USRE18853E - Distbict of coi-trmbia - Google Patents

Description

May 30, 19 c. H. A. F. L. ROSS FLUID REACTIVE SURFACE Original Filed April 21, 1931 3 Sheets-Sheet l ,FIQuZ.

FIG-3.

CHARLES H.111. LRo-ss,

Gum/mp y 3- c. H. A. F. L. Ross Re. 18,853

FLUID REACTIVE SURFACE Original Filed April 21, 1951 3-Shets-Sheet 2 swam KM CHARLES H. AFL. Ross,

May 30, 1933. F oss Re. 18,853

FLUIDREACTIVE SURFACE ori in l Filed April 21,' 1951 s Sheets-Sheet 3 Fla. 6.

LEAD

700Ibs. Owrwg'ghi f 7157:

' ANoT-S CHARLE H. fl. EL; R055,

screw type, although the invention is broadly Reissued May 30, 1933 UNITED :STATES PATENT OFFICE f 7 CHARLES H. A. F. LQROSS, or WASHINGTON, ms'rmc 'r or COLUMBIA rum; nmc'rIvE summon Original No. 1,882,163, dated October 11, 193'2, eria1 No. 531,784, filed April 21, 1931. Application for reissue filed April 12, 1933. Serial No. 665,646.

This invention relates to fluid reactive surfaces One particular application ofthe invention is its use in marine propellers of the susceptible of use in turbines, fans, aeroplane propellers, fluid driven devices such as Wind mills, and, in general, any device having a surface or surfaces driving, or being driven by, a fluid.

In shipbuilding practice, the screw propeller dominates the field of propulsion devices for self-propelled ships, and its use is practically universal on ocean-going steam ers. The use of the more cumbersome paddle wheels has been restricted to the relatively small ships on inland waters. Yet, while the screw propeller has a number of constructional 'advantagea'it has been, as previously made, a relatively. ineflicient device, and Wastes at least forty per cent of the power delivered to it by the driving engines.

In spite of the decided improvements in recent years in other parts of the driving mechanism, such as the use of steam turbines, the use of oil as fuel, etc., the screw propeller has remained a wasteful device. Such improvements as were made therein were largely the result of empirical or cut andtry methods, and in some cases, the result of accidental discoveries. A typical example is the reduction in the number of the blades, which resulted from the observation that a steamer driven by a six-bladed propeller actually went faster after one of the blades was accidentally lost. Other developments were changes in area of the blades, contour or shape of the blades, etc.. made with the hope of producing a more eflicient propeller.

About the time when increased'speeds were beginning to be used in steamers, it was noticed that there was a rapid loss of efliciency'. in the screw propellers at the higher speeds of rotation. This led to the pronouncement of thecavitation theory by Mr. Sidney W. Barnaby. This theory attributes the increased loss of efiiciency to the cavity produced about the propeller after it reaches a certain speed, because of the inability of the fluid to flow fast enough to follow the blade. To avoid this effect, the use of a propeller with larger area was recommended.

Despite all these developments, however, the screw propeller has remained a relatively ineflicient device. This is due, it is believed, to the ignoring of a fundamental factor in the manufacture of propellers. To fully understand this factor, a consideration of what I term the wart? theory is ncces I sary. It may be stated at the outset, howclusion that the screw propeller is inherently ineflicient and that refinements in the accuracy of the surface are a mere waste of time;

In present propellers, therefore, even of the best grade, there exists inequalities in the surfaces, such as lumps or warts. These form high spots and corresponding valleys in the surface, and have been found to have a decided eflect upon the elliciency of the propeller. It is believed that when the propeller is driven at its usual speed, the water hits only these high spots, and skips past the valleys. The water does not follow the blade, and a decided loss in efiiciency consequently results. The action may be compared to a solid tired automobile passing over a rough road at high speed, causing the driving Wheels to be repeatedly in the air. Dur

ing such times, the power delivered to the wheels is entirely lost, so far as propelling the vehicle is concerned, and the efliciency of the automobile is greatly reduced.

, 'be expected from more accurate the unexpected result of. an increase of some twenty-five to thirty per centin efliciency.

The abolitionof the turbulence arising A from warts promotes the maintenance ofethe original even surface. In addition, the smooth passage of thewater over such a surface so greatly reduced vibration that it becomes inappreciable, and this further increases the relative efiiciency of the pr ller.

The term warts or wartless one' which I have employed in connection with p the description-ofmy propeller both in this specification and in scientific papers which I have written. Possibly, phraseology which would be of more universal acceptance would be to say that the drunkenness of the pitch in pro ellers has been eliminated. Elimination ,0 drunkenness in pitch is equivalent to. saying that the propeller is wartless, and

where .I use the term wartless or hrase-' ol'ogy denoting elimination of drun enness in the pitch throughout this specification and the claims I intend to convey the same thought. y authority for usmg the term .drunken is to be found in the Encyclopedia Brittanica,'1 1th edition, volume 24, page i I It isa further object of provide a propeller, the surfaces of which lades approaching their theoretical true sur-] faces within a tolerance of i .003 inch.

It is another object of my invention to providea propeller having reduced v1bra-. tion. I

my invention to will inaintain their original shape and sur face.-

It is a still further object of my invention to provide amethod of producing a propeller of .the type set forth in the above paragraphs As indicated above, my invention is sus-. ceptible .of uses in aeroplane propellers or other propellers acting on a gaseous medium; in turbines, driven elther by a liquid or a gas; in fans or blowers driving 'a gaseous medium;

in devices driven by a fluid medium such as wind mills; or, in fact, any device having amoving surface cooperating with a fluid. Accordingly, while Ishow particularly in this specification a marine screw propeller as the means for carrying my invention into practical efiect, I do not limit myself tothis particular construction, which for purposes of explanation, has been made the subject of illustration. r 7 It is accordingly a further and broader object of my invention to increase the eflicieney;

and methods hereinafter set forth, with the understandin that variations therein may be carried out without departing from the spirit 1 of the invention or the scope of the appended claims.

In the drawings: Figure 1 is the representation of a propeller tested in the investigation.

Figure 2 is the graph of the variation in lead at various portions of the'surface of a prgpeller of good grade.

, igure 3 isa diagrammatic sketch showing howthe various points plotted were measured.

F1gure4 is a corresponding graph of the surfaces of a'propeller produced in accordance with my invention. i y

Figure 5 is a graph of the variation in lead at various po' ions of the surface of another type of propeller.-

Figure 6 is a .corresponding'graph of the surfaces of a similar propeller produced in accordance with my invention.

Figure 7 is a diagram showing the results of a test of a propeller embodying my invention. a a

Figure 1 showsthe'results of a test made on a good grade of propeller of the type now produced. The blades of this propeller were painted with black paint, and the propeller was then usedv inactual service. This figure v shows how the paint was worn, the white portions on the blades being the metal surfaces from which the friction of the water removed thp paint." As'is indicated, the paint is not worn ofl' smoothlyybut is worn ofi at numerone high spotsl-on theblade. About the middle of one of the blades,indicated by the arrow, there is a radially extending valley practically unacted upon. The test conclu si'vely showed the presence of the warts. or

high spots discussed in an earlier part of this specification, and shows that the water, in

-passing over such a surface, merely hits the high spots. Thus, the water is impelled by a succession of sudden bumps, rather than by a smooth impelling action,

The bumping action justreferred to un-' doubtedly causes vibration of thepropeller' and this vibration in turnincreases the bumpiness, causing a vicious circle WhlCh,

'it is believed, causes the relatively low efiiciency of the screw propeller as now made. With a propeller made in accordance with the prese'nt invention, aside from the marked increase in efliciency, there is a decided re- There is another result from the lack of mechanical accuracy in finishing the blades, and this is the wide variation in the lead as determined from various points of the blade. Theoretically, the surfaces of the typical screw propeller is helical, with a certain definite lead. With even the best type of present propeller, however, the lead, as calculated from Various points of the surface, varies greatly. Figure 2 is a graph indicating such variations, and Figure 3 shows how the various points were determined. To draw the graph for the points on the three inch radius, the points are determined as being a certain number of degrees from the base line, which degrees are plotted as abscissac, and the various leads found for these points respectively, are plotted as ordinates. The graph shows that there is no definitely fixed lead, or any definite variable lead bearing a continuous relation to a helical surface. The lead on the propeller graphed is merely a hit or miss value varying from about twenty-two and one-half inches to twentyfourand one-half inches. Such variations mean that the water is impelled at different rates at different parts of the surface, and such action unquestionably causes eddies and other undesirable effects, and decidedly reduces the efficiency of the propeller.

Figure 4 shows a corresponding diagram of a propeller made according to my invention, and the uniform lead thereof, resulting in a uniform and steady impulsion, is apparent from the diagram.

My invention contemplates broadly the utilization of a wartless surface in contact with a fluid and is not limited to strictly helical surfaces. For instance, it is possible that I may want to vary the pitch of a propeller, and construct blades in which the pitch does vary throughout its extent. If I desire to vary the pitch, for instance of a propeller blade, I at least want the variation to be in accordance with the specification, and I do want the blade to be wartless. In one form .of my invention asapplied to a propeller blade, I may desire that the blade represent a true helicoidal surface in which the pitch of the propelling surface is constant throughout its extent as shown in Figure 4. I mention this last type of propeller blade simply as desirable under certain conditions, but do not wish to be limited to this type of blade, only, so long as the blade presents a wartless surface. For instance, I may want to change the lead of the blade gradually from say 22" to 24", but I want this change to occur without the appearance of warty surfaces. Such gradual increase may be a gradual increase radially, arcuately, or both, or other types of surfaces may be used, provided they are smooth, even, and wartless.

The propeller blade therefore in which the surface throughout is wartless, and truly helicoidal comprises but one of the innumerable modifications of a wartless surface, which my method of construction contemplates.

- Figure 5 shows a graph of the lead obtained for various points on a present commercial propeller which is extended to have an arcuately increasing lead. As is evident from the graph, the actual measurements depart from the desired amounts, and produce the warty surface described above.

Figure 6 shows a graph of a similar type of propeller, but constructed according to my invention and having a wartless surface. It will be noted that although the lead varies, it Varies uniformly according to a desired rate, and presents an even, smooth, wartless surface.

Thus it is apparent that the basic feature of my invention is the provision of a regular, even, smooth surface for the blades of a propeller, and a surface which follows, as accurately as possible, the theoretical surface desired. Such a surface I term a wartless surface, and a propeller having such surfaces, a wartless propeller. Both the face and back surfaces of the blades should be such wartless surfaces.

To provide such a surface, I use a profile grinder of the type disclosed in my applicat-ion Serial .No. 501,155, filed December 8, 1930, and my application Serial No. 517,566, filed February 21, 1931. It is to be understood that those disclosures are hereby made apart of the disclosure of this present application. By such machines, the production of a smooth, uniform, wartless surface may easily be produced by one skilled in the .art. Such machines are capable of producing propellers accurate to within i .003 inch.

The propellers made by such machines have the wartless surface described above, and have the desired lead at all points of the surface of their blade. If desired, by

the use of suitable templates, any desired" type of surface may be produced on the blades, and such surface will approach the desired theoretical surface to within i .003 inch.

are apparent.

As previously pointed out, my invention is In actual trial, one of the wartless pro-- obviously susceptible of use in other devices wherein a surface coacts with a fluid.

While I have shown and described the preferred embodiment of my invention, I wish it to be understood that I do not confine myself to the precise details set forth, by way of illustration, as it is apparent that changes, variations therein and other a'ppli"-- cations thereof may be madez -by those skilled in the art, without departing from the spirit of the invention, or exceeding the scope':of the claims.

I claim:

1. A propeller in which the drunkenness of the helical surface is substantially eliminated. I

2. A propellerhaving bladesin which the drunkenness of the helical surface, issubstantially eliminated. I

3. A propeller blade whose actual pitch for any point of its surface does not deviate from the desired pitch more than an amount equal to four per cent of the desired pitch. v

4. A propeller ,whose pitch is uniform for all the points of the propelling surfaces of its blades, such uniformity being within limits of four per cent of the desired pitch.

5. A propeller blade having a helicoidal surface in. which the lead remains substantially constant and in which "the drunkenness of the surface is substantially eliminated.

6. A propeller ,blade having a helicoidal surface in which the drunkenness of the surface is s ubstantially eliminated.

7. A propeller blade havinga surface in which drunkenness is substantially eliminated and whose pitch varies evenly and continuously according -to a'defin'ite desired rate of change. l

In testimony whereof I affix my signature.

CHARLES H. A. F. L. ROSS.

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