Pipe shaping method

Details Pipe shaping method Pipe shaping method

2001-02-22

2002-10-22

Tolan, Ed (Department: 3725)

Metal deforming

By use of tool acting during relative rotation between tool...

Tool orbiting or rotating about an axis

C072S084000, C072S370100, C072S370240, C072S370250

Reexamination Certificate

active

06467322

ABSTRACT:

BACKGROUND OF THE INVENTION
Conventionally, a method of reducing an end portion of a pipe and the like in diameter is referred to as a spinning work.
Japanese Patent Unexamined Publication No. 11(1999)-147138 discloses a method (spinning work) of forming a pipe
4
(workpiece) having a circular cross sectional shape. In this first related art, a roller
28
of a forming apparatus is compressed against a circumferential end portion of a fixed pipe
4
. Simultaneously with this, the roller
28
is revolved and put into the spinning work so as to form a narrow neck
4
c
at the end portion of the pipe
4
. During the spinning work, a revolution axis X
5
of the roller
28
is eccentric from a longitudinal center line X
4
of the pipe
4
, to thereby form the narrow neck
4
c
that is eccentric with respect to the longitudinal center line X
4
of the pipe
4
.
For carrying out the spinning work, the forming apparatus having the roller
28
is needed to be so constructed that the roller
28
is also movable radially with respect to the revolution axis X
5
during its revolution. In the first related art, the forming apparatus has a bracket
27
for supporting the roller
28
. The bracket
27
is provided with a first taper surface
27
a
. Moreover, the forming apparatus has a ring plate
26
which is provided with a second taper surface
26
a
. The first and second taper surfaces
27
a
and
26
a
abut against each other. The ring plate
26
is moved forward and backward relative to the pipe
4
, to thereby allow the roller
28
to move radially with respect to the revolution axis X
5
.
Similarly to the above first related art, Japanese Patent Unexamined Publication No. 11(1999)-179455 discloses a method of forming a narrow neck
44
(reduced diameter portion) of a pipe
42
which is fixed. In this second related art, a roller
27
of a forming apparatus
10
is compressed against an external circumference at an end portion of the pipe
42
, and is revolved during the spinning work for forming the narrow neck
44
with a reduced diameter.
In the forming apparatus
10
according to the second related art, a support shaft
28
for supporting a roller
27
is mounted on a spinning portion
24
via a slide lock plate
26
. A plate cam
29
rotating with the slide lock plate
26
during the spinning work allows the support shaft
28
to move in a radial direction of the spinning portion
24
.
A rod member
19
of a main shaft
18
penetrates through an axial center of the spinning portion
24
. A pivot converting portion
19
A converts an axial displacement of the rod member
19
into a rotation relative to the spinning portion
24
. The plate cam
29
is driven by the pivot converting portion
19
A.
A rotation axis
48
of the spinning portion
24
is deviated from a longitudinal center line
47
of the pipe
42
, to thereby form the narrow neck
44
that is eccentric with respect to the longitudinal center line
47
of the pipe
42
.
The above first and second related arts make it possible to produce casings such as those for catalytic converters for vehicles with a small number of component parts in a short time.
Each of the above first and second related arts requires the pipe (workpiece) that has a “circular” cross sectional shape. However, the casing for the catalytic converter for the vehicle has an overall configuration preferably as flat as possible so that the casing can be mounted below a floor of the vehicle. Therefore, a workpiece shaped into an “elliptical” pipe is needed for the casing, instead of the circular pipe.
However, according to the first and second related arts, spinning an elliptical pipe (workpiece), instead of the circular pipe (workpiece), cannot always produce an elliptical pipe (product) having a desired narrow neck.
More specifically,
FIG. 9
shows an elliptical pipe
70
(workpiece) made of steel having the following dimensions: a wide diameter of 150 mm, a narrow diameter of 105 mm, and a plate thickness of 1.5 mm, with an end portion thereof cut perpendicular to an axial direction. The elliptical pipe
70
(workpiece) is fixed and then put into a spinning work by means of a roller in order to reduce the end portion in diameter to 70 mm. As a result, a gradual reduction in diameter is seen with a pair of slopes
71
(taper) having an intersection angle of 60 degrees (not shown). However, the slope
71
and the narrow neck have an abnormal deformation
72
, that is, a wall surface partly rolled inward. As a result, the thus obtained narrow neck (reduced diameter portion) does not have a cross section shaped into a complete round.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of shaping an elliptical pipe (product) through a spinning work.
It is another object of the present invention to make an elliptical pipe (workpiece) usable for shaping the elliptical pipe (product) having a narrow neck which has a cross section shaped into a complete round.
There is provided a pipe shaping method, according the present invention. The pipe shaping method shapes a workpiece in the form of an elliptical pipe having a cross sectional shape elongated in a predetermined elongating direction and extending longitudinally from a first end to a second end, into a form having a narrow neck at least at the first end of the workpiece. The pipe shaping method comprises the following steps of: cutting the first end of the workpiece into a shape having a projection located at a subsidiary vertex portion and a recess located at a principal vertex portion, the projection projecting in a longitudinal direction of the workpiece, the recess being recessed in the longitudinal direction of the workpiece; mounting the workpiece to a pipe holder; disposing a roller around the workpiece; and reducing a cross sectional size of the first end of the workpiece by applying a compressive force on the circumference of the first end of the workpiece by a relative revolving movement between the roller and the workpiece.


REFERENCES:
patent: 5937516 (1999-08-01), De Sousa et al.
patent: 6233993 (2001-05-01), Irie
patent: 196 42 004 (1997-03-01), None
patent: 11-147138 (1999-06-01), None
patent: 11-179455 (1999-07-01), None

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