Patent Description:
Referring to <FIG>, the fluids are typically conveyed from a fluid source (e.g., an oil tank) <NUM> to the intended destination (e.g., the bearings or an associated bearing compartment) <NUM> by a supply tube <NUM>. The fluid is then returned from the destination <NUM> to the source <NUM> by a return tube <NUM>. In this manner, a closed-loop system <NUM> is established. There may be other components included; the system <NUM> is simplified for the sake of explanation and illustrative convenience. These other components may include additional tubes beyond the tubes <NUM> and <NUM>.

Referring to <FIG>, in order to enhance reliability and avoid a leak impacting the performance/operability of the engine, the tubes (e.g., the tube <NUM> or the tube <NUM>) may be manufactured as a double walled tube <NUM>, where the fluid is intended to be conveyed by a first tube <NUM>. A second tube <NUM> serves to contain any fluid that may leak from the first tube <NUM>. The double walled arrangement <NUM> shown in <FIG> is frequently referred to as a "tube within a tube" as the tube <NUM> has a larger dimension/diameter than the tube <NUM> and the tube <NUM> is contained/nested within the tube <NUM>. In this respect, the tube <NUM> is an inner tube relative to the outer tube <NUM>.

Referring to <FIG>, a system assembly <NUM> incorporating a double walled tube <NUM> attached to a three-flanged fitting <NUM> is shown (in <FIG>, an attachment of the double walled tube <NUM> to an angled, threaded fitting <NUM> is shown for completeness, the details of which are not pertinent to the instant invention), where the fitting <NUM> itself is formed/fabricated as a unitary piece. At an interface <NUM> between the inner tube <NUM> and the fitting <NUM> a brazing operation may be performed and at an interface <NUM> between the outer tube <NUM> and the fitting <NUM> a welding operation may be performed. Brazing may be used at the interface <NUM> to eliminate/minimize the likelihood that a leak path may develop. Also, the use of brazing at the interface <NUM> may help to keep the inner tube <NUM> stationary within a seat of the fitting <NUM>.

Brazing includes strict requirements in terms of coverage and voids. Inspection of a brazed joint can be difficult or time-consuming as x-rays of the joint may be needed. Other difficulties of brazing include the possible rework of the assembly if excess braze is present at the interface <NUM> (or any other sealing surface). Materials used in brazing include silver braze or gold nickel braze; these materials represent an added cost to the overall construction of the assembly <NUM>. Furthermore, a preparatory step of nickel-flashing (which may include an electrodeposition process) the inner tube <NUM> and the fitting <NUM> is performed before the brazing occurs, again representing a cost to the construction of the assembly <NUM>.

<CIT> discloses a prior art method as set forth in the preamble of claim <NUM>. <CIT>, <CIT> and <CIT> also disclose prior art systems.

The following presents a simplified summary in order to provide a basic understanding of some aspects of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to the description below.

According to the present invention, there is provided a method for constructing a double walled tube assembly as set forth in claim <NUM>.

In some embodiments, the method further comprises welding the first tube to a second fitting. In some embodiments, the method further comprises welding the second tube to the second fitting. In some embodiments, the second fitting is an angled, threaded fitting. In some embodiments, the first fitting is a three-flanged fitting.

There is further provided an assembly according to claim <NUM>.

In some embodiments, the assembly further comprises a second fitting, where a second axial end of the first tube is welded to the second fitting, and where a second axial end of the second tube is welded to the second fitting. In some embodiments, the assembly further comprises a channel formed in the second sub-fitting coupled to the second tube and a port. In some embodiments, the channel and the port are configured to convey fluid that is present in a cavity between an inner diameter of the second tube and an outer diameter of the first tube. In some embodiments, the assembly further comprises a first seal, and a second seal located radially outward of the first seal with respect to a longitudinal axis of the assembly, where the port divides the first seal and the second seal. In some embodiments, at least one of the first seal or the second seal is made of at least rubber. In some embodiments, the second sub-fitting includes a divot formed in a surface of the second sub-fitting, where the divot is configured to accommodate a weld torch and provide an area for a weld bead to accumulate. In some embodiments, the plurality of webs includes three webs. In some embodiments, the webs are substantially equidistantly spaced from one another, center-to-center, and where each of the webs consumes approximately fifty degrees of the overall three hundred sixty degree circumference.

The drawings are not necessarily drawn to scale unless specifically indicated otherwise.

It is noted that various connections are set forth between elements in the following description and in the drawings (the contents of which are included in this disclosure by way of reference). It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities.

In accordance with aspects of the invention, apparatuses, systems, and methods are directed to a double walled tube assembly. The tube assembly may be formed from a double walled tube and one or more fittings. In some embodiments, a fitting may be composed of more than one sub-fitting, such as for example a first (inner) tube sub-fitting and a second (outer) tube sub-fitting. The tube assembly may be constructed using welding operations. In some embodiments, brazing operations might not be used such that the construction of the tube assembly may be termed to be "braze-free".

Aspects of the invention may be applied in connection with a gas turbine engine. <FIG> is a side cutaway illustration of a geared turbine engine <NUM>. This turbine engine <NUM> extends along an axial centerline <NUM> between an upstream airflow inlet <NUM> and a downstream airflow exhaust <NUM>. The turbine engine <NUM> includes a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. The compressor section <NUM> includes a low pressure compressor (LPC) section 19A and a high pressure compressor (HPC) section 19B. The turbine section <NUM> includes a high pressure turbine (HPT) section 21A and a low pressure turbine (LPT) section 21B.

The engine sections <NUM>-<NUM> are arranged sequentially along the centerline <NUM> within an engine housing <NUM>. Each of the engine sections <NUM>-19B, 21A and 21B includes a respective rotor <NUM>-<NUM>. Each of these rotors <NUM>-<NUM> includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks.

The fan rotor <NUM> is connected to a gear train <NUM>, for example, through a fan shaft <NUM>. The gear train <NUM> and the LPC rotor <NUM> are connected to and driven by the LPT rotor <NUM> through a low speed shaft <NUM>. The HPC rotor <NUM> is connected to and driven by the HPT rotor <NUM> through a high speed shaft <NUM>. The shafts <NUM>-<NUM> are rotatably supported by a plurality of bearings <NUM>; e.g., rolling element and/or thrust bearings. Each of these bearings <NUM> is connected to the engine housing <NUM> by at least one stationary structure such as, for example, an annular support strut.

During operation, air enters the turbine engine <NUM> through the airflow inlet <NUM>, and is directed through the fan section <NUM> and into a core gas path <NUM> and a bypass gas path <NUM>. The air within the core gas path <NUM> may be referred to as "core air". The air within the bypass gas path <NUM> may be referred to as "bypass air". The core air is directed through the engine sections <NUM>-<NUM>, and exits the turbine engine <NUM> through the airflow exhaust <NUM> to provide forward engine thrust. Within the combustor section <NUM>, fuel is injected into a combustion chamber <NUM> and mixed with compressed core air. This fuel-core air mixture is ignited to power the turbine engine <NUM>. The bypass air is directed through the bypass gas path <NUM> and out of the turbine engine <NUM> through a bypass nozzle <NUM> to provide additional forward engine thrust. This additional forward engine thrust may account for a majority (e.g., more than <NUM> percent) of total engine thrust. Alternatively, at least some of the bypass air may be directed out of the turbine engine <NUM> through a thrust reverser to provide reverse engine thrust.

<FIG> represents one possible configuration for an engine <NUM>. Aspects of the invention may be applied in connection with other environments, including additional configurations for gas turbine engines. Aspects of the invention may be applied in connection with non-geared engines.

Referring now to <FIG> a multi-piece fitting <NUM> is shown. As shown in <FIG>, the multi-piece fitting <NUM> may include an inner tube fitting <NUM> and an outer tube fitting <NUM>. As shown in <FIG>, the outer tube fitting <NUM> may radially surround the inner tube fitting <NUM>, such that the inner tube fitting <NUM> is co-axially seated within the outer tube fitting <NUM>. Thus, unlike the fitting <NUM> of <FIG>, the multi-piece fitting <NUM> is not a unitary piece. Instead, the fitting <NUM> is comprised of sub-fittings <NUM> and <NUM>.

Referring now to <FIG> (in view of <FIG>), a flowchart of a method <NUM> is shown. The method <NUM> may be used to construct an assembly, such as for example an assembly incorporating a double walled tube with one or more axially attached fittings.

In block <NUM>, a first axial end of an inner tube <NUM> (which may correspond to the inner tube <NUM> of <FIG>) may be welded to a fitting <NUM> (see <FIG>). The first axial end of the inner tube <NUM> may abut the fitting <NUM> such that the weld may occur where they abut.

In block <NUM>, a second axial end of the inner tube <NUM> may be welded to an inner tube fitting <NUM> (see <FIG>). The second axial end of the inner tube <NUM> may abut the fitting <NUM> such that the weld may occur where they abut.

In block <NUM>, an outer tube <NUM> (which may correspond to the outer tube <NUM> of <FIG>) may be slid over the inner tube fitting <NUM> and the inner tube <NUM> and a first axial end of the outer tube <NUM> may be welded to the fitting <NUM> (see <FIG>).

In block <NUM>, an outer tube fitting <NUM> may be slid over the inner tube fitting <NUM> (see <FIG>) such that the outer tube fitting <NUM> substantially radially surrounds the interior flow path of the inner tube fitting. The inner and outer tube fittings <NUM>, <NUM> are coaxial. As part of block <NUM>, a second axial end of the outer tube <NUM> may be welded to the outer tube fitting <NUM>.

In block <NUM>, the outer tube fitting <NUM> and the inner tube fitting <NUM> may be welded to one another (see <FIG>). The welding of block <NUM> may be "filler-free" in the sense that, in some embodiments, no additional filler material may be introduced as part of block <NUM>. The mating faces 372a and 376a of the inner tube fitting <NUM> and the outer tube fitting <NUM>, respectively, may be arranged/oriented to facilitate the welding operation of block <NUM>.

As described above in relation to <FIG>, <FIG>, and <FIG>, the fitting <NUM> may be termed a "triple-welded" fitting, as the assembly resulting from the construction may incorporate three welding operations with respect to the fitting <NUM> (e.g., blocks <NUM>, <NUM>, and <NUM>).

In some embodiments, it may be desirable/required to enhance the sealing capability associated with a double walled tube assembly. <FIG> illustrates an example of such an embodiment. As shown in <FIG>, an inner seal <NUM> and an outer seal <NUM> are shown as having been coupled to the inner tube fitting <NUM> and the outer tube fitting <NUM>. The seals <NUM> and <NUM> may be made of one or more materials, e.g., rubber. The seals <NUM> and <NUM> may provide for additional fluid retention capabilities in the event that, e.g., one or more of the weld operations described above in connection with <FIG> is compromised. <FIG> also shows a channel <NUM> formed in the outer tube fitting <NUM> leading to a port <NUM>. The channel <NUM> and the port <NUM> may be configured to convey/drain any (leaking) fluid that may be present in a cavity <NUM> between an inner diameter of the outer tube <NUM> and an outer diameter of the inner tube <NUM>. The port <NUM> may bisect/divide the seals <NUM> and <NUM> from one another. While described as multiple seals <NUM> and <NUM>, the seals <NUM> and <NUM> may be a unitary piece in some embodiments.

Referring to <FIG>, an outer tube fitting <NUM> is shown which falls outside the wording of the claims. The outer tube fitting <NUM> is similar to the outer tube fitting <NUM> of <FIG> and may be included as a part of a double-walled tube assembly in a manner similar to what is described above. The outer tube fitting <NUM> may include a recess/divot <NUM> formed in a surface of the outer tube fitting <NUM>. The divot <NUM> may provide additional space to seat/accommodate a weld torch during an assembly procedure, such as for example the method <NUM> described above (see <FIG>). This additional space may provide an area for a weld bead to accumulate and may limit interference with a packing seal. <FIG> illustrates the outer tube fitting <NUM> (and associated divot <NUM>) in conjunction with the inner tube fitting <NUM>.

Referring to <FIG>, an outer tube fitting <NUM> is shown. The outer tube fitting <NUM> is similar to the outer tube fitting <NUM> of <FIG> and the outer tube fitting <NUM> of <FIG> and may be included as a part of a double-walled tube assembly in a manner similar to what is described above. The outer tube fitting <NUM> includes a weld lip/web-based design incorporated into a drain channel/port (e.g., channel <NUM>/port <NUM> of <FIG>). More specifically, as shown in <FIG>, weld lips/webs <NUM> are present at various circumferential locations (potentially equidistantly spaced, center-to-center) along a surface of the outer tube fitting <NUM>. Each weld lip/web <NUM> consumes a portion of the overall three hundred sixty degree circumference. For example, each weld lip/web <NUM> may consume approximately fifty degrees. The weld lips/webs <NUM> may allow for less heat due to the weld not having to be continuous. Less heat means less potential for weld distortion of fittings and sealing surface(s) of fittings. <FIG> illustrates another view of the outer tube fitting <NUM> (and associated weld lips/webs <NUM>).

Claim 1:
A method for constructing a double walled tube assembly, comprising:
welding a first axial end of a first tube (<NUM>) to a first sub-fitting (<NUM>) of a first fitting (<NUM>);
sliding a second tube (<NUM>) over the first sub-fitting (<NUM>) and the first tube (<NUM>);
sliding a second sub-fitting (<NUM>;<NUM>;<NUM>) of the first fitting (<NUM>) over the first sub-fitting (<NUM>) such that the first and second sub-fittings (<NUM>;<NUM>;<NUM>;<NUM>) are co-axial;
welding a first axial end of the second tube (<NUM>) to the second sub-fitting (<NUM>;<NUM>;<NUM>); and
welding the second sub-fitting (<NUM>;<NUM>;<NUM>) to the first sub-fitting (<NUM>);
characterised in that:
the second sub-fitting (<NUM>;<NUM>;<NUM>) includes a plurality of weld lips or webs (<NUM>) formed at various circumferential locations along a surface of the second sub-fitting (<NUM>;<NUM>;<NUM>), wherein each weld lip or web of the plurality of weld lips or webs (<NUM>) consumes a portion of the overall three hundred sixty degree circumference.