US3258074A

US3258074A - Cycloidal ship propeller

Info

Publication number: US3258074A
Application number: US446203A
Authority: US
Inventors: Blickle Karl; Hoflich Eugen; Hub Wilhelm
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1962-11-14
Filing date: 1965-04-07
Publication date: 1966-06-28
Anticipated expiration: 1983-06-28

Description

June 28, 1966 K. BLICKLE ETAL CYCLOIDAL SHIP PROPELLER Original Filed Nov. 14, 1962 INVENTOR5 Karl Buckle Eugen H6Hich WiLhelrn Hub United States Patent Original application Nov. 14, 1962, Ser. No. 239,866. Divided and this application Apr. '7, 1965, Ser. No.

7 Claims. ((31. 170-151 The present application is a divisional of. our copending application, Serial No. 239,866, filed November 14, 1962, and entitled Cycloidal Ship Propeller.

This invention relates to cycloidal propellers, particularly for ships, which have a blade wheel body adapted to be rotatably supported and carrying a plurality of blades extending substantially parallel to the axis of rotation of the body while being pivotally mounted on the body. These blades are uniformly circumferentially distributed on the body along a blade circle which is coaxial with the axis of rotation of the body.

With propellers of the cycloidal type, the blades are tilted about a central axis thereof conforming to the axis of rotatable support of the blades to change the ange of attack of the blades, thereby to obtain propulsion in a direction at right angles to the axis of rotation of the blade wheel body. The individual blades of the propeller are connected through a blade actuating linkage system, a socalled kinematic, which includes a central control disc common to all of the blades and which is operable from outside the blade body for adjusting the linkage.

The linkage system includes at least one lever fixed to the respective blade, which may be termed a blade lever, and also includes a connecting rod linked to the blade lever and, furthermore, includes a crank lever pivotally connected in the region of the junction of the arms thereof to the blade wheel body with one end of one arm of the crank lever being connected to the connecting rod while the end of the other arm of the lever is connected to the control disc.

With many ships employing cycloidal propellers, two propellers are required to obtain the propulsive effort desired and, when the ship is on a straight course, it is desirable to compensate for the respective torques of the two propellers by causing them to rotate in respectively opposite directions.

With known cycloidal propeller blade actuating linkage systems as set forth, for example, in United States 2,250,- 772 or 2,291,062, the drawback is encountered that, with propellers rotating in respectively opposite directions, the blade wheel body and the blade actuating linkage system has to be designed differently for propellers rotating in clockwise direction than for propellers rotating in counterclockwise direction. This in turn means that for producing clockwise rotating propellers, machine shop drawings, models, devices and similar manufacturing aids have to be produced other than what is necessary for counterclockwise rotating propellers so that the cost for the manufacture and the stockkeeping of the propellers is considerably increased.

It is, therefore, an object of the present invention to provide a cycloidal ship propeller, which will overcome the above mentioned drawbacks.

. It is another object of this invention to provide a cycloidal ship propeller and in particular the blade actuating linkage system in such a way that the same type of blade wheel body may be employed for propellers rotating in clockwise direction and for propellers rotating in counter-clockwise direction.

These and other objects and advantages of the invention will appear more clearly from the following specifi- 3,258,074 Fatented June 28, 1966 cation in connection with the accompanying drawings, in which:

FIGURES 1, 2 and 3 diagrammatically illustrate three embodiments of a cycloidal ship propeller with a blade actuating linkage system according to the present invention;

FIGURE 4 is a view showing the propeller of FIGURE 1 with the control disc shifted oil center; and

FIGURE 5 is a section taken on line V-V of FIGURE 4 showing in more detail the construction of a slide block forming a part of the slide linkage system.

General arrangement In order to overcome the drawbacks outlined above with heretofore known linkage systems for cycloidal ship propellers, according to the present invention, the axis of the pivot by means of which the crank lever of the blade actuating linkage system is linked to the blade wheel body is arranged in a radial plane defined by the axis of rotation of the blade wheel body and the pivot axis of the respective blade actuated by said blade actuating linkage system.

A blade actuating linkage system designed in this way makes it possible to produce one and the same type blade wheel body for propellers rotating in clockwise direction as well as for propellers rotating in counter-clockwise direction. Thus, instead of providing two blade wheel bodies as was heretofore necessary, when employing a blade wheel linkage system according to the invention, only one type of blade wheel body is necessary so that the costs for keeping stock and replacement parts will be greatly reduced and the replacement of the parts Will be greatly simplified.

Structural arrangement Referring now to the drawings in detail, it should be noted that, in FIGURES l, 2 or 3, the blades are illustrated in their middle position, i.e., in a position in which the blade is tangential to the circle which has its center located on the pivot axis of said blade.

As will be seen from the figures in the drawings in which the same elements have been designated with the same reference numerals, within the blade Wheel body 1 of the cycloidal propeller, which blade wheel body is rotatably journalled in the ship body, there is provided a control disc 3 common to all of the blades 2 and operable from the outside of the blade wheel body. In addition thereto, within said rotatable blade wheel body 1 there is provided a number of blade actuating linkage systems corresponding to the number of the blades with which the blade wheel body is equipped. For purposes of clarity, however, each of the various FIGURES 1 to 3 illustrates one blade wheel actuating linkage system only whereas FIGURE 4 shows the cycloidal propeller according to FIGURE 1 with four blades A, B, C, D and all the four actuating linkage systems pertaining thereto.

As will be seen from the FIGURES 1-4, each blade actuating linkage system has a cross head 4 pivotally journalled in control disc 3, and also comprises a crank lever 7 which on one end is slidably journalled in cross head 4 and on the other end is pivotally connected to a connecting rod 5 and is furthermore by means of a pivot 6 pivotally connected to the blade wheel body 1. Each blade actuating linkage system furthermore comprises a blade lever 8. The axis of the pivot 6 mounted on the blade wheel body 1 is located in the radial plane 10 defined by the axis of rotation 11 of the blade wheel body 1 and the pivot axis 12 of the respective blade 2 pertaining thereto.

It will be appreciated that if control disc 3 has been moved out of its central position for instance by a control stick connected to the center of the control disc, 21

controlled oscillating movement about the middle position of blades 2 will be imparted upon said blades through the intervention of the control disc 3. In the middle position, the profile chord 13 is tangent to the blade circle 9.

A favorable design of the blade actuating linkage system is illustrated in FIGURE 1. This design obtains a favorable adjustment of the blade angle between the profile chord 13 of blades 2 and the tangent to the blade wheel circle 9 and, thereby, obtains a favorable course of the so-called blade angle curve and, thus, a high degree of efficiency of the propeller. Furthermore, better lubrication of the individual joints of the blade actuating system is obtained.

More specifically, crank lever 7 is so constructed that when the blades occupy their tangential positions as shown in FIGURE 1, that arm of the crank which is connected to control disc 3 forms an angle of approximately 10 degrees with radial plane 10, while both arms of crank lever 7 are located on one and the same side of the said radial plane 10.

Expressed generally, according to one embodiment of the present invention, the blade actuating linkage system is so designed that in the middle position of the respective blade, the lever arm connected to the control disc and pertaining to the crank lever, confines with the radial plane an angle of 10 while the lever arms of the crank lever are located on one and the same side of the radial plane.

According to a further development of the invention, the blade actuating linkage system is so designed that the lever arms of the crank lever confine with each other an angle of 100 while the said lever arms are located on one and the same side of the radial plane. Such an arrangement is shown in FIGURE 2 according to which the two lever arms of crank lever 7 confine with each other an angle of 100", while that lever arm of two arm lever 7 which is connected to the control disc 3 will be located in the radial plane 10 when the blade 2 occupies its tangential position.

The arrangement shown in FIGURE 3 differs slightly from that of FIGURES 1 and 2 inasmuch as according to FIGURE 3 the angle confined by the two lever arms of crank lever 7 amounts to 100, whereas that lever arm which is connected to control disc 3 is in tangential position of blade 2 inclined with regard to the radial plane 10 by an angle of 10. Also in this instance the two lever arms of the crank lever 7 are located on one and the same side of said radial plane 10.

By appropriately selecting the angles between the lever arm pertaining to the crank lever and connected to said control disc and said radial plane and the angle of the lever arms of the crank lever, it will be possible to adjust the blade pitch to more favorable values than was possible with heretofore known designs of blade actuating linkage systems, so that with the present invention better degrees of efiiciency of the propeller can be obtained than were heretofore possible.

Furthermore, by an appropriate design of the blade actuating linkage system according to the present invention, there will be obtained the advantage that with the control center in a position out of its central position the torques acting on the control disc and varying several times from positive to negative peaks during a rotation of the propeller, will have approximately the same magnitude. Consequently, the peaks of the reciprocating forces in the individual joints of the kinematics will be reduced while simultaneouly a more favorable lubrication will be obtained than was heretofore obtainable.

In FIGURE 4 a cyloidal propeller is shown With the cotnrol disc 3 shifted otf center so that the position of the four propeller blades A, B, C and D in the four quadrants will be seen.

The center point 11 of the control disc 3 is displaced on the transverse diameter 10 from the center point of the blade wheel body 1 by a distance e towards the left. This displacement corresponds to a direction of attack of the force of the water on the propeller and thereby a direction of advancement of the propeller and of the ship in upward direction (with regard to the draw ing), as shown in FIGURE 4 by arrow p.

In both positions A, C of the propeller blade 2 in which the pivot axis 12 of the blade coincides with the point of intersection of the transverse diameter 10 with the blade wheel orbit 9, the blade is tangential to the blade wheel orbit as was the case before.

In the two other positions B, D which correspond to an advancing movement of the blade on the bladewheel orbit by or 270 respectively with respect to the blade position A the blades are tilted out of the tangential position, in such a way that the head of the blade at the top of the view is tilted outwardly, and at the bottom of the view the head of the blade is tilted toward the inside. That blade which is designated A is after a rotation of the wheel body in the direction of the arrow q of 90 in the position of the blade B, after a further rotation of 90 (180 counting from the starting position) it has reached the position of the blade C, namely, again a tangential position, and finally, after a further rotation of 90 (270 from the starting position) it has reached the position of the blade D.

With regard to the slide block element of cross head 4, as will be seen in FIGURE 5, this element slidably rcceives the pertaining arm of the crank lever 7 and is pivotally connected by pivot pin 4a with the control disc 3 for free pivotal movement thereon.

The problem of designing a blade wheel body and blade actuating linkage system for cycloidal propellers which can be employed for both clockwise rotating propellers and counter-clockwise propellers is by no means as simple as by merely pivoting the linkage to the blade wheel body on a line passing through the center of rotation of the blade wheel body and the pivot axis of the respective blade. Many attempts have been made to find such a linkage but heretofore such linkage systems have been defective in providing that the propeller will operate efficiently and substantially free of cavitation.

Freedom of the propeller from cavitation is extremely important, inasmuch as the reliability and safety of the propeller depend largely upon this feature. The propeller at the same time must have a high degree of efficiency throughout the useful range of pitch thereof.

The structure disclosed in the present invention solves this problem satisfactorily for the first time and provides a suitable propeller construction which provides for efficient cavitation-free operation of propeller while one and the same blade wheel body can be employed for both clockwise rotating and counter-clockwise rotating propellers. The blades can, of course, be reversed on the propeller body when the direction of rotation of the propeller body is reversed and by forming the linkage connecting the control plate with the blade levers of fiat members, such as from stamped sheet metals parts or flat cast, or forged members, the linkage members themselves can also be employed for propellers of both senses of rotation.

It will be evident that the provision of a suitable blade actuating linkage system and a suitable blade wheel body in accordance with the principles of the present invention greatly reduces the cost of manufacture of the propellers and reduces the inventory of parts and the like.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions; and accordingly, it is desired to comprehend such modifications within this invention as may fall Within the scope of the appended claims.

What is claimed is:

1. A cycloidal ship propeller comprising: a blade wheel body rotatable on a central axis, a plurality of blades arranged along a circle concentric with said blade wheel central axis and in substantially uniformly spaced relationship to each other, pivot means pivotally supporting said blades on said blade wheel body, each pivot means defining'a pivot axis for its respective blade, said pivot axes being substantially parallel to each other and to said central axis, each of said blades being capable of an oscillating movement about its pivot axis and about a middle position of the blade in which the respective blade is tangential to the circle along which the pivot axes of said blades are arranged, adjustable control means common to all of said blades and movable selectively from a central position coaxial with said central axis of said blade wheel body into any one of a plurality of positions eccentric with regard to said central axis of said blade wheel body and vice versa to govern the oscillating movement of said blades, a plurality of blade actuating linkage systems respectively operatively connecting said adjustable control means with said pivot means so that each of said blades will be operable in response to a rotation of said wheel body and while said adjustable control means occupies any of its possible positions to carry out an oscillating movement having the predetermined magnitude of the blade angles which correspond to the respective circular positions of the pivot axes of the blades during their circular movement with said blade wheel body, each of said blade actuating linkage systems comprising at least one lever operatively connected to the respective blade pivot means and also comprising a connecting rod linked to said lever, each of said blade actuating linkage systems furthermore comprising a crank lever having one of its arms connected to said connecting rod and having its other arm operatively linked to said adjustable control means, the means linking the said other arm of each crank lever to said control means comprising a member tiltably mounted on said adjustable control means and slidably engaging said other arm of said crank lever, means pivotally connecting the crank lever in the region of the junction of the two arms thereof to a point on the blade wheel body, said point on the blade wheel body being located in a radial plane passing through the axis of rotation of said blade wheel body and through the axis of the pivotal connection of the respective blade with said blade wheel body said point on the blade wheel body being located between said areas, said other arm of said crank lever forming with said radial plane an angle of approximately 10, the arrangement being such that for each blade and the bladeadjusting linkage system pertaining thereto, in the central position of said control means, with regard to the direction of rotation of said wheel body,'said lever and said rod and at least that arm of the crank lever which is linked to said rod, all pertaining to said blade actuating linkage system, are located behind said radial plane.

2. A cycloidal ship propeller comprising: a blade wheel body rotatable on a central axis, a plurality of blades arranged along a circle concentric with said blade Wheel central axis and in substantially uniformly spaced relationship to each other, pivot means pivotally supporting said blades on said blade wheel body, each pivot means defining a pivot axis for its respective blade, said pivot axes being substantially parallel to each other and to said central axis, each of said blades being capable of an oscillating movement about its pivot axis and about a middle position of the blade in which the respective blade is tangential to the circle along which the pivot axes of said blades are arranged, adjustable control means common to all of said blades and movable selectively from a central position coaxial with said central axis of said blade wheel body into any one of a plurality of positions eccentric with regard to said central axis of said blade wheel body and vice versa to govern the oscillating movement of said blades, a plurality of blade actuating linkage systems respectively operatively connecting said adjustable control means with said blade pivot means so that each of said blades will be operable in response to a rotation of said wheel body and while said adjustable control means occupies any of its possible positions to carry out an oscillating movement having the predetermined magnitude of the blade angles which correspond to the respective circular positions of the pivot axes of the blades during their circular movement with said blade wheel body, each of said blade actuating linkage systems comprising at least one lever operatively connected to the respective blade pivot means and also comprising a connecting rod linked to said lever, each of said blade actuating linkage systems furthermore comprising a twoarm crank lever having one of its arms connected to said connecting rod and having its other arm operatively linked to said adjustable control means, the means linking the said other arm of each crank lever to said control means comprising a member tiltably mounted on said adjustable control means and slidably engaging said other arm of said crank lever, said one arm together with said other arm forming an angle of approximately means pivotally connecting the crank lever in the region of the junction of the two arms thereof to a point on the blade wheel body, said point on the blade wheel body being located in a radial plane passing through the axis of rotation of said blade wheel body and through the axis of the pivotal connection of the respective blade with said blade wheel body and also being located between said axes, the arrangement being such that for each blade and the blade adjusting linkage system pertaining thereto, in the central position of said control means, with regard to the direction of rotation of said wheel body, said lever and said rod and also at least that arm of the crank lever which is linked to said rod, all pertaining to said blade actuating linkage systems, are located behind said radial plane.

3. A cycloidal ship propeller comprising; a blade wheel body, a plurality of blades pivotally supported by said blade wheel body and having their pivot axes arranged along a circle in substantially uniformly spaced relationship to each other, said pivot axes being substantially parallel to each other, each of said blades being capable of an oscillating movement about its pivot, adjustable control means common to all of said blades and movable selectively from a central position coaxial with said blade Wheel body into any one of a plurality of positions eccentric with regard to said blade wheel body and vice versa to govern the oscillating movement of said blades, each of said blades comprising a pivot and being oscil- 'latable about a middle position thereof in which the respective blade is tangential to the circle along which the pivot axes of said blade ar arranged, a plurality of blade actuating linkage systems respectively operatively connecting said adjustable control means with said blades, each of said blade actuating linkage systems comprising at least one lever operatively connected to the respective blade pivot and also comprising a connecting rod linked to said lever, each of said blade actuating linkage systems furthermore comprising a two-arm lever pivotally connected to said blade wheel body and having one of its arms connected to said connecting rod and having its other arm connected to said adjustable control means, the arrangement being such that for each blade and the linkage system pertaining thereto the axis of the pivotal connection of the two-arm lever of the respective linkage system with said blade wheel body is located in the radial plane which passes through the axis of rotation of said blade Wheel body and through the axis of the pivotal connection of the respective blade with said blade wheel body, and in which middle position of the respective blade that lever arm of said two-arm lever which is connected to said adjustable control means forms with said radial plane an angle of about 10 degrees, the lever arms of said two-arm lever in said middle position of the respective blade being located at one and the same side of said radial plane.

4. A cycloidal ship propeller according to claim 3, in

which each of said blades oscillates about a middle position in which th blade is tangential to the circle along which the pivot axes of said blades are arranged, and in which the lever arms of said two-arm lever confine with each other an angle of about 90 to 100 degrees, the lever arms of said two-arm lever in said middle position of the respective blade being located at one and the same side of said radial plane.

5. A cycloidal ship propeller comprising; a blade wheel body rotatable on a central axis, a plurality of blades pivotally supported by said blade wheel body and having their pivot axes arranged along a circle concentric with said blade wheel central axis and in substantially uniformly spaced relationship to each other, said pivot axes being substantially parallel to each other and to said central axis, adjustable control means common to all of said blades and movable selectively from a central position coaxial with said central axis of said blade wheel body into any one of a plurality of positions eccentric with regard to said central axis of said blade wheel body and vic versa to govern the oscillating movement of said blades, each of said blades comprising a pivot and being oscillatable about a middle position of the blade in which the respective blade is tangential to the circle along which the pivot axes of said blades are arranged, a blade actuating linkage system operatively connecting said adjustable control means with each said blade and comprising at least one lever operatively connected to the respective blade pivot and also comprising a connecting rod linked to said lever, each said blade actuating linkage system furthermore comprising a two-arm lever having the outer one of its arms connected to said connecting rod and have the outer end of its other arm operatively linked to said adjustable control means, means pivotally connecting the two-arm lever in the region of the junction of the two arms thereof to a point on the blade wheel body which is located in a radial plane passing through the said central axis of said wheel body and through the axis of the pivotal connection of the respective blade with said blade wheel body and also being located between said axes, the said one lever and rod and at least that arm of the two-arm lever which is linked to said rod, all pertaining to said blade actuating linkage system, in the central position of said control means, being located behind said radial plane with respect to the direction of rotation of said body.

6. A cyclodial ship propeller according to claim 5, in which each two-arm lever forms an angle and the means linking the said other arm of each two arm-lever to said control means comprises a member tiltably mounted on said adjustable control means and slidably engaging said other arm of said two-arm lever, said last mentioned arm forming with said radial plane an angle of approximately 10.

7. A cycloidal ship propeller according to claim 5, in which each two-arm lever forms an angle and the means linking the said other arm of each two-arm lever to said control means comprises a member tiltably mounted on said adjustable control means and slidably engaging said other arm of said two-arm lever, said one arm together with its other arm forming an angle of approximately 100".

References Cited by the Examiner UNITED STATES PATENTS 2,250,772 7/1941 Mueller et al. 170148 2,859,829 11/1958 Mueller 170-147 FOREIGN PATENTS 114,323 9/1929 Austria. 285,911 10/ 1928 Great Britain. 721,374 1/1955 Great Britain.

SAMUEL LEVINE, Primary Examiner.

E. A. POWELL, JR., Assistant Examiner.

Claims

1. A CYCLOIDAL SHIP PROPELLER COMPRISING: A BLADE WHEEL BODY ROTATABLE ON A CENTRAL AXIS, A PLURALITY OF BLADES ARRANGED ALONG A CIRCLE CONCENTRIC WITH SAID BLADE WHEEL CENTRAL AXIS AND IN SUBSTANTIALLY UNIFORMLY SPACED RELATIONSHIP TO EACH OTHER, PIVOT MEAN PIVOTALLY SUPPORTING SAID BLADES ON SAID BLADE WHEEL BODY, EACH PIVOT MEANS DEFINING A PIVOT AXIS FOR ITS RESPECTIVE BLADE, SAID PIVOT AXES BEING SUBSTANTIALLY PARALLEL TO EACH OTHER AND TO SAID CENTRAL AXIS, EACH OF SAID BLADE BEING CAPABLE OF AN OSCILLATING MOVEMENT ABOUT ITS PIVOT AXIS AND ABOUT A MIDDLE POSITION OF THE BLADE IN WHICH THE RESPECTIVE BLADE IS TANGENTIAL TO THE CIRCLE ALONG WHICH THE PIVOT AXES OF SAID BLADES ARE ARRANGED, ADJUSTABLE CONTROL MEANS COMMON TO ALL OF SAID BLADES AND MOVABLE SELECTIVELY FROM A CENTRAL POSITION COAXIAL WITH SAID CENTRAL AXIS OF SAID BLADE WHEEL BODY INTO ANY ONE OF A PLURALITY OF POSITIONS ECCENTRIC WITH REGARD TO SAID CENTRAL AXIS OF SAID BLADE WHEEL BODY AND VICE VERSA TO GOVERN THE OSCILLATING MOVEMENT OF SAID BLADES, A PLURALITY OF BLADE ACTUATING LINKAGE SYSTEMS RESPECTIVELY OPERATIVELY CONNECTING SAID ADJUSTABLE CONTROL MEANS WITH SAID PIVOT MEANS SO THAT EACH OF SAID BLADES WILL BE OPERABLE IN RESPONSE TO A ROTATION OF SAID WHEEL BODY AND WHILE SAID ADJUSTABLE CONTROL MEANS OCCUPIES ANY OF ITS POSSIBLE POSITIONS TO CARRY OUT ON OSCILLATING MOVEMENT HAVING THE PREDETERMINED MAGNITUDE OF THE BLADE ANGLES WHICH CORRESPOND TO THE RESPECTIVE CIRCULAR POSITIONS OF THE PIVOT AXES OF THE BLADES DURING THEIR CIRCULAR MOVEMENT WITH SAID BLADE WHEEL BODY, EACH OF SAID BLADE ACTUATING LINKAGE SYSTEM COMPRISING AT LEAST ONE LEVER OPERATIVELY CONNECTED TO THE RESPECTIVE BLADE PIVOT MEANS AND ALSO COMPRISING A CONNECTING ROD LINKED TO SAID LEVER, EACH OF SAID BLADE ACTUATING LINKAGE SYSTEMS FURTHERMORE COMPRISING A CRANK LEVER HAVING ONE OF ITS ARMS CONNECTED TO SAID CONNECTING ROD AND HAVING ITS OTHER ARM OPERATIVELY LINKED TO SAID ADJUSTABLE CONTROL MEANS, THE MEANS LINKING THE SAID OTHER ARM OF EACH CRANK LEVER TO SAID CONTROL MEANS COMPRISING A MAMBER TILTABLY MOUNTED ON SAID ADJUSTABLE CONTROL MEANS AND SLIDABLY ENGAGING SAID OTHER ARM OF SAID CRANK LEVER, MEANS PIVOTALLY CONNECTING THE CRANK LEVER IN THE REGION OF THE JUNCTION OF THE TWO ARMS THEREOF TO A POINT ON THE BLADE WHEEL BODY, SAID POINT ON THE BLADE WHEEL BODY BEING LOCATED IN A RADIAL PLANE PASSING THROUGH THE AXIS OF ROTATION OF SAID BLADE WHEEL BODY AND THROUGH THE AXIS OF THE PIVOTAL CONNECTION OF THE RESPECTIVE BLADE WITH SAID BLADE WHEEL BODY SAID POINT ON THE BLADE WHEEL BODY BEING LOCATED BETWEEN SAID AREAS, SAID OTHER ARM OF SAID CRANK LEVER FORMING WITH SAID RADIAL PLANE AN ANGLE OF APPROXIMATELY 10*, THE ARRANGEMENT BEING SUCH THAT FOR EACH BLADE AND THE BLADE ADJUSTING LINKAGE SYSTEM PERTAINING THERETO, IN THE CENTRAL POSITION OF SAID CONTROL MEANS, WITH REGARD TO THE DIRECTION OF ROTATION OF SAID WHEEL BODY, SAID LEVER AND SAID ROD AND AT LEAST THAT ARM OF THE CRANK LEVER WHICH IS LINKED TO SAID ROD, ALL PERTAINING TO SAID BLADE ACTUATING LINKAGE SYSTEM, ARE LOCATED BEHIND SAID RADIAL PLANE.