US3075111A - Carbon brush for the collector current of electrical machines - Google Patents

Description

G. CARBON BRUSH FOR THE COLLECTOR CURRENT OF ELECTRICAL MACHINES Filed Oct. 13, 1959 INVENTOR gerrit star-re AGE- United States Patent Ofilice 3,075,l l l Patented Jan. 22, 1953 3,ii75,111 CARBUBN RRUEH E052 THE QGLLECTQR CURRENT 9F ELEQTREHCAL MACHlNES Gerrit Stacie, Drachten, Netherlands, assignor to North American Philips Cernpany, inc, New York, N.Y., a corpcraticn of Delaware Fiied fi st. 13, 1959, Ser. No. 84d,176 Claims priority, appiication Netherlands Oct. 14, 1953 4 Claims. (Cl. 310-248) The invention relates to a carbon brush to establish the contact with the collector of an electrical machine, particularly a low-power machine, such as used for dry shaving apparatus and is characterized in that the brush has a trapezium configuration.

According to a further feature of the invention the carbon brush is arranged in the electrical machine so that the trapezium section is at right angles to the collector surface, the base extending in the direction of rotation of the collector.

This provides the advantage that the block brush can be utilized to the last part. It has been found that the brush is subject to a maximum wear on the side where the collector or commutator laminations interrupt their contact with the brush i.e. the trailing edge of the brush. This involves that the brush is worn oil? obliquely and will occupy an increasingly more slanting position relative to the col ector surface until this is prevented by the wall of the tubular brush guide, so that by further wear of the brush only one part of the effective brush surface engages the collector. When the brush is almost completely used, the remainder is a piece of triangular section, of which the contact surface decreases gradually and is therefore unserviceable. This remainder therefore means a loss of material. By rendering the brush higher or thicker on the side of maximum wear than on the other side, which is obtained by the trapezium section, this drawback is obviated.

The invention will be described more fully with reference to the accompanying diagrammatical figures.

HG. 1 shows a carbon brush according to the invention,

FIG. 2 shows a side view thereof in a brush guide, used with a fiat collector and FIG. 3 shows the same used with a cylindrical collector.

FIG. 1 shows a block brush 1 with trapezoidal configuration. The arrow 2 indicates the direction of rotation of the collector and the arrow 3 represents diagrammatically the spring pressure exerted on the brush.

When a collector lamination located below the brush leaves the edge 4, a spark is locally produced, so that on this side the brush is worn off more rapidly than at the edge 5.

The brush shown in FIG. 1 is suitable [for use in machines comprising a fiat collector, which is shown in FIG. 2.

To a plate or dish 6 of insulating material, which is arranged on the rotor shaft (not fully shown), are secured three fiat collector segments, of which two are designated by 7 and 8, which are separated by an air gap, 9. A thin plate 10 of electrically conductive material, arranged at right angles to the trapezium section and having an aperture through which the brush slides,

serves as a brush holder for each of the brushes (only one shown) and the current is supplied or conducted away via the connection 11 by a spirallized blade spring 12. Such an arrangement is possible since the height 13 (see FIG. 1) of the trapezium constitutes the largest dimension, so that the brush lies in fiat position on the collector, so that there is no risk of tilting. The edge f the brush 1 prevents a complete wear, by which the blade spring and/or the collector could be damaged.

The end Wall of brush l1, in which is located the edge 4, (see FIGS. 1 and 2), constitutes part of a circle, so that the contact surface of the brushes can be made to remain always constant. However, this wall may be flat as is shown by the broken lines of FIG. 1.

Owin to the large contact surface and the low pressure per square centimetre, the wear both of the brush and of the collector is consider bly diminished. This is, of course, only possible, if the surface of each of the laminations is sufficiently large to permit the use of a fiat brush. Collectors having at the most six laminations are suitable.

Finally, FIG. 3 shows a cylindrical collector 15 with a brush 1.

What is claimed is:

l. A carbon brush tor establishing contact with the collector of an electric machine comprising a carbon body having a largest dimension between the surfaces defining the leading and trailing edge thereof, and the longitudinal side wall surface of said body in the plane normal to said collector defining a trapezium whereby the contact surface of said brush remains substantially constant with wear.

2. A carbon brush for establishing contact with a disk shaped collector of an electric machine comprising a carbon body having a largest dimension between the surfaces defining the leading and trailing edge thereof, and the longitudinal side Wall surfaces of said body in the plane normal to said collector defining a trapezium whereby the contact area of said brush with said collector remains substantially constant with wear, a brush holder, said brush holder comprising a flat plate having an aperture adapted to receive said body, said plate lying in a plane parallel with the said disc shaped collector, and stop means comprising a plate overlying said brush and extending beyond said aperture whereby complete consumption of said brush by wear is prevented.

3. A carbon brush according to claim 1 wherein said brush is characterized by having a curvalinear surface at the trailing edge thereof.

4. A brush assembly according to claim 2 wherein said brush is urged against said collector by spring means operatively associated with said brush guide.

References fitted in the file of this patent UNITED STATES PATENTS 1,116,402 Ferguson Nov. 10, 1914 2,399,935 Morrill May 7, 1946 2,595,621 West May 6, 1952 2,703,372 Savage Mar. 1, 1955 2,773,247 Erhardt Dec. 4, 1956 FOREIGN PATENTS 369,366 Great Britain Mar. 24, 1932 521,453 France Mar. 5, 192 1

Claims (1)

1. 2. A CARBON BRUSH FOR ESTABLISHING CONTACT WITH A DISK SHAPED COLLECTOR OF AN ELECTRIC MACHINE COMPRISING A CARBON BODY HAVING A LARGEST DIMENSION BETWEEN THE SURFACES DEFINING THE LEADING AND TRAILING EDGE THEREOF, AND THE LONGITUDINAL SIDE WALL SURFACES OF SAID BODY IN THE PLANE NORMAL TO SAID COLLECTOR DEFINING A TRAPEZIUM WHEREBY THE CONTACT AREA OF SAID BRUSH WITH SAID COLLECTOR REMAINS SUBSTANTIALLY CONSTANT WITH WEAR, A BRUSH HOLDER, SAID BRUSH HOLDER COMPRISING A FLAT PLATE HAVING AN APERTURE ADAPTED TO RECEIVE SAID BODY, SAID PLATE LYING IN A PLANE PARALLEL WITH THE SAID DISC SHAPED COLLECTOR, AND STOP MEANS COMPRISING A PLATE OVERLYING SAID BRUSH AND EXTENDING BEYOND SAID APERTURE WHEREBY COMPLETE CONSUMPTION OF SAID BRUSH BY WEAR IS PREVENTED.

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