Sentrol, Inc.

Keith E Flint

Thomas J Holce

Charles M Huckins

Robert H Niemeyer, Iii

A plunger-operated switch assembly, useful for sensing the presence of a movable object such as a door or window, in which a magnetic reed contact is actuated by a magnet in the form of a disk-like roller plunger, or by a smaller magnet carried in the center of a roller plunger. The roller plunger is located in a cavity defined by a housing and projects through an aperture in a face plate including a flange by which the housing can be mounted recessed in a desired location. The magnetic reed contact is held alongside the cavity containing the roller plunger, so that the housing can be compact. A magnetic electrical conductor lead connected with a magnetic reed is located so as to be effectively within the magnetic field of the actuating magnet when the roller plunger is depressed a small distance so that the magnetic reed switch is actuated by a small movement of the plunger.

Switch housing with magnetic roller plunger

A magnetically actuated reed switch assembly in which a small permanent helper magnet is attached to a magnetic lead of the reed switch at an end of the reed switch envelope. The lead then may be bent around parallel with a magnetic reed of an encapsulated reed switch. The permanent helper magnet provides an axis of magnetic polarity parallel with the axis of the reed switch, and is magnetized to a level of magnetism which supplies slightly less than enough magnetic flux density to hold the reed switch in a magnetically actuated condition, so that only a small amount of additional flux density needs to be provided. By selecting reed switches within close tolerances and using helper magnets of selected size and strength within close tolerances, satisfactory assemblies may be produced without adjustment of helper magnet position to actuate the switch. The small permanent magnet may alternatively define a bore fitting around the magnetic lead, and may be magnetized after assembly of the magnet and magnetic lead of the switch, thus reducing the amount of time and labor required to manufacture the switch assembly.

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Portland, OR, United States of America

Keith E Flint