棘轮

棘轮包括一个带齿的圆形齿轮或线性齿条，以及一个被称为棘爪的弹簧驱动的旋转手指。牙齿是均匀但不对称的，每颗牙齿在一个边缘上具有中等斜率，另一个边缘在另一个边缘上具有更陡峭的斜率。
When the teeth are moving in the unrestricted (i. e. forward) direction, the pawl easily slides up and over the gently sloped edges of the teeth, with a spring forcing it (often with an audible 'click') into the depression between the teeth as it passes the tip of each tooth. When the teeth move in the opposite (backward) direction, however , the pawl will catch against the steeply sloped edge of the first tooth it encounters, thereby locking it against the tooth and protecting against any further motion in that direction.
反弹
因为棘轮只能在离散点（即，在牙线边界）处仅停止向后运动，所以棘轮确实允许有限量的向后运动。该向后运动 - 限于等于齿之间的间隔的最大距离 - 被称为间隙。在必须最小化间隙的情况下，有时使用平滑，无齿轮棘轮，其中有诸如橡胶的高摩擦表面。棘爪以一定角度抵靠表面以确保任何向后运动将使棘爪堵塞在表面上，从而防止任何进一步的向后运动。由于向后行程距离通常是高摩擦表面可压缩性的函数，因此该机构可能导致急剧减少的间隙。