Patent Application
20090079186
The present invention generally relates to a joint for rigid tubing and, more specifically, to a flexible fitting for rigid pneumatic ducting for apparatus such as gas turbine engines.
Gas turbine (“jet”) engines may be used to provide the thrust needed to propel aircraft. Various fluids necessary to operate gas turbine engines are typically routed through a conduit or plumbing system from one location to another. One type of fluid that may be ducted includes compressed air and oil mist produced by the engine that is ducted to the exhaust section of a turbine engine. Other applications may include redirecting a portion of the compressed air produced by the engine through a conduit or ducting system, the air can be used for a variety of other purposes such as, pressurizing, heating, and cooling the aircraft's cabin, deicing its wings and engine cowlings, and removing moisture from its front windows.
Due to variations in pressure, temperature, assembly, and other factors which influence an aircraft in flight and the stresses caused during takeoffs and landings, the ducting system can experience frequent and sudden changes in its position. To minimize any adverse effect of these changes on the ducting system, flexible fittings connecting rigid duct sections have been proposed and utilized. To be of use, the duct joints should not only permit rotational, translational, and angular movement between the rigid ducts, but they preferably do so with minimum leakage of the compressed air passing through the system. Consequently, such joints must not only permit rotational, translational, and angular movement, but they must also include a low leakage seal to minimize escape of the air.
Of particular interest are tubing assemblies that collect hot vented air, and/or oil mist, from two or more locations. More particularly, of concern are tubing assemblies that combine the vent flow from a first and second vent port or interface and route it to a single exhaust port, or third interface, such as the exhaust section of the turbine engine. Flexibility of the tubing assembly is preferred due to the three interfaces (two vent ports and one exhaust port) being distributed across the length and diameter of the engine. As the engine length and diameter change due to thermal growth, the three interface locations may move significantly with respect to one another. A rigid tubing assembly constructed of relatively small diameter tubes (0.250″ or smaller) may accommodate interface motion by using large bends and offsets which introduce sufficient flexibility. Relatively larger diameter rigid tubes are not as flexible and typically use an alternate provision to allow the tube to bend. High temperatures at the port interfaces and environment requirements of the engine bay may preclude the use of elastomeric hoses. Current design practice for tube assemblies that include at least three interfaces call for two expensive flexible sections of metal braided hose covered with a fireproof coating to be located somewhere between the end fittings and the tee of the rigid tube assembly.
With modern turbomachinery, both overall engine weight and size are issues of concern for engineers. Reduced engine size and lower weight goals have required smaller installation envelopes for the jet engine, including the ducting assemblies used thereupon.
Accordingly, there is a need for an improved flexible duct joint that permits rotational, translational, and angular movement between at least three interfaces of rigid duct sections and allows for simple assembly in an installation envelope of minimal size.
There has now been developed a flexible fitting for a rigid tubing assembly comprising a housing having a plurality of bores defined therein. The housing configured to provide for a flow of a fluid therethrough and a plurality of tube fittings, each fixedly attached to an end portion of one of the plurality of rigid tubings and disposed within one of the plurality of bores. Each of the plurality of tube fittings, further including an o-ring channel and an o-ring disposed within each o-ring channel. Each of the o-rings in sealing contact with a sidewall of the housing to permit movement of each of the rigid tubings about an axis of the tube fitting, permit translation of each of the rigid tubings along the axis of the tube fitting, and provide angulation of each of the rigid tubings relative to the housing.
In yet another embodiment, by way of example only, there is provided a flexible fitting for a rigid tubing assembly comprising a housing having a plurality of bores defined therein. The housing configured to provide for a flow of a fluid therethrough. The flexible fitting further including a plurality of tube fittings each including an o-ring channel and fixedly attached to an end portion of one of the plurality of rigid tubings. Each of the plurality of tube fittings disposed within one of the plurality of bores and a plurality of o-rings, each disposed within an o-ring channel. Each of the o-rings in sealing contact with a sidewall of the housing to permit movement of each of the rigid tubings about an axis of an associated tube fitting, translation along the axis of an associated tube fitting, and provide angulation of the rigid tubing relative to the housing.
In a further embodiment, still by way of example only, there is provided a tubing assembly including a plurality of rigid tubings and a flexible fitting, the tubing assembly comprising: at least two rigid tubings; and a flexible fitting, positioned to fluidically connect the at least two rigid tubings. The flexible fitting comprising: a housing having a plurality of bores defined therein and configured to provide for a flow of a fluid therethrough. The flexible fitting further including a plurality of tube fittings each including an o-ring channel and fixedly attached to an end portion of each of the at least two rigid tubings. Each of the plurality of tube fittings disposed within one of the plurality of bores and a plurality of o-rings, each disposed within an o-ring channel. Each of the o-rings in sealing contact with a sidewall of the housing to permit movement of each of the at least two rigid tubings about an axis of an associated tube fitting, translation along the axis of an associated tube fitting, and provide angulation of each of the at least two rigid tubings relative to the housing.
Other independent features and advantages of the preferred apparatus and method 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.
Before proceeding with a detailed description, it is to be appreciated that the described embodiment is not limited to use in conjunction with a particular type of airplane engine, or even to use in an airplane engine. Thus, although the present embodiment is, for convenience of explanation, depicted and described as being implemented in a turbine engine for an airplane, it will be appreciated that it may be implemented in various other types of systems and environments in which flexibility of a tubing assembly is required, such as, for example, gear pumps used in auxiliary power units and propulsion engine fuel control units.
Briefly, the present invention provides a low cost flexible fitting for a tubing assembly useful as, for example, a flexible fitting for aircraft engine ducting between two vent ports and an exhaust port. The flexible fitting of the present invention may be used to conjoin two or more portions of rigid tubing which make up a tubing assembly capable of carrying vented compressed air and oil mist of a turbomachine.
Unlike conventional styles of flexible fittings, such as ball joints, gimble joints and pressure compensated joints, the low cost flexible fitting of the present invention incorporates a low profile design that allows for rotational, translational and angular movement of at least two rigid ducts connected thereto. In addition, conventional flexible fittings typically lack the ability to provide axial load support. The flexible fitting of the present invention provides a low profile design, permitting installation in a variety of applications, even where the installation envelope is too small for conventional flexible fitting installation.
Regular maintenance of the turbomachine may require removal of the tubing assembly for access. Maintenance specifications may require that no special tools should be needed for the removal nor should adjustments need to be made when the assembly is removed and reinstalled. The low cost flexible fitting of the present invention provides not only a low profile design, that allows for rotational, translational and angular movement of at least two rigid ducts connected thereto while supporting axial load, but also allows for simple removal and reinstallation of the entire tube assembly, or the flexible fitting.
Referring to
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The flexible fitting 114 includes a plurality of tube fittings 122 that are affixed, preferably by welding, onto an end portion of each of the rigid tube portions 112. A plurality of bolted stamped metal retainers 124 and bolts 126 aid in connecting the plurality of rigid tube portions 112 to the flexible fitting 114. As best seen in
Referring now to
Each of the tube fittings 122 may further include an o-ring channel 136 defined by the annular flanges 134 and a secondary annular flange 138 that provides for the seating of an o-ring 128 therein. The o-ring 128 provides a sealing fit with the housing 130 and allows for movement and rotating of each of the plurality of rigid tubes 112 about an axis of the tube fitting 122. In addition, the o-rings 128 provide translation of each of the rigid tube portions 112 relative to the axis of the corresponding tube fitting 122 and provide a small degree of angulation for each of the rigid tube portions 112 relative to the flexible fitting 114.
As previously alluded to, the flexible fitting 114 is described herein as being generally in the form of a t-joint. In an alternative embodiment, the flexible fitting 114 may be formed as a simple flexible union for tube assemblies with only two tubes, or it can join more than three tubes. In addition, a plurality of flexible fittings 114 may be used in a single tubing assembly to provide infinite tube intersections and configurations.
The flexible fitting 114 of the present invention may permit tubing assembly mismatch between the plurality of rigid tube portions 112 and/or the rigid tube portions 112 and the flexible fitting 114. In addition, the flexible fitting 114 may permit unrestrained thermal growth of the plurality of rigid tube portions 112, the housing 130, and/or the tube fitting 122 while supporting the axial loads that exist within the tubing assembly 110 when the rigid tube portions 112 are pressurized. The needed flexibility in flexible fitting 114 may be seen in the various locations that allow movement of the flexible fitting 114. For example, the o-rings 128 may allow for axial flexing and distance variations of the flexible fitting 114 relative to the rigid tube portions 112, and may allow for radial mismatch variations of the rigid tube portions 112. These parameters may permit minor assembly mismatch, thereby requiring less precision in the manufacture of the rigid tube portions 112. Moreover, the flexible fitting 114 of the present invention may also permit rotation of the rigid tube portions 112 relative to housing 130 of the flexible fitting 114, thereby allowing dimensional flexibility in this direction also.
The flexible fitting 114 described herein thus provides an improved means for providing rotation, translation and angulation about the axis of a rigid tubing connected thereto. The flexible fitting 114 utilizes a tube fitting 122 in combination with the o-rings 128 that provides for movement of each of the rigid tube portions 112 relative to the flexible fitting 114.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This invention was made with Government support under funding program G230JSF, bearing contract number N00019-02-3002, awarded by Lockheed Martin-US Government. The Government has certain rights in this invention.
