JP2014101168A - Drop impact relieving device of object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drop impact relieving device capable of relieving impact force of a dropping object, and capable of restraining a collision between the mutual dropping objects, when a plurality of dropping objects drop continuously.SOLUTION: A drop impact relieving device relieves drop impact of a free-fall object C, and comprises: a rotor 6 having a plurality of rotary blades 8 rotatable around the horizontal axis 7 and arranged so that at least one rotary blade is positioned on a drop locus of the object; driving means 10 for rotatingly driving the rotor so that the rotary blade 8 rotates in the same one direction as the drop direction of the object and a peripheral speed of the rotary blade becomes smaller than a drop speed of the object; and recovery means 11 arranged under the rotor 6 and for receiving the object after relieving the impact force by colliding with the rotary blade.

Description

The present invention relates to a drop impact mitigation device that mitigates a drop impact of a free-falling object (for example, a chip part or a granulated material) and receives the object while preventing the object from being damaged or deformed. The object in the present invention is a solid object that can be cracked, chipped, or deformed by a drop impact of a predetermined value or more, and its material and use are not limited.

Conventionally, when a chip component such as a multilayer ceramic capacitor is transported in a manufacturing process, it may be necessary to transport the chip component from a certain transport line to another transport line having a lower height. is there. In that case, conventionally, a method of sliding a chip component along a slide like a shooter is used, but in order to slide a height above a predetermined level, the shooter itself becomes large and the horizontal direction Even a large space is required.

Therefore, conventionally, as shown in FIG. 6, a plurality of conveyor belts 101, 102, 103 are arranged in multiple stages in the vertical direction, and the chip component C conveyed on the uppermost conveyor belt 101 is placed on the next belt 102. There is a method of transporting the chip parts C while mitigating the drop impact of the chip parts C per stage, by dropping the chip parts C onto the lower belt. A chip component such as a multilayer ceramic capacitor is likely to be cracked or chipped due to a drop impact, and therefore it is necessary to manage the drop height H of the chip component per stage below an allowable drop distance.

For example, when a 0.5 × 0.5 × 1.0 mm rectangular parallelepiped multilayer ceramic capacitor is dropped freely from a height of 1 m, the dropping speed is accelerated to about 3 m / s. It was experimentally confirmed that when the chip component collides with a rigid plate (for example, a ceramic plate) at this speed, damage such as cracking or chipping occurs with a probability of 30% or more. On the other hand, when the drop height is 50 to 150 mm, it is confirmed that cracks and chips are almost zero, and the allowable drop distance is 50 to 150 mm. Therefore, when dropping from a height exceeding 150 mm, some kind of drop impact mitigation measures are necessary.

When the chip part is dropped on a soft elastic mat such as urethane or sponge, the mat absorbs the impact, and the chip part can be prevented from being broken or damaged. However, when a large number of chip components are continuously dropped on the mat, the chip component dropped first and the subsequent chip component collide with each other, and cracks and chips are generated by the impact.

Patent Document 1 discloses a conveyor chute for the purpose of mitigating drop impact. This chute apparatus includes a conveyance path arranged in a plurality of stages in the height direction, and among the conveyance paths adjacent to each other in the vertical direction, the upstream end of the conveyance path located on the lower side is located above the conveyance path. It is connected to the downstream end of the path so as to be freely rotatable, and in a free state, it is provided in a drop speed reducing means in which each conveyance path is inclined downward from the upstream side to the downstream side, and a lowermost conveyance path. And a wire that raises or lowers the conveying path and adjusts the height of the drop speed reducing means.

However, in the case of the chute device described in Patent Document 1,
(1) A sufficiently long conveyance path is necessary to sufficiently reduce the drop impact.
(2) Because it is dropped while moving in a zigzag shape, it takes a lot of time to move,
(3) Since it is necessary to connect a plurality of conveyance paths via a hinge shaft so as to be rotatable, there is a problem that the apparatus becomes large and complicated.

JP 2007-153576 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a drop impact mitigation device capable of suppressing collision of fallen objects even when a plurality of fallen objects fall continuously, as well as impact mitigation of individual fallen objects.

In order to achieve the above object, the present invention provides a drop impact mitigation device for mitigating a drop impact of a free-falling object, having a plurality of rotating blades that can rotate about a horizontal axis, and on the fall trajectory of the object. The rotor arranged so that at least one of the rotating blades is positioned, the rotating blade rotates in the same direction as the falling direction of the object, and the peripheral speed of the rotating blade is smaller than the falling speed of the object The drive means for rotating the rotor, and the recovery means that is disposed below the rotor and receives the object after the impact force is alleviated by colliding with the rotating blades. To do.

In general, from the impulse equation, the impact force F generated by the collision of two objects moving in the same direction is expressed by the following equation (1).
F = mΔv / Δt (1)
Here, m is the mass of the object, Δv is the speed difference of the object moving in the same direction, and Δt is the collision time. That is, the impact force F received by the object can be reduced by decreasing the momentum of the right-hand side numerator (= decreasing the speed difference) or increasing the collision time of the right-side denominator.

When a plurality of objects are dropped from above the rotor, the objects collide with one of the rotating blades on the dropping locus. The rotating blade rotates in the same direction as the falling direction of the object and at a peripheral speed smaller than the falling speed of the object, and moves so as to escape at a speed smaller than the falling speed of the object with respect to the falling of the object. The blades collide with a smaller speed difference than when the object collides with a stationary object, and the impact force is reduced based on the equation (1). In addition, the circumferential speed in this invention is the circumferential direction speed of the part of the rotary blade which an object collides. The collision part is preferably the outer peripheral part of the rotating blade as much as possible. For example, when a rotary blade is stationary when a 0.5 × 0.5 × 1.0 mm rectangular ceramic capacitor is dropped freely from a height of 1 m as described later, the multilayer ceramic capacitor and the rotary blade The speed difference Δv is approximately 3 m / s, but by rotating the rotary blades under predetermined conditions, the speed difference Δv between them can be reduced to 1 m / s or less, and the impact that the multilayer ceramic capacitor receives during a collision The force F is reduced to a fraction or less compared to when the rotary blade is stationary.

Since the rotor is provided with a plurality of rotating blades, the subsequent falling object collides with the rotating blade that rotates next, and the collision frequency with the preceding falling object can be lowered. Further, even if the preceding falling object collides with the rotating blade, the rotating blade rotates in the same direction as the falling direction, so that the rebounding of the falling object is suppressed. As a result, the probability of a frontal collision with a subsequent falling object is low, and damage due to the collision between falling objects can be suppressed.

When the allowable drop speed is α, the actual drop speed of the object is Vc, and the peripheral speed of the rotary blade is Vw,
Vc−Vw <α
The rotor should be driven to rotate at a rotational speed satisfying the above. The allowable fall speed α is a drop speed at the time of collision of an object when an allowable fall height is obtained when the object is dropped and collided on a stationary rigid body. The rotating blade is driven to rotate so that its peripheral speed is smaller than the falling speed of the object.However, if the peripheral speed is too low, the impact force caused by the collision between the object and the rotating blade will exceed the allowable impact force, and the object will be damaged. There is a possibility of inviting. Therefore, by driving the rotating blade at such a speed that the difference between the falling speed Vc of the object and the peripheral speed Vw of the rotating blade is smaller than the allowable falling speed α, damage due to the collision between the object and the rotating blade is suppressed. Can do.

While the plurality of rotors alternately shift the position of the horizontal axis of the rotor so that at least one rotor blade of each rotor is positioned on the object's fall trajectory, When the rotor blades are arranged in the opposite direction, the peripheral speed of the rotor rotor blades gradually decreases from the upper stage to the lower stage, and the difference in peripheral speed between the rotor blades of the rotors adjacent to each other in the vertical direction causes the object to fall and collide with a stationary rigid body. The allowable drop speed α is preferably less than. In other words, even if the drop speed cannot be reduced to the allowable speed α by a single collision between the object and the rotating blades, the falling speed can be reduced step by step by collision with a plurality of rotating blades, and the impact force per time can be reduced. Can be small. And by repeating the collision below the allowable impact force, the falling object can be recovered without cracking.

The rotating blades may be made of a rigid body. However, when the rotating blades are made of an elastic mesh that has a clear passage through which an object cannot pass, the collision time Δt between the elastic mesh and the falling object can be further extended, and the impact force Is reduced. In the case of an elastic mesh, air can pass through the gaps of the mesh, so that it is possible to suppress the generation of an air current when the rotating blades rotate at a high speed and to suppress the falling object from being blown away by the air current.

You may provide the shooter which guides the fall position of an object so that an object may collide with the outer peripheral part of the rotary blade | wing in a horizontal attitude | position at the upper part of a rotor. The rotating blade has a small peripheral speed at the inner peripheral portion and a high peripheral speed at the outer peripheral portion. The peripheral speed of the rotating blade is set to be smaller than the falling speed of the object, but by guiding the object with the shooter so that the object falls as much as possible to the outermost peripheral portion that is the maximum peripheral speed of the rotating blade, The speed difference with the rotary blade can be made lower than the allowable drop speed.

As described above, according to the present invention, the rotor having a plurality of rotating blades that can rotate about the horizontal axis is arranged on the falling locus of the object, and the rotating blade rotates in the same direction as the falling direction of the object. And, because the rotor is driven to rotate so that the peripheral speed of the rotating blade is smaller than the falling speed of the object, the rotating blade escapes at a speed smaller than the falling speed of the object with respect to the falling of the object, The object and the rotating blade collide with a smaller speed difference than when the object collides with a stationary object, and the impact force is reduced. In addition, since the rotor is provided with a plurality of rotating blades, the subsequent falling object collides with the rotating blade that rotates next, and the frequency of collision with the preceding falling object can be reduced. Therefore, the fallen object can be recovered without causing cracks or chipping by relaxing the impact force with the rotating blades and avoiding collision between the fallen objects.

1 is an overall cross-sectional view of a first embodiment of a drop impact mitigation device according to the present invention. It is a top view of the drop impact mitigation device shown in FIG. It is a figure which shows a mode that a chip component collides with the rotary blade shown in FIG. It is a timing chart figure at the time of dropping a chip on the collection board which descends. It is a whole sectional view of the 2nd example of the drop impact mitigation device concerning the present invention. It is the schematic of an example of the conventional conveying apparatus.

-1st Example-
1 to 3 show a first embodiment of a drop impact mitigation device according to the present invention. This device 1 is used for mitigating the drop impact of a chip component (object) C such as a multilayer ceramic capacitor. The drawing is shown for easy understanding, and the dimensional relationship between the chip component C and each member is different from the actual one.

The impact mitigating device 1 includes a dropping cylinder 2 at an upper portion, and a housing 5 is connected to the lower portion thereof. A plurality of transport paths 3 for continuously transporting the chip parts C are provided on the top of the dropping cylinder 2, and the chip parts C transported through these transport paths 3 are thrown from the upper end opening of the dropping cylinder 2. . The inner wall of the dropping cylinder 2 is provided with a shooter 4 that guides the chip part C so that the inserted chip part C falls on the outermost peripheral part of the rotary blade 8 described later. If the installation angle of the shooter 4 is adjusted so that the horizontal speed component generated as a result of the chip part C in contact with the shooter 4 rebounding is less than or equal to the allowable drop speed α, the chipping due to the collision of the chip parts in the horizontal direction is lost. Can be prevented. Although this shooter angle depends on the permissible fall speed, a range of approximately 5 to 15 ° with respect to the vertical direction may be assumed.

A rotor 6 having a plurality of rotating blades 8 is accommodated inside the housing 5 so as to be rotatable about a horizontal shaft 7. Here, the horizontal shaft 7 is a cylindrical tube, and 18 rotating blades 8 are attached to the outer periphery of the horizontal shaft 7. The fixing structure of the rotary blade 8 with respect to the horizontal shaft 7 is arbitrary, but here, the rotary blade 8 is placed horizontally in order to prevent the chip component C that has fallen from colliding with the rotary blade 8 from accumulating on the horizontal shaft 7 side. The shaft 7 is fixed so as to extend in the tangential direction and in the rotational direction. The rotor 6 is arranged such that at least one rotary blade 8 is located on the dropping locus of the chip part C. The rotary blade 8 may be a rigid plate, but here, an elastic mesh having a clear aperture through which the chip part C cannot pass is used. For example, a metal mesh having a desired Young's modulus and durability can be used as the elastic mesh. The gap between the rotary blade 8 and the housing 5 is preferably a narrow gap so that the chip component does not come into contact with the rotary blade 8 and does not fall.

A driving motor 10 (see FIG. 2) for driving the rotor 6 is provided outside the housing 5 so that the rotary blade 8 rotates in the same direction as the falling direction of the chip part C. The driving speed of the motor 10 is such that the peripheral speed Vw of the rotary blade 8 is smaller than the drop speed Vc of the chip part C, and the difference between the drop speed Vc of the chip part C and the peripheral speed Vw of the rotary blade 8 is the allowable drop speed α. It is set to be smaller. That is,
0 <Vc−Vw <α

Below the rotor 6, a collection tray 11 that receives the chip component C after the impact force is alleviated by colliding with the rotary blade 8 is installed. The height from the rotor 6 to the collection tray 11 is set to be equal to or less than the allowable drop distance (for example, 50 mm), and the chip component C that has passed through the rotor 6 has a sufficiently low drop energy. Even if it is not comprised by, chip component C can be collect | recovered, without generating a crack and a chip.

Here, operation | movement of the drop impact mitigation apparatus 1 which consists of the said structure is demonstrated, referring FIG. When a plurality of chip parts C are continuously freely dropped through the dropping cylinder 2, some chip parts C collide with the outer peripheral portion of the rotary blade 8, and when the drop impact exceeds an allowable value, the chip The part C is cracked or chipped. In addition, the chip part C that has fallen rebounds on the rotary blade 8 or directly on the chip part C that is stationary on the rotary blade 8 (the chip part C moves at the same speed as the rotary blade 8). In the case of a collision, the impact absorbing effect due to the elasticity of the rotary blade 8 is weakened, and the possibility of chipping of the chip part C is increased. Therefore, the rotor 6 having a plurality of rotating blades 8 is rotated in the same direction as the falling direction of the chip part C, and the speed difference ΔV from the terminal speed of the chip part C is reduced by the peripheral speed.

Assuming that the drop speed of the chip part C is Vc and the rotating blade 8 moves at the peripheral speed Vw in the same direction as the drop direction of the chip part C, the speed difference ΔV = Vc−Vw is equal to or less than the allowable drop speed α of the chip part C. The rotational speed of the rotor 6 is controlled so that For example, if the allowable drop height when the chip part C is dropped and collided on a stationary rigid body is 50 mm, the drop speed α at the time of the collision corresponds to 1 m / s. Therefore, if the rotational speed of the rotor 6 is set so as to satisfy ΔV <1 m / s, the chip component C can be recovered without cracking by one rotor 6 without using an elastic mesh as the rotary blade 8. Become. At this time, even if it collides with the chip component C stationary on the rotary blade 8, the difference in speed is less than the allowable speed, so that damage is allowed. Further, when the relative speed ΔV between the falling chip part C and the rotary blade 8 is 1 m / s level, the chip part C that collides with the rotary blade 8 also has a slight jump, and the chip part C that has dropped and the chip part C that has dropped. It is also possible to avoid cracks and cracks due to collisions.

In principle, the rotating blade 8 does not need to be an elastic body such as a mesh, and may be a rigid body such as a ceramic plate or metal, but it is assumed that a case where the allowable speed is exceeded for some reason may occur. It is better to use a safer mesh. When the chip part C is dropped onto the elastic rotary blade 8, the time Δt for the chip part C to decelerate to zero speed is one digit or more longer than when the chip part C collides with a rigid body such as a ceramic plate. As a result, as shown in the equation (1), the impact force F at the time of collision decreases in inverse proportion to the collision time Δt, and the occurrence rate of cracks and chips of the chip part C can be reduced.

As in the embodiment, the horizontal shaft 7 has a cylindrical shaft whose diameter is larger than the maximum dimension of the chip part C, and the rotary blade 8 is fixed so as to extend in the tangential direction of the horizontal shaft 7 and in the rotational direction. In this case, since the falling chip component C collides with the rotary blade 8 and can be prevented from accumulating on the horizontal shaft 7 side, there is an effect of reducing the collision frequency between the chip components C.

-Mock experiment-
In order to confirm the effect of the first embodiment, the following simulation experiment was conducted. When a rectangular parallelepiped ceramic chip having a size of 0.5 × 0.5 × 1.0 mm is dropped from a height of 1 m, the dropping speed is accelerated to about 3 m / s. It was confirmed that when this was made to collide with a rigid plate such as a ceramic plate at this speed, damage such as cracking or chipping occurred with a probability of 30% or more. On the other hand, when the drop height was 100 mm, the cracks were zero.

Now, a recovery plate having a rigidity of 200 × 200 mm was horizontally arranged at the dropping position. As the chip falls, the recovery plate is accelerated, moved at a constant speed, decelerated, and dropped onto the recovery plate. FIG. 4 shows a timing chart at that time. The time for the falling tip to reach a height of 900 mm was measured in advance, and the recovery plate waiting at a height of 700 mm was accelerated downward at the time when the tip reached 900 mm (time zero). After 100 mm seconds, it reaches 2.25 m / s. Immediately after that, the top chip collides with the recovery plate with a speed difference of 0.75 m / s. The recovery plate is then lowered at a constant speed of 2.25 m / s, and after 210 milliseconds, it collides with the last tip and recovers. The chip that collided with the recovery plate at a speed difference of 0.75 m / s remained at the collision position, although showing a slight bounce on the recovery plate. The recovery plate was then decelerated from the point where it reached a position with a height of 200 mm. When the collected chips were examined, it was confirmed that there was no damage such as cracks due to collision. Although FIG. 4 shows an experiment when the collecting plate is lowered in a horizontal posture, the same effect can be obtained by controlling the peripheral speed even when the rotating blade is rotated as shown in FIG.

-Second Example-
FIG. 5 shows a second embodiment of the drop impact mitigating device according to the present invention. In FIG. 5, the same or corresponding parts as in FIG. In the first embodiment, the drop impact of the chip component C is reduced by using only one rotor. However, in the drop impact mitigating device 20 of the second embodiment, a plurality of (here 3 Rotors 21 to 23 are arranged in the vertical direction, and the rotating blades of the rotors 21 to 23 adjacent to each other in the vertical direction are arranged in opposite directions. When the peripheral speeds of the rotor blades of the rotors 21 to 23 sequentially decrease from the upper stage to the lower stage, and the difference in the peripheral speeds of the rotor blades of the rotors 21 to 23 adjacent to each other in the vertical direction causes the chip part C to drop and collide with the stationary rigid body The allowable drop speed α is less than. Below the housing 5 that houses the rotors 21 to 23, a belt conveyor 25 that is driven in the horizontal direction is disposed as a collecting means. The height between the lowermost rotor 23 and the belt conveyor 25 is set to be equal to or less than the allowable drop height (for example, 50 mm). Therefore, even if the belt conveyor 25 is formed of a hard material, the chip component is not damaged due to the collision with the belt conveyor 25. Further, even if a chip component that has been dropped later collides with the chip component that has been dropped, the chip component is not damaged.

The first-stage (top) rotor 21 includes a horizontal shaft 21a and a plurality of rotating blades 21b fixed around the horizontal shaft 21a. Similarly, the second and third rotors 22 and 23 also include horizontal shafts 22a and 23a and a plurality of rotating blades 22b and 23b fixed around the horizontal shafts 22a and 23a. Driven in opposite directions by the driving means that do not. The horizontal shafts 21a, 22a, and 23a are alternately shifted so that at least one rotary blade of each of the rotors 21 to 23 is positioned on the dropping locus of the chip component C. When the peripheral speed of the rotary blade 21b of the uppermost rotor 21 is V1, the peripheral speed of the rotary blade 22b of the rotor 22 of the second stage 22 is V2, and the peripheral speed of the rotary blade 23b of the third stage rotor 23 is V3,
V1>V2> V3
The circumferential speed difference between the rotor blades of the rotor that is set to
V1-V2 <α, V2-V3 <α
It is set to become.

In this embodiment, even when the drop speed of the chip part C cannot be reduced to the allowable speed α by only one collision between the chip part C and the rotary blade 21 b of the first rotor 21, the second and third rotors 22. , 23 by dropping the dropping speed stepwise by collision with the rotary blades 22b, 23b, the chip component C falling can be recovered without cracking.

Next, the effect of the apparatus according to the second example was confirmed by the following experiment. Twenty metal rotating blades having a length of 150 mm and a width of 60 mm were attached to a metal cylindrical horizontal shaft having a length of 150 mm and a diameter of 20 mm at intervals of 18 °. Three sets of this structure (rotor) were prepared and adjusted so as to be in the position shown in FIG. That is, the outermost peripheral portion of the rotating blade 21b of the first rotor 21 is made to coincide with the extension line of the inner peripheral surface of the dropping cylinder 2 from which the chip component C falls, and the falling chip component C becomes the rotating blade 21b of the rotor 21. Arranged so that it always collides. The second rotor 22 is set below the first rotor 21, and the outermost peripheral portion of the rotary blade 22b of the second rotor 22 is aligned with the position where the rotary blade 21b of the first rotor 21 is vertically downward. It was. The third rotor 23 was also set below the second rotor 22 in the same way as the second rotor 22. The first rotor 21 is rotated at a peripheral speed (here, the outermost peripheral speed) V1 = 2.25 m / s, the second rotor 22 is similarly V2 = 1.5 m / s, and the third rotor 23 is V3 = It was rotated at 0.75 m / s.

The terminal speed of the chip C that has dropped is 3 m / s, collides with the first rotor 21 with a speed difference of about 0.75 m / s, stays on the rotary blade 21 b, and is rotated by the rotation of the first rotor 21. Was dropped onto the rotor 22 at a dropping speed of about 2.25 m / s. The dropped chip C collides with the rotating blade 22b of the second rotor 22 rotating at a peripheral speed of 1.5 m / s, stays on the rotating blade 22b, and rotates the second rotor 22 to cause the third rotor to rotate. 23 was dropped at a dropping speed of about 1.5 m / s. The dropped chip C collides with the rotating blade 23b of the third rotor 23 rotating at a peripheral speed of 0.75 m / s, stays on the rotating blade 23b, and on the belt conveyor 25 by the rotation of the third rotor 23. And dropped at a dropping speed of about 0.75 m / s.

The collision speed of the first to third rotors 21 to 23 to the rotating blades 21b to 23b and the final collision speed to the belt conveyor 25 are 0.75 m / s, which is an allowable drop speed of the chip C of 1 m. / S were both below. As a result of examining the appearance and the like of 100 collected chips, it was confirmed that there was no damage such as chipping. When the behavior during the fall was observed with a high-speed camera, a case where the chip collided with the chip remaining on the first to third rotors 21 to 23 was also seen, but the chip was broken despite the collision of the chips. No damage such as chipping occurred.

The object targeted by the present invention is not limited to a chip component, and may be a granulated body, a molded product, a sintered body, a metal body, or the like. In the case of a granulated body, the present invention is effective because cracks and chips are likely to occur due to a drop impact as in the case of chip parts. In the case of a sintered body or a metal body, the present invention is effective because deformation and distortion occur due to a drop impact. The shape of the object is not limited to a rectangular parallelepiped, and may be a disk shape or a tablet shape.

The shape of the rotary blades constituting the rotor need not be flat, and may be curved in the rotational direction, for example. The structure for fixing the rotating blades to the horizontal axis is not limited to the structure shown in FIG. 1, but may be any shape that can collide with a falling object evenly with an appropriate speed difference.

C Chip parts (objects)
DESCRIPTION OF SYMBOLS 1 Impact mitigation device 2 Falling cylinder 3 Conveyance path 4 Shutter 5 Housing 6 Rotor 7 Horizontal shaft 8 Rotary blade 10 Drive motor 11 Recovery tray 20 Impact mitigation devices 21-23 Rotor 21a-23a Horizontal shaft 21b-23b Rotary blade 25 Belt conveyor

Claims (5)

In a drop impact mitigation device that mitigates the drop impact of a free-falling object,
A rotor having a plurality of rotating blades rotatable about a horizontal axis, and arranged such that at least one of the rotating blades is positioned on a falling locus of the object;
Drive means for rotationally driving the rotor so that the rotating blade rotates in the same direction as the falling direction of the object and the peripheral speed of the rotating blade is smaller than the falling speed of the object;
A drop impact mitigating device, comprising: a recovery unit that is disposed below the rotor and receives an object after the impact force is mitigated by colliding with the rotating blades. When the object is allowed to drop and collide with a stationary rigid body, the allowable fall speed is α, the actual fall speed of the object is Vc, and the peripheral speed of the rotary blade is Vw.
Vc−Vw <α
The apparatus according to claim 1, wherein the rotor is rotationally driven at a rotational speed satisfying the above. The plurality of rotors are arranged so that at least one of the rotor blades of each rotor is positioned on the trajectory of the object, while alternately shifting the position of the horizontal axis of the rotor, and Arranged so that the rotation direction is reversed, the peripheral speed of the rotor blades of the rotor gradually decreases from the upper stage to the lower stage, and the difference in the peripheral speeds of the rotor blades of the rotors adjacent to each other falls on the rigid body where the object is stationary The fall impact mitigation device according to claim 1 or 2, wherein the fall impact mitigation device is less than an allowable fall speed α in the case of collision. The drop impact mitigation device according to any one of claims 1 to 3, wherein the rotary blade is made of an elastic mesh having a clearness that the object cannot pass through. 2. The motor according to claim 1, further comprising a shunt for guiding the position of the object to fall so that the object collides with an outer peripheral portion of the rotary blade in a horizontal posture. 5. The drop impact mitigating device according to any one of items 4 to 4.

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