US1831373A - Propeller - Google Patents

Description

Nov. 10, 1931. l J. sQugREs 1,831,373

l PROPELLER Filed Dec. '20, k1928 A TORNEY gether by a special method Wherebyto insure,

Ijoined together by a Patented Nov. 10, 1931 UNITED STATES JOHN' SQUIRES, 0F DETROIT, MICHIGAN PROPELLER Application filed December 20, 1928. Serial No. 327,227.

This invention relates to propellers and particularly to propellers of that type generally employed in connection with aircraft, the principal object being the provision of a metallic propeller of novel construction that will be light in weight but of sufficiently great strength to withstand the stresses set up therein by the centrifugal forces at high ro-` tational speeds, together with a method of making the same.

Another object is to provide a propeller blade fabricated in two halves from a special alloy steel, the two halves being welded toa clean and perfect union between the two halves.

Another object is to provide a propeller which-outside of certain hub portions is made in two halves suitably shaped and integrally Welding process.

Another object is to provide a metal propeller construction particularly designed to resist centrifugal forces at high rotational speeds, a marked stiifening being effected by asurface treatment.

Another object is, to provide a propeller that will be light in weight, of relatively great strength, impervious to rain or hail, relatively resistant to the effect of bullets, and of relatively great life.

Another object is t'o provide a propeller blade formed of steel or an alloy thereof and having the outer surface thereof case hardened.

A further object is to provide a method of forming a propeller blade which comprises forming said blade from non-hardened steel, carbonizing. the surface of the blade and then quenching the blade whereby to produce a case hardened surface therefor.

e The above being among the objects 'of the present invention, the same consists in certain features of construction and combinations of part-s to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other objects in view.

In t-he accompanying drawings which show a suitable embodiment of the present invention, and in which like numerals refer to vand even metal construction are such as to be liable to like parts throughout the several different views;

Fig. 1 is a face view of a propeller.

Fig. 2 is a longitudinal sectional view taken centrally of the propellershown in Fig. l. v

Fig. 3 is an enlarged sectional ,view taken on the line 3-3 of Fig. l.

Fig. 4 is an enlarged sectional view taken on the line 4 4 of Fig 1.

Fig. 5 is an enlarged section of a fragment of one of the blades showing the same case hardened.

One of the greatest problems in connection with airplane propellers is the designing of the same to withstand the stresses set up in them at high rotational speeds, due to the centrifugal forces acting at such speeds. It is generally necessary 1n connection with the present day airplane practice where high l l speed internal combustlon engines are ein-- ployed as a driving element, to provide a reduction device of one type or another between the propeller and the engine. This has been necessitated not so much by the possibility of less efficient reaction of the propeller on the air at high rotational speeds, as it is by the limitation of the strength in existing propellers. Even with these conventional reduction gears it is not. a relatively uncommon occurrence to have a propeller damaged when the airplane goes into a nose-dive, at which time the propeller may be driven at a speed as high at greater than the normal maximum speed imparted thereto by the engine, and the damage in such cases is usually found vto be due to the large centrifugal forces set up in the propeller by. the high rotational speeds. In this connection, it is generally accepted that direct driven propel- 1ers rotating at relatively high engine speeds would be very desirable in case they could be produced to withstand the high rotational speeds to which they would be subjected, and yet would not be objectionablebecause of being of abnormal weight. Propellers constructed of wood or of a com- 1 position of wood and metal are subjected to relatively rapid wear in rain or hail storms,

propellers of the lconventional all destruction due to bullets from machine guns, rifles, and the like.

The principal object of the present invention is to provide a propeller which will eliminate to a great extent if not entirely, the 0bjections to the conventional types of propellers as above pointed out.

In order to provide a construction that will amply resist high centrifugal forces without being excessively heavy, I prefer to form it as illustrated in the accompanying drawings in which I show a propeller of the conventional two blade type. The propeller is formed of two main parts 11 and 12 each of which represents one half of the propeller, and each half comprises one surface, of each of the blades together with a portion of the connecting hub. These halves 11 and 12 are preferably formed of chrome vanadium steel having a chronium content of .8O to 1.10, a vanadium content of .15 to .18 and a carbon content of .3() to .40 This gives an extremely tough structure. The halves 1()J and 11 extend from the leading edge to the trailing edge of each of the blades and from one end of the propeller to the other, and are forged, rolled, or otherwise formed from minimum thickness at the tips of the blades to maximum thickness in the neighborhood of the hub, and each are formed to the shape of the finished surfaces of the blades which they are to constitute so that when they are secured together with their corresponding edges in alignment, as will hereinafter be described, a hollow structure of great strength radially and axially of the propeller will result. I prefer to secure these two halves 11 and 12 together by welding with a chrome vanadium wire of the same composition as that of the metal of the blades themselves, and to perform the welding operation under conditions which preclude oxidation (as by the so-callec atomic hydrogen process in which all oxygen 1s eliminated from contact with the parts being welded during the welding operation, and which therefore insures a clean weld of maximum strength.

The two halves 11 and 12 are provided with openings such as 13 in their respective hub portions through which a tube such as 14 is threaded and in which the tube is suitably secured by a Weldingl operation such as that above described. and other openings such as 15 may be provided for the purpose of receiving bolts or the like for securing the hub to the driving plane, or for other purposes. After the propeller is thus builtup, the welded portions are suit-ably trimmed and the exterior surface of the propelleris in general finished and preferably polished.

Although it may not be necessary in all cases, I then prefer to case harden the surface of the propeller so as to increase the strength and stiffness of thestructure, as well as to make it more impervious to machine gun or rifle bullets, as well as to the natural elements. The preferred type of steel referred to above is, in and of itself, non-hardening, that is, it does not have suthcient carbon content to be capable of producing what is known as a hard surface upon heating and quenching but requires a carbonizing operation, in order to produce such a hard surface. This may be accomplished bythe ordinary method of packing it in bone, subjecting it to the usual heating, and then quenching it, but I prefer to carbonize it by heating it ina gas fiame such as butane, or other carbonizlng for a suitable length of time and thereafter quenching it, as by this method a quicker and equally eflicient case may be obtained. This case is illustrated in, Fig. 5. The propeller may now again be polished, and is ready for use.

It will be apparent that the propeller manufactured as above described will be of maximum strength and rigidity, will be capable of withstanding extremely high rotational speeds without undulystressing the same, will resist the action of the elements because of the nature of the material from which it is made and the manner in which it is secured together, and if casehardened as described, will be relatively resistive to the effects of bullets and the like.

It will also be apparent that although I have described a particular method of making an entire propeller which is case hardened as a Whole, that a propeller may be built up of separate blades, each of which is any suitable construction and case hardened before assemblying, without materially departing from this particular phase of the present invention.

Formal changes may be made in the specic embodiment of the invention described without departing from the Aspirit or substance of the broad invention, the scope of which is commensurate with the appended claims.

What I claim is:

1. An airplane propeller of the two-blade type formed of two halves leach extending the full length of said propeller, one of said halves serving to form the front face of both blades and the other of said halves serving to form the rear face of both blades, said halves being joined to each other by welding along the leading and trailing edges of said blades, the metal of each of said halves gradually increasing in thickness from the tips of said blades and adjacent the hub of said propeller.

2. An airplane propeller formed of two halves joined together along lines extending lengthwise of said propeller to form a hol'- low structure, said halves being formed of non-hardenin case hardenefsurface.

4. A steel hollow propeller blade having its outer surface hardened to a depth -constituting a material proportion of the average thickness of the walls of said blade.

4 5. A hollow propeller blade formed of tough steel and having walls which outwardly iminish in thickness and which are provided with a hardened outer surface of sufficient thickness to impart a desired rigidity thereto. 'v

6. An airplane propeller having integrally connected hollow steel blades exteriorly case hardened.

7 The method of building an airplane propeller comprising: forging two steel halves, each of said halves representing one surface of said propeller from one end thereof to the other end thereof and increasing in thickness from the ends to adjacent the center, welding to unite said edges, placing said halves together withcontacting edges, and therafter carbonizing the surface of the welded struc-- ture, and then quenching said structure.

8. The method of making an airplane propeller comprising: first forming twol steel halves each representing one surface o'f said propeller from' end to end and each increasing in thickness from theen'ds towards the center,'placing said halves in superposed'position with their corresponding edges in matching relationship, welding said edges to- Oether under conditions which preclude oxi- 'datio-n, subjecting said welded halves, as thus united, externally to the action of a heating gas overrich in carbon until the surfaces of said halves have absorbed a ypredetermined amount of carbon, and then quenching said halves to harden said surfaces. L

9. A propeller blade formed generally of non-hardemng steel and having a case hardened surface.

JOHN sQmREs.

steel and having a complete A.

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