The invention relates to a vibrating device for inserting a foundation element, such as a foundation pile or sheet pile profile, into the ground. Such foundation elements can be inserted into the ground on land or at sea.

Diverse vibrating systems are known in practice which make use of a vibrating device and more particularly of a vibrator block provided with a number of eccentrics. Such a vibrator block exerts vibrations on the foundation element, whereby this element is vibrated into the ground. Such vibrator blocks are usually arranged on the upper side of the foundation element during insertion thereof. These vibrating systems known in practice are usually driven hydraulically, wherein use is made of a so-called power pack comprising a diesel engine and a hydraulic pump. This hydraulic pump drives the hydraulic motor of the vibrating device.

A problem with existing vibrating systems is that they cannot handle variable conditions flexibly. Such variable conditions can be a local variation in ground condition and/or a ground layer with a greater resistance to insertion of the foundation element. The greater resistance entails the danger of overloading of the hydraulic system, so that a safety valve will open and some of the hydraulic oil is discharged, preferably back to the hydraulic oil reservoir. This increases the insertion time of the foundation element and in addition increases the amount of energy required for this purpose.

An object of the present invention is to obviate or reduce the above stated problems and to provide an effective vibrating system for inserting a foundation element into the ground.

This object is achieved with the vibrating system for inserting a foundation element into the ground according to the present invention, wherein the vibrating system comprises:

a vibrating device provided with a number of eccentrics;

a drive operatively connected to the vibrating device, wherein the drive comprises: a motor;

a pump operatively connected to the motor; and

- a drive unit operatively connected to the pump,

wherein the drive is further provided with an adjusting device whereby a drive force of the vibrating system can be set while the power which can be produced by the drive remains substantially constant.

Providing the vibrating device, also referred to as vibrator block, with a number of eccentrics enables a vibration to be exerted on a foundation element, such as a foundation pile, a foundation tube and a sheet pile profile. The drive of the vibrating device, formed by the motor, in a currently preferred embodiment comprising a hydraulic motor, the pump, in a currently preferred embodiment comprising a hydraulic pump, and the drive unit, produces a quantity of hydraulic fluid which determines the frequency of the vibrating device. The effective frequency of the vibrating device is determined in practice by the relation between the quantity of hydraulic fluid and the so-called stroke volume of the hydraulic motor, together with the transmission ratio inside the vibrating device. The frequency of the vibrating device together with the eccentric moment of the vibrating device determine the impact force, i.e. the power produced by the vibrating device.

The maximum available power of the drive for the vibrating system is determined by the (hydraulic) pump, which is operatively connected to the (hydraulic) motor, together with the drive unit for the (hydraulic) pump. Such a drive unit is preferably a diesel engine, although an electrically driven hydraulic pump is also possible.

The hydraulic pressure determines the drive force which can be realized with the vibrating system. The drive force of the vibrating device is substantially used to overcome the resistance which is encountered during insertion into the ground of the foundation element, and some losses. Providing the drive with an adjusting device which is configured to set the drive force of the system achieves an optimal use of the available power, while the power which can be supplied by the vibrating device to the foundation element remains substantially constant.

By making optimal use of the available power according to the invention, and keeping the power which can be transmitted by the vibrating device to the foundation element substantially constant herein during use, the insertion time required and the overall amount of energy required to insert the foundation element into the ground is minimized. The power taken up by the foundation element is determined here by the frequency and the drive force of the vibrating device.

By optimizing the taken-up power with the adjusting device according to the present invention a foundation element can be inserted into the ground in effective manner. It is here possible in practice to dispense with a conventional safety valve, or at least with the practical use thereof, whereby in conventional systems the maximum operating pressure is limited. Hydraulic fluid is carried via such a safety valve back to the reservoir, while the drive force of the vibrating device remains the same. This results in loss of power. The adjusting device according to the invention increases the drive force, while the frequency is reduced. No power is hereby lost, and an effective process is achieved.

In a currently preferred embodiment according to the present invention the adjusting device comprises a stroke volume of the hydraulic motor which can be variably set.

The frequency of the vibrating device can be influenced by modifying the stroke volume of the hydraulic motor. An increase of the stroke volume will thus result in a decrease of the frequency of the vibrating device. This is accompanied by an increase of the drive force. By adjusting the stroke volume of the hydraulic motor the power taken up by the foundation element can hereby remain substantially constant and maximal and can be optimized for the situation, irrespective of the resistance to the insertion into the ground of the foundation element. The insertion time required and energy required can hereby remain limited.

By modifying the stroke volume of the hydraulic motor hydraulic fluid will not flow away via a safety valve and back to the hydraulic oil reservoir, or will at least do so less frequently. By avoiding these energy losses the energy produced with the hydraulic pump and associated drive unit, for instance in combination as a power pack, is utilized optimally.

Applying a hydraulic motor with a variable stroke volume for the vibrating device enables vibrating to take place at a higher frequency in the case of a relatively low resistance. If the resistance to insertion of the foundation elements into the ground increases, the stroke volume of the hydraulic motor can be increased. The overall available power of the hydraulic motor which can be effectively supplied to the vibrating device remains substantially the same here, while the resulting drive force is in that case increased and the frequency reduced. This prevents loss of energy.

In an advantageous preferred embodiment according to the present invention the ratio of the maximum stroke volume and the minimum stroke volume lies in the range of 1 to 4, and preferably amounts to about 2.

Varying the stroke volume in said range achieves that the vibrating device can continue to function as optimally as possible under a considerably wide range of conditions. In practice this provides an effective and sufficiently large operating range for operating the vibrating system according to the invention in effective manner.

In an advantageous preferred embodiment according to the present invention the vibrating system comprises a control system configured to modify the drive force of the vibrating system.

Providing a control system enables the adjusting device to be controlled in effective manner, such that the drive force of the vibrating system can be set and the power which can be transmitted by the vibrating device to the foundation element remains substantially constant.

The control system is preferably provided with a pressure sensor whereby it is possible to determine the current operating pressure and, also on the basis thereof, perform the adjustment of the stroke volume of the hydraulic motor in particular. An effective and efficient modification of the settings of the vibrating system according to the invention can be realized in this way.

In a currently preferred embodiment the control system is configured to modify the adjusting device in automatic manner. Performing the adjustment in automatic manner, i.e. without interruptions as a result of intervention by an operating person, it is possible to react in the short term to changing conditions during the insertion of the foundation element into the ground. The control system according to the invention can for this purpose for instance be set to keep the drive force of the vibrating system at a maximum and/or to keep the power taken up by the foundation element constant and/or as high as possible.

In a further advantageous preferred embodiment according to the present invention the adjusting device comprises a transmission ratio of the vibrating device which can be variably set.

Providing the adjusting device with a transmission which can be variably set, particularly a transmission ratio which can be variably set, makes it possible to vary the frequency of the vibrating device in effective manner. Use can advantageously be made here of a control system as described above for the vibrating system.

In a further alternative embodiment use is made of a combination of a variable transmission and a variable stroke volume for the hydraulic motor. The overall flexibility for insertion of a foundation element under variable conditions is significantly increased in this way.

This reduces the insertion time required for inserting the foundation element into the ground and/or reduces the energy required for the insertion in a wide operating range of occurring conditions, such as insertion resistance. An effective vibrating system is hereby provided.

In an advantageous embodiment according to the invention the vibrating system comprises a compensation system configured to keep a system pressure for a hydraulic leakage fluid above ambient pressure.

In conventional systems a small part of the supplied hydraulic fluid is usually used to lubricate the motors, the so-called hydraulic leakage fluid. In order to prevent damage to the motors, particularly damage to the sealing rings on the drive shafts, it is important for the operating pressure of this hydraulic leakage fluid to remain sufficiently low. Discharge of hydraulic fluid under low pressure is usually also required for the functioning of for instance hydraulic valves and safety valves on the vibrating system. This discharge at low pressure usually requires the use of hoses and connections intended specifically for this purpose. This makes the system expensive and complex. In addition, modifications/connections to the vibrating system regularly have to be made for this purpose in practice.

Providing a compensation system keeps the pressure of the hydraulic leakage fluid in the vibrating system higher than the local ambient pressure. The minimum overpressure preferably lies in the range of 1 to 5 bar, and preferably amounts to about 1 bar. The compensation system is preferably provided with an auxiliary pump for bringing the hydraulic leakage fluid to the system pressure above the ambient pressure. The leakage fluid can hereby be handled in effective manner. It is additionally prevented that the pressure of the hydraulic leakage fluid becomes too low, whereby medium can for instance flow from outside the motor into the leakage hose. This is for instance relevant in use under water at great water depths.

The vibrating system preferably further comprises an integration system configured to feed the hydraulic leakage fluid back to the hydraulic pump and/or hydraulic motor. The hydraulic pump of the vibrating system, usually particularly of the so-called power pack thereof, is operatively connected to the hydraulic motor of the vibrating system. This connection is made in practice by supplying hydraulic fluid via one or more supply hoses to the motor and then discharging it to the power pack via one or more discharge hoses.

In a currently preferred embodiment the hydraulic leakage fluid can be discharged to the power pack with a relatively small hose or fewer hoses, or even be fed back to the discharge hose again, using the integration system in combination with the compensation system. The practical and financial inconvenience of one or more leakage hoses is hereby reduced or even avoided. Power packs and hose reels without provisions for leakage hoses can hereby for instance also be used. The use of greater hose lengths is in addition possible because the pressure of the hydraulic leakage fluid is no longer a limitation. Use of the vibrating device at for instance very great water depths can hereby be made possible.

The auxiliary pump of the compensation system is preferably provided with an auxiliary drive which is operatively coupled to the drive of the vibrating system and is further preferably provided with an auxiliary hydraulic motor with a variable stroke volume. The auxiliary pump can be driven by a separate hydraulic circuit. A controlled driving of the auxiliary pump can hereby be obtained. In an alternative and currently preferred embodiment the pump is therefore operatively connected to the drive of the vibrating system, for instance by means of a mechanical connection to the hydraulic motors of the vibrating system or by means of a separate hydraulic motor which is hydraulically connected to the drive of the vibrating system. In the case of a separate hydraulic motor, a hydraulic motor with a variable stroke volume is preferably applied. The decreased power of the integration system can hereby be adapted in efficient manner to the prevailing operating pressure of the drive of the vibrating system. When the operating pressure of the drive of the vibrating system is relatively low, relatively little hydraulic leakage fluid results. In this situation the motor will take on a relatively great stroke volume and will thereby run slowly, whereby relatively little hydraulic leakage fluid can be discharged by the pump. When the operating pressure of the drive of the vibrating system is relatively high, a relatively large quantity of hydraulic leakage fluid results. In this situation the motor will take on a relatively small stroke volume and will thereby run quickly, whereby a relatively large quantity of hydraulic leakage fluid can be discharged by the pump. Because of the high available operating pressure of the drive of the vibrating device, the available power for the drive of the pump is still sufficient. This results in an effective handling of the leakage fluid.

The integration system preferably comprises a hydraulic compensator in which the leakage oil of the hydraulic motors is collected and brought to an overpressure. An auxiliary hydraulic pump brings the hydraulic leakage fluid to a higher pressure, whereby this hydraulic fluid can be discharged through a relatively small hose or fewer hoses or, in an ideal situation, is even fed back to the discharge hose. A control valve preferably ensures that the volume flow of the auxiliary pump is adapted to the volume flow of the hydraulic leakage fluid. The quantity of hydraulic leakage fluid in the compensator hereby remains substantially constant during use.

The invention further relates to a method for varying the drive force of a vibrating system for inserting a foundation element into the ground, wherein the method comprises the steps of:

providing a vibrating system as described above; and

modifying the adjusting device, such that the drive force is optimal while the power which can be produced by the vibrating device remains substantially constant.

The method provides the same advantages and effects as described for the vibrating system. An optimal drive force with the method according to the invention results in an optimal, i.e. the greatest possible, power take-up by the foundation element, which preferably remains substantially constant under variable conditions. A foundation element can hereby be placed in the ground in effective manner with a short insertion time and/or minimal energy consumption.

For modification of the adjusting device use is preferably made of modification of the stroke volume of the hydraulic motor of the vibrating device and/or modification of the transmission ratio. Use is further preferably made of a controller as described above for the vibrating system. The controller is here preferably configured such that a modification of the adjusting device is performed in automatic manner. Use can for instance be made here of a pressure sensor.

The method preferably further comprises the step of keeping a system pressure for a hydraulic leakage fluid above an ambient pressure with a compensation system. The above stated effects and advantages are hereby achieved.

Further advantages, features and details of the invention are elucidated on the basis of a preferred embodiment thereof, wherein reference is made to the accompanying figures in which:

- Figure 1 shows a view of a vibrating system;

Figure 2 shows a view of the vibrating system according to the invention with drive; and

Figures 3A and B show schematic overviews of an embodiment of the compensation system according to the invention for the leakage fluid.

Foundation element 2 (Figure 1) is held on the upper side by clamping system 4 using one or more clamps 6. Arranged above clamping system 4 is a vibrator block 8 which in the shown embodiment is provided with hydraulic motor 10. Further arranged above vibrator block 8 is a so- called suppressor 12 which ensures inter alia that vibrations are not transmitted via connection 14 to for instance the boom of a lifting device.

In the shown embodiment vibrating system 16 (Figure 2) comprises in addition to vibrator block 8 with hydraulic motor 10 a power pack 18, wherein hydraulic hoses 20 carry hydraulic fluid, for instance an oil, to connections to suppressor 12 and back via hoses 22, wherein via suppressor 12 hydraulic fluid is carried via hydraulic hoses 24 to hydraulic motor 10 and back via hydraulic hoses 26. A different configuration of hydraulic hoses 20, 22, 24, 26 is of course likewise possible.

In the shown embodiment power pack 18 comprises diesel engine 28 and hydraulic pump

30, which are mutually coupled using connection 32.

Vibrating system 16 is further provided with a controller 34 which comprises manual operation 36. Controller 34 sends the desired settings, for instance the setting for the stroke volume, to hydraulic motor 10 via control signal 38. Provided in the shown embodiment is pressure sensor 40, from which measuring signal 42 is sent to controller 34. Vibrator block 8 further comprises transmission 44 and a number of eccentrics 46 for realizing vibrations during use whereby foundation element 2 can be vibrated into the ground.

During insertion of foundation element 2 power pack 18 is set into operation to supply available power. Hydraulic oil is carried to motor 10 with a set stroke volume. Vibrator block 8 is hereby driven and operated at a determined frequency and drive force. In the case of an increase of the resistance to a foundation element 2 being inserted into the ground, the drive force is increased according to the invention, while the frequency of a vibrator block 8 decreases. In the shown embodiment this is achieved using controller 34. The increase of the drive force required can be detected using pressure sensor 40, after which controller 34 implements the desired settings for vibrator block 8. This relates for instance to modification of the stroke volume of hydraulic motor

10, which is for instance embodied as a so-called axial piston variable motor. Controller 34 can alternatively or additionally modify transmission 44 of vibrator block 8.

In the following table an example is given wherein an operating situation with a standard vibrating system provided with a fixed conventional hydraulic motor is compared to a vibrating system according to the invention with a hydraulic motor which can be set.

Standard vibrating device with New vibrating device with non-variable (conventional) variable hydraulic motor hydraulic motor

Stroke volume of vibrating 180 cc 180 cc - 360 cc

device

Max. operating pressure 350 bar 350 bar

Drive force of vibrating 1200 Nm 1200 Nm at 180 cc device 2400 Nm at 360 cc Available power of power 245 Kw 245 Kw unit

Frequency of vibrating 2300 rpm 2300 rpm at 180cc device 1150 rpm at 360cc

The sample values included in the table show that the drive force can increase when frequency decreases, such that the power consumed is utilized to the maximum for inserting foundation element 2 into the ground. A robust operation which remains functioning at a maximum operating pressure of up to for instance 350 bar is obtained in the manner proposed according to the invention, preferably by modification of the stroke volume of hydraulic motor 10.

A compensation system according to the invention can be embodied in diverse ways according to the invention. In the shown embodiment (Figure 3A) the system operates as hydraulic leakage fluid integration system, in this embodiment with operatively connected vibrating device motor and leakage fluid pump. Sump 100 with the eccentrics of the vibrating device is shown schematically. Hydraulic motor 102 provides for the driving on the basis of hydraulic fluid supply 103 and hydraulic fluid discharge 104. In this embodiment hydraulic leakage fluid pump 106 forms together with hydraulic control valve 107 and hydraulic leakage fluid buffer 108 a compensation system.

In another embodiment the compensation system (Figure 3B) is embodied in a slightly different way. Sump 101 with the eccentrics of the vibrating device is also shown schematically in this shown embodiment. Hydraulic motor 102 provides for the driving on the basis of hydraulic fluid supply 103 and hydraulic fluid discharge 104. In this embodiment hydraulic leakage fluid pump 106 forms together with hydraulic leakage fluid buffer 108, hydraulic control valve 107 and hydraulic leakage fluid motor 109, which is provided in this shown embodiment with a stroke volume control for the leakage fluid motor, an alternative compensation system.

It will be apparent that other embodiments for compensation systems are also possible, for instance with additional valves and/or further or alternative components. Buffer 107 can thus form part of an integration system configured to feed the hydraulic leakage fluid back to the hydraulic pump and/or hydraulic motor.

The invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.