Patent Application
20090293226
The present invention generally relates to a wear bushing, and more particularly relates to a composite spring-hook wear bushing for use in an actuator linkage assembly of a control valve.
Fluid control valves and valve actuators are commonly utilized for controlling the flow of fluids in many engine systems, such as those commonly found in aircraft turbine engines. Many of these fluid flow control valves utilize sliding stem control valves or rotary action control valves that rely on a valve actuator to control the flow of fluid through the system. Valve actuators, including pneumatic piston or diaphragm actuators, respond to a valve controller for control of the associated valve. Valve actuators typically employ an actuator linkage assembly including a linearly movable member for control of the valve. In this type of actuator linkage assembly, linear movement of the linear moveable member is translated into rotational movement and actuation of the control valve.
Valve actuator linkage assemblies may employ a helical extension spring formed of a wire to link together rotational and articulating components. In many applications, the helical extension spring is formed having a hook configuration on at least one end. The hooked end provides for assembly about a mounting pin, thus providing the required linkage of the assembly components. Typically, there is provided a means on the mounting pin, such as a slide-off retaining component, or a similar part of the system to keep the spring-hook from sliding off the end of the mounting pin. Wear of the spring wire material is experienced on the hook end due to the spring wire contacting and wearing on interfacing components. More specifically, as the pin rotates during valve actuation, the spring wire wears at the inner diameter of the hook due to the contact with the mounting pin and/or wears on the sides of the hook from contact with the slide-off retaining feature, or from other components of the linkage mechanism.
Therefore, there is a need for a spring-hook wear bushing that provides for less wear on a hook end of the spring-hook. In addition, there is a need for a linkage assembly including the spring-hook wear bushing that provides for the rotating and articulating of linkage components without causing undue wear on the spring-hook. In addition, it is desirable for the spring-hook wear bushing to be relatively low cost and simple to install in the actuator linkage assembly. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.
The present invention provides a spring-hook wear bushing and an actuator linkage assembly including the spring-hook wear bushing. In one embodiment, and by way of example only, the wear bushing comprises a cylindrical body having an annular external surface and including a first end and a second end. The wear bushing further comprises: a bore formed axially through the cylindrical body and extending from the first end to the second end; and a channel formed in the annular external surface of the cylindrical body and extending annular about the cylindrical body. The channel defines a running surface bounded by a plurality of annular retaining shoulders configured to retain therein a spring-hook.
In another particular embodiment, and by way of example only, there is provided a wear bushing comprising: a cylindrical body having an annular external surface and including a first end and a second end, the cylindrical body formed of a composite material; a bore formed axially through the cylindrical body and extending from the first end to the second end; and a channel formed in the annular external surface of the cylindrical body and extending annular about the cylindrical body. The channel defines a running surface bounded by a plurality of annular retaining shoulders configured to retain therein a spring-hook.
In yet another particular embodiment, and by way of example only, there is provided an actuator linkage assembly for use in controlling a valve. The actuator linkage assembly comprising: a linear moveable element configured to receive a linear movement; an actuator link including an arm actuating assembly coupled to the linear moveable element; and a feedback arm coupled to the actuator link via a helical extension spring including a spring-hook. The actuator link and the arm actuating assembly configured to transform the linear movement of the linear moveable element into a rotational movement via the feedback arm. The feedback arm including a mounting pin having a wear bushing disposed thereon, the wear bushing comprising: a cylindrical body having an annular external surface and including a first end and a second end; a bore formed axially through the cylindrical body and extending from the first end to the second end; a channel formed in the annular external surface of the cylindrical body and extending annular about the cylindrical body. The channel formed in the wear annular external surface defines a running surface bounded by a plurality of annular retaining shoulders configured to retain therein the spring-hook.
Other independent features and advantages of the preferred spring-hook wear bushing and linkage assembly including the spring-hook wear bushing will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
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 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 or the following detailed description. This invention addresses the wear problem for helical extension springs utilized in rotational and articulating component applications and more particularly the wear on the spring-hook. This invention provides a composite wear bushing that effectively uses a mounting pin onto which it is disposed as an axle, thereby transferring the rotational motion between the spring-hook and the mounting pin to the wear bushing and the mounting pin. This eliminates the wear point typically formed between the spring-hook and the mounting pin. In addition, the wear bushing is designed to include a slide-off retainer thereby eliminating the wear interface typically formed between the spring-hook and the retaining means.
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While the prior art has reported using bushings, none have established a basis for a specific bushing design that is dedicated to the task of resolving the particular problem at hand. What is needed in this instance is a wear bushing that can be releasably secured to a mounting pin of a linkage assembly, whereby a spring-hook when attached to the wear bushing does not encounter frictional wear due to the rotating and articulating of the actuator linkage assembly components with the spring-hook. 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.
