Bellows-Type Mechanical Seal

Bellows-type mechanical seals are well known in the art. In the conventional seal of this type, the bellows is welded to a support ring which is surrounded by a housing flange. A gasket is positioned in a suitable cavity and the bellows ring is pulled against the flange, thus perfecting the gasket seal between the flange and the ring. Usually one or more set screws are used to pull the ring toward the flange, the set screws being received in openings in the ring bearing against the flange.

In accordance with the invention to be described herein, a bellows-type mechanical seal utilizes a set screw to pull the bellows support ring toward the housing flange to perfect the gasket seal between the ring and the flange. However, the screw opening is partially in the support ring and partially in the body flange, and only the portion of the openings for the set screws in the support ring are threaded. Costly manufacturing steps are eliminated; also manufacturing can be facilitated by using milled parallel threads in the ring set screw opening portion in lieu of the usual machined helical threads. In this alternative construction, the area of contact of the set screw threads and milled parallel threads is generally less than the convention substantially full depth contact between helical threads and the set screw threads.

FIG. 1 is a partial sectional view of a bellows-type mechanical seal utilizing this invention and taken on line 1 of FIG. 2;

FIG. 2 is a partial elevational view of the structure of FIG. 1;

FIG. 3 is an enlarged partial sectional view similar to FIG. 1 showing details of the invention;

FIG. 4 is a view similar to FIG. 2 showing a second embodiment of the invention; and

FIG. 5 is a partial sectional view taken on line 5--5 of FIG. 4 illustrating a detail of the second embodiment.

Referring now to the drawings, and especially FIGS. 1 to 3, there is illustrated a bellows-type mechanical seal assembly 10 associated with a shaft 12 and a housing flange 14. The seal assembly comprises a rotary seal ring 16 supported by a back-up ring 18 axially positioned and fixed to the shaft 10 by a ring collar 20 and a set screw 22, and a stationary seal ring 24, the seal ring 16 having a radially disposed face 26 engaging a radially disposed face 28 of the ring 24. The ring 24 is surrounded by and connected to a metal ferrule 30 to which is welded a bellows 32 constructed, for example, of metal annulii welded together. The actual construction of the bellows is incidental to the invention herein. The bellows 32 is welded, at its opposite end, to a lip of a bellows support ring 34 surrounding the shaft 12. The support ring 34 and the housing flange 14 define a cavity 36 to receive a gasket 38.

When the support ring 34 is drawn toward the flange 14, the gasket 38 provides a fluid tight seal between the flange and the ring. To draw the ring 34 toward the flange 14, a plurality of helically-threaded set screws 40 are used, each being received in an opening 42 defined in part (42A) in the support ring 34 and in part (42B) in the flange 14. The openings 42 are generally equally spaced around the assembly. To facilitate the manufacture of the assembly, only the opening portions 42A in the support ring need be threaded -- the threads 44 matching those of the screws 40. The set screws 40 are shorter than the depth of the openings 42 and bear against the flange 14, so that when driven inwardly, they cause the support ring 34 to move (to the right as viewed in the drawings) and compress the gasket 38.

An alternative arrangement is illustrated in FIGS. 4 and 5. Here the openings defined in part by the support ring 34 and the body flange 14 are identified as 50, the parts being identified as 50A (support ring) and 50B (body flange). The threads 52 in the part 50A are parallel threads, as particularly shown in FIG. 4 and do not match the helical threads of the set screws 40. In this embodiment, the opening part 50A is of smaller size than the opening part 50B; thus the arc of contact between the threads of the screws 40 and the threads 52 is relatively small. Thus the depth of the support ring opening 50A is less than the radius of the set screws 40. The operation of this alternative arrangement is the same as the earlier described embodiment.