US2978036A - Control device for blades of cycloidal propellers - Google Patents

Description

April 1961 E. SCHNEIDER 2,978,036

CONTROL DEVICE FOR BLADES 0F CYCLOIDAL PROPELLERS Filed Dec. 26, 1956 2 Sheets-Sheet 1 FIG. 1a

INVENTOR.

W, f- M #fforngys April 4, 1961 E. SCHNEIDER CONTROL DEVICE FOR BLADES OF CYCLOIDAL PROPELLERS Filed Dec. 26, 1956 2 Sheets-Sheet 2 w mam 2 5 wnm fl 8 Jim MMW CONTROL DEVICE FOR BLADES F CYCLOIDAL PROPELLERS Ernst Schneider, Vienna, Austria, assignor to J. M. Voith G.m.b.H., Heidenheim, Germany Filed Dec. 26, 1956, Ser. No. 654,051

Claims priority, applicafion Austria Jan. 11, 1956 7 Claims. (Cl. 170-451) This invention relates to a control device for the blades of cycloidal propellers. In cycloidal propellers the magnitude and direction of the thrust of the blades is continuously regulated by displacing the point of intersec tion of the normal onto the blades in the blade-pivot with the normal onto the direction of travel at the center of the blade orbit. The point of intersection of these normals onto the blades lies inside or outside the blade orbit or for-one part of the blade orbit it lies inside and for the other part of the blade orbit outside said orbit.

It is known that the control efiect or the kinematics of a'crank-slide oscillator may be approximated without oscillating sliding pivots. The most simple example is the sinusoidal kinematic system where the blades are controlled by a crank drive as in the case of paddle wheels.

It is known to use superimposed interlocking bodies. formed according to three-dimensional curves as control members to regulate the feathering of the blades by means of the links of pantographs'. It is obvious that several bodies formed according to three-dimensional curves and cooperating with pantographs' can never provide a control point from which all blades may bepositively controlled.

To reduce the drawbacks of that kinematic system it has already been proposed to derive the feathering from an arcuately moving crank by means of rocker levers. A special case of a kinematic system comprising an arcuately moving mechanism is also known, which is derived from the pantograph and in which a bell-crank lever having arms of equal length directed at right angles to each other oscillates with the point of intersection of the arms moving on an arc of a circle having a radius equal to the length of the arms of the bell-crank lever. One end of the bell-crank lever is linked by a push' rod to the blade lever; the other end of the bell-crank lever is relatively guided on a circular ring which serves as an intermediate member and whose center is eccentric with respect to the center of the bladeorbit. M For this reason the control of the blades cannot be derived directly from displacements of the center of the blade orbit but the intermediate member consisting of the ring must be driven synchronously or is ochronously with the speed of the cycloidal propeller. Each blade is individually linked by'the levers of the kinematic system to the ring driven by said intermediate member. In order to increase'the pitch it is also known in several variants of sliding crank kinematic systems to'step up the oscillations so that the derived amplitudes of the oscillations performed by the blades exceed the'deriving oscillations of'a sliding crank, the diameters, of the circle'of which are controlledi'n direction and magnitude from a point which can be'displaced in all directions (control point).

The invention provides" akinematic system from which the essential characteristics of the feathering produced by news kinematic systems can-* be derived in succes s'ion witho utan oscillating?slidingpivot merely'byva'ryf ingan angle; and'with' which th'e operationcanbe performed in a single plane without staggering ofthe transmissions, with or without synchronization. V g

v The invention is characterized in that a' bell-crank lever which is guided with the point of intersection of its arms moving along an arc of a circle and with one end of the bell-crank lever moving on a circle has its arms arranged to include an angle exceeding deg. and that the end point of the bell-crank lever which is moved in a circle relative to the blade orbit coincides with the control point. 7 g

Some illustrative embodiments of the invention are shown on the drawings, in which: 1

Fig. la is a fragmentary horizontal sectional view and showing a cycloidal propeller assembly with a control system accordingto the invention for one blade, the system being in the neutral position.

Fig, Ibis a view similar to Fig. 1a and shows the control system in an effective position.

Fig. 2 is a view similar to Fig. 1b and shows a modification, taken on' line IIII of Fig. 3.

. Fig. 3 is a fragmentary vertical sectional view taken on line III-III of Fig. 2. v

1 Fig. 4 i s an enlarged vertical sectional view illustrating as a detail of a control system according to the invention the connection between the control pin and the control linkage for a three-blade propeller.

With reference to the drawings, the cylindrical rotor frame 1 is aflixed to the hull and surrounds a rotor 2 having the center M. Also afiixed to the hull is a bearing body 3 formed with a step bearing 4 carrying the cylindrical extension 5 aliixed to the rotor, e.g., by bolts and nuts, and arranged to be driven by a pinion 5.

The rotor 2 comprises a rotor top 6 and a rotor bottom 7. The members 6 and 7 are provided on their mutually facing surfaces with registering blade bearings 8 and 8, respectively, in which the blade pivot 22 is rotatably mounted at the distance R from the center M. This blade pivot 22 is rigid with the blade 9, which extends below the rotor bottom 7.

A bearing plate 10 is spaced above and rigidly aflix'ed to the rotor bottom 7 by any suitable means, e.g., by being formed with a depending circumferential flange welded to the bottom 7.

A bearing sleeve 15 has horizontal top and bottom flanges in slidable engagement with the underside of the rotor top 6 and the upper side of the bearing plate It Vertically slidably mounted in the bearing sleeve 15 is a spherical bearing or socket 14 for a ball pivot 13 which forms the lower end of a control pin 11, which extends through a central aperture in the rotor top 6 and is formed with an intermediate spherical enlargement 12, which is" mounted in the spherical bearing 12 carried by the bearing body 3.v The top end of the controlpin is formed with a-ball pivot 27 surrounded. by a spherical bearing provided at the end of a control rod 26. The control pin 11 has a top extension which indicates the position of the pin. a

It will be noted that the p'ar'ts 14 and 15 form apa'r'all'el motion. e v

With reference to Figsl la and lb, an annular disc 16 rotatably mounted on the bearing sleeve 15 forms an end portion of a first arm 17a of a two-armed control lever having a-second arm 17h,-which includes an anlge 6=180 with the arm 17a.- A cranklike link 23 is'piv oted atone end at 24 to the junction between" the two arms 17a, 17b and at the'other end at- 25to the rotor top 6; The free end of theleve'r arm 17b'is pivoted at 18' to'one end of'a push" ' r'od 19,1 the other end of pivoted by the pin 20 to ablade lever 21, which is' rigidly connected by the blade pivot 22 to the blade 9.

The mode of operation of the assembly shown in Figs. 1a and lb will be described hereinafter.

In Fig. 1a the system is in its neutral position, the ball pivot 13 of the control pin 11, beingat the center M of the rotor.

In Fig. 1b the control pin 11 hah been moved by the control rod 26 to displace the ball pivot 13 from the center M of the rotor 2 by the eccentricity e. If it is imagined that the drawing revolves with the rotor 2 in the direction the control center consisting of the ball pivot 13, the bearing 14 and the sleeve 15 being held by the pin 11 and rod 26 against a rotation with the rotor 2 the ball pivot 13 will describe in the direction a circle indicated at d in Fig. 1b. During this movement of the steering center 1315, the link 23 will be pivotally moved about 25 to constrain the pivot 24 at the junction between the lever arms 17a and 17b to move along an arc of a circle. The rotation of the steering center 1315 relative to the rotor 2 and the arcuate movement of the pivot 24 relative to the rotor 2 are superimposed at the pivot 18 and cause the same to describe a compound curve K.

In the example shown in Fig. 1b, where the angle 6 between the lever arms 17a and 17b is 180, this compound curve K is an ellipse. The size of this ellipse will increase with the eccentricity e of the steering center 13-15 relative to the center M of the rotor 2. For e= (Fig. la), the compound curve will disappear and the pivot 18 will rotate with the rotor so that the blade will always extend tangentially with respect to its orbit, and will not produce a thrust (zero pitch position of the propeller).

The larger the ratio between the major and minor axes of the compound curve K and the smaller the displacement of the point 18 on the compound curve between the positions corresponding to the 0 and 180 positions, respectively, of the steering center 13-15 on the circle d, the more exact will be the actual oscillation of the blade. This depends on the angle 6 between the lever arms 17a and 17b measured on the side opposite to the link 23. If this angle is 90 or less the ratio between the two axes of the compound curve will be small, resulting in an unsatisfactory loading of the blades as they revolve in their orbit because the velocity of oscillation of the blades of the rearwardly moving half of the rotor must be limited for strength reasons particularly when the blade has a high pitch and this causes an insufiicient load to be placed on the forwardly moving half of the rotor.

If the angle 6 between the lever arms 17a, 17b on the side opposite to the link is substantially increased beyond 90 to as much as 180 the compound curve will be modified in such a manner that a higher load is placed on the blades, in the forwardly moving half of the rotor and, especially at high pitch, a desirable reduction of the velocity of oscillation of the blades in the rearwardly moving half of the rotor is obtained compared to an angle of 90 or less between the lever arms 17a and 17b. These advantages disappear when the angle betweenthe lever arms 17a and 17b on the side opposite to the link 23 is increased substantially above 180.

A preferred arrangement is shown in Figure 2 in the neutral position, where the angle 6' between the lever arms 17a and 17b on the side opposite to the link 23 is such that the arms 17b are aligned with the link 23 in the tangential position of the blade. This results in a compound curve K which is practically an arc of a circle having the center 25 and has a very small distance between the positions assumed by the point 18 in the 0 and 180 positions, respectively, of the steering center 1315 on the circle d. As a result, the blades will extend almost parallel to the direction of flow at any pitch at the points of the blade orbit where =0 and 180. This alignment of the link 23 with the lever arm 17b is not restricted to the angle 6' shown in Fig. 2 but can be obtained for other angles between the lever arms 17a and 17b if the location of the pivot 25 is so selected that the angle between the link 23 and the lever arm 17a is a supplement to the angle between the lever arms 17a and 17b in the tangential position of the blade.

Irrespective of the value of the angle between the lever arms 17a and 1711, these lever arms as well as the link 23 are preferably of equal length so that the points 13, 18 and 25 lie on a circle having its center at 24. In this case the free ends of the lever 17a, 17b will always lie on a chord of this circle so that the angle 132518 at the periphery over this chord will remain constant. When the end 16 of the two-armed lever is moved on a circle d relative to the rotor 2, the lever arm 17a as well as the lever arm 17b will oscillate about the same point 25.

The amplitude of the oscillation of the blade and with it the pitch of the propeller will be increased if the blade lever 21 is reduced in length relative to the distance between the points 18 and 25.

It has been shown hereinbefore that the control system according to the invention enables a particularly desirable control of the direction and magnitude of the propeller thrust by varying the pitch of the blades.

Figure 4 shows how control linkages according to the invention for several blades can be connected to a common control pin 11 so that all linkages lie in a common plane. The bearing sleeve 15 is again embraced by the ring 16 forming the free end of the lever arm 17a and carrying a bearing 28 rotatably surrounding the sleeve 15. A pair of bearings 29, 29' is rotatably mounted on the sleeve 15 above and below the bearing 28 and carried by a fork 30 forming the end of a lever arm 117a which corresponds to the lever arm 17a but forms part of a control linkage for a second blade. A second pair of bearings 31, 31' is rotatably mounted on the sleeve 15 above and below the bearings 29, 29', respectively and carried by a fork 32 forming the end of a lever arm 217a which corresponds to the lever arms 17a and 117a but forms part of a control linkage for a third blade. The bearings 29, 29 and 31, 31 are so arranged that the distance of the bearings carried by each fork form the direction of force through the control pin is equal. With this construction, all control linkages lie substantially in the same plane so that the overall height of the rotor may be minimized. The common control member constituted by the pin 11 may be moved in known manner by a stationary or freely rotatable or pivoted control column in order to vary the direction and magnitude of the thrust of the propeller with the eccentricity e. The arrangement of the pivots around the control pin 11 at the center of the rotor facilitates their accessibility while requiring only a small space so that the inertia of the transmission elements and their resistance to the flow of the .oil which fills the rotor are also reduced. Difficulties resulting from overlapping transmission elements may be overcome by forming said elements with cranks.

The kinematic system according to the invention eliminates the need for a sliding pivot oscillating in a centrally disposed small space and provides blade oscillations which approximate the oscillations of a crank-slide oscillator as closely as possible, whether or not they are stepped up, moreover the kinematic systems for all blades lie in one plane, without staggering, even where no synchronising device is provided.

Whereas some of these advantages are afforded individually by one or the other of the known kinematic systems, none of them affords all advantages as does the kinematic system according to the invention, requiring a minimum of pivots.

I claim:

, 1. A control system for a pivoted blade of a cycloidal propeller which comprises means for revolving the blade in a circular orbit around a center, a control lever having two arms forming a junction, each of said arms having a free end opposite to said junction, means connected to the free end of one of said arms and adapted to hold said free endof said one arm spaced from said center and against revolution with said blade and adjustable to vary the direction and amount of the eccentricity of said free end of said one arm With respect'to said center, a pivot disposed in a fixed relation to the pivotal axis of said blade and the center of said orbit,

a link pivoted to said pivot and to said junction, said two arms of said control lever including an angle exceeding 90 on the side opposite to said link, a blade lever rigidly connected to said blade, and a push rod having one end pivoted to said free end of said other arm and another end pivoted to said blade lever, whereby a revolution of said blade will cause said junction to describe an arc ofa circle about said pivot and cause an oscillation of said blade through the intermediary of said other arm of said control lever, said push rod and said blade lever, in dependence on the direction and amount of said eccentricity.

- 2. A control system as set forth in claim 1 in which said angle between said arms of said control lever is selected to cause said pivot, said junction and said free end of said other arm of said control lever to be aligned when said blade extends tangentially with respect to said orbit.

3. A control system as set forth in claim 2, in which said arms of said control lever are of equal length.

4. A control system as set forth in claim 1, in which said arms of said control lever and said link are of equal length.

5. A control system as setforth in claim 1, in which the length of the arms of said control lever and of said links and the location of said pivot are such that said free ends of said arms and said pivot lie substantially on a circle in all positions which can be assumed by the System.

6. A control system as set forth in claim 1, in which said means connected to saidfree end of said one arm are adjustable to vary the distance of said free end of said one arm from said center.

7. A control system as set forth in claim 6, in which said means connected to said free end of said one arm comprises a fourth pivot and in which said free end of said one arm is formed as a fork which carries two bearings rotatably holding said fourth pivot, said two bearings being equally spaced from the longitudinal axis of said one arm.

References Cited in the file of this patent UNITED STATES PATENTS Franz July 3, 1956

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