Collapsible, shape memory alloy structures and folding fixtures with associated method for collapsing same

Abstract

A shape memory alloy structure comprises at least one tubular member formed of shape memory material, each tubular member including a plurality of panels having side edges, wherein each tubular member is moveable between a radially contracted position and a radially extended position, and wherein the coupled side edges of adjacent panels of each tubular member form hinges for moving the structure between the contracted position and the extended position. Multiple layer tubular structures, methods for forming and fixtures for collapsing same are also disclosed.

What is claimed is: 
     
         1 . An shape memory alloy structure extending along a longitudinal axis and having a radially retracted state and a deployed state, said structure comprising a tubular member including a plurality of substantially solid, concave outer surface panels forming the tubular member circumference, each panel coupled to two adjacent panels on opposed sides at peak portions at radially outermost portions of the tubular member in the deployed state, and wherein each panel extends substantially parallel to the prosthesis's longitudinal axis, and wherein the retracted state has the panels and the peak portions of the tubular member positioned radially inwardly of their respective positions in the deployed state and the retracted state has each panel bending about an axis parallel to the longitudinal axis forming generally greater outer surface concavity than in the deployed state, whereby a substantially tight serpentine structure is formed by the panels and peaks in the retracted state. 
     
     
         2 . The shape memory alloy structure according to  claim 1  wherein the shape memory alloy is a nitinol structure and wherein the effective outer diameter of the structure in the radially retracted state is less than about 6 mm. 
     
     
         3 . A shape memory alloy structure comprising at least one tubular members formed of shape memory alloy and formed of a plurality of substantially solid scalloped panels separated by peaks, wherein the structure is moveable between a radially contracted position and a radially extended position, wherein the effective outer diameter of the structure in the radially extended position is at least 3.5 times the effective outer diameter of the structure in the radially contracted position. 
     
     
         4 . The shape memory alloy structure according to  claim 3  wherein the effective outer diameter of the structure in the radially contracted position is less than about 6 mm. 
     
     
         5 . The shape memory alloy structure according to  claim 3  wherein the shape memory alloy is a nitinol structure. 
     
     
         6 . The shape memory alloy structure according to  claim 3  wherein the structure is a prosthetic cardiovascular stent. 
     
     
         7 . A method of compacting a collapsible shape memory alloy structure comprising the steps of (a) providing a folding fixture with a body member having an inlet opening of a first diameter at one end thereof and a smaller diameter outlet at an opposite end thereof and a converging surface extending between the inlet opening and the outlet opening; and (b) passing the collapsible shape memory alloy structure entirely through the inlet opening and the outlet opening of the folding fixture. 
     
     
         8 . The method of compacting a collapsible shape memory alloy structure according to  claim 7  wherein the passing of the collapsible shape memory alloy structure through the entirely through the inlet opening and the outlet opening of the folding fixture is manual. 
     
     
         9 . The method of compacting a collapsible shape memory alloy structure according to  claim 8  including the step of (c) providing a second folding fixture with a body member having an inlet opening of a first diameter at one end thereof and a smaller diameter outlet at an opposite end thereof and a converging surface extending between the inlet opening and the outlet opening, wherein the second folding fixture is received within the first folding fixture. 
     
     
         10 . The method of compacting a collapsible shape memory alloy structure according to  claim 9  wherein the second folding fixture is received within the outlet opening of the first folding fixture, and wherein the passing of the collapsible shape memory alloy structure entirely through the inlet opening and the outlet opening of the first folding fixture will pass the collapsible shape memory alloy structure entirely through the inlet opening and the outlet opening of the second folding fixture. 
     
     
         11 . The method of compacting a collapsible shape memory alloy structure according to  claim 7  further including a holding fixture wherein the folding fixture is received within the holding fixture during the passing of the collapsible shape memory alloy structure entirely through the inlet opening and the outlet opening of the folding fixture. 
     
     
         12 . The method of compacting a collapsible shape memory alloy structure according to  claim 11  wherein the holding fixture includes a holding pin configured to support the collapsible shape memory alloy structure. 
     
     
         13 . The method of compacting a collapsible shape memory alloy structure according to  claim 12  further including a slot within the folding fixture configured to receive the holding pin during the passing of the collapsible shape memory alloy structure entirely through the inlet opening and the outlet opening of the folding fixture. 
     
     
         14 . The method of compacting a collapsible shape memory alloy structure according to  claim 7  wherein the shape memory alloy structure includes at least one tubular member formed of shape memory alloy, each tubular member formed of a plurality of concave panels wherein circumferentially adjacent panels are coupled at substantial tangential portions of each circumferentially adjacent panels, and wherein these coupled edges form hinges for movement of the shape memory alloy structure between a contracted position and a radially extended position.