Dual-action disposable clamp

Abstract

Disclosed is a clamp that includes a mechanical fastener, an expander including a bulbing portion and a shank wherein the bulbing portion of the expander forms a flange by movement of the mechanical fastener without applying an initial clamping force. After formation, the flange is then drawn into a clamping position by continued movement of the mechanical fastener. Also disclosed is a method of using the disclosed clamp.

I claim: 
     
         1 . A clamp for clamping work pieces together through aligned apertures, the work pieces having a front side surface and a blind surface, the clamp comprising:
 a mechanical fastener comprising a head portion on a proximal end and a distal end;   an expander coupled to said mechanical fastener, said expander comprising a first end portion, a second end portion and a bulbing portion positioned therebetween, wherein said bulbing portion is constructed and arranged to bulb outwardly to form a flange with an enlarged outer diameter when said bulbing portion is compressed between said first and second end portions with a first compressive load, wherein said first end portion of said expander is coupled to said mechanical fastener proximate to said distal end of said mechanical fastener and wherein said expander undergoes substantial plastic deformation when the flange is formed;   a shank positioned on said mechanical fastener between said second end portion of said expander and said head portion of said mechanical fastener, wherein said mechanical fastener is movable relative to said shank;   a spacer positioned on said mechanical fastener constructed and arranged to receive said shank and to permit said shank to move axially through said spacer, wherein said spacer is too large to pass through the aligned apertures;   wherein said expander is constructed and arranged to be insertable through the aligned apertures from the front side;   wherein said expander is constructed and arranged such that it can be compressed by movement of said mechanical fastener relative to said spacer and said shank to cause said bulbing portion to form a flange without applying an initial clamping force to the work pieces;   wherein the formed flange may be drawn into a clamping position against the blind surface to clamp the work pieces together by the continued movement of said mechanical fastener with respect to said spacer; and   wherein said clamp is constructed and arranged to be removed from the work pieces by uncoupling said expander from said mechanical fastener and removing said mechanical fastener from the front side of the work pieces without damaging said mechanical fastener.   
     
     
         2 . The clamp of  claim 1 , further comprising a blocking member that prevents said shank from advancing through said spacer until a second compressive load is exerted that is greater than said first compressive load. 
     
     
         3 . The clamp of  claim 2 , wherein said blocking member is a flange. 
     
     
         4 . The clamp of  claim 2 , wherein said blocking member is a shear washer. 
     
     
         5 . The clamp of  claim 1 , wherein said mechanical fastener comprises a core bolt with an externally threaded portion. 
     
     
         6 . The clamp of  claim 5 , wherein said expander further comprises an internally threaded portion proximate to said second end portion, wherein said internally threaded portion is in threaded engagement with said externally threaded portion. 
     
     
         7 . The clamp of  claim 6 , wherein said expander further comprises a transition portion defining a groove in the outer surface of said expander positioned between said first end portion and said bulbing portion that forms a non-canted transition between the flange and said first end portion after said bulbing portion forms the flange. 
     
     
         8 . The clamp of  claim 1 , further comprising a resilient element constructed and arranged to maintain the load clamping the work pieces together in the event of the work pieces moving closer together due to a sealant squeezing out of a space therebetween. 
     
     
         9 . The clamp of  claim 1 , further comprising a shear washer positioned between said shank and said spacer that prevents said shank from advancing through said spacer until a second compressive load is exerted that is greater than said first compressive load. 
     
     
         10 . The clamp of  claim 9 , wherein said shank further comprises a boss constructed and arranged to interface with said shear washer to align said shear washer with respect to said shank, wherein said boss extends inside of a smallest internal dimension of said shear washer. 
     
     
         11 . The clamp of  claim 10 , wherein said spacer further comprises a recess constructed and arranged to align said shear washer with respect to said spacer. 
     
     
         12 . The clamp of  claim 1 , further comprising a flange on said shank that prevents said shank from advancing through said spacer until a second compressive load is exerted that is greater than said first compressive load. 
     
     
         13 . The clamp of  claim 1 , wherein said expander is compressed by rotating said mechanical fastener with respect to said spacer. 
     
     
         14 . The clamp of  claim 1 , wherein said expander is positioned away from the blind surface when inserted through the aligned apertures. 
     
     
         15 . The clamp of  claim 1 , wherein said expanding nut, said shank and said spacer are substantially rotationally constrained together. 
     
     
         16 . The clamp of  claim 1 , wherein said shank and said spacer are constructed and arranged to be removed from the front side of the work pieces with said mechanical fastener without damaging said shank or said spacer. 
     
     
         17 . A method for clamping two work pieces together through aligned apertures, the work pieces having a front side and a blind surface, the method comprising:
 inserting the clamp of  claim 1  into the aligned apertures from the front side so that the mechanical fastener extends through the aligned apertures with the expander spaced apart from the blind surface;   moving the mechanical fastener to compress the expander;   continued moving the mechanical fastener causing the bulbing portion of the expander to form a flange without applying an initial clamping force to the work pieces; and   subsequent to forming the flange, further moving the mechanical fastener thereby clamping the work pieces between the space and the flange.   
     
     
         18 . The method of  claim 17 , further comprising:
 compressing a resilient element while clamping the work pieces together, wherein the resilient element is constructed and arranged to maintain the compressive load clamping the work pieces together in the event the work pieces move closer together.   
     
     
         19 . The method of  claim 17 , further comprising:
 unthreading the bulbed expander from the mechanical fastener;   removing the mechanical fastener and the shank from the aligned apertures; and   threading a replacement expander onto the mechanical fastener to form the clamp of  claim 1 .   
     
     
         20 . A clamp for clamping work pieces together through aligned apertures, the work pieces having a front side surface and a blind surface, the clamp comprising:
 a mechanical fastener comprising a head portion on a proximal end and a threaded portion on a distal end;   an expander comprising a first end portion, a second end portion and a bulbing portion positioned therebetween, wherein said first end portion defines an internally threaded portion threadingly engaged on said mechanical fastener at said threaded portion, wherein said bulbing portion is constructed and arranged to bulb outwardly to form a flange with an enlarged outer diameter when said bulbing portion is compressed between said first and second end portions with a first compressive load, and wherein said expander undergoes significant plastic deformation when the flange is formed;   a shank positioned on said mechanical fastener between said second end portion and said head portion, wherein said mechanical fastener is movable relative to said shank; and   a spacer positioned on said mechanical fastener constructed and arranged to receive said shank and to permit said shank to move axially through said spacer, wherein said spacer is too large to pass through the aligned apertures;   wherein said expander is constructed and arranged to be insertable through the aligned apertures from the front side, wherein said expander is constructed and arranged such that it can be compressed between said first and second end portions by rotation of said mechanical fastener relative to said spacer to cause said bulbing portion to form a flange without applying an initial clamping force to the work pieces;   wherein the flange may be drawn into a clamping position against the blind surface to clamp the work pieces together by the continued movement of said mechanical fastener with respect to said spacer; and   wherein said expander is constructed and arranged to be removed from said mechanical fastener to remove the clamp by unthreading said mechanical fastener from said expander and removing said mechanical fastener from the front side of the work pieces without damaging said mechanical fastener.   
     
     
         21 . The clamp of  claim 20 , further comprising a blocking member that prevents said shank from advancing through said spacer until a second compressive load is exerted that is greater than said first compressive load. 
     
     
         22 . The clamp of  claim 20 , wherein said expander is compressed by rotating said mechanical fastener with respect to said spacer.