Fitting element with controlled stiffness

Abstract

The invention refers to a body fitting element with negative pressure controlled stiffness comprised of a gas tight envelope (1), a plurality of layers fitted in the envelope (3) and a valve (2) adapted to evacuate the interior of the envelope, characterized in that the layers comprise a core (4a) made of a material with a high Young's modulus and flexibility and a first cover layer at both sides of the core made of a material with high friction coefficient (4b). Orthoses and protective equipments fabricated with the fitting element can be shaped and fitted to the body in an optimal manner.

Claims

1. A body fitting element with negative pressure controlled stiffness for immobilizing an external body member, extremity or part, the body fitting dement comprising a gas tight envelope, a plurality of layers fitted in the envelope and a valve adapted to evacuate the interior of the envelope, wherein the layers comprise a core made of a textile of polyethylene terephthalate fibers and a first cover layer at both sides of the core made of a polyurethane, and wherein the body fitting element generally conforms to a part of the exterior of a body.

2. The body fitting element according to claim 1 wherein the core made of polyethylene terephthalate fibers is comprised of woven ribbons.

3. The body fitting element according to claim 2 wherein the core made of polyethylene terephthalate fibers is comprised of horizontally and vertically positioned ribbons provided with slits so as to enable interconnection of the ribbons.

4. The body fitting element according to claim 2 wherein the woven ribbons are composed of a flexible high Young's modulus textile of a width of 8 mm or less.

5. The body fitting element according to claim 1 further comprising a thin strap-shaped second covering of a material having a low friction coefficient on one side of the core and in contact with the first cover layer.

6. The body fitting element according to claim 5 wherein the thin strap-shaped second covering comprises sewing lines of thread.

7. The body fitting element according to claim 1 further comprising an air permeable layer in contact with an internal side of the envelope where the valve is placed.

8. An orthopedic device comprising a body fitting element as in any one of the previous claims in a C-shape and further comprising an elastic member connecting sides of said body fitting element so that the orthopedic device has a shape of a loop.

9. An orthopedic device comprising at least a body fitting element as in claim 1 and further comprising a thin ramified metal layer inside said body fitting element and a fixation through it accessible from outside the gas-tight envelope adapted to fix the orthopedic device to a mechanical external part.

10. Orthopedic device comprising a pair of independent body fitting elements as claimed in claim 1 and an empty chamber interposed between said pair of body fitting elements.

11. Method of fitting the orthopedic device of claim 10 comprising the steps of: a. applying the device to an external member, extremity or part of a body to be fitted; b. producing a vacuum in a first element of the pair of body fitting elements which is further away from the body; c. inflating the empty chamber; d. producing a vacuum in a second element of the pair of body fitting elements that is closer to the body; e. removing the vacuum in the first element and pressure in the empty chamber; f. applying a vacuum in the empty chamber; g. applying a vacuum in the first element; and h. immobilizing the external member, extremity or part of the body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate preferred embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be embodied. The drawings comprise the following figures:

(2) FIG. 1 shows a sectional view of a fitting element according to the invention.

(3) FIG. 2 is a perspective view of one of the layers inside the fitting element.

(4) FIG. 3 is a perspective view of the fitting element according to the invention.

(5) FIG. 4 is a top view of a ribbon weaving structure according to another embodiment.

(6) FIG. 5 is a sectional view of the structure for automatic installation according to one embodiment of the invention.

(7) FIG. 6 is a representation of the process of automatic installation.

(8) FIG. 7 is an exploded view of a leg orthosis based on the invention.

(9) FIG. 8 is a partial top view of sewing lines according to another embodiment.

(10) FIG. 9 is a partial perspective view of a thin ramified metal layer with a fixation according another embodiment.

(11) FIG. 10 is a partial top view of sewing lines according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(12) In a first aspect of the invention shown in FIG. 1, the fitting element comprises a laminate of several flexible layers (3) inserted into an hermetic stretchable envelope (1) that is suitable for being subjected to a controlled pressure.

(13) When a vacuum is applied, the layers are compressed together increasing the friction between them, which in turn increases the stiffness of the stratified material. The structure therefore has variable state possibilities, from soft at atmospheric pressure to rigid when depressurized.

(14) The novelty of this design is in the structure and materials of the layers (4), that allow the customization of orthopedic devices capable of conforming to the individual shape of the limb of the patient. The soft state permits to shape the limb and the rigid state permits to lock it to provide support and stabilization.

(15) To that purpose, an important issue is to have a high stiffness ratio between the soft and hard states.

(16) To obtain the desired property of the layer in each mode, the layer (4) comprises, in a preferred embodiment shown in FIG. 2, 3 different materials in series. The layers (4) comprise a core layer of high Young's modulus, flexible, high tensile stress at the rupture and thin first material (4a), for example, Dacron a textile made of polyethylene terephthalate (PET) fibres as the 140 TNF MT from dimension Polyant which has a traction Young's modulus of 2 GPa for a thickness of 200 m, coated on both sides with a first cover layer of thin high friction coefficient material (4b), for example, 10 m of polyurethane (PU). As a second layer, straps of, for example, Teflon (4c) are stuck onto one side of the second material (4b). Other materials and coatings other than Teflon in the form of strips or straps are suitable, provided they have a low friction coefficient.

(17) As shown in FIG. 3, a side of the layer onto which Teflon is applied contacts a side of the next layer having only the second material with high friction coefficient. When a negative pressure is applied, the laminated sheets (4) are compressed together and deformed, so that the high friction coefficient surfaces (4b) of the first layer are in contact with one another and the stiffness is high.

(18) When atmospheric pressure is inside the envelope, the layers are uncompressed and only the low friction straps (4c) are in contact with the nearest layer (4). The low friction material (4c) can be made compressible, helping to separate the layers following the removal of the vacuum and thereby allowing rapid separation of the layers (4) of the laminate (3). As shown in FIG. 8, instead of Teflon, sewing lines of polyester thread or any other suitable thread can be used, which lowers the cost of the orthosis.

(19) To apply an homogenous force during compression of the laminate, an air permeable layer, for example foam (5) is inserted parallel with the laminate (3) into the flexible envelope (1). The foam layer (5) allows the force of the vacuum to be well distributed. As the foam layer (5) changes its thickness during the vacuum process, it is recommended that the air permeable layer, is placed on the side of the laminate (3) that is not to be fitted, thus avoiding an unwanted gap.

(20) To help prevent formation of wrinkles between the layers (4), the compressive foam (5) is installed in contact with the internal side of the envelope (1) and the first layer of the laminate (3). This applies a continuous, low orthogonal force on the layers (4), flattening the layers (4) thereby evading the formation of wrinkles. The valve (2) is inserted into the envelope (1) on the side next to the foam (5). This avoids the blocking of the airflow by a layer of the laminate sticking to the valve orifice.

(21) A core material (4 a) with a high Young's modulus is necessary to make a laminate with a high stiffness state; however these materials have a low extensibility. Because they are not extensible they cannot fit all 3D shapes. In order to fit 3D forms, especially the ones with irregular surfaces, the first material with a high Young modulus is provided in the form of ribbon weavings (6), to add degrees of freedom to the fabric, as shown in FIG. 4. To keep this structure organized after many uses and avoid overlaps and loss of the ribbons (7) and (8), the vertical and horizontal translations of the ribbons are limited. These translations are limited by inserting the horizontal ribbons (8) through slits (10) in the vertical ribbons (7) and vertical ribbons (7) through slits (9) in the horizontal ribbons (8). These slits are a little wider than the ribbons to facilitate insertion and allow rotations. Allowing slight rotations between horizontal and vertical ribbons in the plane of the surface is important to permit the structure to change shape.

(22) Due to the high cost of the manufacturing of stable ribbon weavings made with slits, a standard ribbon weaving can be used if the borders are sewn. Any 2D pattern can be sewn and cut, taking care to ensure that both ends of each ribbon in the pattern have been sewn.

(23) The material used to make the ribbons (7) and (8) is composed of the flexible high modulus textile (4a) and forms the core, it is then covered on both sides by the high friction coating (4b). In this particular embodiment using the ribbon shaped high Young modulus first layer, there is no need for the low friction strip (4c), because the wave forms created by the weaving allow the separation of the layers once an internal pressure is applied without any external help.

(24) Making the weaving smaller, i.e. with smaller ribbon's width, allows a better fitting. For human body fitting, a 5 mm width of the standard ribbon weaving and a 8 mm width for a slips ribbon weaving (6) gives a good result, but any width can be used depending on the purpose.

(25) The modulus of elasticity in bending (E.sub.) of the fitting element was experimentally obtained by a three point flexural test. A sample used in an experiment was 50 mm in width and 3.5 mm thickness, and was composed of 8 layers of Dacron 140 TNF MT from Dimension Polyant and coated by a 10 m PVC glass in both sides. An experiment was executed with a support span of 500 mm. The results show: i) the sample under atmospheric pressure is not capable of supporting its own weight, ii) the sample depressurised at 70% of vacuum support its own weight with 11.75 mm deflection and, iii) the sample under the same condition to ii) has a deflection of 60.25 mm when 210 gr are loaded.
This laminated sample has an equivalent flexural modulus of an isotropic material of 600 MPa.

(26) The main advantage of the invention is that the fitting element uses no granules or particles, but only textile layers. This allows a thickness of the device employing the fitting element to decrease in comparison with that using granules or particles. The wide contact area between the layers under negative pressure enables the stiffness of fitting element to increase.

(27) One challenge is ensuring the orthosis is in close contact with the body at the time of fitting, before the vacuum is applied. A second aspect of the invention provides a method of fitting the orthoses to the body automatically. The structure to be used requires 2 independent chambers (24, 26) with laminate (3) inside separated by an empty chamber (25) as shown in FIG. 6.

(28) The following table describes a possible sequence of steps to automatically position a structure to fit a body part.

(29) TABLE-US-00001 Chamber Phase Pressure Number Description A B C 1 The structure is soft, position it by hand around 0 0 0 the body part to be fitted 2 Apply a vacuum in the external chamber 1 0 0 (chamber far from the body) to create an external rigid compartment 3 Inflate the intermediate empty chamber adjacent 1 1 0 to the rigid compartment to compress the internal chamber (the closest one to the body)on the body 4 Apply a vacuum in the internal chamber to 1 1 1 rigidify it, thereby creating an internal rigid compartment 5 Remove vacuum and allow return of atmospheric 0 0 1 pressure in the external rigid comportment and intermediate chamber to make the external compartment soft 6 Apply a vacuum in the intermediate chamber 0 1 1 to press the external soft compartment to the internal rigid compartment 7 Apply a vacuum in the external compartment to 1 1 1 rigidify it

(30) The shape of, for example, a leg changes during the day. Furthermore, the shape of a leg fluctuates in function of muscle activation. The automatic installation of the structure coupled to a real time control permits the orthosis device to fit constantly to the fluctuating shape of the limb.

(31) The present invention can be configured to make functional orthoses, especially knee, neck or elbow orthoses. In a particular embodiment shown in FIG. 10, a collar (50) for the neck is provided. The high modulus material presents a low extensibility and thus, a loop made with this material cannot change its size. This problem is solved by adding, for example by sewing or gluing a stretchable or elastic part (43) into a loop formed by each layer (4). To not weaken the final structure in the elastic part (43), the elastic part (43) of each loop's layer (4) can be installed in a different position to homogeneously distribute the loss of strength in all the structure.

(32) FIG. 7 shows how to combine the stratified structure of the invention with mechanical connection components to provide support in the knee joint motion. A universal knee brace orthosis (14) based on the invention is constructed with a stretchable external envelope (15) made in neoprene rubber and/or nylon. The device can be produced in different generic sizes, i.e. small, medium, large. The orthosis is closed with a self-gripping fastener like Velcro and secured in place by adjustable straps (17). In order to increase the comfort of the othosis, the knee cap (21) and popliteal region (22) remain uncovered.

(33) Two variable stratified stiffness parts (3) are inserted into the external envelope (15), one in the upper leg part (18) and another one in the lower leg part (19). One of the largest problems with knee orthoses is the tendency for the orthosis to slide down the leg, resulting in a loss of function. With this design however, the orthosis is tailored to the individual the result being an excellent and close fit to the patient's leg. This is of particular importance around the area under the knee which has a smaller diameter than the calf and can thus serve to prevent sliding of the orthosis.

(34) In this design the laminate of textile's layers (3) of the variable stratified stiffness is composed of for example 4 layers of the standard ribbon weaving (6). The valves of the hermetic envelopes are connected to control the pressure at only one point. In order to allow hard fixation of polycentric hinges (20) or other type of protective knee joints, two fixations in the variable stiffness structure are inserted. As shown in FIG. 9, this fixation (40) has a part accessible outside the hermetic envelope, which passes through a valve, and fixes the polycentric hinges and an internal part inserted between the textile's layers (3). In order to allow the fixation (40) to fit several 3D shapes without losing its strength capacity, a thin sheet of metal with a ramified form (41) e.g. a star or flake, is used, whose ramifications are inserted through the slits of the vertical or horizontal ribbons (7, 8). These forms distribute the force over a bigger surface area there by allowing the fitting of 3D shapes. To increase rigidity the thin metal is coated with a high friction material, in the drawing a 1 mm aluminium sheet with several ramifications of 10 mm width and a coating of PU glue has been used.

(35) Some additional advantages of this fixation are that the ramifications make the final structure more rigid and also the fixation part does not have to be detachable.

(36) In order to keep in place this fixation between the layers of the laminated structure, one group of ramifications is inserted through slits of one layer, facilitating the insertion of the layers on the flexible envelope without limiting its own flexibility.

(37) The orthosis shall be used as followed. The patient should first wrap the orthosis around the leg when the structure is in its soft state. The orthosis should be closed with a self gripping fastener, followed by closure of the adjustable straps (17), ensuring that the polycentric joint (20) of the orthosis is well positioned by moving his/her articulation: The structure is then made rigid by applying a vacuum inside the envelopes, using a manual self-powered electrical vacuum pump or any other vacuum source. The valve is closed and the pump pulled out. A final re-adjustment to the Velcro and straps, and the orthosis is ready to use.

(38) In addition to knee orthosis application described above, the present invention provides many additional applications. One of them may be incorporation into orthotic devices such as ankle foot orthosis (AFO) and insoles, or shoes. AFO is an orthosis to prevent footdrop problem caused by weakness that occurs in specific muscles of the ankle and the foot. Generally AFOs are made with plastics to support ankle instability. As the fitting element with controlled stiffness is capable of be tailored in various shapes, it enables the AFO to be completely soft and partially hard around ankle when rigidified. As such the fitting element may be employed as sock or shoe liner in shoe as well as in skating and skiing boots in order to provide well-fitting.

(39) Protective equipment in sports, for example, knee and chest guards, helmets, wrist protections and so on, is also a potential area to which the fitting element is applicable. In these equipments, the fitting element around a body part to be protected can provide shock absorbency from external impact.

(40) In this text, the term comprises and its derivations (such as comprising, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

(41) On the other hand, the invention is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.