US18814A - Pbopellee - Google Patents

Description

I A. JOHNSON. Screw Propeller.

Patented Dec. 8,1857.

UNITED STATES PATENT OFFICE.

ALMER JOHNSON, OF BUFFALO, NEW YORK.

PROPELLER.

Specification of Letters Patent No. 18,814, dated December 8, 1857.

To all whom it may concern:

Be it known that I, ALMER JOHNSON, of the city of Buffalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Propeller-VVheels; and I do hereby declare that the following is a full and exact description thereof, reference being had to the annexed drawings, making a part of this specification, in which Figure I, is a plan view of the front surface of the blade. Fig. II, is a plan view of the rear surface of the blade. Fig. III, is a front, isometrical perspective of the wheel. Fig. IV, is a top plan view of the same.

The nature of my invention embodies the following distinguishing features: 1st. That part of the blade contiguous to the hub, and which for distinction I call the stem, is curved in both surfaces thereof, the curved lines in the one surface running in the reverse direction to the curved lines in the other surface. 2d. The stem has an inclination forward, or in a direction toward the bow of the vessel. 3d. That part of the blade above the stem (and which for distinction I call the fan) elongates laterally from the stem, and presents a plane surface (or nearly so) on both sides thereof (except the necessary bevel to form an edge). tth. The fan bears such relation to the stem that if a circumferential line representing the upper edge of the fan, is let fall, in a direction perpendicular to the axis of the wheel, it will clear the stem.

In constructing my wheel I observe the following rules:

1st. Determine the diameter of the propeller to be constructed, or which is the same thing the extreme height of the fan above the hub.

2d. Then determine the extreme length of the fan, which also in connection with the angle upon which it crosses the axis will determine the lead of the propeller.

3. Strike a line at about two-sixths the distance from the hub to the extreme height of the fan. This line indicates the division between the stem and the fan.

4th. Let the base of the stem, as it sits upon the hub, cross the axison an acute angle. The required lead of the propeller, and the length of the fan, will determine the degree of this angle.

5th. Give the stem a sufficient inclination forward, and let the fan bear such relation thereto, so that if a circumferential line representing the upper edge of the fan, is let fall, in a direction perpendicular to the axis, it will fall outside of the stem.

6th. Let the front and rear surfaces of the stem be'curved in opposite directions, that is to say, let the curved lines on the front surface describe a gradually increasing curved surface from front to rear, and let the curved lines on the rear surface describe a gradually increasing curved surface from rear to front. 1!

7th. Make both surfaces of the fan plane, (or nearly so,) exceptthe necessary bevel to form an edge.

The line L (Figs. I, II, and III,) indicates the division between the stem and fan.

The arrow, (Figs. I and II) indicates the entering edge of the propeller.

The arrow 2 (Fig. IV,) indicates the direction in which the wheel revolves.

The lines 1, 2, 3, &c. (Figs. I and II,) indicate the direction which the curves take on each surface of the stem.

The line M (Fig. IV) indicates the circumferential line of the fan which falls outside of the stem.

By observing the rules herein given, and the application of ordinary skill belonging to the art, propellers, including my invention, may be constructed of any required diameter or lead.

Among the advantages I claim for my improvement over propellers in common use are: let. The propeller encounters less resistance in its movement through the water, by reason of the increased room or space obtained between the blades. 2d. The action of the water upon both sides of the stem instead of retarding has the the effect to .propel the wheel. 3d. As soon as the inertia of the water is moved, the fan lets go, that is to say the fan does not hold or carry the water after its inertia has been disturbed. The entire surface of the stem and fan has a propelling effect.

Constructing propellers which embody the distinctive features of my invention substantially as herein set forth.

ALMER J OHNSO Witnesses:

E. B. FORBUSH, W. H. FoRBUsH.

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