Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to surface finishing
apparatus which provides grinding and polishing functions.
Conventional techniques for precision machining of
metal surfaces require that a workpiece be subjected to a
conventional maching operation in a first machine and then
be transferred to a second machine for a precision grinding
and polishing operation. The required use of at least two
processing machines involving the transfer of the workpiece
from one to the other adds significantly to the time and
cost involved in precision surface finishing and limits the
quality which can be achieved. It is therefore desired to
provide apparatus which is capable of producing a precision
finished surface while requiring the use of only a single
machine tool having replaceable finishing elements.
According to one aspect of the present invention
there is provided an apparatus for effecting high tolerance
finishing of a workpiece surface comprising:
a mounting member including attachment means
suitable for attachment to rotary drive apparatus for
~' rotation of the mounting member about a first axis;
at least one resilient abrasive finishing element
rotatably mounted on said mounting member for motion
relative to said workpiece surface in a plane perpendicular
to said first axis;
bearing means supporting said at least one
finishing element on said mounting member for free rotation
of said at least one finishing element relative to said
mounting member; and means for collecting particulate matter
generated during a finishing operation from wear of said
finishing element mounted on said mounting member;
said at least one resilent abrasive finishing
element comprising an annular body of uniformly intermixed
resilient and abrasive substances.
; The invention will be more fully understood and
appreciated from the following detailed description taken in
conjunction with the drawing in which:
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Fig. 1 is a pictorial illustration of finishing
apparatus associated with a workpiece and mounted onto a
rotary milling machine of conventional construction;
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Fig. 2 is a side view illustration of a finishing
device constructed and operative in accordance with an embodiment
of the invention;
F;g. 3 is a bottom view of the finishing device of Fig. 2;
Figs. 4A is a bottom view illustration of an alternative
embodiment of a finishing device;
Fig. 4B is a schematic illustration of a further alternative
embodiment of a finishing device;
Fig. 5 is a detailed illustration of a portion of a
finishing device;
Fig. 6 is a partially cut away illustration of a
finishing device;
Figs. 7, 8 and 9 each illustrate an embodiment of a
finishing element;
Fig. lOA is a sectional side view illustration of a
finishing device useful with a lathe or other turning machine;
Fig. lOB is a plan view of the device of Fig. lOA
taken in a direction indicated by an arrow B.
Fig. 11 is a side view of a fin;sh;ng tool for the
interior surface of a workpiece, and
Figs. 12A and 12B illustrate two alternative mounting
orien~ations for an adjustably positionable finishing tool
constructed and operative in accordance with an embodiment of the
present invention.
The present in~ention provides finishing apparatus which
may be em?loyed selectably for grinding~and polishing by suitable
selection of the characteristics of the resi~ient abrasive finishing
element. When used for polishing or grinding, sufficient pressure is
provided such that the finishing element is compressed by approximately
30 - 300 microns thereby producing an area rather than line contact
between the finishing element and the workpiece surface. Such a
polishing technique provides a reduction of approximately 0.0005 mm
and provides an extremely high quality surface finish of the order
of between 16 and 2 microinch r.m.s., and preferably up to 4 - 2 microinch
r.m.s.
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Such a grinding technique provides a reduction of
approximately 5 - 50 microns.
It is appreciated that the finishing element in
one embodiment of the invention undergoes a complex motion
with respect to the workpiece which greatly adds to the
quality of the surface finish. This complex ~otion
comprises the rotation of the housing or base onto which the
finishing element is mounted, the rotation of each finishing
element about its own axis and the motion of the workpiece
on a moveable table relative to the polishing element.
According to a preferred embodiment of the invention, the
finishing technique includes rotation of the base or housing
in opposite directions which may correspond to opposite
directions of the workpiece movement on the moving table.
Reference is now made to Fig. 1 which illustrates
finishing apparatus constructed in accordance with an
embodiment of the present invention in operative association
with a conventional milling machine for rotational
engagement under pressure with a workpiece. The finishing
apparatus is indicated generally by reference numeral 1 and
comprises a body portion 3 and a shank portion 5 ~hich is
insertable into the chuck of the milling machine 7 for
rotation selectably in opposite directions about the spindle
axis I - I of the milling machine, the body portion 3 and
shank portion 5 constitute a mounting member with the shank
portion 5 providing a means for attachment to the milling
machine 7. The workpiece, 64, is preferably mounted on a
movable table 65 associated with the milling machine.
Normally the finishing apparatus is rotated initially in a
first direction while the movable table moves in a first
longitudinal direction. Thereafter, as the table returns in
an opposite direction, the rotation of the finishing
apparatus may be in an opposite direction. This two
direction capability provides evenly, randomly directly
finishing marks.
The pressure engagement of the finishing apparatus
with the workpiece surface is illustrated in ~ig. 1 by the
extent 67 to which the finishing element indicated by
reference numeral 68 is compressed when it engaged the
workpiece surface. As noted above, this compression is
approximately 30 - 300 microns. Preferably the pressure is
exerted perpendicular to the workpiece surface.
Reference is now made to Figs. 2 and 3 and which
illustrate the finishing apparatus of the present invention
in greater detail. The apparatus comprises a housing base
71 which is fixedly attached to a shank 73 and supports a
housing top portion 74 and bottom portion 76. Disposed
!' mainly within the housing are a pair of finishing elements
75, typically in the form of annular disks. Elements 75 are
mounted rigidly onto respective axles 77 which in turn are
bearing mounted within the housing for relatively free
rotation with respect thereto. The axes of rotation of both
finishing elements 75 are identical and intersect with the
axis of rotation of the housing indicated by reference
numeral 79, as seen in Fig. 3.
It is a particular feature of the preferred
embodiment of the present invention that housing top and
bottom portions 74 and 76 together define means for
collecting particulate matter which is produced as the
result of the wearing down of the resilient finishing
elements.
; As seen in Fig. 3, the finishing elements 75 are
disposed mainly above the bottom surface of bottom housing
portion 76 and only a portion thereof extends outside of the
housing, through openings 81 formed in the bottom surface.
Openings 81 are constructed to be of as small an area as
possible and therefore have a width only slightly greater
than that of the finishing elements, sufficient to prevent
interference with the free rotation thereof. The length of
the openings is less than the diameter of the finishing
elements. Thus particulate matter generated in a
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finishing operation from wear of the finlshing element is
gathered into the interior of the housing bottom portion 76
so as not to interfere with the finishing and not to provide
uneven results and cause damage to the apparatus.
According to a preferred embodiment of the invention,
illustrated schematically in Fig. 4A, the axes of rotation of the
finish;ng elen~ents 75 are offset from each other and do not Is
intersect axis 79. This non-intersection feature provides
an additional vector moment of motion between the finishing element
and the workpiece surface when housing base 71 is driven in rotary
pressurized motion relative to the workpiece surface.
Fig. 4B illustrates finishing apparatus constructed
and operative in accordance with a variation of the embodiment
of Fig. 4A. Here finishing elements 80 and 82 are not mounted
for independent free rotation relative to the housing 84, as in
Fig. 4A but rather are interconnected by a transmission 86,
typically comprising an odd or even number of gears. An even i~;
number of gears comprising gears 88, 90, 92 and 94, for example,
is preferred since it provides rotation of elements 80 and 82 in
respective opposite directions for enhanced finishing action.
It is noted that finishing elements 80 and 82 are offset by different i
amounts from the rotation axis 96 of the housing, thus producing
different speeds of rotation in the finishing elements, were the
elements not connected by a fixed transmission. It is appreciated
that the transmission may be constructed such that a non-unitary
fixed ratio of speeds is maintained between the two finishing ,
elements. The two finishing elements may be constructed to be
of different widths and to have differing abrasive characteristics. ~
Fig. 5 illustrates a preferred construction of a ~,
portion of the bottom housing portion 76 wherein a recess 85 ;s
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defined at the inner periphery of the portion 76 for collection '
of particulate matter along the outermost portions of the interior
of the housing under the influence of centrifugal forces produced
by the high speed rotation of the housing during operation. Portions
87 of the housing bottom surface adjacent the finishing elements
are bent upwardly to define a barrier for preventing, insofar as
possible, particulate matter from escaping from the housing. The
bottom portion 76 is constructed to be removable for easy cleaning.
.
A further development of the apparatus of Fig. 5 is
illustrated in Fig. 6 and comprises a housing wherein the bottom
portion 53 thereof is selectably positionable relative to
finishing elements 75 in order to compensate for wear therein, and
the resulting significant decrease in their diameter. Bottom
portion 53 is spring mounted onto the housing base 71 by means of
a pair of bent leaf springs 55 and is secured to the housing base
by means of a screw fastener 57. The extent to which the screw
fastener 57 is inserted into a corresponding socket 59 formed in
the housing base 71 determines the relative disposition of the bottom
surface of the bottom portion 53.
Figs. 7, 8 and 9 illustrate different embodiments of
finishing elements constructed and operative in-accordance with an
embodiment of the present invention. The element of Fig. 7 is of
generally annular configuration having a truncated conical cross
section of increasing width with decreasing radius and is formed of
a resilient material, typically rubber based, having abrasive material,
typically in the form of grains, dispersed therein throughout the
usable volume thereof. The configuration of Fig. 7 is designed to
maintain the operating characteristics of the element generally
constant notwithstanding wearing down and consequent reduction of the
diameter of the element during use. Thus, as the element is worn
down, the same effective width and pressure is applied to the ~Jorkpiece
surface.
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Fig. S shows an alternative form of finishing element ;
comprising an outer annular ring 61 of generally uniform resilient
abrasive material of the type described in connection with Fig. 7,
prefera~ly with a resiliency greater than 75 of the Shore scale.
The inner core fi3 may be constructed of natural rubber, for example,
for use in polishing applications. For use in grinding applications,
however, the inner core 63 should be formed of metal or hard plastic
or similar material to provide precision mounting of the element on
a mounting shaft, for accurate grinding. It is appreciated that
~hen the finishiny elements of the type described herein are used
for grinding, the resiliency will be less than in polishing
applications and the abrasive will be substantially rougher.
Fig. 9 illustrates the use of a conically shaped finishing
element of generally uniform resilient abrasive composition. In the
illustrated embodiment, the element is arranged such that its radius
about its axis II - II of rotation increases with an increasing
d,stance from the axis I - I of rotation of the housing. Thus the
elen~nt is particularly suited for finishing of interior corners.
Alternatively the finishing ele~ent of Fig. 9 may be oriented
oppositely such that its radius about its axis II - II of rotation
increases with an increasing distance from axis I - I. Thus the
absolutc value of the velocity of rotation at all points along the
element is ~enerally the same.
According to an alternative embodiment of the ~invention, the
finishing elements may comprise a relatively soft resilient elastic
base formed with an abrasive outer surface. The base may be a
resir10id, rubber or a porous polyurethane. The abrasive may conlprise
grains of diamond, borozone or silicone carbide, for example.
R-ference is now made to Fi~s. lOA and lOB uhic:~ show a
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finishing de~ice constructed and operative in accordance with an
en-,bodiment of the present invention and comprising a base 200 on which
are mounted at least two finishing elements 210 and 211. Elemcnts
2l0 and 211 are arranged so as to simultaneously contact a rotating
workpiecc 212 mounted for rotation on a conventional lathe such as
a ~tal lathe. ~ase 200 is in turn rotatably mounted by means of
mGunting means 201 comprising a pin and sprocket 202 and a biasing
spring 204 or simi7ar suitable apparatus onto a tool holder 205 which
mdy be inserted into a conventional tool holidng clamp on the lathe.
Biasing s~ring 204 is operative to maintain the finishing elements in
operative engasement with the workpiece surface.
Elements 21~ and 211 are interconnected by a transmission
typic~lly co~prising a pair of gears 209 which engage corresponding
sedrs 213 and 2'5, having different numbers of teeth, which ~ears
are mounted onto elements 210 and 211 respectively. This arrangement
ir,sures that elem nts 210 and 211 move in respective opposite
dir~stions at different speeds against the workpiece, thus providing
enhanced finishing action. Preferably the faster one of the
finishing el~ments ~ves together with the workpiece in a generally
non-slipping engagement, while the other moves against the
w~rkpi~e surface. Alternatively elements 210 and 211 may be caused
tc move in the same direction at different speeds.
It is noted that the embodiment of Fig. 4B, for example,
may be constructed with a similar transmission.
It is noted that finishing elements 210 and 211 are generally
sur~ounded by a housing 220 which defines a collector for particulate
matter produced by wearing down of the finishing elements. Housing
220 is designed to retain as much as possible of such particulate
matter which is propelled inwardly thereto by the adjacent inward
rctation of the finishing elements 210 and 211. Bottom and top
edges 222 are dis,oosed adjacent the finishing elements to discourage
escape of the particulate matter.
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Referring particularly to Fig. lOB it is noted that
th~ finishing elements 210 and 211 are located at one side of the
apparatus at collector housing 220. Adjacent thereto in the
~:liddle of the apparatus indicated by reference numeral 224, there
are provided the mounting bearings for the finishing elements.
At location 226, entirely sealed from the outside for safety, are
proYided the gears 209, 213 and 215.
It is a particular feature of the present invention that
the gear ratio of the transmission is selected such that the ratio
of the surface speeds of finishing elements ~10 to element 211 is
a~ least 1.1.
It is noted that enhanced surface quality may be realized
by moving ~he finishing apparatus transversely along the workpiece
in opposite directions.
It is appreciated that the apparatus of Figs. lOA and lOB y
may be used also for finishing the flat end face of a surface of
rota~ion mounted on a lathe by arranging the housing such that elements
210 lie against the flat face. A high quality finish on the surface
of rntation may be realized by back and forth movement of the tool
axially along the workpiece. This is equivalent to operation of a
rnilling l~chine in opposite directions in the embodiment of Fi~
Reference is now made to Fig. 11 which illustrates a
finishing tool particularly suitable for the finishing of internal ,
surfaces of a workpiece. A workpiece 300 having formed therein
a bore 30~, whose 1nner surface it is sousht to finish, is secured
in the chuck (not shown) of a conventional lathe for rotation about
an axis 304. The finishing tool, indicated generally by reference
nur,leral 310 comprises a tool holder 312 which is secured in an
appropriate mounting socket (not shown) arranged on the lathe. A
finishing assembly 313 is mounted onto tool hol~er 312 at a selectable
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angular disposition thereto by means of a securing bolt 314.
I.oosening of bolt 314 permits rotation of finishing assembly 313 !
relative to tool holder 312 to define a desired angle with axis 304. ~
Spindle assembly 317 defines a mounting location 322 arranged ~^
symmttrically about axis 320. A selected fin;shing head 324 may be 1'
mounted at location 322 onto spindle assembly 317 for rotation about ,'r
axis 320 and may be secured onto the spindle assembly by means of
a retaining screw 326.
Finishing head 324 is arranged to have a tapered
confiquration defining a rectilinear generatrix 328. A tapered finishing
head of truncated conical configuration is employed herein as illustrated.
It is noted that the finishing tool is a passive element ~3
and engages in a rolling-slipping motion against the workpiece as ~i
is the case in the embodiments of the invention described above.
Reference is now made to Figs. 12A and 12B which illustrate
a spindle assembly 600 and associated tool holder mounting means 602 ,-
in alternative selectable positions with respect to a workpiece 604
m~unted on a lathe (not shown). The mounting means comprises a pair ~'~
Gf channels 606 and 608 angled with respect to each other by a ~,
predeternlined an,ount, onto which a mounting element 607 fixedly
attached to spindle assembly 600 may be selectably mounted for selectable ;'
anguiar disposition of the spindle assembly and the finishing head 610
with respect to the workpiece. Fig. 12A indicates an orientation l~
where the axes of rotation of the workpiece and of the finishing head -
lie in the same plane, while Fig. 12B illustrates an orientation wherein
the two axes of rotation lie in different planes.
It will be appreciated by persons skilled in the art that
the invention is not limited to what has been specifically shown and ,~
described herein. Rather, the scope fo the present invention is ~.
defined only by the claims which follow:
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