and comprising a receiving opening for a buckle tongue and a cavity formed by means of opposite plates, in which cavity two pawls which can be brought into engagement with the buckle tongue are disposed to slide crosswise to the direction of insertion of the tongue and are tensioned toward each other by a spring, an ejector tensioned by a spring being provided movable in lengthwise direction of the locking buckle, characterized in that the spring (1 9) which tensions the two pawls (18) toward each other has a steep characteristic, and the slots (16, 17) in the plates (3, 4) in which the pawls (1 8) move are made so short that the front end (6a) of the buckle tongue (6) can just be moved past the pawls (1 8).

2. Locking buckle according to claim 1, characterized in that part (13a) of the ejector (13) which can be brought into engagement with the buckle tongue (6) is almost as wide as the front end (6a) of the buckle tongue (6) and is disposed, in the unlocked state, between the pawls (18).

3. Locking buckle according to claim 1 or 2, characterized in that guide members (21, 23) protruding crosswise from the plane of the plate are disposed symmetrically to the lengthwise direction (14) of the locking buckle (1) at the end of one and/or the other plate (3, 4) turned toward the buckle tongue (6).

4. Locking buckle according to one of claims 1 to 3, characterized in that the guide members (21, 23) consist of bent, parallel sheet metal clips (21) extending in lengthwise direction of the locking buckle (1) or of correspondingly disposed beads or ribs (23).

5. Locking buckle according to one of claims 1 to 4, characterized in the spring (19) has a generally U-shape the free ends of which are in contact with pawls (18).

6. Locking buckle according to one of claims 1 to 5 including a release button (7) to release tongue (6) from pawls (18), the button (7) having obliquely-shaped cam surfaces (71) which move the pawls (18) laterally apart when the button (7) is depressed.

7. Locking buckle for safety belts constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.