US2702085A - Closure means for hollow type propeller blades - Google Patents

Description

Feb. 15, 1955 A. H. JAcKsoN, JR

CLOSURE MEANS FOR HOLLOW TYPE PROPELLER BLADES Filed May 2s, 1952 INVENTOR. Afr/WP# JPICKS/I/J.

ATYURNEY 2 Sheets-Sheet l wmf 1 I I I l v Feb. l5, 1955 A, H, JACKSQN, JR

CLOSURE MEANS FOR HOLLOW TYPE PROPELLER BLADES Filed May 23, 1952 2 Sheets-Sheet 2 Pfc; 4T

- INVENTOR. Af/UP JACKSON JP W ATTO/@MEV United States Patent CLOSURE MEANS FOR HOLLOW TYPE PROPELLER BLADES Arthur H. Jackson, Jr., West Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application May 23, 1952, Serial No. 289,633

3 Claims. (ACI. 170-159) The present invention relates to aeronautical propeller blades and, more specifically, to improvements in a closure member or cuilE therefor which is adapted particularly for application tothe fairing area at the inboard end of a hollow, core-and-shell type propeller blade.

It is the general aim of the invention to provide a blade cuif which will effectively close the inboard end of the blade to the passage of moisture and which will be constructed and arranged to provide an airfoil extension on the blade to increase its eiciency and to increase the cooling air stream to the aircraft engine.

A more specific object is to provide a cui having the foregoing characteristics and which includes filler means adapted particularly to improve the bond between the blade shell, the cuff, and the core.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description of the drawing which, by way of preferred example only, illustrates one specific embodiment of the invention.

In the drawing:

Fig. 1 is a foreshortened elevational view of an aeronautical propeller blade which includes the cuff of the present invention;

Fig. 2 is a transverse sectional view of the blade taken on line 2-2 of Fig. 1;

Fig. 3 is a transverse sectional View taken on line 3 3 of Fig. l;

Fig. 4 is a perspective view of a preformed pack used in forming the cui of the blade; Fig. 5 is an enlarged transverse sectional view similar to Fig. 2 but showing only the leading edge portion of the blade; and Fig. 6 is a transverse sectional view taken on line 6-6 of Fig. l.

At the outset it should be understood that the cuff or closure member of the present invention is particularly adapted for application to core-and-shell type propeller blades. Such blades are well known in the art and will be only briefly described here to complete the understanding of the present invention. The blade, exclusive of the culi, shown in the drawing is typical of the type mentioned in that it comprises two main parts, namely, a core 10 and a shell 12. It is conventional to provide the shank end of the tubular core with races 14 by means of which the core can be retained within a hub (not shown). The extending or outboard portion of the core 10 is attened into general airfoil configuration and the one-piece airfoil forming shell 12 is enfolded over the attened portion of the core and secured thereto as by brazing with the shank of the core extending through the open inboard end of the shell.

As clearly shown in Fig. 1, the leading and trailing edges 16 and 18 of the shell overhang the corresponding edges 20 and 22 of the core in spaced relation thereto. The marginal edges of the open inboard end of the shell 12 extend from the leading and trailing edges 16 and 18 in substantially straight lines at substantially equal acute angles to the longitudinal center line of the core to define a longitudinally extending projection 24 of the shell which is also brazed to the core. A cuil for closing the inboard end of the shell is indicated generally by the numeral 26 and it is this cui, to be described in detail later, which incorporates the improvements of the invention.

It is conventional practice to ll the space 28 extending from the open inboard end of the shell to the outboard end of the blade and between the leading edges of the shell and core and the space 30 extending from the open substantially homogeneous mass bonded or vulcanized to the core and shell.

In providing for the cui of the present invention, the aforementioned pellet filler is terminated short of the open inboard end of the shell and preformed bulkheads 32 and 34 are inserted through the open inboard end of the shell and disposed within the shell adjacent the leading and trailing edges, respectively. Thus the bulkheadsv 32 and 34 limit the inboard extent of the pellet filler in the spaces 28 and 30, as shown in Fig. l. The bulkheads 32 and 34 are of essentially the same composition as the pellets, but are preformed and precured to form relatively dense packs arranged to snugly fit between the core and shell. The bulkheads prevent expansion ofthe pellet filler toward the inboard end of the shell while the pellets are being cured.

The airfoil configuration of the cuif is provided by two filler packs 36 and 38 which are preformed to lit-.the leading and trailing edges, respectively, of the core with their outer end portions extending into the open end of the shell. The packs 36 and 38 are relatively dense and rigid, but can be compressed sufficiently for insertion within the shell to engage the bulkheads 32 and 34, and the packs 36 and 38 comprise substantially the same material as the pellet filler and will` react to the cure in the same manner as the pellets. i

To make the built up cuff watertight andY for reinforcement purposes, the exposed portions of the packs 36 and 38 and the end portion of the shell are provided with a three layer wrapping. The innermost wrapper 40 comprises a thin sheet of rubber-like material generally similar to the aforedescribed filler elements and packs. The middle wrapper 42 is a five ply laminated sheet of rubber and fiberglass layers which reinforces the cuff. The outer wrapper 44 is a relatively thick sheet of synthetic rubber which prevents the ingress of moisture. The inner and middle wrappers 40 and 42 are each trimmed on the lines 46 and 48 so that the outer wrapper will extend thereover. The open end of the cul is closed at the leading and trailing portions, respectively, by relatively thick sheets of synthetic rubber 50 and 52 fitted within the open end of the outer wrapper 44 as shown in Fig. 6. The sheet 50 is located in the open end of the wrapper 44 at the leading edge portion thereof and abuts preformed pack 36 and extends transversely of the blade to the core 10. The sheet 52 is located in the open end of the wrapper 44 at the trailing edge portion thereof and abuts the pack 38 and extends transversely of the blade to the core 10. To assure a completely moisture proof cuff, a rubber sleeve 54 embraces the core adjacent the shank end thereof and extends into the inboard end of the cuff to be vulcanized to the core and to the cuff closure members 50 and 52 when heat is applied during the cure.

The cure is accomplished by placing the blade and cuff within restraining dies and applying heat suicient to vulcanize the previously described rubber-like elements of the iiller and cui. The cuff then becomes a molded integral piece bonded to the core and to the shell. After the application of heat, the blade and cuff are permitted to cool. In cooling, the packs 36 and 38 take a set, tending to shrink or contract, thereby drawing the cu tighter to the core. This shrinkage also tends to separate the said packs from the shell. It has been observed that there is insuiiicient shrinkage within the conned space at the trailing edge to cause separation. It has been discovered that separation at the leading edge can be prevented by forming the pack 36 with a plurality of longitudinally disposed slots.

The said slots extend through the pack 36 from the leading edge of the core to the leading edge of the shell in the portion of the pack which lits within the shell. It

Patented Feb. 15, 1955 widen the slots, but Vthe, pack will not `separate, fromlhe,

shell. A porous rubber-likesheet 56 is disposed within each of the above described'. slots before the cure, and

Vallient-the*pack shrinksthesheets expand. to ill any voids he scope of the in- Y lshankendV orf lthe core ext-ends, said open end of ythe shell having leading.andtrailingportions overhanging-- the core, and a rubber-like pack extending into the open end of the shell adjacent the shank of the core and adapted to be bonded to the core and shell upon the application of heat, said pack having a plurality of slots extending between the c'f'rdfthe shell, and a readily expansible rubber-like Ysheetf disposed in each Vof said slots. f

3. An aeronautical'ppelfei"Bldiprising in combination, anelongatedigcone havinga'a shankend, ash'eet metal' airfoilfolrningfshell- 'surroundingband supported on said core and having an openlendthrough,whichthe shank end of the core extends, said open end of the shell having.` leading. and .t'riling' ptitionsiA oveh'anging the core, a -rst airfoil-forrning pack extending into said open end of the shell aftheleading potion'th'ereof, a second airfoil-forming pack extending into the open end of the shell at `the trailing portion thereof, each ofsaid packs binfgarr'anged'to extend' between said4 shell and saidY ore d-shen,

slot inthepackf R'efeeiices" citary theme of this patent UNiT'Eij--STATES PATENTS 2211111649Vl Larsen May 21, 1946 2,484,141 Alex oct. 11, 19,49- 2,494625- Martin-- t Jan. 17, 1950 2,623,599 KearnsA 7 Dec. so,v 1952 2,648-,3ss-- Hains'ef a1; Aug. 11, 1953 Y FREI'GN PATENTS 550,305*` Great Bri12a-1n" f l Jjn. 1,1943l 659,344. Great Britain ocu-24," 19SA

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