The invention relates to a doctor apparatus comprising a blade adapted to abut against a roll, a platelike blade holder and support members, said blade being interposed between said support members and said blade holder which is mounted on said support members by means of mounting screws in such a manner that the blade holder engages the blade through a free end thereof, the apparatus further comprising a reinforcing plate superposed and mounted on said blade holder by said mounting screws in such a way that said reinforcing plate has a free end cooperating with the free end of said blade holder, the free end of said reinforcing plate being adapted to be pressed against said blade holder to cause the free end of said blade holder to move to engage said blade. Such an apparatus is known from GB-A-368 472.
Such a doctor blade apparatus is used for permitting raw material to be satisfactorily accumulated on a paper making roll and water to be satisfactorily fed to the roll and removing foreign matters adhered to a surface of the roll such as paper powders, pitch, tailings or the like from the roll to keep it clean, and more particularly to a doctor blade apparatus adapted to permit a pressure distributed at an edge of the blade pressedly contacted with the roll to be adjusted so as to be substantially uniform.
A conventional doctor blade supporting structure which has been known in the art includes an adjusting means which acts to permit a blade for peeling off dusts adhered to a surface of a roll from the roll to be contacted at a tip end thereof with the roll surface at a uniform linear pressure or a contact pressure of the blade uniformly distributed in an axial direction of the roll.
In general, a blade for a doctor blade supporting structure is required to exhibit satisfactory holding force, stability and flexibility; therefore, the blade for the conventional doctor blade supporting structure is generally made of a relatively thin sheet material such as metal, plastic or the like into any desired thickness depending upon applications thereof. Unfortunately, this causes the blade to be pivotally moved with respect to the roll, resulting in the contact pressure of the blade being apt to be varied. In view of such a problem, a structure as shown in Fig. 7 is proposed and used, wherein a blade (G) is vertically interposed between a blade holder (F) made of a relatively rigid plate material and support members (C) and the blade holder (F) keeps the blade (G) at a posture. The support members (C) each are held directly on a doctor bag (E) using a screw means or pivotally supported on a pivot rod (D). Then, the blade (G) is vertically moved through a pressurized air tube (A) and an open tube (B) each interposedly arranged between the doctor bag (E) and the support member (C) to adjust a position of the blade (G).
The blade holder (F) comprises a single plate member formed into a shape of continuously extending in an axial direction of a roll, to thereby prevent a contact pressure of the blade (G) with respect to the roll from being varied in use. However, in order that the contact pressure of the blade (G) can be uniformly distributed in the axial direction of the roll, it is necessary to uniformly adjust contact between a surface of the roll and the blade (G). Unfortunately, this needs a considerable amount of labor. Further, a width of the blade holder (F) is finished by machining, however, a thickness of a blank for the blade holder (F) and its length are used as those of the holder (F) without being subject to finishing by machining, resulting in failing to form a contact end between the blade holder (F) and the blade (G) with high accuracy.
It would be considered that the accuracy of the contact end is increased by various processing techniques. However, this requires a considerable amount of labor and time and many processing machines, leading to a significant increase in manufacturing costs.
In view of the foregoing, the present situation is to escape an error occurring at the contact end utilizing crook of the blade holder (F); however, in order to accomplish the purpose, it is required to reduce a degree of crook of the blade holder (F) when the doctor blade supporting structure is directed to applications wherein the blade (G) is abutted against the roll at a high pressure, resulting in a relief being lost. This requires to further increase the accuracy of the contact end, so that it is highly difficult to press the blade against the roll at a constant linear pressure.
In accordance with the present invention, a doctor apparatus of the kind as described and as defined in the precharacterizing clause of claim 1, is characterized by the free end of said reinforcing plate being pivotally movable with respect to a supporting point; and finely adjusting screws which are threaded into one of the support members and said reinforcing plate and which are abuttedly engaged with the other; the adjusting screws being arranged so as to permit a gap to be defined between said blade holder and said reinforcing plate or support members in a position spaced from said supporting point, and to be adjusted by turning said adjusting screws so that said reinforcing plate pivots at said supporting point to thereby press said free end thereof against said blade holder, which causes said blade holder to move to engage with said blade.
Preferable embodiments are defined in the dependent claims.
Such construction of the present invention permits the structure to effectively absorb strain of each of the roll and blade occurring during operation of the structure while contacting the blade with the roll, so that a linear pressure of the blade with respect to the roll may be automatically corrected so as to be uniform over a whole width of the blade.
In particular, the structure of the present invention is so constructed that the blade holder is pressedly fixed by the reinforcing plate on which the blade holder is mounted by means of the mounting screws and the finely adjusting screws are arranged so as to permit the gap to be defined between the blade holder and the reinforcing plate or support members so as to render the blade holder approachable or accessible to the blade through the free end of the reinforcing plate positioned on the side of the blade. Thus, tightening of each of the finely adjusting screws causes a tip end of the blade to be lowered and pressedly abutted against the roll, whereas loosening of the screw causes pressing force of the blade against the roll to be reduced; thus, adjustment of the pressing force is highly facilitated to satisfactorily increase holding force and stability of the blade, to thereby permit the blade to be uniformly pressed against the roll at a constant linear pressure. Also, the above-described construction permits the crook of the blade holder in a direction of a thickness thereof to be reinforced, so that the blade holder itself may be formed into a reduced thickness as compared with the prior art. This results in distortion and bending of the blade in a longitudinal direction thereof permitting the blade to exhibit improved response performance or characteristics.
Accordingly, the present invention keeps the blade at a satisfactory posture while eliminating a necessity of subjecting the reinforcing plate to fine processing and permits the blade holder to prevent the contact pressure of the blade from being varied because the blade is uniformly abutted against a surface of the roll. Also, the present invention permits the contact pressure of the blade with respect to the surface of the roll to be uniformly distributed in an axial direction of the roll and also permits the reinforcing plate to be formed into a reduced thickness.
In the accompanying drawings,
Figs. 1 to 2 illustrate an embodiment of a doctor blade supporting structure according to the present invention. A doctor blade supporting structure of the illustrated embodiment includes a blade 1 adapted to be abutted against a roll R, which blade is mounted on support members 4 by means of mounting screws 3 provided for assembling a blade holder 2. The doctor blade supporting structure also includes a reinforcing plate 5 arranged in a manner to be laminated or superposed on the blade holder 2. Further, the structure includes finely adjusting screws 10 each of which acts to permit a gap to be defined between the blade holder 2 and the reinforcing plate 5 or each of the support members 4 so that the blade holder 2 may be moved through a free end 51 of the reinforcing plate 5 defined on the side of the blade 1 so as to be approachable or accessible to the blade 1. The blade 1 is firmly held on the support members 4.
The reinforcing plate 5, as shown in Fig. 2, comprises a plurality of rectangular plate elements arranged on the blade holder 2 in a manner to be spaced at intervals. It is preferable that the plate elements of the reinforcing plate 5 are separately fixedly held on the support members 4 by means of the mounting screws 3, respectively. Such arrangement effectively prevents distortion and bending actions of the blade 1 in a longitudinal direction thereof from being deteriorated, to thereby substantially improve responsibility of the blade in the longitudinal direction. In particular, when the blade 1 is pivotally arranged through a support shaft 8 and held on the support members 4 each mounted through air tubes 6 on a doctor bag 7, it is preferable that the plate elements of the reinforcing plate 5 formed into the same width as the support members 4 are fixed together with the blade holder 2 by means of the mounting screws 3.
The finely adjusting screws 10 are threadedly arranged in threaded holes 9 formed through the reinforcing plate 5 in a manner to be movable in an axial direction thereof in the holes 9 and then inserted into through-holes formed via the blade holder 2 so as to be abutted against the support members 4, so that threaded insertion of the finely adjusting screws 10 through the reinforcing plate 5 permits the other end of each of the plate elements of the reinforcing plate 5 to be approachable or accessible to the blade holder 2 to form a gap therebetween.
In another embodiment of the present invention shown in Fig. 3, finely adjusting screws 10 inserted in through-holes formed via a blade holder 2 each are tapped with respect to a support member 4 and abutted at a head portion thereof against a lower surface of a reinforcing plate 5. Also, the reinforcing plate 5 is formed with holes 101 each of which permits a hexagon wrench to operatively engage therethrough with the head portion of the finely adjusting screw 10 to vertically move it, to thereby cause the other end of the reinforcing plate 5 to be vertically moved to define a gap between the reinforcing plate 5 and the blade holder 2, so that a posture of contact of a blade 1 with respect to a roll R may be adjusted.
At least one of the mounting screws 3 may be kept somewhat loosened when the adjustment is carried out, to thereby facilitate operation for the adjustment.
Alternatively, in each of the embodiments described above, the plate elements of the reinforcing plate 5 each may be formed with a hole 11 for receiving the mounting screw therein as shown in Figs. 1 and 3.
In the embodiment of the present invention shown in Fig. 3, the reinforcing plate 5, as shown in Fig. 4, comprises a single plate member of a pectinate or rugged shape so that a free end 51 of the reinforcing plate may be provided with a plurality of projections. Such construction of the reinforcing plate 5 facilitates assembling, mounting and handling of the reinforcing plate 5.
In a still further embodiment of the present invention shown in Fig. 5, between a support member 4 and a portion of a blade holder 2 overlapped with a reinforcing plate 5 and positioned around a mounting screw 3 arranged on the side of a blade 1 is formed a gap 12, so that threaded insertion of the mounting screw 3 into the support member 4 permits the reinforcing plate 5 and blade holder 2 to be moved together, to thereby vertically adjustably move an end of a blade 1 which is contacted with a roll R. Thus, it will be noted that the mounting screws 3 each function also as a finely adjusting screw.
In still another embodiment of the present invention shown in Fig. 6, air tubes 6 and 6 are arranged below an extension line C1 defined by extending a line defined between an edge of a blade 1 and a portion of the blade 1 held on support members 4. Also, the air tubes 6 are arranged opposite to each other in a V-like or Y-like manner about an intersection between a line C2 extending from the edge of the blade 1 at an angle e of 6 to 30 degrees and preferably 10 to 15 degrees below the extension line C1 and a vertical line C3. Such construction permits a contact angle of the blade with respect to a roll R to be increased, to thereby decrease a variation of the contact angle due to wearing of the blade 1, resulting in facilitating adjustment of a contact pressure of the blade with respect to the roll R and removal of any tailings from the roll R. Also, such construction permits the blade 1 to be uniformly pressed against the roll R.
The present invention is so constructed that the reinforcing plate is arranged in a manner to be superposed on the blade holder and the finely adjusting screws each are arranged so as to permit a gap to be defined between the blade holder and the reinforcing plate or support member, resulting in the blade holder being approachable or accessible to the blade through the free end of the reinforcing plate defined on the side of the blade. Such construction provides a relief for fine adjustment without requiring to form the contact end of the blade holder with high accuracy. Also, it permits crook of the blade holder to be reduced during pressing of the blade against the roll, to thereby keep the blade at a natural posture. Further, it permits the blade to be significantly reinforced against the crook of the blade holder while exhibiting a function of pressing the roll at a predetermined line pressure, so that the blade holder may be formed into a reduced thickness as compared with the prior art. This results in distortion and bending of the blade in a longitudinal direction thereof allowing the blade to exhibit a more satisfactory function. In addition, crook of the blade holder in a radial direction of the roll can be reduced to substantially improve response performance or characteristics of the blade in the longitudinal direction and a doctor line pressure can be rendered uniform over a whole width of the roll, so that the doctor blade supporting structure of the present invention is widely and readily applicable to existing apparatus while ensuring positive operation of the blade at a low cost and permitting the blade to positively exhibit satisfactory holding force, stability and flexibility. Thus, the present invention can be highly effectively available as a doctor blade supporting structure for a paper making roll.