Device for internal flaw magnification during wire drawing
View Patent ↗A device for use as an adjunct in assuring that a manufactured wire is substantially free of internal flaws. A plurality of successively adjacent wire bending stations are provided, where each station includes means for bending the wire into bending planes which are different for each of the stations. The wire is passed through the successive stations, whereby the different bending planes at each station subject the wire at each station to tensile bending strain at portions of the wire cross-section which are different for each station. As a result the probability is increased that a given internal flaw in the wire will be exposed to the tensile bending strain condition as the wire passes through the successive stations, increasing likelihood of breakage of the wire at the flaw or of flaw magnification to improve detection of the flaw during subsequent wire inspections.
1. A device for use as an adjunct in assuring that a manufactured wire is substantially free of internal flaws comprising:
a plurality of successively adjacent wire bending stations, each station comprising on a first plane, a means for bending the wire into a second bending plane substantially parallel to the first plane, wherein the first plane and second bending plane are different for each station; and
means for passing the wire through the successive stations;
whereby the different bending plane at each station subjects the wire at each station to tensile bending strain at portions of the wire cross-section which are different for each station, whereby the probability is increased that a given internal flaw in the wire will be exposed to the tensile bending strain condition as the wire passes through the successive stations, increasing likelihood of breakage of the wire at the flaw or of flaw magnification to improve detection of the flaw during subsequent wire inspections.
2. A device in accordance with claim 1 where said means for bending the wire comprises planar rollers.
3. A device in accordance with claim 2 where the number of rollers at each station are two or more.
4. A device in accordance with claim 3 , wherein the number of rollers are two, the wire being bent successively at a first and then at a second of the two rollers; and wherein the relative positions of the two rollers on the first plane are such that the surface of the wire being placed into tension at the first roller becomes the surface in compression at the second roller, whereby after passing through the planar set of rollers at a station, two pie slice sections around a 360° circumference of the wire have been subjected to the maximum flaw-affecting deformations.
5. A device in accordance with claim 4 , where the rollers are disposed at each station on the first plane for the station, and wherein said first planes intersect on a line coincident with the wire drawing axis.
6. A device in accordance with claim 5 , wherein the sets of rollers on successive stations are closely positioned along the wire drawing axis, so as to minimize the likelihood of the wire shifting angular position relative to the 360° wire circumference as the wire moves from one plane of rollers to the other.
7. A device in accordance with claim 5 wherein successive planes are positioned with an angular spacing of 120° apart, from the wire circumference reference.
8. A device in accordance with claim 3 , wherein the wire path results in wire being bent over the rollers at more than 180° of the bending roll.
9. A device in accordance with claim 3 wherein the number of said bending planes are more than two.
10. A device in accordance with claim 2 where the size of the rollers is determined by the diameter of the wire and the desired bending strain to be achieved in the wire.
11. A device in accordance with claim 10 wherein the radius of the rollers is approximately equal to ten times the diameter of the wire.
12. A device in accordance with claim 1 where said subsequent wire inspection is by eddy current testing.
13. A device in accordance with claim 1 where said subsequent wire inspection is by laser micrometer diameter measurement.