The present invention relates to an adjustable chair the seat and backrest of which are mounted to be movable relative to each other on a common fixture at the side pieces of the chair, with movement between seat and backrest, at the same time, being controlled by a spigot In a guiding groove, the seat being mounted to be tiltable about a fixed point on the fixture.

Numerous designs are known of adjustable chairs of the mentioned kind in which the mutual angle may be changed. Generally, however, tilting of the backrest backwards will cause the rear portion of the seat to be moved upwards. This will cause back rest cushions which are preset for an upright position of the backrest, to move out of their correct position relative to the person sitting in the chair when the backrest is moved backwards. This will require resetting of the backrest cushions in the tilted-back position which may, obviously, create certain problems. In a reclining position, it is also most comfortable to the user of the chair that the seat is also tilted slightly backwards. In most ordinary chairs the seat is, however, tilted to approach a horizontal position, and the user may easily slip off the chair or the chair will, at best, be perceived as being less comfortable to sit in.

According to the invention an adjustable chair of the above mentioned kind is thus proposed, the characterizing features of which appear from the following claims, as well as from the following disclosure with reference to the accompanying drawings.

Figure 1 shows the chair with its backrest in an upright position.

Figure 2 shows the chair with its backrest in a tilted-back position.

Figure 3 shows a modified version of the chair of Figures 1 and 2 in a folded position.

Figure 4 shows the chair of Figure 3 in an upright position.

Figure 5 shows the chair of Figures 3 and 4 in a tilted- back position.

Figure 6 shows the chair of Figures 3-5 in another modified version, in a folded position.

Figure 7 shows the chair of Figure 6 in an upright position.

Figure 8 shows the chair of Figures 6 and 7 in a first tilted-back position.

Figure 9 shows the chair of Figures 6 - 8 in a second tilted-back position.

The chair comprises a seat 1 and a backrest 2 which are mutually connected, partly via a stationary fixture 3 on each side piece of the chair, and a spigot 12, which projects laterally from the lower portion of the backrest and enters a slide groove 11 on a lateral member 25 of the seat at its rear portion. Said slide groove 11 is provided at an angle with the longitudinal axis of the seat, 1. e. inclined rearwards and downwards.

At its lower portion backrest 2 is provided with a fixture 13 the upper end of which is pivotally mounted at a point 5 to the above mentioned stationary fixture 3. Lowermost 10 on back rest fixture 13 there is a fastening point 9 for a mechanism 7, 8 of optionally adjustable length, in the preferred embodiment a gas spring which may also optionally

be locked in a desired position. In the shown embodiment piston rod 8 of the gas spring is rotatably connected with said fastening point 9, whereas the end of cylinder 7 is rotatably connected with a fastening point 6 on fixture 3. Fastening point 6 is indicated in Figures 1 and 2 at a short distance behind and below the tilting point 4 of seat 1 relative to fixture 3. The backrest is provided with a headrest cushion 16, although the number of cushions is here only intended to be an example and not to limit the invent¬ ion. '

When backrest 2 is moved rearwards at an angle upon actuation of gas spring 7, 8 for relative movement of cylinder and piston rod, spigot 12 will be moved from the rear edge of slide groove 11 to the front edge of slide groove 11. At the same time the rear edge of the seat will tilt down and cause the seat proper to tilt at an angle β in a rearward direction. The advantage is thus achieved that cushions 15, 16 will remain at a correct position relative to the user, and that the user will at the same time experience a more comfortable sitting position since the seat is also moved slightly rearwards.

In the shown embodiment an especially simple tilting mechanism is achieved in connection with an adjustable chair.

Being quite conventional, the means of actuating said gas spring 7, 8 are not shown in the drawing.

It will be obvious that there is no need for more than one gas spring, e.g. centrally provided under the chair. However, it is also possible to provide one gas spring at each side piece. Also, it is not required that spigot 12 and slide groove 11 are provided at the side pieces of the chair, they may rather be provided approximately midway between the side pieces of the chair.

In Figures 3 - 5 fixture 3 is shown in a design slightl differing from that shown in Figures 1 and 2. It will appear, inter alia, that fastening point 6' of cylinder 7' is placed in front of and slightly beneath tilting point 4' of the seat 1* relative to fixture 3'. Furthermore, the lowermost portion of the backrest comprises two cooperating members 17 and 18. In the shown embodiment member 17 is substantially shaped like a circle sector and its pointed end is pivotally mounted at a point 5' on stationary fixture 3'. Member 17 is provided with a spigot 12' in slidable engagement with a slide groove 11' which is inclined downwards and rearwards In a side member 25' of seat 1'. The end of piston rod 8' of the gas spring is secured to member 17 at a point 9'. The other cooperating member 18 is also shaped like a circle sector and is at its pointed end pivotally mounted at point 5'. Backrest 2' is firmly mounted to member 18 so as to be turnable about point 5' of fixture 3'. Members 17 and 18 are provided with engaging members 19 and 20, respectively, e.g. spigots to prevent member 18 with its spigot 20 from turning beyond spigot 19.

When backrest 2' is, thus, tilted backwa.rds from the position of Figure 3, its movement will be checked by engagement of spigots 19 and 20. Further backward tilting of backrest 2' occurs by activation of gas spring 7', so that point 9' on member 17 approaches gas spring cylinder 7'. Spigot 12' in slot 11' will then move to upper end of slot 11' causing the rear edge of seat 1' to tilt downwards - and at the same time the front edge of seat 1' to tilt slightly upwards - about tilting point 4'.

Obviously, fixture 3', side member 4' of seat, slot 11', member 17 with spigots 12* and 19, as well as member 18 with spigot 20 are present on both sides of the chair. It will also be understood that what is shown in Figures 4 and 5 has exactly the same mode of operation as in Figures 1 and 2,

apart from the difference as regards purely mechanical build up.

In Figures 6 - 9 another modification of the embodiment of Figures 3 - 5 is shown. The mode of operation of the embodiments in Figures 6 - 8 is basically the same as for what is shown in Figures 3 - 6, apart from the fact that spigots 19 and 20 are no longer active, cooperation of member 17 and backrest 2' with member 18 now being adjusted by a gas spring 21, 22 cooperating with, e.g. a spring loaded slide 23 sliding in a groove 24 in backrest 2'.

In Figure 6 the gas spring is shown with its piston rod 22 completely extended and forming the connection with a free end of slide 23. The other end of the gas spring, the free end of cylinder 21, is pivotally mounted on member 17 at a point 19'. Due to the rotatable connection between slide 23 and rod 22, backrest 2' may be turned when the gas spring is operated. The slide will move upwards along groove 24 when the angle betwewn rod 22 and slide 23 has passed a dead point.

With the backrest in an upright position (Figure 7) and with the gas spring locked, slide 23 will be at the bottom of groove 24. Backrest 2' is, thus, localized relative to seat 1'. In Figure 8 the relation between seat 1* and backrest 2' is as shown in Figure 7, since only gas spring 7', 8' is operated, so that the rear edge of seat 1' is tilted down at the same time as backrest 2' is tilted backwards, as disclosed in connection with Figure 5.

In Figure 9 it is shown how backrest 2' may be caused to take a still more backwards tilted position than the position shown in Figure 8. This occurs by operating gas spring 21, 22 to make rod 22 move into cylinder 21 causing gas spring 21, 22 to extend spproximately flush with slide 23.

By the aid of the above indicated concepts of turning seat and backrest of the chair, the user's lumbar region and neck will remain at the same points relative to the backrest in an upright sitting position and all the way to a reclined sitting position.