US1192111A - Construction of propellers. - Google Patents

Description

W. C. PI TTER. CONSTRUCTION OF PROPELLERS.

- APPLICATION F lLED DEC. 5, I910.'

Patented July 25, 1916.

zd anxa as earn CONSTRUCTION OF PROPELLEBS.

Specification of Letters latent.

Patented ma 25. acre.

Application filed December 5, 1910. Serial No. 595,740.

To all whom it may concern: 1

Be .it known that I, WALTER CHARLES Pirrnn, of 38 Nightingale Vale, Woolwich, 1n the county of Kent, England, engineer, have invented certain new and useful Improvements in the Construction'of Propellers, of which the following is-a specification.

This invention relates to improvements in the construction of propellers serviceable for use in air or water, or in other fluids, and it is an object of the. invention to increase the efliciency of propellers or fans by arranging several fan blades in serial alinement on a common support.

I The movement of propeller blades through any fluid will have a tendency to impart motion to the fluid within a zone at each of the two surfaces of the propeller blade. No motion, or verylittle motion, is imparted to the fluid outside this zone, and the extent of the zone is dependent upon the shape of the propeller blade, the speed of rotation of the same and the consistency of the fluid through which it moves.

In a fan which may serve for imparting motion to the air, the serial arrangement of several blades on a common support will have a tendency to increase the efiiciency of the fan beyond the total efliciency of a number of fans corresponding to the number of blades in alinement. The increase over the efficiency of the stated plurality of fans will occur only if the blades are suitably spaced from each other. If the interspace between adjacent blades is too large, dead air will be included between these adjacent blades, this layer of dead air occurring in a zone located midway between the zones of moved air, said last named zones being in contact with the front surface of one blade and the rear surface of the next blade respectively. If the fans in serial alinement are too close to each other, the zone of air acted upon by one blade surface would also be acted upon by the surface of the adjacent blade so that in spite of the multiplication of the blades no increase in efiiciency is noticeable.

The blades, therefore, must be spaced from 'ment.

tion to this eflect may be advisable. The plane of the blade in"v ordinary fans or propellers is frequently disposed at an angle to the axis of the-shaft of the fan or propeller; it is therefore also an object of the invention to arrange the entire series of blades in a line which forms an angle with the axis of the pertaining shaft and to space these blades from each other a distance large enough to let a relatively large volume of air pass between the same while preventing the inclusion of dead air between adjacent blades.

Another object of the invention, especially in connection with propellers, is to be seen in the arrangement of a guide vane for each set or series of blades, said guide vane being connected with its set so as to move through the fluid with the blades; said vane, however, being movably arranged whereby it will assume automatically a position in the direction of the resultant of the forward velocity of the propeller shaft and the linear rotary velocity of the leading edges of the blades. If the set of blades with which the vane is connected is movable with respect to the shaft of the propeller, the vane will have a tendency to alter its position in accordance with the speed of the propeller, and owing to its connection with the propeller blades it will also then alter the angle or pitch of all of the propeller blades in the pertaining set with respect to the axis.

With these and other objects in view, I have illustrated a plurality of embodiments of the invention in the accompanying drawings wherein:

Figure 1 is a diagrammatic sectional view through a fan or propeller blade illustrating the action of a blade on the fluid in which it is operating. Fig. 2 is a similar diagrammaoic View illustrating the action of two fan blades or propeller blades in serial aline- Fig. 3 is a side elevation of a. propeller embodying the invention. Fig. i is a top plan view of the propeller construction illustrated in Fig. 3. Fig. 5 is a partial side elevation of a modified form of a propeller. Fig. 6 is partly side elevation and partly section of a propeller blade suitable for use in a liquid fluid and provided witha guide vane. Fig. 7 is a top plan view of the propeller blade and vane shown in Fig. 6. Fig. 8 is a diagrammatic top plan view of aset of propeller blades in serial alinement, the blades being of different width. Fig. 9

fan blades in alinement on the same shaft.

The direction of rotation of the fanblade Z, shown diagrammatically in Fig. 1 in sectional view, is indicated by the arrow. The

zone of fluid to which motion is imparted by the rotation of said blade within the 1 fluid is indicated by streamlines following more orless closely the curvature of the surface of the fan or propeller blade l said blade having on one surface a concave and on the other surface a convex curvature. From this figure it will also be apparent that at a distance from the surfaces the fluid will not be forced to flow in streamlines so that the zone of action of the propeller or fan blade onthe fluidis limited. The fluid outside this zone is not affected by the rapid motion of the blade through the fluid, and it may be considered as dead or immovable fluid.

Fig. 2 illustrates in a similar diagrammatic view the action of a pair of serially alined propeller or fan blades Z upon the fluid through which they move. It will be noticed that in this instance the entire fluid zone located between two surfaces of the fan blades is moved in streamlines and that zones of fluid contacting the opposite surfaces of the two blades (which surfaces are directed away from each other) also are subjected to the action of these blades. The

moving fan blades cause motion of the fluid adjacent thereto, and this motion of the fluid in the active zone adjacent each fan blade and between the two blades will have a tendency to cause a similar motion to the fluid in that zone between the two blades which in a single blade, propeller or fan, would be in the dead zone. The serial alinement of blades suitably spaced from each other willftherefore, increase the efficiency of the device, so that in case of the fan by a duplicate set of blades a larger volume of air may be conveyed than by two single fans, and in case of the propeller a larger speed may be attained than by means of two separate single blade propellers.

If the two fan blades would be too close to each other, there would be no dead zone between them, but there would also be no zone between them which could be acted on by the fluid carried along, owing to the rapid motion of the propeller; in that instance. the efficiency of the propeller or fan would not exceed that of a single-blade propeller or fan. It is, therefore, necessary that the distance between the two blades should he sutiiciently small so as not to include any space in which dead fluid remains, un-

affected by those zones of fluid which are aflected directly by the fan blades or propeller blades. The distance between the two blades must not be too small; otherwise the zone of fluid moved by the one blade is the same fluid which also is acted on by the other blade, and no perceptible increase of efficiency would result from, this arrangement.

Figs. 3 and 5 illustrate in side elevation embodiments of propellers in which a plurality of blades a are in serial alinement, and from Fig. 4 which is a top plan view of the construction illustrated in Fig. 3, it is apparent that this series of blades is arranged at an angle to the axis of the shaft. The diagrammatical view in Fig. -8 illus- .trates aset of blades (1 in serial alinement,

wherein the width of the blades and the distance between adjacent blades increase in proportion to the radius of the curvature of the blades. No matter what the distance between the blades, it must always be sufficiently large to prevent the action of one fanblade or propeller blade on the same zone of fluid on which the adjacent blade acts, and the distance must be sufiiciently small to prevent the inclusion of dead air between the blades. In Fig. 4 the several blades a have uniform curvature and width,

but the line at which the center points of the curved surfaces are located does not coincide with a central axis of the set connecting the middle point of the rearmost blade with the middle point of the foremost blade. Fig. 9 illustrates in diagrammatic view a similar arrangement wherein the blades a, however, are symmetrical to said axis. blades a have uniform distance from each other and equal width.

Fig. 3 shows an embodiment of the invention in the form of a propeller, suitable especially for aerial vehicles, and wherein the angle of the series of blades with the axis of the propeller shaft is controlled by the attachment of a vane. The propeller shaft indicated at 8 carriesa plurality of arms 2 which are provided with sockets or sleeves 3, said sleeves being in a plane perpendicular to the axis of the shaft 8. In each of said sleeves the stem 9 of a blade support 6 is rotatably located so that the support 6 carrying a series of alined blades a may assume any angle with respect to the axis of the shaft 8. The blade support a is rigidly connected with a vane d, and during the rotation of the propeller this vane (I will have a. tendency to turn the blade In said last named figure all of the same is practically the same as the direction of the resultant it of the forward velocity 2' of the driven machine and the rotary velocity k of the propeller blades.

A modified form of propeller is shown in Fig. 5. The blades or for this propeller are rigidly connected with a support 6' with which the vane (Z is integral and which support is mounted by means of a thin arm 7 on the hub s of the propeller. A deflection of the support 6' for the purpose of forcing the series of blades a into angular relation to the axis of the propeller is made possible in this instance under the influence of the vane d, as the support 6 is connected with the propeller shaft by a plurality of, thin wires 0 similar to the spokes in a wire wheel. If the propeller is rotated at high speed, the vane (i owing to its rigid connection with the propeller blades will be deflected and twist thereby the supporting arm 7 into proper position. Upon decrease of the velocity of the propeller, the arm will be returned to normal position on account of the elasticity of the wires 0.

Figs. 6 and 7 illustrate a form of a propeller blade which is particularly suitable for propulsion of water vehicles. lVhile 1n the constructions illustrated in Figs. 3, 4 and 5 the guiding or directing vane (Z forms part of the support for the propeller blades, in the modification shown in Fig. 6 the directing vane f issecured to the outer end of the propeller blade at which is rotatably mounted by means of the stem '9 in the propeller hub H. The leading edge of the propeller blade on will be deflected owing to the attachment of the vane f and owing to its support in the hub into a direction coinciding with the direction of the resultantpf the rotary velocity and of the axial veloclty of the propeller shaft.

Fig. 10 illustrates in front elevation a fan or propeller blade 29 substantially as shown with reference to Figs. 1, 2 and 9,

said blade having two wing portions which i are diametrically opposite to each other; in its reduced center portion the blade p is provided with an aperture n whereby it may be secured to the propeller shaft. This form of blade is particularly suitable for fans comprising a number of the blades in serial alinement and properly spaced from each other.

I claim:

1. In a fan, the combination of a shaft, a plurality of fan blades in serial alinement carried by said shaft, said fan blades being spaced from each other a distance large enough to permit a relatively large volume of air to pass between adjacent' blades, said distance being not large enough to cause the inclusion of dead air between adjacent blades.

2. In a fan, the combination of a shaft,

a plurality of fan blades in serial alinement carried by said shaft, said fan blades being uniformly spaced from each other, the intervening spaces between each two fan blades being large enough to permit a .relatively large volume of air to pass between adjacent blades, said spaces, however, being not large enough to cause the inclusion of dead air between adjacent blades.

3. In a fan, the combination of a shaft, a plurality of fan blades in serial arrange ment along a line forming an angle with the axis of said shaft, the distance between any two adjacent blades of the series located farther back from the front end of the fan than any other pair being not larger than the distance between the blades of said other air.

4. A propeller comprising in combination a plurality of sets of blades, each set of blades being mounted for independent rotation about an individual axis radiating from the axis of rotation of the propeller as a whole, and a guide vane for each set of blades mounted to rotate with the propeller in air undisturbed by said blades, said vane when the propeller is working lying in the direction of the resultant of the forward velocity and the linear rotary velocity of the meeting edges of the blades.

5. A propeller comprising in combination a plurality of sets of blades, each set of blades being mounted for independent rotation about an individual axis radiating from the axis of rotation of the propeller as a whole, and a guide vane for each set of blades mounted to rotate with the propeller in airundisturbed by said blades, said vane when the propeller is working lying in the direction of the resultant of the forward velocity and the linear rotary velocity of the leading edges of the blades, a plane passing through the centers of the blades of each set including also the individual axis of the set.

6. A propeller comprising in combination a plurality of sets of curved blades, each set of blades being mounted for independent rotation about an individual axis radiating from the axis of rotation of the propeller as a whole, and a guide vane for each set of blades mounted to rotate with the propeller in air undisturbed by said blades. said vane when the propeller is working lying in the direction of the resultant of the current velocity and the linear rotary velocity of the meeting edges of the blades, the curves of all the blades in each set being struck from centers located on an imaginary line running centrally through the blades of the set.

7. A propeller comprising in combination a plurality of sets of curved blades, each set of blades being mounted for independent rotation about an individual axis radiating from the aris of rotation of the propeller as .& 1,192,111

a whole, and a guide vane for each set of blades mounted to rotate With thepropeller in air undisturbed by said blades, said vane when the propeller is Working lying in the direction of the resultant of the current velooity and the linear rotary velocity of the meeting edges of the blades, the curves of all the blades in each set being struck from centers located on an imaginary line running centrally through the blades of the 10 set, said imaginary line also intersecting the individual axis of the set.

In testimony whereof I have afiixed my signature in presence of two witnesses.

WALTER CHARLES-PITTER. Witnesses:

C. P. LIDDON,

B; WILSON.

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