GB2512461A - Mechanism for an office chair - Google Patents

Abstract

A mechanism to allow pivoting of a back rest on an office chair wherein an adjusting device is provided for adjusting the pivoting resistance and wherein the adjusting device is actuated by an electromotive drive 7. The mechanism may employ a spindle 8 and a spring 9 to make adjustments to the tension. A control device 14 may adjust the mechanism based on a measured characteristic of a user of the chair. This may take the form of a weight sensor 13 which can measure the position or weight distribution of a user on a seat 10.

Description

Mechanism for an office chair The invention relates to a mechanism for an office chair.

Numerous techniques for changing the movement characteristic of an office chair mechanism are known

from the prior art. The movement is generally a

pivoting movement. Depending on the mechanism used, it may be for example a combined synchronous seat/backrest movement or an asynchronous seat/backrest movement.

Other movements that are realizable by an office chair mechanism are for example the adjustment of the seat inclination independently of the backrest inclination or the adjustment of the backrest inclination independently of the seat inclination.

An adjusting device for changing the movement characteristic of the mechanism frequently comprises in this case one or more spring arrangements (for example in the form of a pluralicy of compression or tension springs connected in parallel) and associated setting mechanisms (worm gears, gear wheels, threaded rods etc.). If, for example, the pivoting resistance of the backrest of an office chair is intended to be changed, the tension of the spring elements is usually changed with the aid of a manually operable actuating element, for example a handle or crank, and thus a setting between "hard" and "soft" is selected, depending on whether the user of the office chair is a heavy or light person.

Changing the movement characteristic of the office chair mechanism, in particular for example the pivoting resistance of the backrest, is in this case often associated with the exertion of a comparatively high force.

It is an object of the present invention to simplify the manipulation of an adjusting device for changing the movement characteristic of an office chair.

This object is achieved by a mechanism according to Claim 1. Advantageous refinements of the invention are specified in the dependent claims.

It is a core idea of the invention to use an electromotive drive to actuate the adjusting device. As a result, the manipulation of the adjusting device is considerably simplified, since manual operation of an actuating element, associated with the exertion of a comparatively high force, is no longer reguired.

Instead, the user can manipulate the adjusting device without physical effort.

In addition, the use cf an electromotive drive for actuating the adjusting device opens up a multiplicity of further options for improving the office chair mechanism, in particular in connection with changing the movement characteristic of the mechanism. Thils, the movement characteristic can be adapted, for example automatically and without the user being involved, to particular properties of the user and/or to the user's behaviour, as is explained in more detail further below.

In an embodiment of the invention, the mechanism comprises an actuating element for actuating the adjusting device. !I!his actuating element is connected to the electromotive drive and is driveable by the electromotive drive. In a very simple case, the actuating element is a spindle. The actuating element is connected to the drive preferably directly, that is to say without interposition of an additional component. Complicated setting mechanisms, such as worm gears, gear wheels, threaded rods etc., are not necessary as a nile. Therefore, the number of components and the manufacturing costs are particularly low.

In an embodiment of the invention, the adjusting device comprises a spring arrangement having at least one spring element, wherein the spring arrangement is operatively connected to a backrest support of the office chair and determines the pivoting resistance of the backrest support in the event of pivoting from a starting position into a pivoted position. In this case, the actuating element is configured to change the tension of the at least one spring element and/or to change the spring rate (also called spring sriffness, spring hardness or spring constant) of the spring arrangement -The spring arrangement operatively connected to the backrest support of the office chair can be connected either directly or indirectly to the backrest support.

In the event of indirect connection, the spring arrangement is connected to the backrest support preferably via the seat support as coupling element.

The specific structural embodiment is dependent on the construction of the office chair and the type of mechanism (synchronous mechanism, asynchronous mechanism) By way of the actuating element, in partidillar by way of a change in position of the actuating elenent, for example a movement of the actuating element in translation or rotation, the tension of the at least one spring element and/or the spring rate of the spring arrangement is changed. For the purposes of the present invention, any desired types of spring element can be used in the spring arrangement. Helical springs in the form of leg springs, helical compression springs or helical tension springs have proven parricularly advantageous on a000llnt of their simplicity and robustness.

In this case, it is left to the specific configuration of the mechanism as to whether one or more spring elements are tensioned or relaxed when the pretensioning of the spring arrangement is set. In other words, for example, on the one hand a spring element which is completely or partially relaxed in the unloaded state of the office chair can be tensioned in the event of loading, or on the other hand a spring element which is maximally or partially pretensioned in the rest state relaxes when the office chair is loaded.

However, active forcing of the mechanism counter to the movement of the backrest by a number of already pretensioned spring elements preferably already takes place even when the seat support is not loaded by a user. It is likewise left to the specific embodiment of the invention as to whether the spring rate of one or more spring elements is changed and how the change of the spring rates takes place.

The pretensioning of individual spring elements and the spring rate of the spring arrangement can be set fundamentally in two different manners. Firstly, it is possible to change the position of at least one spring end of a spring element of the spring arrangenent with the overall position of the spring element staying the same or changing. This can take place for example by the spring ends of a helical spring being pulled apart or pushed together or by rotation or deflection of one spring leg of a leg spring towards the other spring leg or relative to the other spring leg, about the spring longitudinal axis extending through the spring midpoint, Secondly, it is possible to change the position of the spring element itself relative to its fixed or likewise at least partially movable spring ends. In the case of a leg spring, this can take place for example by displacement of the spring midpoint of the leg spring, when the bearing points are fixed.

Depending on the requirements placed on the structure of the seat mechanism, both variants of spring setting can be realized in the case of the invention. In order to change the spring rate of the spring arrangement, it is also possible for example to change the number of spring elements that act in the spring arrangement.

The invention is not limited to the use of a spring arrangement for changing the movement characceristic.

Instead of a spring arrangement, the adjusting device for changing the movement characteristic may also comprise other components. Thus, for example, instead of a spring arrangement, a variable cam mechanism can be used. What is essential is that the adjusting device or the actuating element of the adjusting devioe is actuated by an electromotive drive.

In a simple embodiment of the invention, the adjusting device is actuated by the electromotive drive in that the drive is operated by the user, in particular switched on and off. However, an embodiment of the invention in which the movement characteristic is changed automatically and without the user being involved has proved to be particularly advantageous.

In such an embodiment of the invention, the mechanism preferably comprises at least one measuring device for detecting at least one user-dependent measured value and also an evaluation and control unit for evaluating the measurement result and for controlling the electromotive drive depending on the measurement result. In other words, the electromotive drive of the adjusting device is controlled on the basis of measured values which are detected in direct temporal conjunction with the use of the office chair. As a result, an individual movement characteristic, matched to the user, of the office chair mechanism is settable.

For this purpose, in an embodiment of the invention, the evaluation and control unit comprises a microcontroller or some other computing unit suitable for data processing, and a memory in which a characteristic curve is stored. With the aid of the characteristic curve, particular control values for controlling the adjusting device are assigned to possible measured values. For example, defined spring-force settings are assigned to various user weights. In this case, it may be a conventional linear characteristic curve or a non-linear characteristic curve. Taking the actually determined measured values into account, the evaluation and control unit selects, from the characteristic curve defining the movement characteristic of the mechanism, the associated control values according to which the electromotive drive is subseguently controlled. To this end, a corresponding control signal is generated which causes the electric motor to move to a position associated with the control signal.

In an embodiment of the invention, different characteristic curves are stored in the evaluation and control unit. In this case, it is advantageous for automatic selection of a characteristic curve which is suitable for the current user or is preferred to take place. A suitable characteristic curve is selected for example on the basis of the results of the measurements of the measuring device that are taking place. A preferred characteristic curve is selected for example on the basis of identification of the current user. In another variant, the user has the possibility of selecting a particular characteristic curve.

In a preferred embodiment of the invention, the measuring device and the evaluation and control unit are configured to continuously measure, evaluate and control. In this oase, not only user-individual control of the drive can take place but also continuous control of the drive which is thus matched dynamically to the current, actual loading of the chair. If a plurality of oharacteristic ourves are available for selection, it is also possible in this case to change the characteristic curve if the evaluation of the measurement results reveals that the currently used characteristic curve is providing a movement characteristic which is nor optimal for the user.

As an alternative to a continuous mode of operation, the mechanism may also be configured such that the setting of the movement characteristic, for example the setting of the spring force for pivoting the backrest, takes place once, when the user sits down on the seat of the office chair. The setting is then initiated preferably by the actuation of an operating clement by the user, for example by the actuation of a button or the like. However, the one-time setting of the movement characteristic can also be initiated automatically when the user sits down on the seat.

In an errbodiment of the invention, the at least one measuring device comprises a device for measuring the weight of a user sitting on the office chair. In a further embodiment of the invention, the at least one measuring device, alternatively or additionally to measuring the weight, comprises a device for detecting the weight distribution and/or for detecting the position of the user on the seat of the office chair.

The selection of the control values, suitable for the user, for controlling the electromotive drive with the aid of the characteristic curve then takes place preferably both with the weight of the user being taken into account and with the weight distribution of the user on the seat of the offioe ohair, and thus his sitting position, being taken into aocount. In other words, the mechanism is set preferably automatically depending on the weight, the weight distribution and/or the position of the user. As a result, an optimal movement characteristic can be selected from ergonomio points of view.

It is particularly advantageous if, in addition to the movement characteristic, Influenced by the evaluation and control unit, of the office chair, selected control values for controlling the electromotive drive are settable by the user in advance on the chair, or on the mechanism, and/or are manually changeable subsequently, or while sitting. As a result, for example a movement characteristic that is perceived to be uncomfortable can be altered by the user. If the user wishes to operate the electromotive drive and/or the evaluation and control unit, the drive or the evaluation and control unit can be operated preferably with the aid of suitable operating elements, for example buttons and/or touch-sensitive surfaces.

The device for measuring the weight of the user is preferably at least one force sensor or the like, which is advantageously installed under the seat of the office chair. In order to measure the weight of the user, it is also possible to provide a plurality of force sensors or the like that are arranged in a spaced-apart manner.

The device for detecting the weight distribution is preferably a number of force sensors or the like, which are arranged in a spaced-apart manner. If both the weight and the weight distribution are intended to be detected, both devices advantageously make use of the same sensors.

The device for detecting the position of the user is advantageously a device which has recourse to the measurement data of the weight distribution and determines the position of the user therefrom. However, the device for detecting the position of the user may also, independently of the force sensors or pressure sensors which may already be present, be a number of touch sensors arranged in or on the seat, wherein these touch sensors react for example to mechanical contacts and/or temperature fluctuations brought about by the user.

In principle, no limits are placed on the type of sensors and measuring devices that are used. What is essential is that the measuring devices used provide measured values that are dependent on the individual user of the office chair and are relevant for changing the movement characteristic of the mechanism in a user-individual manner.

Thus, by way of the invention, a system for changing the movement characteristic of an office chair mechanism, in particular for example for changing the pivoting resistance of the backrest of an office chair, is created, said system being set without the user being involved and differing from the systems known from the prior art in that the movement characceristic, in particular for example the pivoting resistance, is primarily not set arbitrarily by the hand of the user, but automatically and in accordance with the

specifications of the mechanism, in particular in

accordance with the control unit of the mechanism and the calculations that take place there or the characteristic curves stored there. It is primarily advantageous in this case that it is possible to change -1_c -the movement characteristic, in particular for example the pivoting resistanoe, in a particularly simple, reliable and safe manner. The movement oharacteristio oan in this case not only be set in dependence on the weight of the user but also in dependence on the sitting behaviour of the user.

The invention can be used in numerous office chair meohanisms, irrespective of whether it is a synchronous or asynchronous or some other form of mechanism.

An exemplary embodiment of the invention is explained in more detail in the following text with reference to the drawings, in which: Fig. 1 shows a highly simplified schematic illustration of an office chair mechanism, Fig. 2 shows a more detailed schematic illustration of an office chair mechanism, Fig. 3-6 show further application exampes for electromotive drives in office chair mechanisms.

All of the figures show the invention not true to scale, and in the process merely schematically and only with the essential constituent parts. Identical reference signs correspond in this case to elements having an identical or comparable function.

As is illustrated in Fig. 1 and 2, the office chair mechanism 1 has a base support 2 which is connected to the upper end of a chair column (not depicted) . The mechanism 1 furthermore comprises a subsantially frame-like seat support 3 and a backrest support 4, which is fork-shaped in plan view and the side pieces -1_i - (not depicted) of which are typically arranged on either side of the base support 2.

Mounted on the seat support 3 is the seat 10, which is provided with an upholstered sitting surface. Fitted on the backrest support 4 is a backrest (not illustrated in more detail), which is height-adjustable in modern office chairs. The backrest can also be connected integrally to the backrest support 4.

It is obvious that such a description of the nechanism 1 serves merely to identify the essential structural components. A person skilled in the art is familiar with the further structure of an office chair mechanism.

The mechanism 1 comprises an adjusting device 6 for changing its movement characteristic. In order to actuate the adjusting device 6, an electromotive drive 7 is used. This is, for example, a commercially customary electric motor having a gear mechanism, which is operated via a mains connection or by batteries or rechargeable batteries.

The mechanism 1 comprises an actuating element in the form of a spindle 8 for actuating the adjusting device 6. The spindle 8 is directly connected to the electric motor 7 and is driveable by the electric motor 7.

The adjusting device 6 comprises a spring arrangement 5 for forcing the mechanism 1 counter to the movement of the backrest support 4. The spring arrangement 5 comprises at least one spring element in the form of a compression spring 9. The spring arrangement 5 is connected indirectly to the backrest support 4 of the office chair, wherein the seat support 3 serves as a coupling element. The spring arrangement 5 determines the pivoting resistance of the backrest support 4. In -12 -this case, the spindle 8 is configured to change the pretensioning of the compression spring 9. To this end, the spindle 8 acts directly on a spring seat 11 of the compression spring 9, said spring seat 11 being adjustable in the longitudinal direction of the spring.

The opposite spring seat 12 is mounted in a non-movable manner. Thus, a rotation of the spindle 8, brought about by the electric motor 7, results in a reduction in the distance between the two spring seats 11, 12.

The mechanism 1 comprises a measuring device 13 having a plurality of load cells 13 arranged in a spaced-apart manner beneath the seat, to be more precise beneath the seat panel, for detecting the weight of the user.

Instead of load cells 13, force transducers can also be used.

The mechanism 1 furthermore comprises an evaluation and control unit 14 for evaluating the measurement results of the measuring device 13 and for actuating the electric motor 7 in dependence on the measurement results. In this case, the measured values determined by the load cells 13 serve in the evaluation and control unit 14 to simultaneously determine the weight distribution and thus to detect the position of the user on the seat.

The evaluation and control unit 14 comprises a microcontroller 15 and a memory (not depicted) , in which a characteristic curve of the mechanism is stored. This characteristic curve assigns one or more control values for controlling the electric motor 7 to each weight and each sitting position.

In a simple example, the microcontroller 15 receives an analogue voltage signal from the load cells 13 and determines therefrom the weight and the sitting position of the user. Furthermore, the microcontroller -1_3 -receives a signal from the electric motor 7 about the current position of the spindle 8. For this purpose, the electric motor 7 is equipped with a suitable position sensor (not depicted) . The microcontroller 15 contains in its program sequence a characteristic curve which assigns a defined spring force setting to each weight/position combination.

Depending on the weight and the sitting position of the user, the microcontroller 15 selects the corresponding control values. The evaluation and control unit 14 uses these controln values to control the electric motor 7 and a corresponding control signal is output to the electric motor 7. A suitable control loop causes the electric motor 7 to move into the position calculated by the microcontroller 15. The measuring, evaluating and controlling takes place continilously in this case, starting at the time at which the user sits down on the seat of the office chair.

The load cells 13 or force transducers mentioned in conjllnction with the exemplary embodiment described typically use strain gauges to register elastic component deformations. However, it is also possible to use other suitable sensors. Rather than prefabricated assemblies, the strain gauges or other suitable sensors can also be used as individual components. Thus, a strain gauge can be encapsulated for example by a plastics seat panel of the seat or a strain gauge is attached to the housing of the mechanism 1. Individual sensors or assemblies, for example force transducers, may also be installed between components of the chair, as long as such an arrangement is suitable for detecting user-individual measured values, for example between gas spring and base support 2 or between gas spring and foot cross.

It is also not necessary for the sensors to be fitted in or on the seat of the office chair. Thus, the weight -1_4 -of the user or a change in the sitting positicn can for example also be detected in that a pressure sensor senses a rise in pressure within a gas spring fitted in the ohair column.

In addition to the above-described applications, further applications for an electromotive drive come into question in an office chair.

Thus, for example, a variable travel limitation can be brought about by way of the electromotive drive, as is depicted in Fig. 3. In this case, the pivot angle of the backrest support 4 is limited by a stop element 22 that is rotatable about an axis 21. This end stop 22 has a number of steps 23 wherein, by rotation of the end stop 22, in each case a different step 23 comes into engagement with a stop surface 24 provided on the baokrest support 4. The end stop 22 is driveable by a servomotor 25 such that the servomotor 25 can move the end stop 22 into these different predefined positions.

Fig. 4 illustrates a structural arrangement which can be used to actuate or activate backrest stopping or to limit the travel of an office chair mechanism by way of an electromagnetic switch element. In this case, two structural elements 26, 27 which are blockable with respect to one another are used, the connection of said structural elements 26, 27 by a pin 28 resulting for example in the stopping of the synchronous movement function of a synchronous mechanism. For example, a movement of base support 2 and seat support 3, base support 2 and backrest support 4 or backrest support 4 and seat support 3 is blocked thereby. In order to fix the locking bolts 28 in a bistable manner, stationary, spring-loaded ball thrust pieces 29 are used. The ball thrust pieces 29 fit in the receptacles 30 of a holding element 31 connected to the pin 28. The plunger core 32 of an electromagnet is fitted on the holding element 31 -1_S -on the side opposite the pin 28 and coaxially with the pin 28. The plunger core 32 is in this case located in the interior of a coil 33 of the electromagnet.

Depending on how the electromagnet is controlled, the structural unit composed of the plunger core 32, holding element 31 and pIn 28 is moved in the axial direction such that the locking is released or re-established.

An electromotive drive can also be used to actuate the gas spring 34 of the office chair. Fig. 5 illustrates a variant in which a hexagonal shaft 36 connected to the electric motor 35 engages in an actuating element 38 provided with a hexagon socket 37. The actuating element 38 provided with an external thread 39 is guided in the base support 2, whioh has a threaded bore for this purpose. The base support 2 has a gas-spring receptacle 41 for receiving the gas spring 34.

The threaded bore 40 is positioned such that the actuating element 38 is arranged directly above the tripping device 42 of the gas spring 34 in the fitted state. When the electric motor 35 is controlled, the actuating element 38 moves in the direction of the shaft axis towards the tripping device 42 of the gas spring 34 or away from the tripping device 42 and thus actuates the latter.

Another variant for actuating a gas spring 34 is depicted in Fig. 6. Here, the tripping device 42 is actuated via a rotatably mounted two-armed control lever 43, which is actuable with the aid of an eccentric disc 44. An electric geared motor 45 is provided to drive the eccentric disc 44.

All of the features illustrated in the description, the following claims and the drawing can be essential to the invention both individually and in any desired combination with one another.

-16 -List of reference signs 1 office chair mechanism 2 Base support 3 Seat support 4 Backrest support Spring arrangement 6 Adjusting device 7 Electromotive drive, electric motor 8 Actuating element, spindle 9 Spring element, compression spring Seat 11 Adjustable spring seat 12 Fixed spring seat 13 Measuring device, load cell 14 Evaluation and control unit Microcontroller 21 Axis 22 Stop element, end stop 23 Step 24 Contact surface Servomotor 26 First structural element 27 Second structural element 28 Pin 29 Ball thrust piece Receptacle 31 Holding element 32 Plunger core 33 Coil 34 Gas spring Electric motor 36 Hexagonal shaft 37 Hexagon socket 38 Actuating element 39 External thread Threaded bore 41 Gas-spring receptacle 42 Tripping device -1_7 - 43 Control lever 44 Eccentric disc Geared motor