US3479979A - Metal forming - Google Patents

Description

Nov. 25, 1969 v N 3,479,979

METAL FORMING Filed Nov. 16, 1967 2 Sheets-Sheet 1 IHL By WQW? A Harney Nov. 25, 1969 G. DUNN 3,479,979

METAL FORMING Filed Nov. 16, 1967 I02 Sheets-Sheet 2 IN TOR.

LLOYD U/VN By Altar/my 3,479,979 METAL FORMING Lloyd G. Dunn, Lower Burrell, Pa., assiguor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 16, 1967, Ser. No. 685,241 Int. Cl. B21d 47/00, 13/10 US. Cl. 113121 7 Claims ABSTRACT OF THE DISCLOSURE A method of making a boss in sheet metal by positioning a sheet of inetal between mating faces of an anvil and a punch, the face of the punch extending outwardly of the anvil face, and pressing the sheet metal between the anvil and punch to induce outward flow of the metal thereby forming a boss in the sheet metal.

BACKGROUND OF THE INVENTION The invention to which this application pertains relates to forming bosses in sheet metal. Heretofore, bosses have been formed in sheet metal by various methods. One method is by drawing the sheet by a single or multiple number of forming steps to achieve the desired boss height. Drawing a hollow boss in sheet metal will, however, thin the metal over the surface area of the boss and in many cases the metal is fractured either during the draw or in subsequent metal working operations that may be performed on the boss. This is particularly true when the boss is drawn in a single operation. The metal in the boss fractures because the total surface area of the boss is much greater than the area of the sheet metal from which the boss is formed, the metal of the boss being greatly stretched and thinned.

One method of making a boss in sheet metal other than by drawing is by partially punching a sector of metal outwardly of the sheet. In this case the base of the resulting boss, where it departs from the plane of the sheet metal from which it is formed, is very thin. Moveover, the height of the boss must necessarily be something less than the thickness of the metal sheet otherwise the sheet metal would be cut through.

Another method of forming a boss in sheet metal is by compressive forming to cause plastic flow in the sheet metal then reworking the residually compressed region and displaced metal with different forming tools to produce the boss. The difficulty with this method is that two forming operations with different tools is necessary. This prior art method is shown in United States Patent No. 2,697,953.

My invention overcomes the aforementioned problems and others by producing in sheet metal a boss of considerable height that'has the metal at its base as thick as the original sheet metal from which it was formed and the side wall nearly as thick. Moreover, I achieve a boss having these desirable structural features in one forming operation.

SUMMARY OF THE INVENTION In accordance with this invention any suitable sheet of metal, such as aluminum, steel, or other ductile metal, is placed between a first tool, herein referred to as a punch, and a second tool, herein referred to as an anvil, and pressed therebetween as by an impact blow or squeezing to produce sufiicient permanent deformation of the metal to induce outward flow of the metal thereby forming a hollow boss in the sheet metal. The faces of the punch and anvil contacting the sheet metal should mate to such an extent that upon closing to form the boss United States Patent 3,479,979 Patented Nov. 25, 1969 the metal flows uniformly in radial directions. The face of the punch has an area greater than the area of the face of the anvil and extends outwardly of the face of the anvil. The metal being displaced by the pressure applied by closing of the punch and anvil is prevented from flowing along the punch sidewall because the face of the punch overhangs or extends outwardly of the anvil face and as a result it is displaced in the direction of the anvil sidewall and forms a hollow boss around the anvil. The increased sheet metal area necessary to make the boss is obtained largely by thinning the area of the sheet metal initially overlying the face of the anvil. The height of the boss may be controlled by the amount the overlying area of the sheet metal is thinned. Of course, the higher the resistance to deformation of the sheet metal from which the boss is formed the more pressure required to deform the metal to induce the outward flow of metal. Surprisingly, thin gage metal such as aluminum in a hard roll temper or container-grade steel works quite well.

It is an object of this invention to provide a method of forming a boss in sheet metal in a single forming operation.

It is another object of this invention to provide a method of forming a boss having high structural strength in a sheet of ductile metal.

It is another object of this invention to provide a method of forming a structurally strong boss in a sheet of ductile metal by having the base portion as thick as the parent sheet metal it was made from and the side wall nearly as thick with the top of the boss the only area substantially thinner than the parent sheet metal.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an enlarged sectional view showing the sheet metal positioned between the punch and anvil;

FIGURE 2 is a view similar to FIGURE 1 showing the punch and anvil in closed position with the boss formed in the sheet metal;

FIGURE 3 is a perspective view of a metal sheet having a boss formed therein utilizing the invention;

FIGURE 4 is an enlarged sectional view showing one way to reform a boss made by the invention so that the boss is better adapted for heading to make an integral hollow headed rivet.

FIGURE 5 is an enlarged sectional view showing heading the reformed boss shown in FIGURE 4; and

FIGURE 6 is a section view showing utilization of a boss made by the invention to make honeycomb laminated sheet.

DESCRIPTION OF THE EXEMPLARY METHOD Referring to FIGURES 1 and 2 the method of forming a boss in metal sheet according to my invention is sequentially shown. The metal sheet 1 is positioned between a lower die 2 having an upstanding anvil 3 and a punch 4. The anvil 3 has a side wall 3a and a face 312. The punch 4 is an axial alignment with the anvil 3 and has a face 5 which has an area greater than and extends outwardly of the area of the face 3b of the anvil 3. As shown in FIGURE 2, the punch 4 in cooperation with the anvil 3 upon closing applies a sufficient amount of pressure to the metal sheet 1 to induce outward or radial flow of the metal in the metal sheet 1. Either the punch 4 or the anvil 3 or both may be moved relative to each other to apply the necessary pressure to the metal sheet 1. The metal caused to flow by the ap lied pressure cannot move along the side wall of the punch 4 because the outwardly extending face 5 prevents it, and as a consequence metal is displaced in the direction of the side wall 3a of anvil 3, thereby forming a boss 6 around the anvil.

The face 5 of the punch 4 and face 3b of the anvil 3 mate one with the other. Preferably the faces of the punch 4 and anvil 3 are substantially flat as the mating of fiat faces is more easily accomplished when the tools are made initially and are more easily maintained in a mating condition during successive boss forming operations.

Although the anvil may be of various shapes, a right cylinder shaped anvil with a fiat face 3b as shown in FIGURES l and 2 is preferred because the desirable uniformity of metal flow radially outward induced by the pressure on the metal sheet by closing the punch and anvil is readily accomplished.

The anvil 3 may be of any height, however, I have found that control of the height of the boss may be more easily accomplished when the anvil height is equal to the desired height of the boss. The height of the boss may be varied depending upon the height desired for the ultimate use to which the boss will be put. The diameter of the anvil face 3b should be equal to the desired top inside diameter of the finished boss.

It can readily be seen in FIGURE 2 that the boss 6 has a thinned transverse end wall 7 as a result of the thinning of the metal during the forming operation. The metal displaced in forming the thinned end wall 7 provides the additional boss area necessary to obtain a boss of suitable height and forms a side wall 8 of appreciably greater section thickness than that of the transverse end wall 7. In fact, the side wall thickness throughout the major height of the boss 6 is almost equal to the original metal sheet thickness, and the section thickness of the metal in the base 18 of the boss 6 remains unaffected. It should be noted that my method of boss forming is preferably accomplished by cold working but is not limited to such working.

FIGURE 3 shows in perspective the structural characteristics of a boss 6 formed in sheet metal 1 in accordance with my invention described above and shown in FIG- URES l and 2. With the anvil 3 having a right cylinder shape a truncated cone shaped boss is formed.

Bosses formed by my invention may be employed for various purposes. Two such uses for the boss will be hereinafter described. FIGURES 4 and demonstrate the utility of my boss in the formation of a headed rivet to attach a sheet-like element to the metal sheet. ,Specifically such a boss may be employed in the formation of integral rivets useful in attaching opening tabs to easy opening containers designed to be opened manually without the 'use of a special opening tool. As shown in FIGURE 4 reforming die 9 which has a cylindrical recess 10 of the diameter desired for the reforming boss 6 is closed in cooperation with the lower die having an upstanding mandrel 21. By this reforming operation the side wall 8 and base 18 of the boss 6 are moved laterally inward toward the side wall 23 of the mandrel 21. If desired, the reformed boss may be made higher by reforming over a mandrel having a height greater than the inside height of the boss 6. In the case of making integral rivets in easy opening containers there is normally a score line defining the desired tear-out panel configuration. Although such scoring may, if desired, be performed in a separate operation it would be advantageous to simultaneously score the metal sheet as the boss 6 is being reformed. FIGURE 4 shows a scoring rib 11 at the base of the reforming die 9 for this purpose. When the reforming die 9 in cooperation with the lower die 20 is closed to reform the boss 6 the desired scoring Will be impressed into the metal sheet 1.

After the boss reforming operation is completed as shown in FIGURE 4 an opening tab 13 is placed over the reformed boss. FIGURE 5 shows the completed rivet forming operation wherein the reformed boss is headed to' attach an opening tab 13 to the metal sheet 1. A heading punch 14 applies pressure to the transverse end wall 7 of the reformed boss to induce outward flow of the metal in the end wall 7, When the metal of the end wall 7 is caused to be displaced by the applied pressure beyond the peripheral edge 22 of the mandrel 21, the peripheral wall is reversely folded to form a peripheral bead 15 securing the opening tab 13 to the metal sheet 1. During this operation the mandrel portion 21 of the lower die 20 supports the interior of the reformed boss to prevent inward collapse of the reformed boss during the heading operation. When the boss of my invention is to be used for attaching an opening tab to the metal sheet the mandrel 21 should be sufficiently high to permit the metal to reversely fold to form the peripheral head 15. Ordinarily the height of the mandrel 21 will be at least the total original thickness of the sheet metal and the opening tab. The lower die 20 assists in reversely folding the metal to form the peripheral head 15 by supporting the metal of the sheet in the vicinity of the base of the boss during the rivet forming operation.

The sequence of steps shown in FIGURES 4 and 5 are merely one representative method of making an integral rivet from sheet metal using a boss formed by my invention. Other methods of making headed integral rivets can utilize the boss made by my method wherein different subsequent forming or heading techniques are performed on the boss.

FIGURE 6 shows in cross-section metal sheets which have been joined together to form a honeycomb structure utilizing the boss formed in accordance with my invention. The middle sheet 1 has a number of bosses 6 formed therein. A top metal sheet 16 and a bottom metal sheet 17 are placed on the transverse end walls 7 of the bosses 6 and when in position the laminate is brazed in accordance with common brazing practices to unitize the metal sheets and make a rigid honeycomb laminate structure. Fillets 19 produced by the brazing operation join the bosses 6 of sheet 1 to sheets 16 and 17. By employing the boss formations provided by my invention the base and side wall of the boss have high strength and the transverse end wall 7 which was thinned in the process of making the boss is strengthened by the fillets 19.

While only two applications of the use of a boss made by my invention .have been illustrated and discussed, the utilization of such a boss is not limited to these two applications but rather extends to any application that requires or can utilize an upstanding boss of the type herein described. The description in specific detail of the selected practice of the invention will suggest to those skilled in the art, various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

What is claimed is:

1. The method of making a hollow boss in sheet metal comprising, positioning a sheet of metal between mating faces of an anvil and a punch, the face of said punch extending outwardly of the face of said anvil, and establishing relative closing movement between said anvil and said punch to apply a compressive force to the sheet metal between said mating faces to induce outward flow of the metal thereby forming by metal displacement a hollow boss in the sheet metal around the anvil.

2. The method of making a hollow boss in sheet metal according to claim 1 wherein the mating faces of the anvil and punch are substantially flat.

3. The method of making a hollow boss in aluminum sheet comprising positioning a sheet of aluminum between mating faces of an anvil and a punch, the face of said punch having a greater area and extending outwardly of said anvil face, and establishing relative closing movement between said anvil and said punch to apply-sufiicient compressive pressure to the sheet to induce outward flow of the metal and by the displacement thereofto form a hollow boss in the sheet around the anvil.

4. The method of making a hollow boss in sheet metal comprising positioning a sheet of met-a1 between a right cylinder shaped anvil having a substantially flat face and a punch having a face mated with and extending radially outward of the anvil face, and pressing the sheet metal between said anvil and punch faces to induce uniform outward flow of the metal thereby forming by metal displacement a hollow boss in the sheet metal around the anvil.

5. In the method of joining a sheet-like element to a metal sheet by means of an integral hollow headed rivet wherein a hollow boss is formed in the metal sheet, the sheet-like element placed over the hollow boss and the boss headed to join the sheet-like element to the metal sheet, the improvement comprising, forming the upstanding hollow boss by positioning a sheet of metal between mating faces of an anvil and a punch, the face of said punch extending outwardly of the face of said anvil, and pressing the sheet metal between said faces to induce outward flow of the metal thereby forming by metal displacement a hollow boss in the sheet metal around the anvil.

6. In the method of securing a container opening tab to a portion of a sheet metal container member by means of an integral hollow headed rivet wherein a hollow boss is formed in the metal container member, the opening tab placed over the hollow boss and the boss headed to secure the opening tab to the container member, the improvement comprising forming the hollow boss by positioning the sheet metal container member between mating faces of an anvil and a punch, the face of said punch extending outwardly of the face of said anvil, and pressing the sheet metal container member between said faces to induce outward flow of the metal thereby forming by metal displacement a hollow boss in the sheet metal around the anvil.

7. In the method of securing a container opening tab to a portion of a container member made of aluminum sheet by means of an integral hollow headed rivet wherein a hollow boss is formed in said container member, the opening tab placed over the holow boss and the boss headed to secure the opening tab to the container member, the improvement comprising forming the hollow boss by positioning the aluminum container member between a right cylinder shaped anvil having a substantially flat face and a punch having a face mated with and extending radially outward of the anvil face, and pressing the aluminum container member between said anvil and punch faces to induce outward flow of the aluminum thereby forming by metal displacement a hollow boss in the aluminum container member around the anvil.

References Cited UNITED STATES PATENTS 3,404,648 12/1967 Rosbottom 113-121 DONALD D. GREFE, Primary Examiner U.S. Cl. X.R.

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