The invention is directed to a device, system and method for cooling and calibrating sheet material. In particular, the invention is directed to a multi-nip takeoff device which has a combination of fixed and movable rollers to properly cool and calibrate the material.
The invention relates to a method for cooling flat plastic products, in which plasticized plastic compound is fed to a calender via a slot nozzle by means of an extruder and is rolled and calibrated to the desired shape in this calender between at least two smoothing rolls, after which the film or sheet produced in this way is fed to a chill section comprising a plurality of adjustable rolls and passes through this section until it is sufficiently cool and dimensionally stable, at least both the gap width between the rolls and the speed of the rolls being controllable by open- and/or closed-loop control.
Calenders for calibrating and cooling a plastic film or plastic sheet comprising at least two chill or calibrating rolls, a chill section being arranged downstream of the rolls are known in the art. For example EP 1600277 discloses a calender with a downstream chill section which has pairs of rolls arranged one behind the other.
In chill sections of this kind, the position of the rolls can be adjusted, thereby allowing the cooling capacity to be influenced. However, it has been found that, as the rolls are adjusted, the film passing through partially loses contact with the roll, thereby giving rise to differences in the cooling behavior of the film.
U.S. Pat. No. 8,262,966 discloses a method for cooling flat plastic products, in which plasticized plastic compound is fed to a calender via a slot nozzle by means of an extruder and is rolled and calibrated to the desired shape in this calender between at least two smoothing rolls, after which the film or sheet produced in this way is fed to a chill section comprising a plurality of adjustable rolls and passes through this section until it is sufficiently cool and dimensionally stable. Both the gap width between the rolls and the speed of the rolls are controllable by open- and/or closed-loop control. The degree of wrap of the flat plastic product around the respective roll is varied by adjusting the rolls in the chill section into a mutually offset arrangement, hence increasing or minimizing the cooling capacity. The center axis lines of the plurality of rolls of the chill section are held parallel to one another, allowing constant spacing to be maintained between the center axis lines of each two adjacent mating rolls of the plurality of rolls of the chill section. The center axis lines of said each two adjacent mating rolls define a geometric plane, with each plane being rotatable about one of the center axis lines during said adjustment operation of the rolls, thereby varying an angle between adjacent geometric planes. The rolls are in a bellows type configuration, where the planes are folds capable of unfolding relative to each other while pulled open but being connected at respective edges. This type of method and device is complicated and does not provide the ability to simply and accurately control the gaps between the rolls.
It would be beneficial to provide a takeoff feature for a calender which effectively cools and calibrates the material and which allows adjustment of the rolls in a controlled and simple manner.
It is an object of the invention to provide a multi-nip takeoff device, system and method that is simple in construction and offers enhanced operational features.
It is an object to provide a multi-nip takeoff device in which one or more stationary rolls are stationary and one or more movable rolls are movable relative to the stationary rolls. The movable rolls move to create the required gap between the stationary rolls and the movable rolls. The movable rolls are proximate to or adjacent to the stationary rolls.
It is an object to provide a multi-nip takeoff device in which the rolls are driven to provide both nip pressure and gap control. The drivers being located in such a way as to provide stiffness and precise position for final gap.
It is an object to provide a device and process of calibrating the multi-nip takeoff device which includes retracing the movable rolls such that the tops of the movable rolls are moved in line with a series of idler rolls that will facilitate an operator in threading up the machine with a starter sheet by providing basically a level surface on which to push the starter sheet through the machine.
It is an object to provide a device and process of calibrating the multi-nip takeoff device wherein when the movable rolls are in a retracted position, the movable roll support frame sits on a permanently mounted homing or zeroing fixture for each roll, thereby allowing the system to orient itself at power up without going through an elaborate homing sequence each time.
An embodiment is directed to a multi-nip takeoff and cooling section having a first smoothing and a second smoothing roll. A position, calibration and cooling roll is positioned proximate to the second smoothing roll. The position, calibration and cooling roll is movable relative to the second smoothing roll. A first fixed calibration and cooling roll is positioned proximate the position, calibration and cooling roll. The first fixed calibration and cooling roll is in a fixed position relative to the second smoothing roll. A first movable calibration and cooling roll is positioned proximate the first fixed calibration and cooling roll. The first movable calibration and cooling roll is movable relative to the first fixed calibration and cooling roll. A second fixed calibration and cooling roll is positioned proximate the first movable calibration and cooling roll. The second fixed calibration and cooling roll is in a fixed position relative to the second smoothing roll.
An embodiment is directed to a multi-nip takeoff and cooling section having a first smoothing and a second smoothing roll. A position, calibration and cooling roll is positioned proximate to the second smoothing roll. The position, calibration and cooling roll is movable relative to the second smoothing roll. A first fixed calibration and cooling roll is positioned proximate the position, calibration and cooling roll. The first fixed calibration and cooling roll is in a fixed position relative to the second smoothing roll. A first movable calibration and cooling roll is positioned proximate the first fixed calibration and cooling roll The first movable calibration and cooling roll is movable relative to the first fixed calibration and cooling roll. Actuators cooperate with the position, calibration and cooling roll and the first movable cooling roll to provide both nip pressure and gap control between the second smoothing roll and the position, calibration and cooling roll, between the position, calibration and cooling roll and the first fixed calibration and cooling roll, and between the first fixed calibration and cooling roll and the first movable calibration.
An embodiment is directed to a method for multi-nipping and cooling plastic sheet material, the method comprising: running the plastic sheet material through polishing rolls; running the plastic sheet material through calibration and cooling rolls; and adjustably nipping on each pair of respective calibration and cooling rolls, allowing for a gradual change to the thickness of sheet material until sheet material reaches a final calibration and cooling roll. The initial nipping load of the polishing rolls is reduced, allowing the size of the polishing rolls and the power needed to drive them to be reduced due to the multi-nipping technology.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. In the drawings, the relative sizes of regions or features may be exaggerated for clarity. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The description of illustrative embodiments according to principles of the present invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments of the invention disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated as such. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Moreover, the features and benefits of the invention are illustrated by reference to the preferred embodiments. Accordingly, the invention expressly should not be limited to such preferred embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features; the scope of the invention being defined by the claims appended hereto.
An illustrative multi-nip takeoff and cooling section 10 is shown diagrammatically in the illustrative embodiments of
In the illustrative embodiments shown, the calendering device 12 has two polish or smoothing primary rolls 16, 18. In these embodiment, the smoothing roll 16 has a smaller diameter than the smoothing roll 18. However, the smoothing rolls 16, 18 can be either a combination of a larger roll and a smaller roll or two rolls of equal size, depending on the application.
The longitudinal axis of roll 16 is positioned at a 45 degree angle relative to the longitudinal axis of roll 18 and all fixed rolls 24, 28. However, roll 16 can be located in a position that is horizontal, or at any angle from 0 degree to 90 degrees, with respect to roll 18. The orientation changes can be accomplished by changing mounting hardware or other known methods of changing the orientation can be used.
The smoothing rolls 16, 18 function as cooling rolls and function as the primary or major nipping and polishing rolls. In the embodiments shown, approximately 80% to 90% of final thickness of the web of material 30 is formed by the movement and spacing of the smoothing rolls 16, 18.
Roll 20 functions as a position, calibration and cooling roll. Roll 20 is positioned proximate to or adjacent to smoothing roll 18. Roll 20 has a diameter which is smaller than the diameter of roll 18.
Rolls, 22, 24, 26, 28 have the same diameter as roll 20. These rolls perform 22, 24, 26, 28 both calibration (small nipping as further calibration of web thickness and surface polish) and cooling (with equal cooling for upper and lower surface of web on each pair rolls).
The longitudinal axis of roll 16, as shown in the illustrative embodiment of
In various illustrative embodiments, the nip roll 16 may have a skewing device which can compensate for some deflection of roll 16 at higher nipping force of thin gauge processing. With this skewing device the roll 16 can be made smaller than roll 18 to save cost. The manipulation and movement of the nip roller 16 is also made easier, allowing for the space or nipping gap 32 to be precisely established and maintained between the two primary rolls 16 and 18.
In the illustrative embodiment shown in
Servo controlled electric, or hydraulic, lift actuators cooperate with the movable or adjustable rolls 16, 20, 24, 28 to provide both nip pressure and gap control between the respective adjustable rolls 16, 20, 24, 28 and the respective fixed rolls 18, 22, 26. Coordinated control of these lift actuators provides the capability to set the gap between each roll pair, independently. In the embodiments shown in
Mechanical stops (not shown) may be provided to properly datum (or zero) position the adjustable rolls 20, 24 such that the centers of adjustable rolls 20, 24 are located on the same horizontal line as the center of fixed rolls 18, 22, 26, as shown in
In the embodiment shown in
In the embodiment shown in
In various embodiments, the rolls 16, 18, 20, 22, 24, 26, 28, or any combination thereof, may be enclosed, so that no operator can come in contact with the rolls during normal operating mode, including, but not limited to, startup and shutdown.
As shown in
In other embodiments, a startup mode could also be provided that would run the rolls in reverse at a slow rate to help thread the cooling section 10 and the calendaring device 12. Alternatively, one or more of the cooling rolls may be closed as starter sheet passes over them to further assist with threading material back through the cooling section 10 and the calendaring device 12.
In the retracted position shown in
Adjustable nipping on each pair of respective adjacent rolls 20, 22, 24, 26, 28 may be provided. This allows for a gradual change to the thickness of web of material 30 until it reaches the final nipping roller 28, thereby reducing the initial nipping load of the first two polishing or smoothing rolls 16, 18. The reduction in load allows the size of first two polish rolls 16, 18 and the power needed to drive them to be reduced, resulting in energy and cost savings.
The velocity or speed of the rotation of each respective roll 20, 22, 24, 26, 28 will be consistent with other rolls or will vary between rolls. If the speed of the material is varied, the roll speed must be increased in the downstream rolls to keep a tension on the web of the material (for example, roll 28 has a roll speed greater than the roll speed of roll 20). If the volume flow rate is to be kept constant, the volume flow rate is used as a factor to determine the different speeds of each pair of rolls. In addition, if each pair of small rolls is to perform a nipping function, the volume flow rate must be controlled. In such applications, the roll speed must be calculated based on a percentage of nipping versus percentage of the volume flow rate accordingly.
In many applications, when it is not necessary for thin gauge web processing, the number of calibration and cooling rolls with close nipping can be reduced. For example, the configuration shown in
In the embodiment shown in
In the embodiment shown in
Referring to
Referring to
Referring to
Referring to
Referring to
D1=R1+R2+t (1)
And the center distance “D2” between the adjustable positioning, calibration and cooling roll 20 and the fixed calibration and cooling roll 22 is,
D2=2×R2+t (2)
There is a fixed zero position for the adjustable positioning, calibration and cooling roll 20 where the center of the adjustable positioning, calibration and cooling roll 20 is located in the same horizontal plane as the center of the fixed calibration and cooling roll 22. In this position, a final mechanical safety gap “δ” between the fixed primary roll and fixed calibration roll is provided. In the embodiment shown in
δ=0.002″
The fixed distance “XR1” that determines the zero position of movable roll is:
XR1=R1+R2+δ (3)
With the same definition, the fixed distance “XR2” is:
XR2=2×R2+δ (4)
The distance “LR” between the primary polish roll 18 and the fixed calibration and cooling roll 22 is:
LR=XR1+XR2 (5)
The frame on which the primary polish roll 18, the adjustable positioning, calibration and cooling roll 20 and the fixed calibration and cooling roll 22 are positioned is configure such that the “XR1”, “XR2”, and “LR” will be made precisely from machining and assembly. Consequently, the stroke “L” of actuator of the adjustable positioning, calibration and cooling roll 20 is the control variable that can be calculated as follows:
L=√{square root over (D12+XR12−2×D1×XR1×cos(θ1))} (6)
The “L” position is varied with the angle θ1, and is determined by the equal gap “t” on each pair of rolls. Consequently, the guiding path will be given by both parameter of “L” and “β”. Since the angle “β” is different on each position of “L”, angle “β” needs to be calculated through angle “α” as the following:
And, then:
β=90°−θ1−α (9)
Based on the above, the location of the top end of each actuator for the adjustable positioning, calibration and cooling roll 20 is determined.
Referring to
D=2×R2+t (10)
The fixed distance “XR” and “LR” are,
XR=2×R2+δ (11)
LR=2×XR (12)
The stroke is truly vertical and the stroke “Y” is:
Y=√{square root over (D2−XR2)} (13)
And the variable angle “θ” is give,
As the angles “θ1”, “θ2”, and “θ” are small, the force required to be supplied from the actuator is significantly less than the nipping force. As an examples, with each of the angles “θ1”, “θ2”, and “θ” less than 6 degrees for the thin gauge web of 0.05″, the force required to be supplied from the actuator is less than 10% of the nipping force The force “R” of actuator, as shown in
As the nipping force “F1” is given by the material processing, for example about 800 to 1000 lbf/in for thin gauge PP processing and all the angles in the equation (15) are calculated as described above, the actuator force “R” is known.
The forces from the primary polish roll 18 and the fixed calibration and cooling roll 22 are different since the angle “θ1” and “θ2” are different. With force “F1” is determined, force “F2” is given by:
For the roll configuration shown in
R=2×F×sin(θ) (17)
Where, the “F” is equal to “F2” in equation (16) since an equal nipping force is required in each pair of calibration rolls.
Referring to
An alternate embodiment is shown in
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims, and not limited to the foregoing description or embodiments.
Number | Date | Country | |
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62271420 | Dec 2015 | US | |
62271705 | Dec 2015 | US |