Safety valve for discharge chutes on cement mixer

Claim 1

In combination with a redi-mix concrete truck of the type including a discharge chute positionable by a hydraulic cylinder coupled and in circuit with an hydraulic pump by a hose, a safety device for preventing said chute from dropping upon a failure of said hose comprising a flow responsive valve means coupled between said hydraulic cylinder and said hose, said flow responsive valve means having: (a) a first body member attachable to said hydraulic cylinder and including a longitudinal bore for defining a fluid inlet port and a counterbore defining a cylindrical chamber; (b) a second body member attachable to said hose and sealingly fitted into said counterbore of said first body member; (c) a generally tubular spool disposed in said cylindrical chamber for longitudinal movement, said spool being generally closed at one end except for a fluid passageway of a predetermined small diameter relative to that of said fluid inlet port; (d) a valve seat member disposed in said cylindrical chamber of said first body member and aligned with said fluid passage; and (e) spring means for normally maintaining said one end of said spool out of contact with said valve seat member but permitting movement of said spool against said valve seat member upon a predetermined loss of pressure in said hose; and said valve means being normally opened to permit flow of hydraulic fluid therethrough in the event the flow rate exceeds a predetermined value.