US4445773A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exposure indicator
Assignee: Individual
•
Filing: 1982-09-29
•
Granted: 1984-05-01
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Expires: 2002-09-29
Abstract
Abstract An exposure indicator for photographic plate makers including a comparator having a control input, an inverting input and an output; a light emitting diode having its anode connected to the control input for developing a reverse bias signal at said control input in response to illumination from the plate maker light source whereby an output comparator signal is generated when the control input signal exceeds a reference signal at the comparator's inverting input; the output signal forward biasing the light emitting diode to its light emitting state and also fed back to the control input to maintain the light emitting diode in such emitting state; and vacuum operated switch means to provide power to the indicator circuit in response to vacuum actuation of the plate maker flexible blanket.
Inventors
- 👤 William B. Birkett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:20
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/74
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
117 words
In photographic plate makers of the type having a bed for supporting unexposed films or plates; a source of illumination for exposing said films or plates; the improvement of indicator means supported on said bed for signaling that an exposure has taken place, comprising: comparator means for developing an output signal when a first input thereto exceeds a predetermined value; a light emitting diode responsive to illumination from said source for developing a reverse current flow to provide said first signal and forward biased by said output signal to cause emission of radiation therefrom; and said output signal providing feedback to said first input to maintain the light emitting diode in a forward biased, light emitting state.
Claim 2
Dependent Claim
117 words
In photographic plate makers of the type having a bed for supporting unexposed films or plates; a source of illumination for exposing said films or plates; the improvement of indicator means supported on said bed for signaling that an exposure has taken place, comprising: comparator means for developing an output signal when a first input thereto exceeds a predetermined value; a light emitting diode responsive to illumination from said source for developing a reverse current flow to provide said first signal and forward biased by said output signal to cause emission of radiation therefrom; and said output signal providing feedback to said first input to maintain the light emitting diode in a forward biased, light emitting state.
Claim 3
Dependent Claim
14 words
The improvement according to claim 1, wherein: said comparator means comprises an operational amplifier.
Claim 4
Dependent Claim
37 words
The improvement according to claim 1, wherein: a source of vacuum leading to said plate maker; and switch means for applying power to said indicator means and actuable to a closed position by said source of vacuum.
Claim 5
Dependent Claim
82 words
An exposure indicator for photographic plate makers or the like, comprising: comparator means for developing an output signal when a first input thereto exceeds a predetermined value; a light emitting diode responsive to illuminating for developing a reverse current flow to provide said first input signal and forward biased by said output signal to cause emission of radiation therefrom; and said output signal providing feedback to said first input to maintain the light emitting diode in a forward biased, light emitting state.
Claim 6
Dependent Claim
82 words
An exposure indicator for photographic plate makers or the like, comprising: comparator means for developing an output signal when a first input thereto exceeds a predetermined value; a light emitting diode responsive to illuminating for developing a reverse current flow to provide said first input signal and forward biased by said output signal to cause emission of radiation therefrom; and said output signal providing feedback to said first input to maintain the light emitting diode in a forward biased, light emitting state.
Claim 7
Dependent Claim
14 words
The indicator according to claim 4, wherein: said comparator means comprises an operational amplifier.
Claim 8
Dependent Claim
18 words
The indicator according to claim 4, further comprising: vacuum operated switch means for supplying power to said indicator.
References Cited (Backward Citations)
US4111549A
Cited
US4286171A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-05-01 | 1987-10-31 | 1988-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-01 | 1991-10-31 | 1992-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-01 | 1995-10-31 | 1996-05-01 | $7700.00 | Window Closed / Lapsed |