PITCH CHANGING MECHANISM FOR FAN BLADES

Abstract: A non-rotating actuating system for pitch con­ trol of a fan in a bypass turbine engine in which the actuating ring (20), that rotates with the fan and is moved axially to change the pitch of the fan blades (2), is supported by a part of the fixed structure (12) thereby to minimize loading of the disc supporting structure.

Description: This invention relates to a variable pitch control for a bypass fan in a turbine engine installation including a row of fan blades, each having at its inner end a crank arm by which the pitch of the fan blades may be changed, a supporting ring for the fan blades, each blade being mounted at its base in the ring and in a position to rotate on a radial axis, said supporting ring having an inwardly extending flange, a fixed support structure for the ring, a first bearing disposed between said inwardly extending flange and said fixed support structure for supporting the ring to rotate on the fixed structure, a first translatable sleeve splined to the support ring to rotate therewith and to slide axially relative thereto, a row of links connecting said sleeve with the crank arms and the blades, a second non-rotating translatable actuating sleeve within said first sleeve, a second bearing between said sleeves to cause said sleeves to move axially in unison, slines between the fixed structure and said second sleeve to support the second sleeve against rotation, and means for actuating said second sleeve axially to change the pitch of the blades in unison, said supporting ring having a proximal side and a distal side with respect to said actuating means. A variable pitch control of this type for a bypass fan in a turbine engine is disclosed in EP-A- 0 203 881. Where the fan is mounted in surrounding relation to the compressor case of a bypass engine, the construction of the actuating structure is critical. If the actuators are mounted on the supporting ring structure for the fan blades, the high centrifugal loads increase the load on the ring and necessitate a heavier support structure for the blades. Not only is there a high centrifugal load, but the feedback from the actuator to the static points from which the device is controlled results in complications. According to the invention the variable pitch control is characterized in that the inwardly extending flange is provided at the proximal side of the supporting ring, and that the connecting links extend through openings in the inwardly extending flange. The foregoing and other features and advantages of the present invention will become more apparent from the following description and accompanying drawing, wherein: The single figure is a fragmentary longitudinal section view through the blade support disc and the blade actuating structure. The blades 2 in the row of blades have their roots located in radial openings in a ring or disc 4 on bearings 6 to permit each of the blades to rotate on its radial axis for the purpose of changing the pitch of the blade. The ring or disc 4 has an integral inwardly extending flange 8 having a cylindrical inner end on which a bearing 10 is positioned. This bearing engages a fixed supporting structure 12 forming a part of the engine case and the ring or disc 4 is supported for rotation within the supporting structure by this bearing arrangement. Each blade carries at its inner end a crank arm 15 and each crank arm is connected to an actuating link 16 extending rearwardly from the crank arm. The several links extend through openings 18 in the flange 8 large enough to permit the necessary rocking movements of the links as the blades are actuated. The rearward ends of the links are connected to an actuating sleeve 20 supported for axial sliding movement within a supporting element 22 extending rearwardly from the flange in surrounding relation to the links and the sleeve. Cooperating splines 24 and 26 on the outer surface of the sleeve 20 and on the cooperating element 22 assure the rotation of the sleeve 20 with the blade supporting ring or disc and permit the necessary axial movement of the sleeve 20 to actuate the blades in pitch changing, A non-rotating sleeve 28 is supported within the sleeve 20 by a thrust bearing 30 which permits the sleeve 20 to rotate around the sleeve 28, but which causes the sleeve 28 and the sleeve 20 to move axially in unison. The sleeve 28 is kept from rotation by cooperating splines 31 and 32 on the inside surface of the sleeve 28 and on a support flange 34 on the fixed supporting structure 12. The sleeve 28 is moved axially by suitable translating devices 36 connected to axially extending links 38 on the sleeve. The ring or disc 4 has a proximal end and a distal end with respect to the translating devices 38 and the inwardly extending flange 8 is formed on the proximal side of the ring or disc 4. The devices 36 may be of any suitable construction. It should be noted that the several circumferentially spaced devices are all caused to move in unison so that the sleeve 28 will be readily moved axially as a unit. For example, the several devices 36 may be three geared-ball screw actuators connected together and driven by a flexible cable shaft system. Such devices are well-known and will not be described. Although not a part of the invention, the drawing shows a seal support structure 40 mounted on a part of the fixed structure 12 and extending forwardly therefrom in surrounding relation to the sleeve 28 and sleeve 20. This structure 40 carries sealing elements 42 and 44 and is positioned in cooperating sealing arrangement with sealing rings 46 and 48 on the blade support disc 4.

Claims: 1. A variable pitch control for a bypass fan in a turbine engine installation including: a row of fan blades (2), each having at its inner end a crank arm (15) by which the pitch of the fan blades (2) may be changed, a supporting ring (4) for the fan blades (2), each blade (2) being mounted at its base in the ring (4) and in a position to rotate on a radial axis, said supporting ring (4) having an inwardly extending flange (8), a fixed support structure (12) for the ring (4), a first bearing (10) disposed between said inwardly extending flange (8) and said fixed support structure (12) for supporting the ring (4) to rotate on the fixed structure (12), a first translatable sleeve (20) splined to the support ring (4) to rotate therewith and to slide axially relative thereto, a row of links (16) connecting said sleeve (20) with the crank arms (15) and the blades (2), a second non-rotating translatable actuating sleeve (28) within said first sleeve (20), a second bearing (30) between said sleeves (20, 28) to cause said sleeves (20, 28) to move axially in unison, splines (31, 32) between the fixed structure (12) and said second sleeve (28) to support the second sleeve (28) against rotation, and means (36) for actuating said second sleeve (28) axially to change the pitch of the blades (2) in unison, said supporting ring (4) having a proximal side and a distal side with respect to said actuating means (36), characterized in that the inwardly extending flange (8) is provided at the proximal side of the supporting ring (4), and that the connecting links (16) extend through openings (18) in the inwardly extending flange (8). 2. A control according to claim 1, characterized in that the inwardly extending flange (8) terminates within a support flange on the fixed support structure (12) with the first bearing (10) being positioned between the end of the inwardly extending flange (8) and the support flange on the fixed support structure (12). 3. A control according to claim 1, characterized in that the second bearing (30) is a thrust bearing between the first and second sleeves (20, 28) 4. A control according to claim 1, characterized in that the supporting ring (4) has a lateral flange (22) carrying thereon the splines 126) engaging with the splines (24) on the first sleeve (20).

Inventors: DENNISON, WILLIAM T.
Applicants: UNITED TECHNOLOGIES CORPORATION
Application year: 1988
Main classification: F01D7
IPC codes: F01D7, B64C11