GB1421878A - Hydraulic system with selectively actuable shock absorbing means for a motor therein - Google Patents

Abstract

1421878 Hydraulic systems CATERPILLAR TRACTOR CO 2 May 1974 [2 May 1973] 19377/74 Heading F1P [Also in Division F2] An hydraulic system comprises shock absorbing accumulators 48, 49 which are selectively connectable via a lock valve 10 with jacks 12, 13 subject to a load. The lock valve 10 comprises check valves 52, 53 located between lines 42, 43 leading to jacks 12, 13 and lines 50, 51 leading to accumulators 48, 49. Each ball of the check-valves 52, 53 is movable off its seat by a piston 56, 57 actuable by pressure transmitted to a chamber 59 between the pistons. Such pressure is selectively applied by a solenoid-operated pilot valve which in one position connects chamber 59 to drain as shown via line 69 and in its other position connects the output from a pump 15 to the chamber 59 to urge pistons 56, 57 away from each other. The jacks 12, 13 are brought to a fixed position by operation of conventional control means comprising control.valves 18 leading from pump 15 and to reservoir 16 via lines 20, 21 and 22, 23 respectively, lock valves 26 serving to hold the load in a fixed position if the check-valves 52, 53 of lock valve 10 are also closed. However, valves 52, 53 can be opened to permit the jack pistons to move from the fixed position when, for instance, the jacks are being used in earth working implements such as a grader blade of a grading machine which might encounter large obstacles, the accumulators 48, 49 thus permitting retraction of the jacks in such a case. Lock valve 10 and pilot valve 66 may be replaced by a pair of simultaneously operable solenoid valves Fig. 2 (not shown).