US3285045A - Two stage forming with expanding skirt step - Google Patents

Description

Nov. 15, 1966 J. w. BERG 3,235,045

TWO STAGE FORMING WITH EXPANDING SKIRT STEP Filed April 13, 1964 Fig.1

20 Fig.2

Fig. 4 F 5 INVENTOR.

JOHN W. BERG United fitates Patent 3,285,045 TWO STAGE FORMING WITH EXPANDING SKIRT STEP John W. Berg, La Mesa, Calif., assignor, by mesne assignments, to The Bendix Corporation, a corporation of Delaware Filed Apr. 13, 1964, Ser. No. 359,299 3 Claims. (Cl. 72-54) This invention relates generally to -a method of expanding metal by the use of hydraulic pressure and more particularly to a two stage forming process in which a clamping ring having an enlarged internal diameter is used to clamp the material during the second expanding step.

BACKGROUND In the past, it has been common practice to produce deep draws in sheet material by gripping the edge of a blank and either striking it by mechanically operated dies or subjecting it to fluid pressure. These methods resulted in uneven work hardening of the sheet material and to overcome this it was necessary to stretch the material in several stages, removing the material and heat treating it between operations. This produced a fairly uniform hardness in the finished article but added greatly to the expense of producing it.

According to the present invention very deep draws can be made, with a uniform degree of hardness, by utilizing a two step process in which an enlarged diameter clamping ring is used during the second stage of the process.

OBJECTS AND DRAWINGS It is the primary object of this invention to provide an improved method of deep drawing sheet material by which the final properties of the finished article may be accurately controlled.

It is a further object of this invention to provide an improved method of deep drawing sheet material which will produce a finished article having uniform hardness throughout.

It is a still further object of this invention to provide an improved two stage method of facilitating deep draws in sheet material.

With these and other objects definitely in view, this invention consists in the novel construction, combination and arrangement of elements and portions, as will be hereinafter fully described in the specification, particularly pointed out in the claims, and illustrated in the drawing which forms a material part of this disclosure, and in which:

FIGURE 1 is a cross section of a sheet material blank prior to the initial working step;

FIGURE 2 shows a cross section of a suitable fluid pressure drawing apparatus with a sheet material blank therein as it appears at the end of the first stage of the process;

FIGURE 3 is a similar cross section of the apparatus used for the second stage of the process with the blank expanded to finish form;

FIGURE 4 shows the blank on a reduced scale as it appears when removed from the apparatus shown in FIG- URE l; and

FIGURE 5 shows the finished article with a portion of the skirt of FIGURE 3 expanded.

With particular reference to the drawing I have shown, in FIGURE 1, a piece of stock sheet material of any desired thickness. I prefer to use metal but it is within the scope of this disclosure to use any of the well known synthetic plastics such as nylon or Dacron. The blank 10 is shown as being circular in shape but the process is of blank 22.

3,Z85,fi Patented Nov. 15, 1966 ice In FIGURE 2 I have illustrated the basic elements of the apparatus used in the first stage of the process. A base plate 12, suitably mounted on any convenient supporting structure, is provided with a plurality of mounting studs 14 spaced around the periphery thereof. A clamping ring 16 is secured on the studs by the usual nuts 18. This clamping ring is representative only it being understood that other types of clamping means, well known in the art may be substituted therefore. Base plate 12 is connected to a suitable source of fluid under pressure by conduit 20.

With the base plate 12 suitably mounted on a supporting structure, the conduit 20 cut off from the pressure source by any suitable valve means and the clamping ring 16 separated from the base plate, blank 10 is placed on the upper surface of the base plate, properly centered and clamped by placing clamping ring 16 on studs 14 and tightening nuts 18 to hold the periphery of the blank against slipping. Fluid pressure is then admitted to conduit 2t and blank 10 is stretched to an intermediate shape such as 22. in FIGURES 2 and 4. It will be apparent that during this initial stretching stage the central bowed portion of the blank is stretched more than those portions of the blank at points 24, in FIGURE 4, which are adjacent the bend. This uneven stretching produces a work hardening that is greatest at the central portion and gradually tapers ofi toward the edges 24 of the worked portion of the intermediate blank shown in FIGURE 4.

Pressure is now reduced to approximately that of the ambient atmosphere in conduit 21) and clamping ring 16 removed and replaced by clamping ring 26 which is of larger internal diameter than ring 16 as clearly shown in FIGURE 3. Ring 25 is tightened in place to grip and hold the skirt of blank 22 against slipping and fluid-pressure is again applied through conduit 20 to the underside Blank 22 will be expanded and stretched to an increased diameter by this second stage of the drawing process. The skirt 28 of the intermediate blank will be reduced in width as shown by 39 in the finished product of FIGURE 5. During this second stage expansion the greatest proportion of stretching, and consequently work hardening, will take place in the area of point 24- which will have moved to a position, as shown in FIG- shape of the finished product.

URE 5. This will produce, in the finished article, a substantially uniform hardness throughout the worked surface. As soon as the desired finished shape is reached pressure in conduit 20 is reduced and the finished article is removed by releasing the clamping ring.

From the foregoing description it will be evident that the application of my improved two stage deep-drawing process will produce articles having uniform metallurgical characteristics. A deeper draw is possible without the use of intermediate annealing steps thus greatly reducing the cost of the finished article.

While I have shown the finished product as being substantially hemispherical, it is to be understood that hollow bodies of virtually any shape may be formed depending upon the initial shape of the blank 10.

It is understood that minor variation from the form of the invention disclosed herein may be made without departure from the spirit and scope of the invention, and that the specification and drawings are to be considered as merely illustrative rather than limiting.

I claim:

1. A method of forming deep-drawn sheet material parts from generally flat sheet material blanks comprising the steps of:

clamping a peripheral area of said blank to prevent movement of said peripheral area;

producing a drawing fluid pressure on one surface of said blank to partially extend the material and produce a central bowed portion in said blank;

clamping a reduced peripheral area of said blank to prevent movement of said reduced peripheral area and to expose an area of unworked material; and

producing a further drawing fluid pressure on said one surface to extend the newly exposed area While said bulged portion is free to move under said further drawing fluid pressure. 2. A method for forming deep-drawn sheet material parts from generally flat sheet material blanks comprising the steps of:

clamping a peripheral area of said blank on a given diameter to prevent movement of said peripheral area;

producing a drawing pressure by fluid on one surface of said blank to partially extend the material and produce a central bowed portion in said blank;

clamping a reduced peripheral area of said blank to expose an area of unworked material to prevent movement of said reduced peripheral area; and

producing a further drawing pressure by fluid on said one surface to enlarge the newly exposed area while said bowed portion is free to move under said further drawing pressure, whereby the hardness of said finished article will be substantially uniform. 3. A method for forming deep-drawn sheet material parts from generally flat sheet material blanks comprising the steps of:

clamping said blank around its edges to prevent movement of the same; producing a drawing pressure by fluid on one surface of said blank to partially extend the material and pro- 5 duce a central bowed portion in said blank;

clamping a reduced peripheral area of said blank to prevent movement of the same and to expose an area of unworked material; and producing a further drawing pressure by fluid on said one surface to extend the newly exposed area While said bowed portion is free to move under said further drawing pressure, whereby the hardness of said finished article will be substantially uniform.

References Cited by the Examiner UNITED STATES PATENTS 495,591 4/1893 Knight et al. 72349 1,625,914 4/1927 Seibt 72-54 2,232,098 2/1941 Deichman 113l20 FOREIGN PATENTS 785,453 5/1935 France.

CHARLES W. LANHAM, Primary Examiner. RICHARD J. HERBST, Examiner.

Claims (1)

1. A METHOD OF FORMING DEEP-DRAWN SHEET MATERIAL PARTS FROM GENERALLY FLAT SHEET MATERIALS BLANKS COMPRISING THE STEPS OF: CLAMPING A PERIPHERAL AREA OF SAID BLANK TO PREVENT MOVEMENT OF SAID PERIPHERAL AREA; PRODUCING A DRAWING FLUID PRESSURE ON ONE SURFACE OF SAID BLANK TO PARTIALLY EXTEND THE MATERIAL AND PRODUCE A CENTRAL BOWED PORTION IN SAID BLANK; CLAMPING A REDUCED PERIPHERAL AREA OF SAID BLANK TO PREVENT MOVEMENT OF SAID REDUCED PERIPHERAL AREA AND TO EXPOSE AN AREA OF UNWORKED MATERIAL; AND PRODUCING A FURTHER DRAWING FLUID PRESSURE ON SAID ONE SURFACE TO EXTEND THE NEWLY EXPOSED AREA WHILE SAID BULGED PORTION IS FREE TO MOVE UNDER SAID FURTHER DRAWING FLUID PRESSURE.

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