Elongated Gap Press With Adjustable Length

This application claims the priority of German Patent Application No. DE P 44 23 694.8, filed Jul. 6, 1994, the disclosure of which is incorporated herein by reference in its entirety.

1. Field of the Invention

The invention pertains to an elongated gap or extended nip press comprised of two pressing elements, with the pressing elements including pressing areas, wherein the pressing areas are pressed against each other, with each of the pressing areas being formed of a jacket element, with the jacket elements moving around carriers and being supported by at least one support element, with such presses being utilized for the production or treatment of band or web shaped materials, particularly fiber webs.

2. Discussion of the Background of the Invention and Material Information

During the production or treatment of web shaped material it may become necessary, for example during the dehydration of fiber webs, that the length of the press gap or nip and/or the pressure distribution within the press gap be variable for the adaption thereof to changing properties of the material.

European Patent Publication EPS 0 345 500 sets forth a solution in which the pressure distribution within the press gap is influenced via two cylinder-piston units that effect a pressing shoe and are mounted in tandem in the circumferential direction of a press roll. The solution is however too expensive and is not suited for changing the length of the press gap.

The invention thus has the task or object to produce an elongated gap press which permits, at low expenditure, a change in the length of the press gap and/or the pressure distribution or pattern within the press gap.

This task or object was solved or achieved in accordance with the invention via an elongated gap press having an extended nip, comprised of two pressing elements, with the pressing elements including pressing areas, wherein the pressing areas are pressed against each other, with each of the pressing areas being formed of a jacket element, with the jacket elements moving around carriers and being supported by at least one support element, wherein the support surfaces that are formed by portions of the support elements and/or the support elements of at least one pressing element, are displaceable in or against the direction of rotation of the respective jacket element.

In another embodiment of the elongated gap press of this invention, the jacket elements of both pressing elements are comprised of a flexible material and preferably have flat pressing areas.

In a further embodiment of the elongated gap press of this invention, the support surfaces of the support elements of one of the pressing elements, in the direction of rotation of the jacket elements, are smaller in size than those of the opposed support elements of the other one of the pressing elements, with only the portions of the support elements that form the support surfaces of one of the support elements being displaceable in or against the direction of rotation of the respective jacket element for the purpose of influencing the pressure profile in the press nip.

In yet another embodiment of the elongated gap press of this invention, the support surfaces of the support elements of both pressing elements are of about the same size and wherein the support surfaces that are formed by the portions of the support elements and/or the support elements of at least one pressing element, are displaceable in or against the direction of rotation of the respective jacket element, preferably for changing the length of the press nip.

In yet a further embodiment of the elongated gap press of this invention one of the pressing elements includes a concave press area, with the jacket element of the one of the pressing elements being comprised of a flexible material, and wherein the jacket element of the other one of the pressing elements being comprised of a rigid material and being cylindrically shaped, with the support elements of the cylindrical pressing elements being preferably displaceable, via an angular motion of the pressing element, in or against the direction of rotation of the rigid jacket element.

Since the portions of the support elements that form the support surfaces and/or the support elements themselves of at least one pressing element are displaceable in or against the circumferential direction of the corresponding jacket element, there exists a relatively simple possibility for accomplishing the noted task. Since, depending on whether the support elements or the portions thereof that form the support surfaces are changeable during operation, with reference to their location or position relative to the opposing support elements, a choice must be made as to the adjusting devices required so as to achieve these changes.

In case the support elements are moved as a whole, care must be taken that the resulting moments can be absorbed.

Should, for example, the support elements be moved as a whole, it is recommended that this be accomplished via a suitable location or position change of each of the carriers.

While adjustable connections are sufficient to assure the changeability of the position of an element at rest, electrical or hydraulic adjusting devices are more suitable for changes during actual operation.

In case the jacket elements of both of the pressing elements are comprised of a flexible material it is advantageous if the pressing elements, for the protection of the jacket elements relative to the deformation thereof, have even or flat pressing areas or surfaces. These can, however, also be slightly curved wherein, in all instances, a rounding off or curvature of the inlet and outlet regions of the pressing surfaces is recommended.

If the support surfaces of the support elements of a pressing element, in the direction of rotation of the jacket element, are shorter than those of the opposed support elements of the other pressing element, it is logical, for changing the pressure profile within the press gap, if only the portions of the support elements of a pressing element that form the support surfaces are displaced in or against the direction of rotation of the respective jacket element, while the contact pressure elements of the support elements that act on the opposing press element, remain in place. If, however the support surfaces of the opposing support elements of both pressing elements are of about the same size, for a change in the length of the press gap it is possible with at least one pressing element that the portions of the support elements that form the support surfaces, and/or that the support elements themselves, that is with their pressure elements, are displaceable in or against the direction of rotation of the corresponding jacket element. If, in contrast thereto, one of the pressing element has a concave pressing surface, and if the jacket element of this pressing element is comprised of a flexible material and the jacket element of the other pressing element is comprised of a rigid or stiff material and is also of cylindrical shape, then a position or location change of the support elements of the cylindrical press element can be advantageously achieved via the angular displacement of the carrier of this press element in or against the direction of rotation of the rigid jacket element. The rigid jacket element also permits a press gap to be formed with the entire concave press surface, even when the support surface of the cylindrical press element does not cover the entire concave press surface.

The invention which will be described with reference to three embodiments thereof will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein throughout the various figures of the drawings, there have generally been used the same reference characters to denote the same or analogous components and wherein:

FIG. 1 is a partial sectional view of one embodiment of the elongated gap or extended nip press of this invention;

FIG. 2 is also a partial sectional view of another embodiment of the elongated gap or extended nip press of this invention; and

FIG. 3 is a further partial sectional view of a further embodiment of the elongated gap or extended nip press of this invention.

With respect to the drawings it is to be understood that only enough of the construction of the invention and the surrounding environment in which the invention is employed have been depicted therein, in order to simplify the illustrations, as needed for those skilled in the art to readily understand the underlying principles and concepts of the invention.

The elongated gap or extended nip presses of this invention are comprised of two pressing elements 1 and 2, whose pressing areas are pressed against each other, wherein each of the pressing areas is formed of a band-shaped covering, shell or jacket element 7 and 8, with the jacket elements moving or rotating around and being supported by carriers 3 and 4. Through the press gap, that is formed as a result thereof, in addition to a material web or band 12, a dewatering or dehydration web or band 13, can also be conveyed.

As per FIGS. 1 and 2, pressing elements 1 and 2 have flat or even pressing areas and the jacket elements 7 and 8 of both pressing elements 1 and 2 are comprised of a flexible material.

While, in the embodiment of FIG. 1, the single integral portion of support element 5 (depicted in the exemplary illustration as a single integral element) of pressing element 1 that forms the support surface 9, is displaceable, via an hydraulically actuated adjusting device 11 for example, in or against the circumferential direction of jacket element 7, the displacement of the entire support element 6, of the embodiment illustrated in FIG. 2, is accomplished via a suitable position or location change of carrier 4 of this press element 2.

If, as in FIG. 1, the support surface 9 of support elements 5 of pressing element 1, in the direction of rotation of jacket element 7, is smaller than that of the opposed support elements 6 of the other pressing element 2 (depicted in the exemplary illustration as a single integral element), then it is surely logical that the pressure profile of the press gap is changed via the displacement of the portion of support element 5 that forms support surface 9. Since, due to the flexibility of the material of jacket elements 7 and 8, a press gap is only formed in the region where support elements 5 and 6 are opposite to each other, it is only natural that during a sufficient displacement of support element 5 or of the portion of support element 5 that forms support surface 9, it is also possible, as shown in FIG. 2, to reduce the press gap.

In the example or embodiment of FIG. 2, the single integral support surfaces 9 and 10 of opposing support elements 5 and 6 of both pressing elements 1 and 2 are of about the same size, so that, already in contrast to FIG. 1, only a minimal displacement of the portion of support element 6 that forms support surface 10 or of the entire support element 6, already affects the length of the press gap.

Deviating from the structure described to this point, the jacket element 8, of FIG. 3, is comprised of but one pressing element 2 of a flexible material, with the other jacket element 7 being comprised of a rigid material. Commensurately, flexible pressing element (e.g., a press shoe) 2 has a concave pressing area and the jacket element (e.g., a press shoe) 7 of the other pressing element 1 has a cylindrical shape or form. In order to displace support elements 5 of the cylindrical pressing element 1, in or against the direction of rotation, it is sufficient to suitably angularly displace carrier 3. Due to the rigidity or stiffness of jacket element 7 only the pressure profile but not the length of the press gap can be influenced. It is of course also possible, in this embodiment to only displace the portion of support element 5 that forms support surface 9.

In all of the described embodiments, pressing elements 1 and 2 can utilize only one support element 5 or 6 or several support elements 5 or 6 arranged next to each other.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims and the reasonably equivalent structures thereto. Further, the invention illustratively disclosed herein may be practiced in the absence of any element which is not specifically disclosed herein.