Patent GB-386386-A (GB)
Title: Improvements in reciprocating electric motors
IPC: H02K33/18
Filed: 1931-11-04
Abstract: 386,386. Reciprocating motors. DILLSTROM, T. V., 7B, Jungfrugatan, ASTRADSSON, P. A., 65, Karlavagen, both in Stockholm, and DAHLGREN, F., Djursholm, near Stockholm. Nov. 4, 1931, No. 30616. [Class 35.] An electric motor with a reciprocating armature is operated with alternating or polyphase current of substantially only one frequency ; the armature is provided with short-circuited windings and means are provided for reversing its motion at the end of the stroke. Fig. 5 shows an apparatus comprising a field-magnet 17 and armature 19 formed of radial laminations. The armature 19 is surrounded by a number of rings 23 forming short-circuited conductors. The field-magnet is provided with windings 201, 20<11> near the middle of its length and windings 21<1>, 21<11> at its ends. The windings 201, 21<1> are in series with each other and a condenser 281 and in parallel with the windings 20<11>, 21<11> and a condenser 28<11>. When the armature 19 is near the middle of its travel the currents in the windings 20<1>, 20<11> are in the same phase and produce a field which urges the armature in the direction in which it is already moving. When the armature is in the extreme position shown the inductance of the winding 21<11> is greater than that of the winding 21<1> so that the current's in the windings 201, 20<11> are in different phases and impel the armature towards the other end of the field-magnet, whence it is returned by the action of the windings 21<1>, 21<11> which is opposite to that in the first position. A third winding may be employed in parallel with both the sets described giving a threephase effect. The windings 21<1>, 21<11> may be dispensed with and the armature returned at the end of its travel by mechanical means, such as springs, or the armature may form the plunger of an air compressor and be returned by the pressure of the air in the clearance space. The phase-splitting effect may also be produced by variable condensers operated by the motion of the armature. In the arrangement shown on Figs. 9 and 10 the windings 211, 2111 are arranged at the same end of the field-magnet and each consists of two portions occupying two opposite quadrants of the circumference. Opposite portions of the armature are elongated to form projections 31 and the armature is rotated by a winding 30 and supplementary armature 29 of the squirrel-cage or like type. When the projections 31 are opposite to the winding 21<1> the armature is impelled in one direction and when they are opposite to the winding 21<11> it is impelled in the other. In any case the rings 23 at the ends of the armature may be of higher resistance than those in the middle. Figs. 13 and 14 shown an arrangement for use with three-phase current. Two sets of windings 46, 47 each extend round half the circumference, the field produced by one travels in one direction and that produced by the other in the opposite direction. The armature 41 carries a number of semicircular conductors 43 connected at their ends by longitudinal conductors 48. Inside the armature 41 are a number of conductors 42 forming a squirrelcage winding and a core 49 provided with windings 49a to give a rotating field. The rotation of the armature thus produced brings the conductors 43 under the influence of the windings 46, 47 alternately, thus producing a reciprocating motion.