Disengageable axial thrust bearing with internal preload
In a disengageable axial thrust bearing for a rotary machine, an outer ring has first and second outer half-rings ( 114 A, 114 B) centered in a casing ( 116 ) and clamped in the axial direction between a stationary thrust member ( 118 ) and a first pre-loading system ( 120 ) exerting a first predetermined axial force such that, so long as the axial load exerted on the axial thrust bearing via a synchronization element ( 106 ) is greater than a determined threshold value, rolling elements ( 110 ) with oblique contacts present respective single lines ( 130 ) having two points of contact ( 130 A, 130 B) with an inner ring ( 102 ) and with the first outer half-ring ( 114 A), the second outer half-ring ( 114 B) being spaced apart from the first by a second predetermined axial force exerted by a second pre-loading system ( 126 ) inserted in the axial direction between the first and second outer half-rings, and such that the inner ring ( 102 ) is driven in rotation by the synchronization element, whereas, when the axial load exerted on the axial thrust bearing becomes less than this determined threshold value, a second line ( 132 ) having two additional points of contact ( 132 A, 132 B) is created between each of the oblique-contact rolling elements ( 110 ) and the inner ring ( 102 ) and the second outer half-ring ( 103 B) such that the axial thrust bearing is disengaged.
1. A disengageable axial thrust bearing for a rotary machine, the thrust bearing comprising an inner ring arranged around a rotary shaft in radially non-interfering manner on said shaft, a synchronization element mounted on said rotary shaft to drive rotation of said inner ring selectively, an outer ring comprising first and second outer half-rings centered in a casing and clamped in the axial direction between firstly a stationary thrust member and secondly a first pre-loading system exerting a first predetermined axial force, and oblique-contact rolling elements, wherein the thrust bearing further comprises a second pre-loading system inserted in the axial direction between said first and second outer half-rings and exerting a second predetermined axial force less than the first predetermined axial force such that, so long as the axial load exerted on the axial thrust bearing via the synchronization element is greater than a determined threshold value, each of the rolling elements presents a single line with two points of contact respectively with the inner ring and with the first outer half-ring, the second outer half-ring being spaced apart from the first by the second predetermined axial force exerted by the second pre-loading system, and such that the inner ring is driven in rotation by said synchronization element, whereas, when the axial load exerted on the axial thrust bearing becomes less than this determined threshold value, a second line with two additional points of contact is created between each of the rolling elements and respectively the inner ring and the second outer half-ring such that the axial thrust bearing is disengaged, with rotation of the inner ring stopping as a result of inertia and friction internal to the thrust member via the four points of contact between each rolling element and the inner ring and the first and second outer half-rings.
2. A disengageable axial thrust bearing according to claim 1 , wherein the first and second pre-loading systems comprise respective resilient assemblies.
3. A disengageable axial thrust bearing according to claim 2 , wherein said resilient assembly comprises one or more spring washers.
4. A disengageable axial thrust bearing according to claim 1 , wherein the first pre-loading system exerts an axial force in the direction opposite to the axial load exerted on the axial thrust bearing via the synchronization element.
5. A disengageable axial thrust bearing according to claim 1 , wherein the second pre-loading system is held in position by an annular clip that is positioned in respective grooves associated in each of the outer half-rings.
6. A disengageable axial thrust bearing according to claim 1 , wherein the first outer half-ring providing a first line of points of contact includes a width that is greater than a width of the second outer half-ring providing a second line of points of contact.
7. A disengageable axial thrust bearing according to claim 1 , wherein the rolling elements are balls.
8. A disengageable axial thrust bearing according to claim 1 , wherein the stationary thrust member forms a portion of the casing.
9. A disengageable axial thrust bearing according to claim 1 , wherein the thrust bearing includes a clearance localized between the first pre-loading system between the outer half-ring and the casing, wherein said clearance is not zero so long as the axial load exerted on the axial thrust bearing is less than the determined threshold value.
10. The use of a disengageable axial thrust bearing according to claim 1 , in a cryogenic rotary machine, fitted with an active system for axial balancing under steady conditions.