US1878132A - Process of baking molded pieces - Google Patents

Description

Sept. 20, 1932. E. J. HALL I .PROCESS OF BAKING MOLDED PIECES Filed July 20, 1926 Patented Sept. 20, 1932 UNITED STATES PATENT OFFICE EVERETT J. HALL, OF ELIZABETH, NEW JERSEY, ASSIGNOR TO METALS DISINTEGRAT- ING COMPANY, INC., 01 ELIZABETH, NEW JERSEY, A CORPORATION OF NEW JERSEY PROCESS OF BAKING MOLDED PIECES Application filed July 20, 1926. Serial No. 123,699.

This invention aims to provide an improved commutator brush, and includes a manufacturing method appropriate to the product.

An object is the production of an improved commutator brush having a durable pigtail attached thereto in a manner to provide a permanent and perfect contact between brush and pigtail. The invention also involves an expeditious and economical method of producing the brushes, important saving of time, labor, material and fuel being accomplished thereby.

While I have disclosed a preferred form of the invention, it should be understood that various changes may be made without departing from the spirit and scope of the invention as hereinafter set forth and claimed.

In the drawing Fig. 1 shows the processof molding the brush in the pill machine Fig. 2 is a section on line 2-2 of Fig. 1;

Fig. 3 is a section on line 3-3 of Fig. 1;

Fig. 4 is a perspective of the bottom die;

Fig. 5 is a perspective of the completed brush.

Brushes of the type herein disclosed are ordinarily formed by compressing powdere' material in a pill machine of well-known construction. The usual practice is to mold the brush blank on the flat, so that the laminations will run perpendicular to the commutator and in line with the bars. These blanks, after molding, are packed in suitable con-' tainers (a couple of thousand at a time), surrounded either with sand or a sand containing some carbonaceous material, the function of the sand being to separate the brushes and prevent their sticking together during the ensuing baking operation. The containers are then placed in a furnace and fired at a temperature of 650 to 7 (3., and in order for complete heat penetration and uniform baking conditions a 24-hour cycle is usually required. After baking, the brush blanks are separated from the sand and then drilled to permit the introduction of pigtail wires, usually braided wires; the wire connection cleaned, or treated in some way with mercury to insure good intermetallic contact; and the brush then introduced into a forming die, which presses the brush onto the pigtail wire, giving a good contact and the same time compressing the brush to SlZe.

As these brushes are molded'on the flat, and as it has to date been difiicult, if not impossible, to maintain the thickness of the brush within the limits required for a proper fit in the motor brush-holder, it has been necessary to size the brushes, which is done either by grinding, in some instances, or by forcing them to size with a proper die, during the pigtailing operation. Moderate variations in the length of the brush are of no importance whatsoever, as these are taken care of by the spring feed.

The present invention aims to effect economies in the cost of manufacture and at the same time produce a much better pigtail and pigtail connection, by molding the brush around the pigtail wire, and by a novel subsequent treatment.

As shown in Fig. 1 the mold, which may be part of a so-called pill machine, comprises a rectangular sleeve 10 having an opening therethrough of a size corresponding to the J thickness and width of the finished brush.

The bottom die 11 is formed with an indented top and channeled sides as shown in Figs. 2 and 4:. 1 A piece of pigtail wire 12, which may be of ordinary copper, deoxidized copper, or other suitable material, and preferablyv braided, is placed over the bottom die, fitting into the channels, and supported above the bottom of the indentation formed in the top of the die block. The die block is placed in Sleeve 10, which is then filled with the proper amount of powder (a mixture of powdered copper, lead and graphite, for instance) and the plunger 13 is brought down to compress the powder. This action presses the powder under and entirely around the portion of Wire 12 lying above the lower die block, and forces the powder into the interstices and surface irregularities of the wire. At the same time the body 14.- is given its proper lateral size and sh ape,- and since slight variations in length are immaterial, no further sizing of .the brush is necessary. The

lower end of plunger 13 is curved so that the operation of forming the brush body gives the roper radius curve to the contact end of the brush.

In case the wire 12 is made of deoxidized copper or other special material, the brush may now be passed through the usual baking process, but in case the pigtail wire is of ordin'ary copper, the old practice does not give good results. It is well known that all commercial copper contains a certain amount of cuprous oxide in solution, and if this copper wire, or any copper wire, is heated in an oxidizing atmosphere the copper will become embrittled. If copper wire containing oxide is heated in a reducing atmosphere it is also embrittled. Therefore if the wire used is the ordinary commercial article, in order to maintain its brightness and strength, it must be heated in a this purpose I prefer to use steam, as being the cheapest inert atmosphere, also the most readily maintained. The brushes, as they are ejected from the pill machine, are passed to a conveyor which carries them through a heat-treating furnace containing a suitable atmosphere for any desired'interval.

The brus es may be molded together with their pigtails in a continuously operating machine, and discharged as fast as they are made onto a continuously moving conveyor (I include intermittent operation within the intended meaning of the terms continuously operating and continuously moving) the furnace may be tubular, sealed at each end by a water-seal into which the ends of the tube are depressed, and the conveyor may emerge from one water-seal, pass thence through the furnace tube, then down into and through the other water-seal, to a place of discharge.

7 A steam or other neutral atmosphere is maintained in the furnace, for instance, by intro ducing steam at the far end of the tube and allowing it to escape at the inlet end of the tube, that is, the end .where the conveyor enters. The result is that the desired atmosphere is maintainedin the tube, deleterious ga es, &c. coming from the brushes in the course of the baking operation being swept out with the ventilating flow of steam. The furnace tube is heated in any preferred manner, so that the brushes passing through are subjected to direct radiation of heat. Consequently the baking is accomplished very quickly, as compared with the old process, in which an insulating mass of sand had to be heated before the baking heat reached the brushes by conduction. My method shows another advantage in the fact that it minimizes heat losses. With the old practice, each batch of brushes, with its surrounding sand, had to be heated up, heat maintained for a long period and then cooled; whereas, with my method there is no alternate heating and cooling. The furnace remains hot. Furtherneutral atmosphere, and for,

more, I am able to make a test of any individual among the succession of brushes coming out of the furnace, whereas with the old method no test is possible until after a whole batch has been completed beyond the possibility of error-correction.

While such an arrangement would not be essential, I contemplate providing a furnace tube length and/or conveyor speed properly coordinated with the output of the moldin machine, so that a substantially continuous manufacturing process may be had.

It will be understood that the heat maintained in the furnace will be from 650 to 750 C., or whatever temperature may be best for the production of a brush with desired durable mechanical and electrical qualities, and with the adjacent surfaces of pigtail and brush properly alloyed, fused, merged or cemented together.

After the brush is discharged from the furnace the clip 16 is attached to the ends of the pigtail wire in any preferred manner, and the brush is ready for use without any further operations.

In ordinary practice the electrical contact between the pigtail and the brush body presents a very serious problem. Even if the contact is fairly satisfactory when the brush is new, on standing for a period of time oxidizing of the surfaces in contact may take place and the resistance of the contact may increase several hundred or even several thousand per cent. Various means have been resorted to to make pigtail contact electrically permanent, as by the use of mercury or its compounds to produce amalgamation; but trouble has arisen even under these conditions. With my method the pigtail joint is as electrically permanent as the brush itself. This result is obtained because the powdered copper is forced into all the confronting interstices of the wire during the pressing operation, and during the 'bakin there is an actual cementation or fusion of t e powder and the copper comprising the pigtail; or, to put it in another way, there is a mer ing of the surfaces of pigtail and surrounding brush.

The process disclosed reduces the amount of material as well as labor required to produce the finished article, and produces a superior commutator brush inexpensively.

I claim 1. The process of producing a commutator brush which comprises the steps of holding the intermediate portion of an uncoated wire in spaced relation to the die block of a pill machine, pressing suitable powdered material about the wire to form a body having the width and thickness of the finished brush, and subjecting the article to a baking operation in a non-injurious atmosphere.

2. The process of producing a commutator brush which comprises the steps of holding an uneoated wire in spaced relation to the die block of a. pill machine, pressing suitable powdered material about the wire to form a body having the width and thickness of the finished brush, and subjecting the article to a baking operation in a neutral atmosphere to cause alloying between the wire and the powdered material.

3. The process of producing a commutator brush which comprises placing the intermediate part of a piece of wire into a mold having lateral dimensions corresponding to the lateral dimensions of the finished brush, placing a charge of powdered material in the mold, and compressing the charge from a side corresponding to an end of the finished brush.

4. The process of producing a commutator brush which comprises placing part of a conducting wire in a mold having the lateral dimensions of the finished brush, placing a charge of powdered material in the mold, and brush which comprises placing part of a conresponding to an end of the finished brush, thereby simultaneously compressing the powdered material into a cohesive mass surrounding part of the conducting wire and molding the powdered material into a body having the lateral dimensions of the finished brush.

In testimony whereof I aflix my si ature.

EVERETT J. L.

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