GB999686A - Improvements in and relating to electro-pneumatic converter devices - Google Patents

Abstract

999, 686. Controlling fluid flow; fluid-pressure servomotor systems. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Feb. 12, 1964 [Feb.15, 1963], No. 5911/64. Headings G3H and G3P. A frequency sensitive transducer for varying a pneumatic signal in response to an electrical A.C. input consists of a torsional resonator of which a torsion rod 2, Fig. 1, is clamped at 3 and carries a transversely magnetized cylindrical armature 1 arranged so that the poles normally lie as shown in Fig. 18 in relation to fixed pole pieces 8 energized by a winding 9. The upper end of the armature is carried in a bearing in a tubular member 6, and escape of air from lateral openings in this member is normally prevented by a member carried by the armature, but when the latter is angularly de - flected or oscillated, escape of air is permitted. The pressure of air between the escape passage and a restriction in the supply may be applied to a piston (not shown) which may provide a feedback in the form of an electrical signal or an adjustment of the supply restriction. The armature 1 may be brought into oscillation when either a frequency modulated signal applied to the winding 9 coincides with the natural frequency of the armature and torsion rod, or the voltage of a constant frequency signal coinciding with that natural frequency is increased above a certain value. The natural frequency of the armature and torsion rod may be varied by adjustable screws (not shown) projecting laterally from the lower part of the armature, and adjustable damping vanes may also be carried by the armature. Several forms of valve for controlling the escape of air are described. One comprises a rod 14, Fig. 4, in guides 21 which may be oil sealed, and recessed at 15 to control escape from a port 16 communicating with a chamber 20 which is connected with the controlled piston and fed through an adjustable restriction 18 from a supply conduit 17. Other forms of valve are rotar cylindrical elements with multiple porting. Fig. 9 illustrates another form consisting of a spring arm 51 normally pressing against a valve seat 52 but lifting thereform as the armature 14 is oscillated. A single unit may contain a number of armature assemblies tuned to different frequencies and arranged to be controlled from a single input winding. In a modification, the torsional oscillations of the armature are employed to deflect the upper end of the armature laterally so that it will also oscillate, at a lower natural frequency, by bending of the torsion rod. In this way the apparatus can respond to a lower frequency envelope imposed on the higher frequency to which the armature responds torsionally. Fig. 16 shows the upper end of an armature 58 and torsion rod 60 modified for this purpose. A flat-bottomed notch 63 engages a fixed tongue (not shown) so that as the armature moves angularly it is also deflected laterally, and this deflection is transmitted by an abutment 65 to pneumatic control means.