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United States Patent [w]
Scheid et al.
US006102133A [ii] Patent Number: 6,102,133  Date of Patent: Aug. 15,2000
 Inventors: Winfried Scheid, Ebersbach; Stefan Mewes, Satuelle, both of Germany; Eberhard Ranft, Houston, Tex.
 Assignee: Delmag Maschinenfabrik Reinhold Dornfeld GmbH & Co., Germany
 Appl. No.: 09/000,322
 PCT Filed: Aug. 6, 1996
 PCT No.: PCT/EP96/03470
§ 371 Date: Mar. 10, 1998
§ 102(e) Date: Mar. 10, 1998  PCT Pub. No.: WO97/07293
PCT Pub. Date: Feb. 27, 1997
 Foreign Application Priority Data
Aug. 11, 1995 [DE] Germany 195 29 538
 Int. C I. B25D 9 00
 U.S. CI 173/208; 173/1; 173/135;
 Field of Search 173/1, 2, 135,
173/137, 206, 208, 114, 209, 207; 175/19;
123/179.31, 46 H; 405/228, 232
 References Cited
U.S. PATENT DOCUMENTS
2,755,783 7/1956 Kupka 173/209
3,721,095 3/1973 Chelminski 173/2
4,007,803 2/1977 Airhart 173/135
4,096,916 6/1978 Hennecke 173/137
4,100,977 7/1978 Elliott 173/207
4,109,475 8/1978 Schnell 173/2
4,131,164 12/1978 Hague 173/1
4,580,641 4/1986 Holland 173/209
Primary Examiner—Peter Vo
Assistant Examiner—-James Calve
For selective operation in a Diesel mode and a pressure air mode a Diesel type pile hammer is additionally equipped with a pressure air accumulator, which is connected to the working space of the cylinder by a servo valve.
19 Claims, 1 Drawing Sheet
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 10 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 15 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 20 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 25 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.
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 40 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 45 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 50 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 55 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 60 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 65 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 the cylinder of the pile hammer under small throttling of the air. This is advantageous in view of rapid and effective acceleration of the hammering piston.
The pile hammer includes the following advantageous features: the control member is formed as a control plate and the connecting member comprises a plurality of parallel connection passageways. If the servo valve arranged between the pressure air accumulator and the cylinder is designed in accordance with this improvement, there is a high cross section for fluid flow, while the control member of the servo valve is exposed to small flexural loads, only.
The pile hammer includes the following advantageous features: the valve means comprise at least two servo valves, which are sequentially moved from their closing into their opening positions, and that one of the servo valves which is first moved into its open position is connected to a first region of the working space lying beneath a second region of the working space which is connected with that one of the servo valves which is moved into its open position at a later time. In a pile hammer in accordance with this improvement the hammering piston will first be accelerated from its rest position by opening a servo valve associated to a lower connection of the working space. The hammering piston will then later be exposed to the main portion of the pressure air contained in the pressure air accumulator by opening a further servo valve. This is advantageous in view of optimum lifting of the hammering piston.
The pile hammer includes the following advantageous features: a fluid driven actuator of that one of the at least two servo valves, which is moved into its open position at a later time is pressurized via a restriction. This improvement of the invention provides in a simple way for time delayed actuation of the servo valve associated to the upper feed connection of the cylinder.
The pile hammer includes the following advantageous feature: a check valve blocking fluid flow towards the actuator is connected across the restriction. In a pile hammer in accordance with this improvement the pressure fluid can flow out of the actuator associated to the servo valve without being restricted. Thus this servo valve can be rapidly closed after the desired acceleration of the hammering piston has been effected.
The pile hammer includes the following advantageous features: the servo valve actuator is a single acting fluid motor, which is biased into one end position by means of a spring, and a working line connected to this fluid motor in addition to the first restriction controlling the delay in the opening movement of the servo valve comprises a second restriction controlling discharge of working fluid, a check valve opening towards the fluid motor being connected across the second restriction. In a pile hammer in accordance with this improvement closure of said servo valve can be delayed in controlled manner without modifying its opening movement.
The pile hammer includes the following advantageous features: the actuator is connected to the outlet of a still further servo valve, through which a lowermost portion of the working space is connected to the pressure air accumulator. In accordance with this improvement the synchroni- 5 zation of the two servo valves, which control supply of pressure air to axially spaced position of the cylinder of the pile hammer, is obtained in a particularly simple way.
The pile hammer includes the following advantageous features: the still further servo valve comprises two coun- 1Q teracting fluid driven actuators, one of which being active in the opening direction is formed with a larger pressure exposed surface and receives the full pressure prevailing in the pressure air accumulator, while the other of these actuators, which acts in the closing direction receives only part of the pressure prevailing in the pressure accumulator and is assisted by a spring mechanically connected in parallel thereto. If the main control servo valve is designed in accordance with the above improvement and is connected to the other components as denned in this improvement, a fluidic multivibrator circuit controlling cyclic operation of the pile hammer in the pressure air operating mode is obtained in a simple way.
The pile hammer includes the following advantageous feature: the other of the two counteracting fluid driven 2J actuators is pressurized via an adjustable pressure regulator. In connection with this improvement the amplitude of the hammering piston can be adjusted.
The pile hammer includes the following advantageous features: in its rest position the still further servo valve 30 connects its working port to a pressure relief line and in that a connection line extending between its working port and the cylinder includes a check valve opening towards the cylinder. In a pile hammer in accordance with this improvement air can be discharged from the actuator of the servo valve 35 associated to the upper pressure air feed position to the surrounding atmosphere, when the rest position of the servo valve is established, it being warranted, that no pressurized gas can flow back from the working space of the pile hammer to the servo valve. The pile hammer includes the 40 following advantageous features: a feed port of the pressure air accumulator is connected to a feed side of a compressor via a check valve opening towards the pressure air accumulator.
The pile hammer includes the following advantageous 45 features: one of the working gas supply units comprise a fuel trough formed in the upper end face of the hammering member and the lower pressure fuel injection unit to inject a volume of fuel into the fuel trough in response to movement of the hammering piston. In a pile hammer in accor- 50 dance with the improvement an operating mode 'harsh Diesel hammering' can be selectively established, wherein the fuel is injected into a fuel trough, which is formed in the upper end face of the hammering member.
The pile hammer includes the following advantageous 55 features: the working gas supply units comprise a high pressure fuel injection unit, which will discharge an amount of fuel into the lower portion of the working space, which amount of fuel is atomized under high pressure, injection of the fuel being effected in response to the movement of the 60 hammering piston. In a pile hammer in accordance with the improvement an operating mode 'soft Diesel hammering' can be selectively established by actuating a high pressure fuel injection unit, which will discharge fuel into the working space, which is atomized under high pressure. 65
The pile hammer includes the following advantageous features: the working gas supply units each comprise at least
one servo component by dint of which they can be selectively activated, and the control terminals of the different servo components are connected to the activating means, which in accordance with a selected position of a selecting switch will provide an activating signal for one of the servo components at a single of its output terminals at a given time, only. In a pile hammer in accordance with claim 16 there are positive means warranting that only one of the working gas supply units is activated at a given time.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail by way of a preferred embodiment thereof and referring to the enclosed drawings. Therein the only
FIG. 1 is a schematic representation of a pile hammer, which can be operated in pressure air mode and in one of two different Diesel modes, respectively, some of the components being shown in section.
DETAILED DESCRIPTION OF PREFERRED
The pile hammer shown in the drawings has a cylinder 10, the lower end of which slidably receives a hammering member 12. The latter includes an upper piston portion 14, the upper end face of which is formed with a fuel trough 16. A intermediate cylinder portion 18 of the hammering member 12 is guided in an opening 20, which is formed in a lower end plate 22 of the cylinder 10. The intermediate portion 18 carries an exteriorly dish shaped massive hammering portion 24 having a convex curved lower end face.
The upper portion of the cylinder 10 guides a hammering piston 26 comprising a lower piston portion 28, an upper piston portion 30 as well a an intermediate piston portion 32 of somewhat reduced diameter. The lower end face of the piston portion 28 carries a projection 34 of small axial dimension, which is adapted to engage into the fuel trough 16.
The cylinder 10 is formed with a working slot 36, through which the pile hammer will take in air and discharge used working gas (detended pressure air and exhaust gases, respectively, when operating in a pressure air mode and in a Diesel mode, respectively). The wall of the cylinder further carries two fuel injection units 38, 40, which are only schematically shown and are fit into the wall of the cylinder. The fuel injection units comprise actuating levers 42, 44 co-operating with the circumferential surface of the hammering piston 26. Nozzles of the fuel injection units 38, 40 not shown in detail in the drawings provide a fuel jet 46 and a fuel spray 48, respectively.
The fuel jet 46 is provided by the fuel injection unit 38 under low pressure and is directed in such manner, that it will be collected in the fuel trough 16. Upon the hammering piston 26 falling down the fuel present in the fuel trough will then be atomized into the air which is heated by compression thereof.
The fuel spray 48 is discharged by the fuel injection unit 40 under high pression and is directly introduced into the compressed hot air. Thus in the high pressure injection mode combustion will be started at an earlier time (referring to the lower end position of the hammering piston) than in the low pressure injection mode. This results in the fact of the impact obtained upon the hammering piston 26 hitting the hammering member 12 will be somewhat softer. In the low pressure injection mode the mixture will be ignited only after harsh impact of the hammering piston 26 onto the hammering member 12.