US3853274A

US3853274A - Impact crusher

Info

Publication number: US3853274A
Application number: US00352207A
Authority: US
Inventors: H Wright; K Jones
Original assignee: British Iron and Steel Research Association BISRA
Current assignee: British Iron and Steel Research Association BISRA
Priority date: 1971-05-24
Filing date: 1973-04-18
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10

Abstract

Comminution apparatus includes a conveyor belt for throwing a jet of particles to be comminuted; and a target surface arranged for the jet to impact upon the target surface to comminute particles, and to allow comminuted particles and, if present, unchanged particles to be continuously removed from the target surface.

Description

United States Patent [191 Wright et al.

[ Dec. 10, 1974 IMPACT CRUSHER Inventors: Harold Wright, Stockton; Keith Thomas Jones, Norrnanby, both of England The British Iron and Steel Research Association, London, England Filed: Apr. 18, 1973 Appl. No.: 352,207

Related US. Application Data Continuation of Ser. No. 146,062, May 24, 1971, abandoned.

Assignee:

u.s. Cl. 241/40, 241/276 Int. Cl. B02c 19/00 Field of Search 241/5, 40; 274, 275, 276

References Cited UNITED STATES PATENTS I 3/1893 Gamble 241/40 x 1,062,306 5/1913 Stobie 241/5 X 2,128,848 8/1938 Rafetto.... 24-1/5 X 2,553,234 5/1951 Boucherm 241/40 X 2,841,340 7/1958 Muller 241/40 X 3,341,134 9/1967 Meloy 241/5 Primary Examiner-Granville Y. Custer, Jr. Attorney, Agent, or Firm-Bacon 8L Thomas [57 ABSTRACT Comminution apparatus includes a conveyor belt for throwing a jet of particles to be cornminuted; and a target surface arranged for the jet to impact upon the target surface to comminute particles, and to allow cornminuted particles and, if present, unchanged particles to be continuously removed from the target surface.

4 Claims, 5 Drawing Figures IMPACT CRUSHER This is a continuation of application Ser. No. 146,062, filed May 24, l97l and now abandoned.

This invention relates to a method and an apparatus for comminuting particles.

In comminuting particles, particles may be crushed in different ways. For example, the particles may be crushed in jaw, roll or cone crushers, ball mills, rod mills, hammer mills or pin mills. The known mills offer a number of disadvantages, especially as to capital cost, maintenance and. operation. For example, hammer mills, rotary or centrifugal mills and pin mills suffer from extremely high wear rates. Also, these mills, like other known mills, may produce undesirable amounts of fines in certain applications. A comminution method and apparatus are now provided which allow such disadvantages to be reduced or avoided.

According to one aspect of the present invention, a

method for comminuting particles includes throwing by a conveyor belt a jet of particles against a target surface such that impact of particles on the target surface comminutes particles; and continuously removing from the target surface comminuted particles and, if present, unchanged particles.

According to a further aspect of the present invention, an apparatus for comminuting particles includes a conveyor belt for throwing a jet of particles to be comminuted; and a target surface arrangedfor the jet of particles to impact on the target surface to comminute particlesy'and to allow comminuted particles and, if present, unchanged particles to be continuously removed from the target surface. v

with the method or apparatus according to the present invention, the jet of particles produced by the conveyor belt avoids or reduces grinding of the particles with each other during their flight, thereby providing a constraint against the production offmes. The continuous removal of comminuted and, if present, unchanged particles from the target surface hinders production of fines by comminution resulting from freshly arriving particles impacting onto particles present at the'target. Wear is also less inherent in the apparatus than for example with hammer mills, rotary or centrifugal mills or pin mills, because the conveyor belt does not strike its particles forward. And, another practical advantage is that clogging difficulties are less'likely, in view of a jet being an inherently more controlled form of projection than the violent projection in many directions that occurs in for example a hammer mill where impacting hammers strike against particles to be comminuted. The comminution apparatus may be installed at a permanent location or it may be mobile. The suitability of particles to be comminuted by the apparatus will be decided by test on the apparatus. Examples of especially suitable particles are particles of coals, cokes, minerals, sintered feeds for blast furnaces, and blast furnace slags.

The speed with which the conveyor belt will project the jet of particles will be chosen according to the circumstances, for example the nature of the particles to be comminuted. Convenient speeds for particles of cokes and sintered blast furnace feeds are 20 to 100 ft/sec. (i.e. substantially 6 to 30 metres/sec). The conveyor belt may be fed with particles or it may be self feeding. For example, a self feeding conveyor belt may have scoops which when underneath position of the conveyor belt scoop up particles. The self feeding action may be started or stopped by arranging the conveyor belt such that one of its ends can be raised or lowered to cause the scoops to come into or pass out of contact with particles underneath the conveyor belt. The self feeding action may also be performed progressively by making the conveyor belt advanceable. Notwithstanding the above possibilities, many convenient embodiments of the apparatus may nevertheless not be self feeding. In such a case, the carrying surface of the conveyor belt may receive a gravity feed of the particles, for example from a hopper. The carrying surface of the conveyor belt may be plain. The jet of particles thrown by the conveyor belt will diverge under the effect of gravity as it approaches the target surface. However, the targetsurface can be at a distance appropriate to no substantial divergence of the jet having occurred. This may be of practical consequence in that the narrower the jet the greater the control over the production of fines.

The target surface may be orientable to obtain an optimum mean angle of impact for the jet of particles. However, for many applications, the orientation of the target surface may be permanent, as a preselected fixed constant of the apparatus. The target surface may be above the level of the conveyor belt. If the target surface is interrupted, the spaces defining the interruptions may plug and eventually lead to undesirable local concentrations of particle material on the target surface which can give rise the; production of undesired fines by the impact of freshly arriving particles. Therefore, a continuous target surface may be more convenient. The profile of the target surface is conveniently flat, in that other profiles might give rise to undesirable local concentrations of particle matter on the target surface. However, non flat profilesmight be suitable,

for example a profile that is arcuate and optionally scal- The life of the target surface will depend on its material and steel may be very suitable. The target surface may be replaceable or permanent. For example, the target surface may be provided by a replaceable surface or surfaces on a reinforcing plate.

The removal of comminuted and unchanged particles from the target surface is conveniently done by gravity. This may be assisted by a current of air blowing across the target surface in such a way as not to interfere unduly with the jet of particles.

The comminution method or apparatus may be operated in closed circuit. In which case, recycle means may separate oversi'zed particles from the target surface and return the separated oversize particles to the conveyor belt. The separating is conveniently done by screening. 1

The comminuted particles may be treated by separa tion means to separate fines. However, this is an optional refinement to the method and apparatus, in that without this feature the comminution method and ap paratus may provide, as described above, a good control over the production of fines. The use of the separation means is therefore a practical matter to be decided be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a flow sheet schematically indicating an example of the comminution method and apparatus ac cording to the invention.

FIG. 2 is a perspective view of an alternative target plate for the apparatus of FIG. 1 or the apparatus of FIGS. 3 and 4.

FIG. 3 is a flow sheet schematically indicating another example of the comminution method and apparatus according to the invention.

FIG. 4 is sectional view showing the mounting of the target plate in the apparatus of FIG. 3.

FIG. 5 is a sectional view on the line 5/5 of FIG. 4 with the target plate removed.

Referring to FIG. 1, a line 1 leads to a hopper 2, which is mounted on a housing 3 and leads to a conveyor belt 4 within the housing. The hopper 2 feeds the belt 4 with particles to be comminuted. The belt 4 is driven by a system of pulley wheels 5. The particles on the belt are thrown forward by the belt as a jet having speed in the range of 20 to I00 ft/sec (6 to 30 metres/- sec.). The jet passes out of an opening in the side of the housing 3 to enter a corresponding opening in a housing 6 containing a target surface 7 provided by a target plate 8. The housing 6 provides the apparatus with a target zone in which the target surface 7 is above the level of the conveyor belt 4. One common housing might be used instead of the

housings

3 and 6.

The orientation of the target surface 7 is permanent and a preselected fixed constant of the apparatus. The target surface 7 is continuous and flat. The arcuate target surface 9-on the target plate 10 of FIG. 2 may be used instead of the target plate 8. The surface 9 is a continuous arcuate target surface, the profile of which is scalloped as shown. The feed particles impact as a jet on the target surface 7, or 9 of FIG. 2 if used. As a result of the impact, particles are comminuted. The comminuted particles together with unchanged particles fall from the target surface 7 under the effect of gravity and pass via a line 11 into a recyling section 12 of the apparatus. The recycling section 12 screens its incominng particles to reject oversized particles, and returns the oversized particles by the line 13 to the conveyor belt 4 via the hopper 2. The product particles that pass through the recyling section 12 enter a line 14 to pass into a screening section 15. The screening section 15 rejects product particles of a desired mesh size and they leave via an outlet line 16. The fines which pass through the screening section 13 leave via an outlet line 17.

Referring to the embodiment of FIGS. 3 and 4, FIG. 3 shows a line 21 leading to a hopper 22, which is mounted in a housing 23 and leads to a conveyor belt 24 within the housing. The hopper 22 feeds the belt 24 v with particles to be comminuted. The belt 24 is driven by pulley wheels 25. The particles on the belt are thrown forward by the belt as a jet having a speed in the range of 200 to I00 ft/sec (6 to 30 metres/sec). The jet passes out of an opening in the side of the housing 23 to enter a corresponding opening in a housing 26 containing a composite continuous flat target surface 27 mounted on a single reinforcing plate 28. Both these represent a target plate. The surface 27 is made up of replaceable cladding elements arranged side by side and together. The housing 26 provides apparatus with a target zone in which the target surface 27 is above the level of the conveyor belt 24. One common housing might be used instead of

housings

23 and 26.

FIG. 4) and the pin 29 being carried by a bracket 31.

in an extension of the housing 26 (see FIG. 3). The adjustment about the pin 29 is provided by one end of a bar 32 being pivoted on the pin 29. The bar 32 carries a bracket support 33 for the plate 28. The other end of the bar 32 is pivoted on a further horizontal pivot pin 34, which carries a rising rod 35 passing out of the housing 26. The rod 35 is upwardly adjustable in a clamp 36 on top of the housing 26, thereby allowing the bar 32 to be turned around its pivot pin 29 to adjust the orientation of the target surface 27 and the reinforcing plate 28. The adjustment about pivot pin 30 (see FIG. 4) is provided by the reinforcing plate 28 having on its back near its lower edge a pivot block 37 containing the pivot pin 30. Two set

screws

38, 39 enter the pivot block 37 for engaging the pivot pin 30 to allow the orientation of the block to be fixed or changed. Also at the back of plate 28 and near its upper edge are two outstanding spaced apart lugs 40 (only one is shown in FIG. 4). Passing through the lugs 40 is a pivot pin 41, the ends of which do not extend substantially beyond the lugs. Mounted on the pivot pin 41 and between the lugs 40 is the terminal eye 42 of an axially adjustable threaded bolt 43 contained in the plain circular hole of a rectangular sleeve 44 located centrally inside the bracket support 33. The sleeve 44 is welded to and within plates 45, 46 inside the bracket support 33. The plates 45 and 46 represent a composite support bar. The ends of the plates 45, 46 are secured to rectangular hollow sections which are welded to circular necks, supported in swivel bushes 47. The swivel bushes 47 (see FIGS. 3,4) are set in opposite sides of the bracket support 33, to allow the bolt 43 to pivot relative to the bracket support 33 when the bolt 43 is advanced into the housing 31.

The jet of particles thrown by the belt 24 impact against the target surface 27. As a result of the impact, particles are comminuted. The comminuted particles together with uncharged particles fall from the surface 27 under the effect of gravity-and pass via a line 51 into a recycling section 52 of the apparatus. The recycling section 52 screens the incoming particles to reject oversized particles, and returns the oversized particles by the line 53 to the conveyor belt 24 via the hoppper 22. The product particles that pass through the recycling section 52 enter a line 54 to pass into a screening section 55, which rejects product particles of a desired mesh size and they leave via an outlet line 56. The lines which pass through the screening section leave via an outlet line 57.

The two comminution apparatus of the accompanying drawings may be used for many different kinds of particle materials. Examples of especially suitable materials are coals, cokes, minerals, sintered blast furnace feeds, and blast furnace slags.

We claim: I

1. Apparatus for fragmenting pieces of inelastic brittle, fragmentable material into smaller pieces of a desired size comprising: a conveyor belt adapted for throwing a continuous jet of pieces of said fragmentable material; means for continuously feeding pieces of said fragmentable material onto said conveyor belt; a stationary target plate inclined to the direction of the jet and spaced in a generally horizontal direction from the closest end of the conveyor belt, means for changing the angle of inclination of the target plate with respect to the direction of the jet of pieces of fragmentable material; means for adjusting the orientation of the target plate with respect to the jet of said pieces; and means for driving said conveyor belt at a speed required to maintain a speed at thesurface of the conveyor belt of between 20and 100 feet per second, the arrangement being such that all of the pieces to be fragmented are thrown from the conveyor belt and against said target plate as a continuous jet at a speed of between 20-and 100 feet per second and are fragmented solely by the impact of the particles on the target plate,

the pieces of material being continuously removed from the area of the target plate by gravity.

2. Apparatus as claimed in claim 1, in which the tar-' get plate and the means for changing the angle of inclination of the target plate are mounted on the means for adjusting the orientation of the target plate.

3. Apparatus as claimed in claim 1, in which the target plate is disposed in a housing having an inlet opening for passage of the jet of pieces of material to be fragmented and an outlet opening for pieces of the fragmented material falling from the target plate, and the means for adjusting the orientation of the target plate is mounted on said housing.

4. Apparatus as claimed in claim 1, in which the profile of the target plate is arcuate and scalloped.

Claims

1. Apparatus for fragmenting pieces of inelastic brittle, fragmentable material into smaller pieces of a desired size comprising: a conveyor belt adapted for throwing a continuous jet of pieces of said fragmentable material; means for continuously feeding pieces of said fragmentable material onto said conveyor belt; a stationary target plate inclined to the direction of the jet and spaced in a generally horizontal direction from the closest end of the conveyor belt, means for changing the angle of inclination of the target plate with respect to the direction of the jet of pieces of fragmentable material; means for adjusting the orientation of the target plate with respect to the jet of said pieces; and means for driving said conveyor belt at a speed required to maintain a speed at the surface of the conveyor belt of between 20 and 100 feet per second, the arrangement being such that all of the pieces to be fragmented are thrown from the conveyor belt and against said target plate as a continuous jet at a speed of between 20 and 100 feet per second and are fragmented solely by the impact of the particles on the target plate, the pieces of material being continuously removed from the area of the target plate by gravity.

2. Apparatus as claimed in claim 1, in which the target plate and the means for changing the angle of inclination of the target plate are mounted on the means for adjusting the orientation of the target plate.