Small motor stator with improved magnet mounting

A stator for a small electric motor includes two permanent magnets mounted within a flux circulation frame by a single spring formed of a shaped spring steel rod compressed between the two permanent magnets and urging the two permanent magnets apart and toward respective portions of the frame.

BACKGROUND OF THE INVENTION 
The present invention relates to a stator for small electric motors and of 
the type including permanent magnets mounted within a flux circulation 
frame. 
To avoid the use of glue for mounting permanent magnets within the frame, 
and thereby the health problems caused by the constituent elements of the 
glue, it is common practice in the mass production of such small stators 
to mount the magnet by mechanical means such as screws, rivets or 
sheathings formed of synthetic material. However, all such mechanical 
mounting arrangements result in the stator being very expensive, without 
ensuring that the magnets are properly fastened at all times. It also is 
common practice to lock the mountings by a plurality of springs arranged 
between the magnets. This arrangement however has the disadvantage that 
the plurality of springs are difficult to install and thus result in a 
substantial expense. 
SUMMARY OF THE INVENTION 
With the above discussion in mind, it is the object of the present 
invention to provide an improved resilient mounting for two permanent 
magnets within a flux circulation frame, whereby it is possible to 
overcome the above and other prior art disadvantages. 
This object is achieved in accordance with the present invention by the 
provision of a stator for small electric motors and being of the type 
including two permanent magnets, a flux circulation frame, and resilient 
means for mounting the two permanent magnets within the frame, wherein the 
resilient means comprises a single spring formed of a shaped spring steel 
wire or rod compressed between the two permanent magnets and urging the 
two permanent magnets apart and toward respective portions of the flux 
circulation frame, thereby positively retaining the two magnets in desired 
positions within the frame.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in the drawing, the stator of the present invention is of the type 
which is usable for small electric motors. The stator includes a flux 
circulation frame 1 which is generally of a cylindrical shape but with two 
spaced apart parallel flattened portions 1a, the provision of which 
provides the advantage of reducing the space requirred for the stator. 
Such flattened portions 1a provide the additional advantage of 
contributing to the positioning of two permanent magnets 2, 3 each of 
which have a first longitudinal side edge 2a, 3i a positioned adjacent one 
of the two spaced apart portions 1a, 1a of the flux circulation frame 1 
and a second longitudinal side edge 2b, 3b positioned adjacent the other 
one of the two spaced apart portions 1a, 1a of the flux circulation frame 
and which are positioned against and urged toward spaced opposite curved 
portions 1b of frame 1. The longitudinal positioning of members 2, 3 with 
respect to frame 1 may be achieved in a conventional manner such as by 
bearing stops (not shown) and inwardly bent lugs 1c of the frame. 
In accordance with the present invention, the magnets 2, 3 are mounted and 
retained within frame 1 by a novel spring 4 formed of a shaped spring 
steel wire or rod compressed between permanent magnets 2, 3 and urging 
such magnets apart and toward respective portions 1b of frame 1. The 
spring 4 has a pair of portions 4a, 4b, one of the U-shaped, spaced-apart 
portions contacting the first longitudinal side edge 2a, 3a of each of the 
two permanent magnets 2, 3 and the other of the U-shaped, spaced apart 
portions contacting the second longitudinal side edge 2b, 3b of the two 
permanent magnets 2, 3. 
The spring 4 formed of a shaped spring steel wire or rod includes two 
parallel U-shaped, spaced apart portions 4a, 4b which are spaced apart by 
a distance at least equal to the width of the permanent magnets 2, 3 such 
that each of the portions contact both of the two permanent magnets for 
urging the magnets against the frame. Each U-shaped portion includes first 
and second substantially straight legs which are joined at first ends 
thereof (the left ends as shown in the drawing) by a bent or curved 
portion and diverge toward second ends thereof (the right ends as shown in 
the drawing). The lower second ends of first legs of both U-shaped 
portions 4a, 4b are connected together by a first outwardly bent portion 
4d which is cambered or inclined outwardly and are substantially 
perpendicular to the planes containing U-shaped portions 4a, 4b. Second 
outwardly bent portions 4c are cambered or inclined outwardly toward each 
other and are substantially perpendicular to the planes containing 
U-shaped portions 4a, 4b. second outwardly bent portions 4c extend toward 
each other, but are not joined and form free ends of the shaped spring 
steel wire or rod. Outwardly bent portions 4d, 4c are substantially in a 
plane perpendicular to the planes containing U-shaped portions 4a, 4b and 
are inclined arcuately away from the interiors of the two U-shaped 
portions 4a, 4b. 
The spring 4 is positioned within frame 1 with the substantially straight 
legs of each U-shaped portion 4a and 4b compressed toward each other 
between respective longitudinal sides of the two permanent magnets 2, 3. 
In such position, first outwardly bent portion 4d abuts a curved 
transverse end of permanent magnet 3, and the second outwardly bent 
portions 4c abut a curved transverse end of permanent magnet 2. The 
outwardly bent portions 4d, 4c have configurations substantially 
complementary to the internal configuration of the curved portions 1b of 
frame 1. 
The use of the spring 4 according to the present invention results in a 
saving of time during assembly of the stator. Thus, magnets 2, 3, may be 
positioned within frame 1 and adjacent respective portions 1b thereof, and 
further with each magnet bearing against an inwardly bent lug 1c of the 
frame. Outwardly bent portions 4d, 4c are pressed toward each other, 
thereby bringing the diverging legs of each of the U-shaped portions 4a, 
4b toward each other. The thus deformed spring then simply is inserted 
into the frame between the two magnets until the outwardly bent portions 
4d, 4c abut against the curved transverse free ends of respective magnets 
3, 2. The pressure urging the outwardly bent portions 4d, 4c toward each 
other then is relieved, at which time the spring action of the spring will 
cause the legs of the two U-shaped members 4a, 4b to diverge from each 
other and into abutment with respective longitudinal side edges of the 
magnets 2, 3, thereby urging the magnets against internal surfaces of the 
frame 1. By this arrangement, the magnets are firmly retained in position 
within the frame without the need for use of glue or the expensive and 
complicated mechanical structures of the prior art. 
Alternatively, the stator may be assembled by positioning magnets 2, 3 
against respective legs of the two U-shaped portions 4a, 4b and with the 
free end surfaces of the magnets abutting respective outwardly bent 
portions 4d, 4c. This assembly then simply may be inserted longitudinally 
into the frame 1, whereby such insertion will cause the magnets to 
compress the legs of the two U-shaped portions toward each other. 
It is to be understood that except as described above regarding the novel 
features of the present invention the various elements and materials 
thereof of the stator are intended to be conventional, as would be 
understood by those skilled in the art. Furthermore, it is to be 
understood that the diameter of the spring steel wire or rod forming the 
spring 4 will be chosen, as would be understood by those skilled in the 
art, according to the amount of vibration to which the stator will be 
subjected. 
Although the present invention has been described and illustrated with 
respect to a preferred embodiment thereof, various changes and 
modifications to the specifically described structure may be made without 
departing from the scope of the present invention.