JP7613732B2 - Backlash prevention structure for electric winding device - Google Patents

Description

This invention relates to a structure that prevents backlash 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.

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 tangled or entangled in the drum during reversal of rotation. To prevent this backlash phenomenon, Patent Document 1 discloses a device that controls the motor so that, while the motor is driven in the reverse direction, the drum is rotated in the reverse direction in response to a detection signal from a rope tension detection unit if the tension of the rope is equal to or greater than a predetermined threshold, but the drum is not rotated in the reverse direction if the tension of the rope is below the predetermined threshold.

On the other hand, Patent Document 2 discloses a hoist with a mechanical brake in which, if 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 against a friction plate by a feed screw mechanism, generating a braking force, thereby lowering the load at the reverse speed of the motor.

JP 2018-177500 A JP 2016-5972 A

The device in Patent Document 1 is equipped with a rope tension detector (tension sensor) and a motor control unit to prevent backlash, and relies almost entirely on electronic control. Therefore, considering that many of these 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 cold areas, which leads to high costs. Furthermore, the tension detector 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 rejects the use of a clutch or torque limiter (drag device), stating that the installation of a clutch or torque limiter would increase the weight and size of the entire device and increase costs.

On the other hand, the hoist in Patent Document 2 is inherently less susceptible to backlash because the descent speed of the load is synchronized with the rotation speed of the motor by a mechanical brake. 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 unwound, and the backlash phenomenon will be unavoidable.

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 find it difficult to go 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, drive the motor of the hoist in reverse 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 perfectly carry out tasks such as reversing the motor while hovering the drone above the destination and stopping the motor as soon as the suspended load lands while checking the camera monitor, appropriate training and the training of dedicated operators are required, and there are many issues that cannot be resolved by simply using conventional winches.

The present invention has been made to solve the above-mentioned problems, and its purpose 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.

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 the motor between forward and reverse, a ratchet is formed by a ratchet wheel mounted on a support shaft inserted through the rotation center of the drum so that it can rotate forward and reverse in sync with the rotation of the motor, and a pawl mounted on the drum, and the ratchet uses a means in which the pawl engages with the ratchet wheel due to the 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, while when the load torque falls below a certain level, the pawl disengages from the ratchet wheel and the ratchet wheel spins freely, 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 to transmit the power of the motor to the drum in both forward and reverse directions, allowing the load to be raised and lowered. In contrast, if the load torque acting on the drum falls below a certain level before a load is attached or if the load lands during descent, the ratchet will not engage, the ratchet will be able to spin freely, and the transmission of motor power to the drum will be 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 will continue to rotate in reverse, but the ratchet will disengage and the ratchet will spin freely in the reverse direction, cutting off the transmission of power to the drum, which will stop the drum from rotating and prevent the rope from being paid out, so no backlash will occur. It is possible to set the upper limit of the load torque at which the ratchet will disengage from the ratchet, but it is necessary that the ratchet not engage with the ratchet at least when the load torque becomes zero.

On the other hand, it is preferable that the ratchet has a spring that elastically biases the pawl in the direction of engagement. This is because the engagement state between the pawl and the ratchet wheel is maintained when a load torque acts on the drum, and the suspended load can be reliably raised and lowered by the motor power.

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. This is 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 suspended load and to hold the suspended load at a constant height.

Specifically, the braking mechanism comprises a screw shaft connected to the motor so as to be rotatable forward and reverse, 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 with the lining by the thrust force generated when the screwing is performed. It is preferable that the screw shaft is formed with a male thread 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 thread on the ratchet wheel that is screwed into the male thread. According to this means, the rotational motion of the motor and the drum is converted into a linear reciprocating motion in which the pressing nut part composed of a ratchet wheel screws the screw shaft left and right to contact and separate from the clutch by a feed screw mechanism with the support shaft of the drum as the screw shaft. During the reciprocating motion of the pressing nut part (ratchet wheel), the presence or absence of a braking force by the clutch is determined by 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 portion is tightened by the screw shaft which rotates in conjunction with the motor, and the clutch is engaged to transmit the torque of the drive system of the motor and reduction gear mechanism to the drum, but when the motor is stopped, the pressing nut portion is also tightened in conjunction with the rotation of the drum in the payout direction due to the load torque of the load, thereby exerting a braking force to hold the load at a constant height, and functions 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 that during hoisting, displacing the pressing nut portion (ratchet wheel) 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 the rotational speed of the drum during the descent, i.e., the rotational speed of the pressing nut part (rake 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 (rake wheel) in the descending direction becomes dominant, the pressing nut part (rake 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 part (rake wheel) and the screw shaft (drum support shaft), and the load can be lowered until the motor is stopped, preventing the backlash phenomenon during the descent of the load.

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 that 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 reduction gear mechanism has the same configuration (output torque), the thrust of the pressing nut part (ratchet wheel) when tightened to the clutch side will be constant, so simply changing the number of sets of the multi-plate clutch will provide a braking force that matches the weight of the load. 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 provide a braking force to hold a 30 kg load, five sets of multi-plate clutches will be able to hold a 50 kg load.

In addition, by providing a clutch receiving portion facing the pressing nut portion (ratchet wheel) on the screw shaft (drum support shaft) and constantly restricting reverse rotation with 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 is received by the receiving portion, so that the clutch is completely frictionally connected 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 restricted by the restriction of reverse rotation of the receiving portion, preventing the load from falling.

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 an electromagnetic brake or other brake, the load will not be let out 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 excessive loads. This is effective, for example, when this device is installed on a drone to build a load delivery system, and helps to mitigate 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 while the motor is rotating in the reverse direction, 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, 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 rotate in the reverse direction. Therefore, in this 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.

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. This is because the reduction gear mechanism can be made smaller and lighter while still obtaining the necessary torque.

The electric hoisting device of the present invention can be used in all loading and unloading fields, not just general loading and unloading in factories, warehouses, and construction sites. 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 available, and the possibilities are endless.

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. This means that the rotation of the drum stops as soon as the drum is unloaded, for example when the suspended load lands, without the need to stop the motor, thereby reliably preventing backlash. In addition, because backlash is prevented mechanically rather than electronically, measures to protect the electronic circuit from foreign objects and heat are not required, reducing costs, and initial settings according to the rope material, thickness, etc. are not required, making it possible to provide a highly versatile electric hoisting device.

FIG. 1 is an overall perspective view of an electric winding device according to an embodiment of the present invention; FIG. 1 is a perspective view of the main part excluding the frame. Overall cross-sectional view of the same Enlarged cross-sectional view of the main part of the same FIG. 1 is an exploded perspective view of the main part from the left side of the first embodiment. FIG. 1 is an exploded perspective view of the main part from the right side. FIG. 2 is an explanatory diagram showing the ratchet mechanism of the pressing nut portion of the first embodiment. An explanatory diagram of the simplest electric hoisting device to which the present invention is applied.

A preferred embodiment of the present invention will be described below with reference to the attached 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 moves back and forth from side to side 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 starts and stops the motor 1 and switches the direction of rotation between forward and reverse, causing the drum 2 to rotate forward and reverse, raising and lowering the load W or holding it at a constant height.

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, from the motor 1 side, the reduction gear mechanism is made up of 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 that passes through the center of rotation of the drum 2. For ease of explanation, the teeth of each of the gears 7 to 11 have been omitted from the illustration.

The torque of the motor 1 is increased by this reduction gear mechanism and then transmitted to the drum 2 via the braking mechanism. In this embodiment, the braking mechanism 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.

As shown in Figure 4, the feed screw mechanism 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 due to the screw driving. Also, even when the support shaft 12 is stopped rotating (same as 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 W, and screws the support shaft 12.

The multi-plate clutch, which constitutes one component of the braking mechanism, is made up of multiple sets of clutch plates 14 and friction plates 16 arranged alternately on the support shaft 12 with linings 15 between them, as shown in FIG. 4. As shown in FIGS. 5 and 6, the clutch plates 14 have two projections 14a on their outer periphery that fit into notches 17a formed in the housing cylinder of the receiving part 17. On the other hand, the friction plates 16 have a square shaft shape with their central hole 16a matching the shaft base 13a of the pressing nut part 13, allowing them to rotate together with the pressing nut part 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.

The multi-plate clutch is housed in the receiving portion 17 (the housing cylinder portion) that faces the pressing nut portion 13 on the support shaft 12. As shown in Figures 5 and 6, the receiving portion 17 constitutes a first ratchet 18 that uses a ratchet wheel, and the claw 18a meshes with the teeth 17b formed on the receiving portion 17 to constantly restrict reverse rotation of the receiving portion 17. Therefore, even if the pressing nut portion 13 rotates in the payout direction of the load W, the receiving portion 17 does not reverse. The claw 18a is rotatably supported by a pin 18b that is journaled between the frames F1 and F2, as shown in Figure 1.

On the other hand, the pressing nut part 13 in the feed screw mechanism constitutes a second ratchet 19 with a ratchet wheel as shown in Figures 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 part 13. As shown in Figure 7, when the pressing nut part 13 rotates in the lifting direction of the load W by the forward drive of the motor 1 (forward rotation R1), the pawl 19a of this second ratchet 19 meshes with the teeth 13b. 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 claw 19a engages 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. However, when the load torque on the drum 2 side becomes equal to or lower than a certain level, the engagement 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 the backlash prevention structure of the present invention, as described later. In this embodiment, the drum 2 is elastically biased toward the pressing nut part 13 (coil spring 20 in FIG. 3), so that the drum 2 follows the pressing nut part 13 while it reciprocates on the support shaft 12, and the second ratchet 19 does not disengage.

Next, the operation of this electric hoisting device will be described with reference to Figure 4. To clarify the directions, in this embodiment, the rope 3 is wound around the drum 2 counterclockwise, so in the following operation description, the rotational direction (counterclockwise) in which the rope 3 is wound up to raise the load W is taken as forward rotation R1, and the rotational direction (clockwise) in which the rope 3 is paid out to lower the load W is taken as reverse rotation R2. In addition, the support shaft 12 and the pressing nut part 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 part 13 is displaced on the support shaft 12 toward the clutch by the screw propulsion due to the relative forward rotation R1 is taken as forward direction S1, and the loosening direction in which the pressing nut part 13 moves away from the clutch is taken as reverse direction S2.

Now, if a load W is fixed (suspended) to the rope 3 while the motor 1 is stopped, the weight of the load 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, causing the pressing nut portion 13 to rotate 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 due to 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. This thrust of the pressing nut portion 13 causes the clutch plate 14 and friction plate 16 in the clutch to be frictionally joined by the lining 15, providing a braking force. During this time, the reverse rotation R2 torque of the pressing nut part 13 (and thus the load torque on the drum 2 side) is also transmitted to the receiving part 17 via the clutch, but because the reverse rotation R2 of the receiving part 17 is restricted by the first ratchet 18, only the pressing nut part 13 rotates in reverse R2, and the pressing nut part 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 be kept at a constant height by a braking force commensurate with the thrust.

In this embodiment, while the motor 1 is stopped, the static friction torque of the drive system, which is expressed 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, which includes 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 reverse. In this way, the drive system reverses R2 due to the excess load, and the impact on the device side can be mitigated.

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 cargo in which the device is mounted on a drone. In other words, in a delivery system using a drone, unlike normal loading and unloading operations 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 in mid-air) with the motor stopped. Also, if an excess load that exceeds the braking force occurs due to an external force (wind pressure or the load getting caught) during delivery, it is 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.

Next, the lifting and lowering operation of the load W will be explained. First, to raise 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 through 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. In addition, the receiver 17 is regulated from reverse rotation R2 by the first ratchet 18, so even if the drum 2 tries to reverse R2 while the load W is rising, this is regulated, and the drive system, such as the motor 1, will not reverse R2, preventing the load W from falling.

It is not essential that this hoisting operation starts with the load W suspended in mid-air; it is of course also possible to start hoisting with the load W 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.

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 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 against the lining 15 is also lost, and the braking force is released. The drum 2 then becomes free to rotate in the reverse direction R2, and the load W descends by natural fall.

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 part 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 part 13 will relatively prevail. Then, since the pressing nut part 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 at the reverse rotation R2 speed of the drive system.

In the final stage, the motor 1 is stopped when the load W has landed, 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, when the load W lands and the drum 2 becomes unloaded, the pressing nut portion 13 loosens at that moment. In other words, 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 receives a reaction from the clutch in the loosening direction. Therefore, when the load torque becomes zero, the pressing nut portion 13 instantly loosens due to 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), and thereafter, even if the motor 1 continues to be driven in the reverse direction R2, 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 direction R2 that causes the claw 19a of the second ratchet 19 to mesh with the teeth 19b disappears, so that only the pressing nut portion 13 rotates idly in the reverse direction R2. 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 direction 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, if the load torque on the drum 2 side falls below a certain level while the load W is descending, the backlash phenomenon is reliably prevented by two means: the clutch is disengaged by loosening the pressing nut portion 13, and the second ratchet 19 is disengaged. However, what is necessary for the present invention is to employ at least the means using the second ratchet 19.

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 smaller and lighter. In addition, the pressing nut portion 13 of the feed screw mechanism, which is the actuator of the clutch, is not in meshing relationship with the various gears in the reduction gear mechanism, so that no excessive force is applied to the meshing portion of the reduction gear mechanism when the braking force is released or restored, improving durability.

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. However, the ratchet wheel and the pressing nut portion 13 can also 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 sync with the rotation of the motor, without having to reciprocate on the support shaft.

In addition, while part of the reduction gear mechanism is constructed from two sets of planetary gears 7 and 8, it is also 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 being 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 to make it possible for this to mesh with the ratchet 22b provided on the drum 23, thereby forming a backlash prevention structure.

The present invention is not limited to general cargo handling applications; by mounting it on a drone, it can also be used for delivery services that transport cargo by air easily and swiftly.

1 Motor 2 Drum 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 portion 13 Pressing nut portion 14 Clutch plate 15 Lining 16 Friction plate 17 Receiving portion 18 First ratchet 19 Second ratchet W Suspended loads F1 to F4 Frame

Claims (10)

In an electric hoist that can raise and lower a load wound on 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 shaft inserted through the center of rotation of the drum and can rotate forward and reverse in sync with the rotation of the motor, and a pawl mounted on the drum, and the ratchet is configured such that the pawl engages with the ratchet wheel due to the load torque in the payout direction of the drum caused by the load, allowing the power of the motor to be transmitted to the drum via the ratchet wheel, but when the load torque falls below a certain level, the pawl disengages from the ratchet wheel and the ratchet wheel spins freely, cutting off the transmission of the power of the motor to the drum. A backlash prevention structure for an electric hoist that is characterized by the above. The backlash prevention structure for an electric hoist as described in claim 1, wherein the ratchet has a spring that elastically biases the pawl in the meshing direction. The backlash prevention structure for an electric hoisting device according to claim 1 or 2, in which the motor power is transmitted to the drum via a reduction gear mechanism and a braking mechanism, with the ratchet being the final motor power transmission means. The braking mechanism includes a screw shaft that is connected to the motor so as to be rotatable in both forward and reverse directions, 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 with the lining by the thrust force generated when tightening, and the screw shaft is formed with a male thread part that screws into the pressing nut part on a support shaft that is inserted into the center of rotation of the drum, and the pressing nut part is provided with a female thread on the ratchet wheel that screws into the male thread. The backlash prevention structure for an electric hoist according to claim 1, 2 or 3. The backlash prevention structure for an electric hoisting device according to claim 3 or 4, in which 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 suspended load. A backlash prevention structure for an electric winding device according to claim 3, 4 or 5, in which 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 is used as a ratchet that is separate from the ratchet formed by the pressing nut portion, thereby constantly restricting reverse rotation. A backlash prevention structure for an electric winding device according to any one of claims 3 to 6, in which the static friction torque of the drive system, which is expressed as the rotational resistance of the motor and the reduction gear mechanism combined, is set to balance with the load torque on the drum side when the motor is stopped. An electric hoisting device according to any one of claims 4 to 7, in which, when the load torque on the drum side falls below a certain level during the descent of a suspended 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. A backlash prevention structure for an electric winding device according to any one of claims 3 to 8, in which the reduction gear mechanism is at least partially constructed of planetary gears. A drone equipped with an electric hoisting device equipped with a backlash prevention structure as described in any one of claims 1 to 9.

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