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The present invention relates to an apparatus for
stretching web products, such as fabrics and the
like, in the process of formation.
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It is known that when fabrics are subjected to
some treatments - especially to those which
include the use of fluids such as steam for
example - the same fabrics, being picked up from a
pile of material in stock and moved forward over a
path along which finish operations of various
character are carried out, have their longitudinal
edges subjected to a crimping or curling action.
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In order to counteract this phenomenon it is
necessary to intervene continuously on these
materials to keep them in stretched condition
since, failing to do so, would result in their
longitudinal edges being damaged by such
operations, in case of fabrics, as raising and
cutting.
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The apparatuses currently used to maintain the
product in stretched attitude require the use of
elements consisting essentially of single rollers
or pairs of cylindrical or conical rollers, either
idle or motor-driven, which act independently upon
the two long sides of the material in the process
of formation.
However, it is known from experience that the
efficiency of the known systems is not always
sufficient to keep the product in a perfectly
stretched condition for the desired time.
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The main object of the present invention is to
overcome the said drawback.
This result has been achieved, according to the
invention, by providing an apparatus having the
characteristics disclosed in the claim 1. Further
characteristics being set forth in the dependent
claims.
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The present invention allows the product in the
process of formation to be set in a stretched
condition by acting on both its longitudinal edges
in a perfectly balanced way. This makes it
possible to reach the most correct stretching of
the product and perform the treatments provided
downstream, whatever their nature, in yet a more
efficient way. Besides, an apparatus according to
the invention is simple to make, cost-effective
and reliable even after a prolonged service life,
while requiring only one drive motor.
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These and other advantages and characteristics of
the invention will be best understood by anyone
skilled in the art from a reading of the following
description in conjunction with the attached
drawings given as a practical exemplification of
the invention, but not to be considered in a
limitative sense, wherein:
- Fig. 1 is a schematic front view of one
embodiment of the apparatus according to the
invention;
- Fig. 2 is a schematic plan view of the apparatus
of Fig. 1;
- Fig. 3 is a schematic side view of the apparatus
of Fig. 1;
- Fig. 4 is a schematic plan view of a further
embodiment of the apparatus according to the
invention;
- Figs. 5 and 6 are two views similar to those of
Figs. 1 and 2, relating to alternative embodiments
of the present invention;
- Figs. 7-9 are a schematic side view, a cutaway
front view and a plan view of an apparatus which
is structured according to Figs. 5 and 6;
- Fig. 10 is an enlarged detail of the drawing of
Fig. 9;
- Fig. 11 is a view in section taken on line Y-Y
in Fig. 10.
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Reduced to its basic structure, and reference
being made to the figures and the attached
drawings, an apparatus according to the invention
comprises a belt wound up, to form an "eight",
over two pulleys (2) so as to exhibit two crossed
lengths above the product (3) which is moved
forward, as indicated by the arrow "F", relative
to the pulleys (2) and belt (1).
In the description that follows, although
mentioning a belt throughout, it is understood
that reference could be made to equivalent members
such as a web or a rope either elastic or
inextensible, preferably of plastic material.
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The movement of the product (3) is ensured by
traditional driving systems. The element (4) shown
in the figures of the attached drawings represents
a bearing body on which the product (3) is made to
slide, said body being supported by a frame (40)
able to be associated to a fixed structure (S).
Said frame (40) can be mounted on wheels (not
shown in the drawings) to make up a distinct
element, independent from the structure (S). In
the example of the attached drawings, said
structure (S) has a base resting with a plurality
of legs (GS) onto the floor. This structure (S)
makes it possible to guide and wind up the product
(3) to form a coil (B) with the axis (AB) thereof
being driven by an electric motor (MB) in
cooperation with two idle rollers (400) provided
on the side of the frame (40) facing the fixed
structure (S) and developed orthogonally to the
feed direction (F) the product (3). The rotation
of the axis (AB) operated by the motor (MB) causes
the product (3) to advance in the direction of
arrow (F). Alternatively, said frame (40) is able
to be associated to a fixed part of any finish
machine, particularly in correspondence of the
input and/or output sections of the machine. In
such case, the movement of the product to be
treated is ensured by the same finish machine.
One of said pulleys (2) is associated to a drive
motor (66) to allow the rotation thereof about the
respective axis, so that the belt (1) results
subjected to a corresponding winding motion over
the pulleys (2). The said motor (66) is suitably
mounted on one arm (41) of the said frame (40) so
as to oscillate about an axis hinge-connected (44)
thereto and allowing it to be disposed, along with
the respective pulley (2), in the most suitable
position.
The pulleys (2) are on opposite sides with respect
to the product (3) being fed and, therefore, the
belt (1) extends over the whole height of the
latter. Moreover, the pulleys (2) are disposed,
with respect to the plane of the product (3), in
such a position that two branches or lengths (10)
of the belt (1) act upon the surface of the same
product. In other words, because of the way it is
wound on the pulleys (2), the belt (1) exhibits,
at every instant, two inner branches (10) and two
outer branches (11) and each of the two inner
branches (10) has a region in contact with the
surface of the product (3) in correspondence of
the longitudinal edges (30). The terms "inner
branches" and "outer branches" refer to the
branches of the belt (1) which are at any instant
closer to and, respectively, farther away from the
surface of the product (3), that is, the branches
instantly active and, respectively, inactive.
Owing to the continuous winding of the belt (1)
over the pulleys (2), the said inner branches (10)
slip simultaneously in centrifugal direction (G)
onto the longitudinal edges (30) of the product
(3), which edges are in general curled downstream
of the apparatus, as shown in the drawings.
Because of the simultaneous advancement of the
product (3) relative to said "inner" branches of
the belt (1), the same product results perfectly
stretched.
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The thus operated stretching of the product's
edges is perfectly balanced, as a result of the
simultaneous and absolutely synchronous
intervention of the portions (10) of belt (1), the
latter making up a single stretching element,
instead of a multiple stretcher provided in the
traditional apparatuses. The stretching speed, the
tension exerted onto the product and the width of
the regions of contact of the latter with the
belt's inner portions, result equivalent on both
sides. Moreover, even when changing the height (a)
of the product in the course of formation, the
system remains centred. In addition, the present
apparatus is able to act indifferently both on the
straight and reverse side of the product. The
speed of the pulleys (2), that is of the belt (1),
is adjustable at will also in relation to the
feeding speed of the product (3).
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Advantageously, according to the invention, the
position of the pulleys (2) on the respective
supports can be adjusted by the operator, as
indicated by the double arrow "H" in Fig. 3, who
can set at will the angle of incidence of said
active portions (10) of the belt (1) on the
product (3).
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According to the embodiment represented by way of
example in Fig. 4, idle wheels (5) are
correspondingly associated to the pulleys (2),
each wheel having its axis parallel to the
respective pulley and able to be moved from and
towards the product (3), as indicated by the
double arrow "E". This makes it possible to
displace the product (3) relative to the axis (b-b)
of the station of destination without, for this
reason, having to correspondingly displace the
belt/pulleys assembly. In practice, without
displacing the frame (4) and pulleys (2) of the
present apparatus, it is possible, by means of
pulleys (5), to move the crossing point of belt
(1) so that the projection of such point onto the
feeding product (3) will fall onto the axis of
longitudinal symmetry of the latter. For example,
in case the product is a knitted fabric, this
operation results useful should a raising machine
be provided in the station of destination. In
fact, since the operating width of this type of
machine is generally much larger than the height
(a) of the fabric, the displacement of the latter,
according to a technique known per se, ensures a
more uniform wear of the gaskets provided for the
work. Besides, the use of additional pulleys (5)
allows, as above mentioned, the crossing plane of
the belt (1) to be shifted to carry out the
displacements imposed on the product (3) during
the work.
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The stretching effect operated upon the edges of
the product (3) by the present apparatus can be
made more intense by providing, beside each of
said pulleys (2), a further pair of pulleys (6, 7)
having a corresponding belt (8) wound thereon. The
said additional pulleys (6, 7) are positioned, on
the same plate (42) of the arm (41) which supports
the main pulleys (2), on the side opposite to the
product (3), so that the edges (30) to be
stretched of the latter will result interposed
between the main belt (1) and the two additional
belts (8). In this way, the two edges (30) of the
product are subjected to the action of both belts
(1, 8) acting from opposite sides.
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The additional belts (8) receive the motion
directly from the main belt (1), as described in
more details here below.
Moreover, the additional pulleys (6, 7) may be
mounted on supports (71) which allow them to be
moved relative to the product (3) being fed, as
schematically illustrated in Fig. 6, in order to
exert a kind of brushing of the edges of the
product simultaneously to the stretching thereof.
To this end, the support (71) for the additional
pulleys (6, 7) is hinged with vertical axis (72)
to the corresponding plate (42) of the frame (40),
said axis (72) being coincident with that of the
additional pulley (6) which is farther away from
the product (3).
Each of the additional belts (8) is associated to
the main belt (1) so as to be driven into motion
only by the motor (66). According to the
embodiment shown in Figs. 9-11, this is achieved
by means of an idle roller (9) with axis (r-r),
able to be positioned at a preset distance from
the corresponding edge (30) of the product (3) and
acting upon the outer side of the main belt (1),
so as to press the latter against the additional
belt (8). The pressure exerted by the roller (9)
onto the main belt (1) causes the latter to come
in contact with the additional belt (8) which,
therefore, results driven by friction and wound
over the respective pulleys (6, 7) for cooperating
with the main belt (1) in stretching the edges
(30) of the product (3). The arrows (L) and (K) of
Fig. 10 show the directions of motion of the main
belt (1) and, respectively, of the additional belt
(8). The small roller (9) is mounted within a
housing defined by a body (90) fixed, by means of
two rods (91) parallel to each other, to a skid
(92) sliding onto a straight guide (70) parallel
to the support (71) of the additional pulleys (6,
7). The said skid (92) being able to be disposed
in fixed position on the guide (70) by means of
tightening knob (93). The said rods (91) parallel
to the skid (92) make up a fork in which both the
main (1) and additional (8) belts slide. The said
fork acts as an end-of-stroke element for the
product (3) in case the latter is subjected to
undesired side shifts. Although Figs. 8-11 of the
attached drawings show a single group (6, 7, 8)
with relevant support (71), skid (92) and small
roller (90), it is understood that the whole is
present on both sides of the frame (40) to act on
both the longitudinal edges (30) of the product.
