AU760723B2

AU760723B2 - A tiltable guide roller

Info

Publication number: AU760723B2
Application number: AU50806/00A
Authority: AU
Inventors: Heikki Halme; Lasse Lotila
Original assignee: Roxon Oy
Current assignee: Roxon Oy
Priority date: 1999-06-08
Filing date: 2000-06-08
Publication date: 2003-05-22
Anticipated expiration: 2020-06-08
Also published as: FI991303A0; WO2000075054A1; AU5080600A; DE10084683B4; FI107795B; DE10084683T1; FI991303A

Description

WO 00/75054 PCTFI00/00515 1 A tiltable guide roller The invention relates to a guide roller for guiding a conveyor belt of a belt conveyor, the guide roller comprising a casing setting against the belt, an axle arranged through the roller and a bearing arranged on the middle portion of the roller, between the casing and the axle, the bearing allowing the casing to tilt with respect to the axle in a transverse direction to the surface of the belt and which allows the casing to pivot in the direction of the belt surface about a pin or a similar pivot axis transverse to the axle, the guide roller being further arranged to the conveyor in such a way that the pivot axis is at an inclined guide angle with respect to the vertical, whereby when the belt moves off centre, it is arranged to press downward the end of the roller casing where the misaligned belt is and, as a result, the casing, when being pressed downward, is arranged, at the same time, to pivot by impact of the guide angle at its downward pressed end in the direction of travel of the belt by a movement proportional to the guide angle value.

Mass material is typically conveyed on belt conveyors. The belts of the conveyors are usually made of rubber and they are relatively thin. For increased strength, the belts are vulcanized and plastic fibre and/or steel threads are added into the structure of the belts to reinforce them. The belt must be sufficiently strong to ensure that it withstands the force it is subjected to by the drive mechanism of the belt and the tensile load caused by the mass conveyed on the belt. Nevertheless, the belt must be resilient and sufficiently thin to allow for reliable and economical power transmission between the belt and the drum driving the belt and to allow power transmission to be provided with drums of a reasonable size. Due to the above aspects, a thin belt is preferred. A thin belt is not, however, stable in the lateral direction, but various disturbances tend to make the belt drift sideways. Such disturbances may be caused for example by a damaged roller, material being stuck on the belt or the roller, or by incorrect alignment of the rollers/drums. The lateral drifting of the belt may cause the belt to be emptied of the material loaded on the belt. In addition, the belt may rub against the frame of the conveyor structure and become damaged. Since the conveyor belt is usually the most expensive component in a belt conveyor and the most essential one for the operation of the equipment, every effort is made to prevent it from being damaged.

For the purpose of centering the conveyor belt, various guiding WO 00/75054 PCT/FI00/00515 2 roller racks have been constructed, but they have been found operationally unreliable. A further problem they involve is insufficient guiding efficiency. It has proved particularly problematic to construct a belt guide which functions properly in conveyors where the belt is driven in two directions.

Attempts have been made to solve the problem by designing various guide rollers having a central bearing. The belt that moves off centre on the conveyor presses the casing of the guide roller downward with respect to its central bearing at the edge where the misaligned belt is. Since the guide roller is arranged diagonally, at an angle of 450 with respect to the direction of travel of the belt, the roller is arranged to pivot automatically in the direction of travel of the belt by impact of the downward pressing, whereby the guide roller corrects the lateral misalignment of the belt particularly by impact of the pivoting of the guide roller in the direction of travel of the belt. A drawback in known guide rollers having a central bearing is, however, that due to the angle of 450 the vertical and horizontal components caused by the downward pressing of the casing are of an equal magnitude. Because of roller dimensioning, the horizontal component, i.e. the one in the direction of travel of the belt, is small and the casing of the guide roller pivots only a little in the direction of the plane of the belt, as a result of which efficient guidance cannot be provided by applying standard roller dimensioning.

It is an object of the present invention to provide a guide roller which allows problems of the prior art to be avoided.

The guide roller of the invention is characterized in that the value of the guide angle is between 10 and 400, whereby, when guiding the belt, the casing is arranged to always pivot more in the direction of the belt than to tilt in the transverse direction.

An essential idea of the invention is that the pin, or a similar rotation axis arranged at the central bearing about which pin the casing can pivot in the direction of the belt's plane is arranged at an angle of 10-400 with regard to the vertical axis. This angle is called a guide angle k. The horizontal movement component, i.e. the component acting in the direction of the belt, is thus always greater than the downward movement component, i.e. the one acting in the transverse direction to the belt. A value of k between 25 and 350 is preferred. An essential idea of a preferred embodiment of the invention is that the magnitude of the guide angle can be changed, i.e. the relation between the horizontal and vertical components can be adjusted according to the WO 00/75054 PCTIFI00/00515 3 conveyor structure and its diverse purposes of use. Further, a second preferred embodiment of the invention is based on the idea that the guide roller is arranged so that the guide angle k is between 10 and 400 in both directions of travel of the belt. An essential idea of a third embodiment of the invention is that the guide angle can be adjusted in both travel directions of the belt. The advantage of the invention is that since the guide angle is between and 400, the guide roller movement component in the belt direction is always greater than when the prior art angle of 450 is used. Greater pivoting of the roller in the direction of travel of the belt makes the repositioning more efficient and allows the belt to be centered to the normal travel path faster, before it is damaged. Moreover, the possibility to change the relation between the horizontal and vertical components by adjusting the guide angle allows the guide roller to be used in the best possible way in different situations. In addition; the relation of the horizontal and vertical movement components in conveyors driven in two directions can be separately adjusted in both movement directions of the belt.

The invention will be described in greater detail in the accompanying drawings, in which Figures la and lb illustrate solutions based on the prior art; Figures 2a and 2b are schematic views of belt conveyors in which the guide roller of the invention can be used; Figure 3 is a schematic, sectional view of a bearing arranged on the middle portion of the guide roller, seen in the direction of travel of the belt; Figures 4a and 4b are schematic views of the guide roller when the belt runs correctly, Figures 5a and 5b showing the pivoting of the guide roller when the belt has moved off centre; Figure 6 is a schematic view of a prior art solution where the control angle k 450; and Figures 7 and 8 illustrate a solution of the invention.

Figure la is a simplified view of a guide roller 1 seen from the end of the roller, the roller being arranged at the angle of 450 applied in the prior art. Figure lb shows a prior art attaching member for installing the guide roller.

At the end of the guide roller is provided a portion 2 which is arranged to a slot 3 formed to the attaching member at an angle of 45 The direction of travel of the belt 4 in the Figure is shown by arrow A.

Figures 2a and 2b show, by way of example, belt conveyors where WO 00/75054 PCT/FI00/00515 4 the guide roller of the invention can be used. The preferred points of installing the guide roller are shown with arrows in the Figures. In a conveyor, a guide roller is usually arranged on the return side of the belt where it replaces an ordinary roller. The guide roller of the invention can be used in conveyors driven in one direction or conveyors driven in two directions.

Figure 3 shows a sectional view of a bearing 6 arranged on the middle portion of the guide roller 1, the arrangement comprising an outer ring 6a attached to the casing of the roller and an inner ring 6b arranged to an axle 7 of the roller. The bearing allows the roller to swing up and down in direction B shown in the Figure, because the contact surface between the inner ring 6b and the axle 7 is curved. The tilting of the roller in direction B can be seen in Figure 5a. The roller can also pivot about a pin 9 and its rotation axis arranged transverse with respect to the axle 7, in direction C shown in the Figure. This pivoting of the casing 11 that takes place in the direction of the belt plane is in turn illustrated in Figure 5b. The tilting of the casing in direction B and its pivoting in direction C is restricted by the dimensioning of the guide roller. In its extreme positions, the casing can pivot in such a way that its inner surface sets against the axle 7 of the roller, as illustrated in Figures 5a and A more detailed description of the bearing is not needed in this context, because the arrangement is known per se and therefore belongs to the expertise of a person skilled in the art.

Figure 4a shows the guide roller in the direction of travel of the belt, Figure 4b illustrating a top view of the roller. In the situation shown in the Figures the belt 4 runs correctly centered on the guide roller 1, the casing 11 of the roller being substantially parallel with the roller axle 7. For the sake of clarity, broken lines show the belt 4 in Figure 4b. With the attaching members 12 arranged at the ends of the guide roller's axle, the guide roller can be attached to the frame structure of the conveyor. The simplest attaching members are supports made of a bent plate. Furthermore, an adjusting mechanism 5 is arranged between the axle of the roller and the attaching members 12 to allow the rotation axis 13 to be set at the desired guide angle value. The adjusting mechanism may comprise suitable pins, or the like, which can be connected to adjustment holes made to the attaching member. On the other hand, the adjusting mechanism may comprise a steplessly adjustable limiter, such as an adjustment screw, an eccentric member, or the like. The guide roller is further provided with means allowing the pin 9 to pivot in WO 00175054 PCT/FI00/00515 whichever direction of travel of the belt, whereby a guide angle of the invention is achieved in both travel directions of the belt. The guide angle adjustment can also be provided for both travel directions of the belt.

Figure 5a shows a situation seen from the direction of travel of the belt where the belt has shifted to the left side of the roller due to which the centre of gravity of the belt does not coincide with that of the roller, whereby the roller is tilted so that its left-most end, where the misaligned belt is as shown in the Figure, has moved downward and the opposite end has naturally risen correspondingly. Since the pin 9 is arranged diagonally at a desired angle with regard to the belt surface, the downward movement of the casing also pivots the casing about the pin 9 and the rotation axis 10 in the direction of the belt's surface, as shown in Figure 5b. This is illustrated in Figures from 6 to 8 which show the situation as seen from the end of the guide roller. Figure 6 first shows the prior art solution where the rotation axis 10 is fixedly arranged at an angle of 450 to the vertical 13. The angle formed by the rotation axis with respect to the vertical is referred to as the guide angle, hereinafter abbreviated with k. The guide angle k being 450, as shown in the Figure, a downward movement component a 1 i.e. a component transverse to the belt, and a horizontal movement component b, i.e. a component parallel with the direction of travel of the belt, of an equal magnitude are generated. The magnitude of a resultant i.e. the maximum pivot angle, is determined by the dimensions of the guide roller. Although Figure 6 illustrates the geometry of the guide arrangement by showing the axle 7, drawn with a broken line, both at the centre of the roller and set against the inner periphery of the casing, it is nevertheless to be noted that in reality the axle 7 maintains its position, and the casing 11 moves in the direction of the resultant c. After the guide roller has repositioned the belt so that it runs in the middle of the conveyor, the centre of gravity of the belt coincides with that of the guide roller, and the guide roller resumes a horizontal position and pivots back to an aligned position with regard to the belt, whereby it no longer guides the belt.

Figure 7 is a schematic view of the guide roller end of the invention illustrating the lowest guide angle value, Figure 8 illustrating the roller at the highest k value. For the sake of clarity, a movement component b, corresponding to the k value of 450 is shown in both Figures. The Figures clearly show that in both cases b, is smaller than the movement components b 2 and b 3 achieved by the guide angle values of the invention. To ensure that WO 00/75054 PCT/FI00/00515 6 the guide roller will perform the necessary guiding movements when the belt has moved off centre, the guide angle should not be made smaller than in the solution shown in Figure 8 where k=10 0 Consequently, component a 3 is a minimum value which ensures a sufficient guiding force and the operation of the guide roller. All guide roller values provide equal resultants cl-c 3 because their magnitude depends on the dimensioning of the roller. A guide angle value k between 25 and 350 is preferred to provide a proper downward movement and, at the same time, efficient pivoting in the belt direction.

The drawings and the related specification are only intended to illustrate the inventive idea. The details of the invention may vary within the scope of the claims. Consequently, the bearing on the middle portion of the guide roller may equally well be arranged in another way than shown for example in Figure 3. An essential aspect of the invention is that the guide angle k is within the claimed range, whereby the horizontal movement component, which is the more essential one for the guiding of the belt, is always greater than the vertical movement component.

For the purposes of this specification it will be clearly understood that the word "comprising" means oo.o "including but not limited to", and that the words "comprise" and "comprises" have a corresponding meaning.

*It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art, in Australia or in any other country.

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Claims

1. A guide roller for guiding a conveyor belt of a belt conveyor, the guide roller comprising a casing setting against the belt, an axle arranged through the roller and a bearing arranged on the middle portion of the roller, between the casing and the axle, the bearing allowing the casing to tilt with respect to the axle in a transverse direction to the surface of the belt and which allows the casing to pivot in the direction of the belt surface about a pin or a similar rotation axis transverse to the axle, the guide roller being further arranged to the conveyor in such a way that the pivot axis is at a diagonal guide angle with respect to the vertical, whereby when the belt moves off centre, it is arranged to press downward the end of the roller casing where the misaligned belt is and, as a result, the casing, when being pressed downward, is arranged, at the same time, to pivot by impact of the guide angle at its downward pressed end in 20 the direction of travel of the belt by a movement proportional to the guide angle value, characterized in that the value of the guide angle is between 10 and 400, whereby, when guiding the belt, the casing is arranged to always pivot more in the direction of the belt than to tilt in the transverse direction.

2. A guide roller according to claim i, ic.: characterized in that the value of the guide angle oo. is between 25 and 350 3

3. A guide roller according to claim 1 or 2, characterized in that the guide roller comprises means for arranging the rotation axis of the roller to pivot in accordance with the direction of travel of the belt so that the guide angle is 10-400 in both directions of travel of the belt. RA Ar -8-

4. A guide roller according to any one of the preceding claims, characterized in that the guide roller is provided with an adjusting mechanism for adjusting the magnitude of the guide angle.

A guide roller according to claim 3 and 4, characterized in that the magnitude of the guide angle can be adjusted separately for both directions of travel of the belt.

6. A guide roller substantially as hereinbefore described with reference to Figures 2a, 2b, 3, 4a, 4b, 7 and 8 of the accompanying drawings. Dated this 16th day of May 2002 ROXON OY By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and 20 Trade Mark Attorneys of Australia