GB2066904A

GB2066904A - Blade locking system

Info

Publication number: GB2066904A
Application number: GB8041018A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1979-12-21
Filing date: 1980-12-22
Publication date: 1981-07-15
Also published as: DE2951838A1; CH650835A5; JPS56101005A; SE8008960L; DD155445A1; FR2484530B1; FR2484530A1; GB2066904B; SE446281B; DE2951838C2

Abstract

Axial displacement of the pins (3) connecting the webs (1) of a rotor rim with the roots of blades (7) is prevented by at least one locking system formed from balls (4) in complementary annular grooves (5) in the pin (3) and the web (1). The balls may be inserted into each groove through an aperture which is then plugged. The pin may be prestressed. <IMAGE>

Description

SPECIFICATION Lockingsystem to prevent axial displacement of pins connecting the webs of a rotor disc and blade roots in turbines and similar machines This invention relates to a locking system to prevent axial displacement of pins connecting the webs of a rotor disc rim and the tenon roots of the moving blades of a turbine and similar machines.

Axial locking arrangements are known in which the pins are riveted. While riveting has proved successful in many instances, it presents difficulties in the case of larger pins, especially because of the material used. Another method of locking the pins axially is caulking or deforming the outer edges of the holes.

An object of the present invention is to provide an axial locking system without riveting or caulking so as to obtain a connection between the pins and the outer wheel disc webs which is effective in both axial directions and which will resist the bending moments and axial forces arising.

The invention provides a locking system to prevent axial displacement of pins connecting the webs of a wheel disc ring and tenon roots of moving blades in turbines, compressors and similar machines, wherein each pin is held in its respective hole by at least one form-locking system comprising an annular peripheral groove in the pin, a complementary annular groove in the hole, and a plurality of balls engaging both holes thereby preventing axial movement of the pin in the hole.

Not only is axial locating of the pins obtained, but the line contact between the balls and the annular grooves will compensate for any non-uniform stresses - occurring due to eccentric force application - by local plastic flow. Furthermore, there is now a great selection of materials for the pins, because riveting is dispensed with.

Preferably, each pin is held by two form-locking systems each comprising the complementary grooves and the balls in the outer webs of the wheel disc. Thus axial spreading of the wheel head and/or outward bending of the outer wheel webs and loosening of the root fixing is prevented.

Since the annular grooves acting as ball races will deform plastically under high loads, there would be some play between the balls and their allied race as stress is increased. In order to obviate such play, the pins maybe prestressed. This anticipates expected plastification.

Preferably, the or each locking system comprises a filler groove through which the balls may be inserted into the complementary annular grooves, the or each filler groove being closable after insertion of the balls. This prevents the balls dropping out during transport or similar operations.

Two embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cut-out of a side view of a lowpressure rotor disc provided with a locking system in accordance with the invention, Figure 2 is a section taken along the line A-A in Figure 1, and Figure 3 is a section similarto Figure 2 of a rotor disc and blade provided with two locking systems.

A wheel disc rim 1 has webs provided with cylindrical holes 2 through which cylindrical pins 3 are inserted to fix the tenon roots of the moving blades at the base. The pins 3 are locked axially by a form-locking system using small balls 4 of, say, 3 to 5 mm diameter which are arranged in corresponding annular grooves 5 lying perpendicular to the pin axis. The annular grooves 5 are each formed by two semi-circular grooves, one of which is provided in the pin 3 and the other of which is provided in the outer web of the wheel disc rim 1. The balls 4 are inserted into the grooves via a filler groove 6 arranged parallel to the corresponding hole axis.

This filler groove 6 is closable by a plugging fastener, e.g. a notched pin (not shown). As a rule, the annular grooves 5 are completely filled with balls 4.

In order to lock the pins 3 against axial displacement, it is only necessary to provide the formlocking system on one side. However, to avoid spreading of the wheel head rim the form-locking system may be used on both sides, i.e. in at least both of the outer webs as shown in Figure 3. Here the interlocking of the base of the blade 7 with the webs 1 is clearly shown.

In addition, the pins 3 may be prestressed in a manner known per se (axially), for instance, as in the case of bolted joints.

Such a locking system may be used in axial-flow turbines or compressors whose moving blades are subjected to high centrifugal stresses, e.g. long exhaust blades of the low-pressure elements of steam turbines of a high unit output, moving blades of gas turbines, axial-flow compressors in jet engines and similar machines.

1. A locking system to prevent axial displacement of pins connecting the webs of a wheel disc ring and tenon roots of moving blades in turbines, compressors and similar machines, wherein each pin is held in its respective hole by at least one form-locking system comprising an annular peripheral groove in the pin, a complementary annular groove in the hole, and a plurality of balls engaging both holes thereby preventing axial movement of the pin in the hole.

2. A locking system as claimed in Claim 1, wherein each pin is held by two form-locking systems each comprising the complementary grooves and the balls in the outer webs of the wheel disc.

3. An axial locking system as claimed in Claim 1 or 2, wherein the pins are prestressed.

4. An axial locking system as claimed in Claim 1, 2 or 3, wherein the or each locking system comprises a filler groove through which the balls may be inserted into the complementary annular grooves, the or each filler groove being closable after insertion of the balls.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Lockingsystem to prevent axial displacement of pins connecting the webs of a rotor disc and blade roots in turbines and similar machines This invention relates to a locking system to prevent axial displacement of pins connecting the webs of a rotor disc rim and the tenon roots of the moving blades of a turbine and similar machines. Axial locking arrangements are known in which the pins are riveted. While riveting has proved successful in many instances, it presents difficulties in the case of larger pins, especially because of the material used. Another method of locking the pins axially is caulking or deforming the outer edges of the holes. An object of the present invention is to provide an axial locking system without riveting or caulking so as to obtain a connection between the pins and the outer wheel disc webs which is effective in both axial directions and which will resist the bending moments and axial forces arising. The invention provides a locking system to prevent axial displacement of pins connecting the webs of a wheel disc ring and tenon roots of moving blades in turbines, compressors and similar machines, wherein each pin is held in its respective hole by at least one form-locking system comprising an annular peripheral groove in the pin, a complementary annular groove in the hole, and a plurality of balls engaging both holes thereby preventing axial movement of the pin in the hole. Not only is axial locating of the pins obtained, but the line contact between the balls and the annular grooves will compensate for any non-uniform stresses - occurring due to eccentric force application - by local plastic flow. Furthermore, there is now a great selection of materials for the pins, because riveting is dispensed with. Preferably, each pin is held by two form-locking systems each comprising the complementary grooves and the balls in the outer webs of the wheel disc. Thus axial spreading of the wheel head and/or outward bending of the outer wheel webs and loosening of the root fixing is prevented. Since the annular grooves acting as ball races will deform plastically under high loads, there would be some play between the balls and their allied race as stress is increased. In order to obviate such play, the pins maybe prestressed. This anticipates expected plastification. Preferably, the or each locking system comprises a filler groove through which the balls may be inserted into the complementary annular grooves, the or each filler groove being closable after insertion of the balls. This prevents the balls dropping out during transport or similar operations. Two embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cut-out of a side view of a lowpressure rotor disc provided with a locking system in accordance with the invention, Figure 2 is a section taken along the line A-A in Figure 1, and Figure 3 is a section similarto Figure 2 of a rotor disc and blade provided with two locking systems. A wheel disc rim 1 has webs provided with cylindrical holes 2 through which cylindrical pins 3 are inserted to fix the tenon roots of the moving blades at the base. The pins 3 are locked axially by a form-locking system using small balls 4 of, say, 3 to 5 mm diameter which are arranged in corresponding annular grooves 5 lying perpendicular to the pin axis. The annular grooves 5 are each formed by two semi-circular grooves, one of which is provided in the pin 3 and the other of which is provided in the outer web of the wheel disc rim 1. The balls 4 are inserted into the grooves via a filler groove 6 arranged parallel to the corresponding hole axis. This filler groove 6 is closable by a plugging fastener, e.g. a notched pin (not shown). As a rule, the annular grooves 5 are completely filled with balls 4. In order to lock the pins 3 against axial displacement, it is only necessary to provide the formlocking system on one side. However, to avoid spreading of the wheel head rim the form-locking system may be used on both sides, i.e. in at least both of the outer webs as shown in Figure 3. Here the interlocking of the base of the blade 7 with the webs 1 is clearly shown. In addition, the pins 3 may be prestressed in a manner known per se (axially), for instance, as in the case of bolted joints. Such a locking system may be used in axial-flow turbines or compressors whose moving blades are subjected to high centrifugal stresses, e.g. long exhaust blades of the low-pressure elements of steam turbines of a high unit output, moving blades of gas turbines, axial-flow compressors in jet engines and similar machines. CLAIMS

5. An axial locking system substantially as herein described with reference to Figures 1 and 2, or Figure 3 of the accompanying drawings.