DESCRIPTION

Technical Field

This invention relates to fabric treatment machines and, more specifically, to machines in which the fabric is driven pneumatically against an impact member, such as, for example, a grille.

Background Art

It is known that to give fabrics a tumbler effect without using a revolving drum machine, treatment can be performed in machines in which the fabric is pneumatically driven against a perforated plate or a grille designed to separate the fabric from the air used to convey it.

More specifically, document WO03023111A1 describes a fabric treatment machine where the fabric is transferred alternately between two tanks through the agency of a pneumatic duct. In front of the duct, at the first and second tanks, there are two respective grille structures against which the fabric is made to impact thanks to the kinetic energy imparted to it by the pneumatic duct.

Colliding against the plate/grille produces a mechanical effect which soften and swells the fabric. This effect, besides giving the fabric a soft and pleasant hand, improves and embellishes its appearance in terms of surface uniformity, pile straightening, draping, etc.

In prior art machines, the fabric impact plates/grilles have taken on many forms. All the forms are dictated by the need to allow large quantities of air to flow through them while at the same preventing the fabric from passing through.

To allow the fabric to be treated uniformly, however, without causing abrasion, creasing, fraying and similar defects, the impact surface should be as uniform as possible, that is to say, in practice, without any openings in it. This would, however, deviate the flow of the air used to drive the fabric against the impact surface, thereby reducing the force of collision.

The above explains why the industry has, over time, abandoned those solutions which used: perforated metal sheeting, on account of its low permeability to air; netting, on account of the unacceptable ease with which it allows fabric to get tangled in it; and other similar surfaces which do not prevent the fabric from passing through the openings or which hinder its coming loose after impact.

In practice, the solutions have gradually converged on the construction of grilles composed of parallel, near-vertical bars, meaning by this bars which are parallel to the vertical plane containing the trajectory of the fabric prior to impact with the grille and inclined at a suitable angle to the horizontal to allow the fabric to slide downwards easily after impacting the grille.

Examples of grilles of this kind are described not only in document WO03023111A1, but also in EP312509A1, EP341183A2, EP535287A1 and ITFI2007A000292.

The solutions adopted to date do not, however, fully satisfy the treatment needs required of machines of this kind.

In effect, after impact with the vertical bars of the grille and subsequent downward sliding, many fabrics are left with unwanted markings. For example, an unacceptable "rake" effect may appear on pile fabrics.

Furthermore, the hot air - which is normally used to drive and dry the fabric simultaneously - worsens the defects and makes them permanent.

One way of trying to avoid these problems is to reduce the flow rate, and hence the speed, of the air used to drive the fabric. This, however, besides increasing process times, also reduces the energy of fabric impact and, ultimately, the quality of the sought- after effect of the treatment.

Manufacturers of these machines have attempted to overcome the above mentioned problems by varying the spacing, arrangement and size of the grille bars but none of these solutions is totally satisfactory.

Disclosure of Invention

The main aim of this invention is therefore to provide a fabric treatment machine equipped with an impact member which is free of the above mentioned disadvantages. More specifically, this invention has for an aim to provide a grille which does not cause marking, creasing, abrasion, fraying and similar defects in the fabric following impact These aims are achieved by a machine comprising at least one grille provided with a plurality of substantially flat slats, arranged horizontally in partly inclined, louvre-like fashion in such a way as to leave ample space for the passage of air while at the same time preventing the fabric from passing between them and being held back.

Indeed, the slat spacing allows the air to flow through the grille without substantial loss of speed, while the inclined louvre form constitutes a deflecting barrier for the fabric in practically the same way as if it were a single, inclined plane surface.

This has the considerable advantage of allowing the fabric to make full, strong impact against the grille, letting the air flow through and causing the fabric to come away from the grille without the risk of damage to the fabric itself.

In effect, the horizontal orientation - transversal to the impacting fabric - and the flattened shape of the slats, as well as their overlapping arrangement (typical of a louvre configuration), prevent the fabric from wrapping around single slats and forming creases which can become permanently fixed.

Moreover, the action of the horizontal grille slats on the fabric colliding with them across its full width has a uniform effect on the fabric and prevents the lengthwise markings (referred to as "rake" effect) from being formed on the fabric.

These and other advantages, as well as the features of the grille, will be better understood from the following description with reference to the accompanying drawings illustrating preferred, non-limiting embodiments of the invention.

Brief Description of Drawings

In the drawings:

- Figure 1 schematically shows a fabric treatment machine equipped with a grille according to the invention in a cross section through a vertical longitudinal plane;

- Figure 2 shows the grille of Figure 1 in more detail;

- Figure 3 shows a cross section through a vertical plane of a grille in a preferred embodiment of the invention.

Modes for Carrying Out the Invention

Figure 1 schematically illustrates by way of an example a part of a machine for the continuous treatment of a fabric in open-width form.

The machine comprises a duct 10 - typically a Venturi tube - for pneumatically conveying the fabric T and a chamber 12 into which the duct 10 leads. Inside the chamber 12, located in front of the exit of the duct 10, there is an impact member 20 for treating the fabric. The chamber 12 is also equipped with a chute 14 for collecting the fabric on the bottom 16 and with an upper opening 18, behind the impact member 20, for discharging the conveying air. Recovery means, for example a reel 19, are also provided for removing the fabric from the chamber 12 once treatment has been completed. A second chamber and a second impact member, typically present in continuous treatment machines, are not illustrated in Figure 1.

According to the invention, the impact member (see also Figure 2) is a grille 20 with a louvre structure, comprising a plurality of slats 22 extending horizontally in a direction transversal to the direction of motion of the fabric. The slats are substantially flat, of length not smaller than the width of the fabric, of height in the order of a few centimetres and mounted at an angle on a frame 24.

When in use, the frame 24 is located with its upper part close to the exit of the duct 10 and its bottom part spaced from it so that the slats 22 are substantially vertical. Connecting means 26a and 26b are, however, provided for connecting the frame 24 to the walls of the chamber 12 and which allow varying the inclination of the frame and thus also the inclination of the slats. Advantageously, means of per se known type may also be provided for varying the inclination of the slats 22 relative to the frame 24.

As illustrated in Figure 1, the fabric T is projected out of the duct 10, impacts the slats 22 of the louvre grille 20 uniformly across the full fabric width, slides downwards along the grille and falls to the bottom of the chamber 12.

The conveying air, on the other hand, flows through the spaces between the slats 22 to the other side of the grille and out of the chamber 12.

Figure 3 illustrates a preferred embodiment of the invention in which the slats of the grille 200 are shaped and positioned in such way as to give the louvre structure a concave form, with the concavity facing the exit of the duct 10.

More specifically, the height, the horizontal spacing (i.e. distance between the vertical barycentric planes) and the vertical spacing (i.e. distance between the horizontal barycentric planes) of the upper slats 202 are smaller than the respective horizontal and vertical spacings of the bottom slats 204. The upper slats 202 are also preferably partly overlapped to prevent the fabric from penetrating between them.

The latter embodiment just described is particularly effective for treating light fabrics because the concave configuration of the grille guarantees that the fabric correctly impacts the upper part of it, quickly slides down along the bottom part of it and then falls down on the chute and onto the bottom of the chamber. In particular, this prevents the air flow from driving the fabric through to the other side of the grille towards the opening 18.

An impact member according to the invention can advantageously be used in all types of machines for the continuous and discontinuous treatment of fabrics in both open-width and rope form.