This invention relates to a simplified automatic machine
for simultaneously tensioning belts for furniture upholstery, wherein all the said
belts are tensioned at the same time and with the same force.
This machine, compared with the previous machines known
to the art, proposes a simplified model providing for means which, after the operator
has secured the ends of the belts to the piece of furniture frame by staples or
other system known to the art, tension the belts which are then fixed also to the
opposite side of the frame, before being cut.
The said tensioning means are operated by a pneumatic system
which guarantees a good continuity of results.
As known, some pieces of furniture, such as armchairs,
sofas and the like, generally have upholstered seats and backrests and such upholstery
often requires a supporting flexible structure which usually comprises a series
of elastic belts which are fixed and tensioned between to points located on opposite
sides of a rigid frame.
The fastening operation of the said belts provides for
an end of the belt to be fixed to a first point of the frame, which belt is then
tensioned with a preset force, and fixed to a second point of the frame on an opposite
edge and finally cut.
In the large-scale production furniture industry, where
the production times have a significant economic importance, the automation of the
said belt tensioning operations is a prerequisite; on the contrary, if the said
tensioning operations are made manually. they would imply an excessive lengthening
Different machines capable of speeding up the said operations
by providing for the automatic simultaneous tensioning of all the belts, thus making
the operator's tasks easier, are known to the art.
These known machines comprise a series of reels which feed
to a common tensioning roll all the belts, which are engaged to the surface by means
of several types of locking devices.
Once the roll has been rotated, the belts are simultaneously
tensioned with a force which varies with the variation of the roll rotation range.
One of the said machines is described in the
European Patent Nº 0,511,458
filed by the same applicant.
This is a machine requiring a reeling/tensioning roll with
a particular shape suitable to create, on the surface, a cavity parallel to the
axis of rotation, wherein a bar, around which the belts pass through, is lodged.
The said feature considerably increases the cost of the
Other machines known to the art provide also for means
capable of driving, one by one and automatically, the ends of the belts up to a
first locking point of the frame and other automatisms, which are not shown herein,
which allow to tension the belts one by one with a constant force. A machine of
the kind is described in the
European Patent application Nº 1,258,214
filed by the same applicant.
The purpose of this invention is for a simplified tensioning
machine, which is easier to use and, mainly, more affordable then those known to
the art, and which at the same time is capable of simultaneously tensioning all
the belts of the piece of furniture, guaranteeing also a good continuity of results.
According to this invention, the machines provides for
an automatically-drive tensioning device which is common for all the belts.
Each of the said belts passes around a setting roll and
is bent backward, overlapping on a segment of the belt upstream, so that when the
said belt is tensioned, it presses this segment of belt upstream against a fixed
support, blocking it by friction.
The machine according to this invention comprises a height-adjustable
bearing plane, equipped with fast locking means preventing the frame from overturning
once the belts have been tensioned.
These and additional characteristics will be made clearer
by the following description, which is given by way of example but without any limitation
thereto, with reference to the figures annexed hereto, wherein:
- figure 1 is a side view of the tensioning machine according to this invention;
- figure 2 is a front view of the tensioning machine according to this invention;
- figures 3 and 4 show two schematic working phases of the tensioning machine
according to this invention, wherein the belt is, respectively, ready to be fixed
in the first locking point of the frame, and already locked and tensioned, ready
to be fixed to the second point;
- figure 5 is a detail of the belt of figure 4 shown in the segment wound around
two rolls place side by side, wherein it is possible to see the overlapping of the
folded up belt.
With reference to figure 1, 1 indicates the frame of the
piece of furniture, which the belts 2 (figure 3) are to be fitted on, which belts
will form, together with the frame 1, an elastic supporting structure of the piece
of furniture upholstery.
A series of reels 3 feed the belts to a couple of supporting
fixed and setting rolls 4, 5 among which the belts 2 pass through, before being
manually fixed, with the free end coming out of from the reel, to the frame 1 distal
The rolls 4 and 5 are aligned and each belt 1 is wound
up for a segment around the first supporting roll 4 (approx. half turn), then is
let pass around the second roll (setting roll 5) fitted near to the first one, making
a complete turn, and is finally let come back passing above the segment of belt
upstream, wound around the roll 4.
According to this method, by applying a tension to the
belt as indicated by the arrow "F" in figure 5, the said belt rests on the segment
9 of belt wound around the roll 4 and presses it, locking it by friction with a
force which is directly proportional to the tension which is applied.
A tensioning roll 12, activated by tensioning means 6,
which in the specific case consists of a couple of pneumatic cylinders, engages
the belt 2 in the position between the said rolls 4, 5 and an idle roll 10, fitted
just upstream the frame, pulling it downwards (figure 4), so that this portion pushes
against the segment of belt wound around the roll 4.
The details are better visible in figure 5 which shows
the two overlapped segments of belt upstream and downstream the locking rolls 4,
5 just close one to the other and pressed against the roll 4.
In this position the belt, which is pulled by the tensioning
roll 12 in the direction of the arrow "F", is locked by the friction and the pressure
made on the surfaces which are pressed one down the others and against the fixed
roll 4, thus blocking the forward movement of the belt coming out of the reel and
allowing only the other portion of the belt located between the said roll and the
end fixed on the frame to be tensioned when the tensioning means 6 are activated.
The segment of belt between the end previously fixed by
the operator to the frame and the point on which it blocks just near the locking
rolls 4 and 5, is then tensioned by the tensioning roll 12 which, under the action
of the tensioning devices 6, keeps on getting down, thus simultaneously tensioning
the belts with preset force and depending on the pressure applied to the pneumatic
The use of tensioning pneumatic means offers a considerable
continuity of results.
The locking system 7, which is used in the initial phase
of positioning of the frame to the bearing plane is, according to a preferred embodiment
of the invention, "upside down L" shaped and is sliding along the vertical side
from a lifted position, which allows the insertion of a maximum-size frame corresponding
to the maximum travel of the said element 7, to a lowered position, in which it
engages the frame of the piece of furniture to prevent it from overturning when
the belts are tensioned.
The functioning is as follows.
An operator simply leans the frame of the piece of furniture
1 on the bearing plane 8 of the machine, making an edge thereof lean against an
edge 11 of the said plane 8.
The operator then secures the frame from overturning putting
it against, along the opposite edge, the end portion of the locking element 7, adjusts
the height of the frame 1, putting the plane in a working position 8' to adjust
it to the dimensions of the piece of furniture and also to the operator's ergonomic
The operator then takes the ends of each belt coming out
of the reels 3, and makes them pass around the respective locking rolls 4, 5, at
first around one roll, and later around the second roll, but contrariwise, until
the ends come near to the most remote edge of the frame 1, wherein he fixes them,
for example, by using a staple gun.
Each belt is therefore arranged as sown in figure 3, with
its upper segment between the first locking point to the frame 1 and the roll 5,
which has an almost horizontal course, and the bottom end, which goes from the feeding
reel 3 to the locking roll 4, which has an almost vertical or slightly oblique course
according to the reel position with respect to the machine.
Just near the roll 4, the two overlapped segments of belt
are in contact one with the other, so that when the machine is activated, the tensioning
means 6 lower the roll 12, which in turn makes a segment of upper belt 13 press
against the segment of the underlying belt 14, thus locking by compressing against
the roll 4.
Continuing the travel of the tensioning means 6, the roll
12 further pulls the segment of upper belt 13 between the frame and the locking
rolls 4, 5, thus tensioning it for a preset value.
At the point of higher travel of the roll 12, i.e. when
the desired tensioning value is reached, the operator fixes each belt to a second
point of the frame, on the opposite side.
Each belt can now be cut, after having duly checked that
the belts have been tensioned with the preset force, according to the fluid pressure
in the cylinder 6.
A machine made having such features as explained above
is extremely easy to manufacture with a significant cut in the costs of production
compared to the tensioning machines known to the art, resulting to be also light
and very small-sized.
Also the functioning is simplified for the benefit of the
personnel in charge of its use, who will not require any more training periods and
without the need to be flanked by skilled workers.