EP0265566B1 - Electromagnetic percussion pile driver - Google Patents

Description

The invention relates to an electro-magnetic driving hammer, intended to drive into the ground and possibly tear off tubes, sheet piles, piles or any other similar foundation elements, in a vertical or inclined position.

• - les vibrateurs électriques ou hydrauliques, fonctionnant à haute fréquence ;
• - les trépideurs pneumatiques, fonctionnant à moyenne fréquence ;
• - les moutons à masse tombante, avec actionnement "diésel", pneumatique ou hydraulique, fonctionnant à basse fréquence.

Known site materials, intended for driving such elements into the ground, fall into three categories:

• - electric or hydraulic vibrators, operating at high frequency;
• - pneumatic vibrators, operating at medium frequency;
• - falling weight sheep, with "diesel", pneumatic or hydraulic actuation, operating at low frequency.

All these materials have drawbacks, at least under certain operating conditions:

Electric or hydraulic vibrators generate a unidirectional sinusoidal force by the rotational coupling of unbalanced masses, integral with the element to be inserted. This type of material works with good performance in all terrains with a predominantly sandy component; in clay soils, however, the results are poor.

Pneumatic vibrators, which operate on the principle of a piston actuated alternately up and down with shock in the low position, offer better performance in clayey terrains. Their operation is a compromise between that of vibrators and that of dropping sheep, and the intermediate frequency range of shocks, between 2 and 10 Hz, prohibits the use of large masses.

This is also the case in the devices described in the patents DE-A 2 507 676 and JP-A 60 238 520 which can be assimilated to "vibrators" or to "electromagnetic" vibrators "and which do not belong to the category of "falling weight sheep".

In sheep with falling mass, a heavy piston is raised either by a fluid such as air or oil under pressure or by the explosion of a gaseous mixture (diesel), and it falls in free fall on the element to be pushed . The moving mass does not allow operation at medium or high frequency, the maximum frequency being of the order of 1 Hz. The performance of these materials is good in all types of terrain, except for very loose soils, this for "diesel" sheep.

For these latter materials, the stress on the element to be inserted is effected in two ways: on the one hand, during the lifting of the falling mass, by the thrust reaction on the element, thrust which is all the more effective that the duration of the pulse causing uplift is short; on the other hand, during the fall of the piston, by direct action of the shock on the element to be pushed in. The reaction pulse, when the piston is raised, is much too slow to be effective in the case of pneumatic or hydraulic drop-weight sheep. This impulse is excellent with "diesel" sheep, provided, however, that the consistency of the soil is sufficient to avoid excessive sinking of the anvil, in which case the "diesel" effect no longer occurs and the functioning of the sheep s 'stopped.

The present invention provides new equipment which falls under the category of falling weight sheep but uses, for its operation, a different energy from all existing equipment, which eliminates the disadvantages of current equipment.

To this end, in the threshing sheep according to the invention, the falling mass, slidably mounted in an elongated body, is constituted by a movable core of an electromagnet, the armored winding of which is secured to the body, is connected to circuits, electrical supply capable of exciting this winding for a short time to cause the lifting of the movable core, the latter then falling by gravity to strike an anvil linked to an element to be pushed in and transmitting the shock to this element.

The lifting action of the falling mass is thus carried out by electromagnetic means, supplied with electric current and requiring no sealing between the falling mass and the body of the sheep, hence a possibility of correct operation even in the water or in very cold weather, and a great simplicity of manufacture of the whole.

In a preferred embodiment of the invention, the power supply circuits comprise, to excite the winding so as to cause the lifting of the movable core constituting the falling mass, capacitors connected to a charging circuit as well as to winding supply conductors, means being provided on at least one of these supply conductuers to cause the controlled discharge of the capacitors, previously charged, in the winding. The energy required to set the falling mass in motion is thus alternately stored in the capacitors and suddenly released in the winding, which causes a very significant reaction pulse effect, whatever the terrain, adding to the impact on the anvil during the fall of the mobile core.

Advantageously, the capacitor charging circuit comprises a rectifier bridge with controlled thyristors, supplied with alternating current from an external source and having its rectified current outputs connected to the capacitors, preferably by means of a seff coil. -induction and of a load resistance, control means being associated with the thyristors of the rectifier bridge to control the duration of conduction of these thyristors. These control means, in practice constituted by "control electronics", allow easy adjustment of the main operating parameters of the threshing hammer, namely the energy and the frequency of the shocks, by varying the voltage across the capacitors. .

According to another characteristic, the means provided for causing the controlled discharge of capacitors in the winding include another thyristor, inserted on one of the supply conductors of this winding, and controlled from a position sensor of the moving core, placed at the base of the body of the sheep. Always by means of the control electronics, automatic repetitive operation can thus be obtained, the mobile electromagnet core constituting the falling mass, being lifted again practically from the moment when, at the end of fallout , he hits the anvil.

To avoid the self-braking phenomenon of the movable core when it is raised, from the moment it begins to exceed the upper end of the winding, it is advantageously provided to associate, with the thyristor causing the discharge of the capacitors in the winding, an electronic device for defusing this thyristor, controlled from another position sensor of the mobile core, placed substantially at the top of the winding. This defusing device, interrupting the excitation of the winding at a certain moment in the lifting stroke of the movable core, can consist of an additional thyristor, a capacitor and a resistor, the additional thyristor being connected to the means other thyristors.

Relatively simple complementary equipment makes it possible to use the threshing sheep according to the invention for tearing out previously driven elements. For this purpose, the sheep has an additional anvil placed above the winding so as to be struck by the top of the movable core during lifting thereof, the additional anvil being connected by stirrups and by fixing means. , such as a horizontal axis, to the element to be torn off. The tearing shocks, undergone by the anvil placed in the upper position, are thus transmitted to the lower part of the sheep and to the element to be torn off. The fact that the movable core receives its lifting impulse over a relatively short distance of movement allows this use for pulling out, with the addition of an additional anvil.

Another additional equipment may prove to be interesting, in order to limit the lifting stroke of the movable core, in particular in the event of driving in a direction inclined to the vertical, the braking of the core by gravity then being less strong since it is caused only by a component of the core weight. To obtain in this case the slowing down of the moving core, the sheep further comprises, below its winding causing the lifting of the moving core, an armored braking winding of this moving core, inserted in an independent electrical circuit in a loop with capacitors and a controlled switch connected in series with said braking winding. The switch can be controlled from a mobile core position sensor placed on the body of the sheep, substantially at the base of the braking winding. When the lower end of the movable core passes when it rises, the sensor causes the switch to close, and the movement of the core then generates an electric current in the loop circuit which charges the capacitors and the braking of the core. The braking energy is recovered and returned during the descent of the movable core, the capacitors which discharge in the braking winding helping to accelerate the movement of the core downwards, the system behaving like a mechanical spring.

• Figure 1 est une vue en coupe longitudinale d'un mouton de battage électro-magnétique conforme à l'invention ;
• Figure 2 est une vue en coupe longitudinale d'un autre mouton de battage électro-magnétique, équipé en outre d'un dispositif d'arrachement ;
• Figure 3 est une vue en coupe longitudinale d'un mouton de battage selon l'invention, spécialement équipé pour le fonçage incliné ;
• Figure 4 est un schéma des circuits d'alimentation électrique du mouton de battage électro-magnétique selon l'invention ;
• Figure 5 est un schéma des circuits d'alimentation électrique de ce mouton, dans une autre forme de réalisation ;
• Figure 6 montre encore une autre forme de réalisation des circuits d'alimentation électrique.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of nonlimiting examples, some embodiments of this electro-magnetic driving hammer:

• Figure 1 is a longitudinal sectional view of an electro-magnetic driving hammer according to the invention;
• Figure 2 is a longitudinal sectional view of another electro-magnetic driving hammer, further equipped with a tearing device;
• Figure 3 is a longitudinal sectional view of a pile driver according to the invention, specially equipped for inclined driving;
• Figure 4 is a diagram of the electrical supply circuits of the electro-magnetic driving hammer according to the invention;
• Figure 5 is a diagram of the power supply circuits of this sheep, in another embodiment;
• Figure 6 shows yet another embodiment of the power supply circuits.

In Figure 1 is shown an electromagnetic threshing hammer, the falling mass of which is constituted by the movable core 1 of an electromagnet 2. The movable core 1 is mounted to slide, along a vertical axis 3, in the part fixed of the electromagnet 2 formed by a coil 4 surrounded by a ferromagnetic shield 5. The electromagnet 2 is mounted in an elongated tubular body 6, serving as sliding guide for the falling mass 1. The lower part of the body 6 of the sheep is used to house and retain an anvil 7 bearing on the element to be inserted 8, such as, for example, a tube.

When the coil 4 is supplied with electric current by conductors 9, 10 leading to this coil, it generates an electromagnetic induction flux which is channeled by the shield 5. Under the action of the magnetic field, the core moves. 1 rises, guided by the body 6 of the sheep, to a high position indicated by dotted lines. As soon as the supply of the winding 4 ceases, the core 1 falls in free fall and strikes the anvil 7, which transmits the shock to the element to be pushed in. A sensor 11, placed at the base of the body 6, detects the arrival of the movable core 1 in its low position, and then controls the supply of the winding 4 for the next stroke.

The power supply of the electromagnetic sheep, allowing the overall operation described above, is shown in Figure 4 in which are again shown, schematically, the core 1, the coil 4 and the shield 5 of the electromagnet 2, as well as the supply conductors 9, 10 and the position sensor 11.

The assembly is supplied from the three-phase network 12, via an isolation transformer 13. The secondary of the transformer 13 is connected to a three-phase rectifier bridge 14 composed, in the example considered, of three thyristors 15 and three diodes 16. The rectifier bridge 14 charges capacitors 17 through a self-induction coil 18 and a resistor 19 for limiting the load current, connected in series.

The supply conductors 9, 10 of the winding 4 of the electromagnet 2 are respectively connected to the two terminals of the capacitors 17, a thyristor 20 being interposed on one of the conductors 9. Optionally, a diode for recovering current 21 is mounted in derivation of thyristor 20 and in the opposite direction to the latter.

An electronic module 22 is connected to the control electrodes of the various thyristors 15 and 20, as well as to the position sensor 11. The electronic module 22 thus controls the charge and discharge cycle of the capacitors 17, which takes place as follows:

The conduction of the thyristors 15 allows the charging of the capacitors 17, through the self-induction coil 18 and of the resistor 19. The electronic module 22, from which the thyristors 15 are controlled, authorizes the adjustment of the conduction time. of these thyristors 15, and thus makes it possible to obtain a variation of the rectified voltage and a variable energy charge of the capacitors 17.

Then, the thyristor 20 is made conductive, which allows the electrical energy stored in the capacitors 17 to discharge suddenly in the coil 4 of the electromagnet 2, thus causing the attraction and lifting of the movable core 1 The variation of the energy stored in the capacitors 17 makes it possible to vary the lifting height of the core 1 and also the duration of the movement of the latter. It is therefore possible to vary the duration of the cycle, operation on a higher frequency corresponding to a lower amount of energy per stroke, and vice versa.

The position sensor 11 controls the thyristor 20 via the electronic module 22, for automatic repetitive operation, a new cycle starting again as soon as the previous one ends.

FIG. 5 shows a variant of the supply circuits, in which the discharge control thyristor 20 is completed by an extinguishing device consisting of another thyristor 23, a capacitor 24 and a resistor 25, connected as shown in the electrical diagram. All of the components 23, 24, 25 constitute a device for defusing the thyristor 20: the capacitor 24, which is charged through the resistor 25 during the conduction of the thyristor 20, then discharges through the thyristors 23, thus controlling the deactivation of thyristor 20.

The additional thyristor 23 is also controlled by the electronic module 22. More particularly, the operation of this thyristor 23 is triggered from a position sensor 26, placed at the upper end of the winding 4, see also figure 1. The sensor 26 thus positioned detects the instant when the movable core 1 has moved over the entire air gap of the electromagnet 2, and then causes the supply of the winding 4 to be cut off, which avoids a phenomenon of self-braking of the core 1 by its own movement when it exceeds the upper end of the winding 4. A certain loss of energy can, in this way, be avoided.

FIG. 6 shows another variant of the supply circuits, making it possible to obtain the previously described operation without a special extinguishing device. The thyristor for controlling the discharge of the capacitors 17 and its defusing device are here replaced by a "GTO" thyristor or extinguishing thyristor 20 '. This type of thyristor is controlled by a trigger signal of a certain polarity, and it can be turned off by canceling the main current. In addition, it can be extinguished using a trigger control current of different polarity, this extinction mode being of course controlled by the electronic module 22. It is easy to understand, by comparison with FIG. 5 , that the use of such an extinguishing thyristor 20 ′ simplifies the circuits, by eliminating several components.

FIG. 2 represents an electromagnetic threshing hammer comprising all the members described with reference to FIG. 1, and designated by the same references, namely: movable core 1 guided in a body 6, electromagnet 2 with its coil 4 and its shielding 5, and lower anvil 7, this sheep being completed by a mechanical device making it possible to transmit to the depressed element 8 tearing shocks.

The tearing-off device comprises a second anvil 27, placed at the top of the body 6 and comprising a part which penetrates into the central passage of this body 6 up to the level of the shielding 5. On the lateral parts of the upper anvil 27 are fit two stirrups 28, extending vertically outside the body 6 and having their lower parts secured by a horizontal axis 29 which passes through the lower anvil 7 and the element 8.

In operation, a crane not shown exerts an upward traction force on the sheep, by means of at least one cable 30 with elastic damper. When the winding 4 is excited, the core 1 which is violently projected upwards strikes the upper anvil 27. The shock is transmitted to the element 8 by the stirrups 28 and by the axis 29. When the winding 4 is no longer excited, the core 1 falls by gravity onto the lower anvil 7, then creating a driving impulse of small importance. The same cycle can then start again, controlled by the position sensor 11. The electrical supply circuits can be identical to those previously described with reference to FIG. 4, or alternatively produced according to the variant of FIG. 5 using a additional position 26.

Finally, FIG. 3 represents an electro-magnetic driving hammer, intended more particularly to be used with its axis 3 inclined on the vertical, for the inclined driving of the element 8. This sheep comprises the same organs as that of FIG. 1, designated by the same references, and it com further takes a second winding 31 with its shielding 32, placed below the main electromagnet 2. The additional winding 31 is inserted into an independent electrical loop circuit 33, further comprising capacitors 34 and a switch 35 connected in series with this winding 31, but which is not connected to any external power source.

In the use of the sheep in the inclined position, the braking of the movable core 1 by gravity during its ascent is less strong. The additional device described here provides additional braking for the core 1, so as to limit its ascent stroke:

When the lower end of the movable core 1 enters the winding 31, the switch 35 closes. The strongly magnetized core 1 generates in the circuit 33 an electric current which causes the capacitors 34 to charge and, at the same time, brakes the moving mass of the core 1, until it stops. The capacitors 34 then discharge in the winding 31, thus restoring the braking energy to accelerate the movement of the core 1 downwards. The switch 35 opens when the core 1 reaches the low position.

The electrical supply circuits can be produced as described above, with reference to FIGS. 4 or 5. The switch 35 can be produced in the form of a thyristor or a triac, and it is advantageously controlled from an additional position sensor 36 placed on the body 6 of the sheep, substantially at the level of the base of the additional winding 31. The control of the switch 35 can also be carried out by means of the electronic module 22, suitably supplemented as shown very schematically, in dotted lines, at the top of FIG. 5.

It goes without saying that the invention is not limited to the sole embodiments of this electro-magnetic threshing sheep which have been described above, by way of examples: on the contrary, it embraces the variants thereof. consisting in replacing certain components with equivalents in the sheep's power supply circuits, for example by replacing the diodes 16 with thyristors in the rectifier point 14, or alternatively, in the case of a sheep fitted with a device for 'tearing, by replacing the pin 29 visible in Figure 2 by a clamp or by any other suitable fixing means, depending on the nature of the reinforced element 8.

Claims (14)

1. Drop hammer pile driver, characterized in that the drop hammer, slidably mounted in an elongate body (6), is formed by a mobile core (1) of an electromagnet (2), whose screened coil (4, 5) coupled to the body (6), is connected to electric supply circuits (12 to 26) adapted for energizing this coil (4) for a short time so as to cause the mobile core (1) to be raised, this latter then falling by gravity to strike an anvil (7) secured to an element to be driven in (8) and transmitting the shock to this element (8).

2. Pile-driver according to claim 1, characterized in that it comprises de-energizing means (23, 24, 25) for interrupting energization of the coil (4) at a certain moment during raising of the mobile core (1).

3. Pile-driver according to claim 1, characterized in that it comprises an additional coil (31) supplied with power so as to contribute to the acceleration of the downward movement of the mobile core (1).

4. Pile-driver according to claim 1, characterized in that it comprises an additional coil (31), supplied with power so as to cause braking of the mobile core (1) limiting the raising stroke.

5. Pile-driver according to claim 1, characterized in that it comprises an additional coil (31), supplied with power so as to brake the mobile core (1) during raising thereof then accelerate its downward movement.

6. Electromagnetic pile driver according to claim 1, characterized in that the electric supply circuits comprise, for energizing the coil (4) so as to cause the mobile core (1) forming the drop hammer to be raised, capacitors (17) connected to a charging circuit (13, 14, 18, 19) as well as to power supply conductors (9, 10 for the coil (4), means (20) being provided on one at least of these supply conductors (9, 10) so as to cause the controlled discharge of the previously charged capacitors (17) into the coil (4).

7. Electromagnetic pile driver according to claim 6, characterized in that the circuit for charging the capacitors (17) comprises a rectifier bridge (14) with controlled thyristors (15) fed with AC current from an external source (12) and having its rectified current outputs connected to the capacitors (17), control means (22) being associated with the thyristors (15) of the rectifier bridge (14) for controlling the conduction time of these thyristors (15).

8. Electromagnetic pile driver according to claim 6 or 7, characterized in that the means provided for causing the controlled discharge of the capacitors (17) into the coil (4) comprise a thyristor (20, 20') inserted in one of the power supply conductors (9, 10) of this coil (4), and driven from a sensor (11) detecting the position of the mobile core (1), placed at the base of the body (6) of the pile driver.

9. Electromagnetic pile driver according to claim 8, characterized in that there is provided, associated with the thyristor (20) causing the discharge of the capacitors (17) into the coil (4), an electronic device (23, 24, 25) for de-energizing this thyristor (20), driven from another sensor (26) detecting the position of the mobile core (1), placed substantially at the level of the upper part of coil (4).

10. Electromagnetic pile driver according to claim 9, characterized in that the device for de-energizing tha thyristor (20) is formed of an additional thyristor (23), a capacitor (24) and a resistor (25), the additional thyristor (23) being connected to the means (22) controlling the other thyristors (15, 20).

11. Electromagnetic pile driver according to claim 8, characterized in that the thyristor causing discharge of the capacitors (17) into the coil (4) is an extinction thyristor (20').

12. Electromagnetic pile driver according to any one of claims 1 to 11, characterized in that, so as to further make possible removal of a previously driven in element (8), it comprises an additional anvil (27) placed above the coil (4), so as to be struck by the top of the mobile core (1) during raising thereof, the additional anvil (27) being connected by stirrup pieces (28) and means (29) for fixing to the element to be removed (8).

13. Electromagnetic pile driver according to any one of claims 1 to 12, intended more particularly for driving in a direction slanted with respect to the vertical, characterized in that it further comprises above its coil (4), causing raising of the mobile core (1), a screened coil (31, 32) for braking this mobile core (1), inserted in an independent electric circuit looped (33) with capacitors (34) and a controlled switch (35) connected in series with said braking coil (31).

14. Electromagnetic pile driver according to claim 13, characterized in that the switch (35) in series with the braking coil (31) and the capacitors (34) is driven from a sensor (36) detecting the position of the mobile core (1), placed on the body (6) of the pile driver substantially at the level of the base of braking coil (31).

Images