Bladeholders For Doctors And Scrapers

Abstract

A bladeholder for doctors, scrapers and the like has separate regions for a blade and a pressure or rocker plate. The blade can be removed, installed, or adjusted in one region without disturbing the rocker plate and associated parts in the other region. The rocker plate has constant "stick-out," and can be fitted with resilient profiling devices. An improved profiling device is shown having armor cladding to prevent damage due to pressure.

Description

BACKGROUND OF THE INVENTION

The art of making bladeholders for doctors and scrapers is old, yet continues to develop. The task of doctoring or scraping a moving work surface, as on a roll or cylinder, for example, presents problems of approach to the load, operational control, and blade wear and replacement, which continue to engage paper makers and others facing the task. In the paper industry, doctors and scrapers are employed to clean the surfaces of rotating calendar rolls, drier cylinders and the like; and scrapers are used to remove a web of paper as in the manufacture of crepe paper (creping doctor). Scrapers (sometimes called "knives") are used to remove product from drums in flakers and drum driers used to prepare dried products of various kinds (examples being foodstuffs, pharmaceuticals, chemicals, films solidified from liquids) from a starting liquid or paste.

When the surface to be doctored or scraped (working surface) is that of a material soft enough to be damaged by a blade or knife approaching it at an angle that favors digging in, chipping or otherwise injuring the working surface, it is important that the bladeholder control not only the angle at which the blade engages the work surface during operation but also the angle at which the blade approaches the work surface when being brought into position for operation. A blade holder which permits the unloaded blade in it to rock about some axis parallel to its working edge would introduce the danger of injuring the work surface, thereby requiring special precautions to prevent such injury.

Blades wear out in use, and many attempts have been made to extend blade life. Attention has been given to special treatments of the working edges of blades, to improve the lasting qualities and efficiencies of the working edges. Attention has also been given to making blades having reserve body structure and adjustable holding features such that, in combination with a bladeholder incorporating cooperating adjusting features, the blade can be adjusted to compensate for wearing away of its working edge.

Much attention has been given to problems of operational control. Doctor and scraper blades are generally long thin structures approximately four to six inches wide and extending sometimes as much as 30 feet or more from one end to the other, across a working surface perpendicular to the direction of relative motion with respect to the working surface. In paper machinery, the long dimension of the blade is in the "cross-machine direction" (CMD). Obviously, the blade is subject to flexure in the CMD, and a high spot on the working surface, due to debris, for example, can lift the blade from the working surface in the vicinity of the high spot, and create conditions of non-uniform pressure between the blade working edge and the working surface in the CMD. This is a transitory, or dynamic flexure problem. There exists also a static problem of blade flexure to accommodate roll crown and the like. An early solution to these problems is described in U.S. Pat. No. 2,477,339 to Ljungquist, assigned to the predecessor of the assignee of the present application. Examples of the attention given to correcting these problems with yieldable displacement members are found, for example, in U.S. Pat. Nos. 2,914,788 and 3,163,878, both assigned to DST Pattern and Engineering Companty Limited. A more recent improvement in bladeholders providing uniform pressure on the working surface is described in U.S. Pat. No. 3,529,315 of Dunlap and Bedard, which is assigned to the predecessor of the assignee of this application. This last patent describes and claims a bladeholder adapted to position a blade to bear against a work surface with substantially uniform pressure along its entire length, and a yieldable displacement member for a blade assembly which are believed to afford the most satisfactory solution yet available for this particular problem.

The introduction of yieldable displacement members has made bladeholders more complicated, and has brought with it problems of protecting the displacement members from destruction in the working environment, and during replacement or adjustment of blades in the bladeholder, as well as introducing complications in the installation, changing and adjustment of blades.

GENERAL NATURE OF THE INVENTION

The present invention is addressed to all of the foregoing problems. A bladeholder is provided which as in the prior art, has two jaws enclosing a jaw space for receiving the back portion of a blade, and a pair of confronting lips forward through which the blade extends to its working edge. The holder has provision for means, preferably resilient, arranged to apply force through a rocker plate to one side of the blade for holding the blade working edge in engagement with a working surface. The resilient means can optimally be a profiling means, and the rocker plate can be especially adapted for efficiently functioning with a profiling resilient means.

The jaw space is divided into two regions, for example by a partition member in the jaw space which is anchored to the bladeholder separating one region from the other, both regions, however, communicating with the space between the lips. The back portion of the blade is located in one region while the back portion of the rocker plate together with its associated force-applying means is located in the second region. Means are provided to seal the second region against entry of foreign material through the lips. The blade can be installed in, removed from, or in some embodiments of the invention adjusted in, the first region without disturbing the contents of the second region. The contents of the second region, in particular, a resilient force-applying means, can be installed in and removed from the second region without disturbing the blade. In creping applications, where constant "stick-out" of the rocker plate is desirable, embodiments of the invention which provide for independent adjustment of the blade are particularly valuable, and afford flexibility and simplicity of operation which have not heretofore been available.

The arrangement of parts is such that when the blade is not loaded, namely, the working edge is out of contact with a working surface, the blade attitute, or angle is the same or approximately the same, relative to an approaching load as the blade angle under loaded or working condition. To this end, the blade and rocker plate are constrained within limits that are normally not reached during operation but when reached in the absence of a load will maintain the blade at an angle, or in an attitute which closely approximates the working angle or attitude.

Resilient force-applying means for the rocker plate can be solid, as an elongated piece of rubber, or it can be a tubular member charged with a fluid. If a profiling member is desired, the teachings of above-mentioned U.S. Pat. No. 3,529,315 can be incorporated. Tubular members charged with fluid risk loss of the fluid, shut-down and the inconvenience of needing to be changed if they are damaged. To minimize these risks, a metal braid envelope is provided. This provision, combined with installation in a bladeholder which minimizes the occasions for changing or adjusting the rocker-plate and resilient means components, greatly improves the utility and reliability of bladeholders. Preferably this envelope is highly flexible, in order to avoid interference with profiling properties of the resilient means while protecting it from abrasion, cuts and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a first embodiment of the invention;

FIG. 2 is a cross-section of a second embodiment of the invention;

FIG. 3 is a cross-section of a profiling resilient member;

FIG. 4 is a longitudinal end-section of the profiling member shown in FIG. 3; and

FIG. 5 is a partial plan view of a modified rocker plate.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in cross section a blade holder 10 carried by an arm 11 (i.e; doctor back) that is pivotally mounted with respect to a roll 12, the surface of which is the work surface against which a blade 13 is intended to bear at its working edge 14. As is well known, the bladeholder is an elongated structure which may be several feet long. The bladeholder is held to the arm by several bolts of which only one bolt 15 is illustrated. The bladeholder is comprised of a top piece 16 the back portion of which is bolted to the arm 11 and the forward portion of which constitutes a first jaw member 17 that terminates at its forward extremity in a first lip 18. A bottom piece 20 has a back portion 21 fastened to the top piece by several bolts 22 and a forward portion constituting a second jaw member 23 which terminates at its forward extremity in a second lip 24. The jaw members 17 and 23 are spaced apart not only by the back portion 21 but also by a spacer member 25 through which the bolts 22 pass into the back portion 21, and the lips 18 and 24 also are spaced apart, the jaw members rearwardly of the lips bounding between them a jaw space 26. A platform member 28 is held between the bottom piece back portion 21 and the spacer member 25 and extends into the jaw space dividing the jaw space into two distinct regions, here in the form of a first compartment 26A bounded at one side by the first jaw member 17 and a second compartment 26B bounded at one side by the second jaw member 23.

A rocker plate 30 has a rearward portion 30A located in the first compartment 26A, and a forward portion 30B extending out of the first compartment beyond the first lip 18 and terminating in a bearing edge 31. The rocker plate bears at one side (top as seen in FIG. 1) against the first lip 18. Resilient means 32 (to be described in detail below) is located in the first compartment 26A between the platform member 28 and the opposite side (lower as seen in FIG. 1) of the rocker plate 30 at the rearward portion 30A of it. Generally speaking, the resilient means includes an elongated flexible member which preferably has the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length, and will therefore function as a profiling means. For some applications of the invention, it may be satisfactory to use a simple elongated resilient member (a spring or a rubber member, for example) which does not have this profiling property in a significant degree. The resilient means 32 will, in either case, urge the rearward portion 30A of the rocker plate away from the platform member 28, and will thereby urge the rocker plate to pivot around the first lip 18 in a direction tending to displace the bearing edge 31 toward the second lip 24. Retainers in the form of short screw bolts 35 are threaded through the first jaw member 17 far enough to penetrate loosely through holes 36 in the rocker plate, to hold the rocker plate in the first compartment 26A.

A thin strip 38 of buffer material is fixedly located in the jawspace in the vicinity of the platform member, being clamped at a rearward portion between the spacer member 25 and the platform member 28, and extends forward terminating at its forward edge 39 in contact with the under side (in FIG. 1) of the rocker plate 30, just forward of the first lip 18. This sheet may be a sheet of steel, or other spring-like material which is preferably spring-loaded to hold its forward edge 39 resiliently in contact with the rocker plate, so that it aids in sealing the first compartment 26A against the entrance of loose material during operation of the bladeholder. Terminating forward as it does beyond the first lip 18, the spring-loaded buffer strip 38 is effectively dimensioned to cooperate with the resilient means 32 to maintain the rocker plate 30 in contact with the first lip 18 when there is no blade in the second compartment 26B, thereby facilitating the insertion of a blade into, and removal of the blade from the second compartment 26B.

The blade 13 has spring-clips 40 attached with studs 41 along its rearward portion within the second compartment 26B. The studs retain the blade within the second compartment against the up-standing second lip 24, while the spring clips bear against the underside (in FIG. 1) of the platform member 28. This light spring action tends to retain a blade 13 in the blade-holder 10 in its working attitude when it is out of contact with the roll 12, that is, when there is no working load on the working edge 14 of the blade. This is an important feature of the bladeholder, which prevents damage to the surface of a roll or other working surface that is soft enough to be damaged if the blade approaches it at an angle that is not the correct, or at least approximately the correct working angle.

FIG. 2 shows a second embodiment of the invention in which the bladeholder 50 is affixed via its top piece 56 to the underside of a supporting arm or doctor back 51 by a series of bolts of which only one 55 is shown. The top piece extends forward of the doctor back to a first jaw member 57 terminating at its forward extremity in a first lip 58. The bottom piece 60 has its back portion 61 fastened to the top piece by bolts 62 which pass through a spacer member 65 into the top piece 56. In this embodiment the platform member 68 (corresponding to the platform member 28 in FIG. 1) is integral with the spacer member 65, and extends into the jaw space 66 where it divides that space into two regions comprised of a first compartment 66A and a second compartment 66B. The rocker plate 30, resilient means 32, retainers 35 and holes 36 in the rocker plate are all similar to the like-referenced components in FIG. 1. A buffer strip 78 corresponds essentially to the buffer strip 38 in FIG. 1 being in this embodiment bent to form an extended contact at its forward portion 78A with the underside of the rocker plate both before and beyond contact of the rocker plate with the first lip 58. The first compartment 66A and parts contained within it, including the buffer strip 78, are essentially similar to the first compartment 26A and the parts contained within it in FIG. 1, in both structures and function.

The bottom piece 60 has a back portion 61 which extends forward essentially parallel to the platform member 68, and a forward portion which constitutes a second jaw member 63 terminating at its forward extremity in a second lip 64. The confronting surfaces 68.1 of the platform member 68 and 61.1 of the back portion 61 of the bottom piece 60 are each serrated or notched with a series of slots or notches 69A and 69B, respectively, that are in register with eachother forming a ladder-like series of enlarged subdivisions of the second compartment 66B, separated by finger-like projections 70A and 70B, respectively, which extend toward but do not touch each-other.

A blade 53 has its back portion 53A in the second compartment 66A, between but not touching the confronting projections 70A, 70B, and its forward portion 53B extending out of the holder beyond the lips 58 and 64 to terminate in a working edge 54. A base plate 59 is positioned to the rearward extremity of the blade 53, disposed transverse to the thickness of the blade and running its full length, so that in the transverse section shown in FIG. 2 the base plate and the blade form a "T." The base plate 59 generally is continuous. It has a width, across the second compartment 66B which is greater than the distance between any pair of confronting projections 70A, 70B, but somewhat less than the distance between the bottoms of a pair of confronting slots or notches 69A, 69B. By sliding the blade 53 out of the second compartment 66B, perpendicular to the plane of the figure, or through the lips 58 and 64, or both, the blade can be removed from the holder without disturbing the rocker plate 30 or other contents of the first compartment 66A. The base plate 59 can be removed and installed only in the direction perpendicular to the plane of the figure. With the reverse procedure, the blade can be reinserted in the holder 50 while locating the base plate 59 in any pair of confronting slots 69A, 69B, to rest on the rearward-most pair of confronting projections 70A, 70B, respectively, bounding those slots, as is shown in dotted line at 59.1. In this manner the rearward portion 53A of the blade can be located to one of several available depths in the second compartment 66B, and the distance (i.e.: "stick-out") that the forward portion 53B of the blade projects beyond the lips 58 and 64 can be adjusted, independent of the "stick-out" of the rocker plate 30, which remains constant. This permits the blade to be adjusted in the holder 50 for wear, thereby extending the useful life of a blade, as well as to accommodate blades of varying widths.

The embodiment of FIG. 2 has all the advantages and features of the embodiment of FIG. 1. In addition, this embodiment provides for separate adjustment of a blade in a holder which incorporates provisions for hydraulic profiling means, without disturbing the profiling means. It will be noted that, as in FIG. 1, the rocker plate 30 in FIG. 2 bears at its forward edge 31 on the top surface (in the figure) of the blade forward of the second lip 64. The distance between the first lip 58 and the forward edge 31 of the rocker plate 30 (i.e: the rocker plate "stick-out") is a constant in a given structure, which can be chosen to suit the needs of a particular application, while the blade 53 is independently adjustable so that the blade "stick-out" (amount the forward portion 53B extends) beyond the rocker plate edge 31 is independently variable. This feature of the invention is important for example in creping applications, and is available independent of whether or not a resilient force-applying means 32 is employed. With no load on the blade, the blade will approach its load (e.g: surface of the roll 12) at an angle approximately as is shown in FIG. 2, but without the slight curvature imposed by the load which is shown in the figure.

The resilient means 32 preferably has no noticeable spring rate. A yieldable displacement member as described and claimed in U.S. Pat. No. 3,529,315 may be used in place of the particular resilient means 32 shown in FIGS. 1 and 2. Such a displacement member, in elongated tubular form, has the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length. When incorporated as the resilient means 32 in the present invention, it will provide a profiling feature to the invention. Blades for doctoring, calendaring, creping, and the like, being sometimes several feet long are flexible in the direction of the working edge. When a high spot appears on the working surface of the roll 12, tending to lift the nearby lengthwise portion of the blade from the roll, the blade correspondingly tends to urge the same general lengthwise portion of the rocker plate to pivot counter-clockwise around the first lip, 18 or 58, of the holder. This puts an increased pressure on the corresponding lengthwise portion of the resilient means. Employing the substantially-uniform pressure property defined above, the resilient means transmits that pressure throughout its length, and that pressure is applied via the rocker plate 30 to the blade 13 or 53, to hold down against the surface of the roll 12 the remainder of the working edge 14 or 54. As is described in the referenced patent, such profiling means can be made of a pliable tube closed at both ends and charged with a substantially incompressible fluid, preferably a fixed volume of non-compressible fluid to the substantial exclusion of compressible fluid, and the best advantages for profiling will be enjoyed if the material of the walls of the tube is relatively inelastic such that in the range of normal conditions of operation, it is substantially unstretched.

The resilient means 32 shown in FIGS. 1 and 2 can also provide profiling properties to the invention. FIGS. 3 and 4 show enlarged views of it. An elongated tube 75 which has or is given a generally oval cross-section is made of a suitable plastics material, such as Teflon (DuPont trademark for a plastic consisting of a tetrafluoroethylene polymer). The tube can be chosen of any suitable material (e.g: rubber) in a wall thickness having the desired inelastic properties. Tubes of Teflon Type FEP having wall thickness in the range 0.015 to 0.030 inch have been used. A metal-braid protective envelope 76 encloses the tube 75, to prevent damage to the tube from abrasion with the surrounding metal parts when it is installed in the bladeholder and during operation. A protective envelope 76 made of highly flexible fibers will minimize interference of the envelope with the profiling properties of the enclosed profiling tube 75. To this end, stainless steel braid tube size 48-11-36 has been used. After filling with a non-compressible fluid according to the above-referenced patent, the tube 75 is sealed at its ends, by heat sealing in a known manner to provide sealed ends one of which is illustrated at 77 in FIG. 4. The metal-braid envelope 76 is drawn over the sealed tube end 77 and closed with a clamp 78, which can be made, for example, from a ring of 3/8 inch diameter copper tube flattened over the overlapping metal braid.

Sensitivity of the profiling arrangement to distortion of the blade in the cross-machine direction, as by an irregularity on the working surface, may be enhanced by slotting the rocker plate transversely to the cross-machine direction, from one or both of its long edges toward or into its median region, as is illustrated in FIG. 5. In the event a resilient means is used that does not contribute profiling properties, such as a bar of solid rubber, slotting of the rocker plate in this manner will reduce the tendency of neighboring regions of the blade to follow such a distortion of the blade.

When the invention is used without a resilient means 32 selected primarily for or with major interest in its profiling properties a bar of solid rubber (not shown) as mentioned above, or an inflatable tube or hose may be used. Another alternative is a wavy spring (not shown) extending in the cross-machine direction, between the rearward portion 30A of the rocker plate and the platform member 28 or 68, with its wave peaks touching both. Such other resilient means may contribute some profiling properties, or substantially none at all, depending on the particular structure that is chosen in a given installation. Bladeholders according to the invention give the user a full range of options and, regardless of choise of resilient means, a blade can be installed, removed, and in embodiments according to FIG. 2 adjusted, without disturbing the rocker plate and resilient means subassembly.

Claims

I claim:

1. A holder for a doctor blade or the like comprising a pair of jaw members having respective spaced-apart lips said members bounding a jaw space, a partition member in the jaw space dividing that space into first and second side-by-side compartments, a rocker plate having a rearward lockably retained portion in the first compartment and a forward portion extending a fixed distance out of the first compartment beyond the lip of the jaw member bounding the first compartment, the rocker plate being arranged to bear at one side against said lip and terminating at its forward portion in a bearing edge, and resilient means located in the first compartment between the partition member and the rearward portion of the rocker plate; the second compartment being fitted to receive a blade having a rearward portion located in the second compartment and a second portion extending out of the second compartment beyond both lips and said bearing edge so that said blade during operation will be in contact at one side with said bearing edge, said partition member and the jaw member bounding the second compartment being arranged to hold removably between them the rearward portion of said blade, so that a blade can be fitted into and removed from the second compartment independently of the contents of the first compartment.

2. A bladeholder according to claim 1 in which said resilient means incorporates profiling means that includes an elongated flexible member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length.

3. A bladeholder according to claim 2 in which said profiling means comprises a tube of flexible material closed at both ends and charged with a substantially incompressible fluid.

4. A bladeholder according to claim 3 in which said tube contains a fixed volume of non-compressible fluid to the substantial exclusion of compressible fluid, and the material of the walls of said tube is relatively inelastic such that in the range of normal conditions of operation it is substantially unstretched.

5. A bladeholder according to claim 3 including a tubular metal armor having flexibility similar to said tube substantially surrounding the tube.

6. A bladeholder according to claim 1 including a buffer strip of generally rigid but flexible material having a rearward portion fixedly located in said jaw space in the vicinity of said partition member and a forward portion bearing against the opposite side of said rocker plate in the vicinity of said first-named lip, for substantially closing said first compartment to passage of material entering said jaw space between said lips.

7. A bladeholder according to claim 6 in which said forward portion of said buffer strip bears against said rocker plate at a location forward of said first lip.

8. A bladeholder according to claim 1 in combination with a blade having a rearward portion located in said second compartment and a forward portion extending out of said second compartment beyond both said lips and said bearing edge to a working edge, said blade being in confronting relation at a first side with said lip bounding the second compartment and in contact at its other side with said bearing edge, so that when working force is applied to said working edge of said blade in a direction tending into said first side thereof said working force is transmitted via said rocker plate to said resilient means.

9. A combination according to claim 8 in which said resilient means incorporates profiling means that includes an elongated flexible member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length for reacting on said blade differentially along the length thereof in response to working forces tending to deflect said blade differentially along said working edge.

10. A combination according to claim 9 in which said profiling means comprises a tube of flexible material closed at both ends and charged with a substantially incompressible fluid.

11. A combination according to claim 10 in which said tube contains a fixed volume of non-compressible material to the substantial exclusion of compressible fluid, and the material of the walls of said tube is relatively inelastic such that in the range of normal working forces it is substantially unstretched.

12. A combination according to claim 10 including a tubular metal armor having flexibility similar to said tube substantially surrounding said tube.

13. A combination according to claim 8 including a buffer strip of generally rigid but flexible material having a rearward portion fixedly located in said jaw space in the vicinity of said partition member and a forward portion bearing against said opposite side of said rocker plate in the vicinity of said first-named lip, for substantially closing said first compartment to passage of material entering said jaw space between said lips.

14. A combination according to claim 8 including means in said second compartment for adjusting the distance said blade extends out of said second compartment.

15. A bladeholder according to claim 1 including adjustable blade support means between a side of said platform member and the confronting rearward portion of said second jaw member that bounds said second compartment.

16. A bladeholder according to claim 15 in combination with a blade having a rearward portion located in said second compartment and a forward portion extending out of said jaw space beyond both said second named lip and said bearing edge to a working edge, and means at said rearward portion for cooperating with said adjustable support means to adjust the extension of said blade out of said jaw space.

17. A bladeholder according to claim 16 wherein said blade is in confronting relation at a first side with said second named lip and in contact at its other side with said bearing edge, so that when working force is applied to said working edge of said blade in a direction tending into said first side thereof said working force is transmitted via said rocker plate to said resilient means.

18. A combination according to claim 8 including slotted adjustment means in said second compartment to adjust the distance said forward portion of said blade extends beyond said second lip.

19. A combination according to claim 18 in which adjustment means includes a rigid member confined by the slotted means and transversely disposed in said second compartment at the back edge of the rearward portion of said blade.

20. A bladeholder adapted to position a blade to bear against a work surface comprising first and second jaw members terminating in first and second respective spaced-apart lips and rearwardly of said lips bounding a jaw space between them, a platform member fixed in said jaw space between said members dividing said jaw space into a first compartment bounded at one side by said first jaw member and a second compartment bounded at one side by said second jaw member, a rocker plate having a rearward portion located in said first compartment and a forward portion extending from said bladeholder a constant distance beyond said first lip and terminating in a bearing edge, means for causing said rocker plate bear at one side against said first lip, a buffer strip having a rearward portion fixed in said jaw space in the vicinity of said platform member and a forward portion bearing against the opposite side of said rocker plate for closing the first compartment to passage of material entering said jaw space between said lips, a blade having a rearward portion located in said second compartment and a forward portion extending out of said second compartment beyond both said second lip and said bearing edge to a working edge, said blade being in confronting relation at a first side with said second lip and in contact at its other side with said bearing edge, and means in said second compartment for adjusting the distance said blade extends out of said second compartment, independently of said rocker plate.

21. A bladeholder according to claim 20 in which said platform means comprises a rigid member traversing said jaw space dividing said first and second regions into respective first and second compartments, said adjusting means being disposed between said rigid member and the rearward portion of said second jaw member that bounds said second region.

22. A bladeholder according to claim 21 including pairs of confronting slots in said rigid member and said second jaw member and an elongated base member slidably engaged in one such pair of slots for supporting and locating the rearward portion of said blade in said second region.

23. A bladeholder according to claim 21 including a rigid member transversely disposed in said second region for locating said rearward portion of said blade therein.