Patent Application
20180320314
The present invention relates to a doctor blade holder, for example for a creping doctor blade co-acting with a Yankee cylinder or for any doctor blade co-acting with the cylindrical surface of a cylinder or roller rotating around its axis.
In paper making machines, in particular tissue paper, a Yankee cylinder is normally used to dry the paper before winding it in a reel. One or more doctor blades co-act with the Yankee cylinder, with one of their edges pressed against the cylindrical surface of the Yankee cylinder. The purpose of these doctor blades is to detach the ply of cellulosic fibers from the Yankee cylinder and to carry out any other operations, for example cleaning. The Yankee cylinder can be provided with a single doctor blade or several doctor blades placed in sequence.
Doctor blades are also used in combination with other types of cylinders or rollers, for example drying rollers.
The doctor blade of a creping device is usually inserted inside a doctor blade holder that forms a housing seat for the doctor blade. The doctor blade is pressed against the cylindrical surface of the rotating cylinder with a system that can be rigid or flexible. In flexible systems the fingers that support the doctor blade and that define the housing seat for the doctor blade are thrust by a pressurized fluid chamber against the cylindrical surface of the rotating cylinder. The flexibility of the pressurized fluid chamber makes the doctor blade flexible. Flexible systems are described, for example, in the U.S. Pat. No. 3,859,690 and U.S. Pat. No. 3,955,531. These systems have some advantages, in particular as regards the possibility of adapting the profile of the doctor blade to the shape of the cylindrical surface. However, they have some limits. In particular, they are prone to breakages and can be difficult to maintain and use.
The fingers are generally fixed integral to one another by means of a “plate” that extends in transverse direction to the axis of the machine. This “plate” is generally relatively thin, so that it is sufficiently elastic to allow each finger to take a different angular position with respect to the position of adjacent fingers. The assembly of the fingers connected to one another (defining a pressure plate) is mounted on the load-bearing structure, typically a beam, by means of a hole made in each finger, into which a rod of a length corresponding to the doctor blade holder is inserted. When a finger breaks or is damaged and must be replaced, the rod is removed and the pressure plate is then detached. The damaged fingers must be separated from the pressure plate, replaced and reconnected with the plate. To avoid the lengthy machine downtime necessary for these mounting and removal operations, spare pressure plates are normally provided, so that when a finger of the operating doctor blade holder breaks, the whole assembly of fingers is replaced with a single operation and the damaged pressure plate is repaired separately.
In other systems, known as rigid, the housing seat for the doctor blade is fixed rigidly to a support or beam, which is thrust toward the cylinder by suitable actuators. These systems are of much simpler construction than flexible systems, but also have some drawbacks, in particular due to the difficulty of adapting the shape of the doctor blade to the cylindrical surface of the cylinder. This latter can in fact have a shape that differs from the perfectly cylindrical geometrical shape and can have a camber, with a larger diameter in the intermediate portion and a smaller diameter at the ends of the cylinder. This makes it necessary for the doctor blade to be thrust against the cylindrical surface with very high pressures, resulting in increased frictions and torques, as well as wear.
Normally the support, or beam, of the doctor blade holder is mounted on the stationary load-bearing structure so as to rotate around an axis substantially parallel to the rotation axis of the cylinder with which the doctor blade mounted in the doctor blade holder co-acts. The doctor blade approaches the cylindrical surface of the cylinder or roller by means of a pivoting movement of the beam around the respective rotation axis. For this purpose, the beam is supported by means of bearings that define restraint, substantially representing hinges. The beam thus mounted is prone to deformations and vibrations in a non-negligible manner under the thrust generated by the contact pressure between the doctor blade and the cylinder. This deformation can cause difficulties in the operation of the cylinder and of the doctor blade co-acting therewith.
There is therefore a need to produce doctor blade holders that completely or partly overcome the drawbacks and the limits of doctor blade holders of the current art.
According to one aspect, disclosed herein is a doctor blade holder for a doctor blade adapted to co-act with a cylindrical surface of a rotating cylinder, comprising a plurality of fingers mounted on a beam, hinged around a rotation axis and configured to cumulatively form a housing seat for a doctor blade. The fingers are pivotable independently from one another around the rotation axis. The doctor blade holder further comprises at least one elastic thrust member, for example comprising at least one spring or a system of springs, or comprising at least one chamber that can be inflated with a pressurized fluid. The thrust member is configured and arranged to generate a thrust on the fingers to make them pivot around said rotation axis. Each finger can also comprise a locking element, to rigidly lock the finger to the beam. In this way, a doctor blade holder can be obtained that can alternatively act as a flexible doctor blade holder and as a rigid doctor blade holder of the current art, combining in the same device the advantages of the two currently known types of doctor blade holder.
Elastic thrust member can be understood, in this context, as an element that generates a thrust on the fingers, but that is yielding, under the thrust of the same fingers. A thrust member of this type can comprise, for example, one or more air chambers filled with a pressurized fluid, for example a compressible fluid, such as air. In other embodiments, the thrust member can comprise a system of springs, for example tension springs, or preferably compression springs. In some embodiments the springs can be coil springs. However, it would also be possible to use other types of springs, such as Belleville springs.
With this configuration it is for example possible to carry out “profiling” of the doctor blade, i.e. to shape the doctor blade adapting it to the profile of the cylinder, whose cylindrical surface can deviate from a perfectly cylindrical geometry and have, for example, a camber. Using the thrust member comprising a chamber that can be inflated by means of pressurized fluid, through each finger the same pressure (isostatic pressure inside the inflatable chamber) is applied on various areas of the doctor blade; each finger can take a different angular position with respect to the others. In this way, the various areas of the doctor blade and more precisely of its edge deform following the profile of the cylinder applying substantially the same stress along the whole of the extension of the doctor blade. Once this arrangement has been reached, with the edge of the doctor blade that adapts to the profile of the cylinder, the various fingers can be locked in a substantially rigid manner with respect to the beam, thus converting the doctor blade holder from a flexible doctor blade holder to a rigid doctor blade holder. This latter, during operation of the cylinder will offer all the typical advantages of the rigid system, without being affected by the defects and by the drawbacks of these systems, mainly consisting of the impossibility of carrying out correct profiling of the doctor blade.
Using an elastic system comprising spring thrust members, a distribution of forces that may not be uniform is obtained, as the thrust can be a function of the deformation of the single springs, deformation that can vary from point to point. However, advantages are still obtained related to the fact that the doctor blade is thrust elastically and can yield, i.e. can move away from the surface of the cylinder with which it co-acts, overcoming the elastic thrust of the spring.
Through an appropriate choice of the characteristics of the spring, which those skilled in the art can make on the basis of their experience, thrust members with different behaviors can be obtained. For example, the springs can have a linear characteristic, in the deformation range within which they operate, so that the elastic thrust is linearly variable with the deformation. In some embodiments more complex arrangements of springs can be used, for example Belleville springs, coil springs, or combinations thereof, with different characteristics from spring to spring, and arrangements in series and/or in parallel, to obtain profiles of the force/deformation curve more suitable for the single different applications or operating conditions.
In practical embodiments, the deformation of the springs is actually very slight and consequently the variations of elastic force generated by the single springs are also minimal. In this way it is possible to maintain substantially the same elastic load for all the springs fitted on a single doctor blade holder.
When inflatable chambers are used, a pressure controller can be used to obtain similar effects.
In substance, a doctor blade holder of this type allows the doctor blade to be optimally shaped on the profile of the cylinder exerting constant pressure and causing a deformation that can vary locally from area to area, due to the flexibility of the inflatable chamber, or other elastic thrust member, and to the fact that each finger can pivot independently from the others. After reaching the correct shape of the doctor blade, without the need to apply excessive localized pressures as is instead necessary in rigid systems, the fingers can be locked on the beam so that the doctor blade holder as a whole will operate as a normal rigid doctor blade holder.
According to a further aspect, there is provided a doctor blade holder for a doctor blade adapted to co-act with a cylindrical surface of a rotating cylinder, for example a Yankee cylinder or a drying cylinder, comprising a plurality of fingers mounted on a beam, hinged around a rotation axis and configured to cumulatively form a housing seat for a doctor blade. The fingers are pivotable independently from one another around the rotation axis. Moreover, the doctor blade holder is provided with at least one elastic thrust member, for example comprising one or more springs, or comprising one or more chambers that can be inflated with a pressurized fluid; the thrust member is configured and arranged so as to generate a thrust on the fingers to make them pivot around the rotation axis toward the cylindrical surface of the rotating cylinder, with which the doctor blade co-acts. Advantageously, each finger can be mounted and removed independently from the others with respect to the beam.
In this way it is possible to replace each finger independently from the others, without removing a common hinge member and the whole pressure plate. Maintenance of the doctor blade holder is thus simpler and it is no longer necessary to have several spare assembled doctor blade holders for replacement in the case of breakage of one or more doctor blade holder fingers during operation.
According to yet another aspect, there is provided a doctor blade holder for a doctor blade adapted to co-act with a cylindrical surface of a rotating cylinder, comprising a beam extending longitudinally, substantially in a direction approximately parallel to the rotation axis of the cylinder with which the doctor blade co-acts, between two opposite ends and carrying a housing seat for the doctor blade. The beam can advantageously be coupled to the load-bearing structure by means of a system of linear guides, positioned at the two ends of the beam. The guides can be placed to define a direction of movement of the doctor blade mounted on the doctor blade holder toward and away from the cylinder. In other embodiments the beam can be coupled to the load-bearing structure in a fixed position.
There can also be provided actuators configured and arranged so as to move each end of the beam along the system of linear guides and in this way push the beam toward the cylindrical surface of the cylinder or roller with which the doctor blade mounted in the doctor blade holder co-acts.
While in the doctor blade holder of the current art the beam moves toward the cylinder by rotation, according to this embodiment the beam can move toward the cylinder by translation.
The greater rigidity offered by the linear guides reduces the flexural deformability of the beam and consequently the deflection that forms as a result of the stress applied by the cylindrical surface of the roller against the doctor blade mounted on the beam.
A doctor blade holder of the type described above can comprise a counter-blade, on which the fingers act. The counter-blade can be arranged between the fingers and the doctor blade, on the opposite side with respect to the cylindrical surface with which the doctor blade co-acts, to press on the doctor blade housed in its housing seat formed by the fingers of the doctor blade holder.
In some embodiments, a support element can be arranged between the doctor blade and the fingers that form the housing seat for the doctor blade.
When the doctor blade holder comprises a counter-blade housed or that can be housed, together with the doctor blade, in the housing seat formed by the fingers, advantageously a damper element can be arranged between each finger and the counter-blade, while the doctor blade rests directly on the counter-blade.
In a doctor blade holder of the type described above each finger can, for example, comprise a first portion, defining the housing seat for the doctor blade, and a second portion, co-acting with the thrust member. The rotation axis can advantageously be located between the first portion and the second portion.
The first portion and the second portion of each finger can be placed at an angle to one another, preferably at an angle of between 60° and 120°, more preferably between 80° and 100°, for example at 90°. In other embodiments, the first portion and the second portion of each finger can be coplanar, to form an angle of 180° between them.
To facilitate mounting of the fingers on the supporting beam, on a doctor blade holder as described above each finger can comprise a hinge pin, for example arranged in an intermediate position between a first portion of the finger and a second portion of the finger.
In other embodiments, the rotation axis can be arranged at a proximal end of each finger, which extends from the proximal end to a distal end, from which the doctor blade co-acting with the cylindrical surface of the rotating cylinder projects. In this case the hinge pin is positioned at the proximal end of the finger. The thrust member that generates the thrust of the doctor blade against the cylindrical surface of the rotating cylinder is in this case positioned between the rotation axis and the distal end of the fingers.
For each finger the beam can comprise an openable support, in which the hinge pin of the respective finger is rotatingly engaged. Each support can in this way be opened and closed independently from the others and each finger can be mounted on and removed from the beam without the need to act on the adjacent fingers, simply by opening the respective support to remove the hinge pin of a damaged finger, for example, and inserting the hinge pin of a new finger to replace the damaged one.
In the embodiments in which each finger is provided with a locking element to make the doctor blade holder rigid, the locking element can comprise, for each finger, a pair of screws co-acting with the beam and with the finger. In particular, a pair of screws, one configured to push the finger against the beam and the other to pull the finger away from the beam, can be provided. By clamping both screws the finger is rigidly locked in the desired position with respect to the beam.
For example, the locking elements can be arranged so as to co-act with the second portion of the respective finger, i.e., the one adjacent to the portion that contributes to defining the housing seat for the doctor blade.
In a doctor blade holder of the type disclosed herein, in one or other of the aforesaid embodiments, each end of the beam can be provided with an adjustable stop, which defines the working position of the doctor blade holder, and therefore of the doctor blade, with respect to the cylinder with which the doctor blade holder is associated. The stop can be adjusted by means of a servomotor, for example an electronically controlled stepper motor, so as to regulate or adjust the working position precisely. Two stops can be provided, one for each end of the beam. Each stop can be adjusted independently from the other.
In other embodiments, only a system of actuators can be provided, to push the beam toward the cylinder. In further embodiments, only a system of one or more servo-motors to move the beam toward the cylinder or a combination of thrust actuators and manually adjustable stops can be provided.
In some embodiments, each end of the beam can be coupled to a respective slide. Each slide can be movable along a corresponding system of straight guides. The beam can be coupled to the two opposite end slides movable with respect to said slides. For example, in some embodiments the beam can be provided with a reciprocating translation movement parallel to its longitudinal extension, and therefore in a direction substantially parallel to the edge of the doctor blade and to the rotation axis of the cylinder, with which the doctor blade co-acts. The reciprocating movement can be imparted by a suitable actuator, for example an electric motor, a hydraulic motor, a linear actuator such as a piston-cylinder actuator or the like. In substance, in this case, the beam is not directly coupled to the straight guides system, which allow it to move toward or away from the cylinder with which the doctor blade co-acts, but is supported at the ends by the two guides. In this way it is possible to provide the beam, and correspondingly the doctor blade mounted thereon, with a reciprocating movement with a suitable stroke, even a relatively limited one (for example a few centimeters) to prevent concentrated wear of the doctor blade and/or of the cylindrical surface of the cylinder with which the doctor blade co-acts.
For example, the ends of the beam can be coupled to the respective slides by means of sliding guides substantially parallel to the longitudinal extension of the beam.
Also disclosed herein is a system comprising a cylinder rotating around a rotation axis, for example a Yankee cylinder, a drying cylinder or the like, and a doctor blade holder as described above, co-acting with a cylindrical surface of the rotating cylinder. When in use, the system also comprises a doctor blade and optionally a counter-blade inserted in the seat for the doctor blade holder.
To facilitate mounting and removal, the doctor blade and the pressure counter-blade, when present, can in turn be mounted in a cartridge, which is inserted in the seat and removed from the seat housing the doctor blade and the counter-blade, with which the doctor blade holder is provided.
According to yet another aspect, there is provided a doctor blade holder for a doctor blade adapted to co-act with a cylindrical surface of a rotating cylinder, comprising a beam extending longitudinally between two opposite ends and carrying a seat for the doctor blade, wherein there are also provided in combination: thrust actuators to bring the doctor blade holder into contact with adjustable stops, which define a working position of the doctor blade with respect to the cylindrical surface of the rotating cylinder, and servo-actuators for adjusting the position of the adjustable stops. In some embodiments, there are provided two stops and two actuators, positioned at ends of the beam that supports the doctor blade holder.
The invention will be better understood by following the description and accompanying drawings, which show non-limiting practical embodiments of the invention. In particular, in the drawings:
The following detailed description of embodiments given by way of example refers to the accompanying drawings. The same reference numbers in different drawings identify identical or similar elements. Moreover, the drawings are not necessarily to scale. The following detailed description does not limit the invention. Rather, the scope of the invention is defined by the accompanying claims.
Reference in the description to “an embodiment” or “the embodiment” or “some embodiments” means that a particular characteristic, structure or element described in relation to an embodiment is included in at least one embodiment of the object described. Therefore, the phrase “in an embodiment” or “in the embodiment” or “in some embodiments” used in the description does not necessarily refer to the same embodiment or embodiments. Furthermore, the particular characteristics, structures or elements may be combined in any appropriate manner in one or more embodiments.
Hereunder, there will be described in particular a creping device comprising a doctor blade holder and a creping doctor blade, and a system consisting of a Yankee cylinder and a creping device. Nonetheless, it must be understood that the various features and embodiments described herein for the doctor blade holder can also be used in other applications, for example for a doctor blade holder of a scraper blade or a cleaning blade for a Yankee cylinder, and in general for doctor blade holders generically intended to support a doctor blade co-acting with a rotating cylinder or roller.
A first embodiment of a creping device comprising a doctor blade holder and related creping doctor blade in a system including a Yankee cylinder is illustrated in
A creping device, indicated as a whole with 3, co-acts with the Yankee cylinder 1. Besides the creping device 3, other doctor blade systems can co-act with the Yankee cylinder 1, for example a cleaning blade and/or a scraper blade, not shown in the drawings, each of which can be carried by a doctor blade holder having at least some of the features described with reference to the doctor blade holder of the creping device 3.
In fact, features described herein with reference to the creping device 3 can also be used in the production of the doctor blade holder for the scraper blade and/or in the production of the doctor blade holder of the cleaning blade.
The reference numeral 5 schematically indicates a portion of a generic stationary support structure, which can be part of the structure that also supports the Yankee cylinder 1.
The creping device 3 comprises a doctor blade holder 7, which extends approximately parallel to the rotation axis A-A, around which the Yankee cylinder 1 rotates. The doctor blade holder 7 is supported by a beam 9, which can be part of the doctor blade holder itself. The beam 9 can extend longitudinally approximately parallel to the rotation axis A-A of the Yankee cylinder 1. The beam 9 comprises two ends 9A, 9B that can be connected to the stationary support structure 5. In some embodiments, the beam can be connected to the stationary support structure 5 by means of a system of bearings that allow the beam to pivot around an axis substantially parallel to the longitudinal extension of the beam. Another and more advantageous type of connection between the stationary support structure 5 and the beam 9 will be described in detail hereunder.
In some embodiments the beam 9 is not coupled directly to the load-bearing structure 5, but rather at the ends 9A, 9B of the beam 9 there are associated slides 11A and 11B, which support the ends 9A, 9B of the beam 9 in a manner described below. The slides 11A, 11B can in turn be coupled in a movable manner, illustrated below, to the stationary support structure 5.
In the embodiment illustrated, each slide 11A, 11B is slidingly engaged with a system of preferably linear, for example straight, guides 13. In the embodiment illustrated, at each end 9A, 9B of the beam 9, and therefore at each slide 11A, 11B, there is associated a pair of preferably straight linear guides 13, fixed to the stationary support structure 5 and parallel to one another. Each slide 11A, 11B is slidingly engaged with the respective linear guides 13 by means of shoes 14.
In some embodiments, each slide 11A, 11B can be provided with further linear guides 15. These are visible in particular in
With this arrangement the beam 9 can move in a direction fA, substantially parallel to the rotation axis A-A of the Yankee cylinder 1, and in a direction fB at right angles to the direction fA and placed according to the extension of the linear guides 13. The position of the linear guides 13 is such that the movement according to the double arrow fB of the slides 11A, 11B allows the beam 9 to move toward and away from the cylindrical surface 1S of the Yankee cylinder 1 for the purposes that will be clarified below.
The movement according to the double arrow fA is a reciprocating movement that can be imparted by a motor, for example an electric motor, a hydraulic motor, a pneumatic motor, or any other type of actuator, for example also a piston-cylinder actuator. In the embodiment shown the movement according to the double arrow fA is imparted by an electric motor 19 (see in particular
With particular reference to the enlargement of
At each end 9A, 9B of the beam 9 there can be associated a respective actuator 25A, 25B, the purpose of which is to urge the beam 9 toward stops that define a working position, in which the creping doctor blade (described below), carried by the doctor blade holder 7, co-acts with the cylindrical surface 1S of the Yankee cylinder 1 and is pressed with its edge against said cylindrical surface. The actuators 25A, 25B can be linear actuators, for example hydraulic or pneumatic piston-cylinder actuators, mechanical jacks, linear electric motors or the like. In the embodiment illustrated, the actuators 25A, 25B are piston-cylinder actuators.
The piston-cylinder actuators 25A, 25B can be coupled on one side to the stationary support structure 5 and on the other, to the ends 9A, 9B of the beam 9 (see in particular the enlargement of
In some embodiments, the working position of the beam 9 can be defined by adjustable stops. For example, an adjustable stop can be provided for each end 9A, 9B of the beam 9. More in particular, the stops can co-act with the slides 11A, 11B.
The position of the stops 29 can be adjusted in a direction f29 (see
In advantageous embodiments, the stops 29 can be motorized. For example, in embodiments described herein, adjustment of the position of each stop 29 according to the direction f29 can be obtained by a servo-motor 31, for example an electronically controlled electric motor, which rotates a threaded bar 34 by means of a suitable reduction gear 33. The respective stop 29 can be coupled to the threaded bar 34 (
The position of each stop 29 can thus be finely adjusted by operating the respective actuator or servo-motor 31, which can be controlled by a programmable control unit, schematically indicated with 36 (see
With particular reference to
Each finger 35 can be mounted independently from the other fingers 35 on the doctor blade holder 7. For this purpose, for each finger 35 the doctor blade holder 7 can have a respective hinge support 39 (see in particular detail of
In some embodiments the support 39 is double for each finger 35, in the sense that the hinge pin 37 of the finger 35 projects from both sides of the finger 35 and engages in two half supports 39A, 39B on the two sides of the finger, jointly forming the hinge support 39.
The hinge support 39 of each finger 35 can be an openable support. In the embodiment illustrated, each half support 39A, 39B is formed by two portions, the one fixed to the beam 9 and the other removable. The configuration is illustrated in detail in
In advantageous embodiments, each finger 35 can be considered as consisting of two portions 35A and 35B that, in the embodiment of
Each finger 35 defines in the first portion 35A a compartment 41 in which a doctor blade can be inserted, in particular a creping doctor blade, co-acting with the cylindrical surface 1S of the Yankee cylinder 1. Reference 43B indicates the edge of the creping doctor blade 43, which is pressed against the cylindrical surface 1S of the Yankee cylinder 1 by means of the thrust generated by the piston-cylinder actuators 25A, 25B previously described or, depending on the case, by the action of an inflatable chamber, described below.
In the embodiment illustrated, the doctor blade 43 is mounted in a cartridge 45, which is extracted from the doctor blade holder 7 or inserted in the doctor blade holder 7 together with the doctor blade 43.
The compartments 41 defined by the fingers 35, aligned with one another in the direction parallel to the rotation axis A-A of the Yankee cylinder 1, cumulatively form the housing seat for the doctor blade 43.
In some embodiments, a counter-blade 47 is associated with the doctor blade 43. In the embodiment illustrated the counter-blade 47 can be housed, together with the cartridge 45, in the housing seat formed by the compartments 41 aligned with one another of the fingers 35. The counter-blade 47 can be arranged between the fingers 35 and the doctor blade 43. In this way, the action of the fingers 35 on the doctor blade 43 will be mediated by the interposed counter-blade 47.
The fingers 35 can be urged to pivot around the axis 37A of the respective hinge pins 37 by an actuator indicated as a whole with 51. The actuator 51 can comprise an inflatable chamber 53. A compressible fluid, such as air, can be used to inflate the inflatable chamber 53. However, it would also be possible to use another fluid to pressurize the inflatable chamber 53.
As can be seen in particular in
The inflatable chamber 53 can be one, along the whole of the longitudinal extension of the doctor blade holder 7. In this case, a single input point of the pressurized fluid for pressurizing of the inflatable chamber 53 can be provided. In other embodiments, the inflatable chamber 53 can be divided into several sections, for example three sections. Division can be obtained by producing a single tubular shaped inflatable chamber, along the longitudinal extension of which there are provided clamping elements, indicated schematically with 55 (
It would also be possible to design the actuator 51 with several inflatable chambers 53 aligned with one another, associated with distinct and separate feed lines for the pressurized fluid, instead of dividing a single tubular element forming a single inflatable chamber 53 into several areas by means of clamping elements 55, as illustrated by way of example in the embodiment shown in the accompanying drawing.
The inflatable chamber 53 can advantageously be provided with a plurality of pressurized fluid input points corresponding to the number of sections into which the inflatable chamber 53 is divided. If several aligned inflatable chambers 53 are provided instead of a single inflatable chamber 53, each of these will be equipped with a pressurized fluid input point to inflate it.
In the example illustrated three pressurized fluid input points are provided, indicated with 57A, 57B and 57C.
It is thus possible to feed fluid at different pressures into the various sections into which the inflatable chamber 53 is divided, or into the single aligned inflatable chambers 53. For example, it is possible to inflate the end sections through the inflation points 57A, 57C to a higher pressure than the inflation pressure of the intermediate area.
When it is inflated by the pressurized fluid, the inflatable chamber 53 of the actuator 51 generates a thrust according to the arrow f53 (
In some embodiments, each finger 35 can be provided with a support element 61. In the embodiment illustrated in the drawing, the support element 61 is formed by a small cylinder housed in a corresponding seat 63 provided near the distal end of the portion 35A of each finger 35.
The reference numeral 65 (
The components described above define a doctor blade holder 7 of flexible type, in which the doctor blade 43 is urged against the cylindrical surface 1S of the Yankee cylinder 1 in a flexible manner by the inflatable chamber 53. The pressure inside the inflatable chamber 53 causes a substantially uniform thrust to be exerted on each portion of the doctor blade 43 by each of the fingers 35, with the exception of the difference in pressure that can occur in the three sections into which the inflatable chamber 53 can be divided by the clamping elements 55.
Operation of the doctor blade holder 7 of the creping device 3 described above is as follows. By means of the actuators 31 the positions of the stops 29, if present, are adjusted. The beam 9 of the doctor blade holder 7 is pushed into the working position by the piston-cylinder actuators 25A, 25B. This movement is obtained by sliding the slides 11A, 11B along the preferably straight linear guides 13.
The contact pressure of the doctor blade 43 against the cylindrical surface 15 of the Yankee cylinder 1 is generated by the inflatable chamber 53. When the doctor blade holder 7 must be moved away from the cylindrical surface 1S of the Yankee cylinder 1, the piston-cylinder actuators 25A, 25B can be moved back and/or the inflatable chamber 53 can be deflated.
In some embodiments, the beam 9 can be fixed and the movement of the Yankee cylinder 1 toward and away from the cylindrical surface 1S can be obtained by acting exclusively on the inflatable chamber 53. However, this solution has some drawbacks. In particular, the doctor blade 43 can be spaced only at a slight distance from the cylindrical surface 1S of the Yankee cylinder 1.
Vice versa, the embodiment illustrated, in which the beam 9 is movable with respect to the stationary support structure 5 and therefore can be moved further away from the Yankee cylinder 1, ensures better operation of the doctor blade holder 7.
The coupling of the beam 9 to the stationary support structure 5 by means of the preferably straight linear guides 13 makes the beam 9 less flexible and therefore less subject to deformation under the thrust exerted by the cylindrical surface 1S of the Yankee cylinder 1 on the doctor blade 43.
Although in the embodiment illustrated the beam 9 is taken to the working position as a result of the piston-cylinder actuators 25A, 25B co-acting with the adjustable stops 29, in other embodiments there can be provided only a system to push the beam 9 toward the Yankee cylinder 1 for example with electronically controlled electric motors in place of the piston-cylinder actuators 25A, 25B, by means of which a controlled movement is carried out. Alternatively, the movement can be carried out using the intrinsic stops of the piston-cylinder actuators. In yet other embodiments, the working position of the beam 9 and therefore of the doctor blade holder 7 as a whole can be fixed and not adjustable. In this case fixed stops can be provided, for example, instead of the adjustable stops 29 and actuators, for example simple piston-cylinder actuators that push the beam 9 against the fixed stops.
When the doctor blade holder 7 is required to work as a doctor blade holder of rigid rather than flexible type, a locking element, selectively activatable according to operating needs, can be associated with each finger 35.
In some embodiments the locking element can be servo-assisted. For example, clamping jaws can be provided that act on each finger 35, for example on each portion 35B of each finger 35. However, this requires the actuators to be supplied, for example, through a pressurized fluid line or through with an electric line. This might not always be easy, in view of the high longitudinal extension of the doctor blade holder 7, extension that corresponds to the axial length of the Yankee cylinder 1.
In advantageous embodiments, the locking elements can be of manual type. In the embodiment illustrated, each finger 35 is provided with a locking element 67 that is manually operated. The locking elements 67 of each finger 35 are arranged to co-act with the portion 35B of the respective finger 35.
In the embodiment illustrated, each locking element 67 comprises a pair of screws 67A and 67B. The screw 67A can be a screw that thrusts against the beam 9 to generate on the respective finger 35 a force that tends to move the portion 35B of the finger 35 away from the beam 9. Vice versa, the screw 67B can for example be a stud, with which a nut 67C co-acts, and which passes through a slot 35X formed in the respective finger 35. By tightening the nut 67C a force is exerted on the finger 35, which tends to pivot the finger around the rotation axis 37A, to move the portion 35B of the finger 35 toward the beam 9. Acting on the two screw elements 67A, 67B the respective finger 35 is rigidly locked to the beam 9. In this way the doctor blade holder 7 can be converted from a flexible doctor blade holder to a rigid doctor blade holder.
With this particular arrangement it is possible to adapt the doctor blade 43 to the profile of the Yankee cylinder 1, which may not be perfectly cylindrical, applying a substantially uniform thrust on each finger 35 by means of the inflatable chamber 53 when the doctor blade holder is in the flexible arrangement. This thrust causes a flexural deformation of the doctor blade 43 which rests with its edge 43B on the cylindrical surface 1S of the Yankee cylinder 1, adapting to any camber of said cylindrical surface 1S.
Once the doctor blade has been pressed uniformly against the cylindrical surface 1S of the Yankee cylinder 1 under the thrust of the inflatable chamber 53 and of the fingers 35 (operation known as profiling), it is possible to lock the fingers 35 making them rigidly integral with the beam 9 and making the doctor blade holder 7 operate as a rigid doctor blade holder. The profiling operation can take place while the Yankee cylinder 1 is operating, for a given operating time, during which the cylinder can, for example, reach a uniform working temperature and therefore a thermal deformation of the Yankee cylinder 1.
In the embodiment illustrated in
The inflatable chamber 53 of the actuator 51 is preferably under the portion 35B of the fingers 35, between the portions 35B and the beam 9. The locking elements 67, also in this case formed by way of example of two screws 67A, 67B, can co-act with the distal portion (i.e. with end farthest from the hinge pin 37) of the respective portions 35B of each finger 35.
The embodiment of
While in the embodiments described above the doctor blade 43 is pushed by a thrust member 51 with an inflatable chamber 53, in other embodiments the creping doctor blade can be elastically thrust by a different thrust member or actuator, for example a system of springs.
In the embodiment of
With this arrangement each finger 35 can be associated with a respective elastic element, such as the spring 54, to be pushed toward the Yankee cylinder 1 (not shown in
While
The doctor blade holder 7 of
The locking element of each finger 35 can be mounted staggered with respect to the corresponding elastic actuator, i.e. to the spring 54 and related housing. For this reason, the locking element is represented in the section of
In the embodiment of
The rigid locking element 67 functions in the following way, to lock the respective finger 35. The tie rod 76 is secured to the finger 35 and screwed into the threaded hole 70 of the bushing 68. For this purpose the bushing, once housed in the hole 74, can be rotated by means of a tool that acts on a square head 68.1 of the bushing (see
In the present context, the term “spring” can also be understood, for example, as a solid body made of an elastically yielding material, such as rubber, synthetic rubber or natural rubber, or another elastically yielding material, which in substance forms an accumulator of elastic potential energy due to its deformation. Therefore, the term “spring” also generally comprises a body made with a material that, deforming due to an external force, accumulates elastic potential energy.
The above description provided by way of example relates to advantageous embodiments of the invention, which is defined in the appended claims.
Further aspects of the innovations described herein are defined in the following clauses:
1. A scraping system for a cylinder (1), comprising:
2. System according to clause 1, wherein the linear guides (13) comprise a pair of linear guides (13) parallel to each other at each end (9A, 9B) of the beam (9)
3. System according to clause 1 or 2, wherein the sliding guides (15) are adapted to allow a translation of the beam (9) with respect to the slide (11A, 11B) and to prevent a rotation of the beam (9).
4. System according to clause 3, wherein each end (9A, 9B) of the beam (9) is coupled to the respective slide (11A, 11B) by means of a pair of said sliding guides (15).
5. System according to one or more of the preceding clauses, comprising actuators (25A, 25B), configured and arranged to move the beam (9) along the linear guides (13).
6. System according to clause 5, comprising two actuators (25A, 25B), each associated with a respective end (9A, 9B) of the beam (9).
7. System according to one or more of the preceding clauses comprising, at each end (9A, 9B) of the beam (9), an adjustable stop (29), which defines an operating position of the doctor blade holder (7).
8. System according to clause 7, further comprising, for each adjustable stop (29), an electronically controlled electric servo-motor (31) adapted to adjust the position of each adjustable stop (29).
9. System according to clause 8, when dependent on clause 5, wherein the slides (11A, 11B) are urged into a working position by said actuators (25A; 25B), which are adapted to thrust the slides (11A, 11B) in translation along the guides (13) against said adjustable stops (29).
10. System according to one or more of the preceding clauses, comprising:
11. System according to clause 10, comprising a counter-blade (47), on which said fingers (35) act, the counter-blade (47) being arranged between the fingers (35) and the doctor blade (43), to press on the doctor blade (43) housed in the housing seat (41) for the doctor blade.
12. System according to clause 10 or 11, wherein each finger (35) comprises a hinge pin (37) and wherein for each finger (35) the beam (9) comprises an openable support (39), in which the hinge pin (37) of the respective finger (35) is rotatingly engaged.
13. System according to clause 10, 11 or 12, wherein each finger (35) comprises a locking element (67), to rigidly lock the finger (35) with respect to the beam (9).
14. An assembly comprising a cylinder (1) rotating around a rotation axis (A-A) and a system according to one or more of the preceding clauses, co-acting with a cylindrical surface (1S) of the rotating cylinder (1).
15. Assembly according to clause 14, comprising a doctor blade (43) inserted in the housing seat (41) of the doctor blade holder and having an edge (43B) co-acting with pressure against the cylindrical surface (1S) of the rotating cylinder (1).
16. Assembly according to clause 14 or 15, comprising a cartridge (45) for containing the doctor blade (43), housed in the housing seat (41) for the doctor blade.
17. A scraping system comprising a doctor blade holder (7) for a doctor blade (43), adapted to co-act with a cylindrical surface (1S) of a rotating cylinder (1), having a beam (9) extending longitudinally, having two opposite ends (9A, 9B) and carrying a housing seat (41) for the doctor blade (43); and further comprising: linear translation guides (13), straight and at right angles to the longitudinal extension of the beam (9), placed at the two ends (9A, 9B) of the beam (9), and to which the beam (9) is coupled, said linear guides being adapted to allow a translation movement of the beam (9) toward and away from the cylindrical surface (1S) of the cylinder (1) with which the doctor blade (43) co-acts; wherein the ends (11A, 11B) of the beam (9) are coupled to the respective slides (11A, 11B) by means of sliding guides (15) parallel to the longitudinal extension of the beam (9) and at right angles to the linear guides (13); and wherein a drive element (19) is provided to impart a reciprocating movement of the beam (9) with respect to the slides, in a direction substantially parallel to the longitudinal extension of the beam.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017000047275 | May 2017 | IT | national |
| 102017000047279 | May 2017 | IT | national |
