Patent GB-938134-A (GB)
Abstract: 938,134. Electric motors. AUTOMATION DEVELOPMENT CORPORATION. Oct. 27, 1961, No. 38556/61. Class 35. In a 90 degrees stepper motor having first and second stator windings arranged to establish upon energization first and second magnetic fields at right angles, a rotor aligning itself with the resultant of the magnetic fields, first and second control means are connected to the first and second stator windings respectively to reverse the direction of the two magnetic fields ; the control means being applied with electrical pulses passed alternately thereto by actuating means connected to the rotor for movement therewith. As shown in Fig. 1 a permanent magnet rotor 10 has positioned around it first and second pairs of stator windings 11,12 and 13, 14 arranged at right angles to each other, the inner terminals being commonly connected to a conductor 15 energized by a D.C. source and the outer terminals connected to sides 17, 18 and 20, 21 respectively of two bi-stable networks 19, 22. The rotor shaft 23 has keyed thereto two insulating commutator discs 24, 25 having insulated peripheries except for conducting portions 26, 27 which connect with continuous conducting rings 28, 29. Brushes 17<SP>1</SP>, 18<SP>1</SP>, 20<SP>1</SP>, 211 and 17<SP>11</SP>, 18<SP>11</SP>, 20<SP>11</SP>, 21<SP>11</SP> are connected as shown to the bi-stable networks by lines 36, 37, 38, 39 and differentiated inputs are applied to the conducting rings 28, 29 via lines 30,/31. If the rotor 10 is in the position shown in the Figures sides 17, 20 of bi-stable networks 19, 22 respectively will be conducting and the rotor will be in the position corresponding to the resultant of the magnetic fields due to the energization of windings 11, 13. In order to step the rotor in a clockwise direction a pulse is applied to terminal 34, differentiated by capacitor 32 and transmitted via commutator 24 to side 18 of bi-stable network 19 causing the state of this circuit to change and side 18 to conduct so that current flows through winding 12 and not through 11 resulting in a change in direction of magnetic field. Since the other brushes 211, 17<SP>1</SP> and 20<SP>1</SP> are connected to insulating portions of the commutator disc the state of bi-stable network 22 is unchanged and winding 13 remains energized. The rotor 10 therefore after the application of this pulse rotates through 90 degrees to its next position as shown at B. Upon reception of a further pulse at 34 current now passes from the disc 28 to portion 26 and via brush 21<SP>1</SP> and line 39 to side 21 of network 22 when the state of the latter is changed so that side 21 conducts and side 20 non-conducts. Current now flows through winding 14 and since the state of bi-stable network 19 is unchanged current will still flow through winding 12. The rotor therefore rotates through a further 90 degrees as shown at C. The next pulse will pass through brush 17<SP>1</SP> to side 17 of network 19 changing the state of the latter and causing current to flow through winding 11 instead of winding 12, network 22 being unaffected. The rotor will therefore take up position along the resultant of the two magnetic fields as shown at D. The cycle is completed by passing a further pulse through brush 20<SP>1</SP> to alter the state of network 22 and cause current to flow through side 20 and winding 13 so that the rotor takes up the position shown at A. The motor may be made to step in an anti-clockwise direction by passing pulses to terminal 35 instead of terminal 34. Alternatively disc 25 may be omitted and a reversing switch provided in the conductors 36, 37, 38, 39.