Patent ID: 8553309
Filing Date: 2013-10-08
Classification: G03B

Abstract:
1. A blade speed adjustable mechanism of a focal plane shutter, the mechanism comprising: a board having an opening; a shutter blade opening or closing the opening; a drive lever supported by the board and bringing the shutter blade into an overlapped operation or an expanded operation; a biasing member engaging the drive lever and biasing the shutter blade in an overlapped direction or in an expanded direction; a ratchet member engaging the biasing member and having a plurality of ratchet teeth, wherein the plurality of ratchet teeth includes at least a first ratchet tooth and a second ratchet tooth, wherein a phase of the first ratchet tooth differs from a phase of the second ratchet tooth by a distance corresponding to one-third of a pitch of a tooth portion of the first ratchet tooth; an engagement member holding the ratchet member at a desired stop position and adjusting a biasing force of the biasing member by changing the stop position, wherein: the engagement member has a plurality of pawl portions different from each other in length; the plurality of pawl portions engage the plurality of ratchet teeth to hold the ratchet member at the stop position; a difference in length between the pawl portions is shorter than a distance corresponding to a pitch of the plurality ratchet teeth; the ratchet member rotates about an axis; the plurality of pawl portions is arranged in a direction of the axis, and is integrally formed in the engagement member.