US2411143A - Propeller - Google Patents

Description

Nov. 19,1946. A. G. ALlzlER 2,411,143

PROPELLER Ill v Patented Nov. 19, 1946 PROPELLER Andr Georges Alizier, Chicago, Ill., assignor to Cornet Model Airplane & Supply Company, Incorporated, a corporation of Illinois Application November 15, 1943, Serial No. 510,329

4 Claims.

This invention relates to a propeller, and more particularly to a propeller for model airplanes.

One feature of this invention is that it provides an improved propeller for a model airplane; another feature of this invention is that a very eilicient and well balanced propeller may be constructed quickly and eihciently by the model builder; still another feature of this invention is that both dynamic and static balancing of the propeller are practically assured; and yet another feature of this invention is thatv two, three or four bladed propellers can be constructed with equal ease and with equally desirable results. Other features and advantages of this invention will be apparent from the following speciication and the drawing, in which:

, Figure l is aperspective View of a iinished three-bladed propeller embodying this invention; Figure 2 is a partially exploded view of the same propeller; Figure 3 is a fragmentary View of the propeller during assembly, before bringing one of the hub members into place; Figure 4 is an enlarged sectional view of the propeller hub along a diameter thereof (as the line `ll-ll of Figure 3, with the blades removed) and Figure 5 is a View of the propeller strip element in initial plane p0- sition.

The construction of model airplanes is receiving increasingly greater attention, both for purposes of instruction and relaxation. The construction and assembly of the fuselage and wings of a model airplane, by modern methods, is a pleasant and relatively short task; but handshaping of a good propeller, by the methods heretofore conventionally in use, has been dilcult and tedious. Heretofore, it has been common to start with a rectangular block of Wood, or a very roughly shaped piece of wood, and carve and sand the propeller into final shape. Securing good balance and proper symmetry of blade shapes was almost an impossibility by this method, one blade almost always carrying considerably more of the torque than the other, and a dynamically unbalanced propeller resulted. Moreover, this method of construction, as a practical proposition, resulted in the model airplane constructer being limited to two blade propellers whereas models of many modern planes should be equipped with three or four bladed propellers.

I have devised and am here disclosing and claiming an improved method for simply making well balanced and eilicient propellers for model airplanes, it being quite easy to make three and four bladed propellers in the manner here disclosed. Rather than attempting to get the complex curvature necessary for constant pitch and approved airfoil shapes, I use thin, flat propeller blades, which may be die cut from thin sheet `material, as heavy cardboard or Very light wood or hand cut or pre-shaped along lines printed on the sheet material. I- form the hub carrying these blades by spaced parallel front and back members with a peripheral strip element, this strip element having slots at the same angle and symmetrically arranged around the hub. The blades are slipped into the slots, properly centered, and then fastened in place .by cementi-ng or other appropriate means.

Referring now more particularly to the specic embodiment of this `invention illustrated.

herewith, it will be seen that the hub-comprises two flat polygonal members Il) and II (he-reshown as hexagonal) `adapted to be held in spaced parallel relationship by a peripheral strip element I2, shown in its initial or flat form in Figure V5. The members Il) and II are preferablyl of the same size and of sheet material such as light wood or heavy cardboard.

Referring now more particularly to Figure 5, it will be seen that the strip vI 2 is provided with three slots here identified as IZa, IIZb and I2C. These are at an appropriate acute angle to the edges of the strip (and thus at this same angle to the front and back members Il) and -II when the hub is assembled) as, for example, 35; and they are so spaced that, when the hub is assembled, they will be symmetrically arranged or equally spaced about the periphery of the hub. The ends of the strip element are, of course, cemented to each other; and both edges of the element are cemented to the respective front and back members I il and II, so called because they `face to the front and to the back of the airplane when the propeller is in operative position thereon. The word "cemented is used here in a broad sense, being intended to include gluing, lacquer, or any adhesive for binding the parts together.

The three blades, here identified as I3, I4 and I5, are identical with each other, being die stamped or pre-shaped in accordance with a delinite pattern from light sheet material, as thin wood or fairly heavy cardboard. The blades are preferably rounded at the tip, somewhat enlarged toward the outer end, and reduced at the end adapted to be associated with the propeller, hereinafter termed the inner end, as shown. This shaping results in the outer half of each propeller blade developing more than three-quarters of the total possible power, so that there is no appreciable loss in eiciency due to the use of a 3 flat blade, as contrasted with a, constant pitch blade having a greater angle near the hub. As may be best seen in Figures 2 and 3, the inner ends of the blades are provided with identical l-shaped notches, as the notch l3a of the blade In assembling the propeller, the members I and Il are properly related to each other (as by passing a pin I6 through central openings in these members), and the strip element I2 is Wrapped around the periphery of these members,

the ends of the strip element then being cemented to each other, and one edge of the strip element being cemented to one of the members, as the member Il. The reduced ends of the blades I3, i4 and l5 are then slipped into the slots l2a-c and the V-shaped slots interlocked with each other around the pin to ensure proper centering and alignment of the blades. Two of the blades are shown in position in Figure 2 and the third blade in Figure 3. When the parts have been thus assembled, the inner ends of the blade are cemented to each other and the parts passing through the slots are cemented to the strip at that point. After this is vdone the other member l0 is cemented in place and the pin I6 removed, the nished propeller then being as shown in Figure 1.

It will be readily apparent thata light, sturdy, symmetrical and well balanced propeller can be readily made in this manner with any desired number of blades. It has proved somewhat more desirable, for proper inter-relation between the slot and the part of the blade passing through it, to use polygonal end members with double the number of sides that therey are blades, so that a at side is provided for each blade. That is, hexagonal members may be used for a three blade propeller, octagonal members for a four blade propeller, etc.

While I have shown and `described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. A light-Weight propeller for a model air- 4 plane, including: a hub comprising spaced, parallel, similarly polygonal, front and back members having an even number of sides, said sides being at least six in number, a, peripheral element holding the members in said spaced relationship, slots symmetrically arranged in said peripheral lelement between the front and back members with all slots making substantially the same angle withsaid members, said slots being equal in number to one-half the number of polygonal sides in one of said members and each slot being centered between corresponding sides of said polygonal members; and a ilat, planar propeller blade for each slot having a reduced end held by said slot.

2. A method of constructing a propeller for model airplanes, comprising shaping at blades from plane sheet material, shaping front and back hub members from plane sheet material, forming a slotted strip of sheet material around the periphery of one of said members, inserting a small rod-like element through the center of the hub members for centering the inner ends of said blades, inserting the blades in the slots in said strip, removing the rod-like element, iastening the blades together and to the strip, andv bringing the other hub member into place.

3. A light Weight propeller for a model airplane, including: a plurality of flat, pre-shaped blades having one end of each reduced in size; and a hub comprising spaced, parallel front and back members and a slotted peripheral element of sheet material, said slots being symmetrically arranged around the hub and all making the same angle with said members, said slots re,- ceiving the reduced ends of said blade, said ends of said blades interlocking with each other atl the center of said hub.

4. A light weight propeller for a model airl

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