Adjustable chair

An adjustable chair structure comprises a support frame of substantially L-shape conformation supported by a base in the form of an upright column supported on a set of radial feet carried on castors. The L-shape support frame has a horizontal arm for supporting a seat part of a seat body, and an upright (i.e. vertical or inclined at an acute angle to the vertical) arm which supports a seat back part of the seat body. The seat part is connected to the seat back part by means of a flexible tongue projecting from the middle of the rear edge of the seat part of the seat body, which tongue has notches by which the position of the seat back with respect to the seat part can be determined.

BACKGROUND OF THE INVENTION 
There are currently available on the market various types of adjustable 
chairs which are particularly designed for office use. One of the most 
popular structures for an office chair comprises a base which supports a 
seat and a seat back. Both the seat and the seat back may be provided with 
independent means for their positional adjustment to suit individual 
users. 
This type of chair structure has substantial disadvantages in that the use 
of separate mechanisms for the positioning of the seat back and for the 
positioning of the seat significantly increase the manufacturing costs 
because of the complexity of the structure. Moreover, in use, such known 
chair structures have disadvantages due to the fact that, by providing 
separate actuating mechanisms for the two different adjustments it is 
difficult to synchronise their positional variation in relation to the 
positional variation of the human body. In particular, it is not always 
possible to obtain adequate adaptation of the inclination of the seat 
back, with consequent lack of convenience and comfort for the utiliser. 
OBJECTS OF THE INVENTION 
A primary object of the present invention is to overcome the above noted 
disadvantages of the prior art. 
A main object of the invention is to provide an adjustable chair structure 
which is adjustable in such a way that simultaneous adjustment of the 
position of the seat and of the seat back can be obtained. 
Another object of the invention is to achieve the above object without 
needing the actuation of mechanisms which are difficult for the utiliser 
to gain access to. 
A particular object of the invention is to provide a chair structure which 
offers the possibility of obtaining the whole of a wide range of positions 
with an automatic adjustment of the seat back to correspond to different 
selected positions of the seat. 
A further object of the invention is to substantially improve the 
convenience of use and the comfort of an adjustable chair. 
Another object of the present invention is to provide an adjustable chair 
structure which, because of its particular constructional characteristics 
is able to offer the widest guarantees of reliability, comfort and 
security in use. 
Still another object of the present invention is to provide a chair 
structure which, as well as having significantly improved performance over 
chairs of the same general type known from the prior art, has a very much 
simplified structure and is such as to facilitate manufacture and assembly 
thereof. 
SUMMARY OF THE INVENTION 
The present invention relates to an adjustable chair, and particularly to 
an anatomic chair structure which can be adjusted to a plurality of 
different positions. 
According to the present invention, there is provided an adjustable chair 
structure, characterised by the fact that it comprises a support frame 
carried on a base and having a substantially L-shape conformation with a 
horizontal arm for the support of the seat part of a seat body, and an 
upright arm for the support of a seat back part or the seat body, the said 
seat part of the seat body being slidably carried on the said horizontal 
arm and provided at the rear with a flexible projection for connection to 
the seat part of the seat body, which is slidably guided on the upright 
arm such that adjustment of the position of the seat part of the seat body 
causes a corresponding adjustment in the position of the seat back part of 
the seat body. 
Various other features and advantages of the present invention will become 
more clearly apparent from a study of the following detailed description 
in which reference is made to the accompanying drawings given purely by 
way of non-limitative example.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The multiple-position chair structure shown in the drawings is indicated 
generally with the reference numeral 1 and comprises a support frame 2 of 
substantially L-shape conformation which is supported by a base 3. The 
base 3, in this preferred embodiment has a plurality of radially extending 
feet 4 provided with castors 5. The feet 4 support a vertical stem 6 to 
which the support frame 2 is connected. 
The support frame 2, which, as indicated above, has an L-shape 
conformation, comprises a horizontal arm 7 and an upright arm 8. The 
upright arm 8 may be vertical or inclined at a small angle to the vertical 
and is provided for the support of the seat back whilst the horizontal arm 
7 provides support for the seat. 
To the said support frame 2 there is connected a composite body, generally 
indicated with the reference numeral 10, which comprises a seat 11 which, 
by means of a flexible projection 12, is connected to a seat back 
generally indicated 13. In more detail, as can be seen in Figures from 3 
to 5, the seat 11 has longitudinal ribs 20 in its underside which 
constitute guide and slide elements for coupling with corresponding 
recesses 21 formed on the said horizontal arm 7 of the support frame 2. In 
this way the seat 11 is slidable with respect to the horizontal arm 7 so 
as to be able to assume a wide range of positions which may be selected by 
a user. 
Parallel to the ribs 20 and outwardly of these there are provided two 
parallel flanges 22 having an L-shape in cross section, which flanges 
couple with the lateral edges 23 of the horizontal arm 7 in such a way as 
to form an interconnection between the seat 11 and the horizontal arm 7. 
From the middle of the rear portion of the seat 11 there extends a 
flexible projection 12 which, on its rear face (that is to say on the face 
which is not in view during use) there are provided a plurality of spaced 
resilient elongated ridges 30 which allow an adjustable connection to be 
effected with the said seat back 13 as will be described in more detail 
below. More specifically, the seat back 13 has a carrier portion generally 
indicated 40, essentially consisting of a rectangular cross-section body 
in which there are defined slots 40' provided for resiliently engaging, in 
an adjustable way, with the resilient elongated ridges 30 of the flexible 
portion 12, the ridges 30 being specifically arranged and designed to be 
pressure fitted into said slots 40'. As is shown, the carrier portion 40 
is slidably supported by the upright arm 8 by means of central 
longitudinal ribs 41 formed in said arm 8 which engage in longitudinal 
recesses 42 in the carrier 40, and two lateral flanges 43 which function 
as retainers. The main body of the seat back, indicated 13a, is pivoted to 
the upper corner of the carrier 40 as can be better seen in FIGS. 9 and 
10, and has thus the possibility of freely turning about a substantially 
horizontal axis perpendicular to the plane defined by the two arms of the 
support frame 2, thus allowing an automatic adaptation of the inclination 
of the seat back in dependence on the sitting position adopted by a user. 
With this coupling as described above, when sliding of the seat with 
respect to the horizontal arm 7 is effected, there is contemporaneously 
and automatically obtained a corresponding and analogous displacement of 
the seat back which is linked to the seat itself by means of the 
connection made by the flexible projection 12 which follows the 
conformation of the supporting frame 2 and which, in practice, serves as 
displacement transmission means between the seat and the seat back. In 
this way there is always an extremely comfortable positioning of the seat 
in that any forward displacement of the seat causes a corresponding 
lowering of the seat back, therefore allowing the utiliser to assume a 
more extended position, whilst if the seat is adjusted rearwardly a 
corresponding raising of the seat back occurs therefore assuming a more 
erect sitting position for the trunk of the user. 
Moreover, there is no fixed rotational position of the body 13a of the seat 
back 13. It is the contact of the back of a person sitting in the chair 
which causes the pivoting of the seat back, and therefore the positioning 
of the body of the seat back is always adapted perfectly to the back of 
the utiliser. 
The chair of the present invention can thus assume a very wide range of 
positions without requiring a complex adjustment mechanism. Indeed, simply 
by exploiting the slidable coupling between the chair body parts and the 
support frame therefore it is possible to provide a chair with the 
advantage of having the seat back and the seat mutually interconnected by 
means which allow the mutual positioning between the seat and the seat 
back to be predetermined whilst the sitting position of a user is 
nevertheless adjustable over a very wide range.