# US 2009/0260221 A1 · Partial Slot Dovetail for Generator Rotor

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- Number: US 2009/0260221 A1
- Document ID: US20090260221A1
- Status: Published application
- Kind: A1
- Application number: 12/106,496
- Filed: 2008-04-21
- Published: 2009-10-22
- Earliest claimed: 2008-04-21
- Assignees: General Electric Company
- Inventors: Alexander Gabriel Beckford; Madhu Bharadwaj; John Peter Hoffman
- Web page: https://patentgrep.com/patent/US20090260221A1

## CPC

- H02K 15/50: Disassembling, repairing or modifying dynamo-electric machines (repairing of cooling fluid boxes H02K15/38)
- H02K 3/487: Slot-closing devices
- Y10T 29/49012: Rotor
- Y10T 29/49318: Repairing or disassembling
- Y10T 29/4973: Replacing of defective part
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Re-machining a generator rotor tooth dovetail results in a transition zone at an end of the partial re-machined cut, between a newly cut load surface and an original load surface of the rotor tooth. The transition zone is susceptible to stresses that may adversely affect the fatigue strength of the rotor tooth. These stresses can be reduced by the steps of (a) forming at least one axial undercut stress relief groove across the transition zone between the newly cut load surface and the original load surface, (b) cutting and shaping a wedge that will fit in the transition zone, and (c) securing the wedge across the transition zone.

## Claims

### Claim 1

A method of reducing stresses susceptible from partially re-machining a generator rotor tooth dovetail, the re-machining resulting in a transition zone at an end of the partial re-machined cut, between a newly cut load surface and an original load surface of the rotor tooth, the method comprising:
(a) forming a first axial undercut stress relief groove at a first fillet radius below the original load surface; and
(b) forming a second axial undercut stress relief groove at a second fillet radius below the newly cut load surface.

### Claim 2 (depends on 1)

A method according to claim 1, further comprising:
(c) cutting a wedge that will fit in the transition zone;
(d) machining a wedge load surface of the wedge to match a conical shape of the newly cut load surface in the transition zone; and
(e) forming an undercut stress relief fillet at an edge of the wedge load surface.

### Claim 3 (depends on 2)

A method according to claim 2, further comprising:
(f) aligning the wedge with an end of the newly cut load surface;
(g) ensuring proper contact of the wedge with the rotor tooth in the transition zone; and
(h) staking the wedge in position to prevent axial movement of the wedge.

### Claim 4 (depends on 3)

A method according to claim 3, wherein step (g) is practiced using a bluing agent.

### Claim 5 (depends on 2)

A method according to claim 2, wherein step (e) is practiced by forming the undercut stress relief fillet with a radius substantially corresponding to a fillet radius on the rest of the wedge.

### Claim 6 (depends on 2)

A method according to claim 2, wherein step (d) is practiced using a bluing agent.

### Claim 7 (depends on 2)

A method according to claim 2, wherein step (d) is practiced by using a cutting tool having the same radius as a cutter used for the partial re-machining of the rotor tooth dovetail.

### Claim 8 (depends on 1)

A method according to claim 1, wherein step (b) is practiced by extending the second axial undercut stress relief groove beyond the transition zone.

### Claim 9

A method of reducing stresses in a transition zone between a newly cut load surface and an original load surface resulting from partially re-machining a generator rotor tooth dovetail, the method comprising:
(a) forming at least one axial undercut stress relief groove across the transition zone between the newly cut load surface and the original load surface;
(b) cutting and shaping a wedge that will fit in the transition zone; and
(c) securing the wedge across the transition zone.

### Claim 10 (depends on 9)

A method according to claim 9, wherein step (b) is practiced by machining a wedge load surface of the wedge to match a conical shape of the newly cut load surface in the transition zone, and forming an undercut stress relief fillet at an edge of the wedge load surface.

### Claim 11 (depends on 9)

A method according to claim 9, wherein step (a) is practiced by forming a first axial undercut stress relief groove at a first fillet radius below the original load surface, and forming a second axial undercut stress relief groove at a second fillet radius below the newly cut load surface.

### Claim 12

A re-machined generator rotor tooth dovetail with reduced susceptibility to stresses, the re-machining resulting in a transition zone at an end of a partial re-machined cut, between a newly cut load surface and an original load surface of the rotor tooth, the re-machined generator rotor tooth dovetail being constructed according to the steps of:
(a) forming a first axial undercut stress relief groove at a first fillet radius below the original load surface; and
(b) forming a second axial undercut stress relief groove at a second fillet radius below the newly cut load surface.