Control arrangement for a hydraulically operated device

A control arrangement comprising a hydraulically operated cylinder and piston unit having a cylinder and a piston reciprocable therein for raising a load during feeding of hydraulic fluid into said cylinder of the unit, and lowering a load during discharge of said fluid therefrom, said arrangement further comprising a source of hydraulic fluid under pressure;

• an outlet conduit leading to a tank;
• an inlet conduit connected to said source;
• first valve means connected to said inlet conduit and movable between a first position connecting said inlet conduit with said outlet conduit and a second position connecting said inlet conduit with working conduit means leading to said cylinder of the unit;
• precontrol valve means coordinated with said first valve means for controlling the position thereof, said precontrol valve means having a return terminal connected to a return conduit leading to said tank and inlet terminal means leading over said first valve means to said source;
• second valve means in said working conduit means including a release piston movable between a first position directing flow of fluid through said working conduit means to said cylinder of the unit and a plurality of second positions permitting flow of fluid from said cylinder to said return conduit, said second valve means including a damping compartment and a control compartment on opposite sides of said releasing piston;
• passage means connecting said damping compartment to said return conduit and conduit means connecting said control compartment to said precontrol valve means;
• and a throttle in said return conduit, said return terminal of said precontrol valve means being connected to a point of said return conduit located downstream of said throttle so that upon increase of outflow of fluid from said cylinder the pressure in said damping compartment rises and said second valve means being constructed to decrease outflow of fluid from said cylinder as the pressure in said damping compartment rises, whereby the speed of lowering of the load will be independent of the magnitude of the load.