CA2087981A1

CA2087981A1 - Work chair, more particularly an office chair

Info

Publication number: CA2087981A1
Application number: CA002087981A
Authority: CA
Inventors: Peter Tobler
Original assignee: Individual
Current assignee: EQUUS MARKETING AG
Priority date: 1991-05-24
Filing date: 1992-05-22
Publication date: 1992-11-25
Also published as: AU1692092A; ATE142857T1; DE59207171D1; ES2094355T3; EP0540711A1; EP0540711B1; JPH06500944A; WO1992020262A1

Abstract

The working chair has a seat bearer (11), a seat (15) articulated on the seat bearer (11) and a squab bearer (25) with a squab (29). The squab bearer (25) has a spindle (23) on the seat bearer (11). One arm (27) is articulated on the squab (29) and the other (31) on the seat (15). The simple mechanical arrangement (20, 22, 23, 25, 35) thus formed causes the seat to be moved in one direction of rotation (47) when the squab bearer (25) is moved in the other (43). As in lying down and relaxing, the knee and hip joints thus undergo an extension. This produces a sound lordosis. The spindle (23) and the articulation axis (35) lie in a plane (36) inclined at about 70· to the horizontal. Regardless whether a person is heavy or light, relatively little force on the squab (29) is needed to raise the seat (15). As the seat (15) and the squab (29) remain close together during any movement, the tendency for the shirt to be pulled out is prevented. The movement of the seat backwards and downwards when the squab is tipped backwards prevents blood congestion at the back of the knees.

Description

A work chair, more particularly an of~ice chair The in~tention relates to a work chair, more particularly an office chair, comprising: a seat frame, a seat pivotable forwards on the seat frame around a first pivot and also movable substantially horizontally relatively to the seat frame; a back frame articulated by way of a second pivot to the seat frame and connected by way of a third pivot to the seat; and a back coupled with the back frame.

Many of the wor~ chairs whlch are now in production and which are used mainly as office chairs are of the synchronous work chair kind wherein ad]ustment of back frame inclination produces a simultaneous adjustment of seat inclination. In known synchronous work chairs pivoting of the back in one direction causes pivoting of the seat in the same direction. As a rule, however, the pivoting of the seat is only half as great as the pivoting of the back (US-A-2 859 799, CH-A-629 945). Work chairs of this kind suffer more particularly from five disadvantages, viz. a physiologically unna-tural pivoting movement of the chair back, a negative effect on the sedentary posture, absence of weight neutrality, a relatively expensive construction and an ugly appearance out of keeping with present-day aesthetic requirements. These disadvantages are to some extent interrelated. For example, if weight neutrality is absent and if there is maladjustment of the spring force of a compensating device opposing the force applied by the user's weight to the chair back, the sedentary posture may be further ' .

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A consideration of the movement of a person's joints when the person stands up normally shows that extension in the medical sense of the term occurs in the knee joints and hip joints. The same occurs when a person lies down and relaxes. Conversely, the knee joints and hip joints experience flexion when the person sits down. However, for example, in the case of the work chair according to CH-A-629 945, when the back pivots to the rear the back part of the seat descends in contrast to the normal movement pattern, the seat squab pivoting only about half as much as the chair back. The result is a physiologically unnatural movement in which the hip joints experience extension and the knee joinks flexion.

To produce rearwards pivoting in a work chair according to CH-A-629 945 the user presses his or her trunk against the chair back and bears firmly on the floor with his or her feet, with the ris~ of the user sliding forwards, particularly if relatively considerable force must be applied to produce the pivoting. Also, since the ~ront edge of the seat rises, hyperemia may occur in the knee joint region.

~ lever is operated to place the chair-back in the upright position. Operation of the lever releases the springs which were stressed during the rearwards pivoting. The back and the seat then return to their original position or into an intermediate position required by the user. The user, having slid to the - 3 - ~..~ . y ~ ~

rear during pivoting, now finds that his or her pelvis is in a rearwardly inclined position. The user therefore has an unsatisfactory body posture which may readily lead to back pains.

In the subject of CH-A-629 945 the rearwards pivoting of the chair back is effected against the force of a gas spring and of a compression spring, the preloading of the compression spring being variable by the adjustment of nuts. In practice, however, this feature cannot provide satisfactory adjustment to individual user weight. A preloading or presetting is therefore used which is roughly adapted to the weight of the average user. A lightweight person using the chair may find it d~fficult to move the back to the rear and in this operation may slide forwards on the seat. Conversely, a heavy person using the chair ma~
find it unpleasant when adjusting the back when because of the user's considerable weight the back moves rearwardly substantially without perceptible resistance.

In the work chair according to CH-A-629 945 the energy expended to pivot the chair back is stored to a large extent in the springs and upon the release of a locking device is made available to move the chair back and the trunk of the chair user forwards again. If the user leaves the chair without moving the back forwards and if the locking device is released, for example, by cleaners, the chair back moves forwards with considerable force and at a considerable speed, with a consequent serious risk of injury.

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US-A-4 834 454 discloses a chair wherein a seat is pivotable on the seat frame or support aroun~ a pivot at the front of the seat. An L-shaped back frame or support is pivotable around a pivot disposed on the seat frame. The L-shaped back frame is connected to the seat at the end of the horizontal arm of the L by means of a pivot. When the back pivots to the rear, the back frame, which is rigidly connected to the back, raises the back part of the seat, the seat simultaneously moving a little to the rear. What is found to be disadvantageous is that at the start of a rearwards pivoting movement of the chair back very considerable force is necessary to raise the seat on which the user is sitting, for during the first part of the pivoting movement the pivot at the end o~ the horizontal arm of the L must make a steep rising movement. Another disadvantage is that a hea~y user has to use much more force than a light user. Another and considerable disadvantage is that the distance between the seat and the chair back increases considerably as the chair back pivots to the rear, with the unpleasant result that the shirt tends to be pulled out.

It is therefore the object o~ this invention to obviate at least some of the disadvantages hereinbefore described of the known work chairs. The aim of the invention is therefore to provide a work chair having a synchronous mechanism wherein the user's body performs physiologically natural movements. It is also the intention that the pattern of movements leads to a good sedentary posture. It is the intention that the chair be of simple construction. The chair is also required ~a~7s~i .. .

to meet the very high aes~hetic standards to which work chairs, more particularly office chairs, are now expected to conform.

According to the invention, this is achieved in a chair according to claim 1. In such a chair pivoting of the back frame in one direction causes pivoting of the seat in the opposite direction. Conse~uently, when, for example, the back frame pivots to the rear, the rear part of the seat pivots upwardly around a fulcrum in the front part of the seat; the body makes a natural sequence of movements in that, as when a person normally stands up, the hip joint and knee joint experience extension. In addition to this general pattern of movements, details of the pattern are very signiicant. For example, the high anyle of inclination defined in claim 1 results in a relatively substantial rearwards movement of the seat in response to a rearwards pivoting of the chair back. Extension of the knee joint is thus further enhanced and hyperemia in the knee joint region obviated. Another result of the high angle o~ inclination is that relatively little force is required to initiate rearwards pivoting o~ the chair back, and so the user find this movement comfortable. The resulting satisfactory movenlent pattern encourages active sitting. Active sitting promotes blood circulation through organs and limbs and contributes to the general wellbeing of the chair user. The premature fatigue typical of passive sitting is obviated. Another significant feature is the partial compensation for weight provided by force compensation, the latter arising because the force acting on the chair back is .: .

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opposed by the force caused by the user's weight acting on the seat. This force compensation makes weight adjustment for light and heavy users unnecessary.

Another advaniage of the invention is its very simple construction, which also leads to a particularly attractive appearance of the chair. Virtually only a single lever, viz. the back frame, is required.

Advantageously, the angle of inclination o~ the plane in which the second pivot of the back frame and the third pivot of the back frame are disposed on the seat is approximately from 60~ to 70. Tests have shown that the user finds the chair particularly comfortable at such an inclinatioh angle. The movement pattern of the seat and the back at this angle of inclination does not tend to pull out the user's shirt.

Conveniently, the distance between the second pivot and the third pivot is approximately from 80 mm to 120 mm, preferably approximately 100 mm. This optimises conditions for weight compensation and ensures optimal rearwards travel of the seat in response to rearwards pivoting of the chair back.

- Conveniently, the back is pivotally connected to the back frame by way of an articulation. This feature ensures that the movement pattern of the chair back is satisfactory. More particularly, if the chair back is a rocking back, lordosis - i.e., forwards curvature of the chair user's spinal column - is improved.

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~90 1 ~1 Tests have shown that, conveniently, the articulation of the chair back is disposed behind the second pivot at an angle of from 10 to 20, preferably 15, to the vertical through the second pivot.

Advantageously, a spring element tending to move the chair back and the set forwards is provided.
Advantageously, the spring element has a relatively steep characteristic so that the spring force increases with increasing inclination of the chair back and thus opposes the force which the weight of the user's trunk applies to the chair back.

Conveniently, the third pivot is disposed near the rear half of the seat. This arrangement is associated with good conditions for weight compensation.

There are various ways in which the seat can be mounted at the front. For instance, the seat can be connected at the front to the seat frame by means of a flexible connecting member. A convenient embodiment provides a connection by way of a support lever. In the front position of the chair back the support lever is, advantageously, disposed substantially vertically.
Consequently, the front part of the seat is lowered slightly in response to a rearwards pivoting of the chair back. The pressure applied by the user's body in the popliteal region is therefore reduced so that the required relaxation of the body and the blood circulation are enhanced.

Another possibility is that the seat is connected at the front to the seat frame by means of a slide '- ' : ' ' ~ ~ - 8 ~
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block moving in a guide. This provides a simple cons~ruction.

Advantageously, the spring element is an elastomer block. Elastomer blocks known under the "Zellvulkolan"
name have movement-damping properties and thus help to inhi~it an abrupt forwards acceleration of the chair back. An elastomer block or a helical spring is advantageous since unlike a gas spring they have a relatively steep spring characteristic. The restoring force exerted by the elastomer block or the mechanical spring at the start of a rearwards movement of the chair back is therefore slight. Because of the mechanics according to the invention there is considerable force compensation in this zone be-tween the force acting on the seat and the force acting on the back. However, near the end of the rearwards movement of the chair back the force acting on the seat is nothing like sufficient to compensate for the force acting on the chair back. Consequently, the high restoring force of the elastomer block in this zone is very advantageous. The user finds the chair very comfortable and is therefore stimulated into active fitting.

The designer has a variety of options for arranging the spring element. It can, for example, act directly on the chair back. Very advantageously, however, the spring element is arranged substantially parallel to the seat and acts thereon. This feature enables the mechanism below the seat to be very compact, a feat~re which is aesthetically desirable.

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The seat and the back can be made of a single flexurally resilient part, for example, a plastics part. Another possibility is for the seat shell and back shell to consist of a single member~ for example, a plastics member, having an articulation-like part.

Constructions of this kind are possible thanks to the arrangement according to the invention of the second pivot of the back frame and of the third pivot connecting the back frame to the seat since this arrangement obviates unwanted movement between the seat and the back such as might lead to the user's shirt belng pulled out.

Advantageously, clamping means, for example, disc clamping means, are provided to lock the seat and chair back in the required position. Since in the construction according to the invention of the work chair the seat has a relatively long travel in response to a movement of the chair back, a locking device acting on the seat is required to deal with only relatively reduced forces, and so clamping means can be used instead of the conventional gas spring. Clamping means of this kind are cheap to produce and unlike gas springs present no waste disposal problems.

Advantageously, the seat is markedly concave -i.e., the seat is formed with recesses corresponding to the contours of the human body. The recessing reduces the risk of slipping even when the seat is in a relatively steeply inclined position.

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Conveniently, the second pivot, third pivot and articulation are so arranged that in the normal position the angle of inclination of -the seat is approximately 3 to the rear and includes an angle of approximately 103~ with the plane in which the third pivot and the articulation of the back are disposed, and in response to an approximately 34 rearwards pivoting of the back frame the seat pivots upwardly by about 5. This construction has proved very convenient from the ergonomic point of view.

Embodiments of the invention will be described hereinafter with reference to the drawings wherein:

Fig. 1 shows a first embodiment of a work chair in the normal sitting position;

Fig. 2 shows the chair of Fig. 1 in the reclining position in which the chair back has been moved to the rear;

Fig. 3 shows a second embodiment of a work chair in the normal sitting position;

Fig. 3a shows a variant of the chair back frame;

Fig. 4 shows the chair of Fig. 3 in the reclining position;

Fig. 5 shows a third embodiment of a work chair in the normal fitting position, and Fig. 6 shows the chair of Fig. 5 in the reclining position.

- In the embodiment shown in Figs. 1 and 2 the seat frame 11 is supported in conventional manner by a cruciform base comprising an upright 13 and a vertical lift. Only the upright 13 is shown. Advantageously, the seat 15 is markedly concave - i.e., it is formed at the rear with a receQs 16 to inhibit the sitter from sliding forwards. Upholstery 18 can be provided in conventional ~anner. The chair back 29 can have upholstery 30. At its front end the seat 15 is supported on the frame 11, for example, by means of a support lever 17. The same is connected to the frame 11 by way of an articulation 19 and to the seat 15 by way of an articulation 21. However, the seat 15 could be supported on the frame 11, for example, by means of a flexible elastomeric connecting element. The chair has a back frame 25 pivotally connected by way of a pivot 23 to the seat frame 11. The back frame 25 is a two-armed lever. A first arm 27 thereof is coupled with the back Z9 which is a rocking back. The second arm 31 of the lever 25 is coupled with the seat 15.
The arm 27 is coupled approximately at the centre or therehelow of the back 29, for example, by means of an articulation 33. The second arm 31 is coupled by way of the pivot 35 to somewhere in the rear half of the seat 15. A distance of approximately half the seat length or more, for example, two-thirds of seat length, is present between the pivots 21 and 35.

The position of the pivot 35 relatively to the pivot 33 is particularly important~ The pivot 35 is ~. .

~12- ~ U ~ 7~ ~1 disposed at a place before and above the pivot 23. An important consideration is that in the normal sitting position - i.e~, with the chair back 29 substantially upright - the angle of inclination of the plane 36 containing the two pivots 23, 25 is at an angle of approximately from 45 to 80, advantageously from 60 to 70. When the chair back 29 pivots to the rear, the pivot 35 moves in the direction indicated by an arrow 45. Relatively little force is required for this. The seat 15 also moves a relatively considerable distance to the rear. The distance between the pivots 23 and 35 is approximately from 80 to 120 mm, advantageously approximately 100 mm. These dimensions enhance weight compensation.

Disposed on the lever 25 is a finger 37 on which a spring element 39 acts. The same tends to move the chair back 29 forwards - i.e., to restore it to the normal sitting position. Advantageously, the spring element 39 is a helical spring, for example, a compression spring guided by a telescopic device 41.
Very advantageously, however, an elastomer block, for example, of "Zellvulkolan", can be used as spring element 39.

A locking device 42 having an operating lever 44 is shown diagrammatically. The locking device 42 can take the form of a simple clamping device, for example, a plate clamp. Since, as stated initially, there is weight compensation and the seat has a relatively long travel, the forces required for locking are relatively small and so a single clamping device is adequate.

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As a comparison between the positions of the chair in Figs. 1 and 2 will show, a force acting on the chair back 29 in the direction of the arrow 43 moves the seat 15 rearwardly and upwardly in the direction indicated by the arrow 45, the seat 15 rotating as it moves around the pivot 21 in the direction indicated by an arrow 47 so that the seat front edge is lowered. The torques acting on the arms 27, 31 oppose one another and so the chair user, whether light or heavy, needs to expend relatively little energy to change from the position of Fig. 1 to the position of Fig. 2.

Figs. 3 and 4 show clearly that the chair back follows the trunk contour faithfully and so there is no risk of shirts being pulled out.

In short, the ad~antages which the mechanism described provides for users are considerable, vi~. a pleasing, because natural, pattern of movements, comfortable seating ~or light and heavy users thanks to force compensation hetween the seat and the chair back, reduction of hyperemia in the popliteal space because o~ the ergonomic movement o~ the seat, less likelihood of shirts being pulled out and more particularly satisfactory lordosis.

The embodiment shown in Figs. 3 and 4 differs from the embodiment hereinbefore described mainly in the different way in which the seat 15 is supported on the seàt frame 11 and in the arrangement of the spring 39.
The seat frame 11 is formed with an inclined guide 20, for example, a slot, in which a slide block can slide.
The same can be, for example, a rod 22 borne by lugs 24 ~.; .

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of the seat 15. The spring element 39, for example, an elastomer block ~"Zellvulkolan"), is arranged substantially parallel to the seat 15 and bears at one end 26 on the seat frame 11 and acts by way of its other end on the seat 15. The spring element 39 transmits its force by way of the rod 22 and lugs 24 to the seat 15 and tends to move the seat 15 forwards into the position of Fig. 3.

The back frame 25 can have various shapes. Fig.
3a shows one possible variant. The possibility of connecting the pivots 23, 35 and 33 in different ways gives the designer plenty of possibilities for an attractive construction of the chair. For example, a back support 25 can be provided on each side, the two back supports being interconnected by the pivot 23. A
prolongation 46 can serve as arm rest (~ig. 3a).

The embodiment in Figs. 5 and 6 differs from the embodiment of Figs. 3 and 4 mainly in that the rear part of the seat 15 and the bottom part of the chair back (29 to 2~) are pivotally interconnected. The seat shell and the chair back shell can therefore consist of a single resilient member, for example, a plastics member, or of a single member having an articulation-like part 2~.

Claims

C L A I M S

1. A work chair, more particularly an office chair, comprising: a seat frame (11), a seat (15) pivotable forwards on the seat frame around a first pivot (21) and also movable substantially horizontally relatively to the seat frame (11); a back frame (25) articulated by way of a second pivot (23) to the seat frame (11) and connected by way of a third pivot (35) to the seat (15); and a back (29) coupled with the back frame (25), the third pivot (35) being disposed before and higher than the second pivot (23), the angle of inclination of the plane (36) in which the third pivot (35) and second pivot (23) are disposed being approximately from 45° to 80° to the horizontal when the work chair is in its normal position.

2. A work chair according to claim 1, characterised in that the angle of inclination is approximately from 60° to 70°.

3. A work chair according to claim 1 or 2, characterised in that the distance between the second pivot (23) and the third pivot (35) is approximately from 80 mm to 120 mm, preferably 100 mm.

4. A work chair according to any one of claims 1 to 3, characterised in that the back (29) is pivotally connected to the back frame (25) by way of an articulation (33).

5. A work chair according to any of claims 1 to 4, characterised in that the articulation (33) of the chair back (29) is disposed behind the second pivot (23) at an angle of from 10° to 20°, preferably 15°, to the vertical through the second pivot (23).

6. A work chair according to any of claims 1 to 5, characterised in that a spring element (39) tending to move the back (29) forwards is provided.

7. A work chair according to any of claims 1 to 6, characterised in that the third pivot (35) is disposed near the rear half of the seat (15).

8. A work chair according to any of claims 1 to 7, characterised in that the back (29) is a rocking back.

9. A work chair according to any of claims 1 to 8, characterised in that the seat (15) is connected at the front to the seat frame (11) by means of a flexible connecting member.

10. A work chair according to any of claims 1 to 8, characterised in that the seat (15) is connected at the front to the seat frame (11) by way of a support lever (17).

11. A work chair according to claim 10, characterised in that in the normal position of the back (29) the support lever (17) is disposed substantially vertically.

12. A work chair according to any of claims 1 to 11, characterised in that the seat (15) is connected at the front to the seat frame (11) by means of a slide block (22) moving in a guide (20).

13. A work chair according to any of claims 6 to 12, characterised in that the spring element (39) is an elastomer block.

14. A work chair according to any of claims 6 - 13, characterised in that the spring element (39) is a helical spring.

15. A work chair according to claim 10, characterised in that the spring element (39) acts on the back frame (25).

16. A work chair according to claim 10, characterised in that the spring element (39) is arranged substantially parallel to the seat (15) and acts thereon.

17. A work chair according to any of claims 1 to 16, characterised in that the seat (15) and the back (29) are made of a single flexurally resilient part, for example, a plastics part.

18. A work chair according to any of claims 1 to 16, characterised in that the seat (15) and back (29) are made of a single part, for example, a plastics part, having an articulation-like part (28).

19. A work chair according to any of claims 1 - 18, characterised in that clamping means, for example, plate clamping means, are provided to lock the seat (15) and the back frame (25) in the required position.

20. A work chair according to any of claim 1 to 19, characterised in that the seat (15) is markedly concave.

21. A work chair according to any of claims 4 to 20, characterised in that the second pivot (23), third pivot (35) and articulation (33) are so arranged that in the normal position the angle of inclination of the seat (15) is approximately 3° to the rear and includes an angle of approximately 103° with the plane in which the third pivot (35) and the articulation of the back (29) are disposed, and in response to an approximately 34° pivoting of the back frame (25) the seat pivots upwardly by about 5°.