US1830731A - Air screw hub - Google Patents

Description

, H. N. WYLIE 1,830,731

AIR scREw HUB Filed Jan. 24, 1930 4 Sheets-Sheet l NOV. 3, 1931.

H. N WYLIE AIR SCREW HUB Filed Jan. 24. 195(3- 4 Sheets-Sheet 5 Inventor H. N. WYLlE AIR SCR W HUB Nov. 3, 1931.

Filed Jan 4 Sheets-Sheet 4 Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE HAMILTON NEIL WYLIE, OF COVENTRY, ENG-LAN D, A SSIGNOR TO sm W. G. ARMSTRONG WHIIWORT'H AIRCRAFT LIMITED, COVENTRY, ENGLAND AIR SCREW HUB Application filed January 24, 1930, Serial No. 423,190, and in Great Britain February 4, 1929.

This invention relates to air screws of, the kind in which the blades are universally pivoted to the hub so that they are relieved of all bending stresses, and its main object is to provide simple and effective constructions of small weight. Subsidiary objects are to provide for adjustment of pitch of-the blades simultaneously and/or separately and to ensure that centrifugal force exerts no tendency to change the pitch.

According to this invention, the hub is formed with a pair of projections provided with bearings for trunnion-like members on a yoke to which a: blade is pivoted about an axis transverse to that of the trunnion-like members, so that the blade is universally pivoted butcannot twist as a whole in relation to the hub.

If a number of blades is supported in this Way from a pair of spaced plates constituting the projections, and if either or both of these plates is pivotally mounted on the hub for rotation about its main axis, by twisting the one plate in relation to the other all the yokes can be rocked to adjust the bladesv simultaneously as regards their pitch.

Preferably, the yoke of a' blade is tiltable about either trunnion-like member so that the blade may be moved either to adjust its pitch or the distance of its centre of gravity from the axis of the hub; and in a preferred arrangement for effecting this means (such as eccentric bearings in the projections) are provided for adjusting the trunnion-like members in relation to the projections.

In the accompanying drawings,

Figure 1 is a diagrammatic end view of the hub of a two-bladed propeller embodying one application of the invention, I

Figure 2 is a side view of a hub for a three'' bladed propeller showing a further application of the invention,

Figure 3 being an end view thereof with certain parts in section and broken away for clearness,

Figure 4tis an end view, partly in section, of a hub for atwo-bladed propeller illustrating an alternative method of mounting the blades,

Figure 5 being a fragmentary side elevathe universal attachment of the other blade being shown separated from one another and 69 in position for assembly, and

Figures 8 and 9 are respectively diagrammatic side and end views of a two-bladed propeller illustrating two relative movements between the blades and the hub.

In the construction shown in Figure 1, the hub 2 is formed at points diametrically opposite one another with two tangential flat cheeks 3, each with a radial stem 4 which forms a pivot. On each of these pivots is mounted, free to turn, a plate 5. The plates are therefore spaced and, as they are arranged to project at each end beyondthe outside diameter of the hub they form a pair of pr0- jections 50 on each side of the hub, and each projecting end is formed with an eye 6 or bearing to receive the end of a trunnion-like .member. This, in its simplest form, is a yoke 7 formed at or near its centre with an enlargement 8 which is bored transversely at 9 to form a bearing or pivot to which the end v10 of the blade 11 is pivoted.

Thus the axis of each blade can move universally but 'it cannot twist.

The projections 50 may be fixtures but preferably they are constituted by pivoted plates 5 as shown, and means may be provided whereby one plate can be moved angularly about its pivot in relation to the other plate,

0 to vary the p1tch'of both blades s1multaneous- 9 1y. In the construction shown, each plate is movable angularly about its pivot and can be locked in the desired position by the bolts 12 which extend through curved slots 13 in each plate and into the flat cheeks 3. To vary the pitch of one blade 11 in relation to the other, the trunnion-like members 14 on eachyoke 7 may be movable separately in relation to their plates. For example they may be mounted in eccentric bushes 15 in the plates, as more fully described later.

It is not essential that the projections 50 be tangential to the axis of the hub, and in some cases they may be perpendicular and transverse to the axis thereof, an example of which is shown in Figures 2 and 3, for use with a three-bladed propeller. In this the forward plate 5, i. e., that one on the right of Figure 2, is preferably integral with the shell of the hub 2 and is substantially in the form of a triangular flange (Figure 3). The back plate 5 (on the left of Figure 2) is of similar shape but is formed separately from the hub and is free to rotate slightly thereon. Thus the corners of the plates, which are spaced, form three pairs of projections, one pair for each blade.

In each corner of each plate is formed the eye 6 in which is held one trunnion-like member 7. For this purpose, in each eye is mounted a split bush 15 the interior of which is eccentric to the exterior, and in the bush fits the trunnion member 14. By simultaneously adjusting the eccentric bushes at each end of a yoke, the centre of gravity of the blade attached thereto can be radially moved, which is useful for balancing the complete propeller.

Preferably, the trunnion-like members 14 are} parti-spherical and the bushes 15 are in the nature of cups engaged by the partispherical portions. The bushes consequently require to be split and to secure them in position they are provided at one end with a shoulder 16, which may be conical, and are threaded through the correspondingly coned eyes 6 from the inner side of the plates and secured in positionby nuts 17 screwing on the ends of the bushes projecting through the outer sides of the plates. The nuts are subsequently locked by a tab washer. 18 and grub screws 19. On slacking off a nut, the corresponding bush can be rotated.

The provision of the ball and socket mounting just described for the trunnion-like members is to allow the yoke to be moved about either trunnion member to adjust the pitch of the corresponding blade. Furthermore this arrangement enables all the trunnion members to be moved sideways at one end to vary the pitch of all the blades simultaneously by moving the back plate around the axis of the hub.

Preferably some resilient material 20 is interposed, as'shown, between the hub 2 and -'-the part of the yoke adjacent the hub, or it trunnion members without difliculty. When in position the bolts of the strap are slackened so that the resilient pads press the surfaces of the strap against the end faces of the jaw members. In this way'a resilient support is provided to the blades which resists slightly, in the manner required, their free pivotal movement.

A convenient method of adjusting the angularity of the movable plate in relation to the fixed one is to provide one or more tangential screw devices 21 (Figure 3) on the hub and acting upon the movable plate or some part or parts carried thereby, such as the nuts 17, or vice versa. Alternatively, no actual adjusting device need be provided, but, after all the trunnion members have been set exactly alike, or after all the blades have been set to the same pitch and the propeller balanced, radial holes would be drilled through a flange, not shown, on the interior of the movable plate and into the hub to receive a dowel, setscrew, or the like, which would thereby ensure accurate setting and locking of the movable plate and all the blades to a certain pitch. Other holes could be made with the plate moved through certain angles from the first position, corresponding to minute variations of the pitch of the blades, say half a degree.

Thus. when the hub is dismantled, it can easily be accurately re-assembled without likelihood of the blades being of different and inaccurate pitches, and the partsv can easily be set so as to provide for known variations of pitch.

In the alternative arrangement shown in Figures 4-9, the blade 11 is attached to an adaptor 22 which consists of a socket of circular bore and circular periphery near the closed end 23. In the sides of this part are formed two diametrical holes 24 opposite to one another and adapted to receive therein a pin 25 to be more fully described later. At right angles to these holes elongated slots 26 are formed in the sides and parallel to the axis of the socket and adapted to receive transversely a yoke member 27 more fully described hereunder. adaptor consists of two flat plates 28 parallel to the axis of the socket, and-at an angle -which may be about degrees to the slots 26 and to the holes 24. These plates are 111- timately securedto the root of the propeller blade by rivets or other means.

Fitted into the socket is a compression piece 29 which is in the form of a jaw with holes 30 transverse to the jaws and at right angles to the slot 31 between them. Through these holes 30 the pin 25 above referred to is ultimately fitted, and, when the compression piece is in position, the holes 30 are in line with holes 24 in the adaptor. The holes 30 are of the same diameter as the part of the pin 25 which engages them, but the holes The other end of the 24 in the adaptor are larger than the part of the pin which lies in them. 1

When the compression piece 29 is in position in the'adaptor the yoke 27 is then passed through the slots 26 in the adaptor and lies in the slot 31 in the compression piece.

This yoke consists of a fiat block of metal with a trunnion 32 at each side. The flat central portion lies in the slot 31, and each trunnion 32 projects with clearance through one of the slots 26 inthe adaptor. In the flat centreis a transversely bored hole 33 which registers with the holes and 24 in the compression piece and adaptor respectively and is arranged to receive the pin 25.

The latter is for the most part a plain cylindrical rod with a bearing fit in the holes 30 and 33 and terminating in reduced ends 34 which are screw-threaded at 35. The reduced parts 34 have a clearance in the holes 24 in the adaptor,- and the clearance may be rendered still greater by forming flats 36 opposite to one another. This clearance is to enable the adaptor 22 to be moved angularly over a small range relative to the yoke 27, compression piece 29 and in 25 in order to vary the pitch of the blade without varying the distance of the centre of gravity of the blade from the axis of rotation. Between the nuts 37 screwing on the pin ends and the outsides-of the adaptor are arranged saddle-shaped washers 38 which grip the sides of the adaptor when the nuts are tightened up and lock the parts in the desired angular position. Index marks 39 may be provided on the relatively adjustable parts so that pitch setting may be known.

The ends of the trunnions 32 are'screwthreaded at 40, and between the screw-threaded ends and the block are parallel plain portions which take bearings in the projections 50 on the hub. These projections take the form of radially arranged lugs diametrically opposite one another and two on each side of the hub. in the case of a two-bladed propeller. For a three-bladed propeller there would be three pairs of lugs at 120 degrees. For convenience in fitting, the hub is split transversely at 41, each part carrying a pair of the diametrically opposed projecting lugs 50,

each with a hole 42 to receive the plain bearing portions on the yoke trunnions. The two parts of the hub are dowelled together or otherwise located angularly, and are held in position by the means which secure the hub upon the propeller shaft, not shown.

The mouth of the bore in the adaptor is finally closed bv a stiffener 43 which consists of a disc or plug which is riveted in the socket andforme d with a diametrical web which projects along the adaptor-between the plates 28 for any suitable distance to impart stiffness to them.

Each blade 11 is thus universally-jointed to the propeller hub 2, movement in one direction causing the pin 25 to twist in the yoke, and movement at right angles resulting in the yoke swivelling about the projections 50 on the hub. To hold the blade approximately radially to the hub axis there is interposed between the closed end 23, of the adaptor and the periphery of the hub a resilient pad 44 attached to a saddle-shaped piece 45 which in turn is secured to the end of the adaptor.

The invention thus provides for two relative movements between the blade and the hub, which are illustrated diagrammatically in Figures 8 and 9, these-being,-tilt, which is inclination of the blades 11 forwards or backwards in an axial direction and indicated by the angle X in Figure 8, and lag, which is inclination of the blades 11 about the hub projections from a truly radial position and indicated by the angle Y in Figure 9. The blades can, therefore, adjust themselves quite freely. It is, however, very important that the centre of gravity of the two blades combined should lie on the axis of the hub, and this entails that the lag angle Y of the two blades must be identical; that is to say, the angle which the blades take up about the axis of the trunnions in the hub projections in relation to radii from the hub axis passing through the trunnion axis.

xii)

running. Also it is possible to see exactly a the pitch angle to which the blade or blades is set.

What I claim as my invention and desire to secure by Letters Patent of the United..

blade of the air-screw to said yoke about an axis transverse to the axis of said trunnionlike members.

2.In an air-screw, the combination with yoke and said socket aboutan axis transverse to that of said trunnion-like members.

3. The combination claimed in claim 2, in

which the trunnion-like members and transverse pivot in the yoke extend through opposite sides of the socket with clearance to allow of varying the pitch of the blade.

4. In an air-screw, the combination with a hub, a yoke having trunnion-like members, saidmembersbeingcarried in bearings in said projections, a socket receiving said yoke and fitting within said projections, said socket having a blade of the air-screw secured there to, and means pivotally interconnecting said yoke and said socket about an 'axis transverse to that of said trunnion-like members, said trunnion-like members and transverse pivot in the yoke extending through opposite sides of the socket with clearance to allow of varying the pitch of the blade, the yokes of each blade being interconnected for movement in unison to ensure uniform angles of lag.

5. An air-screw comprising a hub having a pair of projections extending therefrom, an

, ada tor housed between said projections and having a socket therein and having elongated aligned slots in opposite sides thereof opening into said socket, said adaptor also having aligned holes in opposite sides thereof at right angles to said slots, a yoke fitted into said socket and having trunnion-like members projecting into said slots, means for connecting said adaptor to said projections, and means for pivotally connecting said yoke a and said adaptor about an axis transverse to that of said trunnion-like members.

In testimony whereof I aflix my signature.

HAMILTON NEIL WYLIE.

Images