Field of Invention
The present invention is related to an apparatus and method of treatment of thermo-plastic like mono filament, thin web strings, multi-filament and plastic woven tapes or yarn. In particular, the invention relates to a heating thermal apparatus with air-regulating mechanism enabling the thermo-plastic to move forward and stretch after being heated to a particular temperature such that grains present inside the plastic aligned them in the direction of the air flow.
Background of Invention
Drying objects by passing hot air in an enclosed chamber is the least sophisticated system and is generally used for product development or laboratory-type applications, where small samples have to be dried simultaneously. There are many sizes and designs of chambers that satisfy different applications. These chambers available include the ones operated on hot air, vacuum, and dehumidifying mechanisms with regenerative desiccant beds. The blower circulates air through a heater, where the air is heated to the desired setpoint and then flows through the heating chamber from bottom to top or in any desired direction as the oriented thermoplastic is moving. In most designs the air is recycled back through the blower and heater. If the relative humidity of the air entering the oven is high, the heating chamber drying capacity gets limited.
At a given temperature, the air can absorb moisture only as long as the moisture in the oriented thermoplastic is greater than the air moisture. At some point the water no longer migrates from the resin to air. Unless the dew point or air moisture content is lowered, hot air continues to circulate around the thermoplastic, but no additional moisture is removed. This results in an inefficient hot air chamber where energy is wasted.
The conventional apparatus of thermal treatment of the moving web as can be seen in Figure 1 and 1A, is a typical hot air heating chamber which consists of

upper and lower chamber particularly of identical in construction which are connected via hinge (12). The air-flow guiding casing (not shown) forms the suction inlet and outlet for each fan. On closure of both chambers, a hot-air channel is formed (at the interface of the chambers). The hot-air channel (4) receives hot air from the top and bottom chambers (2,3) through inlet port(s) forming air inlet (10) provided in the top and bottom chambers (2,3) at one end (the inlet end) of the channel where the web strip inlet (5A) is present. The air from the hot-air channel (4) leaves the channel and re-enters the chambers through the outlet port(s) forming air outlet (11) provided in the chambers at the other end (the outlet end) of the channel where the web strip outlet (5B) is present.
Near to the web strip outlet (5B), casing path is present (not shown), set of heaters are installed enabling the suction of hot air of desired temperature by the fan. The hot air which is being blown by the fan is guided through flow guide channel. There is no provision of the temperature monitoring system or sensors which can detect the temperature of the top and bottom chambers (2,3) and regulate the air flow accordingly or increase or decrease the speed of the fan to blow hot air. Such provision is missing in the conventional system as it is difficult to capture the regulation of temperature and such provision is costly also.
As can be seen further from the figure 1&1A, it is not possible to control the temperature and air flow in the hot air channel to achieve uniformity across the channel. Further, there is no proper regulation of air or regulators to regulate the air inside the top and bottom chambers (2,3) to provide uniform flow of the air across the top and bottom chambers (2,3). Further, the heaters and fan are placed far away from each other which reduces the efficiency of the of the heaters to provide a uniform hot air. In addition to it, placing heaters far away will eventually increase time in maintenance as the operator has to dismantle number of assemblies to reach to the heaters.

These enclosed chambers for thermal treatment can also be termed as Hot air heating chamber which are based on the principle of heat transfer with the help of forced convection heat transfer between thermoplastic and hot air. Forced convection is a special type of heat transfer in which fluids such as air is forced by an external arrangement such as fans and blowers, in order to increase the heat transfer rate. These arrangements can be fitted outside the main convention unit or can be integrated with the main unit.
The rate of convection heat transfer between the flowing fluid such as air and solid surface is expressed by Newton's law of cooling:
Q =hA(T-Tf)b
where Q is the heat transferred per unit time, A is the area of the object or the contact area of the test piece which is placed inside the hot chamber through which heat transfer takes place, h is the convective heat transfer coefficient, T is the object's surface temperature, Tf is the fluid temperature (i.e. temperature of air in this case), and b is a scaling exponent. The convective heat transfer coefficient is dependent upon the physical properties of the fluid and the physical situation, the convection heat transfer coefficient depends firstly on fluid thermophysical properties and secondly on the fluid velocity. Here fluid is more particularly disclosed as air.
Production of thermo-plastic filament requires various machinery units assembled in a straight path. One of those units includes devices that apply heat energy in the form of hot air forced convection for stretching of tapes inside a hot air chamber and up-next stretching unit. In this procedure, a collection of aligned mono-axially oriented thermo-plastic tapes are passed through a uniform duct containing hot air flowing in the direction of thermo-plastic tapes. This unit comprises two separate chambers which are hinged by hinge (12) together along the length whereas the other side is free to open using pneumatic cylinders (13). The thermo-plastic tapes travel from entry of the device to exit. At the exit, the air is again drawn

using suction fan. The suction draws the air axially and blows it air radially after being heated through a channel formed using guided pathways. At the inlet to the fan, air gets heated using circular heaters installed co-axial to the fan. A hot air is blown and fed to the thermo-plastic path on entry side through several air guide vanes located at a distance from each other. These vanes act as guided pathways for proper air flow and help in reduction of turbulence caused as a result of high velocity of air.
The air path channel is formed as a result of closing of both the unit chambers. Air flows in the channel along the length of the unit and sucked back with the aid of perforated sheet installed at the exit side of the device and the cycle of air circulation is repeated.
Temperature monitoring and hot air regulation are very crucial in determining the performance of air channel system as the quality of thermo-plastic is dependent on the volume and temperature of the air from inlet to exit. The desired properties of elongated thermo-plastic are achievable only if uniformity of flow and temperature of air is attained throughout the air channel section. The end product or thermo-plastic, after being exposed to high temperatures, may shrink in lower temperatures which may be unusable in many cases. So, in order to be used as a raw material for different units which process them for their desired product, thermo-plastic has to be of low shrinkage type. Machines such as web strip winding machines which will use the thermo-plastics as a raw material for further processing require low shrinkage thermo-plastic which can be produced only if the hot air heating chamber used has a uniformity in temperature of air. The low shrinkage property allows thermo-plastic to be more uniform in width during their winding onto rotating shafts. These uniform width strings can be further used as raw materials for processing to be used in many other applications.

As we know that the low temperature in the hot air chamber will affect the properties of the web strip a lot, so the temperature inside the hot air chamber is to be maintained or to be constant throughout the process. Further, it has been noticed that the maintenance of adequate temperature inside the hot air chamber is difficult. Due to the conduction, there is a rapid heat exchanges take places through different layers of the chamber, so the heaters are operated at high capacity to provide a constant temperature. Some conventional chambers uses a rubbery layer which traps the heat but the life of the same is very short and need to be replaced frequently.
One such hot air heating chamber is disclosed in German patent DE2614258 ('258) wherein it consists of upper and lower sections with a passageway between them through which a continuous length of material for treatment is passed. This passage has inlets and outlets for the introduction and removal of hot air. This consists of a double circuit system with a single air heater and fan mounted below the heating chamber. The treatment channel is surrounded by an air passage through which the said hot air is first passed before it is released into the main channel. Both sides of the heating chamber are fed from the one fan via ducts containing dampers so that the flows can be balanced. The suction ducts combine to recycle to the fan inlet of use in the continuous stretching of synthetic fibres, ropes, and plastic sheets to increase the strength. The main drawback of such system is that the supply of air is not uniform throughout the hot air heating chamber due to only one air heating system. Further, the '258 patent does not discloses any air regulation knobs or levers to regulate the flow of air. Also, the '258 patent discloses a system which is very complex and requires lot of maintenance which is difficult.
Indian Patent 358027 ('027) discloses an apparatus of thermal treatment of moving webs wherein hot air circulating chamber with air-flow control system used in manufacture of thermo-plastic products such as monofilament, plastic web

strips, narrow film strip, multi-filament. The '027 patent discloses multiple knobs or levers for regulating the flow of air inside the chamber at the web tape inlet which requires precision and skilled labour. Any errors in the setting of the multiple knobs or levers will result in degrading web strip quality. Further, the '027 patent further discloses the regulation of the air near to the inlet of the heating chamber which creates a turbulence during air regulation and provides a non-uniform air flow or can hinders the web strip movement. Another Patent GB1517189A ('189) discloses an apparatus for treating a material web comprising a closed chamber having an entry aperture and an exit aperture for the web with the multiple streams or slots for fluid passage. Patent ('189) further discloses thermally insulted casing but at the entry and exit side only with the disadvantage of non-uniform temperature maintenance. Further, there is no temperature monitoring system. The slots are provided which are in the direction perpendicular to the direction of travel of web only which restrict the air flow in all the direction to flow in single direction, which result in non-uniform hot air supply.
Yet another Patent US4952145A ('145) discloses an apparatus for the heat treatment and/or drying of a web of material, consisting of guiding and transporting means for the web of material, of infrared radiators, which are arranged on one of both sides of the web of material at a distance from it and extending over its width and in its longitudinal direction and which can be heated by ducts which are arranged on the rear sides of its radiating plates, have heating medium flowing through them and are adjustable in heating capacity. Patent (' 145) discloses a complex system with large number valves, ports and heating coils for treatment of web which require greater maintenance and large time for recovery if shutdown happens. Further, there is no provision or lever present for regulating amount of air through the blower.

Due to advancement in technology of plastic processing there may be more need for uniformity and strength of the strip which is dependent on better control over the parameters of processing during the entire production process. These parameters can be controlled by continuous monitoring and feedback systems installed within the machine unit.
With the growing needs of high production speed and stringent product requirements, improved air-flow uniformity and temperature precision in the hot air chamber is very important and necessary. Further, there is a need of a system having ease in maintenance to reduce the breakdown time and increase overall efficiency of the system.
Objects of Invention:
The main object of the invention is to provide an apparatus and a method for thermal treatment of moving monoaxially oriented thermo-plastic sheets, fabric or tapes such that the quality of air (air current and temperature) is uniform throughout the apparatus duct channel which eventually produces high quality treated sheets, fabric or tapes for further processing.
Another object of the present invention is to provide uniform air circulation (constant mass flow rate)across the width and length of hot air channel.
Yet another object of the present invention is to maintain uniform temperature throughout the air duct with precision monitoring and control mechanism.
Another object of the present invention is to provide safe and easy maintenance of fan, heater, and motor assembly when required.
Further object of the present invention is to achieve higher temperature as compared to traditional devices for high quality strings.

Summary Of Invention:
The present invention relates to an apparatus used in production of plastic objects such as mono-filament, multi-filament, thin web string and plastic woven tapes, etc. Conventional systems do not have provision for proper monitoring & controlling of temperature and air-flow regulation in hot air ducts or passage which lack the ability to achieve uniformity. The present invention discloses an apparatus (1) which not only provides for improved air-flow uniformly but also temperature uniformity with air-flow path having provision of number of fans (7), optimization of heater (6) location and one air-flow regulator (8) having manual control lever (9).
In particular, the invention discloses an apparatus for thermal treatment of thermoplastic tapes comprising a top chamber (2) and a bottom chamber (3), with a channel (4) situated between said two chambers to carry hot air from the web strip inlet (5A) to the web strip outlet (5B) during which travelled hot air cools down, and through channel (4) said moving web strips (5) travel in longitudinal direction, each of said top and bottom chambers (2, 3) having at least one separate air outlet (11) and a separate air inlet (10), said at least one air outlet (11) to bring said hot air from said top and bottom chambers (2, 3) into said channel (4), and said air inlet (10) to take air which cools down upon its travel through said channel (4) back into said chambers (2, 3), and wherein each of said air inlets (10) is provided with at least one individual air-flow regulator (8) having operational levers (9), further wherein each of said top and bottom chambers (2, 3) have at least one heater (6) and a fan (7) provided on said top and bottom chambers (2, 3) near the web strip outlet (5B) to heat up the cooled air for further circulation. Some of the key features of the apparatus of the present invention are that said fan (7) is coupled with said heater (6), said operational lever (9) is positioned near said web strip outlet (5B), said top and bottom chambers (2, 3) are provided with an insulation layer (32) on their inside, at least two temperature sensors (23) are provided in the middle of each of said top and bottom chambers (2, 3), a locking

sheet (17) is provided to lock said top chamber (2) in an angular position, and perforated sheets (31) are provided near web strip outlet (5B).
Moving web strings (5) enter apparatus into a hot air channel (4) formed between top chamber (2) and bottom chamber (3). Entry point of moving strings into the hot air channel (4) is the web-strip inlet (5 A). After getting heat treatment, the moving web strings (5) leave the apparatus through the web strip outlet.
Brief Description of Figures:
Figures 1 and 1A show a conventional device for thermal processing of moving thermo-plastic
Figure 2 shows the perspective view of the apparatus of the invention
Figure 3 shows the internal air flow in the apparatus of the invention with its cross-sectional view
Figure 3 A shows another side cross sectional view of the apparatus of invention
Figure 3B shows the air flow deviation by the flapper and directional change of air by the fan
Figure 4 shows the laminar and turbulent behaviour of air inside the apparatus of invention
Figure 5, 5A shows the locking mechanism during web strip intake inside the opening between the top and bottom chambers of the apparatus of invention
Figure 6 shows an isometric/perspective view of heater, fan and motor for easy maintenance.

Figure 7 shows the flow chart of the signal send by the sensor and feedback from the heater through HMI
Figure 8 shows a view of apparatus showing direction of air flow with multiple vain guides

List of parts:
1. Apparatus of invention
2. Top chamber
3. Bottom chamber
4. Hot-air channel or simply channel
5. Web strip
5 A Web strip inlet 5B Web strip outlet
6. Heater
7. Fan
8. Air flow regulator
9. Lever (or control lever or regulating lever)
10. Air Inlet
11. Air Outlet
12. Hinge
13. Pneumatic cylinder
14. Flapper sheet
15. Conventional apparatus
16. Motor

17. Locking sheet
18. First flange
19. Cover Sheet 30 20. Base frame

21. Levelling stud
22. Side plate
23. Temperature sensor
24. Second flange 35 25. Motor flange

26. First set of hardwares
27. Second set of hardwares
28. Third set of hardwares
29. Entry side 40 30. Exit side

31. Perforated sheet
32. Insulation Layer
33. Guide vanes
34. Opening
45 35. Delivery plate

Description Of Invention:
As discussed earlier, for later stage strengthening of thermo-plastic, thermal processing is required. Heat energy required for the thermal processing of thermoplastic is given by the hot air forced convection heat transfer principle.
Taking into account the disadvantages and other issues in conventional hot air heating chamber, the present invention takes care of all the above mentioned issues as shown in figure 2, discloses an apparatus (1) for thermal treatment of moving thermo-plastic. The apparatus (1) consists of a base frame (20) which is constructed by joining structural members of rectangular cross section to form a sturdy base with levelling stud (21) to level the apparatus (1) to counter the floor unevenness. The joining of the members can be by any of the technologies such as welding, seaming, or bolting or any kind of method known to person skilled in art.
Apparatus (1) is further covered or the base frame (20) is covered by cover sheet (19) such that the internal components such as pipes, electrical wiring hardwares (not shown) can be hidden to provide a good aesthetic look. Also, cover sheet (19) serves as a rigid covering to provide additional strength to the base. The web strip (5) after slitting from a sheet from the cutter (not shown) is made to enter into an apparatus (1) from web strip inlet (5 A) and travelled along the direction of the movement of web strip (5) as shown by arrow in Figure 2.

We claim:
1. An apparatus for thermal treatment of thermoplastic tapes comprising a top chamber (2) and a bottom chamber (3), with a channel (4) situated between said two chambers to carry hot air from the web strip inlet (5 A) to the web strip outlet (5B) during which travel said hot air cools down, and through which channel (4) said moving web strips (5) travel in longitudinal direction, each of said top and bottom chambers (2, 3) having at least one separate air outlet (11) and a separate air inlet (10), said at least one air outlet (11) to bring said hot air from said top and bottom chambers (2, 3) into said channel (4), and said air inlet (10) to take air which cools down upon its travel through said channel (4) back into said chambers (2, 3), and wherein each of said air inlets (10) is provided with at least one individual air-flow regulator (8) having control levers (9), further wherein each of said top and bottom chambers (2, 3) have at least one heater (6) and a fan (7) provided on said top and bottom chambers (2, 3) near the web strip outlet (5B) to heat up the cooled air for further circulation characterised in that said fan (7) is coupled with said heater (6), said control lever (9) is positioned near said web strip outlet (5B), said top and bottom chambers (2, 3) are provided with an insulation layer (32) on their inside, at least two temperature sensors (23) are provided in the middle of each of said top and bottom chambers (2, 3), a locking sheet (17) is provided to lock said top chamber (2) in an angular position, and perforated sheets (31) are provided near web strip outlet (5B).
2. The apparatus as claimed in claim 1, wherein said top chamber (2) and bottom chamber (3) are each provided with a motor (16) which is coupled with the fan (7), and wherein said heater (6) is placed just below the motor (16) and encloses the fan (7), and where said heater (6) is co-axial with said fan (7).

3. The apparatus as claimed in claims 1 to 2, wherein said air-flow regulator has butterfly flaps, the angle of which is adjustable using the level (9) to adjust the velocity and flow area of the air-flow passing through the air-flow regulator (8).
4. The apparatus as claimed in claims 1 to 3, wherein a plurality of air guide vanes (33) is provided in each of said top and bottom chambers (2, 3) forming passages between them through which passages air heated by said heaters (7) flows, said heated air being directed to air delivery plates (35) provided in each of said top and bottom chambers (2, 3) at said web strip inlet (5 A).
5. The apparatus as claimed in claim 4, wherein said air delivery plates (35) are curved.
6. The apparatus as claimed in claims 1 to 5, wherein at least two heat sensors are provided inside each of said top and bottom chambers (2, 3), wherein said sensors are located inside said channel (4) in respective top and bottom chambers (2, 3).
7. The apparatus as claimed in claims 1 to 6, wherein said insulation layer is made of the material selected from a group comprising vacuum insulation panels, silica aerogel, glass wool, rock wool, polyuthrane foam, or melamine foam and the thermal conductivity of said insulation layer (32) is between 0.004 - 0.12 w/m-k.
8. The apparatus as claimed in claims 1 to 7, wherein said fan (7) is of radial delivery type and said heater (6) has a circular coil tube.

9. The apparatus as claimed in claims 1 to 8, wherein said top chamber (2) and bottom chamber (3) are hinged together with the help of a hinge (12) along their length with two or more hinged points provided for adequate strength and constrained motion, and where an opening (34) between the top and bottom chambers (2, 3) is achieved by a pair of pneumatic cylinders (13) operated by actuators or electrical switches.
10. A method of thermo-mechanical treatment of thermoplastic tapes using the apparatus (1) of claims 1 to 9, characterised in that the said method comprises the steps of:

a) heating air in the channel (4) with the help of the heater (6) placed coaxially around the radial flowing motor (16) fan (7) arrangement;
b) circulating the heated air to the air outlet (11) at the web strip inlet (5A) in the passages formed between the air guide vanes (33).
c) heating the web strip (5) inside channel (4) having hot air, and stretching the heated web strip (5) and orienting it mono-axially along the length of the apparatus (1);
d) monitoring the temperature of the hot air inside channel (4) with temperature sensors (23) and maintaining it at a required level with the help of a complete feedback loop, wherein whenever the temperature of the air inside the hot air channel (4) goes below a pre-set temperature, the temperature sensor sends a signal to the control unit which in turn sends a signal back to the heater (6) to actuate accordingly to maintain the temperature in the range between 150-160 °C depending upon the stretching ratio and denier of the yarn required;
e) exiting the web strips (5) from the apparatus (1) from the web strip outlet (5b).

11. The method as claimed in claim 10, wherein the hot air generated in step a from each top and bottom chambers (2, 3) is re-circulated near to the exit side area to circular heater (6) and motor fan (7) arrangement with the help of perforated sheet (31).
12. The method as claimed in claims 10 and 11, wherein the lever (9) of the apparatus (1) operating the top and bottom chambers (2, 3) is rotated such that the flapper sheet (14) is rotated to induce more air towards the heater (6).
13. The method as claimed in claims 10 to 12, wherein the air to be heated is sucked by the fan (7) and recirculated towards the passages formed between the guide vanes (33) of the apparatus (1) such that the heated air is uniformly distributed inside the chambers.