chair back

Abstract

To provide a backrest of chair by which low back pain and fatigue are reduced by straight supporting a spine 2.SOLUTION: For the purpose of straight supporting a spine 2 by avoiding influence of both blade bones 3, 3 and both iliac bones 4, 4, the rear of the erector muscles 6, 6 of spine in a range reaching from between both blade bones 3, 3 to between both iliac bones 4, 4 is supported by a flat rigid body. Also, in the backrest 1 of a chair in which the breadth of the supporting flat is laterally spread in the range untouchable from the lower part circumferential of the ribs to both iliac crests 4a, 4a, the size indicating the shape adapted to a person having the body length of approximately 170 cm shown in Fig. 2 is made a reference. In a body length in excess of the adaptable range, the size reference is similarly changed in accordance with the body length difference, with the backrest 1 of a chair adapted to the size of the back.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a chair back. [Background technology]

[0002] There have been many attempts to improve chair backs in order to alleviate lower back pain and fatigue caused by sitting. The present invention addresses this issue by supporting the spine in a straight line, but there have been no specific or suggestive proposals in the past that suggest that supporting the spine in a straight line would address this issue. Meanwhile, there have been many flat backrests since ancient times, but leaning on them does not straighten the spine, and even after years of use, there is still room for improvement in the issues discussed above. Summary of the Invention [Problem to be solved by the invention]

[0003] The problem that this invention aims to improve is the alleviation of lower back pain and fatigue caused by sitting. The main causes of lower back pain and fatigue are the backward tilt of the pelvis caused by sitting and the resulting C-shaped curvature of the lumbar spine. Furthermore, the weight of the upper body is placed on this curvature of the lumbar spine, causing buckling, which further increases the curvature of the lumbar spine and contributes to lower back pain. Buckling of the lumbar spine also acts to displace the lumbar spine further backward, but at the same time, the support pressure on the lumbar spine increases as it is pressed down by the backrest. In addition, the reduced contact area caused by the curvature of the lumbar spine increases the support pressure per unit area, which also contributes to poor blood circulation.

[0004] As mentioned above, if there is a curve anywhere in the spine, the weight of the upper body will cause buckling, which can lead to lower back pain and fatigue. Therefore, buckling can be prevented by supporting the spine so that it is straight. However, since the weight of the upper body on the spine is supported not only by the spine but also by the buttocks through the pelvis, it is necessary to prevent buckling along the entire support path. Therefore, a support position that prevents the pelvis from tilting backward in relation to the spine is also an issue.

[0005] Many chairs have traditionally had flat backrests, but they do not support the spine in a straight line. This is because the human back is not flat. Referring to Figure 3, the shoulder blades 3·3, the iliac crests 4a·4a, and the lower part of the sacrum 5 protrude further back than the erector spinae muscles 6·6 (the parts that support the spine 2 shown in Figure 4), and their positions and influences are different. Therefore, a flat backrest that simply covers the entire back will not straighten the spine 2 even when pressed against it. It is also necessary to prevent the pelvis from tilting backward due to the weight of the upper body, and to achieve this, it is important to support the lumbar spine near the junction between the sacrum 5 and the lumbar vertebrae. Because this area is located between the iliac bones 4·4 and slightly recessed relative to the iliac bones 4·4, a flat backrest spanning the iliac bones 4·4 would create a gap and provide no support. Therefore, the lumbar vertebrae displace backward to fill the gap, inducing a backward tilt of the pelvis and curvature of the lumbar spine. Therefore, to prevent this, it is essential to support the position between the two ilia 4. As mentioned above, in order to support the spine 2 straight, it is important to have a support position that prevents backward tilt of not only the spine but also the pelvis.

[0006] Furthermore, simply supporting the backs of the erector spinae 6 / 6 in the area from between the scapulae 3 / 3 to between the iliac crests 4 / 4 on a flat surface will not straighten the spine 2. The reason for this is that the center of gravity of the upper body is forward of the spine 2, and there are no ribs in the abdominal area, so a force bending the spine 2 near the abdomen acts to bend it forward, and the support pressure in that area is higher than in other areas. As a result, the erector spinae 6 / 6 in this area collapses more than in other areas, and the spine 2 is no longer supported straight. Therefore, it is necessary to make the collapse uniform throughout the entire erector spinae 6 / 6, which requires adjustment to spread the support area left and right from around the lower ribs in the area corresponding to the area but not touching the iliac crests 4a / 4a, thereby making the collapse uniform. [Means for solving the problem]

[0007] The solution to the above problem is a chair back 1 that avoids the scapulae 3 / 3 and iliac crests 4a / 4a, which are areas that protrude further back than the erector spinae muscles 6 / 6 running vertically on both sides of the spinal column 2, and supports the back of the erector spinae muscles 6 / 6 in the area from between the scapulae 3 / 3 to between the iliac crests 4 / 4 with a flat rigid body, and that widens the width of the supporting plane to the left and right in the area from around the lower ribs so as not to come into contact with the iliac crests 4a / 4a.

[0008] The solution to the above problem is to "support the chair with a flat, rigid body," but the impact of the curvature of that plane on the seating sensation is shown below. (The backrest was placed on a flat, uncurved surface, and measurements were taken at the gap in the center, with the distance between the top and bottom of the backrest being 33cm.)

[0009] Experiments have shown that up to 1mm of curvature on the convex side (the direction in which the lumbar vertebrae curve forward) and up to 0.5mm of curvature on the opposite concave side, the sitting sensation is the same as on a flat surface with no curvature. The sensory difference begins to be felt at 2mm of curvature on the convex side and 1mm of curvature on the concave side. The sitting sensation continuously deteriorates as the curvature increases, so the degree of improvement varies depending on where the compromise is made. The compromise is thought to be around 3mm for the convex side and 1.5mm for the concave side.

[0010] The above measurements of curvature were carried out using a backrest 1 made of a rigid body, but it is possible to support the spine 2 straight even when made of a flexible elastic material. This is because, according to the present invention, the support pressure is distributed evenly across the entire surface of the backrest 1, so even if the backrest is made of a flexible elastic material, the entire surface deforms evenly and remains flat. However, when using a flexible elastic material, it is necessary to place a flat rigid base behind the backrest 1 in order to prevent the entire backrest 1 from curving. [Effects of the Invention]

[0011] When spine 2 is supported straight, gravity acting on the upper body can be divided into a component force acting in the direction of spine 2 (along spine 2) and a component force acting perpendicular to the surface of backrest 1. The former component force acting in the direction of spine 2 is received by the buttocks through the pelvis without causing buckling of spine 2. In the process, backward tilt of the pelvis can be prevented by supporting the area between both iliac bones 4 and 4. Meanwhile, the latter component force acting perpendicular to the surface of backrest 1 is distributed evenly across the entire surface of backrest 1 (due to the absence of buckling and the area compensation of backrest 1), making it possible to evenly compress the erector spinae 6 and 6.

[0012] The natural posture that does not place strain on the lumbar spine is related to the tilt of the pelvis. In an upright position, the pelvis tilts slightly forward, and the natural posture of the lumbar spine is a lordotic state. On the other hand, during the sitting process, the pelvis is pulled backward by the gluteus maximus and hamstrings, causing the lumbar spine to deform from this lordotic state to a straight state and then a forward-leaning, C-shaped curve in response to the backward tilt of the pelvis. The posture formed according to the degree of backward tilt of the pelvis is the natural posture, and changing it requires the application of muscle strength or external force. For these reasons, when sitting, the lordotic state of the lumbar spine, as seen in an upright position, is not a natural posture. Therefore, the present invention enables support in a straight position with less curvature of the lumbar spine within this natural posture, thereby reducing lower back pain and fatigue. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing a backrest of the present invention applied to a chair. [Figure 2] FIG. 2 is a dimensional diagram showing the shape of the backrest of the present invention. [Figure 3] 10A and 10B are diagrams showing the positional relationship between the backrest and the back of the present invention. [Figure 4] FIG. 1 is an explanatory diagram showing the position of the erector spinae muscles. [Figure 5] FIG. 1 is a perspective view showing a backrest of the present invention applied to a chair having a backboard that covers the entire back. [Figure 6]FIG. 1 is a perspective view showing a seat back of an automobile in which the backrest of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0014] Figure 1 is a perspective view of the backrest of the present invention applied to a chair. The dimensions of the shape of the backrest 1 are shown in Figure 2. The backrest 1 is formed from a flat, rigid body, and its wider portion is fixed to the chair's support pillars on both sides. The functional role of this wider, flat portion (compensating for support pressure) is up to about 24 cm, and the portions on both sides beyond that serve to fix it to the chair's support pillars. The gap between the seat and the bottom of the backrest 1 is set to 10 cm (suitable for a height of approximately 170 cm), but the backrest 1 can be equipped with a vertical adjustment mechanism to expand the range of suitability. In this embodiment, the seat is set horizontally, and the angle between the seat and backrest 1 is set to 113 degrees. Materials commonly used for chairs, such as wood or plastic, are used.

[0015] Figure 2 is a dimensional drawing showing the shape of the backrest of the present invention. The dimensions when adapted to a person about 170 cm tall are shown below. W=30cm W1=8cm W2=10cm W3=13cm W4=8cm H=33cm H1=6cm H2=13cm R=4cm

[0016] Figure 3 shows the positional relationship between the backrest and the back of the present invention. The upper part of the backrest 1 supports the erector spinae 6-6 in an area that is not affected by the protrusion of the shoulder blades 3-3, and the lower part supports the erector spinae 6-6 between the iliac bones 4-4 in an area that is not affected by the iliac bones 4-4. The area from the lower ribs to the area that does not touch the iliac crests 4a-4a is widened on both sides to increase the support area. A space S is provided between the backrest 1 and the iliac crests 4a-4a.

[0017] Figure 5 is a perspective view of the backrest of the present invention applied to a chair with a backboard that covers the entire back. The backboard 1a and seat are integrally formed from molded plywood (rigid body). The backboard 1a is formed flat, with a urethane foam backrest 1 formed on its surface. The backrest 1 is formed to protrude by about 20 mm to avoid the backboard 1a affecting the shoulder blades 3. The urethane foam will collapse when leaning on it, but it is desirable that a protrusion of about 15 mm remains.

[0018] Figure 6 is a perspective view of the backrest of the present invention applied to an automobile seat back. The relationship between the protrusion amount of seat back 1b and backrest 1 is the same as in the embodiment shown in Figure 5. Behind the covering material on the surface of backrest 1, a urethane foam approximately 10 mm thick is placed, and further behind that is supported by a flat rigid body to maintain the flatness of backrest 1, and seat back 1b and backrest 1 are supported by springs so that they can elastically move back and forth in sync. [Explanation of symbols]

[0019] 1 backrest 1a backboard 1b Seat back 2 spinal column 3. Shoulder blades 4. Ilium 4a iliac crest 5. Sacrum S Space 6 Erector spinae

Claims

1. In order to support the spine 2 straight while avoiding the influence of the scapulae 3 and the ilium 4, a rigid support plane supports the back of the erector spinae 6 in the area from between the scapulae 3 to between the ilium 4, and the width of the support plane is widened to the left and right within an area from the lower periphery of the ribs to the iliac crests 4a, 4a, and the dimensions of the backrest 1 are 33 cm from the bottom to the top, and the width at the bottom is 8 cm. The width at a position 6 cm above the lower end is 10 cm, and this position coincides with the lower end of the part of the support plane that is widened to the left and right, the width of the part that is widened to the left and right is 30 cm, the distance from the lower end to the upper end of the part that is widened to the left and right is 13 cm, the width of the starting end that supports the center above the upper end of the part that is widened to the left and right is 13 cm, and the width of the upper end of the backrest 1 located above the starting end is 8 cm.

2. A chair backrest (1) formed on a flat rigid surface, said backrest (1) supporting the back of the erector spinae muscles (6,6) in the range from between the shoulder blades (3,3) to between the ilium (4,4) on a support plane in order to support the spine (2) straight while avoiding the influence of the shoulder blades (3,3) and the ilium (4,4), and the width of said support plane is expanded on the left and right within a range from around the lower periphery of the ribs to not touching the iliac crests (4a,4a), said backrest (1) having a shape and dimensions of 33 cm from the bottom end to the top end of said backrest (1), a width of 8 cm at said bottom end, and a width of 10 cm at a position 6 cm above said bottom end, said position coinciding with the bottom end of the expanded part of the width of said support plane, and said width The width of the part that is widened to the left and right is 30 cm, the distance from the bottom to the top of the part that is widened to the left and right is 13 cm, the width of the starting end that supports the center above the top end of the part that is widened to the left and right is 13 cm, and the width of the upper end of the backrest 1 located above the starting end is 8 cm.The backrest 1 of the chair has a supporting plane formed from a flexible elastic material.

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