U.S. patent application number 17/588407 was filed with the patent office on 2022-08-18 for opening/closing chuck and method of manufacturing fingers.
This patent application is currently assigned to SMC CORPORATION. The applicant listed for this patent is SMC CORPORATION. Invention is credited to Motohiro Sato.
Application Number | 20220258255 17/588407 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-18 |
United States Patent
Application |
20220258255 |
Kind Code |
A1 |
Sato; Motohiro |
August 18, 2022 |
OPENING/CLOSING CHUCK AND METHOD OF MANUFACTURING FINGERS
Abstract
A finger includes a pair of overhanging portions that project
out laterally from a main body portion. Outer peripheral surfaces
of the overhanging portions are made up from five surfaces
including upper surfaces, side surfaces, lower surfaces, first end
surfaces, and second end surfaces. Crowning is applied to the
intersections between these surfaces.
Inventors: |
Sato; Motohiro; (Toride-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SMC CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SMC CORPORATION
Tokyo
JP
|
Appl. No.: |
17/588407 |
Filed: |
January 31, 2022 |
International
Class: |
B23B 31/19 20060101
B23B031/19 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2021 |
JP |
2021-023916 |
Claims
1. An opening/closing chuck comprising a pair of fingers configured
to slide inside of a guide groove of a body, and which are slidably
supported in directions to approach toward and separate away from
each other; wherein the fingers each include a pair of overhanging
portions configured to project out laterally from a main body
portion, outer peripheral surfaces of the overhanging portions are
made up from five surfaces including upper surfaces, side surfaces,
lower surfaces, first end surfaces, and second end surfaces, and
crowning is applied to intersections between these surfaces.
2. The opening/closing chuck according to claim 1, wherein the
upper surfaces and the lower surfaces are perpendicular to the side
surfaces.
3. The opening/closing chuck according to claim 1, wherein the
upper surfaces and the lower surfaces are tapered surfaces
configured to come into closer proximity to each other toward the
side surfaces.
4. The opening/closing chuck according to claim 1, wherein, in the
guide groove of the body, crowning is applied to an intersection
between a wall surface facing toward the upper surfaces and a wall
surface facing toward side surfaces of the main body portion.
5. The opening/closing chuck according to claim 1, wherein crowning
is applied to a location where stepped portions in the guide groove
face toward the lower surfaces.
6. The opening/closing chuck according to claim 3, wherein the
overhanging portions include recesses centrally in the longitudinal
direction of the upper surfaces, the side surfaces, and the lower
surfaces, together with crowning regions at both ends of the
recesses, and grease reservoirs open on bottom surfaces of the
recesses.
7. A method of manufacturing a pair of fingers configured to slide
inside of a guide groove of a body of an opening/closing chuck, and
which are slidably supported in directions to approach toward and
separate away from each other; wherein the fingers each include a
pair of overhanging portions configured to project out laterally
from a main body portion, and outer peripheral surfaces of the
overhanging portions are made up from five surfaces including upper
surfaces, side surfaces, lower surfaces, first end surfaces, and
second end surfaces, wherein the upper and lower surfaces are
perpendicular to the side surfaces; the method of manufacturing the
fingers comprising a step of applying crowning at intersections of
the five surfaces, by a combination of performing grinding with
respect to the side surfaces by a first machining tool, and
performing grinding with respect to the upper surfaces and the
lower surfaces by a second machining tool.
8. A method of manufacturing fingers configured to slide inside of
a guide groove of a body of an opening/closing chuck, and which are
slidably supported in directions to approach toward and separate
away from each other; wherein the fingers each include a pair of
overhanging portions configured to project out laterally from a
main body portion, outer peripheral surfaces of the overhanging
portions are made up from five surfaces including upper surfaces,
side surfaces, lower surfaces, first end surfaces, and second end
surfaces, and the upper surfaces and the lower surfaces are tapered
surfaces configured to come into closer proximity to each other
toward the side surfaces; the method of manufacturing the fingers
comprising a step of applying crowning at intersections of the five
surfaces, by performing grinding with respect to the side surfaces
and simultaneously performing grinding with respect to the upper
surfaces and the lower surfaces, using a single machining tool.
9. The method of manufacturing the fingers according to claim 8,
wherein: the overhanging portions include recesses centrally in the
longitudinal direction of the upper surfaces, the side surfaces,
and the lower surfaces, together with crowning regions at both ends
of the recesses, and grease reservoirs open on bottom surfaces of
the recesses; and by the step, crowning of the crowning regions is
applied.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2021-023916 filed on
Feb. 18, 2021, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to an opening/closing chuck
equipped with a pair of fingers for gripping a workpiece, as well
as a method for manufacturing the fingers.
Description of the Related Art
[0003] Conventionally, an opening/closing chuck has been known in
which a pair of fingers for gripping a workpiece are slidably
supported in directions to approach and separate away from each
other. For example, in JP 2003-526528 A, a parallel gripper is
disclosed which adjusts a wedge-shaped hook transmission portion by
a piston. The wedge-shaped hook transmission portion brings two
base jaws, which are movably guided in a housing, into closer
proximity or farther away from each other.
[0004] Further, in EP 3563989 A1, in a grip device equipped with a
pair of slides, it is disclosed that ramps are provided on guide
flanks of the respective slides. In accordance therewith, a wedge
gap is formed that widens toward end surfaces of the slides.
SUMMARY OF THE INVENTION
[0005] When a workpiece is gripped using a pair of slidably
supported fingers, due to a reaction force from the workpiece, a
load in a predetermined direction (a vertical direction or a
lateral direction) acts on the fingers. Further, moments act which
attempt to rotate the fingers about various three-dimensional axes.
The loads and the moments that act on the fingers increase as the
gripping force on the workpiece increases. Further, the moments
that act on the fingers increase as the distance between workpiece
gripping positions on gripping members (attachments), which are
provided to extend from the fingers, and the supported positions of
the fingers become longer. When such loads or moments acting on the
fingers are large, concentration of stress occurs on contact
surfaces between the fingers and the body, excessive surface
pressure is generated, and the fingers and the sliding surfaces of
the body are damaged.
[0006] However, a technique that takes into consideration
concentration of stress generated in the fingers and the body has
not yet been sufficiently developed. The technique disclosed in EP
3563989 A1 is somewhat effective in relieving concentration of
stress and preventing excessive surface pressure when opposing ends
of a pair of slides attempt to rotate so as to open at an angle.
However, the disclosed technique does not take into consideration
that various three-dimensional axial moments act on the slides.
[0007] The present invention has the object of solving the
aforementioned problem.
[0008] An opening/closing chuck according to the present invention
comprises a pair of fingers configured to slide inside of a guide
groove of a body, and which are slidably supported in directions to
approach toward and separate away from each other. The fingers each
include a pair of overhanging portions configured to project out
laterally from a main body portion, and outer peripheral surfaces
of the overhanging portions are made up from five surfaces
including upper surfaces, side surfaces, lower surfaces, first end
surfaces, and second end surfaces. Crowning is applied to
intersections between these surfaces.
[0009] According to the above-described opening/closing chuck,
concentration of stress generated in the fingers due to loads
acting on the fingers in a vertical direction and moments about
three axes can be alleviated, and a maximum surface pressure can be
lowered.
[0010] Further, in a first method of manufacturing according to the
present invention, the fingers slide inside a guide groove of a
body of an opening/closing chuck, are slidably supported in
directions to approach toward and separate away from each other,
and include a pair of overhanging portions configured to project
out laterally from a main body portion. Outer peripheral surfaces
of the overhanging portions are made up from five surfaces
including upper surfaces, side surfaces, lower surfaces, first end
surfaces, and second end surfaces, wherein the upper and lower
surfaces are perpendicular to the side surfaces. The first method
of manufacturing comprises a step of applying crowning at
intersections of the five surfaces, by a combination of performing
grinding with respect to the side surfaces by a first machining
tool, and performing grinding with respect to the upper surfaces
and the lower surfaces by a second machining tool.
[0011] Further, in a second method of manufacturing according to
the present invention, the fingers slide inside a guide groove of a
body of an opening/closing chuck, are slidably supported in
directions to approach toward and separate away from each other,
and include a pair of overhanging portions configured to project
out laterally from a main body portion. Outer peripheral surfaces
of the overhanging portions are made up from five surfaces
including upper surfaces, side surfaces, lower surfaces, first end
surfaces, and second end surfaces, and the upper surfaces and the
lower surfaces are tapered surfaces configured to come into closer
proximity to each other toward the side surfaces. The second method
of manufacturing comprises a step of applying crowning at
intersections of the five surfaces, by performing grinding with
respect to the side surfaces, and simultaneously performing
grinding with respect to the upper surfaces and the lower surfaces
using a single machining tool.
[0012] According to the first method of manufacturing and the
second method of manufacturing described above, the crowning
process for alleviating the concentration of stress generated in
the fingers and the body can be easily performed in a fewer number
of steps. The above-described concentration of stress is caused by
loads acting on the fingers in the vertical direction and moments
about the three axes.
[0013] In the opening/closing chuck according to the present
invention, crowning is applied to the intersections of the five
surfaces including the upper surfaces, the side surfaces, the lower
surfaces, the first end surfaces, and the second end surfaces that
make up the outer peripheral surfaces of the overhanging portions
of the fingers. Therefore, it is possible to alleviate
concentration of stress when moments about the three axes or loads
in a vertical direction act on the fingers.
[0014] Further, in the first method of manufacturing the fingers
according to the present invention, grinding with respect to the
side surfaces of the overhanging portions by the first machining
tool, and grinding with respect to the upper surfaces and the lower
surfaces of the overhanging portions by the second machining tool
are combined. Consequently, since crowning is applied to the
intersections of the five surfaces of the overhanging portions, the
crowning process can be easily performed in a fewer number of
steps.
[0015] Further, in the second method of manufacturing the fingers
according to the present invention, using a single machining tool,
grinding is performed with respect to the side surfaces of the
overhanging portions and simultaneously grinding is performed with
respect to the upper surfaces and the lower surfaces of the
overhanging portions. Consequently, since crowning is applied to
the intersections of the five surfaces of the overhanging portions,
the crowning process can be easily performed in an even fewer
number of steps.
[0016] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings, in which preferred embodiments of the present invention
are shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows an external perspective view of an
opening/closing chuck according to a first embodiment of the
present invention;
[0018] FIG. 2 is a cross-sectional view taken along line II-II of
the opening/closing chuck shown in FIG. 1;
[0019] FIG. 3 is a front view of the opening/closing chuck shown in
FIG. 1;
[0020] FIG. 4 is an external perspective view of a finger of the
opening/closing chuck shown in FIG. 1;
[0021] FIG. 5 is a diagram showing a portion of a cross section of
a finger and a body taken along line V-V of FIG. 3;
[0022] FIG. 6A is an enlarged view of a portion A shown in FIG.
3;
[0023] FIG. 6B is an enlarged view of a portion B shown in FIG.
3;
[0024] FIG. 7 is a diagram schematically showing a method of
applying crowning to the finger shown in FIG. 4;
[0025] FIG. 8 is a diagram schematically showing a path over which
a first machining tool is made to move when crowning is applied to
the finger shown in FIG. 4;
[0026] FIG. 9 is a diagram schematically showing a path over which
a second machining tool is made to move when crowning is applied to
the finger shown in FIG. 4;
[0027] FIG. 10 is a front view of an opening/closing chuck
according to a second embodiment of the present invention;
[0028] FIG. 11A is an enlarged view of a portion C shown in FIG.
10;
[0029] FIG. 11B is an enlarged view of a portion D shown in FIG.
10;
[0030] FIG. 12 is a diagram schematically showing a method of
applying crowning to the finger shown in FIG. 10;
[0031] FIG. 13 is a diagram schematically showing a path over which
a third machining tool is made to move when crowning is applied to
the finger of the opening/closing chuck shown in FIG. 10;
[0032] FIG. 14 is a perspective view of a finger of an
opening/closing chuck according to a third embodiment of the
present invention; and
[0033] FIG. 15 is a diagram schematically showing a path over which
a third machining tool is made to move when crowning is applied to
the finger shown in FIG. 14.
DESCRIPTION OF THE INVENTION
[0034] In the description given below, when terms related to the
up, down, left, and right directions are used, the terms refer to
the directions shown in the drawings for the sake of convenience,
and such terms are not intended to limit the actual arrangement or
the like of the respective constituent members.
First Embodiment
[0035] A description will be given with reference to FIGS. 1 to 6
concerning an opening/closing chuck 10 according to the first
embodiment of the present invention. As shown in FIGS. 1 and 2, the
opening/closing chuck 10 includes a rectangular parallelepiped
shaped body 12, and a pair of fingers 14 that are slidably
supported in a longitudinal direction (the X direction) of the body
12. The opening/closing chuck 10 is used by connecting
non-illustrated attachments for gripping a workpiece to the fingers
14. That which is shown by reference numeral 14a are screw holes
used for connecting the attachments.
[0036] The body 12 includes a cylinder chamber 24 at a lower
central part in the longitudinal direction. Further, the body 12
has a guide groove 22 that extends in the longitudinal direction of
the body 12, and both ends of which open on end surfaces of the
body 12 at portions above the cylinder chamber 24. A piston 26
which is capable of sliding in a vertical direction (Z direction)
is disposed in the cylinder chamber 24. The cylinder chamber 24 is
partitioned into a first pressure chamber 24a formed on a lower
side of the piston 26, and a second pressure chamber 24b formed on
an upper side of the piston 26. The first pressure chamber 24a is
closed by a cap 30.
[0037] A piston rod 28 which is connected by a bolt 32 to the
piston 26 extends further upward through the second pressure
chamber 24b. An upper part of the piston rod 28 faces toward the
guide groove 22 and constitutes a cam portion 28a of a known
structure for driving the fingers 14. When air is supplied to the
first pressure chamber 24a and the air in the second pressure
chamber 24b is discharged, the piston 26 and the piston rod 28 are
moved upward. Consequently, the pair of fingers 14 slide in
directions away from each other. When air is supplied to the second
pressure chamber 24b and the air in the first pressure chamber 24a
is discharged, the piston 26 and the piston rod 28 are moved
downward. Consequently, the pair of fingers 14 slide in directions
to approach one another.
[0038] As shown in FIG. 3 and FIG. 4, each of the fingers 14 has an
inverted T-shaped cross section. Each of the fingers 14 includes a
pair of overhanging portions 16 and 18 that project out laterally
from the main body portion 20 over the entire length in the
longitudinal direction (the X direction) of the fingers 14. The
guide groove 22 of the body 12 has an inverted T-shaped cross
section that conforms to the cross-sectional shape of the fingers
14. The fingers 14 slide while undergoing sliding movement inside
the guide groove 22 of the body 12.
[0039] In order to enable the sliding movement of the fingers 14,
upper surfaces 16a and 18a, side surfaces 16b and 18b, and lower
surfaces 16c and 18c of the overhanging portions 16 and 18 face
toward the wall surface of the guide groove 22 with a minute gap
therebetween. A gap which is larger than the aforementioned minute
gap exists between the side surfaces 20a and 20b of the main body
portion 20 and the wall surfaces of the guide groove 22.
[0040] The bottom surface 20c of the main body portion 20 lies
substantially flush with the lower surfaces 16c and 18c of the
overhanging portions 16 and 18. Stepped portions 22a exists between
the wall surface of the guide groove 22 facing toward the bottom
surface 20c of the main body portion 20, and the wall surfaces of
the guide groove 22 facing toward the lower surfaces 16c and 18c of
the overhanging portions 16 and 18 (see FIG. 6B).
[0041] Outer peripheral surfaces of the respective overhanging
portions 16 and 18 of the fingers 14 are made up from five surfaces
including the upper surfaces 16a and 18a, the side surfaces 16b and
18b, the lower surfaces 16c and 18c, first end surfaces (end
surfaces in the direction X1) 16d and 18d, and second end surfaces
(end surfaces in the direction X2) 16e and 18e. The upper surfaces
16a and 18a and the lower surfaces 16c and 18c of the respective
overhanging portions 16 and 18 are perpendicular to the side
surfaces 20a and 20b of the main body portion 20, and are
perpendicular to the side surfaces 16b and 18b of the overhanging
portions 16 and 18.
[0042] Crowning is applied to the intersections between the
above-described five surfaces. More specifically, crowning is
applied to the intersections between the upper surfaces 16a and 18a
and the first end surfaces 16d and 18d, to the intersections
between the side surfaces 16b and 18b and the first end surfaces
16d and 18d, and to the intersections between the lower surfaces
16c and 18c and the first end surfaces 16d and 18d. Similarly,
crowning is applied to the intersections between the upper surfaces
16a and 18a and the second end surfaces 16e and 18e, to the
intersections between the side surfaces 16b and 18b and the second
end surfaces 16e and 18e, and to the intersections between the
lower surfaces 16c and 18c and the second end surfaces 16e and 18e.
Further, crowning is also applied to the intersections between the
upper surfaces 16a and 18a and the side surfaces 16b and 18b, and
to the intersections between the lower surfaces 16c and 18c and the
side surfaces 16b and 18b.
[0043] In these crownings, gaps are formed between the overhanging
portions 16 and 18 of the fingers 14 and the wall surfaces of the
guide groove 22, in a manner so as to continuously and gently
expand from portions where both members are in contact. In this
instance, the meaning of "gaps are formed in a manner so as to
continuously and gently expand from portions where both members are
in contact" is supplemented as follows (the same applies to other
locations of the same description given in the present
specification). When the fingers are placed in contact with the
body under a strong pressure, one or both of the fingers and the
body are elastically deformed, and the boundary between the regions
where both members are in contact and the regions where they are
not in contact is moved. Crowning is applied to a region including
from a starting point of the boundary to a conceivable end point,
and is formed so as to draw a gentle curve across the entire
region. More specifically, it is necessary to prevent locations
from being generated where angles (corners) are formed in the
regions where the fingers are placed in contact with the body.
Crowning, which is applied to the intersection between the first
end surface 16d and the lower surface 16c of the overhanging
portion 16, is shown in FIG. 5. Crowning, which is applied to the
intersection between the side surface 16b and the upper surface 16a
of the overhanging portion 16, is shown in FIG. 6A. Crowning, which
is applied to the intersection between the side surface 16b and the
lower surface 16c of the overhanging portion 16, is shown in FIG.
6B.
[0044] Further, in the guide groove 22 of the body 12, crowning is
applied to the intersections between the wall surfaces facing
toward the upper surfaces 16a and 18a of the overhanging portions
16 and 18 and the wall surfaces facing toward the side surfaces 20a
and 20b of the main body portion 20. Furthermore, crowning is also
applied to locations where the stepped portions 22a face toward the
lower surfaces 16c and 18c of the overhanging portions 16 and
18.
[0045] In these crownings as well, gaps are formed between the
overhanging portions 16 and 18 of the fingers 14 and the wall
surfaces of the guide groove 22, in a manner so as to continuously
and gently expand from portions where both members are in contact.
Crowning, which is applied to the intersection between the wall
surface of the guide groove 22 facing toward the upper surface 16a
of the overhanging portion 16 and the wall surface of the guide
groove 22 facing toward the side surface 20a of the main body
portion 20, is shown in FIG. 6A. Crowning, which is applied to a
location where the stepped portion 22a faces toward the lower
surface 16c of the overhanging portion 16, is shown in FIG. 6B.
[0046] When the workpiece is gripped using the opening/closing
chuck 10, a pitch moment (a moment about the Y axis) acts on the
fingers 14. Further, there may be cases in which loads in the
vertical direction (in the Z direction), loads in the lateral
direction (in the Y direction), a roll moment (a moment about the X
axis), and a yaw moment (a moment about the Z axis) act on the
fingers 14.
[0047] The crowning applied to the intersections between the upper
surfaces 16a and 18a and the first end surfaces 16d and 18d, and to
the intersections between the lower surfaces 16c and 18c and the
first end surfaces 16d and 18d alleviates concentration of stress
primarily when a pitch moment acts on the fingers 14. The crowning
applied to the intersections between the upper surfaces 16a and 18a
and the second end surfaces 16e and 18e, and to the intersections
between the lower surfaces 16c and 18c and the second end surfaces
16e and 18e alleviates concentration of stress primarily when a
pitch moment acts on the fingers 14. Assuming that the radius of
curvature of these crownings is indicated by R1, and the length of
the overhanging portions 16 and 18 in the longitudinal direction
(the X direction) is indicated by L, the value of R1/L preferably
lies within a range of 0.1 to 27.
[0048] The crowning applied to the intersections between the upper
surfaces 16a and 18a and the side surfaces 16b and 18b, and to the
intersections between the lower surfaces 16c and 18c and the side
surfaces 16b and 18b alleviates concentration of stress primarily
when a roll moment acts on the fingers 14. Assuming that the radius
of curvature of these crownings is indicated by R2, and the length
of the overhanging portions 16 and 18 in the widthwise direction
(the Y direction) is indicated by W, the value of R2/W preferably
lies within a range of 0.1 to 27. The crowning applied to the guide
groove 22 of the body 12 also alleviates concentration of stress
when a roll moment acts on the fingers 14.
[0049] The crowning applied to the intersections between the side
surfaces 16b and 18b and the first end surfaces 16d and 18d, and to
the intersections between the side surfaces 16b and 18b and the
second end surfaces 16e and 18e alleviates concentration of stress
primarily when a yaw moment acts on the fingers 14. Assuming that
the radius of curvature of these crownings is indicated by R3, and
the length of the overhanging portions 16 and 18 in the
longitudinal direction is indicated by L, the value of R3/L
preferably lies within a range of 0.1 to 27.
[0050] The crowning applied to the intersections between the lower
surfaces 16c and 18c and the first end surfaces 16d and 18d
alleviates concentration of stress when loads in the vertical
direction act on the fingers 14. The crowning applied to the
intersections between the lower surfaces 16c and 18c and the second
end surfaces 16e and 18e, and to the intersections between the
lower surfaces 16c and 18c and the side surfaces 16b and 18b also
alleviates concentration of stress when loads in the vertical
direction act on the fingers 14. Among the crowning applied to the
guide groove 22 of the body 12, the crowning applied to portions
where the stepped portions 22a face toward the lower surfaces 16c
and 18c of the overhanging portions 16 and 18 also alleviates
concentration of stress when loads in the vertical direction act on
the fingers 14.
[0051] The crowning applied to the intersections between the side
surfaces 16b and 18b and the first end surfaces 16d and 18d
alleviates concentration of stress when loads in the lateral
direction act on the fingers 14. The crowning applied to the
intersections between the side surfaces 16b and 18b and the second
end surfaces 16e and 18e, to the intersections between the upper
surfaces 16a and 18a and the side surfaces 16b and 18b, and to the
intersections between the lower surfaces 16c and 18c and the side
surfaces 16b and 18b also alleviates concentration of stress when
loads in the lateral direction act on the fingers 14.
[0052] In accordance with the opening/closing chuck 10 according to
the present embodiment, crowning is applied to the intersections
between the five surfaces including the upper surfaces 16a and 18a,
the side surfaces 16b and 18b, the lower surfaces 16c and 18c, the
first end surfaces 16d and 18d, and the second end surfaces 16e and
18e that make up the outer peripheral surfaces of the overhanging
portions 16 and 18 of the fingers 14. Further, crowning is applied
to a predetermined location of the guide groove 22 of the body 12.
Therefore, it is possible to alleviate concentration of stress when
moments about the three axes or loads in a vertical direction act
on the fingers 14.
[0053] Next, a description will be given with reference to FIGS. 7
to 9 concerning a method of manufacturing the fingers 14 of the
opening/closing chuck 10, and more specifically, concerning a
method (a crowning process) of applying crowning to the fingers
14.
[0054] This crowning process involves application of all of the
aforementioned crownings, by a combination of performing grinding
with respect to the side surfaces 16b and 18b of the pair of
overhanging portions 16 and 18, and performing grinding with
respect to the upper surfaces 16a and 18a and the lower surfaces
16c and 18c of the pair of overhanging portions 16 and 18. Grinding
with respect to the side surfaces 16b and 18b of the pair of
overhanging portions 16 and 18 is performed using a first machining
tool 34 made up from a grindstone or an end mill. Grinding with
respect to the upper surfaces 16a and 18a and the lower surfaces
16c and 18c of the pair of overhanging portions 16 and 18 is
performed using a second machining tool 36 made up from a
grindstone or an end mill.
[0055] As shown in FIG. 7, the first machining tool 34, which is a
rotating body, is made so that the shape of a surface thereof,
which is in contact with the workpiece to be machined, matches the
shapes of the side surfaces 16b and 18b of the target overhanging
portions 16 and 18. The first machining tool 34 includes crowning
machining portions 34a on both ends thereof. The first machining
tool 34 is arranged so that an axis thereof is arranged so as to be
oriented along the Z direction, and can be rotationally driven
about such an axis. Further, the first machining tool 34 is capable
of being freely moved in the X direction and the Y direction. It
should be noted that, in FIG. 7, one of the fingers 14 having a
shape after the crowning process has been performed thereon is
shown for the sake of convenience.
[0056] In the same manner, the second machining tool 36, which is a
rotating body, is made so that the shape of a surface thereof,
which is in contact with the workpiece to be machined, matches the
shapes of the upper surfaces 16a and 18a and the lower surfaces 16c
and 18c of the target overhanging portions 16 and 18. The second
machining tool 36 includes a crowning machining portion 36a on one
end thereof. The second machining tool 36 is arranged so that an
axis thereof is arranged so as to be oriented along the Y
direction, and can be rotationally driven about such an axis.
Further, the second machining tool 36 is capable of being freely
moved in the X direction and the Z direction.
[0057] When the crowning process is performed, first, the fingers
14 are fixed to a clamp base 38 in a posture with the pair of
overhanging portions 16 and 18 facing upward. At this time, the
first machining tool 34 is placed in a retracted position separated
away from the side surface 16b by a predetermined distance midway
along the longitudinal direction (the X direction) of the side
surface 16b of one of the overhanging portions 16. Further, the
second machining tool 36 is placed in a retracted position
separated away from the lower surface 18c by a predetermined
distance midway along the longitudinal direction (the X direction)
of the lower surface 18c of another of the overhanging portions
18.
[0058] Next, while being rotated about the axis thereof, the first
machining tool 34 is made to move in the Y2 direction and approach
toward the side surface 16b of the one of the overhanging portions
16, and is brought into contact at a predetermined pressure with
the side surface 16b. In accordance therewith, the side surface 16b
of the one of the overhanging portions 16 at a site where the first
machining tool 34 is placed in contact therewith is subjected to
grinding. In order to perform such grinding over the entire side
surface 16b of the one of the overhanging portions 16 and the
entire side surface 18b of the other of the overhanging portions
18, the first machining tool 34 is made to move in a circling
manner around the outer sides thereof.
[0059] More specifically, as schematically shown in FIG. 8, the
first machining tool 34 is made to move in the X1 direction along
the side surface 16b of the one of the overhanging portions 16
until arriving in the vicinity of the first end surface 16d.
Thereafter, the first machining tool 34 is made to move in the Y2
direction until arriving in the vicinity of the side surface 18b of
the other of the overhanging portions 18 while remaining at a
distance from the finger 14, and furthermore, is made to move in
the X2 direction until arriving in the vicinity of the second end
surface 18e along the side surface 18b of the other of the
overhanging portions 18. Next, the first machining tool 34 is made
to move in the Y1 direction until arriving in the vicinity of the
side surface 16b of the one of the overhanging portions 16 while
remaining at a distance from the finger 14, and thereafter, is made
to move in the X1 direction along the side surface 16b of the one
of the overhanging portions 16 until being returned to its original
position.
[0060] When the first machining tool 34 is moved, in order for
crowning to be applied to the intersection between the side surface
16b and the first end surface 16d of the one of the overhanging
portions 16, at the intersection, grinding is performed while
controlling the amount of traveling in the X1 direction and the
amount of traveling in the Y2 direction of the first machining tool
34 toward a target shape. Further, in order for crowning to be
applied to the intersection between the side surface 18b and the
first end surface 18d of the other of the overhanging portions 18,
at the intersection, grinding is performed while controlling the
amount of traveling in the X2 direction and the amount of traveling
in the Y2 direction of the first machining tool 34 toward a target
shape. Similarly, in order for crowning to be applied to the
intersection between the side surface 18b and the second end
surface 18e of the other of the overhanging portions 18, at the
intersection, grinding is performed while controlling the amount of
traveling in the X2 direction and the amount of traveling in the Y1
direction of the first machining tool 34 toward a target shape.
Further, in order for crowning to be applied to the intersection
between the side surface 16b and the second end surface 16e of the
one of the overhanging portions 16, at the intersection, grinding
is performed while controlling the amount of traveling in the X1
direction and the amount of traveling in the Y1 direction of the
first machining tool 34 toward a target shape.
[0061] By causing the first machining tool 34 to circle one time
therearound, grinding with respect to the side surfaces 16b and 18b
of the pair of overhanging portions 16 and 18 is completed.
Rotation of the first machining tool 34 is made to stop, and the
first machining tool 34 is separated and retracted away from the
side surface 16b of the one of the overhanging portions 16.
[0062] Next, while being rotated about the axis thereof, the second
machining tool 36 is made to move in the Z1 direction and approach
toward the lower surface 18c of the other of the overhanging
portions 18, and is brought into contact at a predetermined
pressure with the lower surface 18c. In accordance therewith, the
lower surface 18c of the other of the overhanging portions 18 at a
site where the second machining tool 36 is placed in contact
therewith is subjected to grinding. In order to perform such
grinding over the entire lower surface 18c and the entire upper
surface 18a of the other of the overhanging portions 18, the second
machining tool 36 is made to move in a circling manner around the
outer sides thereof.
[0063] More specifically, as schematically shown in FIG. 9, the
second machining tool 36 is made to move in the X1 direction along
the lower surface 18c of the other of the overhanging portions 18
until arriving in the vicinity of the first end surface 18d.
Thereafter, the second machining tool 36 is made to move in the Z1
direction until arriving in the vicinity of the upper surface 18a
while remaining at a distance from the finger 14. Furthermore, the
second machining tool 36 is made to move in the X2 direction along
the upper surface 18a until arriving in the vicinity of the second
end surface 18e. Next, the second machining tool 36 is made to move
in the Z2 direction until arriving in the vicinity of the lower
surface 18c while remaining at a distance from the finger 14.
Thereafter, the second machining tool 36 is made to move in the X1
direction along the lower surface 18c until being returned to its
original position.
[0064] When the above-described second machining tool 36 is moved,
in order for crowning to be applied to the intersection between the
lower surface 18c and the first end surface 18d, at the
intersection, grinding is performed while controlling the amount of
traveling in the X1 direction and the amount of traveling in the Z1
direction of the second machining tool 36 toward a target shape.
Further, in order for crowning to be applied to the intersection
between the upper surface 18a and the first end surface 18d, at the
intersection, grinding is performed while controlling the amount of
traveling in the X2 direction and the amount of traveling in the Z1
direction of the second machining tool 36 toward a target shape.
Further, in order for crowning to be applied to the intersection
between the upper surface 18a and the second end surface 18e, at
the intersection, grinding is performed while controlling the
amount of traveling in the X2 direction and the amount of traveling
in the Z2 direction of the second machining tool 36 toward a target
shape. Further, in order for crowning to be applied to the
intersection between the lower surface 18c and the second end
surface 18e, at the intersection, grinding is performed while
controlling the amount of traveling in the X1 direction and the
amount of traveling in the Z2 direction of the second machining
tool 36 toward a target shape.
[0065] By causing the second machining tool 36 to circle one time
around the other of the overhanging portions 18, grinding with
respect to the upper surface 18a and the lower surface 18c of the
other of the overhanging portions 18 is completed. Rotation of the
second machining tool 36 is made to stop, and the second machining
tool 36 is separated and retracted away from the lower surface 18c
of the other of the overhanging portions 18.
[0066] Next, the clamp base 38 is rotated 180 degrees in the
horizontal plane so that the second machining tool 36 is positioned
in facing relation to the lower surface 16c of the one of the
overhanging portions 16. Thereafter, while being rotated again
about the axis thereof, the second machining tool 36 is made to
move in the Z1 direction and approach toward the lower surface 16c
of the one of the overhanging portions 16, and is brought into
contact at a predetermined pressure with the lower surface 16c. In
accordance therewith, the lower surface 16c of the one of the
overhanging portions 16 at a site where the second machining tool
36 is placed in contact therewith is subjected to grinding. In
order to perform such grinding over the entire upper surface 16a
and the entire lower surface 16c of the one of the overhanging
portions 16, the second machining tool 36 is made to move in a
circling manner around the outer sides thereof.
[0067] More specifically, the second machining tool 36 is made to
move in the X2 direction along the lower surface 16c of the one of
the overhanging portions 16 until arriving in the vicinity of the
second end surface 16e. Thereafter, the second machining tool 36 is
made to move in the Z1 direction until arriving in the vicinity of
the upper surface 16a while remaining at a distance from the finger
14. Furthermore, the second machining tool 36 is made to move in
the X1 direction along the upper surface 16a until arriving in the
vicinity of the first end surface 16d. Next, the second machining
tool 36 is made to move in the Z2 direction until arriving in the
vicinity of the lower surface 16c while remaining at a distance
from the finger 14. Thereafter, the second machining tool 36 is
made to move in the X2 direction along the lower surface 16c until
being returned to its original position.
[0068] When the second machining tool 36 is moved, the amount of
traveling in the X direction and the amount of traveling in the Z
direction of the second machining tool 36 is controlled, in the
same manner as in the case of the other of the overhanging portions
18, at the intersection between the lower surface 16c and the
second end surface 16e, at the intersection between the upper
surface 16a and the second end surface 16e, at the intersection
between the upper surface 16a and the first end surface 16d, and at
the intersection between the lower surface 16c and the first end
surface 16d.
[0069] By causing the second machining tool 36 to circle one time
around the one of the overhanging portions 16, grinding with
respect to the upper surface 16a and the lower surface 16c of the
one of the overhanging portions 16 is completed. Rotation of the
second machining tool 36 is made to stop, and the second machining
tool 36 is separated and retracted away from the lower surface 16c
of the one of the overhanging portions 16. Due to the steps
described above, crowning can be applied to the intersections of
the five surfaces that make up the outer peripheral surfaces of the
pair of overhanging portions 16 and 18 of the fingers 14.
Second Embodiment
[0070] Next, a description will be given with reference to FIGS. 10
to 13 concerning a method of manufacturing an opening/closing chuck
40 and fingers 42 thereof according to a second embodiment of the
present invention. In the opening/closing chuck 40 according to the
second embodiment, the shape of the pair of overhanging portions of
the fingers and the shape of the guide groove of the body differ
from those of the opening/closing chuck 10 according to the first
embodiment.
[0071] As shown in FIGS. 10 and 12, each of the fingers 42 includes
a pair of trapezoidal overhanging portions 44 and 46 which project
out laterally from a main body portion 48 over the entire length
thereof in the longitudinal direction. Upper surfaces 44a and 46a
and lower surfaces 44c and 46c of each of the overhanging portions
44 and 46 are formed as tapered surfaces, which are inclined so as
to come into closer proximity to each other toward side surfaces
44b and 46b. A guide groove 50 of the body 12 includes a
cross-sectional shape that conforms to the cross-sectional shape of
the fingers 42. In order to enable the sliding movement of the
fingers 42, the upper surfaces 44a and 46a, the side surfaces 44b
and 46b, and the lower surfaces 44c and 46c of the respective
overhanging portions 44 and 46 face toward the wall surface of the
guide groove 50 with a minute gap therebetween. Further, the bottom
surface 48c of the main body portion 48 also faces toward the wall
surface of the guide groove 50 with a minute gap therebetween.
[0072] Crowning is applied to the intersections between the five
surfaces including the upper surfaces 44a and 46a, the side
surfaces 44b and 46b, the lower surfaces 44c and 46c, the first end
surfaces 44d and 46d, and the second end surfaces 44e and 46e that
make up the outer peripheral surfaces of the respective overhanging
portions 44 and 46. More specifically, crowning is applied to the
intersections between the upper surfaces 44a and 46a and the first
end surfaces 44d and 46d, to the intersections between the side
surfaces 44b and 46b and the first end surfaces 44d and 46d, and to
the intersections between the lower surfaces 44c and 46c and the
first end surfaces 44d and 46d. Similarly, crowning is applied to
the intersections between the upper surfaces 44a and 46a and the
second end surfaces 44e and 46e, to the intersections between the
side surfaces 44b and 46b and the second end surfaces 44e and 46e,
and to the intersections between the lower surfaces 44c and 46c and
the second end surfaces 44e and 46e. Further, crowning is also
applied to the intersections between the upper surfaces 44a and 46a
and the side surfaces 44b and 46b, and to the intersections between
the lower surfaces 44c and 46c and the side surfaces 44b and
46b.
[0073] In these crownings, gaps are formed between the overhanging
portions 44 and 46 of the fingers 42 and the wall surfaces of the
guide groove 50, in a manner so as to continuously and gently
expand from portions where both members are in contact. Crowning
that is applied to the intersection between the side surface 44b
and the upper surface 44a of the overhanging portion 44 is shown in
FIG. 11A. Crowning that is applied to the intersection between the
side surface 44b and the lower surface 44c of the overhanging
portion 44 is shown in FIG. 11B.
[0074] Further, in the guide groove 50 of the body 12, crowning is
applied to the intersections between the wall surfaces facing
toward the upper surfaces 44a and 46a of the overhanging portions
44 and 46 and the wall surfaces facing toward the side surfaces 48a
and 48b of the main body portion 48. Furthermore, crowning is also
applied to locations where stepped portions 50a face toward the
lower surfaces 44c and 46c of the overhanging portions 44 and
46.
[0075] In these crownings, gaps are formed between the overhanging
portions 44 and 46 of the fingers 42 and the wall surfaces of the
guide groove 50, in a manner so as to continuously and gently
expand from portions where both members are in contact. Crowning
that is applied to the intersection between the wall surface of the
guide groove 50 facing toward the upper surface 44a of the
overhanging portion 44 and the wall surface of the guide groove 50
facing toward the side surface 48a of the main body portion 48 is
shown in FIG. 11A. Crowning that is applied to a location where the
stepped portion 50a faces toward the lower surface 44c of the
overhanging portion 44 is shown in FIG. 11B.
[0076] In accordance with the opening/closing chuck 40 according to
the present embodiment, crowning is applied to the intersections
between the five surfaces including the upper surfaces 44a and 46a,
the side surfaces 44b and 46b, the lower surfaces 44c and 46c, the
first end surfaces 44d and 46d, and the second end surfaces 44e and
46e that make up the outer peripheral surfaces of the overhanging
portions 44 and 46 of the fingers 42. Further, crowning is applied
to a predetermined location of the guide groove 50 of the body 12.
Therefore, it is possible to alleviate concentration of stress when
moments about the three axes or loads in a vertical direction act
on the fingers.
[0077] Next, a description will be given with reference to FIGS. 12
and 13 concerning a method (a crowning process) of applying
crowning to the fingers 42. In this crowning process, using a third
machining tool 52 (a single machining tool) made up from a
grindstone or an end mill, grinding is performed with respect to
the side surfaces 44b and 46b of the pair of overhanging portions
44 and 46, grinding is simultaneously performed with respect to the
upper surfaces 44a and 46a and the lower surfaces 44c and 46c of
the pair of overhanging portions 44 and 46, and all of the
aforementioned crowning is applied.
[0078] As shown in FIG. 12, the third machining tool 52, which is a
rotating body, is made so that the shape of a surface thereof,
which is in contact with the workpiece to be machined, matches the
shapes of the upper surfaces 44a and 46a, the side surfaces 44b and
46b, and the lower surfaces 44c and 46c of the target overhanging
portions 44 and 46. The third machining tool 52 is arranged so that
an axis thereof is arranged so as to be oriented along the Z
direction, and can be rotationally driven about such an axis.
Further, the third machining tool 52 is capable of being freely
moved in the X direction and the Y direction.
[0079] The third machining tool 52 has a first crowning machining
portion 52a and a second crowning machining portion 52b. The first
crowning machining portion 52a is a machining portion in order to
apply crowning to intersections between the upper surfaces 44a and
46a and the side surfaces 44b and 46b of the overhanging portions
44 and 46. The second crowning machining portion 52b is a machining
portion in order to apply crowning to intersections between the
lower surfaces 44c and 46c and the side surfaces 44b and 46b of the
overhanging portions 44 and 46.
[0080] When the crowning process is performed, first, the fingers
42 are fixed to the clamp base 38 in a posture in which the pair of
overhanging portions 44 and 46 face upward. At this time, it is
assumed that the third machining tool 52 is at a position in
confronting relation to the overhanging portion 44 midway along the
longitudinal direction (the X direction) of one of the overhanging
portions 44.
[0081] Next, while being rotated about the axis thereof, the third
machining tool 52 is made to move in the Y2 direction and approach
toward the one of the overhanging portions 44, and is brought into
contact at a predetermined pressure with the upper surface 44a, the
side surface 44b, and the lower surface 44c. In accordance
therewith, the upper surface 44a, the side surface 44b, and the
lower surface 44c of the one of the overhanging portions 44 at a
site where the third machining tool 52 is placed in contact
therewith are simultaneously subjected to grinding. In order to
perform such grinding over the entirety of the one of the
overhanging portions 44 and the entirety of the other of the
overhanging portions 46, the third machining tool 52 is made to
move in a circling manner around the outer sides thereof.
[0082] More specifically, as schematically shown in FIG. 13, the
third machining tool 52 is made to move in the X1 direction along
the side surface 44b etc. of the one of the overhanging portions 44
until arriving in the vicinity of the first end surface 44d.
Thereafter, the third machining tool 52 is moved in the Y2
direction until arriving in the vicinity of the side surface 46b of
the other of the overhanging portions 46 while remaining at a
distance from the finger 42. Furthermore, the third machining tool
52 is made to move in the X2 direction along the side surface 46b
of the other of the overhanging portions 46 until arriving in the
vicinity of the second end surface 46e. Next, the third machining
tool 52 is moved in the Y1 direction until arriving in the vicinity
of the side surface 44b of the one of the overhanging portions 44
while remaining at a distance from the finger 42. Thereafter, the
third machining tool 52 is moved in the X1 direction along the side
surface 44b or the like of the one of the overhanging portions 44
until being returned to its original position.
[0083] When the above-described third machining tool 52 is moved,
regarding the one of the overhanging portions 44, crowning is
applied to the intersection between the upper surface 44a and the
first end surface 44d, to the intersection between the side surface
44b and the first end surface 44d, and to the intersection between
the lower surface 44c and the first end surface 44d. More
specifically, at these intersections, grinding is performed while
controlling the amount of traveling in the X1 direction and the
amount of traveling in the Y2 direction of the third machining tool
52 toward a target shape. Further, regarding the other of the
overhanging portions 46, crowning is applied to the intersection
between the upper surface 46a and the first end surface 46d, to the
intersection between the side surface 46b and the first end surface
46d, and to the intersection between the lower surface 46c and the
first end surface 46d. More specifically, at these intersections,
grinding is performed while controlling the amount of traveling in
the X2 direction and the amount of traveling in the Y2 direction of
the third machining tool 52 toward a target shape.
[0084] Regarding the other of the overhanging portions 46, crowning
is applied to the intersection between the upper surface 46a and
the second end surface 46e, to the intersection between the side
surface 46b and the second end surface 46e, and to the intersection
between the lower surface 46c and the second end surface 46e. More
specifically, at these intersections, grinding is performed while
controlling the amount of traveling in the X2 direction and the
amount of traveling in the Y1 direction of the third machining tool
52 toward a target shape. Regarding the one of the overhanging
portions 44, crowning is applied to the intersection between the
upper surface 44a and the second end surface 44e, to the
intersection between the side surface 44b and the second end
surface 44e, and to the intersection between the lower surface 44c
and the second end surface 44e. More specifically, at these
intersections, grinding is performed while controlling the amount
of traveling in the X1 direction and the amount of traveling in the
Y1 direction of the third machining tool 52 toward a target
shape.
[0085] In this manner, merely by causing the third machining tool
52 to circle one time therearound, crowning can be applied to the
intersections of the five surfaces that make up the outer
peripheral surfaces of the pair of overhanging portions 44 and 46
of the fingers 42.
Third Embodiment
[0086] Next, a description will be given with reference to FIGS. 14
and 15 concerning fingers 62 of an opening/closing chuck and a
method of manufacturing the same according to a third embodiment of
the present invention. The fingers 62 according to the third
embodiment differ from the fingers 42 of the opening/closing chuck
according to the second embodiment, in that each of the overhanging
portions includes a recess and a grease reservoir.
[0087] As shown in FIG. 14, one of the overhanging portions 64
includes a recess 72 centrally in the longitudinal direction of the
upper surface 64a, the side surface 64b, and the lower surface 64c,
and includes crowning regions CR1 and CR2 at both ends of the
recess 72. A grease reservoir 70 opens in a bottom surface of the
recess 72 that is formed in the upper surface 64a. The other one of
the overhanging portions 66 also includes a similar grease
reservoir 70 therein. Grease that is stored in the grease
reservoirs 70 is supplied to the sliding surfaces of the
overhanging portions 64 and 66, and the lubricating function
thereof is maintained.
[0088] Because the grease reservoir 70 opens on the bottom surface
of the recess 72, an edge portion of the grease reservoir 70 does
not come into contact with the wall surface of the guide groove and
cause concentration of stress to occur. Further, the recess 72 is
connected, via the crowning regions CR1 and CR2 to which crowning
was applied, to sliding surfaces (surfaces in contact with the wall
surfaces of the guide groove) on the upper surface 64a, the side
surface 64b, and the lower surface 64c. Therefore, due to the
presence of the recess 72, concentration of stress within the guide
groove does not occur.
[0089] Crowning is applied to the intersections between the five
surfaces including the upper surfaces 64a and 66a, the side
surfaces 64b and 66b, the lower surfaces 64c and 66c, the first end
surfaces 64d and 66d, and the second end surfaces 64e and 66e that
make up the outer peripheral surfaces of the respective overhanging
portions 64 and 66. Further, in the guide groove of the body 12,
crowning is applied to the intersections between the wall surfaces
facing toward the upper surfaces 64a and 66a of the overhanging
portions 64 and 66 and the wall surfaces facing toward the side
surfaces 68a and 68b of the main body portion 68. Further, crowning
is also applied to locations where the stepped portions of the
guide groove face toward the lower surfaces 64c and 66c of the
overhanging portions 64 and 66.
[0090] Next, a description will be given with reference to FIG. 15
concerning a method (a crowning process) of applying crowning to
the fingers 62. In this crowning process, using the third machining
tool 52 (a single machining tool) also used in the second
embodiment, grinding is performed with respect to the side surfaces
64b and 66b of the pair of overhanging portions 64 and 66, grinding
is simultaneously performed with respect to the upper surfaces 64a
and 66a and the lower surfaces 64c and 66c of the pair of
overhanging portions 64 and 66, applying all of the aforementioned
crowning.
[0091] While being rotated about the axis thereof, the third
machining tool 52 is brought into contact with the upper surface
64a, the side surface 64b, and the lower surface 64c at
predetermined positions in the longitudinal direction (the X
direction) of the one of the overhanging portions 64, and these
surfaces are simultaneously subjected to grinding. In order to
perform such grinding over the entirety of the one of the
overhanging portions 64 and the entirety of the other of the
overhanging portions 66, the third machining tool 52 is made to
move in a circling manner around the outer sides thereof.
[0092] When the third machining tool 52 is moved, at the
intersection between the side surface 64b and the first end surface
64d of the one of the overhanging portions 64 and at the
intersection between the side surface 66b and the first end surface
66d of the other of the overhanging portions 66, similar to the
case of the second embodiment, grinding is performed while
controlling the amount of traveling in the X direction and the
amount of traveling in the Y direction of the third machining tool
52 toward a target shape. At the intersection between the side
surface 66b and the second end surface 66e of the other of the
overhanging portions 66, and at the intersection between the side
surface 64b and the second end surface 64e of the one of the
overhanging portions 64 as well, similar to the case of the second
embodiment, grinding is performed while controlling the amount of
traveling in the X direction and the amount of traveling in the Y
direction of the third machining tool 52 toward a target shape.
[0093] Further, concerning the one of the overhanging portions 64,
in order to form the crowning regions CR1 and CR2 and the recess 72
therein, in a central vicinity in the longitudinal direction of the
one of the overhanging portions 64, grinding is performed while
controlling the amount of traveling in the Y1 direction and the
amount of traveling in the Y2 direction of the third machining tool
52 toward a target shape. Similarly, in a central vicinity in the
longitudinal direction of the other of the overhanging portions 66,
grinding is performed while controlling the amount of traveling in
the Y1 direction and the amount of traveling in the Y2 direction of
the third machining tool 52 toward a target shape.
[0094] In this manner, merely by causing the third machining tool
52 to circle one time therearound, crowning can be applied to the
intersections of the five surfaces that make up the outer
peripheral surfaces of the pair of overhanging portions 64 and 66,
together with enabling the crowning regions CR1 and CR2 and the
recesses 72 to be formed on the pair of overhanging portions 64 and
66.
[0095] The present invention is not limited to the embodiments
described above, but various configurations can be adopted therein
without deviating from the essence and gist of the present
invention.
* * * * *