Method for producing shapes having circular corrugations

Shapes with circular corrugations are produced by spinning a sheet metal blank under the action of oppositely directed deforming and backing forces. The blank is given the configuration of an envelope of revolution with a continuously diverging flare and is secured at the end nearest to the geometrical apex of the flare, and the circular corrugations are formed sequentially from the smaller towards the larger diameter by applying a concentrated deforming force to the inside surface of the blank, the deforming force being directed along the blank axis.

TECHNICAL FIELD 
The present invention relates to metalforming technique and is specifically 
concerned with methods for producing shapes having circular corrugations 
from sheet metal blanks by the spinning process. 
BACKGROUND ART 
Corrugated disk-typed shapes are presently produced from sheet metal mainly 
by stamping. With this technique, however, a blank is subjected to 
deformation over the entire surface simultaneously, which requires 
considerable forces. In addition, producing shapes having deep corrugtions 
involves the use of a set of dies with progressively increasing depth of 
impressions and necessitates annealing between operations. This entails a 
high power consumption with a rather low productive capacity. 
There is also known a method for producing shapes having circular 
corrugations, wherein the corrugations are spinned by acting upon a sheet 
metal blank with oppositely directed deforming and backing forces (USSR 
Inventor's Certificate No. 441,068, issued Aug. 30, 1974 Int. Cl. B21 D 
13/10). In this method, disks having sawtooth-section corrugations are 
produced from blanks in the form of the development of a cone. Such a 
blank is deformed at the points of apices of all the corrugations over one 
of radial sections of the blank; the process proceeds by progressively 
extending the zone of deformation and passing from one radial section to 
another. A corrugated disk thus produced has an unclosed surface, which 
will necessitate an additional operation of joining and fastening together 
edges of a complex contour and hence involve additional labour and power 
consumption. Moreover, accomplishing this method calls for an apparatus 
with shaping members (spinning tools) capable of varying the distance with 
respect to one another; this entails a constructional complexity of the 
apparatus and tooling to practice the method. 
The invention is based on the problem to provide a method for producing 
shapes having circular corrugations from sheet metal, which method makes 
it possible to produce such shapes with a broad range of dimensions and 
substantially any depth of the circular corrugations through changing the 
configuration of a blank by acting thereupon with a concentrated deforming 
force and offers at the same time low labour and power consumption. 
DISCLOSURE OF INVENTION 
The problem is solved by the provision of a method for producing shapes 
having circular corrugations through forming the corrugations by the 
spinning process which involves acting upon a sheet metal blank with 
oppositely directed deforming and backing forces, in which method the 
blank is given the configuration of an envelope of revolution with a 
continuously diverging flare and is secured at the end nearest to the 
geometrical apex of the flare, and the circular corrugations are formed 
sequentially from the smaller towards the larger diameter of the blank by 
applying a concentrated deforming force to the inside surface of the 
blank, the deforming forces being applied along the axis of the blank. 
Such a method for producing shapes having circular corrugations offers a 
low power consumption, inasmuch as a blank in the form of a flare readily 
lends itself to bending (turning out) at the points of application of the 
deforming and backing forces, i.e. at the areas of forming the circular 
corrugations. The same fact accounts for the simplicity of the method and 
possibility of forming corrugations with essentially any depth. 
The small deforming forces in turn lower the requirements placed upon the 
construction of the tooling needed to accomplish the method and reduce the 
metal content of the latter. 
Owing to the fact that the process involves predominantly a bending 
deformation, the surface quality of formed circular corrugations is close 
to that of the blank. 
Finally, one of the prime attractions of the proposed method lies in that 
the corrugated disks produced, when acted upon by external forces (such as 
pressure), can take a configuration close to that of the blank, which is 
essential for displacing diaphragms of fuel systems. 
It is advisable that a blank be pre-extended by the deforming force at the 
circular area of a corrugation to be formed till producing a circular 
shoulder. This will facilitate forming the corrugations when the blank is 
of a higher stiffness. 
It is feasible that the point of application of the deforming force be 
moved along a line corresponding to the contour of that wall of each 
corrugation which is disposed nearer to the blank axis. This will allow to 
increase the depth of the circular corrugations as well as to produce 
disks having circular corrugations from blanks with a spherical, 
parabolic, and like surface.

BEST MODE FOR CARRYING OUT THE INVENTION 
A blank 1 (FIG. 1) in the form of a closed envelope of revolution with a 
continuously diverging flare is installed by its end nearest to the 
geometrical apex of the flare on a die 2, centered, and secured by a 
hold-down 3. The die 2 has concentric ribs 4 spaced from one another at a 
distance equal to the spacing of the corrugations. 
To effect the deforming force, the tooling of the method comprises a 
spinning tool 5 whose thickness and width depend on the dimensions of the 
corrugation to be formed. The working surface (end) of the spinning tool 
5, contacting the surface of the blank 1, is rounded off and made of a 
material which promotes sliding (such as of brass). For the same purpose, 
grease is applied to the inside surface of the blank 1. 
The die 2 with the blank 1 secured thereto is set in rotation. The spinning 
tool 5 is brought within the blank and positioned radially so that its end 
is substantially at the centre of a groove defined by the first and second 
(counting from the mandrel centreline) ribs. 
The spinning tool 5 is moved along the axis of the blank 1 (as indicated by 
the arrow A) until it contacts the inside surface of the latter. 
A further longitudinal motion of the spinning tool 5 gives rise to a 
concentrated deforming force acting from the side of the tool 5 and to a 
backing force acting from the side of that rib 4 of the die 2 which is 
disposed nearer to the axis of the blank 1. Bending and rolling over the 
end of the spinning tool 5, the sheet metal of the blank turns out into a 
mirror position to form a corrugation wall disposed nearer to the blank 
axis. The other wall of the corrugation is formed by the undeformed side 
of the blank 1, displaced to a new position up to the contact with the 
other rib 4 of the groove of the die 2. After the corrugation of a 
predetermined depth has been formed, the spinning tool 5 is withdrawn to 
the initial position and traversed radially from the centre towards the 
periphery of the blank for a distance equal to the spacing of the 
corrugations, and the second (counting from the centreline of the shape) 
corrugation (FIG. 2) is formed. The process is continued until a shape 
(FIG. 3) with the desired amount of corrugations has been produced. 
The spinning tool may take the form of a roller (not shown) with a flange 
whose height somewhat exceeds the depth of the corrugation to be formed. 
According to a modification of the invention, the blank 1 is preextended by 
the deforming force at the circular (FIG. 4) area of a corrugation to be 
formed till producing a circular shoulder 6 (FIG. 4). This operation is 
performed by a spinning tool in the form of a roller 7 whose axis is 
substantially parallel with the axis of rotation of the blank 1. The 
roller 7 is fed along the axis of the blank 1 into contact with the inside 
surface of the latter and until the circular shoulder 6 is formed, after 
which the roller 7 is withdrawn out of the blank 1 and replaced by a 
spinning tool such as the plate 5 or a roller (not shown) whose rotational 
axis is disposed transversely with respect to the blank axis, and forming 
a corrugation in the above-described manner is started. To form the next 
corrugation, the cycle is repeated. 
According to another modification of the invention, the point of 
application of the deforming force, i.e. the end of the spinning tool 5, 
is moved along a line corresponding to the contour of that wall of each 
corrugation which is disposed nearer to the blank axis. 
When producing a shape from a blank having the configuration of a 
cone-shaped envelope (FIGS. 5a, b, c), the spinning tool 5 is fed 
straightlinearly at an angle .rho. equal to the inclination angle of the 
surface of that wall of each corrugation which is disposed nearer to the 
axis of the blank 1. At the initial moment of forming the corrugations, 
the spinning tool 5 should be positioned so (FIG. 5b) that its side 
surface is spaced from the outer side of a corresponding rib at 1.5 to 
2.delta., where .delta. is the thickness of the sheet metal. 
When producing a shape from a blank having the configuration of a 
hemisphere (FIG. 6), the spinning tool is fed so that its end, i.e. the 
point of application of the deforming force, follows a curved line 
corresponding to the contour of that wall of each corrugation which is 
disposed nearer to the axis of the blank 1. 
This is attained firstly by that the spinning tool is caused to follow a 
curvilinear template (not shown) corresponding to the surface of a 
circular area of the sphere, and secondly the surface of the rib 4 
disposed nearer to the axis of the blank 1 is also given the configuration 
of the circular area of the sphere. 
EXAMPLE 1 
A diaphragm was produced from a blank having the configuration of a 
truncated cone with a larger diameter of 620 mm. The sheet metal of the 
blank was 0.15 mm thick low-carbon steel. 
Conditions of the method: 
blank rotation, 80 m/min: 
axial feed of spinning tool, 0.2 mm/rev. 
A disk with fifty 4 mm deep circular corrugations was produced. The surface 
finish of the corrugations was close to that of the blank. The disk with 
circular corrugations was produced for use as a displacing diaphragm of a 
conical tank. 
EXAMPLE 2 
A diaphragm was produced from a blank having the configuration of a 
truncated cone with a larger diameter of 400 mm. The sheet metal of the 
blank was 0.1 mm thick commercially pure titanium. 
Conditions of the method: 
blank rotation, 60 m/min; 
axial feed of spinning tool, 0.1 mm/rev. 
A disk with twenty 5 mm deep corrugations was produced. The surface finish 
of the corrugations was close to that of the blank. 
EXAMPLE 3 
A diaphragm with a single corrugation was produced from a blank having the 
configuration of a truncated cone with a larger diameter of 200 mm. The 
sheet metal of the blank was 0.1 mm thick commercially pure titanium. 
Conditions of the method: 
blank rotation, 50 m/min; 
feed of spinning tool at an angle of .rho.=10.degree., 0.2 mm/rev. 
A diaphragm with a single 50 mm deep corrugation was produced. 
EXAMPLE 4 
A disk with circular corrugations was produced from a blank having the 
configuration of a truncated cone with a larger diameter of 1,200 mm. The 
sheet metal of the blank was 1 mm thick chromium-nickel stainless steel. 
Conditions of the method: 
blank rotation, 35 m/min; 
axial feed of spinning tool, 0.5 mm/rev. 
A disk with twenty 40 mm deep corrugations was produced. 
EXAMPLE 5 
A disk with circular corrugations was produced from a hemispherical blank 
with a base diameter of 500 mm. The sheet metal of the blank was 0.3 mm 
thick chromium-nickel stainless steel. 
Conditions of the method: 
blank rotation, 30 m/min; 
template-controlled feed, 0.2 mm/rev. 
A disk with fifteen circular corrugations with a depth varying from 5 to 20 
mm was produced. 
The disk with circular corrugations was produced for use as a diaphragm of 
a spherical tank of a displacing system. 
INDUSTRIAL APPLICABILITY 
The invention is particularly useful for producing ring-shaped corrugated 
disks used, depending on their purpose, as membranes, diaphragms and other 
shapes capable of varying within a broad range their dimensions along the 
rotational axis under the action of external forces.