Brush holder for dynamoelectric machines

May 27, 1958 h. a. gillie 2,836,745

BRUSH HOLDER FOR DYNAMOELECTRIC MACHINES

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2,836,745

Patented May 27, 1958

United States Patent Office

2,836,745

BRUSH HOLDER FOR DYNAMOELECTRIC MACHINES

Harmon A. Gillie, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York

Application October 12, 1956, Serial No. 615,721

Claims. (Cl. 310—246)

The invention described herein relates to dynamoelectric machines and more particularly to an improved brush holder of the type utilizing a coiled spring designed for applying a constant predetermined pressure on a carbon brush regardless of the state of brush wear.

The brush holders currently used with large dynamoelectric machines are of the torsion spring type wherein a free end or arm of the spring is engageable with a lever arm arranged for applying pressure to the brush during machine operation. In order to maintain constant pressure while compensating for brush wear, the free arm of the spring is progressively moved into notches provided on the lever arm body. Thus, as wear increases, the spring is wound in incremental amounts and therefore compensates for the greater distance the lever arm must act through to provide the necessary pressure for urging the brush face into contact with the commutator.

The principal disadvantage of the above-described structure is that the application of a constant pressure on the brush throughout its life is not obtainable. As a result, pressures less than optimum values may cause uneven brush wear and produce chattering and sparking at the commutator while pressures too great, accelerate wear of the brush at unreasonable rates. The problem of maintenance posed by the construction is evident since continual verification must be made of brush pressures to keep them within acceptable limits. Further, an excessive number of parts of various sizes and shapes are required in the prior construction and since different size brush holders are used for various machines, an unusually large inventory of individual parts must constantly be maintained in stock.

Therefore, an object of the present invention is to provide a brush holder capable of eliminating the abovedescribed deficiencies while further permitting safe and speedy replacement of a brush without resorting to the use of tools or removing any parts from the brush holder assembly.

In carrying out the object of my invention, I have designed the brush holder in the shape of a substantially rectangular box provided with open ends and having a plurality of spaced parallel channels therein. A brush is inserted through the top open end into one of the channels and protrudes at the opposite open end in a direction for contacting the commutator of the machine. A pair of channels are incorporated in the box on opposite sides of the brush channel and are of a size to accept arms of an assembly supporting a constant pressure spring arranged for pressing the brush into firm contact with the commutator. The remaining channel is utilized for securing the brush holder to a supporting yoke adapted for positioning on a frame of the machine.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawing in which:

Figure 1 is a view in elevation, with parts broken away to show details of the brush holder body;

Figure 2 is an end view of the brush holder shown in Figure 1;

Figure 3 is a top view; and

Figure 4 illustrates a constant pressure spring designed for coaction with the brush holder for urging the brush into contact with a commutator.

Referring now to the drawing wherein like reference 10 characters designate like or corresponding parts throughout the several views, there is shown a brush holder 10 of general rectangular configuration made of bronze or other material and being capable of supporting brushes in the usual manner. The brush holder consists of a box 15 12 having generally fiat sides, open at its top and bottom ends, and of a design permitting attachment to a yoke provided on the machine. A plurality of parallel channels or passageways 14, 16, 18 and 2G extend vertically along its length for receiving a carbon brush 22 and spring 20 assembly 24 designed to urge the brush into firm contact with a commutator 26.

Referring now to the box 12, the spaced channels 14, 16, 18 and 20 are positioned in line with one another with the larger of the channels 16 being utilized for re25 ceiving carbon brush 22. The channel 20 shown at the - extreme right of the box 12 is formed by the walls of the box and is equipped with an elongated slot 28 through which a bolt 30 is adapted to extend for attaching the box to a yoke 32 affixed on a side of the machine. 30 Channel 18 positioned adjacent thereto is formed by a pair of oppositely disposed but inwardly directed flanges 34, the bottom of the channel terminating in a stop member 36 for limiting the extent of downward movement of spring assembly 24 and thereby precluding inadvertent 35 contact with the commutator.

As shown in Figure 3, a second pair of inwardly directed flanges 40 coact with flanges 34 in forming the channel 16 which is of a size for receiving the brushes 22. Wire shunts 38 extend from the brushes in the usual manner. The flanges 40 merge into a solid wail 42 which serves as a reaction surface for the brushes during machine operation, while the opposite flanges 34 extend substantially to the bottom of the box 12 and the space between the latter flanges is employed for permitting un⁴⁰ obstructed downward movement of constant pressure spring 44 as it follows the brushes as they wear from use in the machine. It has been found that the coacting effect between the reaction surface, brush and spring imparts excellent stability to the brush when in contact with the ⁵⁰ rotating commutator.

The outermost channel 14 is provided with a smooth outer wall 45 having a slot 46 bridged near the bottom with a horizontal bar 48 for a purpose hereinafter described. The upper ends of the wall 45 on opposite sides of slot 46 are bent over to engage the flanges 40 at 41.

The spring assembly shown in Figure 4 consists of a U-shaped member 5® having legs 52 and 54 which are respectively provided with an outwardly directed projecθθ tion 56 and lugs 58, and a spring 44 attached to an inner portion of leg 54, as by rivets 69. As indicated above, the spring 44 is of a constant pressure type capable of exerting a predetermined pressure on the brushes regardless of the size or state of wear thereby assuring firm contact with the commutator during their useful life. The U-shaped member is made of spring metal with the legs 52 and 54 being spaced a distance slightly greater than the position they assume when the spring assembly is set in the brush holder.

⁷⁰ In operation, after the box 12 has been rigidly⁷ attached to the yoke 32 and the brushes 22 inserted therein, the legs 52 and 54 are pressed inwardly and respectively in

2,836,746 serted in channels 14 and 18 provided in the box. By pressing downwardly on the U-shaped member 50, the spring 44 is caused to unwind as it contacts the top of the brushes 22. Simultaneously, the legs 52 and 54 frictionally engage the walls of their respective channels and when the assembly assumes its final position, leg 54 is held in the channel only by friction of the leg against the inner wall surface. Leg 52 on the other hand, moves against the inner surface of wall 45 until projection 56' slides over the horizontal bar 48 and subsequently snaps outwardly thereby locking the spring assembly in position when downward pressure thereon is removed and the projection 56 permitted to lock itself on the horizontal bar 48. It will be evident that at this time, the upper ends of wall 45 are bent over to contact flanges 40 at 41.

When removal or replacement of the brushes is necessary, downward pressure need only be exerted on the top of U-shaped member 50 by one hand of an operator, such pressure being effective to move the projection 56 out of contact with bar 48. With the parts in this position, removal of the pressure permits the constant pressure spring 44 to move the spring assembly in an upward direction and out of the box 12. Since the top ends of side 45 have been turned over against the flanges 40 at 41, the lugs 58 on leg 52 will hang up at this point thereby maintaining the spring assembly captive on the brush holder.

Reflection on the structure described above will show that only three parts are incorporated in this improved brush holder, namely, the U-shaped member 50, spring 44 and box 12, whereas a multitude of parts are required in prior structures. Further, the process of brush removal is simplified to a single step wherein only a single downward movement of the spring assembly is necessary to effect disengagement from the operative position, and the assembly remains captive on the holder during the brush removal and replacement operation.

Obviously, many modifications and variations are possible in light of the above teachings. It therefore is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.