DRILLING TOOL AND METHOD FOR PRODUCING A BORE IN THE GROUND

Abstract

The invention relates to a drilling tool, in particular for discontinuous earth drilling, with a ground removal means which is arranged in a lower region of the drilling tool and is designed for removing ground material, a receiving space which is designed for receiving the removed ground material above the ground removal means on the drilling tool, at least one passageway which is designed for the passage of the removed ground material from the ground removal means into the receiving space during drilling, a closure means for closing the at least one passageway during withdrawal of the drilling tool from the borehole and a connecting means located in the upper region of the drilling tool for releasable connection with a drill rod. In accordance with the invention provision is made in that a tubular central shaft is designed with a compensating channel which extends from at least one lower channel opening which is arranged below or on the closure means up to at least one upper channel opening which is arranged above the receiving space, wherein the compensating channel is designed for the flowthrough of a medium between the lower region and the upper region of the drilling tool during withdrawal and/or lowering of the drilling tool in the borehole.

Description

The invention relates to a drilling tool, in particular for discontinuous earth drilling, with a ground removal means which is arranged in a lower region of the drilling tool and designed for removing ground material, a receiving space which is designed for receiving the removed ground material above the ground removal means on the drilling tool, at least one passageway which is designed for the passage of the removed ground material from the ground removal means into the receiving space during drilling, a closure means for closing the at least one passageway during withdrawal of the drilling tool from the borehole and a connecting means located in the upper region of the drilling tool for releasable connection with a drill rod, in accordance with the preamble of claim 1.

The invention further relates to a method for producing a bore in the ground in accordance with claim 12.

For instance for the production of foundation piles in the ground it is known to produce a hole in the ground using a ground working tool such as a drilling bucket. Depending on the type of the surrounding ground the bore can be produced as a cased or uncased bore. Especially in the case of an uncased bore a stabilizing liquid is to be provided that stabilizes the borehole from collapsing.

When using a drilling bucket discontinuous drilling has to be carried out. During sinking the drilling bucket fills with removed ground material, in particular until it is completely or at least largely filled. Subsequently, the drilling bucket has to be withdrawn from the hole filled with liquid, and in doing so a drilling apparatus located above the surface swings to an emptying position, in which the drilling bucket can be emptied. Afterwards, the drilling bucket is swung back and moved into the borehole again to carry out a further drilling step.

When producing a hole in the ground that is filled with a stabilizing liquid there is the problem that during withdrawal of the ground working device negative pressure may develop in the hole below the ground working device. If this negative pressure becomes too high ground material can collapse from the side walls into the hole. This collapsed ground material does not only pose additional work to retrieve this from the hole. What is more, in the event of such a collapse there is the risk of so-called ground failure, whereby the surrounding ground is weakened and destabilized to such an extent by the material that has collapsed into the hole that larger settlement movements occur in the surrounding region of the hole. As a result, existing structures can be damaged or construction machines can also tip over. Ground failure poses a significant risk for persons and objects so that comprehensive precautionary measures are to be taken against such ground failure.

To prevent such a risk of negative pressure arising below a ground working device during upward withdrawal it is known to keep the withdrawal speed of the ground working tool on a low level so that sufficient pressure compensation can take place between the upper side and the underside of the ground working device in the hole.

Furthermore, it is known from EP 3 879 064 A1 for example that a lateral recess is provided on a drilling bucket, which recess enabling a fluid flow along the drilling bucket between the upper side and the underside. This restricts the possible receiving space. Moreover, in the case of a partial lateral flow on the circumference of the drilling bucket this can be deflected from its central position in the bore. This can lead to undesired jamming by tilting in the borehole and to an increased degree of wear on the drilling tool and a casing as well as an increased expenditure of force during withdrawing the drilling tool from the borehole.

A further drilling bucket having an approximately annular external passage gap for a fluid flow along the drilling bucket can be taken from DE 34 40 727 A1.

The invention is based on the object to provide a drilling tool and a method with which a hole can be produced in the ground in a particularly efficient way.

The object is achieved on the one hand by a drilling tool having the features of claim 1 and on the other hand by a method having the features of claim 12. Preferred embodiments of the invention are stated in the dependent claims.

The drilling tool according to the invention is characterized in that a tubular central shaft is designed with a compensating channel which extends from at least one lower channel opening which is arranged below or on the closure means up to at least one upper channel opening which is arranged above the receiving space, wherein the compensating channel is designed for the flowthrough of a medium between the lower region and the upper region of the drilling tool during withdrawal and/or lowering of the drilling tool in the borehole.

A basic idea of the invention resides in the fact that in the case of a drilling tool having a lower closure means, with which at least one passageway to the receiving space can be closed in the downward direction, provision is made in a tubular central shaft for a compensating channel which has at least one lower channel opening in the lower region of the drilling tool and an upper channel opening in an upper region of the drilling tool. Especially during withdrawal but basically also during the lowering of the drilling tool into a bore which is in particular filled with suspension or liquid, it is possible by way of the compensating channel when a passageway of the receiving space is closed to take place a targeted central compensation flow between the upper side and the underside of the drilling tool. During withdrawal of a drilling tool, which largely covers the bore diameter and can have the effect similarly as a closure plug when the passageway is closed, in particular pressure compensation can thus take place between the region below the drilling tool and the region above the drilling tool. This counteracts an undesirable suction effect during withdrawal of the drilling tool, through which a borehole wall can be damaged.

By bringing about a central flow through the central shaft opposite to lateral flow channels the risk of the drilling tool getting jammed by tilting in the borehole during vertical movement is counteracted in a particularly reliable way. This is gentle on the drilling tool and the borehole wall. All in all, by way of a central compensating channel in a tubular central shaft that has at least one lower channel opening and at least one upper channel opening an efficient central flow around or through the drilling tool is achieved for pressure compensation or flow compensation during vertical movement in the borehole. This allows a power-saving and quicker movement of the drilling tool in the borehole.

A particularly preferred embodiment of the invention resides in the fact that the lower channel opening and/or the upper channel opening is closable. Especially during the actual drilling process in which ground material is removed in the lower region of the drilling tool it may be expedient to close the lower channel opening. This prevents ground material from entering the channel opening and a possible clogging of the compensating channel. Likewise, it may be expedient to close the upper channel opening to prevent entry or depositing into of depositing ground material from a drilling suspension and a possible clogging of the upper channel opening from above.

According to a further development of the invention a particularly expedient embodiment of the drilling tool is accomplished in that the closure means for closing the passageway to the receiving space is also designed for closing/opening the lower channel opening. For instance in the case of a drilling bucket or a discontinuously operating drilling auger the closure means serves in a generally known manner to keep a passageway open during drilling to enable the removed ground material to pass through into the receiving space and to close the passageway on completion of the drilling step. In the closure position, e.g. during withdrawal of the drilling tool from the borehole, loose, removed ground material is thus prevented from falling out again of the receiving space of the drilling tool back into the borehole.

According to a further development of the invention the closure means can be designed such that it is not only designed for closing and opening the passageway to the receiving space but also for closing and opening the lower channel opening. Therefore, the lower channel opening can in particular be arranged close to the at least one passageway to the receiving space, in particular in a region below the passageway to the receiving space.

According to an embodiment of the invention it is particularly expedient that the closure means has a closure element which is adjustable between a closure position, in which the passageway to the receiving space is closed by the closure element, and a drilling position, in which the passageway is open for the passage of ground material into the receiving space during drilling.

In conjunction with this it is especially preferred that in the drilling position of the closure element the lower channel opening is closed and that in the closure position of the closure element the lower channel opening is open. This allows the passageway and the lower channel opening to be actuated alternately by the closure element. This means that during drilling when the closure element is in the drilling position the passageway is open and at the same time the lower channel opening is closed whereas in the closure position of the closure element the passageway to the receiving space is closed while the lower channel opening is open for flow and/or pressure compensation by way of the compensating channel.

Basically, the closure element can be designed in any suitable manner. According to an embodiment of the invention an especially robust arrangement is achieved in that the closure element is designed as a rotary bottom which can be rotated between the closure position and the drilling position. An axis of rotation of the rotary bottom is in particular coaxial to the central and drilling axis of the drilling tool.

Another preferred embodiment of the drilling tool according to the invention resides in the fact that in an upper region of the receiving space a cover, in particular a cover plate, is arranged which closes off the receiving space in the upward direction and separates it from the upper channel opening. In the case of a drilling bucket this can be the upper housing cover of the box-like drilling bucket. In particular, the cover can also be designed on an auger so that the receiving space of the at least one auger flight is limited in the upward direction by the cover plate.

Above the cover plate the at least one upper channel opening is located. This ensures that in the event of an excessive filling of the receiving space removed ground material cannot enter the upper channel opening.

Basically, the drilling tool is mounted in a changeable manner on a drill rod or drive rod of a drilling apparatus. An especially expedient embodiment of the invention resides in the fact that the connecting means has a Kelly connection. In particular, a Kelly connection comprises a polygonal connection, more particularly a square connection, in which case a connecting sleeve with a polygonal or square receiving hole is preferably designed on the drilling tool for a complementary connecting pin on the drill rod. By way of this polygonal plug connection a torque-proof connection is brought about. By means of one or several insertable transverse bolts an axial securing and connection can be realized.

A particularly advantageous embodiment of the invention resides in the fact that the drilling tool is designed as a drilling bucket with a circumferential wall which encloses the receiving space in a housing-like manner. Here, in the drilling bucket according to the invention the tubular central shaft extends centrally through the preferably cylindrically enclosed receiving space. The upper channel opening of the central compensating channel is located above the cover or the upper cover plate of the drilling bucket. A drilling bucket can also be referred to as a box drilling apparatus.

Alternatively, the drilling tool can be designed as a drilling auger with at least one auger flight that is arranged helically around the central shaft. On the underside of the drilling auger the closure means is arranged, with which the at least one passageway to the at least one auger flight and thus to the receiving space between the flight turns can be opened and closed.

The invention further comprises a drilling apparatus in which the drilling tool according to the invention is arranged. A drilling apparatus can in particular have a carrier unit that can preferably comprise a running gear, more particularly a crawler-track running gear, and an upper carriage rotatably supported thereon. On the upper carriage a mast that is substantially vertical during operation can preferably be mounted by way of a positioning mechanism. On the carrier unit a rotary drive for rotationally driving a drill rod can be arranged. The drilling tool according to the invention can be releasably mounted on the underside of the drill rod.

The drill drive can preferably be movable and/or guided along the mast. The drilling apparatus is in particular designed for earth drilling and by preference for the production of boreholes for foundation piles in the ground.

Furthermore, the invention comprises a method for producing a bore in the ground, in particular for discontinuous drilling, wherein the drilling tool according to the invention or the drilling apparatus according to the invention is used. Through rotational driving by way of the drilling tool ground material is removed and the borehole is thus produced. In discontinuous drilling a receiving space on the drilling tool is filled with the removed ground material and, after closing the passageway, is withdrawn from the borehole for emptying.

Subsequently, the emptied drilling tool is returned into the borehole again to carry out a further drilling step. This process is repeated so long until the desired final depth of the borehole is reached. Drilling can be carried out as cased drilling with a support tube or as uncased drilling.

An embodiment of the method according to the invention resides in the fact that when removing ground material during drilling the passageway to the receiving space is opened and the lower channel opening is closed. Thus, the removed ground material can be received in the receiving space while the lower channel opening is closed at the same time so that no ground material can enter the channel opening.

Another advantageous embodiment variant of the invention resides in the fact that for withdrawal of the drilling tool the passageway to the receiving space is closed and the lower channel opening is opened. This ensures that during withdrawal of the drilling tool no more ground material can fall down through the passageway out of the receiving space.

By opening the compensating channel during withdrawal the undesirable suction effect can be avoided to a large degree by the free channel opening. All in all, this allows a quicker withdrawal of the drilling tool and thus a more efficient production of the borehole. Moreover, the risk of collapse of the borehole wall and of ground failure is reduced.

According to a further development of the method pursuant to the invention it is advantageous that for the lowering of the drilling tool into the borehole the compensating channel is opened. In doing so, the passageway can either be closed or open. With the compensating channel being open during lowering a quicker work flow and thus a more efficient drilling process can also be achieved.

The invention is explained further hereinafter by way of a preferred exemplary embodiment illustrated schematically in the accompanying drawings, wherein show:

FIG. 1 a first side view of a drilling tool according to the invention which is designed as a drilling auger;

FIG. 2 a side view of the drilling tool of FIG. 1 in a view rotated by 90°;

FIG. 3 a perspective view of the drilling tool of FIGS. 1 and 2;

FIG. 4 an enlarged partial cross sectional view according to section A-A of FIG. 1; and

FIG. 5 a view of the drilling tool of FIGS. 1 to 4 from below.

An exemplary embodiment of a drilling tool 10 according to the invention which is designed as a drilling auger with an auger flight 14 is illustrated in FIGS. 1 to 5. The drilling tool 10 has a tubular central shaft 30 that extends along a drilling or center axis 12. In a lower end region of the drilling tool 10 a ground removal means 20 is arranged. The ground removal means 20 can have holders 22 into which removal elements 24 are releasably inserted. In the illustrated embodiment the removal elements 24 are realized by way of example as round shank chisels. Furthermore, at the lower end of the central shaft 30 a centering or pilot tip 26 can be arranged.

At the lower end of the auger flight 14 a plate-shaped bottom 51 with a passageway 28 can be designed. To form a closure means 50 a plate-shaped closure element 52, located directly below the bottom 51, can be pivotably supported about the center axis 12. By pivoting or rotating the closure element 52 with respect to the fixed bottom 51 the passageway 28 can be closed.

In the Figures the drilling tool 10 with the closure means 50 is illustrated in an open or drilling position in which the passageway 28 is freed up or open. This enables removed ground material to pass from the removal means 20 through the passageway 28 into a receiving space 40 lying above.

In its upper end region the drilling tool 10 can have a connecting means 45 with a receiving sleeve 47, in which case the connecting means 45 can be designed in a known manner as a Kelly connection. A complementary connecting pin of a drill rod of a drilling apparatus can be inserted into the receiving sleeve 47 with a square hole to establish a torque-proof connection. By way of locking bolts that are not depicted and can be inserted into transverse bores 49 on the receiving sleeve 47 an axially fixed connection can be formed.

During drilling the drilling tool 10 is rotationally driven about the center axis 12, whereby ground material removed by the removal means 20 can pass through the passageway 28 in the upward direction into a receiving space 40 which is formed by the free space between the turns of the auger flight 14 on the central shaft 30.

Inside the tubular central shaft 30 a compensating channel 32 extends along the center axis 12, which merges at its lower end via a lateral opening 33 into a downward-directed opening channel section 35 that leads into a lower channel opening 34. In the illustrated embodiment the lower channel opening 34 is closed and thus covered by the closure element 52 in the open or drilling position.

At its upper end the compensating channel 32 leads into an upper channel opening 36 that emerges laterally from the central shaft 30, as illustrated graphically in FIG. 2.

The receiving space 40 on the auger flight 14 can be closed off upwards by a plate-shaped cover 42 that can be supported and reinforced by means of reinforcing plates 43 at the upper end of the central shaft 30 or on the closure means 50.

During drilling the receiving space 40 fills with removed ground material which passes from the removal means 20 through the passageway 28 into the receiving space 40. In FIG. 5 the auger flight 14 lying above can be seen through the open passageway 28. After the receiving space 40 has filled up the plate-shaped closure element 52, which can also be referred to as rotary bottom, can be rotated through an opposed rotary movement with respect to the bottom 51 and, in doing so, the passageway 28 can be closed. At the same time the closure element 52 can free up the lower channel opening 34 so that the compensating channel 32 is open, extending from the lower region of the drilling tool 10 below the closure means 50 up to the upper channel opening 36 above the cover 42.

The filled drilling tool 10 can now be withdrawn vertically from a borehole, while the closed closure means 50 ensures that removed ground material cannot fall out again of the receiving space 40 back into the borehole. At the same time the open compensating channel 32 that substantially extends along the central shaft 30 ensures that during withdrawal no or, at the most, only little negative pressure can develop between the underside of the drilling tool 10 and the upper side. This also applies in particular if an external diameter D of the drilling tool 10, as shown in FIG. 5, largely corresponds to a bore diameter. In this state careful and quick withdrawal of the drilling tool 10 from the borehole can take place.

Outside the borehole the drilling tool 10 can be emptied from the ground material and then moved into the borehole again for a new drilling step.

Claims

1. Drilling tool, in particular for discontinuous earth drilling, with a ground removal means (20) which is arranged in a lower region of the drilling tool (10) and designed for removing ground material,a receiving space (40) which is designed for receiving the removed ground material above the ground removal means (20) on the drilling tool (10),at least one passageway (28) which is designed for the passage of the removed ground material from the ground removal means (20) into the receiving space during drilling,a closure means (50) for closing the at least one passageway during withdrawal of the drilling tool (10) from the borehole anda connecting means (45) located in the upper region of the drilling tool (10) for releasable connecting with a drill rod,

2. Drilling tool according to claim 1, characterized in thatthe lower channel opening (34) and/or the upper channel opening (36) is closable.

3. Drilling tool according to claim 1, characterized in thatthe closure means (50) for closing the passageway (28) to the receiving space (40) is also designed for closing/opening the lower channel opening (34).

4. Drilling tool according to claim 1, characterized in thatthe closure means (50) has a closure element (52) which is adjustable between a closure position, in which the passageway (28) to the receiving space (40) is closed by the closure element (52), and a drilling position, in which the passageway (28) is open for the passage of ground material into the receiving space (40) during drilling.

5. Drilling tool according to claim 4, characterized in thatin the drilling position of the closure element (52) the lower channel opening (34) is closed andin that in the closure position of the closure element (52) the lower channel opening (34) is open.

6. Drilling tool according to claim 4, characterized in thatthe closure element (52) is designed as a rotary bottom which can be rotated between the closure position and the drilling position.

7. Drilling tool according to claim 1, characterized in thatin an upper region of the receiving space (40) a cover (42), in particular a cover plate, is arranged which closes off the receiving space (40) in the upward direction and separates it from the upper channel opening (36).

8. Drilling tool according to claim 1, characterized in thatthe connecting means (45) has a Kelly connection.

9. Drilling tool according to claim 1, characterized in thatthe drilling tool (10) is designed as a drilling bucket with a circumferential wall which encloses the receiving space (40) in a housing-like manner.

10. Drilling tool according claim 1, characterized in thatthe drilling tool (10) is designed as a drilling auger with at least one auger flight (14) which is arranged helically around the central shaft (30).

11. Drilling apparatus, characterized in thata drilling tool (10) according to claim 1 is arranged.

12. Method for producing a bore in the ground, in particular for discontinuous drilling, characterized in thata drilling tool (10) according to claim 1 is used.

13. Method according to claim 12, characterized in thatwhen removing ground material during drilling the passageway (28) to the receiving space (40) is opened and the lower channel opening (34) is closed.

14. Method according to claim 12, characterized in thatfor withdrawal of the drilling tool (10) the passageway (28) to the receiving space (40) is closed and the lower channel opening (34) is opened.

15. Method according to claim 12, characterized in thatfor the lowering of the drilling tool (10) into the borehole the compensating channel (32) is opened.