Pipe joints or couplings – Particular interface – Tapered
Reexamination Certificate
2001-09-11
2004-05-04
Nicholson, Eric K. (Department: 3679)
Pipe joints or couplings
Particular interface
Tapered
C285S334400, C285S353000
Reexamination Certificate
active
06729659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to flare fittings and, more specifically, to a flare fitting assembly that interconnects two metal tubes and creates a metal-to-metal line seal used for the transport of pressurized liquids or gasses.
2. Description of the Related Art
It is known to provide a coupling or fitting, for joining a flared tube end to another tube for the transport of pressurized liquids or gasses such as in an air conditioning system of a motor vehicle. Typically, a flare fitting utilizes two coupling members. One of the tube ends to be joined is inserted through a first coupling member and is mechanically flared. The two coupling members of the fitting are engaged together and tightened thereby internally clamping the flared tube end to a conically shaped flare seat, or mating surface within the second coupling member. The practice includes forming the flare with essentially the same angular deflection as the conical seat of the opposing coupling member. In order to have a leak-proof seal within the joint, the inner surface of the flared tube must engage the conical seat of the opposing coupling member along a continuous conical circumferential area. The integrity of the seal generally relies upon the malleability of the flared tube, the seat, or both. One or both of these surfaces are caused to slightly yield, or deform in the coupling process by the application of a reasonably high torquing force being applied to the coupling members. This insures a good seal in the event the flare is misshaped or the seat has some imperfections. In this manner, a relatively wide sealing surface area is produced for systems employing soft metal tubing materials.
Although the fitting works well with soft tube materials, the wide sealing area can withstand only relatively low system stress translating to lower pressure applications. When system applications require either harder materials to be employed, such as stainless steel, or higher system operating pressures to be reached, the standard flare fitting with a flare to conical surface seal cannot provide the necessary sealing contact. First, the harder materials do not yield or deform to the extent necessary to obtain a good wide contact seal. Even if an initial wide area contact seal is achieved by use of the standard flare fitting, high pressures will cause leakage. Secondly, if soft metal tube materials are used for high-pressure applications, additional torque must be applied to the fitting in an attempt to avoid leaks. This additional torque applied to the coupling members can cause negative results. This manifests itself in the shearing off of the flared end, or shearing of the hex surfaces of the couplings, or exceeding the torque limitations of the coupling members thereby stripping their threads.
Therefore, it is desirable to provide a new flare fitting with a seal that can withstand high operating pressures and work with harder materials. It is also desirable to provide a flare fitting that does not shear off the flared tube end if the torque applied to the fitting is excessive.
SUMMARY OF THE INVENTION
Accordingly, the present invention is a flare fitting assembly with a metal-to-metal line seal. The flare fitting assembly mates a flared tube end to an arcuate surface within the opposing coupling member to create a line seal. The line seal provides high stress sealing along a line contact at the flare seat that is not found in the typical flare fitting.
One advantage of the present invention is that the fitting is capable of supporting a tubing with an extremely high burst pressure while maintaining a very low leakage or seepage rate. Another advantage of the present invention is that the flare fitting may be utilized with either a single or double flared tube end. Yet another advantage of the present invention is that the flare fitting may be used with a metal sealing washer to extend the sealing capability of the fitting and prevent galling of the mating surfaces.
Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.
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Schroeder Fred Georg
Zeng Zhongping
Brinks Hofer Gilson & Lione
Nicholson Eric K.
Visteon Global Technologies Inc.
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