Patent Application
20090266256
The present invention is directed generally to a doctor blade system. More particularly, the present invention is directed to a doctor blade system for use in a rotary printing press. Most specifically, the present invention is directed to a doctor blade system for use in a flexographic printing machine. The doctor blade system includes a doctor blade chamber of a light material. A full length support plate carries the doctor blade chamber. That support plate is biased across its width, in the axial direction of a cooperating anilox roller, by a plurality of membrane cylinders. Those several membrane cylinders are secured to a rigid cross member. The result is a lightweight doctor blade chamber which is not subject to the bending and distortion problems that have been prevalent in previous devices.
In the field of rotary printing machines, it is generally well known to provide an inking unit that is equipped with a chamber doctor blade assembly. Such a chamber doctor blade assembly will include an elongated doctor blade chamber which is provided with a central, ink receiving reservoir. The doctor blade chamber central ink receiving reservoir is defined by two spaced doctor blades which extend in the axial direction of a cooperating ink roller, typically an anilox or screen roller. End plates are used at both ends of the doctor blade body to define, in cooperation with the two spaced doctor blades, the ink receiving reservoir.
Ink is supplied to the reservoir in the doctor blade body and is then applied to the surface of the anilox roller from that reservoir while the surface of the anilox roller or other similar inking roller passes through the ink reservoir defined by the two doctor blades and end plates. It is necessary that the ink being applied to the surface of the anilox roller be accurately and uniformly metered. Either too little ink, too much ink or an unequal ink thickness along the axial length of the anilox roller will cause degradation of the quality of the resultant printed product.
The force with which the two spaced doctor blades are engaged against the surface of the anilox roller is one way to meter the thickness of the ink layer which is applied to the surface of the anilox roller. While factors such as ink viscosity, roller rotational speed and the like will also affect the ink thickness, it is the force with which the doctor blades engage the pocketed or cell-covered surface of the anilox roller which is more determinative of the thickness of the ink layer which is applied from the ink reservoir in the doctor blade chamber to the anilox roller.
In early doctor blade systems, which were used with only single or double width printing cylinders, the structure of the doctor blade chamber could be of metal since weight was not a great consideration. The use of metal doctor blade chambers imparted a certain amount of structural rigidity to the doctor blade chamber. Biasing forces could be exerted on the chamber at the ends and would be applied relatively uniformly along the entire lengths of the working and closing doctor blades.
Printing presses now in use are characterized by four wide and six wide printing cylinders. The width of such a cylinder is thus four or six times the width of a newspaper page in broadsheet format. The width of the anilox inking roller thus is typically as great as the width of the printing cylinder. This results in the need for a doctor blade chamber that also has the width of up to six newspaper pages in broadsheet format. A traditional metal doctor blade chamber becomes too heavy to be usable.
The end seals and the doctor blades of the doctor blade chamber themselves are wear items which periodically must be replaced or refurbished. It is also necessary to periodically remove the doctor blade chamber from its associated mounting assemblies so that it can be cleaned or replaced. The doctor blade assemblies are also periodically thrown off or moved out of contact with the anilox roller so that the roller can be removed from the printing press. All of these requirements of the doctor blade chamber also mean that the weight of the doctor blade chamber needs to be kept at a minimum.
One material which has shown itself to be particularly suited for use in the formation of doctor blade chambers is glass fiber reinforced plastic or GRP. Such a material is light in weight and is extremely resistant to chemicals having extreme pH levels. Many currently used printing inks have such high pH levels. While an aluminum or an iron material can be imbued with similar resistance properties, this can be accomplished only through the use of costly and complicated coatings. Such coating are always subject to mechanical damage, such as chipping and scratching. The so-coated aluminum or iron doctor blade chambers are still very heavy and are thus difficult to mount, dismount and handle.
GRP doctor blade chamber structures satisfy the need for being light in weight, having durability and being resistant to high pH levels. Their primary limitation is a lack of structural rigidity, when compared with the previously used metal doctor blade chambers. The lack of structural rigidity results in twisting and bending of the doctor blade chamber across the width of the anilox roller. If the chamber flexes, distorts or bends, the two doctor blades do not contact the anilox roller with uniform pressure along the width of the anilox roller. The result of such non-uniform contact force is variance in the ink thickness application to the anilox roller, uneven wear of the doctor blades, premature end seal failures and other undesirable consequences.
In an effort to counteract or to compensate for the lack of structural rigidity of the GRP doctor blade chambers, as compared to the prior metal structures, various attempts have been made to rigidify such GRP doctor blade chambers. One prior attempt to overcome this lack of structural rigidity of GRP doctor blade chambers is set forth in EP 1 398 152 A1. In the system disclosed in that document, the doctor blade body is provided with elongated stiffening traction elements that extend parallel to the axis of the anilox roller, in the body of the doctor blade. These traction elements extend beyond the ends of the doctor blade body and are supported by. adjustment sleeves. Those sleeves are secured onto the ends of the traction elements and are actuated to impart a flexural movement to the doctor blade body that is asserted to be substantially equal and opposite to the flexural movement generated on the doctor blade body during the inking of the anilox roller.
Another arrangement, as proposed by KBA-Motter, uses a GRP chamber doctor blade that is mounted onto a shaft via plates which are welded to the shaft. That shaft is supported, at its outbound ends by pneumatic or hydraulic cylinders. The force required to adjust the doctor blade chamber is applied by these two cylinders. This is apt to result in a transverse deflection of the supporting shaft and of the doctor blade chamber. As discussed above, such a deflection results in distortion of the GRP doctor blade chamber, a twisting of the blade system and premature wear of the end seals. Another limitation of this prior system is that the working doctor blade is located closer to the axis of rotation of the anilox roller than is the closing doctor blade. The working doctor blade is thus subjected to greater wear and tear than is the closing doctor blade. As a result, more frequent maintenance is apt to be required.
It will be apparent that a need exists for a doctor blade system which overcomes the limitations of the prior device. The doctor blade system, in accordance with the present invention, provides such an assembly and system. It is a substantial improvement over the prior systems.
It is an object of the present invention to provide a doctor blade system.
Another object of the present invention is to provide a doctor blade system including a doctor blade support.
A further object of the present invention is to provide a doctor blade system having a plurality of membrane cylinders distributed over the length of the doctor blade support.
Yet another object of the present invention is to provide a doctor blade system usable with a glass fiber reinforced doctor blade chamber.
Even a further object of the present invention is to provide a doctor blade system having great structural rigidity.
Still yet another object of the present invention is to provide a doctor blade system which facilitates linear adjustment of the doctor blade chamber with uniform load application on both blades.
Yet still a further object of the present invention is to provide a doctor blade system which is structured to facilitate exchange of the anilox roller without removal of the doctor blade system from a press assembly.
As will be described in greater detail in the description of the preferred embodiment, and as depicted in the accompanying drawings, the doctor blade system, in accordance with the present invention utilizes a lightweight doctor blade chamber that provides an ink chamber defined by spaced working and closing doctor blades and cooperating end seals. The doctor blade chamber is preferably formed using glass fiber reinforced plastic GRP which is of reduced weight and which provides the desired high resistance to chemicals, such as printing inks having high pH levels.
The doctor blade chamber is removably mounted to a support plate. That support plate is positioned on linear slides so that it is movable in a direction toward and away from the anilox roller, with which the doctor blade chamber cooperates. The linear slides are secured to pivotable end plates. Quickly releasable blade chamber clamping elements on the support plate provide for efficient yet secure attachment of the chamber doctor blade to the support plate. Detachment of the chamber doctor blade from the support plate is easily accomplished.
A box beam is also attached to the pivotable end plates and is essentially parallel to, and spaced from the support plate. The box beam, as its name suggests, has a substantial amount of structural rigidity while still being relatively light in weight. The box beam is provided with a plurality of membrane cylinders that are located in the space between the box beam and the support plate. These membrane cylinders are aligned with the axis of rotation of the anilox roller and are spaced equally along the width of the box beam. Each membrane cylinder is brought into engagement with the support plate to which the doctor blade chamber is mounted. Suitable force is thus exerted, by the plurality of axially spaced membrane cylinders, against the support plate to insure that the doctor blade chamber is brought into proper, uniform engagement with the surface of the anilox roller. Each of the plurality of membrane cylinders can be provided with its own separate source of fluid under pressure, and with its own separate control so that each such membrane cylinder can be individually controlled. This will insure that the working doctor blade, the closing doctor blade and the end seals all are brought into, and remain in proper engagement with the anilox roller.
The doctor blade chamber itself does not require a great deal of structural rigidity. It is thus ideally suited to be fabricated using lightweight, chemically resistant materials, such as a glass fiber reinforced plastic or GRP. As a result, the doctor blade chamber, even if it has a length corresponding to that of an anilox roller with which it cooperates, and which is suitable for inking a six wide printing cylinder, is still sufficiently light in weight that it can be routinely handled and manipulated.
Attachment of the doctor blade chamber to the support plate is accomplished by the use of spaced blade chamber clamping elements. Since the chamber doctor blade, the support plate and the box beam are all supported by the spaced pivotable end plates, the doctor blade assembly can be pivoted through 90° for routine cleaning or through 120° for doctor blade chamber servicing or removal and replacement.
The doctor blade chamber itself does not require the inclusion of reinforcement bars, strips or other rigidifying elements which only serve to increase its overall weight. Instead, the doctor blade chamber relies on the support plate for its support. That support plate, in turn relies on the force imparted to it by the membrane cylinders carried by the box beam to impart to it the appropriate rigidity. Neither the support plate nor the box beams are intended to be routinely removed from the pivotable end plates. The support plate is supported on those end plates by linear slides so that it can move, without bending, toward and away from the surface of the anilox roller. Since the membrane cylinders are spaced equidistantly along the box beam and bear against the support plate at a multiplicity of points, the support plate can move along its linear guides to position its supported doctor blade chamber in proper, uniform engagement of the working and closing doctor blades with the surface of the anilox roller.
The two pivotable end plates are pivotably connected to exterior plates. Those exterior plates are, in turn, pivotably connected to inner surfaces of side frames of the printing unit. If it is necessary to move the entire doctor blade assembly, such as, for example, to exchange the anilox roller, this can be accomplished by pivoting the exterior plates at their points of attachment to the printing unit side frames. It is not necessary to totally disassemble the doctor blade assembly to allow for exchange of an anilox roller, when such a roller exchange may become necessary.
The doctor blade system, in accordance with the present invention, overcomes the limitations of the prior art. It allows the use of a lightweight, chemical resistant doctor blade chamber that can be moved and manipulated. Despite its lightweight and somewhat flexible nature, the doctor blade chamber is provided with structural rigidity by its positioning on its cooperating support plate. That support plate is positioned on linear guides and is movable toward and away from the surface of the anilox roller by the spaced membrane cylinders. The use of the box beam to carry these membrane cylinders insures their rigidity and accomplishes the accurate positioning of the doctor blade chamber in a highly controllable and reproducible manner.
The doctor blade system of the present invention overcomes the limitations of the prior art. It is a substantial advance in the art.
A full and complete understanding of the doctor blade system, in accordance with the present invention, may be had by referring to the description of the preferred embodiment, as is set forth subsequently, and as depicted in the accompanying sheets of drawings, in which:
Referring initially to
As is well known in the art, a doctor blade chamber, generally at 14 includes a working doctor blade 20 and a closing doctor blade 22 whose outer edges 24; 26, respectively, engage the surface 18 of the anilox roller 18. Suitable end plates 28 and 30, as seen more clearly in
Referring again to
While not specifically shown in
Referring now to
The doctor blade chamber 14 is removably attachable to the support plate 50 and specifically to the central web of the support plate. To accomplish this releasable attachment, the rear wall 40 of the doctor blade chamber 14 is provided with spaced mounting studs 62, which are shown generally schematically in
The support plate central web 52 is provided with a plurality of somewhat ovoid or elongated through bores, which are not visible in the several drawings. These through bores, whose long axes extend vertically in the orientation of the support plate 50 shown in
Referring now to
With the doctor blade system 10 rotated generally 120° in a counter-clockwise direction, in respect to the position shown in
It is essential that the working doctor blade 24 and the closing doctor blade 26 be spaced equidistant from the axis of rotation of the anilox or inking roller 18. As may be seen in
Once the inner wedging surfaces 94 of the tines 92 of the locking levers 80 have been brought into firm engagement with the inner surfaces 70 of the mounting sheet heads 66, by firm downward pressure exerted on the locking lever gripping flanges 82, the gripper heads 90 of the clamping screws 88 can be used to clamp the locking levers 80 in place. This provides for positive securement of the doctor blade chamber 14 on the support plate 50. Removal of the doctor blade chamber 14 from the support plate 50 is accomplished by reversal of this procedure.
The support plate 50 is supported, at each of its ends, in a linear slide assembly, generally at 110, as may be seen in
A support plate mounting flange securement bracket 120 is attached to each one of the linear slide blocks 116, again as may be seen most clearly in
Turning now to
A plurality of membrane cylinders, generally at 140 are attached to a front face 142 of the box beam 130 by suitable fasteners 144. These membrane cylinder fasteners 144 are seen more clearly in
The front face 142 of the box beam 130 is spaced rearwardly from the rear surface 72 of the support plate 50. The membrane cylinders 140 are sized to fit into the resultant space, which is seen most clearly in
Each membrane cylinder 140 will be connected to a supply of fluid under pressure. Such fluid, such as compressed air, is readily available in a printing plant. The specific compressed air lines are not specifically depicted in the drawing figures for clarity of illustration. It will be understood that a suitable control assembly would be available to control the flow of compressed air to the membrane cylinders. While membrane cylinders 140 have been depicted and described in this preferred embodiment, it will be understood that other suitable force applying assemblies, such as linear actuators, piezo-electric devices, and the like could be substituted for the described and depicted membrane cylinders 140, whose function is to provide an equally distributed forward acting biasing force against the support plate 50.
The membrane cylinders 140 are aligned on the box beam 130, and the box beam is situated, with respect to the support plate 50, so that the points of engagement of the membrane cylinder plunger faces 154 will be in alignment with each other and equally as importantly will be aligned with the axis of rotation of the anilox roller. When the membrane cylinders are charged with the requisite amount of compressed air, the plunger faces will push against the rear surface 72 of the support plate 50 with sufficient force to move the support plate 50 forwardly along the linear slide assemblies 110 toward the anilox roller 18. The use of the two linear slide assemblies 110 assures that the support plate 50 will move toward the anilox roller 18 in a smooth linear manner. By controlling the pressure of fluid that is being supplied to the membrane cylinders 140, the force which the doctor blade edges 24 and 26 will exert against the surface 16 of the anilox roller 18 will be carefully controlled. Because there are a plurality of the membrane cylinders 140 spaced along the box beam 130, and due to the rigidity of that box beam 130, a controllable, certain force can be applied to the support plate 50 and thus to the surface 16 of the anilox roller 18 by the working doctor blade and closing doctor blade edges 24 and 26. In a similar manner, the seals, which are held in place by the end plates 28 and 30, are also engaged against the anilox roller with a positive, controllable force. The two desired goals of a lightweight doctor blade chamber and a structurally rigid doctor blade mount are thus provided by the doctor blade system of the present invention.
As mentioned previously, the doctor blade chamber 14, the support plate 50 and the box beam 130 are all attached to a pair of pivotable end plates 58 and 60. As may be seen in
Each of the two spaced end plates 58 and 60 has an upper fin 168, 170 respectively, as may be seen in
As was asserted previously, the end plates 58; 60 are pivotable, with respect to their associated exterior plates 162; 164 through either 90° or 120°, both in a counter-clockwise direction, as seen in
In the use position of the doctor blade chamber 14, the pin shank 190 of each index pin 188 is received in its associated one of the exterior plate blind bores 194. When it is necessary to rotate the doctor blade chamber 14 counter-clockwise through 90°, the tension rods 174 are released by rotation of the tension levers 178 and the tension rods 174 are pivoted up and out of their respective channels 172 about their respective swivel couplers 176. The tension rods can be held in their elevated positions by suitable biasing springs, which are not specifically shown, that are incorporated into the swivel couplings 176. Once the tension rods have been disengaged, the index pins 188 can be moved inwardly to disengage them from their blind bores 194 in the exterior plates 162; 164. The doctor blade chamber handles 48 and 46, and similar box beam handles 198, 200 can be manually engaged and the doctor blade chamber 14, support plate 50, box beam 130 and end plates 58 and 60 can be pivoted through 90° in a counter-clockwise direction. The index pins 188 can be reinserted into the slots 184 to limit the rotation to 90°, as shown schematically in
In certain instances, such as when it is necessary to remove the anilox or similar ink roller 18, it is appropriate to rotate the entire doctor blade system through an upward rotation, in a clockwise direction, with respect to its position as depicted in
As may be seen most clearly in
The base stop block 202 carries a first base stop 216. This first base stop 216 has an enlarged base stop head 218. The base stop head 218 is engagable with an exterior plate stop body 220. The exterior plate stop body 220 is secured to each one of its respective exterior plates by suitable set screws 222. Each of these exterior plate stop blocks 220 is provided with an upwardly extending end plate base stop member 224. That end plate base stop member 224 is provided with an enlarged end plate stop head 226 which engages a stop abutment 228 on the lower surface of each end plate 58; 60. As was the case with the vertical stops, generally at 100, these base stops 216 and 220 are adjusted and are secured in place during assembly of the doctor blade system, typically by factory personnel. They are not intended for adjustment in the field by the press operator.
Turning again briefly to
The doctor blade system, in accordance with the present invention is a substantial improvement over prior systems. In a large printing press system such as one producing upwards of 2-2.5 million copies a day, prior doctor blade systems would require seal and blade replacements or adjustments every three to four weeks. The flexibility of the doctor blade chambers caused ink density variations, which led to print quality problems. These prior systems had high maintenance requirements and low operational stability.
In marked contrast, the doctor blade system in accordance with the present invention, has a seal life of up to 12 weeks. The structural rigidity that is provided by the overall system has greatly improved color density conformity. It is much easier for press personnel to change doctor blades and seals and to maintain the system. The present system can be adapted to existing press structure without particularly great changeover expenses.
While a preferred embodiment of a doctor blade system, in accordance with the present invention, has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes, for example, in the specific structure of the ink roller, the drive for the ink roller, the supply of the printing ink and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the appended claims.
