US3453986A - Reactor seal incorporating a slit orifice - Google Patents

Description

July 8, 1969 c. K. RICE ET A REACTOR SEAL INCORPORATING A SLIT ORIFICE Fild Feb. 27, 968

VIIIIIIIIIf/ljll INVENTORS CHARLES K. RICE JAMES? WHITTIER Y/54AM ATTORN United States Patent Ofifice 3,453,986 Patented July 8, 1969 US. Cl. 118-48 1 Claim ABSTRACT OF THE DISCLOSURE In apparatus wherein a moving wire is drawn through .a reaction tube and deposition is efiected thereon, a reactor seal is provided to isolate the reactant gases within the tube from the atmosphere. The reactor seal comprises an orificed fitting containing a well of liquid metal through which the wire is drawn, the liquid metal being held in the well at the orifice by surface tension forces. The orifice is established as a slit between a pair of closely spaced parallel rods which extend across the passageway provided in the seal beneath the well and through which the wire is drawn.

Background of the invention The present invention relates in general to scaling devices and, more particularly, to reactor seals incorporating a liquid sealant.

It is known that filamentary materials may be conveniently produced by pyrolytic techniques wherein the desired material is deposited on a resistively heated wire which is drawn through a reactant mixture containing the material in vapor form. One such technique is disclosed in a copending application, Ser. No. 618,512, entitled Process for Forming Stoichiometric Silicon Carbide Coatings and Filaments by Malcolm Basche .and Urban E. Kuntz, which shares a common assignee with the present invention. According to these methods, the wire upon which deposition is desired is introduced to and exits from a tubular reactor through a fitting provided at each end thereof, each fitting being fabricated to provide a retention well for a pool of liquid sealant, such as a liquid metal. The liquid metal, typically mercury, normally performs a dual function. It prevents the escape of the reactor gases along the wire as the wire is rapidly drawn through the reactor and, further, affords convenient means for establishing electrical contact with the wire for resistance heating purposes.

The mercury is normally retained in the well through surface tension forces. To accomplish this end, the retension well is orificed .at its lower end to provide an opening through which the wire :may freely pass but which is small enough to, in combination with the wire, retain the mercury in the well by means of surface tension. The orifice has normally been established in the past by drilling a hole of the appropriate diameter in the fitting or in a jewel which is attached to the fitting. However, threading of the wire through the fine holes of this nature, typically 310 mils in diameter, requires disassembly of the reactor and is accordingly accomplished only with considerable difficulty. Furthermore, seals of this nature are subject to frequent replacement due to wear.

Summary of the invention In accordance with the present invention, a reactor seal is provided wherein the orifice necessary to retain the liquid sealant is established as a slit between a pair of closely spaced members which traverse the passageway in the seal through which the wire exits. Because the diameter of the passageway in the seal is no longer critical as to size, threading of the wire therethrough is readily accomplished. Further, orifice replacement due to wear is significantly minimized since, when separate rods are utilized as the members, each may be rotationally and axially adjusted during operation of the reactor to present an unworn exterior adjacent the wire. Still further, since the rods preferably penetrate the seal and, hence, are accessible external of the reactor, replacement of the orifice is greatly simplified and no disassembly of the reactor is necessary for this purpose.

Brief description 0 the drdwings FIG. 1 is a view, taken in cross section, of a typical reactor seal incorporating the teachings of this invention, the particular seal illustrated comprising the bottom end seal of a pyrolytic reactor;

FIG. 2 is a top view of the seal of FIG. 1, not including the sealant, which illustrates particularly the slit orifice formed between individual parallel rods.

Description of the preferred embodiments Referring to FIGS. 1 and 2, the illustrated reactor seal in its preferred embodiment may be seen to comprise an end fitting 2, usually formed of metal in those instances wherein it is to be utilized to establish electrical contact with the wire, having a sealant reservoir or well 4 machined therein. The lower portion of the well communicates with a passageway 6 through which the wire 8 exits from the reactor. This passageway is normally axially aligned with the wire and is sized to permit the wire to be readily threaded therethrough.

A pair of closely spaced parallel rods 10 .and 12 penetrate the fitting at the lower end thereof and traverse the passageway 6, forming between themselves the desired slit orifice 14 in the passageway. The rods are designed to fit closely in the fitting at 16 where penetration thereof is made, to prevent the escape of sealant along the rods. Accordingly, no escape of sealant will occur along the rods during operation of the reactor due to the same surface tension forces which retain the sealant 18 atop the rods at the slit orifice.

Sealing between the tubular reaction chamber 20 and the fitting 2 is conveniently provided by the sealant in the annular space 26 formed on the periphery of the fitting, access to the annular space being provided through conduits 22 and 24.

Since it is preferable that disassembly of the apparatus be limited to minimize contamination in the reactor, a fill tube 30, communicating with the well, is provided external of the reactor. The fill tube serves not only as a convenient means for adding sealant to the system, but it may also be utilized to indicate or maintain the desired sealant level internal of the reactor.

The rods 10 and 12 have at different times been constructed of a variety of materials. They must, of course, be chemically compatible with the sealant at the normal operating temperatures of the system. Initially, tungsten rods were employed in the device with generally satisfactory performance. However, in apparatus wherein electrical contact with the wire is to be made through the fitting and the sealant, the use of rods formed of a hard dielectric material such .as glass would usually be preferred. Similarly, for electrical isolation purposes the tubular reaction chamber member 20 is usually formed of an electrical insulator in apparatus of the type illustrated.

The particular shape of the rods is immaterial except insofar as they cooperate to form the desired slit orifice. Nor in fact need the rods comprise separate elements, except wherein they traverse the filament passageway. The essential element is the use or formation of a slit orifice on which the sealant is retained and the ability in the device for removing the orifice forming members from the filament passageway without a complete disassembly of the reaction apparatus.

In several instances where increased wiping .action has appeared advisable, a second slit has been established above or beneath the first slit orifice and oriented at an angle with respect thereto. The overall effect of the additional slit is to make the projected orifice approach a circle rather than a slit. Although obviously slightly more complex in construction than the single slit orifice device, the overall advantages are nevertheless retained in the alternative construction.

While the invention has been described in connection with .a particular preferred embodiment, no limitation is intended thereby, and numerous modifications thereto will be evident to those skilled in the art within the true spirit and scope of the invention as set forth in the appended claim.

What is claimed is:

1. In a vertically arranged reactor vessel wherein a vapor deposition is effected on a moving substrate, .a reactor seal comprising:

a liquid seal comprising a pool of mercury disposed at an end of the vessel and through which the substrate moves;

an end fitting forming an end closure for the reactor vessel, the fitting having a vertically disposed passageway therethrough through which the substrate is drawn, and the fitting supporting said liquid seal;

said fitting including a horizontally disposed channel which is diametrical with respect to said passageway and which extends at least partially through one fitting wall portion and completely through the opposite fitting wall portion;

said fitting further including a pair of spaced, removable, parallel rods, disposed across said passageway and supported in said fitting wall portions;

the spacing between the rods being wide enough to provide free passage of the substrate therethrough but narrow enough to retain said liquid sealant thereon; and

said rods extending externally of said fitting wall whereby the rod may be rotatably and longitudinally adjusted with respect to presenting a fresh surface to the substrate passing therebetween.

References Cited UNITED STATES PATENTS 1,882,459 10/1932 Tyner 1l8405 2,238,575 4/1941 Alexoy.

2,432,854 12/1947 Bassett et ,al. 118-405 2,507,310 5/ 1950 Lodge 118-405 2,540,006 1/ 1951 Otto 118405 X 2,679,823 6/1954 Denham 118405 3,130,073 4/1964 Van der Linden et a1. 11847 X 3,367,304 2/1968 Robbins 11849.5

30 MORRIS KAPLAN, Primary Examiner.

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