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US2607558A - Hydraulic valve and post - Google Patents

Hydraulic valve and post Download PDF

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Publication number
US2607558A
US2607558A US66553046A US2607558A US 2607558 A US2607558 A US 2607558A US 66553046 A US66553046 A US 66553046A US 2607558 A US2607558 A US 2607558A
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United States
Prior art keywords
valve
passageway
steering
post
hydraulic
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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.)
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Inventor
Fred J Wright
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Galion Iron Works & Manufacturing Co
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Galion Iron Works & Manufacturing Co
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Publication date
Priority claimed from US565356A external-priority patent/US2464110A/en
Application filed by Galion Iron Works & Manufacturing Co filed Critical Galion Iron Works & Manufacturing Co
Priority to US66553046 priority Critical patent/US2607558A/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F15B9/10Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor in which the controlling element and the servomotor each controls a separate member, these members influencing different fluid passages or the same passage
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/6851With casing, support, protector or static constructional installations
    • Y10T137/6855Vehicle
    • Y10T137/6881Automotive
    • Y10T137/6884Steering post or wheel
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87169Supply and exhaust
    • Y10T137/87177With bypass

Definitions

  • This invention relatesto a' hydraulic valve and post particularly designed for controlling various operations or a vehicle, such as a road grader.
  • An objector the'irivention is to provide an improved apparatus' or the above mentioned type.
  • Another object of the" invention is to provide a combination valve and steering post which preferably has feed disch'ar'ge passages which lead to andfrom a valve, preferably arotary valve, in the top thereof, and which in' a more specific aspect of the'inv'enti'on also is” provided with one or more high pressure relief by pass valves in its' base and' in a' still morespec'ific aspect of the invention alsoincludes a drain passagewaylfo'rmed' in the'po'st for draining leakage hydraulic fluid from a valve' in the top of the post toa drainor tankpassag'eway'.
  • Still another object of the invention' is to'p'rovide an improved'hydr'aulic apparatus in the form of an upstanding post wh'ich'housesa steering valve in the top and a relief valve or valves in the bottom.
  • Another object of the invention is toprovide an" improved rotary valve' having a shell formed to obtain the desirable area of hydraulic passage'way, thoughhridged by a core;
  • Fig. 1 is a sectionalelevationalview through the center ofthe steering postand valve of my invention. This figure alsoincludes a portion of theassociated hydraulic circuit;
  • Fig. 2 is a transverse sectional view taken on the lined-f Fig. 1 looking in the direction ofthearrows-1 Fig. 3'is a; transverse sectional view taken on the line 3-3 of Fig'. 1,-10'okirig in the direction of the arrows;
  • Fig.- 4 is an-' enlarged sectional view taken on the line' of Fig. 3;'-lo'oking inthe direction of the arrows, ana with the spider or core omitted;
  • Fig.5 is a view, similar to Fig. l, of a modified form ofpost and steering valve
  • Fig. 6 is a-sectional view taken'on-the line -6+4; ofFigi-Sfand Fig. 7- is an enlargedside view of the'shell of the steering valve of Figs. 5 and 6; withpar'ts broken away andsho'wn in section.
  • the hydraulic apparatus-herein disclosed may be usedin'- a variety of different places or with a variety of different vehicles.
  • One vehicle where it is particularly adapted to be used is a road grader, such as that disclosed in more detail in the patent to Franklin E. Arndt, No. 2,340,169, dated January 25; 1944, for a Road Grader.
  • Said post 46 includes a main body, casting or casing 68 which is in the form of an elongated upwardly extending member having a base portion' 69 at its bottom which has a pair of flat parallel side surfaces preferably having the same distance apart as the fiat parallel side surfaces of a standard style-valve. As clearly illustrated in-Fi'g. l of the drawings, this base portion 69-includes the bores 50 through which tie bolts extend.
  • the steering post 46 is adapted to be banked into or flanked at opposite sides by individual control valves, which as shown and described in my parent application, Serial No. 565,356, above identified, are spool-or slide type valves connected in series. It is pointed out-that in the complete valve assembly including the steering post' and the flanking valves there is a" rotary follow-up type steering valve positioned in the top of post 461 This valve'is fully described hereinafter, and it also is connected in series-with all of the individual valves.
  • the head 70 is provided along its longitudinal axis with acylindrical bore 72 which is closed at its front by" removable'end cap 13 and at its rear by'removable end cap 14.
  • The'axis of bore 12 and the valve therein is-transverse to the axis of the post body 46.
  • Conduits 83 and 84 are cylinder or motor conduits and they are connected with passageways 'I9 and 80, respectively. These two conduits 83 and 84 extend forwardly along the main frame of the road grader or other vehicle and deliver hydraulic fiuid'to and from a double acting hydraulic piston steering motor.
  • a stub shaft 89 which extends through therear end cap 14 and is formed as an integral part of a spider or core 90 of the valve II, the structure of which core or spider is described in full detail hereinafter.
  • the previously de scribed passageway 82 is connected with a return conduit 94 which in practice is a feed conduit for supplying hydraulic fluid pumped by pump 92 to the banked individual spool or slide valves hereinbefore referred to which flank the steering post 46 and are connected in series.
  • a rotatable cylinder, sleeve, or shell 95 which extends longitudinally beyond the end grooves 15 and 18 and abuts the end caps I3 and I4. Adjacent its rear or left-hand end the cylinder 95 is provided with a groove 96 which receives an O-ring 91 providing a seal between this portion of the sleeve 95 and the interior cylindrical surface of the head I0.
  • a cylinder groove and O-ring seal 98 is provided near the right-hand or front portion of the sleeve or shell 95.
  • a steering wheel shaft 99 having a steering wheel I rigidly attached to the right-hand end thereof and within easy reach of the operator.
  • the shaft 99 is provided with a head IOI which extends into a diametrical groove I02 (see Fig. 2) which is formed in the right hand end of the sleeve or cylinder 95.
  • a turning of the wheel I00 will turn the shell or sleeve 95 therewith.
  • the head IOI is provided with a transverse winged groove I03 into which project abutments I04 which are urged outwardly toward said groove I03 by springs I05.
  • the abutments I04 are provided with heads which fit in the bottoms of bores which receive the springs I05 and thus limit their outward movement into the groove I03.
  • Removable caps I06 are provided on the head IM and are removably connected thereto by screws
  • the previously mentioned spider or core 90 extends into and is mounted for rotation with respect to the cylinder or sleeve 95, it being provided at its opposite ends with generally cylindrical end portions having O-ring seals I08 and I09, respectively.
  • the spider or core is formed with four longitudinal grooves or troughs IIO, III, II2 and H3 (see Fig. 3).
  • the troughs or grooves IIO to H3, extend along the spider 90 so as to overlap a distance equal to that between the passageways or grooves I5 to T8, inclusive, in the head I0.
  • the central portion of the spider 90 is provided with a plurality of radial cross bores II5 which are effective to interconnect the grooves or troughs H0 and II2 in one instance, and the grooves III and H2 in the other instance.
  • This provides for a completely balanced arrangement of the valve I I
  • the shell or cylinder is provided with four radial ports H6, H1, H8 and II9 (see Figs. 3 and 4) There is one of these ports for each of the grooves I5 to I8, inclusive, and these ports II6 to I I9, inclusive, are distributed axially along the shell 95 so that one of them is in alignment and communication with each of said passageways 15 to T8 and is individual thereto.
  • port IIB as illustrated in Fig.
  • Port II9 is individual to and communicates with circumferential passageway I1. These are the pressure or feed passageway and port. Port II! is individual to and communicates with circumferential passageway I6. These are one of the cylinder or motor passageways and ports. Port Il8 communicates with and is individual to circumferential passageway I5 which are the other motor or cylinder passageway and port.
  • center lines of the various ports II6 to II9 are important. If horizontal and vertical lines are drawn, intersecting at the center of the core 90, the center lines of the various ports II6 to II9, inclusive, will be as follows: Center line of port II6 will be forty-five degrees from both vertical and horizontal lines; center line of port II! will be fifteen degrees from the vertical line. The center line of port I I8 will be fifteen degrees from the horizontal line, and the center line of port I I9 will be forty-five degrees from both the horizontal and vertical lines.
  • the right-hand end of the spider 90 is provided with a projection I20, the top and bottom surfaces of which are parallel, said projection extending into the winged groove I03 formed in the head IOI of shaft 99.
  • the abutments I04 when in their normal positions as illustrated, just contact the top and bottom surfaces of the projection I20 on opposite sides of the center or axis of rotation of said projection I20 which, of course, is the axis of the spider 90.
  • the wing shape of the groove I03 provides for limited relative rotary movement between the spider 90 and the shell 95 before said projection I20 comes into a solid driving abutment with the walls of said groove I03.
  • the centering means formed by the springs I05 and abutments I04 have a double function and their effectiveness may be adjusted by adjusting the strength of the springs I05.
  • the second function of the spring centering means I04, I05 is to provide a biasing means which will tend to adjust the spider or core 90 to its neutral'position'with respect to the shell or cylinder 95' and this is'particularly desirable to prevent undesirable oscillation of the steering rod-in case there is an appreciable lost motion between the mechanical connection to the piston of the hydraulic steering motor and the stub shaft 89 which will develop particularly in the universal joints leading to said shaft 89 and the reduction gearing.
  • Fig. 4 of the drawings Attention isdirected also to Fig. 4 of the drawings and to a feature of construction of the ports I IE to I I9, which are of similar design, port IIB being illustrated insaid Fig. 4.
  • the ports IIG'to I I9 extend over a limited portion of the circumference of the interior surface of shell 95.
  • the port H6 is bridged by a web of the spider 90. This, of course, appreciably reduces'its effective area or, in other words, the area through which hydraulic fluid can flow, as illustrated in said Fig. 3 by the arrows, when the valve is in its neutral position which is the relative position of the parts as illus trated in said Fig. 3.
  • This outside dimension of the port I I6 can be circumferentially' extended as compared'with the circumferential extent of its" inside surface and this has been done, as clearly illustrated in said Fig. 3, while maintaining its axial dimension or width substantially equal to-that of associated groove 18.
  • the efiective area of the port H6 is substantially the same on both its outer and inner surfaces when the inner surface is bridged by the above mentioned web.
  • the structures of the ports IIl, I I8 and H9 are the same as that of port I I6.
  • the hydraulic fluid in the troughs IIO to H3, inclusive is free to flow through the conduits 83 and 84 by way of circumferential passageways I5 and I6 and connecting passageways I9 and 80, but this is appreciably without eflect on the hydraulic steering motor or if it does have any effect thereon due to the unbalanced nature of said hydraulic jack, this will cause an automatic correcting movement of the spider 90.
  • the return path for the hydraulic fluid from the hydraulic cylinder or motor will be by way of conduit 86, post passageway 88, circumferential passageway I6, port II 1, groove or trough H2, port H6, and circumferential passageway I8 to the post passageway 82 which delivers it to conduit 94 and thence to tank through the group of banked valves in series as above mentioned.
  • the hydraulic circuit is a series circuit
  • the hydraulic fluid flowing in conduit 94 regardless of whether the steering valve is in its neutral position or is in a position to deliver hydraulic fluid to the steering motor, may be employed to operate any one or more of the double acting or reversible hydraulic motors controlled by the individual valves. That is, with this system, any number of control valves, including the rotary control valve, from one to the maximum number, may be operated simultaneously.
  • the steering valve II is operable upon counterclockwise rotation of the wheel I06 in a manner which is comparable to that above described so that power steering may be effected by turning the wheel in either direction.
  • I provide a pair of high pressure relief by-pass valves I23 and I24 which are of duplicate construction, but which provide different functions.
  • the by-pass valve I23 by-passes the rotary valve H and it is preferably set to open at a pressure differential which is lower than that at which by-pass valve I24 opens.
  • the function of the by-pass valve I24 is to control a passageway or chamber providing a by-pass to tank through a conduit I26 a portion of which is formed in the base 59 of post 46 and extends between the opposite fiat parallel side surfaces of the bottom of the steering post 46 whenever a high pressure condition exists anywhere in the system, except on the input side of the double acting steering motor, but this bypassing of the fluid only discharges the fluid to tank after it has passed through the rotary valve II or through its individual relief valve I23.
  • the relief valve I23 provides a high pressure by-pass for the valve 'II since it controls a passageway or chamber interconnecting feed passageway 8I and discharge passageway 82 and obviously upon the appearance of a predetermined high pressure in conduit 9
  • valves I23 and I24 are of essentially standard design and thus need no detailed explanation. It may be pointed out, however, that a hollow springpressed valve closing piston I45 of each is provided with a port I45 so that hydraulic fluid in the passageway 82 will be present on both sides of the piston I45 and hydraulic fluid flowing through passageway I26 in valve I24 will also be on both sides of its piston I45. This is of particular importance in connection with relief valve I23 because it insures that whatever the pressure in passageway 82, by-pass valve I23 will only open in response to a higher predetermined pressure in passageway BI determined by the adjustment of spring of valve I23.
  • valve I23 would only open when the pressure in passageway 8I reached 700 pounds. Because of this fact there is always hydraulic pressure available to control the steering of the vehicle even though the pressure relief valve I24 is open for any reason. Ihis is an important feature of the hydraulic system of my invention.
  • the pressures at which the valves I23 and I M open may be varied by adjusting their compression springs.
  • Figs. 5, 6 and 7 of the drawings I have disclosed a modified form of steering post assembly 2 58 which may be substituted for steering post assembly 46. It is to be understood that unless a contrary fact is indicated, the steeringv post assembly 246 follows the structure of steering post assembly 48. One difference therein is in the structure of the head or cylindrical portion 2W. Said head portion 210 is provided at its top with a drain passageway I30 which extends irom the front to the rear thereof and opens into the cylindrical bore 12 at both ends.
  • the post 248 includes a main body casting or casing 268 which in addition to the four passageways 19, 86, 8I and 82, is provided with a drain passageway I3I which receives leakage fluid collected from a rotary steering valve 21I and delivers it to the drain passageway I26.
  • the rotary, steering valve 2H differs from the steering valve H in a number of particulars. In the first place. the O-nng seals 91, 98, I88 and I08 have been eliminated and the leakage of the valve parts is drained off by the passageways I30 and I3I.
  • I employ a different shell, sleeve or cylinder 295 which is provided with a pair of diametrically opposed ports, as viewed from its interior surface, associated with each of the cylindrical passageways or grooves "I5, 15, ll and I8.
  • Diametrically opposed ports 219 communicate with pas- '9 sageway
  • 1,8 diametrically opposed ports 2 I6 communicate with passageway 11
  • diametrically opposed ports 2I'I communicate with passageway I8
  • diametrically opposed ports 2I8 cornmunicate with passageway I5.
  • the ports 2 I I and 2 I 8 do not extend radially through the shell 295, but extend parallel with the ports 2I9. This is to provide for forming of the sand cores to make the shell 295 so that the core patterns can be separated without destroying the dry sand cores. Functionally, the operation would be the same if all of the ports 2I6 to 2I9, inclusive, extended radially through the shell 295.
  • the spider or core 290 also differs from the spider or core 90 not only in the elimination of the O-ring seals, but also in the elimination of the equalizing cross bores II5. These are not necessary to produce a balanced condition in the valve because of the presence of the diametrically opposed ports 2I6 to 2I9, inclusive.
  • the head ZIII is provided with a circumferential notch, recess or groove I32 which provides a circumferential passageway interconnecting the top passageway I30 and the drain passageway I3I.
  • the action of the rotary steering valve 2II is essentially the same as that of the rotary steering valve II.
  • This valve 2' also provides a direct mechanical drive in case of emergency, since the core or spider 290 is provided with a projection 22!) which projects into the previously mentioned winged groove 203.
  • the post assembly 246 is essentially the same as the post assembly 46 and either may be substituted in the hydraulic system, for the other.
  • a post forming a housing having an elongated upstanding body portion having an attaching base at its bottom for mounting said post and a valve cas ing at its top which includes a valve operably mounted therein, hydraulic feed and return passageways running longitudinally in said body leading to and from said valve casing, said valve controlling the opening and closing of said passageways, a pressure relief valve passageway in the base of said housing for by-passing said valve by placing said feed and return passageways in communication with each other before the latter said passageways communicate with said valve housing, and a second pressure relief valve passageway in the base of said housing connecting the return passageway to drain.
  • a combination valve and steering post including an elongated upstanding housing having valve housing means adjacent its top receiving a rotary steering valve and a bottom portion adapted to be banked between other valves, said bottom portion including opposite parallel surfaces adapted to receive said other valves, means in said housing providing feed and return passageways extending longitudinally thereof and to said rotary valve, means providing motor passageways in said housing connecting with said rotary steering valve, means providing a continuous passageway extending through the bottom portion of said housing between said opposite surfaces, means forming a drain passageway extending between said opposite surfaces, a by-pass passageway in said housing interconnecting said feed and return passageways for by-passing said rotary steering valve, and a second by-pass passagaway in said housing interconnecting said return pa sageway and said drain passageway for ay-passing fluid from the former into the latter.
  • a combination valve and steering post including an elongated upstanding housing having valve housing means adjacent its top receiving a rotary steering valve and a bottom portion adapted to be banked between other valves, said bottom portion including opposite surfaces adapted to receive said other valves, means in said housing providing feed and return passageways extending longitudinally thereof and to said rotary valve, means providing motor passageways in said housing connecting with said rotary steering valve, means providing a continuous passageway extending through the bot- 11 12 tom portion of said housing between said opposite UNITED STATES PATENTS surfaces, and means forming a drain passageway Number Name Date extending between said opposite surfaces. 1,491,248 Schur Arm 22, 1924 FRED WRIGHT- 5 1,991,227 Proctor Feb.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Steering Mechanism (AREA)

Description

Aug. 19, 1952 F. J. WRIGHT 2,607,558
HYDRAULIC VALVE AND POST Original Filed Nov. 27, 1944 2 SHEETS-SHEET 1 105 a? 05-1 I 4G/ 74 V u 120 IL t Alf xl l Fly 3 [NVE/YTO J FEED J. WEIGHT,
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Aug. 19, 1952 F. J. WRIGHT HYDRAULIC VALVE AND POST 2 SHEETSSHEET 2 Original Filed Nov. 27, 1944 fxvvcvvrc Q; Fer-:0 J W IGHT,
KITTY Patented Aug. 19, 1952 UNITED STATES PATENT OFFICE Gallon Ironworks & Manufacturing Company, a corporation of Ohio OriginalapplicationNovember 27, 1944, Serial No. 565,356, now Patent No. 2,464,110, dated March 8,1949. Divided and this application April 27, 1946, Serial No 665,530
3 Claims. 1
This invention relatesto a' hydraulic valve and post particularly designed for controlling various operations or a vehicle, such as a road grader.
An objector the'irivention is to provide an improved apparatus' or the above mentioned type.
Another object of the" invention is to provide a combination valve and steering post which preferably has feed disch'ar'ge passages which lead to andfrom a valve, preferably arotary valve, in the top thereof, and which in' a more specific aspect of the'inv'enti'on also is" provided with one or more high pressure relief by pass valves in its' base and' in a' still morespec'ific aspect of the invention alsoincludes a drain passagewaylfo'rmed' in the'po'st for draining leakage hydraulic fluid from a valve' in the top of the post toa drainor tankpassag'eway'.
Still another object of the invention'is to'p'rovide an improved'hydr'aulic apparatus in the form of an upstanding post wh'ich'housesa steering valve in the top and a relief valve or valves in the bottom.
Another object of the invention is toprovide an" improved rotary valve' having a shell formed to obtain the desirable area of hydraulic passage'way, thoughhridged by a core;
Other objects of the invention will appear hereinafter, the'novel features and combinations beings'et forthin'the appendedclairns.
In the accompanying drawings,
Fig. 1 is a sectionalelevationalview through the center ofthe steering postand valve of my invention. This figure alsoincludes a portion of theassociated hydraulic circuit;
Fig. 2 is a transverse sectional view taken on the lined-f Fig. 1 looking in the direction ofthearrows-1 Fig. 3'is a; transverse sectional view taken on the line 3-3 of Fig'. 1,-10'okirig in the direction of the arrows;
Fig.- 4=is an-' enlarged sectional view taken on the line' of Fig. 3;'-lo'oking inthe direction of the arrows, ana with the spider or core omitted;
Fig.5 isa view, similar to Fig. l, of a modified form ofpost and steering valve;
Fig. 6 is a-sectional view taken'on-the line -6+4; ofFigi-Sfand Fig. 7- is an enlargedside view of the'shell of the steering valve of Figs. 5 and 6; withpar'ts broken away andsho'wn in section.
This application is a division of my" applica tion- Serial No. 565356; entitled Hydraulic System and A'ppar'atus', filed November 27, 1944', now Patent No. 2,464,110 issued March- 8, 1949.
The hydraulic apparatus-herein disclosed may be usedin'- a variety of different places or with a variety of different vehicles. One vehicle where it is particularly adapted to be used is a road grader, such as that disclosed in more detail in the patent to Franklin E. Arndt, No. 2,340,169, dated January 25; 1944, for a Road Grader.
Attention is directed particularly to Fig. 1 of the drawings and to the structure of the steering post designated 46; and its associated valves. Said post 46 includes a main body, casting or casing 68 which is in the form of an elongated upwardly extending member having a base portion' 69 at its bottom which has a pair of flat parallel side surfaces preferably having the same distance apart as the fiat parallel side surfaces of a standard style-valve. As clearly illustrated in-Fi'g. l of the drawings, this base portion 69-includes the bores 50 through which tie bolts extend.
The steering post 46 is adapted to be banked into or flanked at opposite sides by individual control valves, which as shown and described in my parent application, Serial No. 565,356, above identified, are spool-or slide type valves connected in series. It is pointed out-that in the complete valve assembly including the steering post' and the flanking valves there is a" rotary follow-up type steering valve positioned in the top of post 461 This valve'is fully described hereinafter, and it also is connected in series-with all of the individual valves. In practice the steeringvalve'ls the first v'alveof all-0f the-valves to receive hydraulic fluidunder pressure from a hydraulic pump, the hydraulic fluid either after passing through-the-steering valveor lay-passing itbeing conducted-througha return feedpipe or conduit to supply the spool or slide valves into'which the post 46-is banked.
The upper end of the post casting Bars-provided with an integralgenerally cylindrical portion 70 which-forms ahead-and constitutes the main-bodyor casing-0f"a-rotary'steering valve H The head 70 is provided along its longitudinal axis with acylindrical bore 72 which is closed at its front by" removable'end cap 13 and at its rear by'removable end cap 14. The'axis of bore 12 and the valve thereinis-transverse to the axis of the post body 46.
Communicating with the cylindrical bore 72, or, in other-words, formed on the interior surface of the-head 'Hl'are four longitudinally spaced peripheral-passageways 0r g'rooves='l5,-l6, 71 and 18. The passagewaysor'grooves 15; 16 ,11 and 78 communicate with generally axially or longitudinally upwardly extending passageways I9, 80, BI and 82, respectively, which are formed in the intermediate section of the post 46 or, in other words, between the base 69 and the head 10 thereof. v
The rear face of the casting 68 is provided with threaded openings to receive hydraulic conduits, there being a conduit leading to each of the passageways I9, 80, 8| and 82. Conduits 83 and 84 are cylinder or motor conduits and they are connected with passageways 'I9 and 80, respectively. These two conduits 83 and 84 extend forwardly along the main frame of the road grader or other vehicle and deliver hydraulic fiuid'to and from a double acting hydraulic piston steering motor.
Furthermore, the movement of the steering motor is fed back in appropriate gearing to a stub shaft 89, which extends through therear end cap 14 and is formed as an integral part of a spider or core 90 of the valve II, the structure of which core or spider is described in full detail hereinafter.
Connected with the previously mentioned passageway 8I in the casting 68 is a feed or pressure conduit 9I leading from a pump 92 which derives hydraulic fluid from a tank. The previously de scribed passageway 82 is connected with a return conduit 94 which in practice is a feed conduit for supplying hydraulic fluid pumped by pump 92 to the banked individual spool or slide valves hereinbefore referred to which flank the steering post 46 and are connected in series.
Returning to a consideration of the structure which makes up the rotary steering valve II, rotatably mounted within the cylindrical bore I2 and having a close fit therewith is a rotatable cylinder, sleeve, or shell 95 which extends longitudinally beyond the end grooves 15 and 18 and abuts the end caps I3 and I4. Adjacent its rear or left-hand end the cylinder 95 is provided with a groove 96 which receives an O-ring 91 providing a seal between this portion of the sleeve 95 and the interior cylindrical surface of the head I0. A cylinder groove and O-ring seal 98 is provided near the right-hand or front portion of the sleeve or shell 95.
Extending through the cap I3 is a steering wheel shaft 99 having a steering wheel I rigidly attached to the right-hand end thereof and within easy reach of the operator. At its inner end and within the housing provided by the head I0 and the caps 13 and 14, the shaft 99 is provided with a head IOI which extends into a diametrical groove I02 (see Fig. 2) which is formed in the right hand end of the sleeve or cylinder 95. As a consequence of this construction, a turning of the wheel I00 will turn the shell or sleeve 95 therewith. The head IOI is provided with a transverse winged groove I03 into which project abutments I04 which are urged outwardly toward said groove I03 by springs I05. The abutments I04 are provided with heads which fit in the bottoms of bores which receive the springs I05 and thus limit their outward movement into the groove I03. Removable caps I06 are provided on the head IM and are removably connected thereto by screws The previously mentioned spider or core 90 extends into and is mounted for rotation with respect to the cylinder or sleeve 95, it being provided at its opposite ends with generally cylindrical end portions having O-ring seals I08 and I09, respectively.
Intermediate its cylindrical ends which are provided with the seals I08 and I09, the spider or core is formed with four longitudinal grooves or troughs IIO, III, II2 and H3 (see Fig. 3). Thesegrooves IIO to I I3, inclusive, form four radially extending webs I I4 which are preferably 90 apart, as clearly illustratedin Fig. 3 of the drawings. The troughs or grooves IIO to H3, extend along the spider 90 so as to overlap a distance equal to that between the passageways or grooves I5 to T8, inclusive, in the head I0.
The central portion of the spider 90 is provided with a plurality of radial cross bores II5 which are effective to interconnect the grooves or troughs H0 and II2 in one instance, and the grooves III and H2 in the other instance. This provides for a completely balanced arrangement of the valve I I The shell or cylinder is provided with four radial ports H6, H1, H8 and II9 (see Figs. 3 and 4) There is one of these ports for each of the grooves I5 to I8, inclusive, and these ports II6 to I I9, inclusive, are distributed axially along the shell 95 so that one of them is in alignment and communication with each of said passageways 15 to T8 and is individual thereto. For example, port IIB, as illustrated in Fig. 4 of the drawings, communicates with and is individual to circumferential passageway or groove 18. These are the return passageway and port of the valve by which hydraulic fluid is conveyed from it to the system. Port II9 is individual to and communicates with circumferential passageway I1. These are the pressure or feed passageway and port. Port II! is individual to and communicates with circumferential passageway I6. These are one of the cylinder or motor passageways and ports. Port Il8 communicates with and is individual to circumferential passageway I5 which are the other motor or cylinder passageway and port.
Referring particularly to Fig. 3 of the-drawings, it will be noted that the angular relation of the center lines of the various ports II6 to II9 is important. If horizontal and vertical lines are drawn, intersecting at the center of the core 90, the center lines of the various ports II6 to II9, inclusive, will be as follows: Center line of port II6 will be forty-five degrees from both vertical and horizontal lines; center line of port II! will be fifteen degrees from the vertical line. The center line of port I I8 will be fifteen degrees from the horizontal line, and the center line of port I I9 will be forty-five degrees from both the horizontal and vertical lines.
The right-hand end of the spider 90 is provided with a projection I20, the top and bottom surfaces of which are parallel, said projection extending into the winged groove I03 formed in the head IOI of shaft 99.
As clearly illustrated in Fig. 2 of the drawings, the abutments I04 when in their normal positions as illustrated, just contact the top and bottom surfaces of the projection I20 on opposite sides of the center or axis of rotation of said projection I20 which, of course, is the axis of the spider 90. The wing shape of the groove I03 provides for limited relative rotary movement between the spider 90 and the shell 95 before said projection I20 comes into a solid driving abutment with the walls of said groove I03.
The centering means formed by the springs I05 and abutments I04 have a double function and their effectiveness may be adjusted by adjusting the strength of the springs I05. The
5 1 first function of these springs-is to provides certain amount'of"feel in the wheel I so that when wheel" l00-is turned by the operator, there willbe a tendencyfor the rotation of shaft 99 to be transferred mechanically and directly to the shaft 89 through the head IM and the spider Bil-through these spring means I 04, I05. However; under" most normal conditions the springs I'will be too weak to transfer'any appreciable direct driving movement, though, if desired, they may be made strong enough to provide an appreciable direct mechanical driving connection.
The second function of the spring centering means I04, I05 is to provide a biasing means which will tend to adjust the spider or core 90 to its neutral'position'with respect to the shell or cylinder 95' and this is'particularly desirable to prevent undesirable oscillation of the steering rod-in case there is an appreciable lost motion between the mechanical connection to the piston of the hydraulic steering motor and the stub shaft 89 which will develop particularly in the universal joints leading to said shaft 89 and the reduction gearing.
Attention isdirected also to Fig. 4 of the drawings and to a feature of construction of the ports I IE to I I9, which are of similar design, port IIB being illustrated insaid Fig. 4. In order to maintain the relative angular movement between theshell 95 and thespider 90 at a desired amount andconsistent with that provided by the projection I and the winged slot I03, it is necessary that the ports IIG'to I I9 extend over a limited portion of the circumference of the interior surface of shell 95.
As illustrated in Fig. 3 the port H6 is bridged by a web of the spider 90. This, of course, appreciably reduces'its effective area or, in other words, the area through which hydraulic fluid can flow, as illustrated in said Fig. 3 by the arrows, when the valve is in its neutral position which is the relative position of the parts as illus trated in said Fig. 3.
In order-not to increase unduly the velocity of the fluid when it passes along the sides of said web which bridges the inside of port IIB, it is necessary to increase the axial length of the port I IE on the inside surface, as is clearly illustrated in Fig. 4 of the drawings. The outside surface or area of the port I I6 can not be increased undesirably in'an axial direction because if this weredone it would overlap two of the circumferential grooves, such as grooves I1 and I8, or it would undesirably reduce the sealing area between the two adjacent grooves, such as grooves IT and I8. This outside dimension of the port I I6, however, can be circumferentially' extended as compared'with the circumferential extent of its" inside surface and this has been done, as clearly illustrated in said Fig. 3, while maintaining its axial dimension or width substantially equal to-that of associated groove 18.
In view'of this construction, the efiective area of the port H6 is substantially the same on both its outer and inner surfaces when the inner surface is bridged by the above mentioned web. The structures of the ports IIl, I I8 and H9 are the same as that of port I I6.
The operation of the steering mechanism is as follows. pump '92 through the feed conduit 9| and then flows through passageway 8 I, as indicated by the arrows,- and around the circumferential passageway" in head 10. It then flows through port Hydraulic fluid is delivered from the- II 9 in the shell 95 and on opposite sides of a bridging web of spider or core into'the-grooves Since trough' I I0 is con draulic fluid would be flowing in all four of the troughs II 0 to H3, inclusive, throughout their full lengths. As a consequence, the oil flowing in troughs I I I and I I 2 will flow through the port I I 6 on opposite sides of the web of spider 90 which bridges the interior opening thereof, flowing into the circumferential passageway I8 in head I0, as clearly illustrated in Figs. 1 and 3 of thedrawings. As previously stated, this is the normal or neutral position of the valve II and no steering operation is efiected.
The hydraulic fluid in the troughs IIO to H3, inclusive, is free to flow through the conduits 83 and 84 by way of circumferential passageways I5 and I6 and connecting passageways I9 and 80, but this is appreciably without eflect on the hydraulic steering motor or if it does have any effect thereon due to the unbalanced nature of said hydraulic jack, this will cause an automatic correcting movement of the spider 90.
The oil or hydraulic fluid flowing downwardly through passageway 82 continues through said passageway into the base 69 of post 68, thence to conduit 94 and through all of the spool or slide valves lying to one side of the post 46. Since these spool or slide valves are connected in series the hydraulic fluid supplied through conduit 94 to them flows toward the base portion 69 of post 46 and through a by-pass passageway I2I in the base 69 of post 68 which acts as a connecting passageway'between the valves on opposite sides of the post assembly 46. Under normal conditions, there is a no-load circuit through all of the control valves from the pump 92 to the tank. Conduit I2I forms a part of this no-load hydraulic circuit. However, it will be seen that when any one of the spool or slide valves which is supplied with hydraulic fluid passing through conduit I2I in the base I59 of post 46 is actuated the conduit 94, the passageway through the preceding individual spool or slide valves, and the conduit I2I, which in effect form a single passageway, will be subjected to pressure of hydraulic fluid pumped by pump 92.
If the steering wheel I00 is turned in a dockwise direction, the angular movement thereof just described will connect pressure port II9 to interconnected troughs III and H3 and will connect discharge port II 6 to interconnected troughs II 0 and H2. The'hydraulic fluid in passageway 8| will thereupon flow through circumferential passageway II, port II9, groove on trough III and the radial bores H5 in spider 90 to trough or groove II 3; thence by port II8 through circumferential passageway IS-and post passageway I9 to conduit 83 which leads to the Thus, hydraulic fluid will bedelivered to operate the double acting hydraulic hydraulic motor.
piston motor or cylinder.
The return path for the hydraulic fluid from the hydraulic cylinder or motor will be by way of conduit 86, post passageway 88, circumferential passageway I6, port II 1, groove or trough H2, port H6, and circumferential passageway I8 to the post passageway 82 which delivers it to conduit 94 and thence to tank through the group of banked valves in series as above mentioned.
The steering movement of the front wheels of the vehicle in response to operation of the operating motor will be reflected in angular movement of the steering rod 89 which is connected to the spider 90 as above described, so as to produce a follow-up type of system so that whenever the wheels have been adjusted a variable amount as determined by the variable movement of the wheel I00, the relative position of the cylinder 95 and the spider 90 will be restored to that illustrated in Fig. 3, or, in other Words, to their normal position.
Thus in effect the operation of the steering valve 'II simulates ordinary mechanical steering except that hydraulic power is provided to do the actual work. As previously mentioned, in case of failure of the hydraulic system, it is only necessary to disconnect the piston head of the operating motor, so as not to be working against it, and a direct mechanical drive is provided from the wheel I00.
In view of the fact that the hydraulic circuit is a series circuit, in is obvious that the hydraulic fluid flowing in conduit 94, regardless of whether the steering valve is in its neutral position or is in a position to deliver hydraulic fluid to the steering motor, may be employed to operate any one or more of the double acting or reversible hydraulic motors controlled by the individual valves. That is, with this system, any number of control valves, including the rotary control valve, from one to the maximum number, may be operated simultaneously.
The steering valve II is operable upon counterclockwise rotation of the wheel I06 in a manner which is comparable to that above described so that power steering may be effected by turning the wheel in either direction.
In the base 69 of the casting 68, I provide a pair of high pressure relief by-pass valves I23 and I24 which are of duplicate construction, but which provide different functions. The by-pass valve I23 by-passes the rotary valve H and it is preferably set to open at a pressure differential which is lower than that at which by-pass valve I24 opens. The function of the by-pass valve I24 is to control a passageway or chamber providing a by-pass to tank through a conduit I26 a portion of which is formed in the base 59 of post 46 and extends between the opposite fiat parallel side surfaces of the bottom of the steering post 46 whenever a high pressure condition exists anywhere in the system, except on the input side of the double acting steering motor, but this bypassing of the fluid only discharges the fluid to tank after it has passed through the rotary valve II or through its individual relief valve I23.
The relief valve I23 provides a high pressure by-pass for the valve 'II since it controls a passageway or chamber interconnecting feed passageway 8I and discharge passageway 82 and obviously upon the appearance of a predetermined high pressure in conduit 9| or passageway 8| as compared with the pressure in passageway 82, this high pressure relief valve will open, providing a by-pass around valve I I, thus directing the fluid from conduit 9| through the pasageways in by-pass valve I23 to the lower portion of passageway 82 and into the feed pipe or conduit 94.
The structures of the high pressure valves I23 and I24 are of essentially standard design and thus need no detailed explanation. It may be pointed out, however, that a hollow springpressed valve closing piston I45 of each is provided with a port I45 so that hydraulic fluid in the passageway 82 will be present on both sides of the piston I45 and hydraulic fluid flowing through passageway I26 in valve I24 will also be on both sides of its piston I45. This is of particular importance in connection with relief valve I23 because it insures that whatever the pressure in passageway 82, by-pass valve I23 will only open in response to a higher predetermined pressure in passageway BI determined by the adjustment of spring of valve I23. For example, if valve I23 is adjusted to open at 200 pounds per square inch and valve I24 at 500 pounds per square inch, and should the double acting motor controlled by one of the slide valves reach the end of its stroke and thus cause the 500 pounds pressure to appear in conduit 82 and thereby cause valve I24 to open, valve I23 would only open when the pressure in passageway 8I reached 700 pounds. Because of this fact there is always hydraulic pressure available to control the steering of the vehicle even though the pressure relief valve I24 is open for any reason. Ihis is an important feature of the hydraulic system of my invention. The pressures at which the valves I23 and I M open may be varied by adjusting their compression springs.
It is to be particularly noted that, regardless of whether the hydraulic fluid flowing through conduit SI is by-passed by the by-pass valve I23 or flows through the valve H and the motor 85, it is always delivered to the lower portion of passageway 82 and to conduit 54; If, however, high pressure relief valve I24 is actuated, the hydraulic fluid will be by-passed thereby through tank passageway I26 which extends through aligned individual passageways in each of the individual castings or bodies of the banked valves.
In Figs. 5, 6 and 7 of the drawings, I have disclosed a modified form of steering post assembly 2 58 which may be substituted for steering post assembly 46. It is to be understood that unless a contrary fact is indicated, the steeringv post assembly 246 follows the structure of steering post assembly 48. One difference therein is in the structure of the head or cylindrical portion 2W. Said head portion 210 is provided at its top with a drain passageway I30 which extends irom the front to the rear thereof and opens into the cylindrical bore 12 at both ends.
The post 248 includes a main body casting or casing 268 which in addition to the four passageways 19, 86, 8I and 82, is provided with a drain passageway I3I which receives leakage fluid collected from a rotary steering valve 21I and delivers it to the drain passageway I26. The rotary, steering valve 2H differs from the steering valve H in a number of particulars. In the first place. the O-nng seals 91, 98, I88 and I08 have been eliminated and the leakage of the valve parts is drained off by the passageways I30 and I3I. Furthermore, in place of shell, sleeve or cylinder 55, I employ a different shell, sleeve or cylinder 295 which is provided with a pair of diametrically opposed ports, as viewed from its interior surface, associated with each of the cylindrical passageways or grooves "I5, 15, ll and I8. Diametrically opposed ports 219 communicate with pas- '9 sageway 1,8 diametrically opposed ports 2 I6 communicate with passageway 11; diametrically opposed ports 2I'I communicate with passageway I8; and diametrically opposed ports 2I8 cornmunicate with passageway I5.
It 'is to be noted by reference particularly to .Fig. 6 of the drawings, that the ports 2 I I and 2 I 8 do not extend radially through the shell 295, but extend parallel with the ports 2I9. This is to provide for forming of the sand cores to make the shell 295 so that the core patterns can be separated without destroying the dry sand cores. Functionally, the operation would be the same if all of the ports 2I6 to 2I9, inclusive, extended radially through the shell 295.
The spider or core 290 also differs from the spider or core 90 not only in the elimination of the O-ring seals, but also in the elimination of the equalizing cross bores II5. These are not necessary to produce a balanced condition in the valve because of the presence of the diametrically opposed ports 2I6 to 2I9, inclusive.
It is also to be noted by reference particularly to Fig. 7 of the drawings that I no longer employ the particular form of port comparable to port IIB, as illustrated in Fig. 4 of the drawings. It is to be distinctly understood, however, that the ports 2I6 to 2I9, inclusive, may follow the design of said port IIG of Fig. 4.
It is also to be noted that I have eliminated the centering spring means I04, I and the shaft 99 is provided with a substantially solid head 21H provided with a winged shaped groove 203. If desired, the spring means I04 and I05 disclosed in detail in Figs. 1 and 2 of the drawings, may be employed with the valve 2II. In other words, shaft 99, head IN, and associated spring means I04I0I of Figs. 1 and 2 may be employed instead of that illustrated in Fig. 5 of the drawings.
Furthermore, in case these spring means are eliminated, or, in other words, in case the structure shown in Fig. 5 is employed, it may be desirable to add a certain amount of friction to rotation of the shaft 99 and one easy way to accomplish this is to provide an O-ring seal on the shell 295 comparable to the O-ring seal 91 or 98.
To provide free drainage of the oil which is received in the upper drain passageway I30, the head ZIII is provided with a circumferential notch, recess or groove I32 which provides a circumferential passageway interconnecting the top passageway I30 and the drain passageway I3I.
Except for the action of the spring means I04I0I previously described, the action of the rotary steering valve 2II is essentially the same as that of the rotary steering valve II. This valve 2' also provides a direct mechanical drive in case of emergency, since the core or spider 290 is provided with a projection 22!) which projects into the previously mentioned winged groove 203.
Except for the differences above mentioned, the post assembly 246 is essentially the same as the post assembly 46 and either may be substituted in the hydraulic system, for the other.
From the foregoing description of my improved steering post, its associated valve mechanisms and the operation thereof, it will be readily apparent to those skilled in the art that I have provided a new combination and arrangement of elements in such apparatus and particularly that I have provided a steering post that is adapted to be included in or flanked by other valves adapted to control the operation of apparatus other than steering apparatus and that because of the post features of my improved combination, the steering wheel of the steering valve which is located in the top of the steering post is positioned above the other valves thereby permitting the grouping of all of the control valves and the steering valve in one unit with the steering valve and the steering wheel thereof positioned so that an operator of the apparatus of which the valves form a part may have ready access to the control valves as a group without interference from the steering wheel.
Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted to the precise construction herein disclosed.
Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:
1. In a device of the class described, a post forming a housing having an elongated upstanding body portion having an attaching base at its bottom for mounting said post and a valve cas ing at its top which includes a valve operably mounted therein, hydraulic feed and return passageways running longitudinally in said body leading to and from said valve casing, said valve controlling the opening and closing of said passageways, a pressure relief valve passageway in the base of said housing for by-passing said valve by placing said feed and return passageways in communication with each other before the latter said passageways communicate with said valve housing, and a second pressure relief valve passageway in the base of said housing connecting the return passageway to drain.
2. A combination valve and steering post including an elongated upstanding housing having valve housing means adjacent its top receiving a rotary steering valve and a bottom portion adapted to be banked between other valves, said bottom portion including opposite parallel surfaces adapted to receive said other valves, means in said housing providing feed and return passageways extending longitudinally thereof and to said rotary valve, means providing motor passageways in said housing connecting with said rotary steering valve, means providing a continuous passageway extending through the bottom portion of said housing between said opposite surfaces, means forming a drain passageway extending between said opposite surfaces, a by-pass passageway in said housing interconnecting said feed and return passageways for by-passing said rotary steering valve, and a second by-pass passagaway in said housing interconnecting said return pa sageway and said drain passageway for ay-passing fluid from the former into the latter.
3. A combination valve and steering post including an elongated upstanding housing having valve housing means adjacent its top receiving a rotary steering valve and a bottom portion adapted to be banked between other valves, said bottom portion including opposite surfaces adapted to receive said other valves, means in said housing providing feed and return passageways extending longitudinally thereof and to said rotary valve, means providing motor passageways in said housing connecting with said rotary steering valve, means providing a continuous passageway extending through the bot- 11 12 tom portion of said housing between said opposite UNITED STATES PATENTS surfaces, and means forming a drain passageway Number Name Date extending between said opposite surfaces. 1,491,248 Schur Arm 22, 1924 FRED WRIGHT- 5 1,991,227 Proctor Feb. 12, 1935 2,042,186 Peterson May 26, 1936 REFERENCES CITED 2,165,096 Frechette July 4, 1939 The following references are of record in the 2,182,459 Vickers Dec. 5, 1939 file of this patent: 2,221,492 Trambly Nov. 12, 1940 2,227,814 Tyler Jan. 7, 1941
US66553046 1944-11-27 1946-04-27 Hydraulic valve and post Expired - Lifetime US2607558A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843149A (en) * 1952-11-29 1958-07-15 Curtiss Wright Corp Rotary hydraulic valve
US3443586A (en) * 1966-06-07 1969-05-13 Danfoss As Four-way change-over device for hydraulic installations
US3575201A (en) * 1969-02-05 1971-04-20 Dominion Road Machinery Co Ltd Multiple hydraulic valve unit

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1491248A (en) * 1921-12-16 1924-04-22 Brown Co Valve
US1991227A (en) * 1932-07-30 1935-02-12 Commercial Shearing Control valve
US2042186A (en) * 1932-07-13 1936-05-26 Hannifin Mfg Co Valve construction
US2165096A (en) * 1937-03-16 1939-07-04 John S Frechette Serial multiway valve
US2182459A (en) * 1937-01-08 1939-12-05 Vickers Inc Valve housing and rotor
US2221492A (en) * 1940-03-21 1940-11-12 Millard H Sawyer Tractor hitch
US2227814A (en) * 1938-10-10 1941-01-07 Oilgear Co Control for hydraulic transmissions

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1491248A (en) * 1921-12-16 1924-04-22 Brown Co Valve
US2042186A (en) * 1932-07-13 1936-05-26 Hannifin Mfg Co Valve construction
US1991227A (en) * 1932-07-30 1935-02-12 Commercial Shearing Control valve
US2182459A (en) * 1937-01-08 1939-12-05 Vickers Inc Valve housing and rotor
US2165096A (en) * 1937-03-16 1939-07-04 John S Frechette Serial multiway valve
US2227814A (en) * 1938-10-10 1941-01-07 Oilgear Co Control for hydraulic transmissions
US2221492A (en) * 1940-03-21 1940-11-12 Millard H Sawyer Tractor hitch

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843149A (en) * 1952-11-29 1958-07-15 Curtiss Wright Corp Rotary hydraulic valve
US3443586A (en) * 1966-06-07 1969-05-13 Danfoss As Four-way change-over device for hydraulic installations
US3575201A (en) * 1969-02-05 1971-04-20 Dominion Road Machinery Co Ltd Multiple hydraulic valve unit

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