Transplanter

Abstract

To provide a transplanter which can efficiently and speedily perform a detachment operation and storage operation of an outer apron in the vicinity of a lateral side of a middle apron and a storage stand.SOLUTION: A lateral-longitudinal hollow storage space 6a is formed which can insert, in a lateral-oriented state, an outer apron 10s in a detachment state in a lateral direction that has been detached from a middle apron 10n via an attach / detach means 25 at a position close to the middle apron 10n between a lower part on a back side of an inner seedling placement stand 8a and a planting frame 11. A storage stand 35 is provided on which the outer apron 10s is placed which is inserted into the storage space 6a in a lateral direction to be in a storage state. An attachment means 38 is provided which attaches and fixes the placed outer apron 10s on a side of the storage stand 35.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a transplanter having a retractable outer apron for the seedling carrier. [Background technology]

[0002] Conventionally, in transplanters (paddy field working machines) that plant multiple rows of seedlings at the same time, when a large number of rows of seedlings are planted, the width of the seedling carrier becomes larger than the width of the running body, causing it to protrude on both sides, and the aprons are configured to protrude on both sides. For this reason, the outer movable seedling carrier is designed to be foldable relative to the inner seedling carrier when storing the paddy field working machine and when transporting it between the storage location and the field, and the outer apron of the movable seedling carrier is designed to be detachable from the middle apron of the inner seedling carrier. A transplanter is already known in which the removed outer apron is stored and supported by being inserted vertically into an apron support member provided inside a loop-shaped guard member erected at the rear of the steering section (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4417163 Summary of the Invention [Problem to be solved by the invention]

[0004] The transplanter shown in Patent Document 1 above has an apron support member placed within a guard erected at the rear of the running body, and the outer apron is inserted into the apron support member from above and stored. Since the outer apron is protected by the guard, this has the advantage of preventing problems such as deformation of the outer apron. However, the outer apron detached from the middle apron must be stored by hand, walking from the rear planting device to the front running body side. This makes the storage procedure complicated and inefficient, especially when walking with the detached outer apron on a muddy rice field surface or narrow footpath, as the user must bend down to remove the apron, turn around, and take a large step toward the running body side. Furthermore, when the outer apron is removed sideways from the inner apron, it must be turned vertically and inserted into the apron support member, and when the outer apron is reset onto the inner apron, major work movements must be carried out in reverse order, making the storage process complicated. Furthermore, the method and configuration for storing the outer apron on the running body side requires an expensive guard frame, and the outer apron, which is manufactured with a thin-walled hollow structure by aluminum molding processing, is inserted into a vertical apron support member for storage. Therefore, when the end face of the outer apron is subjected to contact impact when inserted or large body vibrations, there are issues such as the apron end being prone to deformation or wear due to rattling caused by shaking. [Means for solving the problem]

[0005] The transplanter of the present invention for solving the above problems comprises: First, a transplanter 1 has a planting frame 11 attached to the rear of a traveling body 2 via a lifting mechanism 5, a seedling carrier 8 on which a large number of mat seedlings are placed in a left-right parallel arrangement is moved back and forth in an inclined position with a high front and a low rear, and a planting device 6 is provided which uses a planting claw 9 to plant the mat seedlings from an apron 10 formed by connecting an outer apron 10s to a middle apron 10n of the seedling carrier 8 into a scraping field. A horizontally long, hollow storage space 6a is formed between the lower back side of the inner seedling carrier 8a and the planting section frame 11, close to the middle apron 10n, into which the outer apron 10s in a horizontally removed position removed from the middle apron 10n via the attachment / detachment means 25 can be inserted in a horizontal position, and a storage stand 35 is provided on which the outer apron 10s which is inserted horizontally into the storage space 6a and placed in a stored position is placed, and an attachment means 38 is provided for attaching and fixing the placed outer apron 10s to the storage stand 35. Secondly, a storage stand 35 on which the outer apron 10s is placed in a horizontal storage position within the storage space 6a is supported by an attachment arm 37 provided on the planting unit frame 11 side. Thirdly, the mounting means 38 is characterized in that a bolt 30 having a mounting piece 28 that can be inserted into the guide groove 10e of the middle apron 10n is provided at the inner end of the mounting member 27 that is attached and fixed along the lower side of the outer apron 10s, and a connecting portion 32a is provided that protrudes inward from the guide groove 10e of the outer apron 10s and is inserted into the guide groove 10e of the middle apron 10n in a manner that allows it to be engaged and disengaged. Effect of the Invention

[0006] According to the invention of claim 1, in the transplanter 1 having the planting section frame 11 attached via the lifting mechanism 5 to the rear of the traveling body 2, the seedling carrier 8 on which a large number of mat seedlings are placed in a left-right parallel arrangement is moved back and forth in an inclined posture with the front high and the rear low, and the mat seedlings are planted in a raking field area by the planting claws 9 from the apron 10 which is formed by connecting the inner apron 10n to the outer apron 10s, the lower rear side of the inner seedling carrier 8a and the planting section frame 11 a storage space 6a having a horizontally long hollow shape, into which the outer apron 10s in a horizontally detached position removed from the inner apron 10n via the attachment / detachment means 25 can be inserted in a horizontally oriented position; a storage base 35 is provided for placing the outer apron 10s inserted horizontally into the storage space 6a to be placed in a stored position; and mounting means 38 is provided for mounting and fixing the placed outer apron 10s to the storage base 35. A storage stand 35 is provided on the lower side of the storage space 6a, which is formed as wide as possible and close to the middle apron 10n on the planting device 6 side, making it easy to place and remove the outer apron 10s and capable of being manufactured with a simple and inexpensive structure. In addition, since the storage stand 35 can be installed near the middle apron 10n, when removing the outer apron 10s and storing it in the storage stand 35, and when removing the outer apron 10s from the storage stand 35 and attaching it to the middle apron 10n, the removal, storage and attachment operations of the outer apron 10s can be performed efficiently and quickly near the side of the middle apron 10n and the storage stand 35, without the need to go to the trouble of searching for a storage location for the outer apron 10s or to walk a long distance. According to the invention of claim 2, the storage table 35 on which the outer apron 10s is placed in a horizontal storage position in the storage space 26a is supported by the mounting arm 37 provided on the planting unit frame 11 side. The storage stand 35 can be freely moved to an appropriate position within the storage space 26a via the attachment arm 37 from the planting section frame 11 side, which has a rigid structure, so that the outer apron 10s can be stably placed on the storage stand 35 to prevent damage, which not only makes it easy to place and remove the outer apron 10s, but also allows for a simple, inexpensive configuration. According to the invention of claim 3, the mounting means 38 is configured such that the bolt 30 having the mounting piece 28 insertable into the guide groove 10e of the middle apron 10n is provided at the inner end of the mounting member 27 which is attached and fixed along the lower side of the outer apron 10s, and a connecting portion 32a is provided which protrudes inward from the guide groove 10e of the outer apron 10s and is insertable into the guide groove 10e of the middle apron 10n in a releasable manner. When attaching the outer apron 10s to the middle apron 10n, the connecting portion 32a of the mounting bar 32 can be inserted into the guide groove 10e of the middle apron 10n to position and support it, and the mounting piece 28 can be fastened and fixed to the middle apron 10n easily, quickly and rigidly by fastening the knobbed bolt 30 which has a sufficient fixing distance from the connecting portion 32a, so that the outer apron 10s can maintain stability even if it is subjected to severe aircraft vibration. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an overall perspective view of a transplanter according to the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 13 is a perspective view of the main part showing the left outer apron in a connected position and the storage means. [Figure 4] 1 is a perspective view of a main part showing a stored state in which the inner apron and the outer apron are stored with the outer apron removed. FIG. [Diagram 5] FIG. 5 is a side view of FIG. [Figure 6] FIG. 2 is a perspective view showing the configuration of the left outer apron. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of the present invention will be described with reference to the drawings. In Fig. 1, a riding transplanter 1 has a running body 2 with a front wheel 1a and a rear wheel 1b on the left and right, an engine is mounted on the front side of the running body 2, which is covered with a bonnet 3, and a control section 4 consisting of a handle 4a of an operation panel section, a seat 4b, and a control floor 4c laid between the two at the feet is installed at the rear, and a floor step 4d is connected to the left and right of the control step 4c.

[0009] The traveling body 2 is attached with a planting device 6 via a three-point link type lifting mechanism 5 provided at the rear of the body so that it can be freely attached, detached, and raised and lowered, and the planting device 6 is supported so that it can be freely rolled via a rolling shaft that protrudes rearward from a link holder (not shown). This planting work device 6 has a configuration similar to that of conventional devices, and can move a seedling carrier 8, which carries eight rows of mat seedlings in a parallel arrangement on the left and right, back and forth from side to side in an inclined position with the front high and the rear low, while planting the seedlings on the seedling carrier 8 from an apron 10 into the field surface (rice field surface) using planting claws 9.

[0010] A number of planting claw transmission cases 12 that rotate and drive the planting claws 9 are attached in the front-to-rear direction at a predetermined interval to the horizontal planting section frame 11 that forms the main frame of the device, and a sled-shaped float 14 is attached and supported to the bottom of each planting claw transmission case 12 via a link mechanism. The traveling body 2 transmits power to the input shaft 15 of the planting device 6 via the rear PTO transmission shaft, and the power is input from the input shaft 15 to each planting claw transmission case 12 via an input conversion transmission case that houses a transmission conversion mechanism, and the seedling carrier 8 is driven to feed seedlings back and forth in the horizontal direction via the seedling carrier drive part of the seedling carrier transmission system (not shown) (Figures 2 and 5).

[0011] On the other hand, the seedling carrier 8 of the planting device 6, like conventional ones, comprises an inner seedling carrier 8a which is integrally configured to carry eight rows of seedlings, and a movable seedling carrier 8b adjacent to the left and right sides of the inner seedling carrier 8a for carrying one row of mat seedlings.The movable seedling carrier 8b is configured to be switchable and fixed in a folded shape toward the upward side via a folding mechanism 16 of a known structure, as shown in Figure 2, making it easier to transport and store the machine. The seedling carrier 8 is supported at its lower front part via support members on a plurality of vertical frames 17 erected from the planting claw transmission case 12 side, with the middle part on the back side connected to a seedling carrier drive part that is installed on the planting claw transmission case 12 side and drives the seedling carrier 8 back and forth horizontally, and the lower end part is supported so as to be freely slidable left and right (horizontally) with the apron 10 placed on it.

[0012] As shown in Figure 3, the apron 10 has a length and shape that is the width of the seedling carrier 8 and a sliding width to the left and right of that for feeding one row of mat seedlings laterally, and the seedling receiving wall 10a is erected opposite the lower end of the seedling carrier 8 to receive the rear end of the mat seedlings, and the apron base 10b has a downward U-shaped cross section that can be slidably engaged with an inverted U-shaped slide piece (sliding piece) 20 fixed laterally to the back side of the seedling carrier 8, and these are integrally formed by a pull-out forming body.

[0013] The seedling receiving wall 10a of the apron 10 is cut out at a position facing the rotation trajectory of the planting claw 9 to form scraping holes 10c corresponding to the planting intervals of the seedlings, through which the planting claw 9 can be inserted to scrape off one seedling. The apron stand 10b has an engagement groove 10d with a concave cross section parallel to the seedling receiving wall 10a formed in the center of the bottom surface. The apron 10 shown in the figure can also be made of aluminum extrusion molding used in conventional planting devices 6.

[0014] On the other hand, each planting claw transmission case 12 has a plurality of rod-shaped apron support rods 22 protruding from the middle of the front-rear direction at an upward inclination angle, and the apron 10 is supported by the plurality of apron support rods 22 so that it can slide freely in line with the inclination direction of the seedling carrier 8 while preventing it from moving laterally (Figure 5). As shown in Figures 3 and 4, on the planting section frame 11 side, a raking adjustment lever 23 for adjusting the amount of seedlings raked is rotatably mounted via a bracket on the front side of the apron support rod 23, and the tip of the raking adjustment lever 23 is engaged in the engagement groove 10d of the apron stand 10b. As a result, the raking adjustment lever 23 moves the apron 10 up and down in stages based on the up and down rotation operation to adjust the amount of seedlings raked.

[0015] In the above configuration, the apron 10 of the embodiment is composed of a middle apron 10n that slidably loads and guides the lower end of the inner seedling carrier 8a, which is configured to carry the eight rows of seedlings, and outer apron 10s that slidably loads and guides the rear part of the movable seedling carrier 8b, which is configured to carry one row of mat seedlings, on both sides of the middle apron 10n. This apron 10 has a middle apron 10n fixed to the planting frame 11, and an outer apron 10s removably attached to both outer ends of the middle apron 10n via a fastening means 25 (FIGS. 3 to 6).

[0016] The middle apron 10n is fixed so as to have a wide horizontal space between the lower back side of the inner seedling carrier 8a and the planting frame 11. In the space, close to the middle apron 10n, a storage space 6a is formed in which the outer apron 10s removed from the middle apron 10n by the removal work described later can be stored in a horizontal position parallel to the underside of the inner seedling carrier 8a. In addition, a storage means 26 is provided in the storage space 6a between the planting frame 11 and the seedling carrier 8 to support the removed outer apron 10s in a horizontal position (Fig. 4, Fig. 5).

[0017] As shown in Figures 5 and 6, the attachment / detachment means 25 makes use of the shape and structure in which the middle apron 10n and the outer apron 10s are manufactured to have a U-shaped hollow cross-section and form the engagement groove 10d, and when the opposing ends of the two are butted together, an attachment piece 28 provided at the inner end of a mounting member 27 made of a thick plate rod attached to the lower side of the outer apron 10s is configured to be slidably inserted into a guide groove (connecting groove) 10e formed inside the middle apron 10n. In this configuration, the mounting piece 28 is provided at the tip side of the threaded portion of a bolt 30 which is screwed into the inner end of the mounting member 27 at a predetermined fixed distance from the inner end of the outer apron 10s, and the bolt 30 integrally forms an axial fastening portion 31 on the other side of the grip portion on the head side.

[0018] The attachment / detachment means 25 has a mounting piece 28 rotatably attached to the tip of the bolt 30 protruding from the screw hole, with the screw portion of the bolt 30 screwed into a screw hole formed at the inner end of the mounting member 27, and the mounting piece 28 is slidably inserted into the guide groove 10e. The mounting member 27 is formed on the outer side of the bolt 30 in the same shape as the guide groove 10e of the middle apron 10n, and an mounting bar 32 made of a plate-shaped rod of a predetermined length is inserted into the guide groove 10e of the outer apron 10s, and its inner end side forms a connecting portion 32a that protrudes with a predetermined connecting length. When the mounting bar 32 inserted into the outer apron 10s is connected to the mounting member 27 that abuts along the underside of the outer apron 10s with multiple connecting bolts 33, the two are connected and fixed with the connecting portion 32a protruding and the outer apron 10s clamped in place.

[0019] As a result, when attaching the outer apron 10s to the inner apron 10n, the bolt 30 can be loosened so that the mounting piece 28, which can be moved freely, can be smoothly inserted into the guide groove 10e of the inner apron 10n.Next, the connecting portion 32a is inserted into the guide groove 10e of the inner apron 10n and the outer apron 10s, with its inner end abutting the outer end of the guide groove 10e, is fastened with the knobbed bolt 30, so that the mounting piece 28 can clamp the groove structure portion of the guide groove 10e of the inner apron 10n at a predetermined fixed distance, thereby positioning and fixing it.

[0020] Therefore, the outer apron 10s can be attached to the outer end of the middle apron 10n, which is fixed to the planting section frame 11, by inserting the connecting portion 32a of the mounting bar 32 into the guide groove 10e of the middle apron 10n to support it in position, and the mounting piece 28 can be easily, quickly and stably fastened to the middle apron 10n by fastening the knobbed bolt 30, which has a sufficient fixing distance from the connecting portion 32a. This increases the stability of the outer apron 10s even when it is subjected to severe machine vibrations or vibrations when the planting device 6 is raised and lowered, and also enables the removal operation of the outer apron 10s from the middle apron 10n to be performed easily and quickly by performing the operations in the reverse order of the above-mentioned installation operation.

[0021] When removing the outer apron 10s, loosening the bolts 30 causes the outer side of the outer apron 10s to tilt downward and fall, but the engagement between the middle apron 10n and the connecting parts 32a prevents a sudden change in posture, rattling, or separation immediately after loosening the bolts 30. The worker can remove the outer apron 10s by holding it with one hand while gripping the bolts 30 with the other, making the removal process efficient and easy. Next, the outer apron 10s removed from the planting device 6 can be stored in the storage means 26 located to the side (left) by an operator maintaining the horizontal, sideways removal position, as described below, without having to significantly change position or walk from the crouching position immediately after removal. The attaching / detaching means 25 constructed as described above has an advantage that when the outer apron 10s is placed on the storage platform 35 of the storage means 26, it can also be used as the mounting means 38, as will be described later.

[0022] Next, the storage means 26 will be described with reference to Figures 3, 4, and 5. The storage means 26 in the illustrated example is composed of a storage platform 35 that is large enough to place the outer apron 10s removed from the middle apron 10n in a stable horizontal position and has an L-shape in a side view, an attachment arm 37 that attaches and supports the storage platform 35 to the planting section frame 11 side so as to face the storage space 6a, a bolt 36 that detachably attaches the attachment arm 37 to the planting section frame 11 side, and an attachment means 38 that attaches and supports the outer apron 10s to the storage platform 35. The attachment means 38 in the illustrated example can be used in combination with the configuration of the attachment and detachment means 25 for the outer apron 10s.

[0023] The storage base 35 of the storage means 26 has a receiving surface 35b of a predetermined height formed by bending the middle of the front side of a mounting surface 35a which is formed as a horizontally long flat plate in a plan view, and has horizontally long bolt-through holes 35c drilled into the rear side of the mounting surface 35a for inserting a plurality of connecting bolts 33 as shown in Figure 6, and also has an engagement notch 35d into which the threaded portion of the knobbed bolt 30 can be inserted and engaged. The storage means 26 is provided with an attachment arm 37 erected on the front side of the loading surface 35a from the planting section frame 11 side or a nearby frame member. The storage means 26 may be formed by integrally bending the storage platform 35 and the attachment arm 37 by pressing, or may be configured by connecting the two as separate members. It is also preferable that the loading surface of the storage platform 35 is inclined downward toward the front and bottom as shown in Figure 5. In this case, there is an advantage that even if the mounting and fixing of the outer apron 10s becomes insufficient due to loosening of the bolts 30, the outer apron 10s is received and supported by the loading surface 35a.

[0024] When the outer apron 10s, which has been removed and turned sideways, is placed in an inverted state on the storage base 35, the storage means 26 of the transplanter 1 configured as above performs the following steps: the connecting bolt 33 is inserted into the bolt through hole 35c of the storage base 35 in a positioning manner, and the bolt 30 is loosened, and the engagement notch 35d of the storage base 35 is inserted between the mounting member 27 and the fastening portion 31 of the bolt 30, as shown in Fig. 4, and the bolt 30 is inserted and engaged in the engagement notch 35. Next, the knob of the bolt 30 is grasped and tightened from the wide space formed on the lower side, whereby the outer apron 10s can be easily and reliably fixed to the storage base 35 with the storage base 35 firmly clamped between the mounting arm 37 and the fastening portion 31. The outer apron 10s can be removed quickly in a sideways position facing outward from the aircraft by loosening the bolts 30 and performing the operations in the reverse order of the installation work, so that it can be quickly reattached to the intermediate apron 10n located nearby below.

[0025] As described above, the transplanter 1 forms a horizontally elongated hollow storage space 6a between the lower back side of the inner seedling carrier 8a and the planting section frame 11, close to the middle apron 10n, into which the outer apron 10s in a horizontally removed position after being removed from the middle apron 10n via the attachment / detachment means 25 can be inserted in a horizontal position, and is provided with a storage stand 35 on which the outer apron 10s is placed when inserted horizontally into the storage space 6a to be placed in a stored position, as well as an attachment means 38 for attaching and fixing the placed outer apron 10s to the storage stand 35. This allows the operator to efficiently store the removed outer apron 10s and attach the stored outer apron 10s to the middle apron 10n without requiring any major movements or movements.

[0026] In other words, the outer apron 10s can be inserted in the same horizontal position as it was removed and placed on the storage table 35 in the storage space 6a formed in a position as close as possible to the middle apron 10n, so that the attachment and detachment operations using the mounting means 38 and the storage operations on the storage table 35 can be easily and quickly performed on the spot without requiring significant walking or changing of working posture. Furthermore, when resetting the outer apron 10s on the inner apron 10n, the outer apron 10s is positioned visible in the storage space 6a formed nearby at the front of the inner apron 10n, so there is no need to go to the trouble of searching for a storage location for the outer apron 10s. In addition, by performing the operations in the reverse order of the removal work, on-site work can be quickly performed near the side of the inner apron 10n, so that the installation work of the outer apron 10s can be performed smoothly and with good workability.

[0027] Furthermore, the storage means 26 configured as described above forms the storage space 6a as wide as possible by placing it close to the middle apron 10n on the planting device 6 side and providing a storage stand 35 on the lower side thereof, thereby having the advantage that the outer apron 10s can be easily placed and removed with a simple and inexpensive configuration without being hindered by surrounding structural members. Furthermore, by supporting the storage table 35 on which the outer apron 10s is placed in a horizontal storage position within the storage space 6a by an attachment arm 37 provided on the planting section frame 11 side, the storage table 35 can be stably and properly positioned in a preferred position in the storage space 6a via the attachment arm 37 from the planting section frame 11 side, which has a rigid structure.This has the advantage that the outer apron 10s can be quickly placed and removed in a horizontal storage position while preventing damage from contact with the surroundings, and that it is easy to perform on-site work without having to significantly change the position for attachment and detachment.

[0028] In addition, the storage means 26 in the embodiment has a structure in which a storage table 35 is attached to the planting section frame 11 via an attachment arm 37, but this is not limited to this, and the storage table 35 can be formed, for example, by utilizing a cover or frame member (not shown) installed on the front or rear side of the storage space 6a. In this case, the long mounting arm 37 attached to the planting section frame 11 side can be omitted, so that the storage means 26 can be made simple and inexpensive, and there are other advantages such as the outer apron 10s, which is detached from the middle apron 10n via the attachment / detachment means 25 and is in a horizontally removed position, being able to be stored in the same position as when it is carried by hand without changing its orientation. In addition, the mounting means 38 for mounting and fixing the outer apron 10s to the storage base 35 may be constructed using a flexible string member, a rubber band, or a one-touch operation clamp, without using the attachment / detachment mechanism 25 as in the illustrated example. [Explanation of symbols]

[0029] 1 transplanter 2 Running body 4. Control Unit 5 Lifting mechanism 6 Planting equipment 8 Seedling stand 8a Inside seedling stand 8b Outside seedling stand 9 Planting Claws 10 Apron 10e Guide groove 10n Middle apron 10s Outer apron 11 Planting frame 25 Attachment / detachment means 26a Storage space 27 Mounting material 28 Mounting piece 30 Volts 32a Connecting part 35 Storage platform 37 Mounting arm 38 Mounting means

Claims

1. A transplanter (1) has a planting frame (11) attached to the rear of a traveling body (2) via a lifting mechanism (5), a seedling carrier (8) on which a large number of mat seedlings are placed in a left-right parallel arrangement, and a planting device (6) that moves the seedling carrier (8) back and forth in an inclined position with a high front and a low rear, and plants the mat seedlings from an apron (10) having an outer apron (10s) connected to a middle apron (10n) of the seedling carrier (8) in a scraping field with a planting claw (9). The transplanter is characterized in that it forms a horizontally elongated hollow storage space (6a) between the lower back side of the inner seedling carrier (8a) and the planting section frame (11) and in the vicinity of the middle apron (10n), into which the outer apron (10s) in a horizontally removed position removed from the middle apron (10n) via an attachment / detachment means (25) can be inserted in a horizontally positioned position, and a storage stand (35) is provided on which the outer apron (10s) is placed when inserted horizontally into the storage space (6a) to be placed in a stored position, and further comprises an attachment means (38) for attaching and fixing the placed outer apron (10s) to the storage stand (35).

2. A transplanter as described in claim 1, characterized in that a storage table (35) on which the outer apron (10s) is placed in a horizontal storage position within the storage space (6a) is supported by an attachment arm (37) provided on the planting section frame (11) side.

3. The transplanter according to claim 1 or 2, characterized in that the mounting means (38) is configured as follows: a bolt (30) having a mounting piece (28) that can be inserted into the guide groove (10e) of the middle apron (10n) is provided at the inner end of a mounting member (27) that is attached and fixed along the lower side of the outer apron (10s), and a connecting portion (32a) that protrudes inward from the guide groove (10e) of the outer apron (10s) and is inserted in a releasable manner into the guide groove (10e) of the middle apron (10n).

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