US2335394A - Molded propeller - Google Patents

Description

Nov. 30, 1943. R. w. 'DEVORE ETAL MOLDED PROPELLER Filed May 9, 1959 j fipezz/ors: I 205622 $.leaore {224.5622 W Patented Nov. 30, 1943 UNITEDYSTATES PATENT OFFICE MOLDED PRDPELLER Robert W- Devore and Ben H. Young, Chicago, Ill.

Application May 9, 1939, Serial No. 272,596 2 Claims. (01. 170-159) The invention relates to propellers, particularly a propeller of the screw type, and has as a general object to provide a propeller of new and improved construction.

There has long been an unfulfilled demand for a sturdy yet economically manufactured propeller, for fans and air circulators, particularly, whose hub and also whose blades are composed of some material that will not corrode and will not deteriorate as a result of the chemical reaction of the fluids, vapors, and the like, to which the propeller is subjected in use, depending upon the place of use for the device utilizing the propeller. Attempts have been made to fulfill this demand by constructing the blades of the propeller of some pressed, non-corrosive'material and securing the same to a metallic hub or by making both the hub and the blades of some pressed, noncorrosive material and securing the same together. However, such attempts have all been unsuccessful because corrosion and deterioration of all of the parts was not avoided, or because of structural defects, or because the cost of manufacture has been prohibitive.

It is a primary object of the invention, therefore, to provide a propeller fulfilling this demand, and, more particularly, to provide a propeller composed of a moldable plastic composition and having its hub and blades molded integrally to form a unitary structure. I

While a plastic composition propeller molded with the hub and blades integral fulfills the demand above pointed out, the construction of such a propeller in and of itself presents a problem which heretofore has been unsolved and which has prevented the manufacture'of such a unitary molded propeller. The molding of a propeller with the hub and blades integral has heretofore proved unsuccessful because the hub and the blades required different curing times, so that if the hub was properly cured, the blades were over-cured, and, conversely, if the blades were properly cured the hub was under-cured. It is a fllrther object of the invention, therefore, to provide a molded propeller of plastic composition having its hub and blades of such propor tion and design as to permit curing thereof in substantially the same time, 'yet provide the necessary strength and rigidity.

Another object of theinvention is to provide a moldedv propeller having a hub made hollow to reduce the maximum thickness thereof to correspond to themaximum thickness of the blades.

and rigidity and suiiicient surface for attachment of the blades to the hub.

Still another object is to provide a propeller of molded plastic composition having a hub with a generally conical shell and blades having a broad base extending spirally, about the hub substantially the full axial width of the hub.

Furthermore, considerable difficulty, and consequently expense, is encountered in balancing a propeller so that it will rotate in true balance on a fan structure. Due to the non-uniformity of a cast metal propeller, this difficulty is increased materially. 1

Another object, therefore, is to perfect a propeller that may be easily and economically manufactured'so that it is substantially identical in each of a desired number of devices, and which in unfinished form is substantially in true balance, thus reducing to a minimum the time and labor spent in placing the finished product in drawing, in which:

Fig. 1 is a front face elevational view of a propeller embodying the features of our invention.

Fig. 2 is an edge elevational view of a portion of the propeller shown in Fig. 1, the view bein taken along the line and in the direction of the arrows indicated by 2--2 in Fig; l.

Fig. 3 is a rear elevational view of the portion A of the propeller shown in Fig. 2. l

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 1.

Fig. 5 is a diametrical, sectional view of the hub of the propeller taken alongthe line 5-5 of Fig. 1.

Whilethe invention is susceptible of various modifications and alternative constructions, it is for purposes of disclosure shown'in the drawing and will hereinafter be described in, detail in a preferred embodiment butit is not intended that the invention is to be limited thereby to the specific construction disclosed, but it is intended to cover all modifications and, alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

, The propeller shownin'the drawing; comprises a hub generally designated l0 and blades there shown as being merely two in numbenalthough it is understood, of course, that more blades might be employed, .or that :afpropeller might'beprovided simplywith but a single blade, a coun A as hereinafter described, the specific shape per se of the blades forms no part of the invention.

Suflice it to say, therefore, that for the most part the blades are of a generally conventional contour, such as found in propellers of the screw type, capable upon rotation of the propeller emciently to displace fluid.

In order that the propeller disclosed and claimed herein may not be subject to corrosion and rapid deterioration, all of its parts, that is, its hub ID as well as its blades H, are, formed from a moldable plastic composition, such as Bakelite," or other resinous condensation product. Further, in order that the propeller may have-a sturdy and rigid construction and at the same time be capable of economical manufacture, the propeller is made unitary, that is, with the blades H molded integrally with the hub l0. Such a propeller, while fulfilling the demand for an all composition yet sturdy and economically manufactured propeller, in itself presented a major manufacturing problem. -Attempts have previously been made to solve this problem but without success due to the difference in time required to cure the hub I and that required to cure the blades H. With such a time differential existing, when the hub was properly cured the blades were over-cured, and conversely when the blades were properly cured the hub was under-cured, with resultant structural defects.

To the end that the propeller herein disclosed may be molded as an integral unit, the hub l0 and the blades H, at their base, are given a unique design and construction resulting in a curing time for the place of maximum thickness on the hub I0 substantially equal to the curing time for the place of maximum thickness on the blades II, and at the same time providing a construction having the necessary strength and rigidity. Accordingly, the hub I0 comprises a shell l2, having generally the shape of a frustum of a cone, providing a surface to which the blades l I are attached, and a tubular member 0! boss l3 extending axially within the shell to provide a bearing for a shaft on which the propeller is to be mounted. The tubular boss i3 is integral 'at one end with the small or apex end of the shell l2 and extends rearwardly, in spaced relation to the shell, just short of the end of the shell to provide a bearing of substantial widthl As best seen in Figs. 3 and 5, added strength may be obtained by means of a plurality of radial webs l4 connecting the boss l3 and the shell l2, though such webs are not essential. The hub is completed by a set screw I5 for non-rotatably securing the hub onto a shaft received. in the tubular boss l3. It is intended that the shaft be received directly in the tubular boss l3, a metallic sleeve or bushing having been found unnecessary and possibly even undesirable.

It can readily be seen. particularly from a consideration of Figs. 4 and 5, that with this hollow construction of the hub H] the maximum thickness thereof compares favorably with the maximum thickness of the blades. Thus, the hub and the blades will require substantially the same; curing time and thus may be molded intesrally. -Such integral moldingof the blades ll and the hub ID in and of itself gives strength and rigidity not obtainable in a non-integral construction.

While the maintaining of a substantially equal curing time for molding of the hub and the blade is the principal and important factor in the manufacture of the propeller, it has been found that slight variations in the maximum thickness factor may be made and still equality of structural strength may be obtained provided compensating changes are made. For instance, if the diameter of the hub shell I2 is increased and yet the wall thickness of the shell decreased slightly, the structural strength of the hub and the blade will still be substantially the same although the hub wall is slightly over cured. Conversely, a slight decrease in hub shell diameter and a corresponding increase in Wall thickness will provide the desired structural strength for the hub even though slightly under cured with reference to the blade, and the structural strength of hub and blade is still, substantially equal. I

It is for the purpose of further increasing the strength and rigidity of the propeller that the hub I 0 is made hollow and conical, for by such construction an unusually large surface is provided to which the blade ll may be anchored.

- Herein, advantage is taken of this large anchoring surface by forming each blade II with a wide base l6 (see Figs. 1 and 4) that spirals about the shell l2 of the hub. The base N3 of each blade ll extends the full distance from face to face of the shell I2 (see Figs. 1, 2 and 4) and because of the spiral mounting has an actual anchorage with the shell that is greater than the width of the shell.

It is believed apparent from the foregoing that we have not only provided a propelle having many unique and improved features; but one which fulfills a long felt want and which solves a problem heretofore unsolved by those skilled in the art. Strength and rigidity, as well as economy in manufacture, are obtained by molding the hub and the blades of the propeller integrally. Such integral molding of the hub andthe blades has now been made possible by the uniqu design and construction of our propeller in which the curing time of the hub and the blades is substantiall equal. By making the hub with an outer shell spaced from the portion providing a bearing for a shaft on which the propeller is to be mounted, sufficient strength could be built into the hub and sufficient area for the anchoring of the blades could be provided, while at the same time the thickness of any one portion of the hub could be substantially reduced and conformed to the maximum thickness of the blades. Also with the propeller thus molded as an integral and unitary, structure, the dies may be made so accurate that the unfinished propeller as taken from the dies is very nearly in true balance and requires very little, if any, balancing, thus further reducing the cost of manufacture of the finished product.

We claim as our invention:

1. A unitary propeller of a moldable resinous material requiring curing during the molding thereof, said propeller comprising a hub and blades extending therefrom, the hub diameter being large in comparison to the thickness of the blades, said hub being hollow so that the shortest path through any part of the entire propeller material is of the same order of thickness as the shortest path through any other part ofthe entire propeller material whereby substantially uniform overall curing of the entire propeller material will result, said hub having a centrally disposed boss with a shaft receiving channel, said shaft receiving channel having a diameter small in comparison to the -hub diameter, said boss having a plurality of webs extending radially to the hub interior.

2. A unitary propeller of a moldable resinous material requiring curing during the molding thereof, said propeller comprising a hub and blades extending therefrom, the hub diameter being large in comparison to the thickness of the blades, said hub being hollow so that the shortest path through any part of the entire propeller material is of the same order of thickness as the shortest path through any other part of the entire propeller material whereby substantially uniform overall curing of the entire propeller material will result, said hub having a generally conical shape and wherein the hubs interior is provided with a boss having a shaft receiving channel with the diameter of the channel small in comparison with the hub diameter and wherein a plurality of webs extend between said boss and the hub interior.

ROBERT W. DEVORE.

BEN H. YOUNG.

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