US1347343A - Means for securing turbine-rotors to their shafts - Google Patents

Description

B. LJUNGSTRUM. MEANS FOR SECIURING TURBINE ROTORS TO THEIR SHAFTS= APPLICATION FILED MAR. 25, ,I9I9.

1,347, 343. Pat nt d uly 20, 1920.

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Inventor:

Bil" erLJun strim, by

His oqtto neg.

UNITED STATES PATENT OFFICE;

BIB-GER LJUNGSTRbM, F STOCKHOLM, SWEDEN, ASSIGNOR TO AKTIEBOLAGET LJ'UNGSTRbMS ANGTURBIN, A. CORPORATION OF SWEDEN.

MEANS FOR SECURING TURBINE-ROTORS TO THEIR SHAFTS.

Patented July 20, 1920.

' Application filed March 25, 1919. Serial No. 285,032.

To all whom it may concern:

Be it known that I, BrRoER LJUNos'rRoM, 21 Narnavagen, Stockholm, in the Kingdom of Sweden, have invented certain new and useful Improvements in Means for Securing Turbine-Rotors to Their Shafts, of which the following is a specificatlon.

The present invention relates to means for securing turbine rotors to their shafts and has for its object to provide means for keeping the parts tight at all times.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and claims appended thereto.

In the accompanying drawing which illustrates one of the embodiments of my invention, Figure 1 is an axial section of a turbine shaft and a part of the rotating blade element or rotor carried thereby, taken on line 1-1 of Fig. 2; Fig. 2 is an end view of the shaft and portion of the rotor, and Fig. 3 is a detailseotional view taken on line 3-3 of Fig. 2. v I

1 indicates a part of a rotor upon which are mounted concentric rows of blades 2. In the type of turbine to which my invention more especially relates two rotors are provided arranged face to 'face with concentric rows of axially extending blades between and through which the steam flows radially outward. The rotor is provided with a hubv 3 containing slots 4 through which steam flows from a suitable source to the inner blade ring. The hub is provided with a conical bore to receive one end of the stub shaft 5, and the two parts are held against relative rotation by a plurality of equally spaced keys 6 which may advantageously be made of round stock finished to the required size, These keys have a slight taper from their inner to their outer ends so that when moved outwardly from the center ofthemachine they will prevent an v on its outer'end which is secured to the main shaft 8 by aseries of equally spaced bolts 9, a shoulder 10 .betweenthetwo serving to hold them central. The main shaft is mounted in a suitable bearing 8 having the usual babbit or other lining containing suitable oil grooves.

In any turbine, and particularly one where boiler steam is-admitted directly to.

the rotor in the manner illustrated, the hub service.

ion shoulder on the shaft.

of the rotor expands due to increase of temperature and if it does so faster than the shaft it will become loose thereon. A loose rotor is highly objectionable since it causes more or less violent vibrations, depending upon the degree of looseness. These vibratlons sometimes cause considerable damage to the blades, packings, etc.', and if serious require the machine to I avoid this objection by the following means The stub shaft is made hollow and inside of it is a long, tubular tension member 11 having a shouldered head on the outer end which-is snugly fitted to a compan- The purpose in making the member hollow is to permit steam to enter it so that it and the stub shaft will be heated to substantially the same temperature as the hub of the rotor. The

stub shaft and tension member are prevented from'turning independently of each other by a suitable means, a screw being shown for the purpose. Near the inner, end the tubular member is provided with a guiding surface 12 which makes a good sliding fit with the inner wall or bore-of the stub shaft so as to hold the parts in their proper relation. The inner end ofthe member is provided with a coarse screw thread to receive the nut 13, the latter serving as a means for putting the member 11 under tension. To prevent the faces of the nut and hub from directly engaging a washer 14 of different metal either harder or softer is interposed between the two.

By calculation or experiment or both I determine how much the bore of the hub will enlarge due to temperature changes. It is evident that ifthe hub expands more quickly than the shaft it will become loose. It is further evident since the contacting surfaces of the shaft and wall of the bore areconical that the parts can again be made tight if some means is provided which acts when'the hub is in its expanded condition to draw the stub shaft and hub together.

Such a means is found in the tension member 11 and nut 13. Having determined what the maximum enlargement of the hub will be and how much axial movement is necessar to bring the parts into firm contactv under al conditions, I so design said tension member that it will, when cold, be stretched by an amount somewhat greater than the total amount of relative axial movement between the hub and stub shaft I at any time. As a result of this when the hub enlarges for any reason the tension member will force the hub farther on to the shaft with the result of keeping it tight. The hub may be advanced on the shaft by one or by several successive heatings of the sired but I prefer to make it hollow because it is highly desirable to heat it and also the hub and shaft to asnearly the same temperature as possible. The outer end of the member is screw-threaded to receive the nut 15 which prevents steam from passing through it into the 'oint between the stub and main shafts.

preferably threaded at 16 so that when it is desired to remove the rotor from the stub shaft a bar may be threaded intothe opening until it engages the nut 15 and by turning the same the member will be put under additional tension with the result of taking pressure off of the nut 13 and permitting it to be easily removed.

To make sure that the nut 13 does not work loose while the machine is in operation, it is provided with a number of equally spaced holes 17 arranged in a circle. In the adjacent part or parts are similar holes 18 arranged in a circle of the same diameter, the number however, differing from that in the nut. After the nut is screwed to its seat, a copper or other pin 19 is driven into the registering holes and slightly upset on its inner end. This looks the arts against relative angular movement. 0 take off the nut the pin is first drilled out after which the nut can be rotated as usual. I may, however, in some cases use an ordinary set screw with apointed end.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof;

but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a turbine, the combination of. a

rotor, a hollow shaft having a tapered end to which the rotor is keyed, a tension member which is carried by the shaft, and means he inner end is also a plurality of ho mounted on the member for holding the rotor on the shaft. and said member under tension.

2. In a turbine, the. combination of a rotor, a hollow shaft having a taper at one end upon which .the rotor is, keyed and a shoulder at a point remote from said end, a tension member which is seated on the shoulder and extends inwardly beyond the hub of the rotor and has a screw-threaded end, and a nut which holds the rotor on the shaft against axial 'movement and also keeps said member under tension.

3. In a turbine, the combination of a bladed rotor having .a hub with openings therein through which steam flows to the blades, a hollow shaft having a taper at its inner end to receive the rotor, a hollow tubular member located in the shaft and to which steam from said openings is admitted, and a shoulder and nut on the ends of the member one of which engages the shaft and the other the rotor, said nut and shoulder hold-J ing the hub against axial movement and also maintaining said member in tension.

4. In a turbine, the combination of a I rotor, a hollow stub shaft which has a taper on its inner end on which the rotor is mounted and a flange and shoulder at its outer end, a tubular member which is seated on the shoulder at its outer end, a mm on the inner-end of the member which maintains it in tension and holds the rotor on the'shaft,

and a main shaft' which is secured to the stub ihzltft by a centering shoulder and retaining 5.- In a turbine, the combination of.a rotor having a tapered bore, a shaft having a tapered endupon whichthe rotor is mounted, tapered keys which prevent the rotor from turning on'the shaft, a member located within-the shaft, and anut and shoulder on the member, one ofwhich engages the shaft, and the other the rotor, said shoulder and nut serving to hold the member in tension at all times and move the rotor and keys axially on the shaft when the rotor enlarges faster than the shaft.

I 6. In a turbine, the combination of -a 4 rotor, a shaft having a taper upon which the rotor is mounted, a tension member within the shaft which is anchored at one end and is provided with a screw thread at the other,

a nut on the member which maintains it in tension and holds the rotor on the shaft, said nut and rotating parts being provided with es arranged in circles of the same diameter, the num r of holes in the nut differing from that in aid parts, and

' a metal plug which is inserted in a pair of registering holes to prevent relative angular movements of the nut and said arts.

In witness whereof, 'I have ereunto set my hand this 4th day of February," 1919.

BIRGER LJUNGSTRCM.

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