US3586457A - A prime mover control system - Google Patents

Abstract

A prime mover control system for controlling the speed of a fluid-actuated machine comprising a rotatable element responsive to the speed of the machine. Connected to rotate with the speed responsive element are a plurality of S-shaped band means. Engaging a first portion of each of the band means and rotatable therewith, is a weight. The centrifugal force produced by the rotating weights causes the weights to move axially and radially relative to the band means, the magnitude of movement being in direct proportion to the centrifugal force and thus also to the speed of the machine. The band means transmits the axial movement of the weights to a roller engaging a second portion of each of the band means, the rollers moving axially relative to the band means in the same direction as the axial movement of the weights and in direct proportion thereto. The roller means connect through means such as levers, a throttle valve controlling the supply of actuating fluid to the machine, the axial movement of the roller means causing a corresponding movement in the throttle valve, thereby either increasing the quantity of actuating fluid or decreasing the quantity of actuating fluid to maintain a predetermined speed for the machine.

Description

United States Patent [72] Inventor Carl H. Geary Greensburg, Pa. [21] Appl. No. 826,107 [22] Filed May 20, 1969 [45] Patented June 22,1971 [73] Assignee Carrier Corporation Syracuse, N.Y.

[54] PRIME MOVER CONTROL SYSTEM 6 Claims, 2 Drawing Figs.

[52] US. Cl n 415/36, 137/57 [51] 1nt.Cl F0ld 1/12, F03b 1/00, F03d 5/00 [50] Field of Search 137/57; 73/547, 530; 415/36; 137/53 [56] References Cited UNITED STATES PATENTS 662,572 11/1900 Milea 137/57 982,819 1/1911 Hodgkinson 415/36 3,452,175 6/1969 Wilkes 73/514 Primary ExaminerCarlt0n R. Croyle Assistant Examiner-R. E. Gluck Atl0rneys-Harry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: A prime mover control system for controlling the speed of a fluid'actuated machine comprising a rotatable element responsive to the speed of the machine. Connected to rotate with the speed responsive element are a plurality of S shaped band means. Engaging a first portion of each of the band means and rotatable therewith, is a weight. The centrifugal force produced by the rotating weights causes the weights to move axially and radially relative to the band means, the magnitude of movement being in direct proportion to the centrifugal force and thus also to the speed of the machine. The

band means transmits the axial movement of the weights to a roller engaging a second portion of each of the band means, the rollers moving axially relative to the band means in the same direction as the axial movement of the weights and in direct proportion thereto. The roller means connect through means such as levers, a throttlevalve controlling the supply of actuating fluid to the machine, the axial movement of the roller means causing a corresponding movement in the throttle valve, thereby either increasing the quantity of actuating fluid or decreasing the quantity of actuating fluid to maintain a predetermined speed for the machine.

PATENIED JUN22 1971 FIG. I

INVENTOR.

CARL H. GEARY.

PRIME MOVER CONTROL SYSTEM BACKGROUND OF THE INVENTION This invention relates to prime mover control systems and more particularly to such systems including a mechanical governor designed to control the speed of a fluid-actuated machine.

Basically, speed responsive mechanisms or governors for fluid-actuated machines, such as turbines, can be separated into two generic classifications: (l) mechanical or fly-ball governors and (2) hydraulic governors. This invention relates primarily to mechanical governors.

Operation of mechanical governors depends upon centrifugal forces exerted by some type of rotating element whose speed is proportional to turbine speed. Generally, mechanical governors comprise a housing connected to the shaft of the machine and rotatable therewith. Pivotally connected to the housing and rotatable therewith are a plurality of weights. The rotational speed of the weights is directly related to the rotating speed of the machine; the centrifugal force developed by the rotating weights will therefore be a direct function of the speed of the machine. The centrifugal force will cause the weights to pivot radially away from the housing. The movement of the weights will be transmitted by means, such as a spindle connected to a lever assembly, to a throttle valve controlling admission of themotivating fluid to the machine.

If the speed of the machine increases, the centrifugal force acting on the weights will increase in magnitude, thereby forcing the weights further away from the housing. The radial movement of the weights will cause a corresponding movement in the throttle valve, the throttle valve being positioned to maintain a predetermined speed. If the speed of the machine has increased beyond the predetermined point, the movement of the weights will position the throttle valve so a lesser quantity of actuating fluid will be admitted to the machine, thereby reducing the speed as desired.

Similarly, if the speed of the machine decreases, the centrifugal force acting on the weights will decrease in magnitude, thereby bringing the weights closer to the housing. If the speed has decreased beyond the predetermined point, the movement of the weights will position the throttle valve so a greater quantity of actuating fluid will enter the machine.

Mechanical governors of the type under discussion normally employ a compression spring to act as a restraining force to prevent the spindle from being moved by the weights at normal speed. Similarly, the spring force acts to restore the spindle to its normal position once the predetermined operating speed has been reached.

Mechanical governors of this type are the simplest type of automatic speed control. They are relatively inexpensive since they have few parts. However, although suitable for many applications, these governors are not highly sensitive and therefore do not permit a high degree of speed control. The basic cause for this lack of sensitivity is the large proportion of inherent friction in the governor mechanism. There is a considerably amount of friction between the pivotal connection of the weights and the spindle, which must be overcome before the spindle will move in any direction. Additionally, the compression spring which acts as both a restoring force and a restraining force also introduces frictional forces to the mechanism.

Attempts have been made to reduce the friction problems presented and to increase the sensitivity of such governors. Generally, increase in sensitivity has been obtained by utilizing hydraulically operated servo motors in combination with the weights. Although sensitivity has been increased, so has manufacturing costs and repair problems.

The object of this invention is a simple, relatively inexpensive and maintenance-free prime mover control system which may be utilized in applications requiring a high degree of speed control.

SUMMARY OF THE INVENTION A novel prime mover control system is herein disclosed, one that utilizes a mechanism known as a rolamite" to reduce the frictional problems heretofore encountered.

The basic design of the rolamite consists of a long band of flexible material curled into the shape of an S. A cylinder or roller is inserted into each of the two curves at the points where the band by virtue of its shape changes direction, the band then being pulled tight or put under tension. The two rollers can roll together, back and forth along the band, with extremely low rolling friction. Utilization of this rolamite concept has produced an improved prime mover control system as will be more fully explained hereinafter.

The novel prime mover control system comprises a speed responsive element connected to the shaft of the machine to rotate therewith. The speed responsive element acts as a housing for a plurality of S-shaped band means, preferably two in number. The band means will rotate simultaneously with the housing. Engaging a first portion of each of the band means and rotatable therewith is a weight. The centrifugal force developed by the rotating weight will cause the weight to move radially away from the band means and simultaneously, axially relative thereto.

Engaging a second portion of each of the band means is a roller. The band means transmits the axial movement of the weight to the roller, causing the roller to also move axially relative to the band means and in the same direction as the weight.

The magnitude of the movement of both the weight and the roller is dependent upon the centrifugal force acting on the weight and is therefore a direct function of the rotational speed of the machine.

Connected to the rollers is a spindle or similar mechanism, designed to transmit the axial movement of the rollers through a lever system to a throttle valve controlling the supply of actuating fluid to the machine, thereby controlling the speed of the machine.

An increase in speed beyond a predetermined point will increase the centrifugal force acting on the weights, thereby increasing the magnitude of movement by the weights. This in turn will position the throttle valve so a lesser amount of motivating fluid will enter the machine, thereby decreasing the speed to the predetermined level. If the speed of the machine decreases below the predetermined point, the reduction in centrifugal force will cause the throttle valve to permit a greater quantity of motivating fluid to be supplied to the machine.

The band means not only transmits motion from the weights to the rollers, but also acts to restore the spindle to its original position once the operating speed has been attained. The band means also acts to restrain the weights from moving unless the speed of the machine and therefore the centrifugal force either exceeds or is less than the predetermined centrifugal force, as determined by the operating speed of the machine.

As discussed hereinbefore, frictional forces between various components of the governing mechanism have prevented this type of mechanical governor from being utilized in applications requiring a high degree of speed control. The rolamite mechanism, utilized in the manner herein discussed, will alleviate the frictional problems and thereby increase the quality of speed control for the basic mechanical governor. The axial movement of the rollers relative to the bands is purely a rolling action with minimal frictional forces developed. Additionally, the bands replace the governor spring which, as discussed previously, produced many frictional problems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a side view, partially broken away, of a typical fluid-actuated machine wherein the novel prime mover control system is embodied; and

FIG. 2 is an enlarged perspective view of the novel prime mover control system.

DESCRlPTlON OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown a typical fluid-actuated machine with which the novel prime mover control system including a mechanical governor herein disclosed will be associated. in referring to the drawings, like numerals shall refer to like parts.

The fluid-actuated machine shown in FIG. 1 is a steam driven turbine which may be used for driving fans, pumps or compressors. Other fluid-actuated devices, such as gas turbines and engines, may be used with the novel prime mover control system disclosed herein.

The turbine comprises a housing 11. Extending axially through the housing 11 is a shaft 14. Supporting the shaft 14 at opposed ends are bearings (not shown) mounted within bearing caps 12 and 13. Connected to one end of the shaft is the machine (not shown) that the turbine is driving. Mounted to rotate on the shaft 14 are one or more wheels (not shown) upon which are mounted'blades (also'not shown) as is well known to those skilled in the art.

Steam from a source of supply (not shown) will enter the steam chest 21 of the turbine via steam inlet 22. The steam leaving the steam chest 21 will be directed to the wheels or rotors mounted on the shaft 14. The steam will impart energy to the wheels. This energy will be transmitted to the shaft and will thereby cause the shaft to rotate within the housing as desired. The rotational speed of the shaft is directly related to the quantity of steam passing through the steam chest 21 and thereafter contacting the wheels. To maintain the speed of the turbine basically constant as is desirable for most applications, it is necessary to control the quantity of steam passing through the turbine.

Disposed in the steam chest 21 is a throttle valve 20, shown as a double seating valve. The function of the valve 20 is to control the quantity of steam gaining admission into the turbine, thereby controlling the speed of the machine. A governor 15, to be explained in detail more fully hereinafter, automatically positions the throttle valve 20 to maintain the predetermined operating speed.

The governor herein disclosed is of the mechanical type.

Mechanical governors depend for their operation upon the centrifugal forces exerted by some type of rotating element whose speed is proportional to the speed of the governed machine. Governors of this type are not highly sensitive and therefore cannot be used for applications where a high degree of speed controlis required. The lack of sensitivity is substantially caused by the inherent friction of the movable parts. The friction can be reduced only by greatly increasing the manufacturing costs and introducing additional repair problems. The novel govemor' 15 affords a highly sensitive speed control mechanism without introducing the concomitant problems.

The governor 15 comprises a housing 16 enclosing the components of the governor. Rotatably secured to the shaft 14 is a member 23, preferably in the form of an E formed by three plates 27, 28 and 29 spaced apart and axially extending from a vertical plate 30. Attached to the inner surfaces of the axially extending plates are bands 31 and 32 formed into the shape of a reverse S. Engaging one of the curved portions of each of the bands 31 and 32 are weights 24 and 53. In a preferred embodiment, the weights comprise two basically cylindrical members 44 and joined together in spaced-apart relation by arms 26 and 46. Engaging the second curved portion of each of the bands are rollers 25 and 34. Four arms 35, 36, 37 and 38 connect the rollers to a bracket 39. Joined to the bracket 39 is a spindle 17, which is connected, via lever 18, to the throttle valve stem 19 operable to control the position of the throttle valve 20 in the steam chest 21, thereby controlling the admission of steam into the turbine 10.

A speed changer assembly 40 exerts a force on the lever 18, which opposes the force exerted by the governor 15, through the spindle 17 on the lever. The magnitude of the force exerted by the speed changer assembly 40 determines the operating speed of the turbine. The magnitude of the force may be varied by rotating the wheel 41 to either increase or decrease the compressive force on spring 42, thus either increasing or decreasing the operating speed.

As the speed of the turbine increases, the weights 24 and 33, rotating within housing 16, will move radially away from the member 23 due to the increased centrifugal force, the magnitude of movement being dependent upon the magnitude of speed. The weights will also move axially in a direction toward the lever 18 due to the increased rotational speed.

The axial movement of the weights will be transmitted by the bands 31 and 32 to the rollers 25 and 34. The rollers 25 and 34 will move in the same axial direction as the weights and in proportion thereto, the movement of the weights and rollers thus being relative to the bands.

The axial movement of the rollers will be transmitted by the arms connected thereto, to the bracket 39 to which the spindle 17 is joined. If the force exerted by the spindle on the lever 18 is of a greater magnitude than that of the speed changer assembly 40, the lever will be rotated about fulcrum 43 so the throttle valve stem 19 will position the throttle valve 20 to pass less steam through the steam chest 21. The reduction in steam passing through the turbine will reduce the speed as desired.

lf the speed of the machine falls below the desired operating point, the force exerted by the speed changer assembly 40 on the link will exceed the force exerted by the spindle 17, thereby causing the lever 18 to pivot about the fulcrum 43 so the throttle valve will pass more steam through the turbine.

The bands 31 and 32 not only transmit the axial movements of the weights to the rollers, but will also act as a restraining force and a restoring force. The weights, by being tightly engaged by the bands, will be restrained from moving excessively due to small increases in centrifugal force. Also, the bands will act to restore the weights to their normal operating position once the speed and thus the centrifugal force has been reduced.

As noted hereinbefore, the problem with governors of this type has been their lack of sensitivity due to the inherent friction between moving parts.

This problem has been reduced by employing the "rolamite" principle as heretofore explained in the manner in which movement of the weights is transmitted to the throttle valve controlling admission of steam to the turbine.

The novel arrangement for the governor weights and rollers may be also utilized in hydraulic governors, wherein the movement of the weights caused by centrifugal force will regulate the hydraulic pressure in a servo motor controlling the position of the throttle valve.

While I have described and illustrated a preferred embodiment of my invention, it will be understood that my invention is not limited thereto, since it may be otherwise embodied within the scope of the following claims.

lclaim:

1. A prime mover control system for controlling the speed of a fluid-actuated machine comprising:

A. a speed responsive rotatable member actuated by said machine;

B. band means connected to said speed responsive member and rotatable therewith;

C. weight means engaging a first portion of each of said band means to rotate therewith, said rotation causing the weight means to move substantially radially to and to move axially relative to said band means, said substantially radial and axial movements occurring simultaneously, the magnitude of said movements being proportional to the speed of rotation of said weight means;

D. roller means engaging a second portion of each of said band means to rotate therewith, said band means transmitting the axial movement of said weight means to said roller means, thereby causing a corresponding axial movement by said roller means;

E. throttle valve means operable to control the supply of said actuating fluid to said machine and thereby operable to control the speed thereof; and

F. means connecting said roller means to said throttle valve of said shaft, said means being effective to translate a means operable to transmit the axial movement of said variable radial movement responsive to changes in the roller means to said valve means, the position of the valve speed of said shaft to axial movement governing the magmeans thus being a direct function of the rotational speed nitude of said force; of said weight means and therefore a function of the 5 C. valve means operable to control the supply of said acspeed of said machine. tuating fluid to said machine and thereby operable to con- 2. A prime mover control system in accordance with claim 1 the Speed thereof; and wherein said band means are shaped in the form of a reverse S. mearlS C ting aid f e pr ducing m ans to said 3. A prime mover control system in accordance with claim 2 Valve means, p ble to r n mit Sai f r to Said valve wherein said weight means engage a first curved section of 10 means, the Position of Said Valve means thus i g a direct function of the rotational speed of said shaft. 6. A prime mover control system in accordance with claim 5 wherein said force producing means includes:

A. a first element shaped in the form of a reverse S; B. a second element engaging a first curved portion of said first element and movable relative thereto, the magnitude of said movement being in proportion to the speed of said said reverse S-shaped band means and said roller means engage a second curved section of said reverse S-shaped band means.

4. A prime mover control system in accordance with claim 1 wherein said weight means comprises two substantially cylindrical members joined together in spaced-apart relationship.

5. A prime mover control system for controlling the speed of a fluid-actuated machine having a power shaft comprising: shaft; and

A. a speed responsive rotatable member actuated by said 0 3 mm! element engagmg a second curve? P of sad first element and movable axially relative thereto, the

machine, having at least one pair of opposed axial surfaces;

B. means associated with at least one pair of said opposed surfaces for producing a force representative of the speed magnitude of said movement being a direct function of the magnitude of movement of said second element.

Claims (6)

1. A prime mover control system for controlling the speed of a fluid-actuated machine comprising: A. a speed responsive rotatable member actuated by said machine; B. band means connected to said speed responsive member and rotatable therewith; C. weight means engaging a first portion of each of said band means to rotate therewith, said rotation causing the weight means to move substantially radially to and to move axially relative to said band means, said substantially radial and axial movements occurring simultaneously, the magnitude of said movements being proportional to the speed of rotation of said weight means; D. roller means engaging a second portion of each of said band means to rotate therewith, said band means transmitting the axial movement of said weight means to said roller means, thereby causing a corresponding axial movement by said roller means; E. throttle valve means operable to control the supply of said actuating fluid to said machine and thereby operable to control the speed thereof; and F. means connecting said roller means to said throttle valve means operable to transmit the axial movement of said roller means to said valve means, the position of the valve means thus being a direct function of the rotational speed of said weight means and therefore a function of the speed of said machine.

2. A prime mover control system in accordance with claim 1 wherein said band means are shaped in the form of a reverse S.

3. A prime mover control system in accordance with claim 2 wherein said weight means engage a first curved section of said reverse S-shaped band means and said roller means engage a second curved section of said reverse S-shaped band means.

4. A prime mover control system in accordance with claim 1 wherein said weight means comprises two substantially cylindrical members joined together in spaced-apart relationship.

5. A prime mover control system for controlling the speed of a fluid-actuated machine having a power shaft comprising: A. a speed responsive rotatable member actuated by said machine, having at least one pair of opposed axial surfaces; B. means associated with at least one pair of said opposed surfaces for producing a force representative of the speed of said shaft, said means being effective to translate a variable radial movement responsive to changes in the speed of said shaft to axial movement governing the magnitude of said force; C. valve means operable to control the supply of said actuating fluid to said machine and thereby operable to control the speed thereof; and D. means connecting said force producing means to said valve means, operable to transmit said force to said valve means, the position of said valve means thus being a direct function of the rotational speed of said shaft.

6. A prime mover control system in accordance with claim 5 wherein said force producing means includes: A. a first element shaped in the form of a reverse S; B. a second element engaging a first curved portion of said first element and movable relative thereto, the magnitude of said movement being in proportion to the speed of Said shaft; and C. a third element engaging a second curved portion of said first element and movable axially relative thereto, the magnitude of said movement being a direct function of the magnitude of movement of said second element.

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