US2398140A - Bladed rotor - Google Patents

Description

April 9, 1946- F. A. M. 'HEPPNER 2,398,140

BLADED ROTOR Filed Aug. 11, 1944 INVENTO/F .524 Ina-. 6

Patented Apr. 9, 1946 BLADED ROTOR Fritz Albert Max Heppner, Leamington Spa, England, assignor to Armstrong Siddeley Motors Limited, Coventry, England Application August 11, 1944, Serial No. 549,037

In Great Britain December 8, 1943 6 Claims.

This invention relates to a rotor having a pcripheral row of blades.

One of my objects is to provide a blade lock. and particularly one which can be used in the casein which the blades carry relatively-thin fiat shrouds at their outer ends which form a ring when the parts are assembled, as the existence of any lock eliminates or at least reduces bending stresses at the blade root.

In the accompanying sheet of drawings:

Figure 1 is a fragmentary, part-sectional; elevational view of a compound rotor according to the invention, the view showing two compressor blades with shrouds carrying externally turbine blades and the view of the rotor being a section taken on the line II of Figure 2;

Figure 2 is a cross-section through a part of the rotor with a compressor and turbine blade shown in elevation, the view being from the right of Figure 1;

Figure 3 is a fragmentary plan view of two shrouds when circumferentially separated from one another; and

Figure 4 is a fragmentary perspective view of the slotted end of a shroud.

According to one feature of the invention, the blades carry relatively-thin shrouds at their outer ends which form a ring when the parts are assembled, and each adjacent pair of shrouds is interlocked against lateral or radial movement by means of oppositely-inclined slots in the mating edge of one shroud of a pair and acomplementary pair of projections on the mating edge of the other shroud, whereby the shrouds can move in a circumferential direction during assembly or dismantling of the parts.

Preferably, there are only two slots in each of the appropriate mating edges, one slot being narrower than and imposed upon the other. The slots may be at right-angles to one another, for example, inclined to the fiat surfaces of a shroud at approximately 45".

In the construction shown in the drawings, the rotor l2 has a deep peripheral groove l3 in it and the walls thereof-are parallel to one another and formed with toothed spiral ridges I4 in the manner disclosed in the specification accompanying my patent application No. 484,915, filed April 28,

1943. Each compressor blade I5, the form of which is indicated by the chain lines I6, is formed with a root l1 opposite faces of which are toothed to enable it to be secured by a screwing action in the peripheral groove l3. The other two opposite faces of the blade root are grooved as shown at l8 for lightening purposes, but there remains between the two grooves l 8 a body of metal through which passes a radial line 20 on which the centres of gravity of various cross-sections of the blade approximately lie. Incidentally, the centres of gravity of various cross-sections of the associated turbine blade 2| also approximately lie on this same radial line.

The compressor blade carries at its outer end a flat shroud 23 which in turn supports the turbine blade (the form of which is indicated by the chain line 24) and it is desirable, as stated, to interlock the abutting edges of each pair of shrouds as the existence of any such lock reduces bending stresses at the blade root to a great extent. Both ends of a compressor blade being in effect held, the result is that bending of a compressor blade is negligible. Actually, bending in a turbine blade takes place in approximately only half its length, and vibrations are only possible on the short length of the turbine blade where bending can occur.

As will be seen particularly from an examination of Figures 3 and 4, the interlock consists of 25 two transverse grooves 25, 26 of which the former is narrower than and imposed upon the latter, whilst the mating edge of the other shroud is formed with complementary projections indicated at 21. Such a form of interlock will allow the shrouds to approach one another in a circumferential direction-as is necessary when the individual compressor blades are being screwed into the rotor, yet when the parts are assembled it is impossible for the shrouds to move radially or laterally with respect to one another.

The particular form of interlock disclosed'can be easily manufactured, and it can be satisfactorily applied to thin shrouds. The lock itself is so sturdy that the shroudswork under safe stresses.

Withthe construction shown it is possible to form a compound rotor for an internal-combustion turbine plantin which some or all of the shrouds carry externally blades forming an outer row, such shrouds being integrally united to their associated supporting blades.

What I claim as my invention and desire to secure by Letters Patent of the United States is 2 1. A rotor having a peripheral row of blades, the latter carrying relatively-thin, flat shrouds at their outer ends, the shrouds forming a ring when the parts are assembled, each adjacent pair of shrouds being interlocked against lateral and radial movement by means of oppositely-inclined grooves in the mating edge of one shroud of a pair dismantling of the parts.

2. A rotor, according to claim 1, in which there are only two grooves in each of the appropriatemating edges, one groove being narrower than and imposed upon the other groove.

3. A rotor, according to claim 1, in which there are only two grooves in each of the appropriate mating edges, one groove being narrower than and imposed upon the other groove, and the grooves being inclined to the flat surfaces of a shroud at approximately 45.

4. A rotor having a peripheral row of blades, the latter carrying relatively-thin, flat shrouds at their outer ends, the shrouds forming a ring and having means at their edges by which they are adapted to interlock with one another (against radial and lateral movement) when the parts are assembled, theinterlocking means being such as to allow or relative circumferential movement between the shrouds, the blade roots being formed. with teeth, and the rotor being formed with complementary spiral ridges in opposite sides of a parallel-sided peripheral groove in the rotor to engage said teeth such that the blades, whilst being screwed in during assembly, will move radially inwardly until their roots abut one another and their shrouds interlock.

5. A rotor, according to claim 4, in which the blade roots are formed with flanges adapted to overlap and engage the side faces of the rotor.

6. A rotor, according to claim 4, in which some at least of the shrouds carry externally blades forming an outer row, such shrouds being in-' tegrally united to their associated blades.

FRITZ ALBERT MAX HEPPNER.

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