MAGNETIC STRUCTURE FOR USE IN A CHAIN SAW OR STRING TRIMMER IGNITION SYSTEM OR THE LIKE

• Main Author: JACKSON, ROBERT V
• Format: Patent
• Language: English; French
• Published: 15.01.1991
• Edition: 5
• Subjects: BLASTING; COMBUSTION ENGINES; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; DYNAMO-ELECTRIC MACHINES; ELECTRICITY; GENERATION; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; IGNITION, OTHER THAN COMPRESSION IGNITION, FORINTERNAL-COMBUSTION ENGINES; LIGHTING; MECHANICAL ENGINEERING; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES; WEAPONS

A magnetic structure for use in a chain saw or edge trimmer ignition system or the like where the ignition system includes a flywheel having a plurality of cooling fins disposed around the peripheral portion thereof and at least one magnetic structure embedded in the periphery, a magnetically permeable core disposed adjacent the flywheel, a coil wound on the core and connected to an ignition circuit so that a voltage waveform is induced in the coil an applied to the circuit each time the magnetic structure passes the coil, the magnetic structure including (a) a magnet having first and second end faces and (b) first and second pole pieces which respectively engage the end faces, the pole pieces being asymmetrical in a plane perpendicular to the plane of the flywheel to thereby effect concentration of the flux produced by the magnet and coupled to the core by the pole pieces to thereby permit a reduction in size of the magnet without substantially lessening the energy in the voltage waveform applied to the ignition circuit and an increase in the size of those cooling fins disposed adjacent the reduced size magnet. The pole pieces may also be asymmetrical in the plane of the rotor.