Thermoregulation system of rotating metal cylinders in plants for extrusion and conversion/transformation of plastic films by infrared heaters

Abstract

A thermoregulation system of rotating metal cylinders in plants for the extrusion and conversion/transformation of plastic films includes heating elements applied to each rotating cylinder, wherein the heating elements are infrared heating elements, and wherein the rotating cylinder includes a metal tube rotating around a fixed shaft, which is rigidly connected to two side plates.

Claims

1. A thermoregulation system of rotating metal cylinders in plants for extrusion and conversion/transformation of plastic films, comprising: one or more heating elements applied to each rotating metal cylinder, wherein said heating elements are infrared heating elements, and wherein said rotating metal cylinder comprises a metal tube rotating around a fixed shaft, which is rigidly connected to two side plates.

2. The thermoregulation system according to claim 1, wherein a plurality of said infrared heating elements is applied to said metal tube.

3. The thermoregulation system according to claim 2, wherein said infrared heating elements are positioned in line, in adjacent groups.

4. The thermoregulation system according to claim 2, wherein said infrared heating elements are positioned circumferentially on an annular supporting structure fixed to the shaft of said rotating metal cylinder, so that said infrared heating elements are stationary and immobile with respect to the rotating metal cylinder.

5. The thermoregulation system according to claim 1, wherein power is fed to said one or more heating elements through an electric cable input.

6. The thermoregulation system according to claim 1, wherein said rotating cylinder is cooled with environmental air collected through an air vent and blown through holes fluidly coupled to an inside of said rotating cylinder.

7. The thermoregulation system according to claim 1, wherein said infrared heating elements are infrared resistances.

8. The thermoregulation system according to claim 1, wherein said one or more infrared heating elements are rotatable together with the rotating metal cylinder.

9. A cylinder for a thermoregulation system, comprising: a plurality of heating elements applied to said cylinder, wherein said heating elements are infrared heating elements, and wherein said cylinder comprises of a metal tube rotating around a fixed shaft, which is rigidly connected to two side plates.

10. A method of heating a rotating metal cylinder in plants for extrusion and conversion/transformation of plastic films, comprising: providing a rotating metal cylinder that comprises a metal tube rotating around a fixed shaft, which is rigidly connected to two side plates; and providing a plurality of infrared heating elements, which are applied to the rotating metal cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The structural and functional characteristics of the invention and its advantages with respect to the known art will appear more clearly understandable from the following description referring to the enclosed schematic drawings, which illustrate a non-limiting practical embodiment of the invention. In the drawings:

[0040] FIG. 1 is a longitudinal section illustrating a cylinder produced according to the invention; and

[0041] FIG. 2 is an enlarged transversal section of the cylinder of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0042] In one embodiment, the invention provides for a rotating cylinder 10 consisting of a tube 11, which can be either iron-steel, or aluminum, or any other material, compatibly with the temperatures to be reached and with the mechanical characteristics that must be ensured, rotating around a fixed shaft or axis 12, which is rigidly connected to two side plates 13.

[0043] According to the invention, depending on the type of material of which the rotating cylinder 10 is composed, various infrared resistances 14, having a wavelength compatible with such material, are applied to the cylinder 10. Said resistances 14 can, for example, be arranged in line, in adjacent groups, as clearly illustrated in FIG. 1 of the drawings.

[0044] The rotation of said cylinder 10 with respect to its fixed shaft 12, ensured by bearings 15 or bushings or any other system that enables its relative rotation, can be induced by an external drive wheel, a connection with a pulley or a toothed wheel, or in any case with any available rotation system, which is operatively connected to a power take-off 16.

[0045] An annular structure 17, circumferentially carrying the infrared resistances 14, is then rigidly fixed to the fixed axis 12 of the cylinder 10, so that said resistances are stationary with respect to the relative movement of the cylinder 1. This arrangement eliminates the use of rotating electric collectors, which would be necessary if the infrared resistances 14 rotated integrally with the cylinder 10.

[0046] In one embodiment, however, elements 14 rotate together with the cylinder, so to ensure different temperature ranges for the cylinder circumferentially.

[0047] Vice versa, when the resistances 14 are kept fixed to the central shaft 12 of the cylinder 10, constancy and homogeneity of the quantity of heat supplied to the cylinder are ensured, also in the event of faults of one or more resistances, because the entire cylinder is cyclically enveloped by the heat supplied by each resistance.

[0048] The almost complete absence of thermal inertia of the present heating system (apart from that of the cylinder itself, related to the type of material used, the thickness of the wall and, therefore, the type of process for which it is intended, but in any case much lower than in the prior art) enables a direct temperature reading of the film by means of infrared sensors, ultrasound, laser or any other system, thus substantially instantaneously intervening on the power supplied by the infrared resistances 14, which are fed through an electric cable input 20.

[0049] The reading of the temperature of the film can be performed in substantially any position, either when the film is still in contact with the cylinder or immediately afterwards. Similarly, the management of the power supplied from the infrared resistances 14 to the cylinder 10 can also be determined by measuring the temperature of the cylinder, when it is impossible, or difficult, or simply not helpful for the process to detect the temperature of the plastic film.

[0050] As previously mentioned, arranging the resistances inside the cylinder in bands having a desired width also provides for an independent management of the power supplied by the resistances, creating different thermal gradients on the cylinder in a transversal direction with respect to the movement of the plastic film.

[0051] In the event of a sudden stoppage of the cylinder for any reason, which may derive from a process fault upstream or downstream of the cylinder or due to the cylinder itself, the surface of the cylinder may have to be rapidly cooled in order to avoid an excessive increase in the temperature of the plastic film present therein, due to the exponential increase in residence time of the plastic film and, therefore, of the quantity of exchanged heat.

[0052] For safeguard in these types of situations, holes 18 can be created, radially positioned on the closing flanges of the cylinder, in turn integral with the cylinder and, therefore, rotating with respect to the fixed shaft. Environmental or cooled air can be blown through these holes 18, fed through a vent 19, to drastically reduce the temperature of both the infrared resistances 14 (in any case having an extremely reduced thermal inertia if compared to any heated fluid) and also of the cylinder 10 itself.

[0053] Different air flow-rates can obviously be provided, depending on the type of application, and also, as already mentioned, cooled air may be used, thus increasing, in one case, the convective thermal exchange coefficient and otherwise the ΔT with respect to the surface of the cylinder.

[0054] The above mentioned objectives have therefore been achieved.

[0055] The scope of protection of the present invention is defined by the following claims.