Patent Application
20160076578
The subject matter disclosed herein relates to threaded mechanical fasteners and, more particularly, to a nut anti-rotation cap associated with threaded mechanical fasteners.
Nuts and threaded members, such as bolts, are employed to fasten a wide variety of machine components. In many applications, however, operation of the machine causes vibrational or other stresses on the threaded member assembly, which may result in loosening or loss of the nut. In such applications, devices may be employed to retain the nut on the threaded member, preventing its loosening or loss. Such devices typically require inclusion with the threaded member assembly stock or fixed attachment to the nut or threaded member, causing damage to either or both and preventing their reuse after disassembly. For example, many such devices require that the threaded member be cut in order to disassemble the threaded member assembly, requiring replacement of the entire assembly.
This process can become quite expensive in applications where the nut and threaded member assemblies are themselves expensive, such as in gas turbine applications. This expense is exacerbated where periodic or frequent disassembly and reassembly of the nut and threaded member assembly is required, such as, for example, machine maintenance or the replacement of machine parts. Each disassembly requires destruction of the nut and threaded member assembly in place and replacement with a new nut and threaded member assembly, to which a new retention device is then applied.
In addition, some applications simply require a greater degree of retentive strength and/or additional points of retention. For example, nut and threaded member assemblies employed in gas turbine applications, particularly in connection with gas turbine combustion components such as the mounting of combustion transition pieces in a gas turbine, are subjected to high stresses during operation of the gas turbine. This situation requires not only a greater degree of retention, but often the use of very strong, expensive nut and threaded member assemblies. While the use of nut retention devices is often necessary in such situations, the destruction of such expensive nut and threaded member assemblies each time disassembly is required greatly increases the cost of operation of the gas turbine.
According to one aspect of the invention, a nut anti-rotation cap includes an end wall having an inner surface configured to be operatively coupled to an end of a threaded mechanical fastener. Also included is at least one sidewall extending from the end wall, wherein the at least one sidewall is a solid wall configured to be secured to a nut engaged with the threaded mechanical fastener and to enclose an exposed portion of the threaded mechanical fastener.
According to another aspect of the invention, a nut retention assembly includes a threaded mechanical fastener. Also included is a nut engaged with the threaded mechanical fastener. Further included is a nut anti-rotation cap having an end wall welded to the threaded mechanical fastener and a cylindrical sidewall extending from the end wall, wherein an inner sidewall surface geometry corresponds to an outer geometry of the nut, wherein the cylindrical sidewall is a solid wall configured to be secured to the nut to prevent rotation of the nut.
According to yet another aspect of the invention, a gas turbine engine includes a first component and a second component. Also included is a threaded mechanical fastener extending through the first component and the second component. Further included is a nut engaged with the threaded mechanical fastener to secure the first component to the second component. Yet further included is a nut anti-rotation cap having an end wall welded to the threaded mechanical fastener and a cylindrical sidewall extending from the end wall, wherein an inner sidewall surface geometry corresponds to an outer geometry of the nut, wherein the cylindrical sidewall is a solid wall configured to be secured to the nut to prevent rotation of the nut.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Referring to
In operation, air flows into the compressor 12 and is compressed into a high pressure gas. The high pressure gas is supplied to the combustor assembly 14 and mixed with fuel, for example natural gas, fuel oil, process gas and/or synthetic gas (syngas), in the combustor chamber 18. The fuel/air or combustible mixture ignites to form a high pressure, high temperature combustion gas stream, which is channeled to the turbine 24 and converted from thermal energy to mechanical, rotational energy.
Referring to
To prevent rotation of the nut 44 while it is subjected to operating conditions of the system that it is employed in, a nut anti-rotation cap 50 (
As can be appreciated, numerous contemplated geometries of the corresponding geometry of the inner sidewall surface 62 and the nut 44 would facilitate the fitted engagement described above. An exemplary, but not exhaustive list of geometries includes a hexagonal geometry and a 12-point geometry.
In addition to, or alternatively, the tight fitted engagement of the nut anti-rotation cap 50 and the nut 44 may be established by other mechanical joining methods. For example, a pin or the like may be inserted through the at least one sidewall 58 and the nut 44 to facilitate securing the nut anti-rotation cap 50 and the nut 44.
The end wall 52 of the nut anti-rotation cap 50 is formed of a “weldable” metal, such as steel or a nickel-based allow, for example. However, as used herein, “weldable” is intended to encompass materials that may be joined to one or more other components, such as by metal welding, melting, and chemical dissolution, for example. In some embodiments, the entire nut anti-rotation cap 50 is formed of such a material. Typically, the same material is used for the end wall 52 and the at least one sidewall 58.
To facilitate anti-rotation of the nut 44 relative to the threaded mechanical fastener 42, the nut anti-rotation cap 50 is operatively coupled to the threaded mechanical fastener 42. In one embodiment, the end wall 52 is welded to an end of the threaded mechanical fastener 42. In some embodiments, the end wall 52 includes a hole 68 that provides an access point for the welding process. This coupling aspect (e.g., welding) of the end wall 52 to the end of the threaded mechanical fastener 42, combined with the tight fitted engagement of the at least one sidewall 58 with the nut 44, ensures that the nut 44 will not rotate relative to the threaded mechanical fastener 42. By welding the nut anti-rotation cap 50 to the end of the threaded mechanical fastener 42 (i.e., not welded to the threaded portion), removal of the nut anti-rotation cap 50 does not require destruction of the threaded portion of the fastener, thereby allowing the threaded mechanical fastener 42, the nut 44 and the nut anti-rotation cap 50 to be reused. The ability to reuse these components advantageously provides an immediate economic benefit by reducing the number of replacement parts.
In certain applications, the operating environment of the nut retention assembly 40 leads to damage to the threaded mechanical fastener 42. An example of such damage is in the form of oxidation that degrades the threaded mechanical fastener 42 over time. To reduce the effects harsh operating conditions, direct exposure of the threaded mechanical fastener 42 is alleviated by fully encasing an outer perimeter of the threaded mechanical fastener 42 within the inner cavity 60 of the nut anti-rotation cap 50.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
