US2419623A - Shaft seal - Google Patents

Description

Patented Apr. 29,1947 I I um 'r zp STATE s PATENT OFFICE sum sear.

' Mortimer L. Bottcher, Montgomerycounty, Ohio,

assignor to The Duriron Company, Inc., Dayton, Ohio, a corporation of New York Application October 4, 194:, Serial No. 504,827

w The present invention relates to shaft seals 3 Claims. (CL 286-11) for centrifugal pumps which are designed to opcrate at considerable velocitiesland adapted to handle corrosive fluids.

In the case of pumps which handle acid-com, Y taining solutions'aud which involve an impeller secured to an overhanging shaft, it becomes necessary to prevent the creepage of the fluid from the position of the impeller along the surface of the shaft, because unless such creepageis blocked the acid-containing liquid might reach the bearings on which the shaft is .lournaled.

It will be understood that in pumps of this character those parts which come directly into contact with the liquid are made of a non-attackable metal such as silicon iron, but metal of this character is so hard that it is practically un-- machinablek Those parts that require finishing to size are necessarily made of a 'machinable metal which is subject to attack by the acid and for that reason the contact of acid with those parts must be avoided.

While a number of seals to prevent creepage phragm which serves to prevent longitudinal flow or creepage of the liquid.

The invention will be better understood when reference is'made to the following description and the accompanying drawings, in which:

Figure 1 represents a fragmentary longitudinal sectional view of the improved seal as applied to a typical form of pump. This view is taken approximately along the line |---l .in Figure 2 and looking in the direction of the arrows but somewhat enlarged:

Figure 2 is a transverse sectional view of the structure shown in Figure 1 taken along line 2--2 and looking in the direction of the arrows. 7

Referring more particularly to Figure 1, reference character 8 generally designatesthe casing of a centrifugal pump of the double walled type, the walls being indicated at 2 and 3 respectively. The casing terminates at its periphery in a volute chamber to which the outlet conduit (not shown) is connected. A large cylindrical portion 4 which serves as the inlet conduit, as indicated by the of liquid have been proposed in the art, many of them are unsatisfactory for different reasons,

mainly due to the fact that they begin to wear after a short period of time and unless immediately adjusted or repaired allow small but important amounts of fluid to get past the seal and damage the shaft, bearings, or other attachable parts.v Still other types of seals are of compiicated construction, hard to assemble,

and dimcult to adjust and to replace.

communicates with the interior 'of the casing NTOW.

The central opening through the cylindrical portion 4 may have a curvilinear surface as indicated at 5 and there is secured to this surface a plurality of equidistantly disposed longitudinally extending guide ribs or lugs 6 which serve to prevent swirling or eddy current motion in the fluid as it enters the casing. The front wall 2 of the casing-has a flat inner surface against which the blades of the impeller The fact that the pumps which handle acidcontaining liquids usually involv fairly heavy impellers and are operated at considerable velocities, also enhances the diillculties of'aflordin'g complete obstruction to creepage liquid without entailing undue friction or excessive wear.

The primary object of the invention is to pro-,- vide an improved form of seal structure and particularly one which employs only relatively sim. ple parts and wherein adjustments to take up wear may be readily effected. 4

Still another object is to provide a seal structure which is particularly adaptable to high pressure pumps involving impellers which travel at considerable speeds and in which even the slight,

est amount of liquid being delivered by the pump is prevented from creeping along the shaft from the impeller casing.

These objects are attained in brief by employing a. graphite seal member for providing the obstruction of radial flow of liquid and replacing the usual type of packing ring by a flat diahave a running clearance, while the other or rear wall 3 of the casing takes on a conical shape which provides a bearing surface for the rear side of the impeller. The latter may include a centrally disposed radially extending web element l which together with the hub 5 forms an annular.

There are a plurality of blades 43- recess i2. secured to the web and equidistantly positioned about the recess H the purpose of these blades being to provide a suction effect at the rear of the impeller. A number of openings ii are abscess o! liquid which is being forced out of the pump by the main blades on The web '5 extends to a cylinder It and the cylinder terminates at its left hand end in an enlarged or flange portion it which forms one of the sealing surfaces. The hub ii and the cylinder it are cored'to leave a relatively large recess il in order to lighten the weight of provide a structure by which the impeller is secured to its shaft.

The flange portion 98 is provided with a centrally disposed opening it for tightly receiving a liner i9. This liner is hollow and the right hand end thereof has s configuration such as snugly to fit the inner surface of the spherical hub portion 8. The liner 8! is threaded over a mrti'on of its length to receive and 2d of the driving shaft 2!. The latter is provided with a shouldered portion 22which fits tightly within the liner or sleeve is as shown on the drawings.

While the structure described up to this point operates quite effectively as a pump when the the left in the form orthe impeller and also to s in line with the left hand surfucc of the, element 23 but as shown on the drawings. the bearing member projects slightly more to the left and the purpose of this is to accommodate wear as the pump is being used.

Directly adjacent the left hand surface of the enlarged portion 26 and the sealing member 23, there is a packing washer 28 which may be made of several thicknesses or zubberiued cloth. This washer has an inner diameter somcwhat larger than the shaft and an outer disme ter of approximately the same size as the em the threaded shaft ii is rotated by an electric motor (not shownl it has been found that notwithstanding the presence of the vanes l3 slight amounts of the fluid being handled by the pump inevitably finds its way by creepage over the shaft. In order to avoid this creepege it has been pro :1 employ a graphltesoaling ring which inst the left hand surface of the flange it to ts. core or the fluid which tends to flow radio: direction, and addition packing rings have been proposed to blocl: any part of orccpagc that tends to flow tudinai direction. While such a structure is completely satisfactory in owrstlon the arrange in the longi ment is somewhat complicated, particularly as regards the use and adjustment of the packing rings.

In accordance with the present invention E propose to discard the packing rings entirely and to use in their place a washer of packing material and to secure the washer at its peripheral edge, leaving the inner annular portion thereof to serve as a seal. It has been found in practice that the washer is not only less expensive than the use of two or more packing rings, but in addition is more effective in providlng an absolute blocking effect for the fluid which tends to move lengthwise between the various parts of the seal at the rear of the impeller.

Thus, the shaft end all other parts which llie subject to attack by the acld containing fluid which is being forced into the White chamber by the impeller are completely protected from such fluid. Directly adjacent the flange portion l8 of'the impeller there is a sealing ring 23 of a self-lubricating material such as graphite which loosely surrounds the shaft and has a diameter substantially equal to the diameter of the flange portion it.

The comically shaped rear wall 8 of the cuslog is extended in the longitudinal direction to form a cylindrical member it which terminates in an enlarged or humped portion 25. The cylinder 24 has an interior diameter such as to receive the sealing member 23. The left hand surface of the enlarged portion 2513 not directly larged portion 25. The washer it? may be merited or otherwise secured to the sealing ring 223.

In order to apply longitudinal pressure against the inner annular portion of the washer 26 there by forcing the sealing ring it to the right. flanged metal ring El which fits loosely over the sbait'fii may be provided. This ring has a flat annular surface which bears against the washer 28. Pressure is applied to the ring 2'5 by means of a plurality of springs indicated at 2t. There is a fairly thick ring generally desig noted by 3b surrounding the shaft H but spaced therefrom. this ring having longitudinally radially extending portions 34 and 32 reepectively. The horizontal portion is provided with three or more openings equldistantly spaced about the periphery and counter-bored from the right hand face in order to accommodate the com pression springs 28. The right hand end of these springs bears against flat surface of the member 2? so as to force the said member against the washer it, which in turn applies pressure between the sealing ring 23 and the sealing our face of the flange id. The force exerted by these springs may be adjusted by means of o plurality oi set screws which are threaded into the hand end of the ring The springs 28 togather with the adjustable set screws 33 serve to provide a yieldable contact between th packing washer and the sealing ring. This, in turn, causes the sealing ring 23 to yieldingly contact the flange portion it.

The member 30 may be secured in place by be in: bolted as indicated at 86 or in any other manner attached to a split ring it. This split ring has an interior configuration such as to fit over the hump portion 25 of the casing, and the two halves of the ring may be secured together by a. pair 01- oppositely disposed clamp bolts 3? which pass through lugs 38.

It is apparent that when the set screws 33 have been given proper adjustment the ring .27 is packing ring 26 and to move the sealing ring 23 more tightly against the flange 56. Conce-= quently, by regulating these various adjustments it is apparent that as much or as little contact pressure can be exercised as desired at the lunetion between the sealing ring and the flange. Thus, any liquid that tends to flow to the rear of the impeller and is not sucked upwardly by the'blades I3 into the openings H is immediately blocked from passing radially downwardly between the sealing ring 23 and the flange i8 is also blocked from creeping longitudinally al 113 the outer periphery of the sealing ring 23 because the packing ring 28 constitutes an effectlve barrier at this point.

Thus, all possible passageways for the leakage liquid to pass from the rear side of the impeller to the bearings in which the shaft 2| is journalecl are completely stopped by the combination of the packing washer 2B and the sealing ring 28.

e the f the m as eifeetive in preventing longitudinal cmme oi the liquid as is the use oi packing r hgm'which' are not only more expensive to make but also re-- quire a more expensive structure to accommodate the rinse. it will be understood in this connection that the packing rings usually necessitate annular recesses of proper dimensions and suitable positions, but no such expense is incurred by the use or a packing washer because the outer edge oi the washer is entirely free from contacting the metal and the washer is securely held by oomprwion between the ring 80 and the flange '28. It is also apparent that'the use of the packing washer Provides a construction which is not only simple to fabricate but in addition is easy to install, dismantle, and reassemble.

It will be understoodthat all of these parts of the structure shown in Figure 1 which come di-' rectly into contact with the acid=oontainlng fluid being pumped at the impeller are made of a nonattachable material such as silicon iron. The

remaining parts, which constitute the seal, may be made of ordinary steel or iron since by reason of the improved combination of parts, including the packing washer and the sealing ring. posimerifiisuuite.

acidosis mounted on the shaft, said casing having a cylindribal member surrounding said sealing ring, said member having an' enlarged end portion, a thick ring surrounding said shaft having longitudinally and radially extending portions, a flexible washer surrounding said shaft, means engaging said radially extending portion and said enlarged end portion for clamping said washer between the enlarged end portion of said member and the radially extending portion of said thick ring, the radially inner portion of said washer engaging said sealing ring. said longitudinally extending portion of said ring having a plurality of openings facing said washer, springs in said openings acting to force said washer and said sealing ring along said shaft to cause engagement of the sealing ring with said part, the other end of said sealin: ring normally extending beyond the enlarged end of said member and in the direction of said thick ring whereby to'initially cause deformation or bending of said washer to oifset the radially inner part of said washer from the outer clamped portion in a direction away from said shaft part,

'tively none of the acid-containing fluid can ever 1 reach thoseparts made of a workable and therefore attachable material.

While the apparatus herein disclosed and de scribed constitutes a preferred form of the invention, yet it is to be understood that the apparatus is capable oi .ralteration without departing from the spirit of the invention and that all such modifications as follow within the scope of the appended claims are intended to be included herein.

Having thus fully described my invention, what llclaimasnewanddesiretosccurc y Fatent, is:

iJlsealincludingacasinmashafmsaidseal comprising a sealing ring surroundlns the shaft and having a side adapted to bear against a part mounted on the shaft, said casing having a cylindrical member surrounding said sealing ring, said member having an enlarged end portion, a thick ring siu'rounding said shaft having longitudinally and a ilanged ring surrounding said shaft and interposed between the ends of said springs and saidwasher. I

3. 11- seal including a casing. a shaft, said seal comprising a graphite sealing ring surroimding the shaft and having a sldeadapted to bear against a part mounted on the shaft, said casing having a cylindrical member surrounding said sealing ring, said member having an enlarged end portion, a thick ringsurrounding said shaft hav= ing longitudinally and radially extending portions, a flexible washer surrounding said shaft, means engaging said radially extending portion and said enlarged end portion for clamping said washer between the enlarged end portion of said member and the radially extending portion of said thick, ring, the radially innerportion of said washer engaging said sealing ring, said longituoxtending portion of said ring having a plurality of openings facing said washer. prings insaid-openings acting to force said washer and and radially extending portions, a flexible washer surrounding said shaft, means engaging said radially extending portion and said enlarged end portion for clamping said washer between'the enlarged end portion of said member and the radially extending portion of said thick ring, the radially inner portion of said washer engaging said sealing rin said longitudinally extending portion of said ring having a plurality of openings facing said washer, springs in said openings actihg to force said washer and said sealing r1118 along said shaft to cause engagement of the sealing ring with said part, the other and of said sealing ring normally extending beyond the eniarged end of said member and in the direction;

of said thick ring whereby to initially cause deformation or bending of said washer to oiiset the radially inner part of said washer from the outer slumped portion in a direction away from said shattpart.

2, A owl in a casing, a shaft, said seal eomm'ising a sealing ring surroimdins the shaft said sealing ring along said shaft to cause on gagement of the sealing ring with said part, the

other end of said sealing ring normally extending beyond the enlarged and of said member and in the direction of said thick ring whereby to initially cause deformation or bending of said washer to oifset the radially inner part ofsaid washer from-the outer clamped portion in a direction toward said springs. and means tor in I NORM 1:.

REFERENCES cm The following references are of record in the his of this patent:

dividuallyadiustingsaid springs. I

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