US4257746A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dosimeter having a low air flow rate
Assignee: Ametek Inc
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Filing: 1978-10-02
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Granted: 1981-03-24
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Expires: 1998-10-02
Abstract
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.
Inventors
- 👤 Adoniram J. Wells
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:50
CPC Classifications
G; G01; G01N; G01N1/00; G01N1/02; G01N1/22; G01N1/2273; G01N33/00; G01N33/0004; G01N33/0009; G01N33/0011; G01N33/0016; G05; G05D; G05D7/00; G05D7/06; G05D7/0617; G05D7/0629; G05D7/0635; G05D7/0676; G01N1/2202; G01N1/2205; G01N1/24
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
307 words
An improved dosimeter that has an electric motor, a power source, an exhaust port, a filter means in which particles or vapors present in an air stream being pumped through the dosimeter at a controlled constant flow rate are collected on the filter means; a variable drive pump having an inlet and an outlet, tubularly connected to the filter means and coupled to the electric motor, draws the air stream through the filter means; an orifice being positioned in a tube attached to the pump and to an exhaust port, wherein the air stream is pumped through the orifice and thereby creates an air pressure drop; means for reducing pulsations in the air stream; a differetial pressure switch positioned in a tube connected in effect parallel to the orifice is activated by a change in the air pressure drop of the air stream and creates a low voltage electrical input signal; an integrator circuit electrically connected to a power source and to the pressure switch uses the low voltage input signal generated by the pressure switch and integrates this signal; an amplifier circuit electrically connected to the power source and connected in series to the integrator circuit and to the electric motor which amplifies the signal generated by the integrator circuit and feeds the amplified signal to the electric motor thereby controlling the speed of the motor driving the pump in relationship to the signal generated by the pressure switch to maintain the air stream at a controlled constant flow rate; the improvement in use therewith comprises; an adjustable by-pass valve connected in parallel with the variable drive pump whereby a fixed quantity of air from the outlet of the pump is recycled to the inlet of the pump allowing the pump to provide a constant low air flow rate of the air stream through the dosimeter.
Claim 2
Dependent Claim
307 words
An improved dosimeter that has an electric motor, a power source, an exhaust port, a filter means in which particles or vapors present in an air stream being pumped through the dosimeter at a controlled constant flow rate are collected on the filter means; a variable drive pump having an inlet and an outlet, tubularly connected to the filter means and coupled to the electric motor, draws the air stream through the filter means; an orifice being positioned in a tube attached to the pump and to an exhaust port, wherein the air stream is pumped through the orifice and thereby creates an air pressure drop; means for reducing pulsations in the air stream; a differetial pressure switch positioned in a tube connected in effect parallel to the orifice is activated by a change in the air pressure drop of the air stream and creates a low voltage electrical input signal; an integrator circuit electrically connected to a power source and to the pressure switch uses the low voltage input signal generated by the pressure switch and integrates this signal; an amplifier circuit electrically connected to the power source and connected in series to the integrator circuit and to the electric motor which amplifies the signal generated by the integrator circuit and feeds the amplified signal to the electric motor thereby controlling the speed of the motor driving the pump in relationship to the signal generated by the pressure switch to maintain the air stream at a controlled constant flow rate; the improvement in use therewith comprises; an adjustable by-pass valve connected in parallel with the variable drive pump whereby a fixed quantity of air from the outlet of the pump is recycled to the inlet of the pump allowing the pump to provide a constant low air flow rate of the air stream through the dosimeter.
Claim 3
Dependent Claim
15 words
The dosimeter of claim 1 in which the by-pass valve is an adjustable needle valve.
Claim 4
Dependent Claim
20 words
The dosimeter of claim 1 in which the by-pass valve is a valve having a fixed opening in the valve.
Claim 5
Dependent Claim
14 words
The dosimeter of claim 3 in which the orifice is an adjustable needle valve.
Claim 6
Dependent Claim
35 words
The dosimeter of claim 4 in which the pressure switch is activated by an air pressure drop of 3 inches of water and an air pressure drop change of 0.01 to 0.5 inches of water.
Claim 7
Dependent Claim
45 words
The dosimeter of claim 5 in which the integrator circuit is biased at about +0.6 volt and the signal from the integrator gradually increases to about +1.2 volts when the pressure switch is activated and gradually decreases to +0.6 volt when the switch is deactivated.
Claim 8
Dependent Claim
40 words
The dosimeter of claim 6 in which the amplifier circuit amplifies the signal from the integrator circuit to a maximum of about 96% of the total voltage of the power source and has an impedance of greater than 10 ohms.
Claim 9
Dependent Claim
34 words
The dosimeter of claim 7 which has electrically attached to the output of the integrator circuit thereto a low air flow detector circuit comprising a bistable multivibrator circuit electrically connected to an indicator light.
Claim 10
Dependent Claim
33 words
The dosimeter of claim 8 which has electrically connected to the power source which is a battery check circuit comprising a precision voltage detector adjusted to the full charge voltage of the battery.
Claim 11
Dependent Claim
37 words
The dosimeter of claim 9 in which the means for reducing pulsations in the air stream comprise a differential pulsation pressure filter positioned in a tube connected to the exhaust port and in parallel with the orifice.
Claim 12
Dependent Claim
14 words
The dosimeter of claim 10 in which the pump is a multicylinder piston pump.
Claim 13
Dependent Claim
15 words
The dosimeter of claim 10 in which the pump is a four cylinder diaphragm pump.
Claim 14
Dependent Claim
49 words
The dosimeter of claim 9 in which the means for reducing pulsations in the air stream comprise an air reservoir connected to the pump and to the orifice wherein the air reservoir retains excess air supplied by the pump and maintains a constant flow rate of the air stream.
Claim 15
Dependent Claim
15 words
The dosimeter of claim 13 in which the pump is a single cylinder diaphragm pump.
Claim 16
Dependent Claim
242 words
The dosimeter of claim 1 in which the adjustable by-pass valve is a valve having a fixed opening in the valve; the pump is a diaphragm pump having four cylinders; the orifice is an adjustable needle valve which causes an air pressure drop of about 3 inches of water; the means for reducing pulsations in the air pressure stream comprise a differential pulsation pressure filter position in a tube connected to the exhaust port and in parallel with the orifice; the pressure switch is activated by an air pressure drop change of about 0.1 to 0.5 inches of water; the integrator circuit is biased about +0.6 volt and the signal from the circuit gradually increases to about +1.2 volts when the pressure switch is activated and gradually decreases to +0.6 volt when the pressure switch is deactivated; the amplifier circuit amplifies the signal from the integrator circuit to a maximum of about 96% of the total voltage of the power source and has impedance less than 10 ohms; the power source is a battery that has a maximum of 5.5 volts and has nickel cadmium cells; and has electrically connected thereto a low flow air detector circuit electrically attached to the output of the integrator circuit comprising a bistable multivibrator circuit electrically connected to an indicator light and a battery check circuit electrically connected to the power source which is a battery comprising a precision voltage detector adjusted to about 5.2 volts.
Claim 17
Dependent Claim
235 words
The dosimeter of claim 1 in which the adjustable by-pass valve is a valve having a fixed opening in the valve; the pump is a diaphragm pump having one cylinder; the means for reducing pulsations in the air stream comprise an air reservoir connected to the pump and to the orifice wherein the air reservoir retains excess air supplied by the pump and maintains a constant flow rate of the air stream; the air pressure switch is activated by an air pressure drop change of about 0.1 to 0.5 inches of water; the integrator circuit is biased about +0.6 volt and the signal from the circuit gradually increases to about +1.2 volts when the pressure switch is activated and gradually decreases to +0.6 volt when the pressure switch is deactivated; the amplifier circuit amplifies the signal from the integrator circuit to a maximum of about 96% of the total voltage of the power source and has impedance less than 10 ohms; the power source is a battery that has a maximum of 5.5 volts and has nickel cadmium cells; and has electrically connected thereto a low flow air detector circuit electrically attached to the output of the integrator circuit comprising a bistable multivibrator circuit electrically connected to an indicator light and a battery check circuit electrically connected to the power source which is a battery comprising a precision voltage detector adjusted to about 5.2 volts.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-23 | 1984-09-22 | 1985-03-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-23 | 1988-09-22 | 1989-03-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-23 | 1992-09-22 | 1993-03-24 | $7700.00 | Window Closed / Lapsed |