US2157354A - Embossing metal plates - Google Patents

Description

y 9, 1939- D. w. SHERMAN 2,157,354

EMBOSSING METAL PLATES Filed Feb. 11, 1958 FIG. 1.

/////, \6 I Z IL 7 Donald Vlijlzerman IN VENTOR.

ATTORNEY.

Patented May 9, 1939 UNITED STATES EMBOSSING METAL PLATES Donald W. Sherman, Shorewood, Wis, assignor to A. 0. Smith Corporation, Milwaukee, Wis., a

corporation of New York 1 Application February 11, 1938, Serial No. 189,925

3. Claims.

This invention relates to embossing metal plates andis'particularly adapted to the embossing of sheet metal for forming a high circular embossment capable of being threaded.

Heretofore, in the embossing or flanging of plates around openings therein it has been the practice to employ male and female die members having a. dilference in radius equal to the thickness of the plate so that the flange produced 10 would be of the same thickness as the original plate. This was thought to be necessary to prevent the metal from tearing around the opening as the flange was formed. In this practice it was necessary to add the step of coining to ob- 15 tain the desired shape of opening and the flange was usually too short for eflicient threading.

The present invention'is based upon the discovery that an embossment can be formed in ordinary sheet steel by a combined forming and 20 extruding operation, with a single stroke of the dies, and in which a higher embossment is produced having better threading quality.

In carrying out the invention the male and female die members are concentric and substan- 25 tially cylindrical in form and have a difference in radius less than the thickness of the sheet stock being worked upon.

The principal object of the invention is to provide a method of embossing sheet metal which 30 will produce a high embossment in a single operation of combined forming and coining.

Another object is to provide an embossment in plate metal which is stronger and more suitable for threading.

Other objects will appear hereinafter.

The practice of 'the invention is illustrated in the accompanying drawing in which:

Figure 1 is a central longitudinal section through the die members before starting a forming operation and showing a sheet metal plate in position therebetween;

Fig. 2 is a similar view showing the dies as they start forming the flange;

Fig. 3 is a similar view showing the completion of the flrst step in the formation of the flange; Fig. 4 is a similar view showing the starting of the second step;

Fig. 5 is a similar view showing the completion" 7 I is provided with a relatively small hole 2 at the center of the proposed embossment to serve as a guide for the die and to prevent tearing of the metal as the dies move together.

The plate I is placed on the female die member 3 with the hole 2 centered .with respect to the opening 4 through member 3. The opening 4 is of greater diameter than the desired final opening in plate I, but is of considerably less diameter relative 'to said final opening than would be necessary to allow for the formation of a flange of the same thickness as the plate I.

Where a very high flange is desired the male die member 5 preferably has two sections. Its forwardsection 5 has a small pilot projection I at the center of its forward end to engage in the hole 2 in plate I for centering the dies and plate relatively. The section 6 is substantially cylindrical and is of a diameter preferably somewhat less than that of the final opening in plate I, but greater than would be necessary to allow for the formation between it and the die member 3 of a flange of the same thickness as that of plate I. 7

At the upper end of section 6 is a circumferential groove 8 which is provided to relieve the metal of the flange from pressure as the second section 9 of the die enters into operation. The second section 9 is substantially cylindrical and has the same diameter as that of the desired final opening in plate I.

Both sections 6 and 9 of the die 5 have rather blunt curved approaches at their forward ends to prevent tearing of the metal. It is understood that die life may be increased by utilizing a good lubricant as employed in general drawing practice and that for the more diiflcult operations a good drawing stock should be employed. Likewise where the embossmei to be formed is of relatively large size the hole 2 in the plate should beformedby, processes which eliminate any burrsor incipient cracks at the edge of the hole and it is well to have the lower corner edge slightly rounded as is clearly indicated in Figure 1 of the drawing.

In carrying out the invention, the metal of the plate I around the hole 2 is pushed into the opening 4 in the die member 3. As the die section 6 advances it starts to extrude the metal ahead of it, thereby forming a flange between it and the die 3 of less thickness than the original stock and counteracting the stretching of the metal immediately adjacent the hole 2. By extruding or pushing the metal ahead of the die the stress on the metal at the edge *of hole 2 f is considerably reduced and tearing is prevented. This is illustrated in Fig. 2.

As section 6 of die 5 progresses through the plate I as illustrated in Fig. 3 a cylindrical flange I is formed between it and die 3 of less thickness than that of the original stock, but preferably of greater thickness and less internal diameter than that of the final desired flange.

The die section 9 progressively pushes the metal ahead of it and by a flowing operation -it gradually reduces the thickness of the flange and enlargesits diameter as shown in Fig. 4. Fig, 5 illustrates the flnal completed operation in which the flange I0 is finally formed having the desired thickness and diameter.

Fig. 6 shows the finished flange or embossment In after the plate I has been removed from the dies. Fig. 7 shows the final threaded flange.

In practicing the invention it is desirable to employ the two section die 5 as illustrated where severe flowing of the metal is desired, but in many cases a single section is sufficient, as where the dimensions of flange ID are satisfactory. With different types of metals there are rather definite optimum limits for the amount of flow that should be obtained with a single die section.

The limits as to metal flow in operation will depend largely upon the characteristics of the metal. A soft, low carbon steel will have a wider range of possible metal flow than will a hard, relatively high carbon steel, and certain brittle or hard steels or metals may not be adaptable in many cases. The invention, therefore, finds its principal use in the softer drawing steels, preferably not in excess of 25% carbon, such as are used in many structures fabricated of sheet metal today.

In general, the amount of metal flow is limited between no reduction in thickness of the metal on the one hand and too great a reduction on the other. Where there is no reduction in thickness the flange It will be of the same thickness as plate I and will not be satisfactory for the present invention. By forming the flange III of less thickness than the plate I, as explained above, tearing of the edges, as the metal around the hole 2 is stretched, is prevented by the extrusion or pushing of the metal ahead of the die 5. If, on the other hand, it is attempted to form flange Ill too thin the metal of plate I will tend to shear off and pass through the opening 4 in die 3 as a slug. It is preferable, however, to extrude as much as possible on the first operation in order to compensate properly for the stretching of the metal.

The amount of metal flow obtainable will also be determined by the size of the opening desired and the relative thickness of the stock. In general, the larger the opening, the more severe the flow of metal, and the thicker the stock, the greater the reduction obtainable with a single die member. The height of'the flange or embossment obtainable will depend upon the thickness of the stock and the diameter of the opening desired.

The following illustration of a specific application of the invention will serve as an example. A .l0-.15% carbon steel of thickness was embossed to a height of approximately 1 around an opening of lsz" diameter and the embossment had a wall thickness of approximately This was accomplished with a single die section similar to section 6 and by providing a starting hole 2 of 1 5" diameter. Similarly, by the use of section 9 of the die the opening was expanded to 1%" in diameter, the embossment was reduced to approximately thick and was heightened to about The embossments formed under the present invention are more suitable for threading since the metal is somewhat hardened by the cold working, thus giving it better machineability without being so hard as to cause excessive wear on cutting tools. Furthermore, the material after extrusion has greater resistance to shear. This, in connection with its increased hardness is important to the final use of articles. Where tapped for bolt attachment the threads have greater resistance to stripping, and where bearing loads are imposed the greater hardness results in longer life. I

It is also possible to utilize more of the plate stock and thereby produce higher flanges since the pilot hole 2 may be made smaller without danger of tearing the metal. The exact size of the pilot hole 2 in any case will be determined by the thickness of stock, the size of opening and the size of flange desired. The edges of the hole 2 should be free from burrs or roughness whic might cause a tendency to start a tear.

The invention is claimed as follows:

1.-'-'I'he method of producing a tubular embossment of substantial length upon plate metal comprising providing a relatively small hole in the plate stock and applying male and female die members having a clearance less than the thickness of the stock, and extruding the metal ahead of the male die member to prevent excessive stress on the metal at the edge of said hole as the metal is flowed to form the embossment.

2. The method of producing a tubular embossment of substantial length upon plate metal comprising providing a relatively small opening in Y the plate stock, applying male and female dies thereto having a clearance less than the thickness of the stock and extruding the metal ahead of the male die member to prevent tearing of the metal at the edge of the opening as it is flowed to form the embossment and thereafter applying a larger male die member to enlarge the opening through the embossment and further refine the embossment.

3. The method of embossing plate metal comprising providing male and female die members, the male die member having a forward section of less diameter than that of the finished opening through the embossment and a second section of substantially the same diameter as that of the finished opening, applying said die members to the plate stock to form an unfinished embossment between the forward section of the male die memberand the female die member of less thickness than the plate stock, relieving said embossment from the pressure of said dies and then applying said second die section to enlarge the opening and produce the finished embossment.

DONALD W. SHERMAN.

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