US2422883A

US2422883A - Method and apparatus for flanging sheet metal

Info

Publication number: US2422883A
Application number: US428094A
Authority: US
Inventors: Henry H Bruderlin
Original assignee: Douglas Aircraft Co Inc
Current assignee: Douglas Aircraft Co Inc
Priority date: 1942-01-24
Filing date: 1942-01-24
Publication date: 1947-06-24
Anticipated expiration: 1964-06-24

Description

June24, 1947. H. H. BRUDERLIN METHOD AND APPARATUS FOR FLANGING SHEETJETAL Filed Jan. 24. 1942 A 2 Sheets-Sheet 1 ll 14 24 Z! A Patented June. 24,. 19 47 UNITED STATES OFFICE METHOD AND APPARATUS FOR FLANGING SHEET METAL Application January 24, 1942, Serial No. 428,094

9 Claims. (Cl. 1113-44) Myinvention relates toan improvement in the art of forming parts from sheet metal wherein a body of rubbery material is applied under pressure.

to the sheet to form it around a die block, and

. relates in particular to an improvement in the art whereby a deeper drawing of flanges may be accomplished. v

The invention is especially suited for the forming of a relatively small number of parts not warranting the making of companion steel punch and die parts, and it is especially valuable in the aircraft industry where many parts are used which are formed from sheet Duralumin. Unless an aircraft has been fully designed and placed in quantity production, the expenditure of many thousands of dollars for companion punch and die parts is not warranted. Each new aircraft designed is as a general rule considered to be an advance over the existing art. In many, instances only relatively few of the designs will be built before a new and'better design is engineered. If punches anddies had been made for the first design, their abondonment would constitute an appreciable loss. The present invention is an improvement in the art of forming parts from sheet metal in the so-called rubber press which makes possible the formation of many difl'erent shapes and sizes of parts within the limitations of the process with regard to depth of draw of flanges around curved edges of a part and depth of draw around curved edges where it is desired to have a relatively sharp corner. Where the sheet material is drawn downward over or from a curved edge or corner of a die block, there is a pronounced tendency for the downwardly bent portion to crinkle, which can beavoided only by drawing or stretching the metal as it is moved I downward adjacent the curved side wall of the die block, such stretching or drawing of the metal elongating the excessive metal which would otherwise go into the formation of a crinkle.

an object of the invention is to provide a method and apparatus for drawing the portions of the sheet in a flange around a curved edge or corner of the formed part, which method and apparatus are simple and inexpensive, yet produce satisfactory depth of draw.

A furtherobject of the invention is to produce parts formed from sheet metal, having a suitably deep drawing of flanges around curved edges, accomplished without scratching Of the surface of Y the metal. A surface scratch in a part drawn from sheet Duralumin and intended for use in aircraft is often ample ground for rejection of the part, since it is considered that such a scratch 2 often furnishes a starting point fdr rupture under the conditions of vibration and stress producEd in the operation of aircraft.

Further objects and advantages of the invention will be brought'out in the following part of the specification. Referring to the drawings which are for illustrative purposes only,

Fig. 1 is a perspective view of a simple article formed in the practice of the invention to give an example of the results obtained.

Fig. 2 is a cross-sectional view showing complementary parts for practice of the invention in place'in a rubber press.

Fig. 3 is a sectional view similar to Fig. 2 showing the position of the cooperating parts at the start of the forming operation.

Fig. 4 is a sectional view similar to Fig. 2 showing a further step in the forming operation.

Fig. 5 is a sectional view similar to Fig. 2 showing the relative positions of the cooperating parts at the completion of the downward movement of the head of the press.

I Fig. 6 is a fragmentary sectional view showing a cooperation of Parts employed to give a more pronounced drawing effect.

Fig. '1 is a perspective view of a curved frame channel formed from sheet metal.

Fig. 8 is a fragmentary sectional view showing the manner in which my invention may be employed in the formation of a channel such as shown in Fig. 7.

Fig. 1 shows an article ID in the condition in which it is taken from the forming press. It comprises a top wall ll having an opening l2 therein and having an edge l3, portions of which are curved. A flange strip l4 projects downwardly from the edge l3. The upper portion iii of this flange strip, or the flange proper of the article I0, is straight and. uncrinkled above the dotted line l6. The lower portion ll of the strip M has crinkles l8 therein. The downwardly projecting skirt or strip I4 is parted along the dotted line 5, removing thecrinkled edge portion I1 and leaving a finished article It! having a properly formed flange l5 along the curved edge thereof.' In the practice of my process, even though the corner formed along the edge I3 is relatively sharp, a suitable deep drawing of the flange l5 may be accomplished. The waste comprising the edge strip I1 is relatively small.

In Fig. 2 I show the table IQ of a forming press eral characteristics of rubber so that it will be conformable under pressure to the contour of parts placed on the table l9. A die block 28 having an upper portion corresponding .to the shape of the part I8 is supported on the table l8. A rubber body 22 of elongated ring form and having an opening 23 therein is placed around the die block in the position shown, and upon the upper face of this rubber body 23 an edge restraining member 24 is placed, this edge restraining member comprising a plate of sufflciently rigid material, such as steel, having an openingtherein corresponding to the peripheral shape of the die block 28, so that the member 24 may be placed in a position surrounding the upper portion of the die block 28, as shown in Fig. 2. The sheet 25 to be formed is placed upon the upper face of the die block, with the edge portions thereof projecting over-adjacent portion of the member 24. The sheet 25 may be held by guide pins 28 in such position that the opening |2 in the plate 25 will be properly aligned with the depression 21 in the upper face of the die block 28.

As the head of the press 28 is moved downward, the press pad 2| will first engage the upper faces of the sheet 25 and the exposed portion of the edge restraining member 24, and the sheet will be forced downward against the upper face of the die block 28 and the upper face of the restraining member 24, and, as shown in Fig. 3, downward movement of the edge restraining member 24 will be initiated and the forming of the plate will be started, the rubber body 22 yielding downward under pressure applied to the edge restraining member by the press pad 2|.

Being formed of a sufficiently strong and rigid material, the member 24 can move only in a downward direction under pressure applied by the press pad'2l. The press pad 2| forces the edge portion H of the sheet 25 against the member 24, producing a frictional engagement of the,

an acute angle bend in the marginal portion of the blank adjacent the-die block, the compression in this area of the marginal portion of the blank is sufficiently resisted to inhibit the formation of wrinkles.

This inhibition of wrinkling is assisted by the clamping of the marginal portion of the blank between the rubber and the floating ring 24. It is also assisted by the continuous pressure of the rubber against the marginal portion of the blank, pushing the marginal portion into the acute angle space between the side face of the die blank and the inclined face. This downward pressure acts to concentrate the components of the circumferential compression above referred to in the direction of increasing the depth of the annular channel and the sharpness of the bend. The excess metal produced bythe drawing action, instead of forming wrinkles, is drawn into the bend in the deepening of the channel, and

formation of wrinkles is restricted to the outerperipheral region of the blank, as indicated in Figure 1.

The clamping of the marginal portion of the blank between the rubber and the ring 24 assists in the inhibition of the wrinkles in the bend area.

In the general practice of the invention it is desirable to undercut the lower portions of the around the corner 30 and the side face 3| of the die block 28, as the continued downward movement of the press pad 2|, as shown in Figs. 3 and 4, compresses the rubber body 22, moves the member 24 downward, and forms the sheet 25 down around the peripheral portion of the die block 28. This action will be continued until the cooperating parts reach the positions in which they are shown in Fig. 5, with the edge restraining member 24 disengaged from the edge portion l4 of the sheet 25. An important feature of the invention is the use of the downwardly and inwardly inclined face on the floating ring 24 resulting in the formation of an acuteangle bend in the marginal portion l4 of the blank, as this marginal portion is pushed downwardly into the acute angle space between the side wall 2| of the die block 28 and downwardly and inwardly inclined face of the ring 24. Thus, there is formed in the marginal portion M an annular channel of acute angle cross-section which provides a greatly increased resistance to the circumferential compression produced in the marginal portion I4 by the drawing operation. A characteristic of such circumferential compression is that it varies from zero where the blank is in contact with the die block to maximum at the outer periphery, of the blank. By forming die block 28 so as to provide spaces, or a continuous peripheral space 32 into which the rub- .substantially flat and straight, and the crinkles I8 willbe confined to the lower portion II. The die block 28 may be formed without great expense from metal, compressed fibrous products, or other materials of sufficient hardness, and the restraining ring 24 may be readily cut from sheet steel. These parts are capable of producing a large number of formed articles at a cost which is very low as compared to the hand forming of such articles, and when the use of any such formed part is abandoned because of changes in design, the loss occasioned by discarding or reworking the die block 28, the edge restraining member 24, and the rubber body 22, will not be great.

Under some conditions in the use of the invention, greater stretching and drawing effect is required than can be obtained from the arrange.- ment of parts shown in Figs. 2 to 5 inclusive. As shown in Fig. 6, additional gripping effect between the edge restraining member and the sheet may be obtained by use of a number of different expedients together or separately. Greater pressure of the edge portion l4 of the sheet 25 may be obtained by increasing the height of the rubber supporting body 22, thereby raising the edge restraining member 24 so that the sheet 25 will be su ported in raised relation to the upper face the upper face of the and therefore the blank member by the time the intermediate portion of the sheet 25 reaches the top face of the form- V ing block 28. In addition to the foregoing, the upper face ofthe edge restraining member 24 may beprovided with sinuous undulations 34 to increase the frictional retarding effect and also to assist in maintaining the edge portion in a substantially fiat condition while in engagement with the upper face of the edge restraining member 24. It will be perceived that the frictional restraining effect on the edge portion of the sheet 25 is increased during the forming of the slieet upon the die block 28, 'as the result of the precompression of the rubber supporting member 22 prior to the engagement of the sheet 25 with die block 28, and the greater force applied to the opposite faces of the edge portion l4 by the rubber insert 33 and the edge restraining member 24 during the performance of the actual forming operation.

The volume of rubber in the supporting body 22 has been increased in Fig. 6. So that suitable lateral deformation of the rubber body 22 may take place without interference as a result of engagement with a portion of the press pad 2|, I provide a dam 35 comprising a wall of rigid material such as metal in spaced relation to the rubber body 22. This dam it may extend entirely around the rubber body 22.

' The rubber forming press is. used for forming of thin walled channels, used as portions of frames. iii in Fig. 7. It comprises a flat web fiflwith curved edges 3% and lii; from which flanges 4| and ii extend downward. The outer flange 42 will be often found to have a slight wave therein, as indicated at 43, in view of excess metal therein. To remove this wave is bothersome, in that it involves hammering of the' flange '42 against a curved forming block.

In Fig. 8 I show a practice of my invention wherein the channel 31 may be initially formed without wave in its outer flange 42, by the simple expedient of using an edge restraining bar 44 along the face 45 of the forming block 46, on which the channel M is formed. This edge restraining member 44 need extend only along the face at, and may be supported in this position on a rubber body 41. In Fig. 8 the edge restraining member 46 is shown in a depressed position resulting from downward application of pressure by the press pad 2|, and the rubber body 41 is shown laterally deformed in the space provided by a dam d8 consisting of a bar in suitably spaced relation to the rightward face 45 of the forming block it. This dam of the press pad 2! against the laterally rubber body 41 so as tions thereof.

from exerting its pressure extending portion of the to resist lateral deforma- It will be understood that after the formation of the channel 41, the waste edge iiil, Fig. 8, will be severed from the flange 42.

The extent and degree of crinkle in the flange Such a channel has been indicated at 48 prevents the portion 49 a ber; means for moving said body toward the" front face of said die block into contact with that part of said sheet which overhang the margin of said die block so that it will apply both inward and rearward pressure to said sheet to form'the same on said die block with a combined compressive and drawing action; an edge restraining member comprising a plate disposed is to be formed; a

with one edge adjacent said side face of said die block, and a front face against which the edge portion of said sheet is forced by said body of conformable material, producing engagement of said edge portion to resist movement of said edge portion toward said side face of said die block as the forming operation progresses; a supporting body of a material having the general characteristics of rubber adjacent said side face of said die block and yieldably supporting said edge restraining member so that it will recede across said side face of said die block as the pressure in said body of conformable material increases and gradually increases the compression'of said supporting body; and a'dam disposed adjacent said supporting body on the side thereof opposite said die block to define a space to receive an edge portion of said supporting body.

2. In a device for forming a flanged article from a sheet, the combination of: a die block having a front face to receive the sheet and a side face over which the edge portion of the sheet body of conformable material having the general characteristics of rubber; means for moving said body toward the front face of said die block into contact with that part of said sheet which overhangs the margin of said die block so that it will apply both inward and rearward pressure to said sheet to form the same on said die block with a combined compressive and drawing action; an edge restraining member comprising a plate disposedface of said die block and yieldably supporting portions are found to vary under different conditions of use of the invention. For example, by use of a specially constructed press, one wherein a pressure of 1500 pounds per square inch or more can be applied to the press pad, and with the flange height not too great, for, example three-quarters of an inch or less, it is possible to draw the flange clear down without wrinkles, may be cut to actual size. The inclination of the inner portion of the face of the ring 24 gives an inward component of the pressure of the rubber against the marsaid edge restraining member so that it will recede across said side face of said die block as the pressure in said body of conformable material increases and gradually increases the compression of said supporting body; and a dam disposed adjacent said supporting body on the side thereof opposite said die block to define a space to receive an edge portion of said supporting body, there being a, recess formed in the lower part of said die block to receive another edge portion of said supporting body as it expands laterally due to compression by said edge restraining member.

3. In a device for forming a flange on a sheet of a material having the gen- ,eral characteristics of rubber adjacent said side of metal over a die, the combination of a base; a die block supported by said base having a front face to receive the sheet and a side face over rearwardly on the front face of the support;

and means for moving the body in a direction toward the front faces of the block and facing to press a sheet of material against said front faces to form the sheet on said die block, the said sheet during the forming operation being held laterally immovably centered on the die block and being slidabiy movable between said facing and the extending portion of the body while pressurally engaged therewith the pressural engagement being such as to produce a progressively increasing drawing action and having an inward component of pressure adapted to produce a mild compressive action in the bend formed in said sheet. 4

4. In a device for forming a flanged article from a sheet, the combination of: a die block having a front face to receive the sheet and a side face over which the edge portion of the sheet is to be formed; a body of conformable material having the general characteristics of rubber; means for moving said body toward the front face of said die block so that it will apply pressure to said sheet to form the same on said die block; and an edge restraining means consisting of a movable ring surrounding said die block, and having a non-conformable rigid front face, inclined inwardly and rearwardly against which said body of conformable material forces an edge portion of said sheet for the purpose of. resisting inward movement of said edge portion toward said die block and thereby produces a progressively increasing stretching and drawing action in the same, and a ring of rubber surrounding said die block and supporting said edge restraining means so that its pressure against said edge portion of said sheet will increase as said edge portion and said edge restraining means are moved rearwardly across the side face of said die block as the pressure applied by said body of conformable material increases.

5. A method of forming a sheet into a flanged article by use of a die block and a body of flowable material, comprising: placing the sheet in proximity to the front face of the die with an edge portion of the sheet projecting from the edge of the die; moving said body of fiowable material towards said die so as to force said sheet toward the die; applying to the rear face of said edge portion of said sheet, with relatively light pressure and at an acute angle relative to the direction of movement of said movingbody, a non-yielding restraining force cooperating with said fiowable material to lightly clamp said edge portion and stretch and draw same, the angle and magnitude of said restraining force being sufficient to urge the peripheral margin of said edge portion laterally toward proximity with the remainder of said edge portion to thereby further move metal from said remainder of the edge portion into the bend formed in said sheet and confine the formation of crinkles to said peripheral portion; moving said restraining means rearwardly across the side face of said die as said edge portion is moved into a position along the side face of said die; and gradually increasing the magnitude of said restraining force as the movement of said restraining means progresses toward the rear of said die block.

- 6. A method of forming a sheet into a flanged article by use of a die block and a body of fiowable material, comprising: placing the sheet in proximity to the front face of the die with an edge portion of the sheet projecting from the edge of the die; moving said body of fiowable material toward said die so as to force said sheet toward the die; applying to the rear face of said edge portion of said sheet, with relatively light pressure and at an acute angle to the direction of the aforesaid movement, a non-yielding restraining force cooperating with said fiowable material to lightly clamp said edge portion and stretch and draw the same, the angle and magnitude of said restraining force being sufficient to urge the peripheral margin of said edge portion laterally toward proximity with the remainder of said edge portion to thereby further move metal from saidremainder of the edge portion into the bend formed in said sheet and confine the formation of crinkles to said peripheral portion; moving said restraining means rearwardly across the side face of said die block as said edge portion is moved into a position along said side face of said die, gradually increasing the magnitude of said restraining force as the movement of said restraining means progresses toward the rear of said die; and gradually forcing the said crinkled peripheral portion rearwardly into alignment with the rest of said edge portion to locate the crinkles at the lower portion, only, of the flange. r

"I. A method of forming a sheet into a, flanged article, comprising: placing the sheet in prox-' imity to the front face of a die with an edge portion of the sheet projecting from the edge of the die; moving a body of fiowable material toward said die so as to force said sheet against said die with a pressure that is exerted both laterally inwardly toward the die and rearwardly toward the back of the die; applying to the rear face of said edge portion, through a surface which is non-yielding laterally, a force that is directed both forwardly in opposition to the rearwardly directed pressure of said fiowable material and inwardly toward the die in assistance of the inwardly directed component of the pressure applied by said fiowable material, whereby to urge .the material of the marginal portion of the sheet into a channel formation of acute angled crosssection which inhibits the formation of wrinkles in aid marginal portion.

8. A device for forming a flanged article from a sheet, comprising the combination of: a die block having a front face to receive the sheet and a side face over which an edge portion of the sheet is to be formed; a body of material having the general characteristics of rubber; means for moving said body toward the front face of said die block so that it will apply pressure to said sheet to form the same on said die block; a movable member surrounding said die block and having a non-yielding front face including a surface inclined acutely toward the side of said die block,

against which acutely inclined surface said flowwhile resisting inward movement of said edge moved rearwardly across said side of said die block. I

9. In a device for forming a'flanged article from a sheet, the combination of: a die block having a front face to receive the sheet and a curved side face over which the, edge portion of the sheet is to be formed; a body of conformable material having the general characteristics of rubber; means for moving said body toward the front face of said die block into contact with that part of said sheet which overhangs .the margin of said die block so that it will apply both inward and rearward pressure to said sheet to form the same on said die block with a combined compressive and drawing action to the 'said side face;

to support said edge restraining means so that tion; an edge restraining means yieldably supported adjacent said side face of said die block, and having a non-conformable rigid front face including a surface inclined acutely toward the side of said die block against which said body of conformable material forces an edge portion of said sheet for the purpose of resisting inward movement of said edge portion toward said die block and thereby drawing action in the same, said edge restraining means having adjacent said die block an produces stretching and Number Number Name 2,132,002 Hight Oct. 4,'1938 2,133,445 Guerin Oct. 18, 1938 2,248,786 Rowe July 8, 1941 1,048,775 Wilkinson Dec. 31, 1912 2,190,659 Guerin -4--- Feb. 20, 1940 1,881,517 Groehn Oct. 11, 1932 1,655,568 Rode Jan. 10, 1928 2,321,075 Frey -June 8, 1943 2,317,869 Walton Apr. 27, 1943 2,342,365 Pease Feb. 22, 1944 FOREIGN PATENTS Country Date 333,104 Great Britain Aug. 7, 1930 edge which is curved in complementary relaand resilient means the pressure thereof against said edge portion of said sheet will increase gradually as said edge portion and said edge restraining means are moved rearwardly across the side face of said she block as the pressure applied by said body of conformable material increases.

HENRY H. BRUDERLIN.

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

UNITED STATES PATENTS Date