Pumps – Condition responsive control of pump drive motor – Responsive to change in rate of pump fluid flow
Patent
1978-10-02
1981-03-24
Croyle, Carlton R.
Pumps
Condition responsive control of pump drive motor
Responsive to change in rate of pump fluid flow
417 45, 417 63, F04B 4900
Patent
active
042577462
ABSTRACT:
An improved dosimeter having a low air flow rate for monitoring working areas in which air is pumped through the dosimeter at a controlled constant low rate of flow and any particles or vapors in the air are collected on a filter, a variable drive pump having an inlet and an outlet is connected to the filter and is driven by an electric motor and controlled by a feed back circuit of an integrator and an amplifier and the pump maintains a constant flow of air through the dosimeter; in operation of the dosimeter the integrator receives a signal from a pressure switch that detects changes in the flow of the air stream through the dosimeter by a change in a pressure drop of the air which is being pumped through an orifice;
The improvement is the use of an adjustable by-pass valve connected in parallel with the variable drive pump in such a manner that regulated quantities of air from the outlet of the pump are recycled to the inlet of the pump thereby allowing the pump to provide a constant low flow rate of air;
In utilization of the dosimeter, the dosimeter is placed in a work area or worn by an individual and at the termination of a period of time, such as a work day, the filter is removed and the contents collected are analyzed by conventional techniques such as gas chromatography to determine a level of exposure of individuals working in that area.
REFERENCES:
patent: 3198121 (1965-08-01), Schaub
patent: 3406895 (1968-10-01), Bauer et al.
patent: 3410059 (1968-11-01), Garnier
patent: 3501899 (1970-03-01), Allen
patent: 3953152 (1976-04-01), Sipin
patent: 4063824 (1977-12-01), Baker et al.
patent: 4123932 (1978-11-01), Baker et al.
Croyle Carlton R.
E. I. Du Pont de Nemours and Company
Look Edward
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