IE60187B1 - A rotary crusher having self-protecting projection vanes - Google Patents

Abstract

The rotor of the crusher receives the stones at its centre. It comprises three blades (20, 21) which, except on the ejecting edges (22), are protected against internal wear by their hollow shape which retains a protective layer of stones. These edges are protected from impacts by protecting plates (24) arranged radially in front of them. <IMAGE>

Description

The present invention relates to crushing rocks, in order to obtain fragments therefrom. The essential problem in making crushers has long been the problem of resistance to wear by the rocks and fragments thereof, and by tbe dust due to crushing.

In order to solve this problem, prior art crushers include the following items which are themselves common to prior art crushers and to a crusher in accordance with the present invention: a rigid projection rotor having a vertical axis and provided with means for guiding it and driving it at high speed about said axis, with its direction of rotation and with the opposite direction respectively constituting a forwards direction and a backwards circumferential direction, said rotor itself comprising: a floor delimited by an outer edge; a ceiling delimited by an outer edge, disposed above said floor, and pierced by a central feed opening for continuously feeding said rocks down into said rotor; and walls connecting said floor to said ceiling.

Some of these walls constitute projection vanes. Each of these vanes extends horizontally from a reception zone formed over a portion of its length in the vicinity of said axis in order to receive the rocks which arrive via said central feed opening in the ceiling. It continues up to a projection edge which is relatively far from said axis and which may be considered as constituting the longitudinally forward end of said vane. A rock received in said reception zone is entrained by the rotation of said vane and is thus subjected to centrifugal force. It moves under the action of this force along said vane r while receiving thrust that progressively increases its circum* k ferential speed. When it reaches said projection edge, it is * projected tangentially outwards. In order to avoid the rocks ft wearing the vane, the shape of the vane in plan is a hollow self-protecting shape: the vane extends rearwards from said projection edge, circumferentially behind the line of natural slope which is defined by said edge, with lines of natural slope being the equilibrium lines of the accumulation slopes which the rocks form spontaneously under the action of the centrifugal force upstream from an obstacle which begins by opposing the flow of rocks. The position of such a line is defined by the position of the flow threshold constituted by said obstacle. This threshold is constituted by the projection edge. The first rocks to arrive over the vane are retained in the hollow of the vane until they have formed a protective layer whose surface follows said line of natural slope.

Said line is approximately a logarithmic spiral about the axis of rotation, i.e. it follows a curve whose tangent is at all points at the same angle with a radial plane passing through said axis and the- point under consideration.

The protective layer formed in this way by the first rock protects the vane against any wear by the rocks which arrive thereafter, except at the projection edge which constitutes the flow threshold.

The projection edge is constituted by a part which is very hard in order to slow down the rate at which it wears. This part is in the form of a vertical blade which may be referred to as the projection blade. It is conventionally constituted by two superposed vertical bars of tungsten carbide which are set in steel supports that are bolted on the leading length of the projection vane.

Circumferentially in front of each projection edge, the peripheral wall of the rotor leaves an outlet opening for the rocks.

The projection rotor is surrounded by an external reception structure with an annular gap being left therebetween. The reception structure has hard shock surfaces for receiving 35 direct shocks from the rocks projected by said rotor and for 4. breaking said rocks to form rock fragments and dust. Sone of the fragments return towards the rotor and subject it to rebound shocks on its peripheral surface constituted by its peripheral walls and by the outer edges of said floor and ffg-i ling. The dust is entrained by the flow of air caused by rotation of the rotor.

The external reception structure is conventionally a fixed stator whose shock surfaces may be constituted by hard plates referred to as anvils, or by fragments of rock retained in the stator in order to reduce wear thereof.

Known crushers of this type are described, for example, in the following patent documents: US-A-3,Ϊ74,697 (Bridgewater), US-A-3,970,257 (MacDonald), which corresponds to French patent document FR-A-2,201,928 (in the same name), DE-U-8,630,185 (SBM Wageneder), and EF-A-0,101,277 (Barmac).

The rotors of prior art crushers described in the abovementioned documents, or at least the floors thereof, are circular in shape. The rotors in the MacDonald, Barmac, and SBM Wageneder documents also include a ceiling which is likewise circular, which is superposed over the floor, and which has a cylindrical peripheral wall connecting the edge of the ceiling to the edge of the floor.

In the SBM Wageneder document, the projection blades are disposed projecting a moderate distance radially from the circular peripheral surface of the rotor which thus forms, circumferentially behind each of said blades, a sector which is set back radially relative to said blade. A degree of protection is thus provided in said sector by said blade against said rebound shocks.

Such a disposition suffers from several severe drawbacks. One of them' is that the projection blades are dangerously exposed to rebound shocks which frequently break them by virtue of the low ductility of the hard material from which they are made. Another drawback is that the peripheral wall of the edges of the floor and the ceiling of the rotor are protected against rebound shocks over only a small circumferential sector _ behind each projection blade, i.e. over a small fraction of said setback sectors. A third drawback is that even in the 4 sector immediately following the projection blade, the peripheral wall of the rotor is worn by dust.

In the embodiment of the MacDonald document and in accordance with the Barmac document the projection blade is, in contrast, radially set back relative to the circular peripheral wall of the rotor. The blade is then protected by the portion of the circular peripheral wall which is situated immediately ahead of said outlet opening. That is to say that said portion of the peripheral wall constitutes a protective element which intercepts the dangerous fragments of rock that could break the projection blade. There is nothing to protect the peripheral wall.

In operation, such rotors are rapidly subjected to considerable external wear. This wear is particularly great on the circular external edge of the floor and also on the corresponding edge of the ceiling, if there is one. The wear also appears on the peripheral cylindrical wall, if present. The crusher therefore needs to be stopped and the worn parts need to be reconstituted by rebuilding using an electric arc or else they need to be replaced. The operating cost of the crusher is considerably increased by these operations.

The aim of the present invention is to reduce the operating cost of a rotary crusher having self-protecting , projection vanes, without reducing the effectiveness of the crusher.

The invention also aims to enable the rotor of the crusher to be manufactured simply and cheaply while still conferring the great strength required by the rotor in view of the forces to which it is subjected.

More particularly, the invention aims to reduce the cost of rebuilding and/or replacing the outer zones of the rotor after they have been worn.

Simultaneously, the invention aims at reducing the rate at which such wear takes place in order to increase the period of operation of the crusher between two interruptions.

The present invention provides a crusher including the above-mentioned, common elements including the presence of such a said protective element, said crusher being characterized by the fact that in said protective element in front of each of said outlet openings is a protective plate extending along a substantially radial direction from said peripheral surface in 'such a manner that said dangerous fragments of rock are intercepted substantially at right angles by said protective plate by subjecting it to frontal shocks which pound it more than they scrape it, with at least the circumferentially front face of said protective plate being made of a protective material which is selected to be less hard than the material of said projection blade in order to avoid being broken by such frontal shocks.

The present inventors have discovered that: external wear of the rotor is due above all to fragments of rock rebounding from the shock surf aces of the stator, as explained above; the trajectories of said rock fragments are random and fairly, widely distributed .in direction and in position within the annular space between the rotor and the stator; the relative speeds between the rotor and said fragments reaching the rotor have a relatively large mean circumferential component due to the rotation of the rotor and a relatively much smaller centripedal radial component; said circumferential component is the cause of the majority of the wear at the periphery of the rotor since a shock having a high tangential component against a plate of steel has a scraping effect which tears more material away from the plate than does a perpendicular shock which operates by hammering, with the energy absorbed in the perpendicular case then going more into deformation, without metal being torn π i away; a substantial portion of the wear is due to rock dust entrained by the air flow resulting from rotation of the rotor, as explained above; and a simple rotor shape is effective in reducing and localizing external wear due both to said mean circumferential component of rebound shocks and to dust.

Preferably, the horizontal direction of said protective plate differs by less than 30* frcm the radial direction.

Preferably said protective plate extends far enough up and down in order to also protect the bottom and top edges of said outlet opening.

Preferably said protective plate, in plan view, forms an obtuse angle with the portion of said peripheral wall situated circumferentially immediately in front thereof, in such a manner as to deflect the streamlines of external air which flow relative to said projection rotor in contact with said wall so as to cause the rock dust in suspension in said air streamlines to move away from said outlet opening.

It is preferable for said protective plate to join the rear end of the main length of said projection vane, with a rear length of said vane being constituted by an extension of said protective plate extending into said projection rotor between said floor and ceiling in such a manner as to hold said protective plate by means of said rear length.

Also, and preferably, said peripheral walls of the rotor are at least for the most part constituted by said projection vanes, said outer edges of said floor and said ceiling following said vanes other than at said outlet openings. The peripheral surface of the rotor is then progressively radially set back relative to the projection blade, thereby protecting said surface against external wear.

Still preferably, the general shape of the rotor in plan is a convex polygon having symmetry of order N about said axis, where N is the number of said projection vanes, said polygon comprising, for each of said vanes, a short side extending along a front length of said vane having a front end constituted by said projection edge, with the rear end of said short side being closer to said axis than said front end and joining a large side which constitutes a main rectilinear length of the same vane, with at least a front fraction of said main length moving closer still to said axis in order to constitute, together with said front length, a sector which is protected against external wear.

Such a polygonal shape is easily made using plane cut and welded metal sheets.

Preferably, a rear fraction of said main rectilinear length extends said front fraction of said length rearwardly progressively away from said axis to the vicinity of a front edge of said outlet opening of the following projection vane.

Naturally, the top and bottom edges of said outlet opening from the following vane need not be exactly in alignment with said main length of the preceding vane.

More particularly, and still preferably, the general shape 20 of said rotor in plan is an equilateral triangle having cut-off comers, said projection vanes being three in number, with the three cut-off comers of said triangle being constituted by said front lengths of said projection vanes, and with the three sides of said triangle being constituted by said main lengths 25 of said vanes.

Various embodiments of the present invention are described in greater detail by way of non-limiting example with reference to the accompanying diagrammatic figures. Unless specified otherwise, these embodiments also implement the dispositions 20 that are mentioned above as being preferred. When the same item is shown in several figures it is given the same reference symbol.

Figure 1 is a side view in axial section of a first crusher assembly in accordance with the invention; Figure 2 is a side view in axial section of a second crusher assembly in accordance with the invention; Figure 3 is a horizontal section view through a three-vane rotor for either of the two crushers, for example for the first crusher; Figure 4 is a plan view of the front length of a projection vane of said rotor, with the ceiling being assumed to be removed therefrom; Figure 5 is a side view of the same front length; Figure 6 is a view similar to Figure 4 showing a plan view of the front length of a rotor projection vane in the other of said two crushers, for example in the second crusher; Figure 7 is a view of the Figure 4 rotor ih section on ah axial plane; and Figure 8 is a horizontal section view through a five-vane rotor.

As shown in Figure 1, a first crusher having selfprotecting projection vanes in accordance with the invention has a vertical axis A and includes a projection rotor 1. This rotor is mounted on a vertical shaft provided with protective bearings that are not visible in the figure. The shaft is rotated at high speed, e.g. at 1110 revolutions per minute, by a motor 5 via pulleys 3A and 3B and belts 4.

The rotor 1 includes a floor 8 and a ceiling 9. The ceiling has a central circular opening passing therethrough into which a vertical duct 6 is engaged to convey rocks from a hopper 7. The duct is provided with a device 15 for adjusting its level inside the rotor to compensate for the rate at which it is worn by the rocks which constitute the material to be crushed.

The floor and the ceiling are interconnected by vertical walls which are described in greater detail below with reference to Figure 3.

The stator of the first crusher is constituted by a horizontal circular ring 11 which constitutes the bottom of a rock box. A vertical cylinder 12 constitutes the outer wall of χβ the stator and of the crusher as a whole. The top of it is armored above the level of crushed material 13. The crushed material is constituted by fragments of the rocks inserted from the hopper 7. A certain volume thereof is retained in the rock box. The stator is closed around the duct 6 by an armored horizontal cover 14.

Vertical radial stiffeners 16 improve the performance of the stator and retain the substance 13 which accumulates in the rock box.

The crushed material exits towards the bottom portion of the stator through an annular gap 10 existing between the rotor and the rock box. This material is removed via a conical bottom 17 and is then conveyed by transportation means such as a conveyor belt to a hopper or to some other storage means.

Figure 2 is a corresponding side view in axial section through a second crusher which may differ from the first crusher solely in the design of its stator. The rock box 13 of the first crusher has been replaced in the second crusher by anvils 19. The cylindrical wall 12 is then fitted with an anvil-carrier ring 18 enabling each anvil 19 to be received and moved vertically by means of three slopes 18A disposed at .120* intervals.

Figure 3 is a horizontal section through a polygonal rotor in which said number N is equal to three. This rotor is substantially in the form of an equilateral triangle having cutoff corners. Its direction of rotation is represented by an arrow F. This rotor of unitary construction comprises a horizontal ceiling 9 (not visible in this figure), a floor 8 which is likewise horizontal, with both the floor and the ceiling being made of thick metal sheet, and vertical plates 20, 21, 24, and 25 which constitute the three projection vanes. Each vane constitutes both a portion of the peripheral wall of the rotor and a wall for guiding and accelerating the material to be crushed. Each of these vertical plates constitute a length of one of said vanes. ίί Each vane is constituted, for the most part, by a main length 20 comprising a major front portion 20A and a minor rear portion 20B on opposite sides of a point situated at a minimum distance from the axis A. The front end of said length is welded to a front length 21. Said front length forms one of the small sides of said polygon and its front end is constituted by the projection edge 22 which may be at a distance 47 cm from the axis A, for example. As shown in Figures 4 and 5, tbe projection edge comprises a projection blade 22A constituted by two superposed removable steel plates 22B and 22C each of which carries two vertical bars of tungsten carbide. One of these bars 22D or 22E constitutes a portion of the projection edge 22, and the other such as 23 constitutes a portion of a protective bar which increases the lifetime of the part. The part is subjected to abrasion not only by the rocks which leave the projection vane by passing over its edge 22, but also to some extent by fragments of rock rebounding from the stator The bars such as 23 provide the blade 22A and the front plate 21 with a degree of protection from abrasion by said fragments. They are situated at the maximum radius points of the rotor.

The parts 22B and 22C are fixed to the fixed portion of the front plate 21 by pairs of bolts 31.

Figure 5 is a side view of the same front plate seen from inside the rotor and shows these two interchangeable superposed parts 22B and 22C which carry respective tungsten carbide bars such as 22D and 22E having identical characteristics. Wear takes place essentially in the middle of the front plate, thereby enabling the portions 22B and 22C to be interchanged in order to extend lifetime.

As shown in Figure 6, the protective bars such as 23 may be replaced by a hard protective coating such as 23A formed on the exposed surface of each of the two parts such as 22F which are analogous to the parts 22B and 22C. This coating is advantageously constituted by small round particles or beads of tungsten carbide embedded in a binder such as a nickel cobalt alloy.

Although such protective bars or coatings have been used by the present inventors, it appears that it is often preferable to make the maximum radius points out of hard steel.

Returning to Figure 3, it appears that the rear end of the V front length 21 is closer to the axis of the rotor than is its front end.

The main length 20 of the vane has its rear end limiting the outlet opening 21A of the following projection vane.

A protective plate 24 projects forwardly from said delivery opening. Its circumferentially forward face is fitted with a removable wear plate 24B having a screw 24C for fixing it by means of a nut 24D on the circumferentially rear face of the plate 24. This wear plate is made of a hard steel alloy or of chromium cast iron that withstands abrasion well, whereas the remainder of the rotor assembly is made of steel which is less hard and which is easier to machine and to weld. Said hard steel alloy is selected to be sufficiently ductile to withstand the hardest frontal shocks and sufficiently hard to withstand scraping erosion for a long time. Equipped in this way, the ' plate 24 intercepts the fragments that ricochet from the stator and also deflects streamlines of air charged with dust and sand as created by high speed rotation of the rotor. By doing this it contributes to most effectively protecting the projection blade 22A and it protects the edges of the floor 8 and the ceiling 9 around the outlet opening.

The radially outer end of the protective plate may be placed at a radius (i.e. at a distance from’the axis A) which is slightly greater than the radius of the projection blade 22A as shown in Figure 3. However, it may also be placed at the same radius or at a slightly smaller radius (see Figure 8) and still provide useful protection to the blade, perhaps with the help of the rocks and the air flow leaving the delivery opening 21 A.

Each protective plate 24 is placed in a substantially radial position. It joins the rear minor fraction of the main ** length 20 of the preceding projection vane with which it makes an obtuse angle facilitating deflection of external air streamlines. Each protective plate also extends inside the rotor.

Its inside portion 24A constitutes both a rear length of the projection vane serving to retain the rear end of the protective layer, and a rear stiffener for the main length 20 of said vane.

Each projection vane is fitted with at least one intermediate stiffener 25 projecting inwardly for reinforcing holding. Said reception zone lies between the stiffeners 24A and 25.

Wear plates 26 protect those zones of the floor 8 which are not naturally protected by the layer of material retained in the rotor. These wear plates are naturally held in place by centrifugal force without requiring bolts, by virtue of cleats 27, 28, and 29 fixed to the floor for this purpose.

In the center of the rotor, a hole 38 through the floor 8 receives a solid disk 30 called the distributor. The diameter of the distributor is about l/3rd the diameter of the rotor, 1. e. of the circle circumscribing the rotor. The distributor projects from the floor 8 and serves two purposes: firstly it distributes the material received towards the projection vanes, and secondly it fixes the rotor 1 on the rotary shaft 2 and explained below with reference to Figure 7.

The rotor 1 is carried and driven via its floor 8. The floor is itself carried and driven, not directly by the shaft 2, but indirectly via a carrier plate 34 which is mounted by conventional mechanical means on the top end of the shaft 2 which is much smaller in diameter. This carrier plate is separable from the rotor. Its diameter is slightly greater than one half of the diameter of the floor 8, and it is sufficiently thick to have all of the rigidity that may be desired.

Horizontal translation displacement of the rotor is prevented by the fact that the floor 8 has a central annular η ifi projection 40 projecting from its bottom face around its central hole 38 which projection is inserted, at rest, with very little clearance in a central housing 44 in the carrier plate 34, and in operation, is pressed against the retaining shoulder 42 which constitutes the edge of the housing.

Vertical separating displacement is prevented by means of the distributor 30. The distributor is fixed to the shaft by a single axial screw 33 disposed in an axial well in. the distributor. In operation, the well is filled with rocks which protect the head of the screw from wear. A small gap is left between the peripheral surface of the distributor and the edge of the hole through the floor 8. This gap is maintained by an intermediate washer 36 which is fixed beneath the distributor 30. In order to make this possible, the peripheral surface of the washer is slightly conical, constituting a downwardly directed male cone which thrusts accurately against the inside surface of the annular projection 40 which is machined to constitute the corresponding female cone. Under these conditions, the risk of the intermediate washer 36 being worn is very low because its position ensures that it is protected by the distributor 30 and the floor 8.

As for rotary displacement of the floor relative to the carrier plate 34, this is prevented by a horizontal radial key 35 which is fixed to the carrier plate by two vertical pins 37.

Recesses are formed in the bottom faces of the washer 36 and the distributor 30 in order to receive said key and hold it in position.

The floor 8 and the ceiling 9 are respectively protected by removable wear plates 26 and 26A.

Figure 8 is a horizontal section view through a five-vane rotor. It includes components analogous to all of the essen- tial components of the above three-vane rotor. These analogous components have the same reference numerals plus 100.

Claims (6)

1./ A rotary crusher having self-protecting projection vanes, said crusher being intended to break rocks and comprising: a rigid projection rotor having a vertical axis and 5 provided with means for guiding and driving it in high speed rotation about said axis, with its direction of rotation and with the opposite direction respectively constituting a forwards circumferential direction and a backwards circumferential direction, said rotor itself comprising: 10 a floor delimited by an outer edge; a ceiling delimited by an outer edge, disposed above said floor and pierced by a central feed opening for continuously feeding said rocks down into said rotor; and walls connecting said floor to said ceiling, seme of said 15 walls constituting angularly successive projection vanes, each of said vanes receiving a fraction of said rocks in the vicinity of said axis and guiding said rocks up to a projection edge which constitutes a longitudinally front end of said vane at the periphery of said rotor, in such a manner that said 20 rocks are projected tangentially out from said rotor via said edge, said vane having a hollow shape in plan with the concave side of the hollow directed circumferentially forwardly so that the rocks are retained behind said projection edge and constitute a protective layer protecting the remainder of said vane 25 from wear; said projection edge being constituted by at least one projection blade which is made of hard material in order to slow down its rate of wear; said walls also forming a circumferential succession of 30< peripheral walls which separate said rotor from the outside face while leaving an outlet opening therebetween for said rocks circumferentially ahead of each of said projection edges, said peripheral walls constituting, together with said outer edges of the floor and the ceiling a peripheral surface of the rotor; said crusher further including an external reception structure which surrounds said projection rotor while leaving an annular gap thereabout and which has hard shock surfaces for receiving direct shocks from the rocks projected by said rotor and for breaking said rocks to form rock fragments, some of said fragments returning towards said rotor and subjecting it to return shocks; and delivery means for said rock fragments; said projection rotor including a protective element disposed circumferentially ahead of each of said outlet openings in order to intercept said fragments of rock which are dangerous for said projection blade because they may strike and break said blade lf not intercepted by said protective element; wherein said protective element ahead of each of said outlet openings is a protective plate extending along a substantially radial direction from said peripheral surface in such a manner that said dangerous fragments of rock are intercepted substantially at right angles by said protective plate, thereby subjecting it to frontal shocks which hammer it more than they scrape it, with at least the circumferentially front face of said protective plate being constituted by a protective material which is selected to be less hard than the material of said projection blade in order to avoid being broken by such frontal shocks.

2. / A crusher according to claim 1, wherein said protective plate extends vertically far enough up and/or down for at least a fraction of said fragments of rock which might otherwise reach the top and/or bottom edges of said outlet opening and erode lt rapidly by nearly tangential return shocks , to be likewise intercepted substantially at right angles by said plate of material for protecting said edges.

3. / A crusher according to claim 1, wherein said protective plate forms, in plan view, an obtuse angle with the portion of said peripheral wall situated circumferentially immediately ahead thereof, thereby deflecting the external air streamlines which flow relative to said projection rotor in contact with said wall so as to move the abrasive rock dust suspended in said air streamlines away from said outlet opening. i?

4. / A crusher according to claim 1, wherein said protective plate includes an internal portion situated between said floor and said ceiling in order to enable it to be fixed to said projection rotor and also to constitute a rear length of said

5. Projection vane. 5/ A crusher acoording to claim 1, wherein said protective plate includes a demountable wear plate constituted by said protective material on its circumferentially front face, said material being chosen to be hard in order to reduce its rate of 10 wear by dust and by those of said dangerous fragments which strike against its edges.

6. / A crusher according to claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.