US3040553A

US3040553A - Sealing of pressure vessels

Info

Publication number: US3040553A
Application number: US119768A
Authority: US
Inventors: Jr Edgar C Rust
Original assignee: Crompton and Knowles Corp
Current assignee: Crompton and Knowles Corp
Priority date: 1961-05-19
Filing date: 1961-05-19
Publication date: 1962-06-26
Anticipated expiration: 1979-06-26
Also published as: BE617587A; GB939397A

Description

June 26, 1962 E. c. RUST, JR 3,040,553

SEALING OF PRESSURE VESSELS Filed May 19, 1961 2 Sheets-Sheet 1 INVENTOR EDGAR C. RUST. JR

FIGZ

June 26, 1962 E. c. RUST, JR 3,040,553

SEALING OF PRESSURE VESSELS Filed May 19, 1961 2 Sheets-Sheet 2 INVENTOR EDGAR c; RUST,JR.

United States Patent Ofiiice Patented June 26, 19 62 3,040,553 SEALING F PRESSURE VESSELS Edgar C. Rust, Jn, Williamstown, Mass assignor, by

mesne assignments, to Crornpton & Knowles Corporation, Worcester, Mass, a corporation of Massachusetts Filed May 19, 1961, Ser. No. 119,768 Claims. (Cl. 68-175) This invention relates to pressure seals and, more especially, to an improved pressure seal for preventing the escapement of relatively high pressure from within a pressure tank or vessel at the points at which web or strand material is introduced into and/or withdrawn from the pressure tank or vessel. The present invention shall be hereinafter described as though it involves the processing of web material or fabric although it should be distinctly understood that the principles of the present invention apply to the processing of single strands or a plurality of strands or the processing of any type of material wherein it is desirable to maintain a high pressure within a vessel and to prevent the escapement of the same when the material enters and leaves the vessel.

In treating textile material, especially fabric made from synthetic polyamide, polyester and acrylonitrile yarns such as nylon, Dacron, Orion and the like for the purposes of dyeing, desizing, boiling off, decatizing and other processes, it is highly desirable that the fabric be immersed in the treating solution while the treating solu-' tion is maintained at a relatively high temperature; substantially higher than the boiling point of water under atmospheric pressure. Accordingly, is necessary to maintain the treating solution at a relatively high pressure.

As disclosed in Fahringer Patent No. 2,873,597, granted February 17, 1959, it has been proposed heretofore to provide for this purpose, at both the web inlet and the web outletof the pressure vessel, 21 pressure'seal comprising a housing containing pairs of opposed pressure sealing rollers which are positively driven and engage the opposite sides of the web to feed it into or from the vessel. According to this Fahringer patent, each pressure sealing roller is in the form of a plurality of juxtapositioned rings with keyways formed on their inner surfaces for being positively rotated by a common shaft loosely encircled by the rings. The shaft has longitudinally positioned keys formed thereon to loosely engage the keyways of the rings to drive the same while permitting each of the rings to have a floating By virtue of the loose mounting of the rotating rings on their respective shafts to which they are keyed, and the fact that opposed rings are urged toward each other under pressure from the pressure vessel, it is intended that opposed rings between which the web moves shall be maintained at their peripheries in close contact with the web despite irregularities or variations in the web thickness, while opposing rings located beyond the lateral edges of the web shall be urged against each other at their peripheries to avoid escape of pressure through the gaps which would otherwise be formed adjacent the selvedges of the web, the seal being completed by bearing plates in the housing against which'the peripheries of the rings are urged under the pressure from the vessel.

It has been found, however, that the sealing rollers disclosed in this Plalm'nger patent do not function as desired. They do not consistently maintain a good seal against escape. of pressure from the vessel as the web is fed through the vessel, especiallyat relatively high 1 rotate, so as to maintain speeds; and this is apparently due at least in large part to inability of the rings to adjust their axes readily relative to the axes of their respective shafts, as the latter good sealing cont-act at their peripheries.

An object of the present invention, therefore, is to provide in a pressure seal of the character described an improved adjustable ring roller for maintainingwa good seal consistently, even when driven at relatively high speed.

An adjustable ring roller made according to the present invention comprises a rotary shaft, a plurality of adjacent annular diiving dogs through which the shaft extends loosely, and a plurality of adjacent sealing rings loosely surrounding the respective driving dogs. Each dog is keyed to the shaftfor rotation therewith by keying means including a keyway in one and a key on the other of the dog and shaft, the key extending lengthwise of the shaft and being slidable radially in the keyway to accommodate radial movements of the dog in opposite directions relative to the shaft. Each sealing ring is keyed to the corresponding interior dog for rotation therewith by keying means including a second keyway in one and a second key on the other of the dog and ring, this second key extending lengthwise of the shaft and being displace-d from the first-mentioned key (by. which the dog is keyed to the shaft) through an angle of substantially 90 degrees about the axis of the shaft. This second key is slidable radially in the second keyway to accommodate radial movements of the ring relative to the dog in opposite directions which are at substantially right angles to the first-mentioned opposite directions.

With this construction of the new adjust-able ring roller, the means for directly keying two of the parts together for rotation of one with the other serves to accommodateradial movements of one part relative to the other in only :two opposite direct-ions, rather than in four opposite directions as disclosed in the above-mentioned Fahn'nger patent. This effect is made possible by the driving dog interposed between each sealing ring and the common shaft and by the two sets of keying means be.

tween the shaft and driving dog and between the driving dog and sealing ring, respectively, one set being displaced substantially 90degrees about the shaft axis from the other set. Thus, the axes of the sealing rings are readily adjustable relative to the shaft taxis during rotation of the shaft at any practicable speed. Moreover,

,ro'ller, each sealing ring has an annular internal flange provided with opposite end faces and formed with diametrically opposed keyways extending lengthwise of the shaft, and the shaft has diametrically opposed keyways extending lengthwise of the shaft and displaced substantially 90 degrees about the shaft axis from the keyways in the sealing rings.- Each driving dog has two pairs of diametrically opposed keys, the first pair fitting closely in the respective keyways in the shaft while the second pair fits closely in the respective keyways in the internal flange of the corresponding surrounding ring, the driving dog opposing an adjacent end face of this flange.

In a pressure seal embodying my invention, the web passes between a pair of rollers of which only one need be an adjustable ring roller as described above. That is, the other roller may be of conventional form. Means are provided for driving the opposed rollers to feed the web into the pressure vessel or to deliver the web from width are held by this pressure against the webas their common shaft is driven, while those rings located beyond the selvedges of the web are held by this pressure against the opposing roller.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIG. 1 is a side elevational view, partly in section, of a pressure vessel embodying a preferred form of the invention;

FIG. 2 is a sectional view on line 2-2 in FIG. 1;

FIG. 3 is an elevational view, partly in section, of an adjustable ring roller shown in FIGS. 1 and 2;

FIG. 4 is an elevational view of the two rollers illustrated in FTGS. 1 and 2, showing the web passing between the rollers;

FIGS. 5, 6 and 7 are cross-sectional views of the adjustable ring roller showing different positions of the parts on the roller shaft, and

FIG. 8 is an exploded perspective view of a sealing ring and a co-acting driving dog of the adjustable ring roller.

Referring to the drawings, the reference numeral 10 in FIG. 1 designates a pressure vessel in which a fabric or other material in the form of a web W is adapted to be treated under substantial pressure, as by immersing it in a dyeing or other solution at relatively high temperature. The vessel 10 includes a circular plate 10a forming a wall of the vessel at its web inlet end, this plate being suitably secured to the main body 16 of the vessel. Plate 1th: has a horizontally elongated opening 11 through which the web W is adapted to pass into the pressure vessel. A plate 12 is secured to plate 101: and has a horizontally elongated opening (not shown) similar to opening 11 and aligned therewith.

Mounted on the plate 12 is a pressure seal housing indicated generally at 13 and comprising a pair of wall members 14 and 15 which are parallel to plates 10a and 12. These wall members have horizontally elongated openings 14a and 15a, respectively, aligned with the vessel inlet opening 11. Wall members 1415 are. spaced from each other by upper and

lower wall members

16 and 17, respectively, so as to define a chamber 18 for a pair of rollers to be described presently. Bolts 19 extend through the housing parts 1417 and are screwed into the plate 12, thereby clamping these parts together and securing the housing to the pressure vessel 10. The ends of roller chamber 18 are closed by plates 20 and 21, respectively, forming side walls suitably secured to the upper and lower wall members 16-17.

The length of the elongated openings 11, 14a and 15a and of the roller chamber 18 is substantially greater than the width of the widest web to be treated in the pressure vessel, thereby ensuring adequate clearance between the selvedges of the web and the ends of these openings and of the roller chamber as the web is fed therethrough.

Rotatably mounted in housing chamber 18 are upper and lower rollers designated generally at 23 and 24, respectively, and which are engageable with opposite sides of the horizontal web W. The lower roller 24 may be of conventional form. As shown, it comprises a hollow cylinder or tube 24a closed at its ends. A trunnion 25 projects axially from one end of cylinder 24a and is loosely received in a cylindrical recess in plate 20 (FIG. 2). A stub shaft 26 projects axially from the other end of cylinder 24a and extends loosely through an aligned opening in plate 21.

The upper roller 23, as shown particularly in FIGS. 38, comprises a shaft 28 having at one end a reduced portion 29 loosely received in a corresponding cylindrical recess in plate 20. At its opposite end, the shaft 28 has a reduced portion 30 extending loosely through a corresponding aligned opening in plate 21. The shaft 28 is provided with diametrically opposed keyways or radial slots 28a and 28]) extending lengthwise of the shaft. Mounted on shaft 28 is a series of adjacent annular driving dogs 31 through which the shaft extends loosely. Each driving dog 31 has a pair of diametrically opposed keys 32 projecting radially inward from the inner periphery of the dog and extending lengthwise of the shaft. The opposed keys 32 are disposed in the respective opposed

keyways

28a and 28b in the shaft 28. As best shown in FIGS. 5-7, the keys 32 have a close sliding fit in their respective keyways, whereby each driving dog 31 is movable radially in opposite directions relative to the shaft but is incapable of any appreciable rotational movement relative to the shaft.

The upper roller 23 also includes a series of adjacent sealing rings 34 loosely surrounding the respective driving dogs 31. Each sealing ring 34 has an annular internal flange 35 provided with diametrically opposed

keyways

35a and 35b extending lengthwise of the shaft 23. Each driving dog 31 has a second pair of diametrically opposed keys 31a and 31b, the latter keys being disposed in the

respective keyways

35a and 35b in the corresponding surrounding sealing ring 34. As best shown in FIG. 8, the keys 31a31b of each driving dog project from an end face of the dog and extend lengthwise of the shaft into the

respective keyways

35a and 35b in the opposing internal flange 35 of the surrounding sealing ring 34, where these keys have a close sliding fit (FIGS. 5-7), which permits radial movements of the sealing ring 35 in opposite directions relative to the corresponding interior driving dog 31 but prevents any appreciable rotational movement of the sealing ring relative to the driving dog.

By reference to FIGS. 58, it will be observed that the diametrically opposed keying means 28a28b and 32 between shaft 28 and the driving dogs 31 are displaced degrees about the shaft axis from the diametrically opposed keying means 31a31b and 35a-35b between each driving dog 31 and its corresponding surrounding sealing ring 34. Thus, each of these keying means accommodates radial movements of each sealing ring relative to the shaft 28 in opposite directions which are at right angles to the opposite directions of those radial movements of the sealing ring (relative to the shaft) accommodated by the other keying means. In this way, each sealing ring 34 is readily displaceable in any radial direction relative to the shaft and to the other rings, while being held by the keying means against any significant rotation relative to the shaft.

The inwardly extending keys 32 of each driving dog 31 project lengthwise of the shaft beyond that end face of the dog from which the keys 31a31b extend (FIG. 8). Each sealing ring 34 is provided in its internal flange 35 with diametrically opposed slots 36 for receiving, re-

spectively, the projecting ends of the keys 32 of the corresponding driving dog 31. The slots 36 are substantially wider than the keys 32 so that these projecting part of keys 32 cannot interfere with those radial movements of the sealing rings which are accommodated by the keying means 31a-31b and 35a35b. As shown in FIG. 3, the. driving dogs 31 are arranged back-to-back in pairs on the shaft, so that each driving dog of each pair has its keys 31a-31b32 extending lengthwise of the shaft in the direction opposite that in which the keys of the other driving dog extend. Likewise, the sealing rings 34 are arranged in pairs, each pair having its internal annular flanges 35 positioned to provide an annular space for the main bodies of the corresponding pair of back-to-back driving dogs 31 (FIG. 3). It will be understood, however, that it is not essential to arrange the driving dogs and sealing rings in pairs as described above. While this arrangement provides more eflicient utilization of the available space, it is possible, for example, to center the internal flanges 35 relative to the ends of the respective sealing rings 34 and to arrange the driving dog 31 so that their respective keys 31a--31b-32 extend in the same direction along the shaft 28.

The shaft 28 is also provided with end rings 38 of substantially a greater length than the intermediate rings 34.

j

43 and 44 are connected These end rings 38 are'mounted directly, though loosely, on shaft 28 and are formed at their outer ends with annular internal flanges 38a, respectively. The latter flanges serve to reduce the diameter of the bores extending axially through the respective end rings and through which the shaft 28 extends loosely. The internal flanges 38a surround the

reduced end portions

29 and 30, respectively, of the shaft; and each of them has a pair of diametrically opposed keyways 39 extending lengthwise of the shaft.

Pins

40 and 41 extend diametrically through the respective

reduced end portions

29 and 30 of the shaft and have their ends disposed in the keyways 39 in the respective end rings. Accordingly, the pins 40-41 serve to key the end rings 38 to the shaft for rotation therewith.

As shown in FIG. 4, the end rings 38 arelocated well beyond the selvedges of the web W, so that only the narrower intermediate rings 34 of roller 23 are engageable with the web. For this reason, it is unnecessary to key the end rings 38 to the shaft through driving dogs as in the case of the rings 34. Due to the loose mounting of the ends of shaft 28 and the opposing lower roller 24 in the housing plates 20-21, the pressure acting on the rollers from pressure vessel causes the end rings 38 to maintain contact at their peripheries with the periphery of the opposing roller 24 as the rollers are driven. The thickness of web W (FIG. 4) is accommodated by the described mounting of sealing rings 34 on shaft 28, which allows those rings opposite the web W to maintain contact at their peripheries with the web while rotating about an axis displaced from the axis of shaft 28 through a distance substantially equal to the web thickness. The

other rotating rings 34 and the end rings 38, being located beyond the selvedges of the web, are maintained under the aforesaid pressure in direct peripheral contact with roller 24 while rotating about the axis of shaft 28. The

rollers

23 and 24 can, of course, accommodate a web having a different width than that shown in FIG. 4, it being understood that as the web width increases, the number of rings 34 maintained in direct contact with the opposing roller 24 will decrease, and vice versa.

The effect of the described mounting of rings 34 on shaft 28 is illustrated in FIGS. 5-7. As shown in FIG. 5, the ring is concentric to the shaft, the opposed keys of each of the two pairs 32-32 and Ella-31b extending equal radial distances into their respective keyways. In FIG. 6, the ring axis has been displaced below the shaft axis, the upper key 32 having slid radially inward in its keyway concurrently with outward sliding of the lower key 32 in its keyway. In FIG. 7, the ring axis has been displaced to the left of the shaft axis, the key 31a having taken a deeper position in its keyway concurrently with v the opposing key 31a taking a shallower position in its Referring to FIGS. 1 and 2, the

rollers

23 and 24 are adapted to be driven in opposite directions to feed the web W between the nip: of the rollers and into the pressure vessel 10. The driving means comprise hollow

flexible tubes

43 and 44 having ends of square cross-section which closely receive the outer end portions of the

parts

30 and 26, respectively More particularly, the end of the reduced portion 30 of shaft 28 and the end of the trunnion 26 of roller 24 are formed with square cross-sections so that they will fit closely in the adjacent squared ends of the respective tubes 43-44, thereby affording readily detachable connections through which rotation of the tubes will drive the corresponding rollers. A gear housing 45 is secured to the seal housing 13 and contains parallel shafts 46 and-47 suitably mounted for rotation about fixed axes. At their outer ends, the tubes to adjacent ends of shafts 46 and 47 through flexible couplings 43a and 44a, respectively. The shafts 46 and 47 are interconnected through intermesh'ing gears 48-49, the shaft 46 extending through the outer end of housing 45. A sprocket wheel 50' is mounted on the outer end of shaft 46 and is adapted to p in series.

be driven through a sprocket chain 51 from an electric motor or other suitable power source '(not shown).

The flexible tubes 43-44 and flexible couplings 43a- 44a serve to drive the

rollers

23 and 24 in opposite directions from the power source while permitting self-adjustment of the roller axes Within the limits of the aforementioned loose mounting of shaft 28 and roller 24 in their hearing plates 20-21. Thus, under the pressure from vessel 10, the driven

rollers

23 and 24 are urged toward each other so as to maintain direct peripheral contact between roller 24 and the opposing end rings 38 as well as the intermediate rings 34 located beyond the web selvedges, as previously described. As shown in FIG. 2, each flexible tube 43-44 is surrounded by a tubular sleeve 52, there being a substantial clearance between the fiexible tube and its surronding sleeve so that the latter will not interfere with rotation or deflection of the flexible tube. The opposite ends of the sleeves 52 are bolted or otherwise secured to the gear housing 45 and the plate 21, respectively, whereby these sleeves serve to support the gear housing on the seal housing 13.

The ends of the rollers 23-24 are in sliding contact with the respective opposed bearing plates 20-21 of the seal housing, so as to prevent any substantial escape of pressure from the vessel around the ends of these rollers. The bearing plates 28-21 may be made of a wear-resistant material adapted to provide a good seal against the opposed ends of the rollers. The seal is completed by bearing

pads

54, 55 and 56 (FIG. 1) secured to the housing 13 within the roller chamber 23 and extending along the entire length of this chamber. As will be observed in FIG. 1, the pressure in vessel 10 is communicated through openings 11 and 14a to the roller chamber 18 and partly around the periphery of upper roller 23 to the upper part of the roller chamber. This pressure is also communicated partly around the periphery of lower roller 24 to the lower left corner portion of chamber 18. According- 1y, as the rollers 23-24 are driven, the pressure from vessel Ill acts upon these rollers to urge them together at their peripheries and to urge upper roller 23 against sealing pad 54 while urging lower roller 24 against sealing pads 55 and 56. As a result, a highly effective seal is provided against pressure from the vessel escaping around the peripheries of the rollers or through the nip between the rollers. The bearing pads 54-56 may be made of any suitable wear-resistant material affording a good sealing action with the roller peripheries. It will be understood, however, that the rollers automatically take up any wear of these pads, due to the loose mounting of the rollers in the seal housing, as previously described.

The

rings

34 and 38 of roller 23 are held in abutting relation end-to-end by theirconfinement between the hearing plates formed by housing walls 20' and 21 (FIG. 2). Thus, escape of pressure through this roller is effectively resisted, and the rings 34 opposite the web W form a substantially continuous cylindrical surface which presses the web against the opposing roller 24 as the web is fed by driving of the rollers.

While I have shown only one pair of rollers in the seal housing 13, an additional pair similar to that illustrated may be arranged in this housing to provide dual seals Also, while I have disclosed a pressure seal for only the inlet of the pressure vessel 10, it will be understood that a similar pressure seal may be used at the outlet end of the vessel. I

To avoid excessive condensation of vapors from the pressure Vessel 10, I have foundit desirable to provide means for heating the seal housing 13. For this purpose, I have shown an electric blanket 58 substantially enclosing the housing, this blanket comprising a fabric covering containing electric wiring 59 adapted to be energized from a current source (not shown).

It will be apparent that the bearing pad 56 serves merely as a vertical positioning or stabilizing element for the rollers 23-24, rather than as sealing element. In fact, the vessel pressure is communicated to the lower righthand corner portion of roller chamber 18 from its lower left-hand corner portion, as through a passage 18a in wall member 17 (FIG. 1). The bearing pads 61 and 62 permit the seal to be used to retain a partial vacuum in the vessel, in which case the rolls are displaced to the left into contact with these pads.

I claim:

1. In combination with a pressure vessel for treating material in the form of a web, a housing forming a passage communicating with the vessel interior and through which the web is adapted to be fed into the vessel, a sealing roller rotatably mounted in the housing in position to engage one side of said web, a shaft rotatably mounted in the housing opposite said roller, a plurality of adjacent annular driving dogs through which the shaft extends loosely, a plurality of adjacent sealing rings loosely surrounding the respective driving dogs, means keying each dog to the shaft for rotation therewith and including a first keyway in one and a first key on the other of said dog and shaft, said key extending lengthwise of the shaft and being slidable radially in the keyway to accommodate radial movements of the dog in opposite directions relative to the shflt, means keying each sealing ring to the corresponding interior dog for rotation therewith and including a second keyway in one and a second key on the other of said dog and ring, said second key extending lengthwise of the shaft and being displaced from said first key through an angle of substantially 90 degrees about the axis of the shaft, said second key being slidable radially in said second keyway to accommodate radial movements of the ring relative to the dog in opposite directions which are at substantially right angles to the first-mentioned opposite directions, whereby said rings are engageable with the opposite side of the web and form with said shaft and dogs an adjustable ring roller, means for driving said rollers to feed the web into the vessel, and sealing elements in the housing against which said rollers are adapted to be urged by pressure in the vessel, the rollers co-acting with said sealing elements and with each other to substantially seal said passage while engaging the opposite sides of the web.

2. The combination defined by claim 1, in which said sealing roller and said shaft are loosely mounted in the housing for movements relative to each other and to the sealing elements, said driving means including flexible driving shafts operatively connected to said sealing roller and shaft, respectively, for accommodating said relative movements.

3. The combination defined by claim 1, comprising also means for heating the housing to prevent excessive condensation of vapors from the pressure vessel.

4. An adjustable ring roller comprising a rotary shaft, a plurality of adjacent annular driving dogs through which the shaft extends loosely, a plurality of adjacent sealing rings loosely surrounding the respective driving dogs, means keying each dog to the shaft for rotation therewith and including a first keyway in one and a first key on the other of said dog and shaft, said key extending lengthwise of the shaft and being slidable radially in the keyway to accommodate radial movements of the dog in opposite directions relative to the shaft, and means keying each sealing ring to the corresponding interior dog for rotation therewith and including a second keyway in one and a second key on the other of said dog and ring, said second key extending lengthwise of the shaft and being displaced from said first key through an angle of substantially degrees about'the axis of the shaft, said second key being slidable radially in said second keyway to accommodate radial movements of the ring relative to the dog in opposite directions which are at substantially right angles to the first-mentioned opposite directions.

5. An adjustable ring roller according to claim 4, in which said first keyway is in the shaft, said second keyway being in the sealing ring, both of said first and second keys being on the driving dog.

6. An adjustable ring roller according to claim 4, in which said first keyway is in the shaft, said second keyway being in the sealing ring, both of said first and second keys being on the driving dog, each sealing ring having an annular internal flange in which said second keyway is formed, said flange having opposite end faces, each driving dog opposing an adjacent end face of the flange of the corresponding surrounding sealing ring.

7. An adjustable ring roller according to claim 4, in which said first keyway is in the shaft, said second keyway being in the sealing ring, both of said first and second keys being on the driving dog, each sealing ring having an annular internal flange in which said second keyway is formed, said flange having opposite end faces, each driving dog opposing an adjacent end face of the flange of the corresponding surrounding sealing ring, each flange also having a lengthwise slot receiving said first key on the corresponding driving dog and substantially wider than said first key.

8. An adjustable ring roller comprising a rotary shaft, a plurality of adjacent annular driving dogs through which the shaft extends loosely, a plurality of adjacent sealing rings loosely surrounding the respective driving dogs, each sealing ring having an annular internal flange provided with opposite end faces and formed with diametrically opposed keyways extending lengthwise of the shaft, the shaft having diametrically opposed keyways extending lengthwise of the shaft and displaced substantially 90 degrees about the shaft axis from said keyways in the sealing rings, a first pair of diametrically opposed keys on each driving dog, said first keys fitting closely in the opposed keyways, respectively, in the shaft and being slidable therein radially of the shaft to accommodate radial movements of the dog in opposite directions relative to the shaft, and a second pair of diametrically opposed keys on each driving dog, the keys of said second pair fitting closely in said opposed keyways, respectively in the internal flange of the corresponding surrounding ring and being slidable therein radially of the shaft to accommodate radial movements of the ring relative to the corresponding dog in opposite directions which are at substantially right angles to the first-mentioned opposite directions.

9. An adjustable ring roller according to claim 8, in which each driving dog opposes an adjacent end face of the internal flange of the corresponding surrounding sealing ring.

10. An adjustable ring roller according to claim 8, in which each driving dog opposes an adjacent end face of the internal flange of the corresponding surrounding sealing ring, said flange also having diametrically opposed lengthwise slots receiving the keys of said first pair, respectively, on the corresponding driving dog, said slots being substantially wider than the keys of said first pair.

References Cited in the file of this patent UNITED STATES PATENTS 2,873,597 Fahringer Feb. 17, 1959