CA1037356A - Controller for fluid pressure operated devices - Google Patents
Controller for fluid pressure operated devicesInfo
- Publication number
- CA1037356A CA1037356A CA234,968A CA234968A CA1037356A CA 1037356 A CA1037356 A CA 1037356A CA 234968 A CA234968 A CA 234968A CA 1037356 A CA1037356 A CA 1037356A
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- valve
- port
- meter
- controller
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/09—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by means for actuating valves
- B62D5/093—Telemotor driven by steering wheel movement
- B62D5/097—Telemotor driven by steering wheel movement gerotor type
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Power Steering Mechanism (AREA)
- Servomotors (AREA)
Abstract
A B S T R A C T
A controller for fluid pressure operated device such as power steering systems. The controller is of the type having a primary, rotatable valve member and a follow-up valve member, the valve members defining a neutral posi-tion. The follow-up valve member is coupled to the primary valve member for limited movement relative to the neutral position. The controller further comprises a fluid meter including a metering member for measuring the volume of fluid passing therethrough, the metering member being coupled to the follow-up valve member. The controller has an inlet port and first and second control fluid ports which may be connected to the opposite ends of the power steering cylinder. The primary and follow-up valve members cooperate with the hous-ing to define a first plurality of fluid passages providing fluid communication between the inlet port and the first con-trol fluid port through the fluid meter when the valve members are relatively displaced in one direction from the neutral position and providing fluid communicating between the inlet port and the second control fluid port through the meter when the valve members are relatively displaced in the other direc-tion from the neutral position. The first and second plur-alities of fluid passages provide substantially the same length of fluid flow path between the inlet port and the correspond-ing control fluid ports in either direction of displacement of the valve member from the neutral position to provide uniform response in either direction. Preferably, the first and second pluralities of fluid passages are arranged in substantially a mirror image of each other with respect to an imaginary plane perpendicular to the axes of rotation of the valve members, to minimize steering wheel precession. In addition, the valve members maintain axial separation of the fluid flowing to a control fluid port and the fluid returning from a control fluid port to minimize internal leakage.
A controller for fluid pressure operated device such as power steering systems. The controller is of the type having a primary, rotatable valve member and a follow-up valve member, the valve members defining a neutral posi-tion. The follow-up valve member is coupled to the primary valve member for limited movement relative to the neutral position. The controller further comprises a fluid meter including a metering member for measuring the volume of fluid passing therethrough, the metering member being coupled to the follow-up valve member. The controller has an inlet port and first and second control fluid ports which may be connected to the opposite ends of the power steering cylinder. The primary and follow-up valve members cooperate with the hous-ing to define a first plurality of fluid passages providing fluid communication between the inlet port and the first con-trol fluid port through the fluid meter when the valve members are relatively displaced in one direction from the neutral position and providing fluid communicating between the inlet port and the second control fluid port through the meter when the valve members are relatively displaced in the other direc-tion from the neutral position. The first and second plur-alities of fluid passages provide substantially the same length of fluid flow path between the inlet port and the correspond-ing control fluid ports in either direction of displacement of the valve member from the neutral position to provide uniform response in either direction. Preferably, the first and second pluralities of fluid passages are arranged in substantially a mirror image of each other with respect to an imaginary plane perpendicular to the axes of rotation of the valve members, to minimize steering wheel precession. In addition, the valve members maintain axial separation of the fluid flowing to a control fluid port and the fluid returning from a control fluid port to minimize internal leakage.
Description
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,` S P E C r F I C A T I O_N
BACK~ ROliND OF THE DISCLOSURE
'' The present invention rela1:es to a controller for fluid I pressure operated devices and, more particularly, to a con-5 ~I troller having an improved spool-sleeve valve arrangement.
~lthough the present invention is equally adapted to any controller for fluid pressure operated devices wherein the 'i controller utilizes a valve spool arrangement, it is especi-il ally advantageous when used in controllers for power steering lO !I systems of the type employed in off-the-road vehicles, and will be described in connection therewith. More specifically, ¦
although the invention will be descr~bed in connection with rotatable spool-sleeve val-ve arrangements, it will be appre- ¦
~ iated that the invention may also be utilized with spool lS ¦ valves which operate in response to axial movement.
A controller for a power steering system of the type to which the present invention pertains is described in ~. S.
-~eissue Patent No~ 25,126, assigned to the assignee of the present invention. Controllers of the type disclosed in the cited reissue patent have become well known in the art and generally comprise a housing having an inlet and an outlet and a pair of control fluid ports, feeding a power steering cylin-der. The vehicle steering wheel is directly connected to the controller and when in the neutral (non-rotating) position, fluld may pass from the inlet through the valve to the outlet (open center system), or fluid rom the inlet may be blocke~
from passiny through the valve (closed center system).
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When the steering wheel is rotated in one direction from the neutral position, the valve is di~placed and fluid fl~ws ~rom the inlet through the valve, to the meter, then to one ` of the control fluid ports to move the power steering cylinder.
5 ; When the steering wheel is rotalted in the opposite direction, the valve rotates in the opposite direction and fluid flows from the inlet port through the valve, then through the fluid li meter in the opposite direction, then to the other of the con-jl trol fluid ports to move the power steering cylinder in the 10 !l opposite direction. I
Conventionally, controllers of the type described have l! utilized rotary spool-sleeve valves to direct the flow of ¦¦ ~luid from the inlet port in accordance with the rotational ¦ position of the steering wheel. In general, rotary spool--15 sleeve valves comprise a primary valve mem~er !spool) con- i nected directed to the steering wheel and a follow-up valve member (sleeve) surrounding the spool. Axially adjacent the spool and sleeve is a fluid meter, generally a gerotor having an externally toothed member orbiting within an internally toothed member. The externally toothed member is splined to a drive shaft, at the opposite end of which the drive shaft i5 ~oupled to the sleeve, such as by a pin passing therethrough.
When the spool is rotated, fluid is permitted to flow to the meter, causing the externally toothed member to orbit and rotate, thus imparting rotary follow-up movement to the sleeve by means of the drive shaft. Generally, the sleeve has a plurality of orifices extending radially therethrough and the spool ha~ a plurality of axially extending grooves on its outer surfa~e to provide communication between certain of the orifices in the 30 ¦ sleeve.
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. ~ :~ ! , ., . '~ _ ~ _ ~1 03~3~6 One o~ the problems associated with conventional power stee~ing systems and the controllers used therein i~ ste0ring wheel "precession", i.e., the position of the steering wheel corresponding to the neutral position of the controller "pre- ;
cesses" or moves slowly in one direction or the other during , operation of the system. It is believed that this is caused primarily by imbalance in the fluid flow paths, i.eO, the fluid is subjected to a longer path and/or more flow restric-tion for one direction of steering than for the other. Among 10 !~ the other problems associated with systems and controllers o~
the type described is internal leakage, primarily between 11 "metered" fluid and "return" fluid. As used herein, the term il "metered" fluid refers to fluid which has been measured by the ¦¦ fluid meter and is then fed to the power steering cylinder.
i 15 ¦I m e term "return" fluid refers simply to fluid displaced by the movement of ihe power steering cylinder which returns to the valve and passes to the outlet port (or tanX port). While the above definitions are strictly true only for a controller in which the flow order is: inlet port - fluid meter - cylinder -outlet port, it will be apparent that the invention is equally adapted for controllers having other flow orders, including but not limited to: inlet port - cylinder - fluid meter -outlet port. In connection with the definitions of "metered"
and "return" fluids for any particular controller, it should ~e noted that the remainder of the fluid passing through the spool-sleeve valve is a~ approximately the same pressure as the "metered" fluid, but has not been metered and hence, may be referred to as "high pressure, non-metered" fluid.
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~0373$6 In many of the conventional spool-sleeve ~alve arrangements, the orifices in the sleeve communicating to and from the control ~luid ports and the grooves in the spool communicating therewith are arranged in such a manner that grooves containing metered fluid and grooves containing return fluid are in an alternating, interdigitated relation-ship with each other, thus greatly increasing the length o~
the interface between metered and return fluid and the oppor~
tunity for internal leakage therebetween (see, for example, -~U.S. Patent No. 3,819,307).
Accordingly, it is an object of the present invention ~`
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to provide a controller for fluid pressure operated devices and a valve spool arrangement therefor which overcome the ;
above-mentioned problems.
It is a more specific object of the present invention ~
to provide a controller or a power steering system which ~ -minimizes steering wheel precession through improve~ design of the valve spool arrangement.
According to the present invention there is provided a controller for fluid pressure operated devices, the con-troller including a housing and valve means disposed in the housing including a primary, rotatable valve member and a ;
cooperating, relatively rotatable follow-up valve member, the valve members defining a neutral position relative to each other and having generally coincidental axis of rotation. Means couple the follow-up valve member to the primary valve member for a limited movement relative to the neutral position and for common rotary movement therewith~
A fluid meter includes a metering member movable to measl1re the volume of fluid which passes therethrough, and means couple the metering member to the follow-up valve member for imparting follow-up movement thereto responsive to jb/ - 4 -..... , ~. . ,. ~ ~ . .
~L037356 movement of the me-tering chamber. The controller includes an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure operated device. The primary and follow-up valve members cooperate with the housing to define a first plurality of fluid passages connecting the inlet port in fluid communication with the first control fluid port through the fluid meter when the valve members are relatively displaced in one direction from the neutral position. A second plurality of fluid passages connect the inlet port in fluid communication ~ -with the second control fluid port through the fluid meter when the valve members are relatively displaced in the other direction from the neutral position. The first and second plurality of fluid passages are oppositely and approximately equally disposed about a reference plane perpendicular to .:~
the axis of rotation of the valve members to provide a ;
controller having uniform response in either direction of relative displacement of the valve members, thus minimizing steering wheel precession.
In accordance with anotheraspect of the present invention, the first and second pluralities of fluid passages defined by the housing in the valve members are arranged in substantially a mirror image of each other with respect to an imaginary plane oriented perpendicular to the axes of rOtation of the valve members, thus providing substantially `~
identical fluid flow paths for either direction of operation of the controller.
In accordance with still another aspect of the present invention, the controller housing defines source ~ .
passage means communicable with the inlet and first and second control fluid passages for connection to the first and second control fluid pcrts, and first and second fluid b/ ~ 5 ~ `~
~37~S6 meter passages for connection to the fluid meter. The valve means defines first and second pressure passage means adapted to communicate, respectively, between the source passage means and the firs-t fluid memter passage when the ~
valve means is rotatably displaced from the neutral position ~.
to a first control position, and between the source passage means and the second fluid meter passage when the valve 8 means is displaced from the neutral position to jb/ - 6 -~. :
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' ~0373S6 a second control position. The first and second pressure pas-sage means are oppositely and approximately equally disposed about the imaginary reference plane. The valve means further ,~ defines first and second operating passage means adapted to communicate, respectively, between the first fluid meter pas-sage and the first control fluid passage when the valve means 'll is in the second control position and to communicate be'cween ji the second fluid meter passage and the second control fluid ,j passage when the valve means is in the first control position. ~ ;
10 ll The first and second operating passage means are oppositely ¦
il and approximately equally disposed about the reference plane.
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¦I B IEF DESCRI?TION OF THE DRAWINGS
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¦ FIGURE 1 is a diagra~matic view of a vehicle powex steering ¦ syst,Pm and controller to which the present invention may be applied.
FIGURE 2 ~s an enlarged view, in axial cross section, of the ~ontroller shown diagrammatically in FIGURE 1.
FIGURES 3 and 4 are fragmentary, overlaying views o~ the I valve me~ers of the present invention, illustrating right and left turn conditions, respectively.
FIGURES 3A and 4A are semi-schematic cross sections taken on lines 3A-3A and 4A-4A of FIGURES 3 and 4, respectively.
~ IGURE ~ is a side elevation of the valve spool used in the ~ontroller.
¦ ~IGURE ~ is a side elevation of the valve sleeve used in ¦ ~he controller.
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~37;35~ i DESCRIPTION OF THE PREFERREI)_EMBODI~lENT ;
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Steering System Referring now to the drawings which are for the purpose of illustrating a preferred embodiment of the invention, and not for limiting the same, FIGURE 1 illustrates diagrammatic-ll ally a vehicle power steering system of the type to which the " present invention is applicable. Such systems have ~ecome l¦.well known in the art and comprise, in general, a steering Il wheel ll operably connected to a controller 13 and,more lO ! specifically, to the valve means 15.. The controller 13 is ¦¦ provided with an inlet port 17 through which the controller ¦1 13 receives the full system fluid flow from a source, such as ! a pump 19, which is ~onnected to a reservoir or tank 21 b~J a ¦ conduit 23. The controller 13 i9 also provided with an outlet port 25 connected to the reservoir 21 by a conduit 27. Asso-ciated with the controller is a fluid meter 29 operably con-nected to the valve means 15 to meter or measure fluid flow :in response to rotational movement of the steering wheel ll ana valve means 15. The controller includes a left turn port 31 and a right turn port 33, the left turn port 31 being fed : by a flow path 35 and the right turn port 33 being ~ed by a flow path 37, the diagram of FIGURE 1 illustrating the system ¦
: in a right tuxn condition, and the flow path 37 being shown ~onnected to the fluid meter 29. A power steering cylinder 39 is operated by the controller 13 by means of a conduit 41 connected to the left turn port 31, and a conduit 43 connected to the right ~urn port 33. The ~ontroller 13 optionally : "' ' ' I
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includes an auxiliary fluid port 45, from which fluid is com-i municated to an auxiliary devic~e 47 by means of a conduit 49.
The auxiliary device 47 is also connected to the reservoir 21 , . .
by a conduit 51.
5 . Controller ~ I .
FIGURE 2 is an axial cross section of the controller 13 I, taken on a plane such th3t none of the ports 17,25,31 or 33 ¦¦ is visible. The ~ontroller 13 includes a housing 53, a plate 55, the fluid meter 29 and an end plate 57. These sec-o !I tions are fastened in tight engagement by a plurality of bolts¦ 59 passing into tapped holes (not shown) in the housing 53.
. I - ~he fluid meter 29 includes an internally toothed member 61 : I held in a fixed relationship with respect to the plate 55 and end plate 57 by the bolts 59. Eccentrically disposed within the internally toothed member 61 is an externally toothed mem- ¦
:ber 63 having a splined central opening 65. The controller housing 53 defines a substantially cylindrical, axially ex-tending opening 67 within which is rotatably disposed the valve .m~ans 15. ~t the forward end of housing 53 is a recess 71 ~0 against which is seated an end cap 73, retained in place by a retaining ring 75.
The valve means 15 comprises a primary, rotatable valve : member (spool) 77, and a cooperating, relatively rotatable . ; f~llow-up valve member ~sleeve) 79. The spool 77 terminates 25 at its forward end in an internal spline portion 80 for con- ¦
nection to an externally splined shaft (not shown) attached to steering wheel 11. The sleeve 79 is coupled to the spool 77 .
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by means of a drive shaft 81 having, at its rearward end, a crowned splined head 83 in engagement with the splined cen-tral opening 65 of the externa:Lly toothed member 63 with the ; drive shaft 81 being restrained from axial movement, in part, by a spacer 84 between splined head 83 and end plate 57. At the opposite end of the drive shaft 81 is a bifurcated end portion 85 through which passes a transverse drive pin 87. The transverse drive pin 87 passes through an opening in the spool 77 and engages the sleeve 79 in a manner well known in the art, 10 !l and which forms no part of the present invention. Disposed approximately at right angles to the pin 87 is a plurality of leaf springs 88 urging spool 77 and sleeve 79 toward the neutral position relative to each other. Certain other details of the construction and operation of such controllers which I also form no part o~ the present invention may be better under-i stood by reference to the previously cited U. S. Reissue Patent ~:
No. 25,126, assigned to the assignee of the present invention.
FIGURES 5 and 6 are side elevations of the valve spool ana ~alve sleeve, respectively, on approximately the same scale as FIG~RE 2. In both FIGURES 5 and 6, there is shown a refer-ence plane RP oriented perpendicular to the axes of rotation of spool 77 ana sleeve 79, the plane RP being included to facilitate an understanding o~ the present invention.
The valve sleeve 79 includes a pair of diametrically opposed pin slots 89 (only one of which is shown in FI~URE 6~, adapted to engage the transverse drive pin 87. Similarly, . the valve spool 77 includes a pair of diametrically-opposed pin slots 91 (only one of which is shown in FIGURE 5), to permit the drive piD 87 to pas~ therethroug} without engaging the . . .
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lon3s6 spool 77, except at maximum deflection. I
In connection with the subsequent description of the spool and sleeve in FIGURES 5 and 6, as well as the operational ~ description of FIGU~ES 3,3A,4 and 4A, it should be noted that many of the apertures, orifices, passages, etc. are arranged in a mirror image with respect wi~h the reference plane RP.
Thus, such elements will be described by a reference numeral followed by either an R or L to indicate that the element is located on the right side or the left side, respectively, of 10 1I the central reference plane RP. On the other hand, certain of the elements do not have a corresponding element oppositely disposed about the reerence plane RP and will be referred to by use by a reference numeral alone. ;
Formed in the outer surface of the valve sleeve 79 is a ;15 l¦ centrally disposed circumferential groove 93 into which a !I plurality of orif~ces 95 open. Oppositely disposed about the planeRP are circumferential grooves 97L and 97R which ~' l communicate, respectively, with pluralities of pressure ports ¦ 99L and 99R. Disposed furthur from the reference plana RPare pluralities of meter ports 101~ and 101R. Finally, valve sleeve 79 includes pluralities of operating ports 103~ and 103R.
It should be noted that in the subject embodiment, for each of the pluralities of ports, the circumfPrential spacing from one port to the next is substantially the same, and further-~5 more, although not all of the ports of each type are shown, there are six of each in the subject embodiment, although the number may vary.
~ he valve spool 77 has formed within its outer surface a pair of ci~<umierential meter grooves 105L and 105R eqUa1b ...'' '' '' .: : . , ,: 1 . . .
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~137356 and oppositely disposed about reference plane RP. It should be noted th~t when the valve slee~e 79 is disposed about the valve spool member 77, the members 77 and 79 will be in the same axial relationship as is shown in FIGURES 5 and 6, with the 5 I reference planeSRP coincidental. Thus, the meter grooves 105L and 105R are axially aliqned with, and in fluid communi-cation with meter ports lOlL and lOlR, respectively. Extend-il ing axially inwardly (toward reference plane RP) from the ! meter grooves 105L and 105R are pluralities of circumfer-10 !l entially spaced apart passages 107L and 107R, which are adaptedi to communicate with the pressure ports 99L and 99R when the Ijl spool 77 and sleeve 79 are in the pxoper relative rotational ¦¦ position, as will be described more fully in connection with li FIGURES 3 and 4. ~xtending axially outwardly from the meter 15 I grooves 105L and 105R are pluralities of operating passages 1 1~9L and lO9R, each of which, in the subject embodiment is axially aligned with one of the passages 107L or 107R. The operating passages lO9L and lO9R are adapted to communicate with the operating ports 103L and 103R, respectively, in response to a certain rotational relationship between the spool 77 and sleeve 79. As was noted in connection with sleeve 79, the individual passages comprising each of the above-described pluralities of passages preferably have uni-form circumferential spacing therebetween, the circumferential spacing between the passages preferably being the same as that between the ports of the valve sleeve 79. Axially dis-. posed between the meter grooves 105L and 105R and circum-ferentially disposed between adjacent passages 107L and 107R
are a plurality of pairs of passages 111 and 113, the passage ., ~ I - 12 -~: ~ . ., : . . . .
~37356 111 being disposed to communicate between pressure port 99L
and auxiliary port 95, while the passage 113 is adapted to communicate between the pressure port 99R and the auxiliary port 95 when the spool 77 and sleeve 79 are in the neutral position with respec-t to each other, as is illustrated and explained in greater detail in applicant's U.S. Patent No.
3,960,234, issued June 1, 1976, by D. Morgan, entitled ~:
"Controller for Fluid Pressure Operated Devices Providing High Pressure to an Auxiliary Device", and assigned to the assignee of the present invention. In addition to the above-described passages formed in the outer surface of valve spool member 77, there is a plurality of tank ports 115L, circumferentially disposed between operating passages .
109L and, oppositely disposed therefrom about reference plane RP, a plurality of tank ports 115R, circumfer~ntially disposed between operating passages 109R. Each of the tank ~ ~.
ports 115L and 115R is disposed to be aligned with, and in fluid communication with one of the operating ports 103L
and 103R, respectively. ... -FIGU~ES 3 and 4, and the semi-schematic cross sec-tions shown in FIGURES 3A and 4A, illustrate r.ight and left . . , turn conditions, respectively, of the controller 13 and valve means 15. In the fragmentary, overlaying views of ~ :
FIGURES 3 and 4, about 180 of both the valve spool 77 and ~:
valve sleeve 79 are shown, with the members 77 and 79 being displaced about 10 with respect to each other from the neutral position, as occurs during steering of the vehicle~
Generally, solid lines indicate ports defined by the valve.:
sleeve 79 whereas the dashed lines indicate ports or passages formed in the valve spool 77, and jb/ - 13 covered by the valve sleeve 79. As is shown schematically in FIGURES 3A and 4A, the controller housing 5~ defines a plurality of passages communicating between the valve means 15 and the various ports, such as inlet port 17, cylinder ports 31 and 33, etc. Among the passages defined by the hous-ing 53 is an auxiliary passaga 117 and a pair of source pas-sages ll9L and ll9R. Also defined by the housing 53 are oppositely disposed meter passages 121L and 121R, and oper-ating passages 123L and 123R. It is a feature of the present 10 ii invention that not only arb the ports and passages defined by the spool 77 and sleeve 79 symmetrical about the reference plane RP, but also, the communicating passages defined by the housing 53 may also be symmetrical, either with respect to the ;, reference plane RP ox the axes of rotation of the valve means 15 ~ 15, but at the very least, such passages should be arranged such that the total flow path for either direction of oper-ation (i.e., either a left turn or a right turn) is sub-stantially the same length and flow resistanceO Thus, the pressure drop along the flow path in either direction will also be the same. It should also be noted in connection with FIGURES 3 and 4 that for purposes of clarity, circumferential : I grooves 93~97L and 97R are not shown. It will be under-. stood however that because of grooves 97L and 97R, pressure ports 99L and 99R are always in fluid communication with passages ll9L and ll9R, respectively, regardless of the relative rotational position of valve spool 77 and sleeve 79.
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373~i6 Operation In the right turn condition illustrated in FI~URE 3, fluid introduced at inlet port 17 flows through passage ll9L, ~ around circumferential groove 97L and into pressure ports 99L. With the spool 77 and sl~seve 79 in the relati~e posi-I tions shown in FIGURE 3, the pressure ports 99L are each Il aligned with one of the passages 107L, thus permitting fluid ~ to pass therethrough, then into meter groove 105L, through i¦ meter ports lOlL, then to the fluid meter 29 through passage 10 1l 121~. Af~er the fluid is metered or measured by the fluid I meter 29 it passes through passage 121R, through meter ports ¦1 lOlR and into meter groove 105R. From groove 105R the fluid ,1 then enters operating passages lO9R which are n~w circumfer- !
I entially aligned with operating ports 103R, permitting the ~luid to pass therethrough, then through passage 123R to the right turn port 33 (see FIGURE 1), from where the fluid passes through conduit 43 to the power steering ~ylinder 39. The fluid introduced into cylinder 39 moves the piston to the left, thus displacing fluid on the left side of the piston foxcing it to return to the controller through conduit 41 where it enters the controller at the left turn port 31 and passes toward the valve means 15 through passage 123L. From there the returning (non-metered) fluid passes through the operating ports 103L, then through the tank ports 115L which 25 ¦ are circumferentially aligne~ therewith, then through the . ¦ interior of the valve spool 77~ and ~inally to the outlet port 25. .
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~ . : . : ~ 15 _ ` 1(~3~356 In the left turn condition shown in FIGURE 4, th~ valve spool 77 and valve sleeve 79 have been rotated in the oppo-site direction with respect to ~each other, thus permitting a ~ flow path which is generally th~e opposite of that for a right turn, and substantially the same path length. Fluid from inlet port 117 flows through passage 119R, circumferential groove 97R, through the plurality of the pressure ports 99R
then through the cir~umferentially aligned passages 107R to 1 the meter groove lO5R. From there the flow is through the 10 1I meter ports 101R, passage 121R to the fluid meter 29, then to passage 121L, in through meter port lOlL to meter groove ~¦ 105L, then axially into operating passages lO9L. From the passages lO9L fluid flows out through circumferentially aligned , operating ports 103~, through passage 123L to the left turn : 15 ¦ port 31, then through conduit 41 to the power steering cylinder 39. Fluid displaced at the opposite end o* cylinder 39 ~eturns by means of conduit 43 to the right turn port 33, then through passage 123~ ~o the valve ~eans 15~ then through operating ports 103X, and through tank ports 115R to the interior of 20 valve spool 77, and then to the outlet p~rt 25.
~t should be noted in ~onnection with both directions of operati~n (i.e., both right turn and left turn conditions), that n~t only are the flow paths s~mmetri~al and therefore, ~balanced`' with regard to the path length, but also, the "metered" and "return" ~luids are maintained axially separated.
~n ~IGURES 3 and 3~J it can be se~n that ~ircum~erential . ~roove 105R and passages 107R and lO9R contain metered fluid while return fluid passes through operating ports 103L and tnnk ports l5L at the oppo~ite end of the spool-sleeve valve.
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~ L~373~i Generally disposed therebetween are passages lO9L,107L,lll and 11~, groove 105L and ports lOlL,99L,95 and 99R all of which contain "high pressure, non-metered~ ~uid serving as a buffer between the metered and return fluids to minimize the tendency for leakage to occur therebetween. A similar, but opposite arrangement of metered, return and high pressure non-metered fluids can be seen in FIGURES 4 and 4A.
While the lnvention has been described with reference to a preferred embodiment, neither the illustrated embodiment nor the terminology employed in describing it is intended to be limiting: rather, it is intended to be limited only by the ~; scope of the appanded claims~ ¦
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,` S P E C r F I C A T I O_N
BACK~ ROliND OF THE DISCLOSURE
'' The present invention rela1:es to a controller for fluid I pressure operated devices and, more particularly, to a con-5 ~I troller having an improved spool-sleeve valve arrangement.
~lthough the present invention is equally adapted to any controller for fluid pressure operated devices wherein the 'i controller utilizes a valve spool arrangement, it is especi-il ally advantageous when used in controllers for power steering lO !I systems of the type employed in off-the-road vehicles, and will be described in connection therewith. More specifically, ¦
although the invention will be descr~bed in connection with rotatable spool-sleeve val-ve arrangements, it will be appre- ¦
~ iated that the invention may also be utilized with spool lS ¦ valves which operate in response to axial movement.
A controller for a power steering system of the type to which the present invention pertains is described in ~. S.
-~eissue Patent No~ 25,126, assigned to the assignee of the present invention. Controllers of the type disclosed in the cited reissue patent have become well known in the art and generally comprise a housing having an inlet and an outlet and a pair of control fluid ports, feeding a power steering cylin-der. The vehicle steering wheel is directly connected to the controller and when in the neutral (non-rotating) position, fluld may pass from the inlet through the valve to the outlet (open center system), or fluid rom the inlet may be blocke~
from passiny through the valve (closed center system).
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', . .. , .
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When the steering wheel is rotated in one direction from the neutral position, the valve is di~placed and fluid fl~ws ~rom the inlet through the valve, to the meter, then to one ` of the control fluid ports to move the power steering cylinder.
5 ; When the steering wheel is rotalted in the opposite direction, the valve rotates in the opposite direction and fluid flows from the inlet port through the valve, then through the fluid li meter in the opposite direction, then to the other of the con-jl trol fluid ports to move the power steering cylinder in the 10 !l opposite direction. I
Conventionally, controllers of the type described have l! utilized rotary spool-sleeve valves to direct the flow of ¦¦ ~luid from the inlet port in accordance with the rotational ¦ position of the steering wheel. In general, rotary spool--15 sleeve valves comprise a primary valve mem~er !spool) con- i nected directed to the steering wheel and a follow-up valve member (sleeve) surrounding the spool. Axially adjacent the spool and sleeve is a fluid meter, generally a gerotor having an externally toothed member orbiting within an internally toothed member. The externally toothed member is splined to a drive shaft, at the opposite end of which the drive shaft i5 ~oupled to the sleeve, such as by a pin passing therethrough.
When the spool is rotated, fluid is permitted to flow to the meter, causing the externally toothed member to orbit and rotate, thus imparting rotary follow-up movement to the sleeve by means of the drive shaft. Generally, the sleeve has a plurality of orifices extending radially therethrough and the spool ha~ a plurality of axially extending grooves on its outer surfa~e to provide communication between certain of the orifices in the 30 ¦ sleeve.
, ' ' ,.
.
. ~ :~ ! , ., . '~ _ ~ _ ~1 03~3~6 One o~ the problems associated with conventional power stee~ing systems and the controllers used therein i~ ste0ring wheel "precession", i.e., the position of the steering wheel corresponding to the neutral position of the controller "pre- ;
cesses" or moves slowly in one direction or the other during , operation of the system. It is believed that this is caused primarily by imbalance in the fluid flow paths, i.eO, the fluid is subjected to a longer path and/or more flow restric-tion for one direction of steering than for the other. Among 10 !~ the other problems associated with systems and controllers o~
the type described is internal leakage, primarily between 11 "metered" fluid and "return" fluid. As used herein, the term il "metered" fluid refers to fluid which has been measured by the ¦¦ fluid meter and is then fed to the power steering cylinder.
i 15 ¦I m e term "return" fluid refers simply to fluid displaced by the movement of ihe power steering cylinder which returns to the valve and passes to the outlet port (or tanX port). While the above definitions are strictly true only for a controller in which the flow order is: inlet port - fluid meter - cylinder -outlet port, it will be apparent that the invention is equally adapted for controllers having other flow orders, including but not limited to: inlet port - cylinder - fluid meter -outlet port. In connection with the definitions of "metered"
and "return" fluids for any particular controller, it should ~e noted that the remainder of the fluid passing through the spool-sleeve valve is a~ approximately the same pressure as the "metered" fluid, but has not been metered and hence, may be referred to as "high pressure, non-metered" fluid.
~.
~0373$6 In many of the conventional spool-sleeve ~alve arrangements, the orifices in the sleeve communicating to and from the control ~luid ports and the grooves in the spool communicating therewith are arranged in such a manner that grooves containing metered fluid and grooves containing return fluid are in an alternating, interdigitated relation-ship with each other, thus greatly increasing the length o~
the interface between metered and return fluid and the oppor~
tunity for internal leakage therebetween (see, for example, -~U.S. Patent No. 3,819,307).
Accordingly, it is an object of the present invention ~`
. :, ~ ...~ ,.
to provide a controller for fluid pressure operated devices and a valve spool arrangement therefor which overcome the ;
above-mentioned problems.
It is a more specific object of the present invention ~
to provide a controller or a power steering system which ~ -minimizes steering wheel precession through improve~ design of the valve spool arrangement.
According to the present invention there is provided a controller for fluid pressure operated devices, the con-troller including a housing and valve means disposed in the housing including a primary, rotatable valve member and a ;
cooperating, relatively rotatable follow-up valve member, the valve members defining a neutral position relative to each other and having generally coincidental axis of rotation. Means couple the follow-up valve member to the primary valve member for a limited movement relative to the neutral position and for common rotary movement therewith~
A fluid meter includes a metering member movable to measl1re the volume of fluid which passes therethrough, and means couple the metering member to the follow-up valve member for imparting follow-up movement thereto responsive to jb/ - 4 -..... , ~. . ,. ~ ~ . .
~L037356 movement of the me-tering chamber. The controller includes an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure operated device. The primary and follow-up valve members cooperate with the housing to define a first plurality of fluid passages connecting the inlet port in fluid communication with the first control fluid port through the fluid meter when the valve members are relatively displaced in one direction from the neutral position. A second plurality of fluid passages connect the inlet port in fluid communication ~ -with the second control fluid port through the fluid meter when the valve members are relatively displaced in the other direction from the neutral position. The first and second plurality of fluid passages are oppositely and approximately equally disposed about a reference plane perpendicular to .:~
the axis of rotation of the valve members to provide a ;
controller having uniform response in either direction of relative displacement of the valve members, thus minimizing steering wheel precession.
In accordance with anotheraspect of the present invention, the first and second pluralities of fluid passages defined by the housing in the valve members are arranged in substantially a mirror image of each other with respect to an imaginary plane oriented perpendicular to the axes of rOtation of the valve members, thus providing substantially `~
identical fluid flow paths for either direction of operation of the controller.
In accordance with still another aspect of the present invention, the controller housing defines source ~ .
passage means communicable with the inlet and first and second control fluid passages for connection to the first and second control fluid pcrts, and first and second fluid b/ ~ 5 ~ `~
~37~S6 meter passages for connection to the fluid meter. The valve means defines first and second pressure passage means adapted to communicate, respectively, between the source passage means and the firs-t fluid memter passage when the ~
valve means is rotatably displaced from the neutral position ~.
to a first control position, and between the source passage means and the second fluid meter passage when the valve 8 means is displaced from the neutral position to jb/ - 6 -~. :
;,.,. ~ - - . . . ~, . ,, ............... , , : - : .
.
' ~0373S6 a second control position. The first and second pressure pas-sage means are oppositely and approximately equally disposed about the imaginary reference plane. The valve means further ,~ defines first and second operating passage means adapted to communicate, respectively, between the first fluid meter pas-sage and the first control fluid passage when the valve means 'll is in the second control position and to communicate be'cween ji the second fluid meter passage and the second control fluid ,j passage when the valve means is in the first control position. ~ ;
10 ll The first and second operating passage means are oppositely ¦
il and approximately equally disposed about the reference plane.
;
¦I B IEF DESCRI?TION OF THE DRAWINGS
11 .
¦ FIGURE 1 is a diagra~matic view of a vehicle powex steering ¦ syst,Pm and controller to which the present invention may be applied.
FIGURE 2 ~s an enlarged view, in axial cross section, of the ~ontroller shown diagrammatically in FIGURE 1.
FIGURES 3 and 4 are fragmentary, overlaying views o~ the I valve me~ers of the present invention, illustrating right and left turn conditions, respectively.
FIGURES 3A and 4A are semi-schematic cross sections taken on lines 3A-3A and 4A-4A of FIGURES 3 and 4, respectively.
~ IGURE ~ is a side elevation of the valve spool used in the ~ontroller.
¦ ~IGURE ~ is a side elevation of the valve sleeve used in ¦ ~he controller.
1 . ' .
,, _q_ . "
~.
..
Il ! !
..
~37;35~ i DESCRIPTION OF THE PREFERREI)_EMBODI~lENT ;
" .
Steering System Referring now to the drawings which are for the purpose of illustrating a preferred embodiment of the invention, and not for limiting the same, FIGURE 1 illustrates diagrammatic-ll ally a vehicle power steering system of the type to which the " present invention is applicable. Such systems have ~ecome l¦.well known in the art and comprise, in general, a steering Il wheel ll operably connected to a controller 13 and,more lO ! specifically, to the valve means 15.. The controller 13 is ¦¦ provided with an inlet port 17 through which the controller ¦1 13 receives the full system fluid flow from a source, such as ! a pump 19, which is ~onnected to a reservoir or tank 21 b~J a ¦ conduit 23. The controller 13 i9 also provided with an outlet port 25 connected to the reservoir 21 by a conduit 27. Asso-ciated with the controller is a fluid meter 29 operably con-nected to the valve means 15 to meter or measure fluid flow :in response to rotational movement of the steering wheel ll ana valve means 15. The controller includes a left turn port 31 and a right turn port 33, the left turn port 31 being fed : by a flow path 35 and the right turn port 33 being ~ed by a flow path 37, the diagram of FIGURE 1 illustrating the system ¦
: in a right tuxn condition, and the flow path 37 being shown ~onnected to the fluid meter 29. A power steering cylinder 39 is operated by the controller 13 by means of a conduit 41 connected to the left turn port 31, and a conduit 43 connected to the right ~urn port 33. The ~ontroller 13 optionally : "' ' ' I
I ... '' ' ,.
., .... , ~' 8--- . - ., : ' :
:: ` . . :
~ 373S~
includes an auxiliary fluid port 45, from which fluid is com-i municated to an auxiliary devic~e 47 by means of a conduit 49.
The auxiliary device 47 is also connected to the reservoir 21 , . .
by a conduit 51.
5 . Controller ~ I .
FIGURE 2 is an axial cross section of the controller 13 I, taken on a plane such th3t none of the ports 17,25,31 or 33 ¦¦ is visible. The ~ontroller 13 includes a housing 53, a plate 55, the fluid meter 29 and an end plate 57. These sec-o !I tions are fastened in tight engagement by a plurality of bolts¦ 59 passing into tapped holes (not shown) in the housing 53.
. I - ~he fluid meter 29 includes an internally toothed member 61 : I held in a fixed relationship with respect to the plate 55 and end plate 57 by the bolts 59. Eccentrically disposed within the internally toothed member 61 is an externally toothed mem- ¦
:ber 63 having a splined central opening 65. The controller housing 53 defines a substantially cylindrical, axially ex-tending opening 67 within which is rotatably disposed the valve .m~ans 15. ~t the forward end of housing 53 is a recess 71 ~0 against which is seated an end cap 73, retained in place by a retaining ring 75.
The valve means 15 comprises a primary, rotatable valve : member (spool) 77, and a cooperating, relatively rotatable . ; f~llow-up valve member ~sleeve) 79. The spool 77 terminates 25 at its forward end in an internal spline portion 80 for con- ¦
nection to an externally splined shaft (not shown) attached to steering wheel 11. The sleeve 79 is coupled to the spool 77 .
~3~3~ I
by means of a drive shaft 81 having, at its rearward end, a crowned splined head 83 in engagement with the splined cen-tral opening 65 of the externa:Lly toothed member 63 with the ; drive shaft 81 being restrained from axial movement, in part, by a spacer 84 between splined head 83 and end plate 57. At the opposite end of the drive shaft 81 is a bifurcated end portion 85 through which passes a transverse drive pin 87. The transverse drive pin 87 passes through an opening in the spool 77 and engages the sleeve 79 in a manner well known in the art, 10 !l and which forms no part of the present invention. Disposed approximately at right angles to the pin 87 is a plurality of leaf springs 88 urging spool 77 and sleeve 79 toward the neutral position relative to each other. Certain other details of the construction and operation of such controllers which I also form no part o~ the present invention may be better under-i stood by reference to the previously cited U. S. Reissue Patent ~:
No. 25,126, assigned to the assignee of the present invention.
FIGURES 5 and 6 are side elevations of the valve spool ana ~alve sleeve, respectively, on approximately the same scale as FIG~RE 2. In both FIGURES 5 and 6, there is shown a refer-ence plane RP oriented perpendicular to the axes of rotation of spool 77 ana sleeve 79, the plane RP being included to facilitate an understanding o~ the present invention.
The valve sleeve 79 includes a pair of diametrically opposed pin slots 89 (only one of which is shown in FI~URE 6~, adapted to engage the transverse drive pin 87. Similarly, . the valve spool 77 includes a pair of diametrically-opposed pin slots 91 (only one of which is shown in FIGURE 5), to permit the drive piD 87 to pas~ therethroug} without engaging the . . .
.. . '' ' '' .
. - 10 ~ ' : . . . ..
`'. :' ~ : ' , .
lon3s6 spool 77, except at maximum deflection. I
In connection with the subsequent description of the spool and sleeve in FIGURES 5 and 6, as well as the operational ~ description of FIGU~ES 3,3A,4 and 4A, it should be noted that many of the apertures, orifices, passages, etc. are arranged in a mirror image with respect wi~h the reference plane RP.
Thus, such elements will be described by a reference numeral followed by either an R or L to indicate that the element is located on the right side or the left side, respectively, of 10 1I the central reference plane RP. On the other hand, certain of the elements do not have a corresponding element oppositely disposed about the reerence plane RP and will be referred to by use by a reference numeral alone. ;
Formed in the outer surface of the valve sleeve 79 is a ;15 l¦ centrally disposed circumferential groove 93 into which a !I plurality of orif~ces 95 open. Oppositely disposed about the planeRP are circumferential grooves 97L and 97R which ~' l communicate, respectively, with pluralities of pressure ports ¦ 99L and 99R. Disposed furthur from the reference plana RPare pluralities of meter ports 101~ and 101R. Finally, valve sleeve 79 includes pluralities of operating ports 103~ and 103R.
It should be noted that in the subject embodiment, for each of the pluralities of ports, the circumfPrential spacing from one port to the next is substantially the same, and further-~5 more, although not all of the ports of each type are shown, there are six of each in the subject embodiment, although the number may vary.
~ he valve spool 77 has formed within its outer surface a pair of ci~<umierential meter grooves 105L and 105R eqUa1b ...'' '' '' .: : . , ,: 1 . . .
.. . . . , ~
~137356 and oppositely disposed about reference plane RP. It should be noted th~t when the valve slee~e 79 is disposed about the valve spool member 77, the members 77 and 79 will be in the same axial relationship as is shown in FIGURES 5 and 6, with the 5 I reference planeSRP coincidental. Thus, the meter grooves 105L and 105R are axially aliqned with, and in fluid communi-cation with meter ports lOlL and lOlR, respectively. Extend-il ing axially inwardly (toward reference plane RP) from the ! meter grooves 105L and 105R are pluralities of circumfer-10 !l entially spaced apart passages 107L and 107R, which are adaptedi to communicate with the pressure ports 99L and 99R when the Ijl spool 77 and sleeve 79 are in the pxoper relative rotational ¦¦ position, as will be described more fully in connection with li FIGURES 3 and 4. ~xtending axially outwardly from the meter 15 I grooves 105L and 105R are pluralities of operating passages 1 1~9L and lO9R, each of which, in the subject embodiment is axially aligned with one of the passages 107L or 107R. The operating passages lO9L and lO9R are adapted to communicate with the operating ports 103L and 103R, respectively, in response to a certain rotational relationship between the spool 77 and sleeve 79. As was noted in connection with sleeve 79, the individual passages comprising each of the above-described pluralities of passages preferably have uni-form circumferential spacing therebetween, the circumferential spacing between the passages preferably being the same as that between the ports of the valve sleeve 79. Axially dis-. posed between the meter grooves 105L and 105R and circum-ferentially disposed between adjacent passages 107L and 107R
are a plurality of pairs of passages 111 and 113, the passage ., ~ I - 12 -~: ~ . ., : . . . .
~37356 111 being disposed to communicate between pressure port 99L
and auxiliary port 95, while the passage 113 is adapted to communicate between the pressure port 99R and the auxiliary port 95 when the spool 77 and sleeve 79 are in the neutral position with respec-t to each other, as is illustrated and explained in greater detail in applicant's U.S. Patent No.
3,960,234, issued June 1, 1976, by D. Morgan, entitled ~:
"Controller for Fluid Pressure Operated Devices Providing High Pressure to an Auxiliary Device", and assigned to the assignee of the present invention. In addition to the above-described passages formed in the outer surface of valve spool member 77, there is a plurality of tank ports 115L, circumferentially disposed between operating passages .
109L and, oppositely disposed therefrom about reference plane RP, a plurality of tank ports 115R, circumfer~ntially disposed between operating passages 109R. Each of the tank ~ ~.
ports 115L and 115R is disposed to be aligned with, and in fluid communication with one of the operating ports 103L
and 103R, respectively. ... -FIGU~ES 3 and 4, and the semi-schematic cross sec-tions shown in FIGURES 3A and 4A, illustrate r.ight and left . . , turn conditions, respectively, of the controller 13 and valve means 15. In the fragmentary, overlaying views of ~ :
FIGURES 3 and 4, about 180 of both the valve spool 77 and ~:
valve sleeve 79 are shown, with the members 77 and 79 being displaced about 10 with respect to each other from the neutral position, as occurs during steering of the vehicle~
Generally, solid lines indicate ports defined by the valve.:
sleeve 79 whereas the dashed lines indicate ports or passages formed in the valve spool 77, and jb/ - 13 covered by the valve sleeve 79. As is shown schematically in FIGURES 3A and 4A, the controller housing 5~ defines a plurality of passages communicating between the valve means 15 and the various ports, such as inlet port 17, cylinder ports 31 and 33, etc. Among the passages defined by the hous-ing 53 is an auxiliary passaga 117 and a pair of source pas-sages ll9L and ll9R. Also defined by the housing 53 are oppositely disposed meter passages 121L and 121R, and oper-ating passages 123L and 123R. It is a feature of the present 10 ii invention that not only arb the ports and passages defined by the spool 77 and sleeve 79 symmetrical about the reference plane RP, but also, the communicating passages defined by the housing 53 may also be symmetrical, either with respect to the ;, reference plane RP ox the axes of rotation of the valve means 15 ~ 15, but at the very least, such passages should be arranged such that the total flow path for either direction of oper-ation (i.e., either a left turn or a right turn) is sub-stantially the same length and flow resistanceO Thus, the pressure drop along the flow path in either direction will also be the same. It should also be noted in connection with FIGURES 3 and 4 that for purposes of clarity, circumferential : I grooves 93~97L and 97R are not shown. It will be under-. stood however that because of grooves 97L and 97R, pressure ports 99L and 99R are always in fluid communication with passages ll9L and ll9R, respectively, regardless of the relative rotational position of valve spool 77 and sleeve 79.
-. , ,. . :. ~
!1, I
373~i6 Operation In the right turn condition illustrated in FI~URE 3, fluid introduced at inlet port 17 flows through passage ll9L, ~ around circumferential groove 97L and into pressure ports 99L. With the spool 77 and sl~seve 79 in the relati~e posi-I tions shown in FIGURE 3, the pressure ports 99L are each Il aligned with one of the passages 107L, thus permitting fluid ~ to pass therethrough, then into meter groove 105L, through i¦ meter ports lOlL, then to the fluid meter 29 through passage 10 1l 121~. Af~er the fluid is metered or measured by the fluid I meter 29 it passes through passage 121R, through meter ports ¦1 lOlR and into meter groove 105R. From groove 105R the fluid ,1 then enters operating passages lO9R which are n~w circumfer- !
I entially aligned with operating ports 103R, permitting the ~luid to pass therethrough, then through passage 123R to the right turn port 33 (see FIGURE 1), from where the fluid passes through conduit 43 to the power steering ~ylinder 39. The fluid introduced into cylinder 39 moves the piston to the left, thus displacing fluid on the left side of the piston foxcing it to return to the controller through conduit 41 where it enters the controller at the left turn port 31 and passes toward the valve means 15 through passage 123L. From there the returning (non-metered) fluid passes through the operating ports 103L, then through the tank ports 115L which 25 ¦ are circumferentially aligne~ therewith, then through the . ¦ interior of the valve spool 77~ and ~inally to the outlet port 25. .
'- Il' ` , . .
. . . .
.~ . .
., .i;.
~ . : . : ~ 15 _ ` 1(~3~356 In the left turn condition shown in FIGURE 4, th~ valve spool 77 and valve sleeve 79 have been rotated in the oppo-site direction with respect to ~each other, thus permitting a ~ flow path which is generally th~e opposite of that for a right turn, and substantially the same path length. Fluid from inlet port 117 flows through passage 119R, circumferential groove 97R, through the plurality of the pressure ports 99R
then through the cir~umferentially aligned passages 107R to 1 the meter groove lO5R. From there the flow is through the 10 1I meter ports 101R, passage 121R to the fluid meter 29, then to passage 121L, in through meter port lOlL to meter groove ~¦ 105L, then axially into operating passages lO9L. From the passages lO9L fluid flows out through circumferentially aligned , operating ports 103~, through passage 123L to the left turn : 15 ¦ port 31, then through conduit 41 to the power steering cylinder 39. Fluid displaced at the opposite end o* cylinder 39 ~eturns by means of conduit 43 to the right turn port 33, then through passage 123~ ~o the valve ~eans 15~ then through operating ports 103X, and through tank ports 115R to the interior of 20 valve spool 77, and then to the outlet p~rt 25.
~t should be noted in ~onnection with both directions of operati~n (i.e., both right turn and left turn conditions), that n~t only are the flow paths s~mmetri~al and therefore, ~balanced`' with regard to the path length, but also, the "metered" and "return" ~luids are maintained axially separated.
~n ~IGURES 3 and 3~J it can be se~n that ~ircum~erential . ~roove 105R and passages 107R and lO9R contain metered fluid while return fluid passes through operating ports 103L and tnnk ports l5L at the oppo~ite end of the spool-sleeve valve.
. ~,~'' ' ' . .
.,`:' ' ~, ~"'.. ' , ~ "' .
li "' ~
~ L~373~i Generally disposed therebetween are passages lO9L,107L,lll and 11~, groove 105L and ports lOlL,99L,95 and 99R all of which contain "high pressure, non-metered~ ~uid serving as a buffer between the metered and return fluids to minimize the tendency for leakage to occur therebetween. A similar, but opposite arrangement of metered, return and high pressure non-metered fluids can be seen in FIGURES 4 and 4A.
While the lnvention has been described with reference to a preferred embodiment, neither the illustrated embodiment nor the terminology employed in describing it is intended to be limiting: rather, it is intended to be limited only by the ~; scope of the appanded claims~ ¦
1, i
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A controller for fluid pressure operated devices, said controller comprising:
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a coop-erating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for common rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define a first plurality of fluid passages connecting said inlet port in fluid communication will said first control fluid port through said fluid meter when said valve members are rela-tively displaced in one direction from the neutral position, and a second plurality of fluid passages connecting said inlet port in fluid communication with said second control fluid port through said fluid meter when said valve members are relatively dis-placed in the other direction from the neutral position;
g. said first and second pluralities of fluid passages being oppositely and approximately equally disposed about a reference plane per-pendicular to the axes of rotation of said valve members to provide a controller having uniform response in either direction of rela-tive displacement of said valve members.
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a coop-erating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for common rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define a first plurality of fluid passages connecting said inlet port in fluid communication will said first control fluid port through said fluid meter when said valve members are rela-tively displaced in one direction from the neutral position, and a second plurality of fluid passages connecting said inlet port in fluid communication with said second control fluid port through said fluid meter when said valve members are relatively dis-placed in the other direction from the neutral position;
g. said first and second pluralities of fluid passages being oppositely and approximately equally disposed about a reference plane per-pendicular to the axes of rotation of said valve members to provide a controller having uniform response in either direction of rela-tive displacement of said valve members.
2. A controller as defined in claim 1 wherein cer-tain of said first plurality of fluid passages are operable to connect said second control fluid port in fluid communication with said outlet port when said valve members are relatively displaced in said one direction from said neutral position and wherein certain of said second plurality of fluid passages are operable to connect said first control fluid port in fluid com-munication with said outlet port when said valve members are relatively displaced in said other direction from said neutral position.
3. A controller as defined in claim 1 wherein high pressure, metered fluid is contained on one side of said refer-ence plane when said valve members are relatively displaced in said one direction from said neutral position, and high pressure, metered fluid is contained on the other side of said reference plane when said valve members are relatively displaced in said other direction from said neutral position.
4. A controller for fluid pressure operated devices, said controller comprising:
a a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a cooper-ating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for com-mon rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure operated device, said primary and follow-up valve members cooperating with said housing to define a first fluid passage therein connecting said inlet port in fluid commun-ication with said first control fluid port through said fluid meter when said valve mem-bers are relatively displaced in one direction from the neutral position, and a second fluid passage connecting said inlet port in fluid communication with said second control fluid port through said fluid meter when said valve members are relatively displaced in the other direction from the neutral position;
g. said first and second fluid passages being constructed and arranged to provide substan-tially the same restriction to fluid flow between said inlet port and said first and second control fluid ports, respectively, through said meter, in either direction of displacement of said valve members from said neutral position; and h. said first and second fluid passages being arranged in substantially a mirror image of each other with respect to a central reference plane disposed generally perpendicular to the axes of rotation of said valve members.
a a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a cooper-ating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for com-mon rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure operated device, said primary and follow-up valve members cooperating with said housing to define a first fluid passage therein connecting said inlet port in fluid commun-ication with said first control fluid port through said fluid meter when said valve mem-bers are relatively displaced in one direction from the neutral position, and a second fluid passage connecting said inlet port in fluid communication with said second control fluid port through said fluid meter when said valve members are relatively displaced in the other direction from the neutral position;
g. said first and second fluid passages being constructed and arranged to provide substan-tially the same restriction to fluid flow between said inlet port and said first and second control fluid ports, respectively, through said meter, in either direction of displacement of said valve members from said neutral position; and h. said first and second fluid passages being arranged in substantially a mirror image of each other with respect to a central reference plane disposed generally perpendicular to the axes of rotation of said valve members.
5. A controller as defined in claim 4 wherein said first fluid passage is operable to connect said second control fluid port in fluid communication with said outlet port when said valve members are relatively displaced in said one direction from said neutral position and wherein said second fluid passage is operable to connect said first control fluid port in fluid communication with said outlet port when said valve members are relatively displaced in said other direction from said neutral position.
6. A controller as defined in claim 4 wherein high pressure, metered fluid in contained on one side of said central reference plane and non-metered fluid is contained on the other side of said central reference plane when said valve members are relatively displaced on said one direction from said neutral position.
7. A controller for fluid pressure operated devices, said controller comprising:
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a coop-erating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited move-ment relative to said neutral position and for common rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define a first plurality of fluid passages therein which connect said inlet port in fluid commun-ication with said first control fluid port through said fluid meter when said valve mem-bers are relatively displaced in one direction from the neutral. position and a second plural-ity of fluid passages which connect said inlet port in fluid communication with said second control fluid port through said meter when said valve members are relatively displaced in the other direction from the neutral position;
g. said first and second pluralities of fluid passages being constructed and arranged to pro-vide substantially the same restriction to fluid flow between said inlet port and said first and second control fluid ports through said meter in either direction of displacement of said valve members from said neutral posi-tion to provide a controller having uniform response in either direction of relative dis-placement of said valve members from said neu-tral position; and h. said first and second pluralities of fluid pas-sages being oppositely disposed about an imag-inary plane perpendicular to the axes of rota-tion of said valve members.
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a coop-erating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited move-ment relative to said neutral position and for common rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which passes therethrough;
e. means coupling said metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet port, and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define a first plurality of fluid passages therein which connect said inlet port in fluid commun-ication with said first control fluid port through said fluid meter when said valve mem-bers are relatively displaced in one direction from the neutral. position and a second plural-ity of fluid passages which connect said inlet port in fluid communication with said second control fluid port through said meter when said valve members are relatively displaced in the other direction from the neutral position;
g. said first and second pluralities of fluid passages being constructed and arranged to pro-vide substantially the same restriction to fluid flow between said inlet port and said first and second control fluid ports through said meter in either direction of displacement of said valve members from said neutral posi-tion to provide a controller having uniform response in either direction of relative dis-placement of said valve members from said neu-tral position; and h. said first and second pluralities of fluid pas-sages being oppositely disposed about an imag-inary plane perpendicular to the axes of rota-tion of said valve members.
8. A controller as defined in claim 7 wherein certain of said first plurality of fluid passages are operable to con nect said second control fluid port in fluid communication with said outlet port when said valve members are relatively displaced in said one direction from said neutral position and wherein cer-tain of said second plurality of fluid passages are operable to connect said first control fluid port in fluid communication with said outlet port when said valve members are relatively displaced in said other direction from said neutral position.
9. A controller as defined in claim 8 wherein said first and second pluralities of fluid passages defined by said housing and said valve members for connecting said inlet to said first and second control fluid ports through said fluid meter are arranged in substanitally a mirror image of each other with re-spect to an imaginary plane perpendicular to the axes of rotation of said valve members.
10. A controller as defined in claim 9 wherein said first and second pluralities of fluid passages contain metered fluid and return fluid, said metered fluid and said return fluid being oppositely disposed about said imaginary plane.
11. A controller as defined in claim 10 wherein said first and second pluralities of fluid passages contain high pressure, non-metered fluid, disposed generally between said metered fluid and said return fluid.
12. A controller for fluid pressure operated devices, said controller comprising:
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a cooper-ating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having gen-erally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for com-mon rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which pas-ses therethrough, e. means coupling and metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet ports and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define first and second source passage means in fluid communication with said inlet port and being oppositely and approximately equally disposed about a reference plane disposed generally perpendicular to said axes of rotation;
g. said primary and follow-up valve members de-fining a first plurality of fluid passages con-necting said first source passage means in fluid communication with said first control fluid port through said fluid meter when said valve members are relatively displaced in one direction from the neutral position, and a second plurality of fluid passages connecting said second source passage means in fluid com-munication with said second control fluid port through said fluid meter when said valve mem-bers are relatively displaced in the other direction from the neutral position; and h. said first and second pluralities of fluid passages being constructed and arranged to provide substanitally the same restriction to fluid flow between said first and second source passage means and said first and second control fluid ports, respectively, in either direction of displacement of said valve mem-bers from said neutral position.
a. a housing;
b. valve means disposed in said housing including a primary, rotatable valve member and a cooper-ating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having gen-erally coincidental axes of rotation;
c. means coupling said follow-up valve member to said primary valve member for limited movement relative to said neutral position and for com-mon rotary movement therewith;
d. a fluid meter including a metering member mov-able to measure the volume of fluid which pas-ses therethrough, e. means coupling and metering member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said metering member;
f. said controller including an inlet port, an outlet ports and first and second control fluid ports for connection to a fluid pressure oper-ated device, said primary and follow-up valve members cooperating with said housing to define first and second source passage means in fluid communication with said inlet port and being oppositely and approximately equally disposed about a reference plane disposed generally perpendicular to said axes of rotation;
g. said primary and follow-up valve members de-fining a first plurality of fluid passages con-necting said first source passage means in fluid communication with said first control fluid port through said fluid meter when said valve members are relatively displaced in one direction from the neutral position, and a second plurality of fluid passages connecting said second source passage means in fluid com-munication with said second control fluid port through said fluid meter when said valve mem-bers are relatively displaced in the other direction from the neutral position; and h. said first and second pluralities of fluid passages being constructed and arranged to provide substanitally the same restriction to fluid flow between said first and second source passage means and said first and second control fluid ports, respectively, in either direction of displacement of said valve mem-bers from said neutral position.
13. A controller for fluid pressure operated devices, said controller including a housing having an inlet and an out-let, and first and second control fluid ports adapted for con-nection to a fluid pressure operated device, said controller comprising;
a. valve means including a primary, rotatable valve member and a cooperating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
b. means coupling said follow-up valve member to said primary valve member for limited move-ment independently thereof and for common move-ment therewith;
c. a fluid meter including a movable member and means coupling said movable member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said primary valve member;
d. said controller having source passage means communicable with said inlet, first and sec-ond control fluid passages for connection to said first and second control fluid ports, and first and second fluid meter passages for con-nection to said first meter;
e. said follow-up valve member defining a refer-ence plane oriented generally perpendicular to said axes of rotation, said follow-up valve member further defining:
i. first and second pressure ports in sub-stantially continuous, open communication with said source passage means, said first and second pressure ports being oppositely and approximately equally disposed about said reference plane, ii. first and second meter ports operable to communicate with said first and second fluid meter passages, respectively, said first and second meter ports being oppo-sitely and approximately equally disposed about said reference plane, and iii. first and second operating ports in sub-stantially continuous, open communication with said first and second control fluid passages, respectively, said first and sec-ond operating ports being oppositely and approximately equally disposed about said reference plane;
f. said primary valve member defining a first fluid passage operable to provide fluid com-munication between said first pressure port and said first meter port in response to relative displacement of said valve members in one direction from said neutral position and a second fluid passage operable to provide fluid communication between said second pressure port and said second meter port in response to relative displacement of said valve mem-bers in the other direction from said neutral position; and g. said primary valve member defining a first operating passage operable to provide fluid communication between said first meter port and said first operating port in response to relative displacement of said valve members in said other direction from said neutral position and a second operating passage oper-able to provide fluid communication between said second meter port and said second oper-ating port in response to relative displacement of said valve members in said one direction from said neutral position.
a. valve means including a primary, rotatable valve member and a cooperating, relatively rotatable follow-up valve member, said valve members defining a neutral position relative to each other and having generally coincidental axes of rotation;
b. means coupling said follow-up valve member to said primary valve member for limited move-ment independently thereof and for common move-ment therewith;
c. a fluid meter including a movable member and means coupling said movable member to said follow-up valve member for imparting follow-up movement thereto responsive to movement of said primary valve member;
d. said controller having source passage means communicable with said inlet, first and sec-ond control fluid passages for connection to said first and second control fluid ports, and first and second fluid meter passages for con-nection to said first meter;
e. said follow-up valve member defining a refer-ence plane oriented generally perpendicular to said axes of rotation, said follow-up valve member further defining:
i. first and second pressure ports in sub-stantially continuous, open communication with said source passage means, said first and second pressure ports being oppositely and approximately equally disposed about said reference plane, ii. first and second meter ports operable to communicate with said first and second fluid meter passages, respectively, said first and second meter ports being oppo-sitely and approximately equally disposed about said reference plane, and iii. first and second operating ports in sub-stantially continuous, open communication with said first and second control fluid passages, respectively, said first and sec-ond operating ports being oppositely and approximately equally disposed about said reference plane;
f. said primary valve member defining a first fluid passage operable to provide fluid com-munication between said first pressure port and said first meter port in response to relative displacement of said valve members in one direction from said neutral position and a second fluid passage operable to provide fluid communication between said second pressure port and said second meter port in response to relative displacement of said valve mem-bers in the other direction from said neutral position; and g. said primary valve member defining a first operating passage operable to provide fluid communication between said first meter port and said first operating port in response to relative displacement of said valve members in said other direction from said neutral position and a second operating passage oper-able to provide fluid communication between said second meter port and said second oper-ating port in response to relative displacement of said valve members in said one direction from said neutral position.
14. A controller as defined in claim 13 wherein said primary valve member defines first and second circumferantial meter grooves, said first and second meter grooves being oppo-sitely and approximately equally disposed about said reference plane.
15. A controller as defined in claim 14 wherein said first fluid passage includes said first meter groove and said second fluid passage includes said second meter groove.
16. A controller as defined in claim 15 wherein said first fluid passage includes a first axial fluid slot communi-cating with said first meter groove, said first axial fluid slot being disposed to communicate with said first pressure port in response to relative displacement of said valve members in said one direction from said neutral position, and said second fluid passage includes a second axial fluid slot communicating with said second meter groove, said axial fluid slot being disposed to com-municate with said second pressure port in response to relative displacement of said valve members in said other direction from said neutral position.
17. A controller as defined in claim 14 wherein said first operating passage includes said first meter groove and said second operating passage includes said second meter groove.
18. A controller as defined in claim 17 wherein said first operating passage includes a first axial operating slot communicating with said first meter groove, said first axial operating slot being disposed to communicate with said first operating port in response to relative displacement of said valve members in said other direction from said neutral position, and said second operating passage including a second axial oper-ating slot communicating with said second meter groove, said second axial operating slot being disposed to communicate with said second operating port in response to relative displacement of said valve members in said one direction from said neutral position.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50701574A | 1974-09-18 | 1974-09-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1037356A true CA1037356A (en) | 1978-08-29 |
Family
ID=24016939
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA234,968A Expired CA1037356A (en) | 1974-09-18 | 1975-09-08 | Controller for fluid pressure operated devices |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS5155881A (en) |
| BE (1) | BE833568A (en) |
| BR (1) | BR7505986A (en) |
| CA (1) | CA1037356A (en) |
| CH (1) | CH615251A5 (en) |
| DD (1) | DD120250A5 (en) |
| DE (1) | DE2541487A1 (en) |
| DK (1) | DK154449C (en) |
| FR (1) | FR2285649A1 (en) |
| GB (1) | GB1524707A (en) |
| IT (1) | IT1046898B (en) |
| NL (1) | NL179084C (en) |
| SE (1) | SE414330B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1077304B (en) * | 1976-06-23 | 1985-05-04 | Eaton Corp | REGULATOR FOR DEVICES OPERATED BY THE PRESSURE OF A FLUID |
| GB1565440A (en) * | 1977-01-24 | 1980-04-23 | Eaton Corp | Controller for fluid pressure operated devices |
| US4311171A (en) * | 1978-09-22 | 1982-01-19 | Trw Inc. | Hydrostatic steering controller with pressure dams |
| FR2437967A1 (en) * | 1978-10-02 | 1980-04-30 | Zahnradfabrik Friedrichshafen | PRESSURE FLUID CONTROL DEVICE, PARTICULARLY FOR HYDROSTATIC STEERING MECHANISMS OF MOTOR VEHICLES |
| DE2906183C2 (en) * | 1979-02-17 | 1986-09-18 | Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen | Hydrostatic steering device for automobiles |
| DE2944883C2 (en) * | 1979-11-07 | 1982-08-26 | Danfoss A/S, 6430 Nordborg | Hydrostatic steering device |
| DE2952674C2 (en) * | 1979-12-28 | 1983-03-24 | Danfoss A/S, 6430 Nordborg | Hydraulic steering device |
| FR2514433A1 (en) * | 1981-10-09 | 1983-04-15 | Dba | HYDRAULIC ROTARY DISPENSER |
| IT1306088B1 (en) * | 1998-07-31 | 2001-05-29 | Ognibene Spa | HYDROSTATIC GUIDE WITH OPERATING MODE BOTH REACTIVE AND NONREACTIVE. |
| DE10147569C1 (en) * | 2001-09-26 | 2003-05-28 | Bosch Rexroth Ag | Hydraulic steering device with change of gear ratio |
| ITRE20020049A1 (en) * | 2002-05-27 | 2003-11-27 | Ognibene Spa | HYDROSTATIC GUIDE FOR QUICK STEERING |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US25126A (en) * | 1859-08-16 | Churn | ||
| US3443378A (en) * | 1967-04-04 | 1969-05-13 | Trw Inc | Hydrostatic single unit steering system |
| US3452543A (en) * | 1967-11-06 | 1969-07-01 | Trw Inc | Hydrostatic device |
| US3819307A (en) * | 1972-10-24 | 1974-06-25 | Eaton Corp | Stability means for a controller for fluid pressure operated devices |
-
1975
- 1975-09-03 GB GB3629075A patent/GB1524707A/en not_active Expired
- 1975-09-08 CA CA234,968A patent/CA1037356A/en not_active Expired
- 1975-09-11 CH CH1182675A patent/CH615251A5/en not_active IP Right Cessation
- 1975-09-15 SE SE7510269A patent/SE414330B/en not_active IP Right Cessation
- 1975-09-16 BR BR7505986A patent/BR7505986A/en unknown
- 1975-09-17 IT IT2733275A patent/IT1046898B/en active
- 1975-09-17 DK DK416175A patent/DK154449C/en not_active IP Right Cessation
- 1975-09-17 DE DE19752541487 patent/DE2541487A1/en active Granted
- 1975-09-18 DD DD18842475A patent/DD120250A5/xx unknown
- 1975-09-18 NL NL7511038A patent/NL179084C/en not_active IP Right Cessation
- 1975-09-18 FR FR7528599A patent/FR2285649A1/en active Granted
- 1975-09-18 JP JP11307775A patent/JPS5155881A/en active Granted
- 1975-09-18 BE BE160163A patent/BE833568A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| BE833568A (en) | 1976-01-16 |
| DD120250A5 (en) | 1976-06-05 |
| NL179084C (en) | 1986-07-01 |
| SE7510269L (en) | 1976-03-19 |
| NL7511038A (en) | 1976-03-22 |
| DK154449B (en) | 1988-11-14 |
| DE2541487A1 (en) | 1976-04-08 |
| JPS5629121B2 (en) | 1981-07-06 |
| BR7505986A (en) | 1976-08-03 |
| GB1524707A (en) | 1978-09-13 |
| FR2285649B1 (en) | 1981-10-30 |
| DE2541487C2 (en) | 1989-07-13 |
| CH615251A5 (en) | 1980-01-15 |
| DK154449C (en) | 1989-04-10 |
| SE414330B (en) | 1980-07-21 |
| DK416175A (en) | 1976-03-19 |
| NL179084B (en) | 1986-02-03 |
| JPS5155881A (en) | 1976-05-17 |
| FR2285649A1 (en) | 1976-04-16 |
| IT1046898B (en) | 1980-07-31 |
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