US1347031A

US1347031A - Attachment of moving blades of elastic-fluid turbines

Info

Publication number: US1347031A
Application number: US145630A
Authority: US
Inventors: Guy Henry Lewis
Original assignee: British Westinghouse Electric and Manufacturing Co Ltd
Current assignee: Metropolitan Vickers Electrical Co Ltd
Priority date: 1917-01-31
Filing date: 1917-01-31
Publication date: 1920-07-20
Anticipated expiration: 1937-07-20

Description

H. L. GUY.

ATTACHMENT 0F MOVING BLADES 0F ELASTIC FLUID TURBINES.

APPLICATION FILED JAN. 31, 1917.

1,347,031, Patented July 20,1920.

D J J Q .w ITN E55 ES I INVENTOR M a il y UNITED STATES PATENT OFFICE. I

HENRY LEWIS GUY, OF MANCHESTER, ENGLAND, ASSIGNOR TO THE BRITISH WEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY LIMITED, A COMPANY OF GREAT BRITAIN.

ATTACHMENT 0F MOVING BLADES 0F ELASTIC-FLUID TURBINES.

Specification of Letters Patent.

Patented July 20, 1920.

Application filed January 31, 1917. Serial No. 145,630.

To all whom it may concern:

Be it known that I, HENRY LEWIS GUY, a subject of the King of Great Britain, and a resident of Manchester, in the county of Lancaster, England, have invented a new and useful Improvement Relating to the Attachments of Moving Blades of Elastic- Fluid Turbines, of which the following is a specification.

This invention has for its object to provide an improved attachment for the moving blades of an elastic fluid turbine of the kind in which the turbine wheel, to which the blades are to be attached, is slotted in an axial direction one slot being provided for the reception of each blade and the blades are furnished with tongues, shaped to fit the axial slots in the wheel, each blade being secured in its slot by two or more rivets or pins located in different pitch circles the holes for the reception of said pins being drilled or formed in an axial direction in such a manner that one half of each pin lies in the side of the slot in the wheel and the other half in the tongue of the blade.

The invention has for its object to provide an improved blade attachment of the above kind which with a similar amount of material will withstand greater operating stresses as rivets or pins of larger diameter can be used to secure the blades in position than with the attachment as hitherto constructed.

According to this invention the slots in the turbine wheel are tapered the greatest width of the slots in a circumferential direction being at their outer ends. The tongues of the blades are tapered to correspond with the slots and are secured in position therein by rivets or pins in the manner above described.

The improved attachment is illustrated in the accompanying drawing in which 3 is a fragment of a turbine wheel having axial tapered slots 4, 4, in its periphery, one slot being provided for each blade. The blades 5 are provided at the root with tongues 6 tapered to fit the slots 4. Two series of holes on different pitch circles are drilled in an axial direction in such a manner that one half of each securing pin or rivet 7 lies in the side of a slot 4 and the other half of said pin or rivet in the tongue 6 of the blade in said slot as shown.

lVhere two securing pins of equal diameter are used, the circumferential thickness of the tongue 6 at the outer pin 7 should preferably be twice the thickness of the tongue at the inner pin 7. If three pins are used the thickness of the tongue at the middle pin should be twice the thickness of the tongue at the pin nearest the wheel axis while the thickness of the tongue 6 at the outermost pin 7 should be three times that of the tongue at the innermost pin. If, however, pins of unequal diameter are used the ratio of the circumferential thicknesses of the tongue at the places adjacent to the pins should be equal to the sum of the diameters of the two pins divided by the diameter of the pin nearest the wheel axis.

The prime object of this invention is to provide a fastening means for a turbine blade which will result in a reduction in the weight of the revolving mass at or near the periphery of the revolving wheels in the turbine. My fastening means is designed to secure the maximum strength per unit weight of the material employed. In a blade fastening of this nature there are two principal stresses to be taken into account, one the shearing stress of the rivets and the other a tensile stress of the blade shank or of the projecting tooth of the wheel at or near where the rivets connect these two parts. The present blade fastening has what might be termed five danger points, namely, the shearing stresses in the two rivets and the tensile or tearing stresses of the blade shank and of the wheel across the narrowest portion, that is opposite the grooves formed for the reception of the rivets. Taking into consideration the materials employed and the relative resistances to the shearing and tensile stresses, the blade fastening is so calculated that all of these stresses are sub stantially equal and therefore the factor of safety of the blade fastening is substantially equal at all. these five different points.

The rivets or pins may be secured in position in any suitable way.

I claim as my invention:

1. In combination with a turbine rotor provided with an axially extending tapered slot having its greatest circumferential width at its outer end, a blade having a tongue tapered to correspond with said slot, and two securing pins for the blade passing half through said tongue and half through the walls of said slot and located in difierent pitch circles.

2. In combination with a turbine rotor provided with an axially extending tapered slot having its greatest circumferential width at its outer end, a blade having a tongue tapered to correspond with said slot, and two securing pins for the blade located on opposite sides of said tongue passing half through said tongue and half through the walls of said slot and located in different pitch circles.

3. In combination with a turbine rotor provided with axially extending tapered slots having their greatest circumferential widths at their outer ends, a blade for each slot having a tongue tapered to correspond with its slot, and two securing pins for each blade located on opposite sides of said tongue and passing half through said tongue and half through the adjacent wall of said slots and located in different pitch circles.

4. In combination with a turbine rotor provided with an axially extending tapered slot having its greatest circumferential width at its outer end, one wall of said slot extending radially of the rotor while the other ary, 1917.

HENRY LEWIS GUY. Witnesses:

F. NIXON, W. MORRIS.