Method for monitoring a chain hoist

Abstract

The invention relates to a method for monitoring a chain hoist (1) having an electric drive motor (2) which is connected on the output side, via a friction clutch (14), to a transmission (7), wherein, via a sensor (18), a speed of the transmission (7) is sensed and the sensed speed of the transmission (7) is compared with an operating speed of the drive motor (2) by means of a control device (19). In order to achieve safe and efficient operation of the chain hoist (1), a vertical position (PLAM) of the load handling device (21) of the chain hoist (1) is also determined by means of the control device (19). The invention also relates to a chain hoist (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 to a chain hoist according to the preamble of claim 8.

[0002] Chain hoists of this type comprise an electric drive motor, a gearbox, and a slip clutch functionally arranged between the drive motor and the gearbox. These components of the chain hoist are typically housed in a drive housing. Chain hoists of this type also feature 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 located on an output shaft of the gearbox. Corresponding control commands are typically issued by an operator via a control switch, and transmitted from the control switch to a control device of the chain hoist.

[0003] It is known to equip chain hoists of this type with one or more limit switches. The limit switch is used to override the control commands transmitted to the control device when indicated accordingly, particularly to the control device. If the limit switch is functioning, the drive motor of the chain hoist can be stopped based on its indication and the resulting intervention by the control device, even if a control command for lifting or lowering has been transmitted to the control device.

[0004] The slip clutch of the chain hoist primarily serves to prevent overloading and the resulting damage to the drive motor, gearbox, and chain. The slip clutch slips, for example, when attempting to lift an excessively heavy load. Slipping can also occur if the load handling device strikes the drive housing or if it hits an end stop at one end of the chain when the chain is fully extended. However, slipping can also occur if the slip 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 fully extending and becoming blocked by the end stop. However, if one of the limit switches is defective, the drive motor will not be stopped in time, and the slip clutch will slip when the load handling device hits the drive housing or strikes the end stop.

[0006] Despite the slipping of the slip clutch, which is intended to prevent chain overload and is also referred to as clutch slippage, depending on the cause of the clutch slippage and the frequency of the (cause-related) clutch slippage, the chain may become overloaded and even break. This is particularly the case if the load handling device repeatedly hits the drive housing due to a defective upper limit switch or repeatedly hits the end stop due to a defective lower limit switch.

[0007] EP 1 510 498 B1 discloses a method for monitoring a chain hoist. A control device of the chain hoist detects a deviation between the actual speed of the gearbox and the target speed of the drive motor, thus allowing slipping of the slip clutch to be determined. However, this method does not allow the cause of the clutch slipping to be determined.

[0008] EP 1 510 498 B1 discloses the preamble of claims 1 and 8.

[0009] DE 199 56 265 A1 and DE 195 12 103 A1 disclose methods for monitoring the operation of cable winches, in particular with regard to the number of cable turns wound on the winch.

[0010] DE 10 2015 105 517 A1 discloses a cable retraction and deployment device for aviation applications and a method for controlling the device, wherein end positions of the cable can be detected by means of a sensor.

[0011] The invention is therefore based on the object of providing a method for monitoring a chain hoist and a chain hoist which enables safe and efficient operation of the chain hoist.

[0012] The object is achieved by a method having the features of claim 1 and by a chain hoist having the features of claim 8. Advantageous embodiments of the invention are specified in the dependent claims and the following description.

[0013] According to the invention, in a method for monitoring a chain hoist with an electric drive motor which is connected to a gearbox on the output side via a slip clutch, wherein a speed of the gearbox is detected via a sensor and the detected speed of the gearbox is compared with an operating speed of the drive motor by means of a control device, a safe and efficient operation of the chain hoist is achieved in that a vertical position of a load-carrying device of the chain hoist is also determined by means of the control device.

[0014] In other words, the method according to the invention provides for determining the vertical position of the load-carrying device in addition to the comparison between the detected transmission speed and the engine operating speed.

[0015] The load handling device, designed as a load hook, for example, is suspended from a chain of the chain hoist. The chain can be arranged in a single or multiple strands, so that the load handling device is attached to a free end of the chain (single strand) or the chain is deflected by the load handling device designed as a bottom block (multi-strand). The chain can be moved via at least one sprocket arranged in a rotationally fixed manner on an output shaft of the gearbox. The rotational movement of the at least one sprocket is transmitted to the chain via a positive connection with the chain, so that - depending on the direction of rotation - the load handling device is raised or lowered. For this purpose, a rotational movement of the electric drive motor is transmitted to the at least one sprocket, with the torque being converted via the gearbox functionally arranged between them.

[0016] Corresponding control commands for lifting and lowering are transmitted, preferably from a control switch on the chain hoist, to the control unit, and from there to the drive motor. During the 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 therefore be changed via the control commands transmitted to the drive motor.

[0017] When the load-handling device is not raised or lowered, its vertical position remains constant. 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 present invention, are then possible.

[0018] The vertical position of the load handling device can be a position between an upper end position and a lower end position located below the upper end position. The upper end position is a position of maximum possible lifting height, which is mechanically limited, for example, by the load handling device hitting the drive housing of the chain hoist. The upper end position is to be distinguished from a vertical position predetermined by an upper limit switch. The lower end position is a position of maximum possible lowering depth, which is also mechanically limited, for example, by the end stop when the load handling device is completely lowered. The lower end position is to be distinguished from a vertical position predetermined by a lower limit switch.

[0019] The at least one limit switch provided on the chain hoist, when functioning properly, indicates when the vertical position of the load-handling device corresponds to the vertical position specified by the limit switch. Based on such an indication, the control device can intervene in the control process of the chain hoist and, for example, override the control commands transmitted from the control switch to the control device.

[0020] The vertical position of the load-handling device determined according to the method according to the invention can be compared by the control device with a known vertical position, for example stored in a memory unit of the control device. The known vertical position is in particular the lower and / or upper end position and / or the vertical position predetermined by the 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 the memory unit of the control device. By storing it in this way, it is particularly possible for the at least one determined vertical position to be used for subsequent evaluation.

[0021] The sensor provided on the chain hoist preferably detects the speed of an individual shaft of the gearbox, so that the speed of the gearbox or gearbox speed refers to the speed of the individual shaft of the gearbox. Alternatively, the sensor can also detect the speed of an individual gear of the gearbox. The sensor transmits the detected speeds to the control unit via sensor signals. The sensor signals can be stored in the form of sensor data in the memory unit of the control unit.

[0022] The operating speed of the drive motor, or motor operating speed, is preferably determined from the drive motor's operating data. This data can be stored in the control unit's memory for different operating states of the chain hoist.

[0023] By comparing the detected transmission speed with the engine's operating speed, a speed deviation or speed difference can be determined. This allows the control device to detect clutch slippage of the slip clutch functionally arranged between the drive motor and the transmission, in particular between a motor shaft and an input shaft of the transmission. Depending on the transmission shaft or gear on which the speed is detected, the transmission's gear ratio must be taken into account when determining the deviation. Preferably, the occurrence of clutch slippage is stored in the memory unit. Provision can also be made for an error message to be generated.

[0024] Due to the functional design of the chain hoist, in particular because the load handling device is connected to the gearbox output shaft (also known as the gearbox output shaft) via the chain and at least one sprocket, a force or force change acting on the chain affects the torque applied to a gearbox input shaft. Therefore, the force acting on the chain changes the torque applied to the gearbox input shaft (also known as the gearbox input shaft); this also changes the torque acting on the gearbox-side part of the slip clutch. If the applied torque exceeds the maximum torque that the slip clutch can transmit, to which the slip clutch is set, the slip clutch slips.

[0025] As a rule, the maximum transmittable torque corresponds to a value corresponding to the rated load of the chain hoist. A slip clutch adjusted in this way will slip if the load being lifted is too heavy, i.e., a load that exceeds the rated load. If the slip clutch is set too sensitively, i.e., to a maximum transmittable torque that is lower than the value corresponding to the rated load of the chain hoist, slipping can occur even at loads lower than the rated load.

[0026] Clutch slippage caused by one of the two aforementioned causes is less critical with regard to preventing chain breakage than clutch slippage caused by the causes described below and can therefore be tolerated with a comparatively higher frequency of occurrence.

[0027] Slipping can also be caused by the load handling device hitting the drive housing or striking the end stop. Both causes can be traced back to a defective upper limit switch or defective lower limit switch. The lifting or lowering movement of the load handling device is abruptly stopped when the load handling device hits the drive housing or strikes the end stop, while the drive motor continues to run. Due to the resulting high load on the chain, particularly due to the high tensile forces acting on the chain, and especially as a result of frequent occurrence of such high loads, the chain can become overloaded and even break.

[0028] The method according to the invention therefore not only makes it possible to determine whether the clutch is slipping, but also the vertical position of the load-handling device at the time the clutch is slipping. If the control device detects clutch slipping based on sensor signals and the determined vertical position of the load-handling device can be assigned to the upper or lower end position, it can therefore conclude, for example, that the respective upper or lower limit switch is defective. If, on the other hand, the vertical position of the load-handling device determined in the event of clutch slipping cannot be assigned to a vertical position stored in the memory unit of the control device, the control device can conclude that the clutch slipping is due to another cause, for example an excessive load on the load-handling device.

[0029] This allows the cause of clutch slippage to be determined and assigned to the clutch slippage. The method according to the invention therefore makes it possible to distinguish between clutch slippage caused by an excessive load on the load-handling device and clutch slippage caused by a defective limit switch. It can therefore also be provided that the optionally generated error message varies depending on the cause.

[0030] The method according to the invention can therefore be used to diagnose the failure of a limit switch and at least reduce the proportion of chain breakages attributable to defective limit switches. This enables safe operation of the chain hoist. Furthermore, the application of the method according to the invention does not negatively impact the production costs required for a chain hoist, since no additional hardware is required compared to the chain hoist known from EP 1 510 498 B1.

[0031] In a first embodiment, the vertical position of the load-handling device is determined based on sensor signals from the sensor.

[0032] In addition to the transmission speed, the vertical position of the load-handling device is also determined based on the sensor signals. The sensor signals are received and evaluated by the control unit. The sensor signals are preferably stored in the control unit's memory. With appropriate sensor design, it is possible to determine the vertical position of the load-handling device based solely on the sensor signals.

[0033] In the first embodiment, it is particularly advantageous that a direction of rotation of the gear is detected based on the sensor signals and the vertical position of the load-carrying device is determined by "counting up" and "counting down" the sensor signals.

[0034] The direction of rotation of the gearbox associated with raising or lowering the load-handling device is recorded to determine whether the sensor signals should be incremented or decremented, i.e., whether the sensor signals should be added or subtracted. Preferably, the direction of rotation of the individual gearbox shaft is recorded. Alternatively, the direction of rotation of the individual gearbox gear can be recorded.

[0035] The starting point for the up and down counting, i.e., the initial vertical position of the load handling device, can be specified, for example, when commissioning the chain hoist. It can also be provided that calibration, in particular a reset, of the starting point is possible during operation of the chain hoist. If the starting point for the up and down counting is known, the change in the vertical position and thus also the (current) vertical position can be determined based on the up and down counting. The control device, which is signal-linked to the sensor, counts up when the load handling device is raised and down when it is lowered, for example.

[0036] The incremental sensor preferably used for counting up and down comprises a fan-shaped disk mounted non-rotatably on a gear shaft and a light barrier, which in particular has two photodetectors for detecting the direction of rotation. With this type of sensor design, the vertical position of the load-handling device can be determined exclusively based on the sensor signals.

[0037] Depending on the direction of rotation, for example, each time a light barrier is interrupted, the corresponding sensor signal in the control system is added to the previous value of the sensor signals (i.e., incremented) or subtracted from it (i.e., decremented). The change in the vertical position of the load handling device during a single light barrier interruption is known, so the vertical position of the load handling device can be derived from the value of the sensor signals.

[0038] In the first embodiment, it may additionally or alternatively be provided that an expression of a change in the sensor signals is determined.

[0039] For example, it can then be determined how quickly the sensor signals used to detect the transmission speed change. When the vertical position of the load-handling device corresponds to the upper or lower limit position, a lifting or lowering movement is abruptly stopped, as described above, so that the transmission speed is decelerated very quickly to zero. The sensor signals used to detect the transmission speed therefore change very rapidly.

[0040] If the load on the load-handling device is too great, however, the sensor signals used to detect the transmission speed change comparatively more slowly, since the force acting on the load-handling device and the chain also changes more slowly.

[0041] This also makes it possible to determine the vertical position of the load-handling device based on the extent of the change in the sensor signals, and thus to assign a cause to the clutch slippage.

[0042] In a second embodiment, which can be provided alternatively or in addition to the first embodiment, the vertical position of the load-handling device is determined by means of time measurement.

[0043] The timing is first used to determine at what point after the start of the timing measurement the clutch slippage occurs. Taking into account the vertical position of the load handling device at the start of the timing measurement and the hoist speed of the chain hoist, or – if several possible hoist speeds are available – based on the currently selected hoist speed, the vertical position of the load handling device can then be determined. In addition, any clutch slippage that may have occurred previously is preferably taken into account in order to determine the vertical position of the load handling device as accurately as possible.

[0044] The respective times for the upper end position, the lower end position, and the vertical position specified by the at least one limit switch, i.e., the time required from the start of the time measurement until reaching the respective position, are preferably stored in the memory unit of the control device. The aforementioned times can be adapted to the respective chain hoist, in particular to the maximum lifting height and lifting speed of the respective chain hoist.

[0045] By measuring the time and thereby determining the vertical position of the load handling device, it is thus possible to assign a cause to the respective clutch slippage. Clutch slippage caused by an 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. By measuring the time, it can therefore be determined whether the clutch slippage occurs 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 slippage is caused by an excessive load on the load handling device, or at least rule out the possibility that the clutch slippage is caused by a defective limit switch.

[0046] Clutch slippage caused by a defective upper limit switch only occurs later, for example, after five or six seconds, because it takes significantly longer for the load handling device to reach the upper limit position. Since the upper limit position is above the vertical position specified by the upper limit switch and thus, in time, behind the vertical position specified by an upper limit switch, the control device can conclude that the clutch slippage is caused by a defective upper limit switch.

[0047] The timing starts when the load attached to the load-handling device is lifted, for example, from the ground. A corresponding command to start the timing can be linked, for example, to activating the lifting mode via the control switch.

[0048] During lowering, for example, the vertical position of the load handling device, at which a previous lifting or lowering movement was interrupted, can be used as the starting point for the timing. Depending on the starting point and the (currently selected) lifting speed, the timing can then be used to determine whether the load handling device is at its lower end position when the clutch slips.

[0049] In the second embodiment, the control device preferably determines whether the lift is being raised or lowered from a direction signal of the control switch, i.e., in particular, whether the lift mode or the lower mode is activated. Alternatively, the control device can determine this from the direction of rotation of the drive motor.

[0050] 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, i.e., to confirm the vertical position of the load-handling device. When combining the embodiments, it is also possible to determine whether the load-handling device is being raised or lowered from the sensor signals detected by the sensor described above.

[0051] In an advantageous and structurally simple manner, all embodiments provide for the sensor to detect the speed of a transmission input shaft connected to the slip clutch.

[0052] The sensor is then located behind the slip clutch, particularly as seen from the drive motor. This makes comparing the transmission speed with the operating speed of the drive motor particularly easy, as no gear ratio needs to be taken into account.

[0053] It can advantageously be provided that when a deviation of the speed of the gearbox 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 issued and / or the chain hoist is only released to lower the load handling device and / or only a creep speed of the chain hoist is released and / or the drive motor is switched off.

[0054] One of the measures mentioned above, which in particular serve to protect the chain hoist, can therefore be initiated depending on the vertical position of the load handling device in the event of clutch slippage and thus depending on the cause of the clutch slippage and / or the frequency of clutch slippage.

[0055] The control device is therefore able to initiate different measures in the event of clutch slippage caused by a defective limit switch than in the event of clutch slippage due to other causes, such as excessive load on the load-handling device. It is also not necessary to initiate a measure every time the clutch slips. If, for example, the clutch slippage is caused by excessive load on the load-handling device or a slip clutch that is set too sensitively, the chain is generally not subjected to such strain that the chain breaks, even if it occurs frequently. Clutch slippage caused by this type of clutch is also referred to as non-critical. In the case of non-critical clutch slippage, no drastic measures such as switching off the drive motor are necessary.

[0056] Therefore, for example, a maximum number of clutch slips caused by a defective limit switch and a maximum number of clutch slips caused by other causes can be stored in the memory unit of the control device. It can be provided that after a cause has been assigned, each clutch slip is added to the previously stored value for this cause, and when the specified maximum number for this cause is reached, the corresponding action is initiated.

[0057] In this context, it can also be considered that the cause of clutch slippage when lowering a load is usually a defective limit switch. At least clutch slippage caused by an excessive load on the load-handling device can be ruled out during lowering.

[0058] By taking cause-related measures in the event of clutch slippage, customer complaints can be avoided and thus both safe and efficient operation of the chain hoist can be enabled.

[0059] The invention further relates to a chain hoist comprising an electric drive motor, a gearbox, and a slip clutch, wherein the electric drive motor is connected to the gearbox on the output side via the slip clutch, as well as a sensor, a load-handling device, and a control device. The control device is designed and configured to carry out the method according to the invention.

[0060] Particularly advantageously, the sensor comprises a fan-shaped disk arranged in a rotationally fixed manner on a shaft of the transmission, preferably the transmission input shaft, as well as a light barrier by means of which the speed of the fan-shaped disk can be detected.

[0061] With this type of sensor, the speed of the fan-shaped pulley and thus also the speed of the gear shaft can be measured. Furthermore, the direction of rotation of the gear shaft can be determined with this type of sensor and the sensor signals can be counted up and down.

[0062] Further advantageous embodiments and details of the invention will become apparent from the following description. It shows: Figure 1 a schematic 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 Figures 2 to 5 a schematic representation of the chain hoist with different vertical positions of the load handling device.

[0063] The Figure 1 shows 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.

[0064] The chain hoist 1 has an electric drive motor 2 with a motor shaft 3 protruding from the output side of the drive motor 2. The motor shaft 3 is mounted on a first bearing 5, which is preferably designed as a roller bearing. The drive motor 2 is controlled by the control device 19.

[0065] The chain hoist 1 also has a gearbox 7, which in the present embodiment is designed as a single-stage gearbox, but can also be designed as a multi-stage gearbox. The gearbox input shaft 4 of the gearbox 7 is arranged coaxially to the motor shaft 3 and is mounted via a second bearing 6, which is preferably also designed as a roller bearing. The gearbox 7 comprises a first gear 8, which is arranged non-rotatably on the gearbox input shaft 4 and meshes with a second gear 9, which is arranged non-rotatably on a gearbox output shaft 10. The gearbox output shaft 10, which is arranged parallel to the gearbox input shaft 4, is mounted 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.

[0066] A sprocket 13 is arranged in a rotationally fixed manner on the transmission output shaft 10, and in this case at one end of the transmission output shaft 10. This sprocket 13 serves, in the usual manner, to provide a positive drive for the chain 22 (not shown) of the chain hoist 1. A load-handling device 21 (not shown) suspended from the chain 22 is raised and lowered by moving the chain 22 over the sprocket. When lifted, the chain 22 runs from the sprocket 13 into a chain storage unit (not shown) of the chain hoist 1.

[0067] 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.

[0068] A slip clutch 14 is arranged between the transmission input shaft 4 and the motor shaft 3. The slip clutch 14 essentially consists of a clutch disc 15 with an annular clutch lining 16, a thrust washer 17, and a spring element (not shown) for generating a preload between the thrust washer 17 and the clutch disc 15 that determines the maximum transmittable torque. The thrust washer 17 is arranged in a rotationally fixed manner on the motor shaft 3, and the clutch disc 15 is arranged in a rotationally fixed manner on the transmission input shaft 4. The slip clutch 14 is set to a maximum transmittable torque that corresponds to the nominal load of the chain hoist 1. If the maximum transmittable torque by means of the slip clutch 14 is exceeded, it slips.

[0069] A brake 20 provided on the transmission input shaft 4 can be braked if necessary or blocked when stationary. The brake 20 is controlled by the control device 19.

[0070] 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-shaped disc (not shown) arranged in a rotationally fixed manner on the transmission input shaft 4, a light barrier (not shown) with two photodetectors arranged in the area of the fan-shaped disc compartments. The light barrier then detects the speed of the fan-shaped disc and thus the speed of the transmission input shaft 4, in particular by determining the frequency of the light barrier interruption.

[0071] The sensor 18 is connected to the control device 19 via signaling, whereby the sensor 18 transmits the rotational speeds it detects to the control device 19 via sensor signals. These sensor signals are processed by the control device 19 and / or stored in the form of sensor data in a memory unit of the control device 19.

[0072] Should the maximum torque that can be transmitted by the slip clutch 14 be exceeded and thus the slip clutch 14 slip, also referred to as clutch slippage, this is detected by a comparison of the speed of the transmission input shaft 4 with an operating speed of the drive motor 2 carried out by means of the control device 19.

[0073] Clutch slippage may be caused by an excessive load on the load-handling device 21. Since the slip clutch 14 is set to a maximum transmittable torque, which corresponds in particular to the rated load of the chain hoist 1, clutch slippage caused by an overly sensitively adjusted slip clutch 14 is not to be expected in this case.

[0074] However, the clutch slippage can also occur when an upper end position OE is reached due to the load handling device 21 hitting a drive housing 23 of the chain hoist 1 (see Figures 2 to 5 ) or when reaching a lower end position UE by striking the end stop (not shown) due to a completely extended chain 22.

[0075] The chain hoist 1 also has an upper limit switch and a lower limit switch (both not shown). When the limit switches are functioning, they indicate that or as soon as the load handling device has reached the vertical position POE, PUE specified by the respective limit switch (see Figures 2 to 5 ). Based on such an indication or the corresponding limit switch signals, the control device 19 overrides the control commands transmitted by the control switch and stops the drive motor 2 in time.

[0076] By providing an upper limit switch, for example, it is possible to prevent the load handling device 21 from hitting the drive housing 23. By providing a lower limit switch, it is possible, for example, to prevent the chain 22 from being fully extended and becoming blocked due to the end stop. However, if one of the limit switches is defective, the drive motor 2 will not be stopped in time, and the slip clutch 14 will slip when the load handling device 21 hits the drive housing 23 or when it hits the end stop.

[0077] A vertical position PLAM of the load-handling device 21 is determined by means of the control device 19. The vertical position PLAM of the load-handling device 21 is used to assign a clutch slippage occurring at the slip clutch 14 to a cause for this clutch slippage, for example, in order to detect a defective limit switch.

[0078] If the control device 19 detects clutch slippage based on sensor signals from the sensor 18 and the determined vertical position PLAM of the load handling device 21 corresponds to the upper end position OE or 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 respective limit switch is defective.

[0079] If, however, the vertical position PLAM of the load-handling device 21 determined in the event of clutch slippage is not assigned to a vertical position stored in the control device 19, the control device 19 concludes that the clutch slippage is due to another cause, for example an excessive load on the load-handling device 21.

[0080] The vertical position PLAM of the load-handling device 21 can be determined using two different embodiments of a method for monitoring the chain hoist 1, wherein the two embodiments can be used independently of one another or in combination with one another. The control device 19 can implement at least one of these embodiments.

[0081] In a first embodiment of the method, the vertical position PLAM of the load-handling device 21 is determined based on sensor signals from sensor 18. In addition to the speed of the transmission input shaft 4, the vertical position PLAM of the load-handling device 21 is also determined based on the sensor signals. For this purpose, the sensor signals are received and evaluated by the control device 19. With the present embodiment of the sensor 18 with a fan-shaped disc and light barrier, it is possible to determine the vertical position PLAM of the load-handling device 21 exclusively based on the sensor signals.

[0082] Using corresponding sensor signals from sensor 18, which is connected to control device 19 for signal processing, the direction of rotation of the transmission input shaft 4 is first determined. For this purpose, the direction of rotation of the fan-shaped disc is detected, in particular using the two photodetectors of the light barrier. The initial vertical position PLAM of the load-handling device 21, i.e., the starting point for the up and down counting, is predetermined. The vertical position PLAM of the load-handling device 21 is determined, given knowledge of the direction of rotation—i.e., whether the load-handling device is being raised or lowered—in particular by "counting up" and "counting down" the sensor signals. For example, control device 19 counts up when the load-handling device 21 is raised and down when the load-handling device 21 is lowered.For this purpose, depending on the direction of rotation, the corresponding sensor signal is added to or subtracted from the previous value of the sensor signals for each light barrier interruption. The change in the vertical position PLAM of the load handling device 21 for a single light barrier interruption is known, so the vertical position PLAM of the load handling device 21 can be derived from the value of the sensor signals.

[0083] Alternatively or additionally, the extent of a change in the sensor signals can be determined. For example, the rate at which the sensor signals change is then determined. 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, a lifting or lowering movement is stopped abruptly, so that the change in the sensor signals occurs very quickly. If the load on the load-handling device 21 is too heavy, however, the change in the sensor signals occurs comparatively slower. This also allows the clutch slippage to be assigned a cause based on the rate of change of the sensor signals.

[0084] In a second embodiment of the method, the vertical position PLAM of the load-handling device 21 is determined by means of time measurement. The time measurement starts, in particular, when a load attached to the load-handling device 21 is lifted from the ground. A corresponding start command for the time measurement can, for example, be linked to the activation of the lifting mode via the control switch. The time measurement is first used to determine at what point in time after the load has been lifted the clutch slippage 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 several lifting speeds are possible - based on the currently selected lifting speed.

[0085] Clutch slippage caused by an excessive load on the load-handling device 21 typically occurs shortly after the load has been lifted, i.e., when the load-handling device 21 is in a vertical position (PLM) close to the ground. Time measurement can be used to determine whether the clutch slippage occurs shortly after the load has been lifted. If this is the case, the control device 19 can conclude that the clutch slippage is caused by an excessive load on the load-handling device 21, or at least rule out the possibility that the clutch slippage is caused by a defective limit switch.

[0086] Clutch slippage caused by a defective upper limit switch occurs later, as it takes significantly longer for the load handling device 21 to reach the upper end position OE. Since the upper end position OE is located behind the vertical position POE specified by an upper limit switch, i.e., is located above the specified vertical position POE (see Figures 2 to 5 ), it can be concluded by means of the control device 19 that the clutch slipping is caused by a defective upper limit switch.

[0087] During lowering, for example, the vertical position PLAM of the load-handling device 21, at which a previous lifting or lowering movement was interrupted, can be used as the starting point for a time measurement. Depending on the starting point, the time measurement can then be used to determine whether the load-handling device 21 is at the lower end position UE when the clutch slips.

[0088] In the second embodiment, prior clutch slippage is taken into account in particular in order to determine the vertical position PLAM of the load-handling device 21 as accurately as possible. Whether lifting or lowering is currently taking place can be determined by the control device 19 from the direction of rotation of the drive motor 2 or from a direction signal of the control switch, or from sensor signals detected by the sensor 18.

[0089] 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, i.e. to confirm the vertical position PLAM of the load-handling device 21.

[0090] If 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 can be issued by the control device 19. Additionally or alternatively, the chain hoist 1 can be enabled only for lowering the load handling device 21. Additionally or alternatively, only a creep speed of the chain hoist 1 can be enabled. Additionally or alternatively, the drive motor 2 can be switched off.

[0091] One of the aforementioned measures, which serve in particular to protect the chain hoist 1, can therefore be initiated depending on the cause of the clutch slipping and / or the frequency of clutch slipping. The control device 19 is thus capable of initiating different measures in the case of clutch slipping caused by a defective limit switch than in the case of clutch slipping caused, for example, by an excessive load on the load attachment device 21. It is also not necessary to initiate a measure every time the clutch slips.

[0092] If the clutch slippage is caused by an excessive load on the load-carrying device 21 or a slip clutch 14 that is set too sensitively, the chain 22 is generally not subjected to such a load that it breaks, even if it occurs frequently. This clutch slippage is also referred to as non-critical.

[0093] Therefore, for example, a maximum number of clutch slips caused by a defective limit switch and a maximum number of clutch slips caused by other causes can be stored in the control device 19 or in the memory unit of the control device 19. It can then be provided that a counter is incremented for each clutch slip, and when the predetermined maximum number is reached, the appropriate measure for this cause is initiated.

[0094] The Figures 2 to 5 show a schematic representation of the chain hoist 1 at different vertical positions PLAM of the load handling device 21.

[0095] During the lifting and lowering of the load handling device 21, the vertical position PLAM of the load handling device 21 changes. Otherwise, i.e. when the load handling device 21 is not lifted or lowered, the vertical position PLAM of the load handling device 21 remains the same.

[0096] The vertical position PLAM of the load-handling device 21 can be a position between the upper end position OE and the lower end position UE. The upper end position OE is a position of maximum possible lifting height, which is mechanically limited by the load-handling device 21 hitting the drive housing 23. The vertical position POE, specified by the upper limit switch, is located below the upper end position OE.

[0097] The lower end position UE is a position of maximum possible lowering depth, which is mechanically limited by the end stop when the load handling device 21 is completely lowered. Above the lower end position UE is the vertical position PUE, which is specified by the lower limit switch.

[0098] In the Figure 2 The vertical position PLAM of the load-carrying device 21 is located between the vertical position PUE specified by the lower limit switch and the vertical position POE specified by the upper limit switch. Clutch slippage occurring at this vertical position is detected by the control device 19 (see Figure 1 ) is not attributed to a defective limit switch, but to another cause, such as an excessive load on the load handling device 21.

[0099] In the Figure 3 the vertical position PLAM of the load-carrying device 21 is equal to the lower end position UE and in the Figure 4the upper end position OE. A clutch slippage occurring in such a vertical position PLAM of the load-carrying device 21 is attributed by the control device 19 to a defective lower ( Figure 3 ) or upper ( Figure 4 ) limit switch assigned.

[0100] In the Figure 5 The vertical position PLAM of the load-handling device 21 equals the vertical position POE specified by the upper limit switch. A functioning upper limit switch would 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 equals the vertical position PUE specified by the lower limit switch. List of reference symbols

[0101] 1Chain hoist 2Drive motor 3Motor shaft 4Gearbox input shaft 5First bearing 6Second bearing 7Gearbox 8First gear 9Second gear 10Gearbox output shaft 11Third bearing 12Fourth bearing 13Sprocket 14Slip clutch 15Clutch disc 16Clutch lining 17Thrust washer 18Sensor 19Control device 20Brake 21Load handling device 22Chain 23Drive housing PLAMvertical position of load handling device POEvertical position of upper limit switch PUEvertical position of lower limit switch OEupper end position UElower end position

Claims

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

2. Method according to claim 1, characterized in that the vertical position (PLAM) of the load handling device (21) is determined on the basis of sensor signals from the sensor (18).

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

4. Method according to claim 2 or 3, characterized in that an amplitude of a change in the sensor signals is determined.

5. Method according to any of the preceding claims, characterized in that the vertical position (PLAM) of the load handling device (21) is determined by means of timing.

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

7. Method according to any of the preceding claims, characterized in that when a deviation of the speed of the transmission (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 the chain hoist (1) is only allowed to lower the load handling device (21), and / or only a creep speed of the chain hoist (1) is allowed, and / or the drive motor (2) is switched off.

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

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

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