US1715071A - Propeller - Google Patents

Description

May 28, 1929. F. J. MARTENS ET AL 1,715,071

PROPELLER Filed June 1928 2 Sheets-Sheet l May 28, 1929. MARTENQ ET AL 1,715,071

- PROPELLER Filed June 6, 1928 2 Sheets-Sheet 2 Patented May 28, 1929.

UNITED STATES '1" CFFICE.

FREDERICK J'. MAR'IENS, OF MILVIAUKEE,-AND CLINTON 0. THOMPSON, OF SOUTH MILWAUKEE, WISCONSIN.

PROPELLER.

Application filed June 6, 1928. Serial no. 283,328.

This invention relates to propellers, and is particularly directed to an aeroplane profor aeroplanes direct the stream of rearwardly passing air against the fuselage and thus increase the resistance of the aeroplane and decrease the overall efliciency of the machine.

This invention is designed to overcome the defects noted above, and a further object of this invention is to provide a novel form of propeller in which the air is delivered rearwardly from the propeller in a divergent manner, so that a central space is left for the fuselage and the air is already directed at an angle to the axis of the propeller so that the fuselage is not the sole means for parting the air, as has heretofore been the case, but in which the air is already caused to flow in a somewhat divergent manner to thus lessen the frictional force on the sides and end of the fuselage.

Further objects of this invention are to provide a propeller which may be made of Wood.

or metal and which is of eminently practical construction and may be easily produced.

An embodiment of the invention is shown in the accompanying drawings in which:

Figure 1 is a face view of the propeller;

Figure 2 is a side elevation thereof;

Figure 3 is a sectional view on the line 33 of Figure 1;

Figure 4 is a side elevation of the propeller taken at right angles to Figure 2;

Figure 5 is a sectional view of one of the vanes drawn to an enlarged scale and corresponding to the section 33 of Figure 1 showing in full lines the initial position of the vane and in dotted lines the position assumed by the vane due to centrifugal action.

Referring to the drawings, it will be seen that the propeller comprises a main body portion constructed substantially like the usual aeroplane propellers. The body portion comprises a hub 1 through which the driving shaft passes, and a pair of outwardly projecting blades 2 and 3 extend from the hub and are identically similar. These blades, in accordance with the usual practice, havea pitch which decreases as the radial distance from the hub increases.

From the leading edges 2 and 3 of these blades, a pair of screw- like vanes 5 and 6 ex tend. These vanes have their inner edges 5 and 6 defining spirals corresponding i-n pitchto the pitch of the main blades, at the point of intersection of these edges with the main blades. In other words, the angularity of the main blade is continued in forming the spiral defining the inner edge of these curved vanes. Their inner edges are concentric throughout a material portion of their length with the center of the propeller, at least through an arc of ninety'degrees, as is apparent from Figure 1, this concentric relation obtains. The outer edges 5 and 6 of these vanes also define spirals but the pitch of these outer spirals is the same asthe pitch of the blades at the point where these outer edges meet the blades. Thus, the inner edges of the vanes define one set of spirals and the outer edges of the. vanes defineanother spiral of lesser pitch than the first spiral, as it is obvious that the angularity of the main blades is lesser at the point of union with the outer spirals than at the point of union with the inner spirals.

The vanes 5 and 6 continue outwardly and terminate in outwardly turned end portions 7 and 8, which correspond in pitch generally to the outer third of the main blades. outer ends 7 and 8 are diametrically opposite to each other, as is obvious from an inspection of Figure 1. Preferably, the vanes 5 and 6 are slightly widened at the point where they oin the main blades 2 and 3. I

It is also preferable to have the outer third of the main blades unobstructed orfree of the The V vanes; that is to say, the outer edges of the creases, and also the width of the vanes in- The rotation of the propeller is in the direction indicated by the arrow in Figure 1; that is to say, the outer ends of the vanes first encounter the air and these outer ends are so arranged that they act precisely as the outer third portion of a propeller blade. The outer third portion of the main blade is not interfered with and consequently these portions which are the most effective parts of the propeller freely operate to secure the thrust of the. propeller.

The propeller may be made of wood, metal, or other suitable material and is preferably formed of resilient material so that thereis a slight yield and shifting of the vanes in actual operation.

For example, as shown in Figure 5, it will be seen that the normal position of Figure 5, for instance, is as shown in full lines. However, due to the action of centrifugal force and also the pull of the air upon the vanes, they move outwardly both axially and radially'with reference to the hub of the propeller. Consequently, their angle is shifted and their pitch increased, as, is obvious from a comparison of the dotted line position of the vane 5 in Figure 5, such dotted indication showing the position of the vane in actual operation. This shifting of the vanes both radially outwardly and axially forwardly increases the pitch of the vanes and also tilts the blades to a certain extent and increases their pitch as well. Thus, as the speed increases, the pitch of the propeller increases, which has been found from actual operation to materially increase the efliciency.

This increase in pitch with increase in speed of the propeller, is of marked advantage for aeroplanes, as it maintains the efficlency of the propeller throughout a wide range of speeds. Also, it is to be noted that the change in pitch is wholly automatic and without any thought on the part of the opera or.

From actual tests conducter with propellers constructed in accordance with this invention, 1t has been found that the thrust or pull from the propeller is increased at least two and even-tenths times that from a normal propeller, such as forms the body portion of this device.

Further, it has been found from actual tests that the air is not thrown inwardly in a converging stream towards the axis of the huhas occurs with the ordinary propellers, but is thrown rearwardly and outwardly in a dlverging stream, so that the central portion normally occupied by the fuselage of the aeroplane has very much reduced flow with reference thereto. Consequently, the skin friction or resistance of the fuselage, is very much decreased when a propeller of this type is mounted in front of the fuselage. In other words, the parting of the air has already been initiated by the propeller and the fuselage merely completes this parting.

It is preferable to construct the blades and the vanes in the shape generally, as shown in Figure 5, so that they have a substantially flat inner face and a streamlined outer face to secure the maximum suction from these blades and vanes.

It has been found also from actual tests conducted with a propeller constructed in accordance with this invention that the vanes move towards the position shown in Figure 5 in varying degrees dependent upon the speed of rotation.

,l/Vhile it is not completely known what precise operation takes place with this propeller, nevertheless it is believed that the vanes compress the air and deliver it to a point adjacent the outer'third of the main blades. The main blades thus Operate particularly at their outer thirds upon a denser air than usual. Consequently, a greater grip upon the air is secured by these outer third portions of the main blades.

Further, the extreme outer ends of the vanes increase their pitch as the speed increases, and thus they also actas the outer third of the propeller blades with an increasing pitch dependent upon the speed. The maximum efliciency is thus, obtained which is borne out by the actual tests conducted with this device.

Although the invention has been described I in considerable detail, such description is in tended as illustrative rather than limiting as the invention may be variously embodied and as the scope of such invention'is to be determined as claimed. We claim. I 1. A propeller comprising a pair of blade iaving a pitch which decreases as the radial distance increases, a screw-like vane secured to the leading edge of each blade'and forming an outwardly progressing spiral about the axis of the propeller, said vanes having end portions corresponding to the ends of said blades, said vanes being resilient and increasing their pitch due to centrifugal action as the speed of the propeller increases. 2. A propeller comprising-a pair of blades having a pitch which decreases as the radial distance increases, and a screw-like vane secured at the leading edge of each blade and extending forwardly therefrom, said vanes forming spirals coaxial with the axis of the propeller. s

3. A propeller comprising a pair of blades having a pitch which decreases as the radial distance increases, and a screw-like vane secured at the leading edge of each blade and extending forwardly therefrom, said vanes forming spirals coaxial with the axis of the propeller and having free outer ends terminating in outwardly turned end portions corfis onding to theend ortions of the main a es.

4. A propeller comprising a pair of blades having a pitch which decreases as the radial distance increases, and a screw-like Vane secured at the leading edge of each'blade and extending forwardly therefrom, said vanes forming spirals about the axis of the propeller, the inner edge of each vane defining a spiral of one pitch and the outer edge of each vane defining a spiral of a lesserpitch.

5. A propeller comprising a pair of blades having a pitch Which decreases as the radial distance increases, and a screw-like Vane secured at the leading edge of each blade and extending forwardly therefrom, said vanes forming spirals about the axis of the propeller, the inner edge of each Vane defining a spiral of one pitch and the outer edge of each vane defining a spiral of a lesser pitch, the pitch of the inner and outer edges of the vanes substantially corresponding, respectively, to the pitch of the blades of the propeller at the points where said inner and outer edges meet said blades.

In testimony that We claim the foregoing We have hereunto set our hands at Milwaukee, in the county of Milwaukee and State of Wisconsin.

FREDERICK J. MARTENS. CLINTON O. THOMPSON.

Images