Method for monitoring a chain hoist

Abstract

The present invention relates to a method for monitoring a chain crane (1) having an electric drive motor (2) connected to a transmission device (7) on its output side via a friction clutch (14), wherein the speed of the transmission device (7) is sensed via a sensor (18), and a control device (19) is used to compare the sensed speed of the transmission device (7) with the operating speed of the drive motor (2). To achieve 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) designed and configured to perform the method according to the invention.

Description

[0001] The present invention relates to a method for monitoring a chain crane and a chain crane.

[0002] This type of chain crane includes 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 crane are typically housed in a drive housing. This type of chain crane 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 above at least one sprocket tooth arranged on the output shaft of the transmission device. Corresponding control commands are typically given by the operator via a control switch and transmitted from the control switch to the chain crane's control unit.

[0003] It is known that this type of chain crane is equipped with one or more limit switches. These limit switches are used to override control commands transmitted to the control device using corresponding signals (particularly signals directed to the control device). When the limit switches are functioning normally, the signal from the limit switches and the resulting intervention from the control device can be used to stop the chain crane's drive motor, for example, even if control commands for raising or lowering have already been transmitted to the control device.

[0004] Friction clutches in chain cranes are primarily used to prevent overload and the resulting damage to the drive motor, transmission, and chain. For example, the friction clutch can slip when lifting excessively heavy loads. Slippage can also be caused by the load handling device striking the drive housing or 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] An upper limit switch prevents the load handler from impacting the drive housing. A lower limit switch prevents the chain from fully extending and being blocked by the end stop. However, if one of the limit switches is faulty, the drive motor will not stop in time, and the friction clutch will slip when the load handler impacts the drive housing or when it impacts the end stop.

[0006] Although friction clutches are designed to prevent chain slippage (known as clutch slip), the chain can become overloaded and even break, depending on the cause of the slippage and the frequency of such slippage. This is especially true if the load handling unit repeatedly strikes the drive housing due to a faulty upper limit switch, or if the load handling unit repeatedly strikes the end stops due to a faulty lower limit switch.

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

[0008] Methods for monitoring the operation of cable winches are known from DE 199 56 265A1 and DE 195 12 103A1, particularly concerning the number of cable turns 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 a sensor.

[0010] Therefore, the present invention is based on the objective of providing a method for monitoring a chain crane and providing a chain crane that enables safe and efficient operation of the chain crane.

[0011] This objective is achieved by a method having the features of this application and a chain crane having the features of this application. Advantageous embodiments of the invention are given in the following description.

[0012] According to the present invention, in a method for monitoring a chain crane having an electric drive motor connected to a transmission device via a friction clutch on the output side, wherein the speed of the transmission device is sensed by 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 safe and efficient operation of the chain crane, wherein the vertical position of the load handling device of the chain crane is also determined using the control device.

[0013] In other words, the method according to the invention determines the vertical position of the load processing device in addition to comparing the sensed transmission speed with the motor operating speed.

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

[0015] The corresponding control commands for lifting and lowering are preferably transmitted from the control switch of the chain crane to the control device and from the control device 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 be changed via control commands transmitted to the drive motor.

[0016] Without raising or lowering the load handling device, its vertical position remains unchanged. For example, only small changes in the vertical position of the load handling device caused by vibration, which are considered negligible within the scope of this invention, are thus possible.

[0017] The vertical position of the load handling device can be between an upper end position and a lower end position located below the upper end position. The upper end position is the position of the maximum possible lifting height, which is mechanically limited, for example, by the load handling device impacting the drive housing of the chain crane. 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 descent depth, which is also mechanically limited, for example, by end stops, 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] During normal operation of the chain crane, at least one limit switch installed on the chain crane 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 crane and, for example, overwrite the control commands transmitted from the control switch to the control device.

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

[0020] Sensors mounted on the chain crane preferably sense the speed of a single shaft of the conveyor, such that the speed of the conveyor or transmission speed is understood to mean the speed of a single shaft of the conveyor. Alternatively, the sensors may also sense the speed of a single gear in the conveyor. The sensors transmit the sensed speed to the control unit via sensor signals. The sensor signals may be stored in the memory unit of the control unit in the form of sensor data.

[0021] The operating speed of the drive motor and / or the motor operating speed is preferably determined by the operating data of the drive motor. For different operating states of the chain crane, this data can be stored in the memory unit of the control device.

[0022] By comparing the sensed transmission speed with the motor operating speed, a speed deviation or speed difference can be determined. This allows the control device to detect clutch slippage of a friction clutch, which is functionally arranged between the drive motor and the transmission, particularly between the motor shaft and the input shaft of the transmission. Depending on which shaft or gear of the transmission is sensed, the gear ratio of the transmission must be taken into account when determining the deviation. Preferably, the occurrence rate of clutch slippage is stored in a memory unit. Error messages can also be generated.

[0023] Due to the functional design of chain cranes, particularly because the load handling unit is connected to the output shaft of the transmission device (also known as the transmission device output shaft) via a chain and at least one sprocket tooth, the force acting on the chain, or changes in that force, affects the torque applied to the input shaft of the transmission device. Therefore, the force on the chain changes the torque applied to the input shaft of the transmission device (also known as the transmission device input shaft); this also changes the torque acting on the transmission portion of the friction clutch. When the applied torque exceeds the maximum torque that the friction clutch can transmit and is adjusted for, the friction clutch slips.

[0024] Typically, the maximum transmittable torque corresponds to the value of the chain crane's nominal load. The friction clutch, adjusted in this way, slips when lifting excessively heavy loads (i.e., loads exceeding the nominal load). Slippage can occur even under loads below the nominal load if the friction clutch is set too sensitively, i.e., set below the maximum transmittable torque corresponding to the chain crane's nominal load.

[0025] Compared to clutch slip caused by the following reasons, clutch slip caused by one of the two reasons mentioned above is less critical to preventing chain breakage and can therefore be tolerated at a relatively higher frequency.

[0026] Slippage can also be caused by the load handler impacting the drive housing or the end stop. Both causes can be traced back to a faulty upper or lower limit switch. The lifting or lowering movement of the load handler stops abruptly by impacting the drive housing or the end stop, while the drive motor continues to run. Due to the resulting high load on the chain, especially due to the high tension acting on the chain, and particularly due to the frequency of such high loads, the chain may become overloaded and even break.

[0027] Using the method according to the invention, not only can clutch slippage itself be determined, but also the vertical position of the load handling device during clutch slippage can be determined. Therefore, if the control device detects clutch slippage 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 be determined, for example, that the corresponding upper or lower limit switch is defective. However, if the determined vertical position of the load handling device in the case of clutch slippage cannot be assigned to the vertical position stored in the memory unit of the control device, the control device can determine that the clutch slippage is due to another reason, such as excessive load on the load handling device.

[0028] This allows for the determination and attribution of the cause of clutch slippage. Therefore, using the method according to the invention, it is possible to distinguish between clutch slippage caused by excessive load on the load handling device and clutch slippage caused by a defective limit switch. It can also be specified that the optionally generated error message varies depending on the cause.

[0029] Therefore, the method according to the invention can be used to diagnose limit switch failures and at least reduce the proportion of chain breaks that may be attributed to defective limit switches. This enables the safe operation of chain cranes. Furthermore, the application of the method according to the invention does not adversely affect the required production costs of chain cranes, as no additional hardware is required compared to chain cranes known from EP 1 510 498 B1.

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

[0031] In addition to the speed of the transmission device, sensor signals are used to determine the vertical position of the load processing device. These sensor signals are received and evaluated by the control device. Preferably, the sensor signals are stored in the memory unit of the control device. With the sensors designed accordingly, the vertical position of the load processing device can be determined uniquely based on the sensor signals.

[0032] In the first embodiment, it is particularly advantageous to sense the rotation direction of the transmission device based on sensor signals, and to determine the vertical position of the load processing device by “counting upwards” and “counting downwards” the sensor signals.

[0033] The rotation direction of the transmission device associated with the load raising or lowering processing device is detected to determine whether the sensor signals need to be counted upwards or downwards, i.e., whether the sensor signals need to be added or subtracted. Preferably, the rotation direction of each axis of the transmission device is detected. Alternatively, the rotation direction of a single gear of the transmission device can be detected.

[0034] The starting point for upward and downward counting, i.e., the initial vertical position of the load handling device, can be specified, for example, when the chain crane is put into operation. It can also be specified that the starting point can be calibrated, specifically reset, during the operation of the chain crane. When the starting point for upward and downward counting is known, changes in the vertical position can be determined from the upward and downward counting, and thus the (current) vertical position is also determined. A control device connected to the sensor via signal transmission counts upward when the load handling device rises and counts downward when the load handling device falls.

[0035] Preferably, the incremental sensors used for upward and downward counting include a fan disc fixed to the shaft of the transmission device in an anti-torque manner and a light-blocking plate, which in particular has two photodetectors for detecting the direction of rotation. Using this type of sensor design, the vertical position of the load processing device can be uniquely determined based on the sensor signals.

[0036] Depending on the direction of rotation, for example, whenever the light-blocking plate is interrupted, the corresponding sensor signal in the control device is added to the previous value of the sensor signal (i.e., counted upwards) or subtracted from it (i.e., counted downwards). The change in the vertical position of the load processing device during the interruption of a single light-blocking plate is known, so that the vertical position of the load processing device can be derived from the value of the sensor signal.

[0037] In the first embodiment, it may be additionally or alternatively specified that the magnitude of the change in the sensor signal is determined.

[0038] Then, for example, it can be determined how rapidly the sensor signal used to sense the transmission speed changes. When the vertical position of the load handling device corresponds to the upper or lower end position, the lifting or lowering motion is suddenly stopped as described above, thereby braking the transmission speed to zero very quickly. The sensor signal used to sense the transmission speed therefore changes very rapidly.

[0039] However, if the load on the load handling device is too large, the sensor signal used to sense the transmission speed changes relatively slowly because the force acting on the load handling device and the chain also changes slowly.

[0040] This also makes it possible to determine the vertical position of the load processing device based on the degree of change in the sensor signal, and thus assign the clutch slippage to the cause.

[0041] In the second embodiment, the second embodiment may replace or be provided in addition to the first embodiment, and the vertical position of the load processing device is determined by timing.

[0042] The timing is first used to determine at what point clutch slip occurs after the timing begins. The vertical position of the load handling device can then be determined by considering the vertical position of the load handling device at the start of the timing and the lifting speed of the chain crane, or, if multiple lifting speeds are possible, based on the lifting speed selected at that time. Furthermore, any previously occurring clutch slip is preferably considered to ensure the vertical position of the load handling device can be determined as accurately as possible.

[0043] The corresponding times for the upper end position, lower end position, and vertical position specified by at least one limit switch—that is, the time required from the start of timing to reaching the corresponding position—are preferably stored in the memory unit of the control device. The aforementioned times are suitable for the corresponding chain crane, particularly for a given chain crane's maximum lifting height and lifting speed.

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

[0045] Clutch slippage caused by a defective upper limit switch occurs only slightly 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 located above the vertical position specified by the upper limit switch, and therefore after the vertical position specified by the upper limit switch in time, the control device can determine that the clutch slippage is caused by the defective upper limit switch.

[0046] Specifically, timing begins when a load attached to the load handling device is lifted from the ground, for example. The corresponding command to start the timing can be associated with the activation of the lifting mode, for example, via a control switch.

[0047] For descent, for example, the vertical position of the load handling device where the previous lifting or lowering motion was interrupted can be used as the starting point for timing. Based on the starting point and the lifting speed (selected in this case), the 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 a lifting or lowering has occurred from the direction signal of the control switch, i.e., specifically whether a lifting or lowering mode is activated. Alternatively, the control device can derive this from the rotational 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., to confirm the vertical position of the load processing device. In a combination of embodiments, it can also be determined whether the load processing device is raised or lowered based on the sensor signals detected by the aforementioned sensors.

[0050] All implementation schemes are specified in an advantageous and structurally simple manner, with the sensor sensing the rotational speed of the input shaft of the transmission device connected to the friction clutch.

[0051] The sensor is located behind the friction clutch, particularly from the perspective of the drive motor. This makes it particularly simple to compare the speed of the transmission device with the operating speed of the drive motor, since the gear ratio of the transmission device does not need to be considered.

[0052] It can be advantageously stipulated that when a deviation between the speed of the transmission device and 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 audible alarm is issued, and / or only the chain crane is allowed to lower the load handling device, and / or only the chain crane's crawling speed is allowed, and / or the drive motor is shut off.

[0053] Therefore, in the event of clutch slippage, one of the measures specifically designed for protecting chain cranes described above can be initiated based on the vertical position of the load handling device, and thus based on the cause of the clutch slippage and / or the frequency of its occurrence.

[0054] Therefore, the control device can initiate different actions in the event of clutch slippage caused by a faulty limit switch compared to those initiated in the event of clutch slippage caused by other reasons, such as excessive load on the load attachment device. Nor does it need to take any action every time clutch slippage occurs. For example, in cases where clutch slippage is caused by excessive load on the load handling device or an overly sensitive friction clutch, the chain is generally not subjected to such loads that would cause it to break, even if this occurs frequently. This type of clutch slippage is also referred to as non-critical. For example, in the case of such non-critical clutch slippage, drastic measures such as disconnecting the drive motor are not required.

[0055] Therefore, for example, the maximum number of clutch slips caused by a defective limit switch and the maximum number of clutch slips caused by other reasons can be stored in the memory unit of the control device. It can be stipulated that, after a cause has been assigned, each clutch slip is added to a pre-stored value for that cause, and a corresponding measure is introduced when the specified maximum number for that cause is reached.

[0056] In this case, it can also be considered that the cause of clutch slippage when the load is reduced is usually a faulty limit switch. During descent, clutch slippage due to excessive load on the load handling device can at least be ruled out.

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

[0058] The present invention also relates to a chain crane having an electric drive motor, a transmission device, a friction clutch, as well as sensors, a load handling device, and a control device, wherein the electric drive motor is connected to the transmission device via a friction clutch on the output side. The control device is designed and configured to perform the method according to the invention.

[0059] Particularly advantageously, the sensor includes a fan disk arranged in an anti-torque manner on the shaft of the transmission device, preferably on the input shaft of the transmission device, and a light-blocking plate used thereto to sense the speed of the fan disk.

[0060] This type of sensor can sense the rotational speed of the fan disc and thus the speed of the drive shaft. Furthermore, it can be used to determine the direction of rotation of the drive shaft and to count the sensor signals upwards and downwards.

[0061] Other advantageous embodiments and details of the invention will become apparent from the following description. In the accompanying drawings:

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

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

[0064] Figure 1 This is a schematic cross-sectional view of a chain crane 1 equipped with a control device 19 for performing at least one embodiment of the method according to the invention.

[0065] The chain crane 1 has an electric drive motor 2, with a motor shaft 3 extending from 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 crane 1 also includes a transmission device 7, which is designed as a single-stage mechanism in this exemplary embodiment, but can also be designed as a multi-stage mechanism. The transmission device input shaft 4 of the transmission device 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 device 7 includes a first gear 8, which is arranged in a torque-resistant manner on the transmission device input shaft 4 and meshes with a second gear 9, which is arranged in a torque-resistant manner on the transmission device output shaft 10. The transmission device output shaft 10, arranged parallel to the transmission device 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] The sprocket tooth 13 is arranged in a torque-resistant manner on the output shaft 10 of the transmission device, and in this case, at one end of the output shaft 10. This sprocket tooth 13 is used in a conventional manner to provide forced drive to the chain 22 (not shown) of the chain crane 1. A load handling device 21 (not shown) suspended on the chain 22 is raised and lowered by moving the chain 22 above the sprocket tooth. When lifted from the sprocket tooth 13, the chain 22 travels into the chain storage unit (not shown) of the chain crane 1.

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

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

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

[0071] A sensor 18 is also arranged on the input shaft 4 of the transmission device. The sensor 18 is used to determine the speed of the input shaft 4 of the transmission device, and in addition to a fan disc (not shown) arranged on the input shaft 4 in an anti-torque manner, a light-blocking plate (not shown) is also included, which has two photodetectors arranged in the area of ​​the compartment of the fan disc. The speed of the fan disc, and thus the speed of the input shaft 4 of the transmission device, is thus detected using the light-blocking plate, and in particular by determining the frequency of the light-blocking plate's interruption.

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

[0073] If the maximum torque that can be transmitted by the friction clutch 14 is exceeded and the friction clutch 14 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 by the control device 19.

[0074] Clutch slippage may be caused by excessive load on the load handling device 21. Since the friction clutch 14 is set to the maximum transmittable torque, which specifically corresponds to the nominal load of the chain crane 1, clutch slippage caused by the friction clutch 14 being set too sensitive is not expected in this case.

[0075] However, when the load handling device 21 impacts the drive housing 23 of the chain crane 1 (see...) Figures 2 to 5When the chain reaches the upper end position OE, or when it reaches the lower end position UE due to the fully extended chain 22 colliding with the end stop (not shown), clutch slippage may also occur.

[0076] The chain crane 1 also has an upper limit switch and a lower limit switch (both not shown). These indicate the position if the limit switches are functioning correctly; or once the load handling device has reached the vertical position POE, PUE (see [reference]) specified by the corresponding limit switch. Figures 2 to 5 This indicates the point. Based on such indications and / or corresponding limit switch signals, 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 impacting the drive housing 23. By providing a lower limit switch, for example, the chain 22 can be prevented from fully extending and being blocked by the end stop. However, if one of the limit switches is defective, the drive motor 2 will not stop in time, and the friction clutch 14 will slip when the load handling device 21 impacts the drive housing 23 or when it impacts the end stop.

[0078] Using control device 19, the vertical position PLAM of load processing device 21 is determined. The vertical position PLAM of load processing device 21 is used to assign clutch slippage occurring on friction clutch 14 to the cause of the clutch slippage, for example, to enable the detection of a defective limit switch.

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

[0080] However, if the vertical position PLAM of the load handling device 21 determined during clutch slippage is not assigned to the vertical position stored in the control device 19, the control device 19 determines that the clutch slippage is due to another reason, such as 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 crane 1, wherein the two embodiments can be used independently 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 processing device 21 is determined based on sensor signals from sensor 18. The vertical position PLAM of the load processing device 21 is determined based on sensor signals in addition to the speed of the input shaft 4 of the transmission device. For this purpose, the sensor signals are received and evaluated by the control device 19. In this embodiment, where sensor 18 includes a fan disc and a light-blocking plate, the vertical position PLAM of the load processing device 21 can be determined solely based on sensor signals.

[0083] First, the rotation direction of the input shaft 4 of the transmission device is determined via a corresponding sensor signal from sensor 18, which is connected to the control device 19. For this purpose, the rotation direction of the fan disc is detected using two photodetectors on the light-blocking plate. An initial vertical position PLAM for the load processing device 21 is predetermined, serving as the starting point for upward and downward counting. Knowing the rotation direction, i.e., whether the load processing device is rising or falling, the vertical position PLAM of the load processing device 21 is determined specifically by performing "upward counting" and "downward counting" on the sensor signals. For example, the control device 19 counts upward when the load processing device 21 rises and counts downward when the load processing device 21 falls. Therefore, depending on the rotation direction, whenever the light-blocking plate is interrupted, the corresponding sensor signal is added to or subtracted from its previous value. The change in the vertical position PLAM of the load processing device 21 during a single light-blocking plate interruption is known, allowing the vertical position PLAM of the load processing device 21 to be derived from the values ​​of the sensor signals.

[0084] Alternatively or otherwise, the magnitude of the change in the sensor signal can be determined. For example, how rapidly the sensor signal changes can then be determined. If the vertical position PLAM of the load processing device 21 is equal to the upper end position OE or the lower end position UE, the lifting or lowering motion stops abruptly, causing the change in the sensor signal to occur very rapidly. However, if the load on the load processing device 21 is too large, the change in the sensor signal occurs relatively slowly. This also allows clutch slippage to be assigned a cause based on the rate of change of the sensor signal.

[0085] In a second embodiment of the method, timing is used to determine the vertical position PLAM of the load handling device 21. Specifically, timing begins 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 timing, the point at which clutch slip occurs after the load is lifted is first determined. Then, the vertical position PLAM of the load handling device 21 can be determined based on the lifting speed of the chain crane 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 typically occurs shortly after the load has been lifted, i.e., when the load handling device 21 is in a vertical position close to the ground (PLAM). Timing can be used to determine whether the clutch slips shortly after the load is lifted. If this is the case, the control device 19 can determine 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 faulty limit switch.

[0087] The clutch slippage caused by the defective upper limit switch occurs only later, because 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., it is positioned above the specified vertical position POE (see...). Figures 2 to 5 Therefore, control device 19 can be used to determine that the clutch slippage is caused by a defective upper limit switch.

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

[0089] In the second embodiment, prior clutch slippage is specifically considered to enable the determination of the vertical position PLAM of the load handling device 21 as accurately as possible. The control device 19 can determine whether lifting or lowering is in progress from the rotational direction of the drive motor 2, from the direction signal of the control switch, or from the sensor signal detected by the sensor 18.

[0090] If a second implementation scheme is provided in addition to the first implementation scheme, one of the two implementation schemes can be used to verify the other implementation scheme, i.e., to confirm the vertical position PLAM of the load processing device 21.

[0091] When a deviation between the speed of the input shaft 4 of the transmission device and 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 audible alarm may be issued by the control device 19. Alternatively, the chain crane 1 may be permitted to reduce the speed of the load handling device 21 only. Alternatively, only the crawling speed of the chain crane 1 may be permitted. Alternatively, the drive motor 2 may be shut off.

[0092] Therefore, one of the measures specifically designed to protect the chain crane 1 described above can be activated based on the cause and / or frequency of clutch slippage. Thus, the control device 19 can initiate measures different from those initiated in the event of clutch slippage caused by a faulty limit switch, compared to those initiated in the event of clutch slippage caused by, for example, excessive load on the load handling device 21. Furthermore, no action needs to be taken every time clutch slippage occurs.

[0093] If clutch slippage is caused by excessive load on the load handling unit 21 or by a friction clutch 14 that is set too sensitively, the chain 22 will not typically be loaded to the point of breaking, even if this occurs frequently. This clutch slippage is also referred to as non-critical.

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

[0095] Figures 2 to 5 A schematic diagram of a chain crane 1 located at different vertical PLAM positions on the load handling device 21 is shown.

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

[0097] The vertical position PLAM of the load processing device 21 can be the position between the upper end position OE and the 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 processing device 21 impacting the driver 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 descent 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 the vertical position PUE designated by the lower limit switch.

[0099] exist Figure 2 In this configuration, the vertical position PLAM of the load handling device 21 is positioned 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 in this vertical position is not caused by the control device 19 (see...). Figure 1 The cause is not attributed 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 middle, the vertical position PLAM of the load processing device 21 corresponds to the lower end position UE, and in Figure 4 The middle corresponds to the upper end position OE. Clutch slippage occurring in this 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 In this configuration, the vertical position PLAM of the load processing device 21 corresponds to the vertical position POE specified by the upper limit switch. An activated upper limit switch will indicate this, allowing the control device 19 to intervene accordingly. This also applies if the vertical position PLAM of the load processing device 21 is equal to the vertical position PUE specified by the lower limit switch.

[0102] List of reference numerals

[0103] 1. Chain crane

[0104] 2. Drive motor

[0105] 3 Motor shaft

[0106] 4. Input shaft of the transmission device

[0107] 5 First bearing

[0108] 6 Second bearing

[0109] 7. Transmission device

[0110] 8 First Gear

[0111] 9 Second gear

[0112] 10. Output shaft of transmission device

[0113] 11 Third Bearing

[0114] 12 Fourth Bearing

[0115] 13 sprocket teeth

[0116] 14 Friction clutch

[0117] 15. Clutch disc

[0118] 16 Clutch Liner

[0119] 17 Pressure Plate

[0120] 18 sensors

[0121] 19. Control device

[0122] 20 Brakes

[0123] 21 Load handling device

[0124] 22 chains

[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 bottom end position

Claims

1. Method for monitoring a chain hoist (1) with an electric drive motor (2), which is connected on the output side to a transmission (7) via a friction clutch (14), wherein the speed of the transmission (7) is sensed via a sensor (18) and the sensed speed of the transmission (7) is compared to 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), based on sensor signals from the sensor (18), which is used to assign clutch slippage occurring on the friction clutch (14) to the cause of the clutch slippage.

2. The method of claim 1, wherein, The rotation direction of the transmission device (7) is detected based on the sensor signal, and the vertical position (PLAM) of the load processing device (21) is determined by "counting upwards" and "counting downwards" on the sensor signal.

3. The method according to claim 1 or 2, characterized in that, Determine the magnitude of the change in the sensor signal.

4. The method according to claim 1 or 2, characterized in that, The vertical position (PLAM) of the load processing device (21) is determined using timing.

5. The method according to claim 1 or 2, characterized in that, The speed of the transmission input shaft (4) connected to the friction clutch (14) is sensed via the sensor (18).

6. The method according to claim 1 or 2, characterized in that, When a deviation between the speed of the transmission device (7) and the operating speed of the drive motor (2) is detected and a predefined vertical position (PLAM) of the load handling device (21) is present, a visual and / or audible alarm is issued, and / or the chain crane (1) is only allowed to reduce the load handling device (21), and / or the chain crane (1) is only allowed to crawl, and / or the drive motor (2) is shut down.

7. A chain hoist having an electric drive motor (2), a transmission (7) and a friction clutch (14) and a sensor (18), a load processing device (21) and a control device (19), the electric drive motor (2) being connected on the output side via the friction clutch (14) to the transmission (7), characterized in that The control device (19) is designed and configured to perform the method according to any one of the preceding claims.

8. The chain hoist of claim 7, wherein, The sensor (18) includes a fan disk arranged on the shaft of the transmission device (7) in an anti-torque manner, and a light-blocking plate that can be used to sense the speed of the fan disk.

9. The chain crane according to claim 8, characterized in that, The shaft of the transmission device (7) is the input shaft (4) of the transmission device.

Images