Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1998-05-27
2001-04-24
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S548000
Reexamination Certificate
active
06220604
ABSTRACT:
FIELD OF INVENTION
This invention relates to an improved self-adjusting throat bushing for extending the life of packing and more particularly to a system for preventing misalignment of the concentric bushing rings during installation and packing compression.
BACKGROUND OF THE INVENTION
As illustrated in U.S. Pat. No. 5,507,502, a packing life extended ring assembly includes first and second annular rings, with the second annular ring concentricity encircling the first ring. Both rings have tapered surfaces which mate with one another such that when placed in a stuffing box ahead of packing rings, the tapered rings self adjust during the packing compression process.
As discussed in the above-mentioned patent, slurries, abrasives, dry product and many chemicals can be hard on shaft packing. Even with sufficient flush back pressure, dimensional wear and shaft runout can render packing all but useless in a matter of weeks, or even days. Prior to the two part bushing, the only solution had been to shut down the associated system and repack the stuffing box.
One of the problems with the above-identified system for extending packing life through the utilization of concentric rings is the problem that the tapered surfaces, while adjusting in some measure for bore size and other inconsistent diameters, oftentimes result in the slipping of the inner bushing ring with respect to the outer bushing ring out of their proper position and prior to the gland being tightened down to compress the packing rings between the gland and the bottom of the stuffing box. The result is a canting of the inner ring of the throat. bushing with respect to the outer ring of the throat bushing. This causes two problems. First, with the inner ring canted with respect to the outer ring, it is possible that a void will exist between the bushing and the shaft through which packing material can and does extrude. It will be appreciated that the extrusion of the packing ring material into this space or void results in packing ring failure, to say nothing of the abrasion associated therewith.
Moreover, if the concentric bushing rings are not aligned properly, the canting of one ring with respect to the other itself wears against the shaft sleeve to accelerate sleeve wear.
Thus, not only does packing ring extrusion between the rings and the shaft result in packing ring failure, the misalignment of the concentric rings and the cocking of these rings in the stuffing box upon the compression of the packing rings scores the sleeves and again results in an unsatisfactory arrangement.
Thus, rather than extending packing life, the system of U.S. Pat. No. 5,507,502 can reduce packing life due to the inability of the concentric rings to be held in position during compression and due to uneven pressures associated with the canting.
SUMMARY OF THE INVENTION
Rather than providing smooth tapered mating surfaces between the inner and outer rings making up the self adjusting throat bushing, in the subject invention, a tongue and groove type structure is provided in the form of an annular V-shaped in slot in the annulus of the outer bushing ring which mates with a correspondingly shaped ridge at the periphery of the inner bushing ring. This maintains the rings in axial position, one with respect to the other, during the installation and compression process. The slot and ridge structure does permit lateral movement to a limited extent due to the tapered mating surfaces of the inner and outer bushing rings. However, this movement is limited due to an annular V-shape notch in the outer ring which coacts with the mating ridge in the inner ring, such that during installation the inner and outer bushing rings are maintained in position and such that during compression, equal pressures are applied about the bushing rings due to the compression of the packing rings against these throat bushing rings.
The result is that sleeve wear acceleration due to the prior art system is eliminated, while at the same time eliminating both cocking of one bushing ring with respect to the other. The further result is that extrusion of packing into the annulus between the shaft and bushing is eliminated by this ring-locking and alignment structure.
In summary, a self-adjusting interlocking throat bushing is provided in which mating concentric bushing rings are provided with an interlocking annular slot in the outer bushing ring and an annular ridge at the periphery of the inner bushing ring to hold the two rings in axial alignment when bushing is installed and the packing gland is tightened to compress the packing rings between the gland and the bushing. The annular slot/ridge structure prevents canting of the parts of throat bushing during packing ring compression thereby eliminating packing extrusion between the shaft and the annulus of the bushing. Before compression, the concentric rings are held together in alignment so that the bottom ring cannot drop out of its proper position prior to compression. After compression, the locking structure comprising the slot and ridge structure results in the bushing being compressed evenly about the shaft, thereby eliminating misalignment and shaft sleeve wear.
REFERENCES:
patent: 609752 (1898-08-01), Angell
patent: 894880 (1908-08-01), Garlock
patent: 1251807 (1918-01-01), Mongan
patent: 1669030 (1928-05-01), Wilkinson
patent: 1763127 (1930-06-01), Beer
patent: 1767498 (1930-06-01), Young
patent: 3810639 (1974-05-01), Scannell
patent: 3833228 (1974-09-01), Gilliam
Knight Anthony
Patel Vishal
Tendler Robert K.
LandOfFree
Self-adjusting interlocking bushing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Self-adjusting interlocking bushing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Self-adjusting interlocking bushing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2490652