Paper making and fiber liberation – Processes and products – Running or indefinite length work forming and/or treating...
Patent
1993-01-05
1994-04-26
Hastings, Karen M.
Paper making and fiber liberation
Processes and products
Running or indefinite length work forming and/or treating...
162355, 162356, 492 36, D21F 120, D21F 140
Patent
active
053063945
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a turbulence roll for generating high-frequency vibration of a forming fabric so as to create fine-scale turbulence into the stock on the forming fabric. The turbulence roll according to the invention can be used in the production of fiber webs such as paper, board and non-woven webs and is particularly suitable for use in multilayer filter paper machines comprising an inclined wire portion in which dilute stocks are dewatered.
BACKGROUND OF THE INVENTION
It is known that the formation can be improved by causing high-frequency small-scale vibration in the fiber suspension on a forming fabric by means of a roll having longitudinal grooves, disposed under the forming fabric, whereby dispersion of fiber flocs is brought about.
In turbulence rolls having a grooved surface such as those described in the German patent application 1611761, the fabric on the roll will move towards the roll center every time a groove passes under the fabric. The displacement of the wire and the frequency of the oscillations caused by the roll depend on the gap of the grooves, the roll diameter and the rotational speed of the roll. The oscillation of the wire keeps the partially formed mat fluidized so that it dewaters more readily, redisperses the stock forming into flocs and prevents sealing of the fabric. It also causes dewatering to a certain degree by means of the repeated pumping action of the fabric against the stock and the mat.
In web formers using dilute stock in which large amounts of water have to be removed through the forming fabric, the flow resistance of the drainage and supporting means should be low. This means that normally rolls cannot be used immediately after the headbox. At high speeds, the land area between the grooves produces pressure pulses detrimental to the sheet quality. Therefore, static elements such as foils must be used. In certain applications, however, for instance in web formers having a curved drainage zone, static elements cause considerable frictional forces and increase the tension of the wire wherefor a rotating roll would be preferred.
The object of the present invention is to provide an improved turbulence roll which can be used in various types of web formers and which is particularly well adapted to be used in a multilayer filter paper machine having an inclined wire portion the inclination of which is gradually decreasing.
Other objects, features and advantages of the invention will be readily apparent from the following description of a representative embodiment thereof, taken in conjunction with the accompanying drawing although variations and modifications may be effected without departing from the spirit and scope of the novel concept embodied in the following detailed description of the invention.
SUMMARY OF THE INVENTION
It is a characteristic feature of the turbulence roll according to the present invention that the roll is formed of a shaft on which a plurality of discs is disposed at a distance from each other and a plurality of lengthwise extending rods is attached to the rims of the discs and spaced apart from each other.
According to a preferred embodiment of the invention, the turbulence roll is used as a supporting roll between two flat sections, forming an angle with each other in the inclined wire portion of a filter paper machine. It is clear that the turbulence roll according to the invention can also be used in the horizontal wire portion.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following description, by way of example, reference will be made to the accompanying drawings, in which
FIG. 1 is a schematic elevational sectional view showing a former for use in the practice of the present invention;
FIG. 2 is an enlarged fragmentary elevational sectional view showing one of the drainage zones shown in FIG. 1;
FIG. 3 is a longitudinal section of the drainage roll shown in FIG. 2; and
FIG. 4 is an enlarged fragmentary elevational sectional view showing the transition region between the inclined wire and the h
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patent: 3577315 (1971-05-01), Franklin
patent: 3913240 (1975-10-01), Flamig
patent: 4048008 (1977-09-01), Skrabak et al.
patent: 4306934 (1981-12-01), Seppanen
A. Ahlstrom Corporation
Hastings Karen M.
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