FR3016017A1 - DEVICE FOR RETAINING A STRAP WITH ENERGY DISSIPATION. - Google Patents

Abstract

The present invention relates to an energy dissipating strap retainer. Retaining device comprising at least one safety strap, characterized in that it comprises means for dissipating the energy applied in tension on said strap, comprising a woven dissipation element, both ends of which are sewn onto said strap. safety, so that said safety strap defines a loop between the two seams.

Description

FIELD OF THE INVENTION The field of the invention is that of the safety of objects and persons, in particular in case of displacement or violent shock, due for example to a accident or sudden change of speed and / or direction. More specifically, the invention relates to the dissipation of the energy following such a shock. The invention can find many applications, for the maintenance of objects (for example nets or straps, in aircraft, ships, trucks ....). Particular applications can also be envisaged, since it is useful to dissipate efficiently and safely energy, for example to hold a seat in a vehicle, or a person in a seat. 2. Prior art Energy dissipation solutions in case of impact have already been proposed. Controlled deformation structures (also known as "crash boxes") are known, which are for example used by the automotive industry, in particular for absorbing energy in the event of a frontal impact. The approach is effective, but complex and expensive to design and implement. It also assumes, of course, the presence of a deformable structure, which can not be implemented in all applications (car seat for example). It is also known, in certain cases where straps, for example on life lines or on safety nets, are used to implement tear seams, as illustrated in FIG. 8. According to this approach , a fold 11 is formed on the strap 12, and the two portions of this fold 11 are sewn to one another by a series of seams 131 and 132. These seams are torn successively, during the impact, dissipating the 'energy. This approach has some efficiency, in terms of energy dissipation, but it remains low. It also presents a number of problems. In particular, it shows a behavior in jerks (with each tearing of a seam). The successive rupture of one or more seams induces very disturbed and uncontrolled stress curves (see curve 33, FIG. 3). Moreover, the dimensioning of the level of effort required to break one or more of the seams (and therefore the dissipated energy) is not easy to define, because it depends on many parameters (son, seams,. ..). As a result, it is not possible to precisely control the level of effort corresponding to a break. In addition, the stability of this level of effort is difficult to control precisely, which may render this approach unsuitable for mass production, especially when it comes to the restraint system for people, and more still to children. It has also been proposed, for example in document GB2487484, to add a seat belt of a car seat elastic part, intended to absorb energy. This technique has at least two disadvantages. Firstly, the implementation of an elastic element introduces difficult to control phenomena of rebounds, after the shock, which are of course not desirable, and potentially dangerous (for example for a child in a car seat). Moreover, the use of an elastic element introduces a progressive deformation, linear function of the effort. Thus, even in the event of a slight impact, or at least potentially acceptable, corresponding for example to a sudden braking or a bend, the strap will extend substantially, at levels of effort or the strap must remain integrates to guarantee the restraint of the room or the person it is supposed to maintain. Again, this is not desirable, and potentially dangerous. OBJECTIVES OF THE INVENTION The objectives of the invention are in particular to overcome at least some of these disadvantages. More specifically, an object of the invention is, according to at least one embodiment, to allow a dissipation of the energy applied to a strap that is effective and controlled, depending on the needs. Thus, an object of the invention is to provide a technique avoiding jolts introduced by a system with tear seams. Another object of the invention is, according to at least one embodiment, to provide such a technique, tolerant without appreciable variation of the forces lower than the predetermined one (to accept without appreciable length variation a sudden braking action. The object of the invention is, according to at least one embodiment, to provide such a technique which is easily adjustable and adaptable to the needs, and reliably reproducible, for example for mass production Another objective of the invention , according to at least one embodiment, is to allow an effective control of the level of displacement with respect to the energy (and / or at the energy level) dissipated Another object of the invention, according to at least one embodiment embodiment, is still to provide an indication that the strap and / or the object held has suffered a significant shock.

The invention also aims, according to at least one embodiment, to provide such a technique, which is simple to implement, and inexpensive. 4. Objective of the invention These objectives, as well as others which will appear later, are achieved by means of a retaining device comprising at least one safety strap and, according to the invention, means of dissipation of the energy applied in tension on said strap, comprising a woven dissipation element, the two ends of which are sewn on said safety strap, so that said safety strap defines a loop between the two seams.

Thus, in the event of a major force applied to the safety strap, the force is initially applied to the woven dissipation element, which will lengthen to dissipate the energy. In contrast, in case of low effort, not requiring such dissipation, the length of the woven element remains constant, or almost constant, which ensures that the role of safety strap is well assured.

This elongation, after a first predetermined level, is of course different from the approach of the prior art proposing to use an elastic band, which comes into action at the least effort, and thus leads to having a strap of variable length whatever the effort, which is usually not suitable. According to a preferred embodiment, the length of said loop is less than the maximum elongation, before rupture, of said woven dissipation element. Thus, beyond a second level, corresponding to the length of the loop, the strap takes its role of restraint. According to a particular embodiment, said woven dissipation element is made from a wire that can extend to at least twice its initial length, from a first predetermined force level. According to a particular embodiment, said woven dissipation element allows dissipation of the progressive energy as follows: voltage rise of said woven dissipation element, with an elongation of the latter zero or very low, up to a first predetermined effort level; progressively extending said woven dissipation element at substantially constant force level to a maximum elongation corresponding to the length of said loop; resumption of efforts by said safety strap, said loop being tensioned. According to the embodiments and applications, said first level of effort can be between 25 kg and 5 tons. Said dissipation element may for example be made using a polyester thread. It may especially be an unstretched polyester yarn before weaving. The invention can be used in many fields to provide security and / or indication of an overload, and in particular for: the securing of a load; lifting a load; - safety belts and harnesses; security in a seat. In particular, in the latter case, the invention can be implemented in a child car seat, in at least one of the following applications: on an anti-tilt strap of said seat, adapted to connect an upper portion thereof to a point of attachment in a vehicle; - on one or more strands of a harness; - on a retaining strap of a harness sheath; - on a strap connecting a folder and a movable headrest relative to said folder; - on a strap connecting a seat to a backrest; on an unlocking strap of one or more securing clips of said seat to corresponding rings in a vehicle. 5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of embodiments of the invention, given by way of illustration and not limitation, and the appended drawings among which: FIGS. 1A to 1C schematically illustrate a device for dissipating energy according to the invention, respectively: FIG. 1A: in a "normal" state, the applied force being less than a first threshold; - Figure 1B: in a state during elongation, when the applied force is equal to the first threshold; - Figure 1C in a state elongated at most; - Figure 2 schematically illustrates the elongation of the device of Figures 1A to 1C, depending on the force applied; FIG. 3 illustrates the energy dissipation behavior of a device according to the invention, as compared with a conventional strap and with a tear-seam strap; - Figure 4 illustrates schematically, and in section, a child car seat, in which several holding devices according to the invention are implemented; - Figure 5 shows another implementation of a retaining device of the invention, on a flexible seat; FIG. 6 illustrates another application of the invention for securing a sensitive load, for example on a truck; - Figure 7 illustrates yet another application of the invention for lifting a load by limiting jolts; - Figure 8 shows the technique of the prior art using tear seams. 6. DESCRIPTION OF EMBODIMENT OF THE INVENTION 6.1 GENERAL PRINCIPLE The invention therefore proposes a new approach for the dissipation of the energy applied in traction on a strap, such as a restraining strap on a car seat for a child, a safety belt...

As illustrated in FIG. 1A, the invention relates to a woven dissipation element 11 on a safety strap 12. This dissipation element 11 is sewn at its two ends on the surface of the strap 12 by two seams 131 and 132. These seams are designed so as to withstand at least the maximum force that the dissipation element 11 must bear (in other words, it is not about seams provided for tearing in the event of impact). The length L1 of the dissipation element 11 is less than the length L2 of the corresponding portion 121 of the strap 12 extending between the two seams. Thus, at rest and in a state of "normal" tension, ie in a situation where the applied force is less than a first threshold from which the dissipation element will come into action by elongation, the portion 121 forms a loop, the linear continuity of the tensioned strap being ensured by the dissipation element 11. The dissipating element 11 is not elastic, the assembly forms a conventional strap, non-extendible, or very slightly extensible, as long as the traction conditions remain acceptable, that is to say less than the first predefined threshold. Thus, for example, for a car seat or a seat belt, the strap remains classically tense, no variation in length, even in the presence of sudden braking or sharp bends. She plays classically, and safely, her role. When the effort reaches the first predefined threshold, which corresponds, for example, to a situation of accident or potential accident, it is desirable to effectively dissipate the energy, which does not allow a conventional strap. It is also desirable that this dissipation is done more gradually, or linearly, possible, and therefore smoothly, difficult to control and sometimes dangerous, as is the case with tear seams. According to the invention, this dissipation is ensured by the dissipation element 11, which progressively elongates, as illustrated by FIG. 1B, when the force reaches the first predetermined threshold.

This progressive elongation is enabled by the use of an elongated wire, for example a polyester yarn, and in particular an unstretched polyester yarn. This allows, in cooperation with the weave, to obtain a progressive elongation, for example up to twice the initial length Li of the dissipation element 11. When the maximum elongation is reached, that is to say before reaching the break point of the dissipation element 11, the strap 12 becomes active alone, as shown in Figure 1C. In practice, therefore, in this embodiment, a loop length L2 of less than or equal to twice Li will be chosen. In other words, when the elongation reaches the length of the loop, the strap 12 resumes its function of conventional restraint (and the dissipation element 11 is no longer active), but a significant part of the energy previously dissipated by the dissipation element 11. FIG. 2 schematically illustrates the principle of the invention, and more precisely the amount of energy dissipated in the context of a tensile test. More precisely, the curves of FIG. 2 make it possible to compare the energy dissipation provided by a conventional strap (curve C1) and by a device according to the invention, a woven dissipation element being added to the same strap, in the manner illustrated in FIG. 1A (curve C2). It is assumed that the conventional strap has a rupture threshold corresponding to a force Fmax, beyond which there is rupture. In a tensile test situation, it is found (curve C1) that the strap elongates very slightly, and linearly, as the tensile force increases, until breaking. The amount of energy El dissipated corresponds to the area under this curve. It is found that it is relatively weak. By adding a dissipation element according to the invention, it immediately appears that the amount of energy E2 dissipated is much greater. More precisely, up to a first threshold, or step, Fse, 'corresponding here to approximately half of Fmax, the curve C2 behaves identically or similar to the curve C1 (part 21). As indicated above, this means that, under normal conditions, the strap according to the invention behaves like a conventional strap (in particular without undesirable elasticity effect). However, as soon as one reaches the level of effort exceeding a first step, corresponding here to about Fmax / 2, the dissipation element 11 will gradually lengthen. As can be seen in curve C2, portion 22, this elongation is made with a constant effort, or almost constant, without particular jerks. This portion 22 corresponds to the situation of FIG. 113. Before reaching the break point of the dissipation element 11 (FIG. 1C), the strap 12 takes over (portion 23) and behaves again like the C1 curve. It is found that the amount of energy E2 is much greater than the amount of dissipated energy E1, and has been increased by AE, corresponding to the elongation period of the dissipation element (portion 22).

FIG. 3 presents, as for it, curves of force during a shock (dynamic test), making it possible to compare the behavior in dissipation of energy of a device according to the invention (curve 31) with a conventional strap (curve 32) and a strap with tear seams (curve 33). It can be seen that, in the same situation, a conventional strap (curve C4) reaches a maximum level of 3250 Newton while the maximum level is less than 2,000 Newton, for the device of the invention (curve 31). Furthermore, after the peak, this curve 31 descends very gradually, unlike the curve C5, which reveals many acceleration peaks, corresponding to the tearing of each seam. The approach of the invention is therefore much more stable and safe. 6.2 Parameterization Moreover, the approach of the invention is reproducible, and therefore easy to implement industrially, the characteristics of the dissipation element 11 (wire and weaving) being mastered. This aspect also makes it possible to easily parameterize the dissipation characteristics, and in particular the first threshold, from which elongation begins. This adaptation will be done by selecting the diameter of the thread, the number of threads and the characteristics of the weaving. This first step is easily defined because it varies linearly according to the number of threads.

A second threshold, corresponding to the recovery of efforts by the strap, corresponds to the length L2 of the loop. It is from this second threshold that the progressive elongation of the retaining element is interrupted, the final elongation being zero or very low, depending on the characteristics of the strap itself. This second threshold can be determined so that the strap comes into action before rupture of the retaining element, considering, in the illustrated embodiment, that the rupture threshold substantially corresponds to twice the length of the dissipation element. resting. Depending on the use and the needs, the maximum elongation, ie the maximum displacement, displacement, can be defined optimally. It is thus possible, during the parameterization, to privilege the displacement and the effort, and to define their respective values. The second threshold can therefore be placed between Fsewi and Fmax (that is to say on the curve portion 23), to ensure that the breaking threshold is not reached. Often, we will choose the second threshold equal to, or substantially equal to, the first threshold, in terms of effort. Thus, in the example of FIG. 2, the maximum displacement L displacement has been fixed in the portion 22 of the curve C2 (preferably in the end zone of this portion), so that it does not reach portion 23 of this curve C2. The parameterization thus makes it possible to fix, on the one hand, the force Fsewi from which the dissipation element begins to lengthen, and on the other hand the maximum elongation L of displacement thereof. 6.3 First Implementation Example: Load Retention As illustrated in FIG. 6, the device of the invention can be used for the securing of a load 61, and in particular of a sensitive load, for example on or in a vehicle such as a truck 62. The device 631, 632 may be present on all straps 641 to 643, or at least some of them. This ensures a good damping during transport, and forms a means of control, to check if the limit load has been exceeded during transport (the dissipation element is then stretched). 6.4 Second Example of Implementation: Lifting The device of the invention can also be implemented for the lifting of load, as illustrated by FIG. 7. Some materials 71 may indeed need to be lifted with care and can not support not the jolts of a crane 72 or other handling means. In this case, the lifting sling 73 may be equipped with a device 74 according to the invention. It reduces the dynamic effects and provides information on the overflow. 6.5 Third Example of Implementation: Child Car Seat As illustrated schematically in Figure 4, a device of the invention can be used in many locations, and for many applications in a child car seat. If the example of Figure 4 includes multiple applications, it is of course clear that the invention can be used for only one of these applications, or a small number of them as needed. A child car seat generally comprises a harness, having shoulder straps 41 and belt elements 42. These two elements may be equipped with a device 43, directly on one or more elements of the harness. The shoulder straps of the harness are generally equipped with a protective shoulder sheath 44, which can be connected to the backrest or to an element thereof by a strap 45. This can also be equipped with a device 46 according to the invention. 'invention. It is also possible to provide a device according to the invention 49 mounted on the strand 410 circulating inside the seat back, and allowing the tension of the harness. In car seats equipped with clamps 411 for securing to rings provided for this purpose on vehicles, conventionally Isofix® standard, a device 412 according to the invention can be used in connection between the clamp 411 and the seat, to ensure the In this case, the unlocking of the clamp 411 can be ensured by an actuator 413 connected to the strap 412. When visible, the device of the invention can also be used as an indicator. of shock or deterioration: if the dissipation element 11 is elongated and therefore deteriorated (it is not elastic, and therefore does not return to its original shape), this means that the first threshold has been exceeded, and that the seat auto must not be used (or, at least, previously checked). 6.6 Fourth Example: Soft Seat for a Helicopter It is also possible, as illustrated in FIG. 5, to place a dissipation element 51 on a flexible seat 52, between a seat portion forming element 521 and a portion forming part of the backrest 522. Such a seat can for example find an application in a helicopter. 6.7 Other applications Many other applications can of course be considered for the device of the invention, particularly in the field of seat belts (in motor vehicles, aircraft, amusement rides, ...).

Claims (10)

REVENDICATIONS1. Retaining device comprising at least one safety strap, characterized in that it comprises means for dissipating the energy applied in tension on said strap, comprising a woven dissipation element, both ends of which are sewn onto said strap. safety, so that said safety strap defines a loop between the two seams. 2. Retention device according to claim 1, characterized in that the length of said loop is less than the maximum elongation, before rupture, of said woven dissipation element. 3. Restraint device according to any one of claims 1 and 2, characterized in that said woven dissipation element is made from a wire that can extend to at least twice its initial length, from a first predetermined level of effort. 4. Restraint device according to any one of claims 1 to 3, characterized in that said woven dissipation element allows a dissipation of the progressive energy as follows: voltage rise of said woven dissipation element, with an elongation from the latter null or very weak, up to a first predetermined level of effort; progressively extending said woven dissipation element at a substantially constant force level to a second predetermined force level corresponding to the length of said loop; resumption of efforts by said safety strap, said loop being tensioned. 5. Restraint device according to any one of claims 2 to 4, characterized in that said first effort bearing is between 25 kg and 5 tons. 6. Restraint device according to any one of claims 1 to 5, characterized in that said dissipation element is made using a polyester thread. 7. Retaining device according to claim 6, characterized in that said polyester thread is unstretched before weaving. 8. Use of a retainer according to any one of claims 1 to 7 for securing a load. 9. Use of a retainer according to any one of claims 1 to 7 for lifting a load. 10. Use of a retainer according to any one of claims 1 to 7 for a seat.