Pipe joints or couplings – Particular interface – Interlocked or overlapped
Reexamination Certificate
1999-12-09
2002-05-07
Browne, Lynne H. (Department: 3629)
Pipe joints or couplings
Particular interface
Interlocked or overlapped
C285S328000, C285S379000, C138S089000, C138S09600T
Reexamination Certificate
active
06382683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to fittings for high pressure and vacuum fluid lines used in environments where high purity is necessary.
2. Description of the Prior Art
Many industrial processes require controlled amounts of very pure gases. Even small amounts of ambient gas or other contaminants can adversely affect the manufacturing process. The pure flows of gas typically are delivered to a specified location in a manufacturing plant by systems of pipes. Valves may be incorporated into the system to precisely control the flow of gas. Fittings may be employed selectively in the system to properly direct a flow of gas to selected locations in the manufacturing facility.
Pipe systems for carrying very pure flows of gases generally do not rely upon welded connections because the weldment may include contaminants that can leak into the system. Additionally, the weld location often defines a weak point that can be affected adversely by vibration or shock.
Additionally, most pipe systems for carrying very pure flows of gases cannot rely upon plastic or elastomeric components that are in communication with the gas flow stream. Plastic and elastomeric components are known to cause a leaching of contaminants into the gas stream. In view of the above, connections of one pipe to another or connections of a pipe to a fitting or valve typically are carried out with threaded metallic couplings.
The typical prior art fitting for a high pressure fluid line includes first and second tubular metallic components having fluid passages extending therethrough. Each component has a mating face to be disposed in juxtaposed relationship to the mating face of the other component. The mating faces each may be characterized by a toroidal sealing bead disposed to register with the toroidal sealing bead of the other component. The components are urged axially toward one another by threaded members. For example, a first of the two components may have an array of external threads integrally formed thereon. The second of the two components may have a shoulder facing in a direction away from the mating face. A nut may be mounted over a second component and may include an inwardly extending flange dimensioned for engaging the shoulder on the second component. The nut may include an array of threads for threadable engagement with the threads formed on the first component. Threaded engagement of the nut with the threads on the first component will urge the mating faces of the two components toward one another. An annular metallic gasket typically is disposed between the mating faces. Thus, the mating faces, and in particular the toroidal sealing beads on the respective mating faces, will be urged into tight sealing engagement with the gasket.
Other prior art fittings include first and second substantially identical components. The first and second components each include a mating face and a shoulder facing away from the mating face. First and second components of such a prior art fitting are used with a mateable pair of male and female nuts. Each nut will include an inwardly extending flange dimensioned for engaging the shoulder on the component. Tightening of the nuts together will cause the inwardly extending flanges on the nuts to engage the shoulders on the coupling components. Thus, threaded tightening of the nuts will urge the coupling components toward one another and into sealing engagement with a gasket disposed therebetween.
Rotation of one or both nuts in the prior art fitting will cause the flange of the nut to wipe over the shoulder of the associated fitting component. Friction between the flange and the shoulder can transmit rotational forces from the nut to the component. Thus, one component may rotate relative to the opposed component. This rotation typically is small, but will cause a wiping of one mating face against the gasket. This wiping can cause a galling or scratching of the mating face, and particularly of the toroidal sealing bead on the mating face. Galling or scratching can be generated each time the coupling is connected and disconnected. The surface discontinuities associated with such galling or scratching can define paths for gas leakage into or out of the fluid coupling. As noted above many industrial processes require very pure gas flows. Galling or scratching can enable the leakage of ambient air into the gas stream and can adversely affect the purity of the gas flowing through a fitting. As a result, it is desirable to prevent rotation of coupling components during the connection of the components with one another.
Some prior art coupling components have included complex and costly arrangements of ball bearings disposed between the flange on the coupling nut and the shoulder on the component being coupled. The costs associated with such ball bearing fixtures make those fixtures undesirable.
A very effective prior art fitting for substantially preventing rotation is shown in U.S. Pat. No. 5,350,205 which is assigned to the assignee of the subject invention. The fitting shown in U.S. Pat. No. 5,350,205 includes a thrust bearing disposed between the flange on the coupling nut and the shoulder on the component being coupled. The thrust bearing is formed from a material having a hardness greater than the hardness of the coupling component with which it is used. The coupling nut used adjacent the thrust bearing is formed from a material that is harder than the thrust bearing. For example, the thrust bearing shown in U.S. Pat. No. 5,350,205 may be formed from a cobalt chromium-nickel alloy provided with a thin coating of silver.
The fitting shown in U.S. Pat. No. 5,350,205 has performed well. However, there is a desire to provide even further improvements.
Components of such gas flow systems are manufactured and partly assembled in ultra clean environments maintained by the manufacturer of such gas flow systems. These components or subassemblies of such components then are transported to the industrial facility that will use the system to deliver highly pure flows of specified gases. The manufacturer of pipes, fittings and valves for such gas flow systems typically will take steps to prevent contamination during transportation. These steps will include sealing the system from ambient atmosphere and charging the system with an acceptable high pressure gas, such as nitrogen. The seals are intended to prevent either an inflow or an outflow of gas. Pressurized nitrogen is intended to prevent a migration of the lower pressure ambient air into the sealed system.
The sealing of the system typically is carried out by merely threadedly engaging a cap over the mating end of a pipe that will subsequently be connected to other parts of a gas flow system. A gasket initially may be positioned in the cap. Thus, threaded tightening of the cap onto the pipe, nipple or other such component will urge the gasket into sealing engagement with the toroidal sealing bead on the mating end of the pipe. Upon delivery of the piping system subassembly to the installation site, the cap will be threadedly removed and the mating end will be joined to other components in the system in the conventional manner described above.
Sealing caps as described above are used in other instances as well. For example, an industrial facility utilizing highly pure gas flows frequently will be reconfigured to meet changing product demands. Reconfigurations of this type may involve sealing off a section of the gas flow system. The prior art threaded cap with a gasket positioned therein may be utilized for this sealing-off of portions of the system. The threaded cap may eventually be removed if and when the system is reconfigured.
Portions of a system may be sealed periodically to permit a purging of at least a section of the system. The above-described prior art sealing caps are threadedly tightened onto the mating end of a pipe in the system and the system is subjected to a pressurized flow of a purging gas. Upon completion of the purging, the sealing cap may be removed and the
Albright John
Aldridge Lewis L.
Barber Patrick P.
Sawyer Kenneth W.
Browne Lynne H.
Casella Anthony J.
Hespos Gerald E.
Parker Hannifin Corp
Thompson Kenn
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