WO2006067499A1

WO2006067499A1 - Reflector system

Info

Publication number: WO2006067499A1
Application number: PCT/GB2005/005066
Authority: WO
Inventors: Malcolm Rae
Original assignee: G.E.W. (Ec) Limited
Priority date: 2004-12-24
Filing date: 2005-12-23
Publication date: 2006-06-29
Also published as: GB0428296D0

Abstract

A reflector assembly for drying and/or curing a coating on a substrate (30) . The assembly has two pivotable reflectors (12, 14), each having a generally concave reflective surface (22, 24) spaced from a source of ultra-violet and infra-red radiation (16) . The assembly also has means for imparting pivotal movement to one or each reflector member (12, 14) to vary the relative amounts of ultra-violet and infra-red radiation (18) emerging from the assembly.

Description

REFLECTOR SYSTEM

The present invention relates to a reflector system. More particularly, the invention relates to a reflector system for drying or curing ink isothermally.

The drying or curing of ink is an essential part of the printing process. During the drying or curing process, a substrate travels along a path whereby a web of substrate is irradiated by an elongate lamp assembly in a continuous process. Such lamp assemblies typically use ultra-violet light generated by hi-powered lamps in a reflector system.

Such systems, however, generate a considerable proportion of infrared energy which can be up to sixty per cent of the total emitted radiation. Although this can accelerate the curing process, the heat emitted can damage heat-sensitive materials, particularly when the web speed through the assembly is reduced.

The infra-red radiation can be reduced by various means of reflector geometry (indirect mirrors) or water-filtration techniques but these commonly result in reduction of the curing efficiency as significant proportion of the UV radiation short-wave ultra-violet radiation is also removed.

The present invention provides a reflector assembly for use inter alia in printing equipment that seeks to overcome the aforementioned problems.

Accordingly, in one aspect the invention provides a reflector assembly for drying and/or curing a coating on a substrate, the assembly comprising at least two pivotable reflector members each having a generally concave reflective surface spaced from a source of uttxa-violet and infra-red radiation, and means for imparting pivotal movement to one or each reflector member to vary the relative amounts of ultra-violet and infra-red radiation emerging from the assembly.

Preferably, the reflective surfaces each comprise one or more inserts lined with a dichroic coating. Alternatively, the inserts may be made or lined with polished aluminium.

Preferably, each insert is attached to a surface of a respective shutter member.

Preferably each reflector member is pivotable about the radiation source.

Preferably the assembly further comprises means to calculate the temperature of the substrate and for automatically imparting pivotal movement to one or both reflector members in response to the measured substrate temperature.

Preferably the assembly further comprises means to measure the speed at which the substrate travels through the assembly and for automatically imparting pivotal movement to one or both reflector members in response to the measure substrate speed.

In a preferred embodiment the assembly includes a control system for processing data relating to the temperature or speed of the substrate for automatically imparting pivotal movement to one or both reflector members in response to the measured speed or temperature data.

An embodiment of the invention will now be described by way of example with reference to the following Figures in which:

Figure 1 is a schematic view of a reflector assembly constructed in accordance with the present invention with the reflectors in a fully-focussing position; Figure 2 is a schematic view of the reflector assembly of Figure 1 with the one reflector pivoted; and

Figure 3 is a schematic view of a reflector assembly constructed in accordance with a second embodiment of the present invention.

With reference first to Figure 1, the reflector assembly comprises a main housing 10 within which are located first and second shutters 12, 14 located generally on each side of a lamp 16. The lamp 16 provides a source of infra-red and ultra-violet radiation 18.

The main housing 10 extends around the back and sides of the lamp 16. A surface 20 of the shutters 12, 14 facing the lamp 16 is generally concave. The concave surface 20 of each shutter 12, 14 has a similarly shaped insert 22, 24 attached thereto which is lined with a dichroic coating. The inserts 22, 24 act as reflectors to reflect the radiation 18 emitted from the lamp 16 away from the shutters 12, 14 and out of the housing 10. The inserts 22, 24 provide an unbroken reflective surface and thereby provide optimum return of emitted light 18 from the ultra-violet lamp 16.

Each shutter 12 ,14 is pivotable about a lamp 16 via a motor 26

Two further inserts 28 lined with a dichroic coating are fixed to the back of the housing 10 directly behind the lamp 16 via fixing legs 29.

Radiation 18 is emitted outwardly from the lamp 16 is reflected by the back and side reflecting inserts 22, 24, 28 such that the radiation 18 is emitted out of the housing 10 and onto a web of substrate 30 carrying ink to be dried and/or cured by the radiation 18.

The main housing 10 has channelled sections 34 through which a coolant such as water can flow to cool the main housing 10 to avoid it being damaged from the heat emitted from the lamp 16.

The main housing may alternatively be air-cooled.

In the arrangement of Figure 1, the first and second shutters 12, 14 are pivoted around the lamp 16 at a specific angle ("the normal") that provide radiation beams 18 emitted from the housing 10 that meet the ink on the web 30 at a single point 32 of focus. The assembly shown in Figure 1 therefore provides the maximum intensity of radiation at that particular point 32 on the printed web 30.

Figure 2 shows the same assembly as Figure 1, but here the first shutter 12 is pivoted at 22 degrees to the normal. In this arrangement the radiation beams emitted from the housing 10 meet the web 30 over an increased area of focus to reduce the intensity of the radiation and heat on the web 30 at any particular point.

In use the angle of pivot of the first and/or second shutters 12, 14 controls the intensity of ultra-violet and infra-red radiation 18 directed onto the printing web 30. As such, the curing process is controllable for any particular item to be cured.

The pivotation required of one or each shutter 12, 14 will be dependent on a number of factors, for example, the speed that the printing web 30 is travelling through the assembly and the temperature of the printing web 30 as it reaches, leaves and it is within, the assembly. To this end, an infra-red sensor (not shown) is located within the assembly to calculate the temperature of the web 30 exiting the assembly. The temperature is relayed to a processor (also not shown) within the apparatus which then controls pivotable movement of the first and/or second shutter 12, 14 via the motors to adjust the intensity of the radiation 18 emitted to the web 30 accordingly.

The speed of the web 30 is also relayed to the processor for corresponding adjustment to the shutters 12, 14.

An alternative reflector assembly is shown in Figure 3. The figure only shows a back housing 36 and shutters 38 of the assembly but it will be appreciated that this assembly includes some or all of the features of the assembly of Figures 1 and 2. In the assembly of Figure 3, the shutters 38 have indented corners 40 adjacent the back housing 36. This optimises and maintains the intensity and focus of the radiation beams emitted from the lamp while the shutters 38 pivot with respect to the back housing 36.

The adjustability of the assemblies described provides an isothermal cure of the printing web 30 which is highly advantageous in many applications.

Although the description refers to the inserts being lined with a dichroic coating it is clearly envisaged that the inserts could be made from or lined with any other suitable reflecting material such as, for example, polished aluminium.

The above described embodiments have been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the present invention.

Claims

1. A reflector assembly for drying and/or curing a coating on a substrate, the assembly comprising at least two pivotable reflector members each having a generally concave reflective surface spaced from a source of ultraviolet and infra-red radiation, and means for imparting pivotal movement to one or each reflector member to vary the relative amounts of ultra-violet and infra-red radiation emerging from the assembly.

2. A reflector assembly according to claim 1, wherein the reflective surfaces each comprise one or more inserts lined with a dichroic coating.

3. A reflector assembly according to claim 1, wherein the inserts may be made or lined with polished aluminium.

4. A reflector assembly according to any one of claims 1 to 3, wherein each insert is attached to a surface of a respective shutter member.

5. A reflector assembly according to any one of claims 1 to 4, wherein each reflector member is pivotable about the radiation source.

6. A reflector assembly according to any one of claims 1 to 5, wherein the assembly further comprises means to calculate the temperature of the substrate and for automatically imparting pivotal movement to one or both reflector members in response to the measured substrate temperature.

7. A reflector assembly according to any one of claims 1 to 5, wherein the assembly further comprises means to measure the speed at which the substrate travels through the assembly and for automatically imparting pivotal movement to one or both reflector members in response to the measure substrate speed.

8. A reflector assembly substantially as hereinbefore described and referred to in the accompanying figures.