US3596494A

US3596494A - Vacuum stripping

Info

Publication number: US3596494A
Application number: US786046A
Authority: US
Inventors: John M Hagan
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1968-12-23
Filing date: 1968-12-23
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03

Abstract

Cup-shaped metal object is stripped from ram of hydraulic press using a stripper plate at end of stroke of the ram, the stripping being accomplished by applying a positive pressure inside the ram and cup-shaped object and a vacuum or substantial negative pressure outside the bottom of the object at the stripper plate.

Description

United States Patent [72] inventor John M- llflg [56] References Cited UNITED STATES PATENTS [21] P 786046 2,990,581 7/1961 ROW6,.I!' 264/89 [22] Filed Dec. 23, 1968 1 3,338,997 8/1967 Tigner 18/19 F {451 Patented Aug. 3, 1971 7 6 96 G l 29 27 [73] Assignee Aluminum Company of America H 4 tamer et a M X Hush h Pa 3,266,451 8/1966 Kraus 113/120 3,270,544 9/1966 Maeder et a1 113/120 3,402,591 9/1968 Maeder 72/345 Primary ExaminerRichard J. Herbst Attorney-Abram W. Hatcher [54] VACUUM STRIPPING 6 Chums 4 Drawing Figs ABSTRACT: C up-shaped metal object is stripped from ram of [52] [1.8. CI 72/344, hydraulic press using a stripper plate at end of stroke of the 1 13/120 ram, the stripping being accomplished by applying a positive [51] Int. Cl B2ld 45/00 pressure inside the ram and cup-shaped object and a vacuum [50] Field of Search 72/344- or substantial negative pressure outside the bottom of the ob- 346; 113/120 H; 29/427, 421 ject at the stripper plate.

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IN VEN TOR.

8 JOHN M. HAGAN mow M m Attorney VACUUM STRIPPING BACKGROUND OF THE INVENTION This invention relates to metal forming. More particularly, it relates to method and apparatus for stripping a can or canister from the ram or metalworking punch used in forming it.

Conventionally a metalworking punch or ram, for example, one operated by a hydraulic press, is stripped at the end of its drawing or ironing stroke from the object which it forms, for example, a cylinder, can or cup of aluminum (including aluminum-base alloys) or the like open at the top, by a mechanical stripping device or by applying pressure inside the punch or ram and object being formed while at the same time employing a mechanical stripper. However, problems have been encountered in using such stripping devices, especially when the thin-walled cans or canisters are being formed. For instance, it is sometimes difficult to position a mechanical stripper so that it will engage the open end of the can, particularly without damaging the end the can. Furthermore, pressure applied internally tends to distort the shape of the can or expand the can beyond allowable diameter tolerances. Therefore, development of a method and apparatus which would substantially avoid such distortion of the cans or other objects formed by drawing or ironing of a metal such as aluminum, including its alloys, represents a highly desireable result.

SUMMARY OF THE INVENTION It is accordingly one object of lthis invention to provide an improved method of stripping an object formed by the stroke of a metalworking punch from the punch. It is a further object to provide an apparatus for minimizing distortion of a can or cup like object when stripped from a ram used in forming same by drawing and ironing or the like. Other objects will be apparent from the description and claims which follow.

In its broader aspects my invention involves applying a positive air pressure inside a metalworking punch or ram and a vacuum or substantial negative-piessure on the outside at the end or bottom of the object being formed, such as a cup, can or canister, that is, on the outside at the point where the stroke of the punch or ram ends. This strips the can from the punch. The application of the vacuum or substantial negative pressure on the outside permits the positive pressure on the inside to be reduced to a level which will not distort the object being formed. A conventional hydraulic ironing press may be used to advance and retract the punch, The substantial vacuum on the outside may be applied through an orifice in a stripper plate positioned at the end of the stroke of the punch, with a pressure seal being obtained by means of an O-ring, or the like. TheO-ring or like means may be so positioned that the substantial vacuum is confined to an area of maximum circumference of about the circumference of the closed end or bottom of the cup or can, Thus the pressure outside the side wall of the cup or can, usually substantially atmospheric or room pressure, is not affected and any tendency of the pressure applied to the inside of the cup or can during stripping to push the sidewall out of shape is thereby minimized.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of my invention may be obtained from an examination of the drawing in which:

FIG. 1 is a schematic representation, in part broken away, depicting the ram in a retracted position and shallow cylinder 12 in a load position prior to ironing through a die 14 and against a stripper plate 16.

FIG. ,2, likewise broken away in part, shows the cylinder (without a top) 12 ironed and sealed against the stripper plate 16 by the ram 10.

FIG. 3 in a similarmanner, depicts the first part of the stripping stepin which a substantial vacuum has been applied outside the bottom of the cylinder 12 by vacuum applying means (such as a vacuum pump) 18 via line 30 which passes through an orifice in stripper plate 16 and a positive pressure inside the hollow ram 10 and cylinder 12 by a positive pressure-applying means (such as a mill air line) 22 via line 2d, the ram 10 has been partly retracted and the cylinder 12 is stillin contact with the stripper plate 16.

FIG. 4 shows the second part of the stripping step with the ram 10 now in a fully retracted position and the cylinder 12 completely stripped from the stripper plate and in an unload position, the O-ring gasket 26 seal having been broken.

A hydraulic press or other mechanism for operating the ram is not depicted as it may be any appropriate conventional system. Means for applying the positive pressure and the vacuum or substantial negative pressure may also be of conventional construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT The following example is illustrative of the invention.

The steps depicted in FIGS. 1 through 4 of the drawing as described hereinabove were employed repetitively to produce by ironing substantially cylindrical-shaped cans having walls about 0.0l0-inch thick and bottoms about 0.030-inch thick and subsequently 200 similar cans with walls about 0.030-inch thick and bottoms about 0.060-inch thick. Stripping of each can from ram and stripper plate was accomplished by applying a positive air pressure (about 25 p.s.i.g.) inside the ironing punch and a vacuum or substantial negative pressure (about --l4.7 p.s.i.g.) on the outside of the end of the can. Uniformity of dimensions of the cans was satisfactory according to commercial standards, and the outside surface finishes were substantially unmarred. A SO-ton hydraulic ironing press was used. A vacuum pump was used to obtain the vacuum or substantial negative pressure and a mill air line to obtain the positive pressure.

From the foregoing description and example it is apparent that the present invention provides means for stripping a canister from a metalworking punch without the use of mechanical devices which might distort, scratch, or otherwise damage the canister. A further advantage of the invention is that the terminal stripper plate may be made movable to an unloading station, for example, by use of a vacuum system in which it serves as a vacuum transfer head, thus additionally minimizing the possibility of damage to the can or cup-shaped object being stripped from the punch, ram, or plunger.

While the invention has been described in terms of preferred embodiments, the claims appended hereto are intended to encompass all embodiments which fall within the spirit of the invention.

Having thus described my invention and certain embodiments thereof, I claim: I

1. A process for stripping a closed end metal object from a metalworking punch and a stripper plate which comprises applying a vacuum or substantial negative gauge pressure outside the end of the object and the stripper plate and a positive gauge pressure inside the punch, holding the end of the object against the plate and withdrawing the punch while the end of the object is so held, thereby effecting the stripping of the object from the punch and stripper plate.

2. The process of claim I wherein the metal object is an aluminum can and the vacuum or substantial negative gauge pressure applied outside the object is applied in the vicinity of the closed end of the can through an orifice in the stripper plate substantially against which the object rests prior to the stripping.

3. The process of claim 2 wherein the vacuum or substantial negative pressure applied outside the aluminum can in the vicinity of the closed end is restricted to a maximum area about the size of the closed end of the can by means of a seal, thereby substantially preventing distortion of the remainder of said can other than said closed end.

4. Apparatus for stripping a closed end metal object from a punch comprising in combination a hollow metalworking punch axially aligned with a metal workpiece adapted to be formed into said closed end metal object, means for forcing said punch against said workpiece to form it into said closed end metal object, means for retracting said punch from against said workpiece formed into said closed end metal object, cooperative means for applying a positive gauge pressure to the inside of said punch and for applying a vacuum or substantial negative gauge pressure outside said punch in the vicinity of the closed end of said metal object, whereby said closed end of said metal object is held against a stripper plate and stripped from said punch and stripper plate after having been formed into said closed end metal object.

5. The apparatus of claim 5 wherein a terminal plate is axican having an annular sidewall joined to said closed end and wherein an O-ring is provided on the surface of said terminal plate next to said punch and said O-ring is of substantially the same diameter as that of the closed end of said can, said O- ring being adapted to seal against said closed end of said can.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,596 ,494 Dated August 3 197].

Inventor(s) John M. Hagan It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 19 Delete "the" after "when".

Col. 1, line 28 Change "desireable" to -desirable--.

Claim 5, line 13 Change "5" to --4-.

Claim 5 line 4 After "negative" insert --gauge--.

Signed and sealed this 25th day of January 1972.

( SEAL) Attest:

EDWARD M.FLJ:.'TCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 FORM PO-1050 {10-69) Us GOVERNMENT wmmms orncr I969 o-aea'sal

Claims

2. The process of claim 1 wherein the metal object is an aluminum can and the vacuum or substantial negative gauge pressure applied outside the object is applied in the vicinity of the closed end of the can through an orifice in the stripper plate substantially against which the object rests prior to the stripping.

5. The apparatus of claim 5 wherein a terminal plate is axially aligned with said punch on the opposite side of said workpiece from said punch and an orifice is provided in said terminal plate, said orifice being connected to said means for applying said vacuum or substantial negative pressure.

6. The apparatus of claim 5 wherein the closed end metal object is a substantially cylindrical-shaped open-top aluminum can having an annular sidewall joined to said closed end and wherein an O-ring is provided on the surface of said terminal plate next to said punch and said O-ring is of substantially the same diameter as that of the closed end of said can, said O-ring being adapted to seal against said closed end of said can.