Device for monitoring and assisting an operator of a construction machine

Abstract

The invention relates to a device for monitoring and assisting an operator of a construction machine, which device comprises a seat contact switch for detecting whether an operator is sitting on a seat of the construction machine, a door lock switch for detecting whether a door of a driver's cab of the construction machine is closed, a handle sensor for detecting whether an operating lever arranged to the left of the seat and / or an operating lever arranged to the right of the seat for controlling a servo circuit of the construction machine is actuated by an operator, and an evaluation unit which is designed to limit or stop a capability of the construction machine depending on the detected states of the seat contact switch, the door lock switch and the handle sensor.

Description

[0001] The present invention relates to a device for monitoring and assisting an operator of a construction machine, in particular an excavator.

[0002] In the world of construction equipment, safety plays a crucial role. Given the potential risks associated with operating heavy equipment, it is essential to implement effective safety mechanisms to protect both operators and their environment.

[0003] A typical safety mechanism is the safety lever, which is located on the seat of an excavator and acts as a barrier for the operator getting in or out of the vehicle. In a first (horizontal) position, the safety lever blocks the seated operator's access to the driver's door, requiring the operator to first move the safety lever to a second (vertical) position. Only then is the operator able to exit the construction machine through the driver's door without contact with the safety lever. In this second (vertical) position, the safety lever ensures that the excavator's controls are deactivated, whereas the excavator's controls are activated when the safety lever is in its second (horizontal) position.

[0004] This safety feature contributes significantly to the safety of the operator and those around him and is particularly important to prevent unintentional movement of the excavator if the operator leaves the seat.

[0005] This is particularly relevant when changing operators or getting in and out, as the folding safety lever ensures that the machine remains in a safe condition until a new operator is ready to take control of the construction machine.

[0006] The safety lever can be coupled to a switch, which is typically designed as a positive opening contact and immediately deactivates a servo control of the construction machine, so that the construction machine does not pose a danger while there is no operator in the driver's cab.

[0007] Nevertheless, it is still desirable to further reduce the risk of accidents posed by construction machinery and to improve safety for the driver and the area surrounding the construction machinery.

[0008] This is achieved with a device for monitoring and assisting an operator of a construction machine, which has all the features of claim 1.

[0009] The device according to the invention can detect safety-critical operator behavior and restrict the functions of the construction machine controlled by the operator. This ensures that the legal requirements regarding the correct behavior of a construction machine operator are implemented while simultaneously achieving an efficient work pace. Furthermore, expected risk-relevant special operating conditions can be detected, such as an operator working while standing, as is often the case during excavation work for canal laying, and can be responded to by restricting the functionality of the construction machine. Furthermore, the operator can be made aware of any incorrect behavior and shown remedial measures. In a construction machine that incorporates the device according to the invention, the safety lever normally required by law can also be dispensed with.

[0010] According to the invention, the device for monitoring and assisting an operator of a construction machine comprises a seat contact switch for detecting whether an operator is sitting on a seat of the construction machine, a door lock switch for detecting whether a door of a driver's cab of the construction machine is closed, a handle sensor for detecting whether an operating lever arranged to the left of the seat and / or an operating lever arranged to the right of the seat for controlling a servo circuit, i.e. the hydraulic system of the construction machine, is actuated by an operator, and an evaluation unit which is designed to limit or stop a capability of the construction machine and / or to output a signal to signal a critical condition depending on the detected states of the seat contact switch, the door lock switch and the handle sensor.

[0011] The basic idea of ​​the invention is to implement various sensors in the driver's cab of the construction machine and logically interconnect them to determine whether the construction machine poses an increased risk. If such an increased risk is detected, appropriate countermeasures are implemented to limit the functionality of the construction machine.

[0012] In the sense of a design as a non-restrictive assistance system, it can also be provided that when an increased risk potential is detected, a signal is issued to indicate a critical condition.

[0013] This signal can be an optical signal that serves to alert the operator of the construction machine to the increased hazard potential. For example, a signal light can be activated if the evaluation unit detects an increased hazard potential. According to an optional development of the present invention, a signal light can be arranged in the area of ​​an operating lever, preferably in the lower third of the operating lever, so that the operator of the construction machine can be easily signaled that he or she is currently in a state in which an increased hazard potential has been detected.

[0014] In addition, it can be provided that a signal light changes its color depending on the hazard potential, so that a particularly dangerous condition is signaled to the operator with red, for example, and a moderately dangerous condition is signaled with yellow, for example.

[0015] This visual warning is intended to make the operator of the construction machine aware of the increased risk potential.

[0016] In this case, it can advantageously be provided that the capability of the construction machine includes a travel speed of the construction machine, a superstructure speed of the construction machine, and / or the operation of the servo circuit of the construction machine. The servo circuit of the construction machine can represent the hydraulic system of the work machine, which serves, among other things, to operate the primary functionality of the construction machine.

[0017] The servo circuit in a hydraulic excavator is a central component of the hydraulic control system, specifically designed to control the excavator's movements and operations precisely and efficiently. A key feature of the servo circuit is its ability to enable precise control of the excavator's hydraulic functions. This allows the operator to move the upper structure and / or the excavator's work tools, such as the arm, bucket, or shovel, with high precision.

[0018] The servo circuit is characterized by its responsiveness to operator inputs. Movements of a control lever are directly translated into hydraulic actions (moving the upper carriage or work tool) of the excavator, with the circuit responding to even the slightest movements and adjustments by the operator to enable precise operations.

[0019] According to an optional development of the present invention, it can be provided that the evaluation unit is designed to limit or stop a capability of the construction machine or to output a signal to limit or stop a capability of the construction machine when the seat contact switch detects that the operator is not sitting on the seat of the construction machine, the door lock switch detects that the door of the driver's cab is open and the handle sensor detects that one or both control levers are actuated, preferably wherein the evaluation unit is designed in such a case to limit a maximum superstructure speed of the construction machine.

[0020] If the evaluation unit detects that the operator is not sitting in their seat but is operating at least one control lever with the driver's door open, this is a strong indication that the construction machine is either being controlled by a person outside the cab or that the operator is standing inside. This situation can be classified as a foreseeable misoperation of a construction machine, since, for example, during excavation work for sewer installation, it is often difficult for an operator sitting in the seat to see the shaft directly in front of an excavator. Therefore, a standing position in the cab is assumed.

[0021] The grip sensor can be designed so that simply touching the handle indicates that the corresponding control lever has been actuated. This does not necessarily require moving or pressing a lever or button on the control lever. Simply moving your hand or touching the control lever can be sufficient.

[0022] If the evaluation unit concludes that such a situation exists, it can react by restricting one of the construction machine's capabilities. For example, the rotation speed of the superstructure can be reduced to prevent the likelihood of an accident. Furthermore, the overall speed of the servo control could also be reduced from its normal level to accommodate the situation where the construction machine is operated by an operator who is not in the driver's seat.

[0023] According to a further advantageous modification of the present invention, it can be provided that the evaluation unit is designed to stop the servo circuit of the construction machine when the seat contact switch detects that the operator is sitting on the seat of the construction machine and the handle sensor detects that neither of the two operating levers for actuating the servo circuit of the construction machine is actuated, preferably wherein the evaluation unit is designed to implement the stopping of the servo circuit of the construction machine only after a certain period of time has elapsed in the state leading to the stopping, for example more than 3 seconds.

[0024] If the evaluation unit detects that the construction machine operator is sitting in the seat and not operating either of the two control levers for activating the servo circuit, the evaluation unit can generate a signal intended to stop the servo circuit. This saves energy, as the servo circuit does not need to be kept running even when the operator is in the cab. For example, with an excavator, this can occur when the excavator is moved around the construction site without the servo circuit, which can be operated via the two control levers, being used.

[0025] Furthermore, according to the present invention, it can be provided that the device comprises a driving function switch, in particular an accelerator pedal switch for detecting whether a driving function or an accelerator pedal of the construction machine is actuated, wherein the evaluation unit is designed to limit or stop a capability of the construction machine depending on the detected state of the driving function switch.

[0026] A driving function switch, in particular an accelerator pedal switch, is provided as a further sensor that the evaluation unit considers to detect the various states. A driving function switch can be implemented not only by an accelerator pedal switch but also, for example, by a joystick or the like, which represents an operating element for controlling the driving functionality of the construction machine. Thus, the activation of the driving function switch can also be checked by the evaluation unit and, in conjunction with the other sensors, lead to the detection of a specific state of the construction machine, in which the evaluation unit limits a capability of the construction machine or outputs a signal to limit a capability of the construction machine.

[0027] The evaluation unit can be designed to limit the maximum travel speed of the construction machine when the seat contact switch detects that the operator is not sitting on the seat of the construction machine and the travel function switch detects that the accelerator pedal or another control element for controlling the travel functionality of the construction machine is actuated, preferably wherein the evaluation unit is designed to initially limit the maximum travel speed of the construction machine for a specific period of time and then to set it to zero.

[0028] This prevents the impermissible condition whereby a construction machine is to be moved while stationary. In such a detected condition, the maximum travel speed of the construction machine can first be reduced before the travel speed is set to zero.

[0029] Alternatively and / or additionally, the evaluation unit can be designed to limit or stop a capability of the construction machine if the seat contact switch detects that the operator is not sitting on the seat of the construction machine, the handle sensor detects that only the left of the two control levers is actuated, and the drive function switch detects that the accelerator pedal or another control element for controlling the drive functionality is not actuated, preferably wherein the evaluation unit is designed to limit or stop the servo circuit in such a case.

[0030] Such a condition may indicate that an operator inadvertently operates the left control lever, i.e., the lever facing the driver's door, when exiting the cab. This can occur, for example, due to the narrow cab, due to a support movement when exiting the cab, so that the resulting movement of the construction machine caused by the actuation of the control lever is unintentional and must be prevented.

[0031] According to a further optional modification of the present invention, it can be provided that the device further comprises a belt buckle switch for detecting whether a safety belt of the seat of the construction machine is locked with a belt buckle, wherein the evaluation unit is designed to limit or stop a capability of the construction machine also depending on the detected state of the belt buckle switch.

[0032] A belt buckle switch is now provided as an additional sensor that the evaluation unit considers to detect the different states.

[0033] Furthermore, the device can comprise a selector switch for detecting one of several possible operating modes of the construction machine, wherein the evaluation unit is designed to limit or stop a capability of the construction machine depending on the detected state of the selector switch, and the operating modes of the construction machine comprise a work mode, a parking mode and a road travel mode.

[0034] "Road Mode," "Parking Mode," and "Work Mode" refer to different machine settings or configurations optimized for specific operating conditions or applications.

[0035] An excavator's road mode is typically used when moving the machine over roads or construction sites. In this mode, the machine is set to move easily and safely, often with a speed limit for safety. Additionally, it is advantageous to disable certain functions, such as the upper carriage swing or boom movement on an excavator, in this mode to increase stability while driving.

[0036] When the excavator is parked or left unused for an extended period, it is placed in parking mode. In this state, all operating systems are typically shut down, and the machine is secured to prevent accidental start-up or movement. This may include engaging safety interlocks, lowering the work tools to the ground, and activating anti-theft systems.

[0037] Work mode is the configuration used for normal operation of the excavator or construction machine during construction work. In this mode, all machine functions are activated to achieve maximum efficiency and performance. For an excavator, this includes the full functionality of the boom, bucket, and other attachments.

[0038] Furthermore, according to a particular embodiment of the present invention, it can be provided that the evaluation unit is designed to limit or stop a capability of the construction machine when the selector switch detects that the construction machine is in road travel mode and the belt buckle switch detects that the safety belt of the seat of the construction machine is not locked with the belt buckle, preferably wherein the evaluation unit is designed in such a case to reduce the maximum travel speed of the construction machine, preferably to zero.

[0039] According to the invention, it can further be provided that the device comprises an emergency stop switch for immediately deactivating the servo circuit of the construction machine.

[0040] The emergency stop switch is typically activated manually by the construction machine operator when they detect a dangerous condition. Activating the emergency stop switch immediately stops the construction machine's movements, preventing any further hazards from the machine.

[0041] According to an advantageous development of the present invention, it can be provided that the evaluation unit is implemented by a logic gate, wherein the logic gate preferably uses only the logical operations AND, OR, NOT, NAND, NOR, XOR and XNOR to check the different states.

[0042] The logical interconnection of the different sensors using a logic gate creates a robust and very easy-to-implement device for monitoring and assisting an operator of a construction machine.

[0043] According to a further development of the present invention, it can be provided that the evaluation unit is designed to only enable safety-relevant operation of the construction machine when the handle switch detects that at least one of the two operating levers has been actuated by the operator, and the seat contact switch detects that the operator is sitting on the seat of the construction machine and / or the evaluation unit is designed to only enable safety-relevant operation of the construction machine when the handle switch detects that both operating levers have been actuated by the operator.

[0044] For example, safety-relevant operation of the construction machine can only be authorized once the evaluation unit determines that the operator has actually sat down in the seat and operated one or both control levers. A specific action of the construction machine that poses an increased risk can be considered a safety-relevant operation.

[0045] According to the invention, it can further be provided that the construction machine is an excavator, in particular a hydraulic excavator, and the servo circuit serves to implement the movements and operations of the excavator, in particular the rotation of the superstructure and the movement of the excavator arm.

[0046] The invention further relates to a construction machine, in particular a hydraulic excavator, having a device according to one of the preceding aspects, preferably wherein the device replaces the normally present safety lever of the construction machine.

[0047] If the device according to the invention is implemented in a construction machine, the functionality previously performed by the safety lever can be taken over by the device according to the invention. This eliminates the need for the safety lever, which is often perceived as annoying by some operators and is sometimes intentionally moved incorrectly to enable what the operator considers an advantageous operation of the work machine in a state that is actually prohibited. To avoid this obvious circumvention of such operation of the work machine, the functionalities of the safety lever can be transferred to the device according to the invention. This is significantly more difficult to circumvent than the safety lever, which only needs to be intentionally moved into its release position, thus increasing the overall safety of the construction machine.Incorrect use of the safety lever is often due to untrained personnel who have not been trained in the correct use of the safety lever.

[0048] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1A: a side view of a driver's cab according to the prior art with the safety lever in the blocking position, Fig. 1B: a side view of a driver's cab according to the prior art with the safety lever folded down, Fig. 2: a schematic plan view of a driver's cab to illustrate the device according to the invention, Fig. 3: an oblique cross-sectional view of a rotary actuator according to the invention, Fig. 4: a representation of the evaluation unit by a logic gate, and Figs. 5-10: different circuits of the evaluation unit for exemplary representation of the states that can be detected with the evaluation unit.

[0049] Fig. 1A shows a side view of a driver's cab of a construction machine according to the state of the art. It can be seen that in the illustration, the safety lever 10 is set to a horizontal position, which prevents access to the driver's seat in the manner of a barrier. If an operator wishes to climb into the seat, they must first move the safety lever 10 to a vertical position, whereby, in the illustrated embodiment, the safety lever must be folded down.

[0050] Fig. 1B shows a view of the driver's cab in which the safety lever 10 is folded vertically downwards. Access to the seat is now free for the operator, or an operator sitting on the seat can now leave the driver's cab.

[0051] The safety lever ensures that the servo circuit for operating the construction machine is interrupted when the boom is lowered or raised from a horizontal position, preventing accidental operation of the construction machine when the operator leaves the cab. This contributes to improved safety of the construction machine, but can easily be bypassed by deliberate misoperation.

[0052] Fig. 2 shows the sensors required according to the device 1 according to the invention in a plan view of the driver's cab.

[0053] You can see a seat contact switch 2, a door lock switch 3, a handle sensor 4, a driving function switch 6, a belt buckle switch 7, a selector switch 8 and an emergency stop switch 9.

[0054] Each of the above-mentioned sensors is equipped with an evaluation unit (not included in Fig. 2 shown, but see reference numeral 5 in Figs. 3-10), which assumes different case constellations for the construction machine depending on the states of the several sensors and, depending on this, limits or prevents the capabilities of the construction machine.

[0055] Fig. 3 shows an implementation of the evaluation unit 5 using a logic gate, wherein the various sensors send binary signals for the presence or absence of the respective state to be detected via a signal line to the evaluation unit 5. It can be provided that the signal is transmitted to the evaluation unit 5 in binary form using a voltage level, e.g., + or - 5V.

[0056] It can also be seen that selector switch 8 can supply a logical 1 to a signal line for each of the different operating modes of the construction machine. For example, if the selector switch is switched to work mode, the corresponding line receives a logical 1. However, if the selector switch is switched to road mode, the corresponding signal line receives a logical 1. The same applies to parking mode.

[0057] The situation is very similar with the other sensors, where the presence of a detected state also leads to a defined signal state of an associated signal line.

[0058] Fig. 4 now shows an application case in which the selector switch 8 is switched to the working mode and the corresponding line is supplied with a logical 1.

[0059] Furthermore, the driver is working with the door open, as can be seen from the corresponding switching state of the door lock switch. An open door is represented by a logic 0. Furthermore, it can be seen that the driver is sitting in his seat and operating both the left and right control levers. Since working with the door open is not classified as a hazardous condition, the logic gate causes the servo circuit to operate normally.

[0060] Figure 5represents an application in which the operator of the construction machine inadvertently touches the left handle when getting out during work, which would result in movement of the construction machine, in particular the excavator. However, since a logical circuit for detecting an open seat contact switch, an actuated left control lever, an open door, an unactuated travel function switch, in particular an accelerator pedal switch, and an unactuated right handle is queried by inverter modules and AND modules, a state can be detected which suggests that the operator inadvertently actuated a left control lever when getting out. In such a case, the servo circuit is stopped immediately or with a slight time delay in order to prevent unintentional movement of the construction machine.

[0061] Fig. 6shows an application in which the operator of the construction machine activates the emergency stop button. This immediately stops the servo circuit, so that no further danger arises from the construction machine. The states of the other sensors are irrelevant, since the emergency stop button always leads to an immediate stop.

[0062] Fig. 7 This shows the state in which the selector switch is switched to road mode, but a control lever for operating the primary functions of the construction machine is still being controlled. However, since the excavator, for example, must not perform its excavator function in road mode, this results in the servo circuit being immediately stopped when road mode is selected. The same applies when parking mode is selected, as the servo circuit is immediately stopped here as well.

[0063] Fig. 8shows an application in which an operator is operating the construction machine while standing and the door is open at the same time. Operation of the construction machine is detected by actuating both the left and right control levers. If it is also detected that the door is open and the seat contact switch is not closed (i.e. the operator of the construction machine is not sitting in the seat), the logic arranged in the evaluation unit leads to the servo control being only possible to a limited extent. This can have an effect by reducing the uppercarriage speed of the construction machine or by reducing the maximum actuation speed of the attachments of the construction machine. Using the example of an excavator, for example, it can be specified that the excavator boom can only be moved at a reduced speed if the Figure 8 the condition shown has been recognized.

[0064] The implementation in the evaluation unit is carried out by connecting an AND gate with the signals from the sensors to be tested. In this case, these are the signals from the seat contact switch, the two control levers, and the door lock switch. Assuming that the seat contact switch outputs a logical 1 when an operator is seated in the seat, the door lock switch outputs a logical 1 when the door is closed, and a logical 1 is output when a respective control lever is operated, the two signal lines of the seat contact switch and the door lock switch must be inverted before being input to the AND gate. If the AND gate then outputs a logical 1, this results in the servo circuit being restricted in order to achieve, for example, the restrictions described above.

[0065] Fig. 9shows a further possibility in which the device according to the invention additionally has an additional sensor that checks whether a safety-critical function of the construction machine is being activated. A safety-critical function of the construction machine can be a function of the construction machine that has a particularly hazardous potential. Using an excavator as an example, such a function could be, for example, the deflection of the excavator arm beyond a certain angular range or something similar.

[0066] In such a case, due to the desired safety-critical function, the device may require the operator to sit in the seat and have both hands on the respective control levers. This reduces the likelihood of an accident, as the operator is forced to sit in the seat and have both hands on the control levers, at least for the purpose of performing the safety-critical function. However, it is still possible to perform other, non-safety-critical functions while standing, allowing the operator as much flexibility as possible to facilitate daily operation of the construction machine.

[0067] For this purpose, the evaluation unit can be equipped with an additional signal line, to which a logical 1 is sent when operation of a safety-critical function is desired. Together with the two signals from the control levers, the three signals are then connected with an AND gate, so that a logical 1 is only output when all three signals are logical 1. Only then is the safety-critical function enabled.

[0068] The definition of what exactly constitutes a safety-critical function of a construction machine is subject to a multitude of aspects and can even affect the general operation of the excavator boom. In such a case, two-handed operation is required, since operating the excavator boom with only one hand would prevent it from operating.

[0069] Fig. 10This example shows an application in which the travel speed of the construction machine is reduced to a speed greater than zero if the operator is not wearing their seat belt. For this purpose, the signal from the belt buckle switch is examined together with the signal from a signal set to road travel via the selector switch. If the selector switch provides the signal for road travel and the belt buckle switch indicates that the seat belt is not fastened, the speed may be limited to a value below the maximum speed of the construction machine (but above 0 km / h).

[0070] For this purpose, another signal is sent to the evaluation unit when the speed exceeds a predetermined threshold. For example, this could be when the speed exceeds 7 km / h, which would then send a signal with a logical 1 to the evaluation unit. These three signals are connected to an AND gate, so that the AND gate outputs a logical 1 if the belt is not fastened, the construction machine is in road mode, and the travel speed exceeds the predetermined threshold (e.g., 7 km / h).

[0071] This signal output by the AND gate then leads to the maximum travel speed of the construction machine being reduced, for example to the predetermined threshold value.

[0072] In other words, it checks whether the operator of the construction machine is wearing a seat belt. If they are not, the construction machine can only be operated at a reduced speed.

[0073] According to the invention, a device for monitoring and assisting an operator of a construction machine is created, which device can also be used, among other things, to replace the safety lever of a construction machine, in particular an excavator, by evaluating various sensors. List of reference symbols:

[0074] 1Monitoring and assisting device 2Seat contact switch 3Door lock switch 4Handle sensor 5Evaluation unit 6Drive function switch 7Seat belt buckle switch 8Selector switch 9Emergency stop switch 10Safety lever

Claims

1. Device (1) for monitoring and assisting an operator of a construction machine, comprising: a seat contact switch (2) for detecting whether an operator is sitting on a seat of the construction machine, a door lock switch (3) for detecting whether a door of a driver's cab of the construction machine is closed, a handle sensor (4) for detecting whether an operating lever arranged to the left of the seat and / or an operating lever arranged to the right of the seat for controlling a servo circuit of the construction machine is actuated by an operator, and an evaluation unit (5) which is designed to limit or stop a capability of the construction machine and / or to output a signal to signal a critical condition depending on the detected states of the seat contact switch (2), the door lock switch (3) and the handle sensor (4).

2. Device (1) according to the preceding claim, wherein the capability of the construction machine comprises a travel speed of the construction machine, a superstructure speed of the construction machine and / or the operation of the servo circuit of the construction machine.

3. Device (1) according to one of the preceding claims, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine when the seat contact switch (2) detects that the operator is not sitting on the seat of the construction machine, the door lock switch (3) detects that the door of the driver's cab is open and the handle sensor (4) detects that one or both control levers are actuated, preferably wherein the evaluation unit (5) is designed in such a case to limit a maximum superstructure speed of the construction machine.

4. Device (1) according to one of the preceding claims, wherein the evaluation unit (5) is designed to stop the servo circuit of the construction machine when the seat contact switch (2) detects that the operator is sitting on the seat of the construction machine, and the handle sensor (4) detects that neither of the two operating levers for actuating the servo circuit of the construction machine is actuated, preferably wherein the evaluation unit (5) is designed to implement the stopping of the servo circuit of the construction machine only after a certain period of time has elapsed in the state leading to the stopping, for example more than 3 seconds.

5. Device (1) according to one of the preceding claims, further comprising a driving function switch (6), in particular an accelerator pedal switch or a joystick, for detecting whether a driving function or an accelerator pedal of the construction machine is actuated, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine depending on the detected state of the driving function switch (6).

6. Device (1) according to the preceding claim 5, wherein the evaluation unit (5) is designed to limit the maximum travel speed of the construction machine when the seat contact switch (2) detects that the operator is not sitting on the seat of the construction machine, and the travel function switch (6) detects that a joystick controlling the travel functionality or an accelerator pedal of the construction machine is actuated, preferably wherein the evaluation unit (5) is designed to initially limit the maximum travel speed of the construction machine for a specific period of time and then to set it to zero.

7. Device (1) according to one of the preceding claims, further developed with claim 5, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine when the seat contact switch (2) detects that the operator is not sitting on the seat of the construction machine, the handle sensor (4) detects that only the left of the two control levers is actuated, and the travel function switch (6) detects that the accelerator pedal or the joystick is not actuated, preferably wherein the evaluation unit (5) is designed to limit or stop the servo circuit in such a case.

8. Device (1) according to one of the preceding claims, further comprising a belt buckle switch (7) for detecting whether a safety belt of the seat of the construction machine is locked with a belt buckle, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine also depending on the detected state of the belt buckle switch (7).

9. Device (1) according to one of the preceding claims, further comprising a selector switch (8) for detecting one of several possible operating modes of the construction machine, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine depending on the detected state of the selector switch (8), and the operating modes of the construction machine include a work mode, a parking mode and a road travel mode.

10. Device (1) according to one of the preceding claims 8 and 9, wherein the evaluation unit (5) is designed to limit or stop a capability of the construction machine when the selector switch (8) detects that the construction machine is in road travel mode and the belt buckle switch (7) detects that the safety belt of the seat of the construction machine is not locked with the belt buckle, preferably wherein the evaluation unit (5) is designed to reduce the maximum travel speed of the construction machine in such a case.

11. Device (1) according to one of the preceding claims, further comprising an emergency stop switch (9) for immediately deactivating the servo circuit of the construction machine.

12. Device (1) according to one of the preceding claims, wherein the evaluation unit (5) is implemented by a logic gate, wherein preferably the logic gate uses only the logical operations AND, OR, NOT, NAND, NOR, XOR and XNOR to check the different states.

13. Device (1) according to one of the preceding claims, wherein the evaluation unit (5) is designed to only enable safety-relevant operation of the construction machine when the handle switch detects that at least one of the two operating levers is actuated by the operator, and the seat contact switch (2) detects that the operator is sitting on the seat of the construction machine and / or the evaluation unit (5) is designed to only enable safety-relevant operation of the construction machine when the handle switch detects that both operating levers are actuated by the operator.

14. Device (1) according to one of the preceding claims, wherein the construction machine is an excavator, in particular a hydraulic excavator, and the servo circuit serves to implement the movements and operations of the excavator.

15. Construction machine, in particular hydraulic excavator, with a device (1) according to one of the preceding claims, preferably wherein the device (1) replaces the normally present safety lever of the construction machine.

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