Apparatus and method for controlling the introduction of chemical foamant into a water stream in fire-fighting equipment
USRE35362E · kind E · reissue
Assignee
Inventors
Key dates
| Filing date | May 18, 1995 |
| Grant date | Oct 29, 1996 |
| Priority date | — |
| Expiry date | May 18, 2015 |
Classification
- Technology area (CPC —)General
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.