Propeller blade retention system

• US 5,263,898 A
• Filed: 12/02/1991
• Issued: 11/23/1993
• Est. Priority Date: 12/14/1988
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Elston, Sidney B. III, Simon, Victor H. III, Butler, Lawrence, Tseng, Wu-Yang
• Primary Examiner(s): KWON, JOHN
• Application Number:
  US07/798,986
• Time in Patent Office: 722 Days
• Field of Search: 416/128, 416/129, 416/135, 416/157 B, 416/206, 416/221, 416/147, 416/153
• US Class Current: 416/147
• CPC Class Codes: B64C 11/06 for variable-pitch blades

Abstract

The invention concerns the mounting of propeller blades to a ring-shaped rotor. The blades are of the variable pitch type, and the shank of each blade extends through a respective hole in the rotor. Each hole contains an annular shelf which is fastened to the wall of the hole and surrounds each shank. Each shank bears a pair of bearing races which sandwich the annular shelf in order to connect the blade to the rotor. Bearing rollers are positioned between the annular shelf and the bearing races.

Claims

1. In a gas turbine engine with a plurality of variable pitch propulsor blades rotatable about a pitch axis, a rotatable blade retention system for supporting said plurality of propulsor blades upon a ring surrounding and driven by a source of motive power, comprising:

a) a plurality of trunnions for supporting said propulsor blades, each trunnion fitting into said ring and comprising radially inner and outer trunnion parts, wherein

i) said ring includes a blade mounting section having an opening with an annular shelf for receiving the trunnions therethrough, and

ii) wherein said trunnions include buttress-type mating threads on the radially inner and outer parts for capturing the bearings and annular shelf therebetween to thereby permit removal of said inner and outer parts from the ring without disassembly of the ring;

b) a plurality of alignment bearing rollers positioned between the outer trunnion part and an upper surface of said shelf;

c) a plurality of thrust bearing rollers positioned between the inner trunnion part and a lower surface of said shelf;

d) wherein said alignment bearing rollers and said thrust bearing rollers each

i) separate the trunnion from the blade mounting section and allow for pitch-change rotation,

ii) ride in hardened races,

iii) comprise tapered roller bearings forming frustrums of cones, each of said frustrums of cones including a small end having a first diameter and a large end having a second diameter, wherein said first diameter of said thrust bearing rollers is approximately the same size as said first diameter of said alignment bearing rollers and wherein said second diameter of said thrust bearing rollers is larger than said second diameter of said alignment bearing rollers in order to accommodate blade centrifugal loads applied to said thrust bearing rollers which are significantly larger than loads applied to said alignment bearing rollers;

e) sealing means for inhibiting pressurized air from escaping from a region near the source of motive power through openings in the ring;

f) a pitch-change mechanism having a bevel drive gear wherein said trunnions include a gear sector along an inner portion of said radially outer part for engaging said bevel gear, and in response to movement of said bevel gear, changing the position of said trunnion and the pitch of said propulsor blades;

g) means for correcting pitch-rigging-error in said propulsor blades, wherein said means for correcting pitch-rigging-error includes

i) a plurality of keys which permit relative positioning between said trunnion radially outer part and said gear sector in controlled increments of 1/4 degree in either direction;

ii) a bolt which fastens a selected one of said keys to said trunnion radially outer part, said bolt passing through respective bolt holes in said selected key and said trunnion radially outer part;

iii) wherein said selected key positions said trunnion radially outer part and said gear sector with respect to a reference comprising said trunnion radially outer part bolt hole;

iv) wherein said bolt is accessible through a hole in said gear sector, thereby facilitating installation of said selected key; and

v) means for positioning the alignment bearing rollers to have axes which lie approximately on the surface of a first cone, and positioning the thrust bearing rollers to have axes which lie approximately on the surface of a second cone, the first and second cones having different respective apex angles;

h) said alignment rollers forming a first row making a first angle with the pitch axis and said thrust bearing rollers forming a second row making a second angle with said pitch axis wherein said first and second angles are different, wherein a load applied to the alignment bearing rollers is borne primarily as hoop stress in the ring and a load applied to the thrust bearing rollers is borne primarily as a shear load applied to the annular shelf.

2. In a gas turbine engine with a plurality of variable pitch propulsor blades rotatable about a pitch axis, a rotatable blade retention system for supporting said plurality of propulsor blades upon a ring surrounding and driven by a source of motive power, comprising:

a) a plurality of trunnions for supporting said propulsor blades, each trunnion fitting into said ring and comprising radially inner and outer trunnion parts, wherein

i) said ring includes a blade mounting section having an opening with an annular shelf for receiving the trunnions therethrough, and

ii) wherein said trunnions include buttress-type mating threads on the radially inner and outer parts for capturing the bearings and annular shelf therebetween to thereby permit removal of said inner and outer parts from the ring without disassembly of the ring;

b) a plurality of alignment bearing rollers positioned between the outer trunnion part and an upper surface of said shelf;

c) a plurality of thrust bearing rollers positioned between the inner trunnion part and a lower surface of said shelf;

d) wherein said alignment bearing rollers and said thrust bearing rollers each

i) separate the trunnion from the blade mounting section and allow for pitch-change rotation,

ii) ride in hardened races,

iii) comprise tapered roller bearings forming frustrums of cones, each of said frustrums of cones including a small end having a first diameter and a large end having a second diameter, wherein said first diameter of said thrust bearing rollers is approximately the same size as said first diameter of said alignment bearing rollers and wherein said second diameter of said thrust bearing rollers is larger than said second diameter of said alignment bearing rollers in order to accommodate blade centrifugal loads applied to said thrust bearing rollers which are significantly larger than loads applied to said alignment bearing rollers;

e) sealing means for inhibiting pressurized air from escaping from a region near the source of motive power through openings in the ring;

f) a pitch-change mechanism having a bevel drive gear wherein said trunnions include a gear sector along an inner portion of said radially outer part for engaging said bevel gear, and in response to movement of said bevel gear, changing the position of said trunnion and the pitch of said propulsor blades;

g) means for correcting pitch-rigging-error in said propulsor blades, wherein said means for correcting pitch-rigging-error includes

i) a plurality of keys which permit relative positioning between said trunnion radially outer part and said gear sector in controlled increments of 1/4 degree in either direction;

ii) a bolt which fastens a selected one of said keys to said trunnion radially outer part, said bolt passing through respective bolt holes in said selected key and said trunnion radially outer part;

iii) wherein said selected key positions said trunnion radially outer part and said gear sector with respect to a reference comprising said trunnion radially outer part bolt hole;

iv) wherein said bolt is accessible through a hole in said gear sector, thereby facilitating installation of said selected key; and

v) means for positioning the alignment bearing rollers to have axes which lie approximately on the surface of a first cone, and positioning the thrust bearing rollers to have axes which lie approximately on the surface of a second cone, the first and second cones having different respective apex angles;

h) said alignment rollers forming a first row making a first angle with the pitch axis and said thrust bearing rollers forming a second row making a second angle with said pitch axis wherein said first and second angles are different, wherein a load applied to the alignment bearing rollers is borne primarily as hoop stress in the ring and a load applied to the thrust bearing rollers is borne primarily as a shear load applied to the annular shelf; and

i) a dovetail connection between said trunnion radially outer part and the blade;

j) spring means for simulating a centrifugal load on the blade, thereby reducing blade clanking when the gas turbine engine is inoperative, wherein said spring means includes a radial leg; and

k) a blade retainer fixedly attached to said trunnion radially outer part with first and second retention bolts, wherein

i) said blade retainer prevents said dovetail connection from sliding out of a slot in said trunnion radially outer part,

ii) said blade retainer abuts said spring means radial leg, thereby locking said spring means against said dovetail connection and preventing said spring means from being dislodged due to vibration, and

iii) said first and second retention bolts react impact loads such as those which occur when a bird strikes the propulsor blades.