Wire electrical discharge machined rupture disk and method

Abstract

The present invention provides an improved method of manufacturing a rupture disk and specifically of forming a score on a rupture disk. The method of the present invention includes the rotating of a rupture disk blank relative to an electrical discharge machining or “EDM” cutting wire and the simultaneous moving of the EDM cutting wire toward the axis of the disk while maintaining the wire in a selected position such as generally parallel to the disk peripheral skirt or flange. The rotation of the disk and the movement of the EDM wire can be precisely controlled with the motion system of a commercially available EDM machine. With the present invention, a precise score is cut a partial distance through the disk thickness and preferably on the convex side of the dome, near the transition from the dome to the flange and in a generally “c” shaped pattern. The formed score creates a pattern of weakness so that the disk will open in either of the forward or reverse buckling direction. Score patterns other than the “c” shaped pattern could be cut.

1 . A method of constructing a rupture disk, comprising the steps of:
 a) providing a disk blank having a peripheral flange and a concave convex portion that is surrounded by the peripheral flange;   b) rotating the disk blank upon a turntable wherein the turntable engages the concave convex portion of the disk blank;   c) during the rotating of step “b”, scoring the surface of the concave convex portion with a wire of a wire electrical discharging machine, said wire having a wire cross section and an outer surface with a shape; and   d) wherein the score includes a shaped part, at least part of the shaped part having the shape of the outer surface of the wire, the shaped part having a transverse cross section that is larger than the cross section of the wire.   
     
     
         2 . The method of  claim 1  wherein the wire is between about 0.004 and 0.0012 inches in diameter. 
     
     
         3 . The method of  claim 1  wherein the wire is about 0.0010 inches in diameter. 
     
     
         4 . The method of  claim 1  wherein in steps “c” and “d” the wire is spaced away from the peripheral flange. 
     
     
         5 . The method of  claim 1  wherein the score formed in step “c” has a transverse cross section that is different in shape than the transverse cross section of the score. 
     
     
         6 . The method of  claim 1  wherein the score formed in step “c” has at least three surfaces that are of different curvatures in transverse cross section. 
     
     
         7 . The method of  claim 6  wherein the surfaces include at least one generally flat surface. 
     
     
         8 . The method of  claim 6 , wherein the surfaces include two flat surfaces of different lengths. 
     
     
         9 . The method of  claim 1  wherein the disk blank has a thickness of between 0.003 and 0.125 inches. 
     
     
         10 . The method of  claim 1  wherein the disk blank has a thickness of between about 0.003 and 0.375 inches. 
     
     
         11 . The method of  claim 1  wherein the distance between the wire and the peripheral flange is between about 0.020 and 2.0 inches. 
     
     
         12 . The method of  claim 1  wherein a convex surface of the disk blank is scored in step “c”. 
     
     
         13 . The method of  claim 1  wherein the disk blank has a central axis and wherein the score in step “c” extends less than 360 degrees around the disk blank central axis. 
     
     
         14 . The method of  claim 1  wherein in steps “b” and “c” rotation of the turntable is controlled by the wire electrical discharge machine. 
     
     
         15 . The method of  claim 1  wherein in step “c” movement of the wire is controlled by the wire electrical discharge machine. 
     
     
         16 . A method of constructing a rupture disk, comprising the steps of:
 a) providing a disk blank having a central axis, a peripheral flange and a concave convex portion that is surrounded by the peripheral flange;   b) rotating the disk blank and a cutting wire relative to each other;   c) during said rotating, scoring the surface of the concave convex portion with the wire to form a scored recess, wherein the wire is an electrical discharging machine wire that contacts the disk concave convex portion while scoring said surface, said wire having a diameter;   d) wherein the wire is advanced toward the disk central axis as the score is formed in steps “b” and “c”;   e) wherein the wire is spaced away from the peripheral flange in step “d”; and   f) the scored recess having a maximum width that is greater than the wire diameter.   
     
     
         17 . The method of  claim 16  wherein the wire is between about 0.004 and 0.0012 inches in diameter. 
     
     
         18 . The method of  claim 16  wherein the wire is about 0.0010 inches in diameter. 
     
     
         19 . The method of  claim 16  wherein in steps “c” and “d” the wire is positioned generally parallel to a plane defined by the peripheral flange. 
     
     
         20 . The method of  claim 16  wherein the score formed in steps “c” and “d” has a cross section that is asymmetrical in transverse cross section. 
     
     
         21 . The method of  claim 16  wherein the score formed in steps “c” and “d” has surfaces that are of different curvatures in transverse cross section. 
     
     
         22 . The method of  claim 16  wherein the score formed in steps “c” and “d” has a generally flat surface. 
     
     
         23 . The method of  claim 16  wherein the wire is positioned in step “c” to cut only partially through the disk blank. 
     
     
         24 . The method of  claim 16  wherein the disk blank has a thickness of between 0.003 and 0.125 inches. 
     
     
         25 . The method of  claim 16  wherein the disk blank has a thickness of between about 0.003 and 0.375 inches. 
     
     
         26 . The method of  claim 16  wherein the distance between the wire and the peripheral flange is between about 0.020 and 2.0 inches. 
     
     
         27 . The method of  claim 16  wherein a convex surface of the disk blank is scored in steps “c” and “d”. 
     
     
         28 . The method of  claim 16  wherein the score in steps “c” and “d” extends less than 360 degrees around the disk blank central axis. 
     
     
         29 . The method of  claim 16  wherein in steps “b” and “c” the disk blank is supported upon a tool and wherein rotation of the tool is controlled by the wire electrical discharge machine. 
     
     
         30 . The method of  claim 16  wherein in step “c” movement of the wire is controlled by the wire electrical discharge machine. 
     
     
         31 . The method of  claim 16  wherein the disk blank is supported by a tool and wherein the tool engages the disk concave convex portion. 
     
     
         32 . The method of  claim 16  wherein the disk blank is supported by a tool and wherein the tool engages the disk peripheral flange. 
     
     
         33 . The method of  claim 1 , further comprising the step of forming an asymmetrical transverse cross section score on the disk blank. 
     
     
         34 . The method of  claim 16 , further comprising the step of forming an asymmetrical transverse cross section score on the disk blank. 
     
     
         35 . The method of  claim 16 , further comprising the step of supporting the disk blank on a tool. 
     
     
         36 . The method of  claim 35 , further comprising the step of engaging the tool to the disk peripheral flange. 
     
     
         37 . The method of  claim 35 , further comprising the step of engaging the tool to the disk concave convex portion. 
     
     
         38 . The method of  claim 35 , further comprising the step of engaging the tool to both the disk peripheral flange and the disk concave convex portion. 
     
     
         39 . A method of constructing a rupture disk, comprising the steps of:
 a) providing a disk blank having a peripheral flange and a concave convex portion having concave and convex surfaces and surrounded by the peripheral flange;   b) rotating the disk blank upon a turntable, wherein the turntable contacts the concave surface of the disk concave convex portion;   c) during the rotating of step “b”, scoring the surface of the concave convex portion with a wire of a wire electrical discharging machine, said wire having an outer surface with a shaped surface; and   d) wherein the score includes a curved part that has the same curvature as the curvature of at least a part of the outer surface of the wire.   
     
     
         40 . A method of constructing a rupture disk, comprising the steps of:
 a) providing a disk blank having a peripheral flange and a concave convex portion that is surrounded by the peripheral flange, said concave convex portion having concave and convex surfaces and a central axis;   b) rotating the disk blank upon a turntable and about said central axis, wherein the turntable contacts the disk concave surface;   c) during the rotating of step “b”, scoring the convex surface with a wire of a wire electrical discharging machine;   d) wherein the wire has a circular cross section and the score has a cross section that is formed by the wire in step “c” and which score has a first part that corresponds in shape to the cross section of the wire and a second part generated by movement of the wire toward the disk central axis.