Patent GB-294674-A (GB)
Title: Improvements in and relating to magnetos
IPC: H02K35/06
Filed: 1927-03-29
Abstract: 294,674. Mills, M. C. March 29, 1027. Reciprocating machines; inductor machines.- In a reciprocating armature type magneto having the generating coils wound on the magnets, a spring associated with the armature is adapted to be stressed to such an extent that the armature is caused to move sharply away from the magnet poles. Where a laminated or leaf spring is employed, the movement of the armature is not necessarily inaugurated by the spring. As shown in Fig. 7; the armature b is provided with a forked member b<1> through which is inserted a pin b<2>. A laminated spring c anchored in a pivoted support d passes between the pin b<2> and the armature and the other end is adapted to be stressed by a cam or eccentric e. When the energy stored in the spring exceeds the retentive energy of the magnet, the armature is withdrawn suddenly from the magnet poles and a spark is produced. The armature may be returned to the poles by means of a compression spring f or the spring c may be extended beyond the pivotal fulcrum and seated against an adjustable abutment. The positions of the fulcrum, armature support and the stressing device e with respect to the spring may be interchanged in various ways, and instead of being pivotally mounted, the spring may be rigidly held at one end, thus serving to reseat the armature. As the speed of operation of the stressing device increases, the spring acts more and more like a rigid bar in consequence of the increased inertia to flexure. and the moment of break and consequently the spark, will be advanced automatically. The cam or eccentric may be provided with a deeply cut-away portion in order to allow the armature to return quickly to the magnet poles. In order that at slow speeds the moment of break shall occur at the same period of the cycle, a stop member such as a finger j, Fig. 10, may be provided so arranged that the spring can contact with it and so inaugurate the movement of the armature. The finger may be constructed in the form of two leaves, one on each side of the spring and joined by a bridge piece adapted to bear on the spring. The gap between the finger and the spring may be adjusted by inserting therein a stepped or wedgeshaped member or the pivot may be adjustable. As the speed of actuation increases, the inertia of the spring bar comes into action and the effect of the stop is automatically cut out. In another modification, Fig. 9, the stop is in the form of a backing member h. In this case, the armature is connected to the backing member by a pin b<2> and slot h<1>, and the member h is longitudinally adjustable for altering the timing by means of a pivoted handle i having a slot h<3> with which engages a pin h<2> carried by the backing member. In another modification, the cam or eccentric acts on the spring through a pivoted tappet. Fig. 15 shows a further form in which the cam e bears on an arm c3 spaced from the spring c and secured to the pivoted housing d. Instead of a rotary cam, a reciprocating stressing device may be employed. In some cases, the laminated or leaf spring may be replaced by a resiliently acting bar. Fig. 5 shows such a modification employing a more or less rigid bar c<3>, the resilient effect being obtained from a spring c<4>. In another form, Fig. 6, two bars c<3>, c<5> are employed kept apart by a spring c'.