US2654349A - Hydraulic control circuit and valve for hydraulic rams - Google Patents

Description

J. F. ZISKAL HYDRAULIC CONTROL CIRCUIT AND Oct. 6, 1953 VALVE FOR HYDRAULIC RAMS. v

2 Sheets-Sheet 1 Filed May 13, 1952 Oct. 6, 1953 Y J. F. ZISKAL' HYDRAULIC CONTROL CIRCUIT AND VALVE .FOR HYDRAULIC RAMS 2 Sheets-Sheet 2 Filed May 13, 1952 log INVENTOR. Juqfi J5. Zwd BY PM o [3 Patented Oct. 6, 1953 HYDRAULIC CONTROL CIRCUIT AND VALVE FOR HYDRAULIC RAMS Joseph F. Ziskal, Brookfield, Ill., assignor to International Harvester Company, a corporation of New Jersey Application May 13, 1952, Serial No. 287,647

Claims. (01. 121-465) This invention has to do with hydraulic fluid power-transmitting apparatus of the type wherein power is hydraulically transmitted to a ram from a fluid source including a constantly driven pump of which the output pressure is diminished to a bypass pressure excepting during periods of fluid delivery to the ram, the invention particularly concerning an improved hydraulic control circuit comprising a novel form of control valve for controlling both the bypass condition of the fluid pressure source and the direction of fluid movement to and from the ram to determine the direction of ram operation. The apparatus of which the present invention is a part is related in character to that disclosed in copending application of Clarence A. Hubert and Joseph F. Ziskal, Serial No. 689,732, filed August 10, 1946, for Hydraulic Ram and Control Therefor, now abandoned and carried on as continuation application Serial No. 294,394, filed June 18, 1952, for Hydraulic Ram and Control Therefor.

In previous hydraulic power-transmitting apparatus of the present type employing a plunger form of control valve, the plunger has included at least four axially spaced port-controlling radial enlargements or lands. These plungers, because of the several lands necessary to control numerous ports in the circuits heretofore employed, have necessarily been relatively long. This substantial length of the control valve plunger and the plunger receiving bore in which it is axially adjusted for controlling the valve ports has incurred manufacturing and assembling problems. For the ports to be properly alternately closed and opened, dimensional tolerances of the valve plunger and the bore receiving the same are small. It has been costly to maintain these small tolerances with a long plunger carrying the several lands.

The principal object of this invention is the provision of a new hydraulic control circuit which diminishes the number of lands required upon the control valve plunger and correspondingly diminishes the required length of this plunger and the number of required control surface edges which must be produced within close dimensional tolerances.

A further object is the provision of a novel control valve body having miniature fluid delivery ports supplemental to a principal fluid delivery port, these supplemental ports being spaced circumferentially of the valve-plunger-receiving bore from the principal port and in respective registry circumierentially of the bore with opposite edges of such port spaced axially of the bore, to expedite attainment of timing accuracy of fluid flow control during initial opening and cut off of the valve.

The above and more specific objects inherent in and encompassed by the invention are elucidated in the ensuing description, the appended claims and the annexed drawings, wherein:

Fig. 1 is a sectional view through a power transmitting unit casing containing passages and a control valve therefor constructed in accordance with this invention, the view illustrating certain of the conduits, a hydraulic ram and an associated constant delivery pump diagrammatically.

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1, this view showing details of a differentially operated control for the valve plunger.

Fig. 3 is a side elevational'view of the tubular control valve body. 7

Fig. 4 is a transverse sectional view taken on the line 4- of Fig. 3.

Fig. 5 is a sectional view taken on the line 55 of Fig. 3.

The hydraulic power-transmitting apparatus herein shown and described for illustrating the invention is a species suitable for use upon farm tractors or the like for operating an implementoperating rock shaft to attain selective groundworking or transport positions of implements mounted upon or propelled by the tractor. Referring now to the drawings, the apparatus which is commonly referred to as a power lift unit, includes a casing I I having a mounting base l2 at its lower side. The left end of this casing l l is in the form of a fiat face 13 having an end plate l4 secured thereto by a plurality of cap screws, not shown.

Said casing ll is a casting and has formed integrally therewith and interiorly of an outer shell l5 thereof, an interior body portion it which is drilled to contain various fluid conducting passages and element-receiving bores. One of the bores within the body it rearwardly of the plane at which this sectioned view is taken and hence not shown, constitutes the cylinder of a hydraulic ram which for convenience is illustrated diagrammatically at ll. The bore or cylinder of this ram I! is designated [8 and the plunger therein IS. The connecting rod for the ram plunger [9 is shown diagrammatically at 2 I. It is the principle of the apparatus to power operate the ram plunger I9 selectively in opposite directions by force derived from fluid delivered by a constant delivery pump P shown diagrammatically in the lower part of Fig. 1. The lower part of the casing shell 15 serves as a reservoir for hydraulic fluid 3 which is delivered to the pump P through a conduit 22. The pump delivers the fluid through a diagrammatically illustrated conduit 23.

Conduit 23 is part of a fluid delivery passage which also includes a chamber 24 and a passage section 25, part of which is shown diagrammatically, communicating between the chamber 24 and a fluid inlet port 26 communicating through the cylindrical wall of a tubular valve body 2'5. The valve body 21 of a control valve 28. is held within a horizontal, bore 29 in the casing body I8. lubular valve body 21 contains exterior circumferential grooves 3|, 32, 33, and 34 which cooperate with the bore 29 in forming an'-- nular passages about the body 21:. Thefluid dcv livery passage section delivers fluid to the annular groove 33 and the fluid inletport 26 communicates between this annular groove and an annular fluid inlet chamber 35 inside the tubular body 21. Control ports 36 communicate between the annular groove 3 I and thevalve body bore 37 wherein a control valve plunger 38- is axially slid able selectively oppositely from the neutral position illustrated in Fig. l. Reversible flow ports 39 communicate between the annular groove 32 and the valve bore 3? Whereas reversible flow ports 4I communicate between the annular groove 34 and the bore 3?.

Control valve plunger 38 has a radial enlargement or land 42 at its inner or left end, a, land 43 shown in registry with the ports 39, and a land 44 in registry with the ports 41. A control cavity 45 is formed inter-iorly of the valve bore 3! between the inner end of the plunger 38 and the inner end of the valve bore 31 which is closed by a sealing plate 46. An annular exhaust cavity 41 is formed in the valve bore 31 between the plunger lands 42 and 43, and a second exhaust cavity 48 is formed in the right 'end of the valve bore 31 rightward of the land 44. An axial bore i 49 is drilled into the valve plunger 38 through its left end and this bore 49 has lateral ports 5| and 52 respectively communicating with the exhaust cavities 4'! and 48. The valve plunger bore 49, together with the ports 5| and 52 and 1 a port 53 through which the bore 49 communicates with the cavity 45, constitutes channel means intercommunicating between the three cavities 45, 41, and 48 exclusively of the annular fluid inlet chamber 35. This channel means, when including the right open end of the valve plunger receiving bore 31, also communicates with the lower part of the casing shell I5 from which the pump P withdraws fluid through the conduit 22 and therefore communicates with the low pressure section of the fluid source including the pump P.

A pair of reversible flow passages 54 and 55 lead upwardly respectively from the annular passages or grooves 32 and 34 respectively to check valves 58 and 5?. Check valve 58 comprises a valve member 58 urged by a spring 59 onto a valve seat 6!. a valve member 62 urged by a spring 63 onto a valve seat 64'. A valve operating plunger 65 axially slidable in a bore 68 has end projections 87 and 69 selectively abuttable against the valve members 58 and 82 for unseating them. When the valve member 58 isunseated, fluid can flow past it from the passage 54 through axial grooves 69 in this member into a channel II and thence through a diagrammatically illustrated conduit I2 to the head end of the ram cylinder I8. When the valve member 62 is unseated, fluid can flow therepast through axial channels I3 in such.

Check valve 51 comprises end of the casing 4 member into a channel 14 and thence through a diagrammatically illustrated conduit I5 into the rod end of the ram cylinder I8.

A bypass or fluid pressure controlling valve BI includes a valve seat 82 and a valve member 83 urged onto said seat by a spring 84. When the valve '8lis open as illustrated in Fig. 1, fluid from the inlet passageportion 24 can flow over the valve seat 82 into a chamber 85 from which the fluid escapes at low pressure through a passage 86 into the low pressure section of the fluid source constituted by the fluid reservoir 81 in the bottom of the casing shell I5. During the low pressure bypass condition established by the valve 81' being opened as shown, the valve member 83 ishel'd away from the seat 82 by a plungerlike valve-operating unit 88 of which a stem 89 ispressed' endwi'se against the left end of the member 83. The assembly 88 is disclosed and claimed in my copending application Serial No. 786,988, filed. November 19,, 1947, for Pilot Operated Quick Opening, Control Valve. Fluid from the fluid. delivery passage section 24 flows through a conduit 91., illustrated diagrammatically,. into a bore 92,. thence through a filtering cap 93 and a restricted passage section 94, and a..passage 95 which through the bore 29 communicates with. the control ports 36 of the control valve 28. While the control land 42 of the valve plunger is in closing relation with the ports 36 as illustrated in Fig. 1, the fluid entering the passage '95 cannot escape and therefore exerts pressure upon the valve-operating unit 88 to open the bypass valve 8|. Even though the fluid pressure upon the left end of the unit 88 is relatively low during bypass of fluid through the valve 81 and the passage 86, this pressure will be substantially equal to the pressure in the inlet passage portion 24 acting upon the right end of. the valve element 83, and since the area on the left end of the unit 88 exceeds the area on the right end of the valve member 83, the total force exerted by fluid on the unit 8 8 will exceed the combined force of the spring 84 and of the fluid .in the passage section 24 and thus cause the valve to remain open.

A difierentially operated control valve-operati'ng unit is generally designated 96 in Figs. 1 and. 2. This valve-operating unit comprises a pair of axially spaced coaxial bevelled gears 91 and 98 oscillatable in casing bearings 99 and I8I.

Gear 91 is constrained for oscillation with a shaft I82 having an arm I03 fixed for oscillation therewith. Arm I83 is connectedby a link I04 with the lower end of an arm I95 constrained for rocking with a rock shaft I88 journaled for oscillation in a bearing I87 mounted on the right II. Also constrained for rocking with the rock shaft I86 is a diagrammatically illustrated operating arm I88 pivotally connected at its upper end with the ram piston rod 2|.

Bevelled gear 98 of the differential valve-operating unit 96 is constrained for oscillation with a shaft I89 having an arm III constrained for oscillation. Oscillative limits for movement of the arm I I I are provided by a pair of stop members H3 and H4 of which the member H4 is shown inFig. 2, the members being illustrated by dot-dash lines in Fig. 1. Arm I l I is manually controlled. A gear carrier shaft II5 is journaled in opposed ends of the bevelled gears 9! and 98 and rotatively carries on a radial shaft-like portion IIB thereof a differentially driven planet gear II! which meshes with each of the gears 9'! and 98. Back lash motion between the gears 91, 98, and II! is eliminated by a spring II? which reacts against a stop member II 9 anchored to the upper end of the shaft iIIi while pressing downwardly upon the gear I IT to maintain the gears firmly meshed. The upper end of the shaft Il a has a spherical terminal IZI at substantially the same elevation as a spherical terminal I22 on the outer end of the valve plunger 38. A sheet metal link I23 interconnects the spherical terminals I2! and I22. Link I23 is U-shaped in cross-section and has a pair of laterally spaced apertured ears I24 which grip onto opposite sides of the terminal i2I while receiving opposite polar portions of this spherical terminal respectively within apertures I25 of these cars. Similar apertured ears 25 at the left end of the link I23 have apertures I21, one being shown in Fig. l, which receive diametrically opposite portions of the terminal I22 attendant to these ears I26 gripping onto such terminal.

Operation of the apparatus With the parts in the status illustrated in Figs. 1 and 2, the control valve plunge 53 is in the neutral position wherein each of the lands 42, 43, and id thereof covers and closes its respectively associated valve ports, and the by-pass valve SI is open wherefore the source of fluid pressure including the pump P is operating under an idling or low pressure condition. At this time fluid drawn by the pump from the low pressure section ill of the fluid source through the conduit 22 and delivered through the conduiit 23 into the fluid delivery passage section 2d flows past the open valve 8i and thence through the chainber 85 and passage 8% back to the low pressure section 8?. The check valves 56 and 5'? are closed, preventing exhaust of fluid from either end of the hydraulic ram I7 and therefore hydraulically locking the ram plunger I9 against endwise movement.

Should it be desired to cause movement of the ram plunger I9 to the right, the manually operated arm I! I will be pivoted counterclockwise as viewed in Fig. l a distance proportional to the amount of movement that is desired for the ram plunger. Such counterclockwise movement of the arm ii! will impart similar rotation to the gear 98 causing the differentially driven gear I ll to rotate about its shaft H5 while this gear Ii'I reacts against and rolls upon the toothed periphery of the gear 9? to cause counterclockwise swinging of the shaft I Hi and leftward movement of the link I23 and the valve plunger 38. This will cause the plunger land 43 to establish communication between the fluid inlet chamber 35 and the ports 33 and to concurrently establish communication between the ports ll and the exhaust cavity 48. Also substantially concurrently with this uncovering of the ports 3- and :iI the control land 2 of the valve plunger establishes communication between the control ports 36 and the exhaust cavity ll. Thereupon fluid pressing against the left end of the valve-operating plunger 88 can escape attendant to permitting this plunger to be moved leftward by the combined force of the spring 84 and fluid pressure upon the right end of the bypass valve member 83 to cause seating of this member upon the valve seat 52. Because of the restricted flow capacity of the constriction iii in the fluid transfer passage 9I@2-95, the control port 36 is operable to permit the escape of fluid from the left end of the plunger 88 sufiiciently fast with respect to the rate at which fluid can be replaced through the restricted port 9 1 that the spring 84 and the pressure of fluid within the passage section 2i will prevail over the force developed by the pressure of fluid against the left end of the plunger 38, wherefore the bypass valve 8| will remain closed until a later time when the control ports 36 are closed.

Upon the closing of the bypass Valve 8|, the pressure will rise in the fluid delivery section 2 3 and 25, the port 2% and. the fluid inlet chamber 35. This fluid at increased pressure will flow outwardly through the reversible flow port the reversible flow passage 54 against the check valve member 58 for unseating this member which permits the fluid to flow therepast through the conduit I2 into the left end of the ram II. Thus the ram plunger I9 is moved to the right. The pressure of fluid flowing upwardly through the reversible flow passage 54 and acting upon the left end of the valve-operating plunger 65 is effective to shift this plunger rightward to cause the stem 68 thereof to unseat the valve member 62 from the seat (i i. Hence, as the ram plunger I9 moves to the right, fluid is exhaustible from the right end of the cylinder I8 through the conduit l5, passage Id, past the valve 5? through the reversible flow passage 55, port ll and through the exhaust cavity 4-3 into the low pressure section 87 of the fluid source. Movement of the ram plunger iii to the right is accompanied by rightward movement of the piston rod 2| for rocking the arm I53 and the rock shaft Hi6 clockwise. Such rocking of the rock shaft for performing work upon the tools or the like attached thereto causes the arm I to swing clockwise and thence to operate the link I04 for pivoting the arm Hi3 clockwise and with it the gear 9'! to cause the differentially driven gear I Il to roll upon the toothed periphery of the gear as attendant to swinging the differential carrier shaft H5 clockwise as viewed in Fig. 1. When the ram plunger I?) has moved an amount correlated with the previous counterclockwise swinging motion of the manually operated control arm III, the diiferential carrier shaft H5 will have been restored in a clockwise direction to the upright position shown in Fig. l for returning the valve plunger 38 to the neutral position. The check valves 55 and 57 will again become effective for hydraulically locking the ram plunger against movement, and upon arrival of the valve plunger to neutral and to close the control ports 35, the fluid admitted slowly through the restricted port 94 will cause an accumulation of fluid for moving the valve-operating plunger 83 rightward to again unseat the bypass valve 8 I.

When it is desired to move the ram plunger is leftward, the control arm I II will be manually rocked clockwise and through the differential unit 96 cause rightward movement of the control valve plunger 38 which this time causes communication of the fluid inlet chamber 35 with the right end of the ram cylinder is through the port M, reversible flow passage 55, check valve 57, and the passages i i and '55. The fluid reaching the right end of the valve-operating plunger 55 through the reversible flow passage 55 will shift this plunger leftward for opening the check valve 55 so that as the ram plunger I9 is forced leftward by the fluid delivered into the right end of the cylinder I3, the fluid exhausted from the left end of this cylinder can exhaust through the conduit 12, check valve 56, reversible flow assage ort 3 ex t cavity p r valve l n eror & p 52, a through the, exhaust cavity 48, into the low pressure sec. tion 81., rightward movement of the valve plunger 38 from neutral causes communication of the control port 36 with the control cavity at in the control valve bore 31 to permit escape of fluid acting upon the left end of the exhaust valve operating plunger 88 thence causing closing of the bypass valve. Sufficient fluid pressure is thus developed for causing movement of the ram plunger [9. As the plunger [9 is moved leftward, the rock shaft N38 is caused to rock counterclockwise as is the arm I03 connected therewith by the link lfl i. Ihe difierential mecha- 96 is thus, operated to shift the control valve plunger 38 leftward for restoring its neutral setting and again establishing a hydraulically locked condition otthe ram plunger l9 and the bypass condition of the bypass valve 81.

In addition to diminishing the difliculty of manufacturing the control valve 28 because of using an arrangement of ports and passages controlled thereby making it necessary to provide only three lands G2, 43, and 44 upon the plunger 38, wherefore this plunger and cylindrical body 2'! therefor can be made shorter, a still further structural improvement is provided for simplifying production. This further improvement consists of the addition of supplemental reversible flow ports l3] and I32 associated with one of the reversible flow ports 39 and auxiliary reversible flow ports I33 and I34 associated with one of the reversible flow ports ii; see Figs. 3 and 5. Referring particularly to the port 319, the supplemental reversible flow ports i3! and are spaced circumferentially of the valve body bore 37 and are substantially smaller in bore than the ports 39, The centers of the supplemental ports l3! and [32 are spaced axially of the valve body plungerereceiving bore 3'5 from the center of the supplemented here as, Fig. 3, such a distance as to place at least part of these supplemental ports out of alignment with the sup-. plemented ports circumferentially of the plunger receiving bore. This, is accomplished by placing the centers of the small diameter supplemental ports I 31 and l32 respectively in alignment circumferentially of the plunger receiving bore with opposite edges 935, and {38 of the supplemented port 39 axially of the plunger receiving bore 3?. Since the supplemental ports i3! and iE-Z are much smaller in diameter than the supplemented port 39, slight inaccuracy in the position of these small bore ports axially of the plunger receiving bore will be less significant than if the large diameter supplemented bore were inaccurately placed, but having in effect established the limits for the. bore 39 axially of the plunger receiving bore by reasonably accurate placing of the small diameter bores 13! and I32, the larger bore 39 can have a tolerance of placement. axially of the plunger receiving bore any place within the span S between the bores 55.! and -32. This same advantage is accomplished by the similarly arranged bores 4|, 133, and [5.4,

Another feature improving the adaptability of accuracy in the production and response sensitivity of the control valve is the provision of control ports 36 which are cut into the sides of the tubular valve body 2! with opposite edges 36:; and 36b in planes perpendicular to the axis of the plunger receiving bore 3?. By using this shape control port, a large communication opening is established therethrough attendant to less axial mo emen of e va ve l ng h n h n cylindrical ports. are used, When uncovering; this type of control port, there is quicker drainage of the fluid on the left side of the bypass valvop crating plunger 88 to enable the bypass valve 8| to close more quickly to establish the high pressure fluid delivery condition of the fluid source. Conversely, as the control valve plunger 38 is approaching its neutral setting, this type of control port will continue to. provide a large es: cape opening for the fluid behind the valve-operating plunger 88 and thus assure the fluid source operating upon the high pressure phase until the control valve plunger actually reaches the neutral setting.

Having thus described a single. embodiment of; the invention with the View of clearly and con cisely illustrating the same, I claim:

1. In apparatus for controlling the delivery of fluid under: pressure from a high pressure out.- let of a fluid source to a fluid operated device concurrently with returning fluid from said de-. vice to a low pressure section of said source, and which source is controllable to deliver fluid at high pressure only pursuant to establishment of communication between a control section thereof and said low pressure section; said apparatus including reversible flow passages communicative with said device for causing operation thereof in respectively opposite directions when fluid is delivered to the device therethrough, each of these passages also being adapted to exhaust fluid from the device pursuant to. delivery of fluid to the device through the other thereof, a control valve body containing a valve-plunger-receiving bore, said passages having respective ports spaced axially of said bore and in communication therewith, a control valve plunger slidable axially in said bore and having axially spaced enlargements respectivel registered with said ports to close the same when the plunger is in a neutral position, said plunger and the enlargements coop--v crating with said bore to form a fluid inlet chamber between opposed ends of said enlargements and further cooperating with said bore to form fluid exhaust cavities. respectively adjacent the opposite ends of said enlargements and communicatively isolated from the fluid inlet chamber, the control valve bore containing a control cavity adjacent one of the exhaust cavities and at the opposite end thereof lengthwise of such bore with reference to the fluid inlet chamber, the control valve plunger having a control enlargement between and separating the control cavity from the one exhaust cavity, the control valve plunger having an axial bore with ports communicating respectively with the three re-, cited cavities, means communicating between one of the cavities and the low pressure section of the fluid source, a fluid inlet passage communicating between the fluid source outlet and the inlet chamber, a fluid conducting control passage leading communicatively from the control section of the fluid source and having a port in the valve bore in registry with the plunger control enlargement to be closed thereby when the plunger is in the neutral position, the valve plunger being oppositely movable axially from the neutral position to selectively register the reversible flow passage ports with the inlet chamber while registering the other of such ports with the exhaust cavity adjacent thereto, and the plunger control enlargement being operable to uncover the control passage port to establish communication thereof with the one exhaust 9 cavity when the plunger is moved one way from neutral and to uncover the control passage port to establish communication thereof with the control cavity when the plunger is moved the opposite way from neutral.

2. In apparatus for controlling the delivery of fluid under pressure from a high pressure outlet of a fluid source to a fluid operated device concurrently with returning fluid from said device to a low pressure section of said source, and which source is controllable to deliver fluid at high pressure only pursuant to establishment of communication between a control section thereof and said low pressure section; said apparatus including reversible flow passages communicative with said device for causing operation thereof in respectively opposite directions when fluid is delivered to the device therethrough, each of these passages also being adapted to exhaust fluid from the device pursuant to delivery of fluid to the device through the other thereof, a control valve body containing a valve-plungerreceiving bore, said passages having respective ports spaced axially of said bore and in communication therewith, a control valve plunger slidable axially in said bore and having axially spaced enlargements respectively registered with said ports to close the same when the plunger is in a neutral position, said plunger and the enlargements cooperating with said bore to form a fluid inlet chamber between opposed ends of said enlargements and further cooperating with said bore to form fluid exhaust cavities respectively adjacent the opposite ends of said enlargements and communicatively isolated from the fluid inlet chamber, the control valve bore containing a control cavity adjacent one of the exhaust cavities and at the opposite end thereof lengthwise of such bore with reference to the fluid inlet chamber, the control valve plunger having a control enlargement between and separating the control cavity from the one exhaust cavity, channel means communicating between the three recited cavities and the low pressure section of the fluid source, a fluid inlet passage communicating between the fluid source outlet and the inlet chamber, a fluid conducting control passage leading communicatively from the control section of the fluid source and having a port in the valve bore in registry with the plunger control enlargement to be closed thereby when the plunger is in the neutral position, the valve plunger being oppositely movable axially from the neutral position to selectively register the reversible flow passage ports with the inlet chamber while registering the other of such ports with the exhaust cavity adjacent thereto, and the plunger control enlargement being operable to uncover the control passage port to establish communication thereof with the one exhaust cavity when the plunger is moved one way from neutral and to uncover the control passage port to establish communication thereof with the control cavity when the plunger is moved the opposite way from neutral.

3. In apparatus for controlling the delivery of fluid under pressure from a high pressure outlet of a fluid source to a fluid operated device concurrently with returning fluid from said device to a low pressure section of said source, and which source is controllable to deliver fluid at high pressure only pursuant to establishment of communication between a control section thereof and said low pressure section; said apparatus including reversible flow passages communica- 10 tive with said device for causing operation thereof in respectively opposite directions when fluid is delivered to the device therethrough, each of these passages also being adapted to exhaust fluid from the device pursuant to delivery of fluid to the device through the other thereof, a control valve body containing a valve-plungerreceivingbore having opposite ends which are respectively open and closed, a pair of reversible flow ports in the side of said bore and spaced apart axially thereof, an inlet port in the side of said bore between the reversible flow ports, and a control port in the side of said bore between the closed end thereof and the reversible flow port most proximiate thereto, a control valve plunger slidable axially oppositely in said bore from a neutral position, the plunger having an inner end portion in axially-spaced contiguity with the inner end of the bore to form a control cavity therebetween, there being an inner radial enlargement on the plunger inner end portion in closing registry with the control port while the plunger is in neutral, the plunger also having an outer radial enlargement spaced axially inwardly from the outer end of the bore and an intermediate radial enlargement between and axially spaced from the other two enlargements, the outer enlargement and the intermediate enlargement beingin respective closing registry with the reversible flow ports while the plunger is in neutral, the bore containing a first fluid exhaust cavity adjacent to one of the reversible flow ports and between the inner and intermediate enlargements, a fluid inlet chamber between the intermediate and outer enlargements, and a second fluid exhaust cavity adjacent to the other reversible flow port and between the outer enlargement and the outer end of such bore and communicative with the loW pressure section of the fluid source through such open end, a fluid inlet passage communicating between the fluid source outlet and the fluid inlet chamber through said fluid inlet port, said reversible flow passages communicating with said reversible flow ports, a fluid conducting passage leading communicatively between the control section of the fluid source and the control port of the valve casing bore, channel means intercommunicatingbetween the three recited cavities exclusively of said chamber, the plunger outer enlargement and intermediate enlargement being operable according to the axial direction of plunger movement from the neutral to uncover and selectively communicate the reversible now ports with the inlet chamber while communicating the other of such ports with the exhaust cavity adjacent thereto, and the plunger inner enlargement being operable to uncover the control passage port to establish communication thereof with said first exhaust cavity When the plunger is moved one way from neutral and to uncover the control passage port to establish communication thereof with the control cavity when the plunger is moved the opposite Way from neutral.

l. The combination set forth in claim 3, wherein said channel means intercommunicative between the three recited cavities is formed in the valve plunger.

5. 'l he combination set forth in claim 3, wherein said channel means consists of a bore extending axially into the valve plunger from its inner end, and ports communicating laterally from such bore respectively with the exhaust cavities.

6. A fluid controlling valve comprising a valve body having a plunger-receiving bore with opportszspeced ia-partiax ell eot ediibue tpmr munieating therewith a n inlet port eg qmn ur-iiegtmg. with ;the bore. between. the reversible fiQW ports,.a;nd a, control port communicating with;the bone -at a position, spaced ,axially thereof, from onexat the reversibleifiom ports and..on the oppositeside. thereof axiallyof. the sbore with; re.- spect-te the inlet port; a.va1ve plunger movable apposite-yew a neutral: position .,m said, bore, se id pluriger having a bodysmaller in diameter thansaid bore and axially spaced radial enlargerrieiit s on siich "body respectively in port-closing if g'fstrytvith the c'ofitrbl port andreversible flow ports wh il'e the neiitriiposition, said bore-eont'e' ih'g wflili c i inietehar'rib'er between the plunger ei i leirgerrient's registering with the reversible flow pbr t s, a fi'rstexh ililst Cavity ajdj'ecent to and between the d itrbr-po t-clbsfiigenlargement and the reyersible-fiow-p'ort-o1osirig en argement in registry w iththe one 'reyersibIe 'fiow p ort 'a set:- or; exhaust cavity d'j t'cefit f 91115 '91? 151129 ,1

1p site sgjde ofth e therretersgtgeam'mmt-c16s- I 7 iih xmel ma t mte k qmmum ati'nebe we nth i tan ent 20 iri said manna means intercqmniumeame peg tween the three recited cavities is formediin the 9., r ha ust .oavit es.

9, r]; goigitiiiahtii 'setforth iipla mew' j there are sqpg1ei'r ehte1 reversible flow ports Q reumterentia liy of. the valve 'o'dy bore ports, w ereirl e h of the js'uppl'ementei ports is 7 y me e m pore mange essoeieteil 1e flow p'ort en d hes itsfeeriter. gpaeu w .p P t Ff i z e om w .Qen te r of sueh steemed port 'a, distance piaeiri'g et-ble i g ptt ,-.th .P i ?n e tHQh b .a l ign n e t with the @ss oei ated port 'ci'r'cuiiifernti 'm the zluri exr eb rev e l -ei e,s= mh n ionv k t fer in la m. 9 .we rqini eere. 15;. @Re'i et up m nte m esr p esi-w h;etlws 9 .95. he eye ib r ew Rem-$ 49.11 u pl m n e p9 hav epnn sit lsid es qqdez i lm the p uneerr eqeiv ne here t e upplemnte per be neeubs nt lly rs alle e-i n ithe ithei eun ementedt ri an e n e e -9m usan. tt. qi cl mt tentia lx I. the "H n 81 me hq eibutre neqti e y re erii g-ti h ei ipmwi e q de 'qirq m ent ai' y p tr e vinemre an t e .s np eta ,fiefils. 9x 9 .et ne x l theplunge jun ryir g bore lgeygnd the port sides respectively registeredtherewith.

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