US2927173A

US2927173A - Governor for small motors

Info

Publication number: US2927173A
Application number: US809678A
Authority: US
Inventors: Edward M Crocco
Original assignee: Reflectone Corp
Current assignee: Reflectone Corp
Priority date: 1959-04-29
Filing date: 1959-04-29
Publication date: 1960-03-01
Anticipated expiration: 1977-03-01

Description

March 1, 1960 c occo 2,927,173

GOVERNOR FOR SMALL MOTORS Filed April 29. 1959 FIG. 2

.FlG.5 FIG. 6

INVENTOR EDWARD M. CROCCO BY Em [5.

AGENT.

Unite States Patent 2,927,173 GOVERNOR FOR SMALL MOTORS Edward M. Crocco, Greenwich, Conn., assignor to The Reflcctone Corporation, Stamford, Conn., acorporation of Connecticut Application April 29, 1959, Serial-No. 809,678

8 Claims. (Cl. 200-80) Patent No. 2,886,666, dated May 12, 1959, and to Serial No. 785,593, filed January 8, 1959, entitled Speed Governor for Motors or the Like. In these applications governor designs are disclosed which are characterized by extreme reliability, accuracy, and minimum space requirements and, in addition, the latter application reveals a rotational speed governor design which maintains high accuracy of speed regulation for either direction ofrotation by taking advantage of the forces acting upon the contact arrangement during acceleration and deceleration of the rotating assembly.

The design described hereafter refers to improvements in the governor contact construction in order to extend the useful life of the unit and concernsv primarily the form and shape of the contact so as to effect a pro-- nounc'ed wiping action between a pair of interrupting. contacts. This wiping action is achievedby providingthe. leaf spring type oscillating contactelement with a formed portion'intermediate its two ends thereby increasing the developed length of the spring. Under the influence of centrifugal force, the contact disposed at the free end of the spring not only is forced away from engagement with a fixed contact, but the leaf spring tends to elongate thereby obtaining a wiping actionduring opening and closing of the periodical interrupting contacts. The im-- provement described in the instant disclosure. refers, therefore, to a governor construction employinga plurality of leaf spring contacts, each ofv the leaf spring contacts having aformed or fluted portion which'substantially increases the developed length of each leaf spring.

One of the objects of this invention, therefore, is the provision of a new and improved governor design which avoids one or more of the disadvantages and limitations of prior art devices.

Another object of this invention is the provision of'a governor design equipped with improved leaf springcontacts.

A further object of this invention'is'the provision of a governor for small direct current motors which employs a set of leaf spring contacts, each leaf spring being provided' with an intermediate formed portion to increase the developed length of the spring.

A still further object of the invention is the provision of a governor design employing leaf spring contacts wherein each leaf spring is provided with means which cause a pronouncedwiping action during opening and closing of the interrupting contact.

2,927,173 Patented Mar. 1, 1960 .provision' of' a governor design employinga set of leaf springs" with increased wiping action between tlieinter= rupting contacts, the assembly being designed for pre=- ferred clockwise or counterclockwise rotation so as to maintain precisespeed regulation. I 1 V Further and still" other objects of'this invention win be apparent by reference to the following specification taken in conjunction with the accompanying drawings in which:

Figure 1 is a plan view of the governor design showing the contact arrangement assembled for clockwise rotation;

Figure 2' is' a side elevational view-asseerr along lines 22 in Figure 1';

' Figure 3 is a plan view atthe underside of the" governnor-d'esign; I

Figure 4 is a schematic circuit diagram showingthc electrical connections of the governor in conjunction with the motor to which the governor is attached;

Figure Sis a sketch showing in anexaggerated manner the effect- 0f certain forces on the leaf spring contact, and r Figure 6 is a typical alternate design for a leaf spring contact embodying the principle described herein.

Referring now to the figures and Figures 1, 2 and 3 in particular, numeral 11 identifies an annular bushing,

A further and other object of this invention is the which together with plate 12 forms a unitaryfiangernade of insulating material, for instance, nylon or other suitable plastic compositions. This-flange is usually mounted by means of aperture 13 on a rotatable shaft tends through theflange.

Onto this flange made of-insulated material, there ismounted a divided flange made of metallic material, for instance, brass, which includes a first flange half comprisinghalf bushing 1-4and plate'15, and a second flange halfcomprising half bushing 16- and plate. 17. Both metallic flange halves are separated by aslot 20 in order to effectelectrical isolation therebetween. It will. be understood, however, that both metal portions and the portions made of plastic material form a unitary molding.

Projecting upward from metal plate 15 there is an upstanding metal block 21 which forms a partof plate 15' and conversely upstanding block 22 formsapart of metal" plate. 17. Each of these blocks is equipped with a transverse. slot 23 and 24, respectively, inwhich there which exis secureda leaf. type contact spring '25 and- '26, respec-- tively. This type of." mounting is commonly known as cantilever type. The leaf contact springs are made of resilient metal, for instance, beryllium-copper alley or similar material in order to be compliant. The contact terial, for example, may be a platinum-iridium alloy andsimilarly, the tips of the screws 30 and-31 may be'made of the same alloy.

When the entire assembly is mounted on a shaft and rotated, by action of centrifugal force the free end: of: eachleaf spring is urged outwardly so as to break con-F tact withthe associated screw contact. Upstanding

bosses

40, 41, 42 and 43 which are made of insulatingmaterial and which form an. integral part with'insulated disk 12 serve as mechanical stops for the springs in the event that the assembly is wired incorrectly into the electrical circuit.

The operation of the governor maybe visualized as follows: The governor is mounted on the rotor shaft of adirect current motor andlconnected in series with a:

supply voltage. Electrical circuit connection'to the gov-- ernor construction'is accomplished by mean's'ofaset of diametrically opposed stationary contact brushes, one;

connection and shows a source of direct current 45 on nected in series with motor 46 and the governor. Numeral 47 represents the rotor winding of the motor. When fixed contact screw 31 engages contact 33 attached to the free end of leaf spring 26, or contact 30 engages contact 34 attached to the free end of leaf spring 25, the circuit from the source of energy is closed and motor winding 47 receives electrical power. As soon as preadjusted speed is reached, centrifugal force urges the free ends of

contact leaf springs

25 and 26 away from engagement with the respective fixed contact screws, thus interrupting the circuit from the power source, causing the motor to slow down, until contact is reestablished. This cycle of events is repeated over and over again as is well known in the art.

It will be apparent that two sets of contact springs and corresponding contact screws are used whereas a single circuit making and breaking arrangement would sufiice. The provision of double contact means increases the life of the governor and, furthermore, assures operation in the event of failure of one of the contacts. In this manner, reliability of operation of the motor is greatly improved and chances of failure due to governor fault are reduced. High impedance resistor 48 connected across the governor assembly provides are suppression. Instead of the resistor, a capacitor quenching circuit may be used with substantially the same results.

The speed of the motor is depending upon the setting of the screw contacts and will increase the farther the screws are adjusted in the direction toward the free end of the opposing leaf spring. Both contact halves must be set for the same speed, a condition which can readily be met by first adjusting one set of contacts and then the other set while using a small piece of insulating material to alternately disable one or the other set of contacts.

It will be noted that each leaf spring has been provided with a formed portion 50 which is disposed intermediate the fixed end and free end of the leaf. This provision serves to increase the developed length of the leaf spring thereby rendering the leaf spring more compliant. More important, however, this formed or fluted portion causes the leaf spring under the influence of centrifugal force, to vary its distance between the two ends thereby producing a wiping action of contacts 33. and; 34 with respect to the associated opposing fixed contacts. This lengthwise expansion of the leaf spring under the influence of centrifugal force is depicted in a somewhat exaggerated manner by the dashed lines in Figure wherein its is shown that the distance of the spring between the end which is secured to the mounting block and the free end which is in engagement with the rigid contact of the opposing mounting block will increase and decrease as the centrifugal force exerts its effect. Gbviously, the spring rate of the leaf material itself must be of such order as to permit the lengthwise flexing motion to take place.

Instead of the design shown in Figure- 5 it will be apparent that the leaf springs may be designed in an alternate manner, Figure 6, to include a curved, bowed, corrugated or similar formed section, either concave or convex, in order to increase the resiliency of the leaf spring and produce flexing motion along the longitudinal direction.

In cop'ending application for U8. Letters Patent, Serial No. 785,593, there is disclosed an arrangement for providing a governor. assembly which will operate with accuracy of speed regulation in either direction of rotation. in general, it can be stated that the assembly must be constructed in such a way that the free end of the leaf spring is disposed at the trailing edge of rotation in order that the moments of f rce due to acceleration and deceleration together with centrifugal force aid the opening and closing of the leaf spring contact.

In the present design the two governor halves and the corresponding contact leaf springs are designed in an identical and interchangeable manner to permit the governor to be assembled for either clockwise or counterclockwise rotation to meet the above stated condition. The assembly depicted in Figure l is assembled for clockwise rotation. It will be noted that the leaf spring contact assemblies and adjusting screws 39 and 31, re spectively, can be reversed to attain the same accuracy of speed regulation in counter-clockwise rotation.

The governor construction described herein, due to its shaped contact leaf springs provides extremely reliable operation. Many hours of testing have shown that adhesion or fusion of interrupting contacts has been substantially eliminated thereby providing speed regulation with utmost accuracy, reliability and long life.

While there have been described certain embodiments of the instant invention, it will be apparent to those skilled in the art that various other modifications may be made without departing from the spirit of the present invention which should be limited only by the scope of the appended claims.

What is claimed is:

1. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting means disposed substantially diametrically opposite one another on said supporting means; a pair of contact leaf springs; each spring secured with one end to one of said mounting means and the free end of each spring extending toward the opposite mounting means; adjustable contact means disposed in each of said mounting means and protruding therefrom to engage the free end of the leaf spring extending thereto, and each of said leaf springs having a formed portion which increases the developed length of the spring between the secured and free ends to cause the free end of each spring under the influence of centrifugal force to change its distance with respect to the secured end.

2. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting means disposed substantially diametri-; cally opposite one another on said supporting means; a pair of contact leaf springs; each spring secured with one end to one of the said mounting means and the free end of each spring extending toward and being in contact with the opposite mounting means when the speed of the motor is below a predetermined rate, and each of said leaf springs having a formed portion intermediate its fastened and free ends, said formed portion increasing the developed length of the spring between its two ends and permitting the free end of each spring under the influence of centrifugal force to change its distance with respect to the secured end.

3. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting means disposed substantially diametrically opposite one another on said supporting means; a pair of resilient contact leaf springs disposed to straddle said center of rotation; each spring secured with one end to one of the said mounting means and the free end of each spring extending toward and being in contact with the opposite mounting means when the speed of the motor is below a predetermined rate, and each of said leaf springs having a formed portion intermediate its secured and free ends, said formed portion increasing the developed length of the spring between its two ends and permitting the free end of the spring under the influence of centrifugal force to change its distance with respect to the secured end.

4. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting means disposed substantially diametrically opposite one another on said supporting means; a pair of contact leaf springs made of resilient material straddling said center of rotation; each spring secured with one end to one of said mounting means and the free end of each spring extending toward the opposite mounting means; adjustable contact means disposed in each of said mounting means and protruding therefrom to engage the free end of the leaf spring extending thereto, and each of said leaf springs having a formed portion which increases the developed length of the spring between its secured and free ends, thereby causing the free end of each spring under the influence of centrifugal force to change its distance with respect to the secured end.

5. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting blocks fastened to said supporting means and disposed opposite one another on an axis through said center of rotation; a pair of contact leaf springs made of resilient material straddling said center of rotation; each spring secured with one end to one of said mounting means and the other end of each spring being free and extending toward the opposite mounting means; contact means disposed in each of said mounting means which are adapted to engage the free end of the leaf spring extending thereto when the rotational speed of said supporting means is below a predetermined value, and each of said leaf springs having between the secured end and free end an undulated portion which increases the developed length of the spring thereby causing the free end of each spring under the influence of centrifugal force to change its distance with respect to the secured end and this change in distance producing a wiping action between the free end and the associated contact means when the speed of the governor approaches the predetermined value.

6. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting blocks fastened to said supporting means and disposed opposite one another on an axis through said center of rotation; a pair of substantially identically shaped contact leaf springs made of resilient material straddling said center of rotation; each spring,

secured with one end to one of said mounting means and the other end of each spring being free and extending toward the opposite mounting means; contact means disposed in each of said mounting means which are adapted to engage the free end of the leaf spring extending thereto when the rotational speed of said supporting means is below a predetermined value and breaking said engagement when the speed is above said value, each of said leaf springs having between the secured end and free end a formed portion which increases the developed length of the spring thereby causing the free end of each spring under the influence of forces effective during rotation of said supporting means to change its distance with respect to the secured end and this changein distance producing a wiping action between the free end and the associated contact means when the speed of the governor approaches the predetermined value.

7. A speed governor for motors of the type described comprising: supporting means having a center of rotation; a pair of mounting means disposed opposite one another on said supporting means; a pair of contact leaf springs straddling said center of rotation; each spring secured with one end to one of the said mounting means and the free end of each spring extending toward and being in contact with the opposite mounting means when the speed of the motor is below a predetermined rate, and each of said leaf springs having a formed portion intermediate its fastened and free ends, said formed portion increasing the developed length of the spring between its two ends and permitting the free end of each spring under the influence of centrifugal force to change its distance with respect to its secured end.

8. A speed governor for motors of the type described including a rotatable body comprising: a pair of flanges electrically insulated from one another; a mounting means disposed on each of said flanges; each of said mounting means provided with a rigid electrical contact; a pair of contact leaf springs straddling the center of rotation of said body; each spring secured with one end to one of said mounting means and the free end of each spring extending toward and being in engagement with the rigid contact of the opposite mounting means when the speed of the motor is below a predetermined rate and being free of said engagement when the speed is above said rate; each of said leaf springs having a formed resilient portion intermediate its fastened and free ends, and

said formed portion increasing the developed length of the spring between its two ends thereby permitting the free end of each spring under the influence of centrifugal force to change its distance with respect to the secured end to produce a Wiping action between the free end and the associated rigid contact as the speed of the body approaches the predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,761,031 McDonald Aug. 28, 1956 2,846,541 Evans et al Aug. 5, 1958 2,886,666 Chichester May 12, 1959