Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1996-02-12
1998-03-17
DePumpo, Daniel G.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277 50, 277123, F16J 1500
Patent
active
057277931
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the sealing of a moving shaft for fluid transfer devices including for example pumps, fans, compressors and agitators. More specifically, the present invention is concerned with a novel packing box configuration.
BACKGROUND ART
In a rotary pump, the shaft projects exteriorly from the pump casing in a zone known as the "packing box" or "stuffing box". These terms were derived from the notion that in order to separate the fluid contained in the casing from the outside environment, some material had to be stuffed or packed around the shaft where it passed through the casing. For example, a common type of rotating shaft seal consists of natural or synthetic fibres or strands which are woven or braided into coils, spirals or die-formed rings. To ensure initial lubrication, the packing material are usually impregnated with a lubricant.
The packing, in order to create an efficient seal, is deformed by compression to reduce any gaps between the shaft and the packing. This compression of the packing generates friction with the shaft, resulting in heat on the shaft.
The traditional packing box design comprises a housing mounted around the shaft and a gland follower. The packing is installed inside the chamber and is deformed by the gland follower against a bushing in the chamber. The more the gland follower is pressed towards the interior of the packing chambers the more the packing rings will be compressed. One main drawback with such a design is that most of the packing compression is applied on the packing rings located farthest away from the casing. Consequently, the greatest friction and thus heat generation is applied on the shaft at some distance from the shaft/casing interface.
To help control heat, a device commonly knows as "lantern ring" is used in conjunction with the packing. It consists of a metal or plastic ring placed between groups of packing rings and around the shaft. Cooling or lubricating fluids are introduced to the packing by way of the lantern ring. When this cooling fluid is fed under pressure it can also counteract fluid pressure coming from the casing at the shaft/casing interface.
It is common to use fresh cooling water as a cooling fluid. One important drawback of such cooling systems is the voluminous consumption of fresh water. Another drawback occurs when the fluid inside the casing is to be maintained at an elevated temperature. Indeed, the cooling water used in the lantern ring will tend to lower the temperature of the fluid inside the casing. Furthermore, in many instances such as in the pulp and paper or traditional chemical industries, the cooling water may be contaminated by the fluid leaking from the casing and it will be required to be recycled or otherwise decontaminated. In a pulp and paper environment, solids from the pump will also infiltrate the packing box, further inducing the efficiency of the packing box.
It is an object of the present invention to provide a packing box design where the packing is compressed from the zone closest to the casing. Thus an annular plate or follower may be provided about the shaft closest to the casing/shaft interface and the annular plate would be pressed away from the casing/shaft interface such as to compress the packing rings in the zone closest to the casing/shaft interface so that it is the first rings that create the seal. Thus the heat may be dissipated by the fluid from the pump.
Although none of the prior art appears to recognize the advantages of compressing the packing rings in the packing box closest to the shaft casing interface, certain patents appear to, at least on the face of it, have a similar construction.
Swiss Patent 34154 which issued to Franz Kales May 20, 1905 shows a conventional packing box with gland followers D pressing against the exterior of the packing rings. However, there is shown an annular plate B which could be drawn outwardly from an inner position near the interface of the casing with the shaft. The plate B is drawn by puller rods C being tightened
REFERENCES:
patent: 795444 (1905-07-01), Kales
patent: 860035 (1907-07-01), Kerr
patent: 1163941 (1915-12-01), Miller
patent: 1902097 (1933-03-01), Penick et al.
patent: 3351350 (1967-11-01), Shepler
patent: 4330135 (1982-05-01), Butterfield
patent: 4411438 (1983-10-01), Scobie
patent: 4717160 (1988-01-01), Zitting et al.
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