Method of Incrementally Reducing and Stretch Straightening Shaped Metal Components

Abstract

A drawing unit with a segment reciprocating die for drawing metal segments comprises a tensioning device arranged to advance a shaped specimen through an array of dies that create a shaped orifice with the spacing formed between the dies. These dies segments act under the influence of a powered unit to move in a reciprocating motion that causes the spacings between segments to increase and decrease synchronously thereby shaping the metal segments.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention is directed to a method for shaping a metal component by cyclically striking the component with multiple reciprocating contact dies as the component is moved along a longitudinal axis relative to the dies.

Background of the Invention

The drawing of shaped specimens involves a die with a specifically shaped inlet and a pulling mechanism to advance, or “draw”, the shaped component through the die in order to force a cross sectional reduction of the shape. Significant levels of surface sliding occur under the compressive loading condition which occurs while in contact with the reducing die. The presence of frictional forces at this interface has two dominating negative implications. The first implication of friction is that it increases tension required for a given reduction and lowers the maximum reduction possible before tensile tearing or necking of the reduced portion of the specimen occurs. The second negative implication is that friction increases the occurrence of sliding defects on the surfaces, such as galling, tearing, or striations. As a result, the success of traditional drawing in delivering adequate “per pass” reductions and acceptable surface quality is tied to maintaining a low coefficient of friction between the die and the specimen.

Maintaining a low coefficient of friction is not always easy or possible, particularly when reducing pieces at elevated temperatures. The most common lubricants in drawing are oil or grease based, which have low thermal stability. Solid film type lubricants such as graphite also thermally degrade below the common hot working temperatures of many metals. As a result, effective lubricants are insufficient to enable effective drawing for many alloys that require deformation to occur at higher temperatures.

In U.S. Pat. No. 2,393,131 a lower observed friction coefficient in drawing is achieved by applying vibration to an otherwise static die geometry. In this, the orifice geometry is constant and fixed, and the entire die exhibits a small vibration. Contrastingly, in U.S. Pat. No. 3,585,832 regarding drawing, a cyclic tensile load was applied by the pulling mechanism to pull a specimen through a static die in order to lower the average tensile force required in drawing. Though both prior arts focus on lowering effective contact friction, the underlying sliding mechanics in the die remain in governance of the draw forces of the drawing process. As a result, difficulties in drawing materials at high temperatures with standard drawing will largely remain congruent, perhaps with marginal improvements from lower friction coefficients.

In U.S. Pat. No. 3,575,029 a roller-based reduction method resulting in higher reduction per pass of the specimen in comparison to simply rotating rollers is achieved by coupling rollers to series of linkages that results in a walking motion when driven by eccentric drives. This concentrates the contact pressures into a small area relative to the specimen transition zone as compared to a simply rotating roller. As a result, the total compressive forces within a given instant are lower and potential specimen per-pass reduction is higher. The shortcoming of the use of this device lies in the complexity and technical difficulty in building long lived rotating and sliding joints exposed to high temperatures for long periods. Operating rotating rollers at or near the temperature desired for difficult to work materials would require complex cooling or expensive connections to achieve operational reliability.

In U.S. Pat. No. 3,727,443 a series of ring—shaped arrays of spherical roller bearings were substituted for a static die to draw and reduce the cross-sectional area of tubes. The rings of spheres were rotated at given speeds while the part advanced through the contact area, while a static mandrel maintained the inner diameter sizing, thus imparting helical reduction of the exterior surface of the tube. Through control of speed and placement of the path of the helical contacts, with two sets of rollers of differing in number, complete reduction of the tube was achievable. While this was effective at lowering friction and in achieving an improved surface finish, the invention is only applicable to the deformation of tube structures. Additionally, the reduction was applied to portions of the cross section at a given time creating differential deformation through the reduction zone. Differential reduction can result in loss of straightness, residual stress, or even strain related microstructure defects in some materials such as shear banding.

Departing from inventions relating to drawbench design, the occurrence of reciprocating dies or hammers to reduce and reshape metal can be found in U.S. Pat. Nos. 391,825, 455,905, 1,180,296, and 2,114,302. All embodiments involved a radial arrangement of reciprocating dies to reduce or re-shape bar and simple shaped specimens. In U.S. Pat. No. 391,825 four radially arranged dies reshaped the end of a round bar. In U.S. Pat. No. 455,905 six alternating radially arranged dies with contact overlap were employed for reducing round material. In U.S. Pat. No. 1,180,296 several sets of radially arranged dies were placed in sequence to impart multiple reductions per pass of a bar or ingot. In U.S. Pat. No. 2,114,302 a radial arrangement of reciprocating dies was used specifically to reshape square metal bar into round metal bar. In all reciprocating die prior arts, the dies are all radially arranged with a common center to only work round, tubular, or other simple geometric shapes (i.e. squares, hexagons, octagons, etc.). This would not enable the imparting of reduction to specimens having complex cross sections of varying geometries. Thus, the prior arts fail to deliver a method to manufacture complex geometry specimen. Also, none of these arts present the coupling of a maintained tensile force on the outgoing material specimen for straightening and residual stress reduction. Failure to tension and/or stretch outgoing material forfeits the ability to straighten or stress relieve through tensile yielding, which results in subsequent and costly straightening processes.

In U.S. Pat. Nos. 535,446, 773,197 2,178,141, 2,999,405, 3,645,126, 3,728,890, and 4,229,963 reciprocating dies were also used in metalworking, however the focus of these arts lies on the arrangement and means of actuation.

In U.S. Pat. No. 535,446 a flexible connection was used to mount the dies to the powering device to allow transfer of die inertia through less constrained impact motions. The downside of this is that limited control exists on the stopping point of the dies. As such, specimen thickness control is diminished.

In U.S. Pat. No. 773,197 a force was imparted on floating dies by a lobed shaft on the back face of the die. This die actuation mechanism allows a high rate of die impulses with lower shaft rotating speed through the back striking of the contact dies. Management of specimen advance would be less consistent because die pieces have minimal position constraint when not under the influence of contacting lobe. This would result in varying reduction bites and potential for distortion in the specimen.

In U.S. Pat. No. 2,178,141 a series of radially arranged reciprocating dies with very long contact down the length of a metal tube straightens the material within the bite, or die clamping, while imparting a minimal level of cold forming reduction on the cross section. The extended length of reduction bite aims to straighten by yielding the pipe while constrained in the straight condition. This straightening technique with an exaggerated contact zone would provide extended contact time with the die material. Reducing the specimen cross section at elevated temperatures would lead to significant heating losses at the contact surfaces and non-uniform strain accommodation.

In U.S. Pat. No. 2,999,405 radially arranged dies were mounted to inwardly sloping supports that imparted compression when the dies slid down the support toward the shared intersection or convergence of all travel axes (plural). A shared actuator allows a high degree of control and consistency of the die reciprocation advancement for shared center architectures. However, this architecture does not allow flexibility to reduce intricate shapes, especially those requiring die reciprocation without a shared convergence point.

In U.S. Pat. No. 3,645,126 radially arranged dies were powered with a series of closed oscillating hydraulic circuits for each die. In the operation of the art at higher frequencies to boost productivity and minimize contact time, water hammering effect and friction heating of the fluid would degrade system performance. Additionally, the compressibility of the working fluid would limit the ability to have highly controlled die stop positions to deliver consistent thicknesses.

In U.S. Pat. No. 3,728,890 six radially arranged dies are physically coupled with flexible shafts for improved control and synchronization compared to prior pneumatic versions of 6 die bar reducers. The physical coupling of reciprocating dies is effective provided a fixed arrangement of reciprocating mechanisms are present, as is the case with this art's radial arrangement of dies. This fixed radial arrangement limits the specimen geometry to rounds with limited adaptability to other geometries.

In U.S. Pat. No. 4,229,963 inward compressions of dies were accomplished through a rotating support frame connected to the dies through connecting rods. This coupled advance design provides a coordinated advancement of the die tools in a radial arrangement. However, this architecture prevents forging of complex geometry specimen due to non-adaptive die motions.

An additional category of loosely related reducing machines exists which are categorized as walking die reducing machines. Unlike drawing based inventions where parts are drawn through a reducing die, in this category, various mechanisms are employed to generate a walking motion of a die along the length of a metal segment. This motion combines the compression and advancing action into a single motion. Patents for such mechanisms include: U.S. Pat. Nos. 1,549,527, 2,153,839, 3,114,276, 3,374,654, and 3,626,746. In U.S. Pat. Nos. 1,549,527, 2,153,839, 3,114,276, and 3,374,654 varying combinations of eccentrics and linkages are presented to generate compressive and axial translation motions of the contact dies onto the workpiece, heretofore called “walking motion”. In U.S. Pat. No. 3,626,746 one or more sliding wedge structures is coupled with eccentrics and levers to generate similar walking motions as other inventions with different mechanism architecture. In these walking motion prior arts, the combination of the compressive reduction action with axial advance results in the advance without any advancing device. As a result, the ability to apply a tensile force to reduced portion of the workpiece in order to stretch straighten finished product is not provided. As such, any distortion imparted during reduction of the specimen will require additional post processing to remove.

BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS

The present invention involves a device for physically reducing the cross section of a shaped component into a finished or near finished condition. The current invention utilizes a series of die segments that exhibit a synchronized reciprocation that imparts cross sectional reduction on a specimen. The segment shape and arrangement create the orifice between the segments to match the specimen being reduced. The arrangement and direction of reciprocation allows tailored opening and closing of specific gaps or spacing to uniformly reduce various specimen features in the reduction pass. The maintaining of tension on the material of the specimen that is exiting the die segments allows optimized tensile loading on the exiting material to yield the highest straightness possible.

When reciprocation is less than the total reduction, the piece is never fully out of the constraint of the die and the amount of specimen advancement is limited before re-engagement is established within the die. The case where reciprocation is more than the total reduction contact is temporarily lost with each reciprocation and highlights the next variant of embodiment.

When reciprocation is chosen to be larger than the total reduction or in cases where higher levels of tension are sought, as in the case with bulky sections, two opposing tensioning devices are used on the end of the specimen entering and exiting the dies. The back tension is insufficient to prevent the mechanism on the exiting material from advancing the specimen through the dies. In the variant where reciprocation is larger than the total reduction, this provides the means for maintaining constant tension on the specimen when die contact is lost during fully retracted states.

The decoupling of the magnitude of the tensile force from the amount of reduction allows for much higher reductions to be imparted per reduction pass, and a specified tensile force to be applied to optimize straightness and residual stress results in the reduced piece. This results in improved straightness and the ability to reduce the number of reduction passes required to yield the final, desired, specimen condition.

The present invention mechanism offers relatively high frequency and relatively small reciprocation travel to deliver very refined and concise final dimensions and surfaces. The high frequency offers high travel velocity of the specimen through the die, low contact times with dies, and more contacts with a given point on the specimen. The high precision of reciprocation travel of the eccentric mechanism and the electromagnetic actuator allow high levels of control of the thickness uniformity of the reduced specimen. The current invention delivers consistent advancement and therefore reduction under the influence of tension. Precision is achieved with each die segment and coordinated with electronic control mechanisms. The current invention allows independent positioning or retracting of the die segments. This offers the ability to adapt to varying shaped specimens as well as an open die array to allow easier loading and unloading of specimen to start reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:

FIG. 1 is a top view of a draw bench constructed in accordance with an embodiment of the present invention depicting a grasping and pulling device on the specimen exiting a series of synchronized reciprocating dies.

FIG. 2 is a cross sectional view of the drawn workpiece depicting the arrangement of synchronized reciprocating dies in the engaged position around a Tee-shaped product being one embodiment of the invention taken along the sight lines A-A of FIG. 1.

FIG. 3 is a cross sectional view of a reciprocating die mounted with an axial sliding constraint, being one embodiment of the reciprocating dies in the current invention utilizing a powered eccentric to generate the motion, taken along sight lines B-B of FIG. 2.

FIG. 4 is a schematic of an embodiment of the present invention showing a synchronized reciprocating die architecture to reduce a rectangular specimen.

FIG. 5 is a schematic of another embodiment of the present invention showing a synchronized reciprocating die architecture to reduce tubular specimen.

FIG. 6 is a schematic of another embodiment of the present invention showing a synchronized reciprocating die architecture to reduce round bar specimen.

FIG. 7 is a cross sectional view of the die architecture for reducing tubes shown in FIG. 5 taken along sight lines C-C.

FIG. 8 is a schematic of an embodiment of the present invention showing a synchronized reciprocating die architecture to reduce a Tee-shaped specimen with unconstrained shape extremities.

FIG. 9 is a schematic of an embodiment of the present invention showing a synchronized reciprocating die architecture to reduce a Tee-shaped specimen with partially constrained shape extremities.

FIG. 10 is a schematic of an embodiment of the present invention showing a synchronized reciprocating die architecture to reduce an asymmetric and unequal thickness specimen of non-uniform thickness with varying shape extremities.

FIG. 11 is a view of the die architecture, when the cam is at bottom dead center.

FIG. 12 is a view of the die architecture when the cam is at top dead center.

FIG. 13 is a view of the die architecture when the cam is in the next cycle bottom dead center position.

FIG. 14 is a view of the die architecture when the cam is in the next cycle top dead center position.

FIG. 15 is a cross sectional view of the drawn workpiece depicting the arrangement of synchronized reciprocating dies in the retracted position around a Tee-shaped product providing sufficient opening to enable uninhibited loading of said specimen prior to grasping, being one embodiment of the invention taken along the sight lines A-A of FIG. 1.

FIG. 16 is a cross sectional view of a reciprocating die, being one embodiment of the reciprocating dies in the current invention generating the reciprocation motion via an electromagnetic actuator, taken along sight lines B-B of FIG. 2.

FIG. 17 is a view of the die architecture, at bottom dead center of the cam, to illustrate the method that the cycling actions, equal to or larger than the total reduction, employs to reduce the Tee-shaped specimen.

FIG. 18 is a view of the die architecture structure when the cam is at top dead center.

FIG. 19 is a view of the die architecture when the cam is in the next cycle bottom dead center position.

FIG. 20 is a view of the die architecture when the cam is in the next cycle top dead center position.

FIG. 21 is a top view of an embodiment of the present invention showing a grasping mechanism for clamping the part while imparting a tensile load to the workpiece generated by a pneumatic or hydraulic cylinder.

FIG. 22 is a side view of an embodiment of the invention shown in FIG. 21.

FIG. 23 is a top view is a top view of a draw bench constructed in accordance with an embodiment of the present invention depicting a grasping and pulling device on the entry and exiting side of a specimen traveling through a series of synchronized reciprocating dies.

FIG. 24 is a top view of an embodiment of the present invention showing a grasping mechanism for clamping the part while imparting a tensile load to the workpiece generated by a linear actuator.

FIG. 25 is a side view of the embodiment shown in FIG. 24.

FIG. 26 is a top view of an embodiment of the present invention showing a grasping mechanism for clamping the part while imparting a tensile load to the workpiece generated by a powered gear drive.

FIG. 27 is a side view of the embodiment shown in FIG. 26.

FIG. 28 is a cross sectional view of a reciprocating die mounted on a pivot to constrain the die to only a reciprocation around the mounting axis, being one embodiment of the reciprocating dies in the current invention, taken along sight lines B-B of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The description of the device is intended for illustrative purposes and not to limit the scope of the invention in any way. Referring first to FIG. 1 there is a machine for tensioning and advancing a shaped specimen through an arrangement of synchronized reciprocating contact dies to reduce the specimen's cross-sectional area. The machine includes a powered jaw 30, attached to a supporting frame to allow the application of a tensile load to the reducing specimen. A jaw on a travelling carriage is the preferred and most common means used in draw bench applications; however, any suitable means of applying tension to exiting material after the reducing dies is compatible with the invention. The specimen, 32 is advanced under tension through an architecture of at least one reciprocating contact die, modules 34, to impart reduction into the specimen during the closing portion of the stroke and to allow axial advancement during the retraction portion of the stroke. In embodiments where two or more reciprocating dies are present, they will be synchronized to compress and retract in unison. The reciprocating die(s) are mounted by a mounting member to transfer loading to the shared frame with the jaw carriage.

Referring to FIG. 2, the arrangement of the reciprocating die modules is shown to form the primary surfaces to reduce a Tee-shaped specimen 32. The contact dies 36 are arranged to form the desired shape with the spacing between the contact faces of the dies. The dies can be made with varying profiles of the contact face to facilitate varying convex, flat, or concave surfaces of shaped components. The axis of reciprocation travel, upon which the die reciprocation 40 lies, is selected to provide a desired reduction imparted into shape segments through the opening and closing of the spacing between the die contact faces. The contact dies are mounted to a translating carriage driven by suitable means to generate a reciprocating motion. In this embodiment an electric motor 42 drives an eccentric shaft 44 inside of the module. In this embodiment the motor rotation is synchronized electronically through a control algorithm. This embodiment also demonstrates a means of opening or retracing the entire module containing the reciprocation mechanism and mounting 34 in and out by means of a hydraulic cylinder 130 attached to the module. The guiding and stop position of the modules when in the closed or advanced position, as this figure illustrates, is constrained by a slotted mount frame 132. During the reduction of specimen 32 the hydraulic cylinders 130 maintain sufficient force to ensure modules 34 remain in contact with the hard stops on the slotted mount frames 132.

Referring to FIG. 3. the die module in this embodiment generates axial reciprocation motion through the powered eccentric shaft 44, in order to reduce the Tee shaped specimen 32. A connecting rod 46 couples the reciprocating carriage 48 with the eccentric shaft. In the preferred embodiment the contact dies 36 are mounted directly to the reciprocating carriage. However, the use of intermediary mounting structures for load distribution, heat flow management, or other functional reasons may be desired. The reciprocating carriage is constrained to axial travel by sliding journals 50 surrounding the sides of the carriage. The sliding journals are mounted in a supporting frame 52 to which the eccentric shaft is also mounted. Coupled with this reciprocating die motion a tensioning device 30 provides axial advance and tension force 54 to the Tee-shaped specimen 32.

Referring to FIG. 4 in one embodiment a four radial die arranged in pairs 56 and 58 architecture can be used to reduce square or rectangular cross—sectional material 60 in the device. In some embodiments the amount of reduction in one directional pair 56 may impart differing strain than in perpendicular directional pair 56. In some embodiments one pair may have negligible lead in and reciprocation travel may be minimal merely to inhibit widening and allow unrestricted advancement via tension through the retract portion of the die cycle.

Referring to FIG. 5 an embodiment of the invention is shown to allow reduction of tube structures 62. In this embodiment at least two radially arranged dies with concave contact face contours 64 are present to impart reduction of the outside surface of the tube structure. A small gap will be present between the contact OD outside diameter contact dies 66. In some embodiments this will form a small raised seam at this interface. In some embodiments the tensioning device imparts adequate rotation upon advance to allow subsequent die contact cycles to smoothen the raised seam resulting from prior contact. In this embodiment a sufficient flat land of the die would be present to fully smooth any remnant of a raised seam in the material. A mandrel 68 is supported from the entry side of the drawing bench mechanism to provide form to establish the inside surfaces of the tube.

Referring to FIG. 6 an embodiment is shown reducing a round bar or wire specimen 70 with three radially arranged synchronized reciprocating dies 72. In some embodiments the specimen may be simply advanced through the reciprocating dies resulting in a raised seam that may need to be removed. In the preferred embodiment a slight rotation around the axial line of travel would be coupled to each axial advancement of the specimen following each reciprocation compression cycle. In this embodiment there is a sufficient flat portion on the die extending past the reduction throat to provide a sufficient overlap to smooth the entire OD surface.

Referring to FIG. 7 the embodiment of the invention which enables the reduction of a tube-shaped specimen. In this embodiment tube specimen 62 are loaded around a static mounted mandrel 68 on the entry side of the synchronized reciprocating dies 64. On the exiting side of the reciprocating dies a powered jaw 74 is present to maintain the reduced section of material under tension and advance the material forward 76. In the preferred embodiment the mandrel would have a forward tapering mandrel to allow free advancement of the piece without sliding on the mandrel surface. In some embodiments the mandrel may be un-tapered provided the friction between the tube and the mandrel is managed to prevent surface defects due to sliding. In all embodiments of this invention tensile forces on exiting material from a drawing action must be present to stretch straighten the component.

Referring to FIG. 8 the embodiment of the invention with the shown die arrangement is used to reduce a Tee-shaped specimen 78 with unconstrained extremities 80. In this embodiment the material at the extremity of the shape would have lower quality surfaces and may require trimming before use as a finished component. The need for end constraints on the reciprocating dies 82 is governed by the predictability and magnitude of widening or outflow of shape extremities. This type of end constraint is considered within the confines of the proposed invention for all conceivable shaped reduction arrangements.

Referring to FIG. 9 the embodiment of the invention with the shown die arrangement is used to reduce a Tee-shaped specimen with partially constrained shape extremities 84. Partial constriction of die spacing 86 beyond the shape on the reciprocating dies 88 allows the mitigation of material outflow—acting perpendicularly to the line of travel—of the extremities during reduction. This type of end constraint is also considered within the confines of the proposed invention for all conceivable shaped reduction arrangements.

Referring to FIG. 10 an embodiment of the invention is shown of an irregular shape 90 that demonstrates the versatility of the proposed invention. In this architecture varying feature thicknesses exist across the section. The current embodiment also demonstrates opening 92 and partially closed end constraints 94 simultaneously on reciprocating die 96 contact faces, as either is considered within the confines of the outlined invention. This shape also demonstrates variation of placement of different features of the shape. In this embodiment the axis of advance 98 of the different synchronized reciprocating die segments do not share a common center or intersect. In a preferred embodiment the axis of advance is selected to deliver comparable levels of strain in varying segments of a shape. In thicker segments 100, the stroke of the reciprocating dies should be proportionally larger than for thinner segments 102 to impart comparable strains and prevent distortion. However, since the presence of a tensile force is present extant for all embodiments of this invention, a means of correcting any distortion is present through the tensile stretching of the specimen. As a result, equal strain in each segment is preferred but not required.

Referring to FIGS. 11, 12, 13, and 14 a time varying cross-sectional view of the opposing die segments 104 reducing a leg of a Tee-shaped specimen 78 is shown. In this embodiment axial tensile loading is placed on the exiting specimen with a tensioning device 30, possessing a means for grasping 1. In each time position the state of the eccentric crank shaft at bottom dead center 106 and top dead center 108 is shown to illustrate whether the die is in the compressed or the retracted state of the reciprocation cycle. In the fully compressed state, a plane demarking the beginning 110 and end 112 of the zone of first deformation in the specimen is shown. In the retraction state shown in FIG. 12 following a compression the specimen is allowed to advance a distance a portion of the way through the total previous bite—or die compression onto the specimen—114. In the next compression cycle shown in FIG. 13 the beginning 116 and end 118 of the second deformation zone is shown in relation to the boundaries of the previous zone. In the subsequent retraction state shown in FIG. 14 the specimen and prior bites are allowed to advance a specified amount 120 to reposition within the upcoming bite region. The magnitudes of these axial advancements area a function of the reciprocation die stroke 122 and the die lead in geometry. Subsequently, the speed that a specimen will travel through the reciprocating reducing die will generally be in proportion to the frequency of reciprocation assuming that the reciprocation stroke and geometry remain constant. In the preferred embodiment each point along the length will be reduced under the influence of several overlapping reciprocation reductions. In this the preferred embodiments of the invention the reciprocation travel or stoke 122 is less than half of the total reduction 124 of the specimen which provides inhibition of unconstrained advancement of the specimen without the need for added devices to constrain advancement through the reciprocating die segments.

FIG. 15 depicts the same machine architecture as described in FIG. 2 with the exception that the means for loading is demonstrated. The retraction of the hydraulic cylinders 130 results in an opening of reciprocating modules 34 and subsequent contact dies 36. This opening is to be sufficient to pass a segment of specimen through in order to be engaged by a grasping mechanism on the exit side of reciprocating dies in order to impart axial tensile force to straighten and advance the specimen. Even in the retracted state the die segment modules 34 are still under the constraining influence of the slotted mount frame 132. In this embodiment the reciprocation motion of the dies 36 would be active as the hydraulic cylinders 130 advanced the module structure 34 to the final stop position prior to drawing the specimen through the reciprocating die architecture.

Referring to FIG. 16 the die module in this embodiment generates axial reciprocation motion through an electromagnetic impulse generator 134, in order to reduce the Tee-shaped specimen 32. The impulse generator is secured to the module supporting frame 52. In the preferred embodiment the contact dies 36 are mounted directly to the reciprocating carriage 48. However, the use of intermediary mounting structures for load distribution, heat flow management, or other functional reasons may be desired and are congruent within the scope of the present invention. The reciprocating carriage is constrained to axial travel by sliding journals 50 surrounding the sides of the carriage. The sliding journals are mounted in a supporting frame 52 to which the eccentric shaft is also mounted. Coupled with this reciprocating die motion a tensioning device 30 provides axial advance and tensile force 54 to the Tee-shaped specimen 32.

Referring to FIGS. 17, 18, 19, and 20 a time varying cross-sectional view of the opposing die segments 104 reducing a leg of a Tee-shaped specimen 78 is shown. In this embodiment of the invention the reciprocation travel or stoke 122 is more than half of the total reduction 124 of the specimen which would otherwise result in the complete disengagement and loss of the required tensile force resulting in the unconstrained advancement of the specimen. In this embodiment a primary tensioning device 126 will be present on the exiting side of the apparatus. A secondary tensioning device 128 will be present on the entry side of the synchronized reciprocating dies to ensure that a continuous tensile force is applied to the specimen and to meter the rate of advancement of the specimen between the compressive strokes of the synchronized reciprocating die segments. In each time position the state of the eccentric crank shaft at bottom dead center 106 and top dead center 108 is shown to illustrate whether the die is in the compressed or retracted state. In the fully compressed state, a plane demarking the beginning 110 and end 112 of the zone of first deformation in the specimen is shown in FIG. 17. In the retraction state following a compression the specimen is allowed to advance a portion of the way through the total previous bite 136 as shown in FIG. 18. In the next compression cycle shown in FIG. 19 the beginning 116 and end 118 of the second deformation zone is shown. In the subsequent retraction state shown in FIG. 20 the specimen and prior bites are allowed to advance a specified amount 136 to reposition within the upcoming bite region. The magnitudes of these advancements are a function of reciprocation die stroke and die lead in geometry. It is desired that each point along the length of a specimen will be reduced under the influence of several overlapping reciprocation reductions. In this embodiment the advancement per reciprocation and subsequently the velocity through the reciprocating dies is dictated by the conjoined travel of the primary tensioning device 126 and secondary tensioning device.

Referring to FIGS. 21 and 22 a top and side view of one of the embodiments of the tensioning device employed by the invention is shown. In this embodiment the specimen exiting the reciprocating reducing dies 32 is partially inserted into the body of the grasping mechanism 138. Inside the grasping mechanism a cam style clamping mechanism 142 is rotated by a hydraulic cylinder 140 to compress all or portion of the specimen in order to prevent the exit of the specimen. The grasping mechanism is powered by a double acting cylinder 144. In some embodiments the available cylinder 144 is actuated with pressurized air. In some embodiments the cylinder 144 is actuated with pressurized hydraulic fluid.

Referring to FIG. 23 another embodiment of the invention is shown where an exit tensioning device 126 and an entry back tensioning device 128 maintain the specimen in tension and while advancing a shaped said specimen through an arrangement of synchronized reciprocating contact dies to reduce said specimen's the specimen cross-sectional area. This architecture of the invention is generally but not necessarily correlated with the die reciprocation depicted in FIG. 11 where the dies completely disengage from the specimen at certain points of reciprocation. The machine includes a primary tensioning specimen device on the exiting specimen 126 and a secondary—back tensioning—device on entering material 128 attached to a supporting frame to allow the application of a tensile load to be applied to the reducing specimen. The specimen 32 is advanced under tension through an architecture of three reciprocating contact die modules 34 to impart reduction into the specimen during the closing portion of the stroke and to allow axial advancement during the retraction portion of the stroke. In embodiments where two or more reciprocating dies are present, they will be synchronized to compress and retract in unison. The reciprocating die(s) are supported in an architecture to form a desired shape of the specimen during reduction.

Referring to FIGS. 24 and 25 a top and side view of an embodiment of the tensioning device employed by the invention is shown. In this embodiment the specimen exiting the reciprocating reducing dies 32 is partially inserted into the body of the grasping mechanism 138. Inside the grasping mechanism a cam style clamping mechanism 142 is rotated by a hydraulic cylinder 140 to compress all or a portion of the specimen in order to prevent the exiting of said specimen. The grasping mechanism in this embodiment is powered by a mechanical belt driven linear actuator 146. In some embodiments a dampening mechanism such as the depicted air spring 148 can be mounted between the grasping mechanism and the powering device to provide a more continuous tensile load regardless of interrupted advancement of the specimen.

Referring to FIGS. 26 and 27 a top and side view of an embodiment of the tensioning device employed by the invention is shown. In this embodiment the specimen exiting the reciprocating reducing dies 32 is partially inserted into the body of the grasping mechanism 138. Inside the grasping mechanism a cam style clamping mechanism 142 is rotated by a hydraulic cylinder 140 to compress all or portion of the specimen in order to prevent the exiting of the specimen. The grasping mechanism in this embodiment is powered by carriage 150 sliding down a guide rail 152. A motor 154 driving one or more pinion gears 156 along one or more rack gears 158 provides advancing force to the carriage 150. In this embodiment a dampening mechanism such as the depicted air spring 148 can be mounted between the grasping mechanism and the powering device to provide a more continuous tensile load regardless of interrupted advancement of the specimen.

Referring to FIG. 28 a cross-sectional view is shown of another embodiment of the die module which generates reciprocating motion through the powered eccentric shaft 44, in order to reduce the Tee-shaped specimen 32. A connecting rod 46 couples the reciprocating carriage 48 with the eccentric shaft. In the preferred embodiment the contact dies 36 are mounted directly to the reciprocating carriage. Just as in other embodiments the use of intermediary mounting structures for load distribution, heat flow management, or other functional reasons may be desired and are congruent within the scope of the present invention. The reciprocating carriage is constrained constrains the reciprocating motion by a mounting pivoting shaft 160 coupled to the reciprocating carriage 48 with a swing arm 162. In this embodiment the reciprocation motion 164 of the contacting dies 36 is not axial but a function of angular rotation around the mounting pivot shaft 160 resulting in a level of rotation component in the reciprocation. This rotation component is not necessary for the operation of the reciprocation dies however small levels of rotation resulting from small reciprocation travel driven by the eccentric and sufficiently long support arms is still considered within embodiments of the invention. The mounting pivot shaft is mounted in a supporting frame 52 also in which the eccentric shaft is also mounted. Coupled with this reciprocating die motion a tensioning device 30, provides axial advance and tension force 54, to the Tee-shaped specimen 32.

The present invention is an improvement of the drawing process or a drawbench device with the use of an array of synchronized reciprocating dies to input compressive work into the cross section of a shaped component that is maintained in position under a desired tension.

The oscillating motion reducing the metal sections provides alleviation for the tendency of the traditional drawing process to result in surface defects resulting from the workpiece being slid through static tapered dies. In the described innovation, deformation occurs as the synchronized oscillating dies close in on one another while the specimen experiences diminished axial advancement due to the tension being insufficient to advance the component through the die under compression. As the dies are allowed to retract on the other portion of the reciprocation cycle, the component is allowed to advance through the bite of the die under lower or absent contact pressure. This diminished sliding during high contract pressure and advancement during lower or zero contact pressure minimizes surface sliding defects during drawing, particularly for galling sensitive materials and during drawing at high temperatures. This invention reduces the requirement of highly effective friction reducing lubricants and allows processing of difficult to lubricate materials and utilization of processing temperatures above the availability of effective drawing lubricants, enabling new product offerings.

The reduction of simple bar such as rounds, squares, rectangles, and tubes can be accomplished enveloping the periphery of the shape exterior with reciprocating dies as shown in FIG. 1. A small gap would exist at the locations where dies meet to allow independent motion. Tubes would require the use of static mandrel on the interior of the tube to yield internal surfaces.

The ability to reduce complex shaped components arises from the arrangement of reciprocating dies to form a series of spaces between the dies. The shape of these spaces can be influenced by profiling the working surfaces of the dies and by changing their orientation relative to one another. The resulting spaces will correspond with the desired shaped component after gage reduction. The extremities of these spaces may be open or partially closed to allow widening of component features or to discourage this widening effect.

The motion or direction of synchronized reciprocation should be such that the spaces between the die segments open and close in unison. In the preferred embodiment, the reduction imparted to material in each individual space between the die segments would receive equal strain from the draw pass to provide the least distortion or residual stress in the drawn component. This is not requisite to the invention as the applied axial tensile load provides a means of straightening and stress relaxation through tensile stretching. The amount of reciprocation may be smaller than the total reduction of the workpiece in the given pass, such that multiple reduction and advancement cycles are necessary for a segment to fully reduce and pass through the bite of the dies. In this embodiment, only certain advancement of the workpiece will occur in a given reciprocation cycle until the die opening motion stops and axial advancement stops. This provides advancement speed regulation tied to reciprocation frequency, reciprocation stroke length, and die lead in geometry. Other embodiments of this invention involve die strokes larger than the total reduction of the workpiece in the given pass. In these embodiments another device is present on the entry side of the reciprocating dies to provide a back tension against the pulling mechanism and to regulate the rate of axial advancement when the dies completely disengage the workpiece.

Higher frequency reciprocation is generally preferred for productivity and die exposure reasons. However, frequency reciprocation must remain low enough to allow axial advancement of the workpiece during the retraction phase of the reciprocation cycle. The invention may utilize any suitable mechanism to power the reciprocation and provide compressive forces to the die. Many different methods for mounting and supporting the various die segments can be utilized. As such, some level of rotational motion and axial translation of the die segment during a reciprocation cycle is considered permissible within the confines of the invention but is not necessary for successful operation of the invention.

In order to provide clearer illustration of the impact, novelty, and advantages of the invention, the specifics of an application are provided. This example is not to constrict the scope of the invention and is to be considered in no way limiting.

Though many different materials are not conducive to working in the low temperature requirements seen in standard draw bench reduction, in this specific example precipitation hardening 17-4 PH illustrates this well. Imparting deformation too cold, or even too hot, results in the presence of delta ferrite within the material and results in loss of transverse ductility. This results in impractically brittle and anisotropic final material. In addition to ductility loss, delivery of desirable grain size is influenced by the amount of deformation and the temperature at the time of deformation, particularly in semi-austenitic grades. To prevent this, a specific window of thermal processing must be maintained, with a targeted temperature of 2150° F. for the case of 17-4 PH stainless steel. The material, when properly hot worked, is desirable for many uses due to considerably higher strengths than austenitic stainless steels or carbon steels which can be delivered in complex shaped structural members, available with prior art.

The aim geometry in this specific example is a Tee-shaped cross section, as illustrated in FIG. 2, and is to be reduced to a finished size in a single pass through the device. Also, the vertical portion of the cross section is a different thickness than the horizontal base. The vertical segment has a final reduced thickness of 0.100″ and a starting thickness of 0.286″. The horizontal segment, for end application reasons, has a thicker final reduced thickness of 0.200″ and a thicker starting thickness of 0.572″. This represents a 65% reduction in all segments of the cross section. This is approximately double the reduction typically achievable with standard draw bench techniques, while achieving similar or faster draw velocities. The delivery of finished segment with one pass has a significant improvement on throughput and processing costs for drawn product. The entry sides of the dies flare outward to create a contact face during the reduction process. Though not always the case, in this example the entry geometry is of constant angle slopes. The entry geometry for die segments contacting the vertical feature of the T shape will have a slope of 7.1° while the die entry for the horizontal segment will have a slope of 14°. In this example the length of segment being reduced, or “transition zone” here forth referred, is 0.75″ long for both vertical and horizontal segments. A short segment of die, 0.5″ long, imparting minimal or no reduction is present to “trowel” or smooth the surface of the drawn Tee.

The dies surrounding this Tee shape will open and close, in synchronous, to impart the reduction into the specimen as it passes through the dies. The two dies adjacent the vertical segment of the Tee-section have both vertical and horizontal motion components as they move upward and off of the horizontal segment and outward and off of the vertical segment. The lower die only has a vertical motion component. The horizontal component of travel of the upper dies is 0.010″ in and out for each side (providing a 0.020″ total gap reciprocation). The vertical component of travel of the upper dies and the only component of travel of the lower die are both 0.021″ per side (providing a 0.042″ total gap reciprocation). Combining the X and Y component for the upper dies results in a reciprocation of 0.023″ of travel in a direction of 63° angle from horizontal. With each opening motion of reciprocation of the dies, the tensioning specimen advances the Tee segment 0.083″ forward prior to re-engagement of the contact faces. As a result, the specimen is reduced by several die reciprocations as it passes between the dies and is fully reduced to the target thickness. A portion of the reduction manifests as a widening of the cross-sectional features on the Tee segment and should be offset by inputting a slightly narrower input stock. However, the majority of the thickness reduction manifests in the form of elongation. In this example, the typical exit velocity ratio of 2.6 to 1. This however can vary with parameters such as contact friction, entry geometry, and die temperatures. With a reciprocation frequency of 1800 reciprocations per minute (30 Hz) coupled with an entry advance of 0.083″ the resulting entry speed of 12.5 ft/minute is generated. Due to the elongation from reduction, an exit velocity of 31.25 ft./minute is generated. The resulting processing speed would yield 20 ft of usable finished length in 38 seconds. Reciprocating frequencies of about 8-3600 rpms and entry speeds of about lft/min to 150 ft/min may be utilized accordingly to the invention.

During this reduction the exit material is maintained under tension by pulling against the reducing die segments. Though die reciprocation results in brief release of the segment, tension is reestablished with contact with die following incremental advancement. The magnitude of tensile force is such as to provide nearly instantaneous advancement of the segment each time the dies open as well as to impart a slight yielding in the axial direction. Given that reduction amounts are so much higher than those in tradition draw bench design, there is no concern that applied tension would advance the segment in the bite of the dies in an unintended way through sliding. This disconnect of tension from the reduction amount allows the magnitude to be adjusted to be high enough to straighten the segments but low enough not to neck the component and compromise dimensional integrity of the section. This ability to adjust tension independently of the reduction amount is unique to the process and historically has been merely a product of the reduction amount in traditional draw bench applications. This ability to deliver robust straightness in the same operation eliminates the cost of either additional draw operations for the purpose of straightening or separate straightening operations with separate equipment, thus further improving the cost structure of drawn components.

This invention's introduction of synchronized reciprocation of die segments to reduce a workpiece on a draw bench allows for performance improvement compared to prior art. In all prior art in draw bench applications the tension force on exiting material was set by the force required to pull the workpiece through a die and impart the reduction of that pass. Limits on reduction strain magnitude arose when the desired reduction strain would require an axial tensile force in excess of what the exiting cross section could support without excessive stretching, deformation, or tearing. In the present invention, the axial tensile load is no longer dictated by the reduction amount, since reduction is largely accomplished by the reciprocating die segments. Reductions much higher than prior art can be achieved with lower axial tensile forces. Simultaneously with much higher reduction strains, the axial tensile force can be adjusted to yield optimum straightness and residual stress levels without significant influence to drawing productivity, provided axial tensile forces are sufficient to adequately advance the workpiece during the retraction phase of the reciprocation cycle and not in excess of axial forces required to slide the piece forward in the bite during the compressive phase of the reciprocation cycle.

A provision for tensioning outgoing material in a traditional draw bench is commonly delivered using a clamping device on a traveling carriage. In this invention the presence of a tensile load of a desired magnitude is the only requirement and is independent of which suitable mechanism is chosen to deliver this tensile load. All suitable mechanisms for delivering tensile load on material exiting after the reduction process are considered embodiments of this core invention.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not structure or function. For example, as used herein “reciprocating die,” “die segment,” “reciprocating contact die,” “reciprocating die module,” “die module,” and similar terms are interchangeable and refer to the die segments cited in the claims. Likewise, “specimen,” “metal segment,” “work piece,” and similar terms are interchangeable and refer to the specimen cited in the claims.

Claims

1. A method of shaping a specimen comprising; a) providing at least one pair of reciprocating dies,b) advancing the specimen under tension through a space between the reciprocating dies, andc) impacting at least two surfaces of the specimen with the reciprocating dies to shape the specimen.

2. The method of claim 1 wherein the dies travel a distance less than an amount of a reduction in size of the specimen in a given pass through the dies.

3. The method of claim 1 wherein the dies travel a distance greater than an amount of a reduction in size of the specimen in a given pass through the dies and further including the step of grasping the segment on an entry side of the reciprocation dies whereby tension is maintained.

4. The method of claim 1 wherein the dies have a contact surface comprising two or more surfaces that intersect each other.

5. The method of claim 1 wherein the cycle time of the reciprocating dies and the travel speed of the specimen is selected based upon the material of the metal segment.

6. The method of claim 1 wherein the final shape of the specimen is determined by the configuration of the contact surfaces of the dies and gaps between the dies.

7. A method for cross sectional reducing and straightening a specimen comprising: advancing a specimen under tension through a plurality of die segments;wherein each die segment has a contact face;at least one of the die segments wherein the contact face has at least two planar surfaces that intersect to form a convex feature;the plurality of die segments configured such that the contact face of each die segment is opposed by the contact face of at least one other die segment to form at least one set of opposing die segments;the plurality of die segments configured such that the geometry of the plurality of die segments is not restricted to converge on a radial center;at least one die gap determined by the distance between the contact faces of the at least one set of opposing die segments;at least one die driving mechanism providing translational motion to at least one die segment, the translation motion being directed toward the opposing die segment;the die driving mechanism configured to provide reciprocating translational motion to at least one die segment and synchronous reciprocating motion to the plurality of die segments, whereby the at least one die gap opens and closes; and,wherein the tension is provided by an exit tensioning device configured to grip a specimen and maintain a continuous tension on the specimen causing the specimen to move with a translational motion through the at least one die gap and cross sectionally reducing the specimen by a predetermined reduction, the reciprocating transitional motion of the opposing die segments being less than the predetermined reduction, the continuous tension being insufficient to provide the translational motion to the specimen during the compression phase;whereby the specimen will be reduced, stretch straightened, elongated, and have enhanced mechanical properties.

8. A method for cross sectional reducing and straightening a specimen comprising: advancing a specimen under tension through a plurality of die segments;wherein each die segment has a contact face;at least one of the die segments wherein the contact face has at least two planar surfaces that intersect to form a convex feature;the plurality of die segments configured such that the contact face of each die segment is opposed by the contact face of at least one other die segment to form at least one set of opposing die segments;the plurality of die segments configured such that the geometry of the plurality of die segments is not restricted to converge on a radial center;at least one die gap determined by the distance between the contact faces of the at least one set of opposing die segments;at least one die driving mechanism providing translational motion to at least one die segment, the translation motion being directed toward the opposing die segment;the die driving mechanism configured to provide reciprocating translational motion to at least one die segment and synchronous reciprocating motion to the plurality of die segments, whereby the at least one die gap opens and closes;wherein the tension is provided by an exit tensioning device and an entry back tensioning device;wherein the exit tensioning device is configured to grip a specimen and the entry back tensioning device is configured to grip the specimen opposite to the exit tensioning device, the exit tensioning device and the entry back tensioning device further configured to maintain constant tension on the specimen, cause the specimen to move with a translational motion through the at least one die gap, and cross sectionally reduce the specimen by a predetermined reduction, the reciprocating translational motion of the opposing die segments being less than or greater than the predetermined reduction, and the tension being insufficient to provide the translational motion to the specimen during the compression phase;whereby the specimen will be reduced, stretch straightened, elongated, and have enhanced mechanical properties.