Note: Descriptions are shown in the official language in which they were submitted.
: ~ ; BACRGROU~D OF TH~ INVENTION ~ :
¦. ~his invention relates to a'new and improved power
. ¦ steering-valve and more speci~ically to a valve sleeve having
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; ~ I relatiYely short internal grooves which may b~ formea by a
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.rotating cutting tool, such as an end mill.
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It has been previously suggested that a plurality of
axially e~tending in~ernal grooves could be sequentially
formed in a hollow cylindrical valve sleeve by using a
rotating cutting tool such as çnd mill. The en~ mill is usea
to form long grooves which extend throughout most of the axial
length of the valve sleeve~ Due to the relatively lon~ length
of the axiall~ extending inner groovesr they must be formed
. one at a time with a single end mill. A complete di sclosure
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of this previously suggested manner of forming grooves in a
valve sleeve with an end mill is set forth in Canadian Patent
Application Serial No. 323,3~, filed March 13, 1979 by Richard
W. Dymond and entitled "Power Steeringr Valve And Method of
Making The Same" (Docket No. TRW(M)7257).
SUMMARY 0~ r~lE PRESENT INVENTION
The present invention provicles a power steering apparatus
comprising hydraulic motor means for assisting in operation of a
vehicle steering gear. The apparatus further comprises a housing
having a plurality of passages connected in comm~mication with a
source o fluid and the hydraulic motor means, and improved valve
means disposed in the housing for use in controlling fluid 10w
through the passage in the housing to thereby control operation
of the hydraulic motor means. The valve means includes an inner
valve member and a Yalve sleeve circumscribing the inner valve
member. The hollow valYe sleeYe includes an array of outer
grooves each which opens outwardly and extends around the sleeve.
The array of outer grooves includes a first outer groove disposed
in a central portion of the valve sleeve and connected in 1uid
communication with a first one of the passages on the housing, a
second outer groove disposed to one axial side of the central
portion of the valYe sleeYe and the first outer groo~e and connected
in fluid communication wi-th a second one of said passages in
the housing, and a third outer groove disposed to another axial
side of the central portion of the valve sleeve and the first
groove and connected in fluid communication with a third one of
the passages in the housing. The valve sleeve further includes a
plurality of axially extending grooves on the inside of the valYe
sleeve. A first one of the plurality o axially extending
grooves has a first end surface disposed in the central portion
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of the valve sleeve adjacent to the first outer groove and a Eirst
main section which extends axlally away from the first end surface
in a first axial direction to a second end surface disposed to the
one axial side of the central portion of the valve sleeve and
adjacent to the second outer groove. A second one of the
plurality of axially extending grooves has a third end surEace
disposed in the central portion of the valve sleeve adjacent to
the first outer yroove and a second main section which extends
axially away from the third end surface in a second axial
direction which is opposite from said first axial direction to a
fourth end surface disposed to the other axial side of the central
portion of the sleeve and adjacent to the third outer groove.
Due to the Eact that the internal grooves extend in opposite
axial directions from a central portion of the valve sleeve, at
least some of the internal grooves are axially offset relative to
other internal grooves. Since each of the internal grooves
extends in only one axial direction from a central portion of the
valve sleeve~ the machining time required to form the groove is
reduced.
A method for manufacturing the improved valve sleeve of the
invention is provided. The method includes the steps of
providing a hollow valve sleeve, rotating first and second
cutting tools about their central axes, engaging the inside of
the hollow valve sleeve with the outer end portions of the
rotating cutting tools at locations spaced apart from axial end
portions of the valve sleeve. The first and second axially
extending grooves having closed end portions inside the valve
sleeve are formed simul~aneously by moving the first and second
rotating cutting tools and valve sleeve relative to each other
while maintaining the rotating cutting tools in engagement with
the inside of the valve sleeve. Subsequently, the valve sleeve
and cutting tools are moved out of engagement with each other.
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Accordingly, it is an object oE this invention to provide
a new and improved valve sleeve havin~ internal grooves which
extend in opposite axial directions from a central portion of
the valve sleeve.
Another object of this invention is to provide a new and
improved method o~ forming a valve sleeve and wherein a pair . .
of rotating cutting tools are simultaneously utilized to forlQ ~:
a pair of axially extending grooves inside a valve sleeve. . .:. .
Another object of this invention is to provide a new and
improved valve sleeve having an array oE annular grooves
formed in the outside of the valve sleeve and axially .
extending grooves formed inside the valve sleeve and wherein
one of the inner grooves extends axially in a first dLrection .
from a central portion of the array of annular grooves and
another inner groove extends in the opposite direction from :
the cen~ral portion of the array of annular grooves~;
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BRIEF DESCRIPTION OF THE DRAWINGS
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. The foregoing and other objects and features of the ~.
.~ present.invention will become more apparent upon a
consideration of the following description taken in connection -
with the accompanying drawings wherein:
Fi~. l is a fragmenta~y sectional view o~ a rack and .
pinion power steering apparatus having a control valve
. ¦assembly constructed in accordance with the present invention;
¦ Fig. 2 is an enlarged fragmentary view further
lillustrating the construction of the valve assembly;
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Fig. 3 is a still further enlaryed secti.onal view
¦illustrating a valve sleeve constructed in accordance with the
present invention and the relat:ionship hetween the valve
sleeve and a pa.ir o~ rotating cutting tools which are u~ilized
to simultaneously Eorm a pair of grooves in the val.ve sleeve;
and
Fig. 4 is a schematic illustrati.on depicting the
relationship between axially extending grooves Eormed in the '
valve sleeve and annula~ grooves formed on the outside of the
valve sleeve, the valve sleeve being shown in a laid out plan
view. ,
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.. DESCRIPTION OF SPECIFIC PRE~RED. .
.EMBODIMEN'rS OF THE IN~ENTION :
A power steering~apparatus 20 (see Fig. 1) is connected
with a pair of steerable vehicle wheels in a known manner by ~ :
a pair of tie rods~ one of which is indicatéd at 22 in Fig.
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. 1. The power steering apparatus 20 includes a power steering
motor 26 having a circular piston 28 disposed in a motor
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.. cylinder 30. The circular piston 2~ is fixedly connected with
. generally cylindrical rack bar 32 upon which a longitudinally ~ .
. extenaing array oE rack gear teeth 34 are disposea. Opposite
ends of the rack bar 32 are connected with the tie rods by .
ball joints. Accordingly, the tie rod 22 is connected with :
the rack bar 32 by a ball joint 36. :
A va]ve assembly 42 is provided to control the operation ~
of the power steering motor 26. The valve assembly 42 .
includes an input section 46 which is connected with a
. rut~table vehicle steerin~ wheel ~not shown) and is integrally
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~ormed with an inner valve member ~8. Upon rot;ltion oE the
input section 46, the ~alve assembl~ ~2 directs Eluid under
pressure from a conduit 50 to either a conduit 52 or a conduit
54 connected with the power steering motor 26. The other one
of the two conduits 52 or 54 is exhausted to a arain or fluid
return conduit 58 through the valve assembly ~2. ~he
relatively high fluid pressure conducted to the power steering
motor 26 results in movement of the piston 28 and rack gear 34 :
to effect turning movement of the vehicle wheels and rotation
of a pinion gear 60.
The pinion gear 60 cooperates with the valve assembl~ 42
to return it to an unactuated condition when the steerable
wheels have been turned to an extent correspondiny to the
extent of rotation of the input section 46. I~ should be
noted that although the rack bar is primarily moved under the
influence of forces applied by the power steering motor 26,
drive forces can also be transmitted directly to the rack bar
by the pinion gear 60 in a known manner. Since the general
construction and mode of operation o~ the power steerlng `
apparatus 20 is well known, it will not be further described
herein to avoid prolixity of description.
The valve assembly 42 (see Fig~ 2) includes a generally
cylindrical inner valve member 48 which is integrally ~ormed
with the input section 46, A torsion spring or rod 66
connects the inner valve member 48 with the pinion gear 60 in
such a manner as to enable the inner valve member 48 to rotate -
through a limited distance before the pinion gear 60 is
rotated. This limited rotation of the valve member 48 is
effective to move the valve member relative to ~ housing 70
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and valve sleeve 72 Erom an ~nactuated condition to an
actuatea condition Actuation of the v~Lve assembly 42 is
e~fective to direct fl~lid pressure from a housin~ inlet
Ipassage 76 connected with the conduit 50 to a housiny passage
j77 connected in fluid communication with the motor conduit
154. At the same time, the motor conduit 52 is connected ~7ith
¦drain conduit through housing passages 82 and ~ This
¦results in the power steering motor being operated to turn the
¦steerable vehicle wheels.
When the valve assembly ~2 is in the unactuated
condition, fluid from conduit 50 is conducted through the
housing passage 76 to an annular groove 80 dispose~ in a
central portion of the valve sleeve 72. The annular groove 80
is connected with a pair o~ longitudinally extending pressure
chambers or passages (not shown) disposed between the inner
valve member 48 and the valve sleeve 7~ by a pair of raaially
extending passages (not shown).
When the valve assembly 42 is in the unactuated
conditiont the fluid in the longitudinally extending pressure
chambers flows to a pair of diametrically opposed
longitudinally extending outlet chambers (not shown~ formed
between the valve sleeve 72 and valve member 48. This fluid
flow between the longitudinally extenaing inlet and outle~
chambers i5 conducted through a plurality of axially extending
grooves 100, 102, 104, and 106 (see Fig. 4) formed in the
one-piece valve sleeve 72. The grooves 100, 102, ]04, and 106
all have arcuate bottom surfaces which promo~es a laminar flow
of fluid through the grooves~ The laminar fluid flow tends to
~reduce valve noise.
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The axially ext:entli.n-J grooves 102 and 106 are connected
jwith an annular ~roove 11~ forrned on the outside o~ the valve
¦sleeve at one axi~l end portion oE the annular array oE
grooves by a pa;r o~ pa~sages 116 and 118 (see Fiys. 2 and 4).
I The annular groove 11~ is connected in fluid communication
¦with the motor conduit 54 through the housing passage 77.
¦ The axially extending inner grooves 100 and 104 are
connected with an annular outer groove 122 by valve passages
124 and 126. The annular groove 122 is connected in fluid
communication with the motor conduit. 52 through the housing .
passage 82. .
. Upon actuation oE the valve assembly 42 to e~fec~ a turn,
the inner valve member 4~ restricts fluid flow from the
. pressure chambers to the axially extending grooves 100 a~d
. 104. At the same time, the inner valve member 48 increases
: the fluid col~munication between the grooves 100 and 104 and .
the relatively low pressure fluid outlet chambers. :,
. While the fluid flow to the grooves 100 and 104 from the
~ . power steering pump is being decreased, ~luid flow to the
.. :' axially extending grooves 102 and 106 is being increased. The '
. axially extending passages 102 and 106 are,connected with an
: . axially outer annular groove 114 formed on the valve sleeve,7~
by the passages 116 and.118. The annular groove 114 is ' ' : .,
connected in ~luid communication with the motor conduit 54 .
through the housing passage 77. ~ .~ :
¦ The axially extending grooves 100 and 104 are connected
with the annular groove 122 (Fig. 2) by passages 124 and 126. :
' This enables the low pressure fluid exhausted from the power
steering motor 26 to be conducted ba-ck to drain. .
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During a turn in the opposite direction, the inner valve
member 48 is rotated in the opposite direction relative to the
valve sleeve 72. Therefore, the axially extending passages 100
and 104 are connected with the longitud:inally extending
pressure chambers and the inlet fluid is conducted to the
annular outer groove 122 through the valve passages 124 and 126
extending between the inner grooves 100 and 104 and the annular
groove 122. The axially outer groove 122 is connected in ~luid
communication with the motor conduit 52 through the housing
passage 82. At this time, the motor conduit 54 is exhausted to
the drain conduit 58 through the axially outer annular groove
114, axially extending inner grooves 104 and 106, and
longitudinally extending outlet chambers formed between the
valve member 48 and valve sleeve 72.
The manner in which the valve member 48 cooperates with the
one-piece valve sleeve 72 is more Eully described in the
aforementioned Canadian Patent Application Serial No. 323,344,
Eiled March 13, 1979, by Richard W. Dymond and entitled "Power
Steering Valve And ~ethod Of Making The Same" (Doclcet No.
TRW(M)7257). Since the manner in which the valve sleeve 72 and
valve member cooperate during steering operations is well known
to those skilled in the art, it will not be further described
herein.
The inner grooves 100, 102, 104, and 106 have a relatively
short axial extent. Thus, the axial grooves 100, 102, 104,
and 106 each have an overall axial length which is equal to
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ppro~imat~ly tl~10 tllircls oE th~ overall axial lengtll o the
array oE annular grooves 80, 114, and 122 on the outside of
the valve s]eeve 72.
The grooves 100 and 102 extend axially in a first
direction from a cent~al portion 132 (see Fiy. 4) of the
~ne-piece valve sleeve 72 toward the annular groove 122 and .,
the axial end surface 134 of the valve sleeve. Similarly, the
inner grooves 102 and 106 extend in the opposite direc~ion
from the central p~rtion 132 of the valve sleeve toward the ' '
opposite axial end surface 138 of the valve sleeve. By
forming the grooves 100, 102, 104~ and 106 with relatively
short axial lengths, the machining time required to form the
grooves tends to be minimized. In addition, the structural
rigidity oE the valve sleeve 72 tends to be enhanced~ ,
The axially extending grooves 100 and 104 have Llat
semicircular axially inner end surfaces 142 and 144. ~The end
surfaces 142 and 144 are disposed in the central portion of
the valve sleeve 72 at a location generally radial~y inwardly ,
of the annular ou~er groove 80 (see Figs. 3 and 4). ~Thus~ the
end surfaces 1~2 and 144 are located radially inwardly from an
annular side surface 145 of the groove 80.
The grooves 100 and 104 have constant depth main sections, ,
146 and 148 which extend axially outwardly toward the leEt (as, '
viewed in Fig. 3) or upwardly tas viewed in Fig. 4) to a ,
location ad~acent to the axially outer annular groove 122.
The main sections 146 and 148 extend parallel to each other
and to a longitudinal central axis 152 of the valve sleeve
72. The constant depth main sections 146 and 148 of the
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grooves 100 and 104 have a generally semicircular
crosssectional conEiguration in ~ plane which extends
perpendicular to the longitudinal central axis 152 of the valve
sleeve 72.
Main sections 146 and 14~ of the inner grooves 100 and 104
end at axially outer end surfaces 154 and 156 which are
disposed adjacent to the axially outer end surface 134 of the
one-piece valve sleeve 72. The end surfaces 15~ and 156 have
an arcuately curving configuration and form a portion of a
cylinder. The sloping end surfaces 154 and 156 are intersected
by the valve passages 124 and 126 which extend between the
axially extending inner grooves 100 and 104 and the annular
outer groove 122. In accordance with the disclosure in the
aforementioned Dymond Application Serial No. 323,344, fi]ed
March 13, 1979 (Docket No. TRW(M)7257) the annular outer groove
122 is deeper than the annular inner groove 80. However, the
central groove 80 has a greater axial extent so that the
grooves 80 and 122 have the same crosssectional area to
accommodate fluid flow.
The axially extending inner grooves 102 and 106 extend in
the opposite direction from the central portion 132 as do the
grooves 100 and 104 (see Fig. 4~. The inner grooves 102 and
106 have flat semicircular end surfaces 160 and 162 (see Figs.
2 and 4) which are disposed in the central portion 132 of the
valve sleeve 72 at a location generally inwardly of the central
annular outer groove 80. Thus, the end surfaces 160 and 162
are located radially inwardly from an annular side surface 163
of the grOQve 80.
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The grooves 102 ancl l.0~ have axlally extendi.ng constant
Idepth mc~ln sect:ions 164 and :l66. The main sections 164 and
¦166 extend axially out~ardly from the central portion 132 in a
directi.on opposite from the grooves 100 and 10~, that is in a
downward direction as vie~ed in Fig. 4 or toward the left as
viewed in Fig. 3. The main sections 164 and 166 oE the
grooves 102 and 106 extend parallel to each other and to the
longitudi.nal central axis 152 of the valve sleeve 72. The
main sections 164 and 166 of the grooves 102 and 106 have the
same semicircular cross sectional conEiguration as the main
. sections 146 and 1~8 of the grooves 100 and 104. .
: The constant depth main sections 164 and 166 o~ the
. grooves 102 and lD6 terminate at axiall.y sloping end surfaces
. 170 and 172 (see Figs. 2 and 4) which are disposed generally
radially inwardly of the axially outer annular groove 11~
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The end surfaces 170 and 172 slope axially outwardly toward
. the outer end surface 138 of the valve sleeve ~72 and have a
arcuately curving configuration corresponding to a portion of
a cylinder. The valve passages 116 and 118 extend between the .
end surfaces 170 and 172 of the axially extending inner
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. grooves 102 and 106 and the annular outer groove 114. :
It should be noted that the annular outer groove 114 has
a sloping bottom surface which enables it to be relatively ~
deep and to have a relatively short axial extent, compared to .
the annuIar center groove ~0, while still havin~ the same
. crosssectional area for handling fluid flo~ as the annular
groove. By providiny both oE the axially outer annular
¦grooves 114 and 122 with sloping bottom surfaces which are
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~djac~nt to the .510ping bottorn sur~clces o~ t.he associated
axially eY.tending inner ~rooves, the overall axial extent o~
the valve sleeve 72 tends to be rninimized.
In accordance with a feature of the present inventi~n,
the relatively short axial length of the inner grooves 100,
102, 104, and 106 enables a pair oE rotatiny cutting tool~,
which have been indicated in dashed lines at 178 and 180 in
Fig. 3, to be utilized to simultaneously form a pair o~ inner
grooves. Although other types oE rotatable cutting tools
could be used, the cutting tools 178 and 180 are end mills.
The end mill 178 has a circular end Eace 184 and a cylindrical
side portion 186. The end mill 180 is identical to the end
mill 178 and has a circular end face and a ~ylindri~al side
portion.
The end mills 178 and 1~0 are simultaneously rotated
about their longitudinally extending central axes by suitable
drive members or chucks (not shown~. ~lthough many difEerent
types of end mills could be utilized, one suitable type o end
mill is of the center cutting t~pe manu~actured by Green~ield
Tap & Die d Green~ield, Massachusetts. ~his particular end
mill has cutting flutes at the circular end face 184 and
cutting ~lutes extending along the side portion 186 so that
material can ~e cut away with either the end face 184 or the
side portion 186 oE the end mill.
When the axially extending grooves 100, 102, 104, and 106
are to be formed in the metal valve sleeve 72, the valve
sleeve is firmly mounted in an indexible holder or chuck (not
shown). The chuck grips the central portion of the valve
sleeve 72 and leaves opposite ends of the valve sleeve open.
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rhe chuck holds tlle valve sleeve 72 with tlle central axis 152
oE the valve sleeve co;ncident ~ith the axis o~ rotation of
the chuck. The chuck is accurately indexible to t~o positions
spaced 180~ apart with each o~ the positions corresponding to
a location in which t~70 of the axially extending grooves are
simultaneously forMed.
In order to simultaneously form the two axially extendinc)
grooves 100 and 102, the end mills 178 and 180 are inserted .
into opposite axial open ends of the valve sleeve 72. The
leading or axially outer end portions oE the end mills 178 and
180 are moved into engagetnent with the valve sleeve 72 at
locations adjacent.to opposike axial ends of the valve
sleeve. This results in the simultaneously forming of the
axially sloping side surfaces 154 ancl 170 with the side
portions of the.rotating end mills 178 and 1800 It should be
noted that the longitudinal central axes o~ the two end mills .
intersect the longitudinal central axis 152 of the valve .
sleeve 72 and extend at the same acute angle relative to the
longitudinal central axis 152 of the valve sleeve 72. .
Therefore, the simultaneously formed end surfaces 154 and 170
of the axially ex-tending grooves 100 and 102 slope inwardly
toward the axis 152 in a direction toward the opposite axial
end suraces 134 and 138 of the valve sleeve 72. It should
also be noted that the sloping end surface 154 of the axially
extending groove 100 is disposed radially inwardly of the
annular outer groove 122 while the axially sloping end surface
170 of the inner groove 102 is disposed radiall~ inwardly of
the annular groove 114.
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In order to simultaneous.l.y Eorrn tlle eon~.tarlt depth main
¦sections 146 ~nd 1~ of the two yroove~ 100 and :lO2, tile
rotating end mi.lls 178 and 180 are simultaneously moved into
the valve sleeve 72 along paths extending paral].el to the
longituclinal central axis 152 of the valve sleeve. As the end
mill 178 moves axially inwardly into the valve sleeve 72, the
circular end face 184 oE the end mill cuts away the material
on the inside of the valve sleeve to form the s~raight groove
100. At the same time, the rotating circular end ace oE the
. end mill 180 is cutting away material on the inside of the
valve sleeve 72 to form the straight groove 102.
. Since the main body portions 146 and 164 of the grooves
lnO and 102 are simultaneously formed by the rotating circular
end faces of the end mills 178 and 180 as they move axially
into the valve sleeve 72, the constant depth main sections o
the grooves 100 and 102 have the same semicircular cross
sectional configurations in a plane extending perpendicular to .
the longitudinal central axis 152 of the valve sleeve 72.
- This arcuate cross sectional configuration promo~es a ~uiet
. laminar flow o fluid through the grooves during operation of
the valve assembly.~
The inward movement oE the end mill 178 into the
one-piece valve sleeve 72 is terminated at the slop.ing end
sur~ace 142. Simultaneously therewith, the axially inward
movement of the rotating end mill 180 is terminated at the
sloping end surface 160. The sloping end surEaces 142 and 160
are formed b~ the circular end Eaces oE the end mills 178 and
180 at locations on opposite axial sides oE the central
portion 132 of the valve sleeve 72.
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~ lhen the end mills 1.7~ ~nd 180 re~ch their end o~ stroke
positions shown in dashed :Lines in Fig. 3, the end mil]s do
not en~age each other or the opposite axial ends of the valve-
s].eevè 72. This is due to the ~act that the grooves 100 and
102 have a relatively short axial extent. IE the groove 100
was substantially longer, the end mill 178 ~Jould nick the
axially outer end of the valve sleeve 72. It should also be
noted that the axes about which the end mills are rotated both
intersec~ the central axis 152 of the valve s.teeve 72.
Therefore, i the end mills 178 and 180 were moved further
into the valve sleeve 72, there would be a tendenc~ for the
end mills to engage each other.
Once the grooves 100 and 102 have been .simultaneously
formed in the manner previously explained, the ro-tating end
mills 178 and 180 will be disengaged from the grooves ana
withdrawn from the valve sleeve 72~ The valve sleeve is then
rotated about its central axis through an arcuate distance of
180~ to position the valve sleeve 72 or the ~ormation of the-
grooves 104 and 106. The groove I04 is formed by the end mill
178 simultaneously with the formation of the yroove 106 by the
end mill 180. It should be noted that the graove 104 will De
identical to the groove 100 and that the groove 106 will be
identical to the groove 102. It should also be noted t'nat the
only difference in the grooves 100 and 104 and grooves 102 and
106 is that they extend .in opposite directions from the
central portion 132 of the valve sleeve 72.
Although the grooves 100 and 102 have been described
herein as being formea by moving the rotating cutting tools
178 and 180 simultaneously inwardly toward the central portion
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tlle valve sleeve, ;t i5 contemplated tl~at the groo-~es 100
and 102 could be simultaneouE;ly forrned by moviny ~he valve
sleeve 72 relative to the ro~ating cuttiny too:Ls 17~ and 1~0.
I this was done, the circular end face o~ one o the cuttiny
tools would be utilized to cut away mekal to forrn one of the
axially extending inner grooves while the side portion of khe
other rotating cutting tool would be utilized to
s;multaneously cut away metal and form the other axially
extending inner groove. I the grooves were to be formed in
this manner, one o the cutting tools would be moved into
engagement with the valve sleeve 72 at a location where an
axially outer end surEace of a groove is to be formed while
the other cutting tool would be moved into engagement with
valve sleeve at a location where an axially inner end sur~ace
of a groove is to be ormed. The valve sleeve would then be
moved axially relative to the rotating cuttiny tools to effect -
the simultaneous formation of the two grooves~
If the grooves 100 and 102 are to be form~d in this
manner, the circular end face 184 o~ the rotating cutting tool
178 may be utilized to cut away metal to form the groove 100.
The side portion of the rotating cuttiny tool 180 coul.d be
utilized to cut away metal to orm the groove 102. Thus~ the
leading end portion of the end mill 178 would be moved into
engagement with the valve sleeve 72 to form the end surface
15~ in the manner previously explained. Simultaneously
therewith, the leading or axially outer end portion of the
rotating cu~ting tool 180 would engage the central portion 132
of the valve sleeve to form the end surace 160 of the axially
¦exten ng inner groove l02.
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Once the two end mills have forlned the axiaLly outer end
surEace 154 and the axially inner surfc~ce 160, the valve
sleeve would be moved axially relative to the rotating end
mills. Thus, the valve sleeve ~70uld be movecl axially toward
the right (as viewed in Fig. 3) to enable the outer face 1~4
of the end mill 17~ to form the constant depth main section .
146 of the groove 100. This axial movement oE the valve
sleeve would also cause the side port;on oE the rotating end
mill 180 to cut away the main portion 16~ of the axially .
extending inner ~roove 102. The axial movement of the valve
sleeve 72 would be stopped when the end mil]. 178 had been
inserted far enough into the valve sleeve 72 to form the en~
face 142 and the end mill 180 and had been withdLawD from the
valve sleeve 72 through a sufficient distance to Eorm the end
surface 170. . ; -
In view of the foregoing remarks it is apparent that the
present invention provides a new and improved one-p1ece valve
sleeve 72 and method by which the valve sleeve is formed. The
hollow cylindrical`valve sleeve 72 has a plurality of .
relatively short axially extending internal grooves 100, 102,
104, and 106. The internal grooves 100 and 104 ex-tena in one
axial direction from a central portion 132 of the valve sleeve
while the grooves 102 and 106 extend in the opposite axial
direction. ~herefore, at least some of the internal grooves
are axially offset relative to other internal grooves. Since -
each o the internal grooves 100, 102, 104, and 106 extends in
only one axial direction from a central portion 132 oE the : -
valve sleeve, the machining time required to form each of the
grooves is xeduced.
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In accorcl~lnce ~1.ith another fe~ture o~ the present
invention, it is possible to sirnultaneously ~orm two of the
short axially extending grooves by using a pair o~ rotary
cutting tools such as end mill.s 178 and 180. When the a%ially
extending grooves 100, 102, 104, and 106 are to be formed in
this manner, the end mills 178 and 180 are inserted into
opposite axial. ends of the valve sleeve. Upon the occurrence
of relative movement between the end mills 178 and 180 and the
valve sleeve 72, the end mills simultaneously cut away metal
to form a pair of axially ext,ending grooves in the one-piece
valve sleeve. However, it is contemplated that the grooves .
100, 102, 104, and 106 could be sequentially formed one at a
time th a singIe ~nd mill if desired.
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.. . .
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