PRINTING WEB SYSTEM

Abstract

A web system, such as a printing web system, having reduced power consumption is disclosed. Power consumption is reduced by joining the unwind and rewind shafts of the web system together through a continuously variable transmission (CVT). The CVT allows the unwind and rewind rolls to provide torque to each other as well, allowing fewer drive motors and/or drive motors of smaller size to be used in the web system.

Description

BACKGROUND

The present disclosure relates to web systems used in printing or coating systems such as a printing press. In particular, the web systems of the present disclosure have reduced power consumption, etc., due to the use of a continuously variable transmission.

Printing web systems are used to produce high-quality reproductions, in both black/white and in color, on paper webs traveling through the system at high speeds. Speeds can be as high as 2,000 feet per minute. The paper web is under tension as it travels through the system. This tension is essential in, for example, maintaining registration of color images as each color is printed onto the paper web.

In a conventional web system, a web (paper or some other suitable substrate) travels from an unwind roll to a rewind roll. At the beginning of the process, the unwind roll contains the entire web and the rewind roll is empty. The web is fed through a first tensioning system and then enters a processing system. Inside the processing system, the web experiences changes in tension, for example, (i) when it moves past various parts, for example, the print cylinder, feed rollers, angle bars, folders, etc.; (ii) as its surface properties change due to, for example, placement of ink on portions of the surface; and (iii) changing properties in the paper as it gets wet and then is dried. After exiting the processing system, the web is fed through a second tensioning system and then onto the rewind roll. At the end of this process, the unwind roll is empty and the web has been collected on the rewind roll.

The tensioning systems are used to ensure proper unwind and uptake on the unwind and rewind rolls, respectively, as well as to prevent the web from exceeding its tensile strength and breaking, which can also cause problems such as damage to fragile print blankets and lengthy downtime in restringing the web. The difference in tension between the unwind roll and rewind roll can be used to pull the web through the processing system. Alternatively, another motor can be included in the processing system to maintain the tension in the web system.

The amount of tension present in the unwind roll can be determined by the formula: Tension=0.5*F/(w×h), where F is the downward force applied to the web, w is the width of the web, and h is the thickness of the web.

In order to move the web through the web system, torque must be provided to both the unwind roll and rewind roll. Generally speaking, for each roll a dancing roll in the tensioning system provides a force and the web has a velocity. The surface velocities of the unwind roll and rewind roll are generally about equal to prevent the web from breaking. However, because the web is continually being unwound from the unwind roll and wound onto the rewind roll, the amount of torque which must be provided to each roll to provide the tension changes continually.

The amount of power needed to provide the torque can be calculated using the formula P=F·v, where P is the power, F is the force and v is the surface speed. It should be noted that because the radius of the roll changes, the angular velocity of the roll also changes according to the relation v=r dθ/dt, where r is the radius of the roll and dθ/dt is the radial velocity (measured in radians/second). With a web system, the tension is set to 0.5-1.0 lbf per inch of width per milli-inch of paper thickness. For paper that is 12 milli-inches thick and 10 inches wide, the required force is 120 lbf, or about 534 newtons (N). At a web velocity of 2 meters/sec, the required power is 1068 Nm/sec, or 1.068 kW.

A motor is attached to each roll (unwind and rewind) to provide this power. Such motors can be expensive. In addition, such motors waste energy because the high power levels they provide are only required when the weight of the roll is high.

It would be desirable to provide a web system that has reduced power consumption and/or reduced fixed initial installation costs.

BRIEF DESCRIPTION

The present disclosure is directed, in various embodiments, to web systems that have reduced power consumption. The web systems comprise a continuously variable transmission.

In embodiments, a web system that provides tension with reduced power consumption is disclosed. The web system comprises:an unwind shaft, a rewind shaft, and a processing system; a drive path running from the unwind shaft through the processing system to the rewind shaft; a drive motor located along the drive path; and a continuously variable transmission comprising a first shaft and a second shaft, wherein the first shaft is connected to the unwind shaft and the second shaft is connected to the rewind shaft.

The continuously variable transmission can be a variable diameter pulley system; a toroidal transmission system; a hydrostatic transmission system, or any other CVT system.

The drive motor can be located at the unwind shaft, at the rewind shaft, or along the drive path of an associated web. The drive motor can be a drive nip.

The web system may further comprise a web differential velocity measurement system. The web differential velocity measurement system may comprise a dancing roll and a position sensor. Alternatively, the web differential velocity measurement system may comprise a stationary roll and a tension sensor. The processing system of the web system may comprise a printing press.

In other embodiments, a method of reducing the power consumption of a web system is also disclosed, the method comprising: providing a web system comprising an unwind shaft, a rewind shaft, and a processing system; and connecting the unwind shaft and the rewind shaft to a first shaft and a second shaft of a continuously variable transmission.

These and other non-limiting characteristics of the exemplary embodiments of the present disclosure are more particularly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which are presented for the purpose of illustrating the exemplary embodiments disclosed herein and not for the purpose of limiting the same.

FIG. 1 is a diagram of a conventional web system.

FIG. 2 is a diagram of an exemplary embodiment of the web system of the present disclosure.

FIG. 3 is another diagram of an exemplary embodiment of the web system of the present disclosure.

FIG. 4 is a diagram of a belt suitable for use in a variable diameter pulley system that serves as the continuously variable transmission.

FIG. 5 is a first diagram of one configuration of the variable diameter pulley system.

FIG. 6 is a second diagram of another configuration of the variable diameter pulley system.

FIG. 7 is a first diagram of one configuration of a toroidal transmission system that serves as the continuously variable transmission.

FIG. 8 is a second diagram of another configuration of the toroidal transmission system.

FIG. 9 is a diagram of a hydrostatic transmission system that serves as the continuously variable transmission.

FIG. 10 is another diagram of an exemplary embodiment of the web system of the present disclosure.

DETAILED DESCRIPTION

A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying figures. These figures are merely schematic representations based on convenience and the ease of demonstrating the present development and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.

FIG. 1 is a diagram showing a conventional web system 10. An unwind roll 20 provides the web 30 (paper or some other suitable substrate) to the rewind roll 40. The web is fed through a first tensioning system 50 and then enters a processing system 60. Inside the processing system, the web experiences changes in tension. After exiting the processing system 60, the web is fed through a second tensioning system 70 and then onto the rewind roll 40. At the end of this process, the unwind roll 20 is empty and the web 30 has been collected on the rewind roll 40.

In order to move the web through the web system, torque must be provided to both the unwind roll 20 and rewind roll 40. At the unwind roll 20 the dancing roll 55 provides a force F1 and the web has a velocity V1. Similarly, at the rewind roll 40 the dancing roll 75 provides a force F2 and the web has a velocity V2. Again, V1 and V2 are generally equal to prevent the web from breaking.

The amount of power needed to provide the torque can be calculated using the formula P=F·v, where P is the power, F is the force (F1 or F2) and v is the surface speed (V1 or V2). The relation between the surface speed of the web and the angular velocity of the roll is given by v=r dθ/dt, where r is the radius of the roll and dθ/dt is the radial velocity (measured in radians/second). It should be noted that because the radius of the roll changes, the angular velocity of the roll will also change.

The web systems of the present disclosure have reduced power consumption compared to the web system of FIG. 1. They achieve this reduced power consumption by the use of a continuously variable transmission (CVT) which is connected to both the unwind roll and the rewind roll of the web system. This connection allows tension to be applied to the web without the use of motors.

FIG. 2 is a diagram showing the setup of a web system 100 of the present disclosure. Similar to FIG. 1, an unwind roll 110 provides a web 120, which moves along a drive path 130 through a processing system 140 and then onto a rewind roll 150. A web differential velocity measurement system 160 measures the difference in the surface velocities of the unwind roll and rewind roll. The unwind roll 110 is mounted on an unwind shaft 170 and the rewind roll 150 is mounted on a rewind shaft 180. The unwind shaft 170 and rewind shaft 180 are connected to each other through a continuously variable transmission 190. As the diameters of the unwind roll 110 and rewind roll 150 change, the web differential velocity measurement system produces a signal indicative of the difference in velocities. The signal is used in a servo control which adjusts the transmission ratio of the continuously variable transmission 190 to allocate the torques and balance the angular velocities of the two rolls. This allocation of torque keeps the web 120 under tension, such that power is generally needed only to make up for friction losses. Put another way, the unwind shaft 170 and rewind shaft 180 also provide torque to each other, so that torque does not need to be provided by a drive motor or the drive motor can be of a smaller size.

FIG. 3 is a diagram showing the web system 100 without the unwind roll and rewind roll. A drive path 130 is defined by the unwind shaft 170, rewind shaft 180, and processing system 140. It should be kept in mind that the drive path 130 will move as the diameters of the unwind roll and rewind roll change.

The processing system 140 may be any system that operates on the web. For example, the processing system can be a printing press or a simple rewind operation.

Exemplary CVT systems include a variable diameter pulley system; a toroidal transmission system; and a hydrostatic transmission system.

A variable diameter pulley (VDP) system is illustrated in FIGS. 4-6. A variable diameter pulley system comprises a first shaft 210 and a second shaft 220. On each shaft are mounted two cones 230, 235 with apexes pointing to each other to form a pulley. A belt 240, typically a V-shaped belt as shown in FIG. 4, rides in the groove formed by the two cones. The distance between the center of the pulley to where the belt makes contact in the groove is known as the pitch radius. The distance between the two cones can be changed. When the cones are far apart, the belt rides lower and the pitch radius decreases. When the cones are close together, the belt rides higher and the pitch radius increases. The belt 240 links the two shafts 210, 220 together by transferring power between them. Hydraulic pressure, centrifugal force or spring tension can be used to create the force necessary to change the distance between cones. When paired together, the ratio of the pitch radius on the first shaft to the pitch radius on the second shaft determines the gear ratio. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios—from low to high and everything in between. FIG. 5 illustrates a “high” gear and FIG. 6 illustrates a “low” gear.

A toroidal transmission system is illustrated in FIGS. 7 and 8. Again, a first shaft 310 and second shaft 320 are present. Attached to each shaft is a cone 330, 340 having a hyperboloid shape, arranged so the apexes face each other. Rollers 350 are placed parallel to and touching the surfaces of the two cones. The rollers act like the belt of the VDP system, linking the two shafts and transferring power between them. As the rollers rotate in the indicated direction 360, the first shaft 310 rotates in one direction 370 and the second shaft 320 rotates in the other direction 380. Tilting the rollers 350 changes the location at which they intersect the two cones 330, 340, creating an infinite number of gear ratios. FIG. 7 illustrates a “high” gear and FIG. 8 illustrates a “low” gear.

A hydrostatic transmission system is illustrated in FIG. 9. Again, a first shaft 410 and second shaft 420 are present. The first shaft 410 is connected to a hydrostatic variable-displacement pump 430 and the second shaft 420 is connected to a hydrostatic motor 440. The rotational motion of the first shaft 410 is converted by the hydrostatic pump 430 into fluid flow (indicated by arrow 450). The fluid travels to the hydrostatic motor 440 of the second shaft 420, which converts the fluid flow back into rotational motion. In this way, the traveling fluid acts as a power transfer linkage. The fluid is then returned to the hydrostatic pump (indicated by arrow 460).

As described above, the continuously variable transmission comprises a first shaft and a second shaft. The first and second shafts are connected to the unwind shaft and the rewind shaft, respectively, or vice versa.

A drive motor is still needed to impart a velocity to the web. The drive motor can be mounted on the unwind shaft, the rewind shaft, or along the drive path. For example, drive motor 195 is a drive nip formed by the use of two driving rolls, such as that shown in FIG. 2. In particular, the drive motor may be of a smaller size than otherwise needed, because the continuously variable transmission provides tension in the web, not just the drive motor itself.

In FIG. 3, the web differential velocity measurement system 160 is a position measurement system. The position measurement system measures the integral of the difference in unwind and rewind velocity. The position measurement system comprises a dancing roll 162 and a position sensor 164. The dancing roll 162 can move and applies a force F3 to provide the tension. The position sensor 164 detects the position of the dancing roil and provides a position signal. The position signal serves as input to, for example, a servo controller 166, which provides an output signal to an actuator 168 that adjusts the continuously variable transmission 190 to keep the dancing roll 162 within a predetermined range. Because the actuation speed is low, the actuator does not need a lot of power. For example, the actuator 168 could be a lead screw driven by a stepper motor or DC motor. In FIG. 3, the tension measurement system 160 is shown as being located between the rewind shaft 180 and the processing system 140. However, the tension measurement system could alternatively be located between the unwind shaft 170 and the processing system 140. In contrast to the system shown in FIG. 1, only one tension measurement system is necessary because the unwind shaft 170 and rewind shaft 180 are connected through the continuously variable transmission 190.

In FIG. 10, another embodiment of the web differential velocity measurement system 160 is shown. Instead of a dancing roll that can move, a stationary roll 163 is present. A tension sensor 165 is attached to the stationary roll 163 and measures the amount of tension placed on the stationary roll, producing a tension signal. The tension signal is proportional to the integral of the difference in unwind and rewind velocities. The tension signal is provided to an actuator 168 that adjusts the continuously variable transmission 190 to keep the tension on the stationary roll 163 within a predetermined range.

As a result, the web system of the present disclosure may have fewer motors than are present in conventional systems. In addition, the motors that are present may be of a smaller size. This allows for reduced fixed initial installation costs and/or reduced power consumption during operation.

While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

Claims

1. A web system that provides tension with reduced power consumption, comprising:

an unwind shaft, a rewind shaft, and a processing system;

a drive path running from the unwind shaft through the processing system to the rewind shaft;

a drive motor located along the drive path; and

a continuously variable transmission comprising a first shaft and a second shaft, the first shaft and second shaft being connected to each other through a power transfer linkage;

wherein the first shaft is connected to the unwind shaft and the second shaft is connected to the rewind shaft.

2. The web system of claim 1, wherein the continuously variable transmission is a variable diameter pulley system.

3. The web system of claim 1, wherein the continuously variable transmission is a toroidal transmission system.

4. The web system of claim 1, wherein the continuously variable transmission is a hydrostatic transmission system.

5. The web system of claim 1, wherein the drive motor is located at the unwind shaft.

6. The web system of claim 1, wherein the drive motor is located at the rewind shaft.

7. The web system of claim 1, wherein the drive motor is a drive nip.

8. The web system of claim 1, further comprising a web differential velocity measurement system.

9. The web system of claim 8, wherein the web differential velocity measurement system comprises a dancing roll and a position sensor.

10. The web system of claim 8, wherein the web differential velocity measurement system comprises a stationary roll and a tension sensor.

11. The web system of claim 1, wherein the processing system comprises a printing press.

12. A web system that provides tension with reduced power consumption, comprising:

an unwind shaft, a rewind shaft, and a processing system;

a drive path running from the unwind shaft through the processing system to the rewind shaft;

a drive motor located along the drive path;

a tension measurement system located along the drive path; and

a continuously variable transmission comprising a first shaft and a second shaft, the first shaft and second shaft being connected to each other through a power transfer linkage;

wherein the first shaft is connected to the unwind shaft and the second shaft is connected to the rewind shaft.

13. The web system of claim 12, wherein the continuously variable transmission is a variable diameter pulley system.

14. The web system of claim 12, wherein the continuously variable transmission is a toroidal transmission system.

15. The web system of claim 12, wherein the continuously variable transmission is a hydrostatic transmission system.

16. The web system of claim 12, wherein the drive motor is located at the unwind shaft.

17. The web system of claim 12, wherein the drive motor is located at the rewind shaft.

18. The web system of claim 12, wherein the drive motor is a drive nip.

19. The web system of claim 12, further comprising a web differential velocity measurement system.

20. A method of reducing the power consumption of a web system, comprising:

providing a web system comprising an unwind shaft, a rewind shaft, and a processing system; and

connecting the unwind shaft and the rewind shaft to a first shaft and a second shaft of a continuously variable transmission.