EP3690099A1

EP3690099A1 - Output head for oven for textile use

Info

Publication number: EP3690099A1
Application number: EP19154519.3A
Authority: EP
Inventors: Stefano Zanardi
Original assignee: Societa Italiana Costruzione Aeromeccaniche SICAM SRL
Current assignee: Societa Italiana Costruzione Aeromeccaniche SICAM SRL
Priority date: 2019-01-30
Filing date: 2019-01-30
Publication date: 2020-08-05

Abstract

An output head (5) to be applied at the exit of an oven (1) for textile use is described, comprising an inlet opening, arranged in succession to the exit (17) of the oven (1), comprising rollers (6A, 6B) for the movement of conveyor belts which advance a fibre bed (7) towards a calender (8, 9) and an outlet opening, through which said outgoing fibre bed (7) is fed to the calender (8, 9). Said oven (1) provides for an air blowing (2) connected to a fan (3) or similar device apt to maintain a constant outgoing air flow rate. Said head (5) comprises two suction hoods (10, 11), connected with respective pipes (12, 13) with the inside of the oven (1), each arranged at one of the faces of a fibre bed (7) in transit on said conveyor belts from the oven (1) to the calender (8, 9).

Description

The present invention relates to an oven for the textile industry, provided with a special output head, in particular for non-woven fabric.
The textile industry is one of the oldest industries in the history of technology, with processing mainly based on the weaving.
More recently, the so-called non-woven fabric was developed. It is a textile material obtained with procedures different from the classic weaving (which involve a weft and a warp) or knitting. In the case of fabrics, the textile fibres are oriented in an orderly arrangement, while in the non-woven fabric fibres are arranged randomly and statistically.
The non-woven fabric can be obtained by processing both natural and synthetic fibres.
Typical features of non-woven fabrics include waterproofness, resistance to low and high temperatures, non-abrasiveness. These features make the non-woven fabrics suitable for several applications, in various technical fields. In the building industry, they can be used to coat or set up ceilings and false ceilings and in the production of the so-called geotextile materials, used for the construction of roads, airports, tunnels, embankments and the like. In the field of home furnishings, they are used for the production of wallpapers, sofas, armchairs, chairs, furniture accessories. In the medical industry, they are used for the production of white coats and other sterile surgical drapes. They are also used for the production of disposable caps and overshoes for swimming pools. There are daily-use objects made of non-woven fabric, such as bags, shoppers and more. In agriculture, they are used for cloth for the protection of the plants, for the collection and the protection of fruit and vegetables, for the development of seeds, for greenhouse cultivations, to prevent the growth of weeds, to protect the more delicate plants from weather, animals and pests. In clothing, they are used to line shoes and shoulder pads of suits. In manufacturing, they are used for packaging and for the production of filters. In photography, they may be excellent materials for backdrops. They are also used to improve the grounds for show jumping tracks in horse riding.
As seen from the above overview - not even complete -, these materials have a wide use and for this reason it is important to produce them under favourable conditions, both economically and industrially.
As already said, the non-woven fabric can be composed of natural and/or synthetic fibres. Normally, it is produced by means of carding machines. The types of traditional cards are those linked to a web laying machine, or it is possible to use airlays. However, the non-woven fabric produced by these machines is totally devoid of mechanical consistency.
A common way to confer consistency to these materials is to mix the fibres with low melting point fibres which, by melting, bind to other fibres, thus creating a robust structure. Once the low melting fibres are mixed to the other fibres, they are molten, placing the material in an oven where a hot air flow passes through the material. Among the low-melting point fibres it is possible to mention polypropylene and polyester, although there are many other.
Such hot air flow is created by means of fans and burners, generally arranged on the inner face of one of the longitudinal walls of the oven.
The traditional ovens currently used for these operations are realised as parallelepiped blocks, with feed on the front faces for entrance and exit of a conveyor belt, in order to insert and extract the material before and after the operation. Generally, the feed of the fibres in the oven takes place by means of a so-called entrance head, which allows the tensioning and the guiding of the conveyor belts to let the fibres pass inside the oven. To obtain flow characteristics apt to confer an even melting of the low-melting-point fibres, the air flow must be periodically reversed during the movement of the material from entrance to exit. For this purpose, shutter valves are normally arranged inside the traditional oven, in order to program the direction sequence of the air according to the change of the characteristics of the different materials to be processed. The longitudinal sides of these traditional ovens are therefore normally blind, except for small inspection openings. The shutter valve assemblies of such traditional ovens have bulky side sizes (1.5 - 2 m) with respect to the useful width of the oven itself, sometimes causing their installation to be difficult and occupying in an oven with useful width of 2 m, 100% more than the space actually useful for the passage of the material. In addition, the air passing treatment of the fibres means that a part of the fibres comes out of the layer of forming non-woven fabric and deposits on the oven parts, making it dirty. It is then necessary to remove some parts of the oven to extract from it the dirty parts and clean them. For these operations, the parts of the oven not being accessible except for the extent allowed by the inspection opening, it is necessary to perform long and difficult cleaning operations. This makes the downtime due to cleaning operations of the parts of the oven relatively long, remarkably affecting productivity.
With its Italian patent application No. 102015000067040 , the Applicant has solved this drawback, making the longitudinal walls completely openable.
After being processed in the oven, the fibres leave the oven, being extracted through a so-called output head, which performs the function of pulling the conveyor belts through special rollers and cleaning them, due to special devices mounted therein.
With its Italian patent application No. 102015000070182 , the Applicant has arranged an oven with a preheated entrance head, using in a preferred embodiment very advanced heat recoveries. In this way, to heat the material to be melted already in an area not normally dedicated to this purpose has become possible.
The output head for ovens for the production of non-woven fabric has conveyor belts that perform the material pulling through special rollers and the cleaning thereof using special devices, with a space overall dimensions of about 1 m. Until now, this space has never been dedicated to heating the material being processed, but only to the mechanical devices that allow the movement of the conveyor belts and therefore of the material through the oven. The output head of traditional construction consists of a unit that contains within the rollers for pulling the conveyor belts that move the material from the entrance to the exit of the oven. Very often, the ovens for producing non-woven fabric have a calender at the exit, consisting of two superimposed cold cylinders. Such a calender, in cold traditional ovens, arranged, as mentioned, at the exit from the oven, is the unit which provides for the calibration of the material and its compression and, for this process to be possible, it is necessary that the outgoing fibres from the oven, composed of a base fibre and a low-melting-point fibre acting as a binder, exhibit the binder still soft and in a plastic state, in order to guarantee the calibration result set. The binder is a thermoplastic product, which means that it softens and has a binding function as the temperature increases, finally consolidating the final state of the material following the subsequent cooling. This cooling will fix the values reached during calendering.
In the traditional output head, it is considered apparent that the material, as coming out from the hot zone of the oven, reaches the calendering cylinders being hot, a very important and necessary condition for achieving the final result, as already explained in the previous paragraph.
The length of the output head is constrained by minimum limits, defined by the presence of the necessary mechanical members which have already been discussed, apt to the operation of the oven. Therefore, it is very difficult to reduce a distance by about 1 m between the end of the hot zone of the oven and the rollers of the calender.
In high-speed production processes, the material leaving the oven passes quickly through the output head, arriving immediately at the rollers of the calender, still with much of the heat stored in the oven and then with the thermobinding fibres still in a sufficiently plastic state. The production of thermal insulators, to obtain better insulation, searches for layers of greater thickness and greater weight per m² (up to 8 kg/m²). This results in very low production speeds (for example, 0.2-0.3 m/min for the highest grammages). The grammage required today is increased, since until a few years ago the maximum was 1 kg/m²). Experience has, however, widely shown that transit in the traditional output head can lead to problems in these productions wherein the process requires low production speeds. Indeed, in materials with a high weight per linear meter of product, the speed of the production line must be low, since the production in kg/h is unchanged and in the output head, the non-woven fabric, passing at low speed, tends to lose the heat stored to a very large extent, thus reaching the calender calibration process with the non-plastic heat-melting fibres, so that the process will no longer have the expected and desired result.
US 7 610 659 discloses a process for the production of a polymer filling, comprising the deposition of a fibre layer, forming a pad, the fibre orientation, the fibre heating and their cooling in a system comprising a lower conveyor and an upper conveyor, the two conveyors being arranged at a mutual distance, forming a space; the two conveyors comprise compressing means of the pad.
US 6 116 895 provides an oven for carrying heat, conveying heat through a hood, through a supply pipe.
US 4 133 636 discloses an oven for textile use, comprising a recycle, wherein the temperature of the exhaust gases is first increased by the combustion of volatile substances, then lowered in a cooler, allowing additional air to enter. Part of the gas is sent back to the oven and part goes to preheat the incoming material.
The underlying problem of the invention is to propose an oven structure for textile use which has an output head which overcomes the aforementioned drawbacks, and which allows, without increasing or only negligibly increasing the energy consumption, to maintain the low-melting fibres plastic at the moment of contact with the calender. This object is achieved through an oven for textile use, comprising an output head to be applied to the output of said oven for textile use, comprising an inlet opening, arranged in succession at the exit of the oven, comprising rollers for the movement of conveyor belts which advance a fibre bed towards a calender and an outlet opening, through which an outgoing fibre bed is fed to said calender, characterised in that said oven provides an air blowing connected to a fan or similar device apt to maintain constant the outgoing air flow rate and that said head comprises two suction hoods, connected by respective tubings with the inside of said oven, each arranged in correspondence of one of the faces of said fibre bed in transit on said conveyor belts from the oven to the calender. The dependent claims describe preferred features of the invention.
Further features and advantages of the invention will anyhow be more apparent from the following detailed description of a preferred embodiment, given by mere way of non-limiting example and illustrated in the accompanying drawings, wherein:
fig. 1 shows schematically and partially in section an oven for the production of non-woven fabric, which carries an output head according to the present invention.
First of all, as a preliminary matter, it is considered necessary to clarify that "output head" of an oven for the production of non-woven fabric starting from textile fibres and low-melting-point fibres, means, as already mentioned in the introduction, a device which is external to the oven itself, although operatively connected thereto, through which the fibre bed is passed during processing and which bears all the mechanisms to obtain the movement of the conveyor belt which carries the fibre bed. Said head, further than exit of the oven, also acts as a feed of a calender, apt to complete the production of the non-woven fabric.
As can be seen in fig. 1, an oven 1 for melting the low-melting fibres carries an outlet pipe 2 for venting hot air, the function of which will be better explained in the following of the present description. Advantageously, the outlet pipe has forced ventilation, so that the outgoing flow rate can be suitably metered and comprises a fan 3 (or a similar device, such as an ejector or a blower). Moreover, the oven 1 has an air intake 4, so as to introduce fresh air into the oven.
Outside the exit of the oven 1, an output head 5 is applied, comprising rollers 6A, 6B for moving the conveyor belts which advance a fibre bed 7 towards a calender, outside the chamber, formed by two rollers 8, 9. This calender is essential to provide the right compactness and the right caliber for the finished product.
According to the present invention, inside the head 5, on the side of each of the faces of the fibre bed 7, there is a suction hood, respectively 10 and 11. The aforesaid hoods 10, 11 carry outlet pipes, respectively 12 and 13, inside each of which a shutter is arranged, respectively 14 and 15, for adjusting the air flow, said pipes 12, 13 being apt to connect the hoods 10, 11 with the inside of the oven 1. Preferably, the pipe 13 merges with the pipe 12, so as to reduce the consumption of metal for the creation of the tubes and for a greater uniformity of the flows. The duct 12, after the joining with the duct 13, leads again inside the oven 1. The duct 12, in correspondence of its outlet in the oven 1, bears a further shutter 16, apt to adjust the air flow rate from the hood into the oven. The passage of the fibre bed 7 from inside of the oven 1 to the output head 5 takes place through a slit 17, so as to create an air passage.
The arrangement of the two hoods 10, 11 in correspondence with the two faces of the fibre bed 7 constitutes a chamber, the walls of which are insulated to prevent the exchange of heat with the outside, so as to prevent, when passing inside it, the-low-melting-point fibres to solidify, losing the plasticity which, as explained in the introduction of the present description, gives a great contribution to the result of the calendering operation.
Preferably, the service members, such as the motors which move the rollers 6A, 6B, bear heat protections, to prevent said members from deteriorating or even partially melting.
When it is desired to proceed with the production of the non-woven fabric, textile fibres of the chosen type are deposited, together with low-melting-point fibres, in the proportion most suitable to the process to be carried out and to the product to be obtained, on a special conveyor belt to form a bed 7. The bed 7 is transported by the conveyor belt, which in turn is dragged by the rollers 6A and 6B inside the oven 1 where, in a known way, the fibres are heated. The heating is sufficient to completely melt the low-melting-point fibres which thus bind the other (textiles) fibres to themselves. At the end of the heating, the bed 7 leaves the oven 1 and enters the head 5 through the slit 17, on the conveyor belt driven by the rollers 6A and 6B.
The heating and the circulation of the air inside the oven 1 are, in a known way, divided into sections, separated from each other. The air flow rate in the individual sections is adjusted, in a known way, so that it balances the one present in the adjacent sections, so as to have an optimal heating, according to the production that is being performed. The air heating is carried out by special burners, located inside the oven 1 and the transport of said air by fans. The air to be heated is fed into the oven 1, partly as combustion air to operate the burners, partly by entering through the air intake 4; in any case, the amount of air inside the oven 1 is adjusted so as to maintain a slight overall depression. In order to maintain the air mass balance, a part of it is expelled through the outlet pipe 2. The presence of the fan 3 helps to maintain the desired depression.
Therefore, according to a particularly preferred embodiment of the present invention, an output head 5 is provided, characterised in that the heating and the air circulation inside the oven 1 to which it is applied are divided into sections, separated from each other, the air flow rate in the individual sections being adjusted, so that it balances the one present in the adjacent sections.
According to the present invention, the suction hoods 10 and 11 are driven inside the head 5, creating an air flow through the bed 7. This air is carried from the outlet pipes 12 and 13, back into the oven 1. Opening the shutter 16, air coming from the hoods 10 and 11, through the pipes 12 and 13, is introduced into the oven 1, such air having passed through the fibre bed 7. The introduction of this air into the oven 1 alters the balance of the air flows inside the oven 1 itself, so that it becomes necessary to increase the air flow rate leaving the oven 1, in order to restore the balance inside the same oven 1. However, such air cannot be expelled, as occurs with that fed according to the prior art through the outlet pipe 2, since the flow rate of the fan 3 is in any case kept constant. For energy saving reasons - i.e. owed to the fact that passage has the less obstacles - the excess air comes out of the oven 1 through the slit 17. The air that passes through the slit 17 brings the balance back into the oven 1. It is at a temperature close to that inside the oven 1, having been circulated therein until coming out, so that, filling the inside of the output head 5, it heats it, keeping it at a high temperature, almost equal to that of the oven.
The air circulation between the inside of the oven and the output head 5 is adjusted by acting appropriately on the shutters 14, 15 and 16.
The shutters 14 and 15 force the air to pass through the fibre bed 7 and recover the air that laps above the same fibre bed 7; and the shutter 16, as already seen above, adjusts the active amount of air. The combination of these three actions ensures that the low-melting-point fibres, contained in bed 7, remain soft, in a plastic state inside the entire head 5, so as to reach the calender 8, 9 in the ideal condition for the best outcome of the non-woven fabric production process.
The solution according to the present invention allows the fibres to be kept at a low melting point in the plastic state, due to the heating inside the output head 5, without having to provide additional units and without requiring an appreciable increase in the installation, maintenance and energy cost, since this heating takes place by recovering the internal heat of the oven 1. Such a heating is necessary for low production rates (for high grammages of the non-woven fabric to be produced), with an apparent increase in processing efficiency. The heating of the head 5 then results in an increase in the length of the heated zone by about 10-20%, which entails an increase in productivity and the achievement of the qualitative and technological result of uniformly binding the fibres of the material and making possible the adjustment of the thickness to the desired values, by means of the cold calender.
It is understood, however, that the invention is not to be considered as limited by the particular arrangement illustrated above, which represents only an exemplary embodiment of the same, but different variants are possible, all within the reach of a person skilled in the art, without departing from the scope of the invention itself, as defined by the following claims.

LIST OF REFERENCE CHARACTERS

1: Oven
2: Outlet pipe (of 1)
3: Compressor (of 2)
4: Air intake (of 1)
5: Output head
6A, 6B: Rollers
7: Fibre bed
8: Calender roller
9: Calender roller
10: Suction hood
11: Blowing hood
12: Pipe (of 10)
13: Pipe (of 11)
14: Shutter (of 12)
15: Shutter (of 13)
16: Shutter (of 12)
17: Slit (of 1)

Claims

Oven (1) for textile use, comprising an output head (5) to be applied at the exit of said oven (1) for textile use, comprising an inlet opening, arranged in succession at the exit (17) of the oven (1), comprising rollers (6A, 6B) for moving conveyor belts which advance a fibre bed (7) towards a calender (8, 9), and an outlet opening, through which said outgoing fibre bed (7) is fed to said calender (8, 9), characterised in that said oven (1) provides for an air blowing (2) connected to a fan (3) or similar device, apt to maintain a constant outgoing air flow rate and in that said head (5) comprises two suction hoods (10, 11), connected with respective pipes (12, 13) with the inside of the oven (1), each arranged at one of the faces of a fibre bed (7) in transit on said conveyor belts, from the oven (1) to the calender (8, 9).
Oven (1) as in 1), characterised in that the heating and the air circulation inside the oven (1) are divided into sections, mutually separated, the air flow rate in the individual sections being adjusted, so that it balances the one present in the adjacent sections.
Oven (1) as claimed in 1) or in 2), characterised in that said hoods (10, 11) bear outlet pipes (12, 13), inside each of which a shutter (14, 15) is arranged for adjusting the air flow, said pipes (12, 13) being apt to connect the hoods (10, 11) with the inside of the oven (1).
Oven (1) as in 3), characterised in that one (13) of the pipes (12, 13) merges with the other pipe (12), the pipe (12) resulting from the joining of the two pipes (12, 13), leading again to the inside of the oven (1).
Oven (1) as claimed in any one of claims 3) and 4), characterised in that the pipe (12), in correspondence of the merger thereof in the oven (1), bears a further shutter (16) for air flow adjustment.
Oven (1) as in any one of the preceding claims, characterised in that the oven (1) bears a venting pipe (2) for the bleeding of hot air, with forced ventilation and which includes a compressor (3).
Oven (1) as in any one of the preceding claims, characterised in that the passage of the fibre bed (7) from the inside of the oven (1) to the output head (5) takes place through a slit (17), so as to create an air passage.