US2920158A - Rotary switch governor - Google Patents

Description

Jan. 5, 1960 E. c. WALKER, JR 2,920,158

ROTARY SWITCH GOVERNOR Filed July 11, 1956 INVENTOR. 52ml 6'. WaZkegJ. M

United States Patent Ofiice "2,920,158 Patented Jan. 5, 1960 ROTARY SWITCH GOVERNOR Emil C. Walker, Jr., Woodstock, Ill., assignor to Comptometer Corporation, a corporation of Illinois Application July 11, 1956, Serial No. 597,231

' 16 Claims. (Cl. 200-80) This invention relates in general to speed governors or controllers for electric motors and has more particular reference to such a governor of the make-and-break, electrical contact type.

An object of the invention is the provision of a novel make-and-break' electrical contact governor adapted to provide improved motor speed regulation or control with reference to a desired or predetermined motor speed.

Make-and-break electrical contactgovernors are, as is well known in the art, essentially electrical switches. Usually such a switch is mounted on, and is rotatable with, the shaft of a motor, and has its contacts electrically connected in series with the field winding of the motor. In a conventional governor switch of such a type a fiat resilient strip of metal mounted at one end outwardly from the axis of the motor shaft and extending from its mounting transversely of, and in spaced relation to, that shaft axis provides a cantilever spring which is rotatable withthe motor shaft. That cantilever spring has secured thereto in spaced relation to its mounting a governor contact and is yieldable under the influence of the centrifugal force exerted on the contact and spring.

Such a cantilever spring is usually so mountedthat the spring is flexed or otherwise provided with an initial stress yieldably holding the cantilever mounted contact in electrical engagement with another governor contact, also rotatable with the motor shaft, when the motor is idle. During operation of the motor, when the rotational speed of the motor shaft, and hence of the governor, exceeds a predetermined speed, the centrifugal force exerted on the cantilever spring and the contact thereof will overcome the initial stress of the cantilever spring and cause the contacts to separate. Separation of the governor or switch contacts opens or breaks the input circuit of the motor, which results in deceleration of the motor and its shaft. When the rotational speed of the motor shaft and the governor decreases to a value at which the centrifugal force applied to the cantilever spring and its contact becomes less than the initial stress in the cantilever spring, that spring moves its contact back into electrical engagement with the other governor contact to reclose or remake the input circuit of the motor.

Such a governor may be constructed which initially provides acceptable speed regulation with respect to a relatively high speed or a relatively low sped by employing a relatively thick or relatively thin cantilever spring, respectively. The speed at which that governor is effective, whether relatively high or low, however, changes to an undesired speed after a relatively short period of use due to deterioration of, for example, the cantilever mounted, governor contact incidental to the operation of the governor.

As examples of such deterioration and the effects thereof, erosion of the cantilever mounted contact causes a decrease in the initial stress of the cantilever spring resulting in a decrease in the speed at which the governor is effective, and migration of the material of that contact causes an increase in that initial stress resulting in an increase in the governed speed. Moreover, a thick cantilever springresults in relatively large decreases or reductions of the governed speed for small amounts of erosion of that contact, whereas, a thin cantilever spring causes relatively small decreases or reductions of the governed speed for the same or even greater amounts of erosion of that contact.

Consequently, while such a governor may be initially effective to maintain the speed of the governed motor substantially constant, i.e., within an acceptable range of fluctuation, at the predetermined speed, that speed, after a relatively short period of operation, will change to a greater or lesser value, depending upon whether migration or erosion has occurred during that period of operation.

Another object of the invention is the provision of an improved make-and-break electrical contact governor wherein the effects of contact erosion, cont-act migration, and perhaps other contact deterioration, incidental to the use of the governor, on the governed motor speed is minimized. I

A further object of the invention is the provision of such a governor, the speed regulation characteristics of which are substantially independent of the changes in dimension of the governor contacts due to erosion or migration.

Another object of the invention is the provision of a make-and-break electrical contact governor which is adapted to maintain a substantially constant predetermined motor speed during relatively long and continuous use of the governor.

A further object of the invention is the provision of such a governor that is readily adjustable to vary the speed at which the governed motor is to operate.

Yet another object of the invention is the provision of such a governor which is adapted to regulate or control the speed of an electric motor at either a relatively high or a relatively low predetermined speed.

A further object of the invention is the provision of such a governor wherein a cantilever spring mounted contact is yieldably held in electrical engagement with another governor contact when the governed motor is idle, and wherein operating means is movable in response to centrifugal force at a predetermined motor speed for operating the cantilever spring to separate thegovernor contact thereof from the other governor contact.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, when taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

In the drawings:

Figure l-is an end view of an electric motor with a governor embodying the features of the invention;

Fig. 2 is a fragmentary side view, partially in cross section, of the motor and governor taken substantially along the lines 2-2 of Fig. l; and

Figs. 3, 4, and 5 are fragmentary views of the novel governor showing the make-and-break governor contacts in their positions while the motor is'idle, during operation just prior to separation, and during operation after separation, respectively.

. According to the present invention, a motor-speed governor of the make-and-break, electrical contact type is provided wherein the'separation of the governor contacts is not determined by the centrifugal force of one of those contacts overcoming the initial stress provided in a resilient member, for yieldably holding it in closed relationship to the other of those contacts. Instead, in the novel governor, one of the governor contacts is yieldably held in closed relationship to the other of those contacts by the centrifugal force of the first mentioned contact during operation of the governed motor at speeds below a desired or predetermined value. When the governed motor is idle, one of the governor contacts is held in engagement with the other of those contacts by governor operating means which is mounted for movement by centrifugal force to release the first mentioned governor contact and, when the motor speed exceeds the predetermined value, to separate that contact from the other governor contact.

That governor operating means is yieldably held in its position for holding the contacts closed by a relatively weak or thin spring and has a mass which is displaceable by centrifugal force against the action of that spring a relatively great distance with respect to the maximum permissible degree of contact deterioration for a small variation in the speed of the motor. By so arranging such a governor operating means as to engage the movable governor contact during displacement of that means by centrifugal force, a switching action is provided which is primarily dependent upon the characteristics of the mass of the switch operating means and its mounting.

That mass is large relative to the mass of the movable governor contact and that governor contact is so mounted that the centrifugal force of the latter during operation of the governed motor results in a small force yieldably holding that contact in engagement with the other governor contact. Consequently, the movement of the mass of the switch operating means by centrifugal force is the dominant factor influencing the separating of the governor contacts. Because that mass is of constant value for each governor, variations of the predetermined speed at which the governor is effective will depend upon or be determined by the ratio of the rotational speed of the motor or governor required to displace that mass sufficiently to separate the governor contacts before deterioration of the movable governor contact to that speed of the motor or governor required to displace that mass suf ciently to separate the governor contacts before deterioration of the movable governor contact to that speed of the movable governor contact. For up to about ten percent reduction in thickness of the movable governor contact, that ratio will remain at about one (1) where, as herein, the displacement of the movable governor contact due to the maximum permissible extent of deterioration thereof is such a small percentage of the displacement provided for the mass of the switch operating means.

Illustrative of the invention, the accompanying drawing shows a preferred embodiment thereof. As therein shown an electric motor 11 has its armature shaft 12 projecting from an end of the motor casing. The novel governor is secured on that shaft by any suitable mounting means and rotates with the shaft outside of the motor casing. The direction of rotation is indicated by the arrow 12a.

As shown in Figs. 1 and 2, the means for so mounting the governor on the motor shaft 12 comprises a metal sleeve 13 fixed on that shaft by a set screw 14 to rotate with the shaft and having a reduced outer end portion 15 providing a shoulder 16 intermediate the ends of that sleeve. Arranged on the end portion 15 of the sleeve 13 in engagement with the shoulder 16 is a centrally apertured disc 17 of Bakelite or other suitable insulation. The disc 17 is clamped between the shoulder 16 and a washer 18 which is arranged on the reduced end portion 15 of the sleeve after the disc has been positioned thereon, the disc and washer being held in place as by peening the outer edge 15a of the reduced portion 15 of the sleeve.

Mounted on the disc 17 at opposite faces thereof by rivets 19 are an outer contact ring 21 of metal and an outer substantially L-shaped metal bracket having an arm 22 extending outwardly from the face of the disc and an arcuate arm 23 integral with the arm 22 and held against the disc by the rivets 19. Similarly mounted on the disc 17 by rivets 24 are an inner contact ring 25 of metal and an inner substantially L-sha'ped metal bracket having an arm 26 extending outwardly from the face of the disc and an arcuate arm 27 integral with the arm 26 and held against the disc by the rivets 24. In so mounting the contact rings 21 and 25 and the L-shaped brackets, the outer and inner rings are fixed at one face of the disc 17 to rotate therewith in concentric relationship with each other and in coaxial relationship with the shaft 12, and the L-shaped brackets are fixed at the opposite face of the disc 17 to rotate therewith, the bracket arms 22 and 26 extending outwardly from the latter face of the disc in substantially parallel relationship to each other with the arm 26 parallel to and spaced from the diameter of the disc 17 which is substantially in the plane of the arm 22. If desired, additional interlocking means may be provided between the rings 21 and 25 and the disc, which may be in the form of pins 26a secured to the rings and extending into apertures in the disc.

The bracket arms 26 and 22 are thus fixed in spaced parallelism to rotate with the disc 17 and the shaft 12 and constitute supporting means for electric make- andbreak contacts 28 and 29, respectively. In the illustrated embodiment of the invention, the contact 28, brazed or otherwise suitably secured to a usual metal backing member 31, is fixed to the arm 26 by riveting or otherwise suitably attaching the bracking member thereto to provide a switch or governor contact which is stationary relative to the contact 29.

The contact 29 is supported by the bracket arm 22 in such position as to engage the relatively stationary contact 28 when the motor is idle and to be movable from and to that position along a definite and predetermined path. To that end, spring means is interposed between the arm 22 and the contact 29. That spring means in the novel governor as illustrated in the accompanying drawing comprises a thin, flat resilient metal strip or leaf 32 which is riveted or otherwise suitably secured at one end to the bracket arm 22 and extends therefrom, in spaced, parallel relationship to a diameter of the disc 17 and between that diameter and the stationary contact 28, to beyond that contact 28. As shown in Figs. 1 and 2, the contact 29, brazed or otherwise suitably secured to a usual metal bracking member 33, is fixed to the resilient metal strip 32, intermediate the ends thereof and in engagement with the contact 28, by riveting or otherwise suitably attaching the backing member 33 to the strip 32, thus providing an end portion 34 at the end of the strip 32 opposite that secured to the bracket arm 22.

As will be understood from the foregoing description and the accompanying drawing, the bracket arm 22 and the resilient strip 32 provide a cantilever support for the movable contact. That cantilever support, when the disc 17 and motor are idle, supports the movable contact in engaged relationship with stationary contact 28. Since the resilient strip 32 is yieldable, the movable contact 29 is urged by centrifugal force into firmer engagement with the stationary contact 28 during rotation of the disc 17 by the motor and is movable in the opposite direction out of engagement with the stationary contact. The metal strip or leaf 32 is so dimensioned that it has a spring constant of approximately 0.7 and a ratio of free length mass to contact mass (mass of contact 29 and backing member 33) on the order of 1:1 or unity. If desired, the resilient strip may be prestressed so as to urge or bias the movable contact into engagement with the stationary contact, or it may be so biased by other means, as referred to below, to aid in maintaining engagement between the contacts when the motor is at rest.

The contacts 28 and 29 are connected in series with the field winding of the motor through wires 28a and 29a leading from the winding, these wires being connected to terminals on plates 28b and 29b, while brushes 28c and 290 lead from the plates and contact the rings 25 and 21. It will be observed from the description hereinahove that manner.

the contact 28 has connection with the ring 25 through the bracket 26, 27 and rivets 24, while contact 29 has connection with the ring 21 through spring means 32, bracket 22, 23, and rivets 19.

The means for so moving the movable contact 29 out of engagement with the stationary contact 28 includes a mass mounted on the disc 17 effective for the purpose under the influence of centrifugal force upon rotation of the disc 17 above a predetermined speed. Such centrifugal force must, of course, be greater than the centrifugal force, mentioned above, urging the movable contact into firm engagement with the stationary contact, and this greater centrifugal force may be the result of greater mass, or greater effective distance from the axis of rotation, or both. Preferably, and as embodied in the present invention, this contact breaking means takes the form of a lever, such as 35 mounted on and rotatable with the disc 17. This lever is rigid and may be U-shape in cross section having flanges 36 by means of which the arm is mounted. The flanges have aligned apertures pivotally receiving a pin 37 mounted in the disc in a suitable The arm 35 extends from its pivot pin in a normal position shown in Fig. 1, when the motor is at rest. In this position, the arm is substantially parallel with a diameter of the disc and substantially parallel with the strip 32 carrying the movable contact 29. The arm 35 is, however, on the side of the axis of the shaft 12 opposite the strip 32 and at a much greater distance from the axis than is the strip. The arm 35 carries a block or member 38 of suitable insulating material engageable with the spring 32 preferably at a location on the latter in alignment with the contacts 28 and 29 for providing solidity when the arm bears on the strip 32 in contact closing direction (clockwise) as it does, as explained below. The free. end of the arm 35 extends beyond the free end of the strip 32 where it has a transverse portion 39 extending beyond the end of the strip and a returnbend hook portion 40 engageable with the end portion 34 of the strip in contact-opening direction (counterclockwise), also as explained below.

The arm 35 is biased in clockwise direction about its pivot pin by a hairpin spring 41 having a loop portion 42 suitably anchored between the flanges 36 of the arm, as on the pin 37, an arm 43 bearing on the operating arm 35 and a second arm 44 engaged with and supported by adjustable stop means indicated as a whole at 45. The stop means 45 includes a bracket 46 having an arm 47 mounted on and held against the face of the disc 17, and an arm 48 extendingperpendicular to the face of the disc. The latter arm has a return-bend portion 49, and the arm portions 48, 49 have an adjusting screw 50 threaded therethrough. The screw has a pointed end engaged in a hole in the arm 44 of the spring 41, aiding in preventing displacement of the spring. Adjustment of the screw 50 inwardly, i.e., toward the axis of the shaft 12, increases the biasing effect of the spring 41 to bias the arm 35 clockwise, and, of course, adjustment in the opposite direction decreases it. The results of these adjustments will be referred to herein below. The outer extremity of the arm 44 serves as a resilient stop for the lever 35, in contact-opening movement of the latter. The divergent arms 48, 49 produce a locking effect on the screw 50.

p In the operation of the governor, assume first a stationary condition of the motor and the disc 17. The spring strip 32 may be prestressed, as explained above, to bias the movable contact 29 into engagement with the stationary contact 28, whereby in the absence of any counter forces against the biasing action of the spring, the contacts remain in engagement to complete circuit to the field winding of the motor. Instead of or in addition to, such prestressed condition, a biasing effect on the strip 32 may be produced by the biasing action of the spring 41 which biases the arm 35 .in clockwise direction, the

6 arm 35, acting through the block 38, biasing the strip 32 in similar direction or in contact-closing direction.

Assume next rotation of the motor, and disc 17, at a speed below the predetermined speed referred to below. The spring strip 32 and the contact 29 carried thereby are so disposed relative to the axis of the shaft 12, that centrifugal force acts to bias the strip 32 in clockwise direction about its point of securement on the arm 22, and thus bias the contact 29 in contact-closing direction. Centrifugal force also acts on the operating arm 35. It will be observed the arm 35 is disposed with its pivoted end in leading position and its free swinging end in trailing position relative to the direction of rotation of the disc 17 (see arrow 12a). In response to rotation of the disc below a predetermined speed the inertia of the arm tends to swing it clockwise about its axis, but above a predetermined speed the centrifugal force increases to such a value that the arm swings in the opposite direction, or counterclockwise. In so swinging, it moves from the normal position of Fig. 1 without consequence to the position of Fig. 4 where the hook portion 40 engages, or is about to engage, the end portion 34 of the spring strip 32. This point is that of the critical or predetermined speed, referred to above, above which the contacts are separated. Upon increase in speed of rotation and greater centrifugal force, the arm 35 is thrown beyond the position of Fig. 4 toward that of Fig. 5 and in so moving, the hook portion 40 carries the strip 32 with it and separates the contacts 28 and 29. As a result, the circuit to the field winding of the motor is broken, the motor decreases in speed and the strip 32 and arm 35 return to the position of Fig. 4 in which the contacts 28 and 29 again engage. The motor circuit is again completed or energized and the motor increases in speed until the centrifugal force becomes great enough to again separate the contacts. The motor thus fluctuates in speed between those limits indicated, and as represented by Figs. 4 and 5.

The strip 32 remains on the same side of the axis of rotation of the motor, regardless of its deflection in contact-opening direction. Upon decrease of speed of the motor in response to opening of the contacts, the strip 32 is returned to its normal position (Figs. 3 and 4) under the influence of centrifugal force, and the influence of the prestressed condition of the strip when such is present, and possibly under the further influence of the operating arm 35 which itself is biased in the appropriate direction by the spring 41.

The forces acting to break contact are entirely independent of the condition of the contacts. For example, in those cases, as heretofore, in which centrifugal force acting on an element such as the strip 32 which carries a contact, is relied on for breaking contact, the condition of the contact itself affects the operation. The contacts, as is well known, become eroded through use, and as the movable contact loses mass because of such erosion, or represents greater effective mass because of migration, it re sponds to centrifugal force at different points in a range of operation; as the contact becomes lighter, greater centrifugal force and hence greater speed of rotation must be attained before the contacts are broken. In the present case, the arm 35 remains constant, in position and in mass, regardless of the condition of the contacts and hence it responds accurately to the predetermined centrifugal force. Regardless of the mass of the contact 29 at any given time, the tendency of the contact is to move in closing direction. The mass of the lever 35 is so much greater than that of the contact 29 and strip 32, on the order of 20 to 1, that any change in mass of the contact, which is small percentage-wise of the original mass of the contact and strip, would as a practical matter not affect the ratio of mass of the contact and strip to the mass of the lever 35. As a consequence, the switch is opened and closed accurately at predetermined points of speed of rotation according to the proportions of the masses of the elements mentioned.

The hook portion 40 of the lever 35 must move a substantial distance (approximately the thickness of contacts 28 and 29 and their respective backing members 31 and 33) from the position of Fig. 3 to that of Fig. 4 before it engages the spring strip 32, and thus separation of the contacts takes place only after large displacement of the lever 35 has taken place. Substantial centrifugal force has at that time been exerted on the lever, and the lever functions while in motion, i.e., moving between the positions of Figs. 3 and 5 to separate the contacts, as contrasted with separating the contacts simultaneously with moving from a position of rest, and hence provides greater accuracy in separating the contacts at a predetermined speed of rotation. The lever has large displacement characteristicsfor small changes in speed.

The consideration of the centrifugal force takes into account not only the relative masses of the elements concerned, but also the relative distances from the axis of rotation of the shaft 12 of the contact 29 and strip 32 on the one hand, and the lever 35 on the other hand. It will be recalled that the strip 32 and lever 35, in their normal rest positions, are substantially parallel to a diameter of the disc, but that the lever is at a considerably greater distance from that diameter than is the strip 32. Thus the center of gravity of the lever and the contact-strip unit are relatively so spaced that the centrifugal force exerted on the lever is many times greater than on the contact-strip unit.

The changing condition of the contact 29 due to erosion or migration theoretically affects the accuracy of the governor. As the contact loses mass because of erosion, or changes condition because of migration, the strip 32 moves further in contact-closing direction and thus its center of gravity is at a greater distance from the axis and the centrifugal force biasing the spring in the direction noted becomes greater. However, the ratio of the distance of the contact-strip unit to that of the lever is so small that any change in the condition of the contact would not affect the accuracy of the governor from this source. It has been found that in the case where centrifugal force is utilized for directly opening contacts, as in governors heretofore in use, a relatively thick or strong spring for carrying the movable contact is required, while for lesser speeds, a relatively thinner or weaker spring is permissible. In the case of a thick or strong spring, a given reduction in mass of the contact does not proportionately affect the point of make or break contact, because of the resistance to flexing of the spring, and the variation in motor speed between make-and-break is objectionally large. This disadvantage is overcome in the present invention because the lever 35 is of constant mass and of much greater mass than the strip 32 and contact 29. The lever is entirely independent of the spring and contact and operates to break contact at a predetermined speed with minimum inaccuracy.

Adjustment of the screw 56) serves to vary the speed range in which the contacts 28, 29 open and close. It will be appreciated that, for example, the backing off the screw 50 lessens the biasing effect of the spring 41 to move the lever 35 in contact-closing direction and the contacts will open at a lesser speed value, and an opposite effect is produced upon running the screw up.

While I have disclosed herein a preferred form of the invention, it will be understood that variations may be made therein without departing from the spirit and scope of the appended claims.

I claim:

1. A rotary switch governor comprising a rotary member, a pair of contacts mounted on the rotary member, means mounting at least one of said contacts for movement along a predetermined line nto and out of engagement with the other contact, means biasing the movable contact into engagement with the other contact, an inertia member, separate from said contacts and their mounting means, mounted on the rotary member for movement from a first position to positions remote therefrom in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, means biasing said inertia member toward its said first position, said inertia member having a portion movable along a line approaching said predetermined line and positioned for engaging said movable contact in movement of the inertia member from its said first position toward a said remote position and being capable, by its movement in response to said centrifugal force, of moving said movable contact out of engagement with the other contact, said contacts and inertia member being movable as a fixed group around the axis of the rotary member in any given speed of rotation of the rotary member.

2. A centrifugal switch governor comprising a rotary member, a fixed contact mounted on the rotary member, a movable contact mounted on the rotary member for movement into engagement with the fixed contact in response to centrifugal force, a movable inertia member mounted on the rotary member and having a first position, and means biasing the inertia member to said first position, the inertia member having greater displacement characteristics due to greater mass than the movable contact so as to be capable, in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, of moving from said first position against the action of said biasing means and the centrifugal force exerted on the movable contact and separating the movable contact from the fixed contact.

3. A centrifugal switch governor comprising a rotary member, a fixed contact mounted on the rotary member, a movable contact mounted on the rotary member for movement into engagement with the fixed contact in response to centrifugal force, a movable inertia member mounted on the rotary member and having a first position, and means biasing the inertia member to said first position, the inertia member having greater displacement characteristics due to greater effective distance from the axis of rotation than the movable contact so as to be capable, in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, of moving from said first position against the action of said biasing means and the centrifugal force exerted on the movable contact and separating the movable contact from the fixed contact.

4. A rotary switch governor comprising a rotary member, a pair of contacts mounted on the rotary member, means including a cantilever spring mounting at least one of said contacts for movement along a predetermined line into and out of engagement with the other contact, means biasing the movable -contact into engagement with the other contact, an operating lever, separate from said contacts and their mounting means, pivotally mounted on the rotary mmeber for movement from a first position to positions remote therefrom in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, means biasing said operating lever toward its said first position, said operating lever having a portion movable along a line approaching said predetermined line and positioned for engaging said movable contact in movement of the operating lever from its said first position toward a said remote position and being capable, by its movement in response to said centrifugal force, of moving said movable contact out of engagement with the other contact, said contacts and operating lever being movable as a fixed group around the axis of the rotary member in any given speed of rotation of the rotary member.

5. A rotary switch governor comprising a rotary member, a pair of contacts mounted on the rotary member, means including a cantilever spring mounting at least one of said contacts for movement along a predetermined line into and out of engagement with the other contact, the cantilever spring having a normal position in which the movable contact is in engagement with the other contact,

an operating lever, separate from said contacts and their mounting means, pivotally mounted on the rotary member for movement from an inactive position to positions remote therefrom in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, means biasing said operating lever toward its said inactive position, said operating lever having a portion movable along a line approaching said predetermined line and positioned for engaging said movable contact in movement of the operating lever from its said first position toward a said remote position and having sufficient displacement value as to be capable, by its movement in response to said centrifugal force, of moving said movable contact out of engagement with the other contact, said contacts and operating lever being movable as a fixed group around the axis of the rotary member in any given speed of rotation of the rotary member.

6. A rotary switch governor comprising a rotary member, a fixed contact mounted on the rotary member, a movable contact, means mounting the movable contact on the rotary-member including a cantilever spring, the movable contact'and cantilever spring forming a unit so mounted relative to the axis of rotation as to bias the movable contact into engagement with the fixed contact in response to rotation of the rotary member, an operating lever pivotally mounted on the rotary member, means biasing the operating lever to an inactive position, the operating lever having greater displacement value than said unit so as to be swingable from said first position in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, and capable of thereby moving the movable contact out of engagement with the fixed contact.

7. A centrifugal switch governor comprising a rotary member, a fixed contact mounted on the rotary member eccentric to the axis of rotation, a movable contact, a cantilever member mounting the movable contact and itself mounted on the rotary member at a position generally opposite the fixed contact and extending para'lel to a diameter of the rotary member and so disposed relative to the axis of rotation as to cause biasing of the movable contact into engagement with the fixed contact in response to centrifugal force, an operating lever pivoted at one end on the rotary member and having an inactive position in which it extends generally parallel with the cantilever member but on the side of the axis of rotation, opposite the cantilever member, the

operating lever having a hook portion at its free end engageable with the free end of the cantilever member, means biasing the operating lever to its said inactive position, the operating lever having greater displacement value than the movable contact and cantilever member so as to be capable, in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, of separating the movable contact from the fixed contact.

8. The construction of claim 7 in which said greater displacement value is due to greater mass.

9. The construction of claim 7 in which said greater displacement value is due to greater effective distance from the axis of rotation.

10. The construction of claim 7 in which the means biasing the operating lever to inactive position includes spring means, and adjusting means is provided for adjusting'the tension in the spring means and thereby varying the speed values at which the contacts are separated and engaged, respectively.

11. The construction of claim 7 in which the means biasing the operating lever to inactive position includes a hairpin spring having a central portion mounted adjacent the pivotal axis of the operating lever, a first arm engaging the lever, and a second arm engaging a fixed portion of the rotary member.

12. The construction of claim 11 in which the extended end of said second arm of the hairpin spring operates as a resilient stop for the operating lever in contact-opening direction.

13. The construction of claim 7 in which the displacement characteristics of the operating lever are so much greater than those of the said unit that a ratio of substantial unity is maintained of the rotational speed required to separate thecontacts before deterioration of the movable contact to that required when the movable contact is reduced in mass up to approximately 10%.

14. A rotary switch governor comprising a rotary member having a predetermined direction of rotation, a fixed contact mounted on the rotary member, a movable contact mounted on the rotary member and biased to a normal position in engagement with the fixed contact, and an operating lever pivotally mounted on the rotary member and positioned ofiset from and parallel to a diameter of the rotary member and having a trailing free end relative to the direction of rotation, said operating lever in response to its inertia in rotation of the rotary member below a predetermined speed of rotation tending to swing toward the axis of rotation and above a predetermined speed to swing outward therefrom, said operating lever having a hook at its free end engageable with said movable contact and capable of moving it out of engagement with the fixed contact in response to outward swinging of the operating lever.

15. A rotary switch governor comprising a rotary member, a fixed contact mounted on the rotary member, a movable contact mounted on the rotary member and biased to a normal position in engagement with the fixed contact, and an operating lever pivotally mounted on the rotary member and positioned offset from and parallel to a diameter of the rotary member, said operating lever in response to its inertia in rotation of the rotary member above a predetermined speed of rotation tending to swing outward from the axis of rotation, said operating lever having a hook at its free end engageable with said movable contact and capable of moving it out of engagement with the fixed contact in response to outward swinging of the operating lever.

16. A rotary switch governor comprising a rotary member, a pair of contacts mounted on the rotary member, at least one of which is movable, means biasing said movable contact into engagement with the other contact, a movable inertia member mounted on the rotary member and having a first position, and means biasing the inertia member toward said first position, the inertia member being capable, in response to centrifugal force exerted thereon above a predetermined speed of rotation of the rotary member, of moving from said first position against the action of said biasing means and separating the movable contact from the other contact and in which the inertia member is disposed for engaging the movable contact, and the inertia member, at least when the rotary member is at rest, under the influence of its biasing means, urging the movable contact into engagement with the fixed contact.

References Cited in the file of this patent UNITED STATES PATENTS 1,630,394 Lee May 31, 1927 2,032,743 Evans Mar. 3, 1936 2,767,273 Ferguson Oct. 16, 1956 2,779,837 Gardes Jan. 29, 1957 UNITED STATES PATENT OFFICE CERT lFlEAT E OF CDRRECTION Patent Non 2,920 158 7 January 5, 1960 Emil c Walker Jrn It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 1, line 59, for sped" read speed column 3 lines 88 and S9, for before deterioration of the movable governor contact to that speed" read after the occurrence of the maximum permissible deterioration column 4 lines 27 and 44, for "bracking" read backing column 8, line 54 for "mmeloer" read member Signed and sealed this 14th day of June 1960,

(SEAL) Attest:

KARL I-l AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT GFFIQE CETH ICATE OF CURECTION Patent N0c 2,920 l58 January 5, 1960 Emil 0., Walker Jr It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 1, line 59, for "sped" read speed column 3, lines 38 and 39, for before deterioration of the movable governor contact to that speed" read after the occurrence of the maximum permissible deterioration column 4, lines 27 and 44, for "bracking" read backing column 8, line 54 for "mmeber" read member Signed and sealed this 14th day of June 19600 (SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents

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