GB2269782A

GB2269782A - Method and apparatus for marking information on the outer surface of a polymer covered cable or wire.

Info

Publication number: GB2269782A
Application number: GB9217745A
Authority: GB
Inventors: Stewart Wynn Williams
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1992-08-20
Filing date: 1992-08-20
Publication date: 1994-02-23
Anticipated expiration: 2012-08-20
Also published as: GB2269782B; GB9217745D0

Abstract

A method and apparatus for marking information on the outer surface 1 of a polymer covered cable or wire 2 includes feeding the cable 2 past an ultra-violet laser marking station 3, 4 to produce a desired shape marking therein, feeding the laser marked cable through an ink printing station 7 and ink printing the desired shape marking on top of the laser marking 5. The UV laser irradiation not only produces a laser marking but makes the marked region more hydrophylic and thus improves ink adhesion thereto at the ink printing stage. If part of the high contrast ink printed marking is erased or becomes removed during use the lower contrast, more resistant to erasure laser marking 5 underneath will be uncovered and become visible thus retaining the marking information. <IMAGE>

Description

METHOD AND APPARATUS FOR MARKING INFORMATION ON THE OUTER SURFACE OF A POLYMER COVERED CABLE OR WIRE This invention relates to a method and apparatus for marking information on the outer surface of a polymer covered cable or wire, particularly, but not exclusively, suitable for use for aerospace applications.

It is known to print information by an ink based system on the outer surface of a polymer covered cable or wire. This conventional ink marking technique has the problem of difficulty in ensuring that the ink sticks to the surface of the polymer particularly when the cable is an aerospace cable where the polymer covering may be a fluoropolymer which is generally very hydrophobic. Conventionally this problem is reduced by roughening the outer surface of the polymer covering which is to carry the printed information.

Generally this can be done by electrical erosion of the outer surface via a corona discharge.

Alternatively it has been proposed to roughen the surface prior to application of the ink by treatment with an excimer laser which locally changes the nature of the outer surface rendering it more hydrophylic.

Whatever technique is used for pretreating the surface by roughening the information subsequently printed on the roughened surface of the polymer covering on the cable or wire is not permanent under certain conditions particularly at elevated temperatures and in aggressive environments such as encountered typically in aerospace applications. This loss of the information printed on the cable or wire is particularly undesirable as removal of even part of the information may render the full text illegible or may dangerously alter the text is a misleading manner so that the cable or wire appears to be suitable for a use for which it is totally unsuitable.

A further conventional alternative is to mark the outer surface of a polymer covered cable or wire by a laser technique. This can be done by using the laser irradiation to remove some of the outer surface of the polymer coating on the cable or wire to expose an underlayer of different colour. This technique is potentially dangerous because it involves a measured amount of destruction of the polymer cover of the cable or wire which can weaken the remainder. A further technique which has been proposed is employed where the polymer of the cable covering is transparent in the ultra-violet and contains a pigment, such as titanium dioxide, which changes colour when irradiated by an ultra-violet laser.

This latter technique is generally successful, and produces markings which are temperature stable and resistant to attack in aggressive atmospheres or fluids, but have a relatively poor contrast between the marking and the cable surface, which contrast is not as strong as that produced by the ink printing techniques. For example the contrast for the ultra-violet laser produced marking using a polymer containing titanium dioxide pigment is approximately 60% in comparison with the contrast produced in an ink printed marking where the contrast is approximately 90% for a white cable.

There is thus a need for a generally improved method and apparatus for marking information on the outer surface of a polymer covered cable or wire which will afford a high contrast between the marking and cable background comparable with that produced by a conventional ink printing technique but with a better capability for retaining legibility when exposed to elevated temperatures and/or aggressive fluids or liquids.

According to a first aspect of the present invention there 5 provided a method for marking information on the outer surface of a polymer covered cable or wire, including the steps of feeding a cable to be marked past an ultra-violet (W) laser, irradiating the cable surface with the W laser to produce a desired shape marking therein, feeding the laser marked cable through an ink printing station and ink printing the desired shape marking on top of the laser marking to provide an at least two layer marking; with the irradiation by the W laser being controlled so as to render the marked regions of the polymer surface more hydrophylic and thus improve ink adhesion thereto, such that the at least two layer marking has a higher contrast with the unmarked cable surface than the laser marking and a higher resistance to removal from the cable surface than a conventional ink printed marking.

With such a method if the high contrast ink marking should be removed or damaged in any way during use of the marked cable or wire the underlying more resistant, but less visible, laser marking will show through sufficiently for the cable marking to remain legible.

Preferably the polymer cover of the cable being marked contains a pigment, more preferably titanium dioxide, which changes colour on irradiation by the W laser.

Conveniently the laser utilised is an excimer laser with a wavelength in the range of from approximately 193 to approximately 400 nanometres, a pulse length in the range of from 1 to 200 nanoseconds, and a fluence in the range of from 0.1 to 10 Joules per square centimetre.

Advantageously the laser wavelength is 308 nanometres, the pulse length is 20 nanoseconds and the fluence is 1 Joule per square centimetre.

Preferably after being passed through the ink printing station the laser marked and ink printed cable or wire is passed through an ink curing station at which it is heated to a temperature for a time sufficient to cure the ink marking.

Conveniently the temperature is in the range of from 300 to 600 degrees Centigrade and the time is the range of from 0.5 to 60 seconds.

Preferably the laser marked cable or wire is fed through the ink printing station and ink curing station at least twice.

According to a further aspect of the present invention there is provided apparatus for marking information on the outer surface of a polymer covered cable or wire, including an ultra-violet (W) laser station operative to apply W laser irradiation to the outer surface of the cable or wire in a selectively adjustable shape to produce a desired shape marking therein and an ink marking station operable to receive the laser marked cable from the W laser station and ink print the desired shape marking on top of the laser marking.

Preferably the apparatus includes an ink curing station operable to receive the ink and laser marked cable or wire and heated to a temperature sufficient to cure the ink marking.

Conveniently the apparatus includes means for feeding the cable or wire through the W laser marking station, ink printing station and ink curing station.

Advantageously the W laser is an excimer laser.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying single figure drawing, in which:- Figure 1 is a schematic diagrammatic view of apparatus according to one embodiment of the present invention for marking information on the outer surface of a polymer covered cable or wire.

According to the present invention information may be marked on the outer surface 1 of a polymer, preferably fluoropolymer, covered cable or wire 2 by feeding the cable 2 to be marked past or through an ultra-violet (W) laser 3. The laser 3 is attached to a mask and optics projection unit 4 which together make up a laser marking station at which the cable surface 1 is irradiated by the W laser to produce a desired shape marking thereon, for example the marking 5. The polymer contains a pigment, such as Titanium Dioxide, which changes colour on W irradiation to provide the marking 5 beneath the surface 1 in the polymer cover. Thus marking 5 is highly resistant to heat and aggressive environments but has a relatively low contrast with the cable background typically 60% for a white cable.

Means 6 are provided whereby the cable 2 is fed through the laser marking station comprising the laser 3 and projection unit 4 to an ink printing station 7 at which the desired shape marking is ink printed on top of the laser marking 5 to produce a combined laser marked and ink printed mark 8. The ink marking is less resistant to heat and aggressive environment than is the laser marking 5 but has a higher contrast, typically 90% for a white cable. Thus the combined mark 8 has a higher contrast than the laser marking 5 and a higher resistance to removal than a conventional ink printed mark.

Optionally the cable 2 carrying the laser marked and ink printed marking is fed from the ink printing station 7 through an ink curing station 9 at which the ink and laser marked cable is heated to a temperature sufficient to cure the ink marking. If desired the laser and ink marking 8 can be passed more than once through the laser marking station, ink printing station 7 and ink curing station 9.

Irradiation by the W laser 4 is controlled so as to render the marked regions of the polymer surface 1 more hydrophylic and thus improve ink adhesion thereto. The polymer cover of the cable 2 being marked contains a pigment such as titanium dioxide which changes colour on suitable irradiation by the W laser. The laser 3 is an excimer laser with a wavelength in the range of from approximately 193 to approximately 400 nanometres, a pulse length in the range of from to 200 nanoseconds, and a fluence in the range of from 0.1 to 10 Joules per square centimetre. Preferably the laser wavelength is 308 nanometres, the pulse length is 20 nanoseconds and the fluence is 1 Joule per square centimetre. The laser 3 is capable of firing at a sufficient repetition rate to put the desired number of marking shapes or characters onto the surface 1.

The mask and optics projection unit 6 converts the rectangular output profile of the laser into the shape of the identification code or marking that is desired to be put down onto the surface 1 of the cable 2. It also converts the fluence so that it is at the correct level for producing the mark in the titanium dioxide containing polymer covering. The fluence must also be at the correct level for preparing the surface 1 for the ink printing station 7. Preferably this fluence is in the range of from 1 to 2 Joules per square centimetre.

At the ink printing station 7 ink is applied to the laser marking 5 in any convenient manner such as by means of a spray or jet system which provides the ink on the cable outer surface 1 where it only adheres in the areas of the laser marking 5 that have been irradiated by the W laser 3. The ink curing station 9 heats the laser and ink marked surface 1 for a time sufficient to cure the ink marked surface. Preferably the temperature is in the range of from 300 to 600 degrees C for a time in the range of from 0.5 to 60 seconds to cure the ink marking. The cured laser and ink marking 8 on the cable surface 1 has a high contrast between the outer ink marking, which is typically of the order of 90% for cables or wires, and an underlying laser marking 5 with a high degree of permanence but lower contrast. If the ink mark or parts of the mark are removed by attack in an aggressive environment this will expose the laser marking 5 underneath so that the mark is still legible under at least some conditions.

Modifications can be made to the foregoing. For example the feed means 6 may be in two separately controllable parts so that the cable 2 can be fed at different velocities through the laser marking station, ink printing station 7 and ink curing station 9. Additionally any suitable method of ink application at the ink printing station 7 can be utilised such as immersion in an ink bath or application with a roller system.

Claims

1. A method for marking information on the outer surface of a polymer covered cable or wire, including the steps of feeding a cable to be marked past an ultra-violet (W) laser, irradiating the cable surface with the W laser to produce a desired shape marking therein, feeding the laser marked cable through an ink printing station and ink printing the desired shape marking on top of the laser marking to provide an at least two layer marking, with the irradiation by the W laser being controlled so as to render the marked regions of the polymer surface more hydrophylic and thus improve ink adhesion thereto such that the at least two layer marking has a higher contrast with the unmarked cable surface than the laser marking and a higher resistance to removal from the cable surface than a conventional ink printed marking.

2. A method according to claim 1, in which the polymer cover of of the cable being marked contains a pigment which changes colour on irradiation by the W laser.

3. A method according to claim 2, in which the pigment is titanium dioxide.

4. A method according to any one of claims 1 to 3, in which the laser utilised is an excimer laser with a wavelength in the range of from approximately 193 to approximately 400 nanometres, a pulse length in the range of from 1 to 200 nanoseconds, and a fluence in the range of from 0.1 to 10 Joules per square centimetre.

5. A method according to claim 4, in which the laser wavelength is 308 nanometres, the pulse length is 20 nanoseconds and the fluence is 1 Joule per square centimetre.

6. A method according to any one of claims 1 to 5, in which after passing through the ink printing station the laser marked and ink printed cable or wire is passed through an ink curing station at which it is heated to a temperature for a time sufficient to cure the ink marking.

7. A method according to claim 6, in which the temperature is in the range of from 300 to 600 degrees Centigrade and the time is in the range of from 0.5 to 60 seconds.

8. A method according to any one of claims 1 to 7, in which the laser marked cable or wire is fed through the ink printing station and ink curing station at least twice.

9. A method for marking information on the outer surface of a polymer covered cable or wire, substantially as hereinbefore described and as illustrated in Figure 1 of the accompanying drawings.

10. Apparatus for marking information on the outer surface of a polymer covered cable or wire, including an ultra-violet (W) laser station operative to apply W laser irradiation to the outer surface of the cable or wire in a selectively adjustable shape to produce a desired shape therein, and an ink marking station operable to receive the laser marked cable from the W laser station and ink print the desired shape marking on top of the laser marking.

11. Apparatus according to claim 10, including an ink curing station operable to receive the ink and laser marked cable or wire and heated to a temperature sufficient to cure the ink marking.

12. Apparatus according to claim 11, including means for feeding the cable or wire through the UV laser marking station, ink printing station and ink curing station.

13. Apparatus according to any one of claims 10 to 12, wherein the W laser is an excimer laser.

14. Apparatus for marking information on the outer surface of a polymer covered cable or wire, substantially as hereinbefore described and as illustrated in Figure 1 of the accompanying drawings.