Method of driving in an earth electrode and driving head for the same

Abstract

 A method of driving in an earth electrode having a conical coupling end with the aid of a driving head having a recess, in which the driving head is placed by its recess on the coupling end and the earth electrode is driven into the ground by means of a striking tool acting on the driving head, comprising placing a driving head having a conical recess fitting to the coupling end on the coupling end and after the earth electrode is driven in, loosening the driving head from the coupling end by releasing means. And driving head for employing the method.

Description

[0001] The invention relates to a method of driving in an earth electrode comprising a conical coupling end, with the aid of a driving head having a recess, the driving head being placed with its recess on the coupling end and the earth electrode being driven into the ground by a striking tool acting on the driving head.

[0002] It is common practice to place a driving head on the coupling end, the recess of the head being cylindrical and fitting loosely over the coupling end of the earth electrode. By causing a striking tool, for example, a Kango hammer to act on top of the striking head the earth electrode is driven into the ground. An earth electrode is usually composed of a plurality of elements of 1.5 or 3 metres in length, which are provided at both ends with conical coupling ends. When one element is driven into the ground, a coupling piece is placed thereon, said piece having two conical recesses, a further element being put on the coupling piece. By again placing the striking head on the coupling end of the topmost element, the two elements can together be driven further into the ground. Subsequently a coupling piece can again be placed and a next element can be put thereon. In this way an earth electrode of the desired length can be inserted into the ground. It has been found that in this known method the coupling pieces frequently crack. Obviously, when a coupling piece already driven into the ground has cracked, the earth electrode is no longer satisfactorily usable so that a new earth electrode has to be driven in.

[0003] The invention has for its object to provide a method of the kind set forth in the preamble in which said disadvantage does not occur.

[0004] According to the invention this is achieved by placing a striking head having a conical recess fitting to the coupling end on the coupling end and by releasing the striking head from the coupling end with the aid of releasing means after the earth electrode has been struck in.

[0005] By placing a striking head having a fitting, conical recess on the coupling end, the coupling end is not upset during the striking operation, in contrast to the known method, so that a coupling piece perfectly fits to the coupling end and no stress concentrations will occur therein, which may produce cracks. Since a conical recess is used which accurately fits the coupling end, the striking head is firmly clamped to the earth electrode when driven in. This on first sight serious drawback is obviated by the invention because it has been found that the striking head can be readily disengaged from the coupling end by releasing means. These releasing means comprise a tool which can exert a downwardly directed force on the earth electrode and at the same time an upwardly directed reactive force on the striking head.

[0006] The invention furthermore relates to and provides a striking head for driving in an earth electrode provided with a conical coupling end, said striking head having a recess open to the underside for receiving the coupling end and an impact surface. According to the invention the recess and the coupling end have complementary conical shapes.

[0007] In a preferred embodiment of the invention the striking head is characterized by releasing means.

[0008] According to the invention the releasing means can comprise an axial channel extending up to the recess, in which may be accommodated a pressure piece coming into contact with the coupling end and being associated with a releasing tool engaging the driving head.

[0009] In a particularly simple embodiment of the invention the channel is formed by a screwthreaded bore so that as a releasing tool a cheap, commercially available screw bolt may be used.

[0010] In a further advantageous embodiment of the driving head according to the invention the releasing means comprise an axial channel and, in addition, a transverse channel for a wedge. In this embodiment a high degree of insensitivity to dirt of the driving head is obtained.

[0011] Further features and advantages of the invention will become apparent from the description of embodiments with reference to the accompanying drawings.

[0012] 

Fig. 1 is a side elevation of a portion of an earth electrode having a conical coupling end.

Fig. 2 shows a driving head in a preferred embodiment of the invention used in the method according to the invention.

Fig. 3 is an elevational view like Fig. 2 of a different embodiment.

Fig. 4 is an elevational view in the direction of the arrow IV in Fig. 3.

Fig. 5 is a sectional view of a releasing tool engaging the driving head embodying the invention.

Fig. 6 is an elevational view in the direction of the arrow VI in Fig. 5.

[0013] The earth electrode 1, which is driven into the ground by the method according to the invention, comprises a conical coupling end 2 having a conicity of, for example, 1°.

[0014] Fig. 2 shows that on the earth electrode 1 a driving head 4 having a recess 5 having a conicity complementary to the coupling end 2 of the earth elecrode 1 is placed. At the top end, in a cavity 7 for receiving an impact end of a Kango hammer 8, the driving head 4 has an impact surface 6. By causing the Kango hammer 8 to act on the driving head 4 the earth electrode 1 is driven into the ground. When the earth electrode 1 has been driven to the desired depth into the ground, the Kango hammer 8 is removed. Since the conicity of the coupling end 2 of the earth electrode 1 has a self-hemming effect, the driving head 4 is clamped tight to the earth electrode 1 when the latter is driven in. According to the invention the driving head 4 is loosened by releasing means from the coupling end 2 of the earth electrode 1.

[0015] As is shown in Fig. 5, the releasing means may be formed by a separate puller 31 and in the driving head 30 the releasing means then have an axial channel extending up to the recess, which channel 40 may accommodate a pressure piece 35 of the puller 31, which piece comes into contact with the coupling end 2 of the earth electrode 1. The pressure piece 35 in the embodiment shown is formed by a piston rod 35 connected with a piston 34. The housing 32 of the puller 31 has a cylindrical recess 33 to which a pressurized fluid can be supplied through ducts 36, 37. The housing 32 of the puller 31 has a cavity 38, which is open to one side of the housing 32 and which can receive a driving head 30 by laterally sliding the puller onto said driving head 30. A rim 39 of the housing then grips below the driving head 30. By pressing fluid, for example, oil via the duct 36 into the space above the piston 34 the piston rod 35 operating like a gland comes into contact with the coupling end 2 and by the reactive force exerted by the rim 39 the driving head 30 is drawn away from the coupling end 2 of the earth electrode 1.

[0016] In the preferred embodiment of a driving head according to the invention shown in Fig. 2 the releasing means have an axial channel 10 partly screwthreaded (11) for receiving a screw bolt 12. In order to loosen the driving head 4 from the coupling end 2 the bolt 12 is screwed down to an extent such that its bottom surface 13 comes into contact with the top surface 14 of the coupling end 2. By the reactive force transferred via the screwthread of the bolt 12 to the driving head 4 the latter is drawn off the coupling end 2.

[0017] In the embodiment shown in Fig. 3 the driving head 20 itself also comprises releasing means. In this embodiment the releasing means are formed by an axial channel 21 and a transverse channel 23 in which a wedge 24 may extend. When the driving head 20 has to be loosened from the coupling end 2 of the earth electrode 1, a pressure piece 22 is introduced into the central channel 21. Then the wedge 24 is inserted into the transverse channel 23. The top surface 25 of the wedge 24, which is rounded off for avoiding stress concentrations, thus comes into contact with a wall 26 of the transverse channel 23 and the bottom surface 28 of the wedge 24 comes into contact with the top surface 27 of the pressure piece 22. The top surface 25 and the bottom surface 28 of the wedge 24 are at a small angle relative to one another in known manner. By exerting a force, for example, by means of a hammer, on the right-hand end (see Fig. 3) of the wedge 24, the pressure piece 22 is urged downwards with respect to the driving head 20 so that a vertically downward force is exerted on the coupling end 2 of the earth electrode 1. At the same time the top surface 25 of the wedge 24 exerts a reactive force in upward direction on the wall 26 of the transverse channel 23. By driving the wedge 24 to a sufficient extent to the left into the transverse channel 23 the vertical upward reactive force increases to an extent such that the driving head 20 releases the coupling end 2 of the earth electrode 1.

[0018] The driving head according to the invention may be made from hard steel, for example, C-45 steel.

[0019] Apart from the possibility of driving the earth electrode 1 with the aid of a Kango hammer 8 into the ground, a heavy hammer may be used to drive in the earth electrode, in which case the hammer strikes the top of the driving head. This was not possible with the conventional driving head having a cylindrical recess, since this driving head will not remain centered on the earth electrode.

Claims

1. A method of driving in an earth electrode having a conical coupling end with the aid of a driving head having a recess, in which the driving head is placed by its recess on the coupling end and the earth electrode is driven into the ground by means of a striking tool acting on the driving head, characterized in that a driving head having a conical recess fitting to the coupling end is placed on the coupling end and in that after the earth electrode is driven in the driving head is loosened from the coupling end by releasing means.

2. A driving head for driving in an earth electrode having a conical coupling end, said driving head having a recess opening towards the underside for receiving the coupling end and an impact surface, characterized in that the recess and the coupling end have complementary conical shapes.

3. A driving head as claimed in Claim 2 characterized by releasing means.

4. A driving head as claimed in Claim 3 characterized in that the releasing means comprise an axial channel extending up to the recess and being adapted to receive a pressure place coming into contact with the coupling end and being associated with a releasing tool engaging the driving head.

5. A driving head as claimed in Claim 4 characterized in that the channel is formed by a screwthreaded bore.

6. A driving head as claimed in Claim 4 characterized in that the releasing means also comprise a transversely extending channel for receiving a wedge.

Drawing