Patent Description:
There are conventional chairs configured to be stackable or nestable. In some cases, a backrest has a reduced thickness in a front-rear direction, in order to reduce a gap in the front-rear direction between chairs when the chairs are stacked. Patent Document <NUM> below discloses a backrest configured with a relatively thick frame and relatively thin plate-shaped members arranged within the frame.

<CIT> discloses a backrest for use in a chair, the backrest comprising a back board arranged in a position to abut a back of a seated person on the chair, wherein a first area including a laterally central area of the back board has a thickness greater than a thickness of a second area of the back board located closer to each of left and right ends of the back board than the first area.

<CIT> discloses a back panel of a chair with a flexible back pad on the inner side of a back frame supported by a backrest. The thickness at the center of the back pad in the vertical direction gradually becomes larger from either left or right side toward the center so that the thickness at the center in the left/right direction is the largest.

<CIT> discloses an L-shaped, molded plastic shell comprising a seat portion and a back portion, both joined by an integrally concavoconvex nonflanged waist portion with a stiffening structure medial of the waist portion.

In a backrest with a thick frame as disclosed in aforementioned Patent Document <NUM>, the frame is likely to have a low flexibility. In particular, since left and right corners of the backrest are less likely to follow body movement, a seated person's action of turning around while keeping seated or stretching out the left or right hand rearward may be hindered.

In one aspect of the present disclosure, it is preferable to propose a backrest that is less likely to obstruct body movement.

The problems are solved by the features of claim <NUM>. In the dependent claims advantageous and appropriately developments are outlined.

One aspect of the present disclosure provides a backrest for use in a chair, and comprises a back board arranged in a position to abut a back of a seated person on the chair. A first area including a laterally central area of the back board has a thickness greater than a thickness of a second area of the back board located closer to each of left and right ends than the first area.

This configuration allows the second area to be relatively deformable. Accordingly, particularly when a seated person turns the body rearward, movement of the seated person is less likely to be obstructed by the backrest. Also, when the seated person is seated in a normal posture (a posture of facing forward), the back can be supported by the first area having a relatively high rigidity.

In the above-described backrest, the back board may comprise a region having a thickness that gradually decreases upward. With this configuration, the back board becomes more deformable as a position becomes upper, and the backrest is less likely to obstruct movement of the body.

According to the invention, the back board comprises a high rigidity portion provided at least in a lower area from a vertical center position at each of the left and right ends of the back board. The high rigidity portion has a rigidity higher than that of a surrounding area of the high rigidity portion in the back board. With this configuration, a lower portion of the backrest can securely support the backrest. Also, an upper portion of the backrest having high flexibility is less likely to obstruct movement of the body.

In the above-described backrest, the backrest may be connected to a seat body of the chair or a support body supporting the seat body by a connecting portion. The connecting portion may be connected to the first area in the backrest. With this configuration, connection with the seat body or the like is achieved using the first area having a relatively high rigidity, and thus the backrest can be held stably.

In the above-described backrest, at least the second area may comprise a flexible structure to improve flexibility of the back board. The first area may comprise no flexible structure. With this configuration, it is possible to achieve an increased flexibility of the second area, while inhibiting decrease in rigidity of the first area.

In the above-described backrest, the back board may comprise a projecting portion projecting rearward at an upper end of the back board. With this configuration, it is possible to hold the projecting portion to carry the backrest (and thus, the chair).

According to the invention, the back board comprises an area having a thickness gradually decreasing from a lateral center of the back board toward the left and right ends. With this configuration, the flexibility of the back board gradually changes toward the left and right ends of the back board. Accordingly, it is possible to reduce an uncomfortable feeling that may be caused to a seated person due to abrupt changes in flexibility of the back board.

According to the invention, at least a part in a vertical direction of each of the left and right ends of the back board may be a portion having a smallest thickness at a same height of the back board. This configuration can achieve increased flexibility at the ends of the back board.

A main part of the above-described back board may be formed from a material that is a thermoplastic elastomer or a mixture including a thermoplastic elastomer. This configuration can achieve increased flexibility at the ends of the back board.

Another aspect of the present disclosure provides a chair that comprises the above-described backrest. Such chair can achieve the effects brought by the above-described backrest.

chair, <NUM>. support body, <NUM>. seat body, <NUM>. backrest, <NUM>. pipe body, <NUM>. front side connector, <NUM>. rear side connector, <NUM>. connecting portion, <NUM>. back board, <NUM>. pipe holder, <NUM>. projecting portion, <NUM>. bent portion, <NUM>. first area, <NUM>. second area, <NUM>. thinnest portion, <NUM>. backrest, <NUM>. first area, <NUM>. second area, <NUM>. backrest, <NUM>. high rigidity portion, <NUM>. backrest, <NUM>. first area, <NUM>. second area, <NUM>. connecting portion , <NUM>. backrest, <NUM>. back board, <NUM>. first area, <NUM>. second area, <NUM>. through hole, <NUM>. dimple, <NUM>. backrest, <NUM>. back board, <NUM>. first area, <NUM>. second area, <NUM>.

A description will be given of embodiments of the present disclosure with reference to the drawings.

As shown in <FIG>, a chair <NUM> comprises a support body <NUM>, a seat body <NUM>, a backrest <NUM>, and other components.

In the present embodiment, configurations of respective components may be described using directions, such as a front-rear direction, a left-right (lateral) direction, and an up-down (vertical) direction, and these directions are indicated with respect to a user who is normally seated on the chair <NUM>. That is, front is a direction that the seated user faces. The chair <NUM> is left-right symmetric.

The support body <NUM> comprises paired left and right pipe bodies <NUM> each formed by bending a tubular metal pipe, and bar-shaped front side connector <NUM> and rear side connector <NUM> each connecting the paired pipe bodies <NUM>. The paired pipe bodies <NUM> each form a substantially rectangular ring shape when viewed from left or right side. The seat body <NUM> is supported by upper ends of the paired pipe bodies <NUM> and the rear side connector <NUM>.

The seat body <NUM> is substantially rectangular when seen in a plan view, and is configured to allow a user to be seated thereon. Left and right ends, and a rear end of the seat body <NUM> are connected to the respective upper ends of the paired pipe bodies <NUM> and the rear side connector <NUM>, and thereby the seat body <NUM> is fixed to the support body <NUM>.

Each of the paired pipe bodies <NUM> comprises a connecting portion <NUM> that deviates from the rectangular ring shape and projects upward from a portion connecting with the rear side connector <NUM>. The backrest <NUM> is connected to the support body <NUM> by the left and right connecting portions <NUM>, and thereby secured to the support body <NUM> through the left and right connecting portions <NUM>.

As shown in <FIG>, the backrest <NUM> for use in a chair is substantially rectangular in a front view. Also, when viewed in a plan view, the backrest <NUM> forms a gentle curve such that both of left and right ends are positioned forward and a central part positioned rearward.

The backrest <NUM> comprises a back board <NUM>, paired pipe holders <NUM>, a projecting portion <NUM>, and a bent portion <NUM>. The back board <NUM> has a substantially rectangular shape. The paired pipe holders <NUM> are provided at left and right ends of the back board. The projecting portion <NUM> is provided at an upper end of the back board. The bent portion <NUM> is provided at a lower end of the back board.

The back board <NUM> is arranged in a position to abut the back of a seated person on the chair <NUM>.

A laterally central area of the back board <NUM> is a first area <NUM>, and areas located closer to the left and right ends of the back board <NUM> than the first area <NUM> are second areas <NUM>. As shown in <FIG>, the first area <NUM> has a thickness L1 greater than a thickness L2 of the second area <NUM>. Also, as shown in <FIG>, an upper area in a vertical direction of each of the left and right ends of the back board <NUM> is a thinnest portion <NUM> having a smallest thickness at a same height of the back board <NUM>.

More specifically, the thickness of the back board <NUM> gradually decreases from a lateral center of the back board <NUM> toward the left and right ends except for areas where the pipe holders <NUM> are formed. In other words, the thickness of the first area <NUM> is greater than the thickness of the second area <NUM>, and the thickness also varies within each of the first area <NUM> and the second area <NUM> depending on a lateral position therein.

A material for a main part of the back board <NUM> is a thermoplastic elastomer. The material for forming the back board <NUM> may be a mixture including a thermoplastic elastomer.

As shown in <FIG>, the back board <NUM> has a thickness greatest at a lower end and gradually decreasing upward. As shown in <FIG>, the thickness of the back board <NUM> decreases upward at any position along the lateral direction.

The paired pipe holders <NUM> are provided at the left and right ends of the back board <NUM> in a lower area from a vertical center position. The paired pipe holders <NUM> each have a greater thickness than a surrounding area, and protrude rearward from the back board <NUM>. The connecting portion <NUM> is inserted in each of the paired pipe holders <NUM>. Thus, the paired pipe holders <NUM> each have a higher rigidity than the surrounding area of the pipe holder <NUM> in the back board <NUM>. The paired pipe holders <NUM> each correspond to a high rigidity portion.

The projecting portion <NUM> is a plate-shaped portion projecting rearward across an entire laterally extending area of the upper end of the back board <NUM>. The bent portion <NUM> is a plate-shaped member projecting rearward across an entire laterally extending area of the lower end of the back board <NUM>.

According to the embodiment detailed above, the following effects can be obtained.

(1a) In the chair <NUM>, the second area <NUM> of the back board <NUM> is relatively more deformable than the first area <NUM>. Thus, for example, as indicated by two-dotted chain lines in <FIG>, end portions of the back board <NUM> are easily elastically deformable rearward. Accordingly, for example, when a seated person turns the body rearward, movement of the seated person is less likely to be obstructed. Also, when the seated person faces forward, the first area <NUM> having a high rigidity sufficiently supports the back, and thus, it is possible to reduce impairment of the function of the backrest due to excessive flexibility of the backrest.

(1b) Since the back board <NUM> gradually becomes thinner upward, an upper part of the back board <NUM> has a relatively high flexibility. Accordingly, when a seated person moves the body, obstruction of the movement by the back board <NUM> can be significantly reduced.

(1c) The backrest <NUM> comprises the pipe holders <NUM> at two left and right positions of its lower end. The pipe holders <NUM> have high rigidity, and thus, provide high rigidity of a lower part of the backrest <NUM> that provides small influence on movements of a seated person, thereby allowing inhibition of unnecessary flexibility of the backrest <NUM>.

(1d) The backrest <NUM> comprises the projecting portion <NUM> and the bent portion <NUM>, and thus can inhibit deformation of the shape of the backrest <NUM> caused by an excessive reduction in rigidity of the backrest <NUM>. The backrest <NUM> is formed from a material containing an elastomer, and thus has a high flexibility. Even in this case, the projecting portion <NUM> and the bent portion <NUM> sufficiently achieve maintenance of the shape.

(1e) Since the backrest <NUM> comprises the projecting portion <NUM>, the projecting portion <NUM> can be used as a handhold for carrying the chair <NUM>. Particularly, it is useful when carrying a relatively light chair, such as a stacking chair and a pipe chair.

(1f) Since the thickness of the back board <NUM> gradually decreases from the lateral center of the back board <NUM> toward the left and right ends, it is possible to reduce an uncomfortable feeling caused to a seated person due to abrupt changes in flexibility of the back board <NUM>. Also, it is possible to inhibit concentration of stress at one place when a load is applied to the back board <NUM>, and thus to inhibit breakage of the back board <NUM>.

The phrase "the thickness gradually decreases" herein does not only mean smooth changes in thickness, but also includes multiple stepwise changes, for example, at three or more levels. Also, in some of the entire area, there may be an area with no change in thickness or an area having a locally large thickness.

(<NUM>) The upper area above each of the paired pipe holders <NUM> at the left and right ends of the backrest <NUM> is the thinnest portion <NUM> having the smallest thickness at the same height. Since the left and right ends of the back board <NUM> do not have high rigidity as described above, reduction in flexibility at the both ends of the backrest <NUM> can be inhibited.

Although an embodiment of the present disclosure has been described above, it is to be understood that the present disclosure is not limited to the above-described embodiment, but may be in various forms within the technical scope of the present disclosure.

(2a) A specific configuration of the backrest is not limited to the configuration shown in the above-described embodiment. For example, the backrest is not required to be rectangular. Various shapes, such as a rounded shape, and a bilaterally asymmetric shape, may be employed for the backrest. Also, there is no limitation to the configuration of the projecting portion <NUM> or the bent portion <NUM>. For example, respective arrangement positions, projecting amounts, thicknesses, widths, etc. of the projecting portion <NUM> and the bent portion <NUM> may be specified optionally. Further, the backrest <NUM> may include one or none of the projecting portion <NUM> and the bent portion <NUM>.

(2b) In the above-described embodiment, an example configuration is shown in which the thickness of the back board <NUM> gradually decreases toward the left and right ends. However, there is no particular limitation to the specific configuration of the back board that includes the second area thinner than the first area. For example, there is no particular limitation to a specific size of the first area as long as the first area includes a laterally central area of the back board. The first area may be a relatively small area in a vicinity of the laterally central area. Also, there is no particular limitation to size of the second area, as long as the second area is located closer to each of the left and right ends than the first area. As in a backrest <NUM> shown in <FIG>, a first area <NUM> and a second area <NUM> may have respective fixed thicknesses. Between the first area and the second area, there may be an area having a thickness greater or smaller than the thicknesses of the first area and the second area. The configuration of the back board may be such that the thickness decreases toward the left and right ends in a stepwise manner. The configuration may be such that the thickness of the back board gradually decreases across the back board along the lateral direction, or the configuration may be such that the thickness of the back board gradually decreases in a part of the back board along the lateral direction.

Further, the first area and the second area may cover the entire area of the back board in the vertical direction, or may cover a part of the area of the back board in the vertical direction. For example, the first area and the second area may cover a range except for an upper end portion and a lower end portion of the back board.

(2c) In the above-described embodiment, an example configuration is shown in which the thickness of the entire back board <NUM> gradually decreases upward. However, the back board need not be configured in such a manner across the entire area in the vertical direction as long as the back board includes a region in which the thickness gradually decreases upward. For example, the back board may include the aforementioned configuration in some part along the lateral direction of the back board, or may include the aforementioned configuration in some part along the vertical direction of the back board. In this regard, if at least the second area includes the aforementioned configuration, an effect can be obtained that obstruction of movement of a seated person is reduced. Further, the back board need not include a region in which the thickness gradually changes in the vertical direction.

(2d) In the above-described embodiment, an example configuration is shown in which the paired pipe holders <NUM> are provided, each as a high rigidity portion, from the lower end to the center. However, the configuration of the high rigidity portion is not limited to that in the above-described embodiment. For example, there is no particular limitation to a specific configuration of the high rigidity portion as long as the rigidity is higher than that of the surroundings. Specifically, the high rigidity portion may have a thickness greater than the surroundings. The high rigidity portion may be configured with a member having a rigidity higher than that of the surroundings of the high rigidity portion, or may include a member having a rigidity higher than that of the surroundings of the high rigidity portion.

The high rigidity portion may be provided at least in respective lower areas of at least the left and right ends of the back board. For example, as a backrest <NUM> shown in <FIG>, high rigidity portions <NUM> may be provided in positions apart from respective lower ends of the left and right ends. Also, the high rigidity portions may be provided at respective upper areas of the left and right ends of the back board. Further, no high rigidity portions need to be provided at both ends in the lateral direction.

(2e) In the above-described embodiment, an example configuration is shown in which the connecting portion <NUM> is provided at each of the left and right ends of the back board. However, the position where the connecting portion is provided in the back board need not be located at the left and right ends. For example, as a backrest <NUM> shown in <FIG>, a connecting portion <NUM> may be connected not to a second area <NUM> but to a first area <NUM>.

Also, the connecting portion may be connected to the seat body of the chair or the support body supporting the seat body. Further, the backrest and the seat body, or the backrest and the support body may be connected through another member along with the connecting portion. In other words, the connecting portion is a component to define a positional relationship between the seat body and the backrest of the chair.

(2f) The back board may comprise a flexible structure to achieve an improved flexibility. A configuration may be such that the flexible structure is provided in the second area and not provided in the first area. For example, a backrest <NUM> shown in <FIG> comprises through-holes <NUM> penetrating from a front surface to a rear surface of a back board <NUM> at least in a second area <NUM>. On the other hand, no through-hole is formed in a first area <NUM>. With this configuration of the back board, an improved flexibility of the second area <NUM> can be achieved by the through holes, and reduction in rigidity of the first area <NUM> can be inhibited. Also, since there is no through-hole in the first area <NUM> that is likely to abut a back in an ordinary posture, it is possible to inhibit a seated person from having an uncomfortable feeling by through-holes. It may be configured such that a hole diameter of the through hole <NUM> becomes smaller as the through hole <NUM> is positioned closer to a lateral outer side. It may be configured such that the hole diameter of the through hole <NUM> becomes smaller as the through hole <NUM> is positioned closer to a vertical upper side. Alternatively, it may be configured such that the hole diameter of the through hole <NUM> becomes larger as the through hole <NUM> is positioned closer to the lateral outer side. It may be configured such that the hole diameter of the through hole <NUM> becomes larger as the through hole <NUM> is positioned closer to the vertical upper side.

Further, as shown in <FIG>, dimples <NUM> may be formed in place of the through hole <NUM>. In this case, it may be configured such that the dimple <NUM> becomes smaller as the dimple <NUM> is positioned closer to the lateral outer side. It may be configured such that the dimple <NUM> becomes smaller as the dimple <NUM> is positioned closer to the vertical upper side. Alternatively, it may be configured such that the dimple <NUM> becomes larger as the dimple <NUM> is positioned closer to the lateral outer side. It may be configured such that the dimple <NUM> becomes larger as the dimple <NUM> is positioned closer to the vertical upper side.

Moreover, as a backrest <NUM> shown in <FIG>, at least a second area <NUM> may comprise slits <NUM> penetrating from a front surface to a rear surface of a back board <NUM>. A first area <NUM> need not comprise any slits.

Claim 1:
A backrest (<NUM>) for use in a chair, the backrest comprising:
a back board (<NUM>) arranged in a position to abut a back of a seated person on the chair,
wherein a first area (<NUM>) including a laterally central area of the back board has a thickness (L1) greater than a thickness (L2) of a second area (<NUM>) of the back board located closer to each of left and right ends of the back board than the first area,
wherein the back board includes a high rigidity portion (<NUM>) provided at least in a lower area from a vertical center position at each of the left and right ends of the back board, and
wherein the high rigidity portion has a rigidity higher than that of a surrounding area surrounding at least an upper part of the high rigidity portion in the back board,
wherein the back board comprises an area having a thickness gradually decreasing from a lateral center of the back board toward the left and right ends,
wherein at least a part in a vertical direction of each of the left and right ends of the back board is a portion having a smallest thickness at a same height of the back board.