chair

Abstract

To reduce the burden on the upper body of the person sitting. [Solution] The chair comprises a seat and a chair body including a backrest. The backrest surface includes an inclined surface that slopes upward and diagonally backward toward the upper end of the backrest, and the chair further comprises a convex portion that protrudes from the inclined surface and has a lower hardness than the chair body. The convex portion applies a partial rebound force to the upper body, preventing specific parts of the upper body from being positioned backward and reducing the burden on the upper body.

Description

Technical Field

[0001] The technology disclosed in this specification relates to chairs.

Background Art

[0002] Conventionally, various technologies regarding chairs with a backrest have been known. For example, the first chair has a convex sponge layer for relieving low back pain. The sponge layer is disposed in a concave portion of the backrest surface of the backrest that faces the waist of the human body (see Patent Document 1). The second chair has a convex auxiliary portion for reducing the load on the back muscles in the S-shaped posture. The auxiliary portion is disposed in a flat portion of the backrest surface of the backrest that faces the waist of the human body (see Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, among chairs with a backrest, there is a chair in which the backrest surface of the backrest includes an inclined surface that slopes upward and obliquely backward toward the upper end of the backrest. In such a chair with an inclined surface, there is a possibility that the upper body of the seated user may fall too far backward. That is, when the user sits on the seat surface and leans against the backrest, the upper body of the user reclines backward along the inclined surface. Along with this, a specific part (for example, the neck, etc.) of the upper body that is located above the backrest is further positioned backward. As a result, for example, there is a risk of burden on the upper body.

[0005] This specification discloses a technology capable of solving the above-described problems. [Means for solving the problem]

[0006] The technologies disclosed herein can be implemented, for example, in the following forms:

[0007] (1) The chair disclosed herein comprises a chair body including a seat and a backrest. The backrest surface of the backrest includes an inclined surface that slopes upward and diagonally backward toward the upper end of the backrest. The chair further comprises a convex portion projecting from the inclined surface, the convex portion having a lower hardness than the chair body.

[0008] The backrest of this chair has an inclined surface that slopes diagonally upward and backward. When a user sitting on the seat leans against the backrest, the user's upper body bends backward along the inclined surface, causing certain parts of the upper body above the backrest (such as the neck) to be positioned further backward, which may result in strain on the upper body. In response to this, this chair has protrusions that protrude from the inclined surface. The protrusions are less rigid than the chair body. Therefore, the protrusions provide partial resilience to the upper body, preventing certain parts of the upper body from being positioned further backward and reducing strain on the upper body.

[0009] (2) In the chair described above, the protrusion may be configured to include a first protrusion positioned on the inclined surface and having a first repulsive force, and a second protrusion positioned on the first protrusion and having a second repulsive force lower than the first repulsive force of the first protrusion. With this chair, the second protrusion with relatively low repulsive force can flexibly accept the upper body, while the first protrusion with relatively high repulsive force can support the upper body.

[0010] (3) In the chair described above, the upper end of the second protrusion may be located below the upper end of the first protrusion, and the lower end of the second protrusion may be located above the lower end of the first protrusion. With this chair, for example, it is possible to suppress the influence of the protrusion on the overall design of the chair.

[0011] (4) The chair may further be configured to include a cover that covers the entire backrest surface, including the protrusion. With this chair, the cover can suppress the effect of the protrusion on the overall design of the chair.

[0012] Furthermore, the technologies disclosed herein can be implemented in various forms, for example, in the form of a chair, a chair frame, a backrest, etc. [Brief explanation of the drawing]

[0013] [Figure 1] This is an explanatory diagram illustrating the configuration of the chair 10 in the first embodiment. [Figure 2] An explanatory diagram showing the XZ cross-sectional configuration of chair 10 at position II-II in Figure 1. [Figure 3] A schematic diagram showing the configuration of the chair body 100. [Figure 4] Figure 3 is an explanatory diagram showing the XZ cross-sectional configuration of the chair body 100 at position IV-IV. [Figure 5] An explanatory diagram showing the posture of a person seated in chair 10X, a comparative example. [Figure 6] An explanatory diagram showing the seated posture of a person in the chair 10 of this embodiment. [Figure 7] This is an explanatory diagram illustrating the configuration of chair 10A in the second embodiment. [Modes for carrying out the invention]

[0014] A. First Embodiment: A-1. External configuration of chair 10: This embodiment will be described with reference to Figures 1 to 6. Each figure shows mutually orthogonal X, Y, and Z axes for specifying direction. The positive Z-axis direction is upward, and the negative Z-axis direction is downward; the positive X-axis direction is forward, and the negative X-axis direction is backward; and the positive Y-axis direction is to the right, and the negative Y-axis direction is to the left.

[0015] The chair 10 is a so-called sofa-type chair for for 2-3 person chair, and is installed and used in, for example, homes, offices, stores, hotels, public facilities, etc. The height of the chair 10 is, for example, 680 mm or more and 880 mm or less (more specifically, about 780 mm), the width of the chair 10 in the left-right direction is, for example, 1600 mm or more and 2000 mm or less (more specifically, about 1815 mm), and the depth of the chair 10 in the front-back direction is, for example, 700 mm or more and 900 mm or less (more specifically, about 800 mm).

[0016] As shown in FIG. 1, the chair 10 includes an outer seat portion 20, an outer backrest 40, and a pair of outer armrests 60. The outer surface N of the chair 10 includes an outer seat surface N20, an outer backrest surface N40, and a pair of outer armrest surfaces N60. The outer seat surface N20 is the upper surface of the outer seat portion 20. The outer backrest surface N40 is the front surface of the outer backrest 40. The outer armrest surface N60 is the upper surface of the outer armrest 60.

[0017] (Outer seat portion 20) The outer seat portion 20 is a portion that mainly supports the buttocks of the seated person. The outer seat portion 20 has a horizontally long shape that is long in the left-right direction. The outer seat surface N20 is inclined so as to gradually become lower from the front to the rear (see FIG. 2). Thereby, the forward slip of the pelvis of the seated person is prevented, and the seated person V is more likely to lean on the outer backrest 40. The height of the outer seat surface N20 from the floor surface at the front end is set to, for example, 395 mm or more and 495 mm or less (more specifically, about 440 mm) so that the feet of the seated person can easily reach the floor surface. Further, the height of the outer seat surface N20 from the floor surface at the rear end is lower than the front end of the outer seat surface N20, and is set to, for example, 285 mm or more and 375 mm or less (more specifically, about 330 mm). The length of the outer seat surface N20 in the left-right direction is set to, for example, 1255 mm or more and 1655 mm or less (more specifically, about 1455 mm). The length of the outer seat surface N20 in the front-back direction is set to, for example, 460 mm or more and 490 mm or less (more specifically, about 475 mm). Thereby, it is possible for 2-3 people to sit on the outer seat surface N20.

[0018] (Outer backrest 40) The outer backrest 40 is mainly a part that supports the back of the seated person V. The outer backrest 40 extends upward from near the rear end of the outer seat part 20. The outer backrest 40 has a horizontally long shape that is long in the left - right direction. The outer backrest 40 has a shape such that the left - right ends protrude forward (see Figure 1). This enables the hands to be placed for easier standing - up operation. The outer shape of the outer backrest 40 is formed as an overall curved surface (flow - surface shape), resulting in a highly - designed appearance.

[0019] (Outer armrests 60) The pair of outer armrests 60 are mainly parts that support the elbows of the seated person V. The left - hand outer armrest 60 extends upward from near the left end of the outer seat part 20. The right - hand outer armrest 60 extends upward from near the right end of the outer seat part 20. Each outer armrest 60 protrudes upward from the outer seat surface N20 as it goes forward (see Figure 2). The outer shape of each outer armrest 60 is formed as an overall curved surface (flow - surface shape), resulting in a highly - designed appearance.

[0020] A - 2. Internal structure of the chair 10: As shown in Figure 2, the chair 10 includes a chair body 100, a cushion member 90, and a cover member 95. The cushion member 90 is arranged on the upper surface of the chair body 100. The cover member 95 is arranged on the upper surface of the cushion member 90.

[0021] (Chair body 100) The chair body 100 is a functional component (core material) that defines the approximate shape of the chair 10, as shown in Figure 3. The chair body 100 has an inner seat 120, an inner backrest 140, and a pair of inner armrests 160. The inner seat 120 is positioned to correspond to the outer seat 20 of the chair 10. The shape of the inner seat 120 is substantially the same as the shape of the outer seat 20 shown in Figure 1, and defines the shape of the outer seat 20. A recess is formed on the upper surface of the inner seat 120. A step is formed on the front surface of the inner seat 120. The inner backrest 140 is positioned to correspond to the outer backrest 40 of the chair 10. The shape of the inner backrest 140 is substantially the same as the shape of the outer backrest 40 shown in Figure 1, and defines the shape of the outer backrest 40. The inner armrests 160 are positioned to correspond to the outer armrests 60 of the chair 10. The shape of the inner armrest 160 is substantially the same as the shape of the outer armrest shown in Figure 1, and defines the shape of the outer armrest 60. The inner seat 120 is an example of a seat, and the inner backrest 140 is an example of a backrest.

[0022] In this embodiment, the chair body 100 comprises a pair of first body members 200 and a second body member 300, as shown in Figure 3. The first and second imaginary lines R1 and R2 in Figure 3 are the boundary lines between the first body member 200 and the second body member 300 in the chair 10. The second body member 300 is located in the center of the chair body 100. Each first body member 200 is located adjacent to the second body member 300 in the left-right direction. Specifically, one first body member 200 is located to the right of the second body member 300 and is adjacent to the right end of the second body member 300. The other first body member 200 is located to the left of the second body member 300 and is adjacent to the left end of the second body member 300. The first body member 200 and the second body member 300 are joined via a connecting member (not shown).

[0023] The first main body member 200 is formed from, for example, a foam. A foam is a porous body formed by finely dispersing gas in a resin and molding it into a foamed state. Examples of foams used to form the first main body member 200 include expanded polystyrene, foamed urethane, and foamed olefin. Expanded polystyrene can be produced in various forms depending on the manufacturing method, such as bead-type expanded polystyrene (EPS), expanded polystyrene sheet (PSP), and extruded expanded polystyrene (XPS). The second main body member 300 is formed from, for example, a non-foamed material. Examples of non-foamed materials include wood, metal materials (iron, stainless steel, etc.), and non-foamed resin materials. In this embodiment, the second main body member 300 is formed from wood. In this embodiment, the second main body member 300 is formed from a material with higher strength than foam (wood), thereby providing the chair body 100 (and consequently the chair 10) with the necessary strength.

[0024] (Cushioning material 90) As shown in Figure 2, the cushion member 90 is positioned to cover the upper surface of the inner seat portion 120 of the chair body 100, the front surface of the inner backrest 140, and the inner sides, upper surface, and front surface of the pair of inner armrests 160. The cushion member 90 is a member for softening the outer seat surface N20, outer backrest surface N40, and outer armrest surface N60 of the chair 10. In this embodiment, the cushion member 90 comprises a first cushion member 91, a second cushion member 92, a third cushion member 93, and a fourth cushion member 94.

[0025] The first cushion member 91 and the second cushion member 92 are approximately the same size and have a roughly rectangular plate shape (not shown). The length of the first cushion member 91 and the second cushion member 92 in the X-axis direction is approximately 0.8 times the length of the seat surface of the inner seat portion 120 in the X-axis direction. The length of the first cushion member 91 and the second cushion member 92 in the Y-axis direction is approximately the same as the length of the seat surface of the inner seat portion 120 in the Y-axis direction. The first cushion member 91 is positioned in a recess provided on the upper surface of the inner seat portion 120 of the chair body 100. The second cushion member 92 is positioned on the upper surface of the first cushion member 91 and is housed in the recess of the inner seat portion 120.

[0026] The third cushion member 93 has a substantially rectangular plate shape (not shown). The length of the third cushion member 93 in the Y-axis direction is the same as the length of the second cushion member 92 in the Y-axis direction. The length of the third cushion member 93 in the X-axis direction is approximately 1.2 times the length of the second cushion member 92 in the X-axis direction. The third cushion member 93 is positioned to cover the upper surface of the second cushion member 92 and the ends of the first cushion member 91 and the second cushion member 92 on the front side of the chair body 100. The third cushion member 93 is housed in a recess provided on the upper surface of the inner seat portion 120. The front end face of the third cushion member 93 is in contact with the surface of the recess provided on the upper surface of the inner seat portion 120.

[0027] The fourth cushion member 94 is positioned to cover the upper surface of the inner backrest 140, the upper surfaces of the pair of inner armrests 160, and the upper surface of the third cushion member 93. The front end face of the fourth cushion member 94 is in contact with the upper surface of the step formed on the front side of the inner seat 120. As a result, the upper surface of the fourth cushion member 94 and the front surface of the inner seat 120 form the same surface. The cushion member 90 is fixed to the chair body 100 by, for example, an adhesive (synthetic rubber solvent). The first cushion member 91, the second cushion member 92, the third cushion member 93, and the fourth cushion member 94 are also fixed together by, for example, an adhesive (synthetic rubber solvent).

[0028] The cushion member 90 can be made of any material that softens the contact area with the outer seat surface N20, the outer backrest surface N40, and the outer armrest surface N60. For example, examples of materials for the cushion member 90 include urethane, chipped urethane, high-rebound urethane, low-rebound urethane, and rubber. In this embodiment, the materials for the cushion member 90 are chipped urethane for the first cushion member 91, high-rebound urethane for the second cushion member 92 and the third cushion member 93, and low-rebound urethane for the fourth cushion member 94.

[0029] (Cover member 95) The cover member 95 is a member that covers the surface of the structure of the chair 10, which comprises the chair body 100 and the cushion member 90. The material of the cover member 95 is, for example, resin cotton. The presence of the cover member 95 prevents soiling of the chair body 100 and the cushion member 90, and provides a cooling or warming sensation to the outer seat surface N20, the outer backrest surface N40, and the outer armrest surface N60. The cover member 95 may cover the entire surface of the structure, or it may cover the structure so that a part of the surface (for example, a part of the bottom surface) is exposed. The cover member 95 is fixed to the chair body 100, for example, by a stapler. Alternatively, the cover member 95 may be fixed to the chair body 100, for example, by a fastener and a pull-in cord provided on the cover member 95.

[0030] A-3. Regarding the protruding part: The chair 10 of this embodiment further includes a protrusion 70. As shown in Figures 3 and 4, the protrusion 70 is positioned on the inner backrest surface M40 of the chair body 100. The inner backrest surface M40 is the outer surface of the chair body 100 that corresponds to the outer backrest surface N40. The inner backrest surface M40 is an example of a backrest surface. Specifically, the protrusion 70 is positioned to protrude from an inclined surface M42 on the inner backrest surface M40. The inclined surface M42 is the inner backrest surface M40 that is inclined diagonally upward and backward toward the upper end 22 of the inner backrest 140. In this embodiment, the inclined surface M42 extends continuously to the upper end 22 of the inner backrest 140 and is inclined continuously so as it approaches the upper end 22 of the inner backrest 140, it is positioned further backward. The inclined surface M42 may be a flat surface that is inclined in a straight line, or it may be a curved surface that is curved in a convex or concave shape.

[0031] In this embodiment, the inclination angle θ1 of the inclined surface M42 with respect to the horizontal plane (XY plane) (see Figure 2) is defined as follows. As shown in Figure 2, the inclination direction of the inclined surface M42 is parallel to the imaginary straight line R connecting the point of contact T1 between the upper end of the convex portion 70 and the inclined surface M42, and the point of contact T2 between the lower end of the convex portion 70 and the inclined surface M42. The inclination angle θ1 is the inclination angle of the imaginary straight line R with respect to the horizontal plane (horizontal line H of the XY plane). The inclination angle θ1 is, for example, 110 degrees (70 degrees). The inclination angle θ1 of the inclined surface M42 may be 95 degrees or more (85 degrees or less), 150 degrees or less (30 degrees or more), 100 degrees or more (80 degrees or less), 135 degrees or less (45 degrees or more), 105 degrees or more (75 degrees or less), or 120 degrees or less (60 degrees or more).

[0032] The hardness of the protrusion 70 is lower than the hardness of the chair body 100. The protrusion 70 is formed from a material that has resilience. Examples of materials used to form the protrusion 70 include cushioning materials such as urethane, chipped urethane, high-rebound urethane, low-rebound urethane, and rubber.

[0033] The protrusion 70 is positioned at a height corresponding to the position of the lower part of the scapula V1 (thoracic vertebrae 5-8) on the seated person's body (for example, an adult with average height). In this embodiment, the height from the outer seat surface N20 of the outer seat portion 20 to the protrusion 70 (center in the vertical direction) (hereinafter simply referred to as "height position L of the protrusion 70"; see Figure 6 below) is set to a height corresponding to the position of the lower part of the scapula V1 (thoracic vertebrae 5-8) on the person's body when seated on the outer seat surface N20. Here, if there is almost no sinking of the outer seat surface N20, the height position L of the protrusion 70 may be within a range that includes at least one of the following height ranges A to D. • Height range A: 471.1 mm or more, and less than 493.7 mm (the position corresponding to the 5th thoracic vertebra) is also acceptable. • Height range B: 448.5mm or more, and less than 471.1mm (the position corresponding to the 6th thoracic vertebra) is also acceptable. • Height range C: 425.9mm or more, and less than 448.5mm (the position corresponding to the 7th thoracic vertebra) is also acceptable. • Height range D: 403.3mm or more, but less than 425.9mm (corresponding to the 5th thoracic vertebra) is also acceptable. Specifically, the height position L of the protrusion 70 may be, for example, within height range C, or within a range that includes all of height ranges A to D (350 mm or more, and 540 mm or less). Furthermore, if there is no sinking of the outer seat surface N20, the height of the protrusion 70 from the seat surface (inner seat surface) of the inner seat portion 120 of the chair body 100 is calculated by the following formula. "The height of the protrusion from the seat of the chair body (100) is 70." = "Height position L of the protrusion 70 (above height range)" + "Thickness of cushion member 90 and cover member 95" (If there is no cushion member, etc., use "0")

[0034] In this embodiment, the outer seat surface N20 sinks down due to the weight of the person sitting on it. The amount of sinking of the outer seat surface N20 depends on the weight of the person sitting on it, but is approximately 20 mm (it may be 10 mm or more and 60 mm, or 15 mm or more and 29 mm or less). Therefore, the height from the outer seat surface N20 of the outer seat portion 20 to the protrusion 70 (center in the vertical direction) in the state before sitting (sinking) (hereinafter simply referred to as "height position of the protrusion 70 before sitting") is calculated by the following formula. "Height position of the protrusion 70 after sitting down" = "Height position L of protrusion 70" - "Amount of sinking" In this embodiment, the height of the protrusion 70 before sitting is, for example, approximately 340 mm. If the outer seat surface N20 sinks, the height of the protrusion 70 from the seat surface (inner seat surface) of the inner seat portion 120 of the chair body 100 is calculated using the following formula. "The height of the protrusion from the seat of the chair body (100) is 70." = "Height position L of the protrusion 70" + ("Thickness of cushion member 90 and cover member 95 before sinking" - "Amount of sinking") = "Height position L of the protrusion 70" + "Thickness of the cushion member 90 and cover member 95 after sinking" The height of the protrusion 70 from the seat surface of the chair body 100 can be, for example, 300mm or more and 700mm or less, 400mm or more and 600mm or less, or 300mm or more and 500mm or less.

[0035] In this specification, the method for measuring the hardness of each component is as follows: (1) Place a sample of the component to be measured in a constant temperature chamber set to 25°C and 50% humidity for 16 hours or more. (2) Remove the above sample from the constant temperature bath and measure its hardness five times using a hardness tester under the following conditions. The five measurements should be taken almost continuously without any time gaps between them. Test environment: Temperature 28.2℃, Humidity 76% (3) Of the five measurement results, the results of the first two measurements will not be used, and the average value of the measurement results from the third measurement onward will be used as the hardness of the material being measured. The first two measurements will result in a harder value, and the results from the third measurement onward will be more stable, so the first two measurements will be used as preliminary measurements.

[0036] The protrusion 70 has a first protrusion 72 and a second protrusion 74. The first protrusion 72 is positioned on the inclined surface M42. The first protrusion 72 is fixed to the inclined surface M42 by, for example, an adhesive (synthetic rubber solvent). The second protrusion 74 is positioned on the first protrusion 72. The second protrusion 74 is fixed to the first protrusion 72 by, for example, an adhesive (synthetic rubber solvent). The first protrusion 72 has a first repulsive force. The second protrusion 74 has a second repulsive force that is lower than the first repulsive force. Specifically, the first protrusion 72 is made of high-rebound urethane, and the second protrusion 74 is made of low-rebound urethane.

[0037] As shown in Figure 2, the fourth cushion member 94 covers the entire inner backrest surface M40, including the protrusion 70. The fourth cushion member 94 is an example of a cover. The repulsive force of the first protrusion 72 may be higher than that of the fourth cushion member 94. The repulsive force of the second protrusion 74 may be higher than, the same as, or lower than that of the fourth cushion member 94.

[0038] In this specification, the method for measuring the repulsive force of each component is as follows: (1) Place a sample of the component to be measured in a constant temperature chamber set to 25°C and 50% humidity for 16 hours or more. (2) Remove the sample from the constant temperature bath and place it flat on the stand of the tensile gauge. The diameter of the pressure lever head of the tensile gauge is 50 mm. Use the tensile gauge and take five measurements under the following conditions. The five measurements should be taken almost continuously without any time gaps between them. The sample is compressed to a thickness of 66 mm at a pressure rate of 100 mm / min. Test environment: Temperature 28.2℃, Humidity 76% (3) Of the five measurement results, the results of the first two measurements will not be used, and the average of the results from the third measurement onwards will be used as the rebound force of the measured material. The first two measurements will result in a firmer value, and the results from the third measurement onwards will be more stable, so the first two measurements will be used as preliminary compression.

[0039] In this embodiment, the relationship between the hardness of the fourth cushioning member 94, the first protrusion 72, and the second protrusion 74 is, for example, as follows. "Hardness of the first protrusion 72 > Hardness of the fourth cushioning member 94 > Hardness of the second protrusion 74" The hardness of the first protrusion 72 is, for example, 65 degrees. The hardness of the first protrusion 72 may be 60 degrees or more and 70 degrees or less, or 63 degrees or more and 67 degrees or less. The hardness of the fourth cushioning member 94 is, for example, 30 degrees. The hardness of the fourth cushioning member 94 may be 25 degrees or more and 35 degrees or less, or 28 degrees or more and 33 degrees or less. The hardness of the second protrusion 74 is, for example, 20 degrees. The hardness of the second protrusion 74 may be 15 degrees or more and 25 degrees or less, or 18 degrees or more and 22 degrees or less. The hardness of the first protrusion 72 may be twice or more the hardness of the second protrusion 74, or three times or more the hardness of the second protrusion 74. The hardness of the first protrusion 72 may be twice or more the hardness of the fourth cushioning member 94.

[0040] In this embodiment, the relationship between the magnitude of the repulsive forces between the fourth cushioning member 94, the first protrusion 72, and the second protrusion 74 is, for example, as follows. "Rebound force of the second protrusion 74 > Rebound force of the fourth cushioning member 94 > Rebound force of the first protrusion 72" The repulsive force of the first protrusion 72 is, for example, 6N. The repulsive force of the first protrusion 72 may be 3N or more and 9N or less, or 5N or more and 7N or less. The repulsive force of the fourth cushion member 94 is, for example, 21N. The repulsive force of the fourth cushion member 94 may be 16N or more and 26N or less, or 19N or more and 23N or less. The repulsive force of the second protrusion 74 is, for example, 22.5N. The repulsive force of the second protrusion 74 may be 17.5N or more and 27.5N or less, or 20N or more and 25N or less. The repulsive force of the second protrusion 74 may be twice or more and three times or more the repulsive force of the first protrusion 72. The repulsive force of the first protrusion 72 may be 1 / 3 or less the repulsive force of the fourth cushion member 94.

[0041] In this embodiment, the relative thicknesses of the fourth cushioning member 94, the first protrusion 72, and the second protrusion 74 are, for example, as follows. "Thickness of the fourth cushioning member 94 > Thickness of the first protrusion 72 = Thickness of the second protrusion 74" The thickness of the fourth cushion member 94 is, for example, 60 mm. The thickness of the fourth cushion member 94 may be 55 mm or more and 65 mm or less, or 58 mm or more and 62 mm or less. The thickness of the first protrusion 72 and the thickness of the second protrusion 74 are, for example, 20 mm. The thickness of the first protrusion 72 and the thickness of the second protrusion 74 may be 15 mm or more and 25 mm or less, or 18 mm or more and 22 mm or less. The thickness of the cover member 95 is 20 mm, but may be 15 mm or more and 25 mm or less, or 17 mm or more and 23 mm or less. The thickness of the third cushion member 93 is 40 mm, but may be 35 mm or more and 45 mm or less, or 37 mm or more and 43 mm or less. The thickness of the second cushion member 92 is 20 mm, but may be 15 mm or more and 25 mm or less, or 17 mm or more and 23 mm or less. The thickness of the first cushion member 91 is 50 mm, but may be 45 mm or more and 55 mm or less, or 47 mm or more and 53 mm or less.

[0042] The protrusion 70 is a convex member that extends linearly in the left-right direction as a whole. In this embodiment, the protrusion 70 is formed continuously along the entire length of the inner backrest 140 (outer backrest 40) in the left-right direction. The length of the protrusion 70 in the left-right direction (length in the long side direction) is, for example, 545 mm, but is not limited to this and may be a length corresponding to the left-right length of the chair 10. The length of the protrusion 70 in the up-down direction (length in the short side direction) is 120 mm, but may be 60 mm or more and 160 mm or less, or 70 mm or more and 130 mm or less.

[0043] Specifically, as shown in Figure 3, both the first protrusion 72 and the second protrusion 74 are flat plate-shaped members that extend linearly in the left-right direction. The left-right length (length in the long side direction) of the first protrusion 72 and the left-right length of the second protrusion 74 are approximately the same, for example, 545 mm. The vertical length (length in the short side direction) of the second protrusion 74 is shorter than the vertical length of the first protrusion 72. The vertical length of the first protrusion 72 is, for example, 120 mm, but it may be between 80 mm and 160 mm, or between 100 mm and 130 mm.

[0044] The vertical length of the second protrusion 74 is set to a size that can correspond to the position of the lower scapula V1 (thoracic vertebrae 5-8). Specifically, the average size of one thoracic vertebra is defined as 17.7 mm or more and 22.6 mm or less, and the vertical length of the second protrusion 74 may be set to be 17.7 mm or more, which is the minimum vertical length corresponding to one thoracic vertebra, and 90.4 mm or less, which is the maximum vertical length corresponding to four thoracic vertebrae. Alternatively, the vertical length of the second protrusion 74 may be 70.8 mm or more and 90.4 mm or less, corresponding to four thoracic vertebrae, 53.1 mm or more and 67.8 mm or less, corresponding to three thoracic vertebrae, 35.4 mm or more and 45.2 mm or less, corresponding to two thoracic vertebrae, or 17.7 mm or more and 22.6 mm or less, corresponding to one thoracic vertebra. Furthermore, considering the durability and versatility of the second protrusion 74, it is more preferable that the vertical length of the second protrusion 74 be in the range of 53.1 mm or more and 90.4 mm or less.

[0045] The upper end of the second protrusion 74 is located below the upper end of the first protrusion 72, and the lower end of the second protrusion 74 is located above the lower end of the first protrusion 72. The first overhang length of the first protrusion 72 extending upward from the second protrusion 74 and the second overhang length of the first protrusion 72 extending downward from the second protrusion 74 are the same (for example, 50 mm). The first overhang length and the second overhang length may be the same (for example, 40 mm or more, or 50 mm or more) or different.

[0046] A-4. Effects of this embodiment: Figure 5 is an explanatory diagram showing the posture of a seated person in the comparative example chair 10X. As shown in Figure 5, chair 10X differs from chair 10 in that it does not have the protrusion 70, but the other configurations are the same. In chair 10X, because the protrusion 70 is not provided, the upper body of the seated person V is in a posture that is bent backward along the outer backrest surface N40 (inner backrest surface M40). Consequently, certain parts of the upper body located above the backrest (e.g., the neck) are positioned even further backward. As a result, the seated person V's neck is tilted too far back and is strained, which may make it impossible for the seated person V to sit for extended periods of time.

[0047] In chair 10X, the seat surface of the inner seat 120 (the outer seat surface N20 of the outer seat 20) is a downward-sloping surface that is angled downwards and backwards toward the inner backrest surface M40. The inner backrest surface M40 (the backrest surface of the outer backrest 40) is a downward-sloping surface that is angled downwards and forwards toward the seat surface of the inner seat 120. In a chair with such a downward-sloping seat and a downward-sloping backrest, the upper body of the sitter is particularly prone to strain. Specifically, the sitter's hips sink lower than their knees due to the slope of the seat, and their center of gravity tends to shift backward due to the slope of the backrest. In response to this, the sitter tries to raise their upper body forward and move their neck forward to maintain balance in the front-to-back direction (bring their center of gravity back forward). As a result, the upper body may be strained.

[0048] Figure 6 is an explanatory diagram showing the seated posture of a person in the chair 10 of this embodiment. As shown in Figure 6, the chair 10 of this embodiment, like the comparative example chair 10X, has a seat that slopes downwards towards the rear and a backrest that slopes downwards towards the front. The inclination angle θ2 of the inner seat portion 120 (see Figure 2) is 25 degrees with respect to the horizontal. The inclination angle θ2 of the seat may be 20 degrees or more and 30 degrees or less. The inclination angle θ3 of the inner backrest surface M40 (the inclination angle of the surface in the approximately central part of the inner backrest surface M40 in the vertical direction, or the inclination angle of the flattest surface, see Figure 2) is 110 degrees with respect to the horizontal. The inclination angle θ3 of the inner backrest surface M40 may be 100 degrees or more and 120 degrees or less. Furthermore, of the backrest surface M40 (the backrest surface of the inner backrest 140), the inclination angle θ4 (see Figure 2) of the lower backrest surface below a predetermined height from the seat (for example, 210 mm or more, or 117 mm or less, and 226 mm or less) may be steeper than the inclination angle of the upper backrest surface above a predetermined height from the seat (the inclination angle θ3 of the inner backrest surface M40 mentioned above). The inclination angle θ4 of the lower backrest surface is 85 degrees with respect to the horizontal. The inclination angle θ4 of the lower backrest surface may be 80 degrees or more and 90 degrees or less. This makes it easier for the seated person to maintain a posture in which the pelvis is in its natural mid-position. The seat inclination angle θ2 may be, for example, the angle of the central part of the seat in the front-to-back direction, or it may be the angle of the "approximately flat and largest area" part of the "seat portion that extends toward the front of the seat from a position moved 15 cm to 20 cm toward the front of the seat from the rear of the seat."

[0049] It is equipped with a protrusion 70. The protrusion 70 is positioned on the inclined surface M42. The protrusion 70 has a lower hardness (Young's modulus) than the chair body 100. Of the fourth cushion member 94 and cover member 95, the portion that covers the protrusion 70 protrudes in a convex shape. In this embodiment, the protrusion 70 is positioned at a height corresponding to the position of the lower part of the scapula V1 of a sitter V seated on the outer seat 20 of the chair 10. Even with the chair 10, the upper body of the sitter V will be in a posture that is bent backward along the outer backrest surface N40 (inner backrest surface M40). However, the protrusion 70 applies a repulsive force to the area around the lower part of the scapula V1 of the upper body, suppressing excessive tilting of the neck and reducing the burden on the upper body. Generally, of the 12 thoracic vertebrae in the human body, the 7th thoracic vertebra is located furthest posteriorly. The protrusion 70 is positioned within the area of ​​the inner backrest surface M40 corresponding to the thoracic vertebrae from the 5th to the 8th thoracic vertebrae, including the 7th thoracic vertebra, thereby stabilizing the head, cervical vertebrae, and thoracic vertebrae in an ideal position that minimizes strain.

[0050] In the chair 10 of this embodiment, the protrusion 70 is configured such that a second protrusion 74, which is relatively low in rebound, is positioned on top of a first protrusion 72, which is relatively high in rebound. As a result, the second protrusion 74, which has relatively low rebound force, can flexibly support the upper body, while the first protrusion 72, which has relatively high rebound force, can support the upper body. In addition, the protrusion 70 tends to take on a smooth shape when covered by the fourth cushion member 94 and the cover member 95. Therefore, according to this embodiment, compared to a configuration in which both the first protrusion 72 and the second protrusion 74 have high rebound force, for example, the presence of the protrusion 70 can suppress its influence on the external shape (design) of the chair 10.

[0051] The upper end of the second protrusion 74 is located below the upper end of the first protrusion 72, and the lower end of the second protrusion 74 is located above the lower end of the first protrusion 72. Therefore, according to this embodiment, by configuring the protrusion 70 in a stepped manner, the height of the protrusion 70 changes in two stages, and the change in height from the chair 100 to the protrusion 70 becomes gradual. Thus, the presence of the protrusion 70 can more effectively suppress its influence on the external shape (design) of the chair 10.

[0052] The performance evaluation of this embodiment will now be explained. The chair 10 of this embodiment can maintain a correct posture that reduces fatigue even after a long period of time. Here, a correct posture is defined as a state in which both the neck and waist are aligned vertically. The following evaluation tests were conducted on the chair 10 of this embodiment and the comparative example chair 10A. • Participants: 19 healthy adult men and women (13 males, 6 females), age 23.4 ± 4.9 years, height 168.9 ± 9.3 cm, weight 64.1 ± 11.5 kg • Test method: Crossover test. Participants were divided into Group A and Group B. Group A sat in chair 10 for the test time (30 minutes) on day 1, and in chair 10A for the test time on day 2. Group B sat in chair 10A for the test time on day 1, and in chair 10 for the test time on day 2. The sitting posture of the participants during the test was captured using a motion capture camera (e.g., Miqus Qualisys). The captured video was analyzed using three-dimensional motion analysis software (e.g., Skeleton Model / Three-Dimensional Motion Analysis Software C-motion) to measure the displacement of the pelvic angle relative to the seat and the trunk angle relative to the ground during the test period. The trunk angle was considered to be the angle of the rib cage (neck).

[0053] The evaluation results showed that, regarding the pelvis of the seated person, the comparative example chair 10A showed a change in pelvic angle during the test period (an angle change of approximately 2 degrees), whereas, in the chair 10 of this embodiment, there was almost no change in pelvic angle during the test period (an angle change of 0.60 degrees or less). Furthermore, when seated, the pelvis was less tilted backward in the chair 10 of this embodiment than in the comparative example chair 10A. Regarding the trunk of the seated person, the comparative example chair 10A showed a change in trunk angle during the test period (an angle change of approximately 3 degrees), whereas, in the chair 10 of this embodiment, there was almost no change in trunk angle during the test period (an angle change of 1 degree or less). Furthermore, when seated, the trunk was less tilted backward in the chair 10 of this embodiment than in the comparative example chair 10A. From these evaluation results, it can be seen that the chair 10 of this embodiment can maintain a correct posture that is less tiring even as time passes, compared to the comparative example chair 10A.

[0054] B. Second Embodiment: Figure 7 is a schematic diagram illustrating the configuration of chair 10A in the second embodiment. Chair 10A is a single-seater chair. As shown in Figure 7, chair 10A comprises a seat 20A, a backrest 40A, and a pair of armrests 60A. The backrest surface of backrest 40A has an inclined surface 42A. The inclined surface 42A is the surface of the backrest surface that is inclined diagonally upward and backward toward the upper end 22A of backrest 40A.

[0055] A protrusion 70A is positioned on the inclined surface 42A. The protrusion 70A is positioned in the center in the left-right direction on the backrest surface. The protrusion 70A is positioned at a height corresponding to the position of the lower part of the shoulder blade V1 of a seated person V who is seated on the outer seat portion 20 of the chair 10. The protrusion 70A is approximately square in shape overall.

[0056] The protrusion 70A has a first protrusion 72A and a second protrusion 74A. The first protrusion 72A is positioned on the inclined surface 42A. The first protrusion 72A is fixed to the inclined surface 42A by, for example, an adhesive (synthetic rubber solvent). The second protrusion 74A is positioned on the first protrusion 72A. The second protrusion 74A is fixed to the first protrusion 72A by, for example, an adhesive (synthetic rubber solvent). The first protrusion 72A has a first repulsive force. The second protrusion 74A has a second repulsive force that is lower than the first repulsive force. Specifically, the first protrusion 72A is made of high-rebound urethane, and the second protrusion 74A is made of low-rebound urethane.

[0057] The upper end of the second protrusion 74A is located below the upper end of the first protrusion 72A, and the lower end of the second protrusion 74A is located above the lower end of the first protrusion 72A. The right end of the second protrusion 74A is located to the left of the right end of the first protrusion 72A, and the left end of the second protrusion 74A is located to the right of the left end of the first protrusion 72A. By configuring the protrusion 70A in a stepped manner, the height of the protrusion 70A changes in two stages, and the change in height from the chair 100A to the protrusion 70A becomes gradual, thereby suppressing the influence of the protrusion 70A on the external shape (design) of the chair 10.

[0058] In the chair 10A of this embodiment, the upper body of the seated person V is in a posture that is bent backward along the backrest surface. However, the protrusion 70A applies a repulsive force to the area around the lower part of the shoulder blade V1 of the upper body, suppressing excessive tilting of the neck and reducing the burden on the upper body.

[0059] C. Variant: The technology disclosed herein is not limited to the embodiments described above and can be modified in various forms without departing from its essence, for example, the following modifications are possible. The configuration of the chair 10 in the above embodiment is merely an example and can be modified in various ways.

[0060] The chair 10 in the first embodiment is a so-called sofa-type chair for 2 to 3 people, but it may also be a sofa-type chair for 1 person. Furthermore, chairs 10 and 10A may have leg members. Chairs 10 and 10A do not necessarily have armrests.

[0061] The shape, dimensions, and manufacturing method of the chair 10 in this embodiment are merely examples and can be modified in various ways. The shape, dimensions, materials, and manufacturing methods of each part of the chair 10 are merely examples and can be modified in various ways.

[0062] The chair 10 of the first embodiment includes a cushion member 90 and a cover member 95, but at least one of these may be omitted. In addition, the cushion member 90 has a four-layer structure in the first embodiment, but the number of layers, the material of each cushioning material, and the size of each cushioning material can be changed as appropriate.

[0063] In the first embodiment, the chair body 100 had a configuration comprising a pair of first body members 200 and a second body member 300, but it may also be a configuration in which the two are integrally formed from the same material.

[0064] In the first embodiment, the protrusion 70 was positioned on the inner backrest 140 of the chair body 100, but it may also be positioned on the outer backrest surface N40 of the outer backrest 40 of the chair 10. Furthermore, the chair 10 of the first embodiment does not need to include at least one of the fourth cushion member 94 and the cover member 95. The thickness of the fourth cushion member 94 may be thinner than the thickness of the protrusion. The fourth cushion member 94 may have a two-layer or three-layer or more structure. Also, in each of the above embodiments, one protrusion 70, 70A was positioned on the inclined surface 42A, M42 of the chair 10, 10A, but multiple (a pair, three or more) protrusions may be positioned on the inclined surface. For example, multiple protrusions may be positioned at distances from each other along at least one of the horizontal and vertical directions. Specifically, a pair of protrusions aligned horizontally may be positioned on the inclined surface at a height corresponding to the position near the sitter's shoulder blades.

[0065] In the above embodiments, the protrusions 70 and 70A were arranged to protrude from the outer surface (outer seat surface N20, etc.) of the chair 10 and 10A. However, the protrusions may also be arranged in a flat configuration on the outer surface of the chair so as to be at approximately the same height as the surrounding portion (cushion member, etc.) located around the protrusions. In other words, the protrusions only need to protrude from the inclined surface of the chair body. In the above flat configuration, it is preferable that the hardness of the protrusions is higher than the hardness of the surrounding portion. This allows the surrounding portion, which is relatively less hard, to sink in when the sitter leans back against the backrest, while the protrusions, which are relatively harder, protrude to support a specific part of the upper body.

[0066] In each of the above embodiments, the protrusions 70, 70A had a two-layer structure consisting of a first protrusion 72, 72A and a second protrusion 74, 74A. However, it is not limited to this, and may be a single-layer structure or a structure with three or more layers. An example of a single-layer protrusion is a structure integrally molded from the same material in the shape of a flat plate or a stepped shape. A multi-layer protrusion is not limited to a structure with steps between layers, but may also be a structure in which the height changes smoothly without steps. Furthermore, the shape of the protrusions 70, 70A is not limited to a rectangle or a square, but may be a circle or an ellipse, for example. Also, the repulsive force of the first protrusions 72, 72A may be the same as the repulsive force of the second protrusions 74, 74A, or it may be lower than the repulsive force of the second protrusions 74, 74A. The first protrusions 72, 72A and the second protrusions 74, 74A may have the same repulsive force and hardness, and their thicknesses may differ.

[0067] The technology disclosed herein may also include, in addition to the following basic configuration of a chair, at least one of the following configurations (a) to (d): <Basic configuration> A chair comprising a seat and a backrest, The backrest surface of the aforementioned backrest includes an inclined surface that slopes upward and diagonally backward toward the upper end of the backrest. The chair further comprises a protrusion projecting from the inclined surface, the protrusion having a lower hardness than the chair body. • Configuration (a): The seat of the chair body has a downward-sloping surface that is angled downwards and backwards toward the backrest. This prevents the sitter's body from sliding forward. In addition, the downward-sloping surface of the seat provides support to the sitter's pelvis. This makes it easier for the sitter to maintain a posture in which their pelvis is in its natural mid-position. • Configuration (b): The backrest surface of the chair body has a forward-sloping surface that is inclined downward and forward toward the seat. This allows the sitter to relax. • Configuration (c): The backrest surface is positioned between the forward-sloping surface (upper backrest surface) and the seat surface, and has a lower backrest surface that is steeper than the forward-sloping surface. The lower backrest surface functions to support the sitter's pelvis. This makes it easier for the sitter to maintain a posture in which their pelvis is in its natural mid-position. In the chair body having configurations (a) and (c), the angle θ5 (see Figure 2) between the seat surface and the lower backrest surface of the chair body may be 100 degrees or less, 90 degrees or less, or 80 degrees or less. • Configuration (d): In configuration (c), the convex portion is positioned on the downward sloping surface (upper backrest surface). The lower backrest surface supports the sitter's pelvis upright, and the convex portion supports the thoracic spine upright, thus maintaining the sitter's S-shaped posture. [Explanation of Symbols]

[0068] 10,10A: Chair 20: Outer seat 20A: Seat 22,22A: Upper end 40: Outer backrest 40A: Backrest 42A,M42: Inclined surface 60: Outer armrest 60A: Armrest 70,70A: Convex part 72,72A: First convex part 74,74A: Second convex part 90: Cushion member 91: First cushion member 92: Second cushion member 93: Third cushion member 94: Fourth cushion member 95: Cover member 100: Chair body 120: Inner seat 140: Inner backrest 160: Inner armrest 200: First main body member 300: Second main body member L: Height position N20: Outer seat surface N60: Outer armrest surface V1: Lower part of shoulder blade V: Seated person

Claims

1. A chair comprising a seat and a backrest, The backrest surface of the aforementioned backrest includes an inclined surface that slopes upward and diagonally backward toward the upper end of the backrest. The chair further comprises a convex portion that protrudes from the inclined surface and has a lower hardness than the chair body.

2. The chair according to claim 1, The chair comprises a first convex portion disposed on the inclined surface and having a first repulsive force, and a second convex portion disposed on the first convex portion and having a second repulsive force lower than the first repulsive force of the first convex portion.

3. The chair according to claim 2, A chair in which the upper end of the second protrusion is located below the upper end of the first protrusion, and the lower end of the second protrusion is located above the lower end of the first protrusion.

4. A chair according to any one of claims 1 to 3, Furthermore, the chair is equipped with a cover that covers the entire backrest surface, including the protrusion.

Images