A TRIGGERING MEANS FOR A SAFETY BELT HAVING A PRE-TENSIONING DEVICE

Abstract: The present invention refers to a triggering means for a safety belt having a pre-tensioning device comprising a shaft of a winding wheel (10) for the safety belt said triggering means comprising a "U" shaped conduct having an enlarged diameter (72) in one leg for receiving an explosive charge, a flexible toothed belt (78) positioned inside the "U" shaped conduct comprising a series of teeth facing the inner portion of said "U" shaped conduct, the teeth of said flexible toothed belt projecting through a slot cut in the opposite leg of said "U" shaped conduct to engage with a toothed gear (68) mounted in one end of the shaft of the winding wheel of the safety belt, whereby when a sensor detects a sudden disacceleration of the vehicle an electrical signal fires the explosive charge thereby causing a displacement of the toothed belt within the "U" shaped conduct to rotate the toothed gear and the winding wheel connected therewith in order to immediately wind up the strap of the safety belt to eliminate any slack that may there exist in the belt.

Description: "A TRIGGERING MEANS FOR A SAFETY BELT HAVING A PRE-TENSIONING DEVICE" Background of the invention Field of the invention The present invention refers to an improved safety belts for vehicles, of the type having a pre-tensioning device and, more specifically, to a triggering means including technical and functional improvements particularly introduced in the safety belt disclosed in Brazilian patent application No. PI 9003144, filed on 14/08/90, entitled "IMPROVED SAFETY BELT WITH DOUBLE LOCK AND RETRACTION MECHANISM". Description of the Prior Art Generally, the present invention refers to a safety belt for vehicles of the type having a safety mechanism known in the art as pre-tensioning device, which purpose is to completely eliminate any possible slack which may there exist between the strap of the safety belt and the passenger. As it is widely known, when a vehicle is submitted to a sudden, momentary disacceleration, any slack in the strap of the safety belt can seriously jeopardize the safety of the passenger, since when such a sudden disacceleration occurs its body tends to continue to move forward until said slack is completely taken, which may cause a strong impact. The purpose of the present device is to completely eliminate any such slack before the body of the passenger has the time to move, thereby considerably enhancing the safety of the passenger. Retractable safety belts having a strap tensioned by a traction spring are widely known in the state of the art and are broadly used in different types and models of vehicles due to the many advantages they provide when compared with the previously used non-retractable safety belts not having a traction spring. By having a free end of the strap that surrounds and "fasten" the passenger's body to the seat of the vehicle wound in a winding wheel whose axis is permanently tensioned by a traction spring in order to retract said strap, this kind of safety belt allows the free end of the strap to be automatically wound by the spring in order to adjust to any small movements of the passenger during normal operation of driving the vehicle, thereby providing some freedom of movement while not affecting the safety of the passenger. This feature is accomplished by providing the shaft of the winding wheel for the strap with a locking device which automatically stops the unwinding of the strap of the safety belt when the vehicle is submitted to strong forces like when making a turn, a sudden stop or a collision. Nevertheless, due to its constructive features, said retractable safety belts having a traction spring always allow a small slack at the free end of the strap, whereby there exists the possibility that the passenger may not be securely "fastened" to the seat of the vehicle when of a sudden disacceleration, thereby being susceptible to being injured when the sudden disacceleration results in a collision. A previously proposed solution to the above problem consisted in providing a pre-tensioning device coupled to the traction spring on the retractable safety belt, in order to maintain the free end of the strap which surrounds and "fastens" the body of the passenger under a permanently tensioned condition while avoiding this tension from becoming unpleasant and/or unbearable for the passenger. However, the pre-tensioning devices known in the art do not provide a satisfactory solution to the problem of firmly "fastening" the body of the passenger to the seat of the vehicle when the vehicle is submitted to a sudden disacceleration, which would significantly reduce the possible injuries that may happen when of an accident. A second solution previously proposed to this problem was the provision of a triggering device positioned to actuate the pre-tensioning device within an extremely short time period, in the order of milliseconds, when a sudden disacceleration occurs, to firmly fasten the body of the passenger against the seat of the vehicle. According to this second solution, a sensor device mounted in a suitable location on the vehicle is used to detect such a sudden disacceleration and to send a signal for firing the triggering device so that it will act upon the winding wheel to wind the strap of the safety belt in order to "fasten" the passenger against the seat of the vehicle. This way, when of a sudden disacceleration of the vehicle, the pre-tensioning device actuated by the firing of the triggering means eliminates any slack that may there exist on the free end of the strap of the retractable safety belt having a traction spring in a very short time period, of no more than a few milliseconds . A major drawback of the retractable safety belts having a pre-tensioning device as described above is the coupling between the pre-tensioning device and the traction spring, which may cause the housing of the belt mechanism to become too bulky and therefore not suitable for use in a vehicle having a modern design where the use of all available inner space is a requirement. Some of the above discussed problems were solved by a pre-tensioning device as disclosed and claimed in Brazilian patent application No. PI 9601457-1, filed on March 25, 1996, entitled "A PRE-TENSIONING DEVICE FOR USE WITH A TRACTION SPRING IN A SAFETY BELT", which specification is hereby incorporated as a reference. The device disclosed in the above patent application comprises a housing, winding wheels formed with toothed gears and a holding constraint. A gas triggering device is also provided as an integral part of the assembly, said gas triggering device being fired by electric sensors when of an accident in order to traction the steel cable of the safety in a very short period of time, short enough to wind the winding wheel of the safety belt so as to firmly "fasten" the passenger against the seat. Although the device as described above has proved to work very satisfactorily, it still showed a number of drawbacks, starting with the response time, which has not reached a desired level of promptness, and also its configuration, which although extremely simplified still is characterized by defining a system that works by applying traction on a steel cable, whereby the explosive charge has to be substantially big. Summary of the Invention The improved safety belt according with the present invention also comprises a pre-tensioning device actuated by an explosive charge as in the system of the prior art, except that the pre-tensioning device according with the present invention comprises a "U" shaped conduct having a flexible toothed belt positioned inside it, with a first end of said toothed belt being positioned in order to be pushed by the firing of the explosive charge while its second, opposite end is engaged to a toothed gear which, by its turn, is coupled to a first end of the shaft of the winding wheel for winding and unwinding the strap of the safety belt. With the device having the above configuration, when the explosive charge in the pre-tensioning device is fired by an electric signal, such as when of an accident, the force resulting from the expansion or pressure of the gases causes a displacement of the toothed belt, which runs as a projectile being fired within the "U" shaped conduct, said displacement causing a rotation of the toothed gear engaged therewith, which acts as a "flywheel" to further cause a rotation of the winding wheel in a direction to wind the strap of the safety belt enough to fasten the body of the passenger against the seat of the vehicle, thereby eliminating any slack that may eventually be a hazard to the safety of the passenger. The device according with the present invention also comprises a torsion bar coupled to said toothed belt, said torsion bar being submitted to a torsion stress when the toothed belt is displaced. The torsion bar is dimensioned to endure a certain load and is provided with deformable portions specifically designed to yield in case the rotation of the winding wheel eventually suffers any interference contrary to its direction of rotation. A number of different reasons can cause such an interference, such as, for example, an excessive winding of the strap of the safety belt. In this and in many other situations, said torsion bar is submitted to a torsion in order to take up the stress that would jeopardize the safety of the passenger. In addition to the above, the improved safety belt according with the present invention, also includes the following new constructive and functional features: a) a retracting assembly that causes the strap of the safety belt to be immediately wound around the winding wheel when it is activated after being used; b) a first lock, hereinafter referred to as "vehicle lock", which is actuated by a change in the direction of movement or in the speed of the vehicle in order to prevent the strap from becoming loose under such a condition, thereby firmly fastening the passenger against the seat; and c) a second lock, hereinafter identified as "strap lock", which is designed to act in order to prevent the strap of the safety belt to become loose when the strap is submitted to an acceleration above a predetermined level. In other words, when the passenger moves forward too fast, voluntarily or involuntarily, the strap is immediately locked to avoid it from becoming loose. By incorporating all the above discussed constructive features, the safety belt according with the present invention is able to provide a higher safety level to the passenger, including the additional protection provided by the pre-tensioning device, without interfering with freedom of movement the system provides to the passenger within the vehicle, as long as these movements are done at a speed below the predetermined levels where the belt is activated. As in the safety belt disclosed in the above cited Brazilian patent application No. PI 9003144, the improved safety belt according with the present invention also includes a pair of locking teeth associated in a single piece, which engages with toothed washers formed on the winding wheel for the strap. In addition to the above, the winding wheel is also provided with a device for allowing its movement relative to its supporting housing so that when the assembly becomes locked, the winding wheel can rest against its metallic housing therefore avoiding the assembly from failing. This is done by transferring from the winding wheel to the metallic housing part of the load being taken up. The foregoing and other additional objects, features and advantages of the improved safety belt having a pre-tensioning device according with the present invention will be understood in greater detail with reference to the detailed description which follows, accompanied by schematic illustrations of the presently preferred embodiment of the invention, as shown in the attached drawings . Brief Description of the Drawings The present invention will be described hereinafter in greater detail with specific reference to a presently preferred embodiment as shown in the attached drawings, which are not in any way a limitation of the scope of the invention, and wherein: Figure 1 is an exploded perspective view of a safety belt having a pre-tensioning device according with the prior art. Figure 2 is cross section of the traction mechanism of the safety belt shown in Figure 1. Figure 3 is a exploded elevation view, partially cut, of an improved safety belt according with the present invention, with the exploded views showing each part of said improvement. Figure 4 is an exploded elevation side view of the improved safety belt according with the present invention with the improved parts shown in detail. Figure 5 is a cross section of the improved safety belt shown in Figure 4 showing the improved parts in detail. Figure 6 is a side view similar to Figure 4 showing the children protection system activated. Figures 7 to 10 are schematic representations showing the operation of the improved safety belt according with the present invention. Description of the Preferred Embodiment of the Invention As shown in the accompanying drawings and in the details of each Figure, and more particularly with reference to Figures' 1 and 2, the safety belt according with the present invention can be incorporated into a number of different types of safety belts, such as the one shown in Figures 1 and 2. From Figures 1 and 2 it can be seen that this safety belt comprises a "U" shaped metallic housing 1 defining a central portion and two side walls 2 provided with spacing bars 3 at its distal ends, each side wall 2 having an outwardly projecting area 4 slightly curved, each with a centrally cut bore 5 where tubular projections 6 surrounding a housing 7 of the traction spring and a housing 8 of the locking mechanism are fitted, said projections 6 being surrounded by slots 9 formed on the housings 7 and 8 in order to allow a small relative movement between the projections 6 and the housings 7 and 8. Housings 7 and 8 are mounted on the metallic housing 1 by expansion members 21 which expand when pins are introduced therein. A winding wheel 10 formed with two radially extending lugs 11, a longitudinal slot 12 for receiving a locking member 13 for the strap, and having a metallic shield 14 surrounding a shaft 15 is positioned in the area defined between the two side walls 2, within the outwardly projecting areas 4, with said shaft 15 being aligned with the centrally cut bores 5. Said winding wheel 10 also has a washer 16 having outer teeth coupled therewith outwardly of each radially extending lug 11, said washers also being received within the outwardly projecting area 4 in each side wall 2. A shaft 17 for the traction spring is received inside the spring housing 7, said shaft 17 being coupled to main shaft 15 through projecting pins 18 formed in one end thereof which engage one end of the main shaft 15. A shaft 19 for the locking mechanism is also coupled with the main shaft 15 through pins 20 formed in one end thereof which engage the opposite end of said main shaft 15, as shown in Figure 1. The housing 7 for the traction spring has an outer, substantially tubular projection 22 where a laminar spring 23 is received, one end 24 of said spring 23 being received in a slot (not shown) formed on the spring shaft 17 while its opposite end 25 is coupled to an inner assembly associated with the housing 7, with a closing lid 26 covering these parts. The assemble of the safety belt mechanism starts with shat 19, around which the mechanism core 27 pivots, with a packing member 28 sliding over grooves 29 formed on the shaft 19 to assist properly positioning said core 27. The mechanism core 27 is formed with outwardly projecting radial lugs 30, 31 which are positioned by stops 32 provided in the mechanism housing 8, projecting lug 30 being formed with an inwardly facing projection 35 that projects through slots 33, 34 cut in the housing 8 and in the side wall 2. This projection 35 is designed to engage a lever 36 of the double lock shaft 37 which pivots in the housing 1 through cylindrically formed ends 38 received in slots 39 cut in said metallic housing 1, the extremities of the lever 36 acting against the teeth of the toothed washer 16 when the mechanism is mounted. Said double lock shaft 37 may be forced to rotate by a disacceleration sensor also known as a strap sensor and/or by a vehicle sensor, both coupled to the safety belt assembly by the mechanism core 27 and by its shaft 29. The sensor for the strap of the safety belt comprises a disk member 40 having a plurality of angled teeth 41 positioned on its periphery, which receives a substantially circular body 42 inside it, said inner body 42 being mounted on said outer disk 40 through a series of locking members in such a manner that it may rotate relative thereto by a limited angle. The body 42 has a cavity where a locking member 43 is received, said locking member 43 having a bore 44 which serves as a pivot for a pin (not shown) formed on the inner face of the disk member 40, the locking member 43 also being provided with a groove 45 where a pin 64 of said inner disk 42 is received, with a guide 47 of the locking member 43 allowing a controlled displacement of the locking member within a groove 48. A spring 49 is mounted to pins provided in both said disk member 40 and said inner body 42, with the locking member 43 engaging a series of teeth 50 formed inside a circular protruding wall 51 of said mechanism core 27, with the disk member 40 being provided with a central projection received in a matching hole formed on the shaft 19 for the locking mechanism. In a rest condition, this constructive arrangement allows the position of the inner body 42 relative to said disk member 40, as determined by the tension exerted by spring 49, to be such that the locking member 43 is perfectly housed inside the recess formed in the body 42. This way, when the strap of the safety belt is suddenly accelerated, winding wheel 10 rotates until it reaches a predetermined speed, at which moment the combination of the forces acting on the spring 49 in one end, and the inertial movement of said body 42, which has a suitably dimensioned mass, at the other end, allows a relative movement of said body 42 relative to said disk 40, whereby it is displaced outwardly of its housing in the locking member 43 in order to engage the teeth 50 of the core 27 forcing it to rotate around its axle against the force of a spring 52 positioned between the housing 27 and the housing 8, causing a displacement of projection 35 and, accordingly, of the double lock 37 in order to safely lock the mechanism. In an extreme situation where the loads acting upon the winding wheel are too high, with the winding wheel supported on its bearing points, as defined by the projections 6 formed on housings 7 and 8, being submitted to an unusually high pressure, the wheel can be minimally displaced by deforming said housings 7, 8 in the area of the slots 9, thereby causing the winding wheel 10 to rest upon the metallic housing 1 and providing a higher level of resistance to the mechanism, avoiding a failure of the more fragile components, the assembly returning to its original position after the loads are removed. The springs 49, 52 return the strap sensor to its original rest position when the loads that caused the displacement stop . The vehicle sensor comprises a cradle member 53 for a sphere 54, said cradle being mounted by its ends on projections 55 formed on the housing 8, the cradle 53 being formed with upwardly facing projections 56 where an actuating lever 57 pivots, said lever 57 resting against the upper side of the sphere 54 and being formed with a projection 58 on its upper surface that engages a locking member 59 which pivots around a pin 60 on the mechanism core 27, next to said spring 52, said locking member 59 having an end shaped as a tooth which engages the teeth 41 on said disk member 40. This sensor detects any change in the movement of the vehicle, whether an acceleration, a disacceleration or a change of direction. When such a change of movement occurs, the sphere 54 positioned between the cradle 53 and the actuating lever 57 causes the lever to move upward to displace the locking member 59 in such a way that its end 61 engages the teeth 41 on the disk member 40, thereby causing a displacement of the mechanism core 27 as in the case of the strap sensor. When the cause of the change of movement stops, the sphere 54 returns to its rest position in the center of the cradle member 53 and the locking engagement is interrupted. The spring 52 on the mechanism core 27 returns the locking member to its rest condition. Figures 3 and 4 illustrate the additional features of the improved safety belt with pre-tensioning device according with the present invention. A torsion bar 63 is positioned inside the metallic shield 14, said torsion bar 63 having a locking pin 64 in one end and a outer portion formed with teeth 65 on its opposite end, said bar 63 being positioned in such a way that both its ends project outwardly of the corresponding radially projecting lugs 11 and the toothed washers 16, which are mounted on the ends of the metallic shield 14. After the torsion bar 63 is positioned, its locking pin 64 is coupled to a modified shaft end 66 which, by its turn, is coupled to the corresponding washer 16 on the right side, the end 66 for mounting the locking mechanism (SV) being closed by a lid 62, while the teeth of its opposite end 65 engage the inner teeth of- a second modified shaft end 67 which likewise is coupled to the corresponding washer 16 on the left side, with the shaft 17 for the traction spring 23 positioned within housing 7 and closed by lid 22 as described above. Said second modified shaft end 67 has a portion (D) formed with outer teeth matching the inner teeth (D' ) of a toothed gear 68 which, as shown in Figure 4, is positioned between said housing 7 and a positioning member 69 in such a manner that the gear 68 is surrounded by the driving means 70. The driving means 70 comprise a "U" shaped conduct 71 having a substantially quadrangular cross section, one leg thereof projects upwardly and slightly inwardly to define a portion having an enlarged diameter 72 where an outer thread 73 is formed, said larger portion being closed by a lid 74 and housing an explosive charge 75, an helical spring 76 and a piston 77. A flexible toothed belt 78 is positioned inside the "U" shaped conduct 71 immediately below piston 77, said flexible toothed belt 78 occupying the whole length of said conduct 71, which opposite end defines a housing 79 for the flexible toothed belt 78. The flexible toothed belt 78 comprises a series of adjacent parallelepipedic blocks 78A, each- having a male-female semi-spherical coupling 80, 81 on opposite sides for matching a similar coupling formed on an adjacent block, and a cut edge on its upper surface for defining a series of teeth 82, facing the inner portion of said "U" shaped conduct 71. Conduct 71, by its turn, is formed with a longitudinal slot 83 cut along the inner face of the leg opposite to said upwardly and inwardly projecting leg 72, the teeth 82 of the flexible toothed belt 78 projecting through said slot 83 in order to engage with matching teeth formed on gear 68. The operation of the improved safety belt having a construction as described above is very simple. Under normal operating conditions, the strap of the safety belt is wound and unwound around the winding wheel in order to adjust to small movements of the passenger during the normal operation of driving the vehicle, thereby providing some freedom of movement while not affecting the safety of the passenger while avoiding this tension from becoming unpleasant and/or unbearable for the passenger. When a sudden disacceleration occurs, such as during a collision, one of the sensors detect this condition and send an electrical signal to fire the explosive charge 75. The ignition of the explosive charge causes a quick expansion of gases inside end 72 of the "U" shaped conduct 71 thereby projecting the piston 77 against the flexible toothed belt 78. This causes a displacement of said flexible toothed belt 78 within the "U" shaped conduct 71 towards the housing 79, which displacement causes a rotation of the toothed gear 68 and, accordingly, of the winding wheel 10 connected therewith, in order to wind up the strap of the safety belt in order to immediately eliminate any slack that may there exist in the belt to firmly "fasten" the passenger against the seat of the vehicle. As mentioned above, the torsion bar 63 is dimensioned to receive a pre-determined load and to absorb part of the impact between the strap and the passenger. Under a critical situation, that is, when eventually said load is above a certain level, the toothed washer 16 on the right side turns itself loose from the shaft 15 in order to immediately release the load, adding an extra protection to the passenger. A presently preferred embodiment of the present invention has been described and illustrated in connection with the accompanying drawings. However, those skilled in the art will readily understand that other modifications and variations may be resorted to without departing from the spirit and scope of the invention. Such modifications and variations as considered to be within the purview and scope of the invention as defined in the attached claims.

Claims: Claims 1. A triggering means for a safety belt having a pre- tensioning device, said safety belt having a strap tensioned by a traction spring designed to surround and fasten the body of a passenger against the seat of a vehicle, the improvement comprising: a substantially "U" shaped metallic housing defining a central portion and two side walls, each having an outwardly projecting area with a centrally cut bore for receiving a shaft of a winding wheel; a winding wheel for the safety belt positioned in the area defined by the side walls, within the outwardly projecting areas, said wheel having a shaft aligned with the centrally cut bores; a toothed gear mounted in one end of said shaft and engaged by a triggering means; first sensor means for detecting a sudden movement of the strap of the safety belt and to send an electrical signal to fire an explosive charge in the triggering means in reply thereto; a second sensor means for detecting a change in the direction of movement of the vehicle and to send an electrical signal to fire an explosive charge in the triggering means in reply thereto; and triggering means containing an explosive charge to be fired by an electrical signal from said sensors, said triggering means comprising a "U" shaped conduct having an enlarged diameter in one leg for receiving said explosive charge, a flexible toothed belt positioned inside the "U" shaped conduct comprising a series of teeth facing the inner portion of said "U" shaped conduct, the teeth of said flexible toothed belt projecting through a slot cut in the opposite leg of said "U" shaped conduct to engage with the toothed gear mounted in one end of the shaft of the winding wheel of the safety belt, whereby when one of the sensors detect a sudden disacceleration of the vehicle an electrical signal fires the explosive charge thereby causing a displacement of the toothed belt within the "U" shaped conduct to rotate the toothed gear and the winding wheel connected therewith in order to immediately wind up the strap of the safety belt to eliminate any slack that may there exist in the belt. 2. The triggering means for safety belt as defined in claim 1, wherein the first sensor means comprise a disk member having a plurality of angled teeth on its periphery and receiving a substantially circular body inside it, said inner body being mounted on said outer disk through a series of locking members in such a manner that it may rotate relative thereto by a limited angle; a locking member received in said body, said locking member having a bore serving as pivot for a pin formed on the inner face of the disk, a groove where a pin of said inner body is received and a guide allowing a controlled displacement of the locking member within a groove, said locking member engaging a series of teeth formed inside a circular protruding wall of a core of said sensor; and a spring mounted to pins provided in both said disk member and said inner body, with the disk member being provided with a central projection received in a matching hole formed on the shaft for the locking mechanism, whereby when the strap of the safety belt is suddenly accelerated the forces acting on the spring and the inertial movement of said body allows a relative movement of said body relative to said disk displacing it outwardly of its housing in the locking member in order to engage the teeth of the core to safely lock the mechanism. 3. The triggering means for safety belt as defined in claim 2, wherein housings are provided for the traction spring and for the locking mechanism of the safety belt, said housings being dimensioned in order to be deformed when the loads acting upon the winding wheel are too high, thereby causing the winding wheel to rest upon the metallic housing. 4. The triggering means for safety belt as defined in claim 2, wherein the second sensor means comprise a cradle member supporting a sphere, said cradle having upward projections for an actuating lever to pivot around, said lever resting against the upper side of said sphere and being formed with a projection on its upper surface which engages a pivotable locking member having a tooth for engaging the teeth on said disk member. 5. The triggering means for safety belt as defined in claim 1, additionally comprising a torsion bar positioned inside the shaft of the winding wheel, said torsion bar having a locking pin in one first end and a outer portion formed with teeth on its opposite end, both ends of said bar projecting outwardly of the shaft . 6. The triggering means for safety belt as defined in claim 5, wherein the locking pin of the torsion bar is coupled to a modified shaft end which, by its turn, is coupled to a washer of the winding wheel while the teeth on its opposite end engage with inner teeth of a second modified shaft end also coupled to a washer on the other side of the shaft. 7. The triggering means for safety belt as defined in claim 6, wherein said second modified shaft end has a plurality of teeth on its outer portion, which match with the inner teeth of the toothed gear engaged by the triggering means.

Inventors: ABBRUZZINI ENZIO, ABBRUZZINI, ENZIO
Applicants: ABBRUZZINI ENZIO, HUZIMET ACOS ESPECIAIS LTDA, ABBRUZZINI, ENZIO, HUZIMET ACOS ESPECIAIS LTDA.
Application year: 1999
Main classification: B60R22
IPC codes: B60R21, B60R22