US 2290607 A
Description (OCR text may contain errors)
July 21, 1942.
R. SENSAUD DE LAVAUD PROPELLER 4 Sheets-Sheet 1 Filed Mgrh 13, 1939 ATTORNEY July 21, 1942. R. sENsAuD DE LAvAuD PROPELLER Filed March 13, 1939 4 Sheets-Sheet 2 INVENTOR ATTORNEY July 2l, 1942. R. sENsAUD DE LAvAUD 2,290,607
PROPELLER Filed March l5, 1939 4 Sheets-Sheet 5 NVENR PROPELLER Filed March 15, 1939 4 Sheets-Sheet 4 INVENTOR ATTORNEY Patented July 21, 1942 FBOPELLER Robert Sensaud de Lavaud, Paris, France `Application March 13, 1939, Serial No. 261,491 In France March 15, 1938 9 Claims. (Cl. 17o-173) This invention relates to propeller mechanisms, and more particularly to means for mounting propeller blades.
In order to fasten wooden blades to a hub member, it has been the practice heretofore to insert each of said blades in a metallic bushing and ll the space between the blade root and the bushing with a material adaptedv to harden, such as synthetic resin or Bakelite. When the material hardened and became solid, it formed a block surrounding the root blade. A serious disadvantage of this method of xing the propeller blade is that the :filling material has a tendency to crack and weaken when subjected to vibrations. Furthermore, the wood, when not perfectly impregnated, has a. tendency to contract and produce hollow spaces between the root and the lling material and thus induces excessive vibrations. If the blade root remains perfectly secure in its mounting, vibrations are transmitted from the motor to the blades and vice versa, which is undesirable.
Accordingly, it is an object of the present invention to provide novel means for mounting a wooden propeller blade whereby the above dis advantages of prior devices are obviated.
Another object is to provide novel means for mounting a propeller blade, for example, of an aircraft, whereby the vibrations of the motor of said craft are absorbed by said mounting means.
A further object is to provide novel means for securing a propeller blade to a hub member, said means being adapted to maintain the blade in central position despite excessive centrifugal forces.
These and other objects and novel features of the present invention will become more fully apparent from the following detailed description when the latter is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as -a denition of the limits of the invention, reference for this latter purpose being had to the appended claims.
In the drawings, wherein like reference characters refer to like parts throughout the several views,
Fig. 4 is a view in side elevation showing an embodiment of the invention in which a. metallic bushing is integral with thehub;
Fig. 5 is a front elevation of the mounting of Fig. 4S
Figs. 6 and 7 are crosssectional views showing two other embodiments of the present invention; and
Figs. 8 to 11, inclusive, are cross-sectional views showing several means for limiting the angular displacement of the blade about its own axis.
The embodimentl of the invention shown in Fig. 1 comprises a blade l having a root 2, which for securing said bushing tothe hub member (not shown). l
A ring 8, preferably formed in two sections and having the inner wall thereof conically shaped to engage sleeve 4, is screwed into the front end of bushing 5 and forms an air-tightv connection by compressing said sleeve. Unvulcanized rubber is then injected under pressure through an opening or nozzle ilv provided in the bottom of bushing. 5 for this purpose, and
said rubber fills the space between said bushing and root 2, air ports Il being provided in said bushing to allow air to escape during this filling operation. 'I'he ports I I are then closed andthe rubber is vulcanized under pressure, -nozzle S being thereafter plugged and the side walls thereof preferably removed. 'I'he vulcanized rubber thus formsa resilient connection between the blade root and the bushing to' prevent vibrations being transmitted from the bushing to'the blade, or vice versa'. Furthermore, the blade is securely maintained in central position and centrifugal forces tending to pull the blade out of the bushing compress the rubber between projections 3 and the walls of grooves E and create a counteracting force which keeps the blade secure'in the bushing. The rubber, because of 'its resilience, also has the effect lof immediately filling any hollow space resulting from the contraction of the wooden blade root.. -It will beunderstood that the above structure may be modiiied in several' ways without departing from the scope of the invention, as for example, by using helical grooves and screwing the root in the bushing with a suilicient space existing between said bushing and root to receive the India rubber. Furthermore, it is possible to spray the surface of the root with metal in a manner well-known in the art in order to` cause the root to adhere more strongly to rubber.
A second embodiment of the invention is shown in Figs. 2 and 3, and comprises a blade root 2 n having a series of annular projections I2 formed lthereon, said projections having a substantially saw-toothed shape in cross-section, and said roqt .being inserted in a sleeve I3 of India rubber. The
, latter may be vulcanized before or after attachment to the root. A bushing I4, preferably formed in two sections from a metal such as tinplated steel and having an internal shape which corresponds to the external shape of. root 2, is secured and tightened around said sleeve until the two sections thereof contact each other. The India rubber is thus compressed and tightly grips root 2, and said bushing sections are fastened together by a hoop member I6. Threads I1 may be provided in the lower end of bushing I4 for securing said bushing to the hub member upon which the propeller blades are to be mounted.
To prevent the two bushing sections from pinching portions of sleeve I3 as said sections are compressed together, thin metallic strips I9 (Fig. 3) may be provided and` are located on the interior of said bushing to overlap the edges of both of said bushing sections at their junctions. If strip I9 is not suiiiciently thin, a groove may be provided in the edges oi said bushing sections, or a groove 2| may be provided in the root member, allowing the rubber sleeve I3 to maintain a substantially constant thickness despite the insertion of said strip. The shape of projections I2 is suitably designed so thatgIndia rubber sleeve I3 and root 2. are compressed against bushing I4 with increased force as the centrifugal force acting on the blade is increased, and this compression offsets the latter force. Furthermore, the resilient sleeve prev-ents the root from contacting the metallic bushing and being'` bruised thereby, and the rubber immediately fills the hollow spaces resulting from the contraction of the wooden root.
The above described embodiment may be modified, for example, by providing a bushing having an inner'suriace and a root having an outer surface which are conical, hoop member I6 being positioned by being slid along the bushing. Hoop member I6 is normally adapted to engage a rim I8 provided upon the upper portion of the bushing, although it will be understood that a rim might instead be provided on the lower part of the bushing. In the latter case, the hoop member is fastened to the hub, for. example, by being threaded thereon in order 'that centrifugal forces will urge the bushing into closer engagement with said member.
Figs. 4 and 5 illustrate still another embodiment of the invention in which the bushing is integral with the hub. The hub, as shown, is
' separated along a central plane perpendicular to the axis of rotation of said hub into two symmetrical portions 22 and 23. 4A plurality of projections 24, 25 and 26, extending radially from each of said hub portions, are formed integrally therewith and said projections register with each other to provide radial openings in said hub member. The interior surfaces of projections 24, 25 and 26 are provided with a series of annular grooves corresponding with annular projections or shoulders located on the blade roots. Each of said roots is covered by an India rubber sleeve and thereafter positioned in one of projections 24, 25 and 26, the annular shoulders being located in the annular grooves. Sections 22 and 23 of the hub member are then drawn together and into contact with each other, for example, by means of bolts or by being pressed together and riveted. The India rubber sleeves on the propeller roots are thus lpressed into engagement with said roots and with the walls of projections 24, 25 and 26, securely holding the blade roots in position on the' hub member.
Another embodiment of the invention is shown, by way of example, in Fig.- 6, and comprises a bushing 33 originally shaped in the form of a cylinder or cone and having a sufllcient diameter to permit the insertion therein of a grooved root 3l covered with a resilient sleeve 32. The root 3l may be forced, if necessary, into said bushing and thereafter bushing 33 is compressed by any convenient means into a shape vconforming to the contours of root 3 I, said bushing being adapted to apply a compressive force to said root and to resilient sleeve 32 which surrounds the latter. In the event metallic blades are being mounted, it is possible to shape the bushing first and then insert the root of the blade which is tubular in shape into said bushing and apply internal pressure to said root to deform it to the shape of the bushing. v
Still another embo f ent of the invention is shown in Fig. '7 and comprises a'blade having a conical root 43, said blade being shown, by way of example, as/xed to a torsion b ar 42. A conical bushing formed with or carried by the end of said torsion bar is adapted to receive root 43 and a layer 44 of resilient material, such as India rubber or the like, is interposed between said root and said bushing. The blade is joined to root 43 by a neck portion 45 shaped as a frustrum of a cone or a tore and having a smaller diameter than that of said root. A collar or sleeve 46..
preferably formed in two sections, is applied to neck portion 45, the two sections being secured to each otherv by suitable means such as screws 41. A layer 48 of resilient material, such as India rubber, is interposed between collar 46 and neck portion 45, and said collar when tightened by said screws compresses said resilient layer into tight engagement withsaid neck portion. Resilient layer 48 may be formed in two parts corresponding to the two parts of said collar.
A ring or sleeve 49, preferably having a shoulder 5I .formed therewith, is internally threaded and adapted to screw onto the end of bushing 4I, the latter being externally threaded at its. upper end to receive said ring. Shoulder 5I of the latter engages collary 46V and by threading said ring on bushing 4I, blade root 43 is forced further into said bushing because of the contraction of resilient layer 44 due to the increased compressive force applied thereto. This pressurev application, due to the threading of said collar,v
shape of a polygon, as shown in Figs. 8 and 10 cover, a strip of iiexible or resilient material is affixed to ring 49 and extends downwardly therefrom to cover 52, being secured to the latter by suitable means, such as a steel wire 54.
It is to be understood that propeller blade mechanisms employing the above described novel mounting means need not be of the type having a torsion bar. If the torsion bar is eliminated, bushing 8| may be attached to or formed integrally with the hub. The resilient material interposed between the root and bushing in all of the above described embodiments may be formed from natural or synthetic India rubber, or from a mixture having India rubber for its base, or from textile fabrics impregnated with one or more .of said materials, said fabrics being reinforced when necessary by metallic wires.
It may be desirable to have the resilient layer adhere to the wooden or metallic surface of the blade root and in some cases it will even Y sible to keep the root fastened to the bushing by adhesion of the resilient layer with said root and said bushing, dispensing with grooves and projections, The size of the resilient layer interposed between the blade root and the bushing is determined by the strain to be exerted on the blade and is of a sucient thickness to prevent the root from contacting any metallic part of the be pos-,
bushing or of the hub. It is desirable that the resilient material should never be deformed to a degree which will permanently affect the thickness of the layer and in many cases it may be desirable to give a resilient layer different thicknesses at dierent points. If a propeller is provided with two blades integral with each other, i
a resilient layer will cover the central part common to both blades and not the separate roots. In order to prevent angular displacement of the blade about the root axis, the resilient layers may be caused to adhere to the root and bushing, or the blade root and the bushing therefor may be selected or constructed to have a shape which will prevent any angular displacement. For example, the bushing 33, resilient layer 32 and blade root 3| may be formed substantially in the or the bushing may have one or more inwardly projecting portions which extend into and engage grooves or openings in the roots (Figs. 9 and 11) There is thus provided novel mounting means for propeller blades, said means being adapted to limit the axial and angular displacement of the bladel and to x the latter on the hub securely enough to withstand the maximum centrifugal forces applied to said blade. The novel mounting means reduce the vibrations imparted to and transmitted from the blade. Furthermore, heat is generated by the internal friction set up in the resilient material as a result of variations in stresses, and this heat protects the blade root from the deleterious eiTects of the low temperatures which occur at high altitudes.
It is to be expressly understood that the in vention is not limited to the several embodiments Vv`which have been illustrated and described. As
will be understood by those skilled in the art, various changes may be made in the design and arrangement of the parts without departing from the spirit and scope of the invention. For a definition of the limits of the invention, reference will be made primarily to the appended claims.
What is claimed is: 1. In apparatus forA mounting a propeller blade,
root and neck portions formed integrally with said blade, said neck portion converging in the direction of the blade tip for at least part of its length, a bushing having an internal shape similar to the external shape of said root, said bushing being adapted to receive said root, a layer' of resilient material interposed between said bushing and said root, a layer of resilient material covering said neck portion, and means fastened to said bushing, said means being adapted to engage and apply a holding pressure to said neck portion through said last-named layer of resilient material.
' 2. In apparatus of the class described, a propeller blade, a root member carried by said blade, said root member having a plurality of circumferentially continuous projections formed therewith, said projections having the walls thereof obliquely disposed relative ,to the root axis, a bushing member having grooves formed in the internal wall thereof, said grooves corresponding in shape to said projections, and said bushing beingadapt'ed to, receive said root with said grooves and projections registering with each other, a layer of resilient material interposed between said root and said bushing, said layer completely separating lsaid root from said bushing, and means secured to said bushing, said means comprising a rigid member surrounding said root and resilient material disposed between said member and said root, said member applying a force to said blade to keep the latter positioned in said bushing.
3. In apparatus of the class described, a hub, propeller blades having rootsformed therewith., bushings having internal walls corresponding in shape to the walls of said roots, the surfaces of said walls being oblique to the axis of said root throughout a substantial part of the areas of said walls', each of said bushing members being adapted to receive one of said roots with corresponding points of the similar wall contours substantially opposite each other, and a layer of resilient material compressed betweenfsaidbushing and said root whereby axial movement of said root increases the compression in said resilient material by varying the distance between wall portions of said bushing and root oblique vto the root axis.
4. In apparatus of the class described, a hub, blades having roots formed therewith, said roots being provided with saw tooth shaped grooves, bushings having saw tooth shaped projections corresponding to the grooves of the roots formed on the internal walls thereof, each of said bushings being adapted to receive one of said roots, collars secured to each of said bushings for applying a holding force to said roots, and layers oi' resilient material compressed between said bushing and said root and between said root and said bushings being shaped substantially like the frustrumof a cone and veach of said bushings being adapted to receive one of said root portions, a layer of resilient 'material surrounding eachroot portion and neck portion, and means secured to said bushing and engaging said neck portion in order to hold said blade on said hub. 6. A propeller comprising a hub, blades having root 'and neck portions formed therewith, said root portion being 'shaped like the frustrum of a cone and being joined to said blade by said neck portion, the latter having a diameter which 1s smaller than the greatest diameter of said root portion, bushings attached to said hub, each of said bushings being adapted to receive oneof said roots, a layer of resilient material covering each root portion and neck portion, an adjustrounding each of said neck portions, a ring threaded at one end and having an inwardly projecting shoulder formed at the other end, said shoulder being adapted to engage said collar when said ring is threaded ori said bushing, a cover attached to the hub, said cover surrounding said bushing, and a strip of flexible material attached to said cover and said ring in order to enclose said bushing. x
8. In apparatus for mounting a propeller blade. root and neck portions formed integrally with said blade, said neck portion converging in the direction of the blade. tip for at least a part of its length, said root portion having walls disposed at an oblique angle to the root axis, a'
bushing having an internal shape similar to the external shape of said root, said bushing being adapted to receive said root, a layer of yielding material interposed between said bushing and said root, a layer of yielding material covering said neck portion, and means fastened to said bushing, said means being adapted to engage and apply a holding pressure to said neck portion through said last-named layer of yielding material.
9. In apparatus for mounting a propeller blade, root and neck portions formed integrally with said blade, said neck portion converging in the direction of the blade tip for at least a part of its length, Vsaid root portion having ciroumferentially continuous saw-tooth shaped grooves therein, a bushing having an internal shape similar to the external shape of said root,'said bushing being adapted to receive said root, a layer of yielding material interposed between said bushing and said root, a layer of yielding material covering said neck portion, and means fastened to said bushing, said means being adapted to engage and apply a holding pressure to said neck portion through said last-named layer. of y yielding material.
v ROBERT SENSAUDnE LAVAUD.