GB1562986A

GB1562986A - Commutator brush assembly

Info

Publication number: GB1562986A
Application number: GB19073/78A
Authority: GB
Original assignee: Siemens Corp
Current assignee: Siemens Corp
Priority date: 1977-05-12
Filing date: 1978-05-11
Publication date: 1980-03-19
Also published as: FR2390837A1; SE7804648L; NL7802617A

Description

(54) COMMUTATOR BRUSH ASSEMBLY (71) We, SIEMENS ATKIENGESELLSCHAFT, a German company, of Berlin and Munich, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to performed, to be particularly described in and by the following statement: This invention relates to a commutator brush assembly for electrical machines, A brush holder is disclosed in German Offenlegungsschrift 17 63 883, wherein there is disposed in a rectangular guide socket of a retangular brush-guiding portion a brush which is adapted to be pressed against the commutator of the machine by means of a spiral brush spring. This brush holder consists of a guide portion which is adapted to be secured to the housing of an electric machine and of separate closure portion adapted to be mounted on the guide portion. Before the closure portion is mounted on the guide portion, the brush spring and the brush itself are introduced into the closure portion and held therein by appropriate detent portions. In the mounting of the closure portion on the guide portion, the detent portions are released, so that the brush is pressed against the commutator of the machine by the brush spring.

The separate closure portion can not only involve higher cost, but can be found to be disadvantageous in manufacture by automatic machines, because the guide portion must first be attached to the housing, and the terminating portion must thereafter be mounted on the guide portion.

The invention is concerned with providing a generally improved commutator brush assembly.

According to the present invention, there is provided a commutator brush assembly comprising: a housing; a commutator brush mounted in the housing for movement towards and away from a commutator-engaging position; resilient means biassing the brush towards said position; and a projection in the housing for frictionally engaging the commutator brush so as to impede but not prevent movement of the brush in the housing when the brush is away from said position, the force of the resilient biassing means alone being insufficient to overcome the frictional force between the projection and the brush.

The brush and the biassing means may be lodged in the housing before the assembly is fitted to a machine. The brush is pushed into the housing until it is jammed therein by the projection and hence held therein. In this way, a single complete assembly can be available for the further mounting of the brush assembly on to a motor housing, for example.

In an embodiment of the invention, a further simplification may be effected by virtue of the fact that the housing is formed as a single part from sheet-metal, and a guide socket for the brush has a slot along the length thereof. Owing to the throughgoing slot, the housing can have a generally U-shaped cross-section. The two arms of the U-shaped housing can be restrained from moving owing to their elasticity. This can have the advantage that, in the forming of the housing from a sheet-metal part, it is unnecessary to ensure very precise final dimensions, because the arms of the Ushaped housing can be accurately positioned by pushing the arms into, for example, retaining slots in a motor housing.

To assist in understanding the invention, an embodiment thereof will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates a complete commutator brush assembly; Figure 2 illustrates the assembly fitted to a motor housing; and Figure 3 is a plan view of the assembly illustrated in Figure 2.

The brush assembly illustrated in Figure 1 consists of a housing 1, in a guide socket 2 of which there are disposed a brush spring 3 and a brush 4. The guide socket 2 and the brush 4 are of corresponding oblong crosssection. An abutment 5 for the brush spring 3 is formed on the housing 1. In addition, a projection in the form of a clamping lug 6 is formed on one narrow side of the housing 1.

The lug 6 is for frictionaly engaging the brush 4 so as to impede but not prevent movement thereof. The distance a of the clamping lug 6 from that end of the housing 1 which is closer to the commutator is equal to or greater than the length of the brush 4.

In this way, it is ensured that when the brush 4 is clamped fast by the clamping lug 6 the latter does not project beyond that end of the housing 1 which is closer to the commutator, while on the other hand the brush 4 is no longer impeded by the clamping lug 6 after it has been released. Also, oppositely directed tongues 7 and 8 are pressed out of one narrow side of the housing 1.

The illustration of Figure 2 shows the brush assembly after it has been fitted in a motor housing 9. One wall of the motor housing is formed with an aperture 10 in which there engage the tongues 7 and 8. The brush assembly is thus secured in the motor housing 9 by the tongues 7 and 8. After the introduction of the brush assembly into the motor housing 9, the brush 4 is pushed against the commutator 11 of the electric machine. The frictional engagement existing between the clamping lug 6 and the brush 4 is thus overcome and the brush 4 is pressed against the commutator 11 by the brush spring 3, the force of which, in itself, is sufficient to overcome the frictional force between the brush 4 and the lug 6. Current is led into the brush 4 by way of a pigtail 12, which is connected to a voltage terminal 14 by way of a plug-in connector 13.

The U-shaped design of the housing 1 is apparent from the illustration of Figure 3.

The two arms la and 1b of the U are passed through retaining slots 15 in the machine housing 9 and accurately aligned. This is possible because the two arms la and 1b are movable owing to the throughgoing slot 16.

As is further apparent from the illustration of Figure 3. the abutment 5 is formed by bulges on the arms la and ib. The throughgoing slot 16 further renders possible unhindered movement of the pigtail 12.

After the introduction of the brush spring 3 and of the brush 4 into the housing 1 and after the brush 4 has been clamped fast on the clamping lug 6. a complete component part is ready for subsequent fitting. This complete brush holder is attached to the machine housing 9 by simply pushing in into the retaining slots 15 in the machine housing 9. In this action, the tongues 7 an 8 become engaged in the aperture 10. After the brush holder has been pushed in, the brush 4 is pushed towards the commutator 11 by means of a pin until the clamping engagement between the clamping lug 6 and the brush 4 has been broken. Thereafter, the brush 4 is pressed against the commutator 11 by the brush spring 3. If the brush holder is fitted by means of an automatic machine, the brush 4 can be released immediately after the pushing of the brush holder into the retaining slots 15, in the same operation.

WHAT WE CLAIM IS: 1. A commutator brush assembly comprising: a housing; a commutator brush mounted in the housing for movement towards and away from a commutator-engaging position; resilient means biassing the brush towards said position; and a projection in the housing for frictionally engaging the commutator brush so as to impede but not prevent movement of the brush in the housing when the brush is away from said position, the force of the resilient biassing means alone being insufficient to overcome the frictional force between the projection and the brush.

2. An assembly according to claim 1, wherein the projection can engage the brush only when the brush is completely within the housing.

3. As assembly according to claim 1 or 2, wherein the brush and biassing means are disposed in a common guide socket in the housing.

4. An assembly according to claim 1, 2 or 3, wherein biassing means comprises a coil spring constrained between the brush and an abutment on the housing.

5. An assembly according to any preceding claim, wherein the brush is of rectangular cross-section and is mounted in a guide socket of corresponding rectangular cross-section in the housing.

6. An assembly according to claim 5, wherein each said rectangular cross-section is oblong, and said projection projects from a narrow side of the guide socket.

7. As assembly according to any preced- ing claim, wherein the housing is formed as a single part from sheet metal, and the brush is mounted in a guide socket which has a slot along the length thereof.

8. As assembly according to claims 6 and 7, wherein the slot extends along a narrow side of the oblong cross-section guide socket for substantially the full length

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Figure
2 illustrates the assembly fitted to a motor housing; and Figure
3 is a plan view of the assembly illustrated in Figure 2.

The brush assembly illustrated in Figure 1 consists of a housing 1, in a guide socket 2 of which there are disposed a brush spring 3 and a brush
4. The guide socket 2 and the brush 4 are of corresponding oblong crosssection. An abutment
5 for the brush spring 3 is formed on the housing 1. In addition, a projection in the form of a clamping lug
6 is formed on one narrow side of the housing 1.

The lug 6 is for frictionaly engaging the brush 4 so as to impede but not prevent movement thereof. The distance a of the clamping lug 6 from that end of the housing 1 which is closer to the commutator is equal to or greater than the length of the brush 4.

In this way, it is ensured that when the brush 4 is clamped fast by the clamping lug 6 the latter does not project beyond that end of the housing 1 which is closer to the commutator, while on the other hand the brush 4 is no longer impeded by the clamping lug 6 after it has been released. Also, oppositely directed tongues
7 and
8 are pressed out of one narrow side of the housing 1.

The illustration of Figure 2 shows the brush assembly after it has been fitted in a motor housing 9. One wall of the motor housing is formed with an aperture 10 in which there engage the tongues 7 and 8. The brush assembly is thus secured in the motor housing 9 by the tongues 7 and 8. After the introduction of the brush assembly into the motor housing 9, the brush 4 is pushed against the commutator 11 of the electric machine. The frictional engagement existing between the clamping lug 6 and the brush 4 is thus overcome and the brush 4 is pressed against the commutator 11 by the brush spring 3, the force of which, in itself, is sufficient to overcome the frictional force between the brush 4 and the lug 6. Current is led into the brush 4 by way of a pigtail 12, which is connected to a voltage terminal 14 by way of a plug-in connector 13.

The U-shaped design of the housing 1 is apparent from the illustration of Figure 3.

The two arms la and 1b of the U are passed through retaining slots 15 in the machine housing 9 and accurately aligned. This is possible because the two arms la and 1b are movable owing to the throughgoing slot 16.

As is further apparent from the illustration of Figure 3. the abutment 5 is formed by bulges on the arms la and ib. The throughgoing slot 16 further renders possible unhindered movement of the pigtail 12.

After the introduction of the brush spring 3 and of the brush 4 into the housing 1 and after the brush 4 has been clamped fast on the clamping lug 6. a complete component part is ready for subsequent fitting. This complete brush holder is attached to the machine housing 9 by simply pushing in into the retaining slots 15 in the machine housing
9. A commutator brush assembly substantially as hereinbefore described with reference to the accompanying drawing.

9. In this action, the tongues 7 an 8 become engaged in the aperture
10. After the brush holder has been pushed in, the brush 4 is pushed towards the commutator 11 by means of a pin until the clamping engagement between the clamping lug 6 and the brush 4 has been broken. Thereafter, the brush 4 is pressed against the commutator 11 by the brush spring 3. If the brush holder is fitted by means of an automatic machine, the brush 4 can be released immediately after the pushing of the brush holder into the retaining slots 15, in the same operation.

WHAT WE CLAIM IS:

1. A commutator brush assembly comprising: a housing; a commutator brush mounted in the housing for movement towards and away from a commutator-engaging position; resilient means biassing the brush towards said position; and a projection in the housing for frictionally engaging the commutator brush so as to impede but not prevent movement of the brush in the housing when the brush is away from said position, the force of the resilient biassing means alone being insufficient to overcome the frictional force between the projection and the brush.

2. An assembly according to claim 1, wherein the projection can engage the brush only when the brush is completely within the housing.

3. As assembly according to claim 1 or 2, wherein the brush and biassing means are disposed in a common guide socket in the housing.

4. An assembly according to claim 1, 2 or 3, wherein biassing means comprises a coil spring constrained between the brush and an abutment on the housing.

5. An assembly according to any preceding claim, wherein the brush is of rectangular cross-section and is mounted in a guide socket of corresponding rectangular cross-section in the housing.

6. An assembly according to claim 5, wherein each said rectangular cross-section is oblong, and said projection projects from a narrow side of the guide socket.

7. As assembly according to any preced- ing claim, wherein the housing is formed as a single part from sheet metal, and the brush is mounted in a guide socket which has a slot along the length thereof.

8. As assembly according to claims 6 and 7, wherein the slot extends along a narrow side of the oblong cross-section guide socket for substantially the full length

of the housing.