EP1211966B1

EP1211966B1 - Ergonomic chair

Info

Publication number: EP1211966B1
Application number: EP00954399A
Authority: EP
Inventors: Esben Skov Nielsen; Axel Pedersen; Birger Trier Larsen
Original assignee: RBM AS
Current assignee: RBM AS
Priority date: 1998-09-18
Filing date: 2000-08-23
Publication date: 2006-06-14
Anticipated expiration: 2020-08-23
Also published as: WO2001013765A1; EP1211966A1; AU6686500A

Description

The invention concerns a chair, preferably comprising a lower frame with a number of castors, which are individually pivotal, a central support column, which is adjustable in height and secured in said frame at its lower end, and which at its upper end is connected with a carrier bracket, which comprises an inner part, which is fixed in relation to the support column, and an outer part, which is movable in relation to the inner part, and to which outer part a seat and a backrest are secured, and where said seat can be tilted around a pivot point placed in the carrier bracket.

The known technique

With known chairs, for example for use for office work or the like, it is a problem today that it is often necessary for the users to change between different working positions. It has gradually become normal practice that the users sometimes sit at their desks writing with a pencil, a pen or the like, and at other times they sit leaning back slightly while talking over the telephone, and later they sit working e.g. at a computer/display terminal etc.
Moreover, it has also become more and more normal for use to be made of desks, which are adjustable in height, where the height of the desk can be adjusted to suit the current work task, i.e. that users sometimes sit at the desk and at other times work while standing up.
Today, there is not a chair on the market, which can satisfy the sitting/supporting requirements that exist in connection with these different positions.
It is known to have a chair which can be adjusted in height, e.g. by means of a gas cylinder and a form of step-less locking for maintaining the adjusted height. It is also known to be able to set the angle of the seat and to be able to adjust the height of the backrest and its distance from the seat.
It is also known, for example from DE 3805771 A1, EP 0 726 723 B1, EP 0 535 262 A1, US 5,397,165 and US 5,685,607, to have a form of forced control between the angle of the seat and the position of the backrest for the adjustment of the backrest to different seat positions. From US 5,685,607 a technique is known, which discloses a stationary bracket on a support column, and a bracket which is movable in relation to the stationary bracket and on which the seat and backrest are secured.
EP 0 726 723 B1 discloses a technique, whereby the backrest is adjusted in accordance with the angle of the seat, both forwards and backwards in relation to the horizontal, in such a manner that the contact plane of the backrest in relation to the user is urged closer to the vertical pivotal axis of the chair when the seat is tipped from the neutral position (horizontal) and forwards. When the seat is tipped from the neutral position and rearwards, the sitting angle is opened approx. 7°, which results in the back no longer being supported, which for the user can feel unpleasant, in that it appears as if the backrest disappears when the seat is tilted to the maximum rearwards.

The new technique

With the invention it is desired to provide a chair, which fulfils the ergonomic demands that can be placed on a chair of this type.
The new aspect of the chair according to the invention is that the height of the backrest in relation to the tilting point of the seat, seen in a direction substantially at right-angles to the seat, is more or less constant.
By the use of guide means, the backrest is moved in a force-controlled manner, so that when the seat is tilted forwards from the neutral position, the sitting angle - which is the angle between the seat and the backrest - is opened, which results in an ergonomically correct sitting position with the seat tilted forwards to a maximum. Since the seat can be tilted forwards more than is possible with the remaining chairs on the present market, it is possible to provide this chair with a central support column, which has a greater lift-height than that which is otherwise normal for office chairs, in that it is hereby still possible for the user to support himself with his feet on the floor.
The lift-height can be increased e.g. by approx. 50%.
When the seat is tilted rearwards, the sitting angle is not changed. This means that there is still support for the back of the user.
At the same time, the rearwards inclination of the seat is limited, so that the chair does not come out into an unstable zone.
In addition, the possibility is provided for the seat to be adjusted in the horizontal direction in order to be adapted in an even better manner to the individual user's requirements for adjustment of the sitting position.
In order to further ensure that the chair is stable when used in its highest position and with the seat tilted forwards to the maximum, an extra support, which is placed in the lower end of the support column, is moved down against the under layer on which the chair is standing, in that this is activated by the weight of the user. It is hereby ensured that the chair cannot roll away from under the user, whereby toppling is avoided.
A further comfort provided by the chair is the ergonomic shape of the sitting cushion itself, which among other things is configured with a front edge which is rounded-off forwards/downwards, together with a rounding-off starting in the centre of the front edge and rounding-off towards the rear edge of the seat, increasing towards the sides of the seat. This rounding-off contributes to the users being able in an easy manner to adapt their different sitting/standing positions to the actual working situation, without the corners or the edges of the sitting cushion causing discomfort or pinching on the back of thighs and/or calves. By avoiding pinching or pressure on the back of thighs and/or calves, a more free circulation of blood in the user's legs is ensured, whereby an increased level of comfort is achieved.
Furthermore, with this seat there is the comfort that between the upholstery of the seat and the seat platform, which forms the underside or bottom of the seat, a cavity is formed which serves as ventilation for the seat during use, whereby e.g. moist air is led away from the upholstery, which is preferably of spongy material such as foam rubber or the like.
The ventilation arrangement is effective with normal use of the chair, i.e. when a person/user sits down on and gets up from the chair.
The material on the seat cushion is preferably a natural product, such as wool or the like, which allows permeation of (moist) air. For example, wool has the characteristic that it is comfort regulating in itself, i.e. it accommodates temperature and humidity, so that these are in balance with that textile, which separates the skin of the user from the upholstery, or with the naked skin.
The material also allows permeation of air (moist) to the padding foam. By ensuring the penetration of air diagonally in the padding foam by perforations/holes in the seat platform, the upholstery chamber is aired more quickly due to the shorter distance that the air-must pass, in that one or more airing holes are placed in the seat platform in a substantially central manner. When the user sits down on the chair, the air is pressed down and out of the foam and the cavity. When the user gets up, new air is sucked into the foam.
Depending on the type of foam, pattern of use by the user (24-hour chair) and the like, this ventilating effect can possibly be reinforced by a non-return valve under/in the seat platform and by a surface-treatment of the foam.

The drawing

In the following, the invention is explained in more detail with reference to the drawing, where

fig. 1: shows a vertical section in a chair with seat and backrest in a position with the seat in a preferably horizontal position,
fig. 2: shows a vertical section in a chair with seat and backrest in a position with the seat tilted forwards,
fig. 3: shows a vertical section in a chair with seat and backrest in a position with the seat tilted backwards,
fig. 4: is a partial view of the seat construction in unloaded condition,
fig. 5: is a partial view of the seat construction in loaded condition, and
fig. 6: shows the underside of the seat platform.

Example embodiments

The chair comprises a frame with a number of castors (not shown), a support column 3, conical parts 4 or other form of releasable fixed connection between the support column 3 and a carrier bracket comprising an inner part 1 and an outer part 2, which can be tilted in relation to each other. The bracket's inner part or support element 1 is fixedly connected to the support column 3 in a releasable manner and constitutes the stationary part of the bracket 1, 2. The support column 3 can be a gas cylinder or other form of height-adjustable support column. The outer part or outer element 2, on which a seat 5 is preferably secured in a displaceable manner, tilts around an axle 6. On the support element 1 a number of lugs or segments 7 are secured by means of a number of securing elements 10, 11, and are herewith also stationary in relation to the support column. The outer element 2 tilts around the axle 6 in relation to the support element 1, which is stationary. A back support yoke 12 is hinged with the outer element 2 in a back support link 15 by means of a securing element 13 and can turn around this. The movement of the back support yoke 12 is controlled by one or more elongated link parts 14, which connect the back support yoke 12 with the support element 1. The link part 14 is pivotally connected to the support element 1 and to the back support link 15. The free end of the back support yoke 12 is surrounded by a tubular element 18, which is arranged to be able to slide in its lengthways direction and thus constitute a form of height adjustment for a backrest 19. The height of the backrest 19 is maintained by means of a holding arrangement 20, which can be in the form of a clamping screw, spring-loaded pin/hole connection or the like. In the upper end of the tubular element 18, the backrest 19 is pivotally secured in a pivot point 21, so that it is possible to turn the backrest 19 approx. 180° around the pivot point 21, and in such a way that by turning the backrest approx. 90°, this can be used as underlayer/support for the forearms and/or elbows when the user sits on the chair in reversed manner, which provides a relaxed sitting position, e.g. in listening situations, alternation of sitting positions at a keyboard and the like.
The movement of the backrest 19 can be described as a translation, whereby the back support yoke 12 is both moved and turned in relation to the starting point. The translation is controlled by four movement centres consisting respectively of the tilt point 6 of the seat 5, the securing element 13 and pivot points 16, 17 for the elongated link part 14. The tilt point 6 and the pivot point 16 are stationary pivot points in relation to the support element 1, while the securing element 13 for the backrest link 15 is moved in an arc around the tilt point 6, and the pivot point 17 is moved in an arc around the pivot point 16 with a radius corresponding to the distance determined by the elongated link part 14. The securing element 13 and pivot point 17 have a constant distance between them, since they are both placed on the back support link 15, and the pivot point 17 will describe a relative movement in the form of an arc around the point 13.
The backrest 19 is hereby moved following a geometry, which provides a special relationship between the angle of the seat 5 and the angle of the back support yoke 12, so that the angle that the elongated part of the back support yoke 12 assumes in relation to the vertical can be described as a function of the angle of the seat 5 in relation to the horizontal.
By changing the position of one or both of the pivot points 16, 17, the movement and the positioning of the backrest 19 can also be changed. Such a change can also be achieved by changing the position of the securing element 13, which can be utilised as an adjustment possibility.
When the seat 5 is tilted all the way forwards, the backrest 19 moves forwards only a small amount, and thus the angle between the seat and the backrest is made larger or is opened. With horizontal seat, the backrest 19 is almost upright and thus the seat/backrest angle is essentially approx. 90°. With the seat 5 tilted all the way backwards in relation to the horizontal position, the seat/backrest angle will similarly be almost unchanged in relation to the horizontal.
The seat angle is locked by a form of segment coupling system, where a threaded part or screw 9 sits firmly in the outer element 2 and is influenced by a spring element (not shown), which presses around the segments or the lugs 7 and a number of segment disks 8. When the segments 7 and the segment disks 8 are pressed together, friction arises between these parts, so that the mechanism is locked in such a manner that the outer part 2 of the carrier bracket cannot tilt in relation to the inner part or the support element 1.
The spring element is loosened by means of a release handle (not shown) on the side of the outer element 2, and the seat 5 can be tilted. The segment disk 8 sits around the securing arrangement 10 and around the screw 9 and, when the seat 5 is tilted, the segment 8 will tilt with it. The screw 9 can thus slide in the curved slot in the segment 7.
In order to increase the comfort when the chair is used, in a preferred embodiment a cavity 22 is formed between a foam material 23 and a so-called sitting platform 24, which forms the underside of the seat 5. The cavity 22 is preferably placed centrally in relation to the sitting platform 24, so that the cavity 22 is substantially demarcated by the user's buttocks and thighs. A number of holes 25 for a through-flow of air to and from the seat 5 can with advantage be placed centrally in the sitting platform 24 to provide the air with the shortest flow-path during ventilation. An upholstery fabric 26, preferably of slip-proof material, is placed over the foam material 23. When the seat 5 is in the unloaded state, the structure of the foam material will result in the cavity 22 in the seat 5 being maintained. Upon transition to the loaded state, i.e. when a user sits down on the chair, the foam layer 23 and the cavity 22 are pressed together, whereby the air, which is in the seat 5, is pressed out through the holes 25 in the sitting platform 24. Upon transition to the unloaded state, new air is sucked in, partly through the holes 25 and partly through the surface of the seat 5 and the surface of the foam layer 23. By quick unloading and loading, as when the user momentarily eases himself/herself up from the seat and then sits down again, an airing or ventilation of the seat 5 is achieved.
The sitting platform 24 can be further provided with mounting holes 27 for mounting on the bracket 1, 2 and for mounting of not-shown operating handles.
The seat can with advantage be upholstered with slip-proof material or fabric.

Claims

Chair comprising a lower frame, preferably with a number of individually pivotal castors, a central, height-adjustable support column (3), which at its lower end is secured in said frame, and which at its upper end is connected to a carrier bracket, which comprises an inner part (1), which is fixed in relation to the support column, and an outer part (2), which can be moved in relation to the inner part, and to which outer part a seat (5) and a back support (19) are secured, and where said seat can be tilted around a pivot point (6) in the carrier bracket, and which seat during tilting, by means of one or more link parts, guides the movement of the backrest depending on the inclination of the seat, characterised in that the height of the backrest (19) in relation to the pivot point (6) of the seat (5), seen in a direction at right-angles to the seat (5), is more or less constant, and in that a plane through the support surface of the backrest (19) and a plane through the sitting surface of the seat (5) form an angle, which angle in an end phase of forward tilting of the seat (5) is increased in relation to the angle in the normal position of the seat (5).
Chair according to claim 1, characterised in that the angle, which is formed by the planes respectively through the backrest (19) and the seat (5), remains more or less constant upon tilting from an area around normal seat position and to maximum tilting rearwards.
Chair according to claim 1 and 2, characterised in that the tilt point (6) of the seat (5) and a pivot point (16) on the inner part (1), to which pivot point (16) an elongated link part (14) constitutes a connection for movement of the backrest (19), are stationary pivot points in relation to the support element (1), so that a securing element (13) for the back support link (15) is moved in an arc around the tilt point (6) of the seat (5), and a pivot point (17) fixed on the back support link (15) is moved in an arc around the pivot point (16) with a radius corresponding to a distance determined by an elongated link part (14).
Chair according to claim 1, 2 or 3, characterised in that the inclination of the seat (5) can be adjusted by a clamping arrangement (7, 8, 9).
Chair according to one of the claims 1 - 4, characterised in that the seat (5) is displaceable in its lengthways direction.
Chair according to one of the claims 1 - 5, characterised in that the seat (5) comprises a sitting platform (24) on which a resilient foam material (23) is secured, and between which an essentially central cavity (22) is formed.
Chair according to claim 6, characterised in that a number of holes (25) are formed in the sitting platform (24) for the ventilation of the chair.
Chair according to claim 7, characterised in that one or more ventilation holes (25) are placed in the sitting platform (24) in a substantially central manner.