Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
1998-07-10
2001-05-08
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C162S204000, C162S275000, C162S280000, C162S358300, C162S361000, C034S117000, C034S114000, C226S097300
Reexamination Certificate
active
06228216
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods and apparatus for making paper in the form of a cellulosic web using a differential velocity transfer of the cellulosic web between spaced apart flexible, elastic transport means, such as felts, fabric, belts, meshes etc., driven by mechanical rolls or rollers. The differential velocity transfer, i.e., processing a cellulosic web on a higher speed transport means and transferring the cellulosic web to a lower speed transport means, improves properties of the transferred web. The invention involves apparatus and process steps used to transfer the web in a differential velocity transfer mode, between spaced apart paper making transport means, in an efficient manner. The invention additionally involves incorporating chemical additives into or onto the cellulosic web during the transfer.
BACKGROUND OF THE INVENTION
In the manufacture of paper products, typically paper or cellulosic webs having increased bulk, the initially formed web can be mechanically processed to introduce properties or features, such as greater ductility, more softness, more fluffiness, more absorbing power, changed texture or modified shape, to the web. Such properties can be introduced into the web by changing the speed or velocity of the paper during transfer between one production or transport means to another similar means. The change in velocity from high velocity to low velocity can cause the paper web to “buckle” or “backup” and can cause a significant change in properties. Such transfers are conventionally done in a surface to surface interface in an area of direct contact between the transport means moving surfaces. Typically, the longitudinal change in the rate of travel of the paper can involve transfer of the cellulosic web from a roller or from a fabric or felt to a similar surface in an area of contact between surfaces. In the area of contact between the surfaces the cellulosic web is modified by both frictional forces in the area of interface and by the velocity change.
Such processes are common in the art and have a degree of utility. However, such methods suffer from limitations including a narrow range of operating variables (change in velocity, web dimensions, etc.) and frictional problems arising at the interface between transfer means in contact. A substantial need in the art has arisen for processes that provide greater flexibility in paper processing in the this differential velocity transfer of a web from transport means to transport means to obtain greater flexibility in paper properties. A still further need exists for processes that can be used to effectively treat the web with chemical additives that can improve the physical properties of the cellulosic or paper web or improve the web processing characteristics.
One contact velocity transfer technology involves the use of an air blowing nozzle in conjunction with a suction zone to remove water in the initial stages of the formation of a high bulk, soft creping process. A particular paper forming process uses an apparatus disposed next to a wire or fabric opposite a paper web, to create a wave of positive air pressure urging the web off the wire in a typical Fourdrinier process. This process is conducted in the initial stages of paper manufacture while the web is still substantially wet in order to direct the web to finishing stages of the manufacturing process. Similar processes known in the art include an air stream and an air foil used in combination to move a newly formed wet web from a roll to a drier fabric or felt. Another known process involves a transfer mechanism for loosening the web from a papermaking screen using a stream of air continuously up into the Fourdrinier screen and against the paper web to loosen the web and facilitate its transfer from the screen to the felt.
Similar transfer processes include methods in which a newly formed web is transferred from a metal roller to a felt, and a doctor blade assembly which uses a cooperating air blast to doctor a paper web from a cylinder surface or to dry a paper sheet by passing the doctor between the web or cylinder using the passage of air. Another method known in the art is a roller to roller transfer, using rollers at constant velocity, of a paper web using an air jet guide. A variation of this is a constant velocity belt to belt transfer of a web using a movable doctor blade/air blower that initiates a surface to surface transfer of a web between surfaces, the surfaces maintained in physical contact. The apparatus comprises a doctor blade that physically begins web removal and then promotes web removal and transfer at constant velocity between surfaces using an air blast. A process is known for introducing a controlled thickness into a web by compressing the web between rollers with a calibrated gap in which the process includes an air jet that promotes removal of the calibrated web from the constant velocity rollers interface.
Paper making is a mature industry in which a variety of process steps have been used to obtain a variety of paper properties and to improve processing conditions. Another technology uses a steam driven coating process in which a steam stream transfers a chemical additive into a paper coating layer. A liquid coating process is known whereby a coating is applied by atomizing material with an air stream to coat a web. The process uses a thin line or stream of pressurized air to act as a doctor blade to maintain coating uniformity. Related art reveals the use of an air jet-like doctor blade to adjust a powder coating thickness and the use of a steam jet to introduce a silicone release additive onto a paper web.
BRIEF DISCUSSION OF THE INVENTION
An improved production method for cellulosic webs is disclosed offering a wide scope of improvement in operational parameters which inherently enhances the bulk, softness and other physical properties and processability of a cellulosic web. In the improved method obtained with differential velocity transfer processes, a non-contacting, non-compressing transfer process is utilized to transfer the web from a first transport surface to a second transport surface in a differential velocity transfer mode in which the surfaces are not in direct contact and are positioned at a spaced apart configuration. The surfaces are typically moving production or transport webs such as belts, fabric, elastic or other transport means, that move through a parallel, spaced apart transfer zone in which the cellulosic web is transferred from one production surface to another. The non-contacting web transfer process relies on a mobile gas stream, such as a stream of air (or, equivalently, any other mobile gas stream, such as nitrogen) used first to help remove the paper web from transport web to a second transport web using the gas stream as a guide and support during the transfer the cellulosic web between the transport means. The air stream supports and guides the web from a first fabric or felt to a second fabric or felt moving at a speed lower than the first or original fabric in a differential velocity transfer mode.
In one embodiment, the stream of air can be directed through the mesh fabric or felt using the air pressure to prompt the web from the higher velocity transfer web, mesh, fabric or felt. The air then promotes and supports transfer of the removed web to the second lower velocity surface. In a second mode, the air stream can be directed at the interface between the web and the transfer web, fabric or felt, on the web side of the felt or fabric, at the point of removal or separation of the web. The pressure of the air can promote the separation of the web and can act to promote the transfer of the web from the higher velocity surface to the lower velocity surface. For the purpose of this invention, the mobile gas stream or air stream uses the ambient atmosphere or commonly available atmospheric gases at ambient room or slightly elevated temperatures that can range from about 20° C. to 105° C. preferably 20° C. to 90° C., or somewhat higher. Preferably, high tem
Kamps Richard J.
Lindsay Jeffrey D.
Croft Gregory E.
Fortuna Jos'e A.
Kimberly--Clark Worldwide, Inc.
Silverman Stanley S.
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