Method for monitoring a chain hoist

Abstract

The present invention relates to a method for monitoring a chain hoist (1) having an electric drive motor (2) connected at its 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 by a control device (19) with the operating speed of the drive motor (2). To achieve safe and efficient operation of the chain hoist (1), the vertical position (PLAM) of a load handling device (21) of the chain hoist (1) is also determined by the control device (19). The present invention also relates to a chain hoist (1) having a control device (19) designed and configured to implement the method according to the present invention.

Description

[Technical Field]

[0001] The present 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] This type of chain hoist includes an electric drive motor, a transmission, and a friction clutch operatively disposed between the drive motor and the transmission. The above-mentioned components of the chain hoist are typically disposed within a drive housing. This type of chain hoist also includes 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 disposed on the output shaft of the transmission. Corresponding control commands are typically given by an operator via a control switch, which transmits the commands to the chain hoist's controller.

[0003] It is known to equip chain hoists of this category with one or more limit switches, which are used in particular to make it possible to override a control command sent to the control device by means of a corresponding signal. If the limit switch is functioning properly, the drive motor of the chain hoist can be stopped using the signal of the limit switch and the resulting intervention of the control device, even if a control command for e.g. raising or lowering has been sent to the control device.

[0004] Friction clutches in chain hoists are primarily used to prevent overloads and resulting damage to the drive motor, transmission, and chain. Friction clutches slip, for example, when very heavy loads are lifted. Slippage can also be caused by the load handling device hitting the drive housing or by the chain hitting an end stop at one end when fully extended. However, slippage can also occur when the friction clutch is set too sensitively.

[0005] The upper limit switch can prevent the load handling device from hitting the drive housing. The lower limit switch can prevent the chain from fully extending and being blocked by the end stop. However, if one of the limit switches fails, the drive motor will not stop in a timely manner and the friction clutch will slip when the load handling device hits the drive housing or when the load handling device hits the end stop.

[0006] Despite slippage of the friction clutch (known as clutch slippage) intended to prevent chain overload, depending on the cause and frequency of the clutch slippage, the chain can become overloaded and even break, especially if the load handling equipment repeatedly strikes the drive housing due to a faulty high limit switch, or if the load handling equipment repeatedly strikes the end stop due to a faulty low limit switch.

[0007] European Patent No. 1510498(B1) discloses a method for monitoring a chain hoist, which enables the chain hoist controller to detect deviations of the actual speed of the transmission from the target speed of the drive motor, and thus to detect slippage of the friction clutch. However, this method does not allow for determining the cause of the clutch slippage.

[0008] From DE 19956265 A1 and DE 19512103 A1 methods are known for monitoring the operation of a cable winch, in particular with regard to the number of turns of cable wound on the winch.

[0009] DE 102015105517 A1 discloses a cable retraction and deployment device for aeronautical applications, in which the end position of the cable can be detected by a sensor, and a method for controlling the device.

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

[0011] This 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 given in the dependent claims and the following description.

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

[0013] In other words, the method according to the present invention provides for determining the vertical position of the load handling 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-lifting hook is suspended from the chain of a chain hoist. The chain can be arranged in a single-leg or multi-leg configuration, so that the load-handling device is attached to the free end of the chain (single-leg) or the chain is deflected by a load-handling device designed as a bottom block (multi-leg). The chain can move via at least one sprocket fixedly mounted on the output shaft of a transmission. The rotational movement of the at least one sprocket is transmitted to the chain via a positive connection with the chain, so that the load-handling device rises or falls, depending on the direction of rotation. For this purpose, the rotational movement of an electric drive motor is transmitted to at least one sprocket, and the torque is converted via a transmission operatively arranged between them.

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

[0016] When the loading equipment is not being raised or lowered, the vertical position of the loading equipment remains the same. Only small changes in the vertical position of the loading equipment are possible, for example caused by vibrations of the loading equipment, which are considered negligible within the scope of the present invention.

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

[0018] When the chain hoist is functioning properly, at least one limit switch provided on the chain hoist indicates when the vertical position of the load handling device corresponds to the vertical position specified by the limit switch. Based on the indication, the control device can intervene in the control process of the chain hoist, for example, by overriding a control command sent from the control switch to the control device.

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

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

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

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

[0023] Due to the functional design of the chain hoist, in particular because the load handling device is connected via a chain and at least one sprocket to the transmission output shaft, also known as the transmission output shaft, any force or change in force acting on the chain affects the torque applied to the transmission input shaft. Therefore, the force on the chain changes the torque applied to the transmission input shaft, also known as the transmission input shaft. This in turn changes the torque acting on the transmission part of the friction clutch. If the applied torque exceeds the maximum torque the friction clutch can transmit and is adjusted for, the friction clutch will slip.

[0024] In principle, the maximum transmittable torque corresponds to the nominal load of the chain hoist. A friction clutch adjusted in this way will slip when too heavy a load is lifted, i.e., when a load exceeding the nominal load is lifted. If the friction clutch is set too sensitively, i.e., when the maximum transmittable torque is set lower than the nominal load of the chain hoist, slippage may occur even when the load is lower than the nominal load.

[0025] Clutch slippage caused by one of the two causes mentioned above is less significant in terms of preventing chain breakage than clutch slippage caused by the cause described below, and therefore can be tolerated at a relatively higher frequency of occurrence.

[0026] The cause of slippage can also be the load handling device hitting the drive housing or hitting an end stop. Both causes can be traced back to a faulty upper limit switch or a faulty lower limit switch. The lifting or lowering movement of the load handling device is abruptly stopped by the load handling device hitting the drive housing or hitting an end stop while the drive motor continues to run. As a result, the chain can become overloaded and even break due to the high loads placed on the chain, especially as a result of the high tensions acting on the chain, which frequently occur.

[0027] The method according to the present invention can determine not only the clutch slip itself but also the vertical position of the load handling device at the time of the clutch slip. Thus, if the control device detects the clutch slip based on the sensor signal and can assign the determined vertical position of the load handling device to the upper or lower limit position, the control device can conclude, for example, that the corresponding upper or lower limit switch is faulty. However, if the determined vertical position of the load handling device in the event of clutch slip cannot be assigned to the vertical position stored in the control device's memory unit, the control device can conclude that the clutch slip is due to another cause, for example, excessive load on the load handling device.

[0028] This allows the cause of the clutch slip to be determined and attributed to the clutch slip. Thus, the method according to the invention makes it possible to distinguish between clutch slip caused by excessive load on the load handling device and clutch slip caused by a faulty limit switch. Therefore, the error message that is optionally generated can vary 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 rate of chain breakage that can be attributed to a faulty limit switch. This allows for safe operation of the chain hoist. Furthermore, application of the method according to the invention does not adversely affect the manufacturing costs of the chain hoist, since no additional hardware is required compared to the chain hoist known from EP 1 510 498 B1.

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

[0031] In addition to the transmission speed, the vertical position of the load handling equipment is also determined using the sensor signals. The sensor signals are received and evaluated by the control device. Preferably, the sensor signals are stored in a memory unit of the control device. If the sensors are designed accordingly, it is possible to determine the vertical position of the load handling equipment based solely on the sensor signals.

[0032] In a first embodiment, it is particularly advantageous that the direction of rotation of the transmission is sensed based on the sensor signal and the vertical position of the loading device is determined by "counting up" and "counting down" the sensor signal.

[0033] The rotation direction of the transmission associated with raising or lowering the load handling device is detected to determine whether the sensor signal needs to be counted up or down, i.e., whether the sensor signal needs to be added or subtracted. Preferably, the rotation direction of each shaft of the transmission is detected. Alternatively, the rotation direction of each individual gear of the transmission can be detected.

[0034] The starting points for the counting up and counting down, i.e. the initial vertical position of the load handling device, can be specified, for example, when the operation of the chain hoist is started. It can also be provided that the starting points can be calibrated, in particular reset, during operation of the chain hoist. If the starting points for the counting up and counting down are known, the change in vertical position, and therefore the (current) vertical position, can also be determined from the counting up and counting down. A control device connected to the sensor via a signal transmission counts up when the load handling device is raised and counts down when the load handling device is lowered.

[0035] Preferably, the incremental sensor used for counting up and down comprises a fan disk fixed in a torque-resistant manner to the transmission shaft and a light barrier with, in particular, two photodetectors for detecting the direction of rotation. With such a sensor design, the vertical position of the loading device can be determined solely on the basis of the sensor signal.

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

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

[0038] It can then be determined, for example, how quickly 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 movement is abruptly stopped as described above, so that the transmission speed is braked to 0 very quickly. Therefore, the sensor signal used to sense the transmission speed changes very quickly.

[0039] However, if the load on the load handling device is too great, the forces acting on the load handling device and chain will also change more slowly, and the sensor signal used to sense the transmission speed will change relatively more slowly.

[0040] This also allows the vertical position of the loading device to be determined based on the degree of change in the sensor signal and therefore allows clutch slip to be assigned as the cause.

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

[0042] The timing is first used to determine when a clutch slip occurs after the start of the timing. The vertical position of the load handling equipment can then be determined by considering the vertical position of the load handling equipment at the start of the timing and the lifting speed of the chain hoist, or based on the lifting speed selected at that time if multiple lifting speeds are possible. Additionally, it is preferable that previous clutch slips be taken into account to enable the vertical position of the load handling equipment to be determined as accurately as possible.

[0043] 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 timing to reach each position, are preferably stored in a memory unit of the control device, and said times can be adapted to the corresponding chain hoist, in particular to the maximum lifting height and lifting speed of a given chain hoist.

[0044] By measuring the time and thereby determining the vertical position of the load handling equipment, it is possible to assign a cause to each clutch slip. Clutch slip caused by excessive load on the load handling equipment typically occurs shortly after the load is lifted, for example, when the load handling equipment is in a vertical position close to the ground. Timing can determine whether the clutch slip occurred shortly after the load was lifted, for example, within 2 to 3 seconds. If this is the case, the control system can conclude that the clutch slip was caused by excessive load on the load handling equipment, or at least rule out the possibility that the clutch slip was caused by a faulty limit switch.

[0045] Because it takes a significantly longer time for the loading device to reach the upper limit position, the clutch slip caused by the defective upper limit switch only occurs later, for example, after 5 or 6 seconds. Because the upper limit position is above the vertical position specified by the upper limit switch and therefore after the vertical position specified by the upper limit switch in terms of time, the control device can conclude that the clutch slip is caused by the defective upper limit switch.

[0046] The timing is initiated in particular when a load attached to the loading device is, for example, lifted off the ground. A corresponding command for initiating the timing can be linked to the activation of the lifting mode, for example via a control switch.

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

[0048] In a second embodiment, the control device preferably derives whether lifting or lowering is taking place from the direction signal of the control switch, i.e. whether the lifting mode or the lowering mode in particular is activated. Alternatively, the control device can derive this from the direction of rotation of the drive motor.

[0049] 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 check the vertical position of the loading equipment. In a combination of the embodiments, it is also possible to determine whether the loading equipment is rising or falling from the sensor signals detected by the sensors described above.

[0050] In an advantageous and structurally simple manner, all embodiments provide a sensor that senses the rotational speed of a transmission input shaft connected to a friction clutch.

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

[0052] Advantageously, when a deviation of the transmission speed from the operating speed of the drive motor is detected and a predefined vertical position of the load handling equipment is present, a visual and / or audible alarm is given and / or the chain hoist is only allowed to lower the load handling equipment and / or only a creeping speed of the chain hoist is allowed and / or the drive motor is switched off.

[0053] Thus, one of the above-mentioned measures, which serves in particular to protect the chain hoist, can be initiated in the event of clutch slippage according to the vertical position of the loading device and therefore according to the cause of the clutch slippage and / or the frequency with which clutch slippage occurs.

[0054] Thus, the control device can initiate different actions in the event of a clutch slip caused by a faulty limit switch than actions initiated in the event of a clutch slip caused by other causes, such as excessive load on the load attachment device. Furthermore, no action needs to be taken every time the clutch slips. For example, if clutch slip is caused by an excessively large load on the load attachment device or an overly sensitive friction clutch, even if it occurs frequently, the chain usually does not experience stress that would cause the chain to break. Such clutch slips are also referred to as non-critical. For example, drastic measures such as turning off the drive motor are not required in the event of such non-critical clutch slips.

[0055] Thus, for example, the maximum number of clutch slips caused by a faulty limit switch and the maximum number of clutch slips caused by other causes can be stored in the memory unit of the control device, whereupon, after the cause has been assigned, each clutch slip is added to the value previously stored for this cause, and once the maximum number specified for this cause is reached, the corresponding measure is initiated.

[0056] In this context, it can also be taken into account that clutch slippage when lowering a load is usually caused by a faulty limit switch. Clutch slippage caused by excessive load on the load handling device can be eliminated, at least during lowering.

[0057] In the event of clutch slippage, customer dissatisfaction can be avoided by taking action related to the cause, thus enabling safe and efficient operation of the chain hoist.

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

[0059] Particularly advantageously, the sensor comprises a fan disk arranged in a torque-resistant manner relative to a shaft of the transmission, preferably a transmission input shaft, and a light barrier by means of which the speed of the fan disk can be sensed.

[0060] A sensor designed in this way can sense the speed of the fan disk, and therefore also the speed of the transmission shaft. Additionally, such a sensor can be used to determine the direction of rotation of the transmission shaft and to count up and down the sensor signal.

[0061] Further advantageous embodiments and details of the invention will become apparent from the following description. [Brief explanation of the drawings]

[0062] [Figure 1] 1 is a schematic cross-sectional view of a chain hoist with a control device for implementing at least one embodiment of the method according to the invention; [Figure 2] 1A-1C are schematic diagrams of a chain hoist in different vertical positions of the load handling device. [Figure 3] 1A-1C are schematic diagrams of a chain hoist in different vertical positions of the load handling device. [Figure 4] 1A-1C are schematic diagrams of a chain hoist in different vertical positions of the load handling device. [Figure 5] 1A-1C are schematic diagrams of a chain hoist in different vertical positions of the load handling device. DETAILED DESCRIPTION OF THE INVENTION

[0063] FIG. 1 is a schematic cross-sectional view of a chain hoist 1 having a control device 19 for implementing 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 supported by a first bearing 5, preferably designed as a roller bearing. The drive motor 2 is controlled by a control device 19.

[0065] The chain hoist 1 also has a transmission 7, which in this exemplary embodiment is designed as a single-stage mechanism, but which may also be designed as a multi-stage mechanism. A transmission input shaft 4 of the transmission 7 is arranged coaxially with the motor shaft 3 and is supported by a second bearing 6, which is also preferably designed as a roller bearing. The transmission 7 has a first gear 8 arranged in a torque-resistant manner with respect to the transmission input shaft 4, which meshes with a second gear 9 arranged in a torque-resistant manner with respect to the transmission output shaft 10. The transmission output shaft 10, which is arranged parallel to the transmission input shaft 4, is supported on either side of the second gear 9 by third and fourth bearings 11 and 12, which are also preferably designed as roller bearings.

[0066] A sprocket 13 is disposed on the transmission output shaft 10, in this case at one end of the transmission output shaft 10 in a torque-resistant manner. This sprocket 13 functions in the usual way to provide positive drive to a chain 22 (not shown) of the chain hoist 1. Moving the chain 22 over the sprocket raises and lowers a load handling device 21 (not shown) suspended by the chain 22. When the chain 22 is lifted from the sprocket 13, it enters a chain storage compartment (not shown) of the chain hoist 1.

[0067] Corresponding control commands for raising and lowering the loading device 21 are received by the control device 19 and transmitted by the control device 19 to the drive motor 2. In this case, the control commands received by the control device 19 are transmitted by the control switch of the chain hoist 1.

[0068] A friction clutch 14 is disposed between the transmission input shaft 4 and the motor shaft 3. The friction clutch 14 essentially comprises a clutch disc 15 having an annular clutch lining 16, a pressure plate 17, and a spring element (not shown) for generating a preload that determines the maximum transmittable torque between the pressure plate 17 and the clutch disc 15. The pressure plate 17 is arranged to withstand torque relative to the motor shaft 3, and the clutch disc 15 is arranged to withstand torque relative to the transmission input shaft 4. The friction clutch 14 is set to the maximum transmittable torque corresponding to the nominal load of the chain hoist 1. If the maximum torque that can be transmitted by the friction clutch 14 is exceeded, the friction clutch 14 slips.

[0069] A brake 20 provided on the transmission input shaft 4 allows the latter to be braked as required or blocked when stationary. The brake 20 is controlled by a 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 a fan disk (not shown) arranged torque-resistant to the transmission input shaft 4 as well as a light barrier (not shown) with two photodetectors arranged in the area of ​​the compartment of the fan disk. The speed of the fan disk and therefore of the transmission input shaft 4 is then sensed by the light barrier, in particular by determining the frequency of light barrier interruptions.

[0071] The sensor 18 is connected to the control device 19 by signals, and transmits the rotational speed sensed by the sensor 18 to the control device 19 by means of sensor signals. These sensor signals are processed by the control device 19 and / or stored in a memory unit of the control device 19 in the form of sensor data.

[0072] If the maximum torque that can be transmitted by the friction clutch 14 is exceeded, and therefore the friction clutch 14 slips (referred to as clutch slip), this is detected by a comparison between the speed of the transmission input shaft 4 and the operating speed of the drive motor 2, which is carried out by the control device 19.

[0073] Clutch slippage can be caused by excessive load on the load handling device 21. Since the friction clutch 14 is set specifically to a maximum transmittable torque corresponding to the nominal load of the chain hoist 1, in this case clutch slippage caused by a friction clutch 14 that is set too sensitively is not to be expected.

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

[0075] The chain hoist 1 also has upper and lower limit switches (both not shown). If the limit switches are functioning properly, they indicate this or they indicate this as soon as the loading device reaches the vertical position POE, PUE specified by the respective limit switch (see Figures 2 to 5). Based on such indications and / or the corresponding limit switch signals, the control device 19 overrides the control command sent by the control switch and stops the drive motor 2 in a timely manner.

[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 to prevent the chain 22 from being fully extended and blocked by an end stop, for example. However, if one of the limit switches is faulty, the drive motor 2 will not stop in a timely manner and the friction clutch 14 will slip when the load handling device 21 hits the drive housing 23 or when the load handling device hits an end stop.

[0077] The control device 19 determines the vertical position PLAM of the load handling device 21. The vertical position PLAM of the load handling device 21 is used to assign clutch slip occurring in the friction clutch 14 to the cause of this clutch slip, in order to be able to detect, for example, a faulty limit switch.

[0078] If the control device 19 detects clutch slippage based on the sensor signal from the sensor 18 and the determined vertical position PLAM of the loading device 21 corresponds to the upper end position OE or the lower end position UE (see Figures 2 to 5), both of which positions are stored in the memory unit of the control device 19, the control device 19 concludes that the corresponding limit switch has failed.

[0079] However, if the vertical position PLAM of the loading device 21 determined during clutch slip cannot be assigned to a vertical position stored in the control device 19, the control device 19 will conclude that the clutch slip is due to another cause, for example, excessive load on the loading device 21.

[0080] The vertical position PLAM of the load handling device 21 can be determined by two different embodiments of the method for monitoring the chain hoist 1, which can be used independently of each other or in combination with each other. 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 a sensor signal from the 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 signal. For this purpose, the sensor signal is received and evaluated by the control device 19. In this embodiment of the sensor 18 having a fan disk and a light barrier, it is possible to determine the vertical position PLAM of the load handling device 21 based on the sensor signal alone.

[0082] The direction of rotation of the transmission input shaft 4 is first determined by a corresponding sensor signal from the sensor 18 connected to the control device 19. For this purpose, the direction of rotation of the fan disk is detected using two photodetectors on the light barrier. The initial vertical position PLAM of the load handling device 21, i.e., the starting point for counting up and counting down, is predefined. Given knowledge of the direction of rotation, i.e., whether the load handling device is rising or falling, the vertical position PLAM of the load handling device 21 is determined by specifically "counting up" and "counting down" the sensor signal. For example, the control device 19 counts up when the load handling device 21 is rising and counts down when the load handling device 21 is falling. For this purpose, depending on the direction of rotation, each time the light barrier is interrupted, the corresponding sensor signal is added to or subtracted from the previous value of the sensor signal. The change in the vertical position PLAM of the load handling device 21 during a single light barrier interruption is known, so the vertical position PLAM of the load handling device 21 can be derived from the value of the sensor signal.

[0083] Alternatively or additionally, the amplitude of the change in the sensor signal can be determined. For example, it is then determined how quickly the sensor signal changes. When the vertical position PLAM of the load handling device 21 is equal to the upper end position OE or the lower end position UE, the upward or downward movement is abruptly stopped, so that the change in the sensor signal occurs very quickly. However, if the load on the load handling device 21 is too great, the change in the sensor signal occurs relatively more slowly. This also makes it possible to assign clutch slip as the cause based on the rate of change of the sensor signal.

[0084] In a second embodiment of the method, the vertical position PLAM of the load handling device 21 is determined by timing. The timing is initiated, in particular, when the load attached to the load handling device 21 is lifted from the ground. A corresponding start command for the timing can be linked to the activation of the lifting mode, for example, via a control switch. The timing first determines the point in time at which clutch slip occurs after the load is lifted. The vertical position PLAM of the load handling device 21 can then be determined based on the lifting speed of the chain hoist 1 or, if multiple lifting speeds are possible, based on the selected lifting speed.

[0085] Clutch slippage caused by excessive load on the load handling device 21 typically occurs immediately after the load is lifted, i.e., when the load handling device 21 is in a vertical position PLAM close to the ground. Timing can determine whether the clutch slip occurs immediately after the load is lifted. If this occurs, the controller 19 can conclude that the clutch slippage was 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.

[0086] Since it takes a significantly longer time for the loading device 21 to reach the upper end position OE, the clutch slip caused by the defective upper limit switch only occurs later. Since the upper end position OE is later in time than the vertical position POE specified by the upper limit switch, i.e., is located above the specified vertical position POE (see Figures 2 to 5), the control device 19 can conclude that the clutch slip is caused by the defective upper limit switch.

[0087] In the case of a lowering movement, for example, the vertical position PLAM of the load handling device 21 at which the previous lifting or lowering movement was interrupted can be taken as the starting point for timing. Depending on the starting point, the timing can determine whether the load handling device 21 is in the lower end position UE when the clutch slip occurs.

[0088] In the second embodiment, in particular, previous clutch slip is taken into account so as to be able to determine as accurately as possible the vertical position PLAM of the loading device 21. The control device 19 can determine whether a lifting or lowering is taking place from the direction of rotation of the drive motor 2, or from the direction signal of the control switch, or from the sensor signal detected by the sensor 18.

[0089] 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 check the vertical position PLAM of the loading device 21.

[0090] If a deviation between the rotational speed of the transmission input shaft 4 and the operating rotational speed of the drive motor 2 is detected and 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 can be issued by the control device 19. Additionally or alternatively, the chain hoist 1 can only allow the load handling device 21 to be lowered. Additionally or alternatively, only a creep speed of the chain hoist 1 can be allowed. Additionally or alternatively, the drive motor 2 can be switched off.

[0091] Thus, one of the above-mentioned measures, which serves in particular to protect the chain hoist 1, can be initiated depending on the cause of the clutch slip and / or the frequency of occurrence of the clutch slip. In this way, the control device 19 can initiate different measures if the clutch slip is caused, for example, by an excessive load on the load attachment device 21 and if the clutch slip is caused by the failure of a faulty limit switch. Also, no action needs to be taken every time the clutch slips.

[0092] If clutch slippage is caused by excessive load on the load handling equipment 21 or a friction clutch 14 that is set too sensitively, even if it occurs frequently, the chain 22 generally will not be loaded to such an extent that it breaks the chain 22. This clutch slippage is also referred to as non-critical.

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

[0094] 2 to 5 show schematic views of the chain hoist 1 in different vertical positions PLAM of the load handling device 21.

[0095] The vertical position PLAM of the loading device 21 changes during lifting and lowering of the loading device 21. Otherwise, i.e. when the loading device 21 is not being raised or lowered, the vertical position PLAM of the loading device 21 remains the same.

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

[0097] The lower end position UE is the maximum possible lowering depth mechanically limited by an end stop when the loading device 21 is fully lowered. Above the lower end position UE is a vertical position PUE designated by a lower limit switch.

[0098] In Figure 2, the height position PLAM of the loading 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. Any clutch slip occurring at this vertical position is attributed by the control device 19 (see Figure 1) not to a faulty limit switch but to another cause, such as excessive load on the loading device 21.

[0099] The vertical position PLAM of the loading device 21 corresponds to the lower end position UE in Fig. 3 and to the upper end position OE in Fig. 4. A clutch slip occurring at such a vertical position PLAM of the loading device 21 is assigned by the control device 19 to a faulty lower limit switch (Fig. 3) or upper limit switch (Fig. 4).

[0100] 5, the vertical position PLAM of the loading device 21 corresponds to the vertical position POE specified by the upper limit switch. A functioning upper limit switch indicates this, so that the control device 19 can intervene accordingly. This is therefore the case when the vertical position PLAM of the loading device 21 is equal to the vertical position PUE specified by the lower limit switch. [Explanation of symbols]

[0101] 1 chain hoist 2 drive motor 3 Motor shaft 4 Transmission input shaft 5 First bearing 6 Second bearing 7. Transmission 8 First Gear 9 Second Gear 10 Transmission output shaft 11 Third bearing 12 Fourth bearing 13 sprockets 14 Friction clutch 15 clutch disc 16 Clutch lining 17 Pressure plate 18 Sensors 19 Control device 20 Brake 21 Cargo handling equipment 22 Chain 23 Drive housing PLAM vertical position, loading equipment POE vertical position, upper limit switch PUE vertical position, lower limit switch OE top position UE bottom position

Claims

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

2. 2. The method of claim 1, wherein the vertical position (PLAM) of the loading device (21) is determined based on a sensor signal from the sensor (18).

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

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

5. Method according to any one of claims 1 to 4, characterized in that the vertical position (PLAM) of the loading device (21) is determined by timing.

6. 6. The method according to claim 1, wherein the speed of a transmission input shaft (4) connected to the friction clutch (14) is sensed via the sensor (18).

7. 7. The method according to claim 1, wherein when a deviation of the speed of the transmission (7) from the operating speed of the drive motor (2) is detected and a predefined vertical position (PLAM) of the load handling device (21) exists, a visual and / or audible alarm is issued and / or the chain hoist (1) is only allowed to lower the load handling device (21) and / or only a creeping speed of the chain hoist (1) is allowed and / or the drive motor (2) is switched off.

8. A chain hoist comprising a sensor (18), a load handling device (21), and a control device (19), as well as an electric drive motor (2), a transmission (7), and a friction clutch (14), wherein the electric drive motor (2) is connected on the output side to the transmission (7) via the friction clutch (14), and the control device (19) is designed and configured to perform the method according to any one of claims 1 to 7.

9. 9. A chain hoist according to claim 8, characterized in that the sensor (18) comprises a fan disk arranged in a torque-resistant manner relative to 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.

Images