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Q.18. Explain with sketch Whitworth’s quick return Mechanism?

Links: Crank BC

Slotted lever EAD


Frame AB (FIXED)

{Link Es is not part of basic mechanism}

Pairs: Crank BC and frame AB : Turning Pair

Slotted lever EAD and frame AB : Turning Pair

Crank Bc and slider : Turning Pair

Slider and Slotted lever EAD : Sliding pair

Construction : This mechanism is an inversion of single slider crank chain, obtained by fixing the crank of the connecting rod. It has three turning pairs and one sliding pair.

It has crank BC turning about point B. Other end of crank carries a slider, connected with turning pair. The slide fits inside the slotted lever EAD. The slider is free to slide inside the slotted lever. The lever is pivoted at point A. The lever rotates about the point A. End E of this lever is connected to the Ram of the shaper machine.

Working: As the crank starts rotating about the point B. It transmits the motion to the Lever EAD through the slider . As a result the lever EAD starts rotating about the point A. As shown in figure the forward stroke of the ram is slower and return stroke is faster ( Angle theta is greater than angle beta). Hence this mechanism is called quick return mechanism.

Application : This mechanism is used in Shaping machine.