GB2314879A - Safety belt buckle with release button counterweight guided by cam - Google Patents

Abstract

A buckle comprises a latch bar 3 for engaging a slot 4 in a tongue plate 1, the latch bar 3 being held in the engagement position on an overlocking surface 5 by a carrier 11 and by a spring bias. A counterbalance mass 14 pivotally mounted and operatively coupled to the sliding carrier 11 via a pivot point 15, compensates for pretensioning forces in the release button 8 acceleration direction 9 by acting through the camming pin 13 on an L-shaped camming slot 12 in the carrier 11, preventing movement of the carrier 11 and thus blocking the latch bar 3. During normal, non-pretensioning, operation of the buckle, the carrier 11 is pushed back by the release button 8 and the counterbalance mass 14 is guided by L-shaped slot 12.

Description

BUCKLE DESCRIPTION The present invention relates to a buckle for a vehicle safety restraint belt and particularly for a buckle which is substantially immune to the inertial effects of a pretensioner mechanism.

Pretensioners are used to rapidly draw in slack in a safety belt at the onset of a crash situation, to more securely restrain the vehicle occupant in the safest position. If the pretensioner is positioned on the buckle side of the belt, then the buckle is subjected to high acceleration and deceleration forces and traditional buckles cannot tolerate such forces and are subject to spurious release.

It is known from EP 212 057 to use a counterbalance mass to compensate for the inertial effects of a pretensioner on the buckle.

The present invention aims to provide an improved counterbalanced mass buckle arrangement.

According to the present invention there is provided a buckle for a vehicle safety restraint seat belt when fitted with a pretensioner, the buckle comprising a tongue receiving part for coupling with a tongue part, wherein the tongue receiving part has a tongue receiving channel, latching means movable between a tongue engaging position and a tongue disengaging position, resilient means biasing the latching means to the tongue engaging position, actuating means for moving the latching means to the disengaging position against the resilient biasing means, a counterbalance mass pivotally mounted and operatively coupled to a sliding carrier member via a pivot point, the magnitude of the mass and the mounting position of the mass being arranged so that inertial forces on the actuating member are substantially balanced by inertial forces on the counterbalance mass, wherein the counterbalance mass is guided by an L-shaped cam or cam follower on the carrier member, during normal, non-pretensioning, operation of the buckle.

Preferably an overlocker is provided which is movable between a position in which the latching means is held in the engagement position, and a position in which the latching means is free to move. Preferably the overlocker is coupled with and operated by the carrier member. For example a recess may be provided on the carrier which engages over the latching means, in the engagement position to secure the latching means against movement in an unlatching direction as may happen under transverse shocks in the plane of movement of the latching means.

According to a preferred embodiment of the invention the centre of gravity of the actuating member, or button, is arranged in line with the centre of gravity of the counterbalance mass.

The arrangement of the present invention has advantages in that it uses less parts than known arrangements with attendant cost and assembly time savings, and also has an improved performance.

The counterbalance mass may be formed in two parts which are spaced apart across the width of the buckle, but the two parts should be rigidly connected together so that the inertia of both parts of the mass act together as one mass. These parts may be resiliently connected to the carrier member, in a closed loop arrangement, for example by means of a compression spring carried at one end between the two mass parts on the connection therebetween. The spring may act at its other end on the latching member, in a tongue engagement direction. Alternatively a separate spring bias, for example a leaf spring, may be mounted within the carrier member to act on the latching means and to couple the counterbalance mass to the latching means.

Other means of biasing the latching means into the tongue engagement position are also envisaged. In another embodiment of the invention the compression spring acts between the carrier member and a spring retainer connected to the buckle frame.

The carrier member is preferably associated with the overlocker, for example, a cut away in one or both of two side extensions is provided on the carrier member to restrain laterally protruding flanges on the latching member and prevent lifting of the latching member (and thus disengagement of the tongue) under lateral jolts which would otherwise tend to move the latching member out of engagement from the normal fastening condition of the buckle.

The actuating member may be a sliding push button for effecting manual release of the tongue and is supported in the buckle frame for longitudinal movement and has means such as ramp or cam surfaces which engage the latching member (or laterally extending shoulders thereof) when the button is depressed, and lift the latching member out of engagement with the tongue in order to open the buckle.

The actuating member abuts the carrier member but is independent of and not connected to it or to the counterbalance mass.

Such a disengagement of the actuating member or button from the counterweight mass and from the overlocker allows the button member to be smaller and to be designed to suit the vehicle in which the buckle is to be fitted. The manually operable button member is visible to the vehicle occupant and can be easily tailored, using this invention, to meet the internal design requirements of a vehicle manufacturer, without compromising the buckle performance.

Size and shape and colour of the button can be adapted as required for any vehicle relatively cheaply and easily.

In one embodiment of the invention an additional floating mass is provided, resiliently mounted between the counterbalance mass and the carrier member. The inertial force acting on the floating mass add to the inertial forces on the main counterbalance mass, both in acceleration and deceleration directions, assisting in an overall balance and resulting in substantially no relative movement between the buckle components so that spurious release under pretensioning conditions is substantially avoided.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawings in which: Figure 1 is a cross-sectional side view of a buckle according to the present invention; Figure 2 is a cross-sectional transverse view of the buckle of Figure 1; Figure 3 is a cross-sectional longitudinal view of the buckle of Figure 1; Figure 4 is a schematic cross-sectional view of one embodiment of the invention; Figure 5 is a schematic cross-sectional view of the embodiment of Figures 1 to 3; and Figure 6 is a schematic cross-sectional view of another embodiment of the invention.

In the Figures like parts are denoted by like reference numbers.

A tongue plate 1 is inserted in tongue passage 2 and is locked in place by a latch bar 3 which engages a slot 4 in the tongue plate 1. The latch bar 3 is held in the engagement position shown by an overlocking surface 5 on a carrier member 11, and also by a spring bias, and is thus generally protected against sudden shocks to the buckle in the direction of disengagement of the latch bar 3.

The latchbar 3 extends across a substantial part of the width of the tongue plate 1, and has laterally extending arms 7(more clearly seen in Figure 2). A manually operable actuating member or button 8 is depressible in the direction of arrow 9 to release the buckle. Ramps 10 are integral with the button 8 and engage under the laterally extending arms 7 of the latch bar 3 to lift the latch bar 3 out of engagement with the tongue, against the action of a latch bar bias spring. The button 8 abuts a carrier member 11 to its rear and movement of the button 8 in the direction of arrow 9 causes the carrier member 11 to also move in the direction of arrow 9. At each side of the carrier member 11 is an L-shaped slot 12, which supports a peg 13 extending laterally from each side of, and integral with, the counterbalance mass 14. Mass 14 is pivoted on the frame about pivot point 15.

As the carrier 11 is pushed by button 8 in the direction 9, the force of the lateral part of L-shaped slot 12 on peg 13 is in the direction 9. This causes mass 14 to pivot about point 15 and rotates it in the counterclockwise direction until the peg 13 is in line with the longitudinal section of L-shaped slot 12. Then the peg can slide along the longitudinal section of the slot 12, in the direction opposite to arrow 9. However it will be seen by the geometry of the arrangement that the pegs 13 can only move along the longitudinal part of the slot after the mass 14 has rotated. If the mass is not rotated then any force on the mass 14 is transferred via pivot 15 and pegs 13, to the carrier member.

The L-shaped slot 12 provides lost motion and allows for a shorter buckle.

Figure 2 is a transverse cross-section of the buckle of Figure 1. The latch bar 3 is seen as a wide bar with a central, downwardly extending portion 23 which engages in a recess or hole in the tongue plate 1. Cut outs on either side of the portion 23 fit over the side parts of the tongue plate. Laterally extending shoulders 7 engage ramp surfaces 10 on the button 8 for lifting the latch bar 3 out of engagement with the tongue plate 1.

The counterbalance mass 14 comprises two parts fixedly joined together by spring carrier 16. The counterbalance mass 14 is pivoted about axis 15 and has side extending pegs 13 on each side which cooperate in L-shaped slots (not shown in Figure 2).

Figure 3 is a longitudinal cross-section of the buckle of Figure 1. The button 8 is shown abutting carrier member 11 which supports the two part counterbalance mass 14. A spring carrier 16 connects the two parts of the counterbalance mass 14 and supports one end of compression spring 17. The buckle engagement tongue is shown generally at 18 and its outline is shown in broken lines within the body of the buckle. A rivet 19 connects the buckle frame to seat belt webbing 20 or other media (such as a cable) by which the buckle is connected to a fixed part of the vehicle.

Figure 4 is a schematic cross-sectional view of one embodiment of a buckle according to the invention. The actuating button 8 has a ramp surface 10 which engages the shoulders 7 of lockbar 3 to lift it out of engagement with the tongue (not shown). The button 8 abuts a carrier subslide member 11 which has an overlocker 5 to retain the lockplate 3 in its tongue engagement position against sudden knocks in the plane of the lockplate, i.e. in a transverse direction. The spring 17 provides resilient bias via the counterbalance mass 14, between the carrier member 11 and a spring retainer 26, which in this embodiment is mounted to the frame. The mass 14 pivots about axis 15 and has a transverse extending peg or arm 13 engaging in L-shaped slot 12 in the carrier member 11.

Figure 5 illustrates, in schematic form, an embodiment of the invention in which the spring 17 terminates at spring carrier 16 which is located between the two parts of counterbalance mass 14. This is very similar to the embodiment illustrated in Figure 3 and forms a closed loop system. The spring carrier 16 is a swivel spring retainer having a generally U-shaped cross-section in the transverse direction, as illustrated in Figure SA.

Figures 6A, B and C show another embodiment of the invention in which an additional floating mass 20 is connected in a resilient manner between sub-slide carrier 11 and counterbalance mass 14.

Figure 6B illustrates a force diagram during acceleration of the buckle in a pretensioning situation.

The acceleration direction 9 causes an inertia force F1 on floating mass 20 and F2 on counterbalance mass 14 since the moving parts of the buckle tend to lag behind the buckle frame which is being accelerated by the pretensioner itself.

The floating mass 20 is arranged so that F1 is greater than F2 and it adds to the force generated by the button 8 and the sub-slide 11. The result, taking into consideration the return torque generated by the arm 13 of the counterbalance mass onto the sub-slide 11, is that substantially no relative motion will occur.

Figure 6C illustrates the situation under deceleration in the direction 29. This is the situation at the end of the pretensioning stroke. F3 indicates the force on the floating mass 20 and F4 the turning torque on the counterbalance mass 14. The masses are arranged such that F3 plus F4 is greater than the inertial forces on the button and on the carrier sub-slide 11, in the direction 29 and thus ensures that none of the parts move relative to each other.

Claims (16)

1. A buckle for a vehicle safety restraint seat belt when fitted with a pretensioner, the buckle comprising a tongue receiving part for coupling with a tongue part, wherein the tongue receiving part has a tongue receiving channel, latching means movable between a tongue engaging position and a tongue disengaging position, resilient means biasing the latching means to the tongue engaging position, actuating means for moving the latching means to the disengaging position against the resilient biasing means, a counterbalance mass pivotally mounted and operatively coupled to a sliding carrier member via a pivot point, the magnitude of the mass and the mounting position of the mass being arranged so that inertial forces on the actuating member are substantially balanced by inertial forces on the counterbalance mass, wherein the counterbalance mass is guided by an L-shaped cam or cam follower on the carrier member, during normal, non-pretensioning, operation of the buckle.

2. A buckle according to claim 1 further comprising an overlocker which is movable between a position in which it holds the latching means in the engagement position, and a position in which the latching means is free to move.

3. A buckle according to claim 2 wherein the overlocker is coupled with and operated by the carrier member.

4. A buckle according to claim 3 wherein the carrier member comprises an abutment which engages the latching means, in the engagement position, to secure the latching means against movement in an unlatching direction as may happen under transverse shocks in the plane of movement of the latching means.

5. A buckle according to any preceding claim wherein the centre of gravity of the actuating member is arranged to be in line with the centre of gravity of the counterbalance mass.

6. A buckle according to any preceding claim wherein the counterbalance mass is formed in two parts spaced across the width of the buckle, the two parts being rigidly connected together so that the inertia of both parts of the mass act together as one mass

7. A buckle according to any preceding claim wherein the counterbalance mass is resiliently connected to the carrier member.

8. A buckle according to claim 7 wherein the mass is connected to the carrier member in a closed loop arrangement.

9. A buckle according to claim 7 or claim 8 wherein the resilient connection comprises a compression spring carried at one of its ends by the mass.

10. A buckle according to claim 9 wherein the spring acts at its other end on the latching member, in a tongue engagement direction.

11. A buckle according to any one of claims 1 to 8 comprising a spring bias mounted within the carrier member to act on the latching means and to couple the counterbalance mass to the latching means.

12. A buckle according to any one of claims 1 to 9 comprising a compression spring acting between the carrier member and a spring retainer connected to the buckle frame.

13. A buckle according to any preceding claim wherein the actuating member is a sliding push button for effecting manual release of the tongue and is supported in the buckle frame for longitudinal movement.

14. A buckle according to any preceding claim wherein the actuating member abuts the carrier member but is independent of and not connected to it or to the counterbalance mass.

15. A buckle according to any preceding claim comprising a second floating mass, resiliently mounted between the counterbalance mass and the carrier member in such a way that the inertial forces acting on the floating mass add to the inertial forces on the main counterbalance mass, both in acceleration and deceleration directions.

16. A buckle for a vehicle safety restraint seat belt with a pretensioner substantially as hereinbefore describ4ed with reference to Figures 1 to 3 and 5 of Figure 4 or Figure 6 of the accompanying drawings.