Thermal Treatment Of Textiles

Abstract

A device for heating and controlling the surface temperature of a cylindrical drum wherein a member is located on the central axis of the drum and in which a plurality of separate heating coils are disposed longitudinally along the length of said drum for the purpose of heating the drum, there being an element for controlling the current to each separate coil and heat sensing devices contacting the outer periphery of the drum and another element controlled by said heat sensitive devices according to the temperature of the outer surface of the drum to vary the current to the heating coils.

Description

BACKGROUND OF INVENTION

This invention is for improvements in or relating to the heating of cylindrical drums for use in the textile industry. It is well established that for a number of different purposes it is requires to heat textile fabrics. Among the principal reasons for heating textile fabrics is the need to set such fabrics. This applies in the case of synthetic plastic fabrics of the polyamide and polyester groups of yarns where it is necessary after formation of the yarn into a fabric either by way of weaving or a knitting process to relax the tensions in the yarn and to set the fabrics in the desired shape. Conventionally, such fabrics can be heat treated on the stentor which may involve the use of heated gases contacting the surface of the fabric or may be heated by staying in contact with the heated surface of a rotating drum. Various means are known for heating the drum. Alternatively, and in some instances, heat setting of fabrics is done by boarding and placing the boarded garment inside a steam autoclave.

In all instances it is desirable that the fabric which is being heat treated shall be uniformly heat treated. That is to say that all parts of the fabric are subjected to substantially the same temperature and pressure and it will be appreciated that in a stentor where heated gases are passing over the fabric all parts of the fabric will be subjected to the same temperature. Similarly, where a garment is placed in a steam autoclave the temperature within the autoclave will be uniform or at least around the garment it will be uniform and so that all parts of the garment or fabric will be subjected to the same temperature. However, in the case of a fabric contacting the surface of a heated drum slight variations in the temperature of the drum may exist causing variations in the effective treatment of the fabric.

In addition to the heat treatment of fabrics for the purpose of heat setting the yarn of which these fabrics are formed, it has in recent times become known to dye textile fabrics by a printing process involving sublimable dyestuffs. In this process the dyestuff is mixed with a carrier so that it may be applied to an intermediate layer, usually paper, by a substantially conventional printing process, usually a gravure printing process but in some instances by a lithographic printing process. The heat sublimable dyestuff is vaporised on the application of heat and if the layer with the printed dyestuff is brought into contact with the undyed textile fabric and the necessary amount of heat applied to the paper layer for the necessary period of time and under other desirable conditions, the dyestuff sublimates and in its vapour state imparts colour to the textile fabric. It has been found that this process may be perfected to dye textile fabrics up to six or even eight colours simultaneously with an extremely accurate register and involving complex patterns. In order to obtain uniformity of effect on the textile fabric it is necessary that the temperature at which the process is carried out is accurately controlled.

It has for example been found out that variations up to 3.degree. on one edge of a fabric being dyed by the aforementioned process can cause marked visual variations in the colour on the final fabric. In general, the higher the temperature the more the dyestuff sublimates and the deeper the colour which is imparted to the fabric. So that if a hot spot is provided during the dyeing a deeper colour on the final fabric results and where such fabrics are required for multiple production processes, for dresses and other similar articles of wearing apparel this variation of colour is highly undesirable.

DESCRIPTION OF INVENTION

It is an object of the present invention to provide means for accurately controlling the temperature of a surface suitable for the treatment of textile fabrics whether for the purpose of heat dyeing those fabrics or whether for use with the heat transfer dyeing process as aforementioned.

Accordingly, the present invention provides means for heating and controlling the surface temperature of a cylindrical drum comprising a member located along the central axis of the drum, a plurality of separate heating coils disposed longitudinally along the axis of the member, means for controlling the current to each separate coil, a heat sensing device contacting the outer periphery of the drum and means controlled by the heat sensitive devices according to the temperature of the outer surface of the drum.

More specifically the present invention provides for a drum or open ended bowl and of cylindrical form around which the fabric to be treated passes. The drum is rotated while the fabric is in contact therewith.

Along the central longitudinal axis of rotation of the drum is provided a member conveniently a steel tube of austentitic steel and mounted on this tube are a plurality of separate heating coils. Conveniently, the heating coils are formed by electrical resistance wire wound on formers mounted on the tube in spiral manner so as to form separate and distinct heating coils along the length of the tube. As viewed in the finished condition the tube will appear as one continuous heating coil consisting of a spiral length of wire from one end to the other but in fact the wire will be separated out into coils of predetermined longitudinal length. The wire will be wound upon formers conveniently of mica which are secured by clamps to the tube and extend radially therefrom.

The outer edges of the mica will be serrated and the electrical resistance wire wound around the tube and held in spaced relation to adjacent turns by passing into separate slots in the mica. Thus by connecting the heating coils to a source of electrical current the interior of the drum may be heated and the heat transfer through the wall thickness of the drum to the outer surface thereof.

It will be appreciated that either the one end or both ends or the central portion or other discrete sections of the drum may be heated to a higher temperature than other sections by connecting the appropriate heating coils to a source of current and not so connecting the others. Thus by switching on and off selected heating coils the temperature of the outer surface of the drum in the immediate radial vicinity of the heating coil can be controlled within surprisingly fine limits of tolerance.

The invention further provides for heat sensing means contacting the outer surface of the drum in the region of each heating coil so that by observing these heat sensing means and ensuring that they are reading a uniform temperature it is possible to control the temperature of the outer surface of the drum within the same fine limits of tolerance. The heat sensing device may consist of one of two different kinds. In the first, a Thermistor being a device whose electrical resistance varies with temperature is used and in the other a known electric thermocouple is used, conveniently a nickel/iron thermocouple. In both instances, the device is lightly pressed by a coil spring on to the outer surface of the drum and connected by appropriate means to a galvanometer which may be calibrated to read directly in degrees of temperature (fahrenheit or centigrade as required).

In an alternative arrangement, the reading obtained from the heat sensitive device may be used to control directly the current to the heating coils. In one particular instance the heat sensitive device operates a galvanometer with an aperture formed in the needle. A source of light is arranged to pass through that aperture and to be detected by a photoelectric cell on the opposite side.

Means are provided for moving the photoelectric cell to a predetermined position so that when for example the heat sensitive device has reached a certain temperature and the needle of the galvanometer has reached a position where the point source of light is able to pass through the aperture the needle can operate to be detected by the photoelectric cell, the cell becomes energised and is arranged to switch off the current to the appropriate heating coil, thus preventing further rise of the temperature of the outer surface of the drum at that point. When the surface temperature has dropped to a predetermined value, the light will not longer reach the photoelectric cell since the aperture in the galvanometer needle will have moved out of register and the current to the heating coil will again be switched on.

Other known arrangements for controlling the current to the heating coils from the heat sensing devices may be used. For example, the output may be fed to a transistorised voltage amplifier whose output may be used to operate a relay for connecting or disconnecting as the case may be the current to the electrical heating coils.

DESCRIPTION OF DRAWINGS

In order that the present invention may be more readily understood, reference is now made to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of apparatus according to the present invention;

FIG. 2 is a cross-sectional view showing the arrangement of the heating coils;

FIG. 3 is a side elevation section of FIG. 2;

FIG. 4 is a schematic view showing one type of heat sensing device;

FIG. 5 is an alternative heat sensing device;

FIG. 6 is a schematic view of a further heat sensing device for use with the present invention; and

FIG. 7 is a detailed view of a galvanometer operated by heat sensing device as used with the present invention.

According to the present invention a cylindrical drum or bowl 1 is mounted for rotation about bearings 2 and it will conveniently be driven by means of gearing or belt drive 6.

The fabric to be treated according to the present invention will contact the outer peripheral surface of the drum 1, be supplied in a roll provided on a beam and will be led to the drum 1 around 300.degree. or more of arc and thence to a cooling station before being wound on to a take up beam. Located within the interior of the drum is a rod 4 around which is located a tube 12 of austentitic steel. The tube 12 is held in spaced relationship to rod 4 by spider arms 4a (FIG. 2). The rod 4 is supported upon end bearers 5. The tube 12 is a support for formers for electrical heating wire 10. The formers comprise mica strips 11 which are held to the surface of the tube 12 so as to extend radially therefrom by clamps 13 bolted to the outer surface of the tube 12. As seen in FIG. 2 six such radially extending formers are provided and the outer edge of the formers is slotted at 11 as seen in FIG. 3. The heating coils are formed of electrical resistance wire 10 which is wound around the formers and into the slots 11 in separate and distinct sections as indicated Z1-Z6 in FIG. 1. The termination of the electrical heating wire is brought to an electrical connector 15 in each zone Z1-Z6 respectively. The ends of the electrical heating wire are then taken by appropriate electrical wires through a non-conductive junction box 7 for coupling up the electrical feed terminates 15 to control switching. On the exterior peripheral surface of the drum 1 are provided heat sensors 8 opposite each of the electrical heating coils mounted on their respective formers. In FIG. 1 these heat sensors are indicated TP1-TP6 respectively opposite each of the electrical heating coils Z1-Z6.

The heat sensing devices may be of any convenient form but particularly there is illustrated in FIG. 4 a thermal junction 16 which is formed into a spring bow by passing the metallic thermal junction material around insulators 17 and connecting by means of electrical connecting metal 18 to the insulator 19 and thence by electrical leads 20 to appropriate control means.

Conveniently, the thermal junction will be of the iron/nickel type. It is necessary to maintain one end of the thermal junction cool while the other is responsive to the temperature of the outer surface of the periphery of the drum 1.

In FIG. 5 an arrangement is shown in which a thermal junction member 23 is held in contact with the outer surface of the drum 1 other than by the spring bow. In this instance, a polytetrafluoroethylene insulating block 21 houses the thermal junction 23 and the block including the junction 23 is biased against the surface of the bowl 1 by a coil spring 22.

In an alternative construction illustrated in FIG. 6, a Thermistor member 25 located on an asbestos insulator 24 is lightly pressed against the surface of the drum 1 by a coil spring 28 acting against a fixed clamp 27 and with the coil spring and the asbestos insulator being guided along a central non-movable rod 26. The leads 20 from the heat sensing device are connected to appropriate means for determining the temperature of the outer surface of the drum 1 and in FIG. 6 such leads 20 are connected to one quarter of a conventional Wheatstone bridge circuit illustrated generally 29 and including the resistors R1, R2, R3 and R4 and in which R1 is the resistance of the Thermistor 25 and R2 is the resistance of a galvanometer. R3 and R4 are conventional variable resistances in order to obtain the proper readings. The circuit may be energised by 2 volts D.C. which is obtained by a half way rectified A.C. current. According to the conventional formula of R1/R2 = R3/R4 it is possible to adjust the values of R3 in order to give a different temperature range and a changeover switch 30 is provided for bringing into operation either the resistance of A or B to give a different temperature range on the scale of the galvanometer forming R2. Conveniently, such ranges may be arranged by appropriate values of the resistors to give a reading of from 20.degree. to 150.degree.C on one scale and from 130.degree. to 250.degree.C on the other scale.

It will be appreciated that the galvanometer is reading the voltage flowing across the resistor R4 and the resistance between the junctions of the bridge which is formed by a coil 31. The coil 31 may be arranged to actuate an electromagnetic switch 33 when the galvanometer reads a predetermined value and on closing of the contacts of the electromagnetic switch 33 an electrical connection to leads 32 to provided which may be arranged to connect the source of electricity to the appropriate electrical heating coil in one of the zones Z1 to Z6 as previously described. Thus by determining the temperature of the surface of the bowl 1 it is possible automatically for the electrical heating coil to be switched on or off according to the pre-setting of the galvanometer or other means responsive to the determination of temperature by the heat sensing device.

In an alternative arrangement illustrated diagrammatically in FIG. 6 the galvanometer indicated at 34 has a needle 35 formed with an aperture 36 therein and a point source of light is arranged to be directed on to this aperture 36. A photoelectric cell on the opposite side of the needle from that on which the point source of light is located may be adjusted relative to the scale on reading of the needle 35 and the arrangement is such that when the corresponding electrical heating coil remains switched on only while point source of light, the aperture 36 and the photoelectric cell, not illustrated, are not in register. Once they are all in register the light energises the photoelectric cell and this is arranged to disconnect the current to the appropriate heating coil.

It will be appreciated that as the surface cools down and the galvanometer needle moves to bring the aperture 36 out of register the photoelectric cell will be de-energised and the circuit re-made to the electrical heating coil.

It will be appreciated that by the present invention it is possible accurately to come within fine limits of tolerance to control the surface temperature of a drum suitable for use with textile materials for the treatment thereof.

Claims

1. In a sublimatic printing system means for heating and controlling the surface temperature of a rotating cylindrical textile drum comprising a fixed member located on the central axis of the drum, a plurality of separate heating coils connected longitudinally along said member, means for controlling the current to each said separate coil, heat sensing devices located outside said drum and contacting the outer periphery of the drum, said heat sensing means being maintained in contact with said outer periphery by spring means, and means, controlled by said heat sensing devices according to the temperature of the outer surface of the

2. Means according to claim 1 in which the means controlled by the heat sensitive devices acts to control the current to one or more of the

3. Means according to claim 2 in which the electrical heating comprises

4. Means according to claim 3 in which the wire is held in spaced relationship relative to the member by formers extending radially from

6. Means according to claim 1 in which the heat sensing devices comprise a

7. Means according to claim 1 in which heat sensing devices comprise a

8. Means according to claim 7 in which the thermocouple junction is an

9. Means according to claim 1 in which the heat sensing devices are held in contact with the outer peripheral surface of the drum by a coil spring.

10. Means according to claim 1 in which an output from the heat sensing devices form a part of a Wheatstone bridge circuit in which a galvanometer

11. Means according to claim 10 in which calibration of the galvanometer is arranged to actuate an electromagnetic switch to control the current to

12. Means according to claim 1 in which the outputs from heat sensing devices are connected directly to a galvanometer having a needle with an aperture therein and arranged to move relative to a photoelectric cell and with a point source of light arranged to direct on to the aperture in the needle so that when the source of light, needle and photoelectric cell are in register the photoelectric cell is energised and is arranged to

13. Apparatus for providing precise temperature control in the range utilized for sublimatic printing of fabrics comprising:

a cylindrical drum at least three feet in diameter;

a fixed shaft member located on the central axis of said drum;

gear means for rotating said drum about said shaft member;

a plurality of electrical heating coils arranged successively along said shaft, each coil providing radiant heat for a different portion of said drum, said coils having heating capacity to maintain said drum in the range of 200.degree.C to 250.degree.C;

a plurality of temperature sensing means located exterior to and in contact with the outer surface of said drum, each of said temperature sensing means including a thermistor located on an asbestos insulator and maintained in position by spring means and a non-movable guide rod;

galvanometer means having a needle, the position of said needle being determined by the electrical current from all of said temperature sensing means, the body of said needle defining an aperture therein;

a point light source directed onto the aperture of said needle;

a photoelectric cell located at a predetermined point in the travel of said needle, said cell being energized when said light source and said aperture are in register therewith; and

control means for developing electrical current in said coils except when said photoelectric cell is energized.