GB2139981A - Partial renewal of flights of scraper chain conveyors - Google Patents

Abstract

A process for the partial renewal of flights in chain belts of scraper conveyors, especially those in underground operations, in which the flight ends running in lateral chain guides are brought up to specified size with the aid of replacement parts 27, welded on to the previously modified part to be repaired, such modification being by grinding a wedge shaped shoulder on the end of the flight formed by respective upper and lower surfaces 20, 21 terminating in steps 24, 25 the replacement part 27 being in the form of a trough which corresponds to the shoulder of the part to be repaired that includes corresponding wedge surfaces, the replacement part 27 being fixed by welds along the steps. The replacement part 27 has a curved outer floor surface as well as flat and straight inner floor surface and facing edges 33, 34 which follow the curve of the flight R2 and have a re-entrant near the floor. <IMAGE>

Description

SPECIFICATION Process and installation for partial renewal of flights in chain belts of scraper conveyers, especially in underground operations The invention concerns a process for the partial renewal of flights in chain belts of scraper conveyors, especially in those of underground operations, and, in addition, an installation for the execution of this process.

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 construction of their stationary component assembled out of steel troughs linked together. The conveying agent consists of one or several parallel chains but the flights are, however, subjected to heavy demands, the flights being above all subject to severe abrasion. As the guidance of the conveying agent takes place with the flight ends in the longitudinal profiles of the conveyor troughs, 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 pertains, therefore, to the ends and makes possible a repeated use of the centre sections of the flights before the flights have to be scrapped. A prerequisite for such partial renewals must be that the repaired flights are true to size and that the repair leaves no losses in tensile strength. An additional consideration for the partial renewal is that the associated losses of material be kept within bounds.

The invention stems from an already known process which does not satisfy these requirements to an acceptable extent and which also demands an excessive expenditure of labour. This 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-offends with the aid of a surrounding fillet weld. These replacement parts cannot be adjusted precisely enough so that the accuracy to size of the repaired flights is not provided. 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 consequently does not attain that of the new article.

The process already known also leads to considerable losses of material, because in burning off the flight ends the whole of their remaining crosssection has to be scrapped.

However, flights that are partially renewed according to another known process are of appreciably superior quality. In this process, only flights that are in need of repair are singled out in the first instance, and then are ground in accordance with 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 thereupon removed by grinding. The resurfacing welding leaves behind an inordinately hard and abrasion-resistant texture, so that the flights re newed accordingly exhibit characteristics which are at least equivalent to those of new parts, and even surpass these in some cases. The process leads also 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, of which in particular the resurfacing welding is carried out by hand, i.e. cannot be rationalised. On the other hand the expense derives from the mechanical technolo gical equipment, especially the machine required for grinding, that is necessary for the absolute accuracy to size the reconditioned flights.

The basic purpose of the invention is to conduct the process initially expounded as known in such a way that in a simple manner avoidable losses of material in the pieces to be repaired and losses in tensile strength are to a large extent prevented and an accuracy to size of the reconditioned flights corresponding to new parts is attained.

In accordance with a first aspect of the invention there is provided a process for the partial renewal of flights in chain belts of scraper conveyors, especially those in underground operations, in which the flight ends running in lateral chain guides are brought to specified size with the aid of replacement parts which are welded on to the previously straightened part to be repaired, wherein the end to be renewed of the part to be repaired is straightened by grinding and in this process a wedge shape of which the surfaces terminate in respective steps, is produced on the upper side and the underside of the part to be repaired, and that a replacement part hollowed out in the form of a trough corresponding to the shape of the end exhibiting the wedge surfaces is pressed on to and affixed to the said end with the side pieces right up to a point ahead of the steps and with the floor of the trough ahead of its wedge back, before welds along the steps are executed.

According to a further aspect, the invention resides in an installation for execution of the above referred to process comprising replacement parts of trough profile with a curved outer floor surface and with side-piece outer surfaces of original dimensions (b,h) and inclinations (x,ss) of the flight ends as well as with a flat and straight inner side to the floor and facing edges which follow an arc corresponding to the curve of the flight and have a re-entrant near the floor.

With these arrangements one removes at the abraded ends only so much material as is required for pre-selected dimensions of the wedge-shaped shoulder, leaving on the other hand no more material on the flight. So that these shoulders may have a constant form and dimensions, the grinding of the flight ends can advantageously be carried out by mechanicalltechnological means. The replacement part adjusted to a given wedge-shaped shoulder is fixed down by its trough shape by means of the shoulder automatically in such a way that the longitudinal dimensions of the flight are maintained.

On the other hand the replacement part is naturally adjusted in its other dimensions exactly to the bulk of the flight. As all critical dimensions are so restrained, the partially renewed flights are subsequently absolutely true to size. As the shoulders are interrupted in step form for the weld seams, one reaches a position on the one hand in which subsequent grinding is either completely unnecessary or is reduced to a few grinding operations. On the other hand, one determines the weld seams to such an extent that they can be located and delimited by computer-aided welding manipulators.

The process according to the invention is extraordinarily economical. Although it leads to partially renewed flights, which in practice are indistinguishable from the new parts in quality, only a minimal loss of material to the parts to be repaired is incurred.

Preferably, one uses the welding heat for the welds at the steps for annealing and, to this end, for reducing stress in the replacement parts, thinskinned because of their trough configuration, in the heat, in order to re-establish in this manner the original tensile strength of the material in the flight.

It is furthermore possible to adapt the new reconditioning process to the various forms of abrasion and degrees of abrasion. In course of this, the trough-shaped replacement parts are used with the least thickness of sidepiece for the abrasion that has progressed least, and those with the greatest thicknesses of sidepice for those parts to be repaired on which the abrasion of the flight has spread furthest.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a flight of known structure for a dual central chain with a reproduction of the abrasion assumed, Figure 2 is a plan view of the device of Figure 1 in a partially broken representation, Figure 3 is a front elevation and, in section, a representation of the lower part of the flight after repair, and Figure 4 is a plan view of the device of Figure 3.

The flights represented in the Figures are flights of chain belts which are used in scraper conveyors in underground operations. The flight 1 according to Figure 1 has a lower section 2 of relatively great volume and an upper section 3 secured by two bolts 6 and 7 which pass vertically through the horizontal plane of the two central chains 4 and 5 and which, for the rest, are fitted outside the chains. The displacement of the two flight components 2,3 is prevented by an additional positive lock, which is provided outside the bolts 6 and 7 by a slot and key fitting which is marked 8 and 9.If the chain beds 10, 11 are considered in the lower section of the flight, which are disposed close together and are available for each central chain, and the intermediately located brackets 12, 13 for the support of the vertical chain links adjacent to the enclosed flat members, then the lower section of the flight is not only an inordinately heavy i.e. metal-intensive, component, but also has a relatively complex configuration, which gives it an appreciable value.

Through circulation in the conveyor troughs, the flights become worn away at their ends 15, 16. In the drawing this is indicated by a dot-and-dash line at 17/18, while in the plan view the abrasion is produced roughly according to the dotted line 19. To this extent the drawing only shows certain possible forms of abrasion. In practice, distinguishable forms and degrees of abrasion arise in the same chain belt.

The partial renewal begins with the grinding of both flight ends as depicted in Figures 3 and 4, relating to the flight end 16. In this process the ends are straightened to produce the wedge surface 20, 21 converging outwards, which are flat and terminate at a vertical face of the back 23 of the wedge, this face likewise having been obtained by grinding. The surfaces 20 and 21 reach as far as outward steps 24, 25. Overall, the result of this is a shoulder 26 which is of converging wedge-shape towards the outside. It is dimensioned and executed in such a way as to correspond to the trough-shaped hollow space of a replacement part 27. The replacement part 27 is trough-like in profile, and its interior is bounded by two sidepieces 28, 29 which are fitted on the back of the flight and on the underside oftheflightwhen the flight has been reconditioned.The internal floor of the trough 22 is flat, and is curved externally at 30.

The external dimensions of the replacement part 27 correspond to the original dimensions of the flight end 16. They are essentially given by the angle of rise of the underside o of the flight, which is approximately 35 , and by the angle of incidence of the upper side p of the flight which is approximately 17 . Further, the dimensions of the end-piece of the repair correspond to the specified flight height h, which amounts to 53mm in the example shown, and to the height h1,which in the example works out to 71.5mm In the plan view it can be recognised that the curve of the outer floor surface 30 of the replacement part 27 corresponds to the radius R which is specified as 342mm in the flight.The breadth b corresponds to the specified flight breadth of 140mm. The two end edges 33,34 of the trough of the replacement part 27 are bent inwards behind the outer curve of the trough bottom 30 and accordingly are curved round a radius R1 which exceeds the radius R2 of the flight that corresponds to it ((sc. R2 corresponds to R1)).

The trough sidepieces 28, 29 form, with the steps 24,25, round which the shoulder 26 is bent, a wedge-shaped cavity 36 which is filled out with a weld bead 37 that extends on the upper side 14 of the flight along the curved facing edges 33,34 and the edge 38, parallel to the floor, of the sidepiece 29.

On the underside of the flight, the weld bead marked 39 runs in a corresponding way. The floor surface 22 does not run parallel to the external curved surface 30 of the trough of the replacement part 27, but is straightened for reasons of simplification, as shown at 40 in Figure 4.

The dot-and-dash line 41 in Figure 3 indicates a replacement part whose side piece exhibits not the breadth b1 but the breadth b2. The dashed line 42 shows a third group of replacement parts which exhibit a still greater breadth b3 of their sidepieces 28,29. The flight ends are ground, i.e. the shoulders 26 are dimensioned, according to these three groups. For the rest, the groups are adjusted accord ing to the degree of abrasion.

The replacement parts are forged and then tempered. Because of their thin-skinned nature the heat of the weld seams 37,39 leads to a reduction of stress in the annealed structure and thereby to an equalisation of tensile strengths in the area of the weld seams.

The chain belts are mostly delivered in an assembled state. The partial renewal begins with dismantling of all the flights and separation of the abraded flight lower sections 2. Then the flights to be partially renewed are divided into three groups, which correspond to the dimensions of the replacement parts bl to b3. Subsequently each flight to be partially renewed is ground at its ends 15, 16 in such a way that the shoulder 26 which has been described is produced and is true to size. In this process the steps 24,25 are also produced.

After both flight ends have been completely reconditioned, the appropriate replacement parts 27 are pressed on to the shoulders of the part to be repaired. The part to be repaired is braced to the superimposed replacement parts 27 and care is thereby taken that the surfaces 20,21 and 23 are located on one another and the ends of the sidepieces 28,29 are situated ahead of the rises of the steps 24, 25. This positioning of the replacement parts is fixed with a spot weld. With the latter, the end pieces 27 are fastened to the parts to be repaired.

The part to be repaired, furnished with the affixed replacement parts 27, is then fixed into an appliance that is suitable for a computer-aided manipulator.

The welding manipulator establishes the two weld seams 37, 39 and can process either only one or both ends of the part to be repaired. Then the part to be repaired is once more reconditioned and can be put into operation as a new flight.

Claims (8)

1. A process for the partial renewal of flights in chain belts of scraper conveyors, especially those in underground operations, in which the flight ends running in lateral chain guides are brought to specified size with the aid of replacement parts which are welded on to the previously straightened part to be repaired, wherein the end to be renewed of the part to be repaired is straightened by grinding and in this process a wedge shape of which the surfaces terminate in respective steps, is produced on the upper side and the underside of the part to be repaired, and that a replacement part hollowed out in the form of a trough corresponding to the shape of the end exhibiting the wedge surface is pressed on to and affixed to the side end with the side-pieces right up to a point ahead of the steps and with the floor of the trough ahead of its wedge back, before welds along the steps are executed.

2. A process according to claim 1, wherein forged ad and subsequently tempered replacement parts are used.

3. A process according to either of claims 1 or 2, wherein groups of replacement parts which are distinguished from one another by distinct strengths of their trough sidepieces and by the adjustment of the step depth to the abrasion present at any given time and to a particular group of replacement parts are used.

4. A process according to any one of claims 1 to 3, wherein each part to be repaired is clamped together with the superimposed replacement parts, the replacement parts being affixed and then the weld seams laid down.

5. An installation for execution of the process according to any one of claims 1 to 3 comprising replacement parts of trough profile with a curved outer floor surface and with sidepiece outer surfaces of original dimensions (b,h) and inclinations (owe,) of the flight ends as well as with a flat and straight inner side to the floor and facing edges which follow an arc corresponding to the curve of the flight and have a re-entrant near the floor.

6. An installation according to claim 5, including groups of replacement parts which are distinct from one another in breadth.

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

8. An installation substantially as hereinbefore described with reference to and as shown in the accompanying drawings.