EP4793430A1

EP4793430A1 - Method for operating an earth compaction device

Info

Publication number: EP4793430A1
Application number: EP25157658.3A
Authority: EP
Inventors: Fabiano Daquilio; Sebastian Reithmeir; Mayank Kumar Jain; David Dimitrov
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2025-02-13
Filing date: 2025-02-13
Publication date: 2026-08-19

Abstract

The present invention relates to a method for operating an earth compaction device, wherein the earth compaction device has an electric motor and a reciprocating mechanism coupled to the motor (5), and wherein the method consists of the following steps: accelerating the motor (5) via a first acceleration profile (110) for a first period of time, following start-up of the earth compaction device; accelerating the motor (5) via a second acceleration profile (114) following the first period of time, wherein a first average acceleration rate of the first acceleration profile (110) is lower than a second average acceleration rate of the second acceleration profile (114).

Description

The present invention relates to a method for operating an earth compaction device, particularly but not exclusively for controlling operation of a rammer. Another aspect of the present invention relates to an earth compaction device configured to operate based on said method.

Background

Rammers and vibrators, also known as earth compaction devices, are construction machines for compacting soil, asphalt and other materials. They are used to ensure that the subsoil is stable and load-bearing, which is particularly important for foundations, paths and roads.
Vibrators, also referred to as plate compactors or wacker plates, compact the soil via vibrating movements. They have a flat, heavy base plate that is set in motion by vibrations. Vibrators have a larger footprint than rammers and are therefore suitable for larger, flatter terrain. They work well on non-cohesive soils such as sand or gravel.
Rammers, also known as vibratory rammers or vibratory tampers, work by repeatedly hitting the ground vertically with a compaction foot arranged at the bottom end of the device. They have a compact design and are usually used in narrow or hard-to-reach areas. Powerful, pulsating movements compact the soil into the depths. Rammers are mainly used on cohesive soils (e.g. loam, clay) that require more energy to be compacted.
Vibratory rammers for earth compaction are based on a multi-spring oscillation system within the device, in which the rotating movement of its combustion engine or electric motor is converted into an upward and downward movement via a gearbox. As a result, the compaction foot lifts several cm from the substrate at high frequency in order to compact it when it hits the ground again.
Some known rammers comprise a combustion engine for driving the compaction foot whilst other rammers have a motor connected to a battery for driving the compaction foot. Rammers with combustion engines typically use a centrifugal clutch to engage the engine with a crank gear of the reciprocating mechanism, once the engine has reached a target speed. This is required to avoid stalling of the combustion engine during start-up of the rammer. This clutch allows the engine to start at low speeds without immediately engaging the vibrating plate. Once the engine reaches a certain speed, centrifugal forces cause the clutch to engage and transfer power to the oscillation system, starting the compaction process.
With the advent of electric rammers, stalling is no longer a concern. Instead electric motors produce what is known as "instant torque", the ability to deliver maximum torque immediately after energising the motor. Consequently, centrifugal clutches are no longer required, saving costs and reducing the complexity of the rammer's transmission.
It was found that by removing the centrifugal clutch the oscillation system is always connected to the motor and, during the ramp-up/start-up, the instant torque of the electric motor generates undesirable behaviour of the rammer. In particular, the rammer was found to oscillate irregularly and unpredictably at least during start-up, rendering handling of the rammer significantly more challenging to the user.
In view of the above, It is an aim of the present disclosure to solve or at least ameliorate one or more problems of the prior art. In detail, it is an object to provide a method for operating an earth compaction device and a corresponding earth compaction device without a centrifugal clutch, which exhibits an improved, predictable start-up behaviour.
Aspects and embodiments of the present disclosure provide a method for operating an earth compaction device and an earth compaction device claimed in the appended claims.
According to a first aspect of the present invention, there is provided a method for operating an earth compaction device, wherein the earth compaction device has an electric motor and a reciprocating mechanism coupled to the motor, and wherein the method consists of the following steps:

accelerating the motor via a first acceleration profile for a first period of time, following start-up of the earth compaction device;
accelerating the motor via a second acceleration profile following the first period of time,

It was found that accelerating the motor and thus the earth compaction device with 2 different acceleration profiles/rates significantly improves the behaviour of the oscillating system within the reciprocating mechanism. The earth compaction device starts oscillating slowly and immediately produces harmonic and consistent movements of the compaction foot. This is achieved by applying a first acceleration rate during a first period of time. An average acceleration rate of the first acceleration profile is slower than a second acceleration rate following the first period of time. According to the present invention, there may be different triggers following which the acceleration profile of the motor is switched from the first acceleration profile to the second acceleration profile. In one example, a change between acceleration profiles may be triggered by a timer. The invention is not restricted to a time trigger. Rather, other parameters, such as the position of the motor, motor voltage, motor current could be used as a trigger to determine that the first period of time has ended, and as result switch over to the second acceleration profile.
Splitting acceleration into two different profiles also has the advantage that the weight of the earth compaction device can be used to assist acceleration of the system, thereby bringing the motor and the reciprocating mechanism to target speed in a shorter period of time, with less power required. In particular, and as will be described in more detail below, the method of the present invention preferably applies the first acceleration profile at a time during which gravity acts against movement of the motor. During this time, the motor is accelerated at a comparatively low rate, such that the motor is able to produce higher torques to overcome the gravitational force created by the earth compaction device's weight. Once the reciprocating mechanism is partly or fully extended, a peak load torque caused by gravity is reached. According to an embodiment of the present invention, it is then, i.e., just after the peak load torque, that the acceleration profile of the motor is switched to the second acceleration profile. During the second acceleration phase, the motor is accelerated comparatively quickly, i.e. when the load torque decreases from peak to 0. Eventually the gravitational load assist the motor in moving the reciprocating mechanism, i.e. during a time when the reciprocating mechanism is compressed.
According to another embodiment, the first period of time ends when the motor has produced a predetermined number of revolutions. As mentioned previously, the end of the first period of time is not necessarily linked to a time threshold. Rather, the end of the first period of time may be linked to a predetermined number of revolutions produced by the motor. Following startup of the earth compaction device, a control unit may count the number of revolutions of the rotor produced by the motor and compare this number with a predetermined trigger-threshold. Once such trigger-threshold is exceeded, the control unit switches from the first acceleration profile to the second acceleration profile, i.e. start accelerating the motor at a higher acceleration rate. This embodiment is particularly advantageous because no new hardware is required to implement it. In particular, counting motor revolutions may be implemented in a very simple manner, i.e. by monitoring the motor current or voltage signals. No further sensors or timers are required.
According to another embodiment, the reciprocating mechanism comprises a crank gear, said crank gear being connected to an output shaft of the motor and configured to convert rotational movement of the motor into a reciprocating movement of a connecting rod connected to the crank gear, and wherein the first period of time ends when the crank gear has rotated between 50° and 190°, preferably between 60° and 120°, with respect to its initial position. According to this embodiment, the point in time when the control unit switches between the first and second acceleration profiles is linked to the position of the crank gear. A rotation of the crank gear of 90° typically corresponds with the aforementioned load torque peak, following which acceleration should be increased, via the second acceleration profile. In this example, rather than looking at the absolute position of the crank gear, it is suggested to determine how far the crank has been rotated from its initial position. This is a particularly simple way of gauging the absolute position of the crank gear. Preferably, a switch between the first and second acceleration profiles happens when the crank gear is at 90°. However, in its resting position, i.e. before startup of the rammer, the crank gear is not always arranged at an angle of 0°. Accordingly, without knowing the initial position of the crank gear, it is not possible to determine when the crank gear reaches its 90° position, without adding a position sensor. Yet, it was found that rotating the crank gear between 50° and 190° from its initial position is sufficient to avoid misbehaviours during startup and achieve the objective of the present invention, even if the starting position of the crank gear is unknown. This is also because the crank gear typically rests within plus or -30° off the uppermost-position (0°).
According to another embodiment, the reciprocating mechanism comprises a spring assembly coupling the motor to a compaction foot, wherein the first acceleration profile is selected in such a way that the spring assembly substantially does not deform during the first period of time. The spring assembly may be coupled to a connecting rod that converts the rotational movement of the crank gear into a reciprocating movement. The connecting rod is coupled to the compaction foot via said spring assembly. In other words, as the connecting rod extends, movement of the connecting rod is transferred to the compaction foot via one or more springs of the spring assembly. If the motor is accelerated slowly (i.e. during the first acceleration profile), movement of the connecting rod is transferred onto the compaction foot without significantly compressing the spring arranged between the connecting rod and the compaction foot. By contrast, fast acceleration, particularly following startup, can cause the spring assembly to compress significantly during extension of the connecting rod. This, in turn, can lead to unpredictable oscillating movements of the reciprocating system. Depending on the flexibility of the spring assembly, the first acceleration profile may be adjusted to not compress the one or more springs during startup. Since the spring assembly does not change during normal use of the rammer, the first acceleration profile can be tailored to the resilience of the spring assembly by the manufacturer.
According to another embodiment, the first average acceleration rate is 10 to 100 times lower than the second average acceleration rate. It was found that this ratio is particularly advantageous when trying to obtain a predictable startup behaviour of the rammer without utilizing a centrifugal clutch.
According to another embodiment, the first acceleration profile comprises a substantially constant first acceleration rate and/or wherein the second acceleration profile comprises a substantially constant second acceleration rate. This is an example of a particularly simple way of controlling the earth compaction device, i.e. with two different, constant acceleration rates. In this regard, "substantially constant" refers to the fact that the acceleration rate will naturally vary slightly depending on the quality of the motor. In this embodiment, the acceleration rate of the first actual acceleration profile is set to a constant first target acceleration value and the second acceleration rate to a constant second target acceleration value.
According to another embodiment, the first acceleration rate is between 1 and 20 rad/s² and/or wherein the second acceleration rate is between 150 and 1000 rad/s².
According to another embodiment, following the first period of time, the motor is accelerated via the second acceleration profile until a speed of the motor reaches a target speed.
According to another embodiment, once the motor has reached the target speed, the motor speed is maintained at substantially constant at the target speed.
According to another embodiment, during the first time period, the motor produces a torque of 0.7 - 1.7 Nm.
According to another embodiment, the first period of time is a period, during which the reciprocating mechanism moves from a first end position towards a second end position. In this example, the first end position may be a fully retracted position of the reciprocating mechanism, i.e. a position in which the compaction foot is at its top end. In contrast, the second end position may be a position in which the reciprocating mechanism is fully extended, i.e. the compaction foot is at its lower end position. According to this embodiment, the slow first acceleration profile is applied only when the reciprocating mechanism is extended for the first time from the first end position towards the second end position. The acceleration profile is preferably switched to the second acceleration profile before the second position is reached, for the first time. In other words, the first acceleration profile preferably is only applied to a first half cycle of the aforementioned crank gear.
In another aspect of the present invention, there is provided an earth compaction device comprising:

an electric motor;
a reciprocating mechanism coupled to the motor;
a control unit for controlling the motor, the control unit being configured to:
accelerate the motor via a first acceleration profile for a first period of time, following start-up of the earth compaction device;
accelerate the motor via a second acceleration profile following the first period of time,

According to another embodiment, the reciprocating mechanism comprises a crank gear, said crank gear being connected to an output shaft of the motor and configured to convert rotational movement of the motor into a reciprocating movement of a connecting rod connected to the crank gear, and wherein during standstill of the earth compaction device, the reciprocating mechanism is in a first end position, in which the connecting rod is retracted, and wherein the first acceleration profile is applied exclusively while the reciprocating mechanism is transferred from the first end position towards a second end position, in which the connecting rod is extended, for the first time, following standstill.
According to another embodiment, the gear ratio between a full rotation of the motor and a full rotation of the crank gear is between 10 and 100, preferably between 20 and 40, more preferably 30.
According to another embodiment, the earth compaction device comprises a compaction foot coupled to the reciprocating drive mechanism and configured to engage a surface to be compacted.
In the following, the invention shall be described in more detail referring to the exemplary embodiments shown in the accompanying drawings.
The Figures show:

Fig. 1: a schematic, perspective view of a rammer known in the art;
Fig. 2: a schematic, cross-section through a transmission of a rammer without a centrifugal clutch;
Fig. 3: a schematic speed/acceleration profile for start-up of a rammer according to an embodiment of the present invention;
Fig. 4: a schematic flow-diagram of an embodiment of the present invention.

Detailed Description

Fig. 1 shows a schematic, perspective view of a rammer 1 known in the art. Fig. 1 is a copy of Fig. 1 of DE 102021116244 A1 filed on 23 June 2021 . In the wording of the present application, the rammer 1 comprises a handle portion 3 connected via dampeners 4 with an upper part of the reciprocating mechanism. The upper part of the reciprocating mechanism comprises a gear assembly received within a gear housing 10. The gear assembly is connected to a lower part of the reciprocating mechanism via a connecting rod 8.
An electric motor 5 is attached to the outside of the gear housing 10. An output shaft 6 of the motor 5 extends into the gear housing 10 and engages a crank gear 7 of the crank drive that is housed within the gear housing 10. A first end 9 of the connecting rod 8 is connected to eccentrically on the crank gear 7.
As will be appreciated, rotation of the crank gear 7 by the motor output shaft 6 will ultimately result in a linear movement of the second end 16 of the connecting rod.
The second end 16 of the connecting rod 8 is connected to a spring assembly 18, 19. The spring assembly comprises a first spring 18 and a second spring 19. The second end 16 of the connecting rod 8 is arranged between the first spring 18 and the second spring 19. The second spring 19 is arranged between the second end of the connecting rod 8 and a compaction foot 12 of the rammer one. The movement of the connecting rod 8 and the spring assembly is guided by two shafts 11, 14. The second shaft 14 may move in a longitudinal direction relative to the first shaft 11 to allow for extension and contraction of the compaction foot 12. An outer bellow 15 extends around and protects the sheaths and the spring assembly. The bellow 15 extends and contracts together with the reciprocating movement of the compaction foot.
It will be appreciated that the prior art example Fig. 1 is only one exemplary way of constructing a rammer that may be operated according to the method of the present invention. In principle, any reciprocating mechanism known for earth compaction devices may be utilized together with the method of the present invention.
Referring to Fig. 2, there is shown a schematic cross-section through the gear housing of a rammer without a centrifugal clutch.
The transmission 100 shown in Fig. 2 comprises an output gear 102 connected to the rotor shaft of the motor. The output gear 102 is in meshing contact with a crank gear 104. In the embodiment of Fig. 2, the crank gear 104 has a larger diameter than the output gear 102. Preferably, a gear ratio between the output gear 102 and the crank gear 104 is between 10 and 100, preferably between 20 and 40, more preferably 30. In the following embodiments, an exemplary gear ratio of 30 shall be explained in more detail. In this example, the output gear 102 and thus the rotor shaft of the motor will complete 30 revolutions for one full rotation of the crank gear 104. This also means that a single revolution of the output gear/rotor shaft of the motor is equivalent to around 12° of rotation of the crank gear 104.
A connecting rod 108 has a first end 106 that is connected to a front face of the crank gear 104. The first end 106 of the connecting rod 108 is connected to the front face of the crank gear 104 eccentrically to convert the rotation of the crank gear 104 into a linear movement, as is well known in the art.
Fig. 2 schematically represents an angular range of a first acceleration profile 110 and a second acceleration profile 114. According to the present invention, the first and second acceleration profiles 110, 114 are controlled via the motor. An average acceleration rate of the first acceleration profile 110 is faster than an average acceleration rate of the second acceleration profile 114.
Fig. 2 shows an ideal starting position, i.e. when the rammer is at an uppermost end at standstill. In this position, the connecting rod 108 is at its first position, e.g. an uppermost position. As the crank gear 104 is rotated counterclockwise in Fig. 2, the first end 106 of the connecting rod 108 moves counterclockwise together with the crank gear and thus towards a lowermost position at a lower end of the crank gear of 104. The second, lowermost position in the example of Fig. 2 is reached when the gear crank 104 is rotated 180° from the uppermost position shown in Fig. 2.
According to the present invention, the first rotation of the crank gear 104, following startup, is divided into two different acceleration profiles with significantly different acceleration rates.
In the embodiment of Fig. 2, a first acceleration profile 110 is applied to the motor until the crank gear has covered an angle of about 135°. In the above example using a gear ratio of 30, this means that the first acceleration profile 110 may be applied to the motor during the first 11 revolutions of the motor shaft, following startup of the rammer. In this example, 11 revolutions of the motor shaft relate to a rotation of the crank gear 104 of around 132° (11 × 12° of rotation).
In one embodiment, a control unit may be provided, which monitors the number of motor revolutions during startup. In one example, the control unit may monitor the motor current to determine each full revolution and count them until a predetermined threshold has been reached. In the above example, the threshold is 11 revolutions. However, as mentioned above, other angles of the crank gear may also be acceptable, thereby changing the number of revolutions before switching to the second acceleration profile. As will be appreciated, the number of motor revolutions also depends on the gear ratio between the output gear 102 and the crank gear 104.
As set out in detail above, the first acceleration profile 110 is applied during a first angular range of rotation of the crank gear 104. In the embodiment of Fig. 2. This angular range is around 135°. This angular range defines a first period of time, during which the first acceleration profile is applied. Once the crank gear 104 has covered the angular range of around 135°, a trigger point 112 is reached and the acceleration of the motor is changed to a second acceleration profile 114.
Using an angular range to determine the trigger point 112 is only one example of various possibilities of determining the end of the first period of time. According to the present invention, another alternative would be to start a timer when starting the motor from standstill and switching from the first acceleration profile to the second acceleration profile after a predetermined time span, e.g., after 0.5 seconds. In this example, the number of revolutions of the motor or the angular range covered by the crank gear is not required to determine the trigger point. Rather, a timer may be used by the control unit and compared to a time threshold, following which the second acceleration profile will be applied.
Other possible ways of determining the trigger point 112 may be the use of mechanical, magnetic, or optical sensors to determine the position of the crank gear 104.
The skilled person will be able to determine further possible triggers for the switch between the first acceleration profile and the second acceleration profile. Importantly, the first acceleration profile will be applied for a first period of time, i.e. until the trigger point is reached. Following the trigger point, the second acceleration profile 114, which is faster than the first acceleration profile, will be applied. Preferably, the second acceleration profile 114 will be applied until the motor reaches a target speed, as will be described in more detail with reference to Fig. 3 below. Once the target speed is reached, acceleration will be reduced to zero and the target speed maintained during the rest of the operation of the rammer.
In some examples, the first and second acceleration profiles are chosen such that the target speed is reached before the crank gear 104 has completed one full rotation, i.e. before the reciprocating mechanism has completed one full cycle of expansion and contraction.
Turning to Fig. 3, there is shown a schematic speed/acceleration profile for start-up of a rammer according to an embodiment of the present invention. The diagram 200 in Fig. 3 shows the motor speed over the angular rotation of the crank gear. The method of Fig. 3 includes two acceleration profiles 202, 206. A first, slow acceleration profile 202 is applied immediately from standstill of the rammer. Once a trigger point 204 is reached, a second acceleration profile 206 is applied. The second acceleration profile 206 has a higher acceleration rate than the first acceleration profile 202. The second acceleration profile 206 is maintained until a target speed 208 is reached.
As will be appreciated, the first and second acceleration profiles 202, 206 in Fig. 3 each comprise a constant acceleration rate, i.e. a constant slope. The slope (acceleration rate) of the first acceleration profile 202 is lower than the slope (acceleration rate) of the second acceleration profile 206. In other words, the slope of the second acceleration profile is significantly steeper than the slope of the first acceleration profile 202.
A switch between the first and second acceleration profiles 202, 206 is applied at a trigger point 204, which is schematically illustrated in Fig. 3. In the above example of Fig. 2, this trigger point 204 may be at roughly 135° angular rotation of the crank gear 104, e.g. 11 full revolutions of the motor shaft.
It should be understood that the acceleration profiles shown in Fig. 3 are exemplary profiles only. It is also feasible to apply acceleration profiles that are not constant, e.g. stepped or curved speed/acceleration profiles with irregular slope. However, in such a case the average acceleration rate of the first acceleration profile is still lower than the average acceleration rate of the second acceleration profile.
Fig. 4 shows a schematic flow diagram of an embodiment of the method of the present invention. The method 300 for controlling earth compaction devices according to Fig. 4 starts at standstill of the Earth compaction device. In step S302, when the user activates the Earth compaction device, e.g., the rammer, a control unit starts accelerating the motor at a first acceleration rate during step S304. In some embodiments, the motor may be a brushless motor and commutated in a way that a first acceleration rate is achieved during a first time period.
Following the application of the first acceleration rate in step 304, the control unit continuously determines if a trigger point (see figures 2 and 3) is reached. The control unit may look at various parameters of the reciprocating mechanism to determine if a trigger point is reached. As explained above, some examples include a number of revolutions of the motor shaft, angular rotation of the crank gear 104, a time that has elapsed since actuation of the rammer, etc. If the controller determines, in step 306, that the trigger point has not yet been reached, the first acceleration profile/rate of step S304 is maintained.
Once, the control unit determines at step S306 that the trigger point, e.g. 11 revolutions of the motor shaft, is reached, the control unit switches the acceleration profile of the motor to a second acceleration profile/rate in step S308. According to the present invention, the second acceleration rate is higher than the first acceleration rate to bring the reciprocating mechanism to target speed as fast as possible. Preferably, the second acceleration rate is chosen such that the target speed is reached before the reciprocating mechanism has a completed one full cycle.
Following application of the second acceleration rate, the control unit may check, intermittently or continuously, if the target speed has been reached. If the target speed has not been reached, the second acceleration rate is maintained. Once the target speed is reached, the control unit stops accelerating the motor and maintains the motor at target speed for the rest of the operation of the earth compaction device.
The present invention is not limited to the specific combination of features disclosed in the above embodiment.

Reference signs

1: rammer
3: handlebar
4: dampener
5: motor
6: motor shaft
7: crank gear
8: connecting rod
9: first end
10: gear housing
11: first shaft
12: compaction foot
14: second shaft
15: bellow
16, 17: second end
18: first spring
19: second spring
100: transmission
102: output gear
104: crank gear
106: first end
108: connecting rod
110: first acceleration profile
112: trigger point
114: second acceleration profile
200: diagram
202: first acceleration profile
204: trigger point
206: second acceleration profile
208: target speed

Claims

A method for operating an earth compaction device, wherein the earth compaction device has an electric motor and a reciprocating mechanism coupled to the motor (5), and wherein the method consists of the following steps:
- accelerating the motor (5) via a first acceleration profile (110) for a first period of time, following start-up of the earth compaction device;

- accelerating the motor (5) via a second acceleration profile (114) following the first period of time,
wherein a first average acceleration rate of the first acceleration profile (110) is lower than a second average acceleration rate of the second acceleration profile (114).
The method of Claim 1,
wherein the first period of time ends when the motor (5) has produced a predetermined number of revolutions.
The method of Claim 1 or 2,
wherein the reciprocating mechanism comprises a crank gear (104), said crank gear (104) being connected to an output shaft of the motor (5) and configured to convert rotational movement of the motor (5) into a reciprocating movement of a connecting rod connected to the crank gear (104), and wherein the first period of time ends when the crank gear (104) has rotated between 50° and 190°, preferably between 60° and 120°, with respect to its initial position.
The method of any one of Claims 1 to 3,
wherein the reciprocating mechanism comprises a spring assembly coupling the motor (5) to a compaction foot (12), and wherein the first acceleration profile (110) is selected in such a way that the spring assembly substantially does not deform during the first period of time.
The method of any one of Claims 1 to 4,
wherein the first average acceleration rate is 10 to 100 times lower than the second average acceleration rate.
The method of any one of Claims 1 to 5,
wherein the first acceleration profile (110) comprises a substantially constant first acceleration rate and/or wherein the second acceleration profile (114) comprises a substantially constant second acceleration rate.
The method of Claim 6,
wherein the first acceleration rate is between 1 and 20 rad/s, and/or wherein the second acceleration rate is between 150 and 1000 rad/s².
The method of any one of Claims 1 to 7,
wherein, following the first period of time, the motor (5) is accelerated via the second acceleration profile (114) until a speed of the motor (5) reaches a target speed.
The method of Claim 8,
wherein, once the motor (5) has reached the target speed, the motor speed is maintained at substantially constant at the target speed.
The method of any one of Claims 1 to 9,
wherein, during the first time period, the motor (5) produces a torque of 0.7 - 1.7 Nm.
The method of any one of Claims 1 to 10,
wherein the first period of time is a period, during which the reciprocating mechanism moves from a first end position towards a second end position.
Earth compaction device comprising:
- an electric motor (5);

- a reciprocating mechanism coupled to the motor (5);

- a control unit for controlling the motor (5), the control unit being configured to:

- accelerate the motor (5) via a first acceleration profile (110) for a first period of time, following start-up of the earth compaction device;

- accelerate the motor (5) via a second acceleration profile (114) following the first period of time,
wherein a first average acceleration rate of the first acceleration profile (110) is lower than a second average acceleration rate of the second acceleration profile (114).
The earth compaction device of Claim 12,
wherein the reciprocating mechanism comprises a crank gear (104), said crank gear (104) being connected to an output shaft of the motor (5) and configured to convert rotational movement of the motor (5) into a reciprocating movement of a connecting rod (108) connected to the crank gear (104),

and wherein during standstill of the earth compaction device, the reciprocating mechanism is in a first end position, in which the connecting rod (108) is retracted,

and wherein the first acceleration profile (110) is applied exclusively while the reciprocating mechanism is transferred from the first end position towards a second end position, in which the connecting rod (108) is extended, for the first time, following standstill.
The earth compaction device of Claim 13,
wherein the gear ratio between a full rotation of the motor (5) and a full rotation of the crank gear (104) is between 10 and 100, preferably between 20 and 40, more preferably 30.
The earth compaction device of any one of Claims 12 to 14,
wherein the earth compaction device comprises a compaction foot (12) coupled to the reciprocating drive mechanism and configured to engage a surface to be compacted.