Novel Elastomeric Gel Liner

Abstract

A method of making a thermoplastic gel prosthetic liner for use with a prosthetic assembly that acts as the interface between the residual limb of an amputee and the socket assembly. The prosthetic liner comprises an open proximal end, a closed distal end, and sidewalls comprising an inner layer of molded thermoplastic gel. The thermoplastic gel is molded over a mandrel that has been sandblasted using #36 grit and, optionally, #320 grit at 100 psi so as to form microcraters and reduce the coefficient of static friction.

Claims

1. A method of making a thermoplastic gel liner comprising: modifying a mandrel surface using the method selected from the group consisting of sandblasting, rolling, chemical etching, laser engraving, computer numerical control engraving, electro-erosion, electrodeposition, laser micro melting, shot blasting, shot peening, and pinwheeling; molding a styrene triblock copolymer gel over the mandrel; forming fabric sidewalls over the styrene triblock copolymer gel creating a composite wherein the composite further comprises an open upper end, a closed bottom end, and fabric sidewalls having a thickness wherein said sidewalls further comprise an inner layer of styrene triblock copolymer gel having a gel thickness wherein said styrene triblock copolymer gel has microcraters having a depth between 0.0100 and 0.0195 millimeters.

2. The method of making a thermoplastic gel liner of claim 1 wherein the thickness of the sidewalls is between 3 and 12 millimeters.

3. The method of making a thermoplastic gel liner of claim 1 wherein the styrene triblock copolymer gel thickness at the bottom end is between 3 and 15 millimeters.

4. The method of making a thermoplastic gel liner of claim 1 further comprises less than 2.4 N of force in pull resistance prior to breaking.

5. The method of making a thermoplastic gel liner of claim 1 wherein the microcraters are further formed by compressing the styrene triblock copolymer gel against a textured surface after molding but before cooling.

6. A method of making a thermoplastic gel liner comprising: modifying a mandrel surface using the method selected from the group consisting of sandblasting, rolling, chemical etching, laser engraving, computer numerical control engraving, electro-erosion, electrodeposition, laser micro melting, shot blasting, shot peening, and pinwheeling; molding an elastomeric gel over the mandrel; forming fabric sidewalls over the styrene triblock copolymer gel creating a composite wherein the composite further comprises an open upper end, a closed bottom end, and fabric sidewalls having a thickness wherein said sidewalls further comprise an inner layer of elastomeric gel having a gel thickness wherein said elastomeric gel has microcraters having a depth between 0.0100 and 0.0195 millimeters.

7. The method of making a thermoplastic gel liner of claim 1 wherein the thickness of the sidewalls is between 3 and 12 millimeters.

8. The method of making a thermoplastic gel liner of claim 1 wherein the gel thickness at the bottom end is between 3 and 15 millimeters.

9. The method of making a thermoplastic gel liner of claim 1 further comprises less than 2.4 N of force in pull resistance prior to breaking.

10. The method of making a thermoplastic gel liner of claim 1 wherein the microcraters are further formed by compressing the elastomeric gel against a textured surface after molding but before cooling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:

[0019] FIG. 1 is a front view of the improved prosthetic liner.

[0020] FIG. 2 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel that has not been sandblasted.

[0021] FIG. 3 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel sandblasted with #36 grit at 100 psi.

[0022] FIG. 4 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel sandblasted with #320 grit at 100 psi.

[0023] FIG. 5 is a graph showing the effect of sandblasting on the pulling force necessary to remove a silicone sheet from a steel substrate showing the effect on the static coefficient of friction.

[0024] Similar reference numerals refer to similar parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.

[0026] The present invention relates to a liner 100 for use with prosthetic devices. As shown in FIG. 1, the liner 100 for use with a prosthetic assembly comprises an open upper end 12 for receiving a residual limb, not shown, a closed bottom end 14, and sidewalls 16 of predetermined thickness. The liner is airtight when donned over a residual limb. The preferred thickness of the sidewalls 16 is about 1.5 mm to 3.0 mm. Note that the thickness is greater at the bottom end than in the sidewalls; the preferred thickness of the silicone at said bottom end 14 is about 3.0 mm to 12.0 mm. The sidewalls 16 have an inner layer 18 of the improved silicone described herein. The sidewalls 16 can be fabric or another layer of more durable and higher friction silicone.

[0027] Prior to molding the silicone, a mandrel is sandblasted using #36 grit at 100 psi. The particular grit and pressure used provide the beneficial characteristics of the present invention. Other grits and pressures did not produce the benefits of reduced frictional hold and less chance of skin irritation. After sandblasting the mandrel, the silicone is molded over it, allowing the silicone to seep into the microcraters formed by the sandblasting. As can be seen in FIGS. 2-4, the size of grit used during sandblasting has a sizeable effect.

[0028] FIG. 2 depicts a sheet of silicone 20 that has not been sandblasted. As can be seen by the cross-section 2-2, not sandblasting the mandrel results in a smooth exterior surface 22 which maintains the high frictional characteristics of silicone. FIGS. 3 and 4, on the other hand, show a microscopic view of exterior surface 22 after having the mandrel sandblasted. FIG. 3 shows the microcratering the exterior surface 22 is subjected to using #36 grit at 100 psi thereby creating microcraters 24. Along line 3-3, the microcraters created generally have a depth of about 0.0195 mm. FIG. 4 shows the microcratering the exterior surface 22 is subjected to using #320 grit at 100 psi. Sandblasting with #320 grit may be done alone or after the mandrel has been sandblasted with #36 grit. Along line 4-4, the microcraters created generally have a depth of about 0.0100 mm. The deeper microcraters create a lower static coefficient of friction for silicone because there is less surface area for the exterior surface 22 to be in contact with, as can be seen when comparing the sheet in FIG. 3 with the sheet in FIG. 4. Sandblasting between #36 and #320 grit may also be performed.

[0029] Alternative methods of creating the microcraters 24 of differing depths include, but are not limited to, modification of the mandrel surface via rolling, compression of the mold against a textured surface, chemical etching, laser engraving, computer numerical control (CNC) engraving, electro-erosion (i.e. electrical discharge machining), electrodeposition, laser micro melting, shot blasting, shot peening, and pinwheeling. Similar methods now known or to be discovered which are equivalent to the methods included (i.e. methods that create microcraters in the exterior surface of a silicone layer in a prosthetic liner) are intended to be included in the above listing.

[0030] Three tests were performed to exhibit the beneficial properties of the present invention, the results of which are shown in FIG. 5. In the first, the mold was sandblasted using #36 grit at 100 psi and it took 1.6 N of force in terms of pull resistance, i.e. prior to tearing. In the second test, the mold was sandblasted using #320 grit. The result was 2.33 N of force in terms of pull resistance. In the final test the mold was not sandblasted at all and required 9.33 N of force. The tests were performed on smooth stainless steel using silicone strips that were 1-inch-wide and 7 inches long while applying 100 grams of weight.

[0031] The present invention can also be modified to improve the functionality of thermoplastic elastomer gel liners. Using thermoplastic molding techniques such as pressure molding or compression molding in combination with the methods described herein, the inner layer 18 of the liner 100 can be made of microcratered thermoplastic elastomer gel comprising a styrene triblock copolymer (such as those as described in U.S. Pat. No. 6,552,109 to Chen), polyurethane, polybutylene, or polypropylene. Unlike silicone, the sidewalls 16 of gel liners are usually thicker and can range from 3 to 12 millimeters in thickness with a preferred thickness at the bottom end 14 between 3 to 15 millimeters.

[0032] The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.

[0033] Now that the invention has been described,