US1769767A - Propeller - Google Patents

Description

y 1930. F. w. CALDWELL 1,769,767

PROPELLER Filed Sept. 20 1924 7 [N VEN T OR 7. Caldwell M ,4 TTORNEY. v

Patented July 1, 1930 UNITED STATES PATENT. OFFICE FRANK CALDWELL, OF DAYTON,OHIO, ABSIGNOR, BY MESNE ASSIGNMENTS, TO THE HAMILTON STANDARD PROPELLER CORPORATION, 01' WEST HOMESTEAD, EENNSYLVANIA, A CORPORATION OF PENNSYLVANIA PROPELLER Application filed September 20, 1824. Serial No. 788,914.

This invention relates to improvements in aeronautical propellers.

The principal object of the invention consists in the provision of a propeller in which the center of gravity of all of th transverse sections of the blade' are located on a straight line at right angles to the axis of revolution of the blade and passing through that axis.

While the invention is of advantage generally as applied to propeller blades of various types, it is designed particularly for detachahle, reversible, and adjustable pitch aeronautical propellersfin which connection the invelition has particular utility in securing a greater uniformity in blades, and lessening the work necessary in the standardizing and balancing operations performed in the production of propeller blades. At the same time blades constructed in accordance-with this invention, whether of wood, composition, or metal, are found to operate with less vibration and give more continued satisfactory service, primaril because they are inherently dynamically alanced when they are in static balance by reason of the manner in which the center of gravity of any section always balances the center of gravity of the corresponding section of an opposite blade, regardless of the pitch of the lades, since these centers are all on the same straight line through the axis of revolution.

In the accompanying drawing illustrating the invention,

Fig. 1 is a front view of a propeller blade of the detachable, pitch-adjustable type constructed in accordance with the invention.

Fig. 2 is a side view of Fig. 1 illustrating the positionment of the transverse sections with their centers of gravity in line passing through the propeller axis and at right angles thereto.

Fig. 3 is a diagrammatic view looking down on a propeller blade mounted on knife edges for balancing and standardizing.

The propeller blade is shown mounted in a hub 2 and secured on a shaft 3, constituting the usual extension of the engine crankshaft. The hub 2 may be of any suitable or preferred form, providing for adjustment of the blade to vary the pitch. The clamping means 4 illustrated serves to secure the blade in its adjusted position. The blade 1 has its shank suitably held in the hub 2 and is laid out on a longitudinal axis y-y at right angles to the axis a:a: of the shaft 3, corresponding to the axis of revolution of the propeller. The axis g y passes through the axis H as shown in Fig. 1 and is at right angles thereto, as shown in Fig. 2. The center of gravit of each of the transverse sections of the lade lies on the line of the axis y-y. Sections a-a, bb, c0, and 0ld are shown in Fig. 2 so located with reference to the axis y-y.

The advantage derived in this design, aside from the fact that the likelihood of vibration due to slight irregularities and uncompensated moments in the blade is minimized, resides in the fact that large quantities of blades of the detachable type may be produced of so uniform a character as to be readily interchangeable and replaceable. This is due to the fact that in the balancing and standardizing of a blade, the described location of the center of gravity of all of the sections renders it easy to locate and properly compensate for any parts out of balance. Thus, as shown in Fig. 3, a particle represented by the dot (1 represents a part out of balance. When the blade is tested for horizontal and vertical balance, this particular part, if compensated for in the horizontal balance, would nevertheless throw the blade out of balance when the blade is rotated, say for example, to the dotted line position which is approximately 90 from the full line position. In this position the particle now represented by the dot at is oil the axis of the shaft 3, which is free to roll on the knife edges represented at 6 and 7. A balancing particle b is therefore necessary on the opposite side of the axis. By displacing the blade 90 from the first position of balance, a very sensitive balance of all unbalanced particles is secured, since the unbalanced particles are thereby given a maximum moment arm. If a blade constructed in accordance with my invention is in perfect balance statically, it will then be also in perfect dynamic balance as a result inherent in the construction; since 'ustable all of the centers of gravity of all the sections of the blade will al be on the same strai ht line through the axis of rotation at e to that axis. This will be true regardes of the an 1e to which the blade is adjusted. The lade will therefore operate without appreciable vibration within the 1. An aeronautical propeller comprising:

a blade-clampin hub, and a pluralit of similar detachable lades adapted to rotatably mounted with respect to the hub to permit pitch-adjustment, each blade having its mass so distributed throughout that its axis of rotation with respect to the hub passes through the centers of mass of all transverse sections of the blade.

2.- An aeronautical propeller comprisin a blade-clampin hub, and a lurality of setachable pitch-adjustable lades radiall disposed relative to the ropeller axis, eac blade having its mass so istributed throughout that the centers of mass of all cross sections lie in a line which passes through the propeller axis, whereby to maintain the dynamic balance of the blades in operation regardless of pitch-adjustment thereof.

3. An aeronautical propeller comprisin a blade-clamping hub and separate remova 1e pitch-adjustable blades constructed and mounted with equal and similar sections at equal distances respectively from the axis of revolution of the blades, each blade having the centers of mass of all of its cross sections lying on a line that passes through the propeller axis.

4. An aeronautical propeller comprisin a blade-clampin hub and separate remova le pitch-adjustab e blades constructed and mounted with equal and similar sections at equal distances res ectively from the-axis of revolution of the lades, each blade having the centers of mass of all of its cross sections lying on a line that passes through the propeller axis at right angles thereto.

5. An aeronautical propeller comprisin a blade-clampin hub and two diametricall oppositel posltioned symmetrical-pitch-ad lades carried b said hub, said lades being constructed wlth e ual and similar sections at equal distances rom the propeller axis, res ectively, and so proportioned and positione that a straight line passes through the centers of mass of all cross sections of the two blades and through the pro peller axis.

6. An aeronautical propeller comprising a blade-clamping hub and two diametrically oppositel positioned s etrical pitch-a 'ustable blades carrie by said hub said lades being constructed with egual and similar sections at equal distances rom the propeller axis, respectively, and so roportioned and positioned that the axis 0 rotation for pitch-adjustment comprises the centers of mass of all cross-sections of the blade.

7. In aeronautical pro llers, a separate blade having a shank a apted to be rotatively engaged by a hub member, said blade having the center of mass of all of its cross sections lying in the axis of its rotation with res ect to the hub.

n testimonlg whereof I aflix m si ature.

RANK W. CAL LL.

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