FR2861846A1 - Pressure measuring system e.g. for sporting boots comprises layer of urethane gel with pressure sensors embedded in it - Google Patents

Abstract

The system (1), designed to be fitted between two bodies e.g. ski boot and a person's foot, to produce signals representing the pressure exercised by one on the other, consists of a layer of urethane gel (7) with pressure sensors (4) embedded in it. The pressure sensors are resistive and flat in shape and positioned to detect pressure in a direction perpendicular to the gel layer's outer surface. The system (1), designed to be fitted between two bodies such as a ski boot and a person's foot to produce signals representing the pressure exercised by one on the other, consists of a layer of urethane gel (7) with pressure sensors (4) embedded in it. The gel layer is 2-10 mm thick and has hardness of 35-40 Shore A. The pressure sensors are resistive and flat in shape and positioned to detect pressure in a direction perpendicular to the gel layer's outer surface.

Description

1 2861846

  PRESSURE MEASURING DEVICE FOR INTERACTION BETWEEN TWO BODIES

  TECHNICAL FIELD The invention relates to the field of measuring devices, and more particularly to pressure measuring devices used in the field of biomechanics. It finds a particular application (but not exclusive) for the realization of a sleeve or sock used in the analysis of the pressures and stresses exerted on different areas of the foot during the practice of skiing. In the remainder of the description, the invention will be more particularly detailed in connection with sliding sports, and in particular alpine skiing, but it may be applied to other sectors generally related to biomechanical measurements.

  PRIOR ART To practice a sport of gliding, it is generally necessary to put on a rigid shoe allowing to temporarily secure a gliding device, which can be either a board for skiing, skiing or surfing, or even a roller skate or ice skate .

  Because of the contact of the foot with this rigid shoe, the foot undergoes pressures that can be significant, both static and dynamic. Indeed, the good behavior of the foot inside the shoe requires a relatively large tightening that can result in high pressure exerted on the foot. These pressures are variable from one user to another, depending on the morphology of his foot, as well as from one shoe to another depending on the configuration of its inner surface.

  Similarly, the pressures exerted on the skin of the foot dynamically vary, depending on the support exerted by the user during the various phases of driving and turning. These pressures are eminently variable depending on the type of practice, but also properties including stiffness of the ski, or more generally the board or gear 2861846 2 slides. These pressures are also a function of the geometry of the shoe, and in particular of the position of hinge zones between the collar and the hull for example, but also of the location of the clamping points. They also depend on the materials used for the manufacture of the shoe, including their flexibility.

  Thus, when designing a shoe, we must take into account the mapping of the pressures exerted to define the shapes and stiffness of the various parts constituting the hull and the boot of the shoe.

  Similarly, the information about this pressure distribution may allow the user to choose the shoe model that is most appropriate for the morphology of his foot and his practice. Indeed, it should be known that significant pressure can be the source of injuries, especially in areas where the skin is directly in contact with the bones. We also know the problem of the sensitivity of the foot caused by too much pressure on the instep, especially in line with the pedal vein.

  We therefore feel the need to be able to measure the pressure exerted on the foot by the shoe. The solution consisting in implanting sensors directly on the skin, although theoretically the most satisfactory, is not really possible, since it requires delicate, long, and difficult to reproduce.

  Devices have already been proposed to measure the pressures exerted on the foot inside a shoe. Devices of this type are described in documents US 6,216,545 and US 6,155,120. However, these devices are essentially intended to measure stresses resulting from shear phenomena. To do this, these devices comprise several superimposed layers between which are integrated piezoelectric type sensors. This construction therefore gives these devices a large thickness, which in fact modifies the interface between the foot and the shoe, and therefore the measured pressures. Moreover, this type of device does not make it possible to measure the pressures exerted perpendicularly to the surface of the skin, whereas these are the most important pressures to be measured in the context of ski boots.

  Moreover, by their constitution, these devices are essentially planar, and can therefore be used effectively at the level of the plantar surface of the foot, and in any case do not allow to form a device for generating a complete mapping of pressures exercised on the foot.

  Finally, the materials used in this type of device are essentially based on silicone. However, these materials have a relatively low remanence, meaning that they resume their shape only after a relatively long time when the mechanical stress has ceased. Such a disadvantage is a brake on the use of this material to produce measuring devices having good repeatability.

  The objective of the invention is therefore to enable pressure measurements to be made with the thinnest possible device, having a particularly small thickness so as not to interfere with the pressure measurements exerted between the two bodies between which it is interposed. Another objective is to allow measurements in the immediate vicinity of the skin, to determine as much as possible the pressures felt by the user. Another object of the invention is to provide a device having characteristics very similar to those of the organ on which the pressures to be measured are exerted, and for example the muscles or the skin.

  SUMMARY OF THE INVENTION The invention thus relates to a pressure measuring device which is intended to be interposed between two bodies to produce signals representative of the pressure exerted from one body to the other, and which includes a plurality pressure sensors.

  According to the invention, this device is characterized in that it comprises a layer of urethane gel conforming to the shape of one of the two bodies, and within which are embedded the pressure sensors. By urethane gel is meant the product of the chemical reaction between isocyanates (RN = C = O) and polyols (R'-OH) in which a proportion of the alcohol (-OH) groups of the polyols do not reacted with the corresponding functions of the isocyanates. This incomplete reaction may be due to non-stoichiometric proportions of the reaction components, or to the presence of plasticizer-type compounds, which by steric hindrance prevent the reaction from being complete. A urethane gel is therefore a casting urethane based on long carbon chain polyols and optionally comprising a plasticizer.

  In other words, the invention lies firstly in the choice of a material in which the sensors are integrated and secondly in the choice of location of the sensors on the device. The chosen material has many advantages over the material employed for purposes similar to today, and in particular silicones. Indeed, this material makes it possible to maintain the pressure sensors as close as possible to the skin, while being slightly extensible to adapt to different foot morphologies. The urethane gel also has mechanical properties of incompressibility which ensures a good distribution of the forces exerted without generating surface tensions likely to generate constraints on the pressure sensors, and thus cause errors in the measurement of pressures.

  Moreover, the urethane gel has mechanical properties in terms of remanence which are relatively close to those of the muscles, so that the measuring sleeve forms, so to speak, an excess thickness of the skin with similar mechanical properties. In other words, the sleeve forms a layer which covers the skin, and which behaves like the latter, with similar mechanical reactions, in terms of elasticity, persistence, resilience etc .... Thus, the measured pressures are in a way very similar to those measured directly in contact with the skin.

  Advantageously, the urethane gels can be rendered hypoallergenic, which enables them to make sleeves that can be directly in contact with the skin, and thus make it possible to develop signals that are very representative of the pressures exerted on the cutaneous surface. However, in practice, it may be provided to coat one and / or the other of the faces of the gel layer with a textile layer, in particular to protect the gel layer from impacts or scratches. In practice, it will be preferable to maintain a direct contact of the skin with the inner face of the sleeve. The textile layer, for example based on Lycra will then be located on the outer face of the sleeve, possibly being embedded in the surface.

  In practice, the urethane gel layer may have a thickness of between 2 and 10 millimeters. This value is to be compared with that of the thickness of a sock, so that for measurement operations, such a device can replace a sock without forming extra thickness inside the shoe.

  In practice, it will be preferred that the urethane gel layer has a low hardness, typically between 20 and 60 Shore A, and preferably between 35 and 40 Shore A. In practice, the device can adopt various very varied forms, and in particular it can be shaped as a sleeve, so as to cover one of the two bodies. It can also be relatively flat, always being shaped to the body on which it is intended to be installed.

  In the case of pressure measurements on the foot, this sleeve may have a sock shape, covering the foot and possibly the lower part of the leg. The invention may also be used to measure head pressures on a helmet, and the device then conforms to a cap shape. Among the other applications of the invention, there may be mentioned shin guards or more generally protection articles of the lower or upper limbs. In this case, the sleeve is a gutter shape adapted to the member to protect.

  Multiple sensors may be employed, and in particular resistive-type pressure sensors, that is to say forming an electrical resistance whose ohmic value varies as a function of the pressure undergone. However, other types of sensors including capacitive or piezoelectric sensors can be used.

  However, the sensors will preferably be substantially flat, so as not to form extra thickness within the device. Their pressure sensing direction is substantially perpendicular to the outer surface of the urethane gel layer in the area where they are implanted.

Brief description of the figures

  The manner of carrying out the invention as well as the advantages which result therefrom will emerge from the description of the embodiment which follows, given by way of non-limiting example, with reference to the appended figures in which: FIG. brief perspective view of a sleeve forming a sock made according to the invention.

  Figure 2 is a sectional view in thickness of a zone of the sleeve of Figure 1 comprising sensors.

  Figures 3 to 7 are respectively views from above, from behind, from below, the outer side face and the inner side face of the sleeve of Figure 1.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS As already mentioned, the invention relates to a measuring device used in the field of biomechanics, which finds application in the field of sliding sports without being however limited to this sector alone.

  The device illustrated in Figure 1 is a sleeve in the form of a sock, intended to cover the foot of a user, before being inserted into a ski boot. Preferably, this sleeve (1) has its inner face (2) which is intended to come into direct contact with the skin of the user, possibly with the interposition of a sock, preferably the finest possible.

  The outer face (3) of the sleeve (1) receives the contact of the soft boot of the ski boot. This sleeve (1) is equipped with a plurality of pressure sensors (4) distributed in different zones (5) located at different locations of the sleeve. Each of these sensors (4) is capable of generating a signal of an electrical nature.

  All of these sensors therefore comprises electrical connection means 15 with a not shown analysis device, via a connector schematically illustrated at the rear of the sleeve.

  As illustrated in Figure 2, each of these sensors (4) has a relatively reduced thickness, which allows it to integrate into the thickness (e) 20 of the sleeve (1).

  According to the features of the invention, the material used to form the sleeve is a urethane gel. This urethane gel is conventionally obtained by a chemical reaction using isocyanates (R -N = C = O) and polyols (R'-OH). The choice of the carbon chains (R ') of the polyols makes it possible to optimize the desired mechanical properties and in particular the strength and the hardness of the gel obtained.

  In a simplified manner, it can be considered that the use of relatively long carbon chains (R ') makes it possible to obtain relatively flexible components, because of the distances between the bonds generated during the reaction between the polyols and the isocyanates. The difference in the proportions of the two reagents with respect to the stoichiometric proportion also makes it possible to limit the number of bonds created, and to give a character of flexibility to the gel obtained. Likewise, the use of softening additives during the reaction, and typically plasticizers, makes it possible to give good elasticity to the gel obtained.

  The operating conditions also make it possible to keep within the materials gas bubbles resulting from the characteristic reaction, thus reducing the liner, in particular with respect to silicone-based materials. This structure also makes it possible to maintain a certain flexibility, at relatively low temperatures, in comparison with those that can be envisaged for silicone, which is preponderant for carrying out shoe tests on the ski.

  Good results have been obtained using a urethane gel marketed under the trade mark ISOPROT by the company Research Electronic Control located in Bédarieux (France). Such a gel has a hardness of about 38 Shore A.

  In practice, the sensors (4) used may be of the resistive type. In particular, it will be possible to use the sensors of the LuSense range marketed by IEE International Electronics and Engineering (Luxembourg).

  In practice, it has been determined that the sensors must have a diameter dimension of not more than 10 to 15 millimeters, to avoid that they undergo a too great curvature when they are set up in areas with strong curvature, and by example in the malleolus.

  As illustrated in FIGS. 3 to 7, the various sensors may be implanted in various zones, depending on the parameters to be studied, so as to obtain a map of the pressures exerted on the whole of the foot. The following list gives for each of these zones, the bone area (s) concerned, as well as the possible muscles situated in the deep plane and / or tendons situated on the mid-plane present in line with this zone, under the upper layer of the epidermis.

  Medial malleolus area (101) (see fig.7): Bone area concerned: Bone protuberance of medial malleolus head Muscle concerned: Flexor insertion Retinaculum Sustentaculum Tali housing area (102) (see fig. 7): Bone area concerned: Medial border of the Calcaneus Muscle concerned: Passage of the Flexor Retinaculum Tendon concerned. Abductor Hallucis Zone of the dorsal crest of the foot (103) (cf fig.3): Bone area concerned: Navicular Bone Muscles involved: Passage of the Anterior Tibial and the Hallux Extender Longus Tendon concerned: Lower Retinaculum of the extensors Zone of the arch (104) (cf fig.7): Muscle concerned: Muscle of the abductor Hallux Tendon concerned: Tendon of the posterior tibial muscle.

  Dorsal zone of the 2nd, 3rd, 4th 5th metatarsal phalanges (105) (cf fig.3): Tendons concerned: Tendons of the short extensor muscle of the toes Zone of the bone tuberosity of the lateral lateral edge of the 1st metatarsal (106) (cf fig 7): Bone area concerned: mediolateral border of ter metatarsal Muscle concerned: Abductor of the hallux Tendon concerned: Metatarsophalangeal ligament Zone of the anterior aspect of the leg (107) (cf fig.3): Bone area concerned: Bone edge tibial Muscles involved: Long stent length, long hallux stent, anterior tibial muscle 2861846 IO External ankle surface area (108) (cf fig.6): Muscles involved: Long Peroneal Muscles, short Peroneal Muscle , Tendon concerned: lower retinaculum of the extensors Zone of the lateral malleolus (109) (cf fig.6): Bone area concerned: bony protuberance of the head of the lateral malleolus Tendon concerned: retinaculum of the fibular muscles Lateral malleolar lateral gullet zone (110) (cf fig.6): Bone area concerned: lateral border of the calcaneus Tendon concerned: Retinaculum of the fibular muscles Posterior area of the ankle (111) (cf fig.4): Tendon concerned : calcaneal tendon Zone of the lower leg (112) (cf fig.4): Muscle concerned: Gastrocnemius muscle Plantar area (113) (see fig.5): Bone area concerned: Os calcaneus Muscle concerned: Bursa Zone of the styloid of the 5th metatarsal (114) (cf fig.5): Bone area concerned: Bone head of the metatarsal Seme Tendon concerned: Tendon of the fibular short muscle Lower support zone of the metatarsal pallet (115) (cf fig.5) : Bone area concerned: Metatarsal phalanges Tendons involved: Tendons of the long and short flexor muscles of the toes Supporting area of the distal phalanges M2, M3, M4, M5 (116) (see fig.5): Bone area concerned: distal phalanges of the 2nd, 3rd 4th and 5th metat Tendons concerned: Tendons of the long and short flexor muscles of the toes Zone head of the 5 metatarsal (117) (cf fig.6): Bone area concerned: lateral border of the 5th metatarsal Tendon involved: Tendon of the abductor muscle of the small toe Zone of the lateral lateral border of the leg (118) (cf fig.6): Muscles concerned: Soleus muscle, peroneal long muscle, short peroneal muscle Zone of the lateral internal border of the leg (119) (cf fig.7): Bone area concerned: body of the tibial bone Muscles concerned: Soleus muscle, common flexor digitorum of the toes It follows from the foregoing that the device according to the invention makes it possible to ensure a pressure measurement which has a high reliability. Indeed, the same device can be used with feet of slightly different size because of its elasticity.

  The small thickness of such a sleeve provides pressure measurements representative of those actually experienced by the foot. 25

Claims (1)

12 CLAIMS   1 / Pressure measuring device (1) intended to be interposed between two bodies to produce signals representative of the pressure exerted from one body to the other, including a plurality of pressure sensors (4), characterized in that it comprises a layer (7) of urethane gel conforming to the shape of one of the bodies, and in which these pressure sensors are embedded.   2 / Apparatus according to claim 1, characterized in that the gel layer. urethane (7) has a thickness (e) of between 2 and 10 millimeters.   3 / Apparatus according to claim 1, characterized in that the urethane gel layer has a hardness of between 20 and 60 Shore A, and preferably between 35 and 40 Shore A. 4 / Apparatus according to claim 1, characterized in that that it marries a form of sleeve adapted to cover one of the two bodies.   5 / Apparatus according to claim 1, characterized in that the sleeve has a sock-like shape, suitable for covering a foot and / or the lower part of the leg.   6 / Apparatus according to claim 4, characterized in that the sleeve has a cap-shaped, adapted to cover a portion of the head.   7 / Apparatus according to claim 4, characterized in that the sleeve has a gutter shape, adapted to cover a portion of an upper or lower member.   8 / Apparatus according to claim 1, characterized in that the pressure sensors (4) are of the resistive type.   9 / Apparatus according to claim 1, characterized in that the sensors (4) are substantially flat, and have a pressure sensing direction substantially perpendicular to the outer surface of the. layer of urethane gel in the area where they are implanted.   10 / Apparatus according to claim 1, characterized in that it comprises a textile layer present on at least one of its faces facing one or the other body.   11 / Apparatus according to claim 5, characterized in that it comprises pressure sensors arranged at least in a zone coming to the regions of the lower limb following: - area of the medial malleolus (101), - housing area of the Sustentaculum Tali (102), - area of the dorsal crest of the foot (103) - area of the arch (104) - dorsal area of the 2nd 3rd, 4th, 5th metatarsal phalanges (105) - area of the bone tuberosity edge Lateral portion of the metatarsal (106) area of the anterior aspect of the leg (107) - area of the external lateral surface of the ankle (108) - area of the lateral malleolus (109) - zone of the lateral retro-malleolar gullet ( 110) - posterior ankle area (111) lower leg area (112) - pad area (113) - 5th metatarsal styloid area (114) lower metatarsal pad area (115) - zone of support of the distal phalanges M2, M3, M4, M5 (11 6) - area of the head of the 5th metatarsal (117) - zone of the lateral external edge of the leg (118) - area of the lateral lateral edge of the leg (119)