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What is Quick return mechanism?
The Quick return mechanism is the inversion of a single slider crank chain.
The main purpose of this mechanism is to convert the rotary motion of the crank into the reciprocating motion of the ram.
This mechanism has a different velocity of ram in the forward stroke and in reversed stroke.
In this mechanism, the movement of reverse stroke is faster than the forward stroke. The mechanism is generally used in applications where the velocity of the tool at return stroke is not considerable.
Therefore the faster movement of the ram, during reverse stroke helps to reduce the total machining time.
Quick return mechanism diagram:
Components of Quick return mechanism:
The Quick return mechanism consist of the following key components:-
1] Crank: The crank is connected to the pinion wheel or motor and rotates with a uniform angular velocity.
2] Slider & Slotted bar: The slider is pivoted at the end of the crank. This slider moves freely into the slotter bar. This component is used to convert the circular motion of the crank into the oscillating motion of the slotted bar.
3] Connecting rod: The purpose of the connecting rod is to convert the oscillating motion of the slotted bar into the reciprocating motion.
4] Ram: The ram reciprocates in the horizontal direction along the line of stroke.
Construction of Quick return mechanism:
1] As shown in the above figure, the link ‘AC’ is fixed.
2] The crank ‘BC’ is pivoted at the end ‘C’ and rotates with constant angular velocity.
3] The slider ‘B’ is connected at the end of the crank & it rotates along with crank ‘BC’.
4] The slotted lever ‘AP’ is pivoted at the end ‘A’. As the slider ‘B’ reciprocates in a slotted bar, the slotted bar performs oscillatory motion in the circular arc from ‘P1’ to ‘P2’.
5] The one end of connecting rod ‘PR’ is connected to the slotted bar and another end is connected to the ram ‘R’.
6] The ram ‘R’ reciprocates from ‘R1’ to ‘R2’.
Quick return mechanism working:
The working of the Quick return mechanism consists of two strokes:- Forward and Reverse stroke.
Forward stroke:-
- For forward stroke, the crank ‘B’ has to move from point ‘B1’ to ‘B2’ in a clockwise direction.
- In above figure, the forward path of crank ‘B’ is denoted by a green dotted line.
- At the same instant, the end of the slotted bar moves from ‘P1’ to ‘P2’ in clockwise direction.
- And the ram ‘R’ moves from position ‘R1’ to ‘R2’ in forward direction.
Reverse stroke:-
- For return stroke, the slider ‘B’ moves from position ‘B2’ to ‘B1’ in a clockwise direction.
- In above figure, the return path for crank ‘B’ is denoted by a red dotted line.
- At the same instant, the end ‘P’ of the slotted bar moves from position ‘P2’ to ‘P1’ in an anticlockwise direction.
- And the ram ‘R’ moves from ‘R2’ to ‘R1’ in the backward direction.
Quick return mechanism video:
The below video will help you to understand the working of the Quick return mechanism in a better way.
Relation between time for forward stroke and return stroke
1] For the completion of the forward stroke of ram from ‘R1’ to ‘R2’, the slider ‘B’ has to move from position ‘B1’ to ‘B2’ with an angle of ‘β’.
Therefore, we can say that,
Time for the forward stroke = Time to cover angle β by crank
2] For the completion of the return stroke of ram from ‘R2’ to ‘R1’, the slider ‘B’ has to move from ‘B2’ to ‘B1’ with angle ‘α’.
Therefore, we can say that,
Time for the return stroke = Time to cover angle α for the crank.
But from the above figure, as β > α and the crank has constant angular velocity.
Therefore, it can conclude that
Time for forward stroke > Time for return stroke
Now the relation between time for the forward stroke and time for return stroke is given by,
`\frac{\text{Time for forward stroke}}{\text{Time for return stroke}}=\frac{\beta }{\alpha }=\frac{\beta }{360-\beta }`
Quick return mechanism advantages:
The advantages of the Quick return mechanism are as follows:-
- Rapid movement while return stroke.
- It is usefull for conversion of rotary motion in reciprocating motion.
- In some machines, the process of material removal is carried out only in forward stroke. Therfore the faster return stroke helps to minimize total working time of machine.
Quick return mechanism applications:
The quick return mechanism is mostly used in machines where the cutting speed is necessary only in the forward stroke while the speed of the return stroke is not considerable. Some of the applications of the Quick return mechanism are as follows:-
- Shaper machine
- Slotting machine
- Mechanical actuators
- Rotary internal combustion engine
- Mechanical cutter
- Air compressors
- Power saws
FAQ’s:
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What is Quick return mechanism?
The Quick return mechanism is the inversion of a single slider crank chain in which the return stroke is quicker than the forward stroke.
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Where is a quick return mechanism used?
The quick return mechanism is used in the following applications:
Shaper machine, slotting machine, mechanical actuators, mechanical cutter, air compressor, power saw, etc. -
Which machine uses quick return mechanism?
The quick return mechanism is used in the following machine’s:
Shaper machine, slotting machine, mechanical actuators, mechanical cutter, air compressor, power saw, etc. -
What are the quick return motion mechanisms make a list about it?
The mechanisms in which the return strokes are comparatively faster than the forward stroke is known as quick return mechanisms. The different types of quick return mechanisms are Crank and slotted lever mechanism, Whitworth quick return mechanism.
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Why return stroke is faster in quick return mechanism?
In the case of return stroke, for the movement of slotted bar the crank has to complete minimum angular displacement in comparison with forward stroke, therefore the return stroke is faster in quick return mechanism.
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Is quick return mechanism is responsible for Ram movement?
The quick return mechanism is responsible for the ram movement with a comparatively faster return stroke.
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How quick return mechanism is obtained in crank and slotted lever mechanism?
In the crank and slotted lever mechanism, for a forward movement of the slotted bar, the crank has to complete more angular displacement while in return movement of the slotted bar, the crank has to complete less angular displacement. And as the crank rotates with constant angular velocity, the return stroke is completed quicker than the forward stroke.
So, in such a way, we have included all the major points about the Quick return mechanism. Hope you will like this article and if you have any doubts then please put them in the below comment box, we will answer you as soon as possible. So if you found this article helpful don’t forget to share it with buddies through social networks.
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