CA1158904A - Method and means for use in the manufacture of fibre pulp - Google Patents
Method and means for use in the manufacture of fibre pulpInfo
- Publication number
- CA1158904A CA1158904A CA000368494A CA368494A CA1158904A CA 1158904 A CA1158904 A CA 1158904A CA 000368494 A CA000368494 A CA 000368494A CA 368494 A CA368494 A CA 368494A CA 1158904 A CA1158904 A CA 1158904A
- Authority
- CA
- Canada
- Prior art keywords
- tight
- steam
- zone
- pressure
- pulp
- 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.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 19
- 239000000835 fiber Substances 0.000 title abstract description 16
- 238000004519 manufacturing process Methods 0.000 title abstract description 3
- 239000000463 material Substances 0.000 claims abstract description 56
- 239000007788 liquid Substances 0.000 claims description 10
- 230000006835 compression Effects 0.000 claims description 8
- 238000007906 compression Methods 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims 2
- 238000000605 extraction Methods 0.000 claims 1
- 230000010006 flight Effects 0.000 claims 1
- 239000012978 lignocellulosic material Substances 0.000 claims 1
- 238000012423 maintenance Methods 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 239000000126 substance Substances 0.000 abstract description 3
- 238000000227 grinding Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 6
- 238000005056 compaction Methods 0.000 description 4
- 208000028659 discharge Diseases 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- 208000036366 Sensation of pressure Diseases 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 241000905957 Channa melasoma Species 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 108091028051 Numt Proteins 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 238000004061 bleaching Methods 0.000 description 1
- 229920005610 lignin Polymers 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C7/00—Digesters
- D21C7/08—Discharge devices
Landscapes
- Paper (AREA)
- Disintegrating Or Milling (AREA)
- Chemical Treatment Of Fibers During Manufacturing Processes (AREA)
- Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
Abstract
ABSTRACT
Method and means for use in the manufacture of fibre pulp from lignocellulose containing material, wherein the fibre material, after treatment (10) under pressure together with steam, water and chemicals dissolved and/or suspended therein, is conveyed (12) to a vessel (14), also pressurized, wherefrom the fibre material is discharged separately.
The material outlet (24) of the vessel is provided with a steam-tight seal consisting only of the discharged fibre material in a compressed state.
Method and means for use in the manufacture of fibre pulp from lignocellulose containing material, wherein the fibre material, after treatment (10) under pressure together with steam, water and chemicals dissolved and/or suspended therein, is conveyed (12) to a vessel (14), also pressurized, wherefrom the fibre material is discharged separately.
The material outlet (24) of the vessel is provided with a steam-tight seal consisting only of the discharged fibre material in a compressed state.
Description
~5~9~
Method and Means for Use in the ~anufacture o~ Fib`re Pulp The present invention is concerned with a method for use in the manu~acture of fibre pulp ~rom lignocellulose containing material, wherein the fibre material, after treatment under pres-sure together with steam, water and chemicals dissolved and/or sus-pended therein, is conveyed to a vessel, also pressurized, where-from the fibre material is dischar~ed separately.
Thus the fibre material, having undergone treatment under pressure, e.g., in a process vessel or process apparatus such as grinding equipment wherein the pressure is generated by the sup-plied grinding energy or by steam, as for the purpose of manu-facturing fibre pulp by the so-called thermo-mechanical method, is thereafter discharged to a pressurized receiver. As disclosed in U.S. Patent No. 4,235,6~5 issued November 25, 1980, water vapor accompanying the material can be separated therefrom in the said receiver while maintaining the high pressure, making po~sible the efficient recovery of the energy of the steam. For this pur-pose the fibre material is discharged to a subsequent process step which takes place at a lower pressure, with the aid of var-ious air-lock devices such as pressure-tight rotary vane feeders, thick stock pumps etc. Thanks to the abrupt pressure drop in the discharged material the residual thermal energy therein causes the sudden evaporation of part of the water accompanying the said material. This sudden evaporation has a separating effect on the discharged material, resulting in a lower bulk density which re-quires special arrangements to be pro~ided for the continued treatment of thc material. Subsequent treatment is further com-plicated by the fact that the material~s bulk density consequently varies with preceding process fluctuations in respect of liquid, such as water, accompanying the material.
\
The main object of the invention is therefore to provide a method and a means fo~ the implementation thereof wherein the above-mentioned drawbacks and difficulties are eliminated by the simultaneous dewatering and compaction of the dischargecl material for the purpose of equalizing the concentration thereof. This object is attained in that the method and the means of the invention are given the features se-t forth in the Claims hereafter.
The invention will be further specified below in an embodiment in conjunction with the figure, which shows a section through a receiver for the implementat~on of the means according to the invention.
The numt~er 10 in the drawing denotes a pressurized grinding device, for example, a disc refiner comprising a housing which encloses two mutually rotatable grinding discs (not illustrated) between which incom-ing raw material passes to be ground or defibred. The ground material is discharged from the grinding device 10 together with accompanying water vapour via a pipeline 12 to a receiver 14, for example, a cyclone where-in the material is separated from the accompanying steam by centrifugal force~ The receiver 14 is given the form of a conventional cyclone but is designed for operation under the pressure in question and is equipped with a vertical conveying and compacting screw 16, 18 which feeds the material downwards. The screw 16, 18 is driven by a driving mechanism 20 comprising the bearings of the screw 16, 18 and a driving motor. The conveying secti.on 16 of the screw is enclosed by a continuous casing 22, while the compacting section 18 is enclosed by a perforated casing 24 which is enclosed in its turn by an continuous, pressure-tight cylinder 26. The screw 16, 18 and the casing 22, 24 taper conically towards the lower end of the cyclone 14. In order to prevent the discharged materi-al from rotating with the compaction screw 18 during the compession phase there is c~nnected to the casing 24 a toothed wheel 28 whose teeth 30 engage with the compacting screw 18 and effectively prevent or coun-teract rotation of the material with the screw, which might cause clog-ging of the discharge means and render it inoperative.
~ ~89~4 The perforated casing 24 of the compacting screw 18 is connected by a pressure-tight union to a pipe 32 which may be cylindrical or a slight taper in the'direction of conveying. The pipe 32 may be equipped with a damper 34, controlled in a suitable manner by means of a control lever 36, for adjusting the back pressure therein. The lower end of the pipe 32 is connected to a screw 40. The conveyor 38 is connected to a subse-~uent process step, such as a grinding apparatus 42 to whose intake opening 44 the material is delivered by means of a feed screw 46.
The excess steam from the steam releasing cyclone 14 is fed via a discharge pipe 48 at the top of the cyclone 14 and a valve 50 with a pressure regulator 52 to some process or plant in which the positive steam pressure is utilized. The regulator 52 controls the valve 50 via the pipeline 54 from the cyclone 14.
The cylinder 26 enclosing the perforated casing 24 of the compact-ing screw 18 is connected via a pipeline 56 to a liquid col'lector 58, which is connected via a pipeline 60 with a valve 66 to the steam dis charge pipe 48 from the cyclone 14. The collector 58 is also connected to a pump 62 which is controlled by a level regulator 64 located in the said collector. The'collector 58 may appropriately be kept at the same pressure as the pressure cyclone by pressure equalization via pipeline 60. If on the other hand it is desired to have the collector 58 at a lower pressure the valve 66 is closed and the pressure is controlled by means of a pressure regulator 68 which governs a steam vent 70.
The arrangement described above operates in the following manner.
The material which has been processed in the grinding apparatus 10 is transferred via pipeline 12 to the pressurized cyclone 14 and, after having been separated from accompanying steam~ is conveyed down towards the discharge opening of the cyclone by the conveying screw 16. The separated steam is carried off by pipeline 48. The material is trans-ferred by the feed screw 16 to the compacting screw 18 wherein the downcoming material is compressed into a pressure-tight plug which serves to maintain the pressure in the cyclone 14. The compression ' : ~
.
, ---" l 15~90~
of the material plug is also maintained by the cylindrical or slightly conical pipe 32 and the damper 34 therein so as to ensure an effective, pressure-tight seal between the pressure cyclone 14 and subsequent proces.s equipment, such as the screw 40 and the grinding apparatus 42.
In the pipe 32 there is provicled after the damper 34 a probe 78 ;nd;cat;ng temperature or pressure or both, which probe 78 influences a valve 74 controlling the supply of pressure medium, such as hyclraulic oil, air or steam, via a pipeline 76 to a cylinder 72 which is connected to the control lever 36 of the damper 34. When the probe indicates a temperature higher than normal in the discharge opening 32, implying that the fibre plug is too loose or that the supply of fibre material is inadequate and that s-team is escaping from the cyclone, the valve 74 will therefore open to admit pressure medium to the cylinder 72, which by actuating the lever 36 will partly or completely close the damper 34.
This prevents the release of the pressure inside the cyclone and a sudden escape of steam. The damper 34 may also be set up for manual operation when starting or stopping the plant or to be biassed with a certain constant pressure to increase the compression of the fibre plug in the discharge pipe, which also affects to some extent the degree of dewatering in the screw 40.
While the material is being compressed in the screw 18 inside the casing 24, wa-ter accompanying the material is pressed out and carried `off via the perforated casing 24 to the collector 5.8. The collector 58 may appropriately be kept at the same pressure as.the cyclone 14 by pressure equalization via pipeli.ne 60. If on the other hand it is desired to have the collector 58 at a lower pressure, the valve 66 can be closed and the collector pressure controlled by means of the pressure regulator 68 and the steam vent 70.
The compacting screw 18 generates a predetermined degree of com-pression depending on the compaction desired and on the nature of the material being processed. Inasmuch as a given compression results in a given proportion of material to residual liquid, such as water, the proportion of material to liquid most suitable for the following process can be maintained in this way within narrow limits. Fluctuations in the material-to-.liquid ratio in the process before the cyclone 14 are thus effectively eliminated.
.
Thanks to the dewatering effect obtained in the compacting screw 18, this compaction step can also be used as a washing step for removing chemicals which have been added earlier in the process or in the pres-sure cyclone 14 to achieve some desired effect, such as lignin libera-tion, bleaching etc., but whose presence is undesirable in subsequent processing steps. This dewatering and/or washing effect can be varied by the amount of washing liquid added to the`material flow before or in the pressure cyclone 14 before the material is compressed. The liquid so removed may be recovered via the collector 58 and the pump 62 for recla-mation and/or recycling.
The dewatering effect of the cyclone further makes it possible to mix screenings, for example, in the form of a pumpable aqueous suspen-sion, with the fibre suspension coming from the grinding apparatus, in which case the added extra liquid, being undesirable in the subsequent treatment (grinding, processing), of the fibre material, is removed by the dewatering effect of the compacting screw. This eliminates the need for special screening dewaterers or presses.
After discharge from the discharge pipe 32 the plug of material enters the casing 38, where it is fragmented by the screw 40 and con-veyed by the said screw to the intake opening 44 of the following grind-ing apparatus 42, where the screw 46 feeds the material into the grind-ing apparatus 42 for further processing.
Method and Means for Use in the ~anufacture o~ Fib`re Pulp The present invention is concerned with a method for use in the manu~acture of fibre pulp ~rom lignocellulose containing material, wherein the fibre material, after treatment under pres-sure together with steam, water and chemicals dissolved and/or sus-pended therein, is conveyed to a vessel, also pressurized, where-from the fibre material is dischar~ed separately.
Thus the fibre material, having undergone treatment under pressure, e.g., in a process vessel or process apparatus such as grinding equipment wherein the pressure is generated by the sup-plied grinding energy or by steam, as for the purpose of manu-facturing fibre pulp by the so-called thermo-mechanical method, is thereafter discharged to a pressurized receiver. As disclosed in U.S. Patent No. 4,235,6~5 issued November 25, 1980, water vapor accompanying the material can be separated therefrom in the said receiver while maintaining the high pressure, making po~sible the efficient recovery of the energy of the steam. For this pur-pose the fibre material is discharged to a subsequent process step which takes place at a lower pressure, with the aid of var-ious air-lock devices such as pressure-tight rotary vane feeders, thick stock pumps etc. Thanks to the abrupt pressure drop in the discharged material the residual thermal energy therein causes the sudden evaporation of part of the water accompanying the said material. This sudden evaporation has a separating effect on the discharged material, resulting in a lower bulk density which re-quires special arrangements to be pro~ided for the continued treatment of thc material. Subsequent treatment is further com-plicated by the fact that the material~s bulk density consequently varies with preceding process fluctuations in respect of liquid, such as water, accompanying the material.
\
The main object of the invention is therefore to provide a method and a means fo~ the implementation thereof wherein the above-mentioned drawbacks and difficulties are eliminated by the simultaneous dewatering and compaction of the dischargecl material for the purpose of equalizing the concentration thereof. This object is attained in that the method and the means of the invention are given the features se-t forth in the Claims hereafter.
The invention will be further specified below in an embodiment in conjunction with the figure, which shows a section through a receiver for the implementat~on of the means according to the invention.
The numt~er 10 in the drawing denotes a pressurized grinding device, for example, a disc refiner comprising a housing which encloses two mutually rotatable grinding discs (not illustrated) between which incom-ing raw material passes to be ground or defibred. The ground material is discharged from the grinding device 10 together with accompanying water vapour via a pipeline 12 to a receiver 14, for example, a cyclone where-in the material is separated from the accompanying steam by centrifugal force~ The receiver 14 is given the form of a conventional cyclone but is designed for operation under the pressure in question and is equipped with a vertical conveying and compacting screw 16, 18 which feeds the material downwards. The screw 16, 18 is driven by a driving mechanism 20 comprising the bearings of the screw 16, 18 and a driving motor. The conveying secti.on 16 of the screw is enclosed by a continuous casing 22, while the compacting section 18 is enclosed by a perforated casing 24 which is enclosed in its turn by an continuous, pressure-tight cylinder 26. The screw 16, 18 and the casing 22, 24 taper conically towards the lower end of the cyclone 14. In order to prevent the discharged materi-al from rotating with the compaction screw 18 during the compession phase there is c~nnected to the casing 24 a toothed wheel 28 whose teeth 30 engage with the compacting screw 18 and effectively prevent or coun-teract rotation of the material with the screw, which might cause clog-ging of the discharge means and render it inoperative.
~ ~89~4 The perforated casing 24 of the compacting screw 18 is connected by a pressure-tight union to a pipe 32 which may be cylindrical or a slight taper in the'direction of conveying. The pipe 32 may be equipped with a damper 34, controlled in a suitable manner by means of a control lever 36, for adjusting the back pressure therein. The lower end of the pipe 32 is connected to a screw 40. The conveyor 38 is connected to a subse-~uent process step, such as a grinding apparatus 42 to whose intake opening 44 the material is delivered by means of a feed screw 46.
The excess steam from the steam releasing cyclone 14 is fed via a discharge pipe 48 at the top of the cyclone 14 and a valve 50 with a pressure regulator 52 to some process or plant in which the positive steam pressure is utilized. The regulator 52 controls the valve 50 via the pipeline 54 from the cyclone 14.
The cylinder 26 enclosing the perforated casing 24 of the compact-ing screw 18 is connected via a pipeline 56 to a liquid col'lector 58, which is connected via a pipeline 60 with a valve 66 to the steam dis charge pipe 48 from the cyclone 14. The collector 58 is also connected to a pump 62 which is controlled by a level regulator 64 located in the said collector. The'collector 58 may appropriately be kept at the same pressure as the pressure cyclone by pressure equalization via pipeline 60. If on the other hand it is desired to have the collector 58 at a lower pressure the valve 66 is closed and the pressure is controlled by means of a pressure regulator 68 which governs a steam vent 70.
The arrangement described above operates in the following manner.
The material which has been processed in the grinding apparatus 10 is transferred via pipeline 12 to the pressurized cyclone 14 and, after having been separated from accompanying steam~ is conveyed down towards the discharge opening of the cyclone by the conveying screw 16. The separated steam is carried off by pipeline 48. The material is trans-ferred by the feed screw 16 to the compacting screw 18 wherein the downcoming material is compressed into a pressure-tight plug which serves to maintain the pressure in the cyclone 14. The compression ' : ~
.
, ---" l 15~90~
of the material plug is also maintained by the cylindrical or slightly conical pipe 32 and the damper 34 therein so as to ensure an effective, pressure-tight seal between the pressure cyclone 14 and subsequent proces.s equipment, such as the screw 40 and the grinding apparatus 42.
In the pipe 32 there is provicled after the damper 34 a probe 78 ;nd;cat;ng temperature or pressure or both, which probe 78 influences a valve 74 controlling the supply of pressure medium, such as hyclraulic oil, air or steam, via a pipeline 76 to a cylinder 72 which is connected to the control lever 36 of the damper 34. When the probe indicates a temperature higher than normal in the discharge opening 32, implying that the fibre plug is too loose or that the supply of fibre material is inadequate and that s-team is escaping from the cyclone, the valve 74 will therefore open to admit pressure medium to the cylinder 72, which by actuating the lever 36 will partly or completely close the damper 34.
This prevents the release of the pressure inside the cyclone and a sudden escape of steam. The damper 34 may also be set up for manual operation when starting or stopping the plant or to be biassed with a certain constant pressure to increase the compression of the fibre plug in the discharge pipe, which also affects to some extent the degree of dewatering in the screw 40.
While the material is being compressed in the screw 18 inside the casing 24, wa-ter accompanying the material is pressed out and carried `off via the perforated casing 24 to the collector 5.8. The collector 58 may appropriately be kept at the same pressure as.the cyclone 14 by pressure equalization via pipeli.ne 60. If on the other hand it is desired to have the collector 58 at a lower pressure, the valve 66 can be closed and the collector pressure controlled by means of the pressure regulator 68 and the steam vent 70.
The compacting screw 18 generates a predetermined degree of com-pression depending on the compaction desired and on the nature of the material being processed. Inasmuch as a given compression results in a given proportion of material to residual liquid, such as water, the proportion of material to liquid most suitable for the following process can be maintained in this way within narrow limits. Fluctuations in the material-to-.liquid ratio in the process before the cyclone 14 are thus effectively eliminated.
.
Thanks to the dewatering effect obtained in the compacting screw 18, this compaction step can also be used as a washing step for removing chemicals which have been added earlier in the process or in the pres-sure cyclone 14 to achieve some desired effect, such as lignin libera-tion, bleaching etc., but whose presence is undesirable in subsequent processing steps. This dewatering and/or washing effect can be varied by the amount of washing liquid added to the`material flow before or in the pressure cyclone 14 before the material is compressed. The liquid so removed may be recovered via the collector 58 and the pump 62 for recla-mation and/or recycling.
The dewatering effect of the cyclone further makes it possible to mix screenings, for example, in the form of a pumpable aqueous suspen-sion, with the fibre suspension coming from the grinding apparatus, in which case the added extra liquid, being undesirable in the subsequent treatment (grinding, processing), of the fibre material, is removed by the dewatering effect of the compacting screw. This eliminates the need for special screening dewaterers or presses.
After discharge from the discharge pipe 32 the plug of material enters the casing 38, where it is fragmented by the screw 40 and con-veyed by the said screw to the intake opening 44 of the following grind-ing apparatus 42, where the screw 46 feeds the material into the grind-ing apparatus 42 for further processing.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the method of producing pulp from lignocellulosic pulp material in which the material is treated in a steam pres-surized, moisture-containing environment and them discharged to-gether with high pressure steam into a vapor-tight vessel wherein excess steam is separated from the material and discharged via valve means, the separated pulp material being passed into a zone of lower pressure; the improvement comprising progressively com-pressing the material while removing moisture therefrom in a vapor-tight compacting zone interposed between said vapor-tight vessel and said zone of lower pressure to form a steam-tight plug providing a pressure-tight seal between said vapor-tight vessel and said zone of lower pressure during its passage into said zone.
2. The method according to Claim 1, in which the moisture-containing environment includes a liquid pulp treating media.
3. The method according to Claim 2, in which a washing liquid is added to the pulp material before said compacting zone to wash treating media from the pulp material during the com-pression step.
4. The method according to Claims 1 or 3, in which the dis-charge of pulp material from said vapor-tight vessel is controlled to maintain a degree of compression sufficient for the formation of the steam-tight plug and to maintain a constant degree of material concentration.
5. In an apparatus for producing pulp from lignocellulosic material, in which the pulp material is first treated in a steam-pressurized moisture-containing environment and the passed into a pressure-tight vessel for separating excess steam and pulp material, said vessel comprising a casing providing means for passing the pulp material into a zone of lower pressure, the improvement comprising:
a) a pressure-tight material compacting portion inter-posed between said casing and said zone of lower pressure; and b) compacting means for advancing the pulp material into said zone of lower pressure while progressively compressing it into a steam-tight plug while removing moisture therefrom to form a pressure-tight seal between said vessel and said zone of lower pressure.
a) a pressure-tight material compacting portion inter-posed between said casing and said zone of lower pressure; and b) compacting means for advancing the pulp material into said zone of lower pressure while progressively compressing it into a steam-tight plug while removing moisture therefrom to form a pressure-tight seal between said vessel and said zone of lower pressure.
6. The apparatus according to Claim 5, in which said com-pacting portion comprises a conical bore and said compacting means comprises a rotatable screw feeder conforming to the inner diameter of said conical bore and having helical flights and an intervening helical groove.
7. The apparatus according to Claims 5 or 6, in which said material compacting portion is provided with perforations per-mitting extraction of moisture from the compressed material, said portion being enclosed within a pressure-tight casing which is connected in a vapor-tight manner to collecting means.
8. The apparatus according to Claim 5, which comprises a sprocket wheel mounted rotatably in a slot in the casing enclos-ing said compacting section, said sprocket wheel having teeth frictionally engaging said helical groove for preventing the material from turning with the screw feeder during the advance-ment step.
9. The apparatus according to Claim 5, comprising means for controlling the advancement of pulp material into said zone of lower pressure to achieve a degree of compression sufficient for the formation and maintenance of the steam-tight plug at a con-stant degree of compression of the material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8000335A SE8000335L (en) | 1980-01-15 | 1980-01-15 | SET AND APPARATUS IN THE FIBER PREPARATION |
| SE8000335-3 | 1980-01-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1158904A true CA1158904A (en) | 1983-12-20 |
Family
ID=20339988
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368494A Expired CA1158904A (en) | 1980-01-15 | 1981-01-14 | Method and means for use in the manufacture of fibre pulp |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1158904A (en) |
| FI (1) | FI810092L (en) |
| NO (1) | NO810118L (en) |
| SE (1) | SE8000335L (en) |
-
1980
- 1980-01-15 SE SE8000335A patent/SE8000335L/en unknown
-
1981
- 1981-01-14 FI FI810092A patent/FI810092L/en not_active Application Discontinuation
- 1981-01-14 CA CA000368494A patent/CA1158904A/en not_active Expired
- 1981-01-14 NO NO810118A patent/NO810118L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| SE8000335L (en) | 1981-07-16 |
| FI810092L (en) | 1981-07-16 |
| NO810118L (en) | 1981-07-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |