Brake system and method for braking with variable brake force

Abstract

A braking system (3), in particular an emergency braking system, in a drive unit comprising at least one motor (8) and at least one unit (6) driven by the motor (8), the braking system comprising: a plurality of controllable brakes (16a-16d) arranged and designed to act on the drive unit; and a control unit (12) designed to pre-select and correspondingly pre-control a number of brakes (16a-16d) from the plurality of brakes (16a-16d) depending on the state or load situation of the drive unit, such that only the pre-selected number of brakes (16a-16d) can act on the drive unit when the brake system (3) is actuated.

Description

[0001] The invention relates to a brake system, in particular an emergency brake system, in a drive unit according to claim 1 .

[0002] The invention also relates, through claim 15 , to a crane or a container gantry crane or the like, which is equipped with a braking system according to the invention.

[0003] Furthermore, the invention relates to a method for braking with a variable braking force in a drive unit according to claim 16 .

[0004] Overdesigned brakes, especially but not exclusively on the transmission output side of the drive unit, can lead to immeasurable damage and failure of the drive system, especially the transmission and the steel structure. In cranes, for example, the brakes are overdesigned with respect to the actually required braking force in many travel situations due to the constantly changing moving loads and the associated travel speeds. A related reason is that for the design of the brakes, the maximum possible loads of the relevant system and the associated travel speeds are specified as conservative safety margins. As a result, the brakes are significantly overdesigned for many applications.

[0005] In the case of larger drive systems, such as those used in steel mill cranes or stacking cranes at container terminals, the main drive system consists of a motor, a gearbox and a rope drum on the gearbox output side (gearbox output side). In order to increase operational safety, such drive units are equipped with brakes on the motor and gearbox output side. For this purpose, the brake design is based on the crane mechanism data (such as the maximum permissible weight under the hook and / or the maximum permissible travel speed) and safety margins. In order to ensure safety in every operating situation, the design is based on the assumption of the worst possible operating situation, i.e., overspeed and simultaneous overload. However, since such load situations rarely or never occur in actual daily operation, the brakes are correspondingly overdesigned in most cases.

[0006] In the event of an emergency stop, all existing brakes are active or activated regardless of the current travel situation, and due to this overdesign, extremely high force and torque peaks can briefly act on the drive unit, in particular on the gearbox and gearbox components (e.g. gearbox gears), as well as on the structure to which the drive unit is fixed (e.g. the steel structure of the crane). This is further aggravated by the fact that, due to design reasons, the brakes for the rope drum or similar drive units (usually actuated by so-called disc springs) can be closed faster than the additional existing brakes on the fast-rotating motor side (usually actuated by spiral springs). Due to this situation, the entire drive train on the transmission output side is locked, while due to the mass inertia of the rotating drive elements (clutch, brake disc, motor shaft, etc.), forces continue to be disadvantageously introduced into the gearbox, which has been locked by the emergency stop brake.

[0007] Furthermore, excessive braking can create unaccountable force peaks in the (steel) load-bearing structure of the entire system, which can have a negative impact on the service life of the load-bearing structure.

[0008] The object of the present invention is to provide a remedy for this and to specify a braking system and a method for braking with variable braking force which avoid the disadvantages mentioned above and in this way help to protect the drive system and the individual components of the drive system together with the supporting structure that accommodates the drive system, so as to extend the service life of the system and reduce expensive maintenance work.

[0009] According to the invention, this object is achieved by a braking system having the features of claim 1 , by a crane or container gantry crane having the features of claim 15 , and by a method for braking with variable braking force having the features of claim 16 .

[0010] Advantageous developments of the system according to the invention are defined in the corresponding dependent claims.

[0011] According to the braking system in the drive unit of the present invention, in particular the emergency braking system, the drive unit includes at least one motor and at least one unit driven by the motor, and the braking system has: a plurality of controllable brakes, which are arranged and designed to act on the drive unit; and a control unit, which is designed to pre-select and pre-control a certain number of brakes from the plurality of brakes according to the state or load condition of the drive unit, so that when the braking system is actuated, only the pre-selected number of brakes can act on the drive unit.

[0012] According to the method for braking with variable braking force in a drive unit, the drive unit comprises at least one motor and at least one unit driven by the motor, the method comprising: a) providing a plurality of controllable brakes, the brakes being arranged and designed to act on the drive unit and thereby providing a corresponding braking system; b) determining a state or a load condition of the drive unit; and c) based on the determined state or load condition, preselecting a certain number of brakes from the plurality of brakes by means of a control unit, the preselection being performed by corresponding precontrol of the brakes so that, when the braking system is actuated, only the preselected number of brakes can act on the drive unit.

[0013] In order to prevent the occurrence of the described situations, the purpose of the brake system (or simply: system) described here is to detect or determine the load and / or travel speed in advance, in particular in a crane or hoist, and to adjust the braking force in advance according to the situation by preselecting the brake to be closed or activated in an emergency situation. As a result, force and torque peaks can be reduced, in particular in the gearbox, and also on the surrounding support structure, in particular on the surrounding support structure of the crane or hoist.

[0014] The basic idea of ​​the braking system or method according to the invention is to prevent excessive braking by preselecting the brake and / or the braking force. This is achieved by switching the brake on or off during the preselection. The corresponding control of the brake can advantageously be carried out by a dedicated control unit of the braking system that is specifically provided for this purpose. However, as an alternative, the brake can also be controlled directly by a control unit of the drive unit that is usually already present, in particular a control unit of a crane or a hoist. In both cases, the effect on the drive unit or the crane or the hoist is the same: braking with an appropriate braking force according to the determined state or load situation, for example a given load and / or (travel) speed.

[0015] The same applies to the load measuring pin, which will be described in more detail below and represents a possible design for determining the state or load situation. For a pure functional principle, the load measuring pin can be provided, for example, by the crane manufacturer or the winch manufacturer; the dedicated control unit then only uses the corresponding signal in order to make a decision with regard to the preselection. As an alternative, the crane or winch control unit itself can also be designed to make a decision with regard to the preselection of the brake configuration.

[0016] Within the scope of the invention, the decision or the preselection with regard to the brake configuration is also made by predefining different load situations. For example, the predefined "load situation 1" can include a crane with a high travel speed and a very small load in the "no load" travel mode. In contrast, the predefined "load situation 2" can include a medium load and a medium travel speed ("medium load" travel mode). In this case, for example, the use of a sensor unit (such as a load measuring bolt) is no longer absolutely necessary for determining the state, because the preselection of the travel situation or the state or the load situation by the relevant signal "crane / hoist is in travel mode X" can already be used to preselect the brake. Here, the intended effect of the described brake system, namely braking with a braking force adapted to the load situation, is also achieved in an advantageous manner.

[0017] A first improvement of the braking system according to the invention comprises a sensor device, which is designed to determine the state or load condition of the drive unit, the sensor device having at least one associated sensor unit, which provides a corresponding sensor signal; wherein the control unit is operatively connected to the sensor unit via signal technology and can determine the load condition of the drive unit based on the sensor signal or each of the sensor signals.

[0018] A corresponding improvement of the method according to the invention provides that, by means of a sensor device having at least one associated sensor unit providing a corresponding sensor signal, the state or load condition is determined based on the sensor signal or each of the sensor signals, for which purpose the control unit is operatively connected to the sensor unit via signal technology.

[0019] Here, the preselection is preferably done by interaction between a load measuring pin (or similar (sensor) device for detecting a moving load), an encoder (or similar (sensor) device for monitoring a rotation or travel speed) and a logic controller or control unit, which acquires the measurement data of the device for detecting a load or monitoring a rotation / travel speed. As already mentioned, the control unit can be a dedicated control unit for the brake system or a control unit that is usually already present in a drive unit (e.g. a crane or a winch).

[0020] The encoder does not have to be a dedicated component of the brake system but may also already be provided by the crane / hoist manufacturer.

[0021] If, as will be described in more detail below, a self-locking valve is used for the preselection of the brake, it retains its position (setting) even in the event of a power failure, such as occurs, for example, in a "normal" emergency shutdown situation. However, in a corresponding development of the invention, it is also possible to provide an uninterruptible power supply ("USV" for short - in principle a battery which can continue to supply power to selected components for a certain period of time) in conjunction with the encoder and the control unit in order to monitor (unwanted) movements of the drive unit and, if necessary, subsequently switch on or off further brakes, for example, when a set braking value is exceeded / undershot. In the previously described design, this is also possible when the power supply is interrupted by an emergency shutdown operation.

[0022] The control unit advantageously precontrols valves or the like based on the aforementioned physically detected values ​​(force and / or speed), which predefine the number and intensity of emergency brakes depending on the load situation.

[0023] In a corresponding embodiment of the invention, a special feature of this valve is that it does not change its predefined position even in the event of a power failure or when the emergency stop switch is pressed, in order to avoid excessive braking by closing all brakes (which may be unnecessary in given situations).

[0024] Here, the encoder or the like advantageously helps to detect the actual movement within the drive system in the sense of a redundant system. By comparing the expected and actual values ​​in the control unit, a control signal can be output if necessary, which causes an additional valve to open, so that in an emergency situation, an additional brake can be closed and a potentially catastrophic load loss can be avoided. The proposed system structure can thus meet the requirements for an autonomous system in an appropriate design.

[0025] In practice, the following embodiments or developments of the brake system according to the invention have proven to be particularly advantageous: In a first embodiment of the braking system according to the invention, it is provided that the drive unit has a gearbox which is operatively connected to the motor, and that the output unit, for example a cable drum, is arranged on the output side of the gearbox. Such a gearbox enables the rotational movement of the motor to be transmitted to the output unit with a defined acceleration or reduction ratio, which significantly expands the possible range of applications of the system according to the invention.

[0026] According to another embodiment of the brake system according to the invention, the brake is designed and arranged to act on the output unit. In this way, the output unit can be braked in a targeted and direct manner in an emergency situation. However, it is within the scope of the invention to design or arrange the brake to act also or even only on the motor.

[0027] A particularly advantageous development of the brake system according to the invention provides that the preselected number of brakes comprises at least one brake, a group of all brakes or all brakes. In this way, the brakes can be gradually adapted to the actual operating situation by corresponding combinations of the individual brakes. For example, if two brakes are present, the brakes can be used individually or in combination with one another.

[0028] In practice, it has proven to be particularly advantageous if, in a corresponding development of the brake system according to the invention, the determined state of the drive system includes at least one of the following variables: the state of the motor, in particular the rotational speed of the motor; the speed of the output unit, in particular the rotational or travel speed; and / or a load acting on the output unit or being delivered by the output unit. In this way, the actual operating situation can be determined particularly well and reliably.

[0029] It has already been pointed out that in a special development of the system according to the invention, the sensor unit is in the form of an encoder arranged on the motor, on the output unit and / or on the gearbox and / or the sensor unit is in the form of a load measuring pin. These devices have proven in practice to be particularly reliable and economical to use.

[0030] In a special development of the braking system according to the invention, it can be provided that the output unit is a rope winch or rope drum with a rope wound or capable of being wound thereon. Such rope winches or rope drums are used in particular in cranes or container gantry cranes, which are a preferred application of the braking system according to the invention.

[0031] In a corresponding development of the brake system according to the invention, it can also be provided that the above-mentioned load measuring bolt is operatively connected to the same above-mentioned rope. In this way, in particular in cranes, container gantry cranes or similar installations, moving loads can be reliably determined.

[0032] A particularly advantageous development of the brake system according to the invention provides that at least one of the brakes is in the form of a hydraulically or pneumatically actuated brake, preferably in the form of a spring-actuated, hydraulically or pneumatically released brake. Such a brake is particularly well suited for implementing the brake system according to the invention or the method according to the invention.

[0033] Therefore, in a corresponding improvement of the brake system according to the invention, it can be provided that the at least one brake comprises at least one locking valve mechanism or a switching valve with a locking function. As mentioned above, such a valve mechanism is characterized in that, for example, when a power failure occurs or an emergency shutdown switch is actuated, the valve mechanism can also maintain a preselected or precontrolled state.

[0034] In another embodiment of the brake system according to the invention, it is also possible to use the blocking valve to select a dual circuit from the respective brake to the (hydraulic oil) tank. When circuit 1 is selected, the brake is closed immediately. When circuit 2 is selected, a throttle valve or orifice can be used for delayed closing.

[0035] It is not important for the system according to the invention whether the brakes are completely removed from the braking process, i.e. deactivated, or whether they are activated only at the end of the actual (emergency) stopping process due to a throttled oil return flow. This is because, independently of whether the brakes are not activated at all or only activate with a delay, depending on the load situation or the actual driving situation, only the braking force preselected accordingly is introduced into the transmission and drive train.

[0036] A particularly advantageous development of the brake system according to the invention can also provide that the valve mechanism or the switching valve is pre-controlled or can be pre-controlled by the control unit. The advantages associated with this have already been pointed out in detail above. As mentioned above, the pre-control can be carried out selectively by a dedicated control unit for the brake system or by an already existing winch or crane controller.

[0037] In practice, a further development of the brake system according to the invention has proven to be particularly advantageous, in which the valve element or the switching valve is a 2 / 2-way directional valve, preferably a 2 / 2-way seat valve.

[0038] In order to be able to reflect as many different operating situations as possible with the brake system according to the invention, another advantageous development also provides that at least some of the brakes are designed to generate different contact pressures or braking forces. In this way, gradually changing braking forces can be achieved by a clever combination of different brakes, which can be adapted to the respective operating situation.

[0039] Further features and advantages of the present invention emerge from the following description of exemplary embodiments with reference to the attached drawings.

[0040] Figure 1 A schematic general view of a crane having a braking system according to the invention is shown; Figure 2 Show Figure 1 Detailed views of the various components of the braking system in FIG. Figure 3 An alternative embodiment of the brake system according to the invention is shown.

[0041] The same reference numerals in all the figures denote identical elements or elements which at least act in the same manner.

[0042] exist Figure 1 Schematically shows a crane 1 with a load 2, which has a braking system 3 according to the invention, which is Figure 1 The rectangle drawn with dotted lines in the figure is a schematic representation.

[0043] exist Figure 1 In the upper part of the drawing, a crane 1 is schematically shown in a simplified manner together with a load 2. The crane 1 has a load-bearing structure 4, which is preferably made of steel or a similar material. The load 2 is suspended on a rope 5, which can be connected to a rope drum 6 (see FIG. Figure 1 The lower part of the load 2 can be wound and unwound so as to raise or lower the load 2.

[0044] according to Figure 1 In the lower illustration, the load 2 can also be suspended on more than one rope 5, without the invention being limited in this respect. The rope 5 or each rope 5 (respectively) is operatively connected to a load measuring pin 7, the function of which will be described in detail below.

[0045] In order to drive the cable drum 6, which represents the output unit in the context of the present invention, a motor 8 is provided, which acts on the cable drum 6 via a gearbox 9. Between the motor 8 and the drive 9 on the output side of the motor 8, a (maintenance) brake 10 is provided, by means of which the drive movement of the motor 8 can be braked in maintenance situations and also in emergency situations.

[0046] Reference numeral 11 denotes an encoder device having two encoders 11a, 11b which are designed and arranged to detect the state of the drive unit, here the rotational speed of the motor 8 or the gearbox 9, and to output corresponding sensor signals or measurement signals MS1, MS2. These measurement signals are transmitted to a programmable, dedicated control unit of the brake system, which is designated by reference numeral 12 and is operatively connected to the encoders 11a, 11b in terms of signal technology. The control unit 12 is, for its part, operatively connected to an additional, usually present crane control unit 13 in terms of signal technology, which in the embodiment described here is intended only for controlling other functions of the crane 1 than the brake system 3 described here.

[0047] However, it has already been pointed out that in an alternative embodiment the crane control unit 13 can be assigned a role similar to the control unit 12 , so that the control unit 12 can in principle be omitted.

[0048] The control unit 12 is in signaling interaction with the already mentioned load measuring pin (LMB) 7 via an analog input module 14 (A / D converter) or respectively via a safety relay 15. The measuring pin preferably outputs a signal between 4 and 20 mA, the measuring range (range of possible loads) being definable in the hoisting mechanism data of the crane 1. In this way, in addition to the above-mentioned measuring signals MS1, MS2 from the motor 8 and the gearbox 9, the control unit 12 also receives further measuring or sensor signals MS3, MS4 from the load measuring pin 7, which are likewise used to determine the current operating state of the drive unit.

[0049] In principle, the signal cable of the load measuring pin may be damaged and measurement errors may occur. Therefore, the load measuring pin 7 preferably has two output channels. The two output signals of the load measuring pin 7 are fed separately, one directly into the input module 14 and one into the input module 14 via the associated safety relay 15. The consistency of the signals is then checked. If the signals are consistent, everything is OK, if not, an error report is issued.

[0050] Such a safety relay 15 may also be provided in order to achieve certain safety standards (eg SIL II or SIL III).

[0051] However, the provision of neither the safety relay 15 nor the load measuring pin 7 is absolutely necessary for the technical functioning of the brake system according to the invention.

[0052] In the above arrangement, the encoders 11a, 11b together with the load measuring pin 7 form a sensor device, which is designed to determine the state of the drive unit. The sensor device has at least one related sensor unit (here the encoder and the load measuring pin), and the sensor unit provides corresponding sensor signals (here the measurement signal) to the control unit 12.

[0053] In the illustrated embodiment of the brake system 3 according to the invention, two emergency brakes 16a, 16b are arranged on the cable drum 6, which emergency brakes preferably have different strengths, that is, they are designed to generate braking forces of different strengths on the cable drum 6. The two emergency brakes 16a, 16b are in the form of hydraulic release brakes and are operatively connected to a hydraulic pressure unit (hydraulic device) 18 via a valve mechanism or a switching valve, each configured as a 2 / 2-way seat valve 17. Here, the valve 17 has a blocking function, which can be pre-controlled by the control unit 12 with a corresponding control signal SS (electrically), so that when the brake system 3 or the emergency brakes 16a, 16b are actuated, these brakes are actuated only according to the pre-control performed by the control unit 12. This can include selectively actuating only one of the two emergency brakes 16a, 16b. However, as an alternative, the pre-control can also be used to ensure that both emergency brakes 16a, 16b are actuated simultaneously in order to achieve a stronger braking effect. In this case the invention is not limited to a specific number of emergency brakes.

[0054] As an alternative, the brakes can also be designed as pneumatic release brakes, which are then operatively connected to the pneumatic pressure unit accordingly. In principle, such brakes and their control are known to those skilled in the art.

[0055] The already mentioned precontrol of the emergency brakes 16a, 16b by the control unit 12 is carried out as a function of the measurement signals MS1 to MS4, which indicate the operating state of the crane 1 in relation to the load 2, i.e. the weight and the movement state of the load. In this way, in particular when large loads 2 are moved at high speeds, the braking effect can be increased in a targeted manner. In contrast, when only small loads 2 are present or when the loads 2 are moved only at low speeds, the braking effect can be reduced in a targeted manner. In this way, despite achieving adequate safety in an emergency, in particular damaging effects on the load-bearing structure 4 of the crane 1 can be reduced.

[0056] The control unit 12 is operatively connected to at least one sensor unit or the sensor units shown (reference numerals 7, 11a, 11b) in terms of signal technology and is designed to preselect and correspondingly precontrol a certain number of brakes from the plurality of brakes 16a, 16b based on the relevant sensor signal or the respective relevant sensor signal, so that when the brake system 3 is actuated, only the preselected number of brakes 16a, 16b can act on the drive unit.

[0057] In particular, encoders 11a, 11b are used here to monitor the braking effect. If the actual braking effect deviates from the value set by the control unit 12, the control unit 12 can respond by presetting the blocking valve 17 in order to adjust the braking force. The more different emergency brakes 16a, 16b there are, the more refined the variation of the braking force can be.

[0058] The invention is not limited in this case to the use of hydraulic release brakes; in principle any other type of controllable brake, in particular a pneumatic release brake, can also be used.

[0059] according to Figure 1 , the precontrol of the emergency brakes 16a, 16b is performed only on the output side of the gearbox 9, and not on the output side of the motor 8 as in the (maintenance) brake 10 mentioned above. This design has proven to be particularly advantageous from the applicant's point of view. However, the present invention also includes such a design in principle, in which, as an alternative or in addition, a motor-side brake corresponding to the brake 10 can be included in the precontrol. For this purpose, it is only necessary in principle to adopt a controllable form for the corresponding brake and to connect it to the control unit 12 in a suitable manner in terms of signal technology. However, this point will not be explained further here and below.

[0060] exist Figure 2 The details are shown in Figure 1 3. These are the rope drum 6 and the emergency brakes 16a, 16b together with the associated valves 17 and the hydraulic device 18, but the specific design of the hydraulic device is not further explained here. It should only be pointed out here that the hydraulic device 18 can also include at least one 2 / 2-way seat valve, which is responsible for returning the hydraulic oil to a tank (not shown) provided for this purpose. However, this valve is usually not controlled by the control unit 12, but by a special unit (also not shown).

[0061] exist Figure 2 The valve 17 mentioned above is shown in detail in its preferred embodiment as a 2 / 2-way seat valve with a blocking function.

[0062] As already mentioned, the emergency brakes 16a, 16b are preferably spring-actuated, hydraulically released brakes on the rope drum 6, which are arranged on the gearbox output side. These brakes 16a, 16b preferably have different pressing forces or braking forces X, Y, which has also been pointed out above. The brakes are applied via the control unit 12 (see Figure 1 ) is preselected. In this way, a total of three different braking forces can be achieved with two brakes: only one brake with braking force X; only the other brake with braking force Y; or both brakes with braking force X+Y.

[0063] Redundant design of the brake system is also possible, according to the following Figure 3 Explain this design in more detail.

[0064] In principle, the choice of the hydraulic device 18 used has no influence on the system according to the invention itself. In principle, the invention can be implemented with any (commercially available) hydraulic device. Figure 2 It is only shown as a dashed rectangle or a black frame.

[0065] The controllable, in particular lockable, valve 18 is controlled according to Figure 1 and Figure 2 The illustration of the valves is connected between the corresponding emergency brake 16a, 16b and the associated hydraulic oil supply or discharge pipe 18a, 18b and is therefore usually not a component of the hydraulic device 18 itself. However, as an alternative, these valves can also be arranged on the hydraulic device 18 or even in the hydraulic device 18.

[0066] However, it is generally applicable that the valve 17 is controlled by the control unit 12 (see Figure 1 ) is directly controlled and acts independently of any control instructions from a control unit (not shown) of the hydraulic device 18.

[0067] Finally, in Figure 3, a redundant design of a braking system 3 according to the invention is partially shown in the figure, in which a total of four hydraulic, i.e. also spring-actuated and hydraulically released, emergency brakes 16a to 16d are provided, of which two (16a, 16c or 16b, 16d) each apply the same braking force X or Y. With such a system, the following braking forces can preferably be achieved: when only the brake with braking force X is actuated, the total braking force is 2X; when only the brake with braking force Y is actuated, the total braking force is 2Y; when all brakes with braking force X and braking force Y are actuated, the total braking force is 2X+2Y. In principle, in this embodiment, it is also possible to actuate only one brake with braking force X, only one brake with braking force Y or also to activate multiple brakes with braking forces X+Y, 2X+Y or X+2Y. In practice, however, this is highly impractical, since this would result in a significant asymmetry in braking. According to Figure 3 The brake system 3 accordingly also comprises two rope drums 6a, 6b, which are driven by two motors 8a, 8b via a common gearbox 9. Figure 1 , a (maintenance) brake 10a, 10b is respectively arranged between each of the motors 8a, 8b and the gearbox 9, but in the illustrated design, the brakes 10a, 10b are not pre-controlled. Brakes 16a and 16b act on the rope drum 6a, while brakes 16c and 16d act on the rope drum 6b.

[0068] The possible application scenarios of the present invention include Figure 1 The crane shown in the figure is also a so-called container gantry crane, for example, in which two rope drums (see Figure 3 Each rope drum 6a, 6b is then equipped with its own hydraulic brake 16a, 16b and 16c, 16d, respectively, as shown.

Claims

1. A braking system (3), in particular an emergency braking system, in a drive unit, the drive unit comprising at least one motor (8; 8a, 8b) and at least one unit (6; 6a, 6b) driven by the motor (8; 8a, 8b), the braking system comprising: a plurality of controllable brakes (16a-16d) arranged and designed to act on the drive unit; A control unit (12) is designed to preselect and correspondingly precontrol a certain number of brakes (16a-16d) from the plurality of brakes (16a-16d) according to the state or load condition of the drive unit, so that when the brake system (3) is actuated, only the preselected number of brakes (16a-16d) can act on the drive unit.

2. The brake system (3) according to claim 1, comprising a sensor device, which is designed to determine the state or load condition of the drive unit, and has at least one associated sensor unit (7; 11a, 11b) which provides corresponding sensor signals (MS1-MS4); wherein: The control unit (12) is operatively connected to the sensor unit (7; 11a, 11b) via signal technology and can determine the load condition of the drive unit based on the sensor signal or the individual sensor signals (MS1-MS4).

3. The braking system (3) according to claim 1 or 2, wherein: The drive unit has a gearbox (9) operatively connected to the motor (8; 8a, 8b), and the driven unit (6; 6a, 6b) is arranged on the output side of the gearbox (9).

4. The brake system (3) according to any one of claims 1 to 3, wherein: The brake (16a-16d) is designed and arranged to act on a driven unit (6; 6a, 6b).

5. The brake system (3) according to any one of claims 1 to 4, wherein: The preselected number includes at least one brake (16a-16d), a group of all brakes (16a-16d) or all brakes (16a-16d).

6. The brake system (3) according to any one of claims 1 to 5, wherein: The determined state of the drive system comprises at least one of the following variables: the state of the motor (8; 8a, 8b), in particular the rotational speed of the motor (8; 8a, 8b), the speed of the driven unit (6; 6a, 6b), in particular the driving speed, and / or a load (2) acting on the driven unit (6; 6a, 6b) or transmitted by the driven unit (6; 6a, 6b).

7. The brake system (3) according to any one of claims 3 to 6, when referring to claim 2, wherein: The sensor unit is in the form of an encoder (11a, 11b) arranged on the motor (8; 8a, 8b), on the driven unit (6; 6a, 6b), and / or when referring to claim 3, the sensor unit is in the form of an encoder (11a, 11b) arranged on the gearbox (9), and / or, in the brake system (3), the sensor unit is in the form of a load measuring pin (7).

8. The brake system (3) according to any one of claims 1 to 7, wherein: The driven unit is in the form of a rope winch or rope drum (6; 6a, 6b) with a rope (5) wound or capable of being wound thereon.

9. Braking system (3) according to claims 7 and 8, wherein: The load measuring pin (7) is operatively connected to the rope (5).

10. The brake system (3) according to any one of claims 1 to 9, wherein: At least one of the brakes (16a-16d) is in the form of a hydraulically actuated brake (16a-16d), preferably a spring actuated, hydraulically released brake (16a-16d).

11. The brake system (3) according to claim 10, wherein: The at least one brake (16a-16d) comprises at least one locking valve mechanism or a switching valve (17) having a locking function.

12. The brake system (3) according to claim 11, wherein: The valve device or the switching valve (17) is pilot-controlled or can be pilot-controlled by the control unit (12).

13. The brake system (3) according to claim 11 or 12, wherein: The valve mechanism or the switch valve (17) is a 2 / 2-way directional valve, preferably a 2 / 2-way seat valve.

14. The brake system (3) according to any one of claims 1 to 13, wherein: At least some of the brakes (16a-16d) are designed to generate different pressing or braking forces (X, Y).

15. A crane (1) or a container gantry crane having a braking system (3) according to any one of the preceding claims.

16. A method for braking with variable braking force in a drive unit, the drive unit comprising at least one motor (8; 8a, 8b) and at least one actuator (8; 8a, 8b) driven unit (6; 6a, 6b), the method comprising: a) providing a braking system (3), the braking system (3) having a plurality of controllable brakes (16a-16d), the brakes being arranged and designed to act on the drive unit; b) determining the state or load condition of the drive unit; c) preselecting a certain number of brakes (16a-16d) from the plurality of brakes (16a-16d) by means of a control unit (12) in accordance with the determined state or load condition, the preselection being performed by corresponding precontrol of the brakes (16a-16d) so that, when the brake system (3) is actuated, only the preselected number of brakes (16a-16d) can act on the drive unit.

17. The method according to claim 16, wherein: The state or load condition is determined by means of a sensor arrangement having at least one associated sensor unit (7; 11a, 11b) which provides a corresponding sensor signal (MS1-MS4), the control unit (12) being operatively connected to the sensor unit (7; 11a, 11b) via signal technology for this purpose, based on the sensor signal or each of the sensor signals (MS1-MS4).

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