US3291221A

US3291221A - Vane adjusting mechanism for variable pitch mixed flow pumps and turbine wheels

Info

Publication number: US3291221A
Application number: US518867A
Authority: US
Inventors: Kovats Andre
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1966-01-05
Filing date: 1966-01-05
Publication date: 1966-12-13
Anticipated expiration: 1983-12-13

Description

Dec. 13, 1966 A. KOVATS fifi fifi i VANE ADJUSTING MECHANISM FOR VARIABLE PITCH MIXED FLOW PUMPS AND TURBINE WHEELS Filed Jan. 5, 1966 5 Sheets-Sheet 1 INVENTOR AN DR E KOVATS ATTORNEY 19(36 A. KOVATS 3,291,223

ANE ADJUSTING MECHANISM FOR VARIABLE PITCH MIXED FLOW PUMPS AND TURBINE WHEELS Filed Jan. 5, 1966 5 Sheets-Sheet 2 INVENTOR.

'ANURE KOVATS Bow WM T ATTORNEY Dec. 13, 1966 A. KOVATS 3,291,221

VANE ADJUSTING MECHANISM FOR VARIABLE PITCH MIXED FLOW PUMPS AND TURBINE WHEELS 5 Sheets-Sheet 5 Filed Jan. 5, 1966 INVENTOR.

KOVATS ANDRE ATTORNEY United States Patent Ofifice 3,291,2Zi Patented Dec. 13, 1%66 3,291,221 VANE ADIUSTHNG MECHANISM FOR VARIABLE PITCH MDZED FLQW PUMPS AND TURBINE WHEELS Andre Kovats, Livingston, N..l., assignor to Foster Wheelg; tlorporation, New York, N.Y., a corporation of New or r Filed Jan. 5, 1966, Ser. No. 518,867 13 Claims. (Cl. l7-16tl.4

This invention relates to variable pitch mixed flow pumps and water turbine wheels. In particular it relates to a mechanism for varying the blade angle or pitch of the blades in variable pitch, mixed flow pumps or water turbine wheels, both types hereinafter referred to as variable pitch mixed flow impellers.

During operation of such pumps or turbine wheels the entire impeller unit revolves about an impeller axis at high speed for pumping, or generating, purposes. In variable pitch impeller units, as the unit revolves, the impeller blade can be rotated about its blade axis through a limited angle relative the impeller housing to regulate flow, or torque. conventionally this blade adjustment has been accomplished by an axial translation of a control rod, or by a rotation of a piston, housed axially with respect to the impeller unit. To adjust the blades while the impeller unit is revolving, the control rod is translated, or the piston is turned relative the unit, causing a coupling mechanism in the unit to rotate the blades relative the housing, through a limited angle.

In variable pitch mixed flow impellers, the blades are oriented so that each blade axis is angularly fixed with respect to the impeller axis, but not perpendicular nor parallel thereto. Hereinafter the term variable pitch mixed flow impellers shall include such definition. In

the past, in such units, where a translation of the control rod, or a rotation of the piston, was converted through a coupling mechanism into a limited rotation of the blade, the coupling mechanism experienced substantial bending moments, or sliding movements, in two degrees of freedom since the blade axis was angularly inclined with respect to the movement of the control rod or piston. Coupling joints, or slider blocks, having and substantially utilizing two degrees of freedom were used. Because of the excessive bending or sliding, these joints, or slider blocks, had excessive wear resulting in frequent unit failure and bearing replacement.

Therefore, it is an object of this invention to provide in a variable pitch mixed fiow impeller, an improved and simplified blade adjusting mechanism having minimum bending moments, minimum wear, and utilizing a minimum force to produce the blade rotation.

It is another object of this invention to provide in a variable pitch mixed flow impeller, an improved and simplified mechanism for converting a translational movement of the control rod into a limited rotational movement of the blade, whereby the mechanism has bending moments almost exclusively confined in a plane perpendicular to the blade axis, minimum wear, and utilizes a minimum force to produce the blade rotation.

Accordingly, this invention provides in a variable pitch mixed fiow impeller having an impeller housing, the impeller housing including a bearing defining an impeller axis of rotation, a blade mechanism comprising: a blade rotatably connected to the impeller housing and defining a blade axis of rotation; a blade turning means rigidly connected to the blade for rotating the blade; a rotatable means axially disposed in the bearing and extending therefrom for axial rotation and translation relative to the bearing and the impeller housing; a connecting rod pivotally connected to the blade turning means at a first joint and to the rotatable means at a second joint, said joints aligned in a plane perpendicular to the blade axis; moving means for axially rotating and axially translating the rotatable means relative the impeller housing so that the second joint moves substantially in said plane. Consequently, the first joint is moved substantially in the plane thereby rotating the turning means and the blade.

With this blade adjusting mechanism both the connecting rod joints are moved substantially in said plane perpendicular to the blade axis. Consequently, the blade adjusting mechanism including the connecting rod and the joints have essentially no bending moments outside of this plane. This minimizes bending moments in the entire mechanism and friction and wear in the coupling joints. It permits the use of joints and coupling bearings having essentially one degree of rotation, and that in said plane. Furthermore, the blade is turned by a force on the blade turning means which is perpendicular to the blade axis. This allows a minimum force to turn the blades, since the minimum force to turn a blade is one perpendicular to the blade axis. It provides for increased unit life, lower maintenance cost and better operating efficiency.

These and other objects and advantages will become apparent from the following description with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical cross-sectional View through a variable pitch mixed flow impeller pump showing the blade adjusting mechanism;

FIGURE 2 is a sectional view of the bearing joint between the connecting rod and lever arm taken along the line Z-2 of FIG. 1;

FIGURE 3 is a sectional view of the bearing joint between the disk and connecting rod taken along the line 3-3 of FIG. 1;

FIGURE 4 is a variant broken away sectional view of the control rod portion and guide bearing with ball bearings;

FIGURE 5 is a geometrical projection in plan, elevation and angular view of the movement produced by the blade adjusting mechanism of FIG. 1, FIG. 5A being the plan view, FIG. 5B being the elevation vie-w taken along the :line 5B5B of FIG. 5A, and FIG. 5C the angular view taken along the line 5C5C of FIG. 5B; and

FIGURE 6A is an isometric view of the movement of the blade mechanism of FIG. 1 as compared with FIG. 6B, an isometric view of the ideal perfect movement it approaches.

Referring now to FIG. 1, there is illustrated a variable pitch mixed flow impeller pump consisting of a rotor impeller housing 12 having a cone-shaped bottom plate 14 and a cover plate 16. The rotor is axially secured to a hollow shaft 18 by means of bolts 20. The cover plate 16 and bottom plate 14 make up the hub 22 of the rotor.

Attached to and pivoted on the hub are a plurality of vanes or blades 24 each having a trunnion 26 which is pivoted about a blade axis 27 in

bearings

28 and 30, the bearing 28 being a part of the bottom plate 14 of impeller hub 22, and the bearing 30 being of the split ring type located in brackets 32 which are fixed to the hub 22 by bolts 34. The trunnion is turned by a lever arm 36 (FIG. 2) keyed to the trunnion bet-ween the bearings 28 and 3h.

Lever arm 36 is moved by connecting rod 38 which pivotally engages the lever arm at one end by a bearing 4t). At its remote end removed from the lever arm, the connecting rod 38 pivotally engages a rotatable means 41 comprising a disk 42 and an elongated control rod portion 43, the connecting rod being pivoted in bearing 44 (also shown in FIG. 3) joined to the disk 42. The connecting rod 38 and the

bearings

40 and 44 are aligned in a rod plane 46 which is perpendicular to the blade axis 27 and parallel to the planes of rotation 48 of the blade and lever arm. These'planes 48 are also perpendicular to the blade axis, being the planes in which the blade and lever arm turn relative the impeller housing when adjusting the blade angle.

The control rod portion 43 to which the disk 42 is keyed supports the disk for axial rotational and translational movement. The control rod portion is axially journaled in hollow shaft 18 and guide bearing 52. Guide bearing 52 being a part of the impeller housing 12 is axially secured and bolted to the top cover plate 16. The lower part of the control rod portion 43 is helically threaded 58 mating with helical grooves 60 in the guide bearing. At the top of the control rod portion is a hydraulic piston 62.

During operation the entire impeller unit revolves about impeller axis 64 being driven by a motor (not shown) connected to shaft 18 (when FIG. 1 represents a turbine, no motor is involved and shaft 18 drives a generator, the shaft being driven by the impeller housing which in turn is driven by the fiuid acting on the blades). Impeller axis 64 coincides with the axes of the bearing 52, the rotatable means 41 and the control rod portion 43. All parts of the unit revolve at the same speed including the rotatable means and control rod portion 43 and the guide bearing 52.

During operation of the unit, when it is desired to change the vane positioning, the hydraulic piston 62 is moved upwardly or downwardly causing the helically threaded control rod portion 43 to turn in and relative to the helically grooved guide bearing 52 describing a helical movement consisting of axial rotation and axial translation. This in turn helically moves the disk 42 and bearing 44, which joins the disk to the connecting rod, in a corresponding manner, causing the connecting rod 38 and bearing 40, which joins the connecting rod to the lever arm, to move in the rod plane 46. In turn, the lever arm 36 and trunnions 26 are rotated thereby adjusting the angle of the blade 24 relative the housing. The pitch and radius of the helical threads 58 and grooves 60 and the radius of disk 42 are adapted so that with a limited movement of the piston 62 the disk and associated bearing 44 are helically moved (rotationally and axially) with respect to the impeller housing and axis 64, substantially within the rod plane 46 parallel to the planes of rotation 48 of the blades and lever arm. Consequently the connecting rod 38 and bearing 40 are moved substantially within the plane 46. This results in negligible bending moments outside of the rod plane which otherwise would tend to bend coupling joints 40 and 44 out of the plane.

The movement of bearing joint 44 substantially in the plane 46 of rotation of the lever arm and joint 40, permits the use of connecting joints and

bearings

40 and 44 having only a single degree of rotation or freedom in said plane without subjecting the joints to excessive stresses, abrasive bending moments or forces which would tend to turn the joints back and forth out of the plane.

FIG. 6A geometrically represents this single rod plane 46 movement of the connecting rod 38 and

bearings

40 and 44, and is to be compared with an idealized single plane movement which it closely approximates in FIG. 6B. The latter figure depicts an idealized single plane movement for a connecting rod 38' (the primes indicating comparison with the corresponding unprimed elements in FIGS. 1-3, 5 and 6A) and lever arm 36 both aligned in rod plane 46' as they move from one position (indicated by solid lines) to another (indicated by dashed lines) to change the angle of the blade 24. The ideal movement is achieved by use of a bar 66' (this bar has no equivalent in the other figures). The bar 66 turns about a fixed pivot 54' (also having no equivalent in the other figures) in the plane 46' which is perpendicular to the blade axis. When bar 66' is moved by a force in the plane 46, the joints 40' and 44 and the connecting rod 38 move in plane 46, turning the lever arm 36' which in turn rotates the blades 24. Since all forces are in plane 46 there is no force component or bending moments out of the rod plane 46' and hence the joints 40' and 44 at the ends of the connecting rod 38 experience no movement in these nonplanar directions.

As shown in FIG. 6B (and FIG. 5), representing the actual movement of the coupling mechanism of FIG. 1, the movement of the connecting rod 38 very closely approximates this perfect planar movement of FIG. 6A (here in FIG. 6B, disk 42 of FIG. 1 is shown as circular). As the disk 42 turns, due to the helical movement of the control rod portion 43 in guide bearing 52 (FIG. 1) the edge of the disk at the bearing 44 is turned along helix path portion 68a which lies substantially in plane 46, supplying a force on bearing 44 almost exclusively within plane 46 thereby moving bearing 44 and the connecting rod 38 substantially in the plane 46. Consequently, joint 40 is moved within plane 46 turning the lever arm 36 which rotates the blade. Since the moving force on bearing 44 is almost exclusively within plane 46, due to the helical movement (rotationally and axially) of the disk 42, there is no force component or bending moment out of the rod plane. Consequently, the

joints

40 and 44 experience substantially no movement or wear in these directions.

Since the disk 42 turns about axis 64, which axis is angularly inclined to the plane 46, the movement of bearing 44 and the connecting rod 38 can only approximate a single plane movement. However, the helical translation and rotation of the disk and bearing 44 are limited, by limiting the movement of the piston 62, to a relatively small portion of the helix 68, namely, path portion 68a, which lies substantially in the rod plane 46, so that the force and movement of bearing 44 is substantially in the rod plane. The radius and pitch of the helical threads 58 as well as the relative radius of the disk 42 are such that helix path portion 68a and hence the movement of the bearing 44 lie substantially within the connecting rod plane 46.

For optimum operation, and to permit rotation of the blades through the largest possible blade angle, yet closely approximating said single plane movement, the radial distance of the connecting rod joint 44 from the impeller axis 64 (for purposes of the claims hereinafter called the radius of the rotatable means) is made approximately equal to the radial distance of the connecting rod joint 40 from the blade axis of rotation 27 (hereinafter called the radius of the turning, means). Unequal radii may be utilized but the limits of rotation (the helical path portion 68a) of the disk and blade would necessarily have to be further limited to obtain satisfactory single plane movement of connecting rod 38 without excessive bending moments out of the plane.

By restricting the limits of the disk rotation (path 68a) to approximately thirty degrees, the maximum deviation of the connecting rod and the bearings from the perfect plane movement 46 may be made to be less than one degree, resulting in completely negligible bending forces out of the plane. To allow for this small bending moment out of the rod plane, the

joints

40 and 44 at the ends of the connecting rod are spherical having curved surfaces curving in a direction out of the rod plane (as shown best in FIG. 3 at 44) thereby having a slight nonplanar degree of freedom (indicated by the curved doubleended arrow 72 in FIG. 1).

It should be apparent from the foregoing that the benefits of this invention are achieved by aligning the connecting

rod joints

40 and 44 in a plane which is perpendicular to the blade axis and by moving the rotatable means and bearing joint 44, rotationally and axially relative the impeller housing, through a helical path portion 68a which substantially lies in the plane. Consequently, the joint between the connecting rod and lever arm 40 is also moved substantially in a path portion in the plane 46 which corresponds to 63a. Accordingly, although the description depicted the connecting rod as being straight, it is fully within the scope of this invention that the connecting rod be of a bent or curved shape as may be desirable for spacing and design objectives, so long as the connecting rod joints 4% and 44- are aligned in a plane perpendicular to the blade axis.

Although only two vanes and associated connecting rods and joints are shown in FIGS. 1 and 3, a plurality of vanes and connecting rods and joints between the vanes and the central disk 42 may be simultaneously operated with the resulting benefits of single plane motion for each vane coupling and associated joint.

Another advantage of this invention is that no special servomotor is required to turn the blades; e.g., as described herein the coupling mechanism operates with a standard hydraulic control piston 62 to supply the initiating translational force to move the control rod portion and disk rotationally and axially. Although not shown, other means may be used to supply the axial translational force, such as a manually operated screw lever which may be desirable for small units.

As shown in FIG. 4 the friction of the guide hearing may be reduced with ball bearings 74 in the helical grooves of the guide bearing and between the helical threads of the control rod.

Although the invention has been described with respect to specific embodiments, many other variations Within the scope and spirit of the invention as defined in the following claims will be apparent to those skilled in the art.

What is claimed is:

1. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, a blade mechanism comprising:

a blade rotatably connected to the impeller housing and defining a blade axis of rotation;

blade turning means rigidly connected to said blade for rotating the blade;

a rotatable means axially disposed in the bearing and extending therefrom for axial rotation and translation relative to the bearing and the impeller housa connecting rod pivotally connected to the blade turning means at a first joint and to the rotatable means at a second joint, said joints aligned in a plane perpendicular to the blade axis;

moving means for axially rotating and axially translating the rotatable means relative the bearing and impeller housing.

2. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 1 wherein the connecting rod is disposed in said plane.

3. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 1 wherein the blade turning means comprises a blade trunnion oriented along the blade axis and a lever arm rigidly secured to the trunion, the lever arm disposed in said plane and the connecting rod pivotally connected to the lever arm at the first joint.

4. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 1 wherein the joints comprise coupling bearings adapted for rotation in said plane and restricted from rotation out of said plane.

5. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 1 wherein the joints comprise spherical bearings adapted for rotation in said plane and for limited rotation out of said plane.

6. In a variable pitch mixed fiow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 1 wherein the moving means comprises an axial translating means for exerting an axial translating force on the rotatable means, the bearing defining a helically grooved bearing opening in which the rotatable means is disposed for axial rotation and translation rela tive the bearing.

7. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 6 wherein the bearing opening is cylindrical having helical grooves therein, the rotatable means comprising a cylindrical control rod portion having helical threads thereon journaled in the bearing opening, the helical threads mating with the helical grooves.

8. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 7 wherein the pitch and radius of the helical grooves are adapted so that the movement of the second joint is substantially within said plane as the control rod portion axially rotates and translates in the bearing.

9. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining .an impeller axis of rotation, the blade mechanism of claim 8 wherein the radius of the rotatable means is approximately equal to the radius of the turning means.

10. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 7 wherein the axial translating means comprises a hydraulic piston formed in the control rod portion.

11. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a bearing defining an impeller axis of rotation, the blade mechanism of claim 9 wherein:

the connecting rod is disposed in said plane;

the blade turning means comprises a blade trunnion oriented along the blade axis and a lever arm rigidly secured to the trunnion, the lever arm disposed in said plane and the connecting rod pivotally connected to the lever arm at the first joint;

the joints comprise spherical bearings adapted for rotation in said plane and for limited rotation out of said plane;

the rotatable means further comprises a disk axially and rigidly secured to the control rod portions, the connecting rod pivotally connected to the disk at the second joint; and

the axial translating means comprises .a hydraulic piston formed in the control rod portion.

12. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a hearing defining an impeller axis of rotation, the blade mechanism of claim 8 further comprising ball bearings disposed in the helical grooves adjacent the helical threads for reducing friction between the control rod portion and the bearing.

13. In a variable pitch mixed flow impeller having an impeller housing, said impeller housing including a hearing defining an impeller axis of rotation, a blade mechanism comprising:

a plurality of blades rotatably connected to the impeller housing equally spaced symmetrically about the impeller housing, each blade defining a blade axis of rotation;

8 a plurality of blade turning means, one for each blade the bearing defining a helically grooved bearing openrigidly connected thereto for rotating the blades; ing in which the rotatable means is disposed for one rotatabl means axially disposed i th bea i axial rotation and translation relative the bearing and extending therefrom; the impeller housing;

a plurality of connecting rods one for each blade, each 5 an axial translating means for exerting an axial force connecting rod pivotally connected to a blade turnon thfl rotatable ing means at a first joint and to the rotatable means NO references Cited at a second oint, sa1d first and second oints of each connecting rod aligned in .a plane perpendicular to MARTIN SCHWADRON, Primary Examinerthe axis of the 'blade associated therewith; 10 POWELL, Assistant Examiner

Claims

1. IN A VARIABLE PITCH MIXED FLOW IMPELLER HAVING AN IMPELLER HOUSING, SAID IMPELLER HOUSING INCLUDING A BEARING DEFINING AN IMPELLER AXIS OF ROTATION, A BLADE MECHANISM COMPRISING: A BLADE ROTATABLY CONNECTED TO THE IMPELLER HOUSING AND DEFINING A BLADE AXIS OF ROTATION; BLADE TURNING MEANS RIGIDLY CONNECTED TO SAID BLADE FOR ROTATING THE BLADE; A ROTATABLE MEANS AXIALLY DISPOSED IN THE BEARING AND EXTENDING THEREFROM FOR AXIAL ROTATION AND TRANSLA-