SOIL COMPACTION METHOD AND CONSTRUCTION MACHINE

Description

[0001] The invention relates to a method for soil compaction using a construction machine, wherein a support cable is guided along a mast, the support cable is wound up and unwound by means of a rotatably mounted winch drum of a cable winch, the winch drum is driven in rotation by means of a winch drive, and a compaction element is arranged on the support cable, which is moved vertically by the support cable, wherein the support cable is unwound from the winch drum of the cable winch and the compaction element is lowered on the support cable from a position above a ground surface to the ground surface, wherein the compaction element impacts the ground surface and thereby compacts the soil, according to the preamble of claim 1.

[0002] The invention further relates to a construction machine for soil compaction comprising a mast, a support cable which is guided along the mast, a cable winch with a rotatably mounted winch drum to which the support cable is attached for winding and unwinding, a winch drive for rotating the winch drum, a compaction element which is attached for vertical movement to the support cable, and a control unit by which the cable winch can be operated to unwind the support cable from the winch drum, wherein the compaction element is lowered on the support cable to a ground surface and the compaction element impacts the ground surface to compact the soil, according to the preamble of claim 11.

[0003] A construction machine of this type is disclosed, for example, in EP 3 708 528 A1.

[0004] When lowering a compaction element using such a construction machine, it is usually provided that after the compaction element hits the ground, the winch drum is decelerated by means of a corresponding braking device. Since the compaction element hits the ground at a relatively rapid lowering speed, so-called slack rope and undesirable rope oscillation can develop on the support cable, which continues via the mast head to a winch drum. This rope oscillation can cause rope windings on the winch drum to jump out of their intended position. If the winch drum is continued to operate, this can lead to incorrect winding of the support cable on the winch drum, with the cable crossing the grooves on the drum.

[0005] Such disordered rope winding on the winch drum can lead to damage to the winch drum and, in particular, to increased wear on the suspension rope. This can not only significantly shorten the service life of the suspension rope, but can also impair the overall maximum load-bearing capacity of the suspension rope.

[0006] To ensure correct winding, EP 3 708 528 A1 teaches the provision of a rope pressure device with at least one pressure element in the area of the winch drum. This reliably prevents the propagation of the suspension rope vibration to the area of the rope wound on the winch drum. The rope pressure device represents additional design effort and requires a corresponding amount of space on the construction machine. Furthermore, the rope pressure device also requires maintenance at regular intervals.

[0007] The invention is based on theTask The aim is to provide a method and a construction machine for soil compaction with which the negative effects of rope vibration of the support rope on the rope winding on the winch drum can be counteracted particularly efficiently.

[0008] According to the invention, the object is achieved, on the one hand, by a method having the features of claim 1 and, on the other hand, by a construction machine having the features of claim 11. Preferred embodiments of the invention are specified in the dependent claims.

[0009] With a suitable arrangement of the winch drum on a construction machine, the winding can be directly observed by a machine operator from an operator's cab. Even with any arrangement of the winch drum according to the invention, a clean cable winding can be ensured by detecting a winding of the support cable on the winch drum using a sensor unit, in particular a camera unit, a radar unit, or another suitable sensor. The image from the camera unit can be displayed to a machine operator in the machine cab. Detection can be optical, contactless via energy waves, tactile, electronic, magnetic, by reed contact, or in another suitable manner.

[0010] Alternatively or additionally, the sensor unit can be connected to the control unit, which uses signals or data recorded by the sensor unit to determine whether the winding on the winch drum is correct. The signal or data can, in particular, be an image. The recorded sensor signal for the rope winding is evaluated electronically, for example using image processing software. Depending on any detected offset of a rope winding on the winch drum, the machine operator or the control unit can individually adjust the amount or dimension of the unwinding of the support rope until the rope is correctly wound on the winch drum. The amount of unwinding can be specified as a rotation angle measurement for the winch drum or a length measurement for the support rope or a time period for controlling the winch drive (at a defined speed).

[0011] According to a further development, it is preferred that the winch drum is decoupled from the winch drive via a coupling device when the support cable is unwound, that the winch drive is driven in a direction of rotation to wind up the support cable before the compaction element hits the ground surface, and that after the compaction element hits the ground surface, the coupling device couples the winch drum to the winch drive which is already driven in rotation.

[0012] This preferred embodiment of the invention is based on the finding that insufficient tension of the support cable in the area of the winch, caused by cable vibration, can lead to cable windings on the winch drum jumping out of their intended position. According to the method according to the invention, the winch drive is decoupled from the winch drum via a coupling device during unwinding of the support cable in a period of time before the compaction element hits the ground surface. The movement of the winch drum is thus independent of the movement of the winch drive. This independence can be used to operate the winch drive early in a direction of rotation required for winding the support cable.The coupling device allows the winch drum to be reconnected or coupled to the winch drive, particularly immediately after the compaction element has hit the ground surface, whereby the torque of the winch drive applied to the drive shaft can have a direct effect on the winch drum and a resulting abruptly starting rotational movement of the winch drum in the direction of winding up the support cable leads to very rapid cable tension in the area of the winch.

[0013] The usual start-up phase of a winch drive is thus avoided. According to the invention, a winding force can be applied to the support cable via the winch drum immediately after or upon impact of the compaction element with the ground surface, so that the cable is immediately tensioned again in the area of the winch. This immediate cable tension significantly counteracts the formation of slack in the winch area and the associated jumping of cable windings on the winch drum from their intended position. This reduces the risk of unwanted misalignment of cable windings on the winch drum.

[0014] The suspension cable can, in principle, be connected directly to the compaction element. Preferably, a chain and / or a steel cable suspension is arranged as a buffer between the suspension cable and the compaction element. This prevents compression of the suspension cable during deceleration due to contact with the compaction element. With a steel cable suspension, at least one additional weight, such as a steel crossbeam, can optionally be arranged between the suspension cable and the steel cable suspension.

[0015] In principle, the soil compaction method can be carried out manually by a machine operator. According to a further development of the invention, it is particularly advantageous for the method to be carried out automatically by means of a control unit. The control unit can, in particular, be connected to the winch drive and the coupling device and actuate them accordingly. The control unit can also be connected to one or more sensors that detect the position of the compaction element and / or the cable tension. The coupling device can be designed as a lockable freewheel clutch, whereby locking or unlocking can be effected by the control unit.

[0016] The coupling device can, in principle, be designed in any suitable manner. According to a further development of the invention, it is particularly expedient for the coupling device to comprise a free-fall brake, whereby the support cable is unwound during the free fall of the compacting element. With a free-fall brake, after the brake is released, the winch drum can be driven with low friction solely by the weight of the compacting element suspended from the support cable, whereby the compacting element can, so to speak, strike the ground surface in free fall. During this free fall, a certain minimum tensile stress is present on the support cable.The free-fall brake can be used electronically or through appropriate mechanical components to terminate a free-fall or free-running mode when the winch hits the ground and the resulting reduction in cable tension. This immediately establishes a coupling, i.e., the creation of a torque-transmitting connection, between the winch drive and the winch drum. The free-fall brake, which can be part of the coupling device or form the entire coupling device, can be connected to the control unit, which can generally comprise an electronic computer unit.

[0017] In principle, the coupling device can be activated at any time. A preferred method variant of the invention is for the coupling device to engage when the compaction element reaches the ground surface. This ensures, on the one hand, that the compaction element's free fall motion is achieved and, on the other hand, that torque is transmitted from the winch drive to the winch drum immediately after impact with the ground, generating the desired cable tension of the support cable in the area of the winch.

[0018] In principle, any torque can be set on the winch drive for any period of time. According to a further development of the method according to the invention, it is advantageous that the winch drive generates a tightening torque during coupling, by means of which the supporting cable is tensioned in the area of the winch. The tightening torque can preferably be designed such that it leads to the desired cable tension, but the compaction element is not lifted from the ground. A second, higher torque can then be set for lifting. However, it is also possible to set a tightening torque at which the compaction element is immediately lifted so that it can be moved back to a starting position above the ground surface in order to carry out another compaction process.

[0019] According to a further method according to the invention, the object is achieved by briefly tensioning the support cable in the area of the winch after the compaction element has hit the ground. Then, before the compaction element is lifted from the ground again, the control unit automatically unwinds the support cable from the winch drum by a certain amount. Preferably, the support cable is rewound immediately thereafter.

[0020] According to this alternative or supplementary method according to the invention, incorrect winding of the support cable on the winch drum is counteracted by first briefly tensioning the support cable in the area of the winch without lifting the compaction element from the ground. Subsequently, before lifting the compaction element from the ground, the control unit automatically unwinds and releases the tension in this way by a certain amount, thereby correcting any misalignment of the winding on the winch drum.

[0021] The support cable can then be automatically wound up again by the control unit and the compaction element can be lifted from the ground until the compaction element reaches the desired starting position above the ground for another compaction process.

[0022] This inventive method ensures that even if an offset occurs in the cable winding, it is reliably corrected automatically by the control unit, preventing a permanent incorrect winding of the support cable on the winch drum. This also reliably counteracts cable wear.

[0023] The amount or degree of unwinding of the support cable before the compaction element is raised again by winding the support cable can be adjusted in any suitable manner. According to a further development of the invention, it is particularly advantageous that the support cable is unwound until it is correctly wound on the winch drum. This ensures a clean winding and thus minimal wear on the support cable over the long term.

[0024] According to a further development of the method according to the invention, the amount of unwinding of the support cable before a new lifting operation of the compaction element is automatically adjusted by the control unit or by a machine operator. This amount can be constant or variable.

[0025] With regard to the construction machine, the invention is characterized in that a control unit is provided which is designed to carry out one of the previously described soil compaction methods. The control unit can, in particular, be an electronic control unit and, in particular, can be integrated into an existing control unit of a construction machine.

[0026] In principle, the winch drum can also be arranged directly on the mast, particularly in an upper area of the mast. According to a further development of the invention, it is particularly expedient for the support cable to be guided over a mast head at the upper end of the mast. The winch drum and the winch drive can thus be arranged directly or close to a carrier device, so that the construction machine as a whole has the lowest possible center of gravity.

[0027] The carrier device may, in particular, comprise an undercarriage with a rotatably mounted superstructure. The undercarriage may, in particular, comprise a chassis, in particular a crawler chassis.

[0028] In order to ensure correct winding on the winch drum, it is expedient according to a further development of the invention that at least one sensor unit, in particular a camera unit, a radar unit or an ultrasound or another suitable sensor, is arranged in the region of the winch drum for detecting a winding of the support cable on the winch drum.

[0029] The invention will be further explained below with reference to a preferred embodiment, which is schematically illustrated in the accompanying drawings. In the drawings: Fig. 1 is a side view of a construction machine according to the invention, and Fig. 2 is a perspective detailed view of a winch drum.

[0030] A construction machine 10 according to the invention designed as a crawler crane from Fig. 1has a mobile carrier device 12. The carrier device 12 comprises a crawler chassis 14 on which an upper carriage 15 is rotatably mounted. A mast 16, also referred to as a boom arm, is mounted on the upper carriage 15 and pivots about a horizontal pivot axis. To pivot the mast 16, a support beam 26, a support beam 28, and an adjusting cable mechanism 27 are provided on the upper carriage 15 in a generally known manner.

[0031] At least one support cable 20 is guided from the superstructure 15 via a mast head 18 of the mast 16, from which a compaction element 30 is suspended, which in the illustrated embodiment is designed as an impact weight 32 for soil compaction. In this embodiment, the support cable 20 is adjustably driven via a double winch arrangement in the superstructure 15, as is generally known from the prior art. To prevent cable oscillation, a cable pressure device 40 can be arranged on each of the two sections of the support cable 20, one of which is attached to the support beam 26, also called an A-frame, and the other to the mast 16. The ends of the support cable 20 are each attached to a cable winch in the superstructure 15, thus providing a double cable winch arrangement for rapid lifting operations. A control unit can be provided on the superstructure 15, in particular in a cabin.

[0032] According to Fig. 2 A possible arrangement of a cable winch 22 for the construction machine 10 according to the invention is shown. The cable winch 22 has a winch drum 24 for winding and unwinding the support cable 20. The winch drum 24 can be driven in rotation in basically both directions of rotation via a winch drive 23 (only partially shown) via an intermediate coupling device 25.

[0033] The coupling device 25 can be designed as a lockable freewheel clutch or a so-called free-fall brake, whereby the support cable 20 is unwound in a kind of free fall solely via the weight of the compacting element 30. When the compacting element 30 impacts a ground surface for soil compaction, the coupling device 25 can immediately reestablish a rotationally fixed connection between the winch drive 23 and the winch drum 24.

[0034] According to the invention, it is provided that even before reconnection by the coupling device 25, the winch drive 23 is driven, preferably via the control unit, in a winding direction, clockwise in the illustrated embodiment. Thus, immediately upon coupling by the coupling device 25, a tightening torque of the winch drive 23 is applied to the winch drum 24. In this way, a desired tension of the support cable 20 can be achieved in the area of the cable winch 22. This effectively counteracts the formation of slack in the cable and, in particular, the transmission of cable vibration of the support cable 20 to the winding of the support cable 20 on the winch drum 24. A clean winding of the support cable 20 on the winch drum 24 can be monitored by a camera unit 50 as a sensor unit. Instead of the camera unit 50, a radar unit, ultrasound unit, or another suitable sensor, such as, for example,an optical sensor, a magnetic sensor or a reed contact can be used.

[0035] Depending on the image or sensor signal captured by the camera unit 50 or the displayed sensor signal, the support cable 20 can be unwound by a machine operator or preferably automatically via the control unit if an undesired offset of the support cable 20 occurs on the winch drum 24 before the compaction element 30 is raised from the ground again.

[0036] In particular, after a cable oscillation has been stabilized, the winch drum 24 can be used to smoothly wind the cable, followed by lifting the compaction element 30 from the ground. This allows for a clean winding of the support cable 20 on the winch drum 24.

[0037] In addition, a further, generally known, rope pressure device 40 with a plate-shaped pressure element 42 can be provided on the winch drum 24. The pressure element 42 is movably mounted by means of a base support 46 and can be pressed against the rope winding on the winch drum 24 by means of a pressure cylinder 48 to further prevent rope misalignment.

Claims

1. Method for soil compaction with a construction machine (10), wherein - a support cable (20) is guided along a mast (16), - the support cable (20) is wound and unwound by means of a rotatably mounted winch drum (24) of a cable winch (22), - the winch drum (24) is rotatably driven by means of a winch drive (23), and - a compacting element (30) is arranged on the support cable (20) and is moved vertically by the support cable (20), wherein the support cable (20) is unwound from the winch drum (24) of the cable winch (22) and the compacting element (30) is lowered on the support cable (20) from a position above a ground surface up to the ground surface, wherein the compacting element (30) strikes the ground surface and compacting the soil in this process, characterised in that - a winding of the support cable (20) on the winch drum (24) is detected by means of a sensor unit, in particular a camera unit (50) or a radar unit.

2. The method according to claim 1, characterised in that - the sensor unit is connected to a control unit which, by means of a signal detected by the sensor unit, determines whether the winding on the winch drum (24) is correct.

3. The method according to one of claims 1 or 2, characterised in that - the winch drum (24) is uncoupled from the winch drive (23) via a coupling device (25) while the support cable (20) is unwound, - in that still before the compacting element (30) strikes the ground surface, the winch drive (23) is driven in a rotation direction to wind the support cable (20), and - in that after the compacting element (30) strikes the ground surface, the coupling device (25) couples the winch drum (24) to the already rotatably driven winch drive (23).

4. The method according to one of claims 1 to 3, characterised in that the method is carried out automatically by means of a control unit.

5. The method according to claim 3 or 4 characterised in that the coupling device (25) comprises a free-fall brake, wherein the support cable (20) is unwound in a free fall of the compacting element (30).

6. The method according to one of claims 3 to 5, characterised in that the coupling device (25) performs a coupling operation when the compacting element (30) reaches the ground surface.

7. The method according to one of claims 3 to 6, characterised in that a tightening torque is generated by the winch drive (23) on coupling, causing the support cable (20) to be tensioned in the region of the cable winch (22).

8. The method according to one of claims 1 to 7, characterised in that after the compacting element (30) strikes the ground, the support cable (20) is first tensioned in the region of the cable winch (22) and then, before the compacting element (30) is lifted up from the ground again, the support cable (20) is automatically unwound by the control unit from the winch drum (24) by a certain amount, which can preferably be set by the machine driver.

9. The method according to claim 8, characterised in that the support cable (20) is unwound until the support cable (20) is correctly wound on the winch drum (24).

10. The method according to claim 8 or 9, characterised in that the amount by which the support cable (20) is unwound before a new lifting operation of the compacting element (30) is set by a machine operator or automatically by a control unit.

11. A construction machine for soil compaction, comprising - a mast (16), - a support cable (20), which is guided along the mast (16), - a cable winch (22) with a rotatably mounted winch drum (24) to which the support cable (20) is attached for winding and unwinding, - a winch drive (23) for rotatably driving the winch drum (24), - a compacting element (30), which is arranged on the support cable (20) for vertical movement, and - a control unit, by which the cable winch can be operated for unwinding the support cable (20) from the winch drum, wherein the compacting element (30) is lowered on the support cable (20) up to a ground surface and the compacting element (30) strikes the ground surface to compact the soil, characterised in that a sensor unit, in particular a camera unit (50) or a radar unit, is provided, which detects a winding of the support cable (20) on the winch drum (24), and in that a control unit is provided, which is configured to carry out the method for soil compaction according to one of claims 1 to 10.

12. The construction machine according to claim 11, characterised in that the support cable (20) is guided via a mast head (18) at the upper end of the mast (16).

13. The construction machine according to claim 11 or 12, characterised in that the at least one sensor unit, in particular a camera unit (50) or a radar unit, is arranged in the region of the winch drum (24) to detect an incorrect winding of the support cable (20) on the winch drum (24).