Patent ID: 7401467

Claim:
Pump assembly for the lift cylinder of a hand fork-lift truck with the following characteristics: A piston pump ( 24 , 80 ), which is activated by a bar on the hand fork-lift truck and has a piston chamber ( 26 , 86 ) and an annulus collector ( 28 , 88 ), a three stage control valve ( 14 , 130 ), which in a lowered lift cylinder ( 10 ) position connects with a tank ( 18 ), in a neutral piston chamber ( 26 , 86 ) setting connects with a tank and in a pump setting connects the piston chamber ( 26 , 86 ) through a first check-valve ( 56 ) with the lift cylinder ( 10 ) and through a second check-valve ( 58 ) with the tank, a third check-valve ( 40 ) between the piston chamber and the annulus collector ( 26 , 28 ), which opens up to the piston chamber, a reversing valve ( 42 , 98 ) between the piston chamber and the annulus collector ( 26 , 28 , 86 , 88 ), which has its valve element pressed into the closed position by a spring ( 48 , 102 ) and on the opposite side is pressed by the pressure of the piston chamber ( 26 , 86 ) whereby the valve element ( 98 ) of the reversing valve ( 42 , 98 ) opens if the pressure in the piston chamber ( 26 , 86 ) achieves a certain predefined value, whereby the valve element ( 98 ) seals on the side of the spring ( 48 , 102 ) and is pressed against with a standard constant pressure.