US 3643964 A
A seal is disclosed which permits a pull rod to be rotated and moved axially with respect thereto and which is provided with a plurality of washers arranged in a stacked relation so that their engagement with the peripheral surface of the rod removes any oxide impurities therefrom and provides for deposition of the impurities into a chamber that is a part of the seal for the rod. The chamber is connected to the atmosphere through a series of radial holes and by a clearance hole surrounding the pull rod to the interior of the furnace. Consequently, the pressurized gas normally in the furnace moves or flows along the pull rod and into the chamber. The gas is still under sufficient pressure so that the impurities deposited in the chamber can be removed through the radial holes.
Description (OCR text may contain errors)
United States Patent Snelling et a1. Feb. 22, 1972  PULL ROD SEAL 2,758,855 8/1956 Russell et a1 ..277/64  Inventors: Christopher Snelling, Penfield; Anthony J.
Gardone, Rochester, both of NY.
Att0rneyLloyd F. Seebach  Assignee: Kayex Corporation, Rochester, NY. 221 Filed: Oct. 12, 1970 [571 ABSTRACT 2 N 80 072 A seal is disclosed which permits a pull rod to be rotated and I l 1 Appl o moved axially with respect thereto and which is provided with a plurality of washers arranged in a stacked relation so that U-S- "277/24, their engagement the surface of the rod 277/64 removes any oxide impurities therefrom and provides for  Int. Cl ..Fl6] 15/10 deposition of the impurities into a chamber that is a pan of the  Field of Search ..277/24, 64, 70, 71, 79; seal for the The chamber is connected to the atmosphere 23/277 259/16 through a series of radial holes and by a clearance hole surrounding the pull rod to the interior of the furnace. Con-  References cued sequently, the pressurized gas normally in the furnace moves UNITED STATES PATENTS or flows along the pull rod and into the chamber. The gas is still under sufficient pressure so that the impurities deposited 863,409 8/ 1907 Leib et ..277/64 in the chamber can be removed through the radial holes 1,272,171 7/1918 Zmssme1ster.. ...259/D1G. 16 1,387,301 8/ 1921 Osborne ..27 7/64 14 Claims, 4 Drawing Figures PAIENTEUFEB22 m2 3643 964 CHR/STOPHER SNELL ING ANTHONY J GAPDO/VE INVENTORS PULL ROD SEAL FIELD OF THE INVENTION The present invention relates to a crystal growing furnace and more particularly to a seal for a pull rod which cleans the rod as it is rotated and moved axially during the crystal growing operation.
BACKGROUND OF THE INVENTION In the art of crystal growing furnaces, a pull rod is rotatable in and axially movable through a wall of the furnace at a rate in accordance with the rate of growth of the crystal. During the course of the crystal growth, various oxides are produced as byproducts within the furnace and some of these are deposited on the pull rod. As the pull rod is moved through the seal in the furnace wall, these byproducts, which are impurities, are scraped or cleaned from the rod by the seal and may find their way into the melt from which the crystal is being grown. The addition of even a small amount of these byproducts or impurities to the melt will affect the size and quality of the crystal. Consequently, it is desirable to provide a seal for the pull rod which will generally eliminate the possibility that such impurities can and will be deposited in the melt.
SUMMARY OF THE INVENTION One object of the present invention is to provide a seal for a pull rod in a crystal growing furnace which will generally remove the oxide impurities from the rod and also remove these same impurities from the furnace.
Another object of the invention is to provide a seal for a pull rod in a crystal growing furnace in which the gas introduced into the furnace is used in conjunction with the seal for removing the impurities that are inherently deposited on the pull rod.
Still another object of the invention is to provide a seal for a pull rod in a crystal growing furnace which can be easily disassembled for cleaning and reassembled so the parts will assume the same aligned and adjusted positions as prior to disassembling.
Other objects and advantages of the invention will be apparent to those skilled in the art from the description which follows.
The objects of the invention are attained by a seal which permits a pull rod to be rotated and moved axially with respect thereto and which is provided with a plurality of washers arranged in a stacked relation so that their engagement with peripheral surface of the rod removes any oxide impurities therefrom and provides for deposition of the impurities into a chamber that is a part of the seal for the rod. The chamber is connected to the atmosphere through a series of radial holes and by a clearance hole surrounding the pull rod to the interior of the furnace. Consequently, the pressurized gas normally in the furnace moves or flows along the pull rod and into the chamber. The gas is still under sufficient pressure so that the impurities deposited in the chamber can be removed through the radial holes. The radial holes can be adjusted in size so as to increase or decrease the rate of gas flow from the chamber thereby controlling the rate of removal of the oxide impurities or any other foreign matter.
DESCRIPTION OF THE DRAWING pull rod in accordance with the invention;
FIG. 3 is a sectional view taken substantially along the line 33 in FIG. 2; and
FIG. 4 is a detailed elevational view showing the manner in which the size of the radial holes can be adjusted.
DESCRIPTION OF THE INVENTION With particular reference to FIG. 1, a crystal growing furnace, generally designated by the numeral 10, comprises a casing 11 into which a gas, such as argon, is introduced at 12 under pressure and withdrawn at 13. Within the chamber 14 of the furnace 10, a support 15 is provided for a crucible 16 which contains a melt 17 from which the crystal C is being formed. The crucible 16 is rotatably mounted with respect to support 15 and a drive means (not shown) is suitably connected to the shaft 18 for rotation of the crucible.
A pull rod 20 extends into the chamber 14 and into close proximity of the melt 17 in crucible 16. As is well known, when the rod 20 is lowered toward the melt 17 it has a crystal seed secured to its end which is brought into contact with melt. The formation of the crystal takes place as the rod 20 is rotated and moved away from the melt 17 at a predetermined rate in accordance with the material or composition of the melt 17. The crucible 16 is provided with means for heating and maintaining the melt at a prescribed temperature and such means is not disclosed inasmuch as the crystal growing operation per se forms no part of the present invention.
As shown in FIG. 1, pull rod 20 extends through the top wall 21 of furnace l0 and a seal 22 is provided at this point which also serves as a bearing for the rod 20. By suitable means not shown, the rod 20 can be rotated and moved axially as is well known in the art. Further, it is well known that in the course of growing a crystal, oxides and other impurities are deposited on the rod 20 while it is in the furnace which should not be allowed to fall back into the furnace and particularly into the melt where they can prevent successful growth of the crystal.
With reference particularly to FIG. 2, the seal 22 comprises a support member 30 which comprises a mounting portion 31 and a bearing portion 32. The mounting portion is provided with an annular groove 33 and is mounted in a sealed relationship with the wall 21 by means of a plurality of clamps 34 and a resilient sealing ring 33' within groove 33 as shown in FIG. 2. The combination of ring 33 with the resilient ring 33 a used with each of clamps 34, provides a resilient orfloating mount for the entire seal assembly, thereby reducing the effect of any bow that might develop in the rod 20 and/or in the lead screw for rotating said rod. The mounting portion 31 is provided with a central bore 35 through which the pull rod 20 extends. The bore 35 is larger in diameter than the pull rod 20 in order to provide a passageway for the gas within the furnace as will be described in more detail hereinafter. The mounting portion 31 is provided with a recessed flange 36 on which a similar flange 37 forming a part of bearing 32 is mounted and clamped thereby with a ring 38. The flanges 36 and 37 are sealed by a suitable packing member 39 so as to provide a seal against the escape of any gas from the furnace at this junction of the mounting and bearing portions 31 and 32.
The bearing portion 32 has a sleeve portion 40 extending from the flange 37 and is provided with an external thread 41 at the end thereof and an external thread 42 intermediate the end of the sleeve and the flange 37. The sleeve 40 is provided with a central bore 44 which is larger in diameter than the pull rod 20 to permit the flow of gas into a chamber 45. This chamber is formed by an annular recess 46 that is enclosed by a metallic washer 47 which rests or is supported by a shoulder 48 within sleeve 40. The washer 47 also serves as a support for a plurality of washers 49 which are arranged in a stacked relation thereon, the outermost washer extending beyond the end of sleeve 40. A clamping ring 51 threadably engages the external thread 41 and has a face 52 which engages the outermost of washers 49. As the ring 51 is rotated into a washer engaging position, face 52 forces the washers into a compressed relationship between surface 52 and washer 47 thereby also urging the washers 49 into an intimate engaging relationship with the peripheral surface of the rod 20. The washers 49 are made of a pure, flexible insulating graphite material which is capable of withstanding the high temperatures that exist within the furnace. Preferably, the topmost washer 49 should be a stainless steel washer having an outside diameter and thickness generally the same as the graphite washers but with an inside diameter generally the same as that of washer 47. With this arrangement, the topmost washer will not deform so as to cause any binding problem. The washers 49 not only provide a seal for the pull rod but also serve as a bearing and a cleaning member for the pull rod. The chamber 45 is interconnected to an axially movable ring 60 by a plurality of angularly spaced, radial holes 61 in sleeve 40 and a corresponding number of similarly spaced, radial holes 62 in the ring 60. An adjusting ring 63 threadably engages the external thread 42 and upon rotation adjusts the position of holes 62 relative to holes 61 in an axial direction relative to rod 20 so as to vary the size of the opening and, hence, the rate of gas flow from the furnace along the pull rod 20 through the central bores 35 and 44 and into the chamber 45 or recess 46.
With the structure set out and described hereinabove, it will be readily appreciated that as pull rod 20 is rotated and moved axially, the washers 49 will remove any oxides therefrom which are then deposited or scraped into the chamber 45. Since a flow of gas is maintained along the pull rod through central bores 35 and 44, the deposits cannot find their way into the furnace but are forced out of the chamber through holes 61-62 and the possibility of contaminating the melt with such impurities for the most part is completely eliminated.
in addition to the removal of foreign matter, it will also be appreciated that the seal described hereinabove can be readily disassembled by removing the clamping ring 51, the washers 49 and the metal washer 47, see FIG. 4. The ring 62 can also be removed. After cleaning, the parts can be reassembled and will assume the same and exact location as before disassembling. In order to insure proper positioning of the ring 60 and sleeve 40 so as to maintain the previously adjusted positions of holes 61 and 62, a key and keyway connection 70 between the sleeve 40 and ring 60 can be provided as shown particularly in FIG. 3.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
We claim: 1. A cleaning seal for a shaft that is rotatable and movable axially relative to an aperture in a wall of a chamber containing a gas under pressure, the combination comprising:
support means positionable relative to said aperture and encircling said shaft, said support means providing a central compartment connected to said chamber and to the atmosphere for establishing a path of flow for said gas;
hearing means carried by said support means adjacent said compartment and engaging said shaft for wiping any foreign matter therefrom for deposit in said compartment; and
means for establishing a rate of gas flow from said chamber through said compartment to said atmosphere for removal of said foreign matter.
2. A cleaning seal in accordance with claim 1 wherein said central compartment is connected to said chamber by said aperture and a clearance hole in said support means for said shaft between said wall and said compartment.
3. A cleaning seal in accordance with claim 1 wherein said support means is resiliently mounted on said wall.
4. A cleaning seal in accordance with claim 1 wherein said bearing means comprises at least one washer of a pure flexible, insulating graphite material.
5. A cleaning seal in accordance with claim 1 wherein said means for establishing a rate of gas flow from said compartment to said atmosphere comprises a plurality of equiangularly spaced holes in said support means, and an axially movable member having a like number of holes positionable relative to said plurality of holes to establish said rate of as flow.
6. A cleaning seal for a shaft that is rotatable an movable axially relative to an aperture in a wall ofa chamber, the combination comprising:
a support member positionable relative to said aperture and having an internal shoulder at one end thereof, a first external threaded portion at said one end, a second external threaded portion generally intermediate the ends thereof, an annular recess contiguous to said shoulder and having a plurality of spaced, radial holes extending therefrom, and a central bore through which said shaft will extend and permit a flow of gas from said chamber into said recess;
a plurality of washers arranged in a stacked relation on said shoulder and overlying said recess with the inner diameters of at least some of said washers engaging the peripheral surface of said shaft to provide a bearing therefor;
clamping means threadably engaging said first threaded portion for movement against the outermost one of said washers for urging at least some of said washers into a sealing and wiping engagement with said shaft; said wiping engagement being sufficient to remove any foreign matter from said shaft for deposit in said annular recess; and a control means provided with a plurality of spaced, radial holes and threadably engaging said secured threaded portion, whereby the extend of alignment of said last-mentioned radial holes with those in said clamping ring dete rmines the rate of gas flow from said recess for removal of said foreign matter.
7. A cleaning seal for a shaft in accordance with claim 6 including means for mounting said support member in a sealed relationship to said wall when arranged relative to said aperture.
8. A cleaning seal for a shaft in accordance with claim 6 wherein said support member is resiliently mounted relative to said wall.
9. A cleaning seal for a shaft in accordance with claim 6 wherein said support member comprises a base portion retainable in a resiliently sealed relationship with said wall and a bearing portion for said shaft that is removably sealed to said base portion.
10. A cleaning seal for a shaft in accordance with claim 9 wherein said support member includes a secured clamping means for retaining said base portion and said bearing portion in a resiliently sealed, operative relation.
11. A cleaning seal for a shaft in accordance with claim 6 wherein said plurality of washers includes a metal washer in engagement with said shoulder for supporting the remaining washers.
12. A cleaning seal for a shaft in accordance with claim 11 wherein said remaining washers comprise a pure flexible, insulating graphite material.
13. A cleaning seal for a shaft in accordance with claim 6 wherein said control means comprises a first ring having a plurality of spaced, radially disposed holes alignable with said spaced, radial holes in said support member and a second ring threadably engaging said second threaded portion and supporting said first ring whereby axial movement of said second ring positions said first ring to establish the relationship of said holes relative to one another in an axial direction and the rate of gas flow from said recess.
14. A cleaning seal for a shaft in accordance with claim 6 wherein said clamping means comprises a ring threadably engaging said first threaded portion and having a surface for engaging the outermost washer for exerting axial pressure against said plurality of washers, whereby a seal is formed between said washers and said shaft.