Adjustable Cone Vibrator.
Fig. 27 shows a form of contact breaker much used in portable medical coils for slow speeds. It consists of a cone of iron H, mounted on the vibrator spring, and furnished with adjustable contact spring and screw A. Its amplitude of vibration is limited by the two pins mounted on the disc, between which the cone vibrates. The disc is turned by hand, thus moving the pins, and so varying the travel of the cone H to and from the core C. It does not give good results from the fact that the rhythmical movements are disturbed every time the cone strikes against the pins, also at the contact spring striking the contact screw. As we showed before, a really satisfactory contact breaker should have a spring, which allows of no sinusoidal movement. Where a pivoted armature is governed by a spiral spring, the result is a series of steady, rhythmical shocks, provided the adjustments are satisfactory.
Fig. 27.