Quick Return Mechanism

Quick Return Mechanism 


The Quick Return Mechanism is a mechanical system that enables a reciprocating motion where the return stroke is faster than the forward stroke, commonly used in machines like shapers and certain types of presses. This mechanism is widely used in shaping, cutting, and stamping machines, where speed is crucial for increased productivity. By employing a unique arrangement of linkages and gears, the quick return mechanism allows machines to perform tasks rapidly in one direction and then swiftly return to the starting position, significantly reducing the cycle time. 

A quick return mechanism is an engineering mechanism that allows a machine or tool to move rapidly in one direction and then return slowly in the opposite direction. It finds applications in devices like shapers and mechanical presses, enhancing their efficiency and reducing cycle times for various industrial processes, such as metal shaping and cutting.

The quick return motion mechanism finds its application in shaping and slotter machines, facilitating the conversion of circular motion into reciprocating motion. This mechanism enables the slider to move back and forth, with the cutting process occurring during the forward motion while no cutting occurs in the reverse direction. 

It is designed to create a reciprocating motion where the return stroke is completed faster than the forward stroke. The mechanism comprises a system of links featuring three turning pairs and one sliding pair, all driven by a circular motion source, typically a motor. A quick-return mechanism is a specialised type of slider-crank linkage, incorporating an offset crank to achieve its distinctive functionality.


Whitworth Quick Return Mechanism

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Fig 1: Whitworth Quick Return Mechanism

The Whitworth Quick Return Mechanism converts rotating motion into oscillatory motion using a bull gear with a crank pinion. An electric motor shaft drives the crank pinion, and the bull gear rotates in synchronisation with the crankpin. The connecting rod is connected to the ram on one end and slides over the crankpin and into the slot of a crank plate on the other end. This arrangement causes the connecting rod to move the ram up and down during operation.

Crank and Slotted Link Mechanism

crank-and-slotted-link-mechanism

Fig 2: Crank and Slotted Link Mechanism

The Crank and Slotted Link Mechanism, devised by Whitworth in the 1800s, consists of a slider, crank, fixed link, slotted lever, connecting rod, and ram. The crank is connected to the slider and fixed link. When the cranks start to rotate, the connecting rod drives the ram forward and backwards. This mechanism translates rotational motion into linear motion and is commonly used in shaping machines such as slotters and shapers to produce flat surfaces on workpieces. Notably, the return stroke is significantly faster than the forward stroke in this mechanism.

Hydraulic Drive

hydraulic-drive-

Fig 3: Hydraulic Drive

The Hydraulic Drive features a reciprocating piston inside a hydraulic cylinder, with the piston rod positioned between the ram and the piston. As a result, the piston reciprocates along with the ram. The hydraulic cylinder has two entries at its end, connected to a control valve with four passages located below it. The remaining two entries from the cylinder to the control valve are linked through a reservoir. This mechanism utilises hydraulic pressure to drive the reciprocating motion of the ram.

Advantages of Quick Return Mechanism

The Quick Return Mechanism offers several advantages:

  • Rapid Return Stroke: One of the significant advantages of this mechanism is the rapid return stroke, which results in higher productivity and reduced machining time.
  • Conversion of Motion: It efficiently converts rotary motion into reciprocating motion, making it suitable for various applications, such as shaping, slotting, and cutting operations.
  • Reduced Machining Time: Material removal operations occur only during the forward stroke in certain machines. As a result, the faster return stroke reduces the overall working time of the machine, enhancing efficiency.
  • Enhanced Cutting Efficiency: The quick return mechanism ensures a faster return of the cutting tool to its initial position after each cut, leading to smoother cutting operations and improved cutting efficiency.
  • Mechanical Advantage: This mechanism provides a mechanical advantage during the cutting stroke, enabling the machine to exert more force on the workpiece and produce precise and accurate cuts.
  • Simple Construction: The quick return mechanism has a relatively simple construction, making it easier to maintain and operate, reducing downtime and maintenance costs.
  • Versatility: It can be incorporated into various machines, allowing its application in different industries and processes, thus increasing its versatility and practicality.

 

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