US 2814517 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
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Nov. 26, 1957 NNNNNNNNNNNN.
United States COATED METAL TUBULAR SEAL Adolph Razdow, Montclair, N. .1. Application September 18, 1956, Serial No. 610,454
3 Claims. (Cl. 288-) The present invention relates to a seal and in particular to such seal adapted for sealing surfaces.
Several different means have been proposed before for the sealing of surfaces, for instance for sealing of a container, and among the known expedients gaskets have been used in many instances which are placed between two mating parts of the container. Other known expedients are rubber O-rings which are placed in specially designed grooves provided in one of the mating surfaces. The use of rubber O-rings is limited, however, because of the restricted temperature range in view of the known rubber characteristics. Rubber becomes brittle at temperatures below -50 F. and is subjected to chemical changes above a temperature of 350 F. Furthermore, rubber O-rings cannot be used at a very high pressure in view of their limited mechanical strength. A further limitation in the use of rubber O-rings for sealing of containers is due to the fact that many chemicals which are stored in the containers attack the rubber O-rings.
It is, therefore, one object of the present invention to provide a seal which avoids all drawbacks experienced in connection with gaskets and with rubber O-rings.
It is another object of the present invention to provide a seal which comprises a comparatively thin metal tube which is filled with a fluid, preferably a gaseous fluid, as for instance nitrogen or helium or a mixture of both said gases or any other suitable gas which remains in its gaseous state within a temperature range of 150 F. to 1200 F., said gas being in the thin metal tube contained under pressure which may have a range from 600 p. s. i. to 1500 p. s. i., preferably however, 1000 p. s. i. pressure, in order to assure resilient characteristics of the thin metal tube.
In order to bring about a satisfactory and efficient seal, it is required that the thin metal tube has intimate contact with the mating surface of the container to be sealed or of the cover thereof. It is a known fact that the degree of efficient contact will depend entirely on the smoothness of the surfaces which are engaged by the thin metal tube. Thus, a high polished finish on the metal surfaces will appreciably contribute to a more etfective seal, yet a special working of the tube engaging surfaces to provide a highly polished finish thereon is comparatively expensive and time consuming. It is also a known fact that even polished surfaces have still very fine irregularities which are not visible with the naked eye but appear quite clearly under a microscope. Depending upon the pressure conditions within the container long term leakages cannot be avoided, even if highly polished surfaces are provided.
It is, therefore, an additional object of the present invention to provide a thin metal tube which has a coating on the outer surface of the thin metal tube, which coating is designed to enter the irregularities on the more or less polished surfaces engaging the thin metal tube and due to the inner pressure present in the thin metal tube to penetrate the crevices in the surfaces engaging the thin metal tube. Such coating material may comprise silicon rubber, polytetrafluoroethylene, also known as Teflon, polymers of trifluorochloroethylene, also known as Kel-F, soft metals, sponge-like metals or any other suitable material having resilient characteristics. Such coating provided on the thin metal tube eliminates the otherwise necessary finishing process of the mating surfaces and results in greater economy in the production of the sealing device. Synthetic materials are not suitable where temperatures above 450 F. are involved. For temperatures of a higher range soft or sponge-like metals will be more appropriate. Thus the choice of the coating material will depend entirely upon the temperature range to which such sealed container is subjected. Any conventional means may be used for the coating step, as for instance plating, spraying, vaporizing or any other suitable process. It has been found that a metal coating stands up very well even at a temperature of up to 1200 F. without damaging or reducing the efiect of the metal seal. While it is more practical to provide the coating on the outer face of the metal tube, it is possible to provide as an equivalent those zones of the metal tube engaging surfaces with such coating layer, which expedient brings about substantially the same result.
It is still another object of the present invention to provide a process for sealing a thin metal tube which contains a fluid under pressure by providing an opening in the thin metal tube and inserting said tube into a container, feeding gas under pressure to the pressure desired in the tube in the container and closing the opening in the thin metal tube by electrical heating means, thereby closing said opening while equal pressure prevails inside and outside of the thin metal tube, then releasing the pressure in the container and removing the thin metal tube therefrom.
With these and other objects in view which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:
Figure 1 is a section through a container equipped with a metal seal in accordance with the present invention;
Fig. 2 is a fragmentary section through a container with another embodiment of the metal seal;
Fig. 3 is a cross section through a metal tube of circular configuration;
Fig. 4 is a cross section through a metal tube of rectangular configuration; and
Fig. 5 is a cross section through a container for closing an opening in the thin metal tube after a fluid under pressure has been supplied thereto.
Referring now to the drawing, Fig. l discloses a container 1 having a cover 2 secured thereto by means of bolts 3 extending through the flanges 4 of the container and the flanges 5 of the cover, respectively. A groove 6 is provided in the cover 2, though it is to be understood that such groove may also be provided in the container, which groove is disposed at the face '7 of the cover 2 engaging the face 8 of the container 1. A thin metal tube 9 which may be of circular, rectangular or any other suitable cross section is disposed in the groove 6, which metal tube 9 contains a fluid 10 and preferably a gaseous fluid, as for instance helium, nitrogen or a mixture thereof which contains preferably to nitrogen and 20% to 10% helium or also any other inert gases. The fluid 10 in the thin tube 9 is subjected to a pressure which ranges preferably from 600 p. s. i. to 1500 p. s. i. The metal tube 9 may be made of cold rolled steel, stainless steel, copper, Monel or any other suitable metal and has preferably a thickness of-.001 to .006 inch. The diameter of the tube 9 of circular cross section, shown in Fig. 2, or the outer distance of the opposite sides of the tube 9 of rectangular cross section, shown in Fig. 3, is slightly less than the distance between the base of the groove 6 and the opposite face 8 of the container 1, so that upon tightening the screw bolts 3 through the flanges 4 and 5 of the container 1 and the cover 2, respectively, the tube 9 or 9' will be slightly compressed and will be pressed against the base face of the groove 6 and the face 8 of the container 1 with the entire pressure of 600 p. s. i. to 1500 p. s. i. prevailing in the tube 9 or 9.
The tube 9 or 9 can easily be manufactured, for in stance by an extrusion process and assumes at first a longitudinal shape, the length of which can be cut to the length required in accordance with the length of the groove in a container or a cover therefor, which tube can be shaped in accordance with the shape of such groove and the ends or the joint of the open ends of the tube can be closed either by soldering, brazing, welding or any other suitable process which will be determined by the temperature range to which the seal is to be subjected.
While a gaseous fluid provides better operative conditions in most instances, it is to be understood that a fluid in the liquid state may also be used under proper conditions.
In order to supply a fluid under pressure in the tube a filling opening 11 must be provided in the tube which upon filling a fluid under pressure into the tube 9 or 9 can be closed again by brazing or any other suitable means.
It has been found that if the sealing tube 9 or 9 is used with unfinished engaging surfaces, a slight long term leak could not be avoided, particularly if the inner pressure of a container to be sealed is appreciably high. In order to overcome also this difiiculty and to provide a seal which stands up even under the highest pressure, the tube 9 or 9' receives a comparatively thin coating 12 or 12 which is provided on the tube 9 or 9'. The coating may be made of silicon rubber, Teflon, Kel-F, soft metals as copper, silver, gold or a combination of these metals or any other suitable material which may be applied either in form of an alloy or by using double layers of two different metals. The thickness of the coating of rubber will be preferably Within a range of .001 to .025 inch While layers of a thickness range of .0005 to .005 inch will suffice. The coating can be applied by any suitable process, such as plating, spraying, electrodepositing, metal vaporizing in vacuo or the like. It has been found of particular advantage to use a spongy type of coating 12 or 12 on the tube 9 or 9, because this type of coating is particularly capable to enter the crevices appearing on the surfaces engaging the tube and a completely perfect seal even under highest pressure in the container to be sealed has been encountered. The same result may be obtained by providing a coating 12 on the faces engaging the outer face of the metal tube, merely by covering a critical zone of the face 8 of the container, and/or on the opposite base face of the groove 6.
Several means are available to inject a fluid under the required pressure of 600 p. s. i. to 1500 p. s. i. in the tube. While any conventional means may be used to achieve this end, the pressure in the tube can be obtained by feeding a small amount of liquid gas at a comparatively low temperature and sealing off the filling opening 11 or by feeding chemicals in their solid state which when heated at once will assume the gaseous state under the pressure required in the tube. Still another method is demonstrated in Fig. 5 of the drawing in which a container 13 is provided which is equipped witha feeding tube 14 and which has also a manometer 15 in operative connection with the container 13. Gas to be filled in the tube 9 is fed into the container 13 under the required pressure of 600 p. s. i. to 1500 p. s. i. .and tube 9 is disposed in the container 13 which receives the gas present in the container 13 through the filling opening 11. While the gas pressure is maintained in the container 13 the filling opening 11 is then closed by brazing or any other suitable means by the use of an electric heating coil 16 and upon permitting the cooling of the brazed filling opening 11 which brought about a closing thereof, the pressure in the container is released and the tube 9 removed therefrom which can then be inserted into the groove provided in a container to be sealed.
While the endless tube 9 and 9' is described above as a metal tube and the seal as a metal seal, it is to be understood that any other suitable material may be used for the tube and theseal, respectively.
While I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.
1. A gasket for sealing a container comprising a completely enclosed pressurized metal member having a wall thickness of no more than .006 inch and having a coating of soft material adapted to engage a surface of said container to be sealed.
2. The gasket, as set forth in claim 1, in which said coating comprises a material selected from the group consisting of silicon rubber, polytetrafluoroethylene, polymers of trifiuorochloroethylene and soft metals.
3. The gasket, as set forth in claim 1, wherein said pressurized member contains a fluid which comprises a material selected from the group consisting of helium, nitrogen and a mixture of nitrogen and helium.
References Cited in the file of this patent UNITED STATES PATENTS 528,820 Stern Nov. 6, 1894 1,965,126 Kojola July 3, 1934 2,6ll,505 Winborn et a1. Sept. 23, 1952 2,638,243 Davies May 12, 1953 2,641,381 Bertrand June 9, 1953 2,726,006 Brewer et al. Dec. 6, 1955 FOREIGN PATENTS 207,855 Great Britain Dec. 4, 1923 474,238 Great Britain Oct. 27, 1937 595,332 France July 13, 1925 696,684 Great Britain Sept. 9, 1953 OTHER REFERENCES Engineering Data Metallic O-rings, May 19, 1954, published by: United Aircraft Products, Inc., Box 1035, Dayton, Ohio. Copy in 288/24 in Division 29.