US3421414A

US3421414A - Flyweight

Info

Publication number: US3421414A
Authority: US
Inventors: Alfred N Peale
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1966-03-15
Filing date: 1966-03-15
Publication date: 1969-01-14
Anticipated expiration: 1986-01-14

Description

A. N. PEALE Jan. 14, 1969 FLYWEIGHT Sheet Filed March 15, 1966 I INVENTOR ALFRED N. PE'ALE ATTORNEY I Jan. 14, 1969 A. N. PEALE 3,421,414

FLYWEIGHT i Filed March 15, 1966 Sheet 2 of 2 26 33 2| 0. If I 32 6 H U "L" L v l Q 24 38 4 A, Ll l F/G'. 4 I (D I v m l LL '1 LL] 8 F x a. 5 2 2 5 g SHIFT OF CG I V'NVENTOR E F x L ALFREOW. PEA/.5

SPEED RPM BY v 2 (Q 15 rv-W F/G. 5

ATTORNEY United States Patent Office 3,421,414- Patented Jan. 14, 1969 6 Claims ABSTRACT OF THE DISCLOSURE A motor speed control mechanism including a variable speed motor, a valve controlling the supply of energy to the motor, a radially movable fiyweight pivoted on the rotary shaft of the motor and a linkage interconnecting the fiyweight to the valve to vary the speed of the motor in response to the radial movement of the fiyweight. The fiyweight includes a bore arranged with one end being closer to the axis of the fiyweight pivot and the other end being closer to the axis of the shaft in the retracted position of the fiyweight. A weight is movably enclosed in the bore whereby the weight is urged by the centrifugal force to the one end of the bore in the retracted position of the fiyweight and to the other end of the bore in the extended position of the fiyweight resulting in the center of gravity of the fiyweight shifting away from the fiyweight pivot as the fiyweight moves radially outward toward its extended position.

This invention relates to motor speed control systems using centrifugally actuated flyweights as speed sensing means.

In certain applications, it is desirable that the speed of a motor be maintained within a relatively narrow speed range. In general, conventional speed control systems using fiyweights do not control speeds within a relatively narrow speed range, particularly, when the flyweights are retracted by strong springs.

The primary object of this invention is to substantially overcome or minimize the above disadvantages in conventional speed control systems of the fiyweight type.

Further important objects of this invention are: to provide a fiyweight speed control system which maintains motor speeds within a relatively narrow speed range; to provide a rapid acting fiyweight speed control system; to provide an improved fiyweight for use in speed control systems; and to provide a fiyweight speed control system which abruptly shifts the forces acting on a fiyweight at some point during its normal operation.

The foregoing objects are attained, in general, by the provision of a fiyweight speed control system having pivoted flyweights with means for abruptly changing the centrifugal torque acting on the flyweights at some point intermediate the limits of pivoting movement of the flyweights. This is accomplished by providing each fiyweight with a means which acts to shift the center of gravity of the fiyweight at a predetermined speed of the shaft or motor driving the fiyweight. This shift in the center of gravity is caused by the centrifugal force acting on the fiyweight.

The invention is described in connection with the accompanying drawings wherein:

FIG. 1 is an elevational view with portions shown in section of an air-powered grinder tool utilizing the improved speed control system of this invention;

FIG. 2 is an enlarged fragment of FIG. 1 illustrating the flyweights and with one of the flyweights being sectioned to show its interior;

FIG. 3 is similar to FIG. 2 and shows plural positions of the flyweights during operation of the tool of FIG. 1;

FIG. 4 is a diagrammatic view illustrating the shift of the center of gravity of a fiyweight;

FIG. 5 is a graph or curve illustrating the centrifugal torque forces acting on a fiyweight in relation to its speed; and

FIG. 6 is an elevational view with a portion cut away illustrating a modified embodiment of fiyweight.

The air powered grinder 1 shown in FIG. 1 comprises a casing 2 including a handle 3 and a head cover 4. The casing 2 contains a conventional air-powered motor 5 having a rotor 6 driving a spindle 7. The spindle 7 carries a grinder wheel 8 rotating within a stationary shield 9 fixed to the casing 2.

The end of the handle 3 is provided with an inlet 11 adapted to be connected to an air supply hose (not shown). The inlet 11 leads to a conventional throttle valve 12 mounted in the forward part of the handle 3. When manually opened, the throttle valve 12 feeds air to a speed control valve 13 which acts to throttle and vary the quantity of air delivered to the motor 5 for controlling and limiting the speed of the motor '5.

The speed control valve 13 includes a valve sleeve 14 carried in the casing 2 and having an air inlet 15- at one end and an air outlet 16 extending through its sidewall. A valve piston 17 reciprocates in the valve sleeve 14 in a manner to vary the effective area of the air outlet 16. The valve piston 17 includes a piston rod 18 which slidably extends through the upper end of the valve sleeve 14, as shown in FIG. 1, for operating the valve piston 17. The valve piston 17 is urged upwardly in. the valve sleeve 14 by a spring 10.

A fiyweight-type of governor 19 is carried by the upper end of the motor rotor 6 and includes a cap plate 20 attached to the end of the motor rotor 6 and a pair of L-shaped fiyweight 21 pivoted at 22 on the cap plate 20. Looking at FIG. 1, each fiyweight 21 includes a foot 23 and a leg 24 extending upwardly from the foot 23 at a right angle. The governor 19 further includes an axial plunger 25 slidably mounted in the cap plate 20 and extending into a cavity provided in the motor rotor 6. The plunger 25 includes a head 26 at its upper end resting on the feet 23 of the fiyweights 21 and a nut 27 threaded at its lower end. A spring 28 is interposed between the nut 27 and the cap plate 20 to urge the plunger head 26 downwardly against the fiyweights 21 for biasing them radially inward.

As is conventional in fiyweight-type speed control systems, as the motor speed increases, centrifugal force acting on the flyweights 21 serves to lift the plunger 25 upwardly, as seen in FIG. 1, against the force of the spring 28. The vertical upward movement of the plunger 25 is transmitted to the speed control piston rod 18 by a bell crank 29 pivoted on a pivot 30 fixed in the head cover 4 and having opposite arms resting respectively on the plunger head 26 and the piston rod 18. All of the foregoing structure is conventional, as shown in United States Patent No. 2,897,832.

The invention in this application is the concept of pro viding each of the flyweights 21 with a means which abruptly shifts the center of gravity of the fiyweights outwardly from the pivot axis 22 of the fiyweight at some point intermediate the limits of the pivot travel of the fiyweights. This expedient is carried out in FIGS. 2 and 3 by providing the legs 24 of each of the flyweights 21 with an elongated bore 32 having a ball 33 which can readily roll or shift between the opposite ends of the bore 32. The outer end of the bore 32 is closed by a plug 34 for trapping the ball 33 therein.

The axis 35 of the bore 32 is arranged so that, when the flyweights 21 are at rest in their retracted positions with the fiyweight feet 23 resting on the cap plate 20, as

shown in FIG. 2, the outer end 37 of each bore 32 remote from the flyweight pivot 22, is closer to the motor axis 36 than the inner end 38 of the bore 32. In this position of the flyweights 21, centrifugal force will maintain the ball in the inner end 38 of the bore 32, as shown in FIG. 2. As centrifugal force on the flyweights increases, the flyweights will pivot outwardly to a position where the axis 35 of the bore 32 pivots through a line parallel with the motor axis 36, as shown in FIG. 3. In the latter position of the flyweights, each bore axis 35 is arranged with the outer end 37 of the bore 32 further away from the motor axis 36 than its inner end 38, and the ball 33 is forced to the outer end 37 of the bore 32 by centrifugal force. This movement of the ball 33 shifts the center of gravity of the flyweights 21 radially outward from the flyweight pivot 22. Shifting the center of gravity of the flyweights 21 radially away from the flyweight pivot 22 increases the torque or moment forcing the flyweights 21 radially outward about their pivots 22. This shift in center of gravity occurs relatively abruptly as the ball 33 shifts from one end of the bore 32 to the other. The amount of the shift in the center of gravity depends on the weight of the ball 33 and the length of the bore 32.

The abrupt shift in the center of gravity of the flyweight 21 as it pivots radially outwardly about its pivot axis 22 is illustrated in FIGS. 4 and 5. Initially, when the ball 33 is located in the inner end 38 of the bore 32, looking at FIG. 4, the center of gravity of the flyweight 21 is located at C6 It will be understood that the center of gravity of the flyweight is determined by the combination of its mass plus the mass of the ball 33. At this time the centrifugal force F acting on the flyweight is acting through C6 The moment arm of the centrifugal force F acting about the pivot 22 is indicated as L The torque or moment of the flyweight 21 is the product of F L As explained earlier, as the motor speed increases, the flyweight 21 is forced to pivot radially outward about its pivot 22 by centrifugal force. The flyweight bore 32 eventually reaches a position relative to the motor axis 36 wherein the centrifugal force acting on the ball 33 forces it outward in the bore 32 to the outer end 37 of the bore, as shown in dotted lines in FIG. 4. When the ball 33 reaches the dotted line position shown in FIG. 4, the center of gravity of the flyweight 21 is shifted away from the flyweight pivot 22 to the position indicated as 06 At this time the centrifugal force F acts through CG and the moment arm of F about the pivot 22 is L Now the torque or moment of F is F XL Since CG is at a greater distance from the pivot 22 than CG F L is greater than F L The result of the shift in the center of gravity of the flyweight is further shown in FIG. 5. FIG. is a curve having a vertical axis indicating the torque of the flyweight 21 about its axis 22 and a horizontal axis indicating the speed of the flyweight 21 about the motor axis 36. The initial portion of the curve, rising from zero torque, indicates the change in the initial torque, F L This torque varies in accordance with the increase in centrifugal force as the rotary speed of the flyweight 21 increases. As is well known, the centrifugal force acting on the flyweight will increase relative to the square of the speed of the flyweight.

The abrupt vertical leg of the curve indicates the shift of the ce ter of gravity of the flyweight 21 from CG to CG due to the movement of the ball 33 between the ends of the bore 32. The final leg of the curve illustrates the torque F L which acts about the center of gravity CG The curve in FIG. 5 further includes a dotted line indicating the nature of the torque curve if the shift in center of gravity had not occurred. As is easily seen from this, the shift in center of gravity of the flyweight 21 causes a substantial change in the value of the torque act ing on the flyweight 21 about its pivot 22.

It has been found that the provision of this abrupt change in torque acting on the flyweight 21 results in causing the speed control means to regulate and maintain the speed of the motor within a much narrower speed range than is possible without the abrupt change of flyweight torque. The disclosed abrupt torque change means is particularly necessary in flyweight speed control systems when relatively strong springs are used for retracting the flyweights.

A second embodiment of the invention is shown in FIG. 6. The only difference between this embodiment and the earlier embodiment is the addition of a light spring 40 to the bore 32 serving to bias the ball 33 toward the inner end 38 of the bore. The spring 40 is so light or weak that it does not substantially interfere with the movement of the ball 33 to the outer end 37 of the bore 32 during operation of the flyweight 21. The only purpose of the spring 40 is to insure that the ball 33 remains in the inner end 38 of the bore 32 at low speeds when the grinding tool 1 is placed in a position where gravity might otherwise move the ball 33 to the outer end 37 of the bore 32.

Although two embodiments of the invention are illustrated and described in detail, it will be understood that the invention is not limited simply to these embodiments but contemplates other embodiments and variations which utilize the concepts and teachings of this invention.

Having described my invention, 1 claim:

1. A motor speed control system comprising:

a rotary motor;

variable valve means for supplying energy to said motor and including means urging it to an open position;

a flyweight pivoted on a shaft driven by said motor and movable between a retracted position and an extended position;

means interconnecting said flyweight to said valve means for progressively closing said valve means as said flyweight moves from said retracted position to said extended position; and

means on said flyweight operative to abruptly shift the center of gravity of said flyweight outward from the flyweight pivot as said flyweight is moved outward by centrifugal force from its retracted position to its extended position.

2. A speed control mechanism for a rotary shaft comprising:

a rotary shaft;

drive means connected to said shaft for driving it at a controlled variable speed;

control means connected to said drive means for varying the driven speed of said shaft;

a flyweight pivoted on said rotary shaft for movement radially outward under centrifugal force from a retracted position to an extended position and connected to said control means for controlling said control means in response to the radial movement of said flyweight; and

3. A speed control mechanism for a rotary shaft cornprising:

a rotary shaft;

means on said flyweight for abruptly changing the magnitude of torque caused by centrifugal force acting on the flyweight as the flyweight moves between its retracted and extended positions.

4. A speed control mechanism for a rotary shaft comprising a rotary shaft;

control means connected to said drive means for varying the driven speed :of said shaft;

a fly weight pivoted on said rotary shaft for movement radially outward under centrifugal force from a retrncted position toward an extended position and connected to said control means for controlling said control means in response to the radial movement of said flyweight;

an elongated closed bore provided in said flyweight with one end of said bore being substantially closer to the pivot of said fiyweight than the other end of said bore;

said bore also being located in said flyweight so that said other end of said bore is located closer to the axis of said shaft than the one end of said bore in the retracted position of said flyweight;

said bore being located so that in the extended position of said flyweight the one end of said bore is located closer to said shaft axis than said other end of said bore; and

an inner weight movably contained in said bore for movement between the opposite ends of said bore wherein in the retracted position of said fly weight, centrifugal force maintains said inner weight at said one end of said bore and as said fiyweight moves to its extended position, the bore eventually moves to a position wherein centrifugal force moves said inner weight to the other end of said bore to shift the center of gravity of the fiyweight away from the flyweight pivot, thus increasing the torque of the centrifugal force acting on said fiyweight.

5. The combination of claim 4 wherein:

said flyweight is pivoted on said shaft to move in a plane parallel to the shaft axis.

6. The combination of claim 4 including:

a relatively weak spring located in said bore biasing the inner weight toward said one end of said bore.

References Cited UNITED STATES PATENTS 723,196 3/1903 Dysterud 73-538 771,771 10/1904 Dysterud 73521 2,422,733 6/ 1947 Jimerson 91-76 2,646,978 7/1953 Barnes 73536 2,906,833 9/1959 Lon-g 73-550 3,071,115 1/1963 Schott 91-76 3,279,485 10/1966 Alexander 13757 FOREIGN PATENTS 467,506 8/1950 Canada.

CAR-ROLL B. DORITY, JR., Primary Examiner.