GB1421177A - Hydraulically operated excavators and the like - Google Patents

Abstract

1421177 Hydraulic control circuits CATERPILLAR TRACTOR CO 13 Dec 1972 [13 Dec 1971] 57579/72 Heading F1P [Also in Division E1] An excavator 10 has a hydraulic control circuit comprising two pumps 42, 44 supplying hydraulic fluid, respective distributer valves 54, 68, 70, 58 for directing fluid from the pumps 42, 44 to respective translation motors 18, 20, from pump 44 to control motor 36 for jib 32 and from the pump 42 to control motor 30 for boom 28, and at least one control valve additional to said distributer valves for combining fluid from both pumps 42 and 44 at the inlet of one of the distributer valves 58 or 70 to operate the associated motor 30 or 36 in at least one direction. Valves 68, 70 are connected in series, and valves 54, 58 are connected in series with a valve 56 between them for directing fluid to a motor 38 for implement 34. A further valve 80 controlling a slow motor 82 for platform 22 may be supplied from a separate pump 76, or may be connected between the valves 68, 70 to supply the motor 82 from the pump 44, Figs. 5-7 (not shown). The valves are controlled by manually operated pilot valves fed from a pilot fluid line 86; alternatively, (Fig. 7), the main valves may be operated manually. Fluid passing through all the valves of a respective series is vented to a return line through valves 62, 74, unless a manuallyoperated pilot valve 148 is actuated. In this case if the boom control motor 30 or the jib control motor 36 is being operated in a given direction, then fluid from the pilot line 86 will pass through the valve 148 to close valve 74 or 62 respectively, causing fluid to back up through check valve 154 or 160 and be available to valve 58 or 70 to operate the motor in question. Alternatively, Figs 3, 6 (not shown) the function of the manually operated pilot valve 148 may be performed automatically by a shuttle valve (212). Or the two valves 62, 74 may be replaced by a single valve (216), (Figs. 4, 7) which moves with the valve 70, so that when the valve 70 is in its neutral position fluid is available to valve 58, while when the valve 70 is operated in either direction it may receive fluid through a check valve in line (228).