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Title:
PILE DRIVER
Document Type and Number:
WIPO Patent Application WO/2017/174862
Kind Code:
A1
Abstract:
The invention relates to a method, a system, and software for controlling the motors of a pull-down winch and a wind-up winch of a pile driving rig. In the method for controlling motors of winches in a pile driving rig, a slide is movable by a pull-down winch (200d) and a pull- up winch (200u) in opposite directions via pulling ropes (222d, 222u). In the method, a displacement of the motor of the pulling winch is adjusted in response to a change in a load effective on said pulling winch in such a way that the pressure in the motor of the pulling winch tends to be maintained at a set constant pressure.

Inventors:
KORPIJAAKKO TAPIO (FI)
LYYTIKÄINEN VILLE (FI)
PUURUNEN TOMMI (FI)
PAAVOLA JAAKKO (FI)
PENTIKÄINEN MINNA (FI)
Application Number:
PCT/FI2016/050226
Publication Date:
October 12, 2017
Filing Date:
April 08, 2016
Export Citation:
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Assignee:
JUNTTAN OY (FI)
International Classes:
E02D7/16
Foreign References:
EP2275604A12011-01-19
EP2570554A12013-03-20
Attorney, Agent or Firm:
BERGGREN OY (FI)
Download PDF:
Claims:
Claims:

1 . A method for controlling motors of winches of a pile driving rig, where a slide is movable by a pull-down winch (200d) and a pull-up winch (200u) in opposite directions via pulling ropes (222d, 222u), the method comprising

- adjusting displacement of the motor of the pulling winch in response to a change in the load effective on said pulling winch in such a way that the pressure in the motor of the pulling winch tends to be maintained at a set constant pressure.

2. The method according to claim 1 , comprising setting the constant pressure control for the motor of the pulling winch, either the motor of the pull-down winch (200d) or the motor of the pull-up winch (200u), that winds up its pulling rope (222d/222u) onto drum.

3. The method according to any of the claims 1 to 2, wherein the constant pressure is determined by the controllable set pressure of the motor of the slide and/or of the implement connected to it.

The method according to any of the claims 1 to 3, wherein the displacement of the motor of the pulling winch is determined by software in response to a change in the load of said winch in such a way that the constant pressure is maintained in the motor.

The method according to any of the claims 1 to 4, wherein the rope speed effective on the slide of the non-pulling winch, either the pull-up winch (200u) or the pull-down winch (200d), is set to correspond to the rope speed effective on the slide of the pulling winch.

6. The method according to any of the claims 1 to 5, wherein the constant pressure control being set, the displacement of the motor of said winch is turned down in response to a decrease in the load of said winch, and the displacement of the motor of said winch is turned up in response to an increase in the load of said winch.

7. The method according to any of the claims 1 to 6, wherein the pressure in the motor of the implement, of the slide, of the pull-down winch (200d) and/or of the pull-up winch (200u) is measured by a pressure sensor, and the displacement of the motor of the pulling winch is con- trolled in response to a change in the value of the pressure sensor.

8. The method according to any of the claims 1 to 7, wherein the slide and the implement connected to it are movable by the pull-down winch (200d) and the pull-up winch (200d).

9. The method according to any of the claims 1 to 8, wherein the slide is pulled downwards by the pull-down winch (200d) and upwards by the pull-up winch (200u), and wherein constant pressure control is set for the motor of the pull-down winch (200d) at a pull-down stage.

10. The method according to any of the claims 1 to 9, wherein the slide is pulled downwards by the pull-down winch (200d) and upwards by the pull-up winch (200u), and wherein constant pressure control is set for the motor of the pull-up winch (200u) at a pull-up stage.

1 1 . The method according to any of the claims 1 to 10, wherein at the a pull-down stage, the pull speed of the pulling rope (222d) of the pulldown winch (200d) is influenced by the volume flow rate supplied to the motor of the pull-down winch and by the displacement effective in the motor of the pull-down winch, and the speed of the pulling rope

(222u) of the pull-up winch (200u), effective on the slide, is set equal to the speed of the pulling rope (222d) of the pull-down winch (200d), effective on the slide. 12. The method according to claim 1 1 , wherein the volume flow rate to be supplied to the motor of the pull-down winch (200d) is determined by the measured rope speeds of the pulling rope (222u) of the pull-up winch (200u) and the pulling rope (222d) of the pull-down winch (220d) so that the rope speeds effective on the slide are of equal speed but of opposite directions.

13. The method according to claim 1 1 , wherein the volume flow rate to be supplied to the motor (200d) of the pull-down winch is determined by the volume flow rate controller by applying feedback of a force value of the pulling rope (222u) of the pull-up winch (200u) and a momentary volume flow rate reference value which is influenced by the displacement of the motor of the pull-down winch (200d) and the rotation speed of the motor of the pull-up winch.

14. The method according to any of the claims 1 to 13, wherein in the pull- up stage, the pulling speed of the pulling rope (222u) of the pull-up winch (200u) is influenced by a volume flow rate of the motor of the pull-up winch and a displacement of the motor of the pull-up winch, and the unwinding speed of the pulling rope (222d) of the pull-down winch (200d) is set equal to the pulling speed of the pulling rope (222u) of the pull-up winch (200u).

15. The method according to claim 12 or 13, wherein the volume flow rate to be supplied to the motor (200u) of the pull-up winch is determined by the volume flow rate controller, which is influenced by a displacement of the motor (200u) of the pull-up winch, in such a way that the rotation speed of the shaft of the motor of the pull-up winch (200u) tends to be maintained constant as the displacement varies.

16. A pile driving rig comprising a winch control system comprising

- a pull-down winch (200d) and a motor of the pull-down winch,

- a pull-up winch (200u) and a motor of the pull-up winch,

- a pulling rope (222d) for connecting the pull-down winch (200d) to a slide of the pile driving rig,

- a pulling rope (222u) for connecting the pull-up winch (200u) to the slide of the pile driving rig,

- means for adjusting a displacement of the motor of a pulling winch in response to a change in a load effective on said pulling winch in such a way that the pressure in the motor of said winch tends to be maintained a set constant pressure.

17. The pile driving rig according to claim 16, wherein the motor of the pull-down winch (200d) and/or of the pull-up winch (200u) is a variable displacement hydraulic motor.

18. The pile driving rig according to any of the claims 16 to 17, comprising a constant pressure controller for setting constant pressure control for the motor of the pulling winch arranged to wind pull up rope on a drum, the motor being either the motor of the pull-down winch (200d) or the motor of the pull-up winch (200u).

19. The pile driving rig according to any of the claims 16 to 18, comprising means for determining a displacement of the motors of the pull-down winch and of the pull-up winch by software.

20. The pile driving rig according to any of the claims 16 to 19, comprising means for setting the rope speed effective on the slide of the non- pulling winch, either the pull-up winch (200u) or the pull-down winch (200d), to correspond to the rope speed effective on the slide of the pulling winch.

21 . The pile driving rig according to any of the claims 16 to 20, wherein the means for controlling the displacement of the motor of the pulling winch comprise means for controlling the displacement of the motor of the pulling winch

- down in response to a decrease in a load effective on said winch, and

- up in response to an increase in a load effective on said winch, when constant pressure control is switched on.

22. The pile driving rig according to any of the claims 16 to 21 , comprising a pressure sensor for measuring the pressure in the motor of the pulling winch, of the non-pulling winch, of the slide, and/or of the implement, and for controlling the displacement of the motor of the pulling winch as a function of the value of the pressure sensor.

23. The pile driving rig according to any of the claims 16 to 22, comprising the hydraulic motor of the pulling winch, where the displacement of the hydraulic motor of the pulling winch (200d, 200u) is controllable, optionally the displacement being adjustable in a continuous and/or stepless manner.

24. The pile driving rig according to any of the claims 16 to 23, wherein an implement is connectable to the slide. 25. The pile driving rig according to any of the claims 16 to 24, wherein the constant pressure control is settable for the motor of the pull-down winch (200d) at the pull-down stage of the pile driving operation, and the constant pressure control is settable for the motor of the pull-up winch (200u) at the pull-up stage of the pile driving operation.

26. The pile driving rig according to any of the claims 16 to 25, wherein in the pull-down stage, the rope speed of the pulling rope (222d) of the pull-down winch (200d), effective on the slide, is configured to depend on

- a volume flow rate supplied to the motor of the pull-down winch,

- a displacement of the motor of the pull-down winch, and

- a reference diameter of a drum of the pull-down winch; as well as

- optionally on a possible rope factor and a possible gear,

where the rope speed of the pulling rope (222u) of the pull-up winch (200u), effective on the slide, is configured to correspond to the rope speed of the pulling rope (222d) of the pull-down winch (200d), effective on the slide.

27. The pile driving rig according to claim 26, comprising a volume flow rate controller for determining the volume flow rate to be supplied to the motor (200d) of the pull-down winch by using a feedback of a force value of the pulling rope (222u) of the pull-up winch (200u) as well as a momentary reference value of the volume flow rate, which is influenced by the displacement of the motor of the pull-down winch (200d) and the rotation speed of the motor of the pull-up winch (200u).

28. The pile driving rig according to any of the claims 16 to 27, wherein in the pull-up stage, a rope speed of the pulling rope (222u) of the pull-up winch (200u), effective on the slide, is configured to depend on

- a volume flow rate supplied to the motor of the pull-up winch, - a displacement of the motor of the pull-up winch, and

- a reference diameter of a drum of the pull-up winch (200u), as well as

- optionally on a possible gear and/or rope multiples,

where the rope speed of the pulling rope (222d) of the pull-down winch (200d), effective on the slide, is configured to correspond to the rope speed of the pulling rope (222u) of the pull-up winch (200u), effective on the slide.

29. The pile driving rig according to claim 28, comprising a volume flow rate controller for determining a volume flow rate to be supplied to the motor of the pull-up winch (200u), influenced by the displacement of the motor of the pull-up winch (200u) in such a way that the rotation speed of the shaft of the motor of the pull-up winch (200u) is arranged to remain constant when the displacement is changed.

30. Software means for moving a slide of a pile driving rig, comprising

- software means for controlling the motor of a pull-down winch (200d) connected to the slide by a pulling rope (200d),

- software means for controlling the motor of a pull-up winch (200u) connected to the slide by a pulling rope (200u), and

- software means for adjusting a displacement of the motor of the pulling winch in response to detection of a change in a load effective on said pulling winch in such a way that the pressure in the motor of said winch tends to be maintained at a set constant pressure.

31 . The software means according to claim 30, further comprising software means for implementing the method according to at least one of the claims 2 to 15.

Description:
PILE DRIVER

Field of the invention

The invention relates to a method, a system, and software for controlling the motors of a pull-down winch and a pull-up winch of a pile driving rig.

Background of the invention

A pile driving rig may be used for driving a pile down into the ground by impact driving or auger drilling. In impact pile driving, a pile is installed in the ground by delivering an impact to the upper end of the pile with a hammer. The lower end or point of the pile is driven into the ground by the impact of the hammer and displaces soil around the pile driven.

In the installation of bored piles, a pile or a tube with a pile point is driven into the ground by rotation. By the rotation, the pile point is bored into the ground, displacing soil around the pile point penetrating into the soil. When the pile point reaches a predetermined target depth, the tube is gradually filled with filling material, such as concrete. The tube is withdrawn, and filling material is supplied so that the pit is filled with the filling material. The installation of bored piles may be installation of displacement bored piles, as described in the previous, installation with continuous flight auger method or with large- diameter bored pile, or another known method for installing bored piles.

In vibratory pile driving, a pile is driven into the ground by vibration. The vibration is generated by a vibrator for driving the pile into the ground. Brief summary of the invention

It is an aim of the invention to control the winches of the pile driving rig according to the pile driving operation and the work stage. The aim is to move the slide and the implement connected to it in a controlled manner by winches and by controlling the motors of the winches. During the pile driving operation, the pile penetrates through different soil layers. Less drilling force is required in relatively loose soil than in stiff or dense soil. The quality of the soil may vary in layers. During the pile driving, it may be necessary to drive the auger into loose and stiff soil in an alternating manner, or to drive or withdraw the tube in the different soil layers accordingly. Controlling the power output for the pile driving makes it possible to optimize the power available for the work stage according to the momentary demand. The slide of the pile driving rig, and the implement mounted on the slide, are moved by means of hydraulic winches. Controlling the motors of the winches makes it possible to adjust the power used for the pile driving operation according to the hardness and/or stiffness of the soil. The pressure levels and the displacements of the hydraulic motors of the winches, and the volume flow rates supplied to them may be controlled.

According to an aspect of the invention, in the method for controlling the motors of the winches of the pile driving rig, a slide is movable in opposite directions via ropes (222d, 222u) by a pull-down winch (200d) and a pull-up winch (200u). In the method, the displacement of the motor of the pulling winch is controlled in response to a change in the load of said pulling winch in such a way that the pressure of the motor of the pulling winch tends to be maintained a set constant pressure. In an aspect of the invention, the pile driving rig comprises a winch control system that comprises a pull-down winch (200d) and a motor of the pulldown winch, a pull-up winch (200u) and a motor of the pull-down winch, a pulling rope (222d) for connecting the pull-down winch (200d) to the slide of the pile driving rig, a pulling rope (222u) for connecting the pull-up winch (222u) to the slide of the pile driving rig, and means for controlling the displacement of the motor of the pulling winch in response to a change in the load of said pulling winch in such a way that the pressure of the motor of the pulling winch tends to be maintained a set constant pressure. In an aspect of the invention, software means for moving a slide of a pile driving rig comprise software means for controlling a motor of a pull-down winch (200d) connected to the slide by a pulling rope (222d), software means for controlling a motor of a pull-up winch (200u) connected to the slide by a pulling rope (200u), and software means for controlling the displacement of the motor of a pulling winch, in response to detecting a change in the load of said pulling winch, in such a way that the pressure of the motor of the pulling winch tends to be maintained at a set constant pressure.

Description of the drawings

In the following, embodiments of the invention will be presented by means of appended drawings. shows a pile driving rig according to an embodiment. Fig. 2 shows a method for installation of bored piles according to an embodiment. shows a pile driving rig according to an embodiment. Fig. 4 shows a system for controlling winches according to an embodiment.

Detailed description of the embodiments

Figure 1 shows a pile driving rig 10 according to an embodiment. The pile driving rig 10 of Fig. 1 is a multipurpose pile driving rig for driving auger drilled piles, rammed piles or sheet piles/steel piles into the ground by vibration or pressing. The multipurpose pile driving rig 10 comprises a leader 17 which may be equipped with a motor, a hammer, or a vibrator, according to a use of the pile driving rig 10. When the pile driving rig 10 is used for driving auger drilled piles, a bore motor as shown in Fig. 1 is mounted on a slide 22 for an implement 26 on the leader 17. When rammed piles are driven into the ground, the slide 22 is equipped with the hammer of the pile driving apparatus. When sheet piles or steel piles are driven into the ground by vibration, a vibrator is mounted on the slide 22. The pile driving rig 10 of Fig. 1 comprises a base machine 1 1 and a pile driving apparatus 12 mounted on it. The base machine 1 1 comprises an undercarriage 13. The undercarriage 13 comprises a crawler track 16 and apparatuses needed for moving the pile driving rig 10. An upper carriage 14 is mounted on the undercarriage 13 by a swivel 15. The upper carriage 14 is mounted on the undercarriage 13 in a horizontally swivelled manner. The upper carriage 14 comprises a driving engine 27 and a cabin 18. Furthermore, the upper carriage 14 comprises fastening structures and equip- ment for fastening and moving the different parts of the pile driving apparatus 12.

The functions are configured to be powered by hydraulics. The base machine 1 1 comprises a hydraulic system for providing its different functions, for controlling the pile driving apparatus 12, as well as a power transmission for moving the crawler track 16 and for changing the travel direction of the base machine 1 1 . The driving engine 27 powers hydraulic pumps belonging to the hydraulic system and generating the flow and the pressure of pressurized medium in the hydraulic system, for driving the actuators belonging to the hydraulic system. The cabin 18 is equipped with controls to be applied by the driver of the pile driving rig 10, for controlling the different functions of the pile driving rig. Furthermore, the cabin 18 is equipped with, inter alia, an electronic control unit for controlling the control valves, such as magnet and/or servo valves, of the hydraulic system, for adjusting and controlling the supply of pressurized medium to the different actuators of the hydraulic system.

The pile driving apparatus 12 comprises a leader 17 and an implement 26 mounted on it. Depending on the use, the implement 26 may be a pile driving auger, a vibrator, or the hammer of the pile driving apparatus. In Fig. 1 , a pile driving auger is mounted on the leader 17. The implement 26 is fastened to the leader 17 in a dismountable way. For fastening the implement 26, the leader 17 is equipped with a slide 22 movable in the longitudinal direction of the leader 17. The slide 22 is equipped with fastening members for fastening the implement 26 to the slide 22. Furthermore, the slide comprises connecting means and hoses for connecting the implement 26 to the hydraulic system of the base machine 1 1 . The slide 22 is mounted on guide tracks 23 on the leader 17. The slide 22 is moved along the guide tracks 23 by ropes pulled by a pull-down winch and a pull-up winch in the base machine 1 1 . Idlers 25 may be provided at different locations by the side of the leader 17 and at the cathead 24 at the top of the leader 17, for guiding the pulling ropes between the pull-down winch and the slide 22 as well as between the pull-up winch and the slide 22. Depending on the implement in question, the pulling ropes are guided via different idlers 25 so that the slide 22 is given the desired velocity and force according to the pile driving operation to be carried out.

Fig. 2 shows a bored piling method according to an embodiment. When a pile is drilled into the ground, it displaces soil around the pile point penetrating into the soil. This method may be called a displacement bored piling method. Figure 2 shows the stages of the bored pile method from the left to the right. At start, a tube is placed against the ground at a desired pile driving point Spt. In the next stage after the tube has been placed at the correct piling point Spt, the tube is installed in the ground. In bored piling, the tube is installed in the ground by drilling Drl. The tube is rotated, whereby it bores into the ground. During the drilling Drl or boring, the tube is pulled (down) into the soil. The tube is pulled (down) into the soil by the pull-down winch. The pull-down force is generated by the pull-down winch. The pull-down force may be, for example, 0 to 500 kN. After the tube has been drilled into the ground, it is strengthened with reinforcement Rfn. When the reinforcement is in place, supporting material Crt, such as concrete, is cast into the tube. After the reinforced tube has been filled with supporting material, the tube is withdrawn from the soil Ext. The tube is pulled out of the soil Ext by means of a pull-up winch. The pull- out force is generated by the pull-up winch. The pull-out force may be, for example, 0 to 1000 kN. The tube is pulled upwards, and it may be subjected by the auger to an oscillating motion around the longitudinal axis. The auger may be configured to alternate its direction of rotation at a given frequency during the pulling out. The rotary motion facilitates the releasing and removal of the tube from between the soil and the concrete. After the tube has been removed, the reinforced concrete pile remains embedded in the ground. What has been presented above in Fig. 2 is also applicable to the installation of auger drilled piles into the soil in general, not only by displacement, which has been presented as an example in Fig. 2. Driven cast-in-situ of piles may be implemented in the same way as the bored drilling method shown in Fig. 2. As a difference to the method shown in Fig. 2, in the driving cast-in- situ of piles, the stage Drl of drilling the pile into the ground is performed by hammer impacts, and the pulling out Ext of the ground is performed by pulling out the tube and by simultaneously tapping it with the hammer. The tapping helps to compact the concrete grout. In the pile driving methods, a number of different soil layers are penetrated through.

Impact pile driving may be applied as a method in a subsequent stage after the driving of bored piles into the soil by displacement, shown in Fig. 2, to make the concrete cast in the drill hole more compact by impacts. In this case, the impact force needed differs from the impact force needed in the stage of impact pile driving.

In an impact pile driving method, the pile is placed against the ground at a desired location in the same way as in the stage Spt of the previously presented installation of bored piles. Before the impact pile driving, a hole for the pile may be pre-drilled in the ground. In the pre-drilling, a small or relatively small auger is used for removing particularly solid soil. This accelerates the pile driving operation and protects the pile from excessive impacts during the pile driving. Furthermore, the pre-drilling reduces noise and vibration caused by impact pile driving. The pile is placed at a desired location for pile driving, on the surface of the ground or in a pre-drilled hole in the ground. After this, the pile is driven into the ground by the hammer. During the pile driving, the ram moving inside the hammer hits the pile. The impact energy drives the pile into the ground. The impact energy is controlled by means of the height level of the moving ram. The ram may be moved by a hydraulic cylinder whose one end is connected to the hammer. The pile is subjected to as many impacts as are needed for driving the pile to the desired pile driving depth. This corresponds to the drilling stage Drl of the method for installation of bored piles, where a pile is installed in the ground. When the rammed pile is at the desired depth in the ground, the pile driving operation is completed. For example, a halfway driven pile may withstand greater impacts than a pile that is still mostly above the ground. Lower impact energy may be applied at the initial stage of impact pile driving, and higher impact energy may be applied at a later stage. Furthermore, during impact pile driving, the quality of the soil has an effect on amount of sinking of the pile driven by an impact with a given force. If it is found that the soil is loose, it is not necessary to apply the maximum impact force, whereas this may be a necessity when the pile is driven into stiff soil. The pull-down winch is configured to keep the hammer abutting the pile.

When the vibration method is applied for pile driving, a vibrator is fastened to the leader. When the pile or tube is driven into the ground, it is subjected to vibration instead of the impacts presented in connection with impact pile driving above. By the vibration, the soil vibrates and gives way to the sinking pile or tube. The vibration is directed to the profile that is driven into the ground by the vibration. In addition to piles and tubes, vibration may be used for driving walls, so-called retaining walls, into the ground, to prevent the ground from falling in. Upon drilling, pre-drilling, impact pile driving and vibrating, controlled pulling up and pulling down is utilized in the pulling down stage (Drl) and in the pulling out stage (Ext). In the pulling down stage, the slide and the implement connected to it are pulled down and supported upwards at the same time. Figure 2 shows soil layers GRD. The soil layers GRD may contain various types of soil, such as sand, rock, gravel, clay, and so on. The soil layers GRD may be different in their composition. The quality of the soil may vary between the different soil layers GRD. During the pile driving operation shown in Fig. 2, the pile is driven through the different ground layers GRD. During the pile driving, it may be necessary to drive the tube or pile through soil layers of different types and different qualities. Penetrating through relatively loose soil requires less power than penetrating through stiff or dense soil. The pile or tube to be driven is to be driven to a stiff soil layer that is deeper than the surface and is steady and settled. At the stage of driving or pulling down (impact pile driving, vibration or drilling stage Drl) and at the stage of withdrawing or pulling out (pull-up of the hammer, removal of the tube Ext), the control of the supplied power makes it possible to optimize the power used according to the momentary demand in the pile driving operation and its stages.

Figure 3 shows a pile driving rig 210 according to an embodiment. The pile driving rig 210 comprises a base machine 1 1 and a pile driving apparatus. The base machine 1 1 comprises a pull-down winch 200d and a pull-up winch 200u. The pulling rope 222d of the pull-down winch 200d is configured to be wound up on the drum of the pull-down winch 200d, whereby the rope may be wound up on the drum and unwound from the drum. The pulling rope 222d of the pull-down winch 200d is connected to the slide 22 via idlers 25. The pulling rope 222u of the pull-up winch 200u is configured to be wound up on the drum of the pull-up winch 200u, whereby the rope may be wound up on the drum and unwound from the drum. The pulling rope 222u of the pull- up winch 200u is connected to the slide 22 via idlers 25. In Fig. 3, the idlers 25 are placed on the cathead 24 and the leader 17. Idlers 25 may be provided in different locations of the pile driving rig 210, and the idlers 25 to be used each time for guiding the pulling rope are selected according to the pile driving method used. The pull-down winch 200d and/or the pull-up winch 200u may be a freely rotating winch equipped with a clutch.

Both the pull-down winch 200d and the pull-up winch 200u are connected by pulling ropes 222d, 222u to the slide 22 and to the implement mounted on it. The movement of the slide 22 and the implement mounted on it is controlled by the pull-down winch 200d and the pull-up winch 200u. When the movement of the slide 22 and the implement is downwards, towards the ground, the pull-down winch 200d is configured to pull the slide and the implement downwards. The pull-up winch 200u is configured to unwind its pulling rope 222u in the opposite direction. When the movement of the slide 22 and the implement is upwards, off the ground, the pull-up winch 200u is configured to pull the slide and the implement upwards. The pull-down winch 200d is configured to unwind its pulling rope 222d in the opposite direction. During pile driving operation, one of the winches, the pull-down winch 200d or the pull-up winch 200u, pulls the slide and the implement in the desired direction. At the same time, the other winch, the pull-up winch 200u or the pull-down winch 200d, rotates either completely freely or possibly decelerating the movement of the slide by means of the rope. One of the winches pulls its pulling rope in the pulling direction, while the other winch unwinds its pulling rope in a direction opposite to the pulling direction. The pull-down winch 200d and the pull-up winch 200u subject the slide 22 to force components of opposite directions. The pull-down winch 200d may be configured to pull/wind up and the pull-up winch 200u may be configured to wind up/pull at the same time. In this way, both of the pulling ropes connecting the winches to the slide 22 are kept taut during each work stage.

In the following, reference will be made to impact pile driving, but the same applies to driven cast-in-situ of piles. For impact pile driving, a hammer is fastened to the slide 22. A pull-down winch connected to the pile may be used for impact pile driving. The pull-down winch 200d is thus used as a pile winch. The pull-up winch 200u may be connected to the hammer, and it is used as a hammer winch for impact pile driving. When the pull-up winch 200u pulls the pulling rope 222u, it winds up the pulling rope 222u on a drum, whereby the slide 22 and the hammer move upwards along the leader. The slide 22 pulls the pulling rope 222d upwards along with it. Thus, the pulldown winch 200d unwinds the pulling rope 222d from the drum. Optionally, the pull-down winch 200d used as the pile winch hoists the pile below the hammer in the air. During an impact, the pull-down winch 200d optionally used as the pile winch is configured to rotate freely. During the impact, the pull-up winch 200u is configured to rotate freely. For impact pile driving, it is also possible to use a winch connected to the hammer and pulling down the hammer during an impact. The winch configured to pull down the hammer may be placed in the leader or in the base machine. For bored piling, for pre-drilling or drilling in general, soil is displaced or removed by drilling the implement into the ground. The slide 22 is equipped with an implement, such as an auger. The pull-down winch 200d is used as a winch pulling down the slide. At the stage of pulling down, the pull-down winch 200d winds up its pulling rope 222d onto a drum and pulls the slide 22 and the implement downwards. The slide 22 and the implement connected to it move downwards. At the stage of pulling down, the pull-up winch 200u unwinds its pulling rope 222u from the drum so that a desired supporting force is maintained at the pulling rope 222u. At the stage of pulling out, the pull-down winch 200d may be released. The pull-up winch 200u is used as an upwards pulling winch, and at the stage of pulling up, it winds up the pulling rope 222u connected to it onto the drum. The pull-down winch 200d unwinds the pulling rope 222d from the drum. When the pull-up winch 200u pulls the pulling rope 222u, the slide 22 and the auger are moved upwards.

In vibration piling, a pile is driven into the ground by vibration. A vibrator is connected to the slide 22. The pull-down winch 200d is used as a downwards pulling winch. During the stage of pulling down, the slide 22 and the vibrator are moved downwards. The pull-down winch 200d is configured to wind up the pulling rope 222d onto the drum. The pull-up winch 200u is configured to unwind its pulling rope 222 from the drum correspondingly. During the pull-up stage, the slide 22 and the auger are moved upwards. The pull-down winch 200d is released during the pull-up, and it unwinds its pulling rope 222d. The pull-up winch 200u is used as an upwards pulling winch. The pull-up winch 200u is configured to wind up its pulling rope 222u onto the drum. The winch may be configured to be released mechanically or hydraulically. Mechanical releasing of the winch may be implemented, for example, by releasing the clutch of the winch. Hydraulically, the winch may be released by means of, for example, a coupling change. An adjustable clutch may be provided between the motor and the drum of the winch, for adjusting the ratio between the rotation speeds of the driving shaft of the drum of the winch and the shaft of the motor of the winch. When the clutch of the winch (200u, 200d) is completely released, the drum of the winch rotates freely while the motor of the winch is, for example, stopped. Thus, the rotation speed of the motor of the winch does not affect the rotation speed of the drum, and vice versa. By means of a steplessly adjustable clutch, it is possible to slow down the rotation of the winch from free rotation to constrained rotation by gradually tightening the coupling strength of the clutch. The slide 22 and the implement subject the winch (200u, 200d) to a force of a given magnitude and direction via the pulling ropes (222u, 222d). The force induces rotation of the released winch (200u, 200d) at a given rotation speed. The pull-down winch 200d may be released at a given stage of the pile driving operation, when no load is suspended from the pulling rope 222d of the pull-down winch 200d. The pull-up winch 200u may be released, for example during an impact upon impact pile driving. The implement of the pile driving rig, for example the auger, is configured to be hydraulically rotated by one or more hydraulic motors. The hydraulic motor of the auger comprises a pressure controller for maintaining the working pressure of the hydraulic motor of the auger at a set value. The value set for the working pressure of the motor of the auger may be, for example, between 200 and 400 bar. When the pressure is maintained constant and the power demand increases, for example upon encountering stiff soil, the displacement of the hydraulic motor(s) of the auger increases while the rotation speed of the auger bit decreases at the same volume flow rate supplied. Typically, the aim is to perform the drilling as fast as possible, that is, at the highest possible rotation speed of the auger bit. Drilling stiff soil may result in seizing up of the auger which will not move because the power supplied by the motor is not sufficient to rotate the auger against the stiff soil. By the control according to the embodiments, the rotation speed of the auger and the speed of driving the auger bit may be turned down. Thus, the drilling will be slowed down but not stopped. When stiff soil is encountered, the power is not necessarily sufficient. The rotation speed of the auger bit may be turned down either by reducing the volume flow rate supplied to the hydraulic motor, whereby the pressure remains substantially constant and the supplied power is reduced as the volume flow rate is reduced; or by increasing the displacement of the hydraulic motor, whereby the supplied volume flow rate remains constant and the supplied power is reduced as the working pressure is reduced. The speed of driving/sinking the auger bit may be influenced by controlling the motors of the winches. In this way, the load on the motors of the auger may be reduced.

If the displacement of the hydraulic motors of the winches were kept constant, the displacement would be dimensioned to output the highest possible power. Thus, even with a small load, upon drilling loose soil, the winch motors have low pressure but high volume flow rate, because the auger bit advances quickly in the loose soil. The highest pressure in the system, supplied by the motors of the auger, determines the working pressure of the hydraulic motors. Such a situation causes a great pressure loss for the winch motors. Therefore, power from the driving engine of the pile driving rig is wasted in the form of lost heat and not used for the pile driving operation. In the following, we shall discuss the control of the motors of the winches during installation of auger drilled piles. In the bored piling or installation of auger drilled piles, both the pull-down winch and the pull-up winch are active, in addition to the auger, at the stage of pulling down. The pressure level of the auger determines the pressure level of the system. The pressure of the auger motor may be a set pressure. The auger motor may comprise a pressure controller for controlling the set pressure. The power demand of the auger motor is dependent on, for example, the rotation speed of the auger motor and the stiffness of the soil. One or more auger motors may be provided, each having substantially the same set pressure. The pressure of the winch motors is set on the basis of the set pressure of the auger motor. The aim is to keep the pressure of the winch motors at a level that corresponds to or is the same as the pressure of the auger motor. The displacement of the winches is controlled to tend to keep the pressure constant. When drilling loose soil, the rotation speed of the motor of the winch that winds up a rope onto its drum is configured to increase, and when drilling stiff soil, the rotation speed of the motor of the winch is configured to slow down, the pressure remaining substantially constant. The displacement of the winch motor is steplessly adjustable by electro-hydraulic means so that the working pressures of the winch motors are close to the set working pressure of the auger motor.

When in the following the winch is referred to generally, the same applies to both the pull-down winch and the pull-up winch. The winch motor has a minimum and a maximum displacement value. The displacement of the winch motor may be configured to be limited (to the minimum and the maximum) either by mechanical or hydraulic means, or by a combination of these. The operation of the winch motor may be controlled between its minimum displacement and maximum displacement. When the slide and the implement are pulled downwards, the pull-down winch 200d winds up the pulling rope 222d onto its drum and the pull-up winch 200u unwinds the pulling rope 222u from its drum. The driver of the rig may control the unwinding speed of the pull-up winch 200u by a control device in the cabin of the base machine 1 1 . The control of the constant pressure of the hydraulic motors of the winches may be turned on and off by applying a switch in the cabin. The control of constant pressure may be set for the motor of the pulling winch. When the control of constant pressure for the motor of the pulling winch has been turned on, the displacement of the motor of the pulling winch is controlled so that the working pressure of the motor tends to follow the set constant pressure. The valve of the winch motor is controlled by software to adjust the displacement. The displacement of the hydraulic motor of the winch may be set to a minimum or a maximum or any value between the minimum or the maximum by said valve. The working pressure of the motor of the pulling winch, and a change therein, is measured by a pressure sensor. The valve adjusting the displacement of the motor of the pulling winch, for which the control of constant pressure has been set, is configured to be adjusted as a function of the value of the pressure sensor. The valve controlling the displacement of the motor may be an electronically or hydraulically controllable proportional valve or servo valve. The value of the pressure sensor refers to a pressure value, a value measured by the pressure sensor, or a value measured as a function of the pressure. When the effective pressure of the motor starts to increase, the displacement of the motor is turned up. When the effective pressure of the motor starts to decrease, the displacement of the motor is turned down.

The force vectors shown in Fig. 3 depict forces present in the initial situation. The slide 22 and the implement attached to it (e.g. auger and drill bit) are subjected to a gravitational force mg towards the ground which is the product of the mass (m) of the slide and the implement and the gravitational acceleration (g). The pull-down winch 200d subjects the implement to a force Fd towards the ground. The pull-up winch 200u subjects the implement to a force Fu upwards from the ground. In the initial situation, the upward pull-up force Fu is of equal value but of opposite direction to the sum of the downward pulling force Fd and the gravitational force mg. The slide 22 and the implement are supported by the pulling rope 233 of the pull-up winch 200u. The hydraulic motor of the hydraulic winch may be, for example, an axial piston motor or a radial piston motor or another motor with controllable displacement. Different motors, such as an electric motor, may also be controlled in a corresponding way. When the displacement is turned down, the rotation speed of the motor increases and the torque output of the motor is reduced. The displacement determines how much oil or other pressurized medium has to be supplied for the motor for one rotation of the motor shaft. When the displacement of the motor increases, more oil has to be supplied. Thus, the rotation speed of the hydraulic motor is lower and the torque is higher than when the displacement of the motor is lower. An increase in the torque of the hydraulic motor increases the force on the rope of the winch. When constant pressure is turned on, the pressure in the motor of the winch is tended to be maintained at a set constant level. The rotation speed of the drum of the winch is adjusted by controlling the volume flow rate supplied to the motor of the winch. When more power is required in a work stage, for example when stiff soil is encountered, the working pressure effective on the implement increases. The working pressure may be measured, for example, in the motor of the implement and/or in the motor of one of the winches. The implement has a set pressure, and a corresponding pressure is arranged to be set for the motors of the winches. In response to an increase in the working pressure of the implement, such as the auger, the pressure value of the pressure sensor for the motor of the winch increases; as a result, the displacement of the motor is turned up. Thus, for example the drilling stage of the pile driving operation is not stopped but slowed down. When the winch is subjected to a smaller load, for example when looser soil is encountered in the pile driving or pulling down stage, the working pressure effective on the implement and the pulling winch decreases. In response to this, the value of the pressure sensor for the motor of the winch decreases, and the displacement of the motor of the winch is turned down. The displacement of the motor of the winch is adjusted by controlling to maintain the set constant pressure in the motor.

For both the pull-down winch and the pull-up winch, constant pressure control may be turned on in the pulling direction of the winch when the winch is winding up the pulling rope onto its drum. In the unwinding direction of the winch, when the pulling rope is being unwound from the drum, the guideline value for the valve that controls the displacement may be determined according to the working method in question. Typically, either a minimum or a maximum displacement or another constant displacement is set for the motor. A given range is defined for the displacement of the motor of the pull- up winch. A given range is defined for the displacement of the motor of the pull-down winch as well, and it may be different from the range defined for the displacement of the motor of the pull-up winch. The winches operate at said displacement values, within the ranges defined for them.

A gear may be provided between the motor and the drum of the winch. Thus, the rotation speeds of the motor and of the drum of the winch correspond to each other. If there is no gear, the rotation speeds of the motor and the drum of the winch may be the same.

The operator may control the rotation speed of the motor of the winch. A predetermined maximum rotation speed is set for the motor of the winch, which may not be exceeded but which may vary for different loads. The maximum rotation speed may be determined by a selected component of the winch, such as one of the following: the hydraulic motor, the gear, the drum, the brake, the clutch. In order that the maximum rotation speed of the motor is not exceeded, the ratio between the volume flow rate supplied to the motor and the displacement is measured and/or monitored, or alternatively, the rotation speed of the shaft or the drum of the motor of the winch is measured or, alternatively, the linear speed of the rope of the winch or the slide is measured. Figure 4 shows a system for controlling the winches of a pile driving rig according to an embodiment. In the following, the pulling down stage will be described. In the pulling down stage, the rotation speeds of the winches are adjusted by means of the volume flow rate supplied to the motor and the displacement. In the pulling down stage, the displacement of the pull-up winch is constant and the operator sets the rotation speed of the pull-up winch. The rotation speed of the pull-up winch corresponds to the speed of lowering the slide and to the unwinding speed of the pulling rope of the pull- up winch. The maximum value for the unwinding speed of the pulling rope of the pull-up winch is limited with respect to the maximum rotation speed of the gear of the motor of the pull-up winch. The rotation speed of the drum of the winch may be limited e.g. according to the maximum rotation speed allowed for the gear of the winch, or the maximum rotation speed may be determined according to a component, such as the hydraulic motor. The maximum rotation speed may vary according to the load. The lowering speed effective on the slide of the pull-up winch may be solved, for example, by measuring the rope speed, the speed of lowering the slide, the rotation speed of the drum of the winch, the rotation speed of the hydraulic motor, the volume flow rate supplied to the hydraulic motor of the winch, the displacement, or by calculations using fixed parameters. The parameters may include, for example, the rope factor of the pull-down winch (k_down), the rope factor of the pull-up winch (k_up), the transmission ratio of the gear of the pull-down winch (i_down), the transmission ratio of the gear of the pull-up winch (i_up), the reference diameter of the drum of the pull-down winch (D_down), the reference diameter of the drum of the pull-up winch (D_up), the volumetric efficiency of the pull-down winch (n ,VO it ), the volumetric efficiency of the pull- up winch (η ν0 ΐν), the displacement of the pull-up winch (V_g,down), the volume flow rate supplied to the pull-up winch (Q_up).

The displacement of the hydraulic motor of the pull-down winch may be controlled by software or hydraulically so that the working pressure of the motor tends to follow a desired constant pressure. The stiffness of the soil affects the working pressure effective on the implement. The working pressure effective on the implement is transmitted to the pulling winch which is, in the pulling down stage, the pull-down winch. The displacement of the pull-down winch varies according to the load effective on the implement when constant pressure control is turned on. In the pull down stage, the pulling speed effective on the slide of the pull-down winch is set equal to the lowering speed effective on the slide of the pull-up winch, so that the rotation speeds of the motors of the winches are dependent on each other. The ratio between the speeds effective on the slide may be adjusted with a speed coefficient (k s ) if needed. The rotation speed of the motor of the pull-down winch (n_down) may be measured, for example, from the speed of the slide, the speed of the rope, the rotation speed of the motor, the rotation speed of the drum or, alternatively, it may be calculated from the following equation, when the volume flow rate (Q_up) set for the pull-up winch by the operator is known. The volume flow rate supplied to the motor of the winch may be determined, for example, by measuring the volume flow rate supplied to or from the winch, by estimating the volume flow rate passed by the directional valve of said motor, or by measuring the volume flow rate passed by its valve.

ndown Wup) - .

"-up ' up 1 -' down * Hup in which k s is a velocity factor, k_down is the rope factor for the pull-down winch, i_down is the transmission ratio of the gear of the pull-down winch, D_up is the reference diameter of the drum of the pull-up winch, η ν0 ι ν is the volumetric efficiency of the pull-up winch, Q_up is the volume flow rate supplied to the pull-up winch, k_up is the rope factor for the pull-up winch, i_up is the transmission ratio for the gear of the pull-up winch, D_down is the reference diameter of the drum of the pull-down winch, and V_g,up is the displacement of the pull-up winch.

When constant pressure control is turned on, the pressure in the motor of the winch is measured by a pressure sensor. The displacement of the motor of the winch is controlled as a function of the measured pressure. The value of the pressure sensor is changed in response to a change in the load. When the value of the pressure sensor increases, the displacement of the motor is increased. When the value of the pressure sensor decreases, the displacement of the motor is decreased.

The pull-down winch is supplied with a volume flow rate (Q_ref) that the pulling speed caused by the pull-down winch on the slide is of equal speed but of opposite direction to the lowering speed caused by the pull-up winch on the slide. In this way, the pulling ropes connecting both winches to the slide remain taut. The reference volume flow rate Q_ref supplied to the pulldown winch may be calculated as follows:

Vvolt where n tm is the rotation speed of the motor of the pull-down winch as a function of the volume flow rate supplied to the pull-up winch, V_g,up is the displacement of the pull-down winch as a function of the stiffness of the soil, and Hvoia is the volumetric efficiency of the pull-down winch.

A given constant force is maintained on the pulling rope of the pull-up winch during the entire work stage in order that the implement fastened to the slide and their movement remain under control. The reference volume flow rate Q_ref calculated in previous is changed as the slide is pulled downwards. This is because the reference diameters of the drums of the winches are changed as the slide moves downwards, because the turns of rope on the drum may change as the slide moves. When pulling rope is unwound from the drum of the winch, i.e. it is pulled off the drum, the reference diameter formed by the drum and the pulling rope decreases if the number of turns of rope on the drum decreases. When pulling rope is wound onto the drum of the winch, the reference diameter formed by the drum and the pulling rope increases, if the number of turns of rope on the drum increases. When the slide moves downwards, the reference diameter of the pull-up winch decreases and the reference diameter of the pull-down winch increases. The above presented reference diameters (D_up, D_down) represent an initial situation in which the slide is up. If a possible change in the reference diameters is not taken into account, it may be possible to supply too much volume flow rate to the pull-down winch with respect to the unwinding speed of the pull-up winch at the end of the pulling down stage when already deep down in the ground. This may be taken into account by means of coefficients. The coefficients may be determined for the pulling direction and the winding up direction of the winch separately.

When the implement is replaced, the weight of the implement is measured. The weight of the implement may be measured, for example, by a load pin for the pull-up winch, a force sensor connected to the pulling rope of the winch, or another strain gauge measuring loads on the structures of the rig. The measured weight of the implements is set as the desired pull-up force Fset, possibly multiplied by a safety factor. In this way, a constant pull-up force is determined. The force of the pull-up winch, effective on the slide, is measured by e.g. a load pin, a force sensor connected to the pulling rope of the winch, or another strain gauge measuring loads on the structures of the rig. The difference AF between the measured value for the momentary pull- up force and the set pull-up force F se t is calculated. When the absolute value of the difference is smaller than a predetermined limit value, the control device will not respond. In determining the limit value, hysteresis may be taken into account. When the absolute value of the difference is greater than the predetermined limit value, the control device will either decrease or increase the volume flow rate. The decrease or increase is multiplied by a factor K f representing the change in the volume flow rate per force unit within a given period of time. The value of the factor K f may be determined manually in different situations, and it may be e.g. the following: min * kN = 1)667 . 10 -8 ^_

' s kg

The change in the volume flow rate is integrated with respect to time. After this, it may be subtracted from the value Q_ref, whereby the difference is the real volume flow rate Q t0 d to be supplied to the pull-down winch.

Qtod = Qrefh - \ Qdt

Figure 4 shows the stage of pulling down the slide and the implement. The mass (m) of the slide and the implement is known or weighed. From the total mass (m) of the implement and the slide, as well as possible other equipment fastened to them, it is possible to calculate the constant pull-up force (Fset=mg), which is set as the constant value for the pull-up force (F_set) for the pull-up winch. In calculations, it is possible to use a safety factor (n) to secure the operation and the safety. The constant pressure controller for the pull-down winch is configured to monitor the difference between the set constant pressure and the momentary working pressure of the pull-down winch. If the pressure difference detected by the constant pressure controller exceeds a given limit value, the constant pressure controller gives an input to a control valve for controlling the displacement of the motor of the pull-down winch. When a constant pressure has been set or turned on in the pulling down stage, the displacement of the motor of the pull-down winch is controlled by a valve VK_down, for example a proportional or servo valve. The valve is controlled by the control pressure controller. When the working pressure increases, the control of the valve is changed so that the displacement of the motor of the winch increases and the pressure of the motor of the winch is restored to the constant value set by the constant pressure controller. In response to the reduction in the working pressure, the control of the valve is changed so that the displacement of the motor of the winch is reduced. As a result, the pressure of the motor will be restored to the value set by the constant pressure controller. The volume flow rate supplied to the motor of the pull-down winch is controlled by a directional valve VT_down. This valve may also be an electronically or hydraulically pilot-controlled proportional or servo valve, or alternatively an electronically or hydraulically directly operated proportional or servo valve. The value Q_down of the volume flow rate supplied to the motor, and the displacement V_g,down of the motor, determine the rotation speed n_down for the motor of the pull-down winch. The displacement V_g,down of the motor of the pulldown winch has an effect on the reference volume flow rate Q_ref. The rotation speed n_down of the shaft of the motor of the pull-down winch, the reference diameter D_down of the drum of the pull-down winch have an effect on the pull down speed v(k)_down of the pulling rope of the pull-down winch. There may also be other factors of the pull-down winch affecting the speed v(k)_down of the pull-down winch pulling down the slide, such as the rope factor k_down of the pull-down winch, indicating how many times the ropes are connected to the slide, and the transmission ratio i_down of the gear of the pull-down winch.

In the pulling down stage of Fig. 4, the constant pressure controller of the pull-up winch is not in use, but the displacement of the pull-up winch is set constant. For the pull-up winch, a constant pressure controller is provided, similar to that for the pull-down winch. The rotation speed n_up of the shaft of the motor of the pull-up winch and the rotation speed n_down of the shaft of the motor of the pull-down winch are determined so that the speeds v(k)_up and v(k)_down of the slide caused by them are equal of speed but opposite of direction. The valve VK_up is used for controlling the displacement of the motor of the pull-up winch. This valve may be, for example, a proportional or servo valve. The displacement V_g,up of the motor of the pull-up winch, and the volume flow rate Q_up supplied to the motor of the pull-up winch determine the rotational speed n_up for the motor of the pull-up winch. The volume flow rate supplied to the motor of the pull-up winch is controlled by a directional valve VT_up. This valve may also be an electronically or hydraulically pre- controlled proportional or servo valve, or alternatively an electronically or hydraulically directly operated proportional or servo valve. The rotation speed n_up of the shaft of the motor of the pull-up winch and the reference diameter D_up of the drum of the pull-up winch influence the pull-up speed v(k)_up of the pulling rope of the pull-up winch. The pull-up speed v(k)_up of the pull-up winch, effective on the slide, may also be influenced by other factors, such as the rope factor k_up of the pull-up winch, indicating multiplicity of ropes connected to the slide, and/or the transmission ratio i_up of the gear of the pull-up winch. The rotation speed n_up of the motor of the pull-up winch is entered in a block calculating the reference value Q_ref for the momentary volume flow rate.

The reference value Q_ref for the momentary volume flow rate is influenced by the rotation speed n_up of the motor of the pull-up winch, produced by software or alternatively measured, and the displacement V_g,down of the pull-down winch, produced by software or alternatively measured. The calculated momentary reference value Q_ref for the volume flow rate is entered in a volume flow rate controller, in which the force F_m,up effective in the pull-up rope is taken into account. The force F_m,up effective in the pull-up rope may be measured, for example, by a force gauge or by strain gauges from the load of the idler of the pull-up winch, from a force sensor fastened to the pulling rope, from other forces caused by the ropes, or from loads effective on the pile driving rig during drilling work. Control hysteresis (Ftot) is determined for the volume flow rate controller, for limiting the operating range outside certain limit values. A force/volume flow rate factor (K f ) is determined for the volume flow rate controller, for influencing the adjustment sensitivity of the controller.

The force pulling the slide (and the implement) momentarily upwards may be measured in the previously mentioned ways (F_m,up). The force difference (AF) is the difference between the measured value (F_m,up) and the set pull- up force (Fset).

The momentary reference volume flow rate Q_ref may be calculated by the equation presented earlier (Q_ref). The change in the volume flow rate per second (AQ) is the product between the force difference (AF) and the force/volume flow rate factor (K f ) of the control device. The change in the volume flow rate at a given moment of review is obtained by integrating the change in the volume flow rate (AQ) over a period of time (t-i ). The period of time (t-i ) may be, for example, the time taken for calculating one control cycle. The time may be manually changeable. The real volume flow rate (Q t0 d) to be supplied to the motor of the winch is the difference between the momentary reference volume flow rate (Q_ref) and the change in the volume flow rate at the moment under review (AQ).

The displacement of the motor of the pulling winch is determined according to the momentary load in such a way that constant pressure is maintained in the motor of the winch. The displacement of the motor is adjusted as a function of the difference between the momentary working pressure in the motor and the control pressure of the constant pressure controller. The value of the volume flow rate supplied to the motor and the displacement of the motor influence the rotation speed of the motor. The rotation speed of the motor of the pulling winch is set substantially so that the rope speed of the pulling winch, effective on the slide, corresponds to the rope speed by the rotation speed of the non-pulling winch, effective on the slide, which is of opposite direction to the rope speed by the rotation speed of the pulling winch, effective on the slide. The rotation speed of the motor of the non-pulling winch is influenced by the displacement of said motor and the volume flow rate supplied to it. The displacement of the pulling winch and the rotation speed of the motor of the non-pulling winch are fed back to the block determining the volume flow rate of the pulling winch.

The pulling force effective on the rope of the pull-up winch is coupled as a pull-up force to the slide. At the stage of pulling down, when the pull-down winch is the pulling winch, the pull-up force pulling the slide upwards is maintained substantially constant at a desired value which may be e.g. equal to the product of a desired factor and the gravitational force of the slide and the implement. The value of the factor may vary e.g. from 0.5 to 5. The rope force of the pull-up winch and/or of the pull-down winch, being effective on the rope, may be measured, for example, by a load pin connected to the rope pulley, or by another force sensor measuring the loads of the rig or the rope, or by a strain gauge based sensor. During pulling down, the force of the pull- up winch, effective on the rope, is measured, and it is substantially entered in the block determining the volume flow rate of the pulling winch. After the pile has been cast and the reinforcement been installed, the tube is pulled out of the ground by the pull-up winch. Thus, the pull-up winch is used as the pulling winch. Constant pressure control may be set in the motor of the pull-up winch. The displacement of the motor of the pull-up winch is controlled in response to the pressure caused by the load on the winch by analogy with the motor of the pull-down winch in previous. The pulling speed of the pull-down winch, effective on the slide, is set of equal speed but of opposite direction to the pulling speed of the pull-up winch, effective on the slide. The force required in the pull down and pull-up stages will depend on, for example, the stiffness and the porosity of the soil encountered. Less force is required in relatively loose soil than in stiff or dense soil. The quality of the soil may vary in the different layers. During the pile driving operation, different soil types of different quality may be encountered. Stiff soil requires more force for driving the implement into it. Also, when the tube is lifted up, the demand for pull-up force varies. For example, less force is required for removing and withdrawing the tube from sandy soil than from more compact loamy soil. For example, the quality and the degree of dryness of the concrete cast in the tube influence the need for lifting force when the tube is lifted up. The adjustment of the winches makes it possible to optimize the available power according to the momentary need in the pile driving operation and the work stage in question. The rotation speed of the hydraulic motors of the pull-up and pull-down winches may be controlled by the volume flow rate supplied to them and by their prevailing displacement at the pulling down and pull-up stages of the pile driving operation or drilling work. The winch motors may be variable displacement motors with a minimum and a maximum displacement, or any displacement therebetween. The control of the winches also makes it possible to synchronize the operation of the winches, whereby the pulling ropes connecting the winch and the slide always remain taut during the different stages of the pile driving operation.

Aspects of the invention and examples of its implementation have been presented in previous. The presented features and examples may be amended, and they may be replaced or left out without deviating from the scope of the invention presented in the following claims.