Patent US4820931A successfully refreshed from Google Patents.
US4820931A
Expired / Lapsed
US
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Wet bench flame and droplet detector
Assignee: Detector Electronics Corp
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Filing: 1988-03-01
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Granted: 1989-04-11
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Expires: 2008-03-01
Abstract
Abstract A system for detecting a flame or droplets of burning polypropylene in an area below an upper surface of a conventional wet bench used in semiconductor production includes at least one sensor, a threshold detector, a discrimination, a counter and a latch. The sensor detects radiation generated by activity in the area and for generating a sensor signal in response to the detected radiation. The threshold detector determines whether the activity has a cross-sectional area which exceeds a predetermined threshold area. The discriminator determines whether the activity displays a flicker rate or a droplet rate that is within the predetermined flicker rate range. The counter determines whether a predetermined number of flickers or droplets has been detected within a predetermined time period, and the latch asserts a true output signal when the detected activity exceeds the predetermined threshold area, the flicker rate or the droplet rate is within the predetermined flicker rate range, and a predetermined number of flickers or droplets have been detected within the predetermined time period.
Inventors
- 👤 Robert A. Dunbar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 12:35
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/12
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
191 words
A system for detecting a flame or droplets of burning polypropylene in an area below an upper surface of a conventional wet bench used in semiconductor production, said flame having a predetermined characteristic flicker rate range and a predetermined characteristic radiation profile, said droplets occurring at a predetermined rate within said predetermined flicker rate range, comprising at least one sensor for detecting radiation generated by activity in said area and for generating a sensor signal in response to said detected radiation, a threshold detector for determining whether said activity has a cross-sectional area which exceeds a predetermined threshold area, a discriminator for determining whether said activity displays a flicker rate or a droplet rate that is within said predetermined flicker rate range, a counter for determining whether a predetermined number of flickers or droplets has been detected within a predetermined time period, and a latch for asserting a true output signal when said detected activity exceeds said predetermined threshold area, said flicker rate or said droplet rate is within said predetermined flicker rate range, and a said predetermined number of flickers or droplets have been detected within said predetermined time period.
Claim 2
Independent Claim
191 words
A system for detecting a flame or droplets of burning polypropylene in an area below an upper surface of a conventional wet bench used in semiconductor production, said flame having a predetermined characteristic flicker rate range and a predetermined characteristic radiation profile, said droplets occurring at a predetermined rate within said predetermined flicker rate range, comprising at least one sensor for detecting radiation generated by activity in said area and for generating a sensor signal in response to said detected radiation, a threshold detector for determining whether said activity has a cross-sectional area which exceeds a predetermined threshold area, a discriminator for determining whether said activity displays a flicker rate or a droplet rate that is within said predetermined flicker rate range, a counter for determining whether a predetermined number of flickers or droplets has been detected within a predetermined time period, and a latch for asserting a true output signal when said detected activity exceeds said predetermined threshold area, said flicker rate or said droplet rate is within said predetermined flicker rate range, and a said predetermined number of flickers or droplets have been detected within said predetermined time period.
Claim 3
Dependent Claim
32 words
The system of claim 1, wherein said threshold detector determines whether said activity has a cross-sectional area which exceeds said predetermined threshold area by comparing said sensor signal to a threshold signal.
Claim 4
Dependent Claim
73 words
The system of claim 1 or 2, wherein said threshold detector generates signal events, each said signal event corresponding to a single flicker or droplet of said activity, and said discriminator determines whether said activity display a rate that is within said predetermined flicker rate range by suppressing operation of said counter unless said signal events are being received at said discriminator at a rate that is within said predetermined flicker rate range.
Claim 5
Dependent Claim
97 words
The system of claim 3, wherein said counter determines whether a said predetermined number of flickers or droplets has been detected within a said predetermined time period by counting said signal events being received by said counter, said counter comprising counting means for asserting a true counter signal when said counter has recieved a number of signal events equal to said predetermined number of flickers or droplets within said predetermined time period, and for maintaining said true counter signal asserted so long as a said number of signal events has been received within said predetermined time period.
Claim 6
Dependent Claim
38 words
The system of claim 4, wherein when said latch asserts a true output signal, said latch continues to assert a true output signal until said counter signal becomes false and remains false for a second predetermined time period.
Claim 7
Dependent Claim
14 words
The system of claim 5, wherein said second predetermined time period is 1 second.
Claim 8
Dependent Claim
13 words
The system of claim 1, further comprising suppression means for extinguishing said flame.
Claim 9
Dependent Claim
18 words
The system of claim 7, further comprising control means, responsive to said latch, for activiating said suppression means.
Claim 10
Dependent Claim
18 words
The system of claim 7 or 8, wherein said suppression means comprises release means for releasing chemical suppressant.
Claim 11
Dependent Claim
71 words
The system of claim 9, wherein said sensor is capable of detecting radiation generated by a flame in an atmosphere containing said chemical suppressant, said control means includes means for controlling said suppression means to halt release of said chemical suppressant when said output signal from said latch becomes false, and means for controlling said suppression means to reinitiate release of said chemical suppressant if said latch reasserts said true output
Claim 12
Dependent Claim
14 words
The system of claim 1, wherein said predetermined threshold area is 3.14 square inches.
Claim 13
Dependent Claim
17 words
The system of claim 1, wherein said predetermined flicker rate range is 1/2 Hz to 30 Hz.
Claim 14
Dependent Claim
18 words
The system of claim 1, wherein said predetermined number of flickers or droplets is between 4 and 12.
Claim 15
Dependent Claim
15 words
The system of claim 13, wherein said predetermined number of flickers or droplets is 8.
Claim 16
Dependent Claim
16 words
The system of claim 1, wherein said predetermined time period is between 0.5 seconds and 3.
Claim 17
Dependent Claim
13 words
The system of claim 15, wherein said predetermined time period is 2 seconds.
Claim 18
Dependent Claim
16 words
The system of claim 1, wherein said sensor comprises a radiation sensor sensitive to infrared radiation.
Claim 19
Dependent Claim
12 words
The system of claim 17, wherein said sensor further comprises a filter.
Claim 20
Dependent Claim
23 words
The system of claim 17 or 18, wherein said radiation sensor is sensitive to electromagnetic radiation having wavelengths between 0.4 microns and 1.1
Claim 21
Dependent Claim
20 words
The system of claim 17, wherein said filter comprising a wratten filter having a pass band from 0.8μ to 1.0μ.
Claim 22
Dependent Claim
10 words
The system of claim 1, further comprising a polyethylene window.
Claim 23
Dependent Claim
15 words
The system of claim 1, wherein said area below said upper surface comprises a plenum.
Claim 24
Dependent Claim
33 words
The system of claim 22, wherein said plenum comprises an atmosphere containing water-based chemical fumes, and said sensor is capable of detecting said flames or said droplets in said atmosphere containing said fumes.
Claim 25
Dependent Claim
16 words
The system of claim 23, wherein said window is interposed between said sensor and said plenum.
Claim 26
Dependent Claim
25 words
The system of claim 1, wherein said sensor is capable of detecting said flames or said droplets at a distance of at least 8 feet.
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) | 1992-04-10 | 1992-10-10 | 1993-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-10 | 1996-10-10 | 1997-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-10 | 2000-10-10 | 2001-04-11 | $7700.00 | Window Closed / Lapsed |