When cam 1 rotates about fixed axis O, lever 2, turning about fixed axis E and having valve member 4 at one end, brings member 4 into contact with one or the other hollow plunger 3, depending upon the position of cam 1. The pertinent plunger 3 is shifted and chambers A and D (or A and D') are disconnected, and chambers D and B (or D' and B') are connected together. If chambers D and D' are connected to the atmosphere, then piston 5, travelling in cylinder 6 whose ends are connected to chambers B and B', is in equilibrium. If a vacuum is set up in chambers D and D', and with lever 2 in the position shown, piston 5 moves to the left because a vacuum is set up at the left end of cylinder 6. The right end is connected through a pipeline and hollow plunger 3 to chamber A and, consequently, to the atmosphere. The motion of piston 5 shifts the gears. When valve member 4 closes upper plunger 3, piston 5 moves to the right.
$3978$LHP,FD$