Device for forming asymmetrical articles by rolling

A pair of dies are provided of which die faces are formed with depressions sequentially brought into engagement with a particular portion of a workpiece as the workpiece rolls between the die faces. By compressing the workpiece while driving the same to roll between the die faces, an excess metal of the workpiece is caused to flow into the depressions sequentially for thereby forming an asymmetrical part of the article.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates in general to rolling by using two or three 
cylindrical dies or a pair of flat or straight dies and more particularly 
to a method of and device for forming an asymmetrical article such as a 
shaft having a radial projection or an eccentric shaft section by rolling. 
2. Description of the Prior Art 
A rolling process has been widely used in production of metal articles such 
as stepped shafts since no stock is wasted in rolling the articles and the 
rolled product is superior in strength to the cut product. However, 
asymmetrical articles such as a shaft having a radial projection or an 
eccentric shaft section cannot be formed by the prior art rolling process. 
For this reason, in production of some asymmetrical aticles, a forging 
process for forming an intermediate product into a finished shape has been 
indispensable in addition to a rolling process for forming a workpiece 
into the intermediate product. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a method of 
forming an asymmetrical article by rolling, which comprises preparing a 
plurality of dies of which die faces are formed with independent patterns 
sequentially brought into engagement with a particular portion of a 
workpiece as the workpiece rolls between the die faces, and compressing 
the workpiece while driving the same to roll between the die faces and 
forming the particular portion of the workpiece into an asymmetrical 
portion of the article by the effect of the patterns of the die faces. 
In accordance with the present invention, there is also provided a device 
for forming an asymmetrical article by rolling, which comprises a 
plurality of dies of which die faces are formed with independent patterns 
sequentially brought into engagement with a particular portion of a 
workpiece for thereby forming an asymmetrical part of the workpiece at the 
particular portion. 
The above method and device make it possible to form an asymmetrical 
article by rolling. 
It is accordingly an object of the present invention to provide a method of 
forming an asymmetrical article by rolling. 
It is a further object of the present invention to provide a device for 
forming an asymmetrical article by rolling. 
It is a further object of the present invention to provide a method of 
forming a crankshaft, which can reduce the manufacturing expense.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show a pair of cylindrical dies 3, 4 according to an 
embodiment of the present invention. The dies 3, 4 are adapted so as to be 
capable of rolling an asymmetrical product or article P as shown in FIGS. 
7 and 8. The article P is in the form of a stepped shaft having a pair of 
smaller diameter sections S.sub.1, S.sub.1 and a larger diameter section 
S.sub.2 interposed therebetween. While the shaft sections S.sub.1, S.sub.2 
are all arranged concentric, the larger diameter section S.sub.2 has a 
pair of axially spaced projections G, G which are aranged asymmetric about 
the axis of the article P. 
As seen from FIG. 1, the dies 3, 4 have substantially the same shape except 
for the number and position of grooves or depressions and adapted to be 
driven by an unshown driving means. Referring to FIGS. 2A and 2B, the die 
face 4a of the die 4 has a pair of first working sections 4c, 4c in the 
form of ridges spaced in the width direction of the die 4. The first 
working sections 4c, 4c each have biting ends 4b, 4b biting into a 
workpiece W at the begining of rolling for forming the smaller diameter 
sections S.sub.1, S.sub.1 of the article P. The die face 4a also has a 
second working section 4d between the first working sections 4c, 4c for 
forming the larger diameter section S.sub.2 of the article P. 
As seen from FIGS. 2B and 2C, rolling of the workpiece W which is 
originally a straight round bar of the diameter d.sub.0 begins as the 
process advances from the stage a--a to the stage b--b. In response to 
this, the opposite ends of the workpiece W start reducing in diameter by 
the effect of the first working sections 4c, 4c and formed into the 
smaller diameter sections S.sub.1, S.sub.1 of the diameter d.sub.3. At the 
stage transitting from b--b to d--d, the central portion of the workpiece 
W reduces in diameter from d.sub.0 to d.sub.l and then d.sub.1 to d.sub.2 
and formed into the larger diameter section S.sub.2 by the effect of the 
second working section 4d which is provided with a predetermined 
inclination in the place corresponding to the stage transitting from b--b 
to d--d. 
The second working section 4d is formed with plural pairs of depressions 5, 
6, 7 for forming the radial depressions G, G of the article P, each pairs 
of which depressions are spaced from each other in the width direction of 
the die 4 by the amount corresponding to the distance between the 
projections G, G. The depressions 5, 6, 7 are arranged at the same 
intervals, i.e., at an equal pitch in the longitudinal direction of the 
die 4. The pitch of the depressions 5, 6, 7 is set substantially equal to 
the distance over which the workpiece W rolls by one revolution, i.e., the 
circumference of the workpiece W so that an excess metal of the workpiece 
W is caused to flow progressively into the depressions 5, 6, 7 and formed 
into the radial prejections G, G as shown in FIGS. 7 and 8. 
Referring to FIGS. 3A to 3E, the rolling process by using the dies 3, 4 of 
this invention will be described more in detail hereinafter. The die 3 is 
substantially similar to the die 4 except for depressions 8, 9. The 
depressions 8, 9 are formed so as to be equal in pitch to the depressions 
5, 6, 7 but differ from same in position relative to the workpiece W by 
the distance over which the workpiece W rolls by about half revolution, 
i.e., differ from the depressions 5, 6, 7 in phase by the amount 
corresponding to about half revolution of the workpiece W so that any one 
of the depressions 8, 9 of one die 4 and any one of the depressions 5, 6, 
7 of the other die 3 do not come in contact with the workpiece W at the 
same time. 
In FIG. 3A, the workpiece W is shown as being coming in contact with the 
depression 5. An excess metal of the workpiece W resulting from the 
reduction in diameter of the central portion thereof is thus caused to 
flow into the depression 5 and formed into a radial projection G as shown 
in FIG. 3B. As the rolling process advances further, the projection G 
having been formed by the depression 5 comes in engagement with the 
depression 8 as shown in FIG. 3C so that another excess metal of the 
workpiece W is introduced into the depression 8 to develop the projection 
G. In like manner, the projection G sequentially comes in engagement with 
the depressions 6, 9, 7 every half revolution of the workpiece W so as to 
develop the projection G further as shown in FIG. 3D. Finally, as shown in 
FIG. 3E, the prejection G is finished by the depression 7, thereby 
completing the rolling process of the asymmetrical article P. By the 
rolling process mentioned above, the asymmetrical article P shown in FIGS. 
7 and 8 can be obtained. 
By the experiments conducted by the applicant, it was found desirable to 
set the pitch l of the depressions 5, 6, 7 or the depressions 8, 9 at a 
value about 1.0-1.2 times as large as the distance over which the 
workpiece W rolls by one revolution (i.e. the circumference of the 
workpiece W) since there is some slippage between the dies 3, 4 and the 
workpiece W during rolling, though the desirable pitch l also varies a 
little depending upon the shape of the article P to be rolled. 
In the foregoing, it will be understood that the number of the depressions 
is not limitative but may be increased in order to form a larger 
projection. It will be further understood that three cylindrical dies may 
be employed to carry out the foregoing rolling process of this invention. 
In such a case, the depressions of each die are arranged to differ from 
each other in phase by the amount corresponding to about 1/3 revolution of 
the workpiece or differ from each other in position relative to the 
workpiece by the distance over which the workpiece rolls by 1/3 
revolution. It will be further understood that the depressions may be 
designed so as to increase in volume progressively as exemplarily shown in 
FIG. 4 with respect to the depressions 5, 6 or on the contrary the 
depressions may be designed so as to reduce in volume progressively as 
exemplarily shown in FIG. 5. 
FIG. 6 shows another embodiment in which a pair of flat dies 1, 2 are used 
for carrying out the foregoing rolling process of this invention in place 
of the cylindrical dies 3, 4. 
FIGS. 9A to 9D show a method of forming a crankshaft P.sub.1 according to a 
further embodiemnt of the present invention. 
In this embodiment, a workpiece W.sub.1 is originally in the form of a 
straight round bar as shown in FIG. 9A and formed into an intermediate 
product shown in FIG. 9B by a single preliminary forming process. The 
intermediate product W.sub.1 is asymmetrical about its axis and includes a 
plurality of symmetrical or concentric shaft sections S.sub.1, S.sub.1 and 
a plurality of asymmetrical or eccentric shaft sections S.sub.2, S.sub.2. 
The shaft sections S.sub.1, S.sub.2 are arranged in compliance with the 
finished shape of the crankshaft or finished product P.sub.1 shown in FIG. 
9D so that the intermediate product W.sub.1 is ready to be forged. The 
preliminary forming of FIG. 9B is carried out by a rolling process using a 
pair of cylindrical dies 13, 14 according to the present invention. The 
dies 13, 14, as shown in FIGS. 10-12 and 13A-13D, are respectively formed 
with die faces 13a, 14a including first working sections 13c, 14c for 
forming the symmetrical or concentric shaft sections S.sub.1 and second 
working sections 13d, 14d for forming asymmetrical or eccentric shaft 
sections S.sub.2 having radial projections G. 
By this rolling process, a prior art bending process can be dispensed with, 
which bending process has been indispensable for forming the asymmetrical 
or eccentric shaft sections S.sub.2 in addition to a prior art rolling 
process. 
Subsequently to the preliminary forming process of FIG. 9B, a forging 
process of FIG. 9C is performed twice, i.e., one for roughing and one for 
finishing. In this forging process, an excess metal portion or flange F is 
inevitably formed similarly to the prior art. However, since the workpiece 
W.sub.1 can be formed into the shape of FIG. 9B more efficiently than 
before by the rolling process of this invention, the metal flow occuring 
in the subsequent forging process becomes more efficient and desirable 
than before, whereby to make it possible to reduce the volume of the 
excess metal portion F. After the forging process of FIG. 9C, the excess 
metal portion F is removed by a trimming process of FIG. 9D, whereby the 
workpiece W.sub.1 is formed into the finished shape of the crankshaft 
P.sub.1. 
By this embodiment, the manufacturing expense of the cranckshaft can be 
reduced considerably since the bending process otherwise necessitated can 
be dispensed with. Further, by this embodiment, it becomes possible to 
employ a straight round bar as a workpiece for producing a crankshaft. 
This is effective for reducing the volume of the excess metal protion to 
be trimmed. 
FIGS. 14 and 15 show a further embodiment in which a pair of cylindrical 
dies 23, 24 are used for rolling an asymmetrical product or article 
P.sub.2 shown in FIGS. 17 and 18. 
FIG. 16A is a developed view of the face 24a of the die 24, and FIG. 16B is 
a sectional view taken along the line 16B--16B of FIG. 16A. The die face 
24a has a pair of first working sections 24c, 24c each having biting ends 
24b, 24b and adapted for forming the symmetrical or concentric smaller 
diameter sections S.sub.1 and a second working section 24d located between 
the first working sections 24b, 24b and adapted for forming the 
asymmetrical or eccentric larger diameter section S.sub.2. The second 
working section 24d is formed with alternate depressions 25, 26, 27 and 
projections 28, 29, 30 in such a manner that the depressions 25, 26, 27 
become deeper the remoter they are located from the biting ends 24b, 24b. 
while on the other hand the projections 28, 29, 30 become higher the 
remoter they are located from the biting ends 24b, 24b. The above 
structure is substantially similar in case of the other die 23, and the 
die 23 is formed with alternate projections 31, 32, 33 and depressions 34, 
35, 36. 
FIG. 16c shows the shapes into which the workpiece W.sub.2 is formed at 
each stages a--a, b--b, c--c, d--d. FIG. 16D shows in side elevation the 
workpiece W.sub.2 at the stages a--a, b--b, c--c, d--d. As seen from FIGS. 
16B and 16C, rolling of the workpiece W.sub.2 begins as the process 
advances from the stage a--a to the stage b--b. In response to this, the 
opposite ends of the workpiece W.sub.2 start reducing in diameter by the 
effect of the first working sections 23c, 24c and formed into the smaller 
diameter shaft sections S.sub.1, S.sub.1 of the diameter d.sub.1. Up to 
this stage, the workpiece W.sub.2 is held symmetrical about its axis and 
the diameter d.sub.0 of the larger diameter section S.sub.2 is maintained 
unchanged. 
Further, at the stage transitting from b--b to d--d via c--c, the diameter 
d.sub.1 of the smaller diameter sections S.sub.1, S.sub.1 is held 
unchanged since the first working sections 23c, 23c have no inclination. 
While the diameter d.sub.0 of the larger diameter section S.sub.2 is held 
unchanged for the similar reason, the eccentricity of the larger diameter 
section S.sub.2 increases progressively. 
As shown in FIG. 15, the pitch of the projections 28, 29, 30 of the die 24 
and the pitch of the projections 31, 32, 33 of the die 23 are set at a 
value substantially equal to the distance over which the larger diameter 
section S.sub.2 of the workpiece W.sub.2 rolls by one revolution, i.e., 
the circumference of the larger diameter section or eccentric shaft 
section S.sub.2. Further, the projections 28, 29, 30 of the die 24 differ 
from the projections 31, 32, 33 of the die 23 in position relative to the 
workpiece W.sub.2 by the distance over which the workpiece W.sub.2 rolls 
by about half revolution, i.e., differ in phase from the projections 31, 
32, 33 by the amount corresponding to about half revolution of the 
workpiece W.sub.2 so that any one of the projections 28, 29, 30 and any 
one of the projections 31, 32, 33 do not come in contact with the workiece 
W.sub.2 at the same time. 
Reference being made by way of example to the projection 29 of the die 24 
which is matched with the depression 35 of the die 23 as shown in FIG. 15, 
the eccentricity of the larger diameter section S.sub.2 relative to the 
smaller diameter sections S.sub.1, S.sub.1 increases progressively during 
the time when the larger diameter section S.sub.1 rolls along the upward 
slope 29a of the top face 29b of the projection 29 and maximized when the 
larger diameter section S.sub.2 comes in contact with the upper most point 
29c of the top face 29b. The above occurs similarly in case of the other 
projections 28, 30 and the projections 31, 32, 33. The larger diameter 
section S.sub.2 is made eccentric in the above manner and constitutes the 
eccentric shaft section of the asymmetrical article P.sub.2 shown in FIGS. 
17 and 18. 
FIGS. 19A-19D show a further embodiment whereby the rolling process of this 
invention is used for manufacturing an asymmetrical article P.sub.3 shown 
in FIGS. 20 and 21. The article P.sub.3 has an eccentric shaft section E 
and concentric shaft sections S.sub.1, all of which sections are of the 
same diameter. In this embodiment, since it is not necessary to change the 
diameter d.sub.0 of the workpiece W.sub.3 but the diameter of the finished 
product P.sub.3 is equal to the diameter d.sub.0 of the workpiece W.sub.3, 
the die faces 43a, 44a of the cylindrical dies 43, 44 are not provided 
with such first working sections as are provided in the previous 
embodiment of FIGS. 14-15 and 16A-16D. 
FIGS. 22A and 22B show a further embodiment in which a pair of flat or 
straight dies 51, 52 are used for carrying out the same rolling process as 
the previous embodiment of FIGS. 19A-19D. 
FIGS. 23A and 23B show a further embodiment wherein a pair of flat or 
straight dies 61, 62 are used for rolling an asymmetrical article P.sub.4 
shown in FIGS. 25 and 26. 
FIG. 24A is a plan view of the die face 61a of the die 61, and FIG. 24B is 
a sectional view taken along the line 24B--24B of FIG. 24A. The die face 
61a is formed with a plurality of projections 63, 64 for forming the 
eccentric shaft sections S.sub.1, S.sub.1 of the asymmetrical article 
P.sub.4. More specifically, the die face 61a consists of a generally 
planar surface section 61b and plural pairs of projections 63, 63 or 64, 
64, each pair of which projections 63, 63 or 64, 64 are aranged so as to 
oppose in the width direction of the die 61 and symmetrically about the 
longitudinal center axis of the die 61. The other die 62 is substantially 
similar to the die 61 except that it is formed with a pair of projections 
65, 65 only. The projections 63, 64, 65 have angled top faces 63b, 64b, 
65b and are of the heights that vary in such a manner that the projections 
65 is higher than the projection 63 and the projection 64 is higher than 
the projection 65. The projections 63, 64, 65 resemble each other in 
shape, and the angled top faces 63b, 64b, 65b are respectively provided 
with upward slopes 63c, 64c, 65c and downward slopes 63d, 64d, 65d in such 
a manner that the upward slopes are more gentle than the downward slopes. 
FIG. 24C shows the shapes into which the workpiece W.sub.4 is formed at the 
stages a--a, b--b, c--c of the rolling process shown in FIG. 24B and FIG. 
24D shows in side elevation the workpiece W.sub.4 at those stages. As seen 
from FIGS. 24B and 24C, rolling of the workpiece W.sub.4 begins as the 
process advances from the stage a--a to the stage b--b whereby the 
opposite end portions of the workpiece W.sub.4 which are to be formed into 
the eccentric sections S.sub.1, S.sub.1 are reduced in diameter to d.sub.1 
(d.sub.0 &gt;d.sub.1) while at the same time the axes of the opposite end 
portions are caused to become eccentric progressively. In this case, the 
diameter d.sub.0 of the larger diameter section S.sub.2 is maintained 
unchanged. 
Further, as the process advances from the stage b--b to the stage c--c, the 
eccentric portions S.sub.1, S.sub.1 are further reduced in diameter to 
d.sub.2 (d.sub.1 &gt;d.sub.2) by the effect of the projection 64, while at 
the same time the eccentricity of the eccentric portions S.sub.1, S.sub.1 
are further increased so that the circumferential surface of the eccentric 
portions S.sub.1, S.sub.1 becomes in part flush with that of the larger 
diameter section S.sub.2. In this stage, the diameter d.sub.0 of the 
larger diameter section S.sub.2 is still maintained unchanged. 
As shown in FIGS. 23A and 23B, the pitch of the projections 63, 64 of the 
flat dies 61 are set at a value substantially equal to the distance over 
which the larger diameter section S.sub.2 rolls by one revolution, i.e., 
equal to the circumference of the larger diameter section S.sub.2, and the 
projection 65 is arranged so as to differ from the projections 63, 64 in 
phase by the amount corresponding to about half revolution of the 
workpiece W.sub.4, i.e., so as to differ from the projections 63, 64 in 
position relative to the workpiece W.sub.4 by the distance over which the 
workpiece W.sub.4 rolls by about half revolution such that the projection 
65 does not come in contact with the workpiece W.sub.4 together with 
either of the projections 63, 64. 
Accordingly, as shown in FIGS. 23A and 23B, the eccentricity of the 
eccentric shaft sections S.sub.1 S.sub.1 is increased as the workpiece 
W.sub.4 rolls along the upward slopes of each projections. At the same 
time when the workpiece W.sub.4 finishes rolling along the downward slope 
of the projection 63, it begins to roll along the upward slope of the 
projection 65. In this manner, the workpiece W.sub.4 rolls from the 
projection 65 to the projection 64. The eccentricity of the eccentric 
shaft section S.sub.1, S.sub.1 is maximized when the eccentric shaft 
sections S.sub.2, S.sub.2 are brought into engagement with the upper most 
point of the top face of the projection 64, whereby the workpiece W.sub.4 
is formed into the asymmetrical article P.sub.4 shown in FIGS. 25 and 26. 
In the meantime, the reduction in diameter of the eccentric shaft sections 
S.sub.1, S.sub.1 and the eccenticity of same can be varied by varying the 
heights of the projections 63, 64, 65. 
In this embodiment, by providing an inclination to the working sections 
61b, 62b of the die faces 61a, 62a, the diameter d.sub.0 of the larger 
diameter section S.sub.2 can be changed. By making the pair of projections 
different from each other in height, the eccentric shaft sections S.sub.1 
can be made different in diameter from each other. Further, it will be 
understood that in place of the flat dies 61, 62 a pair of cylindrical 
dies may be used.