CA1157305A - Method of improving the heat economy in a process of making groundwood - Google Patents
Method of improving the heat economy in a process of making groundwoodInfo
- Publication number
- CA1157305A CA1157305A CA000378112A CA378112A CA1157305A CA 1157305 A CA1157305 A CA 1157305A CA 000378112 A CA000378112 A CA 000378112A CA 378112 A CA378112 A CA 378112A CA 1157305 A CA1157305 A CA 1157305A
- Authority
- CA
- Canada
- Prior art keywords
- water
- pulp
- groundwood
- grinding
- groundwood 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
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
- D21B1/14—Disintegrating in mills
- D21B1/18—Disintegrating in mills in magazine-type machines
- D21B1/24—Disintegrating in mills in magazine-type machines of the pocket type
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
Abstract
Abstract of the Disclosure A method of improving the heat economy in a process of making groundwood pulp by grinding wood with a rotating grinding member (2) in a pressurized grinding space (3) and by spraying warm shower water (G) into the grinding space. The groundwood pulp (C) obtained is thickened by removing water (F) from the pulp and the water removed is again used as shower water (G) for the grinding space.
Simultaneously with the thickening step the groundwood pulp is cooled by spraying thereon cooling water (E) having a lower tempe-rature than the pulp. At least a part (El) of said cooling water is recovered and added to said water (F) removed from the pulp as replacement water for shower water lost in the grinding process.
Thus, the heat energy generated into the groundwood pulp due to the grinding process is utilized for heating the replacement water, thereby avoiding the necessity of using external energy for said heating.
Simultaneously with the thickening step the groundwood pulp is cooled by spraying thereon cooling water (E) having a lower tempe-rature than the pulp. At least a part (El) of said cooling water is recovered and added to said water (F) removed from the pulp as replacement water for shower water lost in the grinding process.
Thus, the heat energy generated into the groundwood pulp due to the grinding process is utilized for heating the replacement water, thereby avoiding the necessity of using external energy for said heating.
Description
mis invention relates to a method of improving the heat economy in a process of making groundwood, according to which method wood is ground with a rotating grinding member in a pressurized grinding space, warm shower water is sprayed into the grinding space, the groundwood pulp that is obtained is thickened by removing water from the pulp, and the thickened pulp is stored and~or bleached after cooling.
It is known to grind under atmospheric pressure blocks of wood which have been debarked and sawn to a certain length. The blocks arebrought in batches on conveyors above a grinding pocket, from where they are dropped into the grind-ing pocket when the previous batch has been ground.
The wood is defibrated by pressing the batch of wood against the grinding stone by means of a hydraulic piston. The friction between wood and the grinding stone warms the wood, and the lignin which binds the fibers is softened, whereby the fibers are separated. The water sprayed onto the grinding stone contributes to the defibration and transfers away from the grinding zone the frictional energy generated by the rotation of the grinding stone and the wood being ground. The shower waters also flush the separated fibers into the pulp chest positioned under the grinding stone. Tests have proved that the temperature of the shower water affects the defibration, when high temper-atures of shower water are used, the separated fibers are more uniform and longer. Due to the long fibers, the strength characteristics of paper made of such fibers are better than that of paper made of fibers produced using low temperature shower water. Tests have proved that in normal grinding the effect of warm shower water is relatively weak.
,~
- 1 - ~g -` 1157305 Also pressurized grinding in a grinding space at a pressure exceeding atmospheric pressure is known (U. S.
Patents Nos. 3,808,090, 3,948,449, 4,207,139, 4,207,703 and 4,274,600, and 9ritish Patent ~o. 1,519,848).
Wood is fed into the pressurized grinding space for instance by means of gate operated pressure equalizing chambers built above the grinding pockets of the grinder.
me grinding space, defined by the gates and the pulp chest, is pressurized preferably by means of air or steam.
The defibratioh takes place as in normal grinding by pressing wood blocks against the grinding stone by means of a hydraulic piston. Vibration caused by the grinding stone, heat caused by the friction, and the shower water separate the fibers from the wood material.
It has been observed that in pressurized grinding the temperature of shower water has greater influence on the defibration than in grinding at atmospheric pressure, The warmer the shower waters are, the longer and more uniform are the fibers separated from the wood material, and the 20 stronger is the paper made of such fibers. Thus the warmer the shower waters are when returned to the grinder, the better for the pressurized grinding.
After defibration the pulp suspension flows out from the grinding space through a pipe in which sticks and bigger slabs of wood are made finer by a stick crusher before adjusting the flow rate. The temperature of the pulp discharged from the grinding space is normally more than 100C. Under practical circumstances the pulp temper-ature may rise up to 145C, which depends on the temperature 30 of the shower water and on the pressure of the grinding space.
The temperature of the shower water when sprayed into the "~p ~ -- 2 --grinding space must be 130-135C and the pressure in the grinding space must be 3 bar. Heat energy contained in the pulp suspension is released in the form of steam in a cyclone in which the pressure is reduced to atmospheric pressure.
From the cyclone pulp can flow directly into a thickener where the hot shower water is separated from the pulp and returned to the grinding space. From the cyclone the pulp can also be discharged into a tank from which it can be pumped to different kinds of screening steps, e.g. to a pressuxized screen or a hydro cleaner, before it flows into a thickener where the hot shower water is separated from the pulp. Also the screen rejects can be processed in the usual manner by thickening, refining and screening before they are passed to the thickener for separating the shower water from the pulp. From this thickener the pulp is dis-charged with a consistency of 10-33%.
A disadvantage of this known method is that to-gether with the discharged pulp the process loses 2-lOyo of the warm shower water. The temperature of the replacement water is often considerably lower, generally 50-60C. This replacement shower water having a low temperature decreases by 2-SC the total temperature of the shower water which is fed into the grinding space.
In addition, the pulp chest must often have large dimensions, whereby there is a large cooling surface and with resulting large loss of heat. The temperature of the pulp leaving the thickener is also too high, 90-100C
At this temperature the pulp is likely to get dark during storage, and is difficult to bleach for instance with peroxide.
The object of this invention is to provide a method eliminating the above-mentioned disadvantages and improving the heat economy in a process of making groundwood under pressure, and to make the groundwood pulp discharged from the thickener more suitable for storage and bleaching.
In accordance with the invention there is provided a method of improving the heat economy in a process of making groundwood. The method requires replacement water for water contained in a groundwood pulp produced by the method.
According to the method, wood is ground with a rotating grinding member in a pressurized grinding space while shower water is sprayed into the grinding space. The groundwood pulp is fed to a thickener in which (a) water at lower temperature than the feed pulp is sprayed onto the feed pulp and (b) water is removed from the groundwood pulp which has been sprayed with the lower temperature water.
Thus, the groundwood pulp is cooled and the lower tempera-ture water is heated. The cooled groundwood pulp is then subjPcted to further treatment. Substantially only the water removed from the groundwood pulp is utilized as the shower water in the grinding space. The lower temperature water is substantially the exclusive source for the replacement water.
The invention is based on the idea of causing heat transfer between the groundwood pulp to be thickened and the cold replacement water added to the shower water, so that heat is transferred from the groundwood pulp to the replacement water. Thus the cold replacement for the shower water becomes warmer and the temperature of the shower water of the pressure grinding process remains high, at the same time the pulp to be discharged from the thickener is cooled.
l 157305 In the simplest embodiment of the method only enough water is sprayed on the groundwood pulp to be thickened as is required for providing the necessary amount of warm replacement water, but it is preferable to spray on the groundwood pulp sufficient water that the pulp is cooled down to a temperature which is suitable for storage and/or bleaching. In this way the groundwood pulp is cooled by the same water spraying step to a temperature required for further treatment.
In one embodiment of the method, water is sprayed in two parts, one part substantially corresponding to the amount of replacement water required for the shower water for the grinding space, and the other part corresponding to the amount of water which in addition to said first part is required for cooling the groundwood pulp down to said further treatment temperature. This facilitates an independent adjustment of both the amount of replacement water for the shower water for the pressure grinding process and the amount of water required for cooling the groundwood pulp.
The invention will be described in the following in more detail with reference to the accompanying drawing which shows schematically a pressure grinding process according to the invention, The drawing shows a grinder 1 comprising a grinding stone 2 rotating in a pressurized grinding space 3. The grinding space forms two grinding pockets 4 above which there are well known pressure equalizing chambers 5 closed by gates. On opposite sides of the grinding stone there are hydraulic pistons 6 for pressing blocks of wood dropped into the grinding pockets against the grinding stone, The grinding space is provided with a number of shower pipes 7 for supplying warm shower water onto the grinding stone.
For collection of the groundwood pulp there is a pulp pit 8 in the lower part of the grinding space.
A pipe 9 for groundwood pulp A extends from the pulp pit of the grinder via a stick crusher 10 to a cyclone 11 which is provided with a steam exhaust pipe 12. From the cyclone the groundwood pulp B, which is relieved of pressure, flows through a pipe 13 to a tank 14~ From this tank extends a pipe 15 through a pump 16 and a pressure screen 17 to a thickener 18 for the groundwood pulp C to be thickened. The thickener is equipped with an outlet 19 for the thickened groundwood pulp D.
The thickener is provided with two shower pipes 20 and 21 for spraying cold water E on the pulp to be thickened. The thickener comprises a vat 22 both for the water F which is removed from the groundwood pulp and for the water El which is sprayed from the first shower pipe, and another vat 23 for water E2 which is sprayed from the second shower pipe. From the vat 22 a pipe 24 extends to a tank 25, and from the vat 23 a pipe 26 extends to a cooling water tank 27. From the tank 25 a pipe 28 extends through a pump 29 to the shower pipes 7 in the grinding space for supplying warm shower water G to said shower pipes.
When groundwood pulp is being made, shower water circulates continuously through the circulation system formed by the pipes 9-13-24-28, As shown in the drawing substantially only water removed from the groundwood pulp is utilized as shower water. A part of the shower water is lost with the thickened groundwood pulp and due to other _ .
losses of water from the process, exhausting steam etc., more water must be fed into the circulation system than escapes from the thickener with the pulp. The water El which is sprayed on the groundwood pulp from the shower pipe 20 is now used as a replacement water and as shown in the drawing, is substantially the exclusive source for the replacement water. This water gets warm at the same time as it cools the pulp, Thus the replacement water is heated by the heat energy of the groundwood pulp which improves the heat economy of the process. By means of cooling water E2 which is sprayed from the shower pipe 21 the groundwood pulp is cooled further to a temperature which is low enough for storing and bleaching.
The groundwood pulp C enters the thickener at a temperature of 99-100C, and the temperature of the outgoing thickened pulp D does not exceed 70C. The temperature of the water which is fed into the shower pipes 20, 21 is not more than 60C.
If for instance the pulp enters the thickener at a temperature of 99C and leaves it with a consistency of 15%, the need of replacement water is 6.7% of the total shower water. If the temperature of this replacement water is 50C, the total temperature of the shower water is 0.067 x 50C + 0,933 x 99C = 95.7C
If the method according to the invention is used and replacement water at 50C is sprayed continuously on the groundwood pulp in the thickener, and if there is one shower pipe, the temperature of the outgoing pulp and the replace-ment water will be:
99C + 50C = 74 5C
:
If there are two shower pipes, the average temper-ature of the replacement water is 99C + 0.5 x 50C + 0,5 x 50C
99C + 0 5 x 50C 1.5 ( 1 5 1.5 ): 2 = 77.2C
and the temperature of the outgoing pulp is 71.7C.
Therefore, with the method according to the invention the total temperature of the circulating water will be 0.067 x 77.2C + 0.933 x 99C = 97.5C and the temperature of the outgoing pulp is 71.7C.
The drawing and the description shall only illustrate the principle of the invention. In its details the method may vary within the scope of the claims.
It is known to grind under atmospheric pressure blocks of wood which have been debarked and sawn to a certain length. The blocks arebrought in batches on conveyors above a grinding pocket, from where they are dropped into the grind-ing pocket when the previous batch has been ground.
The wood is defibrated by pressing the batch of wood against the grinding stone by means of a hydraulic piston. The friction between wood and the grinding stone warms the wood, and the lignin which binds the fibers is softened, whereby the fibers are separated. The water sprayed onto the grinding stone contributes to the defibration and transfers away from the grinding zone the frictional energy generated by the rotation of the grinding stone and the wood being ground. The shower waters also flush the separated fibers into the pulp chest positioned under the grinding stone. Tests have proved that the temperature of the shower water affects the defibration, when high temper-atures of shower water are used, the separated fibers are more uniform and longer. Due to the long fibers, the strength characteristics of paper made of such fibers are better than that of paper made of fibers produced using low temperature shower water. Tests have proved that in normal grinding the effect of warm shower water is relatively weak.
,~
- 1 - ~g -` 1157305 Also pressurized grinding in a grinding space at a pressure exceeding atmospheric pressure is known (U. S.
Patents Nos. 3,808,090, 3,948,449, 4,207,139, 4,207,703 and 4,274,600, and 9ritish Patent ~o. 1,519,848).
Wood is fed into the pressurized grinding space for instance by means of gate operated pressure equalizing chambers built above the grinding pockets of the grinder.
me grinding space, defined by the gates and the pulp chest, is pressurized preferably by means of air or steam.
The defibratioh takes place as in normal grinding by pressing wood blocks against the grinding stone by means of a hydraulic piston. Vibration caused by the grinding stone, heat caused by the friction, and the shower water separate the fibers from the wood material.
It has been observed that in pressurized grinding the temperature of shower water has greater influence on the defibration than in grinding at atmospheric pressure, The warmer the shower waters are, the longer and more uniform are the fibers separated from the wood material, and the 20 stronger is the paper made of such fibers. Thus the warmer the shower waters are when returned to the grinder, the better for the pressurized grinding.
After defibration the pulp suspension flows out from the grinding space through a pipe in which sticks and bigger slabs of wood are made finer by a stick crusher before adjusting the flow rate. The temperature of the pulp discharged from the grinding space is normally more than 100C. Under practical circumstances the pulp temper-ature may rise up to 145C, which depends on the temperature 30 of the shower water and on the pressure of the grinding space.
The temperature of the shower water when sprayed into the "~p ~ -- 2 --grinding space must be 130-135C and the pressure in the grinding space must be 3 bar. Heat energy contained in the pulp suspension is released in the form of steam in a cyclone in which the pressure is reduced to atmospheric pressure.
From the cyclone pulp can flow directly into a thickener where the hot shower water is separated from the pulp and returned to the grinding space. From the cyclone the pulp can also be discharged into a tank from which it can be pumped to different kinds of screening steps, e.g. to a pressuxized screen or a hydro cleaner, before it flows into a thickener where the hot shower water is separated from the pulp. Also the screen rejects can be processed in the usual manner by thickening, refining and screening before they are passed to the thickener for separating the shower water from the pulp. From this thickener the pulp is dis-charged with a consistency of 10-33%.
A disadvantage of this known method is that to-gether with the discharged pulp the process loses 2-lOyo of the warm shower water. The temperature of the replacement water is often considerably lower, generally 50-60C. This replacement shower water having a low temperature decreases by 2-SC the total temperature of the shower water which is fed into the grinding space.
In addition, the pulp chest must often have large dimensions, whereby there is a large cooling surface and with resulting large loss of heat. The temperature of the pulp leaving the thickener is also too high, 90-100C
At this temperature the pulp is likely to get dark during storage, and is difficult to bleach for instance with peroxide.
The object of this invention is to provide a method eliminating the above-mentioned disadvantages and improving the heat economy in a process of making groundwood under pressure, and to make the groundwood pulp discharged from the thickener more suitable for storage and bleaching.
In accordance with the invention there is provided a method of improving the heat economy in a process of making groundwood. The method requires replacement water for water contained in a groundwood pulp produced by the method.
According to the method, wood is ground with a rotating grinding member in a pressurized grinding space while shower water is sprayed into the grinding space. The groundwood pulp is fed to a thickener in which (a) water at lower temperature than the feed pulp is sprayed onto the feed pulp and (b) water is removed from the groundwood pulp which has been sprayed with the lower temperature water.
Thus, the groundwood pulp is cooled and the lower tempera-ture water is heated. The cooled groundwood pulp is then subjPcted to further treatment. Substantially only the water removed from the groundwood pulp is utilized as the shower water in the grinding space. The lower temperature water is substantially the exclusive source for the replacement water.
The invention is based on the idea of causing heat transfer between the groundwood pulp to be thickened and the cold replacement water added to the shower water, so that heat is transferred from the groundwood pulp to the replacement water. Thus the cold replacement for the shower water becomes warmer and the temperature of the shower water of the pressure grinding process remains high, at the same time the pulp to be discharged from the thickener is cooled.
l 157305 In the simplest embodiment of the method only enough water is sprayed on the groundwood pulp to be thickened as is required for providing the necessary amount of warm replacement water, but it is preferable to spray on the groundwood pulp sufficient water that the pulp is cooled down to a temperature which is suitable for storage and/or bleaching. In this way the groundwood pulp is cooled by the same water spraying step to a temperature required for further treatment.
In one embodiment of the method, water is sprayed in two parts, one part substantially corresponding to the amount of replacement water required for the shower water for the grinding space, and the other part corresponding to the amount of water which in addition to said first part is required for cooling the groundwood pulp down to said further treatment temperature. This facilitates an independent adjustment of both the amount of replacement water for the shower water for the pressure grinding process and the amount of water required for cooling the groundwood pulp.
The invention will be described in the following in more detail with reference to the accompanying drawing which shows schematically a pressure grinding process according to the invention, The drawing shows a grinder 1 comprising a grinding stone 2 rotating in a pressurized grinding space 3. The grinding space forms two grinding pockets 4 above which there are well known pressure equalizing chambers 5 closed by gates. On opposite sides of the grinding stone there are hydraulic pistons 6 for pressing blocks of wood dropped into the grinding pockets against the grinding stone, The grinding space is provided with a number of shower pipes 7 for supplying warm shower water onto the grinding stone.
For collection of the groundwood pulp there is a pulp pit 8 in the lower part of the grinding space.
A pipe 9 for groundwood pulp A extends from the pulp pit of the grinder via a stick crusher 10 to a cyclone 11 which is provided with a steam exhaust pipe 12. From the cyclone the groundwood pulp B, which is relieved of pressure, flows through a pipe 13 to a tank 14~ From this tank extends a pipe 15 through a pump 16 and a pressure screen 17 to a thickener 18 for the groundwood pulp C to be thickened. The thickener is equipped with an outlet 19 for the thickened groundwood pulp D.
The thickener is provided with two shower pipes 20 and 21 for spraying cold water E on the pulp to be thickened. The thickener comprises a vat 22 both for the water F which is removed from the groundwood pulp and for the water El which is sprayed from the first shower pipe, and another vat 23 for water E2 which is sprayed from the second shower pipe. From the vat 22 a pipe 24 extends to a tank 25, and from the vat 23 a pipe 26 extends to a cooling water tank 27. From the tank 25 a pipe 28 extends through a pump 29 to the shower pipes 7 in the grinding space for supplying warm shower water G to said shower pipes.
When groundwood pulp is being made, shower water circulates continuously through the circulation system formed by the pipes 9-13-24-28, As shown in the drawing substantially only water removed from the groundwood pulp is utilized as shower water. A part of the shower water is lost with the thickened groundwood pulp and due to other _ .
losses of water from the process, exhausting steam etc., more water must be fed into the circulation system than escapes from the thickener with the pulp. The water El which is sprayed on the groundwood pulp from the shower pipe 20 is now used as a replacement water and as shown in the drawing, is substantially the exclusive source for the replacement water. This water gets warm at the same time as it cools the pulp, Thus the replacement water is heated by the heat energy of the groundwood pulp which improves the heat economy of the process. By means of cooling water E2 which is sprayed from the shower pipe 21 the groundwood pulp is cooled further to a temperature which is low enough for storing and bleaching.
The groundwood pulp C enters the thickener at a temperature of 99-100C, and the temperature of the outgoing thickened pulp D does not exceed 70C. The temperature of the water which is fed into the shower pipes 20, 21 is not more than 60C.
If for instance the pulp enters the thickener at a temperature of 99C and leaves it with a consistency of 15%, the need of replacement water is 6.7% of the total shower water. If the temperature of this replacement water is 50C, the total temperature of the shower water is 0.067 x 50C + 0,933 x 99C = 95.7C
If the method according to the invention is used and replacement water at 50C is sprayed continuously on the groundwood pulp in the thickener, and if there is one shower pipe, the temperature of the outgoing pulp and the replace-ment water will be:
99C + 50C = 74 5C
:
If there are two shower pipes, the average temper-ature of the replacement water is 99C + 0.5 x 50C + 0,5 x 50C
99C + 0 5 x 50C 1.5 ( 1 5 1.5 ): 2 = 77.2C
and the temperature of the outgoing pulp is 71.7C.
Therefore, with the method according to the invention the total temperature of the circulating water will be 0.067 x 77.2C + 0.933 x 99C = 97.5C and the temperature of the outgoing pulp is 71.7C.
The drawing and the description shall only illustrate the principle of the invention. In its details the method may vary within the scope of the claims.
Claims (4)
1. A method of improving the heat economy in a process of making groundwood, the method requiring replacement water for water contained in a groundwood pulp produced by the method, according to which method wood is ground with a rotating grinding member in a pressurized grinding space while shower water is sprayed into the grinding space, the groundwood pulp is fed to a thickener in which (a) water at a lower temperature than the feed pulp is sprayed onto the feed pulp and (b) water is removed from the groundwood pulp which has been sprayed with said lower temperature water, whereby the groundwood pulp is cooled and said lower temperature water is heated, the cooled groundwood pulp is then subjected to further treatment, and substan-tially only said water removed from the groundwood pulp is utilized as said shower water in the grinding space, said lower temperature water being substantially the exclusive source for said replacement water.
2. A method according to claim 1, wherein enough lower temperature water is sprayed onto the feed pulp in the thickener to cool the groundwood pulp to a temperature appropriate for at least one of the operations of storing and bleaching.
3. A method according to claim 2, wherein said lower temperature water is sprayed in at least two separate streams, the quantity of the first stream corresponding substantially to the amount of said replacement water, and the quantity of the second stream corresponding to the amount of water required, in addition to the first stream, for cooling the groundwood pulp to said appropriate temperature.
4. The method of claim 1 in which only enough lower temperature water is sprayed on the feed pulp as is required for providing said replacement water.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI801784A FI59628C (en) | 1980-06-03 | 1980-06-03 | FOERFARANDE FOER FOERBAETTRING AV AVERMEEKONOMIN AV TILLVERKNINGSPROCESSEN FOER TRAESLIPMASSA |
| FI801784 | 1980-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157305A true CA1157305A (en) | 1983-11-22 |
Family
ID=8513535
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000378112A Expired CA1157305A (en) | 1980-06-03 | 1981-05-22 | Method of improving the heat economy in a process of making groundwood |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU7127281A (en) |
| BR (1) | BR8103481A (en) |
| CA (1) | CA1157305A (en) |
| DE (1) | DE3120927A1 (en) |
| FI (1) | FI59628C (en) |
| SE (1) | SE445232B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5060791B2 (en) * | 2007-01-26 | 2012-10-31 | 独立行政法人森林総合研究所 | Method for drying wood, method for penetrating chemicals into wood and drying apparatus |
-
1980
- 1980-06-03 FI FI801784A patent/FI59628C/en not_active IP Right Cessation
-
1981
- 1981-05-22 CA CA000378112A patent/CA1157305A/en not_active Expired
- 1981-05-26 DE DE19813120927 patent/DE3120927A1/en not_active Withdrawn
- 1981-06-02 SE SE8103456A patent/SE445232B/en unknown
- 1981-06-02 BR BR8103481A patent/BR8103481A/en unknown
- 1981-06-02 AU AU71272/81A patent/AU7127281A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| SE8103456L (en) | 1981-12-04 |
| FI59628C (en) | 1981-09-10 |
| FI59628B (en) | 1981-05-29 |
| AU7127281A (en) | 1981-12-10 |
| SE445232B (en) | 1986-06-09 |
| BR8103481A (en) | 1982-02-24 |
| DE3120927A1 (en) | 1982-06-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |