subject: Self-contained Rotary Mechanical Seals [print this page] A self-contained rotary mechanical seal is provided for mounting on a rotating shaft to form a seal between the shaft and structure on a housing through which the shaft extends. The seal includes an annular lug holder to be secured to the shaft as by set screws. A plurality of lugs extend from the lug holder parallel to the shaft.
Tines extend circumferentially from the ends of the lugs concentric to the axis of the lug holder. A belleville washer assembly is disposed within the lugs. An annular carbon seal washer also is disposed at least partially within the lugs. The seal washer includes radially extending shoulders dimensioned to engage the lugs and tines. In assembled form, the shoulders 15 of the carbon seal washer are urged by the spring force of the belleville washers against the tines. The tines retain the carbon seal washer in a position partially within the lugs.
In a rotary mechanical seal of the type having an annular base adapted for mounting on a rotating shaft, a seal washer, and a spring means located between the base and theseal washer for urging said seal washer against a housing through which the shaft extends to form a seal, the improvement comprising:a plurality of longitudinal lugs extending from said annular base in circumferentially and radially spaced-apart relationship with said shaft such that said spring means and seal washer can be received between said lugs and shaft;circumferential projections extending away from said lugs on the ends of said lugs opposite said base; anda plurality of circumferential projections extending radially outward from said seal washer in circumferential spaced-apart relationship sufficient for receiving said lugs therebetween so that said seal washer and base can be engaged for rotationand secured against longitudinal separation under the action of the spring means by inserting said seal washer under said lugs and twisting said seal washer until the seal washer projections are locked behind the lug projections.
Mechanical seals have long been known and used for forming a seal between a rotating shaft and a housing through which the shaft extends. Typically, a carbon seal washer is mounted to rotate on the rotating shaft and to slidably engage a sealseat mounted in the housing. The sliding engagement between the carbon seal washer and the seat forms a fluid-tight seal that, in conjunction with additional stationary seals, is operable to complete a fluid-tight seal between the shaft and the housing.
Often a plurality of coil springs are provided to force the carbon seal washer against the seal seat on the housing. In this assembly, the carbon seal washer is continuously urged along the shaft toward the seal seat so that the washer and theseat are maintained in a firm engagement even after both have been used for long periods of time.
However, problems have been encountered with the use of mechanical seals having coil spring forced carbon seal washers. Conventional mechanical seals utilizing a multiple coil spring arrangement often utilize coil springs mounted in a recess inthe seal housing. The coil springs located in such recesses are susceptible to fouling and clogging by suspended particles and the like. The fouling of the springs may cause the seal to malfunction.
Further, in the assembly of a mechanical seal utilizing a multiple coil spring arrangement, usually, each individual spring must be properly positioned in the mechanical seal housing, and then the carbon seal washer must be forced into the sealagainst the spring force. Finally, some measure must be taken to retain the carbon seal washer within the seal housing resisting the spring force. This assembly procedure has proved difficult, and installation of such seal was often cumbersome. Mechanical seals of this type are generally expensive to manufacture.
The present invention overcomes the foregoing problems and others long associated with mechanical seals by using an anti-clog, self-cleaning, belleville spring arrangement and by using an annular seal housing designed to facilitate assembly. Inthe present invention, a mechanical seal includes an annular base for mounting on a rotating shaft within a housing. A plurality of lugs extend from the base and circumferential projections extend from the ends of the lugs. A seal washer is providedfor being mounted at least partially within the lugs and is dimensioned for snuggly encompassing the shaft. The seal washer includes radial projections for engaging the circumferential projections. A spring is provided within the lugs between the baseand the seal washer for urging the radial projections of the seal washer against the circumferential projections extending from the lugs. In this manner, the seal washer is retained partially within the lugs and mounted on the mechanical seal. When themechanical seal is mounted on the shaft, the spring structure is operable to urge the seal washer against housing structure to form a seal. Also, the lugs will engage the radial projections to force the seal washer to rotate with the lugs and shaft.
In accordance with a particular aspect of the present invention, a mechanical seal is provided for use on a rotating shaft extending through a housing. An annular lug holder is dimensioned to snuggly engage the shaft and includes a plurality offasteners for mounting the lug holder on the shaft. The lug holder includes a plurality of slots, and a plurality of lugs are mounted in the slots and extend from the lug holder in a longitudinal direction parallel to the axis of the lug holder. Aplurality of tines are provided with two tines extending circumferentially from the end of each lug in a direction perpendicular to the lugs and concentric to the axis of the lug holder.
A plurality of belleville washers are dimensioned to snuggly encompass the shaft and for being disposed between the lugs and the shaft adjacent to and engaging the lug holder. The belleville washers have sufficient elasticity to resilientlyoppose compression. A contact washer is provided for encompassing the shaft and for being disposed adjacent the belleville washers. An annular carbon seal washer is center-bored for snuggly encompassing the shaft and is disposed partially within thelugs adjacent the contact washer. The seal washer includes an annular recess adjacent the contact washer and an annular nose surface facing away from the lug holder. An O-ring and a back-up ring encompass the shaft and are disposed within the recess inthe seal washer to form a seal between the shaft and the seal washer.
A plurality of shoulders extend radially outward from the seal washer for engaging the tines to retain the seal washer partially within the lugs. The shoulders have a sufficiently small width to pass between the confronting ends of the tinesextending from adjacent lugs and have a sufficient radial extension to engage the tines and lugs. The mechanical seal may be assembled by inserting the seal washer partially within the lugs to engage the contact washer and to compress the bellevillewashers. The seal washer is then rotated until the shoulders engage the lugs. Then, when the seal washer is released, the belleville washers will urge the seal washer forward until the shoulders engage the tines to retain the washer on the mechanicalseal.
A seal seat is mounted in the housing and includes a face surface for slidably engaging the annular nose surface of the seal washer to form a seal. The mechanical seal is positioned on the shaft relative to the housing such that the seal washeris urged against the seat by the spring force of the belleville washers. In this position, the seal washer is displaced rearwardly toward the lug holder such that the shoulders extending from the seal washer do not engage the tines.
