Tool driving or impacting – Processes
Patent
1993-06-01
1995-06-27
Smith, Scott A.
Tool driving or impacting
Processes
173 91, 173128, 173132, 173 17, F21D 902, F16L 1036
Patent
active
054271878
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a hammer driven by a pressure medium, especially compressed air, a method for adjusting and securing the strength of blow of the hammer, and a method of using the hammer for tunnel drilling in which the hammer is in the working pit at all times during drilling.
BACKGROUND OF THE INVENTION
Previously known, i.e., from Finnish patent application No. 895057, is a method of forcing tandem cylinders into soil by means of a hammer in the working pit. In the method, a conventional, non-rotatable hammer is used. The cylinders can only penetrate soft and granular soil, such as man-made road embankments.
Hammers are known as devices which direct the blows towards a tool while drivers are devices which drive the whole hammer in the direction of blow. Typically, these machines are used for working downwards, such that the hammer functions by means of gravity in all situations if operating in other directions, it is necessary to provide for a counterforce for the hammer so that there will be no stoppage because of dead travel.
In forcing cylinders into soil by means of a hammer, the first cylinder of which has the function of a tool, the disadvantage is that the forward movement stops if a large stone is hit, which cannot give way to the inside or outside of the cylinder. The forward movement can be stopped even by small rock walls which tend to change the direction if the cylinders are not rotated. The disadvantage of conventional hammers is the stopping of blows during operation. This is especially true at the first stage upon starting to force the cylinders into soil when they penetrate easily and there is no counterforce for the hammer, thereby causing the strokes to stop and disturb operation.
SUMMARY OF THE INVENTION
With a hammer and a method for securing and adjusting the strength of blow and use of a hammer for tunnel drilling according to the invention, crucial improvements have been reached on the above described disadvantages.
The most valuable improvement of the invention is the fact that the hammer functions under all conditions and the strength and frequency of its blow can be adjusted according to soil qualities without adjusting the feed pressure of the medium, and by rotating the hammer the tunnel can be drilled with a rotating tube system built of tandem cylinders penetrating the soil by means of hammer blows. Since the frequency of the hammer blows can be adjusted, the rotating cylindric tool can advance even in rock and crush stones when the optimum stone-crushing frequency is selected.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention is described in detail with reference to the enclosed drawings, in which
FIG. 1 is the cross-section of a hammer;
FIG. 2 is an alternative hammer construction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a hammer with a detachable tool 1. Piston 6 in cylinder 7 strikes spindle 22 which transmits the stroke to front side 2 of spindle and to the tool. There is a notch 25 in the piston matching bushing 26 in spindle 22. When the piston hits bushing 26, the access into channel 27 of pressure medium escaping into the front of the piston 6, is prevented and in front of the piston 6 pressure starts to generate, throwing the piston 6 back to the other end of cylinder 7. Travel of stroke is maintained by this function. Value 8 does not allow entrance of further pressure into the cylinder while the piston is striking and reversing. In spindle front space 2 a shell 3 is fastened by threads and moves with spindle 22 and the tool 1. The working cylinder 7 is fixed by screws 5 to guiding part 4. The return system of the hammer requires that the piston 6 hits the spindle 22 at a distance. If, for instance, the spindle has moved as much as a dead stroke or, because of lack of counterforce, to its extreme position, then the piston 6 does not reach the spindle 22 at the right moment necessary for the piston 6 to reverse and the hammer stops.
In order to avoid this, in the outer shell 3 a circular cha
REFERENCES:
patent: 4650374 (1987-03-01), Schmidt
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