Method for monitoring a chain crane

Abstract

The invention relates to a method for monitoring a chain crane (1) having an electric drive motor (2) which is connected on the output side to a transmission device (7) via a friction clutch (14), the speed of the transmission device (7) being sensed via a sensor (18), and comparing the sensed speed of the transmission device (7) with the operating speed of the drive motor (2) using a control device (19). In order to achieve a safe and efficient operation of the chain crane (1), the control device (19) is also used to determine the vertical position (PLAM) of the load handling device (21) of the chain crane (1). The invention also relates to a chain crane (1) having a control device (19) which is designed and configured to carry out the method according to the invention.

Description

[0001] The invention relates to a method for monitoring a chain hoist according to the preamble of claim 1 , and a chain hoist according to the preamble of claim 8 .

[0002] A chain hoist of this type comprises an electric drive motor, a transmission device and a friction clutch functionally arranged between the drive motor and the transmission device. The aforementioned components of the chain hoist are usually arranged in a drive housing. A chain hoist of this type also has a chain and a load handling device suspended via the chain. The load handling device can be raised and lowered by moving the chain over at least one sprocket tooth arranged on the output shaft of the transmission device. The corresponding control commands are usually given by an operator via a control switch and transmitted from the control switch to the control device of the chain hoist.

[0003] It is known that chain hoists of this type are equipped with one or more limit switches. The limit switches are used to enable a control command transmitted to the control device to be overwritten with a corresponding signal, in particular a signal directed to the control device. In the event of a normal functioning of the limit switch, the signal of the limit switch and the resulting intervention of the control device can be used to stop the drive motor of the chain hoist, for example even if a control command for raising or lowering has already been transmitted to the control device.

[0004] The friction clutch of a chain hoist is primarily used to prevent overloads and the resulting damage to the drive motor, transmission and chain. For example, the friction clutch slips when lifting too heavy a load. Slippage can also be caused by the load handling device hitting the drive housing or hitting the end stop at one end of the chain when the chain is fully extended. However, slippage can also occur if the friction clutch is set too sensitively.

[0005] By providing an upper limit switch, the load handling device can be prevented from hitting the drive housing. By providing a lower limit switch, the chain can be prevented from being fully extended and being blocked by the end stop. However, if one of the limit switches is defective, the drive motor is not stopped in time and the friction clutch slips when the load handling device hits the drive housing or when it hits the end stop.

[0006] Although the slipping of the friction clutch is intended to prevent the chain from being overloaded (known as clutch slip), the chain may become overloaded and even break, depending on the cause of the clutch slip and the frequency of the clutch slip caused thereby. This is particularly the case if the load handling device repeatedly strikes the drive housing due to a defective upper limit switch or if the load handling device repeatedly strikes the end stop due to a defective lower limit switch.

[0007] EP 1 510 498 B1 discloses a method for monitoring a chain hoist, with which the control device of the chain hoist can detect the deviation of the actual speed of the transmission device from the target speed of the drive motor and thus detect the slip of the friction clutch. However, this method cannot determine the cause of the clutch slip.

[0008] From DE 199 56 265 A1 and DE 195 12 103 A1 methods are known for monitoring the operation of a cable winch, in particular with regard to the number of turns of the cable wound on the winch.

[0009] DE 10 2015 105 517 A1 discloses a cable retraction and deployment device for aviation applications and a method for controlling the device, wherein the end position of the cable can be detected using sensors.

[0010] The invention is therefore based on the object of providing a method for monitoring a chain hoist and of providing a chain hoist which enables a safe and efficient operation of the chain hoist.

[0011] This object is achieved by a method having the features according to claim 1 and a chain hoist having the features according to claim 8. Advantageous embodiments of the invention are given in the dependent claims and in the following description.

[0012] According to the invention, in a method for monitoring a chain hoist having an electric drive motor, which is connected on the output side via a friction clutch to a transmission device, the speed of the transmission device is sensed via a sensor and the sensed speed of the transmission device is compared with the operating speed of the drive motor using a control device, thereby achieving a safe and efficient operation of the chain hoist in that the vertical position of a load handling device of the chain hoist is also determined using the control device.

[0013] In other words, the method according to the invention determines the vertical position of the load handling device in addition to the comparison between the sensed transport speed and the motor operating speed.

[0014] For example, a load handling device designed as a load hook is suspended on the chain of a chain hoist. The chain can be arranged in a single-leg configuration or in a multi-leg configuration, so that the load handling device is attached to the free end of the chain (single-leg) or the chain is deflected by the load handling device designed as a bottom block (multi-leg). The chain can be moved via at least one sprocket, which is fixedly mounted on the output shaft of the transmission device. The rotational movement of the at least one sprocket is transmitted to the chain via a rigid connection to the chain, thereby raising or lowering the load handling device depending on the direction of rotation. For this purpose, the rotational movement of the electric drive motor is transmitted to the at least one sprocket, wherein the torque is converted via the transmission device functionally arranged between them.

[0015] Corresponding control commands for lifting and lowering are preferably transmitted from the control switch of the chain hoist to the control device and from the control device to the drive motor. During lifting and lowering of the load handling device, the vertical position of the load handling device changes. The vertical position of the load handling device can be changed via the control commands transmitted to the drive motor.

[0016] In the case where the load handling device is not raised or lowered, the vertical position of the load handling device remains unchanged. Only small changes in the vertical position of the load handling device, which are caused, for example, by vibrations of the load handling device and are considered negligible within the scope of the invention, are then possible.

[0017] The vertical position of the load handling device may be a position between an upper end position and a lower end position arranged below the upper end position. The upper end position is the position of the maximum possible lifting height, which is limited mechanically, for example, by the load handling device striking the drive housing of the chain hoist. The upper end position must be distinguished from the vertical position specified by the upper limit switch. The lower end position is the position of the maximum possible lowering depth, which is also limited mechanically, for example by an end stop, when the load handling device is fully lowered. The lower end position must be distinguished from the vertical position specified by the lower limit switch.

[0018] In the case of normal operation of the chain hoist, at least one limit switch arranged on the chain hoist indicates when the vertical position of the load handling device corresponds to the vertical position specified by the limit switch. Based on this indication, the control device can intervene in the control process of the chain hoist and, for example, overwrite the control command transmitted from the control switch to the control device.

[0019] The vertical position of the load handling device determined according to the method of the invention can be compared by the control device with known vertical positions stored, for example, in a memory unit of the control device. The known vertical position is in particular a lower end position and / or an upper end position and / or a vertical position specified by at least one limit switch. The determined vertical position is preferably the current vertical position of the load handling device. The determined vertical position of the load handling device can alternatively or additionally be stored in a memory unit of the control device. By storing data in this way, in particular at least one determined vertical position can be used for a subsequent evaluation.

[0020] The sensor arranged on the chain hoist preferably senses the speed of a single shaft of the transmission device, so that the speed of the transmission device or the transmission speed is understood to mean the speed of a single shaft of the transmission device. Alternatively, the sensor can also sense the speed of a single gear in the transmission device. The sensor transmits its sensed speed to the control device via a sensor signal. The sensor signal can be stored in the form of sensor data in a memory unit of the control device.

[0021] The operating speed of the drive motor and / or the motor operating speed is preferably determined by operating data of the drive motor. These data can be stored in a memory unit of the control device for different operating states of the chain hoist.

[0022] By comparing the sensed transmission speed with the motor operating speed, a speed deviation or speed difference can be determined. This enables the control device to detect clutch slip of a friction clutch which is functionally arranged between the drive motor and the transmission, in particular between the motor shaft and the input shaft of the transmission. Depending on which shaft or gear of the transmission the speed is sensed, the gear ratio of the transmission has to be taken into account when determining the deviation. Preferably, the occurrence of clutch slip is stored in a memory unit. It is also possible to generate an error message.

[0023] Due to the functional design of the chain hoist, in particular because the load handling device is connected to the output shaft of the transmission (also referred to as the transmission output shaft) via a chain and at least one sprocket, the force or change in force acting on the chain has an effect on the torque applied to the input shaft of the transmission. Thus, the force on the chain changes the torque applied to the input shaft of the transmission (also referred to as the transmission input shaft); this also changes the torque acting on the transmission part of the friction clutch. When the applied torque exceeds the maximum torque that the friction clutch can transmit and to which the friction clutch is adjusted, the friction clutch slips.

[0024] Typically, the maximum transmittable torque corresponds to a value corresponding to the nominal load of the chain hoist. When lifting an excessively heavy load, i.e. a load exceeding the nominal load, the friction clutch adjusted in this way slips. When the friction clutch is set too sensitively, i.e. to a maximum transmittable torque below a value corresponding to the nominal load of the chain hoist, slipping may occur even at a load below the nominal load.

[0025] Clutch slippage caused by one of the foregoing two causes is less critical with respect to preventing chain breakage than clutch slippage caused by the causes described below, and can therefore be tolerated at a relatively higher frequency of occurrence.

[0026] The cause of slippage can also be the impact of the load handling device against the drive housing or against the end stop. Both causes can be traced back to a defective upper limit switch or a defective lower limit switch. The lifting or lowering movement of the load handling device is stopped abruptly by the load handling device hitting the drive housing or by hitting the end stop, while the drive motor continues to run. Due to the resulting high loads on the chain, in particular due to the high tensions acting on the chain, and in particular due to the frequent occurrence of such high loads, the chain can become overloaded and even break.

[0027] With the method according to the invention, not only the clutch slip itself can be determined, but also the vertical position of the load handling device at the time of the clutch slip. Thus, if the control device detects clutch slip based on the sensor signal and the determined vertical position of the load handling device can be assigned to the upper end position or the lower end position, it can be concluded, for example, that the corresponding upper limit switch or lower limit switch is defective. However, if the vertical position of the load handling device determined in the event of clutch slip cannot be assigned to a vertical position stored in the memory unit of the control device, the control device can conclude that the clutch slip is due to another reason, such as an excessive load on the load handling device.

[0028] This allows the cause of the clutch slip to be determined and attributed to the clutch slip. Thus, with the method according to the invention, a clutch slip caused by an excessive load on the load handling device and a clutch slip caused by a defective limit switch can be distinguished. It can therefore also be provided that the error message that is optionally generated varies depending on the cause.

[0029] The method according to the invention can thus be used to diagnose failures of limit switches and at least reduce the proportion of chain breaks which can be attributed to defective limit switches. This enables safe operation of the chain hoist. Furthermore, the use of the method according to the invention does not adversely affect the production costs required for the chain hoist, since, in contrast to the chain hoist known from EP 1 510 498 B1, no additional hardware is required.

[0030] In a first embodiment, the vertical position of the load handling device is determined based on a sensor signal from a sensor.

[0031] In addition to the speed of the transport device, the vertical position of the load handling device is determined using the sensor signal. The sensor signal is received and evaluated by the control device. Preferably, the sensor signal is stored in a memory unit of the control device. In the case where the sensor is designed accordingly, the vertical position of the load handling device can be determined solely based on the sensor signal.

[0032] In a first embodiment, it is particularly advantageous if the direction of rotation of the transport device is sensed based on the sensor signal and the vertical position of the load handling device is determined by “counting up” and “counting down” the sensor signal.

[0033] The rotation direction of a transmission device associated with raising or lowering a load handling device is detected in order to determine whether the sensor signals need to be counted up or down, i.e. whether the sensor signals need to be added or subtracted. Preferably, the rotation direction of each shaft of the transmission device is detected. Alternatively, the rotation direction of a single gear of the transmission device may be detected.

[0034] The starting point for the upward and downward counting, i.e. the initial vertical position of the load handling device, can be specified, for example, when the chain hoist is put into operation. It can also be provided that a calibration, in particular a reset, of the starting point can be carried out during operation of the chain hoist. When the starting point for the upward and downward counting is known, the change in the vertical position and thus also the (current) vertical position can be determined from the upward and downward counting. The control device connected to the sensor via signal transmission counts upward when the load handling device is raised and counts downward when the load handling device is lowered.

[0035] The incremental sensor preferably used for counting up and counting down comprises a fan disk fixed in a torque-proof manner on the shaft of the transmission device and a light barrier, which has in particular two photodetectors for detecting the direction of rotation. With such a sensor design, the vertical position of the load handling device can be determined solely on the basis of the sensor signal.

[0036] Depending on the direction of rotation, for example each time a light barrier is interrupted, the corresponding sensor signal in the control device is added to the previous value of the sensor signal, i.e. counted up, or subtracted from it, i.e. counted down. The change in the vertical position of the load handling device during a single light barrier interruption is known, so that the vertical position of the load handling device can be derived from the value of the sensor signal.

[0037] In the first specific embodiment, it can be provided additionally or alternatively that the amplitude of the change of the sensor signal is determined.

[0038] It can then be determined, for example, how quickly the sensor signal for sensing the transport speed changes. When the vertical position of the load handling device corresponds to the upper end position or the lower end position, the lifting or lowering movement is suddenly stopped as described above, so that the transport speed is braked to zero very quickly. The sensor signal for sensing the transport speed therefore changes very quickly.

[0039] However, if the load on the load handling device is too great, the sensor signal for sensing the transmission speed changes relatively slowly because the forces acting on the load handling device and the chain also change slowly.

[0040] This also enables the vertical position of the load handling device to be determined based on the degree of change of the sensor signal and thus the clutch slip to be assigned to the cause.

[0041] In a second embodiment, which may be provided instead of or in addition to the first embodiment, the vertical position of the load handling device is determined by timing.

[0042] The timing is first used to determine at which point after the timing starts a clutch slip occurs. The vertical position of the load handling device can then be determined by taking into account the vertical position of the load handling device at the start of the timing and the lifting speed of the chain hoist, or if multiple lifting speeds are possible, based on the lifting speed selected at that time. Furthermore, any previously occurring clutch slip is preferably taken into account so that the vertical position of the load handling device can be determined as accurately as possible.

[0043] The corresponding times of the upper end position, the lower end position and the vertical position specified by at least one limit switch, i.e. the time required from the start of the timing to the reaching of the corresponding position, are preferably stored in a memory unit of the control device. The aforementioned times can be adapted to the corresponding chain hoist, in particular to the maximum lifting height and lifting speed of a given chain hoist.

[0044] By measuring the time and thereby determining the vertical position of the load handling device, a cause can be assigned to each clutch slip. Clutch slip caused by excessive load on the load handling device typically occurs shortly after the load has been lifted, for example when the load handling device is in a vertical position close to the ground. Using the timing, it can be determined if the clutch slips shortly after the load has been lifted, for example within two to three seconds. If this is the case, the control device can conclude that the clutch slip is caused by excessive load on the load handling device, or at least rule out the possibility that the clutch slip is caused by a defective limit switch.

[0045] The clutch slip caused by a defective upper limit switch occurs only later, for example after five or six seconds, because the load handling device takes significantly longer to reach the upper end position. Since the upper end position is above the vertical position specified by the upper limit switch and is therefore behind the vertical position specified by the upper limit switch in terms of time, the control device can be used to conclude that the clutch slip is caused by a defective upper limit switch.

[0046] In particular, the timing starts when a load attached to the load handling device is lifted, for example from the ground.A corresponding command to start the timing may be associated with the activation of the lifting mode, for example via a control switch.

[0047] For lowering, for example, the vertical position of the load handling device at which the previous lifting or lowering movement was interrupted can be used as the starting point for the timing. Based on the starting point and the lifting speed (selected in this case), this timing can then be used to determine whether the load handling device is in the lower end position when the clutch slips.

[0048] In the second embodiment, the control device preferably derives whether lifting or lowering occurs from the direction signal of the control switch, ie, whether the lifting mode or the lowering mode is activated. Alternatively, the control device can derive this from the rotation direction of the drive motor.

[0049] If a second embodiment is provided in addition to the first embodiment, one of the two embodiments can be used to verify the other embodiment, i.e. confirm the vertical position of the load handling device. In the combination of embodiments, it can also be determined based on the sensor signal detected by the above-mentioned sensor whether the load handling device is raised or lowered.

[0050] All embodiments provide in an advantageous and structurally simple manner that the sensor detects the rotational speed of the input shaft of the transmission connected to the friction clutch.

[0051] The sensor is then located behind the friction clutch, in particular from the perspective of the drive motor. This makes it particularly easy to compare the speed of the transmission with the operating speed of the drive motor, since the gear ratio of the transmission does not need to be taken into account.

[0052] It can advantageously be provided that, when a deviation of the speed of the transport device from the operating speed of the drive motor is detected and when a predefined vertical position of the load handling device is present, a visual and / or acoustic alarm is output and / or only the chain hoist is permitted to lower the load handling device and / or only a creeping speed of the chain hoist is permitted and / or the drive motor is switched off.

[0053] Thus, in the event of a clutch slip, depending on the vertical position of the load handling device and thus on the cause of the clutch slip and / or the frequency with which the clutch slip occurs, one of the above-mentioned measures, in particular for protecting a chain hoist, can be initiated.

[0054] Thus, the control device is able to initiate measures in the event of a clutch slip caused by a defective limit switch that are different from those initiated in the event of a clutch slip caused by other causes, such as an excessive load on the load attachment device. It is also not necessary to take any action every time the clutch slips. For example, in the case where the clutch slip is caused by an excessive load on the load handling device or a friction clutch that is set too sensitive, the chain is generally not subjected to such loads that the chain breaks, even if this often occurs. Such clutch slips are also referred to as non-critical. For example, with such non-critical clutch slips, drastic measures such as disconnecting the drive motor are not required.

[0055] Thus, for example, the maximum number of clutch slips caused by a defective limit switch and the maximum number of clutch slips caused by other causes can be stored in a memory unit of the control device. It can be provided that, after the causes have been assigned, each clutch slip is added to the value previously stored for this cause and that corresponding measures are initiated when the specified maximum number for this cause is reached.

[0056] In this case, it can also be taken into account that the cause of clutch slippage when lowering a load is often a defective limit switch. Clutch slippage due to excessive load on the load handling device can at least be ruled out during lowering.

[0057] By taking cause-related measures in the event of clutch slippage, customer complaints can be avoided and thus safe and efficient operation of the chain hoist can be achieved.

[0058] The invention also relates to a chain hoist with an electric drive motor, a transmission device and a friction clutch, as well as a sensor, a load handling device and a control device, wherein the electric drive motor is connected to the transmission device on the output side via a friction clutch. The control device is designed and configured to carry out the method according to the invention.

[0059] It is particularly advantageous if the sensor comprises a fan disk which is arranged in a torque-proof manner on a shaft of the transmission, preferably on an input shaft of the transmission, and a light barrier with which the speed of the fan disk can be sensed.

[0060] By means of such a designed sensor, the rotational speed of the fan disk and thus also the speed of the drive shaft can be sensed. In addition, such sensors can be used to determine the direction of rotation of the drive shaft and to count up and down the sensor signal.

[0061] Further advantageous embodiments and details of the invention emerge from the following description. In the drawings:

[0062] Figure 1 is a schematic cross-sectional view of a chain hoist with a control device for carrying out at least one embodiment of the method according to the invention; and

[0063] Figures 2 to 5 is a schematic diagram of a chain hoist at different vertical positions of a load handling device.

[0064] Figure 1 is a schematic sectional view of a chain hoist 1 with a control device 19 for carrying out at least one embodiment of the method according to the invention.

[0065] The chain hoist 1 has an electric drive motor 2, wherein a motor shaft 3 projects on the output side of the drive motor 2. The motor shaft 3 is supported by a first bearing 5, which is preferably designed as a roller bearing. The drive motor 2 is controlled by a control device 19.

[0066] The chain hoist 1 also has a transmission 7, which is designed as a single-stage mechanism in the present exemplary embodiment, but can also be designed as a multi-stage mechanism. The transmission input shaft 4 of the transmission 7 is arranged coaxially with the motor shaft 3 and supported by a second bearing 6, which is preferably also designed as a roller bearing. The transmission 7 comprises a first gear 8, which is arranged on the transmission input shaft 4 in a torque-proof manner and meshes with a second gear 9, which is arranged on the transmission output shaft 10 in a torque-proof manner. The transmission output shaft 10, which is arranged parallel to the transmission input shaft 4, is supported on both sides of the second gear 9 by a third bearing 11 and a fourth bearing 12, which are preferably also designed as roller bearings.

[0067] A sprocket 13 is arranged on the transmission output shaft 10 in a torque-proof manner and in this case at one end of the transmission output shaft 10. This sprocket 13 is used in a conventional manner to provide a positive drive for a chain 22 (not shown) of the chain hoist 1. A load handling device 21 (not shown) suspended on the chain 22 is raised and lowered by moving the chain 22 over the sprocket. When lifted from the sprocket 13, the chain 22 runs into a chain storage unit (not shown) of the chain hoist 1.

[0068] Corresponding control commands for raising and lowering the load handling device 21 are received by the control device 19 and transmitted by it to the drive motor 2. In this case, the control commands received by the control device 19 are sent by a control switch of the chain hoist 1.

[0069] The friction clutch 14 is arranged between the transmission input shaft 4 and the motor shaft 3. The friction clutch 14 consists essentially of a clutch plate 15 with an annular clutch lining 16, a pressure plate 17 and a spring element (not shown) for generating a preload between the pressure plate 17 and the clutch plate 15, which preload determines the maximum transmittable torque. The pressure plate 17 is arranged on the motor shaft 3 in a torque-proof manner and the clutch plate 15 is arranged on the transmission input shaft 4 in a torque-proof manner. The friction clutch 14 is set to a maximum transmittable torque corresponding to the nominal load of the chain hoist 1. If the maximum torque that can be transmitted using the friction clutch 14 is exceeded, the friction clutch slips.

[0070] The transmission input shaft 4 can be braked or stopped at rest when necessary by means of a brake 20 arranged on the transmission input shaft 4 . The brake 20 is controlled by the control device 19 .

[0071] A sensor 18 is also arranged on the transmission input shaft 4. The sensor 18 serves to determine the speed of the transmission input shaft 4 and comprises, in addition to a fan disk (not shown) arranged in a torque-resistant manner on the transmission input shaft 4, a light barrier (not shown) with two photodetectors arranged in the region of the fan disk's compartment. The speed of the fan disk and thus of the transmission input shaft 4 is then detected using the light barrier, in particular by determining the frequency of the light barrier interruptions.

[0072] The sensor 18 is connected to the control device 19 using signals, wherein the sensor 18 transmits the rotation speed sensed by it using sensor signals to the control device 19. These sensor signals are processed by the control device 19 and / or stored in a memory unit of the control device 19 in the form of sensor data.

[0073] If the maximum torque transmittable by the friction clutch 14 is exceeded and the friction clutch 14 therefore slips (referred to as clutch slip), this is detected by comparing the speed of the transmission input shaft 4 with the operating speed of the drive motor 2 implemented using the control device 19 .

[0074] Clutch slip can be caused by excessive load on the load handling device 21. Since the friction clutch 14 is set to a maximum transmittable torque, which corresponds in particular to the nominal load of the chain hoist 1, clutch slip caused by a friction clutch 14 being set too sensitively is not to be expected in this case.

[0075] However, when the load handling device 21 strikes the drive housing 23 of the chain hoist 1 (see Figures 2 to 5) and reaches the upper end position OE, or when the lower end position UE is reached due to the fully extended chain 22 hitting the end stop (not shown).

[0076] The chain hoist 1 also has an upper limit switch and a lower limit switch (neither shown). If the limit switches are functioning properly, they indicate this; or once the load handling device has reached the vertical position POE, PUE specified by the corresponding limit switch (see Figures 2 to 5 ) indicates this. Based on such an indication and / or a corresponding limit switch signal, the control device 19 overwrites the control command transmitted by the control switch and stops the drive motor 2 in a timely manner.

[0077] For example, by providing an upper limit switch, the load handling device 21 can be prevented from hitting the drive housing 23. By providing a lower limit switch, for example, the chain 22 can be prevented from being fully extended and blocked by the end stop. However, if one of the limit switches is defective, the drive motor 2 will not be stopped in time and the friction clutch 14 will slip when the load handling device 21 hits the drive housing 23 or when it hits the end stop.

[0078] Using the control device 19, the vertical position PLAM of the load handling device 21 is determined. The vertical position PLAM of the load handling device 21 is used to assign a clutch slip occurring on the friction clutch 14 to a cause for the clutch slip, for example in order to be able to detect a defective limit switch.

[0079] If the control device 19 detects clutch slippage based on the sensor signal from the sensor 18 and the determined vertical position PLAM of the load handling device 21 corresponds to the upper end position OE or the lower end position UE (see Figures 2 to 5 ), both of which are stored in the memory unit of the control device 19, the control device 19 concludes that the corresponding limit switch is defective.

[0080] However, when the vertical position PLAM of the load handling device 21 determined during clutch slip is not assigned to the vertical position stored in the control device 19 , the control device 19 concludes that the clutch slip is due to another cause, such as an excessive load on the load handling device 21 .

[0081] The vertical position PLAM of the load handling device 21 can be determined using two different embodiments of the method for monitoring the chain hoist 1, wherein the two embodiments can be used independently of each other or in combination with each other. The control device 19 can execute at least one of these embodiments.

[0082] In a first embodiment of the method, the vertical position PLAM of the load handling device 21 is determined based on a sensor signal from the sensor 18. The vertical position PLAM of the load handling device 21 is determined based on the sensor signal in addition to the speed of the transmission input shaft 4. For this purpose, the sensor signal is received and evaluated by the control device 19. In this embodiment of the sensor 18 with a fan disk and a light barrier, the vertical position PLAM of the load handling device 21 can be determined based solely on the sensor signal.

[0083] The direction of rotation of the transmission device input shaft 4 is first determined via a corresponding sensor signal from a sensor 18, which is connected to the control device 19. For this purpose, the two photodetectors of the light barrier detect the direction of rotation of the fan disk. An initial vertical position PLAM of the load handling device 21, i.e. a starting point for counting up and counting down, is specified in advance. In the case where the direction of rotation is known, i.e. whether the load handling device is raised or lowered, the vertical position PLAM of the load handling device 21 is determined in particular by "counting up" and "counting down" the sensor signal. For example, the control device 19 counts up when the load handling device 21 is raised and counts down when the load handling device 21 is lowered. For this purpose, depending on the direction of rotation, each time the light barrier is interrupted, the corresponding sensor signal is added or subtracted from the previous value of the sensor signal. The change in the vertical position PLAM of the load handling device 21 during a single light barrier interruption is known, so that the vertical position PLAM of the load handling device 21 can be derived from the value of the sensor signal.

[0084] Alternatively or in addition, the amplitude of the change of the sensor signal can be determined. For example, it is then determined how quickly the sensor signal changes. If the vertical position PLAM of the load handling device 21 is equal to the upper end position OE or the lower end position UE, the lifting or lowering movement is stopped suddenly, so that the change of the sensor signal occurs very quickly. However, if the load on the load handling device 21 is too large, the change of the sensor signal occurs relatively slowly. This also makes it possible to assign clutch slip to a cause based on the rate of change of the sensor signal.

[0085] In a second embodiment of the method, the timing is used to determine the vertical position PLAM of the load handling device 21. In particular, the timing starts when the load attached to the load handling device 21 is lifted from the ground. A corresponding start command for the timing can be associated with the activation of the lifting mode, for example, via a control switch. Using the timing, it is first determined at which point after the load has been lifted the clutch slip occurs. The vertical position PLAM of the load handling device 21 can then be determined based on the lifting speed of the chain hoist 1 or, if multiple lifting speeds are possible, based on the lifting speed selected in this case.

[0086] Clutch slippage caused by excessive load on the load handling device 21 usually occurs shortly after the load has been lifted, i.e. when the load handling device 21 is in the vertical position PLAM close to the ground. Using timing, it can be determined whether the clutch slips shortly after the load is lifted. If this is the case, the control device 19 can conclude that the clutch slippage is caused by excessive load on the load handling device 21, or at least rule out that the clutch slippage is caused by a defective limit switch.

[0087] The clutch slip caused by the defective upper limit switch occurs only later, since the load handling device 21 takes significantly longer to reach the upper end position OE. This is because the upper end position OE is later in time than the vertical position POE specified by the upper limit switch, i.e. is arranged above the specified vertical position POE (see Figures 2 to 5 ), so the control device 19 can be used to determine that the clutch slip is caused by a defective upper limit switch.

[0088] For lowering, for example, the vertical position PLAM of the load handling device 21 where the previous lifting or lowering movement was interrupted can be used as the starting point for the timing. From the starting point, the timing can then be used to determine whether the load handling device 21 is in the lower end position UE when the clutch slip occurs.

[0089] In the second embodiment, in particular, the previous clutch slip is taken into account in order to be able to determine as accurately as possible the vertical position PLAM of the load handling device 21. The control device 19 can determine from the direction of rotation of the drive motor 2 or from the direction signal of the control switch or from the sensor signal detected by the sensor 18 whether lifting or lowering is taking place.

[0090] If the second embodiment is provided in addition to the first embodiment, one of the two embodiments can be used to verify the other embodiment, ie to confirm the vertical position PLAM of the load handling device 21 .

[0091] When a deviation of the speed of the transmission input shaft 4 from the operating speed of the drive motor 2 is detected and if the vertical position PLAM of the load handling device 21 corresponds to the upper end position OE or the lower end position UE, a visual and / or acoustic alarm may be issued by the control device 19. Additionally or alternatively, the chain hoist 1 may only be allowed to lower the load handling device 21. Additionally or alternatively, only a creeping speed of the chain hoist 1 is allowed. Additionally or alternatively, the drive motor 2 may be switched off.

[0092] Thus, one of the above-mentioned measures, in particular for protecting the chain hoist 1, can be initiated depending on the cause of the clutch slip and / or the frequency of occurrence of the clutch slip. Thus, the control device 19 is able to initiate different measures in the case of a clutch slip caused by a defective limit switch than those initiated in the case of a clutch slip caused by, for example, an excessive load on the load attachment device 21. It is also not necessary to take any action every time the clutch slips.

[0093] If the clutch slip is caused by excessive load on the load handling device 21 or a friction clutch 14 that is set too sensitively, the chain 22 will not normally be loaded to such an extent that the chain 22 breaks, even though this often occurs. This clutch slip is also referred to as non-critical.

[0094] Thus, for example, the maximum number of clutch slips caused by a defective limit switch and the maximum number of clutch slips caused by other causes can be stored in the control device 19 or in a memory unit of the control device 19. It can then be provided that each time the clutch slips, a counter is incremented and, when the specified maximum number is reached, appropriate measures are initiated for this cause.

[0095] Figures 2 to 5 Schematic diagrams of the chain crane 1 are shown in different vertical positions PLAM of the load handling device 21 .

[0096] During lifting and lowering of the load handling device 21, the vertical position PLAM of the load handling device 21 changes. Otherwise, in situations where the load handling device 21 is not raised or lowered, the vertical position PLAM of the load handling device 21 remains unchanged.

[0097] The vertical position PLAM of the load handling device 21 may be a position between an upper end position OE and a lower end position UE. The upper end position OE is the position of the maximum possible lifting height, which is mechanically limited by the load handling device 21 hitting the drive housing 23. Below the upper end position OE is the vertical position POE specified by the upper limit switch.

[0098] The lower end position UE is the position of the maximum possible lowering depth which is mechanically limited by the end stop when the load handling device 21 is fully lowered. Above the lower end position UE is a vertical position PUE which is specified by a lower limit switch.

[0099] exist Figure 2 In the embodiment, the vertical position PLAM of the load handling device 21 is arranged between the vertical position PUE specified by the lower limit switch and the vertical position POE specified by the upper limit switch. The clutch slip occurring in this vertical position is not controlled by the control device 19 (see Figure 1 ) is not due to a defective limit switch, but to other reasons, such as excessive load on the load handling device 21.

[0100] exist Figure 3 In the embodiment, the vertical position PLAM of the load handling device 21 corresponds to the lower end position UE, and in Figure 4 The clutch slip occurring in such a vertical position PLAM of the load handling device 21 is assigned by the control device 19 to the defective lower limit switch ( Figure 3 ) or upper limit switch ( Figure 4 ).

[0101] exist Figure 5 , the vertical position PLAM of the load handling device 21 corresponds to the vertical position POE specified by the upper limit switch. An active upper limit switch will indicate this so that the control device 19 can intervene accordingly. This applies accordingly if the vertical position PLAM of the load handling device 21 is equal to the vertical position PUE specified by the lower limit switch.

[0102] Reference numerals list

[0103] 1 Chain hoist

[0104] 2 Drive motor

[0105] 3 Motor shaft

[0106] 4 Transmission input shaft

[0107] 5. First bearing

[0108] 6 Second bearing

[0109] 7 Transmission device

[0110] 8 First gear

[0111] 9 Second gear

[0112] 10 Transmission output shaft

[0113] 11 Third bearing

[0114] 12 Fourth bearing

[0115] 13 sprocket teeth

[0116] 14 Friction clutch

[0117] 15 Clutch disc

[0118] 16 Clutch lining

[0119] 17 Pressure plate

[0120] 18 Sensors

[0121] 19 Control Device

[0122] 20 Brakes

[0123] 21 Load handling device

[0124] 22 Chain

[0125] 23 Driver housing

[0126] PLAM vertical position, load handling device

[0127] POE vertical position, upper limit switch

[0128] PUE vertical position, lower limit switch

[0129] OE Upper end position

[0130] UE lower end position

Claims

1. A method for monitoring a chain hoist (1) having an electric drive motor (2), which is connected on the output side to a transmission device (7) via a friction clutch (14), wherein the speed of the transmission device (7) is sensed via a sensor (18) and the sensed speed of the transmission device (7) is compared with the operating speed of the drive motor (2) using a control device (19), characterized in that The control device (19) is also used to determine the vertical position (PLAM) of the load handling device (21) of the chain crane (1).

2. The method according to claim 1, characterized in that The vertical position (PLAM) of the load handling device (21) is determined based on a sensor signal from the sensor (18).

3. The method according to claim 2, characterized in that The rotation direction of the transmission device (7) is detected based on the sensor signal, and the vertical position (PLAM) of the load handling device (21) is determined by "counting up" and "counting down" the sensor signal.

4. The method according to claim 2 or 3, characterized in that: The magnitude of the change in the sensor signal is determined.

5. The method according to any one of the preceding claims, characterized in that Timing is used to determine the vertical position (PLAM) of the load handling device (21).

6. The method according to any one of the preceding claims, characterized in that The speed of the transmission input shaft (4) connected to the friction clutch (14) is sensed via the sensor (18).

7. The method according to any one of the preceding claims, characterized in that When a deviation of the speed of the transmission device (7) from the operating speed of the drive motor (2) is detected and when a predefined vertical position (PLAM) of the load handling device (21) is present, a visual and / or acoustic alarm is issued and / or only the chain hoist (1) is allowed to lower the load handling device (21) and / or only the creeping speed of the chain hoist (1) is allowed and / or the drive motor (2) is switched off.

8. A chain hoist having an electric drive motor (2), a transmission device (7) and a friction clutch (14), as well as a sensor (18), a load handling device (21) and a control device (19), wherein the electric drive motor (2) is connected to the transmission device (7) on the output side via the friction clutch (14), characterized in that: The control device (19) is designed and configured to carry out a method according to any of the preceding claims.

9. The chain hoist according to claim 8, characterized in that The sensor (18) comprises a fan disk arranged in a torque-resistant manner on a shaft of the transmission (7), preferably the transmission input shaft (4), and a light barrier with which the speed of the fan disk can be sensed.

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