US2365657A - Centrifugal motor speed governor having inertia effect - Google Patents

Description

J. M. NAUL Den;` 19, v1944.

CENTRIFUGAL MOTOR SPEED GOVERNOR HAVING INERTIA EFFECT Filed sept. 2, 194:5

. weights which form a part of the centrifugal Patented Dec. 1,9, 1944 CENTRIFUGAL MOTOR SPEED GOVERNOR HAVING INERTIA EFFECT James M. Naul, Fanwood, N. J., assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation or New Jersey Application September 2, 1943, Serial No. 500,900 7 claims. (C1. zoo-sol In the drawing,

Fig. 1 is a side elevation of an electric'motor embodying the present invention, with certain parts thereof broken away, more clearly to disclose the improved motor speed governor.

Fig. 2 is a. transverse section on the line 2--2 of Fig. 1.

This invention relates to speed governors for electric motors, and more particularly to that type of speed governor which operates, responsively to centrifugal force, to open the electric circuit to the motor when a predetermined speed has been attained and to close the circuit when the motor speed falls below that predetermined value.

While this type of speed governor its fairly Fig. 3 is a detail face view of the combined censatisfactory in .maintaining constant predetertrifugally and inertially actuated element of the mined speeds, there is, however, a certain amount l speed governor. of variation from the desired speeds, commonly Fig. 4 is a top view of the element shown in known as hunting due to the inertia of the Fig. 3.

Fig. 5 is a diagrammatic view of the improved governor. A speed governor of this type is disgovernor illustrating, in dotted lines, the action closed in my United States Patent No. 2,293,996, thereof under an inertia force, and Aug. 25, 1942. Fig. 6 is a diagrammatic illustration of a motor The present invention has as a primary object driving electric circuit embodying the present imto improve the speed governor disclosed in my proved Speed governorpn'or patent, by using the inertia effect oi the Referring more specifically to the drawing, the weights to render the governor more sensitive to 2o invention is disclosed as embodied in an electric changes in speed, thereby to overcome the huntmotor M comprising a casing I which houses the ing tendency of the governor and more nearly usual eld frame, field coils and other elements to maintain the predetermined desired speeds. Common to electric motors, including an arma- Tnis has been attained by so forming the supture shaft 2 which carries a pulley 3 adapted to port for the weights that in each change in speed drive any Suitable mechanism. At one end, the the inertia of the weights reacts through the supmotor Casing iS extended beyond itS Usual lenfsth,

port to actuate the member which effects opening a5 indicated at 4. to I orm a housing for the irnand closing of the motor circuit. This inertia proved governor. Which is designated generally force combines with the centrifugal force, genas G- The opposite Side walls of the extension 4 erated by the rotation of the weights, thereby inare provided With openings- 4' adapted to sive acn creasing the sensitivity of the governor to changes; cess to the governor and these openings are norin speed. mally closed by side cover-plates 5, as shown in It wil1 be understood that the inertia force is Fig- 2. A resistor R and an arc-suppressing conefective instantaneously during a change of denser C. illustrated in Fig 6, are housed within speed, whereas the centrifugal force is slower in a casing 5 secured to the upper side of the motor its action and does not reach its full effect until caeingv a change of speed has been attained. Before describing the improved speed governor, Like the governor disclosed in my prior patent, a brief description will be given oi the motorthe present governor also includes manually con-lz driving electric circuit in Which the governor is trolled means for shifting the circuit-controlling 40, embodied. This circuit is illustrated in Fig. 6 and switch contacts thereby to predetermine the speed comprises line Wires l. and 3 adapted to be conof rotation of the motor. With the present imnested together through the Held coils l'. 8 of proved governor that speed is obtainedmore the motor M1 Emboded in the line 7 iS a line quickly and is held more nearly constant than Switch S comprising contacts 9 and l0 of which is possible with my prior governor which did not the latter is connected to the field coil l through utilize the inertia, of the weights, the resistor R, across which is connected the are- With the above and other objects ln view, as will hereinafter appear, the invention comprises f only iS closed. current flows from the line 1 the devices, combinations and arrangements of through the motor M, but in an amount insufflparts hereinafter set forth and illustrated in the 5o cient to effect rotation of the motor. due to the aocolnpnnying drawing of a preferred embodiaction of the resistor R. Cooperating with the ment of the invention, from which the several line switch S is a speed governor switch T comfeatures of the invention and the advantages atprising contacts ll and 'I2 or which the former tained thereby will be readily understood by those is connected to the contact I0 of the line switch skilled in the art. and the latter is connected with the field coil 'l' suppressing condenser C. When the line switch behind the resistor R. When both the line switch and the governor switch have been closedI full current flows from the line I to the motor without passing through the resistor, thereby tending to rotate the motor at full speed. When a predetermined speed has been attained, as determined by a setting of the contact II, centrifugal and inertia forces acting on the governor G cause contacts II and I2 to be opened, whereupon current flows to the motor through the resistor, thereby causing the motor speed to be reduced. Deceleration of the motor causes the governor again to close the contacts II and I2 to effect acceleration of the motor. This continuous acceleration and deceleration of the motor tends to hold the motor speed at a substantially constant predetermined rate. Obviously, the more sensitive is the governor G the more nearly constant will the motor speed be maintained.

The contacts 9 and I0 of the line switch are preferably carried by spring-arms I3 and I4, respectively, secured, by screws I5, to the inner face of the end wall I6 of the motor housing extension 4. The arm I4 also carries the contact II of the governor switch, while the other contact, I2, of the governor switch is carried by a light springarm I'I secured to the end wall IB by screws I8.

The line switch S and the governor switch T may be closed by any suitable mechanism, to cause the motor to run. One suitable means for this purpose is illustrated in the drawing, but it is to be understood that various other means are contemplated. As shown in the drawing, the switch-actuating means comprises a rod I9 slidingly mounted in bearing-brackets and 20' secured to the motor casing. Secured to one end of the rod 20, byI nuts 2|, 2|, is an arm 22 of insulating material, the upper bifurcated end 22a of which extends into the governor housing and straddles the contact-carrying arm I3. Surrounding the rod I9 between the bracket 29 and the nut 2|, is a coil-spring 23 which tends to shift the rod I9, and, through the arm 22, the contact-carrying arm I3, to the right as seen in Fig. 1 thereby to open the line switch and to. 4 permit the governor switch to open under spring action. On the opposite end of the rod I9 is threaded a thumb-nut 24 which bears against the bearing-bracket 20 and serves, upon rotation, to shift the rod I9 and its switch-actuating arm 22 to the left, in opposition to the spring 23, to-

close the line and governor switches.

The improved governor preferably comprises two interconnected bowed springs b and d of which b is attached to a collare secured upon the armature shaft 2 by set-screw f, while d is arranged diametrically of the shaft and serves as a switch operator. Spring b is of smaller radius than spring d. The springs b and d are secured together at their ends and carry, at their juncture, suitable weights 25 adapted to be moved outwardly under centrifugal force during rotation of the motor. At its mid-portion, in line with the axis of the shaft 2, the diametral spring d carries a button g of insulating material, adapted to act upon the contact arm I1, in opposition to the spring-tension of the latter, to control the opening and closing of the contacts II and I2 in the motor circuit.

As described in my above mentioned Patent No. 2,293,996, the unequal bowing of the elements b and d renders the governor more sensitive to variations in speed than prior governors of this YDG.

As hereinbefore stated, the primary object of this invention is to provide a motor speed governor which is even more sensitive to variations in speed than that disclosed in my prior patent. This has been accomplished by utilizing the inertia of the weights 25 in conjunction with the centrifugal force generated by rotation of the weights. To that end, the oppositely extending arms of the bow spring b are twisted, as indicated at t, so that their outer ends, to which the weights 25 are attached, are arranged at an angle of approximately 60 degrees to the axis of rotation of the governor. Because of this angular arrangement of the arms of the bow spring b, variations in speed of rotation of the governor will, under the influence of the inertia of the weights 25, cause the outer ends of the spring arms to have a circumferential component of motion obliquely of a plane containing the axis of rotation of the governor and the weights 25. This circumferential component of motion will, through the flexing of the opposite ends of the bow spring b, be translated into a radial component, thereby straightening the bowed spring d and withdrawing the button g, when the speed is accelerated, thus opening the contacts of the switch T to reduce the speed of the motor, or, when the -speed is decelerated, to further bow the spring d and effect closing of the contacts to increase the speed` of the motor. For convenience, the bowed spring b may hereinafter bereferred to as a supporting element and the spring d as a connecting element.

It will be understood that acceleration of the shaft 2 will, in opposition to the inertia of the weights25, cause the arms of the spring b to be deflected outwardly and thereby reduce the speed of the motor, while, during deceleration of the shaft, the momentum of the weights will bend the arms of the supporting element inwardly and thus increase the speed of the motor. The inertia of the weights becomes effective instantaneously during a change of speed and works in conjunction with the slower acting centrifugal force of the weights thereby to render the governor more sensitive to variations in speed, whereby a more nearly uniform predetermined speed may be maintained.

Referring to Figs. V2, 3 and 5, let it be assumed that the shaft 2 and governor G are either at rest or arebeing rotated in the direction indicated by the arrows a. Now let it be assumed that the speed of rotation of the shaft is suddenly increased. The inertia of the weights 25 will act in the direction indicated by the arrows i and tend to hold the weights stationary or against acceleration. Thus, at that instant, there will be two opposed forces acting on the twisted arms of the bow spring b, one, the rotation of the shaft 2 which tends to turn the mid-portion of the spring b in the direction indicated by the arrows a, and the other, the inertiafof the weights which opposes such rotation. These opposed forces, acting at radially spaced points on the twisted arms of the supporting element b cause the outer ends thereof to be deflected outwardly and obliquely to the axis of rotation, as indicated by the arrows a: in Fig. 5, and toward the position shown in dotted lines in that figure, thereby causing the contact-controlling button g to be moved from the position shown in full lines toward the position shown in dotted lines, thus opening the circuit and slowing down the motor. Deceleration of the shaft from any acquired speed will cause the parts to react in the opposite direction, as will be readily understood.

, a,ses,osv

Thus the inertia eifect of this governor is combined with its normal centrifugal effect to provide an improved governor of the make-andbreak type which is extremely sensitive to variations in speed and which, therefore, is capable of more nearly maintaining constant any desired .speed of rotation than prior devices of this nature.

In the drawing, the thickness of the metal forming vthe bowed spring members b and d is necessarily shown exaggerated. In practice the metal may be in' the neighborhood of from .005

to .008 inch in thickness. Likewisethe weights V25 have been shown as being relatively small.

It is to be understood that the thickness of the metal of the members b and d and the weight of' the members 25 may be varied as may be required to obtain any desired working condition'.

Having thus set forth the nature of the invention, what I claim herein is:

l. A governor for an electric motor having a rotory shaft, comprising a make-and-break switch controlling the ow of electric current to.4

2. A governor for an electric motor having a rotary shaft, switcheontrolling the flow of electric current to the motor, a supporting element carried by said shaft and having oppositely extending arms, each arm having a portion arranged oblique to the axis of tha shaft, a deformable connecting element secured at its outer ends to the obliquely aranged portions of said arms, weights secured to said connecting element and arms at their points of connection, and a switch-actuating element carried by said connecting element substantially in line with the axis of said shaft, the outer Yends of said anms being arranged to have circumferential and radial components of motion transverselyv of the axis of said shaft under inertia forces exerted by said weights when the speed of rotation of said shaft is varied, thereby to deform said'y comprising a make-and-break` arms and being adapted to be deflected by the movements of said arms under :he combined eentrifugai and inertia forces, and a switch-controlling element carried by said connecting element substantially in line with the axis of said shaft.

4. A governor for an electric motor having .a rotary shaft, comprising a make-and-break switch controlling the now of electric current to the motor, a bowed-spring supporting element secured to said shaft and having oppositely proiecting arms which are twisted in opposite-directions to cause their outer ends tev lie at an angle of approximately sixty degrees to the axis of said shaft and sixty degrees to each other, a

bowed-spring connecting element having its opposite ends connected to the oppositely twisted ends of said arms, weights secured to the connected ends of said arms and connecting element, anda switch-actuating button carried by said connecting element substantially in line with the axis of said shaft, said twisted arms bein subject to the centrifugal force exerted by said weights during rotation of said shaft and to-the inertia forces of said Weights under variationof the speed'ofrotation, said forces acting on said arms to distort them circumferentiaily and radially of saidA shaft thereby to deflect said connecting element and shift said switch-actuating button.

5. A governor for an electric motor having a rotary shaft, comprisingi a make-and-break switch for controlling the flow of electric current to the motor, a supporting element carried by and rotatable with said shaft 'and .having oppositely extending arms, a pair of weights carried by the outer ends of said arms, a deformable connecting element secured tothe outer ends of said arms, a l

switch-actuating Amember carried by said connecting element substantially in line with the axis of the shaft, and means embodied in said'supporting element to cause the free endsof said arms to be moved circumferentially and radially of said shaft under the inertia of said weights during variation in the speed of rotation-of said shaft thereby to deform saidconnecting element and cause it to actuate said switch.

6. In a motor speedogovernor, in combination, a rotary shaft, a pair ofoppositely and radially disposed governor arms carried by said shaft, governor weights carried at the outer ends of said arms, the outer ends of said arms andv saidweights being so constructed and arranged that, under inertia forces, the weights will move in v paths transversely of a plane containing the axis comprising a' make-and-breakswitch controlling theow of electriccurrent to weights and combined circumferential and radial p components of motion obllquely of the axis of the shaft under inertia `forces exerted on said `arms by said weights during speed changes of said shaft, a bowed connecting element having its opposits ends connected with the outer ends of said of said shaft and toward and from said axis, and a diametral switch-operator connected to said weights.

7. A switch actuating element for a speed governorfor an electric motor having a rotary shaft, comprising a pair of oppositely and radially disposed arms can'ied means associated with said arms and actuittiui by the inertia of said weights to cause the weights .mms M. risen by said shaft, g'c'ivernor weights carried at the outer ends of saidarms.

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