U.S. patent number 3,890,819 [Application Number 05/382,506] was granted by the patent office on 1975-06-24 for apparatus for deforming sheet metal blanks by fluid pressure.
This patent grant is currently assigned to Centro Sperimentale Metallurgico S.p.A.. Invention is credited to Bruno DeLuca.
United States Patent |
3,890,819 |
DeLuca |
June 24, 1975 |
Apparatus for deforming sheet metal blanks by fluid pressure
Abstract
A sheet metal blank is clamped between opposed annular members
and deformed in its central area by fluid pressure applied thereto.
The clamping members are urged together by the same fluid pressure;
and to this end, one of the clamping members is mushroom-shaped
with the head of the mushroom comprising a piston urged in a
clamping direction by fluid pressure applied by an annular cylinder
chamber that communicates with a central chamber whose fluid
deforms the blank. In this way, the annular marginal portions of
the blank are tightly gripped and only the central exposed portion
of the blank is deformed.
Inventors: |
DeLuca; Bruno (Rome,
IT) |
Assignee: |
Centro Sperimentale Metallurgico
S.p.A. (Rome, IT)
|
Family
ID: |
11275655 |
Appl.
No.: |
05/382,506 |
Filed: |
July 25, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jul 25, 1972 [IT] |
|
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51741/72 |
|
Current U.S.
Class: |
72/57;
29/421.1 |
Current CPC
Class: |
B21D
26/025 (20130101); B21D 26/02 (20130101); B21D
24/08 (20130101); Y10T 29/49805 (20150115) |
Current International
Class: |
B21D
24/00 (20060101); B21D 26/00 (20060101); B21D
26/02 (20060101); B21D 24/08 (20060101); B21d
026/04 () |
Field of
Search: |
;72/54,57,60
;29/421 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Herbst; Richard J.
Attorney, Agent or Firm: Young & Thompson
Claims
Having described my invention, I claim:
1. Apparatus for deforming only a central portion of sheet material
by fluid pressure, comprising means to clamp a peripherial portion
of said material entirely about said central portion while leaving
said central portion exposed, means mounting said clamping means
for free and unimpeded movement toward said material, means to
apply the pressure of a fluid under pressure to said exposed
central portion of said material to deform only said central
portion of said material, and means to apply said pressure also to
said clamping means so that the force with which said peripheral
portion is clamped by said clamping means varies directly as said
pressure over the entire range of said pressure thereby to maintain
said peripheral portion against substantial radially inward
movement over said entire range of pressure.
2. Apparatus as claimed in claim 1, said clamping means comprising
an annular member, means mounting said annular member for movement
toward and away from the material to be clamped, and means for
applying said fluid to said material centrally of said annular
member.
3. Apparatus as claimed in claim 2, and an annular die on the side
of said material opposite said clamping member, said annular die
having a central opening for receiving material deformed by said
pressure.
4. Apparatus as claimed in claim 1, and a hollow body within which
said clamping means is mounted for sliding movement toward and away
from said material, said clamping means and said hollow body
defining between them an annular cylinder chamber, and means for
applying said pressure within said cylinder chamber to urge said
clamping means in the direction of said material.
5. Apparatus as claimed in claim 4, said clamping means having a
central opening through which said fluid is applied to said
material, said applying means comprising at least one opening
through said clamping means communicating between said annular
chamber and said central opening.
6. Apparatus as claimed in claim 4, the area of said annular
cylinder chamber in a plane perpendicular to the axis thereof being
greater than the area of said material exposed to said
pressure.
7. Apparatus as claimed in claim 4, said clamping member having a
head thereon that defines said annular chamber between said head
and the bottom of a cup-shaped recess within said body.
Description
The present invention relates to deforming sheet metal blanks under
fluid pressure, both for the production of formed workpieces and
also for laboratory testing.
One such method of laboratory testing is to apply hydraulic
pressure to a test blank to cause a circular or elliptical central
portion thereof to bulge. However, the hydraulic pressure machines
designed for this purpose heretofore have suffered from the
disadvantage that portions of the blank outside the central test
area may also be drawn radially inwardly, thereby invalidating the
results of the test. The same problem of course is detrimental to
the production of workpieces.
Accordingly, it is an object of the present invention to provide
apparatus for deforming sheet metal blanks under fluid pressure, in
which only the exposed central portion of the blank is
deformed.
Another object of the present invention is the provision of such
apparatus, in which the peripheral portions of the blank are
gripped with a pressure that varies as the pressure with which the
central portion of the blank is deformed.
Finally, it is an object of the present invention to provide such
apparatus, which will be relatively simple and inexpensive to
manufacture, easy to operate, maintain and repair, and rugged and
durable in use.
Other objects, features and advantages of the present invention
will become apparent from a consideration of the following
description, taken in connection with the accompanying drawing,
which is a cross-sectional view of apparatus according to the
present invention.
Referring now to the drawing in greater detail, there is shown
apparatus according to the present invention, comprising an outer
body 1 which is a figure of revolution and is generally cylindrical
or cup-shaped. A blank holder 2, which is also a figure of
revolution, is axially slidably disposed within body 1. Piston 3
slides coaxially with a fluidtight fit within blank holder 2. An
annular holding die 4, which is also a figure of revolution, is
disposed within body 1 in coaxial superposed relation with holder 2
and piston 3, and has an outwardly directed peripheral flange 4'
which is received beneath an inwardly directed annular flange 1' at
the upper extremity of body 1, and a central opening 4". Die 4 is
releasable from the engaged relationship with body 1 which is shown
in the drawing, by means of a bayonnet lock or detachable
interengaging portions, or other conventional means (not shown). In
this way, the assembly can be opened for the insertion and removal
of workpieces.
Holder 2 has a flat annular surface confronting die 4, which is
faced with a gasket 5 of a material softer than either holder 2 or
the metal sheet to be deformed.
At least one opening 6 extends through the cylindrical
axially-extending stem of holder 2 to convey to the radially outer
side of holder 2 the same fluid pressure that acts on the radially
inner side of holder 2 and on the circular blank 7. To this end,
holder 2 is provided with an axially extending passageway 8; and
the radially inner end of the hole or holes 6 communicates with the
passageway 8, while the radially outer end of hole or holes 6
communicates with an annular cylinder chamber 9 defined between
body 1 and holder 2.
Body 1 is bolted to a support (not shown) by bolts or other
fasteners (not shown) that pass through a flange 10 thereon.
The cavity of body 1 in which the head 11 of holder 2 is disposed
is cup-shaped and of a depth greater than the depth of the head of
holder 2. Seals 12 provide slidably sealed contact between piston 3
and the supporting side walls of passageway 8, and between holder 2
and body 1 on opposite sides of chamber 9.
In operation, with the die 4 removed, a sheet metal blank in the
form of a circular workpiece 7 is placed on gasket 5 and die 4 is
returned to the position shown in the drawing. Holder 2 can then be
urged against the workpiece by any desired means (not shown), after
which piston 3 is advanced upwardly as seen in the drawing.
Passageway 8 and chamber 9 are filled with hydraulic fluid such as
oil, whose pressure is increased by the upward movement of piston
3. This upward movement has two effects: The pressure imparted to
the hydraulic fluid causes workpiece 7 to deform and bulge upwardly
into opening 4", as seen in the drawing; and also the pressure of
the hydraulic fluid transmitted through hole or holes 6 to chamber
9, causes holder 2 to advance in the manner of a piston, thereby
more tightly clamping the annular peripheral portions of the
workpiece against radially inward movement. To this end, it is
preferred that the area of chamber 9, measured in a plane
perpendicular to the axis of the apparatus, should be larger than
the area of workpiece 7 that is exposed to the fluid by passageway
8, the broad range of ratios of these two areas being 1:1 to
10:1.
The higher the pressure against the exposed central portion of the
workpiece, the greater will be the force with which holder 2 clamps
the peripheral portions of the workpiece; and in this way, the
tendency of the workpiece to be drawn radially inwardly toward its
center, upon deformation of the central portion in an axial
direction, is effectively countered. At the same time, it has not
been necessary to provide the clamping surfaces of holder 2 and die
4 with ridges or deformations or other asperities that would
themselves change the shape of the workpiece.
To release the formed workpiece, or to discontinue the test in the
case of testing apparatus, it is necessary only to back off the
piston 3, whereupon the fluid pressure is relieved and die 4 can be
removed upwardly, after which the formed workpiece or the tested
specimen can be removed and replaced with an undeformed or untested
piece.
From a consideration of the foregoing disclosure, therefore, it
will be evident that all of the initially recited objects of the
present invention have been achieved.
Although the present invention has been described and illustrated
in connection with a preferred embodiment, it is to be understood
that modifications and variations may be resorted to without
departing from the spirit of the invention, as those skilled in
this art will readily understand. Such modifications and variations
are considered to be within the purview and scope of the present
invention as defined by the appended claims.
* * * * *