GB2201555A

GB2201555A - Circumferentially adjustable brush gear

Info

Publication number: GB2201555A
Application number: GB08703648A
Authority: GB
Inventors: Roger Frederick Baines
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1987-02-17
Filing date: 1987-02-17
Publication date: 1988-09-01
Also published as: GB8703648D0

Abstract

The casing (10) of a p.m.d.c. motor has an elongate arcuate recess (21) and the end cap (11) has a projection (22) which fits in the recess (21) and which is movable therein during assembly of the motor to adjust the angular position of the end cap relative to the casing and hence the commutating position of the motor. Parts (23) of the casing are then peened over to engage in respective recesses in the casing to fix the end cap in a selected angular position relative to the casing. In an alternative embodiment, the elongate arcuate recess is in the end cap and the projection is on the motor casing. <IMAGE>

Description

Electric Motor This invention relates to a direct current electric motor and more particularly to a fractional horsepower permanent magnet direct current electric motor.

It is known from- GB Patent Specification 1491700 to provide a direct current electric motor with means by which the commutating position of the motor can be adjusted; for a uni-directional motor the commutating position can be advanced from the mechanically neutral point according to the intended direction of rotation of the motor to reduce sparking while running; for a bi-directional motor the commutating position can be set at the mechanically neutral point. This prior art motor has three notches in the casing, and a single projection on the end cap selectively engageable in the three notches.

However it is common knowledge that motors at different load points- require different angles of orientation to optimise their performance at those load points. The prior art motor described above has only three fixed angles of orientation and therefore the performance of the motor is not necessarily optimiz-ed at a particular load point selected by a customer.

The present invention seeks to overcome the advantages of the motor described above and to that end provides a . direct current electric motor comprising a can-like motor casing, permanent magnet means supported within the casing in a fixed angular position relative to the casing, an armature having a commutator mounted for rotation within the casing, an end cap closing the open end of the motor casing and supporting motor brush gear, one of the casing and the end cap having an elongate arcuate recess and the other of the casing and end cap having a projection which fits in the arcuate recess and which was movable in the recess during assembly of the motor to adjust the angular position of the end cap relative to the casing and hence the angular position of the brush gear relative to the permanent magnet means, and means fixing the end cap to the casing in a selected angular position relative to one another.

Preferred and/or optional features of the invention are set forth in claims 2 to 5.

With an arrangement according to the invention the relative orientation of the end cap and casing can be set to optimize the performance of the motor to a load point selected by a customer.

The invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure -1 is an exploded perspective view of one embodiment of a motor according to the invention, Figure 2 is a view partly in section showing a detail of the motor in Figure 1, and Figure 3 is an exploded view of another embodiment of a motor according to the invention, on a reduced scale.

Referring firstly to Figures 1 and 2, the electric motor shown therein is a fractional horsepower permanent magnet direct current electric motor and comprises a cylindrical steel can-like casing 10 closed at one end and a plastics end cap 11 press-fitted in the other end of the casing. Two stator magnets 12 and 13 are fixed within the casing 10 in conventional manner against angular movement relative to the casing by a U-shaped spring (not shown) between adjacent axial edges of the magnets urging the other axial edges of the magnets into engagement with ears pressed out of the casing.

An armature 14 provided with a commutator 15 is supported for rotation within the casing and between the stator magnets 12 and 13 by bearings 16 and 17 mounted, respectively, in the end cap 11 and in the closed end of the casing.

The end cap 11 supports two brush leaves 18 to which brushes proper 19 are secured. The brush leaves 18 have integral terminals 20, which extend through apertures in the end cap.

An elongate arcuate recess 21 is provided in the open end of the casing 10 and a projection 22 is provided on the end cap 11. The projection 22 fits in the arcuate recess 21 and is movable therein during assembly of the motor to adjust the angular position of the end cap 11 relative to the casing 10 and hence the angular position of the brushes 19 relative to the permanent magnets 12 and 13 to, where possible, set the commutating position to optimize the performance of the motor according to its intended direction of rotation and a particular load point selected by a customer. Obviously if the motor is required for operation in both directions this will not be possible and the commutating position will be set at the magnetically neutral point.

The end cap 11 is then fixed to the casing 10 in a selected angular position by peening over or otherwise deforming one or more parts 23 (two are shown in Figure 1) of the casing to engage in a respective recess or recesses 24 (see Figure 2) in the end cap.

A scale 25 may be marked on the outside of the casing along the length of the recess 21 to facilitate assembly of the motor and the end cap in a selected angular position relative to one another.

Referring now to Figure 3, the embodiment shown therein differs from that shown in Figures 1 and 2 only in that the elongate arcuate recess 21' is provided in the end cap 11 and the projection is in the form of a tongue 22' provided at the open end of the casing 10.

The embodiments described above are 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. For example, the two magnets 18 can be replaced by a single ring magnet secured in the casing in an appropriate manner against angular movement relative to the casing.

Claims

1. A direct current electric motor comprising a can-like motor casing, permanent magnet means supported within the casing in a fixed angular position relative to the casing, an armature having a commutator mounted for rotation within the casing, an end cap closing the open end of the motor casing and supporting motor brush gear, one of the casing and the end cap having an elongate arcuate recess and the other of the casing and end cap having a projection which fits in the arcuate recess and which was movable in the recess during assembly of the motor to adjust the angular position of the end cap relative to the casing and hence the angular position of the brush gear relative to the permanent magnet means, and means fixing the end cap to the casing in a selected angular position relative to one another.

2. A direct current electric motor as claimed in claim 1, wherein said means comprises one or more parts of the motor casing deformed to engage in a respective -recess or recesses in the end cap.

3. A direct current electric motor as claimed in claim 1 or claim 2, wherein the elongate arcuate recess is provided in said open end of the motor casing and the projection is provided on the end cap.

4. A direct current electric motor as claimed in claim 1 or claim 2, wherein the elongate arcuate recess is provided in the end cap and the projection is in the form of a tongue at the open end of the casing.

5. A direct current electric motor as claimed in anyone of the preceding claims, wherein a scale is provided along the recess to facilitate assembly of the motor and end cap in a selected angular position relative to one another.

6. A direct current electric motor substantially as hereinbefore described with reference to the accompanying drawings.