GB1266153A - - Google Patents

Abstract

1,266,153. Vibratory electric motors. DERRITRON Ltd. 10 June, 1969 [11 June, 1968], No. 27658/68. Heading H2A. An electromagnetic vibrator comprises a stationary magnet having an annular or part annular air gap in which is suspended a moving conductor unit so as to be capable of vibration about the axis of the air gap when A.C. is passed through conductors extending parallel to said axis, the conductors or groups thereof being connected in series. In the embodiment shown in Fig. 1, a pot magnet comprises inner and outer poles 10, 12 with a D.C. exciting coil 10 and annular air gap 14 between them, the conductor unit 15 in the air gap comprising a cylinder formed of conductors 16 extending between part-annular bus-bars 17, 18 connecting groups of conductors in parallel. The groups are connected in series by stationary conductors 45 and flexible conductors 43. Alternatively, the groups of conductors may be replaced by sections of a tube. The unit 15 is attached to an output disc 20 which is supported on the magnet by a torsion suspension consisting of radial bars 30 attached at their inner and outer ends to the disc and magnet respectively by resilient couplings 31, 32, the disc also having a central pivot 25 or further resilient coupling. In another embodiment, Fig. 3 (not shown), the underside of disc 20 has radial webs (53) and a central boss (52) extending lower than the webs 24 and boss 23 in Fig. 1, the inner pole of the magnet being slotted and apertured to receive them. In the further embodiment shown in Fig. 5, the conductor unit has two sets of conductors provided internally and externally of a tubular former 82, one set of longitudinal conductors 80 producing rotational vibration and the other set 81, in the form of one or more coils, producing axial vibration, the two sets of conductors being independently supplied with A.C. Each conductor may comprise a hollow tube for the passage of cooling fluid and further tubes for cooling fluid may be incorporated in the former. To accommodate both modes of vibration, the suspension arms 85 are pivoted vertically at 86 at their inner ends and horizontally at 87 at their outer ends on flexible couplings as in Fig. 1, the arms also being formed of thin strip twisted at an intermediate point so that they can absorb part of the movement of the output disc by bending. The outer pivots 87 may be biased to take the weight of a test-piece and a central spring 90 may also be provided. The arms 85 may be forked, Fig. 6 (not shown), or have two pivots at right angles at their outer ends, Fig. 7 (not shown), to permit both modes of vibration without flexing of the arms.