US2709933A - Plural forging - Google Patents

Description

June 7, 1955 M. s. REED PLURAL FORGING Filed June 3, 1952 h @in &\\\\\\\\4 mqyyw l ATTORNEYS' United States Patent() "ice PLURAL FORGING Macdonald S. Reed, Erie, Pa.

Application June 3, 1952, Serial No. 291,514 4 claims. (ci. :sv- 552) This vinvention relates to methods of forgingV sheets and particularly to the forging of thin sheets having integral upstanding ribs, usually referred to as integrallystifened panels.

It is desirable, especially in the aircraft industry, to have sheets of relatively large' surface area and quite thin provided with `integral upstanding ribs or flanges v This method offers additional'advantages, among which the ability to forge materials to thicknesses otherformed integrally therewith to provide stiifening whereby such sheets may be employed as a rigid skin for the aircraft. It is usually desirable to have the ribs parallel to each other 'but the present invention is not limited to such an arrangement, as the ribs-may be arranged to form any other necessary or desirable pattern. The forging of such structural sheets-has heretofore been impossible by practical methodsl since it is extremely'v difficult to squeeze a rib or flange of the required height and thickness from a', thin sheet of material.' In gen-v eral, it is desirablethat finished sheets of a: thickness of the order of magnitude of %2 inch beprovided' with integral ribs or flanges projecting from one surface and spaced apart from 11/2l to 3 inches; The ribs are desirably of a height of the general order of l inch or more.

It can readily beseen that integral structural shapes of those dimensions are extremely diiiicult-to-produce by A number of factors contributed to the diiculties, among which were the relation between ribdimensions and skin thickness and the problem of ilowof material as related to pressure placed on fthedie., such'operationsim'v volving press forging of sheets to the required dimensions resulted in defects known as suck-in at the base of the ribs or anges. In causing the material to iiow until the skin thickness reached the desired values the friction against the die surfaces created conditions such that the surface of the sheet opposite each rib cavity developed depressions where the surface material was drawn or pushed into the cavity, thus resulting in a product having grooves on the face opposite the base of each rib. Such defects render the product unacceptable to the aircraft industry.

The present invention relates to a manner of forging such shapes by a method resulting in acceptable products of the desired dimensions without the defects of suckin. It is known that the pressure required to cause ow of the material being forged increases with the ratio of the least lateral dimension to the thickness of the metal in the direction in which the pressure is applied. Thus, if the lateral dimensions of a piece are the same in both cases, it requires considerably less pressure to cause the metal to ow if the sheet is 1A of an inch thick than the pressure required if the piece is only Vs of an inch thick.

The present invention contemplates taking two sheets -of stock material and simultaneously forging opposite faces thereof by means of opposed dies in a suitable press or hammer. Bearing in mind the pressure requirements discussed above, it will be seen that the effective thickness of material between the dies at the time the required reduction has been accomplished is twice that between the diev and bed where a .single sheet is forged to the required thickness.

rib-or-ange-deiining cavities on opposite sides. Thus, for symmetrical designs each sheet may be identical to the other and for non-symmetrical designs each sheet may bea mirror image of theother. sheets may have'different designs consisting of non-opposed ribs. At the completion of a forging operation according to the present invention two finished products result from each strokeof the press or hammer and thev total pressure'required remains less than that which would" be required to Yforge a single sheet by prior methods.

are:

wise not forgeable,V themaking of thin-walled forgingswith less pressure, the making of more than one piece at a time and creating-conditions for better flow of material. The' surfaces-of the two sheets originally placed in abutment remain as at surfaces and are readilyl separable upon removal from the dies.

It is therefore an object of this invention to 'provide a method of forging sheets more eiciently and more economically than by' methods heretofore known.

Another object of this invention is to provide a method of forging integrally stilened panels'of sheet metal' of practical dimensions. i i

It is still' another 'object of this invention to provide ai method for forging sheet material'whereby larger pieces maybe fabricated than possible -with previously known press or hammer forging methods.

hammer than heretofore possible.

Still another object of this invention is the provision of a method for forging structural shapes resulting ing a doubled output for each machine since each stroke thereof produces two finished articles.

Further objects and advantages will appear to 'those skilled vin the art-as the description proceeds in'connection with' the accompanying drawings, wherein:

Fig. l represents a cross-sectional view of an ideal integrally stiffened panel illustrating the approximate desired dimensions;

Fig. 2 is a transverse sectional view through a pair of dies illustrating the production of two finished sheets in accordance with the present invention; and

Fig. 3 is a fragmentary sectional view of a partially preformed sheet of stock material that may be employed to practice the present invention.

Fig. 1 illustrates generally the desired product consisting of a relatively thin skin 2 which may be of aluminum, aluminum alloy, or a suitable magnesium alloy for use in covering aircraft frames, or which may be any other suitable material. The skin 2 has integrally formed thereon spaced parallel upstanding ribs or flanges 4 joined integrally to one surface of the skin 2. In general, a satisfactory stiifened panel may be of a thickness of the order of /g inch having ribs 4 also of about %2 inch and projecting from skin 2 a distance of the order of l inch. In some applications it is desirable that the ribs be closer than illustrated and such stiened panels may readily be produced by the present invention. Fig. 1, in illustrating an ideal or desirable Patented June 7, 1955' The presentinvention contemplates employing two forming dies, each having Also, the two f shape,e-=shows-vopposite vsurfaces-fof the skin 2 as being para1le1and, opposite `facesof theribs .4 as paralleL,... In.

surfaces =may be made to taper slightly in a direction away i from each rib. to thus cause thefmaterialwto lilowf more readily.

Fig;- 2 illustrates an uppendie 6 and a lower-die` 7.

fix'edly .mounted on-.thestatonary bed of a press and the-:.diei6 will be mounted1on the movablehead-.of the press. Each-die is provided :with-'suitable-,cavities-S com` plementary--to the ribsior anges 4 to be produced, andi l0 In ia-practicing-the present k:inventionf-'thedie f7 will'beas -.shown.-are provided with1suftcient ;draft`to facilitateV removal 'ofthefnished` forgingsw The dies 6 and? are mountedwwith-their-cavities 8 (inthe form illustrated* cavities 8 compriseelongatedrparallelfgrooves) opposite each ftother.

The. portions Vof :the die-"faces between grooves A8 are shown as taperedtoward theoppositeldie' Y whereby the finished forgingl is thinner at :101than at`I` 12". adjacentxthe' bases-of ribs 4. A As -is well-known inl press-aforging, this tapering of the skinresults in makingl f theVK material flow more readily and with less pressure and thedifferencein skin -thickness at the base offtheribs and suflicientlygreatto render the productv undesirable.- The".

tapering of thefsurfaces, `commonly known asx-fulleringj also-'causes thematerialto flow into the -die'ffcavities more,y

readily.

If the top die 6 were Vmountedsinwa press-:having a r perfectly' parallel orvatbed andl a single 'sheetof` stock material were employed a product similar to the-top forging A would be produced but if reduced :tothe-di` mensions shown-much greater pressure wouldbe required and: the forging would 'be defective at points AC because By 'employing-two of suck-in previously referred to. sheets-of stock material and a pair: of opposed dies, as shown, vserious suck-in is not encounteredV since the method kcompletely eliminates =die=friction against fthe abutting surfaces of the two work pieces..y

lf desired; the sheets'of stock material placedfhetween the dies 6 and- 7 maybepreformedbya preliminary press forging operation'or by rollingg-or otherwise, to an intermediate form as ,illustratedfin Fig'. 3. In-Fig.-

3 the sheet 14 is thicker than-that desiredin -the nal product and has an integral rib or -body 'of material 16 projecting from one face thereof at the desired position otl each rib or ange d. The bodies 16 are in theV formof parallel stubby ribs spaced'apart a distance corresponding tothe space between the ribs in the final prod-A uct. A pair of such sheetsl as'shownfinFig'fS may be placed in back-to-back relation with their planar faces in A.abutment vand.,positioned...between dies...6 and ,7 with the integral bodies 16 registering with the entrances to cavities 8. By thus preforming the stock sheets suiiicient material is gathered at the location of the ribs so that a minimum amount of flow is necessary to produce the nal shape shown in Fig. 2. It is further contemplated that the dies be soformed and shaped as to produce suitable fillets and radii at the edges and corners of the finished productf'asdictated'by engineering practice.

While a single species of the invention has been shown and described herein; it is 4tobeunderstood that many modifications mayy be resorted to within the scope of the invention as defined by the appended claims.

I claim:

1. In a method of press forging structural shapes from thin sheet stock wherein said shapes comprise thin sheets having .spacedfintegral-xribsifupstanding from one face thereof-and. wherein'the height: landrspacingA of said ribs arexmultiplesofthethicknessof saidvSheetS, by causing the body material of said sheet stock to flow sideways into said..ribs andwherei-nlthe'volume of yand spacing between-saidribs is so related. to` the thickness of said of fdirecting andzconfining thegmaterialxthat ilows out-y wardlysbetween :said areas to l form ribs of predetermined 4. A methodas'denedsin claim 1 including the step ofaapplying pressure to 'said-areas in such mannerY that the central portions thereof are thinned to a greater extent than thefportions adjacent said spaces.

ReferencesCited in the ii'leof -this :patent UNITED STATES-PATENTS.

1,807,141 Wood; May 26, 1931 1,856,898 Wood.' May 3, 1932 2,250,542 Lodges.- Iuly 29, l1941 2,276,035 Guhl- Mar.v 10, 1942 2,430,083.- 1947 Sherman Nov. 4,

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