US1816629A - Pressed collector - Google Patents

Description

July 28, 1931. A. wRNx-:R v1,816,629

PREssED COLLECTOR Filed March 16, 1929 Patented July 28, 1931 FFHCE ANTON WRNER, OF VAIHINGEN-ON-'IE-FXLDEBN, GERMANY PRESSE@ COLLECTOR Application led March 1G, 1929, Serial No.

The present invention relates to commutators of the type in which the means, securing the copper bars or segments, are embedded in a molded insulating composition. The usefulness of this type of commutator is limited, however, since the mechanical properties of the molded composition are insufhcient to take up the various stresses developed by the centrifugal forces during the rotation of the collector, the consequences of this stress being increased on account of the heat which arises simultaneously with the creation of the said stresses.

The invention eliminates these shortcomings by interposing between the copper segments and the molded composition a` body adapted to take up the tensile stresses created within the commutator and to transform them into compressive forces, which act on the molded composition arranged between the said body and segments.

One embodiment of the invention is illustrated by way of example in the accompanying drawings, in which Figure l is an axial section of the loosely assembled commutator,

Figure 2 is a front View of the same,

`Figure Q is a fragmentary front view of the commutator, the ligure being drawn on a slightly enlarged scale and showing the coinmutator before shrinking of the same sets in.

Figure 2b is a fragmentary sectional front view of the commutator on line Ll-l of Fig. 3, the figure being drawn on a slightly enlarged scale and showing the commutator after shrinking of the same sets in.

' Figure 3 is an axial section of the finished commutator and Figure l is a cross section thereof on thel line 4 4 of Figure 3.

The commutator comprises a copper seg- 347,74, and in Germany December 7, 1928.

have the notches d extend from its narrow sides inwardly so that the copper segments a, as arranged in the commutator, are of a perfect lei shape, 2 prongs of the copper segments a extending equidistantly at both sices.

lnto the lopening formed by notches Z on either side of the commutator an annular seamless ring, such as an iron ring e, is inserted into each of said notches, so as to be flush with the outside ends of the copper segments and to have its inner peripheral face in temporary engagement with the upper peripheral face of the lower prongs of the copper segments a. It will further be noted from an inspection of Figure 2 that a space f is still left after the insertion of the iron rings c above the same within the notches (Z, a small space is also left at the rear of the rim of each of said rings e. It i-s thus obvious that the rings c are not in contact with the upper prongs of the copper segments, nor with the bridge which connects both the upper and the lower prongs of the letter H.

It will be also noticed from an inspection of Figure l that the mica bars o are inserted between copper segments aand that they rest with their lower edge upon the outer peripheral face of the iron ring e. These mica bars are of rectangular' shape.

During the shrinking of the commutator, the copper segments a and the mica bars b are forced radially to the inside to suoli an extent that the inner peripheral faces of the upper prongs-of the copper segments a approach somewhat the rings e, but still leave a considerable interstice between each other. This has the consequence that the-upper peripheral'faces of the lower prongs move away from the inner peripheral face of the rings c and thus also create an interstice between each other, whereby all contact between any of the copper segments a and either ofthe l2 iron rings e is prevented.

It is evident from an inspection of Figure 8 that the spaces fl and f2 arranged below and above, respectively, the iron rings within the notches CZ are practically of the same width. Inasmuch as the mica bars b bear against the outer peripheral face of the rings l e before shrinking, Figure 2, it is self-evident that during the shrinking towards the center of the commutator a part of the way is obstructed to the mica bars b and that b y this resistance the inwardly disposed edge of the mica bars b is deformed all along the width of the rings e insofar that the material is spread outwardly as is noticed from Figure 2b.

Vhen the material of the mica bar is pressed towards the center of the commutator it may travel unhindered in the free space at the rear of the rings e so that, according to the Figures 2b and 3, it is protruding slightly beyond the inner peripheral face of the ring e. Th-e mica bars b hold the iron rings e very firmly in a central position and being spread or upset, offer a broad support for the iron rings e. Moreover, they are protected against centrifugal displacement because their face acts like a dove-tail and the latter being firmly embedded in a filler consisting` of an insulating composition, which then in any of the usual ways is pressed into the skeleton formed by the copper segments a, the mica bars b and the iron rings e. The insulating composition forms the hub of the commutator.

The insulating composition f fills up the intervening spaces between the copper segments a, the mica sheets b and the rings c, the interstices f1 and f2 and'any other interstice, except the space which later on is to be filled by the shaft on which the commutator is to rotate during its operation. It is thus obvious that each of the copper segments a is insulated in every direction and particularly from the iron rings e arranged within the notches d.

'A commutator constructed according to vthe invention is capable of withstanding 20,-

O00 revolutions per minute at 200 centigrade without showing the least deformation, because the molded composition is freed completely from unfavorable tensile forces and need take up only compressive stresses between the base of the copper segments a and the rings e, which the composition is perfectly capable of doing. Therefore, the commutator possesses excellent mechanical properties which exclude the possibility of deformation. Moreover, it is extremely simple to manufacture, as the mica bars l) need not be centered any more during assembly, but center themselves by means of the' iron rings e. Furthermore, the otherwise so disadvantageous shrinking of the mica sheets or other similar insulating material, owing to heat, does not influence the commutator as to its firmness of construction, for theinsulating composition molded into the intervening'spaces g between the copper segments keeps the latter absolutely in radial direction. Finally I may state that there is some considerable saving in the expensive mica sheets,

as the mica bars do not cover the entire height of the copper segments, but extend merely up to the rings e.

An additional advantage is that the shaft bearing hitherto required can be dispensed with for the reason that the molded composition f arranged between the shaft and the segments u is subjected to compressive forces only.

It is further evident that instead of two separate rings only one central ring could be provided.

lllhat l claim is:

l. A commutator consisting of electrically conductive segments of rectangular shape and pr vided with notches extending from the narrow sides .inwardly alongl the middle line, insulator segments, of rectangular shape and of smalleiI width than aforesaid conductive segments, havin part of their inner edge spread outwardly, both being alternately arranged in annular form so as to form a cylinder having an annular groove in each of its front and rear sides, a metal ring in each of aforesaid grooves being in contact with the outwardly spread inner edge of aforesaid insulator segments and being substantially equidistantly disposed from the walls of the notches of said conductive segments, and an electrically non-conductive iiller provided with an opening` for the shaft.

Q. A commutator consisting of copper segments of rectangular shape and provided with notches extending from the narrow sides inwardly along the middle line, mica segments, of rectangular shape and of smaller width than aforesaid conductive segments, having part of their inner edge spread outwardly, both being alternately arranged in annular form so as to form a cylinder having anv annular groove in each of its front and rear sides, a steel ring in each of aforesaid grooves being in contact with the outwardly spread inner edge of aforesaid micay segments and being substantially equidistantly disposed from the walls of the notches of said copper segments, and an electrically nonconductive filler provided with an opening for the shaft.

3. The method of making commutators, consisting in setting up alternately rectangular copper segments, provided with notches extending from the narrow side's inwardly along the middle line, and of rectangular insulator segments of smaller width than the copper segments, in an annular arrangement so as to have all notches on each narrow side form an annular groove, arranging a metal ring within each of aforesaid grooves so as to have their inner walls contact the copper segments and with their outer walls a part of the inwardly disposed edge of the insulator segments, causing the annular arrangement of the copper and insulator segments to shrink inwardly thereby creating` an open space bei tween each side ofthe metal ring and the copper segment and spreading outwardly the insulator segments along the metal ring, and filling all the aforesaid open spaces in the annular arrangement with an electrically nonconductive mass.

4. The method of making commutators, consisting in setting up alternately rectangular copper segments, provided with notches extending from the narrow sides inwardly along the middle line, and of rectangular mica segments of smaller width than the copper segments, in an annular arrangement so as to have all notches on each narrow side form an annular groove, arranging a steel ring within each of aforesaid grooves so as to have their inner walls contact the copper segments and with their outer walls Contact a part of the inwardly disposed edge of the mica segments, causing the annular arrangement of the copper and mica segments to shrink inwardly thereby creating an open space between each side of the metal ring and the Copper segment and spreadingoutwardly the mica segments along the steel ring, and

filling all the aforesaid spaces in the annular arrangement with an electrically non-conductive mass.

In testimony whereof I affix my signature.

ANTON WRNER.

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