GB1262855A - Improvements in or relating to rotary solenoids - Google Patents

Abstract

1,262,855. Rotary actuators. SMITHS INDUSTRIES Ltd. 21 May, 1969 [21 Feb., 19681, No. 8443/68. Heading H1P. The rotor and stator of a rotary actuator have co-operating polepieces shaped to arcs of spirals. As shown, Fig. 1, the stator comprises a soft iron core 1 having a stem 2 and a base 3 on to which is fitted a soft iron shell 8 having an inwardly extending flange 9 forming the polepiece. A coil 10 wound on a former 11 surrounds the core stem 2. A soft iron rotor 12 is pivoted on a steel shaft 4 supported in jewel ring bearings 5, 6, and is biased by means of a hair spring 22. The rest position and energized position are determined by stop plates 26 which engage a stop pin 23. As shown, Fig. 2, the rotor and stator pole faces each comprise two 180 degree arcs of Archimedian spirals, the co-operating arcs of the polepieces lying on segments of the same spiral. The rotor is biased anticlockwise to the rest position illustrated in Fig. 2, and when the coil is energized the rotor is moved clockwise to reduce the thickness and hence the reluctance of the air gaps 14. The rotor turns through an angle of about 90 degrees before it is stopped by the engagement of the stop plates 26 with the pin 23. The device has a logarithmic torque characteristic but greater starting torque may be obtained by rotating the rest position of the rotor clockwise, with consequent reduction of maximum rotation angle. The output shaft may protrude from the end of the housing remote from the rotor, to provide an anticlockwise rotation when the coil is energized.