# US 4,395,105 A · Device for adjusting driving spring of focal plane shutter

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- Number: US 4,395,105 A
- Document ID: US4395105A
- Status: Granted
- Kind: A
- Application number: 06/336,497
- Filed: 1981-12-31
- Granted: 1983-07-26
- Earliest claimed: 1981-01-13
- Assignees: Canon Kabushiki Kaisha
- Inventors: Michio Senuma
- Web page: https://patentgrep.com/patent/US4395105A

## CPC

- G03B 9/18: More than two members
- 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 device for adjusting a focal plane shutter driving spring includes a ratchet wheel which holds one end of the shutter driving spring and is arranged to adjust the driving force of the spring by the rotation thereof. The ratchet wheel is provided with a ratchet part having fine teeth arranged to engage a ratchet pawl and a gear part having relatively coarse teeth.

## Claims

### Claim 1

A shutter mechanism including a shutter, a shutter driving spring and an adjusting device for adjusting said shutter driving spring, comprising:
a ratchet wheel capable of adjusting the driving force of said shutter driving spring, said ratchet wheel consisting of a ratchet part which has fine teeth and a gear part which has relatively coarse teeth, said gear part being arranged to engage the gear of an automatic adjuster; and
a ratchet pawl which keeps the ratchet wheel stationary by engaging the teeth of the ratchet part, said ratchet pawl being arranged to be disengaged from one of the teeth of the ratchet part and to come into engagement with another tooth of the ratchet part to consequently have the driving force of said spring adjusted when the automatic adjuster is actuated with the gear thereof engaged with said gear part of the ratchet wheel.

### Claim 2 (depends on 1)

A mechanism according to claim 1, wherein said ratchet part is arranged to be rotatable in either of two directions.

### Claim 3

A shutter mechanism including a shutter, a shutter driving spring and an adjusting device for adjusting said shutter driving spring, comprising:
a driving member for driving said shutter;
a shaft of said driving member, said shaft being arranged to have said driving member rotatable thereon;
said shutter driving spring being wound around said shaft with one end thereof retained by said driving member;
a ratchet wheel which is capable of adjusting the driving force of said spring, said ratchet wheel being rotatably disposed on said shaft and having a ratchet part which is provided with fine teeth and a gear part which is provided with relatively coarse teeth, said ratchet part being arranged to retain the other end of said spring, and said gear part being arranged to engage a gear of an automatic adjuster; and
a ratchet pawl which keeps the ratchet wheel stationary by engaging the teeth of the ratchet part, said ratchet pawl being arranged to be disengaged from one of the teeth of the ratchet part and to come into engagement with another tooth of the ratchet part to consequently have the driving force of said spring adjusted when the automatic adjuster is actuated with the gear thereof engaged with said gear part of the ratchet wheel.

### Claim 4 (depends on 3)

A mechanism according to claim 3, wherein said ratchet wheel is shaped into two parts, one part being said ratchet part and the other said gear part.