US2180312A - Electric commutator - Google Patents

Description

' Nov. 14, 1939. E. H. STIVENDER ELECTRIC COMMUTATOR Filed May 4, 1936 Patented Nov. 14, 1939 UNITED STATES PATENT OFFlCE ELECTRIC COMMUTATOR Application May 4, 1936, Serial No. 77,669

3 Claims.

This invention relates in general to improvements in commutators, and more particularly to a commutator structure consisting of segments fastened independently of each other on a com- 5 mon insulating support and which may be utilized in dynamo electric machines, in rheostats, and in any other control apparatus requiring a commutator presenting a cylindrical contact path.

Commutators presenting a cylindrical contact path are generally constituted of Wedge shaped segments, which may be insulated from each other and from their support by means of mica and are clamped together or which may be imbedded in a mass of molded insulation. Both such constructions present the disadvantages of being expensive and of precluding the removal and replacement of any segment which may be defective or of tightening up loose segments. It is more economical to utilize segments constituted by extensions of a plurality of studs ar ranged in one row or in a plurality of rows and severally fastened on a common supporting plate of insulating material, the extensions being interleaved to form a single cylindrical contact path; If the brush cooperating with the commutator is in the form of a rocking sector, the commutator is not subject to wear and may be plated with a metal giving a low contact resistance with the sector. Means must then be provided for guiding the sector to prevent it from moving out of engagement with the commutator.

It is, therefore, one of the objects of the present'invention to provide a commutator present- 35 ing a cylindrical contact path formed of segments independently fastened on a common insulating support.

Another object of the present invention is to provide a commutator presenting a cylindrical contact path formed of segments constituted by extensions of studs mounted on a common insulating plate.

Another object of the present invention is to provide a commutator presenting a cylindrical contact path formed of segments constituted or interleaved extensions of studs arranged in a plurality of rows.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. l is a view in elevation of one embodiment of the present invention consisting of a commutator comprising segments formed of the extensions of two rows of studs arranged on adjacent concentric arcs of circle and cooperating with a brush of the rocking sector type; and

Fig. 2 is a cross-section taken in the plane of the line IIII in Fig. 1.

Referring'more particularly to the drawing by characters of reference, reference numeral 6 designates a panel which is preferably made of metal, and is designed to support a commutator or a plurality of cooperating commutators with the cooperating brushes thereof and the brush actuating means. The drawing shows only a portion of panel B supporting a single commutator comp-rising a plate I of insulating material of suitable shape fastened on panel 6 by means of bolts 8 and covering an aperture through the panel 6, which aperture is shaped as a sector of an annulus. Plate l is accurately located with respect to panel 6 by means of dowel pins 9 penetrating therethrough and is made of a suitable insulating material, such as laminated Bakelite or impregnated asbestos, and is provided with a plurality of holes to receive a plurality of conductive studs l0 preferably made of brass, of which only four are shown in Figure 2 to retain simplicity in the drawing. The studs penetrate through the plate I and are fastened therein by means of nuts II, and are preferably arranged in two adjacent concentric circular rows. The studs carry brackets I 2 to support the different sections of a resistor it in conductive contact with the studs to thereby permit a variable number of sections of the resistors to be connected in a circuit by means of the commutator. Only two sections of resistors I3 are shown in Figure 2, but it will be understood that in general each segment of one row is connected with the two adjacent segments of the other row through two sections of the resistor. The studs are knurled on a portion of the length thereof, the projections of the knurled portions engaging with the walls of the complementary holes of plate 7 to thereby prevent the studs from turning when the nuts thereof are tightened.

The studs are provided with extensions shaped differently dependent on the number of rows of studs employed. In the embodiment herein illustrated, two rows of studs being used, the studs of the inner row are each provided with an extension l4 coaxial therewith and preferably obtained by milling from material integral with the stud. The studs of the outer row are each provided with an L-shaped extension, the portion of the extension coaxial with the stud being formed ofmaterial integral with the stud having a slot reoeiving a rectangular strip of brass soldered therein. The extensions of all the studs penetrate through the aperture of panel 6 and extend beyond the surface of the panel, and are arranged in side by side spaced relation, the extensions [4 and [6 being interleaved to form the segments of the commutator which are machined after assembly of the studs to form a single cylindrical contact path. It will be seen that although a single row of studs could be used, there would be insufiicient space for the nuts thereof unless such nuts were of a diameter less than the distance between the axes of adjacent segments, thus generally limiting the diameter of the studs to a too low value. When two rows of studs are utilized, the diameter of the nuts may be increased to substantially the distance between the axes of alternate segments, and a strong and rigid construction may then be obtained by correspondingly increasing the diameter of the studs. If it is desired to further increase the rigidity of the commutator, the diameter of the studs may be further increased, such studs then being arranged in three or more rows instead of in only two rows, the extensions thereof being suitably shaped and interleaved to form a single cylindrical contact path.

The assembly of the commutators comprises the steps of drilling a plurality of rows of holes on the circumferences of concentric circles in plate I, forcing studs I!) in such holes, fastening the studs by means of nuts I l, grinding the contact path and plating extensions l4 and It by immersing such extensions exclusively of plate 1 in a plating bath. The contact path is machined by grinding in preference to turning with a lathe tool for the reason that the segments are laterally unsupported and could not be machined with a coarse tool and an accurately polished surface is thus more rapidly obtained by grinding. The segments should then be made of a metal which takes a high polish by grinding, brass being accordingly preferred to copper. The surface of the contact path must then be plated either with a metal which does not tarnish when subjected to the ambient atmosphere such as chromium, or with a metal which retains a low contact resistance even when tarnished, such as silver. In general it is not desirable to immerse plate I in the plating bath, and only extensions ]4 and "5 are immersed in the bath and plated. Because the extensions are insulated from each other and from panel 6 only by air, the extensions may be plated on all sides to within a short distance of plate 1. If desired, the entire studs and their extensions may also be plated prior to being assembled in plate "I to insure that the surfaces of extensions I l, l6 other than the surfaces thereof forming the contact path may be cleaned properly before receiving any of the plating metal.

The commutator above described is more particularly adapted to engage with the rim ll of a conductive section l8 presenting a cylindrical contact surface arranged to engage with the contact path of the commutator. Rim I1 is preferably made of graphite, and sector I8 is preferably made of light sheet metal provided with a needle point l9 resting in a jeweled cup 2! mounted on a spindle 22 through a spring 23. The spindle may be caused to oscillate by means of a link 24 connected with any suitable actuating means (not shown), the spindle then imparting to sector [8 a rocking movement on the contact path of the commutator. Spring 23 urges sector I8 in contact with the commutator, and a pair of springs 26 acting between sector I8 and panel 1 through insulated extensions of bolts 8 prevent sliding movement of sector l8 on the contact path under the action of gravity in directions in a plane parallel to the panel. A pair of guides 21 mounted on panel I prevent movement of sector IS in a direction perpendicular to the panel. Sector I8 is connected by means of a flexible conductor 28 with an insulated terminal 29 mounted on panel 1. The circuit in which resistor I3 is to be variably inserted, such as the field circuit of a dynamo-electric machine for example, is then connected with terminal 29 and with a suitable one of studs l0.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In control apparatus, a metallic panel having an aperture, a plate of insulating material fastened on said panel and covering said aperture, a resistor having a plurality of sections, a plurality of conductive studs extending through said plate and fastened therein, said studs being arran ed in a plurality of adjacent concentric circular rows and having interleaved extensions penetrating through said aperture and insulated by air from each other and from said panel to form the segments of a commutator, said commutator presenting a cylindrical contact path and having means for supporting the sections of said resistor on said studs in conductive relation therewith, a conductive sector having a cylindrical contact surface arranged to engage said contact path, means for imparting to said sector a rocking movement on said contact path, spring means acting between said sector and said panel to prevent sliding movement of said sector on said contact path in directions in a plane parallel to said panel, and guide means for preventing movement of said sector in a direction perpendicular to said panel.

2. In control apparatus, a supporting member,

a resistor having a plurality of sections, a plurality of studs of electrically conductive mate rial extending through said member in mutual insulating relation, said studs being arranged in a plurality of adjacent concentric rows and having interleaved extensions insulated by air from each other to form the segments of a commutator, said commutator presenting a cylindrical contact path and having means for supporting the sections of said resistor on said studs in electrically conductive relation therewith, a conductive sector having a cylindrical contact surface arranged to engage said contact path, means for imparting to said sector a rocking movement on said contact path, and means actingto. prevent sliding movement of said sector in a plane perpendicular to the axis of said contact path and in a direction parallel to the axis of said contact path.

3. In a control apparatus, a plate of insulating material, a plurality of studs of electrically conductive material passing through said plate and insulated from each other therein and arranged in a plurality of parallel rows, said studs being severally connected by sections of a resistor, end portions of said studs being provided with reduced extensions supported only by said studs,

the reduced extensions of the studs of one row"75* extending only axially of said studs, and the reduced extensions of the studs of the other row having a portion projecting towards the said one row and being interleaved with and in spaced relation to the reduced extensions of the studs of said one row, and a face of all of the interleaved reduced extensions of said studs being disposed in a single discontinuous surface serving as a commutator surface, and a movable contact device cooperative with said commutator surface of the extension of said studs for Icy-passing sections of said resistor.

EDWARD H. STIVENDER.

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