FI66445B - BELAGD VALS FOER FRAMSTAELLNING AV PAPPER - Google Patents

Description

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U.S. Pat. No. 3,868.84 (32) (33) (31) Belit Corporation, Beloit, Wisconsin 53511, USA ( US) (72) Donald Arthur Brafford, Beloit, Wisconsin, USA (74) Munsterhielm Ky Kb (54) Coated roll for papermaking - Belagd Vals för framställning av papper

The invention relates to improvements in rolls, and in particular to rolls of the type used in paper machines, which must be able to operate at high speeds with high nip loads continuously.

More specifically, the invention relates to an even better roll and a method of manufacturing the roll, as these are characterized in the appended claim.

Rubber coated rolls have been used in the paper industry for many years. They have been used particularly widely in the press parts of paper machines, often as grooved rolls or suction rollers but also as smooth rolls. These rolls are usually used in a press to form a nip with another roll having a hard outer surface such as a steel roll. The endless blanket carries a wet paper web through the nip, and water is squeezed from the dough into the felt in the nip. Granite stone rolls or hard rubber coated rolls are often used with another hard coated roll made of, for example, a material as described in U.S. Patent 3,588,978.

66445 Such a combination is able to remove water due to its high line pressure, which develops in a relatively narrow or sharp nip. However, such a narrow or sharp nip requires great care in adapting the tele bombing to the nip load, and difficulties arise because a considerable range of nip loads is necessary due to operating conditions or variations in the types of paper produced.

To reduce the roll bombardment and damage problems referred to above, it has been customary to use a hard roll in combination with a softer roll. The coatings on these softer rolls have often been rubber blends such as natural rubber and a rubber type such as polyurethane. The coating of such a roll with these mixtures is carried out by a casting process. Because press rolls exist in very different diameters and lengths, each roll requires a specially made mold so that casting such roll coatings has become quite expensive.

Accordingly, it is an object of the present invention to provide a roll structure made of a material capable of operating at high speeds and high nip loads without wear rapidly and without the deleterious effects of normal operating conditions. It is a further object to provide a roll with a soft coating which can be made quickly and relatively inexpensively.

It is a further object of the invention to provide an improved method of making soft-coated rolls which can produce rolls of different diameters without expensive special equipment for changing the diameter.

The invention is explained in more detail in the following detailed description in connection with the accompanying drawing, in which:

Figure 1 is a schematic axonometric view of two paper machine rolls, the upper of which is constructed in accordance with the present invention, and

Fig. 2 is a schematic view showing a method of manufacturing a roll.

3,66445

As shown in Fig. 1, the two rollers 11 and 15 form a nip N between them. The upper roll 11 has a core 12 of steel or the like with supporting axes, and as is clear, the roll 11 and the lower roll 15 are mounted on suitable bearings provided with a mechanism. to achieve controlled nip pressure. The upper roll 11 has a soft outer surface 14 deposited on the core 12 by the method described below. The lower roll 15 is made of a hard material such as steel and is supported by a shaft 16. In some cases it may be advantageous for a uniform nip pressure that the lower roll 15 is a roll whose inclination can be adjusted. Various types of such rolls are known, and suitable rollers include, for example, those having a fixed inner core that can flex freely away from the nip, and a rotating outer roll shell, and a device for providing hydraulic support between the core and the roll shell to transfer nip load. The hydraulic support may be a closed amount of fluid or an elongate axial piston fitted to the shaft cylinder so that the piston supports a sliding Kingsbury type thrust bearing shoe and a lubricating oil film is formed between the inner surface of the roll shell and the shoe. The lower roll may also be a conventional smooth roll, in which case the upper roll may be a deflection-adjusted roll, the core 12 of which is in the form of a roll shell and is supported, for example, by the deflection adjustment mechanism described above.

Figure 2 shows the deposition of a roll coating on a roll 11. It has been found that a softer roll coating can be deposited using a wet coating method, resulting in considerable savings over a conventional casting process. The roll coating 14 consists of a reinforcing fiber mat, which is preferably a nonwoven fabric made of needle-treated polyester fibers. The mat is impregnated with a liquid rubber type, preferably selected from the group consisting of depolymerized natural rubber, low molecular weight styrene butadiene, liquid urethane or liquid polybutadiene. As shown in Figure 2, the reinforcing felt mat, i.e. the substance 19, is unloaded from the storage space 17 over the guide roll 20, and down into the open liquid rubber container 23. The guide rollers 21 and 22 guide the substance through the liquid rubber so that it can get wet. It has been found that the liquid rubber referred to above has a low enough temperature at room temperature to dip through the reinforcing mat. The wetted reinforcing mat exits the tank 23, passes over the roll 22a and is deposited on the outer surface of the roll 12 as shown in the drawing. This can be done by rotating the roll by means of the drive 25 at a relatively low speed so that the mat is deposited on the roll 11 in overlapping layers.

Once the material has cured, a finishing operation is performed to obtain a uniform, smooth outer surface and uniform diameter for the roll.

This roll coating can withstand higher machine speeds than conventional rubber or molded polyurethane coated rolls, and can easily withstand speeds of 1800 meters per minute, and 107 kg pressures per running centimeter have been reached or approached in the paper industry. Molds are not required in this coating deposition method, as in the conventional casting process.

The rolls of the invention can be used in a wide variety of applications or industries. It is important that the roll has a soft coating, as it brings with it a significant increase in the life of the roll coating, which is important in the paper industry where the delay caused by downtime due to the failure of any part is expensive. The rolls of this invention can be used in many places on a paper machine, but are particularly well suited for use as press rolls.

The hardness can be adjusted by the density of the layer and the choice of dipping agent, and preferably the hardness is between 4-UQ P&J.