US3606575A - Rigid hubs for variable pitch rotors - Google Patents

Rigid hubs for variable pitch rotors Download PDF

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Publication number
US3606575A
US3606575A US797997A US3606575DA US3606575A US 3606575 A US3606575 A US 3606575A US 797997 A US797997 A US 797997A US 3606575D A US3606575D A US 3606575DA US 3606575 A US3606575 A US 3606575A
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Prior art keywords
bundles
arm
strips
hub body
hub
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Expired - Lifetime
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US797997A
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English (en)
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Lucien Edmond Lermusiaux
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SOC D CONST ET D EXPLOIT DE MA
Soc De Construction Et D'exploitation De Materiels Et Moteurs Scemm
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SOC D CONST ET D EXPLOIT DE MA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C27/00—Rotorcraft; Rotors peculiar thereto
    • B64C27/32—Rotors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C27/00—Rotorcraft; Rotors peculiar thereto
    • B64C27/02—Gyroplanes
    • B64C27/021—Rotor or rotor head construction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C27/00—Rotorcraft; Rotors peculiar thereto
    • B64C27/32—Rotors
    • B64C27/33—Rotors having flexing arms

Definitions

  • RIGID HUBS FOR VARIABLE PITCH ROTORS Filed Feb. .10, 1969 f s sheets-sheet s INVENTOR LLLclE/V E. LElmus/nux .iv/Y 'ATTORNEYS United States Patent O 3,606,575 RIGID HUBS FOR VARIABLE PITCH ROTORS Lucien Edmond Lermusiaux, Saint-Etienne, France, as-
  • This invention relates to hubs for variable pitch rotors, lifting rotors, wind motors, fans and axial turbomachines, of the type which, devoid of articulations, are called rigid
  • the invention is more particularly, but not exclusively, concerned with hubs of this type which are intended for rotor craft (helicopters, gyroplanes and the like
  • Tire hubs to which this invention relates comprise a rotary axle, a hub body rigidly secured to this axle and arms fixed to the hub body.
  • the rotor blades are fixed to the free ends of these arms.
  • Each arm comprises at least three bundles of piled strips; these bundles are distributed about the pitch variation axis of the blade fixed to that arm.
  • An object of this invention is to provide hubs of the type in question which are adapted to absorb the high stresses which are applied to them by the blades that they carr Ayhub according to this invention is characterized by the fact that the bundles of strips of any one arm are connected to each other and to the hub body by holding means such that the arm possesses a high resistance to flexion and a relatively low resistance to torsion.
  • FIG. 1, of these drawings shows, in a top view, an arm belonging to a rigid hub constructed according to the invention
  • FIG. 2 shows, in a side view, with parts removed, this same arm
  • FIG. 3 shows a schematic section along III-III of FIG. 2;
  • FIG. 4 shows, in section along IV-IV of FIG. 1, with parts removed, a detail of the arm
  • FIG. 5 shows, in perspective and schematically, the hub constructed according to this invention, with arms analogous to the arm of the preceding figures, in the absence of the braces of the arms, in order to clarify the drawing.
  • each of the blades of a rotor can 3,696,575 Patented Sept. 20, 1971 have to perform three sorts of movements.
  • the first of these movements moves the blade in the plane of rotation of the aerofoil ahead of or behind a substantially radial mean position.
  • the second movement moves the blade in a plane containing this blade and perpendicular to the plane of rotation of the aerofoil.
  • the third movement is a rotation of the blade about a longitudinal axis called hereafter pitch variation axis, the purpose of this rotation being to modify the angle of attack of the blade.
  • This pitch Variation is composed of a general variation of pitch affecting all the blades of the rotating aerofoil in the same manner and possibly of a cyclic variation of pitch affecting each of the blades differently according to the position that the blade occupies with respect to the rotor craft which is equipped with these blades. These two variations are conrtolled by known mechanical. means.
  • this piece is composed of a plurality of thin elements (thin sheets), glued together or not, and piled, the propagation of the cracks from one element to another is avoided.
  • the rupture is thus avoided, or at least, it takes place after a time considerably longer than with a piece of similar shape but composed of a single element.
  • This property is applied to the hub body of the rotor and to the arms.
  • piles of sheets, advantageously glued together, are used, whereas for the arms, the assembly is not effected by gluing.
  • the overall rotor With regard to the overall rotor, it comprises a rotary axle 1 (FIG. 5), a hub body 2, fixed to this axle 1 by appropriate means (not shown), arms 3, to which this invention is particularly directed, and blades 4 (three in number in the embodiment represented) fixed to the free ends of the arms 3.
  • Y rotary axle 1
  • hub body 2 fixed to this axle 1 by appropriate means (not shown)
  • arms 3 to which this invention is particularly directed
  • blades 4 three in number in the embodiment represented
  • the arms 3 are each constituted by at least three bundles 5, 6, 7 and 8, four in number in the example described, each composed of piled strips having the same shape in plan (their thicknesses can be different from one strip to another but constant for each strip) and disposed respectively along the edges of a pyramid or a prism, these bundles 5, 6, 7 and 8 being connected to each other and to the hub body 2 by holding means such that the arms 3 have a high resistance to flexion and a relatively low resistance to torsion.
  • These holding means comprise, for each arm 3, rigid collars constituted by groups of braces 11 disposed at a distance from each other in planes approximatively perpendicular to the pitch variation axis I-I (FIG. l), and which hold, at their peripheries, the bundles 5, 6, 7, 8.
  • These holding means comprise in addition sheets 9 and 10 which connect respectively, at the interior of the volume of the arm and along at least a part of their length, the opposite bundles 5, 7, and 6, 8, and these sheets 9 and 10 pass through the pitch variation axis I-I.
  • the sheet 9 is advantageously provided, adjacent to the hub body 2, with a rst indentation 13, and adjacent to the blade 4, with a second indentation 14.
  • the sheet 10 also called flapping web, advantageously has the same profile as the arm 3, such as this arm appears in FIG. 2, and this sheet is inserted between two consecutive median strips of the bundles of. strips 6 and 8.
  • the sheet 10 is also provided, adjacent to the hub body 2, with an indentation 15, and adjacent to the blade 4, with an indentation 16.
  • the sheets 9 and 10 intersect each other at right angles at the interior of the arm along the axis I-I.
  • the braces 11 (of which a group of four, assembled in a collar, is represented in FIG. 3) are advantageously constituted by channel bars of U cross-section, provided at their ends with recesses 18 permitting them to bear against two consecutive bundles of strips such as 5 and 6.
  • each brace bears, on the one hand, by the recesses 18 of its ends, against half of the strips of the corresponding 'bundles of strips, and on the other hand, by flats 19 provided on the bottom of its channel bar, against the sheets 9 and 10.
  • the braces 11 are placed, as shown in FIGS.
  • the braces 11 are disposed by groups of four regularly spaced along the arm 3.
  • the four braces 11 of each group are fixed to each other by rivets 20 (FIG. 3), or any other mode of connection, which press the ats 19 of neighbouring braces against the sheets 9 or 10 separating them.
  • the ensemble of the braces 11 and the sheets 9 and 10 thus assures the holding of the bundles of strips and confers on the arms 3 appropriate resistances to exion and to torsion, as will be explained during the description of the operation of the hub as a whole.
  • Advantageously forks 12 are provided, which are disposed on each bundle between the groups of braces 11, and which clamp the strips of the bundle.
  • These forks 12 are advantageously constituted by two channel bars of U cross-section, each channel bar bearing against half of the strips of a bundle of strips and against the corresponding sheet 9 or 10, by a recess and a at (not visible in the figures) in a manner analogous to the manner which has been described for the ends of the braces 11.
  • the two channel bars of each fork 12 are disposed back to back on a bundle, and when these two channel bars are fixed by rivets 21, or any other mode of connection, these channel bars press the strips of the bundle in question and hold it with respect to the corresponding sheet 9 or 10.
  • These forks 12 are disposed at regular intervals on the four bundles 5, 6, 7 and 8 between the groups of braces 11.
  • the hub body 2 is advantageously constituted by a pile of sheets which can be glued to each other, and this hub body has approximatively the form of a star having three branches 22 between which are provided three indentations 23.
  • Each arm 3, fixed to a branch 22 of the hub body 2 by fastening means described hereafter, is disposed, with respect to the hub body 2, in the particular case represented, such that the bundles 5 and 7 which separate the most from each other are at least approximatively in the plane of the hub body, and such that the bundles 6 and 8 which separate from each other the least are in a perpendicular plane passing at least approximatively through the axle 1 of the rotor.
  • fastening means are advantageously constituted by fork-joints 24, 25, 26 and 27 connected respectively to the neighbouring ends of the bundles 5, 6, 7 and 8.
  • the fork-joints 24 and 26 are bolted to the hub body 2, on the sides of each branch 22, symmetrically about the pitch variation axis I--I (FIG. l) which coincides with the axis of symmetry of that branch 22. These forkjoints 24 and 26 respectively hold the ends of the bundles of strips 5 and 7 by means of bolts 30 and 31.
  • Supports 28 and 29 are disposed on both faces of the branch 22 being considered, at its free end, such that the fork-joints 25 and 27 which they carry or of which they form part are disposed on opposite sides of the plane of the hub body 2.
  • This free end of the branch 22 penetrates into the interior of the arm 3 in the space left by the indentations 13 and 15 of the sheets 9 and 10, and this free end comprises an indentation 32 whose contour is symmetrical about the axis I-I.
  • Each support 28 or 29 bears against the branch 22 of the hub body 2 by a rounded projection 33 (FIG. 4), 'which is located between the axle 1 and the bottom of the indentation 32, and by heels 34 located on opposite sides of this indentation.
  • the supports 28 and 29 are fixed to the branch 22 by bolts 35 and 36 which pass through both of the supports, the branch 22 and two of the heels 34. These two heels thus press between themselves the pile of thin sheets of the branch 22 on both sides of the indentation 32.
  • a bolt 37 passing through the supports 28, 29 and the branch 22 between the projections 33 and the bottom of the indentation 32, clamps these projections 33 against the pile of sheets of the branch 22.
  • the hole 38 permitting the passage of the bolt 37 in the branch 22 is of a diameter greater than the diameter of the shaft 39 of the bolt 37 in order that this shaft 39 does not come into contact with the sheets of the branch 22 when the free end of that branch bends under the action of the supports 28 and 29, which is the case as will be seen hereafter.
  • the fork-joints 25 and 27 respectively hold the ends of the bundles 6 and 8, in a plane containing the axis I-I and perpendicular to the plane of the hub body 2, by means of bolts 40 and 41.
  • Each arm 3 is provided, at its end situated adjacent to the blade, with a fitting 42 comprising four fork-joints 43, 44, 45 and 46 to which are respectively fixed, by bolts 54, the ends of the bundles 5, 6, 7 and 8.
  • the fitting 42 also carries mechanical means, represented in FIGS. l and 2, adapted to hold the blade 4.
  • This blade rigidly secured to the attachment plate l48, is articulated about a spindle A47.
  • Mechanical means for example an hourglass screw, can be provided to permit the blade to be folded, by pivoting about the spindle 47, into parking position.
  • Each arm 3 is provided with a control arm 49 (FIG. 5) fixed to the fitting 42 and rigid in flexion and in torsion. In the example indicated, it is disposed approximatively in the plane of the hub body 2 and is connected by its free end 50 to a pitch control means such as 51, 52, S3 of a type known in itself.
  • a pitch control means such as 51, 52, S3 of a type known in itself.
  • the arms 3, the control arms 49 and the pitch control device can be contained in stream-lining (not shown) conferring on them good faculties of penetration in the air.
  • Each arm 3 connected to a blade 4 is subjected, independently of the centrifugal force due to the overall rotation of the blades, to various forces due to the three movements that the blade can perform.
  • the bundles of strips 5 and 7 are alternately subjected to traction and compression forces. If it is assumed that the bundle of strips 5 is urged in traction and the bundle of strips 7 is urged in compression, the arm 3 offers a high resistance to such urging, due to the traction exerted on the bundle and to the rigidity to an edge-wise force presented by the sheet 9 holding the bundles 5 and 7 substantially in position with respect to each other.
  • the bundle 5 is stretched and rectilinear and it thus ensures, due to the various groups of four braces 11, the holding of the ensemble of the four bundles 5, ⁇ 6, 7 and 8 and, in particular, of the bundle 7 which, urged in compression, has a tendency towards buckling.
  • the forks 12 serve to hinder local buckling of the strips of the bundle 7, between the groups of braces 11, when this bundle 7 is urged in compression. Without these collars, the strips of the bundle 7 could have a tendency to separate from Veach other. The phenomena are analogous for the other possible case in which the bundle 5 is urged in compression and the bundle 7 in traction.
  • the bundles of strips y6 and y8 are in their turn subjected alternately to forces of traction and of compression, and the sheet 10, which acts as a web for the bundles ⁇ 6 and 8, is subjected to edgewise forces.
  • the arm 3 offers a high resistance to such urging.
  • the forces of traction and of compression applied to the bundles 6 and 8 are transmitted to the fork-joints 25 and 27, themselves rigidly secured to the supports 28 and 29. These forces create a moment applied to the two supports 28 and 29 about their projections 33. This moment bends the branch 22 as a whole, and by the intermediary of the supports 28 and 29, the part of the branch 22 which is clamped between these supports.
  • each arm 3 is relatively low. This permits the pitch variation of each blade to be controlled by applying to the end of each arm 3, adjacent to the blade, an appropriate torsion couple. This is achieved due to the pitch control system which applies, to the end 50 of the control arms ⁇ 49, forces directed parallel to th e axle 1 of the rotor.
  • the flapping movements and the drag movements of the blade 4 result from an equilibrium between the forces acting on these blades and the mechanical reactions of the arms 33 according to the invention, and the pitch variation of the blades is controlled by the pitch control device.
  • the rigid hub, constructed vwith arms according to the invention presents numerous advantages among which can be cited:
  • Hub and rotor blade system having variable pitch blades, which comprises a rotary axle, a hub body rigidly secured to this axle, arms fixed in non-articulated manner to said hub body and said rotor blades xed at the free ends of said arms, each arm comprising at least three bundles of piled strips which bundles are distributed about the pitch variation axis of the blade xed to said arm, the bundles of strips of any one arm being connected to each other and to the hub body by holding means such that the strips are not bonded together whereby the arm possesses a high resistance to llexion and a relatively low resistance to torsion.
  • the holding means comprise rigid collars which are disposed at a distance from each other in planes approximately perpendicular to the pitch variation axis, each of these collars maintaining, at its periphery, the bundles.
  • the holding means comprise sheets which pass through the pitch variation axis and which connect the bundles together along at least a part of their length.
  • each collar is formed of braces, constituted by channel bars of U crosssection, which are joined together, back-to-back, by their ends and which comprise, at these ends, recesses in which the bundles of strips are engaged and clamped.
  • the holding means comprise rigid collars which are disposed at a distance from each other in planes approximatively perpendicular to the pitch variation axis, each of these collars maintaining, at its periphery, the bundles;
  • the holding means further comprise sheets which pass through the pitch variation axis and which connect the bundles together along at least a part of their length;
  • each collar is formed of braces, constituted by channel bars of U cross-section, which are joined together, back-to-back, by their ends and which comprise, at these ends, recesses in which the bundles of strips are engaged and clamped;
  • braces comprise, at their ends, flats bearing against the sheets by which they are xed to said sheets.
  • Hub according to claim 2 wherein forks are inserted between the collars along each bundle of strips, these forks clamping the strips of the bundle.
  • each fork is constituted by two channel bars of U cross-section which are joined together, back-to-back, by two of their ends and which comprise, at the other ends, recesses in which a bundle of strips is housed and clamped.
  • the holding means comprise sheets which pass through the pitch variation axis and which connect the bundles together along at least a part of their length;
  • ends by which the two channel bars of a fork clamping a bundle of strips are joined together comprise flats which bear against the sheet, connected to this bundle, on opposite sides of this sheet;
  • Hub according to claim 1 wherein the hub body has approximately the form of a star having as many branches as there are blades.
  • Hub according to claim 11 wherein at least certain of the bundles of each arm are not disposed in the plane of the hub body, and wherein these certain bundles are connected to the corresponding branch of the star by the intermediary of fork-joints xed to said branch by supports.
  • each support bears against a branch by at least two bearing members one of which is a heel having a plane bearing face and the other of which is a rounded projection, the heal being placed near to the end of the branch and the projection being placed near to the rotary axle at a distance from the heel which determines the resistance to ilexion of the ensemble of the branch and the arm in a plane containing the rotary axle and the pitch variation axis.
  • each support is fixed to a branch by at least one bolt passing through the support, the heel and the branch and at least one bolt passing through the support near to the projection and the branch, this latter bolt applying with force the projection against the hub body.
  • Hub according to claim 11 wherein certain of the bundles of each arm are disposed in the plane of the hub body, and wherein these certain bundles are connected to a branch by the intermediary of fork-joints fixed directly to the sides of the branch.
  • each arm is provided, at its end remote from the hub body, with a blade attachment tting comprising fork-joints to which the bundles are respectively fixed.
  • each arm comprises four bundles of strips disposed along the edges of a pyramid having a diamond-shaped base and whose summit is remote from the hub body and whose height is substantially coincident with the pitch variation axis, the bundles being disposed substantially in the planes joining the opposite edges of said pyramid, the two bundles which separate the farthest from the pitch variation axis being approximately in the plane of the hub body and the two other bundles being in the plane passing through the rotary axle and through the pitch variation axis.
  • the sheet which connects the two bundles which separate the farthest from the pitch variation axis forms a single piece disposed in the plane passing through the edges of the pyramid which correspond to these two bundles
  • the sheet which connects the other two bundles is formed of two pieces disposed on opposite sides of the single-piece sheet, in the plane passing through the edges of the pyramid which correspond to these other two bundles, the two pieces of the two-piece sheet being lixed rigidly to the single-piece sheet in the neighborhood of the pitch variation axis.
  • each arm is provided with a pitch control arm which is fixed to the blade attachment fitting and which extends from this tting towards the hub body in a direction moving away from the pitch variation axis.
US797997A 1968-02-12 1969-02-10 Rigid hubs for variable pitch rotors Expired - Lifetime US3606575A (en)

Applications Claiming Priority (1)

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FR139576 1968-02-12

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US3606575A true US3606575A (en) 1971-09-20

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US (1) US3606575A (xx)
BE (1) BE727547A (xx)
BR (1) BR6906344D0 (xx)
DE (1) DE1906764A1 (xx)
ES (1) ES362800A1 (xx)
FR (1) FR1568117A (xx)
GB (1) GB1245168A (xx)
LU (1) LU57927A1 (xx)
NL (1) NL159053B (xx)
SE (1) SE349530B (xx)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3807897A (en) * 1970-06-11 1974-04-30 Exploi De Materials Et Moteurt Rigid hubs for variable-pitch propellers and gas turbines
US3941503A (en) * 1974-03-07 1976-03-02 Costruzioni Aeronautiche Giovanni Agusta S.P.A. Helicopter rotor hub provided with flexible elements such as virtual hinges
US3967918A (en) * 1973-05-10 1976-07-06 Societe Nationale Industrielle Aerospatiale Rotor for rotating wing type aircraft
DE2645174A1 (de) * 1976-10-07 1978-04-13 Messerschmitt Boelkow Blohm Rotorkopf fuer einen schlag- und schwenkgelenklosen rotor
US4203709A (en) * 1977-09-07 1980-05-20 Westland Aircraft Limited Helicopter rotor and blade connection
US4292009A (en) * 1977-12-24 1981-09-29 Messerschmitt-Boelkow-Blohm Gesellschaft Mit Beschraenkter Haftung Hingeless rotor system
US4352631A (en) * 1979-04-28 1982-10-05 Messerschmitt-Boelkow-Blohm Gmbh Hingeless rotor, especially for a helicopter
US4874292A (en) * 1988-11-18 1989-10-17 The United States Of America As Represented By The Secretary Of The Army Apparatus for damping helicopter rotor blade oscillations
US5100294A (en) * 1989-10-04 1992-03-31 Westland Helicopter Limited Helicopter rotors
US20040037701A1 (en) * 2002-06-14 2004-02-26 Santino Pancotti Helicopter rotor hub, and rotor featuring such a hub

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11103811B2 (en) 2016-11-04 2021-08-31 Icm, Inc. Mechanical separation devices
US20190374883A1 (en) * 2018-06-10 2019-12-12 Icm, Inc. Mechanical separation device

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3807897A (en) * 1970-06-11 1974-04-30 Exploi De Materials Et Moteurt Rigid hubs for variable-pitch propellers and gas turbines
US3967918A (en) * 1973-05-10 1976-07-06 Societe Nationale Industrielle Aerospatiale Rotor for rotating wing type aircraft
US3941503A (en) * 1974-03-07 1976-03-02 Costruzioni Aeronautiche Giovanni Agusta S.P.A. Helicopter rotor hub provided with flexible elements such as virtual hinges
DE2645174A1 (de) * 1976-10-07 1978-04-13 Messerschmitt Boelkow Blohm Rotorkopf fuer einen schlag- und schwenkgelenklosen rotor
US4182597A (en) * 1976-10-07 1980-01-08 Messerschmitt-Boelkow-Blohm Gmbh Helicopter rotor head
US4203709A (en) * 1977-09-07 1980-05-20 Westland Aircraft Limited Helicopter rotor and blade connection
US4292009A (en) * 1977-12-24 1981-09-29 Messerschmitt-Boelkow-Blohm Gesellschaft Mit Beschraenkter Haftung Hingeless rotor system
US4352631A (en) * 1979-04-28 1982-10-05 Messerschmitt-Boelkow-Blohm Gmbh Hingeless rotor, especially for a helicopter
US4874292A (en) * 1988-11-18 1989-10-17 The United States Of America As Represented By The Secretary Of The Army Apparatus for damping helicopter rotor blade oscillations
US5100294A (en) * 1989-10-04 1992-03-31 Westland Helicopter Limited Helicopter rotors
US20040037701A1 (en) * 2002-06-14 2004-02-26 Santino Pancotti Helicopter rotor hub, and rotor featuring such a hub
US6910865B2 (en) 2002-06-14 2005-06-28 Agusta S.P.A. Helicopter rotor hub, and rotor featuring such a hub

Also Published As

Publication number Publication date
ES362800A1 (es) 1970-11-16
NL6902137A (xx) 1969-08-14
SE349530B (xx) 1972-10-02
BR6906344D0 (pt) 1973-04-10
NL159053B (nl) 1979-01-15
BE727547A (xx) 1969-07-01
LU57927A1 (xx) 1969-05-22
GB1245168A (en) 1971-09-08
FR1568117A (xx) 1969-05-23
DE1906764A1 (de) 1971-04-01

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