Thomas Alan Osborne

US Patent:

60678240, May 30, 2000

Filed:

Oct 29, 1998

Appl. No.:

9/182748

Inventors:

Thomas G. Osborne - Highland Village TX

Assignee:

Optek Technology, Inc. - Carrollton TX

International Classification:

B60R 2504

US Classification:

70252

Abstract:

A lock for an automobile ignition system includes a sleeve having a cylindrical inner surface. A lock cylinder is provided which is rotatably mounted within the sleeve and has a cylindrical outer surface defining a cylindrical interface with the inner surface of the sleeve. The cylinder includes a keyway adapted for receiving a key used to rotate the cylinder between an off and start position. A differential magnetic comparator having a pair of magnetically sensitive areas is mounted on the sleeve for detecting when the cylinder is rotated to the start position to generate an ignition signal. A magnet is mounted to the cylinder interface for generating a magnetic flux and for activating the comparator when the cylinder is rotated to the start position. A difference in the magnetic flux density present on the pair of magnetically sensitive areas causes the comparator to generate the ignition signal. However, in the presence of a magnet external to the lock, the magnetically sensitive areas detect no difference in magnetic flux density which prevents the comparator from generating the ignition signal.