US2442456A

US2442456A - Governor

Info

Publication number: US2442456A
Application number: US630914A
Authority: US
Inventors: Robert E Boyden; Edward P Drake
Original assignee: CLARY MULTIPLIER CORP
Current assignee: CLARY MULTIPLIER Corp
Priority date: 1945-11-26
Filing date: 1945-11-26
Publication date: 1948-06-01
Anticipated expiration: 1965-06-01

Description

Patented June 1, 1948 GOVERNOR Robert E. Boyden,

Drake, Glendale,

Multiplier Corporation, n corporation of Californi Application November 26, 1945, Serial No. 630,914

-7Claima.

This invention relates to speed governors and has particular reference to governors for maintaining electric motors at substantially constant speed under varying load conditions.

Heretoi'ore, governors of the above type have generally utilized the differential action between centrifugal force acting on a governor flvw s and a restraining force in the form of a spring to control the speed of an electric motor by opening and closing the switch contacts in the motor circuit by amounts in proportion to the diiilerential action produced.

Also, in the last several years governor manufact'urers have tended to reduce the mass of the flyweights or similar centrifugally operated control means in order to reduce the lag in control introduced by the inertia and momentum of such parts. At the critical control speed of governors of such types, the small amount of movement of the flyweight mass necessary to open and close the contacts in order to control the speed, and the relatively small amount of mass available to cause a controlling action, introduced a detrimental arcing eflect since the contacts are separated only slightly. This arcing effect is accentuated by reason of the fact that since even the maximum separation of the contacts is only a minute amount, the are thus produced still maintains a considerable current carrying capacity. As a result the contacts, instead of completely closing, tend to merely create an arc and then vary the resistance of the are by varying the separation of the contact points. Such arcing necessitates arc damping means such as condensers, etc. to reduce as far as possible the tendency of the contact points to are. Furthermore, such arcing causes loss in electrical power and radio interference as well as deterioration of the contacts.

It therefore becomes the principal object of the present invention to reduce arcing in a motor governor.

A further object of the invention is to obviate the necessity of a condenser or other are damping means for a motor governor.

A further object is to reduce radio interference due to a motor governor.

A further object is to reduce electric power losses in a governor.

A further object is to preduce the frequency at which the contacts of a governor are operated whereby to prolong the life of the contact points.

A further object is to provide an arrangement of governor elements whereby the frequency of switch contact action is automatically regulated Los Angcles, and Edward P.

Calif., ass

inner: to Clary Los Angeles, Calif., a

so that when the motor is runmng idle a minimum frequency of contact action is obtained to decrease contact deterioration and when the motor is running under load the frequency of contact action is automatically increased to maintain a substantially uniform motor speed.

A further object of the invention is to provide a simple and compact governor which is inexpensive to manufacture.

The manner in which the above and other objects of the invention are accomplished will be readily understood on reference to the following specification when read in conjunction with the accompanying drawing;

Fig. 1 is a side view partly in section, of an electric motor governor embodying the present invention.

Fig. 2 is a front view of the motor governor and is taken along the line 2-2 of Fig. 1.

Fig. 3 is a transverse sectional view of the flyweight unit and is taken along the line 33 of Fig. l.

Fig. 4 is a sectional view of a modified form of fiyweight unit.

Fig. 5 is a sectional view through the governor switch arrangement and is taken along the line 5-5 of Fig. 2.

Fig. 6 is a schematic diagram of an exemplary circuit showing the connection of the motor governor to an electric motor.

Fig. 7 is a modified form of switch which may be incorporated in the governor of the present invention.

Referring to the drawing, the governor, generally indicated at I 0, is illustrated as comprising a. main bracket ll attached by screws l2 (Fig. 2) to the end casing of a. motor iii.

The flyweight unit of the governor comprises a hub H attached by a pin i5 to the armature shaft it of the motor. A fiyweight bracket H- is secured to the hub and has mounted thereon on diametrically opposed sides of the motor shaft, a pair of transversely extending pins l8 which pivotably support fiyweight levers IQ for movement about axes extending to right angles to the axis of rotation of the flyweight unit. A ball 20, freely movable in an axially extending hole in the hub i4, is adapted to be forced along the axis of the motor by the tails of the levers l9.

It will be noted that the center of gravity of each of the levers i9 lies to the right (Fig. 1) of its pivotal axis so that, as the motor accelerates, the tails of the levers l9 force the ball 20 outwardly against an car 22 located at one end of a lever 2|. The latter is pivoted on a pin 23 (Figs. 1

and 2) securely mounted on an upturned ear of the main bracket II. An car 24 on the lower end of lever 2| overlies a plunger 25 (Fig. of a switch generaly indicated at 26. 1

The switch 26 comprises a body 21 of insulating material attached by screws 23 to the bracket II. A leaf spring 29 of electrically conductive material is attached at one end by a screw 30 to an electric terminal which is connected by screw 3| to a conductor 32. At its free end 29, the leaf spring has a contact I30 normally engaging a stationary contact 33 secured as by screw 34 to a second terminal to which is attached a second conductor 36.

The spring 23 comprises a main section 31 which extends from the screw 30 and is biased toward the contact 33. One or more toggle sections 33 of the spring are integrally formed or attached at 39 to the main section and are bowed under compression, being held at their free ends by a inlcrum block 33 which is also held in place by the screw 30.

It will be noted that the fulcrum points of the toggle sections 38 are normally below a line passing through the point 33 and the point of attachment of the spring to thescrew 30. Thus, the vertical component of force (as viewed in Fig. 5) exerted by the toggle section 33 normally aids the biasing effect of the main section 31 to press the spring into intimate engagement with the contact 33. Whenever the plunger 25 is pressed inwardly against the action of the main portion 31, the latter will move downward against its own biasing effect as well as against the toggle action of sections 38 until the section 31 passes below the fulcrum point of section 38. At that time, the toggle sections 38 will exert their vertical component of force in a downward direction, aiding the plunger 25. However, the downward component of force is not sufficient to overcome the upward biasing effect of the section 31 so that upon release of pressure upon the plunger 25 the contact spring will assume its normal closed condition illustrated in Fig. 5.

The above described switch is commercially known and available under the name microswitch, being disclosed-and claimed in the patent to P. K. McGall, Number 1,960,020. However, it is to be understood that other types of switches operating under the same basic type of toggle action may be employed without departing from the scope of the present invention.

It will be seen from the above that as the speed of the motor approaches a definite amount, the flyweight levers I9 will rock about their axes, pressing the ball 20 outward to rock lever 22 and thereby cause the plunger 25 to press downward against the spring section 31. As the force against the spring section 31 increases, it will gradually overcome the bias effect of the spring as well as the force exerted by the toggle sections 38 and will finally force the spring into a lowermost position, breaking the circuit. This final action will occur in an abrupt movement, thus reducing the tendency of an arc to form between the contacts. As the speed of the motor is reduced due to breaking of the circuit between the contacts the reduction of centrifugal force developed by the flyweight levers I3 will permit the spring 31 to again assume its closed position. This closing action of the spring will again occur in an abrupt movement due to the toggle action of the spring section'38.

Means are provided for adjusting the governor to control the speed of the motor as desired.

- Referring to Fig.

1 an adjusting screw 40 is threaded in a collet 4| integrally attached to the bracket II. Located between the ends of screw 40 and the ear 22 of lever 2| is a compression spring 42 which may be adjusted by the screw to aid the spring section 31 in opposing the action of the fiyweight levers. the motor may be increased by increasing the pressure of the spring 42 against the lever 2|, requiring greater centrifugal force to be developed in the fiyweight levers by virtue of a higher rotational speed in order to open the switch contacts.

A spring 44 is inserted between the ear 22 of lever 2| and the bracket II to oppose the spring 31 so that the screw 40 may be adjusted to efffect either an aiding or opposing action upon the biasing spring section 31 to vary the controlling,

speed of the motor throughout a relatively wide range of speed.

It will be noted that the spring 44 is considerably weaker than the compression spring 42 since the former is utilized during control of the governor at relatively low speeds wherein the centrifugal force developed by the fiyweight levers is correspondingly weaker. This combination of springs results in a more uniform control throughout the various possible speed ranges of the motor.

During operation of the motor and governor under no-load conditions the switch contacts are opened and closed at a relatively low frequency, such frequency being dependent upon the amount of revoluble mass or flywheel effect of the motor armature and other rotatable parts connected thereto. However, under load conditions, this frequency is increased and such increase is proportional to the increase in load. This feature results in a, considerable saving in contact deterioration.

Fig. 6 illustrates an exemplary connection of the governor to the motor, the latter being illustrated as of the series type comprising a field winding I3a and an armature I3b connected in series with the contacts 33 and I30. A resistance 45 may be shunted across the contacts to reduce the voltage drop during opening and closing of the contacts. The latter is illustrated in Figs. 1 and 2 as being supported in the governor unit by cars 46 extending from the brackets II.

Fig. '7 illustrates a modified form of switch which may be used in lieu of the switch 23 (Fig. 5). This switch comprises a base 21a of insulating material to which is attached, by a screw I40, a flexible terminal I35. The forward end of the terminal is biased downward a slight amount and carries a contact 33a. A second contact I30a is mounted on a pivotal piece |3| fulcrumed on a pivot block 39a suitably attached to the base 210.,

the block 390. also forming the second terminal for the switch. A biasing spring I32 is tensioned between the base and the piece I3I to normally hold the contacts in closed condition.

A spring I33 is tensioned between the block 39a and the outer portion of the piece I3I to exert a toggle action on the piece. That is, in the closed condition of the switch, as illustrated in Fig. 7, the center line of the spring I33 extends above the fulcrum point of the piece I3I, thus exerting an upward force, aiding the spring I32.

When the piece I3I is forced downward by a plunger 25a. the flexible terminal I35 will cause contact 33a to follow the contact I300 until the piece I3I moves to a position wherein the center line of spring I33 passes below the fulcrum point of the piece. The contact I30a will nOW leave Thus, the speed of Y Contact 33a in a somewhat abrupt manner in view of the reversal of the action of spring I". Although the spring I33 will now oppose the tension of spring I32 it will not quite overcome the latter so that when pressure on plunger 25a is released the switch will reassume its closed condition. A limit stop may, if desired, be provided to prevent downward movement of the piece "I beyond a definite limit. For this p pose, a foot ill formed on the lower end of the terminal I" may be extended laterally to limit downward movement of the piece l3l.

Fig. 4 illustrates a modified form of flyweight unit in which the controlling efiect of the flyweight levers l9 may be adjusted. In this figure all elements similar to those shown in Fig, 1 are indicated by the same reference numerals. Threadably attached to the outer ends of the flyweight levers l9 are adjustable screws 41. By adjusting the screws 41 outwardly a greater amount of centrifugal force is developed and therefore a more positive control action is effected by the flyweight levers. The provision of this adjustment enables a minimum flyweight mass to be used whereby to obtain a readily responsive controlling action while at the same time providing a governor which will be efi'ective over a wide range of speed, particularly at low speed since the centrifugal force developed in any rotatable body is proportional to'the square of the speed of such body.

We claim:

1. A motor speed control device, comprising: electric contact means for controlling a circuit to a motor, said contact means being movable between open and closed positions, spring meansnormally holding said contact means in closed position, a governor device adapted to be rotated by said motor and including means displaceable by centrifugal force during rotation thereof for opening said contact means; a snap-over spring means coacting, in a first position thereof, with said first-mentioned spring means, to close said contact means, means operable by said displaceable means upon a predetermined displacement thereof by centrifugal force for causing said snap-over spring means to move from said first position to a second position, said snap-over spring means being effective to substantially abruptly move between said two-mentioned positions, a third spring means opposing the action of said first-mentioned spring means and aiding 6 eratively connected to said dispiaceable means,

and means for adjusting the eflective force of said said governor device and said second spring.

means in opening said contact means, and means for adjusting the effective force of said third spring means.

2. A motor speed control device, comprising: electric contact means for controlling a circuit to a motor, said contact means being movable between open and closed positions, spring means normally holding said contact means in closed position, a governor device adapted to be rotated by said motor and including means displaceable by centrifugal force during rotation thereof for opening said contact means; a snap-over spring means coacting, in a first position thereof, with said first-mentioned spring means, to close said contact means, means operable by said displaceable means upon a predetermined displacement thereof by centrifugal force for causing said snap-over spring means to move from said first position to a second position to open said contact means, said snap-over spring means being eilective to substantially abruptly move between said two-mentioned positions, third spring means 01)- spring means to selectively aid or oppose said governor device. 3. In an electric motor governor having electric contact means for the circuit of said motor, said contact means being movable between open and closed positions, and a governor device adapted to be rotated by said motor and including means displaceable by centrifugal force during rotation thereof; a leaf spring supported in cantilever fashion adjacent one end thereof and adapted to flex at the other end thereof to open and close said'contact means, a spring strip connected at one end to the flexible end of said leaf spring, said spring strip being bowed in longitudinal compression and being pivoted at the other end thereof at a point between the ends of said leaf spring, said leaf spring normally assuming a position on one side of the dead center of the springassembly formed by said leaf spring and said spring strip whereby to close said con tact means, means operable by said displaceable means upon a predetermined displacement thereof by centrifugal force for acting on said leaf spring between said point of support thereof and said pivot point of said spring strip, whereby to cause said spring assembly to open said contact means with a snap action, a second spring means operatively associated with said spring assembly for exerting a biasing effect thereon, and means for adjusting the force of said second spring means to selectively either aid or oppose the action of said device and thereby affect the action of said spring assembly in opening and closing said contact means throughout the range of movement thereof.

4. A motor speed control device comprising: a bracket adapted to be secured in fixed relation to a motor; a centrifugal governor adapted to be driven by said motor and including flyweight means responsive to centrifugal force; a normally closed switch mounted upon said bracket; a lever; means .pivotally mounting said lever upon said bracket at a point intermediate the ends of said lever, one arm of said lever being engageable with said switch for actuating said switch to its open position; a spring connected with the other arm of said lever and continuously biasing said lever in a direction tending to allow opening of said switch, said other arm being operable by said nyweight means to actuate said lever in the same direction as said spring; and a. second spring acting on said lever yieldably opposing the force of said flyweight means and tending to actuate said lever in a direction to allow closing of said switch.

5. A motor speed control device comprising: a bracket adapted to be secured in fixed relation to a motor; a centrifugal governor adapted to be driven by said motor and including fiyweight means responsive to centrifugal force; a normalby closed switch mounted upon said bracket; a lever; means pivotally mounting said lever upon said bracket at a point intermediate the ends of said lever, one arm of said lever being engageable with said switch for actuating said switch to its open position; a spring connected with the other arm of said lever and continuously biasing said lever in a direction tending to allow opening of said switch, said other arm being operable by said fiyweight means to actuate said lever in the same direction as said spring; a second spring acting on said lever yieldably opposing the force of said flyweight means and tending to actuate said lever in a direction to allow closing of said switch; and means carried by said bracket for adjusting the force of said second spring.

6. A motor speed control device comprising: a bracketadapted to be secured in fixed relation to a motor; electric contact means for controlling a circuit to said motor and mounted on said bracket, said contact means being movable between open and closed positions; spring means normally holding said contact means in closed position; a centrifugal governor adapted to be driven by said motor and including means displaceable by centrifugal force during rotation thereof a lever; means pivotally mounting said lever upon said bracket at a point intermediate its ends; one arm of said lever being operable by said displaceable means to cause the other arm thereof to move said contact means to open position; a snap-over spring means coacting, in a first position thereof,, with said first-mentioned spring means to close said contact means, and coacting, in a second position thereof, with said displaceable means upon a predetermined displacement thereof to open said contact means, said snap-over spring means being effective to substantially abruptly move between said twomentioned positions; a spring connected between said lever and said bracket and continuously biasing said lever in a direction tending to open said contact means; a second spring acting on said lever yieldably opposing the force of said displaceable means and said first-mentioned spring; and means carried by said bracket for adjusting the force of said second spring.

7. A motor speed control device, comprising: electric contact means for controlling a circuit from said first position to a second position, said snap-over spring means being effective to substantially abruptly move between said twomentioned positions, a third, spring means'opposing the action of said first-mentioned spring means and aiding said governor device and said second spring means in opening said contact means, and a weight element carried by said flyweight means and adjustable relative thereto to vary the centrifugal force efiective during rotation of said fiyweight means.

ROBERT E. BOYDEN. EDWARD P. DRAKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date McGall May 22, 1934 Warner Nov. 5, 1940 Number