US2965724A - Nutating commutator switch - Google Patents

Description

Dec. 20, 1960 M. v. KIEBERT, JR

NUTATING COMMUTATOR SWITCH Filed April 1, 1958 IN VEN TOR. MAAW/v M M53591; JA.

United States Patent NUTATING COMMUTATOR swrrcrr Martin V. Kiebert, Jr., Pasadena, Calif., assignor to J. K. Nunan Filed Apr. 1, 1958, Ser. No. 725,646

7 Claims. (Cl. 200-23) This invention relates to commutator switches and is more particularly directed to rotary type commutator switches having nutating rotors which may provide, among other things, self-wiping contact action.

Commutating switches generally employ fixed contacts suitably placed on a stator and a brush type contact carried by a rotor, the rotor rotating about a fixed axis to move the brush over the fixed contacts to complete sequentially external circuits. There are various forms of stators and rotors depending upon the use to which they are put and how they are employed. For example, the stator may be in the form of a plate or disc having circumferentially and equally spaced fixed contacts and the rotor shaft placed at the geometric center of the plate. A brush carried by an arm secured to the shaft brushes past the stator contacts to form an engageable contact therewith. Other stators may be in the form of cylindrical drums having the contacts circumferentially and equally placed either on the inside or the outside of the drum, depending upon whether the rotor contact is placed with or without the drum.

All of these types of commutating switches, which are merely exemplary, since there are many other types which exhibit the same tendencies, have certain limitations and shortcomings which represent a definite impediment to high speed efficient switching operations. One of the greatest faults shown by present, commercially available type commutator switches is the tendency towards galling of the relatively movable contact elements at high switching speeds. Galling occurs because of the elevated temperatures that results when a high spot on a contact hits a comparable raised portion of a brush. These high spots on the surfaces of the engaging contacts cannot be avoided regardless of how much surface grinding and polishing is done to produce a com pletely flat surface. When the high spots on the moving and fixed contacts collide relatively high temperatures are generated melting the metal and subsequently carrying the melted metal to the next adjacent contact surface. This occurs as a result of the fact that the localized points of high friction generate heat at a rate greater than the rate of heat away from the raised points to other masses of the contact brush. Thus, the metal flows and galling seriously limits the velocity of the moving contacts.

Other forms of contacts have been used as between rotor and stator, such as rolling contacts, but these fail to demonstrate the ability of maintaining clean contact surfaces. Generally these surfaces exhibit certain oxide film or coating which remain on the contact surfaces. The rolling contacts further result in varying contact potentials. Hence failure to break or clean the oxide film along with such varying potentials produces variable resistances, a factor which results in unsatisfactory commutator operation.

This invention overcomes the shortcomings and limitations of known devices and affords a new and improved arrangement of elements that not only prevents galling but also effects wiping of the contacts to maintain uniform law resistance contact between the commutator elements. Furthermore, the invention, while being particularly useful for operation at high speeds, affords numerous advantages at low speeds not attainable with prior known structures.

It is therefore one object of this invention to provide an improved commutating system particularly useful at high speeds which is eificient, economical, rugged, long lasting and easily operated.

Another object of this invention is to provide an improved nutating commutating system wherein the rotor and stator surface contacts are self-cleaning and selfwiping to avoid surface oxide film and varying contact potentials.

Another object of this invention is to provide a high speed commutator system wherein galling is substantially reduced if not entirely eliminated.

Other objects and advantages will be readily apparent from a reading of the specification and the accompanying drawings, wherein:

Figure 1 is a sectionalized elevational view of a commutator switching device according to one embodiment of the invention, taken along the line 1-1 of Figure 3;

Figure 2 is an end view of the commutator switching device in Figure 1;

Figure 3 is a plan view of a commutator switching device according to the invention;

Figure 4 is a sectional view taken along the line 4-4 of Figure 3;

Figure 5 is a sectionalized elevational view of a commutator switching device according to another embodiment of the invention;

Figure 6 is a plan view taken along the line 66 of Figure 5; and

Figure 7 is a fragmentary cross sectional view of the invention illustrating a modified embodiment thereof.

Figures 1 to 4 show one embodiment of the invention which includes a nutating commutator system employing a self-wiping, self-cleaning contact design and avoids the ordinary sliding rotary motion of the conventional commutator systems. In general, the nutating commutator system embodied in the said figures comprises a stator 10 having a series of circumferentially equally spaced contacts 11 thereon, and a nutating rotor plate 12 which engages each of the contacts as it nutates about the rotor shaft 13. The periphery of the nutating rotor plate is slightly deflected as it engages the stator contact while undergoing nutation so that a sliding and rubbing action takes place between the said plate and contacts. The nutation of rotor plate is effected by affixing the rotor plate bearing assembly 14 to the rotor shaft 13 at a predetermined angle as shown in Figure 1 and then as the shaft rotates the plate will successively engage the contacts. The bearing assembly secures the nutating rotor plate 12 to the shaft 13 while permitting the said shaft to rotate with respect thereto, and the shaft is urged downwardly to obtain the desired contact pressure and cause the outer periphery of the rotor to deflect in a radial direction for attaining the desirable self-cleaning, self-wiping action. The degree of wiping and deflection is a function of the angle between the planes of the rotor plate 12 and the stator plate. The smaller this angle the smaller the degree of rubbing or wiping action between plate and stator contacts. As this angle approaches zero the rubbing action decreases and the number of stator contacts simultaneously en.- gaged by the rotor increases. Therefore it is necessary .to select an angle which will be a fair compromise for clearance between the nutating plate and the next successive fixed contact to be engaged by the rotor and simultaneously therewith providing the necessary rubbing Patented Dec. 20, 1960 action which results in self-cleaning of the contacts undergoing commutation.

Again referring to Figures 1 through 4, there is shown a rotor plate 12 having a flanged hole 15 to which is secured a roller bearing assembly 16 consisting of a lower racer 17 and an upper racer 18 between which roller bearings 19 are free to move. The rotor 12 is carried by a cylindrical body member 20 having a hole 21 Whose axis is at an angle less than 90 degrees to the axis of the body. The disc member 20 is secured to the shaft 13, along the hole 21, by a pair of set screws 22 and 23 threaded in said member and bearing against shaft at different longitudinally placed locations along the said shaft. The shaft 13 rotatably engages a bearing 13a of stator 10 and rotation of the shaft causes the disc member 20 to move through a so-called nutative path. The rotor plate 12 being rotatably carried by the body member 20 does not rotate with the shaft but remains substantially stationary relative to the stator 10 by virtue of the frictional resistance of the said rotor plate 12 and stator contacts 11. However, inasmuch as the rotor plate 12 has an angle of inclination determined by the body member 20 a nutating action of the plate 12 must take place about the shaft 13. It is this nutating action combined with the resilience of the plate and the contact pressure effected by the downward displacement of the shaft 13 which results in the wiping action previously described.

Since it is the defiective action of one contact of a pair relative to the other which causes the wiping action,

either or both contacts may be made resilient to produce the sliding motion. As above described it was the resilience of the nutating rotor which provided the deflection action effecting the self-Wiping action. It is also possible to have the stator contact move relative the nutating rotor plate to effect the same wiping action aforementioned, or to have both the nutating rotor plate and the stator plate both deflect or move relative to each other to create the same wiping or self-cleaning action.

Figures 5 and 6 show a nutating commutator switch similar in design to the switch shown in Figures l-4 but with the rotor plate and stator contact actually deflecting with respect to each other to provide the self-wiping action. The stator contacts 24 are L-shaped and have their flan ed portions 25 directed toward the center of the stator. The flanged portion is flexible and gives when engaged by the nutating rotor during rotation of the shaft 13 as previously described. The nutating plate also deflects outwardly as indicated at 26 so that the combined opposed motion of the contact and plate produces effective wiping action.

Figure 7 illustrates a modified embodiment of the invention showing the nutating and wiping action wherein the rotor 12' is relatively rigid and the contact 24 of the stator 10 has a resilient contact portion 25 to afford the wiping action.

As the commutator switch undergoes commutation, the making and breaking or contacts normally creates certain arcing or other commutation effects as a result of the contact potential between the contacting surfaces. These potentials may be avoided or reduced to a minimum by the creation of opposing contact potentials to balance out the effect resulting from commutation. In the instant case these potentials are balanced out by the addition of another nutating element 27, attached to the nutating rotor plate 12 by electrical conducting means such as the collar 30. The second plate 27 engages a circular contact ring 28 on the stator as the rotor plate undergoes nutation. In this manner the contact potentials are substantially balanced out.

It is understood that changes, alterations and modification may be made in the embodiment of the invention illustrated and described without departing from the true scope and spirit thereof'as defined by the claims.

What is claimed is:

1. A nutating commutator switch comprising a stator having a base and a circular array of fixed contacts on said base and extending therefrom, a rotatable shaft centrally located with respect to the said stator contacts, a circular rotor plate of conductive material, means rotatably securing the plate to the shaft with the plate being fixed at an inclined angle relative to the plane of the fixed contacts and with the center of the plate being coincident with the axis of the shaft to cause the said plate to engage the contacts successively, and means affecting relative radial motion between the said rotor plate and contact surfaces as the said plate nutates to effect self-cleaning and wiping of the said contact at their surface portions.

2. A nutating commutator switch comprising a stator having an arcuate array of spaced solid contacts disposed thereon with the contact surfaces spaced from the stator surface, a shaft centrally located with respect to the said stator contacts and rotatable about an axis perpendicular to the plane of the contacts, an annular rotor plate of resilient material, means for concentrically securing the plate to the shaft with the plate fixed at an inclined angle relative to the plane of the contacts and rotatable about its own axis, whereby rotation of the shaft will cause the said plate to nutate and individually engage the contacts, and means exerting pressure on said plate in the direction of the shaft axis to urge the plate firmly against the contacts with the edge of said plate deflecting outwardly When engaging successive contacts to effect self-cleaning and wiping of the said contact surfaces.

3. A commutator switch comprising a stator having arcuately arranged spaced resilient contacts disposed thereon, a rotatable shaft centrally located with respect to the said stator contacts, an annular rotor plate, means including a bearing concentrically securing the plate to the shaft at a fixed angle relative to the plane of said contacts, said shaft being axially positioned to urge the periphery of said plate against the fixed contacts and deflect said contacts when engaged by the said plate to effect self-cleaning and wiping of its surface portions.

4. A commutator switch comprising a stator having individual fixed contacts angularly disposed thereon and a concentric continuous contact ring thereon, a rotatable shaft centrally located with respect to the said stator contacts, a first rotor plate, a second rotor plate, and means for rotatably securing the said first and second plates to the shaft with said plates fixed at inclined angles relative to the contacts and contact ring to effect notation of the plates when the shaft is rotated, said first plate engaging the fixed contacts and said second plate continuously engaging the continuous ring to effect a potential suflicient to cancel the contact potential of the said first rotor plate and the engaged stator contacts undergoing commutation.

5. A commutator switch comprising a stator having circumferentially spaced resilient contacts and a concentric continuous inner contact ring secured thereto, a rotatable shaft centrally positioned With respect to the said stator contacts, a first flexible rotor plate, a second flexible rotor plate, means for securing the said first and second plates to the shaft at an angle relative to the planes of the contacts and contact ring whereby rotation of the shaft causes the said plates to nutate about the axis of the shaft, said first plate engaging the resilient stator contacts and cause the said plate and contacts to deflect and effect selfcleaning and wiping of the surface portions of the first plate and contacts and said second plate continuously engaging the continuous inner contact ring to effect an opposing potential sufiicient to nullify the contact potential of the said first rotor plate and the engaged stator contacts undergoing commutations.

6. A rotary switch comprising a plurality of arcuately arranged contacts, a rotatable shaft perpendicular to the plane of the contacts, and an inclined nutating contact disk successively engaging said contacts and concentrically carried by said shaft, said contact disk being rotatably fixed at a predetermined angle relative to the shaft, formed of a conductive resilient material and urged into pressure contact with said contacts to effect a wiping action during nutation, said friction between the contact disk and contacts effecting rotation of the contact disk relative to the shaft and producing negligible rotation of the contact disk relative to the contacts.

7. A nutating commutator switch comprising a circular array of contacts disposed in a coplanar relationship, a shaft disposed normally to the plane of said contacts and rotatable relative thereto, a contact disk of conducting material carried by and rotatable relative to said shaft, said contact disk being disposed at an angle relative to the plane of said contacts and nutatable in response to the relative motion between the contacts and shaft to successively engage said contacts, and means in electric circuit with said contact disk including an annular contact ring aligned with and fixed relative to said 6 array of contacts whereby electric circuits are successivcly completed between said ring and each of said contacts in said array with negligible relative motion occurring between the circuit completing contact elements.

References Cited in the file of this patent UNITED STATES PATENTS 947,736 Martin Jan. 25, 1910 1,399,366 Selleck Dec. 6, 1921 1,705,238 Daloz Mar. 12, 1929 2,478,929 Lochrnan Aug. 16, 1949 2,634,342 Baechler et al. Apr. 7, 1953 2,715,163 Haviland Aug. 9, 1955 2,744,972 Davis May 8, 1956 2,847,531 Davis Aug. 12, 1958 FOREIGN PATENTS 448,604 Germany Aug. 27, 1927 717,824 Germany Feb. 23, 1942

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