CA1072481A

CA1072481A - Scraper system for reversible belts

Info

Publication number: CA1072481A
Application number: CA298,307A
Authority: CA
Inventors: Manfred Schattauer
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-03-05
Filing date: 1978-03-03
Publication date: 1980-02-26
Also published as: IT1102703B; ATA154078A; ZA781250B; DE2709714C2; SE7712643L; NL7802443A; SE433739B; CH630315A5; DE2709714A1; AU3376378A; ES467542A1; GB1549976A; IT7848231A0; NL187676C; NL187676B; AT360903B

Abstract

ABSTRACT OF THE DISCLOSURE:

A scraper system for reversible belts comprising a first scraper arranged in the vicinity of the first discharge end of a belt and a second scraper located in the vicinity of a second discharge end, one of the two scrapers being in an inactive position and the other in an active position as a function of the running direction of the belt. Each scraper is provided with a plurality of cutters which extend over the width of the belt, the cutters being individually arranged on an adjustably loaded carrier movably mounted on the carrying frame of belt and moving transversely with respect to belt.
The cutters are pressable against the side of the belt which is to be cleaned and are individually deflectable counter to the tension of a spring mechanism. The cutters on the carrier are deflectable about a clearly defined pivot axis in such a way that, viewed in the belt running direction, in the active position it is at a distance a from the cutting edge and on the side and at a distance h from the side of the belt to be cleaned which represents a multiple of the distance a and the cutting edge of cutters is located in front of the pivot axis A in the inactive position, based on the same belt running direction as hereinbefore. The cutters in the case of a reversal of the belt running direction due to the displacement of cutters by belt or material adhering to belt are automati-cally pivoted out of the active position into an inactive position and during the next change of the belt running direction are automatically pivoted back from the inactive position into the active position.

Description

~0 ~
The invention relates to a scraper system for revers-ible belts comprisiny a first scraper arranged in the vicinity of the first discharge end of a belt and a second scraper located in the vicinity of a second discharge end, one of the two scrapers being i~ an inactive position and the other in an active position as a function of the running direction of the belt.
For the purpose of cleaning reversible endless belts with two spaced discharge ends a scraper is positioned below each of said ends. The scraper associated with the discharge end which has just been used is in an active position and the scraper associated with the unused discharge end is in an inactive position.
In the hitherto known arrangements of scrapers for reversible belts it is necessary in the case of the reversal of the belt running direction to stop the belt, disengage from the belt the scraper which was previously in the active position and then fix it again in a position spaced from the side of the belt to be cleaned. Correspondingly the other scraper is raised from its inactive position spaced from the sicle of the belt to be cleaned until it reaches the active position where it is secured. Scraper systems which have to be changed in this way on modifying the running direction of the belt are used for scrapers of the most varied types and for different stripping capacities. Frequently they have the advantage that the scrapers which are fundamentally designed for only - a single belt running direction have a rela-tively simple construction and a relatively high s-tripping capacity. However, on ~hanging the belt running direction the work which is required for bringing one scraper from the active into the inactive position and the other scraper from the inac-tive into the active position leads to undesired stoppages of the belt - 1 - ~

and relatively high labour costs.
Other known reversible scraper systems which can be easily changed from an active into an inactive position and viceversa by means of an electrical con-trol system have a high capital cost and are usually fault-prone.
Another known scraper is admittedly constructed in such a way that individual scraper elements can closely follow any vibrations of the belt and any reversal of the belt running direction at least causes no serious damage. EIowever, this behaviour is obtained by mounting the scraper elements on solid elastic blocks of rubber material or the like which permit no clearly defined pivot axis for the scraper elements, so that the position of the latter relative to the underside of the belt to be cleaned is not defined. In particular the angle at which the individual scraper elements engage on the underside of the belt to be cleaned is not defined and is consequently not constant in operation. Therefore no constant sharp scraping edge can form on the individual scraper elements and the stripping capacity varies widely due to the frequently changing engagement conditions. In addition, this scraper requires a relatively high contact pressure which is exerted on the carrier which receives the individual scraper elements and is in this way imparted to the latter. Thus, in the case of a reversal of the belt running direction in which the high contact pressure continues to act the scraper elements and the actual belt are subject to a large amount of wear due to relativel~ high frictional forces in the inac-tive position.
Thus, even in this construction a manual adjustment of the scrapers into and out of the active or inactive positions is preferred.
The problem of the invention is therefore -to provide a scraper system for reversible belts of the type indicated .

83l hereinbefore which has a high, constan-t stripping capacity, whilst giving maximum protection to t~e belt and also permits a simple changeover of the stri.ppers from the active into the inactive posi-tion and vice-versa.
According to the invention this problem is solved in that each scraper is provided with a plurality of cutters which extend over the width of -the belt, said cutters being individually arranged on an adjustably loaded carrier movably mounted on the carrying frame of belt and moving transversely with respect to belt, the cutters being pressable against the side of the belt which is to be cleaned and are individually deflectable counter to the tension of a srping mechanism, the cutters on the carrier being deflectable about a clearly defined pivot axis in such a way that, viewed in the belt running direc-tion, in the active position it is at a distance a from the cutting edge and on the side and at a distance h from the side of the belt to be cleaned which represents a multiple of the distance a and the cutting edge of cutters is located in front of the pivot axis A in the inactive position, based on the same belt running direction a.s hereinbefore that the cutters in the case of a reversal of the belt running direction due to the displacement of cutters by belt or material adhering to belt are automatically pivoted out of the active position into an inactive position and during the next change of the belt running direction are automatically pivoted back from the inactive position into the active position.
As a result of this construction according to the invention a reversible scraper system is obtained in which when operating the belt in one direction the scrapers are active and ~hen operating it in the other direction are inactive and can thus neither damage the belt nor the scrapersO Reversal always takes place automatically. In the active positlon a Y~

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high stripping capacity is obt~irled, whilst in the inactive position the scrapers nei-ther damaye nor wear the belt, as will be explained hereinafter.
Due to the construction according to the invention only comparatively small contact pressures are necessary to obtain high stripping capacities. Thus, only a limited force is applied to the carrier for this purpose due to loading by : means of a weigh-t or spring, or alternatively hydraulically or pneumatically and the individual cutters are pressed against the underside of the belt with said limited force. Due to the selected spacing conditions (a compared wlth h) between the pivot axis of the cutters and the side of the belt to be cleaned the cutters engage on the side of the belt to be cleaned with such an angle of attack that material adhering to this belt side is peeled or cut off. If the cutters encounter obstacles which adhere firmly to the belt such as belt damage or the like : they.can individually rapidly deflect and spring back due to their spring mechanism without causing any damage to the belt or to the sharp cutting edge of the cutters.
On changing the belt running direction the cutters which were previously in the active position are taken up from the belt and automatically pivoted into an inactive position.
Such an "overturning" of the cutters is completely safe for the scrapers and the belt due to the construction according to the invention because the cutting edge of the cutter in the active position is always only at a limited distance a from the foo-t of the perpendicular dropped by -the pivot axis on the underside of the belt to be cleaned and is movable along a circular path whose radius is only slightly larger than the above distance h.
Based on the belt running direction prior to the change_over the cutting edge in the inactive position in front of the pivot axis in a correspondingly more acute angle ~ . .

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relative to the underside of th~ belt than in the active pGSi-tion. A sliding engagement occurs between the cutters and the underside of the belt which cannot damage the scraper or the belt. Since, as s-tated hereinbefore, the contact pressures are extremely small no significant wear can be caused by this engagement. If damaged portions of the belt or the like come into contact with the cutters in the inactive position the latter can deflect counter to the tension of the spring mechanism in -the same way as in the ac-tive position.
Since the cutters in the inactive position remain in contact with the belt side it is ensured that a further reversal of the belt running direction again leads to a displace-ment of the cutters and a corresponding pivoting back thereof into the active position.
The carrier is preferably held in a parallel guide so that a sharp curring edge can be formed on the cutters, said sharp edge being maintained. Preferred embodiments for a roller guide or parallel slideway in conjunction with a spring loading or weighting of the carrier will be described in the second part of the description. If a parallel guide comprising two levers is used the articulation axis of the upper-load-transferring lever is level with the side of the belt to be cleaned,so that the line of action of the frictional force acting on the cutting edge of the cu-tters passes through said articulation point and consequently no moment can form which preven-ts constant contact pressures and which in other systems in the case of a change to the bel-t running direction can lead to the cutters being drawn into the belt. ~n the scraper system according to the invention the frictional force is only noticed through the cutters being turned sliyhtly about a clearly defined pivot axis counter to the spring tension of the spring mechanism.

Preferably the spring mechanism is constructed and adjusted in such a way that in both -the active and inactlve positions the cutters are resiliently deflectable. Due to this construction if a damaged portion of the belt comes into con-tact with the cutter in the inac-tive position it can be pivoted out of the path of movement of the damaged area in much the same way as in the active posi-tion, but with the difference that the pivotal movement takes place in the opposite direction to that taking place in the active position. The spring-mecha-nism is advantageously a torsion spring, particularly a rubber torsion spring, as will be explained hereinafter.
In the active position and in operation of the spring mechanism of each cutter the following forces act thereon: The frictional force formed from the product of the contact pressure which acts on the cutter due to the loading of the carrier and which in the case of the construction according to the invention is very small and the friction coefficient, the separating or curring force necessary for removing dirt from the belt and decreases in size in proportion to the increase in the inclina-tion of the cutter towards the underside of the belt, and the actual contact force or pressure. The spring mechanism is set in such a way that it maintains the equilibrium of -the moments formed from the above forces and maintains engagement between the cutters and the belt. Only when unevennesses of the belt and the like strike the cutting edge are forces and moments formed which exceed the opposing moment of the spring mechanism, so that said cutter can be deflected. In the inactive position there are only limited contact and frictional forces which are also counteracted by those of the spring mechanism.
It is also possible to associate a separate spring mechanism with each of the two possible positions of the cutters. However, a torsion spring which can be stressed in both rota-tion directions i5 simpler an~ more reliable. This solution has the aclvan-tage that it is constructionally simple and operationally very reliable because it cannot become soiled and because it can easily be adjusted to the requirements of a reversible operation of the scraper system.
According to a preferred embodiment for stripping off adhesive material and which also permits reversible opera-tion each scraper`comprises two rows with the cutters displaced oppositely to one another. To provide the maximum free space for the passage of the stripped material the rows of cutters are preferably arranged on either side of the carrier on arms which emanate from the latter.
Scraper systems in which two rows of cutters displaced oppositely to one another are arranged on either side of the carrier are preferably used for cleaning belts which have to convey loose materials with a high water content. The rows of cutters positioned downstream have the function of removing residual moisture which the upstream cutters may not have removed from the belt. In this construction it is also possible for the cutters on one side of the carrier to be in the inactive position and those on the other side to be in the active posi-tion! so that in this scraper system one part is active and the other part inac-tive, independently of the belt running direction.
This embodiment is suitable for special purposes.
The invention is described hereinafter relative to non-limitative embodiments and with reference to the drawings, wherein show:
Fig. 1 a side view partly in section of a belt equipped with a scraper system.
Fig. 2 a side view of a detail o~ Fig. 1 showing the position-ing and construction of one cut-ter of the scraper system thereof.

7_ 1~'7;~

Fig. 3 a front view of Fig. 1.
Fig. ~ a diagrammatic side view of a known scraper system.
Fig. S a side view of a preferred embodiment of a scraper and its suspension for the purpose of representing the forces applied.
Figs. 6 to 8 further embodiments of supports and load systems for scrapers.
Figs. 9 to 12a in each case side views and plan views of scrapers with differing arrangements of the cutters.
The belt system shown in exemplified manner in Fig. 1 has 2 frame 1 with pulleys 2, 4 mounted in rotary manner and reversible by means of a motor about which is placed an endless belt 3, which can be driven as desired in a direction indica-ted by arrow 5 and in an opposi-te direction indicated by arrow 5', so that when belt 3 is operating the discharge point is either in the vicinity of guide pulley 2 or in the vicinity of guide pulley 4.
Below belt 3 is provided a scraper system for revers-ible operation which comprises a scraper 6 located below guide pulley 4 and a scraper 7 located below guide pulley 2. Each of the two scrapers 6, 7 comprises a carrier 8 which extends over the width of belt 3 and in the selected embodiment comprising a pipe fixed on either side to in each case one carrying plate 9. A parallel guide comprising two levers 10, 11 is connected to carrying plates 9, whereby in each case one end of the said levers is pin-jointed to the carrying plates 9 and the other end to the bracket 12 fixed to frame 1.
The end of upper lever 11 on the bracket side is Eirmly connect-ed to a shaft 12' pivoted on bracket 12 to which is also fitted a lever 13 loaded by means of a displaceable weight 14. By means of the weight 14 which can be -transferred by lever 13 and lever 10 to carrying plates 9 and carrier 8 the latter is ~7~

guided para]lel to the underside ~' of belt 3.
Arms 15 are fixed -to carrier 8 in longitudinally distributed manner along the same. Upwardly directed supports 16 are mounted on arms 15 either in the arrangement selected in Fig. 1 or in other advantageous manners, examples of which are given in Figs. 9 to 12a. From the upper end of each support 16, constructed as a casting, is bent a square connec-tion 17 which, in the manner shown in the drawing, forms with a square sleeve 19 placed on connection 17 and inserted rubber spring elements 18 a rubber torsion bearing which acts in both rotation directions. Square sleeve 19 forms part of a carrier 20, made for example from cast aluminium, to whose bent upper part can be screwed a cutter 21 whose upper end is provided with a preferably metallic cutting attachment 22.
The rotary resilient mounting of carrier 20 on square connection 17 of support 16 permits a pivotal movement of cutter 21 in two directions. The construction and dimensions of carrier 20 and cutter 21 are made in such a way that when operating belt 3 in the direction of arrow 5 pivot axis A, viewed in the belt running direction, is at a distance a in front of the cutting edge 23 of cutter 21, so that edge 23 can perform a pivotal movement along a circular pa-th 24, whose radius is only slightly larger than the distance h of pivot axis A from the underside 4' of the belt. As can be seen in the drawing distance h is several times larger than distance a.
This arrangement ensures that cutter 21 can be engaged on the ; underside 4' of the belt in the represented inclined position~
This ensures that the material adhering to the underside 4' can easily be peeled or cut therefrom and that along the circu-lar path 24 cutter 21 can pivot out of this active position away from the underside 4' of the belt if the cutter attachment 22 encounters damage on the belt of firmly adhering dirt or _ g , ~ 7~

the like. Due ~o this system the contact pressure exerted by weight 14 on carrier 8 and from the latter to cutters 21 can be kept extremely small.
On reversing the belt running direction into the direction indicated by arrow 5' cutter 21 is driven by belt 3 and is pivoted into the inactive position indica-ted by reference numeral 21'. In this position there is a sliding enyagement between cutters 21 and the underside 4' of the belt which ensures that the cutter 21 automatically returns to the active position when the belt running direction is changed again. If when the cutter 21 is in the inactive position belt damage or the like encounters the back of ~utter 21 due to the con-struction and mounting according to the invention cutter 21 can be deflected for example into the position indicated by reference numeral 21" and can then be returned into position 21' by the rubber torsion mounting. Thus, the advantages of an extremely high stripping capacity in the active position of cutter 21 is combined with the further advantage of safe automatic transfer of the cutter 21 into an inactive position if the belt running direction is changed. As can be gathered from the representation of a known scraper system in Fig. 4 the contact pressures indicated by P and P' therein are not constant because they are dependent not only on the force G
of weight 14, but also to a great extent on the frictional force R, whose magnitude is in turn dependent on the contact pressure and the frictional conditions. Reversible operation is not possible in this case because there is a danger of cutter 25 being drawn into belt 3 in the case of a change of the belt running direction due to the moment brought about by the frictional force R. However, in the construction according to the invention the line of action of frictional force R is as shown in Fig. 5 and passes through the pivot point of the . .
..

load-transferrin~ lever ]1, so that no momen-t caused by frictional force R can be formed and transferred to the cutters.
Thus, the very small contact pressures P are constant.
Figs. 6 to 8 diagrammatically show other embodiments for similar loading systems. together with mounting supports for carrier 8. In place of weight-loading transferred by the levers it is possible for a compression spring 26 or tension spring 27 to act on carrier 8 mounted in the parallel guide 29 (Fig. 6), or alternatively, weigh-t G acts via a cable 30 on carrier 8 (Fig. 7~. Finally in the very simple construction of Fig. 8 an adjustable torsion spring 31 can be used in conjunction with a parallel guide comprising levers.
The inventive system of a scraper system for automatic reversible operation can be used on the most varied arrangements of cutters 21 on carrier 8, as shown in Figs. 9 to 12a. Accord-ing to Figs. 9 and 9a rows of oppositely displaced cutters 21 are provided. According to Figs. 10 and lOa the displaced arrangement is effected by arms which issue from either side of carrier 8, whilst FigsO 11 and lla show a double arrangement in which two rows of cutters 21 are oppositely displaced on either side of carrier 8. In Figs. 12 and 12a two rows of cutters 21 are arranged on either side of carrier 8, but in this arrangement the cutters on one side of the carrier are in the active position and those on the other side thereof are in the inactive position. The represented position of cutters 21 defines the starting position before putting the belt into operation.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A scraper system for reversible belts comprising a first scraper arranged in the vicinity of the first discharge end of a belt and a second scraper located in the vicinity of a second discharge end, one of the two scrapers being in an inactive position and the other in an active position as a function of the running direction of the belt, wherein each scraper is provided with a plurality of cutters which extend over the width of the belt said cutters being individually arranged on an adjustably loaded carrier movably mounted on the carrying frame of belt and moving transversely with respect to belt, the cutters being pressable against the side of the belt which is to be cleaned and are individually deflectable counter to the tension of a spring mechanism, the cutters on the carrier being deflectable about a clearly defined pivot axis in such a way that, viewed in the belt running direction, in the active position it is at a distance a from the cutting edge and on the side and at a distance h from the side of the belt to be cleaned which represents a multiple of the distance a and the cutting edge of cutters is located in front of the pivot axis A in the inactive position, based on the same belt running direction as hereinbefore that the cutters in the case of a reversal of the belt running direction due to the displace-ment of cutters by belt or material adhering to belt are auto-matically pivoted out of the active position into an inactive position and during the next change of the belt running direc-tion are automatically pivoted back from the inactive position into the active position.

2. a scraper system according to claim 1, wherein the carrier is held in a parallel guide.

3. A scraper system according to Claim 2, wherein the parallel guide comprises two levers, whereby the articula-tion axis of the upper, load-transferring lever is level with the side of the belt to be cleaned.

4. A scraper system according to Claim 1, 2 or 3, where-in the spring mechanism is constructed and adjustable in such a way that the cutters are resiliently deflectable in the active and inactive positions.

5. A scraper system according to Claim 1, 2 or 3, wherein the spring mechanism is a torsion spring, particularly a rubber torsion spring.

6. A scraper system according to Claim 1, wherein each scraper comprises two rows of oppositely displaced cutters.

7. A scraper system according to Claim 6, wherein the rows of cutters are arranged on either side of the carrier on arms which issue from said carrier.

8. A scraper system according to Claim 6, wherein two rows of cutters are arranged in oppositely displaced manner on either side of the carrier.

9. A scraper system according to Claim 8, wherein the cutters on one side of the carrier are in the active position and those on the other side of the carrier are in the inactive position.