GB2092957A - Method and composition for cancelling luminescent address codes - Google Patents

Abstract

A previously applied or erroneously applied machine-readable luminescent address code on a postal item 8 is cancelled by the application of an ultraviolet-absorbing ink. The ink is substantially transparent to visible light and includes a substance which absorbs ultraviolet light without luminescing and emitting visible light, and a binder which prevents the ink from soaking into the postal item to an extent such that the effect of the UV- absorbing substance is excessively attenuated. The ink absorbs the ultra- violet light directed towards the previously applied luminescent dot or bar code upon any subsequent interrogation by an address reading machine and so prevents that code from being read by a subsequent address reading machine. A particularly preferred ink includes a benzophenone to absorb the ultraviolet light. <IMAGE>

Description

SPECIFICATION Method and composition for cancelling luminescent address codes A luminescent address code is applied to a predetermined location of a postal item at an early stage in its handling by the postal authorities to provide in a machine-readable form the destination address written on the postal item. This machine readable luminescent address code is then sensed and used to route the postal item through automatic sorting machines used throughout the distribution of the postal item to its destination address. The luminescent address codes are printed on the surface of the postal items in a fluorescent or phosphorescent material which is substantially transparent to visible light so that the luminescent address code does not obscure any writing or any other information present on the postal item.

The luminescent address code may be provided as a series of dots or alternatively as a bar code.

If the wrong code is applied to a postal item or, for example, if a postal item is redirected or an old covering of the postal item for example an old envelope is re-used, then a postal item may already have a previously applied luminescent address code on it before it reaches the sorting office at which the luminescent code is to be applied. In this case, when a luminescent code is subsequently applied to the postal item the automatic sorting machines will be confused since they may read a previously applied luminescent address code or, possibly a combination of the previusly applied address code and the currently valid address code.

Naturally, it would be desirable to be able to prevent this happening by somehow cancelling any previously applied luminescent address code which is already present on the surface of the postal item when it is received by the receiving sorting office for that postal item and before the address written on that postal item is encoded into a machine-readable form. If the previously applied luminescent address code is simply masked with an opaque ink, this is likely to obscure the address written on the postal item and thus prevent the address being read and so prevent the postal item reaching its correct destination. Clearly, such a solution is not acceptable.

According to a first aspect of the invention, a method of cancelling a previously applied machine-readable luminescent address code on a paper-surface layer-provided postal item comprises applying on top of the previously applied luminescent address code an ink which is substantially transparent to visible light and which includes a substance which absorbs ultraviolet light without luminescing and emitting visible light.

the ink including a binder such that it does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent the previously applied luminescent address code from being read upon a subsequent interrogation by an address reading machine.

According to a second aspect of this invention a method of cancelling a previously applied machine-readable luminescent address code on a paper surface-layer provided postal item includes the steps of irradiating the postal item with ultraviolet light, monitoring the surface of the postal item for the presence of a previously applied luminescent address code, and upon detection of a previously applied luminescent address code, applying an ink on top of the previously applied luminescent address code, the ink including a binder such that it does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent the previously applied luminescent address code from being read upon a subsequent interrogation by an address reading machine.

The substance in the ink absorbs the ultraviolet radiation emitted by any subsequent address reading machine and so prevents the previously applied luminescent address code being read by that machine.

Equally, since the ink does not itself luminesce and emit visible light it will not interfere with any subsequently applied luminescent address code. Further, since the ink is substantially transparent to visible light it does not obscure any written information present beneath or adjacent the previously applied luminescent address code.

When operating according to the second aspect of the invention, that is first monitoring a postal item for a previously applied machine-readabe luminescent address code which if present, is to be cancelled, the postal item may be fed to an apparatus which comprises irradiating means which irradiate the postal item with ultraviolet light, monitoring means at which the surface of the postal item is monitored for the presence of a previously applied luminescent address code and an applicator at which an ultraviolet radiation absorbing ink as aforesaid is applied to the postal item on top of the previously applied luminescent address code to absorb ultraviolet light directed towards the previously applied luminescent address code upon any subsequent interrogation by an address reading machine.

The cancellation of any previously applied machine-readable luminescent address codes must take place before the address written on the postal item is encoded into a machine-readable luminescent address code and the code applied to the postal item. Preferably an apparatus as aforesaid for cancelling the luminescent address code forms part of an apparatus for applying a machine-readable luminescent address code to the postal item. The apparatus for cancelling the luminescent address code is located upstream from a coding station at which the address on the postal item is read and a machine-readable luminescent address code applied to the postal item.When the apparatus also includes an automatic letter facer to orient the postal item in the correct way, the apparatus for cancelling the luminescent address code is preferably also located upstream of the automatic letter facer so that the automatic letter facer is not confused by the previously applied address code when orienting the postal items.

Preferably the means for monitoring the surface of the postal item fdr the presence of a previously applied luminescent address code includes a source of ultraviolet radiation having substantially no output below 345 nanometers, and a photodetector responsive to visible radiation which is arranged to scan the surface of the postal item and, in response to any visible radiation emitted by the surface output a signal to indicate the presence of a previously applied luminescent address code.

With the wavelength of the ultraviolet light source restricted in this way a response is obtained from any previously applied address code bars but no response is obtained from the phosphor dots associated with the postage stamps affixed to the postal item. Preferably the ultraviolet light source is formed by a standard 365 nanometer ultraviolet source fitted with a steep cut optical filter to absorb all radiation having a wavelength below 345 nonometers.

The monitoring means for monitoring the surface of the postal item need not be as sophisticated as a conventional luminescent address code reader but it is naturally based on the same principles. The applicator may be formed of similar construction to the applicator for applying the luminescent address codes to postal items, but it is unnecessary for the applicator to be as sophisticated as this and it preferably comprises a simple felt roller with means for impregnating the felt roller with the ink.

According to a third aspect of this invention an ink for cancelling a luminescent address code on a paper-surfaced postal item comprises a substance which absorbs ultraviolet light without luminescing and emitting visible light, a binder, and a solvent, the ink also being substantially transparent to visible light and the binder being such that the ink does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent a previously applied luminescent address code from being read on a subsequent interrogation by an address reading machine.

Preferably the substance is formed by a compound having a C = X group, X being a heteroatom, directly or indirectly conjugated to one or preferably two aromatic nuclei. By "indirectly conjugated" we mean that there may be one or more, but preferably no more than one, vinylidene group between the C = X group and the or each conjugated nucleus. Preferably the C = X group is a carbonyl (CO), an imine (C = NH) or an azine (CH=N-CH) group. The aromatic nuclei are, for example, benzene orfuran rings. Preferably the C=X group is directly conjugated to the or each nucleus, as in benzophenone. The or each nucleus may carry non-interfering or light-stabilising substituents, as in 2,4-dihydroxybenzophenone.

Preferably the substance which absorbs the ultraviolet light is present in the ink in a quantity within a range from 15 to 30% by weight and it is particularly preferred that it is present in a quantity within a range from 20 to 25% by weight. The binder is preferably present as 1 to 4% by weight of the ink and it is preferred that it is present as substantially 2% by weight.

Such an ink absorbs ultraviolet light to such an extent that when it is overprinted on a previously applied luminescent address code a negligible signal is given upon irradiation with ultraviolet light. At the same time the ink must not interfere with any subsequently overprinted luminescent address code and should not soak into the surface of the postal item to a significant extent since, this would reduce its effect in masking the previously applied luminescent address code from ultraviolet light.

Preferred binders for this purpose are non-ionic or ionic cellulose ethers of such molecular weight and degree of substitution as to ensure that they form a stable solution or dispersion in water. Typical examples of non-ionic cellulose ethers of this type are ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, ethoxyethyl cellulose, methyoxyethyl cellulose and methoxypropyl cellulose.

Carboxymethyl cellulose can also be employed, generally in the form of a salt, e.g. as sodium carboxymethyl cellulose, i.e. an ionic cellulose ether.

Substances of a non-cellulosic nature which might have an affinity for cellulosic paper fibres and which may therefore be used as binders as alternatives to cellulose derivatives are for example gum arabic, polyvinyl alcohol, gelatin and animal bone glue. Dextrins, being partially hydrolysed starch products, may also be used as binders. Of this latter class of binders, polyvinyl alcohol is the preferred substance since the remaining substances are subject to microbial attack, as are starch and starch derivatives such as amino pectins.

A particular example of an apparatus for use in the method of this invention for cancelling a luminescent address code and of an ink in accordance with this invention will now be described with reference to the accompanying drawing and examples.

The drawing is a perspective view of an ink applicator forming part of the apparatus.

The apparatus for cancelling a previously applied luminescent address code is arranged to handle machinable letters i.e. those having a thickness below 6mm and being within predetermined overall size limits. The apparatus comprises a detecting station and a cancelling station. A stream of letters is fed to the detecting station by a standard conveyor, for example a pair of opposed belt or ribbon conveyors, and the detecting station includes a source of ultraviolet light. The light source is formed by a standard ultraviolet light source having a maximum output of 365 nanometers, in combination with a steep cut optical filter to absorb all the ultraviolet light having a wavelength below 345 nanometers. The ultraviolet light emitted by this source excites the phosphor of any previously applied luminescent address code into emitting visible radiation but does not excite the phosphors present on stamps on the letters. The detecting station also includes a sensor, for example a photomultiplier tube, to detect visible light emitted from the surface of the letters. A sorting device is located at the output of the detecting station and, the sorting device is coupled to the sensor so that, depending upon the output of the sensor, letters either proceed to an automatic letter facing and stamp cancelling station before then proceeding to an address encoding station or, alternatively, the letters are fed to the previously applied luminescent address code cancelling station.

The letters travelling to the cancelling station are oriented in dependence upon the location of the luminescent address code and then fed to the luminescent address code cancelling station which is illustrated in the drawing. The cancelling station includes an ink bath 1 containing ink in accordance with the third aspect of this invention. Two examples of ink are described subsequently. A first felt faced roller 2 dips into the ink bath 1 through a slot 3 in the cover 4 ofthe ink bath 1 and this first felt roller 2 is slowly revolved so that it is continuously impregnated with the ink from the ink bath 1. A second felt roller 5 rotates about an upright axis and is driven by a motor 6.A ribbon conveyor 7 feeds letters to the previously applied luminescent address code cancelling station and the speed of rotation of the felt roller 5 is matched to that of the ribbon conveyor 7 so that the peripheral speed of the felt roller5 is the same as that of the ribbon conveyor 7.

In use, after having been faced so that the previously applied luminescent address code is at the lowermost part of the letter and facing the felt roller 5, the letters 8 are fed to the cancelling station by the ribbon conveyor 7. As the letters pass the cancelling station the felt roller 5 contacts the face of the letter 8 to deposit a band of ink across the letter over the previously applied luminescent address code. The letters are then forwarded to a stamp cancelling station and preferably this is the stamp cancelling station forming part of the automatic letter facing and cancelling equipment downstream from the detecting station.

Example I An ink was prepared by mixing 30 grams of a 30% (by weight) solution of 2,4 dihydroxybenzophenone in methanol with 10 grams of a 71/2% (by weight) solution of carboxy methylcellulose (sodium salt) in water.

This ink was then applied to the surface of a letter over a previously applied luminescent address code using an applicator as described above and the letter was subsequently subjected to ultraviolet radiation. Some visible light was emitted from the previously applied luminescent address code upon the irradiation but there was sufficient attenuation of the previously applied luminescent address code to prevent it being detected by a conventional luminescent code reader. This ink soaked into the surface of the letter to some extent.

Example 11 An ink was prepared by mixing 30 grams of 30% (by weight) solution of 2,4 dihydroxybenzophenone in methanol with 10 grams of a 7% (by weight) solution of methylhydroxypropylcellulose in water. This ink was tested in the same way as Example I and was found that it soaked into the surface of the letter less than the ink in Example I and that it gave a greater attenuation in the visible light emitted by the previously applied luminescent address code as a result of its irradiation by ultraviolet light.

Example Ill In order to show how the selection and concentration of binder affects the suitability for use in the method of this invention of a cancelling ink containing a substance which absorbs ultraviolet light without luminescing and emitting visible light, there was prepared a series of ink compositions as set out in the following Table. In preparing the ink compositions, there were mixed together three parts by weight of the indicated dihydroxybenzophenone solution with one part by weight of a cellulose derivative solution. In the tests, reference is made to standard mixtures when employing carboxymethyl cellulose and methylhydroxypropyl cellulose respectively. These standard mixtures set out in tests 15 and 16 are in fact the compositions of the foregoing Examples I and II.Where reference is made to carboxymethyl cellulose, it was the sodium salt which was employed.

Test Concentration of Concentration of Remarks 2,4-dihydroxybenzo- cellulose solu phenone tion 1 15% W/w in methanol 21/2% W/w carboxymethyl Solution soaked cellulose in water into the paper to an unaccept able degree 2 15% W/w in methanol 21/2% w/w methyl hydroxy propyl cellulose in water 3 15% W/w in methanol 71/2% W/w carboxymethyl I, cellulose in water Test Concentration of Concentration of Remarks 2,4dEhydroxybenzo- cellulose solu phenone tion Solution soaked 4 15% W/w in methanol 71/2% W/w methyl hydroxy- into the paper propyl cellulose in to an unaccept water able degree 5 15%W/win methanol 10%w/wcarboxymethyl cellulose in water 6 15%W/win methanol 10%W/wmethyl hydroxy- I, propyl cellulose in water 7 20% W/w in methanol 21/2% W/w carboxymethyl Marginally in cellulose in water feriorto standard mix tures. Satis factory.

8 20% W/w in methanol 21/2% W/w methyl hydroxy propyl cellulose in water 9 20% W/w in methanol 71/2% W/w carboxymethyl As good as the cellulose in water standard mix tures 10 20% W/w in methanol 71/2% w/w methyl hydroxy propyl cellulose in water 11 20% W/w in methanol 10% W/w carboxymethyl Marginally in cellulose in water feriorto standard mix tures. Satis factory 12 20% W/w in methanol 10% W/w methyl hydroxy- Slightly better propyl cellulose in than the standard water mixtures 13 30% W/w in methanol 21/2% W/w carboxymethyl Marginally in cellulose in water feriorto standard mix tures Satisfactory 14 30% W/w in methanol 21/2%w/wmethylhydroxy- propyl cellulose in water 15 30% W/w in methanol 71/2%W/wcarboxymethyl Standard mixture cellulose in water 16 30% W/w in methanol 71/2% W/w methyl hydroxy- D propyl cellulose in water 17 30% W/w in methanol 10% W/w carboxymethyl Marginally in cellulose in water feriorto standard mix tures Satisfactory 18 30% W/w in methanol 10% W/w methyl hydroxy- As good as the propyl cellulose in standard mix water tures Test Concentration of Concentration of Remarks Z4-dihydroxyhenzo- cellulose solu phenone tion Test Concentration of Concentration of Remarks 2,4-dih ydroxyb enzo- cellulose solu phenone tion Test Concentration of Concentration of Remarks 2,4-dih ydroxybenzo- cellulose solu phenone tion

Claims (32)

1. A method of cancelling a previously applied machine-readable luminescent address code on a paper surface layer-provided postal item comprising applying on top of the previously applied luminescent address code an ink which is substantially transparent to visible light and which includes a substance which absorbs ultraviolet light without luminescing and emitting visible light, the ink including a binder such that it does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent the previously applied luminescent address code from being read upon a subsequent interrogation by an address reading machine.

2. A method of cancelling a previously applied machine-readable luminescent address code on a paper surface layer-provided postal item which includes the steps of irradiating the postal item with ultraviolet light, monitoring the surface of the postal item for the presence of a previously applied luminescent address code and upon detection of a previously applied luminescent address code, applying an ink on top of the previously applied luminescent address code, the ink including a binder such that it does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent the previously applied luminescent address code from being read upon a subsequent interrogation by an address reading machine.

3. A method as claimed in claim 1 or 2, wherein said substance is formed by a compound having a C=X group, X being a heteroatom directly or indirectly conjugated to one or preferably two aromatic nuclei.

4. An ink according to claim 3, in which the C=X group is a carbonyl (C=O), an imine (C=NH) or an azine (CH=N-N=CH) group.

5. A method according to claim 3 or 4, in which the aromatic nuclei are benzene or furan rings.

6. A method according to any one of claims 3 to 5, in which the substance is a benzophenone.

7. A method according to claim 6, in which the substance is 2,4-dihydroxybenzophenone.

8. A method according to any one of the preceding claims, in which the substance is present in the ink in an amount in a range from 15 to 30% by weight.

9. A method according to claim 8, in which the substance is present in the ink in an amount in a range from 20 to 25% by weight.

10. A method according to any one of the preceding claims, in which the binder is a cellulose derivative.

11. A method according to claim 10, in which the binder is carboxymethyl cellulose or methylhydroxypropyl cellulose.

12. A method according to any one of the preceding claims, in which the binder is present in the ink in an amount in the range from 1 to 4% by weight.

13. A method according to claim 12, in which the binder is present in the ink in an amount of substantially 2% by weight.

14. A method as claimed in claim 2 or any one of claims 3 to 13 when appended to claim 2, which is carried out employing an apparatus comprising irradiating means which irradiates the postal item with ultraviolet light, monitoring means at which the surface of the postal item is monitored for the presence of a previously applied luminescent address code and an applicator at which a said ultraviolet radiation absorbing ink is applied to the postal item on top of the previously applied luminescent address code to absorb ultraviolet light directed towards the previously applied luminescent address code on any subsequent interrogation by an address reading machine.

15. A method as claimed in claim 14, wherein said apparatus includes an automatic letter facer to orient the postal item in the correct way at a downstream portion thereof.

16. A method according to claim 14 or 15, in which a photodetector responsive to visible radiation comprised by the means for monitoring the surface of the postal item for the presence of a previously applied luminescent address code scans the surface of the postal item and, in response to any visible radiation emitted by the surface, outputs a signal to indicate the presence of a previously applied luminescent address code.

17. A method as claimed in any one of claims 14 to 16, wherein the applicator of said apparatus comprises a first absorbent roller with a second absorbent roller and an ink bath for impregnating the first absorbent roller with ink for application to the postal item thereby.

18. A method of cancelling a previously applied machine readable luminescent address code, substantially as hereinbefore described with reference to the accompanying drawing.

19. A method of cancelling a previously applied machine-readable luminescent address code, substantially as described in either of the foregoing Examples I and II.

20. An ink for cancelling a luminescent address code on a paper surface postal item comprising a substance which absorbs ultra-violet light without luminescing and emitting visible light, a binder and a solvent, the ink also being substantially transparent to visible light and the binder being such that the ink does not penetrate the paper surface layer of the postal item to an extent such that said substance exists at a depth therein at which it is unable to prevent a previously applied luminescent address code from being read on a subsequent interrogation by an address reading machine.

21. An ink according to claim 20, in which the C=X group is a carbonyl (C=O), an imine (C=NH) or an azine (CH=N-N=CH) group.

22. An ink according to any one of claims 20 to 21, in which the aromatic nuclei are benzene or furan rings.

23. An ink according to any one of claims 20 to 22, in which the substance is a benzophenone.

24. An ink according to claim 23, in which the substance is 2,4-dihydroxybenzophenone.

25. An ink according to any one of claims 20 to 24, in which the substance is present in an amount in a range from 15 to 30% by weight.

26. An ink according to claim 25, in which the substance is present in an amount in a range from 20 to 25% by weight.

27. An ink according to any one of claims 20 to 26, in which the binder is a cellulose derivative.

28. An ink according to claim 27, in which the binder is carboxymethyl cellulose or methylhydroxypropyl cellulose.

29. An ink according to any one of claims 20 to 28, in which the binder is present in an amount in a range from 1 to 4% by weight.

30. An ink according to claim 29, in which substantially 2% by weight of the binder is present.

31. An ink according to claim 20, substantially as described with reference to either of the accompanying Examples I and ll.

32. An ink according to claim 20, substantially as described with reference to to the accompanying Example Ill.