Apparatus and method for controlling the introduction of chemica

Details Apparatus and method for controlling the introduction of chemica Apparatus and method for controlling the introduction of chemica

1993-02-09

1993-08-03

Mitchell, David M.

Fire extinguishers

Fluid systems

Plural source, mixing in transit

169 15, 169 44, 169 24, A62C 300

Patent

active

052320529

ABSTRACT:
A fire-fighting system in which a liquid chemical foamant is introduced into the water stream in varying amounts so as to maintain a predetermined percentage mixture irrespective of variations in the water flow includes a motor-driven pump where the motor is controlled over a first speed range by pulse width modulating the drive to the motor and over a second speed range, producing intermittent motion, by burst width modulating the drive signal when it is operating at its minimum pulse width modulated duty cycle. Using this technique the range of available motor speeds is extended well beyond that which can be achieved using pulse width modulation of the motor drive signal alone.

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