GB2388652A

GB2388652A - Light shuttering apparatus

Info

Publication number: GB2388652A
Application number: GB0204338A
Authority: GB
Inventors: Marc Boden
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-02-25
Filing date: 2002-02-25
Publication date: 2003-11-19
Anticipated expiration: 2022-02-25
Also published as: GB2388652B; GB0204338D0

Abstract

Shuttering apparatus (10) to cut off the direct transmission of light from a light source (12) to an intended target (15), said apparatus (10) comprising inner and outer generally tubular members (20,22) each having an elongate slot (21,23) through its cylindrical wall, means for mounting the light source (12) within the inner tubular member (20), and bearing means (24) operative between the inner and outer tubular members (20,22) to permit rotation of the inner tubular member (20) with respect to the outer tubular member (22) between <SL> <LI>(a) a non-shuttering position in which the two elongate slots (21,23) overlie one another such as in use to permit light from the source (12) to exit from the apparatus (10), and <LI>(b) a shuttering position which the two elongate slots (21,23) do not overlie one another and thus, in use, the outer tubular member (22) cuts off the direct light path from the source (12) to the target (15). </SL>

Description

- 1 LIGHT SHU1lERING DESCRIPTION

Technical Field

1() This invention relates to light shattering and concerns shattering apparatus used to cut off the direct light transmission path from a light source to an intended target. The term "light" as used herein is to include electro-magnetic radiation both within and outside of the visible spectrum.

1 5 Background

Many biological and production processes effect a physical or chemical change by submitting a target that is responsive to light of at least one predominant wavelength, to such light. Examples of such processes include radiography, spectometry and UV curing of coatings or images on a substrate. The source of the light may run at elevated 2() temperatures and take time both to heat up and to cool down. If the target is close to the source-which is the usual arrangement in order to increase efficiencythere is a danger of the target over-heating and possibly igniting, e.. when relative motion between the target and the source is stopped either accidentally or intentionally, e.g. to make set up adjustments in the process parameters.

Prior Art

In one form of UV-curing of printed material, where the printing ink on a substrate is UV-curable, the substrate is conveyed beneath a mediumdensity mercury vapour lamp that runs at a temperature of approximately 800 C and emits UV-radiation of 3() appropriate spectral characteristics and high intensity. The UV radiation is dangerous to human eyes and is therefore shielded from view. To cater for when there is no 1( bill l t) l At 7122

- 2 relative motion between conveyor and lamp, e.g. during setting up of the printing apparatus or in the event of a sudden cessation of conveyor running during print production, the beam of UV light to the substrate must be cut-off or intercepted very rapidly and reliably to avoid the dangers of over heating of the substrate (or the ink 5 thereon) and a possible fire outbreak. Simply switching off the lamp would not avoid these dangers since the running temperature of the lamp is too high and the time required for the lamp to cool down is too long. Furthermore, such a solution is unsatisfactory on efficiency grounds as it takes a long time for a switched off lamp to regain its proper running temperature following its being switched on again. Moreover, 10 frequent switching of the lamp-an expensive item-reduces its life.

Solutions have been proposed in the past aimed at solving the problem of providing for rapid cut-off or interception of the light beam rapidly and reliably such as to avoid the dangers of over heating of the substrate (or the ink thereon) and a possible fire 15 outbreak. These past proposals have either employed a separate shutter to intercept the light beam, or have made the reflector-that is used to focus light from the lamp onto the target-of two pivoted parts each having first and second edges that are movable arcuately between a reflector" position, in which the two first edges co-operate to one side of the lamp to form the reflector (and the second edges are free), and a 20 "shuttering" position in which the two second edges co-operate to the other side of the lamp to form the shutter (and the first edges are free).

Examples of shattering apparatus comprising a pivoted two-part reflector are the Model "DCR-W" available from VTI International, the Model "NUVA" available from 25 GEW, and the U.V. Dryers available from Natgraph Ltd (Dabell Avenue, Blenheim Industrial Estate, Nottingham, NG6 8WA, UK).

A problem inherent in the design of such pivoted reflectors is the reliability of the pivot axis. If the pivot axis becomes bent or out of parallelism with the reflector edges, 30 pivoting action may be impaired and/or incomplete shattering may result.

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SurnmarY of the Invention With a view to overcoming or at least minimising the above mentioned and/or other disadvantages of the prior art, the present invention envisages the provision of

shattering apparatus to cut off the direct transmission of light from a light source to an 5 intended target, said apparatus comprising inner and outer generally tubular members each having an elongate slot through its cylindrical wall, means for mounting the light source within the inner tubular member, and bearing means operative between the inner and outer tubular members to permit rotation of the inner tubular member with respect to the outer tubular member between 10 (a) a non-shuttering position in which the two elongate slots overlie one another such as in use to permit light from the source to exit from the apparatus, and (b) a shattering position which the two elongate slots do not overlie one another and thus, in use, the outer tubular member cuts off the direct light path from the source to the target.

Preferably the light source comprises a tubular lamp. The mounting means for the tubular lamp preferably comprises, at each end of the inner tube, a two-part disc-like clamping device of which the two parts are releasably fastened to one another, e.g. as by bolts, and serve to clamp between them the associated end of the tubular lamp.

2() Advantageously the bearing means comprises a plurality of individual ball transfer units that are angularly spaced apart at each end of the inner and outer tubular members. 25 Preferably the inner tubular member is provided internally with reflector means to direct light from the lamp towards the elongate slot in the wall of the inner member.

Advantageously the reflector means comprises a separate reflector member, preferably having the form of a conic section (e.g. of generally parabolic or part-elliptic shape), 3() releasably mounted within the inner tubular member.

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Preferably the reflector member is apertured, e.g. perforated, and is mounted within the inner tubular member in spaced relation to the inner surface of the inner tubular member, the gap between them communicating in use with gas extraction means. The latter serves in use to extract ozone and/or other gas arising from the high temperature 5 running of the lamp and/or to cool the apparatus or parts thereof.

Advantageously, the perforations in the apertured reflector member may comprise a plurality of circular holes, arranged in a predetermined array, the holes having diameters that increase progressively with increase in the distance of the holes from the 10 gas extraction means.

Brief Description of the Drawings

by way of example one embodiment of this invention will now be described with reference to the accompanying drawings of which: 15 Figure 1 is a schematic, partly broken away, longitudinal cross-section through shattering apparatus according to this invention (some parts being omitted for clarity), and Figure 2 is a schematic transverse cross- sectional view taken along the line Il-II of Fig 1.

2() Detailed Description of Example(s) of the Invention

The illustrated shattering apparatus 10 is to cut off direct transmission of UV-light from a tubular mercury lamp 12 to an intended target 15 that comprises a substrate 14 printed with a UV-curing ink and conveyed beneath apparatus 10 in a direction normal 25 to the plane of Fig 1 by a conveyor 16. The apparatus 10 extends in a direction transverse to the direction of travel of conveyor l 6 and closely above it. Apparatus 10 comprises inner and outer generally tubular members 20,22 each having an elongate slot 21,23 through its cylindrical wall. The slot 21 in inner member 20 subtends an angle of approximately 180 whereas the slot 23 in outer member 22 subtends a 30 somewhat smaller angle, e.g. approximately 160 .

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- 5 A plurality of individual ball transfer units 24 are angularly spaced apart at each end of the inner and outer tubular members 20,22 to permit both relative rotation and relative axial motion of the members 2O,22. In this embodiment, and as shown in Fig 2, four such units 24 are provided, equi-angularly spaced apart, and mounted on the 5 outer tubular member 22. These ball transfer units 24 provide bearing means operative between the inner and outer tubular members 20,22 to permit rotation of the inner tubular member 20 with respect to the outer tubular member 22 between (a) a non-shuttering position in which the two elongate slots 21,23 overlie one another (the position illustrated in Figs l and 2) such as in use to permit light 10 from the sourcel2 to exit from the apparatus 10, and (b) a shattering position which the two elongate slots 21,23 do not at all overlie one another and thus, in use, the outer tubular member 22 acts as a shutter by cutting off the direct light path from the source 12 to the target 15.

15 The tubular lamp employed is a medium-density mercury vapour lamp generally running at between approximately 100 to 240 watts/cm and having a surface temperature of up to 800 C -hence the need for cooling. Mounting means for the tubular lamp 12 are provided, at each end of the inner tube. Each such mounting means is provided by a two-part disc-like clamping device 25 of which one part, 26, is 2() secured permanently to the inner tubular member 20 and is provided with a semi circular recess to accommodate part of the tubular lamp 12, and the other part, 28, is releasably fastened to part 26 by a pair of bolts engaging in threaded bores 29 such that the two mutually fastened parts 26,28 serve to clamp between them the associated end of the tubular lamp 12.

The inner tubular member 20 is provided internally with reflector means 30 to direct light from the lamp 12 towards the elongate slot 2 l in the wall of the inner member 20.

In this embodiment the reflector means 30 comprises a separate reflector member 32, of generally part-elliptic (or optionally of generally parabolic) shape, that is releasably 30 mounted within the inner tubular member 20 such as to be readily removable for cleaning and/or for replacement. The reflector member 32 is perforated-as by 11(11)1- 1 (I 1.. L ?921*}2

- 6 circular perforations 31- and is mounted within the inner tubular member in spaced relation to the inner surface of the inner tubular member 20, the gap 33 between them communicating in use with gas extraction means 34 via the open ends of both the inner and outer tubular members 20,22. The gas extraction means 34 serves in use to extract 5 ozone and/or other gas arising from the high temperature running of the lamp 12 and/or serves to cool the apparatus or parts thereof.

Advantageously, the circular perforations in the apertured reflector member 32 may be arranged in a predetermined array, the holes having diameters that increase either 1() step-wise or progressively with increase in the distance of the holes from the gas extraction means 34.

At the end of apparatus 10 opposite extractor means 34, the inner tubular member 20 is centrally provided with a socket that matingly accommodates, in a splined or keyed 15 manner, the rotary output shaft 36 of a pneumatic rotary actuator 35. The latter is mounted on the inside of outer tubular member 22 by a disc or spider 38. The splined or keyed connection between the inner tubular member 20 and the drive actuator 35 permits easy withdrawal of the inner member 20 axially out of the outer member 22 (in the direction of Arrow A) for cleaning and/or for lamp replacement, and for easy 2() re-insertion and re-coupling after such operations.

In use of the shattering apparatus 10, the outer tubular member 22 has its slot 23 lowermost and closely adjacent the target 15 provided by substrate 14 on conveyor 16.

If the substrate 14 is absent or the conveyor is stationary, the apparatus-under 25 control of a control unit and sensors (not shown)adopts a default or rest condition in which the inner tubular member 20 has its elongate slot 21 uppermost and diametrically opposite the slot 23 in outer member 22. Since the angular extent of slot 23 is less than 180 (and less than 360 minus the angular extent of slot 21), no light from tubular lamp 12-which is kept in an ON condition-can be directly incident 30 on the target IS. When the conveyor 16 is started and running at the desired speed (e.g. in the range 2 to 30m per minute), and the substrate 14 is being conveyed Ho I)F N l l I..L b22

( therealong, the rotary actuator 35 can be operated to effect a halfturn (i.e. a 180 rotation) of inner tubular member 20 in one direction to bring its slot 21 into an overlying relation with respect to slot 23 in the outer tubular member 22. Light from tubular lamp 12 can then emanate through the overlying slots 21723 and be incident on 5 the target 15. If the conveyor stops, the control unit operates automatically to activate actuator 35 and cause it to effect counter-rotation (i.e. in the opposite direction) of inner member 20 through a half-turn or 180 such that it regains its default condition once more.

10 It will be appreciated that a different number of ball transfer units 24 than four may be provided, e.g. just three or, indeed, a number greater than four.

It will also be appreciated that the angular extent of the slots 21 and 23 may be other than as stated above, as long as they do not exceed in aggregate 360 .

Other modifications and embodiments of the invention, which will be readily apparent to those skilled in this art, are to be deemed within the ambit and scope of the invention, and the particular embodiment(s) hereinbefore described may be varied in construction and detail, e.g. interchanging (where appropriate or desired) different 20 features of each, without departing from the scope of the patent monopoly hereby sought. II()IlI:NIIII..L J212

Claims

- 8 CLAIMS l

l. Shuttering apparatus to cut off the direct transmission of light from a light 5 source to an intended target, said apparatus comprising inner and outer generally tubular members each having an elongate slot through its cylindrical wall, means for mounting the light source within the inner tubular member, and bearing means operative between the irmer and outer tubular members to permit rotation of the inner tubular member with respect to the outer tubular member between 10 (a) a non-shuttering position in which the two elongate slots overlie one another such as in use to permit light from the source to exit from the apparatus, and (b) a shattering position which the two elongate slots do not overlie one another and thus, in use, the outer tubular member cuts off the direct light path from the source to the target.
2.Shuttering apparatus according to Claim l, wherein the light source comprises a tubular lamp.
3. Shuttering apparatus according to Claim 2, wherein the mounting means for the 20 tubular lamp comprises, at each end of the inner tube, a twopart disc-like clamping device of which the two parts are releasably fastened to one another and serve to clamp between them the associated end of the tubular lamp.
4. Shuttering apparatus according to Claim 3, wherein said two parts are releasably 25 fastened to one another by bolts.
5. Shuttering apparatus according to any preceding Claim, wherein the bearing means comprises, at each end of the inner and outer tubular members, a plurality of individual ball transfer units that are angularly spaced apart. i lloDENlOl AL V3
6. Shuttering apparatus according to any preceding Claim, wherein the said inner tubular member is provided internally with reflector means to direct light from the said lamp towards the elongate slot in the wall of the inner member.

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7. Shuttering apparatus according to C laim 6, wherein the reflector means comprises a separate reflector member releasably mounted within the inner tubular member.
8. Shuttering apparatus according to Claim 7, wherein the reflector member has the form of a conic section.
9. Shuttering apparatus according to Claim 7 or Claim 8, wherein the reflector member has a generally parabolic.
lO. Shuttering apparatus according to Claim 7 or Claim 8, wherein the reflector 15 member has a part-elliptic shape.
l l. Shuttering apparatus according to any one of Claims 7 to 10, wherein the reflector member is apertured and is mounted within the inner tubular member in spaced relation to the inner surt'ace of' the inner tubular member, the gap between them communicating 20 in use with gas extraction means.
12. Shuttering apparatus according to any one of Claims 7 to 1 1, wherein the reflector member is perforated.

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13. Shuttering apparatus according to Claim 11, wherein the perforations in the apertured reflector member may comprise a plurality of circular holes, arranged in a predetermined array, the holes having diameters that increase progressively with increase in the distance of the holes from connection means to connect the apparatus to said gas extraction means.

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14. Shuttering apparatus substantially as herein described with reference to and/or as illustrated in the accompanying drawings.

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