Patent ID: 6098647
Filing Date: 2000-08-08
Classification: F15B,Y10T

Abstract:
A hydraulically controllable load-holding brake valve, in particular for a double-acting consumer, which on one end, its load end, is subject to an external load, having the following characteristics:a control chamber (2) is disposed in a valve housing (1);the control chamber comprises chamber segments, preferably arranged in alignment, specifically in this order:pilot chamber (15);annular chamber (70), which communicates via connection B with the lowering line (25) of the consumer (26);return chamber (73), which communicates via connection A with the return line (27) to the tank;opening chamber (21), which communicates with a control conduit (X); between the annular chamber and the return chamber, a valve seat (5) with a central opening is disposed in the control chamber (2) in stationary fashion on the valve housing (1), by way of which opening the connection bores A and B can be connected;the valve seat is closed and opened by a main piston (3);the main piston (3) is embodied as a stepped piston and has the following:a thin piston collar, which with the cylindrical wall of the control chamber (2) forms the annular chamber (70), a sealing face (4) on the thin piston collar, which is oriented toward the valve seat and cooperates with the valve seat (5),a thick piston collar which is guided sealingly on the wall of the control chamber between the annular chamber and the pilot chamber and divides the two from one another;the main piston is axially displaceable in the control chamber (2) by means of pressure imposition on the return chamber (73) or the annular chamber (70) in the direction of lifting away from the valve seat (4) and by means of pressure imposition on the pilot chamber (15) in the direction of closure of the valve seat;the pilot chamber (15) can be connected via a compensation throttle (14) to both the annular chamber (70) and connection B and, via a pilot conduit (34) having a pilot valve seat (6) in the main piston (3), with the return chamber (73) and connection A;the pilot conduit with the pilot valve seat (6) is closeable by means of a closing element, the pilot piston 8, guided concentrically to the pilot conduit (34), with its sealing face (7) by means of pressure imposition in the pilot chamber (15) and preferably the force of a closing spring (12) and can be opened in the opposite direction by a pilot tappet (9), which pilot tappet (9) is guided with play in the pilot conduit (34) and protrudes into the return chamber (73);an opening piston (20) is axially guided in the opening chamber (21) and is displaceable in the direction of the return chamber (73) by pressure imposition on the opening chamber (21) and in the opposite direction by an opening spring (24);the opening piston (20) has an opening shank (19), oriented counter to and coaxially with the pilot tappet (9), which shank protrudes with one end, the opening end (16), into the control chamber (2) and upon axial displacement of the opening piston (20) counter to the force of the opening spring (24) acts upon the pilot tappet (9) and the pilot piston (8) in the direction of opening,characterized in thatthe pilot tappet (9), over its length and beginning at the seat face (7) of the pilot piston (9), has at least the following longitudinal regions:first, a region (142) of maximal cross section, which is guided with minimal play (throttle gap) relative to the pilot conduit (34),then an adjoining throttling region (143), which over its length, with its cross section, forms a throttle gap relative to the pilot conduit (34), which gap begins at the throttle gap of the maximal cross section and then increases steadily, preferably progressively, at least over a partial length (144) of the throttling region (143);then a region (146) of minimal cross section;that preferably the pilot tappet (9) is firmly connected to the pilot piston (8);that the active area (45), acted upon by the control pressure, of the opening piston (20) is in a ratio to the active area of the pilot valve seat (6) of greater than 50:1, preferably greater than 100:1, and that preferably the ratio of the end face (45) of the opening piston (20) to the end face (44) or active area (74) on the opening end (16) is greater than 30:1 and in particular greater than 60:1;that the throttle cross section (throttle restriction 36), which the pilot tappet (9) forms with the pilot conduit (34), is smaller in all the opening positions of the pilot piston (8) than the opening cross section formed between the pilot valve seat (6) and the sealing face (7) of the pilot piston (8); andthat the maximal throttle cross section that the pilot piston (8) forms with the pilot conduit (34) is larger than the flow cross section of the compensation throttle (14).