Thermal Treatment Roll

Abstract

The specification describes a thermal treatment roll, e.g. for heating or cooling a textile yarns etc., wherein a rotor is mounted on a stator which is provided with a heating or cooling means. Between the stator and rotor is a connecting element of a solid, heat-conducting lubricating material, e.g. a ring or rings of sintered metal impregnated with a lubricating oil.

Description

The present invention concerns a thermal treatment roll for treating a material running thereon, such as continuous filaments, yarns formed of fibers, ropes, tows, strips of continuous material or sheets formed of discontinuous elements.

In various treatments, notably in the textile field, it is necessary to bring such a material to a temperature which is both uniform and precise, for example 100.degree. or 200.degree. C., and to correct rapidly any variations which may be caused by any disturbing element, such as a current of air.

In a first type of known roll, heat is supplied to the longitudinal structure by injection of a fluid at appropriate temperature into the rotor. The heat transmission is good, but the supply of fluid at a precise temperature to the roll is difficult to effect. Such feeding complicates the installation of the roll and creates a danger of leakage of fluid through the rotating packing or packings. It has not hitherto been possible to eliminate this danger satisfactorily. In addition, the control of the temperature of the rotating part is difficult to effect and is unsuitable in practice for a precise temperature regulation.

The danger of leakage is obviated if, in accordance with a second type of known roll, the heat is supplied to the roll by radiation between the external periphery of a fixed stator disposed inside the rotor and the internal periphery of the rotor. However, it is then difficult to effect a good heat transmission from the stator to the rotor, and a precise control of the temperature of the rotor.

According to the present invention there is provided a thermal treatment roll, such roll comprising a hollow rotor, a stator disposed inside said rotor, heating or cooling means in said stator and a connecting element, composed at least partly of a solid, heat-conducting, lubricating material, in contact with at least part of the outer periphery of the stator and with at least part of the inner periphery of the rotor.

With a roll according to the present invention, the material is heated or cooled in contact with the external periphery of the rotor, the latter being brought to the appropriate temperature mainly by conduction of the heat produced by the stator through the connecting element. The element is therefore advantageously so shaped and disposed as to be in contact with the greater part of the internal periphery of the rotor and the external periphery of the stator, or at least of their useful part, i.e. of that part of the rotor which is in contact with the material to be treated and of that part of the stator which produces the heat.

These two parts are advantageously disposed opposite to one another and the connecting element disposed between them is advantageously of small thickness. Thus, the losses of heat through the ends in the course of the conduction are reduced, as also is the time necessary for the heat transmission, whereby both the output and the speed of reaction of the roll to any modification in adjustment of the quantity of heat produced by the stator are improved.

Advantageously, the connecting element may serve as a means for centering the rotor, which avoids the use of any ball bearing or like centering device and considerably simplifies the design of the roll. In addition, when the connecting element is in contact with the greater part of the internal periphery of the rotor, the latter is also advantageously of small thickness, whereby the inertia of the rotating part of the roll is reduced and the heat transmission to the material to be treated is further improved.

The connecting element may be secured to the rotor or with the stator or independent of both of them. It may be composed of a number of independent parts of the stator and of the rotor or of parts of which at least one is fixed to the rotor or with the stator. As required, the connecting element may be formed entirely of a solid heat-conducting lubricant or it may comprise one or more heat-conducting supports, of which the surfaces in contact with the rotor, with the stator and with one another, respectively, are formed of a solid-heat-conducting lubricant.

By "solid lubricant" is meant a solid material having a low coefficient of friction which is comparable to that of a liquid employed for lubrication.

Such a solid lubricant may consist of a homogeneous solid material, for example graphite or suitable heavy metal salt, such as MoS.sub.2, WS.sub.2, NbSe.sub.2 or TaSe.sub.2. It may also consist of a heterogeneous solid material comprising either exclusively appropriate solid materials (antifriction alloy on sintered mass based upon metal powder and ethylene polytetrafluoride, for example) or at least one liquid combined with at least one appropriate solid, the combination being such that the material obtained has the characteristics of a solid. This is the case, for example, with a sintered metal or alloy impregnated with a liquid lubricant retained by capillarity in contact with the sintered mass, and hence incapable of separating from it under the normal conditions of use.

When the solid lubricant is in the form of a thin layer distributed over a part of the surface of the connecting element or elements, it may consist, for example, of a heavy metal salt of the type mentioned above, distributed in the form of fine colloidal particles which spontaneously adhere to such surface or are attached thereto by means of an appropriate resin. The lubricant and the mode of attachment must obviously be chosen with due regard, more particularly, to the stability of the connecting element at the service temperature of the roll and of its thermal conductivity in the temperature range reached by the roll.

The connecting element or elements and the rotor are advantageously mounted on the stator by simple fittings. The clearance which must be provided between the elements depends mainly upon the expansion coefficients of the materials of which these elements are made. It is advantageously a few hundredths of a millimeter at the service temperature chosen for the roll.

Rotation of the rotor may be effected by a shaft mounted along the axis of the roll, by driving it by means of a pinion on its periphery or by any other appropriate means. The speed at which the rotor may be driven may vary within wide limits, and it is generally higher in proportion as the load applied to the intermediate element is lower. In particular it should be noted that with the roll of the present invention, it is possible to carry out readily a continuous treatment of chemical filaments travelling at the highest speeds at present known.

The service temperature of the roll may be measured, if necessary, by any known means. Preferably, a temperature measuring probe is fixed in relation to the stator, advantageously in the connecting element or in that fixed part of the connecting element which is closest to the rotor, at a very short distance from the latter, whereby it is possible to detect very precisely the temperature of the internal periphery of the rotor. When the rotor is a cylinder of a very small thickness, the temperature probe is therefore disposed at a short distance from the material to be treated. Since the space corresponding to this short distance is occupied by materials of good thermal conductivity, the probe is therefore subject to excellent conditions for an accurate detection of the temperature of the material and for a rapid detection of the temperature variations thereof.

Simultaneously, it is possible to dispose the probe at a short distance from the heating element, under excellent conditions for an accurate detection of temperature variations of the latter. Thus, the probe is capable of reacting very rapidly to any modification in the adjustment of the heating element or to any thermal disturbance emanating from the outside.

It may therefore with very great advantage be associated with a regulating device of high gain without incurring any danger of hunting. A roll according to the invention thus has remarkable temperature stability, so that it is possible to obtain an excellent regularity in the thermal treatment of the material and consequently an excellent constancy of the characteristics of the latter. Such a result is particularly appreciable where the treatment is applied to continuous thermoplastic filaments, for which the constancy of the characteristics which may be influenced by thermal treatment, namely dynamometric characteristics, dyeing affinity and contraction, is essential.

The present invention will be more readily understood from the following description, given merely by way of example, reference being made to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through one form of roll according to the invention;

FIG. 2 illustrates the roll of FIG. 1 mounted for testing purposes;

FIG. 3 is a view similar to FIG. 1 of a second embodiment of roll according to the present invention;

FIG. 4 is a fragmentary view of a portion of a third embodiment and;

FIG. 5 shows a suitable control arrangement.

As illustrated in FIG. 1, a frame 1 supports the stator, the external periphery of which is formed of a ring 2 consisting of a self-lubricating and sintered bronze containing 25 percent of tin. The ring is impregnated in known manner with a mineral oil having good stability at a temperature of 130.degree. C.

Disposed inside the ring is a heating member formed of an electrical resistor 3 capable of developing a power of 600 watts at an alternating voltage of 220 volts. The resistor 3 is wound upon an insulating support 4 with a turns density which varies along a generatrix of the support, so as to obtain in operation a constant temperature equal to 100.degree. C. along the whole length of any generatrix of the external periphery of the rotor. The ring 2 is in contact at its external periphery with the internal periphery of the rotor 5, which is in the form of a stainless steel tube of a length of 120 mm., of a thickness of 1.5 mm. and of an external diameter of 51 mm. The clearance between the ring and the rotor is 0.06 mm. in the cold and 0.03 mm. at 100.degree. C., taking into account the thermal expansion difference between these two elements. Secured to the rotor 5 is a pinion 6, which can drive the rotor at a speed of 4,000 r.p.m., i.e. at a peripheral speed of about 600 meters per minute.

The rotor 5 is maintained in position along the axis of the roll by a shoulder 7 at the driving end and at the other end by an end plate 8 fixed to the ring 2. In operation, no trace of oil appears in the gap between the rotor 5 and the plate 8.

A heat-resistant platinum probe 9 is disposed in a cylindrical bore in the connecting element and includes two thermocouples (FIG. 5) which are connected to a temperature recording device 24 and to an amplifier and control device 25 for adjusting the current across the resistor 3, the amplitude and control device including a regulator for this purpose. In operation, at a temperature of 100.degree. C. and at 4,000 r.p.m., it is found that the temperature indicated by the probe is constant to within less than 0.1.degree. C.

According to FIG. 2, the stator of the roll of FIG. 1 is mounted on precision ball bearings and the torque necessary for preventing the stator from turning when the rotor is driven by the pinion 6 is measured. It is found that this torque decreases when the driving speed of the rotor increases and that, at 4,000 r.p.m., this torque is distinctly lower than that necessary to rotate the stator mounted on precision ball bearings.

When a roll identical to that illustrated in FIG. 1, but with the connecting element impregnated with a silicone oil which retains good lubricating properties at a temperature of 200.degree. C. was used it was found that the temperature can readily be raised to this value and that the roll could simultaneously be rotated at 12,000 r.p.m., which corresponds to a speed of travel of the material to be treated of about 1,950 meters/min. The temperature variations detected by the probe under these conditions remained lower than 0.1.degree. C. Since the load on the self-lubricating ring was very low, the roll could be rotated at much higher speeds.

In FIG. 3 there is illustrated a heating roll having a diameter of 100 mm. and a length of 140 mm. and including a rotor 10 of a thickness of 2.5 mm. in contact over its entire internal periphery 11 with a ring 12 of oil-impregnated sintered bronze, of the same type as that described with reference to FIG. 1, mounted on a tubular support 13 bolted to a frame 14. The internal periphery of the ring 12 is in contact with a cylindrical heating element 15 comprising a coiled resistor (not shown) which developes a power of 1,000 W at a voltage of 220 volts.

The rotor 10 is driven, from the pinion 16, through the shaft 17 and the disc 18, by means of a screw 19 threaded to the disc, of which the shoulder 20 is adapted to slide in the elongate aperture 21 radially cut in the rotor. Thus, the rotor can turn freely about the axis of the periphery of the ring 12, which axis is not necessarily identical with that of the shaft 17. The device for holding the shaft in position along its axis, which is of a known type and is not shown, axially maintains the rotor.

A cylindrical recess of a diameter of 2.5 mm. and of a depth of 70 mm., in the ring 12, contains a thermocouple 22 substantially midway along the length of the roll. The said thermocouple is connected to a regulator of a type known per se (not shown), the proportional band of which is 1.degree. C.

This roll was experimentally operated at a peripheral velocity of 3,000 meters/min. and at a temperature of 130.degree. C. The combination of the above-described regulation with this type of roll makes it possible to limit the temperature variations indicated by the probe to an amplitude of 0.1.degree. C.

In FIG. 4, the construction is similar to that of FIG. 1 and like reference numerals have been used for like parts. The connecting element includes an outer ring 2A, a central ring 2B and an inner ring 2C, the rings being coaxial and each formed of an oil impregnated sintered material. The ring 2A is secured to the rotor 5 and the ring 2C is secured to the stator mounting member 30.

In the foregoing, reference has been made to a single roll and to a single operating temperature of this roll. It is obvious that it is possible, for applying more complex treatments, to employ in association a number of rolls at various temperatures or even to produce a number of staggered temperature zones along the axis of the same roll. Likewise, rotors having various external surface conditions may be employed, and also stators comprising heating elements or cooling elements of very different natures.

Claims

We claim:

1. A thermal treatment roll comprising, in combination:

a. a hollow rotor having an inner and an outer periphery;

b. a stator disposed inside said rotor and having an outer periphery;

c. a heating means in said stator; and

d. a connecting element composed at least partly of a solid heat conducting, lubricating material in direct contact with the greater part of the outer periphery of the stator and in direct contact with the greater part of the inner periphery of the rotor, effective to provide a conductive heat path between said stator and rotor.

2. A roll as defined in claim 1, wherein the connecting element forms at least part of the external periphery of the stator.

3. A roll as defined in claim 1, wherein the connecting element forms at least part of the internal periphery of the rotor.

4. A roll as defined in claim 1, wherein the connecting element is a sintered metal ring impregnated with a lubricating oil.

5. A roll as defined in claim 1, wherein said connecting element comprises an inner, an outer and central coaxial sintered metal rings, impregnated with a lubricating oil, said inner ring contacting said outer periphery of said stator and said outer ring contacting the inner periphery of said rotor.

6. A roll as defined in claim 1, and further comprising a temperature sensitive probe located within said connecting element, and regulating means connected to said probe effective to control said heating means in response to temperature variations sent by said probe.

7. A thermal treatment roll comprising, in combination:

a. a hollow rotor having an inner and outer periphery;

b. a stator disposed inside said rotor and having an outer periphery;

c. a cooling means in said stator; and

d. a connecting element composed at least partly of solid heat conducting lubricating material in direct contact with the greater part of the outer periphery of the stator and in direct contact with the greater part of the inner periphery of the rotor, effective to provide a conductive heat path between said stator and rotor.