Patent Application
20070157979
The present disclosure relates to fluid-control systems and, more particularly, to fluid-control systems having one or more valve elements configured to control fluid flow through one or more passages.
Many machines include fluid-control systems for controlling fluid flow through one or more passages. Such fluid-control systems generally include one or more moveable valve members and a structure with one or more passages. Each valve member is generally configured such that its position affects whether and/or at what rate fluid flows through one or more passages of the structure. Additionally, many fluid-control systems include valve controls for manually and/or automatically moving one or more of the valve members in order to control the flow of fluid through the passages of the structure.
Some fluid-control systems have configurations that allow some undesirable flow of fluid through one or more passages in the structure under some circumstances. For example, some spool valves have configurations that cause them to leak under some circumstances. Some spool valves have a valve housing with an elongated cavity and plurality of ports connected to the elongated cavity by various passages. Additionally, some valve housings of spool valves include an access passage extending from an opening in an end wall of the elongated cavity.
Spool valves often include a valve member moveably disposed at least partially inside the elongated cavity and a drive member for moving the valve member. In many configurations of spool valves, the valve member and drive member engage one another through the access passage. In such configurations of spool valves, the valve member extends through some or all of the access passage to meet the drive member and/or the drive member extends through some or all of the access passage to meet the valve member.
Some spool valves may be configured with one or more available operating states for preventing fluid flow from the elongated cavity through the access passage. In some such operating states, a portion of the valve member extends through the opening in the end wall of the elongated cavity into the access passage so as to impede fluid flow between the elongated cavity and the access passage. However, when a spool valve has such an operating state, the valve member leaves a portion of the opening between an outer surface of the valve member and the perimeter of the opening exposed. As a result, fluid may flow from the elongated cavity to the access passage by flowing between the outer surface of the valve member and the perimeter of the opening.
U.S. Pat. No. 6,792,975 to Erickson et al. (“the '975 patent”) shows a spool valve having a valve member configured to impede fluid flow between an elongated cavity and an access passage extending therefrom by sealing against an end wall of the elongated cavity. The spool valve of the '975 patent includes a valve housing having an elongated cavity and a plurality of ports, including a supply port, a control port, and an exhaust port, connected to the elongated cavity. The supply and control ports connect to the elongated cavity through openings in the sides of the elongated cavity. The exhaust port connects to the elongated cavity through an access passage that extends from an opening in a first end wall of the elongated cavity. A portion of the first end wall extending around the opening forms an annular sealing surface.
The valve member of the '975 patent is disposed primarily within the elongated cavity of the valve housing. The valve member engages side walls of the elongated cavity in a manner restricting movement of the valve member to sliding along the axis of the elongated cavity. The valve member includes an annular sealing ring configured to mate with the annular sealing surface extending around the opening in the first end wall. Additionally, the valve member of the '975 patent includes a valve stem configured to extend through the access passage when the annular sealing ring mates with the annular sealing surface extending around the opening in the first end wall. Furthermore, the valve member includes an internal passage extending from a first opening disposed inside the annular sealing ring of the valve member to a second opening at an opposite end of the valve member.
The spool valve of the '975 patent also includes valve controls that control fluid flow between the ports of the valve housing by moving the valve member along the axis of the elongated cavity. The valve controls of the '975 patent include a spring that urges the valve member toward the first end wall of the elongated cavity. Additionally, the valve controls include a controllable actuator that is operable to selectively engage the valve stem and drive the valve member toward a second end wall of the elongated cavity. Operating the controllable actuator to drive the valve member toward the second end wall of the elongated cavity separates the annular sealing ring from the first end wall. This allows fluid to flow from the elongated cavity to the access passage through spaces between the annular sealing ring and the first end wall of the elongated cavity. When the controllable actuator of the '975 patent does not oppose the spring, the spring drives the annular sealing ring against the first end wall of the cavity so that fluid in the elongated cavity cannot flow past the annular sealing ring into the access passage.
Although the spool valve of the '975 patent has a valve member configured to seal against the first end wall of the elongated cavity, certain disadvantages persist. For example, even with its annular sealing ring sealed against the first end wall of the elongated cavity, the first valve member does not block the flow of fluid between the elongated cavity and the access passage. When the annular sealing ring of the valve member is sealed against the first end wall of the elongated cavity, fluid may flow from the elongated cavity, through the internal passage in the valve member, to the access passage.
The fluid-control system of the present disclosure solves one or more of the problems set forth above.
One disclosed embodiment relates to a spool valve that may have a valve housing. The valve housing may include a cavity, a first passage extending from the cavity, and a plurality of ports connected to the cavity. The spool valve may also include one or more components blocking the first passage, including a spool valve element disposed in a first position at least partially within the cavity. The spool valve element may be moveable to one or more other positions wherein the spool valve element leaves the first passage unblocked.
Another embodiment relates to a fluid-control system with a structure that includes a first passage between a first space and a second space. The fluid-control system may also include a plurality of components blocking the first passage. The plurality of components blocking the first passage may include a first valve element, wherein a second passage extends through the first valve element. The second passage may be configured to provide fluid communication between the first passage and the second space when the second passage is unblocked. The plurality of components blocking the first passage may also include one or more additional valve elements blocking the second passage. Additionally, the fluid-control system may include valve controls operable to selectively unblock the first passage by moving one or more of the additional valve elements to unblock the second passage and, subsequently, moving the first valve element.
A further disclosed embodiment relates to a method of operating a fluid-control system having a structure including a first passage disposed between a first space and a second space. The method may include blocking the first passage with a plurality of components, the plurality of components including a first valve element having a second passage extending therethrough and one or more additional valve elements blocking the second passage. Additionally, the method may include subsequently unblocking the first passage. Unblocking the first passage may include moving one or more of the additional valve elements to unblock the second passage and, thereby, provide fluid communication between the first passage and the second space through the second passage. Additionally, unblocking the first passage may include subsequently moving the first valve element.
Another disclosed embodiment relates to a valve. The valve may have a valve housing having a plurality of ports. The valve may also include a first valve element disposed at least partially within the valve housing. The first valve element may have a first passage extending therethrough. Additionally, the valve may include one or more additional valve elements for restricting fluid flow through the first passage. The one or more additional valve elements may be moveable between different positions, and the one or more additional valve elements may restrict fluid flow through the second passage by different amounts when in different positions. The valve may also include valve controls. The valve controls may be configured to adjust fluid flow between the ports at least partially by moving the first valve element. The valve controls may also be configured to adjust fluid flow through the first passage by moving one or more of the additional valve members.
Valve housing 12 may include ports 20, 21, 22, passages 26, 27, 28, a cavity 29, a passage 30, and cavities 31, 32, 33. Cavity 31 may extend along an axis 48. As is shown in
First valve element 14 may include a valve member 54, a cap 56, and an insert 58. As is shown in
A passage 76 may extend through valve member 54. Passage 76 may extend from an end 78, along axis 48, to an end 80. As is best shown in
Cap 56 and insert 58 may be mounted to valve member 54 at end 62. Insert 58 may be disposed inside passage 78 at end 80 thereof. Cap 56 may be fixedly attached over portion 72 of valve member 54, such as by an interference fit between portion 72 of valve member 54 and an inner surface of cap 56. Cap 56 and insert 58 may be configured to provide fluid communication between passage 76 and cavity 32 in valve housing 12. Insert 58 may be shaped to leave spaces 90 through which fluid may flow through passage 76 past insert 58. Additionally, cap 56 may have passages 92 that provide fluid communication between spaces 90 and cavity 32.
Second valve element 16 may be configured to selectively block passage 76. Second valve element 16 may be any type of device moveably disposed inside passage 76 and configured to block opening 88 by seating against sealing surface 86. For example, as is shown in
Valve controls 18 may be configured to control the positions of valve elements 14, 16. Valve controls 18 may include springs 94, 96, a member 98, an adjuster 100, and a controllable actuator 102. Adjuster 100 may be disposed inside cavities 32, 33 and secured to valve housing 12, such as by engagement to threads 101 in a side wall of cavity 33. Spring 94 may be compressed between adjuster 100 and cap 56 of first valve element 14 such that spring 94 urges first valve element 14 away from adjuster 100 toward end wall 36 of cavity 31. As a result, when unopposed by controllable actuator 102, spring 94 may cause sealing surface 74 of valve member 54 to abut sealing surface 50 of valve housing 12, as is shown in
Spring 96 and member 98 may control the position of second valve element 16 within passage 76. Member 98 may be disposed on a side of second valve element 16 opposite sealing surface 86. Spring 96 may be compressed between insert 58 and member 98, such that spring 96 urges member 98 and second valve element 16 away from insert 58, causing second valve element 16 to abut sealing surface 86 and block opening 88.
Controllable actuator 102 may include an actuator body 106 and a drive member 110. Controllable actuator 102 may be any type of device configured to provide controlled movement of drive member 110. For example, controllable actuator 102 may be an electric solenoid. Actuator body 106 may be disposed partially within cavity 29 and fixedly engaged to valve housing 12, such as by threaded engagement with a side wall of cavity 29. From actuator body 106, drive member 110 may extend along axis 48, through opening 52, into cavity 31. As is best shown in
Controllable actuator 102 may be operable to move valve elements 14, 16 from the positions shown in
Furthermore, drive member 110 may have means for allowing fluid communication between end 78 of passage 76 and passage 30 when drive member 110 is in the position shown in
Fluid-control system 10 is not limited to configurations shown in the figures. For example, valve housing 12 may include additional ports and/or omit one or more of ports 20-22. Additionally, valve housing 12 may have different numbers and/or configurations of passages and cavities than shown in the figures. For example, the lengths and cross-sections of passages 26-28, cavity 29, passage 30, and cavities 31-33 may differ substantially from the configuration shown in the figures. Additionally, while the figures show cavity 31 having a well-defined end wall 36 marking the end of cavity 31 and the beginning of passage 30, cavity 31 may transition gradually into passage 30. Moreover, fluid-control system 10 may include additional components that cooperate with valve member 54 to block passage 30. Additionally, in place of second valve element 16, fluid-control system 10 may include multiple valve elements configured to selectively block passage 76. Furthermore, in place of one or more valve elements disposed inside passage 76, fluid control-system 10 may include one or more valve elements disposed outside passage 76, such as adjacent end 78 or end 80, and configured to selectively block passage 76.
Additionally, valve controls 18 may differ from the configurations shown in the figures. For example, valve controls 18 may include different numbers and/or configurations of actuators for moving valve elements of fluid-control system 10. Valve controls 18 may include actuators configured to move valve elements of fluid-control system 10 through means other than mechanical engagement, such as moving magnetic fields. Furthermore, rather than a powered actuator, valve controls 18 may include one or more manually operated actuators.
Fluid-control system 10 may have application in any system requiring control of fluid flow through one or more passages. For example, as is shown in
Fluid-control system 10 may be operated to control fluid flow between ports 20-22 by utilizing valve controls 18 to control the positions of valve elements 14, 16. When valve controls 18 cause valve elements 14, 16 to have the positions shown in
With valve elements 14, 16 blocking passage 30, low-pressure fluid source/sink 114 connected to port 20, and high-pressure fluid source 118 connected to port 22, all but one portion of first valve element 14 may be exposed to high fluid pressure. High-pressure fluid source 118 may cause high fluid pressure in passage 28 and the portion of cavity 31 between lands 66, 70. Additionally, with passage 30 blocked, the high pressure from high-pressure fluid source 118 may be transmitted through spaces between metering land 66 and side wall 34 to the portion of cavity 31 disposed between metering land 66 and end wall 36. Similarly, the high pressure from high-pressure fluid source 118 may transmit through spaces between land 70 and side wall 34 to cavity 32 and, from there, through passages 92 and spaces 90 into passage 76. However, with valve elements 14, 16 blocking passage 30, the portion of valve member 54 inside of sealing surface 74 may be exposed to the low pressure of low-pressure fluid source/sink 114.
This distribution of fluid pressures on first valve element 14 may cause an unbalanced fluid force on first valve element 14 that presses sealing surface 74 of valve member 54 against sealing surface 50. The high pressure fluid between lands 66 and 70 may exert approximately equal and opposite forces on lands 66, 70. The high pressure fluid in cavity 32 may exert a net force on first valve element 14 that urges sealing surface 74 of first valve element 14 toward sealing surface 50. In opposition to this force, the fluid in passage 30 and the fluid in the portion of cavity 31 to the left of metering land 66 may exert forces on first valve element 14 urging sealing surface 74 away from sealing surface 50. However, because of the low pressure of the fluid in passage 30, the force of the fluid in cavity 32 urging sealing surface 74 against sealing surface 50 may be significantly greater than the fluid forces urging sealing surface 74 away from sealing surface 50. In some circumstances, the pressure differential between the fluid in passage 30 and the fluid in cavity 32 may high enough that the forces pressing sealing surface 74 against sealing surface 50, including the unbalanced fluid forces and the force applied by spring 94, may be greater than the force capacity of controllable actuator 102.
The disclosed embodiments may help ensure that controllable actuator 102 is capable of moving sealing surface 74 away from sealing surface 50 even if the forces pressing first valve element 14 against sealing surface 50 are initially high. Operating controllable actuator 102 to move valve member 16 from the position shown in
Once first valve element 14 is separated from sealing surface 50, the fluid forces on first valve element 14 may be substantially balanced. With passage 76 unblocked, fluid communication through passage 76 substantially equalizes the fluid pressure between cavity 32 and the portion of cavity 31 to the left of metering land 66 of valve member 54. As a result, the fluid in the portion of cavity 31 to the left of metering land 66 of valve member 54 and the fluid in cavity 32 may exert substantially equal and opposite forces on first valve element 14. Additionally, the fluid in the portion of cavity 31 between lands 66, 70 of valve member 54 may apply opposite and substantially equal forces to lands 66, 70 respectively.
Substantially balancing the fluid forces on first valve element 14 may promote precise, predictable control of the position of first valve element 14 by valve controls 18. With the fluid forces on first valve element 14 substantially balanced, spring 94 and controllable actuator 102 are the sources of the only substantial steady state forces acting on first valve element 14 in the directions of axis 48. This provides a well-defined, repeatable relationship between the force that control actuator 102 applies to first valve element 14 and the position of first valve element 14.
With passage 30 unblocked, the position of metering land 66 of valve member 54 with respect to opening 44 in side wall 34 affects the flow of fluid between ports 20-22. When first valve element 14 is in the position shown in
Fluid may flow between port 21 and port 22 through portion 122 of opening 44. In the application shown in the figures, high pressure fluid from high pressure fluid source 118 may flow from port 22 to passage 27 through portion 122 of opening 44. In such circumstances, the fluid may experience a pressure drop as it flows through portion 122 of opening 44, which may cause the fluid pressure in passage 27 to be lower than the pressure at which high-pressure fluid source 118 provides fluid.
Additionally, fluid may flow between port 20 and port 21 through portion 120 of opening 44. In the application shown in the figures, the pressure of the fluid in passage 27 may be significantly higher than the pressure at port 20. As a result, fluid may flow from passage 27, through portion 120 of opening 44, into the portion of cavity 31 to the left of metering land 66 and, from there, through passage 30 and passage 26 to port 20.
Valve controls 18 may adjust the flow between ports 20-22 by moving first valve element 14 along axis 48 and thereby changing the sizes of exposed portions 120, 122 of opening 44. Moving first valve element 14 to the right of the position shown in
Application of fluid-control system 10 is not limited to that shown in the figures. For example, devices other than low-pressure fluid source/sink 114, fluid-actuated device 116, and high-pressure fluid source 118 may be connected to ports 20, 21, 22, respectively.
It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed fluid-control system without departing from the scope of the disclosure. Other embodiments of the disclosed fluid-control system will be apparent to those skilled in the art from consideration of the specification and practice of the fluid-control system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
