US 3000778 A
Description (OCR text may contain errors)
Sept. 19, 1961 A. M. SIVELY ET AL 3,000,778
WET PRESS FOR PAPER MACHINE Filed July 27, 1959 2 Sheets-Sheet 1 FIG. I.
INVENTORS ANDREW MILTON SIVELY SHERIDAN JAMES MCNAMARA a f AT ORNEYS.
S pt- 19, 1 1 A. M. SIVELY ET AL 3,000,778
WET PRESS FOR PAPER MACHINE Filed July 27, 1959 2 Sheets-Sheet 2 FIG. 3. 68
INVENTORS ANDREW MILTON SIVELY SHERIDAN JAMES MCNAMARA ATTORNEYS.
This invention relates to the avoidance of picking and sticking of paper webs in wet presses of paper manufacturing machines.
Primary objects of the invention have to do with the providing of novel methods and means of avoiding such picking and sticking.
The wet press of a paper machine comprises a soft roll, usually of rubber, a hard pressure roll opposed to the soft roll for squeezing water out of the web as the web passes through the nip formed by the rolls, and an endless, web-supporting felt belt which travels through the nip between the paper web and the soft roll at the speed of the paper web.
The paper web usually travels through the nip in contact with the hard roll. The web tends to stick to the hard roll, and this causes fibers to be pulled from the surface of the web, and at times even causes the web to be ruptured. This has presented a problem which is serious and of long standing.
While the problem is basically the same for soft wood pulps, for hard wood pulps, and for blends which in clude neutral sulfite semi-chemical pulp, and no one of these pulps may be characterized as presenting a more severe problem than the others, it has been found that the several pulps respond differently to different remedial expedients. Some expedients which work beneficially for one pulp are of little or no use with another. No dependably satisfactory solution of the problem has heretofore been contrived for any one of these pulps.
In the past it has been thought desirable to drive the hard roll at a surface speed equal to that of the paper web. In instances where small unplanned differences of speed have been found to exist, remedial steps have been taken to assure equality of speed of the roll surface and the web. When the hard roll presents a paper engaging surface of polished stainless steel, polished chromium, Stonite, rock hard rubber, or the like, the problem is found to be present at equal speeds of the hard roll and the web.
We have found, however, that if the hard, paper engaging roll is faced with a slippery material, such as Teflon (polytetrafluoroethylene), or with a material which can be rendered suitably slippery by the application of certain lubricants in small amounts, the picking problem can be eliminated altogether by running the hard roll at a surface speed substantially different from the speed of the paper web. The minimum speed differential at which picking and sticking are eliminated varies according to the furnish, the surface material of the paper engaging roller, and the kind and quantity of lubricant employed. The minimum speed differential required may be as little as three percent or as much as twenty percent. Picking and sticking may be eliminated when a suitably slippery web engaging roller is employed, whether that roller is driven faster than the web or slower than the web. In the latter case, however, a waviness of the finished paper is likely to result. The faster running slippery roller is therefore preferred.
The frictional effect of a Teflon surface is so slight, even without lubrication, that the web continues to travel in unison with the felt as the roller speed is varied and the relative movement of the paper web and the Teflon 3,000,778 Patented Sept. 19, 19 61 faced hard roll causes the roll to be wiped clean at all times. While, as previously noted, the minimum difference of roll speed and web speed varies with the furnish, speed differences above the minimum are, within limits, not detrimental. Even when the Teflon faced roll is driven twice as fast as the felt belt, picking is eliminated and there is no speeding up of the Web relative to the felt belt. Excessive overdrive of the hard roll should be avoided, however, because it has the drawback that it involves an unnecessary expenditure of energy.
Other smooth faced squeeze rolls of selected surface compositions can also be rendered suitably slippery, by the continual application of selected lubricants, to obviate picking and sticking when driven at least .3 to 20% faster than the paper web. Various combinations of roll composition and lubricant have been empirically worked out for specified pulps, as will be pointed out. Theuse of Teflon faced rolls without lubricant is presently preferred, however, because such use solves the difficulty for all pulps, avoids the expense of continually supplying lubricant, and avoids the addition of a possibly undesired ingredient to the paper web.
Other objects and advantages will hereinafter appear.
in the drawing forming part of this specification,
FIG. 1 is a fragmentary view in transverse section, showing parts of an illustrative wet press which embodies a practical and advantageous form of the invention;
FIG. 2 is a sectional view taken on the line 2-2 of PEG. 1, looking in the direction of the arrows;
PEG. 3 is a sectional view taken on the line 33 of FIG. 1, looking in the direction of the arrows;
FIG. 4 is a fragmentary sectional view taken on the line 4-4 of FIG. 3, looking in the direction of the arrows; and
FIG. 5 is a view similar to FIG. 2, but of a modified form of mechanism adapted for supplying lubricant to the squeeze roll.
The illustrative mechanism of FIGS. 1 to 4 is shown as supported by two floors l0 and 12 of a building. The support for the upper floor 12 consists in part of upright columns 14- (one shown) and horizontal I-beams 16-. Details of the supporting structure form no part of the present invention, and will not be further described. With the exception of the slippery facing of the hard, webengaging roll 18 and the means for over-driving such roll relative to the paper web 20 and a felt belt 22, the press illustrated may be in all respects conventional.
A lower roll 24- of rigid construction, but having a surface portion, at least, composed of soft rubber or other suitably yielding material is made fast on a supporting and driving shaft 26 which is journaled in bearings 28, carried by pedestals 30. An extension 32 of the shaft has fast upon it a bevel gear 34 which is driven by a v bevel gear 36 fast on a shaft 38. The shaft 38 is mounted in bearings carried by a pedestal 40. A tapered pulley 42, fast on the shaft 38, is driven through a belt 44 from an oppositely tapered pulley 46, fast on the line shaft 48 of the paper making machine. The belt 44 is provided with conventional manually adjustable guides 46a for adjusting and setting the speed of the roll 24 relative to the other parts of the paper making machine, as may be required by operating variables.
The belt adjuster 46a is supported by a rigid, stationary upright 46b. Upper and lower yokes 46c embrace both runs of the belt adjacent the tapered pulleys 42 and 46, respectively. Each yoke 46c has two bars 460! afiixed to it, and each bar 46d has rigidly connected with it a guide rod 46c which extends snugly but slidably through the upright 46b. Rods 46 connected to the yokes 46c with freedom for rotation but not for axial movement relative thereto, extend outward from the yokes 46c in parallelism with the rods 46a, and serve as feed screws for the yokes.
Each rod 46 has threaded upon it a flanged, internally threaded sleeve 46g. Each sleeve flange bears against one face of the upright 46b, While the sleeve body, which is rotatably borne by the upright, extends through the upright and has afiixed upon it a sprocket 46h whose hub bears against the face of the upright which is remote from the sleeve flange. A chain 46f runs upon the sprockets 46h for rotating the sprockets and the sleeves '46g in unison. A flanged pin 46k has its flange disposed in engagement with one side of the upright 46b and has fast upon it an operating sprocket 46m for the chain 461, the sprocket being engaged with the side of the upright remote from the flange of the pin 46k. An operating wheel or knob 4611 is made fast on the pin 46k.
The felt belt 22 which carries the paper web 20 through the press, runs in engagement with the roll 24 and is driven by the roll. The belt 22 runs also upon suitable guide rolls 23 as shown.
' The roll 18 is a hard roll of any suitable material. In the illustrative press the roll 18 has its slipperiness increased to a very high degree so that it may be run at a speed substantially different from that of the paper web 20 without materially affecting the speed at which the web is driven and without straining the web. The roll 18 is desirably spray coated with Teflon and the Teflon is then sintered to provide a smooth and very slippery surface. The sintering is performed at a temperature of about 700 to 750 F. and hence the material chosen for the roll body must be capable of withstanding such temperatures. Steel is an example of a very satisfactory material for the roll body. Brass is also suitable, but a film of only about .001 inch thickness can be formed on brass, whereas a film of .005 to .007 inch thick can be formed on steel or cast iron.
The roll 18 is fast on a shaft 50 which is revolubly supported in bearings 52, carried by arms 54 which are swingably mounted on the pedestals 30. Suitable means, not shown, are provided for pressing the roll 18 toward the roll 24 with predetermined force. The shaft 50' is extended through universal joints 56, an intervening link 58, and a terminal shaft section 60. The shaft section 60 is supported in a bearing carried by the pedestal 62 at the line shaft side of the machine, and has a bevel gear 64 fast upon it. The gear 64 is driven by an equal bevel gear 66 fast on a shaft 68. The shaft 68 is mounted at its respective ends in a bearing carried by the pedestal 62 at the line shaft side of the machine, and in a bearing carried by a pedestal 70.
A tapered pulley 72, fast on the shaft 68, is driven through a belt 74 from an oppositely tapered pulley 76, fast on the line shaft 48 of the paper making machine. Conventional guiding and setting means, desirably identical with the corresponding means 46a for the belt 44, is provided for adjusting the belt 74 and thereby adjusting the drive ratio from the shaft 48 to the roll 18.
By means of this change speed device, the roll 18 may be adjusted to run at a surface speed sutficient to meet the minimum requirement for eliminating picking, i.e, 3 to 20% over the speed of the paper Web. The capacity of the change gear unit is desirably sufficient to go beyond the larger minimum requirement of 20%, there being nothing critical about holding the excess of speed down to the minimum requirement.
A number of materials have been tried for the surface coating of the roll 18, these including polished stainless steel, rubber compositions manufactured by Stowe-Woodward of Newton Falls, Mass. and sold under the trademarks Stonite and Microrok, porous surfaced rock-hard rubber roll.
Stonite is used as a cover for press rolls on the wet end of paper making machinery. The standard cover thickness of Stonite is one-half inch. The Stonite cover has a P and J hardness of Zero to one. It consists of a combi nation of natural rubber with tiny particles of granite and was originally developed to replace granite rolls.
4 Teflon has been found to overcome the difiiculty and to operate in a very satisfactory manner.
Notwithstanding the extreme slipperiness of the Teflon surface, it is essential that the Teflon faced squeeze roller 18 be driven at a diiierent rate from the paper web and to a degree dependent upon the characteristics of the pulp of which the Web is composed. The problem of picking can be overcome by driving the squeeze roll slower or faster than the web, but when the squeeze roll is driven slower, waviness of the paper results. Overdn've of the squeeze roll is therefore to be preferred.
With pine pulp, hardwood pulp or a blend including neutral sulfite semi-chemical pulp, the roller 18 can be seen to become coated with fibers when the roll 18 is driven at the same surface speed as the paper web. As the speed of the roller 18 is gradually increased, however, a point is reached at which the picking on the Teflon surface clears up, This corresponds to the minimum degree of overdrive for practical operation. This adjustment is recommended as the most economical adjustment capable of eliminating picking and sticking. The optimum adjustment can be quite readily ascertained for each pulp by trial and observation, so long as care is taken not to permit operation under severe picking conditions, nor for a protracted period under conditions which cause accumulation of fibers on roll 18.
Although facings of neoprene rubber, stainless steel, and Stonite are unsatisfactory without lubrication, they can be rendered sufliciently slippery through limited lubrication to work satisfactorily at least in specific circumstances. In every instance there must be adequate overdrive of the squeeze roll.
An overdriven squeeze roll faced with neoprene rubber can be made slippery enough to work without picking on all pulps tried, including pine pulp, hard Wood pulp and pulp blends containing neutral sulfite semi-chemical pulp, when lubricated with silicone oil or linseed oil. Such a roll can also be made to work without picking when lubricated with wax and used with pine pulp, but not with hard wood or semi-chemical pulp.
An overdriven squeeze roll faced with stainless steel can be made slippery enough when lubricated with linseed oil to eliminate picking when used with neutral sulfite I semi-chemical pulp but not otherwise.
An overdriven squeeze roll faced with Stonite can be made slippery enough when lubricated with linseed oil to eliminate picking when used with pine pulp but not otherwise.
In FIG. 5 a portion of a wet press is illustrated, generaly similar to that of FIGS. 1 to 4, but especially adapted to render the squeeze roll 18a slippery through the application of lubricant. The press of FIG. 5 includes all the structure of FIGS. 1 to 4, corresponding parts being designated by corresponding reference characters with the subscript a added in each instance.
The squeeze roll 18a, however, may be faced with neoprene rubber, say of 70 Shore A durometer hardness. A lubricant such as silicone oil or linseed oil is supplied in small quantity from a pan by a pick-up roll 82, the thickness of the lubricant film being controlled by adjusting the pressure of a doctor blade 84 which bears upon the roll 82. The oil is transferred by the roll 82 to the absorbent cover 86 of a transfer roll 88. Having started the mechanism into operation with the roll 18:; suitably lubricated and running considerably faster than the web the operator may cut down on the rate of operation of the roll 18a until he sees that picking has started, whereupon he may increase the rate of operation of the roll 18a just enough to eliminate picking.
The apparatus of FIG. 5 desirably includes a doctor blade 92 which cooperates with the roller 18a for cleaning the roller, as is usual in conventional presses.
The results of typical runs, made on a laboratory paper machine under experimental conditions, are set forth below. Y
The squeeze roll surfaces were composed, respectively, of Teflon, stainless steel, neoprene rubber of 70 Shore A durometer hardness, and Stonite. The lubricants employed were:
Union Carbide X 522 silicone oil having a viscosity of 95 centistokes at 77 F. This oil is insoluble in water, but is soluble in high and low aromatic solvents. The oil was used as received, without dilution.
Iohnsons wax 912Dl09-II, which has a non-volatile content of 20%. The wax emulsion was used as received, without dilution.
A soap containing calgon (sodium hexametaphosphate).
Commercial raw linseed oil as purchased, without dilu- Table I [Pulpz Unbleached pine refined to 26 seconds Williams ireeness] Degree of Picking Roll Lubricant Same Speed 7.5% Increased Speed Teflon none.
rupture moderate Stainless steel rupture.
hcavy---.. very slight moderate-.-. heavy.
none. Neoprene Rubber Do.
moderate none. rupture---- rupture. moderate--.. very slight Stonite.-.. very slight-. Do. soap -do Do. linseed oil ..do none.
Table II lPulp: Unbleached hardwood refined to 25 seconds Williams freeness} Degree of Picking Roll Lubricant Same Speed 7.5% Increased Speed Teflon nonemoderate..- none.
o-- rupture--.-. rupture. heavy. Stainless Steel rupture.
Do. slight. moderate.
none. Neoprene Rubber. rupture.
Do. itrmirn rupture,
soap Do. linseed oil.-.. heavy.
Table III [Pulpz Bleached neutral sulfite semi-chemical at 47 seconds Williams freeness Degree of Picking Roll Lubricant Same Speed 7.5% Increased Speed Teflon slight none.
moderate...- slight. slight Do. Stainless Steel moderate.... moderate.
-.-- do Do.
slight none. moderateslight. very slight.. none. Neoprene Rubber wax moderate... moderate.
.soap.. o rupture.
linseed oil. none none. none moderate.--. moderate. silicone .do Do. Stonite w r heavy heavy. soap moderate--. slight. linseed 011.. .do Do.
While certain preferred embodiments of the invention have been illustrated and described in detail, it is to be understood that changes may be made therein and the invention embodied in other structures. It is not,therefore, the intention to limit the patent to the specific constructions illustrated, but to cover the invention broadly in whatever form its principle may be utilized.
1. A wet press for paper machines comprising, in combination, a nip forming press couple composed of a comparatively soft roll, a comparatively hard paper-web-engaging squeeze roll opposed thereto, an endless carrying belt of felt for the paper web, driven through the nip by the press couple, and means driving the webengaging squeeze roll at :a surface speed at least 3 to 20% over the speed at which the wet paper web is driven, the squeeze roll having a surface so slippery that picking is completely avoided by the driving of the squeeze roll at a minimum surface speed in the range of 3 to 20% over the speed at which the wet paper web is driven by the press couple.
2. A wet press for paper machines, as set forth in claim 1 which further includes a change speed unit settable to overdrive the squeeze roll at different chosen surface speeds including the range of 3 to 20% over the speed at which the wet paper web is driven.
3. A wet press for paper machines as set forth in claim 1, in which the squeeze roll has a surface of polytetra- .fiuoroethylene which is so slippery, even when run dry,
that picking by the overdriven squeeze roll is completely avoided.
4. A wet press for paper machines as set forth in claim 1, in which the overdriven squeeze roll has a coating of material which is adapted through a restricted application of oil to be rendered sufliciently slippery to avoid picking, and means for supplying oil to the squeeze roll at a regulated low rate adequate to avoid picking.
5. A wet press for paper machines comprising, in combination, a nip forming press couple composed of a comparatively soft roll, a comparatively hard paper-we-h-engaging squeeze roll opposed thereto, an endless carrying belt of felt for the paper web, driven through the nip by the press couple, and means causing the squeeze roll to travel at a surface speed which differs by at least 3 to 20% from the speed at which the wet paper web engaged by it is driven, the squeeze roll having a surface so slippery that picking may be completely avoided by driving the pressure roll at a surface speed which differs from that at which the wet paper web is driven by at least 3 to 20%.
6. The method of reducing the water content of a wet paper web by pressing, while avoiding picking, which comprises passing the paper web together with a contiguous web of felt through a press couple consisting of a felt engaging roll and a hard, slippery surfaced, web engaging, squeeze roll, with the squeeze roll traveling at a surface speed exceeding that of the paper web by at least 3 to 20%, the excess speed and the slippery surface of the squeeze roll having as a combined effect the avoidance of picking.
7. The method as set forth in claim 6 in which the slippery squeeze roll surface is composed of poly-tetra fluoroethylene.
8. The method as set forth in claim 6 in which the surface material of the squeeze roll consists of neoprene rubber rendered sufficiently slippery to avoid picking by the regulated application of oil chosen from the group consisting of silicone and linseed oils.
9. The method as set forth in claim 6 in which the web acted upon is composed of a blend consisting of sub stantially neutral sulfite semi-chemical hardwood pulp and 30% pine pulp, and in which the surface material of the squeeze roll is chosen from the group consisting of stainless steel and neoprene rubber, and is rendered sufficiently slippery to avoid picking by the regulated application of linseed oil.
10. The method as set forth in claim 6 in which the web *acted upon is composed of pine pulp, and in which the irom that of the paper web to an extent which is at'least surface material of the squeeze roll is chosen from the sufficient in view of the slippe-riness of its surface and the .group consisting of neoprene rubber and Stonite and is character of the furnish, to obviate picking.
rendered sufiiciently slippery to avoid picking by the regulated application of linseed oil. 5 References Cited in the file ofthis patent '11. A wet press for paper machines comprising, in
combination, a nip forming press couple composed of a 1 UNITED STATES PATENTS comparatively soft roll and a comparativelyhard, paper- 1,380,687 y. 00L 1932 web-engaging, slippery faced squeeze roll opposed thereto, 1,964,312 Bright June 26, 1934 -an endless carrying belt of felt for the paper web, driven 10 2,798,414 Muggleton July 9, 1957 through the nip by the press couple between the comparaptively soft roll and the paper web, and controlling the TH ERENCES speed of the paper web, means for driving. the rolls of Rudner: Flu0rocarbons, Reinhold Plastic Applica- :said couple in different speed ratios ,so" thatthe squeeze tions.Series:1 95.8, pages 8-13.. 3::. 1: roller may be caused to travel at a speed which differs 5