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A hydraulic percussive machine, for example a jack hammer or a rock drill, has an accumulator with a flexible diaphram (35). A lift valve (40, 41, 42) closes the outlet of the accumulator if the flow exceeds the normal flow substantially and it traps a volume of oil between the diaphragm and the val

A hydraulic percussive machine, for example a jack hammer or a rock drill, has an accumulator with a flexible diaphram (35). A lift valve (40, 41, 42) closes the outlet of the accumulator if the flow exceeds the normal flow substantially and it traps a volume of oil between the diaphragm and the valve when it closes.

대표청구항 ▼

A hydraulically operated percussive machine comprising: a cylinder; pump means coupled to said cylinder and having means for supplying pressurized hydraulic fluid thereto; piston hammer means arranged to reciprocate by a drive stroke and a return stroke in said cylinder for impacting upon an anvil m

A hydraulically operated percussive machine comprising: a cylinder; pump means coupled to said cylinder and having means for supplying pressurized hydraulic fluid thereto; piston hammer means arranged to reciprocate by a drive stroke and a return stroke in said cylinder for impacting upon an anvil means, and including a drive chamber and a return chamber; an accumulator coupled with the cylinder including therein a diaphragm separating an accumulator chamber from an accumulator pressure gas chamber, said accumulator chamber having an inlet/outlet passage, a high pressure side of the hydraulic fluid being in communication with said inlet/outlet passage, said return chamber, and a first valve means; said first valve means subjected to differential pressure communicating said high pressure side of the hydraulic fluid and said inlet/outlet passage with the drive chamber during said drive stroke, and communicating said drive chamber with a low pressure side of the hydraulic fluid during said return stroke; second valve means between said accumulator chamber and said inlet/outlet passage for maintaining communication therebetween in its open position and for at least substantially blocking communication therebetween in its closed position; and piston means coupled with said second valve means and subjected to differential pressure between, on the one hand, said inlet/outlet passage and, on the other hand, said low pressure side of the hydraulic fluid, said differential pressure being directed to keep said second valve means in its open position during both the drive stroke and the return stroke when the percussive machine is operated in a normal reciprocating mode under supply of high pressure fluid to said inlet/outlet from said pump means, and for automatically allowing said second valve means to move to its closed position in advance of said diaphragm due to decrease of said differential pressure and increased outward flow from said accumulator chamber when supply of high pressure hydraulic fluid from the pumping means is terminated.