TREATMENT TUMBLER DESCRIPTION

Technical field

The present invention relates to an improved device for open-width transfer of a fabric in a tumbler for continuous treatment.

Prior art

In the textile industry, process apparatus known as“tumblers” are currently used, in which the fabric is treated, e.g. with mechanical and/or thermal actions, to create characteristic and peculiar effects for the different types of fabric.

In tumblers having a continuous open-width operation, fabric is transferred, according to a well-known method in the art, using a device that substantially consists of a tubular duct having an essentially rectangular cross-section, which has:

- a contouring wall which delimits an inner cavity of the duct;

- passage openings for the passage of an aeriform fluid in the longitudinal direction of the duct, into and out of the inner cavity, and

- at least one lateral opening, formed on the top and/or bottom walls of the duct, for introducing the fluid into the inner cavity.

A manifold for feeding fluid toward the tubular duct abuts the upper and/or lower opening of the duct, and divides it into two distinct sections, located downstream and upstream from its position respectively. This duct is fed with fluid by one or more specific fans controlled by electric motors that are powered by a variable frequency drive system (inverter).

The feeding manifold has aeriform flow diverters associated therewith, which divert the flow toward either section of the duct which, according to the fluid direction, has a delivery or suction operation.

The fluid introduced by the feeding manifold, diverted and flowing along the cavity of the duct toward the outlet provided by one of the two openings, causes the fabric to be drawn in with the air, at the other opposite opening of the duct, toward the interior of the cavity of the duct and is forced to move therealong from one end to the other, by being driven by the airstream in the same direction thereof.

As fabric exits one opening of the duct, it violently hits grids located close to the duct opening and adapted to stop the fabric. The fabric regularly falls into an accumulation located below, at the exit of both openings of the transfer duct.

In the prior art, the tubular duct has equally spaced walls, whereby fluid consistently flows through passage sections having fixed, generally constant sizes.

While these transfer devices are widely used in the art, they still suffer from certain drawbacks which, according to the type of fabric being treated, may have non- negligible problems.

Since the machines that use said devices are intended to treat a very wide variety of fabrics, in terms of type, weave and weight, the consistency, thickness and stiffness may markedly vary according to the type of fabric being treated.

The physical space occupied by the fabric inside the duct is also accordingly variable, and the height dimensions of the duct must allow the passage of the fabric and of an appropriate amount of treatment air.

In particular, in treatments intended to impart softness and bulk to the fabric, in addition to drying, the fabric is caused to repeatedly hit the two impact grids and to be simultaneously gradually dried.

Accordingly, the speed of the fabric before impact against the grid and the speed of air relative to the fabric, which is generally much higher than that of the fabric, must be suitable for treatment purposes.

Nevertheless, if the duct has an excessive height, a large amount of air flows through the duct without impinging on the fabric, whereby the kinetic and thermal energy of air has substantially no effect on the fabric, and is mostly lost.

On the other hand, if the duct has an excessively small height, the space for the passage of air is insufficient and a greater potential energy of air must be provided to overcome the load losses caused by an excessively narrow duct. In extreme cases, air will cease to flow at high speed and the fabric will be stopped.

In both cases, the fabric will hardly move along the duct downstream from the manifold that feeds air into the duct, resulting in the formation of gathers, increased bulk size and progressive reduction of the useful section for air passage.

The residual flow in the duct becomes increasingly turbulent, dissipates motive power and loses carrying capacity, thereby becoming quickly unable to transfer the fabric that eventually stops and blocks the duct.

Disclosure of the invention

The present invention has the object of obviating the above drawbacks. According to the invention, this object is fulfilled by a tumbler for continuous open- width treatment of a fabric, which has a pneumatic duct for transferring the fabric, whose characteristics are defined in the accompanying claims.

The advantages of the present invention, as well as its technical characteristics, will be more clearly explained in the following detailed description of certain non-limiting embodiments.

Brief description of the drawings

In the drawings:

- Figures la and lb are schematic longitudinal sectional views of a known device for transferring fabric in a tumbler machine;

- Figure 2 shows a perspective view of a device according to the invention;

- Figure 3 is a first sectional view of the device of Figure 2;

- Figure 4 is a second sectional view of the device of Figure 2;

- Figure 5 is a sectional view similar to Figure 3, of a first variant embodiment of the device;

- Figure 6 is a sectional view similar to Figure 2, of a second variant embodiment of the device.

Embodiments of the invention

Figures la and lb show a known device for pneumatic transfer of a fabric in a tumbler 1 for continuous open-width treatment of fabrics, with Figure la only showing the basic parts thereof, consisting of:

- a pair of tanks 50 for accumulation of the fabric T;

- a pneumatic duct 2, interposed between and communicating with the tanks 50, for repeated transfer of the fabric T from the first tank to the second tank and vice versa; - two impact grids 52 located in front of the two opposite outlets of the duct 2;

- sensors 54 for detecting the amount of accumulated fabric to control via a control unit, not shown, the reversal of the direction of transfer of the fabric T in the duct 2. More particularly, a device for fluid-driven transfer of a fabric T according to the prior art basically comprises: a tubular duct 2, a manifold 13 for the flows 3,4 of an aeriform fluid fed as mentioned above to the tubular duct 2, and flow diverting means, here embodied by two single-blade deflecting dampers 7, associated with the manifold 13 and contained therein.

The duct 2 has a contouring wall with an essentially rectangular cross section, which delimits an inner cavity 11, and has openings 8, 9 at its opposite open ends, for the passage of the fluid in the form of flows 5 and 6 oriented in the longitudinal direction of the duct 2, one inflowing and the other outflowing.

At its center line, the tubular duct 2 typically has four additional slot-shaped openings 12, which are formed in opposite pairs through the upper and bottom walls 10a and 10b of the duct 2. The manifold 13 is connected to the openings 12 of the duct 2 and, due to its position - substantially in the middle of the duct 2 - divides it into two portions 14a, 14b of equal length, delimited by the manifold 13 itself and by each of the openings 8, 9.

The flows 3,4 are sent to the manifold 13 by means of one or more delivery fans (not shown), controlled by electric motors advantageously driven by a power supply system with frequency inverter.

A duct 20 according to a first embodiment of the invention, as shown in Figures 2 to 4, comprises a top wall 20a, a bottom wall 20b and side walls 20c, which together delimit the cavity 11, and means 22, 24 for varying the height of the duct, i.e. the vertical dimension of the cavity 11.

In particular, the top wall 20a and the bottom wall 20b are adapted to be mutually spaced apart by means of bearing members 22, which are fixed to the upper surface 21a and the lower surface 21b respectively of the top and bottom walls and are vertically actuated by actuators 24.

Advantageously, the top wall 20a has a transverse dimension that is smaller than that of the bottom wall 20b so that the top wall 20a itself can move in the space delimited by the bottom wall 20b and by the side walls 20c.

The drive system, composed by the bearings 22 and the actuators 24, causes the top wall 20a to translate relative to the bottom wall 20b, while keeping the walls parallel to each other,

In order to form a closed cross-section, i.e. to have the cavity 11 formed by a closed contour in the direction transverse to the fabric T and ensure that the only passages for air will be the openings 8, 9 of the duct 20, a flexible membrane 15, having an inverted U shape, is fixed on one side, to the edges of the top wall 20b and, on the other side, to the edge of each of the side walls 20c.

The membrane 15 is deformable and can adapt to the vertical position variations of the top wall 20a of the duct relative to the bottom wall 20b. Figure 5 shows a first variant of the device, in which the cross section of the duct 20 is closed by providing a contact seal 25 which is fixed to the side edges 26 of the top wall 20a and slides on the surface 27 of the adjacent side walls 20c, to provide a sealing action.

Figure 6 shows a further variant of the device, in which the duct 30 comprises a top wall 30a and a bottom wall 30b having substantially the same transverse dimension. The walls 30a, 30b are also connected to each other by two metal sheets 30c, which are elastically deformable and are fixed to the side edges 31,32 of the walls.

A device according to the invention can change the distance between the top wall 20a, 30a and the bottom wall 20b, 30b, as a function of fabric speed.

This is because the power absorption of the fans for delivery of air to the manifold 13 is substantially a function of the speed at which the fabric T must be pushed, the type of fabric in use and the head losses encountered by air inside the duct 2. Given a certain type of fabric, the operator sets a speed to obtain the desired treatment (which is specific to that fabric), so that the desired kinetic impact energy of the fabric T on the grids 52 is selected by the operator.

Due to the above, given the type and speed of the fabric, the power absorption of the fans only depends on the head losses inside the duct, caused by the geometry of the duct and by the obstruction created by the fabric.

Now, by acting on the drive that controls and creates the distance of the top wall 20a, 30a from the bottom wall 20b, 30b, the most efficient working point for the machine may be determined, that is, the point with minimized head losses. Therefore, as the relative position of the top and bottom walls varies, both the head losses in the duct/fabric system and the speed of the fabric also vary.

As losses decrease, speed increases, under the same conditions. In order to restore the fabric speed set by the operator, the control unit automatically reduces the number of revolutions of the air delivery fans until proper fabric speed is restored.

Fabric speed is determined by the system for controlling height variations in the duct, using the sensors 54 that control the accumulations of fabric in the tanks 50, by calculating the variations in the reversal time of the valve 7 as a function of the distance between the top and bottom walls. Following the determination of the maximum fabric speed (minimum head losses) obtained by varying the duct height, the control will act on the speed of the delivery fans until the fabric speed is reduced and restored to the desired operator setting.

In other words, at a given speed of the fabric, the accumulations are filled and emptied in a fixed amount of time, depending on fabric speed. The sensors that monitor the accumulations determine this time. By varying the height of the duct, the speed of the fabric changes and the sensors in the accumulations measure the variation in fabric filling and emptying times. Thus, the control unit acts on the flow rate of the fans to restore the emptying and filling time for the accumulations (and therefore the fabric speed) and to reset the value desired by the operator for that fabric. This involves considerable power savings.

In short, the control is designed to calculate the best conditions every time the operating conditions are changed, such as the type of fabric treated and/or the speed set by the operator.

With a device according to the invention, characterized by the presence of a fabric transferring channel having a continuously varying height and of a control and management unit which optimizes the power absorbed by the pneumatic air injection system as a function of fabric speed, according to the fabric in use and the optimal speed required to obtain a suitable impact on the grids to achieve the desired treatment, the optimum height of the transfer channel may be determined, to minimize power absorption and/or obtain improved drying and/or softening of the fabric.