Note: Descriptions are shown in the official language in which they were submitted.
CA 02076264 2002-11-07
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ABRASIVE FILAMENT HONING TOOL AND METHOD OF
MAKING AND USING SAME
DISCLOSURE
This invention relates generally as indicated to an abrasive filament honing
tool including
a method of making and using the same, and more particularly to a honing tool
including a
bundle of discrete filaments which affords better chip clearance and surface
finish.
BACKGROUND OF THE INVENTION
A honing machine is commonly used for finishing a bore in a workpiece. When a
workpiece, such as a cylinder, is bored out, the boring tool leaves V-shaped
grooves in the
surface of the cylinder wall, much like those on a phonograph record. The
sharp peaks of these
ridges have to be rounded off by finish honing the bore. The typical honing
machine uses a set
of honing tools spaced around a machine body and fed progressively outwardly
into a generally
cylindrical internal wall of a workpiece while the machine body is
simultaneously rotated within
and reciprocated along the workpiece. In this manner, the working face of each
honing tool is
forced into engagement with the wall under selected honing pressure to abrade
and finish the
wall.
The specific honing tools usually include a honing element secured in a
holder. This
honing element is commonly a one-giece element, and in fact is usually
referred to as a "honing
stone". Examples of such honing elements are described in prior U.S. Patents
3,829,299;
2,980,524; 3,352,067; 3,154,893; 3,132,451; 4,528,776; 4,555,875; 3,972,161;
and3,918,218.
In the latter two patents, a plurality of cutting filaments are embedded in a
matrix, however the
resulting honing element is nonetheless a one-piece relatively rigid element.
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In the course of honing, it is common for chips or burrs to be
knocked loose from the cylinder. Because of the solid structure of most
honing elements, no clearance is present between the wall and the working
face of the honing element. These chips may wedge themselves between the
working face of the honing element and the wall. Although a liquid is '
usually flushed through the bore during honing, such has little effect on the
wedged chips. Eventually, either the wall or the honing element must give,
resulting in the damage of a honing element or stone and/or the scarring of
a bore of what may be an expensive cylinder.
Also many bores such as engine bores have lateral ports.
Conventional honing stones or tools cannot radius or finish the edges of such
ports. Thus a need remains for an improved honing tool providing improved
surface finish.
SU1IMARY OF THE INVENTION
The present invention provides a honing tool which affords better
chip clearance and an improved surface finish by using a bundle of discrete
filaments as its honing element. The honing tool includes a cup element in
the form of a rectangular holder having a bottom interior surface, a bundle
of closely packed discrete generally parallel filaments secured in the holder,
and a thin layer of instant adhesive securing substantially all of the
filaments at one end face of the bundle to the bottom interior surface of the
holder.
To make such a honing tool, a measured bundle of uniformly
closely packed nonwoven, generally parallel discrete filaments is formed. A
cup element or holder is supported and a measured amount of liquid adhesive
is placed in the bottom interior of the cup element so that a thin layer of
such adhesive completely covers the bottom of the interior of the cup
element. The bundle is then promptly driven into the cup element so that
all of the filaments at one end of the bundle are in contact with the
adhesive prior to the curing of the adhesive. 'fhe adhesive is then cured
whereby the one end face of the bundle is secured to the bottom interior of
the cup element or holder.
In one embodiment a bundle of relatively short filaments is cut
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to length and formed before being driven into the holder and the adhesive.
In another embodiment a bundle of longer filaments is driven through a
shaping die into the holder and adhesive and then cut to length.
To the accomplishment of the foregoing and related ends the
invention, then, comprises the features hereinafter fully described and
particularly pointed out in the claims, the following description and the
annexed drawings setting forth in detail certain illustrative embodiments of
the invention, these being indicative, however, of but a few of the various
ways in which the principles of the invention may be employed. .
BRIEF DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
Figure 1 is a fragmentary side elevation of an abrasive filament
honing tool according to the present invention employed in a honing
machine, parts of the machine and the associated workpiece being shown in
cross-section;
Figure 2 is a front view of a honing tool which employs filaments
of a rectangular transverse cross-section;
Figure 3 is a rear view of the honing tool but showing a modified
holder;
Figure 4 is a top view of the honing tool of Figure 2;
Figure 5 is a top view of a honing tool which uses filaments of a
circular transverse cross-section;
Figure G is a front view of the honing tool of Figure 5;
Figure 7 is an enlarged transverse section of a rectangular
filam ent;
Figure 8 is an enlarged transverse section of a circular filament;
Figure 9 is a top view of a cylindrical bundle of filaments;
Figure 10 is a top view of the bundle of Figure 9 after being
transformed into an oblong bundle;
Figure 11 is a front view of a support jig useful in making a
honing tool according to the present invention;
Figure 12 is a side view of the support jig of Figure 11 and also a
pusher plate;
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Figure 13 illustrates an alternative method of assembling a honing tool
according to the
present invention which employs a shaping die and longer filaments;
Figure 14 is a view of the die as seen along line 14-14 in Figure 13; and
Figure 15 is a side view of an assembly similar to that of Figure 12 but using
another type
of pusher plate to impart a radius to the tool face.
DETAILED DESCRIPTION OF THF PREFERRED EMBODIMENTS
Referring now to the drawings in detail and initially to Figure 1, a honing
tool 20
according to the present invention is shown installed in a typical honing
machine 22. The honing
machine 22 uses a set of honing tools spaced around a machine body 24 and fed
progressively
outwardly into a generally cylindrical internal wall 26 of the bore 28 of a
workpiece 30. The
tool body 24 includes a wedge cone 32 and a follower 33 for each honing tool
20. The honing
tools 20 and followers 33 are assembled to the machine body 24 by garter
springs 34. In
operation, the machine body 24 is moved axially into the bore 28 as indicated
schematically by
;grow 35. The wedge cones 32 are reciprocated as shown by arrow 36 to radially
expand and
contract the honing tools 20, thereby maintaining the outer working face of
each honing tool 20
i.n engagement with the wall 26 under selected honing pressure.
Simultaneously, the machine
body 24 is rotated within the bore 28 as indicated by arrow 37 thereby
abrading and finishing
the wall 26.
Referring now additionally to Figures 2-6, the honing tool 20 is shown in
detail. The
honing tool 20 comprises a relatively short bundle 40 of plastic abrasive
loaded filaments or
monofilaments and a rectangular cup element 42 which is an integral part of a
holder 44. The
bundle 40 is bonded to the bottom surface or wall 45 of the cup element 42 by
a liquid instant
adhesive seen at 46.
The holder 44 is roughly rectangular in section its length being at least
twice its width.
It may be formed of metal or of a non-brittle plastic such as nylon. The
holder 44 includes a flat
bottom wall 50, two side walls 52, two end walls 54 and a top wall 56. The
side walls 52 are
generally straight and connect the top wall 56 to the bottom wall 50. The end
walls 54 are
curved and include outer straight section 60 adjacent to the bottom surface,
an inwardly and
downwardly sloped section 62, adjacent straight section 60 and an inner
straight section 64
CA 02076264 2002-11-07
adjacent the section 62. The sections 62 and 64 together form an inner corner
66, which may
serve as resting point for a garter spring, such as the garter spring 34 shown
in Figure 1.
The top wall 56 is the same width but is not as long as the bottom wall 50. As
indicated
above, the cup element 42 is an integral part of the holder 44. Specifically,
the cup element
extends downward from the top wall 56 extending a substantial portion of the
height of the
holder, but terminating short of the bottom wall 50. The cup element 42 has
two flat sides 70
connected by two rounded corners 72, the sides and corners together forming an
oblong opening
'73. One side wall 52 includes two spacers 76. In the holder shown in Figure
3, the opposite
side wall 52 may include a slot 78 through which instant adhesive in a gel
form may be injected.
The bundle 40 may comprise plastic abrasive loaded filaments or monofilaments
80
having a rectangular transverse cross-section as shown in Figure 4. An
enlarged view of the
transverse cross-section is shown in Figure 7 and, as shown, the filament has
a width 82 and a
thickness 84.
Typically, the rectangular filament 80 at its major flat face may be
approximately 0.090
inch wide and about 0.045 inch thick. Somewhat wider rectangular filaments may
be employed
having major flat faces up to three to four times the thickness of the
filament. The width is
preferably not greater than four times the thickness, more preferably the
width is not greater than
three times the thickness and still more preferably the width is approximately
twice the thickness.
'fhe length of the monofilament, projecting from the holder, is at least ten
times greater than the
width, and more preferably at least twenty times greater than the width. The
projection from the
holder is nonetheless relatively short.
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The monofilament may be extruded plastic impregnated through-
out uniformly with an abrasive mineral such as aluminum oxide or silicon
carbide. Other more exotic abrasive minerals may readily be employed such
as polycrystalline diamond. Also, the abrasive grit size may be varied from
coarse to fine powders for extra fine polishing and highlighting effects on
work parts.
The plastic material preferably has a Young's modules greater
than 0.10 at 106 psi and more preferably greater than 0.40 at 106 psi.
Young's modules is defined as the amount of force a material can undergo
without permanent deformation when the force is removed. This is a
measure of elasticity or the relationship of stress over strain.
The preferred plastic for extrusion of the monofilament working
element is nylon. The preferred nylon is 6/12 nylon. Nylons are long-chain
partially crystalline synthetic polymeric amides (polyamides). Polyamides
are formed primarily by condensation reactions of diamines and dibasic
acids or a material having both the acid and amine functionality.
Nylons have excellent resistance to oils and greases, in solvents
and bases. Nylons have superior performance against repeated impact,
abrasion, and fatigue. Other physical properties include a low coefficient of
friction, high tensile strength, and toughness. Useful mechanical properties
of nylon include strength, stiffness and toughness. In general, the greater
the amount of amide linkages, the greater the stiffness, the higher the
tensile strength, and the higher the melting point. Several useful forms of
nylon are available and include:
A. Nylon 6/6 synthesized from hexamethylenediamine ~H~SD)
and adipie acid;
B. Nylon 6/9 synthesized from HMD and azelaic acid;
C. Nylon 6/10 synthesized from HMD and sebacie acid;
D. Nylon 6/12 synthesized from HMD and dodeeanedioie acid;
E. Nylon 6 synthesized from polycaprolactam;
F. Nylon 11 synthesized from 11-aminoundecanoie acid;
G. Nylon 12 synthesized from polyaurolactam; and others.
Nylons useful In the present invention have a Young's modules
greater than .05, preferably greater than .1 and preferably greater than .2.
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The preferred nylon is nylon 6/12. The physical properties of
nylon 6/12 include a melting point of 212°C, a dry yield strength at
103 psi
of 8.8 (7.4 at 506 RH), a dry flexural modules of 295 (180 at 50°x6
RH).
Nylon has a higher Young°s modules (0.40 at 106 pal) than rubber (0.01
at 106
psi), which demonstrates the greater stiffness of nylon over an elastomer
such as rubber, for example. As an example, a working element according
to the present invention several feet long when held horizontally at one end
at room temperature would show little or minimal deflection at the opposite
end.
Nylon is partially crystalline, hence has little or no rubbery
regions during deformation. The degree of crystallinity determines the
stiffness and yield point. As the crystallinity decreases the stiffness and
yield stress decreases. Rubber, on the other hand, is an amorphous polymer
and its molecular straightening leads to a low modules of elasticity.
Nylon has a tensile strength of over 8000 pal, rubber has a tensile
strength of 300 pal. Nylon exhibits 2506 breakage during elongation, rubber
exhibits 12006. Nylon has fair moisture resistance, yet rubber absorbs a
large amount of water. Nylon has excellent resistance to oil and greases
and other organic solvents, rubber has extremely poor resistance. Nylon
retains its properties from -75°F to 230°F, while rubber has a
narrow range
around room temperature. Nylon's increased strength, ~esistanee to
moisture and solvents, and its wide usable temperature range make it the
preferred material for this construction.
Another type of polyamide useful in the present invention
include other condensation products with recurring amide groups along the
polymer chain, such as aramids. Aramids are defined as a manufactured
fiber in which at least 85~ of the amide (-C(0)-N(H)-) linkages are
attached directly to two aromatic hydrocarbon rings. This is distinguished
from nylon which has less than 8596 of the amide linkages attached directly
to the two aromatic rings.
The plastic material may also be aramid fibers which are
characterized by high tensile strength and high modules. Two Aramids that
may be useful in the present invention include fiber formed from the
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polymerization of p-phenylenediamine with terephthaloyl chloride and a less
stiff polymer formed from the polymerization of m-phenylenediamine and
isophthaloyl chloride.
Aramids demonstrate a very strong resistance to solvents.
Aramids have tensile strengths at 260°C that are exhibited by textile
fibers
at room temperature.
Also, some thermoset polymers are useful. Polyesters are an
example and are long chain synthetic polymers with at least SS~b of a
dihydric alcohol ester (HOROH) and terephthalie acid
(p-HOOCC6H4COOH). Polyester fibers contain both crystalline and non-
erystalline regions. Polyesters are resistant to solvents and demonstrate a
breaking elongation of 19 to 406.
Polyimides are polymers containing (CONHCO) and are also
useful in the present invention. High temperature stability (up to ?00~') and
high tensile strength of 13,600 psi make polyirnides useful as binders in
abrasive wheels.
Alternatively, the bundle 40 may comprise filaments 86 having a
circular transverse cross-section as is shown in Figure 5. An enlargement of
the transverse cross-section of this filament is shown in Figure 8. The
length of monofilament 86, projecting from the hmlder, is at least ten times
greater than the diameter of the cross-section, and more preferably at least
twenty times greater than its diameter. Again the length of the projection
is nonetheless relatively short. The filament 86 may be made of the same
materials discussed above in reference to filament 80.
Turning now to Figures 9-13, various steps in making a honing
tool 10 are illustrated. Although the method is discussed in reference to
rectangular filaments 80, a similar method would be used with circular in
section filaments 86 and for that mattec filaments of other shapes. In
making the tool, first a plurality of discrete filaments 80 cut to the same
relatively short length are preassembled into a cylindrical bundle 90. After
the bundle 90 is preassembled, it may be temporarily held in shape by an
elastic or rubber band 92. (See Pigure 9). The holder 44 is supported in a
stationary jig 94, which includes two almost symmetrical parts 96 and 98.
The parts 96 and 98 when brought together form a rectangular chamber 100
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surrounding the holder 44. Specifically, the chamber 100 surrounds the
bottom wall 50, the side walls 52, and also the outer edges of the top wall
56, while leaving the cup element 42 exposed. Part 96 has extra clearance
to accommodate the spacers 76. The parts also form a funne1102 above the
chamber 100. (See Figure 12).
A metered amount of liquid adhesive 46 is then placed in the
bottom of the cup element 42. The adhesive may be inserted through the
top of the cup element 42. Alternatively, it may be injected through the
slot 78 if the holder of Figure 3 is employed. As a liquid instant adhesive,
it
is preferred to employ a cyanoacrylate of low viscosity or high fluidity. It
is
important that when the adhesive is applied to the bottom wall 45 of the cup
element 42 that it uniformly cover that wall.
Useful with the present invention are alkyl cyanoacrylates
having the formula:
~N
CH2 _
BOOR
R - CHg
C2H5
C3H7 etc.
A preferred cyanoaerylate adhesive is an alkoxy alkyl cyano-
acrylate having the formula:
N
CH2
OOR
K - CHg - O - C2H5
C2H5 _ O _ C2H5
Suitable adhesives are available from Lootite Corporation of
Newington, Connecticut under the trademark SUPERBONDER R 495,
surface insensitive 454 gel, or the trademark BLACK MAX.
SUPERBONDER is a registered trademark of Loctite Corporation. BLACK
MAX is also a trademark of Loetite Corporation.
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The cylindrical bundle 90 may be formed into an oblong shape,
manually or otherwise, roughly matching the contour of the cup element 42.
(See Figure 10). Because the band 92 is elastic or rubber, it may remain on
the bundle during this transformation. The transformed oblong bundle 90 of
rnonofilaments 80 is then placed within the funnel 102 and driven down-
wardly by a pusher plate 106 driven by a suitable linear actuator such as seen
schematically by arrow 110. In this manner, the end face 112 of the bundle 90
is driven into the liquid adhesive 45 which quickly sets bonding each
monofilament 80 of the bundle 90 to the bottom wail 45 of the element 42.
Because of the low viscosity of the adhesive 45 some of the adhesive will
penetrate between the monofilaments 80 at the end face 112 bonding the
inner end of each monofilament to adjacent monofilaments. The opposite
end 114 of the bundle then may become the working face of the tool without
subsequent trimming. The flat working surface 116 of the pusher plate 106
results in a flat working face of the tool.
A suitable pressure limit may retract the pressure plate 106. The
completed honing tool may then be removed from the support jig 94, and
installed, for example, on honing msehine 22.
Instead of using a pusher plate with a flat working surface, a
pusher plate 120 having a convex working surface 122 may be used. (See
Figure 15). When such a pusher plate is used to drive the bundle 90 into the
liquid adhesive 45, the resulting end face 124 of the tool is provided with a
radius which may correspond to the radius of the bore being honed.
Monofilaments 80 of the same length are used, the curved end face 124 being
the result of the bonding pattern of the filaments 80 to the bottom of the
cup element 42.
The method of manufacture discussed above permits the
formation of a honing tool 20 with a finished tool face without a final costly
trimming operation. Obviously, the more exotic the abrasive material
employed such as polyerysta111ne diamond, the more costly will be the
trimming operation. Without the trimming operation there is no waste of
such expensive fill matecials. With the present invention the materials are
cut one time and pressed into the cup element. Any unevenness is buried
inside the cup element and is held firmly by the instant adhesive.
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Another method of making a honing tool according to the present
invention is shown in Figure 13. In this method, a bundle 130 of mono-
filaments 132 is preassembled. The monofilaments 132 are preferably of the
same length, but are substantially longer than the monofilaments 80 used in
the methods described above. For example, for making a tool with an inch
or so trim, monofilaments several feet long may be used. The holder 44 is
supported in a jig 134, which is similar to the jig 94 except that instead of
being stationary, the jig 134 may be moved up and down by a suitable linear
actuator as seen schematically by arrow 136.
An intermediate portion of the bundle 130 is inserted through a
die 140 which has a hollow center 142 of a contour matching the cup element
42. In this manner, the monofilaments 132 may be neatly and compactly
aligned. The bundle 130 is then positioned so that its lower end fees 144 is
aligned with the cup element 42:
A metered amount of liquid adhesive 45 is then placed in the
bottom of the cup element 42, either through the top opening or side slot 78.
The jig 134 may be moved up and fixed. Almost simultaneously, a pusher
plate 146 is indexed downward by a suitable linear actuator illustrated '
schematically as arrow 150 to cause the end face 144 to engage the adhesive.
The liquid adhesive 45 quickly sets bonding the end face 144 to the bottom
wall of the cup element 42. The bundle 130 is then cut at a height indicated
by cutting blades 152 in Figure 13 adjacent the die. This cut end then
becomes the working face of the honing tool.
1t can now be appreciated that there is provided a simple and
easily constructed abrasive filament honing tool. Because the honing
element is composed of discrete filaments, the tool affords better chip
clearance and surface finish.
Although the invention has been shown and described with
respect to certain preferred embodiments, it is obvious that equivalent
alterations and modifications will occur to others skilled in the art upon the
reading arid understanding of this specification. The present invention
includes all such equivalent alterations and modifications, and is limited
only by the scope of the following claims.
