WIRE TENSIONING DEVICE

Abstract: A tensioning device for adjustment of wire tension, said device comprising substantially horizontal guide tracks (2) provided with supporting surfaces (1), cylinder carriages (4) movable on supporting rollers (3) along the supporting surfaces, a wire tensioning cylinder (5) supported by its ends on the cylinder carriages and a control device connected to the cylinder carriages for moving the cylinder carriages along the guide tracks. The tensioning device further comprises a load surface (6) comprised in the guide track (2), said load surface being parallel to the supporting surface (1) and facing in the opposite direction relative to it, a lever (7) pivotally mounted on the cylinder carriage (4) and provided with a pressure roller (8) rotatably mounted on it, and a force element (9) acting on the lever for pressing the pressure roller against the load surface.

Description: Wire tensioning device The present invention relates to a tensioning device as defined in the preamble of claim 1 for the adjustment of wire tension. The tensioning device of the invention can be used in different paper machines, cardboard machines, pulp machines, coating machines and similar machines having an endless circulating wire whose tension is adjusted. Traditionally, a wire tensioning device comprises rigid guide tracks upon which cylinder carriages moving on rollers and supporting the ends of a wire tensioning cylinder are moved. As the wire runs round the wire tensioning cylinder, the wire tension can be adjusted by moving the cylinder carriages along the guide tracks . This arrangement is very common and it is used in almost all paper and cardboard machines. Prior- rt solutions involve problems caused by transverse vibrations, i.e. vibrations in the ver- tical direction, of the wire tensioning cylinder and of the cylinder carriages connected to it. As the cylinder carriages and the cylinder rest freely on the guide tracks, they are free to vibrate in the upward direction, while the vibration produces slight accel- erations and decelerations of the wire that may even result in the wire being broken. In theory, the problem could be easily eliminated by having the cylinder carriages at either end of the wire tensioning cylinder supported in a manner that keeps them rigidly in position only in the vertical direction. However, this is not possible in practice because the circumstances in which the cylinder carriages move on the guide tracks are very untidy. The guide tracks are often littered with pieces of web or the like, which make it impossible to use close tolerances, because in any case the cylinder carriage has to be allowed to move horizontally along the guide tracks as freely as possible. The object of the invention is to eliminate the above-mentioned drawbacks. A specific object of the invention is to disclose a new type of tensioning device by means of which vertical vibrations of the cylinder carriages and the wire tensioning cylinder supported on them can be eliminated as fully as possible. As for the features characteristic of the invention, reference is made to the claims. The tensioning device of the invention comprises substantially horizontal guide tracks provided with supporting surfaces, cylinder carriages movable on supporting rollers along the supporting surfaces, a wire tensioning cylinder supported by its ends on the cylinder carriages, and a control device connected to the cylinder carriages for moving the cylinder carriages along the guide tracks . According to the inven- tion, the tensioning device comprises a load surface provided in the guide track, said load surface being parallel to the supporting surface and facing in the opposite direction relative to it, a lever pivoted on the cylinder carriage and provided with a pressure roller rotatably mounted on it, and a force element acting on the lever for pressing the pressure roller against the load surface. Thus, according to the invention, the wire tensioning cylinder is supported on the guide tracks via the cylinder carriages in both vertical directions, yet so that the suspension will yield when the cylinder carriage comes across any litter on the guide track surfaces. Thus, there will be no disturbance to uniform and unobstructed wire tension adjustment. In a preferred embodiment of the invention, an oblique support from the cylinder carriage to the load surface is provided. In other words, an arrange- ment is used in which the distance from the pivot of the lever to the load surface of the guide track is shorter than the distance from the pivot to the rim of the pressure roller of the lever. If the length of the lever and its obliquity are sufficient, then the lever with the pressure roller will always turn when any obstructions or litter is encountered, and thus no jamming of the adjustment occurs. The tensioning device of the invention has significant advantages as compared with prior art. The invention makes it possible to eliminate transverse vibrations of the wire tensioning cylinder almost completely, which again allows wire breakages to be prevented and the operating speed to be increased. In practical tests it has been established that, when a tensioning device according to the invention was used, undesirable vibrations were reduced to less than 10 % of the original level, whereas when complicated electronic control systems were used, the vibrations could only be reduced by about 10%. In the following, the invention will be described in detail with reference to the attached drawings, wherein Fig. 1 presents a tensioning device according to the invention in diagrammatic side view, and Fig. 2 presents a part of the arrangement shown in Fig. 1 as seen from another direction. The tensioning device of the invention presented in the drawing employs a downward turned U- shaped guide track 2 attached e.g. to the frame of a paper machine. The guide track is provided with shoulders 10 extending laterally on both sides as extensions of its stem part, and the upper and lower surfaces of the shoulders have been milled to accurate dimensions to form supporting surfaces 1 and load surfaces 6. Supported on the guide track is a cylinder carriage 4 moving on supporting rollers 3 along supporting surfaces 1 and carrying a wire tensioning cylinder 5. A corresponding structure is provided at ei- ther end of the wire tensioning cylinder 5. The cylinder carriage 4 can be moved along the supporting surfaces 1 in a manner known in itself so as to move the wire tensioning cylinder and thus to adjust the wire tension. Hinged on the cylinder carriage 4 via a pivot 11 is an elongated lever 7 with a pressure roller 8 mounted with bearings at its one end and a spring functioning as a force element 9 connected to its other end to allow the lever to be turned about the pivot 11 in a given direction. The pressure roller 8 is so mounted on the lever 7 that the pressure roller runs along the load surface 6 on the underside of the shoulder 10 of the guide track 2. The essential point is that the dis- tance of the pivot 11 from the load surface 6 is shorter than the distance of the pivot 11 from the rim of the pressure roller 8. Thus, in the situation illustrated in Fig. 1, the lever 7 can turn if necessary in a direction perpendicular to the guide track 2 against the pressure of the spring 9 e.g. when the pressure roller 8 comes across litter on the load surface 6. The tensioning device presented in the drawings works as follows. In clean normal conditions, as the cylinder carriage 4 is moving along the guide track 2, the spring 9 turns the lever 7 and presses the pressure roller 8 continuously and steadily against the load surface 6 with a suitable force as selected. Thus, vertical movements and vibrations of the cylinder carriage 4 and therefore also harmful vibrations of the wire tensioning cylinder 5 are prevented. If there is any litter on the supporting surface 1 or on the load surface 6, then, regardless of the direction of movement of the cylinder carriage, the spring 9 will yield and the lever 7 will turn just enough to allow the carriage to pass over the litter on the supporting surface or the load surface. The pressure and vertical support of the lever 7 still remain substantially constant, so that litter will not cause any substantial vibrations in the cylinder carriage and the wire tensioning cylinder. In the foregoing, the invention has been described by way of example with reference to the attached drawing while different embodiments of the invention are possible within the inventive idea defined in the claims.

Claims: CLAIMS 1. Tensioning device for adjustment of wire tension, said device comprising substantially horizontal guide tracks (2) provided with supporting surfaces (1) , cylinder carriages (4) movable on supporting rollers (3) along the supporting surfaces, a wire tensioning cylinder (5) supported by its ends on the cylinder carriages, and a control device connected to the cylinder carriages for moving the cylinder carriages along the guide tracks, characteri zed in that the tensioning device comprises - a load surface (6) comprised in the guide track (2) , said load surface being parallel to the supporting surface (1) and facing in the opposite direction relative to it, - a lever (7) pivoted on the cylinder carriage (4) and provided with a pressure roller (8) rotatably mounted on it, and, - a force element (9) acting on the lever for pressing the pressure roller against the load surface. 2. Tensioning device as defined in claim 1, characterized in that the force element (9) is a spring. 3. Tensioning device as defined in claim 1, characterized in that the profile of the guide track (2) comprises a shoulder (10) , whose upper surface forms the supporting surface (1) and its lower surface forms the load surface (6) . 4. Tensioning device as defined in claim 3, characterized in that a shoulder (10) is provided at both edges of the guide track profile (2) . 5. Tensioning device as defined in claim 3 , characterized in that the supporting surface (1) and the load surface (6) have been milled on the guide track. 6. Tensioning device as defined in claim 1, characterized in that the distance of the pivot (11) of the lever (7) to the load surface (6) of the guide track (2) is shorter than its distance to the rim of the pressure roller (8) . 7. Tensioning device as defined' in claim 3, characterized in that the guide track (2) consists of a downward turned U-profiled member in which the shoulders (10) form horizontal extensions of its stem.

Inventors: KAUPPINEN MIKKO, KAUPPINEN, MIKKO
Applicants: KAUPPINEN MIKKO, TONTTULAN TAKOMO, KAUPPINEN, MIKKO
Application year: 2001
Main classification: D21F7
IPC codes: D21F7