US4150495A
Expired / Lapsed
US
⏱️ 0.0 years remaining
LEL (lower explosive limit) control with automatic calibration capability
Assignee: Bobst Mex SA
•
Filing: 1978-05-03
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Granted: 1979-04-24
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Expires: 1998-05-03
Abstract
Abstract The LEL (Lower Explosive Limit) control includes a gas analyzer normally connected to receive sample gas from the evaporation enclosure of a press dryer section and which, during calibration, is sequentially connected to first analyze solvent free gas and then gas having a known solvent content. Situated with the analyzer is a detector the resistance of which changes in proportion to the temperature within the flame cell of the analyzer. The detector forms a portion of a bridge circuit, which also includes a potentiometer. The output of the bridge is amplified, compared to a selected reference voltage and a signal representing the difference therebetween is processed. The processed signal is combined with a signal representing the web speed to form a resultant signal to control a pneumatically operated damper in the enclosure exhaust conduit. Automatic calibration of the system is initiated periodically and takes place in two phases. During the first phase of calibration, the potentiometer is set in accordance with the difference between the amplifier output derived from analysis of the solvent free gas and a 0% reference voltage. During the second phase of calibration, the gain of the bridge output amplifier is set in accordance with the difference between the amplifier output derived from the analysis of the known solvent concentration gas and a full scale reference voltage. When calibration is taking place, the output of the comparison circuit is inhibited and the damper position is determined in accordance with the web speed alone. Emergency stop of the press occurs when the output of the amplifier exceeds a given level.
Inventors
- 👤 Nathan Stern
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 20:06
CPC Classifications
F; F26; F26B; F26B25/00; F26B25/009; B; B41; B41F; B41F23/00; B41F23/04; B41F23/0403; B41F23/0423; B41F23/0426; F26B21/00; F26B21/30; G; G01; G01N; G01N25/00; G01N25/50; G01N25/54; G01N27/00; G01N27/02; G01N27/04; G01N27/14; G01N27/16
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
109 words
An LEL control for regulating the exhaust from an evaporation enclosure through which a solvent laden web passes comprising means operably connected to the enclosure for sensing the solvent concentration therein and for generating a first signal dependent thereupon, means operably associated with the web for sensing the speed thereof and for generating a second signal dependent thereupon, means for combining said first and said second signals to form a control signal, means for regulating said exhaust in accordance with said control signal, and means for calibrating said first signal generating means, said calibrating means comprising means for inhibiting the output of said first signal generating means during calibration.
Claim 2
Dependent Claim
109 words
An LEL control for regulating the exhaust from an evaporation enclosure through which a solvent laden web passes comprising means operably connected to the enclosure for sensing the solvent concentration therein and for generating a first signal dependent thereupon, means operably associated with the web for sensing the speed thereof and for generating a second signal dependent thereupon, means for combining said first and said second signals to form a control signal, means for regulating said exhaust in accordance with said control signal, and means for calibrating said first signal generating means, said calibrating means comprising means for inhibiting the output of said first signal generating means during calibration.
Claim 3
Dependent Claim
36 words
The control of Claim 1 wherein said calibration means comprises means for calibrating said first signal generating means at the zero setting and means for calibrating said first signal generating means at the full scale setting.
Claim 4
Dependent Claim
41 words
The control of claim 2 wherein said calibration means further comprises means for actuating said zero setting calibration means for a first given time interval and means for actuating said full scale setting calibration means for a second given time interval.
Claim 5
Dependent Claim
31 words
The control of claim 3 wherein said calibration means further comprises means for periodically generating a calibration initiation signal, said zero setting calibration actuation means being actuated by said initiation signal.
Claim 6
Dependent Claim
21 words
The control of claim 4 wherein said full scale setting calibration actuation means is actuated after said first given time interval.
Claim 7
Dependent Claim
16 words
The control of claim 5 wherein said calibration means is deactuated after said second time interval.
Claim 8
Dependent Claim
30 words
The control of claim 2 wherein said calibration means further comprises means for periodically generating a calibration initiation signal, said zero setting calibration means being actuated by said initiation signal.
Claim 9
Dependent Claim
45 words
The control of claim 1 wherein said first signal generating means comprises a gas analyzer and a bridge circuit, said bridge circuit comprising a variable resistance means for sensing the temperature in said analyzer, and amplification means for amplifying the output of said bridge circuit.
Claim 10
Dependent Claim
63 words
The control of claim 8 wherein said first signal generating means further comprises means for processing the output of said amplification means, said processing means comprising means for supplying a plurality of reference voltages, means for selecting one of said reference voltages and means for comparing said amplifier output with said selected reference voltage and producing an output in accordance with said comparison.
Claim 11
Dependent Claim
26 words
The control of claim 9 wherein said combining means comprises means for combining said comparison means output with said second signal to form said control signal.
Claim 12
Dependent Claim
45 words
The control of claim 2 wherein said first signal generating means comprises a gas analyzer and a bridge circuit, said bridge circuit comprising a variable resistance means for sensing the temperature in said analyzer, and amplification means for amplifying the output of said bridge circuit.
Claim 13
Dependent Claim
63 words
The control of claim 11 wherein said first signal generating means further comprises means for processing the output of said amplification means, said processing means comprising means for supplying a plurality of reference voltages, means for selecting one of said reference voltages and means for comparing said amplifier output with said selected reference voltage and producing an output in accordance with said comparison.
Claim 14
Dependent Claim
26 words
The control of claim 12 wherein said combining means comprises means for combining said comparison means output with said second signal to form said control signal.
Claim 15
Dependent Claim
21 words
The control of claim 11 wherein said zero setting calibration means comprises means for adjusting said bridge to the zero setting.
Claim 16
Dependent Claim
26 words
The control of claim 11 wherein said full scale calibration means comprises means for adjusting the gain of said amplification means to the full scale setting.
Claim 17
Dependent Claim
26 words
The control of claim 14 wherein said full scale calibration means comprises means for adjusting the gain of said amplification means to the full scale setting.
Claim 18
Dependent Claim
36 words
The control of claim 14 wherein said bridge circuit further comprises a potentiometer and wherein said zero setting calibrating means comprises means for adjusting said potentiometer to calibrate said bridge circuit to the desired zero setting.
Claim 19
Dependent Claim
16 words
The control of claim 1 wherein said calibration means further comprises means for periodically initiating calibration.
Claim 20
Dependent Claim
22 words
The control of claim 18 wherein said calibration initiation means comprises timing means for generating a calibration initiation signal at preset intervals.
Claim 21
Dependent Claim
22 words
The control of claim 1 further comprising means for generating an emergency stop signal when said first signal exceeds a preset level.
Claim 22
Dependent Claim
20 words
The control of claim 1 further comprising manually actuated means for inhibiting the output of said first signal generating means.
Claim 23
Dependent Claim
19 words
The control of claim 1 wherein said second signal generating means comprises a tachometer operably associated with said web.
Claim 24
Dependent Claim
81 words
The control of claim 1 wherein said first generating means comprises a gas analyzer, a first source of solvent free gas, a second source of known solvent concentration gas, valve means normally conditioned to connect said analyzer to said enclosure, and wherein said calibration means further comprises means for conditioning said valve means to connect said analyzer to said first source, during a zero setting phase of calibration and to said second source, during a full scale setting phase of calibration.
Claim 25
Dependent Claim
44 words
The control of claim 23 wherein said first signal generating means further comprises a bridge circuit said bridge circuit comprising a variable resistance means for sensing the temperature in said analyzer and a potentiometer, and means for amplifying the output of said bridge circuit.
Claim 26
Dependent Claim
62 words
The control of claim 1 wherein said first signal generating means comprises means for generating a signal which varies with the sensed solvent concentration, means for supplying a plurality of reference voltages, means for selecting one of said reference voltages, and means for comprising said preliminary signal and said selected reference voltage and for producing an output in accordance with said comparison.
Claim 27
Dependent Claim
26 words
The control of claim 25 wherein said combining means comprises means for combining said comparison means output with said second signal to form said control signal.
Claim 28
Dependent Claim
36 words
The control of claim 25 wherein said calibration means comprises means for calibrating said first signal generating means at the zero setting and means for calibrating said first signal generating means at the full scale setting.
Claim 29
Dependent Claim
21 words
The control of claim 27 wherein said zero setting calibraton means comprises means for adjusting said bridge to the zero setting.
Claim 30
Dependent Claim
26 words
The control of claim 27 wherein said full scale calibration means comprises means for adjusting the gain of said amplification means to the full scale setting.
Claim 31
Dependent Claim
26 words
The control of claim 25 wherein said reference voltages comprise a preset LEL reference voltage, a zero setting reference voltage and a full scale reference voltage.
Claim 32
Dependent Claim
15 words
The control of claim 30 wherein said calibration means comprises means for periodically initiating calibration.
Claim 33
Dependent Claim
34 words
The control of claim 31 wherein said calibrating means further comprises means, effective when calibration is initiated, for conditioning said reference voltage, such that said comparison means output represents the zero setting calibration signal.
Claim 34
Dependent Claim
31 words
The control of claim 32 wherein said calibration means further comprises timing means for generating a timing signal after a given time interval to initiate the full scale phase of calibration.
Claim 35
Dependent Claim
47 words
The control of claim 33 wherein said calibration means further comprises means, actuated upon receipt of said timing signal, for conditioning said reference voltage selecting means to select said full scale reference voltage, such that the output of said comparison means represents the full scale calibration signal.
Claim 36
Dependent Claim
28 words
The control of claim 34 wherein said calibration means further comprises means for adjusting the gain of said amplification means in accordance with said full scale calibration signal.
Claim 37
Dependent Claim
28 words
The control of claim 35 wherein said calibration means further comprises second timing means for generating a second timing signal after a given time interval to terminate calibration.
Claim 38
Dependent Claim
41 words
The control of claim 35 wherein said calibration means further comprises means, actuated upon receipt of said second timing signal, to actuate said reference voltage selecting means to select said preset LEL reference voltage and to deactuate said output inhibiting means.
Claim 39
Dependent Claim
81 words
The control of claim 25 wherein said first generating means comprises a gas analyzer, a first source of solvent free gas, a second source of known solvent concentration gas, valve means normally conditioned to connect said analyzer to said enclosure, and wherein said calibration means further comprises means for conditioning said valve means to connect said analyzer to said first source, during a zero setting phase of calibration and to said second source during a full scale setting phase of calibration.
Claim 40
Dependent Claim
25 words
The control of claim 38 wherein said reference voltages comprise a LEL reference voltage, a zero setting reference voltage and a full scale reference voltage.
Claim 41
Dependent Claim
53 words
The control of claim 39 wherein said calibration means comprises means, effective when calibration is initiated, to condition said valve means to select said first source and to condition said reference voltage selecting means to select said zero setting reference voltage such that said comparison means output represents the zero setting calibration signal.
Claim 42
Dependent Claim
31 words
The control of claim 40 wherein said calibration means further comprises timing means for generating a timing signal after a given time interval to initiate the full scale phase of calibration.
Claim 43
Dependent Claim
58 words
The control of claim 41 wherein said calibrating means further comprises means, actuated upon receipt of said timing signal, for conditioning said valve means to select said second source and for conditioning said reference voltage selecting means to select said full scale reference voltage such that the output of said comparison means represents the full scale calibration signal.
Claim 44
Dependent Claim
28 words
The control of claim 42 wherein said calibraton means further comprises means for adjusting the gain of said amplification means in accordance with said full scale calibration signal.
Claim 45
Dependent Claim
28 words
The control of claim 42 wherein said calibration means further comprises second timing means for generating a second timing signal after a given time interval to terminate calibration.
Claim 46
Dependent Claim
40 words
The control of claim 44 wherein said calibration means further comprises means actuated upon receipt of said second timing signal, to actuate said reference voltage selecting means to select said LEL reference voltage and to deactuate said output inhibiting means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-04-23 | 1982-10-23 | 1983-04-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-04-23 | 1986-10-23 | 1987-04-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-04-23 | 1990-10-23 | 1991-04-24 | $7700.00 | Window Closed / Lapsed |