JP2025077621A - Chair backrest - Google Patents

Abstract

To make a back plate made of elastomer that is usable without blocking a reclining function in a backrest where an upper back frame rotates forward when a back frame device bends and is reclined.SOLUTION: An upper half part of a back plate 18 is fixed to an upper back frame 9 with a screw 34, and the lower half part of the back plate 18 is connected to a lower side member 8a in the state that it can move relatively vertically with respect to the lower side member 8a. Between the back plate 18 and the side members 8a, 9a, slide auxiliary bodies 39, 40 are disposed. The back plate 18 is made of elastomer, has many small holes and can be formed into a ventilation structure, and is excellent in fitness to a sitter because it warps and deforms. The back plate 18 has a certain degree of thickness, but the lower half part of the back plate 18 escapes and moves to the lower side member 8a, so that back frame device smoothly bends.SELECTED DRAWING: Figure 7

Description

This invention relates to a chair backrest with a reclining function (rocking function).

Reclining chairs, in which the backrest tilts backward against an elastic means, are widely used for office use. In these reclining chairs, there is a demand for users to be able to view the computer monitor (display) in a comfortable position while taking a relaxed posture with their body tilted back.

This requirement can be met by keeping the user's head in an upright position when reclined. In other words, if the backrest is simply tilted backwards, the user's face will change position and turn upwards, causing the line of sight to move away from the computer monitor, and if the user raises the head and faces the computer, this puts strain on the neck and shoulders and can easily lead to stiffness in the neck and shoulders. However, if the user's head is set to be supported in a forward-facing position when reclined, the user can view the computer monitor without getting tired while reclining.

As a technology to meet this demand, Patent Document 1 discloses a high-backed backrest that also supports the user's head, with a mid-height section that is bent and deformed when viewed from the side, so that when reclining, the backrest is bent in a crank shape when viewed from the side, raising the user's head relatively when reclining.

Specifically, in Patent Document 1, a first tilting frame to which the upper end of the backrest is fixed and a second tilting frame to which a portion of the backrest near the bottom is fixed are used, and the portion of the backrest between the fixed portions of the two tilting frames is formed as a curved portion, and the backrest is bent in a crank shape by utilizing the difference in the pivot points of the two tilting frames.

On the other hand, Patent Document 2 discloses a technology in which the backrest is made high-backed so that the user's head is also supported, and the upper part of the backrest is supported and configured to bend in a side view with the base below it, and the pivot point between a tilting frame connected to the upper part of the backrest and the tilting frame to which the base is fixed is shifted in the front-to-rear direction, so that the upper part of the backrest tilts forward relative to the base while the backrest reclines as a whole. Both patent documents disclose a technology in which the head can be kept in a forward-facing position when reclining, which is beneficial because it allows the user to comfortably watch a computer monitor placed on a desk for long periods of time.

U.S. Pat. No. 1,029,9595 Patent No. 4015236

In Patent Document 1, the backrest is constructed by stretching a mesh material over a frame structure that is open at the front and back, and the frame structure is designed to be bent. In this case, since the mesh material is inherently flexible, there is no particular problem even if the frame structure is bent. In other words, there is no problem with load being concentrated on the bent parts of the mesh material, reducing its durability.

In addition, in Patent Document 2, the backrest is constructed with a resin back panel covered with cushioning material, and the cushioning material is originally flexible, so in this case too, there is no inconvenience such as a decrease in the durability of the cushioning material due to the backrest bending.

On the other hand, from the perspective of the user's comfort (softness against the body, comfort against leaning, etc.), the mesh material of Patent Document 1 has the advantage of being highly breathable, but because the mesh material simply stretches and deforms, it is difficult to expect it to fit the contours of the user's back. In contrast, the cushion type of Patent Document 2 has an excellent fit because the cushion material can be recessed in any area, but has the problem of poor breathability. Also, because a shell-shaped back panel is required to support the cushion material, there is also the problem that it is not possible to achieve the sleek appearance of a mesh specification.

In this regard, if a back panel with elasticity, such as an elastomer plate, is used to support the seated person, the back panel can be partially stretched and deformed by drilling many small holes in it, so it is possible to create a simple appearance like a mesh design while still ensuring breathability and a good fit to the body.

However, because the elastic back panel has a certain thickness, if it is fixed to a flexible back frame device, the elastic force of the back panel may create resistance, making it difficult for the back frame device to bend. Furthermore, if the bending part of the back panel is thinned to form a hinge part, other problems such as a decrease in the durability of the back panel may arise.

The present invention was made against this background, and aims to disclose a technology that can ensure smooth bending movement of the back frame device without compromising the functionality or durability of the back panel when using a backrest with a bending structure and a back panel made of elastic material.

The present invention includes various configurations, typical examples of which are specified in each claim. The invention of claim 1 is as follows:
"The back frame device has an upper back frame and a lower back frame connected to each other so as to be bendable in the front-rear direction, and a back plate made of an elastic material is overlapped on the front surface of the back frame device.
The back panel is attached in such a way that a part or the whole of it can slide up and down relative to the upper back frame, the lower back frame, or both the upper and lower back frames.
The structure is as follows.

The invention of claim 2 is an example of the development of claim 1,
"The back panel is held in a state in which it does not move up and down relative to the upper back frame, and is held in a state in which it can move up and down relative to the lower back frame."
The structure is as follows.

The invention of claim 3 is an example of the development of claim 1 or 2,
"The upper and lower back frames form a loop structure to which the back panel is attached, and the back panel is allowed to bend backwards due to the pressure of a seated person."
The structure is as follows.

The invention of claim 4 is an example of the development of claim 3,
The upper and lower spine frames have left and right side members that run vertically, and the upper side members that make up the upper spine frame and the lower side members that make up the lower spine frame are connected by left and right longitudinal pins.
Furthermore, a lower slide auxiliary body in the vertical direction is disposed between the lower side member or the upper side member, or both, and the back plate.
The structure is as follows.

The invention of claim 5 is an example of the development of claim 4,
"The seat is provided with a lower slide auxiliary body arranged only between the lower side member and the back panel, and an upper slide auxiliary body that is vertically elongated and extends across the upper side member and the lower side member, and the upper and lower slide auxiliary bodies partially overlap each other in a front view in a state in which they can slide vertically relative to each other."
The structure is as follows.

The invention of claim 6 is an example of the development of claim 5,
"The back plate is fixed integrally to the upper back frame and the upper slide auxiliary body, and the part of the back plate overlapping the lower back frame is connected to the lower back frame so as to be movable up and down relative to the lower back frame without being separated forward,
The lower slide auxiliary is fixed to the lower back frame in a state in which it can slide up and down relative to the back plate and the upper slide auxiliary.
The structure is as follows.

In the present invention, a part or the front part of the back panel slides up and down relative to the back frame device in conjunction with the bending of the back frame device, so that a heavy load is not placed on a part of the back panel when the back frame device is bent, and the backrest can be bent easily. In other words, the back panel does not impede the bending of the backrest. And because the back panel does not form a weak part like a hinge part, there is no problem with its function of supporting the pressure (body pressure) of the seated person, and the seated person can be firmly supported while allowing backward concave deformation due to body pressure.

The present invention therefore enjoys the benefits of using a back panel made of elastic material, ensuring a high level of fit and breathability while facilitating the bending movement of the backrest. This makes it possible to provide a chair that allows the user to face a desk monitor directly in the reclined position, with excellent design and functionality.

When reclining, the body pressure (pushing force) of the seated person acts strongly on the upper half of the backrest, but in the invention of claim 2, the upper part of the backboard on which the body pressure of the seated person is applied when reclining is fixed to the upper back frame when bending, so there is no gap between the outer periphery of the backboard and the inner periphery of the upper back frame (especially the upper end of the backboard and the upper end of the upper back frame) when reclining, and body pressure can be firmly supported. In addition, there are no aesthetic problems caused by gaps, and no problems such as a shirt getting caught in the gap. Therefore, it is highly practical.

In this case, even if the bottom end of the back panel moves up and down relative to the bottom end of the back frame device, the bottom end of the back panel is basically not visible, so there is no problem with aesthetics. If the lower half of the back panel is supported from behind by the lumbar support device, the lower half of the back panel is prevented from moving backwards, which has the advantage of preventing a strong load from acting on the connection part of the back panel with the lower back frame and making the back panel slide more smoothly with the lower back frame.

When the back frame device is formed into a loop structure with openings at the front and back as in claim 3, the back plate is allowed to escape backwards (to bulge), improving the fit. In particular, when applied to a high-back chair as in the embodiment, it is suitable for providing soft support for the shoulder blades.

Providing a slide assisting body as in claim 4 can promote the relative sliding between the back plate and the back frame device, making the bending movement of the back frame device even easier. Elastomer-based soft resins are suitable for the back plate, but because elastomer-based soft resins have a large coefficient of friction, providing a slide assisting body as in claim 4 is particularly suitable.

When providing a slide auxiliary body, by using upper and lower slide auxiliary bodies and partially overlapping them as in claim 5, the portion of the back panel that is connected to the upper and lower spine frames can be smoothly bent. In other words, the back panel can be curved in a natural way. This further facilitates smooth bending of the back frame device and prevents deterioration of aesthetics.

The invention of claim 6 is also an example of the development of claim 2, but by interposing a slide auxiliary body between the back plate and the lower back frame, it is possible to smooth the downward escape movement of the back plate when the back frame device is bent. This improves the quality of the chair.

1A is a perspective view showing the appearance of an embodiment, in which FIG. 1A is a perspective view seen from above the front, FIG. 1B is a perspective view seen from below the rear, and FIG. 1C is a perspective view seen from above the rear. 1A is a side view showing the state before and after reclining, and FIG. 1B is an exploded front view showing the vertical positional relationship between the upper and lower spine frames and the slide auxiliary body. 1A is an exploded perspective view of all the components, and FIG. 1B is an exploded front view of all the components. FIG. 1A and 1B are diagrams showing the lower part of the back frame device, in which (A) is an exploded perspective view seen from the front and lower, and (B) is an exploded perspective view seen from the rear and lower. (A) is a front view of the back panel and the slide auxiliary body separated, (B) is a partial oblique view of the edge member, (C) is a plan cross-sectional view seen from the CC position in (A), and (D) is a rear oblique view of the lower end portion of the back panel. 1A is an exploded perspective view of the main part, and FIG. 1B is a perspective view of the back panel as seen from behind. (A) is an exploded perspective view from the rear with the slide auxiliary body at the center, (B) is an exploded perspective view showing the relationship between the slide auxiliary body, the lower reinforcement body, and the lower back frame, and (C) is a partially exploded perspective view of the back plate, sleeve, and back plate. 13A and 13B are rear perspective views showing the relationship between the slide auxiliary body and the core material, and FIG. 13C is a rear perspective view showing the overlapping state.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the terms front, back, left and right are used to specify directions, but these directions are defined as directions seen from a person normally seated in a chair. The front view is a view from the direction opposite the seated person.

(1) Basic Structure of the Chair First, an overview of the chair will be described mainly with reference to Figures 1 to 5. This embodiment is applied to a swivel chair that is widely used in offices. The chair comprises a leg device 1, a seat 2, and a backrest 3 as basic elements. The leg device 1 has a structure in which a leg support 4 made of a gas cylinder is erected in the center of a base having five leg blades, and a caster is provided at the tip of each leg blade.

For example, as shown in Figures 1(A) and (B), a base 5 is fixed to the upper end of the leg support 4, and the lower tips of the left and right first tilting frames 6 are connected to the base 5 by a first reference support shaft 7 (see Figure 2(A)). For example, as shown in Figure 1(B), the first tilting frames 6 extend rearward while spreading outwardly to the left and right from the base 5, and then rise upward, and the part that rises upward and spreads widely outwardly to the left and right constitutes the lower side members 8a that make up the lower back frame 8.

The lower ends of the lower side members 8a that make up the lower back frame 8 are connected to the left and right longitudinal lower members 8b. In other words, the lower back frame 8 is formed by connecting the rising parts of the left and right first tilting frames 6 with the lower members 8b.

The upper back frame 9 is disposed on top of the lower back frame 8 and is integrated with the lower back frame 8 to form the back frame device. The upper back frame 9 is configured in a loop shape with upper left and right side members 9a that are long vertically, an upper member 9b connected to the upper ends of the upper side members 9a, and a middle member 9c connected to the lower ends of the upper side members 9a.

As shown in FIG. 4, the lower end of the upper side member 9a of the upper back frame 9 is connected to the upper end of the lower side member 8a by a second reference shaft (pin in the claims) 10 that is long in the left and right direction. The middle member 9c of the upper back frame 9 projects backward, and the upper end of the second tilting frame (center frame) 12, which is long in the vertical direction, is connected to the left and right intermediate portion of the rearward projecting middle member 9c by a third reference shaft 11 that is long in the left and right direction so that it can be tilted backward.

As shown in FIG. 4, the lower end of the second tilting frame 12 is a bifurcated portion 12a having left and right portions, and the front end (lower end) of the bifurcated portion 12a is connected to a bearing portion 13 (see FIG. 1(B)) provided at the rear end of the base 5.

Therefore, the first tilting frame 6, the second tilting frame 12, and the back frames 8 and 9 rotate relative to each other while tilting backward as a whole. Specifically, as can be seen from FIG. 2(A), due to differences in the front-to-back positions and up-to-down heights of the reference support shafts 7, 10, and 11, when reclining, the upper back frame 9 rotates forward relative to the lower back frame 8 (and the first tilting frame 6).

A top rest device 14 is attached to the top end of the upper back frame 9, and when reclining, the upper back frame 9 rotates forward relative to the lower back frame 8, so that the top rest device 14 can hold the user's head in an upright position when reclined. This allows the user to relax their body and naturally look at the computer on the desk, allowing them to perform computer tasks such as operating the keyboard and mouse.

The backward tilt of the backrest 3 is controlled by a gas cylinder (not shown) located between the forked portions 12a of the second tilting frame 12. The chair of this embodiment also has a synchronous structure in which the seat 2 moves backward while tilting backward in conjunction with the reclining. As shown in Figure 5, the lower member 8b is fixed with screws 16 to brackets 15 that protrude inward from the left and right first tilting frames 6.

The lower member 8b is made of synthetic resin, and a reinforcing plate 8c for mounting a lumbar support device is fixed to its rear surface with screws (not shown). A core material (lower reinforcing body, lower auxiliary body) 17 is integrated into the lower member 8b by insert molding, and the core material 17 has an upward portion 17a that enters the inside of the side member 8a of the lower back frame 8 from the front. The core material 17 may be fixed to the lower member 8b with screws.

The backrest 3 is equipped with a back panel 18 made of a flexible resin material such as elastomer (PTE) and upholstery 19 stretched over the front of the back panel 18, and the back panel 18 bends and deforms in response to the bending of the back frame device. The back panel 18 is supported from behind by a lumbar support device 20 shown in Figs. 1(B) and (C). As shown in Figs. 1(B) and (C), a lumbar support 21 is attached to the second tilting frame 12 so that it can tilt back and forth, and a lumbar pad 22 is attached to the lumbar support 21. The lumbar pad 22 supports the lumbar region of the seated person (particularly around the third lumbar vertebra) from behind via the lower half of the back panel 18.

(2) Backrest and its basic mounting structure Next, the structure of the back will be described with reference to Figure 6 and subsequent drawings. As mentioned above, the back panel 18 is made of elastomer, and the part where the body pressure of the seated person is applied is a few mm thick, and when in its stand-alone state, it is elastic enough that a person can easily bend it. In addition, small holes are drilled in a pair except for the outer periphery. The small holes are formed in a square shape and arranged vertically and horizontally, but the shape, size, and arrangement direction can be set arbitrarily.

For example, as can be seen from FIG. 6(C), the side members 8a, 9a have a roughly triangular cross-sectional shape that protrudes rearward, and inside them are formed vertically elongated circumferential grooves 23 that open forward. The front faces of the upper member 9b and lower member 8b are similar, and therefore the circumferential grooves 23 extend all around. The outer periphery of the back plate 18 is formed into a thick portion 24, and the thick portion 24 has a rearward-facing ridge 24a formed therein that fits into the circumferential groove 23.

As shown in FIG. 6(C), an upholstery attachment groove 25 with a depth of a few mm and a width of 10 mm is formed around the entire periphery on the front surface of the thick portion 24 of the back panel 18, and a roughly plate-shaped edge member 26 is placed in this upholstery attachment groove 25. The upholstery 19 overlaps the front surface of the edge member 26, and the peripheral edge 19a of the upholstery 19 is wrapped around the back surface of the edge member 26, and the upholstery 19 is sewn to the edge member 26.

As shown in FIG. 3, the edge member 26 is divided into four parts: an upper part, a side part, and a lower part, and has a loop structure as a whole. The thickness of the edge member 26 is made to differ so that the outer part of the rear surface is stepped down, and the periphery of the upholstery 19 is placed against the wall 27 formed by making the thickness different in this way. In other words, the wall 27 positions the upholstery 19.

Furthermore, the edge member 26 has locking claws 28, which are outwardly hooked in plan view, protruding backward at appropriate intervals, while the thick portion 24 of the back panel 18 has a group of locking holes 29 intermittently formed in the circumferential direction into which the locking claws 28 fit. As shown in FIG. 6(C), the outer periphery of the thick portion 24 of the back panel 18 has forward-facing ribs 30 formed all around the periphery, surrounding the upholstery 19. Therefore, the back panel 18 has a shallow recess surrounded by the forward-facing ribs 30, and when the edge member 26 to which the upholstery 19 is attached is inserted and pushed into the recess, the locking claws 28 fit into the locking holes 29 by elastic deformation, so that the upholstery 19 can be attached to the back panel 18 very easily. The attachment of the upholstery 19 is performed as the final step after the back panel 18 is attached to the back frame device.

As shown in FIG. 6(D), at the lower end of the back plate 18, the locking hole 29 is formed at the location of the rectangular boss portion 31 that protrudes backward. Therefore, as shown in FIG. 5(A), the front surface of the lower member 8b is formed with a relief recess 32 to allow the boss portion 31 to fit in.

Next, the mounting structure of the back plate 18 to the back frame device will be described. As shown in FIG. 7, the portion of the back plate 18 that overlaps with the upper back frame 9 is fixed to the upper back frame 9 with screws 34 and washers 35 so that it cannot slip. Thus, the thick portion 24 of the back plate 18 has a number of countersunk holes 36 intermittently formed in the circumferential direction into which the heads of the screws 34 fit, while the peripheral groove 23 of the upper back frame 9 has a group of front-view angular screw receiving bosses 37 into which the screws 34 are screwed, as shown in FIG. 7(A). Furthermore, as shown in FIG. 7(B), the thick portion 24 of the back plate 18 has a rectangular boss receiving recess 38 that fits with the screw receiving boss 37.

(3) Sliding structure of the backrest As shown in FIG. 3, for example, between the side of the back panel 18 and the back frame device, there are disposed a lower sliding auxiliary body 39 overlapping only the lower side member 8a in a front view, and an upper sliding auxiliary body 40 overlapping both the upper side member 9a and the lower side member 8a, and the upper side member 9a partially overlaps the upper sliding auxiliary body 40 in the front-to-rear direction.

For example, as shown in Figure 8, the upper slide auxiliary body 40 and the lower slide auxiliary body 39 are basically in the form of a plate, and the upper end of the upper slide auxiliary body 40 is fastened together with the back plate 18 to the lower end of the upper side member 9a by the screw 34 that fixes the back plate 18 to the lower end of the upper side member 9a. Therefore, as shown in Figure 7 (B), the portion where the upper end of the upper slide auxiliary body 40 overlaps is not a recess but a land portion 41.

For example, as shown in FIG. 8, the upper slide auxiliary body 40 and the lower slide auxiliary body 39 are arranged so that the upper slide auxiliary body 40 is located in the front and the lower slide auxiliary body 39 is located in the back. In other words, the lower slide auxiliary body 39 overlaps the lower side member 8a, and the upper slide auxiliary body 40 overlaps the lower side member 8a from the front.

The upwardly facing portion 17a of the core material 17 also overlaps the lower side member 8a from the front, below the upper slide auxiliary body 40. The lower slide auxiliary body 39 is fixed to the lower side member 8a at three points, top and bottom, with screws 43 via resin sleeves 42, and a boss body 44 into which the screw 43 is screwed is protruding from the circumferential groove 23 of the lower side member 8a.

As shown in FIG. 8(C), the sleeve 42 has a flange 42a, and is inserted from the front into a rectangular, vertically elongated guide hole 45 formed in the back plate 18. An inward step 45a is formed on the outer side of the guide hole 45, and the flange 42a of the sleeve 42 rests on the step 45a. Therefore, the back plate 18 is held against the lower side member 8a so that it cannot slip out forward, and is held so that it can move up and down relative to the lower side member 8a.

As shown in FIG. 9, the sleeve 42 is not a complete cylinder, but has an inner portion cut away to form a U-shape, but it may be formed into a complete cylinder. The flange 42a is also widely spread outward, which corresponds to the step 45a of the guide hole 45 being formed mainly on the outside. In other words, since the back panel 18 is pulled toward the center in the left-right direction by the body pressure of the seated person, the step 45a of the guide hole 45 and the flange 42a of the sleeve 42 are located mainly on the outside to prevent it from coming loose.

The lower slide auxiliary body 39 is formed with a U-shaped notch 46 into which the sleeve 42 fits so that it cannot move up or down (a hole may be used instead of the notch 46). Therefore, the lower slide auxiliary body 39 moves up and down together with the lower half of the back plate 18 and the lower side member 8a. On the other hand, the upper slide auxiliary body 40 is formed with a vertically long slot (or a slotted groove) 47 that fits loosely into the boss body 44. As shown in FIG. 8(B), it is surrounded from above, below, and from the outside, left and right, by the slot 47 and the forward-protruding surrounding frame 47a.

Therefore, the lower half of the back plate 18 and the upper slide auxiliary 40 can move relative to each other in the vertical direction. The upwardly facing portion 17a of the core material 17 also overlaps the lower portion of the lower slide auxiliary 39 from the front, and a long hole 47 is also formed in the upwardly facing portion 17a of the core material 17. Note that in FIG. 8(A), the upwardly facing portion 17a of the core material 17 is positioned behind the lower slide auxiliary 39, but in reality, as shown in FIG. 8(B), the upwardly facing portion 17a of the core material 17 overlaps the lower slide auxiliary 39 from the front.

As shown in FIG. 9, the lower slide auxiliary body 39 has a frame portion 48 between the vertically adjacent notches 46 that faces backward and opens outward on the left and right, while the upper slide auxiliary body 40 and the upward facing portion 17a of the core material 17 have a U-shaped rearward protrusion 49 that fits into the frame portion 48.

Therefore, the sliding of the upper slide auxiliary body 40 and the lower slide auxiliary body 39 is guided by the frame portion 48 and the rearward protrusion 49. The frame portion 48 and the rearward protrusion 49 also determine the left and right positioning of the upper slide auxiliary body 40 and the lower slide auxiliary body 39. On the other hand, since the core material 17 is fixed to the lower side member 8a, the rearward protrusion 49 of the core material 17 and the frame portion 48 of the lower slide auxiliary body 39 only perform a positioning function. As can be seen from Figure 8 (B), a deep groove portion 50 is formed in the circumferential groove 23 of the lower side member 8a, into which the frame portion 48 of the lower slide auxiliary body 39 fits.

For example, as can be seen from FIG. 8(B), two hook-shaped locking claws 51 are each provided on the upper slide auxiliary body 40 and the upward facing portion 17a of the core material 17, protruding outward and facing forward, while an engagement slot 52 into which the locking claws 51 fit is formed on the side of the back plate 18. A step is formed in the engagement slot 52 into which the locking claws 51 hook. Therefore, the back plate 18 is held by the locking claws 51 against the lower side member 8a so that it cannot come off, while being allowed to move up and down.

As can be seen from Figure 7, the portion of the side of the back plate 18 that forms the guide hole 45 is a vertically long bank-shaped portion 53 that protrudes backward, and the upper slide auxiliary body 40 and the upward portion 17a of the core material 17 overlap the bank-shaped portion 53. For example, as shown in Figure 8 (B), both the upper and lower ends of the lower slide auxiliary body 39 are fixed to the lower side member 8a with screws 54. Also, as shown in Figure 7 (B), the bank-shaped portion 53 has a recess 68 into which the upper slide auxiliary body 40 and the surrounding frame 47a provided on the upward portion 17a of the core material 17 fit.

(4) Summary This embodiment has the above configuration, and when reclining, the upper back frame 9 rotates forward relative to the lower back frame 8, allowing the seated person to keep their head upright in the reclined position, and therefore allows them to operate a desktop computer for long periods of time while tilting their upper body backward in a relaxed position and preventing stiff shoulders and neck. When reclining, the back panel 18 bends in conjunction with the bending movement of the back frame device, while the lower half of the back panel 18 moves downward relative to the lower back frame 8, so that the back panel 18 does not act as a resistance to the bending movement of the back frame device, and the back frame device bends smoothly.

In this embodiment, the lower half of the back panel 18 is pulled downward by the lower slide auxiliary body 39 during reclining, but because the back panel 18 is connected to the lower slide auxiliary body 39 at three points (top, middle, and bottom), the load is not concentrated on a specific part, and the back panel 18 slides smoothly.

In addition, because the back panel 18 is made of elastomer and has a high back, when the seated person's body pressure is strong, the back panel 18 retracts significantly, providing a high level of fit. For example, when the seated person's shoulder blades hit the back panel 18, the back panel 18 is bent backwards at the part where the shoulder blades hit, providing a fit that is not possible with mesh materials.

In this embodiment, the upper slide auxiliary body 40 overlaps the upper back frame 9 with the lower side member 8a, and the lower slide auxiliary body 39 is fixed to the back plate 18, so that the upper slide auxiliary body 40 made of resin slides relative to the lower side member 8a and the lower slide auxiliary body 39, realizing downward movement of the lower half of the back plate 18. Because the back plate 18 does not come into direct sliding contact with the lower side member 8a, even if an elastomer with a large friction coefficient is used for the back plate 18, the lower side member 8a can slide easily relative to the back plate 18.

In addition, when the upper slide auxiliary body 40 is placed on both the upper side member 9a and the lower side member 8a as in the embodiment, the upper slide auxiliary body 40 curves gently in an arch when reclining, preventing the back panel 18 from bending suddenly at the connection point between the upper and lower side members 8a, 9a, and allowing the back panel 18 to bend smoothly. This improves the durability of the back panel 18 and prevents deterioration of its aesthetic appearance.

By providing the lumbar support device 20 as in the embodiment, the lower half of the back panel 18 can be prevented from moving backward due to the body pressure of the seated person, so that the back panel 18 can be reliably moved downward when reclining.

In this embodiment, the back plate 18 moves relative to the flange 42a of the sleeve 42, but by making the sleeve 42 from a resin with a low coefficient of friction such as POM resin, the relative movement can be made smoother. Furthermore, by forming a frame portion 48 and a rearward protrusion 49 on the slide auxiliary bodies 39, 40 as in this embodiment, the relative sliding can be made smoother. Using the upward portion 17a of the core material 17 as in this embodiment is preferable because it allows the lower slide auxiliary body 39 to be stably held.

Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, it can be applied to a type in which the back panel is left exposed without using upholstery. It is also possible to fix or insert-mold guide members made of hard resin or metal to the back surface of the left and right sides of the back panel, and hold these guide members slidably with the lower side members. Furthermore, it is also possible to smooth the curve of the back panel by fixing or insert-mold reinforcing plates to an appropriate range above and below the bent part of the back panel 18.

In the embodiment, it has a loop structure with a middle member, but it may also be a U-shape with an opening facing downwards. It is also possible to form the back frame device into a loop structure with openings at the front and back, and fix this to the tilting frame. In the embodiment, the upper back frame tilts forward relative to the lower back frame when reclining, but the same can also be applied to a type where the upper back frame tilts backward relative to the lower back frame when reclining.

The present invention can be embodied in a chair backrest, and therefore has industrial applicability.

3 Backrest 6 First tilting frame also serving as lower frame 7 First reference support shaft 8 Lower back frame constituting back frame device 8a Lower side member 8b Lower member 9 Upper back frame constituting back frame device 9a Upper side member 10 Second reference support shaft 11 Third reference support shaft 12 Second tilting frame 14 Top rest device 17 Core (lower auxiliary body)
17a Upward portion 18 Back panel 19 Upholstery 20 Lumbar support device 23 Circumferential groove 24 Thick portion of back panel 26 Edge member 34 Screw for fixing back panel 36 Countersunk hole 37 Screw receiving boss 39 Lower slide auxiliary body 40 Upper slide auxiliary body 42 Sleeve 43 Screw 44 Boss body 45 Guide hole 47 Slotted hole

Claims (6)

The book has a back frame device in which an upper back frame and a lower back frame are connected so as to be bendable in the front-rear direction, and a back plate made of an elastic material and overlapped on the front surface of the back frame device,
The back plate is attached in a state where a part or the whole of the back plate can slide up and down relative to the upper back frame, the lower back frame, or both the upper and lower back frames.
Chair backrest. The back plate is held in a state in which it does not move up and down relative to the upper back frame, and is held so as to move up and down relative to the lower back frame.
A chair back according to claim 1. The upper and lower back frames form a loop structure to which the back panel is attached, and the back panel is allowed to be recessed backward by the pressing force of a seated person.
A chair back according to claim 1 or 2. The upper spine frame and the lower spine frame have left and right side members in the vertical direction, and the upper side member constituting the upper spine frame and the lower side member constituting the lower spine frame are connected by left and right longitudinal pins,
And, an upper and lower longitudinal slide auxiliary body is disposed between the lower side member or the upper side member or both and the back plate.
A chair back according to claim 3. The seat includes a lower slide auxiliary body arranged only between the lower side member and the back plate, and an upper slide auxiliary body extending vertically across the upper side member and the lower side member, and the upper and lower slide auxiliary bodies partially overlap each other in a front view in a state in which they can slide vertically relative to each other.
A chair back according to claim 4. The back plate is fixed integrally to the upper back frame and the upper slide auxiliary body, and a portion of the back plate overlapping the lower back frame is connected to the lower back frame so as to be movable up and down relative to the lower back frame without being separated forward,
The lower slide auxiliary body is fixed to the lower back frame in a state in which it can slide up and down relative to the back plate and the upper slide auxiliary body.
A chair back according to claim 5.

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