Abstract:
A drilling tool for drilling bore holes into the ground and for removing the drilled material using an air-lifting process. The drilling tool has a drilling head equipped at its lower surface with curing elements, whose upper surface is connected to hollow drilling rods having an inner conveying channel and from whose lower surface boring material mixed with a rinsing liquid is removed via the conveying channel. At the lower surface of the drilling tool head, inside a radial channel connected to the conveying channel, a cross-flow of the rinsing liquid, flowing radially inwards and having a high flow velocity, is produced for the purpose of carrying along the boring material.

Description:
This patent application is a continuation of application Ser. No. 09/214,585 filed on Dec. 31, 1998 now abandoned, which is a 371 of PCT/DE 97/00966 filed May 14, 1997. 
     The invention concerns a process and a device for drilling bore holes into the ground while the boring material is removed via the air lifting process. 
    
    
     BACKGROUND OF THE INVENTION 
     Drilling tools in this type of tool family and the airlift drilling process are known from the state of the art. When there is a removal of material according to the air-lifting process (reverse circulation), there is a column of liquid in the internal cross-section of the hollow drilling rod, which forms an extraction channel, and air is blown into this extraction channel of the drilling rod above the tool head, so a difference in pressure of the column of liquid in the drilling rod arises between the base of the bore hole and the surface because of the air rising in the drilling rod. The difference in pressure induces a velocity of flow with which the material that has been detached at the base of the bore hole is driven out through the internal cross-section of the drilling rod. The magnitude of the difference in pressure, and thereby the transporting capacity, depends among other things on the amount of air blown in per unit of time, on the depth to which it is blown in and on the lifting height. The material detached from the cutting element is suctioned up from the base through a suction opening; in the process, the suction opening can be centrally located on the bottom side of the tool head or, if the tool head has a pilot tip, for example, on a position offset from the center by around ¼ of the diameter. 
     When “suctioning up” is being discussed here and below, it is not thereby meant that a suction pump should be installed on the drilling rod. A pump is merely involved in order to press in air under high pressure through the drilling tool into the extraction channel. The hydrostatic pressure on the base of the bore hole is, however, higher than further up in the extraction channel in the mixture that exists there of water, drilled material and air. The transport actually takes place because of the higher pressure in the area of the base of the bore hole, but there is still a lower pressure in the extraction channel, and for simplification of expression “suctioning up” is talked about in this sense of a junction in an area of lower pressure. 
     In the case of the drilling tools known from the state of the art, the suction openings are usually designed so as to be circular or oval. In the case of some of the known drilling tools, several suction openings have been arranged, instead of one, distributed over the active surface of the drilling tool, in order to be able to achieve a suctioning of the material as close as possible to each cutting element. This is necessary so that the drilled material detached by the cutting elements is transported away as quickly as possible after it is detached from the base of the bore hole, and so that the drilling tool does not ineffectively operate on a layer of detached, drilled material left behind on the base of the bore hole. The arrangement last mentioned of the suction openings on several points arranged so as to vary in a radial direction requires an expensive arrangement of pipelines to connect the suction openings to the internal cross-section of the drilling rod forming the central extraction channel. 
     A drilling tool is known from U.S. Pat. No. 3,951,220 in which the suction openings are designed so as to be spiral shaped, so that a flow of the scavenging liquid directed from the outside to the inside is generated. It is a disadvantage, in the case of this drilling tool, that the flow is not sufficient to take larger amounts of loosened, drilled material along with it. 
     SUMMARY OF THE INVENTION 
     The problem involved with the invention is to create a drilling tool with efficient suctioning behavior, with which the material detached by the cutting elements is nearly completely suctioned up from the base of the bore hole, without the occurrence of a repeated interaction of the cutting elements with the material that has already been detached. 
     This task is implemented, with regard to technology and process, by providing a process for drilling bore holes into the ground while the boring material is being removed via an air lifting process by means of a drilling tool that is provided with a drilling head. The drilling head is equipped at its lower surface with cutting elements, and its upper surface is connected to hollow drilling rods having an inner conveying channel and from whose lower surface boring material mixed with the rinsing liquid is removed via the conveying channel. The cross-flow of the rinsing liquid, flowing radially inwards and having a high flow velocity, is produced at the lower surface of the drilling tool head for the purpose of carrying along the boring material. 
     A cross-current of the scavenging liquid running in a radial direction towards the center of the drilling tool head is generated on the active surface of the drilling tool head during the drilling; the flow rate of the cross-current is high enough to take in the material that has been detached and take it along. In the process, a lifting effect is achieved by means of the velocity of flow, which increases on the whole the suctioning behavior at the active surface and thereby the effectiveness of the air-lifting process. Because of the rotation of the drilling tool during the drilling, the crosscurrent is moved once completely over the entire cross section of the base of the bore hole per revolution of the drilling tool, so the cutting elements interact in each case with a “cleaned out” bore hole base. 
     In order to increase the lifting effect of the cross-current, fluid currents that are directed from out of the drilling tool head in a downwards direction can be superimposed on this cross-current. The effectiveness of the suctioning is further increased with these “turbulence-style”, superimposed fluid currents, because even comparatively heavy drilled material is lifted to be pulled along by the cross-current. 
     The task of the invention with regard to its function as an apparatus is implemented by a drilling tool for drilling bore holes into the ground while the boring material is being removed via the air lifting process. The drilling tool is equipped with a drilling head whose upper surface is connected to hollow drilling rods. The hollow drilling rods have an inner conveying channel to remove the boring material. The lower surface of the drilling head is provided with cutting elements, distributed across its cross-section, and with at least one suction opening. The suction opening is connected to the conveying channel for the boring material mixed with the rinsing liquid. The suction opening is designed as a radially-extending channel, open below, whose end located towards the center is in a fluid connection with the conveying channel. 
     In the case of the drilling tool in accordance with the invention, the suction opening is designed as an oblong channel that is open at the bottom and that extends in a radial direction, in which a cross-current is generated from the outside to the center of the extraction channel of the drilling rod. An opening is located on the external end of the channel, in its upper wall, through which the liquid from the area of the base of the bore hole can additionally enter, so that a higher speed of the cross-current can be achieved. 
     The channel is preferably closed up to the end of the drilling tool head out to the periphery. The cross-current is prevented from bringing about a “bulging out” of the bore hole, especially in soft stone, because of the closed design of the channel out to the periphery. In one embodiment, the outer end of the channel is radially closed. 
     When operating, the suction opening, designed to be channel-shaped, is guided over the entire cross section of the base of the bore hole during each revolution, and the material that has been drilled loose is transported by the cross-current through the internal cross section of the drilling rod to the surface. 
     In order to avoid a clogging of this opening, especially in the case of drilling at low bore hole depths or in soft stone, a tubular element that extends upwards can be provided at the opening. 
     According to a preferred design, the outer end of the channel is provided at its upper wall with an opening serving as an additional inlet for fluid from the area of the bore hole base, so that a higher cross-flow speed can be obtained. In order to avoid clogging of this opening, particularly when drilling at low bore hole depths or in soft rock, the opening may be provided with a pipe-shaped element extending upwards. In one embodiment, an opening serving as an inlet for the clean rinsing liquid is arranged at the outer end of the channel at the upper part of its wall. In another embodiment, the opening is provided with a pipe-shaped element extending upwards. 
     Equipment can be provided to feed the scavenging agent to the opening in an accelerated manner and to strengthen the cross-current. 
     Components that influence the flow can be arranged in the channel to improve the lifting effect, and/or the wall surfaces of the channel can be designed so as to be helix-shaped or screw-shaped, so that turbulent flow behavior can be achieved in the cross-current. In one embodiment, the channel is surrounded by walls whose side facing the inside of the channel is provided with a flow-influencing profile. 
     Nozzles or jets that are directed downwards and fed through an air line can additionally be installed that increase the lifting effect of the detached material by whirling it up. In one embodiment, at least one side of the channel is provided with jets, essentially directed downwards and fed by air or rinsing liquid, for the purpose of whirling-up loosened material. 
     In order to achieve an adequate supply of the cross-current with scavenging liquid, at least one additional supply line for the scavenging liquid and/or one additional supply line for the air can extend along the drilling rod. For special applications, the tool head can be designed in such a way that drilling is possible from out of a support pipe. In one embodiment, at least one additional air inlet pipe and/or one additional inlet pipe for the rinsing liquid is/are arranged extending along the drilling rods. 
     In summary, there is provided a process for drilling bore holes into the ground while the boring material is being removed via an air lifting process by means of a drilling tool that is provided with a drilling head. The drilling head is equipped at its lower surface with cutting elements, and its upper surface is connected to hollow drilling rods having an inner conveying channel. The boring material at the lower surface of the drilling head is rinsing liquid and is removed via the conveying channel. The cross-flow of the rinsing liquid, flowing radially inwards and having a high flow velocity, is produced at the lower surface of the drilling tool head for the purpose of carrying along the boring material. In one arrangement, additional flows are superimposed on the cross-flow. In another arrangement, there is provided a drilling for drilling bore holes into the ground while the boring material is being removed via an air lifting process. The drilling tool is equipped with a drilling head whose upper surface is connected to hollow drilling rods. The hollow drilling rods have an inner conveying channel to remove the boring material. The lower surface of the drilling head is provided with cutting elements, distributed across its cross-section, and with at least one suction opening. The suction opening is connected to the conveying channel for the boring material mixed with the rinsing liquid. The suction opening is designed as a radially-extending channel, open below, whose end located towards the center is in a fluid connection with the conveying channel. In still another arrangement, the outer end of the channel is radially closed. In yet another arrangement, an opening serving as an inlet for the clean rinsing liquid is arranged at the outer end of the channel at the upper part of its wall. In still yet another arrangement, the opening is provided with a pipe-shaped element extending upwards. In a further arrangement, the rinsing liquid can be passed to the opening in an accelerated way. In yet a further arrangement, components influencing the flow are arranged inside the channel. In still a further arrangement, the channel is surrounded by walls whose side facing the inside of the channel is provided with a flow-influencing profile. In still yet a further arrangement, at least one side of the channel is provided with jets essentially directed downwards and fed by air or rinsing liquid, for the purpose of whirling-up loosened material. In another arrangement, at least one additional air inlet pipe and/or one additional inlet pipe for the rinsing liquid is/are arranged extending along the drilling rods. In still another arrangement, the tool head is designed in such a way that it can be used for drilling from a supporting rod. 
     Further design developments and advantages of the invention are evident from the following description of three design examples, with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a drilling tool with a level active surface in a side view in a profile section that goes through the drilling axis; 
     FIG. 2 shows a view of the active surface of the drilling tool head in accordance with FIG. 1 from below; 
     FIG. 3 shows a cross section through a suction channel; 
     FIG. 4 shows a sectional view corresponding to FIG. 1 of a further design example of the drilling tool; and 
     FIG. 5 shows a sectional view corresponding to FIG. 1 of a third design example of a drilling tool with a W-shaped active surface. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drilling tool  100  shown in FIG. 1 has a barrel-shaped housing  1  with a diameter that can be as large as a few meters, depending on the bore hole diameter. A tool head  10  of the same diameter is attached to the bottom side of the housing  1 ; cutting elements  2  designed in the form of hard carbide inserts are arranged on the underside  20  of the tool head in such a way that the drilling tool  100  has a flat active surface  3  described by a dash-dot segmentation on the whole. Roller bit drilling tools  6  that are distributed over the active surface supplement the cutting elements  2 . The tool head  10  has a connecting plate  21  on its top surface; the connecting plate can be connected to the bottom surface of the housing  1  with a connecting flange  4 . The housing  1  in turn is connected with a hollow drilling rod  50 , which can be put into rotation around the drilling axis A by a rotary drive unit, which is not depicted, engaging at its upper end. The internal cross section of the drilling rod  50  forms an extraction channel  51  and serves to excavate the drilled material according to the air-lifting process. The extraction channel  51  of the drilling rod  50  extends in a direction that is coaxial to the drilling axis A up to a flange connection  24  that is perpendicular to the drilling axis A approximately in which is located approximately halfway down the side of casing  1 ; conveying channel  51  then converges into a suction pipe  11 , arranged at a slight incline within the tool head  10 . For the design type shown, the suction pipe  11  converges from the center (at the level of the flange connection  24 ) at an angle of approximately 20° into a through opening  22  of the upper connecting plate  21  of the drilling head  10 . The through opening  22  is positioned close to the drilling axis A and is connected to a suction opening designed as a radially extending channel  5 . The distance of that end of channel  5  close to the drilling axis A is determined by the dimensions of the holding fixture  7 ′ of a pilot point  7  projecting downwards from the drilling head  10 , in the drilling axis A. Channel  5  has a U-shaped cross-section, open below, it extends radially outwards from the center and is closed off at the circumferential edge of the tool head  10  by the casing wall  8  located there. The cross section of channel  5 , shown in FIG. 3, remains constant along the entire length of channel  5 . For the design type shown, a grille  9  is provided at the open bottom of channel  5  in order to limit the size of the lumps of material entering channel  5 . As is clearly shown in FIG. 2, channel  5  is arranged at only one point, as viewed in the direction of circumference, at the lower surface  20  of the tool head  10 . 
     During operation, the conveying channel  51  of the drilling rods  50  and the suction pipe  11  converging into channel  5  are filled with the rinsing liquid, usually water. An air-inlet jet  53  located at the lower end of conveying channel  51  serves for the injection of air L, via a pipe  52  extending along the drilling rods  50 , upwards into the conveying channel  51 . The injection of the air L causes the difference in pressure between the boring hole base and inside the drilling rods  50 . Following the decrease in pressure, the liquid is forced from the high pressure area at the bore hole base into the area of lower pressure inside the conveying channel  51 . Due to the resulting strong flow, the boring material loosened and crushed at the bore hole base by the cutting elements  20  and the roller drills  6  is swept along and is conveyed to the surface via conveying channel  51  as a mixture B of rinsing liquid F and boring material B. Due to the radial extension of channel  5 , a cross-flow, indicated by the arrow marked Q, occurs within channel  5  during operation, whereby the loosened boring material is collected along the entire radial extension of the channel  5  and is conveyed to the suction pipe  11  or the central conveying channel  51 , respectively. Due to the fact that channel  5  is closed off at the circumferential edge by means of the casing wall  8 , material is prevented from being washed out of the bore hole wall in an undesirable manner. 
     Suction channel  5  passes over the entire cross-section of the bore hole base during a 360° rotation due to the rotating movement of the drilling tool  100 , so that during the air lifting process an automatic “cleansing” of the bore hole base occurs due to the cross-flow Q, as indicated by arrows, and the cutting elements  2 ,  6  do not have to work with already loosened material. 
     In order to intensify the cross-flow Q within suction channel  5 , the outer end of suction channel  5  close to the casing wall  8  of the upper surface of channel  5  is provided with an opening  13  serving as an inlet for the clean rinsing liquid F; this liquid enters channel  5  at its outer end and exits channel  5  at its inner end via the through opening  22 , passing upwards into the suction pipe  11  as the now-loaded rinsing liquid FB. 
     In order to increase the lifting effect of cross-flow Q, jets  15  may be provided which are directed from the sides of channel  5  towards the bore hole base  14 ; even rather large lumps of material  16  which are not easily swept along by the cross-flow Q, can be lifted by means of these jets  15 , so that they can then be conveyed via cross-flow Q into conveying channel  5  and thence to the surface. As shown in FIG. 2, several such jets  15 ′ are preferably arranged along channel  5  in order to obtain an evenly-distributed additional whirling effect. Jets  15  are fed by air or water and are arranged in such a way that the jet-stream direction of the jets  15  is the same as the rotating direction D of the drilling tool  100 . 
     Instead of or in addition to the jets  15 , components serving to influence the flow such as guiding surfaces  17  (cf. FIG. 3) may be arranged inside channel  5 , for the purpose of directing a spin into the cross-flow Q which further increases the lifting effect on the lumps of rock  16  lying at the bore hole base. As an alternative, the wall  18  of channel  5  may be provided with a screw- or spiral-shaped profile, or with indentations or scoring, in order to obtain an additional spin within cross-flow Q in this way. Due to the additional spin within the cross-flow, boring material can also be lifted out of the indentations at the bore hole base  14  caused by the cutting elements  2 . 
     The lower limits of channel  105  inside drilling head  110  of the drilling tool  200 , shown in FIG. 4, is positioned especially close to the bore hole base  114 , whereby the suction pipe  111  is designed as a pipe elbow converging into channel  105  in the longitudinal direction of that channel, i.e. without any abrupt deflection. Due to this difference in construction, the suction pipe  111  and the pilot point  107  do not obstruct each other. At its upper end the suction pipe passes into the drilling rods  150 , at the level of the flange connection  124 . A pipe section  120  is welded to the opening  113  positioned close to the casing wall  108 ; this pipe section  120  extends upwards and its upper end is bent towards the center, i.e. away from the wall of the drilling hole, in order to prevent the inlet opening  122  from being clogged by any material dropping or sliding into the drilling hole. 
     A “free” suctioning of the rinsing liquid at the radially outer end of channel  5 ,  105  from above takes place in the case of the design types shown. By means of additional inlet pipes, extending along the drilling rods  50 ,  150  and serving to supply rinsing liquid under high pressure from the outside to the outer opening, a cross-flow of increased velocity can be obtained within the channel  5 ,  105 , whereby the suction capacity and thus the total efficiency of the drilling tool  100 ,  200  can be further increased. 
     For the drilling tool  300 , shown in FIG. 5, the effective surface  203  of the tool head  210 , which is determined by the roller cutting elements  206  (only one is shown here), is designed as a W-shape, when viewed as a section through the drilling axis A. First-rate results were obtained for drilling tools having W-shaped effective surfaces when the diameter of the drilling tool was approximately 3.60 m, and the flow speeds of the cross-flow Q were approximately 3 m per second. The W-shape which differs from the flat shape of the effective surface interacts with the spin effect, directed towards the bore hole base, of the cross-flow Q within the channel  205 , so that an especially efficient lifting effect as well as the efficient conveyance of the lifted boring material via the suction channel  211  and the drilling rods  250  were obtained. 
     The drilling tools  100  and  300 , respectively, shown in FIG.  1  and FIG. 5, are particularly suitable when drilling is done from the support rods.