Bearings – Rotary bearing – Plain bearing
Patent
1987-05-22
1990-01-23
Hannon, Thomas R.
Bearings
Rotary bearing
Plain bearing
277 57, 277 71, 277 79, 384462, 384477, 384480, F16C 3372, F16C 3380
Patent
active
048954608
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improved seal for bearing assemblies.
Bearing assemblies are used in rotodynamic fluid machines such as pumps, turbines, agitators and the like to house bearings and support a shaft which normally protrudes from both ends of the bearing housing to connect the rotating element(s) of the fluid machine to the fluid machine drive.
Bearings require a clean well lubricated environment to operate. With the shaft protruding from the bearing assembly from either one or two ends, it is necessary to enclose and seal the bearing housing ends. As the shaft rotates in a stationary housing, it is necessary to use seals which minimise the frictional losses and heat generation.
Fluid machines often operate in harsh environments where air or water borne contaminants are present at or near the bearing housing and enclosures. Centrifugal slurry pumps in particular are open to severe environmental influences as the shaft enters the pump by way of a gland arrangement which in its standard form is designed to leak slightly to allow lubrication of the gland sealing elements. This small leakage is in close proximity to the end of the bearing housing.
The bearing seals which fit into the ends of the bearing housing can be selected from any number of known types or special types could be developed. Certain seal arrangements incorporate a labyrinth (small clearance passageway) to effect the sealing and others incorporate element(s) which rub on the rotating shaft or a shaft mounted component. As such all seals have a potential to allow contaminants into the bearing housing which can become worse as the sealing element(s) wear.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a prior art bearing assembly.
FIG. 2 illustrates the present invention seal arrangement.
A typical prior art bearing assembly is illustrated in FIG. 1 in which the pump impeller shaft 7 is held by bearings 8 in the bearing housing 9. This pump uses end closures incorporating two piston rings 1 located in grooves 2 on the shaft collar as the inner sealing elements and a labyrinth passage 3 as the outer sealing elements. This form of sealing has proved more effective when the labyrinth passage 3 is purged with grease. Grease is pumped by means of a grease gun (not shown) being connected to the grease nipple 4 through the flushing bore 5, in the bearing housing end cover 6, to the outside of the outer piston ring 1 into the labyrinth passage 3.
The grease purge is normally applied at regular intervals but in some applications has not proved entirely effective in keeping contaminants away from the piston ring seals which have only limited ability to seal against the usual water borne contaminants experienced in the mining industry.
The main problem with the existing grease purging arrangement is that grease is flung out of the labyrinth passage by centrifugal action when the pump is running. The greasing period, in general practice, is longer than the time taken for the grease to be expelled by centrifugal action. Potential contaminants can more easily enter the labyrinth if no grease is present, especially if the pump is stopped, and work their way past the piston rings to eventually reach the bearings.
The present invention seeks to overcome these disadvantages by providing a bearing assembly comprising at least two seal rings spaced a short distance apart from each other to form the inner sealing elements, a labyrinth passage to form the outer sealing element, a passageway extending externally of the bearing assembly into the space between the at least two of said spaced apart seal rings.
The invention will now be described with reference to FIG. 2 which illustrates one embodiment of the present invention. The designation numerals appearing in this drawing represent the same features as the features designated by the same numerals in FIG. 1.
The sealing arrangement is physically very similar to the seal arrangement shown in FIG. 1 in that it consists of two seal rings 1A and 1B spaced a short distance apart to form the in
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patent: 2195794 (1940-04-01), Weckstein
patent: 2253350 (1941-08-01), Ross et al.
patent: 3512853 (1970-05-01), Petros
patent: 3869131 (1975-03-01), Derner
patent: 4101139 (1978-07-01), Nordin
Hannon Thomas R.
Warman International Limited
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