Press Section for a Paper-Making Machine Having a Movable Cantilever Beam

The invention relates to a press section for a paper-making machine in which a continuous felt web, called a felt, carries a web of paper that is to be dewatered through a nip defined between two press rolls. The continuous felt must be periodically replaced.

It is known to provide the press section with what is called a cantilever beam to facilitate mounting a new felt. One example of a cantilevered press section is shown in U.S. Pat. No. 3,547,776. One of the press rolls, in this case the lower roll, is inside the continuous loop of the felt. The press roll rests on a component of the drier frame that is located on the operating side of the machine, i.e. the side having the machine controls on it, and also on another drier-frame component on the power side, where the drive connections to the rolls may be found. Two cantilever beams extend from the operating-side component to the power-side component and from there to a connection outside the press section. This connection is usually a structural element, although it is not mentioned in the above U.S. patent. When this paper-making machine is ready to operate, the drier-frame component on the operating side rests, through removable intermediate pieces, on one of the bases of the machine. The power-side component also rests on one of the machine bases, although its supports cannot be removed.

As a preliminary to mounting a new felt, the drier-frame component on the operating side of the machine must be slightly lifted to remove the intermediate pieces. One or two pneumatically or hydraulically operated piston cylinder combinations, spring or the like type lifting devices, or other force generators are usually positioned between the machine base and the operating-side component to lift the latter. Once the operating side component has been lifted and the intermediate pieces removed, the piston cylinders must be evacuated, leaving the operating-side drier-frame component supported only by the cantilever beams. In this state, the new felt can be introduced into the press section. The operating-side ends of the cantilever beams tend to sag under the weight of the drier-frame component and the press roll resting on it, so that the operating-side drier-frame component will drop. Since the cantilever beam is rigidly attached to the operating-side drier-frame component, that frame component will assume a skewed position as the cantilever beam deforms. This puts a lot of stress on the bearings that support the press roll because the distance between the operating-side and power-side bearings of each roll, which is resting on the operating-side component of the drier frame, increases. This leads to the risk of an excessive axial force in the roll bearings.

The above noted design has other drawbacks. The severe deformation of the cantilever beams generates powerful forces in threaded connections, especially in the connections between the beams and the operating-side drier frame components. Several time-consuming operations are necessary to insert a new felt. The operating-side component must be lifted, the intermediate pieces removed, the component released, the new felt inserted, the component lifted again, the intermediate pieces replaced, and the component supported on them again.

Another known system of mounting a new felt, described in German OS No. 2,239,267, required fewer operations. The essential characteristics of this known design include a cantilever beam that is non-rigidly attached to the power side drier-frame component by an articulated joint. The end of the cantilever beam outside the press section is connected to the supporting structure by a drawbar. The operating-side end of the beam supports a bearing housing for a press roll and is connected with the machine frame through a removable intermediate piece, which pivots around a vertical axis. A continuous felt and a continuous plastic wire screen, called a wire, travel over the press roll, which in this case is an upper roll.

The only step preliminary to mounting a new plastic wire is to draw down the end of the cantilever beam that is outside the press section with a tensioning device or force generator and only until the operating-side end drier frame component releases the intermediate piece supporting it. The intermediate piece on the operating-side end of the cantilever beam is then removed, the wire is introduced, and the original state is rapidly restored. One drawback to this known design, however, is that the operating-side drier-frame component which is in this case one of the press-roll bearing housings, is rigidly connected to the cantilever beam. Since the cantilever beam is in principle deformed in exactly the same way as in the first mentioned example, the bearing housing will also assume a skewed position, as will the leading-roll bearing housings when mounted on the cantilever beam.

There are also other considerations. Only one of these belts, the plastic wire, is easy to introduce into the press section, in the form of an open loop. In contrast, the felt can be mounted in this way only over the press roll and some of the felt-leading or other felt supporting rolls. To install the felt into its final position, it has to be folded or pleated, because in its final position, it loops around other felt-leading rolls that are supported on longitudinal beams at the top of the press section. Many contemporary felts, however, are too thick to be thus folded or pleated. Also, the folding or pleating cannot be done in the wider paper-making machines. One makeshift approach is to remove the felt-leading or supporting rolls, mount the loop of felt, and remount the rolls inside the felt loop. This method takes a lot of time and is extremely difficult in wide machines.

The present invention is intended to eliminate the drawbacks of the designs described above. According to the invention, the drier-frame component on the operating side will remain essentially in the same position as when the machine is ready to operate while that component is supported only by the cantilever beam. The component will not lie askew in any case. Even though it is very long, the continuous felt can also be introduced in the form of an open loop, i.e. without being folded or pleated, into the press section even when some of the felt-leading rolls rest on the upper surfaces of elevated longitudinal beams.

A system of force generators, like that known from German OS No. 2,239,267, is utilized in the present invention. The force generators engage the cantilever beam and bring it into a "state of tension" so that its operating-side end will exercise an upward force on the operating-side drier frame component to compensate for the inherent weight of that component and the structures attached to it.

The present invention, however, also deviates substantially from the device specified in the above Offenlegungsschrift. First, not only the drier-frame component on the power side of the machine but also that drier-frame component on the operating side can move in relation to the cantilever beam. Second, the operating side drier-frame component is connected to the drier frame component on the power side by at least one additional transverse beam that is preferably rigidly connected to both those drier-frame components. This means that when the cantilever beam is in a state of tension, the operating-side component will largely retain its position in relation to the power-side component, no matter how much the cantilever beam deforms. The only preliminary step to changing a felt is to lift the drier-frame component on the operating side very slightly (about 1-2 mm) while it is subject to the force of the tensioned cantilever beam. This position is maintained after the intermediate pieces have been removed and while the felt is being introduced. There is absolutely no skewing of the operating-side drier-frame components. Even when a very long felt is employed, it now becomes possible to support all the leading or felt supporting rolls inside the loop of felt on the operating-side drier-frame component or on an extension of it, such as a roll bearer oriented upward. The operating-side drier-frame component, including the extension, if any, is often as a whole an extremely complex structure, which usually has to be supported at two or three points with intermediate removable pieces on machine-framework structures below it. The intermediate pieces used with the invention can all be removed simultaneously to permit introduction of the continuous felt in the form of an open loop into the paper-making machine, even a felt that is very long. Since this saves considerable time, paper manufacture needs to be interrupted only briefly to change the felt.

Another deviation from OS No. 2,239,267 is that no roll is directly supported by the cantilever beam. The bearings for all the rolls are instead attached to the drier-frame components. Another significant characteristic of the invention is that the tensioned cantilever beam can be allowed to sag a lot more than the cantilever beam in the known designs because deformation of the beam can occur completely independent of the drier-frame components and rolls. This enables that cantilever beam to be thinner and hence easier and cheaper to manufacture. In calculating the cross-sectional dimensions of the cantilever beam, in other words, it is only necessary to consider material's strength, while the degree of deformation of the beam in the state of tension can be ignored. In previous designs, on the other hand, the beam must be as rigid and hence as heavy as possible to keep it from sagging as much as possible when it is tensioned.

Some embodiments of the invention will now be described with reference to the accompanying drawings, in which

FIG. 1 is a schematic side view of the press section of a paper-making machine,

FIG. 2 is a cross-sectional view through the press section along line II--II in FIG. 1, and

FIGS. 3 through 5 are schematic representations, viewed as in FIG. 2, showing various methods of tensioning the cantilever beam.

FIG. 1 shows a press section employed to dewater a paper web. Web 19 to be dewatered arrives from a wire section 20. The web is removed from the wire by a felt 17 and by a suction roll 17a and is then fed through three roll nips, formed by the press rolls 30, 31 and 31, 32, and 32, 33, in succession. Web 19 is then supplied to the subsequent dry section, of which only the first drying cylinder 21 is illustrated in FIG. 1. As web 19 leaves the second nip formed by rolls 31, 32 along with felt 17, it separates from felt 17 and is carried along alone by the surface of roll 32 into the third nip formed by rolls 32, 33. Another dewatering felt 18 also runs through the third nip. The guide rollers 34 through 39 guide the felt 18.

The design of the press section will now be specified, initially through the example of those frame components that are necessary for rolls 32 through 39.

FIGS. 1 and 2 show how the press roll 32 is mounted in an operating-side structure 1f and a power-side structure 2f of the press section of a paper-making machine. Two drier-frame components, 1e and 2e for press roll 33 and for leading or felt guiding rolls 34, 37, 38 and 39, rest on structures 1f and 2f. Installation of the felt loop 18 from the operating-side is blocked by the unbroken structure extending from the rolls 33-39 to the support base 1 and 1f.

To enable installation and removal of the felt 18, removable intermediate pieces 10 are provided between operating-side drier-frame component 1e and structure 1f. On the other hand, power-side drier-frame component 2e rests directly on structure 2f without intermediate pieces between them. Two mainly horizontally extending roll bearers 1h and 2h are attached to the upper surface of each drier-frame component 1e and 2e, respectively, to support rolls 37 and 38. On the operating side, the outer end of roll bearer 1h rests through a removable intermediate piece 7b on a structure 1i that stands on an elevated longitudinal beam 1g. Beam 1g rests on a large machine framework 1. Felt leading roll 35 and an associated structure 1k are also mounted on the longitudinal beam 1g. Between operating-side drier-frame component 1e and each of the longitudinal beam 1g and another longitudinal beam 1b on opposite sides of the component 1e, there is another respective removable intermediate piece 11.

Drier-frame components 1e and 2e have window-like holes 41 and 42, respectively, through them which receive a cantilever beam 3. Cantilever beam 3 extends conventionally from operating-side drier-frame component 1e to power-side drier-frame component 2e and thence through the press section to a support 4 that is an integral part of the framework. As viewed in section (FIG. 2), cantilever beam 3 is supported at only two points, on an articulated base 43 in the hole 42 in power-side drier-frame component 2e and at support 4.

Cantilever beam 3 has sliding-guide plates 6 in the vicinity of holes 41 and 42 to guide it laterally. Plates 6 are in contact with cooperating guide surface 5 on drier-frame components 1e and 2e.

Since there is no secured connection between cantilever beam 3 and operating-side drier-frame component 1e, aside from vertical sliding guides 5 and 6, drier-frame components 1e and 2e are rigidly attached together by at least one additional transverse beam 44 that is nonshiftably secured to the components 1e and 2e. FIG. 1 shows such an additional transverse beam 44 with broken lines. Another transverse beam of the same kind can be mounted at the free end of roll bearer 1h.

A recess 3a extends down into and partially across the operating-side end of the cantilever beam 3 to accommodate a hydraulic piston-cylinder combination 14 between cantilever beam 3 and drier-frame component 1e. The piston in cylinder 14 can bend the free, operating-side end of cantilever beam 3 downwardly, as illustrated by the dot-and-dash line in FIG. 2. The cylinder combination 14 on component 1e simultaneously exerts an upward force on operating-side drier-frame component 1e. This force is just strong enough to lift the operating-side drier-frame component 1e very slightly off intermediate pieces 10 so that they can be removed. Operating-side drier-frame components 1e and 1h must be lifted slightly to allow a new felt 18 to be introduced. This process will be explained in detail below.

Press roll 33 is mounted on pivotable arms 45, which are located at components 1e and 2e. The press roll 33 is driven by a Cardan shaft 46. Felt-leading roll 34 is also attached to the arms 45. This system allows rolls 33 and 34 to be lifted together when a new felt is introduced.

To change a felt, it is necessary to lift operating side drier-frame component 1e and pivoting arm 45, to then remove intermediate pieces 7b, 10 and 11 on the operating side and to thereafter shift leading roll 36 into the position indicated by the dot-and-dash line, onto roll bearers 1h and 2h.

The spaces now available due to removal of the intermediate pieces permit introduction of a fresh continuous loop felt 18 into the press section. The felt is supported in the vicinity of the operating side of the press section in the form of an open loop and is introduced from left to right, as seen in FIG. 2. Horizontal rods 16 (illustrated in FIG. 1, but not in FIG. 2) can be mounted on the outside of operating-side drier-frame components 1e and 1h or on operating side catwalks (not shown) to facilitate introduction of the felt. The sections of catwalk that must be shifted when changing the felts should fold away to save time.

If it is desired to release the hydraulic cylinder combination 14 during the course of the felt-changing process, additional intermediate pieces (not illustrated) can be inserted between the operating-side drier-frame component 1e after it has been lifted and the operating-side end of the cantilever beam. This is a preventive measure and derives from the impossibility of ruling out cylinder failure.

Another fresh felt 17, which follows a generally C-shaped pathway, can also be introduced into the other part of the press section by using the same method in principle. The design of the respective drier-frame components for this felt, however, differs in detail to some extent from that described above. There is an operating-side drier-frame component 1c that rests through a removable intermediate piece 9 on a base structure 1d. The component 1c supports a roll bearer 1m. Roll bearer 1m has generally a C-shaped opening, to the left in FIG. 1, and toward below-described component 1a and beam 1b. Rolls 17a, 31, 50, 51 and 52 are mounted on drier-frame component 1c and roll bearer 1m. As shown in dash-dot line, roll 53 is also shifted to the roll bearer 1m while the felt is being changed.

Another drier-frame component 1a also rests through removable intermediate pieces 8 on drier-frame component 1c. Longitudinal beam 1b, mentioned above, rests on component 1a. Leading or felt supporting rolls 53, 54 and 55 are mounted on drier-frame components 1a and 1b and thus not on the roll bearer 1m. The felt 17 is wrapped around all of the felt guiding rolls on component 1c and roll bearer 1m, and these rolls are placed to bend the felt 17 into the generally C-shaped pathway shown.

Drier-frame components 1a and 1c have window-like openings like those in drier-frame component 1e, with a cantilever beam 3' extending into each. Beams 3' are designed essentially like beam 3, which is described in detail above. Hydraulic piston cylinder combinations 12 and 13 on drier-frame components 1a and 1c, respectively, have the same function as hydraulic piston cylinder combination 14.

To introduce a fresh felt 17, drier-frame components 1a and 1b are lifted, intermediate pieces 8 are removed, drier-frame components 1c and 1m are lifted, and intermediate piece 9 is removed. Rolls 17a and 31, which are mounted on pivoting arms, still have to be lifted first and roll 53 has to be shifted to roll bearer 1m.

FIGS. 3-5 are schematic illustrations of different methods of tensioning cantilever beams 3 or 3'. All rolls and transverse beam 44 have been omitted from these Figures.

FIG. 3 illustrates the method used with the embodiment in FIG. 2, which was described above, in which the operating-side end of cantilever beam 3 is forced down.

FIG. 4 shows a second embodiment with a hydraulic piston cylinder combination 23 on support 4. When the cylinder is charged, the end of cantilever beam 3 that is positioned at that point is bent down. Since there is another articulated support point 43 in power-side drier frame 2, cantilver beam 3 forces operating-side drier-frame component 1e up through still another articulated support point 43'.

FIG. 5 shows a third embodiment with a hydraulic piston cylinder 24 in power-side drier-frame 2. That can bend up the section of the cantilever beam 3 that is positioned at that point. This will again force operating-side drier-frame component 1e up.

Although the present invention has been described in connection with preferred embodiments thereof, many variations and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.