US1358430A

US1358430A - Propeller

Info

Publication number: US1358430A
Application number: US58094A
Authority: US
Inventors: Faehrmann Hermann
Original assignee: Individual
Current assignee: Individual
Priority date: 1915-10-27
Filing date: 1915-10-27
Publication date: 1920-11-09
Anticipated expiration: 1937-11-09

Description

H. FAEHRMANN.

I PRoPELLERv.' APPLICATION FILED 0CT.27, I9I5.

1,358,430. l Patented Nov. 9, 1920.

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/V VEN TUR /rJ/MJUL 15e/217mm H. FAEHRMANN.

PaoPELLER.

Y APPLICATION FILED OCT-27,1915. 1,358,430', Patented Nov. 9, 1920.

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aan STATES HERMANN FAEHRMANN, OF BROOKLYN, NEW YORK.

PROPELLER.

.i ,atenerse Specification of Letters Patent.

Patented Nov. 9, 1920.

Applicationled October 27, 1915. Seria] No. 58,094.

i! 'o uZZ rtf/lont 'it lmay concern.'

lie it known that l, HERMANN FAEHRMANN, a citizen of the United States, and resident of the borough of Brooklyn, county of Kings, city and State of New York, have invented certain new and useful Improvements in lhaipellers, of which the following is a. specification.

My invention relates to screw propellers .lor aerial or aquatic navigation, and has for its object to provide an exceedingly efiicient propeller of great simplicity of construc- 'tion and susceptible of operation at Very h igh speeds. Experiments which l have been condactingl for years have confirmedthe corria'tness of my opinion that a high number of revolutions is conducive to an increased ellicienoy of such propellers, and my present improvement is designed especially in view ol usingr a high rotary speed.

tiercral examples of .my invention will now be described in detail with reference to the accompanying drawings, and the novel features will then be pointed out in the apjicuded claims.

Figure. l is a side View of one form of my inijpiroved propeller, Fig. 2 'is an end View Vthereof. Fior. 3 is a partial longitudinal section. on an enlarged scale, on line .33 of iiigr. f3. and Fig. l is a cross section on line gimiol` Fin'. Si. the propeller blade being omitted; Vie'. 5 is a front View of a second forni oi' my invention. and Fig. (l is a section on line l--ft of Fig'. shown on an enlarged scale: tig'. T is a longitudinal apj'n'oximately central scr-tion of a third form of my invention. taken on line 'i1-7 of Fig'. 9. Fig". 8 is a kif'ertii-al section on line tl-8 of Finn i, shown on an enlarg'eifl scale, Figi'. 9 is a top View of this forni of my inrention, with part-s in section, and Fig. l is a detail cross section au line -l0 of Fig'. i; Figi'. il. is a cross vsection similar to Fin'. S of still another forni Til.' my invention. Fig. l?) is a section on the lino lil-42 .of Fig'. ll, and Fig. 15:3 is a partial section. of the same character as Fig. L7. but showing the form of my invention vllustratell by Figs. ll and l2.

The leadingr feature of my improved pro* .icllcr structure as represented in the drawuns is the provision of a single propeller Blade. and proper means for coilnterbalancne' it. ln the particular embodiment of my in'cnl'ioii shown in Figs. l to -l. the blade it great thinness, extends farthest out at one side, and is comparatively narrow, measured circumferentially, at said side, while the other portions of the blade project less and less from the center or axis, but increase in width, measured circnniferentially. That 1s, the outer edge of the blade forms a helical spiral which` gradually approaches the center as the blade grows wider circumferentially. The pitch of the blade should be small for the securing of the best results, and I have found it desirable to use a pitch angle not exceeding 150 at the outer edge of the tip (L of the blade. The pitch angle is defined as the angle which the helical or screw-line of the propeller blade, at any point thereof, forms with a plane laid through said point j ierpendicnlar to the axis of rotation. As shown in Figs. l and 2, 'the length of the Iblade A, measured in a direction parallel to said axis, is approximately equal to the maximum distance to which the blade projects radially from the carrier or hub B (at the tip a). Preferably the pitch angle increases gradually from said tip a to the other end of the blade that is to say, the pitch is smallest at that end of the blade which projects farthest from the axis, and greatestat the opposite end of the blade (rightdiand end in Fig'. l) blade is connected rigidly with the hub B, as by casting it integral with said hub. The latter is pointed at the free, end B', and is shown providedat its other end with a. shoulder B adjacent to a shoulder C on the propeller shaft (l. The pointed end B of the hub is represented as a separate piece, secured to the hub body B by screws D and nuts D', the latter conntersunk in recesses and readily accessible from the outside. The outer end of the shaft C, which is screwthreaded, is contained within the end or cap l. and receives' a nut E serving to secure the hub on the shaft. and. as shown, the latter and the axial bore of the hub may bc tapered so as to increase the holding action oi" the nut lil. Uf course, the hub may be secured to the shaft in any other approved manner. The hub is cored out, asindicated at lk. on the side on which the blade .l projects farthest out. so that the side ol' the hub opposite to said blade portion may be heavier and assist in balancing` the blade and hub structure. As shown. the blade extends entirelyV around the hub. so that one portion of the blade is utilized as This a partial counterbalance for another blade portion; the main counterbalancing effect, however, is obtained by coring out the hub at Bf, the form of the cavity being shown in Figs. 3 and L1, that is to say, the cavity is arched both lengthwise and transversely. The outer surface of the hub B, B is torpedoshaped, that is to say, of circular cross section at every point, and tapering toward both ends from the central or widest por tion at which the blade A is placed. The blade and hub are balanced in two senses: first, the weight is balanced, that is to say, if the shaft C is horizontal the blade and hub, if turned to any particular position and stopped, will have no tendency to shift from such position; second, there is also balance of axial thrusts or pressures, that is to say, the sector containing the outer or tip portion of the blade exerts the same pressure on the air or water as the sector of equal angular extent diametrically opposite said tip portion; this latter result is due to the fact that the width of the blade, meas ured circumferentially, as well as the pitch angle of the blade increases from the `tip toward the other, inner end of the blade. It will be observed that at the end or tip where the blade projects farthest from the axis (left-hand end in Fig. 1), where the outer portions of the blade have the highest linear velocity, the pitch angle is smallest, and the width of the blade, measured circumferentially, is least, both the pitch angle and the width of the blade, measured circumferentially, increasing toward the other` end of the blade, where the blade does not project so far from the axis (right-hand end in Fig. 1) and where therefore the linear velocity is relatively low. 0f course, the linear speed is in direct ratio to the distance from the axis, and on the other hand, other things being equal, the axial thrust or pressure increases with the pitch angle. periments have demonstrated that with a high linear speed` the best results are obtained when the pitch angle is small, while with a low linear speed, the best results are obtained with a relatively greater pitch angle. The balancing of the axial thrusts or pressures on different portions of the blade is obtained by a proper proportioning of the three factors, viz.: circumferential width of the blade, its radial. extent or projectlon from the axis, and the pitch angle. Thus, with my improved propeller, the radial length of the helical blade decreases from front to rear, while the pitch increases in the same direction.

The propeller shown in Figs. 5 and G differs from the one illustrated by Figs. 1 to i by the provision of ribs A directed toward the shaft C, on the forward side of the blade A, that is the side toward which the boat or airship is traveling. These ribs, which may be cast integral with the blade, stiften it considerably, and enable it to better resist the considerable strains due to centrifugal force when the blade is rotated at a high speed. The effect of centrifugal force iU beneficial in my propeller, inasmuch as it counteracts the tendency of the pressure to bend the blade lengthwise of the. shaft. Fig. 5 also shows that the blade, instead .of continuing through about 3G00, may be made to extend through a smaller angle, but its general shape, and the manner of balancing it, are the same .as described above.

According to the construction shown in Figs. 7 to 10, the 'hub body is made of two spaced sections B and Bb, with rings or collars Bc ,interposed between them. These rings have openings Bd which register with each other and also with cavities Be and Bf in the hub body portions Ba and Bb respectively, forming together a cavity similar in arrangement and purpose to the one shown at B* in the form of my invention Erst described. The collars Bc engage the shaft C, and have recesses lig at their inner portion to receive the feet A* of ribs A which are held individually within lrecesses B in the adjacent faces of the outer portions of the rings or collars B, the two end recesses extending into the end faces of the hub body portion. The blade Aa is shown of substantially the same form as in Fig. 5, but is a separate member secured to the ribs A in any suitable manner, as by rivets Preferably the width of the collars Bc increases from left to right. Las shownin Figs. 7 and 9, so that the pitch angle will be increased from the tip of the blade to the other end. The inner ends of the ribs A, at the feet LW, are perpendicular to the axis of the shaft, but the outer rib portions are twisted (Fig. 10) so as to bring them into an alining position substantially like the one shown in Fig. 6. The outer portions of the ribs are half-round, the blade being applied against the fiat surfaces. The cross sections in Fig. 9 show the ribs where they emerge from the hub. lf desired, pins F may be provided to anchor the rings Bc to the lbody portions of the hub.

Figs. 11, 12 and 13 illustrate a construcl tion differing from the one shown in Figs. '7 to 10, by the construction of the blade in sections instead of one piece, and the con nection of these sections with each other and with the ribs. and also by the manner of securing the ribs on the shaft. Each of the blade sections Ab is made integral with one of the ribs AC, and the free edge of each blade section is suitably secured to the next following rib, as by rivets 7J. Figs. 11 and 13 also show a different construction of the inner portions of the ribs, which latter in these two views are shown as formed integral with rings d fitting around the shaft C (shown square). In other respects, this construction is substantially the same as in Ifig's. T to l0.

The torpedo shape of the hub also increases the cliciency of the propeller, such shape preventing injurious whirling of the water or air through which the boat or airship (or aeroplane) is being` propelled.

The constructions illustrated by Figs. 5 to 13 may if desired be applied to a blade of large circumferential extent (such as shownin Figs. l and 2).

While I have described my improved structure as a. propeller for aerial or aquatic navigation, it will be obvious that it may be employed for other purposes, thus, when driven by connection With an engine, the structure may also be used as a ventilator (fan) or pump, or, when exposed to the action of a current of air, water, gas or steam, the device will be available for use in turbines, water-motors, anemometers, meters for water and gas, ete-For use in water, I prefer to employ a comparatively long blade (as in Figs. l to 4), while when the blade works in air, I prefer a shorter blade (as in Figs. 5, 8 and 1l) The balancing of the rotary structure may also {be-.obtained by making the portion of the blade on the lower side of the shaft (Fig. 2) heavier than the portion on the opposite side of the shaft, which result can be obtained by varying the thickness of the blade (or of the ribs, when they are employed). Furthermore, by making the shaft very heavy, I may secure a practically suliicient approximation to a perfect balance, the shaft being then able to bear all the strains even though the blade itself is not fully balanced.

Various modifications may be made without departing from the nature of my inventon as set forth in the appended claims.

I claim as my invention:

l. A structure adapted for use as a propeller or for other purposes, provided with a helical blade whose radial length is greatest at one end of the helix and decreases toward the other end of the helix, while the width of the blade, measured circumferentially, and its pitch angle both increase gradually from the portion of greatest radial length to the opposite end of the helix, said radial length, circumferential Width, and pitch angle being proportioned to balance the pressures on different portions of the blade in the direction of axial thrust.

2. A structure adapted for use as a propeller' or for other purposes, provided With a helical blade whose radial length decreases from one end of the helix to the other while its pitch angle increases in the same direction, the parts of the blade being proportioned to balance the pressures exerted in the direction of axial thrust, on diametrically opposite blade sectorsof like angular extent.

3. A structure adapted for use as a propeller or for other purposes, provided with a helical blade whose radial length decreases from front to rear, while the pitch angle i11- creases in the same direction, the parts of the blade bein,fr proportioned to balance the pressures exerted in the direction of axial thrust, on diametrically opposite blade sectors of like angular extent.

4. A structure `adapted for use as a propeller or for other purposes, provided with a hub which is'heavier on one. side than'on the other, and a blade different portions of which project to different distances from the hub, the portion of the blade which projects farthest out,l being located on the lighter side of the hub.

A. structure adapted for use as a propeller or for other purposes, provided with a hub having an interior cavity whereby the hub is made heavier on one side than on the other, and a blade different portions of which project to different distances from the hub, the portion of the blade which projects farthest out, being located on the lighter side of the hub.

In testimony whereof I have signed this specification.

HERMANN FAEHRMANN.