GB2222728A

GB2222728A - Electric motor particularly for a sewing machine

Info

Publication number: GB2222728A
Application number: GB8818956A
Authority: GB
Inventors: Kam-Shing Mok
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1988-08-10
Filing date: 1988-08-10
Publication date: 1990-03-14
Also published as: CN2054586U; GB8818956D0

Abstract

A universal motor, particularly a sewing machine motor has two casing halves 1, 2 having tangs 23, 24 pressed from sidewalls 21, 22. The casing halves 1, 2 enclose a stator 14 and the tangs 23, 24 bear on the stator. Screws 45 pass through tangs 24 and stator 14 to screw into the tangs 23 and so clamp the three parts together. <IMAGE>

Description

ELECTRIC MOTOR PARTICULARLY FOR A SEWING MACHINE The present invention relates to an electric motor and in particular a universal motor, more particularly a sewing machine motor.

A common type of sewing machine motor which has been used for many years comprises two can-like casing halves which enclose a wound stator, and a rotor journalled in bearings in ends of the casing halves. The wound stator and a plate carrying brushgear are supported in the housing formed by the casing halves by two bolts which extend the length of the housing and carry spacers to position the stator- and brushgear in the housing. The overall design makes the motor difficult to assemble and is wasteful of space.

The present invention provides a universal motor comprising a housing having two can-like casing halves, each casing half having a closed end carrying a bearing for a shaft of the motor, a wound stator and brushgear supported in the housing, and a rotor comprising the motor shaft and a wound armature and commutator mounted fast on the shaft, the shaft being supported in the bearings, wherein the stator is supported in the housing by means of a plurality of tangs each extending inwardly from wall of a casing half.

Preferably the stator is sandwiched between a pair of tangs, one on each casing half, and the tangs are screwed together through an aperture in the stator to hold the casing halves together.

Preferably the tangs are pressed from the wall.

Preferably, the motor brushgear comprises a pair of brush cages which are carried on an end wall of a casing half, and the cages are held on the end wall by means of tangs pressed from the end wall.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a sewing machine motor according to the invention; Figure 2 shows a casing half of the motor of figure 1, partly cut away; and Figure 3 is a side view of the motor of Figure 1 assembled.

Figure 1 shows a universal motor which is particularly suitable for use in sewing machines, but has other applications. The motor comprises a housing made up of first and second casing halves 1, 2. Each casing half is deep drawn from steel sheet and given the configuration shown by a number of stamping and drawing operations as generally known in the art. The first casing half 1 carries brushgear 3. A bearing 4 is mounted on an end wall 5 of the first casing half. The bearing sits between a cup 6 formed in the end wall 5 and a plate 7 which is screwed or rivetted to the end wall. A second bearing, not shown, is mounted in an end wall 8 of the second casing half 2.

A rotor 9 comprises a shaft 10 which runs in the two bearings in the casing end walls 5, 8, a wound armature 11 and a commutator 12. A plastic fan 13 is also mounted on the shaft to generate a cooling air flow through the motor when it is running.

A wound stator 14 comprises a lamination stack 15 with two coils 16 which are supplied with power via supply leads, not shown, attached to terminals 17. The coils 16 are wound on a plastic frame work 18 having frame ends 31 which sit on the ends of the lamination stack 15 and support the terminals 17. Throught bores 30 are formed in the frame ends 31 and lamination stack 15 for receiving a mounting screw 45 vide hereinafter).

Each casing half 1, 2 comprises a pair of opposed flat side walls 19, 20 and opposed arcuate walls 21, 22.

Tangs 23, 24 are pressed from each arcuate wall 21, 22 to extend inside the motor generally parallel to the end walls 5, 8. Tangs 24 each have a plain aperture 25 therein and tangs 23 have a threaded aperture 26. The tangs 23, 24 are positioned to bear against the ends 31 of the plstic frame 18 when the casing halves 1, 2 are brought together.

Smaller tangs 29 are pressed from the side walls 21, 22 in the same plane as the larger tangs 23, 24. When pressing the larger tangs 23, 24 from a curved wall they may have a curved surface which is presented to the stator 14. The additional tangs 29 ensure that the stator sits stably on the tangs.

The brush gear 3 comprises two integrally formed plastics cages 32. Each cage 32 comprises a rectangular tube 33 housing a carbon brush 34. A coil spring 35 is mounted on a post 36 adjacent each tube 33. One arm 38a of the spring 35 is arranged to fit in a slot 36 in a wall 37 of the tube 33 to bear against the brush 34 to urge it against the commutator 12. The other arm 38b of the spring is arranged to bear on a terminal 39 on the stator. The cages 32 are each held on the end wall by a pair of fingers 40 which are pressed from the casing end wall and grip flanges 41 on each side of the base of the cages. The underside of each cage has a slot or recess which receives a projection 42 stamped in the casing end wall to align the cages.

To assemble the motor the cages are installed in the first casing part 1. The springs are placed on the posts 32 with the arms 38a, 38b hooked respectively behind an outer end 43 of the tube 33 and a small post 44 (see Figure 1).

The rotor 9 is installed in the second casing part 2. The fan 13 has two cutouts 48 which clear the tangs 24. The stator 14 is then fitted in the casing part 2 to sit on the tangs 24, 29. Fish paper may be hooked under the frame parts 31 to lay along the outside of the stator to ensure that it is electrically isolated from the motor housing. The second casing part 1 is then slid over the end of the stator 14 to abut the first casing part, the tangs 23, 29 bearing against the frame parts 31 of the stator.

The assembly is held together by two screws 45 which pass through apertures 25 in tangs 24, apertures 30 in the stator and are screwed into the apertures 26 in tangs 23, the screw heads 46 engaging the tangs 24. The screws are inserted through holes 47 in the end wall 8, past the cutouts 48 in the fan 13.

The stator 14 and casing parts 1, 2 are thus held securely together by the screws 45, shown in dotted outline in Figure 3.

Brushes 34 are then inserted in the tubes 33 and the spring arms 38a unhooked and released into the slots 36 to bear on the brushes. The spring arms 38b are unhooked and spring onto respective terminals 39 of the stator winding. Access to the brushgear is through apertures 47 in the casing sidewalls 21.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims

1. A universal motor comprising a housing having two can-like casing halves, each casing half having a closed end carrying a bearing for a shaft of the motor, a wound stator and brushgear supported in the housing and a rotor comprising the motor shaft and a wound armature and commutator mounted fast on the shaft, the shaft being supported in the bearings, wherein the stator is supported in the housing by means of a plurality of tangs each extending inwardly from a wall of a casing half.

2. A motor as claimed in claim 1 , wherein a tang is pressed from a casing wall.

3. A motor as claimed in claim 1 or 2, wherein a first said tang is provided on each casing half and the stator is sandwiched between the first tangs, a screw passing through the first tangs and stator to hold the casing halves and stator together.

4. A motor as claimed in claim 3, wherein the first tangs are pressed from an arcuate side wall of the casing halves.

5. A rotor as claimed in claim 4, wherein second tangs are pressed from the arcuate sidewalls on each side of the respective first tangs, to further support the stator.

6. A motor as claimed in any one of claims 1 to 5, wherein caged brushgear is provided and said cages are mounted directly on an end wall of a casing half.

7. A motor as claimed in claim 6, wherein the cages are secured to the end wall by tongues pressed from the end wall and arranged to grip cooperating formations on the cages.

8. A universal motor substantially as hereinbefore described with reference to the accompanying drawings.