WEB TENSIONING APPARATUS

Abstract: A printing press web tensioning system comprising a motion driven belt drive (10) for the paper reel (13), dancer roll means (15), pneumatic means (25) for changing the tension required for deflection of the dancer roll and control means for automatically varying operating values of subcomponents of the tensioning system to carry out webbing, slack removal, start up and normal running operation.

Description: This invention relates to web fed rotary printing presses and more particularly to an apparatus for controlling the feeding of web from a supply reel into a web fed printing press as specified in the preamble of claim 1. Systems for controlling web tension in printing presses have traditionally been designed only to regulate or control web tension during normal running conditions. Generally, web is removed from a large, heavy reel of newsprint by means of belt-like friction means that are in contact with the surface of the reel and are frequently referred to as surface-driven. After leaving the reel, the web is usually, at some point prior to printing, entrained about a biasing roller, such as a dancer roll, the purpose of the dancer roll being to permit regulation of the tension in the web by means of appropriate switching and fluid pressure regulators. Controlling tension is necessary, since it varies greatly during printing operations due to change in the weight, speed and diameter of the reel as web is being payed out. Web tension controls utilized heretofore have frequently included not only means to vary the fluid pressure (usually pneumatic) utilized at the dancer roll but to also control braking means to retard rotation of the paper reel. Typical of prior art devices used for web tension control is that shown in US-A-3,913,900 where a pendulum or dancer roll is utilized. In this device, change in tension in the web causes the roll to pivot, and thereby change the setting of a potentiometer. The potentiometer controls the speed of a drive motor to vary the speed of the web and thereby control web tension. Another example of web tension control is shown in US-A-3,202,376. Here a sensing roller pivots in response to the tension in a loop to effect change in the adjustment means, thereby altering the friction between a roll and belts. Increase or decrease in the frictional engagement between the roll and the belts either increases or decreases the rotative speed of the rolls to vary the tension in the web in direct proportion thereto. Additional examples of mechanisms or systems to control web tension in strands being payed from a supply roll may be found by referring to US-A-3,813,052; 3,811,637; 4,147,516; 1,978,073 and 2,222,462. A review of all the references noted above will show that, as already stated, the prior art displays a variety of mechanisms for controlling the tension of webs during the usual printing operation. What the existing art does not indicate is the importance of being able to effectively control web tension when the web is being threaded around the various rolls prior to press start up. During this threading operation, one man is typically required to control the large, high inertia paper roll, in order to keep the web slack and avoid breakage until the web is fully in the press and ready for tension. In addition, once the web is installed, the tension set on the web is usually decreased until the press and web are running well, then readjusted, back up to the original value. All of these operations require a great deal of manual intervention during the busy start up period. A tension control apparatus of the kind as specified in the preamble of claim 1 which is used to join together two films by stratification is known from FR-A-2 575 448. With this system two supply reels are provided from which the respective films are drawn. The reels are driven by reel service drive belts. Each of the two films are fed to a dancer roll means and thereafter to stratification rolls where the two films are joined together. The tension of the resulting product is measured by a sensor, the output of which is used to control the tension of each of the two films with the tension of each film being maintained within a given range. Apart from the fact that this known tension control system is not utilized in a printing press, this system, too, is designed only to regulate or control the tension during normal running conditions. It is a principal object of this invention to provide an apparatus for controlling the feeding of web from a supply reel through simultaneous monitoring and control of a plurality of feeding conditions. Another object of this invention is to provide an apparatus for removing slack from the web during the process of preparing for printing operations. An additional object of this invention is to provide improved control means for simultaneous control of web speed, direction and tension. In accordance with the present invention, this object is achieved in that said drive control means and the associated operator means are further laid out for an operator selection of predetermined interrelated values of said belt drive motor speed and said pneumatic pressure from said differential pressure means in accordance with the different values required during web-up and web slack removal press operation stages. These and other advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawing, in which: The Figure is a schematic illustrating the main components in the web feeding control apparatus of this invention. As mentioned above, the present invention relates to an apparatus for controlling the feeding of web from a supply reel into a web fed printing press. Particularly concerned here is the type of web fed press that is commonly used in the production of daily newspapers in which reels of newsprint of large weight and large diameter are used to supply newsprint for the press. Prior to start-up of the press, it is necessary for the web to be fed from the reel on which it is stored, around one or more guide rolls and ultimately into the press itself where printing is to be carried out. This operation is normally a manual one in which the reel drive and web feeding mechanism are disconnected and the web is threaded manually through the necessary rolls into printing position within the press. In order to understand the present invention more clearly, reference is made to the Figure of the drawings in which the numeral 10 identifies carriage belt drive means comprised of reel surface drive belts 11 and a drive motor 12. Operation of motor 12 with the belts 11 in contact with the paper stored on storage reel 13 will either pay-out or take-up web 14, depending upon the direction of rotation of motor 12. After being payed off from reel 13, the web 14 moves upwardly toward the dancer roll means 15. Dancer roll means 15 includes a dancer roll 16 which is movable between a lowermost position 17 and an uppermost position 18 in response to forces created against it by the tension contained in the traveling web 14. While this dancer roll may be mounted in any manner appropriate to its being movable through a range of positions, it is here shown as being pivotally mounted about a pivot axis 19. On the pivot end 19, there is located sensor means 20 which is operatively connected to said dancer roll means 15 to generate signals that are reflective of the position of the dancer roll means within the path of its vertical travel. To provide for adjustment of the forces which the web must overcome to effect movement of the dancer roll 16 from the uppermost toward the lowermost position, there is provided pneumatic means 25 which is here shown as being comprised of a piston 26 that is positioned for vertical movement within the cylinder 27. Thus, depending upon the amount of pressure that is contained within the cylinder 27 and against which the piston 26 therefore must act, it will take more or less tension within the web 14 to draw the dancer roll 16 from a position located at or near its uppermost position 18 to its lowermost position 17. Differential pressure means 30 is provided in the present invention which is connected to the pneumatic means 25 and to a source of air. In the present illustration, differential pressure means 30 is shown as being a motorized regulator which can draw air from a source and supply it under pressure to the cylinder side 27 of the pneumatic means 25. One of the most important features of the present control apparatus is the means by which the various subcomponents of the overall apparatus are coordinated. In this invention, drive control means 35 is provided which is effective in coordinating the signals received from dancer sensor means 20, providing instructions to the differential pressure means 30 and providing driving instructions to the belt drive motor 12. In the present case, the drive control means is a microprocessor which permits operator selection of predetermined interrelated values of the speed of drive belt motor 12, selection of the pneumatic pressure which should be provided by the motorized regulator 30 to pneumatic means 25 and the selection of the different values of speed for the carriage belt drive motor 12 when undertaking the various steps that go into the preparation of a press for printing. Specifically, presses must normally be webbed up, any slack that may be present in the system removed, started up at a first speed and then subsequently run at a speed and tension which are greater than those used in all of the preceding operations. In order to select the desired operation of the drive control means 35, there are provided operator means 36 which are associated with the drive control means 35 that permit such operator selection. Specifically, manual devices such as push buttons or levers can be provided which permit an operator to select either a predetermined speed and pressure for the web-up operation, a second and different pressure tension and speed for slack removal operations, yet another combination of speeds and tension for the start up operations and finally, different running conditions for the normal operating situation. Utilizing the control apparatus of this invention to web-up, the web 14 is pulled over the dancer roll 16 and into the unit (press not shown) utilizing the usual lead in means. The drive belts 11 are then lowered into contact with the paper reel 13 and the webbing switch 37 is activated. When this switch is activated, the pneumatic means 25 produces a pneumatic pressure which is just sufficient to support the dancer roll 16 at its uppermost position 18. Simultaneously, drive belt means 10 will cause forward rotation of the reel 13 at a slow rate, for example, on the order of 0,3048 to 0,6096 meter per second (one to two feet per second). In this mode, any web pressure will pull the dancer roll 16 downwardly since the pressure supporting the roll is only sufficient to support the roll itself without the additional force which is provided by the web. When this occurs, the drive control means 35 will activate the drive motor 12 and cause a slow forward pay out of web 14 from reel 13. This then causes the dancer to again move to the full up position, causing the drive motor 12 to stop. Thus, as the pressman pulls paper from the roll and causes the dancer roll 16 to move from its uppermost position, motor 12 is activated to provide additional paper. This feeding of paper results in the dancer roll against moving to its uppermost position where further pay out of web 14 is stopped. Only after the pressman stops pulling paper does the dancer then stay at the top position and the drive remain off. After the web 14 has been threaded around the dancer roll 16 and into the press, the operator can activate the reverse switch 38 in the operator means 36, which will cause the carriage drive belt motor 12 to rotate the reel 13 in the reverse or web take-up direction. At the same time, the drive control means 35 causes the motorized regulator 30 to provide a greater pressure to the pneumatic means 25 so that a tension greater than that used for web-up will be required before any vertical movement of the dancer roll 16 can occur. In this reverse running position, this being done at a rate of 7,62 meter per minute (25 feet per minute), under a pressure in the pneumatic means of about 103,42·10³ to 137,89·10³ Nm⁻² (15 to 20 psi), web is drawn back onto the reel 13 until the dancer is pulled down to a position located intermediate the uppermost position 18 and the lowermost position 17. The pressure that is being supplied by motorized regulator means 30 is that which corresponds to the tension that is desired in the web. When the dancer roll 16 arrives at a preselected intermediate position, the drive stops. Upon this stopping, the selector switch automatically moves the operation to the slow forward start-up position, this being a mechanical function of the switching means. At this time, the switching means automatically initiates normal running condition which provides for a start-up tension approximating that of the reverse tension and starting at a slower speed while the press builds up and full running conditions are finally effected.

Claims: An apparatus for controlling the feeding of web (14) from a supply reel (13) into a web-fed printing press comprising carriage belt drive means (10) including reel surface drive belts (11) and a drive motor (12), dancer roll means (15) disposed to contact said web (14) and move between uppermost (18) and lowermost position (17) in response to changes in the tension in said web (14), sensor means (20) operatively connected to said dancer roll means (15) to generate signals reflective of the positioning of said dancer roll means (15), pneumatic means (25) operatively connected to said dancer roll means (15) to vary the forces required to effect changes in the position of said dancer roll means (15) and thereby the tension in said web (14), differential pressure means (30) connected to said pneumatic means (25) and to a source of air to control the air pressure in said pneumatic means (25), drive control means (35) operatively connected to said belt drive motor (12), to said differential pressure means (30) and to said dancer roll sensor means (20) whereby the speed of said belt drive motor (12) and the pneumatic pressure are controlled simultaneously, and operator means (36) associated with said drive control means (35) for an operator selection of predetermined interrelated values of said belt drive motor speed and the pneumatic pressure from said differential pressure means (30) in accordance with the values required during normal press operation stages, characterized in that said drive control means (35) and the associated operator means (36) are further laid out for an operator selection of predetermined interrelated values of said belt drive motor speed and said pneumatic pressure from said differential pressure means (30) in accordance with the different values required during web-up and web slack removal press operation stages. An apparatus according to claim 1, characterized in that said differential pressure means comprises a motorized regulator (30). An apparatus according to claim 1 or 2, characterized in that during said web-up press operation said belt drive motor speed and said pneumatic pressure are controlled such that said pneumatic pressure is just sufficient to support the dancer roll means (15) at its uppermost position (18) and any web pressure will pull said dancer roll means (15) downwardly, whereupon said belt drive motor speed is set at a predetermined slow forward speed until said dancer roll means (15) again is moved to its uppermost position (18). An apparatus according to anyone of the preceding claims, characterized in that during web slack removal press operation a pneumatic pressure related to the tension desired in said web (14) is provided so that a tension greater than that used during said web-up press operation will be required before any vertical movement of said dancer roll means (15) occurs and said belt drive motor (12) is controlled to rotate said web supply reel (13) in a take-up direction until said dancer roll means (15) is moved to an intermediate position between said uppermost (18) and said lowermost (17) position. An apparatus according to anyone of the preceding claims, characterized in that said drive control means (35) causes said belt drive means (10) to feed out said web (14) for press start up after the desired web tension is achieved following web take-up. An apparatus according to anyone of the preceding claims, characterized in that said operator means (36) comprises switch means (37, 38) permitting selection between webbing and reversing operations. An apparatus according to claim 6, characterized in that said switch means (37, 38) automatically initiates normal running conditions when web slack removal is terminated.

Inventors: HUTH, MICHAEL
Applicants: ROCKWELL INTERNATIONAL CORPORATION
Application year: 1988
Main classification: B65H23
IPC codes: B41F13, B65H23, B41F33