CN208278148U - A kind of baby carriage seat being easy to folding storage - Google Patents

Abstract

The utility model discloses a kind of baby carriage seats for being easy to folding storage, including seat board, backrest plate and two mounting bases arranged side by side；The rear portion of seat board two sides is provided with pedestal, the pivotable inside for being installed on corresponding mounting base of pedestal, is provided on pedestal for by the locking device of seat board and mounting base locking；The lower part of backrest plate two sides is provided with attachment base, the pivotable inside for being installed on corresponding pedestal of attachment base, locking pin is movably set on attachment base, lock slots compatible with locking pin are offered on pedestal, when locking pin is inserted into lock slots, pedestal and attachment base can be locked, be provided with unlock piece on attachment base, when attachment base is rotated relative to pedestal, unlock piece can unlock locking device so that seat board can be freely rotated relative to mounting base.The equal folding storage of seat board and backrest plate in the utility model, take down the exhibits it is convenient, be conducive to carry and storage.

Description

A kind of baby carriage seat being easy to folding storage

Technical field

The utility model relates to stroller technical field, especially a kind of baby carriage seat for being easy to folding storage.

Background technique

Stroller is a kind of for the mobile tool of carrying designed by baby (or child), and adult is facilitated to carry baby It travels outdoors or does shopping, while can also suitably hold light small article, it is deep to be liked by numerous parents.

The seat of stroller is generally made of backrest plate and seat board two large divisions.The baby occurred currently on the market pushes away There are two types of vehicles, the first is that seat is not foldable, and occupied space is big when this stroller is in idle state；It is for second Backrest plate is capable of the seat of folding storage, when this stroller is in idle state, can be folded to backrest plate and seat board It is close to.It is compared with the first seat, second of seat can reduce backrest plate the space occupied, more conducively transports and stores.So And second above-mentioned of baby carriage seat still has shortcoming, the reason is that, the seat board of this seat does not have receipts still The function of exhibition, backrest plate is folded to be close to seat board after, seat board be still it is horizontal positioned, need to occupy biggish laterally empty Between, it has not been convenient to it carries.

Utility model content

In view of this, the purpose of this utility model is to provide a kind of seat board and the equal folding storage of backrest plate, taking down the exhibits Baby carriage seat convenient, conducive to carrying.

The utility model be solve its technical problem and the technical solution adopted is that:

A kind of baby carriage seat being easy to folding storage, comprising:

Two mounting bases arranged side by side, the mounting base can be fixedly connected with the vehicle frame of external stroller；

Seat board, the rear portion of the seat board two sides are provided with pedestal, and the pedestal is pivotable to be installed on corresponding peace The inside of seat is filled, the locking device for locking seat board and mounting base is provided on the pedestal；

Backrest plate, the lower part of the backrest plate two sides are provided with attachment base, and the attachment base is pivotable to be installed on correspondence Pedestal inside, be movably set with locking pin on the attachment base, the inside of pedestal position corresponding with locking pin is opened Equipped with lock slots compatible with locking pin, manual driving device is provided on the backrest plate, the locking pin is by the hand Dynamic driving device drives and can move between insertion lock slots and the position for exiting lock slots along attachment base, the locking pin When being inserted into lock slots, pedestal and attachment base can be locked, be provided with unlock piece on the attachment base, the attachment base is relative to base When seat rotation, the unlock piece can unlock locking device so that seat board can be freely rotated relative to mounting base.

Preferably, the slide opening with the pivoting axis parallel of the pedestal, the locking device are provided on the pedestal Including the locking piece being arranged in the slide opening, the first jack is provided in the mounting base, be provided on the locking piece with The compatible inserted block of first jack, the locking piece can be moved along slide opening so that inserted block is being inserted into the first jack and is exiting It moves, when the inserted block is inserted into the first jack, pedestal and mounting base can be locked, the lock is paid between the position of first jack It is provided with the first pushing inclined-plane on part, is provided on the unlock piece and is pushed tiltedly with the first pushing inclined-plane compatible second Face, when the unlock piece is rotated relative to pedestal, second pushing inclined-plane can be pressed on the first pushing inclined-plane to push Locking piece is moved to the inserted block along slide opening and exits the first jack, and the locking device further includes the first return springs, institute The setting of the first return springs is stated between pedestal and locking piece or between attachment base and locking piece, first return springs Locking piece can be driven mobile by elastic force so that inserted block is inserted into the first jack.

Preferably, first return springs are spring.

Preferably, an accommodating hole is offered in the middle part of the locking piece, is additionally provided with and is extended on the locking piece The first force-bearing piece in the accommodating hole, first pushing inclined-plane are located at the outside of first force-bearing piece, the unlock piece Outside portion have and extend to the second force-bearing piece in the accommodating hole, second pushing inclined-plane is located at second force-bearing piece Inside.

Preferably, the manual driving device includes the second return springs, pull-push piece and tie rod, the pull-push piece With tie rod setting moving up and down on the backrest plate, the lower end of the tie rod is connected with the locking pin, the drawing The upper end of item is connected with the pull-push piece, the pull-push piece can by manual actuation to pull out the locking pin from lock slots, Second return springs are arranged between locking pin and attachment base, and second return springs can drive lock by elastic force Rationed marketing is inserted into lock slots.

Preferably, second return springs are spring.

Preferably, the first guide groove extended obliquely downward from above, the drawing are provided in the load-carrying surface of backrest plate Item is slidably disposed in first guide groove.

Preferably, the second guide groove being aligned with the lock slots, the locking pin are provided on the attachment base It is slidably disposed in second guide groove.

Preferably, the quantity of the lock slots is two or more, and the locking pin is from one of lock slots After exiting, the backrest plate can turn to the locking pin relative to seat board and be aligned with other lock slots.

Preferably, the mounting base can removably be connect with the vehicle frame of external stroller, two installations Seat size shape is all the same, and two mounting bases are symmetrically disposed in the two sides of the seat board.

Preferably, the front of the seat board is pivotable is provided with foot pedal.

Preferably, be provided with the guardrail of curved bar shape on the seat board, the both ends of the guardrail respectively with seat cushion The both sides of plate removably connect.

Preferably, the both sides of the seat board are provided with third jack, and the both ends of the guardrail are inserted respectively It is located in corresponding third jack, lateral button hole is provided on the side wall of the third jack, the guardrail both ends are provided with The buckle for the elasticity being used cooperatively with the button hole, the lower end of the buckle is fixedly connected with the guardrail, the buckle it is upper End is free end, is provided with lug boss compatible with the button hole in the middle part of the buckle, the upper end of the buckle extends to Guardrail and seat board when the lug boss is caught in the button hole, can be locked, press the buckle by the outside of third jack When upper end, it can make the buckle that elastic deformation occur so that the lug boss is exited from the button hole.

Preferably, the both sides of the seat board are provided with handrail.

Preferably, the cape bracket for installing awning is provided on the backrest plate.

Preferably, the cape bracket includes at least two support rods, and the support rod is in "U" shaped, the branch Strut is hinged by its both ends and backrest plate.

The beneficial effects of the utility model are: in the utility model, locking pin can be along under manual driving device driving Attachment base moves between insertion lock slots and the position for exiting lock slots, and locking pin can drive after exiting in lock slots Backrest plate is rotated relative to seat board backrest plate folding storage to get up, and backrest plate turns an angle relative to seat board When, as the unlock piece that backrest plate rotates can unlock locking device, then, seat board can be driven to rotate relative to mounting base Seat board to be stored.To sum up, the seat board in the utility model and the equal folding storage of backrest plate, take down the exhibits it is convenient, sharp In carrying and storage.

Detailed description of the invention

Utility model will be further described in detail below with reference to the attached drawings and specific embodiments.

Fig. 1 is the first usage state diagram for applying the stroller of the utility model；

Fig. 2 is the second usage state diagram for applying the stroller of the utility model；

Fig. 3 is the structural schematic diagram of stroller when storing backrest plate；

Fig. 4 is the structural schematic diagram of the stroller after seat board and the equal folding storage of backrest plate；

Fig. 5 is the structural schematic diagram of the utility model；

Fig. 6 is the explosive view of the utility model；

Fig. 7 is the partial enlarged view of part A in Fig. 6；

Fig. 8 be locking pin insertion locking slot in when and seat board positional diagram；

Fig. 9 is the annexation figure of seat board and mounting base；

Figure 10 is the positional diagram that inserted block is plugged in locking piece and unlock piece when in the first jack；

Figure 11 is the structural schematic diagram for being originally guardrail in utility model.

Specific embodiment

Below in conjunction with attached drawing, the technical scheme in the utility model embodiment is clearly and completely described, shows So, described embodiment is only a part of the embodiment of the utility model, instead of all the embodiments.It is practical based on this Embodiment in novel, every other reality obtained by those of ordinary skill in the art without making creative efforts Example is applied, is fallen within the protection scope of the utility model.

It is to be appreciated that if related in the utility model embodiment directionality instruction (such as up, down, left, right, before and after, Top, bottom, inside and outside, vertical, transverse direction, longitudinal direction, counterclockwise, clockwise, circumferentially, radially, axially ...), then directionality indicates only For explaining in relative positional relationship, the motion conditions etc. under a certain particular pose (as shown in the picture) between each component, if When the particular pose changes, then directionality instruction also correspondingly changes correspondingly.

In addition, if relating to the description of " first " or " second " etc. in the utility model embodiment, should " first " or The description of person " second " etc. is used for description purposes only, and is not understood to indicate or imply its relative importance or is implicitly indicated The quantity of indicated technical characteristic.Define " first " as a result, the feature of " second " can explicitly or implicitly include to Few this feature.It in addition, the technical solution between each embodiment can be combined with each other, but must be common with this field Based on technical staff can be realized, this skill will be understood that when the combination of technical solution appearance is conflicting or cannot achieve The combination of art scheme is not present, also not within the protection scope of the requires of the utility model.

The embodiments of the present invention propose a kind of baby carriage seat for being easy to folding storage.

Referring to figs. 1 to Figure 11, in the embodiments of the present invention, this is easy to the baby carriage seat of folding storage, including Backrest plate 4, seat board 3 and two mounting bases 1 arranged side by side, mounting base 1 can be fixed with the vehicle frame 2 of external stroller Connection；The rear portion of 3 two sides of seat board is provided with pedestal 30, the pivotable inside (peace for being installed on corresponding mounting base 1 of pedestal 30 The inside for filling seat 1, refers to the side wall of the mutual direction of two mounting bases 1), it is provided on pedestal 30 for by seat board 3 and installation The locking device of 1 locking of seat；The lower part of 4 two sides of backrest plate is provided with attachment base 40, and attachment base 40 is pivotable to be installed on correspondence Pedestal 30 inside (inside of pedestal 30 refers to side wall of the pedestal 30 towards the middle part of seat board 3), activity is set on attachment base 40 It is equipped with locking pin 5, the inside of pedestal 30 position corresponding with locking pin 5 offers lock slots 301 compatible with locking pin 5, Manual driving device is provided on backrest plate 4, locking pin 5 is driven by manual driving device and can be inserted into along attachment base 40 It moves between lock slots 301 and the position for exiting lock slots 301, when locking pin 5 is inserted into lock slots 301, by pedestal 30 and can connect Joint chair 40 locks, and seat is in unfolded state.Unlock piece 6 is provided on attachment base 40, attachment base 40 is rotated relative to pedestal 30 When, unlock piece 6 can unlock locking device so that seat board 3 can be freely rotated relative to mounting base 1.

Locking pin 5 can drive backrest plate 4 to rotate relative to seat board 3 with by backrest plate after exiting in lock slots 301 4 folding storages get up, and when backrest plate 4 turns an angle relative to seat board 3, the unlock piece 6 rotated with backrest plate 4 can be incited somebody to action Then locking device unlock can drive seat board 3 to rotate relative to mounting base 1 to store seat board 3.Therefore, originally Seat board 3 and the equal folding storage of backrest plate 4 in utility model, take down the exhibits it is convenient, be conducive to carry and storage.

It should be noted that seat board 3 and backrest plate 4 can preferentially adopt it is made of plastic, adopt it is made of plastic, have molding Convenient, at low cost advantage.Load meanwhile to keep sitting infant comfortable, preferably in the load-carrying surface of seat board 3 and backrest plate 4 It pads and is set by seat cushion flexible and back cushion, for sitting infant respectively in face.

Referring to Fig. 6 to Figure 10, the slide opening 302 with the pivoting axis parallel of pedestal 30 is provided on pedestal 30.Locking device packet The locking piece 7 being arranged in slide opening 302 is included, the first jack 11 is provided in mounting base 1, is provided on locking piece 7 and is inserted with first The compatible inserted block 71 in hole 11, locking piece 7 can be moved along slide opening 302 so that inserted block 71 is in the first jack of insertion 11 and exits It moves between the position of first jack 11, when inserted block 71 is inserted into the first jack 11, pedestal 30 and mounting base 1 can be locked.For Increase the stability of seat board 3, the quantity of the first jack 11 should be multiple, and each first jack 11 is mutually staggered.In order to prevent Locking piece 7 is deviate from from slide opening 302, which is opening blind hole inwardly, correspondingly, the bottom of slide opening 302 offer with One-to-one second jack 303 of each first jack 11.It is provided with the first pushing inclined-plane 70 on locking piece 7, is arranged on unlock piece 6 Have and push the compatible second pushing inclined-plane 60 of inclined-plane 70 with first, when unlock piece 6 is rotated relative to pedestal 30, second is pushed tiltedly Face 60 can be pressed on the first pushing inclined-plane 70 with push locking piece 7 along slide opening 302 be moved to inserted block 71 exit first insert Hole 11.In the present embodiment, the middle part of locking piece 7 offers an accommodating hole 72, is additionally provided on locking piece 7 and extends to accommodating hole 72 In the first force-bearing piece 73, the first pushing inclined-plane 70 is located at the outside of the first force-bearing piece 73, and the outside portion of unlock piece 6 has extension The second force-bearing piece 61 into accommodating hole 72, the second pushing inclined-plane 60 are located at the inside of the second force-bearing piece 61.Seat is in expansion When state, the first force-bearing piece 73 and the second force-bearing piece 61 are staggered certain angle, when folding storage backrest plate 4, unlock piece 6 with Backrest plate 4 rotates, and so that the second pushing inclined-plane 60 is pushed inclined-plane 70 with first and is pressed against each other, the storage of backrest plate 4 is to substantially as shown in Figure 3 State when, then inserted block 71 is extracted out from the first jack 11 to unlock, makes pedestal 30 can be relative to mounting base 1 freely Rotation, then can store the utility model to such as Fig. 4 state.Locking device further includes that the first return springs are not shown, First return springs can be the devices such as spring, torsional spring, the first return springs be arranged between pedestal 30 and locking piece 7 or Between attachment base 40 and locking piece 7, the first return springs locking piece 7 can be driven mobile by elastic force so that the insertion of inserted block 71 the In one jack 11.The seat stored is unfolded in use, unlock piece 6 turns to the first pushing inclined-plane relative to locking piece 7 70 and the second pushing inclined-plane 60 when being separated from each other, locking piece 7 moves under the elastic force effect of the first dynamic clamping head and quiet clamping head towards mounting base 1 It is dynamic, inserted block 71 is inserted into the first jack 11 to lock mounting base 1 and pedestal 30, keeps seat board 3 solid relative to mounting base 1 It is fixed.

In the present embodiment, manual driving device includes that the second return springs 81, pull-push piece 82 and tie rod are not shown, push-and-pull Part 82 and tie rod are moving up and down to be arranged on backrest plate 4, and the lower end of tie rod is connected with locking pin 5, the upper end of tie rod and Pull-push piece 82 is connected, and pull-push piece 82 can be by manual actuation to pull out locking pin 5 from lock slots 301, the first return springs It can be the devices such as spring, torsional spring, the second return springs 81 are arranged between locking pin 5 and attachment base 40, and second resets bullet Property part 81 by elastic force can drive locking pin 5 be inserted into lock slots 301 in.Pull up pull-push piece 82, can by locking pin 5 from It is pulled out in lock slots 301, unclamps pull-push piece 82, locking pin 5 can be inserted under the action of the elastic force of the second return springs 81 In lock slots 301.The wire rods such as steel wire, nylon rope can be used in tie rod.It is provided in the load-carrying surface of backrest plate 4 and is prolonged diagonally downward by upper The first guide groove 41 stretched, tie rod are slidably disposed in the first guide groove 41.It can be led to tie rod by the first guide groove 41 To reduction resistance increases the mobile smoothness of tie rod and accuracy.

Referring to Fig. 7, it is provided with the second guide groove 401 being aligned with lock slots 301 on attachment base 40, locking pin 5 is slidably Setting in the second guide groove 401.It can be oriented to locking pin 5 by the first guide groove 41, reduce resistance, increase locking pin 5 Mobile accuracy.In order to make the adjustable with the angle of seat board 3 of backrest plate 4, the quantity of lock slots 301 is two or more, Each lock slots 301 are arranged on the side wall of slide opening 302, and be staggered certain angle between each other, and locking pin 5 is from wherein one After exiting in a lock slots 301, backrest plate 4 can turn to locking pin 5 relative to seat board 3 and be aligned with other lock slots 301, Then pull-push piece 82 is unclamped, locking pin 5 can be inserted into the locking being aligned with locking pin 5 under the action of the first return springs To lock backrest plate 4 and seat board 3 in slot 301.Angle between the above-mentioned structure backrest plate 4 made and seat board 3 can divide Shelves are adjusted, and can meet the needs of a variety of sitting postures of baby or sleeping position.

In the present embodiment, mounting base 1 can removably be connect with the vehicle frame 2 of external stroller, be torn open for convenience Dress, mounting base 1 and vehicle frame 2 are clamped by plug-type clamping structure.Two 1 size shapes of mounting base are all the same, two installations Seat 1 is symmetrically disposed in the two sides of seat board 3.Therefore, can be as needed, forward or backwards by the seat in the utility model Ground is mounted on vehicle frame 2, as depicted in figs. 1 and 2；Meanwhile no matter seat is being mounted on vehicle frame 2 forward or backwards, seat cushion Plate 3 and the equal folding storage of backrest plate 4 are very convenient to use to state shown in Fig. 4.

In order to increase the comfort of baby, the front of seat board 3 is pivotable to be provided with foot pedal 31.

In order to guarantee safety, be provided with the guardrail 32 of curved bar shape on seat board 3, the both ends of guardrail 32 respectively with seat cushion The both sides of plate 3 removably connect.In the present embodiment, the both sides of seat board 3 are provided with third jack 33, guardrail 32 Both ends are plugged in respectively in corresponding third jack 33, and lateral button hole, guardrail 32 are provided on the side wall of third jack 33 Both ends are provided with the buckle 34 for the elasticity being used cooperatively with button hole, buckle 34 lower end and are fixedly connected with guardrail 32, buckle 34 Upper end is free end, and the middle part for buckling 34 is provided with lug boss 340 compatible with button hole, and the upper end for buckling 34 extends to third The outside of jack 33 when lug boss 340 is caught in button hole, can lock guardrail 32 and seat board 3, the upper end of pressing buckle 34 When, it can make buckle 34 that elastic deformation occur so that lug boss 340 is exited from button hole.When installing guardrail 32, by the two of guardrail 32 End is inserted into respectively in corresponding third jack 33, and the lug boss 340 on buckle 34 can be automatically caught in corresponding button hole； The upper end for buckling 34 is pressed, guardrail 32 can be extracted from third jack 33.

Referring to Fig. 5, in order to improve comfort, the both sides of seat board 3 are provided with handrail 35；It is provided on backrest plate 4 For installing the cape bracket of awning, cape bracket includes at least two support rods 42, and support rod 42 is in "U" shaped, support Bar 42 is hinged by its both ends and backrest plate 4.

The above is only the preferred embodiments of the utility model, as long as realizing the utility model aim with essentially identical means Technical solution belong within the protection scope of the utility model.

Claims (10)

1. a kind of baby carriage seat for being easy to folding storage characterized by comprising

Two mounting bases (1) arranged side by side, the mounting base (1) can be with the fixed companies of vehicle frame (2) of external stroller It connects；

The rear portion of seat board (3), seat board (3) two sides is provided with pedestal (30), the pivotable installation of the pedestal (30) In be provided on the inside of corresponding mounting base (1), the pedestal (30) for by seat board (3) and mounting base (1) locking Locking device；

The lower part of backrest plate (4), backrest plate (4) two sides is provided with attachment base (40), and the attachment base (40) is pivotable It is installed on the inside of corresponding pedestal (30), is movably set with locking pin (5) on the attachment base (40), the pedestal (30) Inside position corresponding with locking pin (5) offers and locking pin (5) compatible lock slots (301), on the backrest plate (4) It is provided with manual driving device, the locking pin (5) is driven by the manual driving device and can inserted along attachment base (40) Enter and is moved between lock slots (301) and the position for exiting lock slots (301), when the locking pin (5) is inserted into lock slots (301), Pedestal (30) and attachment base (40) can be locked, are provided with unlock piece (6) on the attachment base (40), attachment base (40) phase When for pedestal (30) rotation, the unlock piece (6) can unlock locking device so that seat board (3) can be relative to mounting base (1) it is freely rotated.

2. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the pedestal (30) slide opening (302) with the pivoting axis parallel of the pedestal (30) is provided on, the locking device includes being arranged described Locking piece (7) in slide opening (302) is provided with the first jack (11) on the mounting base (1), is arranged on the locking piece (7) There is the compatible inserted block (71) with first jack (11), the locking piece (7) can be mobile so that inserted block along slide opening (302) (71) it is moved between insertion the first jack (11) and the position for exiting the first jack (11), inserted block (71) insertion first is inserted When in hole (11), pedestal (30) and mounting base (1) can be locked,

It is provided with the first pushing inclined-plane (70) on the locking piece (7), is provided on the unlock piece (6) and is pushed with described first Inclined-plane (70) compatible second pushes inclined-plane (60), and when the unlock piece (6) rotates relative to pedestal (30), described second is pushed away Pressure inclined-plane (60) can be pressed on the first pushing inclined-plane (70) described to push locking piece (7) to be moved to along slide opening (302) Inserted block (71) exits the first jack (11),

The locking device further includes the first return springs, and first return springs are arranged in pedestal (30) and locking piece (7) between or between attachment base (40) and locking piece (7), first return springs can drive locking piece (7) by elastic force Movement is so that in inserted block (71) insertion the first jack (11).

3. a kind of baby carriage seat for being easy to folding storage according to claim 2, which is characterized in that the locking piece (7) it is offered in the middle part of an accommodating hole (72), extended in the accommodating hole (72) is additionally provided on the locking piece (7) One force-bearing piece (73), described first pushes the outside that inclined-plane (70) are located at first force-bearing piece (73), the unlock piece (6) Outside portion has the second force-bearing piece (61) extended in the accommodating hole (72), and described second pushes inclined-plane (60) positioned at described The inside of second force-bearing piece (61).

4. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the manual drive Dynamic device includes the second return springs (81), pull-push piece (82) and tie rod, the pull-push piece (82) and tie rod can on move down On the backrest plate (4), the lower end of the tie rod is connected with the locking pin (5) for dynamic setting, the upper end of the tie rod with The pull-push piece (82) be connected, the pull-push piece (82) can by manual actuation with by the locking pin (5) from lock slots (301) It pulls out, second return springs (81) are arranged between locking pin (5) and attachment base (40), second return springs (81) it can be driven in locking pin (5) insertion lock slots (301) by elastic force.

5. a kind of baby carriage seat for being easy to folding storage according to claim 4, which is characterized in that backrest plate (4) Load-carrying surface on be provided with the first guide groove (41) extended obliquely downward from above, the tie rod is slidably disposed in described In one guide groove (41).

6. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the attachment base (40) the second guide groove (401) being aligned with the lock slots (301) is provided on, the locking pin (5) is slidably arranged In second guide groove (401).

7. a kind of baby carriage seat for being easy to folding storage according to claim 6, which is characterized in that the lock slots (301) quantity is two or more, and the locking pin (5) in one of lock slots (301) after exiting, the backrest plate (4) locking pin (5) can be turned to relative to seat board (3) to be aligned with other lock slots (301).

8. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the mounting base (1) it can removably be connect with the vehicle frame (2) of external stroller, two mounting base (1) size shapes are all the same, and two Mounting base (1) is symmetrically disposed in the two sides of the seat board (3).

9. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the seat board (3) front is pivotable to be provided with foot pedal (31).

10. a kind of baby carriage seat for being easy to folding storage according to claim 1, which is characterized in that the seat cushion The guardrail (32) of curved bar shape is provided on plate (3), the both ends of the guardrail (32) are removable with the both sides of seat board (3) respectively The connection unloaded.