# US 4,396,269 A · Shutter release locking device

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,396,269 A
- Document ID: US4396269A
- Status: Granted
- Kind: A
- Application number: 06/256,305
- Filed: 1981-04-22
- Granted: 1983-08-02
- Earliest claimed: 1980-05-09
- Assignees: Nippon Kogaku K.K.
- Inventors: Sakuji Watanabe
- Web page: https://patentgrep.com/patent/US4396269A

## CPC

- G03B 7/26: Power supplies; Circuitry or arrangement to switch on the power source; Circuitry to check the power source voltage
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A camera comprises an automatic exposure control device having a comparing circuit adapted for comparing a time output signal indicating the time from the shutter aperture opening function with a proper output signal indicating an appropriate exposure time and for releasing a comparison signal when a determined relationship is reached between said output signals, and solenoid means adapted for blocking the shutter aperture closing function when energized and being deactivated in response to the comparison signal to cancel the blocking; and a shutter release locking device having a voltage detecting circuit adapted for deactivating the solenoid means prior to the shutter aperture opening function when the power supply voltage becomes lower than a determined limit level, and blocking means for prohibiting the shutter aperture opening function in response to the deactivation of the solenoid means prior to the shutter aperture opening function. The shutter release locking device comprises a limiter circuit for supplying a signal of a determined level instead of the proper output signal to the comparing circuit thereby enabling to obtain the comparison signal therefrom in case the proper output signal exceed a determined level.

## Claims

### Claim 1

In a camera comprising means for generating a first signal of a level corresponding to an apprpropriate exposure time;
means for generating a second signal in synchronization with initiation of exposure effected by a shutter, the level of said second signal changing from a predetermined level in response to elapse of time;
means for generating a third signal when the level of said first signal and the level of said second signal reach a predetermined relationship;
means for completing exposure in response to said third signal, the exposure completing means locking the shutter when said third signal is generated prior to the initiation of the exposure; and
means for locking said shutter when power supply voltage becomes lower than a determined limit level, the improvement comprising:
the first signal generating means including means for detecting the level of said first signal prior to the initiation of the exposure, and means for limiting the level of said first signal to a predetermined value which prevents an initial completion of said determined relationship when the detected first signal exceeds a value which would cause an initial generation of said third signal.

### Claim 2 (depends on 1)

A camera according to claim 1, wherein said locking means includes means for changing the relative level of said first signal and said second signal in order to complete said determined relationship between the level of said first signal and the level of said second signal when the power supply voltage becomes lower than said determined limit level.

### Claim 3 (depends on 1)

A camera according to claim 1, wherein said limiting means limits the level of said first signal to a level corresponding to the minimum exposure time which is controllable by said shutter.

### Claim 4 (depends on 1)

A camera according to claim 1, wherein said limiting means include means for generating a fourth signal having said predetermined level, means for comparing said first signal and said fourth signal, and means for supplying selectively said first signal and said fourth signal to said third signal generating means in response to said comparing means.