GB2120631A - Method for handling stockpiled granular material - Google Patents

Abstract

A method of handling stocks of granular materials in stockpiles, using at least one stacking-recovering machine characterized in that each stacking-recovering machine is automatically controlled with the aid of a control station linked to appropriate detectors, said control station being programmed so that: a. the maximum difference in height between any two points on the ridge of stacked material is never substantially greater than that caused by the last pass of the machine, b. the translation speed of the machine is continuously calculated as a function of the normal input and/or normal output of material. ,

Description

SPECIFICATION Method for handling stockpiled material particularly granular materials The present invention concerns a method for handling stockpiled material, particularly granular materials such as, for example, coal, phosphates, grain and similar materials. The invention includes a stacking-recovering machine and an associated installation arranged to carry out the method.

A machine is known which is particularly well-adapted to the stacking and recovering of a given granular material (U.S. Patent No. 4.018.323). In essence, this machine consists of a self-propeiled platform whereon one extremity of a boom is pivoted, the boom being adjustable in a vertical plane and incorporating two endless chains linked together by scrapers. Means are provided for driving the chains in one direction for stacking the material, and for driving these chains in the reverse direction for recovering the material, the scrapers being the active element in both operations.

In other words, the material is pushed forward by the scrapers on the underside of the boom when stacking and scraped back by the same scrapers on the underside of the boom when recovering.

Means are also provided for controlling the angular position of the said boom. At least one conveyor belt is envisaged for delivering the material to the machine (with an intervening device for raising the conveyor belt, this device forming an integral part of the machine) as well as for removing the recovered material. The said platform additionally incorporates a by-pass arrangement, which allows all or part of the material deiivered to the machine to be fed straight through.

The said platform also features a cabin which houses the controls and provides accommodation for an operator who must be in constant attendance during the working of the machine.

Many variations of such a machine are possible within the framework of the present invention.

For example the platform could be replaced by a gantry mounted on rails situated on both sides of the stockpile of material, at the same level or otherwise.

To clarify the description certain specific terms which will be used are defined below: stockpile: a heap of material in the general form of a prism, having a triangular cross section and having a pyramidal aspect at the extremities; stockpile end: end of a stockpile having a pyramidal aspect/ ridge: highest point of the prismatic heap, which thus excludes the pyramidal extremities.

free face; the longitudinal free face on the far side of the prismatic part of the stockpile not subjected to boom action.

stockpile width: base length of the triangular section of the stockpile.

translation speed: displacement speed of the machine along a stockpile.

boom angle: the angle made by the boom axis at a given moment with the horizontal or alternatively with the vertical.

stacking: mode of machine operation wherein material brought thereto is piled.

recovering: mode of machine operation whereby the material is taken by the machine for deposit elsewhere.

stacking/recovering: mode of machine operation whereby a part of the material arriving at the machine is by-passed, the remainder being stacked.

pass: machine displacement in any operating mode, but in the same direction and with the same boom angle.

pass cross-section: cross sectional area of the layer stacked or reclaimed during a pass.

control station: devices capable of processing and/or memorizing the incoming data in keeping with a pre-arranged program, and of generating therefrom output signals for the machine operation and where necessary memorizing these signals.

When stacking or recovering materials in or from a stockpile or stockpiles it is essential that the shape thereof be as regular as possible for two principal reasons: optimal stocking capacity and especially precise and constant recovery output. The latter reason is particularly important when the recovery process feeds installations associated with the stockpile.

If, for example, a heating centre is to be fed with coal, a constant recovery process avoids the need to provide large buffer-hoppers.

A well-regulated recovery output permits the constitution of precise blends from two stockpiles of different materials, for example, from fine coal and larger-sized coal without the need to feed two two sizes through mixing hoppers.

Using current stockpiling systems, even those employing the stacking-recovering machines described above, it is practically impossible to assure a consistency of stockpile form sufficiently accurately. The human element is the overriding drawback, taking into account the numerous factors the operator must continually survey (such as interruptions of incoming material, irregular modes of operation following one another, inability to see the entire ridge), not to mention the manual dexterity required (difficulties with the stockpile ends) and the continual vigilance.

The purpose of the present invention is to furnish a particularly advantageous solution to these problems.

Generally, a method of handling stocks of material in stockpiles using this invention consists in controlling automatically each stacking recovering machine involved with the aid of an automatic control station equipped with appropriate detectors, said control station being programmed in such a manner that: a.-the maximum difference of height between any two points on the ridge of stockpiled material is never substantially greater than that caused by the last pass, bathe translation speed is continuously calculated at least as a function of the nominal input and/or the nominal output of material.

It is essential, therefore, to measure the arrival rate of the material when stockpiling in order to calculate the machine's translation speed, as well as the distance between the machine and the measuring station.

Preferably, also, the recovery rate is measured and if necessary, the translating speed is adjusted as a function of the difference between this measured recovery rate and a predetermined rate. This double stockpiling/recovery weighing permits of an exact inventory of the stock. When operating in the stockpiling/recovery mode, the translation speed is calculated as a function of the difference between the two measured values.

In any case, a stacking-recovering machine having a boom length substantially equal to the stockpile width is chosen in order to assure that the offside face (the free face) is always in the same plane, irrespective of stockpile height.

This particularly important for preserving the consistency of the pass sections.

In a preferred application of this invention, changes in the boom angle are brought about in steps, differing one from the other, but calculated so that the pass sections remain constant irrespective of boom angle.

Alternatively, changes of boom angle can be made in equal steps, the translation speed then being adapted to the pass section which results therefrom.

Yet another solution consists in modifying the boom chain speeds, with or without constant translating speeds, but in constant steps.

Whatever the operating mode, the end of the run at the stockpile extremity is calculated as a function of boom angle for the pass under consideration, stopping taking place to the right of the theoretical ridge extremity corresponding to the given boom angle.

To satisfy the condition of maximum permissible variation between any two points on the ridge, it is essential to recognize and/or memorize the direction and operating mode of the last pass in order to determine the direction of the following pass as a function of the operating mode for the latter.

The following table sets out the new instructions as a function of the memorized state.

New stacking function Former state New translation direction Stacking towards the right Towards the right Recovery towards the right Towards the left Stacking towards the left Towards the left Recovery towards the left Towards the right New recovery function Former state New translation direction Stacking towards the right Towards the left Recovery towards the right Towards the right Stacking towards the left Towards the right Recovery towards the left Towards the left It must be pointed out, that "stacking" can be replaced by stacking/recovering.

An improved stacking-recovering machine which can be used for the application of the method described above differs from the convention machine insofar as it is equipped with a control station connected to a control desk and with a number of sensors or detectors associated with the said control station, permitting at least measurement of the boom angle, the direction of machine translation, the state of the bypass and the end stops at the stockpile extremity.

It is evident that the machine can be equipped with security detectors for its automatic functioning.

An installation according to the invention incorporates, in addition to the usual infrastructure having an arrival station for the materials, an endless conveyor belt for transporting the material from the arrival point to one or more stacking-recovering machines-improved as described above-and thence to the discharge point, and at least one means for measuring throughput upstream from the stockpile (associated with the conveyor belt) the measuring means being connected to the control station.

Preferably, a second device for measuring throughput should be incorporated in the conveyor system, downstream from the stockpile.

If two or more stockpiles are to be handed, branch conveyors could be installed with switchover arrangements, the installation having the required number of devices for measuring throughput.

It is evident from the foregoing overview, that the invention lends itself to numerous practical forms depending on the specific stockpiling problems.

Claims (13)

Claims

1. A method of handling stocks of materials in stockpiles, using at least one stacking-recovering machine of the type as herein defined characterized in that each stacking-recovering machine in the installation is automaticaliy controlled with the aid of a control station linked to appropriate detectors, said control station being programmed so that: a.-the maximum difference in height between any two points on the ridge of stacked material is never substantially greater than that caused by the last pass, b.-the translation speed is continuously calculated at least as a function of the nominal input and/or nominal output of material.

2. A method according to claim 1 wherein from one pass to the next succeeding pass modifications of the angle of the boom are made in steps, differing from one another, but calculated so that the section of the pass is constant for all boom angles.

3. A method according to claim 1 , wherein from one pass to the succeeding pass, the boom angle remains constant, and the translation speed is so modified that the cross section differences of the passes are compensated.

4. A method according to claim 1 and/or 3 wherein from one pass to the next succeeding pass, the boom angle remains constant, and the chain speed is modified to compensate for the differing cross sections of the passes.

5. A method according to claim 1, wherein the input, at least, is measured to enable the translation speed to be calculated, taking into account said translation speed as well as the distance between the machine and the measuring point.

6. A method according to claim 5, wherein the output of recovered material is measured and, where necessary, the translation speed is adjusted as a function of the difference between this measurement and the desired output value.

7. A method according to claim 6, wherein the input and output of material are measured enabling a stockpile inventory to be established.

8. A method according to any of the preceding claims wherein in the end of a run at the stockpile extremity is calculated, and a stop is effective at the extremity of the stockpile theoretically corresponding to a given boom angle.

9. A method according to any of the preceding claims wherein the sense of the operating mode of any one pass is recognized and/or memorized in order to determine the sense of the next succeeding pass as a function of the operating mode required therefor.

10. A stacking-recovering machine for carrying out a method as claimed in any of claims 1 to 9 said machine being equipped with a control station linked to a control desk and several detectors associated with the control station, thereby permitting the detection of, at least, the boom angle, the translation direction of the machine, the position of the machine with regard to a reference point, the state of the by-pass, and the ends of the run at stdckpile extremities.

1 An installation for carrying out a method as claimed in one or more of claims 1 to 9, using at least one machine according to claim 10, incorporating the conventional infra-structure of an arrival station for material, an endless conveyor belt for transporting material to the machine and from the machine, and having at least one means of measuring throughput upstream from the foot of the boom, this measuring means being linked to the said control station.

12. An installation according to claim 1 wherein at least one means of measuring throughput of material is associated with the said conveyor, but downstream from the foot of the boom.

13. A method of handling stocks of materials in stockpiles as claimed in claim 1, substantially as hereinbefore described.

1 4. A stacking-recovering machine, substantially as hereinbefore described.