US1898929A - Commutator and method of making it - Google Patents

Description

Feb. 21, 1933. v. 6. APPLE 1,898,929

COIIUTATOR AND METHOD OF MAKING IT Filed May 16, 1929 Patented Feb. 21, 1933 UNITED STATES -PATENT OFFICE VINCENT G. APPLE, DAYTON, OHIO; HERBERT P. APPLE, EDWARD H. APPLE ND GOUBLEY DARBOCH EXECUTOBS OF SAID VINCENT G. APPLE, DECEASED comm-rues m un'rnon or me n Application filed Kay 16, 1829. Serial No. 383,460.

This invention relates to commutators and particularly to those wherein a plurality of spaced apart segments are imbedded in a core of molded insulation.

An object of the invention is to generally im rove a commutator of this type.

other object is to produce such a commutator more cheaply than may be done by 4 known methods.

A more specific object is to provide a commutator of the type usually called a flush commutator wherein the insulation composing the core extends also outwardly between the se ents to the brush track, this feature adapting it to use in connection with metal brushes as well as making it less noisy.

Further and still more specific ob'ects will be apparent from a consideration 0 the following description, reference being had to the accompanying drawing, wherein Fi 1 shows a form of sheet metal blank whic I may employ for making segments for my commutator.

, Fig. 2 is a perspective view of a segment 2 bent from a blank Fi 1. V

blFi 3 shows a modified form of segment an Fig. 4 shows how blank Fig. 3 may be bent to compose a segment.

Fig. 5 shows another modification of the se ment blank.

ig. 6 shows blank Fig. 5 bent to form a segment.

Fig. 7 shows the body of a mold which 85 I rovide for molding the insulation portion 0 the commutator.

Fig. 8 shows a set of segments Fig. 2 in the mold body.

Fig. 9 is a vertical axial section through the mold with the stock ring in place, a charge of unmolded insulation in the ring, and a plunger entered, ready to force the insulation about the segments.

Fig. 10 shows the same cross section as Fig.

9 except .that the insulation is forced into place.

Fig. 11 shows a completed commutator.

Similar numerals refer to similar parts throughout the several views.

The wide range in voltage under which dyname electric machines operate necessitates a corresponding variation in the material from which commutator brushes are made, the material ranging from carbon of high resistance to compressed powdered metal of extremely low resistance. I

The older and better known form of commutator consists of a plurality of co per segments held together by a metal bin mg means with the s ments separted from eac other and from t e binding means by thin la ers of insulation, usually mica.

ith this form of commutator a certain difiiculty is experienced because with certain types of brushes the copper segments wear away faster than the mica s acers leaving an uneven surface to the brus track which, at the high surface speed of a commutator, soon destroys the brushes, and the commutator itself.

This difiiculty has been partly met by so determining the composition of the brushes as to cause them to wear the copper and mica uniformly, but the most successful solution is bad by cutting away the narrow spacers o mica between the segments at and near the surface of the brush track.

The latter solution is relatively successful except when metal brushes are employed, for then the metal dust which wears from the brushes fills the spaces between the segments which were made by removal of the mica, and causes shorting between adjacent segments. Used with metal brushes then the undercut commutator is not successful. A further objection to under-cut commutators is that they are noisy at high speed.

In more recent development in the art, commutators are composed of a plurality of segments imbedded in a mass of insulation molded in situ about them. In this class flush commutators have been made by assembling the segments in a ring with narrow mica or similar spacers between them at the brush track, and molding the insulation around the remaining surfaces of the segments. Undercut commutators have been made by assembling the segments in a mold having metal spacers extending slightly inward from the inner wall of the mold between which the segments are held while insulation is molded about their remaining exposed surfaces.

A flush molded commutator suitable for metal brushes, wherein the same continuous mass of insulation forms the core and the spacers between the segments, has not heretofore been made from separate segments because no way has heretofore been proposed to hold the separate segments spaced apart in the mold without having some material substance between the segments which would exclude insulation from therebetween when molding was effected.

On the other hand if the molded commutator has a core of heat hardened resinous condensation product such as is used in the present state of the art, the core should preferably not extend between the segments to the brush track since this form of insulation carbonizes under the arcing of the brushes and shorts the commutator from bar to bar.

It is therefore apparent that if there is provided a means of holding segments spaced apart in a mold without material spacers between, until the core of insulation can be molded to bind them together and to fill the spaces between the segments to the brush track, and if a type of insulation is then used which is highly resistant to carbonization under the arcing of the brushes, a new and useful result will have been accomplished. As insulating compound hi hly suitable for this purpose may comprise a ller of powdered mica or asbestos, or a mixture of both with a binder containing a glycerin phthalic anhydride type of resin.

Referring to the drawing, a segment blank 10 is cut from sheet copper or other suitable conductive material. One end of the blank has a prong 11 and a hole 12 extending through the prong. The other end is slitted on the lines 13, separating it into two prongs 14 and a more or less keystone shaped part 15, having a notch 16 in the end.

The blank 10 is next bent as in Fig. 2 to form the segment 17, the part 18 which is to become the brush track being curved to the proper radius, the prongs 11 and 14 being bent inward to form anchors about which insulation is to be molded, and the part 15 being bent outwardly to form a segment riser, the notch 16 being adapted to receive the armature lead. The hole 12 serves no other purpose than to hold the lower end of the segments spaced apart in the mold while molding the insulation core and will therefore be termed the spacing hole.

A modified form of segment 19 may be made by providing a blank 20, Fig. 3, and bending the edges 21 and 22 downward and the riser part 15 upward, as in Figure 4.

A further modification 23 may consist in cutting away the prongs 14 of Figure 1 and adding two holes 24, as in Figure 5, then bending prong 11 downward and riser 15 upward,

as in Figure 6. Afterward when molding the core the insulation will extend through holes 24 to bind it to the core.

Fig. 7 shows the lower parts of a mold 25 within which I may assemble a number of segments 17 or a number of those of modified form as 19 or 23, the body comprising means to hold the segments spaced apart while molding of the core is being effected.

In the top surface of body 26 of mold 25 are a series of keystone shaped pockets 27 within which the risers 15 may seat themselves. Pins 28 in the base 29 of the mold are preferably provided to enter holes 12 in the lower end of the segments to keep the lower ends spaced apart, although these pins may be readily omitted when the segments are short, as then they are sufliciently held at the riser end. Or pins may be so placed in the bottom of the mold as to extend between adjacent segments to hold them spaced apart, since the exclusion of insulation from between the segments at the end of the commutator does not defeat the object of the invention. A center plug 30 having a keyway 31 is concentrically supported within body 26 on base 29 and is adapted to form the central axial opening through the commutator with an integral key of molded insulation extending inwardly from the wall of the opening.

Fig. 8 shows the same mold parts as are shown in Fig. 7 but with a set of segments in place, the risers 15 of the segments occupying pockets 27 and the holes 12 of the segments (not shown in Fig. 8) extending over pins 28. It may be seen that there is considerable unoccupied space between adjacent segments.

After the segments are placed as in Fig. 8 the stock ring 32 is fastened to body 26 by screws 33, and, since the risers 15 are fully as thick as the pockets 27 are deep, the stock ring clamps the risers securely, and prevents any movement of the segments.

The mold is now brought to a relatively high temperature after which charge 34 of unmolded insulation is placed into the stock ring and plunger 35 is entered at the upper end as shown. When the insulation 34 absorbs sufficient heat from the walls of the mold to become plastic the plunger 35 is pressed downward as shown in Fig. 10, forcing the insulation about the plug 30 of the mold, and about prongs 11 and 14 of the segments, and into the spaces between adjacent segments.

When the insulation 34 is hardened the commutator is removed from the mold and appears as in Fig. 11 where segments 17 are mechanically joined together yet electrically insulated from each other by the same continuous mass of insulation which forms the core 36 having the shaft opening 37 and integral key 38 and extends about the segment anchors and outwardly between the segments filling the space between them as at 39 to the brush track, thereby providing a flush commutator.

While I have shown an embodiment of my invention, and several modifications which some of the details may take, and have shown a mold, and indicated a procedure adapted to carry my invention into effect, a cons' derable variation in the product, the procedure, and the mold may be permitted without departing from the spirit of the invention. For instance, while I show segment risers of keystone shape and corresponding pockets in the molds, these risersand pockets may have parallel sides, and a pin in the middle of the pocket may enter a hole in the riser, similar to the method indicated by holding the lower end of the segment, or, the riser may depend entirely on the clamping effect of the stock ring to prevent it moving radially into the die opening, important points of the invention being the method and means of grasping the segments in such a manner that they are held apart from one another with open spaces between them to the end that a core of insulation may be molded to mechanically join the segments together yet extend between them tokeep'them electrically separated, and in the selection of such aninsulating material as may extend to the brush track and form a part thereof without danger of carbonizing under the arcing of the brushes.

Having described my invention, I claim- 1. The method of making a commutator from a series of separate segments having outwardly turned risers at the one end and inwardly turned prongs with spacing holes t't-erethrough at the other end, which consists in arranging the segments in the form of a cylinder, keeping them in circumferentially spaced apart position and against radial movement by holding them at the one that by the risers and at the other end within the spacing holes, thus leaving a series of vacant spaces between the segments at the outer :surface of the cylinder, and molding a one piece core of insulation into the said cyi ader and into all of the said vacant spaces between the said segments while they are so held.

2. The method of making a commutator from a series of separate segments having outwardly turned risers at the one end and innardly turned prongs at the other end, which consists of arranging the segments in the form of a cylinder, keeping them in circumferentially spaced apart position and against radial movement by holding them at the one end by the risers and at the other end by the prongs, thus leaving a series of vacant spaces between the segments at the outer surface of the cylinder, and moldin a one-piece core of insulation into the said cylinder and into all of the said vacant spaces between the said segments while they are so held.

3. The method of making a commutator from a series of separate segments having outwardly turned risers at the one end, which v consists of arranging the segments in the form of a cylinder, keeping them in circumferentially spaced apart position and against radial movement by holding them by the risers, thus leaving a series of vacant spaces between the segments at the surface of the hand.

VINCENT G. APPLE.

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