US2606044A - Seal - Google Patents

Description

Aug. 1952 c. M. ALLEN ET AL SEAL 2 SHEETS-SHEET 1 Filed May 25, 1950 INVENTORS. Charles M. Allen By Russell W. Dayton AGENTS.

Aug. 5, .1952

C. M. ALLEN ETAL SEAL 2 SHEETSSHEET 2 Filed May 25, 1950 is? f? Ki Q E I\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ INVENTORS. Charles M. Al len Russell W. Dayton AGENTS.

Patented Aug. 5, 1952 ED STATES attain rsNr orrics SEAL , Charles M. Allen; Columbus, and Russell W. Dayton, Worthington, Ohio, assignors, by 'mesne assignments, to Battelle Development Corporation, Columbus, Ohio, a corporation' of Dela- Ware Application May 25, 1950, Serial N0.-164,222

able to withstand and for reducingthe leakage pass or through the seal.

In U. S. patents to Richardson, 1,014,850, Masterson et :al., 1,784,104, and Shaw et a1., 2,447,034. are shown centrifugal fluidshaft seals of representative design with which this invention is generally concerned. Sealing is eifected in these devices by fluid held between thevane or stator and the rotating trough or rotor. As the trough rotates the fluid is thrown outward Claims. (01. 286-9) relates to improvements and builds up a high pressure between the stator dipping into the fluid and the trough of the rotor owing to centrifugal force so that it is able to withstand considerable differences in pressure.

The prior art has also shown that certain modip fications are possible to enable the-seal to be used in a vertical position or when the shaft is stationary. .In such cases double rotors are generally employed which are driven independently of the shaft, and one ofthe cooperating vanes or I stators is attached to the shaft and may rotate at any independent speed while the other is secured to the atmosphere or pressure chamber,

wall, etc. One or more pockets or traps in the.

rotors or stators may also be provided to hold the fluid when the system is not operating in order to prevent its escape from the seal.

It has been found, however, that the maximum benefit in increased pressure and reduced leakage that might possibly be derived from such devices is not achieved due to what is apparently turbuthis turbulence to enable such seals to be used under conditions of increased pressure or differences in pressure'and'without appreciable leakage, and it is, therefore; an important object of this invention to provide a shaft seal having means to reduce the turbulence of the fluid under operating conditions.

It is another object of this invention to provide a centrifugal shaft seal with baffling to reduce the turbulence of the fluid and thereby enable the seal to be used under conditions of increased pressure with reduced leakage.

It is a further object of this invention to provide for a centrifugal fluid shaft seal, a rotor having in it trough continuous baffling characi 2 terized by reducing the turbulence of the sealing fluid. v o

i It is still further object of this invention to provide the rotor of acentrifugal shaft seal with a plurality of equally spaced baffles therein defining pockets for holding a fluid and preventing I turbulence thereof.

These and other objects and advantages of the present invention will become more apparent from the following-detailed description and drawing, in which Figure 1 is a partial vertical, sectional view of a rotor and stator of a representative centrifugal shaft seal with the fluid removed and containing the turbulence-reducing baffling of this invention, and V t Figure 2 is a vertical, sectional view of the baffling to be inserted in the trough, and

Figure 3 is a fractional, sectional view of the device shown in Figure 1, showing, the relationship of the baffle and thesealing fluid, and

Figure 4. is a fractional, sectional view along the line A-A-of Figure 1 showing the pockets formed by the bafiiing, the arrows in the pockets showing the current direction of the fluid in the pockets when the rotor and its ba-filing are moving in the indicated direction, and

Figure 5 is a fractional, sectional viewalong the line 0-0 of Figure 1 showing the serpentine shape of the baffling; and

Figure 6 is a fractional, sectional view of a portion of the device of Figure 5 showing the disposition of the fluid relative to the baffling, and Figure 7 is a fractional, sectional view. similar to Figure 5 but showing a modification of the invention wherein a plurality of baffles are inserted around the outer portion of the trough of the rotonand Figure 8 is a partial vertical, sectional view "of ons of the inserts disclosed'in Figure 7.

It has now been discovered that a substantial reduction in turbulence of shaftseals can be effected resulting in an increase in pressures obtainable with a reduction in leakage by securing baffling in the moving member of a shaft sealin close proximity to the vane or stator. The baffling creates a plurality of interconnected pockets for the sealing fluid in the trough of the rotor. As thefluid in the trough moves past the stator,

eddy currents are created in the fluid in each pocket due to the drag on the fluid by the stator. The currents interfere at the fringes with the currents in the adjacent pockets since the common Walls between the pockets are perforated or interconnected. Thus, the turbulence and velocity of the sealing fluid is reduced, resulting in increased pressure and reduced leakage.

In general, as shown in the drawing, Figures 1 to 6, the annular rotor is designated as l and has dual fins 2--'-2 and sides or walls 3-3 defining internal annular chamber or trough l. The rotor may be driven independently of shaft 5 by any means such as a belt or gearing or may be by suitable gearing connected to the shaft. Spaced about equidistant from the internal sides of the rotor and in the trough is annular member 6 which as a vane may be secured to the shaft and rotate at a speed relatively less than said rotor or as a stator may be fixably secured to concentric sleeve I which is spaced about said shaft and which is attached to wall 8 of a motor housing or atmosphere or vacuum chamber 9. Secured to the rotor in the outer end of the trough throughout its circumferential length is perforated or screen baffling having a generally serpentine shape. While in Figure 5, the baffling [0 has been shown as having a generally serpentine shape with loops-of roundeddesign, it will be understood that the loops can be of any shape, for example, square or triangular, without departing from the scope of the invention or the new and novel results obtained. The baffling is continuous about the annular, generally outer portion or periphery of the trough and has slot ll extending for a portion of the distance from its free end or portion into which the vane freely extends.

In operation of the'shaft seal, the mercury I2 which is used as a sealing fluid is thrown outward by centrifugal force when the rotor moves, and it lies in the outer portion of the trough formed bythe walls of the rotor. Due to pressure differences between the outside atmosphere and the vacuum chamber, it occupies positions l3 and I4 of different height on either side of the peripheral portion l'of the vane. As shown particularly in Figure i, the baffling, walls of the rotor, and stator form a plurality of pockets for the mercury, {the pockets being interconnected since the bafiling is perforated. As the mercury carried by the rotor moves past the stator in the direction indicated by the arrows l6l6 frictional forces set up eddy currents, as shown by arrows ll-I'I, in the fluid in each pocket. These currents tend to meet and counteract each other'by passage through the perforations of the baflling. In this manner the customary turbulence and velocity 'of the mercury is reduced and results in the obtainment of increased pressures and reduction in leakage during sealing operations. The baiiling must be secured to the rotor and not to the vane or stator for otherwise the opposite effect would be obtained as a great increase in turbulence would result providing increased leakage and preventing the useof the seal under conditions of even small pressure differentials.

While many methods for inserting the baffling will suggest themselves readily to those skilled in the art, it has been found best to first form screening, made of about 12 gauge nickel wire, in a serpentine shape and weld it to the inside of the rotor in the outer portion of the trough. After welding, Woods metal is poured in and allowed to solidify. The slot is then machined to the desired dimensions followed by melting out the Woods metal, leaving the bailiing in place with a continuous annular slot in the portions of the baffling extending away from the periphery of the trough to enable movement about the vane.

In the modification of the device shown in Figures 7 and 8, separate, arcuate-ended, generally rectangular perforated, baffles or inserts l8-|8 equidistant from each other and parallel to the radii of the rotor are secured to the rotor in the outer portion of the trough. Each baiile has a slot in which the stator or vane may freely lie, and, thus, the separate bailles carried by the rotor may move about the stator. The results achieved when using a plurality of separate baffles during operation of the device are the same as when the. continuous baffling is used.

In securing the individual baffles to the inside of the rotor, grooves l9-i9 are cut in the inside walls of the rotor, and the side edges 20-29 of the baffles inserted therein. The baffles may then be welded to the rotor or the metal near the grooves mashed or peened to cause it to close about the baffles. Woods metal is then poured in and the bailiemachined as described supra to provide slots of the desired dimensions. The slots, however, can be cut in the baffles prior to insertion in the rotor trough if careful machining techniques are observed.

The baffling material can be of metal or any other material having the requisite strength, capable of being secured to the rotor, and adaptable for use in centrifugal shaft seals. It must be apertured, porous, perforated, etc., in order that the fluid'in eachpocket can readily contact the fluid in the adjacent pocket and in order that the fluid will be in a somewhat continuous fluid mass to provide the necessary sealing under the action of centrifugal force. Examples of preferable materials are wire screening, perforated metal strips or inserts of heavy stainless steel, nickel, etc.

The mesh size of the baflling, where screening is used, can be of any size or number per linear inch provided that substantial interference at the fringes of the eddy currents is produced, adequate consideration being given to the temperature and viscosity of the fluid and the speed of the rotor in order that'the fluid will act as a sealing medium under centrifugal force. Thus, sizes of from 50 to 400 mesh can readily be employed, although with mercury and oils, it is preferred to use mesh sizes of from to 200.

The baffling disclosed herein is particularly useful with centrifugal fluid shaft seals but can be employed with shaft or other similar seals wherein a stationary or relatively stationary annular member contacts or dips into a flu d which is held by a rotating member and which is under the influence of substantially centrifugal force and thereby effects a seal between materials at different pressures. Moreover, this invention is not to be understood as restricted to shaft seals employing only one vane or stator and one rotor but is adaptable for use where a plurality of vanes and/or stators and rotors are used to effect a sealing action whether the rotor, vane, and shaft are independently or dependently driven, whether the vane or shaft is stationary or operational, and. whether they are in a vertical or horizontal position or variation thereof. Itis apparent to those skilled in the art that the vane or stator, and also the rotor where necessary, should be accurately machined and polished to further reduce any turbulence of the fluid that might be caused by surface irregularities, scale,

etc.

Mercury is customarily employed as the sealing fluid or medium and hasbeeniound more desirable when speeds up to' 4 :000"R'. P. M.,are used in; devices employing the present invention.

However, it is feasible that many other materials can be used as the sealing fluid g flSomegexamples thereof are glycerine, oil, and water. Moreover, low-melting point metalssuch as Babbitt, Woods metal, lead and bismuth can be used as the sealoil or water. Molten salts can also be used alone or in combination with some other fluid; for example, tantalum iodide or perfiuoride could be used on the top of the mercury where the shaft seal is being used to seal against gases at low temperatures. It is, of course, apparent that some change in dimensions of the parts of the centrifugal shaft seal may be necessitated where different speeds and sealing mediums are used.

Tests were made using a centrifugal shaft seal comprising a stationary vane, a driven rotor, mercury as the sealing fluid, and with and without the bafiling of this invention. Without baffling, the lowest absolute pressure obtainable was 5.5 microns, Whereas with baffling the seal was able'to sustain a pressure of the order of from 0.15 to 0.50 micron absolute pressure. Without baffling at 4000 R. P. M., leakage was 158 cubic inches of atmospheric pressure air per year, while with baffling it was 22 cubic inches of atmospheric pressure air per year.

A shaft seal embodying the present invention will find particular use in sealing against toxic fumes or vapors, in high-vacuum distillation process, in vacuum smelting, in blower shaft seals, etc.

In summary, this invention teaches that the efliciency of a shaft seal can be greatly increased by providing baifling or bafiles in the trough of the rotor to reduce the fluid turbulence caused by the fluid moving past the vane. The bafiling or baflies provide interconnected pockets where the sealing fluid is partially entrapped although its overall sealing effect under the action of centrifugal force is not adversely affected. In this manner, the fluid in each pocket, due to reaction between it and the stator, develops eddy currents which interfere at the fringes with the eddy currents of the fluid in the adjacent pockets, thereby reducing the turbulence and increasing pressures obtainable with a comparable reduction in leakage. 7

Having thus described the invention, what is claimed as new and novel and is desired to be secured by Letters Patent is:

1. In a centrifugal fluid shaft seal, the combination of a rotor having sides defining an internal annular chamber, a sealing fluid adapted to be held under pressure in the outer portion of said chamber when said rotor moves, continuous, perforated slotted serpentine baffling secured to said rotor in the outer portion of said chamher, a stator having an annular periphery adapted to contact said fluid whensaid rotor moves and to extend into the slotted portion of said baffling, said baflling, said stator and the walls of said chamber defining a plurality of spaced pockets therebetween, said pockets inducing interference at the fringes of the eddy currents of said fluid caused by drag on said fluid by said stator when said rotor and said baffling are moving.

2. In a centrifugal fluid shaft seal, the combination of a rotor having sides defining an internal annular chamber, a sealing fluid adapted 6. to be held underpr'essurein' the outeigj-portion of said chamber when'sai'd rotor 'operatesjcon tinuous perforated serpentine bafiling secured to three sides of said rotor-in the outer portion of said chamber, slotsextending from the free portion of said baffling and adapted to receive the annular peripheral portionof a stator, a stator disposed in said chamber and ab'out'which said rotor is designed to move, anann-ular peripheral portion of said stator 'adaptedrtddip into said fluid when said rotor movesand to freely lie in said slots of said bafiling, 'and,-.said baffles,,,'said stator" and the walls ,of'said chamber defining a plurality of adjacent interconnected pockets therebetween, said pockets inducing interference at the fringes of the eddy currents of said fluid caused by drag on said fluid by said stator when said rotor and said bafiling are moving and thereby reducing the velocity and turbulence of said 3. In a centrifugal fluidshaft seal, the com bination of a rotor having sides defining an internal annular chamber, a sealing fluid adapted to be held under pressure in the outer portion of said chamber when said rotor moves, slotted and perforated bafilingsecured to said rotor in the outer portion of said chamber, a stator having an annular periphery adapted to contact said fluid when said rotor moves and to extend into the slotted portion of said baffling, said baffling, said stator and the walls of said chamber defining a plurality of spaced pockets for said fluid.

4. In a centrifugal fluid shaft seal, the combination of a rotor having sides defining an internal annular chamber, a sealing fluid adapted to be held under pressure in the outer portion of said chamber when said rotor moves, a plurality of separate, radially disposed, slotted and perforated bafiles secured to said rotor in the outer portion of said chamber, a stator having an annular periphery adapted to contact said fluid when said rotor moves and to extend into the slotted portion of said baffles, said baffles, said stator and the walls of said chamber defining a plurality of spaced pockets therebetween.

5. In a centrifugal fluid shaft seal, the combination of a rotor having sides defining an internal annular chamber, a sealing fluid adapted to be held under pressure in the outer portion of said chamber when said rotor moves, slotted and perforated bafiling secured to said rotor in the outer portion of said chamber, an annular. member having a periphery adapted to contact said fluid when said rotor moves and to extend into the slotted portion of said baffling; said baffling, annular member and the walls of said chamber defining a plurality of spaced pockets therebetween.

6. In a centrifugal fluid shaft seal, the combination defined in claim 5 wherein said annular member is a vane attached to the shaft to be sealed.

7. In a centrifugal fluid shaft seal, the combination of a plurality of rotors each having sides defining internal annular chambers, sealing fluid adapted to be held under pressure in the outer portion of said chambers, when said rotors move, slotted and perforated baffling secured to said rotors in the outer portions of said chambers, a plurality of annular members each having a periphery adapted to extend into the slotted portion of the baffling in the annular chamber of a rotor and to contact said fluid when said rotor moves, said baffling, each of said annular members and the walls or said chamber defining Number a plurality of spaced pockets in each rotor. 876,613 a 999,693 CHARLES M. ALLEN. 1,170,279 RUSSELL W. DAYTON. 5 1,879,626 2,127,865

REFERENCES CITED I The following references are of record in the file of this patent: 1 g 2 48 UNITED STATES PATENTS 10 155:953

Number 1 Name Date 822,802 Wilkinson; June 5, 1906 Name Date Wilkinson Jan. 14, 1908 Bleaker Aug. 1, 1911 Knourek Feb. 1, 1916 Mendenhall et a1. Sept. 2'7, 1932 Goddard Aug. 23, 1938 FOREIGN PATENTS Country Date Great Britain Aug. 28, 1906 Germany Dec. 5, 1904

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