Turbomachine With Balancing Means

Abstract

Means for balancing a turbomachine include a plurality of balance weights made readily removable and replaceable from a rotor wheel disc by providing opposed tang members extending from each balance weight for slidably engaging mating grooves cut into integral hook portions which overhang the periphery of the disc.

Description

BACKGROUND OF THE INVENTION

This invention relates to a turbomachine with balancing means and, more particularly, to a turbomachine which may be balanced by a plurality of circumferentially spaced apart balance weights which are easily removed and replaced.

As is well known in the art, all rotating machinery must be balanced so that the effects of centrifugal force are uniformly distributed around each rotating part. An unbalanced condition within a revolving component may lead to severe vibration and fretting, thus drastically reducing the useful life of the component. Therefore, rotating components are generally balanced, both dynamically and statically, by the addition of discrete balance weights to the outer periphery thereof.

In turbomachinery of the axial flow type, there is generally included a rotor wheel disc which supports a plurality of circumferentially spaced apart rotor blades about the outer periphery. Each of the blades includes an airfoil or vane section through which fluid may flow for either compression or extraction of work as is well known in the art. The blades may also include root portions for insertion and retention within spaced apart grooves disposed about the periphery of the rotor wheel disc. In turbomachinery of this type, it is common practice to leave a space between the bottom of the blade root and its associated groove for the insertion of small balance weights. However, there are many instances where due to the configuration of the surrounding turbomachinery, it may prove impractical to insert small balance weights in this manner because of the inability to readily remove the rotor blades for replacement of the balance weights. Balance weights may also be retained relative to a bolting circle around the rotor wheel disc; however, this arrangement may also prove impractical due to the inability to readily remove and replace the balance weights.

Therefore, it is a primary object of this invention to provide a simplified means of balancing a turbomachine wherein a plurality of balance weights may be readily removed and replaced from a rotor wheel disc regardless of the configuration of the surrounding turbomachinery.

It is also an object of this invention to provide a simplified means of balancing a turbomachine wherein a plurality of balance weights may be attached to any rotor wheel disc design which includes rotor blades with overhanging platforms as well as a snap ring blade retainer.

SUMMARY OF THE INVENTION

These and other objects and advantages will be more clearly understood from the following detailed description and drawings, all of which are intended to be representative of, rather than in any way limiting on, the scope of invention. The turbomachine of this invention includes a balancing means and comprises a rotating member having a plurality of circumferentially spaced apart, generally axially, extending grooves disposed about the outer periphery thereof. A plurality of blade members each include root and airfoil vane portions wherein the root portions are received for retention within the grooves. A plurality of circumferentially spaced apart integral hook portions extend from the side of the rotating member such that each integral hook portion has two opposed generally radially extending sidewalls, each one of which is intersected by a generally radially extending groove. A plurality of balance weights are provided wherein each one of the balance weights has a pair of longitudinal and transverse faces intersected by a top and bottom face together with a pair of oppositely projecting tang members wherein each tang member extends from an opposing longitudinal face for engagement within a respective radially extending groove. A snap ring is also provided for insertion between the hook portions and the rotating member for engagement with the bottom faces of the balance weights.

DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims distinctly claiming and particularly pointing out the invention described herein, it is believed that the invention will be more readily understood by reference to the discussion below and the accompanying drawings in which:

FIG. 1 is a partial perspective view in cross-section of the turbomachine and balancing means of this invention.

FIG. 2 is a partial cross-sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is a perspective view of a single balance weight as may be used to balance the turbomachine of FIG. 1.

FIG. 4 is a side view of the balance weight of FIG. 3.

FIG. 5 is a top view of the balance weight of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, there is shown in a partially disassembled view a typical wheel blade assembly for rotating about a central axis as may be utilized in an axial flow turbomachine compressor, or in another type of axial flow turbomachine. In the disclosed embodiment, the blade supporting structure comprises a rotor wheel disc indicated generally at 10 having an enlarged rim portion 12 and a pair of oppositely directed (axially of the rotor) faces 14 and 16. Extending through the rim portion in a generally axial direction relative to the rotor are a plurality of circumferentially spaced apart blade receiving grooves indicated at 18. These grooves, which may be of the dovetail type, comprise a pair of sidewalls 20, 21, the inner ends of which are undercut to provide longitudinally extending angled sidewalls 22, 23, which operate as inwardly directed abutment faces. The grooves also include a wide base or bottom 24.

The rotor disc 10 includes a plurality of circumferentially spaced apart rotor blades or vanes 26 disposed about its periphery. Each of the rotor blades 26 includes an airfoil vane section 28 through which gas may flow for either compression or extraction of work in a manner well known to the art. The blades 26 include platforms 32 from which root portions 30 extend in substantially inward radial directions wherein the platforms 32 generally overhang the root portions. Each root portion 30 is thickened at the inner radial end to provide outwardly extending shoulders with oppositely directed, longitudinally extending, faces 34, 36. In addition, the root portions 30 also include opposed transverse end faces 38, 40, together with a bottom portion 42. The tables 28 are radially and circumferentially retained in a conventional manner by axial insertion of the root portions 30 within the blade receiving grooves 18, such that the oppositely directed, longitudinally extending, faces 34, 36 respectively engage the longitudinally extending angled sidewalls 22, 23 of the blade receiving grooves. As will be obvious from FIG. 1, the general overall shape of the rotor wheel disc 10 or blade receiving grooves 18 corresponds to the shape of the root portions 30 with a slight clearance between the bottom portion 42 of the blade roots and the base 24 of the grooves. Thus, the longitudinally extending faces 34, 36 of the blade roots are shaped to abut and be retained against centrifugal force by the longitudinally extending angled sidewalls 22, 23 of the rotor wheel grooves 18. The means for retaining rotor blades herein described is conventional and well known to the art.

Extending axially from the end face 14 of the rotor wheel disc 10, are a plurality of circumferentially spaced apart integral hook portions 44, each one of which includes a downwardly extending lip portion 46 in spaced apart overlapping relation with the end face 14. Each integral hook portion 44 has two opposed generally radially extending sidewalls 48, 50 in general respective coplanar alignment with the sidewalls 20, 21 of the blade receiving grooves. Each pair of opposed sidewalls 48, 50 is respectively intersected by a pair of radially extending grooves 52, 54 for receipt of a balance weight 56 in a manner to be more fully described in the following discussion. The grooves 52, 54 are illustrated as having one edge coincident with the intersection between the sidewalls 20, 21 and the rotor wheel disc face 14. However, it should be readily apparent that the grooves do not necessarily have to be arranged in this manner and may alternatively be spaced forward of the rotor wheel disc face 14.

As is well known in the art, all rotating machinery must be balanced so that the effects of centrifugal force become uniformly distributed around each rotating component. An unbalanced condition within a revolving component may lead to severe vibration and fretting, thus drastically reducing the useful life of the component. Therefore, rotating components are generally balanced, both dynamically and statically by the addition of discrete balance weights to the outer periphery thereof. In turbomachinery of the type herein described, it is common practice to leave a space between the base 24 of the blade receiving groove 18 and the bottom portion 42 of the blade root 30 for the insertion of small balance weights. As previously discussed, however, this means for balancing turbomachinery may prove impractical due to the inability to readily remove the rotor blades for replacement of the balance weights. Other conventional means for balancing rotor wheel discs in turbomachinery may depend upon access to a bolting circle which may not always be possible to provide. In order to overcome these prior art shortcomings, the balance weights of this invention have been made readily removable and replaceable without having to first remove the rotor blades or without requiring access to a bolting circle.

Referring now to FIGS. 3 through 5, there is shown an enlarged view of a single balance weight 56, which has two longitudinally extending faces 58, 60, together with two opposed transverse end faces 62, 64. The longitudinal and transverse faces are intersected by a bottom face 66 and a top face 68 which respectively define the inner and outer radial limits of the balance weight 56. A pair of oppositely projecting tang members 70, 72 extend respectively from the two longitudinally extending faces 58, 60, wherein the top of the tang members 70, 72 are intersected by an oblique face 74. One edge of each tang member 70, 72 is illustrated as being coincident with the transverse end face 62; however, it should be readily apparent that the tangs do not necesssarily have to be arranged in this manner and may alternatively be spaced apart from the end face 62. A transverse notch 76 extends between the opposed tang members 70, 72 and intersects the transverse end face 62, together with the bottom face 66.

After the individual rotor blades 26 have been inserted in their respective grooves 18 in the aforementioned manner, each balance weight is thereafter inserted between the integral hook portions 44 by first bringing the transverse end face 62 of the balance weight into near engagement with the face 14 of the rotor wheel disc at a position underlying the space between a pair of adjacent integral hook portions. The balance weight 56 must then be circumferentially aligned so that the tang members 70, 72 slidingly engage respective grooves 52, 54 upon outward radial movement of the balance weight. The balance weight 56 can then be pushed radially outward into abutting engagement with the interior surface of the blade platform 32. In this manner, the balance weight 56 is retained from further outward radial movement during centrifugal loading by engagement of the top face 68 with the interior surface of the blade platform 32. Axial movement is restrained by the engagement of the tangs 70, 72, within the grooves 52, 54 while circumferential movement is constrained by engagement of the two longitudinally extending faces 58, 60 between the radially extending sidewalls 48, 50.

A snap ring 78 must then be provided for insertion intermediate the overlapping lip portions 76 of the integral hooks 44 and the face 14 of the rotor wheel disc 10. As is readily apparent, the top of the snap ring 78 engages the top of the notch 76 thereby restraining the individual balance weights 56 from moving radially inward when the rotor wheel disc 10 is stationary. Thus, it will be appreciated that the balance weights 56 may be removed and replaced in an expeditious manner by simply removing the snap ring 78 and thereafter sliding the balance weights radially inward out of engagement with the groovess 52, 54. A new balance weight may thereafter be inserted in like manner after which the snap ring 78 may be reinstalled in a conventional manner. Various numerical weights may be provided for the balance weight 56 by simply adjusting the length of the longitudinally extending faces 58, 60 as indicated by the dimension A.

As is readily apparent, the individual rotor blades are restrained from forward axial translation out of the grooves 18 by the engagement of the end faces 38 with respect to the transverse end faces 62 of the balance weights. Rearward axial translation of the individual rotor blades 26 out of their respective grooves 18 may be restrained in a conventional manner by a second snap ring 82 engaged by a second integral hook portion 80 extending from the rim portion 12.

Accordingly, while a preferred embodiment and a preferred application of the present invention has been depicted and described, it will be appreciated by those skilled in the art that many modifications and changes may be made thereto without departing from the invention's fundamental theme. For example, the oblique surface 74 of the balance weight 56 may be eliminated along with the notch 76 whereupon the bottom face 66 of the balance weight would then be engaged by the top of the snap ring 78. Also, it will be understood that the blade receiving grooves 18 may be skewed in relation to the faces 14, 16 of the rotor wheel disc. In like manner, the longitudinal faces 58, 60 of the balance weights 56 and the sidewalls 20, 21 of the integral hook portions 44 may also be skewed in relation to a true radial plane and are hence referred to as extending in only a general radial direction. Therefore, having described a preferred embodiment of the invention, what is desired to be secured by Letters Patent is as follows.

Claims

What is claimed is:

1. A turbomachine with means for balancing thereof comprising:

a rotating member having a plurality of circumferentially spaced apart, generally axially, extending grooves disposed about the outer periphery thereof;

a plurality of blade members having root and airfoil vane portions wherein the root portions are received for retention within the grooves;

a plurality of circumferentially spaced apart integral hook portions extending from a side of the rotating member wherein each integral hook portion has two opposed generally radially extending sidewalls, each one of which is intersected by a generally radially extending groove;

a plurality of balance weights each one of which has a pair of longitudinal and transverse faces intersected by a top and bottom face together with a pair of oppositely projecting tang members wherein each tang member extends from an opposing longitudinal face for engagement within a respective radially extending groove; and

a snap ring for insertion between the hook portions and rotating member for engagement with the bottom of the balance weights.

2. The turbomachine of claim 1 wherein the blade members include platforms intermediate the airfoil vane portions and root portions wherein the platforms generally overhang the root portions and engage the tops of the balance weights so as to prevent outward radial movement of the balance weights during centrifugal loading.

3. The turbomachine of claim 2 wherein:

the generally axially extending grooves are of the dovetail type, each having a pair of sidewalls, the inner ends of which are undercut to provide longitudinally extending angled sidewalls which operate as inwardly directed abutment faces, and

each blade root portion is thickened at the inner radial end to provide outwardly extending shoulders with oppositely directed longitudinally extending faces for respective engagement with the longitudinally extending angled sidewalls of the axial grooves wherein the two opposed generally radially extending sidewalls of the integral hook portions are in general respective coplanar alignment with the sidewalls of the blade receiving grooves.

4. The turbomachine of claim 3 wherein:

the rotating member comprises a rotor wheel disc having an enlarged rim portion and a pair of oppositely directed faces;

each radially extending groove has an edge coincident with the intersection between a sidewall of the axially extending groove and a face of the rotor wheel disc; and

one edge of both of the opposed tang members of a balance weight is coincident with a transverse end face of that balance weight.

5. The turbomachine of claim 2 wherein:

the top of the opposed tang members of each balance weight are intersected by an oblique face extending between the top face and a transverse end face of the balance weight;

and a transverse notch extends between the bottom of the opposed tang members of each balance weight intersecting the same transverse end face as well as the bottom face of the balance weight such that the snap ring may engage the notch after the tangs of the balance weight are inserted within the radially extending grooves.

6. A balance weight for a turbomachine comprising a pair of longitudinal and transverse faces intersected by a top and bottom face together with a pair of oppositely projecting tang members wherein each tang member extends from an opposing longitudinal face.

7. The balance weight of claim 6 wherein one edge of both of the opposed tang members is coincident with a transverse end face of the balance weight.

8. The balance weight of claim 6 wherein:

the top of the opposed tang members of the balance weight are intersected by an oblique face extending between the top face and a transverse end face of the balance weight; and

a transverse notch extends between the bottom of the opposed tang members of the balance weight intersecting the same transverse end face as well as the bottom face of the balance weight.