CA1128352A - Supporting member for papermaking screen in paper machines - Google Patents
Supporting member for papermaking screen in paper machinesInfo
- Publication number
- CA1128352A CA1128352A CA341,500A CA341500A CA1128352A CA 1128352 A CA1128352 A CA 1128352A CA 341500 A CA341500 A CA 341500A CA 1128352 A CA1128352 A CA 1128352A
- Authority
- CA
- Canada
- Prior art keywords
- screen
- supporting member
- silicon nitride
- sintered body
- papermaking screen
- 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
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/36—Guiding mechanisms
- D21F1/38—Pads
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/48—Suction apparatus
- D21F1/483—Drainage foils and bars
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F9/00—Complete machines for making continuous webs of paper
- D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type
Landscapes
- Paper (AREA)
- Ceramic Products (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A supporting member of the papermaking screen in paper machines is disclosed, which is made of a sintered body consis-ting essentially of silicon nitride having a porosity of less than 0.8 %. The abrasion loss of the papermaking screen is able to be substantially reduced as compared with conventional supporting members made of alumina ceraminc, as a result of which the useful life of the papermaking screen can considerably be lengthened.
A supporting member of the papermaking screen in paper machines is disclosed, which is made of a sintered body consis-ting essentially of silicon nitride having a porosity of less than 0.8 %. The abrasion loss of the papermaking screen is able to be substantially reduced as compared with conventional supporting members made of alumina ceraminc, as a result of which the useful life of the papermaking screen can considerably be lengthened.
Description
~Z835~
This invention relates to a supporting member for a papermaking screen used in paper machines, and more particularly, as a member for contiguously supporting the continuously moving papermaking screen.
Both the prior art and the invention will be described by way of example with reference to the accompanyïna drawings, in which:-Figures 1 (~) and (s) are schematic drawings of papermachines known i~ themselves to which members according to the invention have been applied;
Figure 2 is a longitudinal sectional view showing an embodiment wherein the members accordi.ng to the invention are applied to a forming board;
Figure 3 is a schematic illustration or an abrasion tester with the use of which the performance both of the member according to the invention and of conventional members is tested;
Figure 4 is a graphical representation showing the correlation between both the abraded loss amount of the screen obtained by the same tester as in Figure 3 and the qualities of materials of supporting members of various sorts; and Figure 5 is a graphical representation showing the correlation between the surface roughness and the test time for each of the screens tested.
The long screen type paper making machine shown in Figure l(A) is so designed that the paper material;'namelv slurry consisting of paper pulp and water, is supplied from a head box 1 onto the screen (principally: made of metal~ 2 which is driven by rollers 8,9 in the direction of the arrow shown in the figure. The watery paper pulp 3 is dehydrated progressivelyon the screen 2 with the aid of the tractive force of rollers 12,13 positioned just u.nder the screen 2. These are .
335~
followed by treatment involving rolling, drying, and so on.
With a view partly to effect dehydration and partly to support the screen 2, the paper machine includes a forming board 4, a deflector 5, a foil 6, and a suction box 7, arranged contiguously just under the screen 2 in succession, and furtner tension rollers 10,11. Another kind of paper machine, known as a twin wire machine is shown in Figure l(s). This kind is so designed that the two screens 2,2' are driven by a driving roller 8 and tension rollers 10,11, while paper pulp 3, after having been supplied from the head box 1, is compressed from both sides between the two screens 2,2' supported by ~he support-ing members 14 and is dehydrated by the suction box 7. The resulting dehydrate is treated by rolling and drying.
Now, in these paper machines, the supporting structures such as the forming board 4 and the foil 6 are provided for the purpose of contiguously supporting the screen 2.
.~s shown in Figure 2, the forming board 4 in fact comprises a plurality of supportinJ members 4' extending transversely to the running direction of the screen 2. These members have been ~0 previously made from ceramic obtained from a sintered body of alumina or silicon carbide and have worked reasonably satisfactor-ily. However, -these conventional members bring about a large degree of abrasion on the screen 2 running incessantly over them.
In the latest high speed paper machines the use of conventional apparatus composed of a conventional~forming board, deflector, table roll, and suction box does not allow sufficient dehydration to take place which leads to a deterioration in the quality of the paper. To overcome this problem, the foil is used both for the purpose of supporting the screen and effecting dehydration. However, the foil deteriorates considerably due to abrasion and the efficiency ~2~3352 of dehydration which has a bad influence on the quality of paper. This is alsa true of the supporting member provided on the suction dehydrator, such as a suction box. ~urthermore, previousl~v known supporting members made of alumina ceramic, silicon carbide or the like, also tenaed to cause substantial abrasion of the screen itself.
Accordingly, the present invention provides a support-ing member for a papermaking screen in a paper machine, said supporting member being adapted to extend transversel~ to the running direction of the papermaking screen and comprising a sintered body consisting essentially of silicon nitride having a porosity of approximately 0.8% or less.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings introduced above.
A sintered body consisting essentially of silicon nitride has a number of characteristics such as good high-temperature strength, excellent heat shock resistance, abrasion resistance, and so on, which has led to it being widely used in some special fields as heat resistiVe material. However, silicon nitride it-self, which is a sintering substance having strong covalent bond, is hard to sinter in a dense manner using the simple substance along, unlike alumina ceramic. To achieve this, it has been found desirable to add a sintering aid. The composition of sili-con nitride used ~n an example in accordance with the present invention is as follows:
Si3N4 = 74.0%
FeSi ~ 6.0%
Fe c 1.5%
Fe2 3 To such a compound of silicon nitride is added some metal oxide as a sintering aid, such as, for example, MgO.
~, .
.
335;2 Further, after adding ~o this material an adequate quantity of binders of various kinds and then moldiny it into a desired ~.
~`0~
` - - 3a -: - , ,', .
shape, it is sintered in the range of 1400 to 1700C in an atmosphere of N2 gas. The resultant sintered body is in the state where, except its main phase ~-Si3N4, unreactive ferrosilicon and metal oxide produced in the sintering process remain in crystal or non-crystalloid form. The properties of both sintered body of silicon nitride thus obtained and alumina ceramic heretofore used as the supporting member of the screen are listed in contrast in the following Table 1.
Table 1 material aintered body alumina-~~-___ of ceramic item ~ silicon nitride ___ _ appearance dense dense .
coloration dark graywhite __ bulk specific gravity 3.3 3.8 porosity (%) 0.3 0 __ __ __ , bending strength kg/mm2 25 31 _ _ __.____ Rockwell hardness HRA 87 87 ~oung's modulus (x106) kg/cm2 _ 3.5 linear expansion coefficient 3.5 7.7 ~0 (X-6)/C _ A number of experiments conducted with the use of such a sintered body of silicon nitride wi:Ll now be more particularly described. Figure 3 is a schematic illustration of an abrasion tester of the screen in order to measure the performance of the screen supporting member according to the invention. Figure 4 is a graphical representation showing the correlation between the abraded auantity of the screen due to the abrasion tester and the supporting members different in the quality of material each time. Figure 5 is a graphical representation showing the correlation between the surface roughness and the test time relatively to each screen different from one another in the quantity of material.
.
~8;~5~
The abrasion tester M in question is shown schematically in Figure 3, wherein the paper-making screen 2 having one end fixed and the o-ther end attached to a constant weight A, is suspended on the roller R made of the same quality of material as the supporting member of the screen, and wherein the nozzle N allowing pulp materials 3' to fall on the screen is provided above the roller R. The roller R is made to continuously rotate in the direction of the arrow while the pulp materials 3' fall onto the screen. This arrangement allows the abraded condi.tion of the screen 2 in contact with the surface of the above roller R to be investi.gated. The conditions of the abrasion test conducted simulating the running of the screen
This invention relates to a supporting member for a papermaking screen used in paper machines, and more particularly, as a member for contiguously supporting the continuously moving papermaking screen.
Both the prior art and the invention will be described by way of example with reference to the accompanyïna drawings, in which:-Figures 1 (~) and (s) are schematic drawings of papermachines known i~ themselves to which members according to the invention have been applied;
Figure 2 is a longitudinal sectional view showing an embodiment wherein the members accordi.ng to the invention are applied to a forming board;
Figure 3 is a schematic illustration or an abrasion tester with the use of which the performance both of the member according to the invention and of conventional members is tested;
Figure 4 is a graphical representation showing the correlation between both the abraded loss amount of the screen obtained by the same tester as in Figure 3 and the qualities of materials of supporting members of various sorts; and Figure 5 is a graphical representation showing the correlation between the surface roughness and the test time for each of the screens tested.
The long screen type paper making machine shown in Figure l(A) is so designed that the paper material;'namelv slurry consisting of paper pulp and water, is supplied from a head box 1 onto the screen (principally: made of metal~ 2 which is driven by rollers 8,9 in the direction of the arrow shown in the figure. The watery paper pulp 3 is dehydrated progressivelyon the screen 2 with the aid of the tractive force of rollers 12,13 positioned just u.nder the screen 2. These are .
335~
followed by treatment involving rolling, drying, and so on.
With a view partly to effect dehydration and partly to support the screen 2, the paper machine includes a forming board 4, a deflector 5, a foil 6, and a suction box 7, arranged contiguously just under the screen 2 in succession, and furtner tension rollers 10,11. Another kind of paper machine, known as a twin wire machine is shown in Figure l(s). This kind is so designed that the two screens 2,2' are driven by a driving roller 8 and tension rollers 10,11, while paper pulp 3, after having been supplied from the head box 1, is compressed from both sides between the two screens 2,2' supported by ~he support-ing members 14 and is dehydrated by the suction box 7. The resulting dehydrate is treated by rolling and drying.
Now, in these paper machines, the supporting structures such as the forming board 4 and the foil 6 are provided for the purpose of contiguously supporting the screen 2.
.~s shown in Figure 2, the forming board 4 in fact comprises a plurality of supportinJ members 4' extending transversely to the running direction of the screen 2. These members have been ~0 previously made from ceramic obtained from a sintered body of alumina or silicon carbide and have worked reasonably satisfactor-ily. However, -these conventional members bring about a large degree of abrasion on the screen 2 running incessantly over them.
In the latest high speed paper machines the use of conventional apparatus composed of a conventional~forming board, deflector, table roll, and suction box does not allow sufficient dehydration to take place which leads to a deterioration in the quality of the paper. To overcome this problem, the foil is used both for the purpose of supporting the screen and effecting dehydration. However, the foil deteriorates considerably due to abrasion and the efficiency ~2~3352 of dehydration which has a bad influence on the quality of paper. This is alsa true of the supporting member provided on the suction dehydrator, such as a suction box. ~urthermore, previousl~v known supporting members made of alumina ceramic, silicon carbide or the like, also tenaed to cause substantial abrasion of the screen itself.
Accordingly, the present invention provides a support-ing member for a papermaking screen in a paper machine, said supporting member being adapted to extend transversel~ to the running direction of the papermaking screen and comprising a sintered body consisting essentially of silicon nitride having a porosity of approximately 0.8% or less.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings introduced above.
A sintered body consisting essentially of silicon nitride has a number of characteristics such as good high-temperature strength, excellent heat shock resistance, abrasion resistance, and so on, which has led to it being widely used in some special fields as heat resistiVe material. However, silicon nitride it-self, which is a sintering substance having strong covalent bond, is hard to sinter in a dense manner using the simple substance along, unlike alumina ceramic. To achieve this, it has been found desirable to add a sintering aid. The composition of sili-con nitride used ~n an example in accordance with the present invention is as follows:
Si3N4 = 74.0%
FeSi ~ 6.0%
Fe c 1.5%
Fe2 3 To such a compound of silicon nitride is added some metal oxide as a sintering aid, such as, for example, MgO.
~, .
.
335;2 Further, after adding ~o this material an adequate quantity of binders of various kinds and then moldiny it into a desired ~.
~`0~
` - - 3a -: - , ,', .
shape, it is sintered in the range of 1400 to 1700C in an atmosphere of N2 gas. The resultant sintered body is in the state where, except its main phase ~-Si3N4, unreactive ferrosilicon and metal oxide produced in the sintering process remain in crystal or non-crystalloid form. The properties of both sintered body of silicon nitride thus obtained and alumina ceramic heretofore used as the supporting member of the screen are listed in contrast in the following Table 1.
Table 1 material aintered body alumina-~~-___ of ceramic item ~ silicon nitride ___ _ appearance dense dense .
coloration dark graywhite __ bulk specific gravity 3.3 3.8 porosity (%) 0.3 0 __ __ __ , bending strength kg/mm2 25 31 _ _ __.____ Rockwell hardness HRA 87 87 ~oung's modulus (x106) kg/cm2 _ 3.5 linear expansion coefficient 3.5 7.7 ~0 (X-6)/C _ A number of experiments conducted with the use of such a sintered body of silicon nitride wi:Ll now be more particularly described. Figure 3 is a schematic illustration of an abrasion tester of the screen in order to measure the performance of the screen supporting member according to the invention. Figure 4 is a graphical representation showing the correlation between the abraded auantity of the screen due to the abrasion tester and the supporting members different in the quality of material each time. Figure 5 is a graphical representation showing the correlation between the surface roughness and the test time relatively to each screen different from one another in the quantity of material.
.
~8;~5~
The abrasion tester M in question is shown schematically in Figure 3, wherein the paper-making screen 2 having one end fixed and the o-ther end attached to a constant weight A, is suspended on the roller R made of the same quality of material as the supporting member of the screen, and wherein the nozzle N allowing pulp materials 3' to fall on the screen is provided above the roller R. The roller R is made to continuously rotate in the direction of the arrow while the pulp materials 3' fall onto the screen. This arrangement allows the abraded condi.tion of the screen 2 in contact with the surface of the above roller R to be investi.gated. The conditions of the abrasion test conducted simulating the running of the screen
2 over the supporting members in paper machines are as follows:
(a) rotational frequency of roller : 1500 rpm (b) circumferential speed thereof : 283 m/min (c) concentration of raw material : 2 tulk %
(d) delivery rate of material : 0.6 Q/min (e) tension of screen 2.5 kg/cm (f) width of screen : 40 mm (g) sort of screen :
(g-l) bronze 60 - mesh (g-2) chrome plated 65 - mesh copper alloy (g-3) plastic 60 - mesh (h) material of roller :
(h-l) alumina ceramic (h-~j sintered body essentially of silicon nitride (i) shape of roller : 60 ~ x 60 long (mm) (j) surface roughness of roller : Rmax = 4 (both alumina ceramic and sintered body essentially of Si3N4~
~;~ 1~
" ~283~2 (k) abraded amount of screen :
This is expressed by calculating the loss in weight of the screen per unit time before and after the test.
The test results obtained under the foregoing conditions will be given in Figure 4. Incidentally, each lines given in both Figures 4 and 5 demonstrate such relations to the quantities of rollers and screens as are shown in the following Table 2.
Table 2 .... , . ___ material of ~~ ~ roller sintered body of ~-___ alumina ceramic silicon nitride material of screen _ . _ ._ bronze _ o x ___ _ _ _ plastic _ _ _ O _ _ _ _ - - - x - - -~_~__ _ _ chrome plated copper - o - . - ~ - x - .
. alloy . .. . , _~_~.~
In Figure 4, the bronze screen and the chrome plated copper allov are screen arranged in order of the magnitude of the abraded amount. In either case, when the material forming the roller R is alumina ceramic, the abraded amount of the screen is greatest, while on the contrary when the sintered body is made of silicon nitride the abraded amount is much smaller. This indicates that the degree of the abrasion of the running screen is smaller when using a supporting member made of silicon nitride than is the case with conventional supporting members formed of alumina ceramic.
Table 3 presents the results obtained from the investigation as to what kinds of effect the difference in porosity of the sintered body of silicon nitride has on the 2`~ amount of abrasion.
:i.
.,.
~6--`~:
.
Table 3 nd of sa~ple Our Invention Prior item ~ - - A A~ B C
~ul~cspecific gravity 3.4 3.3 2.9 3.8 2.7 ' . _ ___ xnding stren~th (kg/mm ) 30 25 37 31 25 . ~
?~c ell hardness 87 87 87 87 82 ~oung6s m~du~us 10(x10 kg/cm ) :2.5 2.5 2.5 3.5 2.3 . _ Linear expansion 6 ~oefficient (x10 /C) 3. 7 3.5 2.6 7.7 3.0 ... . _ _ .
~orosity (%) 0. 05 0.3 0.8 0 1.1 ~ u~
o ~ bronze 0.5 0.75 0.851.2 1.46 ~,rt, __ chrcqne copper alloy n .03 O.10 0.15 0.25 O.5 plastic 0.1 O. 2 0.4 1.0 2.48 Note: The composition of silicon nitride in examples A' and A"
is the same as the before-mentioned (referred to as A).
Only the porosity is different, as shown in the table.
Sample B is the case of the well-known alumina ceramic.
Sample C is a silicon nitride composition having greater porosity of the samples A, A', A".
From this table, it is apparent that the amount of abra-sion becomes less as the porosity decreases. Optimum results are obtained when the porosity is less than 0.8~.
Separately from the above, using the same tester, the affect of the surface roughness of the roller made of silicon ni-tride as the abrasion of the screen has been studied. As the re-sult, the following facts have been realized, as apparent fromFigure 5:
(I) With the lapse of time the surface roughness becomes ~-- - 7 .
5~
progressively smaller, displaying the practically stable rou~hness.
(II) The above (I) brings about a reduction of the abraded amount of the screen, (III) Although there is some difference more or less dependlng on the variation in the quality of ma-terial, it is desirable for the surface roughness of the roller R able to achieve a value (I) that it is under 4~.
Description will now be d~rected to an example wherein the sintered body of silicon nitride according to the invention has been applied to a twin wire-type paper machine shown in Figure l(B)-As seen from the Figure, paper pulp coming down from the head box 1 first is caught between the two running screens 2, 2', a~d then is dehydrated by the action of the suppor~ing members 14 designed so as to compress the respective screens 2,2' alterna-tely from both sides. The dehydrating operation is t~en furthered by the suction hox 7. In this case, the paper machine is operated under the following conditions: the running speed of the screen is 700 m/min, the material of the screen 2 is bronze, that of the screen 2~ is plastic, respectively, and that the tension applied to each screen is 4 kg/cm. In this way paper o Einq quality (70 g/m ~ was actually produced.
In this connection, a sin-tered body of silicon nitride was used as the supporting member 14; which compressed the screen 2 made of bronze at its part nearest the headbox 1 (however, in the other part was used ultramacro=molecular polyethylene). The useful life of the b~onze screen 2 was seven (7) days in the case of conventional suppor~in~ members made o alumina ceramic.
Contrary to this, by adopting the above~mentioned new member the lie of the screen could be increased to nine (9) days.
33~
It is now e~ident from the above description that the present invention has many excellent advantages. Tn particular, the life of the papermaking screen is increased without being scarcely abraded irrespecti~e of the quality of material, and it is possible to supply paper of fine quality at ].ow cost and stability for a long time.
. ~
' .
`~` ;!~ g
(a) rotational frequency of roller : 1500 rpm (b) circumferential speed thereof : 283 m/min (c) concentration of raw material : 2 tulk %
(d) delivery rate of material : 0.6 Q/min (e) tension of screen 2.5 kg/cm (f) width of screen : 40 mm (g) sort of screen :
(g-l) bronze 60 - mesh (g-2) chrome plated 65 - mesh copper alloy (g-3) plastic 60 - mesh (h) material of roller :
(h-l) alumina ceramic (h-~j sintered body essentially of silicon nitride (i) shape of roller : 60 ~ x 60 long (mm) (j) surface roughness of roller : Rmax = 4 (both alumina ceramic and sintered body essentially of Si3N4~
~;~ 1~
" ~283~2 (k) abraded amount of screen :
This is expressed by calculating the loss in weight of the screen per unit time before and after the test.
The test results obtained under the foregoing conditions will be given in Figure 4. Incidentally, each lines given in both Figures 4 and 5 demonstrate such relations to the quantities of rollers and screens as are shown in the following Table 2.
Table 2 .... , . ___ material of ~~ ~ roller sintered body of ~-___ alumina ceramic silicon nitride material of screen _ . _ ._ bronze _ o x ___ _ _ _ plastic _ _ _ O _ _ _ _ - - - x - - -~_~__ _ _ chrome plated copper - o - . - ~ - x - .
. alloy . .. . , _~_~.~
In Figure 4, the bronze screen and the chrome plated copper allov are screen arranged in order of the magnitude of the abraded amount. In either case, when the material forming the roller R is alumina ceramic, the abraded amount of the screen is greatest, while on the contrary when the sintered body is made of silicon nitride the abraded amount is much smaller. This indicates that the degree of the abrasion of the running screen is smaller when using a supporting member made of silicon nitride than is the case with conventional supporting members formed of alumina ceramic.
Table 3 presents the results obtained from the investigation as to what kinds of effect the difference in porosity of the sintered body of silicon nitride has on the 2`~ amount of abrasion.
:i.
.,.
~6--`~:
.
Table 3 nd of sa~ple Our Invention Prior item ~ - - A A~ B C
~ul~cspecific gravity 3.4 3.3 2.9 3.8 2.7 ' . _ ___ xnding stren~th (kg/mm ) 30 25 37 31 25 . ~
?~c ell hardness 87 87 87 87 82 ~oung6s m~du~us 10(x10 kg/cm ) :2.5 2.5 2.5 3.5 2.3 . _ Linear expansion 6 ~oefficient (x10 /C) 3. 7 3.5 2.6 7.7 3.0 ... . _ _ .
~orosity (%) 0. 05 0.3 0.8 0 1.1 ~ u~
o ~ bronze 0.5 0.75 0.851.2 1.46 ~,rt, __ chrcqne copper alloy n .03 O.10 0.15 0.25 O.5 plastic 0.1 O. 2 0.4 1.0 2.48 Note: The composition of silicon nitride in examples A' and A"
is the same as the before-mentioned (referred to as A).
Only the porosity is different, as shown in the table.
Sample B is the case of the well-known alumina ceramic.
Sample C is a silicon nitride composition having greater porosity of the samples A, A', A".
From this table, it is apparent that the amount of abra-sion becomes less as the porosity decreases. Optimum results are obtained when the porosity is less than 0.8~.
Separately from the above, using the same tester, the affect of the surface roughness of the roller made of silicon ni-tride as the abrasion of the screen has been studied. As the re-sult, the following facts have been realized, as apparent fromFigure 5:
(I) With the lapse of time the surface roughness becomes ~-- - 7 .
5~
progressively smaller, displaying the practically stable rou~hness.
(II) The above (I) brings about a reduction of the abraded amount of the screen, (III) Although there is some difference more or less dependlng on the variation in the quality of ma-terial, it is desirable for the surface roughness of the roller R able to achieve a value (I) that it is under 4~.
Description will now be d~rected to an example wherein the sintered body of silicon nitride according to the invention has been applied to a twin wire-type paper machine shown in Figure l(B)-As seen from the Figure, paper pulp coming down from the head box 1 first is caught between the two running screens 2, 2', a~d then is dehydrated by the action of the suppor~ing members 14 designed so as to compress the respective screens 2,2' alterna-tely from both sides. The dehydrating operation is t~en furthered by the suction hox 7. In this case, the paper machine is operated under the following conditions: the running speed of the screen is 700 m/min, the material of the screen 2 is bronze, that of the screen 2~ is plastic, respectively, and that the tension applied to each screen is 4 kg/cm. In this way paper o Einq quality (70 g/m ~ was actually produced.
In this connection, a sin-tered body of silicon nitride was used as the supporting member 14; which compressed the screen 2 made of bronze at its part nearest the headbox 1 (however, in the other part was used ultramacro=molecular polyethylene). The useful life of the b~onze screen 2 was seven (7) days in the case of conventional suppor~in~ members made o alumina ceramic.
Contrary to this, by adopting the above~mentioned new member the lie of the screen could be increased to nine (9) days.
33~
It is now e~ident from the above description that the present invention has many excellent advantages. Tn particular, the life of the papermaking screen is increased without being scarcely abraded irrespecti~e of the quality of material, and it is possible to supply paper of fine quality at ].ow cost and stability for a long time.
. ~
' .
`~` ;!~ g
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A supporting member for papermaking screen in a paper machine, said supporting member being adpated to extend transversely to the running direction of the papermaking screen and comprising a sintered body consisting essentially of silicon nitride having a porosity of approximately 0.8% or less.
2. A supporting member as claimed in claim 1 wherein said sintered body includes a sintering aid.
3. A supporting member as claimed in claim 2 wherein said sintering aid is MgO.
4. A supporting member as claimed in any one of claims l to 3 wherein said body is sintered in the range of 1400°C to 1700°C in an inert atmosphere.
5. In a paper machine the improvement comprising a papermaking screen supported by a supporting member extending transversely to the screen, said supporting member comprising a sintered body consisting essentially of silicon nitride having a porosity of approximately 0.8 % or less.
6. A paper machine as claimed in claim 5 of the long screen type wherein the supporting member is one or more of a forming board, deflector or foil.
7, A paper machine as claimed in claim 5 of the long screen type wherein the supporting member is a forming board directly and contiguously supporting the papermaking screen
8. A paper machine as claimed in claim 4 comprising a pair of said paper making screens compressed on each side by a said supporting member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP152889/1978 | 1978-12-09 | ||
| JP15288978A JPS5580591A (en) | 1978-12-09 | 1978-12-09 | Screen net contact element of paper making machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1128352A true CA1128352A (en) | 1982-07-27 |
Family
ID=15550333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA341,500A Expired CA1128352A (en) | 1978-12-09 | 1979-12-07 | Supporting member for papermaking screen in paper machines |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5580591A (en) |
| CA (1) | CA1128352A (en) |
| DE (1) | DE2950024A1 (en) |
| FI (1) | FI793816A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59228095A (en) * | 1983-10-26 | 1984-12-21 | 京セラ株式会社 | Screen support and contact member of papermaking machine |
| DE59207730D1 (en) * | 1991-04-26 | 1997-01-30 | Cerasiv Gmbh | SUPPORTING ELEMENT FOR THE SCREEN OR THE FELT OF A PAPER OR CARDBOARD MACHINE, METHOD FOR PRODUCING IT AND ITS USE |
| JP4628085B2 (en) * | 2004-12-20 | 2011-02-09 | 京セラ株式会社 | Paper making support member, manufacturing method thereof, and paper machine using the same |
-
1978
- 1978-12-09 JP JP15288978A patent/JPS5580591A/en active Pending
-
1979
- 1979-12-05 FI FI793816A patent/FI793816A/en not_active Application Discontinuation
- 1979-12-07 CA CA341,500A patent/CA1128352A/en not_active Expired
- 1979-12-10 DE DE19792950024 patent/DE2950024A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FI793816A (en) | 1980-06-10 |
| DE2950024A1 (en) | 1980-06-26 |
| JPS5580591A (en) | 1980-06-17 |
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