Covering for a prosthetic foot, method and device for manufacturing such a covering

Abstract

The invention relates to a shell (1) for a prosthetic foot of a user, arranged to cooperate with a so-called dynamic-return leaf spring prosthesis, and to a method and to a device for manufacturing a shell of this kind. The shell (1) comprises a sole part (2) made of a flexible elastomer or plastics material and an upper part (3) obtained by injection moulding of expanded EVA (expanded IMEVA) delimiting an inner volume suitable for receiving and entirely covering the body of the blade, said upper part being provided with a through-slot for the frictional passage of the connection end part.

Description

Prosthesis foot covering, method and device for manufacturing such a covering

[0001] The present invention relates to a covering or envelope for a foot prosthesis.

[0002] It also relates to a process and a device for manufacturing such a covering.

[0003] It finds a particularly important, although not exclusive, application in the field of prosthetic feet with dynamic return intended for the active population of amputee patients, and for example and without limitation using so-called class 3 prostheses corresponding to the K3 mobility level, the standard used by the American CMS (Anglo-Saxon initials of Centers for Medicare & Medical Services).

[0004] A prosthetic foot is a medical device designed to replace the missing foot, aiming to restore the function of the natural foot. It allows the amputee to regain mobility and an improved quality of life.

[0005] In the case of prostheses with dynamic return, blades made of composite materials, carbon fibers, metal, or plastic are primarily used today. Manufacturers such as OSSUR (Iceland), PROTEOR (France), and OTTO BOCK (Germany) offer products with a composite material blade that provides a spring-like effect.

[0006] All these prostheses are designed to fit into hollow, shoe-shaped foot shells, open at the top, easily removable to allow cleaning and / or replacement, thus also allowing modification of the external appearance of the shell used (shape, bulk and aesthetics).

[0007] While such prosthetic feet, including a covering that is put on the prosthesis, present excellent results allowing to maximize performance in the specific activity (walking, running, jumping ...) for which they are intended, taking into account the user's needs in terms of comfort and performance, they do not have a waterproof covering, particularly when the user walks in water or sand.

[0008] There are also prosthetic feet known as "SACH" (short for Solid Ankle Cushion Heel). These are simple prostheses, easy to maintain, not really affected by use in water or sand, but very rigid.

[0009] Although they are less expensive than articulated prostheses, unlike K3 type dynamic return prostheses, they do not allow walking at variable speeds on different terrains and / or do not offer the ability to walk at high levels of performance and comfort, including during sporting activities.

[0010] We also know of a complicated sealed prosthetic foot (WO 2023 / 237994), requiring for example a vent tube with a valve which can cause leaks.

[0011] The documents (FR 2 640 499, WO2023031637, EP2040649) describe prosthetic feet or prosthetic foot shells that are not watertight and cannot be made watertight.

[0012] The present invention aims to provide a foot prosthesis shell, a method and a device for manufacturing such a shell which better meets the requirements of practice than those previously known, in particular in that the prosthesis foot obtained with such a shell is closed on the top, watertight and sandproof, in that said shell has a high degree of flexibility, for example greater than 20 shore, for example between 25 and 45 shore, in that it will allow versatile use, in particular allowing walking on all terrains even rough, swimming or walking on a beach, without risk of damaging the blade which it covers, and in that it requires little or no maintenance.

[0013] Another objective of the invention is to overcome the disadvantages of the prior art and to improve the walking comfort of the user of the prosthetic foot with this type of cover.

[0014] Another objective of the invention is to provide a cover that has good abrasion resistance and / or is anti-slip.

[0015] Another objective is to offer an envelope with high tear resistance and good stability over time.

[0016] Another objective of the invention is to propose a manufacturing process for the covering of a foot prosthesis by means of injection molding that is more efficient and controlled than those of the prior art, with a limited rejection rate for an optimized manufacturing cost and number of molds used.

[0017] Another objective of the invention is to provide a molding device for such an envelope, using in particular the optimized process of the invention.

[0018] The invention is based on the idea of ​​obtaining a closed prosthetic foot cover in the shape of a blade with determined characteristics, from at least two cover parts, including an upper part obtained by injection molding of expanded EVA (Ethylene-Vinyl Acetate) (expanded IMEVA) (Anglo-Saxon initials for "Injected Moulded Ethylene Vinyl Acetate") and a lower part or sole part.

[0019] IMEVA refers to EVA material injected into a mold (for example at a temperature between 170 and 200°C) to take a specific shape.

[0020] Expanded EVA is EVA that has been blown or expanded, giving it a lighter, foamy (alveolar) and cushioning structure. Expanded IMEVA is therefore an EVA foam obtained through an injection molding process with expansion. More precisely, it has a foam structure composed of billions of extremely fine, closed cells that are impermeable to fluids and trap air completely. Expanded IMEVA is classified according to its relative density, which is the ratio between the density of the raw material and the density of the expanded material. In this case, expanded IMEVA has a relative density, for example, between 0.4 and 0.7 with closed cells (alveoli). The expansion is achieved in a well-known way, by adding a pore-forming agent, for example, a physical agent such as an inert gas (nitrogen, etc.), which allows for the homogeneous creation of cellular microstructures within the material.

[0021] Advantageously, in addition to the porogen (which therefore has swelling or foaming properties), additives promoting nucleation, such as very fine mineral particles, are introduced. It is observed that, under compression, the Young's modulus of expanded IMEVA is, for example, approximately 40% of the Young's modulus of the solid polymer.

[0022] In an advantageous embodiment, the sole part is made of a more resistant material than IMEVA, for example CMEVA (Compressed Moulded EVA). While the volume of IMEVA is, for example, in a 1:2 ratio with raw EVA, that of CMEVA is practically 1:1 (+ / -5%).

[0023] Raw EVA is known to be a material used in the manufacture of glue, stretch films, and flexible gloves. While it offers good qualities in terms of flexibility and handling, its expanded foam version is unsuitable and difficult to use in injection molding because it expands immediately and is difficult to control during demolding.

[0024] The blade, for its part, is a profiled and curved blade to imitate the natural movements of the foot and ankle. It has a body, for example, roughly L-shaped, with a central section of the underside of the foot connected on one side to a heel section and on the other side to a section of the top of the foot, including a spring-like part extending above and progressively away from the central section and being extended by an end part directed upwards, for example vertical, connecting to a fitting worn by a user's leg.

[0025] To this end the invention proposes in particular a foot prosthesis shell for a user arranged to cooperate with a spring blade prosthesis said to have dynamic return, said blade having a body extended on one side by an end part directed upwards for connection with the leg of said user, characterized in that the shell comprises a sole part made of elastomer or soft plastic material and an upper part obtained by injection molding of expanded EVA (expanded IMVEA) delimiting an internal volume suitable for receiving and completely covering the body of the blade, said upper part being provided with a friction-passage slot for the exit of the connecting end part.

[0026] By flexible we mean for example a shore hardness between 20 and 50 shore A.

[0027] Advantageously, the upper portion forms a foot of a predetermined, variable thickness. More precisely, this upper portion has, for example, a specific thickness, varying according to its position relative to the top of the prosthesis, exceeding several millimeters, for example, 5 mm, 7 mm, 9 mm, and / or at least 1 cm and / or 2 cm, at least in certain areas, and exhibits an external shape resembling a human foot or essentially a human foot. It includes an inner face designed to cooperate in contact with the upper surface of the portion of the foot blade prior to bonding.

[0028] Advantageously, the sole portion has a flattened, flat, or substantially flat shape. For example, it may have the shape of a flattened disc whose outline corresponds to the underside of a foot, for instance, with a regular or irregular thickness between 3 mm and 1 cm. Advantageously, it includes an upper recess designed to receive the lower part of the foot blade, which rests or is at least partially embedded in said recess.

[0029] In advantageous embodiments, one or both of the following arrangements are also made: the peripheral part of the sole is designed to fit together and be bonded to the peripheral part of the upper; the sole is obtained by compression molding of EVA (CMVEA); the peripheral parts of the sole and the upper comprise, respectively, a projecting edge and a corresponding recess, arranged to cooperate with play and adapt to each other before bonding. For example, the projecting edge is on the sole and the recess on the upper. This allows for excellent adaptive interlocking, facilitating the absorption of variations during the injection / expansion of the EVA. The projecting edge and the recess may, for example, have a complementary beveled shape.Such a fit with play allows for excellent fastening of the two parts together while providing an aesthetically pleasing exterior appearance, the joint between the two becoming barely noticeable or visible once the parts are bonded. Furthermore, an even stronger bond can be achieved thanks to the guarantee that such arrangements provide, allowing the parts to be applied to each other over the largest possible contact surface. Alternatively, the protruding edge forms a rounded peripheral lip creating a bead, and the recess forms a rounded groove with which it rubs before bonding, providing similar results. The upper part formed by the expanded IMVEA includes on its internal surface one or more blind recesses or a plurality of blind holes, for example 5, 8, 10, or advantageously 15 or more, and / or 20 holes, for example, from 0.5 to 2 cm in diameter, for example, between 0.8 cm and 1.2 cm.

[0030] For example, they are regularly or substantially regularly arranged in the thickness of the inner part, and are of a variable depth and height depending on the progressive thickness of said upper part of the casing, being less than said thickness (for example, less than 2 mm to 1 cm, for example 5 mm, allowing internal expansion of the expanded IMVEA at the time of demolding; the upper part includes a smooth or substantially smooth upper surface forming the top of the covering in the shape of the instep without protrusion (for example, which would be due to the overhang of the toe in length), the vertical projection of said upper surface thus fitting into the surface of the sole part; the upper part includes a heel part provided externally on either side with a plurality of undulations (for example, two, three or four) forming pre-shock-absorbing folds in case of heel compression;This also makes it easier to accept / normalize the presence of the junction line at the level of the bonding between the upper part and the sole part, which thus tends to blend visually into the mass; the internal faces (to the envelope) of the sole part and the upper part of the envelope are arranged to be fixed by bonding to the opposite prosthesis sections;The cover also includes a cushioning wedge or plug made of EVA or other cushioning material, sized and arranged to be placed between the upper face of the middle section of the underside of the blade and the lower face of the upper section of the foot (extending above and at a distance from said middle section of the underside). This wedge is made of a flexible material, meaning that it deforms reversibly. This cushioning capacity can, for example, be characterized (NF-R 81-009 standard) by an elastic modulus between 68.6 MPa and 686 MPa. The underside of the sole is equipped with anti-slip features (for example, formed by a plurality of grooves or studs) or is made of an anti-slip material.

[0031] The present invention also relates to a combination of a prosthetic blade and a shell as described above, the sole part and upper part being glued to said prosthesis and glued together one on top of the other.

[0032] The present invention also relates to a method for manufacturing an envelope as described above.

[0033] It also relates to a method for manufacturing a two-part shell, a prosthetic foot for a user in the form of a spring blade known as a dynamic return blade, said blade having a body extended on one side by an upward-directed end part, for example vertical, of a determined shape for connection with the leg of said user, in which a first shell part or sole part is manufactured from a resin or an elastomer which is compressed in a mold into a flat block giving it the shape of a determined sole, and a second shell part or upper part is manufactured in parallel by injecting a liquid ethylene vinyl acetate resin under pressure expanded (expanded IMVEA) into a mold comprising an upper component containing the negative shape of the upper part,and a lower organ having one or more protrusions or a plurality of studs, for example cylindrical, distributed (for example regularly) over its surface, as well as a vertical passage block of a shape complementary to the shape of the upward-facing end portion of a blade of determined shape for connection with the leg of said user and containing the positive shape of the upper part to create the final shape of said upper part in expanded IMVEA, the protrusion(s) or stud(s) being arranged to create a blind hole or a plurality of blind holes in the upper part allowing internal expansion of the expanded IMVEA at the time of its demolding.

[0034] With the process according to the invention it is therefore possible to obtain a regular envelope shape on an industrial basis and with virtually no waste.

[0035] Advantageously, the sole part is made of EVA (CMVEA).

[0036] Also advantageously, CMVEA is obtained by mixing an ethylene vinyl acetate resin with a foaming agent in a proportion determined, for example, to obtain a high-density EVA foam greater than 0.8, before compression to obtain said CMEVA without expansion (one for one).

[0037] The present invention also proposes a device for manufacturing a two-part prosthetic foot shell comprising a first mold for manufacturing a first shell part or sole part in EVA by compressing the resulting mixture into a flat block, said mold being arranged to give it the shape of a sole determined in CMVEA, and a second mold for manufacturing a second shell part or upper part by injecting a liquid ethylene vinyl acetate resin under pressure, said mold comprising an upper part containing the negative shape of the upper part, and a lower part having one or more protrusions or a plurality of protrusions, for example cylindrical ones, distributed over its surface,a vertical passage block of complementary shape to the shape of the vertical end part of determined shape connecting with the leg of said user and containing the positive shape of the upper part to create the final shape of said upper part in IMVEA, said lower organ, the protrusions or studs being arranged to create one or a plurality of blind holes in the upper part allowing internal expansion of the expanded IMVEA at the time of its demolding.

[0038] In an advantageous embodiment, the sole part is obtained by mixing an ethylene vinyl acetate resin with a foaming agent in a determined proportion before compression.

[0039] Advantageously the number of protrusions or studs is between 10 and 30, for example 25 studs, of decreasing height in relation to the heel, to take into account the variable thickness of the upper part of the envelope;

[0040] Also advantageously the vertical end part of determined shape connecting with the leg of said user is substantially parallelepiped.

[0041] In an advantageous embodiment, the lower part of the second mold comprises in its peripheral portion a first projecting edge or a first peripheral recess, and the upper part comprises a second recess or a bearing surface arranged to be positioned opposite said first projecting edge or first recess when said lower and upper parts are assembled.the said second mold being adapted to form a first peripheral groove or peripheral rib in the peripheral part of the lower face of the upper part of the casing and in that the first mold is arranged to create a third peripheral recess or peripheral projecting edge in the peripheral part of the upper face of the base part of the casing of substantially complementary shape and arranged to cooperate with the peripheral rib or the first peripheral groove of the upper part when they are placed opposite each other.

[0042] Advantageously the number of protrusions or studs is greater than 20, of decreasing height relative to the heel, to take into account the variable thickness of the upper part of the cover.

[0043] The invention will be better understood upon reading the following description of embodiments given below by way of non-limiting examples. The description refers to the accompanying drawings in which:

[0044] Figure 1 is a side view of a first embodiment of a prosthesis garment or cover according to the invention;

[0045] The, is a perspective view from below of the upper part of the envelope of the;

[0046] This is a top view of the sole part of the;

[0047] This is a top view of another embodiment of the sole part of the;

[0048] Laest is a bottom view of an embodiment of the upper part of an envelope with blind holes according to the invention arranged to cooperate with the sole part of the.

[0049] This is a view from below of the sole part of the casing.

[0050] This is a top view of the envelope.

[0051] This is a lateral perspective view of an example of a prosthetic blade usable with a casing according to the invention.

[0052] This is a top view of the blade, with the end part flattened or in horizontal projection.

[0053] This is a set of three perspective views of a shock-absorbing wedge usable with the blade of the.

[0054] This is a bottom view of the upper part of the envelope as also shown on the other, and a perspective view of the opposite prosthetic blade arranged to cooperate with said upper part.

[0055] This is a side view showing the insertion of the blade into the upper part.

[0056] This is a view of the next step of that illustrated by the, of making the prosthesis itself by inserting the blade, then gluing the two parts, sole and upper, together, to make an excellent watertight and debris-proof joint between blade and upper part according to the invention.

[0057] Laest is a longitudinal cross-sectional view of an envelope according to another embodiment with a joining piece or connection with a user's leg (not shown).

[0058] This is a top view of another embodiment of a part of the sole of the envelope according to the invention.

[0059] This is a top view of an upper part designed to cooperate with the sole part of the...

[0060] This is a flowchart of an embodiment of the manufacturing process for a prosthetic foot shell according to the invention.

[0061] This is a diagram of the operation of a device for manufacturing an envelope according to an embodiment of the invention.

[0062] This is a side view of an embodiment of the device for manufacturing the upper part of the envelope according to the invention.

[0063] This is a detailed view of the expanded EVA injection part of the device.

[0064] This is a top perspective view of a lower mold component for the upper part of a casing according to an embodiment of the invention.

[0065] This is a perspective view from below of an upper mold component for the upper part of a casing according to the embodiment of the invention.

[0066] Lamontre a foot prosthesis envelope 1, an example of which will be described with reference to figures 8 and 9 below.

[0067] More specifically with reference to figures 1 to 7, the envelope 1 comprises a sole part 2 made of elastomer or soft plastic material and an upper part 3 obtained by injection molding of expanded EVA (IMVEA) delimiting an internal volume 4 suitable for receiving and covering entirely the top of the body of the prosthesis, said upper part 3 being provided with a slot 5 (cf) for exiting the junction of the prosthesis with the user's leg (not shown).

[0068] This slot 5, for example parallelepiped, is arranged to allow the prosthesis to cooperate by friction in a close and airtight and watertight manner with the upper part 3 of the envelope.

[0069] The peripheral part 6 of the upper face 7 of the sole part 2 is arranged to cooperate, for example by interlocking, and to be fixed by gluing, on the peripheral part 8 of the lower face 9 of the upper part 3. It is advantageously obtained by compression molding of EVA (CMVEA), for example after a first injection molding to give a first rough sole, before passing into a compression mold giving its final shape to the sole part.

[0070] With reference to figures 4 and 5, the peripheral part 6 includes an edge 10 projecting from said upper face 7 of the sole part 2 and the peripheral part 8 of the upper part 3 includes a corresponding recess 11 arranged to cooperate with a gap (1 to 2 mm) and to fit together with the opposite edge 10 before the faces 7 and 8 are glued with a polymer glue of a type known per se.

[0071] The edges and recesses 10 and 11 (shown schematically in the figures) have, for example, a beveled or beaded shape while allowing easy adjustment during assembly, the junction 12 (see) becoming almost invisible once the parts are glued together.

[0072] In the particular embodiment of the invention described herein, the upper portion 3 formed by the expanded IMVEA comprises, on its inner part 13, a plurality of blind holes 14 (twenty-five are shown here), cylindrical in shape, for example 0.7 cm in diameter and with a height calculated based on the thickness relative to the inner portion. These holes are arranged to allow internal expansion of the IMVEA during demolding so that the external shape 15 (see) is homogeneous, regular, and conforms to the desired external design of the foot. The size of the holes is determined based on the overall expansion volume envisaged for the upper portion 3 in a manner that is within the grasp of a person skilled in the art.

[0073] The sole part is obtained by compression. It may have blind holes 14' (cf) or not ( ), depending on whether the sole part is obtained after a first EVA extension step (presence of holes to compensate) before compression (CMVEA) or directly by compression.

[0074] In an advantageous embodiment, it is planned to fill the holes with EVA plugs (not shown) before forming the final prosthetic foot as will be described with reference to figures 11 to 14.

[0075] Figures 6 and 7 show the underside () and the top () of the envelope. The upper part 3 (cf) includes a heel part 16 externally provided with several undulations 17 on the side and on the back, for example three substantially horizontal and parallel undulations forming cushioning prefolds and also allowing to better conceal the existence of the necessary junction line 12 between upper part and sole part.

[0076] The lower or external face 18 of the sole part 2 is provided with anti-slip means 19, for example formed by concentric undulations 20 on the heel section on one side and on the toe section on the other.

[0077] We will now describe an example of a dynamic return prosthesis 21 usable with an envelope according to the invention. The prosthesis is formed of a spring blade 22 having a body 23 substantially in the shape of an L, having a median section 24 of the bottom of the foot connected on one side 25 to a section 26 of the heel and on the other side 27 to a section 28 of the top of the foot comprising a spring portion 29 extending above and progressively away from the median section 24.

[0078] The median section 24 of the foot bottom (cf) is for example in the shape of an elongated blade 30 hollowed out by a central slit 31 terminated on the side opposite the heel by two fingers 32 thicker and wider than the rest of the blade, further improving the cushioning capacity particularly at the end of the prosthesis.

[0079] The spring-loaded portion 29 is extended by an upward-facing end portion 33, for example vertical or substantially vertical, connecting to a fitting (not shown) carried by the user's leg in a manner known per se (for example, bolted). In the figure, the end 33 has been fictitiously shown flattened from the dividing line L by dashed lines.

[0080] The prosthesis preserves the space Vc or internal compression volume between the median section 24 of the bottom of the foot and the section 28 of the top of the foot connected to the end part 33 of connection.

[0081] Lamontre provides an example of an elastic filling shim 34 for the internal volume 4, designed to fill the compression space delimited by the blade when it is relaxed, as shown in the figure. An elastic filling shim is defined as a shim that can deform plastically to adapt to and allow the spring effect of the blade, without causing air displacement and / or requiring its evacuation and / or entry. For example, it is a shim of a specific shape corresponding to the empty portion of the prosthesis made of expanded IMVEA with a hardness equal to or less than that of the upper portion.

[0082] Shore hardness is measured with a durometer in a way known in itself, for example by reference to the so-called Shore A scale. The hardness of the upper part is for example between 40 and 80 on this scale, and that of the wedge between 20 and 70.

[0083] More specifically, this wedge 34, or EVA or other shock-absorbing filling plug, is sized and arranged to be placed between the free upper surface 35 of the medial section 24 of the footbed of the blade and the lower surface 36 of the upper section 28 of the footbed, extending above and away from said medial section of the footbed. These surfaces are shown as dashed lines in the figure. The rear part 37 of the wedge has a curved surface arranged to cooperate with the inner face 38 (see) of the heel of the upper part 3, with a central edge 39 designed to fit into the slot 31 opposite the blade, allowing for a perfectly fitted contact between the wedge and the prosthesis.

[0084] We will now describe, with reference to figures 11 to 15B, the assembly of the envelope described with reference to figures 1 to 7. This is done after embedding and gluing the wedge 34 described with reference to the around the prosthesis 21 of figures 8 and 9.

[0085] From the upper part 3 of the envelope 1, the end part 33 of the blade connection is inserted into the slot 5 until the middle part 24 of the blade is inserted into the lower recess 40 made in the bottom of the upper part 3 in expanded IMVEA.

[0086] This recess 40 is dimensioned for the insertion of the blade as shown in the figure, so as to allow the blade to be fully embedded in the upper part of the casing and the base, permitting contact between the inner face 41 of the upper part of the casing and the top 42 over the entire surface of the blade. Advantageously, the blade and / or the inner face of the upper part have been previously bonded on all their contact surfaces.

[0087] The upper face 43 of the sole part 2 is then applied to the lower face 44 of the blade 21, after gluing, to obtain a prosthetic foot with a cover according to the invention.

[0088] We have shown on the longitudinal section another embodiment of a prosthetic foot obtained with an envelope according to the invention.

[0089] More specifically, the watch shows a prosthetic foot 45 comprising an upper part 46 in expanded IMVEA, provided with blind holes 47 filled with soft EVA 48 and a sole part 49 in CMVEA glued to the lower face 50 of the upper part opposite and to the lower face 51 of the spring blade 52 whose upper face 53 is itself glued to the inner face 54 of the inner cavity of the upper part 46. The blade 52 includes an end part 55 for joining with a connector 56 for fixing to the stump of the user's leg (known in itself).

[0090] The end portion 55 passes through and is bonded to the passage slot 57 in the upper portion 52 of the casing according to the invention. At this stage, the seal is complete, as the damping due to the deformation of the dynamic blade is absorbed by the elasticity of the casing and that of the wedge 34.

[0091] In the rest of the description, the same reference numbers will be used where appropriate to designate identical or similar elements.

[0092] Lamontre another embodiment of a sole part 2 arranged to cooperate with an upper part 3 in expanded IMVEA of the envelope according to the invention. In this case the upper part (see) does not encompass the entire top of the prosthetic foot but only a part on the heel side, for example over two-thirds or three-quarters of the length of the foot, the sole part 2 being, on the other hand, extended at its end 57 on the toe side 58 by a part 59 covering the end of the blade opposite the heel.

[0093] This is an organizational chart of an embodiment of the manufacturing process for a prosthetic cover and foot according to the embodiment of the invention more particularly described here.

[0094] First, the choice of a prosthesis 21 is made by the user and his doctor, that is to say, the blade of shape and resistance is determined according to the specifications, this being designed separately or chosen from a catalog of suppliers of dynamic return blades.

[0095] The user also determines (step 61) the choice of the specific cover he is looking for (appearance, colors, shape etc.), then we determine more precisely (step 62) in detail the cover (upper part, sole part and cushioning wedge) corresponding to the chosen prosthetic foot.

[0096] Next (general step 63) the first part of the cover or sole part is manufactured by compressing EVA in a mold.

[0097] To do this, a first rough draft (step 64) is formed in a first mold into which liquid EVA is injected, comprising a foaming agent known in itself, and / or rubber or a mixture of the two, roughly blocking the shape of the retained sole, then the said shape is placed in a second mold (step 65) of (high) compression (for example between 50 and 150 bars) allowing to obtain the sole part 2 (step 66) in CMEVA of a determined shape and volume, then it is cooled substantially in ambient air in a wooden shell ((step 67) (in a one-to-one ratio, that is to say with a final volume of the sole after cooling equal or substantially equal to the internal volume of the mold.

[0098] Simultaneously, a second part of the envelope or upper part is manufactured (overall step 68) by injection (step 69) of EVA under pressure (for example between 40 and 100 bars) into a mold, with the addition of a porogenic agent - (foaming gas in Anglo-Saxon terminology) - for example nitrogen and the addition of particles or nucleating agents in a way known and adapted by a person skilled in the art according to the characteristics of the EVA) then it is demolded (step 70) causing the sudden expansion of the expanded EVA (here the ratio is for example one to two), this expansion being nevertheless controlled thanks to the blind holes generated by the protrusions or the studs of the lower organ in the upper part of the envelope.

[0099] Advantageously, a step 71 of filling blind holes, for example with soft EVA plugs—soft EVA being understood as EVA capable of deforming / compressing in a completely reversible manner—is then carried out to obtain, after cooling, for example in a wooden shell (step 72), the upper part 3 ready for insertion. Simultaneously, a step 73 of manufacturing the damping wedge 34 is carried out in a mold by injecting liquid EVA, resulting in a relatively soft and compressible part, similar to the plugs, subject to elastic compression. The chosen prosthesis is then presented (step 74) before a step 75 of gluing the different parts together.To do this, for example, polyurethane glue is used to glue the upper and lower surfaces of the prosthesis, including the connecting end, the wedge, and the upper and lower junction surfaces via their peripheral edges of complementary shapes of the upper part 3 and sole 2 of the envelope 1.

[0100] The wedge is then fitted into the prosthesis at 76 and the prosthesis into the upper part before the final assembly and gluing at 77 of the sole with said upper part whose respective peripheries are arranged to cooperate (with a set of adjustment) by compression for a determined time, sufficient to allow a solid bond making the parts and the prosthesis inseparable except by destruction, for example for one to several minutes.

[0101] We will now describe, with reference to figures 17 to 21, the manufacturing device for the prosthetic foot envelope 1 obtained with said envelope.

[0102] From an EVA (pellets) storage tank 80, it is heated to liquefy it in an oven 81. The EVA is then injected, for example, at a pressure of 40 bars in 82 into an initial mold 83 called a shape-locking mold with a slightly foaming agent, then the resulting paste 84 is compressed (pressure of 100 to 200 bars) in a first mold 85 known in itself allowing the sole part 86 to be obtained in the desired shape.

[0103] Simultaneously, EVA in the form of granules (reservoir 87) is supplied to a heated screw furnace 88 using, for example, the MUCELL process known to those skilled in the art, a process in which liquefied EVA, for example at 180°C, is supplied with foaming agent (gas) and nucleating agents in the said screw furnace 88 (see also figures 18 and 19).

[0104] EVA is then injected, via an injection nozzle 89 for example with a sealing nozzle, into a second mold comprising an upper part 90 of negative shape 91 (in dashed lines on the) of the upper part (see also) and a lower part 92 having cylindrical studs 93 (see also) for forming blind holes of the upper part 94 of the envelope and a vertical block 93' of passage of complementary shape to the shape of the upward-directed end part of the blade of determined shape for connection with the leg of said user and containing the positive shape of the upper part, to create the final shape of said upper part 94 in expanded IMVEA.

[0105] The second mold is then suddenly opened, causing an almost instantaneous expansion of the EVA (expanded IMEVA), a controlled expansion which will take place essentially towards the inside of the blind holes, thus surprisingly maintaining a controlled external shape.

[0106] The two parts sole 86 and upper 94 are then prepared (block 95) an insertion of plugs or plug being made for example in the remaining part of the blind holes not filled by the expansion.

[0107] Note that the cumulative volume of these blind holes must correspond substantially to the expected expansion volume, for example determined empirically and / or by calculation in a known way with the parameters concerning EVA, foaming and nucleating agents and the volumes concerned previously determined during the initial step 62.

[0108] The principle is that the expansion volume of the EVA is provided in the upper part of the mold via one or more solid volumes in the lower part, so that, during demolding, the expansion is inwards and not randomly outwards from the upper part of the resulting envelope.

[0109] The upper part 94 thus prepared and the sole part 86 are then brought to the gluing station 96, as well as the wedge 97 and the prosthesis or blade 98, station where the wedge 97, the blade 98, and the opposite faces of the upper and sole parts are glued.

[0110] Then at stations 99 and 100 the different elements are assembled one inside the other in an irremovable way by gluing before finishing heating at 101 to obtain the prosthetic foot 102 equipped with the cover according to the invention.

[0111] With reference to Figures 20 and 21, the lower member (92) of the second mold includes in its peripheral part a first projecting edge or a first peripheral recess (103) and the upper member (90) includes a second recess or a bearing surface (104) arranged to be placed opposite said first projecting edge or first recess when the lower and upper members are assembled, so that a first peripheral groove or a peripheral stringer is formed in the peripheral part of the lower face of the upper part of the envelope.

[0112] For its part, the first mold is arranged to create a third peripheral obvious or peripheral protruding edge in the peripheral part of the upper face of the sole part of the envelope of substantially complementary shape so that they can cooperate with play with the peripheral spar or the first peripheral groove of the upper part when placed opposite each other.

[0113] As is self-evident and as follows from the foregoing, the present invention is not limited to the embodiments more particularly described but on the contrary embraces all variants and in particular those where the prostheses or blades are of different shapes, those where the internal expansion volume is in one part or in two or three outgrowths or volumes distributed regularly or not on the lower organ.

Claims

A user's foot prosthesis shell (1) arranged to cooperate with a spring-blade prosthesis (21) (22) said to have dynamic return, said blade (22) having a body (23) extended on one side by an end part (33, 55) directed upwards for connection with said user's leg, characterized in that the shell (1) comprises a sole part (2, 49) made of elastomer or soft plastic material and an upper part (3, 46) obtained by injection molding of expanded EVA (expanded IMVEA) delimiting an internal volume (4) suitable for receiving and completely covering the body of the blade, said upper part being provided with a friction-flow slot (5, 57) for the exit of the connecting end part. Envelope according to claim 1, characterized in that the peripheral part (6) of the sole part (2) is arranged to fit together and be fixed by gluing onto the peripheral part (8) of the lower face (9) of said upper part (3). Envelope according to any one of the preceding claims, characterized in that the sole part (2, 49) is obtained by compression molding of EVA (CMVEA). Envelope according to any one of the preceding claims, characterized in that the peripheral parts (6, 8) of the sole part (2) on the one hand and of the upper part (3) on the other hand, comprise for the one a projecting edge (10) and for the other a corresponding recess (11) arranged to cooperate with play and fit together before gluing. Envelope according to claim 4, characterized in that the projecting edge (10) and the recess (11) have a complementary beveled shape. Envelope according to claim 4, characterized in that the protruding edge (10) forms a rounded peripheral lip forming a bead and the recess (11) forms a rounded hollow groove with which it cooperates by friction before gluing. Envelope according to any one of the preceding claims, characterized in that the upper part (3) formed by the expanded IMVEA comprises on its internal part one or more blind recesses or a plurality of blind holes (14, 47) arranged in the thickness of the internal part with a depth of height variable depending on the progressive thickness of said upper part of the envelope, being less than said thickness allowing an internal expansion of the IMVEA at the time of demolding. Envelope according to any one of the preceding claims, characterized in that the upper part (3) comprises an upper surface forming the top of the cladding in the shape of a foot top without protrusion, the vertical projection of said upper surface thus fitting into the surface of the sole part. Envelope according to any one of the preceding claims, characterized in that the upper part (3) comprises a heel part (16) provided externally on either side with a plurality of undulations (17) forming pre-shock-absorbing folds in case of heel compaction. A cover according to any one of the preceding claims, characterized in that the lower face (18) of the sole part (2) is provided with anti-slip means (19) (for example formed by a plurality of grooves (20) or studs) and / or is formed of an anti-slip material. Method of manufacturing a two-part shell (1) of a user's prosthetic foot (21) in the form of a blade (22, 52) with a so-called dynamic return spring, said blade (22, 52) having a body (23) extended on one side by an end part (33, 55) directed upwards in a determined shape of connection with the leg of said user, characterized in that a first shell part or sole part (2) is manufactured (63) from a resin or an elastomer which is compressed (65) in a first mold (85) into a flat block (84) giving it the shape of a determined sole (86) and a second shell part or upper part (3) is manufactured (68) in parallel by injection (69) of a liquid ethylene vinyl acetate resin under pressure (expanded IMVEA) into a second mold comprising an upper component (90) containing the negative shape of the upper part,and a lower component (92) having one or more protrusions or studs (93) distributed over its surface, a vertical passage block (93') of complementary shape to the shape of the end portion directed upwards of a blade of determined shape connecting with the leg of said user and containing the positive shape of the upper portion to create the final shape of said upper portion in expanded IMVEA, the protrusion(s) or stud(s) (93) being arranged to create one or a plurality of blind holes in said upper portion of the casing allowing internal expansion of the expanded IMVEA at the time of demolding. Method according to claim 11, characterized in that the sole part (2) is made of EVA obtained by mixing an ethylene vinyl acetate resin with a foaming agent in a determined proportion. Device for manufacturing a two-part (2, 3) prosthetic foot shell (1) comprising a first mold (85) for manufacturing a first shell part or sole part (2) of EVA by mixing an ethylene vinyl acetate resin with a foaming agent in a determined proportion by compressing the resulting mixture into a flat block, said first mold (85) being arranged to give it the shape of a determined sole (86) in CMVEA, and a second mold for manufacturing a second shell part or upper part (3) by injecting a liquid ethylene vinyl acetate resin under pressure, said second mold comprising an upper component (90) containing the negative shape of the upper component, and a lower component (92) having one or more protrusions or studs (93) distributed on its surface,a vertical (93') block of passage of complementary shape to the shape of the vertical end portion of determined shape of connection with the leg of said user and containing the positive shape of the upper portion to create the final shape of said upper portion in IMVEA, the protrusion(s) or stud(s) being arranged to create one or a plurality of blind holes allowing internal expansion of the IMVEA in the upper portion at the time of demolding. Device according to claim 13, wherein the lower member (92) of the second mold comprises in its peripheral part a first projecting edge or a first peripheral recess (103) and the upper member (90) comprises a second recess or a bearing surface (104) arranged to be positioned opposite said first projecting edge or first recess when said lower and upper members are assembled,the said second mold being adapted to form a first peripheral groove or peripheral rib in the peripheral part of the lower face of the upper part of the casing and in that the first mold is arranged to create a third peripheral recess or peripheral projecting edge in the peripheral part of the upper face of the base part of the casing of substantially complementary shape and arranged to cooperate with the peripheral rib or the first peripheral groove of the upper part when they are placed opposite each other. Device according to any one of claims 13 and 14, characterized in that the number of protrusions or studs is greater than 20, of decreasing height with respect to the heel, to take into account the variable thickness of the upper part of the casing. Device according to any one of claims 13 to 15, characterized in that the vertical end part of determined shape of connection with the leg of said user is substantially parallelepiped.

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