US2311409A - Speed governor - Google Patents

Description

Feb. 16, 1943. F. w. MERRILL 2,311,409

' SPEED eovmmon Filed Dec. {5, 1941 2 Sheets-Sheet 1 Inventor-z Frank W. Merrill,

- His Attorne g.

Feb. 16, 1943. F. w. MERRILL 2,311,409

SPEED GOVERNOR Filed Dec. 3'. 1941 2 Sheets-Sheet 2 Va n55 amass Fig.5. sown/10R warmers w/nmur .sma/uzm 6'0 CYCLE FER SECWVD TIM/N6 WIWE WIT/l STAB/LIZER 6'0 CYCLE PER SECflA/D TIN/1V6 WAVE Ifiventor':

Frank W. Merrill,

His Attorneg.

Patented Feb. '16, 1943 2,311,409 srna'n GOVERNOR Frank W. Merrill, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application December 3, 1941, Serial No. 421,436

8Claims.

This invention relates to speed governors and more particularly to centrifugally operated speed governors of the center contact type.

By center contact governor is meant a governor having a rotatable member carrying a contact which is mounted concentrically with respect to its axis of rotation and which is actuated by means of centrifugal weights so as to movein an axial direction. This so-called center contact cooperates with a fixed contact for opening and closing a speed control circuit. The position of the fixed contact is usually adjustable in the axial direction so as to provide adjustment of the speed setting of the governor. Thus, depending upon the position of this flxed contact, the amount of centrifugal force and hence speed required to move the center contact against the opposing action of the spring will be varied. The governor may be embodied in a number of forms, some of which are shown in Tiffany Patents Nos. 1,136,739 and 1,303,417 and also in Ulmer Patent No. 1,795,240 and Sole Patent No. 1,860,556; All of those governors are characterized by the use of a transversely flat blade spring which carries the center contact and which also carries one or more actuating weights which serve to bend the spring longitudinally under the influence of centrifugal force. This spring is usually made of steel and it may either be normally straight as in the 'I'iflany patents or normally curved, the curve being either concave inwardly as in the Ulmer patent or convex outwardly as in the Sole patent.

he most common use of such a governor is as an automatic speed governor for an electric motor in which case the contacts are connected, either directly or indirectly through an amplifier, in either the motor armature circuit or the moto. field. circuit. t serves to compensate for ovations in motor load, motor supply voltage anti motor temperature. 1 11 these variations norrnahy tend to vary the speed of a motor, the temperature variation causing variation in resistance of the motor windings which in turn varies the current in them and hence the speed.

For ordinary variations in these quantities of a few per cent the regulator operates very satisiactorily to maintain constant speed. However, over a great voltage range, such as a range of 2 or more to 1, typically from 350 volts to 150 volts, combined with load changes, or over a very wide adjustable speed range such as 4 to 1, typically 8,000 R. P. M. to 2,000 R. P. M. combined with load changes on the motor it has been found that the governor becomes unstable and what may be termed rough in operation. In order that the governor be able to maintain constant speed under such wide variations in operating conditions it is necessary that its contacts be able to control a relatively large amount of power, either directly or by means of a suitable amplifier. In either case the power impulses established by the opening and closing of the regulator contacts are so great that any deviation from their normal steady vibratory beat will cause great surges in the valve of the input current to the motor. With a direct current motor these surges act like a superposition of alternating current on the otherwise direct current input and cause abnormal losses and poor commutation.

. I have found that this unstable or rough oper ation and its accompanying power surges may be eliminated by the addition of what I call a stabilizing weight or weights to the center contact spring assembly. These stabilizing weights are so mounted that their center of gravity lies the spring and center contact to sudden jumps or movements in a manner to spring so that it has a fluttering action interferes with the natural steady vihr" tion or the center contact. The stem. weights, however, act like a top or gyrosc produce relatively powerful effect prevent the spring from twisting so c to move its center part out of parallelism with its nor= mal plane of rotation.

In addition to their the gyroscopic effect the stabilizing weights also have a straightforward intertia effect which in many instances substantially improves the governor action. For example, without the stabilizer weights a con ter contact regulator cannot regulate motors with heavy rotors without violent hunting. 'ihis is because the regulator is so much faster mm the inertia response of the motor rotor that the governor contacts will close and remain closed for a large percentage of the cycle, and then open suddenly and remain open for quite a long time while the rotor is responding to the impressed change of flux. When the stabilizer weight is added it slows the period of the spring moving back and forth in an axial direction. After this is sufficiently slowed, the spring takes up a vibratory motion which fits in with the heavy inertia of the motor rotor and good regulation is obtained.

An object of the invention is to provide a new and improved speed governor.

Another object of the invention is to provide novel stabilizing means for centrifugal speed governors of the center contact type.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings Fig.1 illustrates a side view of a regulator embodying my invention in which the governor casing is partly broken away to show its construction; Fig. 2 is a perspective view of the rotating member and-center contact assembly of the governor; Fig. 3 is an oscillogram of the voltage across the governor contacts without my stabilizer, and Fig. 4 is a similar view with my stabilizer.

Referring now to the drawings in which like reference numerals designate the same parts in the two views, the regulator comprises a rotatable member I which may be made of any suitable material and which is adapted to be mounted on the end of a shaft 2, such as the shaft of an electric motor, a part of the housing of which is shown at 3; Mounted on the rotatable member is a transversely flat longitudinally curved spring 4 which is preferably made of suitable spring steel. The ends of this spring are fastened by any suitable means, such as rivets, to the periphery of the rotatable member in such a way that the spring extends across the axis of rotation of the rotatable member. As shown, the spring is curved so as to be concave inwardly as viewed from left to right in the drawings. Fastened to this spring'd by any suitable means, such as rivets, are actuat ng weights 5 which are located near the ends of the spring and on opposite sides of its center. Carried at the center of the spring and mounted concentrically with respect to its axis of rotation is a center contact 6 which cooperates with a normally fixed but axially adjustable contact I carried on the end of a threaded screw b which is turned by means of a knurled knob 9. Electrical connections are made to the center contact through the spring 4 by means of a collector ring ill on the rotatable member and a brushassembly II carried by a housing 82.

The stabilizing means for the governor comprises a thin blade or bar I3 carried by the spring 4 and mounted transversely thereon by means of rivets l4. At the extremities of this bar are stabilizing weights IS. The center of gravity of the weights l5 lies substantially in the plane of rotation of the center part of the spring 4 so that the centrifugal force produced by these weights produces a gyroscopic effect which stabilizes the plane of rotation of the center part of the spring 4 and hence prevents fluttering of the spring and theturning of the face of the center contact out of its normal plane of rotation which is perpendicular tothe axis of rotation. I

It has been found that when the stabilizer bar I3 is riveted flat against'the convex side of the spring 4 it sometimes causes a slight spring distortion which interferes with the best operation of the governor. In order to overcome this small washers are interposed between the surfaces of these elements and the small side rivets and large center contact rivet pass through them. The spacing provided by these washers leaves the spring free to move freely and regulate in its usual manner.

The electrical connections to the stationary center contact are made by a'spring l6 and connector H.

The operation of the illustrated embodiment of the invention is as follows: As the rotatable assembly increases its speed the centrifugal I force developed in the weights 5 bends the spring 4 ,so as to movethe center contact 6 toward the fixed contact I. This action is of course restrained by the spring. At a predetermined "speed the contacts touch thereby completing an electric circuit which by well-known means can be caused to reduce the speed of rotation of the shaft 2. As soon as the speed is reduced slightly the contacts separate whereby the speed is again increased. In this manner the contact 6 has a vibratory motion in the axial direction.

The stabilizing Weights E5 on the cross-bar i4 exert equal and balanced tension on the bar as the speed increases but have no direct ef-' feet on thefunction of the actuating weights. There is an. indirect effect, however, due to the inertia of these weights which must not be overlooked. This is beneficial up to a'certain point in reducing vibration frequencies in an axial direction higher than the fundamental established by the time constant of the fields and the inertia of the rotor; but the stabilizer weights must not be made so heavy as to slow the vibration period below this fundamental frequency or the accuracy of the regulation will be seriously affected.

In Fig. 3 an oscillogram of the voltage across the governor contacts when the governor is not provided with my stabilizing means is compared with a sixty cycle per second timing wave. The regulated device was a three horsepower cross armature reaction excited direct armature reaction compensated motor. As will be seen by a comparison of the curves, the contact frequency was about 7 cycles per second. Furthermore, the voltage range is relatively wide resulting in a large modulation of the power of the regulated motor thereby producing objectionable surges and disagreeable noise. Fig. 4 shows the effect of adding my stabilizing means. No other changes were made. This resulted in such an increase in frequency of the governor contacts .that the timing wave has been shown stretched out so as to make easier a comparison between the two curves. parison, the governor contact frequency has increased to about cycles per second and the amplitude of the contact voltage has been substantially reduced. Furthermore, the contact voltage wave is much more regular when the stabilizer is present than when it is absent.

While there have been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art-that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and. modifications as fall within the true spirit and scope of the invention.

Aswill be seen by such com- What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A centrifugal speed governor of the center contacttype comprising, in combination, a re tatable member, a transversely flat steel spring mounted on said member and extending longitudinally across the axis of rotation of said member with the portion of its flat side which is in the vicinity of said axis being perpendicular to said axis, a center contact mounted on said spring concentrically with said axis, an actuating weight mounted on said spring for bending it under the influence of centrifugal force so as to move said center contact axially, stabilizing weights mounted on said spring on opposite sides of said center contact for holding the face of said spring in the vicinity of said center contact perpendicular to said axis by virtue of their gyroscopic effect, and a fixed contact for cooperation with said center contact.

2. A centrifugal speed governor of the center contact type comprising, in combination, a rotatable member, a center contact, means comprising a transversely fiat steel spring for supporting said contact on the axis of rotation of said member, the portion of said spring in the vicinity of said center contact being in a plane which is substantially perpendicular to said axis of rotation, stabilizing means for said portion of said spring comprising a transverse member fastened to said portion of said spring at a pin" rality oi spaced points and extending outwardly therefrom in both directions in said. plane, and stabilizin weights fastened to the ends of said transverse member and acting under the infiu= ence of centrifugal force to produce a gyroscopic effect tending to prevent said portion of said spring from deviating from parallelism with said plane of rotation.

3. A centrifugal speed governor of the center contact type comprising, in combination, a rotatable member, a center contact, means comprising a transversely fiat steel spring for supporting said contact, on the axis of rotationof said member, the portion of said spring in the vicinity of said center contact being in a plane which is substantially perpendicular to said axis 01' rotation, means including actuating weights carried by said spring on opposite sides of said portion of said spring for bending said spring under the influence of centrifugal force so as to move said center contact axially, a fixed contact for cooperation with said center contact, stabilizing means for said portion of said spring comprising a transverse member fastened to said portion of said spring at a. plurality of spaced points and extending outwardly therefrom in both directions in said plane, and stabilizin weights fastened to the ends of said transverse member and acting under, the influence of centrifugal force to produce a gyroscopic eflfect tending to prevent said portion of said spring from deviating from parallelism with said plane of rotation. r

4. A stablized center contact centrifugal speed regulator comprising, in combination, a rotatable member, a transversely flat blade spring, means .for fastening the ends of said spring to said member on diametrically opposite sides of the lines axis of rotation thereof, said spring being bent longitudinally so that the center part thereof at said axis of rotation and predetermined points thereon on opposite sides of said axis of rotation lie in different planes of rotation, weights fastened to said spring at said points whereby the eiTect-of centrifugal force on said weights as said member rotates about its axis of rotation is to bend said spring so as to move its center part toward the plane of rotation of said weights, a contact mounted on said spring at its center point, a fixed contact for cooperation with said spring carried contact, means for stabilizing said spring comprising a transverse member fastened to said spring at its center part and lying in its plane of rotation, and weights fastened to said transverse member on opposite sides of said center part whereby the effect of centrifugal force on said last-mentioned weights is to produce a gyroscopic effect tending to stabilize the direction of the plane of rotation of the center part of said spring.

5. In a centrifugal speed regulator of the center contact type, a fixed center contact, a rotatable cross bar assembly comprising a transversely fiat longitudinallycurved steel spring, a substantially straight bar fastened crosswise to the center of said spring, a second center contact mounted at the intersection of said spring and bar for era-operation with said fixed center contact, a pair of actuating weights mount-ed ,iacent the ends of said spring and a pair of stabilizing weights mounted adjacent the ends oi said bar,

6.. The combination as set forth in claim 5 wherein said spring and bar are of substantially the same length and said actuating and sta bilizing weights are of substantially the same size.

7. A vibratory contact speed governor for electric motors comprising, in combination, a contact which is normally fixed with respect to said governor, a contact for co-operation therewith which is normally vibrated relative to said governor, a spring for urging said normally vibratory contact in one direction, means including a centrifugally actuated weight for urging said normally vibratory contact in the opposite direction, and a stabilizing weight attached to said normally vibratory contact for increasing its inertia in the direction of its vibratory motion without varying the centrifugal force on it in the direction of its vibratory motion.

8. A stabilized center contact speed governor comprising, in combination, a rotatable contact, a normally fixed contact for co-operation with said rotatable contact, means for vibrating said rotatable contact in its axial direction into and out of engagement with said fixed contact including a centrifugal weight for urging said rotatable contact in one direction and a spring for urging it in the opposite direction, and means for increasing the natural period of vibration of said rotatable contact comprising an additional weight attached to said rotatable contact so that the centers of gravity of said rotatable contact and said additional weight coincide.

FRANK W. MERRILL.

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