Loading tool control apparatus for loading vehicles

Claim 1

A loading tool control apparatus for use with a loading vehicle, said apparatus comprising: a lift arm having its front end hinged to a lower portion at the rear of the loading tool and its rear end hinged to a main body of the loading vehicle for swinging thereabout to raise and lower the loading tool; a tilting cylinder mechanism having its one end attached to a center portion of said lift arm by means of a holding member and the other hinged to an upper rear portion of the loading tool, said tilting cylinder mechanism including a cylinder, front and rear pistons slidably accommodated in said cylinder for defining front, intermediate and rear cylinder chambers, and front and rear piston rods respectively secured to said front and rear pistons, the foremost end of said front piston rod forming the one end of said tilting cylinder mechanism and the rear end of said cylinder forming the other end of said tilting cylinder mechanism for controlling tilt of said loading tool; a boom cylinder mechanism having its one end hinged to the main body of the loading vehicle and the other hinged to that portion of said lift arm which is positioned close to the main body of the loading vehicle, for raising and lowering said lift arm; a level cylinder mechanism having its one end hinged to the main body of the loading vehicle and the other hinged to a central portion of said lift arm and extendible and contractible in response to rise and fall of said lift arm; an oil pump for supplying oil to said tilting, boom and level cylinder mechanisms; an oil reservoir in fluid communication with said oil pump; and an oil pressure change-over valve assembly interposed between said tilting and level cylinder mechanisms and said oil pump and oil reservoir and formed with first and second oil ports, the front cylinder chamber of said tilting cylinder mechanism and a front cylinder chamber of said level cylinder mechanism being in fluid communication with each other by way of an oil conduit and with the first oil port of said oil pressure change-over valve assembly, the intermediate cylinder chamber of said tilting cylinder mechanism being in fluid communication with the second oil port of said oil pressure change-over valve assembly by way of an oil conduit, the rear cylinder chamber of said level cylinder mechanism and the rear cylinder chamber of said tilting cylinder mechanism being in fluid communication with each other by way of an oil conduit, and the front and rear pistons and the front and rear piston rods of said tilting cylinder mechanism being concurrently brought into sliding movement by contact therebetween in the cylinder of said tilting cylinder mechanism in response to the extension and the contraction of said level cylinder mechanism. whereby the loading tool is maintained horizontal during the raising and lowering of said lift arm.