US2112797A - Flexible propeller spider - Google Patents

Description

March 29, 1938.

J. M. TYLER FLEXIBLE PROPELLER SPIDER Filed July 17, 1937 2 Sheets-Sheet 1 A TTORNEY FLEXIBLE PROPELLER SPIDER Filed July 17, 1937 Sheets-Sheet 2 A TToRNEY Patented Manzo, 192.84 I l y 2,112,797

UNITED STATES PATENT OFFICE FLEXIBLE PROPELLER SPIDER John M. Tyler, West Hartford, conn., assignorto United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware,

Application July 17, 1937, Serial No. 154,187

10 Claims. (C1. 170-162) 'I'his invention relates to improvements in aeroable lnterengaging splines, as indicated at I2. nautical prcpellers and has particular reference The spider I is also provided with a plurality of to an aeronautical propeller constructed and arradially extending hollow arms, as indicated at I4, ranged to control the vibration of the propeller there being one arm for each of the several blades and the propeller driving engine during operaof the propeller. 5 tion. s The propeller blades are generally indicated by A n object of the invention resides in the provithe numeral I6 and there may be two, three or sion of an improved aeronautical propeller emmore blades depending upon the particular probodying resilient cushioning means and damppeller installation. As the construction of all of l0 ing means for cushioning and damping out a, the blades and their connections to the hub porlo large portion of the vibrational forces existing in tien 0f the propeller iS the Same, a description the engine and propeller when the propeller is of only one blade and its associated retaining and being driven by the engine, driving connections is considered suiiicient for the A further object resides in the provision of an purposes 0f this disclosure. improved aeronautical propeller having vibra- In theferln 0f the invention illustrated the l5 tion damping features, which do not add to the DI'ODellel blade iS formed 0fl metal and iS DTO- Weight or complication of the propeller and which vided With a substantially cylindrical base or root do not decrease the strength or emciency thereend rotatably mountedA in the Propeller hub and of. retained therein by means of a ange I8, the

2o other objects and advantages will be more parperiphery of which is joined to the adjacent sur- ,20

ticularly pointed out hereinafter or will become face of the base end of the blade by a fillet of app-arent as the description proceeds large radius which bears against an anti-friction In the accompanying drawings in which like bearing retained in the portion 0f the reference numerals are used to designate similarl propeller hub barrel 24, Surl'Ounding the baise parts throughout, there is illustrated a suitable end ofthe blade- The hub barrel 24 ls Split trans' 25 mechanical embodimentl of what is now cons-M versely to the axis of rotation of the propeller and ered to be the preferred form of the ldeo of the the two parts thereof are rigidly secured together invention. The drawlngs, however, are for the by suitable means such as the clamp bolt 26. The purpose of illustration only and are not to be outer race of the bearing 22 is retained in the barso taken as limiting the invention, the scope of rel member by a sU-ltable OVelhanglng flange 3o which is to be measured entirely by the scope of portion 28 surrounding but out of contact with the appended claims the cylindrical base end of the propeller blade.

In the drawings, Fig l ls an elovotlopal View of By this means the propeller blade is rotatably the hub portion of an improved aeronautical mounted in the barrel member and is held therepropeller constructed according to the idea of m agamst the action of Centrifugal force- 'AS 35 this invention, a portion thereof being broken such blajd? mollntmg means are Well'known t0 away and shown in section to better illustrate the the art 1t ls behaved that a' further description is Construction theeoi unnecessary for the purpose of this disclosure.

Fig. 2 is asectional view of aresilient drive arm Each 0f the blades is Provided in its base 0I 4o through which power ls troosmltted from the root end with an elongated substantially conical 4o propellerhub to a propeller blade Shaped hollow'or aperture, as indicated at 30,

Fig. 3 is an elevational view of a resilient tubuand Wlthln the open end 0f the nOllOW 30, there s lar member forming apart of the resilient drive ls inserted a Sleeve member 32, Which has a flange arm. l portion 34 overlying the flattened base end of the 4.', Fig. 4 is an elevational view of another tubular Propeller blade. The Surface 0f the flange DOI- 45` ymember divided into a series of sections and also tion 34 0f the Sleeve 32 OPDOSite the Surface informing a portion of the resilient drive arm, and Contact With the end 0f the propeller blade, bears Fig 5 is an end View of the tubular member upon a suitable bearing Washer 36 of hardened shown in Fig. ,4. material,\ which in turn, rests upon a support Referring to the Adrawings in detau, the numember 38- In a three bladed propeller, such as 50 meral Ill generally indicated the hub spider of the the One illustrated in Fig-v1, each Support member propeller. This spider is adapted to be rigidly is in the form of a triangular section of a cylinder, mounted upon the propeller carrying and driving the angle between the inclined faces thereof being shaft of the engine and restrained against rota- 120 degrees so that when the three support memtion with respect to the shaft by means kof suitbers are assembled together, they entirely sur- 55 round the center portion of the spider member andbear upon one another. The apex of each support member is cut away so that the support members fit about the cylindrical portion of the spider member surrounding the propeller drive shaft, without however, contacting the spider member `at any point. The circular end of each support member is provided with an inwardly projecting flange 40 which surrounds but does not touch the respective spider arm I4. With this construction it vwill be observed that the blades are rmly secured in the barrel member 24 and are solidly supported upon each other but do not contact or derive any support from the propeller drive shaft or the hub spider I4 mounted upon the shaft.

An elongated resilient arm, generally indicated at 42, is rigidly secured in the spider arm I4 by means of an internalA screw-threaded nut 44, which bears at its innerend against an outwardly flared enlarged portion 46 at the base end of the resilient arm, thus rigidly securing the resilient arm 42 in the hollow spider arm I4. A ring of suitable resilient material such as rubber, indicated at 41, is clamped between the outwardly flanged head end of the 'nut 44 and the opposed end of the spider arm I4 and lies between the outer end of the nut 44 and the outer end of the sleeve 32 to provide a resilient bumper between the driving arm and the sleeve in case the arm is moved sufficiently with respect to the blade to bring it into contact with the surface of the hollow 30.

At its outer end the resilient arm 42 is provided with a concave portion 48 about which is disposed a split bearing sleeve 50, slidably received in a cup-shaped bearing member 52, secured in the outer end of the hollow 30. Through this bearing is transmitted the power which rotates the propeller and also the force of the thrust which the propeller blade exerts when rotated.

From an inspection of Fig. 1 it will be observed that the driving arm is much closer to one side of the blade hollow 30than to the other. This point of adjacency is located at the forward side of the blade withinthe angle intercepted b y the plane `of thrust and the plane of rotation of the blade so that as the blade is turned and exerts a thrust force upon the driving arm, the interior of the base end of the blade tends to move away from the adjacent surface of the driving arm, and, under operating conditions, the arm becomes substantially concentric with the longitudinal axis of the blade.

The construction of the driving arm 42 is particularly illustrated in Figs-'2, 3 and 4. From an inspection of these gures it will be observed that the arm has a solid metal core in the form of an elongated rod member having a relatively short outwardly flared enlargement at the base end and a concave reduction at the outer end to receive the bearing 50. The core element 54 is surrounded by concentric pairs of telescopically associated tubes, as indicated at 56, 58, 60, 62, 64 and tube 66. Of these various pairs of tubes the pair immediately surrounding the core 54 is the longest and the other pairs decrease in length as they are located progressively outward from the core, the outermost tube 66 being the shortest and surrounding the base end of the core, 54. Each pair of tubes is ared outwardly at its base end, as indicated at 68, to receive the outwardly flared enlargement on the core land on the successive pairs of tubes and to provide the outwardly flared enlargement 46 at the base end of the arm to provide on the arm a retaining bearing against which the nut 44 presses to` retain the resilient arm in the hollow spider arm I4.

Each pair of tubes, as indicated from 56 to 64 inclusive, comprises an outer tube, as illustrated in Fig. 3, and an inner tube, as illustrated in Fig. 4. As all of the inner tubes and all of the outer tubes with the exception of the outer tube 66,

, 16. Each of the slots extends almost half way through the tube, leaving only a small amountv of metal between the opposed ends of each pair of transverse slots, and alternate slots along the length of the tube are disposed at a circumferential angle at 90 degrees to each other. The outer tube 66 is not slotted.

The inner tube 'IU of any pair, as illustrated in Fig. 4, is also a relatively thin resilient metal tube that has been split longitudinally from end to end. on a plurality of angularly spaced radial planes to provide a group of longitudinal resilient staves. In the form of the invention illustrated each of the staves constituting one of the tubes as, for example the tube 1I), has ay circumerential extent somewhat less than one-eighth of a circle and the sections or staves of all of the tubes are substantially equal in width or circumferential extent. This splitting of the inner tubes decreases their resistance to bending while increasing the total sliding movement between the inner tube and the associated outer tube when the resilient arm is bent.

The core element `54 and the various concentric tubes are all tted together with a slight pressure fit so that, although the various elements will slide relative to each other whenever the arm 42 is distorted by bending forces, they will at the same time oier a large amount of frictional resistance to distortion or bending of the arm.

As is clearly illustrated in Fig. 2, the core member 54 is in the form of an elongated rod. This member is made of some strong resilient material, such as tempered steel, so that it acts as a spring when varying forces are applied to it near its opposite ends. Thus vibrational forcesA transmitted from the engine to the propeller are cushioned by the spring action of the core portion of the rod while the driving forces are transmitted to the propeller blades and the thrust forces are transmitted from the blades back to the propeller hub and to the engine. The resilient action ofthe core member, however, is damped by the frictional resistance of the surrounding pairs of tubes or sleeves so that, while the vibrational shocks is dissipated harmlessly in the form' of heat occasioned by the friction of the tubes. By this arrangement the frequency of a harmonic vibration existing in the propeller and engine crankshaft combination may be so greatly re duced that the vibration will occur at an engine speed that is far below the normal operating speed and at which the power delivered by the engine is suiiiciently low sothat the vibration will have no serious detrimental effect.

While there has been illustrated and described a suitable mechanical embodiment of what is now considered to be thepreferred form of the idea of the invention, it is to be understood that the invention is not limited to the particular construction so illustrated and described but that such changes in the size, shape and arrangement of parts may be resorted to as come within the scope of -the subjoined claims.

Having now described the invention so that others skilled in the art may clearly understand the same what it is desired to secure by Letters Patent is as follows:

1. A drive ai'm for an aeronautical propeller comprising, a resilient core member, and a plusurrounding said core member.

2. A drive arm for an aeronautical propeller comprising, a resilient core member, and a 'plurality of pairs of frictionally associated concentric tubes surrounding said core member, said pairs being substantially flush at one end with the end of said core member and decreasing in length as they are located progressively outwardly from said core member. f

3. A drive arm for an aeronautical propeller comprising, a resilient core member, and a plurality of concentric pairs of friction sleeves surrounding said core member, the inner sleeve of Y each pair being split longitudinally to provide a plurality of separate staves around said core member.

4. A drive arm for an aeronautical propeller comprising, a resilient core member, and a plurality of pairs of friction sleeves surrounding said core member, the outer sleeve of each pair being transversely slotted at spaced intervals along its length.

5. A drive arm for an aeronautical propeller comprising, a resilient core member, and a plurality of concentric pairs of friction sleeves surrounding s'aid core member, the outer sleeve of each pair being transversely slotted at spaced intervals along its vlength by opposed slots each extending slightly less than half the circumference of said tube, alternate slots being disposed atapproximately ninety degrees to `each other on the circumference of said tube.

6. A drive arm for a propeller blade comprising, a resilient core member surrounded by groups of friction elements each group including a plurality o f longitudinal staves surrounded by a plurality of circumferential tubular sections.

7. A hub spider for a propeller comprising, a central member apertured to receive a drive shaft and provided with a plurality of radially extending hollow arms, and a drive arm xed at one end in each of said hollow arms, each drive arm comprising a resilient core surrounded by frictional damping elements.

8. A hub spider for a propeller comprising', a central member apertured to receive a drive shaft and provided with a plurality of radially extending hollow internally screw-threaded arms,

and a resilient drive arm secured in each of said 9. A hub spider for a propeller comprising, a

central member apertured to receive a drive shaft and provided with a plurality of radially extending hollow integral arms adapted to extend into respective hollow propeller blades, and drive arms rigidly secured each by one end in a respective one of said hollow spider arms and provided at its opposite end with a bearing for engaging the wall of the hollow interior of the respective propeller-blade, each drive arm comprising a resilient core member and a plurality of frictional damping elements surrounding said core member.

10. A hub spider for a, propeller comprising, a central member apertured to receive a drive shaft and provided with a plurality of radially extending hollow arms, and a drive arm secured in leach of said hollow arms, each drive arm comprising a resilient core membersurrounded by groups of frictional elements, each group -including a plurality of longitudinal staves sur- JOI-IN M. TYLER.

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