Metal deforming – With cutting – By shearing tool-couple
Reexamination Certificate
2000-09-01
2002-01-22
Crane, Daniel C. (Department: 3725)
Metal deforming
With cutting
By shearing tool-couple
Reexamination Certificate
active
06339948
ABSTRACT:
This application is based on Japanese Patent Application No. 11-246997 filed Sep. 1, 1999, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process of forming an annular member such as a ring used for a manufacturing desired products such as automotive vehicle parts, or used as blanks that are to be cold-forged to manufacture desired products.
2. Discussion of Related Art
There are available various processes of forming an annular member as described below. One of the known processes includes a blanking operation and a piercing operation. In this process, a strip
10
supplied from a coil of strip is subjected to a blanking operation to punch out a plurality of workpieces in the form of circular plates
12
while the strip
10
is fed, as shown in FIG.
1
A. Each circular plate
12
has the same outside diameter and outer profile as a desired ring member
14
to be manufactured. In the left half of
FIG. 1B
(on the left side of a one-dot chain line indicated in the figure), the circular plate
12
is shown in cross section. Then, the circular plate
12
is subjected to a piercing operation to remove a radially inner portion thereof, for thereby obtaining the ring member
14
, as shown in cross section in the right half of FIG.
1
B. The diameter of the radially inner portion to be removed by piercing is equal to the inside diameter of the ring member
14
. However, the process including the blanking and piercing operations described above suffers from a considerably low yield ratio.
Another known process of forming a ring member includes a blanking operation, a compressing operation and a piercing operation. In this process, the strip
10
is initially subjected to a blanking operation to punch out a plurality of workpieces also in the form of circular plates
18
each of which has an outside diameter smaller than that of a desired ring member
16
to be manufactured, as shown in
FIGS. 2A and 2B
. In the left half of
FIG. 2B
(on the left side of a one-dot chain line indicated in the figure), the circular plate
18
is shown in cross section. Then, the circular plate
18
is subjected to a compressing operation to compress a radially inner portion thereof, as sown in the right half of
FIG. 2B
, for thereby reducing the thickness of the radially inner portion and enlarging the diameter of the circular plate
18
to the outside diameter of the ring member
16
. Finally, the compressed circular plate
18
is subjected to a piercing operation to remove a radially inner portion thereof, for thereby obtaining the ring member
16
, as shown in cross section in the right half of FIG.
2
C. The diameter of the inner portion to be removed by piercing is equal to the inside diameter of the ring member
16
. This process assures a comparatively high degree of hardness of the ring member
16
owing to the compressing operation on the circular plate
18
, leading to improved strength of the product to be manufactured from the ring member
16
. Further, this process assures a higher yield ratio than the process of
FIGS. 1A and 1B
. However, the yield ratio in the process of FIGS.
2
A-Ac is still unsatisfactory. Further, the present process is not applicable to a strip (blank sheet) having a comparatively small thickness.
A further alternative known process for forming a ring member includes a roll bending operation on a strip. Described more specifically referring to
FIGS. 3A-3C
, a plurality of narrow strips
20
shown in cross section in
FIG. 3A
each having a relatively small width are formed from the strip
10
. Each narrow strip
20
is formed into an annular member by roll bending. The thus obtained annular member has a seam
22
, as indicated in FIG.
3
B. Finally, the annular member is subjected to a calking operation or a welding operation at the seam
22
, to thereby form a ring member
24
as shown in FIG.
3
C. This process assures a significantly improved yield ratio. In the presence of the seam
22
on the ring member
24
, however, the present process suffers from a low strength of the product to be manufactured from the ring member
24
. Further, the process is not applicable to a strip having a comparatively large thickness.
JP-A-2-27058 discloses a further alternative process of forming a ring member, which includes a forging operation on one longitudinal end portion of a blank in the form of a round bar, and a shearing operation on the formed longitudinal end portion. Described in detail, the longitudinal end portion of the round bar is subjected to a forging operation with a die set including a female die and a male die, such that a punch portion of the male die is moved into a die hole of the female die, to cause deformation of the longitudinal end portion of the rod held in the die hole, so that a circular recess is formed in the end face of the end portion of the rod. Thus, the circular recess is defined by the annular wall whose outside diameter is larger than the original diameter of the rod. The thus forged longitudinal end portion of the rod is subjected to a shearing operation to cut off only the annular wall portion from the forged end portion of the rod, whereby a ring member constituted by the annular wall is obtained. Where the diameter or transverse cross sectional area of the round rod is comparatively large, a large forging force is required to be applied to the longitudinal end portion, for forming the above-indicated recess defined by the annular wall. Therefore, the present process is not available when the ring member to be manufactured has a comparatively large outside diameter.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process which permits an annular member to be formed with a sufficiently high yield ratio, with reduced limitations in the diameter and thickness of the ring member.
The above object may be achieved according to the principle of the present invention, which provides a process of forming at least one annular member from a cylindrical member, comprising the steps of: (a) applying a force to said cylindrical member in an axial direction thereof, to thereby cause plastic deformation at one of opposite axial end portions of the cylindrical member, such that a flange extends in a generally radial direction from one of opposite axial ends of the cylindrical member which corresponds to the above-indicated one of the opposite axial end portions; and (b) effecting a shearing operation on the flange to punch out the annular member.
In the process of the present invention, an axial force is applied to the cylindrical member in its axial direction, in the plastic deformation step, so as to cause plastic deformation at one axial end portion thereof, such that a flange extends from the corresponding one axial end of the cylindrical member in a generally radial direction of the cylindrical member. In the next shearing step, the flange is subjected to a shearing operation to punch out the desired annular member. Therefore, the present process permits the annular member to be formed with reduced limitations in the size and thickness of the annular member.
In a first preferred form of the present invention, a plurality of annular members are successively formed from the cylindrical member, such that the step of applying a force to the cylindrical member and the step of effecting a shearing operation are repeatedly implemented after a first one of the plurality of annular members is punched out. In this instance, the cylindrical member whose flange has been subjected to the shearing operation to punch out each annular member is subjected to the plastic deformation so as to again form the radially extending flange, and this flange is again subjected to a shearing operation to punch out the next one of the plurality of annular members. The process according to the present preferred form of the invention assures a relatively high yield ratio of the annular members.
In a second preferred form of this inve
Crane Daniel C.
Pillsbury & Winthrop
Toyota Jidosha & Kabushiki Kaisha
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