GB2226087A - Propeller blade mounting arrangement - Google Patents

Description

1 13DV-9240 PROPELLER BLADE RETENTION SYSTEM The invention herein

described was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, ]Public Law 85-568 (72 Stat. 435; 42 USC 2457).

The invention relates to the mounting of propeller blades in aircraft engines and, more specifically, to a mounting system in a contra-rotating propeller pair in which propeller blades are supported by a ring. The centrifugal load of the propeller blades is distributed as hoop stress in the ring, and the ring is supported by a turbine which the ring surrounds. The invention concerns mounting the blades to the ring such that they can change in pitch.

BY way of background to the 15 Figure 1 illustrates an aircraft engine unducted fan type, in which the invention can be used. Region 6 of the engine is shown in cross-secltional schematic form in Figure 2, wherein Contra-rotating turbines 9 (decorated with wide hatching) and 12 (narrow hatching) are driven by a hot gas strean, 15 provided by a gas generator (not shown). The turbines 9 and 12, in turn, drive contra-rotating fan blades 18 and 21 shown in Figures 1 and 2. (The term "contra-rotating" means that turbines 9 and 12, as well as blades 18 and 21 to which they are attached, rotate in opposite directions, as shown by arrows 24 and 27 in Figure l.) A view of sub-region 6A in Figure 2 is shown in perspective form in Figure 4. In Figure 4, annulus 29 represents turbine blades 30 in Figure 2.

-:. C, The fan blades 18 in Figure 2 are supported by a polygonal ring 22 in Figure 4. One type of polygonal invention 3 of the 13-DV-9240 ring is described in the U. S. Patent Application entitled "Blade Carrying Means", filed by Hauser, Strock, Morris and Wakeman on November 2, 1984, and having serial Number 667,663.- A cross section 23A of the ring is shown in Figure 2. The ring 22 is connected to the turbine casing 9A in Figures 2 and 4 by schematic brackets 24A in Figure 2. The ring 22 supports a rotating cowling 28, also shown in 3.0 Figure 1, by schematic brackets 25.

The polygonal ring 22 in Figure 4 includes two types of sections: one type is a blade support section 22B, also shown in Figure 3, which includes bearings 22D which facilitate pitch change, indicated by arrow 39, of the fan blades IS. The other type of section is a connector section 22A in Figure 4, including a pair of slender beams 23, which connects neighboring blade support sections 22B.

The fan blades 18 are fastened to the polygonal ring 22 rather than directly to the casing 9A for three principal reasons. one, it is doubtful that a turbine casing 9A of customary design could withstand the centrifugal force applied by the fan blades 18 during operation.- Two, different design considerations govern the size and shape of the fan syster. 33 in Figure 2 as compared with the turbine system 34. consequently, it is not expected that the turbine casing 9A would be of a proper shape and location for mounting of the fan blades 18. Three, the casing 9A experiences wide temperature excursions, and it is preferable to avoid mounting the fan blades to a structure of widely variable temperature.

In addition, the engine 3 shown in Figure I can be in the thrust class of 30,000 pounds, which causes a high loading in the fan blades 18. For example, assuming that a total of sixteen f an blades are used on the engine (eight forward blades 18 and eight aft blades 21), then, as a rough approximation, the thrust force of 30,000 13-DV-9240 pounds, indicated by arrow 35, is shared equally by these sixteen blades: each blade accounts for about.1875 pounds of thrust. If it is assumed that each blade in Figure 4 is four feet long (dimension 37), and if it is further assumed that the thrust load is concentrated at the midpoint 40 of each blade, then a moment of 1875 x 2, or 3750 foot-pounds must be reacted by each mounting apparatus shown in Figure 3. Further, this moment is not static, but changes as pitch changes, which is indicated by curved arrow 39 in Figure 3.

OBJECTS OF THE INVENTION it is an object of the invention to provide a rotatable is mount for mounting an aircraft fan blade to a rotor, especially such a blade which is highly loaded.

In one form of the invention, a plurality of propeller blades are carried by a ring. Each blade is supported by a trunnion which rides in a hole in the ring. The trunnion rides on two sets of bearings, one of which reacts centrifugal load, and both of which react moment loads, such as aerodynamic loads.

In the accompanying drawings:

Figure I illustrates an aircraft with which the invention can be used as already discussed; Figure 2 is a cross-sectional view of region 6 in Figure 1; Figure 3 illustrates schematically the mounting of an aircraft propeller blade 18 of Figures I and 2; Figure 4 illustrates schematically a polygonal ring 22 used to support the propeller blades 18; Figure 4A illustrates one form of the invention.

Figure 5 illustrates, in exploded view, one form of the invention; Figure 6 illustrates, in cross-section, the form of the invention of Figure 5; 13-DV-9240 Figure 6A illustrates threads 55 of Figure 6; Figure 7 is a view, in the direction of arrows 7-7, of the form of the invention of Figure 6; Figure 8 is a type of dual rol ler thrust bearing; Figure 9 is a schematic view of the arrangement of the bearings of Figure 5; Figure 10 is a simplified view of one form of the invention, showing skewing of trunnion part 50; Figure 11 illustrates a roller bearing of the type 70 and 75 of Figure 6; Figure 12 is an alternative to Figure 6; Figure 12A is an exploded view of region 87 in Figure 10; Figure 13 illustrates a key 270 used to fasten a bevel ring gear 230 to the trunnion part 40; Figure 14 illustrates a view of Figure 13, taken along arrows 14-14, but with the key 270 in Figure 14 replaced by that of Figure 15; Figures 15 and 16 illustrate another type of key which provides the function of key 270 in Figure 13; Figure 17 is similar to Figure 14, but showing displacement of the bevel ring gear with respect to the trunnion; Figure 18 illustrates several different types of key 270s Figure 19 shows displacement of the type shown in Figure 17, but in the opposite direction; Figures 20A, 20B, and 20C illustrate a spring used to reduce rocking, or clanking, of the blade when supported by the trunnion; Figures 21A and 21B are simplified views of Figure 7; Figure 22 shows a pinned root which can be used to mount a blade to the trunnion, the outer part 50 of which is shown; Figure 23 schematically illustrates compression of the annular shelf 58 in Figure 5 between bearings 70 and 75.

13-DV-9240 A simplified form of the invention is shown in Figure 4A, wherein a hollow shaft 35A extends through a hole 35B in a polygonal ring 22. The shaft connects to a propeller blade 18. A collar 36, which is larger in diameter than the hole 35B, prevents centrifugal force from driving the shaft 35A out of the hole. The collar 36 acts as an anchor. Alignment bearings 70 prevent the shaft from skewing into phantom position 36B under the influence of moments applied to the blade 18. Such moments can arise from the aerodynamic forces applied to the blade. Thrust bearings 75 react centrifugal force and allow pitch change of the blade, as indicated by arrow 37A.

is A more detailed form of the invention is shown in Figure 6. The fan blades 18 in Figure 1 are mounted to the polygonal ring 22 by trunnions 40 as shown in cross-section Figure 6, and in exploded view in Figure 5. The trunnions 40 are constructed in two parts, namely, a radially inner part 45 in Figure 5 and a radially outer part 50. The two parts are threaded together by threads 55 in order to capture an annular shelf 58 between the two parts when assembled. The annular shelf - 58 is fastened to the blade mounting section 22B of the polygonal ring 22. The trunnion can be disassembled by unthreading threads 55 in order to disassemble the trunnion, thereby releasing the annular flange and allowing removal of the propeller blade from the polygonal ring.

The threads 55 are of the buttress type, meaning that the angle AI of one thread surface in Figure 6A is different from the angle A2 of the other thread surface (AI is 7 degrees, while A2 is 30 degrees), making the included angle, A3, 37 degrees. Further, the surfaces 60 making the seven degree angle with the pitch line 63 are those which abut each other when the trunnion 40 is 13-DV-9240 assembled. The thread pitch is 12 threads per inch. The pitch diameter 61 in Figure 6 is three inches.

Alignment bearings 70 and thrust bearings 75, shown in Figures 5 and 6, separate the trunnion from the blade mounting section 22B, and allow rotation for pitch change. The bearings ride in hardened races 80. (The inner trunnion part 45 contains one of the races 80 integrally formed therein, but such construction is not strictly necessary.) During assembly, the two trunnion parts are threaded together until a predetermined amount of loading is applied to the alignment bearings 70 and the thrust bearings 75. The two trunnion parts are tightened together until the upper edge 77 in Figures 5 and 12 seats against abutment surface 78 in Figure 12. However, random irregularities in size and shape of the components in Figure 6 can cause improper loading. For example, if dimension 79 in Figure 5 is too great, the inner and outer trunnion parts will not be drawn sufficiently close, causing the bearing pre-load to be inadequate.

In order to alter this situation, the components are measured, and shims 82 in Figure 5 in the form of rings are placed between edge 77 and surface 78 in Figure 12, that is, at the location indicated by arrow 84 in Figure 12. A simplified measurement example will be given with reference to Figure 12A. Distances 85 and 86 are measured as shown. When the parts are assembled, distance 85 will nearly equal distance 86. The shim is constructed such that (distance 85 minus distance 86) plus the shim thickness equals about 0.005 inches. That is, the shin takes up all but about 0.005 inches of the clearance between surfaces 77 and 78 in Figure 12. Of course, it may occur that no shims are necessary.

Shims 82, in effect, decrease the loading on the bearings 70 and 75 when the edge 77 in Figure 12 contacts the shim 82 and presses the shin against the surface 78.

Restated, if no shin were installed when the relative 13-DV-9240 distances 85 and 86 called for shims, then the pre-load on the bearings 70 and 75 would be too great when edge 77 met surface 78.

The trunnion parts are 45 and 50 are threaded together until a proper torque is attained. This torque serves to pre-load the bearings 70 and 75 in order to prevent separation of both the bearings from their respective races, and also to prevent separation of edge 77 from surface 78 in Figure 12 under all conditions of engine operation as required to prevent thread failure.

That is, if the bearings 70 and 75 had an improper pre-loading, then, when a moment is applied to the trunnion 40, as from the aerodynamic forces applied to the blade 18 in Figure 3, the trunnion 40 can rotate and assume the skewed position shown in Figure 10. This skewing separates bearings from their races, as shown by separated bearing 75A in dashed circle 87, which transfers the pressure formerly borne by the separated bearing 75A to the other bearings, which is undesirable.

Further, the separation allows the bearings to chatter under some conditions of propeller operation, which is also undesirable. The preloading prevents this separation. Viewed another way, the pre-loading prevents axial movement, along pitch axis 130 in Figure 6, of the trunnion 40 with respect to the blade mounting region 22B of the polygonal ring 22.

A dust cap 90 in Figures 5 and 6 fits onto the inner trunnion part 45 and inhibits entry of debris, as well as preventing airflow through the spaces 99 between the races So. Airflow prevention can be desirable in cases when region 105 in Figures 2 and 6 is kept at a different pressure than region 109, as can occur when pressurized air is used to purge region 105 of volatile gases, such as lubricant vapors.

Several important features of the construction are the following:

-a- 13-DV-9240 1. The radially outer row of alignment bearings 70 in Figures 5 and 6 are of smaller diameter than the radially inner row of thrust bearings 75 because the inner row 75 reacts the thrust load imposed by centrifugal force acting on the blades. The centrifugal force is greater than the moment forces which the alignment bearings 70 react. For example, if each blade 18 and trunnion assembly 40 in Figure 4 is assumed to behave as a point mass located at midpoint 40, weighing 50 pounds, and rotating in a circle 41 of three feet in radius (dimension 92), then the centrifugal load applied to each trunnion 40 is at least 50,000 pounds, computed as follows.

Centrifugal acceleration is equal to w 2 r, wherein w is angular velocity, in radians per second, and r is radius.

If propeller speed is 1200 rpm, which corresponds to 20 revolutions per second, then w equals 20 rev/sec x 2 x pi, or about 126 radians per second.

Consequently, centrifugal acceleration is about 47,000 feet/second 2 (126 2 x 3). Dividing this acceleration by the acceleration due to gravity, namely, 32.2 feet per second 2, gives the centrifugal acceleration in GIs, which is about 1460 G's. Therefore, each blade and trunnion assembly, which was assumed to weigh 50 pounds when at rest, now applies a radially outward (ie, in the direction of arrow 145 in Figures 4 and 12) force of about 73,000 pounds (ie, 1460 x 50) to the thrust bearings 75 in the trunnion 40 because of centrifugal force. The force applied by the alignment bearings 70, in the outer row, is significantly less. Therefore, the outer bearings are smaller than the inner bearings because the load which they bear is smaller.

Both the outer bearings 70 and the inner bearings 75 are tapered roller bearings, as shown in Figure 11. For the alignment bearings 70 which were tested by the inventors, the large diameter 110 is 0.205 inches, the small diameter 115 is 0.20 inches, and the length 120 is -g- 13-DV-9240 0.35 inches. There are 70 bearings in the outer row, which is approximately 4.6 inches in diameter.

For the inner bearings 75 which were tested by the inventors, the large diameter 110 is 0.30 inches, the small diameter 115 is 0.22 inches, and the length 120 is 0.65 inches. There are 52 bearings in the inner row, which is approximately 4.6 inches in diameter.

2. The angles which each bearing row 70 and 75 make with the pitch axis 130 in Figure 6 are different. As Figure 9 shows, the axis 135 of each bearing in each row lies upon a cone. The axes 135A of the bearings 70 in the outer row lie on a first cone, while the axes 135B of those in the inner row 75 lie on a second cone. The first cone can be viewed as pointing radially inward, namely, in the direction of arrow 140, which is also shown in Figure 5.

The second cone can be viewed as pointing radially outward, in the direction of arrow 145, which is opposite. The apex angle 150 of the f irst cone, upon which the axes 135A of the alignment bearings 70 lie, is less than the apex angle 155 of the second cone, upon which the axes 135B of the thrust bearings 75 lie. This difference in apex angle results because the thrust bearings 75 are closer to being aligned normal (ie, perpendicular) with the centrifugal force vector (which is parallel with arrow 145) than are the alignment bearings 70.

These different orientations of the bearings have an effect on the force distribution applied to the polygonal ring 22. For example, even though the alignment bearings are almost directly radial ly outward of the thrust bearings 75 in Figure 6, as indicated by radius line 170, the forces applied to the ring by each type differ significantly.

The thrust load applied by the thrust bearings 75 in Figure 12 is indicated by arrow 190, and it places the annular shelf 58 into shear: the thrust load tends to 13-Dv-9240 shear off the annular shelf 58 along dashed line 195. In contrast, the load of the alignment bearings 70 is indicated by arrow 200, and this load is borne predominantly as hoop stress by the region in phantom circle 205. This load-bearing region is annular about the pitch axis 130, as indicated dotted circle 220 in Figure 5. The alignment bearings 70 cause primarily a hoop stress in the material at the periphery of the hole 225, while the thrust bearings cause primarily a shear load in the annular shelf 58.

3. A gear sector 230 in Figure 5, which extends along only a sector of the trunnion 40, such as between points 240 and 245, is fastened to the trunnion 40 and is driven by a bevel gear 235 in order to change pitch. It is preferred that all blades 18 and 21 in Figure 1 have identical pitch angles. However, it sometimes happens that minute manufacturing irregularities occur in the blades, giving neighboring blades different aerodynamic characteristics, even when they are driven to the same pitch. Further, gear lash and other small deviations fror, theoretical perfection in the mechanism which changes pitch can cause neighboring blades to acquire srnall deviations fror, identical pitch. These and other factors, which cause the pitch of the blades to differ from blade to blade, is called "pitch rigging error."

Pitch rigging error refers to the fact that the mechanism which positions the trunnions may not perfectly position all of then identically. It also refers to the fact that, even if all trunnions are positioned identically, there may be factors which cause different blades to be mounted differently on different trunnions. And it further refers to the fact thatapparently identical blades can have minute differences which affect their aerodynamic performance.

Pitch rigging error causes different angles of attack to exist on different blades on the sarte propeller, thus causing the blades to produce different amounts of lift, 9 1 13-DV-9240 which introduces vibration. The present invention reduces pitch rigging error by using a key resembling key 270 shown in Figure 13. That figure shows trunnion part 50 and gear sector 230. Not only does the key 270 prevent relative movement between the trunnion part 50 and the gear sector 230, but the particular configuration of the key 270 allows one to select the relative position between the gear sector and the trunnion, thus affecting pitch angle, as will now be explained.

The actual shape of the key 270 is not necessarily that shown in Figure 13, but may be closer to that shown in Figure 14, wherein trunnion 40 and gear sector 230 are schematically shown. A bolt (not shown) fastens the key 270 to a hole 271 in the trunnion 40 through hole 273 in Figures 13 and 14, and the bolt is accessible through a hole 271A in gear sector 230.

The arrangement of Figure 14 allows one to control the relative position of gear sector 230 with respect to trunnion part 50 by replacing the key 270 with another key of a different shape. For example, key 270 can be visualized as containing two components, 270A and 270B in Figure 15. By first cutting the key 270 along line 274 in order to separate the two components 270A and 270B, and then sliding component 270A to the right with respect to component 270B, one can obtain the configuration of Figure 16. it is preferred that the hole part 273C remain in its former position, that is, aligned with hole 271 in the trunnion 40 in Figure 14. Otherwise, a new hole 271 (not shown) in the trunnion would be necessary.

When installed, the key 270 of Figure 16 aligns the trunnion and gear sector as shown in Figure 17, wherein the trunnion and sector are now displaced as compared with the situation of Figure 14, as indicated by the non-alignment of reference marks 280 in Figure 17 as 3-5 compared with those marks in Figure 14.

In actual practice, two components of the key 270 are not slid along each other as shown in Figures 15 and 16, -5 13-DV-9240 but a group of different keys is made as shown in Figure 18. Preferably, the keys are manufactured such that the distance 283, first, is not the saine in any two keys and, second, distance 283 changes in increments which change distance 283A in Figure 17 in increments of 1/4 degree. That is, for example, twelve keys can be made such that any selected displacement (ie, distance 283A in Figure 17) from the following sequence can be selected: 0 degrees, 114 degree, 1/2 degree,... 2-3/4 degrees.

In another embodiment, the hole 271 is positioned in the trunnion in Figure 14 such that the key 270 can be inverted, as shown in Figure 19, in order to provide displacement of the gear sector 230 in the opposite direction. In Figure 19, reference mark 280A is on the other side of mark 280B, as compared with the case of Figure 17. Further, in still another embodiment, it may be desirable to remove material from the key 270 as indicated by dashed lines 290 in Figure 18 in order to reduce weight. The edges of the key 270 may need to be chamfered, as indicated by cut 270G in Figure 18, in order to accommodate fillets (not shown) existing in the trunnion or the gear sector. If chamfering is needed, and if the inversion feature'just described is desired, then chamfering of all relevant edges must be done.

It is noted that surfaces 295 and 296 of the key 270 in Figure 14 separate surfaces 297 and 298 of the trunnion and gear sector, respectively. That is, the key 270 acts to maintain surfaces 297 and 298 at selected positions with respect to a reference, which is the bolt hole 271 in the trunnion.

Viewed another way, the surfaces on the trunnion and the gear sector which contact the key, such as surfaces 295 and 296, act as anchor points in the sense that, once a given key has been selected and installed, these surfaces anchor the trunnion and the gear sector in the relative positions determined by the key. For example, if surface 297 were moved to phantom surface 297A, then 13-DV-9240 the gear sector could slide in the direction of arrow 299 by a distance 299A. Gear sector 230 is thus not anchored in this example.

4. When the aircraft in Figure I is parked on the ground, the wind can cause the propeller blades IS and 21 to rotate, or "windmill." Windmilling causes the blades to rock, or "clank" in their dovetail mounts, because the f it is loose. Clanking can damage the blades. (The looseness causes no problem at operational speed because centrifugal force tightly jams the dovetail 250 in Figure 6 into the dovetail slot 253, thus eliminating the loose fit.) An anti- clank spring 307 in Figures 20A, 20B, and 20C is inserted into a slot 308 in Figure 6 in the dovetail 15 250. The spring 307, in pushing the dovetail radially outward from the trunnion, in the direction of arrow 290, partially simulates the centrifugal load and locks the dovetail 250 into the slot 253. The spring 307, in Figure 20B, is arched, in that ends 305 and 310 lie on 20 the same line 315, but the midpoint 312 on the bottom surface 314 is separated from the line by a space 316. The spring 307 in Figure 20A contains flanges 320 which are defined by cut-out regions 325, which have been removed in order to increase the flexibility of the spring. The flanges serve to align the spring 307- within the slot 308. The spring is constructed such that a force of 450 pounds, indicated by arrow 329 in Figure 20B, is applied to the dovetail 250 in Figure 6. 30 in order to allow withdrawal of the spring 307, which is bound in the slot 308 in Figure 6 by the 450-pound force, the spring contains a tapped, threaded hole 331 in a leg 333. The threaded hole 331 accepts a jacking screw 335 which can be driven against the dovetail 250 in order to withdraw the spring. 5. The blade 18 is fastened to the trunnion 40 by means of a dovetail 250 in Figure 6.

is 13-DV-9240 A blade retainer 355, shown hatched in Figure 7, and also shown in Figures 5, 21A, and 21B, is used to fasten the -dovetail 250 in place, in order to prevent the dovetail 250 from sliding out of the the slot 253 in Figure 6, in the direction of arrow 260 in Figure 7. Two bolts 370 and 375, shown in Figures 6. 7t 21A, and.21B, fasten the retainer 355 in place. The retainer 355 also locks the leg 333 of the spring 307 against the dovetail and prevents the spring 307 from emerging from its slot 308 under the influence of vibration.

In addition, -the bolts 370 and 375 react the impact load occurring when a bird strikes the propeller blade. A bird strike applies a force which is genprally in the direction of arrow 270 in Figure 7.

6. An attachment of blade IS to trunnion 40 by means of a dovetail is not considered essential. Other types of fastening are available, such as a pinned root arrangement, as shown in Figure 22. A pin 380 fastens two clevises 382. A pinned root can allow one to better control vibrational modes of the blade and reduce bending moments imparted to the trunnion 40.

7. The blade retention system of Figure 5 can be viewed as comprising an annular flange captured within an annular groove. For example, the annular flange is the annular shelf 56 in Figure 10, while the annular groove is indicated by bold dashed line 301. The bearings 70 and 75 (not all shown in Figure 10) separate the annular flange from the annular groove.

S. The loadings applied to bearings 70 and 75 in Figure 6 as the trunnion parts 45 and 50 are threaded together are not identical, partly because of the different angles 150 and 155 in Figure 9 which each bearing axis makes with the pitch axis 130. The force applied by the threads 55 is generally parallel with the pitch axis 13,0, but the bearings 70 and 75 do not make the same angle with the pitch axis 130, and so the -is- 13-DV-9240 components of the force which are normal (ie, perpendicular) to the bearings are not equal.

For example, if the bearings were parallel (ie, angles 150 and 155 in Figure 9 are equal at 180 degrees) as shown in Figure 23, then threading the inner trunnion part 45 onto the outer trunnion part 50 will apply equal loads to the bearings. That is, the force 400 applied by the bearing 75 to the shelf 58 is opposed by an equal force 401 applied by bearing 70. Further, in applying the forces 400 and 401, each bearing 75 and 70 is subject to a compressive load of the same size as the respective forces.

When the apex angles are unequal, as in Figure 9, the forces corresponding to forces 400 and 401 in Figure 23 become forces 405 and 406, respectively, in Figure 9.

Force 405 is equal to the normal force, or loading, on the bearing 75. Force 405 equals force 400 divided by the sine of angle K1. Angle K1 equals one-half of angle of the outward pointing cone.

Force 406, on alignment bearings 70, equals force 401 divided by the sine of angle K2. Angle K2 equals one-half of the apex angle 150 of the inward pointing cone. The pre-loading on the alignment bearings 10 will be greater than that on the thrust bearings 75 because the sine of angle K2 is less than that of angle K1. Of course, the relative pre-loadings also depends upon geometric factors, such as the relative distances 85 and 86 in Figure 12. Further, relative pre-loading is not to be confused with relative centrifugal loading: the alignment bearings 70 in Figure 9 experience virtually no centrifugal loading.

9.Bearings 70 and 75 in Figure 9 can be viewed as analogous to a pre-loaded thrust bearing pair 70B and 75B, as shown in Figure S. However, unlike the pair shown in Figure 8, the axes of bearings 70 and 75 in Figure 9 make unequal angles with the pitch axis 130. In 13-DV-9240 contrast, the corresponding angles (not shown) in Figure 8 are equal.

10. The invention has been described in connection with a r ing 22 in Figure 4 which surrounds a turbine 29.

The turbine acts as a source of motive power for rotating the ring and the blades IS attached to the ring. However, it is not necessary that the source of motive power be a turbine. Instead, a gearbox, or a type of rotor, may be the source of motive power for the ring. 11. The invention can be used when propeller blades, which are sometimes

called fan blades, depending upon their aerodynamic characteristics, are supported by a ring, such as ring 22 in Figure 4.

12. The alignment bearings 70 in Figures 5 and 6 function to maintain the trunnion 50 in a predetermined alignment with the pitch axis 130. The alignment bearings prevent wobble, or skew, of the trunnion 50. In some situations, the pitch axis 130 is an extension of a radius, similar to radius 401, of the polygonal ring 22 in Figure 4. The pitch axis would then coincide with a radius, or extended radius, of the ring.

13. In the art, an array of bearings, such as bearings 70, is frequently called a row of bearings.

Numerous substitutions and modifications can be undertaken with regard to the embodiments disclosed herein without departing from the invention as defined.in the following claims.

k CLATHS:

13-DV-9240 1. A propeller blade retention system, comprising: a) a plurality of rollers which are annular about the pitch axis of the blade and which carry the centrifugal load of the blade; and b) a plurality of alignment bearing rollers for maintaining the blade in alignment with the pitch axis.

2. A system according to claim 1 in which the alignment bearing rollers carry substantially no centrifugal load.

3. A system for supporting a propeller blade upqn a ring having a hole therethrough and which surrounds and is driven by a source of motive power, comprising:

a) a generally circular bearing surface surrounding the hole and attached to the ring; b) a trunnion which includes i) a radially inner part which can be fastened to ii) a radially outer part in order to capture the bearing surface therebetween.

4. A system according to claim 3 and further comprising bearing rollers which separate the bearing surface from the trunnion.

5. A system for supporting a plueality of propeller blades upon a ring which surrounds a source of motive power, comprising: a) a plurality of holes extending through the ring; b) an anchor located on the radially inner side of each hole and including means for restraining each anchor from passing through its respective hole; and c) means for connecting each anchor to a respective propeller blade.

-Is- 13-DV-9240 6. A system according to claim 5 and further comprising ineans for allowing rotation of each anchor with respect to the ring.

7. A system for supporting a plurality of propeller blades upon a ring which surrounds a source of motive power, comprising: a) first and second bearing races having a plurality of thrust bearings therebetween, the first bearing race being connected to the ring; b) a shaft connected to the second bearing race and extending through the ring; and c) means for connecting a propeller blade to. the shaft.

8. A system according to claim 7 and further comprising a plurality of alignment bearings for preventing moments applied to the propeller blades from skewing the shaft.

9. A system for supporting a plurality of propeller blades upon a ring which surrounds a source of motive power, comprising: a) a plurality of trunnions, each fitting into a hole in the ring and each supporting a propeller blade and b) means for i) preventing centrifugal force from dislodging each trunnion from its respective hole and ii) allowing rotation of each trunnion in order to change blade pitch.

10. A system for supporting a propeller blade upon a ring which surrounds a source of motive power, comprising: a) a shaft connected to the propeller blade and extending through a hole in the ring; j X ----------------- - --- 13-DV-9240 b) ineans for preventing centrifugal force from removing the Ghaft from the hole; and c) raeans for maintaining the axis of the shaft in approximate alignment with a radius of the ring.

11. A system for supporting a propeller blade upon a ring which surrounds a source of motive power, comprising: a) a shaft connected to the blade and extending through a hole in the ring; and b) a collar connected to the shaft, radially inward of the shaft, and of larger diameter than the hole.

12. A trunnion system f or supporting a propeller blade upon a ring which surrounds a source Of Motive power, comprising: a) a trunnion supporting the blade and located in a generally circular hole in the ring; b) a first pair of bearing races, having roller bearings therebetween, for supporting the trunnion in the hole; and C) a second pair of bearing races, having roller bearings therebetween, for supporting the trunnion in the hole, the second pair being located radially inward of the first pair.

13. A system according to claim 12 in which the roller bearings in both the first and second races are pre-loaded.- 14. A gystem according to claim 12 in which the roller bearings in the second pair of bearing races react substantially all centrifugal load imposed by the blade.

15. A system for supporting a propeller blade upon a ring which surrounds a source of motive power, comprising:

A 13-DV-9240 a) a pair of pre-loaded bearing rows, one radially inward of the other, and both annular about a pitch axis, for supporting a trunnion-within a hole in the ring, one pair of which carries substantially all centrifugal load applied by the propeller blade.

16. A system for supporting a propeller blade upon a ring which surrounds a source of motive power, the propeller blade having a pitch axis defined therein, comprising: a) a first bearing set supported by the ring and which comprises a plurality of roller bearings having bearing axes located on a first cone; b) a second bearing -set supported by the ring and which comprises a plurality of roller bearings having bearing axes located on a second cone, the first and second cones having axes which approximately coincide with the pitch axis; and c) a trunnion supported by the first and second bearing sets and which supports the propeller blade.

17. A system or supporting a propeller blade upon a ring which surrounds a source of motive power, comprising:

a) a shaft connected to the propeller blade and extending through the ring; and b) a collar which is i) fastened to, and annular about, the shaft ii) located.radially inward of the hole and iii) which cannot move through the hole.

18. A system according to claim 17 in which the collar comprises a bearing race.

19. A system according to claim 17 and further comprising alignment means, located radially outward of 13-DV-9240 the ring, for maintaining the shaft in alignment with a radius of the ring.

20. A system for supporting a propeller blade j upon a ring which surrounds a source of motive power,, comprising: a) a shaft connected to the propeller blade and extending through a hole in the ring; b) a bearing race fastened to, and annular about, the shaft near the radially inner end of- the shaft; c) a ring of thrust bearings approximately coaxial with the hole and engaging the bearing race; and d) a plurality of bearings located radially outward of the thrust bearings for maintaining alignment -of the shaft with a radius of the ring.

21. A trunnion system for supporting a propeller blade upon a ring which surrounds a source of motive power, comprising: a) first and second rings of bearings. one ring of which bears substantially all centrifugal load of the blade, and both of which: i) are generally coaxial about a pitch axis, ii) support a trunnion located in a hole in the ring, and iii) are both pre-loaded to reduce wobble of the trunnion.

22. A system for supporting a propeller blade upon a ring which surrounds a source. of. inotive power, comprising: a). a shaft connected to the propeller blade and extending through a hole in the ring; b) means for preventing radial movement of the shaft; and c) means for resisting movement of the shaft induced by moments applied by the propeller blade.

1 t 1 1 1 i 1 1 1 1 1 13-DV-9240 23. An aircraft propulsion system comprising: a) a propeller blade; and b) an annular flange mounted to a rotor and captured in an annular groove In a rotatable trunnion which:

i) supports the propeller blade and ii) can be disassembled in order to release the annular flange.

24. A system according to claim 23 and further comprising:

(c) bearing.rollers for suspending the trunnion upon the annular flange.

25. A system according to claim 24 in which the bearing rollers comprise:

i) a first set of rollers for reacting centrifugal load of the propeller blade and ii) a second set of rollers for maintaining the blade in a predetermined alignment with the pitch axis.

26. An aircraft propulsion system, comprising: a) a rotor; b) a ring surrounding the rotor and having a plurality of openings therethrough; c) means for:

i) supporting a mount for a propeller blade ib o e of the opening s; ii) preventing withdrawal of the mount under a centrifugal load exceeding 50# 000 pounds and applied by the propeller blade; iii) allowing the mount to rotate in order to change pitch of the propeller blade; and iv) resisting misalignment of the propeller blade induced by aerodynamic loads upon the blade.

3 1 13-DV-9240 27. A mounting system for aircraft propeller blades, comprising: a) a rotatable mount; b) means for connecting a propeller blade to the rotatable mount; c) an annular groove on the periphery of the rotatable mount; and d) a flange extending into the annular groove for restraining the annular mount against radial movement.

28. In an aircraft propeller system which includes propeller blades, each rotatable about a respective pitch axis, the improvement comprising:

a) a trunnion fastened near the root of each blade and having an axis of rotation approximately coincident with the pitch axis and having an annular groove along its surface; and b) means, connected to a rotor, for reacting centrifugal load of the blade by engaging the annular groove.

29. A system according to claim 28 and further comprising: c) bearing rollers in the annular groove for reducing f riction.

30. A system according to claim 29 and further comprising: d) a second set of bearings for Maintaining alignment of the trunnion axis with the pitch axis.

31. A system according to claim 30 in which both bearing sets are preloaded.

t 13-DV-9240 32. In a blade retention system for an aircraft propeller blade which can change in pitchl the improvement comprising: a) a rotatable trunnion for supporting the blade which includes: i) a first set of roller bearings, in which bearing axes lie on the surface of a first cone which points radially outward, and ii) a second set of roller bearings, in which bearing axes lie on the surface of a second cone -which points radially inward.

33. A blade retention system according to claim 32 in which the apex angle of the first cone is greater than that of the second cone.

34. In an aircraft propeller having a gear attached to a propeller blade which transmits a pitch-changing torque to the blade, the improvement comprising: a) means for adjusting location of the gear on the blade in order to reduce pitch rigging error.

35. A system for changing pitch-rigging error in an aircraft propeller having a gear attached to a propeller blade which transmits a pitchchanging force to the blade, comprising. a) a first anchor on the gear; b) a second anchor on the blade; and c) a -collection of keys, each for providing a different spacing between the first and second anchors, from which one key may be selected for attaining a minimal pitch rigging error.

36. A system for changing pitch-rigging error in an aircraft propeller having a gear attached to a propeller blade which transmits a pitchchanging force to the blade, comprising:

z k (. 1 -25- 13-DV-9240 a) a first slot -on the blade; b) a second slot in the gear; and c) means for adjusting the relative positions of the first and second Glots.

37. A propeller blade wounting arrangement having any of the novel features hereinbefore described with reference to the accompanying drawings.

tied 1990 atThe Patent Office. State House, 6671 HigliHolborn. LondonWClR4TP.FVrther copies maybe obtainedfrom The Patent Office.

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