JPS63118417A - Electromagnetic impact tool - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The invention relates to electromagnetic impact devices and in particular for driving elements, such as tubular piles, sheet driving, piles or similarly functioning elements into the ground in a vertical or inclined direction. This invention relates to an electromagnetic pile driver configured as follows.

[Prior Art] Machines for driving elements into ponds are widely used to form the foundations of all types of structures, and elements that can be driven into the ground can be shaped differently depending on the purpose. .

For example - tube piles, which can be filled with concrete when driven into the earth, are one example of the main type of piling that is widely used. Sheet pilings for damming dams or simply enclosing specific areas or as barriers are also common, with sheet pilings being driven into the ground in interlocking and continuous relationship. Solid or pillow-shaped piles can also be driven into the ground.

Pile drivers traditionally provided for this purpose are typically one of three types:

electric or hydraulic vibrators operating at high frequencies and vibrating the pile into the ground; pneumatic hammers or pile drivers operating at intermediate frequencies and driving reciprocating masses in alternating directions with compressed air; Diesel, pneumatic, steam, or fluid-operated falling mass pile drivers operating at low frequencies, typically using expansion or fluid pressure to lift a mass, and then releasing the expansion or fluid pressure for at least one The section causes the mass to fall under the action of gravity acting on the pile or an anvil acting on it.

Electrical or hydrodynamic vibrators generate a sinusoidal unidirectional force by coupling a rotating eccentric mass to the element to be driven into the ground. These machines generally work effectively in sandy soils and have relatively poor results in clay or rocky geology. Air hammers utilize a piston that is driven alternately upward and downward by the expansion of compressed air. These machines give relatively good results on clayey ground, and the characteristics of these machines are intermediate between those of the above-mentioned vibrating machines and falling mass machines.

The intermediate frequency range of the impact applied to the element is usually between 2 and
10 Hz and large masses are not available for shock transmission, so the amount of energy that can be transferred to the element during each shock is not sufficient for certain types of elements.

In machines with falling masses, the relatively heavy pistons constituting the energy-transferring mass are driven by pressurized air, pressurized steam, pressurized oil, or another gas (e.g. explosively expanding diesel) and free fall. Sometimes it is lifted by a fluid such as a gaseous mixture that falls onto the element to be driven into the ground.

Due to the large size of the M mass used and the characteristics of the mechanism used to lift this large mass, this machine cannot function at intermediate or high frequencies, and the operating frequency of falling mass devices is generally around IH2. . These machines, when utilized with diesel drop hammer machines, are effective in all types of geology except perhaps extremely porous or loose soils.

In drop hammers for dropping masses, good results in terms of lifting performance have been obtained using one of the three modes used over other types: diesel, pneumatic and hydrodynamic; With this machine, good results can be obtained in terms of free fall performance, that is, reaction force relationship.

[Problems to be Solved by the Invention] However, these conventional machines are not effective in all cases, and it is desirable to find an alternative machine for driving piles etc. into the ground.

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide an improved pile driving device that can eliminate the above-mentioned drawbacks of conventional devices.

Another object of the present invention is to provide a single-piece pile driver that utilizes a unique energy source and can therefore operate relatively effectively on all types of soil.

[Means for Solving the Problems] The problem with conventional devices is that the mass that is allowed to fall freely within the guide member and is electromechanically lifted up and enclosed by or within the guide member. They found that this could be overcome by providing a body, which is energized by an electrical circuit that simply energizes the coil, thereby causing the mass to rise, and then is deenergized, causing the mass to fall freely and impact the pile.

Therefore, according to the present invention, an electromagnetic impact tool for driving piles, for example, includes a vertically extending guide member defining a vertical guide passage, an electromagnetic coil attached to the guide member surrounding the vertical guide passage, and the electromagnetic coil mounted on the guide member surrounding the vertical guide passage. a movable electromagnetic core constituting an impact body positioned relative to the electromagnetic coil so as to be able to fall freely in the vertical guide passage and to rise electromagnetically against gravity by excitation of the electromagnetic coil; an anvil movably attached to the lower end and configured to receive an impact from the movable electromagnet core when the electromagnetic coil falls freely due to the gravity of the movable electromagnet core when the electromagnetic coil is demagnetized; It is characterized in that it can be positioned by contacting the driven element.

The electrical circuit connected to the electromagnetic coil may consist of a capacitor, a charging circuit connected across the capacitor for charging the capacitor, and a discharging circuit, the discharging circuit connecting the electromagnetic coil to the capacitor. Two conductors and a device in at least one of said conductors for charging the capacitor by a charging circuit and then discharging the capacitor through a diagonal electromagnetic coil that raises the electromagnetic core.

The charging circuit can include a rectifier bridge, the input of which is connected to an alternating current power supply and the output of the rectifier bridge is connected to a capacitor, the rectifier bridge includes a branch provided with a thyristor, and the rectifier bridge has a branch provided with a thyristor. a device in at least one conductor adapted to control the duration of application of the charging current to the capacitor with a conduction time and for discharging the capacitor connected to the control electrode of the thyristor for controlling the duration of conduction of the thyristor; It has a timed circuit.

The device for discharging a capacitor in at least one conductor comprises a thyristor connected in series between the electromagnetic coil and the capacitor in one conductor and a timer circuit connected to the control electrode of this thyristor and triggering the thyristor into conduction. be able to.

The above device for discharging a capacitor in at least one conductor can be equipped with a position sensor in the lower part of the guide member, which detects the position of the electromagnetic core and triggers the thyristor into conduction.

Advantageously, these devices in at least one conductor for discharging the capacitor include an arc-extinguishing network connected to the thyristor and rendering it non-conducting, and an arc-extinguishing circuit responsive to the electromagnetic core reaching the upper position. and a further position sensor on the guide member for actuating the net.

The arc extinguishing network may also include another thyristor connected in parallel to the thyristor, a resistor connected in series with the other thyristor, and a capacitor connected to the another thyristor, The limiting W electrode of another thyristor is connected to a timing network.

The thyristor can be a self-extinguishing thyristor.

If necessary, this impact tool can be used to remove elements located underground, and the upper part of the guide member is provided with an auxiliary anvil for impact by the electromagnetic core, and the impact tool also and a stirrup connecting the element to the auxiliary anvil, whereby an impact acting upwardly on the auxiliary anvil may cause the element to be pulled out of the ground.

10. Especially when used for shaft bottoming,
The guide member is orientable to a vertically disengaged position and includes a braking coil along the path of the electromagnetic core, and is provided with a separate electrical circuit, the separate electrical circuit comprising:
It has a loop that includes a capacitor and a switch connected in series with the damping coil and the capacitor.

Another independent electrical circuit may include a position sensor for detecting the position of the electromagnetic core in the guide member substantially immediately below the brake coil to control the switch.

Advantageously, the electromagnetic coil is completely enclosed within the guide member and defines a vertical guide path in the area of said electromagnetic coil;
The electromagnetic core can be elongated and have a length that is a multiple of the axial length of the electromagnetic coil, the axial length of the guide member can be greater than the axial length of the electromagnetic core, and the anvil forms an element. and is received within the guide member with an axially extending portion adapted to be received within a tube projecting axially from the guide member and with freedom of axial movement between two stop structures on opposite axial sides. and an annular shoulder. The anvil can include a boss that projects upwardly from the annular shoulder in the vertical guide passage and is engageable with the electromagnetic core.

In one embodiment of the invention, the electrical excitation circuit may have a capacitor connected to the charging circuit and at least one conductor may be provided with a device for initiating a controlled discharge of the capacitor in the electromagnetic coil. . Therefore,
During the free fall of the electromagnet core, the capacitor can be charged by a charging source, and the charge of this charging source is momentarily or abruptly discharged through the electromagnetic coil, creating a reaction force that is Regardless of the impact exerted by the falling electromagnetic core on the element being driven into the ground.

By utilizing electronic control of charging according to the present invention, the basic operating parameters of the electromagnetic hammer, namely the energy and frequency of the strikes, can be easily controlled by changing the terminal voltage of the charging capacitor. .

Further, the electronic command circuit described as a timed circuit in this Meiji MA may be provided to perform repeated automatic operations using the above-mentioned sensor. In other words, a self-lifting pulse can be generated by discharging a capacitor through the electromagnetic coil at the moment when the electromagnetic core actually strikes the anvil that transfers energy to the element to be driven into the ground.

The self-braking phenomenon during the rise of the moving electromagnetic core at the moment when it begins to pass the upper end of the electromagnetic coil causes a capacitor discharge under the control of the position sensor for the moving electromagnet core located substantially at the level of the upper part of the electromagnetic coil. This can be overcome by electronically extinguishing the thyristor. This arc extinguishing circuit demagnetizes the electromagnetic coil at a certain instant during the ascent of the moving electromagnet core.

The above-mentioned device can be relatively simply provided with an auxiliary anvil in the upper part of the guide member, in order to enable it to be used effectively for extracting piles from the ground. It is connected via stirrups to elements that are driven into the ground.

It has also been found to be advantageous to provide the device with another auxiliary device in order to limit the level of rise of the electromagnet core. For example, when driving piles in a direction oblique to the vertical. , in which case the damping of the electromagnetic core by gravity is less strong than the damping that would be applied if the guide member were upright.

In this case, in order to slow the upward movement of the electromagnet core, the device can be provided with a braking coil along the path of the electromagnet core, the braking coil being housed in the guide member;
It is then energized at an appropriate instant to slow down the rise of the electromagnet core. This braking coil may be placed below the lifting coil and may be coupled to a separate electrical circuit forming a loop containing the braking coil, a capacitor, and a switch that closes and initiates the braking action. The braking energy converted to charge in this capacitor can be offset by discharging the capacitor through the braking coil to accelerate the electromagnet core during lowering of the moving electromagnet core.

[Example] The above and other objects, features and effects of the present invention will be readily apparent from the following description of the accompanying drawings.

In FIG. 1 of the drawings, an electromagnetic falling hammer or pile driver is shown, in which the free-falling mass or core 1 is guided in an elongated tubular guide member 6 with a guide hole 6a, the core 1 being e.g. It is possible to move vertically between the positions indicated by solid and dotted lines.

Thus, the core 1 can be slid along a vertical axis 3 through an electromagnet 2, which is made up of a coil 4 and a ferromagnetic housing 5 surrounding the coil 4.

The electromagnet 2 is mounted on the upper part of the elongated tubular guide member 6, the lower part of which receives an anvil 7 whose annular flange 7a has shoulders 6b, 6.
c and the receiving recess 6d of the annular flange 7a. The annular flange 7a is integral with a boss 7b, and the boss 7b is fitted into a pile 8 driven into the ground. When the coil 4 is energized by a circuit of the type shown in FIGS. 4 to 6 through the conductors 9 and 10, the core 1 is attracted upward, and when the coil 4 is deenergized, it falls downward to the anvil. 7, this impact causes pile 8
is transmitted to.

The electrical circuit for energizing the coil 4 of the hammer is shown in FIG. 4, and the core 1, the coil 4 of the electromagnet 2, the ferromagnetic shield or housing 5, the feed conductor 9.10 and the position sensor 11 are shown in FIG. In this manner, the core 1 can be placed at a position along the guide member that the core 1 reaches when applying an impact to the anvil 7.

The circuit of FIG. 4 has a three-phase AC power supply 12 that supplies power to an isolation transformer 13.
A three-phase rectifier bridge 14 is provided at the output of 3.

This three-phase rectifier bridge 14 consists of three thyristors 15 and three diodes 16.

A charging capacitor 17 is connected in parallel to the output of the three-phase rectifier bridge 14, such that a thyristor bridge in series with a resistor 19 and a self-inductance or choke 18 forms the charging circuit.

Resistor 19 is a charging current limiting resistor.

The power supply conductor 9.1o for the coil 4 of the electromagnet 2 is connected to two terminals of the capacitor 17, and the thyristor 20 is connected to one of the power supply conductors 9. The zero recovery diode 21 is connected in parallel with the thyristor 20. Connected in reverse polarity relationship. Electronic control module 22
forms a time circuit and is connected to the control or gate electrode of the thyristor 15.20 and to the position sensor 11. This electronic control module 22 regulates the charging and discharging cycles of the capacitor 17 that occur in the following manner.

During the conduction period of thyristor 15, capacitor 17 is charged through choke 18 and resistor 19. By controlling the conduction duration of the thyristor 15, the timer circuit 22 is able to vary the effective charge in the capacitor 17 and thus the energy due to the discharge from the capacitor to the coil 4 prior to each discharge.

Naturally, this will change the degree to which core 1 rises during each discharge cycle of capacitor 17.

When the thyristor 20 becomes conductive, the energy stored in the capacitor 17 is suddenly discharged through the coil 4 of the electromagnet 2, attracting the movable core 1 and causing it to rise.

By varying the energy stored in the capacitor 17, the lifting height of the core 1 can be varied and thus the duration of the lifting movement of the core 1 can be controlled.

Since the duration of the rising movement will determine the length of each raising and lowering cycle of the core 1, the cycle duration and frequency of the impulses can be controlled. The frequency of shocks is therefore inversely proportional to the charging energy per cycle in the capacitor.

The position sensor 11 is connected to the thyristor 2 via the control module 22 in automatic repetition of the cycle when the movable core 1 impacts the anvil 7 at the end of each preceding cycle.
0 automatically triggers.

FIG. 5 shows a modification of this power supply circuit, in which the capacitor 17
The thyristor 20 which controls the discharge of the thyristor is bridged by a circuit or network which extinguishes this thyristor. This arc-extinguishing circuit consists of another thyristor 23, a capacitor 24 and a resistor 25 connected as shown in the circuit diagram of FIG.

The circuitry 23, 24, 25 serves to extinguish the thyristor in the following manner.

Capacitor 24, which is charged via resistor 25 during the conduction period of thyristor 20, is discharged via thyristor 23 under control of circuit 22, thereby extinguishing thyristor 20.

The thyristor 23 is preferably triggered by a position sensor 26 (see FIG. 1) located at the upper end of the coil 4.

The position sensor 26 is able to detect the moment when the core 1 reaches the top of the coil 4 and leaves the electromagnet, creating a self-braking phenomenon. Therefore, the position sensor 26 de-energizes the coil 4 before this self-braking phenomenon can occur. This avoids energy losses that would occur due to self-braking phenomena.

Referring now to Figure 6, there is shown a third embodiment of a power supply circuit for use with any of the electromagnetic hammers shown in Figures 1-3, in which case special arc extinguishing means are required. I understand what you want to be known as. The discharge thyristor 20' is here a GTO or arc-extinguishing thyristor connected to the discharge circuit of the capacitor 17. This type of thyristor is triggered into conduction by applying a signal of a given polarity to the gate and is automatically extinguished by zeroing the main current flow.

Furthermore, this thyristor can be extinguished by applying a control signal of opposite polarity from the electronic control module 22 to the gate. Clearly, compared to the circuit of FIG. 5, the circuit of FIG. An electromagnetic hammer or piledriver corresponding to that of FIG. 1 is shown, and elements corresponding to those of FIG. 1 are designated with the same reference numerals.

For example, the movable core 1 is shown guided in a guide member 6 and cooperates with a coil 4 with a ferromagnetic shield 5 forming an electromagnet 2. In this embodiment, the lower anvil 7 is provided in the same way, but in addition a mechanism is provided that allows the pile 8 previously buried in the ground to be pulled out.

This pull-out mechanism is a second pull-out mechanism provided at the top of the guide member 6.
The guide member has an anvil 27 and a boss that receives an impact from the core 1 extending into the hole of the guide member.

Next to the guide member 6 there are provided two stirrups 28 which extend vertically and flank the guide member 6, the lower parts of these stirrups traverse the lower anvil 7 and the element 8.
It is fixed at 9. The pin 29 can be inserted laterally through the stirrup, anvil 7 and pile 8.

In operation, the device is pulled upwardly through a resilient cableway or cableway with resilient shock dampers 30 by a hoist, such as a crane cable not shown in the drawings.

When the coil 4 is energized, the core 1 is driven upwards,
A violent impact is applied to the upper anvil 27.

The upward impulse is transmitted to the pile 8 via the stirrup 28 and pin 29. When the coil 4 is deenergized, the core 1 falls onto the anvil 7 due to gravity, but the downward impulse is relatively weak as it pulls the device upwards, and the operating cycle is under the control of the sensor 11. Again, the circuit could of course be that of either FIG. 4 or FIG. 5, if a damping coil is desired to be used to prevent upward transfer of energy to the anvil 27.

FIG. 3 shows an electromagnetic hammer specifically designed for use in driving sloped piles or driving sloped or off-vertical piles.

This electromagnetic hammer uses the same components as those of FIGS. 1 and 2, and therefore those components may be designated by the same reference numerals.

However, in this case an auxiliary coil 31 with a ferromagnetic shield 32 is provided below the main electromagnet 2. This auxiliary coil 31 is connected to a separate electrical circuit or loop 33 comprising a capacitor 34 and a switch 35 in series with the coil 31, but not connected to any other current source. .

When using the driver in a position out of the vertical, the damping of the upward movement of the core 1 due to gravity is less strong than when the assembly is completely upright, in which case the circuit 33 May be activated to limit upward movement of the core.

When the lower end of the movable core 1 passes through the coil 31, the switch 35 is closed, for example by the control module 22. The strongly magnetized core 1 causes a current to be generated in the circuit 33, charging the capacitor 34 and at the same time The upward movement of the mass body formed by the core is braked. Capacitor 34 discharges through coil 31 and generates braking energy that accelerates the motion of core 1 downward. switch 3
5 is released when the core reaches the lower position.

A circuit corresponding to Figs. 4 and 5 can be used,
The switch 35 can also be constituted by a thyristor or a triac, and is further advantageously controlled by a further position sensor 36 provided on the guide member 6 substantially at the bottom position of the auxiliary coil 31. be done. Control of switch 35 may be provided by electronic timer 22, this relationship being shown schematically in FIG.

It is to be understood that the invention is not limited to the embodiments shown and described, but is intended to cover all modifications within the spirit and scope of the invention as set forth in the claims. 6 The present invention may, without limitation, include circuit elements equivalent to those shown in the various circuits, such as rectifier bridge 1.
4 or a pile 8 instead of the bin 29 shown in FIG.
Depending on the type of device, tightening may include using tongs or other devices. Additionally, an auxiliary coil (similar to coil 31 in FIG. 3) may be used to accelerate the downward movement of core 1.

[Brief explanation of the drawing]

1 schematically shows a vertical section through an electromagnetic drop hammer or pile driver according to the invention; FIG. 2 shows another pile driver similar to the device of FIG. 1 with a device for extracting piles from the ground; FIG. 3 is a similar sectional view of a further pile driver according to the invention with a braking coil so that it can be advantageously used for inclined driving; FIG. FIG. 5 is a circuit diagram showing another circuit for this purpose, and FIG. 6 is a circuit diagram showing yet another embodiment of the power feeding circuit according to the present invention. Figure Middle 1: Core 2: IT magnet 4: Coil 5: Ferromagnetic housing 6: Guide member 7: Anvil 8: Pile 9, 10: Conductor 11: Position sensor 12: Three-phase AC power supply 13: Isolation transformer
14: Three-phase rectifier bridge 15: Thyristor
16: Rectifier diode 17: Capacitor 18
: Choke 19: Resistor 20: Thyristor 21: Recovery diode 22: Electronic $ control module Fi6.2 Fi6.3

Claims (1)

[Claims] 1. A vertically extending guide member defining a vertical guide passage;
An electromagnetic coil is attached to the guide member surrounding the vertical guide passage, and the electromagnetic coil is arranged such that the electromagnetic coil can fall freely within the vertical guide passage and can also rise electromagnetically against gravity by excitation of the electromagnetic coil. a movable electromagnet core forming an impact body positioned with respect to the coil; and a movable electromagnet core movably attached to the lower end of the guide member and configured to freely fall due to the gravity of the movable electromagnet core when the electromagnetic coil is demagnetized. an electromagnetic impact tool, characterized in that the anvil is adapted to receive an impact from an electromagnetic impact tool, the anvil being positionable in contact with an element driven by the tool. 2. An electric circuit connected to the electromagnetic coil, the electric circuit consisting of a capacitor, a charging circuit connected across the capacitor to charge the capacitor, and a discharging circuit, the discharging circuit being two conductors connecting an electromagnetic coil to the capacitor, and a device in at least one of the conductors for discharging the capacitor through the electromagnetic coil to raise the electromagnetic core after being charged by the charging circuit. An electromagnetic impact tool according to claim 1. 3. The charging circuit comprises a rectifier bridge, the input of the rectifier bridge is connected to an alternating current power supply and the output is connected to a capacitor, the rectifier bridge comprises a branch provided with a thyristor, and the conduction time of the thyristor A device in at least one conductor for controlling the duration of application of a charging current to the capacitor and for discharging the capacitor comprises a timer circuit connected to the control electrode of the thyristor for controlling the duration of conduction of the thyristor. An electromagnetic impact tool according to claim 2. 4. A device in at least one conductor for discharging a capacitor is connected to a thyristor connected in series between the electromagnetic coil and the capacitor in the one conductor and a control electrode of the thyristor to trigger the thyristor into conduction. An electromagnetic impact tool according to claim 2, comprising a timer circuit. 5. According to claim 4, the device for discharging a capacitor in at least one conductor is provided with a position sensor in the lower part of the guide member for detecting the position of the electromagnetic core and triggering the thyristor into conduction. Electromagnetic impact tool as described. 6. A device in at least one conductor for discharging the capacitor includes an arc-extinguishing network connected to the thyristor and rendering the thyristor non-conducting, and actuating said arc-extinguishing network in response to the electromagnetic core reaching an upper position. 6. The electromagnetic impact tool according to claim 5, further comprising a further position sensor in the guide member for causing the electromagnetic impact tool to move. 7. The arc extinguishing network comprises another thyristor connected in parallel to the thyristor, a resistor connected in series to the another thyristor, and a capacitor connected to the another thyristor, 7. An electromagnetic impact tool according to claim 6, wherein the control electrode is connected to a timed network. 8. The electromagnetic impact tool according to claim 4, wherein the thyristor is a self-arc-extinguishing type arc-extinguishing thyristor. 9. For use in removing elements located underground, the upper part of the guide member is provided with an auxiliary anvil against impact by the electromagnetic core, and furthermore stirrups connecting said element to said auxiliary anvil. 2. An electromagnetic impact tool as claimed in claim 1, wherein said element is pulled out of the ground by an impact acting upwardly on said auxiliary anvil. 10. Particularly for use in bottoming shafts, a guide member is orientable to a vertically disengaged position, said guide member being provided with a braking coil along the path of the electromagnetic core and having a separate independent electrical circuit; Another independent electrical circuit
2. An electromagnetic impact tool as claimed in claim 1, comprising a loop including a capacitor and a switch connected in series with the braking coil and the capacitor. 11. Another independent electrical circuit comprises a position sensor arranged in the guide member substantially immediately below the brake coil to detect the position of the electromagnet core for controlling the switch. Electromagnetic impact tools as described in . 12. An electromagnetic coil is completely enclosed within a guide member and defines a vertical guide passage in the area of the electromagnetic coil, and the electromagnetic core is elongated and has a length that is a multiple of the axial length of the electromagnetic coil; An axially extending portion wherein the axial length of the guide member is greater than the axial length of the electromagnetic core, and the anvil is adapted to be received within a tube forming an element and projecting axially from the guide member. and an annular shoulder received in said guide member with freedom of axial movement between two stop structures on opposite axial sides. tool. 13. The electromagnetic impact tool of claim 12, wherein the anvil is provided with a boss projecting upwardly from the annular shoulder in the vertical guide passage and engageable with the electromagnetic core. 14. An electric circuit connected to the electromagnetic coil, the electric circuit consisting of a capacitor, a charging circuit connected in parallel to the capacitor to charge the capacitor, and a discharging circuit, the discharging circuit being two conductors connecting an electromagnetic coil to the capacitor, and a device in at least one of the conductors for discharging the capacitor through the electromagnetic coil to raise the electromagnetic core after being charged by the charging circuit. An electromagnetic impact tool according to claim 13. 15. The charging circuit comprises a rectifier bridge, the input of the rectifier bridge is connected to an alternating current power source and the output is connected to a capacitor, the rectifier bridge comprising a branch provided with a thyristor, the conduction time of the thyristor A device in at least one conductor for controlling the duration of application of a charging current to the capacitor and for discharging the capacitor comprises a timer circuit connected to the control electrode of the thyristor for controlling the duration of conduction of the thyristor. An electromagnetic impact tool according to claim 14. 16. A device in at least one conductor for discharging a capacitor is connected to a thyristor connected in series between the electromagnetic coil and the capacitor in the one conductor and a control electrode of the thyristor to trigger the thyristor into conduction. 15. An electromagnetic impact tool according to claim 14, comprising a timer circuit. 17. According to claim 16, the device for discharging a capacitor in at least one conductor is provided with a position sensor in the lower part of the guide member for detecting the position of the electromagnetic core and triggering the thyristor into conduction. Electromagnetic impact tool as described. 18. A device in at least one conductor for discharging the capacitor includes an arc-extinguishing network connected to the thyristor and rendering the thyristor non-conducting, and actuating said arc-extinguishing network in response to the electromagnetic core reaching an upper position. 18. An electromagnetic impact tool according to claim 17, further comprising a further position sensor in the guide member for causing the electromagnetic impact tool to move. 19. The arc extinguishing network comprises another thyristor connected in parallel to the thyristor, a resistor connected in series to the another thyristor, and a capacitor connected to the another thyristor, 19. An electromagnetic impact tool according to claim 18, wherein the control electrode is connected to a timed network. 20. For use in removing elements located underground, the upper part of the guide member is provided with an auxiliary anvil against impact by the electromagnetic core, and further includes stirrups connecting said element to said auxiliary anvil. Claim 14, wherein said element is pulled out of the ground by an impact acting upwardly on said auxiliary anvil.
Electromagnetic impact tools as described in section. 21. The electromagnetic impact tool according to claim 1, further comprising an auxiliary coil for accelerating the downward movement of the electromagnetic core.