Patent ID: 7610823

Claim:
A mechanism for causing linear motion, comprising: a first ratchet bar, having a first end and a second end defining an oscillatory axis therebetween; an oscillator, the first ratchet bar being mounted to the oscillator for linear oscillatory motion of a substantially fixed distance along the oscillatory axis but varying sign in a direction along the oscillatory axis, the first ratchet bar having a plurality of portions evenly spaced a first spacing which is less than the fixed distance, each of the plurality of portions defining a first pawl engaging structure and a second opposed pawl engaging structure, wherein the first pawl engaging structures are evenly spaced the first spacing along the first ratchet bar, and the second pawl engaging surfaces are also spaced the first spacing along the first ratchet bar; a first additional portion of the first ratchet bar between the plurality of evenly spaced portions and the first end, wherein the first additional portion has a spacing from an adjacent one of said plurality of evenly spaced portions which is either less than the first spacing, or has at least one first or second pawl engaging structure which is spaced less than the first spacing from an adjacent first or second pawl engaging structure of one of the evenly spaced portions; a second additional portion of the first ratchet bar between the plurality of evenly spaced portions and the second end, wherein the second additional portion has a spacing from an adjacent one of said plurality of evenly spaced portions which is either less than the first spacing, or has at least one first or second pawl engaging structure which is spaced less than the first spacing from an adjacent first or second pawl engaging structure of one of the evenly spaced portions; a pawl pivotally mounted to a piece of equipment, the equipment mounted for linear motion in a direction along the first ratchet bar, the pawl having first portions arranged to engage the first pawl engaging surfaces for motion in a positive direction along the oscillatory axis of the first ratchet bar, and the pawl having second portions arranged to engage the second pawl engaging surfaces for motion in a direction opposite the positive direction; wherein the first additional portion and the first ratchet bar first end are arranged to cooperate to reverse the pawl from a position which engages the first pawl engaging structures to a position which engages the second pawl engaging structures; and wherein the second additional portion and the first ratchet bar second end are arranged to cooperate to reverse the pawl from a position which engages the second pawl engaging structures to a position which engages the first pawl engaging structures.