Patent Number: 048184691
Section: description

In FIG. 1, the housing and, respectively, the mounting of a valve is indicated schematically by the reference character -1-. The housing -1- has an inlet opening -2- and an outlet opening -3- whereby the flow path can be closed off by a valve cone -4-. The valve cone -4- is provided with a passage opening -5- situated in the flow path and effecting an opening or closing of the valve by turning of the valve cone about its own longitudinal axis. Over the valve cone -4- is slid a molded element -6- in the shape of a conical cylinder which is provided on either side with recesses -11- (FIG. 3) opposite the passage opening -5-. The molded element -6- is composed of flexible graphite which, in turn, is coated with a thin, flexible layer of tantalum. The tantalum layer is sufficiently thin so that the flexiblity properties of the graphite are not impaired. The flexible graphite layer may also be built-up of a plurality of thin layers laminated one on top of the other. Cut-outs may be provided in thin, laminated layers of flexible graphite in defined locations in order to create relief surfaces for a more balanced pressure distribution. From FIGS. 2 to 4 it becomes clear that the tantalum coating is of composed an inner tantalum sleeve -7- and an outer tantalum sleeve -8- which, between them, enclose the graphite molded element -6-. At the end faces, and also additionally in the region of the recess -11-, there are provided tantalum covers -9- which, in sections, are placed between the sleeves -7- and as well as over the end face of the molded element -6-. Complete sealing is obtained because the covers -9- are welded (at -10-) together with the inner and outer sleeves -7- and -8-. Advantageously, all welding seams -10- are produced by the precisely focusable electron beam welding process, known in itself. The sealing of the recesses -11- opposite the passage openings -5- is obtained in the same manner as the sealing of the end faces as shown in FIG. 2. Thus, the graphite molded element -6- is hermitically encapsulated within a thin tantalum enclosure. The molded element -6- encapsulated in this manner is fixed on the valve cone -4- by means of a frame-like holding device -12-. Thereby is thus obtained a fixing of the molded element -6- in both the axial direction and the direction of turning. Around the passage openings -5- arranged on either side of the valve cone -4- extends a groove -13- into which is inserted the frame-like holding device -12-. Securing thereof is obtained by a press fit. In the embodiment illustrated, the passage openings -5- and holding device -12- appear rectangular in plan view. Evidently, circular, oval or other openings may be provided. In the exemplifying embodiment shown in FIG. 2, the end face cover -9- is flanged so that it overlaps the graphite molded element -6-. In the embodiment illustrated in FIG. 4, however, the covers are annular disks or rings which without any overlapping are welded to the sleeves -7- and -8- at the welds -10-. In the embodiment represented in FIG. 1 there is also shown in greater detail the arrangement of the valve connected with the seal according to the present invention. At its smaller diameter front end, the valve cone -4- is provided with a cylindrical section -15- which penetrates a cylindrical housing opening -20- (!). Starting from the inlet and outlet openings -2- and -3-, respectively, housing -1- is provided, in the region of the front end of the valve cone -4- with a first conical valve seat -17- in which is guided the molded element -6- of the seal in accordance with the present invention. This is followed, by way of a transverse step or shoulder step -18-, by a second conical valve seat -19- with a smaller diameter, the second diameter corresponding approximately to the diameter there of the valve cone -4-. Thereafter follows a further step or transverse shoulder -20- and, successively, a cylindrical housing recess -21-. On the other side of the valve cone -4- there is also provided a conical valve seat -22- in which is guided the other end of the seal. This is followed by a cylindrical opening -23- of the housing -1- whose diameter is larger (by approximately the wall thickness of the seal -6-) than the diameter of the rear cylindrical portion -16- of the valve cone -4- with the seal mounted on it can slide axially (from the right to the left as shown in FIG. 1). A preferred field of application of the present invention is as a seal for cone valves in the fluidized currents of the Purex process whereby the operational components are comprised of radiation-resistant, flexible and corrosion-resistant materials. By means of the seal according to the present invention there can be achieved a definite increase in service life and also increased maintenance and replacement intervals. Another preferred filed of application of the present invention is the utilization of the seal in chemical plants, e.g., in case of chemicals which do not attack tantalum. In HNO.sub.3 and many other chemicals, tantalum is an absolutely corrosion-resistant material. In contrast to plastics, the flexible graphite enclosed by tantalum retains its characteristics, even at temperatures exceeding 150.degree. C. It does not liquefy and does not change chemically, even on inclusion in tantalum. All technical details contained in the patent claims, the description and the drawing are essential parts of the invention, each by itself and also in any combination whatever.