GB2072079A - Methods and apparatus for treating electrically non-conductive workpieces - Google Patents
Methods and apparatus for treating electrically non-conductive workpieces Download PDFInfo
- Publication number
- GB2072079A GB2072079A GB8108970A GB8108970A GB2072079A GB 2072079 A GB2072079 A GB 2072079A GB 8108970 A GB8108970 A GB 8108970A GB 8108970 A GB8108970 A GB 8108970A GB 2072079 A GB2072079 A GB 2072079A
- Authority
- GB
- United Kingdom
- Prior art keywords
- workpiece
- electrodes
- arc
- electrode
- laser beam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims description 24
- 239000000463 material Substances 0.000 claims description 10
- 230000004907 flux Effects 0.000 claims description 4
- 238000005275 alloying Methods 0.000 claims description 3
- 230000007935 neutral effect Effects 0.000 claims description 3
- 239000012811 non-conductive material Substances 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 2
- 230000003190 augmentative effect Effects 0.000 abstract description 3
- 238000013532 laser treatment Methods 0.000 abstract 1
- 238000003466 welding Methods 0.000 description 12
- 239000007789 gas Substances 0.000 description 11
- 238000005520 cutting process Methods 0.000 description 9
- 239000011261 inert gas Substances 0.000 description 5
- 239000004020 conductor Substances 0.000 description 3
- 239000004744 fabric Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 206010037660 Pyrexia Diseases 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- -1 card Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000010985 leather Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/20—Uniting glass pieces by fusing without substantial reshaping
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/346—Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding
- B23K26/348—Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding in combination with arc heating, e.g. TIG [tungsten inert gas], MIG [metal inert gas] or plasma welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/40—Removing material taking account of the properties of the material involved
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/30—Organic material
- B23K2103/38—Fabrics, fibrous materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/30—Organic material
- B23K2103/40—Paper
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/30—Organic material
- B23K2103/42—Plastics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
- B23K2103/52—Ceramics
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Laser Beam Processing (AREA)
Abstract
Non-conductive workpieces present a problem where laser treatment of a workpiece is to be augmented by the application of an arc, since the arc cannot be struck to the workpiece. In the present invention a laser beam 10 is augmented by an arc struck between an electrode 26 and an electrode 17 which is usually on the other side of the workpiece 15 from the laser beam. The arc then usually either penetrates the workpiece, or two arcs are formed on respective sides of the workpiece. Inert or reactive gas may be directed at the heated zone of the workpiece. <IMAGE>
Description
SPECIFICATION
Methods and apparatus for treating electrically
non-conductive workpieces
The present invention relates to methods and
apparatus for treating non-electrically conducting
workpieces using a laser.
The term "treating" in this specification includes
cutting, welding, drilling, surface hardening, surface
alloying and thermally treating, and the word
"workpiece", particularly in welding, includes the
plural.
UK Patent Specification 1,547,172, US Patent
Specification No. 4,167,662 and the specification for
UK Patent Application No. 6008/78 explain that
methods formerly employed for treating a workpiece
using a laser do not reach the potential performance
indicated by linear extrapolation from low power
work. The above mentioned specifications then dis
close an invention in which an arc is struck between
an electrode and a heat affected zone created in the workpiece by projecting a laser beam onto the work
piece.
According to a first aspect of the present invention there is provided a method for treating a workpiece
comprising projecting a beam of light from a laser
onto a workpiece formed from non-conductive mat
erial, and applying a voltage between at least two
electrodes to strike an arc, the electrodes being so
positioned that the arc impinges on the workpiece within a heat affected zone created by the laser beam
in the workpiece.
In this specification and claims the term "non
conductive material" includes all materials which
are not generally classed as conductors and thus, for
example, the term includes semiconductors in addition to insulators.
The heat affected zone is that zone of the work
piece which is raised to a comparatively high temp
erature by energy from the laser.
Conveniently the workpiece may be interposed
between the, or at least two of, the electrodes.
Preferably the arc extends through the workpiece; for example during cutting the arc may extend through the cut and during welding the arc may
extend through the gap between the unwelded portions of the workpiece adjacent to the point where welding is taking place. lftheworkpiece is thin
and/or porous, for example paper or cloth, the arc
may extend through small holes in the workpiece.
Alternatively, first and second arcs may extend
from a first electrode to the workpiece and from the workpiece to a second electrode, respectively, or a
single arc may extend from one electrode to the
workpiece. The single arc may be on the same side
of the workpiece as the laser beam or when the heat affected zone extends through the workpiece to an
opposite surface thereof, the single arc may extend
from the said opposite surface to one of the elec
trodes.
The main advantage of the present invention is
that the arc travels preferentially down a plasma
induced by the laser to the heat affected zone and
the workpiece burns in a controlled way or increases in electrical conductivity with temperature as in the cutting of glass or paper. In either case heat, useful in the heat treating process is transferred from the arc to the workpiece and hence the heat provided by the laser beam is augmented. The methods and apparatus of the above mentioned specifications are therefore modified in a way which allows a nonconductive workpiece to be treated even though the material of the workpiece cannot, due to its inability to conduct well, be effectively connected in the circuit applying the arc. For example the workpiece could not be effectively connected to earth.
Another advantage is that the additional power supplied to the non-conductive workpiece is expected, for welding, to result in a weld with a narrow heat affected zone and a large depth to width ratio indicating high penetration.
Preferably a jet of gas from a nozzle is also projected at the said heat affected zone; the gas may be inert or may react with either the workpiece, the electrode (for welding) or a flux.
As indicated above the invention may be used, for example, in cutting glass and paper, and cloth, card, leather, plastics, ceramics and semiconductors may also be cut Other applications include welding glass and plastic, vulcanising rubber and thermally setting resins.
The method of the invention may include so causing relative movement between the said zone and the workpiece, while maintaining the arc or arcs between one of the electrodes and the workpiece, that the treatment is carried out as required.
For surface alloying the method according to the invention may include applying material, to be alloyed with a portion of the surface of the workpiece, to the said portion and at the same time, or after, so causing relative movement between the said zone and the workpiece that the said zone visits every point in the area to be surface alloyed.
A multi-phase supply may be used to cause arcing and if so more than two electrodes may be used. For example in a three phase arrangement, three electrodes connected to line voltages may be positioned on one side of the workpiece with another electrode connected to neutral positioned on the other side.
According to a second aspect of the present invention there is provided apparatus for treating a workpiece comprising means for projecting a laser beam on to a workpiece, at least first and second electrodes spaced apart from one another, and means for applying a voltage between the electrodes to strike an arc which, in operation, impinges on the workpiece at a point within a heat affected zone created by the laser beam in the workpiece.
Preferably, in operation, the arc extends through the workpiece from one electrode to the other electrode, the arc either passing through a cut or gap in the workpiece or penetrating the workpiece material.
Apparatus according to the invention may include means for causing relative movement between the said zone and the workpiece while maintaining the arc between one of the electrodes and the said zone.
The apparatus may include means for projecting either a jet of gas from a nozzle towards the heat affected zone from a position opposite one work
piece surface which receives the laser beam or from
a position opposite another workpiece surface, or
projecting jets of gas from first and second nozzles
towards the heat affected zone from positions oppo
site the said one and the said other workpiece sur
faces respectively.
The gas may be exothermically reactive with the
expected workpiece andlor flux expected to be
applied to the workpiece.
The apparatus may include means for deflecting
away from the laser beam at least part of the plume
of gaseous materials andfor particles which is emitted from the point of incidence of the laser beam on the workpiece.
In the method and apparatus of the invention the electrodes, or one of the electrodes, may be positioned nearest the workpiece at a point in the workpiece where treatment is just about to take place.
Certain embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows a first apparatus according to the invention and illustrates the method of the invention, and
Figure 2 shows a second apparatus according to the invention which also illustrates the method.
An arrangement for welding or cutting using an inert gas, or a reactive gas, such as oxygen or chlorine, which takes part in an exothermic reaction is shown in Figure 1. A laser beam 10 is focussed at a point 16 on a workpiece 15 by means of a lens 22. The workpiece 15 is made of non-electrically conducting material and since the figure is intended to show a general arrangement, the workpiece is not shown, for example as being partially cut or as made up of two portions being welded, rather its position and general form only are shown.
The inert gas used for welding or the reactive gas used for cutting passes through an inlet 23 into a housing 24 having a nozzle 25 which is, in operation, just above the point 14.
Afirst electrode 17, for example a block of graphite ortunsten and usually connected as an anode, is positioned on the opposite side of the workpiece from the laser beam. In addition a further electrode 26, usually connected as a cathode, is positioned on the opposite side of the workpiece from the electrode 17 and is shielded by an inert gas directed by gas shield 27 having an inlet 28.
A voltage is applied between the electrodes 17 and 26 to strike an arc between these electrodes through a cut or gap in the workpiece. For example if the workpiece is being cut the arc passes through the cut adjacent to the point at which cutting is taking place.
Similarly if the workpiece is being welded the arc
passes through the gap between the unwelded portions of the workpiece adjacent to the point at which welding is taking place. In this way adjacent to the
point at which welding is taking place. In this way
heat is transferred from the arc to the workpiece to
assist cutting, for example by means of charring, or welding. There are thus two or three sources of heat for use in heat treatment; the laser beam, the reaction between the reactive gas (when used) and the
workpiece, and the arc struck between the electrodes. In other modes of operation the arc may
penetrate the workpiece without forming a cut, for
example if a paper or cloth workpiece is being tre
ated the arc may penetrate minute perforations in the workpiece without cutting the workpiece in two.
The arc may also extend from the electrode 26 to the workpiece and then a separate arc may exist from the workpiece to the electrode 17 and it is also poss
ible that only one of these arcs may be present dur
ing treatment, depending on the relative distances between electrode 17 and the workpiece and between the electrode 26 and the workpiece.
In Figure 2 the same components are used as in
Figure 1 but an additional electrode 30 which is shielded by inert gas in the same way as the electrode 26 is provided. This electrode can be used with the electrode 26 and a further electrode (not shown) for working from a three phase supply. The electrodes 26 and 30 are connected to respective line terminals of the supply by way of conductors 31 and 32 and the further electrode is connected to the other line terminal. A connection 33 connects the electrode 17 to the neutral of the three phase supply.
A further nozzle 34 with an inlet 35 for reactive or inert gas projects gas towards the heat affected zone on the opposite side of the workpiece 15 from the laser beam 10.
A schematic indication of means for moving the workpiece relative to the laser beam is shown in the form of a clamp 36, a lead screw 37 and an electric motor 38. The workpiece may for example move in the direction of the arrow 39 while being cut or welded so that the electrode 26 is nearest to the workpiece where treatment is about to take place.
The arc from this electrode therefore prepares the next part of the workpiece to be treated. In order to allow the laser beam to reach the workpiece more easily, a further gas nozzle, or one of the nozzles shown, may be used to blow the plume of gaseous materials and/or particles which forms above the point at which treatment occurs.
While one embodiment of the invention has been specifically described it will be realised that the invention may be put into effect in many other ways, for example using apparatus based on the disclosures of the above mentioned specifications but modified according to the invention. Many of these mod ifications have been indicated above. It will be realised that, particularly in some modes of operation mentioned above, there are limitations on the size and type of workpiece which can be used. Clearly the workpiece must not be too thick and the applied voltage must be sufficient for striking the required arc.
However these limitations can be resolved by sinfple test procedures.
Claims (24)
1. A method for treating a workpiece comprising projecting a beam of light from a laser onto a workpiece formed from non-conductive material and applying a voltage between at least two electrodes to strike and arc, the electrodes being so positioned that the arc impinges on the workpiece within a heat affected zone created by the laser beam in the workpiece.
2. A method according to Claim 1 wherein the workpiece is interposed between the, or at least two of the, electrodes.
3. A method according to Claim 1 or 2 wherein the arc extends through the workpiece.
4. A method according to Claim 1 or 2 wherein the arc extends from a first of the electrodes to the workpiece and a further arc extends from the workpiece to a second of the electrodes.
5. A method according to any preceding claim wherein gas is projected towards the said heat affected zone.
6. A method according to Claim 5 wherein the gas reacts with the workpiece or with a flux applied in the method.
7. A method according to any preceding claim including so causing relative movement between the said zone and the workpiece while maintaining the arc or arcs between one of the electrodes and the workpiece that the treatment is carried out as required.
8. A method according to any of Claims 1 to 6 for surface alloying, the workpiece including applying material, to be alloyed with a portion of the surface of the workpiece, to the said portion and at the same time, or after, so causing relative movement between the said zone and the workpiece that the said zone visits every point in the area to be surface alloyed.
9. A method according to any preceding claim employing a plurality of arcs wherein a multi-phase electrical supply is used to strike the said arcs.
10. A method according to Claim 7,8 or 9 wherein the electrodes are, or one of the electrodes is, positioned nearest the workpiece at a point in the workpiece where treatment is just about to take place.
11. Apparatus for treating a workpiece comprising means for projecting a laser beam on to a workpiece, at least first and second electrodes spaced apart from one another, and means for applying a voltage between the electrodes to strike an arc which, in operation, impinges on the workpiece at a point within a heat affected zone created by the laser beam in the workpiece.
12. Apparatus according to Claim 11 wherein, in operation, the arc extends through the workpiece from one electrode to the other electrode, the arc either passing through a cut or gap in the workpiece or penetrating the workpiece material.
13. Apparatus according to Claim 11 or 12 including means for causing relative movement between the said zone and the workpiece while maintaining the arc between one of the electrodes and the said zone.
14. Apparatus according to Claim 13 wherein the electrodes are, or one of the electrodes is, so positioned that in operation, the distance between the workpiece and the said electrode or electrodes is a minimum at a point where treatment is just about to take place.
15. Apparatus according to any of Claims 11 to 14 including means for projecting gas towards the heat affected zone.
16. Apparatus according to Claim 15 wherein the means for projecting gas does so from a position opposite one workpiece surface which receives the laser beam or from a position opposite another workpiece surface.
17. Apparatus according to Claim 15 wherein the means for projecting gas does so from a first position opposite one workpiece surface which receives the laser beam and from a second position opposte another workpiece surface.
18. Apparatus according to any of Claims 15 to 17 wherein the gas is exothermically reactive with at least one workpiece material or at least one flux.
19. Apparatus according to any of Claims 11 to 18 including means for deflecting away from the laser beam at least part of the plume or gaseous materials and/or particles which is emitted from the point of incidence of the laser beam on the workpiece.
20. Apparatus according to any of Claims 11 to 19 constructed for operation from a multi-phase electrical supply, wherein the first electrode is arranged for connection to one phase, and at least one other electrode (which may be the second electrode) is arranged for connection to another phase.
21. Apparatus according to Claim 20 wherein one electrode is arranged for connection to the neutral of a multi-phase supply.
22. A method of treating a workpiece substantially as hereinbefore described.
23. Apparatus for treating a workpiece substantially as hereinbefore described with reference to, and as shown in, Figure 1 of the accompanying drawings.
24. Apparatus for treating a workpiece substantially as hereinbefore described with reference to, and as shown in, Figure 2 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8108970A GB2072079B (en) | 1980-03-25 | 1981-03-23 | Methods and apparatus for treating electrically non-conductive workpieces |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8009981 | 1980-03-25 | ||
| GB8108970A GB2072079B (en) | 1980-03-25 | 1981-03-23 | Methods and apparatus for treating electrically non-conductive workpieces |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2072079A true GB2072079A (en) | 1981-09-30 |
| GB2072079B GB2072079B (en) | 1984-07-25 |
Family
ID=26274956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8108970A Expired GB2072079B (en) | 1980-03-25 | 1981-03-23 | Methods and apparatus for treating electrically non-conductive workpieces |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2072079B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0129603A4 (en) * | 1982-12-17 | 1985-06-10 | Inoue Japax Res | Laser machining apparatus. |
| GB2168638A (en) * | 1984-11-19 | 1986-06-25 | Control Laser Limited | Thermal cutting |
| EP0224113A1 (en) * | 1985-11-25 | 1987-06-03 | International Business Machines Corporation | Method and apparatus for laser-cutting of composite materials |
| CN102971121A (en) * | 2010-07-02 | 2013-03-13 | 肖特公开股份有限公司 | Hole creation with multiple electrodes |
-
1981
- 1981-03-23 GB GB8108970A patent/GB2072079B/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0129603A4 (en) * | 1982-12-17 | 1985-06-10 | Inoue Japax Res | Laser machining apparatus. |
| GB2168638A (en) * | 1984-11-19 | 1986-06-25 | Control Laser Limited | Thermal cutting |
| EP0224113A1 (en) * | 1985-11-25 | 1987-06-03 | International Business Machines Corporation | Method and apparatus for laser-cutting of composite materials |
| CN102971121A (en) * | 2010-07-02 | 2013-03-13 | 肖特公开股份有限公司 | Hole creation with multiple electrodes |
| CN102971121B (en) * | 2010-07-02 | 2015-11-25 | 肖特公开股份有限公司 | Multi-electrode is utilized to form hole |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2072079B (en) | 1984-07-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |