The quick return mechanism is a commonly used principle in shaper and slotter machines. This principle helps to change circular motion into reciprocating movement, which in return moves the ram forward and backward.
Well, in this reading, we’ll explore what a quick return mechanism is, its applications, parts, diagrams, types, advantages, disadvantages, and how it works.
Let’s begin!
What is a Quick Return Mechanism?
In the shaper and slotter machine, a quick return motion mechanism converts circular motion into reciprocating rotation, allowing the slider to move forward and backward.
The cutting process occurs in forward motion, but there is no corresponding cutting in the reverse direction. A quick return mechanism is a device that generates a reciprocating motion in which the return stroke takes less time than the forward stroke.
A circular motion source (usually a motor of some sort) drives a system of links with three turning pairs and a sliding pair. With an offset crank, a quick-return mechanism is a subclass of slider-crank linkage.
Applications of a Quick Return Mechanism
The engineering industry is full of machines with quick return mechanisms. Below are the applications of a quick return mechanism.
- Shaper
- Screw press
- Power-driven saw
- Mechanical actuator
- revolver mechanisms
- rotary combustion internal engine
- air compressor
- mechanical cutter.
Related: What is Shaping Machine? Its Diagram and How it Works
Components of a Quick Return Mechanism
The following are the key components of a quick return mechanism:
- Crank: Attached to the pinion wheel or motor, the crank rotates at a constant angle.
- Slider and Slotted Bar: The slider pivots at the crank’s end. This slider is free to move within the slotter bar. This component is responsible for converting the crank’s circular motion into the slotted bar’s oscillating action.
- Connecting rod: The connecting rod’s job is to transform the slotted bar’s oscillating action into reciprocating motion.
- Ram: The ram reciprocates along the stroke line in a horizontal direction.
Diagram
Types of a Quick Return Mechanism
The following are the various types of quick return mechanisms:
Whitworth Quick Return Mechanism
This device converts the rotating motion to oscillatory motion. This device uses a bull gear with a crank pinion. The connecting rod connects the pin at one end to the ram at the other end of the connecting rod, which slides over the crankpin and into the slot of a crank plate.
The electric motor shaft drives a pinion, causing the gear to rotate. The bull gear now rotates in tandem with the crankpin, and the sliding block moves into the crank plate’s groove. As a result of this operation, the connecting rod causes the ram to travel up and down. View the diagram below:
Crank and Slotted Link Mechanism
Whitworth devised this system in the 1800s. A slider, crank, fixed link, slotted lever, connecting rod, and ram make up the mechanism. The crank connects to the slider and fixed link.
When the cranks begin to rotate, the connecting rod pushes the ram forward and backward. Here, we translate the rotational motion into linear motion.
Shaping machines like slotters and shapers commonly use crank and slotted link mechanisms to create flat surfaces on workpieces. In this mechanism, the return stroke is substantially faster than the forward stroke.
Hydraulic Drive
The hydraulic drive has a reciprocating piston inside the hydraulic cylinder. Between the ram and the piston lies the piston rod. As a result, the piston reciprocates with the ram. There are two entries at the cylinder’s end.
A control valve with four passages is installed below it. A reservoir connects the remaining two entries from the cylinder to the control valve.
How Does a Quick Return Mechanism Work?
According to the above diagram, a quick return mechanism consists of two strokes: forward and reverse.
Forward stroke: The crank ‘B’ must move in a clockwise direction from point ‘B1’ to ‘B2’ for the forwarding stroke. A green dotted line marks the forward path of crank ‘B’ in the diagram above.
The end of the slotted bar goes from ‘P1’ to ‘P2’ in a clockwise motion at the same time and the ram ‘R’ advances from position ‘R1’ to ‘R2.’
Return stroke: The slider ‘B’ rotates clockwise from position ‘B2’ to ‘B1’ during the return stroke. A red dotted line in the diagram above indicates the return path for crank ‘B’.
The slotted bar’s end ‘P’ goes from position ‘P2’ to ‘P1’ in an anticlockwise direction at the same time. In the opposite direction, the ram ‘R’ goes from ‘R2’ to ‘R1’.
Advantages and Disadvantages of a Quick Return Mechanism
Advantages:
The following are some of the advantages of the quick return mechanism:
- During the return stroke, there is rapid movement.
- You can use it to transform rotary motion into reciprocating motion.
- Some machines only perform the material removal operation during the forwarding stroke. Consequently, the faster return stroke reduces the machine’s overall working time.
Disadvantages:
The quick return mechanism has the following drawbacks:
- Because there is no contact with the work during the returning stroke, no cutting occurs, and the operation takes a long time to complete.
- In comparison to the return stroke, the forward stroke takes a long time.
- To carry out operations, additional power is required.
- Friction exists between the slider and the piston.
- The piston will not function indefinitely due to the heat it generates, and wear and tear may occur.
- Balancing the linkage is crucial because this gadget also has links.
Related: What is Slotter Machine? its Diagram and How it Works
Conclusion
The quick return mechanism transforms circular motion into reciprocating motion, enabling the slider to move both forward and backward. The cutting process occurs in forward motion, but there is no corresponding cutting in the reverse direction.
This article covers the definition, applications, diagram, parts, types, working principle, advantages, and disadvantages of quick return mechanisms.