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