GB2061220A

GB2061220A - Cable scraper device

Info

Publication number: GB2061220A
Application number: GB8032229A
Authority: GB
Original assignee: Elba Werk Maschinen GmbH and Co
Current assignee: Elba Werk Maschinen GmbH and Co
Priority date: 1979-10-24
Filing date: 1980-10-07
Publication date: 1981-05-13
Also published as: DE2942915B1; FR2475092B1; GB2061220B; DE2942915C2; MX152957A; JPS56103029A; FR2475092A1

Abstract

A cable scraper device (1) for conveying loose materials, in order to charge a feeder (2) comprising a rotatable chassis (5) disposed on the feeder and to which a jib (6) with a free end is pivoted and in which a hoisting cable (9) and a return cable (10) for moving a scraper bucket (8) are guided in mutually independent cable slings over two cable drums which can be connected either freely rotatably or, by way of clutches, torsionally rigid to a common drum shaft which is supported in the chassis and driven by a non-reversible winding drive. According to the invention, there is provided a supplementary drive which during automatic operation supplements the drive for the scraper drum which winds the hoisting cable during the scraping operational stage, and during the return operational stage acts on the scraper drum in such a manner that the hoisting cable and return cable move with approximately the same cable speed. <IMAGE>

Description

SPECIFICATION Cable scraper device The present invention relates to a cable scraper device for conveying loose materials, in particular building materials, in order to charge a feeder for concrete preparation plants in which aggregates are stored in storage areas about the feeder and are banked up against this latter, for manual or fully automatic operation at choice, comprising a rotatable chassis disposed on the feeder and to which a jib with a free end is pivoted, and in which a hoisting cable and a return cable for moving a scraper bucket are guided in mutually independent cable slings over two cable drums which can be connected either freely rotatably or, by way of clutches, torsionally rigid to a common drum shaft which is supported in the chassis and driven by a non-reversible winding drive.

Such cable scraper devices are known, and are characterized by the fact that their working cycles are matched to manual operation during the so-called automatic operation, and their automatic operation is programme-controlled in such a manner that both the scraping process and the swivel process between one storage area and another proceed automatically.

A cable scraper device of the initially described type is known from DE-AS 25 36 557, wherein during the decisive stage of the return operation, the scraper bucket is kept suspended such that the return cable clutch and the uncoupled hoisting cable drum prevent lowering of the scraper bucket by application of the brake of this cable drum with a smaller braking force. When under automatic operation, this known device operates with automatically controllable regulating units which engage with the manually operable control rods of the clutches and brakes. These control rods (shift levers) are moved by this coupling arrangement during automatic operation, and this makes the suitability of the device as a so-called combination device more than questionable.

The known system dispenses with the reverse operation of the winding drive, which can only be attained by electrical reversing devices. This seemingly simple scraper concept, for which automatic operation - at least with regard to the mechanical and motor part - is attained for the same capital cost as the manually operated version, is however difficult to control when in automatic operation during the return stage.This is because whereas the brake which during the return keeps the bucket suspended, namely the hoisting drum brake, can be controlled by means of a foot pedal by the bucket operator when in manual operation in such a delicate extent that it can be matched to the physical conditions of the friction between the brake band and brake disc, this is only possible to a limited extent or not at all during automatic operation. with regard to its effective braking moment, the brake is subject to so many indeterminate influences that a properly limited braking moment which is matched to an optimum degree to the return process cannot be attained.The braking moment, which (matematically) theoretically is dependent only on the braking force, friction coefficient, brake disc diameter and embracing angle, varies as a function of the weather, air humidity, friction coefficient of the brake lining, constancy of the friction coefficient with temperature, increasing temperature during increasing time of operation, and condition of the brake (correctly set, no play in the linkages etc.), and thus the necessary uniformity of the return motion is disturbed. During lengthy daily operation, the brake can become completely uncontrollable in terms of its operation, and this can lead to destruction of the winding system or the jib.

Aid is provided in the form of electronicpneumatic control; however this means that the advantage of simple mechanical construction is nullified. As the requirements which can generally be set for the operating personnel of such a plant cannot be put very high, the possibilities of such a control are mostly not utilized.

In the case of manual operation of the cable scraper device, i.e. during manual scraping, afterthe scraper bucket has been filled, the bucket is so controlled by the scraper superintendent that by tightening the return cable or locking it, the scraper bucket is guided over the surface of the supply store to the so-called active store of the feeder, and thus covers the path of the lowest resistance independently of the shape of the supply store mound.

However, under automatic operation, this varying type of bucket guide is not possible, unless the amount spent on the control system bears no relationship to the total cost of the machine. Unless the guiding of the return cable is controlled in such a manner, the scraper bucket does not take the path of least resistance, but the shortest path, whatever the shape determined by the supply store. In the extreme case, the bucket has to actually pass through the supply mound.

The different resistance which is encountered during the scraping process under manual and automatic scraping thus requires, in the case of so-called combined scraper devices, a motor power for the winding drive which is higher than that which would be required for only a manually operated scraper. However, for safety reasons the winding drive is sized according to the required power for automatic operation, and this means that during manual operation the winding drive is considerably over-sized.

A cable scraper device for manual and automatic operation is already known from DE-OS 27 07 289, which operates with a reversible drive motorforthe cable drums. In this configuration, the return of the scraper bucket is carried out by a special return motor switched to the direction of rotation for bucket return, which keeps the scraper bucket suspended, in cooperation with the hoisting cable motor, which after the scraping process is likewise reversed to the return direction of rotation. The described scraper principle with a reversible drive formed by built-in motors finds however its main limits where directon-line starting and reversal of rotational direction are limited by the supply mains.

The present invention aims to provide a cable scraper device of the initially described type, in which on the one hand the supply mains does not have to be taken into consideration because of the use of a non-reversible motor for the winding drive, and on the other hand the stated drawbacks in connection with the known concept described in DE-AS 2536 557 are obviated.

The present invention provides a cable scraper device for conveying loose materials in order to charge a feeder for a concrete preparation plant in which aggregates are stored in storage areas about the feeder and are banked up against the latter, the device comprising a rotatable chassis disposed on the feeder and to which a jib with a free end is pivoted, and in which a hoisting cable and a return cable for moving a scraper bucket are guided in mutually independent cable slings over two cable drums which can be connected either freely rotatably or, by way of clutches, torsionally rigid to a common drum shaft which is supported in the chassis and driven by a non-reversible winding drive, and further comprising a supplementary drive which during automatic operation supplements the drive for the scraper drum which winds the hoisting cable during the scraping operational stage, and during the return operational stage acts on the scraper drum in such a manner that the hoisting cable and return cable move with approximately the same cable speed.

By the scraper drum there is meant that cable drum over which the hoisting cable is guided.

The supplementary drive can be suitably coupled and uncoupled during the scraping operational stage according to the force to be applied, and is preferably connected to the scraper drum by way of a chain drive.

The supplementary drive may be substantially in the form of a reversible motor which when under automatic operation can be connected to the scraper drum by way of clutch.

The power ratio of the non-reversible motor for the cable drums to the motor for the supplementary drive is preferably approximately 4:1.

The supplementary drive may be also brought into play during the lowering of the scraper bucket into its initial position.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a general view of a cable scraper device mounted on a feeder, and indicating the progression of the working stages; and Figure 2 is a schematic view of the drive of the cable scraper device shown in Figure 1.

Figure 1 shows a cable scraper device 1 mounted on a feeder 2 which acts as the rear closure for sector-shaped aggregate storage areas 3, and against which the aggregates 4 are banked up. The cable scraper device 1 consists substantially of a rotatable chassis 5, a jib 6 pivoted to the chassis and having a free end 6', a jib stay arrangement 7, a scraper bucket 8, a hoisting cable 9, a return cable 10, a remote control and indication device 11, and a cable 12 for protecting the operator during manual operation.

Figure 1 shows certain basic positions of the scraper bucket 8 during the progress of its movement. In position I, the scraper bucket 8 conveys loose material to the active store of the feeder 2. In position II, the empty scraper bucket, suspended overthe loose material store, is guided backfrom the feeder 2 to the end 6' of the jib. In position lil, the scraper bucket is lowered back from the end of the jib to the lose material store. During automatic operation, the progress of the scraper bucket is accomplished completely automatically between positions I and Ill.As the drive allows change-over from automatic operation to manual operation, a further possibility is provided during the progress of the scraper bucket 8, namely that during manual operation it can be thrown outwards by the operator beyond the jib end 6', so that any further aggregates which otherwise could not be reached during the automatic operation of the cable scraper device can be picked up.

Figure 1 shows indicatively only one sectorshaped aggregate storage area. In actual fact, a number of such sectors are disposed adjacent to each other, and, under fully automatic operation, these will be worked one after the other.

The drive for the cable scraper device can be seen from Figure 2. Awinding drive 21 for the cable scraper device 1 drives, by way of a chain drive 22, a drum shaft 23 the direction of rotation of which is continuously in the direction for winding the hoisting cable 9 on to a scraper drum 24. A return drum 25 is supported on the drum shaft 23 in addition to the scraper drum 24. These drums can be coupled in a non-positive (torsionally rigid) manner by way of clutches 26 and 27 to the drum shaft 23, so that, in the stated direction of rotation, they either move the hoisting cable 9 with the scraper bucket 8 in the scraping direction, or the return cable 10 with the scraper bucket 8 in the return direction.The scraper drum 24 can be braked by a first brake 28 when it is in a free condition with no non-positive connection between the clutch 26 and the drum shaft 23.

Likewise, the return drum 25 can be braked by a second brake 29. In the case of large scraper devices, the clutches 26 and 27 are preferably in the form of internal band brakes with pneumatic operation, and during manual operation these can be shifted by corresponding valves. Purely manually operated mechanical clutches require either large shifting forces or long shifting paths if the shifting force is small, and are thus at the present time impractical.

Instead of pneumatically operated internal band clutches, electromagnetic disc clutches can be used.

The first brake 28 is preferably in the form of a band brake, and is operated by a single acting pneumatic cylinder with spring return, by way of a foot valve.

The second brake used for the return drum 25, preferably in the form of a disc brake, is also operable by a foot valve.

The hoisting cable 9 and return cable 10 are guided on to the cable drums 24 and 25 in the normal manner by way of deviation stations 32 and 33 supported on the machine chassis. A cable deviation roller 34 at the jib end 6' guides the return cable 10.

By means of the components described up to this point, manual scraping can be carried out with the cable scraper device in the normal manner, in that a complete scraping cycle can be executed by corresponding operation of the valves for the drums 24 and 25, i.e. the foot valves of the brakes 28 and 29.

The up-grading of this manual scraper to an automatic device or a combined device, i.e. with selective manual or automatic operation, is done by means of the components described hereinafter, which are advantageously so constructed and arranged that they can also be subsequently incorporated into a device originally built as a manual scraper.

To this end, a supplementary drive 37 is provided in the form of a geared motor with a smaller power than the winding drive 21. The ratio of the drive power of the winding drive to that of the supplementary drive 37 is about 4:1. The supplementary drive 37 is fitted with a normal brake 38 for geared motors, and is connected to the scraper drum 24 by way of a chain drive 40. This connection can be released by way of a mechanical clutch 41 and a clutch lever 42, so that during manual operation the clutch is disengaged, and the supplementary drive 37 has no active connection with the scraper drum 24. An electropneumatic limit switch is operated by the clutch lever 42, so that when the lever is in the automatic position, any unauthorised manual operation by means of the unintentional operation of the valves of the clutches 26 and 27 and brakes 28 and 29 is prevented.

The supplementary drive 37, which is connected to the scraper drum 24 by way of the chain 40 and clutch 41, is so arranged that its power when rotating in the scraping direction is added to that of the winding drive 21, if the scraper drum 24 is coupled to the drum shaft 23 by means of the clutch 26.

For automation, a further two cable path switches 50 and 52, known as the scraper drum limit switch and return drum limit switch, are necessary. These two limit switches, which comprise a number of switch contacts corresponding to the travelling positions during the working cycle, are connected directly by way of chains 51 and 53 to the cable drums 24 and 25, so that every longitudinal movement of the cables 9 and 10 leads to a rotation of the limit switches 50 and 52. The individual trip cams can be adjusted relative to each other, and can be set according to the various geometrical relationships of the scraper path, return path, outswing arc and lowering height to each other, as determined by the jib projection.

For completing the automation, a further electrical eddy-current brake 48 is provided, which engages with the return drum 25 by way of a chain drive 49.

An electromagnetic isolating clutch 54 can also be provided as a component part of the winding drive 21, as it enables the continuously running motor to be isolated from the gear portion during automatic operation.

The operation of the drive described above for a cable scraper device is as follows: With reference to Figure 1, the working cycle of the scraper begins at point I. The scraper bucket 8 lies at the foot of the material store. The winding drive 21 rotates in the scraping direction, so that the scraper drum 24 winds up the hoisting cable 9. The clutch 26 is coupled to the drum shaft 23. Previously, the clutch 41 will have been shifted to the automatic position by means of the clutch lever 42. By this means, the supplementary drive 37 is connected in a non-positive and form-fit manner to the scraper drum 24 by way of the chain 40. The supplementary drive 37 rotates likewise in the scraping direction, and its power acts additionally to that of the winding drive 21.

The two drives now pull the scraper bucket 8 to position 1'. In this position, which lies about 2-3 m in front of the cable entry stations 32 and 33, the limit switch 52 of the return drum is activated, and its brake 29 is applied. This prevents the return cable 10 being further unwound. The drives 21 and 37 continue to run, and lift the scraper bucket 8 out of the material while the return cable 10 remains at rest. The scraper bucket is emptied. The limit switch 50 of the scraper drum 24 is activated in position 1".

The clutch 26 of the scraper drum is disengaged, and the flow of force between the winding drive 21 and drum shaft 23 is interrupted. Simultaneously, the supplementary drive 37 is halted, and the motor brake 38 applied. The scraper bucket 8 now hangs, retained by the brakes 29 and 38, freely between the taut cables 9 and 10. This prevents the scraper bucket from being deviated into a possibly empty active store.

Furthermore, the clutch 27 of the return drum 25 is engaged in position I" by a corresponding limit switch. By this means, the return drum 25 is positively connected to the winding drive 21. The return cable 10 is then wound on to the return drum 25 in the return direction by the winding drive 21 which is running in the same direction as previously.

Simultaneously with the shifting of the clutch 27, the brake 29 is released. Because of the changed direction of rotation of the return drum 25, the previously closed limit switch 52 is again opened.

The supplementary drive 37 is now coupled in the direction for unwinding the hoisting cable 9, with simultaneous release of the motor brake 38 of the supplementary drive 37. The scraper bucket 8 thus hangs between the taut cables 9 and 10, and moves in accordance with the synchronously rotating cable drums 24 and 25 along the jib 6 in the direction of position Ill. Finally, in this position the limit switch 52 is operated.

The further progress, i.e. the transfer of the scraper bucket to position Ill' and finally its lowering into position I can take place in various ways.

Outswing - Possilwility 1 The clutch 27 is released, and by this means the flow of force between the winding drive 21, chain 22, drum shaft 23 and return drum 25 is interrupted.

Simultaneously, the brake 29 is applied. The movement of the return cable 10 is thus ended. The supplementary drive 37 now runs further, as previously, in the unwinding direction and the scraper drum 24 releases the hoisting cable 9. The scraper bucket 8 thus swings, while hanging on the restrained return cable 10, about a pivot formed by the deviation roller 34 at the end 6' of the jib, until it reaches position Ill'.

In this position, the limit switch 50 is activated and uncouples the supplementary drive 37. At the same time, the brake 38 of the supplementary drive 37 is applied.

Outswing - Possibility 2 The clutch 27 is opened, and the flow of force between the winding drive 21, chain 22, drum shaft 23 and return drum 25 is interrupted. The brake 29 is simultaneously applied, by which the movement of the return cable 10 stops. Current is removed from the supplementary drive 37, and the brake 38 is kept disengaged. By virtue of its weight, the scraper bucket 8, suspended from the return cable 10, swings about the pivot represented by the deviation roller 34 into position Ill'. In this position, the limit switch 50 is activated, and applies the motor brake 38 of the supplementary drive 37.

Lowering-Possibility 1 Simultaneously with the activation of the limit switch 50, the brake 29 is disengaged. The scraper bucket 8 then moves vertically downwards by virtue of the unwinding of the return cable 10. The contact pressure of the brake 29 is electropneumatically controlled as a function of the rotational speed of the return drum 25 and the friction characteristics between the jaw and disc of the brake 29 during the descent of the scraper bucket, and it thus arrives at the initial position I with a controlled speed. A new working cycle can begin after the tripping of a preset time relay which starts when position III' is attained.

Lowering - Possibility2 The basic progression is as previously described.

However, the lowering speed is now monitored instead of the stated electropneumatic control, by means of an electrical eddy-current brake 48, which is connected by a chain 49 to the return drum 25. The characteristic of this eddy-current brake 48 enables the lowering speed to be influenced by an adjustable resistance. A lowering motor can be used instead of the eddy-current brake.

Lowering - Possibility 3 On reaching position Ill', which in this case desirably does not lie vertically below the deviation roller 34 of the jib 6, the supplementary drive 37 continues to run. Its brake 38 remains disengaged.

By means of an electromagnetic clutch 54 between the motor part and the gear part of the winding drive 21, the flow of force to the drum shaft 23 is interrupted and this latter comes to a halt. Simultaneously, the clutches 26 and 27 are engaged, so that the return drum 25 is connected by way of the drum shaft 23 to the scraper drum 24 which is already rotating in the cable unwinding direction, and the return cable 10 likewise becomes unwound.

The scraper bucket 8 is lowered towards position I.

In this modification, it is desirable to fit the supplementary drive 37 with a pole-changeable motor so that the lowering process of the scraper bucket from position Ill' to position I can take place with a decreased speed.

Finally, it should be noted that the presently described cable scraper device characterised by the supplementary drive completely fulfils the requirements in a satisfactory manner. A preferred embodiment is characterised in that the supplementary drive can be coupled and uncoupled in accordance with the motor loading, i.e. in accordance with the opposing pressure acting on the scraper bucket.

Claims

1. A cable scraper device for conveying loose materials in order to charge a feeder for a concrete preparation plant in which aggregates are stored in storage areas about the feeder and are banked up against the latter, the device comprising a rotatable chassis disposed on the feeder and to which a jib with a free end is pivoted, and in which a hoisting cable and a return cable for moving a scraper bucket are guided in mutually independent cable slings over two cable drums which can be connected either freely rotatably or, by way of clutches, torsionally rigid to a common drum shaft which is supported in the chassis and drive by a non-reversible winding drive, and further comprising a supplementary drive which during automatic operation suppiements the drive for the scraper drum which winds the hoisting cable during the scraping operational stage, and during the return operational stage acts on the scraper drum in such a manner that the hoisting cable and return cable move with approximately the same cable speed.

2. A cable scraper device as claimed in Claim 1, wherein the supplementary drive can be connected and disconnected during the scraping operational stage according to the force to be applied.

3. Acable scraper device as claimed in Claim 1 or 2, wherein the supplementary drive is connected to the scraper drum by way of a chain drive.

4. A cable scraper device as claimed in one of Claims 1 to 3, wherein the supplementary drive is substantially in the form of a reversible motor which when under automatic operation can be connected to the scraper drum by way of a clutch.

5. A cable scraper device as claimed in Claim 4, wherein the power ratio of the winding drive to the supplementary drive is approximately 4:1.

6. A cable scraper device as claimed in one of Claims 1 to 5, wherein the supplementary drive can be connected to the cable drums in such a manner that should its connection to the winding drive become interrupted, it steers the scraper bucket through its lowering process to its initial position.

7. A cable scraper device as claimed in Claim 6, wherein the motor of the supplementary drive is a pole-changeable motor.

8. A cable scraper device according to Claim 1, substantially as herein described with reference to, and as shown in, the accompanying drawings.