EP0638265B1 - Office chair - Google Patents

Abstract

The invention relates to a chair (1), especially an office swivel chair, having a seat support (6) which is held upon a chair lower part (7) and which is pivotably connected to a seat (2) which is motionally coupled via a synchronising sliding guide (5) or suchlike synchronising mechanism to a back rest (3), the seat (2) being supported by a restoring device (5) acting against the pivoting-down movement. Characteristic of the chair (1) according to the invention is that the seat support (6) is movably guided on the chair lower part (7) approximately in the vertical direction, that the seat (2) is supported on the chair lower part (7) by means of the restoring device (5) and that there is provided within the movement-transmission path between backrest (3) and chair lower part (7) a device (14) for blocking and/or compensating the movement transmitted to the restoring device (5) during a pivoting-back movement of the backrest (3). The chair according to the invention, in which the restoring force of the backrest (3) is automatically adapted in dependence on the weight of the person using the chair and rises with increasing backrest inclination, is distinguished by its constructionally simple and compact design.

Description

The invention relates to an office chair with a seat support which is held on a lower part of the chair and which is pivotally connected to a seat which is coupled in motion with a backrest via a synchronous sliding guide or similar synchronous mechanism, the seat being supported by a restoring device acting counter to the pivoting movement .

In order to offer the person sitting on a chair good seating comfort, it is known in high-quality office chairs to connect the seat and the backrest in such a motion-coupled manner via a synchronous mechanism that an adjustment of the backrest also results in a dependent adjustment of the seat surface . This synchronous adjustment of the seat and backrest is intended to adapt the chair to the ergonomics of the user.

When adjusting the backrest of such office chairs, the leaning force of the user is opposed to the restoring force of a restoring device which at the same time supports the seat pivotably connected to a seat support against a pivoting movement. The restoring force counteracting the leaning force of the user must be carried out more strongly in large and heavy people as a result of the greater body weight and is to be additionally raised with increasing backward inclination of the backrest and a correspondingly longer lever arm, this increase in force also remaining dependent on the weight of the user .

In order not to burden the user with the adaptation of the reset device to his body weight and to avoid incorrect settings, various office chairs have already been created in which the adjustment of the restoring force to the leaning force of the user takes place automatically depending on their body weight.

An office chair is already known from the utility model DE-GM 86 14 185.6, the seat of which is connected via a front and rear parallelogram link to a stationary seat support which is attached to a lower part of the chair. The seat of this previously known office chair is coupled to the backrest via a synchronous mechanism consisting of further pivotable handlebar arms, in such a way that the seat is lowered more than the front when the backrest is adjusted out of its normal position and executes a movement following the backrest to the rear. The seat is supported by a return device acting against the pivoting movement, which consists of two return springs which are more or less biased according to the weight of the user. The return device and its return springs ensure that the movement of the backrest is coupled with it Synchronous movement of the seat runs more or less smoothly.

This previously known office chair has a relatively complicated mechanical structure, which is characterized by a large number of articulation points and movable handlebar arms in order to coordinate the movement sequence between the seat and the backrest.

A chair is already known from EP 0 259 609, the seat of which is also motion-coupled via a synchronous mechanism with a backrest. For this purpose, the seat of this previously known chair is connected at its front end via a swivel joint to a seat support which is held in an adjustable manner in the vertical direction on the standpipe of a lower seat part. The backrest and the seat are connected to each other on their mutually facing sides via molded hinges. A back support part is provided on the underside of the backrest, which is movably guided on the seat support via a rotary / sliding bearing. To return the seat to an upper position, the seat support has a torsion spring in the area of the swivel joint provided between it and the seat. This torsion spring, which acts as a restoring force, causes the seat to be adjusted upwards about the swivel joint when the adjustment mechanism is unlocked, while the backrest is simultaneously pivoted forwards about the hinges by connecting the back support part via the rotary / sliding bearing.
A particularly automatic adaptation of the restoring force to the body weight of the respective user is not provided in EP 0 259 609.

There is therefore the task of creating an office chair of the type mentioned, in which the restoring force of the backrest is automatically adjusted depending on the weight of the user and increases with increasing backrest inclination and which is nevertheless distinguished by a simple construction.

The solution to this problem according to the invention consists in the features of claim 1. In the office chair according to the invention, the seat is supported on the lower part of the chair by means of the reset device. The seat support, which is pivotally connected to the seat, is movably guided on this lower chair part in the vertical direction. If the weight of a user acts on the seat, the reset device provided for resetting the seat is prestressed. This bias of the return device does not affect the inclination of the backrest which is coupled to the seat because namely, the seat support can move slightly downward on the lower part of the chair according to the body weight of the user. Seat and backrest are coupled to one another in motion by a synchronous sliding guide or similar synchronous mechanism. When the leaning force of a user acting on the backrest decreases, the synchronous return movement of the backrest and seat is also ensured by the return device. Since the restoring device is simultaneously biased by the weight of the user, the restoring force of the backrest counteracting the leaning force as a counter-moment is automatically adapted to the weight of the user and increases with increasing backrest inclination. The resetting device of the office chair according to the invention therefore basically requires only one resetting spring or similar resetting force, even if several such resetting springs can of course be provided.

By means of a backrest adjustment, the leaning force applied when leaning back is incorporated into the movement transmission path of the chair according to the invention. Through this leaning force, the counteracting reset device is additionally biased beyond the user weight. In order to prevent springing back of the seat when the backrest is adjusted to the rear and thereby to avoid a loss of the weight-dependent pretension of the restoring device, a device for blocking and / or compensating the movement of the backrest onto the restoring device when the backrest is pivoted back is within the movement transmission path transferred movement provided.

It is expedient if the blocking device is effective in the transmission of movement between the seat support and the lower part of the chair and if the blocking device is used for one Swiveling backrest movement can be activated. The blocking device, which acts between the seat support and the lower part of the chair, counteracts lifting of the seat when the backrest is adjusted to the rear. The blocking device is already actuated at a comparatively low leaning force acting on the restoring device if the blocking device can be activated when the backrest is pivoted back. It is particularly advantageous if the blocking device is coupled to the synchronous sliding guide or the like synchronous mechanism.

According to a development according to the invention it is provided that the blocking device is designed as a preferably frictional braking device which is rigidly connected to the seat support and engages the lower part of the chair in its blocking position. A frictional braking device can be activated practically continuously and unnoticed by the user when the backrest is reset.

A preferred embodiment according to the invention, which additionally favors the comparatively low design outlay for the chair according to the invention, provides that the blocking device is a clamp or clamp which preferably engages around a part of the lower part of the chair projecting in a vertical direction and at least in its blocking position partially frictionally abuts this part of the lower part of the chair. So that the clamp or clamp clamps frictionally against the lower part of the chair when the user leans back, it is advantageous if at least on one of the two free clamp arms of the clamp is provided on the outside in particular a helical run-up slope, which has a corresponding counter-slope, which is preferably essentially immovably mounted in the axial direction cooperates, which is motion-coupled to the backrest. By a rotational movement of the rotatably mounted counter bevel, it slides on the run-up bevel, so that these bevel surfaces move away from each other in the axial direction. Since the counter bevel is immovably mounted in the axial direction, only the run-up bevel can deflect towards the opposite clamp arm of the clamp. As a result, the clamp arms of the clamp are pressed against each other, so that the clamping bracket rests frictionally on the lower part of the chair.

In order to be able to operate the clamp, other constructions are also conceivable with which the clamp arms can be pressed against one another. For example, an internal thread could be provided on at least one of the clamp arms, which interacts with the external thread of a rotatably mounted shaft. If such a shaft is rotated during a backrest adjustment, the clamp arms of the clamp are also moved towards or away from each other.

In order to be able to move the two clamp arms as evenly as possible relative to each other and to hold the clamp in its blocking position as firmly as possible on the lower part of the chair, it is advantageous if the clamp has a helical run-up slope on each of its two free clamp arms, if the two run-up slopes each have one in Counter-bevels mounted essentially immovably in the axial direction and if these inclined surfaces on the opposite sides of the clamp have a helical shape oriented in opposite directions of rotation.

The structurally simple and advantageous embodiment of the office chair according to the invention is additionally favored if the restoring device has a torsion spring as the restoring force which is arranged in the pivot axis between the seat and the seat support and if this torsion spring is held on the one hand in a rotationally fixed manner and on the other hand is connected in a rotationally fixed manner to a support lever which is supported at its free end region on the lower part of the chair. Such an embodiment, in which the torsion spring is arranged in the pivot axis between the seat and the seat support, permits a particularly compact construction of the office chair and its restoring device.

In order on the one hand to achieve a height adjustment of the chair according to the invention and on the other hand to ensure the deflection of the seat for the pretensioning of the spring element of the resetting device, it is expedient if the lower part of the chair is adjustable in height and if the lower part of the chair has two vertical guides with preferably two encompassing guide sleeves , of which a first guide sleeve of a gas pressure spring or the like height adjustment element and a second guide sleeve is assigned to the seat support.

Further features of the invention result from the following description of an exemplary embodiment according to the invention in conjunction with the claims and the drawing. The individual features can be implemented individually or in groups in one embodiment according to the invention.

Fig.1

einen Bürostuhl mit Synchronverstellmechanik, bei dem die Rückstellkraft der Rückenlehne automatisch in Abhängigkeit des Gewichts der Benutzerperson angepaßt wird und mit zunehmender Rückenlehnenneigung ansteigt, wobei der Bürostuhl im Bereich seines Unterbaus entlang seiner Längsmittelachse aufgeschnitten dargestellt ist,

Fig.2

den Stuhl aus Fig.1 in einem Teil-Querschnitt durch seinen Stuhl-Unterbau,

Fig.3

eine Blockiereinrichtung des Bürostuhls aus Fig.1 und 2 in einer schematischen Darstellung und

Fig.4

eine Rückstelleinrichtung des Bürostuhls aus den Figuren 1 bis 3 im Bereich ihrer Torsionsfeder, wobei die Rückstelleinrichtung hier ebenfalls nur schematisch dargestellt ist.

It shows:

Fig. 1

an office chair with synchronous adjustment mechanism, in which the restoring force of the backrest is automatically adjusted as a function of the weight of the user and increases with increasing backrest inclination, the office chair being shown cut open along its longitudinal central axis in the region of its base,

Fig. 2

the chair of Figure 1 in a partial cross section through its chair base,

Fig. 3

a blocking device of the office chair from Figures 1 and 2 in a schematic representation and

Fig. 4

a reset device of the office chair from Figures 1 to 3 in the area of its torsion spring, the reset device is also shown here only schematically.

In Fig.1 an office swivel chair is shown, the seat of which is formed by a seat 2 and a backrest 3. The seat 2 and the backrest 3 connected to it via the joint 4 are coupled to one another via a synchronous sliding guide 5 in such a way that an adjustment of the backrest 3 at the same time also results in an adjustment of the seat 2 which is dependent thereon. Such a synchronous adjustment of seat 2 and backrest 3 is intended to adapt the chair 1 to the ergonomics of the user.

The seat 2 is pivotally connected in the front area of its underside to a seat support 6, which in turn is guided in a vertical direction on a lower chair part 7. The seat 2, which is pivotally connected to the seat support 6, is supported on the lower part of the chair 7 by a restoring device 8 acting counter to the pivoting movement of the seat 2. For this purpose, the resetting device has a torsion spring 9 as resetting force, which is arranged compactly in the pivot axis between seat 2 and seat support 6 and exerts a force directed in the direction of rotation M _V on the seat. The torsion spring 9 shown in more detail below is held on the one hand in a rotationally fixed manner on the seat 2 and on the other hand is connected in a rotationally fixed manner to a support lever 10 which with its free end portion applied to the chair base 7.

If the seat 2 is acted upon by the body weight F _{G of} a user, the reset device 8 provided for resetting the seat 2 is prestressed. This prestressing of the resetting device 8 does not affect the inclination of the backrest 3, which is coupled to the seat 2 in terms of movement, because the seat support 6 can deflect slightly downward on the chair lower part 7 in accordance with the body weight of the user. Since the restoring device 8 is biased by the weight of the user, the restoring force F _{R of} the backrest 3 which counteracts the leaning force as a counter-moment is also automatically adapted to the weight of the user and increases with increasing backrest inclination. When the leaning force exerted by a user on the backrest 3 decreases, the synchronous return movement of the backrest 3 and seat 2 via the synchronous sliding guide 5 is also ensured by the resetting device 8. The resetting device 8 of the office chair 1 therefore basically needs a torsion spring or similar resetting force.

As shown in FIG. 1, the backrest 3 is connected to a backrest support 11 which is displaceably guided in the synchronous sliding guide 5 and is designed here as a lumbar support. For this purpose, the synchronous sliding guide 5 has an elongated hole 12 on both sides in the approximately V-shaped seat support 6 in plan view, these elongated holes 12 being penetrated by a continuous axis 13 which is firmly connected to the backrest support 11.

The backrest force applied when leaning back is incorporated into the movement transmission path of the chair 1 by means of a backrest adjustment. Through this leaning force it counteracts Reset device 8 additionally biased beyond the user weight. The bias of the reset device 8 is thus greater than the weight of the user. In order to avoid springing back of the seat 2 and lifting the seat support 6 on the lower chair part 7 and to counteract the loss of the weight-dependent pretension in the resetting device 8, a device 14 for blocking the movement of the backrest 3 and the lower chair part 7 is within the movement transmission path the backrest 3 provided on the return device 8 movement. The blocking device 14 is coupled to the synchronous sliding guide 5 and can be activated when the backrest is pivoted back.

The structure of the blocking device 14 is clear from FIG. 1 in connection with FIG. The blocking device 14 is designed as a frictional and thus stepless braking device and acts on the chair lower part 7 in its blocking position. The blocking device 14 has a clamp or clamp 15 with two clamp arms 16, 17 which are angled outwards and arranged approximately parallel to one another. The clamp 15 has on its two free clamp arms 16, 17 each a helical run-up slope 18, each of these run-up slopes 18 being assigned a counter slope 19 which is essentially immovably mounted in the axial direction. The inclined surfaces formed by the run-up bevels 18 and counter-bevels 19 are helically shaped on the opposite sides of the clamp 15 in opposite directions of rotation.

The run-up slopes 18 each have a central opening 20 which passes through an axis 21. Clamp levers 22 are provided on the two free end regions of the axis 21. The counter bevels 19, the clamping levers 22 and the axis 21 are non-rotatably connected. The clamping levers 22 each have an elongated hole 23 on their end region facing away from the axis 21, these elongated holes 23 being penetrated by the axis 13 of the synchronous sliding guide 5.

If the backrest 3 is now moved backwards, the relative position of the seat 2 is simultaneously changed via the synchronous sliding guide 5. Since the clamping levers 22 engage the axis 13 of the synchronous sliding guide 5, the blocking device 14 is also activated when the backrest 3 is pivoted back. The pivoting movement also moves the axis 13 connected to it via the backrest support 11 so that the clamping levers 22 rotatably mounted about the axis 21 pivot forward. As a result of this rotary or pivoting movement of the clamping levers 22, the counter bevels 19 connected to them in a rotationally fixed manner slide on the run-up bevels 18. The corresponding helical shape of these inclined surfaces and the essentially immovable mounting of the counter bevels 19 in the axial direction cause the ramp bevels 18 and the clamp arms 16, 17 of the clamp 15 connected in one piece with them to be able to move towards one another. This movement of the clamp arms 16, 17 reduces the circumference delimited by the circular partial region of the clamp 15, so that the clamp 15 comes into frictional engagement with the lower part 7 of the chair.

The lower part of the chair 7 is adjustable in height. From Figure 1 it is clear that the lower chair part 7 has two superimposed vertical guides with two encompassing guide sleeves 24, 25, of which a first guide sleeve 24 is assigned to a gas pressure spring 26 and a second guide sleeve 25 is fixedly connected to the seat support 6; in this second guide sleeve 25, the clamping bracket 15 is also immovably inserted in the vertical direction. The cylinder 27 of the rotatably mounted gas pressure spring 26 projects upwards the first guide sleeve 24. The clamp 15 engages on this protruding portion of the vertical gas pressure spring 26, while the support lever 10 is supported on the upper end face of the cylinder 27.

The structure of the reset device is clear from Figures 2 and 4. 4 shows, the torsion spring 9 has a torsion bar 28 with an angular, here hexagonal, cross-section. A tubular sleeve 29, 30, which also has an angular or hexagonal outer contour, is pushed onto the torsion bar 28 on both sides. The tube sleeves 29, 30 each have an outer end region that is round in the outer contour. The clear inner circumference of these outer end regions of the tubular sleeves 29, 30 is adapted in shape to the outer circumference of the torsion bar 28, so that the tubular sleeves 29, 30, which are pushed onto the torsion bar 28 on both sides, are non-rotatably connected to the latter.

The tubular sleeves 29, 30 are each supported on their outer round end regions in a bearing bush 31, 32 provided on the underside of the seat 2. While the tubular sleeve 29 on the right in FIG. 4 is held in a rotationally fixed manner at its opposite inner end region in a central bearing bush 33 with a clear cross section adapted to the outer circumference of the tubular sleeve 29, the tubular sleeve 30 on the left in FIG. 4 is rotatably connected to the support lever 10.

The weight F _{G of} the person located on the seat 2 is thus transmitted to the torsion bar 28 via the bearing bush 33, which is connected in a rotationally fixed manner to the tubular sleeve 29, and continues from there via the tubular sleeve 30 to the support lever 10, which is connected in a rotationally fixed manner. This support lever 10 is rotatably connected to the tubular sleeve 30 and is supported on the upper end face of the cylinder 27 of the gas pressure spring 26, which protrudes inside the guide sleeve 25 over the guide sleeve 24.
The office swivel chair shown here is characterized by a structurally simple and compact design.

Claims (11)

1. A chair, particularly an office chair, comprising a seat support (6) which is held on a lower chair part (7), is guided thereon so as to be movable in an approximately vertical direction and is joined in a swivelling fashion to a seat (2) movably coupled with a backrest (3) by means of a synchronizing sliding guide (5) or by a similar synchronizing mechanism, whereby the seat (2) is supported at the lower chair part (7) by a readjusting apparatus acting in opposition to the swinging movement, and whereby there is provided within the movement transmission path between backrest (3) and lower chair part (7) an apparatus (14) for blocking and/or compensating for the movement transmitted to the readjusting apparatus (8) during a backward swivelling movement of the backrest (3).
2. A chair as claimed in claim 1, characterized in that the blocking apparatus (14) is active in the transmission of movement between seat support (6) and lower chair part (7), and that the blocking apparatus (14) is activable during a backward swivelling movement of the backrest (3).
3. A chair as claimed in claim 1 or claim 2, characterized in that the blocking apparatus (14) is coupled with the synchronizing sliding guide (5).
4. A chair as claimed in any one of claims 1 to 3, characterized in that the blocking apparatus (14) is configured as a braking device, preferably engaged frictionally, that is rigidly joined to the seat support (6) and that, in its blocking position (14), engages with the lower chair part (7).
5. A chair as claimed in any one of claims 1 to 4, characterized in that the blocking apparatus (14) is a clamping collar or clamping shackle (15) that preferably encompasses an approximately vertically protruding section of the lower chair part (7) and, in its blocking position, lies at least in some regions in frictional engagement against said section of the lower chair part (7).
6. A chair as claimed in any one of claims 1 to 5, characterized in that at least one of the two free collar arms (16, 17) of the collar clamp (15) is provided on the outside with a ramp bevel (18), particularly helical in shape, that cooperates with a corresponding matching bevel (19) which is preferably supported so as to be essentially immovable in the axial direction and is movably coupled with the backrest (3).
7. A chair as claimed in any one of claims 1 to 6, characterized in that each of the two free collar arms (16, 17) of the clamping collar (15) has a helical ramp bevel (18), that each of the ramp bevels (18) has an associated matching bevel (19) supported essentially immovably in the axial direction, and that said bevel surfaces on opposite sides of the clamping collar have helical shapes oriented in opposite directions of rotation.
8. A chair as claimed in any one of claims 1 to 76, characterized in that the backrest (3) is joined with a backrest support (11) guided in an adjustable fashion in the synchronizing sliding guide (5), that the backrest support (11) is joined to at least one clamping lever (22) swivel-mounted in the common axis of rotation (21) of the matching bevels (19), and that associated to each clamping lever (22) is a matching bevel (19) non-rotatably connected thereto.
9. A chair as claimed in any one of claims 1 to 8, characterized in that the readjusting apparatus (5) has arranged in the swivel axis between seat (2) and seat support (6) a torsion bar (9) as restoring force, that said torsion bar (9) is on the one hand non-rotatably held at the seat (2) and on the other is non-rotatably connected to a support lever (10), said support lever (10) being supported in the region of its free end at the lower chair part (7).
10. A chair as claimed in any one of claims 1 to 9, characterized in that the lower chair part (7) is adjustable in height and for that purpose has two vertical guides with preferably two enclosing guide bushings (24, 25), of which a first guide bushing (24) is associated with a gas pressure spring (26) or similar height adjustment element, and a second guide bushing (25) is associated with the seat support (6).
11. A chair as claimed in any one of claims 1 to 10, characterized in that in its clamping position the clamping collar or clamping shackle (15) engages with the height adjustment element (26) at the upper section thereof projecting above the first guide bushing (24).

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