GB2141524A - Sectional valve with independent pump and function control spools - Google Patents

Abstract

An hydraulic sectional control valve includes separate pump and function control spools 52, 54. The spools 52, 54 may be actuated independently and sequentially to provide raising, holding, power down and floating functions for earthmoving and construction vehicles. Additional function control spools 55, 56 may be added in the valve structure to provide multiple function control. <IMAGE>

Description

SPECIFICATION Sectional valve with independent pump and function control spools The present invention relates to hydraulic control valves for earth moving and construction equipment, and more particularly to an hydraulic sectional control valve with independent pump and function control spools There have previously been proposed sectional valves which contain a plurality of valve housings that have been machined from several different castings. The sections are bolted together into the desired circuitry and number of sections required to perform the desired operation. Each valve section includes a single independently operable control spool siidably received therein within a bore for moving from a neutral position to each of a pair of operating positions.Each control spool functions to control both the pump flow as well as the directional flow of hydraulic fluid to and from an hydraulic actuator or load. Sectional valves are thus popular because of their interchangeability, adaptability to many different circuits, ease of manufacture and the ability to bolt a plurality of sections into one valve assembly.

Various types of sectional hydraulic control valves are known and commonly used in earthmoving and construction vehicles. See for example U.S. Patent Nos. 3729026 and 3881512, both of which are assigned to the assignee of the present application, as well as U.S. Patent Nos. 4154262 and 3209781. In these types of control valves, a spool connects either of a pair of service or work ports with a bridge-like feeder passage and the other work port with one of a pair of exhaust ports. The spools are generally three position spools which are designed to block the work ports in their neutral positions. In one operating position, the spool directs oil from the pump to one port and oil from the other work port returns to tank. In the operating position, the oil flow is reversed.

In order to accomplish the fine regulation of flow and pressure required, control spools include a plurality of axially spaced circumferential grooves that define a series of lands.

The position of the grooves and lands within the bore thus controls the flow of hydraulic fluid. As a result, the spool-to-bore fit is very critical in order to minimize leakage. Thus, the spools are honed to a select fit within the bore with the maximum spool-to-bore lap possible.

However, in more complex spool designs it becomes difficult to maintain a sufficient spool-to-bore lap and thus fluid leakage becomes more difficult to control. In addition, the more complex the spool the more difficult it becomes to modify the valve function. In other words, the valve sections become less interchangeable and less adaptable to different circuits so that the valving used in a circuit becomes tailored for only one specific machine and one specific circuit. Such valves necessarily become expensive to manufacture.

Another problem with three position spools such as these shown in the above referred to patents is the possible creation of voids or cavitation in the fluid during operation. Voids or cavitation may occur when the spool is being moved from its neutral position to an operating position. During this movement, it is necessary that the pump keep sufficient pressure on the hydraulic actuator to prevent voids and cavitation. However, if the actuator moves faster than the supply of fluid thereto, undesirable voids or cavitation may be created in the circuit.

Another disadvantage of the conventional sectional control valve with three position spools is that it does not permit a "floating" function. A floating function enables the load to be lowered by gravity without pressurizing the pump into the circuit, i.e. a "power down" function. In many applications, a floating function is desired and the conventional three position spools do not allow for such an operation since the work ports are blocked when the control spool is in its neutral position and the pump is pressurized in either of its other two operating positions.

It is an object of the present invention to provide an hydraulic control valve wherein the aforementioned problems and disadvantages are minimised.

According to a first aspect of the present invention there is provided an hydraulic control valve for controlling the flow of pressure fluid from a source to an hydraulically actuated device, comprising: a valve housing having a fluid inlet port connectable to said source of hydraulic fluid and first and second spool-receiving bores, said first bore communicating with said fluid inlet port and a fluid outlet port, and said second bore having an inlet chamber communicating with said inlet port downstream from said first bore so that inlet fluid flows into said first bore prior to reaching said second bore, said second bore further communicating with a pair of work ports connectable to said hydraulically actuated device and a pair of fluid return passages;; {first and second control spools axially slidable within said bores between neutral and operational positions for selectively establishing fluid communication of the inlet port with the outlet port, return passages and work ports; and means for independently actuating said control spools to move said spools between said positions.

In accordance with a second aspect of the present invention there is provided an hydraulic control valve for controlling the flow of pressure fluid from a source to an hydrauli cally actuated device, comprising: a valve housing having a fluid inlet port connectable to said source of hydraulic fluid, and a plurality of spool-receiving bores formed therein, one of said bores communicating with said fluid inlet port and a fluid outlet port, and the other bores each having an inlet chamber communicating with said inlet port downstream from said one bore so that inlet fluid flows into said one bore prior to flowing into said inlet chambers, each of said other bores further communicating with a pair of work ports connectable to said hydraulically actuatable device and said fluid outlet port;; a plurality of control spools axially slidable within said bores between neutral and operational positions for selectively establishing fluid communication of the inlet port with the outlet port and work ports; and means for independently actuating said control spools to move said spools between said positions.

Thus an hydraulic control valve as specified above may include separate pump and function control spools. The spools may be actuated independently and sequentially to provide raising, holding, power down and floating functions for earth moving and construction equipment.

In one convenient form, the valve includes a pump control spool and a function control spool. The two spools separate the functions normally performed by a single spool in conventional sectional valves so that the function control spool directs the flow of fluid to and from a hydraulic actuator and the pump control spool controls pump flow. This provides for precise regulation of the flow and pressure of hydraulic fluid in the circuit.

The position of the pump and function control spools is controlled by pilot operated spring centering mechanisms. By changing the spring forces and varying the relationship between the spring forces on the two spools, their relative movements can be changed depending on the desired function, circuitry or type of control desired. For example, if the pump control spool is moved to its stroked position first, pump pressure can be elevated to a "precharge" level prior to moving or opening the function control spool. This "precharge" pump pressure eliminates voids by providing sufficient pressure in the circuit when the function control spool is opened.In contrast, if the function control spool is moved to an operating position first while maintaining the pump control spool in its neutral position, flow from a work port to tank is initiated first in order to provide a "floating" function to lower a load. Pump flow can thus be delayed or introduced only if demanded by stroking the pump control spool.

The provision of a pair of spools instead of a single spool also eliminates the bridge-like feeder passage which communicates to the opposite ends of a conventional single spool.

This provides a valve housing which is easier and less expensive to manufacture. Separate pump and function control spools also provide maximum spool-to-bore lap for minimum fluid leakage since the complex design of a single spool may be divided into two spools.

Additional function control spools may also be added to the valve structure to provide multiple function control. When more than one function control spool is utilized, the valve functions like a standard parallel valve with the individual spools connected to the input or feed line of the control valve by a common passage so that the spool with the lowest pressure requirement will become operational first. Thus, when a plurality of function control spools are utilized in the present valve, the valve functions can be modified by mèré changing the operational sequencing of 4he spools and not the spool design itself.

The drawings illustrate the best modè~pre- sently contemplated of carrying out th--ihven- tion.

In the drawings: Figure 1 is a schematic sectional view of a hydraulic control valve in accordance with one example of the present invention; Figure 2 is a schematic sectional viet simi- lar to Fig. 1 showing the spools thereof in one of their operation positions; and Figure 3 is a schematic sectional view illustrating a modified form of the hydraulic control valve in accordance with a second example of the present invention.

Referring now to the drawings, Fig. 1 illustrates a hydraulic control valve, generally designated by the numeral 1, constituting a first embodiment of the present invention.

Control valve 1 includes a housing or casing 2 shown in cross sectional detail in Fig. 1.

Housing 2 has a pump control spool 3 slidable within a bore 4 and a function control spool 5 slidable within a bore 6. Bore 4 includes three spaced apart annular grooves comprising a pair of exhaust ports 7 and 8 connected to a reservoir 9 through return conduits 10 and 11, respectively, and an inlet port 1 2 located between exhaust ports 7 and 8 and connected to a pump 1 3 through feed line 14. The ports 7, 8 and 12 are in fluid communication with each other through bore 4.

The pump control spool 3 has a pair of circumferential grooves 1 5 and 1 6 cut therein in axially spaced locations. The grooves -15 and 16 define three lands 17- 19. Lands 1 7-1 9 and bore 4 are machined to close tolerances, as is conventional, to minimize fluid leakage. Land 1 8 is dimensioned to have an axial length which is less than the axial length of lands 1 7 and 19, and which substantially corresponds to the actual distance between inlet port 12 and exhaust ports 7 and 8.

Bore 8 includes a plurality of spaced apart annular grooves formed in housing 2 at axially spaced locations. Inlet chamber 20 is centrally located with respect to bore 6 and is in fluid communication with inlet port 1 2 of bore 4.

Chamber 20 and port 1 2 can thus be more generally termed as a fluid suppry orzfeed passage. A pair of service or work ports 21 and 22 are disposed on either side of inlet chamber 20. Work ports 21 and 22 are in fluid communication with inlet chamber 20 via bore 6, and lead to opposite ends of a fluid actuator, namely, a hydraulic ram (not shown). It is understood that the connection of work ports 21 and 22 to the cylinder and rdd ends of a ram is not intended to be the sole application of control valve 1 but that valve 1 could readily be adapted to other similar applications.

A pair of exhaust or return passages 23 and 24 join with bore 6 at positions axially outwardly of the work ports 21 and 22, respectively. Passages 23 and 24 are connected in the conventional manner to reservoir or tank 9.

Function control spool 5 is provided with a pair of axially spaced circumferential grooves 25 and 26 which define three spaced apart lands 27, 28 and 29 along the longitudinal axis of spool 5. As seen best in Fig. 1, lands 27 and 29 have identical axial length while middle land 28 is slightly shorter in axial length than lands 27 and 29. Lands 27-29 are located on spool 5 in positions which isolate the service or work ports 21 and 22 from the return passages 23 and 24 and from the feeder or inlet chamber 20 in the neutral or hold position of spool 5. This neutral or hold position for spool 5 is shown in Fig. 1.

A conventional spring centering mechanism is connected with the opposite ends of each spool 3 and 5 to yieldingly resist movement thereof out of its neutral position. Since the spring centering mechanisms on opposite sides of each 3 and 5 are identical only one side of the centering mechanisms will be described herein. Referring now to the right hand side of Fig. 1, the centering mechanism.

includes a cap 30 for enclosing the right hand ends of spools 3 and 5. As shown, a plurality of seals 31 provide a fluid tight seal between cap 30 and housing 2. As shown, the centering mechanism for spool 5 includes a spring 32 located within a chamber 33 formed in the upper end of cap 30. Chamber 33 has a diameter greater than bore 6 which enables it to slidably receive land 29 and a washer 34 disposed about the end of spool 5. One end of spring 32 encircles the right hand end of spool 5 and bears against washer 34 while the other end of spring 32 encircles a seat 35 and bears against cap 30.

The centering mechanism for spool 3 includes a spring 36 located within a chamber 37 formed in a lower portion of housing 2.

Chamber 37 has a diameter greater than the diameter of bore 4 for slidably receiving land 1 9 of spool 3 and a washer 38 positioned about the end of spool 3. One end of spring 36 encircles the right hand end of spool 3 and ,bears against washer 38 while the other.

end of spring 36 encircles a seat 39 and bears against cap 30. Thus, when either spool 3 or 5 is moved to the right as shown in Fig.

1, springs 32 and 36 are compressed to yieldingly resist this movement.

Valve spools 3 and 5 are slidable in bores 4 and 6 by means of hydraulic pressure supplied to chambers 37 and 33, respectively. In order to supply the pressure, each cap 30 includes a pair of pilot passageways 40 and 41 which communicate at one end with chambers 37 and 33, respectively, and at their other ends with a threaded pilot port 42.

In operation, when the spools 3 and 5 are in their neutral positions, as shown in Fig. 1, hydraulic fluid flows from pump 1 3 to inlet port 1 2 through bore 4 to exhaust ports 7 and 8 and back through conduits 10 and 11 to tank 9. Fluid cannot flow from inlet port 12 through inlet chamber 20 and then to the work ports 21 or 22 because land 28 of spool 5 blocks any communication between chamber 20 and ports 21 or 22. In this neutral position, the hydraulic actuator or ram receives no fluid pressure from pump 1 3 but remains hydraulically locked in a hold position.

Referring now to Fig. 2, the spools 3 and 5 are shown moved out of their neutral positions and into one of their stroked positions.

As shown, spools 3 and 5 are moved to the left. In this position, land 1 8 of spool 3 blocks communication between inlet port 12 and exhaust port 7 and land 1 9 blocks communication between port 12 and exhaust port 8. In addition, land 28 of spool 5 blocks communication between chamber 20 and work port 21 and land 29 blocks communication between work port 22 and return passage 24.Further, fluid communication is opened between inlet chamber 20 and work port 22 as well as between work port 21 and return passage 23 due to the corresponding positions of grooves 25 and 26 on spool 5. in the positions shown in Fig. 2, fluid flows from pump 1 3 via feed line 14 into inlet port 1 2 and then through inlet chamber 20 and bore 6 to work port 22 and then to one end of a hydraulic ram (not shown). Return fluid from the hydraulic ram passes through work port 21 and bore 6 to return passage 23 and then to tank 9. Thus, the hydraulic ram may be actuated to either extend or withdraw the rod end of the ram.

If the position of spools 3 and 5 in Fig. 2 define a load raising function for the hydraulic ram, it would be necessary to move spools 3 and 5 in the opposite direction, or to the right, in order to define a loal lowering func tion for the hydraulic ram. This position for spools 3 and 5 is generally referred to as a power down" position because pump pressure is being utilized in the circuit to lower the load. In this position, land 18 of spool 3 blocks communication between exhaust port 8 and inlet port 12 and land 17 blocks communication between inlet port 1 2 and exhaust port 7. Also, land 28 of spool 5 blocks communication between inlet chamber 20 and work port 22, and land 27 blocks communication between work port 21 and return passage 23.Thus, fluid communication is open between inlet chamber 20 and work port 21 due to the location of groove 25 to power down" the load and fluid would return to tank 9 via work port 22 and return passage 24.

It should be noted that if the spools 3 and 5 are in their neutral positions as shown in Fig. 1, and pump spool 3 is moved or stroked first to the position shown in Fig. 2, prior to the movement of function spool 5, pump pressure can be elevated to a "precharge" level before moving spool 5. This allows pump 13 to keep sufficient pressure on the hydraulic ram to prevent voids. Since sufficient pressure is applied to the hydraulic ram air cannot be sucked into the system if the rod begins to move faster than fluid pressure would normally allow it. Thus, the independent action of spools 3 and 5 eliminates the time delay between movement of the spool and pressure buildup in the circuit which is normally present in single spool valves.

The independent operation of pump spool 3 and function spool 5 also enables valve 1 to provide a "float" position. In the float position, pump pressure is not utilized to move the hydraulic ram but instead the weight of the load causes movement of the ram via the force of gravity. In order to provide a float function, pump spool 3 needs to be in the position shown in Fig. 1 while function spool 5 needs to be stroked to the right so that land 28 blocks communication between inlet chamber 20 and work port 22. When spools 3 and 5 are in these positions, fluid flow will be initiated from work port 22 through return passage 24 to tank 9, and pump pressure can be delayed or introduced only if demanded.

This of course could be provided by stroking spool 3 to the left or right thereby transforming valve 1 from a float position to a power down position.

Referring now to Fig. 3 there is shown an hydraulic control valve, generally designated by the numeral 50, constituting a second embodiment of the present invention. Control valve 50 includes a housing or casing 51 shown in cross sectional detail in Fig. 3.

Housing 51 has a pump control spool 52 slidable within a bore 53 and three function control spools 54-56 slidable within corresponding bores 57-59.

Housing 51 includes an inlet port 60 and an outlet or exhaust port 61. Inlet port 60 is centrally located in housing 51 and is connected to a pump 62 through feed line 63.

Inlet port 60 functions as a fluid supply or feed passage and opens directly into bore 53 and communicates with each of the other bores 57-59 by means of three centrally located annular grooves 64-66 formed respectively in bores 57-59. As shown, outlet port 61 is substantially U-shaped and is connected to a reservoir or tank 67 through return line 68. Outlet port 61 communicates 'with each of the bores 53 and 57-59 at axially opposite ends thereof to provide a common exhaust port in housing 51.

The pump control spool 52 has a single circumferential groove 69 cut therein which defines a pair of lands 70-71 at axially.;.

spaced locations. As shown, land 70 iSs di- mensioned to have an axial length which;is slightly less than the axial length of lands?1.

A pair of service or work ports 72 anl73 are disposed on either side of inlet groove 64 of bore 57 between the groove 64 andihe outlet port 61. Work ports 72 and 73 are in fluid communication with inlet groove 64 via bore 57, and lead to opposite ends of a:fluid actuator, namely, a hydraulic ram (not shown). As with the first embodiment of~the present invention, it is to be understood that the connection of work ports 72 and 73 to the cylinder and rod ends of a ram is not intended to be the sole application of control valve 50 but that valve 50 could readily be adapted to other similar applications.

As shown, bores 58 and 59 also include a pair of work or service ports 74-75 and 76-77, respectively. Work ports 74-75 and 76-77 function in the identical manner as ports 72-73 except they lead to separate hydraulic acutators or rams which may perform a different and distinct function from that of the hydraulic ram associated with spool 54 and ports 72-73.

Function control spool 54 is provided with a pair of axially spaced circumferentially grooves 78 and 79 which define three spaced apart lands 80-82 along the longitudinal axis of spool 54. Lands 80 and 82 have identical axial length while middle land 81 ig slightly shorter in axial length than lands 80 and 82.

Lands 80-82 are located on spool 54 in positions which isolate the service or work ports 72 and 73 from the return or outlet port 61 -and from the feeder or inlet groove 64 in the neutral or hold soo$ítion of si-'54 This' neutral or hold position for spool 54 is shown in Fig. 3.

Function control spools 55 and 56 are identical in dimensions to spool 54. Thus, spool 55 includes a pair of grooves 83 and 84 which define three lands 85-87, and spool 56 includes grooves 88-89 and lands 90-92. As shown, the spools 55 and 56 are in their neutral or hold positions, and function in the same manner as spool 54.

A conventional spring centering mechanism is connected with the opposite ends of each spool 54-56 to yieldingly resist movement thereof out of its neutral position. Since the spring centering mechanisms on opposite sides of each spool 54-56 are identical only one will be described herein. Referring now to the right hand side of Fig. 3, the centering mechanism includes a cap 93 for enclosing the right hand ends of spools 54-56. As shown, a plurality of seals 94 provide a fluid tight seal between cap 93 and housing 51.

As shown, the centering mechanism for spool 54 includes a spring 95 located within a chamber 96 formed in the upper end of cap 93. Chamber 96 has a diameter greater than bore 57 which enables it to slidably receive land 82 and a washer 97 disposed about the end of spool 54. One end of spring 95 encircles the right hand end of spool 54 and bears against washer 97 while the other end of spring 95 bears against cap 93.

The spring mechanism for pump spool 52 biases spool 52 to the right, as shown in Fig.

3, and includes a spring 98 located substantially within bore 53. One end of spring 98 encircles the left hand end of spool 52 and bears against the side of land 70 while the other end of spring 98 bears against cap 99 which covers the left hand side of housing 51. Thus, when spool 52 is moved to the left as shown in Fig. 3, spring 98 is compressed to yieldingly resist this movement.

Valve spools 52 and 54-56 are slidable in bores 53 and 57-59 by means of hydraulic pressure. In order to supply the pressure, the caps 93 and 99 include threaded pilot ports 100 which communicate at one end with chambers 96, and at their other ends with pilot lines 101 which are connected through a series of check valves 102 with a source of pilot pressure (not shown). Pump spool 52 is actuated by pilot pressure supplied through a threaded pilot port 103 which communicates at one end with a passageway 104 and at its other end with a pilot line 101. Passageway 104 in turn leads to the face of land 71 of spool 52 so that when pressure is applied thereagainst spool 52 moves to the left against the force of spring 98.

In operation, when the spools 52 and 54-56 are in their neutral positions, as shown in Fig. 3, hydraulic fluid flows from pump 62 to inlet port 60 through bore 53 to exhaust port 61 and back through return line 68 to tank 67. Fluid cannot flow from inlet port 60 through inlet grooves 64-66 and then to work ports 72-77 because lands 81, 86 and 91 of spools 54-56, respectively, block any communication between inlet grooves 64-66 and ports 72-77. When spools 54-56 are in their neutral positions, the individual hydraulic actuators or rams controlled by spools 54-56 receive no fluid pressure from pump 62 but remain hydraulically locked in hold positions.

In order to raise or lower a load, pump spool 52 needs to be moved to its operational position, and spools 54-56 need to be moved out of their neutral positions and into one of their stroked positions. The following discussions relates only to the operation of spools 52 and 54. However, it is to be understood that spools 55 and 56 operate in an identical manner to spool 54 to control separate hydraulic actuators. Therefore, if spools 52 and 54 are moved to the left, land 71 of spool 52 blocks communication between inlet port 60 and exhaust port 61 so that full pump pressure is applied to inlet groove 64. In addition, land 81 of spool 54 blocks communication between inlet groove 64 and work port 72 and land 82 blocks communication between work port 73 and return passage 61.Further, fluid communication is opened between inlet groove 64 and work port 73 as well as between work port 72 and return passage 61 due to the corresponding positions of grooves 78 and 79 on spool 54. In this position, fluid flows from pump 62 via feed line 63 into inlet port 60 and then through inlet groove 64 and bore 57 to work port 73 and then to one end of a hydraulic ram (not shown). Return fluid from the hydraulic ram passes through work port 72 and bore 57 to return passage 61 and then to tank 67. Thus, the hydraulic ram may be actuated to either extend or withdraw the rod end of the ram.

If the positions of spools 52 and 54 when moved to the left define a load raising function for the hydraulic ram, it would be necessary to move spool 54 in the opposite direction, or to the right, in order to define a load lowering or power down function for the hydraulic ram. In this position, land 81 of spool 54 blocks communication between inlet groove 64 and work port 73, and land 80 blocks communication between work port 72 and return passage 61. Thus, fluid communication is open between inlet groove 64 and work port 72 due to the location of groove 78 to "power down" the load, and fluid would return to tank 67 via work port 73 and return passage 61.

If spools 52 and 54 are in their neutral positions as shown in Fig. 3, and pump spool 52 is moved or stroked first to the left to its operations position prior to the movement of function spool 54, pump pressure can be elevated to a "precharge" level before moving spool 54. This allows pump 62 to keep sufficient pressure on the hydraulic ram to prevent voids. This operation may also be performed with respect to spools 55 and 56. Thus, the independent action of spools 52 and 54-56 eliminates the time delay between movement of a function spool and pressure buildup in the circuit which is normally present in single spool valves.

The independent operation of pump spool 52 and function spool 54 also enables valve 50 to provide a "float" position. In order to provide a floating function, pump spool 52 needs to be in the position shown in Fig. 3 while function spool 54 needs to be stroked to the right so that land 81 blocks communication between inlet groove 64 and work port 73. When spools 52 and 54 are in these positions, fluid flow will be initiated from work port 73 through return passage 61 to tank 67, and pump pressure can be delayed or introduced only if demanded. This of course could be provided by stroking spool 52 to the left thereby transforming valve 50 from a float position to a power down position.

A hydraulic control valve has been illustrated and described herein that includes independent pump and function control spools.

Various modifications and/or substitutions may be made to components specifically described herein without departing from the scope of the invention. For example, the design of the valve housing and spools may be modified to suit the circuitry and type of control desired. Various types of spool actuating mechanism may also be used.

Claims (9)

1. An hydraulic control valve for controlling the flow of pressure fluid from a source to an hydraulically actuated device, comprising: a valve housing having a fluid inlet port connectable to said source of hydraulic fluid and first and second spool-receiving bores, said first bore communicating with said fluid inlet port and a fluid outlet port, and said second bore having an inlet chamber communicating with said inlet port downstream from said first bore so that inlet fluid flows into said first bore prior to reaching said second bore, said second bore further communicating with a pair of work ports connectable to said hydraulically actuated device and a pair of fluid return passages;; first and second control spools axially slidable within said bores between neutral and operational positions for selectively establishing fluid communication of the inlet port with the outlet port, return passages and work ports; and means for independently actuating said control spools to move said spools between said positions.

2. A control'valve as claimed in claim 1, wherein said fluid return passages communicate with said second bore at axially opposite sides of said inlet chamber.

3. A control valve as claimed in claim 2, wherein one of said work ports communicates with said second bore at a location between one of said fluid return passages and said inlet chamber and the other of said work ports communicates with said second bore at a locaton between the other of said fluid return passages and said inlet chamber.

4. A control valve as claimed in any one of claims 1 to 3, wherein said actuating means includes pilot pressure operated spring centering mechanisms.

5. A control valve as claimed in any one of claims 1 to 4, wherein there are a pair of outlet ports, one disposed on one side of said inlet port and the other disposed on the other side of said inlet port.

6. A control valve as claimed in any one of claims 1 to 5, wherein the outlet port of said first bore is in fluid communication with the return passages of said second bore to define a common outlet.

7. An hydraulic control valve for controlling the flow of pressure fluid from a source to an hydraulically actuated device, comprising: a valve housing having a fluid inlet port connectable to said source of hydraulic fluid, and a plurality of spool-receiving bores formed therein, one of said bores communicating with said fluid inlet port and a fluid outlet port, and the other bores each having an inlet chamber communicating with said inlet port downstream from said one bore so that inlet fluid flows into said one bore prior to flowing into said inlet chambers, each of said other bores further communicating with a pair of work ports connectabie to said hydraulically actuatable device and said fluid outlet port; ; a plurality of control spools axially slidable within said bores between neutral and operational positions for selectively establishing fluid communication of the inlet port with the outlet port and work ports; and means for independently actuating said control spools to move said spools between said positions.

8. A control valve as claimed in claim 7, wherein said outlet port opens into each of said bores at axially opposite ends thereof.

9. A control valve as claimed in claim 7 or claim 8, wherein the work ports of each of said other bores open into said other bores at axially opposite sides of said inlet chamber between said inlet chamber and said outlet port.

1 0. A control valve as claimed in any one of claims 7 to 9, wherein said actuating means includes a plurality of pilot pressure operated spring mechanisms.