Lasted edited by Andrew Munsey, updated on June 15, 2016 at 2:03 am.
'The following images were taken from Patent No. 6342746'
'The following text was taken from Patent No. 6342746'
Reference is made to FIGS. 11A-11F which depict
devices similar to that of FIGS. 5-6 except that a bypass,
formed of magnetic material, is provided in each case. In
device 220 of FIGS. 11A-11C a bypass 222 is provided from
pole piece 224 to pole piece 226 and is located between
permanent magnet 228 and control coils 230, 232, with
armature 234 located adjacent the ends of pole pieces 224,
226. In FIG. 11A with no coil energization, magnet flux
components 236 and 237 travel as shown. When coils 230
and 232 are energized in an aiding or adding manner as in
FIG. 11B, the result is permanent magnet magnetic flux
components 236 and 237 traveling as shown, and with the
added magnetic flux component 238 from coils 230 and 232
also traveling as shown. Thus, in device 220 energizing the
coils in an aiding manner results in an increased magnetic
coupling force on armature 234. In FIG. 11C coils 230,232
are energized in an opposing exceeding manner which
results in permanent magnetic flux components 236 and 237
traveling as shown and excess magnetic flux component 238
traveling as shown. Thus, in device 220 energizing the coils
in an opposing exceeding manner results in magnetic coupling
force on armature 234, albeit smaller than that in the
aiding exceeding case.
In device 240 of FIGS. 11D-11F a bypass 242 is provided
between pole piece 244 and pole piece 246 but is located on
an opposite side of permanent magnet 248 as compared to
control coils 250, 252 and armature 254. Permanent magnet
flux components 256 and 257 are shown for no coil energization
in FIG. 11D. In FIG. 11E the paths of permanent
magnet flux components 256 and 257, as well as excess coil
magnetic flux 258, are shown when coils 250, 252 are
energized in an aiding exceeding manner. In FIG. 11F the
path of each magnetic flux component 256, 257, and 258 is
shown when coils 230, 232 are energized in an opposed
exceeding manner.
FIGS. 12A-12E depict a device 270 similar to that shown
in FIGS. 7-9 except that bypasses 272 and 274 are provided
from pole piece 276 to pole piece 278. Bypass 272 is located
between permanent magnet 280 and control coils 282, 284
and bypass 274 is located between permanent magnet 280
and control coils 286, 288. Armatures 290 and 292 are also
provided. When no coils are energized permanent magnet
magnetic flux components 294, 296, 298, and 300 travel as
shown in FIG. 12A.
If coils 282, 284 are energized in an opposing manner
permanent magnet flux components 295, 297, and 299 travel
as shown, with no flux component traversing the path which
includes armature 290 and therefore no magnetic coupling
force acting thereon. This would be the case for when coils
282, 284 are energized to the level where the coils magnetic
flux just blocks, but does not exceed, the magnetic flux
component 294 (FIG. 12A) from permanent magnet 280. If,
however, coils 282, 284 are energized in an opposed exceeding
manner an excess coil magnetic flux component 301 is
produced which travels a path including armature 290 and
bypass 272 results as shown in FIG. 12C.
Coils 286, 288 may be energized in an aiding manner such
that all permanent magnet magnetic flux travels along the
path which includes armature 292 as shown in FIG. 12D. If
coils 286, 288 are energized in excess of the level of FIG.
12D then the excess magnetic flux component 304 traverses
the path which includes armature 292 and bypass 274 as
shown in FIG. 12E, thereby increasing the magnetic coupling
force on armature 292 as compared to FIG. 12D. The
advantage of incorporating such bypasses into permanent
magnet control components in certain applications will
become apparent below.