US3266281A - Sheet material forming apparatus - Google Patents

Description

Aug. 16, 1966 A. FUST SHEET MATERIAL FORMING APPARATUS 3 Sheets-Sheet 1 Filed April 5, 1963 INVENTOR. ARNOLD FUST ATTORNEY Aug. 16, 1966 A. FUST SHEET MATERIAL FORMING APPARATUS 3 Sheets-Sheet 2 Filed April 5, 1965 INVENTOR. ARNOLD FUST INVENTOR.

ARNOLD FUST Aug. 16, 1966 SHEET MATERIAL FORMING APPARATUS Filed April 5, 1963 United States Patent 3,266,281 SHEET MATERIAL FORMING APPARATUS Arnold Fust, Hnntingdon Valley, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 5, 1963, Ser. No. 270,921 5 Claims. (Cl. 72--177) This invention relates to apparatus for forming sheet material and, more particularly, to apparatus which, while not limited thereto, is especially useful for forming strips of full-hard, austenitic stainless steel.

Full hard, austenitic stainless steel, such as A.I.S.I. type 1, has numerous applications where high strength, hardness and abrasion resistance are important considerations. One such application is an abrasive strip for the leading edge of a helicopter rotor which is subject to abrasion by sand, rain, hail, etc. during operation of the helicopter. However, difiiculties have been encountered in making abrasive strips because the material is difficult to work and form.

One cause of these difficulties or problems arises because the strip is rnade from rolls of strip stock rolled to within the normal mill tolerances of camber and buckle. lrior art apparatus has not been able to satisfactory produce an abrasive strip from such roll stock because of its inability to both shape the part and to prevent the camber and excess material, which produces the buckling, from ending up in and adversely affecting the final prodnot. The problem is further complicated because the material cannot be elongated very much before fracturing (8% for A.I.S.I. type 301 stainless steel) so that other ways, which are successful for more ductile material, cannot be used. It is believed that the present invention is the only successful way presently known for forming abrasive strips and similar elongated, sheet metal objects of full-hard, austenitic stainless steel, such as A.I.S.I. type 301.

Accordingly, one of the objects of the invention is to provide improved means for forming strips of high tensile sheet material.

Another object is to provide apparatus for forming strips of full hard stainless steel into elongated members of smooth or curved cross section.

Still another object is to provide apparatus for forming abrasive strips and similar objects of full hard, austenit-ic stainless steel.

A further object is to provide means for forming elongated, straight sheet metal parts of high strength materials 'wherein any excess material in the stock strip is removed and does not enter into the final product and cause buckling thereof.

Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a drawbench embodying the invention;

FIGS. 2-9 are elevational views of dies shown in FIG. 1, FIGS. 2 and 7 being in section and the others being end views with portions removed;

FIG. 10 is an enlarged and elevational view of one of the forming dies;

FIG. 11 is a vertical, longitudinal sectional view along reference lines 1111 of FIG. 10;

FIG. 12 is an enlarged view of a detail enclosed in reference box 12 of FIG. 11;

FIG. 13 is an enlarged end elevational of a portion of another one of the forming dies;

FIG. 14 is an enlarged cross sectional view along reference lines 1414 of FIG. 1; and

3,266,281 Patented August 16, 1966 FIG. 15 is a schematic representation of a portion of the apparatus illustrated in FIG. 1 to indicate the path of travel of the sheet material as the same is pulled through the successive forming dies of the apparatus.

Referring now to the drawings, there is shown in FIG. 1 a conventional drawbench 15 comprising a bench 16 having a plurality of longitudinally spaced housings .17 adjacent one end for supporting dies described more fully hereafter. The other end of the bench supports a dog 18 that is connected to a power chain 19 driven so as to move the dog along the bench and pull a strip 20 of material from a supply roll 21 through the dies.

The dies, numbered 23-30, are divided into a series of bending dies 2327 and a series of forming dies 28 30. As used in this description and in the claims, the term bending means forcing the material into a different shape without substantially exceeding the elastic limit and incurring any substantial permanent deformation, and the term forming means forcing the material beyond its elastic limit and before its ultimate strength to thereby permanently deform the material but without any appreciable reduction in thickness.

The illustrated embodiment is designed to shape strip 20 so that it is straight longitudinally and has an airfoil cross sectional shape similar to that shown in FIG. 14. This shaped comprises a pair of curved sides 20a and 2% joined by a curved nose 20c substantially symmetrical about an axis extending from the center of the nose between the sides. This cross section is smoothly curved and has no sharp corners or tight bends.

With reference to FIG. 3, each of the bending dies cornprises a pair of hard wood blocks 32 and 33 provided with a downwardly projecting male finger 34 and an upwardly opening female recess 35 shaped similar to the male finger and spaced therefrom a distance equal to or slightly greater than the thickness of the strip.

The bending dies 23-27 are so constructed and arranged that as strip 20 is pulled through them, the sides of the strip are progressively bent upwardly from a flat condition prior to die 23 into vertical positions after die 27 to provide a U-shape for smooth entry into the first forming die. The bending dies thus preliminarily shape the strip prior to forming. If flat strip were to be fed directly to the first forming die, the edges of the strip thus formed would be rippled.

Forming dies 28 and 29 are similar so that only one need be described in detail. With reference to FIGS. 10 and 11, die 28 comprises a leading male member or finger 38 and a trailing male member or finger 39 disposed above a pair of leading and trailing female members 40 and 41 mounted on the leading side of a housing 17 by a plurality of bolts 48. These bolts in conjunction with a pair of stop screws 49 permit vertical and lateral adjustment of the die parts and allow pressure to be applied via the fingers to the strip. The housings .17 upon which the forming dies are mounted are illustrated as being provided with Usha-ped slots 42 for freely passing strip 20.

Fingers 38 and 39 and female members 40 and 41, along with the corresponding parts of dies 29 and 30, are of a die material providing good Wear properties without galling, pickup or die scoring. One suitable material is Ampco .grade 21 bronze, sold by Ampco Metals Inc. of Milwaukee, Wisconsin. This material is an aluminum bronze having the following percentage weight composition:

Copper-Balance. Aluminum12.50-13.60. Iron3.505.00. Others-70.

3 When cast in a sand mold, this material has the following properties:

Tensile strength70,000 p.s.i. Yield strength5 0,000 p.s.i. Elongation (percent in 2 in. )-0.5. Brinell hardness (3,000 kg.)269.

The adjacent surfaces of each finger and the associated female member are parallel, the surfaces being convex and concave, respectively, and curved transversely but straight longitudinally. The surfaces are separated a distance equal to the thickness of strip 20 whereby the strip can be pulled through the dies. Screws 49 force the fingers against the strip but with a pressure below that which would produce tearing or crocking of the strip. The surfaces are shaped to define therebetween a gap having a transverse section similar in shape to that of the finished product.

With reference to FIG. 12, as strip 20 is pulled through forming die 28, successive portions of the strip first pass between edges 43 and 44 and then between edges 45 and 46. Because of the radial offset between finger 38 and member 40 and finger 39 and member 41, edges 43 and 46 act as forming edges and edges 44 and 45 act as guiding edges. As the strip passes over each forming edge, its path of travel changes abruptly and the opposite side of the strip is stretched beyond its elastic limit. Thus, each point on the strip travels along a longitudinal path which has abrupt angular transitions between the forming edges. Guiding edges 44 and 45 hold strip 20 against the forming edges. In the absence of guiding edges, the strip 20 would not incur any abrupt angular transitions and it would tend to follow the dotted line path in FIG. 12 wherein the opposite side would not be stretched sufficiently to incur a permanent set.

It has been found that the amount of deformation or set is dependent on the angular transition, i.e., the degree of offset and the longitudinal gap between the adjacent fingers and female members. In FIG. 12, distance X is the longitudinal gap and distance y is the offset measured in a longitudinal plane passing through the center of curvature of the die parts. The gap can be varied by adding or taking away shims 50 and the offset can be adjusted by loosening bolts 48 and screws 49. With a proper setting, determined by trial and error, the shape thus imparted to the strip will conform substantially to the shape of the space between the trailing finger female member combination. With a given offset, an increase in the gap produces less forming and a decrease in the gap produces more forming.

Die 28, as seen in FIGS. 12 and 15, is arranged to work the cross section of the strip from nominal size as it passes over forming edge 43 to under size as it passes over edge 46. The undersize differs from the nominal size by being smaller an amount equal to the offset. Thus, die 28 works the strip from nominal to undersize.

Die 29 is similar to die 28 except that it is constructed to work the strip from oversize to nominal. In this case, the oversize is greater than the nominal size by the amount of offset.

Die 30 is similar to dies 28 and 29 but differs because it is designed to work only the nose 20c of the strip. To accomplish this, die 30 includes a pair of fingers 38' and 39 which are cut back at 51 along the sides of the strip to provide a finger clearance whereby only the nose portion is worked. Die 30 works the nose portion from oversize to nominal. This step has been found desirable since while, after pasing through dies 28 and 29, the sides are shaped within narrow tolerances, the nose might be out of tolerance and die 30 insures that the nose is shaped to within the tolerances.

The above described embodiment was designed to shape a 5 /2 wide strip of .009" thick, A.I.S.I. type 301, full hard, stainless steel and with the material, the gap was .080" and the offset was .050" in each of dies 28, 29 and 4 30. The mill tolerances for such a strip are A" camber per 8 foot lengths and A" buckle per foot. With other thicknesses, materials or shapes, the number of dies and the gaps and offsets will probably vary.

With this setup, it was also found that any camber and buckle present in the stock strip was removed and the end product was straight and free from buckles and ripples and had the same Width and thickness as the unshaped strip, as measured by conventional shop micrometers. That is, the shaping was accomplished without any noticeable reduction in size or area. As the strip leaves ie 30, it has no transverse spring back.

The dog 18 clamps the end of the strip between a male finger 52 and a female member 53 shaped to conform to the internal and external surfaces of the finished strip. Since the tension necessary to pull the strip through each forming die is well below the yield strength, the tension at the dog can be made less than the yield strength so that the strip will not tear or rupture due to the clamping action of the dog.

While the foregoing describes forming an airfoil cross section, it will be obvious that the dies, by providing appropriate shapes can form other cross sectional shapes, such as airframe skins having only shallow curvatures and can merely be used to remove excess material causing buckling from stock strips, i.e., used to flatten and straighten strips.

While only a single embodiment has been illustrated, it will be apparent that many changes can be made in the details and arrangement of parts without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In apparatus for forming a substantially fiat strip of full hard austenitic stainless steel into a strip of predetermined U-shaped cross-section, the combination comprising: drawbench means, means for mounting a supply of sheet material at one end of said drawbench means, a plurality of bending die means mounted on and adjacent said one end of said drawbench means, a plurality of forming die means mounted on an adjacent the other end of said drawbench means, means for advancing said sheet material through said plurality of bending dies and said plurality of forming dies, each of said bending die means having a male element and a complimental female member spaced therefrom to admit a thickness of sheet material therebetween for movement longitudinally of said drawbench means, said plurality of bending die means being effective to progressively bend said sheet material from a flat condition to a cross-sectional form of U- shape without exceeding the elastic limit of the material, said plurality of forming die means each including leading male and female members with opposed surfaces separated a distance equal to the thickness of said sheet material and extending parallel to its direction of advancement to define a first passageway, and trailing male and female members with like opposed parallel surfaces defining a second passageway, said first and second passageways being laterally offset one with respect to the other relative to the direction of advancement of said sheet material and being operative to stretch the same beyond its elastic limit, means associated with said forming die means to vary the offset distance between said first and said second passageways, and additional means associated with each of said plurality of forming die means to vary the longitudinal distance between said leading male and female members and said trailing male and female members.

2. In the apparatus as set forth in claim 1 wherein said plurality of bending die means is effective to work the sheet material to a U-shaped form of nominal size, and wherein one of said plurality of forming die means has its leading male and female members disposed in an offset relation relative to its trailing male and female members and is effective to work the sheet material so advanced from said nominal size to an undersize dimension.

3. In the apparatus as set forth in claim 2 wherein an additional one of said plurality of forming die means disposed farther along in the direction of advancement of said sheet material has its leading male and female memhers disposed in an offset relation relative to its trailing male and female members and is effective to work the sheet material from an oversized condition of said U- shaped form to a nominal size thereof.

4. In the construction as set forth in claim 3 wherein a farther one of said plurality of forming dies is effective to engage only the base portion of the U-shaped form of said sheet material and coacts therewith to work the same from an oversize dimensional relationship to a nominal size thereof.

5. In the apparatus set forth in claim 1 wherein said plurality of forming die means are of a Wear resistant, antigalling aluminum bronze.

References Cited by the Examiner UNITED STATES PATENTS 1,823,489 9/1931 Ridder 72-176 2,395,651 2/1946 Anderson 72T76 2,960,140 11/1960 Anderson 72--176 10 3,006,401 10/1961 Wognum et al 72-176 FOREIGN PATENTS 131,153 4/1929 Switzerland.

15 CHARLES W. LANHAM, Primary Examiner.

W. H. JUST, Assistant Examiner.

Claims (1)

1. IN APPARATUS FOR FORMING A SUBSTANTIALLY FLAT STRIP OF FULL HARD AUSTENITIC STAINLESS STEEL INTO A STRIP OF PREDETERMINED U-SHAPED CROSS-SECTION, THE COMBINATION COMPRISING: DRAWBENCH MEANS, MEANS FOR MOUNTING A SUPPLY OF SHEET MATERIAL AT ONE END OF SAID DRAWBENCH MEANS, A PLURALITY OF BENDING DIE MEANS MOUNTED ON AND ADJACENT SAID ONE END OF SAID DRAWBENCH MEANS, A PLURALITY OF FORMING DIE MEANS MOUNTED ON AN ADJACENT THE OTHER END OF SAID DRAWBENCH MEANS, MEANS FOR ADVANCING SAID SHEET MATERIAL THROUGH SAID PLURALITY OF BENDING DIES AND SAID PLURALITY OF FORMING DIES, EACH OF SAID BENDING DIE MEANS HAVING A MALE ELEMENT AND A COMPLIMENTAL FEMALE MEMBER SPACED THEREFROM TO ADMIT A THICKNESS OF SHEET MATERIAL THEREBETWEEN FOR MOVEMENT LONGITUDINALLY OF SAID DRAWBENCH MEANS, SAID PLURALITY OF BENDING DIE MEANS BEING EFFECTIVE TO PROGRESSIVELY BEND SAID SHEET MATERIAL FROM A FLAT CONDITION TO A CROSS-SECTIONAL FORM OF USHAPE WITHOUT EXCEEDING THE ELASTIC LIMIT OF THE MATERIAL, SAID PLURALITY OF FORMING DIE MEANS EACH INCLUDING LEADING MALE AND FEMALE MEMBERS WITH OPPOSED SURFACES SEPARATED A DISTANCE EQUAL TO THE THICKNESS OF SAID SHEET MATERIAL AND EXTENDING PARALLEL TO ITS DIRECTION OF ADVANCEMENT TO DEFINE A FIRST PASSAGEWAY, AND TRAILING MALE AND FEMALE MEMBERS WITH LIKE OPPOSED PARALLEL SURFACES DEFINING A SECOND PASSAGEWAY, SAID FIRST AND SECOND PASSAGEWAYS BEING LATERALLY OFFSET ONE WITH RESPECT TO THE OTHER RELATIVE TO THE DIRECTION OF ADVANCEMENT OF SAID SHEET MATERIAL AND BEING OPERATIVE TO STRETCH THE SAME BEYOND ITS ELASTIC LIMIT, MEANS ASSOCIATED WITH SAID FORMING DIE MEANS TO VARY THE OFFSET DISTANCE BETWEEN SAID FIRST AND SAID SECOND PASSAGEWAYS, AND ADDITIONAL MEANS ASSOCIATED WITH EACH OF SAID PLURALITY OF FORMING DIE MEANS TO VARY THE LONGITUDINAL DISTANCE BETWEEN SAID LEADING MALE AND FEMALE MEMBERS AND SAID TRAILING MALE AND FEMALE MEMBERS.

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