Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Reexamination Certificate
1994-10-17
2001-08-07
Crispino, Richard (Department: 1734)
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
C162S123000, C162S128000, C162S183000, C162S298000, C162S300000, C162S301000, C162S322000, C162S336000
Reexamination Certificate
active
06270624
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a stock feed system for a multi-layer headbox and a method in the operation of a multi-layer headbox.
In the prior art, systems for the operation of multi-layer headboxes are known in which there are separate fresh stocks for the surface layers, i.e., the two extreme layers, and for the middle layer or layers. In the prior art systems, there are at least two fresh-stock systems for the formation of both surface layers. The stocks introduced along separate fresh-stock lines, of which there are at least two, are processed in vortex cleaning and in deaeration tanks, and in the system, feeds of fillers or starch complying with the required paper grade are passed into the at least two fresh-stock lines.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and improved stock feed system for a multi-layer headbox and a method in the operation of a multi-layer headbox in which only one freshstock line is required.
To achieve this object and others, the invention is used in a paper machine that comprises a multi-layer headbox and therein at least two separate inlet headers or equivalent, for the inlet headers, separate stocks are prepared out of the same fresh stock and from the same stock tank. According to the invention, the fresh stock passed out of the stock tank is divided or partitioned into two or more stock component flows which are fed into the multi-layer headbox. Chemicals and/or additives purposeful for the quality or the economy of production of different paper grades are passed into these stock component flows.
In the stock system in accordance with the invention for a multi-layer headbox, a stock concept is passed into each inlet header of the multi-layer headbox which is produced out of the same fresh stock by adding the necessary chemicals and fillers to the fresh stock to provide the desired characteristics of each stock concept. Specifically, the stock system comprises means for providing a single flow of fresh stock, means for dividing or branching the single flow of fresh stock into a plurality of stock flows, means for independently adding chemicals and/or fillers to each of the stock flows, and means for passing the stock flows after the chemicals and/or fillers have been added thereto to the headbox. Preferably, the stock system has a single fresh stock tank from which a fresh stock line is led. This fresh stock line is divided at branch points into several branch lines.
In the method in accordance with the invention, the stock for each header is prepared out of one and the same fresh stock by adding the necessary chemicals and fillers to the fresh stock to provide the desired characteristics of the stock for each header. Specifically, a single flow of fresh stock is provided and is divided into a plurality of stock flows. Chemicals and/or fillers are independently added to each of the stock flows and then the stock flows are passed into a respective inlet header.
In a preferred embodiment, the single flow of fresh stock is divided into only two separate stock flows which are passed through branch lines. The branch line of a first stock flow is divided to provide stock concept for an uppermost and lowermost inlet header in the headbox while the branch line of a second stock flow provides the stock concept for a middle inlet header arranged between the uppermost inlet header and the lowermost inlet header.
The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawing. However, the invention is not confined to these embodiments alone.
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Huovila Jyrki
Ilmoniemi Erkki
Odell Michael
Suonpera Antti
Crispino Richard
Steinberg & Raskin, P.C.
Valmet Paper Machinery Inc.
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