WO1996021569A1

WO1996021569A1 - U.v. dryer for flexographic printing press

Info

Publication number: WO1996021569A1
Application number: PCT/GB1996/000066
Authority: WO
Inventors: Malcolm Rae
Original assignee: Gew EC Ltd
Current assignee: Gew EC Ltd
Priority date: 1995-01-12
Filing date: 1996-01-12
Publication date: 1996-07-18
Anticipated expiration: 1997-07-12
Also published as: GB9500559D0; AU4394796A

Abstract

An air-cooled ultra-violet (U.V.) dryer is disclosed which comprises a housing (10), a U.V. lamp (11) and a reflector (12) mounted therein and means for causing cooling air to flow over the lamp and reflector, said housing having a window (13) through which U.V. radiation is projected therefrom, said window being closable by means of a plate (15) slidable in the plane of the window.

Description

U.V. DRYER FOR FLEXOGRAPH IC PRINTING PRESS

This invention relates to L^' V. dryers and in paπicular to a U V dryer for use in a tlexographic printing machine.

In tlexographic printing machines, a continuous web. which may suppoπ individual items such as labels to be printed, is conveyed through a series of sequential linking units at which the desired colours are applied in order to build up a multi-coloured printed image It is necessary' to dry the inks between sequential colour printing stages and. conventionally, air dryers are used for this purpose One reason why U V dryers may not have been used in the past is that they are generally bulky and it would be difficult to fit them into the available space

According to one aspect of the present invention there is provided an air- cooled U V dryer which comprises a housing, a U V lamp and a reflector mounted therein and means for causing cooling air to flow over the lamp and reflector, said housing having an opening through which U V radiation is projected therefrom, the opening being closable by means of a plate slidable in the plane of the opening.

By constructing the U.V. dryer so that it is totally air cooled and providing a shutter which slides in the plane of the opening of the housing, the dryer can be made very compact. It can. therefore, be fitted into a conventional flexographic printing machine without substantial modification.

The invention will now be illustrated by the embodiments shown in the attached drawings, in which -

Figure 1 is a plan in elevation of part of the tlexographic printing machine, showϊnu a U V drver in accordance with the invention fitted thereto. Figure 2 is a similar view on an enlarged scale of the U V dryer itself, and

Figure 3 is a plan view in the direction of the arrow X in Figure 2.

Figure 4 is a partial view of the mechanism for actuating a plate for closing a window of the dryer.

Figure 5 is a cross-sectional view of a modified embodiment of the dryer of figures 1 to 4 showing a position in which the lamp is accessible for changing. and

Figure 6 is a section in elevation of the dryer of Figure 5 showing the cooling air flow currents

Figure 7 is another section in elevation of the dryer of Figure 5 but showing an alternative air flow pattern

Referring to Figure 1. a tlexographic machine is shown schematicalU of the kind manufactured in the USA by the company Mark .Andy Figure 1 shows two sequential colour units I and 2 through which a web 3 is guided over a seπes of guide rollers 105.106. 107. 108 and 109 The first colour printing operation is carried out at the unit 1 and the web carrying the resulting printed impression is then guided through a U V dryer 5 constructed in accordance with the invention. before passing to the next colour printing unit 2 Inking units 4 are shown diagra matically for applying ink to the web the inking unit 4 is shown in slightly more detail at colour unit 2 Ink is taken from a trough 100 by means of an inking roller 101 The ink is then applied to the web 3 by means of transfer rollers 102 and 103

The machine shown in Figure 1 is also fitted with an air drying unit 6. with the thought in mind that either or both the U V dryer 5 and the dryer 6 can be used for a paπicular ink Normally, one or other of the U V or air dryers are operated, the choice of dryer generally depending on the nature of the particular ink being printed at the colour unit .Although not shown in Figure 1. the colour printing unit 2 would also normally also be fitted with a U V dryer in accordance with the invention and also with an air dryer If the tlexographic printing machine is arranged to print additional colours, the subsequent colour printing units would also be fitted with U V dryers in accordance with the invention

As can be seen in Figure 1. the web 3 after application of the ink. passes alongside a window 13 in the housing 10 of the U V dryer where it is subjected to U V radiation from the lamp 1 1. before passing to the down-stream air dryer 6 Cooling air is drawn into the housing 10 around the reflector and out through an exhaust port 56 in a manner described in Figure 5. 6 and 7 The construction of the U V dryer is shown in more detail in Figures 2 to 7

Referring to Figures 2 and 3. the U V dryer is totally air-cooled and comprises a generally rectangular housing 10 in which a parabolic reflector 1 is mounted for directing U V radiation from a lamp 1 1 towards a window 13 (see Figures 4. 5 and 6) in the wall of the housing closest to the line of travel of the web The window 13 is substantially transparent to UV radiation and may comprise or be associated with an infra red filter For example, it may have an IR filter coating. The housing 10 also includes or is attached to a poπion 14 at one or both longitudinal ends of the lamp which serves as a heat sink The web is guided by rollers 106 and 107 to pass close to window 13 in the housing. Cooling for the lamp itself is provided by feeding compressed, filtered air to a passageway or conduit 30 in the reflector Compressed air may be fed to a connection at one end of conduit 30 by a flexible tube (not shown) The conduit 30 is formed with holes spaced along its length so that air jets are directed at the lamp transversely of the length of the lamp This aspect of the construction of the dryer is similar to that described in our PCT application WO 93 02329

Poπion 14 is not essential but by providing additional heat capacity at the end of the housing wide temperature fluctuations can be reduced Referring particularly to Figures 4. 5 and 6. the housing 10 may comprise a generally rectangular box having a side 50 providing a generally flat surtace alongside which the inked web is guided A window 13 comprises a number of quartz sheets 13 A (or other heat resistant material which is transparent to U V light) which are set into or over an opening in the side 50 .Although windo 13 may¬ be simply a hole in the side of the housing, a quartz window restricts the entry of dirt or other foreign materials and makes it easier to control air flow through the housing

Window 13 can be opened or closed by moving a ceramic or metal plate 15 towards or away from the opening Plate 15 is mounted for sliding movement in the plane of the window 13 on a pair of carriages 16. mounted at each end of the housing 10 One carriage 16 is shown in Figures 3 and 4. but the other is not shown since these drawings show only the left-hand side of the dryer However, it will be appreciated that the dryer is symmetrical about the centre-line I-I (see Fig. 3) Carriages 16 are mounted for sliding movement on stainless steel slide bars 17. of which a pair are used to support the carriage at each end of the housing.

Each carriage is moved up and down to close or open the opening 13 by means of a rotary actuator 18 Again. Figure 3 does not show the actuator at the right-hand end of the housing, but it is identical to that shown at the left-hand side The two (preferably air operated) actuators 18 will be linked together by a rod connecting their spindles 1 . so that they move in unison to cause plate 15 to act as a shutter and slide upwards and backwards and downwards to close and open the opening 13 Rotary actuator 18 is fitted with a lever arm 20. which is shown in two extreme positions in Figure 2. and this lever arm is connected to the slide carriage 16 by a link rod 21. A degree of play is provided in the linkage system so as to reduce the chance of the slide carriage jamming on the slide bars

Link rod 21 is pivotally connected at one end to the carriage 16 Carriage 16 is formed with a slot 22 and a right angle pin 68 passes through the link rod 21 and is held in the carriage Carriage 16 may be formed of a suitable metal such as bronze which requires little or no lubrication

The side of the housing behind the reflector 12 is hinged at 22. e by a piano hinge, so that it can be pivoted in the direction of the arrow Y to open the housing and gain access to the lamp and reflector for servicing and lamp changing The back of the housing is formed with a series of holes 23. to allow air to enter the housing in the direction shown by the double-headed arrows in Figures 2 and 6 A baffle or baffles 24 and 25 is provided to guide the air flow around the back of the reflector 12 and around the actuator Additional air flow may enter the housing from below as shown by the triple-headed arrow to cool the rotary actuator mechanism (Figure 2).

The arrangement of baffles and air flow is slightly different in the embodiment of Figures 5 and 6. although in the case of both embodiments air is preferably caused to flow through the housing by applying suction to an exhaust duct 57 connected to exhaust ports 56 at the end of the housing remote from the reflector, e.g. in the region of the actuators It will be appreciated that other arrangements are possible for inducing or conducting air flow through the housing For example, the air flow may enter at the bottom as shown in Figures 2 and 7 and exit through the top

The currently preferred cooling arrangement is shown in Figure 6 in which suction is applied at the exhaust port 56 or to a duct connected thereto Referring to Figure 6. the suction causes air to be drawn into the housing via the inlet ports 55 which are distributed along the upper side 105 This causes air to flow at right angles to the U V. lamp Once it enters the housing, the air splits into two streams; the smaller portion flows through the gap between the mouth of the reflector and the windo 13 The larger poπion flows between baffle 51 and the back of the reflector 12. Additional air is sucked through inlets 23 and flows between the reflector and the baffle 52 The cooling air then passes into the lower part of the housing 10 and out through exhaust ports 56 which are distributed along side 106 of the housin A manifold may be connected to the ports 56 to suck air therefrom and into the exhaust duct This arrangement enables ozone (which is generated by the UV radiation) to be safely ducted away from the equipment

Claims

CLAIMS -

1 An air-cooled ultra-violet (U.V ) dryer which comprises a housing, a U V lamp and a reflector mounted therein and means for causing cooling air to flow over the lamp and reflector, said housing having a windo through which U V radiation is projected therefrom, said window being closable by means of a plate slidable in the plane of the window

2 A dryer as claimed in claim I in which the plate is guided on rails mounted in the housing at opposite ends of the window

3 A dryer as claimed in claim 2 in which a carriage is arranged to slide on said rail or rails and is movable thereon by an actuating arm

4 A dryer as claimed in claim 3 in which the actuating arm is driven by a rotary actuator

5 A dryer as claimed in claim 4 in which a rotary actuator is located at each end of the plate, each actuator being linked to one end of the plate and the actuators being connected so that the ends of the plate are moved in unison

6 A dryer as claimed in any one of the preceding claims in which air inlet holes are formed in the housing in the region of the reflector, and air is caused to flow into the inlet holes over the back of the reflector and out through exhaust holes in the housing.

7 A dryer as claimed in claim 6 in which additional air inlet holes are formed in the housing at a point adjacent to the reflector

8 A dryer as claimed in claim 6 in which one or more baffles are provided in the vicinity of the housing to guide cooling air around the reflector

9 A dryer as claimed in any one of claims 6 to 8 in which suction is applied to the exhaust holes in order to cause cooling air to flow over the reflector 10 A dryer as claimed in any one of the preceding claims in which the housing comprises a first side incorporating said window, and a second side opposite said window on which the U V lamp and reflector are mounted, said second side or a poπion thereof being pivotable outwardly from the housing to expose the lamp to facilitate changing or servicing the lamp