Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
ULTRA-PRECISION GRINDING MACHINE
,
BAC~GROUND OF THE_INVENTION
The present invention relates to an apparatus for finishing
a workpiece ~ltra-precisely, and more particularly to an
apparatus for finishing ultra-precisely the portion to be worked
hereinafter, referred to as a work portion such as a groove~ a
concavity, a hole, or the like of the workpiece ~ainly.
Generally, metal molds and the like which have a work
portion such as a complicated hole, groove or the like are worked
and finished extremely high-accurately after they have been
worked by using an electrical discharge machine. Since the
above-mentioned precise finish-work has been conventionally
performed manually by using an ultrasonic abrasion machine and 80
on, there are drawbacks such that it is remarkably non-efficient
and that it results in lack of uniformity.
Furthenmore, in conventional grinding machines, in the event
where there is a slight difference in direction between the
portion to be worked of the workpiece and a grinding tool of an
abrasion machine and the like, the workpiese has to be ground as
it is so that the workpiece portion could not be worked
correctly. This is another problem of the prior art.
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SUMMARY ~F THE INVENTION
; It is an object of the invention to provide an ultra-
precision grinding machine which can efficiently perform the
ultra-precise finishing by automatically correcting the mismatch
even if there is a slight difference of the directions between
the work portion of the workpiece and the grinding tool.
It is another object of the invention to provide an
ultra-precision grinding machine which can adjust the amplitude
of the grinding tool corresponding to the magnitude of the
clearance between the work portion of the workpiece and the
grinding tool.
It is a fur~her object of the invention to provide an
ultra-precision grinding machine which is provided with a
grinding tool which can vertically and periodically move for
improvement in~ef~clency of grinding of the work portion of the
~orkpiece.
In one aspect the invention provides an ultra-
precision grinding machine comprising: a grinding
tool; means for supporting said grinding
tool in a selected position, ~eans for revolv;ng said grinding
tool; and a workpiece supporting structure for supporting a
workpiece to he machined with said grind;ng tool, said workpiece
supporting structure including a base plat~ on whïch is mounted
x-axis guide rails extendIng in the x-axîs dixection, an x-table
slidably supported on said x-axis guide rails, y-axis guide rails
mounted on said x-ta~le extending in the directi`on perpendIcular
to said x-axis guide rails; a y-ta~le slldably supported on said
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y-axis guide rails, a first rotatable slide table mounted on
said y-table, a second rotatable slide table mounted on said first
rotatable slide table, balls rollably interposed ~etween said
y-table and said first rotatable slide ta~le and also between
said first slide table and said second slide table for free
movement and rotation between them, discoidal retainers to
retain each ball in a desired location, radial bearing means
rotatably supported at a central portion of said first slide
table and of said second slide table so that when each retainer
comes into contact with said radial bearing means, movement of
said first and second slide tables becomes difficult as the
movement of each ball changes from rolling to sliding, with
the movement of each slide table being limited to a range in
which the radial bearing means does not make contact with
any said retainer.
In a further aspect there is provided a grinding machine
for finishing a workpiece, comprising a rotary slide table for
receiving a workpiece, a grinding tool arranged to engage with
a portion of the workpiece and to vibrate horizontally, a
machining head disposed above the workpiece for holding the
grinding tool, a first table supporting the slide table and a
second table supporting the first table, the first and second
tables being horizontally movable in mutually perpendicular
directions.
In a further aspect of the invention there is provided an
ultra-precision grinding machine comprising: a grinding tool;
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means for supporting said grinding tool in a selected position;
means for revolving said grinding tool; and means for supporting
a workpiece to be machined with said grinding tool; said supporting
means including an upper plate on which the workpiece may be
mounted, and a plate-like floating retainer means having ball
bearing means for enabling said upper plate to shift smoothly and
swiftly its horizontal position in a plane by a rolling of balls
of said ball bearins means responsive to an external force being
applied to the workpiece~
In a still further aspect there is provided an ultra-
precision grinding machine for accurately grinding a workpiece,
comprising a rotary slide table for receiving the workpiece having
a work portion thereon, a grinding tool adapted to be engaged with
with the work portion of said workpiece and to freely microvibrate
horizontally; a machining head apparatus disposed upward of said
workpiece, for holding said grinding tool; a Y table supporting
said slide table, said Y table bei~g provided so as to freely move
in the Y-~xis; and an X table supportiny said Y table, said X table
being provided so as to freely move in the X-axis direction.
BRIEF DESCRIPTION OF THE DR~WINGS
Tbe&e ~nd other ohjects, features and advantages of the
present invention will be more apparent from the following
description of a preferred embodiment, taken in conjunction with
the accompanying drawings, in which:
FIG.l is a front elevational partially sectioned view of a
machine according to the present invention ;
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FIG.2 i~ a top plan view ;
FIG.3 is an enlarged cross sectional view of a holder ;
FIG.4~a) and 4(b) are schematic views for explaining the
coordinating function between the workpiece and the machining
tool ;
FIG.5 is a schematic partially sectional view of a spindle
for describing another embodiment of the invention ; and
FIG.6 illustr~Ss a schematic partially sectional view of a
supporting rod of further another embodiment of the invention.
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DESCRIPTION OF THE PR~FERRED EMBODIMENTS
Referring to FIG.l, a grinding machine 1- in accordance with
the present invention is shown, in which a pair of guide rails 4
which extend in the X-axis direction tthe right to left direction
in FIG.l)are mounted to a base plate 3 of the grinding machine 1,
and an X table 5 is slidably supported on the guide rails 4. On
the upper surface of the X table 5, a pair of guide rails 6 which
extend in the Y-axis direction perp~ndicular to the direction of
the movement of the X table 5 is mounted, and a Y table 8 is
likewise slidably supported on the guide rails 6. A first
discoidal slide table 7 is mounted on this Y table 8 so as to
move horizontally and to freely rotate. A second discoidal slide
table 9 is similarly mounted on this first slide table 7 so as to
move horizontally and to freely rotate. A number of balls 11 are
rollably interposed between the Y table 8 and the first slide
table 7 and between the first ~lide table 7 and the second slide
table 9 for extremely smooth movement and rotation, and each ball
11 is held with a proper interval by discoidal retainers 13. A
radial bearing 15 extending in a central hole 13a of each
retainer 13 mentioned above i~ rotatably supported at the central
portions of the above-stated first and second slide tables 7 and
9.. ..
Therefore, whe~ each retainer 13 comes into contact with the
radial bearing 15, the movement of each of the slide tables 7 and
9 becomes relatively difficult since each ball 11 changes from the-
rolling state to the sliding state. Consequently, the smooth
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movement of each slide table is secured in the range where no
radial bearing 15 contacts with each retainer 13. However, since
the slide tables 7 and 9 are supported on the X and Y tables 5
and 8, it is possible to smoothly move the slide tables even in
the case of largely moving them to change the work position of
the workpiece material, and the positional relationship between
the first and second slide tables 7 and 9 and each retainer 13
can be maintained without affecting their accurate location so
largely.
An annular cover 17 surrounding and enclosing the first
slide table 7 and the like is fixed by the bolts or the like on
the bottom surface of the above-mentioned second slide table 9.
An annular plate 21 is attached on the lower surface of this
cover 17 through an annular spacer 19. Thus, the intrusion of
dust or dirt into the first and second slide tables 7 and 9, etc.
is prevented. A plurality of radial T-shaped grooves 23 are
formed in the upper surface of the second slide table 9.
Therefore, it is possible to fix the workpiece W on the upper
surface of the second slide table 9 through a fixing tool such as
T bolts or the like so that the workpiece thus fixed on the
second slide table 9 can reely and smoothly move in any
horizontal directions and freely rotate.
A cylindrical guide post 25 is vertically fixed near one
side portion of th~ afore-mentioned base plate 3 by a plurality
of bolts, and a supporting rod 27 is mounted in this guide post
25 so that the vertical location can be freely adjusted. Namely,
a threaded portion 27a is formed in the lower end portion of this
supporting rod 27, and cleeve nuts 31 are threadably engaged with
this threaded portioD 27a, these sleeve nuts being supported in a
gear box 29 mounted on the lower surface of the base plate 3 so
as to only rotate freely~ A worm wheel 33 is fixed to these
sleeve nuts 31 in a body and a wonm gear 35 which is suitably
conneeted to a motor and the like engages this worm wheel 33. A
key member 37 fixed on the upper end portion of the
above-mentioned guide post 25 engages a key groove 27b which is
formed vertically in the body of the supporting rod 27.
Therefore, the proper rotation of the worm gear 35 allows the
~upporting rod 27 to be moved up and down.
; A pipe member 41 is rotatably supported at the upper end
portion of the supportin~ rod 27 through a plurality of bearings
39. A cover pipe 43 which is slidably surrounding the guide post
25 is attached on the lower surface of this pipe member 41 in a
-
,- body. Ribs 47 for reinforcement are fixed along opposite edges
~ of the upper face of this plate-like arm 45, and a rotation
c~ driving apparatus 51 such as a motor is mounted to the rear end
A_
portion through a brac~et 4g. A machining head apparatus 53 is
mounted to the edge portion of the arm 45. Thus, the machining
head apparatus 53 and the like moYeS vertically in a body
depending upon the ascent or descent of the above-mentioned
supporting rod 27.
The machinin~ head apparatus 53 is so constructed ~s
~ollows. Namely, a rotary tube 57 is ~upported 80 A5 to only
rotate in a sleeve 55 which is fixed at the edge of the arm 45
through a plurality of bearings and a pully 59 is attached in a
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body to the upper portion of this rotary tube 57. A belt 63
installed around a driving pulley 61 which is equipped to the
aforementioned rotation driving apparatus 51 is installed around
this pulley S9. A spindle 65 piercing vertically through the
rotary tube 57 up and down is further supported to the rotary
tube 57 so that it can freely slide in only the axial direction.
Namely, an axial key groove 65a is formed in the body of the
spindle 65, and a key 67 formed on the rotary tube 57 engages
this key groove 65a. Therefore, the spindle 65 rotates together
with the rotary tube 57 in a body and it can freely move solely
in the axial direction.
A tubulax cap 69 is attached to the upper end portion of the
spindle 65 through a plurality of bearings so as to only rotate.
A coupling plate 75 which is pivotally mounted to a swinging
lever 71 through a pin 73 (refer to FIG.2) is connected to thi~
cap 69. The body of the above swinging lever 71 is pivotally
mounted to a bracket 77 which is vertically attached to the
above-mentioned arm 45. A spring member 83 such as a balance
spring which serves to balance with the weight of the
afore-stated machining head apparatus 53 is attached between the
rear end portion of this swinging lever 71 and a threaded rod
member 81 which is suported so as to freely adjus~ the vertical
location thereof relative to a bracket 79 ixed to the
above-stated guide_lQost 25. Thus, the spindle 65 is always
lifted upward by a function of the spring member 83, and it goes
down by operating the swinging lever 71 a~ainst the biasing force
of the spring member 83. In this case, it is possible to pull
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the spindle 65 downward against the biasing force of the spring
member 83 by suitably hanging down a plurality of weights or
weights having different weights (not shown) to the edge of the
swinging lever 71.
A cam-follower 87 is rotatably attached through a pin 85 to
a proper position of the swinging lever 71. A cam 91 contacts
rotatably wi~h the lower side of this cam-follower 87, this cam
91 is connected to the output shaft of a rotation driving
apparatus 89 such as a motor which is attached to the
afore-mentioned arm ~5. Thus, when the cam 91 rotates by the
rotation driving apparatus 89, the swinging lever 71 repeats the
vertical motion periodically, so the spindle 65 moves vertically
in association with this; therefore, suitable control of the
rotation of the rotation driving apparatus ~9 provides the
suitable control of the cycle or period of the vibration. It is
possible to change the amplitude of the vertical motion and the
location of the bottom dead point of the spindle 65 by disposing
detachably or removably either of the cam-follower 87 or the cam
91 or both of them in a conventional manner, thereby coping with
the variations of the thickness of the workpiece and the depth of
the groove or the like of the work portion.
The mechanism for vertical moving the spindle 65 is not
limited to the construction described previously; however, for
instance, it is possible to interpose the cylindrical cam or the
like between the pulley 59 and the sleeve 55 mentioned before, or
other various constructions may be employed. The rotation
driving apparatus 51 can be also used as a driving
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source for moving the spindle 65.
A holder 93 is attached to the lower end portion of the
spindle 65. This holder 93 serves to hold a grinding tool
comprising a grindstone or an appropriate tool steel or a chuck
such as a collet chuck which holds the grinding tool. The
construction of this holder 93 is shown in FIG.3. That is, a
flange 95a is formed horizontally in the lower portion of a
sleeve 95 fixed in a body to a lower end portion of the sindle 65
by using set screws and the like, and arcuate holes 95b are
formed in a plurality of portions of this flange 95a. ~n
eccentric hole 95c is formed in the center of the lower face of
the sleeve 95 with a slight eccentricity relative to the axial
center of the spindle 65. An eccentric disc 99 is attached to
the lower face of the sleeve 95 through a plurality of bolts 97
piercing through the aforementioned arcuate holes 95b so that the
rotating position of the disc 99 can be freely adjusted. An
eccentric height 99a engaged with the eccentric hole 95c is
formed on the upper portion of this eccentric disc 99. Thus, the
eccentric disc 99 is attached with an eccentricity relative to
the axial center of the spindle 65, it is possible to adjust the
location of the axial center of the eccentric disc 99 relative to
the axial center of the spindle 65 by suitably rotating the
eccentric disc 99 after the above-mentioned bolts 97 have been
loosened. ~
A bearing sleeve 101 is fixed in a body on the lower face of
the eccentric disc 99 through a plurality of bolts, and a holder
block 105 is rotatably supported in this bearing sleeve 101
through an eccentric bearing 103. The above eccentric bearing
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103 is so constructed that the axial center of the inner hold of
the inner race is slightly eccentric relative to the axial center
of the eccentric disc 99. Therefore, the axial center of the
holder block 105 is eccentric relative to the axial center of the
eccentric disc 99. A holder machine 107 for holding the grinding
tool and the like is attached in a body through a plurality of
bolts to the lower face of this holder block 105. A pin 109
projecting horizontally in the radial outward direction is fixed
to the lower end portion of the holder block 105. This pin 109
engages slit llla formed vertically on the lower end portion of
a tubular cover 111 which is supported roatably to the sleever 95
through a bearing. The above cover 111 is also formed with a
protruding pin 113 trefer to FIG.1) projecting horizontally, a~d
this protruding in 113 engages a vertical slit ll5a of a bracket
115 which depends from the previously mentioned arm 45.
Consequently, the rotation of the cover 111 and the holder block
105 around the spindle 65 and the like is restricted.
In the above construction, assuming that the a~ial centers
of the spindle 65, the eccentric disc 99, and the holder block
105 are designated by letters O, P and Q, respectively, the
interval between the axial centers O and Q is adjusted by
adjusting the location of the eccentric disc 99 relative to the
spindle 65, so that it is possible to adjust the radius
~amplitude of the microvibration) of the eccentric rotation of
the holder block 105 upon rotation of the spindle 65.
In operation, a workpiece ~ is fixed on the second slide
table 9; a work tool corresponding to the work portion such as a
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hole or the like of the workpiece is installed to the holder 93;
the work tool i5 brought into engagement with the work portion of
the workpiece by operating the swinging lever 71 and at the same
time a lapping agent is supplied therein as required; the
~pindle 65 is rotated by the rota~ion driving apparatus 51
and then the rotation driving apparatus 89 is rotated; hereby the
work tool ~tarts the rotation (microvibration) with a radius
equivalent to a micro-eccentric amount and at the same time it
moves vertically.
Therefore, as ~hown in FIGS.4~a) and 4(b), when the work
tool R performs the eccentric rotation with a micro-radius
counterclockwise as indicated by the arrow A, and in the case
where a part of the work tool R does not coordinate with the work
portion Wa of the workpiece W but they abut at a point B to each
other, the workpiece W is automatically rotated in the direction
indicated by the arrow C so that the directions of the work tool
R and the work portion Wa of the workpiece W coincide, thereby
providing an automatic and accurate coordination. Due tp this,
even in the case where the work tool R i6 not precisely directed
to the work portion Wa of the workpiece W at the initial setting ?
it is automatically adjusted and the correct coordination can be
obtained.
For example, in case of grinding the rectangular groove by
using the work tool having the cross section of square shape, the
deviation of the work tool in the direction perpendicular to the
longitudinal direction.of the groove is absorbed ~ince the
workpiece moves in a body, consequently the work tool micro-
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vibrates in the longitudinal direction and vertically of theabove groove for the workpiece and at the same time it
periodica]ly moves. Therefore, by moving the workpiece to the
longitudinal direction of the groove, the groove is precisely
ground by the work tool. When moving the workpiece to the
longitudinal direction of the groove, even if the workpiece has
been introduced to the direction which will cross the
longitudinal direction of the groove, the workpiece is slightly
rotated as described before to correctly coordinate the groove
with the work tool. In this way, it is possible to extremely
easily perform the precise grinding of the work portion of the
workpiece.
The above explanation has been made with respect to the case
where the workpiece W along with the table in a body moves
horizontaly and rotates; however, the similar functional effects
as described previously can be derived by supporting the work
tool so that it can freely move horizontally and slightly rotate.
That is to say, for instance, as shown in FIG.5, the spindle
which can move vertically is divided into the upper spindle 65a
and a lower spindle 65b; these upper and lower spindles 65a and
65b are coupled with each other through a proper flexible
coupling 117 such as a coil spring; and the lower spindle 65b is
mounted to the upper spindle 65a such that the lower spindle 65b
changes its location slightly and can freely twist. The lower
spindle 65b depends from the arm 45 and is supported through
balls 121 by a supporting member 119 which is suitably mounted so
as to move vertically, so that the lower spindle 65b can freely
move horizontally and rotates (twists) slightly.
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In accordance with this construction as shown in FIG.5,
since the work tool moves horizontally and rotates slightly to
provide the coordination between the work portion o~ the
workpiece and the work tool, it is possible to obtain the
remarkable work effects even if the weight of the workpiece is
very large.
Furthermore, such a construction as shown in FIG.6 is also
possible. Namely, a circular concavity member 123 is fixed on
the upper portion of the supporting rod 27 and a pole 127 having
a disc 125 is vertically mounted in a body downward of he lower
portion of the arm 45. A discoidal retainer 129 having a number
of balls so as to roll freely is arranged to the bottom in the
above-mentioned concavity member 123, and the disc 125 is
supported on this retainer 129. An annular cover member 131 is
fixed in a body above the concavity member 123, and an annular
retainer 133 having a number of balls is sandwiched between this
cover member 131 and the disc 125, so that the arm 45 can freely
move in any horizontal directions and rotate, resulting in the
same effect as the embodiment described previously. The spring
member 83 serves to under load joint the pole 127 and the
swinging lever 71.
As understood from the above-described embodiments,
according to the present invenion, even when the directions of
the workpiece and the grinding tool do not coincide correctly,
since the workpiece instantly conforms and goes with the
deviation of the grinding tool to be automatically corrected, the
correct coordination between the grinding tool and the work
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portion of the workpiece is assured, ~nd it is possible to
easily perform the ultra-precision grinding
finish-work with high accuracy. Therefore, the initial setting
is not always necessary to be done accurately but relatively
rou~h setting may ~e possible, which provides improvements in the
work efficiency. Moreover, it is possible to adjust the
amplitude of the grinding tool according to, for example, the
clearance or the like between the work portion of thè workpiece
and the grinding tool, this enables the precise grinding
finish-work under the suitable condition.
Furthermore, since the work tool vertically and periodically
move, the cutting ratio (worked area per unit time) is further
improved and the work can be done efficiently. In addition, when
the workpiece material is largely moved in order to change the
work location thereof, since the X and Y tables are moved, it is
possible to smoothly and largely move the workpiece.
With this detailed description of the specific ultra-
precision grinding machine used to illustrate the preferred
embodiments of the present invention, it will be obvious to those
skilled in the art that various modifications can be made in the
present method and apparatus described herein without departing
from the spirit and scope of the invention which is limited only
by the appended claims.
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