Pressure controller for a buffer fluid seal

Details Pressure controller for a buffer fluid seal Pressure controller for a buffer fluid seal

1987-06-08

1989-08-22

Shoap, Allan N.

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

91 1, 91 25, 91390, 137554, 251 613, 277 3, 277 27, 277 28, 277 59, 277135, F16J 1540, F16K 31122, F16K 3700

Patent

active

048589373

DESCRIPTION:

BRIEF SUMMARY
This invention relates to sealing apparatus for fluids.
It is common practice to provide a seal arrangement for a shaft or the like in which lubrication for the seals is being provided by the sealed fluid. However, if lubrication from the sealed fluid is insufficient (e.g. in the case of the sealed fluid being a gas), or undesirable in the case of the sealed fluid containing grits and contaminants, then a sealing arrangement can be utilised, where auxiliary seals are fitted inboard of the main seals and a buffer fluid is introduced between the main seal and auxiliary seal. It is advantageous if this buffer fluid is maintained at a pressure above that of the sealed fluid so that any leakage across the auxiliary seal is from the buffer fluid to the sealed fluid effectively excluding any contamination of the buffer fluid from the sealed fluid. This provides a favourable operating environment for the main seals and keeps the sealing surfaces of the auxiliary seals clear of grits and contaminants. The buffer space also provides high integrity containment of the sealed fluid since any failure of the seals will result in buffer fluid leaking into the sealed fluid, or to the environment, but sealed fluid will not leak to the environment except in the event of multiple failures.
An object of the present invention is to provide a means for automatically maintaining the buffer fluid at a pressure above that of the sealed fluid. This is achieved by using a device which supplies or maintains pressure fluid at a specified pressure differential relative to a reference fluid also pressurised with or without flow taking place.
According in one aspect of the present invention there is provided apparatus for automatically maintaining a buffer fluid at a pressure above that of a sealed fluid comprising a piston moveable within a cylinder; a first chamber on one side of the piston for continuous communication with the sealed fluid; a second chamber on the other side of said piston for continuous communication with the buffer fluid; and recharging means associated with said second chamber for automatically modifying said buffer fluid pressure in relation to variation in the sealed fluid pressure in order to maintain the pressure of the buffer fluid at a pressure greater than that of the sealed fluid.
An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:
FIG. 1 (a) illustrates a basic form of prior art seal;
FIG. 1 (b) illustrates an improved form of prior art seal;
FIG. 2 is a sectional view of an embodiment of the apparatus in accordance with the present invention, and
FIG. 3 is a diagrammatic representation showing the relationship of FIG. 1b and FIG. 2 with associated manifold connections.
Referring to the drawings, FIG. 1 (a) illustrates a simple prior art seal arrangement, including seals 102, 104 in which lubrication is provided by the sealed fluid 100. FIG. 1 (b) illustrates an improved form of prior art seal referred to hereinabove in which a buffer fluid is introduced via ports 114, 116 into cavities 120, 118 between auxiliary seals 106, 108 and main seals 110, 112.
The arrangement of an embodiment of the present invention is shown in FIG. 2 which illustrates a cylinder block 1, the cylinder of which is counterbored. FIG. 3 shows the embodiment of FIG. 2 in combination with a seal shown in FIG. 1b with appropriate manifold connections as will be later described in detail.
The lower portion of the cylinder is positively divided into upper and lower chambers by a piston 2, generally indicated by reference numeral 2 containing a double-acting piston seal 3. The piston 2 consists of an upper piston half 4 and a lower piston half 5 with the seal 3 being disposed between the outside of the piston half 5 and the interior of cylinder block 1. The piston 2 has piston rod or valve shaft 8 coupled to the upper piston half 4. An undercut 9 on the upper portion of the valve shaft 8 acts as a cam on which a pair of micro-switches 10 run giving indicatio

REFERENCES:
patent: 933400 (1909-09-01), Stance et al.
patent: 946408 (1910-01-01), Stance et al.
patent: 1158029 (1915-10-01), Dantsizen
patent: 2769912 (1956-11-01), Lupfer et al.
patent: 3568436 (1971-03-01), Heffner et al.
patent: 4483508 (1984-11-01), Marsh et al.

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