Design and draw a circuit using the cascade system to operate two

cylinders (A and B) which, on the operation of a start valve, produces the

sequence A – B + B – A+. The cylinders should park in the positions

B – A + when the start switch is in the ‘off’ position

2)

Modify the circuit designed for question 1 to provide an emergency stop

which will park both cylinders in the extended position (i.e. A + B +).

3)

Modify the circuit designed for question 1 to provide a fail safe. The fail

safe should:

(a) act in the event of a reduced pressure at inlet to the group selecting

valve

(b) park the cylinders in the retracted position.