US3667274A - Apparatus for bending plate - Google Patents

Abstract

The method of forming trough members for use in the fabrication of orthotropic deck bridges which involves applying opposing forces to the edges of a flat plate to move the edges towards each other.

Description

United States Patent Cape 1 June 6, 1972 54 APPARATUS FOR BENDING PLATE [56] References Cited [72] Inventor: Richard Allan Gordon Cape, Lachine, UNITED STATES PATENTS Quebeg Canada 2,123,683 7/1938 [73] Assignee: Dominion Bridge Company Limited, Mon- 2'437092 3/1948 treal, Quebec, Canada 2889865 6/1959 I 2,963,067 12/1960 Fried: p 3, 1969 3,004,584 10/1961 2,428,890 10/1947 21 App]. No.. 813,092 3,448,603 6/1969 Primary Examiner-Charles W. Lanham Assistant Examiner--Gene P. Crosby Attorney-Fetherstonhaugh & Co.

[30] Foreign Application Priority Data [57] ABSTRACT Mar. 4, Canada The method of forming trough members for use in the fabrica tion of orthotropic deck bridges which involves applying op- [52] US. Cl ..72/298, 72/379, 72/390 posing forces to the edges of a flat plate to v the edges [5 l 1 ..B2ld 11/20 towards each m [58] Field of Search ..72/389, 379, 380, 381, 390,

5 Claims, 8 Drawing Figures PATENTEDJUH 6 2972 SHEET 10F 8 INVENTOR R. A. G. CAPE PATENTED H elm 3,667,274

SHEETZUFB FlGZ- INVENTOR R. A. G. CAPE INVENTOR R. A. G. CAPE PATENTEDJUH 6 I972 SHEET U 0F 8 INVENTOR R. A. G. CAPE FATENTEDJUH 61972 3,667, 274

INVENTOR R. A. G. CAPE PATENTEDJUH 6 I972 SHEET 5 OF 8 III/ll] INVENTOR R. A. G. CAPE PATENTEDJUM 6 I972 IDIIUI FIGB INVENTOR R. A. G. CAPE APPARATUS FOR BENDING PLATE BACKGROUND OF THE INVENTION This invention relates to the forming of trough members from elongate planar workpieces.

In the field of bridge fabrication, a new type of bridge developed in Germany has found favour in other parts of the world. This new type is called an orthotropic deck bridge. It owes its popularity to an overall decrease in weight of steel compared to other types of bridge design having a similar length of span. It was developed in principle as a means of reducing the amount of steel required in replacing many of the bridges destroyed in World War 11. Some of the orthotropic deck bridges which have been erected in Germany weigh only 50 percent of the bridges which were replaced.

An orthotropic deck bridge utilizes a continuous deck plate of steel over which is poured a layer of asphalt. The deck plate may be comparatively thin and yet it is rigid and strong. This is due to a unique stiffening system on the underside of the deck consisting of longitudinal stringers at a spacing of about 12 in. extending between transverse floor beams at about 7.5 to 15 ft. intervals. These stringers carry their loads into the floor beams which in turn are supported by side girders. The stringers are welded to the deck plate. By reason of continuous weld attachment, the deck is in reality the top flange of the stringers, the floor beams and the main girders.

The shop fabrication of an orthotropic deck bridge demands careful planning and execution. Shop fabricated units for shipment to the field are made as large as possible, consistent with shipping facilities, in order to minimize field erection costs. The larger such units become, the greater is the difficulty in producing weldments free of distortion and whose component members accurately align with mating members in the field. It is for these reasons that jigs and fixtures are extensively used in conjunction with the welding processes used in joining. By reason of the fact that similarity of shop produced units is feasible, automated welding processes are used whenever possible. Thus floor beams consisting of webs and flanges and all stiffened plate assemblies, such as girder webs, box girder bottom flanges and the deck-stiffener units, are welded by automated machinery. The welding of floor beams and also of plates stiffened by angles or tees involves machine welding whereby two fillet welds are simultaneously deposited on both sides of a common member, i.e. the member in contact with the flange or plate. With deck-stringer members the situation is different. This is due to the fact that stringers having the best engineering properties are U-shaped in cross-section and thus permit welding only from the outside of each U-trough and the welding of the legs of trough members to deck plates must be from one side through the thickness of leg.

U-type trough stringers vary in thickness from V4 to in. Their edges are bevelled in order to pennit fusion through the full thickness of the material since the welds are subject to transverse bending by reason of traffic loads which impose tension and compression straining at the root of the stringerdeck welds. Variable load conditions could lead to fatigue in service in welds which were inadequate in throat thickness. The nature of automatic welding, however, is such that extreme uniformity of the groove defined between the deck plate and the stringer is essential. Thus, a root gap in excess of 1/32 in. is sufficient to permit burn through, which necessitates repair. The need for uniformity of gap tolerances may be further understood by appreciating the fact that no shoulder on the bevelled edge is permissible in order to achieve maximum depth of fusion without overfusing.

The U-shaped trough stringers are not truly U-shaped since the legs are not parallel to one another. Usually the legs are flared to an included angle of to 30 or even greater. It will be seen therefore that any local variation in the distance between legs may cause a direct variation in the root gap of the welding joints. Thus, in a long continuous length of 45 to 60 ft. of stringer, local variations producing a smaller spacing between certain points on the edges of the stringers will result in those points being in contact with the flat surface of the deck plate while the remainder of the length will not be in contact. Local variations producing greater spacing between the edges will cause still greater root gaps. Such gaps are most serious since they affect weld quality and uniformity of fusion.

Two methods of forming U-shaped trough members are currently employed. A first method uses a large die press and produces excellent results when the length of the trough does not exceed the length of the die. Short segments may be welded together to form a required length but this operation is slow and costly since the welded joints must be sound by X-ray standards. Long lengths greatly in excess of the length of the dies may be pressed by moving the material at intervals backwards and forwards through the press while producing partial bends between moves. The final results are, however, not completely satisfactory. At each stroke of the press, the material at the extremities of the die becomes stretched beyond its elastic limit. This results in a permanent deformation which causes uneven edges resulting in unevenness of the welding joints. In addition, the process is slow and expensive.

A second method is roll forming. A machine for this purpose consists of a number of roll stations in which top and bottom mating rolls continuously and progressively shape the material in a single pass through a machine. Such machines must be of exceptional size to accommodate the trough sections required and in consequence are rare and extremely expensive. In addition, roll costs are very high.

Since die-formed troughs are inadequate in shape and are expensive to produce and since cold rolled troughs are difficult to secure and expensive to purchase, there is a real need for a cheaper method of producing satisfactory trough sections. Furthermore, due to the repetitive nature of orthotropic deck bridge construction with its feasibility of line production, there is need also for a trough producing machine which can be readily placed in a production line.

One feature of trough shape is of vital importance in orthotropic deck bridges. The deck and connected material must possess good cold temperature impact properties when used in cold climates. Such material may consequently be rolled to a particular specification and heat treated to achieve resistance to brittle fracture. The method of forming the troughs and the shape'now become important since cold work in fonning drastically increases the transition temperature; i.e. the temperature at which ductile fracture changes to brittle fracture. A rolled formed trough having flared legs joined to a flat base with small comer bends may be cold worked to a much greater extent than a trough having flared legs connected by means of a continuously curved base. Also for a similar width of plate, the latter shape of trough posses greater bending strength. I

SUMMARY OF THE INVENTION It is an object of the present invention to provide a relatively inexpensive and eflicient method of accurately forming elongate trough members.

It is a further object of the present invention to provide a method of forming elongate trough members having a desired cross-sectional profile.

It is a still further object of this invention to provide apparatus which is inexpensive and yet enables the production of accurately formed elongate trough members.

The invention provides a method of forming an elongate trough member from an elongate planar workpiece having a pair of spaced longitudinal edges comprising applying opposing forces to said edges in a direction inward of the edges and generally at right angles to said edges to move said edges towards each other, and constraining said edges to move in a plane common thereto.

The forces may be eccentric to the plane of the workpiece or they may be in the plane of the workpiece. When eccentric to the plane of the workpiece, the forces will cause bending to start midway between edges. When the forces are in the plane of the workpiece, it is desirable that another force at right angles be applied on one side of the plate along its central longitudinal line. When this force is sufficient to produce some bending, the mid portion becomes eccentric to the forces applied at the edges. In both cases, the edge applied forces, if gradually increased, will cause the plate to bend allowing the edges to approach one another.

Simultaneously with the approach of the edges, the central longitudinal portion of the workpiece becomes further and further strained, as bending continues. The strain is at a maximum at the center line and it decreases away from the center line. At any point where strain causes stress beyond yield point stress, permanent plastic deformation takes place. When the edges have been advanced to a predetermined position and are then released, some elastic recovery occurs but the plastic straining can be sufficient to produce a trough shaped section from the original flat plate. The trough will include a middle curved portion where stress exceeded yield as well as two generally straight sides where stress was below yield. By controlling the final approach of the two edges towards one another, it is possible to secure'a trough with parallel sides or a trough with sloping sides which contain the included angle required by the designer for the optimum slope of trough sides.

, The middle curved portion of the trough may not, however, be in agreement with design requirements if forming is done by applying forces to the edges of a freely deformable elongate workpiece of predetermined width. For any given thickness, it has been found that the trough geometry is a direct function of the workpiece width, i.e. narrow widths produce smaller curves than wider widths. For a given width, it is possible, however, to control the resulting trough geometry within wide limits which include the ideal shape required. This can be accomplished by means of opposed pivotable pressure plates or jaws which apply forces and moments to the longitudinal edges of the workpiece through the medium of pivot centers where the loads are applied. When the pressure plates and workpiece are in initial contact, the distance between pivot centers may be less than the width of plate or greater than the width of plate. The trough geometry which results after bending is then a direct function of the distance between hinge centers.

Although the description previously stated has referred to troughs for orthotropic deck construction, the principle as well as the machinery for forming can be applied to flat material varying from several inches wide to many feet in width. Thus, it is quite practical to form a trough girder for a bridge from a single plate 12 ft. wide by any length desired. Since the process of forming can be done in a matter of minutes, it is obvious that a very great saving in shop labor is possible.

BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made to the following drawings which are exemplary of several embodiments of this invention and wherein:

FIGS. 1 and 2, shown in section, are representative of a trough fonning apparatus where the final shape dimensions of the trough are a function solely of the width of the workpiece;

FIGS. 3 and 4, again in section, pertain to a device employing pressure plates pivotable about a point in the same plane as the planar workpiece and spaced outwardly from the edge of the workpiece;

FIGS. and 6, shown in section, illustrate a different form of pressure plates, whereby the pressure plates pivot about points not in the plane of the planar workpiece and spaced outwardly from the edges of the workpiece;

FIG. 7 illustrates a type of pressure plate which locates the pivot centers inwardly of the edges of the workpiece; and

FIG. 8 shows pressure plates similar to those of the apparatus of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIGS. 1 and 2, a rigid frame, generally indicated at 1,

formed from two spaced longitudinal beams 2 and 3, is provided. Transverse reinforcements 4 and 5 are provided intermittent in the length of the beams to maintain the spacing of the beams 2 and 3. The reinforcements 5 function as ways for guides 6 to move therealong. Mounted on top of the frame and secured along one side thereof is an elongate backing member 7 having an elongate pressure plate 8 attached to it such that it faces guides 6. An elongate pressure plate 9, similar to plate 8 on backing member 7, is secured to guides 6 and is parallel with plate 8. Guides 6 and their associated pressure plate 9 are caused to move towards and away from plate 8 of backing member 7 by means of a series of hydraulic piston and cylinder assemblies 10.

Inserted between pressure plates 8 is a workpiece 11. When the pressure plates 8 are in engagement with the longitudinal edges of the workpiece and moved towards one another, the workpiece will bow. In this case, in order to ensure that the workpiece bows in the upward direction only,and along its longitudinal center line, the workpiece 11 may be formed with an initial prebend before inserting it into the pressure plates 8 and 9.

The bottom surfaces of the edges of the workpiece are supported by lips 12 in the plates 8 and 9. Lips 14 support the edges of the workpiece 11 as the pressure plates are brought together.

A limit switch 15, adjustable transversely in the frame 'is provided to limit the inward movement of the guide 6. I

FIGS. 1 and 2 respectively show the initial and final stages in the forming of the workpiece 11 into a trough shape. Upon retraction of the guide 6 the workpiece will relax elastically from the configuration shown in FIG. 2 to the required design shape. By virtue of the construction of the apparatus the pressure plates 8 and 9 are moved toward each other over a common plane and the longitudinal edges of the workpiece are also constrained to remain in a common plane so that a formed trough member can be successfully welded by automatic means to a flat sheet along both longitudinal edges.

The pressure plates 8 and 9 are designed to allow free rotational movement of the longitudinal edges therein. Accordingly the trough geometry will be dependent solely upon the thickness and width of the workpiece. a

The device shown in FIGS. 3 and 4 is similar to that of FIGS. 1 and 2 in that, at least initial1y,-the force applied to the longitudinal edges of the workpiece is in the same plane as the workpiece. l-Iere, pressure plates 20 are mounted on transverse ways 22 of frame 21 by means of guides 23. Guides 23 move uniformly towards and away from each other through interconnection with transverse rightand left-hand screw 24 disposed below ways 22. Each set of pressure plates 20 on one side of the frame mounted on guides 23 pivotably support identical elongate hinged adaptors or jaws 25 extending the full length of the workpiece. Each adaptor ispivotably connected to the pressure plate on its respective side by pivot pins 26. Each adaptor is provided with a lip 27, a recess or channel 28 and an upper lobe 29.

Positioned centrally of the frame and below the workpiece are a series of jacks 30 extending the length of the workpiece. Upon initial compressive force imparted to the workpiece, the jacks engage the central mid-portion of the underside of the workpiece causing it to bow upwardly. The pressure plates 20 including jaws 25 are brought together uniformly and in parallel alignment by virtue of the leftand right-hand screw units acting on the guides 23. As the trough takes shape, jaws 2S pivot about pins 26, taking up the position shown in FIG. 4 when an adjustable limit switch 92 is actuated and further bending action discontinued.

The workpiece 31 is firmly held in the channel 28 by the lip 27 and lobe 29 so as to prevent relative movement between the longitudinal edges of the workpiece and the jaws 25. The

effective width of the workpiece is thereby increased and the trough geometry resulting is that which would result from using in the-apparatus of FIGS. 1 and 2 a plate having a width equal to the distance between pivots 26 when in the position shown in FIG. 3.

In order to avoid the need for providing jacking means as included in the embodiment of FIGS. 3 and 4, the apparatus can be modified as shown in FIGS. 5 and 6 wherein the plate is mounted in the jaws so that the plane is eccentric to the plane of the pivot points. This eccentricity ensures the bending of the workpiece in the correct direction.

In the apparatus shown in FIGS. 5 and 6 and a main frame 41 has longitudinal beams 42 and 43 and transverse beams 44 and 45. A guide 46 is slidably mounted on the beam 45 and a fix-bracket 47 is secured to the beam 42 and extends above the beam 45. Pivotally mounted to the bracket 47 about a pin 48 is a pressure plate 49. The pressure plate 49 is freely pivotal on the pin 48 but is held in approximately the position shown in FIG. 5 by means of a bolt and spring assembly 50 secured to upright 5].

Attached to the pressure plate 49 is a jaw 52 which is spaced from the plate 49 by a fill 53. The jaw 52 has projections 54 and 55 for restraining movement of a workpiece 56 relative to the jaw 52. Secured to the guide 46 is a bracket 57 on which is pivotally mounted a pressure plate 58. Similarly to the pressure plate 49 the plate 58 is freely pivotally mounted on the bracket 57 but is held in approximately the configuration shown in FIG. 5 by a spring and bolt assembly 59 mounted on upright 60. A jaw 61 identical to the jaw 52 is secured to the plate 58 by a fill 62. The guide 46 is moved towards the bracket 47 by means of a cable or chain 63 which extends around a sheave 64 and is connected to a haulage machine not shown. To assist the movement of the guide 46, an air hose 65 is inserted between an upright 66 secured to the beam 42 and a plate 67 secured to the guide 46.

The air hose 65 assists in the initial movement of the guide 46 when an extremely heavy load is required to bend the workpiece 56. After initial bending of the workpiece 56, the force required to bow the plate reduces considerably.

The effective width of the plate 56 is that distance between the pin 48 and its associatedpivot pin 68 in bracket 57. The jaws 52 and 61 hold the longitudinal edge regions of the workpiece 56in fixed relation to the jaws 52 and 61.

Since the plane of the workpiece 56 is eccentric to the plane of the pivot pins 48 and 68, initial application of force through the pins 48 and 68 will cause an upward force on the plate 56 so avoiding need for use of jacks as in the embodiment of FIGS. 3 and 4 or an initial pre-bend as in the embodiments of FIGS. 1 and 2.

As shown in FIG. 6 the apparatus of this embodiment is provided with a limit switch 69 which is adjustable relative to the frame 41 and a return cable 70 for withdrawing the guide 46 from the final stop position. The uprights 51 and 60 are also provided with bend contour stops 71 and 72 as a further insurance that the workpiece 56 obtains the desired trough geometry.

FIG. 7 indicates the form of pressure plates or hinge adaptors for use where it is desired to form a workpiece to a cross configuration which would normally be expected from a workpiece having a width smaller than the actual workpiece being utilized. As shown in FIG. 7, the hinge adaptors 80 have pivot points 81 which can be located inboard of a workpiece 82. The adaptors 80 are formed with a channel 83 defined by a wall 84 and a lip 85. The adaptors 80 prevent relative movement of the longitudinal edge regions of the workpiece 82 with reference to the adaptors 80. In use of these hinge adaptors the force is applied through the pivot points 81 and the adaptors 80 to the longitudinal edges of the workpiece 82. To ensure bending in the correct direction a vertical force is applied to the longitudinal center line of the plate 82 in the direction of arrow V in FIG. 7. The output force is applied to the surface of the workpiece 82 remote from the pivot points 81 so as to ensure that no bending takes place in the longitudinally extending regions of the plate enclosed within the adaptors and adjacent the longitudinal edges of the plate.

FIG. 8 further illustrates the fill 53 and 62 in the apparatus shown in FIGS. 5 and 6. As shown in FIG. 8, the fill 53 is secured between the pressure plate 49 and the jaw 52 by means of nut and bolt assemblies and 91. This allows removal of the fill 53 and its replacement by a fill of different size. Thus, it is possible to adapt the apparatus shown in FIGS. 5 and 6 to varying design requirements of trough geometry.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising a frame, at least two opposed parallel elongate pressure plates on said frame, constraining means on said pressure plates adapted to engage the longitudinal edges of said workpiece, and pressure means for moving said plates towards one another, each of said pressure plates beingpivotable about a horizontal axis and the plane of said constraining means being co-planar with each of said axes and with said planar workpiece positioned in said constraining means prior to forming said trough shape.

2. An apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising a frame, at least two opposed parallel elongate pressure plates on said frame, constraining means on said pressure plates adapted to engage the longitudinal edges of said workpiece, each of said pressure plates being pivotable about a horizontal axis and said constraining means comprises a U-shaped channel, the plane of said channel being offset with respect to said axis, pressure means for moving said plates towards one another, said frame including transverse ways, at least one of said pressure plates being mounted on guides and adapted to move therealong in parallel alignment with the other of said plates, and limit means controlling the relative movement of said plates.

3. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising:

a frame;

at least two opposed parallel elongate pressure plates on said frame, each having a length at least as long as the length of said elongate planar workpiece; constraining means on each of said pressure plates adapted to engage the longitudinal edges of said workpiece; and

means for moving said pressure plates towards one another to bend the elongate planar workpiece into an elongate trough which is U-shaped in transverse section, each of said elongate parallel pressure plates includes an elongate axis, said axes being in a common plane, and wherein each of said pressure plates is freely pivotally mounted on said frame for pivoting about said axis such that said pressure plates are free to pivot about said axes upon motion of said pressure plates towards one another, said pivoting motion being imparted by the resistance to bending of said planar workpiece.

4. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising:

a frame;

at least two opposed parallel elongate pressure plates on said frame, each having a length at least as long as the length of said elongate planar workpiece; constraining means on each of said pressure plates adapted to engage the longitudinal edges or said workpiece; and

means for moving said pressure plates towards one another to bend the elongate planar workpiece into an elongate trough which is U-shaped in transverse section, said constraining means are constructed and arranged to allow free rotational movement of the longitudinal edges therein.

5. An apparatus as claimed in claim 2 wherein the relative movement of said pressure plates is effected by means of screw threads mounted transversely on said frame and operatively connects with said pressure plates.

Claims (5)

1. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising a frame, at least two opposed parallel elongate pressure plates on said frame, constraining means on said pressure plates adapted to engage the longitudinal edges of said workpiece, and pressure means for moving said plates towards one another, each of said pressure plates being pivotable about a horizontal axis and the plane of said constraining means being co-planar with each of said axes and with said planar workpiece positioned in said constraining means prior to forming said trough shape.

2. An apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising a frame, at least two opposed parallel elongate pressure plates on said frame, constraining means on said pressure plates adapted to engage the longitudinal edges of said workpiece, each of said pressure plates being pivotable about a horizontal axis and said constraining means comprises a U-shaped channel, the plane of said channel being offset with respect to said axis, pressure means for moving said plates towards one another, said frame including transverse ways, at least one of said pressure plates being mounted on guides and adapted to move therealong in parallel alignment with the other of said plates, and limit means controlling the relative movement of said plates.

3. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising: a frame; at least two opposed parallel elongate pressure plates on said frame, each having a length at least as long as the length of said elongate planar workpiece; constraining mEans on each of said pressure plates adapted to engage the longitudinal edges of said workpiece; and means for moving said pressure plates towards one another to bend the elongate planar workpiece into an elongate trough which is U-shaped in transverse section, each of said elongate parallel pressure plates includes an elongate axis, said axes being in a common plane, and wherein each of said pressure plates is freely pivotally mounted on said frame for pivoting about said axis such that said pressure plates are free to pivot about said axes upon motion of said pressure plates towards one another, said pivoting motion being imparted by the resistance to bending of said planar workpiece.

4. Apparatus for forming an elongate trough member from an elongate planar workpiece, said apparatus comprising: a frame; at least two opposed parallel elongate pressure plates on said frame, each having a length at least as long as the length of said elongate planar workpiece; constraining means on each of said pressure plates adapted to engage the longitudinal edges or said workpiece; and means for moving said pressure plates towards one another to bend the elongate planar workpiece into an elongate trough which is U-shaped in transverse section, said constraining means are constructed and arranged to allow free rotational movement of the longitudinal edges therein.

5. An apparatus as claimed in claim 2 wherein the relative movement of said pressure plates is effected by means of screw threads mounted transversely on said frame and operatively connects with said pressure plates.

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