US3158772A

US3158772A - Twin electric brush assembly with pressure arm wedge

Info

Publication number: US3158772A
Application number: US245451A
Authority: US
Inventors: Walter G Krellner
Original assignee: Stackpole Carbon Co
Current assignee: Stackpole Carbon Co
Priority date: 1962-12-18
Filing date: 1962-12-18
Publication date: 1964-11-24
Anticipated expiration: 1981-11-24
Also published as: GB991689A

Description

1964 w. s. KRELLNER 3,158,772

TWIN ELECTRIC BRUSH ASSEMBLY WITH PRESSURE ARM WEDGE Filed Dec. 18, 1962 INVENTOR. WALTER aA AsLu/efi- United States Patent PRESSURE ARM WEDGE Walter G. Krellner, St. Marys, Pa., assignor to Stackpole Carbon Company, St. Marys, Pan, a corporation of Pennsylvania Filed Dec. 18, 1962, Ser. No. 245,451 3 Claims. (Cl. 310-246) This invention relates to electric brushes, and more particularly to a brush formed from a pair of thin carbon brush ha1f-sections disposed face to face.

It is common practice to make an electric brush for a rotating electrical machine from two similar half-sections that are disposed face to face. The two sections are thin, by which is meant that their thickness is so small in relation to their length that when they are used with reversible commutators or slip rings they tend to tilt in the brush holder in a clockwise or counterclockwise direction, depending upon the direction of rotation of the electrical collector against which they ride. Any such change in the position of the brush halves, particularly upon and immediately after reversing the direction of rotation of the machine, results in new line contacts with the collector surface and eventually in so called double Seating. Even though the brushes do not get into a chattering condition because of the slight leading angle allowed by the necessary clearance in the brush holder, and do not chip or break before the second seat is formed, the new location of electrical contact results in a different and less favorable time of commutation for each direction of rotation, whereby performance of the machine and the life of the brushes and commutator are impaired.

It is an object of this invention to provide an electric brush of the spilt or two section type, which always engages both sides of the brush holder passage, which does not chatter, regardless of the direction of rotation of the electrical machine with which the brush is used. Other objects are to provide such a brush which can be used with a conventional brush holder without modifying the holder, which is simple in construction, which involves the addition to the brush sections of only a single element, and from which that element cannot escape while the brush sections are near together.

In accordance with this invention a pair of thin carbon brush halves or sections are disposed side by side and their outer end portions are provided with a pair of opposed notches. Each notch has end walls diverging toward the inner end of the brush and spaced apart by a side wall that is inclined across the brush section from near its outer face toward its inner face and end. Together, the notches form a socket having side walls converging toward the inner end of the brush and having end walls diverging toward said inner end. Disposed in the socket is a wedge that has side walls which slidingly engage the inwardly converging side walls of the socket. Consequently, when the wedge is pressed toward the inner end of the brush, it will force the brush sections apart and hold them in engagement with the opposite sides of the brush holder passage in which the brush is disposed. The wedge also has inwardly diverging end walls adjacent the socket end walls in order to keep the wedge from accidentally slipping out of the brush socket when the wedge-pressing member is removed from the wedge.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a view of one end of a brush holder containing my brush, with part of one of the brush sections broken away;

FIG. 2 is a plan view of the brush in the holder taken on the line II-II of FIG. 1;

FIG. 3 is a cross section of the brush and holder taken on the line III-III of FIG. 1;

FIG. 4 is a fragmentary view similar to FIG. 3, but showing the brush-retaining member held away from the brush and the two sections of the brush in engagement with each other;

FIG. 5 is a perspective view of the brush wedge; and

FIG. 6 is a perspective view of a modification.

Referring to FIGS. 1 and 2 of the drawings, a brush holder 1 of suitable well-known construction is mounted beside a rotating cylindrical electrical collector 2, such as the commutator or slip ring of a rotating electrical machine (not shown). For convenience of description only, the rotating collector will be referred to herein as a commutator. The machine is reversible so that the commutator can be rotated in either direction. The brush holder is provided with a rectangular passage 3 that is disposed radially of the commutator and a short distance away from it. Mounted in an opening in the holder outside of the brush passage is a spiral spring 4, the outer end of which carries an insulating pad 5 for pressing a brush B, slidably mounted in the passage, against the commutator at all times. As is common practice, the brush is formed from a pair of thin carbon half-sections 7 and 8 that are disposed face to face. Their outer ends are connected in the usual manner by shunt wires 9 to a common terminal 10.

It is a feature of this invention that, regardless of the direction in which the commutator is rotated, both sections of the brush will continually engage the adjoining opposite sides of the brush holder passage. Accordingly, the outer end portions of the brush sections are provided with a pair of opposed notches that register with each other to form a socket in the brush. Each notch is threesided; that is, it has end walls 12 (FIG. 1) that diverge toward the inner end of the brush and which are spaced apart by a flat side wall 13 (FIG. 3) that is inclined across the brush section from or near its outer face toward or to its inner face and inner end. Consequently, the socket formed from these registering notches has side walls 13 that converge toward the inner end of the brush and it has end walls that diverge toward its inner end.

Disposed in the brush socket is a wedge 14 that has flat side walls which lie fiat against the side walls 13 of the socket as shown in FIG. 3. The wedge projects from the outer end of the brush and its outer surface preferably is transversely convex. For reasons that will appear later, it is highly desirable that the wedge be prevented from escaping from the socket as long as the two halves of the brush are relatively close together. This interlocking of the wedge and the half-sections of the brush is accomplished by providing the wedge with end wall-s 15 (FIGS. 1 and 5) that diverge inwardly toward the oppo site end of the brush. These end walls are close to and may be parallel to the end walls of the socket. The wedge thus is in the shape of an inverted keystone when viewed from the side as in FIG. 1, and cannot be removed from the open side of the socket. To insert the wedge, the half-sections of the brush have to be separated widely enough to permit the wedge to be inserted upwardly into the two notches, which are then brought together to form the socket.

After the wedge has been placed in the brush socket the compact assembly of the three parts is inserted in the brush holder as shown in FIG. 4, and then the previously retracted spring pad 5 is lowered onto the curved outer surface of the wedge. The pressure of the spring against the wedge will cause it to press the inner end of the brush against the commutator and simultaneously will cause the wedge to spread the brush halves apart into engagement with the opposite sides of the holder as shown in FIG. 3. The inclined sides of the wedge are disposed at an angle between about 60 to 120 degrees to each other. A smaller angle would tend to wedge the brush halves in the holder, while a larger angle would not spread them apart effectively. An angle of 90 is ideal.

The wedge may be made of various materials, but preferably from an elastomeric material such as rubber or the like in order to provide additional damping of brush vibrations and to better accommodate itself to-slight variations in the thickness or length of the brush halves. The wedge cannot be fastened to either brush section, because that would prevent it from sliding against both sections, which is necessary in order to insure uniform pressure on both brush sections.

It will be seen that with this invention both half-sections of the brush will always be held against the sides of the bush holder while the commutator is rotating, regardless of its direction of rotation. As a result, vibration, chatter, chipping and breakage are greatly reduced or eliminated, the brush seat is not changed with the reversal of the commutator, the life of the brush and commutator are prolonged, and performance of the machine remains good. It also will be understood that conventional brush holders do not have to be altered to receive this brush.

When there is such a brush at the bottom of a commutator, considerable difliculty would be experienced in inspecting the brush or in replacing it if the wedge were free to fall away from the carbon sections when the retaining spring is removed from the brush. This invention insures that the wedge will remain in place.

To guarantee that the wedge will not become separated from the brush assembly and lost during shipping or handling of the assembly before insertion in the brush holder, one end of the wedge outside of the brush socket may be provided with a longitudinally extending ear 17 that has a hole 18 through it, through which loosely extends one of the shunt wires 9 that are connected to the carbon sections at the opposite ends of the socket. Therefore, even though the wedge may come out of the socket while the brush is not in use, it will remain with the assembly because it cannot leave one of the shunt wires.

A wedge 19 without such an ear is shown in FIG. 6.

I claim:

1. An electric brush assembly adapted to be slidably mounted in a brush holder, comprising a pair of thin carbon brush half-sections disposed side by side and having inner and outer side faces and inner and outer ends, the outer end portions of said sections being provided with a pair of opposed notches each having end walls diverging toward the inner end of the brush and spaced apart by a side wall inclined across the brush section from near its outer face toward its inner face and end, said notches to gether forming a socket having side walls converging toward the inner end of the brush and having end walls diverging toward said inner end, and a wedge in said socket having side walls slidingly engaging said socket side walls, whereby when the wedge is pushed toward the inner end of the brush it will force said sections apart, and said wedge having inwardly diverging end walls adjacent said socket end walls to keep the wedge from accidentally slipping out of the socket.

2. An electric brush assembly according to claim 1, in which the wedge is made of elastorneric material.

3. An electric brush assembly adapted to be slidably mounted in a brush holder, comprising a pair of thin carbon brush half-sections disposed side by side and having inner and outer side faces and inner and outer ends, shunt wires projecting from the outer ends of said sections, the outer end portions of said sections being provided with a pair of opposed notches each having end walls diverging toward the inner end of the brush and spaced apart by a side wall inclined across the brush section from near its outer face toward its inner face and end, said notches together forming a socket having side walls converging toward the inner end of the brush and having end walls diverging toward said inner end, and a wedge in said socket having side walls slidingly engaging said socket side walls, whereby when the wedge is pushed toward the inner end of the brush it will force said sections apart, and said wedge having inwardly diverging end walls adjacent said socket end walls to keep the wedge from accidentally slipping out of the socket, and said wedge being provided at one end with an car outside of said socket, the ear being provided with a hole loosely receiving one of said shunt wires to attach the wedge to that wire.

References Cited in the file of this patent UNITED STATES PATENTS 2,488,788 Weilbaecher Nov. 22, 1949 2,796,544 Silverman June 18, 1957 FOREIGN PATENTS 971,394 Germany Jan. 22, 1959 1,020,066 France Nov. 12, 1952

Claims

1. AN ELECTRIC BRUSH ASSEMBLY ADAPTED TO BE SLIDABLY MOUNTED IN A BRUSH HOLDER, COMPRISING A PAIR OF THIN CARBON BRUSH HALF-SECTIONS DISPOSED SIDE BY SIDE AND HAVING INNER AND OUTER SIDE FACES AND INNER AND OUTER ENDS, THE OUTER END PORTIONS OF SAID SECTIONS BEING PROVIDED WITH A PAIR OF OPPOSED NOTCHES EACH HAVING END WALLS DIVERGING TOWARD THE INNER END OF THE BRUSH AND SPACED APART BY A SIDE WALL INCLINED ACROSS THE BRUSH SECTION FROM NEAR ITS OUTER FACE TOWARD ITS INNER FACE AND END, SAID NOTCHES TOGETHER FORMING A SOCKET HAVING SIDE WALLS CONVERGING TOWARD THE INNER END OF THE BRUSH AND HAVING END WALLS DIVERGING TOWARD SAID INNER END, AND A WEDGE IN SAID SOCKET HAVING SIDE WALLS SLIDINGLY ENGAGING SAID SOCKET SIDE WALLS, WHEREBY WHEN THE WEDGE IS PUSHED TOWARD THE INNER END OF THE BRUSH IT WILL FORCE SAID SECTIONS APART, AND SAID WEDGE HAVING INWARDLY DIVERGING END WALLS ADJACENT SAID SOCKET END WALLS TO KEEP THE WEDGE FROM ACCIDENTALLY SLIPPING OUT OF THE SOCKET.