CA1270687A - Flared pockets for centrifugal grinders - Google Patents
Flared pockets for centrifugal grindersInfo
- Publication number
- CA1270687A CA1270687A CA000518096A CA518096A CA1270687A CA 1270687 A CA1270687 A CA 1270687A CA 000518096 A CA000518096 A CA 000518096A CA 518096 A CA518096 A CA 518096A CA 1270687 A CA1270687 A CA 1270687A
- Authority
- CA
- Canada
- Prior art keywords
- axis
- rotor
- grinding surface
- pockets
- 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 - Fee Related
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
- D21B1/06—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by dry methods
- D21B1/063—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by dry methods using grinding devices
- D21B1/065—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by dry methods using grinding devices of the magazine type
-
- 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)
- Polishing Bodies And Polishing Tools (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A centrifugal grinder has an internal grinding surface-shaped as a surface of revolution, and a rotor mounted within the surface for rotation about the axis of the grinding surface. The rotor defines a generally axial inlet passageway for wood chips to be ground, and at least one pocket extending generally outwardly from the axis of the rotor toward the grinding surface. The pocket is provided with a configuration such that its cross section increases at an increasing rate away from the rotor axis. This encourages the wood chips to orient themselves parallel to the grinding surface, such that they take up such parallel orientation by the time they reach the grinding surface.
A centrifugal grinder has an internal grinding surface-shaped as a surface of revolution, and a rotor mounted within the surface for rotation about the axis of the grinding surface. The rotor defines a generally axial inlet passageway for wood chips to be ground, and at least one pocket extending generally outwardly from the axis of the rotor toward the grinding surface. The pocket is provided with a configuration such that its cross section increases at an increasing rate away from the rotor axis. This encourages the wood chips to orient themselves parallel to the grinding surface, such that they take up such parallel orientation by the time they reach the grinding surface.
Description
lZ7(~87 This invention relates generally to centrifugal grinders of the kind disclosed and claimed in my earlier U.S. Patent No. 4,474,335, issued October 2, 1984. The present invention relates more particularly to an improvement in the shape of the pocket or pockets provided in the rotor of a centrifugal grinder, along which wood chips and the like pass to be pressed by centrifugal force against the internal grinding surface of the stationary grinding stone.
BACKGROUND OF THIS INVENTION
It is generally appreciated in the wood pulp industry that, when grinding wood chips, it is very desirable to orient the grain of the chips parallel to the stone surface for the actual grinding operationO A
typical wood chip may measure about 1" x 1", with a thickness of 1/8" to ~". The grain runs parallel to one of the larger dimensions. When a wood chip is ground by lying against the grinding stone with lts largest surface, i.e. with the grain oriented substantially - parallel with the surface of the grinding stone, it is more likely whole fibres will be produced, rather than small, broken fibre fragments. Generally speaking, the larger the fibres, the better the quality of the resulting pulp.
GENERAL DESCRIPTION OF THIS INVENTION
The aim of an aspect of this invention is to provide a pocket configuration within the rotor of an internal centrifugal grinder which is such as to promote a parallel chip orientation by the time the chip reaches the grinding surface, i.e. an orientation in which the chip grain extends substantially parallel to the internal grinding surface.
I have discovered that by shaping the pocket or pockets in the rotor in a particular way, the desirable orientation of the chips can be to a large extent achieved. It will be understood that it is not a practical goal to seek the proper orientation of all of the wood chips. Because the chips are oriented in a lZ~ i87 random fashion initially, it is unlikely that in any given time span a uniform parallel orientation can be achieved for all of the chips. However, I have found that the pocket configuration provided herein allows better than three quarters of typical wood chips to assume, by the time they reach the grinding surface, an orientation in which they are parallel to the grinding surface and to each other.
More particularly, this invention provides an improvement in a centrifugal grinder having an internal grinding surface shaped as a surface of revolution, and a rotor mounted within the surface for rotation about the axis thereof, the rotor defining a generally axial inlet passageway for material to be ground. At least one pocket extends generally outwardly from the axis of the rotor toward the grinding surface, and the present improvement provides a configuration for the pocket wherein the cross-section of the pocket widens at an increasing rate away from the rotor axis.
GENERAL DESCRIPTION OF THE DRAWINGS
_ _ Three embodiments of this invention are illustrated schematically in the accompanying drawings which show the essential geometry without all of the accessory components, like numerals denoting like parts throughout the several views, and in which:
- Figure 1 is a longitudinal section through a first embodiment;
Figure 2 is a transverse section taken at the line A-A in Figure l;
Figure 3 is a longitudinal section through a second embodiment;
Figure 4 is a transverse section taken at the line A-A in Figure 3;
Figure 5 is a longitudinal section through a third embodiment;
Figure 6 is a transverse section taken at the line A-A in Figure 5;
Figure 7 is a longitudinal sectional view through a prior art construction;
06~37 Figure 8 is a transverse view taken at the line A-A
in Figure 7; and Figure 9 is a graphical representation of the rates at which the cross-sectional area of a pocket increases away from the axis of the rotor.
DETAILED DESCRIPTION OF THE DRAWINGS
.
Attention is first directed to Figures 7 and 8, which shows the prior art construction.
In the prior art construction, a grinding stone 10 defines an internal grinding surface 12 shaped as a surface of revolution, and more particularly as a cylinder having an axis shown at the line 14. Looking at Figure 8, a rotor 16 is provided, the rotor being mounted within the surface 12 for rotation about the axis 14. The rotor 16 defines a generally axial inlet passageway 18 for material such as wood chips to be ground, and two pockets 20 and 22, each extending generally outwardly away from the axis 14 of the rotor and toward the grinding surface 12. In the construction shown in Figures 7 and 8, the two pockets 20 and 22 extend in diametrically opposite directions, and are thus spaced at 180 from each other.
It will be noted in Figure 8 that each pocket 20, 22 is defined between generally rectilinear but slightly diverging walls 24. Figure 7 shows a cross section at right angles to the section of Figure 8, also cutting through the pockets 20 and 22. It will be seen that the pockets are defined by parallel walls 26 and 28, transverse to the axis 14.
If one were to calculate the cross-sectional area of the pockets 20 and 22 by determining, for different radii beginning at the wall of the passageway 18 and ending at the surface 12, the surface area of a series of theoretical cylinders lying within the pocket, the cylinders having the increasing radii, then one would arrive at the line identified by the numeral 27 in Figure 9, the line being also labelled "Fig. 4". As can be seen, this line is essentially a straight line, due to the fact that the walls of the pockets 20 and 22 are lz7a6s7 almost parallel in both directions. Because there is a very slight divergence as can be seen in the section of Figure 8, the cross-sectional area increases slightly in the outward direction, as indicated by the slight upward slope of the line 27 in the graph of Figure 9.
However, I have determined that a mere divergence by itself is not sufficient to encourage a large-scale re-orientation of the wood chips so that they lie, ir.
the main, parallel to the grinding surface by the time they reach the latter. In order to accomplish this large-scale re-orientation, it is necessary to ensure that the transverse section of the pocket widens at an increasing rate away from the rotor axis, and this is best accomplished by providing a flared configuration as seen in Figures 1 through 6.
Attention is first directed to Figures 1 and 2, illustrating the first embodiment of this invention. As can be seen, in Figure 1, the grinding stone 10 is again provided, with an internal cylindrical grinding surface 12. A rotor 30 is provided, rotatable about the axis 14 of the stone 10, the rotor 30 shaped to define an axial passageway 18a which opens into two oppositely extending pockets 32 and 34. As can be seen in Figure 1, each pocket 32, 34 is defined between walls 36 and 38 which widen at an increasing rate away from the axis 14. The section through the wall 36 is thus a curve, as is the section through the wall 38.
Referring to Figure 2, the dimension of each pocket 32, 34 in the direction transverse to the section of Figure 1 also widens at an increasing rate. The pocket 32 is defined between a flat wall 40 and a strongly curved wall 42, and the same is true for the pocket 34.
The strongly curved wall 42 in each case is the trailing wall in the sense of rotation, which in the view of Figure 2 is counter-clockwise.
If one were to utilize the precise geometry shown in Figures 1 and 2, and perform the same calculations as were done to arrive at the line 27 in Figure 9, one would arrive at the line identified by the numeral 44 in ~12~06~37 Figure 9, which is also labelled as "lst Embodiment".
As can be seen, the slope of the line 44 increases at a progressive rate from the left to the right, which corresponds to increasing distance away from the axis 14. The angle alpha drawn adjacent the line 44 in Figure 9 represents the slope of the line 44 at the leftward extremity, whereas the angle beta drawn at the upper right in Figure 9 represents the slope of the line 44 at the rightward extremity. The distance Dl in Figure 9 is proportional to the tangent of the angle alpha, whereas D2 is proportional to the tangent of the angle beta. It can be seen that D2, in effect a measure of the slope of the line 44 at the rightward end, is at least 8 times as large as Dl, which is the slope at the leftward end.
It is pointed out that the curves in Figure 9 are not measured in any specific units, but-are accurate in terms of showing the relative rate of increase of the cross section away from the axis.
Attention is now directed to Figures 3 and 4, which are similar to Figures 1 and 2, but are directed to the second embodiment of this invention. In order to avoid repetition, it is not necessary to again identify all parts of the structure. It will be noted that the Figure 4 section is substantially identical to the Figure 2 section, but that the section represented in Figure 3 differs from that represented in Figure 1 in that the Figure 3 section cuts through flat, parallel walls. Thus, the section of Figure 3 is very similar to the prior art section of Figure 7.
In the embodiment illustrated in Figures 3 and 4, the widening takes place only in the transverse plane, which is cut by the section of Figure 4, and no widening takes place in the longitudinal plane represented by Figure 3. Nonetheless, as can be seen by referring to the line 48 in Figure 9, there is again a progressive increase of the cross section of the pocket in the direction away from the axis 14, such that the rate of increase at the outer extremity of the pocket is 12 ~068 7 greater than the rate of increase at the inside. This again is represented by the curved nature of the line 48, with a steeper slope at the right than at the leftO
Finally, attention is directed to the third embodiment illustrated in Figure 5 and 6. It will be noted that the longitudinal section of Figure 5 is substantially the same as that of Figure 3 for the second embodiment, but that the transverse section shown in Figure 6 includes a double flare with two rounded walls 50 for each of the pockets 51 and 52. This more greatly exaggerates the flare, so that the rate at which each pocket widens away from the axis 14 is greater than in either of the two earlier embodiments. This is particularly seen with reference to the line 55 in Figure 9, which is also labelled "3rd Embod.".
While three embodiments of this invention have been illustrated in the accompanying drawings and described hereinabove, it will be evident to those skilled in the art that changes and modifications may be made thereto ~o without departing from the essence of this invention, as set forth in the appended claims.
BACKGROUND OF THIS INVENTION
It is generally appreciated in the wood pulp industry that, when grinding wood chips, it is very desirable to orient the grain of the chips parallel to the stone surface for the actual grinding operationO A
typical wood chip may measure about 1" x 1", with a thickness of 1/8" to ~". The grain runs parallel to one of the larger dimensions. When a wood chip is ground by lying against the grinding stone with lts largest surface, i.e. with the grain oriented substantially - parallel with the surface of the grinding stone, it is more likely whole fibres will be produced, rather than small, broken fibre fragments. Generally speaking, the larger the fibres, the better the quality of the resulting pulp.
GENERAL DESCRIPTION OF THIS INVENTION
The aim of an aspect of this invention is to provide a pocket configuration within the rotor of an internal centrifugal grinder which is such as to promote a parallel chip orientation by the time the chip reaches the grinding surface, i.e. an orientation in which the chip grain extends substantially parallel to the internal grinding surface.
I have discovered that by shaping the pocket or pockets in the rotor in a particular way, the desirable orientation of the chips can be to a large extent achieved. It will be understood that it is not a practical goal to seek the proper orientation of all of the wood chips. Because the chips are oriented in a lZ~ i87 random fashion initially, it is unlikely that in any given time span a uniform parallel orientation can be achieved for all of the chips. However, I have found that the pocket configuration provided herein allows better than three quarters of typical wood chips to assume, by the time they reach the grinding surface, an orientation in which they are parallel to the grinding surface and to each other.
More particularly, this invention provides an improvement in a centrifugal grinder having an internal grinding surface shaped as a surface of revolution, and a rotor mounted within the surface for rotation about the axis thereof, the rotor defining a generally axial inlet passageway for material to be ground. At least one pocket extends generally outwardly from the axis of the rotor toward the grinding surface, and the present improvement provides a configuration for the pocket wherein the cross-section of the pocket widens at an increasing rate away from the rotor axis.
GENERAL DESCRIPTION OF THE DRAWINGS
_ _ Three embodiments of this invention are illustrated schematically in the accompanying drawings which show the essential geometry without all of the accessory components, like numerals denoting like parts throughout the several views, and in which:
- Figure 1 is a longitudinal section through a first embodiment;
Figure 2 is a transverse section taken at the line A-A in Figure l;
Figure 3 is a longitudinal section through a second embodiment;
Figure 4 is a transverse section taken at the line A-A in Figure 3;
Figure 5 is a longitudinal section through a third embodiment;
Figure 6 is a transverse section taken at the line A-A in Figure 5;
Figure 7 is a longitudinal sectional view through a prior art construction;
06~37 Figure 8 is a transverse view taken at the line A-A
in Figure 7; and Figure 9 is a graphical representation of the rates at which the cross-sectional area of a pocket increases away from the axis of the rotor.
DETAILED DESCRIPTION OF THE DRAWINGS
.
Attention is first directed to Figures 7 and 8, which shows the prior art construction.
In the prior art construction, a grinding stone 10 defines an internal grinding surface 12 shaped as a surface of revolution, and more particularly as a cylinder having an axis shown at the line 14. Looking at Figure 8, a rotor 16 is provided, the rotor being mounted within the surface 12 for rotation about the axis 14. The rotor 16 defines a generally axial inlet passageway 18 for material such as wood chips to be ground, and two pockets 20 and 22, each extending generally outwardly away from the axis 14 of the rotor and toward the grinding surface 12. In the construction shown in Figures 7 and 8, the two pockets 20 and 22 extend in diametrically opposite directions, and are thus spaced at 180 from each other.
It will be noted in Figure 8 that each pocket 20, 22 is defined between generally rectilinear but slightly diverging walls 24. Figure 7 shows a cross section at right angles to the section of Figure 8, also cutting through the pockets 20 and 22. It will be seen that the pockets are defined by parallel walls 26 and 28, transverse to the axis 14.
If one were to calculate the cross-sectional area of the pockets 20 and 22 by determining, for different radii beginning at the wall of the passageway 18 and ending at the surface 12, the surface area of a series of theoretical cylinders lying within the pocket, the cylinders having the increasing radii, then one would arrive at the line identified by the numeral 27 in Figure 9, the line being also labelled "Fig. 4". As can be seen, this line is essentially a straight line, due to the fact that the walls of the pockets 20 and 22 are lz7a6s7 almost parallel in both directions. Because there is a very slight divergence as can be seen in the section of Figure 8, the cross-sectional area increases slightly in the outward direction, as indicated by the slight upward slope of the line 27 in the graph of Figure 9.
However, I have determined that a mere divergence by itself is not sufficient to encourage a large-scale re-orientation of the wood chips so that they lie, ir.
the main, parallel to the grinding surface by the time they reach the latter. In order to accomplish this large-scale re-orientation, it is necessary to ensure that the transverse section of the pocket widens at an increasing rate away from the rotor axis, and this is best accomplished by providing a flared configuration as seen in Figures 1 through 6.
Attention is first directed to Figures 1 and 2, illustrating the first embodiment of this invention. As can be seen, in Figure 1, the grinding stone 10 is again provided, with an internal cylindrical grinding surface 12. A rotor 30 is provided, rotatable about the axis 14 of the stone 10, the rotor 30 shaped to define an axial passageway 18a which opens into two oppositely extending pockets 32 and 34. As can be seen in Figure 1, each pocket 32, 34 is defined between walls 36 and 38 which widen at an increasing rate away from the axis 14. The section through the wall 36 is thus a curve, as is the section through the wall 38.
Referring to Figure 2, the dimension of each pocket 32, 34 in the direction transverse to the section of Figure 1 also widens at an increasing rate. The pocket 32 is defined between a flat wall 40 and a strongly curved wall 42, and the same is true for the pocket 34.
The strongly curved wall 42 in each case is the trailing wall in the sense of rotation, which in the view of Figure 2 is counter-clockwise.
If one were to utilize the precise geometry shown in Figures 1 and 2, and perform the same calculations as were done to arrive at the line 27 in Figure 9, one would arrive at the line identified by the numeral 44 in ~12~06~37 Figure 9, which is also labelled as "lst Embodiment".
As can be seen, the slope of the line 44 increases at a progressive rate from the left to the right, which corresponds to increasing distance away from the axis 14. The angle alpha drawn adjacent the line 44 in Figure 9 represents the slope of the line 44 at the leftward extremity, whereas the angle beta drawn at the upper right in Figure 9 represents the slope of the line 44 at the rightward extremity. The distance Dl in Figure 9 is proportional to the tangent of the angle alpha, whereas D2 is proportional to the tangent of the angle beta. It can be seen that D2, in effect a measure of the slope of the line 44 at the rightward end, is at least 8 times as large as Dl, which is the slope at the leftward end.
It is pointed out that the curves in Figure 9 are not measured in any specific units, but-are accurate in terms of showing the relative rate of increase of the cross section away from the axis.
Attention is now directed to Figures 3 and 4, which are similar to Figures 1 and 2, but are directed to the second embodiment of this invention. In order to avoid repetition, it is not necessary to again identify all parts of the structure. It will be noted that the Figure 4 section is substantially identical to the Figure 2 section, but that the section represented in Figure 3 differs from that represented in Figure 1 in that the Figure 3 section cuts through flat, parallel walls. Thus, the section of Figure 3 is very similar to the prior art section of Figure 7.
In the embodiment illustrated in Figures 3 and 4, the widening takes place only in the transverse plane, which is cut by the section of Figure 4, and no widening takes place in the longitudinal plane represented by Figure 3. Nonetheless, as can be seen by referring to the line 48 in Figure 9, there is again a progressive increase of the cross section of the pocket in the direction away from the axis 14, such that the rate of increase at the outer extremity of the pocket is 12 ~068 7 greater than the rate of increase at the inside. This again is represented by the curved nature of the line 48, with a steeper slope at the right than at the leftO
Finally, attention is directed to the third embodiment illustrated in Figure 5 and 6. It will be noted that the longitudinal section of Figure 5 is substantially the same as that of Figure 3 for the second embodiment, but that the transverse section shown in Figure 6 includes a double flare with two rounded walls 50 for each of the pockets 51 and 52. This more greatly exaggerates the flare, so that the rate at which each pocket widens away from the axis 14 is greater than in either of the two earlier embodiments. This is particularly seen with reference to the line 55 in Figure 9, which is also labelled "3rd Embod.".
While three embodiments of this invention have been illustrated in the accompanying drawings and described hereinabove, it will be evident to those skilled in the art that changes and modifications may be made thereto ~o without departing from the essence of this invention, as set forth in the appended claims.
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a centrifugal grinder having an internal grinding surface shaped as a surface of revolution, and a rotor mounted within said surface for rotation about the axis thereof, the rotor defining a generally axial inlet passageway for material to be ground, and at least one pocket extending generally outwardly from the axis of the rotor toward the grinding surface, the improvement which comprises:
the provision of a configuration for said at least one pocket, wherein the cross-section of said at least one pocket widens at an increasing rate away from the rotor axis.
the provision of a configuration for said at least one pocket, wherein the cross-section of said at least one pocket widens at an increasing rate away from the rotor axis.
2. The invention claimed in claim 1, in which the said at least one pocket widens progressively away from said axis when seen in a cross-sectional plane transverse to the rotor axis.
3. The invention claimed in claim 2, in which the said at least one pocket also widens progressively away from said axis when seen in a longitudinal plane containing both said rotor axis and the pocket.
4. The invention claimed in claim 2, in which the pocket is bi-laterally symmetrical about a mid-longitudinal plane containing said rotor axis.
5. The invention claimed in claim 1, in which there are two pockets at a spacing of 180°.
6. The invention claimed in claim 2, in which there are two pockets at a spacing of 180°.
7. The invention claimed in claim 3, in which there are two pockets at a spacing of 180°.
8. The invention claimed in claim 4, in which there are two pockets at a spacing of 180°.
9. A centrifugal grinder having an internal grinding surface shaped as a surface of revolution, and a rotor mounted within said surface for rotation about the axis thereof, the rotor defining a generally axial inlet passageway for material to be ground, and at least one pocket extending generally outwardly from the axis of the rotor toward the grinding surface, said at least one pocket having a cross-section which increases at an increasing rate away from the rotor axis.
10. The invention claimed in claim 9, in which the said at least one pocket widens progressively away from said axis when seen in a cross-sectional plane transverse to the rotor axis.
11. The invention claimed in claim 10, in which the said at least one pocket also widens progressively away from said axis when seen in a longitudinal plane containing both said rotor axis and the pocket.
12. The invention claimed in claim 10, in which the pocket is bi-laterally symmetrical about a mid-longitudinal plane containing said rotor axis.
13. The invention claimed in claim 9, in which there are two pockets at a spacing of 180°.
14. The invention claimed in claim 9, in which the differential of the expansion rate of said at least one pocket at its outer limit adjacent the internal grinding surface is at least 8 times as great as the differential of the expansion rate of said at least one pocket at the level corresponding to the surface of the said generally axial inlet passageway.
15. The invention claimed in claim 1, in which the differential of the expansion rate of said at least one pocket at its outer limit adjacent the internal grinding surface is at least 8 times as great as the differential of the expansion rate of said at least one pocket at the level corresponding to the surface of the said generally axial inlet passageway.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000518096A CA1270687A (en) | 1986-09-12 | 1986-09-12 | Flared pockets for centrifugal grinders |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000518096A CA1270687A (en) | 1986-09-12 | 1986-09-12 | Flared pockets for centrifugal grinders |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1270687A true CA1270687A (en) | 1990-06-26 |
Family
ID=4133923
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000518096A Expired - Fee Related CA1270687A (en) | 1986-09-12 | 1986-09-12 | Flared pockets for centrifugal grinders |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1270687A (en) |
-
1986
- 1986-09-12 CA CA000518096A patent/CA1270687A/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |