KR100904118B1 - Step device for platform - Google Patents

Abstract

The present invention is used in conjunction with a foam door device requiring a groove on the platform

It is an object of the present invention to provide a platform step device.

The platform step device 1 includes a case 2 that can be embedded in the platform 100, a step 7 supported by the case 2, and a case to move the step 7 forward or backward with respect to the vehicle side. Drive means 17, 18, 19 (refer FIG. 2) for relative movement with respect to (2) are provided. A guide groove 6a extending in parallel with the direction along the platform is formed in the top plate 6 of the case 2, and in the upper part of the case 2 in the vicinity of the guide groove 6a, the platform ( A portion 202 of the door slide mechanism of the foam door device 200 provided in the container 100 is provided as a space that can be accommodated.

Description

Step device for platform {STEP DEVICE FOR PLATFORM}

The present invention relates to a platform step apparatus for preventing a passenger from falling down between a platform and a stopped vehicle.

Conventionally, it is known that it is disclosed by patent document 1 as a platform step apparatus which prevents a passenger from falling down between a platform and a stop vehicle.

The fall-fall prevention device of the platform disclosed in Patent Document 1 is to move the plate-like movable body from the platform side to the vehicle side in parallel to eliminate the gap between the platform and the vehicle.

More specifically, as shown in the same document, the guide 48 fixed to the plurality of base plates 46 and 47 by fixing the central portion and both ends of the fall preventing member 21 with the plates 23 and 24. 49) to support the structure. And the fall prevention member 21 is moved forward and backward with respect to a vehicle by the drive mechanism 30 provided in the substantially center of the fall prevention apparatus, overlying the plate 24.

On the other hand, in recent years, demand for installing form door devices such as a platform screen door (PSD) or an automatic platform gate (APG) has increased. Such a device forms a groove for guiding the door panel or a predetermined space extending along the platform, so that the anti-vibration metal fitting or the drive belt of the door panel that slides along the groove can be inserted into the groove and the space. Deployment is possible, which allows for more advanced functions.

[Patent Document 1: Japanese Patent Application Laid-Open No. 2004-148943]

However, the fall prevention apparatus described in patent document 1 is comprised so that it may not leave a space in an apparatus. Therefore, when the fall prevention device is provided on the platform, the space for forming a groove or the like on the platform is lost, and it becomes difficult to use a foam door device that requires a groove on the platform as described above.

In view of the above circumstances, an object of the present invention is to provide a platform step device that can be used with a form door device that requires a groove on a platform.

The present invention relates to a platform step apparatus for preventing a passenger from falling down between a platform and a stopped vehicle.

And the platform step apparatus which concerns on this invention has the following various characteristics, in order to achieve the said objective. That is, the platform step apparatus of this invention is equipped with the following features individually or in combination suitably.

A first feature of a platform step apparatus according to the present invention for achieving the above object is a platform step apparatus for preventing a passenger from falling down between a platform and a stopped vehicle, and a case embedded in the platform, and the case. And a driving means for relatively moving the step relative to the case so as to move the step forward or backward with respect to the vehicle side, and the case includes a top plate serving as an upper surface when the case is embedded in a platform; A guide groove formed in the top plate and extending in parallel with the direction along the platform, and having an upper portion in the case having a part of the door slide mechanism of the foam door device installed in the platform in the vicinity of the guide groove; have.

According to this structure, it is possible to use with the foam door apparatus which requires a groove on a platform. And since a part of the door slide mechanism of a foam door apparatus can be accommodated in the case of a platform step apparatus, the spatial limitation in the design of a foam door apparatus can be further reduced. As a result, it is possible to prevent the passenger from falling down between the platform and the stopped vehicle, and at the same time, the function of the form door device which can be used simultaneously with the platform step device can be made more substantial.

Moreover, the 2nd characteristic in the platform step apparatus which concerns on this invention is further provided with the frame of the frame shape which is supported by the said case and the said step is fixed to the edge part of a vehicle side, The said drive means is a said frame. The step is moved forwards and backwards, and is located close to the vehicle opposite side of the case so as to be located on the opposite side of the vehicle from the guide groove in the case, and the frame is closer to the lower surface of the case. It is arrange | positioned and extends in parallel with the said advancing direction by the length which the said step moves forward and backward only to the vehicle side rather than the said guide groove.

According to this structure, the drive means is not provided in the position closer to the vehicle side than the guide groove. This makes it possible to secure a space in the case at a position closer to the vehicle side than the guide groove. In addition, a space can be secured above the frame in the case. Moreover, since the step does not move across the lower part of the guide groove, the space at the lower part of the guide groove can be easily secured without the step of narrowing the space at the lower part of the guide groove.

Moreover, the 3rd characteristic in the platform step apparatus which concerns on this invention is that the said drive means is a motor, the pinion which rotates integrally with the drive shaft of the said motor, and the rack provided in the said frame so that it may mesh with each other. The motor is a motor provided with a brake capable of braking rotation of the drive shaft by an external force at the time of stopping the drive.

According to this structure, in the case of a power failure or abnormality, the step can be maintained at the stop position.

As a result, the safety of the passenger can be enhanced by preventing the step from suddenly protruding and drawing.

Moreover, the 4th characteristic in the platform step apparatus which concerns on this invention is that the said frame has a some parallel support member extended in parallel with an advancing direction, and is provided by the said parallel support member which protrudes to a vehicle side. The end of the vehicle side is formed.

According to this configuration, the vehicle side of the parallel support member is applied to the vehicle side end portion of the frame when the external force acts in a direction perpendicular to the stepping direction of the step and in a direction parallel to the upper surface of the step (the vehicle entry direction). Since the end is not constrained, the frame can be more easily deformed. As a result, in a state where the step advances to the vehicle side and stops, even if the vehicle collides with the step, it is possible to suppress the damage to the vehicle or the drive device by deforming or destroying the frame.

Moreover, the 5th characteristic in the platform step apparatus which concerns on this invention is that the said frame extends in the perpendicular | vertical direction and the perpendicular | vertical direction, and has a some vertical support member which connects and supports the said parallel support members. And a top plate support that is in the case and supports the top plate in the vertical direction, wherein the top plate support is located on the side of the vehicle opposite the guide groove, and the vertical support member located on the vehicle side of the top plate support. And the step is disposed so as to be close to the top plate support with respect to the state in which the step is retracted into the case.

According to this configuration, the support position of the parallel support member by the vertical support member can be approached to the opposite side of the vehicle while the support strength of the top plate in the vertical direction is ensured by the top plate support member. At this time, the frame has a frame shape in the cantilever state in which the support position is closer to the opposite side of the vehicle. Therefore, the frame can be more easily deformed in the case where an external force toward the vehicle side end of the frame in the direction of entry of the vehicle is applied. Thereby, even if a vehicle collides with a step, it can suppress that a vehicle or a drive apparatus is damaged by deforming or destroying a frame.

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing this invention is demonstrated, referring drawings.

1 is an overall schematic diagram of a platform provided with a platform step apparatus (hereinafter referred to as a step apparatus) according to an embodiment of the present invention. FIG. 1: has shown the state which applied the platform step apparatus 1 with the movable door type foam door apparatus 200 (APG).

As shown in FIG. 1, the step device 1 provided in the platform 100 can advance the step 7 with respect to the vehicle side. As a result, it is possible to prevent the passenger from falling down between the platform and the stopped vehicle.

On the upper surface of the step device 1, a guide groove 6a extending in the direction along the platform 100 is provided below the pair of doors 201 and 201 in the foam door device 200. Formed. And the door 201 along the guide groove 6a in the state which inserted the antivibration metal fitting 202 (shown in FIG. 4, FIG. 5 mentioned later) fixed to the lower end of the door 201 in this guide groove 6a. ) Is opened and closed. As a result, the door 201 is prevented from swinging back and forth (the direction orthogonal to the guide groove 6a), and the door can be opened and closed stably.

However, the platform step apparatus which concerns on embodiment of this invention is not limited to the case where it installs with the movable door type form door apparatus AGP shown in FIG. 1, As shown in FIG. It is also possible to install together with the screen type foam door device 200 (PSD) which is installed to completely block the side (vehicle side). Also in this case, since the lower part of the door 201 is guided by the guide groove 6a, the stable door 201 can be opened and closed.

2 and 3 are plan views of the step device 1 shown in FIG. 1. FIG. 2 is a diagram showing a state in which the step 7 retreats in the vehicle (hereinafter referred to as a retracted state), and FIG. 3 is a diagram illustrating a state in which the step 7 moves forward with respect to the vehicle (hereinafter referred to as an advanced state). to be.

4 is a schematic diagram of an A-A cross-sectional view of the step device 1 in FIGS. 2 and 3. Fig. 4A is a view showing a retracted state, and Fig. 4B is a view showing a forward state.

5 is a schematic B-B cross section of the step apparatus 1 in FIGS. 2 and 3. Fig. 5A is a view showing a retracted state, and Fig. 5B is a view showing a forward state.

6 is a schematic diagram of C-C cross section in the advanced state shown in FIG. 3, and FIG. 7 is a schematic diagram of D-D cross section in the advanced state shown in FIG. 3.

This step apparatus 1 is comprised so that installation of the platform 100 in the recessed part 100a formed in the edge part which opposes a vehicle (refer FIG. 4, FIG. 5) is carried out. This recess 100a is formed by, for example, shaving concrete into a rectangular shape to form the platform 100. The bottom of the recess 100a is an installation surface for installing the step device 1, and is configured to open the upper surface and the vehicle side.

The step device 1 has a case 2, and the case 2 includes a plurality of flat plate-shaped base plates 3 and side plates which form side surfaces of three sides other than the surface facing the vehicle ( 4), the bottom plate 5 fixed to the recessed part 100a by an anchor, etc., and the top plate 6 (omitted with respect to FIG. 2, FIG. 3) used as the return surface of an ascendant and passenger. 2 and 3, the position of the guide groove 6a of the top plate 6 is indicated by the dashed-dotted line.

The plurality of base plates 3 are fixed to the bottom plate 5 by mounting members such as screws or welding. Moreover, the side plate 4 of cross-sectional "co" shape is fixed by welding to the part of three sides except the side by the side of the bottom plate 5 (refer FIG. 4-FIG. 7). In addition, the top plate 6 is fixed to the upper side of the side plate 4 by bolt fixing. This top plate 6 forms a part of the upper surface of the platform 100 when the case 2 is installed in the recess 100a. The top plate 6 is formed with a guide groove 6a extending in parallel with the direction along the platform. The guide groove 6a is an opening which penetrates the top plate 6, and has a shape in which the top plate is folded and bent downward in the vertical direction at the opening end (see FIGS. 4 and 5).

As mentioned above, the box-shaped case 2 which has an opening in a vehicle side is comprised. This case 2 is provided in the recess 100a, and can be embedded in the platform 100.

And the step 7 of a horizontal flat plate shape is supported with respect to the case 2 (it is a dashed-dotted line with respect to FIGS. 2 and 3). This step 7 is a structure fixed to the upper surface at the vehicle side end part of the frame 8, and the space between the bottom plate 5 of the case 2 and the top plate 6 with the frame 8 is carried out. It is possible to accommodate. However, the step 7 is provided so that the upper surface may be located substantially horizontally with the top plate 6 from the viewpoint of the ease of walking of the ascending and descending passengers.

The frame 8 has a frame-like configuration in which a plurality of square bar members arranged in parallel with the surface of the bottom plate 5 are fixed to each other by welding or the like. Specifically, as shown in FIGS. 2 and 3, the frame 8 is a parallel support member 81a to 81e that extends in parallel with the direction in which the step 7 moves forward with respect to the vehicle. And vertical support members 82a-82f extending vertically (parallel with the direction along the platform).

2 and 3, the parallel support members 81a and 81b positioned in the region on the left side of the step device 1 are connected and supported by the vertical support members 82a near the center in the longitudinal direction. At the same time, it is connected to and supported by the vertical support member 82b with respect to the end opposite to the vehicle. In this way, the parallel support members 81c and 81d positioned in the region on the right side of the step device 1 are connected and supported by the vertical support members 82e and 82f. And parallel support member 81b and 81c are connected and supported by the vertical support member 82c near the center of a longitudinal direction. The parallel support member 81e is connected to this vertical support member 82c so as to be located near the center in the longitudinal direction to the opposite side of the vehicle. Moreover, the vertical support member 82d is connected and supported by the vehicle opposite side edge part of the parallel support member 81e, and the vehicle opposite side edge part of the parallel support part 81b.

Four slide rails 83a, 83b, 83c, 83d extending in parallel with the parallel support member are fixed to the bottom plate 5 of the case 2. The parallel support members 81a, 81b, 81c, and 81d are slidably supported along the slide rails with respect to the slide rails 83a, 83b, 83c, and 83d, respectively. Specifically, the slide rails 83a to 83d are formed with grooves extending in the longitudinal direction, and the convex portions formed on the side surfaces of the parallel support members 81a to 81d are supported by the grooves along the slide rails. Will move. However, it can also be moved along a groove by attaching a cam follower and guide roller to the side surface of parallel support member 81a-81d. As a result, the step 7 and the frame 8 can move back and forth from the platform 100 side to the vehicle side by driving the motor unit 17 described later.

Moreover, the lock mechanism 20 which can restrain the advancing / removing movement of the frame 8 in the position near the edge part on the opposite side of the vehicle in the case 2 is provided in the base board 3. The lock mechanism 20 engages with the engaging portion 8a formed integrally with the frame 8 by protruding and retracting the engaging metal fitting in, for example, a solenoid method, to thereby provide the structure of the frame 8 in the advanced state. The movement in the retreat direction and the movement in the advance direction of the frame 8 in the retracted state can be restrained.

The base plate 3 of the case 2 is provided with a top plate support 9 capable of supporting a load acting downward in the vertical direction through the top plate 6. As shown in FIG. 4 and FIG. 5, the top plate support body 9 is provided in the position near the edge part on the opposite side of the vehicle in the case 2, and the direction parallel to the advancing direction of the step 7 is a long direction. It is arranged to be. The top plate support body 9 is fixed to the base plate 3 by bolts or the like, and is bent in a “co” shape so that the center portion is floated from the base plate 3 and brought into contact with and supported by the top plate 6. It is formed as a shape member. The vertical support members 82b, 82d, and 82f of the frame 8 are located between the base plates 3 by the top plate support 9, and can move in the advancing direction.

Next, the structure for advancing and stepping 7 with respect to the vehicle side is demonstrated. As shown to FIG. 2 and FIG. 3, the motor unit 17 (drive means) is fixed to the edge vicinity of the vehicle opposite side of the base board 3 which comprises the case 2. As shown in FIG. The motor unit 17 has an integrated configuration of an electric motor and a speed reducer that decelerates the rotation of the motor shaft to increase torque, and the drive output shaft (drive shaft) is disposed toward the vertical direction. The pinion gear 18 (drive means) is fixed to the drive output shaft. On the other hand, the rack 19 (drive means) is fixed to the parallel support member 81e of the frame 8 to which the step 7 is fixed so that the pinion gears 18 mesh with each other. By rotating the gear 18, the step 7 can be moved forward and backward with respect to the vehicle.

In this way, the drive means constituted by the motor unit 17, the pinion gear 18, the rack 19, and the like move forward and backward in the case 2 while moving the step 7 through the frame 8. It is arrange | positioned approaching the edge part on the opposite side of a vehicle of the case 2 so that it may be located in the opposite side to a vehicle than the guide groove 6a. That is, the drive means which requires a large space in the up-down direction when installing in the case 2 was not arrange | positioned in the position closer to the vehicle side than the guide groove 6a (refer FIG. 6 and FIG. 7). This makes it possible to secure a space in the case 2 at a position closer to the vehicle side than the guide groove 6a.

Moreover, the said electric motor can be comprised as a motor with a brake which can brake rotation of the drive output shaft by external force at the time of a drive stop. Thereby, in the case of a power failure or abnormality, the step 7 can be maintained at the stop position. This prevents the step 7 from suddenly protruding and pulling in, thereby making it possible to increase the safety of the passenger.

However, the drive means is not limited to the rack pinion mechanism as described above, and the drive means rotates the pulley to drive the belt wound around the pulley to move the frame fixed to the belt forward and backward. It is also possible.

As the base plate 3 which comprises the case 2, retreat position stoppers 11a and 12a and advance position stoppers 11b and 12b are provided. In addition, the base plate 3 is provided with a retreat position detection sensor 13a and a forward position detection sensor 13b. As such a sensor, for example, a proximity switch is used, and when the vertical support member 82b approaches the predetermined position, the rotation of the electric motor can be stopped to stop the movement of the frame 8. The retracted position stoppers 11a and 12a and the forward position stoppers 11b and 12b restrain the movement of the vertical support members 82b and 82f in the retraction direction, thereby preventing excessive movement in the forward and retracted directions due to malfunction. Can be.

For example, when the step 7 moves in the retraction direction, as shown in Figs. 2 and 5A, the vertical support members 82b and 82f contact the retracted position stoppers 11a and 12a. Stop at When the step 7 moves in the forward direction, as shown in Figs. 3 and 5 (b), the vertical support members 82b and 82f are stopped in contact with the forward position stoppers 11b and 12b. do.

Here, the frame 8 is arrange | positioned so that the bottom plate 5 of the case 2 may approach, and it is possible to ensure the space above the frame 8 in the case 2. In addition, the step 7 extends in parallel with the advance direction in the same length as that the step 7 moves forward and backward only on the vehicle side than the guide groove 6a, and the step 7 moves like crossing the lower part of the guide groove 6a. There is no Therefore, the space of the lower part of the guide groove 6a is not narrowed by the advancing / removing movement of the step 7 provided so that the upper surface may be located substantially horizontally to the top plate 6 from the viewpoint of the ease of the passengers walking. It is possible to easily secure the space under the guide groove 6a.

As shown to FIG. 4, FIG. 5, in this embodiment, the dustproof which is a part of the door slide mechanism of the foam door apparatus 200 provided in the platform 100 using the space near the lower part of the guide groove 6a. It becomes possible to accommodate the metal fittings 202. The anti-vibration metal fittings 202 are being fixed to the lower end of the door 201, the roller part which runs around the guide groove 6a and receives rotational support is arrange | positioned in the case 2. As shown in FIG. And with the opening and closing of the door 201, the inside of the case 2 is moved to the direction along the guide groove 6a so that it may follow the rail (not shown) etc. which were provided in the case 2, for example. As a result, vibration of the door 201 can be prevented.

Thus, the step apparatus 1 which concerns on this embodiment can be used with the foam door apparatus 200 which requires a groove on the platform 100. And since a part of the door slide mechanism of the foam door apparatus 200 can be accommodated in the case 2 of the step apparatus 1, the spatial limitation in the design of the foam door apparatus 200 can be further reduced. have. Thereby, it is possible to prevent the passengers from falling down between the vehicles stopped by the step device 1 to the platform 100, and at the same time, the function of the foam door device 200 which can be used simultaneously with the step device 1 is further increased. It can be faithful. As mentioned above, it is not limited to the case of providing the door anti-deviation metal fittings, For example, it is also possible to provide the drive belt of the door of a foam door apparatus, etc. in the space in a step apparatus.

Moreover, the top plate support body 9 is provided in the case 2 so that it may be located on the opposite side to the vehicle than the guide groove 6a, and the case that the case 2 is not destroyed by passing the passengers on the top plate 6 above. In addition to maintaining the strength of (2), it is possible to further increase the space near the vehicle side in the case (2).

Moreover, the vehicle side edge part of the frame 8 is formed of parallel support members 81a-81d which protrude to the vehicle side. In other words, the vehicle side ends of the parallel support members 81a to 81d in the frame 8 are not supported by the vertical support members. Therefore, with respect to the end portion on the vehicle side of the frame 8, an external force acting in a direction perpendicular to the advancing direction of the step 7 and parallel to the upper surface of the step 7 (that is, the entry direction of the vehicle) is applied. On the other hand, the frame 8 is a structure which is easy to deform | transform more easily. As a result, the frame 8 deforms or breaks down even when the vehicle collides with the step 7 with respect to the advanced state of the step 7, thereby absorbing the shock in the frame portion, and thus the vehicle or the step device 1. Damage to drive means such as an electric motor can be suppressed.

Moreover, in the cross section shown to Fig.4 (a), the vertical support member 82c which supports the position closest to the vehicle side edge part of the parallel support member is attached to the top plate support body 9 with respect to the retreat state of the step 7. It is formed to be close. Moreover, in the cross section shown to Fig.5 (a), the vertical support member 82a which supports the position closest to the vehicle side edge part of the parallel support member is attached to the top plate support body 9 with respect to the retreat state of the step 7. It is formed to be close. In this manner, the vertical support member 82e positioned on the right side of the frame 8 with respect to FIG. 2 is also arranged to be close to the top plate support 9.

In this way, the vertical support member located on the vehicle side from the top plate support 9 is disposed so as to be close to the top plate support 9 with respect to the state in which the step 7 retreats into the case 2. It is possible to approach the support position of the parallel support member by the opposite side of the vehicle. At this time, the frame 8 becomes the edge shape of a cantilever state in which the support position became closer to the opposite side of a vehicle. Therefore, when the external force acting on the vehicle side end part of the frame 8 to the direction of entry of a vehicle acts, the frame 8 will become easy to deform | deform further. Thereby, the impact absorption effect of a frame part becomes large more, and it can suppress that a vehicle etc. damage even if a vehicle collides with step 7. In this case, since the top plate support member 9 can support the top plate 6 to a position close to the vehicle side end portion without disturbing the forward / rearward movement of the frame 8, the ascending and descending passengers are placed on the top plate 6. The intensity | strength of the step apparatus 1 with respect to the load which acts at the time of walking can be raised more.

Moreover, it is also possible to make step 7 into the honeycomb structure formed from aluminum, for example. In this case, it becomes possible to improve the shock absorbency of the step 7. Thereby, when the vehicle comes in contact with the step 7, the entire step apparatus 1 can be prevented from being destroyed. In addition, it is possible to reduce the weight while giving the predetermined rigidity, and it is also possible to make the frame 8 supporting the step 7 into a thinner shape.

As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can variously change and implement what was described in a claim.

1 is a flat provided with a platform step apparatus according to an embodiment of the present invention.

The overall schematic of the groove.

FIG. 2 is a plan view of the step apparatus shown in FIG. 1, illustrating a state in which the step retreats with respect to the vehicle. FIG.

3 is a plan view of the step apparatus shown in FIG. 1, illustrating a state in which the step is advanced with respect to the vehicle.

4 is a schematic A-A cross-sectional view of the step apparatus shown in FIGS. 2 and 3.

5 is a schematic B-B cross-sectional view of the step apparatus shown in FIGS. 2 and 3.

It is a C-C cross-sectional schematic diagram of the step apparatus shown in FIG.

FIG. 7: is a schematic diagram of the D-D cross section of the step apparatus shown in FIG.

8 is an overall schematic diagram of a platform in which a platform step device according to an embodiment of the present invention is provided together with a screen-type foam door device.

[Explanation of symbols on the main parts of the drawings]

Step devices for 1 platform

2 cases

6 top plate

6a guide groove

7 steps

8 frames

9 top plate support

17 Motor unit (drive means)

18 pinion gear (drive means)

19 racks (drive means)

81a to 81e parallel support member (frame)

82a to 82f vertical support members (frames)

100 platforms

200 foam door units

202 dustproof metal fittings

Claims (5)

A platform step device for preventing a passenger from falling over between a platform and a stopped vehicle, The case can be embedded in the platform, A step supported by the case, Drive means for relatively moving said step relative to said case so as to advance or retract said step relative to the vehicle side, The case includes a top plate that becomes an upper surface when embedded in the platform, and a guide groove formed on the top plate and extending in parallel with the direction along the platform, The upper part in the case has a space that can accommodate a part of the door slide mechanism of the foam door device provided on the platform in the vicinity of the guide groove, It is further provided with a frame of the frame shape is supported on the case and the step is fixed to the end of the vehicle side, The drive means is disposed close to the vehicle opposite side of the case so as to move the step forward and backward through the frame and to be located on the side opposite the vehicle than the guide groove in the case, The frame is disposed so as to be closer to the lower surface of the case, the platform step apparatus, characterized in that extending in parallel with the advance direction in a length that the step moves forward and backward only on the vehicle side than the guide groove. The method according to claim 1, And a space located at the vehicle side than the guide groove to accommodate the step. The method according to claim 1, The drive means includes a motor, a pinion which is integrally rotated with the drive shaft of the motor, and a rack provided on the frame to mesh with the pinion, The motor is a platform step device, characterized in that the motor with a brake capable of braking the rotation of the drive shaft by an external force at the time of stopping the drive. The method according to claim 1, The frame has a plurality of parallel support members extending in parallel with the advancing direction, and an end portion on the vehicle side is formed by the parallel support member protruding toward the vehicle side. The method according to claim 1, The frame has a plurality of vertical support members extending in a direction perpendicular to the advancing direction and supporting the plurality of parallel support members by connecting them, Further comprising a top plate support in the case for supporting the top plate in the vertical direction, The top plate support is located on the side opposite the vehicle than the guide groove, The vertical support member located on the vehicle side from the top plate support is disposed so as to approach the top plate support in a state where the step is retracted into the case.

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