Tool driving or impacting – Impacting devices – Hammer head constitutes piston of drive motor
Patent
1995-12-28
1998-02-17
Hail, III, Joseph J.
Tool driving or impacting
Impacting devices
Hammer head constitutes piston of drive motor
173112, 173207, 173208, 91290, 91303, B25D 904
Patent
active
057182973
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a hydraulic impact hammer, particularly for advancing objects in the ground.
From patent DE 30 23 538 C2, a hydraulic impact hammer having the features of the precharacterizing part of claim 1 is known. This impact hammer has a pressure gas reservoir connected to the rear chamber of the working cylinder, the gas chamber of said pressure gas reservoir being closed by a membrane upon the outside of which the hydraulic fluid contained in the rear chamber of the working cylinder acts. The rear chamber is connected to a supply line via an inflow line including a pressure-controlled valve. Further, the rear chamber is connected to a control means via a second line in order to reverse the control body of the control means into that state in which the control means causes the return stroke of the working piston. Therefore, the second line is a pure pressure control line through which no pressure fluid is transported. The pressure-controlled valve connects the rear chamber of the working cylinder to the supply line when the working piston has reached its forward end position. During the return stroke of the working piston, the pressure in the rear chamber increases. If this pressure exceeds a determined value, then the pressure-controlled valve will connect the rear chamber with the return line. Thus, pressure fluid is pumped by the working piston and a certain exchange of the fluid quantity contained in the rear chamber is effected. The main portion of the impact energy is applied by the pressure gas reservoir. Because pressure fluid is drained off the rear chamber of the working piston when the pressure in this rear chamber has reached its maximum value, a portion of the pressure energy gets lost, whereby the efficiency of the impact hammer deteriorates.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a hydraulic impact hammer with which the ratio of impact energy to power consumption is improved.
In the impact hammer according to the invention, the rear chamber is completely sealed off when the working piston leaves its forward end position until the rearward return point is reached, and preferably until the working piston has reached its forward end position again. A particular advantage lies in that no pressure energy gets lost. It is true that an increased pressure force has to be expended for the return stroke of the working piston, this additionally expended energy, however, is recovered when the pressure gas reservoir relaxes. Then, the oil displaced by the return stroke surface of the working piston is supplied to the pressure supply system again, so that the hydraulic pressure energy consumption of the impact drilling hammer altogether is not higher than that of an impact drilling hammer without pressure gas reservoir. Nevertheless is the impact energy obtained with the aid of the pressure gas reservoir substantially greater than with a system without pressure gas reservoir. The pressure-controlled valve makes sure that a defined pressure prevails in the rear chamber of the working cylinder at the beginning of the return stroke. In the course of the return stroke of the working piston, this pressure continuously increases because the working piston moves into a completely sealed-off system from which no pressure fluid escapes. Therefore, no energy losses occur, except for frictional losses. Further, it is achieved that the pressure gas reservoir raises a defined braking energy for the return stroke, the braking force continuously increasing with the return stroke path of the working piston without any pressure impacts or shocks occurring.
During the impact operation, the hydraulic fluid sealed in the rear chamber of the working cylinder heats up. In order to avoid an excessive heating of this pressure oil, the rear chamber is suitably connected to an inflow line and an outflow line, which are only open for causing an oil flow through the rear chamber when the working piston is near its forward end position. In this state, the
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patent: 5134989 (1992-08-01), Akahane
patent: 5279120 (1994-01-01), Sasaki
patent: 5392865 (1995-02-01), Piras
Hail III Joseph J.
Klemm Guenter
Stelacone Jay A.
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