Patent ID: 6017015
Filing Date: 2000-01-25
Classification: B66F,F15B

Abstract:
A magnetically operated drain valve of an electrohydraulic lifting module, in particular for stacker trucks, comprising a closing element, which in a closing direction, seats on a main valve seat (S) located between a load pressure on a load pressure side (A) and a drain pressure on a drain pressure side (B), and which in an opening direction is actuatable by said drain pressure and in said closing direction by a variable difference between said drain pressure and a control pressure derived from said load pressure, said closing element being reciprocally movable against said main valve seat into a closing position and away from said main valve seat to open said main drain valve seat, comprising a pilot valve (C) which is operable by means of said magnet (6) and is arranged in a control chamber (27) of a closing element (G) for controlling the magnitude of said control pressure, comprising a throttle (28) located between said control chamber and said load pressure side (A), and a closing member (26) of said pilot valve which is adjustable by said magnet against a spring (22), said closing member being actuable by said magnet against said spring acting either in the closing adjustment direction or in the opening adjustment direction, characterized in that said spring is a spring (22) having a steep characteristic curve (36a,36b) in order to achieve a ramp function for said drain valve, and that said closing element (G) and said main valve seat (S) form a lift-dependent flow-quantity adjusting device (E) composed of a conical surface (31), a cylindrical slide protrusion (32) plunging into said main valve seat (S) and a seat edge (14), a cylindrical slide bore section (15) which extends from said seat edge (14) towards the side of said pressure drain and which cooperates with said slide protrusion (32) with a gap (35), at least over an initial lifting portion from said closing position of said closing element (G).