US3468242A - Paper machinery - Google Patents

Description

p 3, 1969 P. M. SCHAFFRATH 6 PAPER MACHINERY Filed March 30, 1966 INVENTOR. PAUL M. SCHAFFRATH ATTORNEYS States Unite US. Cl. (i121 8 Claims ABSTRACT OF THE DISCLOSURE Liquid is removed from a paper web by carrying the web on a felt through a pressure nip defined by a web contacting roll and a hollow perforated felt contacting roll defining a cylindrical chamber. A flexible seal member is positioned within the chamber in sliding contact with an arcuate section of the roll wall and extends from adjacent the nip in the direction of rotation of the roll. The seal member is rotatably adjustable, and water is removed from the perforations either by pressurizing the chamber or by producing suction adjacent the outer surface of the roll.

This invention relates to apparatus for removing moisture from a paper web, and more particularly, to a novel and economically constructed roll press which is adapted to receive a paper web carried by an endless felt and to squeeze moisture from the web and the felt in such manner that minimum moisture will be reabsorbed by the felt.

Suction rolls including a hollow perforated cylindrical roll having a stationary suction box mounted therein are commonly used to remove moisture from a paper web. In general, however, these rolls have been found to be expensive in construction and, of course, require the operation of a pump for providing suction as well as service for replacing seals and other components.

Accordingly, it is a primary object of the present invention to provide a novel roll press which is of low cost in construction, requires a minimum of maintenance, and is highly effective in removing or separating liquid or moisture from a paper web carried by a felt.

As another object, the present invention provides a novel roll press which can be used in many paper machines in place of a suction press and basically includes a hollow cylindrical roll having circumferentially spaced openings or perforations into which liquid is pressed at a nip formed with a second roll and further includes means for producing an outward flow of liquid from the perforations after the felt has left the roll so that the perforations are open for receiving liquid when passing through the nip.

Still another object of the invention is to provide a roll press as outlined above wherein a sealing member is mounted within the liquid receiving roll adjacent the openings or perforations through the roll wall and is adapted to seal ofI the perforations after they pass through the nip for reducing the tendency of liquid to be thrown centrifugally out of the perforations and back onto the felt.

As another object, the present invention provides a roll press as outlined above wherein a doctor member is positioned adjacent the outer surface of the liquid receiving roll after the felt is separated from the roll to produce a low pressure by venturi action causing the liquid retained within the holes or perforations to be sucked outwardly into a collecting chamber thereby opening the perforations for receiving liquid at the nip.

As another object, the present invention provides a roll press as outlined above wherein the liquid receiving roll includes a cylindrical metal shell covered by a layer of resilient material in which is formed circumferentially spaced openings or perforations for receiving liquid from a felt at the nip, and wherein the metal shell is provided with corresponding aligned perforations which are substantially smaller than the perforations within the resilient layer to avoid a significant decrease in strength of the wall while providing for purging of air entrapped in the openings formed within the outer cover.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawings FIG. 1 is a schematic side view of a roll press constructed in accordance with the invention and with a portion of the liquid receiving roll broken away to show the detailed construction of the roll;

FIG. 2 is an enlarged fragmentary section view showing an alternate construction for the openings or perforations formed within the liquid receiving roll; and

FIG. 3 is a fragmentary side view showing an alternate press construction in accordance with the invention.

Referring to the drawing, which illustrates preferred embodiments of the invention, the press shown in FIG. 1 includes a top press roll 19 rotatably mounted on a horizontal axis 11 and a bottom press or moisture receiving roll 13 having its axis 15 parallel with the axis 11. The rolls lit and 13 are mounted on a suitable frame (not shown) to define a nip 16 into which a felt 18 carrying a paper web 20 is directed for squeezing moisture from the web 20 through the felt 18 and into the roll 13. As shown in FIG. 1, the felt 18 is directed out from the nip 16 away from the rolls 10 and 13 while the paper web 20 is carried with the top roll 10 but is redirected to the felt 18 so that the web is carried by the felt to a successive station.

In accordance with one form of the invention, the cylindrical wall 22 of roll 13 defines an internal chamber 24- and is formed having an inner steel shell 26 covered by an outer resilient layer 28. Formed within the wall 22 around its entire circumferential area are a series of radially extending holes or perforations which are drilled through the resilient layer 28 and the shell 26.

Mounted within the chamber 24 and in sliding engagement with the inner surface of the shell 26 is a flexible sealing member 32 which is carried by a frame 33 so that the sealing member 32 covers the inner ends of the perforations 30 as they pass over the sealing member 32 thereby closing the perforations 36 with the chamber 24. Preferably, the frame 33 is angularly adjustable so that the leading edge 34 of the sealing member 32 can be precisely adjusted in relation to the nip 16.

Mounted adjacent the outer surface of the bottom roll 13 is a vertically extending doctor member 36 which defines a narrow space 38 with the outer surface of the roll 13. A surface doctor 40 is mounted adjacent the lower portion of the roll 13 and in sliding contact with the outer surface of the roll for wiping the water or liquid film from the surface. Connected to the doctor member 36 and positioned .below the surface doctor 40 is a save-all 42 which is connected to a drain line 43.

In operation, when a paper web 20 is carried into a nip 16 by the felt 18, a concentrated pressure, as for example, 375 pounds per linear inch, is exerted on the paper web 20 so that the moisture within the web 20 is pressed through the felt 18 and into the perforations 30. Since the inner ends of the perforations 30 positioned at the nip 16 are open to the chamber 24, the air displaced by the liquid within the perforations 3i enters the chamber 24. Thus air is prevented from being entrapped in the perforations 36} at the nip 16 so that the liquid is readily re- C13 ceived within the perforations. As soon as the perforations have advanced from the nip 16, the resilient sealing member 32 seals the inner ends of the perforations 3t] and thereby prevents the liquid retained within the perforations 35) from being thrown outwardly back onto the felt 18 due to centrifugal forces.

As can be seen in FIG. 1, when the perforations 30 advance past the flexible sealing member 32, the perforations 30 enter the narrow space 38 defined by the doctor member 36 where a venturi action produces a decreased pressure which tends to suck the liquid out of the perforations 39. Since the sealing member 32 is no longer blocking the inner ends of the perforations 30 as the perforations pass the doctor member 36, air is free to flow into the perforations 30 thus providing for a free discharge of the liquid into the collection chamber defined by the save-all 42. As mentioned above, the surface doctor 40 is provided to wipe the remaining film of liquid from the outer surface of the roll 13.

It has been found that in the absence of the sealing member 32, there is some tendency for moisture or liquid pressed into the perforations 30 to be thrown back onto the felt 18. However, even without the sealing member 32, if the perforations 39 are of small diameter, air is not entrapped or pressurized within the perforations 3d, and thus the centrifugal forces acting on the liquid must overcome the capillary attraction or surface adhesion of the liquid within the perforations 30. Thus the smaller the diameter of the perforations 3d, the less tendency there is for liquid to be thrown out of the perforations and back onto the felt 18.

In accordance with another form of the invention, as shown in FIG. 2, the bottom press or liquid receiving roll is formed with an inner metal cylindrical shell 47 and an outer resilient cover 48 in a manner similar to the construction of the roll 14 shown in FIG. 1. In this embodiment, however, the holes or perforations St formed within the metal shell 47 are substantially smaller than the concentric holes or perforations 52 formed within the resilient cover 48. This construction provides the advantage of a roll having greater strength since less metal is removed in forming the perforations '50. On the other hand, the perforations 50 are sufiiciently large to enable displaced air within the perforations 52 to vent into the internal chamber 24. That is, the perforations 50 provide bleed holes for the perforations 52 formed within the resilient cover 48. Otherwise, the perforations 50 and 52 cooperate with the seal member 32 and function in the same manner as that described above for the press shown in FIG. 1.

In accordance with another embodiment of the invention, as shown in FIG. 3, the liquid is removed from the perforations 30 formed within the bottom press roll 13' simply by supplying pressurized air to the chamber 24 through the conduit 55 connected to a suitable air supply (not shown). Thus the liquid is discharged from perforations 3t) and wiped by the surface doctor 40 for collection within the container 57 connected to the drain line 58. That is, instead of sucking the liquid from the perforations 30 by using the doctor member 36 to produce a venturi action, the liquid within the perforations 30 is forced outwardly into the container 57 by providing a supply of pressurized air through the conduit 55.

From the drawing and the above description, it can be seen that a roll press formed in accordance with the present invention provides several desirable features and advantages. Basically, the construction of the press roll 13 with the perforations 30 extending through the wall 22 enables the roll 13 to collect or receive moisture or liquid from the felt 18 and paper web 20 as they extend through the nip 16. Furthermore, since the liquid is free to flow into the perforations 30 without entrapping air, there is no pressurized air within the perforations 30 tending to blow the liquid back onto the felt 18. For example, as a result of one experimental run without the sealing mem- 1 her 32, a paper web having 16% solids or fibers was directed into the nip 16 and was removed from the press roll It having a consistency of 38% solids.

Furthermore, employing the sealing member 32 and the doctor member 36 causes the paper web 20 to be received from the nip 16 having a substantially higher consistency. Thus the sealing member 32 effectively eliminates the centrifugal discharge of liquid from the perforations 30 until they reach the low pressure zone within the narrow space 35. Then .after the moisture or liquid is removed from the perforations 30 by either the doctor member 36 or by pressurizing the chamber 24', the perforations 30 are thereby open for receiving liquid as they pass again through the nip 16. The structure of the roll 45 shown in FIG. 2 provides the additional advantage of a shell 47 having greater strength while at the same time enabling displaced air within the perforations 52 to be purged through the perforations 50 and into the chamber 24.

Whlie the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A roll press for receiving a felt carrying a paper web and adapted to press liquid from both the web and felt, comprising a pair of rolls mounted to define a nip through which the felt and web pass with one roll contacting the web and the other roll contacting the felt, said felt-contacting roll having a cylindrical wall defining an internal cylindrical chamber, means forming a plurality of circumferentially spaced perforations within said wall and extending into communication with said chamber so that as the felt and web extend through said nip, liquid is pressed from the Web through the felt and into said perforations causing displaced air to enter said chamber, means causing an outward flow of liquid from said perforations after the felt is directed from said roll to open said perforations for receiving liquid within said nip, and a flexible seal member mounted within said chamber in sliding contact with an arcuate section of said wall and extending from adjacent said nip for a predetermined arcuate distance in the direction of rotation of said wall for closing said perforations immediately following said nip and thereby reducing the tendency of liquid to be thrown centrifugally outwardly from said perforations back onto the felt.

2. A roll press as defined in claim 1 wherein said means causing an outward flow of liquid from said perforations includes a doctor member positioned adjacent said roll for effecting a venturi action.

3. A roll press as defined in claim 1 including doctor means engaging the outer surface of said felt-contacting roll after liquid is forced out of said perforations for removing liquid film from said surface.

4. A roll press as defined in claim 1 wherein said cylindrical wall of said felt-contacting roll includes a cylindrical metal wall covered by a uniform layer of resilient material, means forming a plurality of circumferentially spaced perforations within said layer, and means forming a corresponding plurality of smaller perforations in said metal wall to avoid a substantial decrease in strength of said roll while providing communication between said perforations in said layer and said chamber.

5. A roll press as defined in claim 1 wherein said means causing said outward fiow of liquid from said perforations includes means for pressurizing the entire said chamber.

6. A roll press as defined in claim 1 wherein said seal member comprises a resilient flexible seal member.

7. A roll press as defined in claim 1 including means for adjustably positioning said seal member in relation to said nip.

8. A roll press for receiving a felt carrying a paper web and adapted to press liquid from both the web and felt, comprising a pair of rolls mounted to define a nip through which the felt and web pass With one roll contacting the web and the other roll contacting the felt, said felt-contacting roll having a cylindrical wall defining an internal cylindrical chamber, means forming a plurality of circumferentially spaced perforations within said wall and extending into communication with said chamber so that as the felt and Web extend through said nip, liquid is passed from the web through the felt and into said perforations causing displaced air to enter said chamber, an arcuate seal member mounted within said chamber in sliding contact with an arcuate section of said wall and extending from adjacent said nip for a predetermined arcuate distance in the direction of rotation of said wall for closing said perforations immediately following said nip and thereby reducing the tendency of liquid to be thrown centrifugally 1,834,852 12/1931 Kutter 100121 3,004,289 10/ 1961 Missbach. 3,198,696 8/1965 Justis 100-121 XR FOREIGN PATENTS 171,206 11/ 1921 Great Britain.

6,404,132 10/1964 Netherlands.

PETER FELDMAN, Primary Examiner US. Cl. X.R.

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