An assembled commutator for use in a fractional horsepower electric motor comprises a base moulded from thermoplastics and a commutator segment mounted on the base. The segment has a tang for electrical connection to an armature coil, the tang comprising a first radially extending portion and second portion connected to the first portion along a fold line. Wire of the coil is passed may be welded or forged to the tang by pressing together the first and second portions, and heating them electrically.

INTRODUCTION 
The present invention relates to assembled commutators, and in particular 
to an improved commutator and method for the attachment of an armature 
coil winding to a commutator. The invention is particularly applicable to 
fractional horsepower PMDC motors. 
BACKGROUND 
It is desirable to manufacture commutators by injection moulding a base 
from plastics material and assembling copper segments onto the base and 
securing them to the base by some means. This method of manufacturing 
allows the production of a very low cost commutator. 
In previous designs the tangs of the copper commutator segments have been 
designed so that wire is hooked into them and then a welding tool is 
brought down on the tangs from above causing heat and pressure to be 
distributed on the commutator body. 
A major disadvantage of such a commutator has been that the winding wire 
cannot be readily welded or hot staked to tangs of the commutator segment 
because the heat and pressure required to make a good joint has caused 
distortion of the low temperature-softening moulding material which makes 
up the base. 
As a result it has been preferable to use low temperature wire grades which 
can be readily soldered to the commutator tangs. This however places a 
limitation on the application of the commutator. It could not be easily 
used when high temperature winding wire is to be used. 
This invention aims to provide a commutator design which allows the use of 
a low cost assembled commutator with high temperature wire welded to the 
tangs without any danger of damage to the commutator base. 
SUMMARY OF THE INVENTION 
A first aspect of the invention provides an assembled commutator for an 
electric motor, comprising a base and a commutator segment mounted on the 
base, the commutator segment having a brush contacting portion for making 
electrical contact with a brush (not shown in the drawings) of a said 
electric motor, and a tang for electrical connection to a wire of an 
armature coil of a said electric motor, wherein the tang comprises a first 
portion extending away from the base and a second portion connected to 
said first portion about a fold line, whereby said first and second 
portions may be pressed together and heated independently of said base to 
forge or weld a wire therebetween. 
Preferably the first and second portions lie generally in planes extending 
in the axial direction of the commutator. 
Very preferably an edge of the tang portion extending from a brush 
contacting surface of the commutator segment to the fold line and facing 
in the direction of the brush contacting surface is sloped, so that the 
wire when drawn around the sloping edge will slide up into the fold. 
The tang may be arranged with the first portion extending radially out from 
the brush contacting surface to the fold line, and the second portion 
forming an acute angle with the first portion so that the two portions can 
be clamped together between an anvil and a welding probe or the like 
brought towards each other to clamp the first and second portions 
therebetween. 
Another aspect of the invention provides a method of manufacturing a rotor 
assembly in an electric motor, the rotor assembly comprising a shaft and 
an armature and an assembled commutator mounted on a shaft for rotation 
therewith, the armature having a coil of electrically conducting wire 
thereon, the commutator comprising a base and a commutator segment mounted 
on the base for contact with a brush of the motor, the commutator segment 
having a brush contacting portion and a tang extending away from the base 
for electrical connection with wire of the coil, wherein a fold is 
provided in the tang to form first and second tang portions at an acute 
angle to each other, the wire is passed into the fold of the tang, and the 
first and second tang portions are urged together and heated to forge or 
weld the wire to the tang. 
The armature coil may be wound with the rotor assembly held in a jig, the 
wire being looped past the tang to engage it in the fold, the rotor may 
then be rotated about its axis so that the first portion of the tang rests 
on an anvil and a probe is then brought down to urge the second portion 
against the first portion to forge or weld the wire to the tang. 
In another embodiment the anvil and probe are both moved inwards, from 
opposite sides of the tang. 
Other preferred features and advantages will be apparent from the following 
description and the accompanying claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 an assembled commutator 1 for a fractional horsepower PMDC motor 
comprises a base 2 moulded from thermoplastics material and having a 
through hole 3 for mounting the base 2 on a motor shaft. Three copper 
commutator segments 4 are mounted on the base 2. 
A segment 4 is illustrated in FIG. 2. The segment comprises a brush 
contacting portion 5 which fits snugly against the surface of a 
cylindrical support portion 9 of base 2, and two rearwardly projecting 
tabs 6 which are received in a blind circumferential recess 7 formed at 
the junction between a collar 8 and cylindrical support portion 9 of the 
base 2 (FIG. 6). 
A tang 10 is formed between the tabs 6, and is for connection of a wire of 
an armature to the segment 4. Tang 10 is integral with the brush 
contacting portion 5 and is formed on a rearwardly extending arm 11. An 
upwardly extending first tang portion 12 projects radially of the 
assembled commutator 1 (FIG. 1), a second tang portion 18 is formed at an 
acute angle to the first portion 12 at a fold 16 and a flange 13 is formed 
on a sloping edge 14 of the first tang portion 12 facing in the direction 
of the brush contacting portion 5. 
A slot 15 is formed in the collar 8 down to the level of the cylindrical 
support portion 9 of the base 2. At the base of the slot 15 the recess 7 
is extended rearwardly to the back of the collar 8 to accommodate the arm 
11. 
The commutator segments 4 are assembled on the base 2 by sliding them 
axially along the supporting portion to engage the first tang portion 12 
in the slot 15 and the tabs 6 and arm 11 in the circumferential recess 7. 
A washer 30 (FIG. 3) is then slid over brush contacting portions 5 to hold 
the segments 4 in position. Flange 13 rests against a chamfer 17 formed on 
the collar 8. 
The commutator segment 5 is shaped so that it can be stamped and formed 
from a flat sheet of copper as illustrated in FIG. 7. The tang 10 is 
formed by bending the blank 19, at the dotted lines shown in FIG. 7. The 
brush contacting area 5 is then formed by curving the blank prior to 
mounting the formed segment 4 on the commutator base 2. 
FIG. 3 shows a schematic side view shown partially in cross-section of a 
rotor assembly comprising a motor shaft 20 carrying the assembled 
commutator 1 and an armature 21. 
The base 2 of the commutator is mounted fast on the shaft 20. The armature 
is mounted fast on the shaft 20 and comprises a number of mushroom-shaped 
cross-section arms 22, which extend radially of the shaft and each have a 
coil 23 wound about their stem 24. 
A wire 26 of the coil 23 is looped 27 around the tang 10 of a respective 
commutator segment, passing between the lower edge 37 of the tang portion 
18 and the collar 8, before passing on to an adjacent arm of the armature 
to form a coil therearound. At the end of a winding operation the wire may 
be looped twice around a tang 10 to tie off the end of the wire. As the 
wire is wound it is held under tension, this will cause the wire to slide 
up the sloping flange 13 of the tang 10 to rest in the inside of the fold 
16. 
Flange 13 provides a wide bearing surface for the wire, to prevent it being 
severed on the otherwise sharp edge of tang portion 12. 
After the winding operation the tang portions 12, 18 are urged together 
under pressure and electrically heated to grip the wire loop 27 and forge 
or weld the wire to the tang. 
FIG. 5a shows schematically a first way of clamping the tang portions to 
weld the wire thereto. The rotor assembly is mounted in a jig, it may be 
the original winding jig, and twisted to lay the first tang portion 12 on 
anvil 28. A probe 29 is then brought down on to the tang portion 18 to 
press it against portion 12, clamping the wire 26 therebetween. Current 
may be passed between the probe 29 and anvil 28 to heat the tang and weld 
the wire thereto. It can be seen that no heat or pressure is applied 
directly to the commutator base 2. 
In another method, FIG. 5b, the anvil 28 and probe 29' are brought together 
at the sides of the tang 10 to clamp the tang before electrically heating 
it to weld the wire 26 thereto. 
The rotor assembly described and its method of manufacture are generally 
well known in the art and embodied, for example, in the applicants small 
electric motor marketed under the catalogue number HC213. The modification 
provided by the invention resides in the construction of the tang 12 in an 
assembled commutator and the method of welding the wire thereto to avoid 
pressure on the commutator base. 
The rotor assembly as illustrated in FIG. 3 may be incorporated in an 
electric motor, such as a fractional horsepower permanent magnet direct 
current motor using a brush gear and a stator and bearing assembly. 
Applicants' motor number is shown in outline in FIG. 8 which shows an 
outer steel casing 31 having a closed end 32 supporting a bearing assembly 
33 for shaft 20, and an open end which is closed by a plastics cap 35 
which supports brush gear for supplying current to the coils of the 
armature 21 via the commutator 1, and a second bearing for shaft 20. 
Apertures 36 are formed in the casing for cooling as is generally known in 
the art. 
Various modifications may be made and it is desired to include all such 
modifications as fall within the scope of the accompanying claims.