Abstract:
An apparatus for doctoring a moving surface includes a blade holder component extending longitudinally across the moving surface and carrying a doctor blade. A support component is parallel to and supports the blade holder component. A first operating mechanism rotatably urges the doctor blade in a doctoring direction into contact with the moving surface, resulting in the doctor blade being acted upon by a reactionary thrust force in the plane of the doctor blade and a reactionary rotational force in a direction opposite to the doctoring direction. A pair of mutually opposed parallel guide rails are provided on one of the components, and rotatable rollers are spaced along the length of the other of the component. The rollers are in rolling contact and in mechanical interengagement with the guide rails to accommodate reciprocal movement of the blade holder component relative to the support component, and to resist both the reactionary thrust force and the reactionary rotational force acting on the doctor blade. A second operating mechanism reciprocally moves the blade holder component relative to the support component.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of U.S. patent application Ser. No. 09/686,507 filed Oct. 11, 2000, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to doctors of the type employed in paper making machines and the like, and is concerned in particular with an improved oscillating doctor blade holder. 
     2. Description of the Prior Art 
     In a known doctor, as disclosed in U.S. Pat. No. 2,300,908 (Broughton), an unduly complex roller arrangement is employed to reciprocally support and guide the blade holder. In particular, mutually spaced sets of at least three rollers are required to act in concert to counteract the reactionary thrust and rotational forces exerted on the doctor blade holder during a doctoring operation. 
     Such arrangements are difficult to maintain, often requiring disassembly of the blade holder when roller replacement becomes necessary. The three roller arrangement is also difficult to seal and thus prone to a build up of contaminants between the roller sets. This in turn requires frequent cleaning and attention by maintenance personnel. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to overcome the disadvantages of known oscillating doctor holders by providing a much simpler yet highly effective support arrangement. 
     To this end, in accordance with the present invention, a blade holder component extends longitudinally across a moving surface to be doctored. A doctor blade is carried by the blade holder component. A support component is parallel to and supports the blade holder component. A first operating means rotatably urges the doctor blade in one direction into contact with the moving surface to be doctored, resulting in the doctor blade being acted upon by a reactionary thrust force in the plane of the doctor blade, and a reactionary rotational force opposite to the direction of rotational blade application. 
     Guide rails on parallel tracks are provided on one of either the blade holder or support components, and rotatable rollers are spaced along the length of the other of the blade holder or support components. Each roller is in rolling contact with a guide rail on a respective one but not the other of the tracks to thereby accommodate reciprocal movement of the blade holder component relative to the support component, and at least some of the rollers coact with their respective guide rails to resist both the reactionary thrust and rotational forces acting on the doctor blade. 
     A second operating means reciprocally moves the blade holder component relative to the support component. 
     In certain preferred embodiments, the rollers have either curved or angularly profiled rims in rolling contact and in mechanical interengagement with mating curved or angularly disposed surfaces on the guide rails. The curved or angularly disposed surfaces of the guide rails may define longitudinal grooves extending in the direction of reciprocal movement of the blade holder component, with the curved or angularly profiled rims of the rollers projecting into the longitudinal grooves. Alternatively, the curved or angularly profiled rims of the rollers may define circular grooves, with the curved or angularly disposed surfaces of the guide rails projecting into the circular grooves. 
     The rollers may advantageously be grouped in pairs mounted on and spaced at intervals along the length of either the blade holder component or the support component. The rotational axes of the roller pairs may be offset in the direction of the length of the component on which they are mounted. 
     The rollers are preferably axially shiftable on their respective support shafts to thereby accommodate any minor misalignment and/or subsequent gradual wear of components. 
     These and other features, advantages and objectives of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of one embodiment of a doctoring apparatus in accordance with one embodiment of the present invention; 
     FIG. 2 is an enlarged view of a portion of the doctoring apparatus shown in FIG. 1, with portions broken away to show the fluid actuated tubes employed to control rotational adjustment of the doctor blade; 
     FIG. 3 is a sectional view taken generally along line  3 — 3  of FIG. 2; 
     FIG. 4 is a view similar to FIG. 2 showing an alternative embodiment of a doctoring apparatus in accordance with the present invention; 
     FIG. 5 diagrammatically depicts the positioning of filler blocks between successive roller sets; 
     FIG. 6 is a sectional view taken along line  6 — 6  of FIG. 3; 
     FIGS. 7 and 8 are enlarged partial sectional views of the roller and guide rail configurations shown respectively in FIGS. 2 and 4; and 
     FIGS. 9-18 are views similar to FIGS. 2 and 4 showing additional alternative embodiments in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference initially to FIGS. 1-3, a doctoring apparatus in accordance with one embodiment of the present invention is shown at  2  comprising a blade holder component  4  extending longitudinally across a moving surface to be doctored, in this case the surface S of a roll  6  of the type typically found in a paper making machine. The blade holder component includes a top plate  7  coacting with underlying jaws  8  to slidably receive and hold a doctor blade  9 . The top plate  7  is mounted on brackets  10  for rotation about an axis A 1  parallel to the rotational axis A 2  of roll  6 . The brackets  10  protrude vertically from a tray-shaped bottom  12 . Fluid-actuated tubes  14 ,  15  are carried on the bottom  12  and bear against the underside of the top plate  7  on opposite sides of the axis A 1 . The blade holder component is carried on a support component  16 . The support component  16  may be fixed as a part of the machine frame, or it may be keyed or otherwise fixed to a shaft  17 , the latter being supported by bearings  18  for rotation about an axis A 3  parallel to the rotational axes A 1  and A 2 . 
     During a doctoring operation, a first operating means applies the doctor blade  9  to the surface S with a force F 1 . The first operating means may entail pressurization of tube  15  to rotate the top plate  7  in a counterclockwise direction about axis A 1 . Alternatively, or in conjunction with pressurization of tube  15 , a crank arm  19  may be operated by a piston-cylinder unit  20  to rotate the support component  16  in a counterclockwise direction about axis A 3 . As shown diagrammatically in FIG. 2, a force F 1  applied to the roll surface by the doctor blade is opposed by an equal and opposite reactionary force F 2 . Reactionary force F 2  may be resolved into a reactionary thrust force F 2a  in the plane of the doctor blade, and a reactionary rotational force F 2b  tending to rotate the doctor blade and blade holder in a clockwise direction. 
     A longitudinally extending base  22  is secured by means of screws  24  or the like to the support component  16 . The base has a generally U-shaped cross section, with a bottom  28  and upstanding mutually opposed sides forming guide rails  30  that extend along parallel tracks and that cooperate with the bottom  28  to define a channel  32 . 
     Pairs of guide rollers  34  project downwardly from the bottom  12  of the blade holder component  4  into the guide channel  32 . As can best be seen in FIG. 3, the roller pairs are arranged at spaced intervals along the length of the blade holder component. The rotational axes “A 4 ” of the rollers of each pair are offset in the length direction of the guide channel  32 . As viewed in FIG. 3, the uppermost rollers  34  of each pair contact the upper rail  30 , but not the lowermost rail. By the same token, the lowermost rollers contact the lower rail, but not the upper rail. 
     As can best be seen in FIGS. 7 and 8, the guide rollers  34  may have angularly profiled rims  36 , each having inner and outer inclined shoulders  36   a ,  36   b . The inner shoulders  36   a  coact to define a peripheral groove  36   c . In the embodiment shown in FIGS. 2 and 7, the rims  36  project radially into grooves  38  in the side rails  30  of the track  22 . The grooves  38  have angularly disposed surfaces  40 . The outer shoulders  36   b  of the rims  36  are in rolling contact and in mechanical interengagement with the mating angularly disposed groove surfaces  40 . The rolling contact accommodates reciprocal movement of the blade holder component  4  relative to and along the length of the track  22 , and also serves to resist the reactionary thrust force F 2a . The mechanical interengagement between the rollers and rails resists the reactionary rotational force F 2b  which tends to twist the blade holder component in a clockwise direction, as indicated at  42  in FIG.  2 . 
     Reciprocal movement may be imparted to the blade holder component  4  by a linear actuator  44  fixed to the support component  16  and joined to the blade holder component by means of a transversely extending bracket  46 . The linear actuator  44  may be positioned as shown, or at any other convenient location, e.g., at an end of and in line with the blade holder component, or inside the blade holder component between spaced sets of guide rollers. 
     In the embodiment shown in FIG. 2 flexible sealing aprons  48 ,  50  are secured by keeper plates  52 ,  54  to the blade holder component  4 . The sealing aprons frictionally contact external surfaces of the base  22  to thereby deflect external contaminants away from the guide channel  32 . 
     Filler blocks  56  may be secured to the underside of the blade holder component  4  by means of screws  58  or the like. The filler blocks are appropriately configured to fill the spaces between the sets of guide rollers  34  and to project into and fill the grooves  38  in the rails  30 . The filler blocks assist in excluding contaminants from the guide channel  32  that might penetrate past the sealing aprons  48 . Additionally, the filler blocks serve as guide elements which coact with the interior surfaces of the guide rails  30  when inserting and removing the blade holder component from the support component. 
     In the embodiment shown in FIGS. 4 and 8, the rails  30  have V-shaped ledges  60  which project into the peripheral grooves  36   c  of the guide rollers. The inner shoulders  36   a  of the profiled roller rims  36  coact with the inclined surfaces of the guide tracks  60  in both rolling contact and in mechanical interengagement. In much the same manner as described previously with respect to the embodiment shown in FIGS. 1 and 6, rolling contact accommodates reciprocal movement of the blade holder component relative to and along the length of the track  22  while also serving to resist the reactionary thrust force F 2a . The mechanical interengagement resists the reactionary rotational force F 2b . 
     It the embodiment of FIG. 4, one side of the blade holder is provided with sealing plates  62 ,  64  configured to establish a sealing labyrinth. The opposite side of the blade holder has a sealing plate  66  configured to coact with external surfaces of the guide rail in providing a second sealing labyrinth. The sealing labyrinths serve to deflect and exclude contaminants from reaching the guide channel  32 . The sealing plates  62 ,  64   66  may either be rigid or flexible. 
     FIGS. 9-18 illustrate other embodiments of the invention. In FIG. 9, the V-shaped ledges  60  face in opposite directions and are arranged on the doctor back component  16  between the guide rollers  34 , the latter again being carried on shafts protruding downwardly from the bottom  28  of the blade holder component  24 . In this arrangement, the rotational axes of the roller pairs need not be offset in the direction of reciprocal movement. 
     In FIG. 10, the V-shaped ledges  60  face inwardly and are mounted on brackets secured to the bottom  20  of the blade holder component. The guide rollers  34  are mounted on the support component between the ledges  60 . 
     In FIG. 11, the guide rails  30  are spaced vertically one from the other by a spacer bar  70  and are secured to the support component  16 . The V-shaped ledges  60  face inwardly. The guide rollers  34  are arranged between the V-shaped ledges  60  and are carried on shafts projecting from the depending sides of an inverted U-shaped bracket  72  secured to the bottom  20  of the blade holder component  4 . The V-shaped ledges  60  project into and coact in rolling and mechanical interengagement with the circular peripheral grooves  36   c  of the guide rollers. 
     FIG. 12 is similar to FIG. 11, except that here the guide rails  30  have longitudinally extending grooves  38  into which project the angularly profiled rims of the guide rollers  34 . 
     In the arrangements shown in FIGS. 9-11, the rolling contact and mechanical interengagement of the rollers  34  with the V-shaped ledges  60  operate as previously described with reference to FIGS. 4 and 8 in accommodating reciprocal movement of the blade holder component while resisting the reactionary thrust and rotational forces F 2a , F 2b . The arrangement shown in FIG. 12 serves the same functions and operates as described previously with respect to the arrangement shown in FIGS. 3 and 7. 
     FIG. 13 is similar to FIG. 12, except that here the guide rollers  34 ′ have cylindrical as opposed to angularly profiled peripheries which are received in flat bottomed grooves  38 ′ in the guide rails  30 . The cylindrical peripheries of the rollers  34 ′ are in rolling contact with the bottoms of the grooves  38 ′, and the roller of flanks are in mechanical interengagement with the edges of the grooves. 
     The arrangement shown in FIG. 14 is generally similar to that shown in FIG. 2, except that here again, the guide rollers  34 ′ have cylindrical peripheries which are received in and which coact in both rolling contact and mechanical interengagement with flat bottomed grooves  38 ′ in the guide rails  30 . 
     In the embodiment shown in FIGS. 15-17, the tray-shaped bottom  12  of the blade holder component  4  is carried on a plate  78 , and the generally U-shaped base  28  is secured to the support component  16 . Rails  80  are secured to the sides of the base. Pairs of rollers  82  are rotatably carried on the underside of plate  78 . The rails  80  have convex sides received in concave rims of the rollers  82 . 
     As can best be seen in FIG. 17, the rollers  82  are preferably provided with wear resistant sleeve inserts  84  journalled for rotation on spacer sleeves  86 . The sleeves  86  are held in an abutting relationship against the underside of plate  78  by machine screws  88  and outer thrust washers  90 . Inner thrust washers  92  are interposed between the rollers  82  and the plate  78 . The axial length of the spacer sleeves  86  is greater than the combined axial thickness of the rollers  82  and inner thrust washers  92 , thus providing a space S (exaggerated for purposes of illustration) which allows the rollers to shift axially and to self align themselves with the rails  80  with which they are in rolling contact and mechanical interengagement. 
     As can best be seen in FIG. 16, gaps  94  are provided between the rails  80 , and filler blocks  96  occupy the spaces between the rollers  82 . The lengths of the rails  80  are sufficient to support and guide the blade holder during its reciprocal movement, and the gaps  94  allow the blade holder to be lifted laterally and removed from the base  28  for repair and maintenance purposes. This is to be contrasted to the arrangement shown, for example, in FIGS. 1-3 where the rails  30  extend continuously, thus requiring the blade holder to be extracted and reinserted longitudinally from the side of the machine. 
     As shown in FIG. 18, the shapes of the rollers  82 ′ and guide rails  80 ′ can be reversed from that shown in FIGS. 15-17, i.e., the rails may have concave surfaces and the rollers may have convex rims. 
     In light of the foregoing, it will now be apparent to those skilled in the art that the present invention offers a number of significant advantages as compared to known prior art arrangements. For example, less than three guide rollers are required at positions spaced out over the length of the blade holder. The guide rollers coact in both rolling contact and mechanical interengagement with complimentary surfaces of adjacent guide rails. The rolling contact accommodates reciprocal movement of the blade holder component relative to the doctor back component while also resisting reactionary thrust forces. The mechanical interengagement serves to resist reactionary rotational forces. The rollers are preferably shiftable axially to provide self alignment with the rails with which they are in rolling contact and mechanical interengagement. Self alignment is further enhanced by providing the rollers and guide rails with curved contact surfaces, as shown in FIGS. 15-18. Any of the various types of known blade holders may be accommodated with this arrangement. The doctor blade may be applied to the surface to be doctored with a force generated by means carried on the blade holder, e.g., the fluid actuated tubes  14 ,  15  shown in FIG.  2 . This makes it possible to eliminate and/or greatly simplify other costly components conventionally employed to apply and oscillate the doctor blade.