Hollow steel propeller construction

D. a. dickey 2,004,102

HOLLOW STEEL PROPELLER CONSTRUCTION

Filed Feb. 24, 1932 2 Sheets-Sheet 1

June 11, 1935.

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June 11, 1935. d. a. dickey 2,004,102

HOLLOW STEEL PROPELLER CONSTRUCTION

Filed Feb. 24, 1932 2 Sheets-Sheet 2

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INVENTOR

DANIEL A.DICKEY.

^^^TORNETS

Patented June 11, 1935

2,004,102

UNITED STATES PATENT OFFICE

2,004,102

HOLLOW STEEL PROPELLER CONSTRUCTION

Daniel A. Dickey, Dayton, Ohio

Application February 24, 1932, Serial No. 594,935

Claims. (Cl. 170—159) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) a matter of extreme importance in the production of .parts for use in airplanes;

d. The deposit will adhere to certain other materials with a tenacity of bond equivalent in strength to that of the deposited material itself. 5 in accordance with my invention, a suitable core material and a structural part of the article to be manufactured are either permanently or temporarily secured together to constitute a composite core structure of suitable configuration 10 about which a metallic material, such as iron is chemically or electrolytically deposited and to· a certain extent to produce or develop a hollow metal article in which the deposited material constitutes a shell or covering that is of sufficient 15 strength to carry the surface loads to which the “^{ay be} subject and unites with the struc7«.'7 -™^{1 manner} that accumulated loads of the article are transmitted to the structural part. ₂₀

I have shown and described my invention by way of one example, as applied to a propeller preferably of the type having separate blades, each independently attached to a hub through the medium of a stalk on the said blade, which en- 25 gages a socket in the hub.

In'accordance with one embodiment of my invention, I produce a novel propeller by providing a composite core structure of suitable configuration to the development of a propeller 30 blade and consisting preferably of a low-meltingalloy, and a plurality of spaced transversely disposed structural parts of the propeller to which the alloy is caused to adhere by appropriate means and with which it is so arranged- as to 35 ^portj^{op of} ,^tbe structural part without - so that by the'electro-, a metal to the composite core .1.311 or covering is formed -----...e core, which covering, by means of the 40 manner of application and the relative arrangeTv*«v»4· λ-Γ XL-— .η___ . ®

.... - ·”—> ~suitably jointed with the structural part or framework. _ , . - ----- —complete removal of the low-melting-alloy and to this end suitable provision is made, such as openings within the structural part or framework, to allow the escape of the alloy or other suitable readily removable material from within the blade and through the open end thereof. In the forming of the composite structure the alloy material is caused to flow in and fill the openings of the structural part and in this manner effect a bonding therebetween. The structural parts are

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a novel method of and means for producing hollow articles of manufacture and by which structural members, khat. ™ “ ^suPPorting and/or attaching means for the hollow article, are incorporated therein and io constitute a part therebf. My invention is particularly applicable to and in the manufacture of devices that are subject to severe stresses and strains, but which are designed to have „the least possible weight per unit of strength. Especially is my invention useful in the manufacture of hollow metal propellers and hollow metal floats in^Uft^{in copnec}*^ion Yi^th aircraft. _{M Iuay De SUI}

In the construction of hollow propellers of large tural part in such size or of short propellers of wide and thick crosssection, some type of internal support against, collapse is necessary if undue weight of outer shell is to be avoided. The area or external surface of a propeller blade must be large enough to develop the necessary air loads. Due to the cantilever nature of a propeller blade and to the action of centrifugal force the total loading _Of the cross-sections of a. blade are. progressively accumulative from the tip to the root. A blade covering too weak to carry more than sectional., ized loads may be employed if an internal structure is supplied to carry the accumulated loads. Coverings that can readily be applied to surfaces of complex curvature are, as a rule, too weak to carry economically (from the standpoint of weight) accumulated loads, whereas coverings favorable in strength to carry accumulated loads _{a FUltluu OI lne}Tn^ethpioff^{lffiCUlt 10 a complex} curvature.^λ the surface of the alloy In the latter case the for ms of the surf aces must be deposition of a metal tc compromisedin design to faVor the application of structure a propeller shell ~----- · * the covering. By the utilization of an internal about the · · structure or framework designed to carry the ac- i------It is well known that by the process of electrolytical deposition of metal, such as iron, shells or sheets can be produced of the following characteristics:

a. Iron of high purity and of evident non-corrosive, properties;

b. Surfaces of any produced complexity of curvature—such as required in propeller blades;

c. Controllable to any gradation of thiclmess— :5

2,004,102 in the shell of the blade, they will resist distortion in any crosswise direction. Openings 18 are provided in the webs and serve a three-fold purpose, one of which is to lighten the structure; the remaining two will become apparent as the 5 description proceeds.

The shell or covering 12 has a varying thickness in cross-section throughout the entire length of the blade, each section being of such thickness and form as to be commensurate with 10 the magnitude and character of the load imposed thereon. The shell is formed about the webs and secured thereto in a manner to provide a plurality of cells whereby to sectionalize ' the load of the shell so that the load on the shell 15 area of each cell is transmitted to its corresponding cell framework as hereinafter described.

Figs. 6, 7 and 8 show a variation from the construction shown in Figs. 2 to 4, in that each transverse web member 14 is made of two parts 20 20 and 22, between which is disposed a longitudinal member 24 of graduated areas in crosssection, that is preferably formed from a bar of metal such as iron into a shape corresponding to the desired longitudinal cross-sectional out- 25 line of the blade at the point where the longitudinal member assumes its position within the blade. There is also provided a tapered sleeve 26 having at its outer end an annular shoulder 28 and at its inner end a series of fingers 30. 30 The outer end of the sleeve serves to provide additional strength to the stock end of the blade and lends itself to the provision of means for attaching to the hub. The fingers on the. inner end of the sleeve afford greater ease of forming 35 this portion of the sleeve to a contour corresponding to that of the shell and provide a gradual blending of the strength of the stock end into the adjacent portion of the blade.

•In this embodiment the wall thickness of the 40 shell is substantially uniform throughout its entire length. The internal bracing structure, consisting of the inner sleeve and the longitudinal and transverse members, cooperates with the shell in such a manner that accumulated loads 45 are transmitted mainly through the bracing

A further variation of my invention is shown in connection with a flotation device for an aircraft as shown in Fig. 9, and it differs from the 50 other above embodiments in that the shell or covering for the flotation device completely encloses and unites with the structural members that provide an internal bracing medium to prevent the collapsing of the walls of the covering 55 and also in that it embraces the incorporation of another type of structural element, such as attaching fittings 32. These fittings protrude upwardly from the shell and are rigidly bonded therewith in a manner similar to and simultane- GO ously with the bonding of the covering to the longitudinal structural member 24 and the transverse structural members 20 and 22, The fittings are preferably attached rigidly to the longitudinal member and project upwardly there- 65 from.

In accordance with a preferred method of manufacturing the above described embodiments, a composite core structure is formed by providing a metallic mold, with smooth internal surfaces, 70 in which to cast the composite core. The mold is provided with means, such as recesses or dowels, by which to secure members that are to form a part of the composite core. Referring to Fig. 10 by way of example, these members shall be the 75 preferably so designed and so disposed that the peripheral surface merges with the surface of the alloy to produce a surface corresponding in contour to the desired contour of the blade.

In another novel construction of propeller of this type, the blade is formed with a longitudinal structural member and transverse members constituting the framework, by my novel method of first, producing a composite core structure of 10 the low-melting-alloy and the structural members or framework and, thereafter, simultaneously forming a shell about the core by the electrodeposition of a metallic material and bonding the deposit to the structural member to thereby 15 consolidate them. The composite core structure in this instance is formed by securing said longitudinal member between pairs of aligned transverse web members and filling the interstices between the longitudinal and transverse members with a low-melting-alloy. The structural members are arranged within the core structure, that is of a desired blade conformation, in such manner as to be capable of uniting or consolidating with the material as it is being electrodeposited 25 about the core to produce a stiff internally braced blade, which in addition to possessing the inherent characteristics of an electrodeposited material, will rigidly resist compression as well as tension stresses and particularly torsion stresses.

Other novel features of my invention will becoine apparent from the detailed description and I will now proceed to describe the several forms or embodiments of my invention, which are illustrated in the drawings forming a part of 35 this application.

In the drawings:

Fig. 1 is a diagrammatic illustration of a propeller embodying my invention;

Fig. 2 is a part sectional plan view of a blade 40 detached from the propeller shown in Fig. 1;

Fig. 3 is a part sectional front elevational edge view of the blade shown in Fig. 2;

Fig. 4 is a plan view of a propeller blade core showing parts of the core in section and the 45 propeller blade shell in phantom;

Fig. 5 is a cross-sectional view taken on the line 5—5 of Fig. 2;

Fig. 6 is a plan view similar to Fig. 2 showing a further embodiment of my invention;

Fig. 7 is a plan view of the core that is used in the construction of the blade shown in Fig. 6, showing the shell of the blade in phantom;

Fig. 8 is a cross-sectional view taken on the line 8—8 of Fig. 6;

Fig. 9 is a part sectional, side elevational view of a flotation device in which my invention is embodied; and

Fig. 10 is a cross-sectional view of a mold showing lugs on members and recesses in the mold.

Similar reference characters will be used to designate similar parts throughout the several views of the drawings.

In Figs. 2 to 4 inclusive I have shown a hollow metal propeller blade 10, that comprises es65 sentially a shell or covering (2 and a plurality of spaced web members 14, that are vertically disposed transversely with respect to the longitudinal axis of the propeller. Each web is laterally shaped from strips of flat thin material, 70 such as sheet iron, to provide a flange 16 about the peripheral edge and to present a contour or outline corresponding to the desired crosssectional outline of the blade at the point where the web is located. The webs are designed of 75 .'•efficient strength that when incorporated withlongitudinal member 24 and the transverse members 14. Each of these members is provided with several protruding lugs 34, which, by being engaged in the recesses provided therefor in the 5 mold, hold the members accurately in place.

After the members are placed and the mold has been closed, the molten metal, preferably an alloy with a relatively low melting point—such as 80 parts tin, 80 parts, bismuth, and 120 parts lead 10 with a melting point of about 132° C.—is forced into the mold. After solidification, the core is removed from the mold and the lugs, which in this case protrude beyond the main surface of the core, are ground away and polished until the core 15 surface is regular and smooth. The entire core surface is then suitably cleaned for the electrodeposition of the metal shell.

This core is then suspended as the cathode in a heated bath containing about 40 oz. ferrous 20 chloride (FeCMIfcO) and from 15 oz. to 45 oz. calcium chloride (CaCl₂) per gallon of solution, the remainder of the solution being water excepting a slight amount of free hydrochloric acid ς (HC1), giving a pH of about 2. The temperature 25 of the bath is about 90° c. In the same bath and surrounded by porous filtering diaphragms are iron anodes of rather high degree of purity, 99.85% Fe. With a current density on the cathode—the core-—of from 50 to 65 amperes per ³⁰ square foot the iron from the anodes is built up on the cathode, the thickness and distribution of thickness being controlled by means well known to the art. The quality Of the deposit is improved by agitation, such as moving the cath35 ode up and down, throughout the period of deposition.

When the deposit has attained the desired thickness, the core with its deposited shell is removed from the bath, cleaned, and heated to ^4U a temperature sufficient to melt the alloy of the core, which is permitted to drain out through the holes provided, ,in part, for this purpose. (This leaves the hollow article, in this example a propeller blade, with the internal· members or ^4j framework that had previously constituted a part of the core, now forming a part of the finished article through the bonding (or union) of the' deposited material to the exposed parts of the „ members. It is to be noted that the melting tem^u perature of the alloy is low enough to have no detrimental effect upon the deposited shell and the internal members. _z

From this point on the blade may be subjected to processes of heat-treating and manhin⁰⁰ ing as are pertinent to the desired refinement of the article. Platihg with nickel· chromium, or other finishes may be effected before or after the removal of the core. ₆₀ It is desired to be understood that the propellers and flotation device shown and described con' stitiite but a few of many embodiments of my invention, and is not to.be taken as definitive or for any other purpose than that of illustration.

_6g It is also desired to be understood that while I described in the method of producing a hollow article, an entirely metal core, a part of which is removable, it will be obvious to those skilled in the art that non-conductihg materials may be ₇₀ used in conjunction with the structural members to form the composite core structure, in which case the surface of the non-conducting material is suitably prepared in a well-known manner for the electrodeposition of the shell. It is obvious that my invention and its various features may ^iS> be embodied in various other forms and construc•4,102 3 tions and my invention is to be understood as limited only to Such features or structures as are clearly defined in the appended claims.