US3015879A - Blank carrier for sheet metal strip and method for making same - Google Patents

Description

G. J. BA BlTT BLANK CARRIER FOR SHEET METAL STRIP AND Y METHOD FOR MAKING SAME Jan. 9, 1962 2 Sheets-Sheet 1 Filed Aug. 11, 1958 INVENTOIS. Geoaaz J. BABITT A TTORNEYS Jan. 9, 1962 G. J. BABlTT BLANK CARRIER FOR SHEET METAL STRIP AND' METHOD FOR MAKING SAME 2 Sheets-Sheet 2 Filed Aug. 11, 1958 INVENTOR. Giokce J. BABITT 2%, 76am 1 Wm H A T RNEY5 United States Patent 3,015,879 BLAYK CARRIER FOR SHEET METAL STRIP AND METHOD FOR MAKING SAME George J. Babitt, Wellington, Ohio, assignor to The Seetional Die Company, Wellington, Ohio, a corporation of Ohio Filed Aug. 11, 1958, Ser. No. 754,379 11 Claims. (Cl. 29-193.5)

This invention relates to metal forming methods and is particularly concerned with a method of holding a blank onto a strip of sheet metal from which the blank is formed, during the passage of the strip through a progressive die for performing a sequence of operations upon the blank.

One method heretofore practiced for holding a blank onto a skeleton strip has embodied what is known in the trade as a double-cut carrier, wherein the carrier legs cross the median line which extends longitudinafly of the strip and passes through the center of a row of blanks thereon. Such carrier legs have necessitated the use of extra stock from which the legs could be formed and has necessitated the use of a narrow strip of stock around the blank. An object of the present invention is to form carrier legs from the material in regions which lie adjacent the edges of the strip on opposite sides of the median line of the row of blanks and in material which otherwise would be lost as scrap. Such construction has advantages in addition to the saving in stock as will hereinafter be set forth.

Briefly, the invention is carried out in one form, by forming the carrier legs in pairs which resemble an ellipse, wherein the inside end of the major axis of each ellipse is attached to the blank, while the outside end is attached to the scrap skeleton. The major axis in the case of a circular blank extends radially, and at about an angle of 38 degrees to the median line passing through the axes of the row of blanks on the strip. The major axis of each ellipse is thus disposed in the direc tion of flow of metal during the draw. Preferably two such sets of carrier legs are used on each blank and are disposed, in the case of the circular blank, at diametrically opposite points with respect thereto.

Referring to the drawings, FIG. 1 shows a portion of a sheet metal strip having a blank and carrier legs thereon embodying the present invention, and FIG. 2 is a top plan view of a portion of a sheet metal strip, showing the blank in progressive stages of work performance thereon, and illustrating the carrier legs shown in FIG. 1.

The invention may be utilized on a sheet metal strip having either one row of blanks or a plurality of rows of blanks thereon. In FIG. 1 there is shown a portion of a strip which is intended for use in connection with a single row of blanks, one of which is indicated at A as circular in formation. In such illustration, the carrier legs are indicated at 15 and 16 at one side of the blank, and above the median line M thereof, while another set of carrier legs is indicated at 17 and 18 on the opposite side of the blank and below the median line. The inner edges 19 and 20 of the legs 15 and 16 are formed by a cut-out portion 21, which in the form shown, is substantially elliptical. Similarly, the inner edges 22 and 23 of the legs 17 and 18 respectively are formed by a substantialy elliptical-shaped cut-out portion 24.

The major axis of each ellipse of the respective cutout portions 21 and 24 extends radially of the blank A, and the axes are in alignment. Thus, the carrier legs are disposed on diametrically opposite sides of the blank, near the edges of the strip, and in the region which having a diameter 7.250 inches, is 7.825 inches.

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otherwise would be regarded as scrap material. Each set of legs lies wholly within the space lying between the median line and one edge of the strip. I

The outer edges 30 and 31 of the legs 15 and 16 are formed by curved cut-outs 32 and 33 respectively, which are so shaped as to form legs of substantially uniform width. In the form shown, the points of intersection 34 and 35 between the periphery of the blank and the outer edges 30 and 31 respectively subtend a circular angle B of about seven degrees. Additionally, the points 36 and 37 at the outer corners of the outer legs s;btend a circular angle C of about four degrees. These angles have been found to be satisfactory for use in the formation of a part from a circular blank having a diameter of 7.25 inches. The circular angle formed between the median line and the major axis of the ellipse is about thirty-eight degrees.

The outer edges 40 and 41 of the legs 17 and 18 respectively, are also formed by cut-out portions 42 and 43 respectively. These are formed similarly to the cutout portions 32 and 33 respectively. Additionally, the circular angle subtended between the points 44 and 45 is the same as the angle B and the angle subtended between the points 46 and 47 is the same as the angle C.

In the carrier leg construction of the prior art, the pitch distance between blanks, in the case of a blank With the carrier legs embodying the invention of the present application, however, the pitch distance need be only 7.450 inches. Utilizing a stock width of 7.625 inches results in a strip area required for each blank of 56.806 square inches, Whereas the corersponding area in the art construction on the same width of strip is 59.666 square inches. Thus there is effected a saving of 2.860 square inches of metal per piece. The foregoing saving in material has resulted in a stock saving by one company of approximately $50,000.00 in one years production of a certain part.

Carrier legs formed in a strip in accordance with the present invention, have such flexibility and holding power that, a cup-shaped part has been twisted a full 360 degrees in one direction, then reversed and twisted for another 360 degrees, and thereafter cycled through the press without any adverse results. The ability of the carrier legs having formation of this invention to stretrh has enabled more compound actions to be employed in the stamping operations and thereby has enabled dies to be shortened, which in turn, has reduced the cost of manufacture.

A further advantage in the use of the present invention is the reduction of slivers which have always been a problem in progressive dies because of the down-time and maintenance cost. The slivers work their way through the die, some dropping off at each station. These must be cleaned frequently or they will dull the cutting edges and destroy the action of the ,die. The present invention results in a very low quantity of slivers from the stock material.

FIG. 2 shows the blank in progressive stages on a multiple die operation wherein the blanks in one row are indicated in various stages of operation by S, 5-1, S2 and S3 respectively, while those in the other row are indicated at T, T-1, T2 and T-3 respectively. The carrier legs 15 and 16 are shown at the progressive stages as being progressively closer together as the strip advances' through the die, and the same is true of the carrier legs 17 and 18. The same change in formation transpires in the carrier legs associated with the blank in connection with the operations indicated at T, T-1, T-Z and T3 respectively. In all such operations the blank is firmly held to the strip skeleton until the completion of the operation.

I claim:

1. The method of making carrier legs for generally symmetrical blanks in a flat longitudinally extending strip of sheet metal for connecting said blanks to the strip skeleton for subsequent work operations, such as stamping operations, on said blanks, and wherein said blanks are adapted to be disposed substantially in alignment lengthwise of said strip for utilization of a minimum width of strip for a predetermined width of blank, and wherein at least a portion of the defining boundary of each of said blanks is of curved configuration in plan view with the material of the strip adjacent said curved portion of the blank normally representing scrap, comprising, forming said blanks in juxtaposed relation longitudinally of said strip, and forming two pairs of relatively curved contiguous flexible carrier legs for each blank in said scrap portions of said strip with said pairs of legs being disposed on opposite side portions of the respective blank and attaching the latter to the strip skeleton, and with said pairs of legs being disposed on opposite sides of the longitudinally extending axis of the respective blank, said legs being adapted for elongation during said work operations on the respective blank, to thereby prevent warping of said strip skeleton.

2. The method of making carrier legs for generally symmetrical blanks defined by curved boundaries, said blanks being adapted to be formed in a flat longitudinally extending strip of sheet metal with the carrier legs connecting said blanks to the strip skeleton for subsequent work operations, such as drawing operations, on said blanks, and

wherein said blanks are adapted to be disposed substantially in alignment lengthwise of said strip. for utilization of a minimum width of strip for a predetermined width of blank, comprising, forming said blanks in juxtaposed relation longitudinally of said strip, the material of said strip intermediate said blanks normally representing scrap, and forming two pairs of relatively outwardly curved contiguous, flexible carrier legs for each blank in said scrap portions of said strip on opposite sides of the respective blank facing in directions generally lengthwise of said strip, with said pairs of legs connecting the respective blank to the strip skeleton and being disposed on opposite sides of the longitudinally extending axis of the respective blank, said legs being adapted for elongation during said work operations on the respective blank, to thereby prevent warpage of said strip skeleton.

3. A method according to claim 2 including forming the carrier legs of each pair symmetrically with respect to each other in the form of an ellipse, and so that the major axis of the ellipse of one pair extends in parallel relation with the major axis of the ellipse of the other pair.

4. A method of making carrier legs according to claim 2, including aligning the major axis of one set of legs with the major axis of the other set of legs.

5. A method of making carrier legs for circular blanks in a flat longitudinally extending strip of sheet metal with the carrier legs being adapted to connect said blanks to the strip skeleton for subsequent drawing operations on said blanks, and wherein said blanks are adapted to be disposed substantially in alignment lengthwise of said strip for utilization of a minimum width of strip for a predetermined diameter of blank, comprising, forming said blanks in juxtaposed relation longitudinally of said strip, the material of said strip. intermediate said blanks normally representing scrap, and forming two pairs of relatively curved contiguous and flexible carrier legs for each blank in saidscrap portions of said strip on opposite sides of the respective blank facing in directions generally lengthwise of said strip, with said pairs of legs connecting the respective blank to the strip skeleton and being disposed on opposite sides of the longitudinally extending axis of the respective blank, said legs of each pair being curved outwardly relative to one another and defining an ellipse, the major axes of said ellipses being in alignment and with extensions of said axes passing through the center of curvature of the respective blank, said legs being adapted for elongation during said drawing operations on the respective blank, to thereby prevent warpage of said strip skeleton.

6. A fiat sheet metal strip having a plurality of generally symmetrical juxtaposed blanks formed from the strip, said blanks being disposed substantially in alignment lengthwise of said strip for utilization of a minimum width of strip for a predetermined width of blank, at least a portion of the defining boundary of each of said blanks being of curved configuration in plan view with the material of the strip skeleton adjacent said curved portion normally representing scrap, and means for holding said blanks onto the strip skeleton for subsequent work operations, such as stamping operations, on said blanks, said means comprising a pair of relatively curved contiguous, flexible legs formed in said scrap section of said strip and non-rigidly connecting the respective blank to the strip skeleton, each of said legs being connected to the respective blank adjacent one end thereof and being connected to the strip skeleton adjacent the other end thereof, said legs being spaced from one another on their confronting inner edges intermediate their ends and being spaced from the strip skeleton at their outer edges intermediate their ends whereby the respective blank is held onto the strip skeleton by the legs at the outer ends of the legs, said legs being disposed laterally of the longitudinally extending axis of the respective blank, said legs being adapted for elongation in the plane of said strip during said work operations on the respective blank, to thereby prevent warpage of said strip skeleton.

7. A sheet metal strip having a support for a blank thereon according to claim 6, wherein one pair of carrier legs is disposed at one side of the blank and another set disposed at the opposite side of the blank facing in directions generally lengthwise of said strip, and wherein said pairs lie on opposite sides of said longitudinal axis of the respective blank.

8. A sheet metal strip according to claim 7, wherein each pair of carrier legs define substantially an elliptical shape.

9. A flat sheet metal strip having a plurality of circular blanks formed from the strip, said blanks being disposed substantially in alignment lengthwise of said strip for utilization of a minimum width of strip for a predetermined diameter of blank, the material of the strip intermediate said blanks normally representing scrap, and means for holding said blanks onto the strip skeleton for subsequent drawing operations on said blanks, said means comprising two pair of relatively curved contiguous, flexible carrier legs extending between the respective blank and the strip skeleton and being connected thereto at the corresponding ends of said legs, said legs of each pair curved outwardly relative to one another, each pair of said legs being formed in said scrap portions of the strip skeleton on opposite sides of the respective blank facing in directions generally lengthwise of said strip, said pairs of legs being disposed on opposite sides of the longitudinally extending axis of the respective blank, each pair of said legs defining a substantially elliptical shape with the major axes of said ellipses being in alignment and with extensions of said axes passing through the center of curvature of the respective blank, said legs being adapted for elongation in the plane of said strip during said drawing operations on the respective blank, to thereby prevent warpage of said strip skeleton, the connecting ends of each of said legs to respectively the respective blank and to the strip skeleton being disposed relative to the corresponding ends of the associated leg in contiguous relation, whereby the respec tive blank may be rotatedv a full 360 out of the plane of said strip and in either a clockwise or a counterclockwise direction, while still maintaining the attached relation of the blank to the strip skeleton.

10. A sheet metal strip in accordance with claim 9 wherein the circular angle between the points of connection of the legs with the blank at the periphery thereof is about seven degrees and wherein the circular angle between the points of the connection of the carrier legs with the strip is about four degrees.

11. A sheet metal strip in accordance with claim 10, wherein the circular angle between the major axis of the ellipse defined by one of said pairs of legs and said longitudinal axis of the blank is about 38 degrees.

References Cited in the file of this patent UNITED STATES PATENTS Poranski Aug. 27, 1929 Kuehner Nov. 1, 1932 Darling Dec. 5, 1933 Martines July 16, 1957 Garbarino Oct. 29, 1957 FOREIGN PATENTS Great Britain July 25, 1939

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