chair

Abstract

By devising a frame structure, we have created a novel and useful chair that allows the upholstery material to be supported by the frame in an appropriate three-dimensional shape. [Solution] A backrest 2 is placed at the rear of the seat 1, and the backrest 2 has a back support 21 and a tensioning material 22 stretched over the back support 21, and the back support 21 has a back frame 201 which has a pair of left and right forward protrusions 211a, 211b, 212a, 212b located at the top and bottom, and an intermediate part 213 located in the vertical middle behind these forward protrusions 211a, 211b, 212a, 212b, and the tensioning material 22 is attached to the back frame 201 to give the tensioning material 22 a three-dimensional shape.

Description

Technical Field

[0001] The present invention relates to a chair preferably used in offices and the like, and the backrest is mainly composed of a stretching material.

Background Art

[0002] As a chair in which the backrest is mainly composed of a stretching material without relying on a cushioning material such as urethane foam, for example, the one shown in Patent Document 1 is known.

[0003] This chair has a pair of left and right front protrusions at the upper and lower parts of the back frame, and a stretching material is attached to the back frame along these front protrusions, so that when leaning against the back, the stretched fabric bends along the curvature of the front protrusions to support the seated person.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when the stretching material is stretched between the upper, lower, left, and right front protrusions of the back frame when not seated, tension is evenly applied and it tends to approach a flat shape. For this reason, the design appearance of the backrest tends to be monotonous.

[0006] In particular, in recent years, in chairs for telework and gaming chairs, the time of continuously sitting in front of a screen such as a PC or monitor has been significantly extended.

[0007] In such a situation, rather than sitting upright with the back muscles stretched, a posture of sitting while leaning the body backward against the backrest may be more suitable, and the number of users who actually use the chair in such a posture is increasing.

[0008] When using a chair in this posture, the chair described in Patent Document 1 has a structure in which the upholstery flexes when the sitter leans against the flatly stretched backrest to support the sitter. Therefore, it is necessary to achieve an appropriately concave three-dimensional shape from an unseated state to a seated state. For this reason, it is necessary to balance the aesthetic design when not seated with the tension and support when seated.

[0009] In particular, in chairs where the backrest does not have a backing material such as a urethane cushion, and the weight of the sitter is supported by the back frame via the upholstery, new ingenuity is required in the back frame to maintain the three-dimensional shape of the upholstery.

[0010] This invention addresses these problems and aims to realize a novel and useful chair that enables the upholstery material to be supported by the frame in an appropriate three-dimensional shape by devising the structure of the frame. [Means for solving the problem]

[0011] To achieve this objective, the present invention employs the following means.

[0012] In other words, the chair of the present invention is A backrest is placed at the rear of the seat. The backrest has a back support and a tensioning material stretched over the back support. The back support has a back frame comprising a pair of left and right forward protrusions located at the top and bottom, and an intermediate portion located midway in the vertical direction behind the forward protrusions. The upholstery material is attached to the back frame, resulting in a three-dimensional shape for the upholstery material.

[0013] With a frame structure that includes such an intermediate section, the upholstery is attached to the forward protrusions on the top, bottom, left, and right of the back frame, as well as to the intermediate section. The position of the center of the upholstery depends on how it is attached to the intermediate section of the back support. Therefore, compared to the case where the upholstery is simply attached to the forward protrusions on the top, bottom, left, and right of the back frame, the upholstery located in the position corresponding to the intermediate section can be engaged with the rear, enabling the creation of a three-dimensional shape for the upholstery when not seated. Furthermore, the recessed three-dimensional shape of the backrest surface when seated and the tension at that time become easier to adjust, allowing for an appropriate balance between the aesthetic design when not seated and the necessary tension and support when seated.

[0014] To avoid interference between the seated person's movements and the back frame, it is preferable that the part of the upholstery corresponding to the middle section of the back frame is attached to the middle section by being spanned across the upper and lower forward protruding parts.

[0015] To prevent the edges of the upholstery material from being located at the left and right edges of the central position of the back frame, it is preferable to attach the left and right edges of the upholstery material at the central position of the back frame to the middle of the back frame with their orientation facing backward.

[0016] In order to apply appropriate tension to both the left and right edges of the tensioning material, it is preferable that the tensioning material, after passing through the U-shaped folded-over portions formed on both the left and right edges and turning towards the rear, extends to the middle of the back frame and stretches in a planar manner, with the extension portion preventing sagging of the folded-over portion.

[0017] In order to properly support the seated person's body from the left and right, it is preferable that the pair of forward protrusions on the left and right have a shape that opens outwards to the left and right in the forward direction.

[0018] To prevent wrinkles from forming in the folded portion, it is preferable that the direction in which the pair of forward protrusions on the left and right located at the top open outwards corresponds approximately to the direction in which the pair of forward protrusions on the left and right located at the bottom open outwards.

[0019] In order to secure sufficient dimensions in the vertical direction for the folding portion, the back frame includes an upper back frame and a lower back frame that form an annular shape each including left and right front protrusions, and these upper and lower back frames are connected by an intermediate portion, and it is preferable that the intermediate portion is attached to a back support rod that supports the back frame.

[0020] In order to firmly support the head and waist of the seated person while ensuring a state where the elbows and arms can move easily, the upper back frame supports the head of the seated person, and the lower back frame supports the waist of the seated person so as to wrap around them respectively, and it is preferable that the position corresponding to the middle of the back frame of the tension member is located inside in the left - right direction from the upper and lower back frames to support the elbows or arms of the seated person without contacting the frame.

[0021] The present invention is particularly suitable for application to a chair in which the backrest and the seat are supported so as to be swingable in the front - rear, left - right directions.

Effect of the Invention

[0022] Since the present invention has the configuration described above, by devising the structure of the frame, it is possible to provide a novel and useful chair that enables the tension member to be supported by the frame in an appropriate three - dimensional shape.

Brief Explanation of the Drawings

[0023] [Figure 1] Front view showing the chair according to an embodiment of the present invention with the tension member of the backrest removed. [Figure 2] Perspective view of the same. [Figure 3] Side view of the same. [Figure 4] Plan view of the same. [Figure 5] Partial exploded view of the same. [Figure 6] Explanatory view of the swing mechanism constituting the same chair. [Figure 7] View for explaining the frame structure of the same chair. [Figure 8] Front view showing the chair according to an embodiment of the present invention with the tension member of the backrest attached. [Figure 9] The same perspective view. [Figure 10] Side view of the same. [Figure 11] The same floor plan. [Figure 12] Rear view of the same object. [Figure 13] A diagram illustrating the support surface formed in the backrest of the chair. [Figure 14] Central longitudinal section view in Figure 1. [Figure 15] A diagram showing the procedure for installing the upholstery. [Figure 16] Plan section views corresponding to the three locations in Figure 14. [Figure 17] A diagram showing the seat swaying from side to side. [Figure 18] A diagram showing the seat rocking back and forth. [Figure 19] A diagram showing the seat tilting further backward. [Figure 20] A diagram showing an example of the chair's use. [Figure 21] A diagram illustrating the support function provided by the upholstery material of the chair. [Figure 22] A diagram illustrating the support function provided by the upholstery material of the chair. [Figure 23] A diagram illustrating the support function provided by the upholstery material of the chair. [Modes for carrying out the invention]

[0024] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0025] Figures 1 to 5 show the chair according to this embodiment with the upholstery material 22 of the backrest 2 removed, Figure 6 is an explanatory diagram of the rocking mechanism that constitutes the chair, and Figure 7 is an explanatory diagram of the frame structure of the chair. Figures 8 to 13 show the chair with the upholstery material 22 of the backrest 2 attached.

[0026] This chair has a backrest 2 positioned at the rear of the seat 1, and the seat 1 is pivotably attached to the legs 4 via a pivoting mechanism 3.

[0027] In this embodiment, when referring to the front-to-back direction, left-to-right direction, and up-and-down direction, the seated person in the chair is used as the reference point.

[0028] The seat 1 consists of a seat support (outer shell) 11, an inner shell 12, and a seat body 13, which is placed on top of the inner shell 12 and is covered with cushioning material and upholstery.

[0029] The legs 4 have casters 42 at the lower end of the leg wings 41, and a leg support column 43 is erected from the center of the leg wings 41. A swing mechanism 3 is attached to a support base 44 provided on the upper end of the leg support column 43. The leg support column 43 is extendable and retractable vertically by a gas spring mechanism (not shown) built inside, and the seat 4 is rotatable around the axis of the leg support column 43. Thus, this chair is configured as a swivel chair with the seat 1 positioned on top of the legs 4 so as to be able to move up and down.

[0030] As shown in Figure 6, the rocking mechanism 3 has an upper base portion 31 and a lower base portion 32 facing each other, the lower base portion 32 is attached to the support base portion 44 of the leg 4, and the seat 1 is attached to the upper base portion 31 via the seat support 11, with a cushioning material 33 interposed between the upper base portion 31 and the lower base portion 32.

[0031] The rocking mechanism 3 allows the upper base portion 31 to tilt relative to the lower base portion 32 in any direction, including the front-to-back and left-to-right directions, up to 360°.

[0032] An example of the rocking mechanism 3 is the configuration shown in Japanese Patent Application Publication No. 2023-053700. In this configuration, the lower base portion 32 is made of a flat surface, and the upper base portion 31 is smoothly curved in a convex shape toward the lower base portion 32. At the reference position, the center of gravity of the upper base portion 31 is located on the center m of the lower base portion 32, at the lowest position. From this reference position, as the mechanism tilts, the center of gravity of the upper base portion 31 rises, and it rolls radially on the lower base portion 32, taking a forward-tilting position in the direction of rolling, and has the function of returning to the reference position from the destination of rolling using gravity. At that time, the upper base portion 32 compresses the cushioning material 33 around the position closest to the lower base portion, and the compression position moves with the rolling motion.

[0033] The rocking mechanism 3 is equipped with a damper mechanism 34 at the position connecting the upper base portion 31 and the lower base portion 32, which can operate in accordance with movement in a 360° direction.

[0034] The damper mechanism 34 is composed of a hole 34a provided in either the upper base portion 31 or the lower base portion 32, a cylindrical member 34b provided in the other and inserted into the hole 34a, and a friction material 34c positioned between the hole 34a and the cylindrical member 34b.

[0035] Furthermore, the rocking mechanism 3 includes a retaining member 35 positioned at the connection point between the upper base portion 31 and the lower base portion 32. This member allows the upper base portion 31 to tilt relative to the lower base portion 32 while restricting its separation from the lower base portion 32.

[0036] The damper mechanism 34 also serves as a rotation stopper, restricting the relative rotational movement of the upper base portion 31 and the lower base portion 32.

[0037] The backrest 2 is supported by a back support rod 5. As shown in Figures 1 to 5, the back support rod 5 is a plate-shaped object with its base end 5a connected to the rear part 11a of the seat support 11, and its upper end 5b side curved upward and rearward, becoming narrower towards the top. A disc-shaped mounting part 51 protrudes forward from the upper end 5b, and a disc-shaped elastic part 52 is attached to this mounting part 51.

[0038] The backrest 2 is constructed by stretching a tensioning material 22 over the back support 21. The back support 21 comprises a roughly frame-shaped back frame 201 and a retraction receiving portion 202. The back frame 201 is composed of an annular upper back frame 211 that forms an opening OP1, an annular lower back frame 212 that forms an opening OP2, and an intermediate portion 213 that connects the upper back frame 211 and the lower back frame 212.

[0039] The upper back frame 211 is composed of left and right front protrusions 211a and 211b that extend vertically while curving to be convex both forward and outward, an upper edge portion 211c that extends horizontally while curving to be convex rearward and upward, and is located in a position continuous with the upper front protrusions 211a and 211b, and is located in a position continuous with the lower front protrusions 211a and 211b, and is located horizontally while curving to be convex rearward and downward.

[0040] The lower back frame 212 is composed of forward projections 212a and 212b that extend vertically while curving to be convex both forward and outward, a lower edge portion 212c that extends horizontally while curving to be convex rearward and downward, and is located below the forward projections 212a and 212b, and is located in a position continuous with the front projections 212a and 212b, and is located above the forward projections 212a and 212b, and is located to be partway across the left and right while curving to be convex rearward and upward.

[0041] The intermediate section 213 is located behind the upper back frame 211 and the lower back frame 212, and has a curved plate shape with a central section that bulges towards the rear and the central section that concaves towards the front. The upper end of the intermediate section 213 and the lower edge 211d of the upper back frame 211 are integrally continuous, and the lower end of the intermediate section 213 and the upper edge 212d of the lower back frame 212 are integrally continuous. Below the intermediate section 213, a disc-shaped mounting portion 213b is provided, protruding downward and towards the rear, and this mounting portion 213b is connected to a disc-shaped elastic portion 52 provided on the upper end 5b of the back support rod 5 described above. The back frame 201 may be constructed by integrally molding the upper back frame 211, the lower back frame 212, and the intermediate section 213, but each may also be molded separately and joined together with screws or the like.

[0042] Although not shown in the figure, the elastic part 52 consists of a roughly disc-shaped front base and a rear base that are in contact with each other in the front-rear direction via an elastic material. The backrest 2 is configured to tilt in any direction around the center due to the oscillating motion of the elastic body 52 relative to the back support rod 5. The specific structure can be the same as the oscillating mechanism 3 of the seat described above, or a simpler configuration that omits the damper mechanism 34, etc.

[0043] When the entire back frame 201, configured in this way, is viewed from the front, as shown in Figure 7(a), the width W1 of the upper back frame 211 and the width W2 of the lower back frame 212 are the same or approximately the same, and the width W3 of the constricted portion of the intermediate section 213 is set to be about 2 / 3 to 3 / 4 of the above widths, so that the entire outer edge forms a gourd shape. The upper front projection 211a and the lower front projection 212a, which form an upper and lower pair on the left side, and the upper front projection 211b and the lower front projection 212b, which form an upper and lower pair on the right side, are positioned in a roughly vertically opposing position with a gap in between, as indicated by arrows T1 and T2, when viewed from the front.

[0044] When the entire back frame 201 is viewed from the side, as shown in Figure 7(b), the protruding ends of the upper forward protrusions 211a and 211b are designated as the first inflection point R1, the recessed end of the rearward-located intermediate portion 213 is designated as the second inflection point R2, and the protruding ends of the lower forward protrusions 212a and 212b are designated as the third inflection point R3. The section between the first inflection point R1 and the third inflection point R3 is recessed to the rear, and the portion above the first inflection point R1 and the portion below the third inflection point R3 are curved backward, resulting in a smooth, continuous shape throughout. On the left side, the upper front projection 211a and the lower front projection 212a, which form an upper and lower pair, and on the right side, the upper front projection 211b and the lower front projection 212b, which form an upper and lower pair, are positioned in a roughly vertically opposing position with a gap in between, as indicated by arrows T1 and T2, whether viewed from the front or the side.

[0045] When the entire back frame 201 is viewed from above, as shown in Figure 4, the direction in which the pair of left and right forward protrusions 211a and 211b located at the top open outwards roughly corresponds to the direction in which the pair of left and right forward protrusions 212a and 212b located at the bottom open outwards.

[0046] As shown in Figure 5, grooves g1, g3, and g2 that open to the rear are continuously formed in a circumferential manner in the region along the outer peripheral edge on the back of the upper back frame 211, the region along the left and right side edges on the back of the intermediate portion 213, and the region along the outer peripheral edge on the back of the lower back frame 212. These grooves g1 to g3 to g2 are for inserting and engaging the insertion parts k1, k3, and k2 provided on their peripheral edges when the tension material 22, shown as dashed lines in Figure 12, is placed over the back frame 201 from the front side and the periphery is folded back to the back side of the back frame 201.

[0047] As shown in Figures 12 and 13, the tensioning material 22 is constructed as a single piece including an upper back support surface A4 positioned in front of the upper back frame 211, a lower back support surface A3 positioned in front of the lower back frame 212, a central back support surface A0 and left and right back support surfaces A1 and A2 positioned in front of the intermediate section 213 in the upper and lower center, and a folded portion A5 and an extended portion A6 positioned in the area that folds back from the side edges of the left and right back support surfaces A3 and A4 and extends to the intermediate section 23. The tensioning material 22 is flexible enough to be unfolded into a planar shape in this manner.

[0048] Mounting margins 221 and 222 are provided around the upper back support surface A4 and the lower back support surface A3, which fold back to the back along the contour of the back frame 201, and a mounting margin 223 is provided around the extension A5 along the contour of the intermediate portion 23, and the aforementioned insertion portions k1, k2, and k3 are formed in a strip shape over the required width on the periphery of these mounting margins 221, 222, and 223.

[0049] In this embodiment, the backrest 2 does not use cushioning material such as urethane foam, but is configured so that the upholstery 22 receives the weight of the seated person and transmits it to the back frame 201 for support. Figures 8 to 12 show the state in which the upholstery 22 is attached to the back frame 201, with the upholstery 22 represented by a semi-transparent mesh. Areas with a higher density of mesh are areas where the upholstery 22 or the upholstery retraction section 23 (described later) overlap, and the light transmittance is reduced. In contrast, Figure 13 shows the upholstery 22 as an opaque surface to explain its surface configuration.

[0050] As shown in the partial extract in Figure 9, the material of the tensioning material 22 consists of a mesh 22a formed from a resin material such as polyester, with elastic threads 22b extending laterally sewn in at appropriate positions. The elastic threads 22b consist of filaments thicker than the mesh material of the mesh 22a, and are made of an appropriate resin material such as elastomer, and are configured to have more limited stretchability and strength than the mesh 22a.

[0051] Then, using this tensioning material 22, as shown in Figures 14 and 16, a back support region S consisting of multiple back support surfaces A0 to A4 is formed at a position recessed behind the back frame 201, specifically, at a position recessed behind the reference surface X0 when using a virtual surface X0 that simultaneously contacts the front protrusions 211a, 211b, 212a, and 212b located in front of the back frame 201 as a reference, as roughly indicated by the dashed line in Figure 13.

[0052] The back support surfaces A0 to A4 are formed to face multiple different directions. "Different directions" means that, when these surfaces are approximated as planes, the normal directions of each surface point in different directions. To achieve this configuration, valley lines B11 to B32 are formed at the points where adjacent surfaces intersect, separating the boundaries.

[0053] To explain in more detail, the left and right back support surfaces A1 and A2, which are spaced apart in the left-right direction, face each other on the left and right with the central back support surface A0, which is located midway in the left-right direction, in between. The lower back support surface A3 and upper back support surface A4, which are spaced apart in the up and down direction, face each other on the up and down with the central back support surface A0, which is located midway in the up and down direction, in between. In other words, the back support region S is configured to appear concave when viewed from all four sides.

[0054] To this end, as shown in Figures 8 and 13, first valley lines B11 and B12 are formed at the boundary between the central back support surface A0 and the left and right back support surfaces A1 and A2, extending parallel to each other in the vertical direction. As shown in Figures 11, 16 and 21(b), the left and right back support surfaces A1 and A2 are inclined surfaces that are connected in a direction that faces inward from the surface that extends the central back support surface A0 in the left and right direction.

[0055] Furthermore, as shown in Figures 8 and 13, second valley lines B21 and B22 are formed at the boundary between the lower back support surface A3 and the left and right back support surfaces A1 and A2, extending diagonally forward and downward and outward from the lower ends of the first valley lines B11 and B12. The lower back support surface A3, located between the left and right second valley lines B21 and B22, is an inclined surface that extends diagonally upward relative to the central back support surface A0, as shown in Figures 10, 14 and 21(a).

[0056] Furthermore, as shown in Figures 8 and 13, etc., third valley lines B31 and B32 are formed at the boundary between the upper back support surface A4 and the left and right back support surfaces A1 and A2, extending diagonally forward and upward and outward from the upper ends of the first valley lines B11 and B12. The upper back support surface A4, located between the left and right third valley lines B31 and B32, is an inclined surface that extends diagonally downward relative to the central back support surface A0, as shown in Figures 10, 14 and 21(a).

[0057] The lengths of the first valley lines B11, B12, the second valley lines B21, B22, and the third valley lines B31, B32, as well as the angles between the second valley line B21 (B22) and the first valley line B11 (B12), and the angles between the third valley line B31 (B32) and the first valley line B11 (B12), are set appropriately according to the purpose, use, and required characteristics of the chair. In this case, the second valley line B21 (B22) and the first valley line B11 (B12) may be smoothly continuous, and the third valley line B31 (B32) and the first valley line B11 (B12) may be smoothly continuous.

[0058] As shown in Figure 22(a), the back of a seated person U gradually narrows along the shoulder blades and sternum, then widens towards the buttocks after passing through the waist. Therefore, the second valley lines B21 and B22 are set based on lines that extend diagonally downward and sideways along the waist (lumbar region) U2, which widens from the waist to the buttocks, and the third valley lines B31 and B32 are set based on lines that extend diagonally upward and sideways along the upper back (upper region) U3, which forms an inverted triangle from the lower edges of the left and right shoulder blades to the shoulders. The first valley line B11 (B12) is set at the position connecting the second valley line B21 (B22) and the third valley line B31 (B32).

[0059] Furthermore, in order to clearly form the first valley lines B11, B12, the second valley lines B21, B22, and the third valley lines B31, B32, and to stably maintain their valley shapes, tension material pull-in sections 23 are provided on the back side of each valley line, as shown in Figure 13, etc., to pull the tension material 22 backward.

[0060] The tension material retraction section 23 is composed of a left-side tension material retraction member 231 that constitutes the first retraction area C11, second retraction area C21, and third retraction area C31 along the first valley line B11, second valley line B21, and third valley line B31, and a right-side tension material retraction member 232 that constitutes the first retraction area C12, second retraction area C22, and third retraction area C32 along the first valley line B12, second valley line B22, and third valley line B32. Here, the tension material retraction members 231 and 232 are made of the same material as or of the same type as the tension material 22, but are not limited to such materials. In addition, here, the edges of the tension material retraction members 231 and 232 are folded and sewn to prevent fraying. Of course, as shown in the modified examples below, the tension material retraction section 23 can be configured in other ways.

[0061] Here, as shown in Figures 13 and 14, the first retraction regions C11 and C12 have a rectangular shape with approximately equal width, while the second retraction regions C21 and C22 and the third retraction regions C31 and C32 have a triangular shape that narrows from the base to the tip.

[0062] In order to accurately achieve the positions of each valley line B11 to B32 with respect to the back frame 201, the tension material pull-in section 23, as shown in Figures 15(a) and (c), has a sewing line 23a set at the end where the edge treatment is applied on one end, sewn to the tension material 22, and a pull-in line 23b set at the end where the edge treatment is applied on the other end, attached to the resin tension material receiving section 202. For the end treatment of the tension material pull-in members 231 and 232, as shown in Figure 15(d), the ends of the tension material pull-in members 231 and 232 are folded inward and sewn with first threads 231x and 232x, and then applied to the position that will become the valley line of the tension material 22 and sewn to the tension material 22 with second threads 231y and 232y. The ends of the tension material pull-in members 231 and 232 are folded inward, so that the folded ends of the tension material pull-in members 231 and 232 and the first threads 231x and 232x are not visible from the side indicated by the arrow in the figure.

[0063] The retraction receiving section 202 serves as a joint for easily attaching the tension material retraction section 23 to the intermediate section 213 that constitutes the back frame 201. It is plate-shaped, and recessed grooves 202a (see Figure 15(c)) are formed on both edges in the width direction toward the back side, into which the retraction lines 23b of the aforementioned tension material retraction members 231 and 232 can be fitted and attached. This retraction receiving section 202 can be attached with a single touch to the mounting section 213a (see Figures 15(a) and (c)) provided on the front surface of the intermediate section 213 that constitutes the back frame 201 via an engagement part (not shown), and a predetermined retraction state can be reliably achieved throughout the tension material 22 via the tension material retraction section 23.

[0064] Figures 14 and 16 show the tension member 22 before retraction with a dashed line (P) and the tension member 24 after retraction with a solid line (Q). By retracting the tension member 22, each of the back support surfaces A0 to A4 shown in Figures 13, 14, and 16(b) is formed in a position recessed from the back frame 201. The position of the tension member 2(P) before retraction basically coincides with the dashed line X0 mentioned above.

[0065] As shown in Figures 12, 15, and 16, the upper corresponding position 221 of the tensioning material 22, which is positioned to cover the opening OP1 of the upper back frame 211, is attached by inserting the insertion part k1 into the groove g1 at a position where it is wrapped around the front protrusions 211a, 211b and the back edge 212 of the upper back frame 211. The lower corresponding position 222 of the tensioning material 22, which is positioned to cover the opening OP2 of the lower frame 212, is attached by inserting the insertion part k2 into the groove g2 at a position where it is wrapped around the front protrusions 221a, 221b and the back edge 211 of the back frame 22.

[0066] On the other hand, the intermediate corresponding position 223 of the tensioning material 2, which is located between the upper back frame 211 and the lower back frame 212 and corresponds to the intermediate section 213, is, as shown in Figure 16(b), not surrounded by frames on either side, with only the intermediate section 213 located behind it at a distance. For this reason, the intermediate corresponding position 223 is provided with an intermediate position widening section 224, which is folded back in a U-shape and then extends backward, and the insertion section k3 at the end of this extension is inserted into the groove g3 on the back of the intermediate section 213 to attach it. In other words, both sides of the intermediate corresponding position 223, including the intermediate position widening portion 224, are folded back along the arrows T1 and T2 shown in Figures 7(a) and (b), as shown in Figures 1 to 4, Figures 8 to 11, etc., in a shape that follows the shape of the flat cross-section of the upper and lower forward protruding edges 211a-212a (211b-212b). This forms a series of folded portions A5 that are connected vertically in a partially bag-like shape without an internal frame, and an extension portion A6 is stretched from this folded portion A5 toward the intermediate portion 213 of the back frame 20.

[0067] As mentioned above, the tensioning material 22 is flexible and can be unfolded into a flat shape, and the folded portion A5 is not formed by resin molding or the like.

[0068] Even though the tensioning material 22 is flexible, as mentioned above, the direction in which the pair of left and right forward protrusions 211a and 211b located at the top open outwards is roughly corresponding to the direction in which the pair of left and right forward protrusions 212a and 212b located at the bottom open outwards. As a result, the folded portion A5 extending vertically is taut with as little twisting as possible.

[0069] The folded portion A5, combined with the support it receives from the extended portion A6 to prevent sagging, forms a three-dimensional support surface in the space on both sides of the frame width W3 shown in Figure 7 when viewed from the front, due to tension, even without immediate backing from the frame. It then appropriately supports the sitter's body while flexibly deforming in response to the load applied by the sitter.

[0070] The extension A6 is formed in such a way that, when viewed from the side in Figure 10, it substantially covers the spatial region (more precisely, the spatial region slightly inside that region) enclosed by the frame line including the inflection points R1, R2, and R3 shown in Figure 7(b). It is preferable that the extension A6 is stretched in a substantially planar shape within this region, but it may also be stretched in a curved planar shape.

[0071] One procedure for installing the tensioning material 2 is to first attach the pull-in receiving portion 202, which is integrated with the tensioning material 22, to the base portion 213a provided in the middle portion 213 of the back frame 201, as shown in Figure 15(a), and then insert the insertion portions k1, k2, and k3 provided on the periphery of the tensioning material 22 into the grooves g1, g2, and g3 of the back frame 201, as shown in Figures 15(b) and 16(a) to (c). Of course, it is also possible to first insert the insertion portions k1, k2, and k3 provided on the periphery of the tensioning material 22 into the grooves g1, g2, and g3 of the back frame 201, as shown in Figures 15(b) and 16(a) to (c), and then attach the pull-in receiving portion 202 to the base portion 213a provided in the middle portion 213 of the back frame 201, as shown in Figure 15(a). In this case, as shown in Figure 12, the issue can be addressed by inserting fingers through openings OP1 and OP2 from the back side of the back frame 201 and attaching the retraction receiving portion 202 to the base portion 213a of the intermediate portion 213 of the back frame 201.

[0072] This chair has a rocking mechanism 3 located between the seat 1 and the legs 4, which allows the seat 1 to rock in any direction of 360°, including forward, backward, left, and right, as shown in Figures 17 and 18. Furthermore, an elastic part 52 located between the back support rod 5 and the back frame 201 allows the backrest 2 to rock relative to the seat 1, around the center of the elastic part 52, as shown in Figure 19. Therefore, when a seated person U leans back against the backrest 2 and shifts their center of gravity backward, the seat 1 tilts backward while lifting the center of gravity, causing the backrest 2 to tilt backward as well (for example, at an angle θ1), and then the backrest 2 tilts further backward (for example, at an angle θ2), as shown in Figure 19. Of course, depending on how it is used, the tilts of θ1 and θ2 may occur in reverse or simultaneously.

[0073] Conversely, this chair is also capable of moving the backrest 2 forward from the reference position together with the seat 1, as shown in Figure 18, by the rocking mechanism 3 (for example, by an angle of -θ).

[0074] Figure 20 shows an example of how this chair can be used. First, this chair uses upholstery material 22 to form a three-dimensional back support area S that is recessed backward in the backrest 2. As a result, a user (sitter) U can sit down and place their body in the back support area S formed in the recess. From this position, by leaning their weight against the backrest 2, the backrest 2 tilts backward due to the rocking of the seat 1 or the behavior of the elastic part 3, allowing the user to sit in front of a wall-mounted large monitor MT or the like and operate a keyboard or other control unit AC that is within reach.

[0075] In this configuration, the chair provides a comfortable fit to the sitter U from all sides by positioning the sitter U's body between the vertically opposing upper and lower back support surfaces A3 and A4 as shown in Figure 21(a), and between the horizontally opposing left and right back support surfaces A1 and A2 as shown in Figures 21(b) and (c).

[0076] Furthermore, when this chair is used with the backrest 2 reclined, as shown in Figure 21(a), the upper back support surface A4 is inclined in the upright direction relative to the central back support surface A0. As a result, the area U3 from the scapula to the shoulder of the seated person U makes contact with the chair further forward than the extension of the central back support surface A0. Therefore, the upper body of the seated person U is raised, and they can comfortably assume a posture where their gaze E is directed horizontally or slightly upward without consciously raising their head U1 while leaning against the backrest 2.

[0077] When the seated person U leans backward from the position shown in Figure 21, the pelvis tilts backward and the body opens up, as indicated by the arrows at both ends. Since the upper body does not follow the movement of the pelvis, although the load is distributed, it opens locally and the load of the upper body tends to be placed as a load on the joint around the fifth lumbar vertebra U5 shown in Figure 21(a2), just above the pelvis. Conventional chairs with lumbar support LS support the fifth lumbar vertebra U5 of the S-shaped spine forward, so the load on the backrest 2 is distributed, but it does not support the load upward.

[0078] In contrast, in this embodiment, the chair allows the sitter U to align the second valley lines B21 and B22 with the area that widens from the waist to the buttocks, making it easier for the lower back to fit against the back support surface A3 as shown in Figure 21(a). When the backrest 2 is tilted backward, as shown in Figure 22(c), the back support surface A3 located between the left and right first valley lines B21 and B22 pushes upward with a resistance force F1 around the so-called thoracolumbar transition area U6. This prevents the load from concentrating around the fifth lumbar vertebra U5 of the sitter U, distributes the weight (resistance force from the seat surface) F0 on the seat 1, and has the effect of reducing the feeling of pressure and fatigue experienced by the sitter U from the seat 1.

[0079] Generally, the upper body of a seated person moves relative to their lower body with the thoracolumbar junction U6 as the pivot point. The thoracolumbar junction U6 is a common area for everyone, and since it is a gently sloping area above the fifth cervical vertebra U5, it can be appropriately supported by the upward-facing lower back support surface A3, even if there are differences in the seated person's physique, compared to when the fifth cervical vertebra U5 is supported at a single point with conventional lumbar support.

[0080] Furthermore, as shown in Figure 22(b), when the user is seated, the area U3 from the left and right scapulae to the shoulders, which forms an inverted triangle shape, is positioned opposite the upper back support surface A4 of the backrest 2. Therefore, if the area U3 from below the scapulae to the shoulders, as shown in Figure 22(a), leans against the upper back support surface A4 along the third valley lines B31 and B32 shown in Figure 13, the area U3ga from the scapulae to the shoulders is pushed upward diagonally by the upper back support surface A4 with a counterforce F2. This also prevents the load from concentrating around the fifth lumbar vertebra U5 of the seated person U, and distributes the load on the seat 1 (counterforce from the seat surface) F0, thereby reducing the feeling of pressure and sitting fatigue experienced by the seated person U.

[0081] In addition, at the intermediate corresponding position 223 of the upholstery material 2, a frameless folded portion A5 is formed on both the left and right edges, along with the intermediate position widening portion 224, connecting the upper and lower protruding portions. Therefore, even if the seated person U leans to the side with their elbow U7 on it as shown in Figure 23(a), or leans against the backrest 2 with their arm U8 behind them as shown in Figure 23(b), or crosses their arms U9 in front of them as shown in Figure 23(c), and their elbow U7 or arm U8 comes into contact with the folded portion A5, the upholstery material 22 of the folded portion A5 elastically flexes and deforms to conform to the seated person U's posture, while appropriately supporting the seated person U under the necessary tension.

[0082] Therefore, as shown in Figure 20, this chair is extremely suitable for tasks such as long-term PC operation where the sitter U leans back against the backrest 2, continuously views the screen MT in front, and moves their hands and arms. Of course, since this posture does not strain the body, it is also suitable for relaxing, resting, or taking a nap when not working.

[0083] Even when comparing the chair of the present invention with conventional cushion-type chairs, the three-dimensional shape of the upholstery material 22 is created in the upholstery material insertion section 23. Therefore, the shape of the backrest can be adjusted to the skeleton even before sitting down, and the softness of the mesh when the sitter leans against it can be adjusted to the muscles. In this respect, it differs from conventional chairs that use a core material to adjust to the skeleton and a cushion to adjust to the muscles, and is also fundamentally different from conventional chairs that simply have upholstery material attached.

[0084] Furthermore, the left and right side edges of the back-to-back correspondence position 223 are folded back together with the intermediate widening section 224 and supported by the intermediate section 213 of the back frame 201. This forms a folded section A5 that creates a partially pocket-like three-dimensional shape on the left and right side edges, ensuring strength while creating a frameless support structure that does not have a core material inside. Therefore, it is fundamentally different from conventional chairs with a frameless structure where the side edges of the upholstery material 22 are simply cut off.

[0085] As described above, the chair of this embodiment is A backrest 2 is placed at the rear of seat 1. The backrest 2 has a back support 21 and a tensioning material 22 stretched over the back support 21, The back support 21 has a back frame 201 comprising a pair of left and right forward protrusions 211a, 211b, 212a, and 212b located at the top and bottom, and an intermediate portion 213 located midway in the vertical direction behind these forward protrusions 211a, 211b, 212a, and 212b. The upholstery material 22 is attached to the back frame 201, thereby creating a structure that gives the upholstery material 22 a three-dimensional shape.

[0086] With a frame structure having such an intermediate section 213, the upholstery material 22 is attached to the upper, lower, left, and right forward protrusions 211a, 211b, 212a, and 212b of the back frame 201, as well as to the intermediate section 213. The position of the central part of the upholstery material 22 depends on how the back support 21 is attached to the intermediate section 213. Therefore, compared to the case where the upholstery material 22 is simply attached only to the upper, lower, left, and right forward protrusions 211a, 211b, 221a, and 221b of the back frame 201, the upholstery material 22 at the position corresponding to the intermediate section 213 can be engaged rearward, enabling the realization of a three-dimensional shape for the upholstery material 22 when not seated. Furthermore, the recessed three-dimensional shape of the backrest surface when seated and the tension at that time become easier to adjust, allowing for an appropriate balance between the aesthetic design when not seated and the necessary tension and support when seated.

[0087] In particular, the back frame intermediate corresponding position 223 of the upholstery material 22, which is located in a position corresponding to the intermediate part 213 of the back frame 201, is attached to the intermediate part 213 while being spanned across the upper and lower forward protrusions 211a-212a (211b-212b).

[0088] Thus, the intermediate position 223 of the back frame of the upholstery material 22 has a frameless structure without a back frame that acts as a core material inside, and is attached to the intermediate part 213 of the back frame 201, so that it is stretched between the upper and lower protrusions 211a, 211b, 212a, 212b and the intermediate part 213. As a result, not only do the elbows, etc., of the seated person U's body not come into direct contact with the back frame 201 at the intermediate position between the upper and lower left and right forward protrusions 211a-212a (the intermediate position between 211b-212b), but it can also deform to follow the movements of the seated person U's shoulders, elbows, etc., and provide flexible support over a wide range of motion.

[0089] In order to achieve this structure, this embodiment attaches the left and right edges of the back frame's intermediate corresponding position 223 of the upholstery material 22 to the intermediate part 213 of the back frame 201, with the orientation changed to face backward.

[0090] In this way, the edge of the tensioning material 22 does not end up at the intermediate position 223 of the back frame, as in the prior art documents. This allows the edge to be properly attached and supported to the intermediate part 213 of the back frame 201. Furthermore, by changing its orientation to the rear, the tensioning material 22 becomes double-stretched, providing appropriate strength and elasticity to both the left and right edges of the intermediate position 223 of the back frame.

[0091] Specifically, the tensioning material 22 changes direction towards the rear after passing through U-shaped folded-over sections A5 formed on both the left and right edges, and an extended section A6 is stretched in a planar manner to the middle section 213 of the back frame 201, and the extended section prevents the folded-over section A5 from sagging.

[0092] In this way, appropriate tension can be applied to the folded portion A5 and the extended portion A6, and a state that is less prone to wrinkles can be maintained.

[0093] Furthermore, the pair of forward projections 211a, 211b (212a, 212b) on the left and right sides are shaped to open outwards to the left and right in a forward direction.

[0094] Therefore, when the seated person U leans against the backrest 2, the intermediate corresponding position 223 of the upholstery material 22 recedes diagonally along the inner surface of the protruding edge and receives the load of the seated person U. Compared to the case where the surfaces of the forward protrusions 211a, 211b (212a, 212b) face forward as in the prior art, the seated person U's body can be properly supported from the left and right directions.

[0095] Furthermore, the direction in which the pair of forward projections 211a and 211b located at the top open outwards roughly corresponds to the direction in which the pair of forward projections 212a and 212b located at the bottom open outwards.

[0096] Therefore, it is possible to prevent the folded portion A5 from twisting and to create a structure that is less prone to wrinkles.

[0097] Furthermore, the back frame 201 comprises an annular upper back frame 211 including left and right front protrusions 211a and 211b, and an annular lower back frame 212 including front protrusions 212a and 212b. These upper and lower back frames 211 and 212 are connected by an intermediate part 213, which is attached to a back support rod 5 that supports the back frame 201.

[0098] In this way, the intermediate section 213 can be used as the base point for connecting the upper and lower back frames 211 and 212, attaching the tensioning material 22, and attaching the back support rod 5. Furthermore, since strength can be ensured even if the upper back frame 211 and the lower back frame 212 are spaced apart in the vertical direction, it is easy to make the backrest 2 taller, and it becomes possible to make the folded-over section A5 have sufficient dimensions in the vertical direction.

[0099] Furthermore, the upper back frame 211 supports the head U1 of the seated person U, and the lower back frame 212 supports the waist U2 of the seated person U, respectively. The intermediate position 223 of the upholstery material 22 corresponding to the back frame is located inward in the left-right direction from the upper and lower back frames 211 and 212, supporting the elbows U7 and arms U8 of the seated person U without them coming into contact with the frame.

[0100] In this configuration, the head U1 and waist U2 are firmly supported, while the elbows U7 and arms U8 are free to move. This does not hinder the movement of the shoulders and arms, making it particularly suitable for seated individuals U who perform tasks using their arms while seated.

[0101] Furthermore, the backrest 2 and seat 1 are supported so as to be able to swing forward, backward, left, and right. If the backrest 2 supports the load with the upholstery 22 without using a backing material such as a cushion, the backrest 2 is prone to swinging, making it easy for the sitter U to interfere with the back frame 201, and the support force of the upholstery 22 is also prone to decrease. Therefore, by applying this embodiment, it is possible to maintain an appropriate support state while avoiding interference between the sitter U and the back frame 201.

[0102] Although one embodiment of the present invention has been described above, the specific configuration of each part is not limited to the embodiment described above, and various modifications are possible without departing from the spirit of the present invention. [Explanation of Symbols]

[0103] 1…za 2...backrest 5…Dorsal rod 21...back support 22...Tension material 52...Elastic part 201...Back frame 211... Upper back frame 211a, 211b...Front protrusion (upper side) 212... Lower back frame 212a, 212b...Front protrusion (lower side) 213...Middle section 223...Rear frame intermediate position A5...Folded part A6…extension part

Claims

1. A backrest is placed at the rear of the seat. The aforementioned backrest comprises a back support and a tensioning material stretched over the back support, The back support has a back frame comprising a pair of left and right forward protrusions located at the top and bottom, and an intermediate portion located midway in the vertical direction behind the forward protrusions. A chair characterized by having a three-dimensional shape for the upholstery material attached to the aforementioned back frame.

2. The chair according to claim 1, wherein the part of the upholstery that corresponds to the middle part of the back frame is attached to the middle part while being spanned so as to connect the upper and lower forward protrusions.

3. The chair according to claim 2, wherein the left and right edges of the upholstery material at the corresponding positions in the middle of the back frame are turned to face backward and attached to the middle of the back frame.

4. The chair according to claim 3, wherein the upholstery material changes direction towards the rear after passing through U-shaped folded portions formed on both the left and right edges, and the extended portion stretches in a planar manner to the middle of the back frame, and the extended portion prevents the folded portion from sagging.

5. The chair according to claim 4, wherein the pair of forward projections on the left and right sides are shaped to open outwards to the left and right toward the front.

6. The chair according to claim 5, wherein the direction in which a pair of forward protrusions located on the upper side open outward corresponds substantially to the direction in which a pair of forward protrusions located on the lower side open outward.

7. The chair according to any one of claims 4 to 6, wherein the back frame comprises an annular upper back frame and a lower back frame, each including the left and right forward protrusions, and these upper and lower back frames are connected by the intermediate portion, the intermediate portion is attached to a back support rod that supports the back frame.

8. The chair according to claim 7, wherein the upper back frame supports the head of the sitter, the lower back frame supports the waist of the sitter, and the intermediate position of the upholstery material corresponding to the back frame is located inward in the left-right direction from the upper and lower back frames, thereby supporting the sitter's elbows or arms without them coming into contact with the frame.

9. The chair according to any one of claims 1 to 8, wherein the backrest and the seat are supported so as to be able to swing forward, backward, left, and right.

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