WEB GUIDANCE SYSTEM

Abstract: A system (20) for handling a web (25) combines guiding and cleaning functions. A guiding roller (22) and upper and lower cleaning rollers (23A, 23B) are mounted in a frame (21) which can be rotated about an axis transverse to the rollers (22, 23A, 23B) to guide the web (25). Other combinations of guiding and cleaning rollers are disclosed.

Description: "Web Guidance System" The present invention relates to a web guidance system and in particular to a web guidance system capable of web cleaning. It is known in production processes to make use of webs which require to be cleaned. Such webs are thin, generally plastic materials and web guidance systems are well known in the art . Webs are prone to run off track easily and the web guidance systems are used to keep the web on a desired track. Web cleaning systems are also known in the art, these cleaning systems being used to remove particulates from at least one surface of the web. In the past it has been the practice to use separate web cleaning systems and web guidance systems. The surface of a cleaning roller is formed of elastomeric material which is compressible. This compressibility means that when the web is placed in tension over the cleaning roller the web can deviate from track, and this factor has caused cleaning rollers to be thought not to be suitable for use also as guidance rollers which has inhibited the development or use of combined cleaning/guidance systems, system can malfunction. According to invention, there is provided a web guidance system which incorporates web cleaning means, the system comprising at least one guiding roller controllable to effect guiding of the web, and at least a first cleaning roller having an outer surface coated with a material having a degree of tackiness capable of removing particulates from a surface of the web. The system may include a second cleaning roller having an outer surface coated with a material having a degree of tackiness capable of removing particulates from the other surface of the web. One of the cleaning rollers may constitute the guiding roller. Preferably, the cleaning roller which constitutes the guiding roller has a surface hardness greater than that of the other cleaning roller. Preferably also, the or each cleaning roller is provided with a respective backup roller arranged to engage the cleaning roller and having a surface coated with a material having a degree of tackiness greater than that of the cleaning roller for removing particulates from the cleaning roller. In preferred embodiments, the several rollers are mounted for rotation about parallel roller rotation axes m a common frame, the frame being rotatable about a frame rotation axis which is perpendicular to said roller rotation axes; and the system suitably includes a feedback control loop which comprises an edge sensor for sensing the position of the web edge at a location downstream of the rollers, and an actuator arranged to rotate said frame about the frame rotation axis m response to the output of the edge sensor. Cleaning may take place at an upstream side or at a downstream side of the system. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, m which: Fig. 1 is a schematic isometric view of a web guidance system as known m the art; Fig. 2 is a schematic isometric view of one embodiment of the present invention; and Figs. 3 to 9 are views similar to fig. 2 of alternative embodiments of the invention. Fig. 1 illustrates web guiding apparatus 10 as is known m the art. The web guiding apparatus 10 comprises a mounting plate 11 on which a first guiding roller 12 and a second guiding roller 13 are mounted for rotation about spaced horizontal axes. A web 15 is placed m tension over the first and second guiding rollers 12 and 13. The web guiding apparatus 10 further comprises an edge sensor 14 for detecting the edge of the web and ensuring that the web 15 is running on track. When the sensor 14 detects that the web 15 is moving off track then a suitable control system is activated. The control system comprises a feedback loop 16A driving a linear actuator 16 which is arranged to rotate the mounting plate 11 about a central vertical axis. Thus, the linear actuator 16 causes the axes of the guiding rollers 12 and 13 to swivel m a horizontal plane, in order to cause the web 15 to track m the desired direction. The feedback loop 16A continues to operate the linear actuator 16 until the sensor 14 detects that the web 15 is m the desired location. Referring to Fig. 2, there is illustrated one embodiment of a web guidance system 20 m accordance with the present invention, which includes web cleaning apparatus for cleaning both the upper and lower surfaces of the web 25. The system 20 comprises mounting plates 21A and 2 IB adapted to mount an input roller 22, an upper cleaning roller 23A, a lower cleaning roller 23B, a first back-up roller 24A and a second back-up roller 24B. The various rollers rotate about parallel, horizontal axes, while the mounting plates are mounted (by means not shown) to rotate about a vertical axis at the midlength of the assembly. The web 25 is fed over the input roller 22 then between the upper and lower cleaning rollers 23A and 23B. The web then passes an anti-static device 26, which removes static built up through the system. An edge sensor 14, feedback loop 16A and linear actuator 16 are provided which operate as m the prior art system to keep the web 25 on the desired track. As will be evident, the lower cleaning roller 23B also acts as a web guiding roller equivalent to the web guiding roller 12 of the prior art design shown m Fig. 1. In order for the web guidance aspect of this embodiment to operate efficiently, the web 25 must be m tension over the guiding roller 23B. Normally, cleaning rollers, by their nature, are not as hard as guiding rollers, because the cleaning rollers generally use elastomeric materials and have a degree of "give" . This means that when the web 25 is put m tension over the lower cleaning roller 23B, it is compressed and the web guiding system may not operate effectively. However, m this present embodiment, the surface of the lower cleaning roller 24B is harder than the surface of the upper cleaning roller 23A. Therefore, the lower cleaning roller 23B has less "give" than the upper cleaning roller 23A thus allowing the guidance aspect of the embodiment to function properly. The web cleaning system operates m a manner that is well known m the prior art, that is, having upper and lower cleaning rollers 23A and 23B respectively, both having first degrees of adhesive tackiness to remove particulates from the upper and lower surfaces of the web 25, respectively. These upper and lower cleaning rollers 23A and 23B engage first and second back-up rollers 24A and 24B, respectively. These first and second back-up rollers 24A and 24B have second degrees of adhesive tackiness for removing the particulates from the upper and lower cleaning rollers 23A and 23B. Alternative embodiments will now be described with reference to Figs. 3 to 9. In these Figures like parts are denoted by like reference numerals, and the anti- static device 2 and the edge detector 14 and feedback system 16, 16A have been omitted but operate as before. In Fig. 3, a mounting plate 11 is pivoted on a support 30. Two rollers are rotatably carried by the mounting plate 11: a cleaning roller 23A at the input side, and a guiding roller 13 at the output side. In Fig. 4, the mounting plate 11 carries guiding rollers 12 and 13, the guiding roller 13 at the output end having associated therewith a cleaning roller 23A and adhesive backup roller 24A. Fig. 5 is similar, but the cleaning roller 23A and backup roller 24A are positioned at the input end. The embodiments of Figs. 3 to 5 are therefore suitable for cleaning only one side of the web. The embodiments shown in Figs. 6 to 9 clean both sides of the web. Fig. 6 is similar to Fig. 5, but the input end guiding roller is replaced by a second cleaning roller 23B and backup roller 24B. Fig. 7 shows an arrangement in which the web 25 passes through the system substantially linearly, supported by non-steerable infeed and outfeed rollers 70 and 71. Upper and lower cleaning rollers 23A and 23B and backup rollers 24A and 24B are rotatably mounted, as shown only schematically, on a carrier 72 to form an assembly 73 which can be rotated about a vertical axis on a base 74. The assembly 73 is rotated under feedback control as before to correct the track of the web. Fig. 8 shows an assembly 73 similar to that of Fig. 7, but mounted within a mounting plate 11 which also carries guiding rollers 12 and 13. Fig. 9 is similar functionally to Fig. 8, but the assembly 73 is secured by readily accessible bolts 90 into a modified mounting plate 91 such that the assembly 73 can readily be removed and replaced in a modular manner. Modifications and improvements may be made to the foregoing within the scope of the present invention.

Claims: CLAIMS 1. A web guidance system which incorporates web cleaning means, the system comprising at least one guiding roller controllable to effect guiding of the web, and at least a first cleaning roller having an outer surface coated with a material having a degree of tackiness capable of removing particulates from a surface of the web. 2. A web guidance system according to claim 1, including a second cleaning roller having an outer surface coated with a material having a degree of tackiness capable of removing particulates from the other surface of the web. 3. A web guidance system according to claim 2, in which one of the cleaning rollers constitutes the guiding roller. 4. A web guidance system according to claim 3, in which the cleaning roller which constitutes the guiding roller has a surface hardness greater than that of the other cleaning roller. 5. A web guidance system according to any preceding claim, in which the or each cleaning roller is provided with a respective backup roller arranged to engage the cleaning roller and having a surface coated with a material having a degree of tackiness greater than that of the cleaning roller for removing particulates from the cleaning roller. 6. A web guidance system according to any preceding claim, m which the several rollers are mounted for rotation about parallel roller rotation axes m a common frame, the frame being rotatable about a frame rotation axis which is perpendicular to said roller rotation axes. 7. A web guidance system according to claim 6, including a feedback control loop which comprises an edge sensor for sensing the position of the web edge at a location downstream of the rollers, and an actuator arranged to rotate said frame about the frame rotation axis m response to the output of the edge sensor. 8. A web guidance system according to any preceding claim, m which cleaning takes place at an upstream side of the system. 9. A web guidance system according to any of claims 1 to 7, m which cleaning takes place at a downstream side of the system.

Inventors: HAMILTON SHEILA, KENNET CHARLES JONATHAN, HAMILTON, SHEILA, KENNET, CHARLES, JONATHAN
Applicants: HAMILTON SHEILA, KENNET CHARLES JONATHAN, TEKNEK ELECTRONICS LTD, HAMILTON, SHEILA, KENNET, CHARLES, JONATHAN, TEKNEK ELECTRONICS LIMITED
Application year: 2000
Main classification: B65H23
IPC codes: B08B7, B65H23, B65H27