JPH0810090A - Back plate attachment structure to shell plate in chair - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a structure for attaching a back plate to a shell plate in a chair in which the back plate can be easily attached to the shell plate. [Structure] When attaching the back plate 5 to the shell plate 3, a claw-shaped positioning projection 35 is provided on the shell plate 3 side, and a positioning hole 54 of the back plate 5 is hooked therein. After that, the screw 38 is passed through the hole 34 of the shell plate 3 and the back plate 3
To the screw hole 53. Such a positioning protrusion 3
5, the positioning hole 54, the screw hole 53, and the hole 34 are formed one each on the left and right sides of the back plate 5 or the shell plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for attaching a back plate to a shell plate in a chair with a backrest, and more particularly to a structure for simplifying the assembly work.

[0002]

2. Description of the Related Art A chair with a backrest has a structure in which a seat plate and a back plate are screwed and fixed to a shell plate serving as a structural core material integrally formed with a seat plate mounting part and a back plate mounting part. It has been known. The back plate is generally fixed with at least four screws in order to secure its mounting strength.

[0003]

In the chair having such a structure, the back plate needs to be attached to the back plate mounting portion of the shell plate which is slightly inclined rearward. Therefore, unlike the case where the seat plate is placed on the horizontal seat plate mounting part and screwed, the screw holes on the back plate are positioned so that they coincide with the screw holes formed on the shell plate side, and this state is maintained. However, it is necessary to screw it. Therefore, the work of attaching the back plate is more difficult than the case of using the seat plate. Further, if the back plate is fastened to the shell with four screws as in the conventional case, the heads of the four screws are always exposed on the back side of the backrest of the chair, which is unattractive.

On the other hand, if the number of screws can be reduced, the work of attaching the back plate can be simplified.

In view of the above problems, the object of the present invention is to
An object of the present invention is to provide a structure for attaching a back plate to a shell plate in a chair that can easily perform the work of attaching the back plate to the shell plate.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a shell plate as a structural core member in which a seat plate mounting portion and a back plate mounting portion are integrally molded, and this shell plate In a chair having a seat plate and a back plate respectively attached thereto, one of the back plate mounting portion and the back plate of the shell plate is formed with a positioning projection protruding toward the other side, and the other The side is characterized in that a positioning hole for inserting the positioning protrusion is formed, and the shell plate and the back plate are fixed by screws with the positioning protrusion inserted in the positioning hole.

According to this structure, the back plate can be positioned on the shell plate by inserting the positioning protrusion into the positioning hole, and the screw holes formed on both sides can be easily aligned with each other. Therefore, the screwing work can be easily performed. Also, by fitting the positioning projections into the positioning holes, the back plate and the shell plate are fixed, so that the number of screws can be reduced and the screw fixing work can be simplified.

Here, it is preferable that the positioning projection is formed on the side of the back plate mounting portion of the shell plate with its tip facing upward so that the positioning projection can be easily inserted into the positioning hole.

In the present invention, it is preferable that the positioning projection and the positioning hole are formed so that the positioning projection fits into the positioning hole near the mounting position of the screw for fixing the shell plate and the back plate. In this case, when a force that causes deformation such as twisting is applied to the back plate, the positioning projection also receives this force. Therefore, the shearing force of the screw can be reduced, and the strength of the fixed portion is improved.

Further, at a mounting position of a screw for fixing the shell plate and the back plate, a cylindrical portion having an inner side as a screw hole of a screw is projected from a back surface side of the back plate toward a back plate mounting portion of the shell plate. It is preferable to form a fitting hole into which the tubular portion fits in the back plate mounting portion of the shell plate.

According to another aspect of the present invention, a shell plate as a structural core in which a seat plate attaching portion and a back plate attaching portion are integrally formed, and a seat plate and a back plate are attached to the shell plate, respectively. In the chair having the above structure, the lower end of the back plate is extended to the seat portion mounting portion of the shell plate, and is fixed in a state of being sandwiched between the seat plate and the seat portion mounting portion.

With this structure, the back plate can be firmly fixed to the shell plate even by the seat plate, so that the number of screws can be reduced. Therefore, the assembly work is simplified. Moreover, it is possible to attach the back plate and the seat plate without a gap by a simple operation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[Overall Structure of Chair] FIG. 1 is a side view showing the overall configuration of a chair having a seat portion and a backrest portion according to the present embodiment, and FIG. 2 is a shell plate, leg portions, back plate, and It is an exploded perspective view showing the structure of a seat plate.

In FIG. 1, a chair 1 of this example includes a leg portion 2 formed of a pipe and a seat portion 1 located above the leg portion 2.
2 and a backrest portion 13 extending obliquely upward from the rear end of the seat portion 12. The basic shape of the seat portion 12 and the backrest portion 13 is the shell plate 3 as the core material for the structure.
Stipulated in. That is, the shell plate 3 is a polypropylene resin molded product integrally molded along the shape of the chair 1 to be configured, and has a seat plate mounting portion 31 and a back plate mounting portion 32. Of these, the seat plate mounting portion 31
The seat cushion 4 and the seat plate 4 on which the seat upholstery 44 is stretched are attached to the upper surface of the seat 12, and the seat portion 12 is configured. On the other hand, on the front surface of the back plate mounting portion 31 of the shell plate 3,
The back plate 5 with the back cushion 57 and the back upholstery 58 stretched is attached to form the backrest portion 13. Here, the seat body 4 is one hard board, and the back plate 5 is
It is a molded plate made of polypropylene resin. The seat cushion 43 and the back cushion 57 are relatively thick cushion materials made of urethane resin, and the seat cushion 44 and the back cushion 58 are thin sheets made of cloth or vinyl chloride resin.

In FIG. 2, the leg portion 2 includes a front leg pipe 21 forming a pair of front legs 211 on the left and right, and a rear leg pipe 22 forming a pair of rear legs 221 on the left and right, two seats on the left and right sides. It has a structure connected by a pipe 23. Further, the front leg pipe 21 and the rear leg pipe 22 are also connected by leg joint bars 24 and 25 which are connected in two stages at the side. The leg caps 28 are fitted on the front ends of the front legs 211 and the rear legs 221, respectively.

[Structure of Shell Plate] The shell plate 3 is composed of a substantially horizontal seat plate mounting portion 31 and a back plate mounting portion 32 that extends obliquely upward from the rear end so as to warp the rear surface.

The seat plate mounting portion 31 has a substantially quadrangular shape in plan view, but has a curved shape in which the central portion is recessed so that the user can sit in a stable state. Seat plate attachment part 3
1, holes 33 for attaching the seat plates 4 are formed at positions near the four corners, and the reinforcing ribs 3 are provided on the upper surface.
10 are formed vertically and horizontally. The end portion of the seat plate attachment portion 31 is formed as a reinforcing portion 311 having a U-shaped cross section, and the inner region of the reinforcing portion 311 is a portion to which the seat plate 4 is substantially attached.

The back plate mounting portion 32 of the shell plate 3 also has a curved shape whose central portion is recessed so that the user can sit in a stable state. The side end portion of the back plate mounting portion 32 is also formed as a reinforcing portion 320 having a U-shaped cross section.
The inner region of 0 is a portion to which the back plate 5 is substantially attached. The seat plate mounting portion 31 and the back plate mounting portion 32 are
The boundary portion 36 is curved and continuous.

In this example, one hole 34 (fitting hole) for mounting the back plate 5 is formed on the left and right sides at a position near the upper end of the back plate mounting portion 32. Further, one positioning protrusion 35 is formed on the left and right below the convex portion 301. These positioning protrusions 35 are provided on the tip side 3
The reference numeral 52 has a claw shape extending upward from the two base portions 351 and is thin on the front end side 352.

Further, the upper end portion 321 of the back plate mounting portion 32
As shown in an enlarged view of the AA ′ cross section in the frame, is bent toward the rear in an L-shape and functions as a reinforcing rib.

[Structure of Seat Plate] Similar to the seat plate mounting portion 31 of the shell plate 3, the seat plate 4 has a curved shape whose central portion is recessed. The rear end portion 41 of the seat plate 4 is cut into a curved shape along a boundary portion 36 between the seat plate mounting portion 31 and the back plate mounting portion 32. In the vicinity of the four corners of the seat plate 41, the seat plate 4
One screw hole 49 formed by a rosette is formed at a position overlapping with the hole 33 of the shell plate 3 when 1 is stacked on the seat plate attachment portion 31 of the shell plate 3.

[Structure of Back Plate] The back plate 5 has a curved shape in which the central portion is recessed, like the back plate mounting portion 32 of the shell plate 3, and the upper half thereof is more warped than the lower half. It has a curved shape. In the back plate 5, one rectangular positioning hole 54 is formed in the left and right positions near the lower end, and one screw hole 53 is formed in the left and right positions above the rectangular positioning hole 54.

As shown in FIG. 3A, the screw holes 53 are formed at positions where they overlap the holes 34 of the shell plate 3 when the back plate 5 is placed on the back plate mounting portion 32 of the shell plate 3. . The screw hole 53 is configured as an inside of a cylindrical rosette 530, and the tip end side of the rosette 530 (cylindrical portion) has a back plate 5.
It slightly protrudes from the back side of the and fits shallowly into the hole 34. The position where the positioning hole 54 is formed is a position where it overlaps with the positioning projection 35 when the back plate 5 is placed on the back plate mounting portion 32. Here, in the positioning hole 54, both the upper surface 541 and the lower surface 542 of the inner peripheral surface are tapered so that the positioning projection 35 can easily enter.

Referring again to FIG. 2, the back plate 5 has its lower end portion 51 bent from the back plate body portion 50 and extending forward. The protruding width of the lower end portion 51 is wide at the central portion and narrows toward both ends. Further, the lower end portion 51 is formed to have a thickness corresponding to about ½ of the thickness of the back plate body portion 50.

On the other hand, the upper end portion 52 of the back plate 5 has the shell plate 3
Similarly to the upper end portion 321, of the back plate main body portion 50, the back plate main body portion 50 is bent in an L shape and extends rearward, and functions as a reinforcing rib.

Further, on the back side of the back plate 5, as shown in FIG.
As shown in (a) and (b), among the side end portions 55,
The portion near the upper end 52 is a single ridge 56 that forms a step along the side edge from the upper end 52. The ridge portion 56 also functions as a reinforcing rib for the vicinity of the upper end portion 52 of the back plate 5, so that the strength of the back plate 5 is high.

[Structure for Attaching Back Plate to Shell Plate] The back plate 5 and the seat plate 4 as described above are attached to the shell plate 3 after being sewn in a state described later. In the step of attaching the back plate 5 to the shell plate 3, as shown by an arrow G in FIG. 3 (a), the shell plate 3 is positioned while the back plate 5 is being displaced downward with respect to the back plate mounting portion 32. The projection 35 is hooked on the positioning hole 54 of the back plate 5. In this state, the back plate 5
Is positioned on the shell plate 3, the tip end side of the rosette 530 is shallowly fitted into the hole 34 of the shell plate 3, and the back plate 5 is temporarily fixed to the shell plate 3. Then, the screw 38 is passed through the hole 34 of the shell plate 3, and the screw 38 is fixed to the screw hole 53 of the back plate 5 as shown in FIG. It is attached.

As described above, in this example, the shell plate 3 and the back plate 5 can be fixed while being positioned by the positioning projections 35 and the positioning holes 54. Further, since the positioning projections 35 and the positioning holes 54 also exert a force for fixing the back plate 5 to the shell plate 3, two screws 38 are sufficient. Therefore, the assembling work can be simplified, and when the backrest portion 13 is viewed from the back side, the backrest portion 13 has only two screw heads, which is good-looking.

Also, by fitting the tip side of the rosette 530 into the hole 34 of the shell plate 3, the screw hole 53 and the hole 34 are formed.
Can be easily aligned with. Moreover, even if a lateral force is applied to the back plate 5, this force is applied to the rosette 53.
0 is received, and the shearing force applied to the screw 38 is reduced. Therefore, the strength of this fixed portion is high.

As shown in FIGS. 2 and 3 (a) and 3 (b), one hole 59 is formed on the left and right near the lower position of the screw hole 53, while the shell plate 3 side is formed. , Backboard 5
You may form the convex part 301 which fits in the hole 59, when it overlaps with the back plate attachment part 32. Here, the convex portion 301 and the hole 59 may be formed together with the positioning protrusion 35 and the positioning hole 54, but may be formed instead of the positioning protrusion 35 and the positioning hole 54. That is, the back plate 5 can be easily positioned on the shell plate 3 by using the hole 59 as a positioning hole and the convex portion 301 as a positioning protrusion. Moreover, the convex portion 301 is not only inserted into the hole 59,
Since the screw 38 is fitted in the hole 59 near the attachment position, when a force is applied laterally to the back plate 5, the convex portion 301 receives a part of this force. Therefore,
Since the shearing force applied to the screw 38 can be reduced, the strength of the fixed portion is improved.

The positioning projection 35 and the positioning hole 5
The back plate 5 may be positioned on the shell 3 by using both the positioning means for the shell 4 and the positioning means for the convex portion 301 and the hole 59. In addition, the positioning projection 35 and the convex portion 3
01 may be formed not on the shell plate 3 side but on the back plate 5 side. Further, the positioning projection 35 and the convex portion 30
1 may be formed on each side of the shell plate 3 and the back plate 5.

[Back Plate Fixing Structure Using Seat Plate] In this example, as shown in FIG. 5A, a seat cushion 43 is overlaid on the upper surface of the seat plate 5 in the sewing process for the seat plate 4, and The surface is covered with a seat cushion 44. In this case also,
Is cut to be larger than the width of the seat plate 4, so the seat upholstery 44 is folded back to the back side of the seat plate 4 and then fixed by the staples 19 or the like.

The sewn seat plate 4 is shown in FIG. 5 (b).
After attaching the back plate 5 to the shell plate 3 as shown in
The shell plate 3 is superposed on the seat plate mounting portion 31, and fixed by the screw 39 from the lower surface side of the shell plate 3. At this time, since the lower end portion 51 of the back plate 5 is in the state of entering the seat plate mounting portion 31 from the back plate mounting portion 32 of the shell plate 3, the rear end portion 41 of the seat plate 4 is the lower end of the back plate 5. The part 51 is sandwiched between it and the shell plate 3. Therefore, since the back plate 5 is firmly fixed to the shell plate 3, the number of screws for fixing the back plate 5 to the shell plate 3 can be reduced and the assembling work can be simplified.

The sewn back plate 5 and seat plate 4 are
Since the ends are in close contact with each other, it looks good. Moreover, since the lower end portion 51 of the back plate 5 is thin, even if the rear end portion 41 of the seat plate 4 is superposed thereon, the seat plate 4 does not float up.

[Exterior structure of the back plate] In the sewing process for the back plate 5, as shown in FIG. 6 (a), a back cushion 57 is overlaid on the front side of the back plate 5, and the surface thereof is covered with a back pad 58. Cover with. The back cushion 57 is approximately the same size as the width of the back plate 5, but the back stretcher 58 is cut larger than the back plate 5. Therefore, the back stretcher 58 is folded back to the back side at the side end portion 55 of the back plate 5 as shown by the arrow E, and then fixed by the staple 19 or the like as shown in FIG. 6B. It Also, as shown by the arrow F, the back stretcher 58 is
After being folded back to the back side at the upper end portion 52 of the back plate 5, as shown in FIG. 6C, it is fixed with staples 19 or the like. Therefore, on the back side of the back plate 5, near the corners,
The back stretcher 58 has a triple portion T (indicated by a shaded area in the drawing).
Then, a portion S having a single back lining is formed. Therefore,
In the conventional chair, a step is generated on the back surface side of the back plate 5 due to the difference in the number of the back upholstery layers 58 overlapped with each other, so that a finish is unsatisfactory such as a gap between the back plate 5 and the shell plate 3. In this example, such a problem is solved.

That is, in this example, the ridge portion 56 is formed on the back surface side of the back plate 5, and the ridge portion 56 forms the back stretcher 5.
8 is made to be a single layer, and the back upholstery 58 is made to be triple at a position adjacent to the ridge 56. As a result, the portion S (the surface of the protruding portion 56) where the back stretcher 58 is single is in a state of being raised by an amount corresponding to the height of the protruding portion 56,
The difference in thickness from the triple portion T is corrected. Therefore, in this example, even when the back stretcher 58 is folded back to the back side of the back plate 5, the back side of the back plate 5 is finished flat, so that a gap is generated between the back plate 5 and the shell plate 3. Absent.

Further, as shown in FIG. 7A, the upper end 52 of the back plate 5 is bent in an L-shape on the back side along the upper end 321 of the shell plate 3, so that the upper end of the shell plate 3 is bent. And the upper end 52 of the back plate 5 completely overlap each other. Therefore, the back cushion 57 can be turned up to the upper end of the backrest 13, so that the finish of the upper end is beautiful and the sitting comfort is good. Further, on either side of the back plate 5 and the shell plate 3, the upper end portions 52 and 321 function as reinforcing ribs, and the bending strength of the back plate 5 and the shell plate 3 is high. Even when a force for peeling from 3 is applied, the back plate 5 is difficult to peel from the shell plate 3.

Here, as shown in FIG. 7B, the back plate 5
When the ridge portion 521 protruding downward is formed along the tip edge of the upper end portion 52 of the back plate 5, the upper end portion 52 of the back plate 5 is formed.
The back stretcher 58 folded back at is hidden by the ridge portion 521. Therefore, the finish at the upper end of the backrest 13 is further improved, and the bending strength of the backboard 5 is further improved.

[Structure of Attaching Shell Plate to Legs] In this example, when fixing the shell plate 3 and the legs 2 to each other, as shown in FIG.
The structure shown in (a) and (b) is adopted.

First, in FIG. 8A, in the seat receiving pipe 23 of the leg portion 2, the tip portion 231 is in a state of further projecting forward from the portion fixed to the front leg 21. On the contrary, the rear end portion 232 of the seat receiving pipe 23 is in a state of further protruding rearward from the portion fixed to the rear leg 22. The front end portion 231 and the rear end portion 232 have holes 23 on the lower surface side.
4, 235 are formed. On the other hand, on the back surface side of the seat portion of the shell plate 3, a pair of front and rear tubular portions 36 and 37 are formed in front and back on either the left or right side. Holes 361 and 371 are formed in the tubular portions 36 and 37, respectively.

Further, in the inner part of the rear tubular portion 37, as shown in FIG.
As shown in (b), a receiving plate 372 is formed, and the receiving plate 372 projects toward the insertion port 370 side of the rear tubular portion 37. The receiving plate 372 extends in the axial direction of the tubular portion 37 at a substantially central position in the tubular portion 37, and its width dimension is
It is smaller than the inner diameter of the seat receiving pipe 23. For this reason,
The rear end portion 23 of the seat receiving pipe 23 is provided inside the rear tubular portion 37.
When the 2 is inserted, the backing plate 372 has the rear end portion 23
It is designed to get inside the 2. Also, the receiving plate 3
72 has a hole 3 at a position overlapping the hole 371 of the rear tubular portion 37.
73 is formed.

In the leg portion 2 and the shell plate 3 thus configured, first, after the tip portion 231 of the seat receiving pipe 23 is deeply inserted into the front tubular portion 36 of the shell plate 3,
When the leg portion 2 (seat receiving pipe 23) is displaced rearward, the rear end portion 232 of the seat receiving pipe 23 is fitted inside the rear tubular portion 37. Further, the front and rear positions of the leg portion 2 (seat receiving pipe 23) are adjusted so that the holes 234 and 235 of the seat receiving pipe 23 are adjusted.
Position, and the front tubular portion 36 and the rear tubular portion 3 of the shell plate 2.
When the positions of the holes 361 and 371 of No. 7 are aligned, the receiving plate 372 enters the inside of the rear end portion 23. After that, through the holes 361 and 371 of the shell plate 2 from the outside,
Insert the tap screw 29 into the holes 234 and 235 of the seat receiving pipe 23.
Then, the shell plate 3 and the leg portion 2 are fixed. At this time, the tap screw 29 also stops in the hole 373 of the receiving plate 372.

As described above, in this embodiment, the seat receiving pipes 23 of the leg portion 2 are fixed by the tap screws 29 while being received in the front and rear at two places in the cylinder. Therefore, even if the tap screws 29 come off, the seat portion 12 (shell plate 3) does not fall off the leg portion 2. In addition, the tap screw 29 has a hole 37 in the rear tubular portion 37.
1 and the hole 373 of the receiving plate 372, it is hard to come off. In this case, since the receiving plate 372 enters the inside of the seat receiving pipe 23, the safety can be improved with a simple structure.

[0045]

As described above, in the back plate mounting structure for a shell plate according to the present invention, the positioning projection is fitted between the shell plate and the back plate and screwed in the positioning hole. It is characterized by Therefore, according to the present invention, by fitting the positioning protrusion into the positioning hole,
Since the screws can be fixed while the shell plate and the back plate are positioned, the assembling work is easy. Further, even when the positioning projection is fitted into the positioning hole, a force for fixing the back plate to the chair shell plate works, so that the number of screws can be reduced. Therefore, the number of screw heads exposed on the back surface of the chair is small, so that the appearance is good.

When the positioning projection is fitted into the positioning hole near the screw mounting position, the force applied to the back plate is also supported by the positioning projection, so that the shearing force applied to the screw can be reduced. .

When the lower end of the back plate is sandwiched between the seat plate and the seat mounting portion, the back plate is also fixed to the shell plate by the seat plate. Can be reduced. Further, at the boundary portion between the back plate and the seat plate, the ends are joined together without a gap, so that the appearance is good.

[Brief description of drawings]

FIG. 1 is a side view of a chair according to an embodiment of the present invention.

FIG. 2 is an exploded view showing structures of a leg portion, a shell plate, a seat plate, and a back plate used in the chair shown in FIG.

3 (a) and 3 (b) are cross-sectional views showing an essential part of the structure for attaching the back plate to the shell plate shown in FIG.

4 (a) is an enlarged perspective view showing an upper end portion and a part of a side end portion of the back plate shown in FIG. 2, and FIG.
It is sectional drawing in a C'line.

5A is a process diagram showing a step of sewing the seat plate shown in FIG. 2, and FIG. 5B is a sectional view showing a state where the seat plate is attached to the shell plate.

6A to 6C are process diagrams showing a sewing process for the back plate shown in FIG.

7A is an explanatory view showing a state in which a back plate is attached to the shell plate shown in FIG. 2, and FIG. 7B is a sectional view showing an improved back plate.

8A is an explanatory view showing a fixing structure of the shell plate and the leg portion shown in FIG. 2, and FIG. 8B is a sectional view of the fixing portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Chair 12 ... Seat 13 ... Backrest 2 ... Leg 23 ... Seat receiving pipe 3 ... Shell plate 301 ... Convex part (positioning protrusion) 31. ..Seat mounting part 32 ... back plate mounting part 321 ... upper end part of back plate mounting part 34 ... hole (fitting hole) 35 ... positioning projection 351 ... base part 36 ... -Front cylinder part 37 ... Rear cylinder part 39 ... Hole (positioning hole) 4 ... Seat plate 41 ... Rear end part of seat plate 5 ... Back plate 51 ... Lower end of back plate Part 52 ... Upper end of back plate 54 ... Positioning hole of back plate 53 ... Screw hole of back plate 530 ... Rosette (cylindrical part)

Claims (5)

[Claims] 1. A shell plate as a structural core material in which a seat plate mounting portion and a back plate mounting portion are integrally molded, and a chair having a structure in which a seat plate and a back plate are mounted on the shell plate, respectively. One of the back plate attachment portion and the back plate of the shell plate is formed with a positioning projection protruding toward the other side, and the other side is formed with a positioning hole into which the positioning projection is inserted. The shell plate and the back plate are screwed and fixed in a state where the positioning projection is inserted into the positioning hole, and a back plate mounting structure for a shell plate in a chair. 2. The shell plate of a chair according to claim 1, wherein the positioning projection is formed so that a tip end thereof is directed upward toward a back plate mounting portion of the shell plate. Back plate mounting structure. 3. The positioning projection and the positioning hole according to claim 1, wherein the positioning projection fits into the positioning hole near a mounting position of a screw that fixes the shell plate and the back plate. A structure for attaching a back plate to a shell plate in a chair, which is characterized in that 4. The tubular portion having an inner side as a screw hole of the screw at a mounting position of a screw for fixing the shell plate and the back plate according to any one of claims 1 to 3. It is formed so as to project from the rear surface side of the plate toward the back plate mounting portion of the shell plate, and the back plate mounting portion of the shell plate is provided with a fitting hole into which the tubular portion is fitted. Back plate attachment structure to the shell plate in the characteristic chair. 5. A shell plate as a structural core in which a seat plate mounting portion and a back plate mounting portion are integrally molded, and a chair having a structure in which the seat plate and the back plate are mounted on the shell plate, respectively. A shell plate in a chair, wherein a lower end portion of the back plate is extended to a seat mounting portion of the shell plate and is sandwiched between the seat plate and the seat mounting portion. Back board mounting structure.