Means for and methods of attaching metal hoses to end fittings

Abstract: An end of a convoluted metal hose (22) is connected to an adaptor (24) having an end surface (R) which is rounded to complement a contour of an endmost convolution. A straight section of the convoluted hose extends unbonded some distance through a bore in the adaptor, where it is welded in place. This way any flexing is by a section of the wrapping over the rounded end (R) , the wrapping section being remote from any heat damage which may result from the welding. The internal transition between the bores of the hose and adaptor is straight and smooth, free of any crevice.

Description: This invention relates to end fittings for convoluted metal hoses and more particularly to end fittings which can absorb violent vibrations at extremely high temperatures, such as might be encountered on an operating jet engine. Convoluted metal hose assemblies of the described type are used primarily in the aerospace industries, usually at temperatures well above 230°C (450° F), although the official specifications require the hose to withstand violent and resonant vibrations at 450°C (850° F). Primarily -- but not exclusively -- these hoses are often used to bleed off hot exhaust gases from areas of very high engine temperatures. These bled off gases might be used to monitor engine performance, for example. Therefore, a failure of the metal hose could spell a catastrophic failure of the entire aerospace vehicle. In addition, the bled off gas may also be used for de-icing a wing, preheating engine fuel, transferring exotic hyperbolic fuels, and the like. For many reasons, these hoses are subjected to very high levels of vibrations, sometimes causing them to go into resonant vibrations. Therefore, the energy of such vibrations has to be absorbed, generally at the fitting interface, which is an area (usually very small) where a flexing body is transformed into a stiff and non-flexing body. Sometimes there is a sudden stiffness in the convoluted hose, which is caused by pressure surges of internal fluids. These and other events tend to concentrate material fatigue at fixed locations along the metal hose. US 2 323 912 discloses an end fitting for a metal hose corresponding to the preamble of claim 1, in which the metal hose is of the annular grooved type. A fluid tight seal is effected between the hose and the device to which the fitting attaches. It is disclosed that swivelling motion occurs between the parts. However, no provision has been made to absorb vibrations which would be encountered if the hose were attached to a jet engine. Heretofore, the interface area of hose-to-end fitting attachment has been one where stiff and flexible bodies are welded together so that bending occurs at a fairly sharp edge. The heat produced during the welding operation causes a heat affected zone in the convoluted metal hose which also appears at a point of maximum mechanical stress. These things combine to produce a weakness in the hose that leads to an early failure. Thus, the weld is a point of inherent weakness. As a result of these considerations, a specification (AS 1424) for the metal hose joint design has been adopted by the commercial aircraft industry. This specification requires vibration testing at 450°C (850° F) in combination with dynamic flexing and pressure surging, such as might be encountered in association with a jet engine. To date, it is thought that the assignee of this invention, the Titeflex Corporation, is the only company which has successfully met these specifications, for all sizes of hoses. When the assignee has encountered failures during their tests, they have occurred in the area of the weld or in the area that is heat affected by the welding process. According to the invention a convoluted metal hose is provided with a feed through weld adaptor, said adaptor having a bore with an end section which is complementary to snugly fit over an end section of said hose, said end section of said hose terminated in a radius of a convolution, said bore terminating on one end in a step which has a height that is substantially the same as the thickness of the material from which said hose is made, the end of the adaptor which surrounds the opposite end of the bore being rounded with substantially the same radius as the hose convolutions whereby there is a rolling contact between a first convolution of said hose and the end of said adaptor with said end section of said hose being unconvoluted and a first portion of said end section of said hose is bonded to said adaptor beginning at said step and a remainder of said end section of said hose being unbonded with respect to said bore. Such a hose with feed through weld adaptor may exceed all known specifications --especially of the aerospace industry-- for such fittings. Also the hose with adaptor may tolerate flexing up to a 90° arc, and may improve the welding of convoluted, thin walled conduits to end fittings. An advantage of the design is that the hose is free to roll and move against the rounded edge and thus distribute the bending forces along a length of the hose. Any increase in intimate contact between the hose and this radiused end greatly improves the reliability of the fitting and may increase the life cycle of the hose. The inventive weld joint greatly improves all known prior art joints of the described type, increasing the performance life cycle by a minimum of twice the official specification requirements. Moreover, the inventive weld joint enables a use of orbital; electron beam, and other weld processes, thereby increasing the flexibility of manufacturing processes and especially of automated welding processes. Preferred embodiments of the invention are shown in the attached drawings, in which: FIG. 1 is a longitudinal, partial cross section view of a hose and end fitting, incorporating the principles of the invention; and FIG. 2 is a fragmentary cross section of an embodiment including a butt welded T-ring which is piloted on both sides. FIG. 1 shows a rigid device 20 which may have any suitable function. For example, it may be a pipe, end fitting, or collar on a larger device for accepting a convoluted metal hose 22, or the like. A convoluted metal hose 22 is connected via the device 20 to any other suitable structure, such as a jet engine, for example. An adaptor 24 is provided to make a transition from the device 20 to the convoluted metal hose 22. The adaptor 24 has a first end 26 with an offset collar (called a piloted butt welded joint) which fits over the end of device 20 to locate the adaptor exactly relative to the convoluted metal hose. As shown in FIG. 2, the pilot offset 26 may be replaced by a butt weld "T-ring" 26a which is piloted on both ends. The choice of which piloting device is used depends upon the welding technique that is used. The inside diameter of the offset collar 26 is over-size relative to the inside diameter of device 20 by a step which is exactly equal to the wall thickness 28 of the convoluted metal hose 22. Therefore, when the hose 22 is attached to the end fitting, the area 30 of transition between device 20 and hose 22 is smooth and without any internal discontinuities which might cause turbulence in fluid flowing within the area. Among other things, this smoothness makes a joint which has no crevices that could entrap and accumulate materials within the hose. The hose end 32 of the adaptor 24 terminates in a smooth curve having a radius R which is substantially equal to a corresponding radius on the convoluted hose 22. Any increase of intimate contact along the radius R greatly improves the damping qualities and capabilities of the end fitting up to a desired 90° arc. The hose 22 has a straight section 34 which is welded to the adaptor 24 over a restricted length 36, which is remote from the highly stressed area of flexing so that the weakened heated zone is not fatigued by the flexing. The highly stressed area of hose flexing is at an end of another and unwelded length 38 which has not been heated and which is not bonded to adaptor 24. Stated another way, the area of maximum stress is isolated from the heat affected area. In the area where there is a freedom to flex, the hose may roll over the radius R on end 32 to provide a progressive contact as the hose flexes. Therefore, there is no single point of contact where the hose must bend. The further the flexible part of the hose is from the welded area 36, the less likely is there to be fatigue from the bending. A basket weave of a stainless steel reinforcing braid 40 fits snugly over the convoluted metal hose 22 and is welded to the adaptor 24 at end 42. A fabric covering may also be provided over the steel wire braid, if desired. Any suitable outer collar or braid retainer 44 slips over the braid and is welded to the adaptor 24 in order to protect the end of the braid where it may fray. This braid retainer 44 is preferably made of any suitable metal, but it may also be made of any material which is compatible with the other materials used in the device. The drawing shows that the area where the hose-to-adaptor connection is made is a cylindrical length 34 of the adaptor which conforms to a cylindrical length of the hose 22. However, other suitable shapes may also be used. For example, sometimes these areas (either adaptor 24 or hose 22, or both) may be conical. The described structure lends itself to many different, and especially automatic, welding processes, which makes for inexpensive welding. This welding is simplified since the hose wall thickness 28 exactly matches the depth of a step in the adaptor in area 30. The area of the weld is outside of the flexing portion of the hose assembly so that an after welding inspection thereof is facilitated. The inspection may be visual, radiographic, or made by a fluoro penetrant. Therefore, the invention has significant advantages over the prior art hose terminations in durability, flow characteristics, weld inspection, and simplicity, and in freedom from crevices for collecting debris.

Claims: A convoluted metal hose provided with a feed through weld adaptor, said adaptor (24) having a bore with an end section which is complementary to snugly fit over an end section (34) of said hose (22), said end section (34) of said hose terminated in a radius (R) of a convolution, said bore terminating one one end in a step (30) which has a height that is substantially the same as the thickness (28) of the material from which said hose is made, the end of the adaptor which surrounds the opposite end of the bore being rounded with substantially the same radius as the hose convolutions whereby there is a rolling contact between a first convolution of said hose and the end of said adaptor, characterized in that said end section (34) of said hose (22) is unconvoluted and, a first portion (36) of said end section of said hose (22) is bonded to said adaptor beginning at said step, and a remainder (38) of said end section of said hose being unbonded with respect to said bore. A convoluted metal hose provided with a feed through weld adaptor according to claim 1, characterized in that said bore has a generally straight inner surface, said step (30) is substantially equal to the thickness (28) of material forming the wall of said hose, the unconvoluted end section (34) fits against said step (30), and an outer end of the remainder (38) of the end section terminating in a convolution forming said rolling contact, whereby said rolling contact is over an area where said hose flexes. A convoluted metal hose provided with a feed through weld adaptor according to claim 1 characterized in that a pilot end (26) on said device centers said bore of said device with a bore on an adjacent structure. A convoluted metal hose provided with a feed through weld adaptor according to claim 3 wherein said pilot end is a T-ring (26a) which is piloted on both ends. A convoluted metal hose provided with a feed through weld adaptor according to claim 1 in which a basket weave of braid (40) surrounds said convoluted metal hose, said braid being welded (42) to said adaptor and fitting snugly over said convoluted metal hose. A convoluted metal hose provided with a feed through weld adaptor according to claim 5 in which a braid retainer (44) surrounds said braid in said area where said hose flexes. A convoluted metal hose provided with a feed through weld adaptor according to claim 6 in which said bonding between said hose and said adaptor is welding whereby the area that is heated during said welding is removed from said radiused area by said remainder of said initial end section. The convoluted metal hose provided with a feed through weld adaptor according to claim 7 in which a braid (42) is snugly fitted over said adaptor and said convoluted metal hose.

Inventors: BESSETTE ARTHUR J, LEFEBVRE KENNETH E, BESSETTE, ARTHUR J., LEFEBVRE, KENNETH E.
Applicants: TITEFLEX CORP, TITEFLEX CORPORATION
Application year: 1993
Main classification: F16L33
IPC codes: F16L33, F16L25