Pumping rings, used to promote circulation in seal systems, were developed in the early s.
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By , mechanical seals were used with such regularity in the refining and process industries that the American Petroleum Institute included seal specifications in the first edition of its Standard 610, Centrifugal Pumps for General Refinery Services. Because of problems when converting from packing to seals, the seal specifications (just over one page in length!) were mostly concerned with stresses, bolting and gasketing. Glands were required to use a minimum of 4 bolts of at least 2 inch diameter and to have a nonferrous close clearance throttle bushing. In , the American Standards Association attempted to standardize some pump dimensions and nomenclature. This work led to the American Voluntary Standard (AVS) pump which eventually became the ANSI pump.
By , many of the conceptual designs and application guidelines that are in use today had been developed (Elonka, ). Commercially available designs included both rotating and stationary flexible elements, balanced and unbalanced hydraulic loading, rubber and metal bellows, and a wide variety of spring designs and types. Secondary sealing elements included O-rings, wedges, U&#;cups and various packings. Carbon-graphite was widely used as a seal face material but the mating seal face was often cast iron, Ni-resist, 400 series stainless steel, Stellite or aluminum oxide ceramic although tungsten carbide was coming into use. Hard facings, especially Stellite, were often applied to stainless steel and used in process pump seals. When two hard faces were used, the carbon-graphite face was usually replaced with cast iron, bronze or sometimes tungsten carbide. Then, as now, stainless steel was widely used for springs, retainers, sleeves and glands. Temperature ratings for these seals were in the ranges of 200 to 800 F depending on design and materials. Pressure ratings were up to psig depending on design and materials. Single and multiple (called &#;double&#; and &#;tandem&#;) seal arrangements were used as necessary to accomplish the required performance. It is doubtless fair to say that the allowable leakage for mechanical seals in the &#;s was significantly more than today. After all, in those days, leakage from seals was compared to leakage from packing and the mechanical seal was a definite improvement!
In , the Japanese NOK Corporation developed its first general purpose mechanical seal.
Karl Schoenherr, himself a major contributor to mechanical seal technology, credits Herbert B. Hummer, chief engineer of Durametallic, with the developing the pressure-velocity product (PV) as a guideline for design and application of mechanical seals (Schoenheer, ). Hummer&#;s work on PV began in the early &#;s. In addition to PV, Hummer demonstrated the effects of shaft deflection on seal performance and developed guidelines for limits. Schoenherr, then Chief Engineer of John Crane, promoted the PV concept as well as published many articles on the basics of mechanical seals.
Metal bellows have been used as sealing elements in mechanical seals, valve stems and other equipment since . In , Sealol introduced the edge welded metal bellows seal. Previously, metal bellows seals had used a formed bellows which was much thicker and stiffer than the edge welded metal bellows. The early focus was on high temperature applications.
DuPont commercialized the first fluoroelastomer, Viton A.
H. A. CLARK June 19, .
OIL SEAL 2 Sheets-Sheet 1 Filed Nov. 2, H. A. CLARK June 19, .
OIL SEAL Filed Nov. 2, 2 Sheets-Sheet 2 Patented June 19, UNITED STATES 01L SEAL Harold A. cal-k, Northbrook, n1., assignor to The Chicago Rawhide Manufacturing Company, Chicago, 111., a corporation of Illinois ApplicationNovember 2, , Serial No. 572,524
3 Claims.
The present invention is concerned with oil seals of the type used in oil-filled housings about moving shafts for the purpose of retaining the oil in the housings and preventing it from leaking out along the shafts.
The principal object of the invention is to provide a self-contained oil seal unit of the type described which will drain freely without trap ping any of the oil or any of the flushing liquid 1 used when changing the oil; which will prevent the axially projecting edge of the sealing leather from coming into contact with the associated bearing; which is exceedingly simple, strong and compact in construction; and which will give an efficient sealing action.
Other more specific objects and advantages of the invention will be evident upon a full understanding of the construction, arrangement and function of the parts combined to produce the improved seal.
Two slightly difierent structural embodiments of the invention are presented herein by way of exemplification, but it will of course be appreciated that the invention may be incorporated in other forms coming equally within the contemplated scope of the appended claims.
In the accompanying drawings:
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Fig. 1 is a diametric section through a housing equipped with the seal of the invention, showing the seal partly in section and partly in side elevation;
Fig. 2 is a diametric section through the seal before installation in the housing;
Fig. 3 is a partially broken away rear end view of the seal; and
Figs. 4, 5 and 6 are views which correspond generally to Figs. 1, 2 and 3 but which show a slightly modified embodiment of the invention.
The embodiment illustrated in Figs. 1 to 3 inclusive will first be described. In Fig. 1, it will be observed that the seal 10 is positioned in a housing 11, adjacent a bearing 12, in encompassing relation to a shaft 13. The seal includes a centrally apertured sheet metal cup 14, a flanged sheet leather packing element 15, a flanged sheet metal multiple-finger spring 16, and a second centrally apertured sheet metal cup 17.
The cup 14 encloses all the other parts, and is preferably provided with a radially extending flange 18 on its rim for abutment with an annular shoulder 19 in the housing. The flange 18 may be employed to advantage in those installations where the cylindrical portion 20 of the bore of the housing in which the bearing 12 is located is of greater diameter than the adjoining portion 21 in which the seal is located. The aperture 22 in the bottom 23 of the cup 14 is somewhat larger than the shaft 13 in order to prevent the cup from contacting with the shaft. The portion 24 of the cup 14 is cylindrical and fits snugly within the portion 21 of the bore of the housing in pressed-fit fluid-tight engagement with the same.
The leather packing element 15 is flexible and is characterized by a flat radially extending portion 25 and a cone-shaped axially extending portion 26. When the seal is applied to the shaft 13, the latter will distend the cone-shaped portion 26 to a certain extent, causing it to assume the more nearly cylindrical form shown in Fig. 1. The packing 15 is positioned in the cup 14 with the fiat portion 25 of the former in contiguous fluid-tight engagement with the flat bottom portion 23 of the latter. The packing is of approximately the same diameter as the inside of the cylindrical portion 24 of the cup, but may be somewhat smaller if desired.
The multiple-finger spring 16 is similar in shape to the packing 15. It has a flat radially extending portion 2'7 which fits tightly against the radially extending portion 25 of the packing, and it has a cone-shaped axially extending portion in the form of a'pl rality of spring fingers 28. The fingers 28 surround the axially, extending portion 26 of the packing and verge gradually into substantial line contact therewith at 29. These fingers exert at all times a'resilient constricting action on the packing close to the edge 30 of the latter and combine with the packing to produce a very effective seal for the shaft at that point.
The inner cup 17 is fixedly positioned with a pressed fit in the cylindrical portion 24 of the outer cup, and is provided with a flat centrally apertured bottom 31 which bears against the flat portion 27 of the spring and clamps the packing and spring together under pressure against the bottom portion 23 of the outer cup.
The above described assemblage of parts is permanent in character and constitutes a com- 1 plete self-contained sealing unit which is entirely separate from and independent of the bearing organization with which it is adapted to be associated.
The improved seal is entirely open at the oilopposing face thereofwhich is. ordinarily the face toward which the edge 30 of the packing projects. This permits the seal to drain out completely when the oil is removed and prevents any trapping of the oil or the flushing liquid by the 110 structure of the cage of the seal. The edge 30 of the leather packing is protected from injury by contact with the bearing by reason of the projection of the rim of the outer cup 14 to a point beyond the edge 30, thereby leaving a little clearance between such edge and the adjacent face 32 of the bearing. v
The modification shown in- Figs. 4, 5 and 6 differs in one respect only from the form shown in Figs. 1, 2 and 3.
It will be observed that the modified form, like the first form, includes an outer cup 33, a leather packing 34, a multiple-finger spring 35 and an inner cup 36. The rim of the outer cup 33, instead of being turned outwardly, however, is turned inwardly in a narrow inwardly spun flange 37 which abuts against the edge of the rim on the inner cup 36 and holds the latter tightly clamped against the spring and packing. Because of this interlock, a pressed fit between the inner cup and the outer cup is not absolutely nec-- essary. In'this form, as in the other, the oilopposing face of the seal is entirely open and the axially projecting edge 38 of the packing terminates short of the plane defined by the inturned flange 3'1 on the outer cup.
I claim:
1. A self-contained seal for insertion as an assembled unit within a tubular housing in encompassing relation to a centrally located shaft, consisting of a fiat centrally apertured sheet metal cup, an annular packing member having a flat radially extending portion and an axially exportion in extended surface contact with the bottomof the cup and with the axially extending portion projecting in the same direction as the rim of the cup,'a fiat ring positioned in the cup against the radially extending portion of the packing in opposition to the bottom of the cup and a plurality of converging spring contact with the axially extending portion of the packing adjacent the free edge .ing portion, which packing member is positioned in the cup with the radially extending portion in extended surface contact with the bottom of the cup and with the axially extending portion projecting in the same direction as the rim of the cup, a flat ring positioned in the cup against the radially extending portion of the packing in opposition to the bottom of the cup and provided with a plurality of converging spring fingers which contact with the axially extending portion of the packing adjacent the free edge of the latter, and a second centrally apertured sheet metal cup of slightly less diameter and depth than the first cup nested within the latter with the bottom of the second cup in engagement with said ring, said outer cup being provided on its rim with an inturned flange in abutment with the rim of the inner cup.
3. A self-contained seal, comprising two centrally apertured generally cup-shaped sheet metal stampings, one of which is nested within the other, with the rims of both stampings pointing in the same direction, a centrally apertured packing having a radially extending portion which is clamped between the'bottoms of the two cupshaped stampings and having an axially extending portion which projects in the same direction as the rims of the stampings, and spring means positioned about the axially extending portion 01' the packing for resiliently constricting the latter on a shaft, said spring means being retained in position by the inner stamping. HAROLD A. CLARK.
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