GB2142874A

GB2142874A - Ink drying apparatus

Info

Publication number: GB2142874A
Application number: GB08410430A
Authority: GB
Inventors: William Kenneth Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-04-21
Filing date: 1984-04-24
Publication date: 1985-01-30
Also published as: GB2142874B; GB8410430D0

Abstract

Apparatus for drying printed ink comprises an emitter of infra-red radiation at a wavelength of between 2.5 mu m and 12.5 mu m. The preferred wavelength emitted is between 3 mu m and 6 mu m, and the infra-red emitter is advantageously a ceramic radiation element heated to a temperature between 300 DEG C and 700 DEG C. The apparatus comprises a conveying means 1 for transporting T-shirts and other garments to be printed with ink past the emitter 4, and the conveying surface is advantageously sloped off each of its opposite longitudinal edges so as to present for example the printed front of the garment closer to the emitter than the unprinted arms of the garment. Uniform curing of the ink is promoted by a fan which circulates air over the printed material. A barrier of refractory material 6 encircles the emitter to maintain a constant temperature across the face of the emitter. The barrier is constructed of firebrick or clinker incorporating concrete. <IMAGE>

Description

SPECIFICATION Ink drying apparatus The present invention relates to an apparatus for drying or "curing" inks which have been printed on to a material, and more particuiarly to an apparatus for curing inks which have been silkscreened on to a fabric garment such as a T-shirt.

It is well known to dry printed garments and materials by exposing them to heated air.

In general, the air is heated by an electric resistance heating element which emits mainly visible radiation at a wavelength below 1 pm.

An example of such a heating element is an electric fire.

This method has disadvantages. Firstly, it is expensive in that even a small drying apparatus requires three elements each of three kilowatt power consumption. Secondly, such apparatus carries with it a greater danger of scorching of the material and a consequent fire if the material is left too long before the heating element. This may happen if the material is being conveyed before the heating element and the conveying means stops, or if the material is allowed to hang before the heating element unattended. Finally, inks suitable for hot air drying are expensive.

It is an object of the present invention to overcome the above disadvantages and to provide an improved apparatus for drying inks and a method of using such apparatus.

According to a first aspect of the present invention, there is provided an apparatus for drying printed ink comprising an emitter of infra-red radiation at a wavelength of between 2.5 ,um and 12.5 ,us.

The preferred wavelength emitted is that at which the ink to be dried absorbs most strongly infra-red radiation. The preferred figure is between 3 ,um and 6 clam, advantageously between 4 im and 5 ,um.

The infra-red emitter may be a ceramic radiation element, which may be heated to a temperature between 300"C and 700"C.

The element may comprise a set of tiles, each tile having a reflective backing.

According to a preferred embodiment of the invention, a barrier of refractory material encircles the emitter. This enables maintainance of a constant temperature across the face of the emitter.

Preferred refractory materials are firebrick and clinker filled concrete.

The barrier may be 25 to 50 mm thick, preferably 35 mm, and 100 mm in height.

The apparatus may further comprise a conveyor means for transporting material printed with ink past the emitter.

The conveyor means may be shaped to present a printed portion of material closer to the emitter than a remaining unprinted portion of the material.

The apparatus may also comprise a fan to circulate air over the material and thereby promote uniform curing of the ink.

According to a second aspect of the present invention there is provided a method of drying printed ink comprising a step of presenting a material printed with the ink within the effective range of an emitter of infra-red radiation.

Preferably the effective range is within 35 to 75 mm.

The method preferably comprises the additional step of transporting the material to a location within the effective range and transporting it from said location.

An embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1 is an end elevation, partially cut away, of an apparatus embodying the invention; and Figure 2 is a side elevation, again partially cut away, of the apparatus.

Referring now to the drawings, the apparatus comprises a conveyor belt 1, of PTFE coated mesh. This is driven by a single phase drive motor and gearbox 2 with a conventional belt and pulley final drive. The speed of the motor may be varied. The conveyor belt has a sloped surface at each side, which is adapted to accommodate the arms of T-shirts, which are in general not printed, in a folded under condition.

The conveyor belt 1 passes into a drying zone 3, in which is located an array of ceramic radiation elements 4. These have a planar lower surface facing the conveyor belt, and a reflector upper surface. Depending on the temperature to which the tiles are heated, infra-red radiation is emitted at a wavelength generally between 3.0 ,um and 6.0 ym. The wavelength of the emission may be varied by varying the temperature to which the tile is heated.

The apparatus may be operated at conveyor belt speeds of between 0.5 and 3.0 inches per second, the tiles are spaced from the surface of the material by a distance of between 35 and 75 mm, and the tiles are heated to a temperature between 300 and 700"C. The temperature may be varied so that the infra-red radiation emitted is of wavelength close to the specific absorption frequency of the printing ink concerned.

Inks used in textile printing have highly selective absorption frequencies in the infrared range. For example spirit based vinyl or polymeric inks absorb strongly at a wavelength of 4.5 item, while water based inks absorb strongly at a wavelength of 4.8 ,um. A small change in the wavelength reduces the efficiency of drying by a marked degree since absorption produces a very rapid curing and drying of the ink. Such rapid curing eliminates any possibility of the printed material charring or scorching.

The wavelength of the radiation emitted by the infra-red emitter is determined by the temperature of the emitter. For example, at a temperature of 370"C, radiation of wavelength 4.5 ym is emitted, while at a temperature of 300"C the wavelength is 5.0 pm. Thus clearly, the temperature is important in the efficiency of the dryer and accurate control of temperature should be maintained.

It has been found that the temperature of the array of ceramic radiation elements 4 is not constant over its area and thus the dryer has impaired efficiency. The temperature of the central ceramic elements can be as much as 70"C higher than that of the peripheral elements. In a preferred embodiment of heater there are twelve elements arranged with two adjacent ones at the centre. Ten peripheral elements surround the central pair but operate at a lower temperature and thus emit infra-red radiation of an inefficient wavelength.

In order to increase the efficiency of the dryer, a barrier 6 of refractory material is arranged immediately surrounding the outer ten elements on all four sides. The barrier 6 is preferably 1-2 inches thick, ideally 35 mm. It is preferably 100 mm deep constructed of firebrick or clinker incorporating concrete.

The presence of barrier 6 evens out the temperature and the radiation emitted is of more uniform wavelength.

The barrier 6 does not extend across the top of the elements, nor beneath them.

The element may comprise three separately switchable portions each of 1.2 kilowatt power consumption.

A low Power fan 5 may be provided to move the air across the material being dried and thereby to promote uniform ink curing. It is not necessary to provide a high power fan as it would be if it were necessary to exhaust heated air from the drying zone.

Claims

1. An apparatus for drying printed ink comprising an emitter of infra-red radiation at a wavelength of between 2.5 ,um and 12.5 ,um and with a barrier of refractory material encircling the emitter to promote maintenance of a substantially constant temperature across the face of the emitter.

2. An apparatus according to Claim 1 in which the refractory barrier material comprises firebrick.

3. An apparatus according to Claim 1 and in which the refractory barrier material comprises clinker filled concrete.

4. An apparatus according to any of the preceding Claims in which the barrier is 25mm to 50mm thick.

5. An apparatus according to Claim 4 and in which the barrier is approximately 35mm thick.

6. An apparatus according to any of the preceding Claims and in which the barrier is approximately 1 00mm in height.

7. An apparatus according to any of the preceding Claims and in which the wavelength emitted is between 4 ,xem and 5 ,um.

8. An apparatus according to Claim 1 and substantially as described herein with reference to and as illustrated in the accompanying drawings.