METHOD FOR SECURING AND ADJUSTING THE STRENGTH OF BLOW OF A HAMMER, APPLICATION OF A HAMMER IN TUNNEL DRILLING AND HAMMER

Abstract: A method for securing and adjusting the strength of blow in a hammer operated by compressive pressure medium, comprised of a working cylinder (7) with a to-and-fro moving percussion piston (6) and a head (2) striking blows on a drilling object and moving with respect to the working cylinder in direction with the blows. From the blow transmitting head (2) a firm connection is formed by means of an outer shell (3) with one of the circular chamber (20) walls, which can move by pressure with respect to each other and through moving these walls with respect to each other by means of pressure directed to said chamber (20) the effect of piston (6) stroke on spindle (22) can be adjusted.

Description: METHOD FOR SECURING AND ADJUSTING THE STRENGHT OF BLOW OF A HAMMER, APPLICATION OF A HAMMER IN TUNNEL DRILLING AND HAMMER The invention relates to a hammer driven by a pressure medium, especially compressed air, a method for adjusting and securing the strength of blow and using a hammer for tunnel drilling, whereby the hammer is all the time during drilling, in the working pit. Previously known, a.o. from the Finnish patent application No. 895057, is enforcement of tandem cylinders into soil by means of a hammer in the working pit. In the method a conventional not-rotatable hammer is used. The cylinders cannot penetrate any other but soft and granular soil, such as man-made road embankments. Hammers are known as ones directing the blows towards a tool in their head and others driving the whole hammer in the direction of blow, i.e. so called drivers. Typical for these machines are that they are used either for working downwards, whereat the hammer funtions by means of gravity in all situations or, 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 the stopping of the forward movement if hit upon a larger stone, which cannot give way neither 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 present hammers is the stopping of blows during operation, especially at the first stage upon starting to force the cylinders into soil when they penetrate easily. Then there will be no counterforce for the hammer and the strokes may stop and disturb operation. 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 improvments 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 strenght 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. In the following the invention is described in detail with reference to the enclosed drawing, in which Fig. 1 is the cross—section of a hammer Fig. 2 is an alternative hammer construction Figure 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 with bushing 26 in spindle 22. When the piston hits bushing 26, the access into channel 27 of pressure medium escaping from front of piston, is prevented and in front of piston pressure starts to generate, throwing the piston back to the other end of cylinder 7. Travel of stroke is maintained by this function. Valve 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 moving with spindle 2 and the tool. The working cylinder 7 is fixed by screws 5 to guiding part 4. The return system of the hammer requires that the piston hits the spindle at a certain distance. If, for instance, the spindle has moved as much as a dead stroke or, because of lack of counterforce, to its extreme position, the piston does not reach the spindel at the right moment necessary for the piston to reverse and the hammer stops. In order to avoid this, in the outer shell a circular chamber 20 within walls 28 and 29 is formed. In leading pressure through opening 21 from the piston front space to this chamber, the spindle and working cylinder are forced to come closer to each other between strokes. By this means the return travel of piston and uninterupted striking frequency are secured. Working pressure is led to the hammer along tube 9 in the cylinder head there is a pressure distributing shut-off device 8. In the hammer head there is a soil penetrating cylinder 2 fastened to tool 1 with a conical compression connection. From piston front pressure can be led into cylinders 24, for instance through boring 27 in spindle 2. Thereby pressure is used as helping means for strokes in emptying soil material from cylinders. This requires that the hammer is fixed to cylinder 24 by appropriate strong means. Also with hammer not in function, soil can be emptied from cylinder 24, whereat cone 1 functions as shut-off plate at cylinder beginning and pressure medium is directed through hammer into the cylinder, whereby soil material is swept out by pressure medium flow from the other end of the cylinder. Figure 2 shows a hammer of somewhat modified contstruction, where piston 23 and tool 10 are one and the same component. Through the piston a boring 17 is made. The piston travels in working cylinder 13 and hits spindle end 23. In the cylinder there is a guiding part 12 which is sliding with respect to outer shell 11 and end 23 as well. Along pipe 14 pressure is led direct from the working pressure supply into a circular pressure chamber 20 within walls 30 and 31. In the tube connector there is a pressure regulating valve. Circular part 19 incl. packing 18 prevents leaks of compressed air from chamber and allows movement between outer shell 11 and working cylinder 13. Oil, contained in compressed air, lubricates sliding surfaces inside hammer. By means of regulating valve 15 the pressure in the circular chamber can be controlled and, accordingly, the striking frequency affected. By means of working pressure adjustment, the strength and frequency of blow can be adjusted. The hammers illustrated in both figures are most excellently applicable to driving cylinders into soil, since the conical tool element can be compressed by strokes into the cylinder without disturbing the hammer function. By using tandem cylinders for drilling, rotation of the same can be arranged advantageously by rotating the hammer, from which the torsion is transmitted to the cylinders. Hammer rotation can be barranged by many familiar technics without disturbing the strenght of blow, for instance by means of an outside rotation engine. In rotating and and striking the cylinders, which function as a tool, especially when the front end of the first cylinder is well fit for strokes, it is possible to penetrate even a rock if you happen to hit one. Thi method is especially applicable for splitting of big stones in front of the cylinders and if the stones are of such size that they cannot give way to the cylinder forward movement. Rotation of this kind of hammer is made easy by a cylinder shell 3,11 at the hammer head, from where the rotation is transmitted direct to the hammer head. The tool head in a hammer according to the invention can even be a rock-drilling tool, used instead of part 1 in the solution in fig. 1, whereby the hammer can be used for drilling big holes in rock. For hammer adjustment the pressure channels or pipes to the circular chamber can be furnished with different control and shut-off means. A hammer in accordance with the invention does not need but one sort of pressure medium and adjustment of function can be carried out with this medium.

Claims: PATENT CLAIMS 1. A method for securing and adjusting the strenght of blow in a hammer operated by compressible pressure medium and comprised of a working cylinder with a to-and-fro moving percussion piston (6) and a hammer head (2,10) transmitting hammer blows against the drilling object and forming by means of an outer shell (3,11) a firm contact to one (28), (30) of the walls (28,29), (30,31) of a circular chamber (20) which can, through the impact of pressure led to said chamber, move with respect to each other and by means of which, due to their mutual position, the impact of piston (6) on spindel (22,23) can be adjusted. 2. A method according to patent claim 1 characterized in that through leading pressure medium into circular chamber (20), the working cylinder (7,13) and the front end spindel (22,2) are forced closer to each other 3. A method according to patent claim 1 or 2 characterized in that the pressure medium is led to chamber (20) from pressure medium feeding line (16). 4. A method according to patent claim 1 or 2 characterized in that pressure medium is led to chamber (20) through channel (21) from front side of piston (6). 5. A method according to patent claims 1, 2 and 4 characterized in that a part of pressure medium from piston (6) front side is led through the front end component (1,2,27) to the front side of tool (1,17). 6. A hammer operated by compressible pressure medium, com¬ prised of a piston (6) moving to-and-fro in order to produce pressure and a percussing head (2.10) with a tool moving in percussion direction with respect to working cylinder (7,13) characterized in that the hammer comprises, as continuation of percussion head (2,10), a shell (3,11) which forms or is firmly fixed to one of the walls of circular chamber (20), which are moving with respect to each other by means of pressure medium fed into said chamber. 7. A hammer according to patent claim 6 characterized in that the hammer comprises an intern channel (21) for feeding pressure from the working cylinder space into pressure chamber (20) . 8. A hammer according to patent claim 6 characterized in that the hammer comprises a pressure tube system (14) for feeding pressure from working pressure supply (16) to pressure chamber (20). 9. A hammer according to patent claims 6-8 characterized in that the hammer comprises flow channels (17,27) for feeding pressure to front side of hammer head (1,17). 10. A hammer according to patent claim 6 characterized in that there are pressure restricting or flow blocking means in delivery pipes or delivery channels leading to pressure chamber (20) 11. Application of hammer according to patent claim 6 in tun¬ nel drilling, whereby a tunnel is drilled by forcing tandem cylinders (24) into the soil with the hammer in the working pit at tunnel opening and fixed to the rearmost cylinder (24) by a conical compression connection characterized in that the hammer is used for drilling a tunnel with a striking and rotating cylindrical tool, whereby the torsion produced by hammer rotation is transmitted to the drilling cylinder at hammer head by means of tandem cylinders. 12. Application according to patent claim 11 characterized in that the hammer is operated with different frequencies of blow depending on soil types to be drilled.

Inventors: ILOMAEKI VALTO, ILOMAEKI, VALTO
Applicants: ILOMAEKI VALTO, ILOMAEKI, VALTO
Application year: 1991
Main classification: B25D9
IPC codes: B25D9