GB2149225A - Electric motor - Google Patents

Abstract

An electric motor is provided with brush retaining means which is arranged to be assembled and secured simply and preferably without the need for screws or adhesive. The retaining means has a channel-section retaining member 15 for a brush. The retaining member 15 is located in a seating 16 by cooperating slots 20 and lugs 28 and by a projecting portion 22 which engages with the seating. The seating includes a channel 26, inverted relative to the channel member 15, and having slots 27 in its base for receiving the ends of the limbs of the member 15. The brush 12 is located in an opening defined between the seating 16 and the member 15. <IMAGE>

Description

SPECIFICATION Electric motor This invention relates to electric motors and in particular to retaining means for the brushes of electric motors.

The brushes of electric motors of the smaller kind are conventionally located by brass securing members which are held in place by various means such as screws, adhesive or by heating and deforming the seating for the securing members. It is desirable that the securing members be assembled and retained by improved arrangements which are simple and effective.

According to the invention an electric motor includes brush retaining means comprising a channel-section metal retaining member and a seating for the retaining member, the retaining member having a slot at the free end of each limb of the channel section, the slot cooperating with a lug defined by the seating to prevent relative movement between the retaining member and the seating in a first direction longitudinally of the channel section, the retaining member also having on the outer sides of said limbs outwardly-projecting portions which engage with the seating to prevent movement of the retaining member relative to the seating in a direction transverse to said first direction.

Preferably the seating includes a base including slots for receiving the free ends of the limbs of the retaining member and the slots in the base each contain at least one of said lugs. The seating may generally be of channel-section with the slots in the base of the channel and the seating channel being inverted relative to the channel section of the retaining member. In this way the internal sides of the seating channel are engaged by the projections on the limbs of the channelsection retaining member.

The outwardly-projecting portions of the retaining member are conveniently formed by deforming the material of the limbs out of the plane of the limbs and the projecting portions may be inclined in a manner to aid location of the retaining member in the seating and to prevent release thereof.

it will be understood that the retaining member and the seating together define a generally rectangular opening for receiving a brush for the motor as a sliding fit in the opening.

Further features of the invention will appear from the following description of an embodiment of the invention given by way of example only and with reference to the drawings, in which: Figure 1 is a plan view of part of an electric motor having assembled retaining members and seatings and showing brushes associated therewith, Figure 2, 3 and 4 are respectively a side elevation, an end elevation and a plan view of a retaining member, and Figure 5 is a perspective view of a seating for the retaining member of Figs. 1-3.

Referring to the drawings and firstly to Fig.

1 an electric motor, only part of which is shown, includes an end cap 10 which surrounds a commutator 11 of an electric motor.

The end cap 10 houses brushes 1 2 for engaging the outer surface of the commutator 11 in spring-loaded engagement therewith, and the end cap is attached at one end of a cylindrical motor housing (not shown).

A conductor 1 3 is attached at the outer end of each brush and a spring 14 mounted on a post 1 5 urges each brush radially inwardly towards the commutator 11.

The brushes 1 2 are each of square crosssection and are slidably received in a retaining assembly defined by a brass retaining member 1 5 and a seating 1 6 for the member 1 5.

As can be seen in Figs. 2, 3 and 4 the retaining member 1 5 is of channel-section having an elongate slot 1 7 in the base 1 8 of the channel-section through which the conductor 1 3 and spring 1 4 pass. Each limb 1 9 of the member 1 5 is formed with a rectangular slot 20 at the free end of the limb 1 9 and each limb 1 9 also has an outwardly-directed projection 22 located adjacent the slot 20.

The projection 22 is formed by deformation of the material of the limb 1 9 out of the plane of the limb and is of a shape such that the projection is inclined outwardly from the free end of the limb to provide an upwardly directed step 23.

The slot 20 and projection 22 of the limb 1 9 is located towards one end of the member 1 5 and the slot and projection of the other limb 1 9 is located towards the other end of the member 1 5.

The seatings 1 6 for the retaining members 15, best seen in Fig. 5, are each defined by the end cap 10 which is conveniently a plastics moulding. The seatings are each formed by spaced ears 25 defining between them a channel-section 26 in the base of which is formed longitudinal slots 27 for receiving the free ends of the limbs 1 9 of the retaining member. At positions along the slots 27 corresponding to the positions of the slots 20 in the retaining member 1 5 are formed lugs 28 which are arranged to engage in the slots 20 and retain the member 1 5 against movement along the channel-section 26 when assembled.

The internal side surfaces of the ears 25 above the lugs 28 are profiled at 29 as a groove to enable the projections 22 to pass between the ears 25 upon insertion of the retaining members 1 5. After insertion the projections 22, in particular the steps 23, engage the internal side surfaces so as to resist movement of the retaining member 1 5 outwardly of the seating 1 6, i.e. in a direction at right angles to the longitudinal direction of the channel section 26.

It will be seen that the retaining members 1 5 are firmly retained in the seatings 1 6 after insertion without the need for screws, adhesive or other fixing elements.

Location of the retaining members 1 5 in the seatings 1 6 is most easily achieved using a tool (not shown) having a square-section member over which the retaining member is placed and which retains the limbs 1 9 of the member 1 5 at their desired spacing during assembly. The tool also has a portion which engages the upper side of the base 1 8 of the channel of the member 1 5 to urge the member into the seating 1 6.

After insertion the square-section portion of the tool is withdrawn in the longitudinal direction.

After insertion of the retaining member 1 5, as described, the member is secured in the seating and the brushes may be assembled into the rectangular section passage defined by the retaining member 1 5 and the base of the seating 1 6.

Claims (7)

1. An electric motor including brush retaining means comprising a channel-section retaining member and a seating for the retaining member, the retaining member having an opening at the free end of each limb of the channel section, the opening cooperating with a lug defined by the seating to prevent relative movement between the retaining member and the seating in a first direction longitudinally of the channel section, the retaining member also having on the outer sides of said limbs outwardly projecting portions which engage with the seating to prevent movement of the retaining member relative to the seating in a direction transverse to said first direction.

2. A motor according to claim 1 wherein the seating includes a base having slots for receiving the free ends of the limbs of the retaining member and the slots in the base each contain at least one of said lugs.

3. A motor according to claim 2 wherein the seating is generally of channel-section with the slots in the base of the channel, and the seating channel being inverted relative to the channel section of the retaining member.

4. A motor according to any one of the preceding claims wherein the outwardly-projecting portions of the retaining member are formed by deforming the material of the limbs out of the plane of the limbs.

5. A motor according to claim 4 wherein the outwardly projecting portions are inclined such as to aid location of the retaining member in the seating and to prevent release thereof.

6. A motor according to any one of the preceding claims wherein the retaining member and the seating together define a generally rectangular opening for receiving a brush as a sliding fit in the opening.

7. An electric motor having brush retaining means substantially as described with reference to the drawings.