Chair seat structure

Abstract

In a chair where the seat moves backward and tilts backward in conjunction with the backward tilting of the backrest, the backward tilt of the seat when the backrest is tilted backward is made less noticeable. [Solution] A chair in which the seat 4 moves backward and tilts backward in conjunction with the backward tilting of the backrest 5, wherein the backrest 5 is provided in a substantially U-shape with a forward-facing opening that surrounds the rear edge 41 and the left and right side edges 42 of the seat 4 in a plan view, and comprises a back plate portion 51 disposed behind the rear edge 41 of the seat and armrest portions 52 disposed to the left and right outer sides of the left and right side edges 42 of the seat. In a side view, the armrest portions 52 cover the seat 4 from the portion in front of the center of the side edges 42 in the front-rear direction to the rear edge 41 of the seat.

Description

TECHNICAL FIELD

[0001] The present invention relates to a chair, and more particularly to a chair in which a seat moves backward and tilts rearward in conjunction with rearward tilting of a backrest. BACKGROUND ART

[0002] As one type of rocking chair, there is a synchro type in which when the backrest tilts rearward (rocks), the seat also moves backward and tilts rearward together. This synchro type chair can improve comfort during rocking by the rearward tilting of the seat, and can prevent the phenomenon of a shirt being rolled up and back slippage due to the seat moving backward. For this reason, it is widely used in office chairs. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2003-135204 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] However, in conventional chairs, while the comfortable posture in which the backrest and the seat are tilted rearward allows the seated person to relax, it also appears to be overly relaxed from the surrounding view, so there is room for improvement in that the seated person hesitates to assume the comfortable posture while being concerned about the surrounding gazes.

[0005] The present invention has been made to improve such a current situation, and an object of the present invention is to provide a chair in which the rearward tilting of the seat when the backrest is tilted rearward is less likely to be visually recognized. MEANS FOR SOLVING THE PROBLEMS

[0006] The present invention relates to a chair in which the seat moves backward and tilts backward in conjunction with the backward tilting of the backrest, wherein the backrest is provided in a substantially U-shape with a forward-facing opening that surrounds the rear edge and left and right side edges of the seat in a plan view, and comprises a back plate portion disposed behind the rear edge of the seat and armrest portions disposed to the left and right outer sides of the left and right side edges of the seat, wherein the armrest portions, in a side view, cover the seat from a portion in front of the center of the front-to-back direction of the side edges of the seat to the rear edge of the seat.

[0007] In the chair of the present invention, since the armrests of the backrest cover the sides of the rear half of the seat, the backward tilt of the seat when the backrest is tilted backward is less visible from the surroundings of the chair. As a result, the sitter can tilt the backrest and seat backward and assume a relaxed posture without worrying about being seen by those around them, thus improving comfort.

[0008] In the chair of the present invention, the armrest portion may cover 60% or more of the front-to-back length of the seat when viewed from the side.

[0009] In this configuration, a portion of the buttocks and thighs of a sitter who is seated deeply in the seat can be hidden from a side view, making it difficult for those around to perceive the sitter's posture when the backrest and seat are tilted backward. As a result, the sitter can adopt a relaxed posture with the backrest and seat tilted backward without worrying more about being seen by others.

[0010] In the chair of the present invention, the armrest portion may be such that the upper edge of the armrest is substantially straight or curved in an upward convex shape, and is inclined diagonally upward from the front edge of the armrest to the rear edge of the armrest.

[0011] In this configuration, when viewed from the side, the upper edge of the armrest is positioned higher than the rear edge of the armrest. This allows the sitter's body to be more concealed when the backrest is tilted backward, and the sitter's posture becomes less noticeable, allowing the sitter to relax with peace of mind.

[0012] In the chair of the present invention, the back of the backrest may be curved in a rearward convex shape when viewed from the side.

[0013] In this configuration, when viewed from the side, the back of the backrest (the back of the back panel) is curved in a backward-facing convex shape, making it difficult for those around to notice the backward tilt of the backrest. As a result, the sitter can tilt the backrest backward and assume a relaxed posture without worrying about being seen by others. [Effects of the Invention]

[0014] In a chair in which the seat moves backward and tilts backward in conjunction with the backward tilting of the backrest, the backward tilt of the seat when the backrest is tilted backward can be made less noticeable. [Brief explanation of the drawing]

[0015] [Figure 1] In this embodiment, (A) is a front view and (B) is a perspective view of the chair. [Figure 2] (A) is a top view of the chair, and (B) is a rear view. [Figure 3] This is a right side view of the chair. [Figure 4] This is a right side view of the chair in the rocking position. [Figure 5] This is a decomposed perspective view of the seat. [Figure 6] This is a plan view showing the seat support member and the rocking mechanism. [Figure 7] This is an exploded perspective view of the locking mechanism. [Figure 8] This is a longitudinal cross-sectional view at position AA in Figure 2(A). [Figure 9] This is a longitudinal cross-sectional view showing the locking state. [Figure 10] This is a longitudinal cross-sectional view showing the seated position. [Modes for carrying out the invention]

[0016] Next, embodiments of the present invention will be described based on the drawings. In the following description, the terms "front-rear" and "left-right" are used to specify directions, and these terms of front-rear and left-right are based on a seated person for the chair embodiment. The front viewing direction is the direction facing the seated person, and therefore, the left and right in front view are opposite to the left and right as seen from the seated person.

[0017] (1). Outline of the chair First, the outline of the chair will be described mainly based on FIGS. 1 to 3. The present embodiment is applied to a swivel chair widely used for office purposes and the like, and the chair includes a leg device 2 having a leg support 1 and casters, a base body 3 fixed to the upper end of the leg support 1, a seat 4 arranged on the base body 3, and a backrest 5 against which a seated person can lean. The base body 3, the seat 4 and the backrest 5 are provided substantially symmetrically in the left-right direction.

[0018] The base body 3 is formed in a box shape opening upward. The backrest 5 is provided in a substantially U-shape (substantially U-shaped in plan view) with a forward opening so as to enclose the seat rear edge portion 41 and the left and right seat side edge portions 42 of the seat 4 in plan view, and includes a back plate portion 51 and left and right armrest portions 52. Although details will be described later, the backrest 5 is supported by the base body 3 so as to be tiltable rearward. The chair of the present embodiment is a synchronous type rocking chair in which when the backrest 5 tilts rearward (rocks), the seat 4 also moves rearward and tilts rearward together.

[0019] (2). Outline of the seat For example, as shown in FIG. 5, the seat 4 includes a seat receiving member 6 made of a metal plate attached to a load applying arm 24 of a rocking mechanism 20 to be described later. A resin seat inner shell 7 is connected to and supported by the seat receiving member 6. A seat cushion material 8 is disposed overlaid on the upper surface of the seat inner shell 7. The seat cushion material 8 is covered with a skin material 10 such as a fabric.

[0020] The seat inner shell 7 is supported at its left and right edges by the seat support members 6, and its central part is configured to sink downward under the weight of the occupant. For example, the seat inner shell 7 is provided with numerous slits 7a so that it can flex freely according to the occupant's sitting posture. The arrangement area of ​​the slits 7a, as well as the shape and size of each slit 7a, can be changed as appropriate.

[0021] In this embodiment, the seat inner shell 7 is supported by the seat support member 6 via elastic bodies 11 (for example, chrysalis or springs) provided at the four corners of the lower surface of the seat inner shell 7, and the seat inner shell 7 is provided to be able to tilt forward, backward, left and right in accordance with the weight shift when seated. However, the seat inner shell 7 can also be supported by the seat support member 6 without the interposition of the elastic body 11.

[0022] A lower cushioning material 9 is positioned between the seat inner shell 7 and the seat support member 6. The material of the lower cushioning material 9 is not particularly limited, but for example, recycled cushioning (chip urethane) or a three-dimensional mesh fiber structure can be used. The lower cushioning material 9 is housed in a receiving recess 61 provided at the rear of the central part of the seat support member 6. In this embodiment, the receiving recess 61 is located below the seater's buttocks 100 (see Figure 10).

[0023] As shown in Figure 10, when a person sits on the seat 4, the seat cushion material 8 undergoes elastic compression deformation and the seat inner shell 7 sinks in, and the lower cushion material 9 undergoes elastic compression deformation in response. In this embodiment, the seat 4 undergoes elastic deformation of both the seat cushion material 8 and the lower cushion material 9 when seated, thus improving cushioning and preventing the seat inner shell 7 from bottoming out even if it deforms significantly, thereby improving seating comfort.

[0024] Furthermore, since the seat 4 can withstand the seating load with the lower cushioning material 9, the seat inner shell 7 can sink in well (become more prone to bending deformation), creating a comfortable seat that envelops the buttocks when seated. In addition, by appropriately selecting the elastic force of the lower cushioning material 9, the amount of compressive deformation of the lower cushioning material 9 when seated, i.e., the amount of sinking of the seat 4, can be controlled.

[0025] As shown in Figure 8, etc., in this embodiment, the upper surface 91 of the lower cushion material 9 (the contact surface with the seat inner shell 7) is slightly curved in a concave shape. By appropriately designing the shape of the upper surface 91 of the lower cushion, the shape of the seat inner shell 7 when seated can be controlled not only by the restorative force of the seat inner shell 7 itself but also by the restorative force of the lower cushion material 9, and the shape of the seat inner shell 7 when seated can be designed to be a desired shape.

[0026] In this embodiment, the seat support member 6 and the seat inner shell 7 are connected in a way that prevents detachment and allows for disassembly by fasteners such as screws (not shown). This makes it possible to replace the lower cushion material 9, allowing users to select their preferred level of cushioning by replacing the lower cushion material 9, thus making it user-friendly. Furthermore, when the cushioning of the lower cushion material 9 deteriorates due to aging or other reasons, the cushioning of the seat 4 can be restored by replacing the lower cushion material 9 with a new one.

[0027] (3) Overview of backrests As shown in Figures 3 and 8, the backrest 5 is connected to the base body 3 via a back connecting arm 12 and a back connecting member 13 so as to be able to tilt backward. As described above, the backrest 5 is provided in a roughly U-shape with a forward-facing opening that surrounds the rear edge 41 and the left and right side edges 42 of the seat 4 in a plan view, and comprises a back plate portion 51 positioned behind the rear edge 41 of the seat 4, and left and right armrest portions 52 positioned to the left and right outer sides of the left and right side edges of the seat 4.

[0028] The back of the back panel 51 is curved in a rearward convex shape when viewed from the side. Also, as shown in Figure 2(A), in a plan view, the back of the back panel 51 is curved in a rearward convex shape, and the outer surface of the armrest 52 is curved in an outward convex shape. Thus, the backrest 5 has an overall rounded shape.

[0029] The lower edge 51a of the backrest 51 and the lower edge 52a of the armrest 52 are positioned at a height lower than the upper surface 44 of the seat 4. In this embodiment, the lower edge 51a of the backrest 5 and the lower edge 52a of the armrest are curved inward from the side of the seat 4 diagonally downward and positioned below the rear edge 41 and the left and right side edges 42 of the seat 4.

[0030] As shown in Figure 3, in a side view, the armrest 52 covers the seat 4 from the front part of the seat edge 42 (the part on the front edge 43 side) to the rear edge 41. In this embodiment, in both the unrocked state (see Figure 3) and the rocked state (see Figure 4), in a side view, the armrest 52 covers the seat 4 such that the rear half or more of the upper part of the seat edge 42 (for example, more than 60% of the front-to-back length of the seat 4) is hidden. In other words, in a side view, the armrest 52 covers more than 60% of the front-to-back length of the seat top surface 44.

[0031] As shown in Figure 2, the rear end portion of the upper armrest portion 52b of the armrest portion 52 is seamlessly connected to both the left and right ends of the upper armrest portion 51b of the backrest portion 51 without any step. The upper armrest portion 51b is provided in a roughly horizontal position and curved in a rearward convex shape. The upper armrest portion 52b curves outward in a left and right convex shape and slopes diagonally upward in a roughly straight line (or an upward convex curve) from the front armrest portion 52c to the rear armrest portion 52d.

[0032] Although detailed illustrations are omitted, the backrest 5 comprises a core material, a back cushion material covering at least the inward-facing surface of the core material, and a surface material such as cloth covering the entire surface of the backrest 5. A back connecting member 13 is fixed to the inward-facing surface of the lower edge 51a of the backrest. The backrest 5 is supported by the base body 3 by the back connecting member 13 and the back connecting arm 12 of the rocking mechanism 20 provided inside the base body 3 being connected.

[0033] (4) Overview of the locking mechanism As shown in Figures 5 to 7, a rocking mechanism 20 for supporting the backrest 5 so that it can tilt backward is housed inside the metal base body 3. The base body 3 has a base body bottom 31 that is roughly rectangular in plan view, and left and right base body sides 32 that extend upward from the left and right edges of the base body bottom 31. An arm housing portion 33 for housing the back connecting arm 12 is recessed and bulges downward in the left-right center of the rear part of the base body bottom 31. A cylindrical leg support connecting portion 34 into which the upper end of the leg support 1 is inserted and fixed is provided integrally with the front surface of the arm housing portion 33 on the lower surface of the base body bottom 31.

[0034] The locking mechanism 20 is generally arranged symmetrically. The rear connecting arm 12, which constitutes a part of the locking mechanism 20, comprises a rear arm 12a extending in the left-right direction, a pair of forward-facing arms 12b extending forward from both ends of the rear arm 12a, and a connecting arm 12c extending in the left-right direction and connecting the intermediate parts of the left and right forward-facing arms 12b.

[0035] The rear arm 12a is made of metal and has a U-shaped cross-section with a downward-facing opening. The back connecting member 13 is connected to the upper surface of the rear arm 12a by fasteners such as screws. The forward arm 12b is formed of an upward-facing, roughly V-shaped metal plate, with its rear end fixed to the rear arm 12a and its front end rotatably connected to a support shaft 21 that extends in the left-right direction.

[0036] The support shaft 21 is made of a metal rod and is fixed to the base body 3 in a horizontal position by a support shaft fixing device 22 provided inside the arm housing portion 33 of the base body 3. The front part of the forward-facing arm 12b, which is pivotally supported on the support shaft 21, is located inside the arm housing portion 33, while the rear part of the forward-facing arm 12b and the rear arm 12a are located near the outside of the rear of the base body 3. The forward-facing arm 12b is positioned in an inclined position with the front lower and the rear higher. The rear connecting arm 12 is connected to the base body 3 so as to be rotatable around the support shaft 21.

[0037] The connecting arm 12c is made of metal and is provided in a roughly box shape with an upward opening. It is provided to be longer in the left-right direction than the distance between the left and right forward-facing arms 12b, and both left and right ends of the connecting arm 12c protrude outward from the left and right forward-facing arms 12b. The left and right side portions of the connecting arm 12c are provided with rear pin support portions 12d that extend upward. The rear pin support portions 12d have rear pin support holes 12e that open in the left-right direction for supporting the left and right inner ends of the rear pin member 23 that extends in the left-right direction.

[0038] Within the base body 3, a pair of left and right load-applying arms 24 extending in the front-rear direction are arranged along the side portion 32 of the base body. The load-applying arms 24 are made of metal and have a linear shape, extending from near the front edge to near the rear edge of the base body 3. The front half portion 24a of the load-applying arms 24 is provided in a substantially U-shaped cross-section with a downward opening, and the rear half portion 24b of the arms is provided in a pair of left and right plate-like shapes extending rearward from the left and right side portions of the front half portion 24a, respectively. The seat receiving member 6 of the seat 4 is connected to the left and right load-applying arms 24 via connecting members (not shown) or directly by fastening means such as bolts or welding.

[0039] The rear end of the rear half 24b of the arm is provided with a pair of left and right rear pin support holes 24c through which the rear pin member 23 is inserted, and is located on the left and right outer sides of the rear pin support portion 12d of the back connecting arm 12. By inserting the elongated rear pin member 23 through the rear pin support holes 12e and 24c and supporting it in a way that prevents it from coming loose, the load-applying arm 24 and the back connecting arm 12 are connected so that they can rotate relative to each other around the rear pin member 23.

[0040] A front pin member 25 extending in the left-right direction is horizontally mounted on the front half 24a of the load-applying arm 24, between the left and right side portions. Upward-facing convex load-applying arm connecting portions 35 are provided protruding from each of the left and right front corner portions of the base body bottom portion 31. The load-applying arm connecting portion 35 is made of metal and has a front pin support elongated hole 35a that opens in the left-right direction and extends in the front-rear direction. In this embodiment, the front pin support elongated hole 35a is formed of a resin or resin bushing member supported by the load-applying arm connecting portion 35.

[0041] The front half 24a of the load-applying arm 24 is placed over the load-applying arm connecting portion 35 from above, while the front pin member 25 is inserted through the front pin support elongated hole 35a. As a result, the load-applying arm 24 is supported with respect to the load-applying arm connecting portion 35 so as to be rotatable around the front pin member 25 and so as to be able to move back and forth. The front pin support elongated hole 35a restricts the range of movement of the load-applying arm 24 in the back and forth direction between a forward movement limit position where the front pin member 25 is positioned at the front end of the front pin support elongated hole 35a and a backward movement limit position where the front pin member 25 is positioned at the rear end of the front pin support elongated hole 35a.

[0042] The front half 24a of the left and right load-applying arms 24 are connected by a front spring support member 26 that extends in the left-right direction. The front spring support member 26 is formed, for example, from a metal rod, and both left and right ends are connected to the portion of the left and right front half 24a of the arms that supports the front pin member 25.

[0043] On the base body 3, at the bottom 31 of the base body, metal rear spring support members 27 are erected on the left and right sides of the base body, respectively, which in a plan view enclose the leg support connecting portion 34. Between the pair of left and right rear spring support members 27 and the front spring support member 26, a pair of left and right spring bodies 28 are arranged. The spring bodies 28 are for providing resistance to the backward tilting of the backrest 5, and in this embodiment, they are composed of compression coil springs arranged to be inclined in a front-high, rear-low posture along the front-rear direction. The spring bodies 28 are interposed in a compressed state between the front and rear spring support members 26 and 27, with their front ends abutting against the left and right edges of the front spring support member 26 and their rear ends abutting against the front surface of the rear spring support member 27.

[0044] As shown in Figure 8, the rocking mechanism 20 biases the front spring receiving member 26 forward by the elastic force of the spring body 28, thereby positioning the left and right load-applying arms 24 at their forward movement limit. As a result, the rocking mechanism 20 maintains the backrest 5 in an upright position (initial position when unloaded) and the seat 4 in a nearly horizontal position in the forward position.

[0045] As shown in Figures 4 and 9, when a seated person H leans against the backrest 5 and a rearward load is applied to the backrest 5, the backrest connecting arm 12 and backrest connecting member 13 rotate downward around the pivot shaft 21. Then, the load-applying arm 24 connected to the backrest connecting arm 12 and the front spring-receiving member 26 fixed to the load-applying arm 24 rotate around the front pin member 25 and are pulled backward, causing the spring body 28 to compress and deform. The seat-receiving member 6 fixed to the load-applying arm 24 moves backward and tilts backward together with the load-applying arm 24. In this way, the rocking mechanism 20 supports the backrest 5 so that it can tilt backward against the elastic force of the spring body 28, and also supports the seat 4 so that it can move backward and tilt backward. The chair of this embodiment is a so-called ankle-move synchronized rocking type, in which, when a seated person H reclines the backrest 5, the angle of the backrest 5 and the seat 4 tilt in conjunction, allowing the posture of the lower limbs and upper body to be changed effortlessly, with the ankles acting as a pivot point for rotation while the soles of the feet remain on the ground. Specifically, the seat surface 44 of the seat 4 moves backward and tilts backward in conjunction with the backward tilting of the backrest 5.

[0046] The range of backward tilt of the backrest 5 is limited by a front pin member 25 that is movable in the front-to-back direction within a front pin support elongated hole 35a. As shown in Figures 3 and 4, the armrest 52 covers the seat 4 from the front of the seat edge 42 to the rear edge 41 in a side view, so when the backrest 5 is tilted backward (see Figure 4), the backward tilt of the seat 4 is less visible from around the chair. Also, in the rocking position (see Figure 4), the armrest 52 covers the seat 4 in a side view, so that it hides more than the rear half of the upper part of the seat edge 42 (for example, more than 60% of the front-to-back length of the seat 4), so the posture of the sitter H's thighs, buttocks, and abdomen is less visible. As a result, the sitter H can tilt the backrest 5 and seat 4 backward and assume a relaxed posture without worrying about being seen by others, thus improving comfort.

[0047] Furthermore, the armrest portion 52 has an upper edge portion 52b that is roughly straight, and an upward slope from the front edge portion 52c to the rear edge portion 52d. In a side view, the upper edge portion 52b is positioned higher towards the rear edge portion 52d. As a result, as shown in Figure 4, the body of the sitter H can be better concealed when the backrest 5 is tilted backward, and the posture of the sitter H is less noticeable, allowing the sitter H to relax with peace of mind.

[0048] Furthermore, in this embodiment, the back of the backrest 5 (the back of the back panel 51) is curved in a backward-facing convex shape when viewed from the side, making it difficult for those around to notice the backward tilt of the backrest 5 (see Figure 4). As a result, the sitter H can tilt the backrest backward and assume a relaxed posture without worrying about being seen by those around them.

[0049] Furthermore, as shown in Figures 1 to 3 and Figure 8, when the backrest 5 is in its initial position with no load, the lower edge 52a of the armrest 52, which tilts backward together with the backrest 51, is located below the seat surface 44. Even when the backrest 5 is tilted backward to its maximum extent (see Figures 4 and 9), the lower edge 52a of the armrest 5 is configured to be located below the upper surface of the seat 4.

[0050] In other words, the backrest 5 is supported by the base body 3 so as to be able to tilt backward, such that even when the backrest 5 changes its position, the lower edge 52a of the armrest does not remain above the upper surface of the seat 4. This prevents foreign objects from getting caught between the armrest 5 and the seat 4 when a sitter H sitting on the seat 4 tilts the backrest 5 backward, thus ensuring safety and making it user-friendly. In addition, when the backrest 5 is in its initial position without load, the lower edge 52a of the armrest 5 is positioned below the seat 4, making the base body 3 less visible when the chair is viewed from the side, thus providing a good appearance.

[0051] (5) Seat configuration As described above, the seat 4 comprises a seat support member 6, a seat inner shell 7, a seat cushion material 8, and a surface material 10 (see Figures 5, 8, etc.). As shown in Figure 8, the seat cushion material 8 is made of an elastic material such as urethane and has a seat cushion recess 81 on its lower surface that accommodates the seat inner shell 7.

[0052] The seat cushion recess 81 is provided to a depth that accommodates the upper part of the base body 3 when the seat cushion material 8 is attached to the seat support member 6 with the seat inner shell 7 interposed therebetween. The seat cushion material 8 may be integrally molded with the seat inner shell 7 by insert molding, or the seat inner shell 7 may be housed and positioned in the seat cushion recess 81 after molding. Furthermore, the seat cushion material 8 is not limited to a molded product, but may be a sheet-like elastic material stretched over the seat inner shell 7.

[0053] As shown in Figures 5 and 6, the seat support member 6 is approximately rectangular in plan view and has a receiving recess 61 in the center for accommodating the lower cushion material 9. The receiving recess 61 is provided in the left and right center of the seat support member 6, extending from the front to the rear, with the first receiving recess 62 provided in the rear portion being deeper than the second receiving recess 63 provided in the front portion. The seat support member 6 has a shape in which the center of the front edge is cut out and the left and right front edge side ends 64 protrude forward, and the front edge of the receiving recess 61 is open toward the front.

[0054] As shown in Figures 8 and 9, the receiving recess 61 is provided in the seat support member 6 in a downward-facing convex recess shape so as not to interfere with the locking mechanism 20. In this embodiment, the receiving recess 61 is provided extending from the front edge to the rear edge portion of the center of the seat support member 6 in the left-right direction. The first receiving recess 62, recessed in the rear edge portion, is provided above the arm receiving portion 33 at a depth that does not interfere with the back connecting arm 12. The second receiving recess 63, recessed in the front edge portion, is provided above the left and right spring bodies 28 and the space between them at a depth that does not interfere with the spring bodies 28.

[0055] In the seat 4, the first receiving recess 62 is located below the seater's buttocks 100 (see Figure 10). The second receiving recess 63 is located in the center of the seat 4, connected to the front of the first receiving recess 62. The seat support member 6 has openings 65 that open vertically on the left and right sides of the first receiving recess 62. The left and right openings 65 ensure ventilation between the seat cushion material 8 and the base body 3 through the slits 7a of the seat inner shell 7. At the four corners of the seat support member 6, there are downward-facing convex recesses 66 for positioning and supporting the elastic body 11 interposed between the seat support member 6 and the four corners of the seat inner shell 7.

[0056] As shown in Figures 5 and 8, the lower cushion material 9 housed in the housing recess 61 is approximately rectangular in plan view and comprises a first lower cushion portion 92 housed in the first housing recess 62 and a second lower cushion portion 93 housed in the second housing recess 63. The first lower cushion portion 92 is thicker than the second lower cushion portion 93. That is, the thickness of the first lower cushion portion 92, which is positioned below the seated person's buttocks 100 (see Figure 10), is greater than the thickness of the second lower cushion portion 93 (the other part). The left and right edges of the first lower cushion portion 92 housed in the first housing recess 62 are positioned to overlap the opening 65 without interfering with the rocking mechanism 20.

[0057] As described above with reference to Figure 10, when a person sits on the seat 4, the seat cushion material 8 undergoes elastic compression deformation and the seat inner shell 7 sinks in, and the lower cushion material 9 undergoes elastic compression deformation in response. In this embodiment, the thickness of the first lower cushion portion 92, which is positioned below the seater's buttocks 100, is greater than the thickness of the second lower cushion portion 93 (other parts). By increasing the thickness of the lower cushion material 9 in the area of ​​the seat 4 where a large seating load is applied, the seating load can be reliably supported by the lower cushion material 9, and the cushioning when seated can be improved.

[0058] Although specific examples of the present invention have been described above, the present invention can be embodied in various other ways. The configuration, arrangement, numerical values, shape, materials, etc. in the embodiments are examples only, and the configuration of each part is not limited to the illustrated embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, the configurations described in the above-mentioned embodiments and modifications (in the notes, etc.) may be combined, and the configurations can be added, omitted, replaced, or otherwise modified.

[0059] For example, the rocking mechanism 20 that moves the seat 4 backward and tilts backward in conjunction with the backward tilting of the backrest 5 is not limited to the configuration of the above embodiment, and a known synchro-rocking mechanism can be used. For example, the rocking mechanism 20 may not only employ a compression coil spring as a means of providing resistance to the backward tilting of the backrest 5, but may also employ various spring bodies (elastic bodies) such as torsion bars, leaf springs, or rubber, or it may be possible to provide a locking means such as a gas cylinder to control the backward tilting position of the backrest 5. Furthermore, the chair of the present invention can also be applied to chairs that do not have a swivel function.

[0060] Furthermore, the shape of the seat 4 and backrest 5 can be arbitrarily set as needed. For example, when the backrest 5 is in a reclined position, the armrest 52 should, in a side view, cover the seat 4 from the part in front of the center of the seat side edge 42 to the rear edge 41 of the seat. Preferably, when the backrest 5 is in a reclined position, the armrest 52 may, in a side view, cover the seat 4 such that at least the top surface 44 of the seat 4 is hidden from the part in front of the center of the seat side edge 42 to the rear edge 41 of the seat.

[0061] Furthermore, the front edge 52c of the armrest 52 is located behind the front edge 43 of the seat in a side view, but it may be positioned at the same position as the front edge 43 of the seat in the front-to-back direction, or it may be positioned in front of the front edge 43 of the seat. Also, the armrest 52 may cover the entire seat 4 in a side view when the backrest 5 is in an upright position when unloaded and in a reclined position, or in at least one of those positions.

[0062] Furthermore, the lower cushioning material 9 may be made of other elastic materials such as sliced ​​urethane, not just recycled cushioning (chip urethane) or a three-dimensional mesh fiber structure, or it may be a configuration in which multiple elastic materials are laminated.

[0063] Furthermore, the lower cushioning material 9 comprises a first lower cushioning portion 92 and a second lower cushioning portion 93 which are integrally formed, but the first lower cushioning portion 92 and the second lower cushioning portion 93 may be provided separately. In this case, the first lower cushioning portion 92 and the second lower cushioning portion 93 may be made of different materials. Also, the shape of the lower cushioning material 9 can be changed as appropriate; for example, the lower cushioning material 9 may be formed with a uniform thickness. Also, the lower cushioning material 9 may be positioned so as to protrude from the receiving recess 61. Furthermore, the shape and depth of the receiving recess 61 can be changed as appropriate. [Explanation of Symbols]

[0064] 4 seats 5 Backrest 20 Locking Mechanism 41 Seat rear edge 42 Seat side edge 43 Seat front edge 44 Seat top surface 51 Back plate part 52 Armrest 52a Lower edge of the armrest 52b Upper edge of armrest 52c Front edge of armrest 52d Rear edge of the armrest

Claims

[Claim 1] A chair in which the seat moves backward and tilts backward in conjunction with the backward tilting of the backrest, The aforementioned backrest is provided in a substantially U-shape with a forward-facing opening that surrounds the rear edge and left and right side edges of the seat in a plan view, and comprises a back plate portion disposed behind the rear edge of the seat and armrest portions disposed to the left and right outer sides of the left and right side edges of the seat. In a side view, the aforementioned armrest extends from a portion in front of the center of the front-to-rear center of the seat's side edge to the rear edge of the seat. chair.

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