US3508841A

US3508841A - Stabilizing device for adjusting the blade setting angle of rotary wing aircraft rotor

Info

Publication number: US3508841A
Application number: US705166A
Authority: US
Inventors: Hans Derschmidt
Original assignee: Bolkow GmbH
Current assignee: Bolkow GmbH
Priority date: 1967-02-25
Filing date: 1968-02-13
Publication date: 1970-04-28
Anticipated expiration: 1987-04-28
Also published as: GB1202291A; FR1559182A; DE1481524A1

Description

A nl 28, 1970 H. DERSCHMlDT STABILIZING DEVICE FOR ADJUSTING THE BLADE SETTING ANGLE OF ROTARY WING AIRCRAFT ROTOR Filed Feb. 13, 1968 INVENTOR Hclns Derschmidt "WM by ATTORNEYS United States Patent Int. Cl. B64c 57/44, 27/76 US. Cl. 416-40 8 Claims ABSTRACT OF THE DISCLOSURE A device for stabilizing a rotor of a high speed balanced blade rotary Wing aircraft rotor includes a setting sleeve which is freely mounted around the main rotor shaft and which may be moved axially along the shaft. The setting sleeve carries an inner ring which rotatably supports an outer ring which is connected through linkages to sleeves mounting each blade for the purpose of tilting the blade about its longitudinal axis in order to change the setting angle of the blade during the rotation of the rotor. The outer ring and the inner ring may be inclined in respect to the axis of the rotor shaft by shifting it over a curved surface of the sliding sleeve. A feature of the construction is that when the setting sleeve is shifted axially, the setting angle of all of the blades of the rotor are changed collectively, whereas the individual setting angles are periodically changed during rotation of the rotor in accordance with the tilt of the inner and outer rings of a first wobble plate as determined by the tilt position of the first wobble plate in respect to the sliding sleeve upon which it is mounted.

SUMMARY OF THE INVENTION This invention relates in general to the construction of the rotor of a rotary wing aircraft and in particular to a new and useful stabilizing mechanism for adjusting the setting angle during rotation of the rotor and for collectively adjusting the initial setting angle of all of the rotor blades and to means for varying the adjustment of the setting angle in accordance with a change of the cone angle of the individual blades which may be produced, for example, by a gust of wind.

The invention concerns a stabilizer for high speed, balanced rotors in which the control of the blade setting angles is influenced by the striking movement of the rotor blades. The term blade setting angle is used herein to designate the angle of pivot of each blade about substantially its own longitudinal axis, i.e. an axis extending in the span-width direction, and it may be measured in a positive manner when the widened profile portion of the blade, that is the blade nose, points upwardly and measured in a negative manner if the nose points downwardly.

The attainable maximum flying speed of pure gyroplanes is determined by several factors: the most important of which is the mach number at the blade tip of the blade which is moving in a forward direction in respect to direction of flight, the stall effects on the blade which is moving in a reverse direction in respect to the direction of flight, and the fact that at high flying speeds the reversely moving blade is approached partly from a rear edge of the profile. A further increase in flying speed can therefore only be achieved if the rotor is balanced at an ever increasing rate and the necessary lift is produced by rigid air foil wings.

A typical property of all gyroplanes in rapid forward flight is a great pitching motion of the rotor plane when flying through vertical squalls. An upwardly directed squall effects on the blade moving in the forward direction a greater lift increase than on the blade moving in the reverse direction. Because of the phase shift of about between the variation of the angle of incidence induced by the squall and the resulting variation of the striking angle, the upwardly directed squall manifests itself in a bucking of the rotor. The sudden lift increase of the leading blade can lead to overloads and the tilting movement of the rotor can start dangerous oscillations of the aircraft about the pitching axis. Various devices have been provided for preventing overloading and sudden tilting movements, principally by varying the setting angle of each blade cyclically during its rotation,

In the blade suspension known as Delta-3 system, the axis of rotation for the striking movement of the blade is not perpendicular to the span-width direction as is customarily but is arranged obliquely thereto. Any variation of the striking angle of the blades effects thus at the same time a variation of the setting angle of the blades and this results in a variation of the lifting force in an opposite direction to the striking motion. In other known stabilizers, the inclination of the rotor plane with regard to a reference plane or planes is fixed in the aircraft or with regard to position gyroscopes. The gyroscopes sense any deviation of the inclination of the rotor plane from the nominal value and act through a control to vary the cyclical variation of the blade setting angles.

A disadvantage of the known devices however is that they are effective only in a flying speed range that can be achieved by pure gyroplanes. At higher flying speeds which can be achieved with balanced rotors, a major part of the blades moving in the reverse direction is approached from the rear edge of its profile. If a cyclic setting angle control is actuated to correct a squall disturbance, the setting angle of the blade moving in a forward direction is reduced and the setting angle of a blade moving in a reverse direction is increased. The forwardly moving blade is correctly influenced. However, the reversely moving blade tends to perform a striking motion in a downward direction with its greatest deflection approximately in a direction opposite to the flying direction because the positive setting angle of the blade acts as a negatve angle of incidence. The tilting movement of the rotor caused by the squall disturbance is thus increased and not damped as desired.

In accordance with the present invention, there is provided a stabilizer mechanism which provides an automatic adjustment of the setting angle of the blades during their rotation with the rotor head so that both the forwardly moving and the reversely moving blades are damped in a correct manner even in the case of a disturbance caused by squalls or steering maneuvers. This is accomplished in accordance with the invention by a transmission mechanism of the rotor head which permits the collective control of the setting angles of all of the blades so that if the blades encounter a striking motion in upward direction, the collective blade setting angles of all blades of the rotor is reduced and in the event that the blades encounter a downward striking motion, the collective setting angle is increased. The setting angle of the blade moving in the reverse direction is reduced when an upward squall is acting. Because the blade which moves in a forward direction encounters the effect of an increase of the effective angle of incidence because of the rear approach of the flow, it is necessary that the damping force imposed on this blade act downwardly contrary to the upward damping force imposed on the blade moving in the reverse direction so that a moment is produced which counteracts the bucking.

In accordance with the invention, the blades are mounted in sleeve members so that they can be pivoted about an axis which is substantially parallel to the longitudinal axis of the blade to permit variation of the setting angle of the blade and in addition the sleeve elements mounting the blades are mounted for pivotal movement so that the cone angle of all of the blades may be changed. The control mechanism includes a sliding sleeve which may be displaced axially in respect to the main rotor shaft around which it is positioned for the purpose of collectively changing the setting angle of all of the blades together. This is effected through a linkage mechanism which connects to the sleeve members mounting each blade so that when the setting sleeve control is moved along the rotor shaft, all of the mounting sleeve members are rotated to vary the setting angle correspondingly in a positive or negative sense in accordance with which direction the setting sleeve is moved.

The blades are supported by linkage arms which are carried on an outer rotatable ring of a secondary wobble plate which may also be shifted in an axial direction in respect to the rotor shaft for the purpose of simultaneously changing the cone angles of all of the blades. A feature of the construction is that the secondary wobble plate is connected through linkages to the setting sleeve so that a proportional shifting of the setting sleeve will be accomplished during any change of the cone angle of the blades which may be encountered, for example, during a squall disturbance. A separate control of the cyclical change of the setting angles of the blades as they are rotated about the rotor head is accomplished by varying the position of an inner support ring and an outer rotation ring which may be tilted on a curved surface of the sliding sleeve in order to actuate through the connecting linkages the shifting of the blades to vary their setting angle during the rotation of the rotor head. The variation of the setting angles will be controlled by the amount of tilt of the inner and outer rings Which in turn varies the degree of shifting of the setting angle during the rotor head rotation.

The transmission of the control of the setting angle is effected in accordance with a preferred embodiment of the invention through a differential lever which effects a variation in accordance with the setting of the secondary wobble plate and in accordance with a pilot-operated control rod for controlling the collective blade setting angle. In this manner the pilot can overtravel the control movements of the stabilizer mechanism by enhancing or counteracting them. The pilot-operated control rod i displaceably mounted in a guide slot of a differential lever and it may be shifted so that the action of the stabilizer can be increased or reduced during the flight.

Accordingly it is an object of the invention to provide a device for collectively adjusting the setting angle of the blades of a rotatable rotor of a rotary wing aircraft and which includes means for varying the amount of collective adjustment of the setting angle in accordance with changes of the cone angles of the blades.

A further object of the invention is to provide a control mechanism for the blades of a rotary wing aircraft wherein the blades are pivotally mounted on the rotor head in a manner to permit their pivotal adjustment for varying the cone angle and are also mounted so that they may be individually and collectively adjusted as to setting angle; and wherein there is a setting sleeve arranged around the rotor shaft which may be shifted axially in respect to the shaft for collectively varying the setting angle of all blades, and wherein there is a secondary wobble plate which carries a rotatable ring which supports a linkage connected to each blade and wherein the secondary wobble plate carries an inner ring which is connected through linkage to the means for setting the position of the slidable setting sleeve for varying the amount of change of the position of the setting sleeve in accordance with the change in position of the secondary wobble plate.

A further object of the invention is to provide a stabilizing control mechanism for a rotary wing aircraft which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understandng of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWmGS In the drawings:

FIG. 1 is a partial sectional and partial side elevational view of a rotor of a rotary wing aircraft constructed in accordance with the invention; and

FIG. 2 is a top plan view of the rotor indicated in FIG. 1.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular, the invention embodied therein comprises a rotor of a rotary wing aircraft which includes a rotor shaft 1 which is continuously rotated by a motor (not shown). The rotor shaft 1 carries at its upper end a rotor head or hub 2 upon which are pivotally mounted rotor blade mounting sleeves 6, 7 and 8 having forked ends which are pivotally supported on horizontal pins or striking joints 3, 4 and 5, respectively. Three rotor blades 9, 10 and 11 include blade butts 12, 13 and 14, respectively, which are disposed in the respective sleeves 6, 7 and 8 and are rotatable therein in order to vary the setting angle of each blade. For this purpose each butt portion 12, 13 and 14 carries an

arm

25, 26 and 27, respectively which extends outwardly through an elongated slot of the associated sleeves 6, 7 and 8 and is pivotally connected to a

respective push rod

22, 23 and 24. The

push rods

22, 23 and 24 are respectively pivoted at their lower ends at

pivot points

19, 20 and 21 to an outer rotatable ring 18 of a first wobble plate. The outer ring 18 is rotatable on an inner mounting or setting ring 17 which includes an inner spherical surface which may be shifted in respect to a spherical surface of a sliding setting sleeve 16 which is mounted around the shaft 1 and may be moved axially in respect to the shaft. A variation of the inclination of the inner ring 17 and the outer ring 18 may be made by shifting these rings over the periphery of the sliding sleeve 16 through the actuation of suitable control levers 28, 29. This will vary the amplitude of rotation of the butt portions 12, 13 and 14 of each blade and the associated blades 9, 10 and 11 during the rotation of the rotor head. The inclination of the primary wobble plate provided by the inner ring 17 and the outer rotatable ring 18 provides a cyclical control of the setting angle of each blade. A displacement of a sliding set ting sleeve 16 along the axis of the rotor shaft 1 provides a collective control of the setting angle. The levers 29 are connected with the control stick of the pilot.

The stabilizer of the invention includes a secondary wobble plate generally designated 30 which comprises an outer ring 31 which is rotatably mounted on an inner ring 32. The outer ring 31 is suspended through

linkages

33, 34 and 35 on the sleeves 6, 7 and 8, respectively, and therefore it follows the rotating and tilting movement of the rotor. The inner ring 32 which does not rotate does take part in the tilting movement of the rotor and the vertical movements of the front end of the rotatable ring 31 and the ring 32 which point in a flying direction V are transmitted through a lever 36 and a connecting bar 37 to an outer end of a differential lever 39 at the location of pivot pin 38. The opposite end of the differential lever 39 is pivoted at 40 to the sliding sleeve 16. The differential lever 39 includes an elongated guide slot which receives a pin 41 of a pilot-operated control rod 42. The elements designated 36 to 42 as shown in the drawing are all arranged forwardly in respect to the direction of flight V.

In normal undisturbed flight, the outer end of the differential lever 39 at the location of the pivot pin 38 forms a fulcrum for the differential lever due to the fact that the rotor plane and thus the secondary wobble plate 30 maintain their position in respect to the rotor shaft 1. Movements of the control rod 42 are thus transmitted to the collective setting control which is operated by the displacement of the sliding setting sleeve 16 in dependence upon the distance between the points of the pivot pin 38 and pivot pin 41, and between the pivot pin 41 and the pivot pin 40.

When there is a tilting movement of the rotor plane to the rear caused by squalls or maneuvers which will manifest itself as a striking movement of the blades with respect to their position in undisturbed flight, the secondary wobble plate 30 is similarly tilted to the rear. This movement is transmitted from the connecting linkage 37 to the differential lever 39. In straight flight, that is if the control rod 42 is not actuated, the journal pin 41 acts as a pivot for the lever 39. The pivot pin 38 will thus move upwardly so that the collective setting angle of the blades is reduced.

The displaceable mounting of the control rod 42 in the guide slot 50 of the differential lever 39 permits a variation of the lever length ratio and thus of the efficiency of the device or the degree of effectiveness of the stabilizing device during operation. In a position of the control rod 42 shown in solid lines in the drawings, the stabilizer is more effective than in a position indicated in dotted lines because there will be a greater displacement of the setting sleeve with a corresponding movement of the wobble plate 30 and the linkage 37. The control rod 42 may be easily shifted by the pilot mechanism (not shown).

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A stabilizer for a rotor of a rotary wing aircraft having a rotatable substantially vertical rotor shaft, a plurality of rotor blades and means pivotally mounting the inner ends of said blades on said shaft for up and down movement and for rotatable setting angle movement, comprising a setting member axially displaceable in respect to said shaft and connected to each of said blades to rotate said blades to adjust the setting angle of said blades when said setting member is shifted in directions axially of said rotor shaft, and stabilizer meansconnected to each of said blades and to said setting member and being tiltable upwardly and downwardly with changes of the tip plane of said blades as the rotor rotates to shift said setting angle member of each of said blades in accordance with the upward and downward movement of the tip plane of said blades in a flight direction.

2. A stabilizer according to claim 1, wherein said stabilizer means is connected to said setting member in a manner to shift said setting member to reduce the setting angle during upward tilting movement of the tip plane of said blades and to increase the setting angle of said blades in a downward tilting movement of the tip plane of said blades.

3. A stabilizer according to claim 1, wherein said stabilizer means comprises a secondary wobble plate disposed around said rotor comprising an outer rotatable ring connected to said blades for rotation therewith and an inner ring about which said outer ring is rotatable, said inner and outer ring being displaceable upwardly and downwardly with said blades and being connected to said setting member.

4. A stabilizer according to claim 3, wherein the connection of said inner ring to said setting member is arranged forwardly in the direction of flight and is through a differential lever which is pivotally connected at one end to said setting member and pivotally connected at its opposite end to said inner ring, and a pilot-operated control rod connected to said differential lever intermediate the connections of said inner ring and said setting member.

5. A stabilizer according to claim 4, wherein said differential lever includes an intermediate elongated slot, said pilot-controlled rod being connected to said differential lever through a pin confined in said slot, said control rod with said pin being displaceable along said slot for varying the amount of pivotal movement of said differential lever in response to displacement of said inner ring of said secondary wobble plate to effect a corresponding shifting movement of said setting member and the adjustment of said setting angles of said blades.

6. A rotor construction for a rotary wing aircraft comprising a normally arranged vertical rotating rotor shaft, a plurality of sleeve members pivotally connected to said rotor shaft for pivotal movement about normally arranged substantially horizontal axes, a blade having a butt portion rotatably mounted in each of said sleeves, said butt portion being rotatable to change the setting angle of each blade, a setting sleeve member axially displaceable along said sleeve, a first wobble plate pivotally supported on the exterior of said setting member in a manner permitting the adjustment of the inclination thereof in respect to said setting member, said first wobble plate including an outer rotatable ring, linkage means connected between said outer rotatable ring and said butt portions of said blades to rotate said butt portions with said blades to vary the setting angle of said blades during rotation of said rotor and in dependence upon the inclination of said first wobble plate, a econdary wobble plate disposed around said rotor shaft and including an inner stationary ring and an outer rotatable ring, a linkage connected between said outer rotatable ring of said secondary wobble plate and said sleeve and being movable upwardly and downwardly with upward and down movement of each blade and its associated sleeve, a differential lever connected at its inner end to said setting member, a linkage connected between said secondary wobble plate and said differential lever adjacent the outer end thereof, and a pilot control rod connected to said lever intermediate the ends thereof, said linkage between said secondary wobble plate and said differential lever pivoting said lever about the connection of said lever to said pilot control rod to shift said setting member and to vary the setting angle of each of aid blades in accordance with the upward and downward movement of said secondary wobble plate with the associated blades.

7. A rotor construction according to claim 6, wherein said pilot control rod includes a pin at its upper end, said linkage having a laterally elongated slot in which plate 8. A rotor construction according to claim 6, including separate control means connected to the inner ring of said first Wobble plate to shift said inner ring and said outer ring in respect to said setting sleeve member.

References Cited UNITED STATES PATENTS Platt 170-16025 Sikorsky 170160.25 Campbell 170-160.25 Sikorsky 170-16025 8 2,670,051 2/1954 Hohenemser 170160.25 2,748,876 6/1956 Daland et al. 170160.2S X

FOREIGN PATENTS 769,206 3/ 1957 Great Britain. 811,211 4/ 1959 Great Britain. 128,218 5/1950 Sweden.

OTHER REFERENCES German Application No. M24,316XI62b, April 1956, 10 to Focke.

EVERETTE A. POWELL, JR., Primary Examiner U.S. c1. X.R. 15 41624, 40