Field of the invention

The invention relates to a leader, a pile driving machine, and a method for increasing the functionality of a pile driving machine.

Background of the invention

A leader is an elongated part of a pile driving machine, having the function of enabling the expedient movement of a pile driving hammer or a pile driving auger in a direction that is transverse or inclined with respect to the ground surface during driving a pile into the ground. In an impact pile driving machine, the leader is formed of a base part mounted in its longitudinal direction, and a so-called telescopic leader which may be moved in the longitudinal direction of the leader with respect to the base leader (and thereby with respect to the base machine). In a drilling rig, the leader is stationary in the longitudinal direction; in other words, no part of the leader is movable in the longitudinal direction of the leader with respect to the base machine. In both pile driving machine types, the leader may normally be tilted, because the position of the pile to be driven into the ground may vary, and the leader has to be tilted to a horizontal position for the time of transport of the pile driving machine. In different types of pile driving machines, the requirements for the functionality of the leader are different. For an impact pile driving machine, it is important that the leader is movable in the longitudinal direction of the leader. This is utilized, among other things, when the pile to be driven into the ground is being hoisted below the hammer before starting impact pile driving. Therefore, in an impact pile driving machine, the leader is often mounted on the upper carriage of the pile driving machine, to be movable in the longitudinal direction of the leader, whereby the leader may be moved either upwards or downwards with respect to the rest of the pile driving machine. In a drilling rig, the leader is normally fixed in its longitudinal direction, because the leader is subjected to heavy loads in its longitudinal direction, for example when pulling up the tube of a bored pile to be cast in situ. Moreover, the leader may often be implemented in such a way that its length may be changed by adding or removing upper and lower extension pieces at the upper end and the lower end of the leader, respectively. At present, both the upper and the lower extension pieces are fastened to the leader when it is in the horizontal (transport) position. Normally, after the assembly, upper extension pieces are only removed from the leader of the pile driving machine when the pile driving method applied by the pile driving machine is changed. Extension pieces to be added to the lower end, however, are added or removed depending on the height position of the pile driving point with respect to the height position of the pile driving machine.

The present method for extending the leader requires that the leader be turned to the horizontal position, and that upper extension pieces be added above the leader and fastened to the leader. This is a slow and laborious operation, because after the extension, the leader cannot be hoisted up merely by applying the actuators and winches of the machine itself, but a separate crane is needed for this. Furthermore, if the same pile driving machine is to be used both for installation of bored piles and for impact pile driving, the problem is that the leader mounted for installation of bored piles makes it difficult to seize the pile, and on the other hand in installation of bored piles, the leader suitable for impact pile driving and movable in the longitudinal direction has to be locked in place with respect to the base part of the leader, because the leader is subjected to heavy loads in the longitudinal direction of the leader during installation of bored piles, as described above. Consequently, the leaders of prior art do not enable the implementation of a pile driving machine that would be suitable for both impact pile driving and the installation of bored piles (i.e. a so- called multipurpose pile driving machine) and would be as efficient as the impact pile driving machine or the drilling rig suitable for only one of the pile driving methods is at present. On the other hand, most pile driving constructors have to apply several different pile driving methods, which is why they end up acquiring separate machines for the different pile driving methods when using pile driving machines of prior art. Brief summary of the invention

It is an aim of the invention to provide a novel leader for increasing the functionality of the pile driving machine in such a way that the same leader may be converted to be suitable for different pile driving methods in a simpler and easier way, whereby the use of the same pile driving machine for different pile driving methods is possible in various situations more frequently than before. Furthermore, it is an aim of the invention to introduce a leader that provides a pile driving machine with various auxiliary functions which facilitate and speed up its usability in different operations relating to pile driving. Moreover, it is an aim of the invention to introduce a pile driving machine based on a leader according to the invention, and a method based on the use of such a leader, for increasing the functionality of the pile driving machine. The aim of the invention is achieved because in the leader according to the invention, the telescopic leader is movable with respect to the lower slide in the longitudinal direction of the leader, and is lockable on the front stabilizers of the pile driving machine, and because an implement fixing device used for connecting an implement is lockable in at least two positions on the telescopic leader, whereby the leader is suitable for use both in various impact pile driving methods and in methods for installing bored piles, because when the telescopic leader is locked on the lower slide the leader withstands the forces caused by the auger in the longitudinal direction of the leader, and when the leader is not locked on the lower slide it may be moved in the longitudinal direction of the leader; that is, it is suitable for impact pile driving. Fastening the implement fixing device in the selected position on the telescopic leader, it turn, makes it possible to use the movable telescopic leader for feeding the implement, which is needed e.g. in the so-called Kelly method. To put it more precisely, the method according to the invention is characterized in what will be presented in the independent claim 1 , the pile driving machine by what will be presented in the independent claim 13, and the method for increasing the functionality of the pile driving machine by what will be presented in the independent claim 14. Dependent claims 2 to 12 disclose some preferred embodiments of the leader according to the invention, and dependent claims 14 to 18 disclose some preferred embodiments of the method according to the invention. The leader according to the invention has the advantage that conversion of the pile driving machine to be suitable for different situations and different pile driving methods becomes easier and faster, because the leader may be moved in its longitudinal direction (i.e. hoisted and lowered) by fewer operations than before, thanks to moving by an actuator with linear movements, and because the leader may be easily and quickly locked in its longitudinal direction to be a stationary leader. Furthermore, the leader which is movable in its longitudinal direction by an actuator with linear movements may be utilized in many work steps of pile driving, such as erecting the pile before starting pile driving. All these new features make the pile driving machine equipped with the leader according to the invention more versatile than before, in a more cost-effective way than before. In a preferred embodiment of the leader according to the invention, the leader comprises at least one lower extension piece that is releasably fastened to the lower end of the telescopic leader, for extending the telescopic leader at its lower end. This is advantageous e.g. when the pile driving machine is used on an uneven terrain where piles have to be driven into the ground in places where the pile installation point is located lower than the pile driving machine.

Description of the drawings

The invention will be described in greater detail in the following, with reference to the accompanying drawings, in which

Fig. 1 shows a pile driving machine equipped with a leader according to the invention in a side view;

Fig. 2 shows the leader of the pile driving machine according to Fig. 1 in a side view, the telescopic leader and the lower slide as well as the hoisting cylinder between these being detached from each other;

Fig. 3 shows the leader of the pile driving machine according to Fig. 1 in a side view, at the connection area between the telescopic leader and the lower slide, the parts of the leader being fastened to each other; shows the leader of the pile driving machine according to Fig. 1 , the hoisting cylinder, and the lower and upper extension pieces to be attached to the leader, detached from each other, in a side view;

shows a perspective view of lower extension pieces to be attached to the leader of the pile driving machine according to Fig. 1 , shown in positions slanting in different directions;

shows a side view of the pile driving machine according to Fig. 1 when the leader is in the upper position and when the leader extended at the lower end is in the lower position and is used for driving a pile into the ground surface lower than the ground surface at the pile driving machine;

shows the leader of the pile driving machine according to Fig. 1 , and the hose bracket therein in a slanted view from the side in its upper extreme position when the leader and the extension pieces fastened to it are against the ground surface on the same level with the pile driving machine;

shows the leader of the pile driving machine according to Fig. 1 and the hose bracket therein in a slanted view from the side, in the lower extreme position when the leader and the extension pieces fastened to it are lowered onto the ground surface which is below the ground surface at the pile driving machine;

shows the leader of the pile driving machine according to Fig. 1 in a slanted view from the side, at the fastening point of the hose bracket, the hose bracket being fastened to the point shown in Fig. 7; and

shows the leader of the pile driving machine according to Fig. 1 in a slanted view from the side, at the fastening point of the hose bracket, the hose bracket being fastened to the point shown in Fig. 8.

A detailed description of certain preferred embodiments of the invention

Figure 1 shows a pile driving machine 10 equipped with a leader 17 operating by a method according to the invention. Thanks to the leader 17 according to the invention, the pile driving machine 10 shown in Fig. 1 may be used for driving bored piles, rammed piles or grooved/steel piles into the ground by vibration or by impact driving. When the pile driving machine 10 is used for driving bored piles, a bore motor as shown in Fig. 1 is mounted on an implement fixing device 22 for an implement 26 on a leader 17. When rammed piles are driven into the ground, the hammer of the pile driving apparatus is installed in the implement fixing device 22, and when grooved/steel piles are driven into the ground by vibration, a vibrator is installed in the implement fixing device 22. Both bored piles and rammed piles may be solid piles or so-called cast piles. Solid piles are piles made of concrete and/or steel which are driven into the ground by hammering or by drilling and which are left in position in the ground after the driving. Cast piles, on the other hand, are piles to be cast on site. For installing cast piles in the ground, a so-called dropchute is first driven into the ground (by hammering or by drilling). After this, reinforcement elements are installed inside the drop chute, and the actual pile to be left in the ground is cast. Right after casting the pile, the drop chute driven into the ground is pulled out of the soil. Of the parts driven into the ground before casting, only the loose tip from the end of the drop chute will remain in the ground. Therefore, the pile driving machine suitable for driving cast-in-situ piles must also be capable of pulling the drop chute, driven into the ground by hammering or drilling, out of the soil.

The pile driving machine 10 of Fig. 1 comprises a base machine 1 1 and a pile driving apparatus 12 mounted on it. The base machine 1 1 consists of an undercarriage 13 movable on the ground by a crawler track 16, by which the pile driving apparatus 12 is moved on the ground surface to a desired location where a pile is to be installed. The undercarriage 13 comprises the crawler track 16 and the required equipment for moving the pile driving machine 10 by them. Above the undercarriage 13, an upper carriage 14 is mounted on the undercarriage 13, to be swivelled in the horizontal direction by means of a swivel bearing 15. A driving engine 27 is provided in the rear section of the upper carriage 14, and a cabin 18, a horizontal boom 34 as well as the mounting structures and devices needed for mounting and moving the different parts, such as the leader 17, of the pile driving apparatus 12 are accommodated in the front section. The different functions of the base machine 1 1 and the pile driving apparatus 12 as well as e.g. the transmission for moving the crawler track 16 and for changing the travel direction of the base machine 1 1 are configured to be hydraulically operated by a hydraulics system in the base machine 1 1 . For providing the different functions, the driving engine 27 powers hydraulic pumps which are part of the hydraulics system and generate the flow and pressure of pressurized medium in the hydraulics system, for driving actuators belonging to the hydraulics system and effecting various functions. The cabin 18 is equipped with control devices to be applied by the driver of the pile driving machine 10 for controlling the different functions of the pile driving machine. Furthermore, the cabin 18 is equipped with, among other things, an electronic control unit for controlling the control valves (magnet and/or servo valves) of the hydraulics system for regulating and controlling the supply of pressurized medium to the different actuators of the hydraulics system. Control commands generated by the control unit may be influenced by control functions effected by control devices, for example by turning control sticks in different directions, or by pedals. In this way, a control system is configured, by which the user of the pile driving machine may perform desired tasks so that the control unit controls the different functions in such a way that they are effected in a way that is expedient for each task, taking work safety aspects into account.

The pile driving apparatus 12 comprises a leader 17 and an implement 26 to be mounted on it, which may be one of those mentioned above, for example a piling auger or the hammer of an impact pile driving apparatus. In the pile driv- ing device 12 shown in Fig. 1 , the implement 26 to be mounted on the leader 17 is a piling auger. For mounting the implement 26 to the leader 17 in a detachable manner, an implement fixing device 22 is movably connected to the leader 17 in its longitudinal direction and equipped with the necessary mounting means for mounting the implement 26 on the implement fixing device 22, as well as with the necessary connecting means and hydraulic hoses for connecting the implement 26 to the hydraulics system of the base machine 1 1 . The implement fixing device 22 is fastened to guide tracks 23 on the leader 17. The implement fixing device 22 is moved along the guide tracks 23 of the leader 17 by pulling ropes (not shown) on the leader 17 of the pile driving machine 10 according to Fig. 1 , driven by a pull-up winch and a pull-down winch. Pulleys 25 are provided in different locations between the upper and lower ends of the leader 17 as well as in the cathead 24 at the top end of the leader 17, for guiding the pulling ropes from the pull-down and pull-up winches placed in the base machine 1 1 , to the implement fixing device 22. According to the implement in question, the pulling ropes are guided via the different pulleys 25 so that in the case of the respective type of implement, the implement fixing device 22 is given the desired velocity and force according to the requirements of the pile driving operation to be performed by using said implement. In the pile driving machine 10 shown in Fig. 1 , the leader 17 is a leader operating by the method according to the invention. To implement this, the leader 17 of the pile driving machine 10 shown in Fig. 1 comprises, as shown in Figs. 2 to 4, a lower slide 19 and a telescopic leader 20, as well as lower extension pieces 31 and upper extension pieces 40 to be connected to it. The telescopic leader 20 is connected to the lower slide 19 mounted on the upper carriage 14 of the base machine 1 1 , to be movable upwards and downwards in the longitudinal direction of the telescopic leader 20 with respect to the pile driving machine 10 by an actuator 28 with linear movements, and to be locked in specific positions by locking devices. The leader 17 (i.e. the lower slide 19 and the telescopic leader 20 movable with respect to it) may also be tilted by actuators 29 and 30 with linear movements in different directions (forward, backward, and to the left and to the right). Moreover, the leader 17 may be moved forward and backward in the travel direction of the pile driving machine 10 so that its position (angle of deflection) is not changed. To provide this function, the fas- tening point of the stationary lower slide 19 of the leader 17 in the upper carriage 14 of the base machine 1 1 is arranged to be movable forward and backward by means of a so-called horizontal boom 34. The leader 17 of the pile driving machine 10 shown in Fig. 1 may also comprise a passenger hoist (movable along guide tracks by the side of the telescopic leader 20), by which the operator of the pile driving machine 10 or an assisting person may be hoisted to a desired point of the leader 17 when various preliminary operations are performed before starting the pile driving, i.e., for example pulling ropes relating to the implement fixing device 22 are installed on pulleys 25 and fastened to the implement fixing device 22. Such an operation is performed, for example, when the transmission ratio provided by the different pulleys of the leader 17 is to be changed, for changing the pull-down/pull-up force and the pull-down/pull-up speed. Further, in the leader 17 of the pile driving machine 10 shown in Fig. 1 , a so-called erecting device is provided between the lower slide 19 and the upper carriage 14 of the base machine 1 1 , by which the leader 17 tilted to the horizontal position may be erected from the horizontal position to an angle of about 45°, from which the leader 17 may be turned further to a desired operating position (for example vertical position) by lateral inclination cylinders 29 and 30.

The lower slide 19 is provided with guide tracks, on which the telescopic leader 20 is mounted to be movable in the longitudinal direction of the telescopic leader 20 and the lower slide 19 parallel with it. The upper slide 21 is provided with guide tracks, by which the lateral inclination cylinders 29 and 30 for allowing the tilting of the leader 17 are fastened to the telescopic leader 20, to be movable in its longitudinal direction. In practice, the magnitude of the angle of inclination is limited by the stability of the pile driving machine, which is influenced by e.g. the position of the stabilizers and the crawlers, and the fact whether the counterweight, detachably fixable in the rear part of the base machine 1 1 , is installed or not. In the pile driving machine 10 shown in Fig. 1 , the actuator 28 (or so-called leader hoisting cylinder) with linear movements, moving the leader 17 in its longitudinal direction, is a duplex double-acting hydraulic cylinder which moves the telescopic leader 20 up and down with respect to the lower slide 19. The leader hoisting cylinder 28 is provided with a central part 28a (cylinder part) between the moving ends, and a first moving end 28b and a second moving end 28c moving outwards from the respective ends and inwards again. The travel length of the first moving end 28b (upper end) of the leader hoisting cylinder 28, parallel to the leader 17, is 6500 mm, and the travel length of the second moving end 28c (lower end) is 1 150 mm. The advantage of the duplex hydraulic cylinder to a conventional double-acting hydraulic cylinder is the fact that it provides a great travel length with a shorter travel length of a single moving end. This, in turn, makes the duplex hydraulic cylinder less expensive to purchase than a hydraulic cylinder with a single moving end having the corresponding travel length, because a great increase in the length of the moving end (i.e. the piston rod) of the hydraulic cylinder requires high strength and dimensional accuracy of the piston rod, which increases the manufacturing costs and thereby the purchase price of the hydraulic cylinder to a significant extent.

The leader 17 is extended by leading the pressurized medium within the leader hoisting cylinder 28 to the piston side, whereby the whole telescopic leader 20 will move upward along the lower slide 19. The leader 17 is shortened (i.e. moved downward) by leading the pressurized medium within the leader hoisting cylinder 28 to the piston rod side, whereby the telescopic leader 20 will move downward along the lower slide 19. These functions are controlled by applying a control stick for controlling these functions, placed in the cabin 18 of the pile driving machine 10.

The telescopic leader 20 may be locked to the lower slide 19 at three points by locking devices operated by actuators between the front stabilizers 46 and the telescopic leader 20. In this embodiment, these locking devices comprise locking sleeves placed in the telescopic leader 20 and a locking pin which fits inside a locking sleeve hydraulically moving (by a double-acting hydraulic cylinder) back and forth and may be moved to the inside of a locking sleeve in a locking position in the telescopic leader 20, whereby the telescopic leader 20 is locked in the longitudinal direction, and out of the locking sleeve, whereby the telescopic leader 20 is released and is movable by the leader hoisting cylinder 28. When the telescopic leader 20 is locked to the front stabilizers 46, it corresponds to a leader fixed to be stationary. In working methods requiring a high pull-up force, such as the installation of bored pipes, the telescopic leader 20 is locked to the front stabilizers 46. For example in the pile driving machine shown in Fig. 1 , the telescopic leader 20 may be subjected to a force of about 1000 kN when the drop chute for the bored pile to be cast in situ is pulled out of the soil. Therefore, the diameters of the locking pins and sleeves should be sufficiently large, in order to achieve a sufficiently strong locking between the telescopic leader 20 and the front stabilizers 46.

The leader 17 of the pile driving machine 10 shown in Fig. 1 may be extended at its lower end. Thus, the telescopic leader 20 is moved from the basic position (the position shown in Fig. 1 where the telescopic leader 20 is in the lowermost position with respect to the lower slide 19) upwards along the lower slide 19, and one or more lower extension pieces 31 are added underneath the telescopic leader 20. The lower extension pieces 31 are pieces corresponding to the leader 20 with respect to their shape and diameter, and having a suitable length (typically 2500 to 3800 mm). The first end of the lower extension piece 31 is equipped with fastening members 36 to be fastened to the fastening members 35 at the lower end 20a of the telescopic leader 20, for connecting the lower extension piece 31 to the lower end of the telescopic leader 20 so that the guide tracks 23 of the implement fixing device 22 movable in the longitudinal direction of the telescopic leader 20, in front of the telescopic leader 20, are aligned with the guide tracks of the lower extension piece 31 which are equal in shape with the guide tracks of the telescopic leader 20.

In this case, the fastening members 36 of the lower extension pieces 31 comprise groove-like fitting openings 36a (4 openings) at the upper end of the lower extension piece 31 , and fastening lugs 35a (4 lugs) on a lower end plate at the lower end of the telescopic leader 20. The fastening lugs 35a of the telescopic leader 20 may be fitted through the fitting openings 36a at the upper end of the lower extension pieces 31 , to the inside of the lower extension piece 31 , and two locking pins 37 (shown in Fig. 5) may be fitted from the side of the lower extension piece 31 to the fitting openings 36a. For the locking pins 37, the lower extension pieces 31 are provided with guide holes 38 placed inside (above) the upper end plate 39, extending through the side wall of the lower extension piece 31 . The guide holes 38 are placed in the side walls of the lower extension piece 31 in such a way that the locking pins 37 may be fitted through them, and through fitting holes 35b at the ends of the fastening lugs 35a fitted through the fitting openings 36b at the upper end 31 a of the lower extension piece 31 . Thus, the locking pins 37 lock the fastening lugs 35a of the lower extension piece 31 in place, and the lower extension piece 31 is mounted against the lower end 20a of the telescopic leader 20.

After the fastening of the lower extension piece 31 , the implement fixing device 22, movable along the telescopic leader 20, may be moved from the telescopic leader 20 to the lower extension piece 31 fastened below it, and back from the lower extension piece 31 to the telescopic leader 20. Because there may be several lower extension pieces 31 , the second end of each lower extension piece 31 is equipped with fastening members 36 corresponding to the fastening members 35 at the lower end 20a of the telescopic leader 20, whereby the next lower extension piece 31 below may be fastened at its first end 31 a to the second end 31 b of the preceding lower extension piece 31 above, so that the implement fixing device 22 may be moved further from the preceding lower extension piece 31 above to the next lower extension piece 31 below, and back from this lower extension piece 31 below to the next lower extension piece 31 above. The implement 26 fastened to the implement fixing device 22, that is, for example a hammer, a bore motor or a vibrator, will need pressurized medium for its operation, and therefore, pressurized medium hoses are led from the base machine to the implement. The pressurized medium hoses have to allow the movement of the implement 26 and thereby the implement fixing device 22 along the guide tracks of the telescopic leader 20 between the upper end and the lower end 20a of the telescopic leader 20. Therefore, the pressurized medium hoses are equipped with a so-called hose bag; that is, they are fastened to the leader 17 in such a way that they enable the movement of the implement 26 but, on the other hand, they do not hang on the ground when the implement 26 is moved to or close to the lower end 20a of the telescopic leader 20. In leaders of prior art, this problem is solved by fixing a so-called hose bracket 41 at a determined height level in the middle of the leader, the pressurized medium hoses (not shown) being fastened to it at a suitable fastening point. This fastening point is normally selected in such a way that when the implement 26 is moved to its lowermost position, the pressurized medium hoses are not so slack that the hose bag would extend down to the ground when the implement is in the vicinity of the lower end of the leader. In the embodiment of the pile driving machine 10 shown in Fig. 1 , however, the situation is changed because when lower extension pieces 31 are used, the implement 26 may be moved several meters lower than the normal level. Furthermore, there are situations in which the implement 26 is moved below the ground level supporting the base machine 1 1 . Applying the method of prior art for supporting the pressurized medium hoses, the pressurized medium hoses would prevent the movement of the implement 26 to the lower extension pieces 31 , because the travel distance allowed by the pressurized medium hoses downwards is already close to its maximum when the implement 26 is at the lower end of the telescopic leader 20. On the other hand, merely extending the length of the pressurized medium hoses would lead to a situation in which the hose bag formed of the pressurized medium hoses would be at least partly against the ground when the implement 26 is at the lower end of the telescopic leader 20 and the lower end 20a of the telescopic leader 20 is against the ground surface. To prevent this undesired situation, the pile driving machine shown in Fig. 1 is equipped with a hose bag whose height position is adjustable. In this case, the adjustment of the height position of the hose bag is implemented by fastening the hose bracket 41 supporting the pressurized medium hoses to the guide tracks on the telescopic leader 20, to be movable in the longitudinal direction of the telescopic leader 20 and to be locked in a desired position. In this embodiment, the hose bracket 41 is moved by a hose bracket cable movable by a cathead winch. The hose bracket 41 may be moved in the direction of the upper end of the telescopic leader 20 by guiding the hose bracket cable directly from the hose bracket by an auxiliary winch, and in the direction of the lower end by gravity so that the hose bracket 41 is supported by the auxiliary winch. The position of the hose bracket 41 in different situations is shown in Figs. 7 and 8, and the principle of operation of the locking mechanism holding the hose bracket in its place is shown in Figs. 9 and 10.

Fig. 7 shows the hose bracket 41 locked in its upper extreme position when two extension pieces 31 are connected to the leader 17 and when the leader 17 is in the normal position so that the lower end of the lower extension piece 31 and the front stabilizers 46 are against the ground surface, flush with the pile driving machine. Figure 8 shows the hose bracket 41 locked and moved to its lower extreme position when two extension pieces 31 are connected to the leader 17 and when the leader 17 is lowered against the ground so that the lower end of the lower extension piece 31 is against the ground surface lower than the ground surface flush with the pile driving machine (that is, the pile is being driven e.g. to the bottom of a pit or a hollow in front of the pile driving machine 10).

In this embodiment, the locking of the hose bracket 41 is arranged by means of a locking pin 42, a locking eyelet 44 and locking frames 43 and 45. Figure 9 shows the locking of the hose bracket 41 by the locking pin 42 when the hose bracket is in the upper extreme position shown in Fig. 8. Thus, the locking pin 42 is fitted through the locking frame 43 in the upper slide 21 and the locking eyelet 44 in the hose bracket 41 . Thus, the movement of the hose bracket 41 with respect to the upper slide is prevented. Figure 10 shows the locking of the hose bracket 41 in its lower extreme position. Thus, the locking pin 42 is fitted through the locking frame 45 in the hose bracket 41 and inserted in the opening in the frame of the telescopic leader 20, whereby the movement of the hose bracket 41 with respect to the telescopic leader 20 is prevented. As shown in the enlarged view of the locking points in Figs. 9 and 10, in the latter case the locking pin 41 is turned 90° with respect to the first mentioned situation. This is due to the fact that in this case, the locking is implemented so that in the upper extreme position, the hose bracket 41 is locked to the upper slide 21 , whereby it remains in its position if the telescopic leader 20 is moved downwards or upwards, and in the lower extreme position it is locked to the tele- scopic leader 20, whereby it moves with the telescopic leader 20 if the telescopic leader 20 is moved downwards or upwards. In fact, the hose bracket 41 may in this embodiment be locked to the telescopic leader 20 as shown in Fig. 10 (by fitting the locking pin through the lock frame 45 and through an opening in the frame of the telescopic leader 20) at any opening in the frame of the telescopic leader 20, in that part of the telescopic leader 20 where the hose bracket 41 may be moved along the guide tracks on the telescopic leader 20.

Lower extension pieces 31 are hoisted to their places by a so-called jib boom 32 in the cathead 14. It comprises both a winch placed in the base machine 1 1 and a hoisting member (e.g. a lifting hook, a shackle, or the like) at the end of its hoisting cable. The lower extension piece 31 to be installed on the telescopic leader 20 is connected to the hoisting member so that it may be hoisted into place below the telescopic leader 20. The jib boom 32 is implemented in such a way that it may be swivelled with respect to an axis parallel to the longitudinal direction of the leader 17 as well as swivelled with respect to the horizontal axis (that is, turned about 80° from the horizontal position to an almost vertical position as well as to a desired position between these positions). This makes it easier to move the lower extension pieces 31 to a suitable location below the lower end 20a of the telescopic leader 20. When installing the lower extension pieces 31 , the leader 17 may be slightly tilted backwards, whereby the lower extension pieces 31 may be easily guided to the guide tracks of the lower slide 19 by moving the jib boom 32 and simultaneously guiding the lower extension pieces 31 manually. To bring the lower extension pieces 31 on the guide tracks of the lower slide 19, the guide surfaces of the lower extension pieces 31 are made expandable so that the lower extension piece 31 may be placed on the guide tracks of the lower slide 19 by moving its front side against the guide tracks and then constricting the guide tracks of the lower extension piece 31 to the guide tracks of the lower slide 19. The lateral inclination cylinders 29 and 30 of the pile driving machine 10 shown in Fig. 1 are double-acting hydraulic cylinders. They may be extended by feeding pressurized medium to the piston side of these hydraulic cylinders 29 and 30, or shortened by feeding pressurized medium to the piston rod side. Also, the inclination of the leader 17 in different directions is controlled by control sticks in the cabin 18.

To facilitate the tilting of the leader 17 (i.e. the lower slide 19 and the telescopic leader 20 mounted on it), the lower slide 19 is fastened to its fastening point in the upper carriage 14 by a tilting joint 33. This makes it possible for the leader 17 to swivel to the right and the left with respect to an axis parallel to the longitudinal (travel) direction of the base machine 1 1 , as well as forward and backward with respect to a transverse axis (perpendicular to the travel direction). As a result, the position of the leader 17 depends on the position of the moving ends of the lateral inclination cylinders 29 and 30 with respect to the fastening point of the leader 17. Because the position of the fastening point of the leader 17 is also movable with respect to the rest of the upper carriage 14, thanks to the horizontal boom 34 in the front part of the upper carriage 14, the position of the leader 17 is dependent on the position of the horizontal boom 34 as well. The lower ends of the lateral inclination cylinders 29 and 30 are fastened to the frame of the upper carriage 14, and the upper ends to the upper slide 21 . The lower ends of the lateral inclination cylinders 29 and 30 are farther from each other than the upper ends, whereby the lateral inclination cylinders 29 and 30 are in an inclined position with respect to the pile driving machine 10 so that the left lateral inclination cylinder 29 and the right lateral inclination cylinder 30 approach each other in the direction towards the upper slide 21 . The control of the leader 17 is configured so that the leader 17 is inclined to the right when the control stick controlling this function is turned to the right. Thus, the right lateral inclination cylinder 29 becomes shorter and the left lateral inclination cylinder becomes longer. The leader 17 is inclined to the left when the above mentioned control stick is turned to the left. Thus, the left lateral inclination cylinder 30 becomes shorter and the right lateral inclination cylinder 29 becomes longer.

When the control stick controlling the tilting forward and backward is pushed forward, each lateral inclination cylinder 29 and 30 becomes longer, whereby the leader 17 is tilted forward. When this control stick is moved backward, both lateral inclination cylinders 29 and 30 become shorter, whereby the leader 17 is tilted backward. For safety reasons, the movements of the actuators controlling the leader 17 may be prevented when the implementation of a movement might cause danger situations. Consequently, the control of the lateral inclination cylinders 29 and 30 is only allowed when it is not prevented by check valves provided for this in the hydraulics system of the pile driving machine 10.

In the pile driving machine shown in Fig. 1 , the lateral inclination cylinders 29 and 30 may also be controlled to move one by one. Thus, the control sticks controlling the position of the leader 17 have to be turned to a cross angle. Thanks to the versatile functions of the leader 17 of the pile driving machine 10, the pile driving machine 10 may be moved from one place to another more independently, easily and faster than before, because the preparatory steps require fewer auxiliary devices separate from the pile driving machine 10 than before. For example, a separate crane is no longer required for erecting the leader 17, because the leader 17 may be turned from a horizontal position to an angle of 45° by the erecting device between the leader 17 and the base machine. Many other preparations have also been made less time-consuming than before, thanks to e.g. the easy and convenient usability of the telescopic leader 20 movable along the lower slide 19 by the leader hoisting cylinder 28, and e.g. by the design of the different pulling ropes so that the ropes do not need to be passed on the pulleys 25 again when the leader 17 has to be tilted to the horizontal position for transportation of the pile driving machine 10.

Thanks to its versatile functions, the leader 17 of the pile driving machine 10 shown in Fig. 1 may be used for various pile driving operations in a more versatile way than before. The leader hoisting cylinder 28 of the telescopic leader 20 may act as a telescopic cylinder for moving the telescopic leader 20 with respect to the lower slide 19 in impact driving, and as a feed cylinder in so- called Kelly work. Further, for example when the pile is to be mounted on the bottom of a pit or a hollow in the ground where the whole pile driving machine

10 cannot be driven, as shown in Fig. 6, it is possible to drive the base machine

1 1 to the brink of this pit or hollow, as shown in Fig. 6, and then to extend the leader 17 by lower extension pieces 31 fastened underneath the lower end of the telescopic leader 20. After this, the telescopic leader 20 and the lower extension pieces 31 fastened to it may be moved from the brink of the pit or hollow downwards so that the lower end of the lowermost lower extension piece 31 is brought against the ground surface on the bottom of the pit or hollow in the same way as the lower end 20a of the telescopic leader 20 is brought against the ground surface in front of the base machine 1 1 when working on level ground.

The leader according to the invention, having more versatile functions than before, may be implemented, in many respects, in a way different from the example embodiment presented above. In an alternative, the actuator with lin- ear movements, used for moving the telescopic leader in the longitudinal direction of the leader, could also be, instead of a duplex double-acting hydraulic cylinder, e.g. an ordinary double-acting hydraulic cylinder having a sufficiently long range and equipped with one moving head. Furthermore, the movement of the leader could, if desired, also be implemented by two single- acting hydraulic cylinders extending in opposite directions (and possibly placed e.g. adjacent to or on top of each other between the lower slide and the telescopic leader). In principle, in an embodiment of the method, of the leader and of the pile driving machine according to the invention, the movement of the telescopic leader in its longitudinal direction could also be implemented by an actuator of a shaft motor type, or by a gear rack and a gear wheel. In this case, the actuator for producing the rotary movement would move the moving end of the the telescopic leader (or the gear rack) moving the telescopic leader with respect to the base leader linearly in the longitudinal direction of the leader. Also, other parts of the leader according to the invention may be implemented in a number of ways different from the example embodiment shown in Figs. 1 to 10. For example, the lateral inclination cylinders may be, in the same way as the hoisting cylinder, various actuators with linear movements, and their fastening points between the base machine and the lower slide may be selected and/or implemented in different ways. In an embodiment of the method, of the leader and of the pile driving machine according to the inven- tion, the lower extension pieces may implemented to have fastening and locking mechanisms operating in different ways, for fastening and locking the lower extension pieces to the telescopic leader and to each other. Also, the adjustment of the hose bag used for guiding the pressurized medium hoses of the implement movable along the telescopic leader may be implemented in vari- ous ways. In the method based on the adjustment of the hose bracket, the movement of the hose bracket along guide tracks on the telescopic leader could be implemented by means of e.g. a screw and a threaded transfer member fastened to the hose bracket, a chain fastened to the hose bracket, a hydraulic cylinder, or by providing the hose bracket with an actuator for moving the hose bracket by means of a gear wheel and a gear rack. The adjustment of the position of the hose bag may also be implemented by adjusting the fastening point of the pressurized medium hoses with respect to the hose bracket which is stationary. This could be done, for example, by providing the hose bracket with two guide rollers (made of e.g. rubber) opposite each other and rotatable in different directions. By threading the pressurized medium hoses from the base machine to the implement between these guide rollers, the fastening point of the pressurized medium hoses may be adjusted by rotating the guide rollers. In such a method for adjusting the hose bag, the pressurized medium hoses are moved in the direction of the implement when the imple- ment is moved to the lower extension pieces, and back to the normal position when the implement moves from the lower extension pieces back to the lower end of the telescopic leader. This arrangement does not require that the hose bracket be fastened to the leader in a movable way, but it requires that the pressurized medium hoses have to be longer than in the above mentioned arrangement for adjusting the position of the hose bag, based on the movable hose bracket. Furthermore, in a method and a leader according to the invention, the locking of the telescopic leader with respect to the lower slide may be implemented by locking devices operating in different ways. These locking devices may be controllable from the cabin, or manually installable between the lower slide and the telescopic leader. There may also be more than one locking device, and the locking provided between the lower slide and the telescopic leader may be arranged so that there may be one or more locking points, e.g. at regular intervals over the whole length of the movement range of the telescopic leader. The method, the leader, and the pile driving machine according to the invention are thus not limited to the above described example application but they may be implemented in various ways within the scope of the appended claims.