Patent ID: 7073803

Claim:
A spring suspension for a working machine, comprising: a suspension cylinder subjected to varying load pressures and having a piston side and a rod side; piston side and rod side suspension reservoirs connectable to said piston side and said rod side, respectively; a locking device selectively connecting said piston and rod suspension reservoirs to said piston side and said rod side, respectively, and locking the suspension, said locking device having a piston locking switching valve with base position blocking fluid flow from said piston side to said piston side suspension reservoir and opening fluid flow to said piston side from said piston side suspension reservoir and having a rod locking switching valve with base position blocking fluid flow from said rod side to said rod side suspension reservoir and opening fluid flow to said rod side from said rod side suspension reservoir; a pressure supply to maintain required system pressure; an equalization device having a piston side equalization switching valve and a rod side equalization switching valve being part of a supply device selectively connecting said piston side and said rod side to said pressure supply to actuate said piston side and said rod side; a load monitoring unit connected to said locking device and said piston side suspension reservoir by a branch line and an opening control line with a openable non-return valve; piston and rod non-return valves spring biased to closed positions thereof in lines connecting said supply device to said piston and rod side suspension reservoirs, respectively, and opening against spring biasing in directions of the respective suspension reservoirs, each of said piston and rod, side suspension reservoirs being connected by lines to the respective side of said suspension cylinder between the respective locking switching valve and the respective non-return valve; and an openable valve in said branch line extending from a line between said piston locking switching valve and said piston side.