Backlash prevention structure for electric winding device

Abstract

To provide an electric hoisting device that can prevent backlash phenomenon by stopping the rotation of a drum as soon as the drum becomes unloaded due to landing of a suspended load or the like, without using an electronic control.SOLUTION: There is provided an electric hoisting machine which can lift a load wound on a drum by switching the rotation direction of a motor between forward and reverse. A ratchet comprises a claw wheel provided on a support shaft inserted through the rotation center of the drum so as to be rotatable forward and backward in synchronism with the rotation of the motor, and a claw provided on the drum. The power of the motor can be transmitted to the drum through the claw wheel by engaging the claw with the claw wheel due to the load torque in the drum feeding direction caused by the suspended load, and, if the load torque falls below a certain level, the claw does not mesh with the claw wheel and the claw wheel becomes capable of idling, thereby cutting off the transmission of the motor power to the drum, so that the ratchet prevents backlash phenomenon.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a structure for preventing the backlash phenomenon from occurring during the descent of a suspended load in an electric hoisting device that raises and lowers a suspended load by switching the rotation direction of a motor between forward and reverse. [Background technology]

[0002] In an electric hoist that raises and lowers a load by switching the rotation direction of the motor between forward and reverse, a backlash phenomenon occurs when the rope being paid out from the drum slackens when the motor is reversed to lower the load. In other words, if the payout speed of the rope is faster than the descent speed of the load, the rope slackens between the load and the drum, and this slack portion becomes entangled or tangled in the drum during the reverse rotation. To prevent such a backlash phenomenon, Patent Document 1 discloses a device that controls the motor so that, during the reverse drive of the motor, the drum is rotated in reverse in response to a detection signal from a tension detector of the rope if the tension of the rope is equal to or greater than a predetermined threshold, but the drum is not rotated in reverse in response to the detection signal from a tension detector of the rope.

[0003] On the other hand, Patent Document 2 discloses a hoist with a mechanical brake in which, when the rotational speed of the drum in the payout direction exceeds the rotational speed of the driven gear meshing with the drive gear while the motor is driving in the reverse direction, the driven gear moves in a direction pressing a friction plate by a feed screw mechanism, generating a braking force, thereby lowering the load at the reverse speed of the motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-177500 A [Patent Document 2] JP 2016-5972 A Summary of the Invention [Problem to be solved by the invention]

[0005] The device of Patent Document 1 is equipped with a rope tension detection unit (tension sensor) and a motor control unit in order to prevent the backlash phenomenon, and almost everything relies on electronic control. Therefore, considering that many of these types of devices are used outdoors, waterproof and dustproof measures are essential, and since electronic circuits are easily affected by temperature, insulation measures are also necessary in anticipation of use in extremely hot or extremely cold areas, which leads to high costs. Furthermore, the tension detection unit must correspond to the material and thickness of the towing member such as the rope used, and the threshold value must be set according to the rotation characteristics of the drum, etc., so initial setup is time-consuming and the device is not very versatile. Patent Document 1 also denies the use of a clutch or torque limiter (drag device), stating that the provision of a clutch or torque limiter would increase the weight and size of the entire device and increase costs.

[0006] On the other hand, in the hoist of Patent Document 2, the descent speed of the load is synchronized with the rotation speed of the motor by the mechanical brake, so the backlash phenomenon is inherently unlikely to occur. However, if the reverse rotation of the motor is not stopped at the same time as the load lands, the rope will continue to be paid out, and the backlash phenomenon will be unavoidable.

[0007] In this regard, a drone-based parcel delivery service is becoming a reality in recent years. In other words, the idea is to equip a drone with a hoist and transport the parcel by air. If this is realized, it will be possible to deliver goods to remote areas where land routes are not well developed, and to elderly people who have difficulty shopping. In this service, even if the recipient finally detaches the suspended load from the rope when handing over the load, the recipient cannot operate the drone or the hoist. Therefore, the drone operator will naturally perform the operations until the recipient receives the load. Specifically, when the drone arrives at the destination, the operator will hover the drone at a safe height, reverse the motor of the hoist to lower the suspended load, and stop the motor when the suspended load lands. However, even if such operations are performed while checking with an aerial camera monitor, it is difficult for the operator to accurately grasp the landing of the suspended load when checking from the sky. Therefore, there is a problem that a time lag is likely to occur between the landing of the suspended load and the stopping of the motor, and the backlash phenomenon is also likely to occur. To begin with, in order to fully carry out tasks such as reversing the motor while hovering a drone above the destination, and then stopping the motor as soon as the load lands while checking the camera monitor, appropriate training and the development of dedicated operators are required, and there are many issues that cannot be resolved by simply using conventional winches.

[0008] The present invention has been made to solve the above-mentioned problems, and its object is to provide an electric hoisting device that can prevent the backlash phenomenon by stopping the rotation of the drum as soon as the drum becomes unloaded, for example when the suspended load lands, without relying on electronic control. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention uses a means in which, in an electric hoist capable of raising and lowering a load wound on a drum by switching the rotation direction of a motor between forward and reverse, a ratchet is formed by a ratchet wheel that is provided on a support shaft inserted through the rotation center of the drum so as to be capable of rotating forward and reverse in sync with the rotation of the motor, and a pawl provided on the drum, and the ratchet uses a means in which the pawl engages with the ratchet wheel due to a load torque in the payout direction of the drum caused by the load, thereby enabling the power of the motor to be transmitted to the drum via the ratchet wheel, and when the load torque becomes equal to or lower than a certain level, the pawl disengages from the ratchet wheel and the ratchet wheel spins freely, thereby cutting off the transmission of the power of the motor to the drum. With this means, as long as a load torque in the payout direction is acting on the drum, such as by suspending a load in mid-air, the ratchet engages and transmits the power of the motor to the drum in both forward and reverse directions, allowing the load to be raised and lowered. On the other hand, if the load torque acting on the drum falls below a certain level before a load is attached or when the load lands during descent, the ratchet does not engage, the ratchet wheel becomes free to spin, and the transmission of motor power to the drum is cut off. Therefore, if the load lands or a person lifts the load while the motor is rotating in reverse to lower it, the motor continues to rotate in reverse, but the ratchet disengages and the ratchet wheel spins free in the reverse direction, cutting off the transmission of power to the drum, which stops the rotation of the drum and prevents the rope from being paid out, so that no backlash occurs. It is possible to set the upper limit of the load torque at which the ratchet disengages from the ratchet wheel, but it is necessary that the ratchet does not engage with the ratchet wheel at least when the load torque becomes zero.

[0010] On the other hand, it is preferable that the ratchet has a spring that elastically biases the pawl in the meshing direction, because this maintains the meshed state between the pawl and the ratchet wheel when a load torque acts on the drum, allowing the suspended load to be reliably raised and lowered by the motor power.

[0011] It is preferable to transmit the power of the motor to the drum via a reduction gear mechanism and a braking mechanism in that order, with the ratchet being the final motor power transmission means, because the reduction gear mechanism increases the torque of the motor, and the braking mechanism makes it possible to slow down the descent speed of the load and to hold the load at a constant height.

[0012] Specifically, the braking mechanism includes a screw shaft connected to the motor so as to be rotatable forward and backward, a clutch in which clutch plates and friction plates are alternately arranged on the screw shaft via a lining, and a pressing nut part that is screwed between the drum and the clutch of the screw shaft so as to be tightened toward the clutch side and that can frictionally join the clutch plates and the friction plates by the lining due to the thrust generated when the screwing is performed, and it is preferable that the screw shaft is formed with a male screw part into which the pressing nut part is screwed on the support shaft of the drum, and the pressing nut part is provided with a female screw on the ratchet wheel that is screwed with the male screw. According to this means, the rotational motion of both the motor and the drum is converted into a linear reciprocating motion in which the pressing nut part formed of a ratchet wheel screws the screw shaft left and right to contact and separate from the clutch by a feed screw mechanism using the support shaft of the drum as the screw shaft. During such reciprocating motion of the pressing nut part (ratchet wheel), the presence or absence of a braking force by the clutch is determined depending on the presence or absence of a thrust force pressing the clutch. That is, when the motor is rotated in the hoisting direction, the pressing nut part is tightened by the screw shaft which rotates in conjunction with the motor, and the clutch is engaged to transmit the drive system torque of the motor and reduction gear mechanism to the drum, but when the motor is stopped, the pressing nut part is also tightened in conjunction with the rotation of the drum in the payout direction due to the load torque of the load, and a braking force is exerted to hold the load at a constant height, functioning as a so-called brake clutch. On the other hand, when the motor is rotated in the payout direction of the load, the screw shaft (drum support shaft) rotates in the opposite direction to when it is hoisted, and the pressing nut part (ratchet wheel) is displaced in the loosening direction opposite to the tightening of the clutch, releasing the braking force, and the drum becomes free to rotate, causing the load to descend due to its own weight. Furthermore, if during this descent the rotational speed of the drum, i.e. the rotational speed of the pressing nut part (ratchet wheel) in the descending direction, exceeds the rotational speed of the motor in the payout direction, i.e. the rotational speed of the screw shaft (drum support shaft) in the payout direction, the rotation of the pressing nut part (ratchet wheel) in the descending direction becomes dominant, and the pressing nut part (ratchet wheel) is tightened again, and the braking force is restored by the thrust.Therefore, the load can be lowered by the rotational torque in the payout direction of the motor, and thereafter, the braking force is repeatedly released and restored depending on the rotational difference between the pressing nut portion (ratchet wheel) and the screw shaft (drum support shaft), allowing the load to be lowered until the motor is stopped, thereby preventing the backlash phenomenon during the descent of the load.

[0013] Furthermore, it is preferable that the clutch is composed of a multi-plate clutch consisting of multiple sets of clutch plates, linings, and friction plates, and the number of sets can be changed to obtain a braking force according to the weight of the load. If the drive system consisting of the motor and the reduction gear mechanism has the same configuration (output torque), the thrust of the pressing nut part (ratchet wheel) when tightened to the clutch side is constant, so that a braking force corresponding to the weight of the load can be obtained by simply changing the number of sets of the multi-plate clutch. This is particularly effective when holding the load at a constant height while the motor is stopped. For example, if three sets of multi-plate clutches can obtain a braking force to hold a 30 kg load, five sets of multi-plate clutches can hold a 50 kg load.

[0014] Furthermore, in a method in which a clutch receiving portion is provided facing the pressing nut portion (ratchet wheel) on the screw shaft (drum support shaft) and this receiving portion constantly regulates reverse rotation by a ratchet, even if the pressing nut portion is tightened by reverse rotation, the ratchet works and the receiving portion does not rotate in that direction, and receives the thrust of the pressing nut portion while the rotation is stopped. Therefore, when the motor is stopped, the thrust of the pressing nut portion toward the clutch side is received by the receiving portion, so that the clutch is completely frictionally joined and a braking force capable of holding the load at a constant height can be reliably obtained. Also, even when the motor is operating in the hoisting direction, the rotation of the drum in the downward direction is regulated by the regulation of reverse rotation of the receiving portion, preventing the load from falling.

[0015] Furthermore, by setting the static friction torque of the drive system, which is the rotational resistance of the motor and the reduction gear mechanism, to be balanced with the load torque on the drum side when the motor is stopped, even if the motor does not have a brake such as an electromagnetic brake, the load is not released from the drum while the motor is stopped, and a braking force capable of holding the load at a constant height can be maintained. Also, if a load that exceeds the braking force acts on the drum while the motor is stopped, the static friction torque is exceeded and the drive system is allowed to rotate in reverse. Therefore, it is possible to mitigate impacts on the hoisting device caused by the excess load. This is effective, for example, when the device is mounted on a drone to construct a load delivery system, and is useful for mitigating impacts on the drone even if the load gets caught on a tree during delivery. On the other hand, when the load torque on the drum side falls below a certain level during the descent of the load by the reverse drive of the motor, the pressing nut receives a reaction from the clutch against the tightening, loosening the tightening, and disengaging the clutch. If the load torque falls below a certain level due to the load landing, for example, the pressing nut loosens and the clutch is disengaged. Once loosened, the pressing nut rotates together with the screw shaft, and the clutch remains disengaged even if the motor continues to be reversed. Therefore, in the present invention, the backlash phenomenon can be more reliably prevented by disengaging the clutch at the same time as the load lands, other than the ratchet of the pressing nut rotating freely.

[0016] Furthermore, although the reduction gear mechanism can be composed of only spur gears, it is preferable to compose at least a part of it with planetary gears, since this allows the reduction gear mechanism to be made smaller and lighter while still obtaining the necessary torque.

[0017] The electric hoist of the present invention can be used in all loading and unloading fields, not just general loading and unloading in factories, warehouses, construction sites, etc. Furthermore, if this device is mounted on a drone, it will be possible to easily deliver cargo to remote areas where land routes are not developed, and the possibilities are endless. Effect of the Invention

[0018] According to the present invention, a ratchet is provided in the power transmission system of the motor for the drum, which disengages the claw from the ratchet wheel when the load torque acting on the drum falls below a certain level, so that the rotation of the drum stops as soon as the drum becomes unloaded, for example when the suspended load lands, without the need to stop the motor, thereby reliably preventing the backlash phenomenon. Also, since the backlash phenomenon is prevented mechanically, rather than by electronic control, there is no need for measures to protect the electronic circuit from foreign objects and heat, which reduces costs, and there is no need for initial settings according to the material and thickness of the rope, making it possible to provide a highly versatile electric hoisting device. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is an overall perspective view of an electric winding device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a perspective view of the main part excluding the frame. [Diagram 3] Overall cross-sectional view of the same [Figure 4] Enlarged cross-sectional view of the main part of the same [Diagram 5] FIG. 1 is an exploded perspective view of the main part from the left side of the first embodiment. [Figure 6] FIG. 1 is an exploded perspective view of the main part from the right side. [Figure 7] FIG. 2 is an explanatory diagram showing the ratchet mechanism of the pressing nut portion of the first embodiment. [Figure 8] An explanatory diagram of the simplest electric hoisting device to which the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is an overall perspective view of an electric hoisting device according to one embodiment of the present invention, in which 1 is a motor and 2 is a drum. A rope 3 is wound around the drum 2 (wound left when viewed from the right side of the drawing), and a load W is fixed to its end. 4 is a level wander, which reciprocates left and right on a traverse cam 5 that rotates in conjunction with the drum 2, thereby winding the rope 3 evenly around the drum 2. A controller (not shown) connected to terminals 6 is used to operate and stop the motor 1 and switch the rotation direction between forward and reverse, thereby rotating the drum 2 forward and reverse to raise and lower the load W or hold the load W at a constant height.

[0021] In this device, the motor 1, drum 2, reduction gear mechanism and braking mechanism are installed between four parallel plate-like frames F1-4. As shown in Figures 2 and 3, the reduction gear mechanism is made up of, from the motor 1 side, two sets of planetary gears 7 and 8, two transmission gears 9 and 10 made of spur gears, and an output gear 11 made of a spur gear with a larger diameter than the transmission gears 9 and 10. Of these, the final output gear 11 is fixed integrally to one end (the right end in the drawing) of a support shaft 12 inserted through the center of rotation of the drum 2. For ease of explanation, the teeth of the gears 7 to 11 are not shown.

[0022] The torque of the motor 1 is increased by this reduction gear mechanism and then transmitted to the drum 2 via the braking mechanism. The braking mechanism in this embodiment is composed of a feed screw mechanism with the support shaft 12 of the drum 2 as the screw shaft, and a multi-plate clutch.

[0023] Of these, the feed screw mechanism, as shown in Fig. 4, is formed by forming a male screw portion 12a on one side of the support shaft 12 to form a screw shaft, and a pressing nut portion 13 is screwed into the male screw portion 12a. Therefore, when the support shaft 12 rotates, the pressing nut portion 13 reciprocates left and right on the support shaft 12 in a direction following the rotation direction of the support shaft 12 by screw driving. Also, even when the support shaft 12 is stopped rotating (synonymous with when the motor 1 is stopped), the pressing nut portion 13 rotates in conjunction with the rotation of the drum 2 in the payout direction due to the load of the suspended load W, and screw-drives the support shaft 12.

[0024] As shown in Fig. 4, the multi-plate clutch, which constitutes one component of the braking mechanism, is composed of multiple sets of clutch plates 14 and friction plates 16 arranged alternately on the support shaft 12 with linings 15 interposed therebetween. As shown in Figs. 5 and 6, the clutch plates 14 have projections 14a provided at two locations on their outer periphery that fit into notches 17a formed in the housing cylinder of the receiving portion 17. Meanwhile, the friction plates 16 have a square shaft shape whose central hole 16a matches the shaft base 13a of the pressing nut portion 13, so that they can rotate together with the pressing nut portion 13. In this embodiment, the multi-plate clutch has five linings 15, but the initial braking force can be increased by increasing the number of sets.

[0025] The multi-plate clutch is accommodated in (the accommodating cylinder portion of) receiving portion 17 which faces pressing nut portion 13 on support shaft 12. As shown in Figs. 5 and 6, receiving portion 17 constitutes a first ratchet 18 which is a ratchet wheel, and a claw 18a meshes with teeth 17b formed on receiving portion 17 to constantly restrict reverse rotation of receiving portion 17. Therefore, even if pressing nut portion 13 rotates in the payout direction of load W, receiving portion 17 will not reverse. Incidentally, claw 18a is rotatably supported by pin 18b which is journalled between frames F1 and F2 as shown in Fig. 1.

[0026] On the other hand, the pressing nut portion 13 in the feed screw mechanism constitutes a second ratchet 19 using the same as a ratchet wheel, as shown in Figs. 5 and 6. The pawl 19a of the second ratchet 19 is rotatably supported in the end face recess 2a of the drum 2, and is constantly biased by a leaf spring 19b so as to mesh with the teeth 13b formed on the pressing nut portion 13. As shown in Fig. 7, the pawl 19a of this second ratchet 19 meshes with the teeth 13b when the pressing nut portion 13 rotates in the hoisting direction of the load W (forward rotation R1) due to the forward drive of the motor 1, and when viewed from the drum 2 side, the pawl 19a meshes with the teeth 13b when the drum 2 tries to rotate in the payout direction (reverse rotation R2) due to the load torque of the load W. Therefore, as long as the load W is wound around the drum 2, the claws 19a mesh with the teeth 13b due to the load torque, and the drum 2 and the pressing nut part 13 rotate together in the forward and reverse directions, but when the load torque on the drum 2 side becomes equal to or lower than a certain level, the meshing is released and the transmission of the motor power to the drum 2 is cut off. In other words, the pressing nut part 13 is the final transmission means for transmitting the power of the motor 1 to the drum 2 in this embodiment, and constitutes a backlash prevention structure of the present invention, as described later. In this embodiment, since the drum 2 is elastically biased toward the pressing nut part 13 (coil spring 20 in FIG. 3), the drum 2 follows the pressing nut part 13 while the pressing nut part 13 reciprocates on the support shaft 12, and the meshing of the second ratchet 19 does not come off.

[0027] Next, the operation of this electric hoisting device will be described with reference to Fig. 4. To clarify the directions, in this embodiment, the rope 3 is wound counterclockwise around the drum 2, and based on this, in the following description of the operation, the rotational direction (counterclockwise) in which the rope 3 is wound up to raise the load W is defined as forward rotation R1, and the rotational direction (clockwise) in which the rope 3 is paid out to lower the load W is defined as reverse rotation R2. Also, the spindle 12 and the pressing nut portion 13 in the feed screw mechanism are screwed together with a left-handed screw (reverse screw), and the tightening direction (rightward in the drawing) in which the pressing nut portion 13 is displaced on the spindle 12 toward the clutch by the screw propulsion due to the relative forward rotation R1 is defined as forward direction S1, and the loosening direction in which the pressing nut portion 13 is separated from the clutch is defined as reverse direction S2.

[0028] Now, if a load W is fixed (suspended) on the rope 3 while the motor 1 is stopped, the weight of the load W will cause the drum 2 to rotate in the reverse direction R2. When the drum 2 rotates in the reverse direction R2, the reverse torque (load torque) is transmitted to the pressing nut portion 13 via the second ratchet 19, and the pressing nut portion 13 rotates in the reverse direction R2. When the pressing nut portion 13 rotates in the reverse direction R2, the pressing nut portion 13 displaces the support shaft 12, which is in a stopped state of rotation, in the forward direction S1 by the left-handed screw action, and is tightened so as to press the clutch. At this time, the pressing nut portion 13 presses the clutch with a thrust force corresponding to the reverse torque R2 of the drum 2. Due to the thrust of the pressing nut portion 13, the clutch plate 14 and the friction plate 16 in the clutch are frictionally joined by the lining 15, and a braking force is obtained. During this time, the reverse rotation R2 torque of the pressing nut portion 13 (and thus the load torque on the drum 2 side) is also transmitted to the receiving portion 17 via the clutch, but because the reverse rotation R2 of the receiving portion 17 is regulated by the first ratchet 18, only the pressing nut portion 13 rotates in reverse R2, and the pressing nut portion 13 can be securely tightened until the set braking force is obtained. After that, as long as the load (load torque) of the load W acts on the drum 2, the load W can continue to be held at a constant height by a braking force commensurate with the above thrust.

[0029] In this embodiment, while the motor 1 is stopped, the static friction torque of the drive system, which is indicated as the rotational resistance of the motor 1 and the reduction gear mechanism combined, is set to balance with the load torque on the drum 2 side including the stationary load W. Therefore, as long as the load W is at the planned weight, the thrust of the pressing nut portion 13 and the braking force of the clutch are maintained constant, and the load W can be held at a constant height as described above. On the other hand, if an excess load that exceeds the set braking force acts on the drum 2 side, the drive system is allowed to rotate in reverse. In this way, the drive system rotates in reverse R2 due to the excess load, thereby mitigating the impact on the device side.

[0030] Up to this point, we have focused on maintaining the load W at a constant height, because this is particularly effective in a system for delivering luggage in which the device is mounted on a drone. In other words, in a delivery system using a drone, unlike normal loading and unloading work in which the load is fixed while the drone is hovering and materials are raised and lowered on the spot (at a fixed position), there is a delivery process by unmanned flight, during which the load must be securely held (suspended) with the motor stopped. In addition, if an excess load that exceeds the braking force occurs due to an external force (wind pressure or load getting caught) during delivery, it is also necessary to absorb this. Therefore, in the present invention, as described above, these issues are addressed by setting the static friction torque of the drive system to balance the load torque on the drum side via a braking mechanism.

[0031] Next, the lifting and lowering operation of the load W will be explained. First, to lift the load W, the motor 1 is driven in the forward direction. The forward driving force of the motor 1 rotates the final output gear 11 in the forward direction R1 via two sets of planetary gears 7 and 8 and two transmission gears 9 and 10 consisting of spur gears, and the support shaft 12 integrated with the output gear 11 also rotates in the forward direction R1. When the support shaft 12 rotates in the forward direction R1, the pressing nut part 13 is displaced in the forward direction S1 on the support shaft 12 by the feed screw action of the left-handed screw. However, since the pressing nut part 13 is already completely tightened at the stage when the load W is fixed in the air, it is in a state where it can rotate together with the support shaft 12, and after the motor 1 is started, the pressing nut part 13 rotates in the forward direction R1 with almost no time lag. Such forward rotation R1 torque of the pressing nut part 13 is transmitted to the drum 2 via the second ratchet 19, and the load W is hoisted up. During this time, the clutch plate 14 and friction plate 16 are in a complete frictional connection state through the lining 15, so the load W can be reliably hoisted by the hoisting torque on the drive system side. Also, because the receiving part 17 is regulated in reverse rotation R2 by the first ratchet 18, even if the drum 2 attempts to rotate in reverse R2 while the load W is being raised, this is regulated and the drive system, including the motor 1, will not rotate in reverse R2, preventing the load W from falling.

[0032] It is not essential that this hoisting operation be started with the load W suspended in mid-air; it is of course also possible to start hoisting with the load W placed on the ground. In this case, even if the pressing nut portion 13 is positioned away from the clutch plate 16 (in other words, even if the pressing nut portion 13 is loose and the braking force is zero), the load W can be hoisted in the same manner as described above by driving the motor 1 in the forward direction. Also, even if the motor 1 is stopped midway through hoisting, the same braking force is obtained and the load W can be held at a constant height.

[0033] On the other hand, to lower the load W, the motor 1 is driven in the reverse direction. When the motor 1 is driven in the reverse direction, the final output gear 11 rotates in the reverse direction R2 via the two sets of planetary gears 7 and 8 and the two transmission gears 9 and 10, which are made up of spur gears. This causes the support shaft 12, which is integrated with the output gear 11, to rotate in the reverse direction R2. When the support shaft 12 rotates in the reverse direction R2, the pressing nut portion 13 displaces the support shaft 12 in the reverse direction S2, loosening the fastening and losing the thrust force against the clutch. In this way, the frictional joining force between the clutch plate 14 and the friction plate 16 and the lining 15 is also lost, and the braking force is released. After that, the drum 2 becomes free to rotate in the reverse direction R2, and the load W descends by natural drop.

[0034] However, the descent speed of the load W is kept almost constant. This is because, if the descent speed of the load W exceeds the payout speed of the drive system, the reverse rotation R2 speed of the drum 2 (synonymous with the reverse rotation R2 speed of the pressing nut portion 13) will exceed the reverse rotation R2 speed of the support shaft 12 (synonymous with the reverse rotation R2 speed of the drive system), and the reverse rotation R2 of the pressing nut portion 13 will relatively prevail. Then, since the pressing nut portion 13 appears to rotate reverse R2 independently by an amount corresponding to the speed difference, the support shaft 12 is tightened in the forward direction S1, a thrust force is obtained against the clutch, and the braking force is restored again. Therefore, while the motor 1 is driving in the reverse direction, the load W can be lowered by the reverse rotation R2 speed of the drive system.

[0035] Then, in the final stage, the motor 1 is stopped just as the load W lands, completing the series of operations. If the timing of stopping the motor 1 is delayed from the landing of the load W, the rope 3 is normally unwound from the drum 2 more than necessary, causing a backlash phenomenon (the tangled line caused by line fraying in fishing). However, in this embodiment, the pressing nut portion 13 is loosened at the moment that the drum 2 becomes unloaded as the load W lands. That is, the pressing nut portion 13 has been tightened to the clutch side by the load torque on the drum 2 side until then, but at the same time, it is subjected to a reaction from the clutch in the loosening direction. Therefore, when the load torque becomes zero, the pressing nut portion 13 is instantly loosened by the reaction from the clutch. When the pressing nut portion 13 is loosened in this way, the braking force of the clutch is also released (the clutch is disengaged). After that, even if the motor 1 continues to be driven in the reverse R2 direction, the pressing nut portion 13 simply rotates together with the support shaft 12 while remaining in the loose state, and since the clutch is disengaged, the power of the motor 1 is not transmitted to the drum 2, and the rope 3 is not unwound from the drum 2, so that the backlash phenomenon does not occur. Furthermore, when the drum 2 is unloaded, the component in the reverse R2 direction that engages the claw 19a of the second ratchet 19 with the teeth 19b disappears, so that only the pressing nut portion 13 rotates idly in the reverse R2 direction. Therefore, even if the timing of stopping the motor 1 is delayed after the load W lands, the pressing nut portion 13 rotates idly at the same time as the load W lands, stopping the reverse R2 of the drum 2, and the rope 3 is not unwound excessively, so that the backlash phenomenon can also be prevented. In other words, in this embodiment, when the load torque on the drum 2 side falls below a certain level during the descent of the load W, the backlash phenomenon is reliably prevented by two means: the clutch being disengaged by loosening of the pressing nut portion 13, and the disengagement of the second ratchet 19. However, what is necessary in the present invention is to employ at least the means by the second ratchet 19.

[0036] As described above, according to the electric winding device of this embodiment, the braking mechanism (feed screw mechanism and clutch) is all concentrated on the support shaft 12 of the drum 2, which contributes to making the device more compact and lightweight. Also, since the pressing nut portion 13 of the feed screw mechanism, which is the clutch actuator, is not in meshing relationship with the various gears in the reduction gear mechanism, no excessive force is applied to the meshing portions of the reduction gear mechanism when the braking force is released and restored, improving durability.

[0037] The present invention is not limited to the configuration of the above embodiment. As one example, the ratchet wheel of the second ratchet 19 that prevents the backlash phenomenon is configured as the pressing nut portion 13 of the feed screw mechanism, thereby integrating the backlash prevention structure and the braking mechanism, but the ratchet wheel and the pressing nut portion 13 can be configured as separate members, and the above-mentioned braking mechanism itself can be omitted. In this case, it is sufficient to provide the ratchet wheel of the second ratchet 19 so that it can rotate forward and backward in synchronization with the rotation of the motor without reciprocating on the support shaft.

[0038] Also, although part of the reduction gear mechanism is constructed from two sets of planetary gears 7 and 8, it is possible to use only one set of planetary gears, and it is also possible to construct the reduction gear mechanism entirely from spur gears, and if a light load is to be handled, it is also possible to omit the reduction gear mechanism itself. In the extreme, as shown in Figure 8, it is also possible to omit both the reduction gear mechanism and the braking mechanism and directly connect the ratchet wheel 22a of the second ratchet 22 to the motor 21, and enable this to mesh with the ratchet 22b provided on the drum 23, thereby forming a backlash prevention structure. [Industrial Applicability]

[0039] The present invention can be used not only in general cargo handling fields, but also in delivery services that easily and swiftly transport cargo by air by mounting it on a drone. [Explanation of symbols]

[0040] 1 Motor 2 Drums 3. Rope 4 Level Winder 5. Traverse Cam 6 Connection terminal 7·8 Planetary Gear 9·10 Transmission gear 11 Output gear 12 Support shaft (screw shaft) 12a Male thread 13 Pressing nut part 14 Clutch plate 15 Lining 16 Friction plate 17 Receiving part 18 The First Ratchet 19 The Second Ratchet W Hanging load F1~F4 Frame

Claims

1. In an electric hoist that can raise and lower a load wound around a drum by switching the rotation direction of the motor between forward and reverse, a ratchet is formed by a ratchet wheel that is mounted on a spindle inserted through the center of rotation of the drum and capable of rotating forward and reverse in sync with the rotation of the motor, and a pawl mounted on the drum, and the ratchet is configured so that the power of the motor can be transmitted to the drum via the ratchet wheel when the pawl engages with the ratchet wheel due to the load torque in the payout direction of the drum caused by the load, while when the load torque falls below a certain level, the pawl disengages from the ratchet wheel and the ratchet wheel spins freely, thereby cutting off the transmission of the power of the motor to the drum.

2. 2. The backlash prevention structure for an electric hoist as claimed in claim 1, wherein said ratchet has a spring for elastically biasing said pawl in a direction of engagement.

3. 3. A backlash prevention structure for an electric hoist as claimed in claim 1, wherein the power of the motor is transmitted to the drum through a reduction gear mechanism and a braking mechanism in that order, with the ratchet being the final motor power transmission means.

4. 4. The backlash prevention structure in an electric winding device according to claim 1, wherein the braking mechanism comprises a screw shaft rotatably connected to the motor in forward and reverse directions, a clutch formed by alternately arranging clutch plates and friction plates on the screw shaft with a lining interposed therebetween, and a pressing nut portion screwed between the drum and the clutch of the screw shaft so as to be tightened toward the clutch side and capable of frictionally joining the clutch plates and the friction plates by the lining due to the thrust generated when the screwing is performed, the screw shaft having a male thread portion which screws onto a support shaft inserted into the center of rotation of the drum and into which the pressing nut portion screws, and the pressing nut portion has a female thread provided on the ratchet wheel which screws onto the male thread.

5. 5. A backlash prevention structure in an electric hoisting device as described in claim 3 or 4, wherein the clutch is composed of a multi-plate clutch consisting of multiple sets of clutch plates, linings, and friction plates, and the number of sets is made changeable to obtain a braking force according to the weight of the suspended load.

6. 6. A backlash prevention structure in an electric winding device according to claim 3, 4 or 5, wherein a receiving portion for the clutch plate and the friction plate is provided on the screw shaft facing the pressing nut portion, and this receiving portion serves as a ratchet separate from the ratchet formed by the pressing nut portion, thereby constantly restricting reverse rotation.

7. 7. A backlash prevention structure for an electric winding device according to claim 3, wherein when the motor is stopped, the static friction torque of the drive system, which is expressed as the rotational resistance of the motor and the reduction gear mechanism, is set so as to balance with the load torque on the drum side.

8. 8. An electric hoisting device as claimed in any one of claims 4 to 7, wherein when the load torque on the drum side falls below a certain level during descent of a suspended load by reverse driving of the motor, the pressing nut portion receives a reaction force from the clutch against the tightening, so that the tightening is loosened and the clutch is disengaged.

9. 9. The backlash prevention structure for an electric winding device according to claim 3, wherein at least a part of the reduction gear mechanism is constituted by a planetary gear.

10. A drone equipped with an electric hoisting device having the backlash prevention structure according to any one of claims 1 to 9.

Images