PIECE OF SEATING FURNITURE WITH A LONGITUDINAL AXIS ABOVE THE SEATING SURFACE

Seating furniture having a longitudinal axis above a seating surface. The seating furniture defines a plane of symmetry and includes a lower part, which has a base or is formed therewith in its upper region, and a seating surface which is movably connected to the base by means of a kinematics about a longitudinal axis which lies at least largely above the seating surface, is inclined forwards and downwards by up to 75° (preferably 45°±20°) relative to the horizontal, lies in the plane of symmetry in the rest position and is optionally formed virtually. A restoring device with an energy accumulator is provided between the base and the seating surface, which restoring device exerts a restoring torque on the seating surface when the seating surface is deflected about the longitudinal axis from the rest position.

TECHNICAL FIELD

The present disclosure relates to seating furniture, including office chairs, having a seating surface and a vertical plane of symmetry, where the seating surface can be swiveled about a longitudinal axis with respect to a base of the seating furniture.

BACKGROUND

A piece of seating furniture is disclosed by EP 1 090 568 that proposes to support a seating surface by means of spherical or ball-shaped rolling elements on an at least approximately spherical base. The instantaneous swivel point, the instantaneous center, which is therefore not fixed in relation to the base, is approximately at chest height of a user, but can also sink. Due to this position, the center of gravity of the combination of user and (movable part of the) furniture is always below the instantaneous center, so that the seating surface and user are always pushed into the upright, stable, “resting position.”

EP 2 381 816 discloses various swiveling piece of seating furniture, some of which have their pivot point in the floor region, some just below the seating surface. Above the seating surface, the position in the thoracic-lumbar spine region is mentioned in order to avoid rotation around this axis when sitting in order to avoid degenerative phenomena when sitting for long periods of time, only one example with an exactly horizontal, physically formed, longitudinal axis is provided.

Seating furniture is known from DE 40 06 608 and EP 780 073 in which longitudinal axes for the seating surface are provided directly below the seating surface.

From WO2016/042127 of the applicant, a piece of seating furniture is known in which a longitudinal axis is virtually formed in the form of a spherical bearing above the seating surface. The kinematics are as follows: at the base, a series of three arms that can be swiveled relative to one another and are arranged in series is formed, the last of which is firmly connected, directly or indirectly, to the seating surface, and the three swivel axes of which intersect each other at one point, the central point, often only in a central region. This central point is located above the seating surface, preferably in the pelvic region of the presumed user, particularly preferably approximately at the height of the user's center of gravity in the plane of symmetry of the seating furniture. Since a spherical motion around this central point is possible, a motion around the (virtual) longitudinal axis is possible without being predetermined or preferred. The three-arm kinematics used, often and actually more accurately referred to as three-axis kinematics, is already known from WO 2012/123102 by the same inventor.

A completely differently structured seating furniture with a “real” longitudinal axis is known from EP 3 890 558 B1. A cantilever that extends diagonally upwards is rotatably mounted on a vertical support. A swivel arm is movably mounted on the cantilever, which can also be swiveled around an axis of rotation lying in a vertical plane, according to its longitudinal axis. The seating surface is then accordingly attached to this swivel arm. The rotation axis or longitudinal axis forms an angle of approximately 65° with a horizontal plane and lies practically entirely below the seating surface. A chair built according to this principle and commercially available from the patent proprietor has a rotation axis/longitudinal axis with an angle of approximately 75° relative to the horizontal plane. This axis lies mostly above the seating surface, the swivel point formed by the vertical axis of rotation lies far above the center of gravity of a user, who is thus always forced into a stable, upright, resting position.

In both cases, a turning motion is only possible in the manner mentioned, the usual “simply leaning back” is not possible.

Due to their spherical bearing, the seating furniture with a virtual longitudinal axis can also perform swiveling motions about a transverse axis and rotational motions about the vertical axis (and due to the nature of the spherical bearing, about any other assumed axis as well), but this is not relevant in the context of the present disclosure. It is also irrelevant for the purposes of the present disclosure whether a backrest and/or armrests are provided and how these are mounted/attached with respect to the seating surface.

What is needed is a piece of seating furniture that helps avoid the health disadvantages of long periods of sitting. Such a chair should be designed to encourage continuous motion and thus stimulate the metabolism and support the cardiovascular system of the user without making the user feel unsafe or unstable.

SUMMARY

The present disclosure is directed to seating furniture that facilitates movement by the user, promoting the health of the spine, and supporting the back muscles. The seating furniture disclosed herein encourage a natural pelvic and lumbar motion, while keeping the head and shoulders in a stable position.

In one example, the seating furniture of the present disclosure defines a plane of symmetry, and includes a lower part, where the lower part includes a base or is formed with a base in an upper region of the lower part; a seating surface that is swivelably connected to the base via a kinematics, such that the seating surface is swivelable about a longitudinal axis by means of the kinematics; where when the piece of seating furniture is in a resting position the longitudinal axis lies in the plane of symmetry in an angular range of between 5° in a backward and downward direction and 75° in a forward and downward direction, relative to a horizontal plane; where the longitudinal axis, when considered in a region of a vertical projection P of the seating surface, or optionally when considered in a region of a vertical projection P of the seating surface combined with a rear seating surface part, lies above the seating surface along more than 50% of the length of the vertical projection P; and further including a restoring device with an energy accumulator disposed between the base and the seating surface, the restoring device configured to exert a restoring torque on the seating surface when the seating surface is deflected about the longitudinal axis from the rest position.

The features, functions, and advantages of the disclosed seating furniture may be achieved independently in various embodiments of the present disclosure, or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure relates to a piece of seating furniture 1 with a plane of symmetry 62 and with: a lower part 2 which has or is formed with a base 3 in its upper region, and a seating surface 4 which is swivelably connected to the base 3 about a longitudinal axis 63 by means of a kinematics 22, where the longitudinal axis 63 lies in the plane of symmetry 62 in the resting position of the piece of seating furniture and is inclined relative to the horizontal from 5° backwards, downwards to 75° forwards, downwards, preferably by 45°±30°, most preferably between 40° and 50° forwards, downwards. Additionally, the longitudinal axis 63 is optionally formed virtually, and the longitudinal axis 63 in the region of the vertical projection P of the seating surface 4, optionally in combination with a rear seating surface part 64, lies above the seating surface 4, optionally in combination with the rear seating surface part 64, along more than 75% of the length thus defined.

The seating furniture of the present disclosure include a seating surface and a vertical plane of symmetry, wherein the seating surface can be swiveled by means of kinematics with respect to a base of the piece of seating furniture about a longitudinal axis which, in the rest position, is in an angular range which lies between 5° backwards, downwards and 75° forwards, downwards, preferably by 45°±30° forwards, downwards, very particularly preferably by 45°±20° forwards, downwards in the plane of symmetry and at least predominantly above the seating surface. The longitudinal axis can also be formed virtually, for example by a spherical bearing of the seating surface around a swivel point above the seating surface, which allows rotation around “all” axes. For the sake of simplicity, in the following usually only the “longitudinal axis” is mentioned. In most cases this is inclined forwards at an angle of 45°±30° (or ±20°) to the horizontal, but a greater inclination of up to 75° (technically precise, not mathematically) is also possible. The kinematics that bring about this are explained in detail in the inventor/applicant's publications discussed below and therefore require no further explanation here.

In one example, the seating furniture of the present disclosure is characterized in that a restoring device 23 with an energy accumulator 6 is provided between the base 3 and the seating surface 4, which exerts a restoring torque about the longitudinal axis 63 on the seating surface when the seating surface 4 is deflected about the longitudinal axis 63 from the rest position.

In another example, if the longitudinal axis of the disclosed seating furniture is inclined by up to 30° relative to the horizontal, the longitudinal axis 63 lies entirely above the seating surface 4 in the region of the vertical projection (P).

In another example, if a backrest 11 is provided for the seating furniture of the present disclosure, the longitudinal axis 63, regardless of its inclination, lies at least in the region extending up to 120 mm in front of the backrest 11 above the seating surface 4.

In another example, an inclination of the longitudinal axis 63 of the disclosed seating furniture that is backwards, or downwards, is possible, but is reasonable only in special cases (medical applications, etc.) and within narrower limits (up to 5°) than when the inclination is forwards, downwards.

With regard to the term “plane of symmetry”, it should be noted that this only applies with a grain of salt, because the individual components and handles of seating furniture, for example office chairs, are certainly one-sided, but there is nevertheless a plane of symmetry for the seating surface and, if present, the backrest and armrests, which runs vertically when the seating furniture is at rest and is swiveled along with the seating surface. It is this plane that will be referred to as the plane of symmetry.

With regard to the term ‘seating surface’, it should be noted that this can be divided, with the two parts being able to swivel relative to each other about a horizontal axis normal to the plane of symmetry and with the rear part being firmly or elastically connected to a backrest. In this case, the kinematics can be connected either to the backrest and thus to the rear part of the seating surface, or to the front part of the seating surface. The seating surface, divided or undivided, can also be upholstered; the position of the longitudinal axis “above” the seating surface is not affected by this; in extreme cases it lies above the cover of the seating surface. If, in the case of an extreme inclination, the front part of the longitudinal axis comes to lie below the seating surface, then, in the rest position, the greater portion of the part of the longitudinal axis which lies within the irregular cylinder formed by the outline of the seating surface in the direction of the vertical lies above the seating surface.

In relation to the use of such seating furniture, hereinafter usually referred to as “chair” or “office chair”, the following must be mentioned:

Almost every day we are confronted with headlines warning about the health risks of sitting. Articles such as “Sitting makes you sick” from Norddeutscher Rundfunk (2022), “Sitting is the new smoking” by Juliet Starrett (2016), “Lack of exercise makes millions sick” from Tagesschau (2022) or “Those who sit longer die sooner!” “Get out of the seating surface trap” by MDR (2022) can be found in both digital media and the traditional press. The World Health Organization (WHO) also emphasizes the importance of regular exercise and recommends standing, walking or exercising more often (2020).

For decades, doctors and experts have warned about the consequences of a lack of exercise and prolonged sitting, including back pain (Lis, Black, Korn, & Nordin, 2007), shortness of breath and digestive disorders (BAuA, 2011), as well as an increased risk of type 2 diabetes and heart attacks (Latza, Bucksch & Wallmann-Sperlich, 2020). These can lead to impaired well-being (Atkin et al., 2012), promote mental illness (Kilpatrick et al., 2013) and promote depression (van Uffelen et al., 2013).

Despite repeated warnings, the number of illnesses caused by excessive sitting continues to rise, according to health insurance reports (e.g. DKV Report, 2021). In Germany, people sit for an average of around 8.5 hours on working days, which is one hour more than in 2018, while young adults (18 to 29 years) reach the peak at 10.5 hours. This contributes to an increase in musculoskeletal disorders, which, together with mental illnesses, contribute significantly to work absences (Techniker Krankenkasse, 2022).

The design of our workplaces contributes to this problem. Around 59% of employees in Germany spend at least half of their working time at an office workplace, mostly sitting (Industrieverband Büro und Arbeitswelt, 2020). Work is also often done sitting down at workbenches and in production. The short break to go to the coffee machine offers little compensation for the physical strain, and there is often a lack of active balance in leisure time too.

Previous approaches to the problem have proven to be ineffective and have not been able to significantly reduce the symptoms mentioned. We therefore take the approach that necessary motions must take place during working hours and therefore while sitting. The office chair must allow for ample motions in order to relieve and load the intervertebral discs, which promotes the supply of nutrients and the maintenance of the health of the spine. In addition, the back should be supported by a suitable backrest in order to avoid permanent static strain on the back muscles.

Many chairs available on the market allow a tilting motion of the pelvis, but do not meet the requirements for a healthy sitting posture. Critical points include the fact that the swivel point is below the seating surface and motions do not follow the human anatomy. This can make it difficult to concentrate on work, as the head and upper body move, requiring the eyes to constantly refocus. In addition, working on texts or tables can be impaired by motions.

An ideal ergonomic chair should mimic the natural pelvic and lumbar motion that occurs when walking, while keeping the head and shoulders in a stable position. In healthy adults, this rolling swiveling motion when walking occurs around an axis directed forwards and downwards at approximately 45°, which passes through the region of the ninth to twelfth, preferably the eleventh thoracic vertebrae. The angular range depends on various circumstances, such as age, general and current physical condition, speed of motion and many more, so that ranges of 45°±30°, at least ±20° and especially ±10° or 5° are favorable.

These ranges are advantageously to be used in seating depending on the habits and constitution of the user. A positioning of the user's center of gravity above the central point is here very advantageous, and a position of the larger part of the longitudinal axis in the seating surface cylinder above the seating surface is necessary.

When sitting, the feet should be firmly on the floor to ensure a stable posture. Traditional chair concepts that use swivel points below the seating surface do not adequately imitate human motion dynamics.

Scientific studies, including the work of R. Kuster (Physiological motion axis for the seat of a dynamic office chair—PMC (nih.gov)) and the as yet unpublished dissertation by Mark Buhrer, have found that the ideal swivel point is at the level of the upper abdomen, near the eleventh thoracic vertebra (thus in the region of the ninth to twelfth, preferably at the level of the eleventh thoracic vertebra). These findings emphasize the importance of seating furniture that promotes the natural motions of the human body when sitting and are illustrated in FIGS. 1A-1D, showing the motion of the pelvis in and across the sitting direction around an instantaneous center at the level of the upper abdomen.

FIGS. 1A-1D show in detail in the four individual representations the specific kinematics of the pelvic motion of a user 19 on the seating furniture 1, a chair with a divided seating surface 4, the rear part of which is a fixed or elastic part of the backrest 11, based on the representation of the user's bones. With regard to such a piece of furniture, it should be noted that a lower part of the furniture (chassis, gas spring, etc.) (not shown here) is connected to the backrest via a kinematics, and the actual (front) seating surface is connected to the rear seating surface part, which is firmly or elastically connected to the backrest, so that it can swivel about a transverse axis. A further kinematics is responsible for the relative position (angular position) between these two parts, as described in detail in the applicant's WO 2022/174945.

The arrow 20 (approximately horizontal and lying in the plane of symmetry 62 of the seating furniture 1, which of course does not take into account details such as the mechanics of the kinematics, etc.) points to the part of the spine in which the bending can be viewed in concentrated form. The arrow 20 thus also symbolically represents, with a grain of salt, the respective motion component around the axis indicated by it. FIG. 1A shows upright sitting with “force-less” contact with the backrest 11, the knee also representing this. FIG. 1B visualizes the forward leaning of the upper body and the changed leg position; in the illustrated construction of the piece of seating furniture 1, the position of the backrest 11 and the relative position of the two parts of the seating surface 4 change. The change in the curvature of the spine is recognizable.

The lower FIGS. 1C and 1D illustrate the lateral tilt of the pelvis to the left and right respectively. It is a precisely isolated motion of the pelvis, again localized by an arrow, arrow 21, but this time running approximately horizontally in a transverse direction and again pointing to the symbolic “bending point” of the spine. The inclination of the pelvis follows the defined axis of rotation of the chair and thus remains stationary with respect to the seating surface 4; the pelvis thus moves synchronously with the seating surface 4 and the backrest 11, while the shoulders and head of the seated person remain relatively stable in space.

This (double) motion dynamic of the pelvis on the chair, characterized by specific angles around the rotation axis(es) in the three spatial dimensions, imitates the natural walking motion of humans. This correlation is demonstrated in the study “Patterns of spinal motion during walking” by Jack Crosbie, Roongtiwa Vachalathitib and Richard Smith, published in December 1994. The study identifies consistent motion patterns: “We found consistent patterns within and between segments and motions, with an obvious follow-up motion of the trunk following pelvic displacements. This suggests that the spinal motions associated with walking are linked to the primary motions of the pelvis and lower limbs.” This observation by the authors was supported by the later measurement studies by R. Kuster.

FIGS. 2A-2D show, only as a counterexample and for explanation, in the upper illustrations FIGS. 2A and 2B, the situation when the user 19 “immovably” follows the motion of the seating surface 4 and the backrest 11 during the sideways swiveling. For this reason, instead of an arrow, only a line was drawn to the now non curved spine region.

FIG. 2C shows the user 19 leaning more strongly against the backrest than in FIG. 1A, which can also be seen from the relative position of the two parts of the seating surface 4 in comparison. Finally, FIG. 2D shows the fully reclined position for completeness.

Based on these findings, a special kinematics was developed that allows the construction of a chair the swivel point of which—following scientific recommendations—is located in the region of the upper abdomen, above the seating surface. This allows motion around all three swivel axes around this central point without the need for back or armrests, as described in WO2016/042127 mentioned above. In addition, a lifting of the front edge of the seating surface can be avoided in an embodiment of this kinematics, as can be seen from WO2022/174945 of the applicant. This also shows, in particular in FIGS. 16a-l, the different possible orientations of the longitudinal axis, which has the reference numeral 16 there.

After development, prototypes of these chairs were manufactured and further optimized over a period of two years. These prototypes were made available to people with musculoskeletal problems. The feedback from these test subjects was predominantly positive. A noticeable reduction in pain was noted in some patients after only a short period of use. After a few months, many test subjects reported a significant improvement or even a complete disappearance of their symptoms. The symptoms examined included lumbago, hip pain, sacroiliac joint problems and aftercare for disc surgery. Although the medical benefits still need to be proven by more extensive studies, feedback to date suggests that chairs of this design may offer significant potential for alleviating health problems such as those caused by a lack of exercise while sitting.

Unfortunately, many test subjects find it difficult to feel safe on a chair with such kinematics. It may take several weeks for this uncertain feeling to diminish or disappear. Some subjects rejected this motion completely. This is especially true if the physical limitation was not yet so pronounced and the suffering was not yet great enough to accept this habituation phase. On the other hand, these were patients who had only recently undergone surgery, especially on the intervertebral disc. They were understandably afraid that their situation could worsen and were consistently unwilling to accept this unusual motion.

Since the test subjects reported that they got used to this motion after some time, but also reported that some of them actually felt sick in the chair during the first few hours, it was initially assumed that this was only a problem with the balance organ, which has to combine the motion of the hips with a stable head. Since the motion of the hips corresponds to a walking motion and people are used to the head moving forward when walking, this was considered the most likely solution for a long time.

In fact, there was a second approach. This was based on the observation that this insecurity was significantly reduced or even disappeared completely as soon as the arms were resting on the desk in order to operate the keyboard of a PC, for example. So it was concluded that this all has something to do with the current motion of a person. If the person moves on the chair as if they were walking, i.e. if they swing or circle their hips around the swivel point of the chair, the insecurity disappears. However, if the same test subject sits freely on the chair in the room, i.e. moves his arms freely, uncertainty arises again. Therefore, the motion in the two situations was examined more closely.

As mentioned, when sitting at a desk and using a PC, the arms rest on the desk and the pelvis moves—so all moving mass points below the chair's swivel point are in stable equilibrium. The person feels safe. However, as soon as a person sits freely, he or she moves the entire upper body rather than the chair. Since not only the pelvis and part of the spine move with the seating surface, but also the body with the shoulders, head and arms remains rather rigid on the chair, the center of gravity of the moving mass moves upwards. The center of gravity then lies above the swivel point (the longitudinal axis, the central point) of the chair—an unstable equilibrium is created, which makes people feel insecure. This is illustrated in FIGS. 2A-2D, which show the motion of the entire upper body during free sitting analogous to FIGS. 1A-1D.

In response, the swivel point of the chair was first adjusted (moved upwards) so that the user's center of gravity always remains in a stable equilibrium (below the longitudinal axis or central point) even during rigid upper body motions (this leads to a situation similar to the office chair sold by Bergardi mentioned above). Although this adjustment reduced the uncertainty among the test subjects, it led to a new problem: wobbling in the shoulder and head region occurred, similar—although less pronounced—to that experienced with a swivel point located under the chair surface (longitudinal axis). The reason for this was that the swivel point of the chair did not coincide with the physiological swivel point of the pelvis, although it was shifted in the opposite direction, namely downwards. Therefore, this adaptation was not a satisfactory solution because, although it solved one problem, it created a new one.

To overcome this dilemma, the possibility of applying a counter-torque was considered. This would make it possible to keep the swivel point (the longitudinal axis) of the chair close to the physiological swivel point of the pelvis, while at the same time generating a torque counteracting the unstable equilibrium, which would bring the system—the chair or its seating surface—into a stable equilibrium. A critical point with this solution, however, was that the counter-torque also acts on pure pelvic motions, thus counteracting the motion of the test person. However, a key feature of the chair is its ability to respond to pelvic motions with great ease, so this effect has been viewed critically.

Tests showed that test subjects performed up to 60 pelvic motions per minute, which underscores the mobility of the chair. This effect should by no means be lost, because the continuous motion stimulates the metabolism and the cardiovascular system, which, in addition to positive effects on the musculoskeletal system, also improves the user's concentration and productivity and can be expected to have other health benefits. Despite this challenge, the decision was made to implement a simple spring mechanism in order to investigate the effects in more detail. Such a chair according to the present disclosure with a simple spring accumulator for building up a counter torque is shown in FIGS. 3A-3D.

FIGS. 3A-3D show (without taking the seating surface height into account) a piece of seating furniture 1 with a lower part 2, supporting or forming a base 3, and a kinematics provided between the base 3 and an (undivided) seating surface 4, designated overall by 22, and a backrest 11 which is elastically connected to the seating surface 4. The kinematics 22 provide a central point 5 around which the seating surface is spherically movable, wherein a longitudinal axis 63 is also formed in the sense explained above.

This kinematics 22 corresponds to the kinematics explained in detail in WO2016/042127 of the applicant and in WO 2012/123102 of the inventor and therefore does not require any further description here (a brief explanation is given in FIGS. 5A-5D).

Advantageously, a restoring device 23, the effect of which is adjustable, is provided between the base 3 and the seating surface 4, which is shown in FIG. 3C in the installed state, without the sleeve for the springs in order to show them, while FIG. 3D shows an exploded sketch to explain the structure. This restoring device 23 is constructed as follows: a flat intermediate blade 24 is articulated so as to be rotatable about a first axis 44 which is approximately horizontal in the exemplary embodiment and stationary with respect to the base 3, on which blade a flat actuator 25 with a main plane is arranged so as to be rotatable about a second axis 45 parallel to the first axis. A spring mechanism 26 is arranged on the actuator 25 so as to be rotatable about an actuator axis 46 which, in the illustrated exemplary embodiment, runs normal to the main plane of the actuator 25. Furthermore, a rotating arm 27 is articulated on the actuator 25 about a rotating arm axis 47 parallel to the actuator axis 46.

At the free end of the rotating arm 27, a connecting piece 28 is spherically articulated, which is firmly connected to the seating surface 4. Instead of this spherical connection, it is possible to arrange a universal joint, which then also blocks the “internal rotation” around the vertical axis, which is explained below, without the need for an additional mechanism. This block is necessary to avoid singularities in the kinematics. Also in the region of the free end of the rotary arm 27, a coupling rod of the spring mechanism 26 is articulated, which carries an adjusting plate 48 at its other end.

The adjustable spring mechanism 26 has, in a sort of tube which is rotatably mounted in its middle portion about the actuator axis 46, two coil springs arranged linearly one behind the other, which fix the adjusting plate 48 of the coupling rod between them. A screw mechanism inside the springs along their axis shortens or lengthens the entire spring length when the adjusting knob 49 is turned, thus changing the preload and thus the restoring force and thus the restoring torque.

By moving the seating surface 4 from its rest position, the free end of the rotary arm 27 and thus the point of application of the coupling rod, the coupling rod itself and thus the adjusting plate 48 are moved, whereby a restoring force and thus a restoring torque is indexed.

This approach proved to be more successful than initially expected. To analyze different conditions, a series of springs were tried to test different restoring torques. Already at the first attempt it turned out that the spring with the lowest tension was sufficient to achieve the desired effect. The chair offered the test subjects stability, both during motions of the entire upper body and during isolated pelvic motions, without the spring force being perceived as disturbing. An impact of the counter torque on the motion frequency could not be detected. The mechanism was then further developed so that the restoring torque could be variably adjusted, which contributes to the desired compactness of the device, which is particularly important for series production. An embodiment is shown in FIGS. 4A-4E, which also show a piece of seating furniture according to the present disclosure with an adjustable spring accumulator.

FIG. 4A shows the entire piece of seating furniture 1 in perspective view. The seating surface is divided into the actual (front) seating surface 4 and a rear seating surface part 64 which is firmly, but optionally resiliently, connected to the backrest 11. Armrests 29 are also shown here purely for illustration purposes; these can of course be provided in all of the exemplary embodiments shown, regardless of the design of the seating surface, the type of kinematics and the choice of the restoring mechanism.

FIG. 4B shows the mechanism provided between the movable and height-adjustable lower part 2, which is also responsible for rotating the backrest 11 and thus the seating surface 4 about a vertical axis 9, and this same seating surface 4: First, the already discussed kinematics 22 with its three arms, which on the one hand is firmly connected to a base 3 fixed to the lower part by means of a mounting part 30 with the backrest 11 and thus is connected (movably about a transverse axis) with the seating surface 4 and carries these parts. Furthermore, there is a similarly constructed seating surface mechanism 31 which connects the base 3 with the seating surface 4, forming its own central point and ensures the relative motion around the virtual longitudinal axis formed by the two central points, as can be seen in FIGS. 1 and 2. The inclination of the longitudinal axis relative to the horizontal can be determined by the independently defined central points. Finally, a restoring device 23 is provided on the base 3, which can swivel about a horizontal axis, the other point of application of which is firmly connected to the seating surface 4 via a mounting plate 32.

As is shown by the analogous structure of the kinematics 22 for the backrest including the rear seating surface part and the seating surface mechanism 31 for the seating surface 4, it is purely a question of point of view as to whether, as in the following, the kinematics 22 or the seating surface mechanism 31 is principally responsible for the motion of the seating surface 4 relative to the base 3.

The structure and mode of operation of the restoring device 23 can be seen in FIGS. 4C-4E. FIGS. 4C and 4D show the tubular energy accumulator 6 and parts of the restoring device 23 in a section through the axis of the tube: FIG. 4C in the neutral position and FIG. 4D in a clockwise rotated position. The structure is as follows: A handle 50 is rotatably arranged in the base-fixed tube 51. Inside the tube 51, a spring package 52 rests on one side against a tube shoulder 53 and is preloaded on the other side by a spring plunger 54 with an internal thread. This preload is achieved because a threaded rod 55 is provided which is rotationally fixed with respect to the tube but axially displaceable, onto one end of which the spring plunger 54 is suitably screwed. The spring plunger 54, shown is a square, is connected in a rotationally fixed, but axially movable manner, to the handle 50, so that when it is rotated the (pre-)load of the spring package 52 is changed.

At the other end of the threaded rod 55, a pin formed from two aligned plates 56 is attached with its first end rotatably about a swivel axis running normal to the axis of the threaded rod. At the other end, the pin is hinged to a rotary lever 57 about a swivel axis parallel to it.

The rotary lever 57 is attached to the base 3 with its lower end near the base so that it can rotate about a rotary lever axis 58. The upper end of the rotary lever 57, close to the seating surface, is cranked and carries a first intermediate link which can swivel about a first swivel axis, a longitudinal swivel axis 59. This is connected to a second intermediate link so as to be rotatable about an intermediate axis 61 (FIG. 4B). This has a second swivel axis, the connection axis 60, which runs parallel to the longitudinal axis of rotation 59 and is thus connected to the mounting plate 32 which is fixed to the seating surface. The rotation about the intermediate axis can be clearly seen in a comparison of FIGS. 4C and 4D in both cases, the connection plane of the mounting plate 32 is approximately horizontal, while the rotary lever 57 is oriented almost vertically in one case and significantly inclined in the other, which is made possible by the rotation about the intermediate axis 61.

If the user now moves the position of the seating surface from the normal position (FIG. 4C), in which the spring assembly 52 has the greatest length, for example into the position shown in FIG. 4D, this is transmitted as a whole to the spring assembly 52 via the restoring device 23 and causes a return torque, the size of which is determined by the presetting by means of the handle 50 and can be regulated. Due to this design, only the motion around the horizontal longitudinal axis of the seating furniture is influenced by a restoring torque.

The results of the first tests have confirmed the assumption that full adjustability is not absolutely necessary. In particular, it is important to avoid users adjusting the chair too rigidly, thereby impairing or even preventing the benefits of the system. For this reason, it was considered to limit the adjustment range so that the spring force can be adjusted in just one or two steps—possibly by switching an additional spring on or off—which is completely sufficient.

As an alternative solution, FIGS. 5A-5D show, in their four representations, a piece of seating furniture 1 according to the present disclosure. It has a lower part 2, which in the illustrated embodiment rests on the floor 8 without rollers, and has a vertically arranged gas pressure spring 10, on which a base 3 (FIG. 6) is arranged so as to be height-adjustable and rotatable about a vertical axis 9 relative to the lower part 2. In the following, the base 3 (as in the other exemplary embodiments) is considered to be “stationary” with respect to the actual kinematics 22, since the above-mentioned motions between the lower part 2 and the base 3 are not necessary for the seating furniture of the present disclosure and have nothing to do with it.

FIG. 6 shows an enlarged view of FIG. 5B, FIG. 7 shows a further enlarged detail in order to better illustrate and explain the structure of the kinematics of the piece of seating furniture: the base 3 is, as already explained, rotatable about the vertical axis 9, it projects radially outwards, thus forming a base arm 15, and carries at its outer end region, an intermediate swivelable articulated arm 16, which in turn carries at its other end a rotatable seating surface arm (also called end arm 17 for short). The three axes (the base axis coincides with the vertical axis 9; the intermediate axis is the one between the base arm and the intermediate arm; the end axis is the one between the intermediate arm and the end arm=seating surface) intersect each other at a central point 5 (which thus lies on the vertical axis 9). Since the end arm is firmly (but possibly elastically) connected to a seating surface 4, the latter is freely spherically movable around the central point 5, and with it everything that is attached to it, in the exemplary embodiment a backrest 11. The illustration of armrests (or a footrest) has been omitted for the sake of clarity, but the skilled in the art can imagine their assembly easily and without being inventive, since they are shown in the literature mentioned at the beginning, almost without being intellectually active. Such a piece of seating furniture corresponds to the prior art mentioned above (three-arm kinematics).

As stated above and clearly shown in FIG. 6, in order to apply a restoring torque to the deflected seating surface 4, one end of an energy accumulator 6, in the exemplary embodiment shown a pneumatic cylinder (gas pressure spring, metal spring), is movably articulated at an arm point 12 on a support arm 7 that is stationary with respect to the base 3. The other end of the energy accumulator is hingedly mounted at a seating point 13 on the seating surface 4. The energy accumulator 6, of whatever type, is designed in such a way that it has a tendency to shorten; the force exerted in this way lies in the connecting line between arm point 12 and seating point 13, the line of action 18.

For the purposes of the present disclosure, the kinematic conditions should be explained before they are described in more detail: The seating point 13 as part of the seating surface 4 performs a spherical motion around the central point 5, thus always remaining at the same distance from the central point. The arm point 12 performs a pure circular motion with the base 3a in a horizontal normal plane around the vertical axis 9, thus always remaining at the same distance from the central point 5.

In the rest position of FIG. 6 (and FIG. 5B), the three points, central point 5—seating point 13—arm point 12 lie on a straight line, which means that any force exerted by the energy accumulator (along its line of action 18) does not exert a torque on the seating surface due to the lack of a lever arm R, regardless of whether it has a preload or not at the rest length A0 specified thereby.

In the following figures and their description, the respective adjusting lever arm, the minimum distance of the line of action 18 of the energy accumulator from the central point 5, is always indicated with “R” regardless of size and position in space and is intended only for illustrative purposes.

In comparison, if one looks at FIG. 5A, in which the seating surface is swiveled to the left (this and all other observations/explanations are always made from the viewer's perspective, unless otherwise stated), one can see that the line of action is more inclined relative to the vertical (than in the rest position) and generates a restoring torque for the seating surface 4 with respect to the central point 5 around the horizontal longitudinal axis through the central point 5 (=normal to the plane of the drawing), since the length AL of the energy accumulator is greater than A0, which inevitably results from the deflection of the seating point 13 from the straight-line connection.

In FIG. 5C, analogous to FIG. 5A, the seating surface 4 is swiveled to the right, the line of action 18 of the energy accumulator 6 runs (in comparison to FIG. 5a) “beyond” the central point 5, and the length AR is again greater than the rest length A0, which inevitably results from the straight-line connection due to the deflection of the seating point 13. This in turn results in a restoring torque for the seating surface 4.

FIG. 5D shows the situation where the seating surface 4 is leaned back about the central point 5, thus about the transverse axis: again, the seating point 13 is deflected from the rest position, whereby the length AH of the energy accumulator is greater than in the rest position, the course of the line of action 18 results in a distance from the central point 5, which leads to a restoring torque for the seating surface 4.

The advantageous properties of the presently disclosed kinematics and the theoretical requirements for them, may be better understood as follows: The three-arm kinematics allows the seating surface 4 (in each of the embodiments shown) to rotate about the vertical axis 9 (internal rotation). This rotation has kinematically nothing to do with the rotation of the seating surface 4 with the base 3 around the vertical axis 9 (external rotation)! The first-mentioned rotation leads to various problems when using the seating furniture because, if nothing is done about it, the entire construction is not free of singularities; reference is also made to the relative angular position of the arm point 12 to the seating point 13 with respect to the vertical axis 9, which can then no longer be maintained! It is therefore necessary, but also sufficient, to prevent the rotation of the seating surface 4 about the vertical axis 9, insofar as it results from the three-arm kinematics, which is known from the prior art and is not a technical problem for the skilled in the art.

An elegant way to prevent this internal rotation is to link the energy accumulator 6 via universal joints 14 and not, as might seem obvious at first glance, via ball joints. It must also be ensured that the energy accumulator cannot rotate in itself, as is the case with many gas pressure springs, for example. There is enough choice on the market for such non-rotating devices.

Another of many possibilities for preventing a rotation is the use of a link chain as described in the applicant's DE 10 2018 114 207 B3 or one of the mechanisms specified in the applicant's WO 2022/174945 A1. When using such a separate anti-rotation device, the energy accumulator can be articulated using ball joints because it is no longer needed for preventing rotation. In order to avoid forced positions and blockages due to unfavorable tolerances or wear, it is even advisable to avoid such a double guidance.

In a further development, it was considered how these findings could be incorporated into the construction of a chair that was as simple as possible. This led to the preferential combined use of the kinematic elements, which are essential for the function of the chair, as energy accumulator.

For example, a chair with a divided seating surface was developed, as shown in FIGS. 8A-8D, which is constructed according to WO2022/174945 and the front seating surface region of which, the actual seating surface 4, has four degrees of freedom. Two of these degrees of freedom were equalized with torsionally flexible elements. These make it possible to generate the required counter-torque and at the same time release the two axes of motion, so that this kinematics, the seating surface accumulator kinematics 33, ultimately only restricts two axes of motion.

FIGS. 8A and 8B show such a piece of seating furniture without a lower part, thus starting from base 3, in frontal view and in side view respectively. The kinematics 22, a known three-arm kinematics, supports the backrest 11 together with the rear part of the seating surface, to which the (actual) seating surface 4 is articulated and can be swiveled about a horizontal transverse axis 34. In this example, the seating surface 4 can therefore also be rotated indirectly, via the backrest, about the longitudinal axis 63. In this example, the longitudinal axis 63 is chosen to extend with a strong inclination forwards and downwards, relative to the horizontal, in order to illustrate the range of possibilities, which is achieved by the combination of the kinematics 22 with a seating surface accumulator kinematics 33. The longitudinal axis 63 (mathematically and theoretically infinitely long, of course) runs over the largest part of its (technical) region in the region of the piece of seating furniture 1 above the seating surface 4, only in the foremost part, in the region of a vertically-arranged squeeze plate 42, does it pass under this part of the seating surface due to the optimal inclination of 45° selected for this exemplary embodiment and the selected kinematics. In the torso region of a user, thus close to the backrest (if there is none, in the “rear” region of the seating surface 4), the longitudinal axis 63 lies above the seating surface 4 or above the rear seating surface part 64 connected to a backrest.

It should therefore be noted that the longitudinal axis 63 in the region of the vertical projection P of the seating surface 4, in the example shown in combination with a rear seating surface part 64, thus the entire seating surface in the plane of symmetry, runs above the entire seating surface 4 for more than 75% of the length thus defined. The position of the “rear” end of the rear seating surface part 64, which is firmly connected, usually in one piece, to the backrest 11, is not critical, as a look at FIG. 8B shows: Since the longitudinal axis lies practically entirely above the entire seating surface even at the selected inclination of 45°, the requirement of 75% will always be met.

This applies to all kinematics used and divided or non-divided seating surfaces. At a slight inclination, this definition problem does not occur at all due to the height of the central point 5, which is below the center of gravity of a user but significantly above the seating surface. For inclinations of up to 30° or less, the longitudinal axis 63 in the region P lies entirely above the seating surface 4 or 4 and 64. An inclination of the longitudinal axis 63 backwards, downwards, is possible, but only makes sense in special cases and within narrower limits than forwards, downwards.

The gas pressure spring (not shown) has its vertical axis with respect to the base 3 in the “front” receptacle in FIG. 8B, to which the lever for height adjustment (not provided with a reference numeral) leads; in FIG. 8C it is the larger of the two cylindrical receptacles, the central point 5 is therefore, when viewed in the usual way, “behind” this vertical axis of rotation (not shown) of the base and all components connected to it.

The rotation about the transverse axis at the central point 5 with the backrest oriented backwards causes a rotation of the (front) seating surface 4 clockwise about the (movable) transverse axis 34 in order to avoid constriction of the back of the knee of a user.

In order to control the relative motion between the backrest 11 and the seating surface 4, a seating surface accumulator kinematics 33 is provided according to the present disclosure between the base 3 and a control arm 43 fixed to the seating surface: A stationary supporting structure 36 consisting of three rods 37 is mounted on a support plate 35 fixed to the base, which forms a support axis 38 at the free end. The three rods 37 are preferably mounted on the support plate 35 so as to be rotatable about axes parallel to the support axis 38 in order to avoid distortions in the resting state. Two side rods form a triangle, the third, middle rod lies (preferably) in the plane of symmetry of the triangle, but not in its plane, so that a pyramid is created including the three rods. At the top (or tip) of the pyramid, two cranked arms 40 are mounted extending laterally outward so as to be rotatable about the support axis 38, which form a triangle which, in the rest position, lies approximately in a vertical plane and whose free side represents a bearing axis 39.

An approximately rectangular support plate 41 is mounted on the support plate 35, preferably rotatable about the axis about which the central rod 37 is mounted, and about the support axis 38. A squeeze plate 42 is rotatably mounted around the support axis 38 and the bearing axis 39. On one side, in the illustrated exemplary embodiment on the viewer's side (right side of the seating furniture), the lower, free end of a control arm 43 fixed to the seating surface is rotatably mounted on the bearing axis 39. This construction provides an elastic deformation of the two plates 41, 42 when the seating surface 4 is swiveled due to the flexible (actually also torsionally flexible and therefore buckling-soft) design, which ensures the restoring torque.

It is of course also possible to arrange a pin along the axis 38, which also passes through the corresponding openings of the plates 41, 42, which therefore makes the entire device more rigid and also includes the rods 37 in the elastic deformation. By appropriate resizing compared to the variant described above, the same or similar restoring behavior can be achieved, depending on the requirements. This variant is particularly advantageous if a stronger counter torque is desired.

The construction with the rods 37 and the arms 40 ensures mechanical robustness in the event that a user only sits herself on the seating surface 4, thus reversing the load ratios of both the kinematics 22 and the seating surface accumulator kinematics 33, significantly increasing them in magnitude. Then, after a slight elastic deformation of all components involved, the seating surface 4 rests centrally in the region of the support axis 38 on the base-fixed supporting structure 36 and the load is transferred without damage.

When simply leaning backwards without twisting about the longitudinal axis 63, the plates 41, 42 twist about the three axes holding them without any deformation and thus without building up a restoring torque. If, regardless of the angular position about the transverse axis at the central point 5, an (additional) swiveling motion with a component about the longitudinal axis 63 occurs, the plates 41, 42 are elastically deformed accordingly and a restoring torque is generated. This also applies to all other illustrated and described exemplary embodiments

FIGS. 9A-9C, 10A-10C, 11A, 11B, 12A, and 12B show examples of strongly inclined longitudinal axes 63; the elongated, almost horizontal lever visible in these figures serves to adjust the height of the gas pressure spring in the region of the lower part 2 and is not part of the furniture of the present disclosure.

FIGS. 9A-9C show an office chair, a piece of seating furniture 1 with lower part 2, base 3, undivided, upholstered seating surface 4, backrest 11 and the kinematics 22 connecting the base 3 with the seating surface 4 in side view and in front view. In this embodiment, the central point 5 is not provided on the vertical axis 9, but is arranged slightly offset towards the backrest 11. This leads to a restoring torque when the seating surface and all components connected to it are tilted backwards, as the user's center of gravity is “in front of” the central point.

The inclination of 55° of the longitudinal axis 63 is achieved by a seating surface accumulator kinematics 33 which is similar to that of FIGS. 8A-8D. A cylindrical stub is firmly connected to the base 3 (and therefore provided with this reference numeral) and carries, swivelable about a horizontal first axis, a first spring plate 65 which is clamped at its other end by a joint body 66. This joint body can be swiveled about a second axis which, when installed, runs horizontally and parallel to the first axis, and carries a second spring plate 67 which is fixed at its other end in a receptacle 68. A holder 69, preferably made of sheet metal, is mounted on the seating surface, symmetrically with respect to the plane of symmetry 62. The holder 69 is essentially U-shaped and is attached with its two legs protruding downwards. A bolt 70 is pushed through holes in the receptacle 68 and also projects through holes in the two legs of the holder 69. Thus, the receptacle 68 is connected to the holder so that it can rotate about the bolt 70.

When the user tilts sideways, the two spring plates 65, 67 bulge and thus create the motion around the longitudinal axis 63. Depending on the bulge (which “forms” the energy accumulator), this is not exactly stationary, but in practice its position varies by a few millimeters in the lower region of the seating surface accumulator kinematics 33, which in practice remains completely unnoticed.

FIGS. 10A-10C show an office chair, a piece of seating furniture 1 with lower part 2, base 3, divided, not upholstered seating surface 4, backrest 11 and the kinematics 22 connecting the base 3 with the seating surface 4 in side view and in front view. Also in this exemplary embodiment, the central point 5 is not provided on the vertical axis 9, but is arranged slightly offset towards the backrest 11. This leads to a restoring torque when the seating surface and all components connected to it are tilted backwards, as the user's center of gravity is “in front of” the central point.

The divided seating surface, namely the front part, the actual seating surface 4, and the rear part 64, which is (elastically) connected to the backrest 11 and to which the three-axis kinematics, the kinematics 22, acts, are connected to one another via the transverse axis 34, which is horizontal in the rest position. This movable connection creates an additional degree of freedom, which is damped by the seating surface mechanism 31, which also serves as an energy accumulator. This is achieved by the stiffening 71, which is added to the otherwise completely corresponding seating surface mechanism of the embodiment of FIGS. 9A-9B. Everything else is the same as in the embodiment shown in FIGS. 9A-9B.

FIGS. 11A and 11B show a situation analogous to FIGS. 9A and 9B with an undivided seating surface 4, wherein a simple seating surface accumulator kinematics 33 is used to achieve an even steeper arrangement of the longitudinal axis 63, namely at 70°: It consists of a kinematics of the same structure as shown in FIG. 9C, its mounting on the base is also the same, but its point of application on the seating surface 4 is not via a U-shaped holder, but by means of the receptacle 68 directly on the underside of the seating surface.

The position of the longitudinal axis is in turn determined by the curvature of the spring plates, which (or the elastic deformation of which) also form the energy accumulator 6 and is thus variable in the millimeter range.

FIGS. 12A-12C show the seating surface of FIGS. 10A and 10B with a divided seating surface 4, 64, with the seating surface accumulator kinematics 33 of the embodiment of FIG. 11, to which is added a stiffener 71, hinged on the one hand to the base 3 and on the other hand to the joint body 66, again to bind the additional degree of freedom created by the transverse axis 34. In this embodiment, too, the position of the longitudinal axis 63 is determined by the elastic deformation of the seating surface accumulator kinematics 33.

Of course, any piece of seating furniture 1 which has an instantaneous center or at least one approximately horizontal (or even more inclined) axis in the plane of symmetry (longitudinal axis) in the region of the upper abdomen of a user (preferably, of course, below his center of gravity) can be equipped with one of the energy accumulators shown or with another of the numerous designs available in the prior art.

The kinematics of the present disclosure therefore provide an efficient and easy-to-install device that provides a compensating torque without additional costs and without requiring additional space.

The balancing torque can be generated by torsion as well as by stretching and compressing components. If required, the energy accumulator effect can be supported and varied in its effect by one or more spring elements that can be switched on and off.

It is also possible to adapt other regions of the kinematics and/or the seating furniture, such as the seating surface itself, as energy accumulators.

No distinction is made in the present disclosure between central point and central region. If the three arm axes do not (technically) intersect each other exactly at one point, then there is a central region instead of a central point. The effects are described in detail in documents discussed previously and therefore require no further explanation here. It should only be noted that extensions of a central region are hardly noticeable in the low decimeter range and not noticeable in the centimeter range and are therefore included in the term “central point”.

The central point is located below the center of gravity of a user including the seating parts that move around the longitudinal axis 63, but above the seating surface 4. It is preferably located at the height of the user's eleventh thoracic vertebra.

If the seating furniture is an office chair, the central point is advantageously located in the region slightly behind or exactly on the vertical axis of rotation of the office chair, the vertical axis 9. The relationship between this axis of rotation, which is “provided” by the lower part and around which the base 3 rotates, and the kinematics between the base 3 and the seating surface 4 has been explained in detail above.

When the seating surface 4 is deflected from the rest position about the longitudinal axis 63, the energy accumulator 6 is “loaded” with energy by the restoring device 23 (optionally in the form of a seating surface accumulator kinematics 33), whereby it exerts a restoring torque on the seating surface 4 about the longitudinal axis 63 in the direction of the rest position.

The scope of the present disclosure is not limited to only the three-arm kinematics shown (often also called two-arm kinematics because the object itself is usually not seen as an “arm”; actually, three-axis kinematics would be more appropriate), it can be universally applied to all technologies that have at least one approximately horizontal longitudinal axis in the plane of symmetry of the seating furniture in the region of the upper abdomen of a user, around which the seating surface is swivelably mounted, or a central point that allows a spherical motion of the seating surface. However, the three-axis kinematics shown is preferred over the other kinematics known from the cited (and other) prior art because of its adaptability, robustness and small space requirement.

Selected Embodiments

It has been discussed in the prior art literature that the three axes of the three-arm kinematics do not have to intersect each other at one point (technically speaking, not mathematically), but rather pass close to each other and thus form a central region in which every conceivable instantaneous center lies. Such a construction also forms a virtual longitudinal axis that is not fixed in position with respect to the base, but can change its position and orientation within limits depending on the relative position of the arms of the three-arm kinematics; one could also say that it is replaced by another, momentary, virtual longitudinal axis. Restoring devices such as those described can also be used with such kinematics; the users of the seating furniture will not notice any difference. This also applies to seating furniture such as that described in FIGS. 4A-4E, if both kinematics used there form central regions.

Regarding the application of the seating furniture of the present disclosure in the case of a physical construction of the longitudinal axis 63, as is the case, for example, in EP 2 381 816 in FIGS. 7-18 and the associated description, it can be said that an energy accumulator, possibly a simple spring mechanism between the base and the seating surface, solves the problem in this case.

In the construction according to EP 1 090 568, in which the individual motion possibilities are created step by step (serially) by partial kinematics, such an energy accumulator would have to be arranged on the side of the part of the partial kinematics facing the base, which enables the motion around the longitudinal axis.

With knowledge of the present disclosure, it is easily possible for a person skilled in the art to provide different solutions. The arrangement and type of energy accumulator, usually a spring mechanism, such as a gas pressure spring, a spring package or similar, can also be easily selected.

Regarding the magnitude of the restoring torque, it can be said that it can be varied to a large extent depending on the user's wishes. It has proven to be effective that the restoring torque is between 1.25 Nm/° swivel angle and 20 Nm/° swivel angle about the longitudinal axis 63, preferably 5±10% Nm/° swivel angle.

As it is used in the present disclosure, the swivel point or at least an axis of rotation in the sitting direction of the seat may be positioned approximately at the level of the user's upper abdomen. This specific positioning is advantageous for the functionality of the chair, as it allows a natural freedom of motion when sitting, which is modeled on the motion when walking.

As it is used in the present disclosure, an integrated energy accumulator creates a counter-torque that supports both the hip motion and the motion of the entire upper body when moving on the chair without the user losing stable balance. This counter-torque is designed in such a way that it does not restrict motion, including hip motion, but rather promotes and supports it.

One of skill in the art that is familiar with the present disclosure may envision additional possible solutions, adjustments and effects for the seating furniture disclosed herein, including but not limited to investigations of the positioning of the swivel point and its influence on balance, development of an approach to utilize counter-torque through an energy accumulator to ensure a stable balance, and adjustments to ensure freedom of motion and health benefits without compromising the safety and comfort of the user.

In the description and claims, the terms “front”, rear”, “top”, “bottom”, etc. are used in their common form and with reference to an item in its usual position of use. Similarly, it should also be noted that in the description and claims, terms such as “lower part” of a hanger, reactor, filter, building, or device or, more generally, an object mean the lower half and in particular the lower quarter of the total height.

In the description and the claims, the term “substantially” means a deviation of up to 10% of the stated value, if this is physically possible, both downwards and upwards, otherwise only in the sensible direction; for degrees (of angle and temperature) ±10° is meant.

All quantities and proportions, in particular those for delimiting the invention, as far as they do not relate to the specific examples, are to be understood with ±10% tolerance, thus, for example: 11% means: from 9.9% to 12.1%. For terms such as: “a microphone” the word “a” is not a numerical word but is to be regarded as the indefinite article or a pronoun, unless the context indicates otherwise.

The term: “combination” or “combinations” means, unless otherwise stated, all types of combinations, from two of the constituents concerned to a large number or all of such constituents; the term: “containing” may also be substituted with “consisting of”.

The characteristics and variants specified for the individual embodiments and examples disclosed herein may be freely combined with those of the other examples and embodiments and may in particular be used to characterize the invention in the claims without necessarily entraining the other details of the respective embodiment or the respective example.

List of reference numerals:

01
piece of seating furniture

02
bottom part

04
seating surface

05
central point

07
support arm

10
gas pressure spring

12
arm point

13
seating point

15
base arm

16
intermediate arm

17
end arm

18
line of action

20
arrow in longitudinal direction

21
arrow in transverse direction

26
spring mechanism

28
connecting piece

30
assembly part

31
seating surface mechanism

33
seating surface accumulator

35
support plate

36
supporting structure

38
support axis

41
support plate

43
control arm

44
first axis

45
second axis

47
rotating arm axis

52
spring package

58
rotary lever axis

59
longitudinal axis of rotation

62
plane of symmetry

64
rear seating surface part

65
first spring plate

66
joint body

67
second spring plate