JP3107498B2 - Multi-layer box-type circulation type parking device and its parking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer, box-type, circulating parking apparatus having three or more storage layers for increasing the number of cars accommodated therein and a parking method thereof.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration of a conventional multilayer box-type circulation type parking device having a four-stage underground type structure. In FIG. 6, 6
1 is a first storage layer, 62 is a second storage layer, 63 is a third storage layer, 64 is a fourth storage layer, and 65 is defined on one end side of each storage layer and each storage layer A first hoistway communicating with 61, 62, 63, 64 is a second hoistway defined at the other end and communicating each of the storage layers 61, 62, 63, 64. Each of the storage layers 61, 62, 63, and 64 includes a pair of front and rear fixed rails 67 and a pair of front and rear movable rails 68 similarly to the fixed rail 67. Each of the fixed rails 67 has a length that allows a plurality of trays 74 to be described later to be arranged, and includes a traversing drive mechanism 69 that laterally feeds the trays 74 to each of the fixed rails 67. Movable rail 6
8 has a length slightly larger than the distance between the wheels 75 in the same row of the tray 74, and is attached to the lifting drive mechanism 70 installed on each of the hoistways 65 and 66, respectively. They are arranged at the same pitch. In addition,
The lifting drive mechanism 70 includes sprockets 71 installed at the four corners of the hoistways 65 and 66, four endless chains 72 wound between the upper and lower sprockets 71,
A motor 73 for rotating and driving the sprocket 71;
Each pair of movable rails 68 is mounted so as to extend between two endless chains 72 in a direction that can take the same arrangement as the pair of fixed rails 77. Reference numeral 74 denotes a tray for automatic mounting on a vehicle. Two wheels 75 on one side, that is, a total of four wheels 75, are mounted so as to protrude from both sides.

[0003] This parking device adopts an end-entry system in which a car rides on a rail from one end.
Denotes a vehicle entrance installed on the first floor above the ground, and is set on the first hoistway 65.

[0004] Next, the operation of the above-described conventional multilayer box-type circulation type parking device will be described with reference to FIG. In FIG. 6, a tray 74 is provided at the entrance 76 on the first floor above the movable rail 6.
8 and is waiting, and at the four levels underground, a plurality of trays 74 are stopped side by side in a row.

[0005] When a car to enter the warehouse gets on the waiting tray 74 at the entrance 76, the movable rails 68 on the first hoistway 65 are first actuated by the operation of the hoisting drive mechanism 70 of the first hoistway 65. Vertically circulates downward, and the tray 74 on which the automobile is mounted is moved down on the movable rail 68. The movable rails 68 are arranged on the extension of the left end of the fixed rail 67 of the first level, and the tray 74 on which the automobile is placed is the first rail.
Is connected to another tray 74 on the fixed rail 67 via an engaging member (not shown).

Next, the lifting drive mechanism 7 of the second lifting path 66
0, each movable rail 6 moves on the second hoistway 66.
8 vertically circulates upward by one layer, the movable rail 68 stopped on the second storage layer 62 rises to the first storage layer 61, and the tray 74 thereabove moves upward to the first storage layer 61. Then, at the same time as being connected to another tray 74 on that level, each movable rail 68 vertically circulates downward by one level on the first hoistway 65 by the operation of the lifting drive mechanism 70 of the first hoistway 65. The movable rail 68 carrying the stopped vehicle on the first storage layer 61 descends to the second storage layer 62 to move the tray 74 thereof.
Moves down to the second storage layer 62 and connects to another tray 74 of that level. Next, the fixed rail 67 of the first storage layer 61 is moved by the traversing drive mechanism 69 of the first storage layer 61.
And at the same time each tray 74 traverses in the direction toward the first hoistway 65 on the movable rails 68 at both ends thereof,
Each tray 74 traverses in a direction toward the second hoistway 66 on the fixed rail 67 of the second hierarchy and the movable rails 68 at both ends thereof by the traverse drive mechanism 69 of the second storage layer 62. By repeatedly performing such a two-step box-type circulation operation, the stored vehicle is stored at a predetermined position in a predetermined hierarchy.

[0007] This box-type circulation operation can be operated in the opposite direction to the above. Here, the box-shaped circulation of the tray 74 is performed between the first storage layer 61 and the second storage layer 62, but the tray 74 is circulated depending on the destination of the vehicle.
Can be performed by a similar operation between the second storage layer 62 and the third storage layer 63 or between the third storage layer 63 and the fourth storage layer 64.

When a car is taken out of the car, a box-type circulation operation is performed between a storage layer in which the car is stored and a storage layer adjacent to the storage layer, and the tray 74 on which the car is placed is moved to the first position.
Is moved on a movable rail 68 on a hoistway 65, and the movable rail 68 vertically circulates therefrom by an operation of an elevating drive mechanism 70 to transfer a tray 74 on which an automobile is mounted to a entrance 76.

As described above, in the above-mentioned conventional multilayer box-type circulation type parking device, a pair of front and rear movable rails 68 are provided on each hoistway 65, 66 on the extension of the pair of front and rear fixed rails 67 on each level. 61, 62, 63, and 64, these movable rails 68 are vertically circulated by the lifting / lowering drive mechanism 70, and the horizontal drive mechanism 69 of each level is combined with the adjacent two levels. For example, between the first storage layer 61 and the second storage layer 62, or between the second storage layer 62 and the third storage layer 63, or between the third storage layer 63 and the fourth storage layer 63. Box-type circulation with each storage layer 64 can be performed.

[0010]

However, in the above-mentioned conventional multilayer box-type circulating parking apparatus, when the box-type circulating operation of the trays is performed between two levels, each movable rail is entirely in one storage layer of each level. If a tray is placed on the hoistway of another stopped level that is not performing box-type circulation, it interferes with the box-type circulation path between the two levels, causing the box-type circulation. I can't take it. Therefore,
There is a problem that only one car can be stored on the hoistway.

The present invention solves such a conventional problem, and adds a tray on a hoistway to another stopped level without performing box-type circulation without interfering with box-type circulation. It is an object of the present invention to provide a multilayer box-type circulation type parking device capable of increasing the number of cars accommodated therein and a parking method thereof.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, each pair of movable rails is formed into a short piece on which the wheels of each tray can be mounted, respectively. each tray is capable of running a contact fixing rails on an extension of the fixed rail in the hoistway each storage layers each disposed the movable rail is provided an insertion and fittable spacer section, the storage layer n hierarchy ( However, if n ≧ 3)
In this case, up to n-1 trays are arranged for each hoistway .

[0013]

According to a second aspect of the present invention, each of the pair of movable rails is formed into a short piece on which the wheels of each tray can be mounted, and the fixed rail of each storage layer on each hoistway is provided. On the extension, a communication fixed rail on which each tray can travel is provided with an intermittent portion where each movable rail can be inserted and fitted, and when a box-shaped circulation is performed between two designated storage layers, each of the hoistways is Trays placed on a non-designated level without box circulation are moved along with other trays on that level by a traverse drive mechanism to move the wheels of the tray on the non-designated level on the hoistway from the movable rail to the fixed rail for communication or the fixed rail. By traversing only by the distance, the trays of the unspecified level on the hoistway can take a position that does not interfere with the vertical circulation of each movable rail.

[0015]

Therefore, according to the present invention, when the plurality of movable rails vertically circulate on the hoistway by the operation of the hoisting drive mechanism according to the above-mentioned claim, each of the storage layers is fixed for communication. A part of each storage layer is formed together with the fixed rail for communication by being fitted and integrated with the intermittent part of the rail, and the movable rails are vertically circulated in opposite directions on both hoistways, and traverse between the two storage layers. The box-shaped circulation is performed by a combination of the trays being moved in opposite directions by the operation of the drive mechanism. In this box circulation,
If a tray is located on another level on each hoistway that does not perform box-type circulation, the tray on that level is traversed by the amount by which the wheels of the tray move from the movable rail to the fixed rail for communication or the fixed rail. By doing so, it is possible to avoid interference with the vertical circulation of the entire movable rail, and perform box-type circulation while leaving the tray on another level where box-type circulation on the hoistway is not performed. Therefore, it is possible to quickly carry out the car entry / exit processing.

[0016] It therefore is arranged the trays to n-1 sheets of setting place the movable rail without the tray on one of the hierarchy of two layers performing each hoistway, a box-circulated to the hoistway Therefore, even if a movable rail on which a tray is placed is placed on another level that does not perform box-type circulation, the tray on that level is moved by the amount that the wheels of the tray move from the movable rail to the fixed rail for communication or the fixed rail. By traversing by the traversing drive mechanism, it is possible to avoid interference with the vertical circulation of the entire movable rail, and perform box-type circulation while leaving the tray on another level where box-type circulation on the hoistway is not performed. Therefore, the number of cars accommodated can be increased by the amount of additional trays arranged on the hoistway.

According to the second aspect of the present invention, the number of trays can be increased and arranged without requiring a specially large space on the hoistway, and the number of cars accommodated can be increased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of an embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. In this embodiment, as in the conventional example, a four-stage multilayer box-type circulation type parking device is exemplified.

In FIG. 1, reference numerals 11 denote a pair of fixed rails, each of which has a length capable of storing a plurality of trays 16 to be described later, and four pairs of fixed rails 11 are vertically arranged in parallel. To form a four-layer storage layer as a whole. Here, for the sake of convenience of the following description, these storage layers are sequentially arranged from the top in the first storage layer 11.
The first storage layer 112, the third storage layer 113, and the fourth storage layer 114 are called.

Reference numeral 12 denotes a first hoistway, and each storage layer 11
One end (left end in FIG. 1) of each of the storage layers 111, 112, 113, and 114 communicates with each of the storage layers 111, 112, 113, and 114. Reference numeral 13 denotes a second hoistway, and each storage layer 1
Each storage layer 111, 112, 113, 114 is defined on the other end (right end in FIG. 1) side of 11, 112, 113, 114.
Contact between

Reference numeral 14 denotes a pair of front and rear movable rails, each of which is formed into a short piece on which a wheel 161 of a tray 16 to be described later can be placed, as shown in FIG. Each of the rail blocks 141 comprises a total of four rail blocks 141.
The mutual interval corresponds to the arrangement interval of the four wheels 161 of the tray 16, and such a pair of movable rails 14 is arranged on each hoistway 12, 13 at the same pitch as the interval of the fixed rails 11 of each layer. ing.

Reference numeral 15 denotes a pair of front and rear connecting fixed rails. As shown in FIG. 2, two rail blocks 14 each having a row of movable rails 14 are provided at an intermediate portion in the longitudinal direction.
1 has an intermittent portion 151 that can be inserted and fitted, and has two storage layers 111, 112, 113, 1 on two hoistways 12, 13.
The intermittent portion 151 is arranged continuously on the extension of the fixed rail 11 for every 14 so as to coincide with the vertical circulation path of the movable rail 14. In addition, compared with the conventional example, the hoistway 1
2 and 13 are slightly widened toward the outer side, and a dimension slightly longer than the conventional movable rail is set in the longitudinal direction of the connecting fixed rail 15.

Numerals 16 denote trays for automatic on-vehicle mounting. As shown in FIG. 2, traversing wheels 161 are arranged on both rails 11, 14 and 15 at both ends thereof so as to protrude laterally. , A plurality of trays 16 are detachably connected to each other via an engaging member (not shown),
11, 112, 113, and 114 are continuously arranged.

Reference numeral 17 denotes a traversing drive mechanism.
The tray 16 is installed on each of the fixed rails 11, 112, 113, and 114, and traverses the tray 16 on each of the storage layers 111, 112, 113, and 114. 18 is the first and second hoistway 1
2 and 13, a lifting drive mechanism installed on the hoistway 1
Two sprockets 181 installed at the upper and lower corners of the two sprockets 2 and 13; a total of eight endless chains 182 wound between the upper and lower sprockets 181;
And a pair of movable rails 14 are attached and mounted between the endless chains 182 in a direction that can take the same arrangement as the pair of fixed rails 11. Then, the pair of movable rails 14 are vertically circulated.

This parking system adopts an end entry system in which a car is driven from the left end to the rail.
Is an entrance for a car installed on the first floor above the ground, and is set on the first hoistway 12.

Next, the operation and the parking method of the above-mentioned multilayer box type circulation type parking device will be described with reference to FIGS. 1, 3 and 4. FIG. In FIG. 1, each storage layer 111, 1
12, 113, 114, the pair of fixed rails 11
Each rail block 141 of the pair of movable rails 14 is fitted and integrated with the intermittent portion 151 of the fixed rail 15 for communication on the extension of both ends, and the tray 16 is placed on the movable rail 14 at the entrance 19 on the first floor above the ground. I'm waiting on the ride.

In the first storage layer 111, the fixed rail 1
A plurality of trays 16 are continuously arranged on one,
The tray 16 is not disposed on the movable rails 14 of the hoistways 12 and 13 at both ends. In the second storage layer 112, a plurality of trays 16 are continuously arranged on the fixed rail 11, and one tray 16 is arranged on the movable rail 14 of the right end second hoistway 13. The tray 16 is connected to another tray 16 on the fixed rail 11, while the tray 16 is not arranged on the movable rail 14 of the first hoistway 12 at the left end. Further, the third and fourth storage layers 113,
At 114, a plurality of trays 1 are mounted on the fixed rail 11.
6 are continuously arranged, and both ends of the hoistway 1
One tray 16 is additionally provided on the movable rails 2 and 13 and connected to another tray 16 on the fixed rail 11.

Here, when the vehicle is stored, the first and the second
Storage layers 111 and 112 are designated as a box-shaped circulation designated hierarchy, and the third and fourth storage layers 113 and 114 are designated as a box-shaped circulation non-designated hierarchy.

Prior to entry of the car, first, in the third and fourth storage layers 113 and 114, the entire tray 16 on each of the storage layers 113 and 114 is slightly moved by the second hoistway by the operation of the traverse drive mechanism 17. 3, the wheels 161 of the tray 16 on both hoistways 12, 13 are moved from the rail block 141 of the movable rail 14 to the fixed rail 15 for communication or the fixed rail 11, as shown in FIG.
After completing the warehousing preparation, enter the garage to
9 on the waiting tray 16, the first hoistway 1
2, all the movable rails 14 vertically circulate downward by the operation of the lifting drive mechanism 18, and each movable rail 1
The fourth rail block 141 is inserted into the intermittent portion 151 of the communication fixed rail 15 of each layer, fitted to the communication fixed rail 15 of the lower layer, and integrated with that layer. here,
In the third and fourth storage layers 113 and 114, as shown in FIG. 4, each of the rail blocks 141 is a tray 16 on which the communication fixed rail 15 or the fixed rail 11 is mounted.
On the other hand, the vehicle passes through the side of the wheel 161 and enters the intermittent portion 151 to be integrated with the story.

By this circulation, the tray 1 on which the automobile is placed
6 is moved down on the first hoistway 12 to the first storage layer 111 and connected to another tray 16 stopped on the fixed rail 11 of that level.

Next, in the second hoistway 13, all the movable rails 16 vertically circulate upward by one level by the operation of the elevation drive mechanism 18, and the movable rails 14 stopped at the second storage layer 112. Rises to the first storage layer 111 and the tray 16 thereabove moves up to the first storage layer 111 and is connected to the other trays 16 stopped on the fixed rail 11 of that level, In the first hoistway 12, all movable rails 14 vertically circulate downward by one level by the operation of the hoisting drive mechanism 18, and the first storage layer 1
The movable rail 14 on which the stopped vehicle is mounted moves down to the second storage layer 112, and the tray 16 thereover moves down to the second storage layer 112, and other movable rails 14 on the fixed rail 11 at that level fall. It is connected to the tray 16. Again, third,
In the fourth storage layers 113 and 114, as shown in FIG.
Alternatively, the tray 16 on the fixed rail 11 passes along the wheel 161 and enters the intermittent portion 151 to be integrated.

Next, the traversing drive mechanism 17 moves the trays 1 on the fixed rail 11 of the first level and the movable rail 14 and the connecting fixed rail 15 integrated at both ends thereof.
6 moves in the direction toward the first hoistway 12, and at the same time, the fixed rail 11 of the second hierarchy, the movable rail 14 integrated at both ends thereof, and the fixed rail 15 for communication are provided.
Each tray 16 traverses upward in a direction toward the second hoistway 13.

By repeatedly performing such a two-step box-type circulation operation, the entered vehicle is stored at a predetermined position in the first or second storage layer 112, 113.
This circulation operation can be performed in the opposite direction to the above. Here, the box-shaped circulation of the tray 16 is performed between the first storage layer 111 and the second storage layer 112, but the box-shaped circulation of the tray 16 is changed to the second storage layer depending on the destination of the car. Between the first storage layer 112 and the third storage layer 113,
Alternatively, the same operation can be performed between the third storage layer 113 and the fourth storage layer 114. FIG. 5 shows an operation example of the tray 16 in the first and second storage layers 111 and 112 when performing box-type circulation between the third storage layer 113 and the fourth storage layer 114.

When the vehicle is taken out of the car, a similar box-shaped circulation operation is performed between the storage layer of the vehicle and the storage layer adjacent thereto, and the tray 16 on which the vehicle is mounted is moved to the first hoistway 12. On the movable rail 14, and from there is transferred to the entrance 19 by the operation of the lifting drive mechanism 18.

As described above, according to the above embodiment, each pair of movable rails 14 is formed into a short piece on which the wheels 161 of each tray 16 can be placed, and two pairs of front and rear rows are formed. It is composed of four rail blocks 141 and has two storage layers 111, 1 on two hoistways 12, 13.
A fixed rail for communication 1 in which each tray 16 can run on an extension of the fixed rail 11 in each of 12, 13, and 114.
5 is an intermittent portion 15 through which each movable rail 14 can be inserted and fitted.
1 and the movable rails 14 are vertically circulated on the hoistways 12 and 13 by the lifting drive mechanism 18 so that each rail block 141 is fitted to the intermittent portion 151 of the fixed rail 15 for communication. When the tray 16 is located on two levels of the non-designated level where the upper and lower shafts 12 and 13 do not perform upper box-type circulation, the wheels 161 are moved from the movable rail 14 to the fixed rail 15 for communication. Alternatively, the entire tray 16 at that level is traversed by the traversing drive mechanism 17 by the amount moved to the fixed rail 11 so as not to interfere with the vertical circulation of each movable rail 14, so that the upper boxes of the hoistways 12, 13 can be moved. Box-type circulation can be performed while the tray 16 is left in a non-designated layer where pattern circulation is not performed.

Therefore, in the parking apparatus having the four storage layers 111, 112, 113, and 114 as in the present embodiment, the tray 16 is provided for each of the hoistways 12, 13 as compared with the conventional one. Two units are added and up to three units are arranged, and box-type circulation can be performed while the trays 16 for the additional units are left on both hoistways 12, 13, increasing the number of cars accommodated by four as a whole. Can be done. Similarly, for example, when three storage layers are provided, one tray can be added to one conventional one for each hoistway, and a total of two trays can be arranged. In the case where the number of storage layers is n, the total number of trays can be arranged by increasing the number of trays by three for each conventional hoistway and three trays for each hoistway. In addition, the number of trays can be increased by n-2 for each conventional hoistway and n-2 for each conventional hoistway, so that the number of cars accommodated can be increased.

As described above, according to the parking apparatus and the parking method of this embodiment, the tray 16 can be additionally arranged without setting a specially large space on the hoistways 12, 13, and the vehicle The number of accommodations can be increased.

In addition to the end-entry type multi-layer box-type circulation type parking device as in this embodiment, an elevator device is installed at an intermediate portion with respect to the rail in addition to the hoistways on both sides. Even in the case of a so-called intermediate entry type parking device having a car entrance on the hoistway, trays can be additionally installed on the hoistways on both sides, so that the number of cars accommodated can be increased. Can be.

[0039]

As described above, each pair of movable rails is formed into a short piece on which the wheels of each tray can be mounted, and the length of the fixed rail is increased on each of the two storage layers on the two hoistways. And a fixed rail for communication on which each tray can run is provided with an intermittent section in which each movable rail can be inserted and fitted, and each storage layer has n levels (where n ≧ 3).
, Up to n-1 trays for each hoistway
By arranging, when performing box-type circulation between the two designated storage layers, the trays arranged on the non-designated level not performing box-type circulation on each hoistway are moved together with the other trays on the level by the traversing drive mechanism. By traversing the wheels of the non-designated tier on the hoistway from the movable rail to the fixed rail for communication or the fixed rail, the position of the tray on the non-designated tier on the hoistway does not interfere with the vertical circulation of each movable rail. Since it is possible to perform the box-type circulation between the designated two levels in the storage layer of the non-designated level which does not perform the box-type circulation while the trays are arranged on the hoistway at both ends of the storage layer, More trays can be installed on the road to increase the number of cars accommodated.

[Brief description of the drawings]

FIG. 1 is a front view of a multilayer box-type circulation parking device according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of the parking device.

FIG. 3 is a front view showing an operation example of the parking device.

FIG. 4 is a partially enlarged front view showing an operation example of the parking device.

FIG. 5 is a front view showing another operation example of the parking device.

FIG. 6 is a front view of a conventional multilayer box-type circulation type parking device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 A pair of fixed rail 111 The 1st storage layer 112 The 2nd storage layer 113 The 3rd storage layer 114 The 4th storage layer 12 The 1st hoistway 13 The 2nd hoistway 14 A pair of movable rail 141 Rail block 15 Fixed rail for communication 151 Intermittent part 16 Tray for automatic in-vehicle installation 161 Wheel 17 Traversing drive mechanism 18 Elevating drive mechanism 181 Sprocket 182 Endless chain 183 Motor 19 Entrance

Claims (2)

(57) [Claims] A plurality of fixed rails forming a pair of storage layers of three or more levels, and a plurality of fixed rails defined at both ends of each of the storage layers, and arranged on a hoistway connecting the respective storage layers; A pair of front and rear movable rails forming a part of each storage layer, and a pair of fixed rails and a pair of wheels capable of traveling on the movable rails of each of the storage layers are disposed so as to protrude to both sides, and each of the storage layers is provided. A plurality of trays for automatic in-vehicle placement continuously arranged on a layer, a traversing drive mechanism for traversing each tray on each of the storage layers, and vertically circulating the pair of movable rails on the hoistway. A lifting drive mechanism for lifting and lowering the trays to the storage layers, and a multilayer box-type circulation type parking apparatus for box-shaped circulation of the trays between the storage layers. Each of the above trays Each of the movable rails is a communication fixed rail on which the tray can run on an extension of each of the pair of fixed rails on each of the storage layers on each of the hoistways, while being formed in a short fragmentary shape on which wheels can be mounted. An intermittent portion that can be inserted and fitted is provided and arranged, and the storage layer is made up of n layers (where n ≧ 3).
A multi-layer box-type circulation type parking apparatus , wherein up to n-1 trays are arranged for each hoistway . 2. A plurality of fixed rails forming a pair of storage layers of three or more levels, and a plurality of fixed rails, which are defined on both ends of each of the storage layers, and are arranged on a hoistway connecting the respective storage layers. A pair of front and rear movable rails forming a part of each storage layer, and a pair of fixed rails and a pair of wheels capable of traveling on the movable rails of each of the storage layers are disposed so as to protrude to both sides, and each of the storage layers is provided. A plurality of trays for automatic in-vehicle placement continuously arranged on a layer, a traversing drive mechanism for traversing each tray on each of the storage layers, and vertically circulating the pair of movable rails on the hoistway. A lifting drive mechanism for lifting and lowering the trays to the storage layers, and a multilayer box-type circulation type parking apparatus for box-shaped circulation of the trays between the storage layers. Each of the above trays Each of the movable rails is a communication fixed rail on which the tray can run on an extension of each of the pair of fixed rails on each of the storage layers on each of the hoistways, while being formed in a short fragmentary shape on which wheels can be mounted. When a box-shaped circulation between two designated storage layers is performed by providing an intermittent portion that can be inserted and fitted therein, trays arranged on a non-designated layer that does not perform the box-shaped circulation on each of the hoistways are placed in the hierarchy. The traverse drive mechanism together with the other trays above moves the wheels of the unspecified tray on the hoistway from the movable rail to the fixed rail for communication or the fixed rail so as to be traversed, whereby the non-designated hoistway is specified. A method of parking a multi-layer box-type circulation type parking device, wherein a tray at a level can take a position that does not interfere with the vertical circulation of each movable rail.