GB2214358A

GB2214358A - A brush leaf assembly for electric motor

Info

Publication number: GB2214358A
Application number: GB8800523A
Authority: GB
Inventors: Roger Frederick Baines
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1988-01-11
Filing date: 1988-01-11
Publication date: 1989-08-31
Also published as: GB8800523D0

Abstract

The brush leaf assembly comprises a terminal part (11) and a more resilient brush supporting part (12) having a brush (13) at one end. The two parts (11,12) have overlying portions and the brush leaf assembly has a bend at the overlying portions to form an acute angle of about 70 degrees between the terminal part (11) and the brush supporting part (12). The portion of the brush supporting part (12) which overlies the terminal part (11) is on the inside of the bend and is secured to the terminal part (11) on the side of the bend remote from the brush (13) such as by upset rivets (20). A mechanical link is provided at the bend between the terminal part (11) and the brush supporting part (12) such as by forcing material (25) from one of the parts into the other part using a punch and die to prevent separation of the parts (11 and 12) at the bend. <IMAGE>

Description

A brush leaf assembly This invention relates to a brush leaf assembly for use in electric motors, particularly permanent magnet direct current (p.m.d.c.) micromotors.

According to the invention there is provided a brush leaf assembly comprising a terminal part and a more resilient brush supporting part having a brush-receiving portion at one end, the two parts having overlying portions and the brush leaf assembly having a bend at the overlying portions to form an acute angle between the terminal part and the brush supporting part, the portion of the brush supporting part which overlies the terminal part being on the inside of the bend and being secured to the terminal part on the side of the bend remote from said one end of the brush supporting part, and there being a mechanical link between the terminal part and the brush supporting part at the bend.

In use, the brush leaf assembly is mounted on a motor frame and supports a brush which bears against a commutator of the motor to urge the brush supporting part against the terminal part. Therefore, the free edge of the terminal part defines a fixed fulcrum to the brush supporting part. By this arrangement, a brush leaf assembly is provided which is able to exert a predictable brush force against the commutator during the life of the motor and the brush. The mechanical link prevents separation of the two parts at the bend during a bending operation which separation would allow the brush supporting part to move in use relative to the terminal part and generally tangentially to the commutator.

Preferably, material of one of the parts has been forced into the other part to create said mechanical link.

Conveniently, the terminal part and brush leaf supporting part are secured together by one or more upset rivets.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of a brush leaf assembly according to the invention, with a brush supported thereby, Figure 2 is a sectional view taken along the longitudinal axis of the brush leaf assembly of Figure 1, Figure 3 is a view looking into an end cap of a p.m.d.c. micromotor, and Figure 4 is an enlarged view of the part encircled in Figure 2.

Referring firstly to Figures 1 and 2 of the drawings, the brush leaf assembly 10 shown therein comprises a terminal part 11, a brush supporting part 12 and a brush 13.

The terminal part 11 is of, for example, brass and comprises a rectangular portion 14, a terminal portion 15, two finger portions 16 on opposite sides of the terminal portion 15, and a bent up portion 17, which defines an acute angle of about 70 degrees with the rectangular portion 14.

The brush supporting part 12 is more resilient than the terminal part 11 and is, for example, of beryllium copper. The part 12 is in the form of an elongate leaf which at one end has an opening receiving a root portion of the brush 13, gripping portions 18 which grip the brush root and hold the brush in the opening, and side walls 19 and which at its other end overlies the bent up portion 17 of the terminal part 11 and is secured to the rectangular portion 14 of the terminal part 11 by at least one but preferably and as shown three upset rivets 20.

The aforesaid brush leaf assembly is made by securing the two parts 11 and 12 together and then forming the bend in the overlying portions of the parts 11 and 12. As the bend is formed the parts 11 and 12 may separate at the bend and this would allow the part 12 to move in use relative to the part 11 in the general direction of the longitudinal extent of the part 12.

This is undesirable and therefore a mechanical link is provided between the parts 11 and 12 at the bend, such as by forcing material 25 from one of the parts 11, 12, preferably part 12, into the other part using a punch and die. This can be done during the bending operation or before bending although in the latter case it may be necessary to hold the parts together during the bending operation to prevent failure of the link.

Two such brush leaf assemblies 10 are supported by an end cap 21 of a motor, typically a p.m.d.c.

micromotor. As shown in Figure 3 the rectangular portion 14 of each terminal part 11 is located in a respective groove 22 in the end cap 21 with the terminal portion 15 extending through a hole (not shown) in the end cap 21 for connection to a supply lead. The finger portions 16 are also located in said hole and after location therein are splayed outwards away from the terminal portion 15 using an appropriate tool to hold the brush leaf assembly 10 captive relative to the end cap 21. Figure 3 also shows a commutator 23 on a motor shaft 24 in order to illustrate the classical cantilever curving of the brush supporting part 12 when the brush 13 is unworn.

The above embodiment is given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention defined by the appended claims.

Claims

1. A brush leaf assembly comprising a terminal part and a more resilient brush supporting part having a brush-receiving portion at one end, the two parts having overlying portions and the brush leaf assembly having a bend at the overlying portions to form an acute angle between the terminal part and the brush supporting part, the portion of the brush supporting part which overlies the terminal part being on the inside of the bend and being secured to the terminal part on the side of the bend remote from said one end of the brush supporting part, and there being a mechanical link between the terminal part and the brush supporting part at the bend.

2. A brush leaf assembly as claimed in claim 1, wherein material of one of the parts has been forced into the other part to create said mechanical link.

3. A brush leaf assembly as claimed in claim 1 or claim 2, wherein the terminal part and brush leaf supporting part are secured together by one or more upset rivets.

4. A brush leaf assembly substantially as hereinbefore described with reference to the accompanying drawings.

5. An electric motor having two brush leaf assemblies according to any one of the preceding claims, each brush leaf assembly supporting a brush which bears against a commutator of the motor to urge the brush supporting part against the terminal part.

6. The motor of claim 5 in the form of a p.m.d.c.

micromotor.