DE29600203U1 - Workplace, in particular a screen workstation, consisting of a work table and a work chair - Google Patents

Description

Workplace, especially a computer workstation, consisting of a work table and a work chair

Description

The invention relates to a workstation, in particular a computer workstation, which consists of a work table and a work chair.

With well-known computer workstations, aesthetic, manufacturing and price aspects are primarily taken into account. Although many manufacturers advertise their products as being ergonomically designed, this office furniture often does not, or only partially, withstand ergonomic testing, so that it is not uncommon to observe inappropriate working heights, postures that are not ergonomically correct, unfavourable lighting conditions, complex, awkward operation, etc.

These deficiencies, which have not been fully mentioned, lead to considerable workloads, fatigue and, in the long term, physical damage. This significantly limits the performance and willingness to perform, especially of employees at computer workstations, because it is precisely at such workplaces that the ergonomic deficiencies accumulate and often have to be endured throughout the entire day’s work. A particular deficiency of the known computer workstations is that the work tables and the work chairs provided cannot be adjusted together with little effort, effortlessly and individually to suit a specific person and, above all, cannot be coordinated with one another. The work table and work chair cannot meet the user’s desire to frequently change working positions.

The object of the invention is to create a workplace

create a workstation that meets all ergonomic requirements for a workplace and ensures in particular that the work table and the associated work chair can be carefully coordinated with one another and individually adjusted and can be easily and quickly transferred to all common and other ergonomically advantageous work positions, whereby additional support can be achieved with appropriate accessories.

According to the invention, this object is achieved in that the work table and the work chair have means for adjustable height adjustment, which allow conversion from a seated workstation via a kneeling seated workstation to a standing seated workstation, as well as devices for attaching and adjusting additional support means and these support means themselves.

The option of optionally implementing a knee-sit/sit or stand-sit workstation means that the requirement and need for frequently changing, health-preserving postures is met in a space-saving and cost-effective manner. The ergonomically designed knee-sit/stand workstation is therefore a uniform, mechanically supported complete solution in which the highest level of ergonomic requirements and findings are implemented in total, which serve to maintain the health of the user and allow effective work with the least physical strain. Additional support devices that can be optionally attached and adjusted or self-adjusted according to the working position adopted advantageously supplement the requirements for a fatigue-free, dynamic workplace.

With regard to essential further developments of the invention, which are set out in claims 2 to 54, reference is made to the description of the individual embodiments, including the associated drawings, which not only explain the invention in more detail, but also contain the advantages that can be achieved with the invention in detail.

Show it:

Fig. 1 a table according to the invention, height-adjustable by roller guide, at the lowest working height

Fig. 2 a height-adjustable table according to Fig. 1 with a roller guide at the highest working height

Fig. 3 a side wall of the table according to Fig. 1 with mounted roller holders and rollers

Fig. 4 a roller holder with rollers according to Fig. 1 for rectangular tubes

Fig. 5 is a perspective view of a frame in the highest position using a pendulum support

Fig. 6 is a perspective view of a frame according to Fig. 5 with the pendulum support in the lowest position

Fig. 7 is a perspective view of a frame according to Fig. 5 with a view under the table body

Fig. 8 a perspective and enlarged view of a locking mechanism for a height-adjustable table in the unlocked position

Fig. 9 a perspective view of the work table according to Fig. 5 with the worktop broken open and armrests

Fig. 10 a perspective view of a frame with force compensation by elastomer bands in the highest position

Fig. 11 a perspective view according to Fig. 10 with force compensation by means of elastomer bands in the lower position

Fig. 12a ..12c Views of various elastomer band guides for force compensation according to Fig. 10

Fig. 13 Table with force compensation according to Fig. 10 in highest and lowest position

Fig. 14 Deflection roller and retaining plates for elastomer band guidance for force compensation according to Fig. 10

Fig. 15 Arrangement of the drive wheels, toothed belt wheels and the pre-assembled lifting spindles for a spindle lifting table

Fig. 16 Table with maximum height adjustment according to Fig. 15

Fig. 17 Arrangement of the pre-assembled lifting spindle with drive pinion etc. according to Fig. 15

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Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24

Fig. 18 Arrangement of the cables and pulleys according to another embodiment of cable adjustment Arrangement with cables according to Fig. 18 in plan view Arrangement with cables according to Fig. 18 in the lowest position

Arrangement with cables according to Fig. 18 in highest position

Complete cable pull device with spring tensioning device (one drum half removed) Construction of one drum half according to Fig. 22

Locked drum consisting of two identical drum halves as shown in Fig. 22

Fig. 25 Bearing bolt with two-edge and bearing pin, spiral spring with suspension lug and bearing block for a cable pull device according to Fig. 22

Fig. 26 Lifting device with a torsion spring in relaxed state

Fig. 27 Lifting device with torsion spring according to Fig. 26 shown in the position it assumes when the table is locked at the lowest height

Fig. 2 8 Torsion spring according to Fig. 2 6 when installed in the lowest position of the work table Torsion spring according to Fig. 26 when installed in the highest position of the work table another height-adjustable table in C-frame design

the table according to Fig. 30 in the highest position the table according to Fig. 30 in the lowest position the arrangement of the mechanics for a table according to Fig. 30 in the guide frame

Fig. 34 a torsion spring for a desk-like adjustable table top of a work table

Fig. 35 the mechanism of a desk-like adjustable table top Fig. 36 an adjustable table top according to Fig. 35 Fig. 37 an armrest for a work table

Fig. 38 a work chair for the work table according to the invention in a first embodiment

Fig. 39 the work chair according to Fig. 38 in the

Fig. 29 Fig. 30 Fig. 31 Fig. 32 Fig. 33

position

Fig. 40 the schematic knee-sitting position of a user Fig. 41 the schematic sitting position of a user Fig. 42 the schematic standing-sitting position of a user Fig. 43 an adjustment or locking device for a

Work chair according to Fig. 38
Fig. 44 another variant of a work chair according to the invention with basic support frame and seat support Details of the seat support according to Fig. 44 Guide tubes and locking pawl according to Fig. 44 Guide tubes and locking pawls according to Fig. 4 6 in section

a variant of the seat support according to Fig. 45 an electric adjustment mechanism for a work chair according to Fig. 44

Backrest adjustment device for a work chair according to Fig. 44

Backrest, lumbar support and adjustment device in perspective view as per Fig. 50 Backrest, lumbar support and adjustment device in section as per Fig. 51

Work chair according to Fig. 44 with height-adjustable rail leg support

Shin leg support according to Fig. 53 the adjustment device for the shin leg support according to Fig. 53.

The workstation, which is designed as a computer workstation, consists of a work table 1 and a work chair 49.

Fig. 1 shows the work table 1, which is essentially made up of two components, whereby the inner one, the frame 2, is inserted into the outer table body 3, which is preferably made of furniture chipboard. The frame 2 consists of the cross members 4 and the table legs 5. The cross members 4, which are designed as square lightweight profiles, are inserted into recesses in the table legs 5 by means of hook-shaped sheet metal parts (not described in more detail).

Fig. 45 Fig. 46 Fig. 47 Fig. 48 Fig. 49 Fig. 50 Fig. 51 Fig. 52 Fig. 53 Fig. 54 Fig. 55

hanged.

The individual parts, worktop 6 as well as side walls 7 and possibly a rear wall, form the component-integrated table body 3 by means of connecting elements that are customary in the furniture industry, which is guided on the table legs 5 of the frame 2.

The guidance of the components could be manufactured very cost-effectively using plastic rails as a simple sliding guide, but requires tight manufacturing tolerances in order to guarantee sufficient stability against lateral vibrations even with maximum height adjustment, especially under the harsh conditions of workshop operation.

If the sliding friction that occasionally occurs between the table frame and the plastic rails is replaced by rolling friction, the play that exists between the table frame and the table body can be completely eliminated by specifically generated clamping forces, while still allowing easy height adjustment.

A particularly advantageous embodiment of a guide for the frame 2 relative to the table body 3 is shown in more detail in Fig. 1 to Fig. 4.

In this example, the table body 3 is guided on the frame 2 by means of a roller guide.

The design and bearing of the guide rollers 8 guarantees a stable guide without play and is also very simple in design, thus inexpensive to manufacture and easy to assemble. The guide on the inside of the widely spaced table legs 5 increases the stability of the work table 1 as a whole. As with the arrangement of the guide surfaces, the arrangement of the guide rollers was also designed to ensure maximum distances from one another, so that a very stable guide is created.

The guide rollers 8 form-fittingly encompass three sides of the

Profile tubes that form the table legs 5. However, other profiles, such as round profiles, can also be surrounded by appropriately designed guide rollers 8 in such a way that just as many degrees of freedom are restricted as with the square profile.

In the embodiment according to Fig. 1 to Fig. 4, the square profile is surrounded by one pair of guide rollers 8 mounted in a roller holder 9 in such a way that, in conjunction with the other pair of guide rollers 8 opposite, the system of table body 3, table frame 2, guide rollers 8 and roller holders 9 is safely deprived of five degrees of freedom and thus a play-free height adjustment is guaranteed. The roller holder 9 is designed as a stamped and bent sheet metal part. Its design can be seen in particular in Fig. 3 and Fig. 4.

The guide rollers 8 are rotatably mounted in the roller holders 9 by means of cylindrical pins 10. The roller holder 9 is attached to the table body 3 using suitable connecting elements, for example direct connection screws. A spring effect is achieved by appropriate design and dimensioning of the two legs of the roller holder 9, at the ends of which the rollers 8 are mounted. This means that the roller holders 9 can be braced when attached to the table body 3 in such a way that, despite existing manufacturing tolerances, a completely play-free bearing is achieved and easy height adjustment is achieved through rolling friction.

Due to the rolling friction achieved by the design of the parts, this type of guide is very low-wear.

A first type of height adjustment mechanism is shown in Fig. 5 to Fig. 9. According to this, three power-operated pendulum supports 11 designed as toggle levers are pivotally connected to the frame 2 by means of bolts (not shown in detail). The pendulum supports 11 have the task of absorbing forces at three points, which are caused by the

torsion springs arranged at the joint 14 of the pendulum support 11.

The two end positions of the pendulum supports 11 for the lowest and highest position of the table body 3 are shown in Figures 5 and 6.

The torsion spring 15 is connected to the pendulum support 11 by means of clamps 16 that can be moved along the pendulum support 11. By moving the clamps 16, the spring characteristics of the torsion spring 15 and thus the lifting force of the pendulum supports 11 can be adjusted. By moving the clamps 16 towards the ends of the pendulum support 11 (away from the joint 14), the lifting force is reduced and by moving the clamps in the opposite direction (towards the joint 14) the lifting force is increased accordingly. Cylindrical rods 17 are inserted between the cross members 4 by means of fastening elements 18. When actuated, a locking mechanism 19 connected to the table body 3 can move on the cylindrical rods 17 in such a way that a continuous locking along the entire height adjustment is possible.

The special, double-acting locking mechanism 19 is shown in Fig. 8. The movement of the locking mechanism 19 relative to the cylindrical rod 17 is prevented by self-locking by pawls 20, which are pressed into the inclined end positions by a locking spring 21. The pawls 20 are rotatably mounted in recesses 22 located on the locking mechanism holder 23. The pawls 20 are pulled towards each other by a Bowden cable 24, one end of which is hooked into a recess 25 in the pawls 20, and the self-locking is thereby canceled in both directions. In order to secure the end positions of the pawls 20 in the contracted state and to prevent unwanted locking, a stop lug 26 is attached to the locking mechanism holder 23, against which the pawls 20 strike.

At the same time, the adjustment path of the Bowden cable 2 4 is limited. The other end of the cable of the Bowden cable 24 is

together with the cable ends of the Bowden cables of the other two locking mechanisms 19 to a lever 27 that is rotatably mounted in the table body 3 (Fig. 9). The abutment for the sleeves 28 of the Bowden cables 24 is formed by recesses 29 in a support crossbar for the table body 3. The lever 27 itself is in a recess

30 is stored in the table body 3, which continues to have a breakthrough

31, through which an actuating tab 32 of the lever 27 extends. When the tab 32 is actuated, the lever 27 rotates about its cylindrically shaped end 33. This enables easy and central actuation of the three locking mechanisms 19 already explained in more detail.

A further advantageous embodiment with approximately equal force compensation over the entire height adjustment range, in which the size of the compensation force can also be adjusted using various technical solutions, is shown in Fig. 10 to Fig. 14.

In this design, force compensation is achieved by one or more rubber bands (elastomer bands) 34, which are arranged in different ways. Fig. 12a and Fig. 13 show what a single-layer arrangement of a rubber band 34 could look like. It is easy to see how the ends of the rubber bath 34 are glued or connected in such a way that loops 35 are created, into which retaining plates 36 are inserted. The retaining plates 36 are hung in corresponding recesses in the side wall 7. The rubber band 34 runs over deflection rollers 37, which are rotatably mounted on a shaft 39 inserted in fastening brackets 38.

Depending on the type of bracing selected, the retaining plates 36 and the deflection rollers 37 are arranged at the appropriate location.

In Fig. 10, a rubber band 34 is shown which is simply tensioned and appropriately held as shown in Fig. 12a and runs over deflection rollers 37 at the highest and lowest table adjustment.

The aim is to achieve a

to achieve the most constant possible compensation of the force generated by the weight of the table body to be moved, with load. This requires a small increase in force along the path, i.e. the angle of increase of the spring rate must be small. This requirement is better met by a longer spring than by a short one. The double-layer arrangement of the rubber band shown in Fig. 12b takes this into account. The rubber band arrangement shown in Fig. 12c also takes into account the increase in the effective spring length and the requirement that the rubber band 34 under the table top moves upwards when the height is adjusted.

The desired basic size of the force compensation can be easily set and regulated through the various options for pre-tensioning, fastening the ends of the rubber bands 34, choosing the width, thickness, material properties and number of rubber bands 34.

An additional adjustment of the basic size of the force compensation can be achieved using the device shown in Fig. 13. Two disks 40, which are mounted next to the rubber band 34 so that they can rotate in a bracket 41, are connected by two rods 42. The rubber band 34 runs over the rods 42 in the form shown, or in the case of a double-layered design, one rubber band 34. If the disks 40 are rotated with the rods 42 in the direction indicated and secured against turning back, the effective length of the rubber band 34 is shortened and the spring force or the compensation force is thus increased. With this device, the compensation force can be changed very easily in this way.

By choosing rubber as the spring element, this design is corrosion-free and, thanks to its simple arrangement, wear-resistant.

Height-adjustable work tables are also required to ensure that the load is distributed very differently and unevenly across the worktop and that the total magnitude of the force

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can be up to 3000 N. Such load cases often occur, especially in workshops and in production areas. This means that systems that require an almost constant load in order to achieve force compensation with relatively little effort can no longer be used. This means that systems that guarantee almost the same force compensation over the entire height adjustment range and can be locked at the desired height must be replaced by driven, preferably self-locking systems.

Two advantageous, cost-effective and space-saving embodiments of the height adjustment are shown in Fig. 15 to and Fig. 18 to Fig. 21.

In the type of height adjustment shown in Fig. 15 to Fig. 17, the pre-assembled lifting spindles 201 are inserted into the preferably four legs 5 made of square lightweight profiles at the corners of the frame 2. In order to pre-assemble the lifting spindles 201, a threaded bushing 202 is screwed onto the lifting spindle 201, which is provided with a self-locking thread, the drive pinion 203 is welded to one end and the guide bushing 204 is placed on the other end and secured against falling off. The frame 2 is thus pre-assembled for further assembly.

Now 6 bearing plates 205, to which bearing bolts 206 are welded, are screwed onto the underside of the worktop. The drive wheels 207, which consist of two equally sized toothed belt wheels 208 and a gear 209, are placed on the bearing bolts 206 and secured accordingly. The three components that form the drive wheel 207 are firmly connected to one another. The eight toothed belt wheels 208 of the four drive wheels 207 form two drive levels with the two toothed belt wheels 208 firmly connected to the drive shaft of a motor 210, into which two toothed belts 211 are inserted in the manner shown.

By moving the carrier plate 212 of the motor 210, the toothed belts 211 can be tensioned. In the underside of the

The thrust bearings 213 are pressed into the work plate 6 as shown.

The assembly - table body 3 - is now pushed over the frame assembly 2 - and the track pins 214 at the ends of the lifting spindles 201 are inserted into the holes of the track bearings 213. The assembly and guidance of the table body 3 relative to the frame 2 has already been described.

An advantageous type of height adjustment can be achieved due to the secure guidance between the table body and the frame by means of cables as shown in Fig. 18 to Fig. 21.

The arrangement of the cable pulleys 215 and the cable pulleys 216, 220 can be seen in Fig. 18. Simple (not shown) bearing plates with welded bearing bolts on which cable pulleys 216 are rotatably mounted and secured are welded to the frame 2 in such a way that the cable arrangement shown is achieved. The cable ends 217 are hooked into hooks 218, which are welded to the roller holders 9. Both cables are pulled through holes 219 in the central cable pulley 220 in the manner shown or inserted into slots. The advantage of this arrangement is that length tolerances are compensated, no additional thimbles are necessary and thus no problems arise when winding up.

In order to achieve the entire height adjustment, a complete rotation of the central pulley 220 is not necessary, so that no difficulties arise due to the ropes winding over each other.

A worm wheel 221 is firmly connected to the central pulley 220 and is driven by a worm 222. The worm 222 is to be driven by a motor 223 on one side and by a hand crank 224 on the other side via a simple coupling (not shown in detail).

In both versions of the height adjustment, the design of the front frame and the other arrangement of the

Components ensure maximum legroom at every workstation height, which far exceeds the ergonomically required values. The additional weight is only slightly greater.

An almost uniform force compensation along the height adjustment path can be achieved by replacing the cable pull drum in the last described type of height adjustment by means of cables with a rotating drum in which there is a pre-tensioned spiral spring.

Such an embodiment is shown in Fig. 22 to Fig. 25. The drum 225 consists of two identical punched and bent parts. The design of one drum half 225 is shown in Fig. 23. By placing the second drum half 225, rotated by 180°, on the first and rotating the second relative to the first, the closed drum 225 shown in Fig. 24 is created, which are secured in position against each other in both the radial and axial directions by the design of the angled tabs 226. The tabs 227 projecting beyond the circumference create a guide track 228 on the circumference of the drum 225, in which the cables (not shown in detail) are guided when they are wound onto or unwound from the drum 225 for height adjustment. The holes 22 9 in the center of the drum halves serve to improve the guidance of the bearing pin 230. This ensures that the drum 225 rotates safely around the bearing pin 230 during height adjustment. A worm gear 231 is fitted onto the bearing pin 230 and is secured against rotation relative to the bearing pin 230 by a two-edge. The bearing pin provided for this purpose on the bearing pin 230 is inserted into the hole 232 in the bearing block 233 and secured in position so that it can rotate quickly by a screw that is screwed into an internal thread in the bearing pin 230. This bearing point, in conjunction with the worm wheel 231 resting flat on the bearing block 233, represents a secure mounting of the entire assembly and at the same time the rapid rotation of the worm wheel 231 is possible when rotating the worm 234, which is mounted in the bearing block 233 as shown in Fig. 22.

·

By turning the worm 234, which is prevented from turning by the self-locking mechanism of the gear, the bearing bolt 230 is also turned and thus the spiral spring 235, which has a tab on its inner end in a slot 236 in the bearing bolt 230, is tensioned. At its outer end, the spiral spring 235 is also hung with a bent hanging tab 237 behind one of the webs that are created by the tabs bent on the drum halves 225, and is thus prevented from turning.

By turning the worm 234, it is possible to generate a preload in the spiral spring 235 and thus in the entire lifting system during assembly, as well as to change the spring tension when the table load changes. The choice of a relatively long spiral spring 235 results in a flat increase in the spring characteristic curve. This, in conjunction with the choice of a small angle of rotation of the drum 225 during height adjustment, leads to an almost constant force along the height adjustment path.

The embodiment of force compensation using spring legs to which torsion springs are connected can be made even more cost-effective if only torsion springs are used, as will be explained using Fig. 26 to Fig. 28. Of course, with this embodiment the possibility of changing the force effect is lost because the described clamp can no longer be moved on the spring leg.

The torsion spring used for this embodiment is shown in a relaxed state in Fig. 26. Tubular sleeves 239 with bearing shells 240 are pushed onto the ends of the torsion spring 238 and soldered. The design of the bearings as half shells makes assembly of the torsion springs 238 very simple and only possible almost at the end of the assembly of the entire work table. A change in the force effect and the force progression of the torsion spring 238 can be achieved by moving two tubular pieces 241, which are pushed onto both legs of the torsion spring, as shown in Fig. 26. The force effect of the torsion spring 238 is thereby increased.

ßert when the pipe sections 241 are moved towards the pivot point of the torsion spring. In Fig. 27, the torsion spring is shown in the position it assumes when the work table is locked at the lowest height. The deflection of the torsion spring legs as a result of the force is not shown, but it is clearly visible that the displacement of the pipe sections 241 would prevent the deformation of the torsion spring legs in the area of the length of the pipe sections 241 and thus the spring characteristics are changed. The bearing plates 242 shown in Fig. 26 with welded bearing bolts 24 3 are screwed to the table body and thus form an abutment for a bearing shell 240 at one end of the torsion spring. The other abutment is formed by a bolt 244 which is welded to the crossbar tube 4 of the work table. In Figs. 28 and 29, the torsion spring 238 is shown in the installed state in the lowest and highest work table positions.

In the versions of the height-adjustable work tables described so far, the outer table body was always made up of closed plate-shaped parts, which gave the table system the required stability in a very simple way and ensured safe guidance.

In order to be able to produce a table in C-design, as shown in Fig. 30 to Fig. 33, i.e. without a closed rear wall, in which the side walls 7 remain on the floor and only the worktop 6 attached to guide tubes can be adjusted with the same stroke path (up to 350 mm), a different structural design is required, which will be described below.

The arrangement of the components can be clearly seen in Fig. 31 and Fig. 32. The above-described smooth, play-free guidance between the inner and outer guide frames 246, 247 is achieved by rollers 245, which are arranged at the greatest possible distance from one another. The rollers 245 rotate on bearing bolts 248, which are pressed into holes 249 in the guide plate. The bearing bolts 248 are designed so that

they can serve as supports for the bearings on the torsion springs 238, but also as roller bearings. To save space, two torsion springs 238 were installed in opposite directions in each side wall 7.

Two locking pawls 252 are inserted into a corresponding recess in the bent tab on the guide plate 250. The way the locking mechanism 19 works has already been described. A locking rod 253, over which the locking pawls 252 are pushed and on which they clamp, is firmly connected at one end to the outer guide frame 247. A perforated plate 254, with which the inner guide frame 246 is covered, has a decorative and stabilizing function.

A support beam 255 and the two profiles that it essentially consists of are arranged in accordance with ergonomic specifications so that the feet can be supported on the profile tubes of the support beam 255, but a device that serves as a footrest can also be hung on these. Another important function of the support beam 255 is to secure the walls 7 of the C-table frame against twisting and thus give the entire work table stability. A cable box 256 designed as a stamped and bent sheet metal part is connected to a cable box cover 257 by hinges and attached to the work table by hanging it.

The mechanism for a height-adjustable table, the upper worktop 6 of which can be pivoted so that the work surface is arranged like a desk, is shown in Fig. 34 to Fig. 36. The mechanism causes the upper worktop 6 to be moved against its gravity into the maximum inclined position by the force of a torsion spring 258 and can be locked in any inclined position by a double-acting locking mechanism 259. A locking mechanism holder 2 60 is inserted into the lower worktop 260 and secured in position by a positive fit. The locking pawls 2 61 are inserted into the locking mechanism holder 260 and are actuated by a locking lever 262 via a Bowden cable 263. A support arm 264 is

firmly connected to the upper worktop 6 and moves through the locking pawls 261 and the locking mechanism 260. In the vicinity of the two worktop ends, the support arms 264 and locking mechanism 259 are arranged in such a way that they dip into the side walls or disappear completely into them, depending on the inclination. The articulation points of the torsion spring 258 are located approximately in the middle of the worktops. The ends of the torsion spring 258 are provided with balls 265 which slide in spherical caps 266 which are on the one hand embedded in the upper worktop 6 and on the other hand firmly connected to the inner guide frame 267. This allows the relative movement of the torsion spring ends in two directions relative to the spherical caps 266 to be accommodated. The rotary movement of the upper relative to the lower worktop is made possible by a film hinge 268.

The worktop 6 according to Fig. 7 and Fig. 9 has two recesses 43 on the operator side, into which padded armrests connected preferably with spring-loaded insert parts 44 can be inserted. One such is shown in more detail in Fig. 37 in two views. The connection between the spring-loaded insert parts 44 and the armrests 45 can be fixed on the one hand, but can also be moved laterally on the other. For this purpose, a ball bearing 48 is provided between two U-rails 46, 47 that are guided one inside the other and are firmly connected to the insert part 44 or armrests 45. This allows the armrests to be easily moved sideways with the balls of the hands or forearms during the work process.

Fig. 38 shows the work chair, which in this first embodiment essentially consists of a base support frame or a base support plate 50 with rollers or balls 51, a support tube 52 with a central tube 53, an upholstered seat 54 and a backrest frame 55 with a backrest 56.

The support tube 52 is attached to the base support plate 50, e.g. by welding, and carries the central tube 53, which can be moved in a sufficiently large area relative to the support tube 52. Four balls 51 are attached to the

the underside 58 of the base support plate 50 is fastened in such a way that when the operator places a load on the work chair 49 and the resulting deformation of the spring-loaded brackets 57, they come into contact with the brake pads 59 located on the underside 58 of the base support plate 50, whereby the base support plate 50 is also equipped with a foot support surface 60 Fig. 39 - for the user and has ends in the shape of a segment of a circle in the area of the balls 51. The central tube 53 can be locked relative to the support tube 52 by means of an operating element at a selectable, continuously adjustable height, whereby a support plate on the seat side and a support frame 62 on the base support plate side are also connected to the central tube 53. Two eyes 64 and 65 arranged on the support frame 62 and the support plate 63, e.g. rolled on, form in conjunction with the two axes 66 and 67 the front bearings for two bars 68 and for the bearing plates 70 provided on the seat surface 54, which also have eyes 69. The bearings 71 of the bars 68 on the backrest side and the bearing brackets 72 connected to the seat surface 54 form in conjunction with the round bars 73 the bearings for the backrest frame 55.

The arrangement implements a parallelogram guide such that when the seat surface 54 is pivoted about the axes 66, 67, the bearing 71 and the axis of the locking device 81 into the desired position, the backrest frame 55 with the backrest 56 attached to it always maintains the same inclination.

With the help of a control element 74 and a clamping plate 75, the backrest 56 can be adjusted relative to the backrest frame 55 so that it can be ergonomically adapted to the user's back in all positions. A double torsion spring 76, whose connected legs 77 rest on the support plate 63, whose spring eyes 78 are guided by lateral recesses 79 on the support plate 63 and whose free legs 80 rest on the underside of the seat surface 54, exerts such a torque on the entire seat mechanism that the seat surface 54 and backrest 56 strive to achieve the uppermost position, i.e. the standing-sitting position shown in Fig. 42.

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·* —

The backrest 56 and the seat 54 are secured in the desired position by a locking device 81, which largely limits the rotation between the backrest frame 55 and the bearing brackets 72 and can be operated with a knob 88. A slight, load-dependent rotation is permitted by the torsion bar 90, which is housed in the crossbar 8 9 of the backrest frame 55. This locking device 81 with the torsion bar 90 will be described later. Two struts 82, which are connected by a crossbar 83, are mounted on the axis 66 at the same time as the bars 68.

Knee pads 84 are pushed onto the ends of a crossbar 83 that protrude beyond the bars 68 and support the user's knees when the work chair 49 is used as a kneeling seat. The knee support consisting of the struts 82 and the crossbar 83 is fixed in the position of use by a holding element 85 in the form of a wire rope. The position of the knee support can be changed by changing the length of the wire rope. If the knee support is not required, it can be brought into the position shown in Fig. 41/42.

The padded seat 54 is provided with a hump-shaped elevation 86 in the area of its end facing the backrest 56, by means of which the buttocks of the user are supported in the standing-sitting working position. The various possible uses of the work chair 49 are shown in Fig. 40 (kneeling-sitting working position), Fig. 41 (sitting working position) and Fig. 42 (standing-sitting working position).

A component of the locking device 81 (Fig. 38, Fig. 39) is inserted into the crossbar 89 of the backrest frame 55, which consists of a square hollow profile. According to Fig. , this component consists of the individual parts torsion bar 90, bearing bush 91, inner conical sleeve 92 and disk 93 with a square cross section, which are connected to form one part, for example by welding. The positive connection between the square crossbar 8 9 and the square disk 93 ensures that the component is prevented from rotating relative to the crossbar 89 and thus the backrest frame 55. The end of the torsion bar that protrudes beyond the disk 93

90, another bearing bush 94/, which is also connected to an inner conical sleeve 92 by welding, is pushed and secured by means of a screw element 95. The two-sided bearing bushes 91, 94 thus form a bearing around which the two bearing brackets 72 and the cross strut 89 can rotate. The end face of the inner conical sleeve 92 facing the bearing bracket prevents the assembly assembled in this way from being moved again in the opposite direction to the assembly direction. An outer conical sleeve 96 is first placed on the threaded end of the torsion bar 90 protruding from the bearing bush 91 and then a knob 88 is screwed on. A firm connection between the outer conical sleeve 96 and the bearing bracket 72 is established by claws 97 arranged on the outer conical sleeve 96, which engage in slot-shaped recesses 87 in the bearing bracket 72. Also on the side facing away from the knob 88, an outer conical sleeve 96 overlaps the inner conical sleeve 92 and also has claws 97 and corresponding slot-shaped recesses 87 in the bearing bracket 72. The outer conical sleeve 96, however, only serves to cover this bearing point.

By tightening the knob 88, the conical surface 98 of the inner conical sleeve 92 is pulled against the conical surface 99 of the outer conical sleeve 96, thus making it impossible for both conical sleeves 92, 96 to rotate relative to one another. If, in this state, the bearing brackets 72 are to be rotated relative to the cross brace 89, this can only be done by rotating the torsion bar 90 under the influence of force. Such an effect of force and the resulting torque acting on the torsion bar 90 is brought about by shifting the effect of force on the seat surface 54 and/or backrest 56. This force shift therefore causes the torsion bar 90 to rotate, which inevitably brings about the desired, favorable changes in the angle between the seat surface 54 and backrest 56 and the user adopts a slightly different working posture.

By loosening the knob 88, the friction between the two conical sleeves 92, 96 can be eliminated and the bearing tabs 72 can

can be easily rotated relative to the cross brace 89 so that a new seat position can be set. If this seat position is secured again by tightening the knob 88, the seat surface 54 and backrest 56 can also move again by small amounts around this new position as a result of the application of force.

In order to keep the backrest and seat in the desired position, a device has been described in the first embodiment of a work chair by which rotation in one of the joints of the movement parallelogram is prevented.

In Fig. 44, another embodiment of the work chair according to the invention is shown in two different positions and the arrangement of the assemblies and components in relation to one another. In this example, the basic support frame is made up of a box profile in a double T shape. In order to hold the backrest and seat in the desired position, a seat support is provided in this further variant. The advantage here is that it also offers very good options for adapting the seat to the requirements of the disabled sector.

The structure of the seat support 101 is shown in more detail in Fig. 45 to Fig. 47. The backrest frame (55) and the support box (104) on the one hand and the square support levers (100) for the backrest frame (55) and the seat plate (111) mounted on the support box (104) by means of square bearing tubes (118, 117) on the other hand form a lifting mechanism that can be adjusted in a parallelogram manner via the telescopically adjustable guide tubes (103, 105).

By arranging the seat support 101 at an angle to the vertical axis of the chair and by using a support roller 102 or a ball bearing, favorable kinematic conditions are achieved.

In the outer guide tube 103, which is firmly connected to a support box 104 as shown, the inner guide tube 105 can move freely and easily. Both tubes

103, 105 are closed at their free ends by discs 106 in such a way that a compression spring 107, which is dimensioned so that the system - seat, backrest and moving parts - is pressed into the uppermost, standing seat position, can be supported on them. A part of the support roller 102, which rotates around a bearing pin 109 that is firmly connected to the disc 106, extends into a recess 108 in the disc 106 on the inner guide tube 105. Two beads 110 in the seat plate 111, which are arranged perpendicular to the axis around which the seat rotates, form a guide path for the support roller 102 when the seat position is changed. In addition to guiding the support roller 102, the beads 110 stiffen the seat plates.

111 is reached. In order to enable the locking of the inner guide tube 105 in the desired position, two pawls 112 are fitted onto the inner guide tube 105. Just like the pawls of the table, the pawls 112 on the seat support 101 are actuated by a Bowden cable 113 and a lever. By rotating the pawls

112 around the support edge on the bearing plate 114 for the pawls 112, the inner guide tube 105 is prevented from moving in both directions due to self-locking.

Depending on the intended use, the locking pawls 112 can be arranged at different heights and different angles to the carrier plate 104. From Fig. 47 and Fig. 48 it can be seen that when the locking mechanism is arranged at the upper end of the carrier box 104, an additional part, the bearing plate 114, is required, while when it is arranged in a lower part of the carrier box 104, the receptacles 115 for the locking pawls 112 can be in the carrier box 104 itself. In both cases, the solution is very easy to install. The locking pawls 112 are actuated by a locking lever, which is rotatably mounted under the seat, and by a Bowden cable 113. The carrier box 104 is firmly connected to a carrier plate 116 towards the seat. The support plate 116 and the support box 104 are additionally stiffened with square bearing tubes 117, 118, which also form the bearing points for the adjustment mechanism. The backrest frame (55) and the support box (104) on the one hand and the support box by means of square bearing tubes (118, 117)

(104) mounted square support levers (10*0) for the backrest frame (55) and the seat plate (111) on the other hand form a lifting mechanism that can be adjusted in a parallelogram manner via the telescopically adjustable guide tubes (103, 105).

Frequently changing the sitting position is particularly important for disabled people. For this purpose and at the same time as a standing-up aid, the seat support for a work chair according to Fig. 44 has been provided with an electric adjustment device according to Fig. 49. This means that the locking pawls, the locking lever, the Bowden cable and the compression spring can be omitted. A threaded bushing 119 is pressed into the inner guide tube 105, in which a lifting spindle 120, which is firmly connected to a lifting spindle wheel 121, is movably mounted. An intermediate wheel 122 can engage in the lifting spindle wheel 121 through the lateral recess in the lower, outer guide tube 103. The lifting spindle wheel 121 is rotatably mounted on a base plate 123. The base plate 123 is firmly connected to the lower, outer guide tube 103. To absorb the axial and radial forces, a bearing pin 124 is mounted on the lifting spindle 120 in a thrust bearing 125. When the lifting spindle 120 is rotated by a motor 126 via a pinion 127, the intermediate gear 122 and the lifting spindle gear 121, the threaded bushing 119 with the inner guide tube 105 and the support roller 102 is moved axially on the lifting spindle 120 in one direction or the other depending on the direction of rotation and thus the seat position is changed.

Of particular importance for healthy sitting is the design, adjustability and adaptability of the backrest. The devices shown in Fig. 50 to Fig. 52 for a work chair according to the invention serve this purpose. By moving it along the backrest frame, the backrest 56, in particular the lumbar support 128, can be adjusted in height above the seat so that the particularly vulnerable area of the back is optimally supported. The distance between the lumbar support 128 and the upholstered surface of the backrest 56, which can also be individually adjusted, serves the same purpose. The spring-loaded, rotating

Design of the backrest holder of a guide plate 12 9. As a result, the backrest 56 always rests completely against the back and, particularly when the back is leaning more, the lumbar region is brought into the favorable back position when standing.

The guide plate 129, to which a backrest plate 130 is attached and which slides easily on the backrest frame 55, is clamped at the set height by a locking device 131, one end of which is designed as a spring-loaded eccentric and can be rotated about a bearing axis 132. To adjust the height, which is possible in a wide range for all body sizes, all that is needed is to open the locking device 131, move the guide plate 129 and close the locking device 131 again.

In order to be able to adjust the distance between the lumbar support 128 and the upholstered surface of the backrest 56, a threaded bushing 133, which is firmly connected to an adjusting disk 134, is rotatably mounted between a sheet metal passage 135 in the guide plate 12 9 and the backrest plate 130 firmly connected to it. When the adjusting disk 134 is turned, a threaded bolt 136, which is firmly connected to the support plate, is moved in the threaded bushing 133 and the distance between the lumbar support 128 and the upholstered surface of the backrest 56 is adjusted. For better adjustability, the lumbar support 12 8 and the backrest cushion 138 were separated.

Fig. 55 shows a foldable, height-adjustable shin support 139 with inclination adjustment. In order to eliminate the defect often associated with knee supports of knee seats, namely excessive strain on the sensitive areas of the body in the knee area when sitting for a long time, the support provided supports primarily the insensitive shin area, is also height-adjustable and adjusts its inclination to the shin so that it rests on the entire surface. A support fork 140 is connected to the support box 104 in a rotatable manner via an axis, the bearing eyes 141 on the support fork and the bearing tube 117 on the support box 104. The entire

The shin support can be folded onto the support box 104 or folded out for the kneeling seat. A stop 142, which rests against the support fork 140, guarantees a preset inclination of the shin pads, from which the inclination is adjusted to the shins when sitting by rotating it around the support tube bearing in the support fork 140. The height of the shin support is adjusted by rotating it around the axis on the box support 104. In order to be able to hold the shin support at the desired height, the end of a carrying strap 143 is attached to the front of the support fork 140. The other end of the carrying strap 143 runs through the slot of a belt hook 144 and is also attached in this way. If the height adjustment is optionally desired, the bearing plate 116 is replaced by one with additional hanging slots 145. The two beveled ends of the belt hook 144 can be hooked into these hooking slots 145 at the point that fixes the desired height of the shin support.

- 52 sheets of drawings -

Work table Table frame Reference symbols Table body 1 Traverses 2 Table legs 3 Worktop 4 Side walls and rear wall 5 Leadership roles 6 Roll holder 7 Cylinder pin 8th Pendulum support 9 role 10 deepening 11 joint 12 Torsion spring 13 Brackets 14 cylindrical rod 15 Fastener 16 Locking 17 pawl 18 Locking spring 19 Recess 20 Locking mechanism 21 Bowden cable 22 Recess 23 Stop lug 24 lever 25 Covering 26 Countersinking in the traverse 27 Recess in the table body 28 Breakthrough in the table body 29 Actuating tab 39 End of the lever 31 rubber band 32 loop 33 Retaining plate 34 35 36

• · ·· — Deflection pulley j7 ·*— · ·· ·* ·· ·· mounting brackets ·· «*· · ··· Wave · 9
·· *· 37 disc 38 Bracket 39 Rod 40 Elaboration 41 Insert part 42 Armrest 43 U-rail 44 U-rail 45 Ball bearing 46 Work chair 47 Base support plate/frame 48 Rollers or balls 49 Support tube 50 Central tube 51 Seat 52 Backrest frame 53 Backrest 56 54 Brackets 55 bottom 56 Brake pads 57 Foot contact area 58 Control element 59 Support frame 60 Carrier plate 61 Eye 62 Eye 63 axis 64 axis 65 Holm 66 Eye 67 Bearing plates 68 storage 69 Bearing tabs 70 Round bar 71 Control element 72 Clamping plate 73 74 75 · · ·

··· « _n IM

7 6 Torsion spring

77 legs

78 Spring Eye

7 9 Recess

80 legs

81 Locking device

82 Strut

83 Cross beam

84 knee pads

85 Holding element

86 Survey

87 recess

88 Knob

89 Cross brace

90 torsion bar

91 Bearing bush

92 Conical sleeve

93 Square disc

94 Bearing bush

95 Screw element

96 Conical sleeve

97 claws

98 conical surface

99 Conical surface

100 square support levers

101 Seat support

102 Support roller

103 Guide tube

104 Carrier box

105 Guide tube 10 6 Ronde

107 compression spring

108 Recess

109 bearing bolts

110 bead

111 Seat plate

112 pawls

113 Floor pull

114 Bearing plate

115 Recording 116 Bearing plate 117 Square bearing tube 118 Square bearing tube 119 Threaded bushing 120 Lifting spindle 121 Lifting spindle wheel 122 Intermediate gear 123 Base plate 124 Bearing journal 125 Track bearing 125 126 engine 127 pinion 128 Lumbar support 129 Guide plate 130 Backrest plate 131 Locking device 132 Bearing axis 133 Threaded bushing 134 Adjustment disc 135 Sheet metal pull-through 136 Threaded bolt 137 Flat sheet 138 Backrest upholstery 139 Shin brace 140 Support fork 141 Bearing eyes 142 attack 143 Carrying strap 144 Belt hook 145 Hanging slot 146 Tread plate 201 Lifting spindle 202 Threaded bushing 203 Drive pinion 204 Guide bush 205 Bearing plate 206 Bearing bolt 207 drive wheel
•j:::..::::·: : : .·

·· ■· Timing belt pulley ·· 208 gear 209 engine 210 Timing belt 211 Carrier plate 212 Track bearing 213 Track pin 214 Cable pull 215 Pulley 216 Rope end 217 Hook 218 Drilling in 210 219 central pulley 210 Worm wheel 221 Snail 222 engine 223 Hand crank drive 224 Cable pull drum 225 angled tab 226 protruding tab 227 Guideway 228 Draft 229 Bearing bolt 230 Worm wheel 231 drilling 232 Bearing block 233 Snail 234 Spiral spring 235 slot 236 Hanging flap 237 Torsion spring 238 Pipe sleeve 239 Bearing shell 240 Pipe section 241 Bearing plate 242 Bearing bolt 243 Bolt on the traverse tube 244 role 245 inner guide frame 246

247 outer guide frame

248 bearing bolts

249 passages

250 guide plate

251 tab

252 pawl

253 Locking rod

254 Perforated sheet

255 Beam

25 6 Cable box

257 Cable box cover

258 torsion spring

25 9 Locking mechanism holder 260 Lower worktop 2 61 Locking pawls 2 62 Locking lever

263 Bowden cable

264 Support arm

2 65 Ball at torsion spring end 266 Ball caps 2 67 Inner guide frame 2 68 Film hinge

Claims (54)

::2 Claims 1. Workstation, in particular a computer workstation, consisting of a work table and a work chair, characterized in that the work table (1) and the work chair (4) have means for mutually adjustable height adjustment, which allow conversion from a seated workstation to a kneeling-sitting workstation to a standing-sitting workstation. 2. Workstation according to claim 1, characterized in that the adjustable height adjustment of the worktop (6) of the work table (1) and the seat (54) of the work chair (4) is carried out via a simultaneous and/or mutually independent control of actuators (210, 126). 3. Work table, in particular for a workplace according to claim 1, characterized in that the work table (1) has a frame (2), a worktop (6) and at least two side walls (7), characterized in that the side walls (7) with the worktop (6) form a table body assembly (3) which is height-adjustable relative to the frame (2) and is guided on the table legs (5) of the frame (2) . 4. Work table according to claim 3, characterized in that the guidance between the table legs (5) of the frame (2) and the table body (3) is carried out by means of a plastic sliding guide. 5. Work table according to claim 3, characterized in that the guidance between the table legs (5) of the frame (2) and the table body (3) is carried out by means of a roller guide. 6. Work table according to claim 3 and 5, characterized in that the roller guide is carried out via pairs of guide rollers (8) accommodated in resilient roller holders (9). 7. Work table according to claim 3, 5 and 6, characterized in that by the roller holders (9) being attached to the table body (3), preferably on the side walls (7), and the guide rollers (8) running along the inside of the table legs (5). 8. Work table according to claim 3, characterized in that power-operated pendulum supports (11) designed as toggle levers are pivotally connected to the frame (2), which have a roller (12) on the worktop side, which in turn engages in a pan-shaped recess (13) in a base plate. 9. Work table according to claim 8, characterized in that the pendulum support (11) includes a joint (14) on which a torsion spring (15) is arranged for the purpose of force transmission. 10. Work table according to claim 8 and 9, characterized in that the torsion spring (15) is connected by means of clamps (16) which can be moved along the pendulum support (11). 11. Work table according to claim 8, characterized in that cylindrical rods (17) are attached to the cross members (4) of the frame (2) connecting the table legs (5), which guide a locking mechanism (19) attached to the table body (3). 12. Work table according to claim 11, characterized in that the locking mechanism (19) consists of a locking mechanism receptacle (23) which has two pawls (20) movably mounted in recesses (22) and acted upon by a locking spring (21), that at the ends of the pawls (20) facing away from the locking spring (21) a recess (25) for receiving a Bowden cable (24) is provided and that the end of the Bowden cable (24) on the worktop side is hooked into an actuating lever (27) and the abutment for the casing (28) of the Bowden cable (24) is designed as a recess (29) in the support cross member of the frame (2). 13. Work table according to claim 3, characterized in that the force compensation over the height adjustment range of the worktop (6) by means of one or more rubber bands (34) he follows. 14. Work table according to claim 13, characterized in that the single or multi-layer rubber band (34) is guided over deflection rollers (37) fixed in the upper corners of the frame (2) and is inserted with both loop-forming ends (35) into retaining plates (36) which are suspended in the lower edge of the side walls (7) by means of a retaining bracket (41). 15. Work table according to claim _13f , characterized in that the rubber band (34) is guided over deflection rollers (37) fixed in the upper corners of the frame (2), then guided over lower deflection rollers (37) connected to the lower ends of the side walls (7) and into the upper cross member (4) of the frame (2) by means of retaining plates (36) and retaining brackets (41) is attached. 16. Work table according to claim 13, characterized in that the basic size of the force compensation by the rubber bands (34) by means of rotatable discs (40) which peripherally support rods (42) over which the elastic band is guided, is adjustable. 17. Work table according to claim 3, characterized in that the height adjustment of the worktop (6) is carried out via lifting spindles (201) which are pre-assembled in hollow profile legs (5) of the frame (2). 18. Work table according to claim 17, characterized in that the lifting spindles (201) can be driven by a motor via drive wheels (207), toothed belt wheels (208) and toothed belts (211). 19. Work table according to claim 3, characterized in that the height adjustment of the worktop (6) can be carried out via cable pulleys (216) and cable pulls (215), the cable pulls (215) being preferably suspended with their cable ends (217) in hooks 218 which are welded to the roller holders 9. 20. Work table according to claim 19, characterized in that the cable pulleys (215) can be operated via a central cable pulley (220) which is driven by a motor or manually via appropriate gears. 21. Work table according to claim 19, characterized in that the cables (215) are actuated via a cable pull drum (225) which accommodates a tensionable spiral spring (235) in the interior and has guide tracks (228) for the cables (215) on the circumference. 22. Work table according to claim 21, characterized in that the cable pull drum (225) can be assembled from two identical drum halves in the manner of a bayonet lock. 23. Work table according to claim 21, characterized in that the cable pull drum (225) is mounted on a bearing block (233) together with a worm wheel (231) driving it and a self-locking worm (234). 24. Work table according to claim 3, characterized in that the height adjustment of the worktop (6) is carried out solely via a drive by means of torsion springs (238) which are mounted in the side walls (7) and are supported with one extended leg against the lower cross member (4) of the frame (2) and with the other extended leg against a bearing plate (242) fastened to the table body. 25. Work table according to claim 24, characterized in that the path-force curve of the torsion springs (238) can be changed by means of pipe pieces 241 that can be moved on the legs of the torsion springs (238). 26. Work table, in particular for a workplace according to claim 1, wherein the work table (1) has a frame (2), a worktop (6) and at least two side walls (7), characterized in that the side walls (7) form a fixed frame body assembly (2) with an outer guide frame (247), to which the worktop (6) together with its inner guide frame (246) is height-adjustable. 27. Work table according to claim 26, characterized in that two torsion springs (238) arranged in opposite directions are inserted in each side wall (7), which are supported on the one hand via supports on the lower cross members (4) of the frame (2) and on the other hand via supports on the beams (255) of the inner guide frame (246). 28. Work table according to claim 26, characterized in that in order to realize the locking mechanism (19), locking rods (253) are connected to the outer guide frame (247), over which two locking pawls (252) are pushed, which in turn are fastened on one side to a guide plate (250) and on the other hand accommodate recesses for a Bowden cable to be hooked in. 29. Work table, in particular for a workplace according to claim 1, characterized in that the worktop (6) is hinged to a lower worktop (260) and can be adjusted like a desk against the force of a torsion spring (258), whereby any working position of the worktop (6) can be fixed by means of a locking mechanism (259) with locking pawls (261) which work together with an arcuate support arm (264) which is attached to the adjustable worktop (6) and extends through the lower worktop (260). 30. Work table according to claim 29, characterized in that the torsion spring (258) carries balls (265) at its leg ends, which are received by spherical caps, one of which is located on the underside of the worktop (6) and the other of which is attached to a leg of the inner guide frame (267). 31. Work table, in particular for a workplace according to claim 1, characterized in that the worktop (6) accommodates an armrest (45) in a recess (43). 32. Work table according to claim 31, characterized in that the armrest has a spring-loaded insert part (44) and a padded armrest (45) and both parts (44, 45) can be moved transversely to one another via a ball bearing guide (46, 47, 48). 33. Work chair, in particular for a workplace according to claim 1, characterized in that it consists essentially of a ball-bearing base support plate (50), a support made of an inner support tube (52) and an outer central tube (53), an upholstered seat (54) and a backrest frame (55) with a backrest (56). 34. Work chair according to claim 33, characterized in that the central tube (53) has a support frame (62) on the base support plate side, on which a bearing for bars (68) is formed, the bars (68) on the other hand are connected in a bearing (71) to the backrest frame (55), a support plate (63) is attached to the central tube (53) on the seat side, which forms a force-loaded bearing in connection with bearing plates (70) and an axle (67), and the backrest frame (55) is connected to the underside of the seat (54) via at least one bearing bracket (72). 35. Work chair according to claim 34, characterized in that a or a double torsion spring (76) is provided for applying force to the bearing, which is held in lateral recesses (79) on the carrier plate (63), with its connected legs (77) on the one hand being designed to rest on the carrier plate (63) and its free legs (80) on the other hand being designed to rest on the underside of the seat surface (54). 36. Work chair according to claim 34, characterized in that on the axis (66) at least one strut (82) is pivotally held on the central tube (53) and a crossbar (83) equipped with knee pads (84) is assigned to the strut (82). 37. Work chair according to claim 34, characterized in that the seat surface (54) has a hump-shaped elevation (86) in the region of its end facing the backrest. 38. Work chair according to claim 34, characterized in that the backrest frame (55) has a cross brace (89) in the area of the bearing brackets (72), in which a torsion bar (90) is mounted, which is connected on the one hand to a bearing bush (91) and an inner conical sleeve (92) attached thereto and on the other hand accommodates a disk (93) that creates the positive connection to the cross brace (89), that the end of the torsion bar (90) that protrudes beyond the disk (93) carries a further bearing bush (94) and is attached by means of a screw element (96) in connection with the inner conical sleeve (95) fixed to the bearing bush (94), the inner conical sleeve (92) being covered by an outer conical sleeve (97) in such a way that their conical surfaces (104, 105) can contact, that the outer conical sleeve (97) has claws (98) which engage in recesses (99) on the bearing bracket (72) and that the torsion bar (90) receives a knob (88) on its threaded end on this side. 39. Work chair according to claim 38, characterized in that the cross brace (89) is designed as a square hollow profile and the disc (94) has a square cross section corresponding thereto. 40. Work chair, in particular for a workplace according to claim 1, characterized in that it consists essentially of a roller-mounted base support frame (50), a seat support (101) with an inner guide tube (103), an outer guide tube (105) and a support box (104), an upholstered seat surface (54) and a backrest frame (55) with a backrest (56), a lumbar support (128) and optionally a shin support (139). 41. Work chair according to claim 40, characterized in that the guide tubes (103, 105) of the seat support (101) are inclined at an angle forward and upward in comparison to the vertical axis of the work chair (49) and are firmly connected to the beveled support box (104). 42. Work chair according to claim 40, characterized in that the telescopically movable guide tubes (103, 105) are closed at the free ends by discs (106) between which a compression spring (107) is supported, wherein the disc (106) of the upper, inner guide tube (105) carries a support roller (102) which, guided between beads (110), supports the seat plate (111) for the seat surface (54) every time the seat position is changed. 43. Work chair according to claim 40, characterized in that two locking pawls (112) are fitted onto the inner guide tube (105), which are supported on the one hand on a bearing plate (114) firmly connected to the outer guide tube (103) and which, on the other hand, have insertion slots for a Bowden cable (113) to be hooked in, by means of which they can be brought into a locking position or release position for the inner guide tube (105) relative to the fixed, outer guide tube (103). 44. Work chair according to claim 40, characterized in that the backrest frame (55) and the support box (104) on the one hand and the square support levers (100) for the backrest frame (55) and the seat plate (111) mounted on the support box (104) by means of square bearing tubes (118, 117) on the other hand form a lifting mechanism that can be adjusted in a parallelogram manner via the telescopically adjustable guide tubes (103, 105). 45. Work chair according to claim 40, characterized in that the bearing plate (114) for the locking pawls (112) is machined directly from the support box (104). 46. Work chair according to claim 40, characterized in that the seat support is provided with an electrical adjustment device (119 to 127). 47. Work chair according to claim 46, characterized in that in the inner guide tube (105) a lifting spindle (120) runs in a threaded bushing (119) firmly connected to the inner guide tube (105) and is driven by a lifting spindle wheel (121), a ••J ·♦ »« , Intermediate gear (122) and a pinion (127) can be driven by an electric motor (126). 48. Work chair according to claim 40, characterized in that the backrest (56) and lumbar support (128) are adjustable both as a whole and relative to one another to form the backrest frame (55). 49. Work chair according to claim 48, characterized in that the backrest plate (130) is attached to a resilient, U-shaped bent arm of a guide plate (129) slidably guided on the backrest frame (55) and the guide plate (129) can be clamped continuously onto the backrest frame (55) by means of an eccentric-shaped locking device (131). 50. Work chair according to claim 48, characterized in that a threaded bolt (136) with which a sheet (137) of the lumbar support (128) is firmly connected, is mounted on an adjusting disk (134) by means of a threaded bush (133) and the adjusting disk (134) is vertically adjustable relative to the spring-loaded arm of the guide plate (129). 51. Work chair according to claim 48, characterized in that a foldable, height-adjustable shin support (139) can be attached to the support box (104). 52. Work chair according to claim 51, characterized in that the shin support (139) is hinged to the square bearing tube (114) of the support box (104) by means of a support fork (140) and can assume a preset inclined position via a stop (142). 53. Work chair according to claim 51, characterized in that the shin support (139) is supported by a carrying strap (143). 54. Work chair according to claim 53, characterized in that a belt hook (144) is attached to the end of the carrying belt (143) which is hooked into a selectable suspension slot (145) in the bearing plate 116.