US 4,671,677 AGranted

Fluid seal with shaft excursion compensation

AssigneeMechanical Technology Incorporated

InventorsHooshang Heshmat, Donald F. Wilcock

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Abstract

Compensation for shaft excursion in a seal housing is achieved with a fluid film bearing in which bearing fluid is supplied to the bearing region at a pressure and flow rate which depend upon shaft rotational speed. In a disclosed embodiment, the bearing fluid is provided from a centrifugal fluid seal which delivers part of its fluid to the bearing region as a function of centrifugal pressure. A magnetic fluid seal is employed for zero and low speed operation. The shaft includes an annular collar which rotates in an annular cavity formed in a seal cartridge which is rotationally stationary but capable of small axial displacements to compensate for axial shaft displacement. A spring biases the cartridge in opposition to the axial forces of the magnetic fluid seal so as to axially balance the system at zero and low shaft speed operation. Relative axial motion of the shaft and cartridge occuring at high rotational speeds is balanced by the increasing pressure of fluid delivered to the bearing from the centrifugal seal.

Claims21

Dependent claims

A seal assembly for hermetically sealing the space between a rotating member subject to axial and radial displacement due to thermal heating and thrust loads and a close-fitting spaced apart non-rotating member comprising:

a circumferentially arranged centrifugal seal forming region located between said rotating and non-rotating members.
means in flow communication with said centrifugal seal forming region for receiving and pooling centrifugal seal fluid such that the fluid is centrifugally thrown radially outwardly during high speed rotation of said rotating member into said centrifugal seal forming region,
fluid film bearing means for providing a fluid film bearing between said rotating and non-rotating members, said fluid film bearing means comprising first and second closely spaced-apart bearing surfaces formed on said rotating and non-rotating members, respectively, and flow passage means connected from said centrifugal seal forming region to the space between said first and second bearing surfaces and responsive to rotation of said rotating member for delivering said centrifugal sealing fluid to the space between said first and second bearing surfaces at a pressure which varies as a function of the rotational speed of said rotating member to thereby increase the fluid pressure between said first and second bearing surfaces with increasing rotational speed of said rotating member, and said non-rotating member comprising means responsive to the balance of forces acting between it and the rotating member and said rotating member comprising means, being axially movable to maintain the relative close clearance conditions between it and the rotating member required in the seal forming region.

A plural fluid magnetic/centrifugal-fluid seal for hermetically sealing the space between a rotating member and a close fitting spaced-apart non-rotating member capable of limited axial movement comprising means formed on said members defining at least one magnetic pole-like close clearance magnetic seal gap region between opposed surfaces of the members, a high viscosity magnetically permeable magnetic fluid normally disposed in said magnetic gap region with said rotating member at rest or low rotational speeds, magnetic filed producing means magnetically coupled to at least portions of said rotating and non-rotating members, to said magnetic seal gap region, and to said high viscosity magnetically permeable magnetic fluid in a closed magnetic circuit, a circumferentially arranged centrifugal seal forming region radially disposed outwardly from said magnetic seal gap region and located between the rotating and non-rotating members, means in communication with said centrifugal seal forming region for receiving and pooling a low viscosity centrifugal sealing fluid, said centrifugal sealing fluid being centrifugally thrown outwardly during high speed rotation of said rotating member into said centrifugal seal forming region to thereby form a centrifugal hermetic seal through the medium of the fluid pooled between the two members by centrifugal force at high rotational speeds of said rotating member, fluid film bearing means for mutual axial providing a fluid film bearing between said rotational and nonrotating members, said fluid film bearing means comprising first and second closely spaced-apart bearing surfaces of said rotating and non-rotating members, respectively, flow passage means connected from said centrifugal seal forming region to between said first and second bearing surfaces and responsive to rotation of said rotating member for delivering said centrifugal sealing fluid to between said fist and second bearing surfaces at a pressure which varies as a function of the rotational speed of said rotating member to increase the fluid pressure between said first and second bearing surfaces with increasing rotational speed of said rotating ember, and said non-rotating member responsive to the balance of forces acting between it and the rotating member being axially movable to maintain the relatively close clearance conditions between it and the rotating member required in the seal forming regions.

Dependencies are inferred from the claim text.