Supporting mechanism for a papermaking machine dewatering blade

A pneumatically actuated doctoring device for paper machine de-watering/paper forming is provided having a base member supported on a papermaking machine structure, and a blade support with a fabric contact element. A single pneumatic air tube having first and second attachments on opposing sides is also provided. The first attachment engages the base member and the second attachment engages the blade support. The tube is configured for connection to a pressurized air source and a vacuum source to extend or retract the blade support. A linkage arrangement is connected between the blade support and the base member and includes first and second links located between the base member and the support member. The links each have a pivotal connection to the base member and provide for a fixed orientation of the blade support relative to the base member as the pneumatic air tube extends or retracts the blade support.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Patent Application No. 62/309,519, filed Mar. 17, 2016.

BACKGROUND

This invention concerns a fabric support element for use in a papermaking machine, and in particular a support mechanism for adjustably supporting a dewatering blade in a papermaking machine, or a forming section thereof.

In the manufacture of paper and board products, a highly aqueous stock consisting of about 98-99.8% water and from 0.2-2% papermaking fibers and other solids is ejected at high speed from a headbox slice onto a moving forming fabric. Adjacent the head box slice, the forming fabric passes in sliding contact over a plurality of static fabric support elements known as blades which serve to support the forming fabric, and to define a reference surface over which the forming fabric moves. Depending on the surface profile chosen for the fabric support elements, they may act as a doctoring device and assist in draining water from and generating turbulence in the stock on the forming fabric. The fabric support surfaces usually include a lead blade located more or less underneath the point at which the stock jet impinges the forming fabric, followed downstream by at least two additional blades, each of which may be flat, or profiled to act as foils (e.g. as disclosed by Wrist in U.S. Pat. No. 2,928,465) or as agitators (e.g. as disclosed by Johnson, in U.S. Pat. No. 3,874,998), although stock agitation is not typically initiated at this very early point in a forming section. The fabric contact elements, which are typically ceramic, are normally mounted onto a vertically adjustable supporting structure using either a dovetail or a T-bar support

U.S. Pat. No. 6,780,286 to Van Essen et al. discloses an apparatus by which a paper maker can alter the number of fabric support elements in contact with the forming fabric in the area immediately after the stock impinges onto the forming fabric adjacent to the head box slice so as either to enhance, to maintain, or to diminish stock activity and thereby optimize agitation in accordance with papermaking conditions to provide a product of acceptable quality. Here, a contact element with a given profile can be vertically adjusted to be out of contact with the forming fabric and a support element with a different profile vertically adjusted to be in contact with the forming fabric.

A number patents show vertically adjustable support element mounting devices for use in papermaking machines. Typical structures are shown by: Bartelmuss et al in U.S. Pat. No. 5,660,689; Bubik et al. in U.S. Pat. No. 5,262,010 and U.S. Pat. No. 5,061,347; and Jaakkola U.S. Pat. No. 5,387,320.

FIGS. 1A-1Cof the present application show some of the current designs for vertically adjustable support element mounting devices on the market.FIG. 1Ashows a prior art blade support device10ahaving a pneumatic air tube12located on a support member20. The pneumatic air tube12contacts the bottom of a blade support18upon which the blade or doctoring element16is mounted. Slide control surfaces14are provided on the support member20to linearly guide the blade support18as it is extended upwardly by inflating the pneumatic air tube12.FIG. 1Bshows a similar arrangement of a prior art blade support device10bin which the blade support18moves linearly upwardly along slide control surfaces14.FIG. 1Cshows a third blade support device10cin which the blade support18is constrained for linear movement via slide control surfaces14on the support member20in order to move the doctoring element or blade16on the blade support18into or out of contact with a fabric surface. In this arrangement, two separate pneumatic air tubes12a,12bare provided with the first pneumatic air tube12abeing inflated in order to raise the blade and the second pneumatic air tube12bbeing inflated in order to retract the blade from contact with the fabric.

These prior art arrangements rely on various methods of pneumatic retraction by a second actuator (tube12b) or no positive retraction at all. All of these prior art devices also provide a linear movement using a linear guide mechanism wherein the support structure of the doctoring blade is constrained by a static bearing surface.

The current designs on the market rely on mating surfaces, which slide to control the movement of the doctoring element. This method inherently has excessive friction, which can increase if paper fibers from the slurry enter into these arrangements resulting in less controllability and loading sensitivity. Further, a complex system is required to provide for positive extension and retraction of the doctoring blade.

SUMMARY

It would be desirable to provide a blade support device which allows for positive extension and retraction of a doctoring element or a blade on a blade support which allows for simple operation and has lower friction than the known prior art arrangements. It would also be desirable to provide a pneumatically actuated doctoring device which is more cost effective than the prior known arrangements.

A pneumatically actuated doctoring device for paper machine de-watering/paper forming is provided. The device includes a base member that is adapted to be supported on a papermaking machine structure, and a blade support with a fabric contact element, which can be a doctoring element or blade. A single pneumatic air tube having first and second attachments on opposing sides of the pneumatic air tube is also provided. The first attachment engages the base member and the second attachment engages the blade support. The pneumatic air tube is configured for connection to a pressurized air source and a vacuum source to extend or retract the blade support relative to the base member. A linkage arrangement is connected between the blade support and the base member. The linkage arrangement includes at least first and second links that are located between the base member and the support member. The links each have a pivotal connection to the base member and provide for a fixed orientation of the blade support relative to the base member as the pneumatic air tube extends the blade support or retracts the blade support which is guided by the linkage arrangement.

In a preferred embodiment the linkage arrangement forms a four-bar linkage arrangement with each of the first and second links also having a pivotal connection to the blade support. Those skilled in the art will recognize that other linkage arrangements can be used. One particular benefit of a four-bar linkage arrangement is that this provides for constrained motion of the blade support relative to the base member in which the orientation of the blade support remains constant even as the blade moves along an arc-shaped path based on the guidance provided by the linkage arrangement.

In a preferred arrangement, the pivotal connections each include a pin that extends through the openings in the base member and the blade support. Optionally, the openings through which the pins extend may each include a bushing to provide for reduced friction.

Preferably, the distance between the pivotal connections of the first and second links on the base member is equal to a distance between the pivotal connections of the first and second links on the blade support such that the blade support orientation remains vertical as it moves between the extended and retracted positions.

Preferably, the pressurized air source and the vacuum source are connected to the single pneumatic air tube by a valve arrangement.

Optionally, at least one flexible cover is connected between the base member and the support member that encloses the linkage arrangement. This prevents the paper slurry from entering into the linkage arrangements.

In one preferred arrangement, the first and second attachments on the single pneumatic air tube have a T-shape and are integrally formed on opposing surfaces of the single pneumatic air tube. The base member and the blade support each include a corresponding T-shaped receptacle for a positive fit connection to the single pneumatic air tube.

In another aspect, a forming section of a papermaking machine is provided. This can be any type of forming section and can include twin wire formers, gap formers, as well as hybrid type formers. The forming section includes at least two rolls as well as a forming fabric that is supported on the at least two rolls. A t least one pneumatically actuated moveable doctoring device as discussed above is provided with one or more of the linkage arrangements as described above connected between the blade support and the base member which guides the blade support as it is extended or retracted into or out of contact with the forming fabric by the pneumatic air tube. Preferably a plurality of the pneumatically actuated moveable doctoring devices can be provided spaced apart from one another in a machine direction of the forming section. Each of the doctoring devices extends across a width of the forming fabric in the cross direction. Depending upon the particular characteristics of the paper being formed in the forming section of the papermaking machine, various ones of the pneumatically actuated moveable doctoring devices can be extended into contact with the forming fabric or be retracted out of contact with the forming fabric.

The linear motion of the doctoring element in the direction of the loading and minimizing friction of the doctoring element movement are critical components of the devices controllability. Providing for positive retraction of the doctoring element from the forming fabric is also beneficial to prevent the unintended loading of the doctoring element caused by diverted water forces. This arrangement has two critical advantages over the current state of art. First, the pneumatic air tube used for loading and unloading the doctoring element against the paper machine fabric has two attachment features on opposing sides of the tube, which act as attachment points. These attachment features allow for the single pneumatic air tube to couple together the base member of the counter blade and movable blade support with the doctoring element of the counter blade. The capability to couple the base and the doctoring element with the single air tube allows for the single pneumatic air tube to provide positive retraction when a vacuum is applied. Second, the doctoring element is connected to the counter blade base with a linkage arrangement which provides a very low friction method of controlling the movement of the doctoring element. The low friction is achieved through the linkage arrangement utilizing pin-bushing arrangements. As the doctoring element is loaded into the forming fabric, the four-bar linkage keeps the elements square to the fabric path, providing linear loading.

In another aspect, a pneumatically actuated moveable doctoring device for a paper machine forming section is provided having a base member adapted to be supported by a papermaking machine structure and a blade support with a fabric contact element. A pneumatic air tube having first and second attachments on opposing sides of the pneumatic air tube is provided, with the first attachment engaging the base member and the second attachment engaging the blade support. The pneumatic air tube is configured for connection to a pressurized air source and a vacuum source to extend or retract the blade support relative to the base member. The first and second attachments on the pneumatic air tube have an enlarged end section with a smaller base and are integrally formed on opposing surfaces of the single pneumatic air tube, and the base member and the blade support each include a corresponding undercut receptacle for a positive fit connection to the pneumatic air tube. A linkage arrangement is connected between the blade support and the base member. The linkage arrangement includes at least first and second links located between the base member and the blade support, with the links each having a pivotal connection to the base member and provide for a fixed orientation of the blade support relative to the base member as the pneumatic air tube extends the blade support or retracts the blade support guided by the linkage arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. These terms and terms of similar import are for ease of description when referring to the drawings and should not be considered limiting. “Machine Direction” refers to a direction in which a papermaking fabric travels in a papermaking machine. “Cross Direction” refers to a direction generally perpendicular to the Machine Direction. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof.

For elements of the invention that are identical or have identical actions, identical reference symbols are used. The illustrated embodiments represent merely examples for how the device according to the invention could be equipped. They do not represent a conclusive limitation of the invention.

Referring now toFIGS. 2 and 3, a pneumatically actuated moveable doctoring device50for a paper machine forming section (shown inFIG. 5) is shown. The doctoring device50includes a base member60which is adapted to be supported by a paper machine structure, for example as shown inFIG. 5. This can include, for example, a T-bar recess70for attachment to a paper machine support rail. While the base member60according to one embodiment of the doctoring device50is as shown inFIGS. 2 and 3, those skilled in the art will recognize that it could include a horizontal mounting arrangement, for example as shown inFIG. 1Caccording to the prior art.

A blade support58having a fabric contact element or doctoring element56, formed for example from ceramic inserts is provided. The blade support58preferably includes a positive fit connection to the fabric contact element56, which can be in the form of an undercut recess, such as a dove tail, to provide for positive engagement of the fabric contact element56to the blade support58. Preferably, a single pneumatic air tube52having first and second attachments53a,53bon opposing sides of the pneumatic air tube52is provided, with the first attachment53aengaging with the base member60and the second attachment53bengaging with the blade support58. The pneumatic air tube52has an inflatable chamber that can be pressurized or depressurized. In one preferred arrangement, the first and second attachments53a,53b, on the single pneumatic air tube52have an enlarged end section with a smaller base, preferably a T-shape, and are integrally formed on opposing surfaces of the single pneumatic air tube52. The single pneumatic air tube52can be molded from rubber or a suitable elastomer with the integrally formed first and second attachments53a,53b. Alternatively, the first and second attachments can be other shapes, such as a dovetail which is adapted to engage in an undercut recess with a corresponding shape in the base member60and the blade support58. Alternatively, other connectors, such as mechanical fasteners or an adhesive can be used to form the first and second attachments.

The pneumatic air tube52is configured for connection to a pressurized air source74, shown inFIG. 4, and to a vacuum source76, also shown inFIG. 4, to extend or retract the blade support58relative to the base member60. Preferably, the pressurized air source74and the vacuum source76are connected to the pneumatic air tube via a control valve78.FIG. 2shows the pneumatic air tube52with no pressurization and/or a vacuum applied in order to retract the blade support58relative to the base member60in the direction of travel D shown inFIG. 2, andFIG. 3shows the single pneumatic air tube52connected to the pressurized air source74to inflate the single pneumatic air tube52and extend the blade support58in the direction of travel D shown inFIG. 3.

Still with reference toFIGS. 2 and 3, in order to guide the blade support58as it travels between the extended and retracted positions, a linkage arrangement61is connected between a blade support58and the base member60. Preferably, a plurality of linkage arrangements61are connected between the blade support58and the base member60, as shown inFIG. 4. The linkage arrangement61includes at least first and second links64a,64blocated between the base member60and the blade support58. The links64a,64beach have a pivotal connection indicated at68aand69ainFIG. 2to the base member60. Preferably, the linkage arrangement61forms a four-bar linkage arrangement with each of the first and second links64a,64balso having a pivotal connection to the blade support58indicated at68band69b. In the arrangement shown inFIGS. 2-4, the base member60includes a first linkage upright62, and the first and second links64a,64bare pivotally connected to the first linkage upright62. As shown inFIG. 4, a plurality of the first linkage uprights62may be spaced in the cross direction along the base member60with pairs of the first and second links64a,64bbeing connected to each of the first linkage uprights62of the base member60. The first linkage upright62may be provided as separate pieces that are connected to the base member60or they may be machined integrally with the base member60. Depending upon the configuration of the base member60, the first linkage uprights62can be omitted and the pivotal connections68a,69acan be made directly to the main body of the base member60.

As shown inFIG. 2, a second linkage upright63may be provided as part of the blade support58. The first and second link64a,64bare preferably also connected via pivotal connections68b,69bto the blade support60on the second linkage upright63. The second linkage upright63can be provided as a separately formed part that is attached to the blade support58or may be integrally formed or machined on the blade support58. As shown inFIG. 4, preferably a plurality of the second linkage upright63are also provided spaced apart in the cross direction on the blade support58in corresponding positions to the first linkage upright62at the location of each linkage arrangement61.

The pivotal connections68a,68b,69a,69bpreferably each include a pin65that extends through openings in the base member60and the blade support58. The openings may include a bushing therein (an exemplary one of which is indicated in broken lines at67inFIG. 3) and the pin65would then extend through such bushings67. The bushings67may be made from a self-lubricating material.

As shown inFIGS. 2 and 3, a distance between the pivotal connections on the base member60is equal to a distance between the pivotal connections on the blade support58in the preferred four-bar mechanism formed by the linkage arrangement61. This arrangement provides that the orientation of the blade support58along with the doctoring element56located thereon remains generally fixed with respect to horizontal and vertical, even as the blade support58travels along an arcuate path defined by the linkage arrangement61as the pneumatic air tube is pressurized or depressurized to extend or retract the blade support58. The amount of travel in the Machine Direction of the blade support58as the blade support58is extended or retracted due to the application of pressure or vacuum to the single pneumatic air tube52is small relative to the vertical travel in the direction of travel D of the blade support58relative to the base member60. The applicants have found that this minimal amount of travel in the Machine Direction can be compensated for in the mounting arrangement of the base member60to the papermaking machine forming section200shown inFIG. 5, and that the MD offset is de minimis.

Those skilled in the art will recognize that various other linkage arrangements can be provided other than a four-bar mechanism to achieve a similar travel path while maintaining a generally fixed orientation of the blade support58relative to the base member60in both the horizontal and vertical directions.

As shown inFIGS. 2 and 3, at least one flexible cover66can be attached between the base member60and the blade support58. In a preferred embodiment, two flexible covers66are shown with either screw attachments73or a keyed attachment feature, such as dove tail slot indicated at72inFIG. 2. Those skilled in the art will recognize that the flexible cover66can be omitted, if desired, allowing the linkage arrangements61to be exposed to the papermaking slurry. In this case, the pivotal connections68a,68b;69a,69bfor the first and second links64a,64bcan be sealed or otherwise protected to prevent higher friction due to paper fibers becoming trapped in the pivotal connections.

Referring now toFIGS. 4 and 5, as shown inFIG. 4the doctoring device50preferably extends across a forming section200of a papermaking machine, shown inFIG. 5. The doctoring elements or blades56connected to the blade support58are preferably provided in segments and made of a ceramic material. While a total of five linkage arrangements61are shown connected between the base member60and the blade support58, those skilled in the art will recognize that a different number of linkage arrangements61could be utilized.

As shown inFIG. 5, the forming section200of the papermaking machine includes a forming roll205and a breast roll210, and preferably an autoslice215. Stock, indicated at240is delivered onto a forming fabric225in a position on an impingement (forming) shoe220, preferably mounted on a support unit221. A backing fabric230travels over the forming fabric225, and the fabrics225,230carry the stock between fixed blades235and counterblades, which in the present case are provided as the pneumatically actuated moveable doctoring devices50as described above in order to remove water from the stock and form a nascent paper web. These pneumatically actuated moveable doctoring devices50are preferably located on a counterblade support unit243, and the opposing fixed blades235are located on a fixed blade support unit245.

The pneumatically actuated moveable doctoring devices50can be individually moved into or out of contact with the forming fabric225by extending the blade support58relative to the base member60by pressurizing the pneumatic air tube52or retracting the blade support58out of contact from the forming fabric104by depressurizing and/or applying a vacuum to the pneumatic air tube52in the particular doctoring device50depending upon the particular properties being achieved by the specific placement of the doctoring elements or blades56, acting as counter blades in the embodiment ofFIG. 5, contacting the forming fabric225.

The present invention provides the advantage of a single pneumatic air tube52that can be used for both loading and unloading the doctoring element56of a particular doctoring device50based on the two attachments providing on opposing sides of the tube52. Further, the linkage arrangements61of each of the doctoring devices50allows for a low friction moveable arrangement that maintains the orientation of the blade support58along with its doctoring element or blade element56as it is moved into contact with the forming fabric225while avoiding the issues associated with a sliding support of the prior art. The low friction linkage arrangements61along with the single pneumatic tube52for each of the doctoring devices50thus provide a simple system with lower cost that provides for both positive extension and retraction.

While a single pneumatic air tube52is preferred, it is within the scope of the present invention to have two pneumatic air tubes arranged side-by-side with both having positive attachments to the base member60and the blade support58, and this still being considered functionally as a single pneumatic air tube as described herein.

Having thus described the present invention in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.

LIST OF ELEMENT NUMBERS