WO2018149931A1

WO2018149931A1 - Chair

Info

Publication number: WO2018149931A1
Application number: PCT/EP2018/053817
Authority: WO
Inventors: Oliver Deichmann; Blasius Osko
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-02-16
Filing date: 2018-02-15
Publication date: 2018-08-23
Anticipated expiration: 2019-08-16
Also published as: DE102017001503A1

Abstract

A chair includes an elastically deformable seat (14), a backrest (10), and a coupling mechanics (12) arranged between the seat (14) and the backrest (10) so that an inclination resistance of the backrest (10) depends on a user's load on the seat (14), and that the seat (14) is, depending on a user's load on the backrest (10), upwardly curved and/or at least partially raised.

Description

CHAIR

TECHNICAL FIELD

[0001] Embodiments of the present invention relate to a chair with a backrest, in particular to a chair having an inclination resistance of its backrest that depends on a user's load on the seat surface.

BACKGROUND

[0002] Due to a permanent internet connection and an increasingly faster mobile phone network, large amounts of data can be transferred in short time. This development is paired with increasingly more powerful portable computing devices such as laptops, tablets and even mobile phones. Accordingly, it is often possible to work from anywhere. During the work, special emphasis should be placed on ergonomics.

[0003] In contrast to chairs for companies or offices, the seating comfort of chairs in the lower or middle price range has however hardly changed. Accordingly, practically all chairs in the public space do not differ in their ergonomics from chairs from 50 years ago.

[0004] From an ergonomic point of view, a movable backrest is particularly important for a chair used for working. In some office chairs the force with which the user weighs on the seat is transferred to the back rest. However, the power transmission is achieved by a relatively complex mechanical system. Furthermore, an additional power accumulator, such as a spring is also usually required. Accordingly, such chairs are comparatively expensive.

[0005] For these and other reasons there is a need for a chair with improved price- performance ratio in terms of ergonomics, in particular a chair that offers a comparable ergonomic comfort of an office chair, but at a lower price, in particular at a price in the price class of all-purpose chairs. SUMMARY

[0006] According to an embodiment of a chair, the chair includes an elastically deformable seat, a backrest, and a coupling mechanics arranged between the seat and the backrest so that an inclination resistance of the backrest depends on a user's load on the seat, and that the seat is, depending on a user's load on the backrest, upwardly curved and/or at least partially raised.

[0007] According to an embodiment of a chair, the chair includes an elastically deformable seat, a backrest, and a rigid first coupling element comprising a first lever arm supporting the backrest, and a second lever arm arranged at the seat so that the elastically deformable seat is deformed when a user is leaning back on the backrest.

[0008] According to an embodiment of a method for manufacturing a chair, the method includes providing a frame, attaching an elastically deformable seat to the frame, mounting a lever to the frame in an articulated manner, the lever including a first lever arm and a second lever arm, and attaching a backrest to the first lever arm, so that the second lever arm is arranged at the seat, typically at a back side of the seat opposite a seat area of the seat.

[0009] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The components in the Figures are not necessarily to scale, instead emphasis being placed upon illustrating the principles of the invention. Moreover, in the Figures, like reference numerals designate corresponding parts. In the drawings:

[0011] FIG. 1 shows a schematic side view of a chair when the backrest of the chair is not loaded according to an embodiment; [0012] FIG. 2 shows a schematic side view of the chair illustrated in Fig. 1 when the backrest is loaded according to an embodiment;

[0013] FIG. 3 shows a schematic front view of the chair illustrated in Fig. 1 when the backrest is not loaded according to an embodiment;

[0014] FIG. 4 shows a schematic front view of the chair illustrated in Fig. 1 when the backrest is loaded according to an embodiment;

[0015] FIGS. 5 and 6 show sections of schematic front views of chair according to embodiments;

[0016] FIGS. 7 and 8 show sections of schematic front views of chair according to embodiments;

[0017] FIGS. 9 and 10 show sections of schematic front views of chair according to embodiments; and

[0018] FIG. 1 1 shows a schematic side view of a chair according to an embodiment.

DETAILED DESCRIPTION

[0019] In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0020] According to an embodiment, a chair includes an elastically deformable seat, a backrest and a coupling mechanics arranged between the seat and the backrest so that an inclination resistance of the backrest depends on a user's load on the seat, and that the seat is, depending on a user's load on the backrest, upwardly curved and/or at least partially raised.

[0021] Typically, the seat, i.e. the seat itself but not a supporting plate or structure, is upwardly curved, more typically upwardly curved and, thus, at least partially raised.

[0022] However, the change of curvature may, depending on the elastic properties of the seat, be comparatively small. The change of curvature may even be hardly recognizable by the user.

[0023] When a user is sitting on a seat area of the seat (in the following also referred to as sitting side and upper side) and leans his back against a support area of the backrest, the seat (upper side as well as back side of the seat) is upwardly curved and at least partially raised, respectively, to an extent increasing with the force exerted by the user on the backrest.

[0024] The coupling mechanics cause a curvature or a decrease of a radius of curvature (increase of the curvature) of the elastically deformable seat in upward direction. This ensures that the user is raised when the backrest is loaded.

[0025] In other words, the seat (area) is upwardly curved and at least partially raised, respectively, to an extent that depends on a balance between a user's load acting on the seat and a user's load acting on the backrest. [0026] Accordingly, the chair enables an ergonomic sitting position without an additional synchronous mechanics.

[0027] Instead, a simple lever mechanism may be used.

[0028] Due to the simple lever mechanism, the chair may even be stackable.

[0029] The lever mechanism (coupling mechanics.) may be provided by a (rigid) first coupling element having a first lever arm to which the backrest is attached, and a second lever arm acting on the seat, in particular from below when the backrest is loaded.

[0030] An upper portion of the first lever arm may also be a part of the backrest.

[0031] In other words, the lever mechanism (coupling mechanics.) may be provided by a (rigid) first coupling element having a first lever arm supporting a support surface (typically provided by a backrest of the chair) for a user's back, and a second lever arm acting on the seat, in particular from below when the support surface is loaded.

[0032] According to an embodiment, a chair includes an elastically deformable seat, a support surface for a user's back, typically provided by a backrest of the seat, and a rigid first coupling element having a first lever arm supporting the support surface, and a second lever arm arranged at the seat so that the elastically deformable seat is deformed, typically upwardly curved and/or at least partially raised, when a user is leaning back on the support surface.

[0033] According to an embodiment, a chair includes an elastically deformable seat, a backrest, and a rigid first coupling element having a first lever arm attached to the backrest, and a second lever arm arranged at the seat so that the elastically deformable seat is deformed, typically upwardly curved and/or at least partially raised, when the backrest and the seat are forced or moved away from each other and/or are braced against each other, e.g. by a user. [0034] Accordingly, the manufacturing costs of the chair may be much lower compared to known office chairs with load-dependent, movable backrest.

[0035] The chair and/or the coupling mechanics may include a second coupling element having a first lever arm to which the backrest is attached, and a second lever arm acting on the seat when the backrest is loaded and/or acting from below on the seat when the backrest is loaded.

[0036] For example, the chair and/or the coupling mechanics may include a left and a right coupling element which are typically arranged mirror-symmetrically.

[0037] Typically, the respective coupling element is, at least in a side view, at least substantially L-shaped.

[0038] Furthermore, the first lever arm of the respective coupling element is typically longer than the second lever arm of the respective coupling element, for example by a factor of at least two or three.

[0039] A remote end of the respective second lever arm, i.e. an end remote from and/or facing away from the respective second lever arm, may act directly on the seat, exerts a force onto the seat and/or presses from below against the seat, at least when the backrest is loaded.

[0040] At least in embodiments in which the free end of the respective second lever arm is configured to act from below, the remote end is typically not fixed to the seat, and therefore also called free end.

[0041] For example, the free end may press from below against the bottom side of the seat. When the backrest is moved relative to the seat, the free end may slide along the bottom side of the seat. As shallow recess or notch at the bottom side may provide guidance for the free end. [0042] Alternatively, the remote end may be arranged in a slot or cavity formed between the bottom side and the upper side of the seat.

[0043] In yet another embodiment, the remote end may be connected with the seat side of the seat, typically covered by a seat upholstery. In this embodiment, the remote end may pull the seat when the user is leaning back.

[0044] However, the setup of the chair is typically simpler if the free end acts from below against the seat.

[0045] Furthermore, a connecting element may connect the second lever arm of the first coupling element and the second lever arm of the second coupling element with each other.

[0046] Typically, the connecting element acts from below on the seat, more typically presses from below towards a central portion (of the back side) of the seat when the backrest is loaded. The connecting element may even directly press from below against the central portion of the seat.

[0047] Accordingly, a better force distribution and/or a higher sitting comfort may be achieved.

[0048] The connecting element may include a rod or a strut connecting the first and second coupling elements.

[0049] For example, the connecting element may be a substantially U-shaped rod or strut having a middle portion adjoining the back side of the seat.

[0050] Alternatively, the connecting element may be substantially Y-shaped or substantially T-shaped, at least when seen from above. [0051] Similar as explained above with respect to the coupling elements, a remote end (free end) of the connecting element may act on and/or is typically in contact with the middle portion of the seat.

[0052] In embodiments in which the connecting element acts from below on the seat, the second lever arms of the first and second coupling element may only act via the connecting element on the seat.

[0053] The chair and/or the coupling mechanics are typically hinge-mounted (hingedly connected) to a frame of the chair.

[0054] For example, the coupling mechanics and/or the coupling element(s) may be in articulated connection with a crossbar of the frame.

[0055] The frame may be a welded round tube frame.

[0056] Furthermore, the seat is typically attached to the frame, more typically in articulated connection with the frame. In these embodiments, the seat is, depending on a user's load on the backrest, only partly raised or lifted (with respect to ground and legs of the chair, respectively).

[0057] Since the seat is typically not lifted from the frame in these embodiments, but only deformed and thus does not move away from the frame during the swiveling process, potential clamping points can be excluded. Accordingly, the chair can be designed in such a way that there is practically no risk of jamming (no danger of jamming).

[0058] The seat may be deformed completely or only partially when the backrest is tilted backwards. Further, the seat may be inclinable, at least to some extent. Thus, the sitting comfort of the chair may be further improved.

[0059] Furthermore, mounting the seat to the frame via hinges may facilitate avoiding unwanted mechanical stress due to the (backward) moving backrest. [0060] For example, the seat may be mounted between two side portions (a left and a right one) of the frame using a respective hinge, in particular a respective hinge joint on both sides.

[0061] Typically, the joint axis of the hinges used for mounting the seat are at least substantially perpendicular to the joint axes of the main hinge(s) used for mounting the coupling mechanics and the coupling element(s), respectively, to the frame. In the following, the main hinge is also referred to as primary hinge.

[0062] The main hinge(s) may be shifted in forward direction (away from the backrest) so that the backrest lowers slightly when swiveling backwards (when the user is leaning backwards). Accordingly, a user's shirt may not be pulled out of the trousers during swiveling backwards.

[0063] The seat may also be screwed to the frame.

[0064] Typically, a spacer, in particular an elastic spacer held by the respective screw is arranged between the seat and the frame. Using elastic spacer(s) may also facilitate avoiding unwanted mechanical stress due to the (backward) moving backrest.

[0065] In the used setup, the seat is operable as a spring and, thus, may store mechanical energy when the user is sitting on the seat and is leaning back on the backrest.

[0066] The seat is therefore also operable as a power accumulator for storing energy when a user is leaning back on the backrest and/or when the seat and the backrest are braced against each other (loaded against each other).

[0067] Typically, the seat is the chairs only power accumulator which is capable of storing energy when the seat and the backrest of braced against each other. [0068] In other words, the chair is typically free of additional springs and/or gas struts for storing the mechanical energy when the user is sitting on the seat and is leaning back on the backrest.

[0069] The chair may even be free of any additional springs and/or gas struts. [0070] The seat may be padded or unpadded.

[0071] Typically, the (unpadded) seat is at least substantially plate-shaped, but may be downwardly curved.

[0072] For example, a horizontal extension of the seat may exceed a vertical thickness (layer thickness) of the seat by at least a factor of 20.

[0073] Typically, the seat is pre-stressed (preloaded, pretensioned) in an unloaded state (without a user sitting on the chair).

[0074] Accordingly, the seat may provide large enough elastic restoring forces to hold the backrest in a desired orientation (an upright starting position) even when no user is sitting on the seat.

[0075] Even if a user specific adjustment of the pre-stress is typically not necessary, the adjustment can be integrated relatively easily if desired. For example, the free end may be jacked up at the position pressing against the seat. This increases the pre-stressing of the seat and a greater force acts via the lever mechanism on the backrest. Alternatively, the pre- stressing may be adjusted at junctions between the seat and the frame.

[0076] Typically, the (pre-stressed) seat is downwardly curved more typically downward concave in the unloaded state when seen in a front view.

[0077] The seat may include or may be made of wood, a metal, a plastic, a composite material and/or another elastic material. [0078] Accordingly, the proposed design can be easily adapted to the location and preferred production methods and materials, respectively.

[0079] Furthermore, the chair can, due to the flexibility with respect of the material, be designed for use in locations with specific requirements for fire protection, cleaning, weather conditions etc., e. g. at the airport, outdoors or in hospitals.

[0080] According to an embodiment, an elastic modulus of the seat is anisotropic.

[0081] Accordingly, the force exerted on the seat by the coupling mechanism and the coupling element(s), respectively, may be better distributed in the seat. This may facilitate avoiding forming a tangible (unpleasant) bulge in the seat when the user is leaning back.

[0082] For example, the composite material of the seat may include a matrix material and fibers and/or rods.

[0083] Alternatively, the seat may have grooves, notches and/or webs.

[0084] Typically, the fibers, the rods, the grooves, the notches and the webs, respectively are, when seen from above, at least on average aligned at least substantially parallel to a lateral edge of the seat and/or extend at least substantially from a rear edge of the seat to a front edge of the seat.

[0085] Due to the simplified design, it is now possible to equip any type of chair, from office chairs to kitchen chairs, with a swiveling backrest. This means that chairs with added comfort and ergonomics can be designed cost-effectively for almost any application. Some of them are described in the following.

[0086] Many people use cafes as temporary work places, e. g. when there is no own workplace available, when travelling or for an informal meeting etc. Cafes are also popular as work places with self-employed people. The typical requirements for a chair in a cafe such as stackability, robustness, suitability for different users, easy cleaning, outdoor use, and/or a four-legged frame can be fulfilled by the chairs described herein at comparatively low costs.

[0087] In particular in large cities, co-working spaces, i.e. a workplace rentable for a temporary period of time, are established. The typical requirements for a chair for co-working space such as stackability, the possibility of using different frames, armrests, suitability for different users, and comfort over a whole working day can also be fulfilled by the chairs described herein at comparatively low costs.

[0088] Canteens in companies, public authorities and universities are used mainly by employees or students and guests for informal exchanges of ideas. The typical requirements for a chair in canteens such as stackability, robustness, suitability for different users, easy cleaning, and a four-legged frame can also be fulfilled by the chairs described herein at comparatively low costs.

[0089] When waiting for longer periods of time, e. g. at the doctor's office or in the airport, increased seating comfort is appreciated. The typical requirements for a chair in waiting areas such as robustness, suitability for different users, easy cleaning, a four-legged or traverse frame as well as requirements due to fire protection regulations can also be fulfilled by the chairs described herein at comparatively low costs.

[0090] In seminar rooms the room layout often varies. The typical requirements for a chair in the seminar room such as stackability, suitability for different users, comfortable over a longer period of time, as well as four-legged frame, optionally with castors, can also be fulfilled by the chairs described herein at comparatively low costs.

[0091] In addition to classic requirements such as comfort, a conference room often has representative features that the furnishings should meet. The typical requirements for a chair in conference rooms such as suitability for different users, upholstered seat and backrest, armrests, star or cross base can also be fulfilled by the chairs described herein at comparatively low costs.

[0092] At home, a classic work chair or office chair is often not desired due to its volume and/or aesthetics. The typical requirements for a chair at home such as an option on different frames, an option on armrests, and an option on upholstered seat and a backrest can also be fulfilled by the chairs described herein at comparatively low costs.

[0093] Due to the typical large number of chairs in multi-purpose halls, special attention is typically paid to the price and the possibility of linking. Higher sitting comfort also improves the attention and absorption capacity of the users in multi-purpose halls. The typical requirements for a chair for multi-purpose halls, in particular stackability, a four-legged or skid frame, low weight, low price and linkability can also met by the chairs described herein.

[0094] According to an embodiment, a method for manufacturing the chairs described the herein includes providing attaching an elastically deformable seat to a frame, hinge- mounting a coupling element having a first lever arm and a second lever arm to the frame, and attaching a backrest to the first lever arm, so that the second lever arm is arranged at the seat, typically at a back side of the seat.

[0095] The assembly may be very simple as only a few parts may be used.

[0096] All common frames may be used, in particular four-legged frame, skid frame, star-foot frame, and a cantilever frame.

[0097] The design allows a wide aesthetic range for a variety of different chair typologies.

[0098] Typically, the seat is mounted in a pre-stressed manner to the frame. [0099] Furthermore, the seat is typically in articulated connection with the frame. [00100] According to an embodiment, a chair, in particular an office chair has a (coupling) mechanics operating between the seat of the chair and the backrest of the chair, by means of which the inclination resistance of the backrest is dependent on the load on the seat by the user. The seat is at least partially raised as a function of the load on the backrest, wherein the mechanics cause the elastically deformable seat to curve upwards. This curvature or bulging ensures that the user is raised when the backrest is loaded.

[00101 ] The design of the (coupling) mechanics is simple and requires no additional power accumulator.

[00102] The (coupling) mechanism may consist of only a few parts and does not require any additional height. Note that no disruptive volume under the seat is required for the power accumulator.

[00103] Still, the force with which the user weighs on the seat is transferred to the backrest (so-called bodyweight function).

[00104] The elements providing the bodyweight function may even be invisible as such from all common perspectives. This increases the design flexibility.

[00105] Due to the low number of components, the chair may have relatively low wear and tear.

[00106] Furthermore, the components are typically easy to replace due to the simple assembly.

[00107] Even further, the chair proposed herein can be designed to be stackable, typically even tightly stackable.

[00108] Compared to other chairs with bodyweight function, the chairs described herein may be relatively light. This may facilitate transport, stacking and rearranging of the chairs. [00109] Typically, the backrest is supported by a long lever arm of at least one L-shaped lever, and the short (r) lever arm of the lever acts with its free end directly on the seat.

[00110] In other words, the (coupling) mechanism is typically implemented as a lever mechanism, more typically as a simple lever.

[00111 ] The relationship between the length of the lever and the maximum angle between the backrest and the seat is preferably chosen in such a way that the middle of the seat is raised by at most 16 mm, more typically at most 15 mm in front view. The low deformation of the seat avoids any unpleasant pressure on the user's lower thigh.

[00112] The seat may be provided with a plurality of weaknesses which are substantially perpendicular to the plane of the (unloaded) backrest so that the elastic curvature or bulging of the seat is uniformly or at least more uniformly formed over the entire extension and/or area of the seat.

[00113] The weaknesses may be formed as grooves.

[00114] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the Figures. Each example is provided by way of explanation, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations. The examples are described using specific language which should not be construed as limiting the scope of the appending claims. The drawings are not scaled and are for illustrative purposes only. For clarity, the same elements or manufacturing steps have been designated by the same references in the different drawings if not stated otherwise. [00115] The terms "above" and "below" as used in this specification intend to describe a relative location of a structural feature to another structural feature with consideration of this orientation when the chair stands in a normal position on a ground such as a floor.

[00116] With respect to Figures 1 to 4, an embodiment of a chair 100 is explained.

[00117] The illustrated chair for a single person 100 has a frame 16 including four exemplary legs, a seat 14 connected to the frame 16 and a backrest 10.

[00118] In the exemplary embodiment, the chair 100 includes and/or consists of the backrest 10 carried by long legs 10a of a pair of L-shaped levers 12, the elastic seat 14 and the frame 16 supporting the seat 14. The free end of the short leg 10b of the L-shaped lever 12, which is connected to the frame 16 at hinge points 18, acts directly on the seat 14, so that the seat 14 is curved upwards and thus raised essentially in the middle when the backrest 10 is subjected to a load.

[00119] The seat surface is connected to the frame 16 via hinges 20. The hinges 20 form pivot points which absorb the vertical forces that occur.

[00120] In the exemplary embodiment, the two L-shaped levers 12 are connected to each other via a rod 19, which acts in its centre on the downwardly concave seat 14. When the backrest 10 is subjected to a load, the seat 14 is arched upwards against the elasticity of the seat and against the load acting on the seat. This curvature ensures that the user is raised. In order to ensure that this curvature is uniformly formed over the entire length of seat 14, a large number of grooves 21 were inserted in seat 14, essentially perpendicular to the plane of the backrest 10 (see Figs. 3, 4). Conversely, the backrest 10 is pushed forward against the force applied by the user to the backrest 10 when the seat surface 14 is loaded.

[00121 ] Without any load on the seat 14 by the user, the backrest 10 is returned to its original position by the elasticity of the seat 14. The seat thus acts as a spring. [00122] There is no firm connection between the backrest 10 and the seat 14. The only hinge is the link between lever 12 and frame 16.

[00123] The chair as proposed herein can be designed to be stackable.

[00124] The mechanism consists of only a few parts and does not require any additional height.

[00125] Accordingly, the manufacturing costs of the chair 100 are comparatively low.

[00126] Nevertheless, the chair 100 is a chair with bodyweight function. The bodyweight function is realized in a cost-efficient manner using the seat as only power accumulator. Without this power accumulator, the backrest 10 would not be able to return to its original position once it has been brought into its final position if the seat is not loaded.

[00127] In addition, the user's load on the backrest changes continuously as the backrest swings backwards. The user exerts less force on the backrest in a starting position than in the end position with backwards tilted backrest. This successive increase in the force acting on the backrest is compensated for by means of the (further deforming) seat acting as power accumulator.

[00128] Most users can stop the movement at any desired angle of inclination of the backrest, both when leaning back and forward. The user can thus determine the degree of inclination at which he wants to sit. Users are not pushed forward in an upright position, nor does their upper body tilt backwards due to too little force from the backrest.

[00129] Without power accumulator, the user would, when leaning backwards, tilt from a certain point to the end position, because the force the user applies to the backrest would exceed his own weight from this point on. In order for this not to happen, the power accumulator has to generate an appropriate counterforce. [00130] In other chairs with bodyweight function, a compression, tension, spiral or worm spring is used as a power accumulator. However, this increases costs and complexity of the chair.

[00131 ] In the chairs described herein, the seat is the only power accumulator for implementing the economically desired bodyweight function. No additional power accumulator other than the seat itself is required. The frame is typically not deformed when the backrest is tilted backwards.

[00132] However, the chair, in particular its frame may have a gas strut as hydraulic chair height adjustment mechanism.

[00133] In contrast to conventional chairs, which require several joints for implementing the bodyweight function, the bodyweight function of the chairs described herein can be achieved with only one main hinge located under the seat.

[00134] Typically, the main hinge connects the lever 12 and a rear crossbar of the frame 16.

[00135] In embodiments referring to a chair with one main hinge, the main hinge is typically arranged in or at least next to a central vertical symmetry axis of the chair when seen in a front view or a back view.

[00136] Alternatively, a left and a right main hinge connect the rear crossbar of the frame 16 with the left lever 12 and the right lever 12', respectively.

[00137] The main hinge(s) may also provide a stopper for the backrest.

[00138] In addition to the main hinge(s), the chair may have secondary hinges for mounting the seat on the frame. Typically, two secondary hinges are used at the connection between the seat and the frame, in particular left secondary hinge and right secondary hinge of the seat arranged in front view at the left side and right side of the seat, respectively. Alternatively, two secondary hinges may be used at both sides.

[00139] The secondary hinges may be designed in different ways. Three examples are explained in the following with regard to figure 5 and 10.

[00140] Figures 5 and 6 show respective sections of a chair 101 in a front view. The chair 101 is typically similar as the chair 100 explained above with regard to figure 1 to figure 4. However, a respective friction bearing is used as left secondary and right secondary hinge between the seat 14 and the frame 16.

[00141 ] Figure 5 illustrates an unloaded state of the chair 101 in which the backrest (not shown) is in the most upright orientation (also referred to as starting position). Figure 6 illustrates loaded state of the chair 101 in which the backrest (not shown) is completely settled back (also referred to as end position).

[00142] In the exemplary embodiment, the frame 16 is implemented as a welded round tube frame. The left side of the seat 14 is screwed from below to a left tube of the frame 16. Likewise, the right side of the seat 14 is screwed to a right tube of the frame. For sake of clarity, only a left seat connecting region next to a left edge 144 of the seat 14 is illustrated in figures 5, 6.

[00143] As indicated by the slotted holes 16a, 16b in figure 5 and 6, a screw 15 leading through two spacers 17 and the right tube sandwiched between the two spacers 17 may be used for mounting the seat 14 to the frame 16 in manner allowing a slight movement of the left edge 144 (and likewise the right edge) of the seat 14 with respect to the frame 16 when the backrest is pivoted with respect to the frame (and the seat 14 deformed). When the backrest is pivoted and the seat 14 is deformed, the screw 15 rotates back and forth in the slotted hole. [00144] As the screw 15 is screwed from the back side 141 of the seat into the seat 14, the upper site 143 of the seat 14 forming the sitting area may not be affected.

[00145] The height of the spacers 17 between the frame 16 and the seat 14 may depend on the curvature of the seat 14 when the backrest (not shown) is in the starting position.

[00146] Figures 7 and 8 show respective left sections of a chair 102 in a front view. The chair 102 is typically similar to the chair 101 explained above with regard to figures 5, 6. However, hinge joints 13 are used as left secondary and right secondary hinge, respectively, between the seat 14 and the frame 16. Figure 7 illustrates the chair 102 when the backrest (not shown) is in the starting position. Figure 8 illustrates the chair 102 when the backrest (not shown) is in the end position.

[00147] The height of the spacer 17 between the frame 16 and the seat 14 may again depend on the curvature of the seat 14 when the backrest (not shown) is in the starting position.

[00148] Figures 9 and 10 show respective left sections of a chair 103 in a front view. The chair 103 is typically similar to the chairs 101 , 102 explained above with regard to figures 5 to 8. However, elastic spacers or buffers 17 the desired function of left secondary and right secondary hinges, respectively, between the seat 14 and the frame 16. Figure 9 illustrates the chair 103 when the backrest (not shown) is in the starting position. Figure 10 illustrates the chair 103 when the backrest (not shown) is in the end position.

[00149] In this embodiment, the spacer 17 becomes deformed when the seat 14 is deformed (when the backrest is moved between the starting position and the end position).

[00150] The elastic spacer(s) 17 may be T-profiles and T-shaped in front view, respectively. [00151 ] The elastic spacer(s) 17 may for example be made of rubber, silicon or another elastic material.

[00152] Irrespective of the type of the secondary hinges, there is only a slight movement of the seat 14 at the edge 141 and in the connection area required, e. g. a few mm, when the backrest is moved between the starting position and the end position.

[00153] It is therefore advantageous if the seat 14 can move at the lateral sides (edges). For best function, the seat 14 should be a few millimetres away from the hinges (joints). This distance may again depend on the degree of curvature/bulging of the seat 14 in the starting position of the backrest.

[00154] Figure 1 1 illustrates a chair 104 in side views when the backrest (not shown) is in a starting position (full lines) and in an end position (dashed lines). The chair 104 is typically similar to the chairs 100 - 103 explained above with regard to figures 1 to 10. Figure 1 1 may even correspond to an enlarged view on the left side of the chair 100. For sake of clarity, only the main hinge 18, a portion of the lever 12, a portion of the back side 141 and a rear edge 142 of the seat 14 are illustrated in figure 1 1 .

[00155] As illustrated in figure 1 1 , the chair 104 may be implemented so that, apart from an at most very slight change in curvature (not shown), the back side 141 (as well as the upper site) are (substantially) parallel displaced in vertical direction over the entire seat depth when the backrest is moved between the starting position and the end position.

[00156] In particular, longitudinal grooves or webs (not shown) at the backside or the upper side of the seat 14 may ensure that the seat 14 is deformed to a correspondingly low extent over the entire seat depth. The webs may ensure that the seat is not deformed at certain points, but in the longitudinal direction of the webs over their entire depth.

[00157] Accordingly, a point deformation at the point where the lever 12' presses at the seat 14 from below may be avoided. Rather, the deformation of the seat 14 may be transmitted to the front edge and rear edge 142 of the seat 14. The advantage of this is that the seat 14 is positioned parallel in the side view during the entire movement of the backrest.

[00158] The front edge of the seat 14 may even be deformed as far up as the seat at the point where the lever 12' acts on the seat 14 from below.

[00159] A length of the second lever arm 10b is typically in a range from about 50 mm to 70 mm, more typically in a range from about 55 mm to 65 mm.

[00160] The lever 12' is preferably 60 mm +/- 2 mm long between the main hinge 18 and the point of contact of the lever 12' and the second lever arm 10b, respectively, on the seat, so that the seat 14 is raised by approx. h=16 mm at the lowest point of the curvature of the seat when the backrest is tilted by 15°.

[00161 ] The main hinge 18 is typically arranged in a vertical position above a lower position of the backside 141 (at the lowest point of the seat's curvature) when the backrest is in the starting position and below an upper position of the backside 141 (at the lowest point of the seat's curvature) when the backrest is in the end position. The distance hi between the vertical position of the hinge 18 and the lower position may be in a range of 40% to 60% of the distance h2 between the vertical position of the hinge 18 and the lower position, ideally both distances hi , h2 are at least substantially equal (h1 =h2, corresponding to 8 mm for h= 16 mm).

[00162] Accordingly, the risk of forming scratches at the backside due to the slightly back and forth slipping free end of the lever 12' maybe efficiently reduced.

[00163] According to an embodiment, a chair includes a frame, an elastically deformable seat, a support surface for a user's back, and a rigid first coupling element which is in articulated connection with the frame and has a first lever arm supporting the support surface, and a second lever arm arranged at the seat so that the elastically deformable seat is operable as a spring and/or as a power accumulator for storing an energy, and typically forms the only spring and power accumulator, respectively, of the chair for this purpose, when the user leans back and/or is leaning back on the support surface.

[00164] The support surface is typically provided by a backrest of the chair.

[00165] The seat is typically upwardly curved and/or at least partially raised, more typically upwardly curved and partially raised, when the support surface and the backrest, respectively, is moved backwards and/or tilted back by the user.

[00166] According to an embodiment, a chair includes a frame, an elastically deformable seat attached to the frame, a coupling element in articulated connection with the frame and including a first lever arm and a second lever arm arranged at the seat, and a backrest attached to the first lever arm.

[00167] According to an embodiment, a method for manufacturing a chair includes providing a frame, attaching an elastically deformable seat to the frame, mounting a coupling element, in particular a lever to the frame in an articulated manner, the coupling element including a first lever arm and a second lever arm, and attaching a backrest to the first lever arm, so that the second lever arm is arranged at the seat, typically at a back side of the seat opposite a seat area of the seat.

[00168] Although various exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. It should be mentioned that features explained with reference to a specific FIG. may be combined with features of other Figures, even in those cases in which this has not explicitly been mentioned. Such modifications to the inventive concept are intended to be covered by the appended claims. [00169] Spatially relative terms such as "under", "below", "lower", "over", "upper" and the like are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the Figures. Further, terms such as "first", "second", and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.

[00170] As used herein, the terms "having", "containing", "including", "comprising" and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles "a", "an" and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[00171 ] With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.

Claims

CLAIMS What is claimed is:

1 . A chair (100 - 104), comprising:

- an elastically deformable seat (14);

- a backrest (10); and

- a coupling mechanics (12) arranged between the seat (14) and the

backrest (10) so that an inclination resistance of the backrest (10) depends on a user's load on the seat (14), and that the seat (14) is, depending on a user's load on the backrest (10), upwardly curved and/or at least partially raised.

2. A chair (100 - 104), comprising:

- an elastically deformable seat (14);

- a backrest (10); and

- a rigid first coupling element (12) comprising a first lever arm (1 Oa)

supporting the backrest (10), and a second lever arm (10b) arranged at the seat (14) so that the elastically deformable seat (14) is deformed when a user is leaning back on the backrest (10).

3. The chair (100 - 104) of claim 1 , wherein the coupling mechanics comprises a first coupling element (12) comprising a first lever arm (10a) to which the backrest (10) is attached, and a second lever arm (10b) acting on the seat when the backrest (10) is loaded and/or acting from below towards the seat (14) when the backrest (10) is loaded.

4. The chair (100 - 104) of claim 2 or 3, wherein the chair and/or the coupling

mechanics comprises a second coupling element (12) comprising a first lever arm (10a) to which the backrest (10) is attached, and a second lever arm (10b) acting on the seat when the backrest (10) is loaded and/or acting from below on the seat (14) when the backrest (10) is loaded.

The chair (100 - 104) of claim 4, wherein the chair and/or the coupling mechanics comprises a connecting element (19) connecting the second lever arm of the first coupling element and the second lever arm of the second coupling element with each other and acting from below on the seat (14) and/or pressing on a central portion of the seat (14) when the backrest (10) is loaded. The chair (100 - 104) of claim 5, wherein the connecting element (19) comprises a rod or a strut, and/or wherein the connecting element (19) presses from below against the seat (14) when the backrest (10) is loaded.

The chair (100 - 104) of any preceding claim, wherein the respective coupling element (12) is at least substantially rigid, wherein the coupling mechanics (12) is implemented as a lever mechanism, wherein the respective coupling element (12) is a lever, wherein the respective coupling element (12) is, at least in a side view, at least substantially L-shaped, wherein the first lever arm (10a) of the respective coupling element (12) is longer than the second lever arm (10b) of the respective coupling element (12), wherein a free end of the respective second lever arm (10b) acts directly on the seat (14), exerts a force onto the seat (14) and/or presses from below against the seat (14) when the backrest (10) is loaded.

The chair (100 - 104) of any preceding claim, further comprising a frame (16), wherein the coupling mechanics (12) and/or the respective coupling element (12) is in articulated connection with the frame (16), typically using a respective main hinge (18) arranged below the seat (14) and/or next to a rear edge (142) of the seat (14).

The chair (100 - 104) of claim 8, wherein the coupling mechanics (12) and/or the respective coupling element (12) is in articulated connection with a crossbar of the frame (16).

10. The chair (100 - 104) of claim 8 or 9, wherein the frame (16) is a welded round tube frame, and/or wherein the seat (14) is attached to the frame (16).

1 1 . The chair (100 - 104) of any of the claims 8 to 10, wherein the seat (14) is in articulated connection with the frame (16), wherein the seat (14) is connected with the frame via at least one hinge joint (13), wherein the seat (14) is screwed to the frame (16), and/or wherein a spacer (17), typically an elastic spacer is arranged between the seat (14) and the frame (16).

12. The chair (100 - 104) of any preceding claim, wherein the seat (14) is operable as a spring and/or as a power accumulator for storing an energy when the user leans back on the backrest (10), wherein the seat (14) is the only power accumulator of the chair for storing an energy when the user leans back on the backrest (10), and/or wherein the chair is free of additional springs and/or gas struts.

13. The chair (100 - 104) of any preceding claim, wherein the seat (14) is

substantially plate-shaped, wherein a horizontal extension of the seat (14) exceeds a layer thickness of the seat (14) by at least a factor of 20, wherein the seat (14) is pre-stressed, wherein the seat (14) is only partly raised, and/or wherein the seat (14) in an unloaded state downwardly curved and/or downward concave when seen in a front view.

14. The chair (100 - 104) of any preceding claim, wherein an elastic modulus of the seat (14) comprises an anisotropy, wherein the seat (14) comprises wood, a metal, a plastic and/or a composite material, wherein the composite material comprises a matrix material and fibers and/or rods, wherein the seat (14) comprises grooves (21 ), notches and/or webs, and/or wherein the fibers, the rods, the grooves, the notches and/or the webs are, when seen from above, at least on average aligned at least substantially parallel to a lateral edge of the seat (14) and or extend at least substantially from a rear edge (142) of the seat (14) to a front edge of the seat (14).

15. The chair (100 - 104) of any preceding claim, wherein the chair is stackable.

16. A method for manufacturing a chair (100 - 104), the method comprising:

- providing a frame (16);

- attaching an elastically deformable seat (14) to the frame (16);

- mounting a lever (12, 12') to the frame (16) in an articulated manner, the lever comprising a first lever arm (10a) and a second lever arm (10b); and

- attaching a backrest (10) to the first lever arm (10a),

so that the second lever arm (10b) is arranged at the seat (14).