CZ272395A3 - Device for attaching a bulkhead to the jacket of a tube mill - Google Patents

Abstract

The invention relates to a novel device for fixing a partition to a shell (4) of a tube mill in which the partition comprises a cast framework (1), in steel or in cast iron, consisting of several sectors (15) provided with a set of fixing holes (32) in their peripheral face (3), each sector (15) being independent of the other sectors, characterized in that it possesses an annular intermediate baseplate (100) arranged facing the said shell (4), providing a space between the shell (4) and the intermediate baseplate (100), which space is chosen so that the inner face of the intermediate baseplate (100) forms a reference surface at the nominal diameter of the periphery of the said cast sectors (15), this space being set with the aid of adjustment elements (110) and the intermediate baseplate (100) being provided with holes (102) which can be matched to the said set of fixing holes (32) in the peripheral face (3) of the sectors (15) in order to enable the latter to be fixed by means of bolts in the holes of the intermediate baseplate (100), means (101, 41, 42) being provided for rigidly fastening the intermediate baseplate (100) to the shell (4). The invention also relates to the method for the operation of the device.

Description

BACKGROUND OF THE INVENTION

Partitions separating two adjacent tubular mill chambers are intended, in particular, to retain the grinding bodies in the grinding chambers - depending on their dimensions - and to prevent their passage from one chamber to the other.

These baffles are also intended to sift the ground material by allowing only sufficiently fine particles to pass to the next chamber.

For this purpose, single or double-walled partitions are suitable. At present, mainly two-wall partitions are used as they have a longer service life and better withstand operational stresses.

The bulkheads of this type generally have a frame structure consisting of several sectors to which grids are attached at the inlet, which grids allow sufficiently ground material to pass beyond the cladding plates which form a central outlet opening through which the material passes into the next chamber.

Grids and cladding boards (so-called friction structure connected by screws).

The friction pieces are usually made of hardness to withstand the impact of the grinding bodies and the wear caused by the ground material (abrasion or abrasion) for a sufficiently long time.

The frame structure carrying the friction pieces must exhibit good pieces) with frame steel of very high abrasion, corrosion and temperature characteristics. This is due to the fact that the material to be ground can have different shapes and, in particular, in the wet process it is in the form of a paste which is abrasive, corrosive and has a density greater than 1. The frame structure is then subjected to particularly demanding working conditions.

For these reasons, it was first proposed to produce the frame structure from cast steel or cast iron. The frame structure thus obtained sufficient abrasion resistance.

However, the frame structure must be capable of being inserted into a tubular mill and therefore must consist of several sectors which must be sufficiently small in size to pass through the inspection door or inlet or inlet.

US-A-1,787,897 discloses a baffle frame. This frame structure is normally a torus shape whose axis coincides with the axis of a tubular mill and whose outer cylindrical surface is laid against the inner cylindrical surface of the mill shell. Both circular fronts (front and rear) are perpendicular to the mill axis and carry grids and tiles.

The grids are pierced by openings or slits, allowing the ground material to penetrate the torus, whereby the ground material exits through a central opening in the rear face of the septum.

The frame torus is radially divided into sectors that are sized to be inserted into the mill through a door or inlet.

The division into sectors is also chosen according to the drilled holes in the shell of the tubular mill. All frame sectors must be the total divisors of the number of drilled holes the mill has on its perimeter. All sectors can therefore be fixed to the inner face of the tubular mill by simply screwing it to the housing.

However, this type of construction is mainly used where the mill dimensions are smaller. In the last few decades, the diameter of tubular mills has practically doubled. As a result, problems have arisen in terms of resistance to stresses caused by increased deformation of tube mills and the lack of impact strength of cast alloys. In addition, problems with on-site assembly have increased. As a result, frame structures made of cast steel or cast iron have been gradually replaced by rolled steel frame structures that are mechanically or welded joined.

DE-A-2,133,431 discloses mechanically joined or welded frame structures which resemble cast structures. The various sectors constituting the frame structure are screwed by means of their peripheral base plates directly to the casing of the tubular mill.

US-3,776,477 discloses a special example of a frame for the partitions made of mild steel, the frame being welded. The mild steel properties make it easy to weld different pieces together. This document discloses a partition comprising a U-shaped ring which is supported directly by the casing of a tubular mill. The ring is therefore directly attached to the housing and consists of several segments which can be inserted through the inspection door into the tubular mill. The disc with a central circular bore also consists of several elements and is attached to that U-ring arm which is located lower with respect to the material flow. The disc elements are attached to the ring segments either by welding or bolts. The T-shaped radial vanes are welded in place to the peripheral ring and to the disc located lower with respect to the material flow, the arm T being perpendicular to the disc.

However, frame structures made of mild steel are not resistant to corrosion and abrasion in the long term; in some cases their service life is shorter than that of the friction pieces. Various means have been proposed to improve their resistance. In particular, it has been proposed to use stainless steel or to coat the various skeleton-forming parts with a thin layer of rubber. However, none of these proposals addresses the problem of abrasion. This is because, in order to produce a structure of rolled stainless steel that is welded in place without final heat treatment, it is necessary to use rolled stainless steel of low hardness. In addition, rubber cannot be used in the dry process, since the operating temperatures are too high for the rubber.

In addition, due to abrasion, it has been proposed to produce a frame structure of high hardness steel, but in this case the cost of welds and heat treatments increases beyond the cost of production. This approach to frame construction is therefore only a partial solution, as production costs are too high.

Finally, numerous other elements can be connected in situ to the frame structure and welded to it only with difficulty. This is because these elements must be cooked without the possibility of subsequent repairs and without having a real reference surface available, except for the cylinder itself, but which is not balanced.

It should also be clear that the assembly of all the pieces constituting the partition should be so accurate that no holes larger than the maximum dimension of the grid slots are formed. (Mostly these slots are smaller than 6 mm). The smallest assembly gaps plus manufacturing tolerances cannot exceed the maximum grid slot dimensions.

A recent solution consists in the production of cast frame structures (similar to the baffles intended for small diameter tubular mills), but using steels of high hardness (HRC value greater than 35) and preferably using stainless steels.

Current foundry processes make it possible to select corrosion resistant alloys and suitable for heat treatment, thereby obtaining a material with mechanical properties that implies abrasion resistance. In addition, the current foundry processes allow a variety of shapes to be easily constructed, in particular those resistant to mechanical stress.

However, the classic problem of inserting a frame structure into a tubular mill can only be solved by splitting the frame structure into segments so that the largest dimensions of all sectors are smaller than the dimensions of the inspection door or inlets. These sectors must therefore be fixed to the casing of the tubular mill by a sufficient number of fixing points. This means that the number of holes drilled in the shell (in order to attach to the shell) must be a multiple of the number of sectors that make up the bulkhead frame, given the maximum dimensions and less than the door dimensions, or inputs.

Although mill diameters have been normalized by all designers in different measurement systems, this does not apply to the number of holes drilled in the casing of the tubular mill and to the dimensions of the various mill inlets. This implies that it is not economically possible to deal with all mills of a given diameter according to the design standards of individual designers, as this would lead to the creation of too many foundry patterns for the construction of the carcass sectors, making the use of carcass castings unprofitable. Ideally, there should be no grounds for numerous different standards regarding drilled holes, and there would be only one pattern for a sector designed on the basis of a tubular mill diameter that could be inserted by the smallest inputs.

SUMMARY OF THE INVENTION

An object of the present invention is a device for attaching a partition to a tube mill; the bulkhead has a frame structure made of cast material, the frame structure being made up of several sectors placed side by side so that a limited number of foundry patterns or only one pattern is constructed for each tube mill diameter, this being done independently of drill hole standards and to the dimensions of the mill inspection door.

The present invention therefore provides a solution in a situation where the fastening means located at the periphery of the sectors do not correspond to the drilled holes in the tubular mill jacket.

The present invention also additionally provides the various sectors forming the frame structure of a precisely assembled partition, which precisely avoids the formation of holes larger than the largest dimension of the existing slots.

Main features of the invention

The present invention relates to a device for attaching a partition to a casing of a tubular mill, wherein the partition has a cast steel or cast iron frame structure, consisting of several sectors provided with a plurality of mounting holes on its peripheral side, the sectors being independent of each other. having an annular intermediate base plate composed of several segments connected to each other to form a single base plate positioned so as to provide clearance against the mill jacket and between the jacket and the intermediate base plate such that the inner side of the intermediate base plate formed a reference surface for the nominal diameter of the cast sectors, this space being adjusted by means of adjusting elements and the intermediate base plate provided with holes which may correspond to a number of fixing holes on the circumferential side of the sectors, allowing the sectors have been fastened by screws in the holes of the intermediate base plate, and means are used to firmly secure the intermediate base plate to the housing.

The outer diameter of the intermediate base plate is chosen so that it can easily fit into a tubular mill of a given diameter which differs from the nominal diameter by the manufacturing tolerances.

For this reason, a free space is created between the intermediate base plate and the sheath, and it is thus possible to produce intermediate base plates of the same diameter for all shells of a given nominal diameter.

The intermediate base plate of relatively small cross-section is preferably cut into three or four segments so that it can be inserted into the housing by the entry point of the tubular mill. These segments are then welded during assembly to form a uniform intermediate base plate.

The adjusting elements filling the space between the intermediate base plate and the housing may be made of a cast metal that melts at low temperature, e.g. zinc. The low-melting metal may form a means to firmly secure the intermediate base plate to the housing.

The intermediate base plate corresponding to the exact inner diameter can serve as a reference surface. The carcass sectors are then attached to the intermediate base plate; their mounting no longer requires special precautions in positioning due to the presence of an intermediate base plate forming the reference surface.

It is found that the baffles mounted according to the fastening method described above do not have undesirable openings through which poorly comminuted material would pass from one chamber to another.

In a first preferred embodiment, the intermediate base plate is screwed to the casing of the tubular mill as well as to various sectors.

The intermediate base plate has on its outer side a series of holes for attaching the plate to the tubular mill housing, which holes may be positioned to correspond to the drilled holes in the tubular mill housing, the layout of which is designed by the mill designer, and has an intermediate foundation the plate on its outer side has a further series of threaded holes, which holes can be positioned exactly to the holes to be fastened

Ί sectors.

In general, it is only necessary to produce one particular type of base plate for each design type of a given tube mill. This makes it possible to balance all the castings and to allow the partition sectors to be cast only in dependence on the diameter of the intermediate base plate and therefore also in dependence on the nominal diameter of the mill and not already on the different types of drilled holes in the tubular mill.

In a preferred embodiment, the intermediate base plate is formed by a rolled steel plate, the composition of which is chosen to resist corrosion and abrasion. The advantage of this plate is that it can be easily machined, especially bent and drilled.

In another preferred embodiment, protection of the intermediate base plate from abrasion is achieved by providing sectors whose base completely covers the intermediate base plate. The device may be supplemented by parts coming from the friction pieces and protecting the transversely intermediate base plate.

This makes it possible to produce only one foundry pattern for sectors corresponding to a given tube mill diameter.

Other objects and advantages of the present invention will be described by means of said preferred embodiment.

Overview of the drawings

Fig. 1 is a partial cross-sectional view of the mill perpendicular to its axis, with the grinding ball and cladding armor removed; the section shows a partition provided with a fastening device according to the invention as viewed from the entrance to the mill, with part of the grid removed to clearly see the two sectors constituting the frame structure of the partition, and removing the front of one of the two sectors to clearly see part of the lift equipment and peripheral sector.

Fig. 2 is a cross-sectional view of the bulkhead taken along a plane passing through the mill axis along line II-II in Fig. 1.

Fig. 3 is a cross-sectional view of the bulkhead taken along a plane passing through the mill axis along line II-II in Fig. 1.

Figure 4 shows the heel of two adjacent sectors whose front side and the outer cylindrical surface covering the intermediate base plate have been removed completely.

Fig. 5 shows an additional threaded element mounted in an intermediate base plate.

DETAILED DESCRIPTION OF THE INVENTION

The described fastening device relates to a partition mounted between two grinding chambers of a rotary ball mill.

The partition consists of a frame structure having the shape of a torus 1, whose axis 2 coincides with the axis of the tubular mill, and further comprises an outer cylindrical surface 3, which is opposite to the cylindrical surface of the tubular mill shell 4.

The two circular faces 5 and 6 (front and rear relative to the direction of movement of the material) are perpendicular to the mill axis 2 and carry grids 7 and cladding plates 8. In the grids 7 are openings 8 (called slots) which allow the ground material to penetrate the torus 1. This material then exits through the central opening 10 located at the rear face of the partition.

In the preferred embodiment shown in FIG. 2, the central opening 10 (located on the side of the rear face 6 of the frame structure) comprises a truncated cone 11 that is coaxial with the torus 1 and whose apex is directed to the next chamber.

The frame torus 1 is regularly divided into a number of sectors 15 which are sized to be inserted into the mill through a control door or one of the inlets. The frame structure sectors 15 are made of cast steel or cast iron.

During rotation of the mill, the mantle deforms and its parts become oval in shape as a result of the movement of the grinding bodies, and the same applies to the cross-section of the mantle where the partition is located. The partition must be designed to withstand these deformations: therefore, the different sectors constituting the frame structure are independent; this allows them to move away from one another or approach one another without changing the shape of the shell to an oval in the frame structure.

Also, the truncated cone 11 is not fixed to the sectors, but through its flange 12 to the annular flange 13 positioned loosely in the annular groove 50 in the grids 2. The screen 14 to prevent grinding bodies or insufficiently comminuted particles closes the truncated cone opening and is tight held between the flange 13 and the truncated cone flange 12.

In Fig. 1, the grids 7 are attached to the front face of the frame structure by means of screws and two grids have been removed to see the front face of the frame structure sector.

These sectors are provided with bolt holes which secure the grids 7 to the front face and the facing plates 8 to the rear face. The front and rear faces of the sectors are widened against the bolts to ensure proper grating.

Furthermore, they have radial vanes 16 which form a network of sectors and extend from the circumference of the bulkhead formed by the outer cylindrical surface 3. These blades serve (due to the rotation of the mill) to transport ground material which penetrates into the bulkhead torus 1 cone, from which the ground material flows into the next mill chamber. These vanes further ensure the rigidity of the sectors 15 against the axial pressures exerted by the grinding balls, which partially fill both chambers adjacent to the partition.

In order to prevent the front and rear faces of the sectors from obstructing the grid slots, thereby reducing material flow or ventilation air flow, the vanes outside the grid-setting zones have a smaller width and further the front and rear faces of the sectors are not planar but follow the contours of the lifting device.

According to the present invention, the single annular intermediate base plate 100 is positioned opposite the housing 4, leaving a gap 105 between this plate and the housing, which is adjusted by the adjusting elements 110 so that the inner surface of the intermediate base plate forms a reference surface exactly in the nominal diameter area of the sectors. The remaining free space 112 between the housing, the base plate and the adjusting elements can then be filled with cast metal melting at low temperature.

The intermediate base plate 100 preferably consists of a plurality of segments, mostly three or four, which can be easily inserted by entering the tubular mill.

After attaching the segments to the casing of the tubular mill, these segments are welded (at position 51) to form a continuous closed ring.

The intermediate base plate 100 is preferably formed by a rolled steel sheet, the composition of which is selected such that the plate is corrosion resistant.

This embodiment has the advantage that said plate can be easily drilled and easily shaped using sheet metal processing methods, and can be carried out according to the individual requirements of each tube mill, eg depending on the drilled holes in the shell and the drilled holes on the circumference of the cast sectors.

The sectors have a U-shaped foot 17 whose outer cylindrical surface 3 is opposite the inner cylindrical surface of the base plate.

In another embodiment shown in FIG. 5, the intermediate base plate is completely protected by the close proximity of the sectors.

It can be seen from Figures 2 and 3 that a part starting from the pieces forming the grids 7 and the cladding boards 8 attached to the sectors of the frame structure is added, which part protects the base plate transversely.

The intermediate base plate has a plurality of holes 101 to correspond to the drilled holes 41 in the casing of the tubular mill, the base plate being secured to the casing by means of screws. The peripheral side of the sectors is provided with a number of x holes to correspond to x threaded holes in the intermediate baseplate, with bolts 32 fixing the sectors to the baseplate.

In another embodiment (not shown), the holes 101 in the intermediate base plate (intended to be attached to the housing) are threaded to allow the screws to be screwed in, with the screw heads outside the housing 4.

In another embodiment shown in Fig. 5, the threaded holes 32 are formed by additional elements added.

In another embodiment (not shown), the low-melting metal is introduced into the void space 112 that is located between the base plate and the shell, and the metal firmly connects the base plate and the shell.

It should be understood that, although the present invention has been described in one embodiment of a partition, it may be extended to other types of partition.

Claims (7)

PATENTOVÉ Claims (100) composed of several segments to form a solid foundation Apparatus for attaching a partition to a tube mill casing (4), the partition having a cast steel or cast iron frame construction (1), consisting of several sectors (15) provided with a plurality of mounting holes (32) on the peripheral side (3), the sectors (15) are independent of each other, and the device is characterized in that it has an annular intermediate base plate interconnected by a plate which is positioned so as to be opposite the mill jacket (4) and between the jacket (4) and the intermediate base plate (100) ) has been provided such that the inner side of the intermediate base plate (100) forms a reference surface at the nominal diameter of the cast sectors (15), the space being adjusted by adjusting elements (110) and the intermediate base plate (100) provided with holes (102) ) that can correspond to a series of mounting holes (32) on the circumferential side (3) of the sectors (15), allowing the sectors (15) to be y fixed by means of screws in the holes of the intermediate base plate (100), and using means (101, 41, 42) for firmly fixing the intermediate base plate (100) to the housing (4). Device according to claim 1, characterized in that the space between the intermediate base plate (100) and the mill jacket (4) and the adjusting elements is formed by a cast metal melting at low temperature. Device according to claim 2, characterized in that the means firmly fastening the intermediate base plate (100) to the housing (4) are formed by a low-melting metal. O '“O 70 «u? cn o o czx OC Device according to at least one of the preceding claims, characterized in that the means firmly connecting the intermediate base plate (100) and the housing (4) comprise openings (101) in the intermediate base plate (100) which correspond to the drilled holes (41) in the intermediate plate. and wherein the base plate is firmly connected to the housing by means of screws. Apparatus according to claim 4, characterized in that the holes (41) in the intermediate base plate (100) are threaded and fastened in the holes (41) by screws (101), the heads of these screws being outside the housing (4). ). Device according to at least one of the preceding claims, characterized in that the holes (101, 102) in the intermediate base plate (100) which are threaded are formed by additional elements. Device according to at least one of the preceding claims, characterized in that the intermediate base plate (100) is formed by a rolled steel sheet, the composition of which is selected so as to resist corrosion of the plate. Device according to at least one of the preceding claims, characterized in that the intermediate base plate (100) is completely protected by the circumferential side or base (3) of the frame-forming sectors (15) and the friction pieces (7, 8). Method for attaching a partition to a casing (4) of a tubular mill, the partition having a cast steel or cast iron frame construction (1), consisting of several sectors (15) provided with a plurality of fastening holes (32) on the peripheral side (3), wherein the individual sectors (15) are independent of each other, and the method is characterized in that a single annular intermediate base plate (100) provided with holes (102) that can correspond to a series of fastening holes (32) on the peripheral side (3) of the sectors (15) ), which allows the sectors (15) to be secured by screws in the holes of the intermediate base plate (100), is positioned against the housing (4) so as to provide such clearance between the housing (4) and the intermediate base plate (100), that the inner side of the intermediate base plate forms a reference surface at the nominal circumference of the cast sectors (15), this space being adjusted by the adjusting elements (110) wherein the attachment of the intermediate base plate (100) to the housing (4) is accomplished by suitable means (101, 41, 42). Z f