US2574980A - Rotary wing blade - Google Patents

Description

Nov. 13, 1951 D. N. MEYERS ROTARY WING BLADE 3 Sheets-Sheet 1 Filed June 5, 1947 v INVENTOR.

' D. N. MEYERS Nov. 13, 1951 ROTARY WING BLADE 3 Sheets-Sheet 2 Filed June 5, 1947 INVENTOR. (fig-714M 77. W

Nov. 13, 1951 D. N. MEY ERS ROTARY WING BLADE 3 Sheets-Sheet 3 Filed June 5. 1947 IN V EN TOR.

Patented Nov. 13, 1951 noraar WING puma Donald N. Meyers, Philadelphia, Pa assignor, by

mesne assignments, to Piasecki Helicopter Corporation, Morton, Pa., a corporation of ,Pennsylvania Application J line 5, 1947, Serial No. 7 52,649

2 Claims. (Cl. 170-159) 1 This invention relates to Rotary Wing Aircraft and more particularly to sustaining blades therefor.

Experience has shown that it is desirable to,

use all metal construction for helicopter blades as it lends itself to mass production methods and provides a longer lasting blade. However, construction of metal blades has proved diflicult because of the limited working space available in the air foils of this nature.

Rotative wing. blade are subjected to high bending and twisting forces which must be resisted to retain the airfoil shape of the blade. The blades are further subjected to high air speeds and this in turn calls for clean design and close tolerance of the airfoil contour.

It is therefore the principal object of this inabove difliculties and provides the advantages inherent in all-metal construction.

Another object of this invention is to provide a blade construction that permits ease of inspection to discover faulty workmanship, and defective materials during the course of construction.

A further object of this invention is to provide a' blade that may be easily dis-assembled for servicing, inspection and repairs.

A still further object of this invention is to provide a root-end attachment wherein the centrifugal forces acting on the forward and rearward sections of the blade are transferred to the root-end fitting independently of each other.

Other objects and advantages will appear in the following specifications when read in conjunction with the accompanying drawings in which:

Figure 1 is a plan view of the inboard portion of the blade showing the root-end attachment.

Figure 2 is a plan view of the outboard portion of the blade.

Figure 3 is an end view of the inboard section of the blade.

Figure 4 is an exploded view of the various elements making up the blade.

vention to provide a blade that overcomes the 2 in Figures 4, 5 and 6 it will be seen that the blade is comprised of four sub-assemblies, l5, l6. l1 and I8, whic are riveted together to form two major sub-assemblies as shown in Figure 5.

The leading edge portion is comprises one subassembly and the rear spar section I6 comprises the second sub-assembly. The upper blade section I'l comprises the third sub-assembly and the lower blade section l8 comprises the fourth sub-assembly.

In manufacturing the blade the leading edge portion I5 is built up of a preformed skin part I! riveted to the channel member 20 by a series of rivets 2| along the top portion thereof and 22 along the lower side thereof. The member 20 forms the front half of the blade spar.

The rear half of spar i6 is comprised of a U shaped metal piece provided with access openings 23 along the rear wall thereof and is also provided with a series of nuts 24 riveted to the under side of the top forwardly extending leg 25 and to the top surface of the lower forwardly extending leg 26 in alignment with holes drilled through said forwardly extending legs.

The upper surface sub-assembly ll of the airfoil is comprised of a skin 21 attached to the half ribs 28 spaced along the span of the blade, by a series of rivets 29. The lower blade section I8 is built up in a similar manner. A reinforcing strip 29 is riveted to the inner surface of the skin 21 along the front edge thereof. This operation permits the use of a forming jig to hold the contours to close tolerances and eliminates the use of blind rivets.

In assembling the various sub-sections the following procedure is used. The sub-assemblies l1 and I8 are brought together in such a manner that the split ribs 28 will overlap each other and are then riveted together by a series of rivets 30 as shown in Figure 5.

This riveting operation is performed by reaching in from the front of the rear blade sections before the rear half of the spar is riveted there- Figure 5 is a view of the two major sub-as- The trailing edge portions of the members I! and I8 are brought together with a reinforcing strip 35 sandwiched therebetween and the three parts are riveted together by a series of rivets 36. The next step is riveting the rear half spar section It to the aft airfoil members I1 and I8. This is accomplished by riveting the upper section II to the rear spar by use of a series of rivets 3| and riveting the lower section It to the spar member by a series of rivets I 3 32 and riveting the ears formed at the front of the split ribs to the spar member by. use of riv ets 33. The last mentioned rivets 33 are bucked" by inserting a tool through the access opening 23 provided in the rear spar member.

The leading edge portion is then slipped over the exposed portion of the spar member l6 so that the bolt holes 34 are in alignment with the nuts 24. Flush headed bolts 31 are then used to secure the sections together. Particular attention is called to Figure 6 of the drawings where it will be noted that the assembled blade provides a box section sparmember giving great rigidity and strength to the-blade. This method of assembly forms an important partof thisinvention as it allows the removal of theleading edge portion for inspection or. replacement.

From the foregoing description and accompanying drawings it can readily be understood and seen how this invention eliminates the use of blind riveting and the hazards and expense attendant thereto. By building up the blade of sub-assemblies outlined above and assembling the same in themanner; described, all riveting is done in the open where the operation can be easily and cheaply performed without the use of expensive jigs and tools. Another important feature of this invention lies in the fact that all operations may be visually inspected as the work progresses.

The root-end fitting I3 of the blade is formed or shapedin such a manner that it is of dog-leg shape when viewed in plan. The forward or outboard portion of the fitting is bolted and riveted to the leading edge portion and the aft portion is bolted to the rear portion of the blade by means of bolts, 38. This method of construction is employed as a safety feature to prevent loss of either of the blade sections should the bolts 31 fall and also avoids stress concentration in the root end portion of the blade and fitting.

It is understood that while the drawing shows the preferred embodiment of my invention, changes in the construction thereof could be made without departing from the spirit and scope of the invention as described in the append claims.

I claim:

- 1. In combination, a rotary wing blade having a spar member made up of two channel members partially telescoped together to form a box section, one of said members constituting the forward member of the spar and the second member constituting the aft member of the spar, said second member being provided with a series of ports to permit internal inspection and assembly, a series of split ribs riveted to the aft member of the spar at spaced intervals along the span of the blade, a metallic covering riveted to the split ribs and to the rear half of the spar in such a manner that a portion of the aft member of the spar is left uncovered, said split ribs and covering riveted thereto being riveted together to form an air foil shape for the aft portion of the blade, a sheet metal leading edge member riveted to the forward member of the spar, said leading edge member abutting the covering of aft portion of the blade, a portion of the forward spar member overlying the uncovered portion of the aft member of the spar, said leading edge member and said aft spar member being bolted together by a series of flush head bolts spaced longitudinally along the span of the spar.

2. A metal blade for rotary wing aircraft, comprising in combination two separable longitudinally extending portions, each of said portions having a U shaped member, said U shaped members forming a box spar when the two portions are Joined together, said portions being joined together by a series of bolts spaced along the spar of the blade, one portion constituting the leading edge, the other portion constituting the trailing edge, a root end fitting, the inner end of said fitting being separably joined to the trailing edge portion, the outer end of said fitting being permanently joined to the leading edge portion.

DONALD N. MEYERS.

REFERENCES CITED The following references are of 'record in the file of this patent:

UNITED STATES PATENTS

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