US2419724A

US2419724A - Method and apparatus for bending plate and the like

Info

Publication number: US2419724A
Application number: US481692A
Authority: US
Inventors: Emmor H Millard; Frederick R Wilson
Original assignee: STEEL PROC Co
Current assignee: STEEL PROC Co; STEEL PROCESSING Co
Priority date: 1943-04-03
Filing date: 1943-04-03
Publication date: 1947-04-29
Anticipated expiration: 1964-04-29
Also published as: GB572845A

Description

April 29, 1947. MlLLARD ET AL 2,419,724

METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 1943 4 Sheets-Sheet l MM w Sm: m R L mm M v v mm m m Hm MW m E 5 April 29, 1947. I E. H. MILLARD ET AL 2,419,724

METHJD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 1943 4 Sheets-Sheet 2 INVENTORS EMMoR hf MIL MR0 and FEEDER/CK R. W/LSO/V,

April 29, 1947. E. H. MlLLARD T AL METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE- Filed April 3, 1943 4 Sheets$heet 3 fig? ll a.

l1 Fig.5. 10

J0 INVENTORS f/hMae/iM/L MR0 and FEEDER/CK A. W/Lso/v,

April 29, 1947.

E. H. MILLARD ET AL 2,419,724

METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 1945 4 Sheets-Sheet 4 Patented Apr. 29, 1947 METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE Emmor H. Millard, Mount Lebanon, and Frederick R. Wilson, Canonsburg, Pa., assignors to Steel Processing Company, Pittsburgh, Pa., a corporation of Pennsylvania Application April 3, 1943, Serial No. 481,692

22 Claims. 1

This invention relates to a method of and apparatus for the bending of plates, strips, bars and the like, and more especially to a method of and apparatus for forming relatively heavy gauge flat plates of considerable length into an elongated structure including a trough-like body portion and lateral side flange portions, the cross-section of which is approximately U-shape with flanges. Such a plate construction describes the well known Isherwood plate, such plates being especially adaptable for use and extensively employed in ship constructions.

Our invention will be particularly described in connection with the method and apparatus for the fabrication of such plates, but our invention is not to be limited to such manufacture, as it is also applicable to the art of bending fiat plates into various angular configurations by the provision of bending means having spaced apart plate supports and bending elements and having a cooperating abutment disaligned with said supports to engage the upper surface of the plate, operable to effect bending of plates along predetermined lines while the plate is unclamped on said supports and movable into engagement with the abutment which may vary in cross-section.

As heretofore fabricated Isherwood plates have been formed by following a plurality of independent bending operations producing too sharp bends, and have frequently been rejected due to the weakness developed at the bending lines of the predetermined shaped plate, and, when not discovered prior to assemblage, have caused serious trouble in use.

An object of our invention is to provide a new and improved simple and efiicient method of bending, whereby to eliminate the several steps of bending heretofore followed and to produce a plate of the character specified having rounded bending lines or zones, free of the weaknesses heretofore present in such plates.

Further objects are; to bend the plates without the employment of the frequently used male and female-die construction, or the like, whereby to effect the desired bending without subjecting th work or plates to harmful pressure along the bending lines or zones to stretch or rupture the fibers of the metal, as frequently hap ns; to provide new and improved bending means for efiecting uniform bends, and a construction of a character permitting a free travel of the material between the opposed upper and lower bending means employed.

In the accompanying drawings, which illustrate a preferred embodiment of apparatus employed in the practice of our invention,

Fig. l is an enlarged transverse sectional view taken on line I-I of Fig. 2;

Fig. 2, a central longitudinal vertical sectional View;

Fig. 3, a horizontal sectional view taken on line III-III of Fig. 2;

Figs. 4-7 are diagrammatic views somewhat similar to Fig. 1, showing the successive stages of bending the work or plate from the initial bending to completion of the final form, as shown by Fig.

Fig. 8, a perspective view of the finished plate;

Fig. 9, a diagrammatic view particularly showing a power mechanism;

Fig. 10, an enlarged sectional view of a control valve; and

Fig. 11, a cross section on line X-X of Fig. 10;

Referring to the drawings, our invention comprises a skeleton frame tunnel-like structure designated generally by 5, made up of structural members including a base portion 6, side portions 1, the latter preferably including vertical extend ing I-beams, and a top portion -8 including cross members 9 suitably connected with and supported by the members entering into the formation of the sides. The frame structure however, may be constructed in any suitable manner provided it is designed to house bending means'of a character embodying our invention and particularly adapted for bending plates, strips and the like, of considerable length and of relatively heavy gauge mate-'- rial.

The bending means or elements as illustrated include a series of independent bending units l0 disposed in alinement and extending longitudinally of and within the housing or framing, thus providing bending means for long sections of plate, etc. In lieu of the separate units l0 they may be joined together to form a unitary elongated unit. Each of the several units comprises a stationary and a movable member or platen, the upper platen II is secured to and supported by the cross members 9. This platen constitutes a stationary member against which the work is carried in the bending operation, the said member or platen I I having mounted thereon suitable forming blocks or abutments for engagement with the work. As illustrated, the forming blocks or abutments on platen ll consist of centrally disposed depending members [2, suspended from the cross members and platen on hanger bolts I3. This member l2, a shown, includes a cap Piece l4 and intermediate removable filler members orshims l5. Said cap piece M has parallel rounded work-contacting edges a and its under surface 14* is preferably concave. Arranged on each side of the center member I2 are spaced apart elongated Work contact members I6 having inclined diverging under surfaces l6 adapted to bend metal plates through contact therewith at outer edges I6 the shape of these surfaces affording an opportunity for the edge portions of the plate to bend slightly beyond the horizontal plane to 3 allow for spring-back of the metal into the horizontal plane.

The lower movable member H is mounted for vertical movement on structural members 18 carried on the plunger 19 of a hydraulic cylinder 20.

Suitable guide means consisting of guide rods 2| secured to the side framing, engage grooves b disposed on the platen in alinement with the work contacting members [3 of the upper platen and extend throughout thelength of the apparatus. This member I7 is further provided with a center block or piece 23 disposed in alinement with the central depending member [2 of theupper platen, both

members

12 and 23 extending the full length of the apparatus. Block or member 23 is raised centrally to provide a work-contacting line or edge 23 The pedestals 22 may be provided with wear-shoes 24 having rounded edges 24*, and the shoes may be raised or lowered slightly by the employment of shims 25, to compensate for wear. It will be noted that the upper surfaces of shoes 24 are parallel to the surfaces Hi. This arrangement or the equivalent provides line contact only of said shoes with the plate and such contact is disaligned with that at the edges lfi Our invention contemplates either a simultaneous operation of all of the units it or an independent operation of one or more units, depending upon the length of plate to be bent into the desired and predetermined configuration. The length of the plates most usually fabricated vary from twelve to forty-two feet and usually of a finished width of five feet. It will also be understood that our invention contemplates the production of plates having a considerable variation in depth as well as in the gauge of material employed and that owing to adjustability and arrangement of the bending means embodied in our invention, all of the said variations may be provided for with comparative case.

In the practice of our invention the plate or other member to be formed into the predetermined configuration'and size, and indicated by the letter p in Figs. 1 and 2, is fed into the apparatus lengthwise from an end thereof and is supported and carried unclamp'ed upon the spaced apart elongated longitudinally extending work supporting elements or pedestals 22, mounted on the several vertically movable members or platens ll. As illustrated and as preferred, in forming Isherwood plates, for example, the plate is positioned on said members 22 in a manner to provide an unsupported central portion between the elements, which portion when brought into contact with the various alined abutments or members l2 of the stationary members on platens II, by the upward movement of members ll, actuated by the hydraulic cylinders 20 or other suitable power means, forms the elongated work into a continuous member having a cross-section including a trough or U-like portion d having inclined walls e, and edge flanges f.

The various stages of bending, are particularly shown by Figs. 4 to 7 inclusive. It will be understood that the work is not clamped, but simply rests above the supports and as the lower platens rise, the unsupported portion of the work between the pedestals orsupporting elements is carried into engagement with the rounded corners of the depending centrally disposed abutments of the upper platens and on its initial bending engagement therewith the plate is caused to assume a generally somewhat U-shape having a slightly dished center or rounded apex, the legs of the U extending or diverging upwardly at an angle defined by a line drawn from a corner of the center abutment to a point short of contact with the outside edge of fixed members it, as clearly shown in Fig. 4. Attention is particularly called to the fact that the plate is bent through fulcruming and slidingon edges of the support elements in cooperation with the fixed abutments.

When the plate has been bent as in Fig. 4, a continued movement of the lower platen or platens will cause the edges of the plate or work to contact with the fixed members 16 as shown by Fig. 5, and thus start the bending to form the flanges, this bend being in anopposite or reverse angle to that of the inclined Walls of the trough portion or body. A continuation of the upward movement, as illustrated by Figs. 6 and '7, will complete the formation of the flange portions and during the formation of the flanges, the blocks 23 are carried sufliciently close to the under faces of the aligned abutments of members [2 to flatten the central portion of the trough into a plane parallel with the plane of the flanges as clearly shown by Fig. 7.

Our invention contemplates an apparatus having a combination and arrangement of operative parts operable in such a manner that the work is not subjected to compressing, compacting, or clamping contact between opposing bending elements, but is only contacted by the apparatus at the lines, zones or fulcrum of bend up to final stage.

Thus, in our illustrative embodiment the upper and lower bending elements do not make compressive contact with the plate or work, or compress the material between the flxed and movable members to the end that the metal is not tightly caught therebetween, and, consequently is free to adjust itself and slide or travel between the opposed bending members with the movement of r' the fibers at all times parallel, therefore resulting in no separation or weakening of the fibers.

Our invention is therefore to be distinguished from a method of fabricating in which the metal of the work is clamped between opposing dies, for, in the latter case, compression of the fiber 0n the inside of the bend is caused, whereas the fibers on the outside in tension are stretched, this causes a definite line of cleavage in the grain of the metal between the portion in compression and the portion in tension, with a weakening at the bends.

It is apparent that at all times bending is efiected solely through edge or line contact with the plate as all edges a, 23, 24 and I6 are parallel and sufficiently smooth or rounded. Said block 23 is centrally raised as shown at 23 particularly to start and carry to completion the last stage of metal flow as shown in Figs. 4 to 7. Cap M of black [2 is preferably concave and block 23 is shaped as pointed out so that minimum pressure is required to produce a flat surface as there is only line contact 50 that metal moves easily. The edge 21*! causes the metal to move right and left around edges (1 without changing the granular or fiber structure in any way, all stresses and strains beingparallel during this operation to avoid mashing or killing of the steel through trappi ng :.of 'the fibers at final bending points with resulting changes in granular structure of metal at these points which would in many instances cause fractures of the metal. The blocks l6 and 24 at edges H5 and 2& enable movement of the metal over rounded corners or edges as the metal movement at this stage comes from the center of block 23, and at the same time the bending is progressing and when metal movement has been completed, the bending has also been completed, and in the process the mill rolling strains have worked out of the edges of the plate, and there is no wavy edge condition on the plate and the flanges of the plate are perfectly flat and in a plane approximately parallel with the bottom of the formed plate. The speed of operation is such, in combination with the minimum number of lines of contact and rounded corners, sufficiently lubricated, allows time for the metal to move freely. The metal movement is reversed in the latter third of the upward stroke of the platen ID as will be noted from considering Figs. 5, 6 and 7.

Any suitable power mechanism may be employed for operating the apparatus provided the mechanism includes means for controlling the length of the stroke of the hydraulic cylinders with distance between the work contacting surfaces of the bending elements on the upper and lower platens whereby the opposing bending elements are never brought into binding contact.

As particularly illustrated by Fig. 9, we employ an associated power mechanism including a pressure fluid system or line extending to the several cylinders 29 from a pump P, and an electrical control circuit.

A designates a fluid control valve in communication with a valve controlled main fluid pressure line or pipe g having a valve h. i designate valve controlled branch lines leading to the respective hydraulic cylinders and :i an exhaust line from the valve A to a fluid storage tank k. The enlarged view of valve A (Fig. 10) shows the hydraulic line from pump to cylinders as being closed to pressure and open for return of fluid to the supply tank, and in the diagrammatic View, Fig. 9, the plungers of the cylinders are shown in lowered position.

To start the bending operation the valve A is opened to pressure from the pump by pressing a push button B of the electric circuit which closes a circuit through a solenoid c which pulls the valve down to open the line and which closes the exhaust 7'.

Attached to any movable part of the apparatus, actuated by movement of the rising plunger, is an arm or switch closing device F. This arm is adjustably mounted, so that it may be adjusted with respect to its distance between its mounting and the switch arm of a switch S. When the piston has moved to bring the arm into contact with the switch arm, a circuit is closed through solenoid E which moves the valve to close the fluid pressure line from the pump and put the line in exhaust.

We claim:

1. In apparatus for forming flat plate into substantially trough-like form having side wall flanges, a plurality of movable bending means disposed in a line, each bending means having supports at spaced apart zones provided with rounded edges as the sole portions thereof on one Or more of which rounded edges the plate is adapted to rest in unclamped condition according to its length, a fixed bending means overhead with respect to the movable bending means providing an abutment edge for each of the latter as the sole plate-contacting portions of the movable bending means at said zones disaligned with respect to the coacting support and adapted to engage the upper surface of the plate, said fixed bending means having spaced parallel platecontacting edges intermediate and spaced from the supports, the movable bending means having a plate-contacting edge parallel to and intermediate the last mentioned edges, means operable to move the foremost movable bending means toward the fixed bending means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of the coacting supports to bend the plate, said mechanism including connections to couple all movable bending means to operate in unitary relation, and control means to cause the movable bending means to cease operation after predetermined movement so that there is clearance for springback action of the plate at the center and both edge portions.

2. In apparatus for forming flat plate into angular configuration, bending means having spaced apart supports on edges of which the plate is adapted to rest in unclamped condition, bending means having edges disaligned with the first mentioned edges and outwardly thereof to engage the upper surface of the plate and having an abutment intermediate said edges disaligned with the said supports provided with spaced edges parallel to said edges to engage the upper surface of the plate, edge means on the first mentioned bending means to engage the lower surface of the plate intermediate the edges of the abutment, mechanism operable to move one of said means relative to the other means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding inwardly and outwardly with respect to the longitudinal median line of the plate on said paralle1 edges of said supports to bend the plate.

3. In apparatus for forming flat plate into substantially trough-like form having side wall flanges, means to initially bow the plate having spaced parallel plate-contacting edges, edge means to support the plate durin said bowing so that the movement of metal thereof will be inwardly toward the first-mentioned means, and means to thereupon line-contact the metal in opposition to the first mentioned and second mentioned means intermediate the said parallel edges and also outwardly of the edge means to bend the metal with outward movement thereof, the construction enabling spring-back action at the center and side wall flanges of the form.

4. The method of forming cold metallic plate into an angular configuration while maintaining parallelism of the fibers of the metal consisting in simultaneously moving the metal thereof inwardly with respect to its side edges and bowing an intermediate portion of the plate, and in thereafter reversing the direction of movement of the metal to move the latter outwardly while reducing the bow of bowed intermediate portion and bending the portions of the plate along said edges into side wall flanges, all parts of the plate during the inward and reverse movements being free to slide.

5. The method of bending a flat metal plate in a machine having two bending means, one

of which has spaced elements, which methodconsists in disposing said plate between the bends 7 ing means and resting it freely on said elements, moving one of the bendin means relatively to the other to an extent short of trapping of the fibers of the plate with such other bending means contacting the plate at spaced parallel lines and thereby bending the plate and pulling the metal inwardly while leaving it opposite side portions free and fulcrumed on edges of said elements, resulting in a central relatively shallow portion and portions diverging therefrom to the side edges of the metal, then bending the metal and its side portions while forcing the metal outwardly on said edges by further relative movement of the two bending means short of trapping of the fibers f the plate.

6. The method of bending a flat metal plate in a machine having two bending means, one of which has spaced elements, which method consists in disposing said plate between the bending means and resting it freely on said elements, hydraulically moving one of the bending means relatively to the other to a limited extent with such other bending means contacting the plate at spaced parallel lines resulting in a concave central portion and portions diverging therefrom, thereby bending the plate and pulling the metal inwardly while leaving its opposite side portions free and fulcrumed on edges of said elements, as another stage in bending the terminals of said side portions in reverse direction into a plane approximately parallel to the plane of the central portion, and as a final stage in simultaneously flattening the central portion through contact at a line intermediate said parallel lines on the opposite sides of the plate and said terminals.

'7. The method of bending a flat metal plate in a machine having two bending means, one of which has spaced elements, which method consists in disposing said plate between the bending means and resting it freely on said elements, moving one of the bending means relatively to the other to a limited extent and thereby bending th plate and pulling the metal inwardly while leaving its opposite side portions free and fulcrumed on edges of said elements, then bending the metal and its side portions while forcing the metal outwardly on said edges by further relative movement of the two bending means.

8. The method of bending a fiat metal plate in a machine having two bending means, one of which has spaced elements, which method consists in disposing said plate between the bending means and resting it freely on said elements, moving one of the bending means relatively to the other to a limited extent and thereby bending the metal and pulling the metal inwardly while leaving its opposite side portions free and fulcruined on edges of said element so as to have a shallow dished central portion and'diverging portions extending therefrom, then bending the metal and its side portions while forcing the metal outwardly on said edges in thereverse direction angularlywith respect to the remainder of the diverging portions into a plane approximately parallel with the central portion by further relative movement of the two bending means through line contact with its convex surface approximately midway of the ends of the dished portion.

9. An apparatus for forming fiat plate into substantially trough-like form having sidewall flanges, bending means having spaced apart supports on which the plate is adapted to rest in unclamped position, bending means in a zone between the zones of said supports having abut- .8 ment edges disaligned with respect to said sup-- ports to engage the upper surface of the plate, mechanism operable to move one of said means relatively to the other means to pull the metal inwardly over edges of the supports from the sides of the plate toward the second bending means through fulcruming and sliding of the plate on said edges to bend the plate.

10. An apparatus for forming flat plate into substantially trough-like form having side wall flanges, bending means having supports at spaced apart zones provided with faces out of parallelism with the horizontal providing edges at their summits as the sole portions thereof on which the plate may rest in unclamped position, bending means in a zone between the zones of said support having abutment edges disaligned with respect to said support as the sole plate-contacting portions of the second-mentioned bending means to engage the upper surface of the plate, mechanism operable to move one of said means relative to the other means to pull the metal inwardly from the sides of the plate toward the second-bending means and reversely push the metal through fulcruming and sliding of the plate on said edges of said supports to bend the plate while enabling movement of the metal outwardly with final spring-back action.

11. An apparatus for forming flat plate into substantially trough-like form having side wall flanges, a plurality of movable bending means, each movable bending means having supports at spaced apart zones provided with edges as the summits thereof and the sole portions thereof on one or more of which the plate is adapted to rest in unclamped condition according to its length, fixed bending means providing an abutment for each movable bending means disaligned with the respective supports thereof and adapted to engage the upper surface of the plate, said fixed bending means having an arched under-surface provided with spaced parallel plate-contacting edges intermediate and spaced from the supports, the movable bending means having a platecontacting edge as its summit parallel to and intermediate the respective last-mentioned edges, and mechanism operable to selectively move one movable bending means or a plurality of movable bending means toward the fixed bending means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of said support to bend the plate.

12. An apparatus for forming flat plate into substantially trough-like form having side wall flanges, a plurality of movable bending means, each movable bending means having supports at spaced apart zones provided with edges as the summits thereof and sole portions thereof on one or more of which the plate is adapted to rest in unclamped condition according to its length, fixed bending means providin an abutment for each movable bending means disaligned with the respective supports thereof and adapted to engage the upper surface of the plate, said fixed bending means having an arched undersurface provided with spaced parallel platecontacting edges intermediate and spaced from the supports, the movable bending means having a plate-contacting edge as its summit parallel to and intermediate the respective last-mentioned edges, and mechanism operable to selectively move one movablebending means or a plurality of movable bending means toward the fixed bend-a ing means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of said support to bend the plate, the bending means accordingly being of a construction which avoids compression of the fibers of the plate and permits final spring-back action of the plate at the center and at both the edge portions approximately simultaneously.

13.' An apparatus for forming fiat plate into substantially trough-like form having side wall flanges, the apparatus being provided with a first bending means having supports at spaced apart zones provided with edges as the summits thereof and sole portions thereof on which the plate is adapted to rest in unclamped condition, a second bending means providing an abutment for the first bending means disaligned with the respective supports thereof and adapted to engage the upper surface of the plate, said second bending means having an arched under-surface provided with spaced parallel plate-contacting edges intermediate and spaced from the supports, the first bending means having a plate-contacting edge as its summit parallel to and. intermediate the last mentioned edges to engage the lower surface of the plate, and mechanism operable to move one of said bending means toward the other bending means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of said supports to bend the plate.

14. An apparatus for forming flat plate into substantially trough-like form having side wall flanges, the apparatus being provided with a first bending means having supports at spaced apart zones provided with edges as the summits thereof and sole portions thereof on which the plate is adapted to rest in unclamped condition, a second bending means providing an abutment for the first bending means disaligned with the respective supports thereof and adapted to en age the upper surface of the plate, said second bending means having an under-surface provided with spaced parallel plate-contacting edges intermediate and spaced from the supports, the first bending means having a plate-contacting surface opposed to the last mentioned edges to engage the lower surface of the plate, and mechanism operable to move one of said bending means toward the other bending means to move the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of said supports to bend the plate.

15. An apparatus for forming fiat plate into substantially trough-like form having side wall flanges, the apparatus being provided with a first bending means having supports at spaced apart zones provided with edges at the summits thereof and sole portions thereof on which the plate i adapted to rest in unclamped condition, a second bending means providing an abutment for th first bending means disaligned with the respective supports thereof and adapted to engage the upper surface of the plate, said abutment being intermediate and spaced from the supports, the first bending means having a platecontacting surface opposed to the abutment and out of parallelism thereto to engage the lower surface of the plate short of clamping thereof.

10 andmechanism operable to move one of said bending means toward the other bending means to move'the metal inwardly from the sides of the plate toward its longitudinal median line and then reversely move the metal through fulcruming and sliding of the plate on said parallel edges of said supports to bend the plate.

16. The method of forming fiat metallic plate into substantially trough-like form having side wall flanges, comprising disposing and resting the plate in cold condition between opposed sections and on the lower sections of at least three spaced apart bending devices wherein the plane offinal coaction of the sections of the intermediate bending device is longitudinally disaligned with respect to the other bending devices, and in moving the sections on one side of the plate relatively to the remainder of the sections at such areas, times and degree of engagement of the said sections with the plate to bend the plate whileleavingall parts of the plate throughout an operation free to slide inwardly and outwardly with respect to the longitudinal median line of the plate, whereby trapping of the metal or distortion of its fiber is avoided.

17. The method of bending a cold metal plate consisting in cold drawing the plate inwardly from an edge thereof to provide a flange adjacent said edge and a bowed portion inwardly spaced from said edge and out of the plane thereof by the action of bending means engaging the plate to a degree short of trapping of the fibers of the plate, and in thereafter reducing the degree of bow of said bowed portion while the plate isengaged by the bending means to a degree short of trapping of the fibers of the plate by reversely drawing the plate from the zone of said bowed portion.

.18. The method of producing a flanged structure from a cold metal fiat plate, which comprises cold working the plate by subjecting it to bending action along spaced bending edges disposed approximately in parallelism and while engaging the plate to a degree short of trapping of the fibers of the metal, and moving the plate while so engaged in reverse directions with respect to opposite sides of and across said edges.

19. A method of forming fiat plate into generally trough-like form consisting in contacting the plate at spaced parallel lines and moving the plate to bend it at said lines while loosely supported and unclamped from said lines to the marginal edges of said plate, resulting in a central relatively shallow channel with sides diverging to said edges, and while the plate is still unclamped, in bending the terminals of the diver ing portions in the reverse direction into a plane approximately parallel to the plane of the central portion.

20. A method according to claim 19 in which the operation is effected in stages the first consisting in contacting the plate at spaced parallel lines and moving the plate to bend it at said lines while loosely supported and unclamped from said lines to the marginal edges of the plate and the second in bending the terminals of the diverging portions in the reverse direction into a plane approximately parallel to the plane of the central portion.

21. A method of forming fiat plate into general- 1y trough-like form consisting in disposing the fiat plate between two bending means and resting freely on spaced elements of one of such means, in moving one of said means relatively to the other means to a limited extent to bend the plate with 11 its opposite side portions free and fulcrumed on edges. of said elements, and in then bending the terminals of said portions on said edges through relative movement of the two bending means.

22. Apparatus for forming fiat plate into substantially trough-like form comprising bending means having spaced apart supports on which the plate is adapted to rest in unclamped condition, bending means having anabutment disaligned with said supports to engage the upper surface of the plate, mechanism operable to move one of said means relative to the other means to bend the plate through fulcruming and sliding on edges 'of said supports.

EMMOR H. MILLARD. FREDERICK R. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Booth Apr, 4, 1854 Worthen et a1 July 5, 1859 Henderson Dec. 22, 1896 Brown Dec. 17, 1901 Frey Feb. 5, 1907 Klocke July 26, 1910 Minshull Nov. 29, 1910 Verdin et a1 Oct. 3,1911 Small Aug. 9, 1921 Briggs et a1 Apr. 30, 1878 Ainsworth Mar. 25, 1884 Barr Nov. 15, 1904 Bunker Jan. 8, 1929 Verson et a1 June 16, 1942 .Klenzle June 27, 1939 Ogden et al Aug. 1, 1922