Source: http://www.google.com/patents/US4639284?dq=7,444,563
Timestamp: 2017-06-24 07:50:26
Document Index: 105354373

Matched Legal Cases: ['art 42', 'arts 49', 'art 49', 'art 50', 'art 49', 'art 42']

Patent US4639284 - Process for manufacturing a variable pitch multi-blade propeller by molding ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA variable pitch multi-blade propeller suitable for use on a helicopter is constructed of a foam preform joined with a fibrous spar enclosed in resin-impregnated foils and fitted with a metal leading edge. Various components are assembled in a mold and the resins, then cured. The structure may further...http://www.google.com/patents/US4639284?utm_source=gb-gplus-sharePatent US4639284 - Process for manufacturing a variable pitch multi-blade propeller by molding resin-impregnated fails around a preformAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS4639284 APublication typeGrantApplication numberUS 06/688,896Publication dateJan 27, 1987Filing dateJan 4, 1985Priority dateMar 18, 1983Fee statusPaidAlso published asCA1264313A, CA1264313A1, CA1278287C, CA1278287C2, DE3467138D1, EP0121462A1, EP0121462B1, EP0212724A2, EP0212724A3, EP0212724B1, US4626172, US4626173Publication number06688896, 688896, US 4639284 A, US 4639284A, US-A-4639284, US4639284 A, US4639284AInventorsRene L. Mouille, Marc Declerco, Jean-Pierre Jalaguier, Bernard JaugeyOriginal AssigneeSociete Nationale Industrielle AerospatialeExport CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (35), Classifications (43), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetProcess for manufacturing a variable pitch multi-blade propeller by molding resin-impregnated fails around a preform
US 4639284 AAbstract
A variable pitch multi-blade propeller suitable for use on a helicopter is constructed of a foam preform joined with a fibrous spar enclosed in resin-impregnated foils and fitted with a metal leading edge. Various components are assembled in a mold and the resins, then cured. The structure may further include a reinforcing yoke of carbon fiber fabrics preimpregnated with a polymerizable synthetic resin. The process may further include a heat treating step to effect polymerization.
1. A process for manufacturing a rotor blade havinga shell with aerodynamic profile having an upper face and a lower face both extending from a blade leading edge part to a blade trailing edge part and each formed of a stacking of at least two foils of high mechanical resistance fiber fabrics rigidified by a polymerized synthetic impregnation resin, a filling body in a foam-like synthetic material which has the same general profile as said shell and is disposed in the latter, extends chordwise from said leading edge part to said trailing edge part and presents a cut-out extending spanwise over all the length of said filling body and opening in a face of said filling body which is turned towards said upper face of said shell, a spar constituted by a single elongated leaf of rovings of fibers with high mechanical resistance agglomerated by a polymerized synthetic resin, said spar having a longitudinal axis substantially parallel to that of the blade and presenting a spanwise extending major part provided with a section corresponding substantially to that of said cut-out, said spar major part being housed and fixed in said cut-out and presenting a spar face turned towards said shell upper face and along which said spar major part is directly fixed against an inner surface part of said shell upper face, said spar further presenting an end part emerging from said shell and arranged as a twistable and flexible spar root part for connecting said spar to a rotor hub, and a metal leading edge cover integrated in said shell in said leading edge part; the process being carried out by means of a lower half mould and a upper half mould provided with complementary impressions having the forms respectively of said lower face and of said upper face and the process comprising the following steps of depositing and stacking in said lower half mould impression said at least two foils of fiber fabrics for forming said shell lower face and which are impregnated with a polymerizable synthetic resin, positioning said filling body, made as a preformed body in a separate equipment, above said stacked foils, disposing a major part of said leaf of rovings of fibers which are agglomerated by a polymerizable synthetic resin in said cut-out of said filling body and arranging an end part of said leaf of rovings beyond spanwise end of said cut-out for forming said spar root part, depositing and stacking said at least two foils of fiber fabrics for forming said shell upper face and which are impregnated with a polymerizable synthetic resin on said stacked foils for forming said shell lower face, said filling body and said leaf of rovings thus assembled in said lower half mould, installing said metal leading edge cover over parts of said stacked foils for forming said shell lower and upper faces which are adjacent to said leading edge part in said lower half mould, placing said upper half mould on said lower half mould so that said stacked foils for forming said shell upper face are positioned in said upper half mould impression, and closing said half moulds against one another, and polymerizing said resins impregnating said foils of fiber fabrics and agglomerating said rovings of fibers of said leaf. 2. The process as claimed in claim 1, further comprising prior to depositing said at least two foils of fiber fabrics for forming said shell lower face in said lower half mould impression, the steps ofcutting out at least two layers of fiber fabrics impregnated with a polymerizable resin, each layer being cut-out in the form of an elongated layer comprising two adjacent foils on either side of a longitudinal median axis corresponding to said leading edge part, a first one of said two adjacent foils being for forming said shell lower face while the second foil is for forming said shell upper face in positioning said at least two layers of fiber fabrics so that their first foils are deposited and stacked in said lower half mould impression and so that their second foils are left outside said lower half mould and over a part of said lower half mould which corresponds to said leading edge part, and, after having positioned said filling body,folding on itself a single bundle of said rovings in two equal halves and spreading it into said cut-out to form said single leaf of rovings, folding said second foils over said filling body and bundle of rovings, before installing said leading edge cover, closing said half moulds, an finally polymerizing each resin. 3. The process as claimed in claim 1, further comprising, after having positioned said filling body in said lower half mould the step ofpositioning on a rear edge of said filling body which is adjacent to said trailing edge part, a substantially V-shaped reinforcing yoke made of carbon fiber fabrics preimpregnated with a polymerizable synthetic resin and preformed in another separate equipment. 4. The process as claimed in claim 3, further comprising the steps ofusing a single thermosetting resin for impregnating said foils of fiber fabrics and said reinforcing yoke and for agglomerating said rovings of fibers of said leaf, and applying a heat treatment after said closing of said half moulds to polymerize said resin. Description
This is a division of application Ser. No. 587,649 filed Mar. 8, 1984.
To this end, this cylindrical bearing is mounted to slide and rotate in a radial sleeve made of relatively supple synthetic material with a low coefficient in friction, which is embedded over about half of its length towards the axis of the propeller in a radial cylindrical bore machined in the hub, and free towards the outside, each sleeve being held in place by a collar which is housed in a corresponding groove in the bore and immobilized in rotation by a stud passing through the wall of the bore. In order to effect such an assembly of the blade root, which constitutes a sort of semi-embedding on the hub, it is indispensable that the latter presents a rim having a large radial thickness, with the result that sufficiently long cylindrical bores may be pierced in this rim to serve as housing for the sleeves, which is disadvantageous from the standpoint of weight, manufacturing costs and the centrifugal efforts which stress this important eccentric mass constituted by two circular cheeks bolted one on the other.
Furthermore, the crankpin for connecting the root of each blade to the axially movable plate in order to control the angle of attack is constituted by a lateral lever, fast with the inner radial end of the cylindrical bearing, and bearing a shaft provided with a spherical ring made of elastomer which just fits inside the eye of an axial yoke fast with the radial periphery of the plate; but nothing positively retains the elastic ring in the eye of the yoke.
Finally, the elongated, twistable element connecting each blade to the central part of the hub surrounding the shaft of the rotor is constituted by one of the arms of a star-shaped member comprising as many arms as the propeller comprises blades, all the arms being fast with one another by a central flat ring of this member, by which this member surrounds the shaft of the rotor and is connected to the latter by the ring of bolts. This star-shaped member is made by superposing a plurality of discs of thin sheet steel which are cut out in star form, with the result that each arm is formed by a bundle of thin leaves joined together, the outside leaves of the bundle being of smaller width than those of the inner leaves in order to distribute the torsional stresses uniformly between the different leaves which are, moreover, coated with an anti-friction plastic coating in order to avoid corrosions caused by contact.
a spar whose longitudinal axis is parallel to that of the blade and constituted by a single elongated leaf of fibers with high mechanical resistance agglomerated by a polymerized synthetic resin, of which the major part is fixed in the shell and of which one end part, emerging from the shell on passing through the blade root, forms a twistable and flexible root part by which the spar is connected to the hub,
and such that the blade root is fast with a blade pitch control member, which is adapted to exert on the shell a torsional moment, substantially centred on the longitudinal axis of the spar, when this member is actuated by an assembly for collectively controlling the angle of attack of the blades, this member being, moreover, mounted to rotate in the hub about the longitudinal axis of the corresponding blade, wherein each blade is individually connected to the hub by the root part of the spar, which is arranged in a loop surrounding, by its inner end, a single connection element bolted on the hub.
Two rigid, radial, flat rings are advantageously disposed on either side of all the connection elements of the different blades and about the central shaft, and each present, for each connection element, a bore adapted to be aligned with the central passage of the corresponding connection element and to receive the shank of the single pin for connecting the connection element to the hub, in order to distribute the centrifugal forces from one connection element to the other. By transmitting the efforts from one of the connection elements to the other, these rings make it possible not to bend the shank of the single pin for connecting the connection element of a blade to the hub.
In the blade root comprises a hollow cylinder whose inner end is truncated in form and a transition zone connecting the hollow cylinder to the shell of the blade, the sleeve comprises, in an embodiment particularly well adapted to its cooperation with the blade root, an outer cylindrical part of large diameter surrounding the hollow cylinder of the blade root and connected by an intermediate truncated part, by which the sleeve bears against the truncated inner end of the hollow cylinder, to an inner cylindrical part of small diameter.
In the second of the last mentioned two U.S. Patents mentioned above, which relates to a helicopter tail rotor with two diametrically opposite blades connected to each other by a common spar, each blade comprises a skin surrounding a preformed honeycomb filling body, the spar being constituted by a thin, flat strip of unidirectional fibers of high mechanical resistance, for example graphite, KEVLAR which is an aramide fiber, or glass, common to the two opposite blades and extending over the whole of their span, and which presents a relatively thick median part, forming the hub, to which are adjacent two finer, twistable and flexible parts which each extend by two end parts themselves each divided into two half-spars of which one is an upper surface half-spar and the other a lower surface half-spar each extending just beneath the corresponding skin part of the blade, between this skin and the filling body.
a shell with aerodynamic profile, constituted by at least one layer of fiber fabrics with high mechanical resistance rigidifed by a polymerized synthetic resin for impregnation,
In order to ensure good torsional rigidity of the whole of the blade, the shell is constituted by a stack, from the outside to the inside, of at least one layer of fabrics of glass fibers or KEVLAR, but preferably of two layers which are crossed and inclined by 45° with respect to the longitudinal axis of the blade, and of at least one layer of carbon fiber fabrics, but preferably two layers likewise crossed and inclined in similar manner.
The auxiliary gear box 5, which is for example such as the one described and shown in U.S. Pat. No. 3,594,097, to which reference may advantageously be made for further details, contains a bevel gear whose input gear is driven by a transmission shaft 7 connecting the main gear box to the auxiliary gear box 5, and passing through a hollow arm 8 connecting the fairing 4 to the casing of the auxiliary gear box 5. The latter also contains a bevel gear 9, stressed by a connecting rod 10 for collectively controlling the angle of attack in order to displace a shaft for collectively controlling the angle of attack, described hereinafter, parallel to the axis of the airflow 2. The bevel gear 9 and the connecting rod 10 have been schematically shown as in FIG. 1 of the Patent mentioned above, for the purposes of clarity, but the connecting rod 10 may possibly also pass through the hollow arm 8.
The shell 37 is made of a stack constituted, from the outside to the inside, by two superposed layers of fabrics of glass or KEVLAR (registered trademark) fibers, which are aramide fibers, disposed such that, for example, their warp yarns are crossed at right angles and inclined by 45° with respect to the longitudinal axis of the blade, and by two layers of carbon fiber fabrics, preferably likewise crossed and inclined at 45°, and the assembly of these four layers is agglometrated by a synthetic resin polymerized by heat-setting, so as to form a hollow body ensuring torsional rigidity of the whole of the blade, in which the filling mass 38 does not present any resistance to shear.
The spar 39 is a solid elongated leaf made of KEVLAR rovings agglometrated by a heat-setting synthetic resin and having, over about two thirds of its length which are received in the general part of the blade 36, a section which corresponds to that of the housing defined by the cut-out 41 of the filling mass 38 and by the lower face of the opposite part of the upper surface of the shell 37.
The spar 39 adapted to make up the centrifugal forces stressing the blade 36 in service constitutes, by the last third of its length which emerges from the general part of the blade, passing through the blade root described hereinbelow, a root part 42 in the form of a loop (cf. FIG. 3) whose thickness increases (cf. FIG. 2) from that part of the spar 39 received in the general part of the blade 36 towards the free end of the loop, which surrounds a metal element or spool 43 forming connection for the blade 36, being wound in a groove around this connection element 43.
This sleeve 48 comprises two coaxial tubular parts 49 and 50, of circular section having different inner and outer diameters, and of which the cylindrical bores are connected by a truncated part. The hollow cylinder 46 of the blade root 44 and its truncated inner radial end are respectively covered by the tubular part 49 of larger inner and outer diameter and by the truncated part of the sleeve 48, and are respectively fixed to these two parts by adhesion. This form of the sleeve 48 promotes support thereof against the hollow cylinder 46 of the blade root 44 under the effect of the centrifugal force.
Around its inner radial end, facing the shaft 11 of the rotor, the part 50 of smaller inner and outer diameter of the sleeve 48 presents a collar 52 of spheroidal form whose maximum outer diameter corresponds to the inner diameter of the self-lubricating ring 35 housed in the opening 33 of the inner wall 31 of the hub 26. Similarly, a collar 51, likewise of spheroidal form, and whose maximum outer diameter corresponds to the inner diameter of the self-lubricating ring 34 housed in the opening 32 of the outer wall 30 of the hub 26, is presented by the part 49 of larger inner and outer diameter of the sleeve 48, about its outer radial end, i.e. in the position in greatest distance vis-a-vis the collar 52 on the sleeve 48.
The latter also comprises a lateral boss 53, connected to the truncated part of the sleeve 48, between the two collars 51 and 52, and extending in a direction substantially perpendicular to the axis of the sleeve 48 as well as to the axis A of rotation of the rotor.
Each boss 53 constitutes with the pin 63, the nut 64, the ball joint 62 and the lug 54 which correspond thereto, a lever for controlling the pitch of the blade 36 of which the root 44 is fast with the corresponding sleeve 48. The different pitch control levers thus contituted, the control plate 55, the cheek 57 and the shaft 59 for collectively controlling pitch, constitute an assembly for collectively controlling the pitch of the blades 36 of the rotor, such that any axial displacement of the shaft 59 in the tubular shaft 11 controls, via the pitch control levers, the application of a torsional moment on the sleeves 48, and therefore also on the blade roots 44 and the blades 36 about the longitudinal axes of these latter. This torsional moment provokes rotation of the sleeve 48 and therefore also of the blades 36 about the longitudinal axes of these latter, causing the root part 42 of the spar 39 to twist. Each pitch control lever is located between the two collars 51 and 52 of the corresponding bearing sleeve, which are in maximum spaced apart relationship with respect to each other, this making it possible to ensure a better support of each blade 36 and reducing the radial efforts exerted by the collars 51 and 52 on the corresponding self-lubricating rings 34 and 35.
Finally, a convex cover 69 fixed, for example by screws, by its outer radial edge on the periphery of the outer radial wall 30 of the hub body 26, covers the assembly for collectively controlling the pitch of the blades 36 and protects the hub against the penetration of dust, stones, etc . . .
Two elongated layers of fabrics of glass or KEVLAR fibers are firstly cut out, then two elongated layers of carbon fiber fabrics, each layer comprising two adjacent foils 37 I and 37 E on either side of a longitudinal median axis corresponding to the leading edge of the shell 37 and adapted to form the lower surface part and the upper surface part of the shell 37 respectively. These layers of fabrics are pre-impregnated with a polymerizable synthetic resin, for example heat-setting. The foils 37 I formed by the two layers of glass or KEVLAR fiber fabrics are then deposited in the impression in the lower half-mould 70, leaving foils 37 E of these two layers outside the lower half-mould 70, on the leading edge side, then the two layers of carbon fiber fabrics are deposited in the same manner on these two layers, so that all the foils 37 I of the four layers of fiber fabrics forming the shell 37 are stacked in the lower half-mould 70, as shown in FIG. 5. The preformed filling mass 38 of cellular material or foam, of which the cut-out 41 opens upwardly, is then placed on this stack of foils 37 I. There is no difficulty in making this mass 38 in the desired shape in a second mould arranged to this end and this operation does not require further explanations. The reinforcing yoke 72 constituted by fabrics of carbon fibers preimpregnated with synthetic resin and preformed as a V in separate equipment is positioned on the rear edge 38a of the filling mass 38. Then the spar 39 constituted by an elongated leaf whose end part is formed as a loop, is deposited in the cut-out 41 in the preformed mass 38 in position in the lower half-mould 70. Manufacture of elongated leaves of this type, intended in particular to constitute the webs of the rotor blades of rotorcraft, is well known and does not need to be described in detail; it suffices to specify that leaves of this type may be constituted not only with rovings of KEVLAR fibers, but also with rovings of glass fibers or carbon fibers. All these rovings may be agglomerated for example by impregnating the bundle which they form with a polymerizable resin, particularly a heat-setting one. This known process makes it possible to produce in particular thin, relatively narrow, elongated leaves which present mechanical properties which are particularly advantageous for making the webs of rotor blades of rotorcraft: in fact, they combine a high mechanical resistance in the longitudinal direction, enabling them to absorb the centrifugal forces applied to the blades of which they constitute the spars, without excessive stress nor fatigue, with relative suppleness, in particular in twist about their longitudinal axis, which makes it possible to control the respective angles of attack of the blades by exerting on the elongated leaves torsional moments centred on their longitudinal axis, and of relatively low value.
In this precise example, the spar 39 is constituted by a single elongated bundle of rovings which is folded on itself at the centre of its length and of which the two end parts extending over about two thirds of each half of the bundle are coupled in order to constitute the portion of the spar intended to extend in the general part of the blade 38, whilst the median part of the bundle, extending over about one third of each half on either side of the centre of the length of the bundle is intended to constitute the twistable, flexible, loop-shaped root portion 42, after folding the bundle on itself in two equal halves. The bundle of rovings impregnated with heat-setting resin is therefore spread out in the cut-out 41 in the filling mass 38, then the foils 37 E of the layers of fabrics of coating fibers are folded onto the mass 38 and the bundle of rovings, and the titanium or stainless steel sheet cover 40 is then installed on the leading edge, as shown in FIG. 6. As shown in FIG. 7, the upper half-mould 71 is then placed on the lower half-mould 70 and the whole of their contents is polymerized by heat treatment, this ensuring integration of the leading edge cover 40 in the fabrics of the rigidified shell and which adheres by the whole of its inner surface either on the mass 38, or at the level of foils 37 E of the upper surface part directly on the spar 39, of which the rovings are agglomerated.
The transition zone 47 and the hollow cylinder 46 of the blade root 44 may be made simultaneously thanks to longitudinal recesses of complementary shape made in that part of the half-moulds corresponding to the blade root and in which is disposed a hollow mandrel, traversed by that portion of the bundle of rovings constituting the loop-shaped root 42. This mandrel, surrounded by the layers of reinforcing fiber fabrics 45 is disposed in the recess of the lower half-mould 70 above the parts of the layers of coating fabrics extending the foils 37 I previously disposed in the impression of this half-mould 70. When the foils 37 E are folded down, parts of coating layers extending the latter are folded down above the mandrel and the reinforcing layers 45. The general part of the blade 36, the corresponding portion of the spar 39, the blade root 44 and the twistable, flexible, loop-shaped root portion 42 of the spar are thus moulded and polymerized in a single mould and by a single heat treatment.
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