Larry B Larsen

US Patent:

40754871, Feb 21, 1978

Filed:

May 14, 1976

Appl. No.:

5/686590

Inventors:

Larry D. Larsen - Palatine IL

Assignee:

Patent Development & Management Company - Elgin IL

International Classification:

G01T 118

US Classification:

250385

Abstract:

Two cup-shaped electrodes respectively defining outer walls of a closed and an open ionization chamber and an insulator wall sandwiched therebetween defining an interior wall of both chambers and carrying both an electrode common to both chambers and at least one circuit element of a sensing circuit responsive to the relative impedances of the two chambers for indicating the presence of smoke in the open chamber. Minimizing leakage current-increasing factors as moisture, dust, etc. , the body of the circuit element is protectively mounted to the insulator wall within the closed chamber by means of a plurality of leads extending through mating holes in the insulator wall with a header surface of the body pressed against the wall. One of the leads is folded around the edge of a hole in the wall wherein the common electrode is mounted and is squeezed between the insulator wall and a part of the common electrode to make electrical contact therewith. Some of the leads which extend out of the chamber for connection with external circuitry are sandwiched between an insulator member and the wall and thereby insulated against electrical contact with either of the cup-shaped electrodes.

US Patent:

40830373, Apr 4, 1978

Filed:

Dec 8, 1975

Appl. No.:

5/638843

Inventors:

Larry D. Larsen - Palatine IL

Assignee:

Patent Development & Management Company - Elgin IL

International Classification:

G08B 1710

US Classification:

340237S

Abstract:

A battery-powered fire alarm including a smoke detector, a controllable horn circuit and a battery monitoring circuit. The smoke detector employs a pair of complementary field-effect transistor switches with gates respectively connected to an ionization chamber and a potentiometer of a Wheatstone bridge circuit connected across the battery. The field-effect transistors are biased off to minimize standby power consumption and are connected such that the threshold voltages thereof are offsetting to minimize supply voltage sensitivity of the detector. When the voltage from the ionization chamber assumes a value approximately equal to the potentiometer voltage, both field-effect transistors turn on to energize an alarm circuit to sound an alarm. The switching circuit is provided with hysteresis through positive feedback. The battery monitoring circuit employs a pair of complementary field-effect transistors connected with each other to establish a reference voltage to which the battery voltage is compared.

US Patent:

D2476657, Apr 4, 1978

Filed:

Feb 23, 1976

Appl. No.:

5/660254

Inventors:

Larry D. Larsen - Palatine IL

Assignee:

Patent Development & Management Company - Elgin IL

International Classification:

D1005

US Classification:

D10121