The present invention generally relates to valve actuators and, more particularly, to an improved fuel powered actuator assembly for use in conjunction with a valve assembly to control pneumatic flow therethrough.
It is well-known that pneumatic valve assemblies may be partially disposed within an airway defined by a flowbody to control flow of a fluid (e.g., air) therethrough and thus perform any one of a number of functions (e.g., temperature regulation). Valve assemblies of this type typically comprise a valve (e.g., a butterfly valve) that is coupled by way of a linkage assembly to an actuator. The actuator includes a piston and an actuator housing, which may be fixedly coupled to the flowbody. The piston has a first end coupled to the linkage assembly and translates within the housing to actuate the valve. The extension of the piston relative to the actuator housing may cause the valve to open and thus permit airflow through the flowbody, and the retraction of the piston may cause the valve to close and obstruct airflow; however, it should be appreciated that the valve assembly may instead be configured such that the valve opens and closes with piston retraction and extension, respectively. In fuel actuated valve assemblies (e.g., bleed valve assemblies, control valve assemblies, cooling valve assemblies, etc.), the pressure differential described above may be externally controlled to command valve positioning within the airway.
The movement of the piston within the actuator housing is dictated by the pressure differential between two hydraulic chambers (i.e., a closing chamber and an opening chamber) within the actuator housing and generally defined by the inner surface of the housing. These chambers may be isolated from each other by a cuffed region of the piston that ends radially outward to sealingly engage the inner surface of the housing. When the pressure in the opening chamber exerts a force on the piston greater than that exerted by the pressure in the closing chamber, the piston extends and the valve opens. Conversely, when the pressure in the closing chamber exerts a force on the piston greater than that exerted by the pressure in the opening chamber, the piston retracts and the valve closes. In some valve assemblies, a linear positioning sensor (e.g., a linear variable differential transformer, or LVDT) is disposed within the actuator housing to facilitate monitoring the displacement of the piston therein and establishing the position of the valve plate within the airway. After determining the current position of the piston, a controller may initiate an appropriate adjustment to move the piston to a target position and thereby actuate the valve in a desired manner.
Due in large part to elevated operational temperatures, leakage is a concern in fuel actuated valve assemblies. For this reason, these valve assemblies are routinely provided with redundant, seals to minimize the likelihood of external leakage. Joints produced when multiple sections of the housing are coupled to form the actuator body, for example, must be provided with appropriate sealing assemblies. As a representative example, a known actuator housing is formed by two separate sections: a main actuator housing section, which substantially contains the linear positioning sensor and the piston when the piston is in a retracted position; and a seal retainer section, which allows the piston rod to translate through the housing and contains a portion of the linkage. These sections are bolted together at their interface to form the actuator housing. This mechanical coupling requires an additional flange/bolt assembly and static seals disposed between the main actuator housing section/seal retainer section interface and between the seal retainer section and the piston.
Considering the above, it is not surprising that jointed actuator housings (i.e., actuator housings formed by coupling multiple sections together) result in a valve assembly of increased complexity, cost, size, and weight. Further, the additional seals required by jointed actuator housings provide other sites at which external leakage may occur thus decreasing system reliability and increasing maintenance demands. Further still, due to the stroke force produced by the action of the piston, such housings may experience structural stress at their joints, which may result in increased wear on the seals and an increased likelihood of fuel leakage.
It should thus be appreciated from the above that it would be desirable to provide an improved fuel powered actuator assembly including a unitary housing that reduces the number of requisite joints and seals, and therefore reduces the overall cost, complexity, weight, and size of the assembly. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
A valve actuator is provided that comprises a unitary housing and a piston translatably mounted within the housing. The piston comprises a first portion having a first diameter and a second portion having a second diameter that is greater than the first diameter. A position sensor having a third diameter at least as large as the second diameter is fixedly coupled to the housing and to the piston for determining the position of the piston.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Valve plate 108 is coupled to a valve actuator 110 by way of a linkage 112, part of which passes through a sealing shaft 114. Actuator 110 comprises an actuator housing 116 and a piston 118 that resides therein. Though multiple sections are coupled together to form housing 116, actuator housing 116 is shown as one body for clarity in
The position of piston 118 within housing 116, and thus the status of valve plate 108, is controlled by the pressure differential between two hydraulic chambers, an opening chamber 120 and a closing chamber 122, which are provided within housing 116. Chambers 120 and 122 are separated within housing 116 by cuffed portion 124 of piston 118, which extends radially outward from the remainder of piston 118 to sealingly engage an interior surface of housing 116. When the pressure in opening chamber 120 exerts a greater force on piston 118 than does the pressure in closing chamber 122, piston 118 extends and valve plate 108 opens. Conversely, when the pressure in closing chamber 122 exerts a greater force on piston 118 than does that in opening chamber 120, piston 120 retracts and valve plate 108 closes. Chambers 120 and 122 are fluidly coupled to suitable hydraulic (e.g., fuel) sources by way of ducts 126 and 128, respectively.
Valve actuator 110 also includes a linear positioning sensor 132 for determining the position of piston 118 within actuator housing 116. Sensor 132 may be an electromechanical transducer such as a linear variable differential transformer (LVDT) and will be referred to as such hereafter for the purposes of illustration only. LVDT 132 comprises a translatable head 136 and a stationary body portion 134 having at least one longitudinal channel or bore 138 provided therein. For increased reliability, a dual-channel LVDT may be utilized as indicated in
As is most clearly shown in
As mentioned above, fuel actuated valve assemblies such as valve assembly 100 employ redundant seals to minimize the likelihood of external fuel leakage. It should be clear, however, that no such seals are shown in
Valve actuator 202 functions in much the same manner as does fuel powered actuator 110 described in detail above in conjunction with
Linear positioning sensor 216 is disposed within housing 204 to monitor the translational position of piston 206. As was the previously case with sensor 132, linear position sensor 216 may be an LVDT and is preferably a dual-channel LVDT as shown in
The inventive valve actuator requires less sealing assemblies than known fuel actuated assemblies and is consequently less costly, less complex, and more reliable (e.g., decreased chance of external fuel leakage). As is most clearly shown in
In the exemplary embodiment shown in
In view of the above, it should be appreciated that an improved valve actuator assembly including a unitary housing that reduces the number of requisite joints and seals, has been provided. Though the exemplary embodiment of the valve actuator assembly has been discussed above as controlling the flow of a pneumatic gas (e.g., air), it should be understood that the inventive valve actuator may be used in any suitable fluidic system. Similarly, it will be appreciated by one having ordinary skill in the art that the translational movement of the actuator's piston may be controlled by means other than the pressure differential between two hydraulic compartments (e.g., by the pressure differential between two pneumatic compartments). While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
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