22STAGE POSITION RETAINING DEVICE

摘要

An operation member slidably supported on a base plate has opposed pawls which are spaced apart and project toward one another. A position control cam and an integral supplementary cam are rotatably supported on the base between the two pawls. The pawls are disposed on different planes so that a first pawl is engageable with the control cam and the second pawl is engageable with the supplementary cam. The operation member is spring biased in a direction to move the first pawl toward the position control cam. The position control cam is provided alternately with deep concaves and shallow concaves. When the first pawl of the operation member engages in a deep concave it is in one position. When it engages a shallow concave it is in a second position. The supplementary cam has teeth at positions corresponding to the concaves of the position control cam. When the operation member is slidably moved in a direction opposite to the spring bias, the second pawl engages a tooth of the supplementary cam so as to rotate the supplementary cam and the position control cam to a new position. For example starting with the first pawl in a deep concave, sliding the operation member against the bias spring causes the second pawl to engage a tooth of the supplementary cam and thereby rotate the cams so that when the operation member is released the first pawl engages in a shallow concave of the position control cam and the operation member is thus in a different position.