WO2008153409A1

WO2008153409A1 - Guidance unit for conveyor belt

Info

Publication number: WO2008153409A1
Application number: PCT/NO2008/000208
Authority: WO
Inventors: Kjell Arne Gaarden
Original assignee: As Techno-Track
Priority date: 2007-06-15
Filing date: 2008-06-10
Publication date: 2008-12-18
Also published as: NO327544B1; NO20073060L

Abstract

The present invention relates to a guidance device for a conveyor belt, which guidance device is arranged transverse to the belt's direction of travel and can guide the position of the belt in the lateral direction and guide the belt's direction of travel. The device according to the present invention is used to correct the belt path or belt movement of the belt over a plurality of supporting rollers in order to ensure that the belt is centered over the supporting rollers as a conveyor belt during operation is susceptible to lateral displacement away from a neutral position in its longitudinal direction.

Description

Guidance unit for conveyor belt

The present invention relates to a guidance device for a conveyor belt, which guidance device is arranged transverse to the belt's direction of travel and can guide the position of the belt in a lateral direction, and guide the belt's direction of travel. The device according to the present invention is used to correct the belt path or belt movement of the belt over a plurality of supporting rollers in order to ensure that the belt is centered over the supporting rollers as a conveyor belt in operation is susceptible to lateral displacement away from a neutral position in its longitudinal direction. According to the invention, the belt guidance unit can be employed in conveyor belts that move in one direction as well as in two opposite directions with only very slight alterations, and the basic constructional features of the belt guidance unit are substantially identical in the two operational situations.

The belt guidance unit according to the present invention is used for guiding conveyor belts particularly in processing plants for various types of materials in bulk format, such as granulated ores, etc.

In connection with plants where such conveyor belts are employed, it is known that for various reasons the belts "wander" laterally on rollers and along their tracks. This is due in part to uneven loading, partly to misalignment of supports and rollers and often a combination of several different factors that produce a random pattern of movement for lateral movement of the belt. This lateral movement may be defined as a deviation from a basic neutral position where the belt travels in its longitudinal direction along an imaginary centre line or other kind of desired path over rollers or guides. Lateral movement in the belt will move the belt to the side of this neutral position or path for the belt, whereupon it should be restored to this neutral position. This creates the need for a guidance device that senses when the belt is out of the neutral position, whereupon it corrects the belt's travel in its longitudinal direction, thus returning the belt to the neutral position. This should also be a dynamic correction device that constantly corrects the belt relative to positions on both sides of the neutral position as well as preferably in relation to both directions of travel in the belt's longitudinal direction.

A belt guidance unit for the above-mentioned tasks and areas of application should furthermore be simple and robust to operate while it must be easy to install and adjust before use. The construction should furthermore be capable of being adapted to the existing conditions and loads either by employing different dimensions for the constructional parts or by being able to adjust the design of the constructional parts that are already installed in an existing system, such as, e. g., rollers, guides, mounting brackets, etc.

From previously known solutions within the field, a device may be mentioned for conveyor belts that travel over rollers or supports, described in DE 174 491, which device corrects for lateral displacements that occur in the belt during operation, causing the belt to be returned to its neutral position. A set of guide rollers for the conveyor belt is mounted on a plate, which is rotatably attached to the base. To the rotatable plate is mounted an arm with a tie bar. The arm may be articulated and rotatable about a pivot that is attached to the base. To the tie bar are attached guide rollers, which move along the edge of the conveyor belt and which, in the event of lateral displacement of the belt, transfer the movement to the tie bar. The movement is transferred to the lever arm, which in turn transfers the movement to the plate, thus causing the guide rollers'axes to be tilted and returning the conveyor belt to its neutral position.

The belt guidance unit described in NO 178 853 is a known solution of a similar type, but where the lever arm is rotatably attached both to the plate holding the guide rollers and the tie bar holding the guide rollers. The lever arm is rotatably attached to a fixed point located at a distance from the rotatable attachments in the plate and the tie bar, and a rotatably parallel stay is mounted parallel to the lever arm, between the tie bar and a fixed base in the form of a beam, with the result that the tie bar always remains at right angles relative to the conveyor belt's centre line.

In NO 306 708, moreover, a reversible belt guidance unit is described for centring conveyor belts, which during operation are susceptible to a lateral displacement away from a neutral position, comprising a rotating mechanism which carries at least one guide roller for the conveyor belt, and which is rotatably mounted in a first fixed beam, which rotatable mounting is arranged about an axis that is perpendicular to the conveyor belt. Furthermore, a first set of guide rollers abuts against the conveyor belt's lateral edges, thereby being displaced laterally depending on the conveyor belt's lateral displacement, and the belt guidance unit comprises a first transfer mechanism for transferring the lateral displacement of the first set of guide rollers to the rotating mechanism, for rotating the guide roller to a position where it guides the conveyor belt towards the neutral position.

Known belt guidance units of the type described in DE 174 491 and the like have a tendency to produce rolling and skewed travel in the conveyor belt, particularly when there is uneven loading or uneven weight distribution, resulting in wear along the edge of the belt.

Compared to these other known belt guidance units, the belt guidance unit known from NO 178 853 provides a far smoother movement of the conveyor belt, resulting in less wear and a longer life for the belt. The belt guidance unit described in NO 178 853, however, only works when the belt moves in one direction, which is not sufficient for a number of purposes.

Furthermore, the belt guidance unit from NO 306 708 is designed so as to work with conveyor belts that move in two opposite directions. Moreover, FR 2728248 describes guidance of a belt that moves over a roller. The guidance is directly towards the edge of the belt which can be seen from, inter alia, Fig. 2. The arm 2 with the roller 1 abuts against the edge of the belt. The arm also rests on a shaft 4 that is spring-loaded by the spring 3. In other words, there is a fixed connection between the roller 7 and the shaft 4, which in turn is subjected to spring loading. US 251 1 194 also describes a solution comprising direct guidance of the belt where the wheels 9 and 1 1 on respectively the upper side and the underside of the belt form an angle relative to the longitudinal direction of the belt if the edge of the belt displaces the guiding device 17 with the wheel 19 towards the left (in Figure 3) as a result of the belt moving askew,

The above-mentioned solutions, however, are relatively complicated in their mechanisms for producing movement and the solutions are therefore expensive and complicated with regard to mounting and adjustment, while also requiring some inspection. It is therefore an object of the present invention to provide a guidance device or a belt guidance unit according to the above wishes and requirements that counteracts the disadvantages and defects of previously known solutions.

The present invention is a simple solution that can easily be mounted, is inexpensive to make and requires little maintenance. Accordingly, there is provided a guidance device for a conveyor belt according to the present invention as disclosed in claim 1 below. Alternative embodiments are disclosed in the subsequent claims.

In one particular embodiment, two guidance devices may be combined such that together they are able to guide in both directions. This can be achieved by placing two guidance devices laterally inversed one after the other so that they guide in their respective directions, whilst the swing of the guidance device is limited in such manner that each guidance device can only guide in one direction. Together, the two guidance devices will thus guide the belt in their respective directions, thereby ensuring a centered positioning of the belt at all times. Two different embodiments of a guidance device according to the present invention are further shown in the attached figures, in which:

Figure 1 is a perspective view of a guidance device in neutral position. Figure 2 shows the guidance device in Figure 1 , seen from the side.

Figure 3 is a perspective view of the guidance device in Figure 1, seen from the opposite side.

Figure 4 is a perspective view of the guidance device in Figure 1 exploded into its individual components. Figures 5 and 6 are perspective views of the guidance device in Figure 1 in respectively a first and a second extreme position, i.e., with fully corrected swing for guiding the conveyor belt.

Figure 7 shows an alternative embodiment of the roller holder where the roller is raised to a higher level.

Figures 1-6 illustrate a guidance device according to the present invention for guiding a conveyor belt (not shown). The guidance device consists of a roller 1 over which roller the conveyor belt runs in its longitudinal direction. The roller 1 is rotatably mounted on a supporting shaft 2 having a first and a second end. This shaft thus functions in this embodiment as a roller holder in that it supports and/or holds the roller. The shaft is further secured to a pivot bearing 3 at its first end. This pivot bearing permits the roller holder, which in this embodiment is the shaft 2, to rotate essentially in the plane of the conveyor belt, and the roller 1 may thus assume different angular positions relative to the longitudinal direction of the conveyor belt, whereby the roller will be able to guide the course and direction of the conveyor belt, and thus also the lateral position of the conveyor belt on the roller.

As is further illustrated in the figures, there is provided an elastic element, which in this embodiment is a spring 5, between the roller holder (the shaft 2) and a fixed point, which is this embodiment is the hook 6, which in turn is secured to the bracket 15 which holds the device into the conveyor belt arrangement. As shown, the length of the hook 6 can be adjusted by the nut 7 so that the spring can be tightened or slackened by adjusting the distance between the attachment 4 on the roller holder and the fixed point 6. When the distance is increased, the spring is tensioned and it will exert a greater force in order to turn the roller holder in the pivot bearing 3. This adjustment will be capable of being carried out to accommodate different belt types and loads on the belt whilst it is adapted for ensuring regular movement of the belt over the guidance device.

The roller holder, which in this embodiment is the shaft 2, is further secured to the pivot bearing which is in turn stationarily fixed to the fastening bracket 15 via a non-rotating shaft or rod 17. In this way, the shaft 2 with the roller 1 will turn in the direction of rotation essentially in the conveyor belt's plane in the pivot bearing 3 whilst the shaft 2 is spring-loaded by the spring 5. When the belt moves either the roller will be rotated because of skewed travel of the belt so that the spring is tensioned, and the spring will then turn the roller relative to the belt so that the belt is guided back into its central position on the roller and in the correct direction of travel.

On the opposite side of the roller holder, i.e., at the other end of the roller and the roller holder, the roller holder is freely supported in the direction of rotation. This is shown in the figures by rollers or wheels 8 which rest on a planar surface 9 and which move along this surface 9. This movement will follow the outer edge in a circle with a radius corresponding to the distance from the pivot bearing 3 to the wheels 8. The surface 9 must therefore be wide enough for this arcuate movement. To ensure that the wheels 8 are not subject to damage from above and to ensure that the roller holder is not lifted up from the surface 9 there is provided an upper supporting surface 10 above the wheels 8. This is an alternative that is indicated in this embodiment.

Also provided in connection with the roller holder (the shaft 2) is a distance spacer 11 having an essentially transverse spacer 12 that holds a guide device 13. This guide device is shown in the figures as a drum or roller which abuts against the side edge of the conveyor belt. If the conveyor belt moves towards this guide device 13 with force, caused by the conveyor belt moving askew towards the guide device 13, the said guide device 13 will turn the roller holder about the pivot bearing 3 so that the roller 1 is skewed relative to the belt's direction of travel, on a par with the force exerted by the spring 5 on the opposite side of the guidance device. This skewing of the roller 1 will guide the belt way from the guide device 13 and the force that the belt exerts thereon will diminish. Subsequently, the spring 5 (which is now tensioned) will pull the roller holder in the opposite direction and the skewing relative to the conveyor belt will diminish after which the skew correction will diminish. In this way, the conveyor belt's direction and position over the roller 1 will be capable of being corrected at all times as a result of the force the spring 5 exerts on the roller holder in the one direction and the force that the belt's skew travel (at the belt edge) exerts on the guide device 13 in the other direction. In Figure 1 where the belt's direction of travel is shown from the right-hand side of the page to the left-hand side, the side edge of the belt will exert a force on the guide device 13 if the belt moves towards the left over the roller 1 and the roller holder 1 will be turned about the pivot bearing 3 thereby tensioning the spring 5. This guides the belt towards the right over the roller and the force from the belt's side edge against the guide device 13 diminishes, after which the spring 5 pulls the roller 1 back into the neutral position. If the belt wanders to the right over the roller, the left side edge of the belt will leave the guide roller 13 and the spring 5 will be tensioned further so that the roller holder 1 is turned in the pivot bearing 3 and guides the belt to the left over the roller 1. In other words, there is a continuous dynamic play of force between the force of the belt against the guide device 13 and the spring 5.

As shown in the figure, there will be a lever arm between the pivot bearing 3 and the attachment 4 for the spring 5. This lever arm multiplied by the force of the spring will, in other words, correct in one direction whilst the belt's force against the guide device 13 will correct in the opposite direction. As shown in Figures 1-6, it is a relatively short lever arm between the attachment 4 for the spring and the pivot bearing 3. This can be varied by attaching the spring 5 at any point along the roller holder. Similarly, the force obtained can be varied by varying the spring stiffness of the spring 5. >

In a number of alternative embodiments, the elastic element 5, which in the illustrated embodiment is indicated as a spring, may also be an elastomer or other elastic material that is arranged between the roller holder and a fixed point.

Alternatively, an elastomer material may also be incorporated into the pivot bearing 3 so that the rotary motion takes place at all times in an elastic material. However, this will have fewer possibilities for adjustment than the embodiment that is shown.

In order that the other end of the roller holder can be freely supported in the direction of rotation, there is shown in the figures and in this embodiment a solution where two rollers or wheels move over a planar surface 9. Alternatively, this can be achieved with a body of a material having a relatively low coefficient of friction that moves against another material in a sliding motion. As shown in the figures, the roller path or the planar surface 9 is fixedly connected to a fixed point via the rod or shaft 16 which is further shown in Figure 2 secured to the fastening bracket 14 via setting screws or bolts 18 and 19. Furthermore, the fastening bracket 14, like the fastening bracket 15, is on the opposite side of the guidance device provided with screw holes 20 and 21 for attachment to the actual roller path and the supporting structure for the conveyor belt. In different alternative embodiments it may be desirable to locate the roller 1 higher than the rest of the actual belt guidance device. In such a case, the roller holder is designed so that it places the roller 1 with roller shaft 2 higher. This is shown in an outline form in Figure 7 where the roller 1 is located on the roller shaft 2 which in turn is supported by a bracket or frame 22. This frame 22 is at one end pivotally secured in a pivot bearing 3 and at its other end is freely supported in the direction of rotation, for example, by means of rollers or wheels 8 on a planar surface 9 as indicated in Figure 7, as in the other figures.

Furthermore, the roller 1 may be self-supporting with a spindle at each end that is secured in a roller holder configured as a cradle, box or frame. The spring 5 will in that case be attached by the fastening device 4 to one of the spindles or the roller holder.

Moreover, in different alternatives, the spring 5 may be secured to the roller holder on one side or the other of the pivot bearing 3. If the spring 5 is secured on the outer side of the pivot bearing 3, this requires that the direction of the spring be changed 180 degrees as the lever arm relative to the pivot bearing 3 moves in the opposite direction upon rotation.

Figure 1 shows a guidance device according to the invention in the neutral position where the wheels 8 are located approximately in the middle of the planar surface 9. In Figure 5, however, the guidance device is shown in full swing where the wheels 8 abut against the front end of the surface 9. In this position, the guidance device will guide the belt to the maximum to the right over the roller relative to the indicated belt direction and the spring 5 is extended and tensioned to the maximum. Conversely, Figure 6 shows full swing in the opposite direction where the wheels 8 abut against the rear end of the surface 9.

If the surface 9 is limited so that the roller holder can only move from a neutral position (where the roller is located transverse to the belt without rotary position) and towards one direction, a guidance device will be obtained that only guides one way. A combination of two such units results in a guidance device that guides both ways independent of the belt's direction of travel.

Claims

PATENT CLAIMS

1. A guidance device for a conveyor belt, which guidance device is provided with at least one roller (1) essentially transverse to the belt's longitudinal direction over which roller (1) the conveyor belt runs and which roller (1) is pivotally arranged in the device in relation to the conveyor belt's longitudinal direction, characterised in that the roller (1) is mounted on a roller holder device which is in turn pivotally secured in the conveyor belt's plane at a first end of the roller holder device, and that there is provided an elastic element (5) between the roller's (1) roller holder device and a fixed point so that the roller (1) in the unloaded state is pre-tensioned in the direction of rotation to the side of the neutral position transverse to the conveyor belt, and that the other end of the roller holder device, opposite the first end, is freely supported in the direction of rotation and that there is provided a guide device (13) in connection with the roller holder device that is adjacent to the conveyor belt's side edge and which is so secured to the roller holder device that it can turn the roller holder device in the opposite direction of the pre-tensioning from the elastic element (5).

2. A guidance device according to claim 1, characterised in that the elastic element (5) is a spring.

3. A guidance device according to claims 1-2, characterised in that the elastic element (5) is connected to the shaft (2) at a point between the first end and the second end.

4. A guidance device according to claims 1-3, characterised in that the elastic element (5) is connected to the shaft (2) at the first end.

5. A guidance device according to claims 1-4, characterised in that the second end of the roller holder device is provided with a support having low friction (8, 9).

6. A guidance device according to claim 5, characterised in that the support is one or more wheels, ball or roller bearings (8) which roll over a planar surface (9).

7. A guidance device according to claim 5, characterised in that the support is a body of a material with a low coefficient of friction that slides over a surface with a low coefficient of friction.

8. A guidance device according to any one of claims 1-7, characterised in that the roller holder device is a shaft (2).

9. A guidance device according to any one of claims 1-7, characterised in that the roller holder device is a frame with a shaft (2).

10. A guidance device according to any one of claims 1-7, characterised in that the roller holder device is a frame with an attachment for each end of the roller (1).