Tool driving or impacting – Impacting devices – Hammer head constitutes piston of drive motor
Patent
1998-03-10
2000-08-15
Vo, Peter
Tool driving or impacting
Impacting devices
Hammer head constitutes piston of drive motor
173 1, 173135, 173209, B25D 900
Patent
active
061021334
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pile hammer with a hammering piston and a hammering member guided in a cylinder.
In such prior art pile hammers the unit for providing working gas includes means for feeding fuel and air to the working space. Thus these means produce an explosive mixture in the working space, which is ignited upon the hammering piston falling down.
2. Discussion of Relevant Art
In such known pile hammers the amplitude of the hammering piston can be adjusted by varying the amount of fuel injected into the working space. The impacts exerted by the hammering member onto an object to be hammered into the soil are thus generally harsh.
There are other prior art pile hammers, wherein a hammering piston is lifted by means-of a hydraulic actuator arranged outside of a guiding cylinder, the hammering piston thereafter being allowed to fall freely onto the hammering member. Such softly operating pile hammers are used particularly, where piles and the like must be hammered into soft soil or where production of heavy noise as produced by Diesel type pile hammers cannot be tolerated.
Diesel type pile hammers and hydraulic pile hammers differ considerably already as to their basic structure. If it is desired to obtain at one and the same operating site the advantages of hard or harsh hammering as well as the advantages of soft hammering, both types of pile hammers must be provided. This means considerable expenditures.
SUMMARY OF THE INVENTION
The object of the present invention is to improve a pile hammer such that its mode of operation can be switched between hard hammering and soft hammering.
In accordance with the invention this object is achieved by a pile hammer comprising a cylinder, a hammering piston guided in the cylinder and a hammering member guided in the lower end portion of the cylinder. A lower end face of the hammering piston forms an upper axial end wall, an upper face of the hammering member forms a lower axial end wall and the cylinder forms a circumferential wall of a variable working space. At least two different controllable working gas supply units and activating means to selectively activate one of said controllable working gas supply units to intermittently pressurize the working space are provided.
The pile hammer in accordance with the present invention can be supplied with pressurized working gas from at least two different working gas supply units, which working gas will lift the hammering piston arranged in the cylinder due to expansion of the working gas. Such a working gas supply unit is of simple structure as compared to the structure of a pile hammer, and consequently the invention allows for considerable savings as compared to simultaneous provision of two different types of hammers. Furthermore, it is possible to switch from one mode of operation to the other one during operation of the pile hammer and during pile-driving of one and the same pile. Thus one can take account in simple manner of the different properties of the soil encountered in different depths without the need of modifying or replacing the hammer.
If one of the working gas supply units is chosen to be a pressure air accumulator a particularly soft and careful way of pile-driving is obtained, when this working gas supply unit is activated. Provision of such a working gas supply unit on a Diesel type pile hammer requires only few and low cost additional structural features. A compressor for feeding the pressure air accumulator is normally available on construction sites anyway.
The pile hammer includes the following advantageous features: the pressure air accumulator is arranged immediately adjacent to the cylinder and connected thereto by means of a short connecting member having at least one control opening co-operating with a control member of a servo valve and being part of the valve means and activated by the activating means. This improvement of the invention is advantageous in that the pressure air accumulator can instantaneously discharge into
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Mewes Stefan
Ranft Eberhard
Scheid Winfried
Calve James
Delmag Maschinenfabrik Reinhold Dornfeld GmbH & Co.
Vo Peter
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