WO2005033407A1

WO2005033407A1 - Holder for rod cradle for revolving coating rod

Info

Publication number: WO2005033407A1
Application number: PCT/SE2004/001294
Authority: WO
Inventors: Tore Eriksson
Original assignee: Btg Umv Coating Systems Aktiebolag
Priority date: 2003-10-09
Filing date: 2004-09-10
Publication date: 2005-04-14

Abstract

A holder for a revolving rod for a coating machine, comprising an attachment part (20), a cradle guide (21) connected to the attachment part, an elongated rod cradle (18) arranged in the cradle guide, which rod cradle has a recess (40) for a revolving rod (10), said recess (40) comprising at least one axial cleansing and lubricating groove (41), and on both axial sides of the recess (40) a sealing lip (25, 26) at which a sealing surface (25a, 26a) is arranged and intended to sealingly bear against said rod (10), and means (22, 23) being arranged to exert a sealing load against said rod (10), via said sealing lips (25, 25) and said sealing surfaces (25a, 26a), said means (22, 23) being arranged to apply a compressive load (F) against said rod cradle (18), whereby the compressive load (F) acts on said rod cradle at a position that coincides with or is adjacent a plane (P) that holds the main sealing line (L) between said sealing surfaces (25, 26).

Description

HOLDERFORACRADLE FORA REVOLVING ROD

TECHNICAL FIELD The present invention relates to a holder for a revolving rod for a coating machine, comprising an attachment part, a cradle guide connected to the attachment part, an elongated rod cradle arranged in the cradle guide, which rod cradle has a recess for a revolving rod, said recess comprising at least one axial cleansing and lubricating groove, and on both axial sides of the recess a sealing surface intended to sealingly bear against said rod, and means being arranged to exert a sealing load against said rod, via said sealing surfaces.

PRIOR ART

A common method of coating a running web, preferably a paper web, is the so called revolving rod method. The principle for this method is that the running web partly encloses a rubber-clad supporting roll. Coating liquid is supplied to the web at a surplus over the entire width of the web, in a position upstream the revolving rod, which rod thereafter performs the final metering of coating liquid.

The revolving rod has a small diameter in relation to its length, and accordingly it must be carried in a bearing over its entire length, in a so called rod cradle. The rod cradle, that usually is made of durable rubber or plastics, is usually provided with one or more groove(s) for lubricating water and cleansing of the rod. Besides constituting a slide bearing, the rod cradle also has the function of scraping and washing coating liquid from the rod. The scraping takes place by two sealing and scraping surfaces, integrated in the rod cradle at the inlet side and outlet side, respectively, of the rod cradle. Since the rod contra-rotates the rotational direction of the paper web, the sealing surface upstream the contact point between the rod and the paper web becomes the surface that scrapes off the major part of the coating liquid.

The lubricating and cleansing water is supplied in one or more groove(s) of the rod cradle. Hence, since it is important that the water is not mixed with the coating liquid, the function of the two sealing and scraping surfaces is of vital importance to the coating result. The load of the rod against the running web is achieved by axial loading devices that apply a controllable load along the rod cradle. The size of the load is the parameter controlling the amount of coating liquid supplied to the web.

As mentioned above, the function of the rod cradle is to support and cleanse the revolving rod. Accordingly, it is important that the rod cradle and its sealing and scraping surfaces have an accurate fit with the rod, so that cleansing water does not leak out and gets mixed with the coating liquid, or the rod starts to oscillate. However, if the fit of the rod cradle against the rod is too tight, there is a risk that the turning force for the revolving gets too large, which results in a considerable wear of rod and rod cradle, and a risk that the rod is wrung off or that the driving motor releases.

The most common way of achieving a correct fit with the rod is to adjust the manufacturing tolerances of the rod cradle in relation to the elasticity of the material. By wear and influence of temperature among other things, the sealing and stabilising ability of the rod cradle however changes during operation. One disadvantage of such a construction is that there is no possibility to compensate for such changes during operation, which means that the entire rod cradle must be exchanged. Exchanging the rod cradle leads to major costs in terms of both material and production losses.

European patent EP 0 541 502 Bl discloses a way of affecting the fit against the rod, by an air hose that is integrated in the rod cradle. However, this design has the disadvantage that the compressive load from the hose must be transmitted by the more or less flexible material of the rod cradle, to the sealing lip, which leads to that a large part of the effect from the pressure change in the hose is not transmitted to the sealing lip. Since this lip has the function of sealing and stabilising, the sealing and stabilising control function will not be satisfactory. Also, the control function will be different for different material properties of the cradle.

BRIEF ACCOUNT OF THE INVENTION

It is an object of the present invention to eliminate, or at least minimise the above mentioned problems, which is achieved by a holder for a revolving rod for a coating machine, comprising an attachment part, a cradle guide connected to the attachment part, an elongated rod cradle arranged in the cradle guide, which rod cradle has a recess for a revolving rod, said recess comprising at least one axial cleansing and lubricating groove, and on both axial sides of the recess a sealing surface intended to sealingly bear against said rod, and means being arranged to exert a sealing load against said rod, via said sealing surfaces, characterised in that said means are arranged to apply a compressive load against said rod cradle, whereby the compressive load acts on said rod cradle at a position that coincides with or is adjacent a plane that holds the main sealing line between said sealing surfaces.

Thanks to the invention, a holder for a revolving rod for a coating machine can be provided, which efficiently affects sealing and stabilising properties in the rod cradle, and as a consequence the running time of the rod cradles can be prolonged.

Another object of the invention, is to achieve a rod cradle that is simple and non- expensive from a production point of view. The invention enables this by the cradle holder, that constitutes the carrying and sealing load controlling part, not being a wearing part. Accordingly, the wearing part constituted by the rod cradle, can be designed without concern of carrying function, which results in a design that is simpler and more easy to produce.

Yet another object of the invention is to facilitate exchanging of the rod cradle. This is enabled by the compressive load that is applied onto the rod cradle by the load- generating means that are arranged in the cradle holder, being controllable such that the sealing load between the rod and the sealing surfaces can be decreased, which contributes to facilitate the mounting of the rod in the rod cradle. Usually, such mounting takes place by inserting the rod into the rod cradle via the opening that forms a space between the two sealing surfaces of the rod cradle. The present invention also enables the rod to be axially inserted into the rod cradle, which in some cases will shorten the time needed for exchanging rods.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail with reference to the attached drawing figures, of which: Fig. 1 shows an example of a coating machine.

Fig. 2a shows an example of a device according to the invention, with the rod unit in a disengaged position.

Fig. 2b shows the device according to the invention, in operating position.

Fig. 2c shows a detail. Fig. 3 shows an alternative embodiment of the cradle guide.

Fig. 4 shows an alternative embodiment of the rod cradle. DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows an example of a coating machine for a revolving rod, in which the running web (1) that usually is of paper or paperboard, partly encloses a rubber-clad supporting roll (2). The coating liquid (3) is supplied to the web by the metering roll (4). The metering roll is immersed in a tray (9) with coating liquid, and feeds the liquid to the wedge-shaped gap (5) that is formed between the supporting roll (2) and the metering roll (4). Levelling out and pre-metering of coating liquid takes place in the gap. In this gap (5), coating liquid is transferred to the running web, by an amount that usually is 10-20 times greater than the final coating amount. The amount of coating liquid pre- metered to the web is thereafter finally metered by a revolving coating rod ( 10), mounted in a rod unit generally denoted (7). The surplus of coating liquid from the rod unit flows back into the rear chamber (8) of the tray.

Fig. 2a shows a cross-section of an example of a device according to the invention, with the rod unit in disengaged position. In this position, the coating rod (10) is not in contact with the web, and neither the supporting roll (2) nor the coating rod are revolving.

The rod unit comprises a blade (20) of a resilient material, hereinafter denoted spring blade, that is clamped between jaws (13). A cradle guide (21) is mounted on the spring blade (20). A rod cradle (18) for a revolving coating rod (10) rests in the cradle guide (21). A device for controlling the sealing load of the rod guide against the rod, is applied on the cradle guide (21). This device comprises a compressed-air hose (22), a compression spring (23) and a hose seat (24). The compressed-air hose (22) is enclosed between the compression spring (23) and the hose seat (24).

The rod cradle comprises a recess (40) for the revolving coating rod (10), in which recess at least one cleansing and lubricating groove (41) is arranged. A sealing lip (25, 25) that sealingly bears against the coating rod, is arranged on both respective sides of the recess (40).

At a relieved pressure in the hose (22), the compression spring (23) is not in contact with the rod cradle (18), whereby the sealing surfaces (25, 26) exert a low load, or no load at all, on the coating rod (10). In this position, both the coating rod and the rod guide can be mounted/dismounted by axial displacement. In this example, the device controlling the bearing load of the rod on the web is traditionally arranged, i.e. with a compressed-air hose (17) acting on the spring blade (20).

It is desired that the rod unit has a certain axial flexibility, and for this purpose the cradle guide (21) is, in a preferred embodiment, divided into sections of about 20-500 mm length, preferably about 100 mm length. The space between sections is about 1 mm. By the term "axial" is intended the extension of the rod unit essentially in parallel with the axis of rotation of the supporting roll (2). In a sectioned embodiment of the cradle guide (21), the hose seat (24) and the compression spring (23) too can be divided into sections, the length of which essentially corresponding to the length of the sections of the cradle guide (21).

It should be understood that the invention is not limited to an embodiment with a sectioned cradle guide, but that it also comprises an embodiment in which the cradle guide is given its flexibility by the properties of the material.

Fig. 2b shows the device according to the invention, in operating position. In this position, the coating rod (10) is in contact with the web (1) and revolves contra the direction of the web, and meters the final amount of coating liquid. The scraped off amount of coating liquid (28) flows along the rod cradle (18) and the cradle guide (21), and back into the recirculation system.

Fig. 2c shows the rod cradle (18) and the coating rod (10) in detail and in operating position. In the operating position, the load between the sealing lips (25, 26) of the rod cradle and the coating rod (10) is controlled to a suitable load by pressurisation of the pressure hose (22) that bends the spring (23) and transfers a compressive load (F) to the sealing surfaces (25, 26). By a device according to the invention, the advantage is obtained that the compressive load (F) acts on the rod cradle (18) at a position that coincides with or is adjacent a plane (P) that holds the main sealing line (L) between said sealing, surfaces (25, 26).

Fig. 3 shows an embodiment of the invention, where the attachment part (20) and the hose seat (24) are integrated parts of the cradle guide (21). In this embodiment, the unit (20, 24, 21) is made of a flexible material, such as reinforced plastics or some other polymeric material, and the unit is designed as an axial element, i.e. it is not divided into sections. In a variant of this embodiment, the part of the unit that is constituted by the cradle guide (21) and the hose seat (24) may however be slotted, to achieve a "sectioned" design.

Fig. 4 shows an alternative embodiment of the rod cradle (18). In this embodiment, the rod cradle has only a single lubricating groove (41). The recess (42) allows a controlled flexion in the area (A), at controlling of the load of the sealing surfaces (25, 26) against the rod. By designing the rod cradle (18) in this way, improved sealing and an increased wear surface can be obtained between the rod cradle and the coating rod.

The description above only deals with a few examples of embodiments according to the invention, which invention may comprise a wide variety of embodiments within the scope of the invention. For example, the clamping of the rod unit between jaws (13) may be moveable (tiltable), instead of fixed. The load device (17) for the load of the rod against the web, can also be divided into sections along the rod unit, in order to allow for a non-uniform (profiled) bearing load between coating rod and web.

Claims

1. A holder for a revolving rod for a coating machine, comprising an attachment part (20), a cradle guide (21) connected to the attachment part, an elongated rod cradle (18) arranged in the cradle guide, which rod cradle has a recess (40) for a revolving rod (10), said recess (40) comprising at least one axial cleansing and lubricating groove (41), and on both axial sides of the recess (40) a sealing lip (25, 26) at which a sealing surface (25a, 26a) is arranged and intended to sealingly bear against said rod (10), and means (22, 23) being arranged to exert a sealing load against said rod (10), via said sealing lips (25, 25) and said sealing surfaces (25a, 26a), characteri sed in that said means (22, 23) are arranged to apply a compressive load (F) against said rod cradle (18), whereby the compressive load (F) acts on said rod cradle at a position that coincides with or is adjacent a plane (P) that holds the main sealing line (L) between said sealing surfaces (25, 26).

2. A holder according to claim 1, characteri se d in that said attachment part (20) comprises an axial spring blade.

3. A holder according to claim 1, characteri se d in that said attachment part (20) is an integrated part of the cradle guide (21).

4. A holder according to any one of claims 1, 2 or 3, characteri s e d in that said means (22, 23) comprises a pressure generating device (22) that acts on an elongated resilient element (23).

5. A holder according to claim 1, characteri sed i n that the cradle guide (21) is bendable in its axial direction.

6. A holder according to claim 5, characteri se d i n that the cradle guide (21) comprises a number of short sections having axial extensions of 20-500 mm, preferably about 100 mm.

7. A holder according to claim 6, characteri se d i n that it comprises a hose seat (24), the hose seat and the elongated resilient element. (23) being divided into sections the length of which essentially corresponding to the length of the sections of said cradle guide (21).