The present invention relates to a device for adjusting the configuration of the back of a chair in correspondence with the area of the loins. Chairs with shapeable backrests are known, the characteristic of which consists in supporting the user's spine in order to keep it in a correct position for long intervals of time.

In particular, these types of chairs have supports in contact with the lumbar area of the user when he is in a sitting position with his back resting on the backrest.

Current adjustment devices have the drawback of a difficult and laborious adjustment to obtain the desired profile.

Another drawback consists in the fact that it is possible to adjust only the height position of the support. DE 20 2017 104716 U1 concerns an office chair, with a seat support and a back support, the back support being vertically displaceable by means of an adjustment device.

The purpose of the invention is to eliminate these drawbacks and to provide a device for adjusting the lumbar profile of a chair that has a simple construction.

Another purpose of the invention is to provide an adjustment device that uses a limited number of components and requires reduced assembly times.

Another purpose of the invention is to make a device that is easy to install. All these purposes and others that will emerge from the following description are achieved according to the invention with a device for adjusting the configuration of the backrest of a chair as described in claim 1

The present invention hereinafter further clarified in a preferred embodiment thereof reported for purely simplifying and non-limiting purposes with reference to the attached drawing tables in which.

Figure 1 shows an exploded perspective view of a chair back equipped with an adjustment device according to the invention,

Figure 2 shows it in an assembled view,

Figure 3 shows the detail of engagement of the device on the chair,

Figure 4 is a front perspective view of the adjustment device,

Figure 5 shows it in a rear perspective view, and

Figures 6-8 show the device in three adjustment configurations in vertical section

As can be seen from the figures, the device for adjusting the configuration of the backrest substantially comprises a band 2 made of substantially rigid material which extends at the ends into two fins 4 provided with coupling elements 6,6', 8. In particular the elements 6, 6' are aligned with each other and are spaced from the element 8 for the reasons that will be explained later.

The band 2 is affected at the ends by two pockets 10 in which the ends 12 of a flexible element 14 are inserted, shaped like a lozenge from whose horizontal edges 16 a series of flexible lamellae 18 branch off.

The two flaps 16 are connected to each other by crosspieces 20, each of which extends into a tab 22 whose end can be slidably engaged in a pocket 24 provided in the band 2. The two crosspieces 20 are connected to each other by a portion 26.

The surface of the band 2 that does not present the pockets 10 has two arms 28 for articulating a lever 30 with eccentric portions 32 which are inserted into corresponding slots 34 provided in the band 2.

The backrest frame is formed by two half-shells 36, 36’, one 36 of which has the two vertical sections 38 presenting a rib 40 presenting seats 42 having a distance between them equal to the distance between the teeth 6, 6'.

To assemble the adjustment device, proceed as follows. The band 2 is constrained with the hooking elements 6, 6’ and 8 to the ribs 40 so that the two elements 6, 6' engage in two of the contiguous seats 42 of the rib and to this are kept stably constrained thanks to the presence of the other item 8.

Once the half-shell 36 has been constrained to the other half-shell 36’, the vertical adjustment in the band can be obtained by simply pushing the band 2 up or towards the ribs 40 for continuous engagement and disengagement of the coupling elements 6 , 6’and 8 in and from seats 42.

As regards the adjustment of the flexible element, this is obtained by rotating the arms 28 of the lever 30 which, thanks to the eccentric portions 32 interfering with the sector 26, moves the flexible element 14 away from the band 2, which interacts with the back of the user.

In a variant embodiment illustrated in Figures 6-8, the eccentric portions 32 are provided with teeth 44 which selectively engage in corresponding notches 46 provided in portion 26.

From what has been said it is clear that the device according to the invention has numerous advantages including:

- presents a simple realization, - uses a limited number of components and requires reduced assembly times,

- it is easy to build,

- it's intuitive,

- it is adjustable both in height and depth.