Vibratory foundation apparatus with linear electromagnetic actuator

Abstract

The present invention relates to a vibratory foundation apparatus (1) for driving or extracting a foundation element (100) into or out of the ground, comprising: - a frame element (20), - a clamping device (30), configured to clamp the foundation element, and - a vibrator device (10), which is functionally arranged in between the frame element and the clamping device and which is configured to subject the clamping device to a vibratory load, characterized in that, the vibrator device comprises a linear electromagnetic actuator (11), configured to generate the vibratory load and comprising: - an electromagnetic inductor (12), configured to induce an electromagnetic field under influence of an electric current guided through the inductor, and - a magnetic element (13), for example a permanent magnet or magnetizable material, such as a soft-iron element, in proximity to the inductor, to be subjected to the electromagnetic field, and wherein the linear electromagnetic actuator is configured to oscillate the magnetic element in a linear vibration direction with the inductor under influence of the electromagnetic field.

Description

[0001] Title: Vibratory foundation apparatus with linear electromagnetic actuator

[0002] Field of the invention

[0003] The present invention relates to a vibratory foundation apparatus for driving a foundation element into the ground and / or for extracting a foundation element out of the ground. The present invention further relates to a method of operating such a vibratory foundation apparatus and to the use of such a vibratory foundation apparatus.

[0004] State of the art

[0005] Foundation elements can be driven into the ground or extracted out of the ground in various ways. Vibratory foundation apparatuses are often found beneficial, as being relatively efficient and having a relatively low degree of noise pollution. Examples thereof are disclosed in EP 0 524 056 A1, which discloses a vibratory foundation apparatus with a number of excentre weights that are driven in rotation about a horizontal axis in a synchronized manner by means of one or more hydraulic motors, in order to obtain a net linear vibratory force.

[0006] Such hydraulic motors may be disadvantageous, for example inducing efficiency losses, excessive wear of bearings due to excentre forces and potentially forming environmental hazards due to potential leakage.

[0007] Attempts have been made, for example in WO 2022 / 023254 A1, to electrify these vibratory apparatuses. This alternative vibratory foundation apparatus, however, still lacks the efficiency losses of rotary excentres that already existed in the known hydraulic vibratory foundation apparatuses.

[0008] Alternative developments have been disclosed in NL 2012101 C, which discloses a vibratory foundation apparatus with a single rotating mass, which is rotated about a vertical axis under influence of a hydraulic motor. The rotating mass is vertically displaceable by selectively operating valves alongside the rotating mass, so that channels inside the rotating mass selectively and alternatingly fluidly interconnect with the valves. This effects an oscillatory displacement of the rotating mass to exert a vibratory force on the foundation element clamped in the vibratory foundation apparatus.

[0009] This alternative design of the vibratory foundation apparatus is able to operate at higher vibration frequencies, due to the lack of excentre weights. However, this vibratory foundation apparatus still has the drawback that a rotating mass is used, whereby the rotation of the mass is indirectly transferred into the linear vibrating force, which may thus result in efficiency losses as well. JP S59 161517 A discloses a vibratory foundation apparatus which comprises a drive coil with a primary core, attached to a ballast frame of the apparatus, and a secondary core made of iron that is attached to a clamp for clamping a foundation pile. During use, the drive coil is subjected to an electric current to generate an electromagnetic field. This field exerts an attracting magnetic force on the secondary core, to pull the cores towards each other. Next, the electric current is terminated, after which compression springs push the cores away from each other. By repeating these steps, a vibratory load can be exerted onto the pile, but the compression springs have a drawback, since they increase inertia and since they may be prone to resonance, which could cause undesirable wear and vibrations.

[0010] JP S59 165730 A, of the same applicant, discloses a similar vibratory foundation apparatus. This apparatus comprises an upper drive coil and a lower drive coil, which can be subjected to the electric current alternatingly, so that they alternatingly apply the electromagnetic field. The secondary core of iron is placed in between the drive coils, so that it is alternatingly attracted by both coils to vibrate the secondary core and thus vibrating the pile. The design of this apparatus is rather complicated with the presence of two driving coils, whereas it still requires springs to effect a return movement of the secondary core.

[0011] EP 1 323 869 A1 discloses a dynamic test method for test bearing capacity of piles that are in the ground already, which relies on a magneto strictive vibrator that is capable of straining under influence of an electric current guided through a coil.

[0012] US 5 769 173 A discloses a vibration exciter machine that comprises magneto striction elements that are capable of expanding and contracting to initiate a vibration on a file member upon insertion in the ground.

[0013] Object of the invention

[0014] It is therefore an object of the invention to provide a vibratory foundation apparatus that is able to exert a vibratory load onto a foundation element at an improved efficiency, or at least to provide an alternative vibratory foundation apparatus.

[0015] Detailed description

[0016] The present invention provides a vibratory foundation apparatus for driving a foundation element into the ground and / or for extracting a foundation element out of the ground, the apparatus comprising: a frame element, with which the apparatus is configured to be suspended, a clamping device, configured to clamp the foundation element, and a vibrator device, which is functionally arranged in between the frame element and the clamping device and which is configured to subject the clamping device to a vibratory load, characterized in that, the vibrator device comprises a linear electromagnetic actuator, configured to generate the vibratory load and comprising: an electromagnetic inductor, for example an electromagnetic coil, configured to induce an electromagnetic field under influence of an electric current guided through it, and a magnetic element, for example a permanent magnet or magnetizable material, such as a soft-iron element, in proximity to the inductor, to be subjected to the electromagnetic field, wherein one of the inductor or the magnetic element is associated with the frame element and wherein another one of the inductor or the magnetic element is associated with the clamping device, and wherein the linear electromagnetic actuator is configured to oscillate the magnetic element in a linear vibration direction with the inductor under influence of the electromagnetic field.

[0017] The vibratory foundation apparatus according to the present invention relies on a different working principle compared to the known vibratory foundation apparatuses, since it lacks rotating masses. Instead, the vibratory load is generated by means of a linear actuator, which is configured to operate in a direction substantially parallel to an elongate axis of the foundation element, so that no transfer is needed from a rotating mass into the linear vibration direction.

[0018] The frame element of the present vibratory foundation apparatus may comprise a suspension element, with which the vibratory foundation apparatus is suspended, for example from a crane. The frame element is configured to be held stationary during use of the vibratory foundation apparatus, i.e. when the vibratory load is exerted therewith.

[0019] The clamping device is configured to clamp the foundation element during use of the vibratory foundation apparatus. The clamping device may comprise at least one jaw element for contacting the foundation element, for example two opposed jaw elements, which can be moved towards each other by means of a clamp actuator, so that the foundation element can be clamped in between the jaw elements.

[0020] The vibratory foundation apparatus may contain a single clamping device, i.e. a single set of jaw elements, in case it is desired to clamp a foundation element at a single location. This may, for example, apply for a situation where the vibratory foundation apparatus is intended to insert a single sheet pile in the ground. The vibratory foundation apparatus may, alternatively, comprise multiple clamping devices attached to the electromagnetic actuator in case it is desired to clamp multiple foundation elements simultaneously, for example multiple connected sheet piles. Multiple clamping devices may also be envisaged when the vibratory foundation apparatus is, for example, intended to insert tubular foundation elements in the ground, so that the tubular foundation element can be clamped at multiple points around its perimeter. The vibrator device is associated with the frame element and the clamping device, so that the vibratory load can be generated relative to the frame element and be transferred onto the clamping device, whereas the frame element is held stationary. The vibrator device may be rigidly connected to the clamping device, for example to offer a rigid and an efficient transfer of the vibratory load from the vibrator device to the clamping device. Furthermore, the vibratory foundation apparatus may comprise a relatively resilient connection between the vibrator device and the frame element, for example to prevent the frame element from being subjected to the vibratory load.

[0021] During use of the vibratory foundation apparatus, the vibratory load is generated by the linear electromagnetic actuator of the vibrator device. This linear electromagnetic actuator is configured to generate the vibratory load directly along the linear vibration direction, which is typically aligned parallel to the foundation element that is clamped in the clamping device, so that the vibratory load is able to exert a standing wave vibration in the foundation element to facilitate insertion thereof in the ground or extraction out of the ground by reducing wall friction alongside the foundation element and / or by fluidizing soil underneath it.

[0022] The linear electromagnetic actuator may typically operate in the absence of hydraulic actuators and without hydraulic fluid for transferring energy towards the vibratory foundation apparatus. Instead, the electromagnetic actuator preferably only comprises the electromagnetic inductor, which is subjected to an electric current, and the magnetic element. The vibratory foundation apparatus thus only consumes electric energy and may, to this effect, for example be connected to a controllable electrical power source via an electricity cable.

[0023] The electromagnetic inductor is configured to receive the electric current, for example an alternating electric current. When the current is guided through the electromagnetic inductor during use of the vibratory foundation apparatus, the electromagnetic field is generated by the electromagnetic inductor, for example inside windings of an electromagnetic inductor embodied as a coil. The vibratory foundation apparatus may comprise a single electromagnetic inductor in each electromagnetic actuator, or may comprise multiple electromagnetic inductors per electromagnetic actuator, so that the overall electromagnetic field generated in the electromagnetic actuator is a cumulative field of all individual electromagnetic fields in combination.

[0024] The magnetic element is made of a magnetizable material, for example a ferromagnetic material, such as iron, soft-iron or steel, or may be formed by one or more permanent magnets, which emits an electromagnetic field. Alternatively, the magnetizable material may comprise a diamagnetic or paramagnetic material or may be an electrically conductive material in which Eddy currents can be induced with the electromagnetic field to obtain a resulting magnetic counter force. The use of a permanent magnet may be beneficial as a result of the magnetic polarity. Such permanent magnets can both be attracted and repelled, depending on the polarity of the electromagnetic field from the inductor. As a result, no spring or other mechanical elastic elements may be needed in the vibrator device. The magnetic element may alternatively comprise a second electromagnetic inductor, that is capable of inducing a secondary electromagnetic field, so that the electromagnetic field and the secondary electromagnetic field are able to interact to effect the vibratory movement.

[0025] Throughout the present application, the wording of magnetic element and magnet is used exchangeably to indicate the part of the vibrator device that is subjected to the magnetic force resulting from the electromagnetic field exerted with the electromagnetic inductor.

[0026] In general, however, the magnetic element is located in proximity to the electromagnetic inductor, for example adjacent one another, or the magnetic element can be located centrally in between multiple electromagnetic inductors or centrally inside winding of an annular inductor, embodied as a coil. The electromagnetic field from the electromagnetic inductor will interact with the magnetic element and a net magnetic force will be obtained between them, which may be an attractive force, pulling the electromagnetic inductor and the magnetic element towards each other, or a repulsive force, pushing the electromagnetic inductor and the magnetic element away from each other.

[0027] When the electromagnetic field is alternated in direction, i.e. by selectively steering the electric current through the electromagnetic inductor, the direction of the resulting magnetic force between the electromagnetic inductor and the magnetic element can be alternated, so that the electromagnetic inductor and the magnetic element can be alternatingly pulled towards each other and pushed away from each other. This reversing movement may induce oscillations of the magnetic element relative to the inductor, therewith effecting the vibratory load. These oscillations may be defined as back-and-forth mutual movements between the inductor and the magnetic element.

[0028] To effectively exert the vibratory load between the frame element and the clamping device, the part of the vibration device associated with, for example attached to, the frame element needs to be held stationary during use, whereas the part of the vibration device associated with, for example attached to, the clamping device needs to be able to vibrate during use. In general, either the inductor or the magnetic element may be the stationary part associated with the frame element, as long as the other, respectively the magnetic element or the inductor, is associated with the clamping device, in order to vibrate the clamping device relative to the frame element under influence of the electromagnetic field interacting with the magnetic element.

[0029] The frequency of the vibratory load may be variable in the range between 1 - 1000 Hz, for example in the range between 20 Hz and 400 Hz, preferably with a maximum frequency of about 200 Hz. The frequency may, for example, be selected in dependence of the type of foundation element, length of the foundation element, soil conditions etc. Furthermore, the frequency may be varied over the course of the inserting or extracting, for example when one or more of the above parameters changes. A frequency of up to 1000 Hz may be much larger compared to known vibratory foundation apparatuses with excentre weights, which may typically reach frequencies of about 2400 rpm, so about 40 Hz.

[0030] Apart from the higher frequencies, further benefits of the present invention may be an improved lifespan, since no rotational bearings need to be provided, so that wear of bearings will become less critical, compared to known vibratory foundation apparatuses. Additionally, the lack of hydraulic fluids may prevent cavitation damage or spilling that could otherwise occur in hydraulic vibratory foundation apparatuses.

[0031] As a further benefit, the startup of the inserting and extracting of foundation elements can be done more smoothly by steering the frequency of the vibratory load, which no longer requires variable angular momentum of excentre weights. Finally, the present vibratory foundation apparatus may require less energy input to offer a similar output energy, compared to known vibratory foundation apparatuses, due to the lack of losses occurring in hydraulic fluids.

[0032] In an embodiment, the inductor is configured to alternate a direction of the electromagnetic field in order to alternatingly apply and attractive and repulsive force on the magnet. The alternating directions of the electromagnetic field provide that the magnetic forces exerted on the magnetic element, e.g. the magnet, is reversed as well. An alternating attracting and repelling magnetic force can therewith be exerted, which means that no other spring, elastic elements, or the like are needed for returning the inductor and the magnetic element after the field has been induced.

[0033] In a further embodiment, the actuator is free of elastic elements for pushing the inductor and the magnetic element, e.g. the magnet away from each other. Instead, the alternating magnetic force may provide for both attraction and repulsion between the electromagnetic inductor and the magnetic element.

[0034] In an embodiment, the inductor is attached to the frame element and the magnetic element is attached to the clamping device. This embodiment relies on a stationary inductor in the frame element and a vibrating magnetic element attached to the clamping device, which may be beneficial from a practical point of view, since the inductor may have all sorts of electric components, such as cables, connectors and sensors attached to it, which can all remain stationary. This may reduce wear and damaging of these components, thereby improving reliability, and may as well reduce the overall weight of all vibrating components, thereby minimizing the energy consumption requiring for exerting the vibratory load and improving the mass spring damper characteristics of the vibratory foundation apparatus.

[0035] In a further embodiment, an outer housing of the vibratory foundation apparatus may be connected to the magnetic element of the linear electromagnetic actuator, so that the entire outer housing will be vibrated relative to inner components of the vibratory foundation apparatus that remain stationary, together with the inductor. In this way, the entire outer housing may be used for attaching the clamping device to the vibrator device. As such, the clamping device can be selectively placed at different locations, for example also allowing foundation elements to be clamped at the side of the vibratory foundation apparatus, instead of only at the bottom.

[0036] In an embodiment, the vibrator device comprises a connection element with which the magnetic element is attached to the clamping device. The connection element may thereby form the physical connection between the magnetic element and the clamping device, in order to transmit the vibratory load from the oscillating magnetic element towards the foundation element clamped inside the clamping device, during use of the vibratory foundation apparatus. The connection element may form a rigid connection between the magnetic element and the clamping device, in order to minimize energy losses.

[0037] In an embodiment, the vibrator device comprises a plurality of the linear electromagnetic actuators. According to this embodiment, the overall capacity of the vibratory foundation apparatus, i.e. the maximum vibratory load that can be exerted with the vibratory foundation apparatus, may be varied by selecting a desired number of electromagnetic actuators. This may also mean that a single vibratory foundation apparatus can be used various times with different numbers of the electromagnetic actuators, for example depending on the type and size of the foundation element, or on the soil condition. This may enable a modular construction of the vibratory foundation apparatus, so that an operator thereof may only need to acquire a single vibratory foundation apparatus and that various energy outputs can be achieved therewith by selectively including a desired number of electromagnetic actuators in the vibratory foundation apparatus.

[0038] In a further embodiment, at least part of the actuators is arranged in parallel, wherein for example multiple actuators are arranged next to each other in a transverse direction perpendicular to the vibration direction. This embodiment allows multiple electromagnetic actuators to be placed next to each other, so that each magnetic element of the respective electromagnetic actuators is associated with the clamping device. Furthermore, this configuration may be beneficial when relative wide foundation elements are inserted in the ground, e.g. being relatively wide in a direction perpendicular to a longitudinal direction of the foundation element. Similarly, the multiple parallel electromagnetic actuators may be placed in an annular pattern, so that a tubular foundation element can be clamped at multiple points round its circumference.

[0039] Alternatively or additionally, at least part of the actuators is arranged in series, wherein for example multiple actuators are arranged in-line along the vibration direction. This placement of the multiple electromagnetic actuators may yield that the magnetic elements of the different electromagnetic actuators are attached to each other, in order to be oscillated in synchronism. This may enable that the output power of vibratory foundation apparatus can be relatively large, whilst still allowing a single clamping device to be connected to the magnetic elements.

[0040] In a further embodiment, comprising the connection element, multiple of the magnetic elements are attached to each connection element. As such, the magnetic elements are connected to the connection element in series, so that the connection element is vibrated under influence of multiple inductors of multiple electromagnetic actuators.

[0041] In an embodiment, the electromagnetic actuators are arranged in a circular pattern, spread in a circumferential direction around the linear vibration direction. Each of the electromagnetic actuators may be associated with a respective clamping device, for example where the clamping devices are spread in the circumferential direction around the vibration direction as well, so that tubular foundation elements can clamped at multiple points around their perimeter and that vibrational energy can be fed into the tubular foundation element at multiple points around its circumference as well.

[0042] Additionally, the electromagnetic actuators and / or the clamping devices may be displaceable inwardly and outwardly along a radial direction relative to the vibration direction, so that the projected radius of the combined electromagnetic actuators and / or clamping devices can be changed and adapted to the radius of the tubular foundation element that is to be clamped.

[0043] In an embodiment, the foundation apparatus is substantially free of elastomeric elements in between the frame element and the vibrator device. In existing vibratory foundation apparatuses, such elastomeric elements were needed to isolate the frame element from vibrations. According to the present invention, the frequency of the vibratory load can be controlled more accurately, possibly even at the Eigen frequency of the foundation element. This may allow the amplitude of the vibratory load to be smaller compared to the known vibratory foundation apparatuses, which may allow for the omission of elastomeric elements.

[0044] Additionally, the present vibratory foundation apparatus may rely on linear bearings between the frame element and the clamping device, in particular between the magnetic element and the inductor of the electromagnetic actuators, in order to ensure that mutual movements between these components is only allowed along the linear vibration direction and that any transverse movements between them are prevented.

[0045] In a further embodiment, the actuator is configured to apply the electromagnetic field with the inductor at a phase shift in relation to the oscillations of the magnetic element, in order to dampen oscillation reversals of the magnetic element. During use, the electromagnetic field is configured to oscillate the magnetic element by means of the magnetic force. The phase shift between the electromagnetic field and the magnetic element implies that a time delay is present between direction reversals of the electromagnetic field, i.e. when the direction of the electromagnetic field reverses, and the reversals of the oscillations of the magnetic element. This means that for a duration corresponding to the phase shift, the movement of the magnetic element and the magnetic force exerted on it by the electromagnetic field will be in opposed directions. This will decelerate the movement of the magnetic element magnetically as a result of this opposed force, possibly no longer causing the magnetic element to reach the outer ends of its path. This may allow for smoother oscillations of the magnetic element, thus reducing wear and possibly even reducing the need for bearings.

[0046] The applied phase shift may depend on the frequency and / or amplitude of the vibratory load. If either one or both of these is set relatively large, the inertia of the magnetic element will become relatively large as well, thus requiring a larger counterforce for reversing the movement of the magnetic element. In such a situation, the phase shift of the magnetic element in relation to the electromagnetic field may be set relatively large.

[0047] In an embodiment, the inductor may be a single-phase inductor. This means that a single induction portion may be provided in the inductor for inducing a single-phase electromagnetic field. The entire oscillation of the magnetic element may be steered with this single-phase electromagnetic field.

[0048] In an alternative embodiment, the inductor may be a multi-phase inductor, for example a three-phase inductor. In this embodiment, multiple inductor portions may be provided in the inductor, wherein each inductor portion is associated with a respective phase of the electric current. For example, a three-phase electric current may be supplied to three respective inductor portions which are spaced from each along the path of the magnetic element. The vibratory foundation apparatus may thereby be configured to initially exert the electromagnetic field with the inductor portion located in closest proximity to the magnetic element, so that the resulting magnetic force exerted on the magnetic element can be maximized. Upon travel of the magnetic element relative to the inductor, the electromagnetic field may be generated by guiding an electric current through a subsequent inductor portion, now located closer to the magnetic element, so that the magnetic force can remain relatively large.

[0049] In an embodiment, the vibrator device is arranged in a rest position in the absence of the electric current through the inductor. The foundation apparatus further comprises a locking device to substantially rigidly interlock the clamping device and the frame element in the rest position of the vibrator device, to enable non-vertical loading of the foundation apparatus.

[0050] The vibratory foundation apparatus according to the present embodiment can be allowed as a lifting device and as upending device for foundation elements, since its vibrator device can be bypassed for external loads in the rest position due to the rigid connection between the frame element and the clamping device. This means that during upending, when the vibratory foundation apparatus is loaded in directions non-parallel to the vertical direction and the longitudinal direction of the foundation element, the vibrator device will not be loaded substantially. As such, the inductor, the magnetic element, and possible elastomeric elements will not need to transfer any forces between the frame element and the clamping device, since such forces can pass through the locking device, resulting in safer operation of the vibratory foundation apparatus.

[0051] The rest position of the vibrator device may be governed by gravitational forces, for example being formed by a position in which the magnetic element is fully lowered. Alternatively, the rest position of the vibrator device may involve actively applying an electromagnetic field to bring the magnetic element in a desired position relative to the inductor, for example a central position of the magnetic element in between the end points of its oscillation.

[0052] The locking device may be a physical element, for example an actuated pin or the like attached to the foundation element, which may be actuated to engage towards the clamping device. The locking device may form a physical and rigid connection between the frame element and the clamping device, when actuated in the rest position of the vibratory foundation apparatus. During use of the vibratory foundation apparatus, i.e. when the vibratory load is to be exerted, the locking device is moved out of engagement, allowing the clamping device to be vibrated relative to the frame element.

[0053] In an embodiment, the vibratory foundation apparatus further comprises a control unit, functionally connected to the vibrator device and configured to control the vibratory load generated by the vibrator device. The control unit may control the frequency and / or amplitude of the vibrational load exerted with the vibratory foundation apparatus. These parameters may, for example, be controlled in dependence of the type of foundation element, length of the foundation element, soil conditions etc. Furthermore, the control unit may be configured to establish a progressive startup of the vibrational load, in order to reduce wear of the vibratory foundation apparatus and to increase its lifespan. This may further be beneficial for avoiding nuisance, such as noises or vibrations of the soil.

[0054] The control unit may for example be configured to control the frequency, phase, and magnitude of the electric current guided through the inductor, so that the electromagnetic field exerted by the inductor can be controlled in accordance. Furthermore, the control unit may set a voltage at which the electric current is supplied to the inductor, wherein the resulting current is governed by the amount of energy needed to oscillate the magnetic element.

[0055] In a further embodiment, the vibratory foundation apparatus further comprises a vibration sensor device, which is associated with the clamping device and the control unit and which is configured to emit a vibration sensor signal representative for a frequency and / or amplitude of vibrations of the clamping device, and the control unit is configured to control the electromagnetic actuator in dependence on the vibration sensor signal.

[0056] The vibration parameters measured at the clamping device with the vibration sensor may be representative for the vibrations of the foundation element, since the foundation element is rigidly clamped in the clamping device. As such, the measured frequency may represent a frequency of the foundation element, which may change during its insertion in, or its extraction out of the ground.

[0057] The vibration sensor signal is thereby used as a feedback signal for the control unit, so that the amplitude and / or the frequency of the vibrational load emitted with the electromagnetic actuator can be adjusted on the basis thereof. This means that the applied vibrational load can be adjusted to the actual conditions of the foundation element during the insertion or extraction thereof. If there is, for example, a mismatch between the frequency applied with the electromagnetic actuator and the frequency measured with the vibration sensor, the control unit may adjust the applied frequency accordingly. In an embodiment, the vibratory foundation apparatus further comprises a current sensor device, which is associated with the inductor and the control unit and which is configured to emit a current sensor signal representative for a magnitude of the electric current, e.g. an electric power input, consumed by the inductor, and the control unit is configured to control the electromagnetic actuator in dependence on the current sensor signal.

[0058] Similar as for the vibration parameters described above, also the electric current parameters measured at the inductor may be used as feedback signal for the control unit. Hence, during operation, the electric current supplied to the inductor may depend on the amount of energy needed to oscillate the magnetic element and that is dissipated into the foundation element. Typically, electric energy is supplied to the inductor at a certain controlled voltage, whereby the electric current drawn by the inductor will depend on the amount of energy, i.e. the magnetic force, that needs to be delivered by the inductor.

[0059] The magnitude of the electric current may, for example, be relatively high if the frequency of the vibrational load is remote from an Eigen frequency of the foundation element, e.g. of a combined resonance frequency of the foundation element and the clamping device in which the foundation element is clamped. To reduce the electric power input of the vibratory foundation apparatus, the magnitude of the electric current is to be reduced, for example by applying the electromagnetic field at a frequency closer to, or preferably corresponding to the Eigen frequency of the foundation element.

[0060] When the current sensor signal is used as a feedback signal for the control unit, the amplitude and / or the frequency of the vibrational load emitted with the electromagnetic actuator can be adjusted on the basis of the current sensor signal. This means that the applied vibrational load can be adjusted to the actual conditions of the foundation element during the insertion or extraction thereof. Hence, the Eigen frequency of the foundation element can change during the insertion, since the part of its length above the ground level will decrease, thus increasing the Eigen frequency. The feedback control loop of measuring the electric current may enable the control unit to change the applied frequency of the vibrational load to the changing Eigen frequency.

[0061] The present invention further provides a vibratory foundation apparatus comprising a frame element, a clamping device and vibrator device as explained above, which may, but necessarily needs to comprise the electromagnetic actuator disclosed herein. The clamping device of this vibratory foundation apparatus does comprise at least one jaw element for contacting the foundation element and an electric clamp actuator, configured to move the at least one jaw element to apply a clamping force on the foundation element therewith. This vibratory foundation apparatus thus comprises a clamping device that operates under influence of electricity, instead of using the hydraulic clamps that are known in the art. This may lead to similar benefits as disclosed herein in relation to the electrically operated vibrator device with the linear electromagnetic actuator, for example improving controllability and reducing complexity.

[0062] The present clamping device comprises at least one movable jaw element, which may be positioned opposite to a stationary counter element, so that the foundation element can be clamped in between the jaw element and the counter element, i.e. in a manner similar to the hydraulically powered jaw elements known from the prior art. Alternatively, the clamping device may comprise two opposed movable jaw elements between which the foundation element is clamped.

[0063] The electric clamp actuator is configured to apply, either directly or indirectly, an actuator force onto the jaw elements. In turn, the jaw element is configured to covert this into a clamping force at which the foundation element is clamped. In a direct conversion, the electric clamp actuator directly acts onto the jaw element. In an indirect conversion, some transmission may be present in between the electric clamp actuator and the jaw element.

[0064] In a further embodiment, the clamping device further comprises a lever assembly, which is functionally arranged in between the at least one jaw element and the clamp actuator, and the lever assembly is configured to amplify an actuator force exerted by the clamp actuator into the clamping force.

[0065] According to this embodiment, the actuator force of the electric clamp actuator is transferred indirectly towards the jaw element, namely via the lever assembly. The lever assembly is configured such, that the clamping force exerted by the jaw element is substantially larger than the actuator force exerted by the electric clamp actuator. This may, for example, be established by the lever assembly by converting a relatively large stroke length of the electric clamp actuator into a relatively small stroke length of the jaw element.

[0066] This amplifying of the actuator force may be beneficial, since electric clamp actuators may typically have lower actuator forces than hydraulic actuators of similar size. However, the clamping force exerted on a foundation element by the clamping device typically needs to be very large, for example up to about 30 kN. Due to the amplification with the lever assembly, the resulting clamping force from the present electric clamp actuators may be similar to that of the hydraulic actuators known in the art.

[0067] In a further embodiment, the lever assembly comprises a two-bar linkage mechanism, comprising two hingedly connected linkage bars, the clamp actuator is connected to the linkage mechanism at a hinge point between two linkage bars of the linkage mechanism, and the at least one jaw element is connected to an opposed end of one of the linkage bars.

[0068] The two-bar linkage mechanism is configured to connect the electric clamp actuator with the jaw element, in order to amplify the actuator force into the clamping force. A first one of the linkage bars may be attached to a stationary portion of the clamping device at one end. At an opposed end, this first one of the linkage bars may be connected to a second one of the linkage bars via the hinge point, where mutual rotations between the linkage bars are allowed. The second linkage bar is connected to jaw element at its opposed second end. The electric clamp actuator is attached to the linkage mechanism at the hinge point, so that a linear movement of the electric clamp actuator in one direction, i.e. when applying the actuator force, will exert the clamping force at the second end of the second lever arm in a direction non-parallel to the direction in which the clamping force is applied.

[0069] This change in directions between the actuator force and the clamping force may allow the electric clamp actuator to travel over a relatively large length at a relatively low actuator force, whereas the jaw element may travel over a relatively short length at a relatively large clamping force, thus amplifying the actuator force into the clamping force.

[0070] In an additional or alternative embodiment, the lever assembly comprises a wedge element connected to the clamp actuator, which comprises a sliding plane at an angle relative to a direction in which the actuator force is aligned, and the at least one jaw element is associated with the sliding plane in order to exert the clamping force in a direction nonparallel to the direction of the actuator.

[0071] According to this embodiment, the actuator force acts on the wedge element, which causes the wedge element to be displaced relative to the jaw element in a direction parallel to the direction in which the actuator force is applied. The angled sliding plane is thereby sidewardly forced away from the wedge element. The sliding plane may, but not necessarily needs to be forced in a direction perpendicular to the movement of the wedge element. However, in a manner similar to two-bar linkage mechanism described above, is the clamping force aligned in a direction non-parallel to the direction of the actuator force, which causes the actuator force to be amplified into the clamping force.

[0072] In a further embodiment, the clamping device may comprise a second electric clamp actuator, configured to initially displace the electric clamp actuator and the lever assembly, for example the wedge element, the sliding plane, and the jaw element, together in a direction parallel to the clamping force. The electric clamp actuator is then actuated subsequently to apply the clamping force via the jaw element. The second electric clamp actuator is thereby able to quickly bring the jaw element in close proximity to the foundation element, after which the second electric clamp actuator may be blocked, prior to actuation of the electric clamp actuator for clamping the foundation element.

[0073] The clamping device according to the above embodiments may be operated at the initial clamping the foundation element, for example to clamp the foundation element at a certain clamping force. During the transmitting of the vibratory load towards the foundation element, the clamping device may be periodically actuated to ensure that the clamping force is maintained. This may form a safety measure to prevent the foundation element from loosening inside the clamping device as a result of the vibrations.

[0074] Furthermore, the above-mentioned clamping devices may additionally be provided with a clamp lock, so that the clamping force, initially exerted wit the electric clamp actuator, can be maintained when the supply of electric power is inadvertently lost during use. For example, the clamp lock may be included in the lever assembly or the wedge element, or it may be provided as a spindle with a self-locking thread. In the latter example, the electric clamp actuator may be a rotary electric actuator for rotating the spindle to exert the clamping force on the at least one jaw element.

[0075] According to a second aspect, the present invention provides a method of operating the vibratory foundation apparatus as disclosed herein, comprising the steps of: suspending the foundation apparatus by the frame element, clamping a foundation element with the clamping device, and guiding an electric current through the inductor to induce an electromagnetic field, therewith oscillating the magnetic element in the linear vibration direction, which is parallel to a longitudinal direction of the foundation element.

[0076] The method according to the present invention may comprise one or more of the features and / or benefits disclosed herein in relation to the vibratory foundation apparatus according to the present invention, in particular as recited in the appended claims.

[0077] The method according to the present invention relies on a different working principle compared to known methods of operating vibratory foundation apparatuses. This is contributed by the fact that the vibratory foundation apparatus lacks rotating masses, but that instead, the vibratory load is generated by means of a linear actuator. Such an actuator is configured to operate in a direction substantially parallel to an elongate axis of the foundation element, so that no transfer is needed from a rotating mass into the linear vibration direction.

[0078] The vibratory foundation apparatus comprises a stationary frame element for suspension and a vibratory clamping device for holding the foundation element during use. The vibrator device is associated with the frame element and the clamping device, so that the vibratory load can be generated relative to the frame element and be transferred onto the clamping device, whereas the frame element is held stationary.

[0079] When carrying out the present method, the vibratory load is generated by the linear electromagnetic actuator of the vibrator device. This linear electromagnetic actuator thereby generates the vibratory load directly along the linear vibration direction, which is typically aligned parallel to the foundation element that is clamped in the clamping device, so that the vibratory load will exert a standing wave vibration in the foundation element to facilitate insertion thereof in the ground or extraction out of the ground by reducing wall friction alongside the foundation element and / or by fluidizing soil underneath it.

[0080] The linear electromagnetic actuator operates in the absence of hydraulic actuators and without hydraulic fluid for transferring energy towards the vibratory foundation apparatus. Instead, the electromagnetic actuator preferably only comprises the electromagnetic inductor, which is subjected to an electric current, and the magnetic element. The vibratory foundation apparatus thus only consumes electric energy and may, to this effect, for example be connected to a controllable electrical power source via an electricity cable.

[0081] The electromagnetic inductor will receive the electric current, for example an alternating electric current. When the current is guided through the electromagnetic inductor, the electromagnetic field is generated by the electromagnetic inductor. The magnetic element is made of a magnetizable material and is located in proximity to the electromagnetic inductor. The electromagnetic field from the electromagnetic inductor interacts with the magnetic element and a net magnetic force will be obtained between them, which may be an attractive force, pulling the electromagnetic inductor and the magnetic element towards each other, or a repulsive force, pushing the electromagnetic inductor and the magnetic element away from each other.

[0082] The electromagnetic field is alternated in direction, by selectively steering the electric current through the electromagnetic inductor, so that the direction of the resulting magnetic force between the electromagnetic inductor and the magnetic element will be alternated as well. As such, the electromagnetic inductor and the magnetic element are alternatingly pulled towards each other and pushed away from each other. This reversing movement induces oscillations of the magnetic element relative to the inductor, therewith effecting the vibratory load.

[0083] The frequency of the vibratory load may be variable in the range between 1 - 1000 Hz, for example in the range between 20 Hz and 400 Hz, preferably with a maximum frequency of about 200 Hz. The frequency may, for example, be selected in dependence of the type of foundation element, length of the foundation element, soil conditions etc. Furthermore, the frequency may be varied over the duration of the method and over the course of the inserting or extracting, for example when one or more of the above parameters changes. A frequency of up to 1000 Hz may be much larger compared to known methods of operating vibratory foundation apparatuses with excentre weights, which may typically reach frequencies of about 2400 rpm, so about 40 Hz.

[0084] Apart from the higher frequencies, further benefits of the present method may be an improved lifespan, since wear of bearings will become less critical. Furthermore, the startup of the inserting and extracting of foundation elements can be done more smoothly by steering the frequency of the vibratory load, which no longer requires variable angular momentum of excentre weights. Finally, the present method may require less energy input to offer a similar output energy, compared to operating known hydraulic vibratory foundation apparatuses, due to the lack of losses occurring in hydraulic fluids.

[0085] In an embodiment of the method, the step of guiding the electric current comprises alternating a direction of the electromagnetic field to alternatingly apply and attractive and repulsive force on the magnet. This alternating of a direction of the electromagnetic field enables that attractive and repulsive forces are exerted on the magnet alternatingly. The alternating directions of the electromagnetic field provide that the magnetic forces exerted on the magnetic element, e.g. the magnet, is reversed as well. An alternating attracting and repelling magnetic force can therewith be exerted, which means that no other spring, elastic elements, or the like are needed for returning the inductor and the magnetic element after the field has been induced.

[0086] In an embodiment, the inductor applies the electromagnetic field at a phase shift in relation to the oscillations of the magnetic element, in order to dampen oscillation reversals of the magnetic element. The phase shift between the electromagnetic field and the magnetic element implies that a time delay is present between direction reversals of the electromagnetic field, i.e. when the direction of the electromagnetic field reverses, and the reversals of the oscillations of the magnetic element. This means that for a duration corresponding to the phase shift, the movement of the magnetic element and the magnetic force exerted on it by the electromagnetic field will be in opposed directions. This will decelerate the movement of the magnetic element magnetically as a result of this opposed force, possibly no longer causing the magnetic element to reach the outer ends of its path. This may allow for smoother oscillations of the magnetic element, thus reducing wear and possibly even reducing the need for bearings.

[0087] The applied phase shift may depend on the frequency and / or amplitude of the vibratory load. If either one or both of these is set relatively large, the inertia of the magnetic element will become relatively large as well, thus requiring a larger counterforce for reversing the movement of the magnetic element. In such a situation, the phase shift of the magnetic element in relation to the electromagnetic field may be set relatively large.

[0088] In an embodiment, the method further comprises, prior to the guiding step, preferably prior to the clamping step, the steps of: substantially rigidly interlocking the clamping device and the frame element in the rest position of the vibrator device by means of the locking device, and upending the foundation element from a substantial horizontal orientation to a substantially vertical orientation.

[0089] This embodiment of the method allows the vibratory foundation apparatus to be used as a lifting device and as upending device for foundation elements, since its vibrator device can be bypassed for external loads in the rest position due to the rigid connection between the frame element and the clamping device. This means that during upending, when the vibratory foundation apparatus is loaded in directions non-parallel to the vertical direction and the longitudinal direction of the foundation element, the vibrator device will not be loaded substantially. As such, the inductor, the magnetic element, and possible elastomeric elements will not need to transfer any forces between the frame element and the clamping device, since such forces can pass through the locking device, resulting in safer operation of the vibratory foundation apparatus.

[0090] The rest position of the vibrator device may be governed by gravitational forces or may involve actively applying an electromagnetic field to bring the magnetic element in a desired position relative to the inductor. The locking device may form a physical and rigid connection between the frame element and the clamping device, when actuated in the rest position of the vibratory foundation apparatus.

[0091] The interlocking occurs before the step of guiding the electric current through the inductor, since the upending takes place before a foundation element is inserted in the ground. Hence, foundation elements are typically supplied laying in a horizontal orientation and need to be lifted substantially vertically for insertion in the ground. To this effect the interlocking is preferably also carried in advance of clamping the foundation element.

[0092] After the clamping device and the frame element have been substantially rigidly interlocked in the rest position, the still horizontal foundation element can be clamped with the clamping device. Next, the foundation element is upended, which may involve lifting the end of the foundation element clamped in the clamping device by means of the vibratory foundation apparatus and let this end travel along a substantially circular path, so that the opposed end of the foundation element will remain in position, resting on the ground. When reaching the highest point of this path, the foundation element has been upended from a substantial horizontal orientation to a substantially vertical orientation and can be vertically lifted and transferred to a location where it is to be inserted in the ground.

[0093] In an embodiment, the method further comprises repeating the steps of: determining an Eigen frequency of the foundation object, and controlling the electromagnetic actuator to set the frequency of the vibratory load at the determined Eigen frequency.

[0094] These repeated steps of the present embodiment typically occur during the step of guiding the electric current through the inductor, so when vibratory load is generated. The Eigen frequency of the foundation element may represent a resonant frequency or natural frequency of the foundation element, at which the foundation element will absorb the energy inserted as a result of the vibrational load and vibrates at a larger amplitude. Hence, less vibrational energy is dissipated internally in the foundation element. This is beneficial for inserting the foundation element in the ground, or for extracting it out of the ground, since a larger vibration amplitude can be achieved with a similar amount of electric input energy and / or since a similar vibration amplitude can be achieved with a smaller amount of electric input energy.

[0095] For applying the vibrational load at the Eigen frequency of the foundation element, the Eigen frequency may be determined first. This is done repeatedly, since the Eigen frequency will change over the course of the inserting in the ground or extracting out of the ground, for example depending on the overall length of the foundation element, the part of the foundation element in the ground, soil conditions etc. In particular during insertion of the foundation element in the ground, the part of its length above the ground level will gradually reduce, thus gradually increasing the Eigen frequency of the foundation element.

[0096] Next, the applied frequency of the vibratory load can be adjusted to the newly measured Eigen frequency, so that the frequency of the vibratory load can be controlled in a feedback manner. As such, the changing Eigen frequency of the foundation element can be accurately followed with the electromagnetic actuator, allowing for an improved controlling of the vibratory load, and thus allowing efficient insertion or extraction of the foundation element at minimal electric energy input.

[0097] The presently utilized vibratory foundation apparatus may be particularly suitable for such changing frequencies of the vibratory load, since they lack the rotating excentre weights that were present in the known vibratory foundation apparatuses, e.g. the rotating excentre masses and the single rotating mass. Those rotating elements did possess a significant rotational inertia, which did not allow them to accurately follow the changing Eigen frequency of the foundation element. The present vibratory foundation apparatus, instead, is free of such rotating masses and may allow for accurately following of the Eigen frequency of the foundation element.

[0098] In an embodiment of the method, the vibratory load generated by the vibrator device can be controlled with a control unit, for example in terms of frequency and / or amplitude of the vibrational load. This may be done by controlling the frequency, phase, and magnitude of the electric current guided through the inductor. Furthermore, the control unit may set a voltage at which the electric current is supplied to the inductor, wherein the resulting current is determined by the amount of energy needed to oscillate the magnetic element and that is dissipated into the foundation element.

[0099] Furthermore, a vibration sensor device may be associated with the clamping device and the control unit to emit a vibration sensor signal representative for a frequency and / or amplitude of vibrations of the clamping device, so that the control unit is configured to control the electromagnetic actuator in dependence on the vibration sensor signal. The vibration parameters measured at the clamping device with the vibration sensor may be representative for the vibrations of the foundation element. The vibration sensor signal is thereby used as a feedback signal for the control unit, so that the amplitude and / or the frequency of the vibrational load emitted with the electromagnetic actuator can be adjusted on the basis thereof.

[0100] Alternatively or additionally, a current sensor device may be associated with the inductor and the control unit to emit a current sensor signal representative for a magnitude of the electric current, e.g. an electric power input, consumed by the inductor, and the control unit is configured to control the electromagnetic actuator in dependence on the current sensor signal. The electric current parameters measured at the inductor may be used as feedback signal for the control unit as well. Hence, electric energy is typically supplied to the inductor at a certain controlled voltage, whereby the electric current drawn by the inductor will depend on the amount of energy, i.e. the magnetic force, that needs to be delivered by the inductor.

[0101] In an embodiment, the step of determining comprises repeating steps of: measuring the magnitude of an electric current consumed by the inductor, controlling the vibratory load with the control unit to vary the frequency thereof, until the measured electric current magnitude has reached a minimum value.

[0102] This embodiment of the method allows the Eigen frequency of the foundation element to be determined implicitly, by searching for a minimum power input level of electric energy fed into the vibratory foundation apparatus. Hence, it was mentioned before that when the foundation element is vibrated at its Eigen frequency, a relatively low amount of energy needs to be fed into the foundation element to maintain it in this resonant state. The Eigen frequency is determined by measuring the magnitude of the electric current drawn by the inductor of the vibratory foundation apparatus and by varying the frequency of the electric current to determine whether the variation effects a change in the magnitude of the electric current. This may be done manually or in an automated manner, by means of a control unit.

[0103] If the electric current increases with the frequency variation, for example when the frequency is lowered somewhat, it follows that the frequency should be varied oppositely to lower the magnitude of the electric current. If the electric current decreases with a frequency variation, it may be beneficial already, but one may further vary the frequency to further lower the electric current. At some point, a frequency variation will only result in an increase of electric current. There, the Eigen frequency is reached, or at least a local minimum of electric current, where the electric current is minimized.

[0104] In addition, the Eigen frequency may also be determined using a predetermined feedforward component. If, for example, the foundation element is inserted into the ground, one knows that the Eigen frequency will increase with increasing insertion depth. For varying the applied frequency of the vibratory load, the applied frequency may be increased at first to follow the increasing Eigen frequency. Normally, such an increased frequency will maintain a low electric current, i.e. when the increasing Eigen frequency is followed. Should the increased frequency result in an increase in current, it may follow that the increase in applied frequency was too large.

[0105] The vibratory foundation apparatus may be provided with the current sensor for measuring the electric current drawn by the inductor, so that its current sensor signal is used as a feedback signal for the control unit of the vibratory foundation apparatus

[0106] The present invention further provides the use of the vibratory foundation apparatus as disclosed herein for driving a foundation element into the ground and / or for extracting a foundation element out of the ground. The use according to the present invention may comprise one or more of the features and / or benefits disclosed herein in relation to the vibratory foundation apparatus according to the present invention and / or the method according to the present invention, in particular as recited in the appended claims.

[0107] The present use may allow both insertion of foundation elements in the ground, which involves subjecting a vibrational load onto the foundation element and letting the foundation element sink in the ground, or optionally drawing the foundation element downwardly into the ground. The extraction of the foundation element may similarly involve subjecting a vibrational load onto the foundation element, but the foundation element is upwardly pulled simultaneously, so that it can be pulled out of the ground in a substantially upward direction. Brief description of drawings

[0108] Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

[0109] Figures 1a - 3b schematically depict various embodiments of the vibratory foundation apparatus according to the present invention,

[0110] Figures 4a and 4b schematically depict closeup views on two embodiments of a linear electromagnetic actuator for use in the vibratory foundation apparatus,

[0111] Figure 5 schematically depicts the vibratory foundation apparatus of figure 1 , including further details on the control features thereof, and

[0112] Figures 6a and 6b schematically depict various embodiments of two clamping devices for use in the vibratory foundation apparatus.

[0113] Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

[0114] Detailed description of embodiments

[0115] Figure 1 schematically depicts an embodiment of a vibratory foundation apparatus for driving a foundation element 100 into the ground and / or for extracting a foundation element 100 out of the ground under influence of a vibratory load F, to which apparatus is referred with reference numeral 1.

[0116] The present vibratory foundation apparatus 1 relies on a different working principle compared to the known vibratory foundation apparatuses, since the vibratory load is generated by means of a, which is configured to operate in a direction substantially parallel to an elongate axis E of the foundation element 100, so that no transfer is needed from a rotating mas into the linear vibration direction.

[0117] The apparatus 1 comprises a frame element 20 with a suspension element 21, with which the apparatus 1 can be suspended. The frame element 20 is held stationary during use of the apparatus 1. The apparatus 1 further comprises a clamping device 30 that is configured to clamp the foundation element 100 during use, which comprises a jaw element 31 for contacting the foundation element 100, so that the foundation element 100 is clamped in with the jaw element 31. In the embodiment in figure 1a, the vibratory foundation apparatus 1 comprises a single clamping device 30, whereas the apparatus 1 in figure 1b comprises multiple clamping devices 30 attached to the electromagnetic actuators 11, for clamping multiple foundation elements 100. The apparatus 1 further comprises a vibrator device 10, in which the linear electromagnetic actuators 11 are included, that is associated with the frame element 20 and the clamping device 30, so that the vibratory load F can be generated relative to the frame element 20 and be transferred onto the clamping device 30, whereas the frame element 20 is held stationary.

[0118] During use of the vibratory foundation apparatus 1, the vibratory load F is generated along the linear vibration direction and the elongate axis E by the electromagnetic actuator 11 of the vibrator device 10. In the figures, the vibratory load F is shown by means of doubleheaded arrows. Each electromagnetic actuator 11 comprises an electromagnetic inductor 12, which is subjected to an electric current, and a magnetic element 13. It is best shown in figure 5 that the vibratory foundation apparatus 1 typically only consumes electric energy and that, to this effect, it can be connected to an electrical power source 50 via an electricity cable 51.

[0119] The electromagnetic inductor 12 receives the electric current during use, which generates an electromagnetic field (not visible in the figures). The shown vibratory foundation apparatuses 1 contain a single electromagnetic inductor 12 in each electromagnetic actuator 11. The magnetic element 13 is made of a magnetizable material and is located in proximity to the electromagnetic inductor 12, so that the electromagnetic field from the electromagnetic inductor 12 will interact with the magnetic element 13 and a net magnetic force will be obtained between them, which may be an attractive force or a repulsive force.

[0120] When the electromagnetic field is alternated in direction, i.e. by selectively steering the electric current through the inductor 12, the direction of the resulting magnetic force between the inductor 12 and the magnetic element 13 is alternated, so that the inductor 12 and the magnetic element 13 are alternatingly pulled towards each other and pushed away from each other. This reversing movement induces oscillations of the magnetic element 13 relative to the inductor 12, therewith effecting the vibratory load F. These oscillations may be defined as back-and-forth mutual movements between the inductor 12 and the magnetic element 13.

[0121] It is best shown in figures 4a and 4b that the inductor 12 can be a single-phase inductor 12’ (in figure 4a), receiving the electric current at a single phase. Alternatively, shown in figure 4b, the inductor 12 can be a multi-phase, for example three-phase inductor 12”, which comprises three inductor portions 14 that are each associated with a respective phase of the electric current. Upon travel of the magnetic element 13 relative to the inductor 12, the electromagnetic field may be generated by guiding an electric current through the inductor portion 14 that is located closest to the magnetic element 13, so that a mutual magnetic force between them can be relatively large.

[0122] It is shown schematically in the figures that the inductor 12 is attached to the frame element 20 and that the magnetic element 13 is attached to the clamping device 30, so that the inductor 12 remains stationary in the frame element 20 and that the magnetic element 13 is attached to the clamping device 30 in order to be vibrated. The apparatus 1 is substantially free of elastomeric elements in between the frame element 20 and the vibrator device 30 and comprises linear bearings between them, in order to ensure that mutual movements between these components is only allowed along the linear vibration direction of the vibratory load F.

[0123] The vibrator device 10 comprises a connection element 15 with which the magnetic elements 13 are attached to the clamping device 30. The connection element 15 serves to transmit the vibratory load F from all oscillating magnetic elements 13 towards the foundation element 100 clamped inside the clamping device 30.

[0124] It is shown in all embodiments in figures 1a - 3b that the vibrator device 10 can comprises a plurality of the linear electromagnetic actuators 11, so that an overall capacity of the vibratory foundation apparatus 1 may be varied by including a desired number of electromagnetic actuators 11. In each of these embodiments, four of these actuators 11 are arranged in parallel, being arranged next to each other in a transverse direction perpendicular to the vibration direction of the vibratory load F.

[0125] Additionally, figure 2 shows that for example pairs of two actuators 11 can be arranged in series, being arranged in-line along the vibration direction of the vibratory load F. The magnetic elements 13 of the pair of serially connected actuators 11 are attached to each other, in order to be oscillated in synchronism. In particular, the pairs of magnetic elements 13 are attached to the connection element 15 in series.

[0126] During use, the actuators 11 can apply the electromagnetic field with the inductors 12 at a phase shift in relation to the oscillations of the magnetic element 13, so that a time delay is present between direction reversals of the electromagnetic field, and the reversals of the oscillations of the magnetic element 13, in order to decelerate the movement of the magnetic elements 13 magnetically as a result of this opposed force.

[0127] It is schematically shown in figure 3a and 3b that the vibrator device 10 can be arranged in a rest position in the absence of the electric current through the inductors 12. The apparatus 1 additionally comprises two opposed locking devices 16 to substantially rigidly interlock the clamping device 30 and the frame element 20 in the rest position of the vibrator device 10 via the connection element 15, in order to enable non-vertical loading of the apparatus 1. As such, the present apparatus 1 can be allowed as a lifting device and as an upending device for foundation elements 100, since the vibrator device 10 can be bypassed for external loads. In the figures, the locking device 16 is shown schematically to be a physical element that forms a physical and rigid connection between the frame element 20 and the clamping device 30 (see figure 3a). During use of the apparatus 1, i.e. as shown in figure 3b when the vibratory load F is exerted, the locking device 16 is moved out of engagement, allowing the clamping device 30 to be vibrated relative to the frame element 20.

[0128] Figure 5 shows that the apparatus 1 can be provided with electrical energy from the electrical power source 50 via an electricity cable 51. Additionally, the apparatus 1 comprises a control unit 40 in between the power source 50 and the inductors 12. The control unit 40 is functionally connected to the vibrator device 10 and configured to control the vibratory load F exerted therewith. The control unit 40 is able to control the frequency, phase and amplitude of the vibrational load F, which parameters may, for example, be controlled in dependence of the type of foundation element 100, length of the foundation element 100, soil conditions etc. The control unit 40 is configured to control the frequency, phase, and magnitude of the electric current guided through the inductors 12, so that the electromagnetic field exerted by the inductors 12 can be controlled in accordance. Furthermore, the control unit 40 may set a voltage at which the electric current is supplied to the inductors 12, wherein the resulting current is governed by the amount of energy needed to oscillate the magnetic elements 13.

[0129] The apparatus 1 further comprises a vibration sensor device 41, which is associated with the clamping device 30 and the control unit 40 and which is configured to emit a vibration sensor signal representative for a frequency and / or amplitude of vibrations of the clamping device 30. The control unit 40 is thereby configured to control the electromagnetic actuators 11 in dependence on the vibration sensor signal, so that the amplitude and / or the frequency of the vibrational load F emitted with the electromagnetic actuators 11 can be adjusted on the basis thereof.

[0130] The apparatus 1 also comprises a current sensor device 42, which is associated with the inductors 12 and the control unit 40 and which is configured to emit a current sensor signal representative for a magnitude of the electric current consumed by the inductors 12. The control unit 40 is thereby configured to control the electromagnetic actuators 11 in dependence on the current sensor signal, so that a voltage at which electric energy is supplied to the inductors 12 can be steered with the control unit 40. The magnitude of the electric current may, for example, be relatively high if the frequency of the vibrational load F is remote from an Eigen frequency of the foundation element 100. To reduce the electric power input of the apparatus 1 , the magnitude of the electric current can be reduced, for example by applying the electromagnetic field at a frequency closer to, or preferably corresponding to the Eigen frequency of the foundation element 100. Furthermore, the Eigen frequency of the foundation element 100 can change during the insertion, since the part of its length above the ground level will decrease, thus increasing the Eigen frequency. The feedback control loop of measuring the electric current with the current sensor device 42 may enable the control unit 40 to change the applied frequency of the vibrational load F to the changing Eigen frequency.

[0131] During use of the apparatus 1, the steps of determining an Eigen frequency of the foundation object 100 and controlling the actuator 11 to set the frequency of the vibratory load F at the determined Eigen frequency can be repeated, so that the changing Eigen frequency of the foundation element 100 can be accurately followed with the electromagnetic actuators 11, allowing for an improved controlling of the vibratory load F and thus allowing efficient insertion or extraction of the foundation element 100. In addition, the control unit 40 may repeatedly measure the magnitude of an electric current consumed by the inductors 12 with the current sensor device 42 and may repeatedly control the vibratory load F to vary the frequency thereof, until the measured electric current magnitude has reached a minimum value, which allows the Eigen frequency of the foundation element 100 to be determined implicitly, by searching for a minimum power input level of electric energy fed into the apparatus 1.

[0132] Figures 6a and 6b schematically depict two embodiments of the clamping device 30 for use in the present apparatus 1 for clamping the foundation elements 100, which both include an electromagnetic actuator. These clamping devices 30 comprise a movable jaw element 31 for contacting the foundation element 100 on one side and a stationary counter element 32 at the other side of the foundation element 100. The electromagnetic actuator is an electric clamp actuator 33, configured to move the jaw element 31 towards the counter element 32 to apply a clamping force on the foundation element 100.

[0133] The electric clamp actuator 33 may be configured to directly apply an actuator force A onto the jaw element 31 , so that the jaw element 31 can covert this into a clamping force C at which the foundation element 100 is clamped. Both of the embodiments shown in figures 6a and 6b rely on an indirect conversion between the actuator force A and the clamping force C, which implies that a transmission is present in between the electric clamp actuator 33 and the jaw element 31.

[0134] In the clamping device 30 in figure 6a, a lever assembly is provided in between the jaw element 31 and the clamp actuator 33, which lever assembly is configured to amplify the actuator force A exerted by the clamp actuator 33 into a larger clamping force C. This is achieved since the lever assembly will convert a relatively large stroke length of the electric clamp actuator 33 into a relatively small stroke length of the jaw element 31.

[0135] The lever assembly is provided as a two-bar linkage mechanism 34, comprising two hingedly connected linkage bars. A first linkage bar 35 is attached to a movable sled 36 at a stationary portion 30’ of the clamping device 30 at one end. At an opposed end, the first linkage bar 35 is connected to a second linkage bar 37 via the hinge point 38, where mutual rotations between the linkage bars 35, 37 are allowed. The second linkage bar 37 is connected to jaw element 31 at its opposed second end. The electric clamp actuator 33 is attached to the linkage mechanism 34 at the hinge point 38, so that a linear movement of the electric clamp actuator 33 in one direction, i.e. when applying the actuator force A, will exert the clamping force C at the second end of the second lever arm 37 in a direction perpendicular to the direction in which the actuator force A is applied. The clamping device 30 is provided with a second electric clamp actuator 33A, configured to initially displace the sled 36 in a direction parallel to the clamping force C relative to the stationary part 30’of the clamping device 30. The second electric clamp actuator 33A is thereby able to quickly bring the jaw element 31 in close proximity to the foundation element 100, after which the second electric clamp actuator 33A may be blocked, prior to actuation of the electric clamp actuator 33 for clamping the foundation element 100.

[0136] In the clamping device 30 in figure 6b, the lever assembly comprises a wedge element 39 connected to the clamp actuator 33, which comprises a sliding plane 39A at an angle relative to a direction in which the actuator force A is aligned. Furthermore, the jaw element 31 comprises a corresponding sliding plane 31A that is associated with the sliding plane 39A of the wedge element 39 in order to exert the clamping force C in a direction non-parallel to the direction of the actuator force A. The actuator force A thereby acts on the wedge element 39, which causes the wedge element 39 to be displaced relative to the jaw element 31 in a downward direction in the plane of the drawing. The angled sliding plane 31A of the jaw element 31 is thereby sidewardly forced away from the wedge element 39 to align the clamping force C in a direction perpendicular to the direction of the actuator force A, which causes the actuator force A to be amplified into the clamping force C.

Claims

CLAIMS1. A vibratory foundation apparatus (1) for driving a foundation element (100) into the ground and / or for extracting a foundation element out of the ground, the apparatus comprising: a frame element (20), with which the apparatus is configured to be suspended, a clamping device (30), configured to clamp the foundation element, and a vibrator device (10), which is functionally arranged in between the frame element and the clamping device and which is configured to subject the clamping device to a vibratory load, wherein the vibrator device comprises a linear electromagnetic actuator (11), configured to generate the vibratory load and comprising: an electromagnetic inductor (12), for example an electromagnetic coil, configured to induce an electromagnetic field under influence of an electric current guided through the inductor, characterized in that, the vibrator device further comprises: a magnet (13), for example a permanent magnet or a second electromagnetic inductor, in proximity to the inductor, to be subjected to the electromagnetic field, wherein one of the inductor or the magnet is associated with the frame element and wherein another one of the inductor or the magnet is associated with the clamping device, and wherein the linear electromagnetic actuator is configured to oscillate the magnet in a linear vibration direction with the inductor under influence of the electromagnetic field.

2. The vibratory foundation apparatus according to claim 1, wherein the inductor is configured to alternate a direction of the electromagnetic field in order to alternatingly apply and attractive and repulsive force on the magnet.

3. The vibratory foundation apparatus according to claim 2, wherein the actuator is free of elastic elements for pushing the inductor and the magnet away from each other.

4. The vibratory foundation apparatus according to any of the preceding claims, wherein the inductor is attached to the frame element and wherein the magnet is attached to the clamping device.

5. The vibratory foundation apparatus according to any of the preceding claims, wherein the vibrator device comprises a plurality of the linear electromagnetic actuators.

6. The vibratory foundation apparatus according to any of the preceding claims, wherein the foundation apparatus is substantially free of elastomeric elements in between the frame element and the vibrator device.

7. The vibratory foundation apparatus according to claim 6, wherein the actuator is configured to apply the electromagnetic field with the inductor at a phase shift in relation to the oscillations of the magnet, in order to dampen oscillation reversals of the magnet.

8. The vibratory foundation apparatus according to any of the preceding claims, wherein the inductor is a multi-phase inductor, for example a three-phase inductor.

9. The vibratory foundation apparatus according to any of the preceding claims, wherein the vibrator device is arranged in a rest position in the absence of the electric current through the inductor, and wherein the foundation apparatus further comprises a locking device (16) to substantially rigidly interlock the clamping device and the frame element in the rest position of the vibrator device, to enable non-vertical loading of the foundation apparatus.

10. The vibratory foundation apparatus according to any of the preceding claims, further comprising a control unit (40), functionally connected to the vibrator device and configured to control the vibratory load generated by the vibrator device.

11. The vibratory foundation apparatus according to claim 10, further comprising a vibration sensor device (41), which is associated with the clamping device and the control unit and which is configured to emit a vibration sensor signal representative for a frequency and / or amplitude of vibrations of the clamping device, and wherein the control unit is configured to control the electromagnetic actuator in dependence on the vibration sensor signal.

12. The vibratory foundation apparatus according to claim 10 or 11, further comprising a current sensor device (42), which is associated with the inductor and the control unit and which is configured to emit a current sensor signal representative for a magnitude of the electric current, e.g. an electric power input, consumed by the inductor, and wherein the control unit is configured to control the electromagnetic actuator in dependence on the current sensor signal.

13. The vibratory foundation apparatus according to the preamble of any of the preceding claims, wherein the clamping device comprises at least one jaw element (31) for contacting the foundation element and an electric clamp actuator (33), configured tomove the at least one jaw element to apply a clamping force on the foundation element therewith.

14. The vibratory foundation apparatus according to claim 13, wherein the clamping device further comprises a lever assembly, which is functionally arranged in between the at least one jaw element and the clamp actuator, and wherein the lever assembly is configured to amplify an actuator force (A) exerted by the clamp actuator into the clamping force (C).

15. The vibratory foundation apparatus according to claim 14, wherein the lever assembly comprises a two-bar linkage mechanism (34), wherein the clamp actuator is connected to the linkage mechanism at a hinge point (38) between two linkage bars (35, 37) of the linkage mechanism, and wherein the at least one jaw element is connected to an opposed end of one of the linkage bars.

16. The vibratory foundation apparatus according to claim 14 or 15, wherein the lever assembly comprises a wedge element (39) connected to the clamp actuator, which comprises a sliding plane (39A) at an angle relative to a direction in which the actuator force is aligned, and wherein the at least one jaw element is associated with the sliding plane in order to exert the clamping force in a direction non-parallel to the direction of the actuator force.

17. Method of operating the vibratory foundation apparatus according to any of the preceding claims, comprising the steps of: suspending the foundation apparatus by the frame element, clamping a foundation element with the clamping device, and guiding an electric current through the inductor to induce an electromagnetic field, therewith oscillating the magnet in the linear vibration direction, which is parallel to a longitudinal direction of the foundation element.

18. Method according to claim 17, wherein the step of guiding the electric current comprises alternating a direction of the electromagnetic field to alternatingly apply and attractive and repulsive force on the magnet.

19. Method according to claim 17 or 18, wherein the inductor applies the electromagnetic field at a phase shift in relation to the oscillations of the magnet, in order to dampen oscillation reversals of the magnet.

20. Method according to any of the claims claim 17 - 19, wherein the method further comprises, prior to the guiding step, preferably prior to the clamping step, the steps of: substantially rigidly interlocking the clamping device and the frame element in the rest position of the vibrator device by means of the locking device, and upending the foundation element from a substantial horizontal orientation to a substantially vertical orientation.

21. Method according to any of the claims 17 - 20, further comprising repeating the steps of: determining an Eigen frequency of the foundation object, and controlling the electromagnetic actuator to set the frequency of the vibratory load at the determined Eigen frequency.

22. Method according to claim 21 , wherein the step of determining comprises repeating steps of: measuring the magnitude of an electric current consumed by the inductor, controlling the vibratory load with the control unit to vary the frequency thereof, until the measured electric current magnitude has reached a minimum value.

23. Use of the vibratory foundation apparatus according to any of the claims 1 - 16 for driving a foundation element into the ground and / or for extracting a foundation element out of the ground.

Images