Drum blade lock in a circumferential rotor groove
The subject application relates to blade root wedging lock in a circumferential groove in a rotor such as the drum of an axial turbomachine compressor. The body ( 32 ) of the lock includes a solid portion ( 38 ) designed to be housed in the groove and having two opposite bearing surfaces ( 40 ) and at least one circumferential wedging surface ( 42 ). The body ( 32 ) further includes an upper portion ( 36 ) in the shape of an elongated generally vertical chamber designed to be flush with the upper surfaces of the platforms of adjacent blades when the lock is correctly positioned. This chamber ( 36 ) is truncated ( 44 ) so as to reduce its length in a direction perpendicular to the circumference, corresponding to the axis of rotation of the rotor. The lock can thus be accommodated in a narrow groove without decreasing the diameter of the clamping screw passing through the hole ( 34 ). The subject application also relates to a rotor and a turbomachine equipped with the lock.
1. An axial turbomachine wheel comprising:
a rotor with at least one circumferential groove having opposed faces, each having a hollow profile;
blades whose roots are located in, and in mechanical engagement with, the at least one circumferential groove; and
at least one blade root lock, each of the at least one blade root lock being mounted in one of the at least one circumferential groove between the roots of two adjacent blades preventing the blades sliding along the at least one circumferential groove; and
each of the at least one blade root lock comprising a body with:
two opposed bearing surfaces configured to bear radially onto the opposed faces of the at least one circumferential groove;
a through hole between the two bearing surfaces extending along an axis an upper portion pierced by the hole; and
a clamping screw housed in the through hole and bearing on the bottom of the at least one circumferential groove;
wherein the upper portion is truncated, so as to form a contour with a truncated section;
wherein the two adjacent blades on either side of the at least one blade root lock each comprise a platform on the adjacent edges thereof having cut-outs that match the contour with the truncated section of a corresponding half of the truncated upper portion of the body of the at least one blade root lock; and
wherein the clamping screw of the at least one blade root lock comprises an upper head for engagement with a tightening tool, with a part thereof that is hidden beneath the two adjacent platforms when viewed from the top, so as to allow a reduction in the length thereof in a plane generally perpendicular to the axis of the hole.
2. The axial turbomachine wheel in accordance with claim 1 , wherein each upper portion of the body is truncated, so as to allow a reduction in the length thereof along the width of the at least one circumferential groove and/or in a direction corresponding essentially to the circumferential direction of the at least one circumferential groove.
3. The axial turbomachine wheel in accordance with claim 1 , wherein each upper truncated portion of the body is truncated at least on an upper part thereof along a longitudinal plane of the at least one circumferential groove, and on a lower part thereof following a developable surface.
4. The axial turbomachine wheel in accordance with claim 1 , wherein each upper truncated portion of the body is truncated on a section thereof between about ¼ and ½ of the outside diameter thereof.
5. The axial turbomachine wheel in accordance with claim 1 , wherein each through hole comprises:
a threaded portion at a distance from an upper edge of the upper truncated portion of the body, such that a head of the clamping screw is disposed at a level below the upper edge, when the clamping screw is engaged in the threaded portion.
6. The axial turbomachine wheel in accordance with claim 1 , wherein each body comprises:
at least one wedge-shaped surface configured to mate with a corresponding slot on one of the opposed faces of the at least one circumferential groove.
7. The axial turbomachine wheel in accordance with claim 1 , wherein each clamping screw mates with a thread in the hole of the body, the clamping screw having a head with a diameter larger than the threaded portion of the screw, the screw and the thread of the body being configured, such that the screw is disposed in a position such that the head thereof is embedded in the upper portion of the body to a level beneath that of an upper edge of the body.
8. The axial turbomachine wheel in accordance with claim 1 , wherein each body comprises:
a solid portion having a longitudinal section in the general shape of an inverted T, the upper portion of the body being arranged directly on the said solid portion, and the truncation being limited to the upper portion.
9. The axial turbomachine wheel in accordance with claim 8 , wherein the through hole at the truncated part of the upper portion of the body corresponds essentially to a corresponding edge of the solid portion.
10. The axial turbomachine wheel in accordance with claim 1 , wherein the longitudinal axis of each through hole is located predominantly on one side of a transverse median plane of the body.
11. The axial turbomachine wheel in accordance with claim 1 , wherein each upper portion is cylindrical.
12. The axial turbomachine wheel in accordance with claim 1 , wherein a profile of the cut-outs on the platforms includes a first circular part of more than 90° and a second straight part generally perpendicular to an edge of the cut-out.
13. The axial turbomachine wheel in accordance with claim 1 , wherein the longitudinal axis of each through hole is substantially included in a median plane of the platforms extending between the adjacent edges.