# US 2010/0166557 A1 · Rotor dovetail hook-to-hook fit

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- Number: US 2010/0166557 A1
- Document ID: US20100166557A1
- Status: Published application
- Kind: A1
- Application number: 12/346,913
- Filed: 2008-12-31
- Published: 2010-07-01
- Earliest claimed: 2008-12-31
- Assignees: General Electric Company
- Inventors: James R. Howes
- Web page: https://patentgrep.com/patent/US20100166557A1

## CPC

- F01D 5/3007: {of axial insertion type}
- F01D 5/3038: {the slot having inwardly directed abutment faces on both sides}
- F05D 2220/31: in steam turbines
- F05D 2300/501: Elasticity
- F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D)
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## Abstract

A male dovetail for a bucket mounted on a drum rotor for a steam turbine is provided by a tight hook-to-hook fit with the female dovetail of a retaining groove around the periphery of the drum rotor wheel. The tight hook-to-hook fit eliminates the use of loading pins which heretofore have been driven between a base of the male dovetail and a bottom of the retaining groove, a manually intensive operation with the potential to damage the bucket and the rotor.

## Claims

### Claim 1

A loading arrangement adapted for radially loading steam turbine buckets on a drum rotor comprising:
a drum rotor of a steam turbine formed with an annular bucket retaining groove configured as a female dovetail slot about the periphery of the wheel including a radially outer wide groove portion, a radially inner wide groove portion, and an intermediate narrow groove portion;
a root portion of a steam turbine bucket with a male dovetail including a radial inner projection and a radial outer projection, spaced by a narrow neck adapted for engaging the female dovetail slot;
an undersurface of the narrow groove portion adapted for engaging with upper surface of inner projection formed on the male dovetail, adapted for retaining the male dovetail within the female dovetail slot; and
an undersurface of radial outer projection of male dovetail closely engaging upper surface of radially outer wide groove portion, adapted for loading the bucket radially against the hook.

### Claim 2 (depends on 1)

The loading arrangement adapted for radially loading steam turbine buckets according to claim 1, further comprising: a clearance of about 0.001 inch to about 0.003 inch between an undersurface of radial outer projection of male dovetail and upper surface of radially outer wide groove portion

### Claim 3 (depends on 1)

The loading arrangement adapted for radially loading steam turbine buckets according to claim 1, wherein the base of male dovetail 16 comprises a nominally flat surface.

### Claim 4 (depends on 1)

The loading arrangement adapted for radially loading steam turbine buckets according to claim 1, wherein the base of male dovetail 16 comprises an arcuate-shaped cutout, centered on the base.

### Claim 5

A steam turbine rotor and bucket assembly comprising:
a drum rotor formed with a bucket retaining groove about a periphery thereof;
a plurality of buckets, each having a mounting portion including a radially inner face received within said bucket retaining groove;
an upper hook formed at an upper end of a narrowed portion of the bucket retaining groove;
a lower hook formed at a lower end of a narrowed portion of the bucket retaining groove;
the mounting portion of each of the plurality of buckets with a male dovetail including a radial inner projection and a radial outer projection, spaced by a narrow neck, adapted for engaging the bucket retaining groove, wherein the upper hook engages the radial outer projection and the lower hook engages the radial inner projection according to a designated loading clearance.

### Claim 6 (depends on 5)

The steam turbine rotor and bucket assembly according to claim 5, further comprising: a designated clearance of about 0.001 inch to about 0.003 inch between the upper hook and the radial outer projection of the male dovetail.

### Claim 7 (depends on 6)

The steam turbine rotor and bucket assembly according to claim 6, a base of the male dovetail comprising: a nominally flat surface.

### Claim 8 (depends on 7)

The steam turbine rotor and bucket assembly according to claim 7, the base of male dovetail comprising an arcuate-shaped cutout, centered on the base.