| 摘要 |
1,210,744. Magnetic holding devices. M. BAERMANN. 7 Oct., 1968 [6 Oct., 1967], No. 47463/68. Heading H1P. [Also in Division H2] A switchable permanent magnet system comprises at least one permanet magnet in a magnet circuit having two interruptions, one of which forms a working air-gap, and an armature which can be moved from a first position bridging one of the interruptions to a second position bridging the other interruption by means of a current pulse applied to a winding surrounding the armature. As shown, Fig. 1, a plurality of annularly disposed, alternately poled permanent magnets 2, 3 are provided with upper pole shoes 5, 4 and lower pole members 7, 6 respectively defining upper and lower air-gaps. Coils 10 are located in the spaces 26 between the magnets and surround armatures 9 which are shown bridging the lower air-gaps 8 in which position the magnet is in the "full on" condition. When a current pulse of correct polarity is applied to a coil, poles are generated in the associated armature in such a sense that it is repelled from the lower pole members and attracted to the upper pole pieces to which it moves and bridges thus shunting the magnetic flux from the working air-gap 11 defined between the upper pole pieces and an eddy current brake disc 12. The braking force may therefore be reduced by switching selected armatures to their upper positions and when all the armatures are so disposed the magnet is effectively switched off. If the magnet system is to be rotated in use the armatures are restrained from radial movement due to centrifugal force by connecting their inner ends to link structures by means of hinges, the links extending radially towards the centre of rotation near which they are hinged to the base-plate. The inner and outer ends of each armature may have recesses which partially surround the opposite sides of the coil, Fig. 3 and 4 (not shown). Spring loaded plungers may be located in the upper and lower polepieces to cushion the movement of the armature and to reduce the current required to move the armature, Fig. 5 (not shown). The structure may be used in stationary and rotary magnetic chucks, locking devices, and value controls as well as eddy current and hysteresis brakes and clutches. Additional permanent magnets may be provided bridging the working air-gaps. |
