US 1445142 A
Description (OCR text may contain errors)
Feb. 13, 1923.
y 1,445,142 C. B. KIRKHAM K PROPELLER MOUNTING Filed Oct. '7, 1918 la# f 1 mi?? C5; g S.' E 5 @Vl/veure@ ano n CHARLES B. KmKHAM.
Patented Feb. 13, 1923.
UNITED STATES `PATENT OFFICE.
CHARLES B. KIRKHAMI, 0F GARDEN CITY, NEW YORK, ASSIGNOR TO CURTISS AERO- PLANE AND MOTOR CORPORATION, A CORPORATION OF NEW YORK.
' Application led October 7, 1918. Serial No. 257,276.
,T0 all whom it mdr] concern.'
Be it known that I, CHARLES B. KIRKHAM, a citizen of the United States, residing at Garden City, in the county of Nassau and State of New York, have invented certain new and useful Improvements in Propeller Mountings, of which the following is a Vspeciication.
My invention relates to propeller mount-- ings and embodies a drive fit, as' distinguished from a. line or snug fit, between the hub of the propeller and the propeller shaft.-
Heretofore a snug or line it between the propeller hub and its driving shaft has been provided. This lit while seemingly tight and more or less snug is veryl often inexact or inaccurate. In machining the parts accuracy'to a thousandths of an inch is required. Even rthe slightest inaccuracy in mating the parts causes a certain amount of play, not noticeable at first, to exist between them. This play, as a result of vibrations set up in the propeller shaft, greatly enlarges until the propeller at the hub, rides loosely on the shaft and finally, when least expected, causes the propeller to break or fracture. Obviously such a condition is dangerous., To eliminate this danger a. drive fit between the propeller and the propeller hub is eiected. In obtaining the drive fit the propeller hub sleeve is provided with an inside taper somewhat less than the outside taper of the driving end of the propeller shaft. This construction, as the propeller hub is driven on the propeller shaft, places the hub under tension at the point of maximum diameter of the propeller shaft with the result that the drive fit is secured and all possibility of even the slightest play or lost motion between the mating parts prevented.
Of the dra-wings: .y
Fig. 1 is a face view of the hub section of a ropeller illustrating its mounting;
ig. 2 is a transverse sectional view of the propeller mounting, and
Fig. 3 is a diagrammatic view illustrating graphically the difference 1n taper and diameter between the hub sleeve and the propeller shaft.
In the embodiment of the invention selected for illustration a two-bladed propeller 19 is shown. At its Ahub section the propeller is rovided with a hub 11 comprising a hub s eeve 12, face lates 13 and 14 and securing bolts 15, the atter being proliicd for securing` the propeller 10 to the In machining thev hub sleeve 12 ot the roelle-r hub the diameter of the bore 16 o the lub sleeve is made larger at its inner end than at i-ts outer end. ameter of the bore throughout its full length corresponds exactly with the diameter of the correspondingly `tapered terminal of the propeller sha-ft 17 whereby inmating the two parts a lime or tight tit is provided. As intimated above, muc-h trouble is encountered in accurately machining these mating parts because of the fact that the slightestvariation in diameter'between them results in a more or less inaccurate it. To secure a perfect tit, if such a fit is possible, (in following the practice hereinbefore outlined) it is necessary that the tapered end ot the propeller shaft and the bore of the hub sleeve be given exactly the same diameter to the thousandths of an' inch. Such exactness or accuracy is next to impossible. In grinding the tapered end of the propeller shaft and in rearning the bore ot' the hub sleeve, inaccuracies, due to improper adjustment of the machining tools, invariably occur. It is for this reason that play or lost motion between the mating parts exists. Moreover` the keys and keyways` even though perfectly mated can not under the old practice be relied upon to prevent lost motion between the propeller hu-b and the propeller shaft in a direction at right angles to the propeller axis.
The present invention contemplates, insteadoftapering. the .propeller shaft terminal and the bore of the hub sleeve to the Vsame extent, a slight difference in ta er.
For instance, the bore of the propeller ub sleeve is provided with a taper of 1.496 in. per ft. whereas the correspondingly tapered part of the propeller shaft is provided with a greater taper, say, a taper'of 1.500 in. lper ft., it being understood that the outer or smaller end of .the propeller shaft and the correspondingly tapered` part of the hub sleeve are provided with substantially the same taper, or at least the difference in taper is substantially less than the difference in taper of the larger end ofthe propeller shaft and the correspondingly tapered part of they hub sleeve. This d'erence in taper puts the walls of the hub sleeve throughout'a portion of its length under direct tension and in consequence thereof necessitates a Ordinarily the diforced or drive fit between the hub sleeve,
and the propeller shaft. In other words, the diameter of t-he stub terminal of the propeller shaft at one end is preferably exactly equal to the diameter ofthe bore ofthe propeller sleeve at its corresponding end while the diameter ofthe stub shaft terminal at its opposite end is several thousandths of aninch greater than the original diameter of the bore of the hub sleeve at a corresponding point.
` As above pointed out, the drive lit between the propeller hub and the propeller shaft forms a true and effective direct driving and torque transmitting engagement between the mating parts and at the same time eliminates allV lost motion and play between them longitudinally of the shaft. By compressing orl contacting the walls of the hub sleeve they are made to yield slightly and at the lsame time firmly grip the propeller shaft and ,follow up its movement relatively to the propeller should slight movement, for any reason, take place. 'Moreoven all hammering or pounding action between the mating parts is eliminated.
The difference in taper between the propeller shaft and the propeller hub sleeve may be more or less than the diierence suggested. lf more, assuming the materials used are of the highest grade, greater driving force will be required in mounting the propeller. If less,'the driving force can be diminished. `It is essential however, that sufficient driving force be exerted to rigidly imbed the stub terminal within the hub sleeve and eliminate altogether even the slightest lost motion between them.
It is immaterial from the standpoint of this invention whether or not keys and keyways are provided of the character illustrated. lt is also immaterial whether or not the means illustrated for locking the mating parts together is used. It is essential however that a slight difference in taper be provided With the yresult that an actual drive fit between the shaft and hub may be effected. A snug fit, a line fit, or even a tight lit` will not answer.
`While ll have described my invention in detail in lits present preferred embodiment, it will be obvious to those skilled in the artafter understanding my invention, that various changes and modifications may be made therein without departing from the spirit or vscope thereof. liaim in the appended claim to cover all such modifications and changes; I
In a'propeller mounting, a propeller shaft havinga tapered terminal, and a propeller hub having a tapered bore within which the tapered terminal of the propeller shaft is fitted, the degree of taper of ,the bore of the propeller hub being lsomewhat less than the degree of taper of the terminal of the propeller shaft whereby a driving force is required in fitting the parts together and whereby the two parts when fitted together produce at one end of the tapered terminal a snug fit and atlthe opposite end a drive t as distinguished from a snug fit, the drive fit being thel direct result of the driving force required in fitting the parts together.
In testimony whereof I hereunto aflix my signature.
CHARLES B. KIRKHAM.