The present invention relates to a friction-plate adjusting device, in particular for chairs, armchairs or the like, and to a method for the manufacture thereof.

The device in question is intended to be used advantageously to vary in a controlled manner the relative position of two mechanically connected parts such as, for example, the seat and the backrest of a chair or an armchair.

Conventionally, in accordance with the known art, the devices for adjusting seats or backrest of chairs and armchairs use, as has been schematically shown in the accompanying Figure A, two separate sets of plates A, B which are differently shaped and pivotably mounted, respectively, on the support structure C of the seat and the support structure D of the backrest. In order to allow relative rotation of the two structures C and D, the said structures are mechanically connected together by means of a connecting pin P which is engaged inside holes formed in both sets of plates along a common section thereof. The plates A, B are mounted, spaced with respect to each other, and are able to be pressed together transversely generally by means an adjusting knob M. It is envisaged using a spring S in order to allow return of the two structures into a predefined position.

By slackening or tightening the knob M, it is possible to define correspondingly for the device in question an adjusting position, in which the plates A, B, slide on each other and allow the two support structures C and D to rotate about the connecting pin P, and a stop position, where the plates A, B are retained against each other by the frictional force which is produced by their compression so as to fix the relative position of seat and backrest.

Embodiments of this type are known, for example, from the patents WO 99/09861 , US 5,066,069 , US 5,423,595 , EP 160221 and US 4, 392, 686 .

The adjusting devices of this type have proved in practice to have certain drawbacks in particular associated with the process for production thereof which, as is known, is excessively complicated and costly.

At present, in fact, the processes for the production of adjusting devices envisage pressing the plates as separate individual elements, which are generally produced in at least two different configurations so as to form two separate sets of plates which are assembled together in a spaced manner on pins to be arranged on the parts to be adjusted.

This assembly operation is performed at present in an exclusively manual manner since the plants for automatically assembling the abovementioned plates are excessively costly and extremely complex to construct.

Consequently, the processes for production of the adjusting devices have proved to be excessively complex hitherto and costly such as to negatively affect the efficiency of the entire process for the production of chairs or the like.

In fact, the manual assembly of the plates negatively affects the production efficiency both in terms of time and in terms of labour used and therefore ultimately in terms of the cost of the finished product.

In order to overcome at least partly this drawback, more recently a solution of the adjusting device has been developed, as described and claimed in the patent EPO 549 538 , wherein the plates forming part of one of the sets of plates are rigidly connected together at one end by a connecting body.

The plates are in this case in the form of tongues which extend parallel to each other from the connecting body. In order to provide the tongues with a transverse mobility comparable to that of separate plates, recesses have been provided on the said tongues in the vicinity of the connecting body. The abovementioned set of plates is obtained by means of fusion in the form of a single body. The remaining set of plates continues to be manufactured by means of pressing of individual separate plates which must then be assembled with positioning of the tongues of the other set in between.

This latter solution of the known art, although limiting the drawbacks of the preceding solutions, does not overcome them entirely and also negatively affects the production process to an excessive degree, in particular owing to the provision of a large number of manual operations.

In this situation the main object of the present invention is therefore that of eliminating the drawbacks of the known art mentioned above by providing a friction-plate adjusting device, in particular for chairs, armchairs or the like, which is provided with two separate sets of plates which can be easily assembled together during the assembly stage of the production process.

A further object is that of providing a friction-plate adjusting device which is constructionally simple and operationally entirely reliable.

Another object of the present invention is that of providing a method for manufacturing a friction-plate adjusting device, which is simple and low-cost.

The technical features of the invention, in accordance with the abovementioned objects, may be clearly understood from the contents of the claims included below and the advantages thereof will emerge more clearly from the detailed description which follows, provided with reference to the accompanying drawings which show a purely exemplary and non-limiting embodiment thereof and in which:

• FIG. 1 shows an overall view of an example of embodiment of the adjusting device according to the present invention;
• FIG. 2 shows a schematic plan view of a first set of plates which are produced, by pressing, from a metal sheet;
• FIG. 3 shows a schematic plan view of a second set of plates produced, by pressing, from a metal sheet;
• FIGURES 4A, 4B and 4C show a plan view and two different side views of the first set of plates according to Figure 2 once folded and arranged on top of each other;
• FIGURES 5A, 5B and 5C show a plan view and two different side views of the second set of plates according to Figure 3 once folded and arranged on top of each other.

In accordance with the figures of the accompanying drawings, 1 denotes in its entirety the adjusting device forming the subject of the present invention.

The reference numbers 2 and 3 denote moreover two different sets of plates, each consisting respectively of single plates denoted by 4 and 5.

The example shown hereinbelow refers in particular to the device for adjusting the angle of inclination of a backrest with respect to the seat of an armchair. This example must be regarded as a possible advantageous application of the present invention, although the device in question may be differently used in order to adjust the position or the angle of inclination of parts which are joined together in numerous other fields of application, without thereby departing from the scope of protection of the present patent. In particular, depending on the application envisaged, the number of sets of plates or the number of plates or also their shape or their assembled arrangement on the parts to be connected may be of any nature depending on the specific requirements.

Therefore, in accordance with the accompanying example of embodiment, the first set of plates 2 is composed of four plates 4 made of sheet metal with a substantially triangular shape and precisely arranged on top of each another, so that first and second circular holes 6 and 7 provided on each plate 4 are perfectly aligned so as to form through-channels for the insertion of corresponding pins 8 and 9.

The second set of plates 3 is in turn formed by five plates 5 made of sheet metal with an elongated shape and also precisely arranged on top of each other so that third and fourth circular holes 10 and 11 provided on each plate 5 are perfectly aligned so as to form through-channels for the insertion of corresponding pins 9 and 10.

Openings 12 are also provided on each second plate 5 so as to form an adjusting eyelet as shown in Figure 5A which is able to receive the pin 9 inside it.

As can be seen in Figure 1, the first plates 4 and the second plates 5 partially overlap each other along a common section 13.

In more detail, the first set of plates 2 is mounted on the frame of the backrest, denoted by 15 in Figure 1, by means of two through-pins 8 and 9 which are supported by its U-shaped side shoulders 15' and 15".

The second set of plates 3 is instead mounted on the frame 16 relative to the seat by means of the pins 8 and 10 which are constrained to the side shoulders 16' and 16''. The pin 8, in common with both the sets of plates, acts as rotational pin for the two frames 15 and 16.

According to the invention, both the sets of plates 2, 3 are provided with respective connecting portions 17, 18 able to connect continuously as one piece the plates 4, 5 forming part of the same set.

Advantageously each connecting portion 17, 18 is formed by a portion of folded sheet metal of limited width since it must substantially perform the sole function of keeping the plates assembled on top of each other and must not satisfy any particular mechanical requirements.

The number of connecting portions for each set of plates n is equal to n-1, the final plates in each set being connected to a single plate.

From a functional point of view, the two sets of plates 2 and 3 mounted as shown in Figure 1 operate as specified hereinbelow.

The first set of plates 2 is connected by means of the pins 8 and 9 to the frame 15 and therefore is integral therewith and is unable to rotate. It defines by means of its four plates eight friction surfaces intended to make contact with the plates of the second set 3. The latter are instead able to rotate through an arc of a circle which corresponds to the extension of the eyelet 12.

A spring 19 keyed onto the central pin 8 presses with its ends against the other two pins 9 and 10 so as to force the two frames 15 and 16 elastically towards each other.

It is also envisaged using an adjusting knob 20 which is screwed onto the pin 9 and which is able to displace, following screwing, a cylindrical bush 21 mounted idle on the pin 9 so as to compress or loosen the two sets of plates 2 and 3 along their common section 13.

In this way, when the knob is tightened, the frictional forces which are exerted between the surfaces of the coupled plates prevent any relative rotation thereof and therefore ultimately determine the position of the two frames 15 and 16 with respect to each other.

For example, a user may push the backrest of a chair with his/her back, overcoming the elastic resistance produced by the spring 19 until the desired angle of inclination is obtained, this angle being then easily maintained by correspondingly tightening the knob - hitherto not tightened - in this position.

According to the present invention, the connecting portions 17, 18 do not interfere substantially with the operation of the plates since the transverse movements imparted to them in order to pass from the configuration where they can slide on each other to the other locked configuration where the plates are clamped together are extremely small.

More particularly, it was observed that, when the knob 20 is not tightened, the plates 4, 5 slide freely on each other without the connecting portions 17, 18, following plastic deformation thereof, exerting between the plates a residual compressive force such as to restrict significantly sliding thereof.

The present invention also relates to a method for the manufacture of a friction-plate adjusting device 1 which is of the type indicated above and in respect of which the same reference numbers are therefore maintained.

The abovementioned method envisages a first pressing step and a second pressing step during which the plates 4 and 5 forming part of the first and second sets of plates 2 and 3 are produced, and a step involving assembly of the abovementioned sets of plates 2, 3 on the two parts to be adjusted 15, 16 so as to assemble them in a parallel manner, spaced from each other and overlapping along a common section 13.

According to the invention, the pressing step envisages a shearing step able to form a connecting portion 17, 18 between the plates 4, 5 of each set, and a subsequent folding step for stacking the plates of each set on top of one another.

At this point, the two sets of plates 2, 3 thus assembled may be easily and rapidly combined with each other, with the plates spaced.

The invention thus conceived therefore achieves the predefined objects.

Obviously it is also able to assume, in its practical embodiment, forms and configurations different from that illustrated above without thereby departing from the present scope of protection. Moreover, all the details may be replaced by technically equivalent parts and the forms, dimensions and materials used may be of any nature depending on the requirements.