WO2015017530A1

WO2015017530A1 - Pilot operated fuel pressure limiting valve for hydraulic motor driven fuel pump

Info

Publication number: WO2015017530A1
Application number: PCT/US2014/048875
Authority: WO
Inventors: Anh Hung VU; James William REINHOLDT; Arthur Voytek GRYSZKIEWICZ
Original assignee: Eaton Corporation
Priority date: 2013-07-31
Filing date: 2014-07-30
Publication date: 2015-02-05

Abstract

A pressure limiting valve (10) for regulating a supply of pressurized fluid may include a housing (12) having a main valve chamber with an inlet port (14) and an outlet port (16), and a pilot valve chamber in fluid communication with the main valve chamber. A control valve may be provided within the main valve chamber and can include a valve spool (40) that is movable between an opened position and a closed position to restrict or prohibit a flow of pressurized fluid through the main valve chamber. A pilot valve may be provided within the pilot valve chamber and can include a pressure sensing port (18) and a pilot valve member. The pilot valve member may be movable between a first position and a second position in response to fluid pressure within the pressure sensing port (18) to regulate a supply of pressurized fluid delivered to the pressure chamber for operation of the valve spool.

Description

PILOT OPERATED FUEL PRESSURE LIMITING VALVE FOR

HYDRAULIC MOTOR DRIVEN FUEL PUMP

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Application Serial No. 61/860,537, filed July 31, 2013, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to pressure limiting valves, including a fuel pressure limiting valve that can regulate a supply of hydraulic fluid being delivered to a hydraulic motor of a fuel pump in response to an outlet pressure of the fuel pump.

BACKGROUND

[0003] Aerial refueling systems can be used to transfer fuel during flight from a tanker aircraft to a receiver aircraft. In a typical aerial refueling system, a flexible hose or boom may generally extend from the tanker aircraft and can include a coupling member configured to connect to a probe on the receiver aircraft. Once a connection is made between the tanker aircraft and the receiver aircraft, a fuel pump provided on the tanker aircraft can pump a supply of fuel through the hose or boom to the receiver aircraft.

[0004] Aerial refueling systems may typically include fuel pressure regulating devices that are configured to regulate an outlet pressure provided by the tanker aircraft and reduce downstream pressure surges, which might otherwise damage fuel system components on the receiver aircraft. An example of a pressure regulating device is a pressure relief valve, which can be located downstream of the fuel pump. Pressure relief valves may operate effectively to limit the downstream pressure in the refueling system, however these valves tend to be relatively large and heavy. Another example of a pressure regulating device is a downstream pressure regulator, which can also be located downstream of the fuel pump. Such pressure regulators may also operate effectively to regulate downstream pressure in the refueling system. However, downstream pressure regulators can increase pressure drops downstream of the fuel pump and reduce the flow rate in the refueling system, which can result in the need for a more powerful and heavier fuel pump. In addition, these types of pressure regulators themselves can be relatively large and heavy.

[0005] Thus, it would be desirable to provide a fuel pressure limiting valve located upstream of the fuel pump that can regulate the outlet pressure of the fuel pump.

SUMMARY

[0006] A pressure limiting valve for regulating a supply of pressurized fluid may include a housing having a main valve chamber with an inlet port and an outlet port, and a pilot valve chamber in fluid communication with the main valve chamber. A control valve may be provided within the main valve chamber and can include a valve spool that is movable between an opened position and a closed position to restrict or prohibit a flow of pressurized fluid through the main valve chamber. A pilot valve may be provided within the pilot valve chamber and can include a pressure sensing port and a pilot valve member. The pilot valve member may be movable between a first position and a second position in response to fluid pressure within the pressure sensing port to regulate a supply of pressurized fluid delivered to the pressure chamber for operation of the valve spool.

[0007] Various aspects of the present disclosure will become apparent to those skilled in the art from the following detailed description of the various embodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present disclosure will now be described, by way of example, with reference to the accompanying drawings.

[0009] FIG. 1 is a perspective view generally illustrating a fuel pressure limiting valve for a hydraulic motor driven fuel pump according to an embodiment of the present disclosure.

[0010] FIG. 2 is an end view of the fuel pressure limiting valve in FIG. 1.

[0011] FIG. 3 is a cross-sectional side view of a portion of the fuel pressure limiting valve as generally indicated by the section lines 3-3 in FIG. 2.

[0012] FIG. 4 is a cross-sectional side view of the fuel pressure limiting valve as generally indicated by the section lines 4-4 in FIG. 2. [0013] FIG. 5 is a cross-sectional top view of the fuel pressure limiting valve as generally indicated by the section lines 5-5 in FIG. 2, shown in an opened position.

[0014] FIG. 6 is an enlarged cross-sectional top view of a portion of the fuel pressure limiting valve as generally indicated by the dashed circle VI in FIG. 5.

[0015] FIG. 7 is a cross-sectional top view of the fuel pressure limiting valve as generally indicated by the section lines 5-5 in FIG. 2, shown in a closed position.

[0016] FIG. 8 is an enlarged cross-sectional top view of a portion of the fuel pressure limiting valve as generally indicated by the dashed circle VIII in FIG. 7.

DETAILED DESCRIPTION

[0017] Reference will now be made in detail to embodiments of the present disclosure, examples of which are described herein and illustrated in the accompanying drawings. While the invention will be described in conjunction with embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

[0018] Referring now to FIG. 1, a fuel pressure limiting valve according to an embodiment of the present disclosure is shown generally at 10. In a non-limiting example, the fuel pressure limiting valve 10 can be used to regulate or control the flow of hydraulic fluid being delivered to a hydraulic motor that, in turn, powers a fuel pump in an aerial refueling system. By regulating the flow of hydraulic fluid being delivered to the motor, the fuel pressure limiting valve 10 can control or limit the outlet pressure of the fuel pump. As will be generally explained below, the fuel pressure limiting valve 10 may use the outlet pressure of the fuel pump to regulate, or limit, the flow of hydraulic fluid being delivered to the motor. It should be appreciated, however, that the fuel pressure limiting valve 10 can be used in any suitable environment and for any suitable purpose.

[0019] The fuel pressure limiting valve 10 may include a housing 12 having an inlet port 14 and an outlet port 16. In an embodiment, as generally shown, the inlet port 14 and the outlet port 16 can extend through another/opposing side wall of the housing 12 for fluid communication with a main valve chamber of the housing 12 (e.g., as generally shown in FIG. 5). The main valve chamber can be a generally cylindrical chamber having an open end and a closed end. The inlet port 14 and the outlet port 16 can be axially spaced apart from one another along a longitudinal axis of the main valve chamber. In other embodiments, however, the inlet port 14 and the outlet port 16 can be arranged along the main valve chamber in any suitable manner. As will be generally described below, the main valve chamber can be configured to house the components of a hydraulic flow control valve.

[0020] The fuel pressure limiting valve 10 may also include a fuel pressure sensing port 18 that can extend through a side wall of the housing 12. As such, the fuel pressure sensing port 18 can be in fluid communication with a pilot valve chamber of the housing 12 (e.g., as generally shown in FIG. 5). The pilot valve chamber can be a generally cylindrical chamber having an open end and a closed end. In an embodiment, for example, the pilot valve chamber can extend generally perpendicular to the longitudinal axis of the main valve chamber. Thus, the fuel pressure sensing port 18 may define an open end of the pilot valve chamber. As will be generally described below, the pilot valve chamber may house a pilot valve that can be configured to actuate the hydraulic control valve in response to the outlet pressure of the fuel pump.

[0021] Referring now to FIGS. 1 through 4, the fuel pressure limiting valve 10 may also include a drain port 20 and a hydraulic return port 22. In an embodiment, for example, the drain port 20 and the hydraulic return port 22 can extend through an end wall of the housing 12. As generally illustrated in FIG. 3, which is a cross-sectional side view of a portion of the fuel pressure limiting valve 10, the drain port 20 may extend generally perpendicular to the pilot valve chamber and can be in fluid communication with a first section of the pilot valve chamber (e.g., via a fluid passage). In an embodiment, the drain port 20 may be configured to drain a liquid such as fuel, for example, from the pilot valve chamber for purposes including those generally disclosed herein.

[0022] As generally illustrated in FIG. 4, which is a cross-sectional side view of the fuel pressure limiting valve 10, the hydraulic return port 22 may extend generally perpendicular to the pilot valve chamber and can be in fluid communication with a second section of the pilot valve chamber (e.g., via a fluid passage). It should be appreciated from FIG. 2 that the second section of the pilot valve chamber (i.e., which is in fluid communication with the hydraulic return port 22) can be spaced from the first section of the pilot valve chamber (i.e., which is in fluid communication with the drain port 20). In an embodiment, the hydraulic return port 22 may be configured to drain a liquid such as hydraulic fluid, for example, from the pilot valve chamber for purposes such as those generally disclosed herein. Referring briefly again to FIG. 4, the hydraulic return port 22 may also be in fluid communication with a section of the main valve chamber (e.g., via a fluid passage) for purposes such as those generally disclosed herein.

[0023] Referring now to FIGS. 5 through 8, internal components of the fuel pressure limiting valve 10 will now be generally described beginning with the hydraulic flow control valve. As shown generally in FIG. 5, the hydraulic flow control valve may include an internal sleeve 30 that can be supported within the main valve chamber of the housing 12. In a non-limiting embodiment, the internal sleeve 30 may include a generally cylindrical body portion and an end plate 32 that can be secured to the open end of the housing 12. The end plate 32 can be configured to support the internal sleeve 30 within the main valve chamber of the housing 12 and also can be configured to close the open end of the main valve chamber. The end plate 32 can be secured to the housing 12 using a plurality of fasteners or any other suitable types of connection such as, for example, a clamped or welded connection. In other embodiments, however, the internal sleeve 30 can be secured within the main valve chamber of the housing 12 other than as described and illustrated herein.

[0024] The internal sleeve 30 can be a generally cylindrical or tubular member having a plurality of apertures that extend through a side wall thereof. In an embodiment, for example, a first set of apertures 34 may extend through a side wall of the internal sleeve 30 and can be circumferentially arranged around the internal sleeve 30. The first set of apertures 34 may be positioned along the internal sleeve 30 so as to generally correspond with the inlet port 14. A second set of apertures 36 may extend through the side wall of the internal sleeve 30 and can be circumferentially arranged around the internal sleeve 30. The second set of apertures 36 may be positioned along the internal sleeve 30 so as to generally correspond with the outlet port 16. It should be appreciated that the first and second sets of apertures 34, 36 may respectively include a single aperture or any number of apertures.

[0025] As shown generally in FIG. 5, the fuel pressure limiting valve 10 may, for example and without limitation, define a primary fluid passageway for the flow of hydraulic fluid being delivered to a hydraulic motor. The primary fluid passageway may enter the housing 12 through the inlet port 14 and flow into the main valve chamber through the first set of apertures 34 in the internal sleeve 30. The primary fluid passageway may then exit the main valve chamber through the second set of apertures 36 in the internal sleeve 30 and exit the housing 12 through the outlet port 16.

[0026] As generally illustrated, the internal sleeve 30 may optionally include a plurality of seals that can circumferentially extend around an outer surface thereof for engagement with an inner surface of the main valve chamber. The seals can be located around any portion of the internal sleeve 30 such as, for example, near opposite ends of the internal sleeve 30 or adjacent to and between the inlet port 14 and the outlet port 16. In other embodiments, the internal sleeve 30 may include any suitable number, arrangement, or various other types of seals for a desired application.

[0027] The hydraulic flow control valve may also include a valve spool 40 movably supported within the main valve chamber of the housing 12. For example, in a non-limiting embodiment, the valve spool 40 may be supported for sliding movement or translation within the internal sleeve 30. As generally described below, the valve spool 40 may be movable between a normal or opened position and a modulated or closed position. In the opened position (e.g., as generally illustrated in FIG. 5), hydraulic fluid may be permitted to flow through the main valve chamber of the housing 12. In the closed position (e.g., as generally illustrated in FIG. 7), hydraulic fluid is prohibited or at least substantially reduced from flowing through the main valve chamber of the housing 12. The valve spool 40 may also be movable to various positions in between for selectively controlling or adjusting the rate of hydraulic fluid flow through the housing 12.

[0028] In an embodiment, an outer surface of the valve spool 40 may include sealing portions (i.e., lands) and a groove (i.e., a recessed portion). For example, as generally shown, the valve spool 40 may include a pair of sealing portions that are respectively located near opposite ends thereof. However, in other embodiments, the valve spool 40 may include any suitable number or arrangement of sealing portions. In general, the sealing portions may have an outer diameter that is generally the same as or slightly smaller than an inner diameter of the internal sleeve 30. As such, the sealing portions may, if desired, create or provide an interference fit with the inner surface of the internal sleeve 30 to facilitate sealing as the valve spool 40 slides within the internal sleeve 30. The valve spool 40 may also include seals or other types of sealing components provided on its outer surface to facilitate sealing with the internal sleeve 30, although such may not be required.

[0029] The groove may be a recessed portion provided in the outer surface of the valve spool 40 and can be generally located between the sealing portions thereof. In general, the groove may have an outer diameter that is generally smaller than the outer diameter of the sealing portions so as to form a fluid pathway around an outer surface of the valve spool 40. As generally illustrated in FIG. 5, the first set of apertures 34 and the second set of apertures 36 of the internal sleeve 30 may be in fluid communication with the groove when the fuel pressure limiting valve 10 is in the opened position, thereby creating a fluid pathway between the first and second set of apertures 34, 36. It should be appreciated that the valve spool 40 can have any suitable shape or configuration of sealing portions and grooves to accomplish the functions generally described herein and below.

[0030] The hydraulic flow control valve of the fuel pressure limiting valve 10 may further include a biasing member to bias the valve spool 40 in the normal or opened position. For example, a spring member 42 may be disposed between an end of the valve spool 40 and an inner surface of the end plate 32. In a non-limiting embodiment, the spring member 42 can be a compression spring or the like. As generally shown, the spring member 42 may be disposed within a spring chamber that is formed by the end of the valve spool 40 and the end plate 32. The spring chamber may be in fluid communication with the hydraulic return port 22 as generally described above (e.g., via a fluid passage). As such, fluid pressure that might otherwise accumulate within the spring chamber can be relieved through the hydraulic return port 22.

[0031] The valve spool 40 may optionally include a pressure chamber 44 that can be formed by an opposite end thereof and the end wall of the main valve cylinder. As will be generally explained below, the pressure chamber 44 may be configured to receive a supply of pressurized hydraulic fluid provided by the pilot valve. The supply of pressurized hydraulic fluid may be configured to move the valve spool 40 from the opened position towards the closed position. As such, it should be appreciated that the pressure chamber 44 can have any suitable size or shape to accomplish the functions generally described herein and below.

[0032] A pilot valve assembly of the fuel pressure limiting valve 10 will now be generally described in additional detail. As generally shown in FIG. 5, a pilot valve assembly 60 may be supported within the pilot valve chamber of the housing 12. In an embodiment, for example, the pilot valve assembly 60 may include a valve housing having an externally threaded portion that can be secured or otherwise supported within the open end of the pilot valve chamber. In other embodiments, however, the pilot valve assembly 60 can be supported within the pilot valve chamber of the housing 12 other than as described and illustrated herein.

[0033] In a non-limiting embodiment, the pilot valve assembly 60 may be a directional control valve. As generally illustrated in FIG. 6, for example, the pilot valve assembly 60 can be a three-way, two-position directional control valve that may include a three-way valve port. More specifically, the pilot valve assembly 60 may include a first valve port 61 A that can be in fluid communication with the inlet port 14 of the housing 12 (e.g., via a fluid passage). The pilot valve assembly 60 may also include a second valve port 6 IB that can be in fluid communication with the pressure chamber 44 of the valve spool 40 (e.g., via a fluid passage). The pilot valve assembly 60 may also include a third valve port 61C that can be in fluid communication with the hydraulic return port 22 of the housing 12 (e.g., via a fluid passage as generally shown in FIG. 4)·

[0034] The pilot valve assembly 60 may also include a pilot valve member 62 movably supported within the three-way valve port. For example, the pilot valve member 62 can be configured to close the first valve port 61 A or the third valve port 61C. In a non-limiting embodiment, the pilot valve member 62 can be a valve stem having ball members provided on opposite ends thereof for closing the respective valve ports. The pilot valve member 62 can be moved, for example, from a normal or first position wherein the first valve port 61 A is closed and the third valve port 61C is opened (e.g., as generally shown in FIGS. 5 and 6), to a modulated or second position wherein the first valve port 61 A is opened and the third valve port 61C is closed (e.g., as generally shown in FIGS. 7 and 8).

[0035] To move the pilot valve member 62 from the first position to the second position, the pilot valve assembly 60 may include a piston 64 that can be movably supported within the pilot valve housing. For example and without limitation, the piston 64 may include a head portion and a stem that extends from the head portion for engagement with the pilot valve member 62. It should be appreciated that the head portion and the stem of the piston 64 can have any suitable shape or dimensions. As will be generally explained below, the fuel pressure sensing port 18 may be configured to receive a supply of pressurized fluid such as fuel, for example, from the fuel pump to operate the pilot valve assembly 60.

[0036] The pilot valve assembly 60 may further include a biasing member that can be configured to bias the piston 64 and the pilot valve member 62 in the first position. As generally illustrated, a spring member 66 may be disposed between the head portion of the piston 64 and an inner surface of the pilot valve housing. In an embodiment, for example, the spring member 66 can be a compression spring or the like. It should be appreciated that the spring member 66 can have a desired spring load and/or spring rate to regulate operation of the pilot valve assembly 60 in response to a predetermined outlet pressure or range of pressures from the fuel pump.

[0037] The pilot valve assembly 60 may also include a plurality of fluid passages that extend through the pilot valve housing. In one embodiment, for example, a first passage 68 can provide fluid communication between a spring chamber of the pilot valve assembly 60 and the drain port 20 to relieve fluid pressure that might otherwise accumulate within the spring chamber. A second passage 69 can provide fluid communication between the third valve port 61C of the pilot valve assembly 60 and the hydraulic return port 22 to relieve fluid pressure from within the pressure chamber 44. The first and second passages 68, 69 may respectively include a single passage or any number of passages and can have various suitable dimensions.

[0038] As generally shown in FIGS. 5 and 6, the pilot valve assembly 60 may optionally include a plurality of seals that extend around an outer surface of the pilot valve housing for engagement with an inner surface of the pilot valve chamber. The seals can be located around any portion of the pilot valve assembly 60 such as, for example, near opposite ends of the pilot valve housing adjacent to and between the chambers and passages that are in fluid

communication with the drain port 20 and the hydraulic return port 22. In other embodiments, the pilot valve assembly 60 may include any suitable number, arrangement, or various other types of seals for a desired application. [0039] It should appreciated that the pilot valve assembly 60 is not limited to the illustrated embodiment, but can be any suitable type of valve mechanism and can have any suitable configuration to accomplish the functions described herein and below and/or other functions.

[0040] An operation of the fuel pressure limiting valve 10 in accordance with the present disclosure will now be generally described with reference to FIGS. 5 through 8. As briefly described above, the fuel pressure limiting valve 10 may normally be biased in the opened position, such as generally illustrated in FIG. 5. In this position, pressurized hydraulic fluid can flow generally unrestricted from the inlet port 14, through the main valve chamber of the housing 12, and out of the outlet port 16 to power a device, such as a hydraulic motor. Further, as perhaps more clearly shown in FIG. 6, the pilot valve assembly 60 may initially be in the first position, wherein the first valve port 61 A is closed by the pilot valve member 62 and the third valve port 61C is opened to provide fluid communication between the pressure chamber 44 of the valve spool 40 and the hydraulic return port 22.

[0041] As generally described above, pressurized fuel from an outlet of the fuel pump may be routed to the fuel pressure sensing port 18 of the pilot valve assembly 60. If the outlet pressure from the fuel pump exceeds a given or predetermined upper limit, then the fluid pressure in the fuel pressure sensing port 18 generates a force on the piston 64, which may overcome a biasing force exerted on the piston 64 by the spring member 66. As a result, the piston 64 may begin to move the pilot valve member 62 from the first position to an intermediate position, thereby beginning to open the first valve port 61 A. This may allow pressurized hydraulic fluid to flow from the inlet port 14, through the pilot valve assembly 60, and into the pressure chamber 44 of the valve spool 40. If fluid pressure in the pressure chamber 44 exceeds the biasing force of the spring member 42, the valve spool 40 will begin to move from a fully opened position to an intermediate position. In the intermediate position, the sealing portions of the valve spool 40 may partially cover or otherwise obstruct the first set of apertures 34 in the internal sleeve 30. As a result, the flow rate and volume of hydraulic fluid passing through the fuel pressure limiting valve 10 may be reduced.

[0042] If the outlet pressure from the fuel pump continues to increase beyond the given or predetermined upper limit, then fluid pressure within the fuel pressure sensing port 18 may continue to force the piston 64 and the pilot valve member 62 to the modulated or second position. In the second position, as generally illustrated in FIG. 8, the pilot valve member 62 may fully open the first valve port 61 A and close the third valve port 61C. As such, hydraulic fluid can continue to flow from the inlet port 14 through the pilot valve assembly 60 and into the pressure chamber 44 of the valve spool 40, thereby causing the valve spool 40 to move from the intermediate position to the closed position, for example as generally illustrated in FIG. 7. In the closed position, the valve spool 40 may fully or substantially cover and seal the first set of apertures 34 in the internal sleeve 30 which correspond with the inlet port 14. As a result, the fuel pressure limiting valve 10 may be configured to prohibit or substantially restrict the flow of pressurized hydraulic fluid being delivered to power the hydraulic motor of the fuel pump.

[0043] The outlet pressure of the fuel pump may be directly proportional to the amount of hydraulic fluid that is delivered to the hydraulic motor, and vice versa. As such, the fuel pressure limiting valve 10 can be configured to automatically regulate the amount of hydraulic fluid that is delivered to the hydraulic motor in response to the outlet pressure of the fuel pump. Thus, it should be appreciated that the fuel pressure limiting valve 10 of the present disclosure may be configured to automatically regulate the outlet pressure of the fuel pump within a desired pressure range. In a non- limiting example, the fuel pressure limiting valve 10 can be configured to control or limit the outlet pressure of the fuel pump between about 100 psig and about 120 psig. In other embodiments, the fuel pressure limiting valve 10 can be used to control or limit the outlet pressure of the fuel pump within any suitable pressure range, such as limits below 100 psig and above 120 psig.

[0044] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and its practical application, to thereby enable others skilled in the art to utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims

CLAIMS What is claimed is:

1. A pressure limiting valve for regulating a supply of pressurized fluid, the pressure limiting valve comprising:

a housing having a main valve chamber with an inlet port and an outlet port, and a pilot valve chamber in fluid communication with the main valve chamber;

a control valve provided within the main valve chamber, the control valve including a valve spool that is movable between an opened position to allow pressurized fluid to flow through the main vale chamber and a closed position to restrict or prohibit a flow of pressurized fluid through the main valve chamber, and a pressure chamber formed between the valve spool and a wall of the main valve chamber that is in fluid communication with the pilot valve chamber; and

a pilot valve provided within the pilot valve chamber, the pilot valve including a pressure sensing port and a pilot valve member that is movable between a first position and a second position in response to fluid pressure within the pressure sensing port, wherein movement of the pilot valve member between the first and second positions regulates a supply of pressurized fluid delivered to the pressure chamber for operation of the valve spool.

2. The pressure limiting valve of claim 1, wherein the control valve includes an internal sleeve supported within the main valve chamber, and the internal sleeve includes a first set of apertures in fluid communication with the inlet port and a second set of apertures in fluid communication with the outlet port.

3. The pressure limiting valve of claim 2, wherein an outer surface of the valve spool includes a groove that provides fluid communication between the first and second set of apertures of the internal sleeve.

4. The pressure limiting valve of claim 2, wherein the valve spool closes at least one of the first set of apertures and second set of apertures of the internal sleeve when the valve spool is in the closed position.

5. The pressure limiting valve of claim 2, wherein the internal sleeve includes an end flange that is secured to the housing at an open end of the main valve chamber.

6. The pressure limiting valve of claim 1, wherein the control valve includes a biasing member configured to bias the valve spool in the opened position.

7. The pressure limiting valve of claim 1, wherein the pilot valve includes a piston supported for movement within the pilot valve chamber, and the piston is configured to move the pilot valve member from the first position to the second position.

8. The pressure limiting valve of claim 7, wherein the piston is movable in response to fluid pressure within the pressure sensing port.

9. The pressure limiting valve of claim 1, wherein the pilot valve is a three-way, two-position directional control valve that includes a first valve port, a second valve port, and a third valve port.

10. The pressure limiting valve of claim 9, wherein the first valve port is in fluid communication with the inlet port of the main valve chamber, the second valve port is in fluid communication with the pressure chamber of the valve spool, and the third valve port is in fluid communication with a hydraulic return port.

11. The pressure limiting valve of claim 10, wherein the second valve port is in fluid communication with the third valve port when the pilot valve member is in the first position, and the first valve port is in fluid communication with the second valve port when the pilot valve member is in the second position.

12. The pressure limiting valve of claim 11 , wherein the pilot valve member includes a valve stem supported between the first and third valve ports, and a pair of ball members are supported at opposite ends of the valve stem and respectively disposed within the first and third valve ports to close the valve ports.

13. A fuel pressure limiting valve for use in an aerial refueling system to regulate a supply of hydraulic fluid delivered to a hydraulic motor of a fuel pump in response to outlet pressure of said fuel pump, the pressure limiting valve comprising:

a housing having a main valve chamber with an inlet port and an outlet port forming a primary fluid passageway configured to supply hydraulic fluid to said hydraulic motor, and a pilot valve chamber in fluid communication with the main valve chamber;

a control valve provided within the main valve chamber, the control valve including a valve spool that is movable between an opened position to allow said hydraulic fluid to flow through the primary fluid passageway and a closed position to restrict or prohibit the flow of hydraulic fluid through the primary f uid passageway, and a pressure chamber formed between the valve spool and a wall of the main valve chamber that is in fluid communication with the pilot valve chamber; and

a pilot valve provided within the pilot valve chamber, the pilot valve including a pressure sensing port configured to receive a supply of pressurized fuel from an outlet of said fuel pump and a pilot valve member that is movable between a first position and a second position in response to fuel pressure within the pressure sensing port, wherein movement of the pilot valve member between the first and second positions regulates a supply of hydraulic f uid delivered to the pressure chamber for operation of the valve spool, which in turn regulates the flow of hydraulic f uid passing through the main valve chamber and delivered to said hydraulic motor.

14. The fuel pressure limiting valve of claim 13, wherein the control valve includes an internal sleeve supported within the main valve chamber, and the internal sleeve includes a first set of apertures in f uid communication with the inlet port and a second set of apertures in fluid communication with the outlet port.

15. The fuel pressure limiting valve of claim 14, wherein the valve spool closes at least one of the first set of apertures and the second set of apertures of the internal sleeve when the valve spool is in the closed position.

16. The fuel pressure limiting valve of claim 13, wherein the pilot valve includes a piston supported for movement within the pilot valve chamber, and the piston is configured to move the pilot valve member from the first position to the second position.

17. The fuel pressure limiting valve of claim 13, wherein the pilot valve is a three- way, two-position directional valve that includes a first valve port, a second valve port, and a third valve port.

18. The fuel pressure limiting valve of claim 17, wherein the first valve port is in fluid communication with the inlet port of the main valve chamber, the second valve port is in f uid communication with the pressure chamber of the valve spool, and the third valve port is in fluid communication with a hydraulic return port.

19. The fuel pressure limiting valve of claim 18, wherein the second valve port is in fluid communication with the third valve port when the pilot valve member is in the first position, and the first valve port is in fluid communication with the second valve port when the pilot valve member is in the second position.

20. The fuel pressure limiting valve of claim 19, wherein the pilot valve member includes a valve stem supported between the first and third valve ports, and a pair of ball members are supported at opposite ends of the valve stem and respectively disposed within the first and third valve ports to close the valve ports.