Vibration exciter for a vibration driver

Abstract

The invention relates to a vibration exciter for a vibratory hammer (4), comprising an exciter housing (51) in which an exciter gearbox (53) is arranged, the gearbox comprising at least two shafts (54) arranged parallel to each other, which are rotatably mounted in bearings (58) received by the exciter housing (51) and which are connected to at least one drive by which they are set in rotation, as well as at least two unbalanced masses (56) which are attached to one or more of the shafts (54), wherein the at least one drive is formed by a drive unit (6) comprising an electric motor (61) and a drive gearbox (63) connected thereto, wherein the at least one drive unit (6) is arranged on the outside of the exciter housing (51) such that it is offset in the direction of the axes of rotation of the shafts (54) relative to the bearings (58) received by the exciter housing (51) and is not positioned axially between two bearings (58) of a shaft.and wherein the drive gear (63) is connected to at least one of the shafts (54).

Description

[0001] The invention relates to a vibration exciter for a vibratory hammer, comprising an exciter housing in which an exciter drive is arranged, comprising at least two rotatably mounted shafts arranged parallel to each other, which are connected to at least one drive by which they are set in rotation, and at least two unbalanced masses which are attached to one or more of the shafts.

[0002] In construction, vibration generators such as vibrators, shakers, or vibratory hammers are used to drive or extract profiles into the ground or to compact soil material. The soil is excited by vibration, reaching a "pseudo-fluid" state. The driven material can then be pushed into or pulled out of the subsoil. The vibration is characterized by a linear motion and is generated by pairs of counter-rotating eccentric masses within a vibrator drive. Vibration generators are characterized by the installed eccentricity (referred to in technical circles as the "static moment"), the vibrating mass, the permissible centrifugal force, and the maximum rotational speed.

[0003] Vibrators are used in vibratory pile drivers, which are typically mounted as leader-guided attachments on a carrier vehicle of a specialist foundation engineering machine. Vibratory pile drivers are also used as excavator attachments or as so-called free-riding units. The vibratory pile driver is powered by hydraulic motors connected to the shafts of the vibratory gearbox inside the vibrator housing. Specialist foundation engineering machines are mobile construction machines that are typically powered by diesel engines. The diesel engine of the carrier vehicle drives hydraulic pumps, which in turn drive the hydraulic motors of the vibratory pile driver via a hydraulic circuit.

[0004] Hydraulic motors have become established as the drive system for vibrators; these are very robust and offer high power and torque density. This means they can provide high drive power and high drive torque in a compact size and with low mass.

[0005] The use of hydraulic pumps has proven effective in such specialized foundation engineering machines, as they offer high power and torque density while maintaining a compact size. By using hydraulic motors with variable displacement, as described in EP2085149A1, operation across different speed ranges is possible without any loss of performance.

[0006] A disadvantage of the previously known vibration generator is that the hydraulic motors themselves have a low energy efficiency. This efficiency is further reduced by the fact that the hydraulic oil used to drive the vibrator's motors is transported over long distances through relatively thin hoses or pipes at high flow rates and pressures, resulting in significant energy losses in the hydraulic circuit. The viscosity of the hydraulic oil is also highly temperature-dependent, leading to particularly high energy losses in the hydraulic circuit at low temperatures. Furthermore, the hydraulic motors require a complex hydraulic system for operation, to which the motors are connected via a system of hydraulic hoses and control blocks to the hydraulic pumps.Leaks in hydraulic hoses, or even when connecting a vibrator to the hydraulic system of, for example, a carrier vehicle, still pose a risk of hydraulic oil escaping into the environment. The hydraulic system, which is also susceptible to contamination, continues to require intensive maintenance.

[0007] WO2022023254 A1 describes a vibratory piling rig with a vibration generator. On each of the two opposite sides of the housing, a permanent magnet synchronous motor (PMSM) is arranged. Each PMSM is connected to a drive shaft, which inside the housing is fitted with a gear that meshes with a gear on an unbalance shaft of the excitation gearbox, driving it. Alternatively, it is proposed to connect the permanent magnet synchronous motors directly to the unbalance shafts and to enable phase adjustment of the unbalances relative to each other via these shafts. A disadvantage of the described solution is that permanent magnet synchronous motors have a significantly lower torque density (torque per unit of space or mass) compared to hydraulic motors, which considerably increases the size of the vibration generator and limits its applicability.Driving piles close to existing obstacles, such as existing buildings or close to other, already installed pile-driving elements, which can come in a variety of different designs, such as pipes, boxes, U- or Z-profiles, is impaired by this. Furthermore, the permanent magnets in permanent magnet synchronous motors require rare earth metals, the use of which is ecologically and socially problematic.

[0008] This is where the present invention comes in. The invention is based on the objective of providing a vibration exciter (also called a vibrator) for a vibratory hammer that avoids the aforementioned disadvantages and has a compact design. According to the invention, this objective is achieved by a vibration exciter with the features of the characterizing part of claim 1.

[0009] The invention provides a vibration exciter for a vibratory hammer that avoids the aforementioned disadvantages and features a compact design. By forming at least one drive unit comprising an electric motor and a drive gearbox connected to it, with the drive gearbox being connected to at least one of the shafts, high efficiency is achieved while maintaining a compact design. Connecting the electric motor to a drive gearbox within the drive unit significantly reduces the required size of the electric motor. The high achievable rotational speed of the electric motors allows for the use of smaller and lighter electric motors with the same power output via the drive gearbox.By arranging the at least one drive unit externally on the exciter housing in such a way that it is offset from the bearings held by the exciter housing in the direction of the shafts' axes of rotation, and not axially positioned between two bearings of a shaft, a compact design is facilitated. The drive units are positioned outside the housing, thereby maximizing the usable space within the housing. The drive units, with their drive gears, are connected externally to at least one shaft, outside the bearings, with the connection preferably being arranged at the smallest possible distance to the adjacent bearing of the shaft.

[0010] In one embodiment of the invention, at least one drive unit, consisting of a drive gearbox and an electric motor, is rigidly connected to the exciter housing. Preferably, all arranged drive units are rigidly connected to the exciter housing.

[0011] In a further embodiment of the invention, the drive gears of all drive units are designed as gear drives and are each directly connected to at least one shaft of the exciter drive. No traction drive such as a V-belt or toothed belt drive is used. This increases the reliability of the drive, which is subject to vibrations.

[0012] Advantageously, each shaft is provided with at least one unbalanced mass, preferably with an intermediate shaft that does not have an unbalanced mass. A shaft provided with at least one unbalanced mass is also referred to as an unbalanced shaft.

[0013] In this embodiment of the invention, at least two shafts of the excitation drive, preferably all shafts, are connected to a drive unit. This results in a further reduction of the required size of the electric motors.

[0014] In a further embodiment of the invention, the drive transmission of at least one drive unit comprises at least two, preferably exactly two, meshing gears, wherein one of the gears is driven by the electric motor and the other gear is connected to one of the shafts. This results in a compact design of the drive unit. Furthermore, with exactly two gears, no additional sliding or rolling bearings are required.

[0015] In a further development of the invention, the drive transmission of at least one drive unit has an output shaft offset radially from the drive axis. This allows for greater flexibility in the arrangement of the motors. For example, it is possible to drive two adjacent shafts of the exciter transmission with separate electric motors, where the circumference diameter of the electric motors is larger than the distance between the two adjacent shafts. This is particularly advantageous when the vibration exciter is designed as an upright vibrator in which at least three unbalanced shafts are arranged one above the other.

[0016] Another advantage is that the electric motor's motor shaft and the unbalanced shaft are coupled in only one degree of freedom (angle of rotation), so no radial or axial forces are transmitted from the unbalanced shaft to the motor shaft. This allows electric motors to be used in excitation gearboxes without specially modified or reinforced bearings for the shaft or rotor, and without having to fear a drastic reduction in bearing life.

[0017] Two designs are distinguished in vibration exciters used in specialist foundation engineering: A vertical vibrator is a vibration generator with a vertical structure, featuring at least three unbalanced shafts, with more shafts arranged vertically than horizontally. This design is suitable for driving and extracting operations on a vibratory pile driver with a mast. The mast guide significantly facilitates the precise alignment of the pile and the application of vertical loads or tensile forces. Because the vibrator is attached to the mast, its rotation around the vertical axis is limited. For this reason, vertical vibrators are designed to be compact in both width and depth to prevent collisions with obstacles such as building walls or already installed piles.In a vertically oriented excitation drive, the horizontal centrifugal force components of the unbalanced weights cancel each other out with an offset. The moment generated in a pair of unbalanced weights by this arrangement is balanced by the arrangement of the unbalanced weight pairs relative to each other. Such a vertically oriented vibrator or vibration generator is described, for example, in EP 2 789 402 A1.

[0018] Horizontally mounted vibration exciters are preferred for use with vibrators suspended from a crane or excavator (so-called free-riding vibratory hammers or free-riding vibratory pile drivers). This allows them to be rotated around their vertical axis and freely positioned. With a horizontally mounted exciter drive, the horizontal centrifugal force components of the unbalanced pairs cancel each other out in a horizontally arranged plane. Moment equilibrium is thus inherently achieved.

[0019] In an embodiment of the invention, the gear driven by the electric motor in the drive transmission of at least one drive unit is designed as an externally toothed spur gear, wherein the output-side gear, which is connected to one of the shafts, is designed as a ring gear, and the motor shaft of the electric motor of the drive unit is arranged with a radial offset to the shaft. This results in a compact, flat design of the drive unit, combined with a high gear ratio. Furthermore, the design as a ring gear with internal teeth allows for a smaller center distance between the motor and the unbalance shaft than with external teeth and the same gear ratio. This combination – a small center distance with a high gear ratio – is ideal for a vibration exciter for a vibratory hammer.

[0020] In a further development of the invention, at least two shafts are connected to each other via gears.

[0021] In one embodiment of the invention, at least one motor of a drive unit is a separately excited synchronous motor, a reluctance motor, or an asynchronous motor. These motors are characterized by the fact that they do not require permanent magnets, thus avoiding the environmentally harmful use of rare earth elements. These motors generally have a lower torque density than permanent magnet synchronous motors. To achieve comparable power output with the same weight and dimensions, these motors must be operated at higher speeds. This is readily achievable in the present case by providing a correspondingly appropriate gear ratio in the drive transmission.

[0022] In a further embodiment of the invention, at least one electric motor is a disc rotor motor. This results in a reduced overall height. The disc rotor motor (also called an axial flux motor) is characterized by its low overall height, large outer diameter, and high torque density. By means of a drive gearbox with a radial offset between the drive and output shafts, several electric motors with an outer diameter larger than the center distance of the unbalanced shafts can be mounted on the housing of the excitation gearbox without having to increase the external dimensions of the vibrator. Furthermore, the disc rotor motor principle offers structural advantages: The air gap between the rotor and the housing is perpendicular to the axis of rotation and thus oriented in a plane parallel to the vibrator's oscillating motion.Consequently, the vibration and the resulting inertial forces have no influence on the size of the air gap, which reduces the requirements for the bearing of the runner and / or allows for smaller air gaps to be achieved.

[0023] In a further embodiment of the invention, the drive transmission of at least one drive unit has a non-integer transmission ratio. This reduces the load on the electric motor, as periodic vibrations and loads resulting from the vibration application are thereby distributed alternately across different areas or parts of the motor. For example, the rotor bearing (inner bearing ring) is not subjected to the maximum load at the same point during every vibration. Furthermore, periodically recurring current peaks act on different coils in the electric motor, thus better protecting them from overheating / overload. The repeated mechanical stress on critical areas is also reduced.A non-integer transmission ratio reduces the load on the electric motor particularly in the case where the phase position of the excitation gearbox is to be adjusted with the drive motor instead of a rotary actuator.

[0024] Furthermore, the non-integer gear ratio affects the cooling of the electric motor: The current-carrying conductors in the electric motor heat up due to power loss and must be constantly cooled during operation. As a result of the oscillating work process, torques occur in the excitation gear, which also exhibit periodic fluctuations over time, with a frequency that is an integer multiple of the excitation frequency. This periodically fluctuating torque results in a periodically fluctuating current flow. If the drive gear is implemented with a non-integer gear ratio, different areas are affected by the high current flow during successive oscillation cycles. Ideally, the gear ratio is chosen so that the high currents act on the conductors or coils of different pole pairs in successive oscillation periods.As a result, the engine heats up more evenly, thus improving cooling and preventing local overheating.

[0025] In a further development of the invention, the circumscribed diameter of at least one electric motor of a drive unit is larger than the distance between the shaft connected to it and an adjacent shaft of the excitation gearbox. This enables a more compact design, in particular a reduced length of the electric motor and thus also of the drive unit.

[0026] In one embodiment of the invention, a baffle is arranged between the electric motor and the drive gearbox, preferably with a gap seal arranged between the baffle and the drive gearbox, particularly between the drive pinion of the drive gearbox and the baffle. This prevents contact between large quantities of gearbox oil and the seal and the end face of the electric motor. This reduces the heat flow from the gearbox oil to the significantly cooler electric motor, allowing it to be operated at higher power. The temperature of the gearbox oil used to lubricate the vibratory gearbox is typically around 80°C to 100°C, whereas in commercially available electric motors, a reduction in power output (derating) occurs at coolant temperatures between 45°C and 65°C. With non-contact seals, such as gap seals, groove seals, and labyrinth seals, the sealing effect of narrow gaps is utilized.The sealing effect is achieved by lengthening the flow path through the gap to be sealed, thereby significantly increasing the flow resistance. Gap seals are wear-free and no significant friction-related performance losses occur.

[0027] The invention further relates to a vibratory hammer with a vibration generator of the aforementioned type according to the invention. Preferably, the vibration generator of the vibratory hammer is designed as a vertical vibrator.

[0028] In a further development of the invention, the vibratory rammer is designed as a free-riding vibratory rammer, also called a free-riding rammer.

[0029] The invention further relates to a vibratory ramming device comprising a carrier device with a mast on which a working tool carriage is slidably arranged, on which a vibratory ram with a vibration generator of the aforementioned type according to the invention is attached.

[0030] Other embodiments and configurations of the invention are specified in the remaining dependent claims. An exemplary embodiment of the invention is illustrated in the drawings and is described in detail below. The drawings show: Fig. 1 is a schematic representation of a vibratory pile driver with carrier and mast; Fig. 2 is a schematic representation of the vibration generator of the vibratory pile driver. Figure 1 in a side view; Fig. 3 the schematic spatial representation of the vibration generator made of Figure 2 with a drive unit in exploded view; Fig. 4 the schematic representation of the vibration generator made of Figure 2 in sectional view AA; Fig. 5 the partial detailed view of a drive unit of the illustration from Figure 4 ; Fig. 6 the schematic representation of the vibration generator made of Figure 2 In the front view and Fig. 7, the schematic representation of the vibration generator is shown. Figure 6 On average, BB.

[0031] The vibratory pile driver 1 selected as an embodiment comprises a carrier device 2, which is connected via a kinematic 21 to a mast 3, on which a work tool carriage 31 is movably arranged, which receives a vibratory pile driver 4, which includes a vibration generator 5 and a clamping jaw 7 for receiving a pile material 8.

[0032] The carrier unit 2 comprises a tracked undercarriage 22 on which a superstructure 23 is rotatably mounted. The superstructure 23 includes a driver's cab 24 and an engine room 25, which houses an internal combustion engine, in particular a diesel engine, for driving a generator to produce an electrical operating voltage, which is connected to a buffer battery.

[0033] The vibration generator 5 is designed as a vertical vibrator and comprises an exciter housing 51, which accommodates an exciter drive 53 formed from four rotatably mounted unbalance shafts 54 – two outer unbalance shafts 542 and two inner unbalance shafts 541 – which are provided with gears 55 and with unbalance masses 56, as well as an intermediate shaft 57 provided with gears 55, which is arranged centrally between two inner unbalance shafts 54. (The intermediate shaft 57 is in Figure 7(Not immediately apparent – ​​reference numeral 57 here points to the visible, stationary rotary union behind which the intermediate shaft is located.) The unbalance shafts 541 and the intermediate shaft 57 are rotatably mounted in the exciter housing 53 by means of two bearings 58, designed as cylindrical roller bearings and each supported by the exciter housing 53, and are connected to each other via the gears 55. The exciter housing 51 has a connecting strip 52 on each of two opposite side walls for guiding it to the working tool carriage 31 of the mast 3. The vertical forces are transmitted from the working tool carriage 31 of the mast 3 to the exciter housing 51 by means of elastomer elements (not shown).

[0034] On its front side opposite the connection strips 52, four drive units 6 are arranged on the outside of the exciter housing 51 of the vibration generator 5, each for driving one of the unbalance shafts 54.

[0035] The drive units 6 each comprise an electric motor 61 connected to a drive gearbox 63. In the exemplary embodiment, the electric motor 61 is a reluctance motor. By using four drive units, each comprising an electric motor 61, the electric motors 61 have a relatively low overall height. This height can be reduced even further if disc rotor motors are used as the electric motors 61.

[0036] The drive gear 63 is formed by a drive pinion 64, which meshes with the internal teeth of a ring gear 65. The tooth configuration of the drive pinion 64 and ring gear 65 is selected such that the drive gear 63 has a non-integer gear ratio. The drive pinion 64 is non-rotatably connected to the motor shaft 62 of the electric motor 61. The ring gear 65 is non-rotatably connected to the respective unbalanced shaft 54 ​​of the exciter gear 53 via a drive plate 651, to which it is attached. A baffle in the form of a baffle plate 66 is arranged between the drive pinion 64 of the drive gear 63 and the electric motor 61. A non-contact seal 67, in this case a gap seal, is arranged between the drive pinion 64 and the baffle plate 66. The motor shaft 62 of the electric motor 61 is arranged radially offset to the unbalanced shaft 54 ​​which is connected to it via the drive gearbox 63.In the exemplary embodiment, two adjacent drive gearboxes 63 are arranged in a common gearbox housing 68, which is attached to the exciter housing 51 of the vibration generator 5 by means of screws. Of course, each drive gearbox (63) can also be arranged in a separate drive housing.

[0037] The electric motors 61 of the drive units 6 are electrically connected to the buffer battery of the carrier device 2 (not shown).

Claims

1. Vibration exciter for a vibratory hammer (4), comprising an exciter housing (51) in which an exciter drive (53) is arranged, comprising at least two shafts (54) arranged parallel to each other, rotatably mounted in bearings (58) received by the exciter housing (51) and connected to at least one drive by which they are set in rotation, and at least two unbalanced masses (56) which are attached to one or more of the shafts (54), characterized by the fact thatthe at least one drive is formed by a drive unit (6) comprising an electric motor (61) and a drive gearbox (63) connected thereto, wherein the at least one drive unit (6) is arranged on the outside of the exciter housing (51) such that it is offset in the direction of the axes of rotation of the shafts (54) to the bearings (58) received by the exciter housing (51) and is not positioned axially between two bearings (58) of a shaft, wherein the drive gearbox (63) is connected to at least one of the shafts (54).

2. Vibration exciter according to claim 1, characterized by the fact that the drive transmission (63) of the at least one drive unit (6) is designed as a gear transmission.

3. Vibration exciter according to claim 1 or 2, characterized by the fact that Each of the shafts (54) is provided with at least one unbalance mass (56), wherein preferably an intermediate shaft (57) is arranged between two of the shafts (54) which does not have an unbalance mass.

4. Vibration exciter according to one of the aforementioned claims, characterized by the fact that at least two shafts (54), preferably all shafts (54) are connected to a drive unit (6) each.

5. Vibration exciter according to one of the aforementioned claims, characterized by the fact that at least one drive unit (6) consisting of a drive gearbox (63) and an electric motor (61) is firmly connected to the excitation housing (51).

6. Vibration exciter according to one of the aforementioned claims, characterized by the fact that the drive transmission (63) of at least one drive unit (6) comprises at least two, preferably exactly two meshing gears (64, 65), wherein one of the gears (64) is driven by the electric motor (61) and the other gear (65) is connected to one of the shafts (54).

7. Vibration exciter according to one of the aforementioned claims, characterized by the fact thatthe drive transmission (63) of at least one drive unit (6) has an output axis offset radially to the drive axis.

8. Vibration exciter according to claim 6, characterized by the fact that The gear (64) of the drive transmission (63) of the at least one drive unit (6), driven by the electric motor (61), is designed as an externally toothed spur gear, wherein the output gear, which is connected to one of the shafts (54), is designed as a ring gear (65), wherein the motor shaft (62) of the electric motor (61) of the drive unit (6) is arranged with a radial offset to the shaft (54).

9. Vibration exciter according to one of the aforementioned claims, characterized by the fact that at least two shafts (54) of the excitation gear (53) are connected to each other via gears (55).

10. Vibration exciter according to one of the aforementioned claims, through this characterized thatat least one motor (61) of a drive unit (6) is a separately excited synchronous motor, a reluctance motor or an asynchronous motor.

11. Vibration exciter according to one of the aforementioned claims, characterized by the fact that the drive transmission (63) of at least one drive unit (6) has a non-integer transmission ratio.

12. Vibration exciter according to one of the aforementioned claims, characterized by the fact that the circumcircle diameter of at least one electric motor (61) of a drive unit (6) is larger than the distance between the shaft (54) connected to it and an adjacent shaft (54) of the excitation gear (53).

13. Vibration exciter according to one of the aforementioned claims, characterized by the fact that A baffle wall (66) is arranged between the electric motor (61) and the drive gearbox (63) of at least one drive unit (6), wherein a non-contact seal (67) is preferably arranged between the baffle wall (66) and the drive gearbox (63).

14. Vibration exciter according to one of the aforementioned claims, characterized by the fact that this one is designed as a vertical vibrator.

15. Vibratory rammer comprising a vibration exciter (5) according to one of the preceding claims, wherein the vibratory rammer is designed as a free-riding vibratory rammer.

16. Vibratory pile driver comprising a carrier (2) with a mast (3) on which a working tool carriage (31) is slidably arranged, on which a vibratory pile driver (4) is attached, comprising a vibration exciter (5) according to one of claims 1 to 14.

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