CA1278449C - Method and apparatus for making paper - Google Patents
Method and apparatus for making paperInfo
- Publication number
- CA1278449C CA1278449C CA000534052A CA534052A CA1278449C CA 1278449 C CA1278449 C CA 1278449C CA 000534052 A CA000534052 A CA 000534052A CA 534052 A CA534052 A CA 534052A CA 1278449 C CA1278449 C CA 1278449C
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- Prior art keywords
- fibre
- stock
- measurement
- distribution
- produce
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- 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 - Lifetime
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Abstract
A B S T R A C T
A method and apparatus for making paper from fibrous stock. The stock is passed through adjustable refin-ing means and the refined stock is analysed using fibre anal-ysing means to obtain characteristic output information. The output information is compared with reference information ob-tained by the prior analysis of stock known to have produced paper of a desired quality, and the refining means is adjust-ed to produce a stock the analysis of which produces output information substantially the same as the reference inform-ation.
A method and apparatus for making paper from fibrous stock. The stock is passed through adjustable refin-ing means and the refined stock is analysed using fibre anal-ysing means to obtain characteristic output information. The output information is compared with reference information ob-tained by the prior analysis of stock known to have produced paper of a desired quality, and the refining means is adjust-ed to produce a stock the analysis of which produces output information substantially the same as the reference inform-ation.
Description
~27~34~
METHOD AND APPARATUS FOR MARING_ PAPER
The present invention relates to the making of paper and paper boards and in particular, to a method and apparatus for adjus-ting fibre treatment appara~us to produce paper having desired qualities.
In the machine manufacture of paper and cellulose products, the paper making materials, known as 'stock"
usually consist of a water suspension of wood or vegetable fibres which have been separated by chemical or mechanical means. These fibres are combined with additional ingredients such as dye stuffs, alum, clay and the like, to impart the desired characteristics to the finished paper product.
Preparation of the ibre stock is a most critical processing phase, which greatly determines the quality and physical characteristics of the finished product. The properties of wood and natural fibres vary, even in the same plant species, due to differences in fact~rs affecting growth. Other variations are introduced by the chemical and mechanical processes which reduce timber logs to individual cellulose fibres. To improve uniformity, the final preparation of the fibres prior to forming into a sheet on the paper machine i5 by treating the slurry of fibres in machines known as beaters and refiners. These machines typically have rotating parts faced with metal or abrasivesr and corresponding fixed parts similarly faced with metal or abrasi~es.
During operation the rotating parts are maintained at a controlled very small spacing from the adjacent corresponding fixed metal or abrasi~e faced parts. The fibres are crushed by being pumped in a slurry -through the spacing. The fibres which are originally relatively smooth and tubular in shape are smashed, and their exteriors develop fine fibrils which interlock or "felt" together when the slurry is formed into a sheet, contributing greatly to the strength of the finished product.
METHOD AND APPARATUS FOR MARING_ PAPER
The present invention relates to the making of paper and paper boards and in particular, to a method and apparatus for adjus-ting fibre treatment appara~us to produce paper having desired qualities.
In the machine manufacture of paper and cellulose products, the paper making materials, known as 'stock"
usually consist of a water suspension of wood or vegetable fibres which have been separated by chemical or mechanical means. These fibres are combined with additional ingredients such as dye stuffs, alum, clay and the like, to impart the desired characteristics to the finished paper product.
Preparation of the ibre stock is a most critical processing phase, which greatly determines the quality and physical characteristics of the finished product. The properties of wood and natural fibres vary, even in the same plant species, due to differences in fact~rs affecting growth. Other variations are introduced by the chemical and mechanical processes which reduce timber logs to individual cellulose fibres. To improve uniformity, the final preparation of the fibres prior to forming into a sheet on the paper machine i5 by treating the slurry of fibres in machines known as beaters and refiners. These machines typically have rotating parts faced with metal or abrasivesr and corresponding fixed parts similarly faced with metal or abrasi~es.
During operation the rotating parts are maintained at a controlled very small spacing from the adjacent corresponding fixed metal or abrasi~e faced parts. The fibres are crushed by being pumped in a slurry -through the spacing. The fibres which are originally relatively smooth and tubular in shape are smashed, and their exteriors develop fine fibrils which interlock or "felt" together when the slurry is formed into a sheet, contributing greatly to the strength of the finished product.
4~
By praotical experience, an optimum degree of refining is determined for any specific product. Under-refining may produce a low strength product; over-refining may affect opacity, texture and other qualities, in addition to wasting considerable energy.
Several beaters and refiners operating in parallel are required to prepare stock for a single pape~ machine. For practical reasons such as routine maintenanc~, the internal mechan~cal condition of the refiners will vary. For example reconditioning of the refiners is performed in se~uence by shutting down a single unit while others in the parallel system continue to operate. Thus, a set of refiners feeding a single paper machine may consist of some new or freshly reconditioned units, while others are worn and ready to be reconditioned. The effect of such unequal refiners on wood fibres will vary greatly, the reconditioned machines requiring less energy input to produce the desired refining result than i5 required of a worn machine. The new or reconditioned machines may also tend to cu~ a greater proportion of fibres than will a worn machine.
To achiev~ the desired degree of fibre treatment, the common practice in paper mills i5 to control the beaters and refiners according to a predetermined energy input per ton of fibre stock, in terms of Horsepower Tons per Day.
The fibre slurry is passed through the beaters or refiners until a desired horsepower per hour has been expended per ton of fibre in the system. But as noted above, a uniform energy input will not necessarily produce a uniformly treated fibre stock, as the internal condition of the machines may vary.
Hitherto, the degree of refining achieved for a particular mixture of fibres has not been able to be con~irmed until the fibre has been formed into a dried sheet, samples of which are periodically subjected to a series of physical tests to check ~uality. To provide for uninterrupted feeding of the continuously running paper machine, yet allow for product and formulation changes, the ~7~
beaters and refiners discharge into large holding tanks which are fed in sequence to the paper machine. Thus, a delay of up to several hours may occur before a batch of xefined stock is formed into sheets so that the result of refining can be confirmed. If the physical tests indica~e that under or over-refining has occurred, any correction made at the baaters or refiners to alter the energy input per ton of stock will not show an effect on the finished paper quality for a long period, during which a non-standard product will continue to be made.
- ~.
X
~LZ~ LA~
The cost in was~ed energy and possible price reduction of a lower grade product may be considerable.
It is an object of the present invention to provide a method of making paper and an apparatus for makinq paper in accordance with the method, which will overcome, or substantially ameliorate, the abovementioned disadvantages.
According to a first aspect of the invention there is provided a method of makinq paper of a selected quality from a type of fibrous stock. The method involves the steps of refining the stock, analysing the refined stock to produce a measurement of the distribution of fibre widths over a selected range of fibre widths, comparing said measurement with ~ reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type of stock refined to a degree known to produce paper of said selected quality, and adjusting the refining of the stock to produce a stock, the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
According to a second aspect of the invention there is provided an apparatus for making paper of a selected quality from a type of fibrous stock. The apparatus includes adjustable refining means to produce refined stock and a fibre fineness distribution analyser to produce a measurement of the distribution of fibre widths over a selected range of fibre widths in a sample of the refined stock. Storage means is provided to store a reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type "
~2~ 4~ .
of stock refined to a degree known to produce paper of said selected quality. The apparatus also includes means to compare said measurement with said reference measurement and means responsive to the difference between the measurement and the reference measurement to adjust the refining means to produce a stock, the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
In a preferred embodiment, the fibre fineness distribution analyser produces output information in the form of a fibre fineness distribution curve obtained by plo-tting fibre width against fibre count over said range of fibre widths and the refining means is adjusted to produce a stock the analysis of which produces a fibre fineness distribution ~; 15 curve substantially the same as a reference curve obtained by analysing stock known to produce paper having desired qualities.
An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which;
Figure 1 is a schematic diagram of part of a paper manufacturing system;
Figure 2 is a plot of fibre width against fibre count for four samples of the same fibre stock, each sample having been subjected to a different refining duration; and Figure 3 is a plot similar to Figure 2 for a different mixture of fibres.
As seen in Figure 1, the paper manufacturing system comprises a pump 11 which pumps stock along pipe 12 through refining means 13 and into a storage chest 15 via 12~ 9 pipe 14. The refining means 13 can be a beater or refiner as described above or any other suitable known means.
F.rom chest 15 the stock is pumped by pump 17 via pipes 16 to a feed tank 18. The level of stock in the t~nk 18 i~
controlled by a float valve 19. The stock feeds ~rom the bottom of tank 18 via nozzle 20 onto a continuous wire gauze belt 21 driven around rollers 22. Movement of the belt 21 causes the stock ~o form a thin layer on the belt 21. The thin layer is dried by being passed around heated surfaces to become paper or paper board.
A sampling device 23 is connected by sampling tube 24 to pipe 14 on the downs~ream side of refining means 13.
The sa~pling device 23 continuously removes a small sample of the stock from pipe 14 and pumps the sample via tube 25 to fibre analysing means 26 comprising a fibre fineness distribution analyser model FDA 200 manufactured by Information Electronics Ltd. of Canberra, Australia.
The fibre fineness distribution analyser (not shown) is characterized by a narrow tube or channel through which a sample of the papermaking fibre slurry 1OWS, and a laser optics arrangement which views the slurry through a transparent section of the channel. Typically~ the transparent section has parallel optically flat sides enclosing a narrow passage, the laser beam is arranged to penetrate transversely through both sides of the channel and the contained fibre slurry, to impinge upon a laser target on the opposite sid~e of the channel.
~he laser beam and target are arranged to view a circular area of the flow channel, the circle having a diameter substantially less than the average length of the fibres to be viewed. A complementary electronic system is arranged to generate a signal at the instant of maximum obscuring of the laser target by an intervening fibre.
Since the diameter of the viewing circle is fixed, the length of any observed fibre is that of the circle diameter, and the magnitude of the signal generated will vary in proportion to the area o~ the target which has been X
-` ~2~ 9 obscured by the fibre, and the signal may then be computed in terms of the fibre width, or fineness~ In further refinement of the fibre fineness distribution analyser, the circular viewing area is divided into two halves, the dividing line being parallel to the flow direction, thus forming the viewing "window" into two semi-circular halves.
The la~er target is similarly arranged to generate a separate signal from each semi-circular area of the viewing window.
In the corresponding electronic measuring system, a fibre must obscure an equal area of each semi-circular target and thus generate two equal simul-taneous electronic signals in order for its measured width to be accepted for recording purposes.
If the electronic signals corresponding to the two semi-circular areas are not equal, it is because a fibre is only partly across the viewing window, or because more than one fibre is passing the laser optics. Such signals may be erroneous, and are not accepted for recording purposes. In practice, fibres accepted for recording comprise 2V% - 35%
of total fibres viewed.
This apparatus produces for a range of fibre widths counts~of the number of fibres in a sample which have a selected fibre width. A fibre fineness distribution curve is obtained by plotting fibre width against fibre count.
Preferably, the range of fibre widths is from 7~m to 64~m and fibre count is obtained a-t increments of l~m. After analysis the sample is discharged ~ia tube 27 to storage chest 15.
The fibre fineness distribution curve is comp~red with a stored reference curve obtained by analysing stock known to produce paper having the desired qualities. A
correction signal determined by the difference in the measured curve and the reference curve is generated by fibre analysing means 26 and transmitted via line 28 to adjust refining means 13. The analysing means 26 continues to generate a correction signal until the fibre fineness ~7~L4~
distribution curve of -the stock being measured is susbtantially the same as the reference curve.
Figure 2 is a plot of fibre width against fibre count for four samples of fibre. The test samples were pure unbleached spruce fibres, prepared by kraft process and separately refined in the same beater for the beating times tabulated below.
Beating Time Equivalent Energy Input Sample No. iminutes~(Horsepower Tons/day) 4 10 2.8~
2 20 5.53 3 4~ 12.72 The fibre fineness distribution of each sample for fibres having a fineness or apparent width between 7~m and 64~m was measured using the FDA 200 analyser in accordance with normal operating procedure. The measurements were 2~ con~uc~ed using 10,000 counted ~ibres and repeated several times, the results averaged and plotted to obtain Figure 2.
The lines marked l J 2, 3 ,4 correspond to the sample numbers used in the above table.
Figure 3 is a similar plot of measurements conducted on four samples of a mixture of spruce and fir fihres, each sample having been subjected to refining times tabulated below.
Refining ~ime Sample No. (minutes~
~ 0 The lines marked 5, 6, 7, 8 correspond to the sample numbers used in the above table.
These lines are the ibre fineness distribution curves of the samples and the present invention is founded on the _ g _ ~2t7~
discovery or appreciation that each curve is uniquely related to the degree of refining of the particular fibxe or mixture of fibres and to the paper making quality of the sample~from which it ls derived. By recording fibre fineness distribu-tion curves of samples of stock and the qualities of the paper produced from the same stock it 1 possible to obtain the abovementioned reference curves corresponding to stock known to produce paper having desired qualities.
It will be apparent that the present invention/ by providing for the sampling and assessment of stock immediately after refining, allows rapid ad~ustment of optimum fibre refining to obtain a uniform paper product of desired quality.
The foregoing describes only one embodiment of the present invention and modifications may be made thereto by persons skilled in the art without departing from the scope of the present in~ention.
r -- 10 ~
By praotical experience, an optimum degree of refining is determined for any specific product. Under-refining may produce a low strength product; over-refining may affect opacity, texture and other qualities, in addition to wasting considerable energy.
Several beaters and refiners operating in parallel are required to prepare stock for a single pape~ machine. For practical reasons such as routine maintenanc~, the internal mechan~cal condition of the refiners will vary. For example reconditioning of the refiners is performed in se~uence by shutting down a single unit while others in the parallel system continue to operate. Thus, a set of refiners feeding a single paper machine may consist of some new or freshly reconditioned units, while others are worn and ready to be reconditioned. The effect of such unequal refiners on wood fibres will vary greatly, the reconditioned machines requiring less energy input to produce the desired refining result than i5 required of a worn machine. The new or reconditioned machines may also tend to cu~ a greater proportion of fibres than will a worn machine.
To achiev~ the desired degree of fibre treatment, the common practice in paper mills i5 to control the beaters and refiners according to a predetermined energy input per ton of fibre stock, in terms of Horsepower Tons per Day.
The fibre slurry is passed through the beaters or refiners until a desired horsepower per hour has been expended per ton of fibre in the system. But as noted above, a uniform energy input will not necessarily produce a uniformly treated fibre stock, as the internal condition of the machines may vary.
Hitherto, the degree of refining achieved for a particular mixture of fibres has not been able to be con~irmed until the fibre has been formed into a dried sheet, samples of which are periodically subjected to a series of physical tests to check ~uality. To provide for uninterrupted feeding of the continuously running paper machine, yet allow for product and formulation changes, the ~7~
beaters and refiners discharge into large holding tanks which are fed in sequence to the paper machine. Thus, a delay of up to several hours may occur before a batch of xefined stock is formed into sheets so that the result of refining can be confirmed. If the physical tests indica~e that under or over-refining has occurred, any correction made at the baaters or refiners to alter the energy input per ton of stock will not show an effect on the finished paper quality for a long period, during which a non-standard product will continue to be made.
- ~.
X
~LZ~ LA~
The cost in was~ed energy and possible price reduction of a lower grade product may be considerable.
It is an object of the present invention to provide a method of making paper and an apparatus for makinq paper in accordance with the method, which will overcome, or substantially ameliorate, the abovementioned disadvantages.
According to a first aspect of the invention there is provided a method of makinq paper of a selected quality from a type of fibrous stock. The method involves the steps of refining the stock, analysing the refined stock to produce a measurement of the distribution of fibre widths over a selected range of fibre widths, comparing said measurement with ~ reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type of stock refined to a degree known to produce paper of said selected quality, and adjusting the refining of the stock to produce a stock, the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
According to a second aspect of the invention there is provided an apparatus for making paper of a selected quality from a type of fibrous stock. The apparatus includes adjustable refining means to produce refined stock and a fibre fineness distribution analyser to produce a measurement of the distribution of fibre widths over a selected range of fibre widths in a sample of the refined stock. Storage means is provided to store a reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type "
~2~ 4~ .
of stock refined to a degree known to produce paper of said selected quality. The apparatus also includes means to compare said measurement with said reference measurement and means responsive to the difference between the measurement and the reference measurement to adjust the refining means to produce a stock, the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
In a preferred embodiment, the fibre fineness distribution analyser produces output information in the form of a fibre fineness distribution curve obtained by plo-tting fibre width against fibre count over said range of fibre widths and the refining means is adjusted to produce a stock the analysis of which produces a fibre fineness distribution ~; 15 curve substantially the same as a reference curve obtained by analysing stock known to produce paper having desired qualities.
An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which;
Figure 1 is a schematic diagram of part of a paper manufacturing system;
Figure 2 is a plot of fibre width against fibre count for four samples of the same fibre stock, each sample having been subjected to a different refining duration; and Figure 3 is a plot similar to Figure 2 for a different mixture of fibres.
As seen in Figure 1, the paper manufacturing system comprises a pump 11 which pumps stock along pipe 12 through refining means 13 and into a storage chest 15 via 12~ 9 pipe 14. The refining means 13 can be a beater or refiner as described above or any other suitable known means.
F.rom chest 15 the stock is pumped by pump 17 via pipes 16 to a feed tank 18. The level of stock in the t~nk 18 i~
controlled by a float valve 19. The stock feeds ~rom the bottom of tank 18 via nozzle 20 onto a continuous wire gauze belt 21 driven around rollers 22. Movement of the belt 21 causes the stock ~o form a thin layer on the belt 21. The thin layer is dried by being passed around heated surfaces to become paper or paper board.
A sampling device 23 is connected by sampling tube 24 to pipe 14 on the downs~ream side of refining means 13.
The sa~pling device 23 continuously removes a small sample of the stock from pipe 14 and pumps the sample via tube 25 to fibre analysing means 26 comprising a fibre fineness distribution analyser model FDA 200 manufactured by Information Electronics Ltd. of Canberra, Australia.
The fibre fineness distribution analyser (not shown) is characterized by a narrow tube or channel through which a sample of the papermaking fibre slurry 1OWS, and a laser optics arrangement which views the slurry through a transparent section of the channel. Typically~ the transparent section has parallel optically flat sides enclosing a narrow passage, the laser beam is arranged to penetrate transversely through both sides of the channel and the contained fibre slurry, to impinge upon a laser target on the opposite sid~e of the channel.
~he laser beam and target are arranged to view a circular area of the flow channel, the circle having a diameter substantially less than the average length of the fibres to be viewed. A complementary electronic system is arranged to generate a signal at the instant of maximum obscuring of the laser target by an intervening fibre.
Since the diameter of the viewing circle is fixed, the length of any observed fibre is that of the circle diameter, and the magnitude of the signal generated will vary in proportion to the area o~ the target which has been X
-` ~2~ 9 obscured by the fibre, and the signal may then be computed in terms of the fibre width, or fineness~ In further refinement of the fibre fineness distribution analyser, the circular viewing area is divided into two halves, the dividing line being parallel to the flow direction, thus forming the viewing "window" into two semi-circular halves.
The la~er target is similarly arranged to generate a separate signal from each semi-circular area of the viewing window.
In the corresponding electronic measuring system, a fibre must obscure an equal area of each semi-circular target and thus generate two equal simul-taneous electronic signals in order for its measured width to be accepted for recording purposes.
If the electronic signals corresponding to the two semi-circular areas are not equal, it is because a fibre is only partly across the viewing window, or because more than one fibre is passing the laser optics. Such signals may be erroneous, and are not accepted for recording purposes. In practice, fibres accepted for recording comprise 2V% - 35%
of total fibres viewed.
This apparatus produces for a range of fibre widths counts~of the number of fibres in a sample which have a selected fibre width. A fibre fineness distribution curve is obtained by plotting fibre width against fibre count.
Preferably, the range of fibre widths is from 7~m to 64~m and fibre count is obtained a-t increments of l~m. After analysis the sample is discharged ~ia tube 27 to storage chest 15.
The fibre fineness distribution curve is comp~red with a stored reference curve obtained by analysing stock known to produce paper having the desired qualities. A
correction signal determined by the difference in the measured curve and the reference curve is generated by fibre analysing means 26 and transmitted via line 28 to adjust refining means 13. The analysing means 26 continues to generate a correction signal until the fibre fineness ~7~L4~
distribution curve of -the stock being measured is susbtantially the same as the reference curve.
Figure 2 is a plot of fibre width against fibre count for four samples of fibre. The test samples were pure unbleached spruce fibres, prepared by kraft process and separately refined in the same beater for the beating times tabulated below.
Beating Time Equivalent Energy Input Sample No. iminutes~(Horsepower Tons/day) 4 10 2.8~
2 20 5.53 3 4~ 12.72 The fibre fineness distribution of each sample for fibres having a fineness or apparent width between 7~m and 64~m was measured using the FDA 200 analyser in accordance with normal operating procedure. The measurements were 2~ con~uc~ed using 10,000 counted ~ibres and repeated several times, the results averaged and plotted to obtain Figure 2.
The lines marked l J 2, 3 ,4 correspond to the sample numbers used in the above table.
Figure 3 is a similar plot of measurements conducted on four samples of a mixture of spruce and fir fihres, each sample having been subjected to refining times tabulated below.
Refining ~ime Sample No. (minutes~
~ 0 The lines marked 5, 6, 7, 8 correspond to the sample numbers used in the above table.
These lines are the ibre fineness distribution curves of the samples and the present invention is founded on the _ g _ ~2t7~
discovery or appreciation that each curve is uniquely related to the degree of refining of the particular fibxe or mixture of fibres and to the paper making quality of the sample~from which it ls derived. By recording fibre fineness distribu-tion curves of samples of stock and the qualities of the paper produced from the same stock it 1 possible to obtain the abovementioned reference curves corresponding to stock known to produce paper having desired qualities.
It will be apparent that the present invention/ by providing for the sampling and assessment of stock immediately after refining, allows rapid ad~ustment of optimum fibre refining to obtain a uniform paper product of desired quality.
The foregoing describes only one embodiment of the present invention and modifications may be made thereto by persons skilled in the art without departing from the scope of the present in~ention.
r -- 10 ~
Claims (6)
1. A method of making paper of a selected quality from a type of fibrous stock, said method comprising the steps of refining the stock, analysing the refined stock to produce a measurement of the distribution of fibre widths over a selected range of fibre widths, comparing said measurement with a reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type of stock refined to a degree known to produce paper of said selected quality, and adjusting the refining of the stock to produce a stock the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
2. A method as claimed in claim 1 wherein said measurement comprises counts of the number of fibres in a sample which have a selected fibre width.
3. A method as claimed in claim 1 wherein said measurement comprises a fibre fineness distribution curve obtained by plotting fibre width against counts of the number of fibres in a sample which have a selected width.
4. A method as claimed in claim 3 wherein said selected range of fibre widths is from 7 µm to 64 µm and fibre count is plotted at intervals of 1 µm.
5. A method as claimed in claim 1 further comprising the step of adjusting the refining of said stock by using a correction signal determined by the difference between said measurement and said reference measurement.
6. An apparatus for making paper of a selected quality from a type of fibrous stock, said apparatus comprising adjustable refining means to produce refined stock, a fibre fineness distribution analyser to produce a measurement of the distribution of fibre widths over a selected range of fibre widths in a sample of the refined stock, storage means to store a reference measurement of the distribution of fibre widths over said selected range of fibre widths obtained from a prior analysis of the same type of stock refined to a degree known to produce paper of said selected quality, means to compare said measurement with said reference measurement, and means responsive to the difference between said measurement and said reference measurement to adjust the refining means to produce a stock the analysis of which produces a measurement of the distribution of fibre widths substantially the same as said reference measurement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000534052A CA1278449C (en) | 1987-04-07 | 1987-04-07 | Method and apparatus for making paper |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000534052A CA1278449C (en) | 1987-04-07 | 1987-04-07 | Method and apparatus for making paper |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1278449C true CA1278449C (en) | 1991-01-02 |
Family
ID=4135383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000534052A Expired - Lifetime CA1278449C (en) | 1987-04-07 | 1987-04-07 | Method and apparatus for making paper |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1278449C (en) |
-
1987
- 1987-04-07 CA CA000534052A patent/CA1278449C/en not_active Expired - Lifetime
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