Note: Descriptions are shown in the official language in which they were submitted.
~2~ 3
"~ IMPROV~D MICROFINIS~ING APPARATUS AN~ MET~OD
BAC~GROUND AND SU~M~RY QF T~F INYENTION
This invention relates to metal surface finishing
and particularly to an improved apparatus and method for
microfinishing meta] surfaces using coated abrasive tape
materials.
Numerous types of machinery components must have
finely controlled surface finishes in order to perform
satisfactorily. For example, surface finish control, also
referred to as microfinishing, is particularly significant
in relation to the manufacturing of journal bearing and cam
surfaces such as are found in internal combustion engine
crankshafts, camshafts and power transmission shafts and
other finished surfaces. For journal type bearings, very
accurately formed surfaces are needed to provide the desired
bearing effect which results when lubricant is forced
between the journal and the associated bearing. Improperly
finished bearing surfaces may lead to premature bearing
failure and can limit the load carrying capacity of the
bearing.
Currently, there is a demand for higher control of
journal bearing surfaces by internal combustion engine
manufactures as the result of; greater durability require-
ments necessary to offer improved product warranties, the
higher operating speeds at which engines (particularly in
automobiles~ are now required to sustain, and the greater
bearing loads imposed through increased efficiency of engine
structures.
In addition to bearing structures, surface finish
mls/lc~
.. . . ~ . . -
.. ..
'.
:-, . .~ - . .. ,. . :
~ .
,:, ~ " ~
~26~i3~3
control must be provided for en8ine cylinder walls in order
to provide the desired oil and gas seal with the piston
rings. Numerous other types of machine components also
require controlled surface finishes, particularly along
areas of sliding contact between parts.
Microfinishing has primarily been accomplished
according to prior art using several different types of
machining techniques. In stone microfinishing, a stationary
honing stone is brought against the desired surface. When
microfinishing cylindrical journal bearing surfaces, the
honing stone is caused to oscillate transversely from one
edge of the journal to another as the workpiece is rotated
with respect to the stone. This process possesses a number
of significant disadvantages. Due to the requirement that
the honing stone be soft enough to be self-dressing and to
provide the desired material removal characteristics, the
stone, through use, takes on the shape of the part being
finished. Therefore, this method, instead of correcting
~ geometry variation~s in the part being microfinished,
actually causes such var1ations to occur. AdditionDlly,
1~ since honing stones are perishable, they must be frequently
; ~replaced and~redressed. Finally, it is extremely difficu1t
to find honing stones with consistent qualities resulting in
significant differences in the~ finished parts when machined
by different stones.
Anothe~r significa~nt~ dlsadvantag~e of stone
microfinishing of jour;nal bearing~6~ ueing a honing stone is
the fact that, since the journal~ generally include
m~1s/1cm ~ 2 - ~ ~
,. .
.....
.. . ... . ~ . .. . .. ~ . . .
i3~
outwardly projecting radius edges, the stone cannot
laterally overstroke portions of the surface being machined
which leads to uneven stone wearing. Such uneven wearing
causes a change in the profile shape of the honing stone,
and this shape is consequently generated in subsequent parts
being machined. Finally, since the honing stone generally
has sharp corner edges, it cannot be used to microfinish
near the radius edges of the bearing surface.
In another ~nown microfinishing process, herein
referred to as conventional coated abrasive tape micro-
finishing, the surface being finished is caused to rotate
and a coated abrasive tape is brought into contact under
pressure with this surface. As the part is rotated, the
abrasive material reduces the roughness of the surface. In
the conventiona] process, the tape is brought into contact
with the rotating surface by pressure exerted by
compressible elastomeric inserts, typically made from
urethane plastic compounds. The cDnventional coated
abrasive tape microfinishing process overcomes several of
the disadvantages associated with stone microfinishi~g.
This process i~ capable of microfinishing in the journal
fillet radius area since the tape is relatively flexible~
In addition, this process uses a renewable abrasive surface
which can be purchased having consistent qualities. This
process, however, does not overcome other disadvantages of
s~tone mlcrofinishing, Principal among these disadvantages
of this process ls the fact that the process does not cor-
rect geo0etry variations in the part being microfinished,
.
~ mlsjlc0 - 3 -
" , , ................ ;. ,: .: . ., ''
- :- ~' ~
since the insert backing the coated abrasive tape is a
flexible material and therefore, the tape conforms to the
surface profile of the component surface being machines.
In still another variation of microfinishing
processes known to the prior art, a rigid insert is used to
press abrasive coated paper or cloth material into contact
with a relatively moving workpiece surface. Abrasive coated
paper or cloth materials are, however, relatively thick and
compressible, and therefore, this method did not enable
significant workpiece geometry corrections since the paper
or cloth would ~Igive9~ and conform to minute i~regularities
in the workpiece surface.
In addition to the above-noted shortcomings
according to the currently known microfinishing processes,
great difficulty has been encountered in removing ferrite
caps which are present on the Einished surfaces o~ nodular
iron workpieces. These hard caps are present on the outside
surface of the bearing and can lead t-o premature bearing
failure.
In view of the above-described shortcomings of
microfinishlng devices and methods according to the prior
art, it is a principal object of this invention to provide a
microfinishing apparatus and method which is capable of
correcting geometry imperfections in finished surfaces. It
is yet another object to consistently produce surfaces
h~aving smoothness characteristics superi;or to those
achievable by conventional means.
The above principal objects of this invention are
mls/lcm - 4 -
:~ .
', ~ . '
~.
- ~ Ei53~3
provided by a microfinishing system which employs an abrasive
coated tape which is brought into contact with a rotating
workpiece, and is pressad into contact with that workpiece by
a rigid precision formed backup insert. This rigid insert does
not cause the abrasive tape to conform to the surface profile
of the workpiece. Instead, the rigid insert causes greater
abrasive tape contact pressure to be applied to portions of the
workpiece surface which extend beyond the desired surface,
thereby causing greater material removal in those areas. This
system therefore permits the microfinishing system to correct
geometry imperfections in the workpiece. In the practice of
this invention, it is essential that the abrasive coated tape
be made of a material which is relatively incompressible such
that the tape will not conform to irregularities but instead
will enable these irregularities to be removed. Since the
insert is not the primary cutting tool, it is not subject to
significant changes in profile with use. With appropriate
additional components, the rigid inserts may be provided with
the capability of polishing fillet radius areas. The
microfinishing system according to this invention has been
found to provide a significant advance in the art of
microfinishing enabling consistent production of surface
finishes unachievable using the devices and processes according
to the teachings of the prior art.
In summaxy, therefore, the present invention may be
broad~y considered as providing a method of microfinishing a
workpiece an outside curved workpiece surface which comprises
the steps of: rotating the workpiece; and causing a rigid shoe
LCM:jj 5
',
. . .
~2~ 3
surface to contact and press a relatively incompressible abrasive
coated tape against the workpiece surface, the rigid shoe surface
having a predetermined shape related to the desired workpiece surface
shape and defining an included angle between the boundaries of contact
between the tape and the shoe oF greater than 120 and preferably about
160 relative to the center of the curved workpiece surface, whereby
a desired workpiece surface shape is generated in the workpiece
surface.
Furthermore, the above method may be carried out by way of a
machine for microfinishing an outside curved surface of a workpiece,
comprising: abrasive coated tape relatively incompressible; a shoe
assembly having means for holding the tape and having a rigid surFace
forming a predetermined surface shape related to a desired workpiece
surface shape, the rigid surface contacting and pressing the tape into
contact with the workpiece surface, the rigid surface defining an included
angle between the boundaries of contact between the tape and the shoe
of greater than 120 and preferably about 160 relative to the center of
the curved workpiece surface; means for causing relative rotation between
the workpiece and the shoe assembly, and an arm which supports the shoe
assembly such that relative movement between the workpiece surface and
the tape occurs as the workpiece is rotated relative to the shoe assembly.
Additional beneflts dnd ddvantages oF the present invention
will become apparent to those skilled in the art to which this invention
relates upon a reading of the
-
,~., .~
.. . sd/~' 5a
.. ".", .. .
,. ,.. :.. , ~. : ..
,', ~ . .
.~, .
3~3
described preferred embodiments of this invention taken in
conjunction wi~h the accompanying drawings.
BRIEF DESCRIPTION OF T~E DRA~INGS
Figure 1 is a pictorial view of a crankshaft being
rotated such that one of its pin journals is being micro-
finished by the clamping of a polishing shoe assembly
against the pin journal;
Figure 2 is a cross sectional view taken through a
polishing shoe assembly according to the prior art;
Figure 3 is a cross-sectional view taken along
line 3-3 of Figure 2;
Figure 4 is a cross-sectional view of a polishing
shoe assembly according to the subject invention;
Figure 5 is a cross-sectional view taken along
line 5-5 of Figure 4;
Figure 6 is a second embodiment of thi9 invention
employing a rigid back-up insert having relieved portions;
Figure 7 i9 a cross-sectional view taken along
line 7-7 of Figure 6;
- - :
: : :
:~ :
;~
~ mls/lcm : - 6 -
~ ~ A
...... . ..
: ~ : . . ,,, . ~ " . ~.
.
..
- .: ,.
.. ~ ~ . .
.:
~Si3~3
Figure 8 shcws a.third en~odi~ent of ~is invention using a
n~difi~d rigid back-up insert;
Figure 9 is a cross-sectional view taken along line 9-9 of
Figure 8;
Fisure 10 illustrates a fourth embcdim, nt of this m~ention
wherein a rigid back-up m sert is used with flexible inse~s such that
the fillet radius portions may be ~iclofinished;
Figure 11 shows a fifth embldiment of this invention wh~ein
sslid back-up inserts are used in conjunction ~ith a perforated coated
abrasive tape which enhanoes lubricant flow to the surfa oe being
microfinished;
Figure 12 shows a sixth embodlment of ~his in~ention w~erein
an alternate %eans of mounting the polishing shoe as~embly is shown;
Figure 13 s ~ s a seventh emboslment of this invention wherein
an elastomeric insert is pxovided to polish the filet radius and side
wall portions of a workpiece; and
Figure 14 is a cross-sectional view taken along l me 14-14 of
Figure 13 particularly shcwing the elastomeric ~sert acoo ~ g to this
embodiment of the inventionO
D ~ DESCRIPTICN OF T9E DR~WINGS
. ~ . .... -- .
A polishing sh~e asse~bl~ is shown by Figure 1 and is
designated there by referen oe character 10. Pvlishing sh oe asse~bly 10
is shcwn with the associated support mechanisms shcwn schematically and
is shown in position to microfini.sh a bearing surface of an in ~
o~mbustion ~ngine crankshaft. As is shown by that ~igure, cranksha~t 12
is supported at opposing ends ky hRadstock 14 and tailsbock 16 which
to~e~her cause the cr~nhshaft to be rotated abcut it~s longitudinal
oenter axis. Crankshaft 12 includes a plurality of cylindri~al bearing
~ur~aces which nust ~e microfinished including p m bearings 18 which, in
use, becon~s ccnnected to a piston connecting rod, and m~in k~arings 20,
:
",
, .`' ,.' . ' ' ~ ~ '
.: .: : ~ ~ ,: ,
,
., . ., : .
3~3
which support the crankshaft for rotation within the en~ine block.
Polishing shoe as.~embly 10 is sh~n nc~nte~ to arm 22. Polishing shoe
assembly 10 is caused to oscillate laterally along the surface being
~achined by oscillating the shoe assembly, or by oscillating the
workpiece relative to the shoe assemhly. Arm 2~ permits polishing shoe
assembly 10 to orbit ~ith pin bearing 18 since that beari~g jcurnal is
positioned eccentrically with respect to the oenter of rotation of
crankshaft main bearings 20.
With particular referen oe to Figure 2, a polishing shoe
asse~bly according to the prior art is illustrated. Pblishing shoe
assembly lO inclu~es two h~lves, upper shoe 32 and lcwer shoe 34 ~shcwn
partially in p~antom lines). me~e halves are each connected to a
support structure which may include hydraulic or pneumatic biasmg
cylinders acting on ~12 shce halves (as shawn in Fhantcm lines in Figure
2~ or ~ay be supported by a scissors type linkage device. This
polishing shoe as~erbly e~plcys a semicircular surface 24 having a
plurality of spaced dovetail-shaped grooves ~6. Within dovetail grooves
26 are ins*alled cccperatively shaped urethane insexts ,28. These
inse~ s, dl~e to the mat~xial frnm which they are made, are oo~paratively
flexible and cc~pressible, having a Durometer hardness of 90 ox less.
Each of the shoe portions include means for engaging coated abrasive
tape 30 which is brought into co~pressive contact with the surface of
pin beaxing 18. At the conclusion of the microfinishing cperation of
one pin bearing 18, upper and lower shoes 32 and 34 are caused to
separate ana are repositioned and clamped ontD another pin bearing 18 or
a main bearing 20. Alternatively, a plurality of polishing shoe
assemblies ~ay be provided such that the entire w~rkpiece may ba
machined in one cperation. Sim~ltaneous with shce di~sengagement and
re-engagement is an index ~ of tape 30 such that a predetermlned l~n
of new abrasive material is brought in~o sh oe assembly 10. ~liS
indexing results in ~he abrasi~e ~urface being oonstantly renewed.
:i:
~', '' .
,
.
'' '. ~ ' :
~, :
i3~3
Figure 3 illustrates a cross-sectional view taken
through Figure 2 and shows contact between insert 28 and pin
bearing 18. Insert 28 is caused to traverse relative to the
surface of pin bearing 18 as indicated by arrow A. Insert
28, being made of a flexible material, is caused to conform
to the existing surface profile of pin bearing 18. There-
fore, if imperfections such as waviness7 taper, convexness
or concavity of the bearing surface exist, coated abrasive
tape 30 will be caused to conform ~o the incorrect shape.
As a result, this prior art microfinishing method does not
correct geometry imperfections in the parts being
microfinished.
Figure 4 shows polishing shoe assembly 60
according to a first embodiment of this invention.
Polishing shoe assembly 60 includes upper shoe 62 and lower
shoe 64. Polishing shoe assembly 60 varies principally from
shoe assembly 10 shown by Figures 2 and 3 in that urethane
inserts 28 are replaced with stone inserts 36. These~
inserts-are preferably made from honing stone material.
~; 20 Stones inserts 36 are characterized in that they are
relatively non-deformable having a Durometer hardness
greater than 90, yet are easily machined and provide a
degree of frictional engagement with coated abrasive tape
30. Each of stone inserts 36 is mounted to a holder 38.
Stone inserts 36 and holders 38 are preferably permitted to
"float" slightly ~ith`;respect to the upper a~d lower shoes,
enabling them to rotate slightly as indicted by arrow B in
Figure 5. Such relative rotation is provided according to
: : .
mlstlcm _ g _ : ~
: ~, : . .,
.. . ~, .. -.. ....
...
Si3~ ~
this embodiment by mounting holders 38 using mounting pins
40. Like shoe assembly 10, coated abrasive tape 30 is
supported by shoes 62 and 64 such that when they engage pin
bearing surface 18, the tape is brought into contact with
the surface being microfinished.
c ;~ ~.L
C The p-~i~6~ advantages of the configuration of
polishing shoe assembly 60 are best explained with reference
to Figure 5. Stone insert 36 is provided which presents a
surface having a predetermined curvature which is rigid and
which exerts a compressive load on tape 30 against pin
bearing 18. Since stone inserts 36 are rigid and relatively
non-conformable, surface waviness, taper, convexity and
concavity of the surface of pin bearing 18 are corrected
since, in these instances, non-conforming portions of the
surface of pin bearing 18 will be brought under greater
contact pressures against coated abrasive tape 30, and
therefore, more material will be removed in those areas
until pin bearing 18 assumes the desired surface profile.
coated abrasive tape 30 ls preferably made of a polymeric
plastic film material which is relatively incompress1ble.
Polyester films made ~rom polyethylene terephthalate such as
MYLAR (a trademark of EI du Pont de Nemours Co.) have been
found satisfactory due to their relatively low
compressibility. The thickness of tape 30 is preferably in
a range of between 2 and 8 mills. The co~bined rigidity or
lack of compressibility of insert 36 and tape 30 insures
that imperfections in the workpiece will be removed.
Abrasive coated paper or cloth products are generally
mls/lcm - 10 -
:~ . `. :
- . .
:: :
-- ........... .
., ~.
, : ;. ~: . -
~2~i3~
unsuitable for use in connection with this invention since
they are relatively compressible as compared to polymeric
plastic tape materials of the type descrlbed above.
Additionally, the grit size of abrasive coated papers is
generally not as uniform as that of abrasive coated
polymeric plastic tape materials. As with the prior art
devices, insert 36 and shoe assembly 60 are caused to
oscillate relative to pin bearing 18 as the bearing is
rotated relative to the shoe assembly, as indicated by arrow
A in figure 5. Such lateral movement is achieved by moving
the workpiece relative to polishing shoe assembly 62, or by
moving the polishing shoe assembly relative to the
workp;ece, or a combina~ion of both. When relative lateral
movement is initiated, frictional engagement between stone
insert 36 and coated abrasive tape 30 is necessary in order
to urge the tape to move laterally, For this reason, hard
materials having a very smooth surface such as machined
metals are generally unsuitable for insert 36, unless they
are sufficiently roughened to frictionally engage the back
of coated tape 30. Materials which have been found suitable
for insert 36 are conventional honing stone materials.
These materials exhibit the desired hardness and frictional
characteristics and have been found to produce excellent
results.
Now with partlcular reference to Figure 4, another
feature in accordance with this invention will be described.
Angle C, shown in Figure 4, designates the maximu~ range of
the point of contacts of the shoes 36 within either of the
mls/lcm
~'.
~,
-
., "~ :
.. . . ..
~2~3~
shoes 62 or 64. The inventors have found that Angle C
should be at least 120 and preferably about 160 to provide
improvements in terms of part geometry correction and rate
of material removal as compared with shoes having a lesser
range of angular contact. Improvements in part geometry
correction are believed attributable to the fact that, with
a larger angle of contact (Angle C), the shoes more closely
approximate a cylinder themselves and therefore force the
workpiece to assume such a configuration. The increase in
material removal rate is believed attributable to a wedging
effect wherein the contact pressures existing at the outer
ranges of contact of the shoe are greater.
During the course of development of this inven-
tion, the inventors further discovered that the rate of
lateral oscillation of upper and lower shoes 6Z and 64 was
lmportant in terms of producing the desired machining ac-
tion. The shoes 62 and 64 are oscillated laterally while
the workpiece is rotated ~or the workpiece may be moved
laterally while the shoes are stationary). Abrasive coated
tape 30 causes a cross hatched pattern to be developed on
~ the workpiece surface. These cross hatch patterns can be
defined by lines which coincide with the direction of rela-
tive motion between the workpiece and abrasive coated tape
30 as best shown in Figure 5. Cross latch angle is a
function of the rate~s of w~orkpiece rotation and shoe oscil-
lation and workpiece surface diameter. The inventors have
f,ound that the cross hatch angle defined by Angle D, must
exceed 2 in the area of the longitudinal center of the
mls/lcm - 12 -
: " . ,
~, , ~.
..: . . ...
. .. ...
~: : . ,., ~ : :
.
bearing in order to provide acceptable finish quality and
bearing performance. This cross hatch angle (Angle D) is
somewhat greater than tha-t according to prior art machines
and methods and contributes toward improving the quality of
bearin8 surfaces generated~
~ odern day crankshafts are often made from nodular
iron which has imbedded ferrite nodules. These nodules
present themselves as caps on the bearing surface which
should be removed in order to provide the desired bearing
characteristics. During the course of development of this
invention, it was discovered that removal of these ferrite
caps was possible by first rotating the workpiece in one
direction and then rotating the workpiece in the opposite
direction. This process is believed effective since the
minute abrasive grains on tape 30 become smoothened on one
side, yet remain sharp on the other side, and reversing
rotation permits the sharp grain sides to also remove
material.
Other types of coated abrasive tape material 30
could be employed in connection with this invention. For
example, a metal backed tape which is coated with abrasive
material could also be used. However, it is essential that
~tape material 30 be relatively incompressible.
~ ~ '
,
~ mls/lcm - 13 -
.
~ :
39~3
Figures 6 and 7 illustrate a second embodiment according to
this invention. For this enbodiment~ portions of insert 136 are
partially relieved such that they do not cause high contact ~xessure
between coated abrasive tape 30 and pin bearing 18~ Figure 6 shcws a
pair of opposed relief portions 142 which ar~ defined by arcuate borders
144. The surface of pin bearing 18 mcves with respect t~ inSert 136 in
the direction indicated by arrow C. This seaxnd en}rdiment ~auses
greater abrasive ~s Prial remcval ta occur at the separated ends of the
surfa oe of pin b~aring 180 This second embodimEnt thexe~ore tends to
cause the pin bearing ~urfaoe to assume a slightly ~arrel shaped
con~iguration, such that its diame~ers at each end are slightly less
than the diametex at the oenber. Such ~barrelling" is sameti~es
desirable bo achieve optimal bearing surfaces.
A third emboiiment according bo this inwention is æhnwn wQth
reference to Figures 8 and 9. Ihis embsdimen~ also p~oes a slightly
barrel shap~d journal bearing surfaoe but achieves this result in a
differ~t manner than that according to Figures 6 and 7. A Ir~dified
cylindrical c~ntour in insert 23S is pro~ce~l 50 that the I:adiUs of ffle
ved ~s~t surface at po~?ts ~ ends l~f the ja:n~al bear~ng is
less than at the oenter of the j~urnal bearing. As sl~;n by Figure 8,
relative m ~ nt of pin bearing 18 w1th respect to insert 236 occurs
along the direction indicated by arrow C. As illustrated ~7 Figure 9,
portions of the surfa oe of insert 236 near the lateral edges are
designated ~y reference characber 254 and have a radius of ~urvature
some~hat less than that of central shoe 6eg~ent 256 (these differences
~n radius are exaggerated in Figure 9 for illustration p~rposesJ. This
embodlment, therefore, provides another ~ s for generating a
nan-cylindrical sur~aoe and a workpiece being ~achined. According to
sh~"~7 ~;7q
this en~rdiment, such ~ results from ~achining the desired
sur~aoe contour directly into stone insert 236 and this cont~ur will be
Impressed and ~achined in the c~rresponding workpiece.
: AL ~Y
~2~ 3
A ~ourth enbcdm ent of this inventi~l is illustrated by Figure
10, w~ich ena~les the side wall portion 68 of p m bearing 18 to be
//e 7~
finished and f~Ither permits any burrs existing betweeni~k~ radius 46
and the bearing surface to be re~oved~ In accordan oe with this
enbodinent, flexible inserts 348 and 350 are prcvided with inserts 36.
~ ~se flexible inserts exert a ccmpressive foroe against coa~ed abrasive
tape 30 when the inserts are brought to their ex*reme la~eral positicns.
Although ~he e~ployment of a flexible m~terial for inserts 348 and 350
results in the same shortoomings associated with conventional processes,
it is generally not necessary to highly cQntrol the profile shape of
these surfa oe s. Sin oe it is neoessary for tape 30 to flex to a
considerable extent when brought into contact with side wall portion 68,
it is sometimes necessary to provide edge cuts within the ooated tape,
according to principles ~ncwn to the prior art. U æ of inserts 348 and
350 further pe~mats the elimination of burrs or sharp edges which may
exist at the edges 51 of the ~earing surface o jouxnal 18 when the
fillet radius are cut deep into the workpiece ~as shcwn by Figure 10).
By ~cunting inserts 348 and 350 such that they exert a slight
compressive load cn the surfac~ of bearLng 1~, t~pe 30 is caused tD
remove such burrs when the insert forces the tape into the fillet.
Figure 11 illustrates a fifth emtodlment according to this
inventicn. T~is enbcdlm~nt employs inserts 36 and ~ and lower sho s
62 and 64 as aescribed in cOnneCtiQn with Figure 4. Ihis embodiment
differs from the previously described enbodinents in that coated
abrasive~tape 430 is used which has a multiplicity of perforations 452
along its lensth. Perfo~ations 452 enable lubricants or cutting fluids
to come in contact wi*h the surfaoe s being ~achinedO ~low of lubricant
or cutting fluids to the workpiece is oonducted thr3ugh passage 70
pper and lcwer shoes 62 and 64.
A sixth emkcc~nent according ~o this invention is described
wqth referen oe to ~igure 12~ As shcwn ~y that Figure, lower shce 56~ is
..~
~' ` ` :'' ,.: "'' .:' ' ` :
. :; :: ' ' ; :
. .
~Si3~3
~ounted within cradle 566 by a mounting pin 540. These ~ wnting pins
p~ it rotation of lower shoe assem~ly 564 with respect to cradle 566.
A similar ~ounting arrangement would also be prc~Tided for upper shoe
as~embly 562 Inot shcwn). This arrange~.ent pruvides the desir~ble
"floatingl' characteristic as describ~ed with referen oe to ~igure 4
~herein individual mounting pins 40 are provided for e~ch of the inserts
36, The c.~nstruction illustrated ~y Figure 12 has the primary adTantage
of being simpler t~ construct. In operation, this em~o~i~ent performs
as described in connection ~ith the earlier described en}odlmEnks.
A seventh em~odime~t according to this invention is shown by
Figures 13 and 14. This embodiment prGvides another means of finishing
the side wall portions 68 of a bearing 18 or 20. In accordance with
this emkodimen~, upper sh oe 62 and/or lower shoe 64 include elastomeric
insert 6~2 which is employed to polish the side wall portions 68. As
shcwn by Figure 13, upper shce 62 and lcwer shoe 64 are constructed
identical to that described with reference to Figure 4 except that one
or more of stone inserts 36 is rep-~ced by elastomeric insert 672.
Elastomeric insert 672 is particularly shcwn in detail by Figure 14. As
s~cw~ ~y that Figure, insert 672 is ~a~e from an elastoo~ric substance
su:~h as a urethane compo~md and includes radiused edge sur~aces 674 and
676. Insert 672 has a lateral width which exceeds that of stone inserts
36 such that as polishing shoe assembly 60 is stroked laterallyj
radiused side surfaces 674 and 676 cause ooate~ abrasive tape 30 to
contact si~e wall portions 68, thereby microfinishing that area.
Preferably, elastcmeric insert 672 is resiliently biased within the
associated shoe Ecrtion, enabl mg it to m~ve radially and laterally with
respect to the associated bearing surface. AS sho~n ~y Figure 14,
ldteral co~pliance of elasbomeric insert 672 is provided ~y e~ploying
drill rcd 678~which flexes, enabling the insert ~o ~ve laterally with
respect bo upp~r shoe ~2. Ihe :aximum extent of lateral compliance i5
limited by oontact between elastcmeric insert 672 and insert holder 682.
~adial compliance or insert 672 is provided ~ ~mploying helica~ coil
fipring 680 w~ich exerts a dswnward oompressi~e ~oroe upo~ coat~d
~2~ 3~3
abrasive tape 300 The maxi~um extent of radial displaoement is
controlled by the position o~ head 684 on drill m d 678. This
~bcdiment provides another nEans of gaining the advantages of a rigid
insert in accordance with this invention and furthex finishing the side
wall and radius portions of the bearing surface being micrDfinished.
~ hile the abcve descripticn oonstitutes the -prefeIred
enbodiments of the present invention, it will be cçprecia~ed that the
in~ention is sus oe ptible to m~dification, variati~n. and change wi~hout
departing from the proper scope and fair meaning of the acoo~pany mg
claIms,
`
, ' `': .
