1] Whitworth quick return mechanism is the inversion of a single slider crank chain.
2] Single slider crank chain consists of three turning pairs & one sliding pair.
3] The main aim is to converts rotary motion into reciprocating motion but reversed stroke is quicker in comparison with forwarding stroke.
4] The name states itself that the forward stroke is slower as it is power stroke while return stroke is quick as it is idle stroke.
5] The Whitworth quick return mechanism is generally used in shaper machines & slotting machine in which forward stroke is slower for machining purposes & return stroke is faster as there is no machining process is to be done.
History :-
It is invented by British manufacturer Joseph Whitworth in 1840.
Construction :-
Whitworth quick return mechanism is consists of the following components:-
1] Crank:- The crank rotates with uniform angular velocity. It gets power from a pinion wheel or motor.
2] Slotted bar & Slider:- It is a bar with a slot for guiding a slider into it. The slider is connected to the end of the crank. The slotted bar is pivoted at a fixed origin. Its other end is connected to the connecting rod.
3] Connecting rod:- The aim of connecting rod is to converts the rotary motion of the end of the slotted bar into reciprocating motion.
4] Ram:- The ram reciprocates in the horizontal direction. The shaper or slotting tool is mounted onto the ram.
Whitworth-quick-return-mechanism
1) As shown in the above figure, link AC is fixed.
2) Crank AB rotates about origin A with uniform angular velocity.
3) The slider b is mounted at end of crank AB which slides into the slotted bar.
4) Slotted bar is pivoted at C & rotates about point C.
5) At the end of the slotted bar, connecting rod is attached which converts rotary motion to reciprocating motion.
6) The ram is connected at the end of the connecting rod. The ram reciprocates & has a cutting tool mounted on it.
Whitworth quick return mechanism working :-
Whitworth quick return mechanism working consists of two strokes:-
1] FORWARD STROKE:-
For forward stroke, the crank AB is moves from B2 to B1 in a clockwise direction.
At the same time point, X on connecting rod moves from B1 to B2 in a clockwise direction & the ram move in forward direction from Y1 to Y2.
[ The movement of forward stroke is shown in the figure with a green dotted line ]
For forward stroke crank AB has to complete angle α.
2] RETURN STROKE:-
For return stroke, the crank AB is move from B1 to B2 in a clockwise direction.
At the same time, the point X on connecting rod moves from B2 to B1 in a clockwise direction & the ram moves in a reversed direction from Y2 to Y1.
For reversed stroke, crank AB has to complete angle β.