Quick Return Mechanism…Sounds interesting isn’t it…Yes it is!! But before diving in the depths of the Quick Return Mechanism, let us first understand what exactly is a mechanism….
Mechanism
A mechanism is a system in engineering that converts input forces and movement into the desired collection of output forces and movement. Mechanisms are made up of moving parts, such as gears and levers.
- Belt and chain drives; Gears and gear trains
Followers and cams
Connections;
Brakes and clutches are instances of friction devices.
A frame, fasteners, bearings, springs, or lubricants are illustrations of structural components.
Splines, pins, as well as keys are illustrations of machine elements.
So now that we exactly know what mechanisms are…lets dive into the topic of the Quick Return Mechanism…..
A simple return mechanism or what we call as a Quick Return Mechanism is a device that generates a reciprocating motion in which the return stroke takes less time than the forward stroke. It uses a system of links with three turning pairs and a sliding pair to be powered by a circular motion source (typically a motor of some sort).
A quick return mechanism is one that produces a reciprocal effect, causing the system to take less time in the return stroke while especially in comparison to the forward stroke. A circular movement, such as the crank and lever mechanism, is converted into a reciprocal movement in the quick-return mechanism, but the return time differs from the forward moment.
This method is being used in a wide range of applications. Shaper, slotter, screw-press, mechanical drive, and so on are a few illustrations. With the assistance of a quick return mechanism, the time required for cutting is reduced.
Quick Return Mechanism Varieties
Quick Return Mechanism by Whitworth
Hydraulic DriveCrank and Slotted Link Mechanism
Whitworth Quick Return mechanism
The rotary motion is converted into oscillatory motion here. The bull gear and a crank pinion are being used in this mechanism.
The connecting rod connects the pin at one end and the ram at the other end of the connecting rod, that further slides over the crankpin and slides inside the slot of a crank plate.
The shaft of an electric motor drives the pinion which rotates the bull gear. The bull gear has a crank pinion. A sliding block slides over this crank pin and slides inside the slot of a crank plate. A connecting rod connects the pin at one end and ram at the other end.
When the pinion rotates, the bull gear is also rotated along with the crank pin. At the same time, the sliding block slides on the slot provided on the crank plate. This makes the ram to move up and down by the connecting rod.
Crank And Slotted Lever Mechanism
The ram in this mechanism is actuated by gear drives driven by an electric motor drive system. The electric motor first drives the pinion gear. The pinion gear then drives the bull gear, which rotates in the opposite direction as a result of external gear meshing. On the bull gear, there’s also a radial slide. On this slide, a sliding block has been assembled.
The block can be positioned in radial direction by rotating the stroke adjustment screw.
A crank pin is situated on the sliding block. This crank pin is freely fitted with something like a rocker arm. The rocker arm sliding block slides into a slot in the rocker arm known as a slotted link. The upper end has a fork that is pin-connected to the ram block, while the bottom end of the rocker arm pivots.
When the pinion gear rotates with the bull gear, the crank rotates as well. As a result, the rocker arm sliding block rotates in the same circle. The sliding block slides up and down in the slot at the very same time. This movement is transferred on to the ram, that reciprocates. As a consequence, rotary motion is converted to reciprocating motion.
Hydraulic Drive
A piston reciprocates within the hydraulic cylinder. A piston rod is connected between the piston and the ram. As a result, the ram reciprocates in tandem with the piston. There are two entries, one at each end of the cylinders. A four-way control valve connects these two entries with the fluid reservoir.
The reservoir is connected to the valve with the help of a drain pipes and a supply pipe.
A pump and relief valve connect the supply pipe to the reservoir yet again. The lever and trip dog attached to the ram execute the valve. The gear pump draws oil from the reservoir at a specific pressure. The four-way valve directs this high-pressure oil to the cylinder.
The oil allowed from the pump is guided to the left side of the piston, triggering the piston to move the ram to the right (R). It is regarded to as a forward or cutting stroke. Throughout this stroke, oil flows out of the reservoir’s right side entry through the use of the four-way valve and drain pipe. At the end of this stroke, the lever hits one trig dog.
The lever position has now been altered. As a consequence, the supply pipe supplies oil to the right side of the piston, triggering the ram to move to the left, a practice called as the return stroke or nan-cutting stroke. The high pressure oil covers a smaller area of the cylinder during this stroke. As a result, the pressure force will increase. As an outcome, by supplying the same amount of oil, this return stroke is faster.
Conclusion
Visual Graphics tend to explain the topic in a better way. The descriptive pictures tend to explain the important concept of understanding one of the most important mechanism in use: The Quick Return Mechanism, in a simple manner.
I would like to thank my group members Shrutish Gadakh, Sanket Dhut, Shrushti Fuley and Dhruv Bansal for their immense contribution in developing a simple way to generate this blog for the understanding of each and every one, in a simple, yet descriptive manner.
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