Note: Descriptions are shown in the official language in which they were submitted.
IMPROVED HO~ING HEAD CONSTRUCTION
_
~ rhe present invention relates to an improved honing mandrel
construction including a construction that has opposed work engaging
hones and guides and means to to move the hones radially on the
mandrel at a different rate than the guides.
PRIOR ART
It has been common practice in the past to construct honing
heads or honing mandrels having body portions with a cen~ral pinion
gear rotatably mounted therein, and wherein a plurality, usually
~our, work engaging assemblies are mounted for radial movement on
the bodyr and each includes rack gear portions which cooperatively
angage the pinion gear and work engaging portions which engage a
work surface to be honed. Typical of such constructions are the
constructions shown in Sunnen Patent Nos. Re 18,763; 1,929,613;
1,94Ç,041; 1,982,836; 2,002,649; 2,0~0,589; 2,040t281 and
3,378,96Z. In the prior ar~ constructions, it has been the usual
practice to use a symmetrical arrangement of the work engaging
members, usually arranged in opposed pairs, wherein one of the pairs
is formed by assemblies with honing stones thereon and the other
~0 opposed assemblies have relatively non-abrasive work engaging
members or guide members thereon. In the prior art symmetrical
constructions all of ~he work engaging assemblies are moved radially
at the same rate, by the same pinion gear, and by rack gears having
idenSical teeth to advance all of the work engaging members equally
into engagement with the work surface or to equally retract all of
the work engaging members in order to facilitate installing and
removing the honing head from the work. Furthermore, in the
conventional constructions it has been the usual practice to have a
single stone member or a single guide member mounted on each of the
work engaging assemblies and to have the stone assemblies arranged
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in a diametrically opposed pair and to have the guide assemblies
arranged in a diametrically opposed pair at locations on the work
surface circumferentially spaced between the stone assemblies. To
some extent the known constructions have limited the rate at which
stock can be removed because of the limited amount of pGWer that can
be effec~ively ~pplied to the honing assemblies against the work
surface. In order to increase the cutting rate by enabling greater
power to be applied, it has been proposed to mownt two
circumferentially spaced stone members such as two vitrified honing
stones on each of the work engaging stone assemblies. Stones
mounted in this manner are currently used to hone bores which have
interruptions in them such as spllnes and keyways. These honing
devices also have two circumferentially spaced guide members on each
of the diametrically opposed guide assemblies so that such
constructions are symmetrical. In the prior art constructions the
work engaging stone and guide members have been mounted on one side
of one piece relatively rigid backing members which have rack gears
attached to their opposite sides. However, it is discovered that
such constructions generate substantial objectionable noise,
vibration and chatter, and these undesirable conditions increase
especially when operated with relatively heavy pressure placed on
the work engaging members.
The present construction overcomes these and other
disadvantages and shortcomings of the known constructions by
teaching a mandrel construction having two diametrically opposed
honing assemblies each having a pair of circumferentially spaced
stones mounted thereon, and two diametrically opposed guide
assemblies positioned circumferentially between the stone
assemblies, each guide assembly having a single work engaging member
mounted thereon, all four assemblies being driven by the same pinion
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gear. In such a construction the stones on each stone assembly are
approximately equally spaced circumferen~ially on opposite sides of
the diameter on which the opposed stone assemblies move and the work
engaging guide members may be mounted in differen~ positions
including in a forward or rearward position corresponding to the
positions of the stones on the stone assemblies or at some position
therebetween including on or approximately on the diameter on which
the opposed guide assemblies move. It is also found that it is
preferred to use an assembly con~truction for the stone and guide
assemblies that is similar to the constructions shown in
Sunnen U.S. patent 4,505,076, dated March l9, 1985
and assigned to applicants' assignee. The assembly
con~tructions shown in the pending case all include a master stone
holde~ member, usually of hardened steel and a member attached
thereto, usually of some material such as zinc to which the stones
are attached. In the case of the guide assemblies the work engaging
portions may also be of zinc attached directly to hardened steel
master holders. It has been discovered that such a construction
u31ng double ~tone and single guide assemb~ies substantially reduces
th~ noiqe, vibratlon ~nd chatter associated with previous designs
and achieves substantially improved honing accuracies and faster
?~tock removal rates.
However, certain of such designs including thos~ where the
stones and guides are located at different positions on their
respective assemblies relative to the diameter on which the
assemblies move present difficulties in maintaining all of the work
engaging members engaged with a work surface. This is especially so
lf such a device is to be used to hone over a substantial range of
diameters or over substantially different diameters, and especially
when the guide members are to be located closer to the diameter of
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the work surface or bore on which the respective assemblies move
than is true of the stone members on the stone assemblies. This is
because the single guide members located on such guide assemblies
will move radially at a somewhat faster rate than the stone members
which move on chords relative to the work surface. To overcome this
difficulty so that all six work engaging members including the four
stones and the two guides remain engaged with the work surface at
all times over a substantial range of diameters, certain forms of
the present construction require the use of rack gear teeth for the
rack gears associated with the stone assemblies that are somewhat
more widely spaced, have a greater pitch, than the teeth of the rack
gears associated with the guide assemblies, and this will be true
even though all four of the assemblies are driven by the same
centrally located pinion gear. The use of different pitch or
spacing of the gear teeth on the rack gears associated with the
stone and guide assemblies enables the use of a construction having
six work engaging members where all of the members move relative to
the work surface at the same effective rate to enable all of the
work engaging members to remain engaged at all times with the work
surface.
It is therefore a principal object of the present invention
to increase the honing rate and honing accuracy and reduce the noise
of pinion driven honing devices.
Another object is to teach the construction of a pinion
driven honing mandrel having six circumferentially spaced work
engaging portions.
Another object is to teach the use of a honing mandrel
having six work engaging members, at least some of which are mounted
on assemblies formed by mastex holders with work engaging members
attached to separate members attached to the master holders.
5~
Another object is to teach the use of relatively resilient
master holders for use under work engaging guides to provide some
flexing action therefor~
Another object is to teach the use of several different
pitch or spaced rack gear teeth for the rack gears used on the
different kinds of work engaging assemblies on a honing device
including assemblies having different construc~ions driven by a
common pinion gear so as to maintain all of the work engaging
members on the device engaged with a work surface over a relatively
wide range of operating diameters.
Another object i5 to reduce noise, vibration and chatter
a~sociated with honing devices having pinion driven work engaging
assemblies.
Another object is to teach the construction of a honing
mandrel having opposed radially movable honing assemblies each
having circumferentially spaced work engaging portions and opposed
radially movable guide assemblies each having one work engaging
guide portion, and rack gear members on each of $he honing and guide
assemblies for engaging a central pinion gear, some of the teeth on
the rack gears associa~ed with at least one set of opposed
assemblies being modified with respect to the teeth on the other set
of opposed assemblies so as to maintain the the work engaging
portions for all of the assemblies effectively on the same
cylindrical area over a predetermined range of radial movement of
the assemblies.
Another object is to provide an improved honing mandrel
with pinion driven work engaging assemblies that can be used on
existing honing machines without requiring modification thereof.
Another object is to provide an improved honing device that
can be operated by persons having relatively little skill and
training.
Another object is to modify the tooth construction on rack
gear members engageable with a pinion gear in order to change the
rate of movement of the modified rack gears for movements of the
pinion gear.
Another object is to teach the construction of a honing
mandrel having radially movable honing assemblies and guide
assemblies mounted thereon, which mandrel includes means to change
the rate of radial movement of the honing assemblies relative to the
rate of radial movement of the guide assemblies to maintain the work
engaging portions thereof approximately on the same cylindrical
surface over a predetermined range of diameters.
Another object is to reduce the effective rate of expansion
oE the work engaging guide members relative to the work engaging
stone assemblies on a honing mandrel, particularly on a mandrel used
to hone relatively fine surface finishes so as to provide the option
of maintaining the guide members under less pressure against the
work surface than the stone membersO
In the drawings which illustrate embodiments vf the
inventiOn:
FIGUR~ 1 is a cross-sectional view through a symmetrical
mandrel assembly having pinion driven work engaging members of
conventional construction;
FIGURE 2 is a cross-sectional view through another
symmekrical mandrel construction having a different form of work
engaging honing and guide members mounted thereon;
FIGURES 3 and 4 are other cross-sectional views similar to
FIGURE 2 but showing alternate embodiments of the present invention
in which use of the one work engaging guide member on the respective
guide assemblies is shown at dif.ferent alternate positions;
s~
FIGURE 5 is a cross-sectional view through a honing mandrel
constructed according to ano~her embodiment of ~he present
invention; and,
FIGURE 6 is a fragmentary cross-sectional view of the
mandrel of FIGURE 5 showing several different positions of a work
engaging honing and guide assembly in solid and in dotted outline,
the guide assembly being shown offset to overlay one o~ the honing
assemblies to illustrate movement of the work engaging members on
the device over a range of diameters.
Referring to ~he drawings more particularly by reference
numbers, number 10 in FIGURE 1 identifies a symmetrical honing
mandrel o~ conventional construction, which mandrel includes two
similar diametrically opposite honing assemblies 12 and 14 and two
similar diametrically opposite guide assemblies 16 and 18. The
honing assemblies 12 and 14 include respective honing stones 20 and
22 and respective rack gear members 24 and 26. The guide assemblies
16 and 18 include respective work engaging relatively non-abrasive
members 28 and 30 and respective rack gears 32 and 34. The rack
gears 32 and 34 on the guide assemblies may be connected to the work
engaging guide members in such a way that spring means such as the
springs 35 of FIGURE 1, urge the guide members toward the work
surface during opera~ion~ The rack gears 24, 26, 32, and 34 all
have similar rack gear teeth which cooperatively engage the teeth of
a centrally located pinion gear 36 mounted in mandrel body 38. The
honing mandrel 10 is operated by positioning it in a work surface
such as in the work surface 40. This is done when the work engaging
members 20l 22, 28, and 30 are in retracted positions. During a
honing operation the pinion gear 36 is rotated in the body 38 to
move the work engag.ing members radially outwardly into engagement
3~ with the work surface 40, and pressure is maintained on the work
3L2~
engaging members by maintaining rota~ional force on the pinion gear
36. In the usual prior art construction the stone assemblies 12 and
14 are diametrically opposite to each other and the guide assemblies
16 and 18 are likewise diametrically opposite to each other and
usually are also at right angles to the stone assemblies. Such a
symmetrical balanced construction has been used for many years. For
some purposes the four contact element construction 10, as
described, has certain shortcomings and disadvantages including
being limited as to the amount of honing pressure that can be
efficiently applied to the work engaging members and particularly to
the stones 20 and 22. This limit on the honing pressure limits the
rate at which material can be removed from a bore.
FIGURE 2 shows another balanced symmetrical mandrel
construction 42 in which two opposite hone assemblies 43 and 44 each
has two circumferentially spaced stones 46 and 48 and 50 and 52
arranged as shown, and each of the guide assemblies 54 and 56 has
two circumferentially spaced work engaging guide members 58 and 60
and 62 and 64 making for an eight work engaging element
construction. Each of the four assemblies also has at least two
20 spaced rack gears such as the respective rack gears 66, 68, 70, and
72, and all o~ the rack gears have similar teeth that mate with the
elongated teeth on pinion gear 74 rotatable in mandrel body 76. One
of the advantages of the construction 42 as compared to the
construction 10 is that by having two work engaging members on each
assembly it is able to hone bores that have interruptions in them
such as interruptions formed by splines and keyways. However, the
construction shown in FIGURE 2 also has an important disadvantage in
that it is relatively noisy in operation and this has substantially
limited its usefulness.
FIGURE 3 shows a mandrel 80 constructed according to one
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embodiment of the present invention. The mandrel 80 differs from
the mandrels 10 and 42 in several important respects including
having opposed stone assemblies 82 and 84 which are formed with
respective master holder portions 86 and 88 of some relatively hard
material such as steel and with replaceable mounting members 90 and
~92 which are of a material such as zinc for mounting on the master
'holders. Stone members 94 and 96 and 98 and 100 are attached to the
mounting members 90 and 92 as shown. The mandrel 80 al80 has
opposed guide assemblies 102 and 104 each of which also has a master
holder portion 106 and 108 and a respective work engaging guide
member 110 and 112 mounted thereon. It is important that master
holders 106 and 108 are able to flex. This can be accomplished
through a number of means, including reducing the area and~or
thickness of the master holders. In the mandrel 80 of FIGURE 3 the
guide members 110 and 112 are shown mounted in forward positions on
the respective a~semblies corresponding to the positions of the
forward stone members 94 and 98. This means that all of the
assemblies 82, 84, 102, and 104 can be equally advanced or retrac~ed
by the same pinion gear 114 which engages similar rack gears 116,
118, 120, and 122 to maintain all of ~he work engaging member on the
~&me circle or cylindrical workpiece surface for all honing
diameters. It is found that a siX element mandrel construction such
as the construction 80 operates quietly and accurately and also
enables greater load~ to be applied to the elements and especially
to the stone elements 94, 96, 98 and 100 to increase the rate of
stock removal. This in part is due to the six element
characteristic and in part due to the use of flexing ~aster holders
of the guide aRsemblies. The use of master holders on honing
as~emblies and mean~ ~or attaching the stone mounting members
thereon is disclosed in detail in Sunnen U.S. patent 4,505,076,
,~ g_
12~25~7
Serial No. 314,856.
FIGURE 4 shows another mandrel embodiment 130 which is
similar in construction to the mandrel 80 shown in FIGURE 3. The
main difference between the mandrel 130 of FIGURE 4 and the mandrel
80 o~ FIGURE 3 is in the construction of the single element guide
assemblies 132 and 134 which have their respective work engaging
guide members 136 and 138 mounted near the trailing rather than near
the leading edges thereof. This provides a somewhat more
cantilevered construction of the guide members 136 and 138 and is an
alternate to the construction of FIGURE 3 and provides the
possibility for greater movement of the guide assemblies. The
cantilever construction of FIGURE 4 enables some spring action for
the guides, thereby obviating some of the possible stiffness of the
construction of FIGURE 3 wherein the guide members are in forward
positions on the guide assemblie~. It is necessary, however, to
carefully select a proper material and design for the members that
form the guide assemblies in order to accomplish the desired degree
of flexing. The construction of FIGURE 4, like the construction of
FIGURE 3, also employs work engaging assemblies that include master
20 holders 140, 142, 144 and 146 with mounting assemblies for the work
engaging elements attached thereto as disclosed above and in the
copending Sunnen application. The work engaging guide members 136
and 138 are preferably formed of a relatively non-abrasive substance
which is characterized by sliding on a work surface rather than
abrading it. Typical materials that can be used for the guide
members include, zinc, aluminum, brass, bronze, plastic and wood.
FIGURE 5 shows a mandrel construction 150, which also has
six contact elements on it rather than four or eight as in the
constructions of FIGURES 1 and 2. The mandrel 150 has its work
engaging elements powered by a single centrally located pinion gear
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152 which drives two oppositely facing honing assemblies 154 and 156
each of which has two spaced stones 158 and 160 and 162 and 164
mounted thereon. Each of the honing assemblies 154 and 156 also has
at least two similar rack gears 166 and 168 mounted thereon. The
rack gears 166 and 168 have identical teeth which mesh with the
; elongated teeth on the pinion gear 152. The stone assemblies 154
and 156 are preferably cons~ructed having master stone holders 170
and 172 with stone support members 174 and 176 attached thereto as
shown.
The mandrel 150 also has two opposed guide assemblies 178
and 180, each of which has a respective master holder 182 and 184
connected to rack gears 186 and 188 on one side and a single work
engaging member or guide shoe 190 and 192 mounted on the opposite
side. However, even though the rack gears 166 and 168 on the honing
assemblies and the rack gears 186 and 188 on the guide assemblies
mesh with the same pinion gear 152, the teeth on the rack gears for
the honing and guide assemblies have different pitches or spacing so
that during rotation of the pinion gear 152 the stone assemblies 154
and 156 will move outwardly relative to the mandrel body 189, and
relative to the work surface 194, at a faster rate than the guide
assemblies. This is necessary, as will be explained in connection
with FIGURE 6, because of the location of the work engaging guide
m~mbers 190 and 192 on their respective guide assemblies 178 and 180
as compared to the location of the work engaging members or stones
on the respective honing assemblies 154 and 156. By having the
pitch or spacing of the teeth on the rack gears 186 and 188 for the
guide assemblies 178 and 180 closer together than the pitch or
spacing oE the teeth on the rack gears 166 and 168 for the honing
assemblies 154 and 156 means that the guide assemblies will expand
or contract, or move radially outwardly or inwardly, at a slower
~2~ 7
rate than the honing assemblies. Nevertheless, it is still
important that the masster holders in the guide assemblies are able
to flex or have some resilience as referred to in the discussion
regarding FIGURE 3. It has been found that by proper selection of
the spacing of the rack gear teeth with a six element contact
construction such as shown in FIGURE 5 and the proper Elexing of the
guide assemblies that the device also operates with substantially
less noise and chatter than conventional constructions and is able
to hone more accurate surfaces than the constructions shown in
FIGURES 1 and 20
The reason the gear tooth spacing for the rack gears lB6
and 188 associated with the guide assemblies 178 and 180 must be
less than the spacing of the gear teeth for the rack gears 166 and
168 associated with the honing assemblies 154 and 156 will be
understood by reference to FIGURE 6 wherein two of the work engaging
assemblies, one a stone assembly 154 and the other a guide assembly
178, are shown superimposed on each other and each is shown in two
different positions. In the inner or more contracted positions of
the assemblies 154 and 178 the honing stones 158 and 160 are shown
positioned extending to the workpiece surface 194 which is shown as
being a circle of relative]y small diameter such as three inches.
In this position the guide member 190 on the guide assembly 178 is
also shown located on the same circular workpiece surface 194. If
the rack gears 166 and 186 for the honing and guide assemblies had
identical teeth, the stones 158 and 160, which do not move on a
diameter when expanding and contracting as does the guide member
190, but move on chords of the expanding circle, are not able to
keep up with the diameter established by the guide members during
expansion. This means that the stones would move progressively
further out of engagement with the work surface as the work surface
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expands, and soon only the guide member 190 (and 192) would be in
engagement therewith, an obviously totally unsatisfactory
condition. To compensate for this and to maintain the stones
engaged with the work, the teeth on one or on both sets of rack
gears 166, 168, 186 and 188 are modified 50 that all of the work
engaging elements will remain approximately on the same circular
work surface over a range of radial movement during rotation of the
pinion gear 152. In the preferred situation, the teeth on the rack
gears 166 and 168 for the stone assemblies 154 and 156 are
constructed to be somewhat further apart than the rack gear teeth on
the rack gears 186 and 188 associated with the guide assemblies 178
and 180. This is done so that for a given rotation of the pinion
gear 152, the honing assemblies 154 and 156 will move further than
the guide assemblies 178 and 180~ This is necessary because the
stones 158, 160, 162 and 164 are mounted for movement on chords of
the work surface, as aforesaid, and therefore the stone assemblies
on which they are mounted must move further radially, i.e., at a
~aster rate, than the guide assemblies 178 and 180 which have their
work engaginy guide members moving on a diameter of the work surface
in order to maintain the stones 158, 160, 162 and 164 on the same
cylindrical surface as the guide members 190 and 192 during
expansion. The same principles apply during contraction.
In FIGURE 6 the leads A, B, C, D and D' are included to
represent distances that can be used to mathematically explain the
error that needs to be corrected by modifying the rack gear teeth in
the manner indicated so that movements of the stones 158, 160, 162
and 164 relative to the work surface keep pace with movements of the
guide members 190 and 192 in going from one honing dia~eter, such as
from a three inch honing diameter, to a four inch honing diameter.
The distance from the center of the left stone 158 to the center of
5~7
the right stone 160 has been selected for the example to be 1 3/4
inches. It is also assumed that the stones 158 and 160 are
infinitely thin so that they touch the bore or workpiece surface at
their cen~ers only when the stone assembly 154 is in its vaeious
operating positions~ In an actual si~uation this will generally not
be the case. In the example shown:
A = 1.500",
B = 2.000", and
C = 0.875"
Therefore:
D = B-A = 0.500", and
D' = ~ ~
=~ 2~o~o2 - 0.8752 - ~ 1.5002 - oO~752
= 1.7g84 -1.2183 = 0.5801"
The radial error is the space between the center of the
stone 160 ~or 158) and the outer circle or workpiece assuming all
assemblies have rack gears with identical teeth. This difference is
the difference between D' and D, or D' - D = 0.5801 -0.5000 =
20 0.0801". The radial error of .0801'l is the error that occurs if the
stone assembly 154 is moved one half inch radially, that is, if the
center point between the stones 158 and 160 moves one half inch
radially outwardly, while the guide member or shoe 190 is also
moving radially outwardly one half inch but on a diameter of the
workpiece surface. It can be seen that when the assembly 154 has
moved one half inch radially outwardly the stones 158 and 160 will
be spaced .0801" from the outer circle or work surface 196 while the
guide member 190 extends to the outer circle 196.
In the table which follows the lefthand column is in equal
0.1" increments oE bore diameter in the range from three to four
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inches, and the r.ighthand column shows the amount of radial error as
defined above for an infinitely thin honing sl:one mounted on an
assembly such as the assemblies 154 and 156 when the assembly moves
radially outwardly by one half of the increments in the lefthand
column.
DIAMETER (.10 inch-increments RADIAL ERROR OF EACH STONE
3,000 .0000
3~1~0 .0111
3.200 .0212
10 3.300 .0305
3.400 .0392
3.500 .0472
3.600 .0547
3.700 .0616
3.800 .0682
3.~00 .0743
.000 .0801
It can be seen that the radial error does not change in a linear
relationship with rad.ial movements of the honing assemblies, and
that after the stone assembly 154 has moved radially one half inch
the total radial error will be .0801 inch for each stone. Because
of this, some means must be provided to move the honing assemblies
154 and 156 at a faster rate radially than the guide assemblies 178
and 180 if all of the assemblies are to remain on the work surface
at all times and in all positions within the range thereof. This
can be accomplished, as indicated, by increasing the spacing between
the gear teeth on the rack gears 166 and 168 associated with the
stone assemblies 154 and 156 relative to the spacing of the rack
gear teeth on the rack gears 186 and 188 associated with the guide
assemblies, or by decreasing the spacing between the rack gear teeth
on the guide assemblies relative to the spacing between the rack
gear teeth associated with the stone assemblies or by a combination
of both of these. Eor a given pinion gear 152 there is a certain
ideal spacing for the rack gear teeth. Thus, if the rack gear tooth
spacing is increased or decreased ~omewhat from the ideal, some
adverse effect from ~he most desired operating condition will take
place but within limits this can be tolerated. To ameliorate this
condition involves a compromise between the spacing of the teeth on
the honing and guide assemblies. The compromise should take into
account that the spacings should not be so such as to cause
excessive binding between any of the rack gear teeth and the teeth
oE the pinion. In an actual construction, it is usually preferred
to achieve the desired result by adjusting the tooth spacing on both
sets of the rack gears. It is also possible to vary the pitch of
the teeth on the individual rack gears in order to more fully
compensate for the non-linearity of the radial error.
Modifying the teeth on the rack gear members in the manners
indicated provides a very satisfactory operating condition for a
honing mandrel that has six work engaging members on it where some
of the members move on or near a diameter and others move on chords
of the expanding work surface, and it has been found that mandrels
so constructed hone to better accuracy, operate relatively quietly
and with less vibration and chatter, and produce a better wear
condition for the guide members. However, as indicated, there are
some limitation as to the range of diameters over which a honing
mandrel such as described herein can operate~ It has been found
that a typical mandrel construction in a midrange of size can
operate over a range of diameters from about an inch to about an
inch and a half very satisfactorily, but this will vary as the
mandrel size is increased or decreased.
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~L2~L~S~t7
Thus there has been shown and described a mandrel
construction having six circumferentially spaced work engaging
members including two multi-element honing assemblies and two single
element guide assemblies arranged in opposed work engaging
relationship, which mandrel fulfills all of the objects and
advantages sought therefor. It ~ill be apparent to those skilled in
the art, however, that many changes, modifications, variations and
other uses and applications for the subject mandrel are possible,
and all such changes, modifications, variations and other uses and
applications which do not depart from the spirit and scope o~ the
invention are deemed to be covered by the invention which is limited
only by the c~aims which follows.
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