JP2007084307A - Moving body lifting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moving body lifting system for minimizing replacing work for a fixed-position dog and a sensor member when there is a change of a lifting stroke while avoiding an increase in rack size. <P>SOLUTION: The system allows the extension of a carriage 25 in the lifting direction from a base portion 2 of the fixed-position dog 1 corresponding to the extension of the lifting stroke b and the shortening of the carriage 25 in the lifting direction in a protruded portion 3 of the fixed-position dog 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lifting system for a moving body such as a carriage provided in a stacker crane, and more particularly to a method for setting a lifting stroke of a moving body.

FIG. 2 is a diagram illustrating an example of a moving body lifting system.
A moving body lifting system 20 shown in FIG. 2 includes a rack 21, a load receiving table 22, and a stacker crane 24 that carries the load 23 between the rack 21 and the load receiving table 22.

  The stacker crane 24 moves between the rack 21 and the load receiving table 22 and scoops / unloads the load 23 on the rack 21 or the load receiving table 22, and a mast 26 for moving the carriage 25 up and down along the lifting direction. And a control device 27 (moving body control means) that performs traveling control of the stacker crane 24, raising / lowering control of the carriage 25, and the like.

  As shown in FIG. 2, when scooping / unloading the load 23 with the rack 21, the carriage 25 moves up and down the distance of the lifting stroke a. Further, when scooping / unloading the load 23 with the load receiving table 22, the carriage 25 moves up and down the distance of the lifting stroke b.

  FIG. 3A is a diagram illustrating an example of a fixed position dog and a sensor member used for setting up and down strokes a and b. FIG. 3B is a perspective view of the home position dog and sensor member shown in FIG. In FIG. 3A, the same components as those shown in FIG.

  As shown in FIGS. 3A and 3B, the fixed position dog 30 has a convex shape including a base portion 31 and a protruding portion 32 located at the center of the base portion 31 in the ascending / descending direction of the carriage 25. It is formed and is provided at a stop position of the carriage 25 when scooping / lowering the load 23 on the mast 26. As an operation control of the stacker crane 24 using such a convex member, for example, an optical sensor provided in the stacker crane 24 with a convex member (striker) installed along the traveling direction of the stacker crane 24 is used. When detected, there is one that stops the traveling stacker crane 24 (for example, see Patent Document 1).

  As shown in FIG. 3B, the sensor member 33 includes three longitudinal portions 33A-1 to 33A-3 arranged at equal intervals in the lifting / lowering direction of the carriage 25 and a longitudinal portion 33A− in the lifting / lowering direction of the carriage 25. Three longitudinal portions 33B-1 to 33B-3 arranged at the same intervals as 1-33A-3 are provided. Light emitting elements 34-1 to 34-3 are provided at the tips of the longitudinal portions 33A-1 to 33A-3. In addition, light receiving elements 35-1 to 35-3 are provided at positions facing the light emitting elements 34-1 to 34-3 at the respective tips of the longitudinal portions 33 B- 1 to 33 B- 3. Further, the longitudinal portion 33A-2 (or the longitudinal portion 33B-2) is formed longer than the longitudinal portions 33A-1 and 33A-3 (or the longitudinal portions 33B-1 and 33B-3).

  2 determines the current position of the carriage 25 by blocking light to the light receiving elements 35-1 to 35-3 by the fixed position dog 30, and the operation of the carriage 25 is performed based on the current position. Control is in progress.

Here, in FIG. 2, the operation of the control device 27 when the carriage 25 scoops the load 23 from the shelf 28 of the rack 21 will be described.
First, the control device 27 moves the carriage 25 to the vicinity of the shelf board 28.

Next, the control device 27 stops the carriage 25 when the light to the light receiving elements 35-1 and 35-2 is blocked by the fixed position dog 30 provided at the stop position in the vicinity of the shelf board 28.
And the control apparatus 27 makes the fork with which the carriage 25 is provided to the rack 21 side, and lifts the carriage 25 by the distance of the raising / lowering stroke a, so that the load 23 is drawn with the fork.

Similarly, in FIG. 2, the operation of the control device 27 when the carriage 25 unloads the load 23 on the shelf board 28 will be described.
First, the control device 27 moves the carriage 25 to the vicinity of the shelf board 28 with the load 23 placed on the fork.

Next, the control device 27 stops the carriage 25 when the light to the light receiving elements 35-2 and 35-3 is blocked by the fixed position dog 30 provided at the stop position in the vicinity of the shelf board 28.
Then, the control device 27 moves the fork to the rack 21 side, and lowers the carriage 23 from the fork to the shelf board 28 by lowering the carriage 25 by the distance of the lifting stroke a.

  FIG. 4 is a diagram schematically showing the positional relationship between the fixed position dog 30 and the sensor member 33 when the carriage 25 moves up and down by a distance of the lifting stroke a. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG.3 (b). The distance that the sensor member 33 moves up and down is equal to the distance that the carriage 25 moves up and down.

  First, the positional relationship between the fixed position dog 30 and the sensor member 33 when the sensor member 33 is raised by the distance of the lifting stroke a will be described. The sensor member 33 is initially stopped at the lowest position of the lifting stroke a (hereinafter referred to as a lower position), the light to the light receiving element 35-1 is blocked by the protrusion 32, and the light receiving element 35. -2 light is blocked by the base 31. Further, when the sensor member 33 is stopped at the lower position, the distance d1 from the upper end of the protruding portion 32 to the longitudinal portion 33B-1 and the distance d2 from the lower end of the base portion 31 to the longitudinal portion 33B-2 are equal to each other. It shall be.

First, when the sensor member 33 is lifted from the lower position, only the light to the light receiving element 35-2 is blocked by the base portion 31.
Next, when the sensor member 33 is further raised and the light to the light receiving element 35-3 is also blocked by the protrusion 32, the control device 27 starts counting the rotation amount of the roller that rolls on the mast 26.

When the rotation amount reaches a predetermined value, the sensor member 33 is stopped. At this time, the distance by which the sensor member 33 is raised is the lifting stroke a.
Next, the positional relationship between the fixed position dog 30 and the sensor member 33 when the sensor member 33 is lowered by the distance of the lifting stroke a will be described. The sensor member 33 is initially stopped at the highest position of the lift stroke a (hereinafter referred to as the upper fixed position), and the light to the light receiving element 35-2 is blocked by the base portion 31, and the light receiving element 35- It is assumed that the light to 3 is blocked by the protrusion 32. Further, when the sensor member 33 is stopped at the upper fixed position, the distance d3 from the lower end of the projecting portion 32 to the longitudinal portion 33B-3 and the distance d4 from the upper end of the base portion 31 to the longitudinal portion 33B-2 are equal to each other. Suppose that

First, when the sensor member 33 is lowered from the upper fixed position, only the light to the light receiving element 35-2 is blocked by the base portion 31.
Next, when the sensor member 33 is further lowered and the light to the light receiving element 35-1 is also blocked by the protrusion 32, the control device 27 starts counting the rotation amount of the roller.

When the rotation amount reaches a predetermined value, the sensor member 33 is stopped. At this time, the distance by which the sensor member 33 is lowered is the lifting stroke a.
The range of the upper fixed position shown in FIG. 4 is a distance that the sensor member 33 can move when the light to the light receiving elements 35-2 and 35-3 is blocked by the fixed position dog 30. It is assumed that the range is set so that the fork does not interfere with the rack 21 or the like when the fork is taken out to the rack 21 side. Similarly, the range of the lower fixed position shown in FIG. 4 is a distance that the sensor member 33 can move when the light to the light receiving elements 35-1 and 35-2 is blocked by the fixed position dog 30. It is assumed that the fork is set in a range that does not interfere with the rack 21 or the like when 25 forks are taken out to the rack 21 side.

Thus, the stop position of the carriage 25 when scooping / unloading the load 23 is two places, the upper fixed position and the lower fixed position.
Incidentally, the lifting stroke a is determined based on conditions such as the size of the opening of the rack 21, the operating range of the loading device such as a fork, or the weight of the load 23, and the dimensions of the fixed position dog 30 and the sensor member 33. A dimension is determined based on the raising / lowering stroke a.

  FIG. 5 is a diagram illustrating a relationship among the lifting stroke a, the dimension of the fixed position dog 30, and the dimension of the sensor member 33. A indicates a dimension of the protruding portion 32 in the up-and-down direction of the carriage 25 and is hereinafter referred to as a dimension A. B represents the distance from the longitudinal portion 33B-1 to the longitudinal portion 33B-2 of the sensor member 33 (or the distance from the longitudinal portion 33B-2 to the longitudinal portion 33B-3). That's it. C indicates half of the distance obtained by subtracting the dimension A from the dimension of the carriage 25 in the ascending / descending direction of the carriage 25, and is hereinafter referred to as dimension C. The fixed value 1 is when only the light to the light receiving element 35-3 is blocked, or the light to the light receiving element 35-3 is blocked and the light to the light receiving element 35-2 is also blocked. It shows the distance that the carriage 25 can move when The fixed value 2 indicates the distance that the carriage 25 can move when the light to the light receiving element 35-3 is blocked and the light to the light receiving element 35-2 is also blocked.

As shown in FIG. 5, since the sensor arrangement distance B is determined by the lift stroke a and the dimension C is determined by the sensor arrangement distance B, one type of fixed position dog 30 is provided for one type of sensor member 33. It is formed. Therefore, the mast 26 is provided only with the fixed position dog 30 having one kind of dimension, and the lifting stroke a and the lifting stroke b are equal to each other. For example, when the lifting stroke b has to be larger than the lifting stroke a due to the convenience of ground facilities, the lifting stroke a also increases in accordance with the lifting stroke b. That is, since the dimension of the fixed position dog 30 and the dimension of the sensor member 33 are determined based on the largest lifting stroke b, the lifting stroke a is also increased according to the lifting stroke b.
JP-A-4-22804

  However, as described above, when the lifting stroke a is increased in accordance with the lifting stroke b due to the convenience of ground facilities, the frontage corresponding to the lifting stroke a needs to be made larger than necessary so as not to interfere with the load 23. There is a problem that a wasteful space is formed in the height direction of the frontage and the entire rack 21 becomes large.

  Further, as described above, when the lifting stroke a is increased in accordance with the lifting stroke b due to ground facilities or the like, the dimensions of the fixed position dog 30 and the dimensions of the sensor member 33 are determined based on the lifting stroke b. Therefore, after the fixed position dog 30 and the sensor member 33 are formed, if the lift stroke b is changed, the dimensions of all the fixed position dogs 30 and the dimensions of the sensor members 33 must be determined again. Therefore, when a change occurs in the lift stroke b, it is necessary to replace all the fixed position dogs 30 and the sensor members 33, and there is a problem that these operations are very troublesome.

  Therefore, the present invention provides a moving body lifting system that can prevent the rack from becoming large and minimize the replacement work of the fixed position dog and the sensor member when the lifting stroke is changed. For the purpose.

In order to solve the above problems, the present invention adopts the following configuration.
That is, the moving body lifting / lowering system of the present invention is provided in a moving body that scoops / unloads a load, and includes a sensor member including three detection sensors arranged in the lifting / lowering direction of the moving body, a base portion, and the above-described base portion. It is formed in a convex shape composed of a protruding portion located in the center in the ascending / descending direction, and the protruding portion faces the sensor member when the moving body stops when the moving body scoops / unloads the load. A fixed position dog provided along the ascending / descending direction and an upper detection sensor of the three detection sensors detect the protruding portion, and a middle detection sensor of the three detection sensors detects the base portion. In the state where the middle detection sensor detects the base portion, the distance that the movable body moves between the three detection sensors until the lower detection sensor detects the protruding portion is set as the shift distance. And a moving body control means for moving the lifting / lowering stroke of the moving body when the body scoops / unloads the load. When the lifting / lowering stroke is changed, according to the change in the lifting / lowering stroke, The dimension in the ascending / descending direction is changed, and the dimension in the ascending / descending direction at the protrusion is changed.

  Thus, by changing the dimension of the fixed position dog without changing the dimension of the sensor member, the lifting stroke corresponding to the fixed position dog can be set. Therefore, by changing the dimension for each fixed position dog, 1 A plurality of lifting strokes can be prepared in one stacker crane. For this reason, it is possible to prevent a wasteful space from being generated in the frontage, thereby preventing an increase in the size of the rack.

  In addition, since a plurality of types of lifting strokes can be prepared in one stacker crane, it is not necessary to change the dimensions of all the fixed position dogs and the sensor members even if the lifting strokes are changed. Therefore, the replacement work of the fixed position dog and the sensor member when the lifting stroke is changed can be minimized.

  Moreover, in the said moving body raising / lowering system, when the said raising / lowering stroke is extended, while the dimension of the said raising / lowering direction in the said base part is extended by the extension of the raising / lowering stroke, the dimension of the said raising / lowering direction in the said protrusion part is extended. Shortened.

  Moreover, in the said mobile body raising / lowering system, when the said raising / lowering stroke is shortened, the dimension of the said raising / lowering direction in the said base part is shortened and the dimension of the said raising / lowering direction in the said protrusion part is shortened by the shortening of the raising / lowering stroke. Extended.

  The moving body lifting system includes two or more fixed position sensors in the moving body, and changes the dimensions of the base portion and the protruding portion of the fixed position dog respectively corresponding to the two or more sensor members. The raising / lowering stroke may be changed for each stage of the rack, for each series of racks, or for each opening of the rack.

  In addition, the fixed position dog of the present invention is provided on a moving body that scoops / unloads a load, and includes a sensor member having three detection sensors arranged in the ascending / descending direction of the moving body, a base portion, and the lifting / lowering of the base portion. Formed in a convex shape including a projecting portion located in the center of the direction, and the lifting and lowering so that the projecting portion faces the sensor member when the moving body stops when the moving body rakes / unloads a load. A fixed position dog provided along the direction, and an upper detection sensor of the three detection sensors detects the protruding portion, and a middle detection sensor of the three detection sensors detects the base portion. The distance that the movable body moves until the middle detection sensor detects the base portion and the lower detection sensor of the three detection sensors detects the protruding portion. The body loads The fixed position dog in the moving body lifting / lowering system including a moving body control means for moving the lifting / lowering stroke of the moving body when performing the lifting / lowering, and when the lifting / lowering stroke is changed, Accordingly, the size of the base portion in the ascending / descending direction is changed, and the dimension of the protruding portion in the ascending / descending direction is changed.

  The moving body lifting / lowering stroke setting method according to the present invention includes a sensor member provided with a moving body for scooping / unloading a load, the sensor member including three detection sensors arranged in the lifting / lowering direction of the moving body, a base portion, and the base thereof. Formed in a convex shape including a projecting portion located in the center of the lifting direction, and the projecting portion faces the sensor member when the moving body stops when the moving body scoops / unloads a load. As described above, the fixed position dog provided along the ascending / descending direction, the upper detection sensor of the three detection sensors detects the protruding portion, and the middle detection sensor of the three detection sensors is the base The distance that the movable body moves from when the middle detection sensor detects the base portion until the lower detection sensor of the three detection sensors detects the protrusion. The A moving body lifting / lowering stroke setting method in a moving body lifting / lowering system comprising: moving body control means for moving / lifting the moving body when the moving body scoops / unloads the load, wherein the lifting / lowering stroke is changed. When doing, it changes the dimension of the said raising / lowering direction in the said base part according to the change of the raising / lowering stroke, It changes the dimension of the said raising / lowering direction in the said protrusion part, It is characterized by the above-mentioned.

  According to the present invention, it is possible to prevent an increase in the size of the rack and to minimize the work for replacing the fixed position dog and the sensor member when the lifting stroke is changed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a fixed position dog in a moving body lifting system according to an embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same structure as FIG.3 (b). Further, the fixed position dog shown in FIG. 1 is a fixed position dog for setting the lift stroke b when the lift stroke b shown in FIG. 2 is extended beyond the lift stroke a.

  1 extends the lifting / lowering dimension of the carriage 25 (moving body) in the base portion 2 by the extension of the lifting / lowering stroke b, and the lifting / lowering dimension of the carriage 25 in the protruding portion 3. Is shortened. In addition, the broken line shown in FIG. 1 has shown the fixed position dog 1 before changing a dimension.

  Specifically, the lower end of the base portion 2 is extended by a distance e that is half of the extension stroke b, and the lower end of the protruding portion 3 is shortened by the distance e. Thereby, the light to the light receiving element 35-1 (upper detection sensor) of the sensor member 33 is blocked by the projecting part 3, and the light to the light receiving element 35-2 (middle detection sensor) is transmitted by the base part 2. After being blocked, the light to the light receiving element 35-2 is blocked by the base portion 2, and the carriage 25 is raised until the light to the light receiving element 35-3 (lower detection sensor) is blocked by the protruding portion 3. The distance (elevating stroke) to be performed can be increased by twice the distance e, that is, the extension of the elevating stroke b.

  Similarly, the upper end of the base portion 2 is extended by the distance e, and the upper end of the protruding portion 3 is shortened by the distance e. As a result, the light to the light receiving element 35-3 is blocked by the projecting portion 3, and the light to the light receiving element 35-2 is blocked by the base portion 2, and then the light receiving element 35-2 is blocked by the base portion 2. In addition, the distance (elevating stroke) by which the carriage 25 descends before the light to the light receiving element 35-1 is blocked by the protrusion 3 is increased by twice the distance e, that is, by the extension of the elevating stroke b. be able to.

  Therefore, when extending the lifting stroke b, the dimension A, the sensor arrangement distance B, and the dimension C shown in FIG. 5 are respectively A = (fixed value 1) − (extension of the lifting stroke b), B = ( Elevating stroke b + (fixed value 2)) / 2, C = B− (fixed value 2) + an extension of the elevating stroke b. It should be noted that (fixed value 1) and (fixed value 2) are set to appropriate values by the lift strokes a and b.

  As described above, the lifting stroke b can be changed by changing the dimension of the fixed position dog 1 without changing the sensor arrangement distance B. Therefore, in the stacker crane 24 shown in FIG. Can be set to appropriate distances. As a result, it is not necessary to increase the lifting / lowering stroke a in accordance with the lifting / lowering stroke b. Therefore, a useless space is not generated in the front opening corresponding to the lifting / lowering stroke a, and an increase in the size of the rack 21 can be prevented.

  In addition, after the fixed position dogs 1 for setting the lifting strokes a and b are installed on the mast 26 shown in FIG. 2, even if the lifting stroke b is changed, the fixed positions for setting the lifting stroke a. Since there is no need to change the dimensions of the dog or the sensor member 33, the work of replacing the fixed position dog or the sensor member 33 for setting the lifting / lowering stroke a can be eliminated.

  In addition, although the said embodiment demonstrated the setting method of the dimension of the fixed position dog 1 when making the raising / lowering stroke b larger than the raising / lowering stroke a, when making the raising / lowering stroke b smaller than the raising / lowering stroke a, raising / lowering stroke By reducing b, the dimension of the carriage 25 in the ascending / descending direction of the base part 2 is shortened, and the dimension of the protruding part 3 in the ascending / descending direction of the carriage 25 is extended.

  In the above embodiment, the carriage 25 includes the single sensor member 33. However, the carriage 25 may include two or more sensor members 33. For example, the carriage 25 is provided with two sensor members 33, and each of the base portion and the protruding portion of the fixed position dog 1 corresponding to the two sensor members 33 is changed to be provided on both sides of the stacker crane 24. The raising / lowering stroke may be changed for every two racks to be used, for each series of racks, for each stage of the rack, or for each frontage of the rack.

  Moreover, in the said embodiment, although it is the structure which detects the fixed position dog 1 using the light receiving elements 35-1 to 35-3, a contact type detection sensor is used instead of the light receiving elements 35-1 to 35-3. It may be used to detect the home position dog 1.

  Moreover, in the said embodiment, although the sensor member 33 is formed in the mountain shape, the shape of the sensor member 33 is not specifically limited, such as a rectangle and a convex type.

It is a figure which shows the fixed position dog in the mobile body raising / lowering system of embodiment of this invention. It is a figure which shows an example of a mobile body raising / lowering system. (A) is a figure which shows an example of the fixed position dog and sensor member which are used in order to set up-and-down stroke. (B) is a perspective view of the home position dog and sensor member shown in (a). It is a figure which shows typically the positional relationship of the fixed position dog and sensor member at the time of a carriage raising / lowering the distance of the raising / lowering stroke a. It is a figure which shows the relationship between the dimension of a raising / lowering stroke, the position dog, and the dimension of a sensor member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed position dog 2 Base part 3 Protrusion part 20 Moving body raising / lowering system 21 Rack 22 Loading base 23 Load 24 Stacker crane 25 Carriage 26 Mast 27 Controller 30 Fixed position dog 31 Base part 32 Protrusion part 33 Sensor members 34-1 to 34 -3 Light emitting element 35-1 to 35-3 Light receiving element

Claims (6)

A sensor member that is provided in a moving body that scoops / unloads the load and that includes three detection sensors arranged in the ascending / descending direction of the moving body;
Formed in a convex shape comprising a base portion and a protruding portion located in the center of the base portion in the ascending / descending direction, and when the moving body stops / moves the load, the protruding portion is A fixed position dog provided along the ascending and descending direction so as to face the sensor member;
Of the three detection sensors, the upper detection sensor detects the protruding portion, and among the three detection sensors, the middle detection sensor detects the base portion, and then the middle detection sensor detects the base portion. Of the three detection sensors in the state in which the lower detection sensor detects the protrusion, the distance that the moving body moves until the moving body scoops / unloads the load. Moving body control means for moving the moving body up and down; and
With
When the raising / lowering stroke is changed, according to the change of the raising / lowering stroke, the dimension in the raising / lowering direction in the base part is changed, and the dimension in the raising / lowering direction in the protruding part is changed,
The moving body raising / lowering system characterized by the above-mentioned. The moving body lifting system according to claim 1,
When the lifting stroke is extended, the lifting / lowering dimension of the base portion is extended and the lifting / lowering dimension of the projecting portion is shortened.
The moving body raising / lowering system characterized by the above-mentioned. The moving body lifting system according to claim 1,
When the lifting stroke is shortened, the dimension of the lifting direction in the foundation portion is shortened and the dimension in the lifting direction of the protruding portion is extended, as the lifting stroke is shortened.
The moving body raising / lowering system characterized by the above-mentioned. The moving body lifting system according to claim 1,
The movable body includes two or more sensor members,
By changing the dimensions of the base portion and the protruding portion of the fixed position dog respectively corresponding to the two or more sensor members, the lifting / lowering is performed for each rack, for each rack, for each rack stage, or for each rack opening. To change the stroke,
The moving body raising / lowering system characterized by the above-mentioned. A sensor member provided on a moving body for scooping / unloading a load and including three detection sensors arranged in the ascending / descending direction of the moving body, and a base portion and a protruding portion located at the center of the base portion in the ascending / descending direction A fixed position dog that is formed along the elevation direction so that the protruding portion faces the sensor member when the moving body stops when the moving body stops scooping / unloading the load. The upper detection sensor of the three detection sensors detects the protruding portion, and the middle detection sensor of the three detection sensors detects the base portion, and then the middle detection sensor is the base. And when the moving body scoops / drops the load until the lower detection sensor of the three detection sensors detects the protruding portion. The transfer of Wherein in the mobile lift system comprising a moving body control means for raising and lowering stroke of the body a fixed position dog,
When the raising / lowering stroke is changed, according to the change of the raising / lowering stroke, the dimension in the raising / lowering direction in the base part is changed, and the dimension in the raising / lowering direction in the protruding part is changed,
A fixed position dog characterized by that. A sensor member provided on a moving body for scooping / unloading a load and including three detection sensors arranged in the ascending / descending direction of the moving body, and a base portion and a protruding portion located at the center of the base portion in the ascending / descending direction A fixed position dog that is formed along the elevation direction so that the protruding portion faces the sensor member when the moving body stops when the moving body stops scooping / unloading the load. The upper detection sensor of the three detection sensors detects the protruding portion, and the middle detection sensor of the three detection sensors detects the base portion, and then the middle detection sensor is the base. And when the moving body scoops / drops the load until the lower detection sensor of the three detection sensors detects the protruding portion. The transfer of A mobile control means and the ascending and descending stroke setting of the movable body in a mobile lift system comprising of a lifting stroke of the body,
When changing the lifting stroke, according to the change of the lifting stroke, while changing the dimension in the lifting direction in the base portion, and changing the dimension in the lifting direction in the protrusion,
A method for setting up and down strokes of a moving body.

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