DEVICE FOR STEERING A CONVEYOR BELT

Abstract: For steering a conveyor belt (11) and centring the same relative to the intended path of travel of the belt, use is made of a belt position detecting means (22, 23) and belt readjusting means (24). The belt readjusting means (24) is a belt support roller (24) which is adapted to engage and roll against the belt and which is pivotable relative to the belt. According to the invention, the belt position detecting means (22, 23) and the belt support roller (24) are arranged on a roller cradle (21) which is connected with a frame (29) by means of inclined links (30) for pivoting and setting the belt support roller (24) in a pivoting position, in which the belt support roller by engaging the belt exerts a readjustment force thereon.

Description: DEVICE FOR STEERING A CONVEYOR BELT Tne present invention relates to a device for steering a conveyor belt m a belt conveyor. A common problem when operating belt conveyors is the tendency of the conveyor belt m operation to move 5 laterally relative to the intended path of travel through the conveyor. Lateral displacement, i.e. displacement of the conveyor belt transversely of its direction of travel, may cause, inter alia, damage to the belt by the belt edges coming into contact with fixed parts on the 1C belt conveyor frame. In order to solve this problem, many conveyors nave been provided with one or more support rollers which support the conveyor belt during its return travel and which are manually angularly adjustable relative to the mtend- ι5 ed direction of travel of the belt. The angular orientation of these support rollers is adjusted during the running- m of the belt conveyor to ensure that m normal operational conditions the belt will travel through the conveyor m a correctly centred manner. If a tendency 2C towards lateral displacement should arise m operation, αue foi instance to elongation of tne conveyor belt during operation or to dirt and deposits accumulating on the end rollers of the conveyor manual postad ustment of the set angular position of these support rollers is 25 necessary. Supplementary work is required therefor and furthermore m many cases the conveyor must be stopped during the adjustment work. By setting a support roller at an angle it is thus possible to compensate for the tendency of the belt to run out of line by moving late- 30 rally relative to its intended direction of travel. Moreover, devices have been suggested serving to automatically adjust the conveyor for adaptation thereof to such lateral motions of the conveyor belt. Such an automatic self-adjusting or self -aligning device is shown and described m NO-C-178853 and the corresponding PCT Publication W09514627. However, this prior-art device does not aim at adjusting the position of the belt to maintain it m a centred position relative to the centre line of the conveyor frame but at ensuring that the support rollers are constantly directed perpendicular to the conveyor belt, whether the conveyor belt is centred or not. This aim is achieved by arranging for the belt side edges to travel along edge guide rollers arranged at one end of a double-arm lever, whose other end supports a stand m which the support roller is mounted. This mounting stand, which m its simplest form is a plate, is m turn pivotally connected with the double-arm lever. When the latter pivots m response to the engagement of the guide rollers with the belt edges, the support roller will automatically set itself at right angles to the belt travelling direction. In this prior-art device, return of the belt to the intended centre line of the path of travel of the belt might be achieved as a result of the edge guide rollers trying to push the belt back to a centred position. It has also been suggested that the belt be centred ty _ettmg it travel over a support roller stand containing two belt support rollers which are inclined and each engage a lateral edge portion of the belt m order to cup the Pelt around the central portion of the belt. This technique of achieving centring, however, does not always give the intended result . An improvement m relation to these prior-art devices is described m SE-C-507733 and the corresponding W09819943. This device for steering a conveyor belt is capable of automatically returning a conveyor belt to the intended central position along a path of travel. Thus the steering device causes the conveyor belt to move as much as possible m a centred fashion over support rollers, drive rollers and end rollers m a belt convevor . Tnis prior-art device for steering a conveyor belt starts from the idea, known per se, of using a belt roller to compensate for the tendency towards lateral displacement of the belt . What differs this belt steer- mg device from those previously known is that the angular orientation of the support roller occurs automatically and that the degree of obliqueness is determined by the extent of the lateral movement of the conveyor belt relative to the intended path of travel along the belt conveyor. For detecting the degree of displacement of the conveyor belt relative to the intended path, use is made of belt position detecting means which are connected with tne belt support roller via a linkage system for pivoting m tne principal plane of the belt and setting of the Delt support roller m a pivoting position, m which the belt support roller, owing to its engagement with the belt, exerts a readjusting force on the belt, so that the conveyor belt is steered back and is centred relative to the intended path of travel of the belt . According to SE-C 507733 and the corresponding W09819943, the belt readjusting means thus is a belt support roller which engages the belt and rolls against the same and which is m the principal plane of the belt, and the Pelt position detecting means is connected with the belt support roller via a linkage system for pivoting and adjusting the belt support roller m a pivotal position, m which the belt support roller, owing to its engagement witn the belt, exerts a readjustment force on the belt. This prior-art conveyor belt steering device func- tions very well but suffers from one drawback - it functions merely m one belt travelling direction. This means that tne prior-art conveyor belt steering device cannot be used m conveyor belt installations having a reversible direction of travel of the conveyor belt since, when reversing the direction of travel of the belt, the belt position detecting means and the belt readjusting means must change places and also the linkage system must be turned around. An object of the invention therefore is to provide a new conveyor belt steering device which functions well independently of the direction of travel of the conveyor belt and which therefore can be used also for conveyor Pelt installations with reversible conveyor belts. The invention is based on the per se known idea of using belt position detecting means which detect the lateral position of the conveyor belt relative to the intended path of travel of the belt and which are ope- ratively connected with belt readjusting means which actuate the conveyor belt to be returned to the intended centred position along the intended path of travel of the belt. The novel feature of the invention is how the belt readjusting means is designed and connected with the belt position detecting means and how the readjustment of the conveyor belt occurs. That characterising the invention is stated m the independent claim while the dependent claims define particularly preferred embodiments of this invention. To sum up, the invention can be considered to reside m belt position detecting means and belt readjusting means being arranged on a roller cradle which is connect- ed with a frame by means of inclined links for pivoting and setting the belt roller m a pivoting position, m which the belt support roller is inclined to exert, by engaging the belt, a readjustment force on the same. The invention will be now be described m more detail with reference to the accompanying drawings which illustrate a few embodiments of a belt steering device according to the present invention. Fig. 1 is a schematic view of a belt conveyor provided with a belt steering device according to the pre- sent invention. Fig. 2 is an end view of a first preferred embodiment of a belt steering device according to the present invention. Fig. 3 is a top plan view of the belt steering device shown m Fig. 2 m its position when the conveyor belt travels m a centred manner along the intended path of travel through the belt conveyor . Fig. 4 is an end view of the belt steering device m Fig. 3 with a section through the conveyor belt. Fig. 5 illustrates the same belt steering device as m Fig. 3 but m a position m which the belt has been displaced m one direction relative to its intended centred position and m which the belt support roller of the belt steering device has been automatically inclined to return the belt to the intended centred position. Fig. 6 is an end view of the same belt steering device as m Fig. 5, with a section through the conveyor belt. Fig. 7 is a top plan view of a second preferred embodiment of a belt steering device according to the invention m its position when the conveyor belt travels m a centred manner along the intended path of travel through the belt conveyor. Fig. 8 is an end view of the same belt steering device as m Fig. 7, with a section through the conveyor belt . Fig. 9 illustrates the same belt steering device as m Fig. 7 but m a position in which the belt has been displaced m one direction relative to its intended centred position and m which the belt support roller of the belt steering device has been automatically inclined to return the belt to the intended centred position. Fig. 10 is an end view of the same belt steering device as m Fig. 9, with a section through the conveyor belt . Fig. 11 illustrates a third embodiment which corresponds to the embodiment according to Figs 2-6 but which has inclined belt support rollers for cupping the conveyor belt. Fig. 12 illustrates a fourth embodiment which corresponds to the embodiment according to Figs 7-10 but which has inclined belt support rollers for cupping the conveyor belt . Fig. 1 illustrates schematically a belt conveyor 10. It comprises an endless conveyor belt 11 which travels between end and drive rollers 12. The belt conveyor has a loading station 13 and an unloading station 14. To support the upper run of the conveyor belt between the eno rollers 12 there are belt support rollers 17. Also under its return run 16, the belt is supported by means of belt support rollers 18, which, however, can be arranged at a greater distance from each other than the belt support rollers 17. According to the invention, the oelt conveyor is provided with an automatic belt steering device 20, whicb m this embodiment is placed along the return run 16 close to the loading end of the belt con- veyci . Within the scope of the invention, a belt conveyor can have a plurality of such belt steering devices 20. A preferred embodiment of the belt steering device 20 is shown m more detail m Figs 2-6. The belt steering device comprises a roller cradle 21, which supports two belt position detecting means 22, 23 and a belt support roller 24 which is directed essentially transversely of tne intended path of the travel of the conveyor belt (arrows 25) . In the shown embodiment, the roller cradle has two transverse bars 26. Roller holders 27 are arrang- ed between the bars 26 and attached thereto by means of sleeves 28. In tne shown emoodiment , two belt detecting means 22 are arranged on one side of the conveyor belt and two belt detecting means 23 on the other side of the conveyor belt, so that the forces exerted on the roller cradle when the conveyor belt moves m the lateral direction, are equalised. However, it is also possible to use only one belt detecting means on each side of the conveyor belt . The belt position detecting means 22, 23 are m the form of rollers which are rotatably mounted to roll against the edges of the conveyor belt m operation. The roller cradle 21 is connected with the frame stand 29 of the conveyor belt installation by means of links 30. The links are pivotable on a pivot 31 on the frame and a pivot 32 on the roller cradle 21 and are inclined because the distance between the pivots 31 on the frame is greater than the distance between the pivots 32 on the roller cradle 21. The pivots 31, 32 on the roller cradle 21 are attached to a crossbar 36 with end sleeves 34, through which the bars 26 are passed and which are attachable to the bars 26 m a suitable posi- tion for controlling the distance between the pivots 32 and, thus, the angle of the links relative to the bars. In this example, there are double links at each end of the roller cradle, but m certain cases one link at each end may be sufficient. The conveyor belt 11 travels m contact with the belt support roller 24 on the far side of the bars 26 of the roller cradle. A pressing force is maintained between the conveyor belt and the belt support roller 24 due to the fact that the belt roller, as is evident from Fig. 2, IS arranged m such a position that the conveyor belt is pressed downwards between two successive belt support rollers 18 m the conveyor belt installation. The function of the device is evident when comparing Figs 3 and 4 with Figs 5 and 6. In Figs 3 and 4, the conveyor belt 11 travels m its neutral position along the intended path of the travel. If the conveyor belt for o^e reason or another should begin to move to the left in respect of Figs 3 and 4 , the left edge of the conveyor belt will be caught by the belt position detecting means or rollers 22, which consequently will be displaced to the left (arrows 35) . Since the rollers 22 are connected with the bars 26 and cannot be displaced along the same, this will cause the roller cradle to be pivoted downwards at tne left side (with respect to Figs 4 and 6) , so that the entire roller cradle is inclined. The inclination causes m turn the left edge of the conveyor belt to have a longer path of travel and thus conveyor belt begins to move back to the starting position (the neutral position according to Figs 3 and 4) . If the belt should move to the right, the effect will be the opposite, i.e. inclination of the roller cradle m the other direction and return of the belt from the right to the left. Since the inclination of the belt support roller 24 occurs m a plane which is angled to the principal plane of the conveyor belt, this conveyor belt steering device is independent of the direction m which the conveyor belt moves through the belt steering device. This means that the conveyor belt steering device will function automatically and m a correct manner also when reversing the belt travelling direction m the conveyor belt installation. This is m contrast to the currently best known belt steering device as disclosed in SE-C-507733 and the corresponding W09819943. The embodiment according to Figs 7-10 differs from the emoodiment according to Figs 2-6 only m respect of how the links are angled and how the conveyor belt engages the belt support roller 24. In this case, the conveyor belt is located on the same side of the roller cradle as the pivots 31 on the frame 29. For a lateral displacement of the conveyor belt 11 to be corrected and the joeit be returned to the intended neutral position, the links 32 must be inclined m opposite directions, i.e. the distance between the pivots 31 of the frame is snorter than the distance between the pivots 32 of the roller cradle. Otherwise, this conveyor belt steering device works m the same manner as the steering device according to Figs 2-6. However, there is one difference since, m the steering device according to Figs 2-6, the conveyor belt has been forced to travel m an arcuate form between two belt support rollers 18 for the belt to travel with pressing force m contact with the belt support roller 24. In the steering device according to Figs 7-10, the required pressing force is achieved by tne belt being pressed by gravity against the belt support roller 24. Figs 11 and 12 illustrate two more embodiments of tne invention. In these two cases, the belt support roller 24 is replaced by two angled belt support rollers 36, 37 which bear on opposite rim portions of the conveyor belt 11 m order to cup the same. Consequently, also the belt position detecting means or rollers 22, 23 nave been inclined to a corresponding degree m order to roll against the lateral edges of the cupped conveyor celt. Also m this case, the roller cradle has two paral- _el bars 26, on which the various components are attachable by means of sleeves 28, 34. In one embodiment (not shown) , the central portion cf the belt can also be supported by a belt support roller which m that case is arranged between the two angled belt support rollers 36, 37 m Figs 11 and 12. As mentioned above, the links 30 are inclined m one or the other direction according to the side of the belt support roller that is pressed against the conveyor belt. The degree of inclination of the links may vary although an angle of 45° has been selected. Both the angle and the _ength of the links affect the degree of inclination of the roller cradle when the conveyor belt is displaced laterally. A greater degree of inclination causes a quicker return of the conveyor belt to the neαtral position. A person skilled m the art can, by simple tests, determine the degree of inclination which is most convenient m the individual case.

Claims: CLAIMS _. A belt steering device for adjusting the lateral position of a conveyor belt (11) relative to an intended belt travelling path, comprising a frame (29) and belt position detecting and readjusting means (21-24; 36, 37), which have at least one belt support roller (24; 36, 37) being arranged for pivotal movement relative to the frame and engaging the belt, and which have belt position detecting means (22, 23) operatively connected with the belt support roller and intended for pivoting and setting the belt roller (24; 36, 37) m a pivoting position, m which the belt roller by its engagement with the belt exerts a readjustment force thereon, c h a r a c t e r i s e d m that the belt support roller (24; 36, 37) and the belt position detecting means (22, 23) are arranged on a roller cradle (21) , that the roller cradle is pivotally connected with the frame (29) by means of at least one inclined link (30) on each side of the intended path of travel of the conveyor belt, that the inclined links (30) are at one end articulated to the stand (29 ' > DV means of a first pivot (31) and at their other end aiticlated to the roller cradle (21) by means of a second pivot (32) , the distance between the first pivots (31) arranged on either side of the belt differing from the distance between the second pivots (32) arranged on either side of the belt, and that the belt position detecting means (22, 23) are attached to the roller cradle (21) . 2. A belt steering device as claimed m claim 1, c h a r a c t e r i s e d m that the distance between said first pivots (31) on the frame (29) is shorter than the distance between said second pivots on the roller cradle (21) , and that the roller cradle (21) and its belt support roller (24) are adapted to support the conveyor belt against the side of the belt support roller facing away from said first pivots (31) of the frame (29) . 3. A belt steering device as claimed m claim 1, c h a r a c t e r i s e d m that the distance between said first pivots (31) on the frame (29) is longer than the distance between said second pivots (32) on the roller cradle (21) , and that the roller cradle (21) and its oelt support roller (24) are adapted to support the conveyor belt against the side of the belt support roller facing said first pivots (31) of the frame (29) . 4. A belt steering device as claimed m claim 1, 2 or 3, c h a r a c t e r i s e d m that the roller cradle (21) comprises belt support rollers (36, 37) which are inclined for cupping the conveyor belt (11) . 5. A belt steering device as claimed m any one of claims 1-4, c h a r a c t e r i s e d m that on each side of the intended path of travel of the conveyor belt (11), the roller cradle (21) has two belt position detecting means (22, 23) which are arranged at a distance from one another, seen m the direction of travel of the conveyor belt . c . A belt steering device as claimed m any one of claims 1-5, c h a r a c t e r i s e d m that the links (30) are inclined at an angle of about 45° to the roller cradle (21) .

Inventors: MALMBERG MATS ANDERS, MALMBERG, MATS, ANDERS
Applicants: MALMBERG MATS ANDERS, SVEDALA TRELLEX AB, MALMBERG, MATS, ANDERS
Application year: 2000
Main classification: B65G15
IPC codes: B65G39