US3426569A - Stretch forming machine and segmental adjustable die combination - Google Patents

Description

Feb. 11, 1969 BRAUER ET AL 3,426,569

STRETCH FORMING MACHINE AND SEGMENTAL ADJUSTABLE DIE COMBINATION Flled Jan. 31, 1967 Sheet 0f 1-,

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Feb. 11, 1969 E. H. BRAUER ET A 3,426,569

STRETCH FORMING MACHINE AND SEGMENTAL ADJUSTABLE DIE COMBINATION Filed Jan. 31, 1967 Sheet 2 off:

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STRETCH FORMING MACHINE AND SEGMENTAL ADJUSTABLE DIE COMBINATION Filed dan. 31, 1967 Sheet 4 of INVENTORS fpm/m/ H. 32/105,? 7. V/fi/d #066577 BY I A 2Z1. ATTOFNEX E H. BRAUER ET AL 3,426,569 TCH FORMING MACHINE AND SEGMENTAL ADJUSTABLE DIE COMBINATION STRE Feb. 11, 1969 Sheet United States Patent Office 3,425,569 Patented Feb. 11, 1969 6 Claims ABSTRACT OF THE DISCLOSURE The invention comprises a bending machine for bending elongated structural members, such as I-beams, channels, bulb beams, and the like. The machine employs two series of companional die segments, each segment of each series being toward and away from the other series, independently of the other segments of the same series, to adjusted positions by individual power means, such as electric motors, which are numerically controlled to drive, through self-locking mechanisms, 50 that each segment remains in the position to which driven. Gripping heads are provided at opposite ends of the dies and are operable to tension the stock lengthwise, transversely of the closing direction of the die segments, into a range above its yield point and to maintain the stock in that condition during bending by the dies. At least one stretch head is movable to and fro in the direction transversely of the tensioning dimension so as to lay the metal progressively from one end toward the other end onto the die segments.

This invention relates to a stretch forming machine and a segmental die combination particularly. adapted for the cold forming of rolled structural members such as I-beams, channels, bulb beams, and the like.

For purposes of illustration, the invention is described hereinafter as applied to the stretch bending of ship ribs, girders, and the like, its application to the stretch forming of other structural members being readily apparent from the illustrative description.

Heretofore, it has been proposed to bend structural members into shape for ship ribs by hot bending the structural members against the forming faces of adjustable segments of an adustable die extending lengthwise of the member. One such procedure is disclosed in U.S. Letters Patent No. 2,347,575, issued Apr. 25, 1944, to H. E. Neverdal, wherein a heated beam, under an imposed weight, is bent to engage the forming faces of a row of adjustable die segments. The segments disclosed are adjustable to preselected positions by individual motors, arranged one for each segment. By suitable proportional driving connections between the die segments and comparator indicating means, the relative final desired positions of the forming faces of the segments with respect to a reduced scale pattern or matrix of the final shape desired in the formed workpiece are reflected and compared.

In U.S. Letters Patent No. 2,334,520, issued Nov. 16, 1943, to T. Walters, the use of dies formed of adjustable segments, each bearing against a flexible face plate are disclosed for bending of such members. In this case, two adjustable segment matching dies are used and are brought into firm bending relation by a hydraulic ram. The procedure is directed to the hot forming of such structural members.

It is found, however, that while such members could be bent while heated to the shapes dictated by the adjustment of the die segments, the members did not necessarily retain their shapes when restored to room temperature. Furthermore, the heating and cooling changed the characteristics of the metal appreciably, often reducing its strength and adversely affecting desired qualities. Again, the required careful heating and cooling of the members and handling them in heated condition rendered such an approach undesirable economically.

To appreciate fully the problems presented, it must be recognized that in ship building a very large number of right and left-hand ribs are arranged in pairs, and the shape of each rib of each pair varies considerably from the shape of each rib of every other pair from the bow of the ship for a very substantial distance rearwardly and from the stern for a substantial distance forwardly. Thus, a problem is presented of bending a large number of structural members each to a different shape than the others.

In hot forming, the relatively "low pressures that could be used made possible relatively light adjustable segmental dies. On the other hand, when cold forming was attempted, such adjustable segment dies did not prove satisfactory. Instead a solid die having a continuous face limited to one specific shape, or two matching solid dies for each shape were used. Considering that a different die or set of dies was required for each member formed, the die cost soon became prohibitive and the procedure cumbersome.

In attempting to use adjustable segmental dies for cold forming such members, it was found that spring back is unpredictable. This was due to the different stresses and characteristics in the metal members imparted during their original formation. Consequently, a great amount of time would be required for continuously resetting the adjustable dies. Generally, the selected setting of the die segments for a particular shape of member is not satisfactory for a duplicate member. Often heavy impact forces have to be applied in the direction toward the 'die face. Thus, in cold bending, the segmental die affords little advantage economically over the use of a continuous non-adjustable die which could withstand heavy impacts and pressures.

In accordance with U.S. Patent No. 2,850,071, issued Sept. 2, 1958, to D. W. Kraybill, the formation of structural members of the T-shaped cross section is effected by stretching the members over a solid continuous face die while pressing it against the solid die face an increment of length at a time progressively from one end to the other by power operated pressing shoes. These shoes, when in final position, may appear somewhat like segments of a segmental die, but instead they are merely individual hold down members requiring a. continuous rigid die opposite to them for limiting them to the proper final position. In such a structure, the necessity still existed that at least one solid die for each different shape of member be provided.

While the advantages of cold bending generally were known, a satisfactory and economical method for bending structural members had not heretofore been devised, and resort had been had to other approaches involving a series of dies and successive steps for each shape, and a great deal of hand work.

In accordance with the present invention, however, it is found that the use of an adjustable segments die is possible'if the structural member to be bent to shape thereagainst is first subjected to stretching above the elastic limit so as to render the metal more readily formable and, while in this condition, is beint against the faces of the segments. Due to such stretching, exceedingly high pressures directed transversely of the member are unnecessary for bending it to the shape imposed by the segment faces. Further, it is found that, combined with the stretching structure, the die could be made sufficiently rugged to withstand the force to which subjected without disproportionately increasing the cost of the machine. Ex-

3 tremely important is the fact that by stretching the member above its elastic limit and bending it while it is in the resulting more readily formable condition, spring back is substantially eliminated. This assures that duplicate shapes can be produced repeatedly for any selected setting of the die segments.

Thus, a new approach in ship building is provided whereby upon determination of the shape desired for any given member, the die segments are set to engage such a shape, and like members can be formed to that precise shape repeatedly.

The combination of such stretching and die adjus-tability opens up the field of applying to shipbuilding and other heavy work, numerical and other types of automatic control which, for proper functioning, must operate on a predictable result from a particular die shape. Thus, in cases where the production of each particular part formed is relatively small, the stretching, due to elemination of springback and to reducing the bending forces required, makes practical the use of an adjustable segmental die, the adjustable die overcomes the economic handicap of requiring a large number of solid dies, and combination of the two factors, an adjustable die and stretch forming, make practical the programing of the die setting by conventional automatic controls, such as tape and numerical controls.

With the present invention, the die segments can readily be set by numerical control to a setting earlier determined, either empirically or by computation. This can be recorded for subsequent duplication of like pieces with assurance 3 that for any die setting for a given size and shape cross section of structural member, the finally shaped member can be accurately reproduced repeatedly.

Various specific objects and advantages will become apparent from the following description wherein reference is made to the drawings in which:

FIG. 1 is a fragmentary top plan view of an apparatus embodying the principles of the present invention;

FIG. 2 is a fragmentary front elevation of the apparatus, showing the left-hand one of the stretching units;

FIG. 3 is a fragmentary left end elevation of the apparatus illustrated in FIG. 1;

FIG. 4 is an enlarged fragmentary side elevation of one of the adjustable die segments used in the apparatus and the driving mechanism therefor;

FIG. 5 is a horizontal sectional view taken on the line 55 in FIG. 4;

FIG. 6 is a vertical sectional view taken on the line 66 in FIG. 4;

FIG. 7 is a fragmentary sectional view illustrating a modification of a die segment;

FIG. 8 is a top plan view of the apparatus showing one setting of the die segments for bending a structural member having a reverse bend, and showing the position of the stretch units for bending the member in conformance with the die face; and

FIG. 9 is a diagrammatic illustration showing the manher of setting and holding the die segments by an automatic control system.

Referring to the drawings the machine comprises a rigid frame or bed 1 having at each end a stretch unit indicated generally at 2. Each stretch unit comprises a rigid carrier 3 supported by suitable rollers 4 on trackways 5 which are fixedly mounted on the frame 1 and extend transversely of the length of the bed so that the carriers can be moved readily generally transversely of the tensioning dimension.

Supported on the carrier 3 is a swivel support 6 pivot-ally connected to the carrier 3 'by a pivot 7 for swinging about an upright axis while being constrained by the pivot 7 to a fixed position forwardly and rearwardly of the carrier 3. The swivel support 6 rides during swiveling on suitable guides 8 on the carrier 3. The guides 8 are coaxial with the pivot 7 and of constant radius.

Mounted on the swivel support 6 is a rigid frame designated generally at 9, in the shape of an inverted U, including side plates 10, top plate 11, and front and rear plates 12. Fixedly connected to the front plate 12 is a tongue 13 which is pivotally secured to a yoke 14 by means of a pivot 15.

The yoke 14 supports a gripper head 16 which is adapted for gripping one end portion of the structural form to be bent for applying endwise tension thereto.

Supported on the frame 9 are suitable rigid guides or tracks 18 which are guided for longitudinal movement in rollers 19 having their axes in fixed position relative to the plate 6.

Fixed-1y connected to the rear plate 12 is a cylinder of a reversible piston and cylinder assemblage 22. The assemblage includes a cylinder 23 and a piston 24 reciprocable in the cylinder and having a piston rod 25. The piston rod 25 is connected at its outer end to a bracket 26 which is mounted on a support 27 which, in turn, is rigid with the swivel support '6.

Thus, by introducing pressure fluid from a source through a conventional reversing and stop valve to the head end of the cylinder, the stretch head 16 is forced to move in a direction toward the adjacent end of the bed. A like stretch unit is provided at the opposite end of the bed.

As illustrated, in order to adjust the stretch units to the proper position endwise of the machine for different lengths of members, a suitable power drive is provided. The entire unit, indicated generally as 30, is mounted on suitable skids 31 on the frame 1 for sliding in the tensioning direction. Carried on the end of the unit is a drive comprising an electric motor 32 drivingly connected by a chain 33 to a sprocket 34 which, in turn, drives a shaft 35. The shaft 35 drives a gear reducer 36 of which a pinion 37 drivingly engages a rack 38 carried on the frame 1. Thus, the entire unit 30 can be moved to the desired position endwise of the frame.

During the stretch bending operation, it is desirable that the entire unit, including the carrier 3, be moved transversely of the tensioning direction. For this purpose, a follower 40 is mounted on the carrier 3 and is drivingly connected to a lead screw 41. The lead screw is mounted at its end in suitable bearings 42 on the frame 1 and is driven by a speed reducer 43 which, in turn, is driven by a reversible electric motor 44. The motor 44 of each unit is controlled independently of the like motor of the other unit, by conventional controls. Thus a structural member can be stretched endwise by gripping it at its opposite ends by heads 16 and introducing the pressure fluid to the head end of the cylinders 23 and during the stretching, each of the carriers 3, and hence the associated stretch head 16, can be moved in such direction as desired transversely of the tensioning dimension. The pivot connection of the head 16 to the plate 12 permits the head to accommodate itself so as to be tangential to the direction of tensioning as the carriage 3 is shifted. Also, due to the swiveling of the support 6, the entire piston and cylinder assemblage can swing so that the axis is directed tangentially to the curved member.

Mounted on the bed 1 is a segmental die comprising a plurality of carriers mounted in suitable parallel guideways 51 for sliding forwardly and rearwardly of the bed or transversely of the tensioning dimension. Each carrier is driven to selected positions transversely of the bed by means of an associated lead or positioning screw 52 which, in turn, is driven by a reversible motor 53. by driving the motor in opposite directions, the associated carrier 50 can be driven to the desired position transversely of the bed. The carriers 50 are arranged in edge to edge relationship. Each carrier, at its upper surfaces, carries a forming shoe or die segment 54 which preferably has a forming surface 55 which is curvilinear about an upright axis so that it can tangentially engage a work piece moved sidewise thereagainst. Thus, as illustrated, in FIG. 8, the die segments 54 may be moved by their carriers 50 to the desired positions so as to present toward the work piece a series of spaced forming surfaces 55 which preferably are merely a few inches apart and define the configuration of the member to be bent thereagainst and assure that, upon bending, it will become substantially a continuous curvilinear shape, rather than a series of chords.

In the form illustrated, a member M is to be bent into the form of a reverse curve and for this purpose part of the die segments-for example, those at the left portion of the bed in FIG. 8present a series of surfaces such that a general configuration is presented which is convex toward the member M, while those at the right are arranged to present a series of surfaces such that a general configuration is presented which is convex toward the member at the opposite side. The segments in between these groups define a transition surface tangent to the reverse curves defined near the ends.

Generally in a machine for universal use, a double group of the segments may be used, a complete set at the front and a complete set at the rear so that any selected curve can be defined, even though only part of each group is used for a given shape.

In forming member M, such as illustrated in FIG. 8, it is placed under tension by the stretch heads 16 which present a line of pull through the tangent point or point of reversal of the curve, as indicated, for example, at 60, and stretched endwise to a degree above its elastic limit. While thus stretched, the left hand head 16 is swung clockwise about the tangent point or rearwardly of the bed and the left hand head clockwise about the tangent point or forwardly of the bed, thus laying the tensioned member M firmly against the faces 55 of the segments.

Due to the stretching, the member is in readily formable condition and hence the pressures against the die faces required to bend it about the surface defined by the faces with assurance that it will remain in the shape defined thereby without substantial spring back are quite modest.

In many instances it is desirable to clamp the member firmly in position after it has been bent and, for this purpose, on all or a spaced number of the carriers 50, hold down clamps 62 are provided. Each hold down clamp 62 is connected to a rocker arm 63 by a pivot 64 operated in a slightly elongated slot 65 to compensate for relative horizontal movement between the rocker after the clamp has engaged the member M. The rocker arm is rockable about a pivot 66 on the carrier 50 and is driven by a suitable piston and cylinder assemblage 67 which is connected by pivots 68 and 69 to the carriage 50 and rocker 63, respectively.

Thus, when the member M has been bent, as illustrated in FIG. 4, against the face 55 of a given segment 54, and then is to be bent about the next succeeding face, the clamp 62 is applied to hold the already bent portion of the member M firmly in position.

In FIG. 4 there is illustrated the bending of an L-shaped section with the flange M at the inside of the bend, in which case a die segment 54 of relatively limited extent transversely of the bed is required. In those instances in which it is desired that the flange M be at the outside of the bend, a longer die segment 70 is employed, as illustrated in FIG. 7. The segment 70 is such that it fits the upper surface of the member M with slight clearance so as to permit the member M to slide relative to the segment. A clamp 71 mounted on the rocker arm, such as 63, is moved to a position to prevent the segment 70 from kicking or swinging upwardly under the stresses imposed by the bending member M, but without frictionally interlocking the under face of the segment with the upper surface of the member M.

As mentioned, it is desirable that the carriers 50 or segments "be readily movable to the desired positions 'at a later time to reproduce the setting already determined. For such purposes, each of the reversible D.C. driving motors 53 is a servo motor for varying the speed and position of the positioning screw 52 and thereby the position of the associated carrier 50. The shaft of the motor 53, in turn, drives a feed-back unit 76. The feed-back unit supplies signals through conduit means 77 to a numerical control unit including a servo amplifier 78, an interpolator 79, and a tape reader 80. A tape which has been prepared for a predetermined setting of the die is fed through the reader and supplies output signals which are a function of the perforations on the tape. These are supplied as command signals to the interpolator 79 which then supplies command signals interpolated in accordance with the tape signals to the servo amplifier 78 which compares this interpolated command signal with the output signal from the motor feed-back unit 76. This structure is a conventional type of numerical control and a specific structure thereof forms no part of the present invention. Adjustment of the die segments is continued until these signals are in balance, whereupon the associated carrier 50 is stopped. The function is subsequently carried out for the segments until all are in selected positions.

Thus the die segments may readily be moved to the proper position in response to the tape, and upon being driven to the predetermined positions, they are automatically stopped by the control and remain in the stopped position, due to the self-locking of the feed screw against rotation by forces imposed on the carriers 50 by the pressure of the member M being formed against the segments 54.

Having thus described our invention, we claim:

1. A stretch bending apparatus comprising a frame;

gripping heads operable to grip opposite ends of an elongated structural member for applying endwise tension thereto when the heads are moved relatively apart;

means supporting the heads on the frame for movement relative to each other in paths extending transversely of the tensioning dimension;

power operable means for moving the heads relatively apart for tensioning in said one dimension; additional power means for moving the heads relatively to each other in said paths;

a segmental die comprising a plurality of segments arranged in a row extending generally endwise of the tensioning dimension;

means supporting the segments for movement to seselected forming positions, respectively, transversely of the row and in the direction of relative movement of the heads along said paths, and transversely of the tensioning dimension; and

drive means for moving the segments, respectively, to

their said selected forming positions and for holding them fixedly in their said positions.

2. The structure according to claim 1 wherein at least one head is supported on a carrier;

means support the carrier on the frame for guided movement to and fro along a predetermined path extending transversely of the tensioning dimension;

a stretch forming piston and cylinder assemblage is mounted on the carrier and is drivingly connected to said one head,

and the power means for driving the head along said paths is drivingly connected to the frame and carrier.

3. The structure according to claim 1 wherein a plurality of carriages are mounted on the frame for guided movement in parallel paths extending transversely of the tensionin g dimension;

the die segments are mounted on the carriages, re

spectively;

reversible electric motors one for each carriage are provided;

transmission means drivingly connect the motors to the carriages, respectively, for driving the carriages from retracted to forming positions, and

control means are provided for controlling the motors,

individually.

4. The structure according to claim 3 wherein said transmission means are self-locking against movement of the carriers out of their selected forming positions by forces applied to the die segments by the stock.

5. The structure according to claim 1 wherein the drive means are power driven for driving the segments to said forming positions,

means are provided to constrain the segments to said positions against forces applied thereto other than by the drive means,

automatic programs means are connected to the drive means for controlling the drive means so as to move the segments to pre-programed forming positions, respectively.

6. The structure according to claim 5 wherein the program means includes a tape reader for providing command signals from a program tape,

means driven in fixed relation to the drive means of References Cited UNITED STATES PATENTS Yoder 72-295 Kraybill 72297 Jones 72296 Bowser 72297 Ro'hlfs 72297 5 CHARLES W. LANHAM, Primary Examiner. RONALD D. GREFE, Assistant Examiner.

US. Cl. X.R.

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