GB1211757A - Improved machine for digging trenches - Google Patents

Abstract

1,211,757. Endless chain excavators. J. R. CRAMPTON. 1 May, 1968 [2 May, 1967], No. 20679/68. Heading E1F. In a trench-excavating machine having digging tools mounted on endless chains circulating about a vertically swingable boom pivoted on a crawler track-mounted chassis all the movements of the operable parts of the machine are hydraulically controlled and the hydraulic circuitry involved is such as to permit of automatic regulation of the movements of said parts in accordance with any variation in operating conditions encountered by the machine. The hydraulic actuators of said parts are motors 29, 30 for driving the tracks 31, 32 of the machine, motors 5, 6 for driving the endless chains, motors 88, 89 for driving an endless belt ejector provided in the machine for ejection clear to one side of the machine of material dug up by digging tools mounted on the endless chains, jacks 82, 83 controlling the vertical position of the telescopic boom and a jack 68 for maintaining a desired tension on the endless chains during extension or contraction of the boom. The circuitry is such that there is, where the machine is digging, automatic regulation of the low speed advance of the machine in accordance with the resistance to digging encountered by the machine. The parts of the circuitry then involved are a small output pump 28, a distributor 33, a flow regulator 34 dividing and directing flow from the pump to either the motors 29, 30 through distributor 35 and/or to the supply circuit of motors 5, 6 through valve 52 and distributors 10, 12. The regulator 34 involves a throttle valve, the setting of which is determined by the pressure in the supply line 8 coupling the motors 5, 6 as this pressure is a measure of the resistance encountered by the digging tools. For faster traversal of ground when the machine is not digging the motors 29 and 30 are powered from two pumps or a duooutput pump 3, 4 of large capacity through distributors 9, 10. When the machine is digging power from these pumps is solely directed through the distributors 9, 10, 11 and 12 to the motors 5, 6. When the digging load on the motors 5, 6 approaches the available power from the prime mover 1 driving the pumps 3, 4, 28 and 10 of the circuitry a regulator in the feed circuit of the motor 6 directs the flow to this motor to the reservoir of the circuitry so that the hydraulically shunt-connected motors apply more torque at a lesser speed of rotation to the endless chains. Pump 100 drives ejector motors 88, 89. Overload valves are provided in all parts of the circuitry.