US909246A - Propeller. - Google Patents

Description

E. D. SPEAR.

' PROPELLER.

Patented Jan. 12, 1909.

V Il!! M BNITED 'UATFQNT @ldlltlli EDMUND D. SPEAK, OF BOSTON, MASSACHUSETTS.

PROPELLER.

AppIication led December 19, l.

To all whom tt 'may concern.'

Be it known that T. llnirifno D. Srnrxn, of Boston, in the county of Suffolk and State of l/lassachusetts, have invented a new and useful Improvement in Propellers, of which the following is a specification.

In designing propeller blades so far as l have been able to learn, Jthere has been a great deal of experiment with comparatively little satisfactory result. lhat shall be the shape of the blade in any given case, while it may have been figured out by the rules of physics and by various formulae, has never 'been decided without some qualification which has prevented the propeller from being the success, from a mechanical standpoint, which has been intended.

ln studying the subject of wave motion as occurs in any fluid medium such as water or an allied substance, the air, l have noted. the fact that when waves are set in motion or cu-rrents formed,- they have been produced the most quickly and with the least loss of power' where the opposing or actuating surface which causes this motion is curved with the curve known as the conchoidal curve. As a curved surface of this description. can from its nature present no focus or center for converging` air waves or liquid waves, as of water. but distributes such waves or currents without so doing, z'. c., focusing them, it has seemed best suited to my purposes in the construction of my propeller blades. lts utility may be readily shown by forming an ear trumpet in such manner that the passage through it shall be of this conchoida-l shape, that is, substantially the shape of the passages from the exterior to t-he interior of a conch shell, and comparing its efficiency with the efliciency of any of the ear trumpets of ordinary construction. The reason for this, as l believe. is that there is practically no chance for interference between the various waves which are received at the embouchure (bell mouth entrance) of such an ear trumpet and are conveyed along therefrom to the small opening made for application to the external canal of the ear. ln such case aerial vibrations Within the ear trumpet may be considered as conveyed towards the smaller end without meeting with or obstructing the passage of similar vibrations taking the same course. My invention is based upon the application of this same discovery to the construction of propellers, and it con- Specication of Letters Patent.

Patented aan. 1a, reco.

Serial No. 86,548.

sists in a propeller provided with two or more blades, one or both surfaces of which blades are conchoidal.

lily invention will be understood by reference to the drawings, in which- Figure i is an end elevation of a propeller embodying my invention, Fig. 2 being a side elevation thereof, and F ig. 3 a top View.

A is the hub of ordinary construction, from which project the two blades B, B. I prefer to make the blades with a double curve as shown in Fig. 3, one half of the blade projecting rearward and the other half 1 projecting forward in order that the blade may be equally eflicient whether it is working forward or backward. ln any case the peculiarity of the blade is such that its working surface being conchoidal in shape the particles impinging upon it are forced from its surface practically in one given direction, that is, in a constantly increasing and diverging direction from each other without interference, and hence with but slight resistance other than -that due to friction against the surface of the blade.

ln operation the leading edge and advancing surface of each blade B when r0- tating enters new water to advance the propeller and ship to which it is attached, but because of the curved shape of this advancing surface and because of the absence of those foci and of eddies usually produced by other curved surfaces having foci, there is no interference, that is, no tendency on the part of one wave (of water) to interfere in any way with another wave (of water). Hence the resistance in front of the blade is reduced to a comparatively lsmall amount while the pressure behind the propeller is not materially reduced.

l prefer to so locate the blades about the hub that their bases will be at an angle of between 20 and 300 with its aXis. As each blade spreads preferably from the hub to its extremity the leading edge or entering corner of the blade is in a plane nearly parallel with the axis of rotation so that it cuts the new water with practically no resistance. This result is in my opinion, due entirely to the peculiar property which the convex surface, in this case also conchoidal, has of behaving in the same manner as the concave, and conchoidal surface, as regards interference.

l have described my propeller as for use in Water, but I believe it would bey equally eliicient in air.

I am aware that propellers have been constructed, the blades of which have cross sections representing reversed or inflected Y plurality of bladeseach projecting from said hub, each of said blades having a lateral cross section m the formof reversed oonchoidal curves, the said conchoidal curves appearing in every part of the blade. i

Q. A propeller comprising a hub and a plurality of blades each of which has a driving'V surface in the form of a conveXed conchoidal curve extending transversely thereof.

,In testimony whereof, I hereunto set my pname this thlday of October, 1901.

, EDMUND D. SPEAK.

lVit'n'esses ALFRED Slimm- Gnonon O. Gr. CoALE.

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