Patent Description:
The following description relates to clamps and, more specifically, to a clamp for use in a fire and overheat detection system (FODS).

A FODS assembly can be mounted on an aircraft structure. A typical FODS includes sensing elements that extend along a rail tube between opposite connectors. The rail tube extends between saddle brackets at one end of the rail tube and end brackets at the other end of the rail tube. Dual element clamps are arrayed along the rail tube to constrain the sensing elements. Each dual element clamp includes a dual element clamp body, which is welded to the rail tube and which is formed to define holders at opposite sides of the dual element clamp body, and grommets. The grommets are inserted into the holders and are formed to define through-holes through which the sensing elements extend at the opposite sides of the dual element clamp body.

During operational conditions, a FODS assembly is subjected to various forms of loading. A predominant form of this loading is vibrational loading and this, along with bending and twisting modes of the rail tubes, tends to be a significant factor in damage and failures of FODS assemblies. In many cases, vibrational loading as well as bending and twisting modes of rail tubes cause welds between dual element clamp bodies and the rail tubes to fail.

The failures of the welds between dual element clamp bodies and rail tubes in FODS assemblies has led to the dual element clamp bodies being made of relatively costly materials. <CIT> discloses a clamp assembly and corresponding fabrication methods. <CIT> discloses rapidly-detached hoop of line type sensor. <CIT> discloses high temperature bushings for securing sensors, wires and other objects and methods of making the same. <NPL> discloses fire protection systems used in aircraft. <NPL> discloses various additive manufacturing technologies.

According to a first aspect of the present invention, there is provided a method of fabricating a clamp as claimed in claim <NUM>.

In accordance with additional embodiments, the LMD of the clamp body onto the rail tube includes executing LMD onto a pre-made rail tube.

In accordance with additional embodiments, the clamp body includes stainless steel.

In accordance with additional embodiments, the additively manufacturing of the clamp body includes building up a base of the clamp body on an exterior surface of the rail tube, sequentially building up portions of the locking feature and the holders of the clamp body on the base and sequentially building up remaining portions of the holders and the flanges of the clamp body on the base.

In accordance with additional embodiments, the additively manufacturing of the clamp body further includes at least one of mounting the rail tube on a rotary axis, programming a machine to execute the additively manufacturing of the clamp body and cleaning the clamp body at a completion of the additively manufacturing of the clamp body.

In accordance with additional embodiments, the securing of the grommet in each of the holders using the top clamp parts includes anchoring lip arrangements of the top clamp parts in the grooves, wrapping curved sections of the top clamp parts over the grommets and fastening the top clamp parts together by inserting the locking pin through overlapping apertures of the top clamp parts and into the locking feature.

In accordance with additional embodiments, the locking of the locking pin in the locking feature includes quarter-turning the locking pin.

In accordance with additional embodiments, the additively manufacturing of the clamp body further includes forming an axial restraint for the locking pin into the locking feature.

According to a second aspect of the present invention, there is provided a rail tube comprising a clamp, as claimed in claim <NUM>.

In accordance with additional embodiments, the locking feature includes an axial restraint for the locking pin.

As will be described below, a FODS assembly is provided in which one or more clamps are manufactured onto a rail tube by additive manufacturing. The additive manufacturing is laser direct metal deposition (LMD). In any case, additively manufacturing the one or more clamps onto the rail tube in a FODS will enhance the strength of the joints between the one or more clamps and the rail tube and will result in the one or more clamps and the rail tube being provided as one single unit. In addition, since the one or more clamps are being additively manufactured onto the rail tube, the costs associated with the additive manufacturing can be limited as compared to additive manufacturing the one or more clamps and the rail tube.

With reference to <FIG>, a FODS assembly <NUM> is provided and includes a rail tube <NUM> that extends between end lugs <NUM> and <NUM>, first and second sensing elements <NUM> and <NUM> that extend between end brackets <NUM> and <NUM> and terminal lugs <NUM> and <NUM> and clamps <NUM>. The FODS assembly <NUM> further includes a J-bracket <NUM> by which external features are attachable to the rail tube <NUM>, saddle brackets <NUM> disposed at the end brackets <NUM> and <NUM> and lock nuts <NUM>, which are components of the terminal lugs <NUM> and <NUM>. The clamps <NUM> are arranged at intervals along the rail tube <NUM> to support the first and second sensing elements <NUM> and <NUM> at opposite sides of the rail tube <NUM>. The first and second sensing elements <NUM> and <NUM> can be provided as relatively thin and elongate sensors and are disposed and configured to sense various fire and overheat conditions of an aircraft, for example. To operate properly, the first and second sensing elements <NUM> and <NUM> should remain secure in their respective positions relative to the rail tube 110despite the occurrence of vibrational loading and the application of bending and twisting loads. The clamps <NUM> are disposed and configured to accomplish the securing of the first and second sensing elements <NUM> and <NUM>.

With reference to <FIG>, each clamp <NUM> includes a clamp body <NUM>, grommets <NUM> and top clamp parts <NUM> (see <FIG>) as well as a locking pin <NUM> (see <FIG>). The clamp body 210is additively manufactured onto a premade rail tube (i.e., the rail tube <NUM> of <FIG>). Thus, the FODS assembly <NUM> of <FIG> is characterized in that each of the clamps <NUM> are attached to the rail tube <NUM> with an absence of a weld joint which would otherwise be a site of a failure mode of a conventional FODS assembly. In addition, due to the clamp body <NUM> being additively manufactured onto a premade rail tube, the additive manufacturing process can be limited in time and costs at least as compared to a case in which the rail tube is also additively manufactured.

In accordance with embodiments, the additive manufacturing of the clamp body <NUM> is executed by laser direct metal deposition (LMD). As such, the clamp body <NUM> includes a metal or a metal alloy that is compatible with LMD processing. In some cases, the clamp body <NUM> can be formed of stainless steel or another suitable material that is generally less costly and expensive than materials typically used for clamps of conventional FODS assemblies.

To the extent that the clamp body <NUM> is formed by LMD processing on the rail tube <NUM> of <FIG>, the rail tube <NUM> of <FIG> can be placed in a rotary axis proximate to an LMD nozzle that is movable relative to the rail tube <NUM> with at least five degrees of freedom (rotation of the rail tube <NUM> about the rotary axis would provide for movement in a sixth degree of freedom). The LMD processing can be initiated with a creation of a melt pool on an external surface of the rail tube <NUM> of <FIG> (i.e., a substrate) using a laser beam. The melt pool is then fed with metal powder or a powder of a metal alloy through a depositional process using a shield inert gas. The deposition occurs along the external surface of the rail tube <NUM> of <FIG> in a preprogrammed profile or pattern and a deposition head of the LMD nozzle is moved upwardly relative to the external surface of the rail tube <NUM> of <FIG> in order to deposit layers over previous layers to create a three-dimensional shape.

The clamp body <NUM> includes a base <NUM> that is built up from the external surface of the rail tube <NUM> of <FIG> and an upper portion <NUM>. The upper portion <NUM> includes a locking feature <NUM>, first and second grommet holders (hereinafter referred to as "holders") <NUM> and <NUM> that are defined at opposite sides of the locking feature <NUM> and first and second flanges <NUM> and <NUM>. The first and second flanges <NUM> and <NUM> extend from the first and second holders <NUM> and <NUM>, respectively, to form first and second grooves <NUM> and <NUM> (see <FIG>) at each of the first and second holders <NUM> and <NUM>. Each of the grommets <NUM> can be formed of elastomeric or compliant materials and is formed to define a central through-hole through which a corresponding one of the first and second sensing elements <NUM> and <NUM> is extendible and each of the grommets <NUM> is installed into a corresponding one of each of the first and second holders <NUM> and <NUM>. Each of the top clamp parts <NUM> can be formed of a rigid or semi-rigid material and is anchored in a corresponding one of the first and second grooves <NUM> and <NUM> and wrapped over the corresponding one of the grommets <NUM>. The locking pin <NUM> is locked in the locking feature <NUM> to fasten the top clamp parts <NUM> together to thereby secure the grommets <NUM> in the corresponding ones of the first and second holders <NUM> and <NUM>.

As shown in <FIG>, the locking feature <NUM> includes an L-shaped opening <NUM> that is defined from an exterior surface of the upper portion <NUM> of the clamp body <NUM> and includes transverse portions that meet at an angle with a curved end in an interior of the upper portion <NUM>. The transverse portions thus form a shoulder element <NUM> in the upper portion <NUM> that will mechanically interfere with the locking pin <NUM> (see <FIG>). As shown in <FIG> and <FIG>, the locking feature <NUM> also includes an axial restraint <NUM> for axially restraining the locking pin <NUM>.

As shown in <FIG>, each of the top clamp parts <NUM> includes lip arrangements <NUM> which are receivable in the first and second grooves <NUM> and <NUM>, a curved section <NUM> from which the lip arrangements <NUM> extend in a first direction and an end section <NUM>. The end section <NUM> defines an aperture <NUM>, through which the locking pin <NUM> is extendible, and extends from the curved section <NUM> in a second direction opposite the first direction.

As shown in <FIG>, once the clamp body <NUM> is completely built up and the grommets <NUM> are installed in the first and second holders <NUM> and <NUM>, the grommets <NUM> and secured in the first and second holders <NUM> and <NUM> with the top clamp parts <NUM>. That is, the lip arrangements <NUM> of a top clamp part <NUM> is inserted or engaged in one of the first and second grooves <NUM> and <NUM> and the curved section <NUM> is wrapped over and around the grommet <NUM>. The end section <NUM> is then forced into an overlapping condition with the end section <NUM> of the other top clamp part <NUM> such that the apertures <NUM> align with the locking feature <NUM>. The securing process is completed by the locking pin <NUM> being inserted through the apertures <NUM> and into the locking feature <NUM> and by the locking pin <NUM> being turned through a quarter turn within the locking feature <NUM>. The quarter turn of the locking pin <NUM> brings an end of the locking pin <NUM> into mechanical interference with the shoulder element <NUM> (see <FIG>).

With reference to <FIG>, a method of fabricating each of the clamps <NUM> is provided. As shown in <FIG>, the method includes additively manufacturing the clamp body <NUM> onto the rail tube <NUM> as described above (block <NUM>), installing a grommet <NUM> into each of the first and second holders <NUM> and <NUM> (block <NUM>), securing the grommets <NUM> in each of the first and second holders <NUM> and <NUM> using the top clamp parts <NUM> being anchored in the first and second grooves <NUM> and <NUM>, wrapped over the grommets <NUM> and fastened together using the locking pin <NUM> (block <NUM>) and locking the locking pin <NUM> in the locking feature <NUM> (block <NUM>).

With reference to <FIG>, the additive manufacturing of the clamp body <NUM> initially includes mounting the rail tube <NUM> on a rotary axis and programming a machine to execute the additively manufacturing of the clamp body <NUM> and subsequently building up the base <NUM> on the exterior surface of the rail tube <NUM> (item <NUM>), sequentially building up portions of the locking feature <NUM> and the first and second holders <NUM> and <NUM> of the upper portion <NUM> (items <NUM>, <NUM>, <NUM> and <NUM>) and sequentially building up remaining portions of the first and second holders <NUM> and <NUM> and the first and second flanges <NUM> and <NUM> (items <NUM> and <NUM>). The additive manufacturing of the clamp body <NUM> can further include cleaning the clamp body <NUM> at a completion of the additively manufacturing of the clamp body <NUM>.

Technical effects and benefits of the FODS assembly and the additive manufacturing processes described herein are the elimination of clamp welding and the resulting eliminations of weld cracking in high vibration load applications, enhanced strength and fatigue life of the FODS assembly, the ability to use lesser cost and higher strength materials, weight reductions from the formation of clamps with lattice structures, improved manufacturing/assembly leads times as well as reduced costs.

Claim 1:
A method of fabricating a clamp (<NUM>) for a fire and overheat detection system (FODS) assembly, the method comprising:
additively manufacturing, by laser direct metal deposition (LMD) a clamp body (<NUM>) comprising a metal or a metal alloy compatible with LMD onto a rail tube (<NUM>) such that the clamp body (<NUM>) comprises a locking feature (<NUM>), holders (<NUM>, <NUM>) defined at opposite sides of the locking (<NUM>) feature and flanges (<NUM>, <NUM>) forming grooves (<NUM>, <NUM>) at each of the holders (<NUM>, <NUM>);
installing a grommet (<NUM>) into each of the holders (<NUM>, <NUM>);
securing the grommets (<NUM>) in each of the holders using top clamp parts anchored in the grooves (<NUM>, <NUM>), wrapped over the grommets (<NUM>) and fastened together using a locking pin (<NUM>); and
locking the locking pin (<NUM>) in the locking feature (<NUM>).