A motion conversion device including a body, a first double-acting cylinder movable along a first axis and a second double-acting cylinder movable along a second axis angled relative to the first axis. The body includes several bores which form a closed circuit and house the first and second double-acting cylinders. Movement of the first double-acting cylinder along the first axis hydraulically or pneumatically pushes the second double-acting cylinder along the second axis. Also disclosed is a valve incorporating a motion conversion device with angled double-acting cylinders for moving a closure member between an open position and a closed position, and a method for opening and closing a valve by way of angled double-acting cylinders.