Patent Application
20100044605
This application relates to a servo valve wherein a piezoelectric bending element moves a valve body.
Fluid valves are utilized in a number of applications. A fluid valve may be utilized to control the flow of a pressurized fluid to various elements, such as to supply hydraulic fluid to power various devices.
Very complex valves are known, and can be relatively expensive. One type of valve is a dog servo valve. In a dog servo valve a valve body is movable between extreme positions within a housing. A source of pressurized fluid is communicated to ports that selectively communicate with downstream uses of the fluid. The position of the valve controls whether fluid is communicated, and how much may be communicated.
One well known application of a dog valve communicates fluid to alternative ports. Known dog valves typically include an actuator at a central location for moving the valve between extreme positions in the housing. These actuators have utilized motors, such as stepper motors, and are expensive.
Piezoelectric elements are known to move valves; however, they have not been utilized at a central location in a valve body.
A valve assembly includes a valve housing. A valve body is movable within the housing. The valve body has a land to selectively communicate a chamber in the valve housing to a supply port. An outlet port communicates the chamber to a location outwardly of the housing. A piezoelectric bending element actuator moves the valve body to selectively communicate the supply port to the outlet port.
In disclosed embodiments, the piezoelectric bending element is positioned between two piloting nozzles. As the piezoelectric bending element moves, it restricts one of the piloting nozzles. Pressurized hydraulic fluid associated with the piloting nozzles will tend to center the valve body relative to the piezoelectric bending element, and thus move the vale body to a desired position.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A valve arrangement 20 includes a piezoelectric bending actuator 22 having a mount 24. The mount 24 will mount the actuator 22 in an appropriate manner. A control 25 communicates with the actuator 22, and can cause a remote end 23 of the actuator to bend vertically upwardly or downwardly from the position illustrated in
The valve body 26 has lands 28 and defines chambers 38 between the lands and an end of the valve body. As shown in
A passage 100 extends through each land 28 to pressurized chambers 101 on opposed sides of the valve body 26. Piloting nozzles 27 are formed at an end adjacent to the piezoelectric bending actuator 22, and its end 23.
When it is desired to communicate the supply port 42 to one of the ports 30, then the control 25 actuates the piezoelectric bending element such that its end 23 bends. As shown in
As can be appreciated from
In the
An opposed piloting nozzle 214 receives its pressurized fluid from a tap 228 receiving pressurized fluid from a chamber 226 having its own supply port 224. The chamber 226 also communicates pressurized fluid through a passage 222 to an opposed chamber 220.
The outlet ports 30 are similar to the first embodiment, and a port 230 returns to a return line or sump from a chamber 231. A restriction 232 is placed upstream of the lines 204, 222, 212 and 228 to modulate the pressure reaching the chambers 202.
Similar to the prior embodiment, as the end 23 of the piezoelectric bending element 22 approaches one of the piloting nozzles 214, it will restrict flow. As an example, if the end 23 bends upwardly from the position of
The present invention thus provides a relatively inexpensive and precise way to control a valve body position.
One known piezo actuator element that may be utilized in this invention whether it be a standard four-layered element such as is available from Piezo Systems, Inc. of Cambridge Mass. Information can be obtained at www.piezo.com.
While the end 23 is disclosed as being at a “central portion” of the valve body, it need not be centered. Simply, the description simply means it is at a position of the valve body intermediate its extreme ends.
While one valve application has been disclosed, this application would extend to other valve applications. As an example, any valve which utilizes an actuator to move a valve body between extreme positions within a housing could benefit from this invention.
While an embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
