GB1416494A - Extended reach mechanism and truck - Google Patents

Abstract

1416494 Luffing arm apparatus CLARK EQUIPMENT CO 25 Jan 1973 [27 Jan 1972] 3819/73 Heading B8H The extended reach mechanism of a truck comprises a pair of members 30 (32), Fig. 4 (not shown) which are pivotal at their lower ends by means of a respective hydraulic ram 90, an arm structure 44 pivotally attached to the upper ends of the members 30 and pivotally carrying an upright 60 which supports a fork lift attachment 70 for movement therealong, the arm structure 44 being movable relative to the posts 30 by means of a pair of hydraulic rams 100 (one of which is shown), the arrangement being such that after the mechanism has raised a load located on the attachment 70 by extending the rams 100 and the truck is driven to a location where the load is to be deposited at a height above ground level, then as the members 30 are rotated to the left in Fig. 2 by retracting the rams 90 a control mechanism in the hydraulic circuit of the rams is effective to cause extension of the rams 100 thus maintaining the movement of the arm structure 44 and attachment 70 substantially in a horizontal plane, and similarly on rightward rotation of the members 30 the rams 100 are retracted. Each of the rams 90, 100 are controlled respectively by valves 130, 158, Fig. 5, through which fluid is fed to the said rams by a pump 124 from a sump 126 and the control mechanism comprises a ram 186 whose piston 192 is connected to the arm structure 44 by a rod 190, the ram cylinder being connected by a rod 188 to a valve 182 which controls fluid flow from a further pump 210 to the ram 100, the lower end of the valve 182 being connected to the truck frame 24 by a rod 184. While the valve 130 is operative to control the ram 90, the valve 158 is rendered inoperative, and when the valve 130 is inoperative fluid flows to the valve 158 and in addition, passes from its supply line 160 along a line 206 to open check valves 202, 204 so that the opposite sides of the piston 192 are in fluid communication through lines 196, 198, 200 so that as the arm structure is raised and lowered the piston 192 is freely movable up and down in the ram 186. However, when the valve 130 is operative to cause rotation of the member 30, the valve 158 is inoperative as stated previously, and thus the check valves 202, 204 are closed which means that the ram 186 and the rods 188, 190 act together as a rigid link, with the result that the rotation of the members 30 causes the said linkage to move and thus operate the valve 182 which permits fluid to flow between the further pump 210 and the ram 100 to cause extension and retraction of the said ram which maintains the movement of the arm structure 44 and attachment 70 substantially in a horizontal plane.