Patent Application
20080116413
The present invention generally relates to a valve assembly and, more particularly, to a pneumatic valve assembly including a pneumatic tube assembly for dissipation of static electrical discharge.
Many relatively large turbine engines use pneumatic valves for the control of fluid there through. Some specific examples of pneumatic valves utilized in turbine engines include high stage bleed air valves, mid-stage bleed air valves, bleed air isolation valves, pressure regulating and shutoff valves, load control valves, anti-ice valves, trim air valves, and temperature control valves.
In one specific example, an air turbine starter (ATS) within a turbofan jet engine may be coupled to a high pressure fluid source such as compressed air. The flow of compressed air may be controlled by, for example, a valve, such as a pneumatic valve. The flow of compressed air impinges upon a turbine wheel in the ATS causing it to rotate at a relatively high rate of speed.
It is well-known that pneumatic valve assemblies may be partially disposed within an airway to control flow of a fluid (e.g., air) there through 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. During operation, static electrical discharge is generated by the valve assembly and may damage the turbine engine as well as other aircraft systems. Previous attempts to alleviate this problem include the fastening of a p-clamp and/or ground strap to a portion of the pneumatic tubing coupled to the valve assembly and the attachment of the p-clamp and/or ground strap to a remote ground point, such as an associated component. The p-clamp or ground strap provides a discharge path for the static electricity in the device. Although this type of bonding or grounding of the valve operates safely this method can suffer certain drawbacks. For instance, the p-clamp may rotate or move about the pneumatic tubing and/or corrode about the tubing where clamping takes place. This relative motion of the p-clamp or ground strap and corrosion about the clamp can potentially result in an increase in the bonding resistance across the joint and the build up of static electricity within the valve assembly.
It should thus be appreciated from the above that it would be desirable to provide an improved valve assembly including a means for bonding the assembly for the discharge of static electricity during operation of the valve 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.
There has now been developed a pneumatic tube assembly, comprising a pneumatic tub; and at least one retaining plate coupled to the pneumatic tube and at least one pneumatic component and providing a bonding path between the pneumatic tube and the at least one pneumatic component. The retaining plate comprises a first surface, an opposed second surface, and a first opening extending between the first surface and the opposed second surface. The retaining plate further comprises a second opening extending between the first surface and the opposed second surface, and through which the pneumatic tube extends.
In a further embodiment, still by way of example only, there is provided a valve assembly, comprising at least one valve body having a flow passage and a tube insertion bore formed therein and a pneumatic tube assembly disposed within the tube insertion bore. The pneumatic tube assembly comprises a pneumatic tube, at least one retaining plate coupled to the pneumatic tube and the at least one valve body and providing a bonding path between the pneumatic tube and the at least one valve body. The retaining place comprises a first surface, an opposed second surface, a first opening extending between the first surface and the opposed second surface, and a second opening extending between the first surface and the opposed second surface, and through which the pneumatic tube extends.
In still a further embodiment, and still by way of example only, there is provided a valve assembly, comprising at least one valve body having a flow passage and a tube insertion bore formed therein, a pneumatic tube disposed within the tube insertion bore, and fixedly coupled to the valve body, and at least one retaining plate coupled to the pneumatic tube and the at least one valve body and providing a bonding path between the pneumatic tube and the at least one valve body. The at least one retaining plate comprising a first surface, an opposed second surface, a first opening extending between the first surface and the opposed second surface, a second opening extending between the first surface and the opposed second surface and through which the pneumatic tube extends, and a retaining sleeve defined by a sidewall extending substantially perpendicular to the second surface and in alignment with the second opening.
Other independent features and advantages of the improved valve assembly and pneumatic tube assembly 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 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.
The valve housing 104 further includes a tube insertion bore 110 that extends through a portion of the valve housing 104 into which a pneumatic tube 108 is positioned. The pneumatic tube 108 is seated upon a portion of the valve housing 104 and held in sealing engagement with the valve housing 104 by an o-ring 112, or the like. A tube sleeve 106 is positioned within tube insertion bore 110 and about the pneumatic tube 108. A separately formed tube retaining plate 114 in conjunction with a retaining bolt 116 provides a means for retaining the pneumatic tube 108 within the valve housing 104. The tube retaining plate 114 is positioned to exert a force upon a sidewall of the pneumatic tube 108 at a joint 109, thereby retaining it in place. This means of retaining the pneumatic tube 108 within the valve housing 104 is sufficient in many applications, yet during operation it is susceptible to motion of the pneumatic tube 108 relative to the tube retaining plate 104. In addition, the tube retaining plate 114, the tube sleeve 106 and the pneumatic tube 108 are subject to corrosion and thus a subsequent increase in bonding resistance across these attachment joints. Furthermore, to achieve bonding of the valve assembly 100, a grounding strap may need to be incorporated in cooperation with the tube retaining plate 114 to allowing a bond path to exist between the pneumatic tube 108 and the valve housing 104.
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The valve assembly 150 further includes a tube insertion bore 160 that extends through a portion of the valve housing 154 into which a pneumatic tube assembly 157, and more particularly a pneumatic tube 158 is positioned. The pneumatic tube 158 is seated upon a portion of valve housing 154 and held in sealing engagement with the valve housing 154 by an o-ring 162.
A tube retaining plate 164 in conjunction with a retaining bolt 166 provides mechanical retention and electrical bonding of the pneumatic tube 158 and the valve housing 154. As previously stated, in a preferred embodiment, the tube retaining plate 164 is formed of a corrosion resistant steel, such as stainless steel. More particularly in a preferred embodiment, the tube retaining plate 164 is formed of CRES 316L commonly used in high-pressure hydraulic/pneumatic 18-8 (low carbon) systems. The tube retaining plate 164 provides electrical bonding of the pneumatic tube 158 and the valve housing 154, and more specifically provides a means for the dissipation of static electricity during operation of the pneumatic valve assembly 150.
When the tube retaining plate 164 is properly positioned relative to the valve assembly 150, the second surface 174 of the tube retaining plate 164 abuts with a portion of the surface of the valve housing 154, which serves as a bonding surface 182. The retaining sleeve 178 is positioned within a portion of the tube insertion bore 160 formed in the valve housing 104, and the pneumatic tube 158 is positioned through the opening 170 formed in the tube retaining plate 164 and in sealing engagement with the valve housing 154. The pneumatic tube 158 has an exterior dimension substantially less that of the opening 170 formed in the tube retaining plate 164 to allow for the positioning therein within close tolerance. A retaining bolt 166, including a plurality of threads 184, is positioned through the opening 176 and into a threaded bore 186 formed in a portion of the valve housing 154. The retaining bolt 166 provides mechanical retention of the tube retaining plate 164 against the bonding surface 182 and generates a grounding path through contact force.
Subsequent to positioning the pneumatic tube 158 relative to the valve assembly 150, the pneumatic tube 158 is brazed or welding to the tube retaining plate 164. The brazing or welding process provides a further means for securely retaining the pneumatic tube 158 within the retaining sleeve 178 and thus to the valve housing 154. In contrast to the prior art valve previously described with regard to
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Accordingly, disclosed is an improved valve assembly including a means for bonding the valve assembly to dissipate static electricity. 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.
