US1708192A - Manufacture of bodies from metal powder - Google Patents

Description

7 April ,1929. c. F. SHERWOOD 1,708,192

MANUFACTURE OF BODIES FROM METAL POWDER Filed May '7, 1927 gwumtox M fm TES'

PATENT o 1,708,192 Fries.

CHARLES FREDERIO SHERWOOD, OF DETROIT, MICHIGAN.

IMANUFACTURE OF BODIES FROM METAL POWDER.

Application filed May 7,

This invention relates to the manufacture of bodies by compressing and sintering serlq block 12.

finely divided substances including finely divided metals, and particularly to the manufacture of electrically. .conducting bOClIQS such as brushes for dyhamo electric machines.

One of the objects of the present invention 'is 'to provide an integral structure comprising a body of sintered powdered materials including powedered metals and a previously formed rod or wire extending therefrom, the structure being such that the metal of said body merges directly into the metal of the rod without any intermediate bond. In respect to the application of this inventlon to the manufacture of electrical brushes, it is an object to provide a brush of sintered metal and, integral therewith, a flexible conductor or pigtail. Further objects and advantages of the present invention will be apparent from the following description, reference be1ng had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a side elevation, partly in vert cal section, showing apparatus for compressing powdered metals while at the same time embedding into the compressed form the end of a flexible stranded conductor or pigtail.

Fig. 2 is a perspective view of the com- .pressed form with two flexible conductors extending therefrom.

Fig. 3 is a longitudinal sectional new of a completed brush showing the conductors or pigtails permanently attached thereto. The sectional view is-taken on the plane of line A- B of Fig. 2. r

In Fig. 1 of the drawings numeral 10 designates the bed plate of a molding press which supports a die 11 containing an 1n- The insert block 12 supports two flexible strand conductors or pigtails 13, the upper ends of which extend above the upper end of the insert block 12 as shpwn. The die is filled with a predetermined quantity ,of a mixture 14: of metal powders and graphite or other suitable filler. A briquetting plunger or ram 15 compresses the powder 14 into a briquette of the size desired for a. brush. The formed body is shown in Fig. 2 in which numeral 13 designates the pigtails, the numeral 16 the brush body. This body with the pigtails is im- 1927. Serial No. 189,697.

mersed in a bath of molten salts, preferably the salts of alkaline metals for a time sufficient to sinter the metallic particles and to form a coherent mass. After sintering the body is quenched in water and is ready for grinding its commutator'engaging surface.

The present invention is not limited to any particular mixture of powdered materials; but, by way of example, I have found that satisfactory results may be obtained from a mixture of metalpowders containing,

by weight: 87 parts copper, 7 parts lead, 1 parts tin, 4 parts graphite. lhe sintering bath should be approximately 1400 F.,

and for this purpose I prefer to use a bath of sodium cyanide. However, it is possible to use other salts or salt mixtures having approximately this melting point provided the salts do not materially affect the body to be sintered during the time of immersion of the body in the salt bath. The sintering time will of course depend ,on the-size of the body to be sintered. I have found that, for a small brush such as used in electric motors for starting the internal combustion cordance with the present invention, this.

section being shown approximately or diagrammatically in Fig. 3, that the ends of pigtails: 13 which were embedded in the brush body 16 have completely lost their identity and have merged with the metal of the brush to form an integral structure including the brush body and the pigtails. I have found that it is not necessary to fray out the ends of the pigtails which are embedded in the briquetted metal powder form in order to provide means for anchoring the ends of the pigtails in the brush body. The pigtails 13 may be cut off at right angles to their length as shown in Fig. 1. What becomes of the end portions .of the pigtails during the sintering operation I cannot definitely state but I presume that these ends may alloy with some of the finely divided metal particles contained in the brush body. It may be that the ends of the pigtails may alloy with the tin particles of the brush specified by way of example and thus form a bronze included in the structure of the brush body;

One important feature is the use of a sintake place. If any metallic oxides are present within the briquetted form, these oxides will be reduced in the bath.

Whilel have used the term bond it will be understood that there is nointervening bonding metal joining the pigtails and the brush body. The union OftllC pigtails and brush body isso perfect that careful examination does not reveal where one part begins and the other ends.

By eliminating a joint between the brush. body and the pigtail I have greatly prolonged the life of the brush since there is no possibility of corrosion at the joint, as occurs especially when the joint is formed by soldering. Furthermore, by providing an in- .tegralv structure, I have provided a body which has substantially the same electrical conductivity throughout. In this respect my invention is superior to structures having a joint between the brush body and the pigtail which has greater electrical resistance than the body or the pigtail.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to. be understood that other forms might be adopted, all com; ing within the scope of the claims which follow.

What is claimed is as follows:

1. The method of making an integral structure including a body of united metallic particles and a preformed metal body which consists in compressing powdered metallic particles with a portion of the preformed body embedded in the compressed form, and in heating the whole at a temperature and for a time suflicient to cause the metallic particles to unite, and the embedded portion of the preformed body to unite with a port-ion of the metallic structure of the other body, the heating taking place in a molten salt bath having a melting point between 1200 F. and i500 F. and

having a fiuxing action which dissolves the oxides on the metal particles thereby facilitating their alloyage;

2. The method of making an integral I structure including a body of united metal lic particles andla preformed metal body which consists in compressing powdered metallic particles with a portion of the preformed body embedded in the compressed form, and in immersing the whole in a molten salt bath having a-melting point be- .tween 1200 F. and 1500 F. and having a fluxing action on themetals being sintered,

the temperature of the bath and the time of immersion being sufiicient to cause the me-' tallicparticles to uniteand-the embedded portion of the preformed body to unite with a portion of the metallic structure of the other body.

3. The method of making-a dynamo brush having a preformed conductor integral therewith which consists in compressing abouta portion of the preformed conductor a mixture of powdered materials including powdered metals, and in immersing the whole in. a bath of molten sodium cyanide maintained at a temperature of about 1400 F., the time being sufiicient to cause the metallic particles to unite to form the brush body and the embedded portion'of the preformed conductor to unite with themetallic structure of the brush body. 4. The method of making a dynamo brush having a preformed conductor integral therewith comprising: molding powdered metals inthe form of a brush with a portion of said preformed conductor molded in place therein, and then sintering said molded unit to form an integral structure in a bath of molten sodium salt having a melting point between 1200 F. to 1500 F. and having a fluxing action on the metals being sintered.

In testimony whereof I hereto aflix' my signature.

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