A chair equipped with a back support and a rotating top rail that fits the back.

Abstract

To provide a chair which firmly supports the lower back and stabilizes the pelvis when working, etc., where an upright posture is often taken, and which quickly fits the back and optimally supports the spine when relaxing, such as when watching television, where various backward-leaning postures are taken, and which can achieve both stability and comfortable sitting comfort according to the usage scene. [Solution] Two back pillars 14L, 14R extend upward from the rear of the seat body 11, and a back brace 15 that abuts the occupant's waist is connected left and right to the lower part between the two back pillars, and a top board 16 that abuts the occupant's back is connected left and right to the upper part between the two back pillars via support shafts 18L, 18R so that it can rotate forward and backward.

Description

[Technical Field]

[0001] This invention relates to a chair with a back support that supports the lower back and a rotating top board that fits the back. More specifically, it relates to a chair designed based on ergonomics, which has a back support that supports the lower back and stabilizes the pelvis, and a rotating top board that fits the back and provides optimal support for the spine, providing both stability and comfort depending on the situation. [Background technology]

[0002] Conventionally, attempts have been made to improve the functionality and comfort of chairs by making the backrest of a chair tiltable in the forward and backward directions and the seat movable in the forward and backward and up and down directions, allowing the backrest and seat to follow the posture and movements of the person sitting on them.

[0003] For example, high-end office chairs are widely used that have a synchronous rocking function, where the seat moves in conjunction with the tilt of the backrest. A link mechanism is often used to link the seat to the backrest, but this synchronous rocking mechanism has a complex structure, which makes it heavy, increases manufacturing costs, and limits its applications.

[0004] Therefore, chairs have been proposed that have a simple structure in which the seat moves in conjunction with the tilting of the backrest.For example, Patent Document 1 discloses a rocking chair in which an upward-facing passive arm 42 is provided at the rear of the seat 2 or the seat support body to which the seat 2 is attached, and a pushing part 43 that pushes the passive arm 42 is provided at the lower end of the backrest 3, so that the seat 2 moves forward in conjunction with the backward tilting of the backrest 3.

[0005] Patent Document 2 also discloses a tilting chair in which a flexible seat body (1), in which the backrest (1b) and seat surface (1a) are integrated, is supported by a seat frame (4) attached to the upper part of the legs (5), the backrest (1b) is connected to the back frame (3) so that it can be tilted backward, a guide rail with a high arc-shaped groove (11a) in the center is fixed to the seat frame (4) so ​​that the seat surface (1a) moves forward and upward in a curved line as the backrest (1b) tilts backward, and a guide member (12) that fits into the arc-shaped groove (11a) and rolls is supported by an axis bracket (12) on the underside of the seat surface (1a).

[0006] The chairs in Patent Documents 1 and 2 have a simpler structure than conventional synchronous rocking mechanisms, and achieve a rocking function that allows the seat to move in conjunction with the tilt of the backrest. Moderate rocking provides adequate support for the body in response to various postures and their changes, improving functionality and comfort while reducing weight and costs. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-4323 [Patent Document 2] WO2020 / 255195A1 publication Summary of the Invention [Problem to be solved by the invention]

[0008] When relaxing and relieving tension, such as watching television or movies, having an evening drink, or chatting with family or friends, people often maintain a posture with their spine tilted back at an angle of 100 to 120 degrees for long periods of time. In this posture, as in the chairs of Patent Documents 1 and 2, the seat moves forward and backward or up and down in conjunction with the backward tilt of the back, allowing the backrest to fit the back in accordance with the natural posture and movement of the body, resulting in a comfortable posture and enhanced relaxation.

[0009] On the other hand, when concentrating on work, study, writing, or other tasks, people often assume an upright posture with a spinal angle of 90-100 degrees, albeit for relatively short periods of time. In this upright posture, if the seat moves in conjunction with the movement of the back, as in the chairs of Patent Documents 1 and 2, the pelvis and spine become unstable, which has become a problem in terms of stability and comfort when sitting. This lack of stability and comfort can affect concentration and work efficiency.

[0010] Furthermore, the chairs in Utility Model Registration Documents 1 and 2 do not have a structural member in the backrest that ensures that the occupant's lower back is in firm contact with and supports the chair, and therefore do not have sufficient pelvic support functionality to firmly support the lower back when in an upright position while working and to stabilize the position and tilt of the pelvis when seated.

[0011] Furthermore, although the structure is simpler than conventional synchronous locking mechanisms, in addition to the structure in which the backrest portion rotates via a support shaft, it is necessary to provide a passive arm and a pushing portion that pushes it, a guide rail with an arc-shaped groove and a guide member that fits into and rolls on it, etc., and the simple structure is not sufficient in terms of low manufacturing costs.

[0012] This invention was made in consideration of the above-mentioned problems, and is based on ergonomics, focusing on comfort when working in an upright position, something that has not been given much consideration in the past.The purpose of this invention is to provide a chair that not only provides a comfortable sitting experience by fitting to the back and supporting the spine when working in a reclining position, but also supports the lower back and stabilizes the pelvis when working in an upright position, providing a calm sitting experience, and is both comfortable and stable depending on the usage situation, with a simple structure and at low cost. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a chair comprising a seat on which an occupant sits, legs extending downward from the seat, and a backrest extending upward from the rear of the seat, wherein the backrest is composed of at least two spine pillars, one on the left and one on the right, a back beam that abuts the occupant's lower back, and a top board that abuts the occupant's back, the two spine pillars extending upward from the rear of the seat approximately vertically or diagonally backward, the back beam connected in the left-right direction to the lower part between the two spine pillars, and the top board connected in the left-right direction to the upper part between the two spine pillars via a support shaft so that it can rotate in the front-to-rear direction.

[0014] The chair of this invention has a fixed seat and a back brace connected to the lower part of the back column to support the occupant's lower back. This stabilizes the position of the legs and buttocks, provides firm support for the lower back, and provides a stable pelvis, providing a sense of stability and a comfortable, relaxed sitting experience during work, study, or other upright tasks. This stable and comfortable sitting experience helps the occupant maintain concentration and reduces fatigue during long periods of work.

[0015] In addition, the top rail that abuts and supports the back of the occupant is connected to the top of the back column so that it can rotate forward and backward, allowing it to quickly follow the posture and angle of the upper body and fit the back when relaxing in various backward positions such as watching TV or a movie, providing a comfortable and relaxing seating experience with optimal support for the spine.The highly comfortable seating experience increases the occupant's sense of rest and satisfaction, contributing to the recovery from fatigue.

[0016] Furthermore, a preferred embodiment of the present invention is the chair described above, characterized in that, when viewed from the front, the vertical center line of the back beam is located 50 to 200 mm above the average height of the upper surface of the seat body.

[0017] It has traditionally been considered most desirable to provide support (lumbar support) for the lumbar lordosis portion below the S-curve of the spine, specifically around the third lumbar vertebra, located approximately 23.5 cm above the seat. By providing physical support in this position, the angle and shape of the spine are stabilized, resulting in a comfortable and stable sitting experience.

[0018] However, after careful consideration, the inventors discovered that by physically supporting the area around the pelvis below the lumbar lordosis, the position and tilt of the pelvis is stabilized, and the angle and shape of the spine extending from there are also stabilized, resulting in a more stable and comfortable sitting experience. By setting the attachment position of the back support within the above range, it is possible to firmly support the lumbar area around the pelvis, stabilizing the pelvis and further enhancing the sense of stability, security, and comfort of sitting.

[0019] Furthermore, a preferred embodiment of the present invention is the above-mentioned chair, characterized in that, when viewed in cross section from the left to right, the horizontal cross section of the front of the back beam and the top board is an approximately circular arc shape or an approximately elliptical arc shape that bulges toward the rear.

[0020] By forming the front of the back brace and top board with a curved surface that fits the occupant's waist and back, the waist is firmly supported, the position and tilt of the pelvis are more stable, and the chair quickly fits to the back, optimally supporting the spine, further improving the stable and calm sitting comfort when working, which often requires an upright posture, and the high level of comfort when relaxing, in various reclining positions.

[0021] Furthermore, a preferred embodiment of the present invention is the chair described above, characterized in that the back support is connected to the lower part between the two left and right spine columns via a support shaft so as to be rotatable in the front-to-back direction.

[0022] In addition to the top rail that is connected to the upper part of the back columns via a support shaft so that it can rotate in the front-to-back direction, the chair is equipped with a back brace that is connected to the lower part of the back columns via a support shaft so that it can rotate in the front-to-back direction.This allows the chair to quickly adapt to various sitting positions and postures of the lower body, providing optimal support for the lower back.When working, which often requires an upright posture, the pelvis is stabilized, further enhancing the sense of stability, security, and calm comfort of sitting.

[0023] Furthermore, one preferred embodiment of the present invention is the above-mentioned chair, characterized in that, when viewed from the front, the central axis of the cap board's support shaft is located 200 to 400 mm above the average height of the upper surface of the seat, the vertical center line of the cap board is located in a position that approximately coincides with the central axis of the cap board's support shaft or is located 1 to 10 mm below said central axis, and the vertical length of the cap board is in the range of 50 to 300 mm.

[0024] By setting the mounting position and shape of the cap within the above range, the cap can be made to conform to various postures and angles of the upper body, further enhancing the fit and support for the back. In addition, by positioning the vertical center line of the cap below the center axis of the support shaft, i.e., by positioning the center of gravity of the cap below the rotation axis, the cap will naturally return to its initial position under gravity after rotation when the load is released, allowing the chair to maintain its shape and function when waiting.

[0025] Furthermore, one preferred embodiment of the present invention is the above-mentioned chair, characterized in that, when viewed from the front, the central axis of the support shaft of the back beam is located 50 to 200 mm above the average height of the upper surface of the seat body, the vertical center line of the back beam is located in a position that approximately coincides with the central axis of the support shaft of the back beam or is located 1 to 10 mm below said central axis, and the vertical length of the back beam is in the range of 50 to 200 mm.

[0026] By setting the mounting position and shape of the back support within the above range, the back support can be improved to follow various seating positions and postures of the lower body, further enhancing the fit and support for the lower back. As above, by placing the center of gravity of the back support below the rotation axis, the back support will naturally return to its initial position due to gravity after rotation when the load is released, allowing the shape and function of the chair to be adjusted when waiting.

[0027] Furthermore, a preferred embodiment of the present invention is the chair described above, characterized in that, when viewed from the side, the angle between the central axis of the two left and right spine columns and the vertical line is in the range of 0 to 30 degrees, and the rotation angle of the top rail relative to the central axis of the two left and right spine columns is in the range of 0 to 45 degrees backward.

[0028] By keeping the inclination angle of the spine and the rotation angle of the top rail within the above ranges, the fit and support of the upper part of the backrest can be improved for various postures and angles of the upper body, further increasing comfort and relaxing sitting experience when relaxing.

[0029] Furthermore, a preferred embodiment of the present invention is the chair described above, characterized in that, when viewed from the side, the angle between the central axis of the two spine columns and the vertical line is in the range of 0 to 30 degrees, and the rotation angle of the spine support relative to the central axis of the two spine columns is in the range of 0 to 30 degrees forward.

[0030] By keeping the tilt angle of the spine column and the rotation angle of the back support within the above ranges, the fit and support of the lower part of the backrest can be improved for various seating positions and postures of the lower body, further enhancing the sense of stability, security, and comfort when sitting while working. [Effects of the Invention]

[0031] The chair of this invention provides a stable and comfortable seating experience, with a fixed seat and back support that provides firm support for the lower back and stabilizes the pelvis during work, which often requires an upright posture. Furthermore, when relaxing and taking various reclining postures, the rotating top rail quickly fits to the back, providing optimal support for the spine, resulting in a comfortable and relaxing seating experience. Despite its simple and low-cost structure, it offers both stability and comfort, suited to various usage situations. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a side view of the chair 1 of the first embodiment as seen from the left side. [Figure 2] 1 is a front view of a chair 1 of a first embodiment as seen from the front. [Figure 3] 1 is a plan view of a chair 1 of a first embodiment as viewed from above. [Figure 4] 1 is a photograph of the chair 1 of the first embodiment, viewed from the left front. [Figure 5] 1 is a photograph of the chair 1 of the first embodiment, viewed from the right rear. [Figure 6] 1 is a partially enlarged view from the left side showing the rotated state of the head rail of the chair 1. FIG. [Figure 7] 1 is an explanatory diagram showing a seated state in a working position (upright posture) on the chair 1 as viewed from the left side. [Figure 8] 1 is an explanatory diagram showing a seated state in a relaxed position (backward leaning posture) of the chair 1 as seen from the left side. [Figure 9] FIG. 10 is a side view of the chair 2 of the second embodiment as seen from the left side. [Figure 10] FIG. 10 is a rear view of the chair 2 of the second embodiment as seen from behind. [Figure 11] 10 is a partially enlarged view from the left side showing the rotation state of the back support of the chair 2. FIG. [Figure 12] 1 is an explanatory diagram showing the seating state of the chair 2 in the working position (upright posture) as seen from the left side. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described in detail below with reference to the drawings, in which: The present invention is not limited to these embodiments, and various modifications are possible without departing from the technical concept of the present invention.

[0034] Furthermore, materials, structures, manufacturing methods, etc. for which explanations are omitted may be the same or substantially the same as those known to those skilled in the art of furniture, etc. In each drawing, the same reference numerals represent the same or equivalent components, and redundant explanations will be omitted. To make the drawings easier to understand, some structures are omitted as necessary.

[0035] In this specification, the position and direction of a seated person sitting in the chair of this invention and facing forward is used as the reference, and the direction in front of the seated person is defined as front (+Y), the direction behind the seated person is defined as back (-Y), the direction to the right hand is defined as right (+X), the direction to the left hand is defined as left (-X), the direction above the head is defined as up (+Z), and the direction below the feet is defined as down (-Z).

[0036] In addition, in this specification, the term "approximately" is not limited to being strictly identical, but is a concept that includes errors or deformations to the extent that identity is not lost. For example, "approximately vertical" is not limited to being completely vertical, but includes a form that can be regarded as being the same as vertical from the viewpoint of action and effect.

[0037] [First embodiment] First, a chair 1, which is a first preferred embodiment of the present invention, will be described with reference to Figures 1 to 8. As shown in Figures 1 to 5, chair 1 comprises a seat body 11 on which an occupant sits, four legs 12FL, 12FR, 12RL, and 12RR extending downward from four positions on the front, back, left, and right of seat body 11, and a backrest 13 extending upward from the rear of seat body 11. Backrest 13 is composed of at least two back pillars 14L and 14R on the left and right, a back beam 15, and a top rail 16.

[0038] The seat body 11 is composed of a flat seat surface 111 and a rectangular seat frame 112 to which it is attached. If the seat surface 111 includes a thick bottom plate or the like and has sufficient mechanical strength on its own, the seat body 11 may be composed of the seat surface 111 alone. To provide cushioning to the seat surface 111, urethane foam is laid on the bottom plate and cloth is stretched over it to create a fabric upholstery. The seat surface 111 may be formed from a solid board, or its upper surface may be hollowed out to form a gentle recess to fit the curve of the buttocks. To provide the seat surface 111 with the ability to deform appropriately in response to weight, the bottom plate may be formed from a highly flexible synthetic resin. In this embodiment, two layers of urethane foam, one hard and one soft, are laid on plywood, and hemp cloth is stretched over them.

[0039] The seat 111 is preferably inclined slightly downward and backward at an angle of 1 to 5 degrees relative to the horizontal installation surface G, making it easier to maintain a correct posture and relax. The seat height is preferably in the range of 360 to 450 mm (1 / 4 of the height of the seated person) from the installation surface G. In chair 1, the seat 111 (seat body 11) is attached at an angle of 2 degrees relative to the installation surface G and is inclined slightly downward and backward, and the average seat height (average of the maximum and minimum seat heights) of the upper surface of the seat 111 (upper surface of seat body 11) from the installation surface G is 380 mm.

[0040] The two front legs 12FL, 12FR are formed from rectangular pillar-shaped members and attached at an angle to the front left and right side surfaces of the rectangular seat frame 112, which is formed from four square timbers. In a side view, the angle of the central axes of the front legs 12FL, 12FR with respect to a vertical line perpendicular to the installation surface G is 14°, extending diagonally downward and forward. The upper ends of the front legs 12FL, 12FR extend further diagonally upward and rearward to form armrests 17L, 17R. Similarly, the two rear legs 12RL, 12RR are formed from rectangular pillar-shaped members and attached at an angle to the rear left and right side surfaces of the rectangular seat frame 112. The angle of the central axes of the rear legs 12RL, 12RR with respect to the vertical line is 10°, extending diagonally downward and rearward. The shape of the legs and their attachment are not limited as long as they can perform the desired function as a chair.

[0041] The two left and right spine columns 14L, 14R are formed from rectangular column-shaped members and are attached at an angle to the left and right rear side surfaces of the rectangular seat frame 112. In a side view, the angle of the central axis of the spine columns 14L, 14R with respect to a vertical line perpendicular to the installation surface G is 10°, and they extend diagonally upward and rearward. To achieve both excellent stability and comfort, the angle of the central axis of the two left and right spine columns with respect to the vertical line in a side view is preferably in the range of 0 to 30° toward the rear, more preferably in the range of 5 to 20°. Two cylindrical support shafts 18L, 18R are protruding near the upper ends of the spine columns 14L, 14R, extending inward in the left-right direction.

[0042] In this specification, the central axis of a rectangular pillar-shaped component such as a spine means a straight line connecting the midpoints of the short-side length of the component and extending longitudinally when viewed from the left and right sides of the chair to which the component is assembled, and when viewed from the front and back sides of the chair.

[0043] The back support beam 15, which contacts and supports the occupant's lower back, is a horizontal component connecting the lower portion of the two left and right back columns 14L, 14R in the left-right direction, and is formed from a rectangular, flat, or rectangular member. The lower portion between the two left and right back columns refers to the portion located below the vertical center point between the average seat height of the seat surface and the height of the top ends of the two left and right back columns. This back support beam 15 mechanically connects the back columns 14L, 14R in the left-right direction, ensuring the strength of the backrest 13, which bears the load. To improve the fit, the front surface is formed in an arc to match the curve of the lower back. For appropriate cushioning, urethane foam may be attached to the front surface and then covered with fabric.

[0044] The attachment and shape of the back brace 15 should be set so that the occupant's lower back is reliably supported and a stable, comfortable sitting experience is achieved. As mentioned above, the inventor's research has shown that by supporting the area around the pelvis below the lumbar lordosis, the position and tilt of the pelvis when seated is stabilized, resulting in a more stable, secure, and comfortable sitting experience than ever before. When viewed from the front, the attachment of the back brace 15 is preferably such that the vertical centerline of the back brace 15 is 50 to 200 mm above the average seat height of the seat surface 111, and more preferably 75 to 150 mm.

[0045] In order to provide a good fit to the lower back near the pelvis of a seated person, the shape of the back brace 15 is preferably a substantially circular or elliptical arc shape in which the horizontal cross section parallel to the installation surface G at its front bulges backward when viewed in left-right cross section. In this embodiment, the back brace 15 is formed from laminated plywood, which is bent to form an arc with a radius of curvature of 300 cm. When the back brace is formed from a wooden material such as laminated plywood, if the curvature of the bending process is made too small, it becomes more susceptible to breakage, so the radius of curvature of the substantially circular arc shape is preferably in the range of 100 to 700 cm, and more preferably in the range of 300 to 500 cm.

[0046] When the back brace is formed by special molding of wood material, or when it is formed using synthetic resin such as polypropylene or light metal such as aluminum alloy, there are fewer constraints on the manufacturing process, so it may be formed into an approximately circular or approximately elliptical shape that is closer to the curved surface of the human body. For example, for an approximately circular shape, the radius of curvature is preferably in the range of 30 to 100 cm, and more preferably in the range of 50 to 80 cm. For an approximately elliptical shape, the major axis radius is preferably in the range of 15 to 60 cm and the minor axis radius is 10 to 40 cm, and more preferably in the range of 20 to 55 cm and the minor axis radius is 15 to 35 cm.

[0047] To ensure reliable support for the lower back, the vertical length of the back beam is preferably in the range of 50 to 200 mm, more preferably 75 to 150 mm. The left-right width of the back beam is preferably in the range of 200 to 600 mm, more preferably 300 to 500 mm. If the left-right width is shorter than the distance between the two spine pillars, an additional connecting member can be added to connect the back beam to the spine pillars, and if it is longer, the mounting position of the back beam can be offset and connected to the front of the spine pillar.

[0048] The cap 16, which abuts against and supports the back of the seated person, is a horizontal component connecting the upper part of the two left and right back pillars 14L, 14R in the left-right direction, and is formed from a rectangular flat plate or rectangular parallelepiped member. The upper part between the two left and right back pillars refers to the part located above the vertical center point between the average seat height of the seat surface and the height of the top ends of the two left and right back pillars. To improve the fit, the front is formed in an arc shape to match the curve of the back. To provide appropriate cushioning, urethane foam may be attached to the front and then cloth may be stretched over it.

[0049] Cylindrical shaft holes 19R, 19L are recessed in the center of the left and right sides of the capping board 16. By fitting support shafts 18L, 18R protruding from the inner surfaces of the spine columns 14L, 14R into shaft holes 19R, 19L recessed in the outer surface of the capping board 16, the capping board 16 is mounted left and right near the upper end between the spine columns 14L, 14R so as to be rotatable in the front and rear directions. To ensure smooth rotation of the capping board 16, rolling bearings or plain bearings may be embedded in the shaft holes 19R, 19L on both the left and right sides of the capping board 16, and the support shafts 18L, 18R may be fitted into the bearing holes to be supported via the bearings.

[0050] FIG. 6 is a partially enlarged view from the left side showing the rotational state of the head board 16 of the chair 1. The head board 16 can rotate in the front-to-rear direction, and the rotation angle can be set so that it fits the back and provides appropriate support. When viewed from the left side, the rotation angle of the center line of the head board 16 in the front-to-rear direction (thickness direction) relative to the central axis of the two left and right spine columns 14L, 14R is preferably in the range of 0 to 45 degrees backward (clockwise), more preferably in the range of 0 to 30 degrees. To increase the degree of freedom of the movable part, it may be rotated forward, preferably in the range of 0 to 15 degrees forward (counterclockwise), more preferably in the range of 0 to 5 degrees. In this embodiment, it can be rotated backward by 30 degrees and forward by 5 degrees (-5 to +30 degrees).

[0051] To prevent accidents such as pinching fingers, a stopper may be provided to limit the rotation angle of the coping 16. An example of a structure is one in which convex portions are provided on both the left and right sides of the coping 16 in positions concentric with the shaft holes 19R, 19L, and arc-shaped concave grooves are provided on the inside surfaces of the two left and right spine columns 14L, 14R in positions concentric with the support shafts 18L, 18R, and the convex portions are fitted into the concave grooves so that they butt against each other, and the rotation range is determined by the arc length of the concave grooves.

[0052] A biasing member such as a torsion spring may be attached between the two left and right spine columns 14L, 14R and the head board 16 so that the head board 16 remains stationary in its initial position when no load is applied and rotates when a seated person leans against it. An example of a structure is one in which the rotation range is limited to 0 to 30° by the stopper, and one end of a torsion spring with an arm angle of 180° is fixed to the outer side of the head board 16 on the left or right and the other end is fixed to the inner side of the spine columns 14L, 14R when the rotation angle is at the initial position of 0°, generating a biasing torque that returns the head board 16 to its initial position when it rotates backward.

[0053] The attachment and shape of the head board 16 may be set so that the back of the seated person is adequately supported and a comfortable sitting experience is achieved. The head board 16 is preferably attached so that, when viewed from the front, the vertical center line of the head board 16 and the central axis of the support shafts 18L, 18R (and shaft holes 19R, 19L) are approximately aligned, and the head board rotates around the vertical center as a fulcrum. The central axes of the support shafts 18L, 18R are preferably positioned 200 to 400 mm above the average seat height of the seat surface 111, and more preferably 250 to 350 mm above.

[0054] Furthermore, by positioning the vertical centerline of the head board 16 below the central axis of the support shafts 18L, 18R (and shaft holes 19R, 19L) that support the head board 16, i.e., by positioning the center of gravity of the head board below the pivot axis, the head board, when released from use, naturally returns to its initial position due to gravity, allowing the chair to maintain its shape and function when standby. In this configuration, when viewed from the front, the vertical centerline of the head board 16 is preferably located 1 to 10 mm below the central axis of the support shafts 18L, 18R, and more preferably 2 to 8 mm below. In this embodiment, the vertical centerline of the head board 16 is set to be located 3 mm below the central axis of the support shafts 18L, 18R.

[0055] In this specification, the central axis of a cylindrical component such as a support shaft is the center of rotation of that component when it rotates, and means a straight line connecting the midpoints of the short-side lengths of those component parts and extending in the longitudinal direction when the chair to which those component parts are assembled is viewed from the front and back from the front and back, and from the top and bottom.

[0056] In order to provide a good fit to the back of a seated person, the shape of the head board 16 is preferably a substantially circular or elliptical arc shape in which the horizontal cross section parallel to the installation surface G at its front bulges backward when viewed in cross section in the left-right direction. In this embodiment, like the back beam 15, the head board 16 is formed from laminated plywood, which is bent to form an arc with a radius of curvature of 300 cm. For the same reasons as the back beam 15, when the head board is formed from a wooden material such as laminated plywood, the radius of curvature of the arc shape is preferably in the range of 100 to 700 cm, and more preferably in the range of 300 to 500 cm.

[0057] When the cap is made of synthetic resin or light metal and there are fewer constraints on the manufacturing process, it may be formed into an approximately circular or elliptical shape that more closely matches the curved surface of the human body. For an approximately circular shape, the radius of curvature is preferably in the range of 30 to 100 cm, more preferably 50 to 80 cm. For an approximately elliptical shape, the major axis radius is preferably in the range of 15 to 60 cm and the minor axis radius is 10 to 40 cm, more preferably 20 to 55 cm and the minor axis radius is 15 to 35 cm.

[0058] To ensure reliable support for the back, the vertical length of the cap board is preferably in the range of 50 to 300 mm, more preferably 100 to 250 mm. The horizontal width of the cap board is preferably in the range of 200 to 600 mm, more preferably 300 to 500 mm. If the horizontal width is shorter than the distance between the two spine columns, a connecting member may be added to connect the cap board and spine columns.

[0059] Two armrests 20L, 20R, made of rectangular pillar-shaped members and extending forward, are fixed to the center of the two left and right back pillars 14L, 14R, and their front ends are joined to the upper ends of the armrests 17L, 17R extending from below to form armrests on which the seated person can rest their elbows. In this embodiment, by integrating the front legs and the armrests, the feeling of pressure from the armrests is reduced, making it easier to sit down.

[0060] The structural members forming each of the above components are not limited to materials that have a predetermined strength, are lightweight, easy to process, and are inexpensive. Examples include softwoods such as cypress, cedar, and pine; hardwoods such as oak, beech, and walnut; solid wood, laminated wood, and plywood made from these materials; synthetic resins such as polypropylene and polyethylene; and metal pipes such as steel, stainless steel alloys, and aluminum alloys. Combinations of these materials may also be used. In this embodiment, the frame is made of solid yellow poplar, with its surface coated with a dark brown cashew paint. The back beams and top boards are made of larch plywood, with their surfaces coated with shellac.

[0061] The joining method for the structural members that form each of the above components is not limited as long as it has the required strength and durability and is inexpensive. Examples include joints and joints using tenon processing, dowel processing, etc., bonding using adhesives suited to the material, and fastening using bolts and nuts or screws and screw holes. A combination of these methods may also be used for joining. In this embodiment, the members are primarily joined using tenon processing joints, and reinforced by bonding with a vinyl acetate resin-based wood glue.

[0062] Figures 7 and 8 are explanatory diagrams of occupant H seated in chair 1, viewed from the left side. Figure 7 shows the seating situation in a usage scenario where occupant H often assumes a nearly upright posture while concentrating on work, study, writing, or other tasks. In this usage scenario (work position), occupant H's legs and buttocks are firmly supported by the fixed seat body 11, and the lower back near the pelvis is firmly supported by the back support 15, stabilizing the pelvis. The back is also appropriately supported by the rotatable head rail 16 in accordance with the posture of the upper body. This stabilizes the position and tilt of occupant H's pelvis, the angle and shape of the spine extending from the pelvis, and the position and line of sight of the head, which is located at the top of the spine, providing a stable and comfortable sitting experience. A highly stable and comfortable sitting experience helps maintain concentration while working and reduces fatigue during long periods of work.

[0063] On the other hand, Figure 8 shows seating situations in which seated persons H often adopt postures that lean back at various angles to relax and unwind, such as watching television or a movie, having an evening drink, or chatting with family or friends. In this posture (relaxed position) for this usage scenario, the rotating headboard 16 rotates backward to fit the back of the seated person H, corresponding to the seated position of the lower body and the leaning back posture of the upper body, providing optimal support at the desired angle. When relaxing, comfort is more important than stability, and by maintaining the angle and shape of the spine, head position, and line of sight of seated person H in the desired comfortable position, a highly comfortable and relaxing sitting experience can be achieved. A highly comfortable sitting experience enhances feelings of rest and satisfaction, helping to relieve fatigue.

[0064] [Second embodiment] Next, a chair 2 according to a second preferred embodiment of the present invention will be described with reference to Figures 9 to 12. As shown in Figures 9 to 10, in chair 2, back support 21 is connected to the lower part between two left and right spine columns 14L, 14R via support shafts 22L, 22R in the left-right direction so as to be rotatable in the front-rear direction.

[0065] Two left and right cylindrical support shafts 22L, 22R extending inward in the left-right direction are protruding below the vertical center of two left and right spine pillars 14L, 14R extending diagonally upward and rearward from the left and right rear side surfaces of the seat frame 112.

[0066] The back beam 21, which abuts against and supports the waist of a seated person, is formed from a rectangular plate-like or rectangular parallelepiped member, and has cylindrical shaft holes 23R, 23L recessed in the vertical center of its left and right side surfaces. By fitting support shafts 22L, 22R protruding from the inner surfaces of the back pillars 14L, 14R into shaft holes 23R, 23L recessed in the outer surface of the back beam 21, a cap rail 16 is attached left and right below the vertical center between the back pillars 14L, 14R so as to be rotatable in the front and rear directions.

[0067] A horizontal beam 24 is installed near the vertical center between the two left and right spine columns 14L, 14R, connecting the spine columns in the left-right direction. This beam 24 is offset so as not to come into contact with the back of the seat occupant and is joined to the rear surface of the spine columns 14L, 14R, forming a U-shape integrated with the armrests 20L, 20R in a plan view from above. The horizontal mechanical connection at the center between the spine columns 14L, 14R ensures the strength of the backrest 13, which bears the load.

[0068] FIG. 11 is a partially enlarged view from the left side showing the rotational state of the back support 21 of the chair 2. The back support 21 can rotate in the front-to-rear direction, and the rotation range can be set so that it fits and supports the lower back appropriately. When viewed from the left side, the rotation angle of the center line of the back support 21 in the front-to-rear direction (thickness direction) relative to the central axis of the two left and right spine columns 14L, 14R is preferably in the range of 0 to 30 degrees forward (counterclockwise) and backward (clockwise), more preferably in the range of 0 to 15 degrees. In this embodiment, it can rotate within a range of 15 degrees forward and 15 degrees backward (-15 to +15 degrees).

[0069] The shape, structure, operation, function, materials, and manufacturing method of the rotating back beam 21 and other components of chair 2 are the same as those of the rotating headboard 16 and other components of chair 1 in the first embodiment. The back beam may be supported via a bearing to ensure smooth rotation, or a stopper may be provided to limit the rotation angle of the back beam. Also, a biasing member may be attached between the back pillar and the back beam so that the back beam automatically returns to its initial position when no load is applied, and the back beam may be supported so that its center of gravity is located below the rotation axis.

[0070] FIG. 12 is an explanatory diagram of a seated person H seated in chair 2, viewed from the left side. Similar to FIG. 7 of embodiment 1, FIG. 12 illustrates a seated state in a usage scenario in which the person often assumes a nearly upright posture while concentrating on work or other tasks. In this usage scenario (work mode), the legs and buttocks of seated person H are firmly supported by fixed seat body 11, and the pivoting back support 21 pivots forward to fit the lower back near the pelvis in accordance with the seating position of seated person H's lower body, providing optimal support in the desired position. Furthermore, the back is also appropriately supported by pivoting head rail 16 in accordance with the posture of the upper body. This stabilizes the position and tilt of seated person H's pelvis, the angle and shape of the spine, and the position and line of sight of the head, providing a more stable and comfortable sitting experience.

[0071] The chair of the present invention is not limited to the present embodiment and can be modified in various ways. For example, the seat and the lower back, including the back support, can be integrally formed from synthetic resin to fit the curves of the buttocks and lower back, improving the fit. Furthermore, a support column can be extended downward from the seat, and multiple caster-equipped legs can be provided at the bottom to allow for mobility. [Explanation of symbols]

[0072] 1...chair 1, 11...seat, 111...seat surface, 112...seat frame, 12FL, 12FR...front legs, 12RL, 12RR...rear legs, 13...backrest, 14L, 14R...back pillar, 15...back beam, 16...cap (rotating), 17L, 17R...armrest, 18L, 18R...support axis, 19R, 19L...axis hole, 20L, 20R...armrest, G...installation surface (horizontal surface), H...seater.

[0073] 2...Chair 2, 21...Back support (rotating type), 22R, 22L...Support axis, 23R, 23L...Axis hole, 24...Horizontal member.

Claims

1. A chair comprising a seat body on which a seated person sits, legs extending downward from the seat body, and a backrest extending upward from the rear of the seat body, The backrest is at least composed of two back pillars on the left and right, a back beam that abuts the waist of the seated person, and a cap that abuts the back of the seated person, The two left and right spine columns extend upward from the rear of the seat body substantially vertically or diagonally rearward, The back beam is connected in the left-right direction to the lower part between the two left and right spine columns, The chair is characterized in that the cap rail is connected to the upper part between the two left and right back pillars via a support shaft so as to be rotatable in the left and right directions.

2. The chair according to claim 1, characterized in that, when viewed from the front, the vertical center line of the back support is located 50 to 200 mm above the average height of the upper surface of the seat body.

3. The chair according to claim 1 or 2, characterized in that, when viewed in cross section from the left to right, the horizontal cross section of the front of the back beam and the top rail is an approximately circular arc shape or an approximately elliptical arc shape that bulges toward the rear.

4. 2. The chair according to claim 1, wherein the back support is connected to the lower portion between the two left and right back pillars via a support shaft so as to be rotatable in the left-right direction.

5. A chair as described in claim 1 or 2, characterized in that, when viewed from the front, the central axis of the cap board's support shaft is located 200 to 400 mm above the average height of the upper surface of the seat, the vertical center line of the cap board is located at a position that approximately coincides with the central axis of the cap board's support shaft or is located 1 to 10 mm below said central axis, and the vertical length of the cap board is in the range of 50 to 300 mm.

6. The chair described in claim 4, characterized in that, when viewed from the front, the central axis of the support shaft of the back support is located 50 to 200 mm above the average height of the upper surface of the seat body, the vertical center line of the back support is located at a position that approximately coincides with the central axis of the support shaft of the back support or is located 1 to 10 mm below the central axis, and the vertical length of the back support is in the range of 50 to 200 mm.

7. The chair according to claim 1 or 2, characterized in that, in a side view, the angle of the central axis of the two left and right spine pillars relative to a vertical line is in the range of 0 to 30 degrees, and the rotation angle of the top rail relative to the central axis of the two left and right spine pillars is in the range of 0 to 45 degrees backward.

8. In a side view, the angle of the central axis of the two left and right spine columns relative to a vertical line is in the range of 0 to 30 degrees, and the rotation angle of the spine support relative to the central axis of the two left and right spine columns is in the range of 0 to 30 degrees forward. A chair according to claim 4 or 6.

Images