US2651494A - Turbine disk - Google Patents

Description

p 8, 1953 T. A. PERSSON 2,651,494

TURBINE DISK Filed Dec. 8, 1950 Patented Sept. 8, 1953 TURBINE DISK Thure Albert Persson, Trollhattan, Sweden, as-

signor to Svenska Flygmotor Aktiebolaget, Trollhattan, Sweden, a Swedish joint-stock company Application December 8, 1950, Serial No. 199,761 In Sweden November 24, 1949 4 Claims. 1

This invention relates to blade supporting discs especially of gas turbines and internal combustion turbines. More particularly, the invention has reference to the fastening of separately manufactured blades to such discs.

In turbines of the kinds stated, above all in internal combustion turbines, the bladings are subjected not only to the action of great centrifugal forces due to the high rate of flow of the gases with resulting high stresses on the bladings, but also to a relatively high temperature; These combined influences of great centrifugal forces and high temperatures give rise to many problems of mechanical and thermic nature in con structing the bladings and act as a bar to the obtainment of a good thermic eificiency. A particularly delicate problem is to eliminate the tendency of the blades towards elastic vibrations. Forming the blades integrally with the turbine discs gives the greatest strength, provided elastic vibrations could be avoided. It is a well known fact, however, that the integral blades are most liable to get into resonance vibrations and for this reason it is preferred to use separately manufactured blades and attach them to the turbine disc. The bladings thus resulting counteract the comparatively small forces which give rise tothe resonance vibrations, thereby eliminating the dangerous elastic vibrations appearing in such bladings, particularly if the blades are relatively loosely fastened to the disc.

According to a hitherto preferred method of fastening loose blades to turbine discs, the roots of the blades are formed with parallel grooves and teeth, a corresponding groove being formed in the turbine disc for each individual blade. This working of the blades and the turbine disc must be made with a very high accuracy and with such a, snug fitting that each blade root may be rigidly secured to the disc by forcing its root into engagement with the respective groove. This is a difficult and expensive work: in addition, blades fastened in this way will not obtain an equally good protection against elastic vibrations as blades with a less snug fitting.

The object of this invention is to provide a fastening of separately manufactured blades to a turbine disc in a simple and inexpensive way with a resulting elimination of elastic vibrations.

The invention is illustrated in the accompanying drawing, in which:

Fig. l is an elevation of a portion of a turbine disc with blades, looking in a direction parallel with the axis of the turbine disc,

Fig. 2 is a section on the line IIII of Fig. 1;

2 Fig. 3 is a section on the line III-III of Fig. 1

and

Fig. 4 is an end View of Fig. 1 looking in the direction of the arrow IV, that is to say, in a radial direction with relation to the axis of the disc.

Formed in the turbine disc I, as by a milling operation, are prismatic grooves 2 extending in a direction parallel with an axial and tangential plane touching the periphery of the respective groove, said plane being further either parallel with the axis of rotation or forming an angle therewith (in the drawing the grooves are also parallel with the axisfof rotation). Each groove is bounded laterally by plane ornearly plane surfaces 3 and 4 substantially extending radially in the plane of rotation. The roots 5 of the blades are worked so as to fit in the grooves with a slight degree of clearance sufficient for allowing the roots to easily slide therein.

With the blades fitted in the grooves of the turbine disc borings B and l are formed partly in. the tooth-like portions of the disc remaining between the grooves and partly in the roots of the blades with the axes of the borings situated in the contact surfaces 3 and 4 and extending in directions forming an angle with an axial plane touching the periphery at the respective blade root. The borings ii and l are not throughextending but bounded by bottoms 8 and 9 respectively. The borings 6 and I extend from opposite sides of the turbine disc in inclined directions with their open ends l0 and II located at a shorter radius than the bottom ends 8 and 9. Inserted in the borings so as to loosely fit therein are pins l2 and 13. In order to prevent said pins from dropping out of the borings, when the turbine disc is at rest, caulking impressions are made adjacent the edge of the borings, as indicated at i and [5. When the turbine disc rotates at a certain speed, the pins l2 and [3 are pressed by the action of the centrifugal force against the bottoms '8 and 9 of the borings.

Since the pins l2 and i3 extend in oppositely inclined directions from opposite sides of the disc, as shown in Figs. 2 and 3, they may counteract any tendency of the blade roots towards displacing in the grooves and, as a result, the blades will remain in their proper positions, though the roots may have a slight play in their grooves.

Due to the oppositely inclined directions of the borings 5 and l the weakening caused by the, borings will not be essentially greater than that caused by a single pin in each blade root. It is only at the place where the directions cross each other, that is to say, at the middle of the blade roots and the respective teeth of the turbine disc, that two oppositely oblique pins give rise to a more weak point than a single pin would do. On the other hand, the blade root and the respective teeth of the turbine disc will. be. subjected to somewhat higher stresses at their ends than in the middle portion of the material.

It is evident from the drawing and the foregoing description that the invention results in a very simple and easily manufactured construe:- tion as compared with those hitherto known. In addition, the invention eliminates or. counteracts to a high extent dangerous elastic: vibrations. of. the blading.

I claim:

1. In a turbine, a rotor di'schaving a= rim with a set of grooves in the periphery thereof, each groove extending in a transverse direction. from one side of the rim to the other, a corresponding set of blades having roots. engaging: said grooves, one side surface of each groove andithe side surface of the: respective blade root-in contact therewith having a hole extending from one side surface of the rim of the. rotor disc to a point at a distance from the opposite side surface of the rim, the other side surface of the groove and the blade root surface. in contact therewith having a hole extending from said last-mentioned side surface of the rim to a point 39 2. In a turbine as set forth in claim 1, and in which the blade roots are fitted in the grooves of the rim of the rotor disc with clearance.

3. In a turbine as set forth in claim 1, and in which the pins are fitted in the holes of the groovetsides andblade roots with a certain degree of clearance.

4. In a turbine, a rotor disc having a rim with aicircular set of grooves in the periphery thereof,

' each groove extending in an axial direction from oneside of the rim to the other, a corresponding circular set of blades, having roots engaging the grooveswith a certain degree of clearance, side surfaces of the grooves and the blade roots in contact with" each other having bottomed holes extending alternately from opposite sides of the rim ofthe rotor' disc with bottoms positioned at a greater radius of the rotor disc than the open ends of the holes, pins fitted in said holes with a certain degree of clearance and sealed against unintentional dropping out through the open endsof' the holes, the pins of the circular set of blades and grooves being inclined alternately in opposite directions.

THURE ALBERT PERSSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,347,031 Guy July 20, 1920 1,452,602 Herr Apr. 24, 1923 2,317,338 Rydmark Apr. 20, 1943 2,445,154 Reed July 13, 1948

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