# Patent

## Title
Seat

## Abstract

A seating structure including a base, a pair of laterally spaced support arms each having a seat portion and a backrest portion and a transition portion joining the seat portion and backrest portion, wherein the support arms are coupled to the base. A body support member extends between and is connected to the support arms and includes at least a seat portion and a backrest portion. A support element is coupled to the base and includes a central support arm extending upwardly along a centerline of the backrest portion of the body support member. The central support arm is spaced rearwardly from the backrest portions of the support arms and further includes a pair of laterally extending struts connecting the central support arm and the laterally spaced support arms.

## Background
This application is a continuation of U.S. application Ser. No. 12/225,335, filed Sep. 18, 2008 now U.S. Pat. No. 7,992,936, which was the National Stage of International Application No. PCT/IB07/00745, filed Mar. 22, 2007, the entire disclosures of which are hereby incorporated herein by reference.


FIELD OF INVENTION
The invention relates to a seat which comprises an underframe and a seat element, the seat element comprising a front seat part, a rear seat part, a lower backrest part and an upper backrest part.
BACKGROUND
DE 42 35 691 C2 describes a seat in which the seat is to be automatically adapted to the body weight of the particular user. A drawback of seats of this type is the enormous constructional complexity which leads to high costs and to the seat being heavy.
BRIEF SUMMARY
The invention is based on the object of developing a seat, in which, in order to provide basic compensation for different body weights of the individuals using the seat, the use of a weighing device in the sense of a complex mechanism, in which movements are used to automatically change spring forces or spring characteristics, is to be omitted.
This object is achieved, for example and without limitation, by the features of Claim 1. Advantageous and expedient developments are provided in the subclaims.
The seat according to the invention has a front seat part, a rear seat part, a lower backrest part and an upper backrest part, which comprise at least one supporting arm, the supporting arm being composed of at least one upper support and at least one lower support, the upper support being guided in a region A of the front seat part by at least one guide element, the upper support and the lower support being connected to each other in a region D of the upper backrest part, the upper support and the lower support having an arcuate profile in the region B of the rear seat part and in the region C of the lower backrest part, the upper support and the lower support being positioned with respect to each other in the region B of the rear seat part or in the region C of the lower backrest part by at least one connecting link, and the front seat part being able to be pulled back by the upper support with a pulling-back movement directed towards the backrest parts C, D if, when the backrest part is loaded by an individual leaning against it, the seat element is displaced from a basic position I into a resting position II. By this means, a movement by means of which the seat part is actively pulled back can be produced by the seat element. The active displacement or deformation of the seat element makes it possible to influence the position of an individual sitting on the seat relative to the underframe of the seat and, by this means, to counteract the loss of potential energy when the individual leans back into the resting position II. This compensation takes place in order to keep the restoring force, which has to be applied by the backrest part to comfortably move the individual from the resting position II into the basic position I, low or to make it entirely superfluous. The core of the invention is a seat with at least one supporting arm by means of which an active movement of the front seat part can be produced by a largely defined change in shape.
Furthermore, the invention makes provision, by means of the pulling-back movement, to bring about a movement of the front seat part or of the upper support with a horizontal component or a vertical, upwardly directed component. By means of the movement of the front seat part upwards and in the direction of the backrest part, it is possible, as an individual sitting on the seat leans back, to raise his lower body gently from the basic position I into the resting position II or into any intermediate position by means of the front seat part. By this means, a loss of potential energy due to the lowering of the upper body of the individual can be compensated for by the backrest part. The opposed movements of the seat part and of the backrest part permit a seesaw movement or rocking movement, similar to a seesaw or a beam-balance, of the individual on the seat, which movement can take place very substantially independently of the individual's body weight. A presetting of a spring that is dependent on the body weight of the individual using the seat can therefore be basically or very substantially omitted, since the deformation of the seat element brings about a compensation which is independent of the body weight. That is to say, each individual using the seat forms a counterweight as a function of the body weight with a proportion of the body weight itself and thereby brings about intrinsic compensation.
According to the invention, elastic deformability of the supporting arm or of the upper support and/or of the lower support is provided at least in the region B of the rear seat part and in the region C of the lower backrest part. This makes it possible to change a radius of curvature of the supports and therefore also a relative movement between the two supports, by means of which the front seat part can then also be moved.
According to the invention, the guide element, which guides the upper support in the region of the front seat part on the lower support or on the underframe, is essentially designed as a lever arm which is fastened rotatably to the upper support and rotatably to the lower support or to the underframe. This makes it possible, using simple means, to define a movement on a circular path, which movement has a horizontally directed component and a component directed vertically upwards during a movement from the basic position I into the resting position II.
Alternatively, the invention makes provision to design the guide element as a slotted-guide mechanism in which the upper support is movable in the region of the front seat part relative to the lower support or to the underframe. In the case of a slotted-guide mechanism, a curve on which the front seat part or the upper support moves can be very substantially freely selected. By this means, a complicated coupling mechanism for defining a curve for the movement of the upper support can be omitted.
According to a first variant embodiment, as the connecting link or mechanical connecting link between the upper support and the lower support, the invention provides a lever which is connected rotatably in each case to the upper support and the lower support. This makes it possible to define the profile of a relative movement executed by the two supports during the transition from the basic position I into the resting position II, with the supports being pulled towards each other or pushed apart from each other during their opposed displacement depending on the positioning of the bearing points of the lever. Instead of a lever which is mounted by means of bolts, use of clasps or clips is also provided.
According to a second variant embodiment, the invention makes provision to form the connecting link between the upper support and the lower support by at least one slotted-guide mechanism. It is possible to define, by means of a connecting link of this type, any desired curves on which the supports move during corresponding loading.
According to a third variant embodiment, the invention makes provision to form the connecting link between the upper support and the lower support by an elastic element. This makes it possible to reduce the elastic deformation of the upper and/or lower support, since the bearing element used as the bearing can also be deformed and therefore can store energy. In particular, a rubber block which is adhesively bonded to the supports is provided as the bearing.
The invention provides an energy store which, in particular, is adjustable. By this means, for example, particular seat loads caused, for example, by the body build of individuals using the seat can be compensated for.
The invention provides, as energy store, for example, a spring element counter to which the upper support can be pulled back in the direction of the backrest part. A spring element of this type can be realized with little outlay and requires little construction space.
The invention also provides a guided rocking movement of the seat element on the underframe, with there being approximately an equilibrium of forces between the seat part and the backrest part in every seat position between the basic position I and the resting position II. By this means, the function of the seat is largely independent of the body weight of an individual using the seat.
Furthermore, the invention makes provision to fasten the lower support of the supporting arm to the underframe. By this means, the upper support of the supporting arm obtains the required degrees of freedom in order, despite the guide element, despite the at least one connecting link and despite the connection to the lower support in the region of the upper backrest part, to compensate for the shifting of the weight of an individual using the seat.
The invention also provides an L-shaped profile of the supporting arm or of the supports of the supporting arm in the side view of the seat. This makes it possible to use the supporting arm as a supporting component of the seat element and to use it both to control the sequence of movement of the seat element and to form the seat part itself. In principle, every supporting arm is designed as an arcuate clamp which has two legs running next to each other and at a distance from each other, the legs forming the supports. Between a clamp head, in which the two legs are connected to each other or merge one into the other, and free ends of the legs, the legs are connected by at least one connecting link. The free end of the upper leg of the clamp, which end forms the seat surface or bears the latter, is guided on the lower leg or on the underframe by a guide element.
According to the invention, in the basic position I and in the resting position II, an upper pivotal point of the guide element is located higher than a lower pivotal point of the guide element, the upper pivotal point being at a greater distance from the backrest part than the lower pivotal point. This defines a movement clearance of the front seat part, in which the front seat part rises continuously from the basic position I into the resting position II and moves continuously in the direction of the backrest.
According to the invention, during a loading of the seat element by a person leaning back against the backrest part, the connecting link is rotatable by the supports and is displaceable with the latter. The connecting link therefore constitutes a connection between the supports, which connection permits the supports or the supporting arm to have a delimited movement.
A variant embodiment of the invention provides a seat in which the supporting arm is formed by a left, upper support and a right, upper support and a lower support situated between them, the lower support being connected to the left, upper support by at least one mechanical connecting link, and the lower support being connected to the right, upper support by at least one mechanical connecting link. By this means, with just one supporting arm, a seat or a seat element can be brought about, in which a supporting arm suffices in order to carry a covering which serves as the seat surface and backrest.
Furthermore, in the case of a supporting arm with two upper supports, the invention provides an upwardly directed limb of the lower support, which limb is divided into two struts and merges by means of the latter into upwardly directed limbs of the upper supports. Such a transition of the lower support into the upper supports changes a torsional rigidity of the seat element and is suitable for a single-piece design of the supporting arm.
The invention also makes provision, in the case of a supporting arm with two upper supports, to guide the upper supports on the lower support or on the underframe by means of a respective guide element. The use of two guide elements enables the divided upper support also to be guided along a desired curve.
According to the invention, the front seat part can be raised by deformation of the supporting arm, which is necessitated by an individual leaning back against the backrest part, along a path in the direction of the backrest part, with the supporting arm deformed in such a manner resuming its original shape by load alleviation of the backrest part, and with the front seat part being lowered again along the path mentioned during the re-forming. The lowering of the front seat part makes it easier for the individual to return into an upright sitting position.
Finally, the invention makes provision to connect the upper support and the lower support of the supporting arm in the region of the lower backrest part by at least one connecting link and to connect them in the region of the rear seat part by at least one connecting link. By this means, buckling of the supports during the deformation between the basic position I and the resting position II can be effectively prevented.
In particular, it is also provided to connect a central section of the upper support of the supporting arm and a central section of the lower support of the supporting arm to each other by at least three connecting links. By this means, the forces occurring during the deformation of the supporting arm between the basic position I and the resting position II can be distributed particularly uniformly to the supports. This distribution of the load leads to an increase of the service life of the supporting arm.
Further details of the invention are described in the drawing with reference to schematically illustrated exemplary embodiments.



BRIEF DESCRIPTION OF THE DRAWINGS
In this case:
FIG. 1a shows: a simplified side view of a first variant embodiment of a seat according to the invention in a basic position I;
FIG. 1b shows: a perspective schematic diagram of the seat shown in FIG. 1a; 
FIG. 2 shows: the seat shown in FIG. 1a in a resting position II;
FIG. 3 shows: a second variant embodiment of a seat according to the invention in a basic position;
FIG. 4 shows: the seat shown in FIG. 3 in a resting position II;
FIG. 5 shows: a superimposed illustration of the illustrations shown in FIGS. 3 and 4;
FIG. 6 shows: a third variant embodiment of a seat according to the invention in a basic position,
FIG. 7 shows: a simplified perspective illustration of a fourth variant embodiment of a seat according to the invention;
FIG. 8 shows: a simplified side view of a fifth variant embodiment of a seat according to the invention;
FIG. 9 shows: an enlarged illustration of the supporting element of the seat, shown in FIG. 8, in a basic position;
FIG. 10 shows: an enlarged illustration of the supporting element of the seat, shown in FIG. 8, in an intermediate position;
FIG. 11 shows: an enlarged illustration of the supporting element of the seat, shown in FIG. 8, in a resting position;
FIG. 12 shows: a superimposed illustration of the positions, shown in FIGS. 9 to 11, of the supporting element;
FIG. 13 shows: a simplified perspective view of a sixth variant embodiment of a seat according to the invention;
FIG. 14 shows: a simplified perspective view of a seventh variant embodiment of a seat according to the invention;
FIG. 15 shows: a perspective view of a seat element of an eighth variant embodiment of a seat according to the invention;
FIG. 16 shows: a side view of the eighth variant embodiment of the seat;
FIG. 17 shows: a further perspective view of the seat element known from FIG. 15, and
FIGS. 18-20 show: side views of a ninth, tenth and eleventh variant embodiment of a seat according to the invention.
FIGS. 1a to 20 show schematic diagrams of eleven variant embodiments of a seat according to the invention.



DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED EMBODIMENTS
FIG. 1a illustrates a seat 1 in side view. The seat 1 includes a seat element 2 and an underframe 3. The seat element 2 has a seat part 4 which is divided into a front seat part 4a and a rear seat part 4b. Furthermore, the seat element 2 has a backrest part 5 which is divided into a lower backrest part 5a and an upper backrest part 5b. The seat element 2 includes two supporting arms 6, 7 which are each formed by an upper support 6a or 7a and a lower support 6b, 7b (also see FIG. 1b). A fabric 8, which is only visible in FIG. 1b, is stretched between the two supporting arms 6, 7 and the upper supports 6a, 7a thereof. Other body support components, such as a shell or membrane, alone or in combination with the fabric, can also bridge between the two supporting arms. FIG. 1b shows a simplified perspective view of the seat 1 illustrated in FIG. 1. For simplification, the seat 1 is described in more detail below only in the region of the first supporting arm 6. The upper support 6a is connected in a region A of the front seat part 4a to the lower support 6b by a guide element 9. The guide element 9 is designed as a lever 10 which is connected rotatably at pivotal points D91 and D92 to the upper support 6a and the lower support 6b. The second supporting arm 7 is in each case of corresponding design. The supports 6a, 6b of the supporting arm 6 merge into each other as a single part in a region D of the upper backrest part 5b and, according to a variant embodiment (not illustrated), are screwed or riveted to each other. From the region D, the supports 6a, 6b have an intermediate space 11 with respect to each other over their entire extent. In particular in a region B of the rear seat part 4b and in a region C of the lower backrest part 5a, the supports 6a, 6b run in an arcuately curved manner and approximately at the same distance from each other. In this curved region B or C, the two supports 6a, 6b are connected to each other by a connecting link 12. The connecting link 12 is designed as a lever 13 which is fastened rotatably to the supports 6a and 6b at pivotal points D121 and D122. The underframe 3 has a transverse support 14 to which the right and the left supporting arms 6, 7 of the seat element 2, and in particular the lower seat support are fastened. In particular, the lower seat support is fixedly connected to the support 14. FIGS. 1a and 1b both show the seat 1 in a basic position I in which the seat 1 is upright, if it is unloaded or if an individual is sitting on the seat 1 and is not leaning or is only slightly leaning against the backrest part 5.
In one embodiment, the upper support 6a, 7a has a cross sectional area of 1 inch3 and a moment of inertia of 0.005000 inch4 in the sections B and C. In various exemplary and suitable embodiments, the cross sectional area can be from 0.3 inch2 to 4 inch2 and the moment of inertia can be from 0.000172 inch4 to 0.011442 inch4. Preferably, the cross-sectional area is at least 0.3 inch2 and the moment of inertia is at least 0.000172 inch4. In one embodiment, the connecting links are spaced apart about 3 inches. In various exemplary embodiments, the connecting links are spaced at least 0.5 inch, but preferably no more than 8 inches. In the section A the moment of inertia of the first upper support 6a, 7a increases in direction to front seat part 4a in comparison with the moment of inertia in the sections B and C. In the section D the moment of inertia of the upper support 6a, 7a is comparable with the moment of inertia of the upper support 6a, 7a in the sections B and C. In all sections A, B, C and D the lower support 6b, 7b is dimensioned comparably to the corresponding section of the upper support 6a, 7a. In various exemplary embodiments, the values for the moment of inertia and cross sectional areas differ from the values of the upper support 6a, 7a by a factor from 0.5 to 1.5. Preferably the upper and lower support 6a, 7a, 6b, 7b have a cross sectional area of the same shape. According to the embodiment of FIGS. 1a and 1b the cross sectional area has the shape of a rectangle. In various exemplary and suitable embodiments, the cross sectional area of the supports 6a, 7a, 6b, 7b has the shape of a circle or an oval or a polygon.
The supports can be made, for example and without limitation, of glass filled Nylon, unfilled Nylon, glass filled polypropylene, unfilled polypropylene, polycarbonate, polycarbonate/ABS blend, acetal, or combinations thereof. The connecting links and/or the levers can be made of the same materials, or of various elastomeric materials, including without limitation, Hytrel, Nylon blended with elastomers, thermoplastic urethane or combinations thereof. The connecting links and/or the levers can also be made of rigid materials, including various rigid plastics or metal.
FIG. 2 illustrates the seat 1 known from FIGS. 1a and 1b in a resting position II. The seat 1 or the seat element 2 takes up a resting position II of this type if an individual sitting on the seat 1 leans back in an arrow direction x against the backrest part 5. The action of leaning back changes an inner opening angle α of the seat element 2 between the seat part 4 and the backrest part 5 from α=90° (see FIG. 1a) to α=80° (see FIG. 2). This change in the inner opening angle α is produced by the supporting arm 6 being bent, which takes place essentially in the regions B and C and at the transition of the region B into the region A, and by the front seat part 4a being raised or inclined. An opening angle W6 relevant to the sitting comfort therefore increases from the basic position I into the resting position II by 10° from W6=90° to W6=100°. By the supporting arm 6 being bent, the upper support 6a thereof is pulled, in particular in the region A, in the arrow direction x. This leads, because of the guide element 9, to the front seat part 4a being raised or inclined. Said seat part can only move out of the basic position I, shown in FIG. 1a, on an arcuate path K9 which is predefined by the guide element 9 and is designed as a circular path K. In other words, the seat element 2 tips or sways or rocks about a rocking point WP in a manner similar to the beam of a beam-balance, with the two supporting arms 6 of the seat element 2 being deformed in the process as a function of their particular position. In the resting position II, not only has an orientation of the guide element 9, which is designed as a lever 10, but also an orientation of the mechanical connecting link 12, which is designed as a lever 13, then changed. When the supporting arm 6 is bent up, the upper support 6a thereof is forced to describe a relatively large radius. However, this is only possible if the upper support 6a with the pivotal point D121 for the lever 13 moves approximately in a direction m. The movement of the pivotal point D121 is predefined by the coupling of the upper support 6a to the lower support 6b by the mechanical connecting link 12 in order to prevent buckling or to obtain a defined movement. By means of the described active movement or deformation of the seat element 2 or of the front seat part 4a, an individual sitting on the seat 1 is slightly raised in the region of his thighs as he leans back. This facilitates reaching the basic position I from the resting position II without energy having to be stored to a considerable extent in a spring element. The points of application of the weight of an individual sitting on the seat are therefore changed between the basic position I and the resting position II in order to obtain, as a function of the position of the seat element 2, a position which is oriented to an equilibrium. This makes it largely superfluous, during the leaning-back action, to store potential energy of the upper body in a force store, such as, for example, a spring, since the potential energy of the upper body of an individual is supplied by the kinematics of the seat element to the lower body of the individual as potential energy. For this reason, with the seat according to the invention similar sitting comfort is basically possible even for individuals of very different body weight without a spring having to be adjusted to the weight of the particular individual.
FIGS. 3 and 4 show a second variant embodiment of a seat 1 according to the invention in a basic position I and in a basic position II. Like the first variant embodiment, the second variant embodiment of the seat 1 has two supporting arms 6, the second supporting arm being concealed in the side view. In contrast to the first variant embodiment, in the second variant embodiment a right supporting arm 6 and a left supporting arm are of rigid design at free ends E1, E2 of their supports 6a, 6b. The free end E2 of the lower support 6b therefore behaves, in principle, as an underframe 3, and an elastic region of the lower support 6b is of shortened design in comparison to the first variant embodiment (see FIGS. 1a to 2).
In FIG. 5, the illustrations of FIGS. 3 and 4 are shown superimposed. This illustration reveals how a guide element 9, which is designed as a lever 10, rotates by an angle β=25° in an arrow direction w between the basic position I and the resting position II. By this means, a front seat part 4a is raised at its pivotal point D91 by a height H1 in an arrow direction y and is pushed rearwards by a distance L1 in an arrow direction x. A connecting link 12, which is designed as a lever 13, also rotates in the direction of rotation w, changes its angle by γ=10° and drops slightly.
FIG. 6 illustrates, as an analogy with FIG. 1a, a third variant embodiment of a seat 1 according to the invention with a seat element 2 in a basic position I. The description for FIGS. 1a to 2 basically applies to this seat 1. In addition, the seat 1 of FIG. 6 has an energy store or force store 15 which comprises a leaf spring 17 as the spring element 16. The leaf spring 17 is fastened in a lower support 6b of a first supporting arm 6 and stands in the way of a stop 18 belonging to the energy store 15. The stop 18 is fastened to an upper support 6a of the supporting arm 6. As soon as the seat element 2 moves from the illustrated basic position I into a resting position (not illustrated here) according to FIG. 2, the stop 18 presses against the leaf spring 17. By this means, the energy store 15 damps the movement of the support 6a and assists a return movement into the basic position I. By displacement of a contact body 19 of the stop 18 in an arrow direction y′ by, for example, a displacement distance V1, a resetting force produced by the energy store 15 can be adjusted. The embodiment of a corresponding energy store is provided on a left supporting arm of the seat 1, which supporting arm is not visible in the illustration of FIG. 6.
FIG. 7 illustrates a fourth variant embodiment of a seat 1 in a simplified perspective view. The seat 1 includes a seat element 2 and an underframe 3. The seat element 2 has a seat part 4 which is divided into a front seat part 4a and a rear seat part 4b. Furthermore, the seat element 2 has a backrest part 5 which is divided into a lower backrest part 5a and an upper backrest part 5b. The seat element 2 comprises two supporting arms 6, 7 which are each formed by an upper support 6a or 7a and a lower support 6b, 7b. A fabric 8, or other body support structure, is stretched between the two supporting arms 6, 7 or the upper supports 6a, 7a thereof. The seat element 2 is fastened on a transverse support 14 of the underframe 3 by the lower supports 6b, 7b. The supporting elements 6, 7 or the lower supports 6b, 7b thereof are furthermore connected to each other via two transverse struts 20, 21 in order to couple the supporting elements 6 and 7 to each other so that the latter can mutually support each other if the seat 1 is loaded on one side. In addition to the transverse support 14, the underframe 3 also comprises a footplate 22 which is connected to the transverse support 14 via a strut 23. The seat 1 is in a basic position I.
FIG. 8 illustrates a fifth variant embodiment of a seat 1 in a simplified side view. A seat element 2 is screwed here by lower supports 6b of two supporting arms 6 (only one supporting arm is visible in the side view) to a transverse support 14 of an underframe 3 at two fastening points 24, 25. The lower support 6b and an upper support 6a of the supporting arm 6 are connected in a region A of a front seat part 4a via a guide element 9. The guide element 9 is integrally formed as a single piece with the upper support 6a and the lower support 6b of the supporting arm 6. In a region B of a rear seat part 4b and a region C of a lower backrest part 5a, the upper support 6a and the lower support 6b are connected to each other by seven connecting links 12 which are likewise integrally formed as a single piece with said supports. The upper support 6a is formed in the regions B and C by a central section Q, and the lower support 6b is formed in the regions B and C by a central section R. Instead of a fabric, in this embodiment the upper supports 6a of the two supporting arms 6 bear a multiplicity of transverse slats 26 which connect the two supports 6a. It should be understood that a fabric, or other body support member, is also suitably employed. Only two transverse slats are illustrated by way of example. The guide element 9 and the connecting links 12 are designed as spokes 27 and the latter, like the upper and the lower support 6a, 6b, are made from plastic. The seat 1 is in a basic position I.
FIGS. 9, 10 and 11 exclusively illustrate the supporting arm 6 and part of the transverse support 14 of the seat 1 shown in FIG. 8. FIG. 9 shows the supporting arm 6 in the basic position I, FIG. 11 shows the supporting arm 6 in a resting position II, and FIG. 10 shows the supporting arm 6 in an intermediate position III located between the basic position I and the resting position II. In the three positions I-III illustrated, the following values then arise for an opening angle W6 between seat part 4 and backrest part 5, for an angle W4 between the seat part 4 and a horizontal H, for an angle W5 between the backrest part 5 and a vertical V, and for an angle W9 taken up by the guide element 9 with respect to a further horizontal H:
















W6
W4
W5
W9




















I - BASIC POSITION
105
2
18
32


III - INTERMEDIATE POSITION
118
6
33
40


II - RESTING POSITION
130
8
48
46









The guide element 9 rotates about a pivotal point or elastic region D92 from the basic position I in the clockwise direction in a direction of rotation w into the resting position II (compare FIGS. 9 and 11). In this connection, the guide element 9, which is designed as a spoke 27, is situated in all possible positions between 9 o'clock and 12 o'clock between the basic position I and the resting position II. The angle W9 taken up in this case by the guide element 9 changes from 32° to 46° and therefore increases by β=14° (also see FIG. 12). During the rotation, the guide element 9 raises the upper support 6a or the region A of the front seat part 4a at a pivotal point or elastic region D91. In the elastic region D91, the guide element 9 merges into the upper support 6a. Upon rotation of the elastic region 91 on an arcuate path K9, the region A is raised upwards by a distance H1 in an arrow direction y and is displaced to the right by a distance L1 in an arrow direction x (see FIG. 12). This movement can be described by a type of rocking movement of the supporting arm 6 at a rocking point or rocking region WP. The rocking region here is arranged approximately wherever the lower support 6b of the supporting arm 6 leaves the transverse support 14 as a cantilever or wherever elastic deformation of the lower support 6b is possible. The supporting arm 6 is bent up in particular as a result of loading of a region D of an upper backrest part 5b. The upper support 6a here, as it is bent up from the lower support 6b, is pulled rearwards and downwards in the arrow direction x and an arrow direction y′. During this bending-up movement, the upper support 6a is guided by the guide element 9 and by the connecting links 12 on the lower support 6b on a multiplicity of paths K9 and K12. As an individual leans back, this pulling-back action of the upper support 6a causes the upper support 6a to be raised on the left from a point P6 and causes the upper support 6a to be lowered on the right from the point P6. Therefore, during the movement into the position II, the seat part 4 is raised and, at the same time, the backrest part 5 is lowered. During the transition from the basic position I into the resting position II, the connecting links 12 all rotate to the right in the arrow direction w about pivotal points or elastic regions D112 on the lower support 6b. In the process, the elastic regions D112 also change their position by the lower support 6b being bent up.
FIG. 13 illustrates a sixth variant embodiment of a seat 1 according to the invention in a simplified perspective view. A seat element 2 is essentially formed solely by a supporting arm 6 with supports 6a and 6b. For this purpose, the supporting arm 6 has a width B6 required for the seat element 2. The lower support 6b is fastened on an underframe 3 of the seat 1. The seat 1 or the seat element 2 is in a basic position I.
FIG. 14 illustrates a seventh variant embodiment of a seat 1 according to the invention in a simplified perspective view. A seat element 2 is essentially formed by a supporting arm 6 (only partially illustrated) with supports 6a and 6b and transverse slats 26. The transverse slats 26 are arranged on the upper support 6a of the supporting arm 6 and are movable in relation to one another in order not to inhibit or obstruct the deformation of the upper support 6a, which deformation arises as a basic position I illustrated is left. The lower support 6b is fastened on an underframe 3 of the seat 1.
FIG. 15 illustrates a perspective view of a seat element 2 of an eighth variant embodiment of a seat 1. The seat element 2 has a supporting arm 6 which bears a covering 28 which forms a seat surface 29 and a backrest 30. The supporting arm 6 comprises a left, upper support 6a, a right, upper support 6a′ and a lower support 6b located between them. The lower support 6b is connected to the left, upper support 6a by mechanical connecting links 12 and to the right, upper support 6a′ by further mechanical connecting links 12. The upper supports 6a and 6a′ are connected to each other by two transverse supports 31 and 32. An upwardly directed, approximately vertically situated limb 33 of the lower support 6b is divided into two struts 33a, 33b and merges with the latter into upwardly directed limbs 34, 35 of the upper supports 6a, 6a′. By this means, the upper supports 6a and 6a′ and the lower support 6b form the single-part supporting arm 6. An approximately horizontally running limb 36 of the lower support 6b is connected at a free end 37 via a guide element 9 to an approximately horizontally running limb 38 of the left, upper support 6a and to an approximately horizontally running limb 39 of the right, upper support 6a′. 
FIG. 16 shows a side view of the seat 1, the seat element 2 of which is already known from FIG. 15. The side view also illustrates an underframe 3 of the seat 1. The underframe 3 is connected to the limb 36 of the lower support 6b. Only the left, upper support 6a of the upper supports can be seen in the side view, the right, upper support is completely concealed. The supporting arm 6 which is of single-part design is connected between its upper support 6a and its lower support 6b via the guide element 9 and six connecting links 12. The guide element 9 and the connecting links 12 are designed as struts 40 which are mounted rotatably in the upper support 6a and the lower support 6b. A variant embodiment for the arrangement of the guide element 9, which arrangement replaces the guide element 9 (illustrated by solid lines), is illustrated by dashed lines. The guide element 9 shown by dashed lines connects the underframe 3 and the upper support 6a. A seat part 4 of the seat 1 is situated with a rear seat part 4b in a region B, and a backrest part 5 is situated with a lower backrest part 5a in a region C. In the regions B and C, the upper supports 6a, 6a′ are formed by central sections Q and Q′. The lower support 6b is formed in these two regions B and C by a central section R. All six connecting links 12 visible in FIG. 16 are arranged between the central section Q of the upper support 6a and the central section R of the lower support 6b. A further six connecting links are arranged between the upper support 6a′ and the lower support 6b (see FIG. 17).
FIG. 17 illustrates, in a further perspective view, the seat element 2 shown in FIG. 15. It can be seen from this view that the seat element 2 or the supporting arm 6 is formed mirror-symmetrically with respect to a plane 41 situated vertically in space.
FIGS. 18 to 20 illustrate three further variant embodiments of seats 1 according to the invention. The three seats 1 are designed according to the seat shown in FIG. 1b and each have two supporting arms 6 which bear a fabric 8 as the covering 28. In the side views, the second supporting arm is entirely concealed by the first supporting arm 6. For simplification, only the supporting arm 6 is described in each case. The other supporting arm is constructed comparably in each case and is comparably fastened to an underframe 3.
In the case of the ninth variant embodiment shown in FIG. 18, a lower support 6b of the supporting arm 6 is fastened to the underframe 3 of the seat 1 by two bolts 42, 43. A connecting link 12 for connecting the supports 6a and 6b is formed by two slotted-guide mechanisms 44, 45. The slotted-guide mechanisms 44, 45 respectively comprise a pin 44a and 45a and a slot 44b and 45b. The slots 44b and 45b are formed on the underframe 3, and the pins 44a and 45a are connected to the supports 6a and 6b. A free end E1 of the upper support 6a is guided on the lower support 6b by means of a guide element 9.
In the case of the tenth variant embodiment shown in FIG. 19, a connecting link 12 between an upper support 6a and a lower support 6b of the supporting arm 6 is formed by an elastic element 46. The elastic element is arranged in an intermediate space 11 between the supports 6a and 6b. In order also to be able to transmit shearing forces, the elastic element 46 is adhesively bonded to an upper side 47 of the lower support 6b and to a lower side 48 of the upper support 6a. The elastic element 46 is designed, for example, as a rubber block 49. The supporting arm 6 is fastened by its lower support 6b on the underframe 3. A free end E1 of the upper support 6a is guided on the lower support 6b via a guide element 9.
In the case of the eleventh variant embodiment shown in FIG. 20, a connecting link 12 between an upper support 6a and a lower support 6b of the supporting arm 6 is designed as a lever 13, as already known from preceding exemplary embodiments. In contrast to the preceding exemplary embodiments, a guide element 9 is formed by a slotted-guide mechanism 50. The latter comprises a pin 50a and a slot 50b. The pin 50a is fastened to a free end E1 of the upper support 6a and slides in the slot 50b, which is formed on the lower part 3. During a movement of the seat element 1 from the basic position I illustrated in FIG. 20 into a resting position, the pin 50a and the upper support 6a connected thereto move upwards on a curve K50 in the direction of a backrest part 5. The lower support 6b is screwed at a free end E2 to the underframe by means of two screws 51, 52.
The invention is not restricted to exemplary embodiments illustrated or described. On the contrary, it includes developments of the invention within the scope of the claims.
LIST OF DESIGNATIONS


    1 SEAT
    2 SEAT ELEMENT
    3 UNDERFRAME
    4 SEAT PART
    4A FRONT SEAT PART
    4B REAR SEAT PART
    5 BACKREST PART
    5A LOWER BACKREST PART
    5B UPPER BACKREST PART
    6 SUPPORTING ARM
    6A UPPER SUPPORT OF 6
    6A′ SECOND, UPPER SUPPORT OF 6
    6B LOWER SUPPORT OF 6
    7 SUPPORTING ARM
    7A UPPER SUPPORT OF 7
    7B LOWER SUPPORT OF 7
    8 FABRIC
    9 GUIDE ELEMENT
    10 LEVER
    11 INTERMEDIATE SPACE BETWEEN 6A, 6B AND 7A, 7B
    12 CONNECTING LINK
    13 LEVER
    14 TRANSVERSE SUPPORT BETWEEN 6B AND 7B
    15 ENERGY STORE
    16 SPRING ELEMENT
    17 LEAF SPRING
    18 STOP ON 6A
    19 CONTACT BODY
    20 TRANSVERSE STRUT BETWEEN 6 AND 7 AND 6B AND 7B
    21 TRANSVERSE STRUT BETWEEN 6 AND 7 AND 6B AND 7B
    22 FOOTPLATE OF 3
    23 STRUT BETWEEN 22 AND 14
    24 FASTENING POINT OF 6B/7B ON 14
    25 FASTENING POINT OF 6B/7B ON 14
    26 TRANSVERSE SLAT
    27 SPOKE
    28 COVERING
    29 SEAT SURFACE
    30 BACKREST
    31 TRANSVERSE SUPPORT BETWEEN 6A AND 6A′
    32 TRANSVERSE SUPPORT BETWEEN 6A AND 6A′
    33 APPROXIMATELY VERTICALLY SITUATED LIMB OF 6B
    33A STRUT ON 33
    33B STRUT ON 33
    34 UPWARDLY DIRECTED LIMB OF 6A
    35 UPWARDLY DIRECTED LIMB OF 6A′
    36 APPROXIMATELY HORIZONTALLY SITUATED LIMB OF 6B
    37 FREE END OF 36
    38 APPROXIMATELY HORIZONTALLY SITUATED LIMB OF 6A
    39 APPROXIMATELY HORIZONTALLY SITUATED LIMB OF 6A′
    40 STRUT
    41 VERTICAL PLANE
    42 BOLT
    43 BOLT
    44 SLOTTED-GUIDE MECHANISM
    44A PIN
    44B SLOT
    45 SLOTTED-GUIDE MECHANISM AS CONNECTING LINK
    45A PIN
    45B SLOT
    46 ELASTIC ELEMENT BETWEEN 6A AND 6B
    47 UPPER SIDE OF 6B
    48 LOWER SIDE OF 6A
    49 RUBBER BLOCK
    50 SLOTTED-GUIDE MECHANISM AS GUIDE ELEMENT
    50A PIN
    50B SLOT
    51 SCREW FOR FASTENING 6B TO 3
    52 SCREW FOR FASTENING 6B TO 3
    I BASIC POSITION OF 1 AND 2
    II RESTING POSITION OF 1 AND 2
    III INTERMEDIATE POSITION BETWEEN I AND II
    A REGION OF 4A
    B6 WIDTH OF 6
    B REGION OF 4B
    C REGION OF 5A
    D REGION OF 5B
    D91 PIVOTAL POINT OF 9 ON 6A
    D92 PIVOTAL POINT OF 9 ON 6B
    D121 PIVOTAL POINT OF 12 ON 6A
    D122 PIVOTAL POINT OF 12 ON 6B
    E1 END OF 6A
    E2 END OF 6B
    H1 DISPLACEMENT OF D91 IN Y DIRECTION
    H HORIZONTAL
    K9 ARCUATE PATH OF D91
    K12 ARCUATE PATH OF D121
    K50 CURVE OF 50A
    K CIRCULAR PATH OF D91 ABOUT D92
    L1 DISPLACEMENT OF D91 IN X DIRECTION
    M PULLING DIRECTION OF 6A
    P POINT ON 6
    Q CENTRAL SECTION OF 6A
    Q′ CENTRAL SECTION OF 6A′
    R CENTRAL SECTION OF 6B
    W4 ANGLE BETWEEN 4 AND H
    W5 ANGLE BETWEEN 5 AND V
    W6 OPENING ANGLE BETWEEN 4 AND 5
    W9 ANGLE BETWEEN 9 AND H
    WP ROCKING POINT
    V1 DISPLACEMENT DISTANCE OF 19 IN Y′ DIRECTION
    V VERTICAL
    α INNER OPENING ANGLE
    β DIFFERENCE BETWEEN THE ANGLES W9
    γ DIFFERENCE BETWEEN DIFFERENT ANGLES OF 12

## Claims

1. A seating structure comprising:
a base;
a pair of laterally spaced support arms each comprising a seat portion, a backrest portion and a transition portion joining said seat portion and backrest portion, wherein said laterally spaced support arms are coupled to said base;
a body support member extending between and connected to said laterally spaced support arms and comprising at least a seat portion, a backrest portion, and a transition portion integrally formed with said seat portion and said backrest portion;
a support element coupled to said base and comprising a central support arm extending upwardly along a centerline of said backrest portion of said body support member, wherein said central support arm is spaced rearwardly from said backrest portions of said laterally spaced support arms, said support element further comprising a pair of laterally extending struts connecting said central support arm and said laterally spaced support arms.

2. The seating structure of claim 1 further comprising a cross member connecting upper ends of each of said backrest portions of said laterally spaced support arms.

3. The seating structure of claim 1 wherein said body support member comprises a flexible membrane.

4. The seating structure of claim 3 wherein said flexible membrane comprises a fabric.

5. The seating structure of claim 1 wherein each of said laterally spaced support arms is generally L-shaped.

6. The seating structure of claim 1 wherein said struts are connected to said laterally spaced support arms at a location spaced below upper ends of said laterally spaced support arms.

7. The seating structure of claim 1 wherein said support element comprises a forwardly extending limb spaced below the seat portions of said laterally spaced support arms.

8. The seating structure of claim 7 wherein said limb is connected to said base.

9. The seating structure of claim 7 wherein said limb is connected to said seat portions of said laterally spaced support arms with at least a pair of links.

10. The seating structure of claim 1 wherein said seat portion of each of said laterally spaced support arms is pivotally coupled to said base with a link.

11. A seating structure comprising:
a base;
a support member comprising a seat portion, a backrest portion and a transition portion joining said seat portion and backrest portion, wherein said support member is coupled to said base, said backrest portion moveable relative to said seat portion as said support member is moved between upright and reclined positions, wherein said support member is elastically deformed as said support member is moved between said upright and reclined positions, wherein said support member comprises a pair of laterally spaced support arms each having said backrest and transition portions; and
a support element coupled to said base and having an upper portion connected to said backrest portion of said support member at a location above a lumbar region of said backrest portion, wherein said support element comprises a central support arm extending upwardly between said laterally spaced support arms, said support element further comprising a pair of laterally extending struts connecting said central support arm and said laterally spaced support arms.

12. The seating structure of claim 11 wherein said central support arm is spaced rearwardly from said backrest portions of said laterally spaced support arms.

13. The seating structure of claim 11 further comprising a body support member extending between and connected to said laterally spaced support arms and comprising at least a seat portion and a backrest portion.

14. The seating structure of claim 11 further comprising a cross member connecting upper ends of each of said backrest portions of said laterally spaced support arms.

15. The seating structure of claim 11 wherein said support element comprises a forwardly extending limb spaced below the seat portions of said laterally spaced support arms.

16. The seating structure of claim 15 wherein said limb is connected to said base.

17. The seating structure of claim 15 wherein said limb is connected to said seat portions of said laterally spaced support arms with at least a pair of links.

18. The seating structure of claim 11 wherein said seat portion of each of said laterally spaced support arms is pivotally coupled to said base with a link.