is correspondingly rotated and since the upper square end of spool 80 is fitted snugly within the square opening 71 in valve element 70 valve element 70 is also correspondingly rotated this moves the valve element 70 from the neutral or off position shown in fig6 and 7 to the close jaws position shown in fig7 a in the neutral or off position pressurized hydraulic fluid is applied through hose 110 to the in port 42 this fluid pressure is applied through port 45 cross duct 44 and port 46 to out port 43 and then through hose 111 back to the source of pressurized fluid when however valve element 70 is rotated clockwise from the off position shown in fig7 to the close jaws position shown in fig7 a the ports 45 and 46 at the ends of the cross duct 44 become covered by the solid material of the disc valve element 70 while ports 47 and 48 become exposed in the circumferential slots 72 and 73 respectively thus fluid communication is established between in port 42 and port 47 and also between port 48 and out port 43 as a result pressurized hydraulic fluid flows through in port 42 valve slot 72 port 47 duct 147 in manifold 40 fig5 and down fluid duct 38 in piston rod 30 this fluid discharges into lower chamber 22 in cylinder 20 located below piston head 35 since piston rod 30 and piston head 35 are fixed against movement by lift.