US3036622A - Process of bending metal by wave formation - Google Patents

Description

y 1962 G. L. HlTZ v 3,036,622

PROCESS OF BENDING METAL BY WAVE FORMATION Filed Feb. 28, 1958 2 Sheets-Sheet 1 'G/FFOHD L. 19/ T2 INVENTOR.

May 29, 1962 G. L. HlTZ PROCESS OF BENDING METAL BY WAVE FORMATION Filed Feb. 2a, 1958 2 Sheets-Sheet 2 g/FFO/PD L. H/ TZ INVENTOR.

3,036,622 PRQCESS F EENDIL 1G METAL BY WAVE FORMATION Gifford L. Hitz, 166i Bel Air Road, Les An eies, Calif. Filed Feb. 28, 1953, Ser. No. 718,277 17 Claims. (Cl. 153-42) This invention relates generally to mechanical deformation of metal members such as plate, rod and tube, and more particularly has to do with methods of forming bends, turns or curvatures in such members, having the beneficial mechanical and metallurgical effects of (1) producing short radius curvatures or bends at any point along a metal member without stretching, cracking or thinning the outer radius section, or thickening, wrinkling or distorting the inner radius section,

(2) providing in the bent or curved area of the metal member accurate retention of original dimensional characteristics, or close control of changes which may be desired in dimension or configuration,

(3) maintaining a preferred metal micro-structure, eliminating or minimizing residual tension stresses encountered in conventional bending methods, and minimizing and equally distributing desirable residual compressive stresses, and

4) facilitating the bending or curving of metals which have small elongation factors as no stretching is involved in the present method.

The invention is generally predicated upon an application of the rather new concept that metal behaves differently under compressive loading beyond its yield point than under tensile loading beyond the yield point, contrary to the wide-spread older view that for all practical purposes the effects of tensile and compressive loading upon the crystal structure of metal can be treated as closely similar if not the same.

The present application of this newer concept concerns methods of forming turns or curves in elongated metal members, and is to be distinguished from older known methods of deforming metal to produce bends, wherein proper recognition was not given to the difference in behavior of the crystal structure of metal loaded in compression as distinct from tension. Thus in prior processes the metal was deformed either hot or cold in a manner calculated to produce a resultant configuration with attention given to grain structure, rather than to the arrangement of atoms in the crystal or lattice structure of the metal. As a result, metal being bent (particularly at temperatures below that required for recrystallization) was subject to undesirable and non-uniform strain hardening, cracking and distortion, and also, the force required to advance the metallic member relative to the deforming dies was undesirably great in order to overcome the resistance to member bending, which is related to the amount, direction and character of metal movement, and to the degree of strain hardening of the metal being bent.

The present novel method represents an application of the principle that the bonding forces acting to hold int-act metals of a crystalline character, and the disposition of crystal imperfections and atomic dislocations within the metal are affected by compressive loading of the metal beyond its yield point in a manner permitting more deformation or plastic flow before the metallic structure reaches a condition where further deformation would cause rupture, than if the metal were loaded in tension.

Applying the theory that dislocations in the atomic structure of crystalline metals are a prime factor permitting such metals to be plasticly deformed at temperatures below that of recrystallization, and that stretching such metals (as is typical of conventional bending techniques) tends to concentrate the dislocations from ceri be tain slip planes at crystal or grain boundaries, then it becomes obvious that the stretching force being applied is able to utilize only a comparatively limited number of slip planes before this concentration of dislocations causes cracking. Visible striations in metal loaded in tension beyond the yield point illustrate the concentration of slippage and strain in a few separated areas.

in bending by wave formation, continuous and uniformly increasing compressive force within the crystal structure of the metal causes the propagation of dislocations in a spiral effect within each crystal and thus makes use of a much larger number of slip planes than would be utilized if the metal were being loaded in tension.

Basically, the method of the present invention contemplates advancing an elongated metal member into compressive engagement with forming bodies arranged in such relation that the metal is not subjected to tension loading beyond the yield point, but is deformed beyond the yield point by compressive loading. The preferred steps of the method include compressively advancing the elongated member in the elongation direction, retarding metal advancement at one side of the member (which is to become the inner radius side) so that retarded metal is compressed beyond its yield point, and is guided and gathered into a protrusion of increased cross sectional area at said side, and consecutively impressing on said inner radius side the true curvature of the finished bend, this impressing being done at a tangent angle opposite to that of the finished bend, and the protrusion, and without unduly restricting the movement of the opposite side of the member (the outer radius side), and subsequently compressively side loading the member beyond its yield point and at an advanced opposite side (the outer radius side) to the protrusion, in a direction toward retarded metal at the member inner radius side advancing forwardly of the protrusion, so that the outer radius portion of the member is permanently turned away from the initial direction of advancement, and the member is reduced from the enlarged cross sectional area and thickness created by the protrusion, to the original (or desired) cross-sectional area and configuration.

The application of metal retarding and side loading forces in effect produces what may be termed a protrusion or wave-shaped gathering of metal at one side of the member. In the case of plate or rod the retarding effect is preferably carried out by compressing one side of the advancing member so that not only is the metal retarded at said side but is subsequently compressively side loaded at the forward side of the protrusion beyond the metal yield point and in a direction toward the member opposite side. Thus, the retarded metal is compressively directed toward the opposite side of the plate or rod. In the case of tubing or pipe the retardation effect is better accomplished by utilizing a mandrel with a protrusion formed thereon to guide one side of the advancing tube into the desired standing wave or protrusion configuration. The protrusion on the mandrel may be fixed or solid, or it may be retractable (collapsible) to facilitate entry and withdrawal of the mandrel, or it may consist of hydraulic pressure, limited internally by seals applying against the inside of the tube. In this hydraulic arrangement, a concave die is required on the outside of the tube protruberance to control the size and shape thereof.

It should be noted from the above description of the method that live coordinated actions are utilized, none of which are common with conventional bending or forming practices. These actions can be separately described as follows:

(1) Retarding and shortening the inner radius section of the member by formation of a protrusion,

(2) coincidentally with (l), gathering metal in the protrusion area to have an increased total cross sectional 3 area from which to later compressively form the bend or curve,

(3) sequentially further retarding and setting back the inner radius section of the member, by arranging the protrusion and the radius die so that a devious or indirect route is followed by the metal of the inner radius section,

(4) Coincidentally with (3), preforming the actual inside radius of the bend at a tangent angle opposite to the final angle of the bend, and while the outside radius section is unrestricted,

(5) sequentially, applying compressive force, in three directions simultaneously, to the outer radius section, to cause accelerated metal flow in that section.

A further explanation of these actions is as follows:

1) Retarding at prtrusi0n.-When the side of the metal member which is to become the inner radius side of the completed bend, is guided or confined by suitable toolin members into the form of a standing wave or protrusion, resistance to the compressive advancement of the metal member by the tooling or die member, causes the metal of the inner radius side to widen out, and gather up, and consequently to slow down before passing beyond the protrusion, thus effecting a setting back of that side relative to the opposite side, which is to become the outer radius side of the bend.

(2) Increase in total cross-secti0nal.-Additionally, the widening out and gathering up of metal in the protrusion serves to create an increased total cross-sectional area in the metal member, from which metal can later be directed compressively, under controlled extrusion-type orifice conditions, into the desired bend or curve configuration, Without reducing the member below its original dimen sions.

(3) Further retarding inner radius side by creating a devious path-A further retarding of the inner radius side relative to the opposite side is developed by positioning the radius die immediately beyond the protrusion so that a further change is caused in direction of the path of travel taken by the inner radius side of the metal rnember, which requires that this side must travel a longer distance than the opposite side.

(4) Preforming inner radius.l ressures controlled by the position of guide blocks, guide rolls, or mandrel relative to the radius die, compressively create the sharp curvature of the inside radius of the bend, at a tangent angle opposite to the final angle of the bend, this being accomplished while the guide members, mandrel, radius die and other tooling members are so positioned that the opposite side is free to continue in a straight path or actually joggle slightly away from the final direction of bending, thus permitting this critical part of the bend to be formed wtihout wrinkling, thickening, or distortion. The pressure caused by the resistance of the metal to the changed direct-ion augments the force exerted by the guide roll or mandrel suificiently to create the inside radius configuration on the metal without causing appreciable diminishing of the cross-sectional area at this point.

Increasing rate of metal flow in outer radius section by multiple angular forces-43y placing a pressure die angularly in the path of travel of the metal member, and in proper relationship to the radius die, the outer radius section of the metal member is turned in the direction of the bend, and the cross-sectional area of the member is reduced back down to original size (or such other dimension as may be desired within practical limits). This restrictive change in direction of the member results in the metal of the outer radius section being acted on simultaneously by three compressive forces, as follows:

(a) From directly behind, as a result of the movement of the means advancing the member.

(b) From the restrictive, angularly placed pressure die, which is acting to turn the metal member at an angle relative to the original direction of member movement, and reduce it in cross-sectional area,

(c) From the thickened middle section of the member, which was created by the forming of the protrusion, and which is now impelled by the inner radius section in a direction causing this metal to impinge on the redirected course of the metal of the outer radius section. The inherent stiffness of the metal acts to prevent this middle section metal from returning to rejoin the inner radius section (from which it was evolved in the formation of the protrusion) and carries it toward the outer radius section, of which it becomes a contiguous part. The action of the three compressive forces just described cause a relative increase in the rate of travel of the metal in the outer radius section, in somewhat the same man ner as a cone-shaped charge in explosive practice causes an increased speed of explosive force. known as the Monroe effect. The coordinated action of the three forces and the flow pattern cause an increased flow rate, while the forward motion of the metal of the middle section acts to prevent thinning. The result is that the outer radius section of the completed bend has been lengthened compressively with controlled dimensional characteristics.

Refinements of the new method include supporting the member opposite the protrusion to prevent side deflec tion thereof, exerting compressive side loading on the member in a direction toward the axis about which the member is turned or bent and at a preferred angle with respect to a normal to the direction of initial member advancement, the normal extending through that axis, compressively side loading the permanently turned portion of the advancing member to control the degree of final turning, and pulling the permanently turned portion of the advancing member around the axis of turning with sufficient tension normally below the yield point of the metal, to control the size of the protrusion formed by the metal, and to control the radius of the finished bend.

Other features and objects of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following detailed description of the drawings, in which:

FIG. 1 is an elevation showing an elongated metallic plate being formed or bent in accordance with the methods of the invention;

FIG. 2 shows sections through plate, rod and tube members which may be bent or turned in accordance with the present methods;

FIG. 3 is an enlarged elevation illustrating the application of compressive loading on the metal member and the path taken by the metal of the member as it is bent or turned;

FIG. 4 is a view similar to FIG. 1 showing a tube being bent or turned by somewhat modified apparatus;

FIG. 5 is a section taken on line 55 of FIG. 4;

FIG. 6 is a view similar to FIG. =1 illustrating another modified method of bending or turning a plate member; and

FIG. 7 is a section showing tube being engaged by a concavely curved forming means.

In FIG. 1, the elongated metal member 10 is shown being compressively advanced in the direction of arrow 11 by the plunger 12 hydraulically actuated by pressure within cylinder 13; the member 10 comprising for example a plate as shown at 14 in FIG. 2. The principles of the present method are equally applicable to rod and tube members shown at 15 and 16 in FIG. 2, and are discussed in terms of a plate as regards FIGS. 1 and 3 merely for purposes of illustration.

The plate member 10 is advanced between what may be termed a radius roll 17 about the axis 18 of which the member is permanently turned or bent, and a larger pressure roll 19 opposite from radius roll 17 in the direction of initial member advancement, as will be described. The metal member is first acted upon by the radius roll which retards advancement of the metal at the upper side 20 of the member so that the retarded metal is compressed beyond its yield point and protrudes at 21 in the form of a standing wave. In addition, the radius roll compres sively side loads the forward slope 22 of the protrusion beyond its yield point and in a direction toward the directly opposite side portion 23 of the metal member with the result that the retarded metal at the forward slope of the protrusion is laterally compressively displaced. In the case of tube members, the retarded metal is thus displaced in directions as shown by arrows 24 in FIG. 2 toward the opposite outer side portion 23 of the member.

The member opposite or underside 25 in general advances in the direction of member elongation over a sup port roll 26 which does not compressively load said side beyond its yield point, following which said side is compressively loaded by the forming roll 19 beyond the metal yield point and in a direction toward the radius roll 17 and the retarded metal 27 at the member side advancing forwardly of the protrusion 21, so that the loaded portion 28 of the member is permanently turned away from the direction of advancement 11.

Extending the description to FIG. 3, stationary dies 29 and 129 having fiat surfaces 3t? engaging the outer side 25 of the metal member are substituted for the rolls 19 and 26 but otherwise the elements remain the same as described in FIG. 1, and the method remains the same in both FIGS. 1 and 3. Compression induced relative slippage of a typical block section of metal generally indicated at 31, during formation of the turn, is illustrated by the subsequent relative locations of greatly enlarged body centered cubic crystals 131 of the metal in the block section as it progresses around the bend. Thus, broken line IR-OR shows a reference alignment of metal molecules at the front of the block section sufficiently in advance of the protrusion 21 that said line is normal to the direction of application of the force F parallel to the initial advancement direction indicated at 11. Broken line IR OR illustrates a subsequent position of the front, the metal at outer radius point 0R being relative ly advanced beyond the metal at 1R at the upper side 24 of the member. Thus, the IR, metal is shown as being relatively retarded by the compressive action of the radius roll 17 upon the forward slope 22 of the protrusion 21, the compressive gathering of retarded metal forming the protrusion in wave shape as shown. With the size of the protrusion controlled, as will be described, it will remain as a standing wave in the metal.

The broken line OR IR extending between the lower and upper sides of the member 10 as it is fed through the restricted opening between the roll 17 and die 2? shows that the metal at the member outside has greatly advanced relative to the retarded metal at the upper side of the member and relatively more than the degree of advancement illustrated by line OR lR the broken line O-R IR also shows that the outside of the block section front has disengaged the die 39 while the inside of the front remains compressively engaged by the radius roll. Arrows 33 and 34 illustrate the application of side loading exerted by the radius roll and the die on the upper and lower sides on the metal member 10 and productive of formation of the turn 32.

It will be observed in FIGS. 1 and 3 that the thickness of the member between the upper and lower outer sides thereof at the turn 32 and at the initially nondeformed advancing portion of the member are approximately the same, showing that the member has been turned or bent to a predetermined degree without reducing its overall thickness. At the same time, deformation of the member has been carried out as explained in the introduction, so as to squeeze out and accelerate the flow of metal at the outer radius side of the member through creation of a middle section 68 at the protrusion 21 that squeezes against and becomes a contiguous part of the flattened outer radius section 61, broken line 62 demarking the boundary therebetween by the application of compressive loading so as to provide uniformly distributed metal motion with minimum strain concentrations or work hardening of the metal. By varying the clearance space between the forming die 29 and the radius roll 17, the thickness (or diametric size) of the member may be controlled to less than, or slightly more than, the original thickness or size. in the case of plate or rod, initial starting or formation of the protrusion 21 required for retarding the metal at the upper side 26 of the member may be carried out by decreasing the relative distance between the radius roll and the die 23 when the member forward end is initially fed between these forming devices, and then when the protrusion has been formed the radius roll may be retracted slightly away from the die, or vice versa, so as to maintain the desired thickness relationship of the member at the formed turn 32 and at the undeformed portions of the member.

By the present method it is possible to lengthen compressively the outer radius side of the member by without thinning of the overall member thickness at the resultant bend. If for example 30% thinning is tolerable, then it is possible to lengthen the outer radius side by 200%, all the bending forces being compressive.

In FIG. 1, the permanently turned portion 32 of the member 10 is shown to have a curvature of less than that of the radius roll, with a slight gap 34 developing between the turn and said roll as the turn proceeds around the roll. A pair of control rolls 35 are shown compressively loading the outer side of the permanent turn so as to accurately control the final radius or curvature of the turn. In practice, the approximate optimum direction of application of side loading by the die 29 or roller 19 so as to produce the turn 32; is such that its angularity with a normal to the initial member advancement direction extending through the axis 18 about 28, as shown in FIG. 3. However, this angle may vary with different metals, thicknesses, ductility, degree or radius of bend, from about 10 to about 50.

The control of the size of protrusion 31 may be obtained by positively driving the radius roll 17 or the fenning roll 19 or die 29 substituted therefor, or both. Alternatively, the forward end portion of the member 10 turning around the radius roll may be clamped at 44 by an arm 41 that is positively driven as shown in FIG. 6 to pull the bend or turn around the axis of the radius roll 17. FIG. 6 also illustrates a plate it} being driven in the direction of advancement thereof by a large number of power rollers 42 disposed at intervals along the direction of plate advancement both above and below the plate to frictionally engage its opposite sides. The use of a number of rollers 42 for advancing the plate permits a reduction in the amount of normal force required to be exerted by each roller against the side of the plate and below the yield point of the plate metal, without sacrificing the desired total force exerted on the plate in the direction of advancement for securing the formation of the turn 32. A forming shoe 43 substituted for a forming roller constitutes the final change in the turn forming apparatus, the shoe having a curved forming surface 44 for exerting compressive loading on the outside of the plate over a considerable portion thereof.

In FIG. 4, a tube 45 is shown being subjected to the turn forming operation or method constituting the present invention. A protrusion 21 is formed at the tube upper side by the guiding action of a mandrel 46 extending within the tube and having a suitable guide protrusion 47. The mandrel protrusion does not act to stretch the tube metal beyond its yield point but merely guides it as the metal gathers compressively to form the desired shaped protrusion. In addition, the forward end 49' of the mandrel guides the tube metal being compressively side loaded by a platform die 59 serving the same function as the forming roller 19 in FIG. 1. This platform is mounted on rollers 51 so that it moves with the tubing being permanently turned and thereby eliminates sliding fraction which would otherwise exist at the platform and tubing interface. Finally, a pair of control rollers 35 compres- 7 sively side load the tubing in the manner discussed in FIG. 1.

So as to properly shape the tubing being permanently turned or bent by the action of the radius roller 17 and the platform, each of these latter elements may have concavely curved or specially shaped, surfaces 53 with curvature similar to that of the tubing curvature as shown in FIG. 7.

I claim:

1. The method of forming a turn in an elongated metal Work member having elongated opposite sides, that includes advancing the member in said elongated direction, retarding metal advancement at one side of the member traveling in said direction relative to metal advancement at the opposite side thereof so that retarded metal is compressed beyond its yield point and protrudes at said one side, and side loading the member beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said member one side forwardly of the protrusion so that the member is permanently turned away from said direction of advancement, and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

2. The method of forming a turn in an elongated metal work member having elongated opposite sides, that includes compressively advancing the member in said elongated direction, retarding metal advancement at one side of the member traveling in said direction relative to metal advancement at the opposite side thereof so that retarded metal is compressed beyond its yield point and protrudes at said one side, side loading the forward portion of the protrusion beyond its yield point and in a direction toward said member opposite side, and side loading the mem ber beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said member one side forwardly of the protrusion so that the member is permanently turned away from said direction of advancement, and so that the turned member has thickness less than the maximum member thickness at said protrusion, and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

3. The method of forming a turn in an elongated metal member having elongated opposite sides, that includes simultaneously compressively advancing the member in said elongated direction, retarding metal advancement at one side of the member traveling in said direction relative to metal advancement at the opposite side thereof so that retarded metal is compressed beyond its yield point and protrudes at said one side, side loading the member beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said member one side forwardly of the protrusion so that the member is permanently turned away from said direction of advancement, and pulling the permanently turned portion of said member with sufficient tension below the yield point of the metal to control the size of said protrusion, and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

4. The method of forming a turn in an elon ated metal member having elongated opposite sides, that includes advancing the member in said elongated direction, rolling one side of the advancing member traveling in said direction to retard metal advancement at said side relative to metal advancement at the member opposite side so that retarded metal is compressed beyond its yield point and protrudes at said one side and also to side load compressively the forward portion of said protrusion beyond its yield point and in a direction toward said member opposite side for laterally displacing said retarded metal, and side loading the member beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said member one side forwardly of said protrusion so that the member is permanently turned away from said direction of advancement, and so that the turned member has thickness less than the maximum member thickness at said protrusion and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

5. The method of claim 4 including supporting the opposite side of said member relatively in advance of the protrusion.

6. The method of claim 4 comprising exerting said side loading on the member advanced opposite side in a direction toward an axis about which said member is turned.

7. The method of claim 6 comprising exerting said side loading at an angle of between 10 and 50 degrees with respect to a normal to the member initial advancement direction extending through said axis.

8. The method of claim. 4 in which side loading said opposite side of the advancing permanently turned portion of said member is directed generally toward an axis about which said member is turned to accurately control the degree of final turning.

9. The method of claim 4 including pulling the permanently turned portion of the advancing member around the axis of turning with sufficient tension below the yield point of the metal to control the size of said protrusion.

10. The method of claim. 4 including compressively advancing said member by compressively rolling without permanently deforming said opposite sides thereof in said direction and in advance of said protrusion.

11. The method of forming a turn in an elongated metal plate having elongated opposite sides that includes advancing the plate in said elongated direction, rolling one side of the advancing plate traveling in said direction to retard metal advancement at said side relative to metal advancement at the plate opposite side so that retarded metal is compressed beyond its yield point and protrudes at said one side and also to side load the forward portion of said protrusion beyond its yield point and in a direction toward said plate opposite side for laterally displacing said retarded metal, and side loading the plate beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said plate one side forwardly of said protrusion so that the plate is permanently turned away from said direction of advancement and maintaining the protrusion while the plate is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the plate and at a location therealong beyond which the advancing plate commences to turn permanently.

12. The method of forming a turn in an elongated metal rod having elongated opposite sides that includes advancing the rod in said elongated direction, rolling one side of the advancing rod traveling in said direction to retard metal advancement at said side relative to metal advancement at the rod opposite side so that retarded metal is compressed beyond its yield point and protrudes at said one side and also to side load the forward portion of said protrusion beyond its yield point and in a direction toward said rod opposite side for laterally displacing said retarded metal, and side loading the rod beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said rod one side forwardly of said protrusion so that the rod is permanently turned away from said direction of advancement and maintaining the protrusion while the rod is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the rod at a location therealong beyond which the advancing rod commences to turn permanently.

13. The method of forming a turn in an axially extending metal tube having elongated opposite sides, that includes advancing the tube in said axial direction, rolling one side of the tube traveling in said direction to retard metal advancement at said side relative to metal advancement at the tube opposite side so that retarded metal is compressed beyond its yield point and forms an enlarged protrusion at said one side and also to load the forward portion of said protrusion beyond its yield point and in a direction toward said tube opposite side for laterally displacing said retarded metal, and side loading the tube beyond its yield point and at the advanced opposite side thereof in a direction toward retarded metal at said tube one side forwardly of said protrusion so that the tube is permanetly turned away from said direction of advancement and maintaining the protrusion while the tube is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the tube at a location therealong beyond which the advancing tube commences to turn permanently.

14. The method of claim 13 including supporting the bore of said tube at said protrusion for retardation of said metal by compressive rolling thereof.

15. The method of forming a short radius bend at a selected location along an elongated metal member having elongated opposite sides without stretching or thinning the outer radius section, or thickening, wrinkling or distorting the inner radius section, and wherein original cross-sectional dimensional characteristics can be retained or otherwise controlled as desired, and wherein a preferred metal microstructure can be maintained, free from undesirable residual tension stresses, and with desirable, uniformly distributed, minimum residual compressive stresses, that includes advancing the metal member in said elongated direction principally by applying mechanical force in the direction of member advancement and at a point preceding the area in which the forming is to be done, retarding advancement of one side of the metal member relative to advancement of the opposite side of the member in such a manner that the retarded metal is compressed beyond its yield point and gathers at said one side into a protrusion of increased metal cross-sectional area, further advancing the metal member in the same continuing elongated direction and side loading the advanced opposite side of the metal member beyond the yield point of the metal and in a direction toward the retarded metal of the member one side forwardly of the protrusion, further advancing the metal member and continuing to side load the said advanced opposite side so that said opposite side and also the one side are guided into a restricted opening of less cross dimension than the cross-dimension which the metal member acquired during said gathering, and further advancing the metal member through said restricted opening and compressing said member therein to accelerate member advancement at said opposite side relative to said one side, and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

16. The method of forming a short radius bend at a selected location along an elongated metal member having elongated opposite sides without stretching or thinning the outer radius section, or thickening, wrinkling or distorting the inner radius section, and wherein original cross-sectional dimensional characteristics can be retained or otherwise controlled as desired, and wherein a preferred metal micro-structure can be maintained, free from undesirable residual tension stresses, and with de sirable, uniformly distributed, minimum residual compressive stresses, that includes advancing the metal member in said elongated direction principally by applying mechanical force in the direction of member advancement and at a point preceding the area in which the forming is to be done, retarding advancement of one side of the metal member relative to advancement of the opposite side of the member in such a manner that the retarded metal is compressed beyond its yield point and gathers at said one side into a protrusion of increased metal cross-sectional area, subsequently further advancing the metal member and side loading the said one side at a point contiguous with and beyond the protrusion, so that the metal of said one side is compressed beyond its yield point into a curved configuration similar to the curved configuration required for the inner radius side of the completed bend, allowing the member opposite side to advance free of side loading opposite the protrusion, further advancing the metal member in the same continuing elongation direction and, subsequent to preforming the said one side, side loading the advanced opposite side of the metal member beyond the yield point of the metal and in a direction toward the retarded metal of the member one side forwardly of the protrusion, further advancing the metal member and continuing to side load the advanced opposite side so that said opposite side and also the one side are guided into a restricted opening of less cross-dirnension than the cross-dimension which the metal member acquired during said gathering, and further advancing the metal member through said restricted opening and compressing said member therein to accelerate member advancement at said opposite side relative to said one side and maintaining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

17. The method of forming a short radius bend at a selected location along an elongated metal member having elongated opposite sides without stretching or thinning the outer radius section, or thickening, wrinkling or distorting the inner radius section, and wherein original cross-sectional dimensional characteristics can be retained or otherwise controlled as desired, and wherein a preferred metal micro structure can be maintained, free from undesirable residual tension stresses, and with desirable, uniformly distributed, minimum residual compressive stresses, that includes advancing the metal member in said elongated direction principally by applying mechanical force in the direction of member advancement and at a point preceding the area in which the forming is to be done, side loading one side of said member so that the metal of said one side is compressed beyond its yield point into a curved configuration similar to the curved configuration required for the inner radius side of the completed bend, allowing the member opposite side to advance free of side loading opposite the protrusion, further advancing the metal member in the same continuing elongation direction and, subsequent to preforrning the said one side, side loading the advanced opposite side of the metal member beyond the yield point of the metal and in a direction toward the retarded metal of the member one side forwardly of the protrusion, further advancing the metal member and continuing to side load the said advanced opposite side so that said opposite side and also the one side are guided into a restricted opening of less cross-dimension than the crossdimension which the metal member acquired during said gathering, and further advancing the metal member through said restricted opening and compressing said member therein to accelerate member advancement at said opposite side relative to said one side and main- 1 1 taining the protrusion while the member is advanced and side loaded to produce said turn and so that the protrusion exists only at said one side of the member at a location therealong beyond which the advancing member commences to turn permanently.

Williams May 1, 1934 Snell Apr. 9, 1935 12 Taylor Nov. 28, 1939 Taylor Nov. 12, 1940 Lignian June 10, 1941 Kepler Feb, 2, 1943 Ottie Aug. 17, 1943 FOREIGN PATENTS Germany Feb. 13, 1933 Great Britain July 21, 1932 Great Britain Nov. 9, 1936

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