Tool driving or impacting – Impacting devices – Hammer head constitutes piston of drive motor
Patent
1996-09-20
1999-03-02
Smith, Scott A.
Tool driving or impacting
Impacting devices
Hammer head constitutes piston of drive motor
173 17, 173212, 173128, B25D 912
Patent
active
058758577
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field Of The Invention
This invention relates to an accumulator charging system for a hydraulically operated rock drill.
2. Description of The Related Art
In a hydraulically operated rock drill kinetic energy of a reciprocating piston is converted to hydraulic energy on a return stroke and stored in one or more hydraulic accumulators by opening an operating valve as the piston moves to a limiting position.
The high pressure hydraulic fluid is passed through the valve behind the piston during the return stroke. The kinetic energy of the returning piston causes the pressure of the fluid to rise behind the piston and in a high pressure oil feed line.
The piston continues on its return stroke until the piston kinetic energy and the hydraulic energy are equalized. The kinetic energy is transformed to hydraulic energy which is stored in the hydraulic accumulator which is thereby charged with a certain volume of pressurized oil.
When the piston has fully retracted its kinetic energy is zero. At this point, on the high pressure hydraulic side, the constant flow of incoming pressurized oil and the charged accumulator contain substantial energy The accumulator has a charging area behind the piston which is the same as the accelerating area. As stated the accumulator is connected to the high pressure oil inlet side.
Problems encountered with the aforementioned arrangement include the following: hydraulic inlet power is fairly low, for example of the order of from 0,55 to 0,65; the temperature of the rock drill and operating oil. The hot oil returning from the drill to a tank must be cooled before being pumped back to the drill. Oil cooling is a major problem, especially in a hot environment. If the temperature of the cooling air or water is close to the acceptable oil temperature, large coolers must be used. The cooling medium heats up the working environment; sufficient operating energy to the rock drill. substantial and expensive.
BRIEF SUMMARY OF THE INVENTION
The invention provides a hydraulically operated rock drill which includes a cylinder, a piston which is mounted for reciprocating movement in the cylinder, a hydraulic fluid line which is connected to the cylinder, and an accumulator, and which is characterized in that a chamber with a section of reduced dimensions is formed in the cylinder, in that the piston includes an annular formation which moves within the chamber and into and out of the section as the piston reciprocates, the accumulator being connected via a port to the section, and in that the hydraulic fluid line is connected to the chamber and is in communication with the accumulator when the annular formation is out of the section and which is cut off from the accumulator, by the annular formation, when the annular formation moves in to the section, the annular formation then pressurizing hydraulic fluid in the section whereby hydraulic energy, produced by kinetic energy developed over at least part of a return stroke of the piston, is stored in the accumulator.
Preferably the hydraulic fluid line is a high pressure line.
In one form of the invention a second accumulator is connected at least to the high pressure line.
The rock drill may include a further accumulator and an operating valve which is adapted to open as the piston moves to a limiting position on its return stroke thereby to store hydraulic energy, derived from the kinetic energy of the piston, in the further accumulator.
The invention is further described by way of example with reference to the accompanying drawing which illustrates from the side and partly sectioned a portion of a hydraulically operated rock drill according to the invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a partial cross-section view of a portion of a hydraulically operated rock drill with an accumulator charging system representing the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The accompanying drawing illustrates a portion of a rock drill 10 according to the invention which includes a front cylind
REFERENCES:
patent: 4179983 (1979-12-01), Wallace
patent: 4676323 (1987-06-01), Henriksson
patent: 4852663 (1989-08-01), Hunt
patent: 5056606 (1991-10-01), Barthomeuf
patent: 5392865 (1995-02-01), Piras
patent: 5479996 (1996-01-01), Jonsson et al.
Briggs Roger Robarts
Leppanen Jarmo Uolevi
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