Smart Material Actuated Fasteners

Abstract

A smart material actuated fastener is provided. In another aspect, a fastener includes a shape memory material and a non-shape memory material with the shape memory material being a minority of the total fastener materials. A further aspect provides a fastener having workpiece-engaging surfaces made of an inactive and non-shape memory material.

1 . A fastener comprising:
 a smart material comprising a shape substantially defined as one of: (a) W; (b) hourglass; (c) diamond; and (d) S; in at least one condition;   the smart material changing at least one of: shape, size and flexibility, when actuated; and   an inactive material attached to the smart material, the smart material moving at least a portion of the inactive material when the smart material is energized.   
     
     
         2 . The fastener of  claim 1 , wherein the smart material is a shape memory metal. 
     
     
         3 . The fastener of  claim 1 , wherein the smart material is a shape memory polymer. 
     
     
         4 . The fastener of  claim 1 , wherein the smart material is a minority of the total fastener weight, further comprising workpiece-engaging surfaces being of the inactive material. 
     
     
         5 . The fastener of  claim 1 , wherein a middle segment of the smart material has the substantially W-shape when the fastener is in a fastened condition, and the inactive material includes a laterally enlarged head and a pair of polymeric legs. 
     
     
         6 . The fastener of  claim 1 , wherein a middle segment of the smart material has the substantially hourglass-shape when the fastener is in a fastened condition, and the inactive material includes a laterally enlarged head. 
     
     
         7 . A fastener comprising:
 a shape memory material being longitudinally longer than a width thereof when the fastener is in an unfastened condition;   a non-shape memory polymeric material;   the shape memory material being a minority of the total fastener materials;   a laterally overhanging head having a workpiece-contacting surface of the non-shape memory polymeric material;   a least two laterally spaced apart side walls longitudinally extending substantially perpendicularly from the head when the fastener is in the unfastened condition;   at least a portion of the shape memory material being located between exterior planes of the side walls; and   the shape memory material laterally moving a middle portion of the non-shape memory polymeric material beyond ends of the side walls opposite the head, for workpiece engagement when the shape memory material is energized.   
     
     
         8 . The fastener of  claim 7 , wherein a section of the shape memory material is attached to and laterally extends within the head. 
     
     
         9 . The fastener of  claim 8 , wherein the section of the shape memory material includes distal ends thereof which outwardly project away from each other with a substantially U-shaped middle segment of the shape memory material longitudinally extending from the ends, when the fastener is in the unfastened condition. 
     
     
         10 . The fastener of  claim 7 , wherein the portion of the shape memory material is encapsulated within the side walls. 
     
     
         11 . The fastener of  claim 10 , wherein longitudinally elongated intermediate sections of the shape memory material are exposed internally and externally through openings in the side walls. 
     
     
         12 . The fastener of  claim 7 , further comprising a tapered leading end of the fastener, and a middle of the shape memory material spanning between the side walls adjacent the leading end, the side walls being flexibly movable legs. 
     
     
         13 . The fastener of  claim 7 , wherein:
 the side walls are flexibly movable legs;   the shape memory material includes a metallic alloy having a substantially U-shape when in the unfastened condition and a substantially W-shape when in a fastened condition; and   the shape memory material outwardly flexing the middle portion of the non-shape memory polymeric material which are knees of the legs.   
     
     
         14 . The fastener of  claim 7 , wherein the shape memory material longitudinally retracts and laterally expands when energized such that the shape memory material fills up a majority of space between the side walls when activated. 
     
     
         15 . The fastener of  claim 14 , wherein the shape memory material has a substantially hour-glass shape in the unfastened condition. 
     
     
         16 . The fastener of  claim 7 , wherein:
 the middle portion of the non-shape memory polymeric material includes flexible legs located laterally outboard of the shape memory material;   the legs operably flexing about pivots that are closer to an insertion bottom end of the fastener than is the head; and   the legs being space away from the adjacent side walls extending from the head.   
     
     
         17 . The fastener of  claim 7 , further comprising:
 a first semi-box including the head and part of the side walls;   a second semi-box including another part of the side walls, the middle portion of the non-shape memory polymeric material and a bottom wall spanning between the side walls;   the semi-boxes being longitudinally movable relative to each other; and   the shape memory material longitudinally spanning between and operably moving the semi-boxes relative to each other.   
     
     
         18 . A fastener comprising:
 a shape memory material being longitudinally longer than a width thereof when the fastener is in an unfastened condition;   a non-shape memory polymeric material;   the shape memory material being a minority of the total fastener materials;   a laterally overhanging head having a workpiece-contacting surface of the non-shape memory polymeric material;   a least two laterally spaced apart legs, at least partially made of the non-shape memory material, longitudinally extending substantially perpendicularly from the head when the fastener is in the unfastened condition;   the shape memory material laterally moving the legs for workpiece engagement when the shape memory material is energized;   a section of the shape memory material being attached to the head; and   the shape memory material including a substantially U-shaped middle segment of the shape memory material, when the fastener is in the unfastened condition.   
     
     
         19 . The fastener of  claim 18 , wherein a portion of the middle segment of the shape memory material is encapsulated within the legs. 
     
     
         20 . The fastener of  claim 19 , wherein longitudinally elongated sections of the shape memory material are exposed internally and externally through openings in the legs. 
     
     
         21 . The fastener of  claim 18 , further comprising a tapered leading end of the fastener and a middle of the shape memory material spans between the legs adjacent the tapered leading end. 
     
     
         22 . The fastener of  claim 18 , wherein:
 the shape memory material includes a metallic alloy having a substantially W-shape when in a fastened condition;   the shape memory material outwardly flexing a middle knee portion of each of the legs.   
     
     
         23 . A fastener comprising:
 a shape memory material being longitudinally longer than a width thereof when the fastener is in an unfastened condition;   a non-shape memory polymeric material;   the shape memory material being a minority of the total fastener materials;   a laterally overhanging head of the non-shape memory polymeric material;   a least two spaced apart side walls longitudinally extending from the head when the fastener is in an unfastened condition;   the shape memory material laterally moving a portion of the non-shape memory polymeric material for workpiece engagement when the shape memory material is energized; and   the shape memory material longitudinally retracting and laterally expanding when energized such that the shape memory material fills up a majority of space between the side walls when activated.   
     
     
         24 . The fastener of  claim 23 , wherein the shape memory material has a substantially hour-glass shape in the unfastened condition. 
     
     
         25 . The fastener of  claim 23 , further comprising:
 a first semi-box including the head and part of the side walls;   a second semi-box including another part of the side walls, the middle portion of the non-shape memory polymeric material and a bottom wall between the side walls;   the semi-boxes being longitudinally movable relative to each other; and   the shape memory material longitudinally spanning between and operably moving the semi-boxes relative to each other.   
     
     
         26 . The fastener of  claim 23 , wherein the shape memory material is attached to a surface adjacent the head and a bottom wall spaced away from the head, with a middle of the shape memory material being laterally thinner than a thickness adjacent the top surface and the bottom wall.