US1912979A - Propeller - Google Patents

Description

June 6, 1933.

C. H. HAVILL PROPELLER Filed Dec. 3, 1929 2 SheetS -She'et l June 6, 1933. 'c HAvlLL I 1,912,979

PROPELLER Filed Dec. 3, 1929 2 Sheets-Sheet 2 Patented June 6, 1933 UNITED STATES PATENT- OF'FIGE CLINTON H. HAVILL, 0]? ORANGE, NEW JERSEY, ASSIGNOR 'IO ECLIPSE AVIATION COR- PORATION, OF EAST ORANGE, JERSEY, A CORPORATION OF NEW JERSEY 'PROPELLER Application filed December 3, 1929. Serial No. 411,352.

This invention relates to propellers and more particularly to a propeller of the type adapted for use on aircraft.

It has been proposed to provide hollow metal propellers for use on aircraft and such propellers offer certain well known advantages over the old wooden type propeller. As heretofore constructed, however, these metal propellers have had certain disadvantages, among which may be mentioned exc'essive weight when made sufficiently strong to withstand the enormous forces evolved at high speeds of rotation, and this is true whether the propeller is hollow, solid, or is built up from a plurality of relatively thin sheets. Other disadvantages include excessive deflections, fatigue failures, vibrations, and unusually noisy operation. It is accordingly one of the ob ects of the present invention to provide a metal propeller particularly adapted for use in aircraft, which is so constructed as to overcome the above difliculties.

Another object of the invention is to provide a novel metallic propeller which is built up of a plurality of laminations.

A further object is to provide a relatively light, metal propeller blade characterized by an initial stress distribution, which is so modified when the blade is in operation that said blade is substantially free from the disadvantages heretofore noted as inherent in metal blades.

Another object isto provide a metallic propeller blade, the outer faces of which are initially in a state ofcompression.

A further object is to provide in a metal propeller a novel means and method for maintaining the outer faces thereof initially in compression.

A still further object is to provide a hollow metal propeller which combines lightness in weight with great strength and durability, and one which may be easily manufactured.

Another object is .to provide a new and improved method of making a propeller blade.

In the manufacture of metal propeller blades, due to the difficulty of making two blades of exactly the same weight and crosssection throughout, various means have been proposed for balancing the propeller both vertically and horizontally before used on a rcraft. It is another object of this invention to provide novel means whereby such balancing operation may be quickly and efliciently accomplished.

Other objects and features of novelty will be apparent from the following detailed description when taken 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 designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein similar reference characters refer to like parts throughout the several views Fig. 1 is a plan view of the inner surface of the thrust face half of a blade embodying thepresent invention, with the elements of the blade-half being partially assembled;

Fig. 2 is a View similar to Fig. 1 but showing the laminations of the blade in assembled position;

Fig. 3 is a perspective view' of the two halves of the blade prior to the final assembly of the same;

Fig. 4 is a plan view, partly in section, of a finished blade constructed in accordance with the invention;

Figs. 5 and 6 are plan views of the camber face half of the blade;

Fig. 7 is a longitudinal section of the camber face half of the blade; and

Fig. 8 is a transverse section of the completed blade.

In the form of the invention illustrated there is shown a propeller blade made in two portions, each of said portions comprising a plurality of metal laminations, said portions being welded or secured together in any suitable manner adjacent the meeting edges thereof.

Preferably the laminations are assembled and secured together in such a manner as to be under 1n1t1al tenslon. Due to such con struction, as w1ll be hereinafter more specifically set forth, an initial compression will exist in the outer faces of the propeller blade, so that during rotation of said blade, the maximum tension therein, due to centrifugal force will be materially less than usual, it being apparent that a portion of the tension load will be offset by the initial compression load. The outer faces of the blade thus be ing relieved of a large port-i011 of the load due to centrifugal force will be able to more efliciently carry the loads due to thrust, torsion, etc., to which they are subjected.

Referring more particularly to Figs. 1-4, the propeller blade, indicated generally at 9, comprises two coacting shells or blade halves 10 and 11 constituting respectively the thrust and camber face halves of the blade which are secured to each other, as by welding or other suitable means, adjacent their meeting edges. Each of said shells or blade halves is built up of aseries of laminations or members which are designed and 21SSQ111 bled in such a manner as to insure maximum strength and long life together with minimum weight.

The shell 10 constituting the thrust face half, Fig. 1, preferably comprises an outer face or member 12 and a plurality of inner members 13 and 11. All of these members are pressed, stamped or rolled into the desired shape.

Members 13 and 14 are preferably so assembled with respect to the face 12, that the fibres of said members are under tension. In the form shown, member 13 is placed on the inner surface of member 12 in such a position that the hub portion thereof will be spaced a small distance 15 from the hub por tion of the face or member 12. This distance may be accurately gauged by first drawing lamination 13 firmly up into the hub portion of the outer face and then tapping the inner end of said lamination lightly in order to force the same outwardly the required distance. The lamination is then preferably secured, as by spot welding or other suitable means at its outer portion 16 to member 12.

In order to place the lamination 13 under tension, a pull is exerted on the inner end thereof bygripping the lamination by means of a pair of pliers or other suitable clamping device 13*, this force being sufiicient to bring the hub portion of the lamination into close engagement with the hub portion of outer lamination 12, as shown in Fig. 2. Lamination 13 is then secured in any suitable manner, to member 12 in regions 17 and 18 in .order that the tension in said lamination will be maintained. It will be understood that when tension is applied to the inner end of lamination 13, the outer face 12 is held stationary in any suitable manner.

The lamination 14 is now assembled on laminations 12 and 13, in a similar manner,

that is, after spacing the hub portion of member 14 from the hub portion of member 12,

as indicated at 19, the lamination is secured in place at its outer end by welding or other suitable means, a tension force is applied to the inner end of the lamination, and the latter is then firmly attached, as by welding, to member 13 in the hub region 18 in order to maintain the tension in the fibres of the lamination.

After the above-mentioned operations have been performed, all of the laminations are preferably spot-welded together at a plurality of points to form a strong and substantially integral shell or blade half.

The camber face blade half or shell 11, illustrated in Figs. 5-7, is preferably formed in a. manner similar to that above described with relation to the construction of the thrust face blade half 10. In the form shown, laminated shell 11 is constituted by an outer member 21 and a plurality of internal members 22, 23 and 24 which may be pressed or rolled into the desired shape. As illustrated, members 22 and 23 are preferably constructed in a manner such that a greater amount of metal lies adjacent the leading edge than the trailing edge of the blade in order that the former may possess the necessary strength and rigidity.

In assembling the shell 11. internal member 2 is placed within outer member 21 and welded thereto at 25, the hub portions of these members being spaced slightly apart as indicated at 26. 'lhereafter, member 21 is held stationary while a tension force is applied to the inner end of the lamination 22 by clamping member 22*, for example, which causes longitudinal expansion of said lamination throughout its length. the hub portion of said lamination then fitting tightly within the hub portion of the outer member as shown in Fig. 6. The two members are then welded or secured together in any other suitable manner, in the hub region27. If desired an opening 28 may be provided in the lamination 23 in order to expose an inner portion of member 22 after the parts are assembled whereby the exposed portion may thereafter be secured to member 21 independently of assembled lamination 23.

Each of the laminations 23 and 21 are assembled separately with respect to the shell and are secured thereto under tension in a manner similar to that described in connection with member 22, the outer end portions of said laminations being secured to the next adjacent member as at 29 and 30. An opening 31 may be provided in lamination 24 for a purpose similar to that of opening 28 if desired. After all of the elements constituting thecamber face blade-half have been assembled, the parts may be further secured together at a plurality of points other than those indicated.

The two completed shells 10 and 11 are shown in juxtaposed relation in Fig. '3, it being here pointed out that each of said shells is curved inwardly due to the stresses in the compression and tension members, the shape assumed tending to diminish such stresses. The two shells are now pressed together and held in such position by any suitable means while they are welded adjacent the meeting edges as at 32 and 33, Fig. 8. After the shells are moved from the position indicated in Fig. 3, tothe position wherein the edges thereof are in engagement throughout the length thereof, an initial compression will exist in the fibres of outer members 12 and 21. In the finished blade this initial compression Will substantially offset the tension normally set up in said outer members by centrifugal force during normal operation of a propeller embodying said blade. -The tension in the inner members will, however, be increased during such operation, said inner members then carrying a tension load equal to the initial tension setup during assembly plus the tension resulting from centrifugal force imparted to the blade during its rotation.

After the shells have been welded together adjacent the edges thereof, a hub sleeve 34, Fig. 4, the outer contour of which corresponds to the inner contour of the usual pro peller hub, is fitted over the hub portion or root of the blade and the inner end. of the blade is flanged outwardly into intimate engagement with the sleeve, and may be welded thereto, if desired, as indicated at 35.

Means are provided in each propeller blade whereby the completed propeller may be easily and efiiciently balanced both horizontally and vertically. In the form shown, such means are constituted by a hollow member 35 arranged transversely to the longitudinal axis of the blade and adapted to house a plurality of lead wires or other material 36 acting as balancing weights. The open ends of member 35 are closed by suitable plugs 37 and 38. With two blades, carrying the above described balancing means and properly assembled in the usual balancing stand, the addition or subtraction of weights 36 from one blade or the other will enable an accurate horizontal balance to be attained, While the position of the center of gravity of ,the weights with respect to the longitudinal axis of the blade will enable an accurate vertical balance to be attained in a simple-"and efficient manner. As shown, the plugs 37 and 38 are adapted to maintain the weights in their proper position after a balance has been made.

There is thus provided by the present invention a novel and eflicient propeller blade of the hollow metallic type, and one which is not only light in weight and possesses great rigidity but which is also so constructed as to provide maximum strength in the regions of the blade where most needed in order to successfully withstand the various forces imposed thereon during rotation. By providing internal members under initial tension, the outer faces of the finished blade are initially in compression, which compression counteracts a portion of the centrifugal load during rotation of th blades, thus permitting these faces to more efficiently withstand other forces of torsion, thrust, etc. Due also to this construction, the greater tension load due to centrifugal force will be carried by the inner laminations, which are not subjected to torsion and thrust forces equivalent to those in the outer members. It is pointed out that the laminations may assume various sizes and outlines, it being borne in mind that normally more metal must be provided adj acent the leading edge than the trailing edge and that more metal is required adjacent the root end of the blade than in the outer portion thereof.

WVhile there has been shown and described one embodiment of the invent-ion, it is to be understood that the invention is not limited thereto. Various changes in the shapes, sizes and manner of assemblying the various component parts may be resorted to without departing from the scope of the invention, as will occur to those skilled in the art. Reference will therefore be had to the appended claims for a definition of the limits of the invention.

lVhat is claimed is 1. A hollow metal propeller blade comprising a plurality of coacting shells each of said shells including an outer member and a plurality of inner members, means for fastening the outer portions of said inner members to said outer member, and means for maintaining said inner members under tension.

2. A metal propeller blade comprising two coacting and rigidly connected shells, each of said shells including an outer member and a plurality of inner members, means for attaching said inner members to said outer member, and means for maintaining the inner members under tension.

3. In a metal propeller, an outer member, a plurality of relatively thin metal sheets secured at their outer portions to said member, and means for maintaining said sheets under tension.

4. In a hollow metallic propeller blade, means for placing the fibres of the outer faces initially in compression, said means including a plurality of interiorly disposed metallic sheets.

5. In a propeller blade, means for initially placing the fibres of the outer faces thereof in compression including a plurality of members secured to said faces, the fibres of said members being under tension.

6. A hollow metal propeller blade comprising two shells, each shell including an outer face and means for maintaining the fibres of said outer face initially in compression, said means including a plurality of laminations.

7. A metal propeller blade comprising two shells, each shell including an outer member and a plurality of inner members, and means for maintaining the fibres of said inner members under tension.

8. In a metallic propeller blade of the laminated type, a plurality of laminations under tension.

9. A metal propeller built up of laminations, at least one of said laminations being initially in compression.

10. A propeller blade built up of metal laminations, one of said laminations being initially in compression while another of said laminations is initially under tension.

11. In a propeller blade, means for intially specification.

CLINTON H. HAVILL.

causing compression of one of the outer faces thereof including a lamination secured at one extremity to said face, and means for securing said lamination adjacent its other extremity to said face, said lamination being under tension.

12. A hollow metal propeller, each blade of which comprises two shells built up of laminations, a hollow member carried by each blade adjacent the inner end thereof and arranged transversely with respect to the longitudinal axis of the blade, and a plurality of balancing weights removably mounted in said member whereby said propeller may be vertically and horizontally balanced.

13. In a propeller having a plurality of blades, balancing weights in the root portion of each blade adjustable transversely of the longitudinal axis thereof, and means for retaining said weights in operative position.

14. The method of constructing a propeller blade having an outer face and a plurality of laminations, which consists in securing one end of each of said laminations to said outer face, placing each of said laminations under tension and securing the other end of said laminations to said face and to each other while'maintaining the tension on said laminations.

15. The method of making a metal propeller blade which consists in forming the two facesthereofofrelativelythinmetal,securinga plurality of laminations at one end thereof to each of said faces, exerting a tension force on the free end of eachof said laminations, securing the last named ends to said faces while maintaining said tension and joining said faces together adjacent their meeting edges.

16. A metallic propeller blade in which inner members under tension create an initial compression in the fibres of the outer blade surface.

17. A propeller having a plurality of blades, a housing adjacent the root portion of

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