# Patent

## Title
Body support structure

## Abstract

A body support structure includes a body support member and a base having an upper component coupled to the body support member and a lower component adapted to be supported on a floor. An adjustable spring mechanism biases the body support member. A weighing mechanism is coupled to the adjustable spring mechanism. The weighing mechanism includes a height adjustment device disposed between the upper and lower components of the base. The height adjustment device includes a pneumatic spring having a pressure tube coupled to the lower component and a piston rod extending upwardly from and moveable relative to the pressure tube. A housing is disposed around the pneumatic spring and is coupled to the upper component. An adapter is coupled to the piston rod. A weighing spring is disposed between the adapter and the housing, with the housing moveable relative to the adapter between first and second weighing positions.

## Background
This application claims the benefit of U.S. Provisional Application No. 60/994,721, filed Sep. 20, 2007 and entitled “Body Support Structure,” the entire disclosure of which is hereby incorporated herein by reference.


FIELD OF THE INVENTION
The invention relates to a body support structure, including for example a piece of furniture for sitting on or a piece of furniture for lying on, such as, for example, chair, armchair, stool, bed or sofa, having a self-adjusting spring mechanism.
BACKGROUND
DE 37 00 447 A1 discloses a piece of furniture for sitting on, in which the body weight of a person is detected via the loading of a seat part and in which the leaning force required in order to adjust the inclination of the back part is to be adjusted as a function of the weight force of the person. This automatic adaptation takes place by a spring being compressed by the weight force of the person, with the backrest carrier acting against this compressed spring. A disadvantage of a piece of furniture of this type for sitting on is that, here, only the weight force acting on the seat part can be detected. A weight force introduced via the back part or armrests which may be present cannot be correctly detected by the mechanism, since it is dissipated via the coupling of the carrier of the back part also to the seat carrier. This may possibly result in too weak a reaction force of the carrier of the back part.
Furthermore, U.S. Pat. No. 5,080,318 discloses a control device for the inclination of a chair comprising a weighing device which causes an adjustment of a tension device for a leaf spring which cushions an inclination of the seat, the adjustment travel being dependent on the weight of a user. A control device of this type has the disadvantage that the weighing of a user and therefore the setting of the leaf spring take place under load and are therefore sluggish and consequently slow and inaccurate.
SUMMARY
In one aspect, the invention is directed to a body support structure in which a spring mechanism which cushions a reclining of a person can be adapted to the weight of the person, while weighing is to be smooth and is to take place quickly and accurately. The body support structure can be configured in one embodiment as a piece of furniture, in particular a piece of furniture for sitting or lying on, with a weighing mechanism for controlling the spring mechanism, in which the weighing mechanism can be produced cost-effectively.
In one aspect, a body support structure includes a body support member and a base having an upper component coupled to the body support member and a lower component adapted to be supported on a floor. An adjustable spring mechanism biases the body support member. The spring mechanism is adjustable between at least a first and second biasing force. A weighing mechanism is coupled to the adjustable spring mechanism. The weighing mechanism is moveable between at least a first and second weighing position, wherein the spring mechanism is adjusted between the first and second biasing forces and as the weighing mechanism is moved between the first and second positions. The weighing mechanism includes a height adjustment device disposed between the upper and lower components of the base. The height adjustment device is adjustable between at least a first and second height. The height adjustment device includes a pneumatic spring. The pneumatic spring includes a pressure tube coupled to the lower component and a piston rod extending upwardly from and moveable relative to the pressure tube. A housing is disposed around the pneumatic spring and is coupled to the upper component. An adapter is coupled to the piston rod, and a weighing spring is disposed between the adapter and the housing. The housing is moveable relative to the adapter between the first and second weighing positions. In this way, the weighing mechanism also provides for height adjustment, which increases the functionality of the body support structure without incurring substantial additional costs or complicated mechanisms.
In one embodiment, a movement converter, including a cable assembly, is connected between the spring mechanism and the weighing mechanism. In this embodiment, only a single cable is needed, and does not require a coupling or rotary system, since the adapter, connected to the cable, rotates with the upper base component, connected to the cable guide. In addition, the aesthetics of the body support structure are improvised by providing a visually uniform center support column. In particular, the housing extends between the upper and lower base components as the body support member is moved between minimum and maximum height positions, such that the pressure tube and/or piston rod are hidden from view.



BRIEF DESCRIPTION OF THE DRAWINGS
Further details of the invention are described by means of exemplary embodiments illustrated diagrammatically in the drawing in which:
FIGS. 1a-1d show diagrammatic views of four basic variants of a piece of furniture designed as a chair;
FIGS. 1e-1h show diagrammatic views of a standing and sitting person;
FIGS. 2a-2c show a diagrammatic illustration of a piece of furniture according to the invention in two positions;
FIG. 3 shows an enlarged illustration of a weighing mechanism, a spring mechanism and a movement converter of a piece of furniture according to the invention;
FIGS. 4a-4c show diagrammatic illustrations of further design variants of a piece of furniture according to the invention;
FIGS. 5a-5c show a diagrammatic illustration of a further piece of furniture according to the invention in a nonloaded and a loaded position;
FIGS. 6a-6e show five variants of a weighing mechanism, a spring mechanism and a movement converter of a piece of furniture according to the invention;
FIGS. 7a-7f show six illustrations of a further design variant of a piece of furniture according to the invention;
FIGS. 8a-8c show three illustrations of a movement converter;
FIGS. 9a-9c show diagrammatic illustrations of three further design variants of a piece of furniture according to the invention;
FIGS. 10a-10d show four illustrations of a further design variant of a piece of furniture according to the invention; and
FIGS. 11a-11e show five illustrations of a further design variant of a piece of furniture according to the invention.



DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
FIGS. 1a to 1d illustrate four basic variants of a body support structure according to the invention, which are shown for example and without limitation as a piece of furniture for sitting on 2 in the form of a chair 3. All four pieces of furniture 1 comprise essentially a lower part 4, a middle part 5, an upper part 6 and a seat 7. It should be understood that the invention can also be incorporated, without limitation, into other body support structures such as beds, sofas, benches, vehicle and/or aircraft seats, etc. All the components 4, 5, 6 carrying the seat 7 are also designated in summary as a base C. The seat 7 is in each case articulated on the upper part 6 which is connected to the middle part 5. The middle part 5 is carried by the lower part 4. The lower part 4 is designed in FIG. 1a as a foot 8, in FIG. 1b as a wall holder 9, in FIG. 1c as a ceiling holder 10 and in FIG. 1d as a swing 11. FIG. 1a also shows, in principle, the arrangement of a height adjustment device 12 between the lower part 4 and the middle part 5.
FIGS. 1e to 1h show diagrammatic views of a person P and of a piece of furniture 1. In FIG. 1e, the person P is standing in front of the piece of furniture 1. In FIG. 1f, the person P is sitting upright in an upright sitting posture P1 on a seat part 13 of a seat 7 of the piece of furniture 1 and in this case subjects a back part 14 of the seat 7 to no or only insignificant load. In FIG. 1g, the sitting person P reclines backward into a rearwardly inclined sitting posture P2 and in this case experiences a counterforce due to the back part 14 of the seat 7 of the piece of furniture 1. In FIG. 1h, the person P leans forward into a forwardly inclined sitting posture P3.
FIGS. 2a and 2b show diagrammatic illustrations of a piece of furniture 1 according to the invention in two positions I (see FIG. 2a) and II (see FIG. 2b). The piece of furniture 1 comprises a lower part 4, a middle part 5, an upper part 6 and a seat 7. The seat 7 comprises a seat part 13 and a back part 14 which are connected to one another in an articulated manner by means of an axis of rotation 15. The seat part 13 is articulated rotatably with an axis of rotation 16 on the upper part 6, and the back part 14 is guided via an arm 17 with an axis of rotation 18 on the upper part 6, the arm 17 also being connected rotatably with an axis of rotation 19 to the back part 14. A first spring element 20 designed as a leaf spring 21 is fastened to the upper part 6. The first spring element 20 extends as a lever arm 51 approximately horizontally beneath the seat part 13 of the seat 7, and the seat part 13 lies with a projection 22 on the first spring element 20 in the region of a free end 23 of the latter. The first spring element 20 has a prestress and is supported between a tension end 24 and the free end 23 by a support 25 only when there is a corresponding load. The support is held by a slide 26. The support 25 and the spring element 20 form a spring mechanism SM. The support 25 is designed as a roller 27. The slide 26, which carries the support 25, is guided laterally movably in a guide 28 on the upper part 6 and lies with a lower end 29 on an inclined plane 30 of the middle part 5. The upper part 6 is guided movably upward and downward on the middle part 5 via two arms 31, 32 oriented parallel to one another, the arms 31, 32 being connected in each case to the middle part 5 and the upper part 6 rotatably about axes of rotation 33 to 36 running into the drawing plane. The downward movement or the upward movement of the upper part 6 together with the seat 7 is braked or assisted by a second spring element 37. The second spring element 37 is arranged between the upper part 6 and the middle part 5 and is designed as a helical spring 38. The spring element 37 and the arms 31 and 32 form a weighing mechanism WM. Finally, the middle part 5 is mounted on the lower part 4 rotatably about a vertical axis of rotation 39.
In FIG. 2a, which shows the piece of furniture 1 in the position I, the piece of furniture 1 or the seat 7 is nonloaded and is in a position of rest. That is to say, no person is sitting on the piece of furniture 1. The upper part 6 therefore stands at a level N1 at which the second spring element 37 has to compensate only the weight of the upper part 6 and of the seat 7. In this position I of the piece of furniture 1, the slide 26 stands in a left position S1. A cushioning of an inclination movement of the nonloaded seat 7 about the axis of rotation 16 in a direction of rotation w on the projection 22 takes place via the first spring element which is not in contact with the support 25. The nonloaded piece of furniture 1 according to the invention has to generate by means of its first spring element 20 only a comparatively low reaction force R1 to an inclination of the seat 7 about the axis of rotation 16 in the direction of rotation w, since, in this situation, only a torque M generated due to the dead weight of the seat 7 is to be absorbed. Basically, an interspace 95 having a thickness D95 lies between the support 25 or its contact surface KF and the first spring element 20 or the leaf spring 21 (see FIG. 2c with a diagrammatic sectional view along the sectional line IIc-IIc illustrated in FIG. 2a). This interspace 95 is brought about by a prestress of the leaf spring 21 which is selected such that the leaf spring 21 stands with play above the contact surface KF of the support 25 and a movement of the support 25 can take place according to a weight force 40 (see FIG. 2b), without the leaf spring 21 impeding or braking the support 25.
In FIG. 2b, which shows the piece of furniture 1 in the position II, the piece of furniture 1 or the seat 7 is loaded by the weight force 40 of a person, not illustrated, sitting upright and is in a working position. The upper part 6 is lowered to a level N2 at which the second spring element 37 has to compensate the weight of the upper part 6, the weight of the seat 7 and the weight force 40. In this position II of the piece of furniture 1, the slide 26 is in a middle position S2 and with its support 25 supports the first spring element 20 between its tension end 24 and its free end 23, insofar as the person leans backward and thereby increases the loading of the spring element 20. An increased reaction force R2 is available for cushioning an inclination movement of the person together with the seat 7 about the axis of rotation 16 in a direction of rotation was soon as the leaf spring 21 comes to lie on the support 25 as a result of the displacement of the person and locks said support under itself with a locking force LF. The loaded piece of furniture 1 according to the invention thus generates a reaction force R2 to an inclination of the seat 7 about the axis of rotation 16 in the direction of rotation w. The reaction force R2 is higher than the reaction force R1 due to an additional support of the leaf spring 21 on the support 25 and is thus adapted to the loading of the piece of furniture 1. As soon as the person sitting on the piece of furniture 1 resumes an upright sitting position, this also gives rise in the position II to an interspace 95, shown in FIG. 2c for the position I, between the leaf spring 21 and the support 25 or its contact surface KF. That is to say, the piece of furniture 1 regains the smooth movability of the support 25 with respect to the leaf spring 21 as soon as the person changes from a reclined sitting position into an upright sitting position. Between the position I and the position II, the spacings F1, F2 between the support 25 and the projection 22 vary as a function of the person's weight.
The difference between the levels N1 and N2 of the upper part 6 in positions I and II is designated as the weighing distance W1, and the spacing between the positions S1 and S2 of the slide 26 is designated as the displacement distance V1.
The upper part 6 and the middle part 5 thus form with one another a movement converter 41 which converts the weighing movement against the second spring element 37 into a displacement movement, by which the first spring element 20 is influenced in its reaction force R1 or R2 on the seat 7. The second spring element 37 or the spring mechanism SM is influenced as a function of the weighing movement, although the weighing movement cannot be influenced by an inclination movement of a person sitting on the piece of furniture 1 and reclining. The weight force 40 of the person is detected completely, independently of his position on the seat 7, solely due to the articulation of the seat 7 on the upper part 6. The seat 7, shown in FIGS. 2a and 2b, is designed in the manner of a known synchronous mechanism which, when a person reclines in the seat 7, gives rise to a different increase or decrease in the inclination of the seat part 13 or of the back part 14. The arms 32, 33 and the spring element 37 form the weighing mechanism WM by means of which the weight force 40 of a person sitting on the seat can be detected. The weighing mechanism WM gives rise via the movement converter 41 to a setting of a spring mechanism SM according to the weight force 40 of the person using the piece of furniture 1. The spring mechanism SM is formed essentially by the first spring element 20 or the leaf spring 21 and the support 25, the support 25 cooperating with the leaf spring 21 only when a person sitting on the piece of furniture 1 reclines into a rearwardly inclined sitting position P2 described in FIG. 1g. 
FIG. 3 illustrates a diagrammatic view of a movement converter 41 which is constructed in a similar way to the movement converter shown in FIGS. 2a to 2c and is arranged between a weighing mechanism WM and a spring mechanism SM. For simplification, an upper part 6 is shown here without articulation points for a seat.
The movement converter 41, the weighing mechanism WM and the spring mechanism are illustrated in three positions I, II and III. In position I, shown by thick unbroken lines, the arrangement is nonloaded.
The arrangement is therefore not loaded by a person sitting on the seat, not illustrated. When the arrangement is loaded via the seat, not illustrated, with a first weight force 40 of a first person, the upper part 6 is lowered counter to a second spring element 37 in the direction of an arrow y′ downward toward a middle part 5 into the second position II. The second position II is illustrated by thin unbroken lines. Lowering takes place according to the articulation of the upper part 6 on the middle part 5 via two parallel arms 31 and 32 on a circular path 42.
When the arrangement is loaded via the seat, not illustrated, with a second weight force 40a of a second person which is greater than the first weight force, the upper part 6 is lowered counter to the second spring element 37 in the direction of the arrow y′ downward toward the middle part 5 into the third position III. The third position III is illustrated by thin broken lines. Lowering again takes place according to the articulation of the upper part 6 on the middle part 5 via two parallel arms 31 and 32 on the circular path 42. In positions I and II, the upper part has levels N1 and N2, the difference of which corresponds to a weighing distance W1. This weighing distance W1 is converted via a drive 43 and an output 44 into a displacement distance V1 which is defined as a path difference between positions S1 and S2 of a slide 26. The drive 43 comprises a guide 28 on the upper part 6 and an inclined plane 30 on the middle part 5. These two components give rise, due to a lowering of the guide 28 together with the upper part 6, to a lateral displacement movement of the slide 26 which forms the output 44. In other words, the upper part 6, together with the middle part 5 or with the transmission mechanism operating as a movement converter 41, forms a gear 45 for converting a weighing movement into a displacement movement. In positions I and III, the upper part has the level N1 and a level N3, the difference of which corresponds to a weighing distance W2. This weighing distance W2 is converted via the gear 45 into a displacement distance V2 which is defined as the path difference between the position S1 and a position S3 of the slide 26. The slide 26 slides in the guide 28 from the position S1 into the position S2, a support 25, fastened vertically movably to the slide 26, for a first spring element 20 moving on the upper part 6 along a curved path 46 which runs at an approximately constant spacing with respect to a curved run of the first spring element 26 designed as a leaf spring 21. By the path 46 being coordinated with the run of the leaf spring 21, it is possible to avoid a jamming of the support 25 under the spring element 20 in any position of the support 25 or slide 26 and to ensure a smooth movement of the support 25. The smooth movement of the support 25 is implemented by the formation of an interspace 95, 96 and 97 in any position of the support 25, insofar as the piece of furniture 1 is not loaded by a reclining person. As regards the structural implementation of the interspaces, reference is made to FIG. 2c which has similar validity for FIG. 3. Owing to the smooth moveability which the support achieves as soon as the person sitting on the chair assumes an upright sitting position, a sensitive readjustment of the position of the support 25 is also possible if, for example, the person using the chair grasps a heavy file and puts this down again later. The vertical moveability of the support 25 is achieved by the guidance of a shaft 47 of the support 25 in long holes 48 arranged on the slide 26. As a result, during the displacement of the slide 26, the support 25 can follow the path 46 independently of the run of the guide 28. In the position S3 of the slide 26, belonging to position III, the support 25 has been lowered, according to the run of the path 46, in the direction y′ downward in the long holes 48. The path 46 is configured in its run in such a way that an undesirable jamming of the support 25 between the path 46 and the leaf spring 21 during weighing is prevented. The run of the path 46 is adapted to the run of the leaf spring 21. A return of the slide 26 out of the position S3 or S2 into the position S1 takes place, when the seat is relieved of the weight force acting on it, for example, by means of a tension spring 49 which connects the slide 26 to the upper part 6. Such a tension spring 49 is also provided, for example, for the pieces of furniture illustrated in FIGS. 2a and 2b. As already mentioned in the description of FIGS. 2a and 2b, the displacement of the support 25 influences the hardness of the leaf spring 21 with which the latter cushions an inclination movement of a seat, not illustrated, on the upper part 6. In the nonloaded position I, the first spring element 20 basically already has a prestress, by means of which the seat, not illustrated, is already cushioned against a basic loading of the piece of furniture with, for example, 40 kg. Such a prestress is generated in a tension slit 72 for the leaf spring 21 by the leaf spring 21 being fixed between an upper counterbearing OG and a lower counterbearing UG. In a consideration of the lower counterbearing UG and the support 25, the lower counterbearing UG is to be defined as a first support and the support 25 as a second support for the leaf spring 21.
Furthermore, with regard to the weighing movement on the circular path 42, FIG. 3 depicts a vertical component VK of the weighing movement and a horizontal component HK of the weighing movement. In the case depicted, the vertical component VK of the weighing movement corresponds to the weighing distance W2. In the present case, the vertical component VK is substantially greater than the horizontal component HK. Thus, the weighing result, while having the required accuracy, is falsified at most minimally.
FIGS. 4a and 4b show two variants of a piece of furniture 1 in a diagrammatic illustration. In both variants, the illustration of a lower part of the piece of furniture 1 has been dispensed with. FIG. 4a shows a middle part 5 which carries an upper part 6 via two arms 31 and 32. A seat 7 is articulated on the upper part 6 by means of a synchronous mechanism already described with regard to FIGS. 2a and 2b. In contrast to the pieces of furniture described above, a first spring element 20, which cushions an inclination movement or rotational movement of the seat 7 about an axis of rotation 16 in a direction of rotation w, is designed as a helical spring 50 which is arranged on a slide 26. The slide 26 is guided, in a similar way to the designs shown in FIGS. 2a to 3, on the upper part 6 in a guide 28 and slides with a lower end 29 on an inclined plane 30 which is formed on the middle part 5. The upper part 6 guided upward and downward on the middle part 5 on arms 31 and 32 is cushioned against the middle part 5 by means of a second spring element 37. Between a projection 22 of the seat 7 and the first spring element 20 is arranged a lever 51 which is articulated on the upper part 6 rotatably about an axis of rotation 52. The seat 7 is supported from above on the lever 51 via a projection 22. The lever 51 is supported, in turn, by the first spring element 20 acting against the lever 51 from below as a support 25, when a person, not illustrated, sitting on the piece of furniture 1 reclines. As long as the person sitting on the piece of furniture 1 does not recline, the lever 51 is sufficiently supported by the force of a spring 98 which is designed as a helical spring 99. Owing to the spring 98, during a traveling movement of the first spring element 20 there is always an interspace 96 between the first spring element 20 and the lever 51, insofar as the person sitting on the piece of furniture 1 does not recline. FIG. 4c illustrates, in this regard, a view of a detail, designated in FIG. 4b as IVb, which applies to FIGS. 4a and 4b. The lever 51, the spring 50 and the spring 98, together with a spring mechanism SM, and the arms 31, 32 and the spring 37 thus form a weighing mechanism WM. A movement converter 41 connecting the weighing mechanism WM and the spring mechanism SM is designed according to the movement converter shown in FIGS. 2a and 2b. As a function of a position S1, S2 or S3 of the slide 26 together with the first spring element 20, different engagement points 53 of the first spring element 20 operating as a support 25 give rise on the lever 51 to a supporting force of differing magnitude against an inclination of the seat 7 about the axis of rotation 16. The description relating to FIG. 4a applies likewise to the piece of furniture 1 shown in FIG. 4b. The only difference from FIG. 4a is that, here, a seat part 13 and a back part 14 of the seat 7 stand at a fixed angle to one another.
FIGS. 5a and 5b show a further design variant of a piece of furniture 1 according to the invention in two different positions I and II, the illustration of a lower part of the piece of furniture 1 having been dispensed with in both figures. An upper part 6 is guided movably upward and downward on a middle part 5 by means of an arm 31 rotatably about axes of rotation 33, 34 and a roller 55 guided on a cam 54 and is cushioned on the middle part 5 via a second spring element 37. Arranged on the upper part 6 is a first spring element 20, on which a seat 7 articulated on the upper part 6 rotatably about an axis of rotation 16 is supported with a projection 22 against an inclination movement about the axis of rotation 16 in a direction of rotation w. A displacement of a support 25 under the first spring element 20 designed as a leaf spring 21 is achieved by means of a movement converter 41 which connects a weighing mechanism WM and a spring mechanism SM to one another. The movement converter 41 comprises an articulated lever 56 which is composed of a lower lever 56a and an upper lever 56b. The lower lever 56a is connected fixedly to the middle part 5 and is connected to the upper lever 56b in a rotationally articulated manner about an axis of rotation 57. The upper lever 56b carries the support 25 which is articulated on this rotatably about an axis of rotation 58. A lowering of the upper part 6 together with the seat 7 as a result of loading of the seat 7 by a weight force 40 causes a displacement movement of the support 25 out of a position S1 into a position S2, said displacement movement being caused by the articulated lever 56. The movement converter 41 converts a weighing movement of the upper part 6, in which the support 25 is taken up on the upper part 6, into a displacement movement directed laterally in the direction of an arrow x. In the position II of the piece of furniture 1, as illustrated in FIG. 5b, the support 25 stands in the position S2 as a result of the loading of the seat 7 with the weight force 40 and causes the seat 7 to be supported against an inclination movement according to the weight force. When the piece of furniture 1 is relieved of the weight force 40, the second spring element 37 raises the upper part 6, together with the seat 7, and the support 25 is retracted by the articulated arm 56 in the direction of an arrow x′ into the position I shown in FIG. 5a. The seat 7 is composed of a seat part 13 and of a back part 14, the back part 14 being articulated resiliently on the seat part 13 via an elastic element 59. In the seat 7 illustrated in FIGS. 5a and 5b, therefore, essentially an inclination movement of the seat part 13 is cushioned by the first spring element 20. The back part 14 can spring back even further, independently of this, about an axis of rotation 15 of the seat 7. The cooperation of the support 25, of the upper part 6 and of the leaf spring 21 is shown as a detail in FIG. 5c according to the section Vc-Vc marked in FIG. 5b. As in the previous exemplary embodiments, the support 25 and the leaf spring 21 are spaced apart from one another due to an interspace 96 having a thickness D96, as long as a person sitting on the piece of furniture 1 does not recline. The support 25 is guided in a slot N on the upper part 6.
FIGS. 6a to 6e illustrate diagrammatically further design variants of weighing mechanisms WM and movement converters 41 for pieces of furniture 1 according to the invention. The arrangement shown in FIG. 6a comprises a middle part 5 and an upper part 6, the upper part 6 being guided movably upward and downward in a bore 60 in the middle part 5. The upper part 6 is seated with a column 61 in the bore 60, the column 61 having a duct 62 which opens toward the bore 60 and leads into a boom 63 of the upper part 6. The duct 62 is provided for conducting a hydraulic fluid 64 out of a reservoir 65, formed by the bore 60, through the duct 62 into the boom 63 as a function of a weight force, acting on the upper part 6, of a person, not illustrated, sitting on a seat articulated on the upper part 6. In the boom 63, the hydraulic fluid 64 acts on a piston 66 which is supported against the upper part 6 by means of a second spring element 37. The piston 66 carries a support 25 which is displaceable on a path 46 beneath a first spring element 20 and which determines the counterforce of the first spring element 20 against an inclination movement of the seat, not illustrated. When the seat is relieved of the weight force, the hydraulic fluid is pressed back through the duct 62 into the reservoir 65 by the piston 66 onto which the second spring element 37 presses. The upper part 6 together with the seat is raised by means of the hydraulic fluid 64 which then presses onto a piston surface 67 of the column 61.
The design variant, illustrated in FIG. 6b, of a weighing mechanism WM and a movement converter 41 has an operating mode and design comparable to the arrangement shown in FIG. 6a. In contrast to this, here, the force transmission medium used is a magnetorheological fluid 68 which is guided in the reservoir 65 and in the duct 62 in concertinas 69 and 70 in order to ensure optimal sealing off.
The arrangement illustrated in FIG. 6c has an operating mode comparable to the arrangement shown in FIG. 6b. In contrast to this, the upper part 6 is not guided in the middle part 5 via a column, but, instead, has a guide by means of arms 31, 32 which is known, for example, from FIGS. 2a and 2b. 
FIG. 6d shows a purely mechanical variant. In this, an upper part 6 is guided with a column 61 in a bore 60 of a middle part 5, a second spring element 37 designed as a helical spring 38 being arranged between the column 61 and the middle part 5. A slide 26 is guided in a way known from previous exemplary embodiments on a boom 63 of the upper part 6 in a guide 28. The slide 26 has a support 25 and cooperates with an inclined plane 30. As a result, during a weighing movement of the upper part 6, the slide 26 is moved laterally under a first spring element 20. When the movement converter 41 is relieved of a weight force causing the weighing movement, a tension spring 49 draws the slide 26 in the direction of the column 61 again.
The arrangement illustrated in FIG. 6e has an upper part 6 which is guided with a column 61 in a bore 60 of a middle part 5 against a second spring element 37. A weighing distance occurring during the compression of the upper part 6 as a result of a loading of a seat, not illustrated, articulated on the upper part 6 is detected by a sensor 71. A piston 66 is movable motively in a guide 28 according to the detected weighing distance. The transfer of control signals between the sensor 71 and the motively movable piston 66 takes place in wired or wireless form. A support 25 is arranged with play in the vertical direction on the motively movable piston 66 in a way known from previous exemplary embodiments. This moves the piston 66 under a first spring element 20, designed as a leaf spring 21, as a function of the detected weighing distance. When the upper part 6 or the seat arranged on the upper part 6 is relieved, the upper part 6 is raised by the second spring element 37. This lifting movement is likewise detected by the sensor 71 and causes a return movement of the motively movable piston 66.
In the design variants illustrated in FIGS. 6a to 6e, the first spring element 20 and the support 25 cooperate according to the description relating to FIGS. 2a to 2c. In particular, the supports 25 are designed according to FIG. 2c, and between the first spring element 20 and the support 25 there is no interspace only when a person sitting on the piece of furniture 1 reclines.
FIG. 7a shows a perspective illustration of a piece of furniture 1 according to the invention. The piece of furniture 1 stands in a nonloaded position I and comprises a base C and a seat 7 arranged on the latter. The base C comprises a lower part 4, a two-part middle part 5a, 5b and a two-part upper part 6a, 6b. The lower part 4 comprises a base 75 with wheels W, a height adjustment device 12 and a carrier 76 arranged on the latter. The carrier 76 has two carrying arms 76a and 76b, on which the middle parts 5a, 5b are arranged. On each of these two middle parts 5a, 5b is articulated one of the upper parts 6a, 6b (see also FIGS. 7b and 7c). The two upper parts 6a, 6b carry the seat 7. The seat 7 comprises a right carrier 77 and a left carrier 78 (see also FIG. 7c), and these carry a cloth covering B. The two carriers 77 and 78 have in each case an upper leg 77a and 78a and a lower leg 77b, 78b. These are connected in each case by means of at least two linking members 79, 80 (see also FIG. 7c).
In FIG. 7b, the piece of furniture 1 shown in FIG. 7a is illustrated in the nonloaded position I in a side view from the direction of an arrow IXb. This side view shows how the upper part 6b is guided on the middle part 5b via arms 31b and 32b. The upper part 6a is also guided correspondingly on the middle part 5a via arms 31a and 32ab (see FIG. 7a).
FIG. 7c illustrates the piece of furniture 1 without the cloth covering and without the height adjustment device and the base, once again in the nonloaded position I. It can be seen in this view that the upper parts 6a, 6b of the piece of furniture 1 are not connected to one another directly. In the exemplary embodiment illustrated, the carriers 77, 78, too, are connected to one another only by means of the cloth covering, not illustrated. According to design variants indicated by broken lines, the upper parts 6a, 6b and/or the carriers 77, 78 are connected by means of at least one flexible or rigid crossmember 81 or 82. Alternatively or additionally to this, there is also provision for connecting the upper part 6a and the carrier 78 and/or the upper part 6b and the carrier 79 via at least one diagonal crossmember. The upper legs 77a and 78a of the two carriers 77 and 78 are supported in each case with projections 22a and 22b on spring elements 20a, 20b of the two spring mechanisms SM, the spring elements 20a, 20b being designed as leaf springs 21a and 21b. 
FIG. 7d illustrates a sectional view, from a direction IXd shown in FIG. 7a, of the movement converter 41a formed between the middle part 5a and the upper part 6a, the piece of furniture 1 also standing in the nonloaded position I here. The middle part 5 is carried by the carrying arm 76a belonging to the lower part 4 and is screwed to said carrying arm via screws 83a, 83b. The upper part 6a is articulated movably upward and downward on the middle part 5a via the parallel arms 31a, 32a which are mounted rotatably with axes of rotation 33 to 36 on the upper part 6a and the middle part 5a respectively. The seat 7 is articulated rotatably on the upper part 6a via two axes of rotation 16 and 84. The seat 7 is articulated at the axis of rotation 16 via the upper leg 77a of the carrier 77 and at the axis of rotation 84 via the lower leg 77b of the carrier 77. Furthermore, the first spring element 20a is tension-mounted with a tension end 24a into the upper part 6a. The upper leg 77a of the right carrier 77 of the seat 7 bears with the projection 22a against a free end 23a of the leaf spring 21a. The seat 7 or the right carrier 77 is thereby cushioned on the first spring element 20a in a direction of rotation w. The leaf spring 21a is not only tension-mounted into the upper part 6a, but is supported in a middle region 85 against the upper part 6a by a support 25a when a person sitting on the seat reclines. In the nonloaded position I shown in FIG. 7d, there is an interspace 95 between the support 25a and the leaf spring 21a, and therefore these two components have no operative connection, so as not to brake a displacement of the support 25a taking place during a loading of the seat 7. This interspace 95 is achieved by means of a corresponding prestress or orientation and/or a corresponding shaping of the leaf spring 21a. The leaf spring 21a and the support 25a form a spring mechanism SM. The support 25a is arranged on a toothed slide 86 which is guided laterally displaceably in a guide 28a on the upper part 6a and forms an output body 86a. The toothed slide 86, or linear/curvilinear rack or gear, cooperates with a toothed quadrant 87, or rotary gear, which is fastened to the upper part 6a rotatably about an axis of rotation 88 and forms a drive body 87a. The toothed quadrant 87 has a slotted guide which is designed as a long hole 89. A pin 90 which is fastened to the middle part 5a engages into the long hole 89. The upper part 6a is guided on the arms 31a, 32a against a downwardly directed movement and is cushioned via a second spring element 37a. The second spring element 37a is designed as a leaf spring 91a and is held with a tension end 92a in the middle part 5a. The upper part 6a acts with a bolt 93a on a free end 94a of the leaf spring 91a. The leaf spring 91a and the arms 31a, 32a together form a weighing mechanism WM. A mechanical interlinking of the weighing mechanism WM and of the spring mechanism SM takes place by means of the movement converter 41a. When the seat 7 is loaded with a weight force, the upper part 6a, on which the seat 7 is supported, is cushioned on the second spring element 37a and in this case is lowered slightly with respect to the position I shown in FIG. 7d. Along with the upper part 6a, the toothed quadrant 87 is also moved downward, and the pin 90 fastened rigidly to the middle part 5a with respect to the upper part 6a causes a rotation of the toothed quadrant 87 about its axis of rotation 88 in the direction of rotation w. The rotating toothed quadrant 87, during its rotational movement, takes up, or meshes with, the toothed slide 86 and the support 25a fastened to the latter and transports or translates this support to the left in the direction of the free end 23a of the leaf spring 21. A spacing F1 between the support 25a and the projection 22a is thereby reduced (see FIG. 7d). This reduced spacing between the support 25a and the projection 22a then causes a greater cushioning of the seat 7 against an inclination movement of the seat 7 about the axes of rotation 16, as compared with the position shown in FIG. 7d, when the person sitting on the seat 7 reclines (see also FIG. 7f). A left movement converter 41b (see FIG. 7c) is designed similarly to the right movement converter 41a described above in detail. The piece of furniture 1 thus has a seat 7 which has two weighing mechanisms WM and two spring mechanisms SM which are connected in each case by means of a movement converter 41a, 41b. As a function of the position of a person sitting on the seat 7 of the piece of furniture 1, these two components are loaded proportionately with a weight force of the person and have corresponding reaction forces of the spring mechanisms SM against an inclination movement of the seat 7 directed in the direction of rotation w.
FIG. 7e again depicts, in an enlarged illustration, the right movement converter 41a shown in FIG. 7d, with the associated weighing mechanism WM and the associated spring mechanism SM, in the nonloaded position I. An illustration of the seat 7 and of the lower part 4 has been dispensed with here. Reference is made to the description relating to FIG. 7d. 
FIG. 7f then shows a position II in which the seat 7, not illustrated, is loaded with a weight force of a person sitting upright. In comparison with FIG. 7e, the rack 86 together with the support 25a of the spring mechanism SM has been displaced in the direction of the free end 23a of the leaf spring 21a. This displacement movement over the displacement distance V1 is the result of a weighing movement of the upper part 6a over a weighing distance W1, where, for example, W1=2.5×V1. A step-up of the weighing movement generated by the weighing mechanism WM thus takes place in the movement converter 41a. That is to say, even with a small weighing movement, a sensitive setting of the spring mechanism SM can be carried out on account of the step-up. The setting of the spring mechanism SM and consequently the counterforce against an inclination movement of the seat about the axis of rotation 16 are generated as a function of the weight force with which a person acts on the seat. The counterforce is set by the variation in the spacing between the support 25a and the projection, acting on the leaf spring 21a, of the seat 7. In the loading situation illustrated in FIG. 7f, too, there is still an interspace 96 between the support 25a and the leaf spring 21a, as long as the person sitting on the seat does not recline.
FIGS. 8a to 8c show once again in detail the weighing and inclination on a further structural unit consisting of the weighing mechanism WM, movement converter 41a and spring mechanism SM, the structural unit being modified slightly, as compared with FIGS. 7a to 7f. FIG. 8a shows a support 25a in a nonloaded position I of the piece of furniture. The seat, not illustrated, is cushioned via a projection 22a, symbolized by a triangle, on a first spring element 20a which is designed as a leaf spring 21a and which is tension-mounted on an upper part 6b between a lower counterbearing UG and an upper counterbearing OG. In the nonloaded position I illustrated, there is no operative connection between the support 25a and the leaf spring 21a. Instead, to avoid friction, a first interspace 95 having a thickness D95 is formed between the support 25a and the leaf spring 21. As soon as the seat part of the seat, not illustrated, is loaded by a person sitting down in an approximately upright sitting position, the support 25a moves under the leaf spring 21a into a position II shown in FIG. 8b. During this movement of the support 25a, there is no operative connection to the leaf spring 21a. As long as the person does not recline out of the upright sitting position, an interspace 96 having a thickness D96 is still maintained between the support 25a and the leaf spring 21a, although, under certain circumstances, the weight force of the person already acts in a small fraction on the leaf spring 21a via the projection 22a. Thus, while the person is sitting down and as long as the person remains seated in the upright sitting position, a very smooth and therefore rapid follow-up of the support 25a under the leaf spring 21a is still possible, since an interspace 95 is constantly present. This is advantageous, for example, when the person sitting upright subsequently increases his weight by grasping a heavy file and reclines with this. Owing to the rapid and smooth adjustability of the support 25a, the weight of the heavy file is detected for the counterforce to be generated, even before the person reclines. Cushioning which is too soft can thereby be avoided. An operative connection or contact between the support 25a and the leaf spring 21a occurs only when the person reclines out of his upright sitting position, since weight-dependent cushioning is required only for reclining. The increased and weight-dependent counterforce is generated, after a slight compression of the leaf spring 21a over a spring travel W96 (see FIG. 8b) corresponding to the thickness D96 of the second interspace 96, by the leaf spring 21a coming to lie on the support 25 (see FIG. 8c). The leaf spring 21a locks the support 25a under itself with a locking force LF and thus prevents a displacement of the support 25a until the person resumes an upright sitting position according to FIG. 1f or stands up. The contact thus occurring or operative connection thus occurring between the leaf spring 21a and the support 25a leads to an increase in the spring force which acts counter to the seat at the projection 22a of the latter. The support 25a then forms a second lower counterbearing UG2, the two lower counterbearings UG and UG2 having a spacing L2 with respect to one another (see FIG. 8a). This spacing L2 varies in proportion to the weight force of a person sitting on the piece of furniture. In position I, the lower counterbearing UG and the second lower counterbearing UG2 have a smaller spacing L1 with respect to one another.
FIG. 9a illustrates a further design variant of a piece of furniture 1 according to the invention. The piece of furniture 1 is designed as a piece of furniture 2 for sitting on or as a chair 3 and comprises a seat 7 which is arranged on a base C. The chair 3 is shown in a nonloaded position I. The base C comprises a lower part 4, a middle part 5 and an upper part 6. The middle part 5 is formed essentially by a housing 200 which is designed as a quiver 201 and is plugged in a bore 202 of the lower part 4. The upper part 6 comprises a carrier 203 for the seat 7 and is connected to the middle part 5 by means of a height adjustment device 12. The height adjustment device 12 comprises a settable spring AS designed as a pneumatic spring 204, an axial bearing 208 and a spring element designed as a helical spring 38. A pressure tube 205 of the pneumatic spring 204 is fastened in a known way in a bore 206 of the carrier 203. In addition to the pressure tube 205, the pneumatic spring 204 comprises a piston rod 207 which is guided in the pressure tube 205. The axial bearing 208 comprises an upper disk-shaped ring 209 and a lower pot-shaped ring 210 which has a collar 211. The axial bearing 208 is fastened to a free end 207a of the piston rod 207. The pneumatic spring 204 is supported via the collar 211 of the axial bearing 208 on a bottom 212 of the middle part 5 via the helical spring 38. Above the helical spring 38, the pneumatic spring 204 is guided slidably with its pressure tube 205 on the lower part 5. A weighing mechanism WM is thus formed between the middle part 5 and the upper part 6 by the height adjustment device 12. A movement converter 41 comprises a Bowden cable 213 and a lever mechanism LM designed as a lever 214. The Bowden cable 213 consists of a wire 215 and of a hose 216 in which the wire 215 is guided. The lever 214 is fastened to the upper part 6 or the carrier 203 rotatably about an axis of rotation 217. The lever 214 has a lower free end 214a and an upper free end 214b. On the upper free end 214b is formed a long hole 218 in which a support 25 is guided. The support 25 is movable on a sliding surface 219 of the carrier 203 under a spring element 20 designed as a leaf spring 21 in the direction of an arrow x′, the traveling movement being generated by a rotation of the lever 214 about its axis of rotation 217. The lower end 214a of the lever 214 is connected to the collar 211 of the lower ring 210 of the axial bearing 208 by means of the wire 215 of the Bowden cable 213. The housing 200 which forms the middle part 5 and the carrier 203 form in each case a counterbearing 220, 221 for the hose 216 in which the wire 215 is guided. During a loading of the seat 7, the lowering of the upper part 6 counter to the helical spring 38 leads, independently of a height setting preselected by means of the pneumatic spring 204, to a traveling movement of the support 25 in the direction of the arrow x′. The wire 215 of the Bowden cable 213 is drawn downward by the lower ring 210 of the axial bearing 208 in the direction of an arrow y′. The lower ring 210 of the axial bearing 208 forms a fastening device CD for the Bowden cable 213. After a relief of the seat 7, a spring 222 draws the lever 214 back again into the position shown in FIG. 9a. The leaf spring 21 and the support 25 form a spring mechanism SM. The distance over which the upper part 6 travels into the middle part 5 when the seat 7 is loaded by a person sitting down upright onto the seat 7 against the helical spring 38 is converted via the Bowden cable 213 and the lever 214 into a traveling movement of the support 25. The support 25 is thereby displaced under the leaf spring 21 as a function of the weight of the person sitting upright on the seat 7. The leaf spring 21 comes to lie on the support 25 only when the person sitting on the seat 7 reclines and generates an increased torque about a horizontal axis of rotation 16, via which the seat 7 is connected pivotably to the upper part 6. A torque which the person in the upright sitting position generates about the axis of rotation 16 is absorbed via a prestress of the leaf spring 21. This prevents the situation where the leaf spring 21 comes to lie on the support 25 before the latter has reached a position appropriate to the person's weight. An operating element A, which is connected to the Bowden cable 213 instead of the lower ring 210, is also illustrated as a design variant in FIG. 9a by broken lines. The operating element A allows a manual setting of the body weight of a person sitting on the piece of furniture 1. The operating element can be operated with minimal effort by a person sitting upright or bent forward on the piece of furniture 1.
FIG. 9b illustrates a view of a detail of the chair 3 shown in FIG. 9a. The view of a detail shows a design variant in which the seat 7 and the upper part 6 are connected by means of a toggle lever 223. The toggle lever 223 serves for absorbing the torque M which the person sitting in an upright sitting position on the seat 7 generates about the axis of rotation 16. The above-described prestress of the leaf spring 21 may thereby be largely dispensed with. The toggle lever 223 comprises an upper lever 224, which is articulated rotatably on the seat 7, and a lower lever 225, which is articulated rotatably on the upper part 6. The upper lever 224 and the lower lever 225 are connected to one another by means of a joint 226. The joint 226 forms an axis of rotation 227. A spring element 228, which is designed as a spring 228a, is connected to the joint 226 and draws the lower lever 224 of the toggle lever 223 against an abutment 229 which is fastened to the carrier 203. The toggle lever 223 is thereby brought into an approximately extended position. The abutment 229 is designed such that the levers 224 and 225 form with one another an angle α of about 175°. The toggle lever 223 consequently buckles only when the person reclines and therefore generates an increased torque about the axis of rotation 16. Owing to the choice of the angle α, at which the levers 224 and 225 stand in relation to one another, and/or to the choice of the spring force of the spring element 228 and/or to the arrangement of the toggle lever 223 between the seat 7 and the upper part 6, it is possible to adapt a blocking mechanism 230 to the special geometry of the chair 3. When the toggle lever 223 buckles as a result of loading, the leaf spring 21 assumes the support or cushioning of the seat 7. At the point in time when the toggle lever 223 buckles in the direction of an arrow x, the support 25 has already been displaced in the direction of the arrow x′ by the person according to the loading of the seat 7.
FIG. 9c illustrates once again the view, known from FIG. 9b, of a detail of the chair 3 shown in FIG. 9a. In contrast to FIG. 9b, the seat 7 is articulated on the upper part 6 via two additional levers 230 and 231. By means of the lever 231, a projection 22 with which the seat 7 lies on the leaf spring 21 is forced onto a circular path 233 predetermined by the lever 231.
FIGS. 10a-10d illustrate a design variant of the seat shown in FIGS. 7a to 7d, in which a weighing mechanism WM and a movement converter 41 are designed similarly to the chair shown in FIG. 9a. FIGS. 11a-11e illustrate another design variant of the body support structure, which also incorporates a height adjust device into the weighing mechanism.
FIGS. 10a and 11a shows a side view of a chair 3. The chair 3 comprises a base C and a seat 7. The base C comprises a lower part 4, which receives a middle part 5 in a bore 202, and an upper part 6, which is connected to the middle part 5 via a weighing mechanism WM designed as a height adjustment device 12. As shown in FIG. 11a, a weighing mechanism 312 is disposed between and connects the upper and lower parts 6,4. In the side view illustrated in FIG. 10a, a carrier 77 can be seen, which is articulated on the upper part 6 with an upper leg 77a rotatably about an axis of rotation 16 and rotatably with a lower leg 77b about an axis of rotation 84. As shown in FIG. 11a, upper leg 77a of the carrier is pivotally connected to the upper part with a pair of front links 316 and a pair of rear links 317. In one embodiment, the rear links 317 can be connected to the upper part at a plurality of locations, such that the orientation of the link 317 can be changed and optimized. In one embodiment, the links 316 are substantially vertical, and the links 317 have a vertical vector component, such that the links 316, 317, especially the front link 316, carry the load of the user when the user initially sits on the seat before recline, thereby permitting the weighing mechanism to work more efficiently. The links 316, 317 define the path of motion of the upper leg 77a of the carrier. The chair 3 also has a second carrier which is concealed by the first carrier 77 in the illustration of FIGS. 10a and 11a. As regards the arrangement of the second carrier, reference is made to FIG. 7c which shows a chair with a comparable construction. The seat 7 is formed essentially by the two carriers 77 and a body support member, configured in one embodiment as a cloth covering B, which bridges and connects the carriers 77.
The two legs 77a and 77b are connected to one another via a plurality of linking members 79. The two carriers 77 of the seat 7 are cushioned on the upper part 6 in each case via a spring mechanism SM. The seat 7 is rotatable together with the upper part 6 about a vertical axis of rotation 39 with respect to the middle part 5 and to the lower part 4. The weighing mechanism WM comprises a settable spring AS which is designed as a pneumatic spring 204, 304. The upper part 6 comprises a carrier 76 which is composed of two mirror-symmetrically designed carrying arms 76a, only one of the carrying arms 76a being visible in the illustration of FIGS. 10a and 11a. As regards the basic design, reference is made once again to FIG. 7c which shows a chair in which the carrying arm is of comparable design.
For the embodiment of FIGS. 10a-10e, of the movement converter 41, three Bowden cables 234a, 234b and 234c can be seen in FIG. 10a. Furthermore, the movement converter 41 comprises a coupling 235, by means of which the Bowden cables 234a, 234b and 234c are decoupled from a rotation of the upper part 6 with respect to the middle part 5. The coupling 235 is designed as a rotor system RS. As shown in the embodiment of FIG. 11a, only a single Bowden cable 234c is used.
FIGS. 10b and 11b show enlarged and slightly perspective illustrations of the chairs 3 shown in FIGS. 10a and 11a, in the region of the carrying arm 76a of the upper part 6. The carrying arm 76a consists of an upper leg 236 and of a lower leg 237. The two legs 236, 237 are connected rigidly to one another. The carrying arm 76a is fastened with a free end 238 of the lower leg 237 to a pressure tube 205 of the pneumatic spring 204 in FIG. 10a, and to the upper end of a cylindrical housing in FIGS. 11a-d. A spring element 20 is mounted in the upper leg 236 of the carrier 76a, and in one embodiment is configured as a leaf spring 21 on which the lower leg 77b of the carrier 77 is supported with an adaptor 239. In essence, the spring 21 is prestressed in bending. A link 361 is pivotally connected to the upper leg and to the adaptor 239, for example with pin 259 or at some other location. A cross member 363, or spreader, is further connected to the link 361 and spans between the laterally spaced carriers 77 so as to maintain a lateral distance therebetween and tension in the membrane secured to the carriers. An additional spreader 365 is connected between the opposite first links 316.
FIGS. 10c and 11c show a perspective view of the adaptor 239 of the lower leg 77b, the middle part 5 and all the components lying between these. For the sake of clarity, once again, of the upper part 6 with the carrying arm 76a, only one of the carrying arms is illustrated. When the upper part 6 is loaded via the seat, not illustrated, the upper part 6, together with the pneumatic spring 204, is compressed with respect to the middle part 5. In the embodiment of FIG. 10c, the rotor system RS comprises a lower ring 242, an upper ring 243 and an inner ring 243a. These are arranged on the pressure tube 205 of the pneumatic spring 204. The lower ring 242 is mounted on the pressure tube 205 rotatably about the longitudinal axis 39 of the latter and forms a counterbearing 244 for the hoses 241a and 241b of the Bowden cables 234a and 234b. The middle part 5 is designed as a housing 200 and forms a further counterbearing 246 for the hoses 241a and 241b of the Bowden cables 234a and 234b. The upper ring 243 is mounted on the pressure tube 205 rotatably about the longitudinal axis 39 of the latter and vertically displaceably in the direction of the longitudinal axis 39 or in the directions of the arrows y′ and y. The wires 240a and 240b of the lower Bowden cables 234a and 234b are fastened to the upper ring 243. The inner ring 243a is mounted in the upper ring 234 and is freely rotatable about the axis of rotation 39 with respect to the upper ring 234 and with respect to the pressure tube 205. A wire 240c of the upper Bowden cable 241c is fastened to the inner ring 243a. In a comparable way, a wire of a further upper Bowden cable, not illustrated, is fastened in a slit 234b of a tab 243c belonging to the inner ring 243a. This further upper Bowden cable, not illustrated, is connected to the second spring mechanism which is arranged on the second carrier, not illustrated. The movement converter 41 thus connects the weighing mechanism WM to two spring mechanisms SM, each of the two spring mechanisms SM assuming half the cushioning of an inclination movement of the seat 7 about the axis of rotation 16. The hose 241c of the upper Bowden cable 234c is supported on the lower leg 237 in the carrier arm 76a. During a rotation of the seat or of the upper part 6 in a direction of rotation v or v′ about the axis of rotation 39, the upper Bowden cables 234c rotate together with the pneumatic spring 204 and with the inner ring 243a fastened to the pressure tube 205. Due to the lower Bowden cables 234a and 234b connected to the stationary middle part 5, the rings 242 and 243 are held in their position shown in FIG. 10c. During a loading of the seat or of the upper part 6, the wires 240a and 240b are drawn downward in the direction of an arrow y′. These then draw the upper ring 243 onto the lower ring 242. The upper ring 243 takes up the inner ring 234a in the direction of the arrow y′.
The wire 240c of the Bowden cable 234c in FIGS. 10c and 11c, which connects the inner ring 243a and a first lever 248 of a toggle lever 249 in FIG. 10c and the plate 346 and lever 249 in FIG. 11c, thereby draws the first lever 248 in the direction of a lug 247 counter to the force of a spring 222. The lever 248 is mounted on the upper part rotatably about the axis of rotation 16 of the seat. A second lever 250 of the toggle lever 249 is connected to a support 25 rotatably about an axis of rotation 251. The support 25 is fastened to the second lever 250 via a shaft 252 and is guided in the upper leg 236 of the upper part 6 beneath the leaf spring 21. For this purpose, the upper leg 236 has a long hole 253. The two levers 248 and 250 are connected to one another rotatably about an axis of rotation 255 by means of a pin 254. During the loading of the seat, the support 25 is therefore displaced in the direction of an arrow x′. With reference to FIG. 10c, when the seat is relieved and the upper ring 243 is thereby released by the Bowden cables 234a and 234b, or with respect to FIG. 11c the cable 234c is released, the spring 222 presses the first lever 248 of the toggle lever 249 back again into the position shown in FIG. 10c. During this rotational movement of the first lever 248 about the axis of rotation 16, the support 25 is also drawn back in the direction of an arrow x. The upper ring 243 is simultaneously raised again via the wire 240c of the Bowden cable 241c into the position shown in FIG. 10c. It can be seen clearly in FIGS. 10c and 11c how the upper leg 236 and the lower leg 237 of the carrying arm 76a are welded to one another by means of a triangular steel plate 256 so as to form a unit.
Referring to FIGS. 10c and 11c, arranged mirror-symmetrically to a contact surface 257 of the carrying arm 76a is the abovementioned second carrying arm which carries the abovementioned second carrier. A bar 258, only half of which is illustrated, connects the carrying arm 76a to the carrying arm not illustrated. The lower leg, not illustrated in FIG. 10c or 11c, of the carrier is articulated on the upper part 6 rotatably about the axis of rotation 84 by means of the adaptor 239 and is cushioned on the leaf spring 21 via a bolt 259. Depending on the design of the seat or of the carriers, the bolt 259 may be installed in the adaptor 239 in four different positions 260a to 260d. As long as the seat is loaded by a person sitting upright, the support 25 is displaceably under the leaf spring 21, without the support 25 touching the leaf spring 21. This is achieved by means of a prestress of the leaf spring 21 which can be set via screws 261a and 261b. 
FIG. 10d, then, shows the weighing mechanism WM and the movement converter 41 in a sectional view, a hatching of the parts shown in section having been dispensed with so as to keep the illustration clearer. The weighing mechanism WM comprises the pneumatic spring with a piston rod 207 guided in the pressure tube 205, an axial bearing 208, a cup 262 and a helical spring 38. The cup 262 is supported with a collar 263 on the helical spring 38, and the pneumatic spring 204 stands on the axial bearing 208 in the cup 262, the piston rod 207 of the pneumatic spring 204 penetrating through a bottom 264 of the cup 262, and the axial bearing. 208 being fastened to a free end 265 of the piston rod 207. The axial bearing 208 allows a free rotatability of the pneumatic spring 204 and of the upper part 6 fastened to the latter, together with the seat, not illustrated, about the axis of rotation 39. The pneumatic spring 204 is guided rotatably with its pressure tube 205, above the helical spring 38, in a housing 200 formed by the middle part 5. The collar 263 of the cup 262 has two slits 265a and 265b, in which the wires 240a and 240b of the Bowden cables 234a and 234b are suspended.
The slits 265a and 265b in each case form a device CD for fastening the Bowden cables 234a and 234b of the movement converter 41. By means of abutments 266a and 266b, the middle part 5 forms the counterbearing 246 for the hoses 241a and 241b of the Bowden cables 234a and 234b. A height adjustment of the pneumatic spring 204, in which the piston rod 207 moves further in the pressure tube 205 in the direction of the arrow y or moves further out of the pressure tube 205 in the direction of the arrow y′, is compensated by the S-shaped run of the Bowden cables 234a and 234b (see also FIG. 10c). During a loading of the seat by a person sitting down on the seat, the pneumatic spring 204 presses the cup 262 via the axial bearing 208 in the direction of the arrow y′ counter to the helical spring 38 and at the same is lowered, together with the cup 262, in the direction of the arrow y′. During this lowering movement, the cup 262 tightens the wires 240a and 240b of the Bowden cables 234a and 234b. The upper ring 243 is thereby drawn onto the lower ring 242 and the pull is transmitted to the Bowden cable 234c which is fastened to the inner ring 234a. The Bowden cable 234c then causes a displacement of the support 25 (see FIG. 10c). Since the rings 242 and 243 are mounted on the pressure tube 205 of the pneumatic spring 204 rotatably about the axis of rotation 39, they can maintain their position with respect to the middle part 5, even when the seat, the upper part 6 and the pneumatic spring 204 are multiply rotated about the vertical axis of rotation 39 on the axial bearing 208. The rings 242 and 243 thus act as free-running rotors.
FIGS. 11a-11e disclose a design variant of the weighing mechanism, which can be used with any of the previously described movement converters and spring mechanisms. In a broad sense, the weighing mechanism shown in FIGS. 11a-11e is achieved by turning the weighing mechanism of FIGS. 10a-10d, modified as noted below, upside down. This provides significant advantages as noted below.
The weighing mechanism WM includes a height adjustment device 312 configured with a pneumatic spring 304 having a pressure tube 346 and a piston rod 348 extending from the pressure tube. An annular fitting 350 is secured in the bottom of a cavity 352 formed in a lower base component 4. A lower end 356 of the pressure tube is non-rotatably connected to the annular fitting 350, and is thereby coupled to the lower base component 4. The term “coupled” as used herein means connected, whether directly or indirectly, for example with an intervening component. The lower base component 4 includes an upper annular hub 356 extending upwardly and a lower annular hub 358 extending downwardly. The annular fitting 350 is mounted in the lower annular hub 358. An annular recess 360 is formed between an interior wall of the lower component cavity 352 and the exterior surface of the pressure tube 346, and is shaped to receive the cylindrical wall of the housing 320 of the height adjustment device as the housing moves up and down relative to the lower base component 4. The housing 320 is moveably (translatably and rotatably) disposed around the pressure tube 346. An upper portion 366 of the housing is received and non-rotatably mounted in a cavity of the carrying arm, or upper base component 6, which in turn is coupled to the seat as described above. An annular, or tubular bearing support 362, includes an annular flange 364 that supports the bottom of the housing 320, and includes an interior cylindrical surface that is shaped to receive the pressure tube 346.
An adapter 322, configured as a cup, is supported on an axial bearing 344 coupled to the distal end of the piston rod 348, with an end of the rod and actuator button 370 extending through an opening 326 formed in the top of the cup. The cup includes an annular flange 330 configured along a bottom rim thereof. A weighing spring 328 is disposed in an annular cavity formed between the exterior surface of the adapter 322 and an interior surface of the housing 320. The weighing spring is preferably configured as a helical spring, but can alternatively be formed as a elastomeric spring, tension spring, torsion spring, leaf spring, or any other suitable type of spring. The weighing spring 322 is engaged with a bottom surface of the top of the housing, or a washer 342 or other bearing member disposed in the housing, and is further engaged with the annular flange 330 of the adapter.
The pneumatic spring 304 further includes an actuator button 370 extending upwardly from the distal end of the piston rod. The button can be moved between a release position, wherein the piston rod can be raised and lowered between a maximum and minimum height positions relative to the pressure tube. A plate 346 is connected to the top of the adapter, for example with a clip or nut engaging the piston rod and sandwiching the plate between the clip/nut and adapter. A lever arm 348, or actuator, includes a lip that engages a corresponding lip on the plate, such that the actuator 348 forms a lever pivotally connected to the plate 346 about a horizontal pivot axis, with the corresponding lips forming a hinge. A cable guide 380 is connected to the actuator, with the actuator coupled to and engaging the actuator button 370 intermediate the cable guide and the pivot axis. A cable 382, extending through the guide, is connected to the plate. To adjust the height of the seat, the user simply moves the cable 382, for example with a button, lever or other remote actuator accessible to the user, with the retraction of the cable 382 pivoting the actuator 346 about the pivot axis and thereby moving the button 370 to the release position. When in the release position, the gas cylinder 304 extends, thereby raising the seat to a desired height. The user then releases the cable 382, with the button 370 biasing the actuator about the pivot axis and thereby moving the pneumatic spring to a lock position. It should be understood that the cable and cable guide can be reversed, with the cable secured to the actuator and the guide secured to the plate.
As the piston rod 348 is extended and retracted relative to the pressure tube 346, and lower base component 4, the housing 320 moves within the recess 360 formed in the cavity of the lower base component. At a maximum height of the seat, or maximum extension of the piston rod, at least a portion of the housing 320 remains engaged with and/or disposed in the cavity 352 of the lower base component. This, in turn, provides for an improved aesthetic of the body support structure, with the housing 320 providing a uniform and monolithic column between the lower and upper base components 4, 6 for all height positions, rather than a two-stage appearance as shown for example in the embodiments of FIGS. 9a and 10a. 
Cable assembly 234c includes a cable 240c connected to the plate and a cable guide 388 connected to the upper base component, or carrying arm. It should be understood that in alternative embodiments, the plate 346 can be secured to the piston rod. In addition, the cable guide 388 can be secured directly to the adapter. It also should be understood that the connections of the cable 240c and cable guide 388 can be reversed, with the cable being secured to one of the carrying arm or adapter and the guide secured to the plate.
In operation, the user sits in the seat, with the weight of the user pushing the carrying arm/upper base component 6 and connected housing 320 downwardly against the biasing force of the weighing spring 328. As the carrying arm/upper base component and housing 320 moves relative to the adapter 322 and piston rod 348 and connected plate 346, the cable 240c is pulled relative to the cable guide 388, which draws the first lever 248 and adjusts the biasing force of the spring mechanism as described above.
In the embodiment of FIGS. 11a-11e, there is no need for a rotor system, and the accompanying, additional rings and cables. Rather, the adapter 322 and plate 346 are rotated with the housing 320 and upper base component 6, so as to maintain the alignment of the cable and cable guide for all rotation positions. In addition, there is no need for an excess length of cable to accommodate a height adjustment of the device, since both cables move with the upper base component.
The invention is not restricted to exemplary embodiments illustrated or described. On the contrary, it embraces developments of the invention within the scope of the claims.

## Claims

1. A body support structure comprising:
a body support member;
a base comprising an upper component coupled to said body support member and a lower component adapted to be supported on a floor;
an adjustable spring mechanism comprising a biasing spring biasing said body support member upwardly, said spring mechanism adjustable between at least a first and second biasing force; and
a weighing mechanism coupled to said adjustable spring mechanism, said weighing mechanism moveable between at least a first and second weighing position, wherein said spring mechanism is adjusted such that said biasing spring applies said first and second biasing forces as said weighing mechanism is moved between said first and second positions, wherein said weighing mechanism comprises a height adjustment device disposed between said upper and lower components of said base, said height adjustment device adjustable between at least a first and second height, wherein said height adjustment device comprises:
a pneumatic spring comprising a pressure tube coupled to said lower component and a piston rod extending upwardly from and moveable relative to said pressure tube;
a housing disposed around the pneumatic spring and coupled to said upper component;
an adapter coupled to said piston rod; and
a weighing spring separate from said biasing spring disposed between said adapter and said housing, said weighing spring supporting said housing, wherein said housing is moveable relative to said adapter between said first and second weighing positions.

2. The body support structure of claim 1 further comprising an axial bearing disposed between said adapter and said piston rod.

3. The body support structure of claim 1 wherein said weighing spring comprises a helical spring.

4. The body support structure of claim 1 further comprising a cable coupled between said weighing mechanism and said spring mechanism.

5. The body support structure of claim 4 wherein said cable is coupled to at least one of said piston rod and said adapter, and comprising a cable guide connected to one of said housing and said upper component, wherein said cable is moved relative to said cable guide as said housing is moved relative to said adapter.

6. The body support structure of claim 5 comprising a plate connected to said adapter, wherein said cable is coupled to said plate.

7. The body support structure of claim 6 further comprising an actuator button extending upwardly from said piston rod, wherein said actuator button is moveable between a release position and a lock position, an actuator connected to said button, and a cable connected between said actuator and said plate, said cable moveable between at least a first and second position so as to move said actuator button between said release and lock positions.

8. The body support structure of claim 1 wherein said adapter comprises a cup.

9. The body support member of claim 1 wherein said lower component comprises a cavity, and wherein said housing comprises an upper portion coupled to said upper component and a lower portion moveably disposed in said cavity.

10. The body support member of claim 9 wherein at least a portion of said pressure tube extends downwardly from said housing, wherein said downwardly extending portion is disposed in said cavity such that said pressure tube is not visible.

11. The body support member of claim 1 further comprising an actuator button extending upwardly from said piston rod, wherein said actuator button is moveable between a release position and a lock position.

12. A method of using a body support structure comprising:
supporting a lower component of a base on a floor;
positioning a user on a body support member coupled to an upper component of said base, wherein a height adjustment device is disposed between said upper and lower components of said base, said height adjustment device comprising a pneumatic spring comprising a pressure tube coupled to said lower component and a piston rod extending upwardly from and moveable relative to said pressure tube; a housing disposed around the pneumatic spring and coupled to said upper component; an adapter coupled to said piston rod; and a weighing spring disposed between said adapter and said housing;
moving said upper component relative to said lower component against a biasing force of said weighing spring in response to said positioning said user on said body support member;
adjusting a biasing force of a biasing spring in response to said movement of said upper component relative to said lower component against the biasing force of said weighing spring;
rotating said body support member relative to said lower component; and
applying a biasing force to body support member with said biasing spring as said body support member is rotated relative to said lower component.

13. The method of claim 12 wherein said adjusting said biasing force comprises moving a cable coupled to one of said adapter and said upper component relative to a cable guide coupled to the other of said adapter and said upper component.

14. The method of claim 13 wherein said cable is coupled to at least one of said piston rod and said adapter, and wherein said cable guide is connected to at least one of said housing and said upper component.

15. The method of claim 12 further comprising adjusting a height of said body support member by adjusting a length of said height adjustment device.

16. The method of claim 15 wherein said adjusting said height of said body support member comprises moving an actuator button extending upwardly from said piston rod from a lock position to a release position.

17. The method of claim 15 wherein said lower component comprises a cavity, and wherein said housing comprises an upper portion coupled to said upper component and a lower portion moveable relative to said lower component, wherein said adjusting a height of said body support member comprises adjusting a height of said body support member between a maximum height and a minimum height, wherein said lower portion is moveably disposed in said cavity as said body support member eat is moved between said maximum and minimum positions.

18. The method of claim 17 wherein at least a portion of said pressure tube extends downwardly from said housing, wherein said downwardly extending portion is disposed in said cavity, and wherein said pressure tube is not visible as said body support member is moved between said maximum and minimum positions.