A tilting pad journal bearing, an annular housing for an array of arcuate bearing pads resiliently mounted by spring means which biases the pads against heads of restraining bosses that limit radial displacement and cause the bearing pads to define a shaft space. The pads have associated therewith s
A tilting pad journal bearing, an annular housing for an array of arcuate bearing pads resiliently mounted by spring means which biases the pads against heads of restraining bosses that limit radial displacement and cause the bearing pads to define a shaft space. The pads have associated therewith support pegs (60) secured to housing or pad at one end and movable relative to the pad or housing at the other, and the spring means comprises stacks of individually deflectable elements mounted between relatively moving pad, housing or peg and pre-loaded by adjusting the effective gap with the pads against the bosses. Relative movement between springs provide friction damping. The restraining bosses may be displaceable together to eliminate the shaft space clearance if the magnetic suspension fails or shows signs of failing.
대표청구항▼
The invention claimed is: 1. A journal bearing arrangement for a rotatable shaft comprising: (i) a housing configured to surround a shaft space and having a housing surface facing into the shaft space, (ii) a plurality of arcuate bearing pads arrayed about the shaft space overlying the housing surf
The invention claimed is: 1. A journal bearing arrangement for a rotatable shaft comprising: (i) a housing configured to surround a shaft space and having a housing surface facing into the shaft space, (ii) a plurality of arcuate bearing pads arrayed about the shaft space overlying the housing surface, each having a bearing face adjacent the shaft space and a body face adjacent the housing surface, and (iii) a mounting arrangement, arranged to support at least one bearing pad with respect to the housing surface movable relative thereto in a direction to and from the housing surface, including associated with each said movable pad, a stop comprising a restraining boss and a shoulder provided one each by the housing and bearing pad, said boss having a head portion arranged to overlie the shoulder to limit the extent of pad movement away from the housing surface and permit displacement of the bearing pad towards the housing surface, and a spring arrangement, operable to bias the pad away from the housing surface to the limit imposed by the stop and exert on said pad stopped by the stop a predetermined level of pre-load and, in response to load applied to the bearing surface exceeding said pre-load level, permit displacement of the pad towards the housing surface, the spring arrangement further comprising a plurality of individually deflectable resilient elements, with the individually deflectable resilient elements comprising leaf springs extending circumferentially with respect to the housing and shaft space, and the spring arrangement comprises, associated with each bearing pad between the pad and the housing surface a stack of said leaf springs arranged to bear one on another in a radial direction, said stack of leaf springs comprises associated with each bearing pad at least a first spring terminating adjacent one end region of the pad and pivotally secured thereto, a second spring terminating adjacent the opposite end region of the pad and pivotally secured thereto, and a third spring mounted at its centre on a spigot extending along a radial axis and constrained by the spigot to sliding motion along the spigot and in respect of displacement from the housing surface. 2. A journal bearing arrangement as claimed in claim 1 in which each of the stacked leaf springs has a substantially cylindrical curvature centered on the housing axis and substantially equal to that of the others whereby the circumferentially overlapping springs are able to stack nested one within another. 3. A journal bearing arrangement as claimed in claim 2 in which the leaf springs associated with said bearing pads are arranged each to extend circumferentially with respect to the housing and shaft space and effect support for at least three circumferentially spaced bearing pads adjacent each other, each of said springs being offset circumferentially with respect to adjacent springs of the stack such that for each said bearing pad the associated first spring secured to said one end region comprises a third spring of a pad spaced circumferentially in a direction towards said opposite end region of the bearing pad and the associated second spring secured to said opposite end comprises a third spring of a pad spaced circumferentially in a direction towards said one end of the bearing pad. 4. A journal bearing arrangement as claimed in claim 2 in which for each said bearing pad the associated third spring extends from its mounting spigot through an angle in the range ��(60 to 120)��. 5. A journal bearing arrangement as claimed in claim 2 in which the first and second springs associated with a said bearing pad comprise respectively the third springs of the adjacent circumferentially spaced bearing pads. 6. A journal bearing arrangement as claimed in claim 2 in which the stop associated with each said movable bearing pad comprises at least one pair of shoulders spaced apart at opposite ends of the bearing pad in the circumferential direction, each shoulder having a surface facing towards the shaft space and rebated with respect to the bearing surface, and associated with each said shoulder a said restraining boss disposed with the head portion arranged to overlie one end shoulder of at least one adjacent pad and in which at least one said restraining boss passes through an aperture in each leaf spring extending circumferentially between spaced bearing pads and each said leaf spring has, in the vicinity of a said aperture, strengthening means to maintain spring deflection within elastic limits. 7. A journal bearing arrangement as claimed in claim 2 in which each spigot includes an axially positionable spring stop to define the limit of third spring displacement radially away from the housing surface, the stop associated with each said movable bearing pad comprises at least one pair of shoulders spaced apart at opposite ends of the bearing pad in the circumferential direction, each shoulder having a surface facing towards the shaft space and rebated with respect to the bearing surface, and associated with each said shoulder a said restraining boss disposed with the head portion arranged to overlie one end shoulder of at least one adjacent pad, in which the restraining bosses are disposed so as to maintain each spigot-mounted spring in tension with its ends splayed apart by abutment of bearing pad shoulders, at which the ends of said springs are secured to the pad, with the heads of the restraining bosses. 8. A journal bearing arrangement as claimed in claim 7 in which the head portion of each restraining boss defines a cam surface and the associated pad end shoulder a co-operable cam follower permitting the shoulder to move radially and circumferentially with respect to the shaft space in abutment with the restraining boss and for the bearing pad to tilt as a result of differential movement between the shoulders at opposite ends of the bearing pad. 9. A journal bearing arrangement as claimed in claim 8 in which the mounting includes a damper comprising coupling within the spring arrangement between the stack of circumferentially extending springs associated with a said bearing pad and at least one bearing pad spaced therefrom circumferentially about the shaft space, whereby each bearing pad, in response to application of force to the bearing pad in excess of the bias force exerted thereon by the spring stack, is displaceable with the springs of the stack towards the housing until restrained by abutment, and displacement of the third spring of the stack creates, at each end of the third spring secured to an end shoulder of a circumferentially spaced bearing pad, a component of bias force acting substantially in the direction of said displacement and operable to slide the cam follower surfaces of the circumferentially spaced pad end shoulders along the cam surface of the respective restraining boss such that the distal end of the circumferentially spaced bearing pad is displaced by the cam surface towards the shaft space such that a part of the bearing surface of that pad is tilted and displaced towards the shaft space. 10. A journal bearing arrangement as claimed in claim 1 in which the mounting includes a damper comprising coupling within the spring arrangement between the stack of circumferentially extending springs associated with a said bearing pad and at least one bearing pad spaced therefrom circumferentially about the shaft space, whereby displacement of a said bearing pad in a direction towards the housing surface results in displacement of at least part of a said circumferentially spaced bearing pad away from the housing surface towards the shaft space. 11. A journal bearing arrangement as claimed in claim 10 in which the damper comprises friction damping means operable to effect Coulomb damping between relatively sliding, abutting surfaces of the spring arrangement.
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