Quick return mechanism

A quick return mechanism is an apparatus that converts circular motion (rotating motion following a circular path) into reciprocating motion (repetitive back-and-forth linear motion) in presses and shaping machines, which are utilized to shape stocks of metal into flat surfaces, throughout mechanical engineering. The quick return mechanism is the foundation behind the energy of these machines.

The mechanism consists of an arm attached to a rotating disc that moves at a controlled uniform speed. Unlike the crank, the arm of the mechanism runs at a different rate than the disc. By having the disc run at a different rate than the attached arm, productivity increases because the amount of time needed for a cut is reduced. The design of this mechanism specializes in vector calculus and the physical aspects of kinematics (study of motion without the effects of forces) and dynamics (study of forces that affect motion).

During the early-nineteenth century, cutting methods involved hand tools and cranks, which were often lengthy in procedure. Joseph Whitworth changed this by creating the quick return mechanism in the mid-1800s. Using kinematics, he determined that the force and geometry of the rotating joint would affect the force and motion of the connected arm. From an engineering standpoint, the quick return mechanism impacted the technology of the Industrial Revolution by minimizing the duration of a full revolution, thus reducing the amount of time needed for a cut or press.

Quick return mechanisms are found throughout the engineering industry in different machines:

All mechanisms are formed upon the combination of two gears, where one drives the force of the other. The disc influences the force of the arm, which makes up the frame of reference of the quick return mechanism. The frame continues to an attached rod, which is connected to the circular disc. Powered by a motor, the disc rotates and the arm follows in the same direction (linear and left-to-right, typically) but at a different speed. When the disc nears a full revolution, the arm reaches its furthest position and returns to its initial position at a quicker rate, hence its name. Throughout the cut, the arm has a constant velocity. Upon returning to its initial position after reaching its maximum horizontal displacement, the arm reaches its highest velocity.

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