GB2139980A - Process for the partial renewal of flights of chain belts in trough conveyors - Google Patents

Abstract

A process for the partial renewal of flights of chain belts in trough conveyors, especially those in underground operations, in which abraded partial areas of the flight are brought to specified size, includes operating a tool 34 with rectilinear motion to press into at least one of the two surfaces or into a longitudinal surface of the part to be repaired that is perpendicular to said surface and local pressure is applied and the area of the part to be renewed is compressed with the material displaced into a cavity 37 of a drop-forge die 30 that has the specified dimensions of the flight. <IMAGE>

Description

SPECIFICATION Process for the partial renewal of flights of chain belts in trough conveyors The invention concerns a process for the partial renewal of flights of chain belts in trough conveyors, in particular in underground operations.

In underground operations, particularly those of pit-coal mining, chain conveyors solve the most diverse conveying problems because of the low and at the same time stable form of their stationary component assembled out of steel troughs linked together. The conveying agent, consisting of one or several parallel chains and the flights is, however, subjected to heavy demands. As a result, the flights above all are subject to severe abrasion. As the guidance of the conveying agent takes place with the flight ends in the longitudinal profiles of the con veyortroughs, it is, according to experience, at these places that the material of the flights is worn away most powerfully and most quickly. In this manner the flights already become in need of repair before they are perceptibly weakened between the ends.

The partial renewal of such flights extends therefore in the first place to the ends and makes possible a repeated use of the centre sections of the flights before the flights have to be scrapped.

It is, of course, possible to counteract the abrasion of the chain beds of such a flight. This happens, for example, with two-part flights whose plane of division runs parallel and angular to the longitudinal central plane of the flight and through a positive lock which is provided by slot- and key connections in the upper and lower parts as well as being brought about by bolts that pass through the two parts of the flight perpendicularly to the plane of division. Nevertheless even with these flights the chain beds become worn down in the long run because of the operating loads. This leads to the necessity of permaturely scrapping the centre sections of the flights too. A prerequisite for the partial renewal of the flights is that the repaired flights are true to size and that the repair produces no loss in tensile strength in the flights.It is further decisive for the partial renewal that the associated losses of material are kept within bounds.

The invention stems from an already known process with which the flight ends can be renewed, but which does not satisfy these requirements to an acceptable extent and which also demands an excessive outlay of labour. This known process consists in burning off the flights, irrespective of their varying abrasion, along a specified transverse plane and welding on replacement parts that correspond exactly to the burnt-off ends with the aid of a surrounding fillet weld. These replacement parts cannot be sufficiently precisely adjusted, so that the accuracy to size of the repaired flights is not reliable.

The welding operation leads to the annealing of the replacement parts, so that an appreciable loss of tensile strength arises in the area of the weld seam.

The quality of the partially renewed flights therefore does not attain that of the new article. The process already known leads to considerable losses of material, because in process of burning off the flight ends their entire remaining cross-section has to be scrapped. The process is furthermore not applicable to the replacement of the chain beds.

However, flights whose ends are repaired according to another known process are, by contrast, of appreciably superior quality. In this process, flights that are in need of repair are singled out in the first instance and then their abraded ends are ground according to the abrasion at any given time. The missing material is brought up to excess through resurfacing welding. The surplus material from the resurfacing welding is then removed by grinding.

The resurfacing welding leaves behind an inordinately hard and abrasion-resistant texture, so that the flights renewed accordingly exhibit characteristics which are at least equivalent to those of new parts, but even surpass these in some cases. The process leads to a minimum in material losses, but demands an inordinate expenditure. The latter is based on the one hand on the numerous machining operations that are required for this process, and of which in particular the resurfacing welding is carried out by hand, i.e. cannot be rationalised or can only be rationalised with difficulty. On the other hand the outlay is to be ascribed to the mechanical technological equipment, in particular the machine required for grinding, that is necessaryforthe absolute accuracy to size of the reconditioned flights.

Not yet in the realm of the previously published state of technology is a further process for the partial renewal of the flights through trough-shaped replacement parts, which are superimposed on the flights after the latter have been ground to a wedge shape and which substantially obviate avoidable material losses in a simple manner as well as losses of tensile strength. In addition this process yields an accuracy to size on the part of the reconditioned flights which corresponds to that of new parts.

However, it too is not suited to the renewal of the chain beds.

It is peculiar to the partial replacement processes that pertain to the state of the art that at the flight ends, i.e. the so-called blocks of the flights by which the latter are guided in the troughs, are limited to a specific degree of abrasion, because they can only replace a specific quantity of material. In general, however, entire chain belts are delivered to the repair works in an assembled state, and the partial renewal of the flights has to begin by singling out those flights which according to known processes can no longer be renewed, because the abrasion at the blocks is too marked and/or the chain beds are worn down. Up to the present there has been no question of a partial renewal of these flights. Consequently the incidence of scrapping in the repair of chain belts is considerable. On the other hand the input of weldable metal and shoulderpieces is appreciable.

The object of the invention is to conduct the process initially expounded as known in such a way that the incidence of scrapping is reduced and new material is not required, in process of which the partially renewed flights are to be brought to their requisite final tensile strength with known measures.

According to one aspect of the invention there is provided a process for the partial renewal of flights of chain belts in trough conveyors, especially in underground operations, in which abraded partial areas of the flight are brought to specified size, by forcing a tool with rectilinear motion into at least one of two surfaces or into a longitudinal surface of the part to be repaired that is perpendicularto said surface and local compression takes place, with the material displaced being forced into a cavity of a drop-forge die that has the specified dimensions of the flight.

According to a further aspect the invention resides in an installation for executing the process, including a two-part drop-forge die with a horizontal plane of division which runs in the longitudinal direction of the flight, an upper matrix serving as a tool which has a cavity corresponding, with the exception of the tool, to the flight sector directed towards it, a lower matrix with a cavity corresponding to the specified dimensions of the flight sector directed towards it, ejectors extending through cutouts directed towards them in the cavity in the lower matrix and further stamps which serve to make the hollows in the flight ends and are guided through horizontal cutouts in one or both matrices.

The solution stems from pressing material at points of the flight which either are considerably unsusceptible to this, or from attaining by means of pressure on the material, a gain in tensile strength in consequence of the increase in tensile strength of the mold associated with the indentation, which counteracts again, at least in part, the effect of the weakening. This adaptation of the local conversion of the flight to its wear and tear in the operation of the chain belt makes possible a moving of material which allows the worn material to be put into operation without practical losses of tensile strength and thereby bring the part to be repaired up to its specified dimensions.

In new production, involving pressure by forging at least once, in a closed die, the flights are produced with an addition of material which is determined by the requirement to fill the drop-forge die and by the unavoidable pressure ridge. Through the fact that, in this process, only local pressure is applied, no reserve of material is needed even when abrasion has progressed far, to take away at another point in flight the material necessary for its elimination. As on the other hand the partial renewal of the flights, like their new production, is effected through forging, the partially renewed and the new production flights are alike in this respect.Consequently the partially renewed flights can be subjected to a subsequent heat treatment, which corresponds to that for the new production flights, so that the same ultimate tensile strength is established for the partially renewed flights as in the new production flights.

In this process the piece to be repaired may be bellied out on the chain bed side by means of forcing of material and, through this, the cavity of the die is filled. As relatively little material is necessitated for this, the reduction of the material arising through the slot in an underside or upper side of a flight plays no practical role.

A relatively large quantity of material may be removed from the flight, so that even considerable abrasion of the blocks can be compensated for. As the bending loads in the blocks are relatively low in comparison with the loads of the central section of the flight and the bowl shape of the hollows does not lead to local concentrations of tension in the flight, the flights partially renewed in this way likewise have a good ultimate tensile strength.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a known flight for dual central chains viewed after partial renewal of its chain beds and its blocks, Figure 2 is a plan view of the device of Figure 1, Figure 3 shows in outline and in vertical section a multi-part drop-forge die constructed in accordance with the invention, with which the process described is executed, Figure 4 is a section along the line IV/IV of Figure 3 and Figure 5 is a plan view of the lower section of the drop-forge die of Figures 3 and 4.

The flight 1 depicted in Figure 1 is in two parts and has an upper section 2 as well as a lower section 3.

The plane of division runs horizontally in the central area of the flight at 4 and is angled off upwards to the blocks 7 and 8. On the inner side of each block there is a slot and key fitting 9/10 which provides for a positive lock between the two flight sections 2, 3.

The maintenance of the positive lock is achieved with one bolt in each case (11, 12) which passes through the plane of division vertically and thereby braces together the chain beds and the two enclosed chain links 13, 14 at the same time. Such a chain bed has a curved recess 15 with a flange 16 adjacent to it which is interposed between the two sidepieces of the relevant chain link 13 and exhibits on each of its front and rear sides respective losses 17, 17' to support the adjoining vertical chain links, When in operational conditions the flat chain links 13, 14 become loose, the chain beds become flattened which leads to a corresponding loss of flight material in the area of the chain beds. The lower section 3 of the flight is naturally affected by this in the first place, although in the long run the upper section 2 of the flight can also be damaged in this way.

With a tool that is not depicted, and with a one-part drop-forge die, into which the lower section 3 of the flight is inserted from above, the process described as follows can be implemented: The tool has a protruding ridge that corresponds to the bollow 25 of a slot 26 which remains behind in the floor surface 27 of the lower section 3 of the flight after the latter has been partially renewed. This tool is moved rectilinearily to the flight lying in the cavity of the die and is embedded under the side 27 of the lower section 3 of the flight. By this means the slot 26 is forged, which is connected with a local compression conversion.The material displaced in this process leads to a bellying-out of the abraded areas of the lower section 3 of the flight, so that these parts of the flight are pressed into the cavity of the dropforge die that has the specified dimensions of the flight. In this connection the slot 26 is dimensioned in such a way that the material is applied to the cavity of the drop-forge die. As a result of this, the lower section 3 of the flight, after the hollow-forging, once again exhibits all specified dimensions of the chain beds.

In the Figures of the drawings the repairs to the blocks 7 and 8 are furthermore seen. Such a block has on its exterior a rising bottom face 18 and a declining spinal face 19, which are joined together via a radius 20. In the plan view the block is bounded by two concave faces 21, 22 corresponding to one another.

Abrasion of the blocks that has been incurred abrades the faces 18 and 19 as well as the radius 20.

A tool with rectilinear motion has roughly hemispherical end shape and consequently leaves behind a cup-shaped hollow, as is reproduced in outline in the Figures 23 and 24. This hollow in the block leads to a lateral displacement of material into a cavity of a drop-forge die that exhibits the specified dimensions of the block. In course of this the material is compressed and applied laterally to the cavity.

Hence, at the end of the hollow-forging, the block has also attained its original dimensions once again.

As can be seen from the Figures, both blocks 7,8 can in case of need be repaired in the way described.

The flights that have been partially renewed by means of the hollow-forging processes described are then subjected to a heat treatment like that likewise undertaken with new flights. By this means the partially renewed flights attain the same tensile strengths.

The process described is especially suitable for heavily abraded flights, which could not previously be repaired at all.

According to the illustration in Figures 3 to 5, the re-establishment of the specified dimensions of the flight in the area of the chain beds and of the blocks is executed with the aid of a multipart drop-forge die 30. The drop-forge die has a horizontal plane of division 31, which runs in the longitudinal direction of the flight 1 which is reproduced only in outline in this diagram. This results in the emergence of an upper matrix 32, which exhibits a cavity 38 corresponding to the sector 33 of the flight directed towards it, with the exception of the tool 34, for the production of the slot 26. In addition, the division along the plane 31 results in a lower matrix 35, that for its part exhibits a cavity 37, which corresponds to the flight sector 36 directed towards it, i.e. which exhibits the latter's specified dimensions.In the lower matrix 35 there are cutouts, e.g. boreholes 39 and 40 for rod-shaped ejectors 41,42 which can take effect on the sector 36 of the flight 1 because the cutouts 39,40 reach as far as the cavity 37 of the die.

In both matrices 32 and 35 the cutouts 47 to 50 are provided for further stamps 43 to 46 which serve to make the hollows in the flight blocks.

The lower matrix 35 is mounted on a press table that is not depicted. The abraded and previously heated flight 1 is laid into the cavity 37 of the lower matrix 35 with the drop-forge die 30 open. The upper matrix 32 is pressed with its cavity 38 and with the tool 34 against the lower matrix. In process of this, the slot 26 is forged in the side 27 of the lower section of the flight 3. The material displaced hereby is forced into the central area of the flight and defines the latter's chain channels.

The stamps 43 to 46 are then pressed in through the lateral cutouts 47 to 50 in the matrices 32 and 35.

The material displaced in the blocks in this operation is thereby forced into the hollows between the cavities of the matrices.

The forging processes are controlled in travel and force. This means that as the hollows of the upper and lower matrices are filled out, the stamps penetrate more or less deeply into the area of the block according to the abrasion of the flight.

After withdrawal of the stamps 43 to 46, the flight 1, now true to size once more, is expelled from the lower matrix 35 with the aid of the ejectors 41,42.

Claims (8)

1. A process for the partial renewal of flights of chain belts in tough conveyors, especially in underground operations, in which abraded partial areas of the flight are brought to specified size, by forcing a tool with rectilinear motion into at least one of two surfaces or into a longitudinal surface of the part to be repaired that is perpendicular to said surface and local compression takes place, with the material displaced being forced into a cavity of a drop-forge die that has the specified dimensions of the flight.

2. A process according to claim 1, in which, for the renewal of chain beds a slot running in the longitudinal direction ofthe part to be repaired is sunk into the side of the flight that lies opposite to them.

3. A process according to claim 1, in which, for the renewal of one of the flight ends, a hollow is made in its face.

4. A process according to claim 3, wherein the hollow has a hemispherical internal contour.

5. An installation for executing the process according to one of claims 1 to 3, including a two-part drop-forge die with a horizontal plane of division which runs in the longitudinal direction of the flight, an upper matrix serving as a tool which has a cavity corresponding, with the exception of the tool, to the flight sector directed towards it, a lower matrix with a cavity corresponding to the specified dimensions of the flight sector directed towards it, ejectors extending through cutouts directed towards them in the cavity in the lower matrix, and further stamps which serve to make the hollows in the flight ends and are guided through horizontal cutouts in one or both matrices.

6. An installation according to claim 5, wherein the initially proceeding motion of the lower matrix and the subsequently proceeding motions of the stamps are controlled in travel and force.

7. A process for the partial renewal of flights of chain belts in trough conveyors substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

8. An installation for executing the process sub stantially as hereinbefore described with reference to and as shown in the accompanying drawings.