GB2042053A - Belt clamps for vehicle passenger restraint belts - Google Patents

Abstract

A belt clamp for use in a vehicle passenger restraint belt system comprises a pair of jaws, one of which 220 is movable relative to the other 216, as by a lever 222, is normally held away from the other by a spring 226, and is moved toward the other in response to an abnormally high pull-out force to engage a restraint belt 210 guided between the jaws. A multiplicity of spaced-apart, elongated straight teeth 104 oriented widthwise of the belt and of uniform, smoothly curved cross section frictionally clamp the belt against pulling out by tucking loops of the belt into complementary recesses 106 in the other jaw. Preferably, both jaws have substantially identical teeth and recesses to. Advantageously, small variations in gripping faces of the jaws compensate for variations in the properties of the belt (e.g. thickness, density and elasticity) and for deformation of the jaws. <IMAGE>

Description

SPECIFICATION Belt clamps for vehicle passenger restraint belts FIELD OF THE INVENTION The present invention reiates to belt clamps for limiting the extent to which a vehicle occupant restraint belt is pulled from a retractor after the retractor reel becomes locked.

BACKGROUND OF THE INVENTION Most vehicle seat belt retractors being manufactured currently are of the emergency locking type in which the reel onto which the belt is wound is locked against rotation automatically in response to a device which senses acceleration or deceleration of the vehicle, most commonly upon a collision or upset.

Such retractors, though they are recognized to be generally reliable and effective in improving the safety of the vehicle occupant, have one disadvantage; even though the reel may lock reliably and promptly, some extension of the belt can nonetheless occur due to withdrawal of the belt from several loops which remain wound onto the reel, such loops usually being wound relatively loosely and being unwound from the reel by reason of tightening of the loops under the high force imposed on the belt in a collision. This problem has been recognized, and various ways have been proposed for solving it. Most of the proposed solutions involve one form or another of a belt clamping device in which some sort of movable belt-gripping element tightly engages and grips the belt in response to a high force imposed on the belt.Some types of gripping elements, such as curved gripping shoes or eccentric rollers having knurled or otherwise roughened surfaces, are very prone to allowing the belt to slip, inasmuch as the contact area is relatively small. Clamping bars which force the belt into a narrow slot or otherwise produce a sharp fold in the belt, often in conjunction with clamping the belt against a surface, sometimes produce a belt failure by cutting into the belt. It has also been proposed (see U.S. Patent No. 4,120,466) to clamp a restraint belt between planar clamping surfaces, but it is open to question whether sufficient frictional surface area with a sufficiently high coefficient of friction can be provided in a device of a practical size which can function reliably over a long useful life.

SUMMARY OF THE INVENTION There is provided, in accordance with the present invention, an improved belt clamp for use in vehicle passenger restraint belt systems which comprises a pair of gripping jaws, each of which is carried by a support member. At least one of the jaw support members is movable in response to a high pull-out force on the belt. The belt clamp is characterized in particular by effective clamping surfaces on the gripping jaws which present virtually no risk of allowing the belt to slip or contributing to belt failure. The belt clamp is intended for use in conjunction with a retractor onto and from which the belt is wound and unwound and can be located remotely from the retractor or can be integrated with the retractor on an integral or assembled frame.

In accordance with one aspect of the present invention, at least one of the jaws of the belt clamp has a multiplicity of closely spaced teeth which lie transversely to the direction of movement of the belt. Each tooth is straight, is of a length not less than the width of the belt, is smoothly curved in end profile and is of substantially uniform cross section along its length, except that small variations may be introduced with certain advantages, as described below. The other jaw has a multiplicity of recesses, each of which generally matches a corresponding tooth on the other jaw and receives such corresponding tooth and a widthwise strip of the belt upon engagement of the belt between the jaws, each such strip of the belt being formed into a smoothly curved loop by being tucked by a tooth into a recess.Preferably, each recess is a straight, elongated concavity having a shape generally complementary to that of the corresponding tooth of the first jaw such that each belt loop is frictionally clamped between the surfaces of each tooth and corresponding recesses upon engagement of the belt between the jaws. The jaws of the belt clamp may have identical gripping surfaces, each having straight, smoothly curved, transverse teeth alternating with generally complementary shaped re cesses which receive the teeth on the other jaw. Alternatively, and in some cases, prefera bly, the gripping surfaces of the jaws differ from each other.

As mentioned above, the improved belt clamp, according to the present invention, grips the belt frictionally between the smoothly curved teeth and generally corresponding recesses. The gripping surfaces are engaged with the belt to develop frictional gripping forces by the force applied to the belt which, in turn, is imparted to the jaws by a lever or a wedge carrying at least one of the jaws. Accordingly, the greater the force on the belt, the greater the frictional force restraining the belt. An important advantage of the for mation of loops in the belt section engaged by the clamping jaws is that any extension of the belt from the retractor is compensated for by the formation of loops between the jaws.

There are actually two modes of develop ment of frictional forces at work when the jaws grip the belt. One mode occurs at each loop in the belt where it turns over the tip (or tips) of a tooth. The loop is pulled toward the tip of the tooth due to tension in the belt.

There is actually a gradient in the belt tension along the length of the part of the belt between the jaws, because frictional forces dissipate the tension that exists at the outgoing end of the gripped segment so that the belt tension drops to zero somewhere along the gripped part. The increment of tension over each belt loop where it wraps a curved surface produces pressure and results in the development of friction between the jaw tooth and the belt loop.

The other mode of friction development results from pressure build up in the belt where it is squeezed between the gripping surfaces of the jaws. This mode can exist over all or only part of the total surface area of the jaws, depending on whether the belt is squeezed over the entire or over only part of the portion received between the jaws.

The extent to which each mode contributes to the total friction depends, of course, on the precise configuration of the gripping surfaces, but it also depends on many physical characteristics (e.g., stiffness, density, thickness, elasticity and so forth) of the belt and on the magnitude of the force on the belt. Aso, the jaws may undergo deflection of sufficient magnitude to warrant taking it into account in the design of the gripping surfaces. It is apparent, therefore, that the mechanical phenomena occurring when the jaws grip the belt are highly complex. This means that the designing of the gripping surfaces is largely empirical.

It may suffice in some cases-i.e., with some belts and belt load curves-to have teeth and recesses of exactly uniform crosssections along their lengths which mesh with a substantially uniform gap at a certain load on the-belt. In most cases, however, it will be preferable to take several things into account in the design of the teeth and recesses of the jaws. One is the variation in belt thickness under squeezing pressure comparable to that occurring in the jaws. Generally, the selvages are thicker than the center of the belt. Accordingly, the gaps between the gripping surfaces when they grip the belt should be greater at the edges than in the center in order to even out the squeezing pressure across the belt width and avoid a dangerously high pressure anywhere in the gripped part.

The selvages are also usually less elastic than the center part, which may warrant varying the heights of the teeth along their lengths so that the lengths of belt gripped along the selvages are a little less than the length along the center, thereby evening out the tension across the width of the gripped portion. Deflection of the jaws can be compensated for by crowning the gripping surfaces. Some examples of various gripping surface configurations are shown in the drawings and described below.

Some guidelines for the design of the gripping surfaces of the jaws are: 1. The radii of the tips of the teeth should not be less than approximately equal to the belt thickness, lest the belt be looped too sharply and be too highly tensioned at the outside of the loop.

2. It is very difficult to adjust the radii of the tips of the teeth and the bases of the recesses to produce a uniform gap at a design gap of the engaged jaws at a design load, and the gap will vary at other than the design load anyway. It is best, therefore, not to provide squeezing at the curved (in profile) areas of the gripping surfaces.

3. The walls of the teeth and recesses should be surfaces generated by parallel lines oblique to the major plane of the jaw, so that at all locations transversely of the belt, the gap between the opposed walls which squeeze the belt is uniform. As mentioned above, the sizes of the gaps are selected along the width of the belt taking into account belt thickness and density variations (and other relevant physical characteristics of the belts) and any deflection of the clamp.

4. All changes in tooth and recess shape should be relatively smooth-sharp breaks which could produce high pressure zones and possible cutting or other local failure should be avoided.

5. The heights of the teeth should be from about two to about eight times the thickness of the belt.

The jaws can be used in various clamp devices. For example, one jaw can be fixed to a frame and the other jaw mounted on a lever arm pivoted at one end on the frame and having a roller at the other end around which the belt turns (after passing between the jaws) and then leads away in a direction to pull the lever and the jaw on the lever toward the fixed jaw. A spring holds the lever and movable jaw away from the felt when the belt is under moderate tension, e.g., the tension generated by the retractor and moderate pull-out forces.

In another embodiment one jaw is fixed and the other jaw is mounted on a movable support which has a wedge surface acted on by a translatable belt turning roll.

Both jaws can be mounted on a springloaded lever which is subject to belt tension.

One jaw moves relative to the lever and the other jaw when it engages a fixed abutment on the frame upon movement of the lever in response to belt tension.

For a better understanding of the invention and a description of further preferred features, reference may be made to the following description of exemplary embodiments, taken in conjunction with the figures of the accompanying drawings.

DESCRIPTION OF THE DRAWINGS Figures 1A and IB are pictorial views of a preferred form of clamping jaw for use in belt clamps embodying the present invention; Figure 2 is a fragmentary end cross-sectional view of the clamping jaw shown in Figs.

1Aand 1B; Figure 3 is an end view of a pair of side-byside retractors, each of which has associated with it a belt clamp embodying the present invention, part of the retractor and clamp assembly being broken away in cross section; Figure 4 is an end elevational view partly broken away in section, showing another embodiment of belt clamp built into a tandem assembly of retractors; Figure 5 is an end cross-sectional view of another retractor and belt clamp assembly; Figure 6 is an end cross-sectional view of a retractor having another embodiment of belt clamp associated therewith, the belt clamp being shown in its normal disengaged configuration; Figure 7 is an end cross-sectional view of the retractor and belt clamp of Fig. 6 showing the belt clamped;; Figures 8 and 9 are side elevational views in generally schematic form showing another embodiment of a belt clamp, according to the present invention, in the disengaged and engaged positions, respectively; Figures 10 and ii are side elevational views of another embodiment of the invention, the views being generally schematic and showing the belt clamp in the disengaged and engaged positions, respectively; Figures 12A and 12B are diagrams illustrating two conditions that should be taken into account in the design of the clamping members; and Figures 13 through 16 illustrate different ways of designing the clamping members to offset the conditions illustrated in Figs. 1 2A and 12B.

DESCRIPTION OF EXEMPLARY EMBODI MENTS The embodiments of the present invention shown in Figs. 3 to 7 have clamping jaws that are manufactured separately from the levers or other supports of the belt clamps and then installed on such levers and supports, but as exemplified by the belt clamps shown in Figs.

8 to 11, the jaws can take various forms. In all cases, the important thing is the configuration of the gripping surfaces of members which engage the belt in response to a relatively high force on the belt in the pull-out direction.

The jaw member 100 shown in Figs. 1A, 1 B and 2 is a rectangular body of metal forged, cast or machined to provide a corrugated clamping surface 102 composed of a series of teeth 104 separated by recesses 106. Each tooth 104 of the clamping jaw extends straight in a transverse direction, relative to the path of the belt, is relatively smoothly curved in end profile and is of uniform cross section along its length. Each recess 106 has a shape generally complementary to that of a corresponding tooth of the other jaw but is somewhat larger in size to provide space between each tooth and recess for reception of the belt. When the jaws are closed under an abnormally high tension applied by the outgoing section of the belt, each tooth forms a small transverse loop in a section of the belt, and the belt is frictionally engaged by the surface of each tooth and the corresponding recess.The formation of a series of loops in the belt takes up a significant part or all of the extra length of belt that might otherwise be pulled from the retractor and ensures a minimum of elongation of the restraint portion of the restraint or control belt.

The teeth and recesses of the clamping jaws may be of various specific shapes and sizes, provided that certain requirements are fulfilled. For example, the side walls of each tooth and recess can be parallel but are preferably oblique to the plane of the belt, the side walls of the tooth being tapered toward each other in a direction toward the belt in the preferred case so that each tooth and each cavity of each jaw are symmetrical about a medial plane perpendicular to the plane defined generally by the tips of the teeth. In all cases, there should be no sharp corners anywhere along the gripping surfaces of the jaws so that there will be no danger of the belt being cut into and severed.Similarly, the recesses should be slightly larger than the teeth to allow space for the belt when the jaws are closed, but the spacing between the sides of the teeth which are the clamping surfaces of the jaws should generally be less than the thickness of the belt when the jaws are closed to ensure development of pressure to generate friction over a substantial area of the clamped portion of the belt; the total friction forces generated between the belt and the clamping surfaces of the jaws should not be less than the minimum tensile strength of the belt to ensure that the clamp is not a weak part of the restraint system. To this end, the teeth of each jaw should be of a height of from about two to eight times the thickness of the belt. On the other hand, the total contact area of each jaw should not exceed about 950 mm2 in order to avoid the risk of belt failure.

Each jaw has a pair of mounting lugs 108 which are received in matching slots in a support element of the belt clamp and compressed to provide a force fit.

Fig. 2 gives the dimensions of clamping surfaces that have been found to be highly effective with belts having thicknesses in the range of from about 1.2 to about 1.6 mm.

The shapes and sizes of the teeth 104 and recesses 106 of the two jaws of a clamp using those jaws may be identical. Each jaw has teeth 3.0 mm in height and spaced uniformly at a 6.0 mm pitch distance. The tips of the teeth are arcuate (radius 1.0 mm), the bases of the recesses are likewise arcuate (radius 1.5 mm), and the walls of the teeth and recesses are flat and tangent to the radii.

Any of the belt clamps shown in Figs. 3 to 11 can be a self-contained unit for installation in the vehicle at a suitable location remote from the belt retractor somewhere along the path of the belt between the retractor and the vehicle occupant. For example, the retractor can be located under the vehicle seat and the belt clamp can be located on the inboard side of the seat generally below and behind the occupant, in which case it also guides the inboard end of a lap or shoulder restraint belt or the control belt of a three-point restraint belt. The retractor for a passive shoulder belt is advantageously located in the lower rear part of the door between the inner and outer door panels and leads up to a guide at the upper rear corner of the door-that guide can be a belt clamp embodying the present invention.Usually, however, convenience of installation and economy of manufacturing are best served by incorporating the belt clamp as a subassembly with a separate frame or an integral assembly (single frame) into a retractor, as exemplified in the following embodiments.

In the embodiment shown in Fig. 3 a pair of emergency locking retractors are mounted side-by-side for installation as a unit between separate driver and front passenger seats in an automobile or other vehicle. Each retractor 200 has a belt reel 2Q2 which can be locked against rotation (in a direction such that the belt is pulled from the reel) by engagement of a pawl 204 with a ratchet wheel 206 connected to the reel. The pawl 204 is actuated by a pendulum 208.The restraint belt 210 (or a control belt) leads upwardly from the reel and around a guide roller 212 mounted between the side walls of a generally tubular belt clamp frame 214, then leads laterally outward between a fixed clamping jaw 216 mounted on a bracket 21 8 attached to the top wall of the frame 214 and a movable clamping jaw 220 carried by a lever 222 mounted to pivot on the axis of the roller 21 2. The belt then turns around a second guide roller 224 and leads away from the lever in a direction to pivot axis against the restraining force of a torsion (mouse-trap type) spring 226.

Under the forces on the belt 210 in the unwinding direction (represented by the arrowed line) which are ordinarily encountered when the belt is withdrawn with the reel unlocked, the spring 226 holds the lever 222 in the position shown in Fig. 3 in which the belt is guided between the rollers along a path clear of the fixed jaw 216. When the reet locks and a relatively large force.(one sufficient to overcome the force of the spring on the lever) is exerted on the belt in the pull-out direction, the belt pulls the lever 222 toward the fixed jaw 216 and clamps the belt between the corrugated clamping surfaces, thereby preventing by frictional gripping forces the belt from slackening due to withdrawal of an additional length of belt from the reel by tightening of the remaining turns of the belt on the reel.The greater the belt pullout force, the greater the force applied to the lever 222 via the roller 224 and the greater the frictional forces gripping the belt against pulling through the belt clamp.

The tandem retractor and belt clamp assembly shown in Fig. 4 is very similar to the one shown in Fig. 3-the differences inuolve, in essence, relocating the belt clamps 230 to positions below the retractors 232 and some relatively minor changes in the detailed designs of the belt clamps. For example, the fixed jaw 234 is carried by a bracket 236 of slightly different form, the lever 238 is modified and the shape and manner of installation of the spring 240 differ somewhat from that of Fig. 3. The similarities and differences are apparent from the drawings, and the operation is clearly apparent from the above description.

The retractor and belt clamp shown in Fig.

5 comprises a frame 250 made by stamping out and shaping a blank to provide side members 252 and a base part 254 having an inturned transverse arm portion 256. The belt reel 258 is mounted between the side frame portions 252 and is lockable against belt pullout by a pendulum and pawl mechanism 260.

A lever 262, mounted to pivot about a first guide roller 264, is urged into the position shown in the drawing by a spring 266 which yields to an abnormally high pull-out force such that the belt 268, which leads from the clamp around a second guide roller 270 on the lever 266, is pivoted to engage the belt between the clamping jaw 272 on the lever and the fixed clamping jaw 274 mounted on the arm 256.

The emergency locking retractor and belt clamp assembly shown in Figs. 6 and 7 comprises a frame 300, and end plates 302 of which support the belt reel 304, the pendulum and pawl locking mechanism 306 and the first guide roller 308 on which the lever 310 is pivoted. The lever includes a pair of spaced-apart mounting plates 312 and 314.

One jaw 316 of the clamp is affixed to the plate 312, and the other jaw 31 8 is received in an opening in the second plate 314 and is normally held in an upward position in the opening by a spring 320. The belt 322 leads from the reel around the first guide roller 308, passes between the clamping jaws and then turns around and leads up from a second guide roller 324. A spring 326 restrains the lever against pivoting in response to normal pull-out forces on the belt (Fig. 6) but yields to abnormally high pull-out forces on the be!t such that the lever pivots up to bring the jaw 31 8 into engagement with a fixed abutment 328 attached between the side parts 302 of the frame.Upon such engagement the jaw 31 8 moves down against the holding spring 320 relative to the lever and clamps the belt frictionally between the gripping surfaces of the jaws 316 and 318.

The embodiment of Figs. 8 and 9 includes an emergency locking retractor having a generally U-shaped frame 350, a belt reel 352 and a pendulum and pawl locking mechanism 354 which locks the reel automatically in response to acceleration of the vehicle. The belt B leads from the reel 352 over a first guide roller 356, then along a path closely adjacent, but not touching, the teeth of a fixed clamp member 358 mounted between the side plates of the frame 350 to and around a second guide roller 360, and away from the guide roller 360 in a direction generally opposed to the direction from which it is taken from the reel 352. A generally Ushaped lever 362, which includes a pair of spaced-apart arms 364 located on either side of the belt and joined to the frame side plates by a pivot pin 366, supports a movable clamping jaw 368.The lever arm 362 is urged in a direction to hold the movable clamping jaw 368 away from the fixed clamping jaw 358 by a spring or springs 370.

The guide roller 360 includes shaft portions 372 which extend out from either end, are received in slots 374 in the side plates of the frame 350, and bear against the edges 364(a) of the lever arms 364. The edges 364(a) lie oblique to the path of the belt B between the guide rollers 356 and 360, and the guide slots 374 for the shafts 372 of the guide roll 360 lie oblique to the edges 364(a). A spring (or srings) 376 normally urges the guide roller in a direction away from the lever 362.The forces of the springs 370 and 376 act on the roller 360 in a direction against a pull-out force applied to the belt B and resiliently oppose movement of the roller and the lever arm (in the manner described below) under normal pull-out forces on the belt, "normal" referring to the forces which the user exerts on the belt in the process of applying it or the forces which are applied in the operation of a passive belt system.

When a force in excess of the resultant of the spring forces acting in a direction aligned with the slots 374 is applied to the belt B when the belt reel 352 has been locked by the inertia-responsive or other locking mechanism of the retractor component of the assembly, the guide roll 360 is shifted along the guide slots 374 in a direction toward the lever 362, and the shaft portions 372 of the guide reel work against the edges 364(a) of the lever arm 364 and pivot the lever about the pivot pin 366 in a direction to move the movable clamping member 368 toward the fixed clamping member 358 and ultimately clamp the belt B between the clamping faces of the clamping members, as shown in Fig. 9.

The greater the pull-out force on the belt, the greater is the force applied by the shafts 372 to the lever arm 364, and the greater is the clamping force which holds the belt against withdrawal from the reel 352. When the pullout force is removed from the belt, the springs 370 and 376 restore the belt clamp to the release configuration shown in Fig. 8.

Figs. 10 and 11 illustrate an emergency locking retractor and belt clamp assembly which is quite similar to the one shown in Figs. 8 and 9. Accordingly, the elements of the embodiment of Figs. 10 and 11 which are substantially the same as those of Figs. 8 and 9 are assigned the same reference numerals and are not redescribed. The principal differences between the two embodiments are as follows: Instead of a lever arm carrying a movable clamp member, there is a movable clamp member 400 which has guide lugs 402 extending out from either side that are received in guide slots 404 in the side members of the frame 350. The clamp member 400 normally is held close to, but out of engagement with, the belt B by gravity.A camming surface 406 on the guide member lies oblique to the path of the belt between the clamp members and is engageable by a guide roller 408 which corresponds to the guide 360 of the embodiment of Figs. 8 and 9 but differs in that it has a corrugated surface. The surface 406 of the clamp member 400 has corrugations generally matching the corrugations of the surface of the guide roller 408. As shown in Fig. 11, the corrugations ensure better engagement between the guide roller and the clamp member and enhance the clamping action.As is apparent from the above description of Figs, 8 and 9 and from a comparison of Figs. 10 and 11, when the belt reel is locked and a force is applied to the belt of a magnitude sufficient to overcome the force of the spring or springs 410 associated with the guide roller 408, the guide roller 408 is pulled toward the clamping member 400, the corrugated surfaces of the roll 408 and the clamping member 400 engage, and the roll pushes the movable clamping member obliquely toward and into engagement with the belt and clamps the belt against the fixed clamping member. When the force on the belt is removed, the spring 40 pulls the guide roller 408 back to the release position, and the clamp member falls back along the guide slots 404 to the normal position (Fig. 10) out of engagement with the belt B.

Although both clamping members of any of the belt clamps described above may have matching teeth and recesses of uniform cross section along the width, thus to define a space of uniform thickness and of corrugated configuration over the entire area which engages the belt, there are two important characteristics of the belt and the belt clamp structure which are, preferably, taken into account in the design of the clamping surfaces. One of them, as illustrated in Fig. 12A, is a lack of uniform thickness across the width of the belt. Most webbing materials used for vehicle occupant restraint belts have greater thicknesses along the selvage edges at either side than in the center portion.If, as depicted in Fig. 12A, the gap between the clamping surfaces of the clamp members is of uniform width across the width of the belt, the edges of the belt B are subjected to substantially higher pressures than the center portion of the belt, thus creating a greater risk of damage to the belt or possibly even rupture. A related aspect of the physical properties of webbings commonly used in seat belts is variable elasticity, the selvage edges of most webbings being somewhat less elastic than the center portion.

A characteristic of the belt clamp that should be considered in the design of the clamping members, as shown in Fig. 12B, is the possibility of deflection of the clamp member. In the example shown in Fig. 12B, the upper clamp member U may be of the type shown, for example, in Figs. 6 and 7 in which the backup member is relatively stiff and, together with the clamp member U, resists deformation in the transverse direction, whereas the movable clamp member L is carried by a generally U-shaped plate P and is subject to transverse deformation.

The characteristics depicted in Figs. 1 2A and 1 2B can be compensated for in the design of the clamping surfaces of the clamping members in a number of ways, some of which are illustrated in Figs. 13 to 16. As shown in Fig. 13, one clamping member X has teeth Tx and recesses Rx, each of which is of uniform profile entirely across the width of the clamping member. The other clamping member Y has recesses Ry of uniform profile along the width of the member and teeth Ty which are higher in the center portion and curve down in regions corresponding generally to the selvage portions of the belt B.The reduced heights of the teeth of the member Y along the side portions provide gaps between the teeth of the member Y and the recesses of the member X of greater width than the gaps between the teeth and recesses of the members in the center portion. Accordingly, the selvage portions are under lesser average pressure as compared to the situation depicted in Fig. 12A, and the example shown in Fig. 1 3 provides more uniform distribution of clamping pressure across the width of the clamping surfaces. Moreover, the axis of the belt along the edge portions when the belt is clamped between the members X and Y is of lesser length because the small loops in the belt selvages where they pass over the side portions of the teeth Ty of the member Y are of lesser length than the loops over the Teeth Ty at the center.The configuration of the teeth of the member Y shown in Fig. 1 3 also tends to compensate for deformation of the clamp member Y (see Fig. 12B).

In the example shown in Fig. 14, the upper clamping member X has teeth Tx and recesses Rx that are straight and of uniform profile along the width. The other clamping member Y has teeth Ty and recesses Ry which are cambered (uniformly convexly curved in the upward direction) so that the gaps between the teeth of X and the recesses of Y and between the teeth of Y and the recesses of X are greater at the edges than at the center.

When the clamping members X and Y are loaded, i.e., when the belt is clamped between them, deformation of the clamping member Y (see Fig. 12B) tends to make the gaps between the teeth and recesses uniform, thereby evening out the average pressure on the belt across the width of the clamping surfaces.

Fig. 1 5 illustrates a variation of the concept shown in Fig. 1 3 in that the teeth Tx and the teeth Ty of both clamp members X and Y are of lesser heights along the side portions than in the center portions. This design compensates for greater belt thickness along the selvage edges, or for reduced elasticity along the selvage edges, or both.

In the example shown in Fig. 16, the clamping member X has teeth and recesses that are straight and of uniform profile entirely across the width, and the clamping member Y has straight recesses R and teeth Ty of maximum height at the center and of uniformly decreasing height moving in either direction from the center toward either side. Both clamping member deformation and the variable belt characteristics shown in Figs. 1 2A and 1 2B are compensated for when the belt is clamped between the clamping members.

The above-described examples of configurations of the clamping surfaces to compensate for characteristics of the belt and of the clamping members and their supports are merely representative, as are the guidelines set forth above in the Summary section. In each case, the amounts of variations in the teeth and recess heights are greatly exaggerated in the drawings to show the concept more clearly.

Thus, there is provided, in accordance with the present invention, a belt clamp in which, preferably, the belt can move freely between the jaws without engaging the clamping surfaces under normal force, but which is engaged evenly between smoothly curved gripping surfaces of a pair of jaws which are shaped to form a series of small loops and take up some or all of the length of the belt released by a locking retractor and frictionally hold the belt against being pulled out. The clamp produces little wear on the belt in either normal use or in emergency locking conditions.

The above described embodiments of the invention are merely exemplary, and numerous variations and modifications of the embodiments will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included in the scope of the invention, as defined in the appended claims.

Claims (16)

CLAIMS:

1. A belt clamp for a vehicle occupant restraint system which includes a restraint belt and a belt retractor onto and from which the belt is selectively wound and unwound and having a pair of jaws, one on either side of the belt, at least one of which is mounted to move toward and away from the other in response to a high pull-out force on the belt characterized in that at least one of the jaws has a multiplicity of closely spaced teeth lying transversely to the direction of movement of the belt, each tooth being generally straight, being of a length not less than the width of the belt, being smoothly curved in end profile, and being of generally uniform cross section along its length in the transverse direction, and the other jaw having a multiplicity of recesses, each of which generally matches a corresponding tooth on the other jaw and receives such corresponding tooth and a widthwise strip of the belt upon engagement of the belt between the jaws, each such strip of the belt being formed into a smoothly curved loop by being tucked by a tooth into a corresponding recess of the other jaw and being gripped under pressure between opposed gripping surfaces of the teeth and recesses.

2. A belt clamp according to claim 1 and further characterized in that each recess in said other jaw is a generally straight elongated concavity having a length in the transverse direction of the belt not substantially less than the width of the belt and a generally uniform cross section along its length generally complementary to that of the corresponding tooth of said one jaw, such that each loop is clamped between the surfaces of each tooth and corresponding recess upon engagement of the belt between the jaws.

3. A belt clamp according to claim 1 or claim 2 and further characterized in that said one jaw has recesses and said other jaw has corresponding teeth, each tooth of each jaw forming a loop in a widthwise strip of the belt by tucking the strip into a corresponding recess of the other jaw.

4. A belt clamp according to claim 3 and further characterized in that each jaw has teeth alternating with recesses.

5. A belt clamp according to claim 3 and further characterized in that both jaws have substantially identical teeth and substantially identical recesses.

6. A belt clamp according to claim 5 and further characterized in that the tip of each tooth and the base of each recess are arcuate in end cross section.

7. A belt clamp according to claim 4 or claim 5 and further characterized in that the distance between the tips of the teeth and the bottoms of the recesses of the jaw is from about two to about eight times the thickness of the belt.

8. A belt clamp according to claim 4 or claim 5 and further characterized in that the wall portions of each jaw which connect each arcuate portion of each tooth to the arcuate portion of the adjacent cavity are generally planar and lie oblique to a plane defined generally by the tips of the teeth of the respective jaw.

9. A belt clamp according to claim 8 and further characterized in that each tooth and each cavity of each jaw are symmetrical about a medial plane perpendicular to the plane defined generally by the tips of the teeth.

10. A belt clamp according to claim 1 and further characterized in that both jaws are mounted on a lever which is mounted to pivot about an axis spaced apart from the jaws, one of the jaws being mounted on the lever for movement toward the other jaw, in that there is a spring urging the movable jaw in a direction away from the other jaw and in that there is a fixed abutment positioned to be engaged by the movable jaw upon pivoting of the lever in response to belt tension, thereby to move the movable jaw into engagement with the other jaw.

11. A belt clamp according to claim 1 or claim 2 characterized in that the teeth of at least one of the jaws are of lesser height in portions adjacent the edges of the jaw than in the center portion.

1 2. A belt clamp according to claim 1 or claim 2 characterized in that the teeth of one of the jaws are of maximum height at the center and are of gradually reduced height moving from the center toward each side.

1 3. A belt clamp according to claim 1 or claim 2 characterized in that the clamping surface of at least one of the jaws is transversely cambered, the teeth and recesses being concavely curved in a direction transverse to the axis of the belt to compensate for deflection of the jaw when the belt is clamped between the jaws.

1 4. A belt clamp according to claim 1, substantially as described with reference to Fig. 3, Fig. 4, Fig. 5, Figs. 6 and 7, Figs. 8 and 9, or Figs. 10 and 11, with or without the feature of Fig. 13, Fig. 14, Fig.

15 or Fig.

16.