US2043474A - Method and blank for making brushes - Google Patents

Description

June 9, 1936.. H B EYNQN 2,043,474

METHOD AND BLANK FOR MAKING BRUSHES Filed Sept. 27, 1954 HOWARDBEYNON BY ATTOzEY L INVENTCR Patented June 9, 1936 UNITED STATES PATENT OFFICE METHOD AND BLANK FOR MAKING BRUSHES Application September 27, 1934, Serial No. 745,665

10 Claims.

My invention relates to brushes used in electrical rotatable machinery, and particularly relates to metal-graphite brushes having a flexible conductor attached thereto.

Heretofore, it has been customary to attach flexible cables in metal-graphite brushes by forming the brushes to its approximate final size and shape, drilling a hole or aperture in the upper portion of the brush, inserting the electrical conductor of wire in the hole, and simultaneously forming, by means of pressure, the brush to its final form and, also, securely fastening the conductor in place.

It is apparent that the material which is drilled from the brush is lost or wasted. Although the material lost is not large and valuable, the extra step of drilling, as well as the material lost or removed, is of great value and importance in manufacturing brushes on a quantity scale.

It is, therefore, an object of my invention to reduce the number of operations in forming and attaching a flexible conductor to a metal-graphite brush.

Another object of my invention is to attach a flexible conductor to a brush so that the connection is mechanically strong and the electrical resistance is reduced to a minimum value.

Another object of my invention is to reduce the quantity of material used in the formation of a brush.

Another object of my invention is to disclose a method of uniting a wire conductor to a brush blank so that substantially they are integrally formed.

Another object of my invention is to simultaneously form a brushinto its final shape and to securely attach a wire conductor thereto.

Another object of my invention is to disclose a method of forming a brush and attaching a wire conductor thereto without wasting any material.

Other objects of my invention are to provide an improved device of the character described, that is easily and economically produced, which is sturdy in construction, and the efficiency of which is high.

With the above and related objects in view, my invention consists in the following details of construction, and combination of parts, as will hereinafter be more fully described when the .description is read in conjunction with the accompanying drawing, in which:-

Fig. 1 is a perspective view of a brush in its initial state of production;

Fig. 2 is a fragmentary sectional view of the brush, solder, and pigtail conductor, as assembled in a wiring machine (not shown);

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is a sectional view similar to that taken on the line 3-3 of Fig. 2, but the ears of the brush of Fig. 4 have been compressed together;

Fig. 5 is a perspective view of a piece of low melting point metal, such as solder, lead, tin;

Fig. 6 is a fragmentary front elevational View of a die and its complementary punch, together with a brush and its conductor after the brush has been compressed;

Fig. '7 is a fragmentary side elevational view of the elements shown in Fig. 6; and

Fig. 8 is a perspective View of a brush in its final form after pressure has been applied thereto in the power press; the lug connecting the ends of the wire conductor is inserted in a separate machine.

Referring in greater detail to the drawing, I disclose in Fig. 1 a brush, generally designated as A, in its initial state of formation, which is larger in size than the finished product. The brush blank, A, is comprised of compressible metallic-graphite material, and the quantity of graphite and metal is varied according to the specific characteristics desired in the brush. The metal used is generally metallic powders, such as copper, zinc, lead, and tin, either used singly or compounded together.

Integrally formed with a substantially rectangular shaped prism having a body portion ill of the brush blank A are two vertically extending ears I2 and M. A surface [6, concave along its transverse axis and straight along its longitudinal axis, connects the interior lower longitudinal edges of the ears l2 and I4. A base ll of the brush blank is substantially fiat.

In Fig. 5, I disclose a U-shaped piece of material, generally designated as B, of low melting point for joining metallic surfaces to effect a good electrical union, and the material B is shaped to provide a convex outer surface 18 and a concave inner surface 20. The material B should provide the characteristic of melting at a low temperature, and may be solder, lead, tin, zinc, and so forth; and the material B may also be an alloy containing a flux.

The convex surface H! of solder B is adapted to be laid upon the concave surface N5 of the brush A with the concave surface 20 of the solder extending upwardly.

The brush A is placed in a wiring machine (not shown), and after the solder B and an electrical conductor of wire, generally designated as C, has been placed in position, the wire is cut to the desired length leaving ends 22 and 24 protruding. A punch clamps the top of the ears I2 and I4 together, and so fastens the wire to the brush.

The ears I2 and I4 are firmly compressed together forming a very close and tight fit about the solder B and the elongated flexible braided wire C, see Fig. 4. The wire or pigtail conductor C is substantially encased by the solder both as to its circumference and its length within the brush, thus making a good electrical connection between the wire and the brush. Moisture is excluded from the electrical connection formed between the brush and the conductor to such extent that corrosion is negligible and good electrical contact between the two parts is maintained over a long period of time.

The brush A having the wire C attached is thereafter placed in a die, generally designated as D, of a power press (not shown) for a stamping or pressure applying operation. The forming chamber 25 of the die D is defined by vertically extending walls 26, 28 and'3ll, 32, see Figs. 6 and '7, corners joining the walls being beveled. The chamber has a base 38 which is convex along its shorter transverse axis in order to impart a concave-shaped base to the base I! of the brush A.

Upon the introduction of a brush blank into the die and applying pressure to the punch, the brush is pressed in one operation to its predetermined size, the shoulders are finished, the corners are beveled, and the bottom is formed to th predetermined concave shape.

The punch E is comprised of a body portion 34 having a slot 36 defined by an arcuate inclined wall 38, the slot is inclined towards a horizontal base 40 from a vertical side wall 44.

The slot 35, defined by the wall 38, is adapted to permit one end of the wire 24 extending from the brush to project therethrough.

An arcuate inclined wall defining a second inclined slot, similar in details of construction and function as the arcuate wall 38 and the slot 36, is in a vertically extending side wall 42, in order to permit the second end 22 of the wire extending from the brush to project therethrough. Extending downwardly from the corners of the punch are four projections 46, 48, 56, see Figs. 6 and '7, one of the projections not being shown upon the drawing. Each projection is of similar construction, and one projection 48 will be described. However, two projections are for the left hand side of the brush, as the brush is viewed in Figs. 6 and 8, and two projections are for the right hand side, thus a symmetrically arranged brush is formed. The projection 48 has vertically extending parallel walls 52 and 54 and a vertically extending outside end wall 56 joining the walls 52 and 54, the inner end wall 58 is convex upward relative to a vertical plane, and the convex wall substantially joins the projection of the arcuate curved wall 38. The vertically extending corners of the punch are beveled, as at 59.

The four projections at the corner of the punch serve to form concave shoulders, designated as 50, upon the upper portion of the brush. However, it is particularly to be noted that the form of the punch E allows a small quantity of surrounding material, designated as 62, to abut one end of the wire prior to its exit from the brush in substantially a vertical direction from the brush body.

The horizontal base 40 of the punch E flattens the upper surface 64 of the finished brush A, see Fig. 8, so that a spring member, whereby the brush is held in contact with an electrical conducting rotating member, may be seated thereon.

After the brush A and its attached wire is placed in the die D and the punch E forced therein, the brush is formed to its final shape, see Fig. 8. I

In the final operation of manufacture, the brush is welded so that line designated as 65 in Fig. 8, marking the junction of the ears I2 and I4, is not seen in the finished product. The heat applied in this last operation fuses the solder with the metal of the brush and the wire, thus making the brush integral in most respects. This intimate bonding of the wire conductor and the brush reduces the contact resistance to a negligible value and also prevents corrosion.

The finished brush A, shown in Fig. 8, is adapted for use on commutators and slip rings of electrical generators, motors and/ or converters.

Tin powder or lead powder, or mixtures of both, together with a flux may be inserted with the wire C, and after the projecting ears have been compressed and the brush has been formed to its final size and shape, the application of a certain amount of heat, in order to cause a soldering effect, results in a good electrical connection to overcome any effect of surface oxidation in the slot of the brush or on the surface of the Wire C itself.

It is also to be pointed out that the pressure exerted on the brush by the punch E closely compresses the metal about the wire C near the central portion of the brush, but the wire is not materially distorted at the points where it emerges from the brush. The wire C, when originally placed on the surface I6, is substantially straight, but after it is finally formed as hereinbefore described, the portion of the wire within the brush is curved. This is an advantageous method of applying the pressure as it insures a good union between the brush and the Wire conductor, and tends to prevent the shearing or the breaking of the wire at the points where the wire emerges from the brush.

Although this invention has been described in considerable detail, such description is intended as illustrative rather than limiting, as the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

I claim as my invention:

1. A method of forming a brush which comprises the steps of forming a plurality of projecting ears which define a slot in the top of the brush, placing a piece of solder in said slot, inserting a cable in engagement with said solder in said slot, and compressing the ears about the cable and the solder.

2. A method of forming a brush which comprises the steps of forming a plurality of ears which define a slot in the top of the brush, placing a piece of solder in said slot, inserting a cable in engagement with said solder in said slot, compressing the ears about the cable and the solder, and pressing the brush to its final form.

3. A method of forming a brush of metalgraphite material which comprises the steps of forming a plurality of projecting ears on the brush, forming a piece of solder into a substantially U-shaped member, placing said solder be- 75 tween said ears, laying an electrical conducting cable between said ears and adjacent said piece of solder, and compressing the ears securely about said solder and said cable.

4. A method of manufacturing a commutator brush which comprises the steps of: forming the brush with its dimensions slightly greater than the dimensions of the finished brush and with a groove in its upper longitudinal portion; inserting a piece of solder in said groove; inserting an elongated flexible wire in engagement with said solder; compressing the ends defining said groove securely about the wire; and applying pressure to said brush and wire unit to simultaneously bond the wire to the brush and to finish the brush to its desired shape as by finishing its shoulders, beveling its corners, as well as inserting the bottom radius thereon.

5. A method of manufacturing a brush which comprises the steps of: forming the brush wherein the dimensions are slightly greater than the dimensions of the finished brush and having a groove or slot in its upper longitudinal portion; inserting a piece of solder in said slot; inserting an elongated flexible wire adjacent said solder in said slot; compressing the walls defining said groove securely about the wire; applying pressure to said brush to simultaneously bond the wire to the brush and to finish the brush to its desired shape as by finishing its shoulders, beveling its corners, as Well as inserting the bottom radius thereon; and heat-treating the brush so that it is substantially an integral unit.

6. A method of manufacturing a metallicgraphite brush which comprises the steps of forming the brush with its dimensions slightly larger than the dimensions of the finished brush and having a plurality of projecting ears thereon, inserting a cable between said ears, compressing the ears to retain the cable, pressing the brush to its final form, and heat-treating the brush so that it is substantially an integral unit.

7. A method of attaching a conductor to a metallic-graphite brush which comprises providing a blank for said brush having two upstanding ears spaced from one another by a longitudinal groove on its upper surface; inserting a piece of solder within said groove; inserting an elongated flexible wire in engagement with said solder; compressing the upstanding ears together whereby the solder and the wire will be held within the longitudinal groove, and applying pressure by means of a stamping press to the upper surface of said brush in a direction toward the base thereof to attain the desired final form of said brush and to depress the metal at the upper surface of said brush whereby intimate contact with the metal of said brush with said conductor is attained, and in the same operation forming an are along the contact portion of said conductor.

8. A blank for an electrical apparatus brush comprising a substantially solid prism of electrical conducting compressible material, and a plurality of spaced projecting ears integrally formed with one surface of said prism.

9. A blank for an electrical apparatus brush comprising a substantially solid prism of electrical conducting compressible material, and two spaced ears extending from one surface of said prism.

10. A blank for an electrical apparatus brush comprising a substantially solid prism whose faces are parallelograms, and two substantially parallel ears extending from one of the prism faces.

HOWARD B. EYNON.

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